This study employed numerical simulations to explore the impact of varying ice nucleation processes on the microphysics and electrification within thunderstorm clouds.A two-dimensional cumulus model,incorporating both...This study employed numerical simulations to explore the impact of varying ice nucleation processes on the microphysics and electrification within thunderstorm clouds.A two-dimensional cumulus model,incorporating both noninductive and inductive charge separation schemes,was utilized.The findings revealed that the freezing nucleation mechanism significantly influenced the microphysical development,electrification,and charge structure of thunderstorms.Homogeneous freezing generated a large quantity of small ice crystals near the cloud tops,which were primarily responsible for the development of positive charge regions through a non-inductive charging process.Conversely,heterogeneous freezing resulted in larger ice crystals,enhancing graupel formation and leading to a more rapid and intense charge separation rate of around-15°C.Ice crystals formed heterogeneously and charged negatively during the development stage,resulting in an inverted dipole charge structure.When both immersion and homogeneous freezing processes were considered,the competition between these two distinct freezing processes resulted in reduced cloud water content and weaker electrification.Under conditions of low cloud water content at lower storm levels,graupel particles were negatively charged through non-inductive charging,causing the charge structure to quickly revert to a normal dipole structure.展开更多
Efficient photogenerated carrier migration/separation plays a critical role in increasing the photocatalytic performance of g-C_(3)N_(4).Herein,sulfonic acid group-functionalized g-C_(3)N_(4)(SACN)was synthesized and ...Efficient photogenerated carrier migration/separation plays a critical role in increasing the photocatalytic performance of g-C_(3)N_(4).Herein,sulfonic acid group-functionalized g-C_(3)N_(4)(SACN)was synthesized and then synchronously strengthened by a facile-solid-state thermal reaction of g-C_(3)N_(4)and sulfamic acid.As a solid strong acid,sulfamic acid can be used to achieve acid etching on the surface of g-C_(3)N_(4)with the assistance of thermal treatment,leading to an enlarged specific surface area and increased surface catalytic reaction sites.More importantly,our experiments and density functional theory calculations indicate that the driving force generated by the negative inductive effect of sulfonic acid groups significantly improves the charge transfer dynamics and effectively inhibits their recombination.Moreover,the negative inductive effect can induce charge redistribution,which reduces the conduction band potential of g-C_(3)N_(4)to enhance the reduction ability of photo-induced electrons.As a result,the SACN-400 sample showed excellent photocatalytic performance in H2 generation with an apparent quantum efficiency of 11.03%at 420±15 nm,as well as an efficient photodegradation rate for organic pollutants.展开更多
本研究利用加入起电、放电参数化方案的数值模式(Weather Research and Forecasting Model(Version 3.7.1),WRF3.7.1_ELEC),通过设计五组不同非感应起电及感应起电参数化方案敏感性试验,对发生在青藏高原东北部青海大通地区的一次雷暴...本研究利用加入起电、放电参数化方案的数值模式(Weather Research and Forecasting Model(Version 3.7.1),WRF3.7.1_ELEC),通过设计五组不同非感应起电及感应起电参数化方案敏感性试验,对发生在青藏高原东北部青海大通地区的一次雷暴过程进行模拟研究,对比分析了不同非感应起电机制及感应起电机制对雷暴云电荷结构的影响.结果表明:在雷暴云发展旺盛阶段,Saunders(S91)、Riming Rate(RR)、和Saunders和Peck(SP98)三种非感应起电方案模拟的雷暴云最低层均为负电荷区,而混合方案(Brooks and SP98,BSP)模拟的雷暴云最低层为正电荷区,主电荷区自下而上为“+-+-”排列的四层电荷结构.与甚高频辐射源定位法推算的结果对比,BSP方案模拟的本次高原雷暴云电荷结构更接近实际情况;几种不同非感应起电方案模拟的主电荷区外围与主电荷区电荷结构不同,说明在雷暴发展的不同阶段雷暴云的电荷结构是不同的;几种非感应起电方案模拟的电荷结构不尽相同,主要是由于霰、冰和雪粒子在不同高度所带电荷的极性及电量的大小不同,霰粒子的电荷密度对低层的影响较大,冰粒子和雪粒子的电荷密度对中上层的影响较大;加入感应起电机制后,雷暴云电荷结构分布几乎没有变化,但能使雷暴云发展旺盛阶段低层和中层的正负电荷区电荷密度有所加强.展开更多
