Exploring the atmosphere with lidars

In Part 1¹, we described the basic principle of the lidar (Light Detection and Ranging), the different scattering processes in the atmosphere and the Mie and Rayleigh lidars. In this part, we describe three other types of lidars: Raman lidar, differential absorption lidar (DIAL) and doppler lidar. A lidar system consists of a pulsed laser which sends out pulses of laser light and a sensor that senses the scattered light from the different molecules and aerosols in the atmosphere. The characteristics of the scattered light are used to determine the nature and amount of the constituents.     

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.     

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.     

Climate change,greenhouse gases and aerosols

The surface temperature of the earth is controlled by the balance between the absorbed solar radiation and the emitted infrared radiation. During the past 150 years the amount of carbon dioxide in the earth’s atmosphere has increased from 280 parts per million to more than 380 parts per million on account of burning of fossil fuels. The higher absorption of infrared radiation by the atmosphere (on account of higher carbon dioxide) has resulted in an increase in the surface temperature of the earth. The burning of fossil fuels has also caused an increase in sulphate and soot aerosols in the atmosphere. Both these aerosols reduce the solar radiation incident at the earth surface. Hence the surface of the earth has cooled on account of increase in aerosols. The sulphate aerosols have also cooled the atmosphere but the soot aerosols, which absorb solar radiation, have heated the atmosphere. The net impact of increase in carbon dioxide and aerosols has been an increase in the surface temperature of the earth by 0.7 degrees centigrade in the past 100 years. J Srinivasan is a Professor at the Centre for Atmospheric and Oceanic Sciences at Indian Institute of Science, Bangalore. He was a lead author in the second and fourth reports of the Intergovernmental Panel on Climate Change (IPCC).     

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。     

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。     

Virtual Reality Training Environments: Contexts and Concerns

Abstract

Virtual reality (VR) is a rapidly developing medium for training, entertainment and education. As yet little research exists into the efficacy of VR systems. Because of the current high cost of VR training systems, careful consideration should be given to their use. This article will discuss contexts where VR might be appropriate, present advantages and disadvantages of VR as a training technology, and present a case study of a VR training environment, used at the NASA Johnson Space Center in preparation for the repair of the Hubble Space Telescope.     

论流空间及其对地区经济发展的影响

信息和通信技术（Information and Communication Technologies,ICTs）的发展使空间已经或正在发生变革,具体表现为由静态的位空间向流动的流空间转变.流空间是信息社会占支配地位的空间形态.当前国外就流空间所展开的相关研究尚不成熟,国内更是少有人涉及.通过对流空间出现的技术支撑、流空间的出现背景、演进和空间结构4个方面的研究,对流空间本身予以揭示,并就其对地区经济发展的影响给以说明.     

水下激光目标单个回波信号滤波研究

研究水中激光雷达回波信号特征与处理,对水下目标的探测具有十分重要的意义。文章首先介绍了水下激光雷达的应用领域,然后从频域角度对激光雷达探测的回波信号特征进行了分析,最后根据探测回波信号的特征设计了一些对单个回波信号处理的方法以及特征量的提取方法,为今后激光雷达的探测和应用提供了理论基础和处理方法。     

LTSD与环境气压对激光诱导等离子体激发温度的影响

用高能量钕玻璃激光器烧蚀光谱标钢获得等离子体，以氩气作为保护气体，分析了LTSD(Len To Sample Distance，激光器透镜到样品表面的距离)和环境气压对等离子体激发温度的影响．结果表明，当激光束焦斑围绕样品表面上下移动时，等离子体激发温度的分布具有不对称性：当焦斑样品表面以下0．4mm左右时，等离子体的激发温度接近最大值；随着环境气压的增大，等离子体的激发温度明显增强．     

With Their Help: How community members construct a congruent Third Space in an urban kindergarten classroom

Through the use of narrative enquiry, this paper tells the story of how a kindergarten teacher in an all-girls' school incorporates family and community members' involvement to the construction of the congruent Third Space present in the classroom, and the ways the girls respond to this involvement, thereby providing a successful model for other schools in marginalized communities. In this study, the author sought to understand how this teacher and the community members' in this classroom create a congruent Third Space. This research enquiry includes the systematic use of the methodology portraiture with analysis of critical events. The portraits are titled: Mutual Desire for the Girls to Succeed and Community Members' Involvement. This paper moves Third Space theory towards praxis through concrete examples in an urban, kindergarten classroom.     

基于MATLAB和SPSS的空气质量数据建模及分析校准

利用Excel对空气质量国控点与自建点的"两尘四气"浓度日平均数据进行透视分析,得到二者相对应的变化趋势,发现大部分数据波动比较大;再利用SPSS对"两尘四气"数据与风速、压强、降水量、温度、湿度的相关性进行分析,结果表明,PM2.5、PM10与湿度呈中度相关,SO₂与风速、湿度基本不相关;最后以自建点整点时刻"两尘四气"的平均数据与国控点数据的差值为因变量,风速、压强、降水量、温度、湿度为自变量,用MATLAB进行多元线性回归,建立自建点数据的矫正模型,模型校验效果达到预期。     

Effect of relative humidity on non-refractory submicron aerosol evolution during summertime in Hangzhou,China

