Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesi...Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesis environment.During the reaction,the feed molar ratio of the two precursors was carried over to the final products,which have a narrow size distribution with a mean size of approximately4nm.The catalytic activity for methanol oxidation reactions possible depends closely on the composition of as‐prepared PtPd alloy NPs,and the NPs with a Pt atomic percentage of approximately75%result in higher activity and stability with a mass specific activity that is7times greater than that of commercial Pt/C catalysts.The results indicate that through composition control,PtPd alloy NPs can improve the effectiveness of catalytic performance.展开更多
To study the influence of B4C particle size on the microstructure and damping capacities of(B_(4)C+Ti)/Mg composites,in situ reactive infiltration technique was utilized to prepare Mg-matrix composites.The microstruct...To study the influence of B4C particle size on the microstructure and damping capacities of(B_(4)C+Ti)/Mg composites,in situ reactive infiltration technique was utilized to prepare Mg-matrix composites.The microstructure,produced phases and damping capacities of the composites prepared with different particle size of B4C were characterized and analyzed.The results show that the reaction between B4C and Ti tends to be more complete when finer B_(4)C particle was used to prepare the composites.But the microstructure of the as-prepared composites is more homogenous when B4C and Ti have similar particle size.The strain-dependent damping capacities of(B_(4)C+Ti)/Mg composites improve gradually with the increase of strain amplitude,and composites prepared with coarser B4C particles tend to have higher damping capacities.The temperature-dependent damping capacities improve with increasing the measuring temperatures,and the kind of damping capacities of the composites prepared with 5mm B4C are inferior to those of coarser particles.The dominant damping mechanism for the strain-damping capacity is dislocation damping and plastic zone damping,while that for the temperature-damping capacity is interface damping or grain boundary damping.展开更多
The combined effects of equal channel angular pressing (ECAP) and subsequent heating to a semi-solid temperature on the microstructural characteristics of the 7075 aluminum alloy were investigated. The microstructure ...The combined effects of equal channel angular pressing (ECAP) and subsequent heating to a semi-solid temperature on the microstructural characteristics of the 7075 aluminum alloy were investigated. The microstructure is influenced by several parameters including the number of ECAP passes, ECAP route, consequent heating temperature, and holding time. The effects of these parameters on the microstructural characteristics including grain size and shape factor of the 7075 aluminum alloy were studied using experimental tests and Taguchi method. The results indicate that five-pass ECAP in route BA and subsequent isothermal holding at 630 °C for 15 min are more appropriate for achieving a semi-solid microstructure. The processing route and holding time have the highest impact on the grain size while the number of ECAP passes and heating temperature have the least impact on the grain size. Meanwhile, the shape factor is significantly influenced by the processing route, holding time and heating temperature while it is less influenced by the number of ECAP passes.展开更多
An integrated simulation of powder effects on particle temperature and microstructural evolution in laser directed energy deposition additive manufacturing process was carried out.The spatial distribution of the flyin...An integrated simulation of powder effects on particle temperature and microstructural evolution in laser directed energy deposition additive manufacturing process was carried out.The spatial distribution of the flying powder particles was simulated by the discrete element method to calculate the energy for the flying powder particles under the laser−particle interaction with electromagnetic wave analysis.Combined with the phase field method,the influence of particle size on the microstructural evolution was studied.The microstructural evolution is validated through comparison with experimental observation.Results indicate that the narrow particle size distribution is beneficial to obtaining a more uniform temperature distribution on the deposited layers and forming smaller equiaxed grains near the side surfaces of the sample.Appropriate powder particle size is beneficial to the conversion of the electromagnetic energy into heat.Particles with small size are recommended to form equiaxed grains and to improve product quality.Appropriate powder flow rate improves the laser energy efficiency,and higher powder flow rate leads to more uniform equiaxed grains on both sides of the cross-section.展开更多
The particle size distribution, heavy mineral constituents and rare earth elements (REE) characteristics of the Quaternary red clay of southern Anhui Province were studied to explore the origin of the clay. The resul...The particle size distribution, heavy mineral constituents and rare earth elements (REE) characteristics of the Quaternary red clay of southern Anhui Province were studied to explore the origin of the clay. The results showed that the clay had some properties of areolian deposits, which could be compared with those of the loess in North China; and its chondrite normalized curves of REE were similar to those of the Xiashu loess, implying that they shared the same origin. It was concluded in combination with the results reported by other researchers that the Quaternary red clay of southern Anhui Province originated from aeolian deposits, and this could reveal the cycles of warm and cold climates in the area during the Quaternary period.展开更多
