Supercapacitors(SCs)stand out among various energy storage devices owing to their high power density and long-term cyc-ling stability.As new two-dimensional material,MXenes have become a research hotspot in recent yea...Supercapacitors(SCs)stand out among various energy storage devices owing to their high power density and long-term cyc-ling stability.As new two-dimensional material,MXenes have become a research hotspot in recent years owing to their unique structure and rich surface functional groups.Compared with other materials,MXenes are more promising for SCs owing to their tunable precurs-ors,structural stability,and excellent electrical conductivity.However,the rate performance and electrochemical reaction activity of MXene materials are poor,and stacking severely limits their application.Therefore,various modification strategies are employed to im-prove the electrochemical performance of MXene materials.As the modification strategy of MXene electrode materials often involves in-creasing the number of ion transport channels to expose more active sites,the packing density is also affected to different degrees.There-fore,achieving a balance between high volumetric capacitance and rapid ion transport has become a key issue for the application of MXene-based SCs in wearable devices and microdevices.In this paper,the latest progress in the preparation methods and modification strategies of MXenes in recent years is reviewed with the aim of achieving both high volumetric capacitance and high ion transport for ex-panding the application of MXene-based SCs in microdevices and wearable devices.展开更多
Aqueous zinc-ion batteries(ZIBs) have attracted great attention as the candidates for large-scale energy storage system,recently,because of their low cost,environment-friendly,high safety,and high theoretical energy d...Aqueous zinc-ion batteries(ZIBs) have attracted great attention as the candidates for large-scale energy storage system,recently,because of their low cost,environment-friendly,high safety,and high theoretical energy densities.Among the numerous cathode materials,layered structure vanadium based polyanionic compounds,such as VOPO_(4),exhibit high specific capacity for Zn ion storage.However,the low Zn ion diffusion coefficient and limited interlayer spacing make the cathodes low reversible capacity and inferior cycling stability.Herein,K ions were pre-intercalated into the VOPO_(4) layers via ions exchange adopting VOPO_(4)·2 H_(2) O as the precursor.When evaluated as the cathode for ZIBs,an excellent cycle stability of 400 cycles under a current density of 500 mA g^(-1) was achieved by the obtained KVOPO_(4) electrode,verifying the positive effect of intercalation engineering.Furtherly,a solid-solution reaction Zn ion storage mechanism was confirmed.This study provides a new insight to explore high performance cathode materials for ZIBs.展开更多
The diamond-like compound Cu_(3)PSe_(4)with low lattice thermal conductivity is deemed to be a promising thermoelectric material,which can directly convert waste heat into electricity or vice versa with no moving part...The diamond-like compound Cu_(3)PSe_(4)with low lattice thermal conductivity is deemed to be a promising thermoelectric material,which can directly convert waste heat into electricity or vice versa with no moving parts and greenhouse emissions.However,its performance is limited by its low electrical conductivity.In this study,we report an effective method to enhance thermoelectric performance of Cu_(3)PSe_(4)by defect engineering.It is found that the carrier concentrations of Cu_(3-x)PSe_(4)(x=0,0.03,0.06,0.09,0.12)compounds are increased by two orders of magnitude as x>0.03,from 1×10^(17)to 1×10^(19)cm^(-3).Combined with the intrinsically low lattice thermal conductivities and enhanced electrical transport performance,a maximum zT value of 0.62 is obtained at 727 K for x=0.12 sample,revealing that Cu defect regulation can be an effective method for enhancing thermoelectric performance of Cu_(3)PSe_(4).展开更多
The surface properties of catalysts determine the intrinsic activity and adaptability.Ruthenium is regarded as a potential candidate to substitute platinum for water electrolysis due to the low cost and analogous elec...The surface properties of catalysts determine the intrinsic activity and adaptability.Ruthenium is regarded as a potential candidate to substitute platinum for water electrolysis due to the low cost and analogous electronic structures while it suffers from severe dissolution and stability problems.Herein,the modification of Ru/C with atomically dispersed cobalt atoms is achieved via a simple thermal doping method.The newly formed amorphous shell with Ru-Co sites on the Ru/C catalyst improved the hydrogen evolution reaction activity and stability significantly.Impressively,the obtained Co1Ru@Ru/CN_(x)catalyst exhibited an overpotential as low as 30 mV at 10 mA cm^(-2)in an alkaline medium,which is among the best HER catalysts reported so far.The oxygen oxophile Co prevents the fast oxidation and dissolution of Ru species,ensuring outstanding long-term durability up to 70 h.Theoretical calculations reveal that the Ru-Co coordination acts as a more active site for water dissociation than the Ru-Ru.Meanwhile,the"Ru-Co shell/Ru core"structures show high adaptability for the reaction conditions.This simple doping strategy offers prospects for scalable preparation of highly active electrocatalysts.展开更多
