在高三力学复习过程中,学生感到最困难的是动量守恒的应用,分不清谁是系统外力,谁是系统内力;判断不出守恒条件:是合外力为零,还是内力远远大于外力;区别不开每时每刻守恒还是瞬间守恒。这些情况导致物理场景不能建立,情境不清,公式、...在高三力学复习过程中,学生感到最困难的是动量守恒的应用,分不清谁是系统外力,谁是系统内力;判断不出守恒条件:是合外力为零,还是内力远远大于外力;区别不开每时每刻守恒还是瞬间守恒。这些情况导致物理场景不能建立,情境不清,公式、定律应用不准,结果自然乱成一团。要解决上述问题,必须选择好题,针对一两个习题讲清讲透,使学生感受到分析清楚物理过程是多么重要。例如,一平板小车放在光滑水平面上,今有质量均为 m 的物体 A 和 B 分别以2v<sub>0</sub>和 v<sub>0</sub>的初速度沿同一直线从小车 C 两端相向水平地滑上小车,设 A、B 两物体与小车间的动摩擦因数均为μ,小车的质量为 m,求:（1）为使 A、B两物体不相撞,小车的板长至少应为多少?（2）由开始滑上平板车到两物体都静止在小车上为止,B 通过的总路程是多少?此题过程复杂多变,学生很难下手,细细分析可知,涉及到的知识点都是常见的,此题关键是 A、B展开更多
This paper describes the development of an expert system(ES) on earth retaining structures for the selection and design.The ES retaining is an interactive menudriven system and consists of two main parts—the selectio...This paper describes the development of an expert system(ES) on earth retaining structures for the selection and design.The ES retaining is an interactive menudriven system and consists of two main parts—the selection part,selectwall and the design part.Selectwall is developed using the knowledge base and it makes a choice of the most appropriate retaining structure.The design part is developed by three independent subprograms which perform detailed design including strength,deformation,stability of the retaining structure.The calculation results are illustrated by plotting the diagram.Using this program,the design procedure of the retaining structure can be performed automatically.展开更多
The effect of hydrostatic pressure on the vibration dispersion characteristics of fluid-shell coupled structures was studied.Both fluid-loaded cylindrical shells and fluid-filled cylindrical shells were considered.Num...The effect of hydrostatic pressure on the vibration dispersion characteristics of fluid-shell coupled structures was studied.Both fluid-loaded cylindrical shells and fluid-filled cylindrical shells were considered.Numerical analysis was applied to solve the dispersion equations for shells filled with or loaded with fluid at various hydrostatic pressures.The results for external pressure showed that non-dimensional axial wave numbers are nearly independent when the pressure is below the critical level.The influence of internal pressure on wave numbers was found significant for the real branch s=1 and the complex branches of dispersion curves.The presence of internal pressure increased the cut on frequencies for the branch s=1 for high order wave modes.展开更多
Under the environment of electric power market, economic dispatch (ED) problem should consider network constraints, unit ramp rates, besides the basic constraints. For this problem, it is important to establish the ef...Under the environment of electric power market, economic dispatch (ED) problem should consider network constraints, unit ramp rates, besides the basic constraints. For this problem, it is important to establish the effective model and algorithm. This paper examines the decoupled conditions that affect the solution optimality to this problem. It proposes an effective model and solution method. Based on the look-ahead technique, it finds the number of time intervals to guarantee the solution optimality. Next, an efficient technique for finding the optimal solution via the interior point methods is described. Test cases, which include dispatching six units over 5 time intervals on the IEEE 30 test system with line flows and ramp constraints are presented. Results indicate that the computational effort as measured by iteration counts or execution time varies only modestly with the problem size.展开更多
The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loo...The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loop anchorage prestressing loss(PL) values of inner lining(IL)in Yellow River-crossing tunnel under two anchorage systems,including twice- tension anchorage system and HM(Chinese transliteration is huanmao)anchorage system,are introduced. The software ANSYS is selected to realize the three-dimensional(3D) finite element modeling to accomplish simulation and calculation works under the two anchorage systems,respectively. Stress processes of IL under the two working conditions,of which one is completed cable tensioning(CCT) and the other is water in the tunnel with the designed water pressure(DWP),are contrasted and analyzed. Impacts of prestressing forces of anchor cables on structural safety under the two anchorage systems are contrasted. The calculation results show that the twice-tension anchorage system can reduce PL effectively and then increase prestresses of wall concrete(WC). Meanwhile,the anchorage system has the advantages of improving security and stability of tunnel structure,reducing project costs and saving steel consumption. The research work is available to related design and construction of anchor cable,and is worthy of promotion and application.展开更多
