The new accelerator project （ HIRFL-CSR ） constructed at the Heavy Ion Research Facility in Lanzhou （HIRFL） is approaching completion. It is a multipurpose cooler-storage-ring system, consisting of a maim ring （C...The new accelerator project （ HIRFL-CSR ） constructed at the Heavy Ion Research Facility in Lanzhou （HIRFL） is approaching completion. It is a multipurpose cooler-storage-ring system, consisting of a maim ring （CSRm）, an experimental ring （CSRe） and two transfer beam lines. The UHV system of CSRm is the most representative subsystem in the project. To minimize the beam loss due to charge exchange of the heavy ions with the residual gas molecules, the pressure of the CSRm vacuum system should reach 3.5 × 10^-9 Pa （N2 equivalent） and the pressure of 8 × 10^-10 Pa is expected for very heavy ion such as uranium to make its lifetime longer than 50 s in the ring. Now, the vacuum system of CSRm has been completed and a pressure less than 5 × 10^-10 Pa has been obtained. In this paper the layout of the CSRm vacuum system, the vacuum equipment in CSRm, the treatment method for the CSRm vacuum chambers, and the installation and operation of the system will be reported.展开更多
When diecasting large and thin Mg alloy parts,material defects occur,which include porosity,nonuniform mechanical properties,irregular surfaces,and incomplete filling.To resolve these problems,it is necessary to have ...When diecasting large and thin Mg alloy parts,material defects occur,which include porosity,nonuniform mechanical properties,irregular surfaces,and incomplete filling.To resolve these problems,it is necessary to have uniform injection velocities and temperatures as well as control the melt.This study investigated the feasibility of producing large and thin components using a die caster by attaching a high vacuum system.In particular,the effects of injection velocity on surface quality and the mechanical properties of the products were investigated.Hence,an injection velocity scheme and a die structure capable of casting in a vacuum were proposed.As a result,it was found that the critical low injection velocity was 0.2 m/s to produce large thin Mg alloy structures having good mechanical properties.展开更多
An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for t...An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts.Herein,we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques.The proposed system consists of four parts:preparation chamber,temperatureprogrammed desorption(TPD)chamber,quick load-lock chamber,and in situ reaction cell.The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization,including an Ar+sputter gun,Auger electron spectrometer,and a low-energy electron diffractometer.After a well-defined model catalyst was prepared,the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule,or to the reaction cell,to measure the catalytic activity.A thermal desorption experiment for methanol on a clean Cu(111)surface was conducted to demonstrate the functionality of the preparation and TPD chambers.Moreover,the repeatability of the in situ reaction cell experiment was verified by CO_(2) hydrogenation on the Ni(110)surface.At a reaction pressure of 800 Torr at 673 K,turnover frequencies for the methanation reaction and reverse water-gas shift reaction were 0.15 and 7.55 Ni atom^(-1) s^(-1),respectively.展开更多
To reach the design parameter of CSR, vacuum system (≤3.5x10^(-9) Pa), besides the high requirement for quality of the material and vacuum sanitation of the vacuum cells, the seal function is the most important. All ...To reach the design parameter of CSR, vacuum system (≤3.5x10^(-9) Pa), besides the high requirement for quality of the material and vacuum sanitation of the vacuum cells, the seal function is the most important. All cells of vacuum system for CSR are limited by the situations and rooms of gap of magnets, radio frequency system, diagnostic devices and others, and must meet the assemble and disassemble requirements of every devices.展开更多
A new gas-filled recoil spectrometer device will be built as a terminal of HIAF which will be used for a new element search with Z>119 and physics studies of the super-heavy nuclei.The vacuum pressure inside the te...A new gas-filled recoil spectrometer device will be built as a terminal of HIAF which will be used for a new element search with Z>119 and physics studies of the super-heavy nuclei.The vacuum pressure inside the terminal is 200 Pa when filled with helium gas however the vacuum pressure of main system is lower than 1106Pa,therefore it is necessary to design a differential vacuum system for vacuum transition more than eight orders of magnitude.Herein,a calculation of five-stage differential system is presented.展开更多