With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components ...With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.展开更多
In order to improve Englishlistening more effectively, the application status of metacognitive strategies and autonomouslearning competence is exploredbased on a questionnaire investigation among 120 civil engineering...In order to improve Englishlistening more effectively, the application status of metacognitive strategies and autonomouslearning competence is exploredbased on a questionnaire investigation among 120 civil engineering major in BJUT. The methods of correlation analysis and an independent sample t-test are employed.The results indicated that 1) their metacognitivestrategies, and the planning, monitoring strategy have positive significant correlations with the students'listening performance and listening auton-omous learning competence;2) There are significant differences in the use of metacognitivestrategies,the level of autonomous learn-ing competence between different levels of listening performance;3) The more accuracy of self-judgment is, the higher level Eng-lish listening performance is.展开更多
Founded in 2012,the National Joint Engineering Research Center of High Performance Metal Wear Resistant Materials Technology at Jinan University,one of the'211'key national universities in China,specializes in...Founded in 2012,the National Joint Engineering Research Center of High Performance Metal Wear Resistant Materials Technology at Jinan University,one of the'211'key national universities in China,specializes in the research and development of iron based wear resistant materials and their casting technologies to provide support to the production process.The Research Center serves the'Guangdong Province Ceeusro Innovation Platform for Common Technology of High Performance Wear Resistant Materials”,“Guangdong Province Engineering Research Center for Wear Resistant and Special Functional Materials”.展开更多
All-inorganic CsPbIBr_(2) perovskite has attracted widespread attention in photovoltaic and other optoelectronic devices because of its superior thermal stability.However,the deposition of high-quality solutionprocess...All-inorganic CsPbIBr_(2) perovskite has attracted widespread attention in photovoltaic and other optoelectronic devices because of its superior thermal stability.However,the deposition of high-quality solutionprocessed CsPbIBr_(2) perovskite films with large thicknesses remains challenging.Here,we develop a triple-component precursor(TCP) by employing lead bromide,lead iodide,and cesium bromide,to replace the most commonly used double-component precursor(DCP) consisting of lead bromide and cesium iodide.Remarkably,the TCP system significantly increases the solution concentration to 1.3 M,leading to a larger film thickness(~390 nm) and enhanced light absorption.The resultant CsPbIBr_(2) films were evaluated in planar n-i-p structured solar cells,which exhibit a considerably higher optimal photocurrent density of 11.50 mA cm^(-2) in comparison to that of DCP-based devices(10.69 mA cm^(-2)).By adopting an organic surface passivator,the maximum device efficiency using TCP is further boosted to a record efficiency of 12.8% for CsPbIBr_(2) perovskite solar cells.展开更多
Background With an increasing number of vehicles becoming autonomous,intelligent,and connected,paying attention to the future usage of car human-machine interface with these vehicles should become more relevant.Severa...Background With an increasing number of vehicles becoming autonomous,intelligent,and connected,paying attention to the future usage of car human-machine interface with these vehicles should become more relevant.Several studies have addressed car HMI but were less attentive to designing and implementing interactive glazing for every day(autonomous)driving contexts.Methods Reflecting on the literature,we describe an engineering psychology practice and the design of six novel future user scenarios,which envision the application of a specific set of augmented reality(AR)support user interactions.Additionally,we conduct evaluations on specific scenarios and experiential prototypes,which reveal that these AR scenarios aid the target user groups in experiencing a new type of interaction.The overall evaluation is positive with valuable assessment results and suggestions.Conclusions This study can interest applied psychology educators who aspire to teach how AR can be operationalized in a human-centered design process to students with minimal pre-existing expertise or minimal scientific knowledge in engineering psychology.展开更多
