The analytical method based on "Hertz theory on normal contact of elastic solids" and the numerical method based on finite element method (FEM) calculating the contact stress of face-gear drive with spur inv...The analytical method based on "Hertz theory on normal contact of elastic solids" and the numerical method based on finite element method (FEM) calculating the contact stress of face-gear drive with spur involute pinion were introduced, and their relative errors are below 10%, except edge contact, which turns out that these two methods can compute contact stress of face-gear drive correctly and effectively. An agreement of the localized bearing contact stress is gotten for these two methods, making sure that the calculation results of FEM are reliable. The loaded meshing simulations of multi-tooth FEM model were developed, and the determination of the transmission error and the maximal load distribution factor of face-gear drive under torques were given. A formula for the maximal load distribution factor was proposed. By introducing the maximal load distribution factor in multi-tooth contact zone, a method for calculating the maximal contact stress in multi-tooth contact can be given. Compared to FEM, the results of these formulae are proved to be reliable, and the relative errors are below 10%.展开更多
This paper presents the design, analysis and experimental study of a loading system for heavy-duty nodes test based on a large-scale multi-directional in-plane loading device, which has been used in a full-scale heavy...This paper presents the design, analysis and experimental study of a loading system for heavy-duty nodes test based on a large-scale multi-directional in-plane loading device, which has been used in a full-scale heavy-duty support node test. Test loads of the support reached 6 567 kN with multi-directional loading requirements, which outrange the capacity of the available loading devices. Through the reinforcement of a large-scale multi-directional inplane loading device, the innovative design of a self-balanced load transferring device, and other arrangement considerations of the loading system, the test was implemented and the loading capacity of the ring was considerably enlarged. Due to the heavy loading requirements, some checking computations of the ring and the load transferring device outranged the limit of the Chinese national code "Code for Design of Steel Structures (GB 50017—2003)", thus elastic-plastic finite element (FE) analysis was carried out on the two devices, and also the real-time monitoring on the whole loading systems during experiments to ensure test safety. FE analysis and test results show that the loading system worked elastically during experiments.展开更多
A multi-objective particle swarm optimization (MOPSO) approach for multi-objective economic load dispatch problem in power system is presented in this paper. The economic load dispatch problem is a non-linear constrai...A multi-objective particle swarm optimization (MOPSO) approach for multi-objective economic load dispatch problem in power system is presented in this paper. The economic load dispatch problem is a non-linear constrained multi-objective optimization problem. The proposed MOPSO approach handles the problem as a multi-objective problem with competing and non-commensurable fuel cost, emission and system loss objectives and has a diversity-preserving mechanism using an external memory (call “repository”) and a geographically-based approach to find widely different Pareto-optimal solutions. In addition, fuzzy set theory is employed to extract the best compromise solution. Several optimization runs of the proposed MOPSO approach were carried out on the standard IEEE 30-bus test system. The results revealed the capabilities of the proposed MOPSO approach to generate well-distributed Pareto-optimal non-dominated solutions of multi-objective economic load dispatch. Com- parison with Multi-objective Evolutionary Algorithm (MOEA) showed the superiority of the proposed MOPSO approach and confirmed its potential for solving multi-objective economic load dispatch.展开更多
Traditional seawater desalination requires high amounts of energy, with correspondingly high costs and limited benefits, hindering wider applications of the process. To further improve the comprehensive economic benef...Traditional seawater desalination requires high amounts of energy, with correspondingly high costs and limited benefits, hindering wider applications of the process. To further improve the comprehensive economic benefits of seawater desalination, the desalination load can be combined with renewable energy sources such as solar energy, wind energy, and ocean energy or with the power grid to ensure its effective regulation. Utilizing energy internet(EI) technology, energy balance demand of the regional power grid, and coordinated control between coastal multi-source multi-load and regional distribution network with desalination load is reviewed herein. Several key technologies, including coordinated control of coastal multi-source multi-load system with seawater desalination load, flexible interaction between seawater desalination and regional distribution network, and combined control of coastal multi-source multi-load storage system with seawater desalination load, are discussed in detail. Adoption of the flexible interaction between seawater desalination and regional distribution networks is beneficial for solving water resource problems, improving the ability to dissipate distributed renewable energy, balancing and increasing grid loads, improving the safety and economy of coastal power grids, and achieving coordinated and comprehensive application of power grids, renewable energy sources, and coastal loads.展开更多
