Lead-free halide double perovskites have recently attracted significant attention due to their exceptional stability and favorable band gaps,making them promising candidates for solar cell applications.However,the rel...Lead-free halide double perovskites have recently attracted significant attention due to their exceptional stability and favorable band gaps,making them promising candidates for solar cell applications.However,the relationship between their structural characteristics and intrinsic band gap remains under-explored.This study presents a method to investigate the structure-band gap correlation in a typical halide double perovskite,MA_(2)Pt_(6)(MA^(+)=CH_(3)NH_(3)^(+)),using high pressure techniques.The band gap of MA_(2)PtI_(6)is effectively reduced at two different rates of 0.063 eV/GPa and 0.079 eV/GPa before and after 1.2 GPa,and progressively closes as pressure further increases.These optical changes are closely related to the pressure induced structural evolution of MA_(2)PtI_(6).Moreover,a phase transition from trigonal(R-3m)to monoclinic(P2/m)occurs at 1.2 GPa and completes by 2.0 GPa,driven by pressure-induced distortion of the[PtI_(6)]^(2-)octahedra,which is responsible for the variation of the band gap.These promising findings pave the way for potential applications in the structural and band gap tuning of halide double perovskites.展开更多
With a focus on an industrial multivariable system, two subsystems including the flow and the level outputs are analysed and controlled, which have applicability in both real and academic environments. In such a case,...With a focus on an industrial multivariable system, two subsystems including the flow and the level outputs are analysed and controlled, which have applicability in both real and academic environments. In such a case, at first, each subsystem is distinctively represented by its model, since the outcomes point out that the chosen models have the same behavior as corresponding ones. Then, the industrial multivariable system and its presentation are achieved in line with the integration of these subsystems, since the interaction between them can not actually be ignored. To analyze the interaction presented, the Gershgorin bands need to be acquired, where the results are used to modify the system parameters to appropriate values. Subsequently, in the view of modeling results, the control concept in two different techniques including sequential loop closing control(SLCC) scheme and diagonal dominance control(DDC) schemes is proposed to implement on the system through the Profibus network, as long as the OPC(OLE for process control) server is utilized to communicate between the control schemes presented and the multivariable system. The real test scenarios are carried out and the corresponding outcomes in their present forms are acquired. In the same way, the proposed control schemes results are compared with each other, where the real consequences verify the validity of them in the field of the presented industrial multivariable system control.展开更多
Understanding the stress-strain relationship and permeability change for contact compression fracture at closing stage has been a hot issue for a long time.Previous investigations of this topic were mainly focused on ...Understanding the stress-strain relationship and permeability change for contact compression fracture at closing stage has been a hot issue for a long time.Previous investigations of this topic were mainly focused on experimental tests;however,theoretical approaches were rarely reported.Based on this,this paper focuses on the contact fracture at closing stage when rock is uniaxially loaded,and then a theoretical model is proposed.Based on the change of fracture elasticity modulus,it shows that as crack apertures are gradually reduced in the loading process,the permeability of rock sample will decrease progressively.This scenario shows that theoretical computation matches well with the experimental results.Finally,the effects of ratio of sample size to fracture aperture(n).pore pressure(P),and initial aperture(b) on stress-strain relationship and permeability change for contact compression fracture at closing stage are analyzed.展开更多
A coaxial multi-gap multi-channel spark switch with stainless-steel-spring ring gap electrodes is designed and investigated. The switch is triggered by a pulse applied to the cylindrical electrode outside the discharg...A coaxial multi-gap multi-channel spark switch with stainless-steel-spring ring gap electrodes is designed and investigated. The switch is triggered by a pulse applied to the cylindrical electrode outside the discharging channel through a parasitic capacitance coupling. The jitter of the switch is reduced by several short-distance gas gaps in series, and its inductance is reduced by a multi-channel discharge on account of the inductance isolation between the coils of the spring ring electrode. The experimental results indicate that the switch is of low inductance (15-30 nH), low jitter (-3 ns), and stable breakdown performance展开更多
In this study,a one-dimensional simulation was performed to evaluate the performance of in-cylinder combustion to control NO_(x) emissions on a four-stroke,six-cylinder marine medium-speed diesel engine.Reducing the c...In this study,a one-dimensional simulation was performed to evaluate the performance of in-cylinder combustion to control NO_(x) emissions on a four-stroke,six-cylinder marine medium-speed diesel engine.Reducing the combustion temperature is an important in-cylinder measure to decrease NO_(x) emissions of marine diesel engines.The Miller cycle is an effective method used to reduce the maximum combustion temperature in a cylinder and accordingly decrease NO_(x) emissions.Therefore,the authors of this study designed seven different early intake valve closing(EIVC)Miller cycles for the original engine,and analyzed the cycle effects on combustions and emissions in high-load conditions.The results indicate that the temperature in the cylinder was significantly reduced,whereas fuel consumption was almost unchanged.When the IVC was properly advanced,the ignition delay period increased and the premixed combustion accelerated,but the in-cylinder average pressure,temperature and NO_(x) emissions in the cylinder were lower than the original engine.However,closing the intake valve too early led to high fuel consumption.In addition,the NO_(x) emissions,in-cylinder temperature,and heat release rate remarkably increased.Therefore,the optimal timing of the EIVC varied with different loads.The higher the load was,the earlier the best advance angle appeared.Therefore,the Miller cycle is an effective method for in-engine NO_(x) purification and does not entail significant cost.展开更多