With the rapid development of computer science and artificial intelligence technology, the complexity and intelligence of the neural network models constructed by people have been greatly improved. When the complex ne...With the rapid development of computer science and artificial intelligence technology, the complexity and intelligence of the neural network models constructed by people have been greatly improved. When the complex neuron system is subjected to the impact of ＂catastrophic＂, its original characteristics may be changed, and the consequences are difficult to predict. Catastrophe dynamics mainly studies the source of the sudden violent change of nature and human society and its evolution. The impact of the system can be divided into endogenous and exogenous shocks. In this article, catastrophe theory is used to study the neuron system. Based on the mean field model of Hurst and Sornette, introducing the weight parameters, mathematical models are constructed to study the response characteristics of the neuron system in face of exogenous shocks, endogenous shocks, and integrated shocks. The time characteristics of the shock response of the neuron system are discussed too, such as the instantaneous and long-term response of the system in face of shocks, the different response forms according to the weight or linear superposition, and the influence of adjusting parameters on the neuron system. The research result shows that the authoritarian coefficient and weight coefficient have a very important influence on the response of neuron system; By adjusting the two coefficients, the purpose of disaster prevention, self-healing protection and response reducing can be well achieved.展开更多
We analyze in detail the quantum phase transitions that arise in models based on the u（2） algebraic description for bosonic systems with two types of scalar bosons. First we discuss the quantum phase transition that...We analyze in detail the quantum phase transitions that arise in models based on the u（2） algebraic description for bosonic systems with two types of scalar bosons. First we discuss the quantum phase transition that occurs in hamiltonians that admix the two dynamical symmetry chains u（2） u（1） and u（2） so（2） by diagonalizing the problem exactly in the u（1） basis. Then we apply the coherent state formalism to determine the energy functioned. Finally we show that a quantum phase transition of a different nature, but displaying similar characteristics, may arise also within a single chain just by including higher order terms in the hamiltonian.展开更多
This paper discusses recent research findings together with management schemes in preventing and managing of thermal stress by handling external and internal factors in livestock production systems. Preventive measure...This paper discusses recent research findings together with management schemes in preventing and managing of thermal stress by handling external and internal factors in livestock production systems. Preventive measures against thermal stress are described as basic structural adjustments and the modifications that can be implemented readily, according to animal health and welfare requirements and refer to （1） environmental modification and thermal comfort in various housing systems; （2） action on animals, such as genetic selection for breeds resistant to infectious disease, parasites and climate extremes; （3） action on feed and （4） action on staff handling the animals. Moreover, measures to be taken both in situations of chronic thermal stress and heat or cold strokes are presented as they are applied to （1） limit stress, （2） monitor the temperature felt by animals, （3） adapt diet and drinking water supplies and （4） correct physiological imbalances. Examples are given for different farm species （cattle, sheep, goat, poultry and pigs） and different production systems （intensive, extensive and alternative）. The paper concludes with a practical guide for the effective handling of thermal stress at farm level, summarizing the results from recent research studies on the specific topic.展开更多
Based on the fact that the house dust usually falls on the ground, the floor level slit exhaust ventilation system including inlet located at the ceiling and outlet of slit exhaust installed at comer between wall and ...Based on the fact that the house dust usually falls on the ground, the floor level slit exhaust ventilation system including inlet located at the ceiling and outlet of slit exhaust installed at comer between wall and floor was considered. Experiments and simulations were performed to investigate the flow and diffusion fields that are affected by this floor level slit exhaust ventilation system. The characteristics of airflow with experiments and computation fluid dynamics （CFD） are generally similar except airflow at the location of impinging flow and the location right below the inlet. Riboflavin particles were used as the house dust. For the spatial distribution of riboflavin particles in the ventilation system before operation, due to the influence of gravity, different sizes of particles show smooth decay curve. After floor level slit exhaust ventilation system is operated, the decay rate of the particles becomes faster than that after the ventilation system is powered on, and the particles with diameter of 0.5-3.0 μm in the experimental data and calculated values show good agreement.展开更多