The shakedown analysis of structures under variable multi-loadings is considered, and the corresponding simple shakedown condition is presented in this paper. Distribution of fixed stresses field is given, and the sel...The shakedown analysis of structures under variable multi-loadings is considered, and the corresponding simple shakedown condition is presented in this paper. Distribution of fixed stresses field is given, and the self-equilibrium of fixed stresses field is analyzed. Elastic shakedown and plastic shakedown conditions are presented based on the fixed stresses field. The theorem is convenient to evaluate the shakedown limit of structures under cyclical variable multiloadings through solving positive scalar fields and fixed stresses field factors at a series of dangerous positions of the structure, and tedious computations are avoided. Finally the theorem is applied to a thick-walled cylindrical tube under variable pressure and temperature, and the rolling contact problem. The results are in good agreement with some computational results.展开更多
The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A...The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A/SSSS) were studied by performing numerical stress analysis on blocks having multi flaws at close spacing's under uniaxial loading using PFC3 D. The following findings are obtained: SCI,B/SUC,B has an average value of about 0.5 with a variability of ± 0.1. This range agrees quite well with the values obtained by former research. For joint inclination angle, β=90°,B,UCB,CI,A,A/SSSS is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found betweenB,UCB,CI,A,A/SSSS and β; however, the average B,UCB,CI,A,A/SSSS seems to slightly decrease with increasing k. The variability ofB,UCB,CI,A,A/SSSS is found to increase with k.Based on the cases studied in this work,B,UCB,CI,A,A/SSSS ranges between 0.3 and 0.5. This range is quite close to the range of 0.4to 0.6 obtained for SCI,B/SUC,B. The highest variability of ± 0.12 forB,UCB,CI,A,A/SSSS is obtained for k=0.8. For the remaining k values the variability ofB,UCB,CI,A,A/SSSS can be expressed within ± 0.05. This finding is very similar to the finding obtained for the variability of SCI,B/SUC,B.展开更多
Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross val...Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross valve under multi-way loading due to the complexity of loading path and the multiplicity of associated processing parameters.A model of the process was developed under DFEORM-3D environment based on the coupled thermo-mechanical finite element method.The comparison between two process models,the conventional isothermal process model and the non-isothermal process model developed in this study,was carried out,and the results indicate that the thermal events play an important role in the aluminum alloy forming process under multi-way loading.The distributions and evolutions of the temperature field and strain filed are obtained by non-isothermal process simulation.The plastic zone and its extension in forming process of cross valve were analyzed.The results may provide guidelines for the determination of multi-way loading forming scheme and loading conditions of the forming cross valve components.展开更多
The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number o...The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number of the supporting legs,the increased overdetermination of the multi-leg platform systems leads to leveling coupling problem among legs and virtual leg problem in which some of the supporting legs bear zero or quasi zero loads.These problems make it quite complex and time consuming to level such a multi-leg platform.Based on rigid body kinematics,an approximate equation is formulated to rapidly calculate the leg extension for leveling a rigid platform,then a proportional speed control strategy is proposed to reduce the unexpected platform distortion and leveling coupling between supporting legs.Taking both the load coupling between supporting legs and the elastic flexibility of the working platform into consideration,an optimal balancing legs’ loads(OBLL) model is firstly put forward to deal with the traditional virtual leg problem.By taking advantage of the concept of supporting stiffness matrix,a coupling extension method(CEM) is developed to solve this OBLL problem for multi-leg flexible platform.At the end,with the concept of supporting stiffness matrix and static transmissibility matrix,an optimal load balancing leveling method is proposed to achieve geometric leveling and legs’ loads balancing simultaneously.Three numerical examples are given out to illustrate the performance of proposed methods.This paper proposes a method which can effectively quantify all of the legs’ extension at the same time,achieve geometric leveling and legs’ loads balancing simultaneously.By using the proposed methods,the stability,precision and efficiency of auto-leveling control process can be improved.展开更多
This paper is devoted to investigate the robust H∞sliding mode load frequency control(SMLFC) of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of re...This paper is devoted to investigate the robust H∞sliding mode load frequency control(SMLFC) of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of renewable energies,a new sliding surface function is constructed to guarantee the fast response and robust performance, then the sliding mode control law is designed to guarantee the reach ability of the sliding surface in a finite-time interval. The sufficient robust frequency stabilization result for multi-area power system with time delay is presented in terms of linear matrix inequalities(LMIs). Finally,a two-area power system is provided to illustrate the usefulness and effectiveness of the obtained results.展开更多
Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on a...Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on an unit length of a breakwater with wave direction, the longitudinal distribution of wave forces, as well as the longitudinal load reduction are analyzed. Some empirical formulae of the longitudinal distribution coefficient and the longitudinal load reduction factor are presented for practical use.展开更多