This paper presents a new type of fault current limiter (FCL) based on fast closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast closing switch connecte...This paper presents a new type of fault current limiter (FCL) based on fast closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. It can response the order within 1 ms. When fault occurs, the switch closes and the capacitors are bypassed, and the fault current is limited by the reactor. Simulation analysis and experiment show that the electromagnetic repulsion force actuator can meet the demand of fast closing switch, it is feasible to develop the FCL with low cost and high reliability.展开更多
Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled an...Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.展开更多
In order to improve the registration accuracy of brain magnetic resonance images(MRI),some deep learning registration methods use segmentation images for training model.How-ever,the segmentation values are constant fo...In order to improve the registration accuracy of brain magnetic resonance images(MRI),some deep learning registration methods use segmentation images for training model.How-ever,the segmentation values are constant for each label,which leads to the gradient variation con-centrating on the boundary.Thus,the dense deformation field(DDF)is gathered on the boundary and there even appears folding phenomenon.In order to fully leverage the label information,the morphological opening and closing information maps are introduced to enlarge the non-zero gradi-ent regions and improve the accuracy of DDF estimation.The opening information maps supervise the registration model to focus on smaller,narrow brain regions.The closing information maps supervise the registration model to pay more attention to the complex boundary region.Then,opening and closing morphology networks(OC_Net)are designed to automatically generate open-ing and closing information maps to realize the end-to-end training process.Finally,a new registra-tion architecture,VM_(seg+oc),is proposed by combining OC_Net and VoxelMorph.Experimental results show that the registration accuracy of VM_(seg+oc) is significantly improved on LPBA40 and OASIS1 datasets.Especially,VM_(seg+oc) can well improve registration accuracy in smaller brain regions and narrow regions.展开更多
Distinguished vips,Ladies and gentlemen,friends,With the joint efforts of all of you,the 2013"Understanding&Cooperation"Dialogue,held by the Chinese Association for International Understanding(CAFIU)ha...Distinguished vips,Ladies and gentlemen,friends,With the joint efforts of all of you,the 2013"Understanding&Cooperation"Dialogue,held by the Chinese Association for International Understanding(CAFIU)has successfully completed all items on its agenda.It’s time to bid farewell.During the past 4 days,we came across over half China from Beijing to Jiangxi Province,feeling the hot summer days and witnessing展开更多
The existing research of the automotive side swing door and the closing angle via tests and simulations. In these tests, the closing energy is mainly conducted by measuring the closing energy door closing velocity and...The existing research of the automotive side swing door and the closing angle via tests and simulations. In these tests, the closing energy is mainly conducted by measuring the closing energy door closing velocity and initial door closing angle are usually not taken into consideration, so the accuracy of the test data cannot be ensured, and, meanwhile, simulations require a great deal of manpower and time. Moreover, frequent tests would give rise to the increasing research and development costs. In this paper, in response to the deficiencies of these current methods, the complicated door closing process is decomposed into the closing processes of different subsystems of door, which includes weather strip seal＇, air-binding effect, door weight, hinge, check-link and latch. Mathematical models of those subsystems are established according to their working principles during the door closing process. In addition to the theoretical research, an Excel-based software using Visual Basic Application programming language is developed to realize the mathematical models, which aims to calculate the energy consumption of the subsystems. The energy consumption of different subsystems of a production vehicle door is measured to verify the accuracy of the calculation sottware developed. The proposed research provides not only the theoretical basis for the future door closing energy research, but also an interactive method and system, effectively improving the quality and efficiency of vehicle door design.展开更多
A logaritmic series distribution model was used to evaluate the index of population diversity (α value) inQuercus mongolica forest in Zhanguangcai Mountains, Heilongjiang, Northeastern China. The α value went up fro...A logaritmic series distribution model was used to evaluate the index of population diversity (α value) inQuercus mongolica forest in Zhanguangcai Mountains, Heilongjiang, Northeastern China. The α value went up from 1.07 to 4.46–6.98, after closing hillsides for 20 years. The spatial distribution of the α value was calculated among the hill slopes. The results were as follows: middle of hill>bottom of hill>top of hill.展开更多