为了研究1200 V SiC MOSFET在重复非钳位感性开关(Unclamped-Inductive-Switching,UIS)应力下的电学参数退化机制,基于自行搭建的UIS实验平台以及Sentaurus仿真设计工具,首先深入分析了重复UIS测试后器件静态参数与动态参数的退化;接着...为了研究1200 V SiC MOSFET在重复非钳位感性开关(Unclamped-Inductive-Switching,UIS)应力下的电学参数退化机制,基于自行搭建的UIS实验平台以及Sentaurus仿真设计工具,首先深入分析了重复UIS测试后器件静态参数与动态参数的退化;接着基于FN隧穿公式对栅极漏电流数据进行拟合,得到随着UIS测试次数增加SiC/SiO2界面的势垒高度从2.52 eV逐渐降低到2.06 eV;最后解释了SiC MOSFET在重复UIS测试后的电流输运过程。结果表明,在重复雪崩应力的作用下,大量的正电荷注入至结型场效应管区域上方的栅极氧化层中,影响了该区域的电场分布以及耗尽层厚度,导致被测器件(Device Under Test,DUT)的导通电阻、漏源泄漏电流、电容特性等电学参数呈现出不同程度的退化,并且氧化物中的正电荷的积累也使电子隧穿通过栅介质的电流得到了抬升。展开更多
在三维强风暴动力—电耦合数值模式中引入基于Saunders et al.(1991)实验结果的非感应起电参数化方案S91,在此基础上,利用云水饱和度替代环境温度和有效液水含量将S91方案变形。对比分析一次雷暴单体首次放电前,变形后的S91方案和原S91...在三维强风暴动力—电耦合数值模式中引入基于Saunders et al.(1991)实验结果的非感应起电参数化方案S91,在此基础上,利用云水饱和度替代环境温度和有效液水含量将S91方案变形。对比分析一次雷暴单体首次放电前,变形后的S91方案和原S91方案模拟得到的非感应转移电荷的极性、量级、电荷结构以及与霰和冰晶粒子分布之间的关系。结果表明,虽然两种方案采用的电荷密度变化率以及每次碰撞平均转移的电荷量均相同,但不同方案中决定粒子间电荷转移的因子不同对电荷的分布存在较大的影响。加入云水饱和度的S91方案,非感应转移电荷的极性多为正极性,电荷结构先呈单极性后转变为三极性,并有进一步转变为偶极性的趋势。但这两种方案模拟得到的霰与冰晶粒子电荷分布的重合区的范围、大小均不同,这也是造成两种方案电荷结构和转移电荷分布不同的主要原因。展开更多
pH titration of the fluorescence of N-(1-naphthyl)aminoacetic acid(NAA) was performed in aqueous solution over pH range of 1 5—12 5. Despite no shift in the fluorescence maximum wavelength, the titration curve showed...pH titration of the fluorescence of N-(1-naphthyl)aminoacetic acid(NAA) was performed in aqueous solution over pH range of 1 5—12 5. Despite no shift in the fluorescence maximum wavelength, the titration curve showed an Ω-shaped profile with increasing pH with two inflection points at pH 4 1 and pH 11 5, respectively. These values correspond to the excited-state pK *_a s of carboxylic group and ammonium cation, respectively, which are both higher than those of the corresponding ground-state pK_as of 2 64 and 11 83, of which the former changes more. The substantial weakening of the proton dissociation of carboxylic group in the excited state should be indicative of the decrease in the inductive +I-effect of the ammonium cation at the β-position due to the excited-state intramolecular charge transfer from naphthalene moiety to ammonium. The latter was also confirmed by the slight increase in the exited-state pK *_ a2. The fact that the increase in pK *_ a1 is larger than that in pK *_ a2 suggests that the effect of the intramolecular charge transfer on the involved moiety be weaker than that on a remote moiety in the same species. This could be taken into consideration for designing means of tuning the structures and properties of peptide and protein via photo-excitation. It was identified that the NAA zwitterion(Ⅱ) was the emissive species. The fluorescence quenching at high pH was assumed to be due to the photo-induced intramolecular electron transfer between carboxylate anion and the excited naphthalene moiety. The present case represents an example in which both intramolecular charge transfer and electron transfer occur to shape the pH titration profile.展开更多
A self-consistent model of high-frequency electrodeless lamps with internM coils is developed. Radial distributions of the plasma parameters are obtained. Mercury lines with wavelength of 435.8 nm and 365 nm are measu...A self-consistent model of high-frequency electrodeless lamps with internM coils is developed. Radial distributions of the plasma parameters are obtained. Mercury lines with wavelength of 435.8 nm and 365 nm are measured to testify the model. Based on the model, the population of resonance state 63p1 of mercury in dependence on the argon pressure and driving frequency is calculated. It is shown that the population of 63p1 of mercury is larger when the argon pressure is between 26.6 Pa and 53.2 Pa. Meanwhile the driving frequency has little influence on the population of 63P1.展开更多