AZ91Mg alloy was considered and friction stir processing(FSP)was adopted to achieve grain refinement to investigatethe effect of grain size and secondary phase on machining characteristics during drilling at various s...AZ91Mg alloy was considered and friction stir processing(FSP)was adopted to achieve grain refinement to investigatethe effect of grain size and secondary phase on machining characteristics during drilling at various speeds and feeds.Super saturatedAZ91Mg alloy was obtained after FSP and the grain refinement was achieved from(166.5±8.7)μm to(21.7±13.5)μm.Surprisingly,hardness reduced for FSP AZ91Mg alloy(88.95±6.1)compared with AZ91alloy(108.2±15.6),which was attributed to the reducedsecondary phase.However,the mean cutting force for FSP-treated(FSPed)AZ91Mg alloy was marginally increased.The edgedamage of the drilled holes was lower for FSPed AZ91Mg alloy compared with unprocessed AZ91Mg alloy.Hence,it can beunderstood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achievedin machining of AZ91Mg alloy.展开更多
The microstructural evolution and precipitation location of the secondary phase of an as-cast Ti-25 V-15 Cr-0.3 Si titanium alloy were investigated via isothermal compression experiments and heat treatment. The averag...The microstructural evolution and precipitation location of the secondary phase of an as-cast Ti-25 V-15 Cr-0.3 Si titanium alloy were investigated via isothermal compression experiments and heat treatment. The average aspect（length-to-width） ratio, average area and size of the grains at different heat treatment temperatures and holding time were analyzed and the effects of deformation and annealing time on the grain area and size were considered. It was found that the grain size was strongly influenced by the height reduction and holding time. Grain growth was significant when annealing time increased from 10 min to 2 h at 950 °C and height reduction of 30%; however, grain growth was minimal at annealing time between 2 and 4 h. Many dispersion particles were observed to form in continuous chains; the precipitation location was confirmed to be along initial grain boundaries, and the dispersion particles were identified to be Ti5 Si3 phase by TEM.展开更多
A vast number of researches and studies have been conducted on narcissism, since the term was used to explain a psychological phenomenon in 1898. However, the discussions about narcissists as organization members or l...A vast number of researches and studies have been conducted on narcissism, since the term was used to explain a psychological phenomenon in 1898. However, the discussions about narcissists as organization members or leaders have recently become a research topic in the organizational sciences. In this scope, the recent research on narcissism indicates that narcissistic leaders can either cause organizational tragedies or contribute to organizational success by their great vision. In addition to narcissism, another popular leadership feature is political skill which has attracted considerable attentions in recent years, and become one of the important topics of management studies. Moreover, political skill has been asserted to be a positive characteristic which is related to develop vision and team insight as well as to increase in members＇ trust and support; whereas narcissism has both harmful and beneficial effects on organizations. In this study, the relationships between the dimensions of narcissism and political skill are examined via the 16-item Narcissistic Personality Inventory （NPI） and the 18-item Political Skill Inventory. Analysis has shown that the authority, which is the adaptive dimension of narcissism, correlates positively with social astuteness and networking ability dimensions of political skill. Accordingly entitlement, which is one of the maladaptive dimensions of narcissism, correlates significantly and negatively with the networking ability, interpersonal influence and apparent sincerity dimensions of political skill. When political skill is considered as a composite score, the findings indicate that the authority dimension of narcissism has a positive effect whereas, the entitlement dimension has a negative effect on political skill. Besides, implications for future studies are discussed展开更多
This paper presents a new study on optimum determination of the partial ratios of coupled planetary gear sets for getting minimum radial size of the gear sets. In this paper, based on moment equilibrium condition of a...This paper presents a new study on optimum determination of the partial ratios of coupled planetary gear sets for getting minimum radial size of the gear sets. In this paper, based on moment equilibrium condition of a mechanic system including two-row planetary gear sets and their regular resistance conditions, an explicit model for calculating the partial ratios of coupled planetary gear sets was proposed. In addition, by giving this effective model, the partial ratios can be calculated simply and accurately.展开更多
基金supported by the National Natural Science Foundation of China (21373272)~~
文摘Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesis environment.During the reaction,the feed molar ratio of the two precursors was carried over to the final products,which have a narrow size distribution with a mean size of approximately4nm.The catalytic activity for methanol oxidation reactions possible depends closely on the composition of as‐prepared PtPd alloy NPs,and the NPs with a Pt atomic percentage of approximately75%result in higher activity and stability with a mass specific activity that is7times greater than that of commercial Pt/C catalysts.The results indicate that through composition control,PtPd alloy NPs can improve the effectiveness of catalytic performance.