Some significant progress has been made for HIAF vacuum system in 2022,such as the development of the ultra-thin wall XHV chamber with titanium alloy lining(a key technology of HIAF),the construction of BRing demonstr...Some significant progress has been made for HIAF vacuum system in 2022,such as the development of the ultra-thin wall XHV chamber with titanium alloy lining(a key technology of HIAF),the construction of BRing demonstration section in Tianshui,the procurement of most vacuum acquisition equipment,and so on.展开更多
HIAF Fragment Separator(HFRS)is the only beam line that connected Booster Ring(BRing)and Spectrometer Ring(SRing)in the HIAF and used to transfer both the primary ion beams and secondary radioactive beams.The beam pas...HIAF Fragment Separator(HFRS)is the only beam line that connected Booster Ring(BRing)and Spectrometer Ring(SRing)in the HIAF and used to transfer both the primary ion beams and secondary radioactive beams.The beam passed once in HFRS so low vacuum degree was required.But HFRS connects with extremely high vacuum systems of BRing and SRing,so it is related to the gradual transition of pressure,the vacuum pressure can’t be too high.Taking into account the above situation,the vacuum degree of HFRS should be better than 1×10^(−7)mb.展开更多
HL-2A is the first divertor tokamak in China. The vacuum system is one of the important parts of the HL-2A tokamak, which has to be work well during the physics campaign in 2004. As the tokamak machine is separated fr...HL-2A is the first divertor tokamak in China. The vacuum system is one of the important parts of the HL-2A tokamak, which has to be work well during the physics campaign in 2004. As the tokamak machine is separated from the operation staff during discharges, to guarantee the safe and reliable operation of the vacuum system, it is necessary to watch the vacuum system outside the machine hall with an automatic monitoring system. The paper describes the design and manufacture of the monitoring system.展开更多
The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investi...The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole-dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms-field, atom-atom, and atom-field can be prepared via two two-level atoms interacting with a single-mode vacuum field.展开更多
Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the e...Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with ＂programmable logic controller（PLC） ＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.展开更多
A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prep...A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prepared, in which the conductivity and permittivity of the Mo/Al2O3 cermets were controlled through different amount of metallic molybdenum powder added. The effects of both conductivity and permittivity of Mo/Al2O3 cermets on the DC and impulse surface flashover voltage in vacuum were experimentally investigated. The result showed that the DC and impulse surface flashover voltage were improved by 52% and 95%, respectively. For the distribution of electric field, two triple junctions, i.e., vacuum-layer A-cathode （TJ1） and vacuum-layer A-layer B （TJ2） were prepared with the introduction of layer A into the A-B-A insulation system. Based on the electric field distribution obtained via electrostatic field simulation and Maxwell-Wagner three-layer model, the electric field of T J1 decreases while that of T J2 increases with the increase in conductivity and permittivity of layer A under applied DC and impulse voltage, respectively. Therefore, the improvement of surface flashover performance of A-B-A insulators has been reasonably explained.展开更多
A novel vacuum ice slurry producing system with jet-pumps was proposed to deal with the problems of high energy consumption and ice blockage.In this novel system,one steam driven by a jet-pump was used to create vacuu...A novel vacuum ice slurry producing system with jet-pumps was proposed to deal with the problems of high energy consumption and ice blockage.In this novel system,one steam driven by a jet-pump was used to create vacuum in a hermetic vessel where water was sprayed through a nozzle to produce ice slurry,while the other steam was used to provide enough cold energy to make the left vapor in the hermetic vessel condense.Mathematical models of this novel system were established and theoretical simulation on the performance characteristics was also implemented based on the MATLAB program.Results show that the novel system is feasible and practicable,and the system performance is affected by many factors,such as the temperature of the generators,condensing temperature,evaporation temperature,and the cooling load of the refrigerator sub-system.The findings are helpful to improve the performance of ice slurry producing system.展开更多
