Laser radar: A technique for studying the atmosphere

Laser radar, also called lidar, is proving to be a powerful technique for helping us to understand the world in which we live. It can provide information on topography, vegetation canopies, and on characteristics of Earth’s atmosphere. This article describes how laser light scattering can be used in lidar systems to help visualize the structure of our atmosphere and to address a wide variety of important scientific questions from air pollution to climate issues. The article focuses on two specific examples of ground-based elastic lidar, the Micro Pulse Lidar System and the CLidar system, to provide an introduction to the methods of atmospheric lidar measurements and their applications.     

Exploring the atmosphere with lidars

Lidar is a powerful technique for the study of atmospheric structure and dynamics. The spatial and temporal variability of minor constituents of the atmosphere such as aerosols, dusts, clouds, water vapour, and wind speed and temperature structure of the upper atmosphere can be studied using lidar. This article describes the basic principle of lidar operation, types of laser used for the remote sensing of the atmosphere and mechanism of scattering/absorption processes when the laser interacts with the atmosphere. Part 1 gives the basics and applications of lidar. Also, one type of lidar—Mie and Rayleigh lidar is described. S Veerabuthiran is working as a research fellow in Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum. His research involves the study of aerosols, dusts, and clouds in the lower atmosphere and temperature structure in the upper atmosphere.     

Atmospheric corrosion mapping of copper surfaces from diffuse light scattering measurements by an optoelectronic sensor system

A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprising a thin beam light emitting diode （LED） illuminating a small spot on the metal surface, and a matched pair of photodetectors, one for capturing the reflected light and the other for sampling the scattered light. The analog photocurrent signals are digitized and processed online by a per- sonal computer （PC） to determine the corrosion factor defined in terms of the two current values. By scanning the sample surface using the light beam and by computing the corrosion factor values simultaneously, a three dimensional graph and a two dimensional contour map are generated in the PC using Matlab tools. The values of the corrosion factor measured in different durations of exposure to atmosphere, which obey a bilogarithmic law, testify to the validity of our mathematical model.     

基于激光雷达的移动机器人三维建图与定位

针对室外环境建图与定位缺乏有效的回环检测导致累计漂移误差以及点云地图形式不够紧凑,提出基于Livox(览沃)激光雷达采集数据模块,使用三维点云片段匹配方法消除室外建图出现的误差。首先,对激光雷达采集的三维点云数据进行采样和体素滤波完成数据预处理?然后,使loam(lidarodometryandmappinginreal-time)算法作为前端,采用ICP算法实现快速有效的帧间匹配?最后,结合三维点云片段匹配与GSTAM优化位姿累计误差获得全局一致的的轨迹,并将点云地图优化成为立体占用地图输出。通过将点云片段匹配方法作为回环检测在实际室外环境进行三维激光建图实验证明,该方法能够解决实际室外环境建图中存在的建图不精准的问题。     

激光光谱分析装置的原理与应用

本文以Nd:YAG激光器为例,介绍了激光光谱分析的实验装置、工作原理及其应用;并以此实验装置为基础,实验测得了等离子体的激发温度与环境气压间的关系。     

Towards skin polarization characterization using polarimetric technique

Measurement of optical properties of skin is an expanding and growing field of research. Recent studies have shown that the biological tissue, especially skin, changes the polarization state of the incident light. Using this property will enable the study of abnormalities and diseases that alter not only the light intensity but also its polarization state. In this paper we report an experimental study for measuring changes of polarization state of the light scattered from a phantom similar to a sample model of scattering skin. Using the notation of Stokes vector for the polarized light and Mueller matrix for the sample with its polarization properties, we have shown that some elements of the matrix were particularly sensitive to the changes of the polarization-altering physical properties of the scatterers within the phantom.      

不同条件下激光诱导金属铝等离子体的发射谱研究

用钕玻璃激光器(～25J)烧蚀铝靶获得等离子体，以氩气作为保护气体，分析了环境气压、等离子体的观测高度、激光功率密度对谱线强度的影响，并进行了讨论．     

激光束扩展效应的统计分布的实验研究

本文给出湍流大气斗激光束扩展效应的—新的测量技术,并在本实验条件下,测量出光束的扩展值及其统计分布,并对测量结果进行了讨论。     

Microstructures and mechanical properties of SiBCNAl ceramics produced by mechanical alloying and subsequent hot pressing

Amorphous SiBCNAl powders were prepared via a mechanical alloying (MA) technique using crystalline silicon (Si), hexagonal boron nitride (h-BN), graphite (C), and aluminum (Al) as starting materials. SiBCNAl powders were consolidated by a hot pressing (HP) technique at 1800 °C under a pressure of 30 MPa in argon and nitrogen. The sintering atmosphere had a great influence on the microstructures and mechanical properties of the ceramics. The two ceramics had different phase compositions and fracture surface morphologies. For the ceramics sintered in argon, flexural strength, fracture toughness, elastic modulus and Vickers hardness were 421.90 MPa, 3.40 MPa·m1/2, 174.10 GPa, and 12.74 GPa, respectively. For the ceramics sintered in nitrogen, the mechanical properties increased, except for the Vickers hardness, and the values of the above properties were 526.80 MPa, 5.25 MPa·m1/2, 222.10 GPa, and 11.63 GPa, respectively.     

