The synchronous virtual machine uses inverter power to imitate the performance of the conventional synchronous machine.It also has the same inertia,damping,frequency,voltage regulation,and other external performance a...The synchronous virtual machine uses inverter power to imitate the performance of the conventional synchronous machine.It also has the same inertia,damping,frequency,voltage regulation,and other external performance as the generator.It is the key technology to realize new energy grid connections’stable and reliable operation.This project studies a dynamic simulation model of an extensive new energy power system based on the virtual synchronous motor.A new energy storage method is proposed.The mathematical energy storage model is established by combining the fixed rotor model of a synchronous virtual machine with the charge-discharge power,state of charge,operation efficiency,dead zone,and inverter constraint.The rapid conversion of energy storage devices absorbs the excess instantaneous kinetic energy caused by interference.The branch transient of the critical cut set in the system can be confined to a limited area.Thus,the virtual synchronizer’s kinetic and potential energy can be efficiently converted into an instantaneous state.The simulation of power system analysis software package(PSASP)verifies the correctness of the theory and algorithm in this paper.This paper provides a theoretical basis for improving the transient stability of new energy-connected power grids.展开更多
Reducing the impact of power outages and maintaining the power supply duration must be considered in implementing emergency energy dispatching in micro-networks.This paper studies a new emergency energy treatment meth...Reducing the impact of power outages and maintaining the power supply duration must be considered in implementing emergency energy dispatching in micro-networks.This paper studies a new emergency energy treatment method based on the robust optimal method and the industrial park micro-network with the optical energy storage system.After controlling the load input,a control strategy of adjusting and removing is proposed.Rolling optimal theory is applied to emergency energy scheduling based on a robust optimal mathematical model.A weighting factor is introduced into the optimal model to balance the importance of reducing and retaining the power supply.Uncertainty is designed to adjust the effect of uncertainty on the problem.The example shows that this method can flexibly set the weight coefficient and uncertainty value according to the actual situation so that the input of the control load can be optimized.展开更多
The characteristics and sensitivity of solidification cracks in peritectic steels were investigated using directional solidifi-cation technology.Interdendritic cracks were observed in both hypoperitectic steels(12CrlM...The characteristics and sensitivity of solidification cracks in peritectic steels were investigated using directional solidifi-cation technology.Interdendritic cracks were observed in both hypoperitectic steels(12CrlMoV,15CrMo)and hyper-peritectic steel(20CrMo)during solidification at growth velocities of 15,50,and 80 pm/s.At the dendritic boundaries,sulphide precipitates were found,promoting crack formation.Based on the statistical analysis of interdendritic cracks in peritectic steels,the area ratio(RA)of interdendritic cracks in a directional solidification structure was proposed to evaluate the crack sensitivity of peritectic steels.Furthermore,the crack sensitivities of peritectic steels(12CrlMoV,15CrMo,and 20CrMo)were tested,evaluated,and compared with the surface crack rates of three types of steels produced from a steel plant.The results demonstrated that RA was in good agreement with that of the steel plant,and the crack sensitivity of 12CrlMoV steel was the strongest,followed by that of 15CrMo and 20CrMo steels.Thus,RA can be used to evaluate the crack sensitivity of peritectic steel.展开更多
In response to thermal runaway(TR)of electric vehicles,recent attention has been focused on mitigation strategies such as efficient heat dredging in battery thermal management.Thermal management with particular focus ...In response to thermal runaway(TR)of electric vehicles,recent attention has been focused on mitigation strategies such as efficient heat dredging in battery thermal management.Thermal management with particular focus on battery cooling has been becoming increasingly significant.TR usually happened when an electric vehicle is unpowered and charged.In this state,traditional active battery cooling schemes are disabled,which can easily lead to dangerous incidents due to loss of cooling ability,and advanced passive cooling strategies are therefore gaining importance.Herein,we developed an enhanced thermal radiation material,consisting of~1μm thick multilayered nano-sheet graphene film coated upon the heat dissipation surface,thereby enhancing thermal radiation in the nanoscale.The surface was characterized on the nanoscale,and tested in a battery-cooling scenario.We found that the graphene-based coating's spectral emissivity is between 91% and 95% in the mid-infrared region,and thermal experiments consequently illustrated that graphene-based radiative cooling yielded up to15.1% temperature reduction when compared to the uncoated analogue.Using the novel graphene surface to augment a heat pipe,the temperature reduction can be further enlarged to 25.6%.The new material may contribute to transportation safety,global warming mitigation and carbon neutralization.展开更多