Even though switching in vacuum is a technology with almost 100 years of history,its recent develop-ments are still changing the future of power transmission and distribution systems.First,current switch-ing in vacuum...Even though switching in vacuum is a technology with almost 100 years of history,its recent develop-ments are still changing the future of power transmission and distribution systems.First,current switch-ing in vacuum is an eco-friendly technology compared to switching in SF 6 gas,which is the strongest greenhouse gas according to the Kyoto Protocol.Vacuum,an eco-friendly natural medium,is promising for reducing the usage of SF 6 gas in current switching in transmission voltage.Second,switching in vacuum achieves faster current interruption than existing alternating current(AC)switching technolo-gies.A vacuum circuit breaker(VCB)that uses an electromagnetic repulsion actuator is able to achieve a theoretical limit of AC interruption,which can interrupt a short-circuit current in the first half-cycle of a fault current,compared to the more common three cycles for existing current switching technologies.This can thus greatly enhance the transient stability of power networks in the presence of short-circuit faults,especially for ultra-and extra-high-voltage power transmission lines.Third,based on fast vacuum switching technology,various brilliant applications emerge,which are benefiting the power systems.They include the applications in the fields of direct current(DC)circuit breakers(CBs),fault current lim-iting,power quality improvement,generator CBs,and so forth.Fast vacuum switching technology is promising for controlled switching technology in power systems because it has low variation in terms of opening and closing times.With this controlled switching,vacuum switching technology may change the“gene”of power systems,by which power switching transients will become smoother.展开更多
A novel pressure and vacuum continuous control system,which adopts a hybrid pump as pressure and vacuum source,is presented.The mathematical model of the system is developed.The theoretical simulation and analysis on ...A novel pressure and vacuum continuous control system,which adopts a hybrid pump as pressure and vacuum source,is presented.The mathematical model of the system is developed.The theoretical simulation and analysis on the system are implemented in order to study the relationships among the characteristics,parameters and working points of the system.The experimental investigations on the system characteristics are presented with the adoption ofa fuzzy-PID controller.The simulation and experimental results indicate that the pressure and vacuum continuous control system based on hybrid pump has good dynamic and static performance,strong robustness and satisfactory adaptability to various system parameters.According to the results,system can successfully gain high accuracy and fast response signal.Also,the mathematical model of system is also testified by the experimental results.展开更多
The vacuum sanitation is the safe and sound disposal approach of human excreta under the specific environments like flights, high speed trains and submarines. However, the propulsive force of current systems is not ad...The vacuum sanitation is the safe and sound disposal approach of human excreta under the specific environments like flights, high speed trains and submarines. However, the propulsive force of current systems is not adjustable and the energy consumption does not adapt to the real time sewerage requirement. Therefore, it is important to study the sewerage force adjustment to improve the energy efficiency. This paper proposes an energy conservation design in vacuum sanitation systems with pneumatic ejector circuits. The sewerage force is controlled by changing the systematic vacuum degree according to the amount of the excreta. In particular, the amount of the excreta is tested by liquid level sensor and mass sensor. According to the amount of the excreta, the relationship between the excreta amount and the sewerage force is studied to provide proper propulsive force. In the other aspect, to provide variable vacuum degrees for different sanitation requirements, the suction and discharge system is designed with pneumatic vacuum ejector. On the basis of the static flow-rate characteristics and the vacuum generation model, the pressure response in the ejector circuit is studied by using the static flow rate characteristics of the ejector and air status equation. The relationship is obtained between supplied compressed air and systematic vacuum degree. When the compressed air is supplied to the ejector continuously, the systematic vacuum degree increases until the vacuum degree reaches the extreme value. Therefore, the variable systematic vacuum degree is obtained by controlling the compressed air supply of the ejector. To verify the effect of energy conservation, experiments are carried out in the artificial excreta collection, and the variable vacuum-degree design saves more than 30% of the energy supply. The energy conservation is realized effectively in the new vacuum sanitation systems with good application prospect. The proposed technology provides technological support for the energy conservation of vacuum sanitation systems.展开更多