基金Project(51901095)supported by the National Natural Science Foundation of China。
文摘To study the influence of B4C particle size on the microstructure and damping capacities of(B_(4)C+Ti)/Mg composites,in situ reactive infiltration technique was utilized to prepare Mg-matrix composites.The microstructure,produced phases and damping capacities of the composites prepared with different particle size of B4C were characterized and analyzed.The results show that the reaction between B4C and Ti tends to be more complete when finer B_(4)C particle was used to prepare the composites.But the microstructure of the as-prepared composites is more homogenous when B4C and Ti have similar particle size.The strain-dependent damping capacities of(B_(4)C+Ti)/Mg composites improve gradually with the increase of strain amplitude,and composites prepared with coarser B4C particles tend to have higher damping capacities.The temperature-dependent damping capacities improve with increasing the measuring temperatures,and the kind of damping capacities of the composites prepared with 5mm B4C are inferior to those of coarser particles.The dominant damping mechanism for the strain-damping capacity is dislocation damping and plastic zone damping,while that for the temperature-damping capacity is interface damping or grain boundary damping.
文摘The combined effects of equal channel angular pressing (ECAP) and subsequent heating to a semi-solid temperature on the microstructural characteristics of the 7075 aluminum alloy were investigated. The microstructure is influenced by several parameters including the number of ECAP passes, ECAP route, consequent heating temperature, and holding time. The effects of these parameters on the microstructural characteristics including grain size and shape factor of the 7075 aluminum alloy were studied using experimental tests and Taguchi method. The results indicate that five-pass ECAP in route BA and subsequent isothermal holding at 630 °C for 15 min are more appropriate for achieving a semi-solid microstructure. The processing route and holding time have the highest impact on the grain size while the number of ECAP passes and heating temperature have the least impact on the grain size. Meanwhile, the shape factor is significantly influenced by the processing route, holding time and heating temperature while it is less influenced by the number of ECAP passes.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(No.11572074)the Liaoning Provincial Natural Science Foundation,China(No.2019-KF-05-07)。
文摘An integrated simulation of powder effects on particle temperature and microstructural evolution in laser directed energy deposition additive manufacturing process was carried out.The spatial distribution of the flying powder particles was simulated by the discrete element method to calculate the energy for the flying powder particles under the laser−particle interaction with electromagnetic wave analysis.Combined with the phase field method,the influence of particle size on the microstructural evolution was studied.The microstructural evolution is validated through comparison with experimental observation.Results indicate that the narrow particle size distribution is beneficial to obtaining a more uniform temperature distribution on the deposited layers and forming smaller equiaxed grains near the side surfaces of the sample.Appropriate powder particle size is beneficial to the conversion of the electromagnetic energy into heat.Particles with small size are recommended to form equiaxed grains and to improve product quality.Appropriate powder flow rate improves the laser energy efficiency,and higher powder flow rate leads to more uniform equiaxed grains on both sides of the cross-section.
文摘The particle size distribution, heavy mineral constituents and rare earth elements (REE) characteristics of the Quaternary red clay of southern Anhui Province were studied to explore the origin of the clay. The results showed that the clay had some properties of areolian deposits, which could be compared with those of the loess in North China; and its chondrite normalized curves of REE were similar to those of the Xiashu loess, implying that they shared the same origin. It was concluded in combination with the results reported by other researchers that the Quaternary red clay of southern Anhui Province originated from aeolian deposits, and this could reveal the cycles of warm and cold climates in the area during the Quaternary period.
