Nanjing, China
Nanjing, China

Hohai University is a research university in Nanjing, China under the direct jurisdiction of the Ministry of Education of China. From 1958 to 2000 it was administered by the Ministry of Water Resources.The university's main focus is the research and study of water resources, and it primarily educates engineering subjects, with coordinated development of engineering, science, economics, management, arts and law. It is part of Project 211 and has set up a graduate school. Wikipedia.

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A facility secondary NO_(3)^( )salinized soil modifier and a modification method are disclosed. The present invention involves the preparation processes of two biological soil modifiers A and B and application methods thereof, which are specifically described as follows: (1) soil modifier A.: solid, obtained by microbial fermentation with straw powder and rice bran and the like as raw materials. C/N between 30-50, applied by uniformly mixing at 1-1.4% by mass with facility ploughing soil, co-culturing at 35-50 C. for 5-7 days, and then returning to fields; and (2) soil modifier B: liquid, subjected to salt tolerance acclimation to have effective microbial populations, and used in the crop growth period. Based on the microbial techniques, the present invention can improve soil structureness, enhance microbial activity and promote biological immobilization on inorganic nitrogen in soils, significantly increasing the facility cultivation crop yield, and improving the product quality.

Zhang J.,Hohai University | Lou Y.,Jiangsu
Proceedings of 2016 IEEE Advanced Information Management, Communicates, Electronic and Automation Control Conference, IMCEC 2016 | Year: 2016

For in RBF neural network prediction results by random sample of thus affecting prediction accuracy, using the grey prediction model of RBF network is trained, can weaken the randomness of data greatly, so the combination of neural network and grey prediction, construct grey RBF neural network by network model, and hydrological forecasting can improve the accuracy of hydrological forecast. But if the gray scale data is large, due to the parameters of the model of GM (1,1, θ), leads to poor prediction accuracy. In this regard, GM (1, 1, θ) model and use ant colony algorithm to improve its, and the prediction precision can be improved In the construction of RBF network, due to the implicit function node has been relying on the actual experience to determine, with instability, and choose to use the golden section method to determine the hidden nodes. The forecast results show that the grey RBF neural network forecasting model has higher precision and better generalization ability, and it has practical value. © 2016 IEEE.

Salvekar A.V.,Nanyang Technological University | Huang W.M.,Nanyang Technological University | Xiao R.,Hohai University | Wong Y.S.,Nanyang Technological University | And 3 more authors.
Accounts of Chemical Research | Year: 2017

Conspectus The phenomenon of recovering the permanent shape from a severely deformed temporary shape, but only in the presence of the right stimulus, is known as the shape memory effect (SME). Materials with such an interesting effect are known as shape memory materials (SMMs). Typical stimuli to trigger shape recovery include temperature (heating or cooling), chemical (including water/moisture and pH value), and light. As a SMM is able not only to maintain the temporary shape but also to respond to the right stimulus when it is applied, via shape-shifting, a seamless integration of sensing and actuation functions is achieved within one single piece of material. Hydrogels are defined by their ability to absorb a large amount of water (from 10-20% up to thousands of times their dry weight), which results in significant swelling. On the other hand, dry hydrogels indeed belong to polymers, so they exhibit heat- and chemoresponsive SMEs as most polymers do. While heat-responsive SMEs have been spotted in a handful of wet hydrogels, so far, most dry hydrogels evince the heat and water (moisture)-responsive SMEs. Since water is one of the major components in living biological systems, water-responsive SMMs hold great potential for various implantable applications, including wound healing, intravascular devices, soft tissue reconstruction, and controlled drug delivery. This provides motivation to combine water-activated SMEs and swelling in hydrogels together to enhance the performance. In many applications, such as vascular occlusion via minimally invasive surgery for liver cancer treatment, the operation time (for both start and finish) is required to be well controlled. Due to the gradual and slow manner of water absorption for water-activated SMEs and swelling in hydrogels, even a combination of both effects encounters many difficulties to meet the timerequirements in real procedures of vascular occlusion. Recently, we have reported a bioabsorbable radiopaque water-responsive shape memory embolization plug for temporary vascular occlusion. The plug consists of a composite with a poly(dl-lactide-co-glycolide) (PLGA) core (loaded with radiopaque filler) and cross-linked poly(ethylene glycol) (PEG) hydrogel outer layer. The device can be activated by body fluid (or water) after about 2 min of immersion in water. The whole occlusion process is completed within a few dozens of seconds. The underlying mechanism is water-responsive shape recovery induced buckling, which occurs in an expeditious manner within a short time period and does not require complete hydration of the whole hydrogel. In this paper, we experimentally and analytically investigate the water-activated shape recovery induced buckling in this biodegradable PEG hydrogel to understand the fundamentals in precisely controlling the buckling time. The molecular mechanism responsible for the water-induced SME in PEG hydrogel is also elucidated. The original diameter and amount of prestretching are identified as two influential parameters to tailor the buckling time between 1 and 4 min as confirmed by both experiments and simulation. The phenomenon reported here, chemically induced buckling via a combination of the SME and swelling, is generic, and the study reported here should be applicable to other water- and non-water-responsive gels. © 2017 American Chemical Society.

Zhang Y.-Q.,Dalian University of Technology | Gong J.-X.,Dalian University of Technology | Zhang Q.,Hohai University | Han S.,Dalian University of Technology
Engineering Structures | Year: 2017

To describe the hysteretic behavior of flexure-shear critical reinforced concrete (RC) columns realistically, a hysteretic loop expression of flexure-shear critical RC columns under complete cyclic loading is proposed by investigating the characteristics of column specimens in PEER - Column Database. For the proposed expression, important characteristics of flexure-shear critical RC columns under cyclic loading, including pinching and stiffness degradation, are covered. And then, an equivalent damping ratio model suitable for flexure-shear critical RC columns is proposed by using the proposed hysteretic loop expression based on the Jacobsen's approach. The relationship between the equivalent damping ratio formula of two-column pier supported bridge and that of its columns is developed based on the energy dissipation capacity. A design example is provided to illustrate the application of the proposed model. © 2016 Elsevier Ltd

Zhuo T.,Hohai University | Zhuo T.,Nanjing Institute of Technology
International Journal of Services Operations and Informatics | Year: 2017

This paper explains the relationship between knowledge management capability and human resource management system implementation, and answers the question of whether knowledge acquisition, conversion, application and protection management capabilities can affect human resource management system effective implementation or not in state-owned enterprises of China. Based on the influence model of knowledge management capability on human resource management system implementation, after reliability analysis, validity analysis and regression analysis, it can be concluded that improvement of knowledge management capability can promote implementation of human resource management system. Knowledge acquisition capability can impact economic effect of human resource management system implementation. Knowledge conversion capability can impact target function of human resource management system implementation. Knowledge application capability can impact technical performance of human resource management system implementation. Knowledge protection capability can impact the enterprise support of human resource management system implementation. Copyright © 2017 Inderscience Enterprises Ltd.

Li F.,Hohai University | Du C.L.,Hohai University
IOP Conference Series: Earth and Environmental Science | Year: 2017

This paper presents a research on the interdisciplinary nature of 167 water-related programs in 46 selected American public universities. Using keyword coding and Classification method, and the results show that water-related disciplines largely focus on environment, natural resources, engineering, ocean and agricultural studies, which are all applied disciplines. Moreover, water-related disciplines lay great emphasis on the interdisciplinary research and research platforms construction with the research fields of environment, natural resources and agricultural. © Published under licence by IOP Publishing Ltd.

Gu X.,Hohai University | Zhang Q.,Hohai University
Journal of Hohai University | Year: 2017

Research progress and development trends in numerical simulation methods for analyzing the dynamic response and failure process of dams under blast and impact loads are reviewed. Research findings regarding the dynamic response and failure process of dams under blast loading obtained through the existing numerical simulation methods for the computation of explosion mechanics are focally summarized. It is pointed out that the dam dynamic response analysis under blast loading involves an explosion, the formation and propagation of a shockwave, the interaction between the shockwave and the dam body, and the dynamic response of the dam body. The classification and characteristics of the blast loads exerted on dams and their damage effects on dams are summarized, and issues that require more attention in dam explosion simulation under explosion conditions are pointed out. Based on current research, the latest research achievements of computational mechanics should be absorbed into future research to develop high-precision numerical methods and high-efficiency numerical solution systems, and to realize the entire process simulation of the dam dynamic response to explosions. © 2017, Editorial Board of Journal of Hohai University (Nature Sciences). All right reserved.

Zhuang Y.,Hohai University | Wang K.,Hohai University
Road Materials and Pavement Design | Year: 2017

This paper develops rigorous lower-bound shakedown solutions for pavement structures subjected to Hertz loads both in plane strain and three-dimensional (3D) models. Firstly, a necessary shakedown condition is derived based on Melan’s shakedown theorem and the use of Prandtl–Reuss theory in conjunction with von Mises criterion, which gives a maximum value to the rigorous shakedown limit. Secondly, the rigorous lower-bound shakedown solution is established uses a self-equilibrated critical residual stress field with an optimisation procedure. As expected, the necessary shakedown condition gives larger values of normalised shakedown limits than that of the normalised rigorous lower-bound shakedown solution, with the maximum difference of 93%. Also observed is that the 3D model always overestimates the normalised rigorous shakedown limits of the plane strain model by approximately 8–13%, while the two models capture approximately the same trend of normalised rigorous shakedown limits varied with frictional coefficient. Finally, the parametric studies on normalised rigorous shakedown limit of pavements in terms of frictional coefficient and Poisson’s ratio are performed. It shows that the normalised rigorous shakedown limits are proportional to material yield stress but decrease markedly with raising frictional coefficient; while the effect of the Poisson’s ratio on normalised rigorous shakedown limits is marginally. In addition, the critical residual stress fields lie between two residual stress limits, which intersect beneath the surface for small μ, while tend to converge at the half-space surface when μ = 0.3, indicating that the failure mode of the pavement changes from subsurface failure to surface failure when increasing the frictional coefficient μ. As a result, the present shakedown solutions can provide reference to the design of pavements subjected to rolling and sliding loading contact. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Hu H.-X.,Hohai University | Hu H.-X.,Tibet University
Journal of Computational and Theoretical Nanoscience | Year: 2016

Genetic Algorithm (GA) is an adaptive algorithm of global search optimization formed through the simulation of biological heredity and evolution in the natural environment. By the random selection, the algorithm requires no special needs for the search space and derivations, which is featured with simple operation, rapid convergence, and other advantages. Therefore, it is especially applicable for complex and non-linear problems that are difficult to be solved by the conventional search methods. However, this algorithm is strong in global search capability but insufficient in the local search capability. Simulated annealing (SA) is an algorithm possessed with the stronger local search ability and widely used in combinatorial optimization problems. Due to the inadequate local search capability of GA and deficient global search capability of SA, they were combined in the paper to complement their mutual advantages and take use of the global search capability of GA and local search capability of SA. The poor local search ability of GA and its premature convergence as well as the bad global search capability of SA and its low efficiency were overcome, and the SA-based mixed GA was constructed. Then, standard data sets of wine and letter-recognition in the UCI database were applied for the verification of the algorithm. It was indicated that the convergence rate was improved to some extent by the mixed algorithm proposed in this paper. Finally, the improved genetic algorithm was applied to the actual projects, which indicated the feasibility of the algorithm in engineering. © Copyright 2016 American Scientific Publishers All rights reserved.

Zhang Z.-C.,Key Laboratory of Geohazard Prevention of Hilly Mountains | Chen Y.-M.,Hohai University | Liu H.-L.,Hohai University | Liu H.-L.,Chongqing University
Computers and Geotechnics | Year: 2017

The Micropile-MSE Wall, specially designed for mountain roadways, is used to simultaneously increase the MSE wall's local stability, global stability and impact resistance of road barriers. Model tests were conducted first to validate the viability of the Micropile-MSE Wall. The impact resistance of the road barrier is then studied numerically. The test results indicate that the surcharge-induced earth pressure, base pressure and lateral displacement of Micropile-MSE Wall panels are effectively reduced. The impact loading on the barriers of the Micropile-MSE Wall is actually supported by the whole retaining structure, which increases the impact resistance of the road barrier significantly. © 2016 Elsevier Ltd

Gan L.,Hohai University | Shen X.,Hohai University | Qing W.,Yichun Water Conservancy Bureau
Key Engineering Materials | Year: 2017

The safety operation of a concrete face rockfill dam (CFRD) built on covering layers depend on the integrity of its water stop system. So analyzing the dam seepage field before and after joint sealing damaged is significant, which includes the study of the influence on the dam seepage behavior when the water stop of peripheral joint and slab joint were damaged. In this paper, taken a specific hydropower station project as an example, the numerical analysis models of a CFRD for simulating the different water stop damage and failure types were established. Then the influence mechanism how the damage of the peripheral joint and slab joint affects the seepage gradient, saturated surface and seepage discharge inside the dam was analyzed, and the influence values were obtained. Therefore, the water stop area that needs to focus on is ascertained when the dam anti-seepage system was arranged. © 2017 Trans Tech Publications, Switzerland.

Liu C.-S.,Hohai University | Liu C.-S.,National Taiwan Ocean University | Li B.,University of Science and Technology Beijing
Composite Structures | Year: 2017

For the free vibration of composite beams and non-uniform beams we propose a new upper bound theory to approximate the first few natural frequencies. The Rayleigh quotient is expressed in terms of boundary functions, instead of that in terms of eigenfunctions. The boundary function satisfies all boundary conditions of the given beam, and is at least the fourth-order polynomial with leading coefficient to be one. We prove that the maximality of the Rayleigh quotient in the space of the kth order boundary functions is equivalent to the orthogonality of the kth order boundary function to lower order optimal boundary functions. Hence, we can easily find the kth order natural frequency through an orthogonalization technique provided. When the first three natural frequencies are compared with the exact or numerically found ones, good results are obtained, which confirm the applicability of the present upper bound theory. We address the inverse problems of composite beam equations, where we use the orthogonal system of boundary functions as bases to expand the unknown functions and derive linear algebraic equations to determine the expansion coefficients. As a consequence, we can fast and accurately estimate the unknown rigidity function and planar inertial function with the help of the first three natural frequencies, and the supplemented measured data of recovered function on two boundaries. The robustness of the present inversion methods is demonstrated by numerical examples. © 2017 Elsevier Ltd

Liu Y.,Hohai University | Feng J.,Hohai University | Lu J.,Hohai University
Proceedings of the 11th International Conference on Ubiquitous Information Management and Communication, IMCOM 2017 | Year: 2017

Collaborative filtering, a successful and wildly used technique in personalized recommender systems, generates recommendations by similar users. Cosine similarity and Pearson correlation coefficient are widely used in collaborative filtering to calculate the similarity; however, the similarity is not accurate in some cases because of the defects of the algorithm. To solve these issues, this paper proposes a novel similarity calculation method which combined information entropy with compressive distance weight based on the probability distribution of rating distance. Experiment results show that the proposed method get better performance than conventional Pearson correlation coefficient method. © 2017 ACM.

Liu J.,Hohai University | Wu F.,Hohai University
Forests | Year: 2017

Forestry is an effective strategy for climate change mitigation. However, forestry activities not only sequester carbon but also release CO2. It is therefore important to formulate carbon subsidy and carbon taxation policies on the basis of the price of carbon. In this study, a forestry-based Computable General Equilibrium (CGE) model was built by using input-output data of China in 2014 to construct a Social Accounting Matrix (SAM). The model simulates different carbon price scenarios and was used to explore the effects of carbon subsidy and carbon taxation policies on the forestry economy. The main results can be summarized as follows: When the carbon price is low, the implementation of the policy increases forestry output and causes forest product prices to rise. When the carbon price is high, the carbon tax will produce an inhibitory effect, and output and prices will decline. With the constant rise of the carbon price, value addition will decrease, with flow to other industries. For the carbon sequestration policy, there is a reasonable carbon price range bound. In light of these results, relevant policies are proposed. © 2017 by the authors.

Chen Y.-M.,Hohai University | Wang R.,Hohai University | Zhang Y.-P.,Hohai University
Yantu Lixue/Rock and Soil Mechanics | Year: 2017

Saturated sand in liquefied state exhibits the characteristics of a non-Newtonian fluid, while it is difficult to obtain a stable liquefied state using a conventional dynamic test. A sample mixing plastic sand and the sodium chloride solution of equal density is prepared to obtain a stable state of almost zero effective stress. According to the theory of low Reynolds number flows around a sphere, the test device for flow characteristics of saturated suspended plastic sand is developed based on the particle image velocimetry (PIV) technology. A half sphere on the inner wall of the transparent model box is embedded in the saturated suspended plastic sand, and it can move in a vertical direction. The movement of the particles around the half sphere which recorded by a PIV device indicates the flow characteristics of the plastic sand in a almost zero effective stress state. The apparent viscosity of the plastic sand is obtained by measuring the movement velocity and force applied on the half sphere. The test results show that the saturated suspended plastic sand is a non-Newtonian fluid, and it can be used as an equivalent material of liquefied sand. Same important concepts, including the zero-velocity bounding line, shearing zone, shearing angle and height of the shearing zone, are proposed based on the micro investigation on the pulling ball tests. The shearing angle of the shearing zone increase with the ball's velocity increasing. The influencing zone in the direction of dragging ball can be described in the height of the shearing zone. The minimum distance between the ball center with the bounding wall of the model box should be larger than six times of the ball diameter. The hole below the moving ball is due to the high apparent viscosity of the saturated suspended plastic sand. The moving velocity of the ball or pipe in the dragging tests should be as low as that satisfying the theory of the low Reynolds number flows. © 2017, Science Press. All right reserved.

Fei J.,Hohai University | Chu Y.,Hohai University
Proceedings - 2016 Joint 8th International Conference on Soft Computing and Intelligent Systems and 2016 17th International Symposium on Advanced Intelligent Systems, SCIS-ISIS 2016 | Year: 2016

This paper derived a dynamic global proportional integral derivative (PID) sliding mode control based on adaptive radial basis function (RBF) neural controller for a micro electromechanical systems (MEMS) gyroscope. This approach gives a new dynamic global PID sliding mode manifold, which not only enables system trajectory to run on the global sliding mode surface at the start point more quickly and eliminate the reaching phase of the conventional sliding mode control, but also restrains the steady-state error and reduces the chattering via a dynamic PID sliding surface. Meanwhile, a RBF neural network (NN) system is employed to estimate the lumped uncertainty and eliminate the chattering phenomenon. Additionally, adaptive laws and dynamic global PID sliding control gains that ensure system stability in a Lyapunov sense are proposed, together with the techniques for deciding which basis function should be selected. Finally, the effectiveness of RBFNN dynamic global PID sliding mode control method is demonstrated. © 2016 IEEE.

Zhou L.,Hohai University | Li Q.,Hohai University | Huo G.,Hohai University | Zhou Y.,Hohai University
Computational Intelligence and Neuroscience | Year: 2017

As a typical deep-learning model, Convolutional Neural Networks (CNNs) can be exploited to automatically extract features from images using the hierarchical structure inspired by mammalian visual system. For image classification tasks, traditional CNN models employ the softmax function for classification. However, owing to the limited capacity of the softmax function, there are some shortcomings of traditional CNN models in image classification. To deal with this problem, a new method combining Biomimetic Pattern Recognition (BPR) with CNNs is proposed for image classification. BPR performs class recognition by a union of geometrical cover sets in a high-dimensional feature space and therefore can overcome some disadvantages of traditional pattern recognition. The proposed method is evaluated on three famous image classification benchmarks, that is, MNIST, AR, and CIFAR-10. The classification accuracies of the proposed method for the three datasets are 99.01%, 98.40%, and 87.11%, respectively, which are much higher in comparison with the other four methods in most cases. © 2017 Liangji Zhou et al.

Andam-Akorful S.A.,Kwame Nkrumah University Of Science And Technology | Ferreira V.G.,Hohai University | Ndehedehe C.E.,Curtin University Australia | Quaye-Ballard J.A.,Kwame Nkrumah University Of Science And Technology
International Journal of Climatology | Year: 2017

After the frequent and long drought episodes of the 1980s, a plethora of case studies have shown that West Africa remains a hot spot in the continent where despite its numerous water resources, extreme rainfall variability remains a profound challenge to the availability of freshwater for agriculture and ecosystem services. In this paper, we assess the recent flux in water availability over West Africa by investigating variations in net-precipitation (i.e. the maximum available freshwater flux) using wavelet analysis. Net-precipitation was obtained as a residual of the atmospheric water balance, and its variability compared to precipitation, temperature, evaporation, soil moisture and normalized difference vegetation index using wavelet power transforms and coherence analysis. Results from the study indicate that the variance in water flux over the region has been progressively reducing, suggesting a relative reduction in extreme hydrological conditions. Also, the wavelet coherence analysis revealed that the observed decreasing rate of available freshwater is highly coupled to a low frequency modulating El-Niño activity that induced lower changes in rainfall variance, as well as higher evaporation variance. Spatial trends in the annual-scaled average wavelet power indicated that the south-western parts of the region experienced the most reduction in rainfall flux. The highest deficit in net-precipitation flux was found in the dry sub-humid climatic zone, which is drained by major regional rivers, including the Niger and Volta. Considering the long-term variability in freshwater (i.e. from 1979 to 2010), we found the 1980s to be the driest decade and the 1990s being its recovery period, while the 2000s proved to be a considerably dry decade, suggesting a strong multi-decadal variability. © 2017 Royal Meteorological Society.

Zhu Y.,Changzhou University | Jiang A.,Hohai University | Kwan H.K.,University of Windsor
International Conference on Digital Signal Processing, DSP | Year: 2017

In this paper, a novel algorithm is proposed for locating sensor networks. In general, Euclidean distance matrices are incomplete due to their limited communication power. Furthermore, distance measurements are contaminated by noise. For the purpose of localization, unknown distances are first estimated via low rank approximation. Relative coordinates of sensors are then obtained by eigenvalue decomposition of the Gram matrix, which is constructed by the Euclidean distance matrix estimated. To improve the localization accuracy, subnetworks are constructed by each sensor and its neighbors. Since neighboring sensors of each sensor are more prone to communicate with each other, the local Euclidean distance matrix could be denser than the global one, leading to a more accurate estimate. Another advantage of the proposed algorithm is that it can be implemented in a distributed manner, which is desirable for sensor networks without central computational unit. Two sets of simulations demonstrate that the proposed algorithm can achieve better localization accuracy than other localization algorithms using global Euclidean distance matrices. © 2016 IEEE.

Wang C.,Hohai University | Zhang Z.-Y.,Hohai University | Liu Y.,Hohai University | Fan S.-M.,Hohai University
Soil and Tillage Research | Year: 2017

Desiccation cracks detrimentally affect the hydraulic and mechanical properties of soils. Soil cracking dynamic subjected to wetting-drying (W-D) cycles aids in the understanding of soil shrinking-swelling mechanism and the regularity of water movement in unsaturated soils with variable solid phase. In the present paper, we experimentally investigate the geometric and fractal features of dynamic cracking patterns with the soils undergoing four W-D cycles. Crack patterns were recorded by a digital camera mounted above the soil specimen. Digital image processing and morphological algorithms were employed to yield the geometric and fractal indexes that depict crack patterns (incl. crack ratio, length, mean width, similarity degree, box-counting fractal and multifractal dimensions). The analysis of dynamic crack patterns suggest an inconsistency exhibited in the crack morphology towards the drying (DR) process and backwards the wetting (WT) process, which could be possibly attributed to the different suction stress between soil particles during moisture desorption and sorption, closely analogous to the hysteresis phenomenon of soil-water characteristic curve. The gradient of crack propagating and dissolving related to water content reaches different peak values during an individual W-D cycle. High repeatability is found across the stabilized crack patterns in the four drying cycles and the cracking degree reaches equilibrium with the increasing number of W-D cycles. The crack patterns in the subsequent drying processes are significantly dominated by the first cracking. The similarity degree between the first and respectively the second, third, fourth crack patterns decreases with the increasing W-D cycles, suggesting the soil cracked in the previously cracking vicinity, and saturated wetting/submerge hardly healed the failure zones that caused the repeatable cracking. Attempt of fractal and multifractal methods applied to the crack networks corroborates the applicability of the scaling method to the crack patterns. The analysis indicates that soil cracks progress in hierarchical networks in the first drying cycle, while the gradational crack segments nearly simultaneously emerged or vanished in the subsequent drying or wetting cycles. The study reveals the discrepancy of crack morphology between the crack formation and dissolution during W-D cycles, and demonstrates the repeatability degree and hierarchy of cracks across W-D cycles, which would aid in quantifying physical processes in cracked soil shrinking/swelling and modelling of water transport in unsaturated soils of dynamic structure. © 2017 Elsevier B.V.

Tang C.,Hohai University | Zhang X.,Hohai University | Zhou X.,Hohai University
Physical Chemistry Chemical Physics | Year: 2017

Density functional calculations were used to investigate the hydrogen storage abilities of Na-atoms-decorated BN sheets under both external biaxial strain and a vertical electric field. The Na atom generally has the weakest binding strength to a given substrate compared with the other elements in the periodic table [PANS, 2016, 113, 3735]. Consequently, it is understudied in comparison to other elements and there are few reports about the hydrogen storage abilities of Na-decorated nanomaterials. We calculated that the average binding energy (Eb) of Na atoms to the pure BN sheet is 1.08 eV, which is smaller than the cohesive energy of bulk Na (1.11 eV). However, the Eb can be increased to 1.15 eV under 15% biaxial strain, and further up to 1.53 eV with the control of both 15% biaxial strain and a 5.14 V nm-1 electric field (E-field). Therefore, the application of biaxial strain and an external upward E-field can prevent clustering of the Na atoms on the surface of a BN sheet, which is crucial for the hydrogen storage. Each Na atom on the surface of a BN sheet can adsorb only one H2 molecule when no strain or E-field is applied; however, the absorption increases to five H2 molecules under 15% biaxial strain and six H2 molecules under both 15% biaxial strain combined with a 5.14 V nm-1E-field. The average adsorption energies for H2 of BN-(Na-mH2) (m = 1-6) are within the range of practical applications (0.2-0.6 eV). The hydrogen gravimetric density of the periodic BN-(Na-6H2)4 structure is 9 wt%, which exceeds the 5.5 wt% value that should be met by 2017 as specified by the US Department of Energy. On the other side, removal of the biaxial strain and E-field can help to desorb the H2 molecule. These findings suggest a new route to design hydrogen storage materials under near-ambient conditions. © the Owner Societies 2017.

Liu M.,Zhejiang University of Technology | Gao Y.,Hohai University
International Journal of Geomechanics | Year: 2017

Coarse-grained materials (CGMs), including gravel, ballast, and rockfill material, exhibit a complicated stress-strain-volume change behavior, which is state dependent and influenced by considerable particle breakage even under relatively low pressure. A generalized plasticity model with a multiaxial formulation is developed for CGMs based on the critical state concept. The effect of particle breakage on their critical state behavior, including the nonlinear variation of both shear strength and void ratio with the mean effective stress, is fully incorporated with an implicit form in the current model. Two state functions and the corresponding virtual stress ratios are proposed to construct the new formulation of dilatancy, plastic flow, loading direction, and plastic modulus in the present model. The numerical analyses are performed for a series of true triaxial tests on CGMs, and model predictions are in good agreement with experimental results of true triaxial tests over a wide range of pressures. In summary, the proposed model is capable of accurately characterizing the highly nonlinear shear behavior due to particle breakage of CGMs, particularly including their strain softening/hardening and plastic dilation/contraction in various load paths. © 2016 American Society of Civil Engineers.

Hou S.,Hohai University | Fei J.,Hohai University
Turkish Journal of Electrical Engineering and Computer Sciences | Year: 2017

In this paper, a robust adaptive fuzzy control system using feedback linearization is proposed for a three-phase active power filter (APF). The APF system is divided into two separate loops: The current dynamic inner loop and the DC voltage dynamic outer loop. Adaptive fuzzy tracking control using feedback linearization is employed for the current dynamic inner loop to overcome the drawbacks of the conventional method. The proposed controller can ensure proper tracking of the reference current and impose desired dynamic behavior, giving robustness and insensitivity to parameter variations. Adaptive fuzzy proportional{integral control is applied to the DC voltage dynamics outer loop to improve the dynamic response and reduce the error of the stable state. Simulation results demonstrate the high performance of the proposed adaptive fuzzy control strategies. © 2017 TÜBITAK.

Xu J.,Hohai University | Huang L.,East China University of Technology | Yang L.,East China University of Technology
Journal of Applied Geophysics | Year: 2017

Reduced to the pole is a problem that seriously affects the accuracy of aeromagnetic exploration in low-latitude regions. To eliminate the reduced to the pole effect, we proposed a transform modulus of the magnetic anomaly. This method has been used to process aero magnetic data in a low-latitude region, i.e., the eastern region of Jiangxi, China. The calculated result of the transform modulus is not significantly affected by the magnetization direction. Results clearly indicated anomaly shape, size, and location. The magnetic anomaly conversion modulus showed good effects on regional aeromagnetic data processing at low latitudes. © 2017 Elsevier B.V.

Bie Y.,Hohai University | Qiang S.,Hohai University | Sun X.,Michigan Technological University | Song J.,The First Bureau of Henan Province Hydraulic Engineering
Construction and Building Materials | Year: 2017

When simulating the temperature field of concrete, the conventional adiabatic temperature rise models, which only take the age of concrete into account, can lead to a significant deviation (the maximum relative error nearly 73%) from predicted values to measured values under extreme conditions. To solve this problem, a new prediction formula is presented in this paper for estimating the final temperature rise of concrete, by considering ultimate hydration based on the equivalent age. The formula is developed on the basis of measured data obtained in some real construction cases during the recent years. It essentially reveals the ultimate degree of hydration for concrete with a variation in the placing temperature at the construction site. The degree of hydration at the construction site is not as accurate as measured with an adiabatic calorimeter. Also, the measured data shows that the ultimate degree of hydration of concrete under the non-adiabatic condition is related to its placing temperature. A logarithmic function is proposed to approximate this relationship. The equivalent age is developed to consider the effects of both the age of concrete and its temperature. The comparison shows that the proposed combination of equivalent age and the new formula can reduce the maximum relative error substantially from 73% to 15% than those algorithms which do not consider equivalent age or our proposed formula. © 2017

Cao J.-J.,Hohai University | Gou X.-F.,Hohai University
Journal of Physics and Chemistry of Solids | Year: 2017

The newly discovered Ba2Bi3 phase has attracted attentions in search of new superconductors, mainly because of the layered structure with two-dimensional superconducting Bi planes intercalated by Ba atoms. To clearly reveal what features the layered structure of the Ba2Bi3 phase correlates with, especially under pressure, we have systematically investigated the structural, mechanical, electronic and thermodynamic properties under the equivalent hydrostatic pressures up to 14 GPa by means of first-principle calculations with the Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA) approaches. The results indicate that the pressure effect on the crystal structure is performed as a compression of the unit-cell volume, mainly along the c-axis. Specifically for the mechanical related properties, the elastic constants and polycrystalline elastic moduli monotonically increase with the pressure. The calculated ductile factors show that the Ba2Bi3 lies in between the brittle and ductile border line at 0 GPa and the pressure makes the ductility enhancement. Besides, the anisotropic properties of the Ba2Bi3 under various pressures are discussed. The electronic energy band structure and density of states under pressure are analyzed. Moreover, the pressure and temperature dependence of the thermodynamic properties through the quasi-harmonic Debye model, together with the pressure dependence of the Debye temperature calculated from elastic constants has been obtained. The calculated results of the variation of the Debye temperature and total density of states at Fermi level show that the pressure can lead to the superconducting transition temperature (Tc) of the Ba2Bi3 decreasing. © 2017 Elsevier Ltd

Hassan M.,Nanjing Agricultural University | Ding W.,Nanjing Agricultural University | Umar M.,University of Agriculture at Faisalabad | Rasool G.,Hohai University
Bioresource Technology | Year: 2017

The present study focused on carbon to nitrogen ratio (C/N) and organic loading rate (OLR) optimization of goose manure (GM) and wheat straw (WS). Dealing the anaerobic digestion of poultry manure on industrial scale; the question of optimum C/N (mixing ratio) and OLR (daily feeding concentration) have significant importance still lack in literature. Therefore, Batch and CSTR co-digestion experiments of the GM and WS were carried out at mesophilic condition. The alkali (NaOH) solubilization pretreatment for the WS had greatly enhanced its anaerobic digestibility. The highest methane production was evaluated between the C/N of 20–30 during Batch experimentation while for CSTRs; the second applied OLR of (3 g.VS/L.d) was proved as the optimum with maximum methane production capability of 254.65 ml/g.VS for reactor B at C/N of 25. The C/N and OLR regression optimization models were developed for their commercial scale usefulness. © 2017 Elsevier Ltd

Wang T.-T.,Hohai University | Han X.,Hohai University
Proceedings - 2016 International Conference on Information System and Artificial Intelligence, ISAI 2016 | Year: 2016

In this paper, an automatic control method is proposed for a two rotational degrees-of-freedom (DOF) video tracking system to track a flying object. An acoustic passive localization algorithm based on planar five-element array is adopted, to focus on the flying target when it first appears. The kinematic of the video tracking system is analysed. Then the interaction matrix based on the target centroid feature is derived for the target with irregular and complicated shape. Finally a predictive control approach is developed to facilitate an effective tracking. The experimental results show the effectiveness of the proposed control scheme. © 2016 IEEE.

Zhang J.,Chang'an University | Zhu C.,Chang'an University | Li X.,Chang'an University | Pei J.,Chang'an University | Chen J.,Hohai University
Construction and Building Materials | Year: 2017

A reliable UMAT subroutine of selected constitutive model of asphalt mixture is developed and applied to characterize the three-stage rutting behavior of asphalt pavement by using ABAQUS. It is indicated that the heavier traffic load not only induces the greater rutting depth, but also accelerates the rutting rate, causing the pavement earlier enter into rutting failure with shortened service life. The damage evolution and axle-load conversion are further discussed. Results show that the pavement subjected to heavier axle loads has the greater damage and faster damage evolution. The axle-load conversion index is 5.97 according to rut equivalence principle. © 2017 Elsevier Ltd

Gao Y.,Hohai University | Jiang D.,Hohai University | Liu M.,Hohai University
Electronics Letters | Year: 2017

A method for wideband transmit beamforming using integertime- delayed and phase-shifted waveforms is proposed. Unlike traditional true-time-delayed digital methods, which employ variable fractional delay filters or discrete Fourier transforms to create fractional time delays, the proposed method uses only integer-time-delayed waveforms with phase shifts corresponding to fractional time delays. Furthermore, the shifted phase can be directly generated; this generation can be simply achieved by controlling the parameters of a direct digital synthesiser. A beam pattern simulation confirms that the integer-time-delayed and phase-shifted waveforms are capable of synthesising wideband transmitting beam patterns. Finally, a power synthesis efficiency analysis demonstrates that the synthesis loss caused by phase shifting is negligible. © The Institution of Engineering and Technology 2017.

Liu B.,Hohai University | Ma H.,Hohai University | Ju P.,Hohai University
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2017

Protrusion defects on inner conductor can seriously weaken the dielectric strength of gas insulated switchgear (GIS). In practice, pulse current method (IEC 60270) and vibration method sometimes are ineffective for this type of defect. Clarification of coincidence of partial discharge (PD) characteristics measured with both methods is very important for further application of the vibration method. In this paper, PD pulses and vibration signal recorded on enclosure generated from artificial protrusions mounted on inner conductor with different lengths and diameters were measured synchronously by using a 252 kV GIS PD test system. The test GIS was filled with the gas SF6 of the standard atmosphere pressure (i.e. 101 kPa), and the power frequency of the test voltage was 50 Hz. The pulse repetition frequency (PRF) characteristics and frequency-resolved vibration (FRV) characteristics under different discharge level were investigated. The dynamic response (DR) characteristics of the experimental GIS are also obtained by using the force hammer test. For a good understanding of PD vibration characteristics, the relationship between FRV, PRF and DR was analyzed in detail. To make more reliable operations of GIS, an improvement vibration method for protrusion defect detection was developed and applied. © 1994-2012 IEEE.

