Increasing occurrences of oscillations of unknown mechanisms in today's power systems ask for recalling the first principle of operating.AC systems in general work with all units of supplies and loads to build up ...Increasing occurrences of oscillations of unknown mechanisms in today's power systems ask for recalling the first principle of operating.AC systems in general work with all units of supplies and loads to build up internal voltage of a certain amplitude/frequency,ensuring transferring and balancing of power in the system while subjected to varied disturbances.The dynamics following are therefore closed-loop iterations between power balancing-internal voltage relations in units and internal voltage-power relations in networks.Operating points and small disturbances associated will then have to be defined from such iterative processes with nonlinear relations among the increments that can be approximated at the initial period of disturbance,so linear system mathematics will be applicable for dynamic analysis.Conventional methodologies from varied fields are unfortunately not rooted from first principle physics and are therefore especially not suited for today's new scenario with increasing penetration of renewables.Taking a small disturbance dynamic process of a converter interfaced system as an example,this paper thus aims to propose an operating-point identification methodology from dimensions of AC signal by first revealing the incremental iterative mapping mechanism from the first principle of operating,and by then clarifying the self-consistency of the relevant electrical variables,as well as relations among them during iterations.It is recognized that during a certain time period following the disturbance,amplitude/frequency of internal voltage in the converter and active/reactive current at the network interface evolve in the form of the complex exponential,among which we can see linearizable weak-nonlinear relations,and thus should be defined as operating points.Based on the above operating points and relevant increments of the internal-voltage amplitude/frequency and active/reactive current,fundamental steps and challenges linearizing AC systems are finally summarized for analyzing grid dynamics.展开更多
In wind and solar renewable-dominant hybrid alternating current/direct current(AC/DC)power systems,the active power of high-voltage direct current(HVDC)system is significantly limited by the security and stability eve...In wind and solar renewable-dominant hybrid alternating current/direct current(AC/DC)power systems,the active power of high-voltage direct current(HVDC)system is significantly limited by the security and stability events caused by cascading failures.To identify critical lines in cascading failures,a rapid risk assessment method is proposed based on the gradient boosting decision tree(GBDT)and frequent pat-tern growth(FP-Growth)algorithms.First,security and stability events triggered by cascading failures are analyzed to explain the impact of cascading failures on the maximum DC power.Then,a cascading failure risk index is defined,focusing on the DC power being limited.To handle the strong nonlinear relationship between the maximum DC power and cascading failures,a GBDT with an update strategy is utilized to rapidly predict the maximum DC power under uncertain operating conditions.Finally,the FP-Growth algorithm is improved to mine frequent patterns in cascading failures.The importance index for each fault in a frequent pattern is defined by evaluating its impact on cascading failures,enabling the identification of critical lines.Simulation results of a modified Ningxia–Shandong hybrid AC/DC system in China demonstrate that the proposed method can rapidly assess the risk of cascading failures and effectively identify critical lines.展开更多
单级式双有源桥(dual active bridge,DAB)DC/AC变换器控制自由度多,变压器匝比、漏感、开关频率等参数相互耦合,导致变换器效率优化面临多重制约。该文分析变压器匝比、漏感与软开关范围、漏感电流有效值、漏感电流峰值之间的约束关系,...单级式双有源桥(dual active bridge,DAB)DC/AC变换器控制自由度多,变压器匝比、漏感、开关频率等参数相互耦合,导致变换器效率优化面临多重制约。该文分析变压器匝比、漏感与软开关范围、漏感电流有效值、漏感电流峰值之间的约束关系,提出直接表征DAB-DC/AC变换器效率的物理量:效率敏感因子。通过研究效率敏感因子对系统损耗的影响机理,实现变换器效率最优的硬件参数设计,为多参数耦合的单级式DAB-DC/AC变换器效率优化提供理论指导。最后通过一台450 W样机验证所提理论的正确性。展开更多
Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis(Bt)have proven to be highly effective in managing some key pests.However,the evolution of resistance by the target pests threa...Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis(Bt)have proven to be highly effective in managing some key pests.However,the evolution of resistance by the target pests threatens the sustainability of Bt crops.The L31S mutation in a tetraspanin encoded by Harm TspC5(previously known as Ha TSPAN1)has been shown to confer dominant resistance to the Bt protein Cry1Ac in Helicoverpa armigera,a globally damaging lepidopteran pest.However,the broader implications of the L31S mutation in the tetraspanins of other lepidopteran species remain unclear.The evolutionary analyses in this study indicate that TspC5s have evolved in a species-specific manner among the lepidopteran insects.To investigate the role of TspC5s in conferring dominant resistance to Cry1Ac,we used the piggyBac-based transformation system to generate four transgenic H.armigera strains that express exogenous TspC5 variants from three phylogenetically close species(Helicoverpa zea,Helicoverpa assulta and Heliothis virescens)and one phylogenetically distant species(Plutella xylostella).In comparison with the background SCD strain of H.armigera,the transgenic strains expressing HzeaTspC5-L31S,HassTspC5-L31S,or HvirTspC5-L31S exhibited significant resistance to Cry1Ac(10.0-,21.4-,and 81.1-fold,respectively),whereas the strain expressing PxylTspC5-L27S remained susceptible.Furthermore,the Cry1Ac resistant phenotypes followed an autosomal dominant inheritance pattern and were closely linked to the introduced mutant TspC5s.These findings reveal the conserved role of TspC5s from Helicoverpa and Heliothis species in mediating the dominant resistance to Cry1Ac,and they provide crucial insights for assessing resistance risks related to mutant tetraspanins and devising adaptive resistance management strategies for these major lepidopteran pests.展开更多
Heating,ventilation,and air conditioning(HVAC)systems contribute substantially to global energy consumption,while rejecting significant amounts of low-grade heat into the environment.This paper presents a nonintrusive...Heating,ventilation,and air conditioning(HVAC)systems contribute substantially to global energy consumption,while rejecting significant amounts of low-grade heat into the environment.This paper presents a nonintrusive spiral-coil heat exchanger designed to recover waste heat from the outdoor condenser of a split-type air conditioner.The system operates externally without altering the existing HVAC configuration,thereby rendering it suitable for retrofitting.Water was circulated as the working fluid at flow rates of 0.028–0.052 kg/s to assess thermal performance.Performance indicators,including the outlet water temperature,heat transfer rate,convective coefficient,and efficiency,were systematically evaluated.The system achieved a maximum outlet water temperature of 67℃and a peak thermal efficiency of 91.07%at the highest flow rate.The uncertainty analysis confirmed reliable measurements within±3.45%.The monthly energy savings were estimated at 178.35 kWh,accompanied by a reduction in CO_(2)emissions of up to 187.26 kg,yielding a short payback period of 1.06 years.These results demonstrate the feasibility of spiral-coil heat exchangers as cost-effective and eco-friendly alternatives to conventional electric water heaters.The proposed approach not only enhances the overall energy utilization but also contributes to energy conservation and climate mitigation objectives.展开更多
This paper proposes a multiport bidirectional non-isolated converter topology that provides advantages in terms of simultaneous multiple operations,single-stage conversion,high power density and reduced power losses d...This paper proposes a multiport bidirectional non-isolated converter topology that provides advantages in terms of simultaneous multiple operations,single-stage conversion,high power density and reduced power losses due to the lower number of switches.The proposed multiport converter uses a centralized non-linear controller known as a finite control set model predictive controller to manage the flow of power between different ports.It deals with the parallel operation of photovoltaic and battery energy storage systems for stand-alone alternating current(AC)systems.The converter connects the lower voltage battery to the photovoltaic port using a bidirectional buck/boost converter and the photovoltaic port is linked to the stand-alone AC load through a three-phase full-bridge inverter.Each leg of the three-phase converter will act as a bidirectional direct current(DC)/DC converter as well as an inverter simultaneously.Only six switches manage the power transfer between all the connected ports of photovoltaic-battery energy storage system linked to the stand-alone AC load.The proposed multiport converter is mathematically modelled and controlled by a finite control set model predictive controller.The system is validated in simulation(1-kW rating)and experimental environment(200-W rating).The hardware prototype is developed in the laboratory and the controller is implemented on the field-programmable gate array board.Two independent case studies are carried out to validate the efficacy of the system.The first scenario is for a change in solar irradiance,while the second scenario is for a change in the output load.展开更多
