Aim To study the influence of restraint system performance upon the occupant's response during impact, and provide a scientific base for occupant restraint system design. Methods \ In the light of basic th...Aim To study the influence of restraint system performance upon the occupant's response during impact, and provide a scientific base for occupant restraint system design. Methods \ In the light of basic theory of multibody system dynamics and impact dynamics on the basis of classical theory of impact, R W method is adopted to construct the vehicle occupant system model consisting of fourteen rigid bodies, thirty seven DOFs and slip joints for the simulation. A software named SVC3D(3 dimensional simulation of vehicle crash) is developed in the FORTRAN language. Results\ The results of simulation have a good coincidence with those of tests and the restraint system with low elongation webbing and equipped with pretensioner provides better restraint effect for the occupant. Conclusion\ The model of vehicle occupant multibody system and SVC3D are suitable for use. Occupant should be belted with low elongation webbing to a certain degree and occupant restraint system should be equipped with pretensioner.展开更多
System dynamics (SD) theory has long been deployed in modeling complex non-linear interrelationships but, so far it has not been common to do the kind of modeling in support of bringing environmental sustainability po...System dynamics (SD) theory has long been deployed in modeling complex non-linear interrelationships but, so far it has not been common to do the kind of modeling in support of bringing environmental sustainability policies to practice. This is largely because the challenge of including spatial data has not yet been well met. Potential for adoption of SD and GIS methods in combination is exemplified with the results of a decision-support exercise designed for simulation and prediction of the dynamic inter-relationships between socio-economic development and environmental quality for the "Wen, Pi, Du" county in Sichuan province, southwestern China.展开更多
The chief production elements of an agricultural enterprise are its biological assets and the choice and practical application of the evaluation methods, as the assets directly affect many aspects： decision making of...The chief production elements of an agricultural enterprise are its biological assets and the choice and practical application of the evaluation methods, as the assets directly affect many aspects： decision making of economic character by the financial statement user, indicators of financial operation analysis, inter-comparison of sector enterprises, assessment of the company value and taxes on its economic activity, and statistical data of the agricultural sector. The authors have used the discounted cash flow （DCF） as an alternative method and a model of system dynamics. Such a system dynamics method has not been used for assessment of biological assets so far. In the operating process, the company acquires or loses possession of the resources. It is vital to analyze the resources to see whether they comply with the concept of the assets and the terms of recognition. It is necessary for the same company as well as for external users of financial statements to get true information about the business and the value of money. Biological assets may be recognized in the company＇s accounting only when it is predictable that future benefits associated with these assets will flow into the enterprise. It is also important that the fair value or the cost can be measured reliably.展开更多
Solid oxide fuel cell (SOFC) has been identified as an effective and clean alternative choice for marine power system.This paper emphasizes on the dynamic modeling of SOFC power system and its performance based upon m...Solid oxide fuel cell (SOFC) has been identified as an effective and clean alternative choice for marine power system.This paper emphasizes on the dynamic modeling of SOFC power system and its performance based upon marine operating circumstance.A SOFC power system model has been provided considering thermodynamic and electrochemical reaction mechanism.Subcomponents of lithium ion battery, power conditioning unit, stack structure and controller are integrated in the model.The dynamic response of the system is identified according to the inertia of its subcomponent and controller.Validation of the whole system simulation at steady state and transit period are presented, concerning the effects of thermo inertia, control strategy and seagoing environment.The simulation results show reasonable accuracy compare with lab test.The models can be used to predict performance of a SOFC power system and identify the system response when part of the component parameter is adjusted.展开更多
One of the most interesting outcomes from the recent collaboration between natural and social scientists is the concept of resilience, which imported from engineering to ecology. The problem with that concept is that ...One of the most interesting outcomes from the recent collaboration between natural and social scientists is the concept of resilience, which imported from engineering to ecology. The problem with that concept is that it is hard if not impossible to get simple measures for resilience as far as social-ecological systems are complex ones. Using a system dynamics model, the author shows that, for assessing resilience of systems like irrigation systems, it probably helps to see the process of resilience loss as a systemic one, in which dynamics is given by positive self-reinforcing loops, like the one we have labeled in this paper--the death spiral. The author also presents a list of symptoms of collapse in irrigation systems, in order to assess the resilience of those systems, and suggest some future avenues of research on the subject.展开更多
The theoretic renormalization group approach is applied to the study of the critical behavior of non-interacting system with long-range correlated quenched impurities, which has a power-like correlations . To two-loop...The theoretic renormalization group approach is applied to the study of the critical behavior of non-interacting system with long-range correlated quenched impurities, which has a power-like correlations . To two-loop order, the asymptotic scaling laws and the critical exponents are studied in the frame of a double expansion with ρ of order . In , it is argued that the initial slip exponent θ = 0 together with the dynamic exponent is exact in this kind of random system.展开更多
A stochastic celhflar automaton （CA） model for activated sludge system （ASS） is for- mulated by a series of transition functions upon realistic treatment processes, and it is tested by comparing with ordinary diff...A stochastic celhflar automaton （CA） model for activated sludge system （ASS） is for- mulated by a series of transition functions upon realistic treatment processes, and it is tested by comparing with ordinary differential equations （ODEs） of ASS. CA system performed by empirical parameters can reflect the characteristics of fluctuation, com- plexity and strong non-linearity of ASS. The results show that the predictions of CA are approximately similar to the dynamical behaviors of ODEs. Based on the extreme experimental system with complete cell recycle in model validation, the dynamics of biomass and substrate are predicted accurately by CA, but the large errors exist in ODEs except for integrating more spatially complicated factors. This is due to that the strong mechanical stress from spatial crowding effect is ignored in ODEs, while CA system as a spatially explicit model takes account of local interactions. Despite its extremely simple structure, CA still can capture the essence of ASS better than ODEs, thus it would be very useful in predicting long-term dynamics in other similar systems.展开更多
文摘Aim To study the influence of restraint system performance upon the occupant's response during impact, and provide a scientific base for occupant restraint system design. Methods \ In the light of basic theory of multibody system dynamics and impact dynamics on the basis of classical theory of impact, R W method is adopted to construct the vehicle occupant system model consisting of fourteen rigid bodies, thirty seven DOFs and slip joints for the simulation. A software named SVC3D(3 dimensional simulation of vehicle crash) is developed in the FORTRAN language. Results\ The results of simulation have a good coincidence with those of tests and the restraint system with low elongation webbing and equipped with pretensioner provides better restraint effect for the occupant. Conclusion\ The model of vehicle occupant multibody system and SVC3D are suitable for use. Occupant should be belted with low elongation webbing to a certain degree and occupant restraint system should be equipped with pretensioner.