The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator cont...The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator control scheme. To this end, we consider a nonlinear interconnected model for multiarea power systems which also include uncertainties and timevarying communication delays. The design procedure is formulated using semi-definite programming and linear matrix inequality(LMI) method. The solution of the proposed LMIs returns necessary parameters for the tracking controllers such that the impact of model uncertainty and load disturbances are minimized. The proposed controllers are capable of receiving all or part of subsystems information, whereas the outputs of each controller are local. These controllers are designed such that the resilient stability of the overall closed-loop system is guaranteed. Simulation results are provided to verify the effectiveness of the proposed scheme. Simulation results quantify that the distributed(and decentralized) controlled system behaves well in presence of large parameter perturbations and random disturbances on the power system.展开更多
Because of different system capacities of base station(BS)or access point(AP)and ununiformity oftraffic distribution in different cells,quantities of new call users may be blocked in overloaded cell incommunication ho...Because of different system capacities of base station(BS)or access point(AP)and ununiformity oftraffic distribution in different cells,quantities of new call users may be blocked in overloaded cell incommunication hot spots.Whereas in some neighboring under-loaded cells,bandwidth may be superflu-ous because there are only few users to request services.In order to raise resource utilization of the wholeheterogeneous networks,several novel load balancing strategies are proposed,which combine the call ad-mission control policy and multi-hop routing protocol of ad-hoc network for load balancing.These loadbalancing strategies firstly make a decision whether to admit a new call or not by considering some param-eters like load index and route cost,etc.,and then transfer the denied users into neighboring under-load-ed cell with suiplus channel according to optimum multi-hop routing algorithm.Simulation results showthat the proposed load balancing strategies can distribute traffics to the whole heterogeneous wireless net-works,improve the load balance index efficiently,and avoid the call block phenomenon almost absolutely.展开更多
The mass production of primed electronics can be achieved by roll-to-roll(R2R) printing system, so highly accurate web tension is required that can minimize the register error and keep the thickness and roughness of...The mass production of primed electronics can be achieved by roll-to-roll(R2R) printing system, so highly accurate web tension is required that can minimize the register error and keep the thickness and roughness of printed devices in limits. The web tension of a R2R system is regulated by the use of integrated load cells and active dancer system for printed electronics applications using decentralized multi-input-single-output(MISO) regularized variable learning rate backpropagation artificial neural networks. The active dancer system is used before printing system to reduce disturbances in the web tension of process span. The classical PID control result in tension spikes with the change in roll diameter of winder and unwinder rolls. The presence of dancer in R2R system shows that improved web tension control in printing span and the web tension can be enhanced from 3.75 N to 4.75 N. The overshoot of system is less than ±2.5 N and steady state error is within ± 1 N where load cells have a signal noise of ±0.7 N. The integration of load cells and active dancer with self-adapting neural network control provide a solution to the web tension control of multispan roll-to-roll system.展开更多
The load distribution of multi-row bearings of large strip rolling mill is fully analyzed by 3D contact boundary element method (BEM). It is found out that bearings are frequently worn out due to serious uneven load...The load distribution of multi-row bearings of large strip rolling mill is fully analyzed by 3D contact boundary element method (BEM). It is found out that bearings are frequently worn out due to serious uneven load on the multi-row rollers. The constraint mechanism of the previous rolling system is found to be unreasonable by theoretical analysis on heavy machinery structure. A mechanism of self-aligning even load for workroll bearing of 2 050 mm hot rolling mill of Baoshan I&S Co. is developed. This device is manufactured with particular regard to the structure of 2 050 mm hot rolling mill mentioned above. Hence, uneven load on multi-row bearings is greatly relieved and their lives are remarkably prolonged. Meanwhile, theoretical analysis and on-spot tests prove the rationality and validity of the device.展开更多
In order to investigate the energy absorption characteristics of multi-cell polygonal tubes with different cross-sectional configurations,firstly,the theoretical formulae of the mean crushing force under axial load fo...In order to investigate the energy absorption characteristics of multi-cell polygonal tubes with different cross-sectional configurations,firstly,the theoretical formulae of the mean crushing force under axial load for four multi-cell polygonal tubes were derived by combining the Super Folding Element theory with Zhang’s research results.These formulae can be used to validate the numerical model and quickly evaluate the energy absorption ability of multi-cell polygonal tubes.Furthermore,a comparative study on the energy absorption performance of eight multi-cell polygonal tubes under axial and oblique loads was conducted.The results show that all tubes have a stable mixed deformation mode under axial load.The multi-cell decagon tube has better energy-absorption ability compared with other tubes.Whenθis less than 10°,all the tubes maintain a stable deformation mode,and the multi-cell decagon tube also has the biggest crushing force efficiency and specific energy absorption among these eight tubes;meanwhile compared with the results atθ=0°,the specific energy absorption of all tubes decreases by about 8%-21%,while the crushing force efficiency increases by 20%-56%.However,at large angles 20°and 30°,all of the tubes collapse in bending modes and lose their effectiveness at energy absorption.展开更多