Jiang H.,Hohai University | Yu Z.,Hohai University | Mo C.,Guangxi University
Journal of Water Resources Planning and Management | Year: 2017

The practical reservoir flood season segmentation is crucial to dynamically adjusting the flood-limiting water level in flood seasons. An ensemble method structure (EMS) was designed to screen out the most suitable method structure for segmenting flood season. The performance of the proposed EMS approach was evaluated in a case study in Chengbihe Reservoir, China. The results indicate that the method structures containing flood volume series sampled by using the peaks-over-threshold (POT) technique outperform the other method structures. To further explore the impacts of the flood volume index and the POT sampling technique on segmentations, the 1-, 3-, and 5-day flood volume series sampled by using the POT1, POT2, and POT3 techniques, respectively, were used to segment the flood season by using the method of directional statistics. The main findings are as follows: (1) the segmentation is most sensitive to the selected indices, sensitive to the sampling techniques, and least sensitive to the segmentation methods; and (2) the variance of the segmentations increases with the amount of flood data used in segmenting flood season. Thus, the segmentations of the flood season in the Chengbihe Reservoir can be obtained by averaging the dates obtained with the latter constructed method structures. The case study demonstrates that the proposed EMS approach can be an effective tool for flood season segmentation. © 2016 American Society of Civil Engineers.

Liang Z.,Hohai University
Journal of Dynamical and Control Systems | Year: 2017

In this paper, we study the existence of radially stable periodic solutions of radially symmetric Keplerian-like systems. The proof is based on the third-order approximation method combined with the averaging method. © 2016, Springer Science+Business Media New York.

Yu G.J.,Jiangsu University | Lin X.G.,Ningbo University of Technology | Guo F.,Hohai University
Key Engineering Materials | Year: 2017

In this paper, on the basis of the viscoelastic fractional derivative model, Mittag-Leffler function is applied to deduce the expression of stress relaxation modulus for magnetorheological elastomers according to its form and main properties. Furthermore, the relaxation modulus for polyurethane rubber matrix cured magnetorheological elastomers at different applied magnetic fields and shear strains is tested by rheometer. The results indicate that magnetorheological elastomers exhibit obvious relaxation behavior and the magnetic field strength and shear strain exert significant influence on the relaxation behavior: the relaxation modulus of magnetorheological elastomers increases with the magnetic field strength but decreases with the shear strain. Besides, the model agrees well with the experimental data which indicates that the model is suitable for characterization of relaxation behavior for magnetorheological elastomers. © 2017 Trans Tech Publications.

Guo F.,Hohai University | Lin X.G.,Ningbo University of Technology | Yu G.J.,Jiangsu University
Key Engineering Materials | Year: 2017

The modified carbonyl iron powders with single particle size(single-grading) and binary particle sizes (double-grading) were added in the composite gel, which was prepared by using methyl silicone oil, gelatin and agaropectin colloids as raw materials, and then the single- and double-grading magnetorheological composite gels(MRCGs) were prepared by vacuum decompression. The effects of particle size and gradation of carbonyl iron power on the rheological behavior of the MRCGs were studied. The results show that the shear strength of single-grading MRCGs decreased gradually with the decrease of the carbonyl iron particle size. However that the shear strength of the double-grading MRCGs with the gradation of 90 wt% un-ball-milled and 10 wt% ball-milled carbonyl iron powders first increased then decreased with the elongation of milling time (the decrease of carbonyl iron paticle size) and reached 99.6kPa when ball milling time for 24h, which was 17.8kPa larger than that of un-ball-milled single-grading MRCGs. © 2017 Trans Tech Publications.

Pang G.,Hohai University | Chen W.,Hohai University
Guti Lixue Xuebao/Acta Mechanica Solida Sinica | Year: 2017

The fractional acoustic wave models that describe the ultrasound propagation in biological tissues can be constructed from the perspectives of time-fractional derivative or space-fractional integral viscoelastic constitutive relations. These two modeling perspectives treat the biological tissues as non-local viscoelastic material, respectively. The first perspective has been proposed in literature whereas the second one is rarely reported. The paper mainly concerns the second modeling perspective. A new stress-strain constitutive relation in the form of Riesz potential is derived after replacing the exponential kernel function in the conventional Eringen nonlocal model by the power kernel function. Using the new relation, the conventional viscoelastic elements, i.e., spring and dashpot, are extended to their nonlocal counterparts. Through the series and parallel connections of such elements, the Kelvin and the Maxwell non-local constitutive models in arbitrary spatial dimensions are obtained, and the creep compliance and the relaxation modulus of one-dimensional models are also given. The Riesz potential order and the material internal characteristic length are two primary parameters of the nonlocal models, and the retardation time of both the Kelvin and the Maxwell non-local constitutive models gets larger as the internal characteristic length increases. Data fitting of the experiment data of a kind of soft soil implies that the nonlocal models could give better descriptions of the viscoelastic behaviors of complex media, say, creep of soft soil, ultrasound in biological tissues, and vibration of nano-composites. The non-local constitutive models of different series and parallel connections of nonlocal spring and dashpot, complemented with the momentum conservation and the displacement-strain relations, lead to a family of space-fractional wave equations, which describe the power-law frequency-dependent wave dissipation and dispersion in biological tissues. This is a potential application of the non-local constitutive models. © 2017, Editorial Department Chinese Journal of Solid Mechanics. All right reserved.

Wei Z.,Hohai University
Journal of Computational and Theoretical Nanoscience | Year: 2017

In this research, Shuffled frog-leaping algorithm (SFLA) has long been considered as new evolutionary algorithm of group evolution, and has a high computing performance and excellent ability for global search. Knapsack problem is a typical NP-complete problem. For the discrete search space, this paper presents the improved SFLA, and solves the knapsack problem by using the algorithm. Experimental results show the feasibility and effectiveness of this method. Copyright © 2017 American Scientific Publishers.

Chen R.,Hohai University | Chen R.,Hubei University of Education
Journal of Computational and Theoretical Nanoscience | Year: 2017

The music teaching is an integral part of college student quality education. However, many colleges do not pay attention to the music teaching. In addition, different regions of the colleges have a different attitude to the music teaching. Therefore, it is important to evaluate the music education. The fuzzy evaluation method is an important part in the evaluation methods. The method can apply the fuzzy language to evaluate the target. Therefore, the evaluated results of the method are more practical. In this paper, we combine the fuzzy analytic hierarchy process, AHP method with the Gray correlation method and put forward the TFAHPGC method. Then, we use the method to evaluate the music teaching in different regions of the colleges in China. The final experimental results show that the method is very effective. Copyright © 2017 American Scientific Publishers.

Ullah A.,Hohai University | Chen W.,Hohai University | Khan M.A.,Hohai University | Sun H.G.,Hohai University
PLoS ONE | Year: 2017

This paper proposes a new variational model for jointmultiplicative denoising and deblurring. It combines a total generalized variation filter (which has been proved to be able to reduce the blocky-effects by being aware of high-order smoothness) and shearlet transform (that effectively preserves anisotropic image features such as sharp edges, curves and so on). The new model takes the advantage of both regularizers since it is able to minimize the staircase effects while preserving sharp edges, textures and other fine image details. The existence and uniqueness of a solution to the proposed variational model is also discussed. The resulting energy functional is then solved by using alternating direction method of multipliers. Numerical experiments showing that the proposed model achieves satisfactory restoration results, both visually and quantitatively in handling the blur (motion, Gaussian, disk, and Moffat) and multiplicative noise (Gaussian, Gamma, or Rayleigh) reduction. A comparison with other recent methods in this field is provided as well. The proposed model can also be applied for restoring both single and multi-channel images contaminated withmultiplicative noise, and permit cross-channel blurs when the underlying image has more than one channel. Numerical tests on color images are conducted to demonstrate the effectiveness of the proposed model. Copyright: © 2017 Ullah et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Wang Y.-X.,Jiangnan University | Cao J.,Hohai University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2017

The low-dimensional electron gas owing topological property has attracted many interests recently. In this work, we study the influence of the electron-electron interaction on the arbitrary Chern number insulator. Using the mean-field method, we approximately solve the Hubbard model in the half-filling case and obtain the phase diagrams in different parametric spaces. We further verify the results by calculating the entanglement spectrum, which contains C chiral modes and corresponds to a real space partitioning. © 2017 Elsevier B.V.

Fan L.W.,Hohai University | Pan S.J.,Nanjing University of Aeronautics and Astronautics | Liu G.Q.,Xi'an Jiaotong - Liverpool University | Zhou P.,Nanjing University of Aeronautics and Astronautics
Journal of Cleaner Production | Year: 2017

Energy-intensive firms are confronted with increasing pressure to improve energy efficiency and reduce energy consumption. This paper explores the relationship between the energy efficiency and financial performance of a sample of firms in China based on a panel dataset for the period 2010–2014. Six financial indicators representing the benefits of different stakeholders are used in the analysis. Our empirical results show that energy efficiency is positively related to return on equity, return on assets, return on investment, return on invested capital and return on sales but has no significant relationship with Tobin's q. In addition, we examine the interaction effect between energy intensity and firm growth and find that firm growth helps to enhance the positive relationship between energy intensity and financial performance. Our findings provide incentive for firms to be proactive in their efforts towards energy conservation and emissions reduction. © 2017 Elsevier Ltd

Luo Y.L.,Hohai University | Kong X.F.,Hohai University
Hydraulic Engineering IV - Proceedings of the 4th International Technical Conference on Hydraulic Engineering, CHE 2016 | Year: 2016

This paper presented a series of hydro-mechanical suffusion experiments to study the effect of the load history of hydraulic gradient on the evolution of suffusion. Four different increase velocities of hydraulic gradient were used to simulate the different load histories of hydraulic gradient. The results indicate that the load history of hydraulic gradient has a significant influence on the evolution of suffusion. The faster the increase velocity of hydraulic gradient, the smaller the suffusion failure hydraulic gradient, and the larger the cumulative eroded mass. A fast increase velocity of hydraulic gradient is harmful for the safety of hydraulic structures. The results presented here explain the reason why suffusion always happens when the water level at the upstream side rises quickly during flood season. © 2016 Taylor & Francis Group, London, UK.

Wang L.,Hohai University | Jiang Q.,Hohai University | Zhang C.,Hohai University
International Journal for Numerical Methods in Fluids | Year: 2017

Precise simulation of the propagation of surface water waves, especially when involving breaking wave, takes a significant place in computational fluid dynamics. Because of the strong nonlinear properties, the treatment of large surface deformation of free surface flow has always been a challenging work in the development of numerical models. In this paper, the moving particle semi-implicit (MPS) method, an entirely Lagrangian method, is modified to simulate wave motion in a 2-D numerical wave flume preferably. In terms of consecutive pressure distribution, a new and simple free surface detection criterion is proposed to enhance the free surface recognition in the MPS method. In addition, a revised gradient model is deduced to diminish the effect of nonuniform particle distribution and then to reduce the numerical wave attenuation occurring in the original MPS model. The applicability and stability of the improved MPS method are firstly demonstrated by the calculation of hydrostatic problem. It is revealed that these modifications are effective to suppress the pressure oscillation, weaken the local particle clustering, and boost the stability of numerical algorithm. It is then applied to investigate the propagation of progressive waves on a flat bed and the wave breaking on a mild slope. Comparisons with the analytical solutions and experimental results indicate that the improved MPS model can give better results about the profiles and heights of surface waves in contrast with the previous MPS models. © 2017 John Wiley & Sons, Ltd.

Chu Y.,Hohai University | Fei J.,Hohai University
2016 European Control Conference, ECC 2016 | Year: 2016

An adaptive backstepping global proportional integral derivative (PID) sliding mode fuzzy control with a radial basis function (RBF) neural network (NN) estimator is proposed for a micro electromechanical systems (MEMS) gyroscope. First of all, a backstepping sliding mode controller is designed to compensate the external disturbances and a RBF neural network controller is employed to approach the system unknown dynamic characteristic. Additionally, sliding mode term in the backstepping global PID sliding mode controller is adjusted by the adaptive fuzzy system to compensate for the NN approximation error and the external disturbances, reducing the chattering phenomenon. Finally, simulation results demonstrate the effectiveness of the backstepping global sliding fuzzy controller with RBF neural approximator. © 2016 EUCA.

Tang L.,Hohai University | Xu C.,Hohai University | Liu Z.,CAS Institute of Electrical Engineering
IOP Conference Series: Materials Science and Engineering | Year: 2017

Zn diffusion in III-V compound semiconductorsare commonly processed under group V-atoms rich conditions because the vapor pressure of group V-atoms is relatively high. In this paper, we found that group V-atoms in the diffusion sources would not change the shaped of Zn profiles, while the Zn diffusion would change dramatically undergroup III-atoms rich conditions. The Zn diffusions were investigated in typical III-V semiconductors: GaAs, GaSb and InAs. We found that under group V-atoms rich or pure Zn conditions, the double-hump Zn profiles would be formed in all materials except InAs. While under group III-atoms rich conditions, single-hump Zn profiles would be formed in all materials. Detailed diffusion models were established to explain the Zn diffusion process; the surface self-diffusion of matrix atoms is the origin of the abnormal Zn diffusion phenomenon. © Published under licence by IOP Publishing Ltd.

Liu N.,Hohai University | Fei J.,Hohai University
19th International Conference on Electrical Machines and Systems, ICEMS 2016 | Year: 2016

This paper presents an Active Disturbance Rejection Control (ADRC) technology and PI-fuzzy compound technology method for Active Power Filter (APF). The ADRC consists of Tracking Differentiator (TD), Extended State Observer (ESO) and Nonlinear State Error Feedback law (NLSEF). This control method makes full use of the error driven control law, the modern control theory and the nonlinear feedback control. The APF control system is designed with two closed loop; reference current tracking loop with ADRC and the voltage controlling loop with the PI-fuzzy compound controller. Comparing with the direct current control technique, simulation results verify that the proposed control method has excellent dynamic performance and strong robustness in the presence of model uncertainty as well as external disturbances. © 2016 The Institute of Electrical Engineers of Japan.

Ning X.,Hohai University | Liu X.,Hohai University
Hydraulic Engineering IV - Proceedings of the 4th International Technical Conference on Hydraulic Engineering, CHE 2016 | Year: 2016

Given that the dam monitoring model based on the conventional Radial Basis Function (RBF) neural network cannot screen the remarkable factors and is liable to fall into the local optimum, this paper establishes a fusion monitoring model that combines the Mean Impact Value (MIV), improved fruit Fly Optimization Algorithm (FOA), and the RBF neural network. First, the MIV is introduced to screen three kinds of forecast factors, namely, water pressure, temperature, and aging. Then, the improved FOA algorithm is adopted for searching the optimal spread value of the RBF network. By using these two methods, the MIV-improved RBF neural network model is set up. To verify the validity of the model, taking the displacement monitoring data of the gravity dam into account, the multiple linear regression model, the conventional RBF model, and the MIV-improved RBF model are also built. The calculation results show that the MIV-improved RBF neural network model has characteristics such as great generalization ability, stable prediction, and high precision. Furthermore, this model can be applied to the dam deformation for monitoring and warning. © 2016 Taylor & Francis Group, London, UK.

Gao Y.,Hohai University | Jiang D.,Hohai University | Liu M.,Hohai University
Signal Processing | Year: 2017

The Sequential Monte Carlo (SMC) implementation for the probability hypothesis density (PHD) filter, referred to as the SMC-PHD filter, is a good candidate for multi-target tracking (MTT) problems. It recursively propagates the weighted particle set that approximates the multi-target posterior density. In this paper, we propose an improved SMC-PHD filter for MTT called the particle-gating SMC-PHD filter. First, a robust gating based on particles propagated from a previous time period is proposed to select the observations of survival targets. Second, a sigma-nearest-gating is proposed to accurately select the observations of new targets. By employing only the observations obtained by the above algorithms to update the state estimations, the overall processing speed of the filter is significantly improved. In addition, a softening factor is suggested to lower the average number of clutters in the updater. This provides more accurate estimation compared with the basic SMC-PHD filter. Finally, the respective real-time and tracking performances of the proposed SMC-PHD filter are verified by the simulation results. © 2016 Elsevier B.V.

Gao W.,Hohai University | Ge M.M.,Hohai University
Geomechanics and Engineering | Year: 2016

As one natural material, the physical and mechanical properties of rock will be affected very largely by chemical erosion environment. Under chemical environment, the strength of rock will be reduced. Considering the effect of the chemical erosion, fracture factor of rock is reduced. The damage variable is applied to express the change of fracture stress. Therefore, the fracture criterion of rock under chemical environment is constructed. By one experiment of rock fracture under chemical erosion environment, the proposed fracture criterion is verified. The results show that, the fracture path by theory is agree with the testing one well. © 2016 Techno-Press, Ltd.

The Ediacaran Doushantuo Formation at Weng'an, South China hosts well-preserved phosphatized microfossils known as the Weng'an biota. A laser ablation ICP-MS analysis of rare earth element (REE) characteristics of the fossil-bearing black phosphorite unit of the Doushantuo Formation at Weng'an was conducted, with the aim of unravelling the depositional conditions and diagenetic processes during formation of the phosphorites. Spherical phosphatized microfossils and phosphatic clasts were analysed, and the REE data display middle REE (MREE) -enriched shale-normalized REE patterns. The spherical phosphatized microfossils show an increase in total REE contents (∑REE) from core to rim. Negative correlations between ∑REE and the extent of MREE enrichment over the other REE (indicated by LaN/SmN, YbN/SmN) are observed for analysed spots within individual phosphatic grains, which may be due to complex diagenetic history of the phosphatic grains, with fluctuations in REE sources and chemical parameters in a high-energy shallow-water environment being additional factors. The LaN/YbN and LaN/SmN characteristics of the phosphatic grains suggest they were mostly influenced by early diagenetic alteration rather than late extensive recrystallization. The negative Ce anomalies in the samples suggest they formed under oxic-bottom-water conditions. Positive Eu anomalies are present in all samples, and are likely to reflect involvement of hydrothermal fluids rather than changes in redox conditions of porewater. Overall this study has major implications for phosphorites as important archives for the study of geochemical proxies, the Ediacaran period and also evolutionary changes. Copyright © Cambridge University Press 2017

Liu C.-S.,Hohai University | Liu D.,Shanghai University
Numerical Heat Transfer, Part B: Fundamentals | Year: 2017

As to recover a time-dependent heat source under an extra temperature measured at an interior point, we can reformulate it to be a three-point boundary value problem. We can develop a coupled boundary integral equation method, wherein by selecting two sets of adjoint test eigenfunctions in two sub domains and using polynomials as the trial functions of unknown heat source, the time-dependent heat source is recovered very well and quickly. Four numerical examples, including a discontinuous one, demonstrate the efficiency for the ill-posed inverse heat source problem in a large time duration and under a large noise up to 10–30%. Then, selecting three sets of adjoint test eigenfunctions in three domains: problem domain and two sub domains, and using the Pascal polynomials as trial functions, the unknown space-time-dependent heat source is recovered very fast and accurately from the solution of three coupled boundary integral equations. © 2017 Taylor & Francis.

Xie X.,Hohai University | Wang T.,Hohai University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

In this paper, a nonlinear least square twin support vector machine (NLSTSVM) with the integration of active contour model (ACM) is proposed for noisy image segmentation. Efforts have been made to seek the kernel-generated surfaces instead of hyper-planes for the pixels belonging to the foreground and background, respectively, using the kernel trick to enhance the performance. The concurrent self organizing maps (SOMs) are applied to approximate the intensity distributions in a supervised way, so as to establish the original training sets for the NLSTSVM. Further, the two sets are updated by adding the global region average intensities at each iteration. Moreover, a local variable regional term rather than edge stop function is adopted in the energy function to ameliorate the noise robustness. Experiment results demonstrate that our model holds the higher segmentation accuracy and more noise robustness. © 2017 SPIE.

Cheng X.,Hohai University | Li Z.,University of Tokyo | Yamamoto M.,University of Tokyo
Mathematical Methods in the Applied Sciences | Year: 2017

This article discusses the analyticity and the long-time asymptotic behavior of solutions to space-time fractional diffusion-reaction equations in ℝd. By a Laplace transform argument, we prove that the decay rate of the solution as t→∞ is dominated by the order of the time-fractional derivative. We consider the decay rate also in a bounded domain. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Purpose: The purpose of this paper is to explore the determinants of continuance intention of social networking site (SNS) users through a new perspective and discuss how to retain SNS users. Design/methodology/approach: The author proposed a research model by integrating network externalities and social support. Three dimensions of social support and two types of network externalities were analyzed, respectively, to explore the direct and indirect effects on continuance intention. Online questionnaires were adopted to collect data, and 513 valid samples were analyzed by structural equation modeling approach. Findings: The findings show that network externalities have a significant indirect effect on user’ continuance intention through the mediation effects of social support, and among the three dimensions of social support, network management plays a more important role on continuance intention. Research limitations/implications: The findings suggest that network externalities can trigger the function of social support to keep the “stickiness” of SNS users, and network management is the key dimension of online social support. Some other theoretical and practical implications are also provided. Originality/value: The study is novel in exploring users’ continuance intention of SNSs by integrating social support and network externalities. Meanwhile, the author also intends to compare the effect of different dimensions of social support on SNS usage and discuss their internal relationships. © 2016, © Emerald Group Publishing Limited.

Wang C.,CAS South China Sea Institute of Oceanology | Wang X.,Hohai University | Weisberg R.H.,University of South Florida | Black M.L.,National Oceanic and Atmospheric Administration
Climate Dynamics | Year: 2017

The paper uses observational data from 1950 to 2014 to investigate rapid intensification (RI) variability of tropical cyclones (TCs) in the North Atlantic and its relationships with large-scale climate variations. RI is defined as a TC intensity increase of at least 15.4 m/s (30 knots) in 24 h. The seasonal RI distribution follows the seasonal TC distribution, with the highest number in September. Although an RI event can occur anywhere over the tropical North Atlantic (TNA), there are three regions of maximum RI occurrence: (1) the western TNA of 12°N–18°N and 60°W–45°W, (2) the Gulf of Mexico and the western Caribbean Sea, and (3) the open ocean southeast and east of Florida. RI events also show a minimum value in the eastern Caribbean Sea north of South America—a place called a hurricane graveyard due to atmospheric divergence and subsidence. On longer time scales, RI displays both interannual and multidecadal variability, but RI does not show a long-term trend due to global warming. The top three climate indices showing high correlations with RI are the June-November ENSO and Atlantic warm pool indices, and the January-March North Atlantic oscillation index. It is found that variabilities of vertical wind shear and TC heat potential are important for TC RI in the hurricane main development region, whereas relative humidity at 500 hPa is the main factor responsible for TC RI in the eastern TNA. However, the large-scale oceanic and atmospheric variables analyzed in this study do not show an important role in TC RI in the Gulf of Mexico and the open ocean southeast and east of Florida. This suggests that other factors such as small-scale changes of oceanic and atmospheric variables or TC internal processes may be responsible for TC RI in these two regions. Additionally, the analyses indicate that large-scale atmospheric and oceanic variables are not critical to TC genesis and formation; however, once a tropical depression forms, large-scale climate variations play a role in TC intensification. © 2017 Springer-Verlag Berlin Heidelberg

Chang X.,Hohai University | Zhao Y.,Hohai University
Proceedings - 2016 3rd International Conference on Trustworthy Systems and Their Applications, TSA 2016 | Year: 2016

Nowadays, big data has brought us a lot of results which we did not expect as before. Development of cultural and creative enterprises is greatly significant to enhance the country's cultural soft power, which is every enterprise managers need to consider. Innovation behavior of cultural and creative talents affects the relationship between incentives and analysis, whereby incentives make recommendations on the construction of cultural and creative enterprises. Using crowdsourcing method, through the cultural and creative enterprises, Jiangsu Province, dividing the questionnaire survey to obtain the relevant data, factor analysis by SPSS (Statistical Product and Service Solutions), statistical methods, correlation and regression analysis for data analysis. Finally got there is a significant correlation between incentives and technological innovation behavior. © 2016 IEEE.

Huang G.,Hohai University | Zhou X.,Hohai University
Proceedings - 2016 8th International Conference on Intelligent Human-Machine Systems and Cybernetics, IHMSC 2016 | Year: 2016

According to the characteristics of the hydrological time series data, such as the linear drift, the amplitude expansion, the steady migration and the time curve, a new piecewise linear representation method of hydrological time series based on curve feature is proposed in this paper. The method is based on the characteristic points of time series to obtain the characteristic angle and time sampling interval, in the effective extraction of the curve characteristics of the time series, the original data is compressed effectively. The experimental results show that the method has the advantages of high efficiency, simple realization and direct effect, and has good adaptability to the data in hydrology field. © 2016 IEEE.

Chen X.,Hohai University | Ge L.,Hohai University | Zhou J.,Hohai University | Wu S.,Hohai University
Materials and Structures/Materiaux et Constructions | Year: 2017

To research the fracture pattern of concrete specimens, the dynamic splitting tensile tests are conducted in different arc loading angles and impact velocities. The stress state of the specimens can be calculated by analyzing the strain gauges data on the split Hopkinson pressure bar. The specimens under the lower impact velocity achieves the stress equilibrium in loading direction, and the stress-state of the specimen is similar to that of quasi-static condition, in which the initial crack occurs at the center of the specimen and propagates along the loading diameter direction. When the impact velocity increases, the stress equilibrium is difficult to attain, and multiple cracks sometimes even ribbon fracture fragments appear at the center of specimens. The impact velocity plays a significant role in the failure pattern of concrete specimens, and different angles arc loading affect the local stress distribution of the specimens. The suitable load angle can reduce the local failure and improve the failure pattern of specimens. The stress state and failure pattern of specimens simulated by LS-DYNA coincide with the test results. © 2016, RILEM.

Yang S.,Hohai University | Liu X.,Hohai University | Xu J.,Hohai University
Paddy and Water Environment | Year: 2017

Water management is an important factor in regulating soil respiration and the net ecosystem exchange of CO2 (NEE) between croplands and atmosphere. However, how water management affects soil respiration and the NEE of paddy fields remains unexplored. Thus, a 2-year field experiment was carried out to study the effects of controlled irrigation (CI) during the rice season on the variation of soil respiration and NEE, with flooding irrigation (FI) as the control. A decrease of irrigation water input by 46.39% did not significantly affect rice yield but significantly increased irrigation water use efficiency by 0.99 kg m−3. The soil respiration rate of CI paddy fields was larger than that of FI paddy fields except during the ripening stage. Natural drying management during the ripening stage resulted in a significant increase of the soil respiration rate of the FI paddy fields. Variations of NEE with different water managements were opposite to soil respiration rates during the whole rice growth stages. Total CO2 emission of CI paddy fields through soil respiration (total Rsoil) increased by 11.66% compared with FI paddy fields. The increase of total Rsoil resulted in the significant decrease of total net CO2 absorption of CI paddy fields by 11.57% compared with FI paddy fields (p < 0.05). There were inter-annual differences of soil respiration and the NEE of paddy fields. Frequent alternate wetting and drying processes in the CI paddy fields were the main factors influencing soil respiration and NEE. CI management slightly enhanced the rice dry matter amount but accelerated the consumption and decomposition of soil organic carbon and significantly increased soil respiration, which led to the decrease of net CO2 absorption. CI management and organic carbon input technologies should be combined in applications to achieve sustainable use of water and soil resources in paddy fields. © 2017 The International Society of Paddy and Water Environment Engineering and Springer Japan

Li Y.,Hohai University | Wang K.,Jiangsu University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

In order to timely gain working status parameters of operating parts in combine harvester and improve its operating efficiency, fault diagnosis and load feedback control system is designed. In the system, rotation speed sensors were used to gather these signals of forward speed and rotation speeds of intermediate shaft, conveying trough, tangential and longitudinal flow threshing rotors, grain conveying auger. Using C8051 single chip microcomputer (SCM) as processor for main control unit, faults diagnosis and forward speed control were carried through by rotation speed ratio analysis of each channel rotation speed and intermediate shaft rotation speed by use of multi-sensor fused fuzzy control algorithm, and these processing results would be sent to touch screen and display work status of combine harvester. Field trials manifest that fault monitoring and load feedback control system has good man-machine interaction and the fault diagnosis method based on rotation speed ratios has low false alarm rate, and the system can realize automation control of forward speed for combine harvester. © 2017 SPIE.

Liu D.,Hohai University | Liu D.,Clemson University | Mishra A.K.,Clemson University
Journal of Hydrology | Year: 2017

In this study, we evaluated the performance of community land surface model (CLM4.5) to simulate the hydrologic fluxes, such as, soil moisture (SM), evapotranspiration (ET) and runoff with (without) remote sensing data assimilation. The Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR_E) daily SM (both ascending and descending) are incorporated into the CLM4.5 model using data assimilation (DA) technique. The GLDAS data is used to validate the AMSR_E SM data and evaluate the performance of CLM4.5 simulations. The AMSR_E SM data are rescaled to meet the resolution of CLM4.5 model. By assimilating the AMSR_E SM data into the CLM4.5 model can improve the SM simulations, especially over the climate transition zones in Africa, East Australia, South South America, Southeast Asia, and East North America in summer season. The Local Ensemble Kalman Filter (LEnKF) technique improves the performance of CLM4.5 model compared to the directly substituted method. The improvement in ET and surface runoff simulations from CLM4.5 model assimilated with AMSR_E SM data shares similar spatial patterns with SM. © 2017 Elsevier B.V.

Qu W.,Shandong University of Technology | Zhang Y.,Shandong University of Technology | Liu C.-S.,Hohai University
Archive of Applied Mechanics | Year: 2017

This paper presents new regularized boundary integral equations (BIEs) for elastic displacement gradients in three dimensions and then combines them by the generalized Hooke’s law to calculate the boundary stress. In the new regularized BIEs, two special tangential vectors are designed with the normal vector to construct a transformation system. Based on this system, the displacement gradient in any direction can be transformed into a linear combination of the normal gradient and tangential gradients along the two special vectors. Moreover, a theorem related to some integral properties of the fundamental solution is introduced. Finally, the regularized indirect BIEs are developed by using the above-mentioned technique of linear combination and theorem. The proposed method has some advantages over the direct boundary element method, such as the relaxed continuity requirement of density function, no hypersingular integral, and being available to calculate the displacement gradient in any direction. The numerical implementation of the developed integral equation is provided, and the accuracy and convergence of the approach are also illustrated through four numerical examples. © 2017 Springer-Verlag Berlin Heidelberg

Hu D.L.,Hohai University | Liu X.B.,Nanjing University of Aeronautics and Astronautics | Chen W.,Hohai University
Nonlinear Dynamics | Year: 2017

In this paper, the moment Lyapunov exponent and stochastic stability of binary airfoil under combined harmonic and Gaussian white noise excitation are investigated. Via the singular perturbation method, the first-order expansions of the moment Lyapunov exponent are obtained, which agree well with the results obtained by the Monte Carlo simulation. Finally, the effects of the noise and parametric resonance (such as subharmonic resonance and combination additive resonance) on the stochastic stability of the binary airfoil system are discussed. © 2017 Springer Science+Business Media Dordrecht

This paper presents a simple method for determining the coefficients of thermal expansion (CTEs) of micro-machined polysilicon thin films. The structure is composed of the clamped-clamped beam and heated by applying direct current between two anchors. Based on the electrothermal properties of the test structure and the resonance frequency approach, an analytical model and an extracting method for the CTEs of the polysilicon thin films are developed. The proposed method applies to both flat and buckled beams. The finite element software ANSYS is used to verify the analytical model. Measured average value of the CTE is 2.68×10-6K-1 with a relative deviation of 12.3%. © 2016 IEEE.

Liu H.,Chongqing University | Liu H.,Hohai University | Liu H.,Flinders University
Computers and Geotechnics | Year: 2017

This paper presents a theoretical model for investigating the installation effect of high pressure jet grouting column in soft clay. The model is formulated by assuming the installation process as a series of pressure-controlled spherical cavity expansion in semi-infinite soil, of which the approximate solutions are derived by combining use of two fundamental solutions of spherical cavity expansion in finite spherical symmetry soil and displacement-controlled spherical cavity expansion in semi-infinite soil. The approximate solutions are then validated by comparing the predictions with FEM results as well as published results. The comparison results show that the presented approximate solutions are suitable for the problem of pressure-controlled spherical cavity expansion in semi-infinite soil, particularly in evaluating the limit expansion pressure as well as the expansion pressure-ground surface displacement relation. Subsequently, the proposed approximately solutions are applied to interpret the limit injection pressure and the grouting pressure-ground surface displacement during the installation process of HPJ-GC. Some parametric studies are also conducted. Furthermore, an instrumented field test study of HPJ-GC is conducted in the thick soft soils comprising quaternary alluvial and marine deposits of the Lianyungang-Yancheng Highway located in Jiangsu Province, China. The measured ground heave is compared with the analytical predictions using the proposed theoretical model. Reasonable agreement is achieved. © 2017 Elsevier Ltd

Zhu K.,Nanjing Southeast University | Mei F.,Hohai University | Zheng J.,Nanjing Southeast University
Neurocomputing | Year: 2017

High voltage circuit breakers (HVCBs) are among most important pieces of equipment in the power system, and thus its fault diagnosis is quite essential for efficient operation. Most related research can only diagnose the known fault. However, the diagnosis may fail to work when an unknown fault occurs. Aimed to address the lack of new knowledge acquisition and real-time model classification updating, a novel method based on particle swarm optimization-support vector domain description (P-SVDD) and particle swarm optimization-kernel-based fuzzy c-means (P-KFCM) is proposed for adaptive fault diagnosis of HVCBs in this paper. In the proposed method, P-SVDD can detect the unknown fault sample by particle swarm optimization (PSO) parameter optimization while P-KFCM is used in known sample category recognition and its modified partition coefficient (MPC) cluster validity is used in unknown fault category search. The proposed method's operation process is introduced in detail, and the principles underlying the adaptive fault diagnosis model are discussed as well. In engineering application of an online monitoring system with fault diagnosis, the simulation results based on the measured HVCB closing coil current show that the proposed adaptive model can acquire new knowledge and update model classification in real-time with a higher diagnostic accuracy, compared with the existing algorithms. © 2017 Elsevier B.V.

Chen Y.,Hohai University | Chen Y.,Ningbo University
RISTI - Revista Iberica de Sistemas e Tecnologias de Informacao | Year: 2016

On the basis of related research, we constructed an evaluation index system of talent competitiveness. Values are assigned to the indices with the use of the entropy weight method, so that reflecting the characteristics of competitiveness between different evaluation objects. In order to include more uncertainties of raw data in the evaluation process, the evaluation results were expressed by intuitionistic fuzzy sets and the data output was aggregated accordingly. By using the intuitionistic fuzzy information based data mining comprehensive evaluation method, a comparative research was conducted on different levels of talent competitiveness in eastern China. Meanwhile, some targeted advices were offered with respect to promoting the competitiveness levels of talents in eastern China. © AISTI 2016.

Xiao N.,Hohai University
RISTI - Revista Iberica de Sistemas e Tecnologias de Informacao | Year: 2016

Being the primary resource of development, talent is the main driving force of the regional economy in Xinjiang. Based on the actual situation of talents in the autonomous region, this paper constructs the evaluation index system of talent attractiveness in Xinjiang, and applied the data mining method to evaluate the talent competitiveness of Xinjiang. According to the research, the overall talent competitiveness in Xinjiang increases rapidly from 2005 to 2014. However, Xinjiang still lacks attractiveness to talents as it still lags far behind than the developed areas in eastern China. In the future, Xinjiang should speed up the establishment and perfection of talent cultivation, introduction, utilization and management, aiming at promoting the rapid regional development through the systematic training system of scientific and technological talents. © AISTI 2016.