As the key component of electrochemical energy storage devices, an electrode with superior ions transport pores is the important premise for high electrochemical performance. In this paper, we developed a unique solut...As the key component of electrochemical energy storage devices, an electrode with superior ions transport pores is the important premise for high electrochemical performance. In this paper, we developed a unique solution process to prepare freestanding TiO_2/graphene hydrogel electrode with tunable density and porous structures. By incorporating room temperature ionic liquids（RTILs）, even upon drying, the non-volatile RTILs that remained in the gel film would preserve the efficient ion transport channels and prevent the electrode from closely stacking, to develop dense yet porous structures. As a result, the dense TiO_2/graphene gel film as an electrode for lithium ion battery displayed a good gravimetric electrochemical performance and more importantly a high volumetric performance.展开更多
A thrust estimator with high precision and excellent real-time performance is needed to mitigate perfor- mance deterioration for future aero-engines. A weight least squares support vector regression is proposed using ...A thrust estimator with high precision and excellent real-time performance is needed to mitigate perfor- mance deterioration for future aero-engines. A weight least squares support vector regression is proposed using a novel weighting strategy. Then a thrust estimator based on the proposed regression is designed for the perfor- mance deterioration. Compared with the existing weighting strategy, the novel one not only satisfies the require- ment of precision but also enhances the real-time performance. Finally, numerical experiments demonstrate the effectiveness and feasibility of the proposed weighted least squares support vector regression for thrust estimator. Key words ： intelligent engine control; least squares ; support vector machine ; performance deterioration展开更多
In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, i...In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, integration design and reliability, are reviewed. The development history of aerospace engine bearing is recalled briefly at first. Then today＇s material technologies and the high bearing performances of the bearings obtained through the new materials are introduced, which play important roils in the aeroengine bearing developments. The integration design ideas and practices are explained to indicate its significant advantages and importance to the aerospace engine bearings. And the reliability of the shaft-bearing system is pointed out and treated as the key requirement with goals for both engine and bearing. Finally, as it is believed that the correct design comes from practice, the pre-qualification rig testing conducted by FAG Aerospace GmbH ＆ Co. KG is briefly illustrated as an example. All these lead to the development trends of aerospace engine bearings from different aspects.展开更多
The rotating propagation of a continuous detonation engine(CDE)with different types of nozzles is investigated in three-dimensional numerical simulation using a one-step chemical reaction model.Flux terms are solved b...The rotating propagation of a continuous detonation engine(CDE)with different types of nozzles is investigated in three-dimensional numerical simulation using a one-step chemical reaction model.Flux terms are solved by the so-called monotonicity-preserving weighted essentially non-oscillatory(MPWENO)scheme.The simulated flow field agrees well with the previous experimental results.Once the initial transient effects die down,the detonation wave maintains continuous oscillatory propagation in the annular chamber as long as fuel is continuously injected.Using a numerical flow field,the propulsion per-formance of a CDE is computed for four types of nozzles,namely the constant-area nozzle,Laval nozzle,diverging nozzle and converging nozzle.The gross specific impulse of the CDE ranges 1540-1750 s and the mass flux per square meter ranges 313-330 kg/(m2·s)for different nozzles.Among these four types of nozzles,Laval nozzle performs the best,and these parameters are 1800 N,1750 s and 313 kg/(m2.s).A nozzle can greatly improve the propulsion performance.展开更多
In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main...In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel.Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10%（by volume） of hexanol and 90%（by volume） neat cashew nut shell biodiesel was referred to as CNSBD900 H100 and fuel comprising 20%（by volume） of hexanol and 80%（by volume）of neat cashew nut shell biodiesel was referred to as CNSBD800 H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at10% and 20%（by volume） to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine.展开更多
The alternative working modes and flexible working states are the outstanding features of an adaptive cycle engine, with a proper control schedule design being the only way to exploit the performance of such an engine...The alternative working modes and flexible working states are the outstanding features of an adaptive cycle engine, with a proper control schedule design being the only way to exploit the performance of such an engine. However, unreasonable design in the control schedule causes not only performance deterioration but also serious aerodynamic stability problems. Thus, in this work,a hybrid optimization method that automatically chooses the working modes and identifies the optimal and smooth control schedules is proposed, by combining the differential evolution algorithm and the Latin hypercube sampling method. The control schedule architecture does not only optimize the engine steady-state performance under different working modes but also solves the control-schedule discontinuity problem, especially during mode transition. The optimal control schedules are continuous and almost monotonic, and hence are strongly suitable for a control system, and are designed for two different working conditions, i.e., supersonic and subsonic throttling,which proves that the proposed hybrid method applies to various working conditions. The evaluation demonstrates that the proposed control method optimizes the engine performance, the surge margin of the compression components, and the range of the thrust during throttling.展开更多
