Numerous studies conducted on educational leadership have generally emphasized the role of principal,whereas,research on middle leadership remains limited[1].The purpose of this paper is to explore and investigate the...Numerous studies conducted on educational leadership have generally emphasized the role of principal,whereas,research on middle leadership remains limited[1].The purpose of this paper is to explore and investigate the development of middle leadership and seeks to fill in the gap by providing the analysis from a Chinese context.The author found that middle leaders are positioning at a challenging role,in which they are required to take charge of responsibilities of both a leader and a teacher,and in the meantime,they also need to negotiate between the senior leader,the colleagues.and subordinates.Furthermore,personal factors such as self-awareness and resilience are discovered to be pivotal for middle-leadership development.Apart from that,the principal plays a critical role in establishing collaborative school culture that facilitates the development of middle leaders based on the influences from the school’s history,culture,and policies.展开更多
While Unleaded gasoline has the advantage of eliminating lead from automobile exhaust, its potential to reduce the exhaust gas and particles, merits further examination. In the present studies,the concentrations of hy...While Unleaded gasoline has the advantage of eliminating lead from automobile exhaust, its potential to reduce the exhaust gas and particles, merits further examination. In the present studies,the concentrations of hydrocarbons (HC) and earbon monoxides (CO) in emissions were analyzed on Santana engine Dynamometer under a standard test cycle, and total exhaust particles were collected from engines using leaded and unleaded gasoline. It was found that unleaded gasoline reduced the emissions of CO and HC, and decreased the quantity of vehicle exhaust particulate matters by 60%.With the unlead gasoline, only 23 kinds of organic substances, adsorbed in the particles, were identified by gas chromatography/mass spectrometer (GC/MS) while 32 components were detected using the leaded gasoline. The results of in vitro Salmonella/ microsomal test and micronucleus induction assay in CHL cells indicated that both types of gasoline increased the number of histidine-independent colonies and the frequencies of micronucleus induction; no significant differellce was found in their mutagenicity.展开更多
Total suspended particulate mater （TSP） concentrations were monitored for one year from July 2000 and for one year from April 2003 in Jakarta City. Thirteen elemental TSP components, aluminum （Al）, sodium （Na）, ...Total suspended particulate mater （TSP） concentrations were monitored for one year from July 2000 and for one year from April 2003 in Jakarta City. Thirteen elemental TSP components, aluminum （Al）, sodium （Na）, iron （Fe）, lead （Pb）, potassium （K）, zinc （Zn）, titanium （Ti）, manganese （Mn）, bromine （Br）, copper （Cu）, chromium （Cr）, nickel （Ni）, and vanadium （V） were analyzed by a sequential X-ray fluorescence spectrometer. Al, Na, Fe, K, and Pb were major components at most of the sampling locations in 2000. However, only Pb in 2003 dramatically decreased to one tenth. The phase-out of leaded gasoline began on July 1, 2001 in Jakarta City and lead content in gasoline decreased to one tenth, too. The decrease in Pb concentration was a result of the phase-out of leaded gasoline, as lead emissions mainly are exhaust gas from vehicles.展开更多
In this study, Pb was separated and used to prepare BaPbO3 conductive ceramics from leaded waste.The experimental results show that BaPbO3 powder synthesized at 700 °C has particle size of 2–5 lm. The powders we...In this study, Pb was separated and used to prepare BaPbO3 conductive ceramics from leaded waste.The experimental results show that BaPbO3 powder synthesized at 700 °C has particle size of 2–5 lm. The powders were densified by sintering at 1,000 °C for 2 h in the air.Synthesized BaPbO3 ceramics have high Curie temperature and high-temperature positive temperature coefficient（PTC） resistivity characteristics. Electrical resistivity of BaPbO3 compact increases from 5 × 10^-6Ω·m at room temperature to 4 × 10^-4Ω·m at 750 °C. Compared with the one prepared by pure chemical reagents, the BaPbO3 prepared from leaded waste has the similar characteristics of high Curie temperature and PTC resistivity.展开更多
Leaded brass alloys used progressively in many applications such as gas valves production owing to their excellent machinability, corrosion resistance and some other specifications. However, the production processes o...Leaded brass alloys used progressively in many applications such as gas valves production owing to their excellent machinability, corrosion resistance and some other specifications. However, the production processes of these alloys involve some problems appearing in the last activities of production as a result of cumulative defects of previous production processes. Therefore, the current investigation studies the effect of process parameters during casting, hot extrusion and cold drawing production stages of CuZn40Pb2 leaded brass alloy on the mechanical properties. Starting with casting process, two types of charges were used. The first charge consists of 100% recycles while the second contains 30% of pure materials such as Cu, Zn and Pb in addition to the recycles. For each production stage, alloy hardness, micro-hardness, ultimate tensile strength and elongation were examined. The results illustrated that high hardness values are obtained during casting process due to some impurities such as iron and the effect of cooling rate through solidification. The hardness values decrease during extrusion process and then rise again by cold drawing for the charge of 30% pure materials. Micro-hardness values for the fractured tensile test samples appeared higher than others due to work hardening effect. The best mechanical properties as ultimate tensile strength of CuZn40Pb2 alloy products are appeared into cold forming samples with the 30% pure material added.展开更多
This paper empirically investigates into the business performance benefit that lead users or opinion leaders among small business owners draw from their higher involvement in management accounting or marketing topics....This paper empirically investigates into the business performance benefit that lead users or opinion leaders among small business owners draw from their higher involvement in management accounting or marketing topics. This work also contributes to a better identification of network members’ roles solely through their ties between each other. Indeed, lead users and opinion leaders can be differentiated by a higher degree centrality in comparison to their peers. However, being an opinion leader or a lead user does not yield a measurable business benefit to the small businesses studied in this sample.展开更多
ZTE Corporation announced on July 14, 2010 that it has been positioned in the leaders quadrant in Gartner＇s Magic Quadrant for Softswitch Architecture Report.
