The intelligent optimization of a multi-objective evolutionary algorithm is combined with a gradient algorithm. The hybrid multi-objective gradient algorithm is framed by the real number. Test functions are used to an...The intelligent optimization of a multi-objective evolutionary algorithm is combined with a gradient algorithm. The hybrid multi-objective gradient algorithm is framed by the real number. Test functions are used to analyze the efficiency of the algorithm. In the simulation case of the water phantom, the algorithm is applied to an inverse planning process of intensity modulated radiation treatment (IMRT). The objective functions of planning target volume (PTV) and normal tissue (NT) are based on the average dose distribution. The obtained intensity profile shows that the hybrid multi-objective gradient algorithm saves the computational time and has good accuracy, thus meeting the requirements of practical applications.展开更多
We apply reweighted inversion focusing to full tensor gravity gradiometry data using message-passing interface (MPI) and compute unified device architecture (CUDA) parallel computing algorithms, and then combine M...We apply reweighted inversion focusing to full tensor gravity gradiometry data using message-passing interface (MPI) and compute unified device architecture (CUDA) parallel computing algorithms, and then combine MPI with CUDA to formulate a hybrid algorithm. Parallel computing performance metrics are introduced to analyze and compare the performance of the algorithms. We summarize the rules for the performance evaluation of parallel algorithms. We use model and real data from the Vinton salt dome to test the algorithms. We find good match between model efficiency and feasibility of parallel computing gravity gradiometry data. and real density data, and verify the high algorithms in the inversion of full tensor展开更多
On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang...On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace (i.e., the T3 terrace) tread is 38 - 39 m above fiver level, and the top of the gravels is generally covered by 3 - 10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the early- middle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modem Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang River .展开更多
Aiming at the diversity and nonlinearity of the elevator system control target, an effective group method based on a hybrid algorithm of genetic algorithm and neural network is presented in this paper. The genetic alg...Aiming at the diversity and nonlinearity of the elevator system control target, an effective group method based on a hybrid algorithm of genetic algorithm and neural network is presented in this paper. The genetic algorithm is used to search the weight of the neural network. At the same time, the multi-objective-based evaluation function is adopted, in which there are three main indicators including the passenger waiting time, car passengers number and the number of stops. Different weights are given to meet the actual needs. The optimal values of the evaluation function are obtained, and the optimal dispatch control of the elevator group control system based on neural network is realized. By analyzing the running of the elevator group control system, all the processes and steps are presented. The validity of the hybrid algorithm is verified by the dynamic imitation performance.展开更多
A terrain-following coordinate (a-coordinate) in which the computational form of pressure gradient force (PGF) is two-term (the so-called classic method) has significant PGF errors near steep terrain. Using the ...A terrain-following coordinate (a-coordinate) in which the computational form of pressure gradient force (PGF) is two-term (the so-called classic method) has significant PGF errors near steep terrain. Using the covariant equations of the a-coordinate to create a one-term PGF (the covariant method) can reduce the PGF errors. This study investigates the factors inducing the PGF errors of these two methods, through geometric analysis and idealized experiments. The geometric analysis first demonstrates that the terrain slope and the vertical pressure gradient can induce the PGF errors of the classic method, and then generalize the effect of the terrain slope to the effect of the slope of each vertical layer (φ). More importantly, a new factor, the direction of PGF (a), is proposed by the geometric analysis, and the effects of φ and a are quantified by tan φ.tan a. When tan φ.tan a is greater than 1/9 or smaller than -10/9, the two terms of PGF of the classic method are of the same order but opposite in sign, and then the PGF errors of the classic method are large. Finally, the effects of three factors on inducing the PGF errors of the classic method are validated by a series of idealized experiments using various terrain types and pressure fields. The experimental results also demonstrate that the PGF errors of the covariant method are affected little by the three factors.展开更多
Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary...Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary to establish an eco-compensation mechanism for them. As the compensation standard is one of key issues in establishing eeo-compensation mechanism, this paper calculated the standard based on the farmers' willingness to accept (WTA) and the input-output analysis of eco-compensation. We took the traditional rice-fish eco-agriculture as the research object, conducting field surveys in Hani Terrace of Honghe County. Through the questionnaires in 2o11, we obtained the farmers' willingness to accept government compensation and market compensation. Then, the research evaluated the output of eco-compensation, the economic value of rice-fish paddy ecosystem services. Finally, under different market compensation standards, we compared the input and output of government compensation. The results show that, in 2011 the government should to pay farmers 7462 yuan.ha^-1·a^-1 to meet their willingness, but the output (ecological benefit) was only 7393 yuan.ha^-1·a^-1. However, whenthe rice price increases 1 yuan·kg-1 because of the limited use of chemicals in the next year, the government just has to pay farmers 4062 yuan.ha^-1·a^-1 and the surplus will be 3331 yuan.ha^-1·a^-1.展开更多
Based on the stress distribution characteristics of rock burst multiple sites, the criterion of horizontal stress inducing layer dislocation rock burst was established. Accordingly, the influencing factors were analyz...Based on the stress distribution characteristics of rock burst multiple sites, the criterion of horizontal stress inducing layer dislocation rock burst was established. Accordingly, the influencing factors were analyzed. The analysis results indicate that the stress condition, edge of etastic zone depth, supporting strength, and the friction angle and cohesion among coal stratum, roof and floor are sensitive factors. By introducing double-couple model, the layer dislocation rock burst was explained and the energy radiation characteristics were analyzed. The SOS micro-seismic monitoring system was applied to observe the rock burst hazards about a mining face. The results show that P- and S-wave energy radiations produced by rock burst have directional characteristics. The energy radiation characteristics of the 22 rock bursts occurring on 79Z6 long-wall face are basically the same as theoretical results, that is, the ratio of S-wave energy of sensor 4 to 6 is about 1.5 and that of P-wave is smaller than 0.5. The consistency of the monitored characteristics of the energy radiation theoretically increases with the total energy increasing.展开更多
Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanoc...Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanocomposite, is optimally designed for the purpose of torque transmission. The main confining parameters of a rotating shaft in torque transmission process are mass of the shaft, critical speed of rotation and critical buckling torque. It is required to solve a multi-objective optimization problem(MOP) to consider these three targets simultaneously in the process of design. The three-objective optimization problem for this case is defined and solved using a hybrid method of FEM and modified non-dominated sorting genetic algorithm(NSGA-II), by coupling two softwares, MATLAB and ABAQUS. Optimization process provides a set of non-dominated optimal design vectors. Then, two methods, nearest to ideal point(NIP) and technique for ordering preferences by similarity to ideal solution(TOPSIS), are employed to choose trade-off optimum design vectors. Optimum parameters that are obtained from this work are compared with the results of previous studies for similar cylindrical tubes made from composite or a hybrid of aluminum and composite that more than 20% improvement is observed in all of the objective functions.展开更多
Spectral conjugate gradient method is an algorithm obtained by combination of spectral gradient method and conjugate gradient method,which is characterized with global convergence and simplicity of spectral gradient m...Spectral conjugate gradient method is an algorithm obtained by combination of spectral gradient method and conjugate gradient method,which is characterized with global convergence and simplicity of spectral gradient method,and small storage of conjugate gradient method.Besides,the spectral conjugate gradient method was proved that the search direction at each iteration is a descent direction of objective function even without relying on any line search method.Spectral conjugate gradient method is applied to full waveform inversion for numerical tests on Marmousi model.The authors give a comparison on numerical results obtained by steepest descent method,conjugate gradient method and spectral conjugate gradient method,which shows that the spectral conjugate gradient method is superior to the other two methods.展开更多
In this paper, an objective-based gradient multi-objective optimization (MOO) technique, the Objective-Based Gradient Algorithm (OBGA), is proposed with the goal of defining the Pareto domain more precisely and ef...In this paper, an objective-based gradient multi-objective optimization (MOO) technique, the Objective-Based Gradient Algorithm (OBGA), is proposed with the goal of defining the Pareto domain more precisely and efficiently than current MOO techniques. The performance of the OBGA in locating the Pareto domain was evaluated in terms of precision, computation time and number of objective function calls, and compared to two current MOO algorithms: Dual Population Evolutionary Algorithm (DPEA) and Non-Dominated Sorting Genetic Algorithm I1 (NSGA-II), using four test problems. For all test problems, the OBGA systematically produced a more precise Pareto domain than DPEA and NSGA-II. With the adequate selection of the OBGA parameters, computation time required for the OBGA can be lower than that required for DPEA and NSGA-II. Results clearly show that the OBGA is a very effective and efficient algorithm for locating the Pareto domain.展开更多