The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-,...The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-, in the form of a yellow-green crystalline solid in a yield of 94%. This two-core ruthenium complex is a selective catalyst for ring closing metathesis of unsubstituted terminal dienes. More importantly, no isomerized byproduct was observed for N-substrates when the two-core ruthenium complex was used as the catalyst at an elevated temperature（137 °C）, indicating that the complex is a chemo-selective catalyst for ring closing metathesis reactions.展开更多
A microscopic damage model of ellipsoidal body containing ellipsoidal void for nonlinear matrix materials is developed under a particular coordinate. The change of void shape is considered in this model. The viscous r...A microscopic damage model of ellipsoidal body containing ellipsoidal void for nonlinear matrix materials is developed under a particular coordinate. The change of void shape is considered in this model. The viscous restrained equation obtained from the model is affected by stress ?ij, void volume fraction f, material strain rate exponent m as well as the void shape. Gurson's equation is modified from the numerical solution. The modified equation is suitable for the case of nonlinear matrix materials and changeable voids. Lastly, the model is used to analyze the closing process of voids.展开更多
Phosphorus （P） reserve, largely derived from phosphate rock, is essential for crop growth to support the growing world population. However, a significant proportion of phosphorus used as a fertilizer runs into natur...Phosphorus （P） reserve, largely derived from phosphate rock, is essential for crop growth to support the growing world population. However, a significant proportion of phosphorus used as a fertilizer runs into natural waters, causing eutro- phication and ecological damage. Moreover, most P in the food is eventually discharged as waste after being digested by human and animals. Thus, industrial activities have created a one-way flow of non-renewable P from rocks to farms to lakes, rivers and oceans.展开更多
The water resisting property of aquiclude is the key factor of water conservation and safety mining, and the mining induced cracks in aquiclude is major factor of water resisting property. The aquiclude is composed by...The water resisting property of aquiclude is the key factor of water conservation and safety mining, and the mining induced cracks in aquiclude is major factor of water resisting property. The aquiclude is composed by loess layer and red clay layer in Yushuwan Coal Mine, and the water reaction property of clay and loess of aquiclude was tested by soil mechanics method. The permeability coefficient of the loess is 0.856 m/d and the clay is 0.434 m/d. The dilatability coefficient of the loess is 16.1% and the clay is 14.6%. Through physical solid-liquid simulation with whole stress-stain similarity, the distribution of ＂downward crack zone＂ and ＂upward crack zone＂ was found to be the major factor of aquiclude stability. The downward crack closing length is about 30% of the downward crack length. The expanding of clay and loess with water are principal factors of downward crack closing. At last, the mechanical model of downward crack closing was constructed, and the criterion of crack closing was put forward at all. This work will provides the theoretical base for aquiclude stability research and safety mining in shallow seam.展开更多
The Francis turbine governing system models in PSD-BPA can’t precisely reflect the actual characteristics. Endeavor was done in this paper to solve the problem. An improved model of actuating mechanism was developed,...The Francis turbine governing system models in PSD-BPA can’t precisely reflect the actual characteristics. Endeavor was done in this paper to solve the problem. An improved model of actuating mechanism was developed, which could reflect the step closing characteristic of hydro guide vanes. The effect of the inflection point value of actuating mechanism on load rejection was analyzed based on simulation. The non-linear Francis turbine model with power versus gate position module was researched in this paper. Based on field test, comparisons of simulation results with measured data were presented. The analysis demonstrates that the improved models of Francis turbine and governor proposed in this paper are more realistic than the models of BPA, and can be applied in power system simulation analysis better.展开更多
Until late in this century,most Ameri-cans spent time with people of all generations.Now baby boomers may not have muchcontact with old people until they re relativelyold themselves.That s because we group people by a...Until late in this century,most Ameri-cans spent time with people of all generations.Now baby boomers may not have muchcontact with old people until they re relativelyold themselves.That s because we group people by age.We put our three-year-olds together in day-care centers,our 13-year-olds in schools展开更多
The model QQCplankton net closing gear is a device designed to control the stratifiedsampling of the plankton net by means of a messenger. The device in its fie1d use has met with98% success in 766 times of strtified ...The model QQCplankton net closing gear is a device designed to control the stratifiedsampling of the plankton net by means of a messenger. The device in its fie1d use has met with98% success in 766 times of strtified sampling of plankton at 157 stations during separatesurveys of Fujian coast zone, the Taiwan Strait, and the central section of the South China Sea,展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12474414)the Natural Science Foundation of Henan(Grant No.242300421157)the ADXRD measurement was performed at the 4W2 beamline,the Beijing Synchrotron Radiation Facility(BSRF).
