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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.

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.

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.

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.

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.

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.

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.

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.

Xu Y.,Hohai University | Da Q.,Nanjing Southeast University | Liu X.,Nanjing Southeast University
Journal of Systems Engineering and Electronics | Year: 2010

The group decision making problem with linguistic preference relations is studied. The concept of additive consistent linguistic preference relation is defined, and then some properties of the additive consistent linguistic preference relation are studied. In order to rank the alternatives in the group decision making with the linguistic preference relations, the weighted average is first utilized to combine the group linguistic preference relations to one linguistic preference relation, and then the transformation function is proposed to transform the linguistic preference relation to the multiplicative preference relation, and thus the Saaty's eigenvector method (EM) of multiplicative preference relation is utilized to rank the alternatives in group decision making with the linguistic preference relations. Finally, an illustrative numerical example is given to verify the proposed method. A comparative study to the linguistic ordered weighted averaging (LOWA) operator method is also demonstrated.

Fei J.,Jiangsu Key Laboratory of Power Transmission and Distribution Equipment Technology | Yang Y.,Hohai University
Mathematical Problems in Engineering | Year: 2011

Fabrication defects and perturbations affect the behavior of a vibratory MEMS gyroscope sensor, which makes it difficult to measure the rotation angular rate. This paper presents a novel adaptive approach that can identify, in an online fashion, angular rate and other system parameters. The proposed approach develops an online identifier scheme, by rewriting the dynamic model of MEMS gyroscope sensor, that can update the estimator of angular rate adaptively and converge to its true value asymptotically. The feasibility of the proposed approach is analyzed and proved by Lyapunov's direct method. Simulation results show the validity and effectiveness of the online identifier. © 2011 Juntao Fei and Yuzheng Yang.

Xiao P.,Nanjing University | Feng X.,Nanjing University | An R.,Hohai University | Zhao S.,Nanjing University
International Journal of Remote Sensing | Year: 2010

Image segmentation has been recognized as a valuable approach that performs a region-based rather than a pixel-based analysis of high-resolution satellite imagery. A scheme for segmenting the multispectral IKONOS image based on frequency-domain filtering is presented. The frequency spectrum of typical landscape objects is analysed first. The spectrum curves are comparable in logarithmic coordinates rather than in Cartesian coordinates; therefore the Gabor filters are superseded by log Gabor filters to extract the multiscale texture features from panchromatic band. Edge features then are calculated from the pan-sharpened multispectral bands based on the vector field model. Finally, the texture-marked watershed segmentation algorithm is implemented and the segmentation accuracy is assessed. The experimental results show that the developed scheme generated an effective tool for automatic segmentation of multispectral high-resolution satellite imagery and suppressing the over-segmentation problem of watershed transform. © 2010 Taylor & Francis.

Zheng D.,Hohai University | Yuan J.,China Yangtze Power Co.
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.

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.

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.

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.

Dong L.,Hohai University | Dong L.,University of California at Irvine | Gamal S.H.,King Abdulaziz University | Atluri S.N.,University of California at Irvine | Atluri S.N.,King Abdulaziz University
Computers, Materials and Continua | Year: 2013

In this paper, a simple and reliable procedure of stochastic computation is combined with the highly accurate and efficient Trefftz Computational Grains (TCG), for a direct numerical simulation (DNS) of heterogeneous materials with microscopic randomness. Material properties of each material phase, and geometrical properties such as particles sizes and distribution, are considered to be stochastic with either a uniform or normal probabilistic distributions. The objective here is to determine how this microscopic randomness propagates to the macroscopic scale, and affects the stochastic characteristics of macroscopic material properties. Four steps are included in this procedure: (1) using the Latin hypercube sampling, to generate discrete experimental points considering each contributing factor (material parameters and volume fraction of each phase, etc.); (2) randomly generating Representative Volume Elements (RVEs) of the microstructure for each discrete experimental point, and compute the effective macro-scale material properties at these points, using the computationally most efficient Trefftz Computational Grains; (3) relating the macro-scale material properties to the microscale random variables using the Kriging method; (4) taking advantage of the approximate macro-micro relation, and using the Monte Carlo simulation, to establish the probabilistic distribution of the macro-scale material properties. By considering the Al/SiC composite as an example, we give step-by step demonstration of the procedure, and give some comparisons with experimental results. The obtained probabilistic distributions of the effective macro-scale material properties have fundamental engineering merits, which can be used for reliability-based material optimization, and integrated-design of micro-as well as macro-structures. The studies in this paper are germane to the concepts of the Materials Genome Initiative (MGI), and Integrated Materials Science, Mathematics, Modeling, and Engineering (IMSMME). Copyright © 2013 Tech Science Press.

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.

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.

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.

Song Z.,Nanjing University | Geng X.,Nanjing University | Kusiak A.,University of Iowa | Xu C.,Hohai University
Expert Systems with Applications | Year: 2011

Extracting important statistical patterns from wind speed time series at different time scales is of interest to wind energy industry in terms of wind turbine optimal control, wind energy dispatch/scheduling, wind energy project design and assessment, and so on. In this paper, a systematic way is presented to estimate the first order (one step) Markov chain transition matrix from wind speed time series by two steps. Wind speed time series data is used first to generate basic estimators of transition matrices (i.e. first order, second order, third order, etc.) based on counting techniques. Then an evolutionary algorithm (EA), specifically double-objective evolutionary strategy algorithm (ES), is proposed to search for the first order Markov chain transition matrix which can best match these basic estimators after transforming the first order transition matrix into its higher order counterparts. The evolutionary search for the first order transition matrix is guided by a predefined cost function which measures the difference between the basic estimators and the first order transition matrix, and its high order transformations. To deal with the potential high dimensional optimization problem (i.e. large transition matrices), an enhanced offspring generation procedure is proposed to help the ES algorithm converge efficiently and find better Pareto frontiers through generations. The proposed method is illustrated with wind speed time series data collected from individual 1.5 MW wind turbines at different time scales. © 2011 Published by Elsevier Ltd.

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.

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.

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.

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.

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.

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.

Hu F.,Hohai University
AIP Conference Proceedings | Year: 2015

This paper is concerned with the dynamic response of pile embedded in elaso-viscoplastic soil under vertical loading. The interaction between soil and pile is described by a five element model with a spring in series with a parallel dashpot and a spring combined with a parallel slider and spring, while the pile is treated as a column and described by elastic column vibration theory. In this model, total displacement of pile is assumed to be divided into three parts: elastic displacement, visco-elastic displacement and visco-plastic displacement. The final physical equations of pile embedded in elaso-viscoplastic soil under vertical vibration are established. Due to the nonlinearity of this problem, we use the finite differential method to solve the nonlinear partial differential equation. Numerical results indicate that the parameters of soil and the character of creep have considerable influences on the dynamic response of the pile. © 2015 AIP Publishing LLC.

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.

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.

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 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.

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.

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.

Wang Y.,Nanjing University | Xia Z.,Hohai University | Wang D.,Nanjing University
Aquatic Ecology | Year: 2011

Chinese sturgeon (Acipenser sinensis) is a protected anadromous fish species. The migration pattern of the fish has been blocked by the construction of Gezhouba Dam, reducing the natural spawning site length to less than 7 km along the Yangtze River. However, the fish has since established an alternative spawning ground in the narrow reach downstream of Gezhouba Dam. To enhance navigation, a Separation Levee Project (SLP) was implemented in the new-found spawning habitat of the fish. To therefore evaluate the effect of the SLP on Chinese sturgeon spawning habitat suitability, the conditions in the spawning habitat were simulated using River2D (a two-dimensional hydrodynamic model). Two main approaches (habitat kinetic energy and circulation metrics) were used in the simulation. The study showed that SLP only slightly changed the physical conditions in the spawning habitat. Using hydrodynamic simulation, the weighted usable area (WUA) before and after the SLP construction was also computed and habitat preference curve developed for water depth and velocity. On the average, SLP reduced WUA-a finding that was consistent with field-measured data. Based on WUA, the habitat conditions were more sensitive to SLP proximity than metrics based on velocity gradients. SLP posed detrimental impacts on the suitability of spawning habitats of Chinese sturgeon. The findings in this study provide further basis for the protection and restoration of Chinese sturgeon spawning habitats in especially the lower reach of Yangtze River. © 2011 Springer Science+Business Media B.V.

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.

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.

Tian X.,Hohai University
AIP Conference Proceedings | Year: 2015

Atomistic simulations are used to study the deformation behavior of twinned Cu nanowires with a <111> growth orientation under tension. Due to the existence of the twin boundaries, the strength of the twinned nanowires is higher than that of the twin-free nanowire and the yielding stress of twinned nanowires is inversely proportional to the spacings of the twin boundaries. Moreover, The ductility of the twin-free nanowire is the highest of all and it grows with the increasing spacings of the twin boundaries for twinned nanowires. Besides, we find that the twin boundaries can be served as dislocation sources as well as the free surfaces and grain boundaries. © 2015 AIP Publishing LLC.

Wang Z.,Nanjing University | Gong J.,Nanjing University | Gong J.,Hohai University | Su Y.,Nanjing University | And 2 more authors.
Crystal Growth and Design | Year: 2010

Herein we present the successful synthesis of aligned arrays of single-crystalline, 6-fold-symmetrical, hierarchical ZnO nanostructures via a two-step vapor-phase transport method. The X-ray diffraction and transmission electron microscopy results illustrate that the backbones of the as-grown product have excellent orientation along the [001] direction, and the branches epitaxially grow on the backbone along the ?100? direction. At room temperature, the 6-fold-symmetrical hierarchical ZnO nanostructure arrays exhibit a very strong green luminescence centered at 515 nm. The field emission measurements show that they have a turn-on field of 5.6 V/μm and field-enhancement factor of 1351, which indicate their potential application in field emission nanodevices. © 2010 American Chemical Society.

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.

Ismail A.,Shanghai JiaoTong University | Ismail A.,University of Dundee | Jeng D.-S.,Shanghai JiaoTong University | Jeng D.-S.,University of Dundee | And 2 more authors.
Engineering Applications of Artificial Intelligence | Year: 2013

In this study, a new procedure to determine the optimum activation function for a neural network is proposed. Unlike previous methods of optimising activation functions, the proposed approach regards selection of the most suitable activation function as a discrete optimisation problem, which involves generating various combinations of function then evaluating their performance as activation functions in a neural network, returning the function or combination of functions which yields best result as the optimum. The efficacy of the proposed optimisation method is compared with conventional approaches using the data generated from several synthetic functions. Numerical results indicate that the network produced using the proposed method achieves a better accuracy with a smaller network size, compared to other approaches. Bridge scour problem is used to further demonstrate the performance of the proposed algorithm. Based on the training and validation results, a better estimation of both equilibrium and time dependent scour depth is produced by the neural network developed using the proposed optimisation method, compared to networks with a priori chosen activation functions. Furthermore, the performance of the proposed model is compared with predictions of empirical methods, with the former making more accurate predictions. © 2013 Elsevier 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.

Devineni N.,City University of New York | Lall U.,Columbia University | Etienne E.,City University of New York | Shi D.,Columbia University | Xi C.,Hohai University
Geophysical Research Letters | Year: 2015

A new indicator of drought-induced water stress is introduced and applied at the county level in the USA. Unlike most existing drought metrics, we directly consider current daily water demands and renewable daily water supply to estimate the potential stress. Water stress indices developed include the Normalized Deficit Cumulated to represent multiyear droughts by computing the maximum cumulative deficit between demand and supply over the study period (1949-2009) and the Normalized Deficit Index representing drought associated with maximum cumulative deficit each year. These water stress indices map directly to storage requirements needed to buffer multiyear and within-year climate variability and can reveal the dependence on exogenous water transferred by rivers/canals to the area. Future climate change and variability can be also incorporated into this framework to inform climate-driven drought for additional storage development and potential applications of water trading across counties. ©2015. American Geophysical Union. All Rights Reserved.

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.

Chen C.,Hohai University | Fu S.,Yunnan Agricultural University
Computers and Mathematics with Applications | Year: 2016

In this work, we study the existence of multiple solutions to the quasilinear Schrödinger system (0.1)(-δpu+a(x)|u|p-2u=κd-1Fu(x,u,v)+λ|u|m-2u,x∈RN,-δqv+b(x)|v|q-2v=κd-1Fv(x,u,v)+μ|v|m-2v,x∈RN,u∈W1,p(RN),v∈W1,q(RN), where N≥3,10 and m,d∈(q,p*),κ∈R. The potential functions a(x),b(x)∈L∞(RN) are positive in RN. A major point is that we use the technique in Chen (2015) to verify the (PS) conditions and then apply a version of mountain pass lemma to prove the existence of infinitely many solutions of system (0.1). © 2016 Elsevier Ltd.

This paper presents a numerical solution for the dynamic response of a simply supported bridge with a switching crack subjected to seismic excitations and moving trains. The train vehicle is represented by a four degrees-of-freedom model, and the seismic excitation is exerted using the acceleration input. While the crack state remains constant, the bridge vibration is evaluated through a modal analysis. When the crack is switching, the equilibrium position is taken into account to analyze the change of the displacement components. The proposed method is used to study the response characteristics of a numerical bridge, and the results show that under the independent action of seismic load, the equilibrium position changes suddenly at the switching instant and an added vibrational displacement appears. Finally the vibrational displacement is increased by the crack switching and the vibration amplitude becomes larger. Under the combined action of the seismic excitation and the train, the equilibrium position is shifted down, and the effect of the added displacement is reduced. So the vibration amplitude is smaller under the combined action than under the independent action. Meanwhile, the amplitude also is affected by the train weight and velocity. © 2015 Elsevier Ltd.

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.

He R.,Hohai University | Wang L.,Zhejiang University
Applied Ocean Research | Year: 2016

Gravity Base Foundation is one of the main foundations in offshore wind turbine structure, and the foundation rocking stiffness mostly controls the structure fatigue life. This study models the rocking vibration of a rigid disc foundation on a poro-elastic seabed, covered by a compressible inviscid seawater half-space. The coupled rocking problem is solved using the 3-dimensional elastic wave theory. The behavior of seawater and soil are depicted with the Euler equations and the Biot's theory, respectively. The contact surface of the disc foundation with the soil and the water is assumed to be smooth. The solutions are expressed in Fredholm integral equations of the second kind and solved numerically. The obtained dynamic impedances are used to study the dynamic behavior of Gravity Base Foundations of offshore wind turbines, which are very sensitive to dynamic moments. It is found that foundation with a permeable surface has much smaller dynamic amplitudes, compared to the one with an impermeable surface. The existence of seawater half-space will also alleviate the dynamic amplitudes, but decreasing the natural frequency of the foundation. © 2015 Elsevier Ltd.

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.

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.

Zhou J.,Hohai University
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2013

By employing the 2-regularized determinant technique about Hilbert- Schmidt operators and creating what we call the contraposition return difference relationship for finite-dimensional linear continuous-time periodic (FDLCP) feedback systems, a contraposition 2-regularized Nyquist stability criterion is developed for asymptotic stability analysis in this study. The stability conditions of the contraposition 2-regularized Nyquist stability criterion are necessary and sufficient, which can be implemented graphically in a way similar to what we do in linear time-invariant cases but without involving open-loop poles distribution and encircling orientation counting of the Nyquist loci. A numeric implementation algorithm for the contraposition 2-regularized Nyquist criterion is also proposed via truncating the harmonic transfer operator of the FDLCP systems. © 2013 IFAC.

Wang H.-L.,Hohai University | Chu W.-J.,Hydrochina Huadong Engineering Corporation | He M.,Jiangsu Transportation Research Institute
Journal of Hydrodynamics | Year: 2012

The rock permeability is an important parameter in the studies of seepage and stress coupling. The micro-cracks and pores can initiate and grow on a small scale and coalesce to form large-scale fractures and faults under compressive stresses, which would change the hydraulic conductivity of the rock, and therefore, the rock permeability. The rock permeability is, therefore, closely related with the micro-cracking growing, coalescence, and macro new fracture formation. This article proposes a conceptual model of rock permeability evolution and a micro kinematics mechanism of micro-cracking on the basis of the basic theory of micromechanics. The applicability of the established model is verified through numerical simulations of in situ tests and laboratory tests. The simulation results show that the model can accurately forecast the peak permeability evolution of brittle rock, and can well describe the macro-experimental phenomenon before the peak permeability evolution of brittle rock on a macro-scale. © 2012 Publishing House for Journal of Hydrodynamics.

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.

Wang F.,Hohai University
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2015

In order to recover the reference signal of the passive bistatic radar exploiting sky wave transmission and ground wave reception, a kind of combined blind equalization algorithm is proposed to combat the reference signal distortions caused by the multipath reflections of the ionosphere. Super exponential (SE) algorithm with fast convergence rate is utilized to initialize the weight of a constant modulus equalizer based on auto-regressive and moving average (ARMA) model. The combined algorithm has the advantages of the fast convergence rate and low computational complexity, and is appropriate for the equalization of severe multipath fading ionospheric channels with zeros near the unit circle. The performance of the proposed algorithm is proven by computer simulations. Copyright © 2015 by Editorial Department of Chinese Journal of Radio Science

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.

Cheng X.,Lanzhou University | Lu H.,Hohai University
Nonlinear Analysis: Real World Applications | Year: 2012

In this paper, we establish the product formula for the fixed point index on product cone, and the relation between LeraySchauder degree and a pair of strict lower and upper solutions for a (p 1,p 2)-Laplacian system. Based on the product formula of the fixed point index and LeraySchauder degree theory, we deal with the multiplicity of positive solutions for a class of (p 1,p 2)-Laplacian systems. As applications, we prove the global existence of positive solutions for a multi-parameter system of (p 1,p 2)-Laplacian equations with respect to parameters. © 2012 Elsevier Ltd. All rights reserved.

This paper reveals the dynamical behaviors of a neural network consisting of a pair of bidirectional loops each with three identical neurons and two-way couplings between neurons of each individual loop. Time delays are introduced not only in the couplings between the loops but also in the internal connections within the individual loops. The study derives the conditions for the local stability of the network equilibrium and the existence of Hopf bifurcation. Afterwards, the study turns to showing the rich dynamical behaviors of the network through numerical analysis, such as multiple stability switches of network equilibrium, synchronous/asynchronous periodic oscillations, and the coexistence of bifurcated solutions. © 2011 Springer Science+Business Media B.V.

Zhang Y.,East China Jiaotong University | Huang D.,East China Jiaotong University | Chen J.,Hohai University
Applied Computational Electromagnetics Society Journal | Year: 2013

The combination of asymptotic phase basis functions and matrix impedance method is proposed and used for fast computation of monostatic scattering from electrically large object. Since asymptotic phase (AP) basis function can be defined on large patches, less number of unknowns is required than that when using traditional Rao-Wilton-Glisson (RWG) vector basis function. In order to efficiently compute electromagnetic scattering, the flexible general minimal residual (FGMRES) iterative solver is applied to compute the coefficients of the basis functions and the sparse approximate inversion (SAI) preconditioning technique is used to accelerate the iterative solver. However, the impedance matrix varies with incident angles, resulting in significant computation time cost for construction of impedance and SAI preconditioning matrices. This difficulty can be alleviated by using the model-based parameter estimation (MBPE) technique. Both the impedance and SAI preconditioning matrices are interpolated at intermediate angles over a relatively large angular band with rational function interpolation method. Numerical results demonstrate that this method is efficient for monostatic RCS calculation with high accuracy. © 2013 ACES.