基金National Natural Science Foundation of China (41805002)Joint Funds of the Zhejiang Provincial Natural Science Foundation of China (LZJMZ24D050009)+1 种基金Startup Foundation for Introducing Talent of NUIST (2016r042)Hubei Provincial Natural Science Foundation of China (2021CFB571)。
文摘This study employed numerical simulations to explore the impact of varying ice nucleation processes on the microphysics and electrification within thunderstorm clouds.A two-dimensional cumulus model,incorporating both noninductive and inductive charge separation schemes,was utilized.The findings revealed that the freezing nucleation mechanism significantly influenced the microphysical development,electrification,and charge structure of thunderstorms.Homogeneous freezing generated a large quantity of small ice crystals near the cloud tops,which were primarily responsible for the development of positive charge regions through a non-inductive charging process.Conversely,heterogeneous freezing resulted in larger ice crystals,enhancing graupel formation and leading to a more rapid and intense charge separation rate of around-15°C.Ice crystals formed heterogeneously and charged negatively during the development stage,resulting in an inverted dipole charge structure.When both immersion and homogeneous freezing processes were considered,the competition between these two distinct freezing processes resulted in reduced cloud water content and weaker electrification.Under conditions of low cloud water content at lower storm levels,graupel particles were negatively charged through non-inductive charging,causing the charge structure to quickly revert to a normal dipole structure.
文摘Efficient photogenerated carrier migration/separation plays a critical role in increasing the photocatalytic performance of g-C_(3)N_(4).Herein,sulfonic acid group-functionalized g-C_(3)N_(4)(SACN)was synthesized and then synchronously strengthened by a facile-solid-state thermal reaction of g-C_(3)N_(4)and sulfamic acid.As a solid strong acid,sulfamic acid can be used to achieve acid etching on the surface of g-C_(3)N_(4)with the assistance of thermal treatment,leading to an enlarged specific surface area and increased surface catalytic reaction sites.More importantly,our experiments and density functional theory calculations indicate that the driving force generated by the negative inductive effect of sulfonic acid groups significantly improves the charge transfer dynamics and effectively inhibits their recombination.Moreover,the negative inductive effect can induce charge redistribution,which reduces the conduction band potential of g-C_(3)N_(4)to enhance the reduction ability of photo-induced electrons.As a result,the SACN-400 sample showed excellent photocatalytic performance in H2 generation with an apparent quantum efficiency of 11.03%at 420±15 nm,as well as an efficient photodegradation rate for organic pollutants.
文摘本研究利用加入起电、放电参数化方案的数值模式(Weather Research and Forecasting Model(Version 3.7.1),WRF3.7.1_ELEC),通过设计五组不同非感应起电及感应起电参数化方案敏感性试验,对发生在青藏高原东北部青海大通地区的一次雷暴过程进行模拟研究,对比分析了不同非感应起电机制及感应起电机制对雷暴云电荷结构的影响.结果表明:在雷暴云发展旺盛阶段,Saunders(S91)、Riming Rate(RR)、和Saunders和Peck(SP98)三种非感应起电方案模拟的雷暴云最低层均为负电荷区,而混合方案(Brooks and SP98,BSP)模拟的雷暴云最低层为正电荷区,主电荷区自下而上为“+-+-”排列的四层电荷结构.与甚高频辐射源定位法推算的结果对比,BSP方案模拟的本次高原雷暴云电荷结构更接近实际情况;几种不同非感应起电方案模拟的主电荷区外围与主电荷区电荷结构不同,说明在雷暴发展的不同阶段雷暴云的电荷结构是不同的;几种非感应起电方案模拟的电荷结构不尽相同,主要是由于霰、冰和雪粒子在不同高度所带电荷的极性及电量的大小不同,霰粒子的电荷密度对低层的影响较大,冰粒子和雪粒子的电荷密度对中上层的影响较大;加入感应起电机制后,雷暴云电荷结构分布几乎没有变化,但能使雷暴云发展旺盛阶段低层和中层的正负电荷区电荷密度有所加强.