Wei Z.,Hohai University
RISTI - Revista Iberica de Sistemas e Tecnologias de Informacao | Year: 2016

How to reconcile water ecological civilization construction with big data technology has become one of the most critical points of the research projects. Our research was based on the domestic and foreign research data of China's water conservancy development trends. Based on the inter-provincial panel data in 2015, this paper employed the entropy weight method to analyze the weight of six tiertwo indexes (i.e. water resource, water safety, water efficiency, water utilization, waterscape, and aquatic culture) and 23 tier-three indexes, as well as their mutual inhabitation effect and interaction with each other. Meanwhile, the data of water ecological civilization construction in 22 Chinese provinces, 5 autonomous regions, and 4 direct-controlled municipalities were summarized and analyzed from the perspective of spatial differentiation. The research results show that the overall level of the sustainable development capacity is low, that the provincial-level difference is remarkable and space-varying, and that all regions are confronted with the pressure of water ecological civilization construction, albeit of different degrees. © AISTI 2016.

Kang G.,Hohai University | Kang H.,Hohai University
Proceedings - 2016 International Conference on Cyber-Enabled Distributed Computing and Knowledge Discovery, CyberC 2016 | Year: 2016

Because the handover process based on the value of received signal strength can not be completed on time under a high speed mobile environment, the quality of service for user is greatly declined. Through the construction of cell clusters, a new quasi-periodic triggering mechanism based on sending the handover invitation is proposed in the paper in order to overcome the limitation of the handover based on the received signal strength. The handover is more timely, accurate and reliable by the mechanism in the communication environment which the mobile line is relatively fixed and mobile speed is relatively high. But also the mechanism can make the handoff process to simplify, shorten the time of handover, and improve the speed and efficiency of handover. Moreover, it can prevent the occurrence of "ping pong handover" phenomenon. © 2016 IEEE.

Shao K.,Hohai University | Zhou X.,Hohai University
Proceedings - 2016 International Conference on Cyber-Enabled Distributed Computing and Knowledge Discovery, CyberC 2016 | Year: 2016

In this paper, an improved classification method NCEEP based on EP is proposed, and this algorithm is improved on the basis of the original CEEP classification algorithm. In this paper also cited a optimal discretization method to discretize pre process data set, and select the most effective minimum support and minimum growth rate threshold. Experiments on the data set in the UCI machine learning database show that the efficiency of the improved classification algorithm proposed in this paper is obviously improved. © 2016 IEEE.

Zhu X.,Hohai University | Yang Y.,Hohai University
Proceedings - 2016 9th International Congress on Image and Signal Processing, BioMedical Engineering and Informatics, CISP-BMEI 2016 | Year: 2016

Cellular self-organization in extracellular matrix (ECM) is a complex process highly related to ECM proteins, cytokines, growth factors, cell-cell contacts, and mechanical stimuli, and study on the underlying mechanism is vital for rationally tuning the self-organization of cells. Here, we investigate the 3D pattern formation process of vascular mesenchymal cells (VMCs) at the interfaces between hydrogels with different components in a mathematical model. A reaction-diffusion model based on Turing's instability is derived and utilized to simulate the self-organized VMC patterns according to the biochemical interactions of activator, inhibitor and cells. The simulation results show that 3D hollow tubular and spherical structures with large lumen diameters generated around interfacial regions between different hydrogels, which are not observed in a two-dimensional study. The multicellular morphology changes from the branched tubes to the short-length tubes with the variation of parameter values. The short-length tubes also can evolve to hollow sphere-like structures in specific parameter ranges. The hollow structure which emerges is mainly because of the concentration gradients of proteins and cells across the hydrogel interfaces. This study provides flexible predictions, which may be useful for engineering 3D artificial tissue that highly dynamic and variable in terms of their 3D structure, mechanical properties and biochemical microenvironment. © 2016 IEEE.

Xie X.,Hohai University | Wang T.,Hohai University
M2VIP 2016 - Proceedings of 23rd International Conference on Mechatronics and Machine Vision in Practice | Year: 2016

This paper presents an alternative criterion derived from the least squares projection twin support vector machine (LSPTSVM) for image segmentation. The proposed model treats image segmentation as pattern classification problem, and hence tries to seek the projected axis and center for the foreground and background intensities respectively. With level set representation, the discriminative function of LSTSVM is incorporated into the energy function of the active contour model (ACM), and drives the contour evolution accordingly. Experiment results demonstrate that our model holds the higher segmentation accuracy and more noise robustness, compared with the stand-alone CV and LSPTSVM models. © 2016 IEEE.

Sun X.,Hohai University | Fang H.,Hohai University
2016 IEEE International Conference on Information and Automation, IEEE ICIA 2016 | Year: 2016

An improved artificial fish swarm algorithm with selection behavior was put forward in this paper and applied to optimize the PID gains of hydraulic turbine generator speed governor. The ITAE criterion of hydraulic turbine generator speed relative errors was taken as the fitness function of the improved artificial fish swarm algorithm. The computer simulation was conduct on an actual hydropower plant in China after its PID gains were optimized by the improved artificial fish swarm algorithm. The simulation results indicate that the PID controller optimized by the improved artificial fish swarm algorithm could effectively improve the dynamic performance of hydraulic transients on isolated operation conditions. © 2016 IEEE.

Sun H.,Hohai University | Chen W.,Hohai University | Li C.,Shanghai University | Chen Y.,Utah State University
International Journal of Bifurcation and Chaos | Year: 2012

Variable-order fractional diffusion equation model is a recently developed and promising approach to characterize time-dependent or concentration-dependent anomalous diffusion, or diffusion process in inhomogeneous porous media. To further study the properties of variable-order time fractional subdiffusion equation models, the efficient numerical schemes are urgently needed. This paper investigates numerical schemes for variable-order time fractional diffusion equations in a finite domain. Three finite difference schemes including the explicit scheme, the implicit scheme and the Crank-Nicholson scheme are studied. Stability conditions for these three schemes are provided and proved via the Fourier method, rigorous convergence analysis is also performed. Two numerical examples are offered to verify the theoretical analysis of the above three schemes and illustrate the effectiveness of suggested schemes. The numerical results illustrate that, the implicit scheme and the Crank-Nicholson scheme can achieve high accuracy compared with the explicit scheme, and the Crank-Nicholson scheme claims highest accuracy in most situations. Moreover, some properties of variable-order time fractional diffusion equation model are also shown by numerical simulations. © 2012 World Scientific Publishing Company.

Li W.,Beijing University of Chemical Technology | Chen C.,University of Texas at Dallas | Su H.,Hohai University | Du Q.,Mississippi State University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2015

It is of great interest in exploiting texture information for classification of hyperspectral imagery (HSI) at high spatial resolution. In this paper, a classification paradigm to exploit rich texture information of HSI is proposed. The proposed framework employs local binary patterns (LBPs) to extract local image features, such as edges, corners, and spots. Two levels of fusion (i.e., feature-level fusion and decision-level fusion) are applied to the extracted LBP features along with global Gabor features and original spectral features, where feature-level fusion involves concatenation of multiple features before the pattern classification process while decision-level fusion performs on probability outputs of each individual classification pipeline and soft-decision fusion rule is adopted to merge results from the classifier ensemble. Moreover, the efficient extreme learning machine with a very simple structure is employed as the classifier. Experimental results on several HSI data sets demonstrate that the proposed framework is superior to some traditional alternatives. © 1980-2012 IEEE.

Hua M.,Hohai University
International Journal of Innovative Computing, Information and Control | Year: 2014

A more effective Lyapunov functional has been constructed to investigate the Hoo filtering problems for a class of neural networks with time-varying delay. By combining with some inequality technic or free-weighting matrix approach, the delay-dependent conditions have been proposed such that the filtering error system is globally asymptotically stable with guaranteed ffoo performance. The time delay is divided into several subintervals; more information about time delay is utilized and less conservative results have been obtained. All results are expressed by the form of linear matrix inequalities, and the filter gain matrix can be determined easily by optimal algorithm. Examples and simulations have been provided to illustrate the less conservatism and effectiveness of the designed filter. © 2014, IJICIC Editorial Office. All rights reserved.

Su H.,Hohai University | Su H.,Nanjing University | Sheng Y.,Nanjing Normal University | Du P.,Nanjing University | Liu K.,University of Texas at Dallas
Applied Optics | Year: 2012

Band selection is a commonly used approach for dimensionality reduction in hyperspectral imagery. Affinity propagation (AP), a new clustering algorithm, is addressed in many fields, and it can be used for hyperspectral band selection. However, this algorithm cannot get a fixed number of exemplars during the message-passing procedure, which limits its uses to a great extent. This paper proposes an adaptive AP (AAP) algorithm for semi-supervised hyperspectral band selection and investigates the effectiveness of distance metrics for improving band selection. Specifically, the exemplar number determination algorithm and bisection method are addressed to improve AP procedure, and the relations between selected exemplar numbers and preferences are established. Experiments are conducted to evaluate the proposed AAP-based band selection algorithm, and the results demonstrate that the proposed method outperforms other popular methods, with lower computational cost and robust results. © 2012 Optical Society of America.

Wen W.,Hohai University | Li H.-J.,Zhejiang Normal University
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2013

We investigate the interference of the superfluid Fermi gases released from a double-well potential in the crossover from the unitarity limit to the Bose-Einstein condensate (BEC) limit. For two initially coupled Fermi superfluids, we show the formation of the clear and nonuniform interference fringes, in which the fringe spacing grows linearly in the evolution time, and the expansion velocity of the fringes increases significantly from the BEC limit to the unitarity limit. For two spatially separated Fermi superfluids, however, we show that in the strongly interacting regime, the interference patterns are characterized by the complicated spatial structures. By studying the interferences in the unitarity limit under different values of the strength of the double-well potential, we find that these complicated structures actually originate from the formations of spontaneous vortex rings, due to the transverse instability. © 2013 IOP Publishing Ltd.

Li Q.,Yamanashi University | Li Q.,Hohai University | Ishidaira H.,Yamanashi University
Journal of Hydrology | Year: 2012

The biosphere and hydrosphere are intrinsically coupled. The scientific question is if there is a substantial change in one component such as vegetation cover, how will the other components such as transpiration and runoff generation respond, especially under climate change conditions? Stand-alone hydrological models have a detailed description of hydrological processes but do not sufficiently parameterize vegetation as a dynamic component. Dynamic global vegetation models (DGVMs) are able to simulate transient structural changes in major vegetation types but do not simulate runoff generation reliably. Therefore, both hydrological models and DGVMs have their limitations as well as advantages for addressing this question. In this study a biosphere hydrological model (LPJH) is developed by coupling a prominent DGVM (Lund-Postdam-Jena model referred to as LPJ) with a stand-alone hydrological model (HYMOD), with the objective of analyzing the role of vegetation in the hydrological processes at basin scale and evaluating the impact of vegetation change on the hydrological processes under climate change. The application and validation of the LPJH model to four basins representing a variety of climate and vegetation conditions shows that the performance of LPJH is much better than that of the original LPJ and is similar to that of stand-alone hydrological models for monthly and daily runoff simulation at the basin scale. It is argued that the LPJH model gives more reasonable hydrological simulation since it considers both the spatial variability of soil moisture and vegetation dynamics, which make the runoff generation mechanism more reliable. As an example, it is shown that changing atmospheric CO 2 content alone would result in runoff increases in humid basins and decreases in arid basins. Theses changes are mainly attributable to changes in transpiration driven by vegetation dynamics, which are not simulated in stand-alone hydrological models. Therefore LPJH potentially provides a powerful tool for simulating vegetation response to climate changes in the biosphere hydrological cycle. © 2011 Elsevier B.V.

Xu Y.,Hohai University | Zeng X.,Hohai University | Han L.,Hohai University | Yang J.,Beijing Normal University
Neural Networks | Year: 2013

We use a supervised multi-spike learning algorithm for spiking neural networks (SNNs) with temporal encoding to simulate the learning mechanism of biological neurons in which the SNN output spike trains are encoded by firing times. We first analyze why existing gradient-descent-based learning methods for SNNs have difficulty in achieving multi-spike learning. We then propose a new multi-spike learning method for SNNs based on gradient descent that solves the problems of error function construction and interference among multiple output spikes during learning. The method could be widely applied to single spiking neurons to learn desired output spike trains and to multilayer SNNs to solve classification problems. By overcoming learning interference among multiple spikes, our method has high learning accuracy when there are a relatively large number of output spikes in need of learning. We also develop an output encoding strategy with respect to multiple spikes for classification problems. This effectively improves the classification accuracy of multi-spike learning compared to that of single-spike learning. © 2013 Elsevier Ltd.

Hua Z.,Hohai University | Dai Z.,Hohai University | Bai X.,Hohai University | Ye Z.,Peking University | And 2 more authors.
Journal of Hazardous Materials | Year: 2015

Highly ordered iron, nitrogen, and fluorine tri-doped TiO2 (Fe, (N, F)-TiO2) nanotube arrays were successfully synthesized by a facile one-step electrochemical method in an NH4F electrolyte containing Fe ions. The morphology, structure, composition, and photoelectrochemical property of the as-prepared nanotube arrays were characterized by various methods. The photoactivities of the samples were evaluated by the degradation of phenol in an aqueous solution under visible light. Tri-doped TiO2 showed higher photoactivities than undoped TiO2 under visible light. The optimum Fe3+ doping amount at 0.005M exhibited the highest photoactivity and exceeded that of undoped TiO2 by a factor of 20 times under visible light. The formation of N 2p level near the valence band (VB) contributed to visible light absorption. Doping fluorine and appropriate Fe3+ ions reduced the photogenerated electrons-holes recombination rate and enhanced visible light photoactivity. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results indicated the presence of synergistic effects in Fe, N, and F tri-doped TiO2, which enhanced visible light photoactivity. The Fe, (N, F)-TiO2 photocatalyst exhibited high stability. © 2015.

Xu B.,Hohai University | Yin Z.-Z.,Hohai University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

A series of tests were done to study the influences and variation of strength of a single kind of expansive soil in the process of changing the soil state from nature and unsaturated and no cracks to saturated and no cracks to saturated and cracks fully developed by shear test and triaxial test. Test results show that water content and density and cracks influence the expansive soil strength; and water content and cracks influenc strength more than density does. It is concluded that cracks should be considered within the method of determining expansive soil strength. It is suggested that the strength of sample after 5 cycles of wet-dry should be used as the strength of cracks fully developed expansive soil. By residual strength tests, a conclusion is drawn that the residual strength of expansive soil was in proximity to the strength of cracks fully developed expansive soil; as a result, the residual strength could be used approximately as the strength of expensive soil in the region of cracks developed.

Jiang A.,Hohai University | Kwan H.K.,University of Windsor | Zhu Y.,Changzhou University
IEEE Transactions on Signal Processing | Year: 2012

In this paper, a novel algorithm is proposed to design sparse FIR filters. It is known that this design problem is highly nonconvex due to the existence of l 0 -norm of a filter coefficient vector in its objective function. To tackle this difficulty, an iterative procedure is developed to search a potential sparsity pattern, which is then used to compute the final solution by solving a convex optimization problem. In each iterative step, the original sparse filter design problem is successively transformed to a simpler subproblem. It can be proved that under a weak condition, globally optimal solutions of these subproblems can be attained by solving their dual problems. In this case, the overall iterative procedure converges to a locally optimal solution of the original design problem. The design procedure described above can be repeated for several times to further improve the sparsity of design results. The output of the previous stage can be used as the initial point of the subsequent design. The performance of the proposed algorithm is evaluated by two sets of design examples, and compared to other sparse FIR filter design algorithms. © 2012 IEEE.

Jiang A.,Hohai University | Kwan H.K.,University of Windsor
ISCAS 2012 - 2012 IEEE International Symposium on Circuits and Systems | Year: 2012

A novel algorithm is presented in this paper to design sparse FIR filters in the weighted least-squares (WLS) sense. The original design problem is cast as a constrained l0-norm optimization problem. To tackle the nonconvexity, an efficient iterative procedure is developed. In each iterative step, a subproblem in a simpler form is constructed. It can be demonstrated that in each iteration an optimal solution to each subproblem can be efficiently and reliably attained by the successive activation algorithm proposed in this paper, such that the overall design algorithm can converge to a local solution of the original design problem. Since its major part only involves scalar operations, compared with other sparse filter design approaches, the proposed design algorithm is computationally efficient. The effectiveness of the proposed design algorithm is demonstrated by numerical examples. © 2012 IEEE.

Zhang Q.,Sun Yat Sen University | Singh V.P.,Texas A&M University | Sun P.,Sun Yat Sen University | Chen X.,Hohai University | And 2 more authors.
Journal of Hydrology | Year: 2011

Extensive investigation was done on the changes in precipitation and streamflow in both space and time across China based on monthly precipitation data from 590 rainfall stations and on monthly streamflow data from 382 hydrological stations covering 1960-2000. Causes behind the precipitation changes were studied based on NCAR/NCEP reanalysis dataset. Influences of agricultural irrigation on availability and variability of water resources and related implications were also discussed. The results indicate that: (1) decreasing precipitation is found mainly in the regions between 105°E and 115°E and in the northeast China. Scarce precipitation is observed mainly in spring and autumn and winter seems to be wetter; (2) alterations of the East Asian monsoon activities should be the causes behind the spatial patterns of precipitation changes. Large-scale circulation of water vapor flux can well explain the spatial distribution of precipitation changes in China; (3) streamflow changes are mainly the results of precipitation changes. Agricultural irrigation heavily influences the variability and availability of water resources. Increasing water consumption due to booming socio-economy and fast growing population will further deteriorate the water status of China. In this sense, scientific and effective water resource management and advanced agricultural technology are urgently called for to ensure the sustainable socio-economy and social stability of China. © 2011 Elsevier B.V.

Zhang Q.,Sun Yat Sen University | Xu C.-Y.,University of Oslo | Chen Y.D.,Chinese University of Hong Kong | Ren L.,Hohai University
Stochastic Environmental Research and Risk Assessment | Year: 2011

Based on daily meteorological data at 43 gauging stations in the Pearl River basin and 65 gauging stations in the Yellow River basin, we analyze changing properties of actual evapotranspiration (ET a), reference evapotranspiration (ET ref) and precipitation in these two river basins. In our study, Pearl River basin is taken as the 'energy-limited' system and the Yellow River basin as the 'water-limited' system. The results indicate decreasing ET a in the Pearl River and Yellow River basin. However, different changing properties are detected for ET ref when compared to ET a. The middle and upper Yellow River basin are characterized by increasing ET ref values, whereas the Pearl River basin is dominated by decreasing ET ref values. This result demonstrates enhancing drying force in the Yellow River basin. ET a depends mainly on the changes of precipitation amount in the Yellow River basin. In the Pearl River basin, however, ET a changes are similar to those of ET ref, i. e. both are in decreasing trend and which may imply weakening hydrological cycle in the Pearl River basin. Different influencing factors are identified behind the ET a and ET ref in the Pearl River and Yellow River basin: In the Pearl River basin, intensifying urbanization and increasing aerosol may contribute much to the evapotranspiration changes. Variations of precipitation amount may largely impact the spatial and temporal patterns of ET a in the Yellow River basin. The current study is practically and scientifically significant for regional assessment of water resource in the arid and humid regions of China under the changing climate. © 2010 Springer-Verlag.

Xu Y.,Hohai University | Li K.W.,University of Windsor | Wang H.,Hohai University
Information Sciences | Year: 2013

Abstract This paper proposes a distance-based consensus model for fuzzy preference relations where the weights of fuzzy preference relations are automatically determined. Two indices, an individual to group consensus index (ICI) and a group consensus index (GCI), are introduced. An iterative consensus reaching algorithm is presented and the process terminates until both the ICI and GCI are controlled within predefined thresholds. The model and algorithm are then extended to handle multiplicative preference relations. Finally, two examples are illustrated and comparative analyses demonstrate the effectiveness of the proposed methods. © 2013 Elsevier Inc. All rights reserved.

Xu Y.,Hohai University | Chen L.,Hohai University | Li K.W.,University of Windsor | Wang H.,Hohai University
Information Sciences | Year: 2015

This paper proposes a chi-square method (CSM) to obtain a priority vector for group decision making (GDM) problems where decision-makers' (DMs') assessment on alternatives is furnished as incomplete reciprocal preference relations with missing values. Relevant theorems and an iterative algorithm about CSM are proposed. Saaty's consistency ratio concept is adapted to judge whether an incomplete reciprocal preference relation provided by a DM is of acceptable consistency. If its consistency is unacceptable, an algorithm is proposed to repair it until its consistency ratio reaches a satisfactory threshold. The repairing algorithm aims to rectify an inconsistent incomplete reciprocal preference relation to one with acceptable consistency in addition to preserving the initial preference information as much as possible. Finally, four examples are examined to illustrate the applicability and validity of the proposed method, and comparative analyses are provided to show its advantages over existing approaches. © 2015 Elsevier Inc. All rights reserved.

Xu Y.,Hohai University | Li K.W.,University of Windsor | Wang H.,Hohai University
Computers and Industrial Engineering | Year: 2014

This paper investigates incomplete interval fuzzy preference relations. A characterization, which is proposed by Herrera-Viedma et al. (2004), of the additive consistency property of the fuzzy preference relations is extended to a more general case. This property is further generalized to interval fuzzy preference relations (IFPRs) based on additive transitivity. Subsequently, we examine how to characterize IFPR. Using these new characterizations, we propose a method to construct an additive consistent IFPR from a set of n - 1 preference data and an estimation algorithm for acceptable incomplete IFPRs with more known elements. Numerical examples are provided to illustrate the effectiveness and practicality of the solution process. Crown Copyright © 2013 Published by Elsevier Ltd. All rights reserved.

Su H.,Hohai University | Hu J.,Hohai University | Wu Z.,Hohai University
International Journal of Geomechanics | Year: 2013

The rock foundation of a gravity dam is usually cut into slide blocks by the structural surfaces. Its stability is controlled by the characteristics and the combining action of these structural surfaces. The failure of a gravity dam can be caused by the destruction or large deformation of local rocks under the condition of certain loads. The coupling of continuous-discontinuous deformation is a typical characteristic of the process. As a new design idea, the powerhouse and dam are combined into an integer with one structural pattern to improve the antisliding stability of the gravity dam. The external loads are undertaken together by the powerhouse and dam. The loads acting on the dam can be transferredpartly to the powerhouse, and the powerhouse weight and tail water pressure can increase the dam's stability. The optimal design of a gravity dam section can be implemented, decreasing the project quantity, and reducing construction costs. This design idea has been adopted by the Yangtze Three Gorges Project in China. The coupling methods of discontinuous deformation analysis (DDA) and FEM are used to implement the deep antisliding stability evaluation for a gravity dam under the combining action of both the powerhouse and dam. The blocks are subdivided into the finite element meshes; the displacement field and stress field in the blocks are solved by FEM, and the contacts betweenthe deformable blocks are simulated and analyzed with theDDAmethod. The description ability for the block deformation can be increased, the calculation precision for the stress field in block can be improved, and the ability ofDDAin solving the large deformation of a multiblock system can be inherited. Therefore, the destructive form determined by this coupling method is closer to the actual situation. As an example, thecoupling methods ofDDAandFEMare used to analyze and assess the deep antisliding stability of the No. 3 left powerhouse-dam section of one dam when the upstream loads are taken together by the high gravity dam and the combined powerhouse located behind dam. The effect of combining the action of the powerhouse and dam is appraised by the numerical analysis for the mechanism transferring force between the dam and powerhouse, the influence on the deformation and stress of dam and powerhouse under the combining action of powerhouse and dam, the interaction of structural planes, etc. The entire instability process of the dam is simulated and analyzed by means of reducing the mechanical parameters. Last, the qualitative and quantitative analyses are implemented to evaluate the local and the whole stability of the gravity dam underthe combining action of the powerhouse and dam. © 2013 American Society of Civil Engineers.

Zhu X.,Queensland University of Technology | Zhang S.,Zhejiang Normal University | Jin Z.,Peking University | Zhang Z.,Southwest University | And 2 more authors.
IEEE Transactions on Knowledge and Data Engineering | Year: 2011

Missing data imputation is a key issue in learning from incomplete data. Various techniques have been developed with great successes on dealing with missing values in data sets with homogeneous attributes (their independent attributes are all either continuous or discrete). This paper studies a new setting of missing data imputation, i.e., imputing missing data in data sets with heterogeneous attributes (their independent attributes are of different types), referred to as imputing mixed-attribute data sets. Although many real applications are in this setting, there is no estimator designed for imputing mixed-attribute data sets. This paper first proposes two consistent estimators for discrete and continuous missing target values, respectively. And then, a mixture-kernel-based iterative estimator is advocated to impute mixed-attribute data sets. The proposed method is evaluated with extensive experiments compared with some typical algorithms, and the result demonstrates that the proposed approach is better than these existing imputation methods in terms of classification accuracy and root mean square error (RMSE) at different missing ratios. © 2006 IEEE.

Chiu C.F.,Hohai University | Yan W.M.,University of Hong Kong | Yuen K.-V.,University of Macau
Canadian Geotechnical Journal | Year: 2012

This study proposes two empirical relationships to estimate the parameters of van Genuchten's formula for modeling the water retention curve from the particle-size distribution. The relationships are determined by the Bayesian probabilistic method for selecting the most plausible class of models based on a database of 90 soil samples. The highest plausibility model among the selected relationships shows that the parameter α can be expressed as a first-order function of the particle size at 50% passing (d 50) and parameter n is expressed as a third-order polynomial of the reciprocal of the standard deviation of geometric mean particle size (σ g). The predictability of proposed relationships for other soils outside the calibrated database is also presented. It is found that the model prediction is highly consistent with the measurements for sands. However it only matches well with the measurements in the low suction regime for soils with at least 20% of fines content.

Chiu C.F.,Hohai University | Yan W.M.,University of Hong Kong | Yuen K.-V.,University of Macau
Engineering Geology | Year: 2012

Soil-water characteristic curve (SWCC) is a crucial input for modeling the geotechnical problems with unsaturated soil. The accuracy of modeling relies on the assessment of the model parameter uncertainty. In this paper a Bayesian framework is presented to evaluate the updated probability density function (PDF) of the uncertain model parameters for SWCC. The Bayesian analysis is applied to derive the PDF of the model parameters in various forms of van Genuchten equation using the observed data of sand, sandy loam and silty loam. The analysis demonstrates that a 2-parameter model is sufficient for curve-fitting of the SWCC and the two model parameters are approximately statistically independent. Furthermore, the model parameters are influenced by the soil texture. Finally, an engineering example of the probabilistic slope stability analysis is used to illustrate the application of the reliability of SWCC. © 2012 Elsevier B.V.

Zheng J.,Hohai University | Yang K.,Hohai University | Lu X.,Sichuan Agricultural University
Hydrology Research | Year: 2013

A limited adaptive genetic algorithm (LAGA) is proposed in the paper for inner-plant economical operation of a hydropower station. In the LAGA, limited solution strategy, with the feasible solution generation method for generating an initial population and the limited perturbation mutation operator, is presented to avoid hydro units operating in cavitation-vibration regions. The adaptive probabilities of crossover and mutation are introduced to improve the convergence speed of the genetic algorithm (GA). Furthermore, the performance of the limited solution strategy and the adaptive parameter controlling improvement are checked against the historical methods, and the results of simulating inner-plant economical operation of the Three Gorges hydropower station demonstrate the effectiveness of the proposed approach. First, the limited solution strategy can support the safety operations of hydro units by avoiding cavitation-vibration region operations, and it achieves a better solution, because the non-negative fitness function is achieved. Second, the adaptive parameter method is shown to have better performance than other methods, because it realizes the twin goals of maintaining diversity in the population and advancing the convergence speed of GA. Thus, the LAGA is feasible and effective in optimizing inner-plant economical operation of hydropower stations. © IWA Publishing 2013.

Wang P.,Hohai University | Wang P.,University of California at Riverside | Liu D.Y.,Hohai University | Xu C.,Hohai University
Applied Energy | Year: 2013

The present numerical simulation investigates the effect of inserting metal foams in receiver tube of parabolic trough collector on heat transfer. The effects of layout (top/bottom), geometrical parameter (H), and porosity (φ) of metal foams on the flow resistant, heat transfer and thermo-hydraulic performance are analyzed. Optimum thermo-hydraulic performance considering the flow resistance increase is obtained when H= 0.25 (bottom), Nu increases about 5-10 times with the increase of f 10-20 times and the PEC range from 1.4 to 3.2. Optimum thermal performance is obtained when H= 0.75 (top), Nu increases about 10-12 times with the increase of f 400-700 times and the PEC range from 1.1 to 1.5. The maximum circumferential temperature difference on the out surface of receiver tube decreases about 45% which will greatly reduce the thermal stress. The result shows that for constant layout and φ, the H effects on the thermal performance greatly, but for constant layout and H, the φ effects on the thermal performance slightly. Moreover, the layout in view of no-uniform heat flux boundary affects the heat transfer significantly. These methods and results can be extended to the heat transfer enhancement of all the solar concentrated receivers. © 2012 Elsevier Ltd.

Wang P.,Hohai University | Wang P.,University of California at Riverside | Vafai K.,University of California at Riverside | Liu D.Y.,Hohai University
Numerical Heat Transfer; Part A: Applications | Year: 2014

The effect of thermal radiation within a porous medium while incorporating local thermal nonequilibrium (LTNE) is investigated in this work, with specific application to solar air receivers. It is shown that the radiation effect is significant. The temperature distributions for both solid and fluid phases are affected by conduction-radiation parameter N, the ratio of solid to fluid phase conductivities ζ, and the interphase convection parameter H. The limiting interactions between conduction and thermal radiation incorporating convection are revealed. The impact of conduction and convection versus radiation is systematically analyzed in this work and displayed through a number of contour maps. © 2014 Copyright Taylor & Francis Group, LLC.

Tan X.,Hohai University
Journal of Food, Agriculture and Environment | Year: 2012

Freshwater lakes provide water sources for drinking, aquaculture, agricultural irrigation, and so on, but many eutrophic lakes around the world are suffered by cyanobacterial blooms. These harmful cyanobacteria (such as Microcytis, Anabaena, Aphnizomenon, and so on) are capable of nuisance growth and producing toxins, which pose serious threats to water safety and human health. Based on most of the literature, this paper reviewed the progress made in following fields: physiological and ecological characteristics of bloom-forming cyanobacteria in their annual life cycle, internal regulation mechanisms and environmental factors for blooms formation. In winter, dormant period is regarded as the continuation of cyanobacteria populations, which conserve "seed bank" for the following year. In spring, recruitment can be defined as an inoculation of overwintering cyanobacteria to the pelagic phase after growth recovery under suitable conditions. Temperature, resuspension and bioturbation had been recognized to be the main driving factors for recruitment. Shortly after recruitment, cyanobacteria establish dominance by fast growth rate (i.e. r-type ecological strategy) and colony enlargement. Under suitable meteorological and hydrological conditions, cyanobacterial colonies aggregate and float up to form heavy blooms, which can lead to water supply crisis and ecological disaster. From late autumn, blooms disaggregate and decline. The sinking process is not only a periodic life cycle but also an irregular mechanical movement. Cyanobacteria accumulation areas in late autumn might highly related to the first occurence of blooms in the following year. The time series of bloom-forming cyanobacteria in lakes of temperate and subtropical zones could be summarized as the four-stage hypothesis, but the spatial patterns of blooms in large lakes were rarely explored. Moreover, further studies are needed to explore the threshold values of environmental factors at each stage, and compare the ecophysiological differences between cyanobacteria and other algae, which could provide valuable information for the prediction and prevention of harmful blooms, so as to establish a sound and stable lacustrine ecosystem.

Jiang A.,Hohai University | Kwan H.K.,University of Windsor
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2013

In this paper, we propose a novel algorithm for sparse finite impulse response (FIR) filter designs. The objective of the sparse digital filter design problem considered in this paper is to reduce the number of nonzero-valued filter coefficients, subject to a weighted least-squares (WLS) approximation error constraint imposed on the frequency domain. The proposed design method is inspired by the iterative shrinkage/thresholding (IST) algorithms, which are used in sparse and redundant representation for signals. The basic idea of the proposed design algorithm is to successively transform the original nonconvex problem to a series of constrained subproblems in a simpler form. Despite of their nonconvexity, these subproblems can be efficiently and reliably solved in each iterative step by a numerical approach developed in this paper. Furthermore, it can be demonstrated that the obtained solutions are essentially optimal to their respective subproblems. Since its major part only involves scalar operations, the proposed algorithm is computationally efficient. Three sets of numerical examples are presented in this paper to illustrate the effectiveness of the proposed design algorithm. © 2004-2012 IEEE.

Su H.,Hohai University | Hu J.,Hohai University | Wen Z.,Nanjing Institute of Technology
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2012

Numerical simulation methods are extensively used to analyze the stress and displacement of concrete-faced rockfill dams (CFRD). The results of these methods are influenced by fuzzy factors, i.e. geometric features, material properties, loads and boundary conditions, which exist widely in the engineering of CFRD as a kind of commonly uncertain factor. To solve this problem, the information entropy theory and the conventional method of structure analysis, namely, finite element method (FEM), were combined in this work. Information entropy, as an effective tool of measuring uncertainty, was used to represent the uncertainty of CFRD. Based on the model that can transform fuzzy information entropy into random information entropy, fuzzy structure can be transformed into equivalent random structure, then mechanical characteristics of CFRD were analyzed by well-developed stochastic FEM. As an example, one CFRD was chosen to analyze the structure, and the result shows that this method is effective. © 2011 John Wiley & Sons, Ltd.

Chen R.H.,Hohai University | Chen R.H.,Jianghai Polytechnic College
Advanced Materials Research | Year: 2014

Developing low-carbon economy is an inevitable choice for China. This paper builds an evaluation index system of low-carbon economy and uses the fuzzy comprehensive evaluation model to evaluate the development level of China's low-carbon economy. Then, according to China's actual conditions, some proposals are put forward accordingly. © (2014) Trans Tech Publications, Switzerland.

Su F.,CAS Institute of Tibetan Plateau Research | Duan X.,CAS Institute of Tibetan Plateau Research | Chen D.,Gothenburg University | Hao Z.,Hohai University | Cuo L.,CAS Institute of Tibetan Plateau Research
Journal of Climate | Year: 2013

The performance of 24 GCMs available in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) is evaluated over the eastern Tibetan Plateau (TP) by comparing the model outputs with ground observations for the period 1961-2005. The twenty-first century trends of precipitation and temperature based on the GCMs' projections over the TP are also analyzed. The results suggest that for temperature most GCMs reasonably capture the climatological patterns and spatial variations of the observed climate. However, the majority of the models have cold biases, with a mean underestimation of 1.1°-2.5°C for the months December-May, and less than 1°C for June-October. For precipitation, the simulations of all models overestimate the observations in climatological annual means by 62.0%-183.0%, and only half of the 24 GCMsare able to reproduce the observed seasonal pattern, which demonstrates a critical need to improve precipitationrelated processes in these models. All models produce a warming trend in the twenty-first century under the Representative Concentration Pathway 8.5 (rcp8.5) scenario; in contrast, the rcp2.6 scenario predicts a lower average warming rate for the near term, and a small cooling trend in the long-term period with the decreasing radiative forcing. In the near term, the projected precipitation change is about 3.2% higher than the 1961-2005 annual mean, whereas in the long term the precipitation is projected to increase 6.0% under rcp2.6 and 12.0% under the rcp8.5 scenario. Relative to the 1961-2005 mean, the annual temperature is projected to increase by 1.2°-1.3°C in the short term; the warmings under the rcp2.6 and rcp8.5 scenarios are 1.8° and 4.1°C, respectively, for the long term. © 2013 American Meteorological Society.

