有限温度下腔光机械系统中N个二能级原子的相变和热力学性质

研究了含有非线性相互作用的腔机械系统中N个二能级原子在有限温度下的相变和相关的热力学性质,采用虚时路径积分方法推导出系统的配分函数,求得系统的有效作用量.通过对有效作用量进行变分得到系统的热力学平衡方程和原子布居数期待值的解析表达式,重点研究了原子-场耦合强度、非线性原子-光相互作用、非线性声子-光子相互作用等影响下系统的相变,发现除了会发生由正常相到超辐射相的二阶相变外,还会出现正常相和亚稳的超辐射态共存的现象,同时会发现三相(正常相、超辐射相、亚稳的超辐射态)共存点.有限温度的升高,会使正常相到超辐射相的二阶相变点向原子-场耦合强度增大的方向移动;当非线性原子-光相互作用(正或负)增强时,相变点会向原子-场耦合强度弱的方向移动;声子-光子相互作用会导致出现超辐射不稳定态;有限温度下,在正常相区熵为定值,而在超辐射相区熵随原子-场耦合强度的增强迅速递减为零.     

正切平方势与平面沟道系统的本征值和本征函数

讨论和分析了常用的平面连续势，引入了新的正切平方势描写粒子-晶体相互作用.在量子力学框架内，把系统的本征值和本征函数问题化为超几何方程的本征值和本征函数问题.将 低位能级之间的自发辐射同实验进行了比较，结果表明理论和实验符合很好. 关键词： Schrdinger方程 超几何函数 沟道辐射 本征值 本征函数     

单模光腔中N个二能级原子系统的有限温度特性和相变

本文研究单模光场中N个二能级原子Dicke模型的有限温度特性和相变. 把原子赝自旋转换为双模费米算符, 用虚时路径积分方法推导出系统的配分函数, 对作用量变分求极值得到系统的热力学平衡方程, 及原子布居数期待值和平均光子数随原子-光场耦合强度变化的解析表达式. 重点研究了在量子涨落起主导作用的低温区, 由耦合强度变化产生的从正常相到超辐射相的相变, 指出该相变遵从Landau连续相变理论, 平均光子数可作为序参数, 零值表示正常相, 大于零则为超辐射相. 在零温极限下本文的结果和量子相变理论完全符合. 另外, 本文也讨论了系统的热力学性质, 比较有限温度相变和量子相变的异同. 发现, 在强耦合区低温稳定态的光子数和平均能量都和绝对零度的值趋于一致, 而超辐射相的熵则随耦合强度的增强迅速衰减为零.     

有限尺度下弱相互作用费米气体的热力学性质

基于巨正则系综理论和数值模拟方法，研究有限尺度下弱相互作用费米气体的热力学性质，给出系统低温下的化学势、能量及热容量的解析式，分析弱相互作用、有限尺度效应对系统热力学性质的影响.研究表明，有限尺度和排斥相互作用增大了系统的化学势、能量,吸引相互作用减小了系统的化学势、能量.相互作用受到尺度的调制，尺度变大，相互作用影响变小，相互作用和尺度效应都受到温度的调制，温度升高，相互作用和尺度的影响减小.尺度和相互作用的一级修正对热容量无影响.     

反比相关的双曲余弦平方势与电子的面沟道辐射

带电粒子在晶体沟道中的运动行为决定于粒子-晶体相互作用势.常用的粒子晶体相互作用势有Lindhard势、Moliere和正弦平方势.当超相对论电子沿着晶体的低晶面指数方向入射时,电子和晶体之间的相互作用势可用反比相关的双曲余弦平方势描写.在量子力学框架内,利用这一相互作用势成功地将系统的Schrodinger方程化为超几何方程,从而简化了系统本征值和本征态问题的计算和讨论.考虑到质量的相对论效应和频率的Doppler效应,导出了实验室坐标系中电子的能级分布和辐射谱分布.并以电子的Si(110)面沟道辐射为例,选定一组与入射粒子有关的参数和一组与晶体有关的参数,计算了能量为E=0.5GeV的电子在低位能级之间的跃迁,导出了电子面沟道辐射能量ΔE=49.1MeV,得到了与实验符合的结果.     