The temperature field variation law and distribution characteristics of an orthotropic flat steel box girder under sunny conditions were analyzed through a field temperature test on the steel box girder of the operati...The temperature field variation law and distribution characteristics of an orthotropic flat steel box girder under sunny conditions were analyzed through a field temperature test on the steel box girder of the operational Runyang Yangtze River Bridge(the suspension bridge part).Function optimization fitting and error analysis of the test data were conducted.A temperature gradient distribution curve applicable to a hexagonal flat steel box girder was proposed.Based on the measurement results,the temperature effect of an orthotropic flat steel box girder was analyzed using finite element method and the effects of different temperature gradient modes on the mechanical characteristics and stress distribution of the steel box girder were compared.Under sunny conditions,heat conduction in the flat steel box girder structure shows distinct "box-room effect" characteristics,and the actual temperature gradient distribution is inconsistent with the one suggested by the existing standards.The thermal stress of a steel box girder calculated from the measured temperature gradient mode exceeds that calculated from the standard,and the intensity approximates that under the action of designed vehicle loads.The temperature-induced stress is distributed centrally near the manufacturing welds of the orthotropic steel box girder,which should be considered in design,construction and research.Results from this study could supplement the existing bridge and culvert design standards.展开更多
This paper derives first order necessary and sufficient conditions for unconstrained coned.c. Programming problems where the underlined space is partially ordered with respect to acone. These conditions are given in t...This paper derives first order necessary and sufficient conditions for unconstrained coned.c. Programming problems where the underlined space is partially ordered with respect to acone. These conditions are given in terms of directional derivatives and subdifferentials of thecomponent functions. Moreover, conjugate duality for cone d.c. Optimization is discussed andweak duality theorem is proved in a more general partially ordered linear topological vectorspace (generalizing the results in [11]).展开更多
In the Three Gorges Area of China, soil erosion and the resultant non-point source pollution and ecological degradation have endangered agricultural ecosystems and fresh water reservoirs. Although efforts have been un...In the Three Gorges Area of China, soil erosion and the resultant non-point source pollution and ecological degradation have endangered agricultural ecosystems and fresh water reservoirs. Although efforts have been undertaken to reduce soil and water losses from slope land used for citrus production, information on the effects of management practices on soil fertility indices is either limited or nonexistent. This study was conducted to compare the effects of 10 years of various management practices, citrus intercropped with white clover (WC), citrus mulched with straw (SM), citrus intercropped with contour hedgerows (CH), citrus orchard land with impermeable membrane (IM), and citrus intercropped with wheat (Triticum aestivum) and peanut (Arachris hypogaea) (WP), as treatments on soil fertility indices with that of the conventional citrus management (CM). Results showed that the soil organic carbon, total and available nitrogen, available potassium, and water-stable aggregate (> 0.25 mm) contents at the 0–5 cm depth were higher for the WC and SM treatments than the CM treatment. There was also spatial variation in soil fertility along slopes of the WC and SM treatments. The soil total and available nitrogen, phosphorus, and potassium, and water-stable aggregate (> 0.25 mm) contents at both the 0–5 and 5–20 cm depths were higher for the CH and IM treatments than the CM treatment. The average soil available nitrogen and available potassium contents were higher for the WP treatment than the CM treatment, but the WP treatment had little effect on the soil organic carbon, total nitrogen, and water-stable aggregate (> 0.25 mm) contents. These suggested that white clover intercropping and straw mulching were the most effective approaches to improve soil fertility in citrus orchard land of the Three Gorges area.展开更多
For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be...For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains.In this paper,according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters,a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system.Then,these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation.The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm.It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally.Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency.展开更多