Temperature and humidity independent control(THIC)air-conditioning system is a promising technology.In this work,a novel temperature and humidity independent control(THIC)system is proposed,namely VMD-ACERS,which inte...Temperature and humidity independent control(THIC)air-conditioning system is a promising technology.In this work,a novel temperature and humidity independent control(THIC)system is proposed,namely VMD-ACERS,which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system.This work establishes a novel coefficient of performance(COP)model of VMD-ACERS.The main parameters affecting the COP of conventional fan coil unit cooling system(FCUCS)and VMD-ACERS are investigated.The performance of FCUCS and VMD-ACERS are compared,and the energy-saving potential of VMD-ACERS is proved.Results indicate that,for FCUCS,the importance ranking of parameters is basically stable.However,for VMD-ACERS,the importance ranking will be affected by FCU and refrigerant.The most important parameters of VMD-ACERS are condensation temperature and permeate side pressure.On the contrary,superheating,subcooling are relatively less important parameters.For VMD-ACERS,it is not necessary to pursue the membrane with very high selectivity,because the selectivity of membrane would also be a less important parameter when it reaches 500.The COP of VMD-ACERS is higher than that of FCUCS when the permeate side pressure is higher than 8 k Pa.The VMD-ACERS solves two technical problems about power-saving and thermal comfort of conventional THIC,and can extend the application of THIC air-conditioning system.展开更多
In this paper we prove the local well-posedness of strong solutions to a chemotaxisshallow water system with initial vacuum in a bounded domainΩ■R^(2)without the standard compatibility condition for the initial data...In this paper we prove the local well-posedness of strong solutions to a chemotaxisshallow water system with initial vacuum in a bounded domainΩ■R^(2)without the standard compatibility condition for the initial data.This improves some results obtained in[J.Differential Equations 261(2016),6758-6789].展开更多
In this paper,we study the one-dimensional motion of viscous gas near a vacuum,with the gas connecting to a vacuum state with a jump in density.The interface behavior,the pointwise decay rates of the density function ...In this paper,we study the one-dimensional motion of viscous gas near a vacuum,with the gas connecting to a vacuum state with a jump in density.The interface behavior,the pointwise decay rates of the density function and the expanding rates of the interface are obtained with the viscosity coefficientμ(ρ)=ρ^(α)for any 0<α<1;this includes the timeweighted boundedness from below and above.The smoothness of the solution is discussed.Moreover,we construct a class of self-similar classical solutions which exhibit some interesting properties,such as optimal estimates.The present paper extends the results in[Luo T,Xin Z P,Yang T.SIAM J Math Anal,2000,31(6):1175-1191]to the jump boundary conditions case with density-dependent viscosity.展开更多
The time evolution of the quantum entropy in a GaAs/AlAs one-dimensional photonic crystal(1DPC) with an atomic system defect layer is investigated in this work. The entanglement between atomic system and their spontan...The time evolution of the quantum entropy in a GaAs/AlAs one-dimensional photonic crystal(1DPC) with an atomic system defect layer is investigated in this work. The entanglement between atomic system and their spontaneous emission fields near the edge of the photonic band gap(PBG) is coherently controlled by the coupling field. Comparison between the atom-photon entanglement of the atomic system in the vacuum surrounding and that near the PBG of the 1DPC shows that the degree of entanglement strongly depends on the PBG. We find that degree of entanglement is strongly dependent on the intensity and detuning of the coupling and probe fields. Furthermore, the effect of the phase difference between applied fields on the atom-photon entanglement is studied. The potentially possible technological applications can be provided by the proposed model in the quantum optics and quantum communications based on photonic crystal.展开更多