Achieving simultaneous reduction of NOx,CO and unburned hydrocarbon(UHC) emissions without compromising engine performance at part loads is the current focus of dual fuel engine research.The present work focuses on an...Achieving simultaneous reduction of NOx,CO and unburned hydrocarbon(UHC) emissions without compromising engine performance at part loads is the current focus of dual fuel engine research.The present work focuses on an experimental investigation conducted on a dual fuel(diesel-natural gas) engine to examine the simultaneous effect of inlet air pre-heating and exhaust gas recirculation(EGR) ratio on performance and emission characteristics at part loads.The use of EGR at high levels seems to be unable to improve the engine performance at part loads.However,it is shown that EGR combined with pre-heating of inlet air can slightly increase thermal efficiency,resulting in reduced levels of both unburned hydrocarbon and NOx emissions.CO and UHC emissions are reduced by 24% and 31%,respectively,The NOx emissions decrease by 21% because of the lower combustion temperature due to the much inert gas brought by EGR and decreased oxygen concentration in the cylinder.展开更多
The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and sca...The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and scavenge processes based on the open thermodynamic systems were presented. A simulation was executed at given geometric parameters and initial conditions. The results manifest that the working principle of MFPSE is feasible.展开更多
In the condition of constant speed and light load, an experimental study of a turbocharged and intercooled diesel engine with exhaust gas recirculation （EGR） system focuses on the influence of different EGR rates on...In the condition of constant speed and light load, an experimental study of a turbocharged and intercooled diesel engine with exhaust gas recirculation （EGR） system focuses on the influence of different EGR rates on combustion process, dynamic performance, economic performance and emission performance of a diesel engine. With the increase of EGR rate, the oxygen concentration of the intake-side decreases, the fuel air equivalence ratio increases, and the maximum explosion pressure in the cylinder decreases. Meanwhile, the average temperature in the cylinder drops, the ignition delay is prolonged, the ignition timing delays, and the maximum heat release rate decreases. The increase of EGR rate makes NOx emissions decrease obviously and continue to decline. When EGR is low, the smoke rate enlarges slowly with the increase of EGR rate, and enlarges greatly at the rate higher than 43% and reaches the maximum at the rate of 57%. When EGR rate is higher than 61%, the smoke rate drops rapidly, and the content of CO and hydrocarbon （HC） increases rapidly with high EGR rate.展开更多
This study paves the way on reducing smoke emission and NO_x emissions of research diesel engine by detailing the e ect of water addition in biodiesel. Fuel samples were prepared with di erent concentrations of water ...This study paves the way on reducing smoke emission and NO_x emissions of research diesel engine by detailing the e ect of water addition in biodiesel. Fuel samples were prepared with di erent concentrations of water in orange peel oil biodiesel(94% waste orange peel oil biodiesel + 4% water + 2% Span 80(WOPOBDE1) and 90% waste orange peel oil biodiesel + 8% water + 2% Span 80(WOPOBDE2). Span 80 was employed as a nonionic surfactant, which emulsifies water in biodiesel. Experimental results revealed that the nitrogen oxides and smoke emission of orange peel oil biodiesel emulsion were reduced by 11%–19% and 3%–21%, respectively, compared to that of neat orange peel oil biodiesel(WOPOBD). In addition, the introduction of orange peel oil–water emulsions in the diesel engine considerably reduced the emissions of unburned hydrocarbons and carbon monoxide. The overall hydrocarbon emission of WOPOBDE2 was 12.2% lower than that of WOPOBD and 16.3% lower than that of diesel. The overall CO emission of WOPOBDE2 was 17% lower than that of base fuel(WOPOBD) and 21.8% lower than that of diesel. Experimental results revealed that modified fuel had higher brake thermal e ciency and lower brake specific fuel consumption than that of base fuel at all engine brake power levels.展开更多
基金supported by the National Natural Science Foundation of China(No.52272242)the Provisional Key Research and Development Program of Henan Province,China(No.231111240600)+1 种基金the Natural Science Foundation of Henan Province,China(No.242300421428)the Start-up Funding for Scientific Research of Zhengzhou University,China(No.32310221).
