气体放电实验与帕邢定律

利用真空镀膜机的离子轰击装置研究了气体放电电压与气体压力的关系．在保持气体放电电流不变的情况下，气体放电电压是气体压力的函数．改变气体压力时，放电电压有一极小值．这种关系可用帕邢定律来解释。     

基于气体浓度定量的嗅觉刺激器优化设计

现有的基于磁共振测量的嗅觉刺激器，通过调节嗅剂液体浓度的方法可以实现不同浓度的嗅觉刺激，但随着实验进行，受到嗅剂挥发以及实验环境（温度、湿度、气流量）变化的影响，很难确保输送至鼻腔的嗅剂气体浓度的稳定性，进而影响实验结果的准确性．本研究对本实验室前期开发的嗅觉刺激装置进行改进，实现了气体浓度精确定量．改进后的嗅觉刺激器主要分为三个部分：控制系统、反馈系统和气路系统．控制系统主要实现气路系统的送气控制和嗅剂气体浓度调节；反馈系统则负责对气体浓度进行测量；气路系统则在原有基础上添加活性炭装置，降低无关因素干扰．装置改进之后，不同气路切换时间为75.2 ms，比原装置减少了1 s，有效提高刺激精度．实验结果显示，气体浓度调节前，300 s内乙醇、吡啶、乙酸戊酯嗅剂气体浓度分别下降6.7%、71.4%、79.2%，嗅剂气体浓度短时间内发生较大改变．加入气体浓度调节功能后，当气体浓度下降至目标浓度的90%时，可通过调节气泵电压改变嗅剂气流与空气气流比例，从而调节嗅剂气体浓度至目标值，其中吡啶、乙酸戊酯用时13 s．     

从气体吸附率看范德瓦耳斯气体模型的局限性

利用占据数方法和正则系综理论分别求出了费米气体、玻色气体和范德瓦耳斯气体的化学势,比较了这三种气体与理想气体吸附率的差异.指出:费米气体的吸附率高于理想气体,玻色气体则低于理想气体.存在一个临界温度,高于此温度,用范德瓦耳斯气体描述费米气体不如理想气体模型;低于此温度,用范德瓦耳斯气体描述玻色气体不如理想气体模型.     

激光冷却气体原子

激光冷却气体原子是近十年来量子光学研究领域中最前沿的研究课题。最新的研究成果表明，激光冷却气体原子可广泛地应用于物理学研究，并对其发展将起促进作用。本文介绍了激光冷却气体原子研究的发展和现状，重点介绍了利用自发辐射力冷却气体原子的“光学粘胶”（ｏｐｔｉｃａｌ　ｍｏｌａｓｓｅｓ）和利用迟后偶极力的“受激光学粘胶”（ｓｔｉｍｕｌａｔｅｄ　ｏｐｔｉｃａｌ　ｍｏｌａｓｓｅｓ）的工作原理。文中还讨论了激光冷却气体原子应用于物理学研究的可能性。     

弱相互作用费米气体的不稳定性判据

根据由赝势法得到的弱相互作用费米气体的自由能，利用热力学方法研究了无外场时弱相互作用费米气体的稳定性.结果表明，无外场情况下理想费米气体与存在弱排斥相互作用的费米气体是稳定的；而具有弱吸引相互作用的费米气体在一定条件下可出现不稳定性.给出了不稳定性的粒子数密度判据和温度判据，就不同逸度情况下临界粒子数密度的具体表达结果以及温度、粒子质量和吸引相互作用对临界粒子数密度的影响进行了讨论. 关键词： 费米气体 相互作用 不稳定性判据     

高压火花隙开关中气体冷却的数值模拟

 高温气体的冷却对火花隙开关的重复运行具有重要的影响。利用流体方程、热传导方程和理想气体状态方程构建的方程组，对火花隙开关中高温气体冷却的过程进行了数值模拟。分析了气体导热系数、粘性系数、对流及气体压强等要素对气体冷却速度的影响，得到了气体冷却的基本规律：火花隙开关内气体的冷却以传导为主；若不采用其他手段，气体在十几ms内冷却较困难；对流的作用经数十ms后才显著；气体的粘性系数对气体冷却的影响可以忽略。可以通过选用导热系数高的气体，优化电极结构或采用吹气方法提高气体冷却速度的办法。     

极高压强下气体的性质

气体在极高压强下不再遵从玻意耳定律和盖·吕萨克定律，而代之以 Ｌｅｖｉｔｔ建议的两个经验公式 ｐ＝ ＣｅＢ／Ｖ及＝Ｖ０＋αｐＴ．根据这两个经验公式，我们计算了在极高压强下气体的各种热力学性质，讨论了它们随压强和温度的变化趋势，并且与理想气体和范德瓦耳斯气体的情形进行了比较     