<div style="text-align:justify;"> In the multi-objective of intelligent building load scheduling, aiming at the problem of how to select Pareto frontier scheme for multi-objective optimization algorith...<div style="text-align:justify;"> In the multi-objective of intelligent building load scheduling, aiming at the problem of how to select Pareto frontier scheme for multi-objective optimization algorithm, the current optimal scheme mechanism combined with multi-objective multi-verse algorithm is used to optimize the intelligent building load scheduling. The update mechanism is changed in updating the position of the universe, and the process of correction coding is omitted in the iterative process of the algorithm, which reduces the com-putational complexity. The feasibility and effectiveness of the proposed method are verified by the optimal scheduling experiments of residential loads. </div>展开更多
Based on ServiceBSP model, a hierarchical resource load balancing algorithm with Multi-Agent is put forward in this paper which achieves the goal of dynamic load balancing and favorable Fault-tolerant. The algorithm c...Based on ServiceBSP model, a hierarchical resource load balancing algorithm with Multi-Agent is put forward in this paper which achieves the goal of dynamic load balancing and favorable Fault-tolerant. The algorithm calculates the load value according to the attributes of resource and scheduling tasks relies on the load value, while updating the load information dynamically depending on Multi-Agent. The method avoids frequent communications on load information. Furthermore, the paper introduces the function of agents, relations and communications among agents in details. Finally, by comparing response time and distribution of load using proposed method with other available methods such as without no load balancing and load balancing only giving regards to CPU, the experimental simulation shows that the load balancing based on Multi-Agent possesses superior performance on response time and load balancing.展开更多
This paper proposes a novel dual layered multi agent system (MAS) based control system for the use in microgrid operations. In developing a smarter grid capable of withstanding disturbances and/or outages and providin...This paper proposes a novel dual layered multi agent system (MAS) based control system for the use in microgrid operations. In developing a smarter grid capable of withstanding disturbances and/or outages and providing quality service to the consumers, reliable microgrid control architecture is vital. The innovative microgrid control system proposed, makes the microgrid capable of isolating the local grid from effects of any upstream disturbances in the main utility grid by operating disconnected from the main utility via islanding, and it allows the most critical local loads to be supplied by any, available, local power source during such islanded operation. The proposed MAS control architecture is developed using the JADE platform and it is used to control a test network simulated in MATLAB. The results of these simulations show the capability of developing MAS based reliable control mechanism for islanding and load management of microgrids based on the proposed concept.展开更多
With the rapid and large-scale development of renewable energy, the lack of new energy power transportation or consumption, and the shortage of grid peak-shifting ability have become increasingly serious. Aiming to th...With the rapid and large-scale development of renewable energy, the lack of new energy power transportation or consumption, and the shortage of grid peak-shifting ability have become increasingly serious. Aiming to the severe wind power curtailment issue, the characteristics of interactive load are studied upon the traditional day-ahead dispatch model to mitigate the influence of wind power fluctuation. A multi-objective optimal dispatch model with the minimum operating cost and power losses is built. Optimal power flow distribution is available when both generation and demand side participate in the resource allocation. The quantum particle swarm optimization (QPSO) algorithm is applied to convert multi-objective optimization problem into single objective optimization problem. The simulation results of IEEE 30-bus system verify that the proposed method can effectively reduce the operating cost and grid loss simultaneously enhancing the consumption of wind power.展开更多
基金Project(50875263) supported by the National Natural Science Foundation of ChinaProject(2011CB706800) supported by the National Basic Research Program of ChinaProject(2010ssxt172) supported by the Natural Science Foundation of Hunan Province,China
文摘The analytical method based on "Hertz theory on normal contact of elastic solids" and the numerical method based on finite element method (FEM) calculating the contact stress of face-gear drive with spur involute pinion were introduced, and their relative errors are below 10%, except edge contact, which turns out that these two methods can compute contact stress of face-gear drive correctly and effectively. An agreement of the localized bearing contact stress is gotten for these two methods, making sure that the calculation results of FEM are reliable. The loaded meshing simulations of multi-tooth FEM model were developed, and the determination of the transmission error and the maximal load distribution factor of face-gear drive under torques were given. A formula for the maximal load distribution factor was proposed. By introducing the maximal load distribution factor in multi-tooth contact zone, a method for calculating the maximal contact stress in multi-tooth contact can be given. Compared to FEM, the results of these formulae are proved to be reliable, and the relative errors are below 10%.
