Quantitative measurement of the phonon energy transmission coefficient for a silicon-Hell boundary

In a novel experiment we quantitatively determine the energy flux of heater generated phonons incident on an interface between silicon and liquid helium. By measuring also the energy flux transmitted into the Hell we obtain a transmission coefficient of 23% for heater temperatures between 5 K and 15 K.     

Pore-size dependence of the heat conduction in porous silicon and phonon spectral energy density analysis

Semiconductor devices made of silicon material have been widely used due to its excellent thermoelectrical properties. Here, the silicon material with aligned distributed rectangular-shaped holes is proposed for the manufacture of semiconductor device. Comprehensive understanding the heat conduction is of great significance to improve the efficiency of the thermoelectrical materials. This letter investigates the thermal conductivity of nanoscale porous silicon structures by adopting the nonequilibrium molecular dynamics method. The results demonstrate that the temperature is sensitive to the sizes of the rectangular-shaped holes. Additionally, it is found that the effective thermal conductivity significantly decreases with the increase of the dimensions of the holes. Our work reveals that the key to reduce the effective thermal conductivity is to disturb the distribution of heat flux. Furthermore, the phonon spectral energy density method is used to obtain the phonon dispersion and phonon energy in the frequency domain.     

MgB2超导体能隙与比热的关系

基于双带模型,通过引入非电子—声子相互作用并利用自洽近似方法在BCS理论框架内讨论了硼化镁超导体的能隙及电子比热。     

Anomalous energy diffusion and heat conduction in one-dimensional system

We propose a new concept, the centre of energy, to study energy diffusion and heat conduction in one-dimensional hard-point model. For diatom model, we find an anomalous energy diffusion as $\langle x^2 \rangle\sim t^\beta$ with $\beta=1.33$, which is independent of initial condition and mass rate. The present model can be viewed as the model composed by independent quasi-particles, the centre of energy. In this way, heat current can be calculated. Based on theory of dynamic billiard, the divergent exponent of heat conductivity is estimated to be $\alpha=0.33$, which is confirmed by a simple numerical calculation.     

利用透射系数研究周期势的能带结构

利用一维方位势透射系数的递推公式研究了周期势的能带结构,文中考察了能 结构与垒宽、阱宽及位势个数的关系。     

On the relation between monovacancy formation energy and surface energy for metals

An empirical relation between vacancy formation energy, surface energy and nearest-neighbor separation for metals is presented and the basis for this correlation is discussed.     

Oxyfluoroborate host glass for upconversion application: phonon energy calculation

Reducing the glass phonon energy is an essential procedure to achieve high efficient radiative upconversion process. The degree of covalence of chemical bonds is responsible for the high oscillator strength of intracenter transitions in rare-earth ions. So, conversion covalent to ionic glass character is proposed as a structure-sensitive criterion that controls the phonon energy of the glasses. A series of oxyfluoro aluminum-borate host glasses used for upconversion application is prepared by the conventional melt-quenching technique. Through lithium oxide substitution by lithium fluoride, the ionic-covalent property of Li⁺ ion successes to regulate the band gap energies of the studied glasses. Furthermore, a new method to determine the glass phonon energy is offered.     

Dispersive effects and correction term in two-mode phonon conduction model for Ge

A complete analysis of the phonon conductivity κ, still lacking in the literature, is presented in the two-mode conduction model for Germanium. First a method is derived from which the correction term κ_c of the Callaway model is separated into its longitudinal and transverse parts and then the effects of strong phonon dispersion and the role of longitudinal and transverse phonons on κ_c are studied. For this purpose we have also proposed some new empirical expressions for the three phonon relaxation rates τ_3ph⁻¹'s which are valid in the entire temperature range. This improvised model, when applied simultaneously to the phonon conductivity data of both normal and enriched Ge, yields some new results. These are (i) κ_c neglected by the earlier workers in the two-mode phonon conduction model, gives a substantial contribution beyond the conductivity maximum and (ii) the longitudinal phonons are the major carriers of heat at high temperature.     

Steady-state thermodynamics for heat conduction: microscopic derivation

Starting from microscopic mechanics, we derive thermodynamic relations for heat conducting nonequilibrium steady states. The extended Clausius relation enables one to experimentally determine nonequilibrium entropy to the second order in the heat current. The associated Shannon-like microscopic expression of the entropy is suggestive. When the heat current is fixed, the extended Gibbs relation provides a unified treatment of thermodynamic forces in the linear nonequilibrium regime.     

Generalized Landauer Bound for Information Processing: Proof and Applications

A generalized form of Landauer’s bound on the dissipative cost of classical information processing in quantum-mechanical systems is proved using a new approach. This approach sidesteps some prominent objections to standard proofs of Landauer’s bound—broadly interpreted here as a nonzero lower bound on the amount of energy that is irreversibly transferred from a physical system to its environment for each bit of information that is lost from the system—while establishing a far more general result. Specializations of our generalized Landauer bound for ideal and non-ideal information processing operations, including but not limited to the simplified forms for erasure and logical operations most familiar from the literature, are presented and discussed. These bounds, taken together, enable reconsideration of the links between logical reversibility, physical reversibility, and conditioning of operations in contexts that include but are far more general than the thermodynamic model systems that are most widely invoked in discussions of Landauer’s Principle. Because of the strategy used to prove the generalized bounds and these specializations, this work may help to illuminate and resolve some longstanding controversies related to dissipation in computation.     

