考虑量子化效应的MOSFET阈值电压解析模型

根据改进后的三角势阱场近似，并考虑量子化效应，提出了一种基于物理的阈值电压解析模型，给出了MOSFET的阈值电压解析表达式，并与经典理论和数值模拟结果进行了比较. 关键词： 量子效应 阈值电压 反型层 表面势     

醋酸泼尼松龙的荧光分析法研究

肾上腺皮质激素类药物醋酸泼尼松龙被浓H2 SO4氧化 ,生成有荧光的反应产物 ,据此建立了一种测量醋酸泼尼松龙的荧光光度分析新方法 ,考察了醇、表面活性剂和 β 环糊精对产物荧光性质的影响 ,提出了醋酸泼尼松龙被氧化及荧光增强的作用机理 ,检出限为 4 .96× 10 -7mol·L-1,荧光强度与醋酸泼尼松龙在 0～ 1.2 4× 10 -5mol·L-1浓度范围内呈良好线性关系     

Raman spectroscopy studies of structural changes in hydrated titanium and tin dioxide gels under drying

Raman spectroscopy is used in this work to reveal an increase in the size of anatase crystallites in the process of drying of hydrated titanium dioxide gel and ordering of the structure of primary particles of hydrated tin dioxide gel under drying. Raman spectra are interpreted with account of dimensional effects. It is found that mechanical stresses that arise in the materials under drying have a great effect on the structural changes found there. TERMOXIDE Research and Production Company, 624051 Zarechnyi, Sverdlovsk Region, P/O Box 94, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 266–268, March–April, 1997.     

The variable viscoelasticity oscillator

The complex dynamics of a variable viscoelasticity oscillator is studied using the novel concept of Variable‐Order (VO) Calculus. The damping force in the oscillator varies continuously between the elastic and viscous regimes depending on the position of the mass. The oscillator considered here is composed of a linear spring of stiffness k that inputs a restitutive force F_k = ‐k x, a VO damper of order q(x(t)) that generates a damping force F_q = ‐c_q ??^q(x(t)) x, and a mass m. A modified Runge‐Kutta method is used in conjunction with a trapezoidal numerical integration technique to yield a second‐order accurate method for the solution of the resulting VO Differential Equation (VODE). The VO oscillator is also modelled using a Constant Order (CO) formulation where a number of CO fractional order differentials are weighted to simulate the VO behavior. The CO formulation asymptotically approaches the VO results when a relatively large number of weights is used. For the viscoelastic range of 0 ≤ q ≤ 1, the dynamics of the oscillator is well approximated by the CO formulation when 5 or more fractional terms are included (e.g., 0, 1/4, 1/2, 3/4, and 1).     

HTSC grain boundary weak links employing high-quality ICM sputtered YBCO films

Summary Bicrystal grain boundary junctions of YBCO have been fabricated by using the Inverted Cylindrical Magnetron d.c. sputtering technique. The main characteristics of the junction behaviour are reported. Some aspects of the experimental results are discussed in the framework of existing models developed for describing weak-link structures. Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994.     

Cesium ordering and electron localization-delocalization phenomena in the quasi-one-dimensional diphosphate tungsten bronzes: Cs1‒xP8W8O40

We present a structural investigation of the family of quasi-one-dimensional (quasi-1D) conductors, which exhibit intriguing charge transport properties where, for x small, the conductivity exhibits a crossover from a semiconducting to a metallic like regime when the temperature decreases. In these materials the double zig-zag chains, together with the diphosphate groups, delimit channels which are partially filled with the ions. It is found, from an X-ray diffuse scattering investigation, that at room temperature the ions are locally ordered on a lattice of well-defined sites in the channel direction and not ordered between neighboring channels. These ions form 1D incommensurate concentration waves whose periodicity depends on the stoichiometry. In upon cooling, the intrachannel order increases significantly, and an interchannel order between the 1D concentration waves develops. But, probably because of kinetic effects, no tridimensional (3D) long range order of the ions is achieved at low temperature. The 3D low-temperature local order has been determined and it is found that the phase shift between the concentration waves minimizes their Coulomb repulsions. This local order is increasingly reduced as the Cs concentration diminishes. We interpret the intriguing features of the electrical conductivity in relationship with the thermal evolution of the Cs ordering effects. We suggest that in , for x small, a localization-delocalization transition of the Anderson type occurs due to the thermal variation of the Cs disorder. When x increases, the enhancement of the disorder leads to a localization of the electronic wave function in the whole temperature range measured. Finally, and probably because of the disorder, no charge density wave instability is revealed by our X-ray diffuse scattering investigation. Received: 10 October 1997 / Received in final form: 11 December 1997 / Accepted: 16 December 1997     

Optimal coupled-cluster approximation for the ground-state properties of a spin-boson model

In the present work we have developed an optimal coupled-cluster approximation, which can take care of both the accuracies of the ground-state energy and the wavefunction estimates, for the ground state of a two-state system coupled to a dispersionless boson bath. This new approach is also able to give a tight upper bound to the ground-state energy of the system. Up to the fourth level of this approximation our results show excellent agreement with the numerical exact diagonalization results. In particular, our results suggest no discontinuous localization-delocalization transition of the two-state system. This is consistent with the exact result. Received: 11 March 1998 / Accepted: 23 June 1998     

The analytical investigation of the super-Gaussian pump source on the thermal, stress and thermo-optics properties of double-clad Yb:glass fiber lasers

Fiber lasers have attracted considerable attention when their power can realistically be scaled to kilowatt level and beyond. In this paper, we assumed that the fiber core and first clad are exposed to a pump source with a super-Gaussian profile of order four. The effects of this non-uniform heat deposition on thermal, stress and thermooptics properties such as temperature-dependent change of refractive index and thermally induced stress have been comprehensively studied and their equations analytically derived.