A National Cotton Council leadership team visited China June 20-30 to see its cotton industry development and continued building a relationship with U.S. raw cotton’s No. 1 customer.
Purpose:Drawing on distributed leadership and motivation theories,this study investigates teachers’perceptions of resource and agency distributions and identifies the key factors motivating leadership among teachers....Purpose:Drawing on distributed leadership and motivation theories,this study investigates teachers’perceptions of resource and agency distributions and identifies the key factors motivating leadership among teachers.Design/Approach/Methods:This quantitative study collected data from 327 teachers in nine schools in Shanghai.Chi-square tests of independence were conducted to examine the associations between leadership structures and power distance,while Spearman’s correlation tests were used to identify changes in leadership resource impact.A nonparametric Friedman’s test was applied to detect discrepancies between the agency of principals,team leaders,and teachers.Finally,Chi-square tests were conducted to discern the associations between teachers’workload and motivation to lead.Findings:Most teachers identified the pyramid and spider’s web structures—which feature one power center and a high power distance—in their schools.The leadership resources and agency distributions corresponded to the school hierarchy:the higher position held by a teacher or a leader,the more resources they received,and the greater the agency they exercised.Results indicate that support from the principal is the most important factor in teachers’participation in distributed leadership,while extra pay and leadership title are the least effective motivators.Originality/Value:This study has theoretical and practical value.First,it demonstrates the value of the resource-agency duality model for analyzing distributed leadership.Second,this study shows that promoting distributed leadership in Shanghai schools requires re-designing organizational resources and individual agency.展开更多
China’s shipbuilding industry maintained the world’s largest market share in terms of three major indicators for the 16th consecutive year in 2025,according to data released by the Ministry of Industry and Informati...China’s shipbuilding industry maintained the world’s largest market share in terms of three major indicators for the 16th consecutive year in 2025,according to data released by the Ministry of Industry and Information Technology on 1 February.展开更多
For hypersonic air-breathing vehicles,the V-shaped leading edges(VSLEs)of supersonic combustion ramjet(scramjet)inlets experience complex shock interactions and intense aerodynamic loads.This paper provides a comprehe...For hypersonic air-breathing vehicles,the V-shaped leading edges(VSLEs)of supersonic combustion ramjet(scramjet)inlets experience complex shock interactions and intense aerodynamic loads.This paper provides a comprehensive review of flow characteristics at the crotch of VSLEs,with particular focus on the transition of shock interaction types and the variation of wall heat flux under different freestream Mach numbers and geometric configurations.The mechanisms governing shock transition,unsteady oscillations,hysteresis,and three-dimensional effects in VSLE flows are first examined.Subsequently,thermal protection strategies aimed at mitigating extreme heating loads are reviewed,emphasizing their relevance to practical engineering applications.Special attention is given to recent studies addressing thermochemical nonequilibrium effects on VSLE shock interactions,and the limitations of current research are critically assessed.Finally,perspectives for future investigations into hypersonic VSLE shock interactions are outlined,highlighting opportunities for advancing design and thermal management strategies.展开更多
Although lead(Pb)-based perovskite solar cells(PSCs)have garnered intense attention for their remarkable photovoltaic conversion efficiency,their commercial process is urgently in need of an effective damage-evaluatio...Although lead(Pb)-based perovskite solar cells(PSCs)have garnered intense attention for their remarkable photovoltaic conversion efficiency,their commercial process is urgently in need of an effective damage-evaluation system for the early diagnosis of faulty PSCs.The main cause of microdamage in perovskite films is the outflow of Pb,which significantly impacts device performance.However,no reliable correlation has been established between classical damage detection techniques and Pb detection,resulting in limited detection sensitivity.Here,we report an in situ visual microdamage evaluation method of PSCs by coating the device surface with a silica gel encapsulation layer containing porphyrin molecules.This detection technology enables high selectivity and sensitivity based on the strong complexation between the porphyrin ring and trace Pb outflow from degraded PSCs.By establishing the linear relationship between the fluorescence intensity and Pb concentration in PSCs,trace Pb outflow is pinpointed and quantified with a low detection limit of 0.65μg cm^(-2).An applet is developed for the insitu visual fluorescence detection method to facilitate the continuous real-time monitoring of series-type PSCs,thereby enabling the prompt identification and replacement of damaged PSCs and ensuring the swift restoration of high efficiency.展开更多