Early warning of financial crisis will greatly promote the stable development of small and medium-sized listed enterprises(listed SMEs).In this article,13 warning indicators were selected for financial crisis predicti...Early warning of financial crisis will greatly promote the stable development of small and medium-sized listed enterprises(listed SMEs).In this article,13 warning indicators were selected for financial crisis prediction from five aspects:profit level,debt service level,business level,cash level,and development level.Then,the parameters of the long short-term memory(LSTM)neural network model were optimised by the whale optimisation algorithm(WOA),resulting in the WOA-LSTM model.The WOA-LSTM model achieved an accuracy of 0.975 in predicting financial crises for listed SMEs.The performance of the WOA-LSTM model was significantly enhanced when using the filtered 13 indicators as inputs,compared to using the original 24 indicators.The findings prove the dependability of the WOA-LSTM model in warning financial crises of listed SMEs and the feasibility of its application in practice.展开更多
Semiconductor photocatalysis holds significant promise for addressing dye-pollution in water.However,the efficiency of photocatalytic water purification is constrained by the weak light absorption capacity and low act...Semiconductor photocatalysis holds significant promise for addressing dye-pollution in water.However,the efficiency of photocatalytic water purification is constrained by the weak light absorption capacity and low active site distribution of photocatalysts.Utilizing a bottom-up approach,carbon-doped TiO_(x)(C-TiO_(x))nanosheets with high concentrations of Ti^(3+)active sites were fabricated by etching the Al element in Ti_(3)Ai C_(2)with H_(2)O_(2).Experimental evidence demonstrates that the optimal C-TiO_(x)nanosheets exhibit high activity for the photocatalytic degradation of methylene blue,achieving a degradation rate of 100%within 50 min.The introduction of carbon into the C-TiO_(x)nanosheets induces a red shift in the absorption edge,boosting the migration of photo-generated charge carriers.Moreover,there is a significant correlation between the concentration of Ti^(3+)active sites and the density of oxygen vacancies in the C-TiO_(x)nanosheets,which synergistically influence the photocatalytic degradation performance of MB dye wastewater.展开更多
Energy-saving in China's iron and steel industry still relies on the development and improvement of short-term energy saving technologies.Therefore,a special converter smelting technology incorporating energy savi...Energy-saving in China's iron and steel industry still relies on the development and improvement of short-term energy saving technologies.Therefore,a special converter smelting technology incorporating energy saving was proposed.To evaluate the energy-saving potential of the CO_(2)–O_(2)mixed injection(COMI)technology,collected production data were used to develop an improved techno-economic model.Calculations reveal that the technology can save energy through auxiliary material consumption,sensible heat of solid by-product,iron loss reduction,and energy recovery.The application of COMI technology in an enterprise is cost effective,involving the energy saving potential of 0.206 GJ/t,the cost of conserved energy of−48.83 yuan/GJ,and a simple payback period of 0.35 year for a 60-million-yuan investment.Sensitivity analysis shows that the investment cost and discount rate primarily influence the cost of conserved energy of the technology.As the discount rate increased,the cost of conserved energy also gradually increased.Overall,the COMI technology is an energy-saving technology with good development prospects.展开更多
The crashworthiness and energy absorption optimization of automobile structure is an importantresearch content of the modern automobile industry. Facing the problem that traditionaloptimization methods are difficult t...The crashworthiness and energy absorption optimization of automobile structure is an importantresearch content of the modern automobile industry. Facing the problem that traditionaloptimization methods are difficult to find the optimal solution for multi-objective parametersof vehicle structure crashworthiness problem, a multi-objective optimization method of vehiclecrash safety based on improved particle swarm optimization is proposed. Through the collectionand optimization of vehicle collision safety parameters, the vehicle structure performance isimproved, and the vehicle regression model is constructed. Using this method, the front-endstructure reinforcement of the vehicle is taken as the design variable. In order to realize themulti-objective optimization design method of vehicle collision safety, the multi-objective optimizationparameters of vehicle frontal collision and offset collision are taken as the objectivefunction. Finally, the simulation results show that the multi-objective optimization method basedon an improved particle swarm optimization algorithm has an obvious effect on the optimizationof vehicle structure crash safety.展开更多
文摘The synchronous virtual machine uses inverter power to imitate the performance of the conventional synchronous machine.It also has the same inertia,damping,frequency,voltage regulation,and other external performance as the generator.It is the key technology to realize new energy grid connections’stable and reliable operation.This project studies a dynamic simulation model of an extensive new energy power system based on the virtual synchronous motor.A new energy storage method is proposed.The mathematical energy storage model is established by combining the fixed rotor model of a synchronous virtual machine with the charge-discharge power,state of charge,operation efficiency,dead zone,and inverter constraint.The rapid conversion of energy storage devices absorbs the excess instantaneous kinetic energy caused by interference.The branch transient of the critical cut set in the system can be confined to a limited area.Thus,the virtual synchronizer’s kinetic and potential energy can be efficiently converted into an instantaneous state.The simulation of power system analysis software package(PSASP)verifies the correctness of the theory and algorithm in this paper.This paper provides a theoretical basis for improving the transient stability of new energy-connected power grids.