Zhang Q.,CAS Nanjing Institute of Geography and Limnology | Li L.,Hohai University | Li L.,University of Queensland | Wang Y.-G.,University of Queensland | And 4 more authors.
Geophysical Research Letters | Year: 2012

The Three-Georges Dam holds many records in the history of engineering. While the dam has produced benefits in terms of flood control, hydropower generation and increased navigation capacity of the Yangtze River, serious questions have been raised concerning its impact on both upstream and downstream ecosystems. It has been suggested that the dam operation intensifies the extremes of wet and dry conditions in the downstream Poyang Lake, and affects adversely important local wetlands. A floodgate has been proposed to maintain the lake water level by controlling the flow between the Poyang Lake and Yangtze River. Using extensive hydrological data and generalized linear statistical models, we demonstrated that the dam operation induces major changes in the downstream river discharge near the dam, including an average "water loss". The analysis also revealed considerable effects on the Poyang Lake water level, particularly a reduced level over the dry period from late summer to autumn. However, the dam impact needs to be further assessed based on long-term monitoring of the lake ecosystem, covering a wide range of parameters related to hydrological and hydraulic characteristics of the lake, water quality, geomorphological characteristics, aquatic biota and their habitat, wetland vegetation and associated fauna. © 2012. American Geophysical Union. All Rights Reserved.

Wu Y.,Hohai University
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2011

There will be a big pressure on the emission reduction of liquid fossil fuel. Developing the liquid biomass can accelerate the process of emission reduction and ease food security crisis in China. A theoretical model and analytic framework exampled by fuel ethanol was established to analyze the possible effects of biomass development on the Chinese emission reduction methods and food security in the cases of both short-term and long-term dynamic equilibrium. The results showed that to achieve emission reduction targets, the Chinese government should take the initiative to assume the costs of energy structure adjustment and support the sustainable development in fuel ethanol industry by subsidizing non-food energy crops planting, fuel ethanol producing and fuel ethanol consuming for the purpose of easing emission reduction resistance and food security threat.

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.

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

Preventive resettlement is one of the effective measures to prevent geological disasters. However, there is a lack of definite theoretical system to guide how to deal with the potential disasters and risks and provide migration decision-making. The paper selects disaster risk management as the theoretical guidance and the risk assessment of the framework system as the focus to explore hazard identification and characterization, identification of exposed elements, vulnerability assessment and determination of risk levels, through which the paper gets risk cognition and obtains the basis for risk management. Besides, the paper combines with the different characteristics and factors of geological disasters to expound on the strategy of risk reduction and put forward the possible solutions to avoid and alleviate risks. Furthermore, under certain conditions, the disaster-avoiding migration strategy is adopted. © (2014) Trans Tech Publications, Switzerland.

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.

Xu J.,Nanjing University | Ao Y.,Hohai University | Chen M.,Nanjing University
Materials Letters | Year: 2013

Reduced graphene oxide/Bi2WO6 (RGO-Bi 2WO6) composite photocatalysts were prepared by a simple one-pot method. Namely, the reduction of graphene oxide and the growth of Bi2WO6 crystal occurred simultaneously in one single process. The obtained samples were characterized by XRD, SEM, and DRS. The photocatalytic activities of as-prepared samples was investigated by degradation of MB under visible light irradiation. An enhancement in photocatalytic activities were observed in RGO-Bi2WO6 composites compared with pure Bi2WO6. We also investigated the effect of graphene amount on the photocatalytic activity of the as-prepared composite photocatalysts. Results showed that there was an optimal amount of 2.5%. © 2012 Elsevier B.V.

Li H.,Hohai University
Metallurgical and Mining Industry | Year: 2015

Stadium buildings are important population-intensive buildings where various social activities are held frequently. The quakeproof property of stadium buildings directly concerns safety and image of social people and the cities. This research takes sports stadium buildings for example, combines architectural characteristics and quakeproof requirements of sports stadium and introduces fuzzy assessment theory. Deep analysis is carried out from the site environment, foundation, major structure, building materials and components which influence quakeproof property. On this basis, this paper proposes a set of scientific comprehensive assessment index system, and applies fuzzy comprehensive assessment to construct quakeproof property assessment model of sports stadium. Meanwhile, based on case study of Wukesong Stadium, this paper verifies feasibility of this assessment system. The research shows that this method has certain reference significance for quakeproof property assessment of similar stadiums.

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.

Dong L.,Hohai University | Alotaibi A.,King Abdulaziz University | Mohiuddine S.A.,King Abdulaziz University | Atluri S.N.,University of California at Irvine
CMES - Computer Modeling in Engineering and Sciences | Year: 2014

In this expository article, a variety of computational methods, such as Collocation, Finite Volume, Finite Element, Boundary Element, MLPG (Meshless Local Petrov Galerkin), Trefftz methods, and Method of Fundamental Solutions, etc., which are often used in isolated ways in contemporary literature are presented in a unified way, and are illustrated to solve a 4th order ordinary differential equation (beam on an elastic foundation). Both the primal formulation, which considers the 4th order ODE with displacement as the primitive variable, as well as two types of mixed formulations (one resulting in a set of 2 second-order ODEs, and the other resulting in a set of 4 first-order ODEs), which consider both displacement and its derivatives as mixed variables, are used as strong forms of the problem. Through integration by parts of the weighted residuals, different global and local, unsymmetric and symmetric weak-forms are derived. Both global (harmonics, polynomials, Radial Basis Functions, Trefftz and Fundamental solutions), and local interpolations (element-based interpolations, meshless Moving Least Squares) are used as trial functions of primal and mixed variables. By using Dirac Delta function, Heaviside function, Galerkin and Petrov Galerkin type of function, as well as fundamental solutions as test functions of various weak-forms, primal and mixed implementations of Collocation, Finite Volume, Finite Element, Boundary Element, Meshless Local Petrov Galerkin (MLPG), Trefftz and Method of Fundamental Solutions are developed. Applications of these methods are illustrated for solving problems with well-posed boundary conditions (BCs), which are the physically-consistent BCs of a solid-body (beam on elastic foundation), as well as for ill-posed boundary conditions, where the Cauchy type of B.C. are over-prescribed on a part of the boundary. The advantages & disadvantages of various primal & mixed, symmetric & unsymmetric weak forms are discussed, on the admissible order of continuity for trial & test functions, the requirement of evaluating higher-order differentials, as well as the enforcement of well-posed & ill-posed BCs. The relationship between various trial & test functions and the resulting sparse or dense, symmetric or non-symmetric, well-conditioned or ill-conditioned coefficient matrices are also demonstrated and discussed. This paper thus presents a unification of a variety of concepts in developing numerical methods for problems of multidisciplinary engineering and sciences, which are often presented in an ad hoc manner, in contemporary literature. The MATLAB codes pertaining to all the methods presented here are presented for free download at the website: www.care.eng.uci.edu/pubs.htm. This expository article will be a part of soon to be published introductory textbook by Atluri and Dong (2015). Copyright © 2014 Tech Science Press.

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.

Elgohary T.A.,Texas A&M University | Dong L.,Hohai University | Junkins J.L.,Texas A&M University | Atluri S.N.,University of California at Irvine
CMES - Computer Modeling in Engineering and Sciences | Year: 2014

In this study, the Scalar Homotopy Methods are applied to the solution of post-buckling and limit load problems of solids and structures, as exemplified by simple plane elastic frames, considering only geometrical nonlinearities. Explicitly derived tangent stiffness matrices and nodal forces of large-deformation planar beam elements, with two translational and one rotational degrees of freedom at each node, are adopted following the work of [Kondoh and Atluri (1986)]. By using the Scalar Homotopy Methods, the displacements of the equilibrium state are iteratively solved for, without inverting the Jacobian (tangent stiffness) matrix. It is well-known that, the simple Newton's method (and the Newton-Raphson iteration method that is widely used in nonlinear structural mechanics), which necessitates the inversion of the Jacobian matrix, fails to pass the limit load as the Jacobian matrix becomes singular. Although the so called arc-length method can resolve this problem by limiting both the incremental displacements and forces, it is quite complex for implementation. Moreover, inverting the Jacobian matrix generally consumes the majority of the computational burden especially for large-scale problems. On the contrary, by using the presently developed Scalar Homotopy Methods, convergence near limit loads, and in the post-buckling region, can be easily achieved, without inverting the tangent stiffness matrix and without using complex arc-length methods. The present paper thus opens a promising path for conducting post-buckling and limit-load analyses of nonlinear structures. While the simple Williams' toggle is considered as an illustrative example in this paper, extension to general finite element analyses of space frames, plates, shells and elastic-plastic solids will be considered in forthcoming studies. Copyright © 2014 Tech Science Press.

Qian K.,Glasgow Caledonian University | Zhou C.,Glasgow Caledonian University | Allan M.,Glasgow Caledonian University | Yuan Y.,Hohai University
International Journal of Electrical Power and Energy Systems | Year: 2011

Distributed Generation (DG) is gaining in significance due to the keen public awareness of the environmental impacts of electric power generation and significant advances in several generation technologies which are much more environmentally friendly (wind power generation, micro-turbines, fuel cells, and photovoltaic) than conventional coal, oil and gas-fired plants. Accurate assessment of energy losses when DG is connected is gaining in significance due to the developments in the electricity market place, such as increasing competition, real time pricing and spot pricing. However, inappropriate modelling can give rise to misleading results. This paper presents an investigation into the effect of load models on the predicted energy losses in DG planning. Following a brief introduction the paper proposes a detailed voltage dependent load model, for DG planning use, which considers three categories of loads: residential, industrial and commercial. The paper proposes a methodology to study the effect of load models on the assessment of energy losses based on time series simulations to take into account both the variations of renewable generation and load demand. A comparative study of energy losses between the use of a traditional constant load model and the voltage dependent load model and at various load levels is carried out using a 38-node example power system. Simulations presented in the paper indicate that the load model to be adopted can significantly affect the results of DG planning. © 2011 Elsevier Ltd. All rights reserved.

Zhou P.,Nanjing University of Aeronautics and Astronautics | Zhou X.,Nanjing University of Aeronautics and Astronautics | Fan L.W.,Hohai University
Applied Energy | Year: 2014

Undesirable outputs (or bads) refer to the byproducts accompanied with desirable outputs (or goods) in a production process, e.g. sulfur dioxide and carbon dioxide in coal-fired power generation. The shadow price of undesirable output, which may be interpreted as the opportunity cost of abating one additional unit of undesirable output in terms of the loss of desirable output, could provide valuable reference information for policy analysis and making. A prevalent practice is to use the Shephard or directional distance function to derive the shadow price, which can be further calculated by parametric or nonparametric efficiency models. In application, earlier studies have estimated shadow prices at plant, sector and even economy levels. This study aims to conduct a systematic review of the studies on estimating shadow prices of undesirable outputs with efficiency models. We first introduce the methodological framework for deriving shadow prices as well as the nonparametric/parametric efficiency models for calculating their values. A systematic summary of over forty earlier studies in this field is then conducted, through which the key features of the existing studies are summarized and possible future research directions are identified. © 2014 Elsevier Ltd.

Liu J.,Ryerson University | Liu M.,Henan Electrical Power Survey And Design Institute | Zhu Z.,Hohai University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2012

This paper presents an experimental investigation on soil deformation around uplift plate anchors in sand by using digital image correlation (DIC). The experimental setup consists of a camera, loading frame, plexiglass mold, and computer, which is developed to capture soil deformation during anchor uplifting. A series of model tests are performed to investigate the influence of particle size, soil density, and anchor embedment depth on soil deformation. A set of images captured during anchor uplifting are used to calculate soil displacement fields by DIC. The failure surface is studied by tracking the points with maximum shear strain values. On the basis of this study, it is found that soil deformation and the pullout resistance of plate anchors are substantially influenced by soil density and anchor embedment depth, whereas particle size within the studied range has limited influence. In dense sand, the shape of the failure surface changes from a truncated cone above a shallow anchor to a combined shape of a curved cone and a truncated cone for a deep anchor. In contrast, in loose sand a cone-shaped failure surface is formed within the soil mass above a shallow anchor; however, no failure surface is observed for a deep anchor, where the compressibility of soil is the dominating factor that influences the behavior of deep plate anchors in loose sand. © 2012 American Society of Civil Engineers.

Zhihua L.,Hohai University
IEEE Transactions on Instrumentation and Measurement | Year: 2014

A novel fault diagnostic method based on node-voltage vector ambiguity sets for analog circuits is presented in this paper. The method uses a sinusoidal stimulus instead of a dc-based stimulus. It employs steady-state node-voltage responses on observable nodes under different fault conditions to establish node-voltage vector ambiguity sets for fault diagnosis. An ellipse-based measurement solution to measure node-voltage vectors is also described. A frequency selection algorithm for a sinusoidal stimulus is introduced. A fault diagnostic example based on the node-voltage vector ambiguity sets is presented. Finally, a programming strategy to extend the method to large-scale analogue circuit designs is described. © 2014 IEEE.

Tang Y.,Nanyang Technological University | Tang Y.,Hohai University | Lu Y.,Nanyang Technological University
IEEE Transactions on Antennas and Propagation | Year: 2014

This communication presents a new multi-resolution composite array (MRCA) concept for digital beamforming (DBF) array to achieve very high angular-resolution with considerably less array elements. Furthermore, the beamforming performances of DBF radars with two proposed multi-resolution composite arrays were investigated with numerical experiments and compared to a conventional full-filled array and a multiplicative array to verify our concepts. © 2014 IEEE.

Hu Z.,Hohai University | Lu Y.Y.,City University of Hong Kong
Journal of Optics (United Kingdom) | Year: 2015

Guided modes of a periodic waveguide usually exist below the light line, if the minimum period of the waveguide is used in the definition, but for some periodic waveguides, there are standing waves with the same period as the waveguide. These non-propagating waves localized around the waveguide core are special guided modes above the light line with a zero wavenumber, and they are related to transmission anomalies and other resonant phenomena. In this paper, we analyze the standing waves on two periodic waveguides: a periodic array of circular dielectric cylinders, and a dielectric slab with a periodic array of circular air-holes. Based on an efficient semi-analytic method, the frequencies of standing waves are calculated as functions of the dielectric constant and the radius of cylinders. Our work provides a basis for further studies on these waves and for realizing their potential applications. © 2015 IOP Publishing Ltd.

Wu Q.-Y.,Tsinghua University | Li Y.,Hohai University | Hu H.-Y.,Tsinghua University | Sun Y.-X.,Tsinghua University | Zhao F.-Y.,Shaanxi University of Science and Technology
Environmental Science and Technology | Year: 2010

Chlorination of wastewater can form genotoxic, mutagenic, and/or carcinogenic disinfection byproduct (DBPs). In this study, the effect of bromide on genotoxicity in secondary effluent of a municipal wastewater treatment plant during chlorination was evaluated by the SOS/umu test. The presence of bromide notably decreased the genotoxicity in secondary effluent during chlorination, especially under conditions of high ammonia concentration. Bromide significantly decreased the concentration of ofloxacin, a genotoxic chemical in secondary effluent, during chlorination with high concentration of ammonia, while genotoxic DBPs formation of humic acid and aromatic amino acids associated with bromide limitedly contributed to the changes of genotoxicity in secondary effluent under the conditions of this study. By fractionating dissolved organic matter (DOM) in the secondary effluent into different fractions, the fractions containing hydrophilic substances (HIS) and hydrophobic acids (HOA) contributed to the decrease in genotoxicity induced by bromide. Chlorination of HOA without bromide increased genotoxicity, while the addition of bromide decreased genotoxicity. © 2010 American Chemical Society.

Liang G.-L.,Hohai University
Disaster Advances | Year: 2012

The study takes the high rock slope of Jinping-I stage hydropower station as an example to analyze the stability of high rock slope based on safety monitoring data. Through a comprehensive analysis of field data measured by multi-point extensometers, rock bolt dynamometer, graphite bar-type convergence gauge, shearing-resistance tunnel and electronic total station, the deformation character and deformation law are studied. The results are summarized as follows: (1) Due to deep fissure development, large unloading depth, extensive excavation, the slope shows large excavation deformation, in situ monitoring should be strengthened and timely supporting measures should be adopted to prevent landslide. (2) Unloading rebound and tensile crack are caused by slope excavation. The deformation near to the structural planes such as F42-9, F5 and F8 is large because of poor rock quality confirmed by the monitoring result of multi-point extensometers, bolt dynamometers, joint meters across through structural planes. (3)The disturbance of construction on rock, especially near to monitoring instruments, should be further reduced in order to ensure the normal operation of monitoring equipments and the reliability of monitoring data. The displacement back-analysis and the visualized data-mining system are studied and applied to the high rock slope engineering of Jinping hydropower station.

Zhang Y.-M.,Shandong University of Technology | Zhang Y.-M.,Dalian University of Technology | Qu W.-Z.,Hohai University | Chen J.-T.,National Taiwan Ocean University
Engineering Analysis with Boundary Elements | Year: 2013

A new boundary element method is developed for solving thin-body thermoelastic problems in this paper. Firstly, the novel regularized boundary integral equations (BIEs) containing indirect unknowns are proposed to cancel the singularity of fundamental solutions. Secondly, a general nonlinear transformation available for high-order geometry elements is introduced in order to remove or damp out the near singularity of fundamental solutions, which is crucial for accurate solutions of thin-body problems. Finally, the domain integrals arising in both displacement and its derivative integral equations, caused by the thermal loads, are regularized using a semi-analytical technique. Six benchmark examples are examined. Results indicate that the proposed method is accurate, convergent and computationally efficient. The proposed method is a competitive alternative to existing methods for solving thin-walled thermoelastic problems. © 2012 Elsevier Ltd.

Liu J.,Hohai University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2011

Project scheduling depends on various risk factors, and they should be related by certain relationships that are usually represented by a correlation matrix in the existing methods. The practical difficulty is that, however, in some cases this matrix is too complicated to evaluate. This paper introduces a new approach and develops a BN-CPM model that incorporates the project network and risk factors into a Bayesain network for modeling uncertainty and relationship in project scheduling. Hence the new model can be used for calculation of the correlation between risk factors and also for analysis of schedule risks. It is a useful tool for managers to understand project risk factors and to improve their decision making. © Copyright.

Li M.,Taiyuan University of Technology | Chen W.,Hohai University | Chen C.S.,Taiyuan University of Technology | Chen C.S.,University of Southern Mississippi
Engineering Analysis with Boundary Elements | Year: 2013

In this paper we present a localized meshless method using radial basis functions (RBFs) for solving up to six dimensional problems. To improve the difficulty of selecting a shape parameter of RBF-MQ, a normalized scheme is introduced. We also make a comparison between the global and local RBF methods in terms of stability and accuracy. To demonstrate the applicability of the localized RBF method for high dimensional problems, two numerical examples with Dirichlet boundary conditions are given. © 2013 Elsevier Ltd.

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.