Although G-coordinate is one of the most popular methods used in marine and estuarine modeling, it has long suffered from the so-called "steep boundary problem", namely, the PGF problem. In this paper, a new method ...Although G-coordinate is one of the most popular methods used in marine and estuarine modeling, it has long suffered from the so-called "steep boundary problem", namely, the PGF problem. In this paper, a new method called the "σ-sharpen immersed boundary method" (σ-SIBM) is put forward. In this method, the virtual flat bottom boundary is creatively introduced in regions with the steep boundary and is taken as the boundary of numerical domain. By this, OH/Ox of numerical domain changes to be a controllable value and the steep bottom problem is then transformed to the non-conforming boundary problem, which is, in turn, solved by the SIBM. The accuracy and efficiency of the σ-sharpen immersed boundary method (σ-SIBM) has been showed by both comparative theoretical analysis and classical numerical tests. First, it is shown that the σ-SIBM is more effective than the z-level method, in that σ-SIBM needs special treatment only in the steep section, but the z-level method needs the special treatment in each grid note. Second, it is superior to the p-method in that it is not restricted by the density distribution. This paper revisits the classical seamount numerical test used in numerous studies to prove the sigma errors of the pressure gradient force (PGFE) and their long-term effects on circulation. It can be seen that, as for the maximum erroneous velocity and kinetic energy, the value of σ-SIBM is much less than that of the z-level method and the traditional σ-method.展开更多
A method was developed for the analysis of hydroxylated brominated diphenyl ethers (OH-PBDEs) in plant samples using an ultra performance liquid chromatography-triple quadrupole mass spectrometer (UPLC-ESI-MS/MS) in n...A method was developed for the analysis of hydroxylated brominated diphenyl ethers (OH-PBDEs) in plant samples using an ultra performance liquid chromatography-triple quadrupole mass spectrometer (UPLC-ESI-MS/MS) in negative mode. Plant samples were extracted and cleaned up through florisil column, resolved on a 100 mm C18 column with linear gradient elution and detected by mass spectrometry in multiple reaction monitoring (MRM) mode. The method provided good recoveries rang- ing from 68.2% to 94.6%, relative standard deviation (RSD) in the range of 3.2% - 9.1%, and limits of quantification (LOQ) defined as the signal-to-noise ratio of 10 of 0.3-2.1 ng/g. It allowed a fast separation and sensitive quantification of the isomers and homologues of seven OH-PBDE congeners 2′-OH-BDE-3, 3′-OH-BDE-7, 4′-OH-BDE-17, 3′-OH-BDE-28, 3-OH-BDE-47, 5-OH-BDE-47 and 6-OH-BDE-47. The method was successfully applied to identify and quantify the formation of hydroxylat- ed metabolites in alfalfa exposed to BDE-209. Five OH-PBDEs were detected in plant tissues, and more congeners were found in roots than in shoots. To our knowledge, this work represents the first attempt to validate UPLC-MS/MS method to quantify OH-PBDEs in plant samples without derivatization.展开更多
基金Supported by the National Basic Research Program of China ("973" Program)the National Natural Science Foundation of China (60872112, 10805012)+1 种基金the Natural Science Foundation of Zhejiang Province(Z207588)the College Science Research Project of Anhui Province (KJ2008B268)~~
文摘The intelligent optimization of a multi-objective evolutionary algorithm is combined with a gradient algorithm. The hybrid multi-objective gradient algorithm is framed by the real number. Test functions are used to analyze the efficiency of the algorithm. In the simulation case of the water phantom, the algorithm is applied to an inverse planning process of intensity modulated radiation treatment (IMRT). The objective functions of planning target volume (PTV) and normal tissue (NT) are based on the average dose distribution. The obtained intensity profile shows that the hybrid multi-objective gradient algorithm saves the computational time and has good accuracy, thus meeting the requirements of practical applications.
基金supported by the Sino-Probe09(No.201011078)National High-tech R&D Program(No.863 and2014AA06A613)
文摘We apply reweighted inversion focusing to full tensor gravity gradiometry data using message-passing interface (MPI) and compute unified device architecture (CUDA) parallel computing algorithms, and then combine MPI with CUDA to formulate a hybrid algorithm. Parallel computing performance metrics are introduced to analyze and compare the performance of the algorithms. We summarize the rules for the performance evaluation of parallel algorithms. We use model and real data from the Vinton salt dome to test the algorithms. We find good match between model efficiency and feasibility of parallel computing gravity gradiometry data. and real density data, and verify the high algorithms in the inversion of full tensor
基金financially sponsored by the National Natural Science Foundation of China(Grant No.41301011,41301029,41201008)
文摘On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace (i.e., the T3 terrace) tread is 38 - 39 m above fiver level, and the top of the gravels is generally covered by 3 - 10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the early- middle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modem Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang River .
