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Mechanical behavior of segment rebar of shield tunnel in construction stage

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第7期9卷 888-899页

作者： Jun-sheng chen Hai-hong MO Department of Civil Engineering South China University of Technology Guang＇zhou 510640 China State Key Laboratory of Subtropical Building Science South China University of Technology Guang＇zhou 510640 China

In this paper, a 3D finite element （FE） program ADINA was applied to analyzing a tunnel with 9 segment tings. The loads acting on these segment tings included the squeezing action of tail brush of shield machine under attitude deflection, the jacking forces, the grouting pressure and the soil pressure. The analyses focused on the rebar stress in two statuses：（1） normal construction status without shield machine squeezing; （2） squeezing action induced by shield machine under attitude deflection. The analyses indicated that the rebar stress was evidently affected by the construction loads. In different construction status, the rebar stress ranges from -80 MPa to 50 MPa, and the rebar is in elastic status. Even some cracks appear on segments, the stress of segment rebar is still at a low level. It is helpful to incorporate a certain quantity of steel fiber to improve the anti-crack and shock resistance performance.

关键词： Shield tunnel Construction Segment Rebar Finite element (FE) analysis

Novel Adaptive Learning Control of Linear Systems with Completely Unknown Time Delays

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International Journal of Automation and computing 2009年第2期6卷 177-185页

作者： Wei-sheng chen Department of Applied Mathematics Xidian University Xi＇an 710071 PRC

A novel output-feedback adaptive learning control approach is developed for a class of linear time-delay systems. Three kinds of uncertainties： time delays, number of time delays, and system parameters are all assumed to be completely unknown, which is dfferent from the previous work. The design procedure includes two steps. First, according to the given periodic desired reference output and the allowed bound of tracking error, a suitable finite Fourier series expansion （FSE） is chosen as a practical reference output to be tracked. Second, by expressing the delayed practical reference output as a known time-varying vector multiplied by an unknown constant vector, we combine three kinds of uncertainties into an unknown constant vector and then estimate the vector by designing an adaptive law. By constructing a Lyapunov-Krasovskii functional, it is proved that the system output can asymptotically track the practical reference signal. An example is provided to illustrate the effectiveness of the control scheme developed in this paper.

关键词： Linear system unknown time delay output-feedback learning control Fourier series expansion (FSE).

MULTI-AGENT AGGREGATION BEHAVIOR ANALYSIS: THE DYNAMIC COMMUNICATION TOPOLOGY

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Journal of Systems Science & Complexity 2008年第2期21卷 209-216页

作者： sheng chen Lindu ZHAO Ying HAN Institute of Systems Engineering Southeast University Nanjing 210018 China

The authors extend the Gazi＇s swarm model with local neighbor rules and the dynamic communication topology, and study its aggregation properties. Results of analysis show that all agents in the models aggregate and eventually form a cohesive cluster of finite size around the swarm center or the appointed point. Finally, simulations are provided to testify some of the results. Models in the paper are more applicable to the reality for the advantage that each agent only needs the partial information of the entire dynamic system when making motion decision.

关键词： Aggregation behavior dynamic communication topology local neighbor rules multi-agent system.

Natural convection of SiO_2-water nanofluid in square cavity with thermal square column

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Applied Mathematics and Mechanics(English Edition) 2017年第4期38卷 585-602页

作者： Xiaopeng XIONG sheng chen Bo YANG State Key Laboratory of Coal Combustion Huazhong University of Science and Technology Institute for Modelling and Simulation in Fluodynamics Nanoscience and Industrial Mathematics "Gregorio Millan Barbany"Universidad Carlos III de Madrid Faculty of Engineering The University of NottinghamUniversity Park

A square with a thermal square column is a simple but nontrivial research prototype for nanofluid research. However, until now, the effects of the temperature of the square column on the heat and mass transfer of nanofluids have not been revealed comprehensively, especially on entropy generation. To deepen insight into this important field, the natural convection of the SiO2-water nanofluid in a square cavity with a square thermal column is studied numerically in this study. The effects of the thermal column temperature （T = 0.0, 0.5, 1.0, 1.5）, the Rayleigh number （ranging from 103 to 106）, and the volume fraction of the nanoparticle （varying from 0.01 to 0.04） on the fluid flow, heat transfer, and entropy generation are investigated, respectively. It is found that, no matter at a low or high Rayleigh number, the volume fraction of the nanoparticle shows no considerable effects on the flow field and temperature field for all the temperatures of the thermal column. With an increase in the volume fraction, the mean Nusselt number increases slightly. At the same time, it is found that, with an increase in the temperature of the thermal column, the average Nusselt number gradually decreases at all values of the Rayleigh number. Meanwhile, it is found that, at a high Rayleigh number, the heat transfer mechanism is the main parameter affecting the increase in the total entropy generation rather than the volume fraction. In addition, no matter at a high or low Rayleigh number, when T = 0.5, the total entropy generation is the minimum.

