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Li C.,CAS Wuhan Institute of Rock and Soil Mechanics | Li C.,Hubei Water Resources Technical College | Zheng H.,CAS Wuhan Institute of Rock and Soil Mechanics | Zheng H.,Beijing University of Technology | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2016

The contact problem is one of the key mechanical problems in the discontinuous medium such as rock. Based on the physical meaning of 3D contact problem, the equivalent complementary models were established in normal and tangential directions, respectively. A new approximating smooth function was proposed for the nonlinear property of the complementary model. The approximating function is equivalent to the complementary model when the parameter tends to 0+. Since the approximation function is C1 continuous, the corresponding Jacobian matrix is nonsingular under any condition which enables the successful solution for the conventional Newton algorithm. By introducing the direction vector, the constraint function method proposed in 2D frictional contact problems was extended to 3D ones. Hence the stability problem caused by the periodicity of the direction angle in 3D contact problems was resolved. Then, the 3D point-surface contact for finite element model was established. At last, the validity of the proposed method was verified with several classical cases. © 2016, Science Press. All right reserved.

Xu X.,Hohai University | Zhong K.,Hohai University | Bai J.,Hubei Water Resources Technical College
Journal of Hohai University | Year: 2014

Based on analysis of the flow-dividing characteristics and riverbed evolution of the Xiaohuangzhou bifurcated reach of the Yangtze River, the influence of the evolution of the Xiaohuangzhou bifurcated reach on the Xinjizhou bifurcated reach downstream of the Yangtze River was studied using a mathematical model. According to the results, the evolution of the Xiaohuangzhou bifurcated reach has a significant influence on the flow-dividing characteristics of the downstream Xinjizhou bifurcated reach. In the current situation, the recession of the left branch of the Xiaohuangzhou bifurcated reach will lead to the recession of the left branches of the Xinshengzhou and Xinjizhou bifurcated reaches and development of the left branch of the Xinqianzhou reach, while development of the left branch of the Xiaohuangzhou bifurcated reach will lead to development of the left branches of the Xinshengzhou and Xinjizhou bifurcated reaches and a small change in the left branch of the Xinqianzhou bifurcated reach.

Zhao W.,Nanjing University of Aeronautics and Astronautics | Han Q.-X.,Nanjing University of Aeronautics and Astronautics | Wang J.-H.,Nanjing University of Aeronautics and Astronautics | Zhang G.-H.,Hubei Water Resources Technical College
Hangkong Dongli Xuebao/Journal of Aerospace Power | Year: 2015

To study the effect of hot jet ignition on flame acceleration and detonation initiation in detonation tube, 2-D numerical simulations with propane mechanism including 34 reaction steps among 26 chemical species were performed, and the flame propagation law in detonation tube and deflagration to detonation transition (DDT) time and distance were obtained with 5 different configurations of hot jet sub-chamber. The results show that turbulence plays a key role during flame acceleration process in detonation tube, and the shock/flame interaction dominates the detonation initiation. According to the definition of DDT process, the DDT time is between 1.4-2.0 ms, and the minimum value is obtained in the hot jet sub-chamber with 150 mm length and 8 mm in orifice diameter. The hot jet sub-chamber length and orifice diameter exert a minor effect on the DDT distance. ©, 2015, BUAA Press. All right reserved.

Yang B.,Wuhan University | Yang B.,Hubei Water Resources Technical College | Liu L.,Wuhan University | Zhang S.,Hubei Water Resources Technical College
Applied Mechanics and Materials | Year: 2012

Base on the principle of nonlinear calculation, the mechanical models and the method of models experiment, we have provided a numerical analysis method of fitting hyper-elastic material constitutive relations. The method educed material spacial constitutive relations expressed by tensor through strain energy theory. After that, deduced material uniaxis constitutive models and use BP neural network to fit coefficients. Constitutive relations are the base of material deformation research. However we just paid attention to deformation experimental result before, rather than theoretical analysis. The theoretical analysis method this paper researching is convenient and precise and scientific, so it has theoretical meaning and practical value.

Li C.-H.,Wuhan University | Li C.-H.,Hubei Water Resources Technical College | Jiang Q.-H.,Wuhan University | Zhou C.-B.,Wuhan University
Gongcheng Lixue/Engineering Mechanics | Year: 2014

Mohr-Coulomb criterion leads to convergence difficulties in the numerical calculation due to the presence of singularity. Firstly, the singularity problem is mainly caused by the principal stress's nonsmoothness when Lode angle changes, and then the theoretical basis of the principal stress space are given. Mohr-Coulomb criterion's equivalent complementary model is presented in the principal stress space based on Koiter's rule, and the Fischer-Burmeister complementarity function is used to describe the model, which makes the Newton algorithm be successfully solved. The proposed algorithm can remove the singularity of the Mohr-Coulomb criterion and avoid the trial process of the conventional methods, and it also improves the accuracy of the Mohr-Coulomb criterion. Examples verify the validity and reliability of this method.

