The Pseudogaps of HTSC

The problem of the pseudogaps in oxide HTSC is analyzed by means of the off-diagonal propagators, in analogy with the method of Nambu in superconductivity. We conjecture that the small pseudogap is obtained as the Fock diagram and the large pseudogap as the total off-diagonal self-energy (which is the sum of the Hartree diagram and the Fock diagram). We obtain real gap for undoped materials, and pseudogaps (with states in the gap) for doped and conducting materials. We find that disorder is essential for the results of the doped materials.     

The Field Perturbation Theory of the Double Correlated Phase in HTSC

The double-correlated phase in HTSC, and its treatment by field perturbation theory, is being established. In particular, we define the ground state, the quasiparticle excitations, and construct an appropriate field. We also derive the unperturbed Hamiltonian, and the propagators for the unperturbed state. Then, we discuss the perturbation Hamiltonian, and show that the Hartree Diagram is significant for both the pseudogap and the superconductive order parameters, and suggest that it yields the major contribution to these parameters.     

Complementary Analysis of the Field Perturbation Theory of Superconductivity

We reexamine the Nambu–Gorkov perturbation theory of superconductivity. We suggest that any field perturbation theory of superconductivity should be based on the Bogoliubov–Valatin (BV) quasi-particles. We show that two such different fields (and two additional analogous fields) may be constructed on the basis of this suggestion. The Nambu field is only one of them. For the field that is different than Nambu’s, the coherence field, the interaction is given by means of two interaction vertices that are based on the Pauli matrices τ₁ and τ₃. Consequently, the Hartree integral for the off-diagonal pairing self-energy may be finite, and in some cases large. We interpret the results in terms of conventional superconductivity and also discuss briefly the possible implications to HTSC.     

An Equation of State for the Hard-Sphere Chain Fluid Based on the Thermodynamic Perturbation Theory of Sequential Polymerization

New equations of state for freely jointed hard-sphere chain fluids are developed. The equations of state are based on the thermodynamic perturbation theory. The new equations of state use the contact values of the radial distribution function (RDF) for monomer–dimer mixtures, which is derived from the multidensity Ornstein–Zernike theory. These RDFs are composed of a monomer reference term, the Carnahan–Starling or the Percus–Yevick expression, and an additional bond contribution. These equations of state are then extended to real fluids. To calculate the phase equilibrium properties of nonassociating chain fluids, a dispersion contribution is added to the repulsive hard-chain reference term. With the new equations of state of chain fluids supplemented with the dispersion term, the vapor pressures and the coexisting densities of several real fluids are calculated.     

Analytic Equation of State for Lennard-Jones Fluids Based on the Ross Variational Perturbation Theory

By using a previously developed analytic expression for the radial distribution function of hard spheres, a simple analytic equation of state (EOS) for fluids with a continuous Lennard-Jones potential is established based on Ross's variational perturbation theory. The main thermodynamic quantities have been analytically derived, the resulting expressions are surprisingly simple, the variational procedure is greatly simplified, and the calculations are absolutely convergent. The numerical results are compared with the Monte-Carlo data and the original Ross variational theory. It is shown that the precision of the analytic EOS is as good as the original non-analytic one, and their applicable range is believed identical. A comparison with the recently proposed mean-sphere-approximation theory shows that the analytic equation of state developed here has wider applicability and precision.     

The Breakdown of Migdal's Theorem and the Divergence of Electron Polarizations in HTSC

We assume that Fermi surface nesting is a common feature in all oxide high temperature superconductors (HTSC) of perovskite or layered-perovskite structure. We show that this feature results in the breakdown of the Migdal's theorem, and the singularity of some electronic polarizations. These singularities trigger various kinds of instabilities in these materials.     

Synthesis and characterization of the Me–HTSC composite

This study shows that homogeneous composite compacts with improved superconducting and mechanical properties can be successfully prepared from pure Me–HTSC powders (Me=Ag, Cu, Al; HTSC=YBA₂Cu₃O_7−x). Composites were produced under the following conditions: the mass fraction of the metal phase was in the range 2.5–40 wt%, the compacting pressure was 30 kN/cm², the sintering temperature was from 270 to 950°C and the cooling rate was 50°C/h and 220°C/min. Microstructure and X-ray diffraction analysis have been done, alongside the T_c value determination.     

