The dynamic response involved in car-roadside barrier impacts is studied. Therisk of occupant injures in such accidents is investigated. An approach based on accident analysisand mathematical modeling is developed and...The dynamic response involved in car-roadside barrier impacts is studied. Therisk of occupant injures in such accidents is investigated. An approach based on accident analysisand mathematical modeling is developed and described in three steps. Firstly a study of car-roadsidebarrier impact accidents is carried out with available data to define a system including car, road,roadside barrier, and occupant. Secondly a mathematical model to simulate car-to-barrier impact isdeveloped by using multi-body program MADYMO. Finally, dynamic responses of the occupant duringimpact are simulated using a car compartment model with a HYBRID III occupant model and an inputload pulse calculated in the second step. The dynamic responses of the car are analyzed by changingimpact conditions such as impact angle and impact velocity. The injury risks of the occupants arediscussed in terms of the occupant kinematics and calculated parameters: accelerations of the head,chest, and pelvis, as well as HIC value. Verification of model with experimental data is performed.Possible counter-measures for highway vehicle traffic safety and improvement of roadside barrierdesign are presented. Research prospects in this field are also proposed.展开更多
Block piezoelectric ceramics(PZTs)are often used in impact igniters to provide activation energy for electric initiators.Under the action of strong impact stress,PZTs release electric energy accompanied by crack initi...Block piezoelectric ceramics(PZTs)are often used in impact igniters to provide activation energy for electric initiators.Under the action of strong impact stress,PZTs release electric energy accompanied by crack initiation,propagation and crushing.At present,the electrical output performance of PZTs in projectile is usually calculated by quasi-static piezoelectric equation without considering the dynamic effect caused by strong impact and the influence of crack propagation on material properties.So the ignition parameters are always not accurately predicted.To tackle this,a PZT dynamic damage constitutive model considering crack propagation is established based on the dynamic impact test and the crack propagation theory of brittle materials.The model is then embedded into the ABAQUS subroutine and used to simulate the electromechanical response of the impact igniter during the impact of a small caliber projectile on the target.Meanwhile,the experiments of projectile with impact igniter impact on the target are carried out.The comparison between experimental and numerical simulation results show that the established dynamic damage model can effectively predict the dynamic electromechanical response of PZTs in the missile service environment.展开更多
Abstract The dynamic response of pipe-on-pipe impact is described by an analytical model. The model considers the impact of a whipping pipe with one end hinged and the other end free on a simply-supported target pipe ...Abstract The dynamic response of pipe-on-pipe impact is described by an analytical model. The model considers the impact of a whipping pipe with one end hinged and the other end free on a simply-supported target pipe at its midpoint. Combining with the contact theory, the Laplace transformation, and the inverse Laplace transformation method, an analytical model based on the tubular beam theory is proposed to study the elastic-plastic behavior of a target pipe laterally impacted by a whipping pipe. Numerical simulations using the explicit finite element code MSC/DYTRAN are also performed. The results are coincident with the theoretical prediction.展开更多
An innovative floating mooring system with two or more independent floating mooring platforms in the middle and one rigid platform on each side is proposed for improving efficiency and safety in shallow water. For thi...An innovative floating mooring system with two or more independent floating mooring platforms in the middle and one rigid platform on each side is proposed for improving efficiency and safety in shallow water. For this new system, most of collision energy is absorbed through the displacement of floating platforms. In order to illustrate the validity of the system, a series of model tests were conducted at a scale of 1:40. The coupled motion characteristics of the floating mooring platforms were discussed under regular and irregular waves, and the influences of wave direction and other characteristics on dynamic response of the system were analyzed. The results show that the mooring system is safest at 0° of wave incident angle, whereas the most dangerous mooring state occurs at 90° of wave incident angle. Motion responses increase with the increase of wave height, but are not linearly related to changes in wave height.展开更多
Density-graded cellular materials have tremendous potential in structural applications where impact resistance is required.Cellular materials subjected to high impact loading result in a compaction type deformation,us...Density-graded cellular materials have tremendous potential in structural applications where impact resistance is required.Cellular materials subjected to high impact loading result in a compaction type deformation,usually modeled using continuum-based shock theory.The resulting governing differential equation of the shock model is nonlinear,and the density gradient further complicates the problem.Earlier studies have employed numerical methods to obtain the solution.In this study,an analytical closed-form solution is proposed to predict the response of density-graded cellular materials subjected to a rigid body impact.Solutions for the velocity of the impinging rigid body mass,energy absorption capacity of the cellular material,and the incident stress are obtained for a single shock propagation.The results obtained are in excellent agreement with the existing numerical solutions found in the literature.The proposed analytical solution can be potentially used for parametric studies and for effectively designing graded structures to mitigate impact.展开更多