Zhou Y.,Hohai University | Deng A.,University of Adelaide | Wang C.,University of Adelaide
Computers and Geotechnics | Year: 2013

Small strain consolidation theories treat soil properties as being constant and uniform in the course of consolidation, which is not true in the case of electro-osmosis-induced consolidation practices. Electro-osmotic consolidation leads to large strain, which physically and electro-chemically affects to a non-negligible extent the nonlinear changes of the soil properties. For the nonlinear changes, iterative computations provide a mathematical approximation of the soil consolidation when the time steps and spatial geometry are intensively meshed. In this context, this paper presents a finite-difference model, EC1, for one-dimensional electro-osmotic consolidation, and this model is developed based on a fixed Eulerian co-ordinate system and uses a piecewise linear approximation. The model is able to account for the large-strain-induced nonlinear changes of the physical and electro-chemical properties in a compressible mass subjected to electro-osmotic consolidation and to predict the consolidation characteristics of the compressible mass. EC1 is verified against exact analytical solutions and test results obtained from an experimental program. Example problems are illustrated with respect to the numerical solutions of large-strain electro-osmotic consolidation. © 2013 Elsevier Ltd.

Fan H.,Hohai University | Fan H.,Dalian University of Technology | Yang L.,Hohai University | Sun F.,Hohai University | And 2 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2013

To restrict debonding, carbon fiber reinforced lattice-core sandwich composites with compliant skins were designed and manufactured. Compression behaviors of the lattice composites and sandwich columns with different skin thicknesses were tested. Bending performances of the sandwich panels were explored by three-point bending experiments. Two typical failure mechanisms of the lattice-core sandwich structures, delaminating and local buckling were revealed by the experiments. Failure criteria were suggested and gave consistent analytical predictions. For panels with stiff skins, delamination is the dominant failure style. Cell dimensions, fracture toughness of the adhesives and the strength of the sandwich skin decide the critical load capacity of the lattice-core sandwich structure. The mono-cell buckling and the succeeding local buckling are dominant for the sandwich structures with more compliant skin sheets. Debonding is restricted within one cell in bending and two cells in compression for lattice-core sandwich panels with compliant face sheets and softer lattice cores. © 2013 Elsevier Ltd. All rights reserved.

Sun F.,Hohai University | Fan H.,Hohai University | Fan H.,Nanjing University of Aeronautics and Astronautics | Zhou C.,Nanjing University of Aeronautics and Astronautics | And 2 more authors.
Composite Structures | Year: 2013

Sandwich cylindrical shells are the major components of aerospace structures. In this paper, an analytical investigation was carried out to examine the response of carbon fiber reinforced composite (CFRC) sandwich cylinders with lattice cores. An equivalent monocoque shell theory, was developed in this paper to predict mechanical behaviors of the quasi-isotropic sandwich cylinder, including the deformation and the multi-mode failure criterion. Five failure modes were suggested for the sandwich cylinder, including global buckling, face sheet mono-cell buckling/dimpling, face sheet local buckling, lattice rib crippling and strength failure. Using the suggested criterion, failure mode maps of the sandwich cylinder were acquired to instruct the design of the hierarchical sandwich cylinder with five geometrical variables. The method also correctly predicted the failure modes of the tested sandwich cylinder within acceptable errors. © 2013 Elsevier Ltd.

Zhang Z.,Hohai University | Si H.,Hohai University
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Non-point source pollution is the main factor affecting water-soil environment. Based on the SWAT model and GIS technology, spatial and temporal distributions of organic nitrogen (ON) and organic phosphorus (OP) were analyzed in Chahe watershed at the lower Yangtze River. Simulation of non-point source pollution was performed under different irrigation methods. The results showed that SWAT model was applicable for the simulation of non-point source pollution in the study area. Precipitation had strong correlation with runoff, ON and OP, with correlation coefficients 0.897, 0.762 and 0.713, respectively. Runoff during flood season accounted for 56.40% of the annual total, while ON and OP accounted for 64.89% and 59.70%, respectively. Loss of ON had a significant correlation with OP loads. At the spatial scale, high loads areas of ON and OP were mainly concentrated in the central and south of the watershed, and as a whole showed a distribution gradually characteristic to the Chahe main channel aggregation with surface runoff. The distribution of ON and OP loads were not only related to the runoff, but also impacted by the land use obviously. Average ON and OP loads of soybean fields were highest at 56.70 and 8.80kg/hm2, respectively, while the total contribution amount of ON and OP in rice fields accounted for 67.87% and 65.72% of the entire watershed, the main contribution of non-point pollution source, respectively. Through scenario simulations, the implementation of optimizing irrigation on rice fields such as shallow irrigation and deep storage, can effectively control nitrogen and phosphorus losses and improve the soil and water environment of small watersheds. This research provides important reference for scientific farmland management of small watershed.

Lei Y.,Hohai University | Ling H.,Xinjiang Institute of Ecology and Geography
Environmental Earth Sciences | Year: 2014

The Keriya River Basin was chosen as the study site in this paper in order to investigate the suitable scales of natural and artificial oases with a certain water resource quantity. A calculation model was constructed and the suitable scales of natural and artificial oases were analyzed using remote sensing images, water resources, weather and socioeconomic data. The results showed that (1) high- and low-flow variations were apparent for the Keriya River. The mean values for the high-flow period, normal flow period and low-flow period were 9.23 × 108 m3, 7.177 × 108 m3and 5.741 × 108 m3, respectively. (2) The ecological water demand of natural oasis in the lower reaches of the Keriya River Basin was 2.561 × 108 m3. (3) In the Tarim Basin, the proportion of natural and artificial oases was 6:4. (4) In the middle reaches, after guaranteeing the unchangeable scale of artificial oases, the most suitable size of a natural oasis was 798–1,157 km2. Under the reasonable proportion (i.e. proportion of 6:4 for the natural and artificial oases), the respective suitable scales of natural and artificial oases in the middle reaches were 831–1,003 km2and 554–669 km2. This study constructed a model for calculating the suitable scale of an oasis, verified the suitable proportions of natural and artificial oases and discussed the reasonable scales of oases in order to provide a new theoretical basis for determining reasonable development planning in similar river basins located in extremely arid regions. © 2014, Springer-Verlag Berlin Heidelberg.

Li W.,Nanjing University of Posts and Telecommunications | Li W.,Hohai University | Yang Z.,Nanjing University of Posts and Telecommunications | Hu H.,Nanjing University of Posts and Telecommunications
IEEE Transactions on Vehicular Technology | Year: 2013

Graphical models have been widely applied in solving distributed inference problems in wireless sensor networks (WSNs). In this paper, the factor graph (FG) is employed to model a distributed inference problem. Using particle filtering methods, a sequential particle-based sum-product algorithm (SPSPA) is proposed for distributed inference in FGs with continuous variables and nonlinear local functions. Importance sampling methods are used to sample from message products, and the computational complexity of SPSPA is thus linear in the number of particles. The SPSPA is applied to a distributed tracking problem, and its performance is evaluated based on the number of particles and the measurement noise. © 2012 IEEE.

Yu Y.,Hohai University | Shi Q.,Nanjing University of Posts and Telecommunications
Expert Systems with Applications | Year: 2014

Data envelopment analysis (DEA) has been proved to be an excellent approach for measuring performance of decision making units (DMUs) that use multiple inputs to generate multiple outputs. In many real world scenarios, inputs or outputs may be shared among various activities. This paper proposes a two-stage DEA model with additional input in the second stage and part of intermediate products as final output. We first discuss the non-cooperative condition in order to determine the upper and lower bounds of the efficiencies of sub-DMUs in different stages. A parametric transformation is described to solve the non-linear programming of the overall cooperative efficiency model. An application is provided. © 2014 Elsevier Ltd. All rights reserved.

Wu L.,Hohai University | Wang X.L.,Environment Canada | Feng Y.,Environment Canada
Journal of Geophysical Research: Oceans | Year: 2014

This study reconstructs 6 hourly significant wave heights (Hs) in the South and East China Seas for the period 1871-2010, using the Twentieth Century Reanalysis ensemble of mean sea level pressure (SLP) fields and a multivariate regression model to represent the Hs-SLP relationship in each study area. The regression model was calibrated and validated using the ERA-Interim reanalysis of Hs and SLP for the period 1981-2010. These reconstructions were found to reproduce reasonably well the seasonal mean and maximum Hs climates as represented by the ERA40 and ERA-Interim wave reanalyses. For each study area, an ensemble of 56 members of 6 hourly H s was reconstructed for each grid point. The regional mean series of the ensemble mean of the reconstructed consecutive monthly mean Hs was tested for temporal homogeneity, which identified a few discontinuities in the pre-1946 period and led to the exclusion of the reconstructed Hs for 1871-1910 from trend analysis (due to data uncertainty and inhomogeneity). Each 6 hourly Hs time series for the period 1911-2010 was homogenized for the identified discontinuities, before being used to derive annual and seasonal mean and maximum Hs for trend analysis. The trend analysis results show that, in both study areas, the 1911-2010 wave height trends are dominantly negative, with the exception that the seasonal maximum significant wave heights seem to have increased in summer and spring in the central South China Sea and in summer in the East China Sea. Key Points This study produced the first century long wave height data for the China Seas The seasonal maximum wave heights seem to have increased in warm seasons The seasonal mean wave heights have decreased in all seasons in both areas © 2014 Her Majesty the Queen in Right of Canada. Journal of Geophysical Research: Oceans © 2014 American Geophysical Union.

Li C.,Hohai University | Li C.,Nanjing Institute of Technology | Ge X.,Hohai University | Zheng Y.,Hohai University | And 4 more authors.
Energy | Year: 2013

In this paper, based on renewable energy resources and load data research, a techno-economic feasibility study of an autonomous hybrid wind/photovoltaics (PV)/battery power system for a household in Urumqi, China, has been form carried out using Hybrid Optimization Model for Electric Renewables (HOMER) simulation software. The effects of ambient temperature, the variation of load and PV module tilt angles are considered in this simulation. The hybrid wind/PV/battery system with 5kW of PV arrays (72% solar energy penetration), one wind turbine of 2.5kW (28% wind energy penetration), 8 unit batteries each of 6.94kWh and 5kW sized power converters comprises an optimal power system for the household; it reduces the total net present cost (NPC) about 9% and 11% compared with PV/battery and wind/battery power systems, which has a similar consequence for the levelized cost of energy (COE). The economical, sensitivity and PV module tilt angle analyses of the proposed hybrid wind/PV/battery power system are discussed in this paper. © 2013.

Gu H.,Hohai University | Gu H.,University of Connecticut | Wang G.,University of Connecticut | Yu Z.,Hohai University | And 2 more authors.
Climatic Change | Year: 2012

This paper assesses future climate changes over East and South Asia using a regional climate model (RegCM4) with a 50 km spatial resolution. To evaluate the model performance, RegCM4 is driven with "perfect boundary forcing" from the reanalysis data during 1970-1999 to simulate the present day climate. The model performs well in reproducing not only the mean climate and seasonality but also most of the chosen indicators of climate extremes. Future climate changes are evaluated based on two experiments driven with boundary forcing from the European-Hamburg general climate model (ECHAM5), one for the present (1970-1999) and one for the SRES A1B future scenario (2070-2099). The model predicts an annual temperature increase of about 3°-5° (smaller over the ocean and larger over the land), and an increase of annual precipitation over most of China north of 30°N and a decrease or little change in the rest of China, India and Indochina. For temperature-related extreme indicators in the future, the model predicts a generally longer growing season, more hot days in summer, and less frost days in winter. For precipitation-related extremes, the number of days with more than 10 mm of rainfall is predicted to increase north of 30°N and decrease in the south, and the maximum five-day rainfall amount and daily intensity will increase across the whole model domain. In addition, the maximum number of consecutive dry days is predicted to increase over most of the model domain, south of 40°N. Most of the Yangtze River Basin in China stands out as "hotspots" of extreme precipitation changes, with the strongest increases of daily rain intensity, maximum five-day rain amount, and the number of consecutive dry days, suggesting increased risks of both floods and droughts. © 2012 Springer Science+Business Media B.V.

Li H.,North China University of Water Conservancy and Electric Power | Arditi D.,Illinois Institute of Technology | Wang Z.,Hohai University
Construction Management and Economics | Year: 2012

Transaction cost economics deals with costs incurred at the pre-contract phase such as the costs of conducting market research, exploring financial opportunities, conducting a feasibility study, organizing a bidding/negotiation and managing design; and with costs incurred in the post-contract phase such as the costs of administering the contract, administering change orders and claims, resolving disputes and managing incentives. Many researchers have investigated the factors that affect project performance over the years, but neglected to consider transaction-related issues. The effects of transaction-related issues on project performance are investigated in this study. Project performance is measured on the basis of completion within budget and on schedule, compliance with quality standards, and satisfaction of the owner. Transaction-related issues include the magnitude of transaction costs, the uncertainty in the transaction environment, and the owner's and the contractor's roles in the transaction. Hypotheses are tested by using a structural equation model using data collected from a survey administered to construction owners. The findings indicate that project performance can be stronger if the uncertainty in the transaction environment is minimized, transaction costs are kept low, and owners and contractors are sensitive to transaction-related issues. © 2012 Copyright Taylor and Francis Group, LLC.

Wu Z.Y.,Hohai University | Lu G.H.,Hohai University | Wen L.,McGill University | Lin C.A.,Environment Canada
Hydrology and Earth System Sciences | Year: 2011

The 1951-2009 drought history of China is reconstructed using daily soil moisture values generated by the Variable Infiltration Capacity (VIC) land surface macroscale hydrology model. VIC is applied over a grid of 10 458 points with a spatial resolution of 30 km Ã-30 km, and is driven by observed daily maximum and minimum air temperature and precipitation from 624 long-term meteorological stations. The VIC soil moisture is used to calculate the Soil Moisture Anomaly Percentage Index (SMAPI), which can be used as a measure of the severity of agricultural drought on a global basis. We have developed a SMAPI-based drought identification procedure for practical uses in the identification of both grid point and regional drought events. As a result, a total of 325 regional drought events varying in time and strength are identified from China's nine drought study regions. These drought events can thus be assessed quantitatively at different spatial and temporal scales. The result shows that the severe drought events of 1978, 2000 and 2006 are well reconstructed, which indicates that the SMAPI is capable of identifying the onset of a drought event, its progression, as well as its termination. Spatial and temporal variations of droughts in China's nine drought study regions are studied. Our result shows that on average, up to 30% of the total area of China is prone to drought. Regionally, an upward trend in drought-affected areas has been detected in three regions (Inner Mongolia, Northeast and North) from 1951-2009. However, the decadal variability of droughts has been weak in the rest of the five regions (South, Southwest, East, Northwest, and Tibet). Xinjiang has even been showing steadily wetter since the 1950s. Two regional dry centres are discovered in China as the result of a combined analysis on the occurrence of drought events from both grid points and drought study regions. The first centre is located in the area partially covered by the North and the Northwest, which extends to the southeastern portion of Inner Mongolia and the southwest part of Northeast. The second one is found on the central to southern portion of the South. Our study demonstrates the applicability and the value of using modeled soil moisture for reconstructing drought histories, and the SMAPI is useful for analyzing drought at different spatial and temporal scales. © 2011 Author(s).

Han J.,University of Wollongong | Han J.,Hohai University | Susilo W.,University of Wollongong | Mu Y.,University of Wollongong
Future Generation Computer Systems | Year: 2013

Identity-based proxy re-encryption schemes have been proposed to shift the burden of managing numerous files from the owner to a proxy server. Nevertheless, the existing solutions suffer from several drawbacks. First, the access permission is determined by the central authority, which makes the scheme impractical. Second, they are insecure against collusion attacks. Finally, only queries from the same domain (intra-domain) are considered. We note that one of the main applications of identity-based proxy re-encryption schemes is in the cloud computing scenario. Nevertheless, in this scenario, users in different domains can share files with each other. Therefore, the existing solutions do not actually solve the motivating scenario, when the scheme is applicable for cloud computing. Hence, it remains an interesting and challenging research problem to design an identity-based data storage scheme which is secure against collusion attacks and supports intra-domain and inter-domain queries. In this paper, we propose an identity-based data storage scheme where both queries from the intra-domain and inter-domain are considered and collusion attacks can be resisted. Furthermore, the access permission can be determined by the owner independently. © 2012 Elsevier B.V. All rights reserved.

Chen Y.,University of Warwick | Chen Y.,Hohai University | Shi R.,University of Warwick | Long M.,Changsha University of Science and Technology
IEEE Transactions on Vehicular Technology | Year: 2013

The performance of an amplify-and-forward (AF) relaying system is analyzed in Nakagami- $m$ fading channels when the links are correlated and each node has a single antenna. Blind fixed-gain relaying, semiblind fixed-gain relaying, and variable-gain relaying schemes are considered. Exact expressions for the moment-generating functions in different cases are derived for integer values of the Nakagami-$m$ parameter when the correlated links have the same Nakagami-$m$ parameters. Numerical results show that the link correlation has a considerable effect on blind and semiblind fixed-gain relaying when the source-to-destination and source-to-relay links are correlated, whereas for variable-gain relaying, it has a considerable effect when the source-to-destination and source-to-relay links are correlated or when the relay-to-destination and source-to-destination links are correlated. Moreover, the effect of correlation is often noticeable when the correlation coefficient is larger than 0.5. © 1967-2012 IEEE.

Wang X.,Shanghai JiaoTong University | Yin C.,Hohai University | Sun J.,Shanghai JiaoTong University | Li H.,Shanghai JiaoTong University | And 3 more authors.
Optics Express | Year: 2013

A high-sensitivity temperature sensor based on the enhanced Goos-Hänchen effect in a symmetrical metal-cladding waveguide is theoretically proposed and experimentally demonstrated. Owing to the high sensitivity of the ultrahigh-order modes, any minute variation of the refractive index and thickness in the guiding layer induced by the thermooptic and thermal expansion effects will easily give rise to a dramatic change in the position of the reflected light. In our experiment, a series of Goos-Hänchen shifts are measured at temperatures varying from 50.0 °C to 51.2 °C with a step of 0.2 °C. The sensor exhibits a good linearity and a high resolution of approximately 5 × 10-3 oC. Moreover, there is no need to employ any complicated optical equipment and servo techniques, since our transduction scheme is irrelevant to the light source fluctuation. © 2013 Optical Society of America.

Tong K.,Hohai University | Tong K.,CAS Institute of Tibetan Plateau Research | Su F.,CAS Institute of Tibetan Plateau Research | Yang D.,CAS Institute of Tibetan Plateau Research | And 3 more authors.
International Journal of Climatology | Year: 2014

The European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis ERA-40, ERA-Interim, University of Washington (UW) data, APHRODITE's Water Resources (APHRODITE), and Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) precipitation estimates are compared with each other and with the corrected gauge observations over the Tibetan Plateau (TP) at both basin and plateau scales. The ERA-40 generally can capture the broad spatial and temporal distributions in the gauge-based precipitation estimates over the TP. However, the ERA-40 shows little agreement with the gauge-based precipitation in annual variations for the years before 1979. The anticipated improvements in the ERA-Interim precipitation relative to ERA-40 have not been realized in this study. It greatly overestimates the Corrected-China Meteorological Administration (CMA) (by 74-290%) and other datasets, although the ERA-Interim has a better correspondence than ERA-40 with the Corrected-CMA data at both annual and monthly scales among the selected basins. All the products can detect the large-scale precipitation regime, including the monsoon-dominated precipitation in summer and the westerly-wind-induced precipitation in winter. The Corrected-CMA and APHRODITE estimates generally show decreasing trends in summer and increasing trends in spring and winter precipitation during 1961-2007 at both basin and plateau scales. However, the Corrected-CMA shows larger values in trends and more cases with significance than the APHRODITE, suggesting the effects of the undercatch corrections on the precipitation trends. The use of precipitation derived from current reanalysis projects is less preferable for hydrology analysis than the TP observational data at basin scales. However, using gauge-based precipitation datasets as hydrologic model forcings should be careful in the river basins where gauge station network is spare, such as in the Yarlung zangbo river basin. Satellite products still hold a great potential for providing high-resolution precipitation information in remote regions such as the western TP, although more evaluations are needed on the feasibility of satellite precipitation products on the TP where the topography is complex and rainfall rate is highly variable. © 2013 Royal Meteorological Society.

Hai Y.,North China University of Water Conservancy and Electric Power | Hai Y.,Hohai University | Li X.,North China University of Water Conservancy and Electric Power
International Journal of Advancements in Computing Technology | Year: 2012

Web Services play an important role in the SOA paradigm, as they allow services to be selected onthe- fly to build applications out of existing components. With the rapid development of web service technology, people are becoming more and more dependent on the convenience from it. Yet there are many similar or identical function to provide the services, how to make a reasonable choice from these services become a primary problem for solution regarding this problem, a web service QoS predicting algorithm based on Qos Ontology and BP neutral networks is proposed in this paper and Qos Ontology is constructed and BP neutral network are trained accordingly, the evaluating and predicting process is described in detail. The result of simulation experiment show that compared with the existing method, the algorithm proposed can greatly improve the accuracy of web service predicting.

Mei R.,University of Connecticut | Wang G.,University of Connecticut | Gu H.,University of Connecticut | Gu H.,Hohai University
Journal of Hydrometeorology | Year: 2013

This study investigates the land-atmosphere coupling strength during summer over the United States using theRegional ClimateModel version 4 (RegCM4)-Community LandModel version 3.5 (CLM3.5). First, a 10-yr simulation driven with reanalysis lateral boundary conditions (LBCs) is conducted to evaluate the model performance. The model is then used to quantify the land-atmosphere coupling strength, predictability, and added forecast skill (for precipitation and 2-m air temperature) attributed to realistic land surface initialization following the Global Land-Atmosphere Coupling Experiment (GLACE) approaches. Similar to previous GLACE results using global climate models (GCMs), GLACE-type experiments with RegCM4identify the central United States as a region of strong land-atmosphere coupling, with soil moisture- temperature coupling being stronger than soil moisture-precipitation coupling, and confirm that realistic soil moisture initialization ismore promising in improving temperature forecasts than precipitation forecasts. At a 1-15-day lead, the added forecast skill reflects predictability (or land-atmosphere coupling strength) indicating that that model can capture the realisticland-atmosphere coupling at a short time scale. However, at a 16-30-day lead, predictability cannot translate to addedforecast skill, implying that the coupling at the longer time scale may not be represented well in the model. In addition,comparison of results fromGLACE2- type experiments with RegCM4 driven by reanalysis LBCs and those driven by GCM LBCs suggest that the intrinsic land-atmosphere coupling strength within the regional model is the dominant factor for the added forecast skill at a 1-15-day lead, while the impact of LBCs from the GCM may play a dominant role in determining the signal of added forecast skill in the regional model at a 16-30-day lead. It demonstrates the complexities of using regional climate model for GLACE-type studies. © 2013 American Meteorological Society.

Zhang Y.,Shanghai JiaoTong University | Jeng D.-S.,Shanghai JiaoTong University | Jeng D.-S.,University of Dundee | Gao F.P.,CAS Institute of Mechanics | Zhang J.-S.,Hohai University
Ocean Engineering | Year: 2013

In this paper, an analytical approximation for the evaluation of the pore pressure and effective stresses in marine sediments under combined wave and current loadings is derived. Unlike previous investigations, non-linear interactions between waves and currents are considered in this study. An analytical solution for the wave-current induced oscillatory soil response in marine sediment is presented first. Based on the proposed analytical solution, a parametric study for the liquefaction potential will be carried out. Parametric study results indicate that the influence of current and non-linear waves on the maximum liquefaction depth is significant. © 2012 Elsevier Ltd.

Xiong J.-F.,Nanjing University of Information Science and Technology | Xiong J.-F.,Hohai University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

The interharmonics, either close to harmonics or fundamental wave, is the direct cause of voltage flicker, so interhammics detection has important significance for improving power quality. The limitations of windowed interpolation algorithm and spectral estimation method are analyzed with the consideration of the wide and multi-frequency characteristic in a real power network. An interharmonic detection algorithm is proposed based on the windowed interpolation and the Prony method. The interpolation method calculates each parameter of signals and frequency analysis method is used to identify the frequency interval in which two adjacent components and interhamonics are located, and then the Prony algorithm is used to compute residual components filtered by time domain. Matlab simulation shows that the new method has higher frequency resolution and is more precise than windowed interpolation algorithm, it need not estimate the numbers of signals and can eliminate the influence of pseudo-spectra.

Ao Y.,Hohai University | Xu J.,Nanjing University of Information Science and Technology | Zhang S.,Hohai University | Fu D.,Nanjing Southeast University
Applied Surface Science | Year: 2010

N-doped titania hollow spheres (NTHS) were prepared by a one-pot hydrothermal method using urea as precursor of nitrogen. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectrum (DRS). The photocatalytic activity of as-prepared titania hollow spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation, and was compared to non-doped titania hollow spheres and commercial P25 titania. Results indicated that the as-prepared NTHS showed highest photocatalytic activity. © 2009 Elsevier B.V. All rights reserved.

Hai Y.,Hohai University | Hai Y.,North China University of Water Conservancy and Electric Power | Wang Z.,Hohai University
Advances in Information Sciences and Service Sciences | Year: 2012

Web service which is a kind of component on the Internet shows good encapsulation, loosely coupled and cross-platform. However, the single Web service has inevitable limitations in functionality; it can't provide people with more function and complex service. In order to reduce the cost and time of developing, and achieve services value-added and reuse, we need to combine existing services to form a combination of services which can satisfy user's demand. There are a lot of services with the same functions in the process of service composition; one of the key issues is to select service by using Qos (Quality of Service). The response time is a significant factor in the process of Web service composition; it is affected by network load and service itself. It is modeled by using finite state continuous time Semi-Markov Decision Process (SMDP), and then Q learning algorithm is used to obtain the optimal service composition policy.

Zhao L.,Hohai University | Zhao L.,PLA University of Science and Technology | Zheng Q.,PLA University of Science and Technology | Zheng Q.,Tsinghua University | And 3 more authors.
Materials and Design | Year: 2012

Hierarchical structures are predicted to have ultra-light weight and superior mechanical properties, including excellent anti-buckling ability and energy absorption capability. Based on the improvement of making technology, hierarchical composite honeycombs (HCHs) have been designed, made and tested. With woven textile sandwich walls, the HCH is ultra-light and renders relatively ideal complete stress-strain curve with a stable displacement plateau at a relative high stress level in compression. A plastic model was suggested based on tested failure maps to reveal the plastic deformation and energy absorbing mechanism of the HCH. The plastic model well fitted the tested curves and defines a lower limit of the plastic deformation curve. © 2012 Elsevier Ltd.

Tong K.,CAS Institute of Tibetan Plateau Research | Su F.,CAS Institute of Tibetan Plateau Research | Yang D.,CAS Institute of Tibetan Plateau Research | Yang D.,Environment Canada | Hao Z.,Hohai University
Journal of Hydrology | Year: 2014

In this study, we evaluate four widely used global high-resolution satellite precipitation products against gauge observations over the Tibetan Plateau (TP). We also investigate the capability of the satellite products in streamflow simulations using the VIC hydrological model. Results show that the 3B42 and CMORPH perform better than the 3B42RT and PERSIANN at both plateau and basin scales. The 3B42RT and PERSIANN considerably overestimate the gauge precipitation estimates almost over the entire plateau, and the PERSIANN fail to capture the spatial and temporal pattern of the gauge precipitation estimates. For different satellite estimates, the error sources are systematically different for various seasons. For the 3B42, the miss bias is the main problem. The CMORPH exhibits obvious negative hit bias and miss bias in the rainy season and false-rain bias in the non-rainy season. The total bias in the 3B42RT and PERSIANN mainly attribute to positive hit bias in the rainy season and false-rain bias in the non-rainy season. The 3B42RT and PERSIANN show little capability for streamflow simulations over the TP, while the CMORPH exhibits an encouraging potential for hydrological applications in this regions in spite of the general underestimates. The 3B42 shows comparable performance to the CMA (China Meteorological Administration) data in both monthly and daily streamflow simulations mostly due to the monthly gauge adjustment involved in it. © 2014 Elsevier B.V.

Wang Y.,Nanjing University of Information Science and Technology | Liu B.,Hohai University | Su B.,National Climate Center | Zhai J.,National Climate Center | Gemmer M.,National Climate Center
Journal of Climate | Year: 2011

Actual evaporation in the Yangtze River basin is calculated by the complementary relationship approach-that is, the advection-aridity (AA) model with parameter validation from 1961 to 2007-and simulated by the general circulationmodel (GCM) ECHAM5-Max Planck InstituteOceanModel (MPI-OM) from1961 to 2000. Trends of annual and seasonal estimated actual evaporation and air temperature, net radiation, saturation vapor pressure deficit, wind speed, and precipitation are examined by the linear regression method and nonparametric Mann-Kendall test. The stepwise regression method is used to analyze the significance to reference evapotranspiration of independent variables. Results show that a significant decreasing trend in annual reference evaporation is caused by a significant decline in wind speed. The annual actual evaporation decreases in the upper and midlower Yangtze reaches; more significantly in the AA model [-9.3 mm (10 yr)-1] than in the GCM [23.6 mm (10 yr)-1]. Significant negative trends are found in spring and autumn, but they show reverse trends in summer and winter within the two methods, which is caused by the different contributors to the seasonal actual evaporation in the two methods. Decreasing net radiation is the main contributor to annual and spring actual evaporation in the two methods. Decreasing precipitation and net radiation are the main contributors to decreasing autumn actual evaporation in the AA model and the GCM. Increasing net radiation and decreasing precipitation are the main contributors to summer and winter actual evaporation in the GCM. Decreasing net radiation and increasing precipitation are the main contributors to decreasing summer and increasing winter actual evaporation in the AA model. © 2011 American Meteorological Society.

Li H.,North China University of Water Conservancy and Electric Power | Arditi D.,Illinois Institute of Technology | Wang Z.,Hohai University
Journal of Construction Engineering and Management | Year: 2013

The actual cost of a construction project is comprised of not only production costs, but also transaction costs. Transaction costs include but are not limited to the costs of preparing the bidding package, estimating, drawing up a contract, administering the contract, and dealing with any deviations from contract conditions. Transaction costs constitute an important part of the construction owner's budget. However, understanding transaction costs is difficult because of the inconsistency and ambiguity in defining transaction costs in the literature. The objective of this paper is to identify methods to minimize the transaction costs borne by the construction owner. A structural equation model is tested on data collected by means of a survey administered to construction owners. The findings indicate that the transaction costs borne by the owner can be minimized if the owner minimizes the uncertainties inherent in the transaction environment by (1) ensuring the engineering design is as complete as possible before bids are sought from contractors, (2) exploring the possibility of adopting integrated project delivery methods that would allow the owner to engage the services of a contractor early in the design phase, (3) agreeing to share some of the risks with the contractors, (4) understanding well the behavior of contractors, and (5) paying close attention to project management efficiency. © 2013 American Society of Civil Engineers.

Khan F.A.,Electrical Engineering at KAUST | Chen Y.,University of Warwick | Alouini M.-S.,Hohai University
IEEE Transactions on Wireless Communications | Year: 2012

New coherent receivers are derived for a pilot-symbol-aided distributed space-time block-coded system with imperfect channel state information which do not perform channel estimation at the destination by using the received pilot signals directly for decoding. The derived receivers are based on new metrics that use distribution of the channels and the noise to achieve improved symbol-error-rate (SER) performance. The SER performance of the derived receivers is further improved by utilizing the decision history in the receivers. The decision history is also incorporated in the existing Euclidean metric to improve its performance. Simulation results show that, for 16-quadrature-amplitude-modulation in a Rayleigh fading channel, a performance gain of up to 2.5 dB can be achieved for the new receivers compared with the conventional mismatched coherent receiver. © 2012 IEEE.

Yang J.,Hohai University | Zeng X.,Hohai University | Zhong S.,Nanjing University of Information Science and Technology | Wu S.,Nanjing University of Information Science and Technology | Wu S.,University of Ulster
IEEE Transactions on Neural Networks and Learning Systems | Year: 2013

This paper, with an aim at improving neural networks' generalization performance, proposes an effective neural network ensemble approach with two novel ideas. One is to apply neural networks' output sensitivity as a measure to evaluate neural networks' output diversity at the inputs near training samples so as to be able to select diverse individuals from a pool of well-trained neural networks; the other is to employ a learning mechanism to assign complementary weights for the combination of the selected individuals. Experimental results show that the proposed approach could construct a neural network ensemble with better generalization performance than that of each individual in the ensemble combining with all the other individuals, and than that of the ensembles with simply averaged weights. © 2012 IEEE.

Gao W.,Hohai University | Zhang F.-J.,Wuhan Construction Engineering Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2014

The search of non-circular critical slip surface is a key problem in slope stability analysis. Essentially, this problem is a path search problem; so the ant colony algorithm is a very suitable method to solve this problem. To overcome the shortcomings of traditional ant colony algorithm, from the principle of combing one whole road by forward and reverse search of ants, here a new algorithm, meeting ant colony algorithm, is proposed. And then this meeting ant colony algorithm is used to locate the critical slip surface of slopes. Through two typical examples and an engineering application of a reservoir bank slope, the effectiveness of the new algorithm is verified. The results show that, from not only the whole search scope but also one point search scope, the meeting ant colony algorithm are all better than traditional ant colony algorithm; so the solutions diversity to search the critical slip surface of slopes by meeting ant colony algorithm is better. And then, to meeting ant colony algorithm, the global optimal solution can be included in the search scope by the larger probability; and the global optimal solution can be obtained by the larger probability. At last, by meeting ant colony algorithm, the critical slip surface of slopes can be found on larger scope and by larger speed.

Chen W.,Hohai University | Zhang X.-D.,Hohai University | Korosak D.,University of Maribor
International Journal of Nonlinear Sciences and Numerical Simulation | Year: 2010

Stress relaxation and damped oscillation of viscoelastic soft materials are characterized with memory effect which is very difficult to describe with the classical integer-order derivative equation models. This study introduced novel relaxation-oscillation models for soft materials by using positive fractional derivative and fractal derivative and investigated their properties against the corresponding fractional derivative model through analytic and numerical solutions. In the relaxation process, the stretched exponential stress relaxation of the fractal derivative model is found to decay fastest, while the slowest decay is with the positive fractional derivative model. In the oscillation process, the fractional and the positive fractional derivative models are observed frequency-dependent dissipative oscillation. We also found that the fractional derivative model is more dissipative than the positive fractional derivative one. © Freund Publishing House Ltd.

Lu X.B.,Hohai University | Wang X.F.,Shanghai JiaoTong University | Fang J.Q.,China Institute of Atomic Energy
Physica D: Nonlinear Phenomena | Year: 2010

Many networks are made up of a few groups, with nodes in the same group having the same kind of function. In this work, the problem of controlling a complex dynamical network to attain an inhomogeneous equilibrium point is investigated, which means that nodes in the same group achieve the same equilibrium point as an isolated node, while different groups correspond to different equilibrium points. An open-loop constant control approach is first proposed to obtain the inhomogeneous equilibrium point of the network. Then, the feedback pinning control approach is applied to make the inhomogeneous equilibrium point asymptotically stable. © 2009 Elsevier B.V. All rights reserved.

Lei G.H.,Hohai University | Fu C.W.,Hohai University | Ng C.W.W.,Hong Kong University of Science and Technology
Geotextiles and Geomembranes | Year: 2016

An analytical solution is derived to predict consolidation with vertical drains under impeded drainage boundary conditions and multi-ramp surcharge loading. The impeded drainage is modelled by adopting the third type boundary condition with a dimensionless characteristic factor of drainage efficiency developed by Gray (1945) for one-dimensional consolidation. Fully drained and undrained boundary conditions can also be modelled by applying an infinite and a zero characteristic factor, respectively. The combined effects of drain resistance and smear are taken into account fully. An explicit, rigorous analytical solution is derived using the method of separation of variables to calculate excess pore-water pressure at any arbitrary point in soil and to derive the overall average degree of consolidation. The proposed solution can also be used to analyse one-dimensional consolidation without vertical drains but with an impeded drainage boundary. Its validity and accuracy are verified by comparing the proposed solution with the solutions developed by Gray (1945) and Terzaghi (1943). Its practical applicability is also evaluated by analysing a case history involving a fill embankment, which was constructed over a crust layer of hard soil overlying soft clay improved with stone columns. The crust layer is modelled as an impeded drainage. Reasonably good agreement is obtained between the consolidation results obtained from the proposed analytical solution and available three-dimensional finite-element predictions. With the further consideration of smear effects, good agreement is achieved between the consolidation results obtained from the proposed analytical solution and field measurements. © 2015 .