目的探究间质性肺疾病(interstitial lung disease,ILD)患者血清和支气管肺泡灌洗液(bronchoalveolar lavage fluid,BALF)中冷诱导RNA结合蛋白(cold-inducible RNA-binding protein,CIRBP)、黏蛋白(mucin,MUC)5AC的水平及临床意义。方...目的探究间质性肺疾病(interstitial lung disease,ILD)患者血清和支气管肺泡灌洗液(bronchoalveolar lavage fluid,BALF)中冷诱导RNA结合蛋白(cold-inducible RNA-binding protein,CIRBP)、黏蛋白(mucin,MUC)5AC的水平及临床意义。方法收集2022年1月—2024年2月在兰州大学第一医院呼吸与危重症医学科住院的ILD患者63例,其中特发性肺纤维化(idiopathic pulmonary fibrosis,IPF)患者22例,结缔组织疾病相关间质性肺疾病(connective tissue disease-interstitial lung disease,CTD-ILD)患者20例,其他类型的ILD患者21例。选取同时间段人口学特征匹配的健康人30例作为健康组。采用酶联免疫吸附试验检测健康组血清和ILD患者血清及BLAF中CIRBP、MUC5AC水平,比较健康组和ILD组血清及不同类型的ILD患者血清和BALF中CIRBP、MUC5AC水平及其与患者的肺功能、血气分析及6分钟步行距离(6-minute walk distance,6MWD)之间的相关性。依据血清CIRBP、MUC5AC水平绘制受试者操作特征曲线,确定其诊断ILD的最佳临界值、敏感性和特异性。结果三组ILD患者血清CIRBP水平均高于健康组(P<0.01),但三组ILD患者间血清CIRBP水平差异无统计学意义(P>0.05);三组ILD患者与健康组以及三组ILD患者间血清MUC5AC水平差异均无统计学意义(P>0.05);三组ILD患者BALF中CIRBP、MUC5AC水平差异均无统计学意义(P>0.05)。IPF患者BALF中CIRBP与6MWD呈负相关,CTD-ILD患者血清CIRBP与动脉血氧分压和氧饱和度均呈负相关,其他ILD患者血清CIRBP与肺总量占预计值百分比(total lung capacity as a percentage of predicted value,TLC%pred)、用力肺活量占预计值百分比(forced vital capacity as a percentage of predicted value,FVC%pred)、一氧化碳弥散量占预计值百分比(diffusion capacity of carbon monoxide of lung as a percentage of predicted value,DLCO%pred)、6MWD均呈负相关,BALF中CIRBP与DLCO%pred呈负相关;IPF患者BALF中MUC5AC与DLCO%pred呈负相关,CTD-ILD患者BALF中MUC5AC与TLC%pred、DLCO%pred及6MWD呈负相关,其他ILD患者血清MUC5AC与FVC%pred、DLCO%pred、6MWD呈负相关。血清CIRBP诊断ILD的敏感性和特异性分别为77.6%、96.7%。血清MUC5AC诊断ILD的敏感性和特异性分别为55.1%、76.7%;将两指标联合诊断ILD的敏感性为87.8%,特异性为86.7%。结论CIRBP和MUC5AC的高水平表达对ILD具有一定的诊断效能和病情评估作用,有可能成为ILD的潜在生物标志物。展开更多
基金supported by the National Natural Science Foundation of China under Grant U1866601。
文摘Increasing occurrences of oscillations of unknown mechanisms in today's power systems ask for recalling the first principle of operating.AC systems in general work with all units of supplies and loads to build up internal voltage of a certain amplitude/frequency,ensuring transferring and balancing of power in the system while subjected to varied disturbances.The dynamics following are therefore closed-loop iterations between power balancing-internal voltage relations in units and internal voltage-power relations in networks.Operating points and small disturbances associated will then have to be defined from such iterative processes with nonlinear relations among the increments that can be approximated at the initial period of disturbance,so linear system mathematics will be applicable for dynamic analysis.Conventional methodologies from varied fields are unfortunately not rooted from first principle physics and are therefore especially not suited for today's new scenario with increasing penetration of renewables.Taking a small disturbance dynamic process of a converter interfaced system as an example,this paper thus aims to propose an operating-point identification methodology from dimensions of AC signal by first revealing the incremental iterative mapping mechanism from the first principle of operating,and by then clarifying the self-consistency of the relevant electrical variables,as well as relations among them during iterations.It is recognized that during a certain time period following the disturbance,amplitude/frequency of internal voltage in the converter and active/reactive current at the network interface evolve in the form of the complex exponential,among which we can see linearizable weak-nonlinear relations,and thus should be defined as operating points.Based on the above operating points and relevant increments of the internal-voltage amplitude/frequency and active/reactive current,fundamental steps and challenges linearizing AC systems are finally summarized for analyzing grid dynamics.
基金supported by the National Key Research and Development Program of China"Key technologies for system stability and HVDC transmission of large-scale renewable energy generation base without conventional power support(2022YFB2402700)"the project of the State Grid Corporation of China(52272222001J).