基金Supported by National Natural Science Foundation of China (No. 50878066)the National Key Technology R&D Program in the 11th Five-Year Plan of China (No. 2006BAJ01B02)the Key Technologies R&D Program of Heilongjiang Province, China (No. GB02C204)
文摘This paper presents the design, analysis and experimental study of a loading system for heavy-duty nodes test based on a large-scale multi-directional in-plane loading device, which has been used in a full-scale heavy-duty support node test. Test loads of the support reached 6 567 kN with multi-directional loading requirements, which outrange the capacity of the available loading devices. Through the reinforcement of a large-scale multi-directional inplane loading device, the innovative design of a self-balanced load transferring device, and other arrangement considerations of the loading system, the test was implemented and the loading capacity of the ring was considerably enlarged. Due to the heavy loading requirements, some checking computations of the ring and the load transferring device outranged the limit of the Chinese national code "Code for Design of Steel Structures (GB 50017—2003)", thus elastic-plastic finite element (FE) analysis was carried out on the two devices, and also the real-time monitoring on the whole loading systems during experiments to ensure test safety. FE analysis and test results show that the loading system worked elastically during experiments.
基金Supported by National Natural Science Foundation of China (60674039, 60704004) and Innovation Fund for Outstanding Scholar of Henan Province (084200510009 )
基金Project (Nos. 60074040 and 6022506) supported by the NationalNatural Science Foundation of China
文摘A multi-objective particle swarm optimization (MOPSO) approach for multi-objective economic load dispatch problem in power system is presented in this paper. The economic load dispatch problem is a non-linear constrained multi-objective optimization problem. The proposed MOPSO approach handles the problem as a multi-objective problem with competing and non-commensurable fuel cost, emission and system loss objectives and has a diversity-preserving mechanism using an external memory (call “repository”) and a geographically-based approach to find widely different Pareto-optimal solutions. In addition, fuzzy set theory is employed to extract the best compromise solution. Several optimization runs of the proposed MOPSO approach were carried out on the standard IEEE 30-bus test system. The results revealed the capabilities of the proposed MOPSO approach to generate well-distributed Pareto-optimal non-dominated solutions of multi-objective economic load dispatch. Com- parison with Multi-objective Evolutionary Algorithm (MOEA) showed the superiority of the proposed MOPSO approach and confirmed its potential for solving multi-objective economic load dispatch.
基金supported by the State Grid Science and Technology Project, “Study on Multi-source and Multiload Coordination and Optimization Technology Considering Desalination of Sea Water” (No. SGTJDK00DWJS1800011)
文摘Traditional seawater desalination requires high amounts of energy, with correspondingly high costs and limited benefits, hindering wider applications of the process. To further improve the comprehensive economic benefits of seawater desalination, the desalination load can be combined with renewable energy sources such as solar energy, wind energy, and ocean energy or with the power grid to ensure its effective regulation. Utilizing energy internet(EI) technology, energy balance demand of the regional power grid, and coordinated control between coastal multi-source multi-load and regional distribution network with desalination load is reviewed herein. Several key technologies, including coordinated control of coastal multi-source multi-load system with seawater desalination load, flexible interaction between seawater desalination and regional distribution network, and combined control of coastal multi-source multi-load storage system with seawater desalination load, are discussed in detail. Adoption of the flexible interaction between seawater desalination and regional distribution networks is beneficial for solving water resource problems, improving the ability to dissipate distributed renewable energy, balancing and increasing grid loads, improving the safety and economy of coastal power grids, and achieving coordinated and comprehensive application of power grids, renewable energy sources, and coastal loads.