基金Supported by National Natural Science Foundation of China (No60874077) Specialized Research Funds for Doctoral Program of Higher Education of China (No20060056054) Research Funds for Scientific Financing Projects of Quality Control Public Welfare Profession (No2007GYB172)
文摘Aiming at the diversity and nonlinearity of the elevator system control target, an effective group method based on a hybrid algorithm of genetic algorithm and neural network is presented in this paper. The genetic algorithm is used to search the weight of the neural network. At the same time, the multi-objective-based evaluation function is adopted, in which there are three main indicators including the passenger waiting time, car passengers number and the number of stops. Different weights are given to meet the actual needs. The optimal values of the evaluation function are obtained, and the optimal dispatch control of the elevator group control system based on neural network is realized. By analyzing the running of the elevator group control system, all the processes and steps are presented. The validity of the hybrid algorithm is verified by the dynamic imitation performance.
基金jointly supported by the National Basic Research Program of China[973 Program,grant number 2015CB954102]National Natural Science Foundation of China[grant numbers41305095 and 41175064]
文摘A terrain-following coordinate (a-coordinate) in which the computational form of pressure gradient force (PGF) is two-term (the so-called classic method) has significant PGF errors near steep terrain. Using the covariant equations of the a-coordinate to create a one-term PGF (the covariant method) can reduce the PGF errors. This study investigates the factors inducing the PGF errors of these two methods, through geometric analysis and idealized experiments. The geometric analysis first demonstrates that the terrain slope and the vertical pressure gradient can induce the PGF errors of the classic method, and then generalize the effect of the terrain slope to the effect of the slope of each vertical layer (φ). More importantly, a new factor, the direction of PGF (a), is proposed by the geometric analysis, and the effects of φ and a are quantified by tan φ.tan a. When tan φ.tan a is greater than 1/9 or smaller than -10/9, the two terms of PGF of the classic method are of the same order but opposite in sign, and then the PGF errors of the classic method are large. Finally, the effects of three factors on inducing the PGF errors of the classic method are validated by a series of idealized experiments using various terrain types and pressure fields. The experimental results also demonstrate that the PGF errors of the covariant method are affected little by the three factors.
基金supported by the China National Natural Science Foundation (Grant Nos. 41201586, 41201580)Visiting Professorship for Senior International Scientists (2013T2Z0011)
文摘Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary to establish an eco-compensation mechanism for them. As the compensation standard is one of key issues in establishing eeo-compensation mechanism, this paper calculated the standard based on the farmers' willingness to accept (WTA) and the input-output analysis of eco-compensation. We took the traditional rice-fish eco-agriculture as the research object, conducting field surveys in Hani Terrace of Honghe County. Through the questionnaires in 2o11, we obtained the farmers' willingness to accept government compensation and market compensation. Then, the research evaluated the output of eco-compensation, the economic value of rice-fish paddy ecosystem services. Finally, under different market compensation standards, we compared the input and output of government compensation. The results show that, in 2011 the government should to pay farmers 7462 yuan.ha^-1·a^-1 to meet their willingness, but the output (ecological benefit) was only 7393 yuan.ha^-1·a^-1. However, whenthe rice price increases 1 yuan·kg-1 because of the limited use of chemicals in the next year, the government just has to pay farmers 4062 yuan.ha^-1·a^-1 and the surplus will be 3331 yuan.ha^-1·a^-1.
基金Project(2012LWB63) supported by the Fundamental Research Funds for the Central Universities, ChinaProject(SZBF2011-6-B35) supported by the Priority Acadamic Program Development of Jiangsu Higher Education Institutions (PAPD),China
文摘Based on the stress distribution characteristics of rock burst multiple sites, the criterion of horizontal stress inducing layer dislocation rock burst was established. Accordingly, the influencing factors were analyzed. The analysis results indicate that the stress condition, edge of etastic zone depth, supporting strength, and the friction angle and cohesion among coal stratum, roof and floor are sensitive factors. By introducing double-couple model, the layer dislocation rock burst was explained and the energy radiation characteristics were analyzed. The SOS micro-seismic monitoring system was applied to observe the rock burst hazards about a mining face. The results show that P- and S-wave energy radiations produced by rock burst have directional characteristics. The energy radiation characteristics of the 22 rock bursts occurring on 79Z6 long-wall face are basically the same as theoretical results, that is, the ratio of S-wave energy of sensor 4 to 6 is about 1.5 and that of P-wave is smaller than 0.5. The consistency of the monitored characteristics of the energy radiation theoretically increases with the total energy increasing.
