Since an engine is seen as the″heart″of an airplane,the objective and scientific evaluation of it is significant to ensure normal operation of airlines.Aiming at the limitations of current studies on selecting engin...Since an engine is seen as the″heart″of an airplane,the objective and scientific evaluation of it is significant to ensure normal operation of airlines.Aiming at the limitations of current studies on selecting engines,a quantitative comprehensive evaluation system of engine options was established and an optimization model based on the utility theory and analytic hierarchy process(AHP)was proposed.Considering the judgement of different customers on the balance between income and risk,the utility of each evaluation index was determined by utilizing the piecewise utility function.The AHP was used to analyze individual demands of customers.Finally,the optimal scheme was selected through calculating the weighted utility value.According to the actual needs of a domestic airline,the utility of three engine options was calculated.The results showed that the value of risk factor can be set to determine the selection scheme based on the degree of preferences(conservative type,neutral type or adventurous type).展开更多
Agricultural land development is a pivotal strategy for addressing the global food security crisis.Barren grassland,especially those in mountainous regions,constitutes critical areas where cultivation can substantiall...Agricultural land development is a pivotal strategy for addressing the global food security crisis.Barren grassland,especially those in mountainous regions,constitutes critical areas where cultivation can substantially enhance land resources.This study highlights the necessity for a precise correlation between land development initiatives and constraints in order to optimize efficiency and enhance the effectiveness of such projects,with the core being the seamless integration of land development engineering and techniques to eliminate agricultural constraints.This study employs a systems engineering approach to classify improvement factors into mobile and fixed categories,elucidating the integration methods of constraint factors.Adhering to the Wooden Barrel Principle,these constraints were rigorously analyzed based on soil quality,land topography,water availability,and agricultural infrastructure.An innovative method of engineering type combination is proposed,which effectively explains the correlation between natural factors combination,project type combination,and target factors combination.It provides a convenient way for the selection of barren grassland development projects and lays a foundation for land planning,development project establishment,program selection,engineering design,and budget preparation.Taking Tang County of China as an example,it is divided into 19 factor improvement areas,a quick reference table of engineering types is established,and 14 main types of engineering combinations are obtained,which lays a foundation for the application of theoretical framework in practice.展开更多
A job shop scheduling problem with a combination processing in complex production environment is proposed. Based on the defining of ＂non-elastic combination processing relativity＂ and ＂virtual process＂, the proble...A job shop scheduling problem with a combination processing in complex production environment is proposed. Based on the defining of ＂non-elastic combination processing relativity＂ and ＂virtual process＂, the problem can be simplified and transformed to a traditional one. On the basis of the dispatching rules select engine and considered factors of complex production environment, a heuristic method is designed. The algorithm has been applied to a mould enterprise in Shenzhen for half a year. The practice showed that by using the method suggested the number of delayed orders was decreased about 20% and the productivity was increased by 10 to 20%.展开更多
It is well known that hydrogen has less undesirable exhaust emissions as compared with other types of liquid fuels.It can be used as an altemative fuel for a hybnid buoyant aircraft in which half of the gross takeoff ...It is well known that hydrogen has less undesirable exhaust emissions as compared with other types of liquid fuels.It can be used as an altemative fuel for a hybnid buoyant aircraft in which half of the gross takeoff weight is balanced by the aerostatic lift.In the present study,weight advantage of liquid hydrogen as an ideal fuel has been explored for its further utilization in such aircraft.Existing relationships for the estimation of zero lift drag of airship is discussed with special focus on the utilization of such analytical relationships for the aircraft whose fuselage resembles with the hull of an airship.Taking the analytical relationship of aircraft and airship design as a reference,existing relationships for estimation of power budget are systematically re-derived for defined constraints of rate of climb,maximum velocity and takeoff ground roll.It is perceived that when the propulsion sizing for liquid hydrogen is required,then the presented framework for estimation of its power budget will provide a stating point for the analysis.An example for estimation of the power requirement is also presented as a test case.展开更多
A model of an energy selective electron (ESE) engine with linear heat leakage and Lorentzian transmission probability is established in this paper.The expressions for the main performance parameters of the ESE engine ...A model of an energy selective electron (ESE) engine with linear heat leakage and Lorentzian transmission probability is established in this paper.The expressions for the main performance parameters of the ESE engine operating as a heat engine or a refrigerator are derived by using the theory of finite time thermodynamics.The optimum performances of the ESE engine are explored and the influences of the heat leakage,the central energy level of the resonance,and the width of the resonance on the performance of the ESE engine are analyzed by using detailed numerical examples.The optimal operation regions of power output and efficiency (or cooling load and coefficient of performance (COP)) are also discussed.Moreover,the performances of the ESE engine with Lorentzian transmission probability are compared with those with rectangular transmission probability.It is shown that the power output versus efficiency (or cooling load versus COP) characteristic curves with and without heat leakage are all closed loop-shaped ones.The efficiency (or COP) of the ESE engine decreases as the heat leakage increases.It is found that as the resonance width increases,the power output and efficiency (or cooling load and COP) increase to a maximum and then decrease due to the finite range of energies which contribute positively to the power generation or refrigeration in the electron system.Especially,when heat leakage is taken into account,the characteristic curves of maximum efficiency (or maximum COP) versus half resonance width are parabolic-like ones,which are quite different from the monotonic decreasing characteristic curves obtained in previous analyses without considering heat leakage.The results obtained in this paper can provide some theoretical guidelines for the design and operation of practical electron energy conversion devices such as solid-state thermionic refrigerators.展开更多
