Most research on carbon storage in forests has focused on qualitative studies of carbon storage and influ-encing factors rather than on quantifying the effect of the spatial distribution of carbon storage and of its i...Most research on carbon storage in forests has focused on qualitative studies of carbon storage and influ-encing factors rather than on quantifying the effect of the spatial distribution of carbon storage and of its influencing factors at different scales.Here we described the spatial dis-tribution of aboveground carbon storage(ACS)in a 20-ha plot in a subtropical evergreen broad-leaved forest to evalu-ate and quantify the relative effects of biotic factors(species diversity and structural diversity)and abiotic factors(soil and topographic factors)on ACS at different scales.Scale effects of the spatial distribution of ACS were significant,with higher variability at smaller scales,but less at larger scales.The distribution was also spatially heterogeneous,with more carbon storage on north-and east-facing slopes than on south-and west-facing slopes.At a smaller scale,species diversity and structural diversity each had a direct positive impact on ACS,but soil factors had no significant direct impact.At increasing scales,topographic and soil fac-tors gradually had a greater direct influence,whereas the influence of species diversity gradually decreased.Structural diversity had the greatest impact,followed by topographic factors and soil factors,while species diversity had a rela-tively smaller impact.These findings suggest studies on ACS in subtropical evergreen broadleaf forests in southern China should consider scale effects,specifically on the heterogene-ity of ACS distribution at small scales.Studies and conser-vation efforts need to focus on smaller habitat types with particular emphasis on habitat factors such as aspect and soil conditions,which have significant influences on community species diversity,structural diversity,and ACS distribution.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
在两级式AC-DC变换器中,前级功率因数校正(power factor correction,PFC)固有的瞬时功率波动特性会造成母线电压存在二倍频纹波,影响后级CLLLC谐振变换器的输出电压质量。针对以上问题,该文提出了基于二阶广义积分(second order general...在两级式AC-DC变换器中,前级功率因数校正(power factor correction,PFC)固有的瞬时功率波动特性会造成母线电压存在二倍频纹波,影响后级CLLLC谐振变换器的输出电压质量。针对以上问题,该文提出了基于二阶广义积分(second order generalized integral,SOGI)的可变增益母线电压纹波前馈控制方法。采用SOGI提取母线电压纹波信息,基于品质因数Q与电压增益的关系和母线电压纹波对归一化频率的影响,解析了母线电压纹波对CLLLC谐振变换器输出电压的影响机理,得到Q值与前馈增益系数Ka的关系,采用仿真寻优加数据拟合的方法得到前馈可变增益系数曲线。仿真和实验结果表明,相比于无前馈控制,所提控制方法对CLLLC谐振变换器的输出电压纹波具有较好的抑制效果,输出电压纹波降低了72%,验证了所提算法的有效性。展开更多
The effect from the interaction of the alternating current(AC)magnetic field with kilogram-level test mass(TM)limits the detectivity of the TianQin space-based gravitational wave detection.The quantifed effect require...The effect from the interaction of the alternating current(AC)magnetic field with kilogram-level test mass(TM)limits the detectivity of the TianQin space-based gravitational wave detection.The quantifed effect requires the determination of the AC magnetic susceptibilityχ(f)of the TM.A torque method is proposed to measure theχ(f)of kg-level samples at the mHz band with a precision of 1×10^(-7).Combined with our previous work[Phys.Rev.Appl.18044010(2022)],the general frequency-dependent susceptibility of the alloy cube with side length L and electrical conductivityσis determined asχ(f)=χ0+(0.24±0.01)σμ0L^(2)f from 0.1 mHz to 1 Hz.The determination is helpful for the preliminary estimation of the in-band eddy current efect in the TianQin noise budget.The technique can be adopted to accurately measureχ(f)of the actual TM in other precision experiments,where the magnetic noise is a signifcant detection limit.展开更多
This article reviews the characteristics of psychological disorders in young and middle-aged acute coronary syndrome(ACS)patients,the mechanisms and effects of various psychological intervention strategies,factors inf...This article reviews the characteristics of psychological disorders in young and middle-aged acute coronary syndrome(ACS)patients,the mechanisms and effects of various psychological intervention strategies,factors influencing return to work,and current research problems and development trends,to provide scientific evidence for psychological rehabilitation and social function recovery of young and middle-aged ACS patients.展开更多
The effect of a metal shell on the launch efficiency of an asynchronous coil launcher(coil AC pulse linear motor)remains insufficiently understood in terms of the underlying mechanisms and principles.To address this g...The effect of a metal shell on the launch efficiency of an asynchronous coil launcher(coil AC pulse linear motor)remains insufficiently understood in terms of the underlying mechanisms and principles.To address this gap,this study conducted extensive modelling simulations and calculations,varying the shell's conductivity,permeability,and dimensions.Through comparative analysis of these models,this paper identifies a unique‘tick-shaped efficiency curve’for the asynchronous coil launcher:the launch efficiency first decreases and then increases as the shell's electromagnetic parameters are enhanced.Enhancements that bolster the electromagnetic induction effect within the shell-such as increased conductivity,permeability and dimensions-are termed as the augmentation of electromagnetic parameters.This study delves into Lenz's law of electromagnetism to elucidate the observed phenomena,attributing them to the spatio-temporal force characteristics of the multipeak and multi-valley armature of the transmitting device,and the resulting‘tick-shaped efficiency curve’.A comprehensive summary of shell-related research in electromagnetic emission reveals that the driving current fundamentally dictates the shell's impact on launch efficiency.DC-driven launchers conform to the monotonic effect efficiency curve,whereas AC-driven launchers conform to the tick-shaped efficiency curve.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
基金supported by the Guangxi Natural Science Foundation Program(2022GXNSFAA035583,2021GXNSFBA196052)the National Natural Science Foundation of China(32060305,32460270).