文摘Carbon nanotube(CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded(FG) PmP V/CNT nanocomposite, is optimally designed for the purpose of torque transmission. The main confining parameters of a rotating shaft in torque transmission process are mass of the shaft, critical speed of rotation and critical buckling torque. It is required to solve a multi-objective optimization problem(MOP) to consider these three targets simultaneously in the process of design. The three-objective optimization problem for this case is defined and solved using a hybrid method of FEM and modified non-dominated sorting genetic algorithm(NSGA-II), by coupling two softwares, MATLAB and ABAQUS. Optimization process provides a set of non-dominated optimal design vectors. Then, two methods, nearest to ideal point(NIP) and technique for ordering preferences by similarity to ideal solution(TOPSIS), are employed to choose trade-off optimum design vectors. Optimum parameters that are obtained from this work are compared with the results of previous studies for similar cylindrical tubes made from composite or a hybrid of aluminum and composite that more than 20% improvement is observed in all of the objective functions.
文摘Spectral conjugate gradient method is an algorithm obtained by combination of spectral gradient method and conjugate gradient method,which is characterized with global convergence and simplicity of spectral gradient method,and small storage of conjugate gradient method.Besides,the spectral conjugate gradient method was proved that the search direction at each iteration is a descent direction of objective function even without relying on any line search method.Spectral conjugate gradient method is applied to full waveform inversion for numerical tests on Marmousi model.The authors give a comparison on numerical results obtained by steepest descent method,conjugate gradient method and spectral conjugate gradient method,which shows that the spectral conjugate gradient method is superior to the other two methods.
文摘In this paper, an objective-based gradient multi-objective optimization (MOO) technique, the Objective-Based Gradient Algorithm (OBGA), is proposed with the goal of defining the Pareto domain more precisely and efficiently than current MOO techniques. The performance of the OBGA in locating the Pareto domain was evaluated in terms of precision, computation time and number of objective function calls, and compared to two current MOO algorithms: Dual Population Evolutionary Algorithm (DPEA) and Non-Dominated Sorting Genetic Algorithm I1 (NSGA-II), using four test problems. For all test problems, the OBGA systematically produced a more precise Pareto domain than DPEA and NSGA-II. With the adequate selection of the OBGA parameters, computation time required for the OBGA can be lower than that required for DPEA and NSGA-II. Results clearly show that the OBGA is a very effective and efficient algorithm for locating the Pareto domain.
基金supported by the Engineering Section of the Jiangsu Runyang Bridge Development Co.,Ltdthe National Science & Technology Support Program of China (Grant No. 2009BAG15B03)the National Science Foundation of China (Grant No. 51078080)
文摘The temperature field variation law and distribution characteristics of an orthotropic flat steel box girder under sunny conditions were analyzed through a field temperature test on the steel box girder of the operational Runyang Yangtze River Bridge(the suspension bridge part).Function optimization fitting and error analysis of the test data were conducted.A temperature gradient distribution curve applicable to a hexagonal flat steel box girder was proposed.Based on the measurement results,the temperature effect of an orthotropic flat steel box girder was analyzed using finite element method and the effects of different temperature gradient modes on the mechanical characteristics and stress distribution of the steel box girder were compared.Under sunny conditions,heat conduction in the flat steel box girder structure shows distinct "box-room effect" characteristics,and the actual temperature gradient distribution is inconsistent with the one suggested by the existing standards.The thermal stress of a steel box girder calculated from the measured temperature gradient mode exceeds that calculated from the standard,and the intensity approximates that under the action of designed vehicle loads.The temperature-induced stress is distributed centrally near the manufacturing welds of the orthotropic steel box girder,which should be considered in design,construction and research.Results from this study could supplement the existing bridge and culvert design standards.
文摘This paper derives first order necessary and sufficient conditions for unconstrained coned.c. Programming problems where the underlined space is partially ordered with respect to acone. These conditions are given in terms of directional derivatives and subdifferentials of thecomponent functions. Moreover, conjugate duality for cone d.c. Optimization is discussed andweak duality theorem is proved in a more general partially ordered linear topological vectorspace (generalizing the results in [11]).
