With the wide application of renewable energy power generation technology,the distribution network presents the characteristics of multi-source and complex structure.There are potential risks in the stability of power...With the wide application of renewable energy power generation technology,the distribution network presents the characteristics of multi-source and complex structure.There are potential risks in the stability of power system,and the problem of power quality is becoming more and more serious.This paper studies and proposes a power optimization cooperative control strategy for flexible fast interconnection device with energy storage,which combines the flexible interconnection technology with the energy storage device.The primary technology is to regulate the active and reactive power of the converter.By comparing the actual power value of the converter with the reference value,the proportional integral(PI)controller is used for correction,and the current components of d and q axes are obtained and input to the converter as the reference value of the current inner loop.The control strategy in this paper can realize power mutual aid between feeders,and at the same time,the energy storage device can provide or absorb a certain amount of power for feeders,so that the power grid can realize stable operation in a certain range.展开更多
Heat dissipation is an important part of light-emitting diode(LED)filament research and has aroused constant concern.In this paper,we studied the thermal performance of flexible LED filament by numerical simulation an...Heat dissipation is an important part of light-emitting diode(LED)filament research and has aroused constant concern.In this paper,we studied the thermal performance of flexible LED filament by numerical simulation and through experiment.The heat dissipation characteristics of spring-like structure flexible LED filament were computed by finite volume method,and it was found that the chip junction temperature was closely related to the pitch and the bending radius.The effect of inclination angle of lighting LED filament was discussed because it is relevant to the spring-like structure flexible LED filament in geometry.The results demonstrated that the temperature of the filament increases as the inclination angle improves.展开更多
To reduce current harmonics caused by switching frequency,T-type grid-connected inverter topology with LCL filter is adopted.In view of the disadvantages of the slow response speed of the traditional current control a...To reduce current harmonics caused by switching frequency,T-type grid-connected inverter topology with LCL filter is adopted.In view of the disadvantages of the slow response speed of the traditional current control and the failure to eliminate the influence of the LCL filter on the grid-connected current by using current PI control alone,a current double closed loop PI current tracking control is proposed.Through the theoretical analysis of the grid-connected inverter control principle,the grid-connected inverter control model is designed,and the transfer functionmodel of each control link is deduced,and the current loop PI regulator is designed at last.The simulation results show that the control strategy is feasible.展开更多
This paper studies the proximate satellite interception guidance strategies where both the interceptor and target can perform orbital maneuvers with magnitude limited thrusts. This problem is regarded as a pursuit-eva...This paper studies the proximate satellite interception guidance strategies where both the interceptor and target can perform orbital maneuvers with magnitude limited thrusts. This problem is regarded as a pursuit-evasion game since satellites in both sides will try their best to capture or escape. In this game, the distance of these two players is small enough so that the highly nonlinear earth-centered gravitational dynamics can be reduced to the linear Clohessy-Wiltshire（CW） equations. The system is then simplified by introducing the zero effort miss variables. Saddle solution is formulated for the pursuit-evasion game and time-to-go is estimated similarly as that for the exoatmospheric interception. Then a vector guidance is derived to ensure that the interception can be achieved in the optimal time. The proposed guidance law is validated by numerical simulations.展开更多
Variations of levels,possible source and air mass transmission were investigated for 16 USEPA priority-controlled PAHs in PM2.5 during 2018 Chinese Spring Festival(CSF)in Xiangyang City,central China which is the Nort...Variations of levels,possible source and air mass transmission were investigated for 16 USEPA priority-controlled PAHs in PM2.5 during 2018 Chinese Spring Festival(CSF)in Xiangyang City,central China which is the North-South pollutant airmass transport channel of China.Totally 37 samples were collected.Mass concentrations of 16 PAHs for the Pre–CSF day(Pre–CSFD),during the CSF day(CSFD)and after the CSF day(Af–CSFD)are 33.78±17.68 ng/m3,22.98±6.49 ng/m3,and 8.99±4.44 ng/m3,respectively.High resolution samples showed that 16 PAHs are higher in the morning(06:00–11:00)or afternoon(11:30–16:30),than those in the evening(17:00–22:00)and at night(22:30–05:30),whereas the result is reversed during the CSFD.Fireworks burning can obviously increase the mass concentration of PAHs.Air mass trajectory indicated that Xiangyang is a sink area of pollutants for northwest and southeast,and the sources of the northeast and southwest.The air mass only can be transmitted out through northeast and southwest.It is effective for improvement of air quality in Wuhan and Hunan to control fireworks emission in Henan and local areas.Fireworks burning was an important source for PAHs during CSFD,biomass,coal combustion,and traffic emission were the main sources of PAHs for Pre–CSFD and Af–CSFD periods.The health risk on the CSFD was higher than the acceptable levels,especially during the intensive fireworks burning,the risk value far exceed 1.0×10^-4,controlling burning fireworks is required.展开更多