Surface modification of graphene oxide(GO)is a powerful strategy to develop its energy density for electrochemical energy storage.However,pre-modified GO always exhibits unsatisfactory hydrophilia and its ink-relevant...Surface modification of graphene oxide(GO)is a powerful strategy to develop its energy density for electrochemical energy storage.However,pre-modified GO always exhibits unsatisfactory hydrophilia and its ink-relevant utilization is extremely limited.Although GO ink is widely utilized in fabricating micro energy storage devices via extrusion-based 3D-printing,simultaneously obtaining satisfactory hydrophilia and high energy density still remains a challenge.In this work,an in-situ surface engineering strategy was employed to enhance the performance of GO micro-supercapacitor chips.Three dimensionally printed GO micro-supercapacitor chips were treated with pyrrole monomer to achieve selective and spontaneous anchoring of polypyrrole on the microelectrodes without affecting interspaces between the finger electrodes.The interface-reinforced graphene scaffolds were edge-welded and exhibited a considerably improved specific capacitance,from 13.6 to 128.4 mF·cm^(-2).These results are expected to provide a new method for improving the performance of micro-supercapacitors derived from GO inks and further strengthen the practicability of 3D printing techniques in fabricating energy storage devices.展开更多
The reasonable calculation of ground appropriateness index in permafrost region is the precondition of highway route design in permafrost region. The theory of knowledge base and fuzzy mathematics are applied, and the...The reasonable calculation of ground appropriateness index in permafrost region is the precondition of highway route design in permafrost region. The theory of knowledge base and fuzzy mathematics are applied, and the damage effect of permafrost is considered in the paper. Based on the idea of protecting permafrost the calculation method of ground appro- priateness index is put forward. Firstly, based on the actual environment conditions, the paper determines the factors affecting the road layout in permafrost areas by qualitative and quantitative analysis, including the annual slope, the average annual ground temperature of permafrost, the amount of ice in frozen soil, and the interference engineering. Secondly, based on the knowledge base theory and the use of Delphi method, the paper establishes the knowledge base, the rule base of the permafrost region and inference mechanism. The method of selecting the road in permafrost region is completed and realized by using the software platform. Thirdly, taking the Tuotuo River to Kaixin Mountain section of permafrost region as an example, the application of the method is studied by using an ArcGIS platform. Results show that the route plan determined by the method of selecting the road in perma-frost region can avoid the high temperature and high ice content area, conform the terrain changes and evade the heat disturbance among the existing projects. A reasonable route plan can be achieved, and it can provide the basis for the next engineering construction.展开更多
Atomic composition tuning and defect engineering are effective strategies to enhance the catalytic performance of multicomponent catalysts by improving the synergetic effect; however, it remains challenging to dramati...Atomic composition tuning and defect engineering are effective strategies to enhance the catalytic performance of multicomponent catalysts by improving the synergetic effect; however, it remains challenging to dramatically tune the active sites on mulficomponent materials through simultaneous defect engineering at the atomic scale because of the similarities of the local environment. Herein, using the oxygen evolution reaction （OER） as a probe reaction, we deliberately introduced base-soluble Zn（II） or AI（III） sites into NiFe layered double hydroxides （LDHs）, which are one of the best OER catalysts. Then, the Zn（II） or AI（III） sites were selectively etched to create atomic M（I0/M（IIo defects, which dramatically enhanced the OER activity. At a current density of 20 mA.cm-2, only 200 mV overpotential was required to generate M（II） defect-rich NiFe LDHs, which is the best NiFe-based OER catalyst reported to date. Density functional theory （DFT） calculations revealed that the creation of dangling Ni-Fe sites （i.e., unsaturated coordinated Ni-Fe sites） by defect engineering of a Ni-O-Fe site at the atomic scale efficiently lowers the Gibbs free energy of the oxygen evolution process. This defect engineering strategy provides new insights into catalysts at the atomic scale and should be beneficial for the design of a variety of catalysts.展开更多
文摘Since an engine is seen as the″heart″of an airplane,the objective and scientific evaluation of it is significant to ensure normal operation of airlines.Aiming at the limitations of current studies on selecting engines,a quantitative comprehensive evaluation system of engine options was established and an optimization model based on the utility theory and analytic hierarchy process(AHP)was proposed.Considering the judgement of different customers on the balance between income and risk,the utility of each evaluation index was determined by utilizing the piecewise utility function.The AHP was used to analyze individual demands of customers.Finally,the optimal scheme was selected through calculating the weighted utility value.According to the actual needs of a domestic airline,the utility of three engine options was calculated.The results showed that the value of risk factor can be set to determine the selection scheme based on the degree of preferences(conservative type,neutral type or adventurous type).