The principle and working process of Vacuum Resin Shot Dosing Equipment(VRSDE) are analyzed and the characteristics of IP1612-220PLC (Programmable Logical Controller) areintroduced briefly at first. Then the authors d...The principle and working process of Vacuum Resin Shot Dosing Equipment(VRSDE) are analyzed and the characteristics of IP1612-220PLC (Programmable Logical Controller) areintroduced briefly at first. Then the authors discuss the flow of program, the assignment of PLCI/O ports, the wiring diagram, and the ladder logic program of the PLC control system of VRSDE indetail. Some application issues of the system are accounted for in addition. Finally, according tothe information acquired from users, the authors draw the conclusion: this system owns a highreliability and a-vailability and greatly improves the automatic degree of VRDE.展开更多
文摘The new accelerator project （ HIRFL-CSR ） constructed at the Heavy Ion Research Facility in Lanzhou （HIRFL） is approaching completion. It is a multipurpose cooler-storage-ring system, consisting of a maim ring （CSRm）, an experimental ring （CSRe） and two transfer beam lines. The UHV system of CSRm is the most representative subsystem in the project. To minimize the beam loss due to charge exchange of the heavy ions with the residual gas molecules, the pressure of the CSRm vacuum system should reach 3.5 × 10^-9 Pa （N2 equivalent） and the pressure of 8 × 10^-10 Pa is expected for very heavy ion such as uranium to make its lifetime longer than 50 s in the ring. Now, the vacuum system of CSRm has been completed and a pressure less than 5 × 10^-10 Pa has been obtained. In this paper the layout of the CSRm vacuum system, the vacuum equipment in CSRm, the treatment method for the CSRm vacuum chambers, and the installation and operation of the system will be reported.
基金Acknowledgement This work was supported by the National Core Research Center Program from MOST/KOSEF （No. R15- 2006-022-02001-0）.
文摘When diecasting large and thin Mg alloy parts,material defects occur,which include porosity,nonuniform mechanical properties,irregular surfaces,and incomplete filling.To resolve these problems,it is necessary to have uniform injection velocities and temperatures as well as control the melt.This study investigated the feasibility of producing large and thin components using a die caster by attaching a high vacuum system.In particular,the effects of injection velocity on surface quality and the mechanical properties of the products were investigated.Hence,an injection velocity scheme and a die structure capable of casting in a vacuum were proposed.As a result,it was found that the critical low injection velocity was 0.2 m/s to produce large thin Mg alloy structures having good mechanical properties.
基金supported by the National Natural Science Foundation of China (Nos.21802096,21832004,21902179,21991152,and 21991150)the Shanghai XFEL Beamline Project (SBP) (31011505505885920161A2101001)the support of the Shanghai Sailing Program (19YF1455600)。
文摘An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts.Herein,we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques.The proposed system consists of four parts:preparation chamber,temperatureprogrammed desorption(TPD)chamber,quick load-lock chamber,and in situ reaction cell.The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization,including an Ar+sputter gun,Auger electron spectrometer,and a low-energy electron diffractometer.After a well-defined model catalyst was prepared,the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule,or to the reaction cell,to measure the catalytic activity.A thermal desorption experiment for methanol on a clean Cu(111)surface was conducted to demonstrate the functionality of the preparation and TPD chambers.Moreover,the repeatability of the in situ reaction cell experiment was verified by CO_(2) hydrogenation on the Ni(110)surface.At a reaction pressure of 800 Torr at 673 K,turnover frequencies for the methanation reaction and reverse water-gas shift reaction were 0.15 and 7.55 Ni atom^(-1) s^(-1),respectively.
文摘To reach the design parameter of CSR, vacuum system (≤3.5x10^(-9) Pa), besides the high requirement for quality of the material and vacuum sanitation of the vacuum cells, the seal function is the most important. All cells of vacuum system for CSR are limited by the situations and rooms of gap of magnets, radio frequency system, diagnostic devices and others, and must meet the assemble and disassemble requirements of every devices.