In this review, first, we discussed the effect of phosphor features on optical properties by the software simulation in detail. A combination of these parameters: phosphor material, phosphor particle size and particle...In this review, first, we discussed the effect of phosphor features on optical properties by the software simulation in detail. A combination of these parameters: phosphor material, phosphor particle size and particle distribution, phosphor layer concentration, phosphor layer thickness, geometry, and location of the phosphor layer, will result in the final optical performance of the phosphor layer. Secondly, we introduced how to improve light extraction efficiency with various proposed methods. Thirdly, we summarized the thermal models to predict the phosphor temperature and the junction temperature. To stabilize the optical performance of phosphor-converted light emitting diodes (PC-LEDs), much effort has been made to reduce the junction temperature of the LED chips. The phosphor temperature, a critical reliability concern for PC-LEDs, should be attracted academic interest. Finally, we summed up optical-thermal coupled model for phosphors and summarized future optical- thermal issues exploring the light quality for LEDs. We foresee that optical-thermal coupled model for PC-LEDs should be paid more attention in the future.展开更多
Consumption inequality may impede economic development and hinder the achievement of common prosperity.Using three waves of the China Family Panel Studies from 2014 to 2018,this paper investigated the impact of e-comm...Consumption inequality may impede economic development and hinder the achievement of common prosperity.Using three waves of the China Family Panel Studies from 2014 to 2018,this paper investigated the impact of e-commerce on consumption inequality,as measured by the Kakwani index.The results indicate that e-commerce can reduce household consumption inequality.A mechanism analysis shows that e-commerce can narrow household income inequality,increase the purchasing power of low-income households,and promote the consumption of households with limited access to ofline markets,thereby reducing the consumption gap.A heterogeneity analysis suggests that the positive role of e-commerce in reducing consumption inequality can be more significant among vulnerable households,such as households with elderly members and less-educated households.E-commerce can have varying impacts on consumption inequality across different subcategories of household expenditure,with the greatest impact seen in entertainment and education expenditure.These findings provide new evidence for the role of e-commerce in reducing consumption inequality in the digital economy,and the implications of this are discussed.展开更多
This paper develops a game-theoretic spatial model featuring consumer heterogeneity in online vs. offline retailers* spatial competition. We find that consumers1 browse-and-switch behavior intensifies the competition ...This paper develops a game-theoretic spatial model featuring consumer heterogeneity in online vs. offline retailers* spatial competition. We find that consumers1 browse-and-switch behavior intensifies the competition because both offline and online retailers' price and profit decline when the behavior occurs, but it is not necessarily a threat to offline retailers especially when the product relates more closely to experience. We consider six equilibrium seenarios for different combi nations of consumer behaviors when considering a hybrid retailer. The analysis taking consumer heterogeneity into consideration shows that the hybrid retailer operating both online and offline is not always the winner. Particularly, the business opportunity for the offline retailer lies in consumersz willingness to pay in store, and whether the retailer launches an online store depends on the type of products and services provided.展开更多
This paper proposes a model featuring the heterogeneity of consumer preferences and analyzes the multiple equilibrium of retail formats by building a map of the relationships between consumer heterogeneity and retail ...This paper proposes a model featuring the heterogeneity of consumer preferences and analyzes the multiple equilibrium of retail formats by building a map of the relationships between consumer heterogeneity and retail formats. The key questions analyzed in this paper are how the retailer adjusts its combination of marketing elements through repositioning and how innovation in retail formats is implemented to match consumers＇ heterogeneous preferences in a market with consumer search costs. Unlike recent research, our model, by taking different consumer preference structures into account, introduces consumer psychological costs into the Ehrlich-Fisher model and deduces the existence of different retail formats and their multiple equilibriums. We find that consumer heterogeneity, retailers＂ diversified transfer costs and economies of scale are endogenous drivers of prosperous retail formats. Accordingly, diversified retail formats with complementary functions and differentiated services can be described as the horizontal extensions and interface changes of the retailing industry.展开更多