The relationship between forms and forces is one of the main topics of structural morphology. This harmonious coexisting link is very strong for systems in tensegrity state, commonly called ＂tensegrity systems＂. It ...The relationship between forms and forces is one of the main topics of structural morphology. This harmonious coexisting link is very strong for systems in tensegrity state, commonly called ＂tensegrity systems＂. It is currently apparent that, among the tensegrity systems, there also exist cable-bar cells with a discontinuous network of cables. It is possible to design a separate set of cables inside the cable-bar elementary cell and to establish a self-stress state of equilibrium. In this connection, the author of this paper suggested to assume a new Class-Theta tensegrity systems. Each of the basic tensegrity systems termed Class-Theta possesses an external and internal set of tension components. The shape of Greek capital letter 69 （Theta） reflects two sets of such components （two sets of tendons, cables, etc.）. This notation corresponds to Skelton＇s Class-k tensegrity structure. As shown in this paper, the Class-Theta tensegrity cell can exemplify a geometrically and practically useful form for the lightweight and long-span modular structures, mainly but not only in view of civil engineering and architecture.展开更多
Aimed at attaining to an integrated and effective pattern to guide the port design process, this paper puts forward a new conception of feature solution, which is based on the parameterized feature modeling. With this...Aimed at attaining to an integrated and effective pattern to guide the port design process, this paper puts forward a new conception of feature solution, which is based on the parameterized feature modeling. With this solution, the overall port pre-design process can be conducted in a virtual pattern. Moreover, to evaluate the advantages of the new design pattern, an application of port system has been involved in this paper; and in the process of application a computational fluid dynamic analysis is concerned. An ideal effect of cleanness, high efficiency and high precision has been achieved.展开更多
Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunologi- cal response. The present study investigated the impact of a 3-min mechanical perturbation mimicking...Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunologi- cal response. The present study investigated the impact of a 3-min mechanical perturbation mimicking the grading procedure on neuroendocrine and immune parameters of the sea cucumber Apostichopusjaponicus. During the application of stress, concentrations of noradrenaline and dopamine in coelomic fluid increased significantly, indicating that the mechanical perturbation resulted in a transient state of stress in sea cucumbers. Coelomocytes concentration in coelomic fluid increased transiently after the beginning of stressing, and reached the maximum in 1 h. Whereas, coelomocytes phagocytosis at 3 min, superoxide anion production from 3 min to 0.5 h, acid phosphatase activity at 0.5 h, and phenoloxidase activity from 3 min to 0.5 h were all significantly down-regulated. All of the immune parameters recovered to baseline levels after the experiment was conducted for 8 h, and an immunostimulation occurred after the stress considering the phagocytosis and acid phosphatase activity. The results suggested that, as in other marine invertebrates, neuroendocrine/immnne connections exist in sea cucumber A. japonicus. Mechanical stress can elicit a profound influence on sea cucumber neuroendocrine system. Neuroendocrine messengers act in turn to modulate the immunity fimctions. Therefore, these ef- fects should be considered for developing better husbandry procedures.展开更多