文摘Supercapacitors(SCs)stand out among various energy storage devices owing to their high power density and long-term cyc-ling stability.As new two-dimensional material,MXenes have become a research hotspot in recent years owing to their unique structure and rich surface functional groups.Compared with other materials,MXenes are more promising for SCs owing to their tunable precurs-ors,structural stability,and excellent electrical conductivity.However,the rate performance and electrochemical reaction activity of MXene materials are poor,and stacking severely limits their application.Therefore,various modification strategies are employed to im-prove the electrochemical performance of MXene materials.As the modification strategy of MXene electrode materials often involves in-creasing the number of ion transport channels to expose more active sites,the packing density is also affected to different degrees.There-fore,achieving a balance between high volumetric capacitance and rapid ion transport has become a key issue for the application of MXene-based SCs in wearable devices and microdevices.In this paper,the latest progress in the preparation methods and modification strategies of MXenes in recent years is reviewed with the aim of achieving both high volumetric capacitance and high ion transport for ex-panding the application of MXene-based SCs in microdevices and wearable devices.
基金financially supported by the National Natural Science Foundation of China (52025013,52071184,and 21835004)the Ministry of Science and Technology of China(2017YFA0206702, and 2016YFB0901502)+2 种基金the 111 Project(B12015)the Natural Science Foundation of Tianjin(18ZXJMTG00040, and 19JCZDJC31800)the Fundamental Research Funds for the Central Universities。
文摘Aqueous zinc-ion batteries(ZIBs) have attracted great attention as the candidates for large-scale energy storage system,recently,because of their low cost,environment-friendly,high safety,and high theoretical energy densities.Among the numerous cathode materials,layered structure vanadium based polyanionic compounds,such as VOPO_(4),exhibit high specific capacity for Zn ion storage.However,the low Zn ion diffusion coefficient and limited interlayer spacing make the cathodes low reversible capacity and inferior cycling stability.Herein,K ions were pre-intercalated into the VOPO_(4) layers via ions exchange adopting VOPO_(4)·2 H_(2) O as the precursor.When evaluated as the cathode for ZIBs,an excellent cycle stability of 400 cycles under a current density of 500 mA g^(-1) was achieved by the obtained KVOPO_(4) electrode,verifying the positive effect of intercalation engineering.Furtherly,a solid-solution reaction Zn ion storage mechanism was confirmed.This study provides a new insight to explore high performance cathode materials for ZIBs.
基金the Graduate Scientific Research and Innovation Foundation of Chongqing,China(No.CYB 19064)the Project for Fundamental and Frontier Research in Chongqing(No.CSTC2017JCYJAX0388)+2 种基金Shenzhen Science and Technology Innovation Committee(No.JCYJ20170818155752559)the National Natural Science Foundation of China(Nos.51772035,11674040 and 51472036)the Fundamental Research Funds for the Central Universities(No.106112017CDJQJ308821)。
文摘The diamond-like compound Cu_(3)PSe_(4)with low lattice thermal conductivity is deemed to be a promising thermoelectric material,which can directly convert waste heat into electricity or vice versa with no moving parts and greenhouse emissions.However,its performance is limited by its low electrical conductivity.In this study,we report an effective method to enhance thermoelectric performance of Cu_(3)PSe_(4)by defect engineering.It is found that the carrier concentrations of Cu_(3-x)PSe_(4)(x=0,0.03,0.06,0.09,0.12)compounds are increased by two orders of magnitude as x>0.03,from 1×10^(17)to 1×10^(19)cm^(-3).Combined with the intrinsically low lattice thermal conductivities and enhanced electrical transport performance,a maximum zT value of 0.62 is obtained at 727 K for x=0.12 sample,revealing that Cu defect regulation can be an effective method for enhancing thermoelectric performance of Cu_(3)PSe_(4).
基金support from the National Natural Science Foundation of China(21802120,21872121,and 21908189)the National Key R&D Program of China(2016YFA0202900)+3 种基金the Key R&D Project of Zhejiang Province(2020C01133)the Fundamental Research Funds for the Central Universities(G2019KY05119)the China Postdoctoral Science Foundation(2021 M692634)the Natural Science Basic Research Program of Shaanxi Province(2022JQ-118)are greatly appreciated.