Lanthanide ions(Ln^(3+))doping provides a potential strategy to control over the luminescent properties of lead-free halide double perovskite nanocrystals(DP NCs).However,due to the low energy transfer efficiency betw...Lanthanide ions(Ln^(3+))doping provides a potential strategy to control over the luminescent properties of lead-free halide double perovskite nanocrystals(DP NCs).However,due to the low energy transfer efficiency between self-trapped exciton(STE)and Ln^(3+)ions,the characteristic emissions of Ln^(3+)ions are not prominent.Furthermore,the energy transfer mechanism between STE and Ln^(3+)ions is also elusive and requires in-depth study.We chose trace Bi^(3+)-doped Cs_(2)Ag_(0.6)Na_(0.4)InCl_(6-x)Br_(x) as a representative DP matrix to demonstrate that by tuning the bromide concentration,the Ln^(3+)emission can be greatly enhanced.Such enhanced STE and Ln^(3+)ions energy transfer originates from the high covalency of Ln-Br bond,which contributes to improve ment of the characteristic emission of Ln^(3+)ions.Furthermo re,optical spectroscopy reveals that the energy transfer mechanism from DP to Eu^(3+)ions is different from all the other doped Ln^(3+)ions.The energy transfer from DP to Eu^(3+)ions is mostly through Eu-Br charge transfer while the other Ln^(3+)ions are excited by energy transfer from STE.The distinct energy transfer mechanism has resulted from the energy separation between the excited energy level of Ln^(3+)ions and the bottom of conduction band of DP.With increasing the energy separation,the energy transfer from STE to Ln^(3+)ions is less efficient because of the generation of a larger number of phonons and finally becomes impossible for Eu^(3+)ions.Our results provide new insight into tuning the energy transfer of Ln^(3+)-doped DP NCs.展开更多
This study investigates the potential of Prosopis cineraria Leaves Powder(PCLP)as a biosorbent for removing lead(Pb)and zinc(Zn)from aqueous solutions,optimizing the process using Response Surface Methodology(RSM).Pro...This study investigates the potential of Prosopis cineraria Leaves Powder(PCLP)as a biosorbent for removing lead(Pb)and zinc(Zn)from aqueous solutions,optimizing the process using Response Surface Methodology(RSM).Prosopis cineraria,commonly known as Khejri,is a drought-resistant tree with significant promise in environmental applications.The research employed a Central Composite Design(CCD)to examine the independent and combined effects of key process variables,including initial metal ion concentration,contact time,pH,and PCLP dosage.RSM was used to develop mathematical models that explain the relationship between these factors and the efficiency of metal removal,allowing the determination of optimal operating conditions.The experimental results indicated that the Langmuir isotherm model was the most appropriate for describing the biosorption of both metals,suggesting favorable adsorption characteristics.Additionally,the D-R isotherm confirmed that chemisorption was the primary mechanism involved in the biosorption process.For lead removal,the optimal conditions were found to be 312.23 K temperature,pH 4.72,58.5 mg L-1 initial concentration,and 0.27 g biosorbent dosage,achieving an 83.77%removal efficiency.For zinc,the optimal conditions were 312.4 K,pH 5.86,53.07 mg L-1 initial concentration,and the same biosorbent dosage,resulting in a 75.86%removal efficiency.These findings highlight PCLP’s potential as an effective,eco-friendly biosorbent for sustainable heavy metal removal in water treatment.展开更多
Lead chalcohalides(PbYX,X=Cl,Br,I;Y=S,Se)is an extension of the classic Pb chalcogenides(PbY).Constructing the heterogeneous integration with PbYX and PbY material systems makes it possible to achieve significantly im...Lead chalcohalides(PbYX,X=Cl,Br,I;Y=S,Se)is an extension of the classic Pb chalcogenides(PbY).Constructing the heterogeneous integration with PbYX and PbY material systems makes it possible to achieve significantly improved optoelectronic performance.In this work,we studied the effect of introducing halogen precursors on the structure of classical PbS nanocrystals(NCs)during the synthesis process and realized the preparation of PbS/Pb_(3)S_(2)X_(2) core/shell structure for the first time.The core/shell structure can effectively improve their optical properties.Furthermore,our approach enables the synthesis of Pb_(3)S_(2)Br_(2) that had not yet been reported.Our results not only provide valuable insights into the heterogeneous integration of PbYX and PbY materials to elevate material properties but also provide an effective method for further expanding the preparation of PbYX material systems.展开更多
Owing to their low toxicity and remarkable stability, perovskites based on antimony and bismuth have garnered significant interest in recent years. However, A_(3)B_(2)X_(9) perovskite materials derived from antimony a...Owing to their low toxicity and remarkable stability, perovskites based on antimony and bismuth have garnered significant interest in recent years. However, A_(3)B_(2)X_(9) perovskite materials derived from antimony and bismuth face several challenges, including excessively wide band gaps, elevated defect densities, and suboptimal film quality, all of which hinder advancements in device efficiency. While extensive studies have been undertaken to investigate the effects of modulating the A-site and X-site elements in lead-free A_(3)B_(2)X_(9) perovskites, there remains a notable scarcity of reports addressing the impact of modifications to the B-site element. In this study, we investigated the alloying of antimony and bismuth within the 2D Cs_(3)B_(2)I_(6)Br_(3) perovskite. By systematically varying the ratios of two elements, we found that the incorporation of both antimony and bismuth at the B-site significantly enhances the quality of the perovskite films. Our findings indicate that a 1 : 1 ratio of antimony to bismuth produces the densest films, the highest photoluminescence intensity, and superior photovoltaic performance. Ultimately,the devices fabricated using this optimal ratio achieved an open-circuit voltage(VOC) of 1.01 V and a power conversion efficiency(PCE) of 0.645%.展开更多
In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-c...In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-cation perovskites(MCPs) have been extensively used as absorber thin films in perovskite solar cells(PSCs), achieving high power conversion efficiencies(PCE) over 26%^([1, 2]).展开更多