文摘System dynamics (SD) theory has long been deployed in modeling complex non-linear interrelationships but, so far it has not been common to do the kind of modeling in support of bringing environmental sustainability policies to practice. This is largely because the challenge of including spatial data has not yet been well met. Potential for adoption of SD and GIS methods in combination is exemplified with the results of a decision-support exercise designed for simulation and prediction of the dynamic inter-relationships between socio-economic development and environmental quality for the "Wen, Pi, Du" county in Sichuan province, southwestern China.
文摘The chief production elements of an agricultural enterprise are its biological assets and the choice and practical application of the evaluation methods, as the assets directly affect many aspects： decision making of economic character by the financial statement user, indicators of financial operation analysis, inter-comparison of sector enterprises, assessment of the company value and taxes on its economic activity, and statistical data of the agricultural sector. The authors have used the discounted cash flow （DCF） as an alternative method and a model of system dynamics. Such a system dynamics method has not been used for assessment of biological assets so far. In the operating process, the company acquires or loses possession of the resources. It is vital to analyze the resources to see whether they comply with the concept of the assets and the terms of recognition. It is necessary for the same company as well as for external users of financial statements to get true information about the business and the value of money. Biological assets may be recognized in the company＇s accounting only when it is predictable that future benefits associated with these assets will flow into the enterprise. It is also important that the fair value or the cost can be measured reliably.
文摘Solid oxide fuel cell (SOFC) has been identified as an effective and clean alternative choice for marine power system.This paper emphasizes on the dynamic modeling of SOFC power system and its performance based upon marine operating circumstance.A SOFC power system model has been provided considering thermodynamic and electrochemical reaction mechanism.Subcomponents of lithium ion battery, power conditioning unit, stack structure and controller are integrated in the model.The dynamic response of the system is identified according to the inertia of its subcomponent and controller.Validation of the whole system simulation at steady state and transit period are presented, concerning the effects of thermo inertia, control strategy and seagoing environment.The simulation results show reasonable accuracy compare with lab test.The models can be used to predict performance of a SOFC power system and identify the system response when part of the component parameter is adjusted.
文摘One of the most interesting outcomes from the recent collaboration between natural and social scientists is the concept of resilience, which imported from engineering to ecology. The problem with that concept is that it is hard if not impossible to get simple measures for resilience as far as social-ecological systems are complex ones. Using a system dynamics model, the author shows that, for assessing resilience of systems like irrigation systems, it probably helps to see the process of resilience loss as a systemic one, in which dynamics is given by positive self-reinforcing loops, like the one we have labeled in this paper--the death spiral. The author also presents a list of symptoms of collapse in irrigation systems, in order to assess the resilience of those systems, and suggest some future avenues of research on the subject.
文摘The theoretic renormalization group approach is applied to the study of the critical behavior of non-interacting system with long-range correlated quenched impurities, which has a power-like correlations . To two-loop order, the asymptotic scaling laws and the critical exponents are studied in the frame of a double expansion with ρ of order . In , it is argued that the initial slip exponent θ = 0 together with the dynamic exponent is exact in this kind of random system.
基金This research was supported by the National Natural Science Foundation of China （No. 30870397） and the State Key Laboratory of Vegetation and Environmental Change.
文摘A stochastic celhflar automaton （CA） model for activated sludge system （ASS） is for- mulated by a series of transition functions upon realistic treatment processes, and it is tested by comparing with ordinary differential equations （ODEs） of ASS. CA system performed by empirical parameters can reflect the characteristics of fluctuation, com- plexity and strong non-linearity of ASS. The results show that the predictions of CA are approximately similar to the dynamical behaviors of ODEs. Based on the extreme experimental system with complete cell recycle in model validation, the dynamics of biomass and substrate are predicted accurately by CA, but the large errors exist in ODEs except for integrating more spatially complicated factors. This is due to that the strong mechanical stress from spatial crowding effect is ignored in ODEs, while CA system as a spatially explicit model takes account of local interactions. Despite its extremely simple structure, CA still can capture the essence of ASS better than ODEs, thus it would be very useful in predicting long-term dynamics in other similar systems.