文摘In wind and solar renewable-dominant hybrid alternating current/direct current(AC/DC)power systems,the active power of high-voltage direct current(HVDC)system is significantly limited by the security and stability events caused by cascading failures.To identify critical lines in cascading failures,a rapid risk assessment method is proposed based on the gradient boosting decision tree(GBDT)and frequent pat-tern growth(FP-Growth)algorithms.First,security and stability events triggered by cascading failures are analyzed to explain the impact of cascading failures on the maximum DC power.Then,a cascading failure risk index is defined,focusing on the DC power being limited.To handle the strong nonlinear relationship between the maximum DC power and cascading failures,a GBDT with an update strategy is utilized to rapidly predict the maximum DC power under uncertain operating conditions.Finally,the FP-Growth algorithm is improved to mine frequent patterns in cascading failures.The importance index for each fault in a frequent pattern is defined by evaluating its impact on cascading failures,enabling the identification of critical lines.Simulation results of a modified Ningxia–Shandong hybrid AC/DC system in China demonstrate that the proposed method can rapidly assess the risk of cascading failures and effectively identify critical lines.
文摘单级式双有源桥(dual active bridge,DAB)DC/AC变换器控制自由度多,变压器匝比、漏感、开关频率等参数相互耦合,导致变换器效率优化面临多重制约。该文分析变压器匝比、漏感与软开关范围、漏感电流有效值、漏感电流峰值之间的约束关系,提出直接表征DAB-DC/AC变换器效率的物理量:效率敏感因子。通过研究效率敏感因子对系统损耗的影响机理,实现变换器效率最优的硬件参数设计,为多参数耦合的单级式DAB-DC/AC变换器效率优化提供理论指导。最后通过一台450 W样机验证所提理论的正确性。
基金primarily funded by a grant from the National Natural Science Foundation of China(31930093)Additional support was provided by the Natural Science Foundation of Jiangsu Province,China(BK20230983)the Project of Fund for Stable Support to Agricultural Sci-Tech Renovation,China(xjnkywdzc-2022004)。
文摘Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis(Bt)have proven to be highly effective in managing some key pests.However,the evolution of resistance by the target pests threatens the sustainability of Bt crops.The L31S mutation in a tetraspanin encoded by Harm TspC5(previously known as Ha TSPAN1)has been shown to confer dominant resistance to the Bt protein Cry1Ac in Helicoverpa armigera,a globally damaging lepidopteran pest.However,the broader implications of the L31S mutation in the tetraspanins of other lepidopteran species remain unclear.The evolutionary analyses in this study indicate that TspC5s have evolved in a species-specific manner among the lepidopteran insects.To investigate the role of TspC5s in conferring dominant resistance to Cry1Ac,we used the piggyBac-based transformation system to generate four transgenic H.armigera strains that express exogenous TspC5 variants from three phylogenetically close species(Helicoverpa zea,Helicoverpa assulta and Heliothis virescens)and one phylogenetically distant species(Plutella xylostella).In comparison with the background SCD strain of H.armigera,the transgenic strains expressing HzeaTspC5-L31S,HassTspC5-L31S,or HvirTspC5-L31S exhibited significant resistance to Cry1Ac(10.0-,21.4-,and 81.1-fold,respectively),whereas the strain expressing PxylTspC5-L27S remained susceptible.Furthermore,the Cry1Ac resistant phenotypes followed an autosomal dominant inheritance pattern and were closely linked to the introduced mutant TspC5s.These findings reveal the conserved role of TspC5s from Helicoverpa and Heliothis species in mediating the dominant resistance to Cry1Ac,and they provide crucial insights for assessing resistance risks related to mutant tetraspanins and devising adaptive resistance management strategies for these major lepidopteran pests.
文摘Heating,ventilation,and air conditioning(HVAC)systems contribute substantially to global energy consumption,while rejecting significant amounts of low-grade heat into the environment.This paper presents a nonintrusive spiral-coil heat exchanger designed to recover waste heat from the outdoor condenser of a split-type air conditioner.The system operates externally without altering the existing HVAC configuration,thereby rendering it suitable for retrofitting.Water was circulated as the working fluid at flow rates of 0.028–0.052 kg/s to assess thermal performance.Performance indicators,including the outlet water temperature,heat transfer rate,convective coefficient,and efficiency,were systematically evaluated.The system achieved a maximum outlet water temperature of 67℃and a peak thermal efficiency of 91.07%at the highest flow rate.The uncertainty analysis confirmed reliable measurements within±3.45%.The monthly energy savings were estimated at 178.35 kWh,accompanied by a reduction in CO_(2)emissions of up to 187.26 kg,yielding a short payback period of 1.06 years.These results demonstrate the feasibility of spiral-coil heat exchangers as cost-effective and eco-friendly alternatives to conventional electric water heaters.The proposed approach not only enhances the overall energy utilization but also contributes to energy conservation and climate mitigation objectives.
