Photorefractive materials for nonvolatile volume holographic data storage

Optically gated recording and nonvolatile readout in a digital volume holographic data storage system that uses a pair of mutually incoherent light sources during recording and only one for readout were demonstrated recently. This approach used stoichiometric lithium niobate, which after post-growth processing gave rise to an at least two orders of magnitude improvement in sensitivity over the best materials reported previously. It is also shown that by adding certain dopants (iron and manganese) to near-stoichiometric lithium niobate, the dark storage time and gating efficiency can be increased compared with previous work. The underlying physical mechanisms of gated recording and the effectiveness of the gating process responsible for this manifold improved performance are discussed, and bipolarons and small polarons are identified as the responsible photorefractive species.     

Volume holographic storage and retrieval of digital data

A multiple page fully digital holographic data storage system is demonstrated. This system is used to store and retrieve digital image and compressed video data with a photorefractive crystal. Architecture issues related to spatio-rotational multiplexing and novel error-correcting encoding techniques used to achieve low bit-error rates are discussed.     

Research in instrument sharing

Continued progress in many areas of science depends on access to advanced modern instruments and the data they provide. Costly instruments have been shared in a number of disciplines for many years, and common patterns of shared usage have developed independently. The scientific and financial aspects of large instrument usage are discussed from the points of view of the instrument centers, the users, and the funding agencies. The instrument problem is not one problem but many, and coordinated solutions must be implemented with well-defined goals based on knowledge of the needs of the users and developers of instruments.     

仪器分析的教学方法探讨

仪器分析是用精密仪器测量物质的某些物理或化学性质,以确定其化学组成、含量及结构的一类分析方法,是分析化学的一个分支。其发展迅速、方法门类繁多,能够适应诸多领域分析任务的需要,已成为现代分析化学的主干。在医药卫生事业方面,临床检验、疾病诊断、病因调查、新药研制、药品质量的全面控制、中草药有     

Ruby laser as a microsurgical instrument

Morphological changes at the cell level have been produced experimentally by a pulsed ruby laser (optical maser). A pulse duration of approximately 500 microseconds caused discrete damage to structures in the cell without irreversible damage to the surrounding area.     

正确选用气体超声流量计

气体超声流量计已在天然气贸易计量领域中得到了广泛的应用,根据国内已使用气体超声流量计企业的使用经验,作者对气体超声流量计在使用过程中遇到的计量问题进行了分析研究,列出了在设计、使用过程中应注意的有关问题并提出了相关建议.     

超声计量系统的远程诊断

以西气东输天然气管道为例,论述了超声计量系统远程诊断平台的功能需求和实现过程.结合计量设备自身的诊断功能,通过构建远程网络,可在控制中心开发出功能强大的诊断平台.利用诊断平台,可自动实现对超声流量计量系统的增益、信噪比、声速等各种参数的实时监视和诊断,实现自动诊断、远程维护和计量数据存档,并可方便地实现流量计的使用中检验,将设备的维护管理任务集中于一地,提高了工作效率,开创了贸易计量管理的新模式.     

超声数据采集系统设计

本文涉及水下微地形超声探测仪的研发，主要探讨超声探测仪核心系统-超声数据采集系统的设计。首先确定该数据采集系统的基本结构，然后依据探测精度要求对数据采集卡进行选型，最后完成基于PCI-1714高速数据采集卡的超声数据采集软件系统设计，成功开发超声数据采集系统。     

超声波对粘虫的处理效果

以常见害虫粘虫为试验材料,用不同剂量超声波处理成虫,观察处理后期粘虫发育阶段的死亡率和羽化率变化情况。结果表明:随着超声波剂量的增大,粘虫死亡率呈明显上升趋势,羽化率有明显下降趋势,超声波作用生物效应显著,当作用时间为140 s时,成虫死亡率急剧升高,高于50%,当作用时间超过180 s时,几乎没有羽化的粘虫。     

钢管混凝土超声波检测试验

阐述了超声波检测钢管混凝土质量的基本原理，以及带有各种缺陷的钢混凝土试件的制作方法及试件的测试程序。给出了部分试件的实测声学参数和波形。并通过实测波形和声学参数的分析，总结出超声波在带有多种缺陷的钢混凝土中传播时波形和声学参的变化规律，可供采用超声波检测钢混凝土地质量时参考。     

气体超声流量计干标方法

介绍了气体超声流量计的工作原理、干标方法在气体超声流量计标定中的可行性和使用气体超声流量计干标技术的各个步骤及应遵循的几点要求.指出在实际应用中该方法本身也会引起测量的不确定性.     

超声波管道腐蚀检测器现场检测

介绍了从德国引进的φ７２０型超声波管道腐蚀检测器和φ７２０型管道通径检测器的技术性能，及共在鲁宁输油管道首次现场检测的过程和结果，这两种检测器都是在不中断输油生产的条件下进行在线性测的设备，检测时先运行通径检测器，检测管道通径变化量，看其是否满足管道腐慢检测器通过的要求，然后进行一系列的清管工作，刮除管道内壁的结蜡层，以减少超声波信号的衰减，最后才运行管道腐蚀检测器，两种检测器在管道中随油流推动运     

利用虚拟仪器技术改革创新实验教学模式

针对测控实验室和机械测试实验室进行实验教学中存在的问题,提出了将虚拟仪器引入到实验教学中,采用以＂虚＂代＂实＂,虚拟实验与实物实验有机整合等多种实验教学模式,促进了实验室的实验教学改革,从而提高了实验课程的教学质量和水平,培养了学生的综合实践能力和创新能力。