All-perovskite tandem solar cells(ATSCs) have the potential to surpass the Shockley-Queisser efficiency limit of conventional single-junction devices. However, the performance and stability of mixed tin–lead(Sn–Pb) ...All-perovskite tandem solar cells(ATSCs) have the potential to surpass the Shockley-Queisser efficiency limit of conventional single-junction devices. However, the performance and stability of mixed tin–lead(Sn–Pb) perovskite solar cells(PSCs), which are crucial components of ATSCs, are much lower than those of lead-based perovskites. The primary challenges include the high crystallization rate of perovskite materials and the susceptibility of Sn^(2+) oxidation, which leads to rough morphology and unfavorable p-type self-doping. To address these issues, we introduced ethylhydrazine oxalate(EDO) at the perovskite interface, which effectively inhibits the oxidation of Sn^(2+) and simultaneously enhances the crystallinity of the perovskite. Consequently, the EDO-modified mixed tin-lead PSCs reached a power conversion efficiency(PCE) of 21.96% with high reproducibility. We further achieved a 27.58% efficient ATSCs by using EDO as interfacial passivator in the Sn-Pb PSCs.展开更多
Objective:Osteoporosis is a systemic metabolic disease characterized by decreased bone mass,deterioration of bone microstructure,and increased fracture risk.Its occurrence is closely related to sex,age,and lifestyle f...Objective:Osteoporosis is a systemic metabolic disease characterized by decreased bone mass,deterioration of bone microstructure,and increased fracture risk.Its occurrence is closely related to sex,age,and lifestyle factors.Environmental exposure to heavy metals and metalloids may also influence its development,although existing findings remain inconsistent.The sex differences in the association between mixed metal exposure and osteoporosis are still unclear.This study aims to investigate whether sex differences exist in the associations between cadmium(Cd),lead(Pb),mercury(Hg),selenium(Se),manganese(Mn),and their mixtures and osteoporosis among men aged≥50 years and postmenopausal women,and to analyze the potential moderating effect of dairy product consumption on these associations.Methods:Data from the National Health and Nutrition Examination Survey(NHANES)2013−2014 and 2017−2018 cycles were used.In men and women separately,generalized linear regression models(univariate regression analysis and multivariate logistic regression)were applied to examine the relationships between single-metal exposure and osteoporosis at the femoral neck and vertebrae.A weighted quantile sum(WQS)model was used to construct a weighted index of mixed metal exposure to quantify the joint effects of multiple metals.Bayesian kernel machine regression(BKMR)was used to systematically evaluate the associations between blood Cd,Pb,Hg,Se,Mn,and their mixtures and osteoporosis at different skeletal sites,capturing potential nonlinear relationships and interactions among metals.Participants were further stratified into high dairy consumption(≥7 times/week)and low dairy consumption(<7 times/week)groups to explore the potential moderating effect of dairy consumption on the association between Cd exposure and osteoporosis.Results:Multivariate logistic regression analysis showed that,in the fully adjusted model,Cd was positively associated with femoral neck osteoporosis in men aged≥50 years[odds ratio(OR)=8.563,95%confidence interval(CI)1.888 to 38.845,P<0.05],whereas Se was negatively associated with femoral neck osteoporosis(OR<0.001,95%CI 0 to 0.150,P<0.05).In postmenopausal women,Cd was positively associated with femoral neck osteoporosis risk(OR=2.148,95%CI 1.038 to 4.443,P<0.05),while Se was negatively associated with femoral neck osteoporosis risk(OR=0.027,95%CI 0.001 to 0.986,P<0.05).No significant association was observed between any metal and vertebral osteoporosis(all P>0.05).The WQS model indicated that mixed metal exposure was positively associated with vertebral osteoporosis in men(OR=1.452,95%CI 0.277 to 2.626,P<0.05),whereas no significant association was observed in women.BKMR analysis showed that mixed metal exposure was positively associated with osteoporosis risk at the femoral neck and vertebrae in men,with Cd contributing most to osteoporosis risk,while no association was observed between mixed metal exposure and osteoporosis risk in women.The positive association between mixed blood metal exposure and osteoporosis risk might be partially offset by Se.In stratified analysis,the association between Cd exposure and osteoporosis was stronger in the high dairy consumption group(OR=1.19,95%CI 0.51 to 2.78,P>0.05)than in the low dairy consumption group(OR=3.12,95%CI 1.84 to 5.30,P<0.05),suggesting that frequent dairy consumption may attenuate the positive association between Cd exposure and femoral neck osteoporosis in women.Conclusion:In men aged≥50 years,mixed metal exposure was positively associated with osteoporosis risk at different skeletal sites(femoral neck and vertebra),with Cd contributing most to the risk.In postmenopausal women,no association between mixed metal exposure and osteoporosis risk was observed,indicating clear sex differences.Selenium and dairy consumption may be potential protective factors for osteoporosis in women,whereas such protective effects were not observed in men.展开更多
文摘Numerous studies conducted on educational leadership have generally emphasized the role of principal,whereas,research on middle leadership remains limited[1].The purpose of this paper is to explore and investigate the development of middle leadership and seeks to fill in the gap by providing the analysis from a Chinese context.The author found that middle leaders are positioning at a challenging role,in which they are required to take charge of responsibilities of both a leader and a teacher,and in the meantime,they also need to negotiate between the senior leader,the colleagues.and subordinates.Furthermore,personal factors such as self-awareness and resilience are discovered to be pivotal for middle-leadership development.Apart from that,the principal plays a critical role in establishing collaborative school culture that facilitates the development of middle leaders based on the influences from the school’s history,culture,and policies.
