考虑热效应的Vinet状态方程及其应用

 基于爱因斯坦模型将Vinet等人提出的关于金属固体的通用物态方程推广到包括热效应。采用最近邻普遍化Lennard-Jones势描述金属离子之间的有效配对相互作用,将每个离子的势能展开为离子位移的二阶泰勒级数,从而推导出爱因斯坦温度和Grüneisen常数的解析表达式,该表达式只与体积有关而与温度无关。推广方程包括的7个参数只有5个是独立的,在高于德拜温度时,只需要4个参数。对典型金属及两种非金属材料计算的结果与实验符合得很好。     

重离子束在热靶中的电子阻止本领与有效电荷数

采用线性介电响应理论,研究了重离子束在热靶中的有效电荷数和电子阻止本领。为了考虑入射离子的束缚电荷分布,我们将Brandt-Kitagawa的有效电荷理论推广到热靶。在低速和高速情况下,分别得到了有效电荷数和电子阻止本领的解析表示式。数值结果表明,对于低速离子,有效电荷数随电子气的温度增加而增加;在一定的温度范围内,低速离子的阻止本领与冷靶相比有明显增加。对于高速离子,我们的理论结果与实验值符合得较好。 关键词：     

三芯非线性光纤耦合器中的短脉冲光开关

利用变分法研究三芯非线性光纤耦合器中的短脉冲光开关,解析分析线性三耦合非线性Schr?dinger方程的结果与数值模拟符合得很好.并且得到在非线性光纤耦合器中孤子的耦合长度和开关阈值,与连续波情况和两芯光纤耦合器的结果不同. 关键词： 光纤耦合器 光开关 耦合长度 开关阈值     

超短脉冲激光烧蚀金属靶热分布的数值解与解析解

研究了超短脉冲激光烧蚀靶材的整个过程,对描述超短脉烧蚀过程热行为的双温度方程进行了分析简化,得出了超快激光烧蚀金属材料的解析解. 以铜靶材为例,对双温度模型的数值解与解析解做了对比分析,得到了靶材温度随时间和深度的变化规律,结果显示解析解的计算结果比较好的符合了数值解的计算结果.     

压强梯度对托卡马克等离子体有理面上由磁场曲率驱动的漂移模的稳定效应

在流体模型内，我们导出了一个托卡马克等离子体内环形漂移模的色散关系，该色散关系包含了离子压强梯度、磁场梯度与曲率。一方面，磁场梯度与曲率驱动有理面上的不稳定性。另一方面，压强梯度使这些不稳定性稳定。通过解析和数值两种方法，我们获得了把不稳定性增长率压缩到零的临界压强梯度阈值。     

Pr:YIG晶体抗磁性Faraday转动谱的研究

在单电子模型下，用量子理论研究了Pr:YIG晶体中Pr3+离子的抗磁性Faraday转动（FR）谱.分别在温度为77K和300K时，计算了Pr3+离子的λF-1/2θ-λ2的变化关系，计算结果与实验值符合较好.证实了晶场为单态的离子，其抗磁性FR比顺磁性FR对交换场（或外场）有更大的依赖性，且与温度有关.在强交换场环境中，两种转动对FR的贡献有相同的重要性. 关键词： Pr:YIG晶体 单离子模型 抗磁性Faraday转动     

R_2Fe_(14)B(R=Ce,Pr,Gd)磁晶各向异性常数K_1,K_2随温度的变化

本文在1.5—300K温度范围内测量了R_2Fe_(14)B(R=Ce,Pr,Gd)各向异性常数K_1,K_2和各向异性场H_A随温度的变化。同时用单离子模型计算了Pr~(3 )离子对Pr_2Fe_(14)B磁晶各向异性的贡献,得到与实验值半定量符合的结果。     

双离子成份等离子体的离子声色散关系

 以离子温度与电子温度之比为参数,将等离子体介电函数作展开,由此解析地求解了双离子成分等离子体的离子声快、慢波模的色散关系。与现有的其它解析理论相比较,所得到的解析公式更加准确。     

C60团簇与稠密等离子体相互作用的数值模拟

采用球壳层模型研究了C60团簇与稠密等离子体的相互作用．假定离子团中离子之间的位置矢量的取向是随机的，在线性化的伏拉索夫一泊松理论框架下，借助于经典的等离子体介电函数，推导出C60离子团簇的自能和阻止本领的解析表达式．通过数值求解离子团半径变化的运动方程，研究了团簇的库仑爆炸过程，并讨论了入射速度、等离子体密度和电子温度对自能、阻止本领和库仑爆炸的影响．结果发现自能中的尾流效应降低了C60团簇离子的库仑爆炸速度，甚至可以稳定C60团簇的结构．     

应用阈值光电子-光离子符合成像研究能态选择的离子解离动力学

阈值光电子-光离子符合测量是制备和分析能态选择离子性质的高效实验方法.本文回顾了这一技术与合肥同步辐射真空紫外光电离相结合的近期应用,特别是在离子基本参数测量和解离动力学中的研究.通过对电子和符合离子的同步速度聚焦测量,带电粒子的收集效率、电子能量分辨和离子平动能分辨率都得到了大幅提高,通过对特定能态离子解离碎片平动能和角度分布的直接测量,研究了各种非绝热效应,如椎间贯穿、内转换等,在解离过程中的重要作用.此外,在此基础上质量选择的阈值光电子能谱在复杂体系的同分异构体甄别方面也展示出超乎寻常的优势.     

