Active-clamp ZVS converter with step-up voltage conversion ratio

This article presents the circuit implementation and design considerations of a zero voltage switching (ZVS) converter with voltage step-up for battery-based applications. An active-clamp circuit including one auxiliary switch and one clamp capacitor is connected in parallel with the main switch to allow resonant behaviour by the output capacitances of switches and transformer leakage inductance during the transition interval. Thus, the ZVS turn-on of switches can be achieved. The switching losses and thermal stresses of the semiconductors are reduced. The circuit configuration, operation principle and design considerations of the converter are discussed in detail. Finally, experiments conducted on a laboratory prototype rated at 200 W are provided to verify the theoretical analysis and the effectiveness of the proposed converter.     

Correlated imaging with partially coherent light for remote sensing

Based on the extended Huygens–Fresnel integral and the theory of coherence of light field, we have investigated the correlated imaging by using the transverse normalized second-order intensity fluctuation correlation function with partially coherent light radiation. The imaging for a reflected object with relative long distance is determined by the feature of speckle-to-speckle correlation. By using the correlation function, we study the effects of imaging distance, the sizes of object lens and reference lens, the source’s transverse coherent width and its transverse size on the quality of correlated imaging. Numerical results show that the parameters of imaging system and the properties of partially coherent light source have significant influences on the imaging resolution and visibility. For an object lens with large enough diameter, the resolution is determined by the transverse coherent width of light source. On the contrary, it depends on the aperture of object lens. The magnification of the system depends only on the propagation distance. This speckle-to-speckle correlated imaging with unbalanced arms have potential applications in remote sensing due to its unique features.     

A note on resource allocation scheduling with position-dependent workloads

In this note, single machine scheduling with concurrent resource allocation and position-dependent workloads is studied. The aim is to find jointly the optimal sequence and the optimal resource allocation. A bicriteria analysis of the problem is provided where the first criterion is to minimize the scheduling cost (i.e. makespan, total completion time, total absolute differences in completion times, total absolute differences in waiting times) and the second criterion is to minimize the total resource consumption cost. It is proved that four bicriteria problems can be solved efficiently.     

基于机器视觉的微型摆轮质量检测系统

摆轮在精密仪器设备中经常使用,其平整度与整个仪器的精密准确性密切相关.传统摆轮检测以人工为主,本文提出一种基于机器视觉的摆轮平整度检测系统,先校正摆轮图像,然后提取其亚像素边缘信息,并通过投影映射精确计算边界信息.系统支持连续采样计算,并以摆轮边缘的动态极差作为零件的合格标准.实验结果表明,该方法实时性好,准确率高,可以满足工业检测需求.     

边坡勘察若干重要问题——《工程地质勘察规范》(DBJ50-043-2005)讲座之二

引言重庆市的工程建设经常遇到边坡问题,边坡勘察是工程地质勘察的重要内容。重庆市工程建设标准《工程地质勘察规范》(DBJ50-043-2005)(以下简称本标准)用专章对边坡勘察进行了规定,在多个方面对原标准《工程地质勘察规范》(DB50/5005-1998)作了调整。为帮助勘察工程师更好地理解本标准关于边坡勘察的规定,本文对编制岩质边坡岩体分类、边坡强度参数、边坡坡率允许值和斜坡勘察等方面规定的背景和思路进行介绍。1岩质边坡的岩体分类1.1分类的修改情况本标准修订的岩质边坡的岩体分类方案见表1。边坡岩体分类是岩质边坡勘察中非常重要的内…     

喷焰内氧化铝粒子光辐射特性研究

分析了Al2O3粒子在喷焰内流动冷却过程中不同相态对其光学性质的影响,重点研究凝固过程中三种相态(液态、γ相、α)Al2O3粒子的吸收指数随相态的变化关系,考虑了紫外到近红外光谱范围内,Al2O3粒子的不同辐射机制.基于Drude模型所得到的氧化铝粒子不同相态吸收指数的计算模型建立了描述Al2O3粒子相变过程紫外与可见光辐射特性数学计算模型.通过与实验数据的对比分析表明,本模型是可行的.在此基础上,分析了不同相态Al2O3粒子辐射特性随温度和波长的变化关系.     

Surface plasma resonance spectra of Au nanoparticles formed from dewetted thin films

We investigated surface plasma resonance (SPR) properties of gold (Au) nanoparticles formed by step-by-step thermal annealing of Au films deposited onto substrates. We found that the averaged sizes of the Au particles formed in the annealing process depend on the initial thicknesses of the films. Using the geometric parameters extracted from the images of Au particles, the optical transmission spectra measured can be completely described in terms of SPR in the particles. The results suggest that annealing of Au films can be a simple and effective approach for producing Au nanoparticles with desired optical transmission properties, and the approach can be easily integrated into thin film fabrication processes.     

From nanorings to nanodots by patterning with block copolymers

We demonstrate three different transfer patterns that can be achieved by use of a surface reconstructed block copolymer film where metal is evaporated onto the surface of the film, providing the contrast. Thin films of diblock copolymers having cylindrical microdomains oriented normal to the surface with long-range lateral order were used. Solvent reconstruction of the film, followed by a glancing angle metal evaporation and thermal annealing, led to three different decorations of the films with gold. These films were used as masks for pattern transfer of pores, columns, and rings to underlying substrate with high fidelity.     

机车车轮轮缘探伤方法及定量标准的探讨

针对机车车轮轮缘形状的特殊性,对机车车轮轮缘部位的探伤方法进行了探索,研制了轮缘周向缺陷及纵向缺陷探伤对比试块,研制了相应的WM2R型双晶纵波探头和双晶双向扫查横波斜探头;利用数字式超声波探伤仪制作波幅-当量曲线,提出了确定轮缘缺陷当量方法,在应用实践中得到了验证。     

Suppression of radiative decay of CdTe quantum dots in a photonic crystal with a pseudogap

Abstract

Observation-angle dependence of the spontaneous emission life-time of CdTe quantum dots (QDs) embedded in a pseudogap photonic crystal (PC) film has been demonstrated. Comparison of two PC films with different photonic band-gaps (PBGs) differentiates the PBG effect from the electronic and/or chemical interactions between CdTe QDs and the host medium. This lifetime modification of QDs by a PC with pseudogap can be very useful in applications for optoelectronic devices such as QD lasers and QD switches.