Go-no go avoidance discriminations in rats with simple “go” and compound “no go” signals: Stimulus modality and stimulus intensity

Four groups of 16 rats were trained in a go-no go discrimination with symmetrical negative reinforcement (active-passive avoidance task). A 2 by 2 design was used with stimulus combinations as one factor [light-go, noise/light-no go, (L⁺ NL^?) vs noise-go, light/noise-no go (N⁺ LN^?)] and noise intensity as the other factor (90 dB, high, vs 70 dB, low). The two N⁺ LN^? groups learned both active and passive avoidance responses much more rapidly than the L⁺ NL^? groups. In later phases of training, high noise intensity facilitated passive avoidance in the L⁺ NL^? condition and exerted a slight effect in the opposite direction in the other condition. While the differences in active avoidance learning were the same as in previous work on light and noise CSs, the interactions between stimuli of different modalities appeared to be more important than stimulus modality or stimulus intensity per se in determining rate of passive avoidance learning.     

基于CCD的回波信号图预处理软件设计与实现

随着光散射法测量PM2.5颗粒物浓度技术的发展,该技术成为测量大气PM2.5浓度的主要手段之一。散射激光雷达接收到的信号为回波信号图,通过建立回波信号图灰度值与PM2.5浓度的关系模型,实现对颗粒物浓度的测量。该技术需要对回波信号图进行预处理并提取散射信号,为了实现一种高性能、可实时测量的回波信号图预处理系统,设计一款基于Delphi7语言的实时图像处理软件。该软件通过对内存分配双缓冲区域、设置采集频率以及图像裁剪等方法,提高图片的采集与处理速率。实验结果表明,该软件操作简单、运行稳定且可扩展性较强。     

飞秒激光诱导硼酸盐基团的转变

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｓｉｎｃｅｔｈｅ 90’ｓ ,ｔｈｅｆｅｍｔｏｓｅｃｏｎｄｌａｓｅｒｔｅｃｈｎｉｑｕｅｓｈａｖｅｂｅｅｎｕｓｅｄｔｏｓｔｕｄｙｖａｒｉｏｕｓｕｌｔｒａ ｐｒｏｃｅｓｓｗｉｔｈｉｎｍａｔｅｒｉａｌｓ,ｂｅｃａｕｓｅｏｆｉｔｓｈｉｇｈｔｉｍｅ ｒｅｓｏｌｕｔｉｏｎ .Ｉｎｃｈｅｍｉｃａｌｒｅａｃｔｉｏｎｓ ,ｃｈｅｍｉｃａｌｂｏｎｄｂｒｅａｋｉｎｇｏｒｂｏｎｄｆｏｒｍａｔｉｏｎｉｓｏｎｔｈｅｓｃａｌｅｏｆｆｅｍｔｏｓｅｃｏｎｄ (10 - 15ｓｅｃ ｏｎｄ) [1] .Ｗｉｔｈｆｅｍｔｏｓｅｃｏｎ…     

大气激光雷达技术的研究进展

激光是20世纪60年代发明的最重大的科学技术成果之一,它是在有理论准备和生产实践迫切需要的背景下应运而生的.激光雷达目前涉及的应用领域十分广泛,本文着重介绍了其在大气方面的应用,其中主要包括对气溶胶、云和边界层的探测,大气成分的探测,温度的探测,反演PM2.5浓度的精度等研究.同时介绍了相关的原理,并给出部分实验测试结果,指出了大气激光雷达的未来发展趋势.     

Measurement of conversion efficiency of soft X-ray from 0.35μm laser-irradiated aluminum planar targets

Conversion efficiency of soft X-ray from 0.35 μm pulse laser-irradiated aluminium planar target at laser intensities 10¹³–10¹⁵ W/cm² on the Xingguang-II facility (laser energy 5–90 J, focal spot ⊃ Ф 200 μm full width of half maximun (FWHM) 400–800 ps) was measured. A simple model was given to explain soft X-ray conversion efficiency. In this model, because of the heat conduction from the laser-heated spot, the conversion was very small at lower irradiance limit, while at higher limit it was bounded by the energy lost in blow off plasma. Consequently, at the laser intensity around 2×10¹⁴ W/cm², the X-ray conversion efficiency reaches a maximum. Project suppoted by Shanghai Leading Academic Discipline Foundation (Grant No. T0104), and Science Foundation of Shanghai Municipal Commission of Education (Grant No. 214680)     

Role of CD97stalk and CD55 as molecular markers for prognosis and therapy of gastric carcinoma patients