文摘AZ91Mg alloy was considered and friction stir processing(FSP)was adopted to achieve grain refinement to investigatethe effect of grain size and secondary phase on machining characteristics during drilling at various speeds and feeds.Super saturatedAZ91Mg alloy was obtained after FSP and the grain refinement was achieved from(166.5±8.7)μm to(21.7±13.5)μm.Surprisingly,hardness reduced for FSP AZ91Mg alloy(88.95±6.1)compared with AZ91alloy(108.2±15.6),which was attributed to the reducedsecondary phase.However,the mean cutting force for FSP-treated(FSPed)AZ91Mg alloy was marginally increased.The edgedamage of the drilled holes was lower for FSPed AZ91Mg alloy compared with unprocessed AZ91Mg alloy.Hence,it can beunderstood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achievedin machining of AZ91Mg alloy.
基金Projects(51501122,51604181) supported by the National Natural Science Foundation of ChinaProject(20172009) supported by the Postdoctoral Sustentation Fund of Taiyuan University of Science and Technology,China+3 种基金Project(20132016) supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProject(201501004-8) supported by the Jincheng Science and Technology Plan Project,ChinaProject(U1510131) supported by NSFC-Shanxi Coal-based Low-carbon United Fund and"Shanxi Young Scholars"Program,ChinaProject(201603D121010) supported by Key R&D Program of Shanxi Province,China
文摘The microstructural evolution and precipitation location of the secondary phase of an as-cast Ti-25 V-15 Cr-0.3 Si titanium alloy were investigated via isothermal compression experiments and heat treatment. The average aspect（length-to-width） ratio, average area and size of the grains at different heat treatment temperatures and holding time were analyzed and the effects of deformation and annealing time on the grain area and size were considered. It was found that the grain size was strongly influenced by the height reduction and holding time. Grain growth was significant when annealing time increased from 10 min to 2 h at 950 °C and height reduction of 30%; however, grain growth was minimal at annealing time between 2 and 4 h. Many dispersion particles were observed to form in continuous chains; the precipitation location was confirmed to be along initial grain boundaries, and the dispersion particles were identified to be Ti5 Si3 phase by TEM.
文摘A vast number of researches and studies have been conducted on narcissism, since the term was used to explain a psychological phenomenon in 1898. However, the discussions about narcissists as organization members or leaders have recently become a research topic in the organizational sciences. In this scope, the recent research on narcissism indicates that narcissistic leaders can either cause organizational tragedies or contribute to organizational success by their great vision. In addition to narcissism, another popular leadership feature is political skill which has attracted considerable attentions in recent years, and become one of the important topics of management studies. Moreover, political skill has been asserted to be a positive characteristic which is related to develop vision and team insight as well as to increase in members＇ trust and support; whereas narcissism has both harmful and beneficial effects on organizations. In this study, the relationships between the dimensions of narcissism and political skill are examined via the 16-item Narcissistic Personality Inventory （NPI） and the 18-item Political Skill Inventory. Analysis has shown that the authority, which is the adaptive dimension of narcissism, correlates positively with social astuteness and networking ability dimensions of political skill. Accordingly entitlement, which is one of the maladaptive dimensions of narcissism, correlates significantly and negatively with the networking ability, interpersonal influence and apparent sincerity dimensions of political skill. When political skill is considered as a composite score, the findings indicate that the authority dimension of narcissism has a positive effect whereas, the entitlement dimension has a negative effect on political skill. Besides, implications for future studies are discussed
文摘This paper presents a new study on optimum determination of the partial ratios of coupled planetary gear sets for getting minimum radial size of the gear sets. In this paper, based on moment equilibrium condition of a mechanic system including two-row planetary gear sets and their regular resistance conditions, an explicit model for calculating the partial ratios of coupled planetary gear sets was proposed. In addition, by giving this effective model, the partial ratios can be calculated simply and accurately.