Xin P.,University of Queensland | Li L.,University of Queensland | Li L.,Hohai University | Barry D.A.,Ecole Polytechnique Federale de Lausanne
Water Resources Research | Year: 2013

To better understand how tides affect the soil conditions of salt marshes, pore-water flow in a modeled 3-D creek-marsh system was simulated under the influence of both monochromatic and spring-neap tides. In analyzing the simulation results, six indices, viz., marsh surface elevation (SE), hydroperiod (HP), shortest distance to creeks (SDC), mean soil water saturation (MSS), soil saturation index (SSI), and net water flux (NWF), were examined across the marsh surface. The results demonstrated that MSS, SSI, and NWF exhibited corresponding patterns of spatial variations, which were related to marsh SE, HP, SDC, and tidal regime. Although the relationships could be described by a simple function under monochromatic tides, under spring-neap tides, the relationships were more complex with different behaviors in the lower and upper marsh areas. The SDC was a critically important factor affecting soil conditions. Well-aerated and -drained zones coexisted near the creek under both monochromatic and spring-neap tides. Spring-neap tides led to improved soil aeration in the upper marsh, including the interior section (away from the creek) where the HP and inundation frequency were reduced during neap tides. However, the local flushing condition did not improve correspondingly. The study suggests that single morphological index cannot describe the soil conditions adequately. A proper representation of the soil conditions for plant growth and distribution should take into account not only the aeration condition but also the flushing condition. For that purpose, a composite index is needed to combine the soil water saturation index and the net flux index. © 2013. American Geophysical Union. All Rights Reserved.

Zhu P.,Hohai University | Li H.-M.,Jiangxi Academy of Environmental science
Journal of Molecular Structure | Year: 2011

A novel 2D layer complex [Mn(TPA)Cl(H2O)]n (1) has been synthesized by two methods through the reaction of MnCl2 and TPC or TPA under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectrometry (IR), powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA), where heterocyclic carboxylic acid ligand TPA = 2-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)acetic acid, TPC = 2-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)acetonitrile. The distorted octahedral Mn(II) centers are bridged by carboxylic O atoms resulting in the formation of a 1D chain. Then the 1D chains are connected with each other through TPA ligands into a 2D (3,3)-connected topology framework. The H-bonding interactions extend the complex into a three-dimensional network, and such weak interactions further stabilized the complex. Furthermore, solid-state fluorescence spectrum of complex 1 exhibits intense broad emissions at 396 nm at room temperature, which is red-shifted by 21 nm relative to that of free ligand TPA. © 2011 Elsevier B.V. All rights reserved.

The objective function of displacement back analysis for rock parameters in underground engineering is a very complicated nonlinear multiple hump function. The global optimization method can solve this problem very well. However, many numerical simulations must be performed during the optimization process, which is very time consuming. Therefore, it is important to improve the computational efficiency of optimization back analysis. To improve optimization back analysis, a new global optimization, immunized continuous ant colony optimization, is proposed. This is an improved continuous ant colony optimization using the basic principles of an artificial immune system and evolutionary algorithm. Based on this new global optimization, a new displacement optimization back analysis for rock parameters is proposed. The computational performance of the new back analysis is verified through a numerical example and a real engineering example. The results show that this new method can be used to obtain suitable parameters of rock mass with higher accuracy and less effort than previous methods. Moreover, the new back analysis is very robust. © 2015 Taylor & Francis.

Guo Q.,Wuhan University | Guo Q.,Temple University | Guo Q.,Hohai University | Li H.,Wuhan University | And 2 more authors.
Journal of Geophysical Research: Oceans | Year: 2010

This paper investigated the interaction of groundwater and seawater in a tidally influenced gravel beach. Field observations of water table, pore water salinity were performed. The two-dimensional finite element model MARUN was used to simulate observed water table and salinity. Based on field observations and model calibrations, a two-layered beach structure was identified which is characterized by a high-permeability surface layer underlain by a low-permeability lower layer. The salt wedge seaward of the low tide line was almost invariant in comparison with the strong fluctuations of the salinity plume in the surface layer of the intertidal zone. The presence of the two layers prevented the presence of a freshwater discharge "tube" between the upper saline plume and salt wedge. This is in contrast with the previous works where freshwater discharge tube was observed. The tide-induced submarine groundwater discharge (SGD) was estimated at 9 m3 d-1 m-1, a large value that is probably due to the large tidal range of ∼4.8 m and the very permeable surface layer. The freshwater-seawater dynamics revealed here may provide new insights into the complexity, intensity, and time scales of mixing between fresh groundwater and seawater in tidal beaches. The simulated water table of the beach was higher than the interface between the surface layer and the lower layer, which prevented Exxon Valdez oil from penetrating into the lower layer in 1989. Copyright 2010 by the American Geophysical Union.

Kong D.-A.,Hohai University
Shuili Fadian Xuebao/Journal of Hydroelectric Engineering | Year: 2013

To realize the Going Global strategy, the international business of Chinese hydropower enterprises is now increasingly demanding the acceptance of Chinese hydropower technical standards in the international markets. This paper, from the view point of business ecosystem, analyzes the hierarchy structures, contents, structural characteristics and features of Chinese Going Global business by developing a model and using the method of 4P3S. This is based on an analysis on the development of business ecosystem of hydropower technical standards at four stages, development, expansion, authority, and updating and elimination, and also on a comparison of three ecosystems in competition, cooperation and evolution. As a conclusion, the business ecosystem of Chinese hydropower technical standards still remains at its initial stage of development and expansion, and the Going Global management strategy proposed by this paper based on the characteristics of this stage, must be adopted for these standards.

Wang M.,Hohai University
Advanced Materials Research | Year: 2014

Water resource allocation was carried out by a serious of engineering and nonengineering measures. These measures would influence region water cycle on two aspects, cycling process and cycling ways. Based on the data of Ningxia, water cycle changes in different areas caused by different water resource allocation measures were analyzed. A quantificational method about how to affect region water cycle by water resource allocation was also presented. At last, the water cycle changes happened in plain area, Yanghuang area, and south mountainous area were forecasted, that would give some special support for people to carry out water resource allocation rationally. © (2014) Trans Tech Publications, Switzerland.

Dong L.,Hohai University | El-Gizawy A.S.,King Abdulaziz University | Juhany K.A.,King Abdulaziz University | Atluri S.N.,University of California at Irvine
Computers, Materials and Continua | Year: 2014

In this study, a simple 4-node locking-alleviated mixed finite element (denoted as CEQ4) is developed, for the modeling of homogeneous or functionally graded or laminated thick-section composite beam structures, without using higher-order (in the thickness direction) or layer-wise zig-zag theories of composite laminates which are widely popularized in current literature. Following the work of [Dong and Atluri (2011)], the present element independently assumes a 5-parameter linearly-varying Cartesian strain field. The independently assumed Cartesian strains are related to the Cartesian strains derived from mesh-based Cartesian displacement interpolations, by exactly enforcing 5 pre-defined constraints at 5 pre-selected collocation points. The constraints are rationally defined to capture the basic kinematics of the 4-node element, and to accurately model each deformation mode of tension, bending, and shear. A 2 by 2 Gauss quadrature is used when each element is used to model a piece of a homogeneous material or structure, but over-integration (using a higher-order Gauss Quadrature, a layer-wise Gauss Quadrature, or a simple Trapezoidal Rule in the thickness direction) is necessary if functionally-graded materials or thick-section laminated composite structures are considered. Through several numerical examples, it is clearly shown that the present CEQ4 is much more accurate than the well-known Pian-Sumihara (1984) element as well as the primal four-node element, for the modeling of homogeneous beams. For functionally-graded materials, the presently-developed element can accurately capture the stress distribution even when very few elements are used; but the Pian-Sumihara element fails, because the assumption of linearly-varying stressfield is generally invalid unless a very fine mesh is used in the thickness direction. For thick-section laminated composite beams, reasonably accurate solutions (for axial as well as transverse stresses) are obtained even when only one CEQ4 element is used in the thickness direction. Without using higher-order theories or layer-wise zig-zag assumptions for displacement or stress fields in the thickness direction, for thick-section laminates, the present method can accurately compute the jumps in axial stresses at the interfaces of layers. Extension of the present CEQ4 concept to C0 elements of higher-order, for plates and shells as well as for multi-physics will be pursued in future studies. Copyright © 2014 Tech Science Press.

Pappenberger F.,European Center for Medium Range Weather Forecasts | Pappenberger F.,Hohai University | Dutra E.,European Center for Medium Range Weather Forecasts | Wetterhall F.,European Center for Medium Range Weather Forecasts | And 2 more authors.
Hydrology and Earth System Sciences | Year: 2012

Global flood hazard maps can be used in the assessment of flood risk in a number of different applications, including (re)insurance and large scale flood preparedness. Such global hazard maps can be generated using large scale physically based models of rainfall-runoff and river routing, when used in conjunction with a number of post-processing methods. In this study, the European Centre for Medium Range Weather Forecasts (ECMWF) land surface model is coupled to ERA-Interim reanalysis meteorological forcing data, and resultant runoff is passed to a river routing algorithm which simulates floodplains and flood flow across the global land area. The global hazard map is based on a 30 yr (1979-2010) simulation period. A Gumbel distribution is fitted to the annual maxima flows to derive a number of flood return periods. The return periods are calculated initially for a 25 × 25 km grid, which is then reprojected onto a 1 × 1 km grid to derive maps of higher resolution and estimate flooded fractional area for the individual 25 × 25 km cells. Several global and regional maps of flood return periods ranging from 2 to 500 yr are presented. The results compare reasonably to a benchmark data set of global flood hazard. The developed methodology can be applied to other datasets on a global or regional scale. © Author(s) 2012.

Guangbao C.,Hohai University
KSCE Journal of Civil Engineering | Year: 2015

Combining the construction technology of control to large open caisson underwater with quaternion theory, a new algorithm based on a non-iterative strict mathematical method is used to calculate the parameters of caisson spatial geometric states. Firstly, the spatial rotational matrices are derived from quaternion; then, the positive definite matrices and unit quaternion are calculated through minimization of objective function; and finally, parameters of caisson spatial geometric states are derivate by the new algorithm. The proposed method is applied for the caisson sinking of mid-tower in Tai Zhou Yangtze River Bridge, China. The results show that the method for calculating parameters of caisson spatial geometric states is suitable for layout of monitoring points in open caisson anywhere, when monitor points are three or more. © 2014 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg

Tao H.,CAS Nanjing Institute of Geography and Limnology | Gemmer M.,National Climate Center | Jiang J.,CAS Nanjing Institute of Geography and Limnology | Lai X.,CAS Nanjing Institute of Geography and Limnology | Zhang Z.,Hohai University
Climatic Change | Year: 2012

The projected changes of precipitation and temperature in the Yangtze River Basin in the 20th Century from 20 models of the CMIP3 (phase 3 of the Coupled Model Inter-comparison Project) dataset are analyzed based on the observed precipitation and temperature data of 147 meteorological stations in the Yangtze River Basin. The results show that all models tend to underestimate the annual mean temperature over the Yangtze River Basin, and to overestimate the annual mean precipitation. The temporal changes of simulated annual mean precipitation and temperature are broadly comparable with the observations, but with large variability among the results of the models. Most of the models can reproduce maximum precipitation during the monsoon season, while all models tend to underestimate the mean temperature of each month over the Yangtze River Basin. The Taylor diagram shows that the differences between modeled and observed temperature are relatively smaller as compared to differences in precipitation. For a detailed investigation of regional characteristics of climate change in the Yangtze River Basin during 2011-2050, the multi-model ensembles produced by an upgraded REA method are carried out for more reliable projections. The projected precipitation and temperature show large spatial variability in the Yangtze River Basin. Mean precipitation will increase under the A1B and B1 scenarios and decrease under the A2 scenario, with linear trends ranging from -21 to 28. 5 mm/decade. Increasing mean temperature can be found in all scenarios with linear trends ranging from 0.15 to 0.48°C/decade. Grids in the head region of the Jingshajiang catchment show distinct increasing trends for all scenarios. Some physical processes associated with precipitation are not well represented in the models. © 2011 Springer Science+Business Media B.V.

Phi S.,University of Queensland | Clarke W.,University of Queensland | Li L.,University of Queensland | Li L.,Hohai University
Journal of Hydrology | Year: 2013

Runoff is a key process that controls the behaviour of a hillslope hydrological system. The study presented here aims to examine the mechanisms of runoff generation due to saturation excess by investigating the development of the subsurface saturated zone. Experiments were conducted on a hillslope system with a uniform slope (0.2) and a relatively homogeneous and highly permeable medium (Ks=. 1.28. cm/min), subjected to high and constant surface recharges (0.51-0.69. cm/min). Two initial conditions prior to the rainfall events were set up in the experiments to represent relatively dry and wet antecedent soil conditions, respectively. Measurements showed that during vertical infiltration, local pressure head and soil moisture remained constant for a certain period, showing a 'waiting' behaviour. The saturated area formed initially at the slope toe, quickly rose to the surface and subsequently expanded to the upslope. When propagating in the upslope direction, the wetting front caused the pore-water flow to deflect in areas above the wetting front and at the slope base. With a wetter initial condition, the soil responded to the rainfall more quickly. The initial moisture conditions also altered the relation between the subsurface discharge and pressure head. Under the applied rainfall rates, the system reached a fully saturated condition and produced surface runoff. The rainfall intensity was found to affect the temporal variations and magnitude of surface runoff characteristics; however it did not seem to impose any significant effect on the maximum subsurface discharge rate. These results provide insight into the behaviour of the hillslope system in response to rainfall. © 2013.

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.

Su H.-L.,Nanjing University of Finance and Economics | Lu Y.-S.,Hohai University
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2014

The measurement of particle density is affected by particle size and color in the optical method. The KML (Kumbelka-Munk-Lu) back extinction scattering equations were built that included the particle density, size and color of uniform suspension. The III function was concluded from KML back extinction scattering equation. The III function is composed of spectrum factor and particle spectrum factor. Particle size can be measured by KML back scattering with particle spectrum factor. Finally, the KML method was tested to be practicable, and the accuracy could meet engineerings.

Jiang Y.,Hohai University
Advanced Composites Letters | Year: 2015

The composite lattice structure is regarded as a porous materialin the present work, and then the corresponding compression mechanismis clearly interpretedby a simple but reasonable phenomenologicalmodel, which containing a damage elementto account for the micro-buckling progressionand a reinforcementelementfor the reductionof void volume fraction. Moreover, a micromechanics model is developed to quantitatively characterizethe stiffness degradation induced by the micro-bucklingdeformation.Theaccuracy of the analytical model is verified by the comparison with experiments.

Dong Y.-W.,Chongqing Jiaotong University | Ren Q.-W.,Hohai University
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2011

Hydraulic fracture is a main inducement leading to high dam failure under the loading of large water pressure. Aiming at the drawback of FEM in modeling hydraulic fracture, an extended finite element method (XFEM) for modeling hydraulic fracturing process in gravity dam is studied. The governing equation of XFEM for hydraulic fracture modeling is derived by building the virtual work principle of the fracture problem considering water pressure loading on the crack surface. Then the implement method of XFEM for hydraulic fracture modeling is deduced, such as numerical integration of discontinuous functions reflecting discontinuity of the crack surface, crack growth criteria, integral method of stress intensity factors, and the modeling method of crack propagation. Finally, the feasibility and superiority of this method are exhibited through numerical analysis of the Xiangjiaba gravity dam with XFEM. Comparing with classical FEM, the crack growth in the gravity dam can be modeled by XFEM without making the crack surface associated to the mesh, without setting dense mesh near the crack tip and without remeshing after crack growth. Thus the disadvantages of hydraulic fracturing analysis with FEM are avoided and the pre-processing work is simplified.

Tan X.,Hohai University
2011 International Conference on Multimedia Technology, ICMT 2011 | Year: 2011

Microcystis is the most common dominant species in bloom-forming cyanobacteria, which are influenced by some environmental factors. Among these factors, epiphytic bacteria are one of the important biotic factors for Microcystis growth. In this paper, four kinds of antibiotics (penicillin, chloramphenicol, polymyxin, rifampin) were used to inhibit epiphytic bacteria of Microcystis aeruginosa, aiming to study sensitivity and growth condition of Microcystis aeruginosa under different antibiotics concentration. Results showed that lethal concentration sequence of these antibiotics for Microcystis aeruginosa was as following: penicillin (100μg/mL) > chloramphenicol (10μg/mL) > polymyxin (1μg/mL) > rifampin (0.1μg/mL). Under the lethal concentration, no significant differences were observed in algal growth curves among control and treatment groups (P >0.05), thus influences of epiphytic bacteria on the growth of Microcystis aeruginosa were not obvious. © 2011 IEEE.

Ji L.,Nanjing University | Ji L.,Hohai University | Chen W.,Nankai University | Xu Z.,Nanjing University | And 2 more authors.
Journal of Environmental Quality | Year: 2013

Graphenes are an emerging class of carbon nanomaterials whose adsorption properties toward organic compounds have not been well understood. In the present study, graphene nanosheets were prepared by reoxidation and abrupt heating of graphite oxide, which was prepared by sequential chemical oxidation of commercial nonporous graphite powder. Adsorption properties of three aromatic compounds (naphthalene, 2-naphthol, and 1-naphthylamine) and one pharmaceutical compound (tylosin) on graphene nanosheets and graphite oxide were examined to explore the potential of these two adsorbents for the removal of organic contaminants from aqueous solutions. Compared with the literature data of adsorption on carbon nanotubes, adsorption of bulky, flexible tylosin on graphene nanosheets exhibited markedly faster adsorption kinetics, which can be attributed to their openedup layer structure. Graphene nanosheets and graphite oxide showed similar sequences of adsorption affinity: 1-naphthylamine > 2-naphthol > tylosin > naphthalene (with much larger differences observed on graphite oxide). It was proposed that the strong adsorption of the three aromatic compounds was mainly due to π-π electron donor-acceptor interactions with the graphitic surfaces of adsorbents. Additionally, Lewis acid-base interaction was likely an important factor contributing to the strong adsorption of 1-naphthylamine and tylosin, especially for the O-functionalityabundant graphite oxide. After being normalized on the basis of adsorbent surface area, adsorption affinities of all four tested adsorbates on graphene nanosheets were very close to those on nonporous graphite powder, reflecting complete accessibility of the adsorbent surface area in adsorption. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Bishay P.L.,University of California at Irvine | Bishay P.L.,Saint Martins 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.

Lu Y.,Hohai University
Communications in Computer and Information Science | Year: 2011

Certificate-based encryption (CBE) is a new asymmetric encryption paradigm which combines traditional public-key encryption and identity-based encryption (IBE) while preserving some of their most attractive features. It provides an efficient implicit certificate mechanism which eliminates the third-party queries and simplifies the certificate revocation problem in the traditional PKI. It also solves the key escrow problem and the key distribution problem inherent in IBE. In this paper, we propose a quite efficient CBE scheme which is chosen-ciphertext secure in the random oracle model. The proposed CBE scheme requires computing only one bilinear pairing and introduces no redundancies in ciphertext. Compared with the existing CBE schemes, our scheme enjoys better performance on both the computation efficiency and the communication bandwidth. © 2011 Springer-Verlag.