如何促进农业机械化可持续发展是一项重要的研究课题,其首要任务是科学评价农业机械化可持续发展(The Evaluation of the Sustainable Development of Agricultural Mechanization,ESDAM)质量。农业机械化可持续发展受诸多因素影响和制...如何促进农业机械化可持续发展是一项重要的研究课题,其首要任务是科学评价农业机械化可持续发展(The Evaluation of the Sustainable Development of Agricultural Mechanization,ESDAM)质量。农业机械化可持续发展受诸多因素影响和制约,该研究通过文献分析、调查和数据解析,利用模糊决策试验与评价实验室(DecisionMakingTrialand Evaluation Laboratory,DEMATEL)和解释结构模型(Interpretive Structure Modeling,ISM)组合方法,分析了影响农业机械化可持续发展各因素之间的关联关系,构建了农业机械化可持续发展评价指标体系。模糊DEMATEL-ISM法能较好地综合主观和客观评价意见,有助于厘清农业机械化可持续发展的主要影响因素。运用ESDAM-PSIR(压力-状态-影响-响应,Pressure-State-Impact-Response,PSIR)模型,对湖北省农业机械化可持续发展进行评价,并对2004—2020年湖北省的13项指标具体数据进行纵向比较,量化结果与湖北省农业机械化发展现状基本一致,所提方法具有可行性。分析结果表明,经济因素是目前农业机械化可持续发展最重要的影响因素,环境因素日益成为值得着重关注的因素,农机工业和科技的发展是将来需要重点考虑的问题。最后根据评价结果提出相应政策建议,为湖北省农业机械化可持续发展提供指导。展开更多
The capability of an improved Dynamic Global Vegetation Model (DGVM) in reproducing the impact of climate on the terrestrial ecosystem is evaluated. The new model incorporates the Community Land Model- DGVM (CLM3.0...The capability of an improved Dynamic Global Vegetation Model (DGVM) in reproducing the impact of climate on the terrestrial ecosystem is evaluated. The new model incorporates the Community Land Model- DGVM (CLM3.0-DGVM) with a submodel for temperate and boreal shrubs, as well as other revisions such as the "two-leaf" scheme for photosynthesis and the definition of fractional coverage of plant functional types (PFTs). Results show that the revised model may correctly reproduce the global distribution of temperate and boreal shrubs, and improves the model performance with more realistic distribution of di?erent vege- tation types. The revised model also correctly reproduces the zonal distributions of vegetation types. In reproducing the dependence of the vegetation distribution on climate conditions, the model shows that the dominant regions for trees, grasses, shrubs, and bare soil are clearly separated by a climate index derived from mean annual precipitation and temperature, in good agreement with the CLM4 surface data. The dominant plant functional type mapping to a two dimensional parameter space of mean annual temperature and precipitation also qualitatively agrees with the results from observations and theoretical ecology studies.展开更多
This paper proposes a holistic framework for the development of models for the assessment of research activities and their impacts. It distinguishes three dimensions, including in an original way, data as a main dimen...This paper proposes a holistic framework for the development of models for the assessment of research activities and their impacts. It distinguishes three dimensions, including in an original way, data as a main dimension, together with theory and methodology. Each dimension of the framework is further characterized by three main building blocks: education, research, and innovation (theory); efficiency, effectiveness, and impact (methodology); and availability, interoperability, and "unit-free" property (data). The different dimensions and their nine constituent building blocks are attributes of an overarching concept, denoted as "quality." Three additional quality attributes are identified as implementation factors (tailorability, transparency, and openness) and three "enabling" conditions (convergence, mixed methods, and knowledge infrastructures) complete the fi-amework. A framework is required to develop models of metrics. Models of metrics are necessary to assess the meaning, validity, and robustness of metrics. The proposed framework can be a useful reference for the development of the ethics of research evaluation. It can act as a common denominator for different analytical levels and relevant aspects and is able to embrace many different and heterogeneous streams of literature. Directions for future research are provided.展开更多
文摘The dynamic response involved in car-roadside barrier impacts is studied. Therisk of occupant injures in such accidents is investigated. An approach based on accident analysisand mathematical modeling is developed and described in three steps. Firstly a study of car-roadsidebarrier impact accidents is carried out with available data to define a system including car, road,roadside barrier, and occupant. Secondly a mathematical model to simulate car-to-barrier impact isdeveloped by using multi-body program MADYMO. Finally, dynamic responses of the occupant duringimpact are simulated using a car compartment model with a HYBRID III occupant model and an inputload pulse calculated in the second step. The dynamic responses of the car are analyzed by changingimpact conditions such as impact angle and impact velocity. The injury risks of the occupants arediscussed in terms of the occupant kinematics and calculated parameters: accelerations of the head,chest, and pelvis, as well as HIC value. Verification of model with experimental data is performed.Possible counter-measures for highway vehicle traffic safety and improvement of roadside barrierdesign are presented. Research prospects in this field are also proposed.