类谐振子的周期与能量的关系

利用能量曲线的分析方法,建立了类谐振子的周期和系统能量的数学表达式．     

二静电体系相互作用力与相互作用能一般关系的正确表达式

指出二静电体系的相互作用力的普遍表达式F=-↓△w1=-↓△w并不恰当。正确的表达式应当是Fj=δW1/δqj=-δW1/δqj，其中Fj是沿广义坐标qj方向的广义力，W1是静电场总能量，W1是二静电体系的相互作用能，qj为表征二静电体系相对位移的某一广义坐标。     

A relation between X-ray diffraction based liquid structure and packing coefficient

A relation between the liquid structure and the molecules packing coefficient has been derived on the grounds of the experimental results of X-ray diffraction studies. The packing coefficientk was assumed to be a criterion of correctness of the structural models of 2-methyl-1-propanol and 2-methyl-2-propanol based on experimental results. This coefficient was estimated from the specific volumes of moleculesV ₀, volumes of elementary pseudocellsV and the number of molecules comprised into these pseudocells. The volumesV of pseudocells were estimated from the same X-ray diffraction pattern as was used for determination of the liquid structure. The determined values of the packing coefficient support the chain-like structure of associates of liquid 2-methyl-1-propanol and reject the chain-like structure for liquid 2-methyl-2-propanol.     

Transmission coefficient and heat conduction of a harmonic chain with random masses: Asymptotic estimates on products of random matrices

We find upper and lower bounds for the transmission coefficient of a chain of random masses. Using these bounds we show that the heat conduction in such a chain does not obey Fourier's law: For different temperatures at the ends of a chain containingN particles the energy flux falls off likeN ^–1/2 rather thanN ^–1.Research supported by a ZWO fellowship and in part by U.S.A.F.O.S.R. grant no. 78-3522     

A generalized Uhlenbeck and Beth formula for the third cluster coefficient

Relatively recently (Amaya-Tapia et al., 2011), we presented a formula for the evaluation of the third Bose fugacity coefficient–leading to the third virial coefficient–in terms of three-body eigenphase shifts, for particles subject to repulsive forces. An analytical calculation for a 1-dim. model, for which the result is known, confirmed the validity of this approach. We now extend the formalism to particles with attractive forces, and therefore must allow for the possibility that the particles have bound states. We thus obtain a true generalization of the famous formula of Uhlenbeck and Beth (Uhlenbeck and Beth, 1936; Beth and Uhlenbeck, 1937) and of Gropper (Gropper, 1936, 1937) for the second virial. We illustrate our formalism by a calculation, in an adiabatic approximation, of the third cluster in one dimension, using McGuire’s model as in our previous paper, but with attractive forces. The inclusion of three-body bound states is trivial; taking into account states having asymptotically two particles bound, and one free, is not.     

Aspects of improved heat conduction relation and chemical processes in 3D Carreau fluid flow

A new fourth-order memristor chaotic oscillator is taken to investigate its fractional-order discrete synchronisation. The fractional-order differential model memristor system is transformed to its discrete model and the dynamic properties of the fractional-order discrete system are investigated. A new method for synchronising commensurate and incommensurate fractional discrete chaotic maps are proposed and validated. Numerical results are established to support the proposed methodologies. This method of synchronisation can be applied for any fractional discrete maps. Finally the fractional-order memristor system is implemented in FPGA to show that the chaotic system is hardware realisable.     

The stochastic heat equation: Feynman-Kac formula and intermittence

We study, in one space dimension, the heat equation with a random potential that is a white noise in space and time. This equation is a linearized model for the evolution of a scalar field in a space-time-dependent random medium. It has also been related to the distribution of two-dimensional directed polymers in a random environment, to the KPZ model of growing interfaces, and to the Burgers equation with conservative noise. We show how the solution can be expressed via a generalized Feynman-Kac formula. We then investigate the statistical properties: the two-point correlation function is explicitly computed and the intermittence of the solution is proven. This analysis is carried out showing how the statistical moments can be expressed through local times of independent Brownian motions.     

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根据ITER装置对CTB盒技术性能的要求,对CTB盒中冷屏的支撑部件进行了结构和传热的分析和设计。对结构形式的选择、结构强度的理论计算和支撑结构总的热损失进行了设计和计算,用ANSYS软件对该结构的非线性接触结构-热耦合问题进行了仿真分析。研究结果表明,球支撑结构既能够满足系统对支撑的结构安全要求,在有压接触情况下的漏热量符合ITER设计文集的规定。