Design aspects of planar and conventional SMPS transformer: a cost benefit analysis

The intent of this paper is to design a high-frequency transformer that is to be incorporated into the DC/DC pulsewidth-modulated switch-mode power supplies by two different technical approaches: a conventional wound-coil magnetic using copper wires, and a planar magnetic with layered copper tracks on laminated printed circuit board. Comparisons will be made between the two approaches in terms of profile: mounting height and surface area, and performance: power losses and efficiency. Other indicators like temperature rise and leakage inductance that causes electromagnetic interference, and cost, materials, and process fluency are also to be looked into. A sandwiched configuration for primary and secondary windings is proposed for the planar type. Issues arising and typical phenomena encountered will be discussed in detail. Primarily, the dominating factor in performance, cost effectiveness, or circuit compactness that restrains the choice of a particular type is to be evaluated.     

On Donaldson’s flow of surfaces in a hyperkähler four-manifold

We prove some basic properties of Donaldson’s flow of surfaces in a hyperkähler 4-manifold. When the initial submanifold is symplectic with respect to one Kähler form and Lagrangian with respect to another, we show that certain kinds of singularities cannot form, and we prove a convergence result under a condition related to one considered by M.-T. Wang for the mean curvature flow.     

Nanoparticle composites: FePt with wide-band-gap semiconductor

We present a simple way to synthesize FePt and ZnO (wide-band-gap semiconductor) nanoparticle composites. The FePt nanoparticles were fabricated using the method reported by Sun et al. By controlling the heating rate, 3 nm FePt nanoparticles were synthesized. Well-dispersed FePt and ZnO nanoparticle composites were prepared by further adding zinc acetate and oleyl amine into the 3 nm FePt nanoparticle dispersion. By controlling the molar ratio of the FePt and zinc acetate, FePt and ZnO nanoparticle composites with different FePt particle fractions were obtained. The intensity of photo luminescence spectra of the nanoparticle composites increases very much with decreasing FePt particle fraction, whereas the peak position shifts a little. After annealing at 550 °C for half an hour, the nanoparticle composites become magnetically hard or semi-hard with coercivity much dependent on the FePt particle volume fraction. The coercivity of the composites increases with annealing temperature. The composites hold the promise of applications in new generation recording and/or optical devices.     

A Rapid Solid-phase Synthesis to Soluble Oligothiophene Molecular Wires

A novel method for the preparation of oligothiophene molecular wires is described via a bi-directional solid-phase synthesis. Using an alternating sequence of bromination and Stille coupling reactions, oligomers were obtained up to the heptamer in excellent yield and purity.     

Eu3+离子在微晶玻璃研究中的探针作用

制备出单掺Eu3+离子的氟氧化物玻璃陶瓷系列样品,利用Eu3+离子作为荧光探针,通过热处理前后Eu3+离子发射光谱中电偶极子跃迁与磁偶极子跃迁强度比值的变化表征在玻璃材料中微晶是否形成,分析了Eu3+离子荧光发射谱中电偶极子跃迁与晶体场对称性的关系,进一步表征了稀土离子所处微晶晶格场的变化.     

Analyses of the practical adhesion strengths of the metal/polymer interfaces in electronic packaging

There is a plethora of techniques to measure the adhesion strength of metal/polymer interfaces. However, the practical adhesion strength, which is the work done in separating the film from the substrate (or one film from another), is very sensitive to the test methods and the mechanical effects, such as the residual stress, thickness and mechanical properties of the layers, strain rate, and phase angle. Deriving intrinsic-adhesion properties of the interfaces, which are independent of such parameters, from the practical adhesion-strength measurements is a formidable task. In the present work, data from the three commonly used adhesion tests; pull-out, 90°-peel, and T-peel tests are compared with the intrinsic-adhesion properties of the interface, such as the interface-fracture toughness or the interface-fracture energy, and their implications are discussed. Material systems analyzed were Cu-based lead frame/epoxy-molding compound (EMC) and Cu/Cr/polyimide.     

Optical spectroscopy of Yb/Er codoped NaY(WO4)2 crystal

Erbium and ytterbium codoped double tungstates NaY(WO₄)₂ crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er³⁺ ions in NaY(WO₄)₂ crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb³⁺ to Er³⁺ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels.     

MPEG-4自然视频编码技术

对MPEG－4自然视频编码的关键技术作了详细的分析和阐述。首先介绍MPEG－4频语法结构，并对视频编码的框架概要分析。接着分析了自然视频编码中涉及到的关键技术，包括：VOP的产生；二值和灰度级α平面的编码技术；运动估计和补偿方法；纹理编码；基于对象的时间分级和空间分级；MPEG－4提供的再同步和各种错误掩盖，刷新方法，精 编码技术和零树小波基的静止图像编码技术。指出MPEG－4和MPEG－1，MPEG－2等标准的异同，突出MPEG－4的三个主要特点。最后给出MPEG－4技术在网络视频传输中的应用，并给出测试和分析。     

液晶显示器生产中的激光退火和缺陷修复

由于在大面积玻璃基底上制备由多层材料构成的高质量薄膜晶体管象元驱动阵列工艺的复杂性，使有源矩阵液晶显示器（AMLCD）的成品率低、价格高。利用激光对AMLCD进行非晶硅薄膜的退火和电路缺陷的修复，可有效的改善AMLCD的性能，提高成品率和降低成本。本文在介绍了激光对非晶硅薄膜退火和电路缺陷修复常用激光器的特性后，讨论了激光对不同类型缺陷修复的原理和过程。最后，分析比较了不同类型激光退火方法的特点。     

基于超分子结构共掺杂纳米复合薄膜的制备与荧光特性

为改善功能分了的特性,提出一种基于金属纳米粒子-偶氮染料复合物共掺杂超分子结构功能材料的设计新方法.并依照此方法制备出复合材料,观测了其显微结构,测量了其紫外-可见光吸收,研究了该超分子结构复合体系的荧光特性.实验发现,由于金属银纳米粒子的掺杂,使得超分子结构复合体系中功能分子甲基橙在溶液态体系的荧光强度增强近5倍,而在两种不同结构(共混结构和包覆结构)的薄膜态超分子结构体系中,其荧光强度分别被猝灭15%和20%.研究结果表明,复合膜中采用超分子结构完全能够改善功能分子的特性.