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关键词： Accerator   Cavity   Nb3Sn   Niobium-3 Tin   SRF   Temperature-mapping  

摘要： Niobium-3 Tin (Nb3Sn) is the most promising alternative material for Superconducting Radiofrequency (SRF) particle accelerator cavities. Current SRF accelerators use superconducting niobium accelerator cavities, which are nearing their theoretical limits of performance. Nb3Sn promises increased quality factors, twice the operational temperature (4.2 K instead of 2K), and almost twice the theoretical accelerating gradient--96 MV/m in a TESLA elliptical style cavity. These advances can reduce the size and complexity of particle accelerators while simultaneously making them more efficient. The capability of operating at 4.2 K enables the creation of small-scale superconducting accelerators that are run off cryocoolers and could be used in research and industrial applications. Current Nb3Sn cavities achieve quality factors of 2·1010 at 4.2 K. The accelerating gradient, however, is limited far below the theoretical potential of this material, with the best recorded reaching 24 MV/m. In this work we present studies on what is limiting the maximum accelerating gradients in these cavities. We study cavity performance under RF testing, make dynamic measurements of cavity heating during operation, study samples with microscopy, and develop models of Nb3Sn material growth. In the process we develop new diagnostic tools for SRF development: a dynamic/high speed temperature mapping system that measures the spatial heat distribution on a cavity at 50 ksps, and high-power test system for measuring the ultimate critical fields (theoretical limit of the accelerating gradient) of new materials. We explore models of cavity losses/heating that limit the accelerating gradient and propose modifications to the material growth process to create Nb3Sn cavities with higher accelerating gradients and quality factors. We conclude with results from a new cavity coating wherein we have suppressed multi-gap superconductivity that has been seen in these cavities and was a limitation to the quality

关键词： VDT办公室照明   光分布   亮度分布   视觉功效   作业绩效  

摘要： 本文依托国家自然科学基金面上项目(项目名称:基于体质适应性的VDT办公光环境研究,编号:51778081)。当前,视觉显示终端(Visual Display Terminal)在工作中的应用日渐普遍,依赖计算机执行的工作任务增多,VDT作业目前已成为现代企业中最具代表性的工作模式。VDT作业者的职业健康问题是目前社会普遍关注的热点。VDT作业与非VDT作业相比,其更易引发工作者的视疲劳和心理疲劳等问题,进而影响工作表现。因此探索有利于VDT作业者的视觉功效和作业效率的办公室光环境是有研究意义的。建筑勘察设计企业的从业人员每日持续使用VDT的时间长、强度大,视频显示终端画面经常在负对比(例如Word软件等)和正对比(例如Auto CAD软件等)间来回切换再加上思考和电脑绘图同时进行,设计师们的脑力劳动较VDT文字编辑等简单工种更为繁重,神经系统紧张程度更高,因此尤其需要被高度关注。因此本研究针对建筑勘察设计企业的开放式VDT绘图室的光环境展开研究,研究的光环境指标为光分布,通过改变照明方式来改变光分布,通过测量亮度分布来量化光分布。(1)理论研究:本部分通过梳理国内外文献,从照明标准、VDT办公室照明方式和光分布相关理论入手,对VDT办公室照明设计进行详细分析后发现:TAL照明方式在VDT开放式办公室具有能满足个人光环境偏好且节能的应用优势,针对其容易使室内显得阴暗的问题,发现可行性较高的措施是对墙面进行照明,提升空间明亮感,为后续的研究提供理论支撑。(2)调查研究:本部分通过对中国的建筑勘察设计企业的青年VDT作业者进行问卷调查后发现,“90”和“00”后青年设计师群体的VDT作业强度过高,是青年设计师群体中更需要高度关注的群体,为后续的研究细化了研究对象。此外调查结果显示TAL照明方式是被青年设计师们接受的,表明了研究的现实意义。(3)实验室模拟实验:本部分通过两个实验室模拟实验——亮度分布偏好选择实验和亮度分布对比评价实验发现:①:青年设计师普遍感到满意的是低平均亮度的工作光环境,具体的光环境参数为正对比显示界面下屏幕亮度0.35cd/m左右、水平桌面中心区域39 cd/m左右、水平桌面边区域40cd/m左右、背景墙面26cd/m左右。当需要较高的水平桌面亮度进行纸面阅读等作业时,青年设计师倾向于仅增加桌面中心区域的亮度,而不喜好空间整体变亮。因此在未来的VDT开放式绘图室人工照明设计中应尽量避免恒定高亮度水平。②:桌面亮度的均匀度似乎不会影响青年设计师对VDT作业光环境的满意度评价。从主观满意度、视觉功效和作业绩效来看追求均匀的水平桌面亮度分布并无实际意义,显示了VDT绘图室的照明节能潜力。③:色温似乎并不影响VDT作业者的亮度分布主观偏好。青年设计师普遍不适应的是整体较亮的光环境,在正对比和负对比显示界面下有相同的趋势,因此建议进行VDT开放式绘图室人工照明设计时,使用TAL照明方式,一般照明提供工作周围和背景区域的较低平均亮度水平,当有高亮度作业需求时再开启局部照明对作业中心区域进行补光。最后,对上述3部分研究成果进行总结分析,并对之后的研究工作进行展望,以期结论能为VDT开放式绘图室光环境的设计提供新思路,为TAL照明设计提供参考。