基金funded by Science and Technology Project of Hebei Education Department[QN2023085].
文摘Agricultural land development is a pivotal strategy for addressing the global food security crisis.Barren grassland,especially those in mountainous regions,constitutes critical areas where cultivation can substantially enhance land resources.This study highlights the necessity for a precise correlation between land development initiatives and constraints in order to optimize efficiency and enhance the effectiveness of such projects,with the core being the seamless integration of land development engineering and techniques to eliminate agricultural constraints.This study employs a systems engineering approach to classify improvement factors into mobile and fixed categories,elucidating the integration methods of constraint factors.Adhering to the Wooden Barrel Principle,these constraints were rigorously analyzed based on soil quality,land topography,water availability,and agricultural infrastructure.An innovative method of engineering type combination is proposed,which effectively explains the correlation between natural factors combination,project type combination,and target factors combination.It provides a convenient way for the selection of barren grassland development projects and lays a foundation for land planning,development project establishment,program selection,engineering design,and budget preparation.Taking Tang County of China as an example,it is divided into 19 factor improvement areas,a quick reference table of engineering types is established,and 14 main types of engineering combinations are obtained,which lays a foundation for the application of theoretical framework in practice.
基金Supported by Research Fund for the Doctoral Program of Higher Education of China(20060487072)National Key Technology R&D Program(2006BAF01A43)
文摘A job shop scheduling problem with a combination processing in complex production environment is proposed. Based on the defining of ＂non-elastic combination processing relativity＂ and ＂virtual process＂, the problem can be simplified and transformed to a traditional one. On the basis of the dispatching rules select engine and considered factors of complex production environment, a heuristic method is designed. The algorithm has been applied to a mould enterprise in Shenzhen for half a year. The practice showed that by using the method suggested the number of delayed orders was decreased about 20% and the productivity was increased by 10 to 20%.
文摘It is well known that hydrogen has less undesirable exhaust emissions as compared with other types of liquid fuels.It can be used as an altemative fuel for a hybnid buoyant aircraft in which half of the gross takeoff weight is balanced by the aerostatic lift.In the present study,weight advantage of liquid hydrogen as an ideal fuel has been explored for its further utilization in such aircraft.Existing relationships for the estimation of zero lift drag of airship is discussed with special focus on the utilization of such analytical relationships for the aircraft whose fuselage resembles with the hull of an airship.Taking the analytical relationship of aircraft and airship design as a reference,existing relationships for estimation of power budget are systematically re-derived for defined constraints of rate of climb,maximum velocity and takeoff ground roll.It is perceived that when the propulsion sizing for liquid hydrogen is required,then the presented framework for estimation of its power budget will provide a stating point for the analysis.An example for estimation of the power requirement is also presented as a test case.
基金supported by the National Natural Science Foundation of China (Grant No. 10905093)the Program for New Century Excellent Talents in Universities of China (Grant No. NCET-04-1006)the Foundation for the Author of National Excellent Doctoral Dissertation ofChina (Grant No. 200136)
文摘A model of an energy selective electron (ESE) engine with linear heat leakage and Lorentzian transmission probability is established in this paper.The expressions for the main performance parameters of the ESE engine operating as a heat engine or a refrigerator are derived by using the theory of finite time thermodynamics.The optimum performances of the ESE engine are explored and the influences of the heat leakage,the central energy level of the resonance,and the width of the resonance on the performance of the ESE engine are analyzed by using detailed numerical examples.The optimal operation regions of power output and efficiency (or cooling load and coefficient of performance (COP)) are also discussed.Moreover,the performances of the ESE engine with Lorentzian transmission probability are compared with those with rectangular transmission probability.It is shown that the power output versus efficiency (or cooling load versus COP) characteristic curves with and without heat leakage are all closed loop-shaped ones.The efficiency (or COP) of the ESE engine decreases as the heat leakage increases.It is found that as the resonance width increases,the power output and efficiency (or cooling load and COP) increase to a maximum and then decrease due to the finite range of energies which contribute positively to the power generation or refrigeration in the electron system.Especially,when heat leakage is taken into account,the characteristic curves of maximum efficiency (or maximum COP) versus half resonance width are parabolic-like ones,which are quite different from the monotonic decreasing characteristic curves obtained in previous analyses without considering heat leakage.The results obtained in this paper can provide some theoretical guidelines for the design and operation of practical electron energy conversion devices such as solid-state thermionic refrigerators.