As the opening year of the ＂Twelfth Five-Year Plan,＂ driven by the steady and fast economic growth, the year of 2011 saw China＇s rising demand for electricity, resulting in regional power shortages. Sub）ected to m...As the opening year of the ＂Twelfth Five-Year Plan,＂ driven by the steady and fast economic growth, the year of 2011 saw China＇s rising demand for electricity, resulting in regional power shortages. Sub）ected to multiple factors such as the weather conditions, the contradictions between coal supply and power generation and the structural problems in the power system, power supply shortage across the nation became increasingly critical At the same time, the Northeast and Northwest China, plus Inner Mongolia, often experienced power generation surplus and difficulties in sending power to other regions. This paper reviews the overall situation of the national electric power supply in 2011, elaborates on the current contradictions in the power demand and supply and presents an in-depth analysis of causes and corresponding countermeasures.展开更多
文摘在高三力学复习过程中,学生感到最困难的是动量守恒的应用,分不清谁是系统外力,谁是系统内力;判断不出守恒条件:是合外力为零,还是内力远远大于外力;区别不开每时每刻守恒还是瞬间守恒。这些情况导致物理场景不能建立,情境不清,公式、定律应用不准,结果自然乱成一团。要解决上述问题,必须选择好题,针对一两个习题讲清讲透,使学生感受到分析清楚物理过程是多么重要。例如,一平板小车放在光滑水平面上,今有质量均为 m 的物体 A 和 B 分别以2v<sub>0</sub>和 v<sub>0</sub>的初速度沿同一直线从小车 C 两端相向水平地滑上小车,设 A、B 两物体与小车间的动摩擦因数均为μ,小车的质量为 m,求:（1）为使 A、B两物体不相撞,小车的板长至少应为多少?（2）由开始滑上平板车到两物体都静止在小车上为止,B 通过的总路程是多少?此题过程复杂多变,学生很难下手,细细分析可知,涉及到的知识点都是常见的,此题关键是 A、B
文摘This paper describes the development of an expert system(ES) on earth retaining structures for the selection and design.The ES retaining is an interactive menudriven system and consists of two main parts—the selection part,selectwall and the design part.Selectwall is developed using the knowledge base and it makes a choice of the most appropriate retaining structure.The design part is developed by three independent subprograms which perform detailed design including strength,deformation,stability of the retaining structure.The calculation results are illustrated by plotting the diagram.Using this program,the design procedure of the retaining structure can be performed automatically.
文摘The effect of hydrostatic pressure on the vibration dispersion characteristics of fluid-shell coupled structures was studied.Both fluid-loaded cylindrical shells and fluid-filled cylindrical shells were considered.Numerical analysis was applied to solve the dispersion equations for shells filled with or loaded with fluid at various hydrostatic pressures.The results for external pressure showed that non-dimensional axial wave numbers are nearly independent when the pressure is below the critical level.The influence of internal pressure on wave numbers was found significant for the real branch s=1 and the complex branches of dispersion curves.The presence of internal pressure increased the cut on frequencies for the branch s=1 for high order wave modes.
文摘Under the environment of electric power market, economic dispatch (ED) problem should consider network constraints, unit ramp rates, besides the basic constraints. For this problem, it is important to establish the effective model and algorithm. This paper examines the decoupled conditions that affect the solution optimality to this problem. It proposes an effective model and solution method. Based on the look-ahead technique, it finds the number of time intervals to guarantee the solution optimality. Next, an efficient technique for finding the optimal solution via the interior point methods is described. Test cases, which include dispatching six units over 5 time intervals on the IEEE 30 test system with line flows and ramp constraints are presented. Results indicate that the computational effort as measured by iteration counts or execution time varies only modestly with the problem size.
基金National Natural Science Foundation of China(No.51079107)Fundamental Research Funds for the Central Universities(No.5082022)
文摘The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension(referred to as twice-tension anchorage system) is proposed in the paper. Calculation results of loop anchorage prestressing loss(PL) values of inner lining(IL)in Yellow River-crossing tunnel under two anchorage systems,including twice- tension anchorage system and HM(Chinese transliteration is huanmao)anchorage system,are introduced. The software ANSYS is selected to realize the three-dimensional(3D) finite element modeling to accomplish simulation and calculation works under the two anchorage systems,respectively. Stress processes of IL under the two working conditions,of which one is completed cable tensioning(CCT) and the other is water in the tunnel with the designed water pressure(DWP),are contrasted and analyzed. Impacts of prestressing forces of anchor cables on structural safety under the two anchorage systems are contrasted. The calculation results show that the twice-tension anchorage system can reduce PL effectively and then increase prestresses of wall concrete(WC). Meanwhile,the anchorage system has the advantages of improving security and stability of tunnel structure,reducing project costs and saving steel consumption. The research work is available to related design and construction of anchor cable,and is worthy of promotion and application.
