Several studies have shown a positive relationship between high quality outdoor environments and users’health.Education of agricultural professionals also demands high quality outdoor environments in order to promote...Several studies have shown a positive relationship between high quality outdoor environments and users’health.Education of agricultural professionals also demands high quality outdoor environments in order to promote students’wellbeing,which in turn supports scientific researches.This study analyzed relationship between students’actual uses and campus outdoor environments,identified what environmental characteristics that students prefered,how they used and why they participated in the outdoor activities.The results could be used as guidance of campus design and management.Investigation of three universities in Harbin provided 686 valid questionnaires.The results suggested that health awareness effectively promoted students’use frequencies of outdoor environments.Environment with"natural"and"cultural"characteristics,especially undulating landform,vibrant plants and landmarks in a serpentins design style attracted more uses.Female students showed more preferences on social interaction activities than males.Students who had good economic consumption levels and participated in outdoor activities frequntly in childhood prefered to join all the kinds of activities after university enrollment.展开更多
As computer simulation increasingly supports engine er ing design and manufacture, the requirement for a computer software environment providing an integration platform for computational engineering software increas e...As computer simulation increasingly supports engine er ing design and manufacture, the requirement for a computer software environment providing an integration platform for computational engineering software increas es. A key component of an integrated environment is the use of computational eng ineering to assist and support solutions for complex design. Computer methods fo r structural, flow and thermal analysis are well developed and have been used in design for many years. Many software packages are now available which provi de an advanced capability. However, they are not designed for modelling of powde r forming processes. This paper describes the powder compaction software (PCS_SU T), which is designed for pre- and post-processing for computational simulatio n of the process compaction of powder. In the PCS_SUT software, the adaptive analysis of transient metal powder forming process is simulated by the finite element method based on deformation theories . The error estimates and adaptive remeshing schemes are applied for updated co -ordinate analysis. A generalized Newmark scheme is used for the time domain di scretization and the final nonlinear equations are solved by a Newton-Raphson p rocedure. An incremental elasto-plastic material model is used to simulate the compaction process. To describe the constitutive model of nonlinear behaviour of powder materials, a combination of Mohr-Coulomb and elliptical yield cap model is applied. This model reflects the yielding, frictional and densification char acteristics of powder along with strain and geometrical hardening which occurs d uring the compaction process. A hardening rule is used to define the dependence of the yield surface on the degree of plastic straining. A plasticity theory for friction is employed in the treatment of the powder-tooling interface. The inv olvement of two different materials, which have contact and relative movement in relation to each other, must be considered. A special formulation for friction modelling is coupled with a material formulation. The interface behaviour betwee n the die and the powder is modelled by using an interface element mesh. In the present paper, we have demonstrated pre- and post-processor finite elem ent software, written in Visual Basic, to generate the graphical model and visua lly display the computed results. The software consist of three main part: · Pre-processor: It is used to create the model, generate an app ropriate finite element grid, apply the appropriate boundary conditions, and vie w the total model. The geometric model can be used to associate the mesh with th e physical attributes such as element properties, material properties, or loads and boundary conditions. · Analysis: It can deal with two-dimensional and axi-symmetric applications for linear and non-linear behaviour of material in static and dyna mic analyses. Both triangular and quadrilateral elements are available in the e lement library, including 3-noded, 6-noded and 7-noded (T6B1) triangles and 4 -noded, 8-noded and 9-noded quadrilaterals. The direct implicit algorithm