Relative humidity (RH) has a significant and complex effect on aerosols because of the aqueous phase process and gas-particle partition. The mass concentration and size distribution of organic aerosols, sulfate, nitrate, ammonium, and chloride were measured using high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS). These measurements were recorded from Aug. 5 to Sept. 23, 2016 in Binjiang District, Hangzhou, China, during which period more than 78% of the readings showed an RH over 60%, while the average temperature was 26 °C. Correlation analysis was applied to inorganic aerosol measurements while positive matrix factorization (PMF) was applied for source apportionment of organic aerosols (OA). The pattern of fixation of ammonium in aerosols changed as the RH increased, suggesting that RH enhances nitrate participation in particles, while sulfate is scavenged by droplets. All species of non-refractory submicron particles (NR-PM₁) showed an increase in their peak size as the RH increased. Primary OA (POA) continuously accumulated as the RH increased. When RH<60%, oxygenated OA (OOA) increased with increasing RH because of oxidation; semi-volatile OOA (SV-OOA) had a higher mass concentration during the daytime than at nighttime, indicating that the aqueous phase process and photochemistry synergistically affect the formation of oxygenated SV-OOA. When RH>60%, there was a relatively slow decrease in OOA, dominated by the wet removal effect rather than oxidation. The degree of oxidation of OA decreased as RH increased; this can be explained by most of the OOA with higher hygroscopicity being removed as droplets.     

语境表示式与记忆

HNC理论提出语言概念空间是由概念基元、句类、语境单元和语境组成的4层级结构体,每一层级都有自己的数学和物理表示式,分别表示成（HNCm）和（HNC-m）。本文在兼顾（HNC-（～4））的情况下,着重论述语境表示式（HNC-4）的物理意义以及（HNC-m）与记忆的关系,引进了共相记忆和殊相记忆这对重要概念：共相记忆区分为共相记忆1（概念基元）、共相记忆2（句类）和语言理解基因（语境单元）,都存在大脑皮层中,是思维主体无法意识到的,又称隐记忆;殊相记忆即（HNC-4）记忆形态,分为实记忆和虚记忆两种索引模式,存在海马中,又称显记忆。此外还有一种不经过理解的长时记忆叫鹦鹉记忆。     

Conflicts and resistance: potentials for democracy learning in preschool

The study aims to develop knowledge about learning for democracy in ECEC, through investigating acts of resistance in conflicts and examine these as potentials for democracy learning. The study is informed by Mouffe's theoretical ideas about conflicts as a prerequisite for democracy. The research questions are: What kind of conflicts can be identified in everyday interactions in preschool? How do children and teachers express and maintain resistance in conflicts? What potentials for democracy learning are there in such acts? Data consist of video observations of interactions in four Swedish preschools. The analyses of the interactions comprised various readings to identify expressions of conflicts and ways to communicate resistance. Ethical considerations were paramount to ensure that the studies met the ethical requirements. Identified conflicts are described in terms of qualities of space: (a) Space for diversity illustrates openness for different opinions to be articulated and heard: (b) Space for unity illustrates how alliance-building and authority create conditions and restrictions for opinions to be articulated, heard and/or neglected. Playfulness, courage and emotions are important traits for resistance and both agonism and antagonism appear to be at play. The conflicts identified offer both possibilities and obstacles in learning for democracy.     

Factors that influence learning during a scientific field trip in a natural environment

This study deals with the educational effectiveness of field trips. The main purpose was to obtain insight concerning factors that might influence the ability of students to learn during a scientific field trip in a natural environment. The research was conducted in the context of a 1-day geologic field trip by 296 students in Grades 9 through 11 in high schools in Israel. The study combined qualitative and quantitative research methods. Data were collected from three different sources (student, teacher, and outside observer) in three stages (before, after, and during the field trip). Using observations and questionnaires we investigated: a) the nature of student learning during the field trip, b) student attitudes toward the field trip, and c) changes in student knowledge and attitudes after the field trip. Our findings suggest that the educational effectiveness of a field trip is controlled by two major factors: the field trip quality and the “Novelty space” (or Familiarity Index). The educational quality of a field trip is determined by its structure, learning materials, and teaching method, and the ability to direct learning to a concrete interaction with the environment. The novelty space consists of three prefield variables: cognitive, psychological, and geographic. The learning performance of students whose “Novelty Space” was reduced before the field trip was significantly higher than that of students whose “Novelty Space” had not been so reduced. Thus, the former group gained significantly higher achievement and attitude levels. It is suggested that a field trip should occur early in the concrete part of the curriculum, and should be preceded by a relatively short preparatory unit that focuses on increasing familiarity with the learning setting of the field trip, thereby limiting the “Novelty Space” factors.     

浅谈高职院校学风建设

学风是读书之风、治学之风、做人之风,是一所院校的灵魂和气质所在,更是一个学院的立院之本。目前,高职院校的学风普遍都存在着一些问题,并引起社会的广大关注。改善高职院校学风,有助于高职院校自身的长远发展及社会对高职教育的认同。     

实境·幻境·空境——《雪国》三元空间叙事探析

空间与时间是不可分割的统一体,但是由于种种原因,长期以来叙事学研究的焦点是叙事作品的时间维度,而忽略了空间维度,其实在叙事研究中对空间维度的研究同样重要。空间在叙事作品中可以参与叙事和影响叙事。川端康成正是在《雪国》中通过书写第一空间——“实境”、第二空间——“虚境”以及第三空间——“空境”来传达对生命的思考和憧憬的。     

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．     

数据中心列间空调气流组织分析与优化

以小型数据服务机房为研究对象,对机房使用列间空调后的气流组织进行了分析。利用CFD(流体动力学)软件对房间内的气体流动情况进行模拟,绘制温度、矢量风速计算云图,对比了冷通道封闭前后房间温度场、风场的变化,分析封闭前后室内换热情况。研究发现,冷通道封闭后离地0.5、1.5m处平均温度较封闭前平均温度下降2℃左右,机柜顶面下降1℃左右。封闭冷通道能够优化气流组织,有效避免气流短路,机房内局部热点消失,无效换热减少。