文摘Lead-free halide double perovskites have recently attracted significant attention due to their exceptional stability and favorable band gaps,making them promising candidates for solar cell applications.However,the relationship between their structural characteristics and intrinsic band gap remains under-explored.This study presents a method to investigate the structure-band gap correlation in a typical halide double perovskite,MA_(2)Pt_(6)(MA^(+)=CH_(3)NH_(3)^(+)),using high pressure techniques.The band gap of MA_(2)PtI_(6)is effectively reduced at two different rates of 0.063 eV/GPa and 0.079 eV/GPa before and after 1.2 GPa,and progressively closes as pressure further increases.These optical changes are closely related to the pressure induced structural evolution of MA_(2)PtI_(6).Moreover,a phase transition from trigonal(R-3m)to monoclinic(P2/m)occurs at 1.2 GPa and completes by 2.0 GPa,driven by pressure-induced distortion of the[PtI_(6)]^(2-)octahedra,which is responsible for the variation of the band gap.These promising findings pave the way for potential applications in the structural and band gap tuning of halide double perovskites.
文摘With a focus on an industrial multivariable system, two subsystems including the flow and the level outputs are analysed and controlled, which have applicability in both real and academic environments. In such a case, at first, each subsystem is distinctively represented by its model, since the outcomes point out that the chosen models have the same behavior as corresponding ones. Then, the industrial multivariable system and its presentation are achieved in line with the integration of these subsystems, since the interaction between them can not actually be ignored. To analyze the interaction presented, the Gershgorin bands need to be acquired, where the results are used to modify the system parameters to appropriate values. Subsequently, in the view of modeling results, the control concept in two different techniques including sequential loop closing control(SLCC) scheme and diagonal dominance control(DDC) schemes is proposed to implement on the system through the Profibus network, as long as the OPC(OLE for process control) server is utilized to communicate between the control schemes presented and the multivariable system. The real test scenarios are carried out and the corresponding outcomes in their present forms are acquired. In the same way, the proposed control schemes results are compared with each other, where the real consequences verify the validity of them in the field of the presented industrial multivariable system control.
基金the National Natural Science Foundation of China(Grant Nos.51374215,11572343,51622404)Beijing Major Scientific and Technological Achievements into Ground Cultivation Project(Grant No.Z151100002815004)+2 种基金Fok Ying Tung Education Foundation(Grant No.142018)the State Key Research Development Program of China(Grant No.2016YFC0801404)Outstanding Young Talents of"Ten Thousand People Plan"
文摘Understanding the stress-strain relationship and permeability change for contact compression fracture at closing stage has been a hot issue for a long time.Previous investigations of this topic were mainly focused on experimental tests;however,theoretical approaches were rarely reported.Based on this,this paper focuses on the contact fracture at closing stage when rock is uniaxially loaded,and then a theoretical model is proposed.Based on the change of fracture elasticity modulus,it shows that as crack apertures are gradually reduced in the loading process,the permeability of rock sample will decrease progressively.This scenario shows that theoretical computation matches well with the experimental results.Finally,the effects of ratio of sample size to fracture aperture(n).pore pressure(P),and initial aperture(b) on stress-strain relationship and permeability change for contact compression fracture at closing stage are analyzed.