文摘为了研究1200 V SiC MOSFET在重复非钳位感性开关(Unclamped-Inductive-Switching,UIS)应力下的电学参数退化机制,基于自行搭建的UIS实验平台以及Sentaurus仿真设计工具,首先深入分析了重复UIS测试后器件静态参数与动态参数的退化;接着基于FN隧穿公式对栅极漏电流数据进行拟合,得到随着UIS测试次数增加SiC/SiO2界面的势垒高度从2.52 eV逐渐降低到2.06 eV;最后解释了SiC MOSFET在重复UIS测试后的电流输运过程。结果表明,在重复雪崩应力的作用下,大量的正电荷注入至结型场效应管区域上方的栅极氧化层中,影响了该区域的电场分布以及耗尽层厚度,导致被测器件(Device Under Test,DUT)的导通电阻、漏源泄漏电流、电容特性等电学参数呈现出不同程度的退化,并且氧化物中的正电荷的积累也使电子隧穿通过栅介质的电流得到了抬升。
文摘在三维强风暴动力—电耦合数值模式中引入基于Saunders et al.(1991)实验结果的非感应起电参数化方案S91,在此基础上,利用云水饱和度替代环境温度和有效液水含量将S91方案变形。对比分析一次雷暴单体首次放电前,变形后的S91方案和原S91方案模拟得到的非感应转移电荷的极性、量级、电荷结构以及与霰和冰晶粒子分布之间的关系。结果表明,虽然两种方案采用的电荷密度变化率以及每次碰撞平均转移的电荷量均相同,但不同方案中决定粒子间电荷转移的因子不同对电荷的分布存在较大的影响。加入云水饱和度的S91方案,非感应转移电荷的极性多为正极性,电荷结构先呈单极性后转变为三极性,并有进一步转变为偶极性的趋势。但这两种方案模拟得到的霰与冰晶粒子电荷分布的重合区的范围、大小均不同,这也是造成两种方案电荷结构和转移电荷分布不同的主要原因。
文摘pH titration of the fluorescence of N-(1-naphthyl)aminoacetic acid(NAA) was performed in aqueous solution over pH range of 1 5—12 5. Despite no shift in the fluorescence maximum wavelength, the titration curve showed an Ω-shaped profile with increasing pH with two inflection points at pH 4 1 and pH 11 5, respectively. These values correspond to the excited-state pK *_a s of carboxylic group and ammonium cation, respectively, which are both higher than those of the corresponding ground-state pK_as of 2 64 and 11 83, of which the former changes more. The substantial weakening of the proton dissociation of carboxylic group in the excited state should be indicative of the decrease in the inductive +I-effect of the ammonium cation at the β-position due to the excited-state intramolecular charge transfer from naphthalene moiety to ammonium. The latter was also confirmed by the slight increase in the exited-state pK *_ a2. The fact that the increase in pK *_ a1 is larger than that in pK *_ a2 suggests that the effect of the intramolecular charge transfer on the involved moiety be weaker than that on a remote moiety in the same species. This could be taken into consideration for designing means of tuning the structures and properties of peptide and protein via photo-excitation. It was identified that the NAA zwitterion(Ⅱ) was the emissive species. The fluorescence quenching at high pH was assumed to be due to the photo-induced intramolecular electron transfer between carboxylate anion and the excited naphthalene moiety. The present case represents an example in which both intramolecular charge transfer and electron transfer occur to shape the pH titration profile.
文摘A self-consistent model of high-frequency electrodeless lamps with internM coils is developed. Radial distributions of the plasma parameters are obtained. Mercury lines with wavelength of 435.8 nm and 365 nm are measured to testify the model. Based on the model, the population of resonance state 63p1 of mercury in dependence on the argon pressure and driving frequency is calculated. It is shown that the population of 63p1 of mercury is larger when the argon pressure is between 26.6 Pa and 53.2 Pa. Meanwhile the driving frequency has little influence on the population of 63P1.