Phosphor in glass（PiG） employing Ce:Y3Al5O12（YAG）-doped boro-bismuthate glass via low-temperature cosintering technology was successfully prepared, using Bi2O3-B2O3-ZnO glass as the base material. The photolumines...Phosphor in glass（PiG） employing Ce:Y3Al5O12（YAG）-doped boro-bismuthate glass via low-temperature cosintering technology was successfully prepared, using Bi2O3-B2O3-ZnO glass as the base material. The photoluminescence（PL） of PiG co-sintered at times ranging from 20 min to 60 min at 700°C was investigated.As a result, the relative PL intensity of PiG under a reducing atmosphere of CO showed significant enhancement of about 7–14 times that under air atmosphere sintering for 20–50 min. The PL intensity decreased gradually with the co-sintering time, which may be due to the corrosion of the YAG lattice structure.展开更多
This paper introduces a new type of spiral white light-emitting diodes（WLED） filament with high luminous efficiency and uniform optical performance. The optical and thermal properties of the flexible filament were i...This paper introduces a new type of spiral white light-emitting diodes（WLED） filament with high luminous efficiency and uniform optical performance. The optical and thermal properties of the flexible filament were investigated at different stretching heights, namely 0, 1, 2, and 3 cm. The results indicated that the filament showed the best optical characteristics at the stretching height of 2 cm, because of good heat dissipation. In addition, the radiation temperature of the filament was inversely proportional to the output luminous flux. The reliability of the filament at a stretching height of 2 cm was also evaluated after 1000 h of use. The result demonstrated that the luminous flux decay of the bulb was only 0.85%. The flexible spiral WLED filament exhibiting high luminous flux and good reliability could be adapted to promote industrial development in the near future.展开更多
基金Supported by Science and Technology Projects of State Grid Corporation of China(JF2021018).
文摘With the wide application of renewable energy power generation technology,the distribution network presents the characteristics of multi-source and complex structure.There are potential risks in the stability of power system,and the problem of power quality is becoming more and more serious.This paper studies and proposes a power optimization cooperative control strategy for flexible fast interconnection device with energy storage,which combines the flexible interconnection technology with the energy storage device.The primary technology is to regulate the active and reactive power of the converter.By comparing the actual power value of the converter with the reference value,the proportional integral(PI)controller is used for correction,and the current components of d and q axes are obtained and input to the converter as the reference value of the current inner loop.The control strategy in this paper can realize power mutual aid between feeders,and at the same time,the energy storage device can provide or absorb a certain amount of power for feeders,so that the power grid can realize stable operation in a certain range.
基金Project supported by the National Natural Science Foundation of China(Grant No.51302171)Science and Technology Commission of Shanghai Municipality,China(Grant No.14500503300)+2 种基金Shanghai Municipal Alliance Program,China(Grant No.Lm201547)Shanghai Cooperative Project,China(Grant No.ShanghaiCXY-2013-61)Jiashan County Technology Program,China(Grant No.20141316)
文摘Heat dissipation is an important part of light-emitting diode(LED)filament research and has aroused constant concern.In this paper,we studied the thermal performance of flexible LED filament by numerical simulation and through experiment.The heat dissipation characteristics of spring-like structure flexible LED filament were computed by finite volume method,and it was found that the chip junction temperature was closely related to the pitch and the bending radius.The effect of inclination angle of lighting LED filament was discussed because it is relevant to the spring-like structure flexible LED filament in geometry.The results demonstrated that the temperature of the filament increases as the inclination angle improves.
基金Supported by Science and Technology Projects of State Grid Corporation ofChina(J2022019).
文摘To reduce current harmonics caused by switching frequency,T-type grid-connected inverter topology with LCL filter is adopted.In view of the disadvantages of the slow response speed of the traditional current control and the failure to eliminate the influence of the LCL filter on the grid-connected current by using current PI control alone,a current double closed loop PI current tracking control is proposed.Through the theoretical analysis of the grid-connected inverter control principle,the grid-connected inverter control model is designed,and the transfer functionmodel of each control link is deduced,and the current loop PI regulator is designed at last.The simulation results show that the control strategy is feasible.