文摘The surface properties of catalysts determine the intrinsic activity and adaptability.Ruthenium is regarded as a potential candidate to substitute platinum for water electrolysis due to the low cost and analogous electronic structures while it suffers from severe dissolution and stability problems.Herein,the modification of Ru/C with atomically dispersed cobalt atoms is achieved via a simple thermal doping method.The newly formed amorphous shell with Ru-Co sites on the Ru/C catalyst improved the hydrogen evolution reaction activity and stability significantly.Impressively,the obtained Co1Ru@Ru/CN_(x)catalyst exhibited an overpotential as low as 30 mV at 10 mA cm^(-2)in an alkaline medium,which is among the best HER catalysts reported so far.The oxygen oxophile Co prevents the fast oxidation and dissolution of Ru species,ensuring outstanding long-term durability up to 70 h.Theoretical calculations reveal that the Ru-Co coordination acts as a more active site for water dissociation than the Ru-Ru.Meanwhile,the"Ru-Co shell/Ru core"structures show high adaptability for the reaction conditions.This simple doping strategy offers prospects for scalable preparation of highly active electrocatalysts.
文摘With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.
文摘In order to improve Englishlistening more effectively, the application status of metacognitive strategies and autonomouslearning competence is exploredbased on a questionnaire investigation among 120 civil engineering major in BJUT. The methods of correlation analysis and an independent sample t-test are employed.The results indicated that 1) their metacognitivestrategies, and the planning, monitoring strategy have positive significant correlations with the students'listening performance and listening auton-omous learning competence;2) There are significant differences in the use of metacognitivestrategies,the level of autonomous learn-ing competence between different levels of listening performance;3) The more accuracy of self-judgment is, the higher level Eng-lish listening performance is.
文摘Founded in 2012,the National Joint Engineering Research Center of High Performance Metal Wear Resistant Materials Technology at Jinan University,one of the'211'key national universities in China,specializes in the research and development of iron based wear resistant materials and their casting technologies to provide support to the production process.The Research Center serves the'Guangdong Province Ceeusro Innovation Platform for Common Technology of High Performance Wear Resistant Materials”,“Guangdong Province Engineering Research Center for Wear Resistant and Special Functional Materials”.
基金The authors acknowledge the financial support by the National Natural Science Foundation of China(52161145408 and 21975038)the Research and Innovation Team Project of Dalian University of Technology(DUT2022TB10)+2 种基金the Fundamental Research Funds for the Central Universities(DUT22QN213)the Innovation Technology Fund(MRP/040/21X)the Green Technology Fund(GTF202020164)for their financial support。
文摘All-inorganic CsPbIBr_(2) perovskite has attracted widespread attention in photovoltaic and other optoelectronic devices because of its superior thermal stability.However,the deposition of high-quality solutionprocessed CsPbIBr_(2) perovskite films with large thicknesses remains challenging.Here,we develop a triple-component precursor(TCP) by employing lead bromide,lead iodide,and cesium bromide,to replace the most commonly used double-component precursor(DCP) consisting of lead bromide and cesium iodide.Remarkably,the TCP system significantly increases the solution concentration to 1.3 M,leading to a larger film thickness(~390 nm) and enhanced light absorption.The resultant CsPbIBr_(2) films were evaluated in planar n-i-p structured solar cells,which exhibit a considerably higher optimal photocurrent density of 11.50 mA cm^(-2) in comparison to that of DCP-based devices(10.69 mA cm^(-2)).By adopting an organic surface passivator,the maximum device efficiency using TCP is further boosted to a record efficiency of 12.8% for CsPbIBr_(2) perovskite solar cells.
基金Supported by the‘Automotive Glazing Application in Intelligent Cockpit Human-Machine Interface’project(SKHX2021049)a collaboration between the Saint-Go Bain Research and the Beijing Normal University。
文摘Background With an increasing number of vehicles becoming autonomous,intelligent,and connected,paying attention to the future usage of car human-machine interface with these vehicles should become more relevant.Several studies have addressed car HMI but were less attentive to designing and implementing interactive glazing for every day(autonomous)driving contexts.Methods Reflecting on the literature,we describe an engineering psychology practice and the design of six novel future user scenarios,which envision the application of a specific set of augmented reality(AR)support user interactions.Additionally,we conduct evaluations on specific scenarios and experiential prototypes,which reveal that these AR scenarios aid the target user groups in experiencing a new type of interaction.The overall evaluation is positive with valuable assessment results and suggestions.Conclusions This study can interest applied psychology educators who aspire to teach how AR can be operationalized in a human-centered design process to students with minimal pre-existing expertise or minimal scientific knowledge in engineering psychology.