文摘Most research on carbon storage in forests has focused on qualitative studies of carbon storage and influ-encing factors rather than on quantifying the effect of the spatial distribution of carbon storage and of its influencing factors at different scales.Here we described the spatial dis-tribution of aboveground carbon storage(ACS)in a 20-ha plot in a subtropical evergreen broad-leaved forest to evalu-ate and quantify the relative effects of biotic factors(species diversity and structural diversity)and abiotic factors(soil and topographic factors)on ACS at different scales.Scale effects of the spatial distribution of ACS were significant,with higher variability at smaller scales,but less at larger scales.The distribution was also spatially heterogeneous,with more carbon storage on north-and east-facing slopes than on south-and west-facing slopes.At a smaller scale,species diversity and structural diversity each had a direct positive impact on ACS,but soil factors had no significant direct impact.At increasing scales,topographic and soil fac-tors gradually had a greater direct influence,whereas the influence of species diversity gradually decreased.Structural diversity had the greatest impact,followed by topographic factors and soil factors,while species diversity had a rela-tively smaller impact.These findings suggest studies on ACS in subtropical evergreen broadleaf forests in southern China should consider scale effects,specifically on the heterogene-ity of ACS distribution at small scales.Studies and conser-vation efforts need to focus on smaller habitat types with particular emphasis on habitat factors such as aspect and soil conditions,which have significant influences on community species diversity,structural diversity,and ACS distribution.
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supported by the National Key R&D Program of China(Grant No.2020YFC2200500)the Key Laboratory of Tian Qin Project(Sun Yat-sen University),Ministry of Education+1 种基金the National Natural Science Foundation of China(Grant Nos.12075325,12005308,and 11605065)the Doctoral Research Foundation Project of Hubei University of Arts and Science(Grant No.kyqdf2059017)。
文摘The effect from the interaction of the alternating current(AC)magnetic field with kilogram-level test mass(TM)limits the detectivity of the TianQin space-based gravitational wave detection.The quantifed effect requires the determination of the AC magnetic susceptibilityχ(f)of the TM.A torque method is proposed to measure theχ(f)of kg-level samples at the mHz band with a precision of 1×10^(-7).Combined with our previous work[Phys.Rev.Appl.18044010(2022)],the general frequency-dependent susceptibility of the alloy cube with side length L and electrical conductivityσis determined asχ(f)=χ0+(0.24±0.01)σμ0L^(2)f from 0.1 mHz to 1 Hz.The determination is helpful for the preliminary estimation of the in-band eddy current efect in the TianQin noise budget.The technique can be adopted to accurately measureχ(f)of the actual TM in other precision experiments,where the magnetic noise is a signifcant detection limit.
基金Supported by Humanities and Social Sciences Project of Hubei Provincial Department of Education(22Q149&19Y090).
文摘This article reviews the characteristics of psychological disorders in young and middle-aged acute coronary syndrome(ACS)patients,the mechanisms and effects of various psychological intervention strategies,factors influencing return to work,and current research problems and development trends,to provide scientific evidence for psychological rehabilitation and social function recovery of young and middle-aged ACS patients.
基金supported by Scientific Instrument Developing Project of Chinese Academy of Sciences(Grant/Award YJKYYQ20200011)Chinese Academy of Sciences‘Light of West China’Program(Grant/Award xbzg-zdsys-202317).
文摘The effect of a metal shell on the launch efficiency of an asynchronous coil launcher(coil AC pulse linear motor)remains insufficiently understood in terms of the underlying mechanisms and principles.To address this gap,this study conducted extensive modelling simulations and calculations,varying the shell's conductivity,permeability,and dimensions.Through comparative analysis of these models,this paper identifies a unique‘tick-shaped efficiency curve’for the asynchronous coil launcher:the launch efficiency first decreases and then increases as the shell's electromagnetic parameters are enhanced.Enhancements that bolster the electromagnetic induction effect within the shell-such as increased conductivity,permeability and dimensions-are termed as the augmentation of electromagnetic parameters.This study delves into Lenz's law of electromagnetism to elucidate the observed phenomena,attributing them to the spatio-temporal force characteristics of the multipeak and multi-valley armature of the transmitting device,and the resulting‘tick-shaped efficiency curve’.A comprehensive summary of shell-related research in electromagnetic emission reveals that the driving current fundamentally dictates the shell's impact on launch efficiency.DC-driven launchers conform to the monotonic effect efficiency curve,whereas AC-driven launchers conform to the tick-shaped efficiency curve.
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.