基金co-supported by the National Natural Science Foundation of China (Nos.61603115,91438202 and91638301)China Postdoctoral Science Foundation (No.2015M81455)+1 种基金the Open Fund of National Defense Key Discipline Laboratory of Micro-Spacecraft Technology of China (No.HIT.KLOF.MST.201601)the Heilongjiang Postdoctoral Fund of China (No.LBH-Z15085)
文摘This paper studies the proximate satellite interception guidance strategies where both the interceptor and target can perform orbital maneuvers with magnitude limited thrusts. This problem is regarded as a pursuit-evasion game since satellites in both sides will try their best to capture or escape. In this game, the distance of these two players is small enough so that the highly nonlinear earth-centered gravitational dynamics can be reduced to the linear Clohessy-Wiltshire（CW） equations. The system is then simplified by introducing the zero effort miss variables. Saddle solution is formulated for the pursuit-evasion game and time-to-go is estimated similarly as that for the exoatmospheric interception. Then a vector guidance is derived to ensure that the interception can be achieved in the optimal time. The proposed guidance law is validated by numerical simulations.
基金supported by the National Key Research and Development Program of China(No.2017YFC0212603)the National Natural Science Foundation of China(No.41773124)+2 种基金the Open Research Program of Laboratory of Basin Hydrology and Wetland Eco-restoration,China University of Geosciences(Wuhan)(No.BHWER201503(A))the Open Research Fund of Hubei Key Laboratory of Mine Environmental Pollution Con-trol&Remediation,Hubei Polytechnic University(No.201702)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(No.CUGL170208)。
文摘Variations of levels,possible source and air mass transmission were investigated for 16 USEPA priority-controlled PAHs in PM2.5 during 2018 Chinese Spring Festival(CSF)in Xiangyang City,central China which is the North-South pollutant airmass transport channel of China.Totally 37 samples were collected.Mass concentrations of 16 PAHs for the Pre–CSF day(Pre–CSFD),during the CSF day(CSFD)and after the CSF day(Af–CSFD)are 33.78±17.68 ng/m3,22.98±6.49 ng/m3,and 8.99±4.44 ng/m3,respectively.High resolution samples showed that 16 PAHs are higher in the morning(06:00–11:00)or afternoon(11:30–16:30),than those in the evening(17:00–22:00)and at night(22:30–05:30),whereas the result is reversed during the CSFD.Fireworks burning can obviously increase the mass concentration of PAHs.Air mass trajectory indicated that Xiangyang is a sink area of pollutants for northwest and southeast,and the sources of the northeast and southwest.The air mass only can be transmitted out through northeast and southwest.It is effective for improvement of air quality in Wuhan and Hunan to control fireworks emission in Henan and local areas.Fireworks burning was an important source for PAHs during CSFD,biomass,coal combustion,and traffic emission were the main sources of PAHs for Pre–CSFD and Af–CSFD periods.The health risk on the CSFD was higher than the acceptable levels,especially during the intensive fireworks burning,the risk value far exceed 1.0×10^-4,controlling burning fireworks is required.
文摘In this review, first, we discussed the effect of phosphor features on optical properties by the software simulation in detail. A combination of these parameters: phosphor material, phosphor particle size and particle distribution, phosphor layer concentration, phosphor layer thickness, geometry, and location of the phosphor layer, will result in the final optical performance of the phosphor layer. Secondly, we introduced how to improve light extraction efficiency with various proposed methods. Thirdly, we summarized the thermal models to predict the phosphor temperature and the junction temperature. To stabilize the optical performance of phosphor-converted light emitting diodes (PC-LEDs), much effort has been made to reduce the junction temperature of the LED chips. The phosphor temperature, a critical reliability concern for PC-LEDs, should be attracted academic interest. Finally, we summed up optical-thermal coupled model for phosphors and summarized future optical- thermal issues exploring the light quality for LEDs. We foresee that optical-thermal coupled model for PC-LEDs should be paid more attention in the future.