多方过程几种定义说法等效性的证明

本以范德瓦尔斯气体为例，证明了在Cv为常数的条件下多方过程几种定义说法的等效性，并给出了范氏气体多方过程的功容定义，最后指出功容为常量才是多方过程最基本的特征。     

温室气体遥感探测仪器发展现状

阐述了温室气体遥感探测技术的发展历程。详细介绍了几种国外先进的高光谱分辨率温室气体遥感探测仪器的设计理念、工作方式、谱段设置和主要技术指标。综述了温室气体探测技术从综合性探测仪器到专用温室气体探测仪器的发展过程,指出了温室气体探测仪器未来发展方向,包括高光谱分辨率、高空间分辨率,宽覆盖范围,短覆盖周期以及高信噪比等。     

热电气体发电机原理探索

介绍一种热电气体发电机，以单原子气体为工质，通过吸热升温，加速摩擦，电晕放电，生成等离子气体，再把它输入发电通道，发出电能．     

平面三维显示技术的研究现状

平面三维显示技术是近年来最新出现的虚拟现实显示技术,其最大的特点是观察者无需使用任何辅助附加设备,直接用肉眼就可看到屏幕上显示的三维图像。为推进三维显示技术的发展,进一步研究了视差立体成像原理,并据此介绍几种平面三维显示方法及其工作原理,包括障栅立体显示、微柱透镜阵列立体显示、偏振片立体显示和基于微柱透镜立体显示原理的多视点系统,阐述并分析了系统的优缺点。以日本三洋公司的四视角立体显示装置、南京大学的多视点三维显示系统和NEC液晶科技的HDDP三维显示系统为例,描述了国内外该项技术近期的研究现状,分析了存在的技术难点,展望了该应用领域的发展前景。     

Three-dimensional polarimetric integral imaging

A three-dimensional (3D) polarimetric image sensing and display technique based on integral imaging is proposed. Three-dimensional polarization distribution of reflected light from a 3D object can be measured as elemental image arrays by a rotating linear polarizer. After the measurement of the polarization of the 3D object, the 3D polarimetric object can be reconstructed optically by displaying the polarization-selected elemental images in spatial light modulators with two quarter-wave plates. Experimental demonstration of 3D polarimetric imaging of a 3D object attached to two orthogonal linear polarizers is presented. To the best of our knowledge, this is the first report on 3D polarimetric sensing imaging and 3D optical reconstruction by integral imaging.     

Evaluation of the inner ear by 3D fast asymmetric spin echo (FASE) MR imaging: phantom and volunteer studies

The 3D fast asymmetric spin echo (FASE) method combines the half-Fourier technique and 3D fast spin echo (FSE) sequence. The advantage of this method is that it maintains the same spatial resolution as FSE while markedly reducing the imaging time. The purpose of the present study was to evaluate the usefulness of the 3D FASE technique in displaying the inner ear structure using phantom and volunteer studies. 3D FSE sequence images were obtained for comparison, and the optimum 3D FASE sequence was investigated on a 1.5T MR scanner. The results of phantom experiments showed increased signal-to-noise ratio (SNR) with prolonging repetition time (TR) on both 3D FASE and 3D FSE sequences. Although the SNR of 3D FASE images was 20-25% lower than that of 3D FSE images with the same TR, the SNR per minute with 3D FASE was about twice that with 3D FSE. On 3D FASE images, a higher spatial resolution was obtained with 2- or 4-shot images than with single-shot images. However, no significant difference was observed between 2-shot and 4-shot images. In the volunteer study, 3D FASE images using a TR of 5000 ms and an effective echo time (TEeff) of 250 ms showed a high SNR and spatial resolution and provided excellent contrast between cerebrospinal fluid and nerves in the internal auditory canal. The highest contrast was achieved in the 2-shot/2 number of excitations sequence. 3D FASE provides the same image quality as 3D FSE with a significant reducing in imaging time, and gives strong T2-weighted images. This method enables detailed visualization of the tiny structures of the inner ear.     

Preoperative fast MRI of brain tumors using three-dimensional segmented echo planar imaging compared to three-dimensional gradient echo technique

The purpose of this study was to compare the diagnostic efficacy of a newly developed T(1)-weighted three-dimensional segmented echo planar imaging (3D EPI) sequence versus a conventional T(1)-weighted three dimensional spoiled gradient echo (3D GRE) sequence in the evaluation of brain tumors. Forty-four patients with cerebral tumors and infections were examined on a 1.0 T MR unit with 23 mT/m gradient strength. The total scan time for the T(1) 3D EPI sequence was 2 min 12 s, and for a conventional 3D GRE sequence it was 4 min 59 s. Both sequences were performed after administration of a contrast agent. The images were analyzed by three radiologists. Image assessment criteria included lesion conspicuity, contrast between different types of normal tissue, and image artifacts. In addition, signal-to-noise and contrast-to-noise-ratio (C/N) were calculated. The gray-white differentiation and C/N ratio of 3D EPI were found to be inferior to conventional 3D GRE images, but the difference was not statistically significant. In the qualitative comparison, lesion detection and conspicuity of 3D EPI images and conventional 3D GRE images were similar, but a tow-fold reduction of the scanning time was obtained. With the 3D EPI technique, a 50% scan time reduction could be achieved with acceptable image quality compared to conventional 3D GRE. Thus, the 3D EPI technique could replace conventional 3D GRE in the preoperative imaging of brain.     