文摘Reducing the impact of power outages and maintaining the power supply duration must be considered in implementing emergency energy dispatching in micro-networks.This paper studies a new emergency energy treatment method based on the robust optimal method and the industrial park micro-network with the optical energy storage system.After controlling the load input,a control strategy of adjusting and removing is proposed.Rolling optimal theory is applied to emergency energy scheduling based on a robust optimal mathematical model.A weighting factor is introduced into the optimal model to balance the importance of reducing and retaining the power supply.Uncertainty is designed to adjust the effect of uncertainty on the problem.The example shows that this method can flexibly set the weight coefficient and uncertainty value according to the actual situation so that the input of the control load can be optimized.
基金financially supported by the Science and Technology Plan Foundation of Xingtai,China (Grant No.2022zz099)the Jiangsu Key Laboratory of Oil-Gas Storage and Transportation Technology (Grant No.CDYQCY202204)Science and Technology Project of Hebei Education Department (Grant No.ZD2021338).
文摘The characteristics and sensitivity of solidification cracks in peritectic steels were investigated using directional solidifi-cation technology.Interdendritic cracks were observed in both hypoperitectic steels(12CrlMoV,15CrMo)and hyper-peritectic steel(20CrMo)during solidification at growth velocities of 15,50,and 80 pm/s.At the dendritic boundaries,sulphide precipitates were found,promoting crack formation.Based on the statistical analysis of interdendritic cracks in peritectic steels,the area ratio(RA)of interdendritic cracks in a directional solidification structure was proposed to evaluate the crack sensitivity of peritectic steels.Furthermore,the crack sensitivities of peritectic steels(12CrlMoV,15CrMo,and 20CrMo)were tested,evaluated,and compared with the surface crack rates of three types of steels produced from a steel plant.The results demonstrated that RA was in good agreement with that of the steel plant,and the crack sensitivity of 12CrlMoV steel was the strongest,followed by that of 15CrMo and 20CrMo steels.Thus,RA can be used to evaluate the crack sensitivity of peritectic steel.
基金supported by the National Natural Science Foundation of China(no.52106114)Beijing Natural Science Foundation(no.3234061)Hong Kong Scholars Program(no.XJ2022027)。
文摘In response to thermal runaway(TR)of electric vehicles,recent attention has been focused on mitigation strategies such as efficient heat dredging in battery thermal management.Thermal management with particular focus on battery cooling has been becoming increasingly significant.TR usually happened when an electric vehicle is unpowered and charged.In this state,traditional active battery cooling schemes are disabled,which can easily lead to dangerous incidents due to loss of cooling ability,and advanced passive cooling strategies are therefore gaining importance.Herein,we developed an enhanced thermal radiation material,consisting of~1μm thick multilayered nano-sheet graphene film coated upon the heat dissipation surface,thereby enhancing thermal radiation in the nanoscale.The surface was characterized on the nanoscale,and tested in a battery-cooling scenario.We found that the graphene-based coating's spectral emissivity is between 91% and 95% in the mid-infrared region,and thermal experiments consequently illustrated that graphene-based radiative cooling yielded up to15.1% temperature reduction when compared to the uncoated analogue.Using the novel graphene surface to augment a heat pipe,the temperature reduction can be further enlarged to 25.6%.The new material may contribute to transportation safety,global warming mitigation and carbon neutralization.