Thresholds and hysteresis of surface ionization under nonuniform conditions

The influence of nonuniformity of the atom arrival rate, of the emitter temperature and of the adsorption properties of its surface on characteristics of thresholds and hysteresis of the surface ionization is analyzed. It is shown that, unlike the uniform conditions, in the threshold zone the ion current changes with the emitter temperature monotonically and not in a form of a jump ; the width of hysteresis is substantially diminished ; the slope of the first threshold curve is not obligatory equal to the heat of ion adsorption; for a polycrystalline surface the critical temperature for hysteresis to vanish is related to the minimum work function and not to the effective work function.     

Subthreshold sputtering at high temperatures

The sputtering of tungsten from a target at a temperature of 1470 K during irradiation by 5-eV deuterium ions in a steady-state dense plasma is discovered. The literature values of the threshold for the sputtering of tungsten by deuterium ions are 160–200 eV. The tungsten sputtering coefficient measured by the loss of weight is found to be 1.5×10^?4 atom/ion at a deuterium ion energy of 5 eV. Previously, such a sputtering coefficient was usually observed at energies of 250 eV. The sputtering is accompanied by a change in the target surface relief, i.e., by the etching of the grain boundaries and the formation of a wavy structure on the tungsten surface. The subthreshold sputtering at a high temperature is explained by the possible sputtering of adsorbed tungsten atoms that are released from the traps around the interstitial atoms and come to the target surface from the space between the grains. The wavy structure on the surface results from the merging of adsorbed atoms into ordered clusters.     

Ion-beam erosion of carbon fibers of the composites

The results of experimental studies of the structural and morphological changes of the surface of carbon PAN fibers of a carbon-carbon KUP-VM (1D) composite as a result of high-dose irradiation (10¹⁸–10¹⁹ ion/cm²) with Ne⁺ and Ar⁺ ions with an energy of 10–30 keV are presented. The threshold values of radiation damage, resulting in an amorphization of the PAN carbon fibers at room temperature and ion-induced crimping at temperatures greater than the annealing temperature of the radiation damage, are determined.     

钠离子和钾离子通道噪声扰动对神经网络 时空模式的影响

研究了钠离子和钾离子通道噪声扰动对Hodgkin-Huxley神经网络放电时空模式的影响. 发现无论钠离子通道噪声还是钾离子通道噪声扰动, 当取定一组温度、噪声强度, 随着耦合强度的增大, 神经网络放电时空斑图总能演化出螺旋波, 而且存在形成螺旋波所需的临界耦合强度. 分析发现钠离子通道噪声有利于神经网络螺旋波的形成, 而钾离子通道噪声不利于螺旋波形成. 结果还表明较低的温度能够使神经网络对噪声更加敏感. 最后, 讨论了特定参数下螺旋波与靶波之间的转化现象.     

Instability Limit on Throughput for Calutrons. (Electromagnetic Isotope Separators)

Using a model of two interpenetrating ion streams in a background of magnetically immobilized electrons, I obtain a density threshold for separation disruption that agrees with the values observed. The density threshold for disruption is far above that for instability production. The inference is that in ordinary operation a calutron is operating in an unstable mode, but this unstable level is tolerable.     

Studies on threshold pressures of sonoluminescence for bubbles with different noble gases

Large oscillations of gas and vapor filled bubbles in liquid during acoustic cavitation. This highly nonlinear bubble motion is accompanied by the emission of light-sonoluminescence (SL)[1, 2]. The noble gases inside the bubble can influence the SL[3—5]. At an acoustic pressure, the intensity of SL increases with the molecular mass of noble gas inside the bubbles[6]. There are several kinds of theories about SL mechanism. At present, the bremsstrahlung mechanism is widely admitted. The b…     

HT-6M中性注入加热电荷交换能谱分析

用电荷交换中性粒子能谱分析的方法,研究了HT-6M托卡马克中性注入加热期间的氢离子能谱,得到了离子温度的增加。测量结果与实验定标律的估算在误差范围内相符;并与根据Fokker-Planck方程计算的注入过程中的离子能谱和温度变化进行了比较。 关键词：     

用负温度高能离子束的相对论多普勒效应实现从红外到X射线连续调谐激光器

利用负温度高能离子束的相对论多普勒效应,可能实现从红外到X射线连续调谐激光器。调谐范围△ν_T=2ν₀βγ。离子束从零到c调速时,激光频率为0—∞。本文给出了激光参数的相对论变换式,计算了负温度相对论离子束激光器的增益、阈值和输出特性,提出了用激光束对相对论离子束进行共振激发的方法,并讨论了He⁺离子束及Ar⁺离子束激光器的设计参数。 关键词：     

Thermal impact on spiking properties in Hodgkin-Huxley neuron with synaptic stimulus

The effect of environmental temperature on neuronal spiking behaviors is investigated by numerically simulating the temperature dependence of spiking threshold of the Hodgkin-Huxley neuron subject to synaptic stimulus. We find that the spiking threshold exhibits a global minimum in a specific temperature range where spike initiation needs weakest synaptic strength, which form the engineering perspective indicates the occurrence of optimal use of synaptic transmission in the nervous system. We further explore the biophysical origin of this phenomenon associated with ion channel gating kinetics and also discuss its possible biological relevance in information processing in neuronal systems.      

Correlation between yttrium segregation at the grain boundaries and the threshold stress for plasticity in yttria-stabilized tetragonal zirconia polycrystals

Nowadays, the high-temperature plasticity of yttria-stabilized tetragonal zirconia polycrystals (YTZPs) is successfully explained in terms of a threshold stress. Despite the fact that its existence is very well proved experimentally, the origin and nature of the threshold stress are still unexplained. This work develops a possible explanation for the threshold stress in YTZPs. The model developed in this paper is able to explain quantitatively the dependence of this threshold stress with temperature and grain size. The model is able to predict the influence of a glassy phase present at grain boundaries and the values of the threshold stress in YTZP nanocrystals. The theoretical results are discussed and compared with the available data in the literature.