Hester-Dendy (HD) multi-plate samplers have been widely used by state and federal government agencies for bioassessment of water quality through use of macroinvertebrate community data. To help guide remediation and r...Hester-Dendy (HD) multi-plate samplers have been widely used by state and federal government agencies for bioassessment of water quality through use of macroinvertebrate community data. To help guide remediation and restoration efforts at the Niagara River Great Lakes Area of Concern site, a multi-agency study was conducted in 2014 to assess the contribution of seven major urban tributaries on the US side of the river toward the impairment of the Niagara River. As part of this study, macroinvertebrate communities were sampled using two co-located versions of HD samplers: one version used by the New York State Department of Environmental Conservation (NYSDEC) and another by the US Environmental Protection Agency Office of Research and Development. Samplers were deployed in tributaries in highly developed watersheds with high percent impervious surface. The two sampling methods varied in terms of number and size of plates, between-plate spacing, and deployment method. Comparison of the similarity/grouping of communities with multivariate ordination techniques, Nonmetric Multidimensional Scaling and Multi-Response Permutation Procedure, showed that both methods were able to detect differences in communities at stations, despite some grouping by month and method. The indices and metrics derived from the two HD methods were found to give comparable but not identical assessments of water quality. Despite their differences, the methods were robust with respect to water quality categories derived from indices used nationally (HBI) and by NY state (BAP). For the common richness metrics, total taxa and EPT richness, there was no statistical difference between means from 3 samplings. Some metrics, especially percent tolerant collector-gatherer individuals, did show significant differences at certain stations. Indicator Species Analysis showed some taxa associated with each method. The observed community differences were thought mostly due to the difference in sampler deployment position. .展开更多
The purpose of this study is to verify an 1D multi-plate heat-transfer model estimating the temperature distribution on the interface between polymer electrolyte membrane and catalyst layer at cathode in single cell o...The purpose of this study is to verify an 1D multi-plate heat-transfer model estimating the temperature distribution on the interface between polymer electrolyte membrane and catalyst layer at cathode in single cell of polymer electrolyte fuel cell, which is named as reaction surface in this study, with a 3D numerical simulation model solving many governing equations on the coupling phenomena in the cell. The results from both models/simulations agreed well. The effects of initial operation temperature, flow rate, and relative humidity of supply gas on temperature distribution on the reaction surface were also investigated. It was found in both 1D and 3D simulations that, the temperature rise （i.e., Treact-Tini） of the reaction surface from initial operation temperature at 70℃ was higher than that at 80℃ irrespective of flow rate of supply gas. The effect of relative humidity of supply gas on Treact- Tini near the inlet of the cell was small. Compared to the previous studies conducted under the similar operation conditions, the Treact - Tini calculated by 1D multi-plate heat-transfer model in this study as well as numerical simulation using 3D model was reasonable.展开更多
Heat exchanger networks(HENs)in separated plants can be simultaneously synthesized through process streams directly or intermediate fluids indirectly.However,the direct and indirect methods are studied separately in m...Heat exchanger networks(HENs)in separated plants can be simultaneously synthesized through process streams directly or intermediate fluids indirectly.However,the direct and indirect methods are studied separately in most existing researches.As the result,conventional designs are probably suboptimal,because optimal solutions may call for hybrid approach wherein direct and indirect integration methods are used synchronously.To circumvent this drawback aforementioned,we propose in this research a novel methodology to synthesize multi-plant HENs considering both direct and indirect approaches.The methodology employs a novel superstructure covering most potential topologies for both interplant and intra-plant heat integration.We also take into account multiple kinds of intermediate fluids for indirect integration and this has not been fully addressed in previous research.A mixed-integer nonlinear programming(MINLP)is formulated to optimize multi-plant HENs involving indirect and direct methods.One example from existing literature and one industrial problem are solved to demonstrate the methodology’s capability.展开更多