文摘While Unleaded gasoline has the advantage of eliminating lead from automobile exhaust, its potential to reduce the exhaust gas and particles, merits further examination. In the present studies,the concentrations of hydrocarbons (HC) and earbon monoxides (CO) in emissions were analyzed on Santana engine Dynamometer under a standard test cycle, and total exhaust particles were collected from engines using leaded and unleaded gasoline. It was found that unleaded gasoline reduced the emissions of CO and HC, and decreased the quantity of vehicle exhaust particulate matters by 60%.With the unlead gasoline, only 23 kinds of organic substances, adsorbed in the particles, were identified by gas chromatography/mass spectrometer (GC/MS) while 32 components were detected using the leaded gasoline. The results of in vitro Salmonella/ microsomal test and micronucleus induction assay in CHL cells indicated that both types of gasoline increased the number of histidine-independent colonies and the frequencies of micronucleus induction; no significant differellce was found in their mutagenicity.
基金The authors greatly appreciate the financial support of the Nissan Science Foundation for part of this study. Gratitude is also extended to EMC staff, and to the JICA Decentralized Environmental Management System Project.
文摘Total suspended particulate mater （TSP） concentrations were monitored for one year from July 2000 and for one year from April 2003 in Jakarta City. Thirteen elemental TSP components, aluminum （Al）, sodium （Na）, iron （Fe）, lead （Pb）, potassium （K）, zinc （Zn）, titanium （Ti）, manganese （Mn）, bromine （Br）, copper （Cu）, chromium （Cr）, nickel （Ni）, and vanadium （V） were analyzed by a sequential X-ray fluorescence spectrometer. Al, Na, Fe, K, and Pb were major components at most of the sampling locations in 2000. However, only Pb in 2003 dramatically decreased to one tenth. The phase-out of leaded gasoline began on July 1, 2001 in Jakarta City and lead content in gasoline decreased to one tenth, too. The decrease in Pb concentration was a result of the phase-out of leaded gasoline, as lead emissions mainly are exhaust gas from vehicles.
基金financially supported by the Beijing Nova Program (No.Z141103001814006)the National Key Technology R&D Program (Nos. 2012BAC12B05 and 2012BAC02B01)+1 种基金the National Natural Science Foundation of China (Nos. 51174247 and U1360202)the National High-Tech Research and the Development Program of China (No. 2012AA063202)
文摘In this study, Pb was separated and used to prepare BaPbO3 conductive ceramics from leaded waste.The experimental results show that BaPbO3 powder synthesized at 700 °C has particle size of 2–5 lm. The powders were densified by sintering at 1,000 °C for 2 h in the air.Synthesized BaPbO3 ceramics have high Curie temperature and high-temperature positive temperature coefficient（PTC） resistivity characteristics. Electrical resistivity of BaPbO3 compact increases from 5 × 10^-6Ω·m at room temperature to 4 × 10^-4Ω·m at 750 °C. Compared with the one prepared by pure chemical reagents, the BaPbO3 prepared from leaded waste has the similar characteristics of high Curie temperature and PTC resistivity.
文摘Leaded brass alloys used progressively in many applications such as gas valves production owing to their excellent machinability, corrosion resistance and some other specifications. However, the production processes of these alloys involve some problems appearing in the last activities of production as a result of cumulative defects of previous production processes. Therefore, the current investigation studies the effect of process parameters during casting, hot extrusion and cold drawing production stages of CuZn40Pb2 leaded brass alloy on the mechanical properties. Starting with casting process, two types of charges were used. The first charge consists of 100% recycles while the second contains 30% of pure materials such as Cu, Zn and Pb in addition to the recycles. For each production stage, alloy hardness, micro-hardness, ultimate tensile strength and elongation were examined. The results illustrated that high hardness values are obtained during casting process due to some impurities such as iron and the effect of cooling rate through solidification. The hardness values decrease during extrusion process and then rise again by cold drawing for the charge of 30% pure materials. Micro-hardness values for the fractured tensile test samples appeared higher than others due to work hardening effect. The best mechanical properties as ultimate tensile strength of CuZn40Pb2 alloy products are appeared into cold forming samples with the 30% pure material added.
文摘This paper empirically investigates into the business performance benefit that lead users or opinion leaders among small business owners draw from their higher involvement in management accounting or marketing topics. This work also contributes to a better identification of network members’ roles solely through their ties between each other. Indeed, lead users and opinion leaders can be differentiated by a higher degree centrality in comparison to their peers. However, being an opinion leader or a lead user does not yield a measurable business benefit to the small businesses studied in this sample.
文摘ZTE Corporation announced on July 14, 2010 that it has been positioned in the leaders quadrant in Gartner＇s Magic Quadrant for Softswitch Architecture Report.
文摘A National Cotton Council leadership team visited China June 20-30 to see its cotton industry development and continued building a relationship with U.S. raw cotton’s No. 1 customer.