基金supported by grants from the National Natural Science Foundation of China(21303251)Innovation Program of Shanghai Municipal Education Commission(16SG17)the Shenzhen Science and Technology Foundation(JCYJ201419122040621)
文摘As the key component of electrochemical energy storage devices, an electrode with superior ions transport pores is the important premise for high electrochemical performance. In this paper, we developed a unique solution process to prepare freestanding TiO_2/graphene hydrogel electrode with tunable density and porous structures. By incorporating room temperature ionic liquids（RTILs）, even upon drying, the non-volatile RTILs that remained in the gel film would preserve the efficient ion transport channels and prevent the electrode from closely stacking, to develop dense yet porous structures. As a result, the dense TiO_2/graphene gel film as an electrode for lithium ion battery displayed a good gravimetric electrochemical performance and more importantly a high volumetric performance.
基金Supported by the National Natural Science Foundation of China(51006052)the Nanjing University of Science and Technology Outstanding Scholar Supporting Program~~
文摘A thrust estimator with high precision and excellent real-time performance is needed to mitigate perfor- mance deterioration for future aero-engines. A weight least squares support vector regression is proposed using a novel weighting strategy. Then a thrust estimator based on the proposed regression is designed for the perfor- mance deterioration. Compared with the existing weighting strategy, the novel one not only satisfies the require- ment of precision but also enhances the real-time performance. Finally, numerical experiments demonstrate the effectiveness and feasibility of the proposed weighted least squares support vector regression for thrust estimator. Key words ： intelligent engine control; least squares ; support vector machine ; performance deterioration
文摘In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, integration design and reliability, are reviewed. The development history of aerospace engine bearing is recalled briefly at first. Then today＇s material technologies and the high bearing performances of the bearings obtained through the new materials are introduced, which play important roils in the aeroengine bearing developments. The integration design ideas and practices are explained to indicate its significant advantages and importance to the aerospace engine bearings. And the reliability of the shaft-bearing system is pointed out and treated as the key requirement with goals for both engine and bearing. Finally, as it is believed that the correct design comes from practice, the pre-qualification rig testing conducted by FAG Aerospace GmbH ＆ Co. KG is briefly illustrated as an example. All these lead to the development trends of aerospace engine bearings from different aspects.
基金Aeronautical Science Foundation of China(2008ZH71006)
文摘The rotating propagation of a continuous detonation engine(CDE)with different types of nozzles is investigated in three-dimensional numerical simulation using a one-step chemical reaction model.Flux terms are solved by the so-called monotonicity-preserving weighted essentially non-oscillatory(MPWENO)scheme.The simulated flow field agrees well with the previous experimental results.Once the initial transient effects die down,the detonation wave maintains continuous oscillatory propagation in the annular chamber as long as fuel is continuously injected.Using a numerical flow field,the propulsion per-formance of a CDE is computed for four types of nozzles,namely the constant-area nozzle,Laval nozzle,diverging nozzle and converging nozzle.The gross specific impulse of the CDE ranges 1540-1750 s and the mass flux per square meter ranges 313-330 kg/(m2·s)for different nozzles.Among these four types of nozzles,Laval nozzle performs the best,and these parameters are 1800 N,1750 s and 313 kg/(m2.s).A nozzle can greatly improve the propulsion performance.
文摘In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel.Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10%（by volume） of hexanol and 90%（by volume） neat cashew nut shell biodiesel was referred to as CNSBD900 H100 and fuel comprising 20%（by volume） of hexanol and 80%（by volume）of neat cashew nut shell biodiesel was referred to as CNSBD800 H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at10% and 20%（by volume） to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine.