Paerl H.W.,University of North Carolina at Chapel Hill | Xu H.,CAS Nanjing Institute of Geography and Limnology | McCarthy M.J.,University of Quebec at Montreal | McCarthy M.J.,University of Texas at Austin | And 4 more authors.
Water Research | Year: 2011

Harmful cyanobacterial blooms, reflecting advanced eutrophication, are spreading globally and threaten the sustainability of freshwater ecosystems. Increasingly, non-nitrogen (N2)-fixing cyanobacteria (e.g., Microcystis) dominate such blooms, indicating that both excessive nitrogen (N) and phosphorus (P) loads may be responsible for their proliferation. Traditionally, watershed nutrient management efforts to control these blooms have focused on reducing P inputs. However, N loading has increased dramatically in many watersheds, promoting blooms of non-N2 fixers, and altering lake nutrient budgets and cycling characteristics. We examined this proliferating water quality problem in Lake Taihu, China's 3rd largest freshwater lake. This shallow, hyper-eutrophic lake has changed from bloom-free to bloom-plagued conditions over the past 3 decades. Toxic Microcystis spp. blooms threaten the use of the lake for drinking water, fisheries and recreational purposes. Nutrient addition bioassays indicated that the lake shifts from P limitation in winter-spring to N limitation in cyanobacteria-dominated summer and fall months. Combined N and P additions led to maximum stimulation of growth. Despite summer N limitation and P availability, non-N2 fixing blooms prevailed. Nitrogen cycling studies, combined with N input estimates, indicate that Microcystis thrives on both newly supplied and previously-loaded N sources to maintain its dominance. Denitrification did not relieve the lake of excessive N inputs. Results point to the need to reduce both N and P inputs for long-term eutrophication and cyanobacterial bloom control in this hyper-eutrophic system. © 2010 Elsevier Ltd.

Li Y.,State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | Li Y.,Desert Research Institute | Li Y.,Hohai University | Acharya K.,Desert Research Institute | And 2 more authors.
Ecological Engineering | Year: 2011

To improve water quality and alleviate eutrophication in Lake Taihu, the third largest freshwater lake in China, a Yangtze River water transfer project was initiated in 2002 to bring water from the Yangtze River to Lake Taihu to dilute and divert pollutants out of the lake. We used a three-dimensional numerical model, Environmental Fluid Dynamics Code, to study the impacts of water transfer on the transport of dissolved substances in the lake by using the concept of water age. In particular, the influences of inflow tributaries and wind forcing on water age were investigated. Model results showed that the effect of water transfer on transport processes in the lake is strongly influenced by hydrodynamic conditions induced by wind and inflow/outflow tributaries. During the simulation year (2005), the water ages in Lake Taihu were highly variable both spatially and temporally, with a mean of approximately 130 days in summer and 230 days in the other seasons. Southeasterly winds-dominant in the summer-could improve the quality of water by reducing the water age in the eastern areas of the lake, which are used as a drinking water source, and in Meiliang Bay, the most polluted bay. In terms of dilution, the most efficient flow rate for transferred water was predicted to be approximately 100m3/s. The spatial distribution of water ages showed that water transfer may preferentially enhance exchanges in some areas of the lake unless nutrient concentrations in the transferred water are reduced to a reasonable level. This study provides useful information for a better understanding of the complex hydrodynamic and mass transport processes in the lake, which is important for developing and implementing effective ecological restoration strategies in the region. © 2010 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.

Zhai J.,Hohai University | Tian W.,Ocean University of China | Liu K.,Ocean University of China
Environmental Monitoring and Assessment | Year: 2011

In this study, 16 polycyclic aromatic hydrocarbons (PAHs) were detected in sewage sludge samples from four wastewater treatment plants (WWTPs) in Qingdao, China. These WWTPs differ in the type of treatment used and in the origin of the wastewater. The total amounts of PAHs in digested sludges ranged from 1.9645 to 6.5752 mg/kg, which did not exceed the projected European Union cut-off limits (6 mg/kg) for sludge found in farmland, except for the Haibohe WWTP. Significant differences were observed in overall PAH values between WWTPs receiving domestic effluents and those receiving industrial effluents. The total amounts of PAHs in digested sludge from the Licunhe and Haibohe WWTPs, which mainly received industrial effluents, were markedly higher than those of the Tuandao and Huangdao WWTPs, which received only domestic effluents. The distribution of PAH compounds in digested sludges were analysed. At the Tuandao, Huangdao and Licunhe WWTPs, 2-, 3-, 4-benzene rings were predominant, accounting for 100%, 99.8% and 99.0% of the sum concentration of 16 PAHs (∑PAHs), respectively. At the Haibohe WWTP, a large number of high molecular weight PAHs (5-, 6-benzene rings) were observed, accounting for 30% of the ∑PAHs. The sum of seven carcinogenic PAHs (∑PAHs-c) ranged from 0.8694 to 3.0389 mg/kg in four WWTPs. The highest value was found in the Haibohe WWTP. Moreover, the PAH concentrations in sludges from the different treatment processes in the Licunhe and Tuandao WWTPs are discussed. © 2011 Springer Science+Business Media B.V.

Hu Z.,Hohai University | Lu Y.Y.,City University of Hong Kong
Optics Communications | Year: 2011

For two-dimensional photonic crystals involving infinitely long dielectric rods or air-holes on square or triangular lattices, a number of high performance 60° and 90° waveguide bends are obtained by solving optimization problems involving the radii of a few rods or air-holes as the degrees of freedom. In particular, the proposed 60° bends significantly outperform previous designs that insert three or five identical air-holes in the bend. The optimization problems are solved using a recently developed method based on the so-called Dirichlet-to-Neumann (DtN) maps of the unit cells. © 2011 Elsevier B.V. All rights reserved.

Zhuang Y.,Hohai University | Ellis E.,University of Plymouth
Geotechnique | Year: 2014

The British ‘Code of practice for strengthened/reinforced soils and other fills’ (BS 8006) was substantially revised in 2010, with a further ‘Corrigendum’ in 2012. Historically, BS 8006 considered arching in a piled embankment, based on an interpretation of the ‘Marston’ equation. The 2010 revision included an alternative method related to the analysis of arching in a piled embankment, which was proposed by Hewlett and Randolph in 1988, and later itself amended in the 2012 Corrigendum. This contribution considers BS 8006 predictions of reinforcement tension using these methods as a basis for embankment load on the reinforcement, for a wide range of piled embankment geometries. The predictions are compared with results from three-dimensional finite-element analysis, demonstrating encouraging correspondence with the Hewlett and Randolph approach (but noting that the 2010 revision overpredicts the data whereas the 2012 revision underpredicts it). Good predictions of maximum reinforcement sag are also achieved by slight modification of the BS 8006 method. © 2014, Thomas Telford Services Ltd. All Rights Reserved.

Wu Q.-Y.,Tsinghua University | Hu H.-Y.,Tsinghua University | Zhao X.,Tsinghua University | Li Y.,Hohai University
Chemosphere | Year: 2010

Recently, NH4+ has been reported to induce potential risks during wastewater chlorination. Thus, the effects of chlorination on genotoxicity and fluorescence spectra of secondary sewage effluents, were investigated in this study before and after adding a high NH4+ quantity. Chlorination decreased the genotoxicity of secondary sewage effluent, while the presence of a high level of NH4+ inhibited this decrease. By further ultrafiltration following XAD-8 resin fractionation, it was found that, with a high NH4+ concentration, the genotoxicity in the fraction of hydrophobic acids (HOA) increased after chlorination and a sub-fraction of HOA with molecular weight less than 1. kDa was the key fraction resulting in this increase. Similar to genotoxicity changes, NH4+ was also found to influence the changes in fluorescence spectra during chlorination. After chlorination, the fluorescence intensity of the dissolved organic matter (DOM) notably decreased, and the emission band of DOM fluorescence spectra shifted to a lower wavelength. However, the presence of NH4+ inhibited both the decrease in intensity and shift. The changes in fluorescence spectra suggested that the fluorescent structure of secondary effluent may decompose during chlorination, but NH4+ could inhibit this decomposition. © 2010 Elsevier Ltd.

Liu R.,Hohai University | Liu Y.,Tongji University
Journal of Constructional Steel Research | Year: 2015

The auxiliary ribs are utilized to reinforce the steel-concrete joints (SCJs) of hybrid girders. However, the demands of the ribs and the design of orthotropic steel decks with the auxiliary ribs are not addressed in design specifications. Solid element models are used to study the auxiliary ribs of the SCJ. The joints with and without auxiliary ribs are analyzed to clarify the demands and the reinforcing effects of the ribs. Stress dispersal efficiency of three typical auxiliary ribs is investigated. The trough-auxiliary rib (TA) joint is analyzed to check the steel deck design assumption and the approach to suppress stress concentration is discussed. The effective length of the auxiliary ribs is studied considering the geometric variations. Results show that the auxiliary ribs enlarge the steel deck and narrow the steel-concrete centroid deviation. The auxiliary ribs disperse about 50% axial force and the stress transmission of the joint is improved. The T-rib inserted in the trough is efficient to reinforce the SCJ with the effective length of 2-4 times the concrete slab thickness. The TA joint with abrupt tip suffers stress concentration and the safety margin of the steel deck is reduced. The joint is improved with about 60% hot spot stress decrease using the gentle tip with crossbeam constraint. © 2015 Elsevier Ltd. All rights reserved.

Liang H.,Hohai University
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2014

There is higher fault probability under the bad work conditions of rod pumping system. Because of the large amount of sample and the long-time steady status, this paper proposes hierarchical fault diagnosis method. Fault distinguishing and fault identification are two phases in this method. In fault distinguishing, fault phase and normal phase are classified according to statistical rule of normal sample in dynamometer card. Combining statistical theory and search-tree, fault identification is processed in fault sample. Using this method, mechanical model of rod pumping system is not to be established and training set of fault sample is not necessary. Fault distinguishing process includes: fault taring phase and fault distinguishing phase. In fault training phase, stochastic distribution rule and parameters of samples are determined by χ2 goodness-of-fit test after abnormal samples are rejected, then normal area and fault area is calculated. In fault distinguishing phase, classification of fault is estimated according to whether or not feature value of test sample is in fault area. Examples indicate fault samples can be selected from large number of samples in distinguish fault and correct rate of fault distinguishing is high. Statistical rule of training samples can reflect the actual production of oil well.

Xiuxiu S.,Hohai University
Advance Journal of Food Science and Technology | Year: 2015

Based on stakeholder theory, through an empirical analysis of the enterprises in food manufacturing industry which people are very concerned about, the study researched the correlation between food enterprises' Corporate Social Responsibility (CSR) and enterprise value. The result of the study indicated that food enterprises fulfilling the responsibility to shareholder was significantly positively related to enterprise value and fulfilling the responsibility to the creditors, suppliers, consumers, government and society donation had a not significantly positive correlation with corporate value. But the responsibility to the staff has a not significant negative correlation with enterprise value, indicating that food companies should enhance the concern of efficiency for human input. © Maxwell Scientific Organization, 2015.

Hu M.,Hohai University
Advance Journal of Food Science and Technology | Year: 2015

Food companies present the variety, quantity and characteristics of all sizes in the development of the market. When consumers choose the food company, the difference is big, but the brand image is the core factor of the food enterprises to gain advantages in competition. In the brand crisis, how to carry out the brand crisis management is very important for food industry. In this study, by KFC occurred two big events that "Sudan" event and "seckill scandal" event, using the method of case analysis method and brainstorming method to analysis that the KFC, the successes and failures of such large-scale enterprise in dealing with such a brand crisis and hope that the companies similar to the KFC food enterprises can use some strategies to get out of their own brand crisis. Finally, based on the whole food enterprises, learning from the KFC brand crisis management, we put forward some countermeasures of food enterprise brand crisis management. © Maxwell Scientific Organization, 2015.

A method incorporating the optically induced electrorotation (OER) and alternating current electroosmotic (ACEO) effects, for the formation and motion control of microparticle chains, is numerically and experimentally demonstrated. In this method, both the rotating electric field and ACEO fluid roll are generated around the border between light and dark area of the fluidic chamber in an optoelectronic tweezers (OET) device. The experimental results show that the particle chains can self-rotate in their pitch axes under the rotating electric field produced due to the different impedances of the photoconductive layer in light and dark areas, and have a peak self-rotating rate at around 1 MHz. The orbital movement of entire particle chain around the center of ACEO fluid roll can be achieved from 0.5 to 600 kHz. The strength of OER motion and ACEO-caused orbital movement of particle chains can be adjusted by changing the frequency of alternating current (AC) voltage. This non-contact method has the potential for spatially regulating the posture, orientation and position of microparticle chains. © 2015 by the authors.

Rui M.,Hohai University
Advance Journal of Food Science and Technology | Year: 2015

This study from the perspective of the quality of the signal by 191 consumers in Nanjing questionnaire using SPSS statistical software factors to consider when consumers choose yogurt were analyzed, analysis safety certification, durability, price, brand awareness and whether the quality of the signal in the supermarket to buy consumer willingness to buy influence in varying degrees and finally put forward specific recommendations based on the analysis results. © Maxwell Scientific Organization, 2015.

Cheng J.B.,Hohai University | Cheng J.B.,National Key Laboratory for Remanufacturing | Liang X.B.,National Key Laboratory for Remanufacturing | Xu B.S.,National Key Laboratory for Remanufacturing
Surface and Coatings Technology | Year: 2014

The microstructure and mechanical properties of the CoCrCuFeNiNb high-entropy alloy coating prepared by plasma transferred arc cladding process were investigated. Two phases are found in the prepared coating with Nb: one is face-centered-cubic solid solution phase; the other is the Laves phase of (CoCr) Nb type. The nano-indentation testing indicates that the microhardness (H), elastic modulus (E), the hardness/modulus of elasticity ratio (H/E ratio) and high resistance to plastic deformation (H3/E2) of the coating with Nb are 6.13GPa, 221GPa, 0.028 and 4.7×10-3 respectively. The CoCrCuFeNiNb coating displays excellent wear and corrosion resistance. The wear resistance of the coating with Nb is about 1.5 times higher than that of the coating without Nb under the same wet sand rubber wheel abrasion testing conditions. Compared with the coating without Nb and as-cast 304 stainless steel, the coating with Nb shows the lowest icorr values in polarization curves and the highest fitted Rf values in EIS plots in 6N hydrochloric acid solution. © 2013 Elsevier B.V.

Li X.,Hohai University
ICNSC 2015 - 2015 IEEE 12th International Conference on Networking, Sensing and Control | Year: 2015

The global spread revolution of information and information technology is playing a decisive role to social change. Internet has become the most effective way for information transmission, whose role is network security. How to guarantee network security has become a serious and worrying problem. Biometric identification technology has some advantages including universality, uniqueness, stability and hard to be stolen. Through comparing with the other methods of biometric identification technology, such as fingerprint recognition, palm recognition, facial recognition, signature recognition, iris recognition and retina recognition, gene recognition has advantages of exclusiveness, never change, convenience and a large amount of information, which is thought to be the most important method of biometric identification technology. With the development of modern technology, the fusion of biological technology and information technology has become an inevitable trend. Biometric identification technology will necessarily replace the traditional identification technology and greatly change the life-style of people in the near future. © 2015 IEEE.

Chen Y.,Hohai University
World Transactions on Engineering and Technology Education | Year: 2016

To explore the main factors influencing civil engineering students' artistic accomplishments, a survey questionnaire was developed covering the professional knowledge of structures, creative thinking, cultural accomplishments, artistic ability and interpersonal communications. Based on factor analysis, the factors influencing the engineering artistic accomplishments of Chinese engineering students are: engineering humanities; professional technical ability; aesthetic and design ability; and interpersonal co-ordination ability. The four factors make varying contributions, but all are significant in improving students' artistic accomplishments. © 2016 WIETE.

Liu B.,Tianjin University | Shen Y.,Hohai University | Chen Y.,Tianjin University | Chen X.,Central South University | Wang Y.,Tianjin University
Information Fusion | Year: 2015

We propose a two-layer weight determination model in a linguistic environment, when all the clustering results of the experts are known, to objectively obtain expert weights in complex multi-attribute large-group decision-making (CMALGDM) problems. The linguistic information considered in this paper involves both linguistic terms and linguistic intervals. We assume that, for CMALGDM problems, the final expert weights should be determined based on the expert weight in the cluster and on the cluster weights. This is mainly because experts in the same cluster will certainly make varying contributions to the cluster's overall consensus, and different clusters will also obtain the distinctive "cluster information quality". Hence, a Minimized Variance Model and an Entropy Weight Model are proposed to determine the expert weights in the cluster and the cluster weights, respectively. We then synthesize these two types of weights into the final objective weights of the CMALGDM experts. The feasibility of the two-layer weight determination model method for the CMALGDM problems is illustrated using a case study of salary reform for professors at a university. © 2014 Elsevier B.V. All rights reserved.

Yan Q.,Hohai University | Vaseghi S.,Brunel University
Computer Speech and Language | Year: 2010

This paper provides an introduction to the acoustic-phonetic structure of English regional accents and presents a signal processing method for the modeling and transformation of the acoustic correlates of English accents for example from British English to American English. The focus of this paper is on the modeling of intonation and duration correlates of accents as the modeling of formants is described in previous papers (Yan et al., 2007; Vaseghi et al., 2009). The intonation correlates of accents are modeled with the statistics of a set of broad features of the pitch contour. The statistical models of phoneme durations and word speaking rates are obtained from automatic segmentation of word/phoneme boundaries of speech databases. A contribution of this paper is the use of accent synthesis for comparative evaluation of the causal effects of the acoustic correlates of accent. The differences between the acoustics-phonetic realizations of British Received Pronunciation (RP), Broad Australian (BAU) and General American (GenAm) English accents are modeled and used in an accent transformation and synthesis method for evaluation of the influence of formant, pitch and duration on conveying accents. © 2010 Elsevier Ltd. All rights reserved.

Zhou J.,Hohai University
International Journal of Robust and Nonlinear Control | Year: 2015

Absolute stability with the spatially defined linear time-invariant (LTI) state-space modelings is scrutinized by means of what we call the sequential Lyapunov approach, which possesses independent significance in stabilization when gain-scheduling control laws are adopted. Then, this theoretical result is exploiting for stabilization of individual generators via SVC actions. More precisely, by remodeling the perturbed swing equations of synchronous generators in multimachine networks through spatially defined LTI state-space expressions subjected to uncertainties and power disturbance, which are viewed as sector nonlinearities, we introduce frequency responses for coping with nonlinear power swing dynamics of individual generators. By sequentially relating the frequency responses to the circle criterion (substantially, the KYP theorem or the positive real lemma) claimed for LTI systems subject to sector disturbances, output feedback control laws for static VAR compensators are worked out to stabilize individual generators. The frequency-domain approach is also useful in steady-state specification besides stabilization in individual generators. Examples show efficacy of the suggested stabilization and steady-state specification technique. Copyright © 2014 John Wiley & Sons, Ltd.

Tang B.,Hunan University of Science and Technology | Wang Y.,Hohai University
Research Journal of Applied Sciences, Engineering and Technology | Year: 2012

In large-scale Wireless Sensor Networks (WSNs), with limited computing power and storage capacity of sensor nodes, there is an urgent demand of high performance sensory data processing. This study studies the interconnection of wireless sensor networks and cloud-based storage and computing infrastructure. It proposes the idea of distributed databases to store sensory data and MapReduce programming model for large-scale sensory data parallel processing. In our prototype of large-scale sensory data processing system, Hadoop Distributed File System (HDFS) and HBase are used for sensory data storage, and Hadoop MapReduce is used for data processing application execution framework. The design and implementation of this system are described in detail. The simulation of environment temperature surveillance application is used to verify the feasibility and reasonableness of the system, which also proves that it significantly improves the data processing capability of WSNs. © Maxwell Scientific Organization, 2012.