Objectives: To explore the mechanism of development and aggressiveness in gastric carcinomas by investigating the expression and role of CD97 and its cellular ligand CD55 in gastric carcinomas. Methods: Tumor and corresponding normal mucosal tissue, collected from 39 gastric carcinoma patients, were examined by immunohistochemistry and RT-PCR for the expression of CD97 and CD55. Results: CD97^stalk was strongly stained on scattered tumor cells or small tumor cell clusters at the invasion front of gastric carcinomas. The expression of CD97^stalk was frequently observed in tumors of stage I and T1 gastric carcinoma patients. The expression of CD97^stalk between Stage I and Stage II, III, IV specimens showed significant difference (P<0.05), between T1 and T2, T3, T4 specimens also showed significant difference (P<0.05). Specimens with tumor invasion depth limited in mucosa of T1 specimens showed higher positive CD55 expression than specimens with the same tumor invasion depth in T2, T3, T4 specimens, the expression of CD55 between T1 and T2 T3, T4 specimens was significantly different (P<0.05). There was strong correlation between the distribution patterns of CD97^stalk and CD55 on tumor tissues (r=0.73,P<0.05). Signet ring cell carcinomas frequently contained strong CD97^stalk and CD55-staining. Conclusions: Our results suggest that CD97^stalk is probably involved in the growth, invasion and aggressiveness of gastric carcinomas by binding its cellular ligand CD55. CD97^stalk and CD55 could be useful as molecular markers for prognosis and therapy of gastric carcinoma patients. Project (No. 2004C34010) supported by the Science and Technology Bureau of Zhejiang Province, China     

A disputed evidence on obesity: comparison of the effects of <Emphasis Type="Italic">Rcan2</Emphasis><Superscript>−/−</Superscript> and <Emphasis Type="Italic">Rps6kb1</Emphasis><Superscript>−/−</Superscript> mutations on growth and body weight in C57BL/6J mice

It is widely accepted that body weight and adipose mass are tightly regulated by homeostatic mechanisms, in which leptin plays a critical role through hypothalamic pathways, and obesity is a result of homeostatic disorder. However, in C57BL/6J mice, we found that Rcan2 increases food intake and plays an important role in the development of age- and diet-induced obesity through a leptin-independent mechanism. RCAN2 was initially identified as a thyroid hormone (T3)-responsive gene in human fibroblasts. Expression of RCAN2 is regulated by T3 through the PI3K-Akt/PKB-mTOR-Rps6kb1 signaling pathway. Intriguingly, both Rcan2^?/? and Rps6kb1^?/? mutations were reported to result in lean phenotypes in mice. In this study we compared the effects of these two mutations on growth and body weight in C57BL/6J mice. We observed reduced body weight and lower fat mass in both Rcan2^?/? and Rps6kb1^?/? mice compared to the wild-type mice, and we reported other differences unique to either the Rcan2^?/? or Rps6kb1^?/? mice. Firstly, loss of Rcan2 does not directly alter body length; however, Rcan2^?/? mice exhibit reduced food intake. In contrast, Rps6kb1^?/? mice exhibit abnormal embryonic development, which leads to smaller body size and reduced food intake in adulthood. Secondly, when fed a normal chow diet, Rcan2^?/? mice weigh significantly more than Rps6kb1^?/? mice, but both Rcan2^?/? and Rps6kb1^?/? mice develop similar amounts of epididymal fat. On a high-fat diet, Rcan2^?/? mice gain body weight and fat mass at slower rates than Rps6kb1^?/? mice. Finally, using the double-knockout mice (Rcan2^?/?Rps6kb1^?/?), we demonstrate that concurrent loss of Rcan2 and Rps6kb1 has an additive effect on body weight reduction in C57BL/6J mice. Our data suggest that Rcan2 and Rps6kb1 mutations both affect growth and body weight of mice, though likely through different mechanisms.     

Investigation of absorption and scattering characteristics of kiwifruit tissue using a single integrating sphere system

For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters: the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts (including the flesh part, the seed part, and the seed-base part) were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient μ_a and the reduced scattering coefficient μ_s′ of kiwifruit tissue were calculated using the inverse adding-doubling (IAD) method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation. The mean values of μ_a and μ_s′ of different parts of the kiwifruit were 0.031–0.308 mm^?1 and 0.120–0.946 mm^?1, respectively. The results showed significant differences among the μ_a and μ_s′ of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits.     

On pythagorean triples of the form (i, i + l, k)

A Pythagorean triple is a triad of positive integers (x, y, z) which satisfy the Pythagoras’ equation x ² + y ² = z ². In this article, we shall consider triples of the form (i, i + 1, k), and the recurrence relations governing them. In the process, we also solve completely the equation i ²+ (i + 1)² = k ².     

外语学习动机及策略研究

学习动机在学习活动中起着至关重要的作用，本阐述了学习动机在外语教学中的作用，并对如何激发和培养学生外语的学习动机提出了几点建议，一是创造轻松的课堂环境；二是采用灵活多样的教学方法；三是正确发挥考试的导向作用，四是增强学生自信心，调动学习积极性。     

光影艺术融合建筑与景观

通过案例分析,总结光与影在景观和建筑之间的运用方法：光塑造形体虚实;光渲染情绪氛围;使用人工光源等,从而利用光达到的更好地景观效果．自然光和人工光源在景观与建筑之间起到了良好的中介作用．强调要合理地运用光．