bas ed on the generalized Newmark scheme is used for the time integration and an aut omatic time step control facility is provided. For non-linear iteration, choice s among fully or modified Newton-Raphson method and quasi-Newton method, using the initial stiffness method, Davidon inverse method or BFGS inverse method, ar e possible. · Post-processor: It provides visualization of the computed resu lts, when the finite element model and analysis have been completed. Post-proce ssing is vital to allow the appropriate interpretation of the completed results of the finite element analysis. It provides the visual means to interpret the va st amounts of computed results generated. Finally, the powder behaviour during the compaction of a multi-level component is numerically simulated by the PCS_SUT software, as shown in Fig.1. The predict ive compaction forces at different displacements are computed and compared with the available experimental展开更多
The Law of Soil and Water Conservation entitles the administrations of water resources at various level to monitor ecological environment and to proclaim status of soil erosion periodically.Monitoring units of soil an...The Law of Soil and Water Conservation entitles the administrations of water resources at various level to monitor ecological environment and to proclaim status of soil erosion periodically.Monitoring units of soil and water conservation approved by local governments are obliged to undertake this work.How to develop a monitoring program needs an overall and long-term concept.Particularity and objectives of ecological environment monitoring was discussed. Monitoring at provincial level may be divided into two levels:province-wide and at project level. Those indicators meaningful,sensitive to any disturbances,and simple to measure may be selected to test status of ecosystem stability and health.It makes sense to have an integrated sampling design,to set up permanent observation plots and to collect data, so that to have a relative timely,accurate understanding of ecosystems in the province.A program regarding sampling design,field methods, data analysis,documentation and implementation was detailed.展开更多
【目的】步行空间作为城市公共空间的重要组成部分,其安全品质是构建宜步行城市的重要基础,直接影响居民出行意愿和步行体验。【方法】以Web of Science和CNKI数据库1975—2022年步行安全相关文献为研究对象,通过计量分析与人工检阅相...【目的】步行空间作为城市公共空间的重要组成部分,其安全品质是构建宜步行城市的重要基础,直接影响居民出行意愿和步行体验。【方法】以Web of Science和CNKI数据库1975—2022年步行安全相关文献为研究对象,通过计量分析与人工检阅相结合的方式,分析当前与步行安全及其环境影响要素研究相关文献的分布特征,梳理研究脉络,分析研究热点。【结果】1)步行环境安全性与行人安全感知主导步行安全研究发展方向,建成环境对行人安全事故以及行人安全感知的影响成为研究者关注的重点,新数据和新技术为分析步行安全环境核心影响要素提供支持。2)在城市建成环境中,街区、街道和交叉口等不同层级的环境要素,从活动安全、交通安全和防卫安全3个维度,对行人步行安全产生重要影响。3)研究对象从客观的建成环境拓展到主观的心理感知,研究内容从个案的安全事故分析拓展到综合的城市环境建设,研究方法方面多维度集成研究逐步替代单专业技术分析。【结论】揭示了步行安全与环境影响要素研究的发展方向、主要脉络以及关注重点,凸显多层级建成环境要素对步行安全事故和行人安全感知的重要影响,为开展步行安全环境实证研究提供理论支持。未来研究中,需对步行安全性和行人安全感知进行协同思考,推进相关研究技术的适用性,关注新兴交通技术发展对步行环境安全品质的影响。展开更多
针对航空装备在寿命周期内不只经历一个任务阶段,而当前加速寿命试验(accelerated life test,ALT)优化设计大多仅关注单一任务阶段的情况,提出一种综合环境下两阶段ALT优化设计方法。该方法采用拉丁超立方设计(Latin hypercube design,L...针对航空装备在寿命周期内不只经历一个任务阶段,而当前加速寿命试验(accelerated life test,ALT)优化设计大多仅关注单一任务阶段的情况,提出一种综合环境下两阶段ALT优化设计方法。该方法采用拉丁超立方设计(Latin hypercube design,LHD)确定两阶段试验整体的应力水平组合方式,解决前后阶段应力水平的组合问题;以两阶段试验中产品正常应力水平下P阶分位寿命估计的渐近方差之和最小为优化目标,构建优化设计的数学模型,解决前后阶段的样本分配问题。算例分析表明两阶段ALT优化设计方法的预测精度优于传统方法,参数敏感性分析表明该方法确定的最优试验方案具有一定的稳健性。该方法为实际工程中多任务阶段产品的ALT优化设计提供了一种新思路。展开更多
基金Supported by the Natural Fund Project of Heilongjiang Province(E2018009)Heilongjiang Higher Education Teaching Reform Project(SJGY20170111)Great Northern Agricultural Scholar Program(SBJY 17024)。
文摘Several studies have shown a positive relationship between high quality outdoor environments and users’health.Education of agricultural professionals also demands high quality outdoor environments in order to promote students’wellbeing,which in turn supports scientific researches.This study analyzed relationship between students’actual uses and campus outdoor environments,identified what environmental characteristics that students prefered,how they used and why they participated in the outdoor activities.The results could be used as guidance of campus design and management.Investigation of three universities in Harbin provided 686 valid questionnaires.The results suggested that health awareness effectively promoted students’use frequencies of outdoor environments.Environment with"natural"and"cultural"characteristics,especially undulating landform,vibrant plants and landmarks in a serpentins design style attracted more uses.Female students showed more preferences on social interaction activities than males.Students who had good economic consumption levels and participated in outdoor activities frequntly in childhood prefered to join all the kinds of activities after university enrollment.