Gao W.,Hohai University
Materials Research Innovations | Year: 2015

From the generalised constitutive law of rheological constitutive model of rock material, the model identification is transformed to parameter identification. To improve the efficiency of the traditional evolutionary algorithm, a new immune continuous ant colony algorithm proposed by the author is applied in this study, based on which one new model identification method is proposed. Using this new method, a real engineering example is applied to verify the computing ability of the new algorithm. The results show that the effect and efficiency of the new method are very good. © W. S. Maney & Son Ltd 2015.

Yu D.,Zhejiang University of Finance and Economics | Zhang W.,Zhejiang University of Finance and Economics | Xu Y.,Hohai University
Knowledge-Based Systems | Year: 2013

In many personnel evaluation scenarios, decision makers are asked to provide their preferences anonymously to both ensure privacy and avoid psychic contagion. The use of hesitant fuzzy sets is a powerful technique for representing this type of information and has been well studied. This paper explores aggregation methods for prioritized hesitant fuzzy elements and their application on personnel evaluation. First, the generalized hesitant fuzzy prioritized weighted average (GHFPWA) and generalized hesitant fuzzy prioritized weighted geometric (GHFPWG) operators are presented. Some desirable properties of the methods are discussed and special cases are investigated in detail. Previous research has indicated that many existing hesitant fuzzy aggregation operators are special cases of the proposed operators. Then, a procedure and algorithm for group decision making is provided using these proposed generalized hesitant fuzzy aggregation operators. Finally, the group decision making method is applied to a representative personnel evaluation problem that involves a prioritization relationship over the evaluation index. © 2013 Elsevier B.V. All rights reserved.

Yan B.,Hohai University | Yan B.,Changjiang River Scientific Research Institute | Fang N.F.,CAS Institute of Soil and Water Conservation | Zhang P.C.,Changjiang River Scientific Research Institute | And 2 more authors.
Journal of Hydrology | Year: 2013

Understanding how changes in individual land use types influence the dynamics of streamflow and sediment yield would greatly improve the predictability of the hydrological consequences of land use changes and could thus help stakeholders to make better decisions. Multivariate statistics are commonly used to compare individual land use types to control the dynamics of streamflow or sediment yields. However, one issue with the use of conventional statistical methods to address relationships between land use types and streamflow or sediment yield is multicollinearity. In this study, an integrated approach involving hydrological modelling and partial least squares regression (PLSR) was used to quantify the contributions of changes in individual land use types to changes in streamflow and sediment yield. In a case study, hydrological modelling was conducted using land use maps from four time periods (1978, 1987, 1999, and 2007) for the Upper Du watershed (8973km2) in China using the Soil and Water Assessment Tool (SWAT). Changes in streamflow and sediment yield across the two simulations conducted using the land use maps from 2007 to 1978 were found to be related to land use changes according to a PLSR, which was used to quantify the effect of this influence at the sub-basin scale. The major land use changes that affected streamflow in the studied catchment areas were related to changes in the farmland, forest and urban areas between 1978 and 2007; the corresponding regression coefficients were 0.232, -0.147 and 1.256, respectively, and the Variable Influence on Projection (VIP) was greater than 1. The dominant first-order factors affecting the changes in sediment yield in our study were: farmland (the VIP and regression coefficient were 1.762 and 14.343, respectively) and forest (the VIP and regression coefficient were 1.517 and -7.746, respectively). The PLSR methodology presented in this paper is beneficial and novel, as it partially eliminates the co-dependency of the variables and facilitates a more unbiased view of the contribution of the changes in individual land use types to changes in streamflow and sediment yield. This practicable and simple approach could be applied to a variety of other watersheds for which time-sequenced digital land use maps are available. © 2013 Elsevier B.V.

Zeng X.,Nanjing University | Wang D.,Nanjing University | Wu J.,Nanjing University | Chen X.,Hohai University
Human and Ecological Risk Assessment | Year: 2013

The hydrologic model is the foundation of water resource management and planning. Conceptual model is the essential component of groundwater model. Due to limited understanding of natural hydrogeological conditions, the conceptual model is always constructed incompletely. Therefore, the uncertainty in the model's output is evitable when natural groundwater field is simulated by a single groundwater model. A synthetic groundwater model is built and regarded as the true model, and three alternative conceptual models are constructed by considering incomplete hydrogeological conditions. The outputs (groundwater budget terms from boundary conditions) of these groundwater models are analyzed statistically. The results show that when the conceptual model is closer to the true hydrogeological conditions, the distributions of outputs of the groundwater model are more concentrated on the true outputs. Therefore, the more reliable the structure of the conceptual model is, the more reliable the output of the groundwater model is. Moreover, the uncertainty caused by the conceptual model cannot be compensated by parameter uncertainty. © 2013 Copyright Taylor and Francis Group, LLC.

Dong L.,University of California at Irvine | Dong L.,Hohai University | Atluri S.N.,University of California at Irvine | Atluri S.N.,King Abdulaziz University
Computers, Materials and Continua | Year: 2013

In this study,SGBEM Voronoi Cells (SVCs), with each cell representing a grain of the material at the micro-level, are developed for direct micromechanical numerical modeling of heterogeneous composites. Each SVC can consist of either a (each with a different) homogenous isotropic matrix, and can include micro-inhomogeneities such as inclusions, voids of a different material, and cracks. These inclusions and voids in each SVC can be arbitrarily-shaped, such as circular, elliptical, polygonal, etc., for 2D problems. Further, the cracks in each SVC can be fully-embedded, edge, branching, or intersecting types, with arbitrary curved shapes. By rearranging the weakly-singular boundary integral equations, a stiffness matrix and a force vector are developed for each SVC with inclusions, voids, and micro-cracks. The stiffness matrix of each SVC is symmetric, positive semidefinite, and has the correct number of rigid-body modes. The stiffness matrix of each SVC and the force vector can also be interpreted to have the same physical meaning as in traditional displacement finite elements, and related to strain energy and the work done. Therefore, the direct coupling of different SVCs (each with a different isotropic material property, and each with heterogeneities of a different material), or the coupling of SVCs with other traditional or special elements, can be achieved by the usual assembly procedure. Moreover, because the heterogeneous micro-structures are modeled directly in the most natural way, as in the present work, by using an SVC to model each grain, one not only saves the labor of meshing and re-meshing, but also reduces the computational burden by several orders of magnitude as compared to the usual FEM. Through several numerical examples, we demonstrate that the SVCs are useful in not only estimating the overall stiffness properties of heterogeneous composite materials, but they are most useful in capturing the local stress concentrations and singularities in each grain, which act as damage precursors, efficiently. Several examples of interaction of cracks with inclusions and voids within each SVC (or material grain) are also presented. Accurate results are obtained for stress intensity factors. Non-collinear fatigue growth of micro-cracks in heterogeneous materialis also modeled very efficiently, with these SVCs, without a need for the complicated re-meshing as is common when using the traditional displacement-based finite element methods. Copyright © 2013 Tech Science Press.

Qin B.Z.,Nanjing College of Chemical Technology | Lu X.B.,Hohai University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010

Global synchronization of directed networks with switching topologies is investigated. It is found that if there exists at least one directed spanning tree in the network with the fixed time-average topology and the time-average topology is achieved sufficiently fast, the network will reach global synchronization for appreciate coupling strength. Furthermore, this appreciate coupling strength may be obtained by local adaptive approach. A sufficient condition about the global synchronization is given. Numerical simulations verify the effectiveness of the adaptive strategy. © 2010 Elsevier B.V. All rights reserved.

Jian W.,Hohai University
Journal of Magnetism and Magnetic Materials | Year: 2012

The La 0.833K 0.167MnO 3:Ag 2O and the La 0.833K 0.167MnO 3:SrTiO 3 samples are fabricated by the solgel method. The microstructure, magnetic and transportation properties have been systematically studied. X-ray diffraction patterns show that the La 0.833K 0.167MnO 3:Ag 2O (abbreviated as LKMO/Ag) sample is a two-phase composite and consists of a magnetic La 0.833K 0.167MnO 3 (abbreviated as LKMO) perovskite phase and a nonmagnetic Ag metal phase, while the structure of the La 0.833K 0.167MnO 3:SrTiO 3 (abbreviated as LKMO/STO) sample is a homogeneous solid solution phase. Comparing with the pure LKMO sample, the room temperature magnetoresistance (MR) effect for the LKMO/Ag sample is enhanced significantly due to the addition of Ag metal. The MR ratio increases from ∼25% for the pure LKMO sample to 65% for the LKMO/Ag sample under a higher field of 5.5 T at 300 K. For the LKMO/STO sample, however, the room temperature MR effect is weakened dramatically and is almost close to zero due to the addition of SrTiO 3 insulator. In the low temperature regime below the Curie temperature, the MR behaviors are different from that of the room temperature; that is, the MR effect is decreased for the LKMO/Ag sample and increased for the LKMO/STO sample with temperature decrease. In fact, the low-field (μ 0H=0.5 T) MR decreases from 32% to 5% for the LKMO/Ag sample, while increasing from 0.07% to 25% for the LKMO/STO sample with decreasing temperature from 300 to 4 K. The relative change between the intrinsic and the extrinsic MR, and varied roles of the spin-polarized-tunneling and the spin-dependent scattering mechanisms in different temperature regimes are employed to interpret the anomalous transport behaviors. © 2012 Elsevier B.V. All rights reserved.

Wang W.,Hohai University | Liu J.,Lille Laboratory of Mechanics | Agostini F.,Lille Laboratory of Mechanics | Davy C.A.,Lille Laboratory of Mechanics | And 2 more authors.
Cement and Concrete Research | Year: 2014

We assess the durability of an Ultra High Performance Fiber Reinforced Concrete (UHPFRC) after accelerated aging, i.e. after partial drying, or 105 C oven-drying (dry reference state), 200, 300 or 400 C heat-treatment, or progressive splitting (Brazilian test). Our key experimental tool is gas permeability Kgas under varying confinement Pc, coupled to MIP and SEM analysis. UHPFRC properties are compared to standard mortar and ordinary concrete. Whereas usual UHPFRCs involve pozzolanic additions and thermal curing, this UHPFRC does not, and is significantly more porous (by 9-10%). However, 74% of its porosity comprises pores smaller than 4 nm, i.e. located within the C-S-H. Dry reference state UHPFRC lies in the range of very high durable materials, with an average Kgas = 10- 18 m2. Damage by heat-treatment at 400 C induces limited de-bonding at the fiber/paste interface, which increases Kgas up to 10 - 17 m2 at Pc = 6 MPa. While sustaining more than 300 μm/m tensile strain, Kgas of UHPFRC remains virtually identical. © 2013 Elsevier Ltd.

Rui X.,Hohai University
Advances in Science and Technology of Water Resources | Year: 2013

The origin of the runoff formation theory is reviewed. Horton's runoff formation theory, the rainfall-runoff relation curve of the form of five variables found by Kohler and Linsley and Dunne's runoff formation played the foundational role in runoff formation theory and runoff yield calculation. The main Chinese practice and theory research in this field since the 1950s are summarized and it is pointed out that the "runoff formation at the natural storage", the "runoff formation in excess of infiltration", and the partial area contribution to storm runoff discovered by Chinese scholars are a great contribution to hydrology. Through review and summary, the relationships between runoff formation theory, the rainfall-runoff relation curve, and runoff formation models are deeply discussed to develop and perfect the calculation method of watershed runoff yield.

Chen D.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Sun H.,Hohai University | Zhang Y.,Desert Research Institute
Journal of Hydrology | Year: 2013

This study proposes a stochastic approach to simulate sediment vertical dispersion in turbulent solid-liquid flows by developing a fractional advection-diffusion equation (fADE) to characterize the dynamics of sediment suspension. The fADE is a generalization of the traditional advection-diffusion equation (ADE) where the first-order spatial derivative is replaced with a fractional derivative of order α (0. <. α≤. 1). Many previous investigations of sediment suspension in steady sediment-laden flows apply the classic or improved Rouse equation, which was derived from the traditional ADE by assuming Fick's first law for the sediment dispersive flux. Recent observations in field and laboratory studies, however, have indicated that large errors may arise from the traditional ADE when applied to flows with coarse sediments. Instead, the vertical dispersion of suspended sediment is most likely a space nonlocal transport process in flows with turbulent bursting because particle vertical jumps with ejection events are no longer constrained to a small distance defined by the representative elementary volume. In other words, the vertical random displacements of suspended particles follow Lévy motion instead of Brownian motion. After validating against field measurements in the Las Vegas Wash as well as a set of published experimental data, we find that the proposed fractional model can describe the real-world vertical distribution of suspended sediment concentration in steady turbulent flows. © 2013 Elsevier B.V.

Rui X.,Hohai University
Advances in Science and Technology of Water Resources | Year: 2016

The characteristics and advantages of the big data method are discussed in this paper. In the method, mathematical formulas are replaced by intensive data in order to precisely describe the temporal and spatial variation of hydrological phenomena or the solution of a differential equation. The reasons why hydrology needs big data and technical support for obtaining hydrological big data are also discussed. The big data method may inspire the innovation of scientific thinking and become a way of solving complex problems in hydrology. © 2016, Editorial Office of Journal of Hohai University (Nature Sciences). All right reserved.

Yu Prof. J.,Hohai University | Tan Prof. K.H.,Nanyang Technological University
Magazine of Concrete Research | Year: 2014

Compressive arch action (CAA) is a favourable structural mechanism to mitigate progressive collapse of reinforced concrete (RC) frames. To quickly and accurately predict the CAA capacity of RC sub-assemblages under a columnmissing scenario, an engineering analytical model is proposed. The model considers all the design parameters in beams and the imperfect boundary conditions of sub-assemblages, including partial axial and rotational restraints, and connection gaps at beam ends if any. The proposed model is then validated with experimental results and extended to calculate progressive collapse resistance due to CAA with dynamic increase factors. Finally, the model isemployed in parametric studies. It is found that CAA capacity increases with restraint stiffness only in the regime of weak restraints; in the regime of strong restraints, CAA capacity is not sensitive to variation in restraint stiffness. Furthermore, CAA enhances structural resistance more evidently for sub-assemblages with small span-to-depth ratios and low mechanical reinforcement ratios, and RC slabs help to increase the CAA capacities of RC frames.

Yang J.,Hohai University
Proceedings - 4th International Congress on Image and Signal Processing, CISP 2011 | Year: 2011

Image inpainting refers to restoring a corrupted image with missing information. When the damaged region (inpainting domain) of image is assumed to be known beforehand, the inpainting problem has been extensively studied by many researchers. However, in many applications, the inpainting domain may not be readily available. In this essay, based on a TV model, we will propose an explicit iterative algorithm to simultaneously detect and recovery damaged pixels of the given image. The experiments on some image restoration task indicate that our algorithms is efficient and fast. © 2011 IEEE.

Ni C.,Jiangnan University | Wu G.,Jiangnan University | Zhu C.,Hohai University | Yao B.,Jiangnan University
Journal of Physical Chemistry C | Year: 2010

Amphiphilic star-shaped block copolymers of poly(ε-caprolactone-star- N-isopropylacrylamide) were synthesized by using hydroxyl-functionalized polyhedral oligomeric silsesquioxanes (POSS) as a core to initiate ring-opening polymerization of ε-caprolactone, followed by atom transfer radical polymerization of N-isopropylacrylamide. The sizes of the core and shell could be controlled through adjusting feed ratios of the reactants. The structure of the star block copolymers were confirmed by FTIR, 1HNMR, 29SiNMR, and DSC. Nano micelles were formed by adding water to the copolymer solution (DMF). The critical water concentration for the formation of the micelles were determined by UV. The results of TEM and DLS showed that the micelles were well-defined three-dimensional spherical particles with an average diameter of 155 nm. A hydrophobic drug ibuprofen could be loaded on the micelles effectively, and the release behavior was temperature dependent. © 2010 American Chemical Society.

Chen J.,Hohai University
2010 International Conference on E-Product E-Service and E-Entertainment, ICEEE2010 | Year: 2010

By selling own brand, the retailer becomes at once the manufacturer's customer and his competitor. The paper gave Equilibrium strategies of cooperative and non-cooperative advertising. We concluded that the manufacturer's profit increases and the retailer's profits decrease with the co-op advertising program, Our findings suggest that the co-op plan is an efficient counterstrategy for the manufacturer and the retailer would accept its implementation only if the national brand competes strongly with the private label. ©2010 IEEE.

It is of great help to take a new looking at our findings. For the questions put forward by Dr. Rawal, our response is presented in this paper. The description of permeable formwork in the original paper was simplified due to space limitations. The external pressure has little impact on the pore structure of the permeable formwork. © 2014 Elsevier Ltd. All rights reserved.

Li Y.,Nanjing University | Wang Y.,Hohai University | Zhang J.,Nanjing University | Sun C.,Nanjing University
Environmental Monitoring and Assessment | Year: 2012

The study on the performance of a fluorinated polyaniline (PANI) as a fiber coating for solid-phase microextraction (SPME) had been reported and 16 polycyclic aromatic hydrocarbons (PAHs) were selected to evaluate the performance of this fiber. Various parameters including sample volume, extraction temperature, time of desorption and extraction, pH and ionic strength were investigated intensively. A direct comparison between PANI-SPME fiber and commercial fiber was conducted. The results showed that the PANI-SPME coating had high affinity towards target compounds and the proposed method was successfully applied for the detection of real samples: rainfall and Taihu Lake water collected from Southern China. The whole PANI-SPME-GC method offers acceptable accuracy, precision and sensitivity and low detection limits, which is applicable to monitor trace levels of PAHs in real water bodies. © Springer Science+Business Media B.V. 2011.

Wu T.,Hohai University | Li X.-X.,Nanjing Institute of Environmental Sciences
Journal of Hydrodynamics | Year: 2010

Channel excavation is an important project measure in channel dredging, which is widely applied in channel regulations. Since channel excavation changes the original channel's bed morphology, the pattern of flow becomes more complicated and the relative balance between water flow and sediment is broken. The paper constructed a vertical 2-D numerical model of excavated channel focusing on the sediment deposition and flow distribution, which takes the hydrodynamic pressure into account and adopts auto-mesh technique. The model can effectively reduce the error caused by calculating meshes not completely matching with the calculating region. By introducing the hydrodynamic pressure, the mode can overcome the difficulty in modeling the severely changing velocity caused by the channel excavation. To verify the reliability of the model, Alfrin's experimental datum is adopted in the paper, and the calculating results agree well with the experimental datum. © 2010 Publishing House for Journal of Hydrodynamics.

Xin P.,Hohai University | Xin P.,University of Queensland | Robinson C.,University of Western Ontario | Li L.,University of Queensland | And 2 more authors.
Water Resources Research | Year: 2010

Wave and tide are important forcing factors that typically coexist in coastal environments. A numerical study was conducted to investigate individual and combined effects of these forces on flow and mixing processes in a nearshore subterranean estuary. A hydrodynamic model based on the shallow water equations was used to simulate dynamic sea level oscillations driven by wave and tide. The oscillating sea levels determined the seaward boundary condition of the coastal aquifer, where variably saturated, variable density flow was modeled. The simulation results showed that waves induced an onshore upward tilt in the phase-averaged sea level (wave setup). The resulting hydraulic gradient generated pore water circulations in the nearshore zone of the coastal aquifer, which led to formation of an upper saline plume (USP) similar to that formed due to tides. However, mixing of recirculating seawater in the USP with underlying fresh groundwater was less intensive under the high-frequency wave oscillations. In the case of combined forcing, wave-induced circulations coupled with the intratidal flows strengthened the averaged, circulating pore water flows in the nearshore zone over the tidal period. The circulating flows increased exchange between the subterranean estuary and ocean, contributing 61% of the total submarine groundwater discharge for the simulated condition in comparison with the 40% and 49% proportions caused by the same but separate tidal and wave forcing, respectively. The combined forces also created a more extensive USP with the freshwater discharge zone shifted farther seaward. The freshwater flow paths in the intertidal subterranean estuary were modified with a significant increase in the associated transit times. The interplay of wave and tide led to increased mixing between discharging fresh groundwater and recirculating seawater. These results further demonstrate the complexity of nearshore groundwater systems and have implications for future investigations on the fate of land-sourced chemicals in the subterranean estuary prior to discharge to the ocean. Copyright 2010 by the American Geophysical Union.