文摘Purpose:Drawing on distributed leadership and motivation theories,this study investigates teachers’perceptions of resource and agency distributions and identifies the key factors motivating leadership among teachers.Design/Approach/Methods:This quantitative study collected data from 327 teachers in nine schools in Shanghai.Chi-square tests of independence were conducted to examine the associations between leadership structures and power distance,while Spearman’s correlation tests were used to identify changes in leadership resource impact.A nonparametric Friedman’s test was applied to detect discrepancies between the agency of principals,team leaders,and teachers.Finally,Chi-square tests were conducted to discern the associations between teachers’workload and motivation to lead.Findings:Most teachers identified the pyramid and spider’s web structures—which feature one power center and a high power distance—in their schools.The leadership resources and agency distributions corresponded to the school hierarchy:the higher position held by a teacher or a leader,the more resources they received,and the greater the agency they exercised.Results indicate that support from the principal is the most important factor in teachers’participation in distributed leadership,while extra pay and leadership title are the least effective motivators.Originality/Value:This study has theoretical and practical value.First,it demonstrates the value of the resource-agency duality model for analyzing distributed leadership.Second,this study shows that promoting distributed leadership in Shanghai schools requires re-designing organizational resources and individual agency.
文摘China’s shipbuilding industry maintained the world’s largest market share in terms of three major indicators for the 16th consecutive year in 2025,according to data released by the Ministry of Industry and Information Technology on 1 February.
基金funded by the Research Fund of National Key Laboratory of Aerospace Physics in Fluids,grant number 2024-APF-KFZD-01Guangdong Basic and Applied Basic Research Foundation,grant number 2025A1515012081+1 种基金National Natural Science Foundation of China,grant number 12002193Shandong Provincial Natural Science Foundation,China,grant number ZR2019QA018.
文摘For hypersonic air-breathing vehicles,the V-shaped leading edges(VSLEs)of supersonic combustion ramjet(scramjet)inlets experience complex shock interactions and intense aerodynamic loads.This paper provides a comprehensive review of flow characteristics at the crotch of VSLEs,with particular focus on the transition of shock interaction types and the variation of wall heat flux under different freestream Mach numbers and geometric configurations.The mechanisms governing shock transition,unsteady oscillations,hysteresis,and three-dimensional effects in VSLE flows are first examined.Subsequently,thermal protection strategies aimed at mitigating extreme heating loads are reviewed,emphasizing their relevance to practical engineering applications.Special attention is given to recent studies addressing thermochemical nonequilibrium effects on VSLE shock interactions,and the limitations of current research are critically assessed.Finally,perspectives for future investigations into hypersonic VSLE shock interactions are outlined,highlighting opportunities for advancing design and thermal management strategies.
基金financial support from the Shccig-Qinling Program(SMYJY202300294C)the Science,Technology,and Innovation Commission of Shenzhen Municipality(GJHZ20220913143204008,JCYJ20220818103417036)+1 种基金the National Natural Science Foundation of China(22261142666,52172237,52372225)the Shaanxi Science Fund for Distinguished Young Scholars(2022JC-21)。
文摘Although lead(Pb)-based perovskite solar cells(PSCs)have garnered intense attention for their remarkable photovoltaic conversion efficiency,their commercial process is urgently in need of an effective damage-evaluation system for the early diagnosis of faulty PSCs.The main cause of microdamage in perovskite films is the outflow of Pb,which significantly impacts device performance.However,no reliable correlation has been established between classical damage detection techniques and Pb detection,resulting in limited detection sensitivity.Here,we report an in situ visual microdamage evaluation method of PSCs by coating the device surface with a silica gel encapsulation layer containing porphyrin molecules.This detection technology enables high selectivity and sensitivity based on the strong complexation between the porphyrin ring and trace Pb outflow from degraded PSCs.By establishing the linear relationship between the fluorescence intensity and Pb concentration in PSCs,trace Pb outflow is pinpointed and quantified with a low detection limit of 0.65μg cm^(-2).An applet is developed for the insitu visual fluorescence detection method to facilitate the continuous real-time monitoring of series-type PSCs,thereby enabling the prompt identification and replacement of damaged PSCs and ensuring the swift restoration of high efficiency.
基金Project supported by the Research Project of Mindu Innovation Laboratory(2021ZZ114)Natural Science Foundation of Xiamen(3502Z20227255)+1 种基金Major Research Project of Xiamen(3502Z20191015)the Science and Technology Major Project of Fujian Province(2021HZ021013)。
文摘Lanthanide ions(Ln^(3+))doping provides a potential strategy to control over the luminescent properties of lead-free halide double perovskite nanocrystals(DP NCs).However,due to the low energy transfer efficiency between self-trapped exciton(STE)and Ln^(3+)ions,the characteristic emissions of Ln^(3+)ions are not prominent.Furthermore,the energy transfer mechanism between STE and Ln^(3+)ions is also elusive and requires in-depth study.We chose trace Bi^(3+)-doped Cs_(2)Ag_(0.6)Na_(0.4)InCl_(6-x)Br_(x) as a representative DP matrix to demonstrate that by tuning the bromide concentration,the Ln^(3+)emission can be greatly enhanced.Such enhanced STE and Ln^(3+)ions energy transfer originates from the high covalency of Ln-Br bond,which contributes to improve ment of the characteristic emission of Ln^(3+)ions.Furthermo re,optical spectroscopy reveals that the energy transfer mechanism from DP to Eu^(3+)ions is different from all the other doped Ln^(3+)ions.The energy transfer from DP to Eu^(3+)ions is mostly through Eu-Br charge transfer while the other Ln^(3+)ions are excited by energy transfer from STE.The distinct energy transfer mechanism has resulted from the energy separation between the excited energy level of Ln^(3+)ions and the bottom of conduction band of DP.With increasing the energy separation,the energy transfer from STE to Ln^(3+)ions is less efficient because of the generation of a larger number of phonons and finally becomes impossible for Eu^(3+)ions.Our results provide new insight into tuning the energy transfer of Ln^(3+)-doped DP NCs.
