Theoretical investigation of an acoustic wave in molecular magnets via electromagnetically induced transparency

Using the Schrödinger-Maxwell equations, we theoretically investigate the propagation properties of a transverse acoustic wave in a crystal of molecular magnets in the presence of two strong ac resonant magnetic fields and a weak acoustic wave. The acoustic wave can freely propagate in the magnetic molecule medium (under appropriate conditions) due to quantum interference. Furthermore, using the slowly varying envelope approximation, we discuss the propagation equation of the acoustic wave, which includes the high order nonlinear term. The results show that a crystal of molecular magnets can support the propagation of acoustic wave solitons via electromagnetically induced transparency. We also obtain the analytical expressions for the phase shift and absorption coefficient of the acoustic wave within certain parameters.     

Electrical transport and high pressure studies on bulk Ge20Te80 glass

The electrical resistivity of bulk Ge₂₀Te₈₀ has been measured as a function of pressure and temperature. At 5 GPa, an amorphous semiconductor-to-crystalline metal transition has been observed. The sample recovered from the high pressure cell, after the application of 7 GPa, has a face-centred cubic structure with a lattice constant of 6·42 A. In crystalline sample, the semiconductor-to-metal transition occurs at 7 GPa. The thermoelectric power has also been measured for glassy samples in the temperature range 300–240 K.     

A bound on the number of bound states in the Schrödinger equation

A boundS _l is given for the number of bound statesn _i in thelth partial wave corresponding to a spherically symmetric potential in non-relativistic quantum mechanics. This bound is given by whereV _a(l, r) is the attractive part of the effective potentialV(r)+l(l+1)/r ². Extensive comparative study ofS _i and the Bargmann inequality is made.     

Millimeter and submillimeter detection using Ga1?xAlxAs/GaAs heterostructures

We have shown that a Ga_1–xAl_xAs/GaAs heterostructure can be used as a sensitive tunable detector of mm-wave/sub-mm-wave radiation. The mechanism for detection requires the application of a magnetic field varying from approximately 0.2T at 94GHz (3.2mm wavelength) to 6.2T at 2500GHz (119m wavelength). The responsivity and N.E.P. at 3.2mm have been roughly estimated at 200V/W and 5×10^–11W/Hz respectively. The speed of such a detector could be several orders of magnitude greater than comparable InSb detectors.     

复杂应力构件弹性失效疲劳失效新判据——动态静态八面体应力强度理论

本文,在研究现代和经典强度理论的基础之上,提出了一个在复杂应力下弹性失效与疲劳失效的总准则,即动态静态八面体应力强度理论,同时建立了并分析了一个独立的比较完整的理论体系,给出了36种材料广义失效系数,和一点复杂应力的11个状态的计算理论,导出了广义允许强度算子方程.给出了总准则能应用到静态、动态的计算方法,通过8个工程实例的计算,表明该方法有很高的精度,因而笔者建议广泛地应用到工程.     

The Dirac-Ramond operator on loops in flat space

In this paper, a rigorous construction of the S¹-equivariant Dirac operator (i.e., Dirac-Ramond operator) on the space of (mean zero) loops in is given and its equivariant L²-index computed. Essential use is made of infinite tensor product representations of the canonical anticommutation relations algebra.     

平行机半在线排序问题研究(Ⅰ)

对半在线平行机排序问题的研究进展作了详细综述和进一步探讨。文章给出半在线排序问题的背景、定义、分类和求解。介绍它们定义和在不同机器环境和目标函数下半在线排序问题分类，以及第一类半在线模型的近似算法的设计及其竞争比分析。     

Biomagnetic measurements utilising a superparamagnetic marker: a feasibility study

Summary A preliminary study is here reported on a new potential marker for biomagnetic measurements. The marker consists of superparamagnetic polymer microspheres which were detected in the presence of external steady magnetic fields by means of an r.f.-SQUID magnetometer. The particles were prepared in samples differing in the concentration value and immersed in a homogeneous magnetic field of variable intensity. A simple model was taken into account for the distribution of the microspheres in the samples, so that the theoretical values were compared to the marker field values measured by the biomagnetic sensor. The overall sensitivity of the experimental apparatus and the minimum concentration value of the marker were then estimated.     

Uniform Continuity of a Family of Weakly Regular Set Functions on Topological Spaces

Conditions for the uniform continuity of a family of weakly regular set functions defined on an algebra of subsets of a -topological space (T,) and taking values in an arbitrary topological space are found.     

某工程地基基坑支护探讨

软土地基中的支护是基础工程的关键,在节约成本的前提下,选择合理的支护结构至关重要．通过对某公司将要开发的2个基坑支护方案的项目进行的相关分析、计算和探讨,总结出了软土地基中的基坑支护方案的选择原则及其相对应的施工措施等．