Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of ...Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.展开更多
Intergroup conflicts occupy a special place in the interaction of social groups and of necessity form the basic building blocks for the integration of previously fragmented groups. The Western Niger delta obviously ha...Intergroup conflicts occupy a special place in the interaction of social groups and of necessity form the basic building blocks for the integration of previously fragmented groups. The Western Niger delta obviously has since been a theatre of socio-political conflicts. Viewed from the contemporary clime, there is a lacuna in the formulation of theories and concepts in understanding and explaining the nature and pattern of intergroup relations in the region from the pre-colonial period. This work therefore attempts an exploratory analysis of some theories and concepts of intergroup relations in the Western Niger Delta of Nigeria using the historical approach with the use of secondary source materials. The paper concludes that the relation among the diverse ethnic groups in Nigeria, especially the Western Niger Delta, may not have been as intense, or as hostile as it has become since the attainment of independence in 1960. This paper no doubt is essential for the understanding and tackling of the problem of intergroup relations and conflict in the region in particular and Nigeria at large.展开更多
Stacking nanoscale-building blocks into onedimensional(1D)assemblies with collective physical properties is a frontier in designing materials.However,the formation of 1D arrays using weak magnetic fields and an in-dep...Stacking nanoscale-building blocks into onedimensional(1D)assemblies with collective physical properties is a frontier in designing materials.However,the formation of 1D arrays using weak magnetic fields and an in-depth understanding of their magnetic properties remain challenging.Here,low-dimensional assemblies of iron oxide nanocubes with a disordered arrangement are fabricated at the diethylene-glycol/air interface in the presence of assembly fields(0/1/3/5/30/50 mT).Ring-shaped assemblies gradually transform as the assembly field increases from 0 to 50 mT,first to a porous network consisting of elongated assemblies and then to an aligned array of filaments,in which the aligned filaments are formed when the assembly field is≥3 mT and duration t>14 min.Spin-glass characteristics and static(dynamic)anisotropy factors~2(3)are achieved by tuning the strength of the assembly field.In the presence of a relatively weak assembly field,the interplay between dipolar interactions and disorder with respect to magnetic easy axis alignment leads to spin-glass characteristics.The alignment of the magnetic easy axes and the strength of the dipolar interactions increase with increasing assembly field,resulting in the disappearance of spin-glass characteristics and enhancement of the magnetic anisotropy.This study presents a strategy for obtaining magnetic assemblies with spin-glass behavior and controllable anisotropy while shedding light on the magnetic interactions of low-dimensional assemblies.展开更多
基金Supported by the China Postdoctoral Science Foundation(2014M552195)the State Key Laboratory Foundation of Subtropical Building,South China University of Technology(2013ZC13)the Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization,South China University of Technology(2013A061401005)
文摘Auto cascade refrigeration(ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.
文摘Intergroup conflicts occupy a special place in the interaction of social groups and of necessity form the basic building blocks for the integration of previously fragmented groups. The Western Niger delta obviously has since been a theatre of socio-political conflicts. Viewed from the contemporary clime, there is a lacuna in the formulation of theories and concepts in understanding and explaining the nature and pattern of intergroup relations in the region from the pre-colonial period. This work therefore attempts an exploratory analysis of some theories and concepts of intergroup relations in the Western Niger Delta of Nigeria using the historical approach with the use of secondary source materials. The paper concludes that the relation among the diverse ethnic groups in Nigeria, especially the Western Niger Delta, may not have been as intense, or as hostile as it has become since the attainment of independence in 1960. This paper no doubt is essential for the understanding and tackling of the problem of intergroup relations and conflict in the region in particular and Nigeria at large.
基金financially supported by Shenzhen Science and Technology Project(CYJ20180507182246321 and JCYJ20200109105825504)Swedish Research Council VR(2016-06959)financial support from the Doctoral Joint-Training Program of China Scholarship Council.
文摘Stacking nanoscale-building blocks into onedimensional(1D)assemblies with collective physical properties is a frontier in designing materials.However,the formation of 1D arrays using weak magnetic fields and an in-depth understanding of their magnetic properties remain challenging.Here,low-dimensional assemblies of iron oxide nanocubes with a disordered arrangement are fabricated at the diethylene-glycol/air interface in the presence of assembly fields(0/1/3/5/30/50 mT).Ring-shaped assemblies gradually transform as the assembly field increases from 0 to 50 mT,first to a porous network consisting of elongated assemblies and then to an aligned array of filaments,in which the aligned filaments are formed when the assembly field is≥3 mT and duration t>14 min.Spin-glass characteristics and static(dynamic)anisotropy factors~2(3)are achieved by tuning the strength of the assembly field.In the presence of a relatively weak assembly field,the interplay between dipolar interactions and disorder with respect to magnetic easy axis alignment leads to spin-glass characteristics.The alignment of the magnetic easy axes and the strength of the dipolar interactions increase with increasing assembly field,resulting in the disappearance of spin-glass characteristics and enhancement of the magnetic anisotropy.This study presents a strategy for obtaining magnetic assemblies with spin-glass behavior and controllable anisotropy while shedding light on the magnetic interactions of low-dimensional assemblies.