For amorphous polymers, the thermally-activated and solvent-activated shape-memory effect share the same physical mechanism. The programmed shape can be recovered either by increasing the environment temperature above the activation temperature (thermally-activated mechanism) or decreasing the activation temperature below the ambient temperature (solvent-activated mechanism). An equivalent role exists for solvent and heat in activating shape recovery. Based on this assumption, we presented a method to simulate solvent-activated shape-memory behaviors through the widely available models developed for the thermally-activated mechanism. The recovery in the solvent was treated as increasing the temperature of the specimen, while the diffusion of the solvent into the polymer matrix was analogous to heat conduction. The model was employed to simulate the solvent-activated temperature memory effect of Nafion in acetone and ethanol. The model predictions showed good agreement with the experimental results. © 2016 The Royal Society of Chemistry.

Han J.,University of Wollongong | Han J.,Hohai University | Susilo W.,University of Wollongong | Mu Y.,University of Wollongong | Yan J.,University of Wollongong
IEEE Transactions on Parallel and Distributed Systems | Year: 2012

Decentralized attribute-based encryption (ABE) is a variant of a multiauthority ABE scheme where each authority can issue secret keys to the user independently without any cooperation and a central authority. This is in contrast to the previous constructions, where multiple authorities must be online and setup the system interactively, which is impractical. Hence, it is clear that a decentralized ABE scheme eliminates the heavy communication cost and the need for collaborative computation in the setup stage. Furthermore, every authority can join or leave the system freely without the necessity of reinitializing the system. In contemporary multiauthority ABE schemes, a user's secret keys from different authorities must be tied to his global identifier (GID) to resist the collusion attack. However, this will compromise the user's privacy. Multiple authorities can collaborate to trace the user by his GID, collect his attributes, then impersonate him. Therefore, constructing a decentralized ABE scheme with privacy-preserving remains a challenging research problem. In this paper, we propose a privacy-preserving decentralized key-policy ABE scheme where each authority can issue secret keys to a user independently without knowing anything about his GID. Therefore, even if multiple authorities are corrupted, they cannot collect the user's attributes by tracing his GID. Notably, our scheme only requires standard complexity assumptions (e.g., decisional bilinear Diffie-Hellman) and does not require any cooperation between the multiple authorities, in contrast to the previous comparable scheme that requires nonstandard complexity assumptions (e.g., q-decisional Diffie-Hellman inversion) and interactions among multiple authorities. To the best of our knowledge, it is the first decentralized ABE scheme with privacy-preserving based on standard complexity assumptions. © 2012 IEEE.

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.

Fu Z.-J.,Hohai University
Proceedings of the ASME Design Engineering Technical Conference | Year: 2015

This study presents on a recent semi-Analytical boundary collocation technique, the singular boundary method (SBM), for exterior wave propagation analysis. The SBM is mathematically simple, easy-To-program, meshless and applies the concept of source intensity factors to eliminating the singularity of the fundamental solutions and avoiding singular numerical integrals in the boundary element method. The Burton and Miller's method is introduced to the present SBM to enhance the quality of the solution, particularly in the vicinity of irregular frequencies. Then the present SBM is applied to water wave-structure interaction with four-cylinder structure and SH wave scattering in 2D hill. Copyright © 2015 by ASME.

Fu Z.-J.,Hohai University
Proceedings of the ASME Design Engineering Technical Conference | Year: 2015

In recent decades, the theoretical researches and experimental results show that fractional derivative model can be a powerful tool to describe the contaminant transport through complex porous media and the dynamic behaviors of real viscoelastic materials. Consequently, growing attention has been attracted to numerical solution of fractional derivative model. Radial basis function (RBF) meshless technique is one of the most popular and powerful numerical methods, which are mathematically simple, and avoid troublesome mesh generation for high-dimensional problems involving irregular or moving boundary. Recently, RBF-based meshless methods, such as the Boundary Particle Method and the Method of Approximate Particular Solutions, have been successfully applied to fractional derivative problems. The Boundary Particle Method is one of truly boundary-only RBF collocation schemes, which employs both the semi-Analytical basis functions to approximate the FDE solutions. Inspired by the boundary collocation RBF techniques, the Method of Approximate Particular Solutions is one of the domain-Type RBF collocation schemes with easy-To-use merit, which employs the particular solution RBFs for the solution of FDEs. This study will make a numerical investigation on the abovementioned RBF meshless methods to fractional derivative problems. The convergence rate, numerical accuracy and stability of these schemes will be examined through several benchmark examples. © Copyright 2015 by ASME.

Kong J.,Hohai University | Xin P.,University of Queensland | Song Z.-Y.,Nanjing Normal University | Li L.,University of Queensland
Journal of Hydrology | Year: 2010

Built upon the work of Yuan et al. (Yuan, D., Lin, B., Falconer, R.A., 2008. Simulating moving boundary using a linked groundwater and surface water flow model. Journal of Hydrology 349, 524-535), we present in this note an integrated, vertically averaged numerical model based on an unstructured finite volume/finite difference method for simulating coupled surface and subsurface water flows in a coastal hydrological system. The modelled domain was divided into a surface water flow layer and a groundwater flow layer, with the former overlying the latter across the interface. In contrast to the work of Yuan et al. (2008), the governing equations for describing these two different flows were discretised using an unstructured triangular mesh and then assembled into a single set of linear algebraic equations for computing the solutions. A semi-implicit Eulerian-Lagrangian method was used to deal with the momentum convection term of the surface flow equation. In this method, the constraint on the model's time step imposed by the Courant-Friedrichs-Lewy condition for stable solutions is relaxed. The model was validated against the results of a previous experiment on the interaction of surface and subsurface flows in a coastal lagoon. This showed that the new model retained the same degree of accuracy in its predictions even with time steps increased by two orders of magnitude from those allowed in the model of Yuan et al. (2008). The resulting increase of computational efficiency will enable model applications to large scale hydrological systems commonly encountered in the coastal zone. © 2010 Elsevier B.V.

Fan X.,Hohai University | Fan X.,Nanjing Hydraulic Research Institute | Hu S.,Nanjing Hydraulic Research Institute
Applied Clay Science | Year: 2013

For the purpose of discussing the fracture features of high strength reinforced concrete, under the conditions of the fundamental assumptions to reinforced concrete, the calculating process of fracture parameters for three point bending beam of high strength reinforced concrete is given, and through a total of 16 specimens with the same sizes, with the different initial crack length 40. mm to 100. mm on three point bending beam of high strength reinforced concrete, it is performed to examine the calculation method. The results show that the fracture features of high strength reinforced concrete are different from normal concrete, both the initiation toughness and the unstable toughness of high strength reinforced concrete gradually increase with the crack-to-depth ratios, and the ratios of initial load to maximum load are different depending on the initial crack length, the bigger the crack-to-depth ratios, the lower the ratio, and the ductility is best to the high strength reinforced concrete. © 2013 Elsevier B.V.

Pan T.,Nanjing University | Zhu X.-D.,Nanjing University | Ye Y.-P.,Hohai University
Ecological Engineering | Year: 2011

This study aims to estimate the three greenhouse gas (GHG) emissions (i.e. CO2, CH4, N2O) from a vertical subsurface flow constructed wetland (VSSF CW, 1000m2) and a cluster of conventional wastewater treatment plants (WWTPs) in the city of Changzhou, China. The two estimated emissions are set up for comparison. The results show that the WWTP system emits 7.3kg CO2-eq to remove 1kg BOD in the studied life cycle, while the VSSF system only emits 3.18kg CO2-eq, which is only half of the amount given off by the WWTP system. Especially at the treatment stage, the WWTP system's GHG emissions are almost 7 times higher than the VSSF system's. N2O emissions in both systems are only a minor fraction of the total emissions. Therefore, this study has concluded that the VSSF system is an effective option for GHG emissions mitigation in the wastewater sector. The study further suggests that developing countries like China should extensively build up VSSF systems for decentralized wastewater treatment, which could also potentially reduce GHG emissions by 8-17 million ton CO2-eq per year compared with the centralized scenario. © 2010 Elsevier B.V.

Xu C.,Zhejiang University | Yue D.,Hohai University
Tectonophysics | Year: 2015

We explore the capability of singular spectrum analysis (SSA) to extract time-variable seasonal oscillations from continual GPS observations and demonstrate the statistical assessment on the colored noise (in particular the first-order autoregressive AR(1) noise) using Monte Carlo SSA (MCSSA) methodology. We provide example applications to ~. 15-year vertical coordinate time series for 36 globally distributed International GNSS Service (IGS) sites. We find the SSA-filtered seasonal signals can easily pass the confidence interval and hypothesis tests of MCSSA. However, maximum likelihood estimate (MLE) results show that 72% of sites have their flicker noise amplitudes reduced after removing SSA-filtered annual signal, implying that the SSA-filtered seasonal signals may contain an artificial signal driven by colored noise. Therefore, the AR(1) null hypothesis noise model may be misleading in surrogate data tests for GPS seasonal signals. Moreover, comparison between SSA-filtered GPS annual signals and joint geophysical model predictions (non-tidal atmospheric loading. +. non-tidal ocean loading. +. hydrological loading) confirms that seasonal signals are resulting from a combination of mass loading and systematic error. © 2015 Elsevier B.V.

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.

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.

Liu C.-S.,National Taiwan University | Liu C.-S.,Hohai University
International Journal of Heat and Mass Transfer | Year: 2016

The Trefftz method, endowing with polynomial type trial solutions of the high-dimensional heat conduction equation in an arbitrary simply-connected domain, is a cheap boundary-type meshless method to solve the high-dimensional backward heat conduction problem (BHCP), which is well-known a highly ill-posed problem. For solving the BHCP we develop a multiple/scale/direction polynomial Trefftz method (MSDPTM), of which the directions are uniformly distributed on a hyper-sphere and the scales are determined in advance by the collocation points on boundary. A post-conditioner for the resultant linear system is introduced by using the derived multiple-scale, and then use the conjugate gradient method (CGM) to solve the post-conditioned linear system, of which the expansion coefficients are determined fast. The MSDPTM can find the missing initial data very well, with several two- and three-dimensional numerical examples of the BHCP to evaluate the performance. Although under a very large relative noise from 30% to 80% with the maximum absolute noisy error being 2.17, the presented method still recovers the unknown initial temperature quite accurately. It is worthy to notice that the CPU time does not exceed two seconds for 2D examples and seven seconds for 3D examples. © 2015 Elsevier Ltd. All rights reserved.

Jeng D.-S.,University of Dundee | Ye J.-H.,University of Dundee | Zhang J.-S.,Hohai University | Liu P.L.-F.,Cornell University
Coastal Engineering | Year: 2013

In this study, an integrated model (PORO-WSSI II) for wave-seabed-structure interactions (WSSI) is developed by combining (i) the Volume-Averaged Reynolds-Averaged Navier-Stokes (VARANS) equations for wave motions in a fluid domain and the porous media flows in porous structures, and (ii) the dynamic Biot's equations for a porous elastic seabed. The effects of the porous flow in seabed and marine structures, and the fluid exchange at the interface between the fluid domain and solid domain on wave characteristics are considered. The finite difference two-step projection method and the forward time difference method are adopted to solve the VARANS equations. The volume of fluid (VOF) method is applied to track water free-surface. The finite element method and the Generalized Newmark method are respectively adopted for the space discretization and time discretization of the dynamic Biot's equations. A one-way integrating method is developed to integrate the VARANS equations with the dynamic Biot's equations. Several experimental data available in the literature are used to validate the integrated model. An overall agreement between the numerical results and the experiment data indicates that the integrated model developed for the WSSI problem is highly reliable. The integrated model is then applied to investigate the dynamic response of a large-scale composite breakwater on a seabed, and the mechanism of WSSI. Numerical results indicate that there are intensive fluid exchanges between the water body and the seabed and strong seepage forces in the seabed under the ocean wave loading. The excessive upward seepage force leads to the liquefaction of the seabed in the region under wave trough. There is a liquefaction zone in the seabed close to the bottom corner of the rubble mound, which may lead to foundation instability of the composite breakwater. The parametric study indicates that the wave characteristics have a significant impact on the liquefaction properties (depth, width and area). © 2012 Elsevier B.V.

Kong G.,Hohai University
Advanced Materials Research | Year: 2011

The belled wedge pile, which can improves the friction of pile shaft, tip resistance and reduce the influence of negative skin friction, is introduced. In this paper, the accuracy of FLAC3Dmodel is verified with field load test results. Subsequently, the numerical model was used to study the compressive behavior of belled wedge pile, conventional belled pile, wedge pile, and uniform section pile with the same concrete volume. Furthermore, the compressive behavior of belled wedge pile group was studied in terms of influencing factors such as pile spacing, stiffness of soil at the pile end, and diameter of enlarged pile head. The numerical results show that the compressive advantages of belled wedge pile can be developed adequately when the distributions of the friction of pile shaft and pile tip resistance are equilibrium, and it increases with increasing pile spacing, increasing stiffness of soil at the pile end, and increasing diameter of the enlarged pile head. © (2011) Trans Tech Publications, Switzerland.

Liu C.-S.,Hohai University | Liu C.-S.,National Taiwan University
Engineering Analysis with Boundary Elements | Year: 2016

In this paper we develop a global domain/boundary integral equation method for the Laplace and Poisson equations, which is based on the Green's second identity. A derived global relation links the source term to the Dirichlet and Neumann boundary conditions into a single integral equation in terms of the Trefftz test functions. By suitably choosing the Trefftz test functions, which are not the usual Green functions as that used in the conventional boundary integral method, the present boundary integral equation method (BIEM) can find the unknown boundary conditions for the inverse Cauchy problems very well. Even under a large noise to 10% and the data over-specified in a 25% portion of the whole boundary, the recovered result is still accurate. The inverse source problems of the Poisson equation are resolved numerically by using the BIEM which is stable and effective for strongly ill-posed case with a large noise being imposed on the supplementary data. © 2015 Elsevier Ltd. All rights reserved.

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.

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.

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.

Liu C.-S.,Hohai University | Liu C.-S.,University of Taipei
Engineering Analysis with Boundary Elements | Year: 2016

In this paper we numerically solve the direct as well as the inverse Cauchy problems of the three-dimensional Helmholtz equation in an arbitrary bounded region by using a multiple/scale/direction Trefftz method (MSDTM), which is a simple extension of the two-dimensional Trefftz method to a Trefftz method for the three-dimensional Helmholtz equation. In the MSDTM the directions are uniformly distributed unit vectors in the plane (y,z), and the scales are determined by the boundary collocation points. The regularization of the MSDTM roots in a small number of unknown coefficients, a simple three-dimensional Trefftz basis and a simple multiple-scale post-conditioner, which are very easy to be numerically implemented. The three-dimensional numerical examples of direct and the inverse Cauchy problems in irregular domains guarantee the efficiency of the MSDTM. Although under a large noise, the solutions of inverse Cauchy problems are quite accurate. © 2015 Elsevier Ltd.

Wan Z.,Hohai University
Proceedings - 2011 4th International Symposium on Computational Intelligence and Design, ISCID 2011 | Year: 2011

To allow frequent key-updates without increasing the risk of helper key-exposure, Hanaoka et al. proposed parallel key-insulated mechanism where distinct helpers are independently used in key updates. In this paper, we propose a new identity-based parallel key-insulated signature scheme which is provably secure without resorting to the random oracle methodology. Compared with the known identity-based parallel key-insulated signature (IBPKIS) scheme secure in the standard model, our scheme enjoys more efficient verification. © 2011 IEEE.

Hu Z.,Hohai University | Lu Y.Y.,City University of Hong Kong
Journal of the Optical Society of America B: Optical Physics | Year: 2014

Wavelength demultiplexers based on photonic crystal resonators are attractive because they may be realized in very small sizes. However, existing designs have a limitation on the size since they all require one resonator for each wavelength and these resonators must be separated. As a possible approach to reduce the size further, we show that a single multimode resonator may be used to separate different wavelengths corresponding to the different resonant frequencies. Specifically, we propose an ultra-compact three-wavelength demultiplexer based on a single multimode resonator in a photonic crystal. The design is obtained by an efficient optimization procedure, and its property is analyzed rigorously by a numerical method, as well as approximately by the temporal coupled mode theory. © 2014 Optical Society of America.

Zhang L.-H.,Hohai University
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2014

Research on velocity distribution is the key to reveal the characteristics of the water flow, and a quantitative description of sediment concentration distribution is the basis for studying suspended sediment movement. Since the classic formulas obtained by current flume test data have a big gap comparing with the measured data from natural rivers, in this paper, based on the review of previous research and the vorticity and momentum transfer theory, a formula for vertical velocity distribution in turbulent flow has been deduced by solving the mean motion equations of two-dimensional steady and homogeneous turbulence with the average of integrated mixing length on the eddy model. Using the formula to determine the diffusion coefficient of suspended sediment and to solve the diffusion equation under equilibrium conditions, and then a formula has been obtained for the vertical distribution of suspended sediment. The test results by observed data show that the two formulas established in this paper can better describe the natural river flow and vertical distribution law of sediment concentration, which overcome the deficiencies of previous classic formulas.

Bi L.,Hohai University | Yao S.,Chinese Academy of Agricultural Sciences | Zhang B.,Chinese Academy of Agricultural Sciences
Soil and Tillage Research | Year: 2015

Soil puddlability measures the susceptibility of a soil to puddling, and can influence transplantation and the growth of rice plants. The effects of chemical fertilizers and organic amendments on soil puddlability of paddy soils are poorly understood. This study used two 26-year field experiments (1) to compare the effects of chemical and organic fertilization on soil puddlability by measuring sinkage resistance and hard clod content after puddling, (2) to characterize physical properties of hard clods and (3) to explain the change in soil puddlability. Each of the two experiments consisted of nine treatments of chemical fertilizers alone or in combination with organic amendments. The sinkage resistance and the content of hard clods were higher in the treatments with chemical fertilization alone than in the treatments with organic amendments. The sinkage resistance was positively correlated with the content of hard clods and negatively correlated to content of soil organic C (SOC) and mean weight diameter (MWD). The bulk density, water sorptivity and apparent porosity were similar among individual hard clods from different treatments, suggesting that the hard clods were formed under the same processes. The formation of hard clods was likely attributed to the breakdown of the compacted topsoil by puddling tillage, which formed due to clogging pores by fine particles produced during previous puddling tillage and due to shrinkage upon drying during rice growth period. Compared with the organic amendment treatments, the chemical fertilization treatments contained more and larger hard clods, indicating that the compacted topsoil was thicker due to higher soil dispersibility due to N fertilization and lower SOC content in the chemical fertilization treatments than in the organic amendment treatments. The study also suggests that continuous input of organic C at an annual rate of >2.5Mgha-1 is needed to maintain SOC content and soil structure under chemical fertilization in the study region. © 2015 Elsevier B.V.