Competing and Cooperative Effects of Spin, Charge, and Phonon Degrees of Freedom in HTSC

The phase diagram of high-T _c superconducting copper oxides (HTSC) exhibits an unusual complexity which is, at present, beyond any microscopic modeling. Motivated by very recent experimental findings—(i) a giant isotope effect on T* and (ii) doping-dependent phonon anomalies and extra modes—the role played by the lattice is reinvestigated and the consequences arising for the striped phase are discussed. By including nonlinear higher-order phonon–phonon and density–density interactions in the Hamiltonian, an isotope effect on T* is obtained, as well as substantial q-dependent phonon anomalies, where both effects are strongly doping dependent.     

Thermodynamic Properties of Sutherland Fluids from an Analytical Perturbation Theory

Analytical expressions are obtained for the thermodynamic properties of fluids with potentials consisting of a spherical hard core plus an attractive tail of the form 1/r (Sutherland fluids). To this end, use is made of the Barker–Henderson perturbation theory together with an analytical expression for the first coordination shell of the radial distribution function of the reference hard-sphere fluid. This expression was derived previously on the basis of the analytical solution of the Percus–Yevick integral equation theory. The results are compared with available simulation data for a wide range of densities, temperatures, and values of the potential parameter . The overall agreement is good, and the accuracy is similar to that obtained using more accurate solutions for the radial distribution function of the hard-sphere fluid leading to nonanalytical expressions for the thermodynamic properties of the fluid considered.     

高温超导薄膜YBa2Cu3O6.5正常态电荷传输特性研究

介绍了50T左右脉冲强磁场的实验技术,诸如脉冲磁体设计、实验探针设计及测量线路设计等.随后,对高温超导薄膜YBa2Cu3O6.5在强磁场中的磁阻进行了实验研究.进而揭示正常态时超导薄膜YBa2Cu3O6.5随温度降低展现由导体向绝缘体的过渡过程.     

Controlled Modifications of HTSC Thin-Film Properties by Tailoring Substrate Surfaces

This chapter introduces the use of substrates for high-temperature superconductor (HTSC) thin-film deposition beyond their usual purpose as chemically inert, lattice-matched support for the films. Substrates are used as functional elements in order to controllably modify the growth mode of YBa₂Cu₃O_7–x thin films in the case of vicinal-cut SrTiO₃ single crystals or to locally modify the surface morphology and film/substrate lattice mismatch in the case of ion implanted SrTiO₃. Furthermore, the use of biaxial epitaxial strain is briefly reviewed for HTSC thin films, and the application of this concept to tailor the properties of perovskite thin films in general is shown.     

Acoustic Eigenvalues of a Quasispherical Resonator: Second Order Shape Perturbation Theory for Arbitrary Modes

The boundary-shape formalism of Morse and Ingard is applied to the acoustic modes of a deformed spherical resonator (quasisphere) with rigid boundaries. For boundary shapes described by r = a [1 − ε ℱ(θ, ϕ)], where ε is a small scale parameter and ℱ is a function of order unity, the frequency perturbation is calculated to order ε². The formal results apply to acoustic modes whose angular dependence is designated by the indices ℓ and m. Specific examples are worked out for the radial (ℓ = 0) and triplet (ℓ = 1) modes, for prolate and oblate spheroids, and for triaxial ellipsoids. The exact eigenvalues for the spheroids, and eigenvalue determined with finite-element calculations, are shown to agree with perturbation theory through terms of order ε². This work is an extension of the author’s previous papers on the acoustic eigenfrequencies of deformed spherical resonators, which were limited to the second-order perturbation for radial modes [J. Acoust. Soc. Am. 71, 1109-1113 (1982)] and the first order-perturbation for arbitrary modes [J. Acoust. Soc. Am. 79, 278–285 (1986)].     

About the peak in the real part of the AC conductivity nearTc in HTSC films

The origin of the peak in the real part of the conductivity of HTSC films nearT _c as a function of temperature and frequency has been analyzed in our experimental setup. It is shown that the peak is the result of a parasitic reactance in the measurement circuit related to the series and parallel equivalent schemes of the measurement circuit. It is demonstrated that the top of the peak is reached when the film resistivity becomes equal to the value of the imaginary part of the circuit impedance. Thus, its location at the temperature scale is determined by the resistance curve. Simultaneously the peak height becomes correspondingly equal to half the inverse value of the imaginary part.     