基金the National Social Science Foundation of China(No.18FJY018)the National Natural Science Foundation of China(No.41401124)。
文摘Consumption inequality may impede economic development and hinder the achievement of common prosperity.Using three waves of the China Family Panel Studies from 2014 to 2018,this paper investigated the impact of e-commerce on consumption inequality,as measured by the Kakwani index.The results indicate that e-commerce can reduce household consumption inequality.A mechanism analysis shows that e-commerce can narrow household income inequality,increase the purchasing power of low-income households,and promote the consumption of households with limited access to ofline markets,thereby reducing the consumption gap.A heterogeneity analysis suggests that the positive role of e-commerce in reducing consumption inequality can be more significant among vulnerable households,such as households with elderly members and less-educated households.E-commerce can have varying impacts on consumption inequality across different subcategories of household expenditure,with the greatest impact seen in entertainment and education expenditure.These findings provide new evidence for the role of e-commerce in reducing consumption inequality in the digital economy,and the implications of this are discussed.
基金the National Natural Science Foundation of China under grant number 41401124the National Social Science Foundation of China under grant number 18FJY018.
文摘This paper develops a game-theoretic spatial model featuring consumer heterogeneity in online vs. offline retailers* spatial competition. We find that consumers1 browse-and-switch behavior intensifies the competition because both offline and online retailers' price and profit decline when the behavior occurs, but it is not necessarily a threat to offline retailers especially when the product relates more closely to experience. We consider six equilibrium seenarios for different combi nations of consumer behaviors when considering a hybrid retailer. The analysis taking consumer heterogeneity into consideration shows that the hybrid retailer operating both online and offline is not always the winner. Particularly, the business opportunity for the offline retailer lies in consumersz willingness to pay in store, and whether the retailer launches an online store depends on the type of products and services provided.
文摘This paper proposes a model featuring the heterogeneity of consumer preferences and analyzes the multiple equilibrium of retail formats by building a map of the relationships between consumer heterogeneity and retail formats. The key questions analyzed in this paper are how the retailer adjusts its combination of marketing elements through repositioning and how innovation in retail formats is implemented to match consumers＇ heterogeneous preferences in a market with consumer search costs. Unlike recent research, our model, by taking different consumer preference structures into account, introduces consumer psychological costs into the Ehrlich-Fisher model and deduces the existence of different retail formats and their multiple equilibriums. We find that consumer heterogeneity, retailers＂ diversified transfer costs and economies of scale are endogenous drivers of prosperous retail formats. Accordingly, diversified retail formats with complementary functions and differentiated services can be described as the horizontal extensions and interface changes of the retailing industry.
基金supported by the Science and Technology Planning Project of Zhejiang Province,China(No.2018C01046)the Enterprise-funded Latitudinal Research Projects(Nos.J2016-141,J2017-171,J2017-293,and J2017-243)
文摘Phosphor in glass（PiG） employing Ce:Y3Al5O12（YAG）-doped boro-bismuthate glass via low-temperature cosintering technology was successfully prepared, using Bi2O3-B2O3-ZnO glass as the base material. The photoluminescence（PL） of PiG co-sintered at times ranging from 20 min to 60 min at 700°C was investigated.As a result, the relative PL intensity of PiG under a reducing atmosphere of CO showed significant enhancement of about 7–14 times that under air atmosphere sintering for 20–50 min. The PL intensity decreased gradually with the co-sintering time, which may be due to the corrosion of the YAG lattice structure.
基金supported by the National Nature Science Foundation of China(No.51302171)the Science and Technology Commission of Shanghai Municipality(CN)(No.14500503300)+2 种基金the Shanghai Municipal Alliance Program(No.Lm201547)the Shanghai Cooperative Project(No.Shanghai CXY-2013-61)the Jiashan County Technology Program(No.20141316)
文摘This paper introduces a new type of spiral white light-emitting diodes（WLED） filament with high luminous efficiency and uniform optical performance. The optical and thermal properties of the flexible filament were investigated at different stretching heights, namely 0, 1, 2, and 3 cm. The results indicated that the filament showed the best optical characteristics at the stretching height of 2 cm, because of good heat dissipation. In addition, the radiation temperature of the filament was inversely proportional to the output luminous flux. The reliability of the filament at a stretching height of 2 cm was also evaluated after 1000 h of use. The result demonstrated that the luminous flux decay of the bulb was only 0.85%. The flexible spiral WLED filament exhibiting high luminous flux and good reliability could be adapted to promote industrial development in the near future.