文摘This paper proposes a multiport bidirectional non-isolated converter topology that provides advantages in terms of simultaneous multiple operations,single-stage conversion,high power density and reduced power losses due to the lower number of switches.The proposed multiport converter uses a centralized non-linear controller known as a finite control set model predictive controller to manage the flow of power between different ports.It deals with the parallel operation of photovoltaic and battery energy storage systems for stand-alone alternating current(AC)systems.The converter connects the lower voltage battery to the photovoltaic port using a bidirectional buck/boost converter and the photovoltaic port is linked to the stand-alone AC load through a three-phase full-bridge inverter.Each leg of the three-phase converter will act as a bidirectional direct current(DC)/DC converter as well as an inverter simultaneously.Only six switches manage the power transfer between all the connected ports of photovoltaic-battery energy storage system linked to the stand-alone AC load.The proposed multiport converter is mathematically modelled and controlled by a finite control set model predictive controller.The system is validated in simulation(1-kW rating)and experimental environment(200-W rating).The hardware prototype is developed in the laboratory and the controller is implemented on the field-programmable gate array board.Two independent case studies are carried out to validate the efficacy of the system.The first scenario is for a change in solar irradiance,while the second scenario is for a change in the output load.
文摘目的探究间质性肺疾病(interstitial lung disease,ILD)患者血清和支气管肺泡灌洗液(bronchoalveolar lavage fluid,BALF)中冷诱导RNA结合蛋白(cold-inducible RNA-binding protein,CIRBP)、黏蛋白(mucin,MUC)5AC的水平及临床意义。方法收集2022年1月—2024年2月在兰州大学第一医院呼吸与危重症医学科住院的ILD患者63例,其中特发性肺纤维化(idiopathic pulmonary fibrosis,IPF)患者22例,结缔组织疾病相关间质性肺疾病(connective tissue disease-interstitial lung disease,CTD-ILD)患者20例,其他类型的ILD患者21例。选取同时间段人口学特征匹配的健康人30例作为健康组。采用酶联免疫吸附试验检测健康组血清和ILD患者血清及BLAF中CIRBP、MUC5AC水平,比较健康组和ILD组血清及不同类型的ILD患者血清和BALF中CIRBP、MUC5AC水平及其与患者的肺功能、血气分析及6分钟步行距离(6-minute walk distance,6MWD)之间的相关性。依据血清CIRBP、MUC5AC水平绘制受试者操作特征曲线,确定其诊断ILD的最佳临界值、敏感性和特异性。结果三组ILD患者血清CIRBP水平均高于健康组(P<0.01),但三组ILD患者间血清CIRBP水平差异无统计学意义(P>0.05);三组ILD患者与健康组以及三组ILD患者间血清MUC5AC水平差异均无统计学意义(P>0.05);三组ILD患者BALF中CIRBP、MUC5AC水平差异均无统计学意义(P>0.05)。IPF患者BALF中CIRBP与6MWD呈负相关,CTD-ILD患者血清CIRBP与动脉血氧分压和氧饱和度均呈负相关,其他ILD患者血清CIRBP与肺总量占预计值百分比(total lung capacity as a percentage of predicted value,TLC%pred)、用力肺活量占预计值百分比(forced vital capacity as a percentage of predicted value,FVC%pred)、一氧化碳弥散量占预计值百分比(diffusion capacity of carbon monoxide of lung as a percentage of predicted value,DLCO%pred)、6MWD均呈负相关,BALF中CIRBP与DLCO%pred呈负相关;IPF患者BALF中MUC5AC与DLCO%pred呈负相关,CTD-ILD患者BALF中MUC5AC与TLC%pred、DLCO%pred及6MWD呈负相关,其他ILD患者血清MUC5AC与FVC%pred、DLCO%pred、6MWD呈负相关。血清CIRBP诊断ILD的敏感性和特异性分别为77.6%、96.7%。血清MUC5AC诊断ILD的敏感性和特异性分别为55.1%、76.7%;将两指标联合诊断ILD的敏感性为87.8%,特异性为86.7%。结论CIRBP和MUC5AC的高水平表达对ILD具有一定的诊断效能和病情评估作用,有可能成为ILD的潜在生物标志物。