基金This work was supported by the National Natural Science Foundation of China, Grant No. 10035020
文摘A coaxial multi-gap multi-channel spark switch with stainless-steel-spring ring gap electrodes is designed and investigated. The switch is triggered by a pulse applied to the cylindrical electrode outside the discharging channel through a parasitic capacitance coupling. The jitter of the switch is reduced by several short-distance gas gaps in series, and its inductance is reduced by a multi-channel discharge on account of the inductance isolation between the coils of the spring ring electrode. The experimental results indicate that the switch is of low inductance (15-30 nH), low jitter (-3 ns), and stable breakdown performance
基金Supported by the Industry-University-Research Collaboration Project of Jiangsu Province(Grant No.BY2019048)the 19th batch of student scientific research projects of Jiangsu University(19A306)。
文摘In this study,a one-dimensional simulation was performed to evaluate the performance of in-cylinder combustion to control NO_(x) emissions on a four-stroke,six-cylinder marine medium-speed diesel engine.Reducing the combustion temperature is an important in-cylinder measure to decrease NO_(x) emissions of marine diesel engines.The Miller cycle is an effective method used to reduce the maximum combustion temperature in a cylinder and accordingly decrease NO_(x) emissions.Therefore,the authors of this study designed seven different early intake valve closing(EIVC)Miller cycles for the original engine,and analyzed the cycle effects on combustions and emissions in high-load conditions.The results indicate that the temperature in the cylinder was significantly reduced,whereas fuel consumption was almost unchanged.When the IVC was properly advanced,the ignition delay period increased and the premixed combustion accelerated,but the in-cylinder average pressure,temperature and NO_(x) emissions in the cylinder were lower than the original engine.However,closing the intake valve too early led to high fuel consumption.In addition,the NO_(x) emissions,in-cylinder temperature,and heat release rate remarkably increased.Therefore,the optimal timing of the EIVC varied with different loads.The higher the load was,the earlier the best advance angle appeared.Therefore,the Miller cycle is an effective method for in-engine NO_(x) purification and does not entail significant cost.
文摘This paper presents a new type of fault current limiter (FCL) based on fast closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. It can response the order within 1 ms. When fault occurs, the switch closes and the capacitors are bypassed, and the fault current is limited by the reactor. Simulation analysis and experiment show that the electromagnetic repulsion force actuator can meet the demand of fast closing switch, it is feasible to develop the FCL with low cost and high reliability.
文摘Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.
基金supported by Shandong Provincial Natural Science Foundation(No.ZR2023MF062)the National Natural Science Foundation of China(No.61771230).
文摘In order to improve the registration accuracy of brain magnetic resonance images(MRI),some deep learning registration methods use segmentation images for training model.How-ever,the segmentation values are constant for each label,which leads to the gradient variation con-centrating on the boundary.Thus,the dense deformation field(DDF)is gathered on the boundary and there even appears folding phenomenon.In order to fully leverage the label information,the morphological opening and closing information maps are introduced to enlarge the non-zero gradi-ent regions and improve the accuracy of DDF estimation.The opening information maps supervise the registration model to focus on smaller,narrow brain regions.The closing information maps supervise the registration model to pay more attention to the complex boundary region.Then,opening and closing morphology networks(OC_Net)are designed to automatically generate open-ing and closing information maps to realize the end-to-end training process.Finally,a new registra-tion architecture,VM_(seg+oc),is proposed by combining OC_Net and VoxelMorph.Experimental results show that the registration accuracy of VM_(seg+oc) is significantly improved on LPBA40 and OASIS1 datasets.Especially,VM_(seg+oc) can well improve registration accuracy in smaller brain regions and narrow regions.
文摘Distinguished vips,Ladies and gentlemen,friends,With the joint efforts of all of you,the 2013"Understanding&Cooperation"Dialogue,held by the Chinese Association for International Understanding(CAFIU)has successfully completed all items on its agenda.It’s time to bid farewell.During the past 4 days,we came across over half China from Beijing to Jiangxi Province,feeling the hot summer days and witnessing
基金supported by Shanghai Automotive Industry Development Foundation of China (Grant No. 0903)R&D Project of Science and Technology Commission of Shanghai Municipality of China (Grant No. 08DZ1150306)
文摘The existing research of the automotive side swing door and the closing angle via tests and simulations. In these tests, the closing energy is mainly conducted by measuring the closing energy door closing velocity and initial door closing angle are usually not taken into consideration, so the accuracy of the test data cannot be ensured, and, meanwhile, simulations require a great deal of manpower and time. Moreover, frequent tests would give rise to the increasing research and development costs. In this paper, in response to the deficiencies of these current methods, the complicated door closing process is decomposed into the closing processes of different subsystems of door, which includes weather strip seal＇, air-binding effect, door weight, hinge, check-link and latch. Mathematical models of those subsystems are established according to their working principles during the door closing process. In addition to the theoretical research, an Excel-based software using Visual Basic Application programming language is developed to realize the mathematical models, which aims to calculate the energy consumption of the subsystems. The energy consumption of different subsystems of a production vehicle door is measured to verify the accuracy of the calculation sottware developed. The proposed research provides not only the theoretical basis for the future door closing energy research, but also an interactive method and system, effectively improving the quality and efficiency of vehicle door design.