基金supported by the National Key Research and Development Program of China(No.2020YFA715000)the National Natural Science Foundation of China(No.51802239)+3 种基金the National Key Research and Development Program of China(No.2019YFA0704902)Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(Nos.XHT2020-005 and XHT2020-003)the Natural Science Foundation of Hubei Province(No.2019CFA001)the Fundamental Research Funds for the Central Universities(Nos.2020III011GX,2020IVB057,2019IVB054,2019III062JL,and 2019-YB-008).
文摘Surface modification of graphene oxide(GO)is a powerful strategy to develop its energy density for electrochemical energy storage.However,pre-modified GO always exhibits unsatisfactory hydrophilia and its ink-relevant utilization is extremely limited.Although GO ink is widely utilized in fabricating micro energy storage devices via extrusion-based 3D-printing,simultaneously obtaining satisfactory hydrophilia and high energy density still remains a challenge.In this work,an in-situ surface engineering strategy was employed to enhance the performance of GO micro-supercapacitor chips.Three dimensionally printed GO micro-supercapacitor chips were treated with pyrrole monomer to achieve selective and spontaneous anchoring of polypyrrole on the microelectrodes without affecting interspaces between the finger electrodes.The interface-reinforced graphene scaffolds were edge-welded and exhibited a considerably improved specific capacitance,from 13.6 to 128.4 mF·cm^(-2).These results are expected to provide a new method for improving the performance of micro-supercapacitors derived from GO inks and further strengthen the practicability of 3D printing techniques in fabricating energy storage devices.
基金support provide by Special Fund for Basic Scientific Research of Central Col leges, Changan University (310821172002)Postdoctoral Science Foundation of China (2016M590915)+2 种基金Basic Research Func of Ministry of Transportation (2014319812170)National Sci Tech Support Plan (2014BAG05B01)Basic Research Program of Natural Science in Shaanxi Province (S2017-ZRJJ-MS0603)
文摘The reasonable calculation of ground appropriateness index in permafrost region is the precondition of highway route design in permafrost region. The theory of knowledge base and fuzzy mathematics are applied, and the damage effect of permafrost is considered in the paper. Based on the idea of protecting permafrost the calculation method of ground appro- priateness index is put forward. Firstly, based on the actual environment conditions, the paper determines the factors affecting the road layout in permafrost areas by qualitative and quantitative analysis, including the annual slope, the average annual ground temperature of permafrost, the amount of ice in frozen soil, and the interference engineering. Secondly, based on the knowledge base theory and the use of Delphi method, the paper establishes the knowledge base, the rule base of the permafrost region and inference mechanism. The method of selecting the road in permafrost region is completed and realized by using the software platform. Thirdly, taking the Tuotuo River to Kaixin Mountain section of permafrost region as an example, the application of the method is studied by using an ArcGIS platform. Results show that the route plan determined by the method of selecting the road in perma-frost region can avoid the high temperature and high ice content area, conform the terrain changes and evade the heat disturbance among the existing projects. A reasonable route plan can be achieved, and it can provide the basis for the next engineering construction.
文摘Atomic composition tuning and defect engineering are effective strategies to enhance the catalytic performance of multicomponent catalysts by improving the synergetic effect; however, it remains challenging to dramatically tune the active sites on mulficomponent materials through simultaneous defect engineering at the atomic scale because of the similarities of the local environment. Herein, using the oxygen evolution reaction （OER） as a probe reaction, we deliberately introduced base-soluble Zn（II） or AI（III） sites into NiFe layered double hydroxides （LDHs）, which are one of the best OER catalysts. Then, the Zn（II） or AI（III） sites were selectively etched to create atomic M（I0/M（IIo defects, which dramatically enhanced the OER activity. At a current density of 20 mA.cm-2, only 200 mV overpotential was required to generate M（II） defect-rich NiFe LDHs, which is the best NiFe-based OER catalyst reported to date. Density functional theory （DFT） calculations revealed that the creation of dangling Ni-Fe sites （i.e., unsaturated coordinated Ni-Fe sites） by defect engineering of a Ni-O-Fe site at the atomic scale efficiently lowers the Gibbs free energy of the oxygen evolution process. This defect engineering strategy provides new insights into catalysts at the atomic scale and should be beneficial for the design of a variety of catalysts.