Yan L.,Nanjing Southeast University | Yang F.,Hohai University
Engineering Analysis with Boundary Elements | Year: 2013

In this paper, an efficient Kansa-type method of fundamental solutions (MFS-K) is extended to the solution of two-dimensional time fractional sub-diffusion equations. To solve initial boundary value problems for these equations, the time dependence is removed by time differencing, which converts the original problems into a sequence of boundary value problems for inhomogeneous Helmholtz-type equations. The solution of this type of elliptic boundary value problems can be approximated by fundamental solutions of the Helmholtz operator with different test frequencies. Numerical results are presented for several examples with regular and irregular geometries. The numerical verification shows that the proposed numerical scheme is accurate and computationally efficient for solving two-dimensional fractional sub-diffusion equations. © 2013 Elsevier Ltd.

Lu Y.,Hohai University | Lu Y.,Nanjing Southeast University | Wu Z.,Nanjing Southeast University
Applied Acoustics | Year: 2013

In this paper, we propose a model adaptation algorithm based on maximum likelihood subband polynomial regression (MLSPR) for robust speech recognition. In this algorithm, the cepstral mean vectors of prior trained hidden Markov models (HMMs) are converted to the log-spectral domain by the inverse discrete cosine transform (DCT) and each log-spectral mean vector is divided into several subband vectors. The relationship between the training and testing subband vectors is approximated by a polynomial function. The polynomial coefficients are estimated from adaptation data using the expectation-maximization (EM) algorithm under the maximum likelihood (ML) criterion. The experimental results show that the proposed MLSPR algorithm is superior to both the maximum likelihood linear regression (MLLR) adaptation and maximum likelihood subband weighting (MLSW) approach. In the MLSPR adaptation, only a very small amount of adaptation data is required and therefore it is more useful for fast model adaptation. © 2012 Elsevier Ltd. All rights reserved.

Sun Y.,Hohai University | Sun Y.,City University of Hong Kong | Feng G.,City University of Hong Kong | Cao J.,Nanjing Southeast University
Neurocomputing | Year: 2012

This paper studies the robust stochastic stability of uncertain stochastic genetic regulatory networks with disturbance attenuation. A novel delay-dependent robust stability condition with disturbance attenuation, in the form of linear matrix inequalities (LMIs) is derived for the uncertain stochastic genetic networks with time-varying delays and intrinsic and extrinsic noises. These stability conditions can be tested efficiently by the available commercial software packages such as Matlab LMI Control Toolbox. Two numerical examples with simulations are given to illustrate the effectiveness and validity of the derived theoretical results. © 2011 Elsevier B.V.

Liu L.,Hohai University | Shen D.,Hohai University | Chen H.,Nanjing Southeast University | Xu W.,Hohai University
Computers and Structures | Year: 2014

This paper investigates the influence of aggregate shape on the diffusivity of mortar in three dimensions by random packing models of ellipsoidal and convex polyhedral particles. From a digital mesostructure and by a lattice approach, the diffusivity of mortar can be predicted. Simulations are compared with experimental results from literature and are discussed for mono-sized and multi-sized particle packing with and without interfacial transition zones (ITZ). It was found that the shape of aggregate has a significant effect on the diffusivity of mortar, and for oblate ellipsoids, the shape effect is most pronounced comparing to prolate ellipsoids and polyhedrons. © 2014 Elsevier Ltd. All rights reserved.

Bishay P.L.,University of California at Irvine | Bishay P.L.,Saint Martin's University | Dong L.,Hohai University | Atluri S.N.,University of California at Irvine | Atluri S.N.,King Abdulaziz University
Computational Mechanics | Year: 2014

Conceptually simple and computationally most efficient polygonal computational grains with voids/inclusions are proposed for the direct numerical simulation of the micromechanics of piezoelectric composite/porous materials with non-symmetrical arrangement of voids/inclusions. These are named “Multi-Physics Computational Grains” (MPCGs) because each “mathematical grain” is geometrically similar to the irregular shapes of the physical grains of the material in the micro-scale. So each MPCG element represents a grain of the matrix of the composite and can include a pore or an inclusion. MPCG is based on assuming independent displacements and electric-potentials in each cell. The trial solutions in each MPCG do not need to satisfy the governing differential equations, however, they are still complete, and can efficiently model concentration of electric and mechanical fields. MPCG can be used to model any generally anisotropic material as well as nonlinear problems. The essential idea can also be easily applied to accurately solve other multi-physical problems, such as complex thermal-electro-magnetic-mechanical materials modeling. Several examples are presented to show the capabilities of the proposed MPCGs and their accuracy. © 2014, Springer-Verlag Berlin Heidelberg.

Fei J.,Hohai University | Chowdhury F.,National Science Foundation
International Journal of Innovative Computing, Information and Control | Year: 2010

This paper presents an adaptive variable structure controller with on-line identification of the upper bounds of uncertainties and disturbance for MEMS triaxial angular sensors device that is able to detect rotation in three orthogonal axes, using a single vibrating mass. A robust adaptive sliding mode controller is developed and the stability of the closed-loop system can be guaranteed with the proposed adaptive robust sliding mode control strategy. The on-line identification of the upper bounds of uncertainties and disturbance can be incorporated into sliding mode controller to alleviate the chartering. The proposed adaptive sliding mode controller updates estimates of all stiffness, damping errors, input rotation parameters, upper bound of uncertainties and disturbance in real time, removing the need for any offline calibration stages. The numerical simulation for MEMS gyroscope triaxial angular sensor is investigated to verify the effectiveness of the proposed robust adaptive sliding mode control scheme. © ICIC International 2010.

Ng C.W.W.,Hohai University | Ng C.W.W.,Hong Kong University of Science and Technology
Journal of Zhejiang University: Science A | Year: 2014

Geotechnical centrifuge modelling is an advanced physical modelling technique for simulating and studying geotechnical problems. It provides physical data for investigating mechanisms of deformation and failure and for validating analytical and numerical methods. Due to its reliability, time and cost effectiveness, centrifuge modelling has often been the preferred experimental method for addressing complex geotechnical problems. In this ZENG Guo-xi Lecture, the kinematics, fundamental principles and principal applications of geotechnical centrifuge modelling are introduced. The use of the state-of-the-art geotechnical centrifuge at the Hong Kong University of Science and Technology (HKUST), China to investigate four types of complex geotechnical problems is reported. The four geotechnical problems include correction of building tilt, effect of tunnel collapse on an existing tunnel, excavation effect on pile capacity and liquefied flow and non-liquefied slide of loose fill slopes. By reporting major findings and new insights from these four types of centrifuge tests, it is hoped to illustrate the role of state-of-the-art geotechnical centrifuge modelling in advancing the scientific knowledge of geotechnical problems. © 2014 Zhejiang University and Springer-Verlag Berlin Heidelberg.

Xu Y.-J.,Hohai University | Da Q.-L.,Nanjing Southeast University
Expert Systems with Applications | Year: 2010

This paper proposes two methods for multi-attribute decision making problems with linguistic information, in which the preference values take the form of linguistic variables. Based on the ideal that the attribute with a larger deviation value among alternatives should be assigned a large weight, two methods named standard deviation method and mean deviation method are proposed to determine the optimal weighting vector objectively under the assumption that attribute weights are completely unknown. Two numerical examples are examined using the proposed methods to show the advantages from the other methods. It is shown that the proposed methods are straightforward and no loss of information. © 2010 Elsevier Ltd. All rights reserved.

Liu L.,Hohai University | Chen H.,Nanjing Southeast University | Sun W.,Nanjing Southeast University | Ye G.,Technical University of Delft
Construction and Building Materials | Year: 2013

The diffusivity of cement-based materials can be significantly increased because of the presence of defects, and in consequence, the service life of concrete structures is reduced. Numerical simulations present an alternative approach to track the property changes of cement-based materials during a specific degradation process on the basis of microstructure evolution. This paper illustrates numerical simulations of the diffusivities of cement pastes with micro-cracks caused by tensile loading and frost action, respectively. Based on a numerical model HYMOSTRUC3D, an original microstructure of cement paste is first generated. Then, the creation of micro-cracks in the microstructure of cement paste where uni-axial tensile load or frost action is applied is simulated by a 3D lattice fracturing model. The diffusivity changes of cement pastes are predicted from a series of 3D diffusive lattice networks which are converted from the microstructures of cement pastes with micro-cracks. Simulations illustrate that the diffusivity of cement paste attributed to tensile loading increases with the increasing tensile strain and the diffusivity increase perpendicular to loading direction is higher than that in the loading direction because of the orientation of micro-cracks. For cement paste subjected to frost action, the diffusivity increases with the decreasing temperature and no direction dependence is found. © 2012 Elsevier Ltd. All rights reserved.

Zhou G.-D.,Hohai University | Yi T.-H.,Dalian University of Technology | Yi T.-H.,Nanjing Southeast University
Mathematical Problems in Engineering | Year: 2013

Structural health monitoring (SHM) systems have shown great potential to sense the responses of a bridge system, diagnose the current structural conditions, predict the expected future performance, provide information for maintenance, and validate design hypotheses. Wireless sensor networks (WSNs) that have the benefits of reducing implementation costs of SHM systems as well as improving data processing efficiency become an attractive alternative to traditional tethered sensor systems. This paper introduces recent technology developments in the field of bridge health monitoring using WSNs. As a special application of WSNs, the requirements and characteristics of WSNs when used for bridge health monitoring are firstly briefly discussed. Then, the state of the art in WSNs-based bridge health monitoring systems is reviewed including wireless sensor, network topology, data processing technology, power management, and time synchronization. Following that, the performance validations and applications of WSNs in bridge health monitoring through scale models and field deployment are presented. Finally, some existing problems and promising research efforts for promoting applications of WSNs technology in bridge health monitoring throughout the world are explored. © 2013 Guang-Dong Zhou and Ting-Hua Yi.

Hong Z.-S.,Nanjing Southeast University | Yin J.,Hohai University | Yin J.,Jiangsu University | Cui Y.-J.,ParisTech National School of Bridges and Roads
Geotechnique | Year: 2010

Oedometer tests starting from a very small effective vertical stress of 0.5 kPa were performed on three reconstituted clays with different liquid limits. The soils were prepared at various initial water contents, ranging from 0.7 to 2.0 times their corresponding liquid limits. It is observed that the e-log v compression curves show an inverse 'S' shape due to suction pressure resisting deformation, similar to that of soft natural clays caused by consolidation yield stress. The suction pressure s of the reconstituted clays can be correlated with the ratio of initial void ratio to void ratio at liquid limit e0/eL. The suction pressure curve defined by a unique relationship between suction pressure s and the normalised void ratio at suction pressure es/eL is also proposed to distin- guish between the pre-suction and the post-suction states. In addition, Burland's concept of the intrinsic compres- sion line is adopted for correlating the compression curves of various reconstituted clays at high initial water contents. It has been found that the void index is a powerful parameter for normalising the compression curves in the post-suction state. Nevertheless, it seems that Burland's intrinsic compression line slightly under- estimates the void index at the low stresses considered in this study. An extended intrinsic compression line is then derived in order to better fit the data for stresses lower than 25 kPa.

Xu W.,Nanjing Southeast University | Xu W.,Hohai University | Chen H.,Nanjing Southeast University | Liu L.,Hohai University
Industrial and Engineering Chemistry Research | Year: 2013

Random packing of particles has served as a topic of intense research in the chemical, physical, engineering, and material fields. The majority of previous works focused on the random packing models of spherical, cylindrical, and ellipsoidal particles, whereas little is known about polyhedral particles. In this article, a modeling study of the random packing of convex polyhedral particles is presented in detail, using an interparticle contact detection algorithm, a particle-to-container wall intersection detection algorithm, and a random sequential packing algorithm for hard particles, and the accuracy and efficiency of the contact detection algorithm are compared with those of methods from the literature. With the random packing model and a specified particle size distribution, mesostructure models of particulate composites with mono-/polydisperse particles were generated and validated by a sectioning analysis algorithm. Based on quantitative stereological theories and the sectioning analysis algorithm, the effects of particle shape on the mesostructures composed of the monodisperse and polydisperse particles were evaluated. Further, the statistical results were verified by validation against experimental results from the literature and theoretical results. © 2013 American Chemical Society.

Chiu C.F.,Hohai University | Ng C.W.W.,Hohai University | Ng C.W.W.,Hong Kong University of Science and Technology
Canadian Geotechnical Journal | Year: 2012

Although it is generally recognized that unsaturated soil behavior is governed by two constitutive variables (matric suction and net normal stress) and that the hydromechanical behavior of unsaturated soil is coupled, a water retention curve obtained from tests under zero stress and assuming no volume change is still fairly common. A relatively limited number of studies on the stress path-dependent water retention curve (SDWRC), particularly under a broader range of stress paths, exist in the literature. In this paper, the SDWRC, shrinkage curve, and swelling curve of a compacted silt subjected to isotropic and deviatoric stress paths are presented. The test results show that the air-entry value (AEV) increases, but the hydraulic hysteresis loop decreases with an increase in net mean stress. Furthermore, for a given stress level, the.K o-compressed specimen exhibits higher AEV, but a smaller hysteresis loop than that of the isotropically compressed specimen. A nonlinear shrinkage curve is observed and the gradient of the post-yield shrinkage curve depends on the degree of saturation and net mean stress, but is independent of the stress path. For the range of suction studied, the gradient reduces with a decreasing degree of saturation, but with an increasing net mean stress. Finally, the test results are compared with the prediction of a model based on two independent constitutive stress variables.

Gao Y.F.,Hohai University | Zhang F.,Hohai University | Lei G.H.,Hohai University | Li D.Y.,Shandong University of Science and Technology
Geotechnique | Year: 2013

A three-dimensional rotational failure mechanism for earth slope is extended from toe failure to include face failure and base failure. An efficient optimisation method is simultaneously employed to find the least upper bounds to the critical height in order to avoid missing the global minimum. Compared with the results from analysis based on toe failure alone, best estimates of the critical height and the critical failure mechanism are obtained. The calculated results are given in the form of graphs and tables for a wide range of parameters. The critical failure surfaces are also investigated to assess the influences of geometrical constraint and soil property on failure mechanism. © 2013 Thomas Telford Ltd.

Hong Z.-S.,Nanjing Southeast University | Bian X.,Nanjing Southeast University | Cui Y.-J.,ParisTech National School of Bridges and Roads | Gao Y.-F.,Hohai University | Zeng L.-L.,Fuzhou University
Geotechnique | Year: 2013

Isotropically consolidated undrained triaxial compression shear tests were performed on three reconstituted clays to investigate the effect of initial water content w0 on undrained strength behaviour. The values of w0 were adjusted within the range of 10-20 times the liquid limit. The predominant clay mineral is identified as illite for the considered clays, based on a semi-quantitative analysis of the X-ray diffraction patterns. The laboratory tests show that the stress-strain curve in terms of deviator stress against axial strain and the effective stress path in terms of deviator stress against effective mean stress are significantly affected by w0. The undrained strength ratio R*su, defined as the ratio of the undrained shear strength S*u to the isotropic consolidation stress, varies with w0 within a wide spectrum, ranging from 0. 28 to 0. 60 for the three reconstituted clays investigated. The relationship between void index Iv and S*u changes with R*su, and becomes identical to the intrinsic strength line proposed by Chandler when R*su = 0.33. It is also evidenced from the laboratory tests that the value of S*u depends on both the water content and the liquid limit. © 2013 Thomas Telford Ltd.

Liu L.,Hohai University | Wang X.,Hohai University | Chen H.,Nanjing Southeast University | Wan C.,Chongqing University
Construction and Building Materials | Year: 2016

In order to comprehensively understand the drying behavior of cementitious materials, this paper presents a microstructure-based model to simulate the water evaporation process in capillary pores, the drying-induced deformation of cement paste with free boundary condition and the microcracking of cement paste under constraint. This model is applicable to high relative humidity ranges where the capillary pressure effect quantified by the Kelvin equation is the primary loading stimulus. Mainly two parts of modeling work are carried out. (1) From a microstructure model of cement paste HYMOSTRUC3D, the water evaporation in capillary pores is captured by a multi-step digitalization algorithm. (2) The drying-induced shrinkage deformation and internal microcracking of hardened cement paste with different boundary constraints are simulated by a 3D lattice fracture model. In order to reduce the computational cost, a two-scale modeling regime is employed where the microstructure of cement paste and the nanostructure of C-S-H are incorporated. Experimental test about free shrinkage of cement paste is utilized to validate the model. At last, the model is compared with poro-elastic-mechanical models, and is applied to study the influences of water-to-cement ratio and hydration time on the free shrinkage as well as the influence of constraints on the internal microcracking. © 2016 Elsevier Ltd

Wu Y.,Hohai University | Gao Y.,Hohai University | Li D.,Shandong University of Science and Technology
Earthquake Engineering and Engineering Vibration | Year: 2011

A new model to simulate spatially correlated earthquake ground motions is developed. In the model, the main factors that characterize three distinct effects of spatial variability, namely, the incoherency effect, the wave-passage effect and the site-response effect, are taken into account, and corresponding terms/parameters are incorporated into the well known model of uniform ground motions. Some of these terms/parameters can be determined by the root operation, and others can be calculated directly. The proposed model is first verified theoretically, and examples of ground motion simulations are provided as a further illustration. It is proven that the ensemble expected value and the ensemble auto-/cross-spectral density functions of the simulated ground motions are identical to the target spectral density functions. The proposed model can also be used to simulate other correlated stochastic processes, such as wave and wind loads. © 2011 Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag Berlin Heidelberg.

Xu Y.,Hohai University | da Q.,Nanjing Southeast University | Wang H.,Hohai University
Soft Computing | Year: 2011

In a very recent paper by Xu and Chen (Soft Comput 12:515-521, 2008), a novel procedure for group decision making with incomplete reciprocal relations was developed. In this note, we examine the function between the fuzzy preference relation and its corresponding priority vector developed by Xu and Chen with a numerical example and show that the function does not hold in general cases. Then, we deduce an exact function between the additive transitivity fuzzy preference relation and its corresponding priority vector. Based on this, we develop a procedure for the decision making with an incomplete reciprocal relation and also develop a procedure for the group decision making with incomplete reciprocal relations. In order to compare the performances of our method with Xu and Chen's method in fitting the reciprocal relation, we introduce some criteria. Theoretical analysis and numerical examples have shown that the function deduced by us is more reasonable and effective than Xu and Chen's. © 2010 Springer-Verlag.

Liu X.,Nanjing Southeast University | Pan Y.,Nanjing Southeast University | Xu Y.,Hohai University | Yu S.,Deakin University
Fuzzy Sets and Systems | Year: 2012

In this paper, we explore the group decision making (GDM) problems with incomplete additively consistent fuzzy preference relations. Some properties of additively consistent fuzzy preference relations are also discussed. A sufficient and necessary condition is proposed to keep the additive consistency of fuzzy preference relations. Methods for determining the priority weights of fuzzy preference relations are provided. Least square completion and inconsistency repair methods are developed to deal with incomplete and inconsistent fuzzy preference relations. Some numerical examples are also given to illustrate the proposed approaches. © 2011 Elsevier B.V.

Guan X.,Nanjing Southeast University | Zhang B.,Hohai University
Journal of Global Optimization | Year: 2012

The inverse 1-median problem consists in modifying the weights of the customers at minimum cost such that a prespecified supplier becomes the 1-median of modified location problem. A linear time algorithm is first proposed for the inverse problem under weighted l ∞ norm. Then two polynomial time algorithms with time complexities O(n log n) and O(n) are given for the problem under weighted bottleneck-Hamming distance, where n is the number of vertices. Finally, the problem under weighted sum-Hamming distance is shown to be equivalent to a 0-1 knapsack problem, and hence is Nmathcal Pmathcal-hard. © 2011 Springer Science+Business Media, LLC.

Wu X.,Hohai University | Zhang A.,China Agricultural University
Atmospheric Environment | Year: 2014

N2O emissions simulated by WNMM, DAYCENT and Crop-DNDC models were compared to the observed data sets from rice-wheat rotation systems under water-saving irrigation at Kunshan City, Jiangsu Province, China. On the basis of the correlation and paired t-test for evaluation, the simulation of N2O emission by Crop-DNDC and WNMM models provided better agreement with the observed data than by DAYCENT model. The daily time step, Crop-DNDC model was consistently the best for predicting daily N2O emissions (R2 = 0.892, n = 28, p > 0.05), and WNMM model performed better (R2 = 0.87, n = 28, p > 0.05). The Crop-DNDC model simulated the seasonal cumulative N2O emissions were the closest to the measured value of 1.07 kg N ha-1, and WNMM and DAYCENT models predicted 8.4% and 15.0% more N2O emissions than that in field experiments. The three models predicted well the seasonal cycle of soil temperature, soil moisture and could provide reliable estimations. The simulation of daily average soil temperature at 10 cm were consistently with the field observed data, which by Crop-DNDC (R2 = 0.92, n = 67, p > 0.05) and WNMM (R2 = 0.91, n = 67, p > 0.05). The comparison of observed to simulated results indicated that soil WFPS was simulated by Crop-DNDC (R2 = 0.52, n = 50, p > 0.05), WNMM (R2 = 0.56, n = 50, p > 0.05) and DAYCENT (R2 = 0.37, n = 50, p > 0.05). Accurate simulation of soil moisture, soil temperature and accurate partitioning of gaseous nitrogen loss into NO, N2O and N2 are challenges for all models. © 2014 Elsevier Ltd.

Guan X.,Nanjing Southeast University | Zhang B.,Hohai University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

The inverse 1-median problem is concerned with modifying the weights of the customers at minimum cost such that a prespecified supplier becomes the 1-median of modified location problem. We first present the model of inverse 1-median problem on trees. Then we propose two algorithms to solve the problem under weighted l∞ norm with bound constraints on modifications. Based on the approach of the unbounded case, we devise a greedy-type algorithm which runs in O(n2) time, where n is the number of vertices. Based on the property of the optimal solution, we propose an O(n log n) time algorithm using the binary search. © Springer-Verlag Berlin Heidelberg 2010.

Yao Y.,Beihang University | Zhang B.,Tsinghua University | Zhu J.,Hohai University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2012

According to the degree of influence on stress-strain relationship, soil behaviors can be categorized as essential behaviors, expressional behaviors and relative behaviors. The essential behaviors including compressive hardening, dilatancy and friction are those fundamental characteristics differing soils from other continuous materials. The expressional behaviors include such as stress history dependence, stress path dependence, softening, anisotropy, structure, creep, particle crushing, and temperature effect. They indirectly influence the stress-strain relationship of soils through affecting the essential behaviors of soils. The relative behaviors consist of such as yielding, normality flow, associated flow, coaxiality, and critical state. They are basic concepts or assumptions to be incorporated into an elasto-plastic constitutive model if such model is desired. Following a detailed discussion on the soil behaviors and their mutual relations, a comprehensive review is provided on a few representative constitutive models, e.g., the Duncan-Chang nonlinear elastic model, the Cam-clay elastio-plastic model and the UH model, the Asaoka model, the Li-Dafalias model, the Yin-Graham EVP model and other constitutive models developed by Chinese researchers. The focus is placed mainly on how to conceptualize the intrinsic soil behaviors and lead to constitutive models, and which behaviors can be reflected by each constitutive model and how. Afterwards some considerations and personal experiences are shared on implementing constitutive models into numerical simulation. The discussion focuses on the accuracy of numerical simulation and the influencing factors, selection of proper constitutive models and parameters, consideration of spatial variation of soil modulus in deformation calculation, the strain localization and some solutions for fixing the problems caused by displacement discontinuity at soil-structure contacts in numerical simulation.

Xu W.,Hohai University | Xu W.,Nanjing Southeast University | Chen H.,Nanjing Southeast University | Chen W.,Hohai University | Jiang L.,Hohai University
Soft Matter | Year: 2014

The effect of microstructures of interfacial layers on transport behaviors of particulate composites has been found to be significant, thus microstructural characteristics of interfacial layers should be considered in the analysis for better prediction of transport properties of particulate composites. However, it is very difficult to determine the volume fraction of soft interfacial layers around polydisperse three-dimensional (3D) ellipsoidal aggregate particles and to practically estimate the influence of such a microstructural characteristic on transport properties of particulate composites by traditional experimental methods and simple models proposed so far. In this article, an approximate analytical model for the volume fraction of soft interfacial layers is proposed on the basis of a theory of the nearest-surface distribution functions and geometric characteristics of polydisperse ellipsoidal particle systems. A theoretical model that adopts a three-phase composite ellipsoid structure by a generalized self-consistent scheme is further presented to predict the effective transport properties of particulate composites containing such soft interfacial layers. To test the developed models, numerical results of the soft interfacial volume fraction from the previous work, experimental data in the literature, the Hashin-Shtrikman bounds model and the Maxwell-Garnett model for the effective electrical conductivity are compared respectively. Finally, by virtue of the present models, the effects of key factors on the effective electrical conductivity of particulate composites are investigated in a quantitative manner. © 2014 The Royal Society of Chemistry.

Wang Y.,Hohai University | Feng D.,Hohai University | Ng C.W.W.,Hohai University | Ng C.W.W.,Hong Kong University of Science and Technology
Computers and Geotechnics | Year: 2013

Cracks on a natural soil surface provide preferential pathways for water infiltration and contaminant solute transport. Before the mechanical property and permeability of cracked soil can be studied, a crack network model must first be established. Based on statistical analysis of crack geometry from field observations, a new method of representing a 3D crack network was developed. A horizontal plane of a crack network was derived using the Voronoi diagram. Each vertical crack was idealized as an inverted triangular prism. The 3D permeability tensor was determined by modeling the water flow through the crack network. A computer program was developed to generate a 3D crack network automatically and compute the permeability tensor of cracked soil at different depths. The model was verified by comparing the measured permeability and computed permeability of cracked soil. The results showed that the computed permeability was consistent with the measured permeability. © 2013 Elsevier Ltd.

Chen Z.,Nanjing Normal University | Chen Z.,Hohai University | Wang H.,Hohai University | Qi X.,Hong Kong University of Science and Technology
Water Resources Management | Year: 2013

The eastern route of the South-to-North Water Diversion (SNWD-ER) project is a massive-scale interbasin system to transfer water from the Yangtze River to North China. With the infrastructure construction close to completion, the project is now faced with many complicated operations management problem at different levels. The problems are unique in that, on the one hand, the project is expected to be financially self-sustainable by charging water usages, and on the other hand, the water price is regulated for its nature as a social product. One such problem is to achieve a rational water allocation among different users by appropriate pricing schemes. In this paper, we study how to use a two-tier pricing scheme to balance the water allocation by using a Stackelberg game model. From the study, we find that (1) the Stackelberg game always has equilibrium solutions to balance the benefit of every party in the system, which implies that the two-tier pricing scheme can effectively coordinate the water allocation; (2) the two-tier pricing scheme can also result in multiple desirable by-products such as encouraging the implementation of water saving mechanism and giving the local water users certain priority; and (3) the government can adjust the pricing parameters to control and balance the profit of every party. As such we conclude that the two-tier pricing scheme is an effective way that integrates both the government control and market powers to ensure the public interest and the economic benefit, which is suitable for SNWD-ER project. © 2013 Springer Science+Business Media Dordrecht.

Zhijia L.,Hohai University | Penglei X.,Nantong Substation | Jiahui T.,Nantong Maritime Safety Administration of the Peoples Republic of China
Journal of Hydrologic Engineering | Year: 2013

The Xinanjiang model parameter calibration is an optimization problem that aims to determine the values of model parameters that provide the best fit between observed and estimated flows. Many researchers have used the shuffled complex evolution (SCE-UA) algorithm in the Xinanjiang model parameter calibration and have found some problems in its application. Identifying methods in choosing an objective function, the amount of calibration data to be used, and the best calibration steps in searching for the best parameters are just some of the application problems that must be solved. The goal of the present study is to resolve the aforementioned problems. This work calibrates the Xinanjiang model for the Yuetan basin in China based on the SCE-UA method. In the objective function study, six objective functions are commonly used. Results demonstrate that the water quantity balance error function is the best choice in both daily and hourly Xinanjiang model calibrations. During the experiment, 20 sets of observed data with length differences of 1-20 years are used. The results reveal that data amounting to a period of 16 years are needed to obtain a relatively stable parameter set. Meanwhile, the objective optimization method is introduced in the calibration step study. This method combines the coupling of the objective optimization method with the SCE-UA algorithm. Parameter calibration results reveal that the combined method can increase the calibration speed and reduce the influence of the calibration data period on the results. © 2013 American Society of Civil Engineers.

Gu Y.,Hohai University | Gu Y.,Duke University | Chen W.,Hohai University | Zhang C.,University of Siegen
International Journal of Solids and Structures | Year: 2013

In this paper, the boundary element method (BEM) based on the elasticity theory is developed for two-dimensional (2-D) thin-structural problems with thickness-to-length ratio in the micro (10-6) or nano (10 -9) scales. An efficient non-linear co-ordinate transformation, based on the sinh function, is developed to deal with the troublesome nearly-singular integrals arising in the BEM formulation for thin structures. The proposed BEM formulation with thin-body capabilities is also extended to the multi-domain problems and applied to the stress analysis of multilayered coating systems. Promising BEM results with only a small number of elements are obtained for thin films and coatings with the thickness-to-length ratio is as small as 10 -9, which is sufficient for modeling most thin layered coating systems as used in smart materials and micro-electro-mechanical systems. The advantages, disadvantages and potential applications of the proposed method, as compared with the finite element method (FEM), are discussed in the last section. © 2013 Elsevier Ltd. All rights reserved.

Yang J.,Hohai University | Tao J.,Hohai University
Journal of Coastal Research | Year: 2016

The transport and dilution processes of pollutants are complex due to complicated morphology and dynamic factors in the radial sand ridges. The "moving stationary tidal wave" formed by progressive tidal wave from the East China Sea and the anti-clockwise rotary tidal wave from the Yellow Sea, together with the multiple radial tidal channels and flats, make the patterns different for exchange and retention of pollutants. Two retention timescales, the residence time and exposure time, were employed as diagnostic tools to the radial sand ridges, and surface wind was shown to be a significant factor to affect the transport patterns. Meanwhile, Lagrangian particles denoting pollutants were introduced for analyzing their transport trajectories and obtaining the retention timescales. Additionally, the finite-time Lyapunov exponents (FTLE) fields were integrated to locate Lagrangian coherent structures (LCSs). As time evolved, in most of the snapshots obvious longshore LCSs were detected at Xiyang, which is one of the deepest tidal channels and is demonstrated to be an important pathway of mass transport. Furthermore, the tidal channels were shown to have effects on confining the movements of water parcels or pollutants. © Coastal Education and Research Foundation, Inc. 2016.

Ruan X.-B.,Hohai University | Sun S.-L.,Hohai University
Journal of Central South University | Year: 2013

In order to evaluate the seismic stability of reinforced soil walls against bearing capacity failure, the seismic safety factor of reinforced soil walls was determined by using pseudo-dynamic method, and calculated by considering different parameters, such as horizontal and vertical seismic acceleration coefficients, ratio of reinforcement length to wall height, back fill friction angle, foundation soil friction angle, soil-reinforcement interface friction angle and surcharge. The parametric study shows that the seismic safety factor increases by 24-fold when the foundation soil friction angle varies from 25 to 45, and increases by 2-fold when the soil-reinforcement interface friction angle varies from 0 to 30. That is to say, the bigger values the foundation soil and/or soil-reinforcement interface friction angles have, the safer the reinforced soil walls become in the seismic design. The results were also compared with those obtained from pseudo-static method. It is found that there is a higher value of the safety factor by the present work. © 2013 Central South University Press and Springer-Verlag Berlin Heidelberg.

Wu D.,Hohai University | Hua Z.,Hohai University
Ecological Engineering | Year: 2014

This study was conducted to investigate the effect of vegetation on sediment resuspension and phosphorus release in response to hydrodynamic disturbances in shallow lakes using a unique instrument to simulate wind-driven current. Two common types of vegetation, Vallisneria natans and Acorus calamus of Taihu Lake (a typical shallow lake), were planted in an experiment system. The results indicated that bed shear stress in the presence of vegetation was much less than critical shear stress which led to lower resuspension. Acorus calamus led to a much greater reduction in bed shear stress and better inhibitory effects on sediment resuspension due to its robust stem and better resisting capacity. Additionally, vegetation had a significant inhibitory effect on the release of total phosphorus (TP). The effect was larger for Acorus calamus, especially under hydrodynamic disturbance induced by moderate and high wind speed. TP release by Vallisneria natans was dominated by particulate phosphorus (PP) and that of Acorus calamus was dominated by dissolved total phosphorus (DTP). PP release mechanism was same in flume SV and EV that it was mainly relevant to bed shear stress and SSC. DTP release mechanism was different between plant species. © 2014 Elsevier B.V.

Jiang F.-Y.,Hohai University | Gao L.-K.,Nanjing University
Gongcheng Lixue/Engineering Mechanics | Year: 2011

A new method of calculating earthquake response based on the cosine transform is proposed in order to improve the calculating accuracy of earthquake response spectra. Convolution and differential theorems of cosine transform are put forward and proved. By employing the transform as well as considering SDOF system's dynamic differential equations as a starting point, the formula of cosine-transform-spectrum of earthquake responses is deduced, and then a general expression of response spectrum is obtained. For approaching the calculating accuracy, the response spectra of harmonic conditions is calculated by using exact and cosine transforms respectively. Meanwhile the error analysis is done. It is concluded that the mean square deviation of displacement, velocity and accelerate response spectra are 0.0012 m, 0.003 m/s and 0.16 m/s 2 respectively calculated by exact, while the result of cosine transform fit very well with theory, and the mean square deviation are 0.0002 m, 0.002 m/s and 0.36 m/s 2, when the load input is cos4πt, which shows the accuracy of displacement and velocity increased nearly 6 and 1.5 fold, although the mean square deviation of acceleration response spectrum is a little greater than that of an exact one; for the long period, the method of cosine transform is markedly superior to that of an exact one. And in the result of EI Centro, the shape of three type response spectra is similar, further confirmed the accuracy and reliability of the cosine transform method.

Zhao J.-Q.,Hohai University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

A practical two-dimensional parameter stability boundary tracing method is proposed. Assuming that the system within the stability boundary is composed of saddle node bifurcation points and limit induced bifurcation points, without double saddle node bifurcation points. By applying trajectory tracing and bifurcation point seeking and identification alternatively to the two parameters, at the expense of some additional points, the proposed method overcomes the difficulties of online application of traditional two-dimensional parameter bifurcation boundary tracing method, in which a second order Hessian matrix has to be computed and factorized. The numerical results about a 3000 bus actual system show that the proposed method is very efficient, robust, and suitable for on-line application.

Fan L.W.,Hohai University | Wu F.,Nanjing University of Aeronautics and Astronautics | Zhou P.,Nanjing University of Aeronautics and Astronautics
Journal of Air Transport Management | Year: 2014

This paper employs directional distance function to evaluate the technical efficiency of twenty major Chinese airports from 2006 to 2009 within a joint production framework of desirable and undesirable output (i.e. flight delays). The results indicate that the overall average efficiencies of Chinese airports increased over the period of time. The international hub airports are found to operate at higher efficiency level, which indicates that these airports run well in producing more desirable outputs and controlling flight delays. Although the average efficiency score of listed airports is higher than non-listed ones, the difference between the two group is statistically insignificant. A comparison between the results without and with flight delays show that several airports experienced significant changes in their efficiency scores after considering undesirable output. © 2013 Elsevier Ltd.

Zhang J.,Hohai University
Mathematical Problems in Engineering | Year: 2015

Starting a parallel code from scratch is not a good choice for parallel programming finite element analysis of elasticity problems because we cannot make full use of our existing serial code and the programming work is painful for developers. PETSc provides libraries for various numerical methods that can give us more flexibility in migrating our serial application code to a parallel implementation. We present the approach to parallelize the existing finite element code within the PETSc framework. Our approach permits users to easily implement the formation and solution of linear system arising from finite element discretization of elasticity problem. The main PETSc subroutines are given for the main parallelization step and the corresponding code fragments are listed. Cantilever examples are used to validate the code and test the performance. © 2015 Jianfei Zhang.