超热电子产生的靶后相干渡越辐射光谱实验研究

利用OMA光学多道分析仪测量了激光与薄膜靶相互作用中产生的辐射光谱，在靶后观察到红移的二次谐波发射. 这种二次谐波是v×B加热产生的、具有微脉冲结构的超热电子束在等离子体-真空边界产生的相干渡越辐射(CTR). 随着激光能量的增大，红移峰向长波方向移动，光谱同时发生展宽. 分析认为，等离子体临界面的迅速膨胀是导致二次谐波红移的主要原因. 随着预脉冲能量的增大，临界面膨胀速度增大，导致了发射峰更大的红移. 实验还测量了靶面法线方向的辐射光谱，观察到基频辐射的红移和展宽. CTR为诊断临界面的运动方向和速度提供了一种新的方法. 关键词： 相干渡越辐射 超热电子 超短超强激光 等离子体相互作用     

超热电子的产生与输运背向辐射的实验研究

报道了在100TW fs激光器上采用电子磁谱仪和光学CCD积分成像相机分别对激光-固体靶相互作用在靶背方向产生的超热电子能谱及其光学渡越辐射进行的测量.能谱测量结果显示:超热电子能谱呈单温类-麦克斯韦分布,拟合的温度为107 keV;光学渡越辐射(OTR)测量结果显示:OTR是由于超热电子输运穿越固体靶所致,而辐射区域呈圆盘状、有发散角、有光强分布;如果考虑超热电子的产生和加热机制,则占主导地位的加热机制是共振吸收对电子的加热.     

利用韧致辐射诊断激光等离子体相互作用产生的超热电子

超短脉冲强激光与等离子体相互作用时产生的向靶内传输的超热电子在“快点火”方案中起着极其重要的作用.对于这部分向靶内传输的超热电子，韧致辐射方法是一种能有效、全面获得超热电子各方面信息的诊断方法.通过三维蒙特卡罗程序MCNP模拟了超热电子在靶材料中的输运以及它们在靶后方向产生的韧致辐射的性质，论证了韧致辐射诊断方法的可行性. 关键词： 超热电子 韧致辐射 诊断 MCNP程序     

相互作用对玻色气体热力学性质及稳定性的影响

根据由赝势法得到的非理想玻色气体的自由能和状态方程，研究了相互作用对凝聚温度的影响.从热力学角度揭示了存在引力作用时定压热容量、等温压缩系数、定压膨胀系数的反常热力学特性.研究了引力作用下玻色气体系统的不稳定性，给出了不稳定性的温度判据和粒子数密度判据. 关键词： 相互作用 玻色气体 热力学性质 不稳定性判据     

超精细结构效应对辐射光谱圆极化特性的影响

在相对论多组态Dirac-Fock方法和密度矩阵理论的基础上,利用发展的全相对论扭曲波程序,系统研究了超精细结构效应对纵向极化电子碰撞激发过程以及退激发辐射光谱圆极化特性的影响.计算得到了类氦Sc~(19+)和~(205)Tl~(79+)离子1s~2 ~1S_0→1s2p ~3P_2超精细结构层次上M_F能级的碰撞强度,考察了辐射衰变过程中发出特征光子的极化特性,并分析了E1-M2量子干涉效应以及电子-电子间相互作用的相对论修正对退激发辐射光子圆极化度的影响.     

双导带Anderson晶格的Slave-Boson平均场理论

应用Slave-Boson技术和泛函积分方法,处理了双导带Anderson晶格模型。在鞍点近似下,求得了系统的电子态密度和一些低温热力学量。结果表明,由于系统的相干性和f-c混合作用,电子态密度在费密面附近出现赝能隙结构。系统的低温热力学量具有重费密子特性。 关键词：     

A field analysis of nonlinear irreversible thermodynamic processes

The generalized thermodynamic potential analysis of nonlinear irreversible processes precludes the analysis of rotational processes. The nonexistence of scalar potential functions necessitates a thermodynamic analysis of the system forces. A field analysis in the phase space of the generalized displacements and velocities treats the force components as tensors of second order that tend to deform and rotate the irreversible process, which is viewed as an elastic material. The analysis of chemical oscillatory processes involves the introduction of the thermodynamic vector potential, which is subsequently used in the formulation of a variational principle and to define an energy flux vector. The direction of energy flow elucidates the mechanism by which steady motion is maintained and it is a characteristic property of open systems. Field analyses of systems that are described by half and single degrees of freedom are contrasted.     