基金Project(CX2016B142)supported by the Hunan Provincial Innovation Foundation for Postgraduate,China
文摘With the rapid development of computer science and artificial intelligence technology, the complexity and intelligence of the neural network models constructed by people have been greatly improved. When the complex neuron system is subjected to the impact of ＂catastrophic＂, its original characteristics may be changed, and the consequences are difficult to predict. Catastrophe dynamics mainly studies the source of the sudden violent change of nature and human society and its evolution. The impact of the system can be divided into endogenous and exogenous shocks. In this article, catastrophe theory is used to study the neuron system. Based on the mean field model of Hurst and Sornette, introducing the weight parameters, mathematical models are constructed to study the response characteristics of the neuron system in face of exogenous shocks, endogenous shocks, and integrated shocks. The time characteristics of the shock response of the neuron system are discussed too, such as the instantaneous and long-term response of the system in face of shocks, the different response forms according to the weight or linear superposition, and the influence of adjusting parameters on the neuron system. The research result shows that the authoritarian coefficient and weight coefficient have a very important influence on the response of neuron system; By adjusting the two coefficients, the purpose of disaster prevention, self-healing protection and response reducing can be well achieved.
文摘We analyze in detail the quantum phase transitions that arise in models based on the u（2） algebraic description for bosonic systems with two types of scalar bosons. First we discuss the quantum phase transition that occurs in hamiltonians that admix the two dynamical symmetry chains u（2） u（1） and u（2） so（2） by diagonalizing the problem exactly in the u（1） basis. Then we apply the coherent state formalism to determine the energy functioned. Finally we show that a quantum phase transition of a different nature, but displaying similar characteristics, may arise also within a single chain just by including higher order terms in the hamiltonian.
文摘This paper discusses recent research findings together with management schemes in preventing and managing of thermal stress by handling external and internal factors in livestock production systems. Preventive measures against thermal stress are described as basic structural adjustments and the modifications that can be implemented readily, according to animal health and welfare requirements and refer to （1） environmental modification and thermal comfort in various housing systems; （2） action on animals, such as genetic selection for breeds resistant to infectious disease, parasites and climate extremes; （3） action on feed and （4） action on staff handling the animals. Moreover, measures to be taken both in situations of chronic thermal stress and heat or cold strokes are presented as they are applied to （1） limit stress, （2） monitor the temperature felt by animals, （3） adapt diet and drinking water supplies and （4） correct physiological imbalances. Examples are given for different farm species （cattle, sheep, goat, poultry and pigs） and different production systems （intensive, extensive and alternative）. The paper concludes with a practical guide for the effective handling of thermal stress at farm level, summarizing the results from recent research studies on the specific topic.
基金Project supported by Ministry of Land, Infrastructure, Transport and Tourism of Japan Project(DUT10RC(3)103) supported by the Fundamental Research Funds for the Central Universities in China+2 种基金 Project(20111027) supported by the Liaoning Provincial Scientific Research Foundation, China Key Project (2012BAJ02B05) supported by the Twelfth Five-Year National Technology Program of China Project supported by Dalian Municipal Construction Technology Program, China
文摘Based on the fact that the house dust usually falls on the ground, the floor level slit exhaust ventilation system including inlet located at the ceiling and outlet of slit exhaust installed at comer between wall and floor was considered. Experiments and simulations were performed to investigate the flow and diffusion fields that are affected by this floor level slit exhaust ventilation system. The characteristics of airflow with experiments and computation fluid dynamics （CFD） are generally similar except airflow at the location of impinging flow and the location right below the inlet. Riboflavin particles were used as the house dust. For the spatial distribution of riboflavin particles in the ventilation system before operation, due to the influence of gravity, different sizes of particles show smooth decay curve. After floor level slit exhaust ventilation system is operated, the decay rate of the particles becomes faster than that after the ventilation system is powered on, and the particles with diameter of 0.5-3.0 μm in the experimental data and calculated values show good agreement.