基金funded by National Nature Science Foundation of China(Nos.51776010 and 91860205)supported by the Academic Excellence Foundation of BUAA for PhD Students,China。
文摘The alternative working modes and flexible working states are the outstanding features of an adaptive cycle engine, with a proper control schedule design being the only way to exploit the performance of such an engine. However, unreasonable design in the control schedule causes not only performance deterioration but also serious aerodynamic stability problems. Thus, in this work,a hybrid optimization method that automatically chooses the working modes and identifies the optimal and smooth control schedules is proposed, by combining the differential evolution algorithm and the Latin hypercube sampling method. The control schedule architecture does not only optimize the engine steady-state performance under different working modes but also solves the control-schedule discontinuity problem, especially during mode transition. The optimal control schedules are continuous and almost monotonic, and hence are strongly suitable for a control system, and are designed for two different working conditions, i.e., supersonic and subsonic throttling,which proves that the proposed hybrid method applies to various working conditions. The evaluation demonstrates that the proposed control method optimizes the engine performance, the surge margin of the compression components, and the range of the thrust during throttling.
文摘Achieving simultaneous reduction of NOx,CO and unburned hydrocarbon(UHC) emissions without compromising engine performance at part loads is the current focus of dual fuel engine research.The present work focuses on an experimental investigation conducted on a dual fuel(diesel-natural gas) engine to examine the simultaneous effect of inlet air pre-heating and exhaust gas recirculation(EGR) ratio on performance and emission characteristics at part loads.The use of EGR at high levels seems to be unable to improve the engine performance at part loads.However,it is shown that EGR combined with pre-heating of inlet air can slightly increase thermal efficiency,resulting in reduced levels of both unburned hydrocarbon and NOx emissions.CO and UHC emissions are reduced by 24% and 31%,respectively,The NOx emissions decrease by 21% because of the lower combustion temperature due to the much inert gas brought by EGR and decreased oxygen concentration in the cylinder.
基金National Natural Science Foundation(50375078)Key Discipline Construction Program of Beijing.
文摘The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and scavenge processes based on the open thermodynamic systems were presented. A simulation was executed at given geometric parameters and initial conditions. The results manifest that the working principle of MFPSE is feasible.
基金Supported by the Major Plan Projects of Science and Technology of Jiangxi Provincial Department of Education(GJJ151145)the Youth Science Fund Project Science and Technology of Jiangxi Provincial Department of Science and Technology(20114BAB216002)the Plan Projects of Science and Technology of Jiangxi Provincial Department of Science and Technology(2016BBE50074)
文摘In the condition of constant speed and light load, an experimental study of a turbocharged and intercooled diesel engine with exhaust gas recirculation （EGR） system focuses on the influence of different EGR rates on combustion process, dynamic performance, economic performance and emission performance of a diesel engine. With the increase of EGR rate, the oxygen concentration of the intake-side decreases, the fuel air equivalence ratio increases, and the maximum explosion pressure in the cylinder decreases. Meanwhile, the average temperature in the cylinder drops, the ignition delay is prolonged, the ignition timing delays, and the maximum heat release rate decreases. The increase of EGR rate makes NOx emissions decrease obviously and continue to decline. When EGR is low, the smoke rate enlarges slowly with the increase of EGR rate, and enlarges greatly at the rate higher than 43% and reaches the maximum at the rate of 57%. When EGR rate is higher than 61%, the smoke rate drops rapidly, and the content of CO and hydrocarbon （HC） increases rapidly with high EGR rate.
文摘This study paves the way on reducing smoke emission and NO_x emissions of research diesel engine by detailing the e ect of water addition in biodiesel. Fuel samples were prepared with di erent concentrations of water in orange peel oil biodiesel(94% waste orange peel oil biodiesel + 4% water + 2% Span 80(WOPOBDE1) and 90% waste orange peel oil biodiesel + 8% water + 2% Span 80(WOPOBDE2). Span 80 was employed as a nonionic surfactant, which emulsifies water in biodiesel. Experimental results revealed that the nitrogen oxides and smoke emission of orange peel oil biodiesel emulsion were reduced by 11%–19% and 3%–21%, respectively, compared to that of neat orange peel oil biodiesel(WOPOBD). In addition, the introduction of orange peel oil–water emulsions in the diesel engine considerably reduced the emissions of unburned hydrocarbons and carbon monoxide. The overall hydrocarbon emission of WOPOBDE2 was 12.2% lower than that of WOPOBD and 16.3% lower than that of diesel. The overall CO emission of WOPOBDE2 was 17% lower than that of base fuel(WOPOBD) and 21.8% lower than that of diesel. Experimental results revealed that modified fuel had higher brake thermal e ciency and lower brake specific fuel consumption than that of base fuel at all engine brake power levels.