基于奇异摄动理论的电驱动机器人神经网络控制

在驱动回路电容较小的情况下,对电驱动刚性机器人操作手的轨迹跟踪问题,提出了一种基于奇异摄动理论的神经网络控制设计方法。稳定性分析表明系统跟踪误差最终一致有界,数值实验验证了所提的算法的可行性和有效性。     

Three-Dimensional Static Analysis of Nanoplates and Graphene Sheets by Using Eringen's Nonlocal Elasticity Theory and the Perturbation Method

A three-dimensional (3D) asymptotic theory is reformulated for the static analysis of simply-supported, isotropic and orthotropic single-layered nanoplates and graphene sheets (GSs), in which Eringen's nonlocal elasticity theory is used to capture the small length scale effect on the static behaviors of these. The perturbation method is used to expand the 3D nonlocal elasticity problems as a series of two-dimensional (2D) nonlocal plate problems, the governing equations of which for various order problems retain the same differential operators as those of the nonlocal classical plate theory (CST), although with different nonhomogeneous terms. Expanding the primary field variables of each order as the double Fourier series functions in the in-plane directions, we can obtain the Navier solutions of the leading-order problem, and the higher-order modifications can then be determined in a hierarchic and consistent manner. Some benchmark solutions for the static analysis of isotropic and orthotropic nanoplates and GSs subjected to sinusoidally and uniformly distributed loads are given to demonstrate the performance of the 3D nonlocal asymptotic theory.     

除湿空调器传质性能的场协同理论研究

利用场协同理论分析了除湿空调器传质性能的提高问题，主要是从调整速度场与浓度场之间的夹角，以强化除湿空调器传质性能；引用一种螺旋型蜂窝填料结构的除湿空调器和带倾角的螺旋折流板式除湿空调器，验证并总结其强化传质的性能，阐明其在工程中的推广应用价值。     

Local Electric Field Effects in Microwave and dc Electrodynamics of High-T c Metal Oxides

The model of the paraelectric, which is close to the point of the Mott–Hubbard instability, is shown to explain the dc resistivity and Hall effect temperature behavior for high-T _c superconductor metal oxides (HTSC). In the ground state the current is carried by a liquid of boson-like pairs of carriers in upper and lower Hubbard bands. The Mott–Hubbard instability corresponds to the order-of-lattice-constant length of the mean free path and results in the temperature insensitivity of Drude conductivity. Nearly linear on T resistivity results from the Curie law via the local (acting) electric field. Fermion-like carriers, temperature excited over the energy of boson-like pair dissociation (pseudo gap), explain the temperature behavior of Hall effect. Available data are compared with the model.     

基于场协同理论的冷藏展示柜内流体对流换热分析

目的研究冷藏柜内对流换热机理,增强冷藏柜内流体对流换热效果,提高冷气流冷却效率。方法从冷藏柜出风口角度出发,建立数学模型,通过Ansys流体分析软件对冷藏柜内流场进行模拟仿真,应用场协同理论研究冷藏柜内流体流动及传热机理。结果出风口角度在30°附近时冷藏柜内换热效率较高且温度分布较为均匀,此时商品壁面的存在改变了冷气流流动方向。在壁面增加半圆突起后,气流沿圆弧切线方向流动,改善了速度与温度梯度之间的协同程度,从速度场、温度场及其相互作用的角度增强了冷藏柜内的对流换热效果,整体换热效率提高了38.65%。结论冷藏柜内流体流动及传热强化的根本在于流体的扰动,而出风口角度的改变和壁面凸起的存在加强了商品对流体的扰动,两者共同作用改变了冷藏柜内场的分布,进而提高了冷藏柜整体的冷藏效率,该研究可为冷藏柜的工厂化生产提供参考价值。     

MATHEMATICA 在摄动法中的应用

应用MATHEMATICA符号运算，推导摄动法公式。以单自由度系统强非线性振动改进的L—P方法的公式推导为例，详细介绍MATHEMATICA符号运算，代替以往繁复的人工推导，既方便，又准确：此法可以方便地推广应用于其它摄动法或多自由度系统强非线性振动改进的L—P方法的公式推导，MATHEMATICA源程序在附录中给出。