任意维固体的热力学性质的研究

精确地计算了n维固体的热力学函数、热容,讨论了极端高、低温近似时的结果;并将不同维数的热力学性质统一地由一组公式表达了出来.     

A quantum version of the classical Szilard engine

A reinvention of the classical Maxwel demon was proposed by Szilard around the time quantum mechanics was developed. His model continues to attract great interest, especially quantum versions of it. A quantum formulation of the Szilard engine is introduced and investigated here. It is made to operate through specified cycles in such a way that all thermodynamic quantities which pertain to the system can be evaluated exactly in closed form along each sequence of steps through a cycle. It is shown that as a result of the structure of the model, it is possible to calculate and compare various thermodynamic quantities as the engine proceeds around a well defined specific cycle.     

A new expansion in the theory of polar liquids

The Boltzmann factor for a pair of molecules interacting as coplanar nonpolarizable point dipoles is expanded as a double Fourier series in the orientation angles enabling the angle integrations in the partition function to be performed. This leads to an expansion for the thermodynamic properties of such a system as a perturbation on those of a spherically symmetric liquid.     

A Hamilton-Jacobi formalism for thermodynamics

We show that classical thermodynamics has a formulation in terms of Hamilton-Jacobi theory, analogous to mechanics. Even though the thermodynamic variables come in conjugate pairs such as pressure/volume or temperature/entropy, the phase space is odd-dimensional. For a system with n thermodynamic degrees of freedom it is 2n+1-dimensional. The equations of state of a substance pick out an n-dimensional submanifold. A family of substances whose equations of state depend on n parameters define a hypersurface of co-dimension one. This can be described by the vanishing of a function which plays the role of a Hamiltonian. The ordinary differential equations (characteristic equations) defined by this function describe a dynamical system on the hypersurface. Its orbits can be used to reconstruct the equations of state. The ‘time’ variable associated to this dynamics is related to, but is not identical to, entropy. After developing this formalism on well-grounded systems such as the van der Waals gases and the Curie-Weiss magnets, we derive a Hamilton-Jacobi equation for black hole thermodynamics in General Relativity. The cosmological constant appears as a constant of integration in this picture.     

The density of states for an antiferromagnetic Ising model on a triangular lattice

The Wang-Landau algorithm is an efficient Monte Carlo approach to the density of states of a statistical mechanics system. The estimation of state density would allow the computation of thermodynamic properties of the system over the whole temperature range. We apply this sampling method to study the phase transitions in a triangular Ising model. The entropy of the lattice at zero temperature as well as other thermodynamic properties is computed. The calculated thermodynamic properties are explained in the context of the magnetic phase transition.      

核动力航空推进探析

文献调研国外核动力航空推进相关技术研究,美国GE与PW公司通过ANP计划已试验验证了核动力航空推进的可行性;分析认为核动力航空推进当前最佳用途是长航时无人机与巡航导弹动力,关键技术是核屏蔽的轻量化设计、热交换效率与速率、热力系统设计与新型结构问题;核动力航空推进若采用蒸汽介质的二回路闭式循环驱动螺旋桨,蒸汽透平及动力系统设计没有技术障碍,闭式循环蒸汽流量关键取决于蒸汽透平汽耗率与热交换循环时间。     

Thermodynamics and phase transition of topological dS black holes with a nonlinear source

We discuss black hole solutions of Einstein-Λ gravity in the presence of nonlinear electrodynamics in d S spacetime. Considering the correlation of the thermodynamic quantities respectively corresponding to the black hole horizon and cosmological horizon of dS spacetime and taking the region between the two horizons as a thermodynamic system, we derive effective thermodynamic quantities of the system according to the first law of thermodynamics, and investigate the thermodynamic properties of the system under the influence of nonlinearity parameter α. It is shown that nonlinearity parameter α influences the position of the black hole horizon and the critical state of the system, and along with electric charge has an effect on the phase structure of the system,which is obvious, especially as the effective temperature is below the critical temperature. The critical phase transition is proved to be second-order equilibrium phase transition by using the Gibbs free energy criterion and Ehrenfest equations.