Since the 1970s, the studies on the geography of enterprise have become increasingly concerned with the spatial evolution of an enterprises in the West developed countries. However, little attention has so far been g...Since the 1970s, the studies on the geography of enterprise have become increasingly concerned with the spatial evolution of an enterprises in the West developed countries. However, little attention has so far been given to the spatial evolution of an enterprise in China. With China's ongoing economy and political reforms, a number of fundamental changes of enterprise behavior have occurred. These changes have certainly important influences on the evolution of industrial location. Therefore, there is a need for examining the spatial evolution of an enterprise in China. The purpose of the paper is to review the mapjor models of both the growth,and associated spatial evolution of an enterprise, with an illustrative case study of the HeaVy Automobile Enterprise Group of China. The paper is organized by three parts. The first examines the spoilal groWth and location adjustment of multi-plant enterprise. The second reviews mapjor models of the spatial evolution of an enterprise. And the third analyzes the spatial evolution, over a period of time, of a representative sample of the Heavy Automobile Enterprise Group of China, and illustrates the findings with case studies. It is suggested that the models of spatial evolution of an enterprise would provide more evidence about micro-mechanism for evolution of micro- regional economic systems.展开更多
现代金属切削加工正向着高速、高精度和高效的方向发展,对刀具的性能有着越来越高的要求。利用表面技术对刀具表面进行改性,是提高刀具性能和寿命的有效途径。使用多弧离子镀膜技术在YG6硬质合金以及三刃立铣刀表面制备了Cr Al N/CrN/Cr...现代金属切削加工正向着高速、高精度和高效的方向发展,对刀具的性能有着越来越高的要求。利用表面技术对刀具表面进行改性,是提高刀具性能和寿命的有效途径。使用多弧离子镀膜技术在YG6硬质合金以及三刃立铣刀表面制备了Cr Al N/CrN/Cr、TiAlN/CrN/Cr、Cr Al N/TiAlN/CrN/Cr三组涂层,并对三种涂层的制备技术、微观结构与性能差异、及耐磨与切削寿命提高机制进行研究。X射线衍射分析表明,三种涂层均为面心立方结构,其中TiAlN涂层表现出(200)晶面择优取向,而CrAlN和Cr Al N/TiAlN涂层则表现出(111)面的择优取向。使用显微硬度计和划痕仪对涂层的显微硬度和结合力进行测试,结果表明Cr Al N/TiAlN多层涂层的显微硬度和膜基结合力分别为2651 HV和59.2 N,显著高于TiAlN和CrAlN涂层。采用高温摩擦试验机评价了三种涂层的摩擦学性能,结果表明Cr Al N/TiAlN多涂层的摩擦性能优于TiAlN涂层和CrAlN涂层,室温下其平均摩擦因数和磨损率分别为0.603和2.92×10^(-6)mm^(3)(N·m)^(-1)。当温度增加到400℃时,Cr Al N/TiAlN涂层的平均摩擦因数进一步降低为0.467,磨损率增加至1.31×10^(-5)mm^(3)(N·m)^(-1)。铣削试验结果显示,TiAlN涂层刀具、CrAlN涂层刀具和Cr Al N/TiAlN涂层刀具的铣削寿命相对于无涂层刀具分别提升了80%、140%和200%,被加工样件的表面粗糙度分别降低至462 nm、415 nm和402 nm。研究结果表明Cr Al N/TiAlN涂层在现代切削加工领域有着良好的应用潜力。展开更多
文摘Hester-Dendy (HD) multi-plate samplers have been widely used by state and federal government agencies for bioassessment of water quality through use of macroinvertebrate community data. To help guide remediation and restoration efforts at the Niagara River Great Lakes Area of Concern site, a multi-agency study was conducted in 2014 to assess the contribution of seven major urban tributaries on the US side of the river toward the impairment of the Niagara River. As part of this study, macroinvertebrate communities were sampled using two co-located versions of HD samplers: one version used by the New York State Department of Environmental Conservation (NYSDEC) and another by the US Environmental Protection Agency Office of Research and Development. Samplers were deployed in tributaries in highly developed watersheds with high percent impervious surface. The two sampling methods varied in terms of number and size of plates, between-plate spacing, and deployment method. Comparison of the similarity/grouping of communities with multivariate ordination techniques, Nonmetric Multidimensional Scaling and Multi-Response Permutation Procedure, showed that both methods were able to detect differences in communities at stations, despite some grouping by month and method. The indices and metrics derived from the two HD methods were found to give comparable but not identical assessments of water quality. Despite their differences, the methods were robust with respect to water quality categories derived from indices used nationally (HBI) and by NY state (BAP). For the common richness metrics, total taxa and EPT richness, there was no statistical difference between means from 3 samplings. Some metrics, especially percent tolerant collector-gatherer individuals, did show significant differences at certain stations. Indicator Species Analysis showed some taxa associated with each method. The observed community differences were thought mostly due to the difference in sampler deployment position. .