文摘The shakedown analysis of structures under variable multi-loadings is considered, and the corresponding simple shakedown condition is presented in this paper. Distribution of fixed stresses field is given, and the self-equilibrium of fixed stresses field is analyzed. Elastic shakedown and plastic shakedown conditions are presented based on the fixed stresses field. The theorem is convenient to evaluate the shakedown limit of structures under cyclical variable multiloadings through solving positive scalar fields and fixed stresses field factors at a series of dangerous positions of the structure, and tedious computations are avoided. Finally the theorem is applied to a thick-walled cylindrical tube under variable pressure and temperature, and the rolling contact problem. The results are in good agreement with some computational results.
基金Project(11102224)supported by the National Natural Science Foundation of ChinaProject(201206370124)supported by the China Scholarship Council,China
文摘The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A/SSSS) were studied by performing numerical stress analysis on blocks having multi flaws at close spacing's under uniaxial loading using PFC3 D. The following findings are obtained: SCI,B/SUC,B has an average value of about 0.5 with a variability of ± 0.1. This range agrees quite well with the values obtained by former research. For joint inclination angle, β=90°,B,UCB,CI,A,A/SSSS is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found betweenB,UCB,CI,A,A/SSSS and β; however, the average B,UCB,CI,A,A/SSSS seems to slightly decrease with increasing k. The variability ofB,UCB,CI,A,A/SSSS is found to increase with k.Based on the cases studied in this work,B,UCB,CI,A,A/SSSS ranges between 0.3 and 0.5. This range is quite close to the range of 0.4to 0.6 obtained for SCI,B/SUC,B. The highest variability of ± 0.12 forB,UCB,CI,A,A/SSSS is obtained for k=0.8. For the remaining k values the variability ofB,UCB,CI,A,A/SSSS can be expressed within ± 0.05. This finding is very similar to the finding obtained for the variability of SCI,B/SUC,B.
基金Project(50735005) supported by the National Natural Science Foundation for Key Program of ChinaProject(2006AA04Z135) supported by the National High-tech Research and Development Program of China+1 种基金Project supported by the Foundational Research Program of National Defence, ChinaProject supported by Northwestern Polytechnical University Foundation for Fundamental Research, China
文摘Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross valve under multi-way loading due to the complexity of loading path and the multiplicity of associated processing parameters.A model of the process was developed under DFEORM-3D environment based on the coupled thermo-mechanical finite element method.The comparison between two process models,the conventional isothermal process model and the non-isothermal process model developed in this study,was carried out,and the results indicate that the thermal events play an important role in the aluminum alloy forming process under multi-way loading.The distributions and evolutions of the temperature field and strain filed are obtained by non-isothermal process simulation.The plastic zone and its extension in forming process of cross valve were analyzed.The results may provide guidelines for the determination of multi-way loading forming scheme and loading conditions of the forming cross valve components.
基金supported by Shandong Provincial Natural Science Foundation of China(Grant No.ZR2010EL003)
文摘The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number of the supporting legs,the increased overdetermination of the multi-leg platform systems leads to leveling coupling problem among legs and virtual leg problem in which some of the supporting legs bear zero or quasi zero loads.These problems make it quite complex and time consuming to level such a multi-leg platform.Based on rigid body kinematics,an approximate equation is formulated to rapidly calculate the leg extension for leveling a rigid platform,then a proportional speed control strategy is proposed to reduce the unexpected platform distortion and leveling coupling between supporting legs.Taking both the load coupling between supporting legs and the elastic flexibility of the working platform into consideration,an optimal balancing legs’ loads(OBLL) model is firstly put forward to deal with the traditional virtual leg problem.By taking advantage of the concept of supporting stiffness matrix,a coupling extension method(CEM) is developed to solve this OBLL problem for multi-leg flexible platform.At the end,with the concept of supporting stiffness matrix and static transmissibility matrix,an optimal load balancing leveling method is proposed to achieve geometric leveling and legs’ loads balancing simultaneously.Three numerical examples are given out to illustrate the performance of proposed methods.This paper proposes a method which can effectively quantify all of the legs’ extension at the same time,achieve geometric leveling and legs’ loads balancing simultaneously.By using the proposed methods,the stability,precision and efficiency of auto-leveling control process can be improved.