文摘This study investigates the potential of Prosopis cineraria Leaves Powder(PCLP)as a biosorbent for removing lead(Pb)and zinc(Zn)from aqueous solutions,optimizing the process using Response Surface Methodology(RSM).Prosopis cineraria,commonly known as Khejri,is a drought-resistant tree with significant promise in environmental applications.The research employed a Central Composite Design(CCD)to examine the independent and combined effects of key process variables,including initial metal ion concentration,contact time,pH,and PCLP dosage.RSM was used to develop mathematical models that explain the relationship between these factors and the efficiency of metal removal,allowing the determination of optimal operating conditions.The experimental results indicated that the Langmuir isotherm model was the most appropriate for describing the biosorption of both metals,suggesting favorable adsorption characteristics.Additionally,the D-R isotherm confirmed that chemisorption was the primary mechanism involved in the biosorption process.For lead removal,the optimal conditions were found to be 312.23 K temperature,pH 4.72,58.5 mg L-1 initial concentration,and 0.27 g biosorbent dosage,achieving an 83.77%removal efficiency.For zinc,the optimal conditions were 312.4 K,pH 5.86,53.07 mg L-1 initial concentration,and the same biosorbent dosage,resulting in a 75.86%removal efficiency.These findings highlight PCLP’s potential as an effective,eco-friendly biosorbent for sustainable heavy metal removal in water treatment.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0110300)the National Natural Science Foundation of China(Grant Nos.52372215,92163114,and 52202274)+5 种基金the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20230504)the Special Fund for the"Dual Carbon"Science and Technology Innovation of Jiangsu province(Industrial Prospect and Key Technology Research program)(Grant Nos.BE2022023 and BE2022021)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.21KJA430004)Gusu Innovation and Entre preneurship Leading Talent Program(Grant No.ZXL2022451)the China Postdoctoral Science Foundation(Grant No.2023M732523)supported by Suzhou Key Laboratory of Functional Nano&Soft Materials,Collaborative Innovation Center of Suzhou Nano Science&Technology,the 111 Project.
文摘Lead chalcohalides(PbYX,X=Cl,Br,I;Y=S,Se)is an extension of the classic Pb chalcogenides(PbY).Constructing the heterogeneous integration with PbYX and PbY material systems makes it possible to achieve significantly improved optoelectronic performance.In this work,we studied the effect of introducing halogen precursors on the structure of classical PbS nanocrystals(NCs)during the synthesis process and realized the preparation of PbS/Pb_(3)S_(2)X_(2) core/shell structure for the first time.The core/shell structure can effectively improve their optical properties.Furthermore,our approach enables the synthesis of Pb_(3)S_(2)Br_(2) that had not yet been reported.Our results not only provide valuable insights into the heterogeneous integration of PbYX and PbY materials to elevate material properties but also provide an effective method for further expanding the preparation of PbYX material systems.
基金financially supported by the Natural Science Foundation of Zhejiang Province, China (Grant No. LQ22F040001)China Postdoctoral Science Foundation (Grant No. 2022M723281)Science and Technology Planning Project of Shaoxing City (Grant No. 2023B41006)。
文摘Owing to their low toxicity and remarkable stability, perovskites based on antimony and bismuth have garnered significant interest in recent years. However, A_(3)B_(2)X_(9) perovskite materials derived from antimony and bismuth face several challenges, including excessively wide band gaps, elevated defect densities, and suboptimal film quality, all of which hinder advancements in device efficiency. While extensive studies have been undertaken to investigate the effects of modulating the A-site and X-site elements in lead-free A_(3)B_(2)X_(9) perovskites, there remains a notable scarcity of reports addressing the impact of modifications to the B-site element. In this study, we investigated the alloying of antimony and bismuth within the 2D Cs_(3)B_(2)I_(6)Br_(3) perovskite. By systematically varying the ratios of two elements, we found that the incorporation of both antimony and bismuth at the B-site significantly enhances the quality of the perovskite films. Our findings indicate that a 1 : 1 ratio of antimony to bismuth produces the densest films, the highest photoluminescence intensity, and superior photovoltaic performance. Ultimately,the devices fabricated using this optimal ratio achieved an open-circuit voltage(VOC) of 1.01 V and a power conversion efficiency(PCE) of 0.645%.
基金financially supported by the National Natural Science Foundation of China (52462032, 62274018, 52462031)Natural Science Foundation of Yunnan Province (202501AT070353, 202101BE070001-049)+2 种基金the Xinjiang Construction Corps Key Areas of Science and Technology Research Project (2023AB029)the Tianchi Talent Program of Xinjiang Uygur Autonomous Region (2024, Jiangzhao Chen)the Key Project of Chongqing Overseas Students Returning to China Entrepreneurship and Innovation Support Plan (cx2023006)。
文摘In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-cation perovskites(MCPs) have been extensively used as absorber thin films in perovskite solar cells(PSCs), achieving high power conversion efficiencies(PCE) over 26%^([1, 2]).