文摘A new gas-filled recoil spectrometer device will be built as a terminal of HIAF which will be used for a new element search with Z>119 and physics studies of the super-heavy nuclei.The vacuum pressure inside the terminal is 200 Pa when filled with helium gas however the vacuum pressure of main system is lower than 1106Pa,therefore it is necessary to design a differential vacuum system for vacuum transition more than eight orders of magnitude.Herein,a calculation of five-stage differential system is presented.
文摘Some significant progress has been made for HIAF vacuum system in 2022,such as the development of the ultra-thin wall XHV chamber with titanium alloy lining(a key technology of HIAF),the construction of BRing demonstration section in Tianshui,the procurement of most vacuum acquisition equipment,and so on.
文摘HIAF Fragment Separator(HFRS)is the only beam line that connected Booster Ring(BRing)and Spectrometer Ring(SRing)in the HIAF and used to transfer both the primary ion beams and secondary radioactive beams.The beam passed once in HFRS so low vacuum degree was required.But HFRS connects with extremely high vacuum systems of BRing and SRing,so it is related to the gradual transition of pressure,the vacuum pressure can’t be too high.Taking into account the above situation,the vacuum degree of HFRS should be better than 1×10^(−7)mb.
文摘HL-2A is the first divertor tokamak in China. The vacuum system is one of the important parts of the HL-2A tokamak, which has to be work well during the physics campaign in 2004. As the tokamak machine is separated from the operation staff during discharges, to guarantee the safe and reliable operation of the vacuum system, it is necessary to watch the vacuum system outside the machine hall with an automatic monitoring system. The paper describes the design and manufacture of the monitoring system.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole-dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms-field, atom-atom, and atom-field can be prepared via two two-level atoms interacting with a single-mode vacuum field.
基金supported by Fujian Provincial Natural Science Foundation of China (Grant No.2007J0170)Xiamen Municipal Natural Science Foundation of China (Grant No.3502Z20093034)
文摘Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with ＂programmable logic controller（PLC） ＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.
基金supported by National Science Fund for Outstanding Young Scholars of China (No. 50625721)
文摘A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prepared, in which the conductivity and permittivity of the Mo/Al2O3 cermets were controlled through different amount of metallic molybdenum powder added. The effects of both conductivity and permittivity of Mo/Al2O3 cermets on the DC and impulse surface flashover voltage in vacuum were experimentally investigated. The result showed that the DC and impulse surface flashover voltage were improved by 52% and 95%, respectively. For the distribution of electric field, two triple junctions, i.e., vacuum-layer A-cathode （TJ1） and vacuum-layer A-layer B （TJ2） were prepared with the introduction of layer A into the A-B-A insulation system. Based on the electric field distribution obtained via electrostatic field simulation and Maxwell-Wagner three-layer model, the electric field of T J1 decreases while that of T J2 increases with the increase in conductivity and permittivity of layer A under applied DC and impulse voltage, respectively. Therefore, the improvement of surface flashover performance of A-B-A insulators has been reasonably explained.
基金Project(51376198)supported by the National Natural Science Foundation of ChinaProject(11JJ22029)supported by the Hunan Provincial Natural Science Foundation of China
文摘A novel vacuum ice slurry producing system with jet-pumps was proposed to deal with the problems of high energy consumption and ice blockage.In this novel system,one steam driven by a jet-pump was used to create vacuum in a hermetic vessel where water was sprayed through a nozzle to produce ice slurry,while the other steam was used to provide enough cold energy to make the left vapor in the hermetic vessel condense.Mathematical models of this novel system were established and theoretical simulation on the performance characteristics was also implemented based on the MATLAB program.Results show that the novel system is feasible and practicable,and the system performance is affected by many factors,such as the temperature of the generators,condensing temperature,evaporation temperature,and the cooling load of the refrigerator sub-system.The findings are helpful to improve the performance of ice slurry producing system.