基金supported in part by the National Natural Science Foundation of China(61673161)the Natural Science Foundation of Jiangsu Province of China(BK20161510)+2 种基金the Fundamental Research Funds for the Central Universities of China(2017B13914)the 111 Project(B14022)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘This paper is devoted to investigate the robust H∞sliding mode load frequency control(SMLFC) of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of renewable energies,a new sliding surface function is constructed to guarantee the fast response and robust performance, then the sliding mode control law is designed to guarantee the reach ability of the sliding surface in a finite-time interval. The sufficient robust frequency stabilization result for multi-area power system with time delay is presented in terms of linear matrix inequalities(LMIs). Finally,a two-area power system is provided to illustrate the usefulness and effectiveness of the obtained results.
文摘Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on an unit length of a breakwater with wave direction, the longitudinal distribution of wave forces, as well as the longitudinal load reduction are analyzed. Some empirical formulae of the longitudinal distribution coefficient and the longitudinal load reduction factor are presented for practical use.
文摘The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator control scheme. To this end, we consider a nonlinear interconnected model for multiarea power systems which also include uncertainties and timevarying communication delays. The design procedure is formulated using semi-definite programming and linear matrix inequality(LMI) method. The solution of the proposed LMIs returns necessary parameters for the tracking controllers such that the impact of model uncertainty and load disturbances are minimized. The proposed controllers are capable of receiving all or part of subsystems information, whereas the outputs of each controller are local. These controllers are designed such that the resilient stability of the overall closed-loop system is guaranteed. Simulation results are provided to verify the effectiveness of the proposed scheme. Simulation results quantify that the distributed(and decentralized) controlled system behaves well in presence of large parameter perturbations and random disturbances on the power system.
基金Supported by the National Natural Science Foundation of China (No. 60672059, 60496315 )the National High Technology Research and Development Programme of China (No.2006AA01Z233)
文摘Because of different system capacities of base station(BS)or access point(AP)and ununiformity oftraffic distribution in different cells,quantities of new call users may be blocked in overloaded cell incommunication hot spots.Whereas in some neighboring under-loaded cells,bandwidth may be superflu-ous because there are only few users to request services.In order to raise resource utilization of the wholeheterogeneous networks,several novel load balancing strategies are proposed,which combine the call ad-mission control policy and multi-hop routing protocol of ad-hoc network for load balancing.These loadbalancing strategies firstly make a decision whether to admit a new call or not by considering some param-eters like load index and route cost,etc.,and then transfer the denied users into neighboring under-load-ed cell with suiplus channel according to optimum multi-hop routing algorithm.Simulation results showthat the proposed load balancing strategies can distribute traffics to the whole heterogeneous wireless net-works,improve the load balance index efficiently,and avoid the call block phenomenon almost absolutely.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF),Ministry of Education,Science and Technology,Korea(Grant No.2010-0026163)Strategy Technology Development Project,Ministry of Knowledge Economy,Korea(Grant No.10032149)
文摘The mass production of primed electronics can be achieved by roll-to-roll(R2R) printing system, so highly accurate web tension is required that can minimize the register error and keep the thickness and roughness of printed devices in limits. The web tension of a R2R system is regulated by the use of integrated load cells and active dancer system for printed electronics applications using decentralized multi-input-single-output(MISO) regularized variable learning rate backpropagation artificial neural networks. The active dancer system is used before printing system to reduce disturbances in the web tension of process span. The classical PID control result in tension spikes with the change in roll diameter of winder and unwinder rolls. The presence of dancer in R2R system shows that improved web tension control in printing span and the web tension can be enhanced from 3.75 N to 4.75 N. The overshoot of system is less than ±2.5 N and steady state error is within ± 1 N where load cells have a signal noise of ±0.7 N. The integration of load cells and active dancer with self-adapting neural network control provide a solution to the web tension control of multispan roll-to-roll system.
基金This project is supported by National Ninth-five Key Technologies R&D Program of China(No.9552801-0201)National Natural Science Foundation of China(No.50575155).
