光盘系统中的伺服控制要求

1.引言光盘系统是光存储技术的典型代表之一。从上个世纪八十年代CD光盘的最初面市至今,经过30多年的发展,光盘系统已经在出版发行和信息存储领域中取得了广泛的应用,并在这期间衍生出了许多类型的物理和应用格式。在这些格式中,CD、DVD和BD这三大格式无疑是其中最具有代表性的光盘格式。     

激光准直高斯光斑中心位置计算方法分析

结合一种用于大孔同轴度测量的激光准直系统,分析高斯光斑能量中心坐标的几种常用计算方法:对称法、曲线拟合法和重心法。准直系统用单模尾纤半导体激光器作光源,用CCD探测器接收激光光斑。重心法计算时该实验装置实验室内6m距离上的方向稳定性达到1 5×10-6的量级。实验表明重心法有效利用光斑全场数据,对光强分布缺陷不敏感,分辨率和示值重复性都优于对称法和曲线拟合法。     

两性田菁胶在处理高浓度印染废水中的应用

研究了以聚合硫酸铁(PFS)为主凝剂、两性田菁胶(ASG)为助凝剂处理高浓度印染废水的各种影响因素。实验结果表明：PFS和ASG分别以2000mg／L和100mg／L的复配浓度、pH值接近中性时混凝效果为最佳，CODCr去除率达到80％，色度与浊度去除率均达99％以上。     

四氢吡咯烷离子液体液晶研究

合成了亲水性和疏水性的饱和杂环类离子液体N-十六烷基-N-甲基四氢吡咯烷溴化物与四氟合硼酸盐,采用偏光显微镜、变温X射线衍射仪和热化学等方法,研究两类离子液体液晶结构、自组装过程和相转变等特性,研究负离子对饱和杂环类离子液体自组装行为的影响.结果发现,该两种离子液体均可在熔点以上形成层状液晶,负离子结构与大小对离子液体液晶的结构与性质具有非常重要的影响,BF4-比Br-体积大,使吡咯烷环和环上的长碳链以较大的间隔排列,形成分子在近晶平面层内有序分布,结构非常接近固态的近晶型液晶.     

激光预辐照提高ZrO_2薄膜损伤阈值的研究

为了探究激光预辐照的工艺参数对提高光学薄膜抗激光损伤性能的影响,在1064nm的Nd∶YAG激光器组成的薄膜阈值测试平台上,对电子束热蒸发镀制的ZrO2单层薄膜进行了小光斑扫描的激光预处理.研究了不同能量阶单次扫描、单一能量阶多次扫描及不同能量阶多次扫描的激光预辐照对薄膜损伤阈值的提高效果.结果表明：不同能量阶单次扫描中,提高阈值效果最好的是采用原始样片损伤阈值的39%的能量扫描,可提高阈值13%;采用39%的阈值能量阶进行了多次预辐照实验,扫描3次效果最好,阈值提高了56%;在能量递增的多次预辐照实验中,递增能量多次预辐照与单一能量阶多次预辐照的预处理效果相似.     

沿层微测井插值方法反演复杂地区近地表模型

复杂地区近地表低降速带速度和厚度剧烈的横向变化会导致严重的静校正问题.为了解决这类静校正问题,提出利用调查点的微测井信息,沿近地表构造变化趋势构建近地表模型,并将其作为层析成像反演技术的初始模型,来改善反演的准确性.通过修改模型并进行多次迭代来最终得到准确的近地表模型,然后利用该近地表模型计算出静校正量.实际应用表明,该方法能够有效解决复杂地形地区的静校正问题.     

环境友好的近自然型鱼道

鱼道是帮助鱼类顺利通过闸坝等障碍物的专用设施,在维系河流连续性与生物种群交流方面具有不可替代的作用。近自然型鱼道是目前国际上十分流行的鱼道布置形式,其典型特点是利用漂石与天然河道床沙质构建尽可能接近于天然河流的水流流态。与传统的工程鱼道相比,近自然型鱼道由于构建了鱼类熟悉的水流流态,因而往往具有更高的过鱼效率。本文全面介绍了近自然型鱼道的设计理念、类型、构造布置特点、设计原则、以及水力计算方法,并对我国鱼道技术的进一步发展提出了若干建议。     

圆形料场典型布置分析

圆形料场因技术先进完善、自动化程度高、无污染、安全可靠而被广泛应用。论述了圆形料场的主要构成及装卸工艺,以某工程为例,介绍了该圆形料场的平面布置情况及装卸能力。     

Scattering wave field around a cavity with circular cross-section embedded in saturated soil using boundary element method

Based on Biot＇s theory and considering the properties of a cavity, the boundary integral equations for the numerical simulation of wave scattering around a cavity with a circular cross-section embedded in saturated soil are obtained using integral transform methods. The Cauchy type singularity of the boundary integral equation is discussed. The effectiveness of the properties of soil mass and incident field on the dynamic stress concentration and pore pressure concentration around a cavity is analyzed. Our results are in good agreement with the existing solution. The numerical results of this work show that the dynamic stress concentration and pore pressure concentration are influenced by the degree of fluid-solid coupling as well as the pore compressibility and water permeability of saturated soil. With increased degree of fluid-solid coupling, the dynamic stress concentration improves from 1.87 to 3.42 and the scattering becomes more significant. With decreased index of soil mass compressibility, the dynamic stress concentration increases and its maximum reaches 3.67. The dynamic stress concentration increases from 1.64 to 3.49 and pore pressure concentration improves from 0.18 to 0.46 with decreased water permeability of saturated soil.     

Fluid flow characteristics of single inclined circular jet impingement for ultra-fast cooling

The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities, nozzle diameters, jet angles and jet-to-target distances for ultra-fast cooling technology. The results show that the peak pressure varying significantly from nearly 0.5 to above 13.4 kPa locates at the stagnation point with different jet diameters, and the radius of impact pressure affected zone is small promoted from 46 to 81 mm in transverse direction, and 50 to 91 mm in longitude direction when the jet flow velocity changes from 5 to 20 m/s. However, the fluid flow velocity is relatively smaller near the stagnation point, and increases gradually along the radius outwards, then declines. There is an obvious anisotropic characteristic that the flow velocity component along the jet direction is about twice of the contrary one where the jet anlge is 60°, jet diameter is 5 mm, jet length is 8 mm and jet height is 50 mm.