关键词： natural convection SiO2-water nanofluid Rayleigh number volume fraction entropy generation

A REVISED SOLUTION OF EQUIVALENT PERMEABILITY TENSOR FOR DISCONTINUOUS FRACTURES

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Journal of Hydrodynamics 2012年第5期24卷 711-717页

作者： HE Ji chen sheng-hong SHAHROUR Isam State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University 430072Wuhan China Laboratoire Genie Civil et geo-Environnement University Lille 1 59650 Villeneuve d Ascq France

The equivalent permeability tensor is essential to the application of the equivalent porous media model in the numerical seepage simulation for fractured rock masses. In this paper, a revised solution of the equivalent permeability tensor is proposed to represent the influence of the fracture connectivity in discontinuous fractures. A correction coefficient is involved to reflect the com- plex seepage flow type through the rock bridge. This correction coefficient is back analyzed from single-hole packer tests, based on the Artificial Neural Network （ANN） back analysis and the Finite Element Method （FEM） seepage simulation. The limitation of this back analysis algorithm is that the number of single-hole packer tests should be equal or greater than the number of fracture sets, and three is the maximum number of the fracture sets. The proposed solution and the back analysis algorithm are applied in the permea- bility measurement and the seepage simulation for the Xiaowan arch dam foundation.

关键词： discontinuous fractures permeability tensor back analysis packer test Artificial Neural Network (ANN)

Dynamic model and performance analysis of landing buffer for bionic locust mechanism

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Acta Mechanica Sinica 2016年第3期32卷 551-565页

作者： Dian-sheng chen Zi-Qiang Zhang Ke-Wei chen Robotic Institute Beihang University

The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is *** the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance,and it establishes a theoretical basis for studies and engineering applications.

关键词： Bionic locust mechanism Landing and buffering Dynamic model Buffering performance

Newly Identified Silicate Carbon Stars from IRAS Low-Resolution Spectra

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Chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 697-704页

作者： Pei-sheng chen Pin Zhang National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 Cosmic Ray Institute Yunnan University Kunming 650091

The discovery of silicate carbon star poses a challenge to the theory of stellar evolution in the late stage, hence it is important to look for more silicate carbon stars. To this end we have carried out cross-identifications between the new IRAS Low-Resolution Spectrum （LRS） database and the new carbon star catalog, CGCS3. We have found nine new silicate carbon stars with silicate features around 10μm and/or 18 μm. These newly identified stars are located in the Regions Ilia and VII in the IRAS two-color diagram, which means they indeed have typical far infrared colors of silicate carbon stars. The infrared properties of each of these sources are discussed.

关键词： stars AGB and post-AGB - star carbon - infrared stars

Data-driven decision-making model for determining the number of volunteers required in typhoon disasters

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Journal of Safety Science and Resilience 2023年第3期4卷 229-240页

作者： sheng-Qun chen Jie Bai School of Information Engineering Fujian Business UniversityFuzhou 350506China School of computer and information Fujian agriculture and Forestry UniversityFuzhou 350002China

Volunteer teams provide valuable support after large-scale ***,excessive volunteer participation poses challenges for formal ***,an appropriate decision-making method is required to quickly determine the number of volunteers required after a *** study proposes a data-driven decision-making(D^(3)M)method for typhoon disaster volunteerism that can effectively predict the number of volunteers *** data from actual cases were gathered,analyzed,and preprocessed to prepare the *** selection,D^(3)M model training and optimization,and model validation were performed to fine-tune the volunteer participant *** data from an actual typhoon in the Philippines,the rationality and efficacy of the method were verified through a comparative analysis of the experimental *** proposed method learns from disaster-event data to quickly predict the number of volunteers needed,such that it not only reasonably allocates volunteers to assist professional teams in rescue but also avoids secondary problems caused by an overwhelming response.

关键词： Data-driven decision-making Optimization Rescue Typhoon

Load Shedding Control Strategy in Power Grid Emergency State Based on Deep Reinforcement Learning

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CSEE Journal of Power and Energy Systems 2022年第4期8卷 1175-1182页

作者： Jian Li sheng chen Xinying Wang Tianjiao Pu China Electric Power Research Institute Haidian DistrictBeijing 100192China

In viewing the power grid for large-scale new energy integration and power electrification of power grid equipment,the impact of power system faults is increased,and the ability of anti-disturbance is decreased,which makes the power system fault clearance more *** this paper,a load shedding control strategy based on artificial intelligence is proposed,this action strategy of load shedding,which is selected by deep reinforcement learning,can support autonomous voltage ***,the power system operation data is used as the basic data to construct the network training dataset,and then a novel reward function for voltage is *** value function,which conforms to the power grid operation characteristics,will act as the reward value for deep reinforcement learning,and the Deep Deterministic Policy Gradient algorithm(DDPG)algorithm,with the continuous action strategy,will be ***,the deep reinforcement learning network is continuously trained,and the load shedding strategy concerning the grid voltage control problem will be obtained in the power system emergency control situation,and this strategy action is input into the Pypower module for simulation verification,thereby realizing the joint drive of data and *** to the numerical simulation analysis,it shows that this method can effectively determine the accurate action selection of load shedding,and improve the stable operational ability of the power system.

关键词： Artificial intelligence deep reinforcement learning load shedding control power system emergency state