文摘The load distribution of multi-row bearings of large strip rolling mill is fully analyzed by 3D contact boundary element method (BEM). It is found out that bearings are frequently worn out due to serious uneven load on the multi-row rollers. The constraint mechanism of the previous rolling system is found to be unreasonable by theoretical analysis on heavy machinery structure. A mechanism of self-aligning even load for workroll bearing of 2 050 mm hot rolling mill of Baoshan I&S Co. is developed. This device is manufactured with particular regard to the structure of 2 050 mm hot rolling mill mentioned above. Hence, uneven load on multi-row bearings is greatly relieved and their lives are remarkably prolonged. Meanwhile, theoretical analysis and on-spot tests prove the rationality and validity of the device.
基金Projects(U1334208,51405516,51275532)supported by the National Natural Science Foundation of ChinaProjects(2015zzts210,2016zzts331)supported by the Fundamental Research Funds for the Central Universities,China
文摘In order to investigate the energy absorption characteristics of multi-cell polygonal tubes with different cross-sectional configurations,firstly,the theoretical formulae of the mean crushing force under axial load for four multi-cell polygonal tubes were derived by combining the Super Folding Element theory with Zhang’s research results.These formulae can be used to validate the numerical model and quickly evaluate the energy absorption ability of multi-cell polygonal tubes.Furthermore,a comparative study on the energy absorption performance of eight multi-cell polygonal tubes under axial and oblique loads was conducted.The results show that all tubes have a stable mixed deformation mode under axial load.The multi-cell decagon tube has better energy-absorption ability compared with other tubes.Whenθis less than 10°,all the tubes maintain a stable deformation mode,and the multi-cell decagon tube also has the biggest crushing force efficiency and specific energy absorption among these eight tubes;meanwhile compared with the results atθ=0°,the specific energy absorption of all tubes decreases by about 8%-21%,while the crushing force efficiency increases by 20%-56%.However,at large angles 20°and 30°,all of the tubes collapse in bending modes and lose their effectiveness at energy absorption.
文摘<div style="text-align:justify;"> In the multi-objective of intelligent building load scheduling, aiming at the problem of how to select Pareto frontier scheme for multi-objective optimization algorithm, the current optimal scheme mechanism combined with multi-objective multi-verse algorithm is used to optimize the intelligent building load scheduling. The update mechanism is changed in updating the position of the universe, and the process of correction coding is omitted in the iterative process of the algorithm, which reduces the com-putational complexity. The feasibility and effectiveness of the proposed method are verified by the optimal scheduling experiments of residential loads. </div>
文摘Based on ServiceBSP model, a hierarchical resource load balancing algorithm with Multi-Agent is put forward in this paper which achieves the goal of dynamic load balancing and favorable Fault-tolerant. The algorithm calculates the load value according to the attributes of resource and scheduling tasks relies on the load value, while updating the load information dynamically depending on Multi-Agent. The method avoids frequent communications on load information. Furthermore, the paper introduces the function of agents, relations and communications among agents in details. Finally, by comparing response time and distribution of load using proposed method with other available methods such as without no load balancing and load balancing only giving regards to CPU, the experimental simulation shows that the load balancing based on Multi-Agent possesses superior performance on response time and load balancing.
文摘This paper proposes a novel dual layered multi agent system (MAS) based control system for the use in microgrid operations. In developing a smarter grid capable of withstanding disturbances and/or outages and providing quality service to the consumers, reliable microgrid control architecture is vital. The innovative microgrid control system proposed, makes the microgrid capable of isolating the local grid from effects of any upstream disturbances in the main utility grid by operating disconnected from the main utility via islanding, and it allows the most critical local loads to be supplied by any, available, local power source during such islanded operation. The proposed MAS control architecture is developed using the JADE platform and it is used to control a test network simulated in MATLAB. The results of these simulations show the capability of developing MAS based reliable control mechanism for islanding and load management of microgrids based on the proposed concept.
文摘With the rapid and large-scale development of renewable energy, the lack of new energy power transportation or consumption, and the shortage of grid peak-shifting ability have become increasingly serious. Aiming to the severe wind power curtailment issue, the characteristics of interactive load are studied upon the traditional day-ahead dispatch model to mitigate the influence of wind power fluctuation. A multi-objective optimal dispatch model with the minimum operating cost and power losses is built. Optimal power flow distribution is available when both generation and demand side participate in the resource allocation. The quantum particle swarm optimization (QPSO) algorithm is applied to convert multi-objective optimization problem into single objective optimization problem. The simulation results of IEEE 30-bus system verify that the proposed method can effectively reduce the operating cost and grid loss simultaneously enhancing the consumption of wind power.