To investigate the effects of thickness and grain size on mechanical and deformation properties of C5210 phosphor bronze thin sheets, samples with different grain sizes were obtained through annealing heat treatment a...To investigate the effects of thickness and grain size on mechanical and deformation properties of C5210 phosphor bronze thin sheets, samples with different grain sizes were obtained through annealing heat treatment at different temperatures; and then tensile tests of samples with different thicknesses and grain sizes were conducted at room temperature. The results show that yield strength increases with decreasing thickness from 800 to 50 μm, but work hardening exponent and total elongation decrease, and a modified model was proposed to describe the relation between yield strength and thickness; yield strength decreases as the grain size increases, but work hardening exponent shows an increasing trend, total elongation increases to a peak and then decreases. Fracture morphology of tensile specimens was observed by SEM, which indicates that all tensile specimens are ductile fracture. The dimple intensity increases as the specimen thickness increases but reduces with the specimen grain size increasing.展开更多
This research sought to improve the properties of SAC305 solder joints by the addition of 1 and 2 wt.%Bi.The effects of bismuth doping on the microstructure,thermal properties,and mechanical performance of the SAC305−...This research sought to improve the properties of SAC305 solder joints by the addition of 1 and 2 wt.%Bi.The effects of bismuth doping on the microstructure,thermal properties,and mechanical performance of the SAC305−xBiCu solder joints were investigated.Bi-doping modified the microstructure of the solder joints by refining the primaryβ-Sn and eutectic phases.Bi-doping below 2 wt.%dissolved in theβ-Sn matrix and formed a solid solution,whereas Bi additions equal to or greater than 2 wt.%formed Bi precipitates in theβ-Sn matrix.Solid solution strengthening and precipitation strengthening mechanisms in theβ-Sn matrix increased the ultimate tensile strength and microhardness of the alloy from 35.7 MPa and 12.6 HV to 55.3 MPa and 20.8 HV,respectively,but elongation decreased from 24.6%to 16.1%.The fracture surface of a solder joint containing 2 wt.%Bi was typical of a brittle failure rather than a ductile failure.The interfacial layer of all solder joints comprised two parallel IMC layers:a layer of Cu6Sn5 and a layer of Cu3Sn.The interfacial layer was thinner and the shear strength was greater in SAC305−xBiCu joints than in SAC305Cu solder joints.Therefore,small addition of Bi refined microstructure,reduced melting temperature and improved the mechanical performance of SAC305Cu solder joints.展开更多
An improved spherical, movable transfer skirt for autonomous submersibles has been devised. It was designed to permit the transfer of equipment and personnel from a submersible to the pressure chamber of an oil storag...An improved spherical, movable transfer skirt for autonomous submersibles has been devised. It was designed to permit the transfer of equipment and personnel from a submersible to the pressure chamber of an oil storage sea-bed structure. It also allowed mating at large vertical angles while the submersible remained horizontal. Seal failure modes and procedures for analyzing the sealing ability of the mating flange of the hull transfer skirt were thoroughly analyzed using conservative estimation methods. In the analysis, sea currents and mating angles were considered. Results showed that when considering the effects of currents, spherical radius and mating angle, their influence on seal ring failure should be considered first. The critical mating depth for a seal ring failure was larger than for either sliding or rotational failure modes. The critical mating depth can be used to determine the mating method of the submersible. The analytical procedures and results can be used as a reference for the design of spherical hull transfer skirts.展开更多
Practical teaching is an important way to improve the capability of NCO students, trader the environment of combating, in order to improve the combat effectiveness of close to the war as the fundamental task of the te...Practical teaching is an important way to improve the capability of NCO students, trader the environment of combating, in order to improve the combat effectiveness of close to the war as the fundamental task of the teaching activities. Carry out the practical teaching is the objective requirement of cultivating high quality personnel, scientific and promote practical teaching is the embodiment of practicing the goal of a strong army NCO academies. In the face of the new situation and mission, how to carry out combat Sergeant college teaching, enhance the practical teaching level, training with the ability to win the qualified personnel in the future battlefield, becomes suspends in front of us to explore and solve the problem.展开更多
This article explored the definition, dimensions, and building mechanisms of drug regulatory capabilities（DRC） and their relationship with regulatory performance. Based on the theories on organizational capability a...This article explored the definition, dimensions, and building mechanisms of drug regulatory capabilities（DRC） and their relationship with regulatory performance. Based on the theories on organizational capability and their application in public sector, interviews with officers from drug regulatory agencies and analysis of its three determinations, the DRC was defined as the follows： a learned pattern through which the drug regulatory agencies acquire, reconstruct and utilize organizational resources to protect and advance public health. DRC can be divided into different dimensions and structured as the basic capabilities and functional capabilities. This research also introduced three learning mechanisms for DRC construction, which include learning by doing, organizational learning, and exploratory learning. Finally, a qualitative case study of drug application and approval in China was conducted to explore the relationship between regulatory capabilities and performance.展开更多
文摘To investigate the effects of thickness and grain size on mechanical and deformation properties of C5210 phosphor bronze thin sheets, samples with different grain sizes were obtained through annealing heat treatment at different temperatures; and then tensile tests of samples with different thicknesses and grain sizes were conducted at room temperature. The results show that yield strength increases with decreasing thickness from 800 to 50 μm, but work hardening exponent and total elongation decrease, and a modified model was proposed to describe the relation between yield strength and thickness; yield strength decreases as the grain size increases, but work hardening exponent shows an increasing trend, total elongation increases to a peak and then decreases. Fracture morphology of tensile specimens was observed by SEM, which indicates that all tensile specimens are ductile fracture. The dimple intensity increases as the specimen thickness increases but reduces with the specimen grain size increasing.