Chen C.,Hubei Water Resources Technical College | Zhao C.,Huazhong Agricultural University | Zhang J.,Huazhong Agricultural University | Ding S.,Huazhong Agricultural University | Xu J.,Huazhong Agricultural University
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

In order to solve the cooling problem for greenhouse in the humid and hot area in summer, liquid dehumidifying and cooling system with CaCl 2 liquid was proposed. Under the condition that the dehumidifying and cooling system was operated in greenhouse, the experimental target about the relative humidity of the air on the spray room exit was determined, and the factors affecting on the experimental indexes were analyzed, such as inlet air flow, liquid desiccant flow concentration and temperature, inlet air temperature and humidity and so on. By the single factor and multi-factor orthogonal experiment, when the system was operating, the significant factors included desiccant concentration and temperature, inlet air temperature and humidity. Through the regression analysis, the mathematical model of spraying and dehumidifying with CaCl 2 was established and verified, and the maximum relative error of model was less than 5%. This paper provides a reference for greenhouse cooling under high temperature and high humidity condition in summer in the South China.

Sun T.,Wuhan University | Zhang L.,Wuhan University | Chen W.,Wuhan University | Tang X.,Hubei Water Resources Technical College | Qin Q.,Wuhan University
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2013

The aim of this paper is to propose a more practical mountain fire spread model for fire behavior prediction and management in Southwest forest area of China. These areas are covered mainly with spatial heterogeneous flammable forest and are characterized by undulating terrain and steep slopes. This model can produce more accurate fire propagation maps by combining CA (Cellular Automaton) framework with Wang Zhengfei fire physical velocity model in fine scale. Considering the inherent uncertainties of fire propagation, the model has been built on multi-dimension geophysical and environmental components and also sound knowledge of fire spread physical mechanism. Regarding small fuel patches as spatial homogenous cells, this approach makes it easier to generate higher level complex fire behavior maps from CA simple local rules and local behavior integrated with high resolution vegetation images, fine scale terrain maps and surface wind field. Because the model focuses primarily on the study of surface fire front propagation behavior, it attempts to simplify complex fuel modeling. Additionally, this Wang-Geophysical-CA model is able to analyze the time series spatial pattern of fire-front spread and model local behavior instead of the final fire spread pattern of the conventional approach. In this work, not only single influence verification tests have been made, but also simulation tests with multiple influences are carried out to demonstrate the capability of the model with fine scale vegetation maps, surface wind field, terrain, moisture content and man-made structures. © 2008-2012 IEEE.

Liu L.,Hubei Water Resources Technical College | Lv P.,Wuhan Institute of Technology
International Journal of Digital Content Technology and its Applications | Year: 2012

With the ubiquity of information networks and their broad applications, the issue of similarity computation between entities of an information network arises and draws extensive research interests. In this paper, three kinds of similarity measures link-based of information network are presented according to the conceptual representation of information network respectively. The main advantage of these types of methods resides in their ability to produce systematically better correlation with human judgments compared to the traditional method such as the text-based ones. Moreover, this paper surveys effectives and quality of query of three the kinds of similarity measures. By presenting these methods in the same link-based framework, we hope this paper may shed some light on deciding which methods are more suitable to use in different situations.

Li C.-H.,Wuhan University | Li C.-H.,Hubei Water Resources Technical College | Jiang Q.-H.,Wuhan University | Zhou C.-B.,Wuhan University
Yantu Lixue/Rock and Soil Mechanics | Year: 2013

Strength reduction technique by finite element method is an effective method for slope stability evaluation; and it has been used more and more widely. There are many factors influence the result of this method; the order of finite element is an important one of them. The effect of element order on the strength reduction method is analyzed through three classical examples, i.e. 2D foundation problem, 2D slope stability problem and 3D slope stability problem. The results show that both linear element and quadratic element will approach to the exact solution from the upper side as the number of elements increases; but for linear element is too 'rigid'; and it will overestimate the safety factor, so it is dangerous for engineering practice. The error with linear element is about eight times larger than that of quadratic element under the same meshes. The shortage of strength reduction method with linear element can be made up by replacing the linear element with quadratic element based on the convergence of the maximum displacement in the system as the stability criteria. Quadratic element is more suitable than linear element for the shear strength reduction finite element method.

Yu X.,Wuhan University of Science and Technology | Luo M.X.,Hubei Water Resources Technical College
Applied Mechanics and Materials | Year: 2013

The method of retaining piles working as an anti-floating piles has advantages of lesser environmental impact, high utilization of resources and good in economic benefits, but the method effecting on underground structure was worthy of further study and exploitation. According to the practical underground projects, this paper has proposed three possible connections between underground structure, shear connectors and retaining piles. The analysis showed that the internal force and displacement of underground structural is affected distinctly by the method. In addition, characters and applicable ranges of the three different connections is introduced with the finite element analysis and calculation of stress and displacement of the main parts like base plate, top plate,and so on. © (2013) Trans Tech Publications, Switzerland.

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