基金Supported by the Chinese National Public Benefit Program for Forestry (No. 200804040)the Program of Introducing International Advanced Forestry Technique of the State Forestry Administration of China (948 Program) (No. 2005-4-17)the National Natural Science Foundation of China (Nos. 30870410, 40871147, and 30271069)
文摘In the Three Gorges Area of China, soil erosion and the resultant non-point source pollution and ecological degradation have endangered agricultural ecosystems and fresh water reservoirs. Although efforts have been undertaken to reduce soil and water losses from slope land used for citrus production, information on the effects of management practices on soil fertility indices is either limited or nonexistent. This study was conducted to compare the effects of 10 years of various management practices, citrus intercropped with white clover (WC), citrus mulched with straw (SM), citrus intercropped with contour hedgerows (CH), citrus orchard land with impermeable membrane (IM), and citrus intercropped with wheat (Triticum aestivum) and peanut (Arachris hypogaea) (WP), as treatments on soil fertility indices with that of the conventional citrus management (CM). Results showed that the soil organic carbon, total and available nitrogen, available potassium, and water-stable aggregate (> 0.25 mm) contents at the 0–5 cm depth were higher for the WC and SM treatments than the CM treatment. There was also spatial variation in soil fertility along slopes of the WC and SM treatments. The soil total and available nitrogen, phosphorus, and potassium, and water-stable aggregate (> 0.25 mm) contents at both the 0–5 and 5–20 cm depths were higher for the CH and IM treatments than the CM treatment. The average soil available nitrogen and available potassium contents were higher for the WP treatment than the CM treatment, but the WP treatment had little effect on the soil organic carbon, total nitrogen, and water-stable aggregate (> 0.25 mm) contents. These suggested that white clover intercropping and straw mulching were the most effective approaches to improve soil fertility in citrus orchard land of the Three Gorges area.
基金supported by the National Key Basic Research Project of China under Grant No.2011CB302400the National Natural Science Foundation of China under Grant Nos.50975274 and 50975495
文摘For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains.In this paper,according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters,a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system.Then,these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation.The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm.It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally.Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency.
基金supported by the National Natural Science Foundation of China(Grant Nos.51209239,51109194)"985 Project"of Minzu Univer-sity of China(Grant No.MUC98507-08)
文摘Although G-coordinate is one of the most popular methods used in marine and estuarine modeling, it has long suffered from the so-called "steep boundary problem", namely, the PGF problem. In this paper, a new method called the "σ-sharpen immersed boundary method" (σ-SIBM) is put forward. In this method, the virtual flat bottom boundary is creatively introduced in regions with the steep boundary and is taken as the boundary of numerical domain. By this, OH/Ox of numerical domain changes to be a controllable value and the steep bottom problem is then transformed to the non-conforming boundary problem, which is, in turn, solved by the SIBM. The accuracy and efficiency of the σ-sharpen immersed boundary method (σ-SIBM) has been showed by both comparative theoretical analysis and classical numerical tests. First, it is shown that the σ-SIBM is more effective than the z-level method, in that σ-SIBM needs special treatment only in the steep section, but the z-level method needs the special treatment in each grid note. Second, it is superior to the p-method in that it is not restricted by the density distribution. This paper revisits the classical seamount numerical test used in numerous studies to prove the sigma errors of the pressure gradient force (PGFE) and their long-term effects on circulation. It can be seen that, as for the maximum erroneous velocity and kinetic energy, the value of σ-SIBM is much less than that of the z-level method and the traditional σ-method.
基金funded by the National Natural Science Foundation of China (40730740 & 20921063)the National Basic Research Program of China (2009CB421603)
文摘A method was developed for the analysis of hydroxylated brominated diphenyl ethers (OH-PBDEs) in plant samples using an ultra performance liquid chromatography-triple quadrupole mass spectrometer (UPLC-ESI-MS/MS) in negative mode. Plant samples were extracted and cleaned up through florisil column, resolved on a 100 mm C18 column with linear gradient elution and detected by mass spectrometry in multiple reaction monitoring (MRM) mode. The method provided good recoveries rang- ing from 68.2% to 94.6%, relative standard deviation (RSD) in the range of 3.2% - 9.1%, and limits of quantification (LOQ) defined as the signal-to-noise ratio of 10 of 0.3-2.1 ng/g. It allowed a fast separation and sensitive quantification of the isomers and homologues of seven OH-PBDE congeners 2′-OH-BDE-3, 3′-OH-BDE-7, 4′-OH-BDE-17, 3′-OH-BDE-28, 3-OH-BDE-47, 5-OH-BDE-47 and 6-OH-BDE-47. The method was successfully applied to identify and quantify the formation of hydroxylat- ed metabolites in alfalfa exposed to BDE-209. Five OH-PBDEs were detected in plant tissues, and more congeners were found in roots than in shoots. To our knowledge, this work represents the first attempt to validate UPLC-MS/MS method to quantify OH-PBDEs in plant samples without derivatization.