共查询到20条相似文献，搜索用时 421 毫秒
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激光信息存贮技术(简称光盘技术)是七十年代后期发展起来的,它是应用激光与微电子相结合的一门新技术。经十来年的发展,特别是近几年来光盘技术的应用,不少国家都很重视,使光盘技术达到了相当高的程度。光盘教学机就是应用光盘技术研制成功的。他能把记录在电视唱盘中的信息用激光线进行重放。电视唱盘是在其表面下1.1毫米处用排列成螺旋状的小孔(坑)把信息记录下来,激光唱机把激光聚焦于小坑,再把反射光转换成图象信号和音响信号,送到电视或电视监示器映出。该机内还装有中央处理机(微型计算机),可从大量的记录内容中快速寻找出所需的信息,还能把各种形式的播放编 相似文献
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自1982年Philips公司和Sony公司共同推出激光唱盘cD(Compact Disc的英文缩写)以来，激光唱盘、激光视盘(LD)得到了迅猛的发展，各式各样VCD(Video CD)激光视盘、以及DVD(Digital VD)数码光碟机和DVD数码碟片已进入到普通百姓家，然而，由于商家及媒体那气势袭人的广告宣传，使得人们对各种光碟机的款式、功能了解不少，但对其工作原理、内部结构及发展前景还知之甚少．为了使人们对各种光碟机有一个洁晰的认识．特撰此文．以给谴者． 相似文献
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随着电化教育事业的发展,学校在教学过程中普遍使用音像教材,音像资料的数量和种类不断增多,应用范围不断扩大。因此学校音像资料的管理工作应进一步规范化、科学化。现就音像资料的收集、分类及使用管理等问题谈几点意见。一、收集收集音像资料应注意针对性、配套性。根据学校设备条件来选择相应载体(投影片、幻灯片、录音带、录像带、激光唱盘、影碟、电子计算机软件等)的资料,考虑课程设置要求和教师需要来选择资料内容。注意资料的准确性、实用性、趣味性及技术质量,尤其要收集利用率高而本校缺的资料。同时还要注意收集与载体配套的文… 相似文献
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宏业 《启蒙(3-7岁)》2011,(10)
几乎家家都有CD(激光唱盘),CD上面能存贮很多好听的音乐和歌曲,你知道CD是怎么大批量复制生产出来的吗?音像出版单位将载有内容的原版盘交给光盘复制单位。复制单位要先将刻 相似文献
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Zhiwei SU Mingxing LI Ling ZHANG Chaoyang WANG Leiqing ZHANG Jingqiu XU Baiping FU 《Journal of Zhejiang University. Science. B》2021,22(3):214-222
Objective:To coat a zirconia surface with silica-zirconia using a dip-coating technique and evaluate its effect on resin-zirconia shear bond strength(SBS).Methods:A silica-zirconia suspension was prepared and used to coat a zirconia surface using a dip-coating technique.One hundred and eighty-nine zirconia disks were divided into three groups according to their different surface treatments(polishing,sandblasting,and silica-zirconia coating).Scanning electron microscopy(SEM),energy dispersive X-ray(EDX),and X-ray diffraction(XRD)were used to analyze the differently treated zirconia surfaces.Different primer treatments(Monobond N,Z-PRIME Plus,and no primer)were also applied to the zirconia surfaces.Subsequently,180 composite resin cylinders(Filtek Z350)were cemented onto the zirconia disks with resin cement(RelyX Ultimate).The SBS was measured after water storage for 24 h or 6 months.The data were analyzed by two-way analysis of variance(ANOVA).Results:SEM and EDX showed that the silica-zirconia coating produced a porous layer with additional Si,and XRD showed that only tetragonal zirconia was on the silica-zirconia-coating surface.Compared with the control group,the resin-zirconia SBSs of the,andblasting group and silica-zirconia-coating group were significantly increased(P<0.05).The silica-zirconia coating followed by the application of Monobond N produced the highest SBS(P<0.05).Water aging significantly reduced the resin-zirconia SBS(P<0.05).Conclusions:Dip-coating with silica-zirconia might be a feasible way to improve resin-zirconia bonding. 相似文献
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YU Yong-jun YANG Shi-zhong 《重庆大学学报(英文版)》2006,5(1):24-26
1 Introduction In recent years, the need for ultra-wideband (UWB) antenna with an omni-directional coverage and compact antenna geometry increases in many applications, for example the Federal Communications Commission (FCC) released the unlicensed freque… 相似文献
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A specialised electrochemical measurement cell was plugged into a pilot water distribution system to simulate the pipe inner-wall corrosion. The linear polarisation resistance(LPR) technique and electrochemical impedance spectroscopy(EIS) were measured in real time to study the variation of the corrosion rate(CR) and scale of cast iron. Three corrosion stages were observed according to the LPR analysis: an initial stage with significantly fluctuating CR, a developmental stage with slowly decreasing CR, and a stable stage with a low CR of approximately 0.157 5 mm·a~(-1). The EIS revealed that the scales with a compact outer layer and a porous inner layer finally formed in the stable stage, and the polarisation resistance was approximately 2 175 ?·cm~2. A physicochemical analysis of the scales showed that ferric oxides, oxyhydroxides and calcite made the outer layer compact and effectively limited the diffusion of oxygen through the scales, which resulted in a low CR. 相似文献