Gou X.,Hohai University | Schwartz J.,North Carolina State University
Superconductor Science and Technology | Year: 2013

Multifilamentary round wires (RWs) of Bi2Sr2CaCu 2Ox (Bi2212) superconductor in a Ag/AgMg matrix have complex microstructures that strongly influence their electrical and mechanical behavior. The Bi2212/Ag interfaces, which in some locations are characterized by Bi2212 growths into the Ag matrix that result in rough, jagged interfaces, and in other locations are characterized by Bi2212 growths that bridge and connect to neighboring Bi2212 filaments, are believed to be amongst the most important microstructural features; yet their role is not well understood. In this work, a fractal-based framework is created in an effort to understand the role of the structure of individual filaments and the Bi2212/Ag interfaces in determining the macroscopic electromechanical behavior of Bi2212 RW. Scanning electron micrographs of an individual Bi2212 filament extracted from a Bi2212 RW are used to analyze the rough Bi2212/Ag interface and develop a fractal model using the Weierstrass-Mandelbrot (W-M) fractal function. The W-M fractal function is then used to generate simulated Bi2212/Ag microstructures. Finally, the mechanical behavior of the microstructures is investigated. It is found that the interfilamentary bridges which play a significant role in Bi2212 transport are not likely to be the cause of electromechanical degradation and failure. Instead, large stress concentrations are identified at the concave tips that occur along the jagged Bi2212/Ag interface. In particular, locations where the concave tips are within the Bi2212 filament are the likely initiation points of failure in Bi2212 RWs. © 2013 IOP Publishing Ltd.

Zhang Y.,Hohai University | Zhang Y.,Desert Research Institute | Green C.T.,U.S. Geological Survey | Baeumer B.,University of Otago
Journal of Hydrology | Year: 2014

Time-nonlocal transport models can describe non-Fickian diffusion observed in geological media, but the physical meaning of parameters can be ambiguous, and most applications are limited to curve-fitting. This study explores methods for predicting the parameters of a temporally tempered Lévy motion (TTLM) model for transient sub-diffusion in mobile-immobile like alluvial settings represented by high-resolution hydrofacies models. The TTLM model is a concise multi-rate mass transfer (MRMT) model that describes a linear mass transfer process where the transfer kinetics and late-time transport behavior are controlled by properties of the host medium, especially the immobile domain. The intrinsic connection between the MRMT and TTLM models helps to estimate the main time-nonlocal parameters in the TTLM model (which are the time scale index, the capacity coefficient, and the truncation parameter) either semi-analytically or empirically from the measurable aquifer properties. Further applications show that the TTLM model captures the observed solute snapshots, the breakthrough curves, and the spatial moments of plumes up to the fourth order. Most importantly, the a priori estimation of the time-nonlocal parameters outside of any breakthrough fitting procedure provides a reliable "blind" prediction of the late-time dynamics of subdiffusion observed in a spectrum of alluvial settings. Predictability of the time-nonlocal parameters may be due to the fact that the late-time subdiffusion is not affected by the exact location of each immobile zone, but rather is controlled by the time spent in immobile blocks surrounding the pathway of solute particles. Results also show that the effective dispersion coefficient has to be fitted due to the scale effect of transport, and the mean velocity can differ from local measurements or volume averages. The link between medium heterogeneity and time-nonlocal parameters will help to improve model predictability for non-Fickian transport in alluvial settings. © 2014 Published by Elsevier B.V.

Zeng C.,Hohai University | Li C.-W.,Hong Kong Polytechnic University
Environmental Fluid Mechanics | Year: 2014

The hydrodynamics of flows through a finite length semi-rigid vegetation patch (VP) were investigated experimentally and numerically. Detailed measurements have been carried out to determine the spatial variation of velocity and turbulence profiles within the VP. The measurement results show that an intrusion region exists in which the peak Reynolds stress remains near the bed. The velocity profile is invariant within the downstream part of the VP while the Reynolds stress profile requires a longer distance to attain the spatially invariant state. Higher vegetation density leads to a shorter adjustment length of the transition region, and a higher turbulence level within the VP. The vegetation density used in the present study permits the passing through of water and causes the peak Reynolds stress and turbulence kinetic energy each the maximum at the downstream end of the patch. A 3D Reynolds-averaged Navier-Stokes model incorporating the Spalart-Allmaras turbulence closure was employed subsequently to replicate the flow development within the VP. The model reproduced transitional flow characteristics well and the results are in good agreement with the experimental data. Additional numerical experiments show that the adjustment length can be scaled by the water depth, mean velocity and maximum shear stress. Empirical equations of the adjustment lengths for mean velocity and Reynolds stress were derived with coefficients quantified from the numerical simulation results. © 2013 Springer Science+Business Media Dordrecht.

She D.,Hohai University | Liu D.,Hohai University | Xia Y.,CAS Nanjing Institute of Soil Science | Shao M.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research
Water Resources Management | Year: 2014

Vegetation restoration is helpful in preventing soil erosion but aggravates water scarcity, thus resulting in soil desiccation on the wind-water erosion crisscross region (WWECR) of the Loess Plateau in Northwestern China. However, no guideline currently exists on the selection of plant species and density for restoration purposes. Based on the process model of soil water-carrying capacity for vegetation (SWCCV) originally developed in this region, this study validated the model under a broad range of weather regimes, soil types, and land uses. The SWCCV model was applied as a diagnostic tool to obtain insights into the separate effects of vegetation density and land use on soil water dynamics on the WWECR of the Loess Plateau. Results showed that the total water loss at semi-natural grasslands was close to rainfall while significantly decreasing runoffs, thus indicating that semi-natural grass was suitable for vegetation restoration on the WWECR. If Caragana korshinskii is planted for agronomic and economic benefits, a density of 3,400 trees ha-1 will yield the most optimal soil water conservation benefits at study site. Our recommended land use and vegetation density were directive and instructional for vegetation restoration on the WWECR and that our modeling approach could be extended to applications in other arid and semi-arid regions. © 2014 Springer Science+Business Media Dordrecht.

Yong B.,Hohai University | Liu D.,Hohai University | Gourley J.J.,National Oceanic and Atmospheric Administration | Tian Y.,NASA | And 4 more authors.
Bulletin of the American Meteorological Society | Year: 2015

Accurate estimation of high-resolution precipitation on the global scale is extremely challenging. The operational Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) has created over 16 years of high-resolution quantitative precipitation estimation (QPE), and has built the foundation for improved measurements in the upcoming Global Precipitation Measurement (GPM) mission. TMPA is intended to produce the "best effort" estimates of quasi-global precipitation from almost all available satelliteborne precipitation-related sensors by consistently calibrating them with the high-quality measurements from the core instrument platform aboard TRMM. Recently, the TMPA system has been upgraded to version 7 to take advantage of newer and better sources of satellite inputs than version 6, and has attracted a large user base. A key product from TMPA is the near-real-time product (TMPA-RT), as its timeliness is particularly appealing for time-sensitive applications such as flood and landslide monitoring. TMPA-RT's error characteristics on a global scale have yet to be extensively quantified and understood. In this study, efforts are focused on a systematic evaluation of four sets of mainstream TMPA-RT estimates on the global scale. The analysis herein indicates that the latest version 7 TMPA-RT with the monthly climatological calibration had the lowest daily systematic biases of approximately 9% over land and -11% over ocean (relative to the gauge-adjusted research product). However, there still exist some unresolved issues in mountainous areas (especially the Tibetan Plateau) and high-latitude belts, and for estimating extreme rainfall rates with high variability at small scales. These global error characteristics and their regional and seasonal variations revealed in this paper are expected to serve as the benchmark for the upcoming GPM mission. ©2015 American Meteorological Society.

Zhu Q.-Z.,Hohai University
Rock Mechanics and Rock Engineering | Year: 2016

A proper criterion describing when material fails is essential for deep understanding and constitutive modeling of rock damage and failure by microcracking. Physically, such a criterion should be the global effect of local mechanical response and microstructure evolution inside the material. This paper aims at deriving a new mechanisms-based failure criterion for brittle rocks, based on micromechanical unilateral damage-friction coupling analyses rather than on the basic results from the classical linear elastic fracture mechanics. The failure functions respectively describing three failure modes (purely tensile mode, tensile-shear mode as well as compressive-shear mode) are achieved in a unified upscaling framework and illustrated in the Mohr plane and also in the plane of principal stresses. The strength envelope is proved to be continuous and smooth with a compressive to tensile strength ratio dependent on material properties. Comparisons with experimental data are finally carried out. By this work, we also provide a theoretical evidence on the hybrid failure and the smooth transition from tensile failure to compressive-shear failure. © 2016 The Author(s)

Gu P.,Hohai University | Dao M.,Massachusetts Institute of Technology | Suresh S.,Carnegie Mellon University
Acta Materialia | Year: 2014

Nanotwinned structures offer the potential to effectively enhance strength while preserving ductility and damage tolerance. In this paper we present an analytical model for quantifying slip transfer across twin boundaries and for deriving the attendant flow stress as a function of the twin lamellae size in nanotwinned face-centered cubic metals. The mechanistic models investigate how single or piled-up screw and non-screw dislocations interact with twin boundaries, by establishing connections with the size dependence of the activation volume. The models correctly predict the trends from a variety of independent prior experimental observations of the dependence of flow stress on twin lamella size in nanotwinned copper. They also rationalize a number of observations made from previous molecular dynamics simulations of the deformation of nanotwinned metals. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Wang X.,Hohai University | Lv G.,Hohai University | Xu L.,Hohai University
Infrared Physics and Technology | Year: 2012

Accurate and fast detection of infrared (IR) dim target has very important meaning for infrared precise guidance, early warning, video surveillance, etc. Based on human visual attention mechanisms, an automatic detection algorithm for infrared dim target is presented. After analyzing the characteristics of infrared dim target images, the method firstly designs Difference of Gaussians (DoG) filters to compute the saliency map. Then the salient regions where the potential targets exist in are extracted by searching through the saliency map with a control mechanism of winner-take-all (WTA) competition and inhibition-of-return (IOR). At last, these regions are identified by the characteristics of the dim IR targets, so the true targets are detected, and the spurious objects are rejected. The experiments are performed for some real-life IR images, and the results prove that the proposed method has satisfying detection effectiveness and robustness. Meanwhile, it has high detection efficiency and can be used for real-time detection.

Gong Y.,Hohai University | Hu N.,Hohai University | Zhang J.,Hohai University | Liu G.,Hohai University | Deng J.,Hohai University
Computers and Industrial Engineering | Year: 2015

In this paper, we investigate the fuzzy multi-attribute group decision making (FMAGDM) problems in which all the information provided by the decision makers (DMs) is expressed as the trapezoidal interval type-2 fuzzy sets (IT2 FS). We introduce the concepts of interval possibility mean value and present a new method for calculating the possibility degree of two trapezoidal IT2 FS. Then, we develop two aggregation techniques called the trapezoidal interval type-2 fuzzy geometric Bonferroni mean (TIT2FGBM) operator and the trapezoidal interval type-2 fuzzy weighted geometric Bonferroni mean (TIT2FWGBM) operator. We study its properties and discuss its special cases. Based on the TIT2FWGBM operator and the possibility degree, the method of FMAGDM with trapezoidal interval type-2 fuzzy information is proposed. Finally, an illustrative example is given to verify the developed approaches and to demonstrate their practicality and effectiveness. © 2015 Elsevier Ltd.

Zeng J.,CAS Nanjing Institute of Geography and Limnology | Zhao D.-Y.,Hohai University | Huang R.,Hohai University | Wu Q.L.,CAS Nanjing Institute of Geography and Limnology
Canadian Journal of Microbiology | Year: 2012

The abundance and community composition of ammonia-oxidizing archaea and ammonia-oxidizing bacteria in the surface sediments of 2 different zones (Meiliang Bay and Eastern Lake Taihu) of Lake Taihu were investigated using real-time quantitative polymerase chain reaction and clone libraries. The amoA gene copy numbers in the surface sediment of Meiliang Bay ranged from 4.91 × 105 to 8.65 × 106 copies/g dry sediment for the archaeal amoA gene and from 3.74 × 104 to 3.86 × 105 copies/g dry sediment for the bacterial amoA gene, which were significantly higher than those of Eastern Lake Taihu (P < 0.05). Concentrations of ammonia (NH4+), total nitrogen, organic matter, and pH of the sediments exhibited significantly negative correlations with the abundance of ammonia-oxidizing archaea or ammonia-oxidizing bacteria (P < 0.05 or P < 0.01, respectively). The potential nitrification rates show remarkable correlations with the copy numbers of the archaeal amoA gene. Diversity of the archaeal amoA gene in Eastern Lake Taihu was significantly higher than that of Meiliang Bay, whereas the bacterial amoA gene diversity was comparable for the 2 lake zones. The data obtained in this study would be useful to elucidate the role of ammonia-oxidizing archaea and ammonia-oxidizing bacteria in the nitrogen cycle of freshwater ecosystems.

Yu H.,Hohai University | Yu H.,Henan Polytechnic University | Ruan H.,Hohai University | Chu W.,Hydrochina Huadong Engineering Corporation
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Numerical model of rock joint was generated and direct shear tests at different normal stresses were conducted using PFC2D. Shear behavior of the rock joint, along with development and evolution law of microcracks at different normal stresses were examined. It is shown that the shear behavior of simulated joints corresponds well to that observed in real joints; and the dependencies of shear strength and peak dilatation angle on normal stresses conform well to predict results of the JRC-JCS model. Compressive contact force mainly concentrates nearby asperities on both sides of the joint plane. The larger the normal stress is, the more concentrated areas of confact force will appear, and the higher the concentration degree is. As normal stress continues to enhance, the developing rate of microcracks within the specimen gradually increases; and the proportion of shear cracks to the total number of microcracks gradually enlarges; but they still far less than the tension cracks. The distribution characteristics of compressive contact force on joint surface are consistent with the development law of microcracks in the specimen. Shear failure of joint under external load results from convergence and correlation of microcracks in the joint plane; and the effect of compression induced tensile cracking plays a dominant role in the process of joint shear failure.

Kong G.-Q.,Hohai University | Liu L.,Hohai University | Liu H.-L.,Hohai University | Zhou H.,Hohai University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Based on the transparent soil materials and digital imaging technology, the model tests on geotextile can be visualized. Transparent glass sand is one kind of new transparent synthetic soil materials, which is composed by glass sand, twelve alkane and white mineral oil mixture (1:4). This new material has good transparency, and its properties are similar to those of natural soil. Hence, it can be used in visualization model test technique. Based on the consolidated undrained triaxial compression tests and consolidated drained triaxial compression tests, the deformation properties of the transparent glass sand with different size ranges are studied. For comparative analysis, the deformation properties of standard sand are also obtained. Then stress-strain curves and pore pressure-strain curves of the soil are measured. The laboratory test results show that the stress-strain relation is transited from strain hardening to strain softening, and the pore pressure coefficient and deformation modulus decrease with the increase of the relative density. The peak of the stress-strain curve of the transparent glass sand is relatively slower compared with that of the standard sand.

Yin D.,Hohai University | Wu H.,Hohai University | Cheng C.,Hohai University | Chen Y.,Utah State University
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2013

Fractional calculus has been successfully applied to characterize the rheological property of viscoelastic materials; however, geomaterials were seldom involved in fractional order constitutive models (FOCM), and the topic of first loading and then unloading is rarely discussed through fractional calculus. In this paper, mechanical properties are considered as a 'spectrum', both ends of which are elasticity and viscosity, and the fractional order can be utilized to describe such properties quantitatively. In addition to conditions such as creep, stress-relaxation, and constant-strain-rate loading, stress-strain relationship under the condition of first loading and then unloading was also derived using FOCM. FOCM is then adopted to simulate triaxial tests of geomaterials under corresponding conditions. A comparison of test and numerical results demonstrates that FOCM can reasonably describe the mechanical characteristics of geomaterials. © 2012 John Wiley & Sons, Ltd.

Wang Y.,China Railway Siyuan Survey and Design Group Co. | Zhao X.,China Railway Siyuan Survey and Design Group Co. | Wang B.,Hohai University
Journal of Rock Mechanics and Geotechnical Engineering | Year: 2013

A method which adopts the combination of least squares support vector machine (LS-SVM) and Monte Carlo (MC) simulation is used to calculate the foundation settlement reliability. When using LS-SVM, choosing the training dataset and the values for LS-SVM parameters is the key. In a representative sense, the orthogonal experimental design with four factors and five levels is used to choose the inputs of the training dataset, and the outputs are calculated by using fast Lagrangian analysis continua (FLAC). The decimal ant colony algorithm (DACA) is also used to determine the parameters. Calculation results show that the values of the two parameters, γ and δ2 have great effect on the performance of LS-SVM. After the training of LS-SVM, the inputs are sampled according to the probabilistic distribution, and the outputs are predicted with the trained LS-SVM, thus the reliability analysis can be performed by the MC method. A program compiled by Matlab is employed to calculate its reliability. Results show that the method of combining LS-SVM and MC simulation is applicable to the reliability analysis of soft foundation settlement. © 2013 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences.

Liang Y.,Hohai University | Chen W.,Hohai University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015

This paper develops a relative entropy method to measure non-exponential random data in conjunction with fractional order moment, logarithmic moment and tail statistics of Mittag-Leffler distribution. The distribution of non-exponential random data follows neither the exponential distribution nor exponential decay. The proposed strategy is validated by analyzing the experiment data, which are generated by Monte Carlo method using Mittag-Leffler distribution. Compared with the traditional Shannon entropy, the relative entropy method is simple to be implemented, and its corresponding relative entropies approximated by the fractional order moment, logarithmic moment and tail statistics can easily and accurately detect the non-exponential random data. © 2014 Elsevier B.V. All rights reserved.

Wu J.-W.,Hohai University | Sarma A.K.,Indian Institute of Technology Guwahati
Optics Communications | Year: 2010

We present an integrated Silicon-on-Insulator (SOI) based Mach-Zehnder interferometer (MZI) in order to perform ultrafast all-optical XOR logic gate operation with a bit rate of ∼0.33 Tb/s. A numerical simulation is carried out in order to study various parameters such as extinction ratio and eye-opening parameters, characterizing the performance of the XOR logic gate. The output XOR logic gate signal can have improved extinction and eye margin if the initial powers of primary signals and the probe continuous-wave (CW), and SOI waveguide length are judiciously adjusted. © 2010 Elsevier B.V. All rights reserved.

Yu T.T.,Hohai University
Engineering Computations (Swansea, Wales) | Year: 2011

Purpose - The purpose of this paper is to achieve numerical simulation of discontinuous rock masses. Design/methodology/approach - The extended finite element method (XFEM) was used. Discontinuities (such as joints, faults, and material interfaces) are contained in the elements, thus the mesh can be generated without taking into account the existence of discontinuities. When one element contains no discontinuity, the displacement function is degenerated into that of the conventional finite element. For the element containing discontinuities, the standard displacement-based approximation is enriched by incorporating level-set-based enrichment functions that model the discontinuities, and an element subdivision procedure is used to integrate the domain of the element. Findings - Mesh generation can be simplified considerably and high-quality meshes can be obtained. A solution with good precision can also be achieved. It is concluded that the XFEM technique is especially suitable in simulating discontinuous rock masses problems. Research limitations/ implications - Crack initiation and propagation should be considered in further studies. Practical implications - The paper presents a very useful numerical method for a geotechnical engineering problem that has the ability to simulate the failure process of discontinuous rock masses. The method is expected to be used widely in the deformation and stability analysis of complicated rock masses. Originality/value - The paper provides a new numerical method for discontinuous rock masses that is very convenient for pre-processing. © Emerald Group Publishing Limited.

Tan G.,Hohai University | Herfet T.,Saarland University
IEEE Wireless Communications Letters | Year: 2016

To analyze the mean square error (MSE) performance of orthogonal matching pursuit (OMP)-based compressed channel estimation with deterministic pilot patterns, we propose a closed form mathematical framework. The studies show that, given the knowledge of a statistical channel model, the expected MSE of OMP can be predicted well by this proposed framework. The framework establishes a connection between the MSE to be expected and the following four decisive parameters: 1) the deterministic pilot pattern; 2) the maximum Doppler shift; 3) the number of dominant multipath components; and 4) the SNR. © 2012 IEEE.

Zhonggen Y.,Hohai University
International Journal of e-Collaboration | Year: 2016

Nowadays, information technologies are catching growing attention and their application to English language learning is also prospering. Using a Foreign Language Classroom Anxiety Scale and College English Test Band 4, this study explored the different impacts of the e-collaborative learning via QQ group and the traditional multimedia learning on learning outcomes and anxiety among tertiary students. Around 70 participants were involved in different styles of learning and instruction and received both surveys and tests. The results showed that the QQ group-based e-collaborative learning could significantly decrease anxiety but no significant gain was found in learning outcomes compared with the traditional multi-media learning. Correlation between learning outcomes and variables of anxiety was also studied, which resulted in no significant findings. Both disadvantages and advantages of this study were discussed and future research and advice to practitioners were recommended as well. Copyright © 2016, IGI Global.

Min F.,Hohai University | Zhu W.,Hohai University | Han X.,Hohai University
Tunnelling and Underground Space Technology | Year: 2013

For slurry shield tunneling projects excavated in the highly permeable soils, the slurry usually passes through the ground without forming a filter cake. As a result it may be impossible (depending on the yield strength of slurry) to built up the required support pressure which would lead to a face instability. This kind of face instability is influenced by the factors, such as the permeability of ground, the slurry pressure and the properties of slurry. How to form a thin and lowly permeable filter cake efficiently and quickly on the tunnel face becomes a crucial engineering problem for the slurry shield tunneling in the coarse-grained and highly permeable grounds. In this paper, a new apparatus was developed to study the filter cake formation on the surface of coarse-grained sands under elevated pressure. A series of pressure filtration tests were carried out on nine different slurries and five different soils. By measuring the quantities of discharged water during the test and observing the state of filter cakes formed on the soil surface, the criteria of filter cake formation was identified. The test results indicated three different types of slurry infiltration. Correspondingly, the following three different types of filter cakes were observed: a filter cake, a filter cake with an infiltrated zone, and infiltrated zone without filter cake. It was found that the ratio between the average pore size of soil (D0-) and the particle size for which 85% by weight of particles in the slurry (d85) may be used to classify the types of filter cake formation. © 2013 Elsevier Ltd.

Huang D.-Q.,Nanjing University | Zhu J.,Hohai University | Zhang Y.-C.,Nanjing University | Huang A.-N.,Nanjing University
Journal of Geophysical Research: Atmospheres | Year: 2013

Based on 14 climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), uncertainty on the simulated summer precipitation over Eastern China is analyzed by investigating the intercomparison between individual model and multimodel ensemble (MME). Generally, MME has the ability in reproducing summer precipitation over Eastern China. However, large model spread exists among models in both climatology and interannual variation. The possible reason for the large model spread lies in the uncertainties on simulating large-scale circulations, e.g., East Asian subtropical westerly jet, western Pacific subtropical high, and East Asian summer monsoon. To investigate uncertainties in different regions, Eastern China is divided to four subregions: South China (SC), Yangtze-Huaihe River Basin (YHRB), North China (NC), and Northeast China (NEC). The annual cycle of regional mean precipitation from 14 CMIP5 models indicates that the model spread approaches maximum in early summer over SC and YHRB and in middle summer over NC and NEC. Uncertainties generally decrease from south to north, with the most sensitive region of SC. For different-class precipitation, the uncertainties of 14 models are small in relatively weak rain, but large in heavy and nonrainfall for all the four regions. We propose two possible reasons for the large uncertainties: different partitioning of stratiform/ convective precipitation and horizontal resolutions. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union.

Cao M.,Hohai University | Cao M.,Szewalski Institute of Fluid Flow Machinery | Xu W.,Hohai University | Ostachowicz W.,Szewalski Institute of Fluid Flow Machinery | And 2 more authors.
Journal of Sound and Vibration | Year: 2014

Modal curvatures have been widely used in the detection of structural damage. Attractive features of modal curvature include great sensitivity to damage and instant determination of damage location. However, an intrinsic deficiency in a modal curvature is its susceptibility to the measurement noise present in the displacement mode shape that produces the modal curvature, likely obscuring the features of damage. To address this deficiency, the Teager energy operator together with wavelet transform is tactically utilized to treat modal curvature, producing a new modal curvature, termed the Teager energy operator-wavelet transform modal curvature. This new modal curvature features distinct capabilities of suppressing noise, canceling global trends, and intensifying the singular feature caused by damage for a measured mode shape involving noise. These features maximize the sensitivity to damage and accuracy of damage localization. The proposed modal curvature is demonstrated in several analytical cases of cracked pinned-pinned, clamped-free and clamped-clamped beams, with emphasis on characterizing damage in noisy conditions, and it is further validated by an experimental program using a scanning laser vibrometer to acquire mode shapes of a cracked aluminum beam. The Teager energy operator-wavelet transform modal curvature essentially overcomes the deficiency of conventional modal curvature, providing a new dynamic feature well suited for damage characterization in noisy environments. (The Matlab code for implementing Teager energy operator-wavelet transform modal curvature can be provided by the corresponding author on request.) © 2013 Elsevier Ltd.

Sun H.,Hohai University
Microsystem Technologies | Year: 2014

Nanoimprint lithography is a low cost and high throughput technology to fabricate nanostructures with excellent resolution. However, traditional thermal nanoimprint limits its application field because high temperature induces many problems. Low temperature nanoimprint lithography, including ultraviolet nanoimprint lithography and room temperature nanoimprint lithography, can reduce or remove thermal cycle, overcome the sticking problem, alleviate the alignment errors due to different coefficients of thermal expansion and pattern polymer based materials that are intolerant to high temperature. Recent development of these three low temperature NIL techniques was discussed from the aspects of new resist, stamp, process and application. Low temperature nanoimprint has wide application in the fields of optoelectronics, displays and bio-applications. © 2014, Springer-Verlag Berlin Heidelberg.

Chen D.,China Three Gorges University | Birk C.,University of New South Wales | Song C.,University of New South Wales | Du C.,Hohai University
International Journal for Numerical Methods in Engineering | Year: 2014

A high-order time-domain approach for wave propagation in bounded and unbounded domains is proposed. It is based on the scaled boundary FEM, which excels in modelling unbounded domains and singularities. The dynamic stiffness matrices of bounded and unbounded domains are expressed as continued-fraction expansions, which leads to accurate results with only about three terms per wavelength. An improved continued-fraction approach for bounded domains is proposed, which yields numerically more robust time-domain formulations. The coefficient matrices of the corresponding continued-fraction expansion are determined recursively. The resulting solution is suitable for systems with many DOFs as it converges over the whole frequency range, even for high orders of expansion. A scheme for coupling the proposed improved high-order time-domain formulation for bounded domains with a high-order transmitting boundary suggested previously is also proposed. In the time-domain, the coupled model corresponds to equations of motion with symmetric, banded and frequency-independent coefficient matrices, which can be solved efficiently using standard time-integration schemes. Numerical examples for modal and time-domain analysis are presented to demonstrate the increased robustness, efficiency and accuracy of the proposed method. © 2013 John Wiley & Sons, Ltd.

Lin J.,Hohai University | Chen W.,Hohai University | Chen C.S.,Hohai University | Chen C.S.,University of Southern Mississippi
Journal of Sound and Vibration | Year: 2014

The singular boundary method (SBM) is a novel boundary-type meshless method based on the fundamental solution of the given governing equation. The SBM employs the origin intensity factors to circumvent the singularities resulting from the fundamental solutions. In this paper, we investigate the acoustic problems with boundary singularities using the SBM. This is achieved by combining the SBM with the singularity subtraction techniques where the solution is decomposed into the singular solution and the regular solution. The singular solution is derived analytically which satisfies the governing equation and the corresponding boundary conditions containing the singularities. Then the regular solution is obtained by the SBM. Numerical examples show the excellent performance of the proposed technique. © 2014 Elsevier Ltd.

Zhu Y.,Hohai University
Advances in Science and Technology of Water Resources | Year: 2015

This paper introduces the collection of essays for Toward a Sustainable Water Future: Visions for 2050, which is organized by Environmental and Water Resources Institute (EWRI) of the American Society of Civil Engineers (ASCE). These essays, written by 52 American scientists, analyzed and described development road of water resources and environment in science and engineering technology aspects. There are three parts in the collection: Planning and Policy, Education, Science and Technology. ©, 2015, Editorial Office of Journal of Hohai University (Nature Sciences). All right reserved.

Fu Z.,Hohai University | You K.,Tsinghua University
International Journal of Distributed Sensor Networks | Year: 2013

This paper proposes an optimal mobile sensor-scheduling algorithm for recovering the failure sensors in hybrid wireless sensor networks (WSNs). To maintain a guaranteed coverage over the area of interest, spare mobile sensors in WSNs will be activated to replace the failure sensors. The optimal scheduling problem is formulated into two optimization problems, one of which precisely determines the minimum value of the largest distance required to travel for mobile sensors, while the other one gives the optimal dispatch for mobile sensors to minimize the total travel distance. Furthermore, a distributed suboptimal scheduling, which only requires the local matching information of mobile sensors, is developed as well. Both regular and random network topologies are provided to illustrate the proposed algorithms in the simulation. © 2013 Zhixin Fu and Keyou You.

Pan H.,Hohai University
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2014

For a transient signal of a hydropower unit, the existing processing methods for non-stationary signal are unable to get a high time-frequency resolution currently, and the time-frequency characteristics cannot be extracted effectively as well. Therefore, a new method, in which the local mean decomposition (LMD) and Wigner-Ville distribution have been combined together, was proposed to analyze vibration signals of hydropower unit; further it was applied into the analysis on run-out signals in the upper guide bearing of a hydropower unit in its load rejection operation. According to comparison of the time-frequency spectra determined respectively by short-time Fourier transform, wavelet transform and Wigner-Ville distribution, the spectrum given by the present method can capture the instantaneous amplitude and frequency of a transient signal directly. This implies that the proposed method has taken the advantages of both LMD and Wigner-Ville distribution. Meanwhile, the inherent defect, i.e. cross-term interference in Wigner-Ville distribution has been removed. This new method can be used as an effective analysis tool for condition monitoring and fault diagnosis of hydropower units in future.

Ma H.,Hohai University | Liu L.,Hohai University | Chen T.,Hohai University
Environmental Monitoring and Assessment | Year: 2010

Kendall τ has reasonable theoretic background than Pearson correlation. It can be applied more widely in all aspects. Instead of using widely adopted Pearson correlation or its extensions in a large number of principal component analysis (PCA) instances, we introduce the Kendall τ into the PCA method. PCA is a well-known statistical data analysis algorithm and is aimed to extract feature from high-dimensional data. It is designed to reduce the number of variables to a small number of indices while attempting to preserve the relationships present in the original data. This paper uses PCA based on Kendall τ in water security assessment of Haihe River Basin. © 2009 Springer Science+Business Media B.V.

Fu Z.,Hohai University | Yuan Y.,Hohai University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

Due to the severe offshore environments, the maintenance of offshore wind turbine is very difficult and the failure rate is very high. To improve the condition monitoring technologies will be beneficial to promote the performance of offshore wind turbine and the productivity of offshore wind farm. Some recent novel theories and methods about the condition monitoring technologies of offshore wind turbine are reviewed and classified, including monitoring system development, condition information collection, condition information transmission, fault diagnosis, state control, operation cost analysis, and so on. Outstanding issues and development trends are also summarized. The results of this work will contribute to the support for constructing the high-performance condition monitoring and control system for offshore wind farm. © 2012 State Grid Electric Power Research Institute Press.

Fu Q.,Hohai University | Zheng C.,Hohai University
The Scientific World Journal | Year: 2014

A three-dimensional finite element model was developed to investigate dynamic response of track-embankment-ground system subjected to moving loads caused by high speed trains. The track-embankment-ground systems such as the sleepers, the ballast, the embankment, and the ground are represented by 8-noded solid elements. The infinite elements are used to represent the infinite boundary condition to absorb vibration waves induced by the passing of train load at the boundary. The loads were applied on the rails directly to simulate the real moving loads of trains. The effects of train speed on dynamic response of the system are considered. The effect of material parameters, especially the modulus changes of ballast and embankment, is taken into account to demonstrate the effectiveness of strengthening the ballast, embankment, and ground for mitigating system vibration in detail. The numerical results show that the model is reliable for predicting the amplitude of vibrations produced in the track-embankment-ground system by high-speed trains. Stiffening of fill under the embankment can reduce the vibration level, on the other hand, it can be realized by installing a concrete slab under the embankment. The influence of axle load on the vibration of the system is obviously lower than that of train speed. © 2014 Qiang Fu and Changjie Zheng.

Li X.,Hohai University | Chen W.,Hohai University
Journal of Physics A: Mathematical and Theoretical | Year: 2010

In this study, anomalous diffusion in a half-plane with a constant source and a perfect sink at each half of the boundary is considered. The discontinuity of the boundary condition is erased by decomposing the solution into two parts-a symmetric part and an antisymmetric part. The symmetric part which has been studied extensively can be solved by an integral transform method, Green's function method or others. To obtain the solution of the antisymmetric part, a separable similarity solution is assumed and the Erdélyi-Kober-type fractional derivative is used. By doing so, the partial differential equation reduces to an ordinary one. Using the Mellin transform method, the solution of the antisymmetric part in terms of a Fox-H function is obtained. Some figures are given to show the characters of the diffusion process and the influences of different orders of fractional derivatives. © 2010 IOP Publishing Ltd.

Xu Y.-J.,Hohai University
Computers and Industrial Engineering | Year: 2010

In this short communication, we will show that the condition of the theorem does not hold in general cases in a recent paper "The induced continuous ordered weighted geometric operators and their application in group decision making" [Computers & Industrial Engineering 56 (2009) 1545-1552] by Wu et al., and also illustrate an example to show that we cannot construct a consistent interval multiplicative preference relation according to the condition of theorem in general case. Furthermore, we present a more reasonable condition to satisfy Theorem 1 so that we can construct a consistent interval multiplicative preference relation. © 2010 Elsevier Ltd. All rights reserved.

Jiang S.,Hohai University | Ren L.,Hohai University | Hong Y.,University of Oklahoma | Yong B.,Hohai University | And 3 more authors.
Journal of Hydrology | Year: 2012

This study first focuses on comprehensive evaluating three widely used satellite precipitation products (TMPA 3B42V6, TMPA 3B42RT, and CMORPH) with a dense rain gauge network in the Mishui basin (9972km 2) in South China and then optimally merge their simulated hydrologic flows with the semi-distributed Xinanjiang model using the Bayesian model averaging method. The initial satellite precipitation data comparisons show that the reanalyzed 3B42V6, with a bias of -4.54%, matched best with the rain gauge observations, while the two near real-time satellite datasets (3B42RT and CMORPH) largely underestimated precipitation by 42.72% and 40.81% respectively. With the model parameters first benchmarked by the rain gauge data, the behavior of the streamflow simulation from the 3B42V6 was also the most optimal amongst the three products, while the two near real-time satellite datasets produced deteriorated biases and Nash-Sutcliffe coefficients (NSCEs). Still, when the model parameters were recalibrated by each individual satellite data, the performance of the streamflow simulations from the two near real-time satellite products were significantly improved, thus demonstrating the need for specific calibrations of the hydrological models for the near real-time satellite inputs. Moreover, when optimally merged with respect to the streamflows forced by the two near real-time satellite precipitation products and all the three satellite precipitation products using the Bayesian model averaging method, the resulted streamflow series further improved and became more robust. In summary, the three current state-of-the-art satellite precipitation products have demonstrated potential in hydrological research and applications. The benchmarking, recalibration, and optimal merging schemes for streamflow simulation at a basin scale described in the present work will hopefully be a reference for future utilizations of satellite precipitation products in global and regional hydrological applications. © 2012 Elsevier B.V.