文摘This research sought to improve the properties of SAC305 solder joints by the addition of 1 and 2 wt.%Bi.The effects of bismuth doping on the microstructure,thermal properties,and mechanical performance of the SAC305−xBiCu solder joints were investigated.Bi-doping modified the microstructure of the solder joints by refining the primaryβ-Sn and eutectic phases.Bi-doping below 2 wt.%dissolved in theβ-Sn matrix and formed a solid solution,whereas Bi additions equal to or greater than 2 wt.%formed Bi precipitates in theβ-Sn matrix.Solid solution strengthening and precipitation strengthening mechanisms in theβ-Sn matrix increased the ultimate tensile strength and microhardness of the alloy from 35.7 MPa and 12.6 HV to 55.3 MPa and 20.8 HV,respectively,but elongation decreased from 24.6%to 16.1%.The fracture surface of a solder joint containing 2 wt.%Bi was typical of a brittle failure rather than a ductile failure.The interfacial layer of all solder joints comprised two parallel IMC layers:a layer of Cu6Sn5 and a layer of Cu3Sn.The interfacial layer was thinner and the shear strength was greater in SAC305−xBiCu joints than in SAC305Cu solder joints.Therefore,small addition of Bi refined microstructure,reduced melting temperature and improved the mechanical performance of SAC305Cu solder joints.
文摘An improved spherical, movable transfer skirt for autonomous submersibles has been devised. It was designed to permit the transfer of equipment and personnel from a submersible to the pressure chamber of an oil storage sea-bed structure. It also allowed mating at large vertical angles while the submersible remained horizontal. Seal failure modes and procedures for analyzing the sealing ability of the mating flange of the hull transfer skirt were thoroughly analyzed using conservative estimation methods. In the analysis, sea currents and mating angles were considered. Results showed that when considering the effects of currents, spherical radius and mating angle, their influence on seal ring failure should be considered first. The critical mating depth for a seal ring failure was larger than for either sliding or rotational failure modes. The critical mating depth can be used to determine the mating method of the submersible. The analytical procedures and results can be used as a reference for the design of spherical hull transfer skirts.
文摘Practical teaching is an important way to improve the capability of NCO students, trader the environment of combating, in order to improve the combat effectiveness of close to the war as the fundamental task of the teaching activities. Carry out the practical teaching is the objective requirement of cultivating high quality personnel, scientific and promote practical teaching is the embodiment of practicing the goal of a strong army NCO academies. In the face of the new situation and mission, how to carry out combat Sergeant college teaching, enhance the practical teaching level, training with the ability to win the qualified personnel in the future battlefield, becomes suspends in front of us to explore and solve the problem.
文摘This article explored the definition, dimensions, and building mechanisms of drug regulatory capabilities（DRC） and their relationship with regulatory performance. Based on the theories on organizational capability and their application in public sector, interviews with officers from drug regulatory agencies and analysis of its three determinations, the DRC was defined as the follows： a learned pattern through which the drug regulatory agencies acquire, reconstruct and utilize organizational resources to protect and advance public health. DRC can be divided into different dimensions and structured as the basic capabilities and functional capabilities. This research also introduced three learning mechanisms for DRC construction, which include learning by doing, organizational learning, and exploratory learning. Finally, a qualitative case study of drug application and approval in China was conducted to explore the relationship between regulatory capabilities and performance.