Xiao R.,Hohai University
EPL | Year: 2016

In this study, we present a constitutive model to couple the shape memory and dielectric behaviors of polymers. The model adopted multiple relaxation processes and temperature-dependent relaxation time to describe the glass transition behaviors. The model was applied to simulate the thermal-mechanical-electrical behaviors of the dielectric elastomer VHB 4905. We investigated the influence of deformation temperature, voltage rate, relaxation time on the electromechanical and shape-memory behavior of dielectric elastomers. This work provides a method for combining the shape-memory properties and electroactive polymers, which can expand the applications of these soft active materials. © CopyrightEPLA, 2016.

Lin P.,University of Sichuan | Liu X.,Hohai University
Advances in Science and Technology of Water Resources | Year: 2015

In this paper, the application of smoothed particle hydrodynamics (SPH) in hydraulic and ocean engineering is divided into four categories: wave and current simulation, fluid-solid coupling simulation, sediment transport simulation, and water-air two-phase flow simulation. The paper describes the research status and corresponding technical treatments of SPH application, especially with regard to the difficulties of non-reflection wave generation, inflow and outflow boundaries, fluid-solid interface movement, and bed scour; elaborates on the advantages and disadvantages of different SPH models; summarizes the development characteristics of SPH over the past decade; and proposes that the future work on SPH application in the hydraulics field focus on developing a high-accuracy and efficient algorithm model, mature turbulence model, and parallel computing model. ©, 2015, Editorial Office of Journal of Hohai University (Nature Sciences). All right reserved.

Wu D.,Nanjing University of Aeronautics and Astronautics | Zhu D.,Nanjing University of Aeronautics and Astronautics | Shen M.,Hohai University | Zhu Z.,Nanjing University of Aeronautics and Astronautics
IET Radar, Sonar and Navigation | Year: 2012

This study introduces a new type of space-time autoregressive (STAR) filtering algorithm for space-time adaptive processing (STAP) operating in a clutter environment that is not strictly stationary in slow time. The original STAR approach based on stationary autoregressive (AR) model, despite enjoying a fast convergence rate, suffers significant performance degradation when dealing with non-stationary clutter processes. To remedy this, the new proposed algorithm invokes a 'relaxed' AR model, that is, the time-varying autoregressive (TVAR) model, and is called time-varying space-time autoregressive (TV-STAR) filtering. The authors demonstrate that, for stationary case, the two filters have identical output signal-to-interference plus noise ratio (SINR) with known interference covariance, but the convergence rate of TV-STAR is somewhat inferior to STAR with finite sample support. However, in the non-stationary case, the STAR filter totally fails because of 'model-mismatch' whereas TV-STAR exhibits a commensurate performance with respect to the stationary case. Meanwhile, TV-STAR is shown to offer a favourable convergence rate over reduced-rank STAP techniques such as eigencanceler method in both cases. Simulated data as well as two sets of measured airborne radar data are used to demonstrate the performance of TV-STAR algorithm. © 2012 The Institution of Engineering and Technology.

Li M.,City University of Hong Kong | Chen W.,Hohai University | Tsai C.H.,University of Southern Mississippi
Engineering Analysis with Boundary Elements | Year: 2012

Radial basis functions (RBFs) have proved to be very flexible in representing functions. Based on the idea of the analog equation method and radial basis functions, in this paper, ill-posed Cauchy problems of elliptic partial differential equations (PDEs) with variable coefficients are considered for the first time using the method of approximate particular solutions (MAPS). We show that, using the Tikhonov regularization, the MAPS results an effective and accurate numerical algorithm for elliptic PDEs and irregular solution domains. Comparing the proposed MAPS with Kansas method, numerical results show that the proposed MAPS is effective, accurate and stable to solve the ill-posed Cauchy problems. © 2011 Elsevier Ltd. All rights reserved.

Zhang X.,Hohai University
WIT Transactions on Information and Communication Technologies | Year: 2014

This paper made a brief overview of the data mining theory and makes the analysis and comparison for performance of several typical association rules algorithm, and find a suitable for the data mining algorithm of association rules-the improve average clustering algorithm; finally, the mining results are analyzed and found problems in scientific researches, which make an effective reference for the next step of scientific research management. © 2014 WIT Press.

Gehin A.-L.,Lille University of Science and Technology | Hu H.,Hohai University | Bayart M.,Lille University of Science and Technology
Engineering Applications of Artificial Intelligence | Year: 2012

Systems are built by connecting different components (e.g.; sensors, actuators, process components) that are, in turn, organized to achieve system objectives. But, when a system component fails, the systems objectives can no longer be achieved. For many years, numerous studies have proposed efficient fault detection and isolation (FDI) and fault-tolerant control (FTC) algorithms. This paper considers faults that lead to the complete failure of actuators. In this specific case, the systems physical structure changes, and the system model thus becomes incorrect. The potential that the system has to continue to achieve its objectives has to be re-evaluated from a qualitative point of view, before recalculating or modifying the control algorithms. To this end, this paper proposes a self-updating system model to reflect the current system potential, a formulation of system objectives using temporal logic, and a verification method based on model checking to verify whether the objectives can still be achieved by the faulty system. The systems considered are discrete-continuous systems. © 2011 Elsevier Ltd. All rights reserved.

Li M.,East China Normal University | Chen W.-S.,Shenzhen University | Han L.,Hohai University
Telecommunication Systems | Year: 2010

The stationarity test of long-range dependent (LRD) traffic remains a challenge problem in the field of traffic engineering. Due to the importance of traffic theory in the Internet, to find a solution to that problem is greatly desired. This paper presents a method of the weak stationar-ity test of a single history LRD traffic series of finite length. How to apply this method to testing the stationarity of real traffic is demonstrated. The results in this paper suggest that there may be no general conclusion that traffic is either stationary or non-stationary since the stationarity of traffic is observation-scale dependent. Some of the investigated real-traffic traces that are stationary in an observation scale may be non-stationary in a larger observation scale. © Springer Science + Business Media, LLC 2009.

Gao W.,Hohai University
Journal of Computing in Civil Engineering | Year: 2016

Determining the noncircular critical slip surface is the key problem in slope stability analysis. Essentially, this problem is a path search, and therefore, ant colony optimization is an extremely suitable method to use to obtain a solution. To overcome the shortcomings of ant colony optimization, using the principle of searching an entire road by forward and reverse searches of ants, a new algorithm, meeting ant colony optimization, is proposed. Then, combined with typical mature limit equilibrium analysis (Spencer method), meeting ant colony optimization is used to locate the critical slip surface of a slope. Through two typical examples the effectiveness of the new algorithm is verified. The results show that for both the entire search scope and the search scope from one point, the meeting ant colony optimization performs better than ant colony optimization, which shows that in searching for the critical slip surface of a slope, meeting ant colony optimization provides better solution diversity. Using meeting ant colony optimization, the critical slip surface of a slope can be located in a larger scope and more rapidly than by ant colony optimization. © 2015 American Society of Civil Engineers.

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.

Gu Y.,Qingdao University | Chen W.,Hohai University | Zhang C.,University of Siegen | He X.,City University of Hong Kong
International Journal of Heat and Mass Transfer | Year: 2015

The singular boundary method (SBM) is a relatively new meshless boundary collocation method for the numerical solution of certain elliptic boundary value problems. The method, based on the notion of the boundary element method (BEM) and method of fundamental solutions (MFS), fully inherits the merits of both and in the meantime possessing its unique advantages. Due to the boundary-only discretizations and its semi-analytical nature, the method can be viewed as an ideal candidate for the solution of inverse problems. In this study, we document the first attempt to apply the SBM, together with several regularization techniques, for the solution of inverse heat conduction problems in three-dimensional (3D) anisotropic media. Four benchmark numerical examples are well-studied which indicate that the proposed scheme is accurate, computationally efficient and numerically stable for the solution of 3D inverse problems with various levels of noisy input data. ©2015 Elsevier Ltd. All rights reserved.

Jun C.,Hohai University
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2013

Jiangsu coast is located on the central coast, China. The total area of the tidal flat is about 5000km2 which is about 1/4 of the total tidal flat area in China. The reclamation engineering of the tidal flat has a long history and has brought a series of impacts on the coast geomorphology development. The supratidal area reduced significantly. The coastline length changes obviously and becomes straight gradually because of the reclamation. The core area reclamation of the Radial Tidal Sand Ridges causes the geomorphology adjustment of the outer edge region of the Radial Tidal Sand Ridges. Backfill sediment dredging from the underwater slope causes the coastal profile erosion. Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE).

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.

Jiang F.-Y.,Hohai University | Gao L.-K.,The First Geological Brigade of Jiangsu Geology and Mineral Exploration Bureau
Applied Geophysics | Year: 2012

In order to enhance geological body boundary visual effects in images and improve interpretation accuracy using gravity and magnetic field data, we propose an improved small sub-domain filtering method to enhance gravity anomalies and gravity gradient tensors. We discuss the effect of Gaussian white noise on the improved small sub-domain filtering method, as well as analyze the effect of window size on geological body edge recognition at different extension directions. Model experiments show that the improved small sub-domain filtering method is less affected by noise, filter window size, and geological body edge direction so it can more accurately depict geological body edges than the conventional small sub-domain filtering method. It also shows that deeply buried body edges can be well delineated through increasing the filter window size. In application, the enhanced gravity anomalies and calculated gravity gradient tensors of the Hulin basin show that the improved small sub-domain filtering can recognize more horizontal fault locations than the conventional method. © 2012 Editorial Office of Applied Geophysics and Springer-Verlag Berlin Heidelberg.

Yan S.,Hohai University
Journal of Information and Computational Science | Year: 2015

This paper proposes a modified generalized dynamic fuzzy neural network (M-GDFNN) for the application of Adaptive Noise Cancellation (ANC). As system error cannot be evaluated on-line in ANC, e-Completeness of fuzzy rules is selected as the only criteria of fuzzy rules generation in this novel algorithm. To improve system performance, a simple Self-organizing Mapping (SOM) technique is introduced to adjust the center clustering. Additionally, Eigenvalue Decomposition (ED) method is applied to prune unimportant rules. In the last part of this paper, simulation studies illustrate that proposed M-GDFNN is able to achieve better results compared with ANFIS and standard GDFNN in noise cancellation thus prove the suitability of proposed M-GDFNN in the field of ANC. Copyright © 2015 Binary Information Press.

Zhou G.-D.,Hohai University | Yi T.-H.,Dalian University of Technology | Li H.-N.,Dalian University of Technology
International Journal of Structural Stability and Dynamics | Year: 2014

The optimal placement of wireless sensors is very different from conventional wired sensor placement due to the limited transmission range of the wireless sensors. This constraint on the inter-sensor distance makes the optimization problem difficult to solve with conventional gradient-based methods. In this paper, an improved generalized genetic algorithm (GGA) based on a self-adaptive dynamic penalty function (SADPF) is proposed for the optimal wireless sensor placement (OWSP) in bridge vibration monitoring. The mathematical model of the OWSP problem is established, and it considers both the bridge vibration monitoring requirements and the constraints of the data transmission range in wireless sensor networks (WSNs). SADPF, which can automatically adjust the amount of penalization for constraint violations according to the evolution generation number and the degree of violation, is then developed so that the wireless sensor placement can be optimized using GGA. Subsequently, the GGA is improved by implementing an elite conservation strategy, a worst elimination policy and a dual-structure coding system. Finally, a numerical experiment is presented with a long-span suspension bridge to demonstrate the feasibility and efficiency of the proposed method, and some indispensible discussions are also given. The results indicate that the wireless sensor configurations that are optimized by the improved SADPF-based GGA can simultaneously meet the data transmission demands in a WSN and fulfill the requirements for structural condition assessment. The developed SADPF can minimize the influence of the limited data transmission range on the search process for the OWSP. The improved SADPF-based GGA quickly and robustly converges to the global optimal solution. © 2014 World Scientific Publishing Company.

Luo Y.L.,Hohai University
International Journal of Civil Engineering | Year: 2013

The occurrence of piping failures in earth structures demonstrates the urgency and importance of studying piping. With this intention, a new piping model was developed in the framework of continuum mixture theory. Assuming that porous media are comprised of solid skeleton phase, fluid phase and fluidized fine particles phase, the fluidized fine particles phase is considered to be a special solute migrating with the fluid phase. The three phases interact while being constrained by the mass conservation equations of the three phases, and a sink term was introduced into the mass conservation equation of the solid skeleton phase to describe the erosion of fluidized fine particles, then a new continuum fluid-particle coupled piping model was established and validated. The validation indicates that the proposed model can predict the piping development of complicated structures under complex boundary and flow conditions, and reflect the dynamic changes of porosity, permeability and pore pressure in the evolution of piping.

Su Y.,CAS Nanjing Institute of Geography and Limnology | Xiao Y.,Nankai University | Li Y.,Hohai University | Du Y.,CAS Nanjing Institute of Geography and Limnology | Zhang Y.,Nankai University
Materials Chemistry and Physics | Year: 2011

Fe-N-codoped TiO2 powder prepared by sol-gel method is loaded on low-density polyethylene film to obtain immobilized photocatalyst. The obvious agglomeration phenomena exist in the annealed samples with nanometer size, as observed in SEM images. XRD results suggest that the adding amount of impurities has a great effect on the crystallinity and particle size of TiO2. Compared with undoped and Fe/N-doped TiO2, Fe-N-codoped TiO 2 shows an obviously higher catalytic activity under visible irradiation. The DFT calculations indicate that the doping of nitrogen and Fe induced the formation of new states between the valence band and conduction band. The codoping of TiO2 with nitrogen and Fe leads to the much narrowing of the band gap and greatly improves the photocatalytic activity under visible irradiation. Moreover, the Fe-N-codoping can promote the separation of the photogenerated electrons and holes to accelerate the transmission of photocurrent carrier. © 2010 Elsevier B.V. All rights reserved.

Hu Z.,Hohai University | Lu Y.Y.,City University of Hong Kong
Journal of the Optical Society of America B: Optical Physics | Year: 2015

Sensitivity analysis provides important information on the tolerance to fabrication imperfections for any designed devices. Standard sensitivity analysis relies on the first-order partial derivatives of a response function of the device with respect to the design parameters. These derivatives are also useful in the device optimization process when a gradient based optimization method is used. The first-order sensitivity analysis becomes inadequate if the first-order derivatives are small or zero. In this paper an efficient method for computing second-order partial derivatives is developed for idealized two-dimensional photonic crystal (PhC) devices with circular cylinders. The response function is the normalized power-transmission coefficient in an output waveguide and the design parameters are the radii of the cylinders. Based on that, a second-order sensitivity analysis is performed for a 90° PhC waveguide bend at the frequency where the transmission coefficient is close to 1. © 2015 Optical Society of America.

Xiao J.-K.,Hohai University | Xiao J.-K.,State Key Laboratory of Millimeter Waves | Huang H.-F.,South China University of Technology
Progress In Electromagnetics Research Letters | Year: 2010

New dual-band bandpass filters with compact coupling and sizes reduction are proposed by using split ring stepped-impedance resonators and two paths coupling. In the new design, split ring SIR and defected ground structure are applied not only to reduce filter size but also to improve the filter performances. The presented filters have advantages of compact and novel structures, miniaturization and dual-band with nicer performances such as high selectivity, low passband insertion losses and so on, and these performances are demonstrated by measurement. The new design may be quite useful in wireless communication systems.

Wang K.,Hohai University
ACRS 2015 - 36th Asian Conference on Remote Sensing: Fostering Resilient Growth in Asia, Proceedings | Year: 2015

The technology of hyperspectral remote sensing image improves the capability of collecting the objects such as lakes, rivers, farmlands, buildings, forest and desert in the ground surface. Since the spatial resolution is becoming higher recently, image segmentation of hyperspectral remote sensing is important to the next step of remote sensing image classification and object recognition. In this paper, we proposed a new algorithm using mean shift filtering, and watershed transform, for hyperspectral image segmentation. Usually, hyperspectral image has hundreds of spectral bands, thus, it is difficult for image segmentation. First, the mean shift algorithm is used for smoothing these all bands. Second, Canny edge detection method and vector field model are used to calculate edge strength of these bands, respectively. Finally, automatic marker watershed transform is applied for the edge strength to obtain the segmentation result. In order to evaluate the efficiency of the novel hyperspectral image segmentation algorithm, an unsupervised entropy based evaluation method, is performed on the segmentation result from AVIRIS hyperspectral data. The experimental results illustrate that the proposed algorithm can be used to obtain better segmentation results for hyperspectral data.

Hu X.H.,Hohai University
Advanced Materials Research | Year: 2014

Environmental pollution has become a severe threat to the sustainable development of China's rural areas. The economic source of China's rural environmental pollution consists of three factors which are the assumption of "rational economic person" the externalities of environmental pollution and the quasi-public characteristic of natural resources. The political source of rural environmental pollution is the failure of government regulation. In order to solve market failures and government failures we need to establish a long term mechanism to solve rural pollution via moral economic and legal measures. © (2014) Trans Tech Publications, Switzerland.

Liu J.-C.,Nanjing University of Technology | Lei G.-H.,Hohai University | Zheng M.-X.,East China Jiaotong University
Geotextiles and Geomembranes | Year: 2014

A quasi-analytical method is newly introduced to solve the equal-strain consolidation problem of multilayered soil with a vertical drain system. Both vertical and radial drainage conditions are considered, together with the effects of drain resistance and smear. By using the method of Laplace transform with respect to time, a general explicit analytical solution for the consolidation in transformed space is obtained. Numerical inversion of the Laplace transform in the time domain is then applied to obtain the solution for calculating excess pore-water pressure. This solution is explicitly expressed and conveniently coded into a computer program for ease and efficiency of practical use. Its validity and accuracy are verified by comparing the special cases of the proposed solution with a finite-element solution and an available analytical solution. Moreover, the consolidation behavior of a four-layered soil with a vertical drain is investigated. The order of soil layers is shown to have a significant effect on the behavior of consolidation. This highlights that caution should be exercised when weighted average consolidation parameters of multilayered soil are used to analyze the consolidation behavior. © 2014 Elsevier Ltd.

Lu H.,Hohai University
Information Technology and Applications - Proceedings of the 2014 International Conference on Information technology and Applications, ITA 2014 | Year: 2015

As the information technology of Chinese industries and enterprises has been developed further, the IT industry has a good prospect. As the most important factor in the formation of corporate governance mechanism, the conditions of ownership structure directly affect the company operational efficiency. This paper empirically analyses the relationship between ownership structure and corporate performance, using listed companies of IT industry from 2010 to 2012 as research samples. It can be found that ownership concentration has a U-shaped curve with corporate performance, and equity restriction is significantly and positively correlated with corporate performance. © 2015 Taylor & Francis Group, London.