Liang Z.,Hohai University | Chang W.,Hohai University | Li B.,Hohai University
Stochastic Environmental Research and Risk Assessment | Year: 2012

The specific objective of the paper is to propose a new flood frequency analysis method considering uncertainty of both probability distribution selection (model uncertainty) and uncertainty of parameter estimation (parameter uncertainty). Based on Bayesian theory sampling distribution of quantiles or design floods coupling these two kinds of uncertainties is derived, not only point estimator but also confidence interval of the quantiles can be provided. Markov Chain Monte Carlo is adopted in order to overcome difficulties to compute the integrals in estimating the sampling distribution. As an example, the proposed method is applied for flood frequency analysis at a gauge in Huai River, China. It has been shown that the approach considering only model uncertainty or parameter uncertainty could not fully account for uncertainties in quantile estimations, instead, method coupling these two uncertainties should be employed. Furthermore, the proposed Bayesian-based method provides not only various quantile estimators, but also quantitative assessment on uncertainties of flood frequency analysis. © 2011 Springer-Verlag.

Xiao Y.,Hohai University | Liu H.,Hohai University | Chen Y.,Hohai University | Jiang J.,University of Kansas
Journal of Engineering Mechanics | Year: 2014

Density and pressure have great influences on the strength and stress-strain behaviors of rockfill material. A series of triaxial compression tests were conducted for Tacheng rockfill material with different initial consolidated void ratios and initial confining pressures. From the experimental results, Tacheng rockfill material presents behaviors of strain hardening, postpeak strain softening, volumetric contraction, and expansion with a range of densities and pressures. For the sake of simplicity, the critical state line (CSL) is linear in the plane of the mean effective stress versus the deviatoric stress.Asimple expression related to the initial consolidated void ratio was proposed for the CSL of rockfill material in the plane of the void ratio versus the logarithm of mean effective stress. A comprehensive equation incorporating a state parameter is proposed to describe the complex dilatancy behaviors of Tacheng rockfill material with a range of densities and pressures. The stress ratios at the dilatancy and the peak stress ratio states are both formulated as exponential functions of the state parameter. A bounding surface model that incorporates the proposed CSL in both planes of the mean effective stress versus the deviatoric stress and the void ratio versus the logarithm of mean effective stress was established. The model, which has a set of the same model parameters, can well predict the behaviors of strain hardening and volumetric contraction for rockfill material with a loose state or in a high confining pressure and the behaviors of postpeak strain softening and volumetric expansion for rockfill material with a dense state or in a low confining pressure. © 2014 American Society of Civil Engineers.

Liu P.,Hohai University | Yu T.,Hohai University | Bui T.Q.,University of Siegen | Zhang C.,University of Siegen
Computational Materials Science | Year: 2013

We study transient dynamic fracture behaviors of stationary cracked functionally graded piezoelectric materials (FGPMs) under impact loading by using the extended finite element method (X-FEM). The material properties are assumed to be varied exponentially along one direction. A dynamic X-FEM model associated with the stable implicit integration technique is developed to serve that purpose, while the contour interaction integral technique is employed to accurately evaluate the relevant dynamic fracture parameters of FGPMs. Extensive numerical examples with the electrically impermeable crack-face boundary condition are considered, and the dynamic intensity factors (DIFs) obtained by the X-FEM are investigated in details. The accuracy of the developed model is verified by comparing the calculated dynamic responses with the solutions derived form the meshless local Petrov-Galerkin (MLPG) method and the finite element method (FEM), which shows an excellent agreement. The effects of the impact loads, poling direction, material gradation, electric displacements, material gradient coefficients, etc. on the DIFs are investigated in details. We have found that the dynamic crack behaviors in the non-homogeneous FGPMs are much more complicated than those in the homogeneous materials. © 2012 Elsevier B.V. All rights reserved.

Lu J.,Hohai University | Dai H.C.,Hohai University
Advances in Water Resources | Year: 2016

Existence of vegetation plays a significant effect on the flow velocity distributions, turbulence structures and solute mixing in an open channel. This paper has implemented a 3D large eddy simulation model for the flow and scalar transport in the open channel with vegetation. The model can produce a typical turbulence characteristics and concentration distribution with vegetation. The scalar transport mechanism is quantitatively explained by the turbulent Schmidt number, Reynolds flux, coherent structures and quadrant conditional analysis. A dominance of ejection-sweeping events occurs in the process of the momentum and scalar flux transport. The spectral analysis is used to identify the Kelvin–Helmholtz frequency. The turbulence characteristics of the length scale of vortexes, Kelvin–Helmholtz frequency and Reynolds stress etc. are analyzed with the vegetation density. The model quantitatively predicts the trend of decreasing in the concentration distribution along the flow direction with the increasing of vegetation density. © 2016 Elsevier Ltd

Wu Y.,Hohai University | Gao Y.,Hohai University
Journal of Sound and Vibration | Year: 2016

The dynamic response of a double-beam system under the moving oscillator is investigated. The double-beam system is made of two elastic homogeneous isotropic Euler-Bernoulli beams, which are identical, parallel with each other and supported continuously by a foundation of elastic springs provided with viscous damping. The moving oscillator is simplified by the single degree of freedom (SDoF) system. The coupled equations governing the vibration of beams are decoupled by a simple change. Then a state-space equation governing the vibration of both beams and the moving oscillator is established by introducing some state variables, and solved by a single-step scheme. Numerical examples are employed to investigate the effects on the response of some important parameters, such as initial condition of the oscillator, and the mechanical properties of the oscillator and foundation. Some interesting tendencies in the response of beams and oscillator are highlighted. © 2016 Elsevier Ltd

Cheng J.B.,Hohai University | Cheng J.B.,National Key Laboratory for Remanufacturing | Liang X.B.,National Key Laboratory for Remanufacturing | Wang Z.H.,Hohai University | Xu B.S.,National Key Laboratory for Remanufacturing
Journal of Thermal Spray Technology | Year: 2013

In this study, FeBSiNb coatings were prepared by twin wire arc spraying process. The microstructure and mechanical properties of as-sprayed coatings were characterized. The results show that the coating is adhering well and very compact with porosity of 1.2% (the value range is 0.9-1.7%). The microstructure of the coating consists of full glassy structure. The crystallization temperature, microhardness, elastic modulus, and average adhesive strength of the coating are 819 K, 16.42 GPa (the value range is 14.38-18.46 GPa), 219 GPa (the value range is 201-237 GPa), and 57.4 MPa (the value range is 55-64 MPa), respectively. The relatively wear resistance of the coating is about three times than that of 3Cr13 martensite stainless steel coating. The reasons for excellent wear resistance of FeBSiNb metallic glass coating are attributed to a uniform amorphous structure, the high ratio of hardness to elastic modulus (H/E) and the ratio of the elastic deformation energy to the total deformation energy (η value). The main failure mechanism of the coating is brittle failure and fracture. © 2013 ASM International.

Xiao N.,Hohai University
Chemical Engineering Transactions | Year: 2016

Based on the systematic analysis of relevant researches in China and beyond, this paper built the system of Jiangsu province ecological competitiveness evaluation indices. The set pair and entropy methods were adopted to comprehensively analyze the ecological competitiveness of all regions in Jiangsu, leading to the following findings. Firstly, different regions in Jiangsu province differ greatly in the evaluation results of such subsystems as economic growth, social harmony, ecological health and environmental friendliness. Secondly, despite the relatively high level of overall ecological competitiveness, significant differences still exist among regions, with the northern region ranking first, the central ranking second and the southern ranking third. Specifically, Xuzhou has the highest ecological competitiveness and Suzhou's the lowest. Thirdly, such great differences are attributable to the pressure of their distinct natural resources, development paths and industrial structures on the ecological environment to different degrees. © 2016, AIDIC Servizi S.r.l.

Chen J.,Hohai University | Yang Y.,Hohai University
Procedia Engineering | Year: 2011

With the global climate change, drought disasters occur frequently and caused huge economic loss. In this paper, a drought risk assessment model based on fuzzy Analytic Network Process (ANP) method is put forward. ANP is an extension of AHP method and can more reasonably reflect the interdependence between the same layers of evaluation index system. The index system of agricultural drought risk assessment is established. An application is demonstrated by Hunan Province agricultural drought in China from 2007 to 2009. The result shows that the method is effective for agricultural drought risk assessment. © 2011 Published by Elsevier Ltd.

Gu Y.,Hohai University | Fang Y.,Hohai University
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2012

Alkali-activated slag cement (AASC) is distinguished due to its high strength and high durability. However, its great shrinkage and easy-cracking have restricted the application. Some previous studies on the characteristics of the shrinkage and cracking of AASC and the developments on shrinkage-reducing and toughening of the AASC, were reviewed. The issues on the great shrinkage and easy-cracking were discussed. It was proposed that some approaches, i.e., additions of expansive agent, fibers, mineral particle and spray shring kage-reducing agent, could reduce the shrinkage and increase the toughness to prevent the cracking of AASC.

Cheng J.B.,Hohai University | Cheng J.B.,National Key Laboratory for Remanufacturing | Wang Z.H.,Hohai University | Xu B.S.,National Key Laboratory for Remanufacturing
Journal of Thermal Spray Technology | Year: 2012

FeCrBSiNbW coatings were synthesized using robotically manipulating twin wires arc spraying system. The microstructure and mechanical properties of the coating were characterized. The coating has a laminated structure, and its porosity is 2.8%. The microstructure of the coating consists of amorphous and α-(Fe,Cr) nanocrystalline. The nanocrystalline grains with a scale of 20-75 nm are homogenously dispersed in amorphous matrix. The results show that FeCrBSiNbW coating has excellent wear and corrosion resistance. The wear resistance of the coating is about 4.6 times higher than that of 3Cr13 coating under the same testing condition. In 3.5% NaCl aqueous solution, the amorphous/nanocrystalline coating presents lower I corr values in polarization curves and higher fitted R t values in EIS plots than that of the 0Cr18Ni9 coating (chemical composition by EDAX analysis: C1.07-O12.38-Si0.49-Cr15.18-Mn0.89-Ni7.09-Fe62.24 at.%). © 2012 ASM International.

Yang J.,Hohai University | Zeng X.,Hohai University | Zhong S.,Hohai University
Neurocomputing | Year: 2013

The sensitivity of a neural network's output to its inputs' perturbations is an important measure for evaluating the network's performance. To make the sensitivity be a practical tool for designing and implementing Multilayer Perceptrons (MLPs), this paper proposes a general approach to quantify the sensitivity of MLPs. The sensitivity is defined as the mathematical expectation of absolute output deviations due to input perturbations with respect to all possible inputs, and computed following a bottom-up way, in which the sensitivity of a neuron is first considered and then is that of the entire network. The main contribution of the approach is that it requests a weak assumption on the input, that is, input elements need only to be independent of each other without being restricted to have a certain type of distribution and thus is more applicable to real applications. Some experimental results on artificial datasets and real datasets demonstrate the proposed approach is highly accurate. © 2012 Elsevier B.V.

Wang S.,Hohai University | Ren Q.,Hohai University
Science China Technological Sciences | Year: 2012

Damage in the structures alters the structural dynamic behavior. Damage generally occurs locally in the components of structures, and its effect often exhibits in the changes of both local and global characteristics of structures. Better understanding of this relationship helps to monitor and assess the condition of structures and develop dynamics-based structural health monitoring techniques. In this study, the relationship between the local damage and structural dynamic behavior is investigated. To validate the concept, an experiment of a three-dimensional (3-D) steel frame structure with different magnitudes of local damage is illustrated. The experimental results indicate that the change of global resonant response between the intact and damage structure is not obvious. The change of local resonant responses measured near the location of saw-cut crack damage is quite significant. The experimental study conducted indicates that the local resonant responses at the low order resonance can be used as an effective damage identification method to detect and quantify the local damage in the 3D frame structures. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

Yang K.,Hohai University | Yang Q.,Hohai University | Bao Y.,Hohai University
Applied Surface Science | Year: 2013

The present work reports the effect of carbonitride precipitates on the solid/liquid erosion behaviour of hardfacing alloy. Two kinds of Fe-Cr13-C hardfacing alloy (with and without nitrogen) were deposited on a carbon steel substrate. The microstructure of the hardfacing alloy was studied. Solid/liquid erosion tests were carried out with quartz sand particles under impact angles of 30, impact velocity of 25 m/s for 45 min to explore the erosion behaviour of the hardfacing alloy. It is found that the erosion damages of hardfacing alloy were microcutting and impinging caused by the erosion of sand particles. Fine carbonitride precipitates can obviously refine the microstructure and make a dispersion strengthening effect on the matrix, leading to the enhancement of hardness of hardfacing alloy. In addition, lots of carbonitride precipitates can effectively protect the surface of hardfacing alloy against wearing of erosion sand particles. So the erosion resistance of hardfacing alloy could be improved significantly owing to the strengthening and protecting effect of carbonitride precipitates, and solid/liquid erosion mechanisms were found to be microcutting and impinging with shallow grooves, fine pits and tiny lips. © 2013 Elsevier B.V. All rights reserved.

He R.,Hohai University
Soil Dynamics and Earthquake Engineering | Year: 2016

This paper models the rocking vibration of a rigid disc embedded in a visco-poro-elastic seabed, covered by a compressible inviscid seawater half-space. The behavior of water and soil are governed by Euler equations and the Biot[U+05F3]s theory, respectively. The contact surface of the disc with the soil is smooth. The coupled rocking vibration problem is formulated using Helmholtz potentials combined with boundary conditions at the seawater-seabed interface and plane passing through the disc. With the help of integral transforms, the governing dual integral equations are changed to Fredholm integral equations of the second kind. The dynamic impedances for both permeable and impermeable discs are obtained with different embedded depths, soil conditions, and frequencies of excitation. It is found that when the embedded depth is larger than the diameter of the disc, increasing the embedment depth will not increase the rocking impedances any more. © 2016 Elsevier Ltd.

Xue M.-A.,University of Sichuan | Xue M.-A.,Hohai University | Lin P.,University of Sichuan
Computers and Fluids | Year: 2011

A three-dimensional (3-D) numerical model NEWTANK was developed to study viscous liquid sloshing in a tank with internal baffles of different shapes and arrangements. The numerical technique named virtual boundary force (VBF) method was used to model the internal baffles with complex geometries. Laboratory experiments were conducted for non-linear sloshing in a rectangular tank with and without vertical baffle. The numerical model was validated against the measured data together with other available theoretical solutions and numerical results for liquid sloshing under surge and pitch motions. Liquid sloshing in a 3D prismatic tank with different ring baffle arrangements (e.g., height, width, etc.) were further investigated under near-resonant excitations of surge and pitch motions. The fast Fourier transform (FFT) technique was used to identify the dominant response frequencies of the liquid system to external excitations. The effects of ring baffles on reducing violent liquid sloshing were investigated and discussed in detail. Finally, a demonstration of liquid sloshing in the tank under six degree-of-freedom (DOF) excitations was presented. © 2011.

Gao W.,Hohai University
Computational Intelligence and Neuroscience | Year: 2016

Clustering analysis is used in many disciplines and applications; it is an important tool that descriptively identifies homogeneous groups of objects based on attribute values. The ant colony clustering algorithm is a swarm-intelligent method used for clustering problems that is inspired by the behavior of ant colonies that cluster their corpses and sort their larvae. A new abstraction ant colony clustering algorithm using a data combination mechanism is proposed to improve the computational efficiency and accuracy of the ant colony clustering algorithm. The abstraction ant colony clustering algorithm is used to cluster benchmark problems, and its performance is compared with the ant colony clustering algorithm and other methods used in existing literature. Based on similar computational difficulties and complexities, the results show that the abstraction ant colony clustering algorithm produces results that are not only more accurate but also more efficiently determined than the ant colony clustering algorithm and the other methods. Thus, the abstraction ant colony clustering algorithm can be used for efficient multivariate data clustering. © 2016 Wei Gao.

Ni J.,Hohai University | Yang S.X.,University of Guelph
International Journal of Robotics and Automation | Year: 2012

This paper investigates the foraging of multiple robots in completely unknown environments. The onboard robot sensor information and expert knowledge of foraging are used to forage the targets. The foraging problem in this paper is defined as a searching task, where the robots cooperate to find and reach all the targets in an efficient way. A novel fuzzy-logic based chaos genetic algorithm (FCGA) is proposed for target foraging in unknown environments. The fuzzy logic is used to avoid the disorder of the robot movement and reduce the search time when there is no information about the targets or the information density around the robots is the same. The chaos genetic algorithm enables the robots find the targets efficiently. In the proposed approach, the robot motion can be dynamically adjusted to guarantee that all the targets can be found, even in some difficult situations such as targets are at some locations difficult to find or obstacles are linked together. The proposed approach is capable of dealing with uncertainties, e.g., some robots break down. In comparison to the pure chaos genetic algorithm (PCGA) and the random-search approach, experimental results show that the proposed approach is more efficient in foraging all the targets.

Li W.,Hohai University
Applied Mechanics and Materials | Year: 2013

As more and more non-public fund entering rural drinking water safety engineering project market; it becomes very necessary to built rural drinking water safety engineering project guarantee mechanism. This paper proposes three steps of mechanism design. Firstly, history data is used to fit multivariate linear equation set up describing relationship between bank loss and key risk factors. Secondly, guarantee fee is calculated through model regression, which is threefold of possible bank loss. Thirdly, guarantee fee is adjusted according to variety of key risk factor in the process of project construction and operating. © (2013) Trans Tech Publications, Switzerland.

Su H.,Hohai University | Hu J.,Hohai University | Wen Z.,Nanjing Institute of Technology
Journal of Performance of Constructed Facilities | Year: 2013

The 50-year design reference period is coming to an end for many dam projects in China. In the last decade, it has become clear that remaining service life analysis of existing dams must be used to optimally manage the growing number of aging and deteriorating structures. The uncertainties associated with deteriorating dams require the use of probabilistic methods to properly assess their lifetime performance. A dam system involves multiple failure modes; however, conventional assessment and prediction models often neglect the correlations among failure modes. As a result, the remaining service life predicted by these methods is relatively rough. First, in this paper, conventional lifetime distribution functions are introduced. The influences of the correlations among failure modes on series, parallel, or series-parallel structure are discussed, respectively, and the approach for calculating correlation coefficients is proposed. Second, on the basis of the analysis of dam failure causes, failure modes of concrete gravity dams are defined, and the concrete gravity dam is reviewed as a series system with parallel subsystems. Third, the limit state functions for failure modes are given, and quantified progressive deterioration functions for various random variables to describe the aging process of gravity dams are obtained. Based on the correlation analysis and time-varying theory, a prediction model of remaining service life for gravity dam systems is finally proposed. An existing concrete gravity dam is investigated. Failure modes and deterioration mechanisms are studied. The results can be used to better predict the remaining service life of deteriorating dams. © 2013 American Society of Civil Engineers.

Yang G.,Hohai University | Ju J.,Hohai University
Applied Mechanics and Materials | Year: 2013

The construction workers' unsafe behavior is the direct cause of security incidents. Analysis the formation mechanism of construction workers' unsafe behavior from the perspective of behavior psychology,and find out the factors affecting the safe behavior of construction workers,among the factors,the most critical is fostering safe behavior habits. Through the questionnaire survey on the management of the building units in Nanjing and using the SPSS software to conduct the statistical analysis of the four methods of fostering safe behavior habits. The conclusion is that the safe education and training is the most important to foster safe behavior habits. At last,the paper gives the feasible measures combined with foreign experience in safety training mode. © (2013) Trans Tech Publications, Switzerland.

Gu Y.,Hohai University | Chen W.,Hohai University | He X.-Q.,City University of Hong Kong
Computers, Materials and Continua | Year: 2012

This paper applies an improved singular boundary method (SBM) in conjunction with domain decomposition technique to stress analysis of layered elastic materials. For problems under consideration, the interface continuity conditions are approximated in the same manner as the boundary conditions. The multi-layered coating system is decomposed into multiple subdomains in terms of each layer, in which the solution is approximated separately by the SBM representation. The singular boundary method is a recent meshless boundary collocation method, in which the origin intensity factor plays a key role for its accuracy and efficiency. This study also introduces new strong-form regularization formulas to accurately evaluate the origin intensity factors for elasticity problem. Consequently, we dramatically improve the accuracy and convergence of SBM solution of the elastostatics problems. The proposed domain-decomposition SBM is tested on two benchmark problems. Based on numerical results, we discuss merits of the present SBM scheme over the other boundary discretization methods, such as the method of fundamental solution (MFS) and the boundary element method (BEM). Copyright © 2012 Tech Science Press.

Zhong S.-Y.,Zhejiang University | Xu W.-Y.,Hohai University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

Complicated material fabrics are the main factors to control the mechanical characteristics of rock mass; currently the anisotropic problems caused by structural planes are the most hot topics. As a special structure rock mass, the discontinuity and anisotropy of rock mass with columnar joints is very typical. The microstructure can be represented by a second order tensor whose eigenvectors specify the orientation of the axes of material symmetry, which is an effective new method to study structure plane caused anisotropy. Microstructure tensor and loading direction are important parameters for this theory. With projection relation of multiple joint surface between spatial local coordinate system and integral coordinate system considered, microstructure tensor is derived. Using Ψ describes the projection of the microstructure tensor on the loading direction. The modified anisotropic failure criterion, which incorporating a microstructure for columnar joints based on Jaeger proposed for failure along the material fabrics, is used to study anisotropy of the multiple joint surface. Meanwhile, we use it to consider the Baihetan hydropower station columnar joint-project and analyze columnar joint anisotropy caused stability problem.

Peng Z.,Hohai University
Advanced Materials Research | Year: 2014

The article describes and analyzes the process of mass concrete casting and crack problems during the period of construction. The article illustrates the necessity of crack control for mass concrete structures and introduces the present application situation of commercial software used to analyse the temperature field and stress field. Combining the engineering practice, the article sums up the measures to deal with hydraulic mass concrete structure cracks and the application situation of various methods. Then the article puts forward the future research direction to solve the problem of hydraulic mass concrete crack. © (2014) Trans Tech Publications, Switzerland.

Qi L.,Shandong Electrical Power Engineering Consulting Institute Co. | Shi J.-Y.,Hohai University | Hou Q.,Shandong Survey and Design Institute of Water Conservancy
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

As an important part of load transfer behavior and settlement, the research for pile penetration into cushion would improve and perfect the theory of composite ground. There are only few studies of penetration. We analyze the shortcomings of existent calculating methods for penetration, and obtain the more rational method. Finally, this method is compared with the existent methods and model experimental results; it is shown that this method is reasonable and feasible.

Gu P.,Hohai University | Dao M.,Massachusetts Institute of Technology | Zhu Y.,North Carolina State University
Philosophical Magazine | Year: 2014

This paper analyses slip transfer at the boundary of nanoscaled growth twins in face-centred cubic (f.c.c.) metals for strengthening mechanism. The required stress for slip transfer, i.e. inter-twin flow stress, is obtained in a simple expression in terms of stacking fault energy and/or twin boundary (TB) energy, constriction energy and activation volume. For nanotwinned Al, Cu and Ni, inter-twin flow stress versus twin thickness remarkably shows Hall-Petch relationship. The Hall-Petch slope is rationalized for various reactions of screw and non-screw dislocations at the TB. Additionally, strengthening at the boundary of nanoscaled deformation twins in f.c.c. metals is analysed by evaluating required twinning stress. At small nanograin size, the prediction of deformation twin growth stress shows inverse grain-size effect on twinning, in agreement with recent experimental finding. © 2014 Taylor and Francis.

Wu J.-H.,Hohai University | Yuan J.-P.,Hohai University | Lu T.-H.,Hohai University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

Water swelling and drying shrinkage due to moisture change is the expansive soil's characteristic which is similar to the thermal effect of material. Stress is generated by the swell-shrinking deformation constraints and the concept of moisture change stress is put forward. The moisture change stress is adopted to calculate swell-shrinking deformation based on the thermal stress and elasticity theory. A theoretical model which could calculate the moisture change stress resulted from moisture change is established. The mechanism of cracking is the different rates of water loss in different depths which caused the uneven shrinkage deformation. The critical value of moisture change for initial cracking is presented, which is consistent with measured result. The initial depth of expansive soil cracks is put forward by proposed model. The relationship between the depth of initial cracking and soil parameters such as deformation modulus, swell-shrinking characteristics, etc. are discussed in detail.

Fei K.,Hohai University | Fei K.,Yangzhou University | Wang J.-J.,Yangzhou University | Chen Y.,Yangzhou University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

In order to improve the understanding of soil arching effect in the piled embankment, a series of three-dimensional model tests were carried out. The stress reduction ratio and the vertical stress distribution in the embankment fill were studied in detail. Based on the measured and the computed results, the applicability of Terzaghi method and Hewlett & Randolph method were verified. Three-dimensional finite element analysis was also performed in this research; the computed orientation of maximum principal stresses, the stress level and the settlement pattern were analyzed in detail. Based on the test and numerical results, it is found that the value of stress reduction ratio computed by Terzaghi method is closed to that of Hewlett & Randolph method; but the vertical stress distributions of the two methods are different considerably. If the failure surface observed from the numerical result is used, the prediction of vertical stresses using Terzaghi's method is found to be coincident with the measured value.

Cao M.,Hohai University | Cao M.,Hong Kong Polytechnic University | Cheng L.,Hong Kong Polytechnic University | Su Z.,Hong Kong Polytechnic University | Xu H.,Hong Kong Polytechnic University
Mechanical Systems and Signal Processing | Year: 2012

Damage identification using wavelet-transform (WT)-processed vibration signals has been practiced over the years. In most studies, WT was used as an effective signal analysis tool to filter out noise and bring damage-incurred singularities into prominence. In spite of its proven effectiveness, such a processing is often carried out without theoretical footstones sustained by solid mechanics models, which are able to link characteristics of WT with features of damage. In the present work, a multi-scale pseudo-force model over wavelet domain was developed for vibration-based damage identification. By canvassing damage-caused local perturbance to dynamic equilibrium characteristics of a structural component, the underlying hypostasis of the model has explicit physical implication, addressing features of damage (e.g., a slot or a fine crack) and enabling a sophisticated solution to multi-scale modeling and identification of damage. In the model, WT was used as a multi-scale differential operator to acquire higher-order derivatives of equation of motion for characterizing damage of tiny dimension. The multi-scale nature brings additional benefits to enhance robustness of the detection under noisy measurement conditions. Without loss of generality, an EulerBernoulli beam component (EBC) was considered to facilitate understanding of the principle of the model. As proof-of-concept validation, a fine crack in an EBC was quantified using the model through numerical simulation and experiment. Satisfactory results have demonstrated the effectiveness of the model in evaluating fine damage and enhancing tolerance of the detection to measurement noise. © 2011 Elsevier Ltd. All rights reserved.

Jiang J.,Hohai University | Yuan Y.,China University of Mining and Technology
Magazine of Concrete Research | Year: 2013

Variations of temperature and moisture content in concrete arise as the effects of climate load in a natural environment; because it can be easily measured, relative humidity is often used as a transition index reflecting moisture content. Determination of the relationship between moisture content and temperature/humidity in concrete is of great significance in accurate prediction of the durability of reinforced concrete structures. Under constant temperature conditions, measurements of both relative humidity and moisture content in concrete are carried out synchronously. Results show that pore water saturation, considered as the characterisation of moisture content, changes non-linearly with relative humidity in concrete; the evolution is significantly influenced by the water- cement ratio and temperature. Finally, based on experimental results and theoretical analysis, a model of the relationship between pore water saturation, temperature and relative humidity in concrete is established, and its feasibility is verified through an independent test.

Chen X.,Hohai University | Wu S.,Hohai University | Zhou J.,Hohai University
Construction and Building Materials | Year: 2013

An experimental investigation was carried out to generate the mechanical behavior of normal concrete cores with a strength range of 10-50 MPa, including the compressive strength, elastic modulus, strain at peak stress and stress-strain relationships. From several formulations for concrete in this study, it was observed that a conservative estimation of the elastic modulus and strain at peak stress can be obtained from the value of compressive strength. The accuracy of predictions of a number of analytical models available in the literature is discussed. This paper shows the development of a statistical damage mechanics model for concrete at uniaxial loading in compression to ultimate failure. This model is formulated by using Weibull's statistical theory of the strength of materials. The body of heterogeneous concrete material is simulated as a continuum comprising a large population of microscopic "weakest-link" elements. This model provides a good prediction of experimental results in this study. When compared other existing models, it gave better prediction. © 2013 Elsevier Ltd. All rights reserved.

Jiang J.-H.,Hohai University | Yuan Y.-S.,China University of Mining and Technology
Construction and Building Materials | Year: 2013

A long-term test on the steel corrosion in concrete was conducted under the sheltered conditions of a natural climate environment. A synchronous test under the sheltered and unsheltered conditions was performed to determine the microenvironment response and steel corrosion in concrete. The effect of environmental climate on the steel corrosion rate in concrete was further determined. The results show that the steel corrosion rate in concrete fluctuates and is time-dependent under natural climatic conditions. The changes of environmental conditions in the concrete microenvironment are less than those in a natural climate environment, particularly relative humidity. The steel corrosion rate in concrete is directly affected by the microenvironment of concrete, which depends on the random fluctuations of natural climate. Temperature is the primary climatic factor that affects the steel corrosion rate in concrete under an atmospheric environment. The pore water saturation of concrete is also a key factor that causes the differences between the steel corrosion rates in concrete under sheltered and unsheltered conditions. A prediction strategy for the steel corrosion rate in concrete under natural climate is proposed based on the effects of environment on the corrosion rate as well as on the responses of the concrete microenvironment. © 2013 Elsevier Ltd. All rights reserved.

Zhou J.,Hohai University | Chen X.,Hohai University
Journal of Materials in Civil Engineering | Year: 2013

The effects of strain rate on the dynamic stress-strain behavior of cement mortar were investigated in split Hopkinson pressure bar (SHPB) tests; the resulting strain rates ranged from20 to 280 s-1. A total of 39 specimens were subjected to static and dynamic axial compressive loadings. The results showed that cement mortar is a typical strain-rate dependent material. Both dynamic compressive strength and critical strain increased with strain-rate increases. However, there seemed to be no strain-rate effects on the initial elastic modulus of cement mortar. Based on the stress-strain curves of different strain rates, as well as the random statistical distribution hypothesis for strength, a dynamic damage constitutive model of cementmodel under compression was used. The relationships of the primary parameters for strain rate are also presented in this paper. The simulated stress-strain curves matched the experimental results well. The results showed that the strength of cement mortar obeyed a Weibull distribution. © 2013 American Society of Civil Engineers.

Chen X.,Hohai University | Wu S.,Hohai University
Construction and Building Materials | Year: 2013

The effect of water-to-cement ratio (w/c) and age on the pore structure of cement mortar was determined through mercury intrusion porosimetry (MIP). The cement mortar specimens were prepared with w/c of 0.4, 0.5 and 0.6, and were tested at different curing ages (14, 28, 180 days). The degree of hydration of the cement in cement mortar was obtained by determining the non-evaporable water content. Test results have shown that, the degree of hydration increased with increasing curing time and water-to-cement ratio of the cement mortar for the ages of cement mortar varying between 14 and 180 days. An increase in the water-to-cement ratio increases the total porosity. In addition, the existing models of pore size distribution of cement-based materials has been reviewed and compared with test results in this investigation. © 2012 Elsevier Ltd. All rights reserved.

Chen Y.,Coventry University | Chen Y.,Hohai University | Karagiannidis G.K.,Aristotle University of Thessaloniki | Lu H.,Hohai University | Cao N.,Hohai University
IEEE Transactions on Vehicular Technology | Year: 2012

A novel analytical framework for evaluating the statistics of the product of independent random variables is proposed. Compared with other methods, which use either infinite series or special functions, the new method provides simple and efficient closed-form approximations, in terms of elementary functions, such as powers and exponentials. Numerical results, which are used to check the accuracy of the new approximations, show that it is quite accurate in most regions of interest. As an application, the proposed analytical results can be efficiently used in wireless communications theory to evaluate in closed form the outage probability of cascaded fading channels, as well as the rate offset of the hybrid automatic repeat request (H-ARQ) transmission. Numerical examples show that the derived expressions provide significant insights on the behaviors of important system parameters as the outage probability and the rate offset. © 2011 IEEE.

Gong Y.-B.,Hohai University
Kongzhi yu Juece/Control and Decision | Year: 2012

The multi-attribute decision making problem is studied, in which the information on alternatives preference is given, attribute weights are unknown partly and the attribute values are given in the forms of triangular fuzzy numbers. Two decision methods are proposed, one is the fuzzy proportional value decision method, and the other is the degree of fuzzy deviation decision method. By using two methods, two linear programming models are established firstly, and the attribute weights are derived by solving two models. And then based on a possibility degree formula for comparing two triangular fuzzy numbers and a formula for priorities of triangular fuzzy numbers, the decision alternatives are ranked. Finally, a numerical example shows the feasibility and effectiveness of the two methods.

Ji X.,Hohai University | Zhao J.,Hohai University | Zhang X.,Hohai University | Zhou M.,Hohai University
Tribology International | Year: 2013

Bulk metallic glass (BMG) is supposed to have a good erosion-corrosion (E-C) resistance due to its high hardness and good corrosion resistance. To reveal the E-C behavior, Zr55Cu30Ni10Al 5·BMG is investigated using a slurry pot erosion tester. Experimental results show the volume loss rate of BMG increases with an increase in the particle size, sand concentration or impact velocity. The corrosion current density and the synergism rate increase with the increasing impact velocity. During E-C process, the surface microstructure transforms gradually from pure amorphous to composite mixture of crystalline and amorphous phases. The E-C resistance of BMG is better than that of 304 stainless steel, but not as expected as its high hardness. Crown Copyright © 2012 Published by Elsevier Ltd. All rights reserved.

Jiang L.,Hohai University | Song Z.,Hohai University | Yang H.,Hohai University | Pu Q.,Hohai University | Zhu Q.,Hohai University
Construction and Building Materials | Year: 2013

The rapid chloride migration test is widely used in estimating the diffusivity of cement-based material. However, the concentration profile predicted in the conventional method was found different from the realistic one. In this paper, the current models attempting to describe the concentration profile are introduced. Experimental test is carried out to found the realistic concentration profile. A system of general Poisson-Nernst-Planck (PNP) equations is formed by considering the influence of electrophoreses, relaxation, etc. A new model is built up based on the general PNP equations and a hypothesis of pore structure to explain the realistic concentration profile. A semi-empirical model is simplified from the new model according to the experimental evidence. And the semi-empirical model is applied to analyze the influence of source concentration on the chloride penetrability. © 2012 Elsevier Ltd. All rights reserved.

Chen X.,Hohai University | Wu S.,Hohai University | Zhou J.,Hohai University
Construction and Building Materials | Year: 2013

The compressive, flexural and splitting tensile strength of cement mortar has been measured and interpreted in terms of its porosity. The authors first reviewed the existing porosity-strength relationships (Ryshkewithch, Schiller, Balshin and Hasselman model) and assessed the suitability of existing relationships. The Zheng model for porous materials has been used to evaluate the porosity-strength relationship of cement mortar. Over the porosity ranges examined, the extended Zheng model is good representation of the experimental data on the strength of cement mortar. Based on the generality of the assumptions used in the derivation of the extended Zheng model, this model for cement mortar can be applied for other cement-based materials. The experimental data also show that the ratio between compressive strength and indirect tensile (splitting tensile and flexural) strength of cement mortar is not constant, but is porosity dependent. The ratio decreases with increase porosity values of cement mortar. © 2012 Elsevier Ltd. All rights reserved.

Cheng J.B.,Hohai University | Cheng J.B.,Academy of Armored force Engineering | Liang X.B.,Academy of Armored force Engineering | Wang Z.H.,Hohai University | Xu B.S.,Academy of Armored force Engineering
Tribology International | Year: 2013

The wire arc spraying process was used to prepare FeB-based metallic glass coating and 3Cr13 coating. The effects of wear parameters, such as sliding distance, linear speed and normal loads, on the wear performances of the coatings were analyzed in detail. The results showed that, with increase in sliding distance, linear speed and normal loads, the volume losses of the metallic glass coatings increased. The relationships between wear behavior and microstructure of the coatings were discussed. The metallic glass coating had excellent wear resistance. The relatively wear resistance of the metallic glass coating was about 2.6 times that of the 3Cr13 coating under the same testing conditions. The main failure mechanism of the metallic glass coating was brittle failure and fracture. © 2012 Elsevier Ltd.