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In this paper, equivalent surface impedance boundary condition (ESIBC), which takes fractal parameters (D, G) into SIBC, is implemented in the 4-component 2-D compact finite difference frequency domain (2-D CFDFD) method to an- alyze the propagation characteristics of lossy circular waveguide with fractal rough surface based on Weierstrass-Mandelbrot (W-M) function. Fractal parameters’ effects on attenuation constant are presented in the 3 mm lossy circular waveguide, and the attenuation constants of the fi... 相似文献
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Topological inverse semigroups 总被引：5，自引：0，他引：5
ZHUYongwen 《重庆大学学报(英文版)》2004,3(1):82-85
That the projective limit of any projective system of compact inverse semigroups is also a compact inverse semigroup,the injective limit of any injective system of inverse semigroups is also an inverse semigroup, and that a compact inversesemigroup is topologically isomorphic to a strict projective limit of compact metric inverse semigroups are proved. It is alsodemonstrated that Horn (S,T) is a topological inverse semigroup provided that S or T is a topological inverse semigroup withsome other conditions. Being proved by means of the combination of topological semigroup theory with inverse semigroup theory,all these results generalize the corresponding ones related to topological semigroups or topological groups. 相似文献
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张剑锋 《浙江大学学报(A卷英文版)》2005,6(4)
INTRODUCTION Let Mn be a connected and oriented submanifoldisometrically immersed in a space form Mc n p(c ≥ 0).We say Mn is closed if it is compact and withoutboundary. Denote by R, H and S, the normalized sca-lar curvature, mean curvature, and square of thelength of the second fundamental form of Mn, re-spectively. Application of the approach of Simons (1968)yields many rigidity results for minimal submanifoldsand submanifolds with parallel mean curvature v… 相似文献
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LIU Cheng-ze ZHU Xin-jian 《浙江大学学报(A卷英文版)》2006,7(11):1878-1885
INTRODUCTION Proton Exchange Membrane Fuel Cell (PEMFC) is being rapidly developed in recent years because of its compact structure, light weight, low working temperature and rapid startup characteristics. But its E-I characteristic curve reveals its decreasing per- formance when confronted with suddenly increasing power demand, and high cost also restrains the ap- plication of the fuel cell. So the hybrid power scheme is the most suitable selection presently. Most of researches on fu… 相似文献
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交互作用玩具熊谷平，章立在许多人看来，高技术玩具还是难以接受的东西，但是玩具制造商却一直在不断尝试。穿着全息技术舞袍的巴比娃娃、能和电视屏幕上的人物谈话、并能和芝麻街激光唱盘交互作用的玩具熊是今年才进入圣诞商品货架上的仅有的几个未来型玩具。虽然像这样... 相似文献
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求解有约束最优化问题的不连续罚函数积分总极值法 总被引：1，自引：0，他引：1
1IntroductionLetXbe a topological space ,Sa nonempty subsetofXandf:X→Ra real-valued function.Consider thefollowing constrained opti mization problem:c*=infx∈Sf(x) , (1)and the set of global mini mizers :H*={x∈S|f(x) =c*} (2)under the assumptions (see Refs .[1] and [2]) :(A) :fis lower semi-continuous ,Sis closed andthere is a real numberbsuch that the setHb={x∈S|f(x)≤b} is a nonempty compact set ;(R) :fis upper robust onS,i.e.,{x∈S|f(x) 相似文献
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Wenjing HUANG Shenglin LUO Dong YANG Sheng ZHANG 《Journal of Zhejiang University. Science. B》2021,22(3):171-189
The role of point-of-care(POC)diagnostics is important in public health.With the support of smartphones,POC diagnostic technologies can be greatly improved.This opportunity has arisen from not only the large number and fast spread of cell-phones across the world but also their improved imaging/diagnostic functions.As a tool,the smartphone is regarded as part of a compact,portable,and low-cost system for real-time POC,even in areas with few resources.By combining near-infrared(NIR)imaging,measurement,and spectroscopy techniques,pathogens can be detected with high sensitivity.The whole process is rapid,accurate,and low-cost,and will set the future trend for POC diagnostics.In this review,the development of smartphone-based NIR fluorescent imaging technology was described,and the quality and potential of POC applications were discussed. 相似文献