Transport of waves in disordered waveguides: A potential model

We study the statistical properties of wave transport in a disordered waveguide. We first derive the properties of a “building block” (BB) of length δL starting from a potential model consisting of thin potential slices. We then find a diffusion equation—in the space of transfer matrices that describe our system—which governs the evolution with the length L of the disordered waveguide of the transport properties of interest. The latter depend only on the mean free paths and on no other property of the slice distribution. The universality that arises demonstrates the existence of a generalized central-limit theorem. We have developed a numerical simulation in which the universal statistical properties of the BB found analytically are first implemented numerically, and then the various BBs are combined to construct the full waveguide. The reported results thus obtained are in good agreement with microscopic calculations, for both bulk and surface disorder.     

An orbifold relative index theorem

In this paper we prove a relative index theorem for pairs of generalized Dirac operators on orbifolds which are the same at infinity. This generalizes to orbifolds a celebrated theorem of Gromov and Lawson.     

差分输入双积分电路在热电阻测温中的应用

针对常规分立双积分AD只能处理单端信号的问题,给出了一种输入和基准电压均支持差分信号的分立差分双积分AD。在热电阻测量中,把热电阻和基准电阻串联同一回路,以基准电阻压降作为基准,对热电阻的压降进行测量,并从软硬件两个方面对常见的误差因素进行对消处理。实验表明,该电路用于PT100测温时,跳字不超过0.1℃,精度可以达到±0.1℃,且对运放型号无特殊要求,是一种低成本、高精度的温度测量方案。     

The A = 51 mirror nuclei 51Fe and 51Mn

Eighteen previously unknown γ-ray transitions were identified in the T _z = - 1/2 nucleus ⁵¹Fe following the fusion-evaporation reaction ³²S(²⁸Si,2α1n)⁵¹Fe. The level scheme reaches the fully aligned I ^π = 27/2^- terminating state of the five holes in the f _7/2 shell. The 17/2^- state was found to be isomeric, and the lifetime was measured to be 2.87 ns. The mirror symmetry of ⁵¹Fe and ⁵¹Mn is discussed, and the level scheme of ⁵¹Fe is compared to shell-model calculations. Received: 20 July 2000 / Accepted: 1 August 2000     

Detection of acoustic emission and simultaneous observation of nuclear quadrupole resonance in the α ⇋ β phase transition of paradichlorobenzene

Acoustic emission has been observed in the α ? β transition of monocrystalline samples of paradichlorobenzene. No acoustic emission has been detected in the β → α transition of single crystals nor in the α ? β transitions in polycrystalline samples. The simultaneous observation of acoustic emission and Nuclear Quadrupole Resonance when several α ? β transition cycles are carried out reveals some features of this solid state phase transition.     

Na2GdPO4F2:Tb3+绿色荧光粉阴极射线发光研究

通过高温固相法制备Na2GdPO4F2:Tb3+绿色荧光粉,并利用X射线粉末衍射(XRD)和阴极射线光谱分别对其物相、阴极射线发光性能进行研究.结果表明,Tb3+作为绿色发光中心进入到Na2Gd2PO4F2的晶格中取代Gd3+的格位,在低电子束(0.5～5 kV)激发下主要表现出Tb3+的特征跃迁(5D3.4→7FJ,J=6～2),其中以5D4→7F5跃迁(546 nn)为主.样品Na2Gd0.95Tb0.05PO4F2在阴极射线激发下的色坐标为(0.240 3,0.438 6).随着电压、电流和掺杂量的增加,荧光粉的发光强度逐渐提高,其中,最佳的样品为Na2Gd0.9Tb0.1PO4F2.     

Numerical study of nonlinear Schrödinger and coupled Schrödinger equations by differential transformation method

This paper presents the coupled version of a previous work on nonlinear Schrödinger equation [23]. It focuses on the construction of approximate solutions of nonlinear Schrödinger equations. In this paper, we applied the differential transformation method (DTM) to solving coupled Schrödinger equations. The obtained results show that the technique suggested here is accurate and easy to apply.     

Low Pass metallic mesh interference filters for operation in the 165 GHz to 880 GHz region

Low Pass metallic mesh interference filters have been designed and constructed for operation in the region 340 m (880 GHz) to 1.8 mm (165 GHz). These filters have been shown to have excellent edge characteristics and good rejection regions. The results show that the mesh filter can be effectively used in both millimetre and submillimetre regions.Part of this work was performed while this author was at Heriot-Watt University, Edinburgh, U.K.     

Performance of a Nd: YAG oscillator/ampflifier with phase-conjugation via stimulated Brillouin scattering

Phase conjugation via stimulated Brillouin scattering in CH₄ gas has been used to correct amplifier aberrations in a Nd: YAG oscillator/amplifier system. The single amplifier stage has been used in two-pass and four-pass arrangements. Using the four-pass arrangement incorporating compensation for thermal birefringence, a single-frequency diffraction-limited output of 350 mJ, in a compressed 6 ns pulse is achieved at 15 Hz repetition rate.     

Quantum-resolved fluorescence excitation spectra of SnO free radical

TheA ¹ –X ^{1 +} system of SnO is studied by laser- induced fluorescence excitation spectroscopy using isotopically enriched tin Sn¹¹⁶. The rotational structure analysis has been carried out for 6-0, 5-0, 2-0 bands. All these spectra were well resolved only with few perturbed lines in 2-0 band. Rotational constantsB ₂,B ₅,B ₆ and henceB _e , _{e e} have been obtained for the Sn¹¹⁶O molecule. An extension of perturbation study on 4-0 band has been made showing the maximum perturbation occurs at different J values for different isotopes.