Gou X.,Hohai University | Shen Q.,Hohai University
Physica C: Superconductivity and its Applications | Year: 2012

An analysis model of the bending strain dependence of the critical current in multifilamentary Bi2223/Ag composite tapes is presented. To investigate the effect of the mechanical properties of the Bi2223 superconducting filament, the actual part for carrying current, its damage stress and elastic modulus are introduced. The calculated result of the variation of the critical current with the bending strain is well agreed with the experimental one. The further studies find that the mechanical properties of the filament have a remarkable effect on the bending strain dependence of the critical current. Specifically, the larger the damage stress and elastic modulus of the filament are, the higher the critical current is, when the bending strain increases to a larger value beyond the critical one. © 2012 Elsevier B.V. All rights reserved.

Jin P.,Hohai University
2015 IEEE International Magnetics Conference, INTERMAG 2015 | Year: 2015

This paper presents a three-dimensional (3-D) analytical magnetic field analysis of an air-cored axial flux Halbach permanent-magnet machine (AFPMM with Halbach). The 3-D analytical magnetic distribution is established using the magnetic scalar potential and modified BESSEL functions in the cylindrical coordinate system. The analytical magnetic field distributions and electromagnetic force are derived and verified by the computational results using finite element method. © 2015 IEEE.

Wei L.,Hohai University
Advanced Materials Research | Year: 2013

The project of rural drinking water safety project mainly involves three types of investors as the government, market investors and farmers. Starting from the behavioral characteristics of the investors, using game method of symmetric information and asymmetric information, this paper constructs mathematical model describing decision-making process through game between government and farmers, government and market investors and central government and local government in rural drinking water safety project. © (2013) Trans Tech Publications, Switzerland.

Zhang J.,Hohai University | Wang Z.,Hohai University | Lin P.,Huazhong University of Science and Technology
Surface Engineering | Year: 2013

Plasma-sprayed Cr2O3-8 wt-% TiO2 coatings were deposited on mild steel and sealed by epoxy resin and silicone resin in different processes. The microstructure and corrosion resistance of all coatings were investigated. The results showed that silicone resin sealant can seal the coating well and 91% of interconnected porosity was blocked. The sealant can penetrate into the coating by more than 280 μm. The coating sealed with silicone resin in vacuum conditions had the highest corrosion potential E corr (-375 mV) and lowest corrosion current density icorr (17 mA m-2) in electrochemical tests. Correspondingly, the unsealed coating had the lowest Ecorr and highest icorr. The corrosion resistance of the coatings was in the following order: coating sealed with silicone resin in vacuum>coating sealed with silicone resin in air>coating sealed with epoxy resin in vacuum>coating sealed with epoxy resin in air>unsealed coating. © 2013 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute.

Wu S.,Hohai University | Chen X.,Hohai University | Zhou J.,Hohai University
Nuclear Engineering and Design | Year: 2012

This paper presents a comparative experiment and analysis of three different methods (direct tension, splitting tension and four-point loading flexural tests) for determination of the tensile strength of concrete under low and intermediate strain rates. In addition, the objective of this investigation is to analyze the suitability of the high stressed volume approach and Weibull effective volume method to the correlation of the results of different tensile tests of concrete. The test results show that the strain rate sensitivity of tensile strength depends on the type of test, splitting tensile strength of concrete is more sensitive to an increase in the strain rate than flexural and direct tensile strength. The high stressed volume method could be used to obtain a tensile strength value of concrete, free from the influence of the characteristics of tests and specimens. However, the Weibull effective volume method is an inadequate method for describing failure of concrete specimens determined by different testing methods. © 2012 Elsevier B.V.

Fan X.D.,Hohai University | Men H.,Ningbo Institute of Materials Technology and Engineering | Ma A.B.,Hohai University | Shen B.L.,Ningbo Institute of Materials Technology and Engineering
Journal of Magnetism and Magnetic Materials | Year: 2013

The dependence of Cu addition on magnetic properties of Fe 84-xB 10C 6Cu x nanocrystalline alloys prepared by annealing the melt-spun amorphous ribbons was investigated. It was found that the coercivity (H c) of the nanocrystalline Fe 84-xB 10C 6Cu x alloys decreased with increasing Cu addition and exhibited a minimum value with composition of x=1 after appropriate annealing, while the saturation magnetic flux density (B s) shows an increasing trend owing to the increasing volume fraction of nanocrystalline phase. And the alloy with composition of x=1 exhibits excellent magnetic properties, i.e., high B s of 1.78 T, low H c of 5 A/m and low core loss (P) of 0.34 W/kg at 1 T and 50 Hz. © 2012 Elsevier B.V.

Jiang T.,Hohai University | Shao J.F.,Hohai University | Shao J.F.,Lille University of Science and Technology | Xu W.Y.,Lille University of Science and Technology | Zhou C.B.,Wuhan University
International Journal of Rock Mechanics and Mining Sciences | Year: 2010

Induced anisotropic damage and related permeability variation in brittle rocks are investigated. Triaxial compression tests with permeability measurement are first performed. It is found that the permeability can significantly increase with the growth and coalescence of microcracks. The permeability change can be related to the density and opening of microcracks. Based on various experimental evidences, a micromechanics-based damage model is proposed for the description of anisotropic damage. This model takes into account unilateral effects and frictional sliding in closed microcracks. The normal opening of microcracks generated by the frictional sliding due to the roughness of crack surface is also considered. The overall permeability of cracked medium is estimated by the volumetric averaging of the local permeability in microcracks, which is described by an extended cubic law. Comparisons between numerical predictions and experimental data are presented for different mechanical and hydromechanical tests. © 2010 Elsevier Ltd.

Lu Y.,Hohai University | Li J.,Hohai University
Journal of Networks | Year: 2010

In this paper, we introduce a new asymmetric encryption paradigm called Forward-Secure Certificate-Based Encryption. It preserves the advantages of certificate-based encryption (CBE) such as implicit certificate and no private key escrow. At the same time it also inherits the properties of the forward-secure public key encryption. In a forward-secure CBE scheme, all users' private keys are updated at regular periods throughout the lifetime of the system; exposure of a user's private key corresponding to a given time period does not enable an adversary to break the security of the ciphertext sent to this user for any prior time period. We first provide the formal definition for forward-secure CBE and its security model. Then we propose a generic construction of forward-secure CBE and prove it to be secure against chosen plaintext attacks in the standard model. We also describe how this construction can be enhanced to achieve security against adaptive chosen-ciphertext attacks both in the standard model and in the random oracle model. Finally, a concrete forward-secure CBE scheme is constructed. © 2010 ACADEMY PUBLISHER.

Gong Y.,Hohai University
Journal of Intelligent and Fuzzy Systems | Year: 2014

Fullér and Majlender (Fuzzy Sets and Systems 136 (2003) 363-374) introduced the notation of weighted interval-valued possibilistic mean value of fuzzy numbers and investigate its relationship to the interval-valued probabilistic mean. In this paper, we introduce the new notation of lower and upper weighted magnitude mean values of a fuzzy number. The new interval-valued weighted magnitude mean and variance are defined, which differs from the one given by Fullér and Majlender. We will show the relationship of interval-valued weighted magnitude mean and interval-valued weighted possibilistic mean. Furthermore, we shall also introduce the notations of crisp weighted magnitude mean value, variance and covariance of fuzzy numbers, which are consistent with the extension principle. Finally, some comparative examples are used to illustrate the advantage of the proposed weighted magnitude mean value and variance method to order fuzzy numbers. © 2014 - IOS Press and the authors.

Wei Z.-N.,Hohai University | Xie T.-M.,Hohai University | Sun G.-Q.,Hohai University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

There are measurements of the wide area measurement system (WAMS) and supervisory control and data acquisition (SCADA) available for power system nowadays. This paper presents a new linear dynamic state estimation (DSE) algorithm in rectangular coordinates. Branch power and node injection power measurements of SCADA system were transformed to equivalent current phasor measurements to mix with the measurements of WAMS. The high-precision ultra-short term load forecasting and load flow were used to realize the real-time tracking of state prediction. This algorithm considerably reduces the time for calculation and improves the accuracy of computation. Test results of the application of this algorithm in IEEE 14-bus test system were presented to show the effectiveness of the proposed algorithm. © 2010 Chin. Soc. for Elec. Eng.

Zhang X.-H.,Hohai University | Zhao J.-Q.,Hohai University | Chen X.-Y.,Hohai University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

It is necessary to cut green house emission and develop energy-saving and emission-reducing in power generation scheduling. A multi-objective unit commitment model was presented. Primary energy consumption costs, sulfur dioxide and carbon emission reducing were synthetically considered. Every objective function was fuzzied through defining objective membership function, then this multi-objective optimization problem was reformulated into a single objective nonlinear programming problem by means of the fuzzy satisfaction maximum-minimum technique. Genetic algorithm was used to solve it. The simulation results of a 10 unit system demonstrate that the proposed multi-objective unit commitment model can take energy saving and the emission reduction of sulfur dioxide into account. At the same time, the emission of carbon dioxide is greatly cut. It is important for controlling the green house effect, developing low carbon power production and realizing sustainable development strategy. © 2010 Chin. Soc. for Elec. Eng.

Fang H.-Q.,Hohai University | Chen L.,Hohai University | Li X.-M.,Hohai University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

The differential equations of the closed-loop system with proportional-integral-derivative (PID) control law for hydro turbine regulating system based on linear model, as well as nonlinear model were deduced, respectively. Then, the integral of time multiplied by the absolute value of error (ITAE) performance criterion of hydro turbine speed relative error was applied as fitness function of particle swarm optimization (PSO) algorithm to optimize tuning hydro turbine governor PID gains based on different mathematical models. The calculating results indicate that PSO algorithm can effectively optimize the control parameters for nonlinear control system. Additionally, the optimized PID gains are different between linear model and nonlinear model. The results are relatively better if the nonlinear model is applied. © 2010 Chin.Soc.for Elec.Eng.

Zheng D.,Hohai University | Yuan J.,China Yangtze Power Co Ltd
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2012

Choosing the least points to monitor hydraulic structure behavior is the hard core of hydraulic structure safety monitoring design. In this work, spatial monitor-value sample of hydraulic structure and its typical curve surface, such as monitor-value curve surface, are obtained first, using FEM analysis result of the structure. Then this surface is divided into several parts, through cluster analysis and principal component analysis on the spatial character of hydraulic structure monitor value, and each part is assigned one monitoring point to represent its regional safety behavior of the entire structure. Finally, monitoring point layout of hydraulic structure safety is optimized and its assessment method is established based on B-spline surfaces and modeling error theory. Engineering case studies show that the optimization method, a new approach for optimizing monitoring points layout, is effective and practical. © right.

Chen Z.,Hohai University
2015 IEEE International Magnetics Conference, INTERMAG 2015 | Year: 2015

Permanent-magnet (PM) synchronous machine nowadays has been widely used in industrial applications due to its high efficiency, power factor and torque density [1]. However, torque ripple is a major concern in applications where speed and position accuracy is great important. It is supposed to be a constant value, if the back-EMF and armature current are both ideal sinusoidal waves. In actually, neither of them is ideal sinusoidal because of the distributions of poles/slots and the nonlinear characteristics of power electronic devices. © 2015 IEEE.

Aimin Y.,Hohai University | Yuli D.,Harbin Institute of Technology | Litang G.,Qingdao Technological University
Fire Safety Journal | Year: 2013

This paper presents the results from four three-span unbonded prestressed continuous concrete slabs that were 12.6 m×1.5 m×0.12 m in size. The tests were designed to show the effect of the negative reinforcement length in the zone of negative moment and the influence of the sequence of the middle span and the edge span exposure to fire. Based on the standard temperature-time curve (ISO 834) used in the test, the processes involving water and cracks in the slabs were described. After the analysis, the deformation, the mechanism of the failure mode, the regularity of the prestressing and the force redistribution of the support were investigated. The study demonstrated that the failure mode of a slab under fire is mainly due to tensile fracture of the concrete and tendons. The sequence of spans under fire and the length of negative reinforcement have important effect on the deformation and the failure mode. Different lengths of negative reinforcement lead to destructive hinge presence at the different position. The presence of cracks and is attributed to the thermal bowing action and stiffness redistribution. The crack extending to the top surface along the tendons is the effect of tensile splitting due to the lower temperature in the tendon. The reinforcment perpendicular to the trajectory of the tendon should be laid out and the minimum steel ratio 0.2% is recommended. The support force redistribution is attributed to the structural system change, which is caused by the fracture of the concrete and tendon under fire. © 2012 Elsevier B.V. All rights reserved.

Li C.,Hohai University | Ren H.,Nanjing University | Xu M.,Hohai University | Cao J.,Hohai University
Bioresource Technology | Year: 2015

Denitrifying MFC was successfully coupled with anaerobic ammonium oxidation process in this study. With the help of cathode electrons, the stoichiometry relationship δ-NH3-N:δ-NO2 --N:δ+NO3 --N was approximate 1:1.37:0.03 during the stable operation, which demonstrated its further nitrite and nitrate reduction. According to microbial community analysis, Candidatus Brocadia sinica was the main anammox community, and Rhodopseudomonas palustris with electrochemical driven denitrifying ability, especially enriched in biofilm. Higher abundance of nirK genes in biofilm (compare to the control) and invariable amx genes in suspended sludge were responsible for its better nitrogen removal. The sludge and biofilm performed their own duties on anammox and denitrification, respectively, according to genes quantification. Under the totally autotrophic system, electron donors were "concentrated supplied" and easy to control, which avoided the suppression of anammox growth, making this autotrophic coupling process appears to be more promising. © 2014 Elsevier Ltd.

Wang H.,Dalian Ocean University | Li J.,Hohai University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

When the clients store their data in public cloud, the stored data is out of their control. In order to ensure the remote data integrity, the remote data integrity checking (RDIC) is indispensable. In order to overcome the certificate management problem in PKI and the key escrow problem in identity-based setting, we propose a novel remote data integrity checking model, i.e., certificate-based remote data integrity checking (Cert-RDIC). This paper formalizes the private Cert-RDIC model which consists of system model and security model. Then, this paper presents the first private Cert-RDIC protocol whose security is based on the hardness of the standard computational Diffie-Hellman (CDH) problem. Our concrete private Cert-RDIC protocol can also be transformed into public Cert-RDIC protocol. At the same time, by using our proposed private Cert-RDIC protocol, the malicious clients can also be detected by the public cloud servers (PCS). © Springer International Publishing Switzerland 2015.

Lu X.,Water Resources University | Lu X.,Hohai University | Jin M.,Water Resources University | Van Genuchten M.T.,Federal University of Rio de Janeiro | Wang B.,Water Resources University
Ground Water | Year: 2011

Accurate estimates of groundwater recharge are essential for effective management of groundwater, especially when supplies are limited such as in many arid and semiarid areas. In the Hebei Plain, China, water shortage is increasingly restricting socioeconomic development, especially for agriculture, which heavily relies on groundwater. Human activities have greatly changed groundwater recharge there during the past several decades. To obtain better estimates of recharge in the plain, five representative sites were selected to investigate the effects of irrigation and water table depth on groundwater recharge. At each site, a one-dimensional unsaturated flow model (Hydrus-1D) was calibrated using field data of climate, soil moisture, and groundwater levels. A sensitivity analysis of evapotranspirative fluxes and various soil hydraulic parameters confirmed that fine-textured surface soils generally generate less recharge. Model calculations showed that recharge on average is about 175 mm/year in the piedmont plain to the west, and 133 mm/year in both the central alluvial and lacustrine plains and the coastal plain to the east. Temporal and spatial variations in the recharge processes were significant in response to rainfall and irrigation. Peak time-lags between infiltration (rainfall plus irrigation) and recharge were 18 to 35 days in the piedmont plain and 3 to 5 days in the central alluvial and lacustrine plains, but only 1 or 2 days in the coastal plain. This implies that different time-lags corresponding to different water table depths must be considered when estimating or modeling groundwater recharge. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

Jiang Q.,Hohai University | Cheng H.,North China University of Technology | Chen J.,Jiangyin Peoples Government Key Project Construction Office
Modern Tunnelling Technology | Year: 2013

The fact of large-diameter slurry shield construction related to problems of high ground losses (caused by low cutting face pressures and high grouting pressures) is not sufficiently considered in transverse settlement trough theory. Therefore, a modified formula for the GAP parameter is proposed. Using the construction of the Chengjiang west road river-crossing tunnel in Jiangyin City as an example, a modified GAP parameter was incorporated into the modified Peck formula and the analytical solution based on the Sagseta theory in order to study the influence of large-diameter slurry shield construction on soft soil. It was verified that due to the equivalent ground losses caused by factors such as construction quality, under-pressure of the cutting face, and high grouting pressures, calculated settlements are larger, but are more consistent with the measured data and more reasonable theoretically.

Li J.,Dalian University of Technology | Li J.,Hohai University | Wang Z.,Dalian University of Technology | Liu S.,Dalian University of Technology
Coastal Engineering | Year: 2012

A wave basin experiment has been performed to investigate the interactions between multi-directional focused wave and vertical bottom-mounted cylinder. In this paper, a study on wave run-up on a vertical bottom-mounted cylinder is presented. For all experimental cases, the ratio of the water depth and cylinder diameter ratio (d/D) is equal to 2.0 and the ratio of the wave height and water depth (2. A/d) is varied in the range of (0.12, 0.60), where A is the focused amplitude. The experimental results showed that the focused wave parameters, including wave steepness, frequency bandwidth, and directional spreading index, had significant impacts on the wave run-up on a cylinder. More specifically, the focused wave run-up increased as these parameters increased, and the maximum value of the measured wave run-up ratio could be as high as 1.68. The variations of the multi-directional focused wave run-up around the cylinder were also analyzed. The wave run-up at the front of the cylinder was greater than that at the other positions around the cylinder. The wave run-up reached the lowest values at 135°. The associated focused wave parameters also impacted the wave run-up distribution around the cylinder. © 2012 Elsevier B.V.

Di S.-J.,Hohai University | Xu W.-Y.,Hohai University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

Based on the sliding plane hypothesis of Coulumb's earth pressure theory and the Culmann's graphical construction for the active earth pressure of non-cohesive soil, a new method to calculate the active earth pressure of cohesive soil is derived considering the cohesion force on the sliding surface and the adhesive force on the interface of retaining walls. The assumption of sliding surface for programming is employed to obtain the active earth pressure and the sliding plane angle. Using programming language design, the procedures are developed. The calculated results show that the proposed method is of simple principle and high precision. It can be easily popularized and applied in projects.

Zhang G.-K.,Ertan Hydropower Development Co. | Xu W.-Y.,Hohai University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

The deformation of rock mass is considered as the summation of the linear elastic deformation of intact rock block and nonlinear elastic deformation of joints. On the basis of deformation characteristics of joints, a new constitutive model for normal displacement of joints is presented. It considers the influence of the initial stress state on the deformation. The computation method for jointed rock mass equivalent strain is studied by use of the joint network and the theory of equivalent continuous strain. According to the elastic orthotropic constitutive model, the rock mass is regarded as orthotropic continuous material, and the orthotropic equivalent deformation parameters are computed. The computation codes of orthotropic equivalent deformation parameters are developed. The example verification is carried out to test the rationality of the analytic results and the codes.

Ni L.,Hohai University | Ni L.,Desert Research Institute | Acharya K.,Desert Research Institute | Hao X.,Shanxi Luan Engineering Investigation and Design Co. | Li S.,Nanjing Normal University
Chemosphere | Year: 2012

The goals of this work were to isolate and identify an anti-algal compound from extracts of Artemisia annua and study its mode of action on Microcystis aeruginosa. The anti-algal compound was isolated from the extracts using column chromatography and activity-guided fractionation methods. Artemisinin with strong anti-algal activity was identified by gas chromatography-mass spectrometry and 1H Nuclear Magnetic Resonance. The EC50 of artemisinin on M. aeruginosa was 3.2mg L-1. Artemisinin decreased the soluble protein content and increased the superoxide dismutase activity and ascorbic acid content of M. aeruginosa, but exerted no effect on soluble sugar content. The results suggested the mode of action of artemisinin on algae may primarily be the increasing level of reactive oxygen species in algae cells. The results of our research could aid in the development of new anti-algal substances and lead to further study of mechanisms of inhibitory effect on algae. © 2012 Elsevier Ltd.

Zhang K.-Y.,Hohai University | Wang Y.,City University of Hong Kong | Ai Y.-B.,Hohai University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

A kind of closed-form analytical solution to the interaction between pipelines and soils induced by nearby excavation process is presented. It is suitable for describing any kinds of displacement profile caused by various excavation processes, including tunnels, trenches and many other excavation projects. As the typical application, the effects on pipelines of ground settlement induced by tunneling are evaluated by the proposed analytical solutions and computer techniques. The analytical results are compared with finite element method solutions based on ABAQUS PSI elements, which are proved to be effective and convenient to describe the interaction between pipelines and nearby soils. There is very good agreement between the suggested closed-form solution and FEM results. The efficiency of the proposed closed-form analytical solution is validated.

Xu F.,Hohai University | Xu W.-Y.,Hohai University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

Rock burst is one of the main engineering geological hazards of underground rock engineering in deep high ground stress zone. The prediction of rock burst intensity is a complex systematic problem of uncertainty. Based on the projection pursuit (PP), the particle swarm optimization (PSO) and the logistic curve function (LCF), a new model for rock burst prediction is developed, which is referred to as projection pursuit based on particle swarm optimization (PSO-PP). The ratio of the maximum tangential stress of the cavern wall to the uniaxial compressive strength, the brittleness coefficient and the elastic energy index of rock are regarded to as the discrimination indices of PSO-PP. The model, on the one hand, uses the PSO to optimize the projection index function and the parameters of LCF so as to ensure the accuracy of the parameters used in the model. On the other hand, the nonlinear relationship between projection values and empirical grades is established according to LCF. The test results of the model show a very good precision. In this study, the prediction results obtained by applying the developed model to Qinling Tunnel and Dongguashan Mine are well consistent with the practical situation. It indicates that the model is feasible and effective for rock burst prediction.

Xu H.,Hohai University | Feng J.,Hohai University | Li S.,Hohai University
Automation in Construction | Year: 2014

In the last decade, building information modelling (BIM) has emerged as one of the most powerful dynamic decision-making tools throughout a project lifecycle, as its encapsulated information synchronises with construction practices. Many reports indicate that BIM has entered the mainstream use in some countries. However, BIM has experienced slow and limited spread adoption in other countries. We propose a comprehensive research model to examine the factors that influence the adoption of BIM. The model draws on technology acceptance model and innovation diffusion theory and is validated using survey data from the construction industry in China. The findings demonstrate that attitude, technological, and organisational dimensions indirectly affect the actual use of BIM through perceived usefulness (PU) and perceived ease of use (PEU), with PU and PEU being the primary determinants of BIM adoption. Furthermore, a striking finding was the positive influence of the attitude dimension on the actual use of BIM. © 2013 Elsevier B.V.

Tian Z.,Hohai University | Bian C.,Hohai University
KSCE Journal of Civil Engineering | Year: 2014

An integrated visual monitoring system to determine trajectory and duration on each vibrating motion of vibrator during concrete placed on construction site was introduced, which could graphically display vibrating status of fresh concrete. Defects on concrete placing process such as missed vibration, insufficient vibration, or excess vibration could be quantifiably assessed, and therefore, precise and suitable remedy could be offered timely. The system consisted of four functional parts, namely, vibrating trajectory spatial coordinate collected subsystem, vibrating duration-collected subsystem, data process subsystem, and real-time display and assesses subsystem of vibrating status. The principle of operation was explained in this article. Firstly, accurate signals combined spatial coordinates were achieved by dual-satellite systems, e.g., GPS (Global Position System) and GLONASS (Global Navigation Satellite System), with RTK (Real Time Kinematics) mode and, duration of each vibration from start to end was determined by electrode device, respectively. Secondly, the wireless signals were sent to the terminal computer via MCC (Mono-Chip Computer) integrated. Finally, the worked status of vibrator on terminal was displayed simultaneously supported by assessment programm on compacting concrete. Tests results from outdoor and application in-situ proved that the system could monitor the vibration process in real-time reliably and quantifiably while fresh concrete was placed, and an innovative informationaized method might be realized. © 2014 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.

Gao J.,Hohai University | Xu L.,Hohai University
AEU - International Journal of Electronics and Communications | Year: 2014

Remote sensing image classification is different to identify the best classification model due to lack of a suitable classification method. Most traditional approaches only focused on using the spectral or spatial information to train classification model. However, these methods may ignore the related information of the image-itself. Remotely data not only a mere collection of independent and identically distributed pixels. Therefore, an efficient classification method is introduced in this paper. The proposed method deals with the information provided by the remote sensing image. Based on the idea of fisher linear discriminant analysis (FLDA), a definition of the same areas and different areas are considered in images, the information of same areas associated with each pixel is modeled as the within-class set, and the information of different areas associated with mean pixel of each same areas is modeled as the betweenclass set. Therefore, a projection matrix (PM) can be obtained by using within-class and between-class sets with the help of FLDA criterion. Then the PM is jointly used for the classification through a support vector machine (SVM) or K-nearest neighbor (KNN) classifiers formulation. Experiments on two remote sensing images are performed to test and evaluate the effectiveness of the proposed method. © 2014 Elsevier GmbH.

Zhang Z.,Hohai University | Wang X.,Hohai University | Fan T.,Nanchang Institute of Technology | Xu L.,Hohai University
Flow Measurement and Instrumentation | Year: 2013

Large-Scale Particle Image Velocimetry (LSPIV) is an image-based technique for nonintrusive streamflow monitoring, where the visibility of flow tracers is one of the main limitations to its application in field conditions. Based on the target characteristics of flow tracers as well as the optical environment of river surface, the paper presents a target enhancement and background suppression method that innovatively combines near-infrared (NIR) imaging and spatial high-pass filtering (SHPF) to solve the above problem. An NIR smart camera was developed as the experimental instrument for image acquisition and preprocessing. Three sets of evaluations were performed at pixel-level, feature-level and vector-level. Results show that the NIR imaging not only enhances the contrast between targets and background, but also improves the peak signal-to-noise ratio (PSNR) of correlation plane in motion vector estimation. Moreover, the SHPF effectively suppresses the river background and strong noises, and consequently increases the percentage of correct vectors in the instantaneous flow field. Due to its strong operability, this method offers promising potential for the unseeded LSPIV. © 2013 Elsevier Ltd.

Jiang Y.,Hohai University | Fan H.,Hohai University
Computational Materials Science | Year: 2013

In this paper, a simple micromechanics model has been developed for predicting the effective stress-strain relations of filled elastomers. The present model constitutes of the instantaneous Young's modulus and Poisson's ratio characterizing rubber-like material, a double-inclusion configuration taking account of the absorption of rubber chains onto carbon-black (CB) particles, and the incremental Mori-Tanaka method to compute the effective stress-strain curves. The subsequent predictions are capable of reflecting the well-known S-shape of hyper-elastic composites, and verified via the comparison to the available experiments and analytical models. Parametric analysis is fatherly conducted on the microstructure effect. © 2011 Elsevier B.V. All rights reserved.

Jiang C.,Hohai University | Fan K.,Hohai University | Wu F.,Hohai University | Chen D.,Hohai University
Materials and Design | Year: 2014

With high ductility and sufficient durability, fibre reinforced concrete (FRC) is widely used. In this study, the effects of the volume fraction and length of basalt fibre (BF) on the mechanical properties of FRC were analyzed. Coupling with the scanning electron microscope (SEM) and mercury intrusion porosimeter (MIP), the microstructure of BF concrete was studied also. The results show that adding BF significantly improves the tensile strength, flexural strength and toughness index, whereas the compressive strength shows no obvious increase. Furthermore, the length of BF presents an influence on the mechanical properties. Compared with the plain concrete, the compressive, splitting tensile and flexural strength of concrete reinforced with 12. mm BF increase by -0.18-4.68%, 14.08-24.34% and 6.30-9.58% respectively. As the BF length increasing to 22. mm, corresponding strengths increase by 0.55-5.72%, 14.96-25.51% and 7.35-10.37%, separately. A good bond between the BF and the matrix interface is observed in the early age. However, this bond shows degradation to a certain extent at 28. days. Moreover, the MIP results indicate that the concrete containing BF presents higher porosity. © 2014 Elsevier Ltd.

Tan X.,Hohai University
African Journal of Microbiology Research | Year: 2011

Effects of temperature on phytoplankton recruitment and variations in phytoplankton community were studied by using hiemal sediment from Taihu Lake and performing a simulation experiment. Sediment samples were cultured in filtered lake water with elevated temperatures. Recruitment patterns and photosynthetic capacity of cyanobacteria, chlorophytes and diatoms were recorded, respectively. Results showed that recruitment of chlorophytes and diatoms was observed above 9°C, but recruitment of cyanobacteria was not evidently detected until 12.5°C. Chlorophytes dominated the phytoplankton community at 12.5 and 16°C, subsequently cyanobacteria established dominance above 19.5°C. In this study, algal cells remained weak photochemical vitality at lower temperatures before recruitment, which reactivated and increased gradually with elevated temperatures. © 2011 Academic Journals.

Liang Y.,Hohai University | Chen W.,Hohai University
International Journal of Damage Mechanics | Year: 2016

This paper aims to develop a regularized Miner's rule to assess the fatigue reliability of composites in conjunction with the Mittag-Leffler Monte Carlo method. The proposed strategy is validated by analyzing experimental data to investigate the fatigue reliability of carbon fiber/epoxy composites under different stress amplitudes. The estimated results are feasible for preliminary analysis at the design stage. The regularized Miner's rule, a scale transform of fatigue life simulations, accurately describes the damage accumulation rate. It is stressed that the Mittag-Leffler Monte Carlo method is mathematically simple and easy-to-program for researchers and nonexpert engineers. © SAGE Publications.

Du Y.,CAS Nanjing Institute of Geography and Limnology | Du Y.,Hohai University | Fu Q.S.,CAS Nanjing Institute of Geography and Limnology | Li Y.,Hohai University | Su Y.,CAS Nanjing Institute of Geography and Limnology
Journal of Hazardous Materials | Year: 2011

In this article, the photo-degradation of 4-chlorophenol (4-CP) under UV irradiation was studied with focus on the photodecomposition of 4-CP by reactive oxygen species (ROS). 4-CP underwent much faster and more complete degradation in UV/air system than in UV/N2 system. In UV/air system, the addition of t-butanol, a well-known OH scavenger, significantly impeded the degradation of 4-CP. In the presence of t-butanol, the tendencies for the degradation of 4-CP and the formation of intermediates in UV/air system were very similar to those in UV/N2 system. In UV/air system, 4-CP was degraded by two pathways, direct photolysis by absorbing the photons and the oxidation via OH. The contribution of direct photolysis and the oxidation via OH to 4-CP decomposition were 17.2% and 82.8%, respectively based on the apparent kinetic constants. Hydrogen peroxide, which could produce OH through photolysis, was formed in UV/air system. It was shown that dissolved oxygen, organic matter in excited state and hydrogen ion are all necessary for the formation of hydrogen peroxide. The formation mechanism of H2O2 was proposed based on experimental evidence. © 2010 Elsevier B.V.

Juan W.,Hohai University | Fei J.,Hohai University
Transactions of the Institute of Measurement and Control | Year: 2013

In the practical control of microelectromechanical system (MEMS) gyroscopes, dead-zone non-linearity often exists, which has negative influence on the resolution and performance of the gyroscope system. System non-linearities are inevitable in actual MEMS gyroscopes and require the controller to be either adaptive or robust to these non-linearities. In this paper, an adaptive fuzzy compensator is designed to compensate the dead-zone non-linearities for MEMS gyroscope. A fuzzy logic system is used for dead-zone non-linear switching function and an optimal algorithm is designed to make the dead-zone compensator to tune the parameters adaptively. The closed-loop stability can be guaranteed with the proposed adaptive fuzzy dead-zone compensation. Simulation results demonstrate that the tracking error can be attenuated efficiently and robustness of the control system can be improved with the proposed adaptive fuzzy non-linearity compensator. © The Author(s) 2013.

Fei J.,Hohai University | Hou S.,Hohai University
Transactions of the Institute of Measurement and Control | Year: 2013

In this paper, an adaptive fuzzy-sliding control system is proposed to improve the dynamic performance of a three-phase active power filter (APF). Adaptive fuzzy controllers are employed to approximate both the equivalent control term and the switching control term in the sliding mode controller. An online adaptive tuning algorithm for the consequent parameters in the fuzzy rules is also designed. The switching control becomes continuous and the chattering phenomena can be attenuated. Simulation demonstrated that the proposed control method has an excellent dynamic performance such as small current tracking error, reduced total harmonic distortion (THD), strong robustness in the presence of parameter variation and non-linear load. © The Author(s) 2013.

Feng X.,Hohai University | Zheng J.,Hohai University | Yan Y.,Hohai University
Coastal Engineering | Year: 2012

The East China Sea is a hot area for typhoon waves to occur. A wave spectra assimilation model has been developed to predict the typhoon wave more accurately and operationally. This is the first time where wave data from Taiwan have been used to predict typhoon wave along the mainland China coast. The two-dimensional spectra observed in Taiwan northeast coast modify the wave field output by SWAN model through the technology of optimal interpolation (OI) scheme. The wind field correction is not involved as it contributes less than a quarter of the correction achieved by assimilation of waves. The initialization issue for assimilation is discussed. A linear evolution law for noise in the wave field is derived from the SWAN governing equations. A two-dimensional digital low-pass filter is used to obtain the initialized wave fields. The data assimilation model is optimized during the typhoon Sinlaku. During typhoons Krosa and Morakot, data assimilation significantly improves the low frequency wave energy and wave propagation direction in Taiwan coast. For the far-field region, the assimilation model shows an expected ability of improving typhoon wave forecast as well, as data assimilation enhances the low frequency wave energy. The proportion of positive assimilation indexes is over 81% for all the periods of comparison. The paper also finds that the impact of data assimilation on the far-field region depends on the state of the typhoon developing and the swell propagation direction. © 2012 Elsevier B.V.

Jin X.,Nanjing University | Huang J.,Hohai University | Zhou Y.,Nanjing University
Biology and Fertility of Soils | Year: 2012

A 15N dilution experiment was carried out to investigate effects of cultivation on the gross N transformation rate in coastal wetland zone. Microbial community composition was estimated by phospholipid fatty acid (PLFA) analysis and abundance of soil ammonia-oxidizing bacteria (AOB) was quantified by real-time polymerase chain reaction (PCR). Soil salinity decreased significantly, while total N increased after coastal wetland was cultivated. Microbial biomass (total PLFA), bacterial biomass, fungal biomass, and actinomycete biomass of the native coastal wetland soils were significantly (p<0.05) lower than those of the cultivated soils whereas AOB population size also significantly increased after coastal wetland cultivation. Multiple regression analysis showed that total PLFA biomass and soil total N (TN) explained 97% of the variation of gross N mineralization rate in the studied soils (gross mineralization rate = 0.179 total PLFA biomass + 5.828TN - 2.505, n = 16, p<0.01). Gross nitrification rate increased by increasing the soil AOB population size and gross mineralization rate (M) (gross nitrification rate = 3.39AOB + 0.18 M - 0.075, R 2 = 0.98, n = 16, p<0.01). Management of salt discharge and mineral N fertilization during the cultivation of wetland soils might have changed composition of soil microflora and AOB population size, thus influencing mineralization and nitrification. Probably, the cultivation of coastal wetland soils increased the risk of N losses from soil through nitrate leaching and gas emission (e.g., N 2O and NO). © 2011 Springer-Verlag.