Rockburst is an important accident scenario in deep underground engineering. Because there are numerous, complicated factors that lead to rockbursts, their forecasting is a difficult task, which, based on an engineering analogy and geological analysis, requires the use of clustering methods in rockburst forecasts. Because the environmental causes of rockbursts are complicated, this clustering problem makes for a complicated random optimization problem (that is also a fuzzy optimization problem) that cannot be solved in a satisfactory manner using traditional methods. To improve the computational efficiency and accuracy of the traditional ant colony clustering algorithm, an abstraction ant colony clustering algorithm using a data combination mechanism is proposed. Based on an analysis of rockburst sample data and using an engineering analogy thinking by the abstraction ant colony clustering algorithm, a new method for forecasting rockbursts in deep underground engineering is proposed. A set of common engineering examples are used to verify the new algorithm. The engineering applications prove that, compared with the traditional ant colony clustering algorithm and based on their similar computational difficulty and complexity, the abstraction ant colony clustering algorithm produces results that are not only more accurate but are also determined more efficiently. As the complexity of the problem increases, the algorithm’s computational efficiency increases. In other words, the more complicated the problem is, the more efficient the algorithm becomes. Thus, the abstraction ant colony clustering algorithm is well suited to large complicated engineering problems. © 2014, Springer Science+Business Media Dordrecht.

Fu Y.-J.,Hohai University
Information Technology and Applications - Proceedings of the 2014 International Conference on Information technology and Applications, ITA 2014 | Year: 2015

On the basis of the data of Chinese IT listed companies which can be widely obtained, this paper tries to extract the key factors that affect the growth capacity of IT listed companies, and seek out the internal relationship between the growth ability and its main influential elements by using factor analysis. The five key factors can be defined as innovation; growth speed; growth efficiency, and growth equality. Next, comprehensive evaluation of Chinese IT listed companies is gotten by using entropy method creatively. Finally, some suggestions are presented to optimize the growth ability of IT listed companies in China based on the above evaluation. © 2015 Taylor & Francis Group, London.

Zhang D.,Hohai University
Information Technology and Applications - Proceedings of the 2014 International Conference on Information technology and Applications, ITA 2014 | Year: 2015

Based on the domestic and international studies about the capital structure and corporate performance, this paper first introduces the general situation of the information technology industry. Then the concept of capital structure and corporate performance are defined. Ninety-five listed companies in information technology industry from Shanghai stock exchange and Shenzhen stock exchange are chosen as the research subjects. The comprehensive evaluation of the companies’ corporate performance from 2011 to 2013 is calculated by using factor analysis. Then this paper use regression analysis methods to study the impact of capital structure on corporate performance. Finally, combined with the above analysis, some suggestions are presented to improve the corporate performance of listed companies in information technology industry. © 2015 Taylor & Francis Group, London.

Water culture is dependent on the landscape of water area space. The unification of cultural connotations and water area space-the former bringing out the great charm and individuality of the latter, makes water area space a major component of natural and human landscape and facilitates the development, inheritance and innovation of water culture. While following Chinese traditional thoughts on the layout of water bodies that "humans and nature should be integrated as a whole, and it is best to keep things as they were originally", this paper intends to unearth and draw on the strengths of traditional designs of the layout of waters through sustainable approach to development, explore the protection and renovation of natural, cultural and historical heritages in water area space in the context of cultural fusion and modern technology. Traditional Chinese culture of the layout of water bodies, which lays emphasis on integrity, is sought to elaborate the concept of era features in city waterscape designs so as to achieve the vision of "poetic habitation for human beings".

Bai J.,Hohai University
International Journal of Computers, Communications and Control | Year: 2013

This paper presents an adaptive incremental fuzzy PI controller (AIFPI) for a heating, ventilating, and air conditioning (HVAC) system capable of maintaining comfortable conditions under varying thermal loads. The HVAC system has two subsystems and is used to control indoor temperature and humidity in a thermal zone. As the system has strong-coupling and non-linear characteristics, fixed PI controllers have poor control performance and more energy consumption. Aiming to solve the problem, fuzzy control and PI control are combined together organically. In the proposed control scheme, the error of the system output and its derivative are taken as two parameters necessary to adapt the proportional (P) and integral (I) gains of the PI controller based on fuzzy reasoning according to practical control experiences. To evaluate the effectiveness of the proposed control methods in the HVAC system, it is compared with a fixed well-tuned PI controller. The results demonstrate that the AIFPI controller has more superior performance than the latter. © 2006-2013 by CCC Publications.

Li Y.,Hohai University
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2013

The technology of airborne Light Detection And Ranging (LIDAR) is capable of acquiring dense and accurate 3D geospatial data. Although many related efforts have been made by a lot of researchers in the last few years, LIDAR data filtering is still a challenging task, especially for area with high relief or hybrid geographic features. In order to address the bare-ground extraction from LIDAR point clouds of complex landscapes, a novel morphological filtering algorithm is proposed based on multi-gradient analysis in terms of the characteristic of LIDAR data distribution in this paper. Firstly, point clouds are organized by an index mesh. Then, the multigradient of each point is calculated using the morphological method. And, objects are removed gradually by choosing some points to carry on an improved opening operation constrained by multi-gradient iteratively. 15 sample data provided by ISPRS Working Group III/3 are employed to test the filtering algorithm proposed. These sample data include those environments that may lead to filtering difficulty. Experimental results show that filtering algorithm proposed by this paper is of high adaptability to various scenes including urban and rural areas. Omission error, commission error and total error can be simultaneously controlled in a relatively small interval. This algorithm can efficiently remove object points while preserves ground points to a great degree.

Cheng J.B.,Hohai University | Cheng J.B.,National Key Laboratory for Remanufacturing | Liang X.B.,National Key Laboratory for Remanufacturing | Xu B.S.,National Key Laboratory for Remanufacturing
Surface and Coatings Technology | Year: 2013

FeBSiNb amorphous coatings were synthesized by arc spray processing. The effects of annealing treatments on the microstructure, elastic and mechanical properties of the coatings were investigated. Annealing below 650°C induces the formation of α-Fe phase nanocrystals. Annealing at 650°C promotes the formation of Fe3B, Fe23B6 phases and α-Fe solid solution. The as-sprayed coating displays ultra-high hardness (H>16GPa), high reduced Young's modulus (Er>210GPa) and good wear resistance. These properties are further improved after annealing treatments (H>20GPa and Er>260GPa are achieved in the fully crystallized coating). The mechanical hardening is accompanied with an increase of the ratio of hardness to elastic modulus (H/Er), the yield pressure (H3/Er2) and the elastic recovery (η value). The different microstructural mechanisms responsible for these annealing-induced changes in mechanical and elastic properties are discussed. © 2013 Elsevier B.V.

Yang G.-M.,Hohai University
Applied Mechanics and Materials | Year: 2011

Combining the successful applications in AI, in this paper, an expert system is studied and designed for evaluating the safety of hydraulic metal structures, whose goal is compute the reliability of hydraulic metal structures. Applying the techniques of AI, a framework is made up for evaluating the safety of hydraulic metal structures. The framework of knowledge base system is designed and presented with the domain knowledge. Based on the theory of relational database, the conceptual and logical views of database system are designed and analysed. Additionally, method base system is designed. A practical example is given to illustrate the process of using this system. This system has features of practical and advanced and expand. © (2011) Trans Tech Publications.

Zhang P.,Hohai University
Information Technology and Applications - Proceedings of the 2014 International Conference on Information technology and Applications, ITA 2014 | Year: 2015

The phenomenon of IPO underpricing prevalently exists in the worldwide stock market. It is found that the IPO underpricing in China’s stock market is the most severe around the world. Small and medium-sized enterprises board occupies a very important position in the capital market system, and there are unique reasons for the underpricing phenomenon. This paper selects initial public offering stocks in small and medium-sized market (2006 to 2013) as samples, analyzing factors that influence IPO underpricing, degree of influence, and reasons account for such phenomenon. © 2015 Taylor & Francis Group, London.

Lu Y.,Hohai University
KSII Transactions on Internet and Information Systems | Year: 2015

Nowadays, public cloud storage is gaining popularity and a growing number of users are beginning to use the public cloud storage for online data storing and sharing. However, how the encrypted data stored in public clouds can be effectively shared becomes a new challenge. Proxy re-encryption is a public-key primitive that can delegate the decryption right from one user to another. In a proxy re-encryption system, a semi-trusted proxy authorized by a data owner is allowed to transform an encrypted data under the data owner’s public key into a re-encrypted data under an authorized recipient’s public key without seeing the underlying plaintext. Hence, the paradigm of proxy re-encryption provides a promising solution to effectively share encrypted data. In this paper, we propose a new certificate-based proxy re-encryption scheme for encrypted data sharing in public clouds. In the random oracle model, we formally prove that the proposed scheme achieves chosen-ciphertext security. The simulation results show that it is more efficient than the previous certificate-based proxy re-encryption schemes. © 2015 KSII.

Wu X.L.,Hohai University
Advanced Materials Research | Year: 2014

Errors are common human failures occurring in information interface and its cognition mechanism of errors is an important hitting-point for improving interface design as well as the key for reducing cognition difficulties. This paper studies error factors of information interface in human-computer interaction based on visual cognition theory. A feasible attention failure model is established to solve some design problems which result in serious failures in information recognition and analysis, and even in operation and execution processes. © (2014) Trans Tech Publications, Switzerland.

Response surface method (RSM) is widely accepted as an efficient method for reliability analysis, especially when the limit state function (LSF) is supposed to be highly nonlinear or closed-form mechanical models to describe the complex structural systems are not available. However, the selection of different response surface functions may result in different computational accuracy and computing time. In this paper, stochastic response surface method (SRSM), in which Hermite polynomials are employed to approximate the real LSF, is adopted in this paper to analyze the fuzzy reliability of structural systems. With a beam presented as an example, traditional methods, such as FORM, JC method and sequence response surface method, and the method raised in the context are compared in case of the study on solving the reliability. The results show that fuzzy reliability analysis with SRSM is relatively much more efficient and less time-consuming, thus the method raised is more suitable for the analysis of this kind of problems. © (2014) Trans Tech Publications, Switzerland.

Large long corridor surge chambers have unique form. As a typical hydropower underground structure, its stability of surrounding rock in the process of excavation and force features of structure are affected by particular structure form. Take a hydropower station for example, by using the finite difference method, we simulated two different schemes in process of excavation and analyzed its displacement, stress, plastic zone of surrounding rock as well as force feature of structure. Appropriate law of large long corridor surge chamber during excavation is summarized which will provide the reference for the similar project. © (2014) Trans Tech Publications, Switzerland.

Mao Y.,Hohai University | Wu J.,Temple University
Ad-Hoc and Sensor Wireless Networks | Year: 2014

Mobile phones are increasingly being equipped with hardware and software services that allow them to determine their locations; however, support for building location-based applications remains a challenging problem. The most widely used localization technology in smart phones is GPS, but it rarely works indoors and provides low energy efficiency. Cell tower-based localization is widely available, but can provide very poor accuracy without a fingerprint profile. WiFi localization, when available, provides reasonable accuracy, but is also much less effective in other areas. Constandache et al. proposed an Escort system to assist in localizing and tracking others in a public place without requiring either GPS, WiFi, war-driving, maps, or floor plans. However, the Escort system may route one person on a long path even though the person being tracked may be close by. In this paper, we will investigate the problem of finding better tracking paths in the Escort system. We propose a GFG routing assisted human tracking algorithm to reduce the length of the tracking path for every pair of users using smart phones in mobile social networks. Through adding one seeker in the Escort system, whose main function is to find better paths between any pair of two intersections by applying the GFG routing algorithm, the localization and tracking algorithm in the Escort system is more effective than the original algorithm. Finally, we conduct simulations of our proposed algorithm at the main campus of Temple University with different numbers of mobile users and different duration times. The simulation results show that the human tracking performance has been greatly enhanced. © 2014 Old City Publishing, Inc.

Liu W.,Hohai University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Outlier detection in high dimensional data is one of the hot areas of data mining. The existing outlier detection methods are based on the distance in Euclidean space. In high-dimensional data, these methods are bound to deteriorate due to the notorious "dimension disaster" which leads to distance measure cannot express the original physical meaning and the low computational efficiency. This paper improves the method of angle-based outlier factor and proposes the method of variance of angle-based outlier factor outlier in mining high dimensional. It introduces the related theories to guarantee the reliability of the method. The empirical experiments on synthetic data sets show the method is efficiency and scalable to high-dimensional data sets. © 2015 SPIE.

Huang J.,Laval University | Huang J.,Hohai University | Rodrigue D.,Laval University
Materials and Design | Year: 2013

Carbon nanotubes (CNTs), as a reinforcing material, are extensively used in nanocomposites for their high stiffness and high strength. To analyze the mechanical properties of CNT reinforced polymer composites, continuum mechanics combined with finite elements methods (FEMs) is a very effective tool. However, adopting different numerical models will directly affect the computing efficiency. In this work, solid element, shell element and 3-D truss element are separately used to simulate single wall carbon nanotube (SWCNT). In addition, the effects of CNT aspect ratio on the mechanical properties of CNT reinforced polypropylene composites are investigated. As a first approximation, the polypropylene matrix material is assumed to be a linear elastic or an elastic-plastic material, while CNT is assumed to be a linear elastic material. A series of direct tensile numerical tests were carried out to get the elastic modulus of SWCNT/polypropylene composites and the transverse deformations of the composites are determined for the range of conditions tested. © 2013.

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.

Qian K.,Glasgow Caledonian University | Zhou C.,Glasgow Caledonian University | Allan M.,Glasgow Caledonian University | Yuan Y.,Hohai University
IEEE Transactions on Power Systems | Year: 2011

This paper presents a methodology for modeling and analyzing the load demand in a distribution system due to electric vehicle (EV) battery charging. Following a brief introduction to the common types of EV batteries and their charging characteristics, an analytical solution for predicting the EV charging load is developed. The method is stochastically formulated so as to account for the stochastic nature of the start time of individual battery charging and the initial battery state-of-charge. A comparative study is carried out by simulating four EV charging scenarios, i.e., uncontrolled domestic charging, uncontrolled off-peak domestic charging, smart domestic charging and uncontrolled public chargingcommuters capable of recharging at the workplace. The proposed four EVs charging scenarios take into account the expected future changes to the electricity tariffs in the electricity market place and appropriate regulation of EVs battery charging loads. A typical U.K. distribution system is adopted as an example. The time-series data of EV charging loads is taken from two commercially available EV batteries: lead-acid and lithium-ion. Results show that a 10% market penetration of EVs in the studied system would result in an increase in daily peak demand by up to 17.9%, while a 20% level of EV penetration would lead to a 35.8% increase in peak load, for the scenario of uncontrolled domestic chargingthe worst-case scenario. © 2010 IEEE.

Wang Y.,Hohai University
Journal of Geometry and Physics | Year: 2014

A deformation theory of generalized holomorphic structures in the setting of (generalized) principal fibre bundles is developed. It allows the underlying generalized complex structure to vary together with the generalized holomorphic structure. We study the related differential graded Lie algebra, which controls the deformation problem via the Maurer-Cartan equation. As examples, we check the content of the Maurer-Cartan equation in detail in the special cases where the underlying generalized complex structure is symplectic or complex. A deformation theorem, together with some non-obstructed examples, is also included. © 2013 Elsevier B.V.

Zentar R.,Ecole Des Mines de Douai | Wang D.,Ecole Des Mines de Douai | Wang D.,Hohai University | Abriak N.E.,Ecole Des Mines de Douai | And 2 more authors.
Construction and Building Materials | Year: 2012

The effectiveness of using siliceous-aluminous fly ash and cement in solidifying Dunkirk marine sediments was investigated by means of laboratory tests to evaluate the compatibility of solidified material as roadbed materials. For this purpose, the mechanical properties of various designed mixes were investigated by the modified Proctor compaction tests, the tensile strength tests and the unconfined compressive strength tests. The swelling properties and bearing capacity changes were studied under water immersion condition for 4 days by standardized swelling test. For evaluating the impact of freezing-thawing cycles and water immersion damage on strength properties of cement/fly ash-sediment mixes, 20-cycle freezing-thawing tests and 32-day water immersion tests were realized on standard cured cylindrical samples. A coefficient of strength loss was defined to quantify the effect of freezing-thawing damage and water immersion aging on durability of designed mixes. XRD tests were carried out to verify the formation of cementitous compounds CSH and highlight the chemical transformation in sediments. The techniques help explain the change in mechanical properties of cement/fly ash-based sediments. © 2012 Elsevier Ltd. All rights reserved.

Wang Y.,Hohai University
Journal of Geometry and Physics | Year: 2014

We define the notion of generalized holomorphic principal bundles and establish that their associated vector bundles of holomorphic representations are generalized holomorphic vector bundles defined by M. Gualtieri. Motivated by our definition, several examples of generalized holomorphic structures are constructed. A reduction theorem of generalized holomorphic structures is also included. © 2014 Elsevier B.V.

Hu Z.,Hohai University | Lu Y.Y.,City University of Hong Kong
Journal of Lightwave Technology | Year: 2015

Photonic crystal (PhC) heterostructures combining segments of slightly different PhCs have been used to develop photonic devices, such as high-performance add/drop filters and microcavities with ultrahigh-quality factors. In this paper, we present a highly efficient computational method for simulating PhC heterostructure devices based on a two-dimensional (2-D) model. The method delivers high-accuracy results with ultrasmall-computational domains and an exponential convergence rate, and it takes full advantage of the existence of many identical unit cells and the circular shape of the air holes in typical slab-based PhC heterostructure devices. The 2-D model can capture many features of realistic PhC heterostructure devices fabricated on silicon slabs. Our method can be used to explore a large number of parameters in the design and optimization process. © 2015 IEEE.

Zheng J.,PLA University of Science and Technology | Zheng J.,Beijing Institute of Technology | Zhao L.,PLA University of Science and Technology | Zhao L.,Beijing Institute of Technology | And 2 more authors.
Composites Part B: Engineering | Year: 2012

Hierarchical cellular materials are predicted to have superior energy absorption capability. To enhance the energy absorption of the woven lattice sandwich panels, hierarchical square lattice panels were designed and manufactured. With sandwich walls, the hierarchical square lattice panels are light but render ideal complete stress-strain curves with high compression strengths, stable displacement plateau at a relative high stress level and large densification strain in experiments. A plastic model has been suggested to predict the limits of the deformation plateau after the peak stress. It is shown that hierarchical lattice structures obviously enhance the energy absorption capability of the light-weight woven textile material. © 2011 Elsevier Ltd. All rights reserved.

Erfani Joorabchi A.,Arup | Liang R.Y.,University of Akron | Li L.,University of Akron | Liu H.,Hohai University
Soil Dynamics and Earthquake Engineering | Year: 2014

In this paper, a method for estimating yield acceleration of a slope reinforced with a row of equally spaced drilled shafts under a seismic excitation is presented. The method is based on a concept of soil arching due to rigid inclusions of drilled shafts on slope, which in turn reduces the driving force on the down-slope side of drilled shafts. Considering soil arching effects and earthquake-induced inertia forces, a limiting equilibrium based formulation was derived. A computer program was coded to allow for calculations of yield acceleration of a drilled shafts reinforced slope with complex slope geometry and soil profiles. Once yield acceleration is determined, then Newmark's method can be evoked to estimate permanent displacement of a slope reinforced with a row of drilled shafts under an earthquake excitation. A total of seven cases were presented to show that the proposed Newmark type calculation is adequate when compared to 3-D finite element analysis results. © 2013 Elsevier Ltd.

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.

Zhou A.-Z.,Jiangsu University of Science and Technology | Lu T.-H.,Hohai University
Yantu Lixue/Rock and Soil Mechanics | Year: 2012

In simple shear test, under the constant stress increment ratio (CSIR) stress path, some soil-structure interfaces have the mechanical properties of strain softening and shear dilatation. B