文摘As computer simulation increasingly supports engine er ing design and manufacture, the requirement for a computer software environment providing an integration platform for computational engineering software increas es. A key component of an integrated environment is the use of computational eng ineering to assist and support solutions for complex design. Computer methods fo r structural, flow and thermal analysis are well developed and have been used in design for many years. Many software packages are now available which provi de an advanced capability. However, they are not designed for modelling of powde r forming processes. This paper describes the powder compaction software (PCS_SU T), which is designed for pre- and post-processing for computational simulatio n of the process compaction of powder. In the PCS_SUT software, the adaptive analysis of transient metal powder forming process is simulated by the finite element method based on deformation theories . The error estimates and adaptive remeshing schemes are applied for updated co -ordinate analysis. A generalized Newmark scheme is used for the time domain di scretization and the final nonlinear equations are solved by a Newton-Raphson p rocedure. An incremental elasto-plastic material model is used to simulate the compaction process. To describe the constitutive model of nonlinear behaviour of powder materials, a combination of Mohr-Coulomb and elliptical yield cap model is applied. This model reflects the yielding, frictional and densification char acteristics of powder along with strain and geometrical hardening which occurs d uring the compaction process. A hardening rule is used to define the dependence of the yield surface on the degree of plastic straining. A plasticity theory for friction is employed in the treatment of the powder-tooling interface. The inv olvement of two different materials, which have contact and relative movement in relation to each other, must be considered. A special formulation for friction modelling is coupled with a material formulation. The interface behaviour betwee n the die and the powder is modelled by using an interface element mesh. In the present paper, we have demonstrated pre- and post-processor finite elem ent software, written in Visual Basic, to generate the graphical model and visua lly display the computed results. The software consist of three main part: · Pre-processor: It is used to create the model, generate an app ropriate finite element grid, apply the appropriate boundary conditions, and vie w the total model. The geometric model can be used to associate the mesh with th e physical attributes such as element properties, material properties, or loads and boundary conditions. · Analysis: It can deal with two-dimensional and axi-symmetric applications for linear and non-linear behaviour of material in static and dyna mic analyses. Both triangular and quadrilateral elements are available in the e lement library, including 3-noded, 6-noded and 7-noded (T6B1) triangles and 4 -noded, 8-noded and 9-noded quadrilaterals. The direct implicit algorithm bas ed on the generalized Newmark scheme is used for the time integration and an aut omatic time step control facility is provided. For non-linear iteration, choice s among fully or modified Newton-Raphson method and quasi-Newton method, using the initial stiffness method, Davidon inverse method or BFGS inverse method, ar e possible. · Post-processor: It provides visualization of the computed resu lts, when the finite element model and analysis have been completed. Post-proce ssing is vital to allow the appropriate interpretation of the completed results of the finite element analysis. It provides the visual means to interpret the va st amounts of computed results generated. Finally, the powder behaviour during the compaction of a multi-level component is numerically simulated by the PCS_SUT software, as shown in Fig.1. The predict ive compaction forces at different displacements are computed and compared with the available experimental
基金the Scientific Research Foundation for the Returned Overseas Chinese ScholarsState Education Ministry"Response ofForest Regeneration in Alpine Region to Global Climate Change"( 2 0 0 2 -2 0 0 4) Shaanxi Provincial Foreign Expert Bu-reau"Trial on Vegetation Rehabilitation in Degraded Mountain Ecosystem"( 2 0 0 2 -2 0 0 3 )
文摘The Law of Soil and Water Conservation entitles the administrations of water resources at various level to monitor ecological environment and to proclaim status of soil erosion periodically.Monitoring units of soil and water conservation approved by local governments are obliged to undertake this work.How to develop a monitoring program needs an overall and long-term concept.Particularity and objectives of ecological environment monitoring was discussed. Monitoring at provincial level may be divided into two levels:province-wide and at project level. Those indicators meaningful,sensitive to any disturbances,and simple to measure may be selected to test status of ecosystem stability and health.It makes sense to have an integrated sampling design,to set up permanent observation plots and to collect data, so that to have a relative timely,accurate understanding of ecosystems in the province.A program regarding sampling design,field methods, data analysis,documentation and implementation was detailed.
文摘【目的】步行空间作为城市公共空间的重要组成部分,其安全品质是构建宜步行城市的重要基础,直接影响居民出行意愿和步行体验。【方法】以Web of Science和CNKI数据库1975—2022年步行安全相关文献为研究对象,通过计量分析与人工检阅相结合的方式,分析当前与步行安全及其环境影响要素研究相关文献的分布特征,梳理研究脉络,分析研究热点。【结果】1)步行环境安全性与行人安全感知主导步行安全研究发展方向,建成环境对行人安全事故以及行人安全感知的影响成为研究者关注的重点,新数据和新技术为分析步行安全环境核心影响要素提供支持。2)在城市建成环境中,街区、街道和交叉口等不同层级的环境要素,从活动安全、交通安全和防卫安全3个维度,对行人步行安全产生重要影响。3)研究对象从客观的建成环境拓展到主观的心理感知,研究内容从个案的安全事故分析拓展到综合的城市环境建设,研究方法方面多维度集成研究逐步替代单专业技术分析。【结论】揭示了步行安全与环境影响要素研究的发展方向、主要脉络以及关注重点,凸显多层级建成环境要素对步行安全事故和行人安全感知的重要影响,为开展步行安全环境实证研究提供理论支持。未来研究中,需对步行安全性和行人安全感知进行协同思考,推进相关研究技术的适用性,关注新兴交通技术发展对步行环境安全品质的影响。
文摘针对航空装备在寿命周期内不只经历一个任务阶段,而当前加速寿命试验(accelerated life test,ALT)优化设计大多仅关注单一任务阶段的情况,提出一种综合环境下两阶段ALT优化设计方法。该方法采用拉丁超立方设计(Latin hypercube design,LHD)确定两阶段试验整体的应力水平组合方式,解决前后阶段应力水平的组合问题;以两阶段试验中产品正常应力水平下P阶分位寿命估计的渐近方差之和最小为优化目标,构建优化设计的数学模型,解决前后阶段的样本分配问题。算例分析表明两阶段ALT优化设计方法的预测精度优于传统方法,参数敏感性分析表明该方法确定的最优试验方案具有一定的稳健性。该方法为实际工程中多任务阶段产品的ALT优化设计提供了一种新思路。