文摘Early warning of financial crisis will greatly promote the stable development of small and medium-sized listed enterprises(listed SMEs).In this article,13 warning indicators were selected for financial crisis prediction from five aspects:profit level,debt service level,business level,cash level,and development level.Then,the parameters of the long short-term memory(LSTM)neural network model were optimised by the whale optimisation algorithm(WOA),resulting in the WOA-LSTM model.The WOA-LSTM model achieved an accuracy of 0.975 in predicting financial crises for listed SMEs.The performance of the WOA-LSTM model was significantly enhanced when using the filtered 13 indicators as inputs,compared to using the original 24 indicators.The findings prove the dependability of the WOA-LSTM model in warning financial crises of listed SMEs and the feasibility of its application in practice.
基金supported by the Hebei Province Natural Science Foundation(Grant No.B2023108012)the Science Research Project of Hebei Education Department(Grant No.BJK2024137)+2 种基金the National Natural Science Foundation of China(Grant No.62004143)the Key R&D Program of Hubei Province(Grant No.2022BAA084)the S&T Program of Xingtai(Grant No.2023ZZ096)。
文摘Semiconductor photocatalysis holds significant promise for addressing dye-pollution in water.However,the efficiency of photocatalytic water purification is constrained by the weak light absorption capacity and low active site distribution of photocatalysts.Utilizing a bottom-up approach,carbon-doped TiO_(x)(C-TiO_(x))nanosheets with high concentrations of Ti^(3+)active sites were fabricated by etching the Al element in Ti_(3)Ai C_(2)with H_(2)O_(2).Experimental evidence demonstrates that the optimal C-TiO_(x)nanosheets exhibit high activity for the photocatalytic degradation of methylene blue,achieving a degradation rate of 100%within 50 min.The introduction of carbon into the C-TiO_(x)nanosheets induces a red shift in the absorption edge,boosting the migration of photo-generated charge carriers.Moreover,there is a significant correlation between the concentration of Ti^(3+)active sites and the density of oxygen vacancies in the C-TiO_(x)nanosheets,which synergistically influence the photocatalytic degradation performance of MB dye wastewater.
基金the National Natural Science Foundation of China(Nos.52204342 and 52201073)Natural Science Foundation of Hebei Province(No.E2022208019)+1 种基金Natural Science Foundation of Hebei Education Department(Nos.BJK2024194 and BJK2024024)Natural Science Foundation of Hebei Education Department(No.QN2021058)for financial support.
文摘Energy-saving in China's iron and steel industry still relies on the development and improvement of short-term energy saving technologies.Therefore,a special converter smelting technology incorporating energy saving was proposed.To evaluate the energy-saving potential of the CO_(2)–O_(2)mixed injection(COMI)technology,collected production data were used to develop an improved techno-economic model.Calculations reveal that the technology can save energy through auxiliary material consumption,sensible heat of solid by-product,iron loss reduction,and energy recovery.The application of COMI technology in an enterprise is cost effective,involving the energy saving potential of 0.206 GJ/t,the cost of conserved energy of−48.83 yuan/GJ,and a simple payback period of 0.35 year for a 60-million-yuan investment.Sensitivity analysis shows that the investment cost and discount rate primarily influence the cost of conserved energy of the technology.As the discount rate increased,the cost of conserved energy also gradually increased.Overall,the COMI technology is an energy-saving technology with good development prospects.
文摘The crashworthiness and energy absorption optimization of automobile structure is an importantresearch content of the modern automobile industry. Facing the problem that traditionaloptimization methods are difficult to find the optimal solution for multi-objective parametersof vehicle structure crashworthiness problem, a multi-objective optimization method of vehiclecrash safety based on improved particle swarm optimization is proposed. Through the collectionand optimization of vehicle collision safety parameters, the vehicle structure performance isimproved, and the vehicle regression model is constructed. Using this method, the front-endstructure reinforcement of the vehicle is taken as the design variable. In order to realize themulti-objective optimization design method of vehicle collision safety, the multi-objective optimizationparameters of vehicle frontal collision and offset collision are taken as the objectivefunction. Finally, the simulation results show that the multi-objective optimization method basedon an improved particle swarm optimization algorithm has an obvious effect on the optimizationof vehicle structure crash safety.