文摘The relationship between forms and forces is one of the main topics of structural morphology. This harmonious coexisting link is very strong for systems in tensegrity state, commonly called ＂tensegrity systems＂. It is currently apparent that, among the tensegrity systems, there also exist cable-bar cells with a discontinuous network of cables. It is possible to design a separate set of cables inside the cable-bar elementary cell and to establish a self-stress state of equilibrium. In this connection, the author of this paper suggested to assume a new Class-Theta tensegrity systems. Each of the basic tensegrity systems termed Class-Theta possesses an external and internal set of tension components. The shape of Greek capital letter 69 （Theta） reflects two sets of such components （two sets of tendons, cables, etc.）. This notation corresponds to Skelton＇s Class-k tensegrity structure. As shown in this paper, the Class-Theta tensegrity cell can exemplify a geometrically and practically useful form for the lightweight and long-span modular structures, mainly but not only in view of civil engineering and architecture.
文摘Aimed at attaining to an integrated and effective pattern to guide the port design process, this paper puts forward a new conception of feature solution, which is based on the parameterized feature modeling. With this solution, the overall port pre-design process can be conducted in a virtual pattern. Moreover, to evaluate the advantages of the new design pattern, an application of port system has been involved in this paper; and in the process of application a computational fluid dynamic analysis is concerned. An ideal effect of cleanness, high efficiency and high precision has been achieved.
基金financially supported by the 863 High Technology Project of the Ministry of Science and Technology (No. 2012AA10A412-4)the Special Funds for the Basic B & D Program in the Central Non-profit Research Institutes (No. 2010-cb-03)+1 种基金Science and Technology Development Planning Project of Shandong Province (No. 2012GGA06021)Science and Technology Development Fund of Shinan district of Qingdao (No. 2011-5-023-QT)
文摘Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunologi- cal response. The present study investigated the impact of a 3-min mechanical perturbation mimicking the grading procedure on neuroendocrine and immune parameters of the sea cucumber Apostichopusjaponicus. During the application of stress, concentrations of noradrenaline and dopamine in coelomic fluid increased significantly, indicating that the mechanical perturbation resulted in a transient state of stress in sea cucumbers. Coelomocytes concentration in coelomic fluid increased transiently after the beginning of stressing, and reached the maximum in 1 h. Whereas, coelomocytes phagocytosis at 3 min, superoxide anion production from 3 min to 0.5 h, acid phosphatase activity at 0.5 h, and phenoloxidase activity from 3 min to 0.5 h were all significantly down-regulated. All of the immune parameters recovered to baseline levels after the experiment was conducted for 8 h, and an immunostimulation occurred after the stress considering the phagocytosis and acid phosphatase activity. The results suggested that, as in other marine invertebrates, neuroendocrine/immnne connections exist in sea cucumber A. japonicus. Mechanical stress can elicit a profound influence on sea cucumber neuroendocrine system. Neuroendocrine messengers act in turn to modulate the immunity fimctions. Therefore, these ef- fects should be considered for developing better husbandry procedures.
文摘As the opening year of the ＂Twelfth Five-Year Plan,＂ driven by the steady and fast economic growth, the year of 2011 saw China＇s rising demand for electricity, resulting in regional power shortages. Sub）ected to multiple factors such as the weather conditions, the contradictions between coal supply and power generation and the structural problems in the power system, power supply shortage across the nation became increasingly critical At the same time, the Northeast and Northwest China, plus Inner Mongolia, often experienced power generation surplus and difficulties in sending power to other regions. This paper reviews the overall situation of the national electric power supply in 2011, elaborates on the current contradictions in the power demand and supply and presents an in-depth analysis of causes and corresponding countermeasures.