基金supported in part by the National Natural Science Foundation of China (51937009 and 51877166)the Key Research and Development Program of Shaanxi Province (2019ZDLGY18-04)
文摘Even though switching in vacuum is a technology with almost 100 years of history,its recent develop-ments are still changing the future of power transmission and distribution systems.First,current switch-ing in vacuum is an eco-friendly technology compared to switching in SF 6 gas,which is the strongest greenhouse gas according to the Kyoto Protocol.Vacuum,an eco-friendly natural medium,is promising for reducing the usage of SF 6 gas in current switching in transmission voltage.Second,switching in vacuum achieves faster current interruption than existing alternating current(AC)switching technolo-gies.A vacuum circuit breaker(VCB)that uses an electromagnetic repulsion actuator is able to achieve a theoretical limit of AC interruption,which can interrupt a short-circuit current in the first half-cycle of a fault current,compared to the more common three cycles for existing current switching technologies.This can thus greatly enhance the transient stability of power networks in the presence of short-circuit faults,especially for ultra-and extra-high-voltage power transmission lines.Third,based on fast vacuum switching technology,various brilliant applications emerge,which are benefiting the power systems.They include the applications in the fields of direct current(DC)circuit breakers(CBs),fault current lim-iting,power quality improvement,generator CBs,and so forth.Fast vacuum switching technology is promising for controlled switching technology in power systems because it has low variation in terms of opening and closing times.With this controlled switching,vacuum switching technology may change the“gene”of power systems,by which power switching transients will become smoother.
基金This project is supported by National Natural Science Foundation of China(No.50675075).
文摘A novel pressure and vacuum continuous control system,which adopts a hybrid pump as pressure and vacuum source,is presented.The mathematical model of the system is developed.The theoretical simulation and analysis on the system are implemented in order to study the relationships among the characteristics,parameters and working points of the system.The experimental investigations on the system characteristics are presented with the adoption ofa fuzzy-PID controller.The simulation and experimental results indicate that the pressure and vacuum continuous control system based on hybrid pump has good dynamic and static performance,strong robustness and satisfactory adaptability to various system parameters.According to the results,system can successfully gain high accuracy and fast response signal.Also,the mathematical model of system is also testified by the experimental results.
基金supported by Doctor Innovation Fund of Nanjing University of Science and Technology of China(Grant No. 20080407)Joint-PhD Program of China Scholarship Council(Grant No.2008104777)
文摘The vacuum sanitation is the safe and sound disposal approach of human excreta under the specific environments like flights, high speed trains and submarines. However, the propulsive force of current systems is not adjustable and the energy consumption does not adapt to the real time sewerage requirement. Therefore, it is important to study the sewerage force adjustment to improve the energy efficiency. This paper proposes an energy conservation design in vacuum sanitation systems with pneumatic ejector circuits. The sewerage force is controlled by changing the systematic vacuum degree according to the amount of the excreta. In particular, the amount of the excreta is tested by liquid level sensor and mass sensor. According to the amount of the excreta, the relationship between the excreta amount and the sewerage force is studied to provide proper propulsive force. In the other aspect, to provide variable vacuum degrees for different sanitation requirements, the suction and discharge system is designed with pneumatic vacuum ejector. On the basis of the static flow-rate characteristics and the vacuum generation model, the pressure response in the ejector circuit is studied by using the static flow rate characteristics of the ejector and air status equation. The relationship is obtained between supplied compressed air and systematic vacuum degree. When the compressed air is supplied to the ejector continuously, the systematic vacuum degree increases until the vacuum degree reaches the extreme value. Therefore, the variable systematic vacuum degree is obtained by controlling the compressed air supply of the ejector. To verify the effect of energy conservation, experiments are carried out in the artificial excreta collection, and the variable vacuum-degree design saves more than 30% of the energy supply. The energy conservation is realized effectively in the new vacuum sanitation systems with good application prospect. The proposed technology provides technological support for the energy conservation of vacuum sanitation systems.