基金supported by the National Natural Science Foundation of China(Grant No.12172232)the project of Key Laboratory of Impact and Safety Engineering(Ningbo University,China)+1 种基金Ministry of Education(CJ202206)supported by the scientific research support plan of introducing high-level talents from Shenyang Ligong University。
文摘Block piezoelectric ceramics(PZTs)are often used in impact igniters to provide activation energy for electric initiators.Under the action of strong impact stress,PZTs release electric energy accompanied by crack initiation,propagation and crushing.At present,the electrical output performance of PZTs in projectile is usually calculated by quasi-static piezoelectric equation without considering the dynamic effect caused by strong impact and the influence of crack propagation on material properties.So the ignition parameters are always not accurately predicted.To tackle this,a PZT dynamic damage constitutive model considering crack propagation is established based on the dynamic impact test and the crack propagation theory of brittle materials.The model is then embedded into the ABAQUS subroutine and used to simulate the electromechanical response of the impact igniter during the impact of a small caliber projectile on the target.Meanwhile,the experiments of projectile with impact igniter impact on the target are carried out.The comparison between experimental and numerical simulation results show that the established dynamic damage model can effectively predict the dynamic electromechanical response of PZTs in the missile service environment.
基金Project supported by the National Natural Science Foundation of China (No. 11032001)
文摘Abstract The dynamic response of pipe-on-pipe impact is described by an analytical model. The model considers the impact of a whipping pipe with one end hinged and the other end free on a simply-supported target pipe at its midpoint. Combining with the contact theory, the Laplace transformation, and the inverse Laplace transformation method, an analytical model based on the tubular beam theory is proposed to study the elastic-plastic behavior of a target pipe laterally impacted by a whipping pipe. Numerical simulations using the explicit finite element code MSC/DYTRAN are also performed. The results are coincident with the theoretical prediction.
基金the support of the National Natural Science Foundation of China (Grant No. 51309179)the National High Technology Research and Development Program of China (863 Program, Grant No. 2012AA051705)+2 种基金the International S&T Cooperation Program of China (Grant No. 2012DFA70490)the State Key Laboratory of Hydraulic Engineering Simulation and Safety (Tianjin University)the Tianjin Municipal Natural Science Foundation (Grant Nos. 14JCQNJC07000 and 13JCYBJC19100)
文摘An innovative floating mooring system with two or more independent floating mooring platforms in the middle and one rigid platform on each side is proposed for improving efficiency and safety in shallow water. For this new system, most of collision energy is absorbed through the displacement of floating platforms. In order to illustrate the validity of the system, a series of model tests were conducted at a scale of 1:40. The coupled motion characteristics of the floating mooring platforms were discussed under regular and irregular waves, and the influences of wave direction and other characteristics on dynamic response of the system were analyzed. The results show that the mooring system is safest at 0° of wave incident angle, whereas the most dangerous mooring state occurs at 90° of wave incident angle. Motion responses increase with the increase of wave height, but are not linearly related to changes in wave height.
基金the financial support provided by the US Army Research Office under grant number W911NF-18-1-0023.