Holovideo: Real-time 3D range video encoding and decoding on GPU

We present a 3D video-encoding technique called Holovideo that is capable of encoding high-resolution 3D videos into standard 2D videos, and then decoding the 2D videos back into 3D rapidly without significant loss of quality. Due to the nature of the algorithm, 2D video compression such as JPEG encoding with QuickTime Run Length Encoding (QTRLE) can be applied with little quality loss, resulting in an effective way to store 3D video at very small file sizes. We found that under a compression ratio of 134:1, Holovideo to OBJ file format, the 3D geometry quality drops at a negligible level. Several sets of 3D videos were captured using a structured light scanner, compressed using the Holovideo codec, and then uncompressed and displayed to demonstrate the effectiveness of the codec. With the use of OpenGL Shaders (GLSL), the 3D video codec can encode and decode in realtime. We demonstrated that for a video size of 512×512, the decoding speed is 28 frames per second (FPS) with a laptop computer using an embedded NVIDIA GeForce 9400 m graphics processing unit (GPU). Encoding can be done with this same setup at 18 FPS, making this technology suitable for applications such as interactive 3D video games and 3D video conferencing.     

动态全息三维显示研究最新进展

全息三维显示是真三维显示技术, 其原理是利用光学干涉记录和衍射再现将物体或场景的三维信息全部重建出来, 所以观看全息三维图像与观看真实物体或场景的效果一样. 近期全息研究领域有一些突破性的成果被报道, 将推动全息显示的应用不断走向成熟. 本文将重点介绍基于光学材料和空间光调制器为全息图承载载体的动态全息三维显示最新发展状况. 虽然动态全息三维显示研究仍然存在挑战, 但最近研究中已经利用光学材料实现了实时动态全息三维视频显示, 这为未来实现大尺寸、高分辨率、彩色全息真三维视频显示提供了可能.     

Application d'un modéle de l'état liquide à une monocouche de xénon ou de krypton adsorbées sur la surface (0001) du graphite

A phenomenological model of three-dimensional (3D) liquids is applied to a xenon or krypton monolayer adsorbed on (0001) graphite. The rare-gas atoms are assumed to be mobile with a short-range order as in 3D liquids. From the study of the equilibrium 3D gas ? 2D solid and 3D gas ? 2D liquid, one can find with reasonable agreement the pressures and temperatures of the 2D triple point determined experimentally by other authors.     

Characterization of the 3D resolution of topometric sensors based on fringe and speckle pattern projection by a 3D transfer function

The increasing importance of optical 3D measurement techniques and the growing number of available methods and systems require a fast and simple method to characterize the measurement accuracy. However, the conventional approach of comparing measured coordinates to known reference coordinates of a test target faces two major challenges: the precise fabrication of the target and - in case of pattern projecting systems - finding the position of the reference points in the obtained point cloud. The modulation transfer function (MTF) on the other hand is an established instrument to describe the resolution characteristics of 2D imaging systems. Here, the MTF concept is applied to two different topometric systems based on fringe and speckle pattern projection to obtain a 3D transfer function. We demonstrate that in the present case fringe projection provides typically 3.5 times the 3D resolution achieved with speckle pattern projection. By combining measurements of the 3D transfer function with 2D MTF measurements the dependency of 2D and 3D resolutions are characterized. We show that the method allows for a simple comparison of the 3D resolution of two 3D sensors using a low cost test target, which is easy to manufacture.     

A 3D shape retrieval method for orthogonal fringe projection based on a combination of variational image decomposition and variational mode decomposition

The orthogonal fringe projection technique has as wide as long practical application nowadays. In this paper, we propose a 3D shape retrieval method for orthogonal composite fringe projection based on a combination of variational image decomposition (VID) and variational mode decomposition (VMD). We propose a new image decomposition model to extract the orthogonal fringe. Then we introduce the VMD method to separate the horizontal and vertical fringe from the orthogonal fringe. Lastly, the 3D shape information is obtained by the differential 3D shape retrieval method (D3D). We test the proposed method on a simulated pattern and two actual objects with edges or abrupt changes in height, and compare with the recent, related and advanced differential 3D shape retrieval method (D3D) in terms of both quantitative evaluation and visual quality. The experimental results have demonstrated the validity of the proposed method.     

360°连续扫描的便携式三维激光雷达设计与开发

针对三维激光雷达在国内有巨大的应用市场,而国外商业三维激光雷达十分昂贵的现状,开发了一种360°连续扫描的便携式三维激光雷达系统。采用一个二维激光扫描仪与高精度转台连接,通过步进电机控制形成三维激光扫描。在分析系统误差来源的基础上,提出了系统误差校正方法,给出了三维坐标精确计算公式。实验结果表明,系统测量精度高,数据质量好。系统作用距离80 m,测距精度可达6 mm,测量速度每秒7256点,可满足室内室外大规模场景三维数据快速获取的需求,而成本仅是国外同类商业三维激光雷达价格的四分之一左右,且重量轻体积小,携带方便。