文摘The purpose of this study is to verify an 1D multi-plate heat-transfer model estimating the temperature distribution on the interface between polymer electrolyte membrane and catalyst layer at cathode in single cell of polymer electrolyte fuel cell, which is named as reaction surface in this study, with a 3D numerical simulation model solving many governing equations on the coupling phenomena in the cell. The results from both models/simulations agreed well. The effects of initial operation temperature, flow rate, and relative humidity of supply gas on temperature distribution on the reaction surface were also investigated. It was found in both 1D and 3D simulations that, the temperature rise （i.e., Treact-Tini） of the reaction surface from initial operation temperature at 70℃ was higher than that at 80℃ irrespective of flow rate of supply gas. The effect of relative humidity of supply gas on Treact- Tini near the inlet of the cell was small. Compared to the previous studies conducted under the similar operation conditions, the Treact - Tini calculated by 1D multi-plate heat-transfer model in this study as well as numerical simulation using 3D model was reasonable.
基金Financial supports from the National Natural Science Foundation of China(No.21476256)Science Foundation of China University of PetroleumBeijing(Nos.2462017BJB03&2462018BJC004)are gratefully acknowledged.
文摘Heat exchanger networks(HENs)in separated plants can be simultaneously synthesized through process streams directly or intermediate fluids indirectly.However,the direct and indirect methods are studied separately in most existing researches.As the result,conventional designs are probably suboptimal,because optimal solutions may call for hybrid approach wherein direct and indirect integration methods are used synchronously.To circumvent this drawback aforementioned,we propose in this research a novel methodology to synthesize multi-plant HENs considering both direct and indirect approaches.The methodology employs a novel superstructure covering most potential topologies for both interplant and intra-plant heat integration.We also take into account multiple kinds of intermediate fluids for indirect integration and this has not been fully addressed in previous research.A mixed-integer nonlinear programming(MINLP)is formulated to optimize multi-plant HENs involving indirect and direct methods.One example from existing literature and one industrial problem are solved to demonstrate the methodology’s capability.
文摘Since the 1970s, the studies on the geography of enterprise have become increasingly concerned with the spatial evolution of an enterprises in the West developed countries. However, little attention has so far been given to the spatial evolution of an enterprise in China. With China's ongoing economy and political reforms, a number of fundamental changes of enterprise behavior have occurred. These changes have certainly important influences on the evolution of industrial location. Therefore, there is a need for examining the spatial evolution of an enterprise in China. The purpose of the paper is to review the mapjor models of both the growth,and associated spatial evolution of an enterprise, with an illustrative case study of the HeaVy Automobile Enterprise Group of China. The paper is organized by three parts. The first examines the spoilal groWth and location adjustment of multi-plant enterprise. The second reviews mapjor models of the spatial evolution of an enterprise. And the third analyzes the spatial evolution, over a period of time, of a representative sample of the Heavy Automobile Enterprise Group of China, and illustrates the findings with case studies. It is suggested that the models of spatial evolution of an enterprise would provide more evidence about micro-mechanism for evolution of micro- regional economic systems.
文摘现代金属切削加工正向着高速、高精度和高效的方向发展,对刀具的性能有着越来越高的要求。利用表面技术对刀具表面进行改性,是提高刀具性能和寿命的有效途径。使用多弧离子镀膜技术在YG6硬质合金以及三刃立铣刀表面制备了Cr Al N/CrN/Cr、TiAlN/CrN/Cr、Cr Al N/TiAlN/CrN/Cr三组涂层,并对三种涂层的制备技术、微观结构与性能差异、及耐磨与切削寿命提高机制进行研究。X射线衍射分析表明,三种涂层均为面心立方结构,其中TiAlN涂层表现出(200)晶面择优取向,而CrAlN和Cr Al N/TiAlN涂层则表现出(111)面的择优取向。使用显微硬度计和划痕仪对涂层的显微硬度和结合力进行测试,结果表明Cr Al N/TiAlN多层涂层的显微硬度和膜基结合力分别为2651 HV和59.2 N,显著高于TiAlN和CrAlN涂层。采用高温摩擦试验机评价了三种涂层的摩擦学性能,结果表明Cr Al N/TiAlN多涂层的摩擦性能优于TiAlN涂层和CrAlN涂层,室温下其平均摩擦因数和磨损率分别为0.603和2.92×10^(-6)mm^(3)(N·m)^(-1)。当温度增加到400℃时,Cr Al N/TiAlN涂层的平均摩擦因数进一步降低为0.467,磨损率增加至1.31×10^(-5)mm^(3)(N·m)^(-1)。铣削试验结果显示,TiAlN涂层刀具、CrAlN涂层刀具和Cr Al N/TiAlN涂层刀具的铣削寿命相对于无涂层刀具分别提升了80%、140%和200%,被加工样件的表面粗糙度分别降低至462 nm、415 nm和402 nm。研究结果表明Cr Al N/TiAlN涂层在现代切削加工领域有着良好的应用潜力。