文摘Density-graded cellular materials have tremendous potential in structural applications where impact resistance is required.Cellular materials subjected to high impact loading result in a compaction type deformation,usually modeled using continuum-based shock theory.The resulting governing differential equation of the shock model is nonlinear,and the density gradient further complicates the problem.Earlier studies have employed numerical methods to obtain the solution.In this study,an analytical closed-form solution is proposed to predict the response of density-graded cellular materials subjected to a rigid body impact.Solutions for the velocity of the impinging rigid body mass,energy absorption capacity of the cellular material,and the incident stress are obtained for a single shock propagation.The results obtained are in excellent agreement with the existing numerical solutions found in the literature.The proposed analytical solution can be potentially used for parametric studies and for effectively designing graded structures to mitigate impact.
文摘如何促进农业机械化可持续发展是一项重要的研究课题,其首要任务是科学评价农业机械化可持续发展(The Evaluation of the Sustainable Development of Agricultural Mechanization,ESDAM)质量。农业机械化可持续发展受诸多因素影响和制约,该研究通过文献分析、调查和数据解析,利用模糊决策试验与评价实验室(DecisionMakingTrialand Evaluation Laboratory,DEMATEL)和解释结构模型(Interpretive Structure Modeling,ISM)组合方法,分析了影响农业机械化可持续发展各因素之间的关联关系,构建了农业机械化可持续发展评价指标体系。模糊DEMATEL-ISM法能较好地综合主观和客观评价意见,有助于厘清农业机械化可持续发展的主要影响因素。运用ESDAM-PSIR(压力-状态-影响-响应,Pressure-State-Impact-Response,PSIR)模型,对湖北省农业机械化可持续发展进行评价,并对2004—2020年湖北省的13项指标具体数据进行纵向比较,量化结果与湖北省农业机械化发展现状基本一致,所提方法具有可行性。分析结果表明,经济因素是目前农业机械化可持续发展最重要的影响因素,环境因素日益成为值得着重关注的因素,农机工业和科技的发展是将来需要重点考虑的问题。最后根据评价结果提出相应政策建议,为湖北省农业机械化可持续发展提供指导。
基金supported by Chinese Academy of Sciences (KZCX2-YW-219, 100 Tal-ents Program)Ministry of Science and Technology of China (2009CB421406)
文摘The capability of an improved Dynamic Global Vegetation Model (DGVM) in reproducing the impact of climate on the terrestrial ecosystem is evaluated. The new model incorporates the Community Land Model- DGVM (CLM3.0-DGVM) with a submodel for temperate and boreal shrubs, as well as other revisions such as the "two-leaf" scheme for photosynthesis and the definition of fractional coverage of plant functional types (PFTs). Results show that the revised model may correctly reproduce the global distribution of temperate and boreal shrubs, and improves the model performance with more realistic distribution of di?erent vege- tation types. The revised model also correctly reproduces the zonal distributions of vegetation types. In reproducing the dependence of the vegetation distribution on climate conditions, the model shows that the dominant regions for trees, grasses, shrubs, and bare soil are clearly separated by a climate index derived from mean annual precipitation and temperature, in good agreement with the CLM4 surface data. The dominant plant functional type mapping to a two dimensional parameter space of mean annual temperature and precipitation also qualitatively agrees with the results from observations and theoretical ecology studies.
基金financial support of the Italian Ministry of Education and Research(through the PRIN Project N.2015RJARX7)Sapienza University of Rome(through the Sapienza Awards no.6H15XNFS)the Lazio Region(through the Project FILAS-RU-2014-1186)
文摘This paper proposes a holistic framework for the development of models for the assessment of research activities and their impacts. It distinguishes three dimensions, including in an original way, data as a main dimension, together with theory and methodology. Each dimension of the framework is further characterized by three main building blocks: education, research, and innovation (theory); efficiency, effectiveness, and impact (methodology); and availability, interoperability, and "unit-free" property (data). The different dimensions and their nine constituent building blocks are attributes of an overarching concept, denoted as "quality." Three additional quality attributes are identified as implementation factors (tailorability, transparency, and openness) and three "enabling" conditions (convergence, mixed methods, and knowledge infrastructures) complete the fi-amework. A framework is required to develop models of metrics. Models of metrics are necessary to assess the meaning, validity, and robustness of metrics. The proposed framework can be a useful reference for the development of the ethics of research evaluation. It can act as a common denominator for different analytical levels and relevant aspects and is able to embrace many different and heterogeneous streams of literature. Directions for future research are provided.