基金financially supported by National Key R&D Program of China (2025YFE0100300)the National Natural Science Foundation of China (52202293 and 52330004)the Fundamental Research Funds for the Central Universities (WUT: 2023IVA075 and 2023IVB009)。
文摘All-perovskite tandem solar cells(ATSCs) have the potential to surpass the Shockley-Queisser efficiency limit of conventional single-junction devices. However, the performance and stability of mixed tin–lead(Sn–Pb) perovskite solar cells(PSCs), which are crucial components of ATSCs, are much lower than those of lead-based perovskites. The primary challenges include the high crystallization rate of perovskite materials and the susceptibility of Sn^(2+) oxidation, which leads to rough morphology and unfavorable p-type self-doping. To address these issues, we introduced ethylhydrazine oxalate(EDO) at the perovskite interface, which effectively inhibits the oxidation of Sn^(2+) and simultaneously enhances the crystallinity of the perovskite. Consequently, the EDO-modified mixed tin-lead PSCs reached a power conversion efficiency(PCE) of 21.96% with high reproducibility. We further achieved a 27.58% efficient ATSCs by using EDO as interfacial passivator in the Sn-Pb PSCs.
基金supported by the Science and Technology Innovation Program of Hunan Province(2025RC3061)the Natural Science Foundation of Hunan Province(2022JJ30828)+2 种基金the Grants from Hunan Provincial Clinical Medicine Research Center for Intelligent Management of Chronic Disease(2023SK4042)the Innovation Foundation For Postgraduate of Hunan Province(CX20240310)the Postgraduate Innovative Project of Central South University(2023XQLH183),China。
文摘Objective:Osteoporosis is a systemic metabolic disease characterized by decreased bone mass,deterioration of bone microstructure,and increased fracture risk.Its occurrence is closely related to sex,age,and lifestyle factors.Environmental exposure to heavy metals and metalloids may also influence its development,although existing findings remain inconsistent.The sex differences in the association between mixed metal exposure and osteoporosis are still unclear.This study aims to investigate whether sex differences exist in the associations between cadmium(Cd),lead(Pb),mercury(Hg),selenium(Se),manganese(Mn),and their mixtures and osteoporosis among men aged≥50 years and postmenopausal women,and to analyze the potential moderating effect of dairy product consumption on these associations.Methods:Data from the National Health and Nutrition Examination Survey(NHANES)2013−2014 and 2017−2018 cycles were used.In men and women separately,generalized linear regression models(univariate regression analysis and multivariate logistic regression)were applied to examine the relationships between single-metal exposure and osteoporosis at the femoral neck and vertebrae.A weighted quantile sum(WQS)model was used to construct a weighted index of mixed metal exposure to quantify the joint effects of multiple metals.Bayesian kernel machine regression(BKMR)was used to systematically evaluate the associations between blood Cd,Pb,Hg,Se,Mn,and their mixtures and osteoporosis at different skeletal sites,capturing potential nonlinear relationships and interactions among metals.Participants were further stratified into high dairy consumption(≥7 times/week)and low dairy consumption(<7 times/week)groups to explore the potential moderating effect of dairy consumption on the association between Cd exposure and osteoporosis.Results:Multivariate logistic regression analysis showed that,in the fully adjusted model,Cd was positively associated with femoral neck osteoporosis in men aged≥50 years[odds ratio(OR)=8.563,95%confidence interval(CI)1.888 to 38.845,P<0.05],whereas Se was negatively associated with femoral neck osteoporosis(OR<0.001,95%CI 0 to 0.150,P<0.05).In postmenopausal women,Cd was positively associated with femoral neck osteoporosis risk(OR=2.148,95%CI 1.038 to 4.443,P<0.05),while Se was negatively associated with femoral neck osteoporosis risk(OR=0.027,95%CI 0.001 to 0.986,P<0.05).No significant association was observed between any metal and vertebral osteoporosis(all P>0.05).The WQS model indicated that mixed metal exposure was positively associated with vertebral osteoporosis in men(OR=1.452,95%CI 0.277 to 2.626,P<0.05),whereas no significant association was observed in women.BKMR analysis showed that mixed metal exposure was positively associated with osteoporosis risk at the femoral neck and vertebrae in men,with Cd contributing most to osteoporosis risk,while no association was observed between mixed metal exposure and osteoporosis risk in women.The positive association between mixed blood metal exposure and osteoporosis risk might be partially offset by Se.In stratified analysis,the association between Cd exposure and osteoporosis was stronger in the high dairy consumption group(OR=1.19,95%CI 0.51 to 2.78,P>0.05)than in the low dairy consumption group(OR=3.12,95%CI 1.84 to 5.30,P<0.05),suggesting that frequent dairy consumption may attenuate the positive association between Cd exposure and femoral neck osteoporosis in women.Conclusion:In men aged≥50 years,mixed metal exposure was positively associated with osteoporosis risk at different skeletal sites(femoral neck and vertebra),with Cd contributing most to the risk.In postmenopausal women,no association between mixed metal exposure and osteoporosis risk was observed,indicating clear sex differences.Selenium and dairy consumption may be potential protective factors for osteoporosis in women,whereas such protective effects were not observed in men.