基金The National Key Technology Support Program(2015BAJ03B01)the Hunan Provincial Innovation Foundation for Postgraduate Studies(CX20190287)。
文摘Temperature and humidity independent control(THIC)air-conditioning system is a promising technology.In this work,a novel temperature and humidity independent control(THIC)system is proposed,namely VMD-ACERS,which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system.This work establishes a novel coefficient of performance(COP)model of VMD-ACERS.The main parameters affecting the COP of conventional fan coil unit cooling system(FCUCS)and VMD-ACERS are investigated.The performance of FCUCS and VMD-ACERS are compared,and the energy-saving potential of VMD-ACERS is proved.Results indicate that,for FCUCS,the importance ranking of parameters is basically stable.However,for VMD-ACERS,the importance ranking will be affected by FCU and refrigerant.The most important parameters of VMD-ACERS are condensation temperature and permeate side pressure.On the contrary,superheating,subcooling are relatively less important parameters.For VMD-ACERS,it is not necessary to pursue the membrane with very high selectivity,because the selectivity of membrane would also be a less important parameter when it reaches 500.The COP of VMD-ACERS is higher than that of FCUCS when the permeate side pressure is higher than 8 k Pa.The VMD-ACERS solves two technical problems about power-saving and thermal comfort of conventional THIC,and can extend the application of THIC air-conditioning system.
基金supported by NSFC(11971234)supported in part by NSFC(11671193)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘In this paper we prove the local well-posedness of strong solutions to a chemotaxisshallow water system with initial vacuum in a bounded domainΩ■R^(2)without the standard compatibility condition for the initial data.This improves some results obtained in[J.Differential Equations 261(2016),6758-6789].
基金supported by the NSFC(11931013)the GXNSF(2022GXNSFDA035078)。
文摘In this paper,we study the one-dimensional motion of viscous gas near a vacuum,with the gas connecting to a vacuum state with a jump in density.The interface behavior,the pointwise decay rates of the density function and the expanding rates of the interface are obtained with the viscosity coefficientμ(ρ)=ρ^(α)for any 0<α<1;this includes the timeweighted boundedness from below and above.The smoothness of the solution is discussed.Moreover,we construct a class of self-similar classical solutions which exhibit some interesting properties,such as optimal estimates.The present paper extends the results in[Luo T,Xin Z P,Yang T.SIAM J Math Anal,2000,31(6):1175-1191]to the jump boundary conditions case with density-dependent viscosity.
文摘The time evolution of the quantum entropy in a GaAs/AlAs one-dimensional photonic crystal(1DPC) with an atomic system defect layer is investigated in this work. The entanglement between atomic system and their spontaneous emission fields near the edge of the photonic band gap(PBG) is coherently controlled by the coupling field. Comparison between the atom-photon entanglement of the atomic system in the vacuum surrounding and that near the PBG of the 1DPC shows that the degree of entanglement strongly depends on the PBG. We find that degree of entanglement is strongly dependent on the intensity and detuning of the coupling and probe fields. Furthermore, the effect of the phase difference between applied fields on the atom-photon entanglement is studied. The potentially possible technological applications can be provided by the proposed model in the quantum optics and quantum communications based on photonic crystal.
文摘The principle and working process of Vacuum Resin Shot Dosing Equipment(VRSDE) are analyzed and the characteristics of IP1612-220PLC (Programmable Logical Controller) areintroduced briefly at first. Then the authors discuss the flow of program, the assignment of PLCI/O ports, the wiring diagram, and the ladder logic program of the PLC control system of VRSDE indetail. Some application issues of the system are accounted for in addition. Finally, according tothe information acquired from users, the authors draw the conclusion: this system owns a highreliability and a-vailability and greatly improves the automatic degree of VRDE.