文摘A logaritmic series distribution model was used to evaluate the index of population diversity (α value) inQuercus mongolica forest in Zhanguangcai Mountains, Heilongjiang, Northeastern China. The α value went up from 1.07 to 4.46–6.98, after closing hillsides for 20 years. The spatial distribution of the α value was calculated among the hill slopes. The results were as follows: middle of hill>bottom of hill>top of hill.
基金Supported by the National Natural Science Foundation of China(No.20872108)
文摘The reaction of a ruthenium carbide complex RuCl2（C：）（PCy3）2 with [H（Et2O）x]＋[BF4]- at a molar ratio of 1：2 produced a two-core ruthenium carbene complex, {[RuCl（=CHPCy3）（PCy3）]2（μ-Cl）3}＋·[BF4]-, in the form of a yellow-green crystalline solid in a yield of 94%. This two-core ruthenium complex is a selective catalyst for ring closing metathesis of unsubstituted terminal dienes. More importantly, no isomerized byproduct was observed for N-substrates when the two-core ruthenium complex was used as the catalyst at an elevated temperature（137 °C）, indicating that the complex is a chemo-selective catalyst for ring closing metathesis reactions.
文摘A microscopic damage model of ellipsoidal body containing ellipsoidal void for nonlinear matrix materials is developed under a particular coordinate. The change of void shape is considered in this model. The viscous restrained equation obtained from the model is affected by stress ?ij, void volume fraction f, material strain rate exponent m as well as the void shape. Gurson's equation is modified from the numerical solution. The modified equation is suitable for the case of nonlinear matrix materials and changeable voids. Lastly, the model is used to analyze the closing process of voids.
基金supported by the National Key Research and Development Program of China (No. 2017YFA0207204)
文摘Phosphorus （P） reserve, largely derived from phosphate rock, is essential for crop growth to support the growing world population. However, a significant proportion of phosphorus used as a fertilizer runs into natural waters, causing eutro- phication and ecological damage. Moreover, most P in the food is eventually discharged as waste after being digested by human and animals. Thus, industrial activities have created a one-way flow of non-renewable P from rocks to farms to lakes, rivers and oceans.
文摘The water resisting property of aquiclude is the key factor of water conservation and safety mining, and the mining induced cracks in aquiclude is major factor of water resisting property. The aquiclude is composed by loess layer and red clay layer in Yushuwan Coal Mine, and the water reaction property of clay and loess of aquiclude was tested by soil mechanics method. The permeability coefficient of the loess is 0.856 m/d and the clay is 0.434 m/d. The dilatability coefficient of the loess is 16.1% and the clay is 14.6%. Through physical solid-liquid simulation with whole stress-stain similarity, the distribution of ＂downward crack zone＂ and ＂upward crack zone＂ was found to be the major factor of aquiclude stability. The downward crack closing length is about 30% of the downward crack length. The expanding of clay and loess with water are principal factors of downward crack closing. At last, the mechanical model of downward crack closing was constructed, and the criterion of crack closing was put forward at all. This work will provides the theoretical base for aquiclude stability research and safety mining in shallow seam.
文摘The Francis turbine governing system models in PSD-BPA can’t precisely reflect the actual characteristics. Endeavor was done in this paper to solve the problem. An improved model of actuating mechanism was developed, which could reflect the step closing characteristic of hydro guide vanes. The effect of the inflection point value of actuating mechanism on load rejection was analyzed based on simulation. The non-linear Francis turbine model with power versus gate position module was researched in this paper. Based on field test, comparisons of simulation results with measured data were presented. The analysis demonstrates that the improved models of Francis turbine and governor proposed in this paper are more realistic than the models of BPA, and can be applied in power system simulation analysis better.
文摘Until late in this century,most Ameri-cans spent time with people of all generations.Now baby boomers may not have muchcontact with old people until they re relativelyold themselves.That s because we group people by age.We put our three-year-olds together in day-care centers,our 13-year-olds in schools
文摘The model QQCplankton net closing gear is a device designed to control the stratifiedsampling of the plankton net by means of a messenger. The device in its fie1d use has met with98% success in 766 times of strtified sampling of plankton at 157 stations during separatesurveys of Fujian coast zone, the Taiwan Strait, and the central section of the South China Sea,