关键词： SPOC   混合学习模式   艺术设计   计算机绘图  

摘要： 高职艺术设计类专业教学长期沿用传统的教学模式,出现诸多问题,需适应新时代学生的学习特点进行信息化教学改革。项目结合高职艺术设计类学生特点构建SPOC混合学习模式,并在通用专业基础课计算机绘图实践应用,结果表明:SPOC混合学习模式在提高艺术设计类学生自主学习能力、信息化能力等方面有积极的作用,而且能够明显提高学生的学习兴趣、学习效果以及学习效率等。

关键词： Aerospace engineering   Computer science   Engineering   Mathematics   Operations research   Remote sensing   Robotics   Transportation  

摘要： This thesis investigates the design of an autonomous navigation algorithm in GPS-denied environments. The performance of the current navigation solutions is dictated by the change in the operating environment. As a result, in the past two decades, various Simultaneous Localization and Mapping (SLAM) formulations have been proposed to adapt various operating conditions and improve robustness. Multi-sensor fusion has been one of the solutions. Every sensor has its own strengths and weaknesses to a given environment. By using multiple sensors, the weaknesses of one sensor can be counterbalanced by strengths of others. To this end, the proposed approach presents a novel tightly-coupled LIDAR-Inertial-Visual Odometry in a sliding window framework. Inertial measurement unit (IMU) provides high frequency inertial measurements, LIDAR provides an accurate map of surrounding, and visual odometry provides detailed information about the scene. Current state-of-the-art multi-sensor fusion works around coupling various odometry solutions in a pose-graph formulation. Such method is referred as loosely-coupled system where each sensor provides the robot pose estimate with uncertainty. However, a tightly-coupled system where all the sensor measurements are optimized in a factor-graph has been shown to achieve better accuracy and robustness compared to a loosely-coupled framework. In particular, the vision community has seen major improvements since adopting a tightly-coupled sensor fusion framework. This thesis investigates the performance of a tightly-coupled multi-sensor fusion in an optimization level. Further, inspired by the recently developed invariant extended Kalman filter (IEKF), the proposed odometry solution provides an accurate uncertainty estimate using matrix Lie group theory. The pipeline is validated, tested, and compared to the state-of-the-art SLAM algorithms.

关键词： 小学数学   绘图教学   策略  

摘要： 新课改背景下,有效开展小学数学的绘图教学活动,可以加深学生对于绘图的认识,帮助他们构建完整的知识体系,同时促进小学生对数学知识的有效学习,揭开素质教育的崭新篇章。在小学数学绘图教学的实践环节,教师应采用多种策略,活跃小学生的数学思维,提高绘图教学质量,形成和谐的师生互动关系,这对于小学生数学素养的不断进步也将起到一定的促进作用。

摘要： 隋鸿锦、于胜波教授所著《零基础绘图学解剖》已于2020年9月由人民卫生出版社出版。人体解剖学知识常被认为枯燥和难以记忆。本书以满足人体解剖学的教学与学习需要为目的,力求适合解剖学教与学的实际需求,从《系统解剖学》与《局部解剖学》中共选取130个较难讲解和理解的内容,制作出系列绘图。每套系列图均将复杂的解剖绘图进行分解简化,帮助更多没有绘图技巧,甚至是零基础的青年解剖学教师,可以通过本书的学习,能在课堂上轻松地绘制出既简练又通俗易懂的粉笔图画。同时,医学生在学习解剖绘图过程中,对难理解的形态结构知识达到充分理解。书中还收录了近年来在中国解剖学会举办的"全国医学生解剖绘图大赛"的部分优秀作品。本书的读者主要面向医学生、研究生、解剖学青年教师以及解剖学爱好者。

关键词： 前哨淋巴结活检   淋巴绘图   早期外阴癌  

摘要： 外阴癌在女性恶性肿瘤患者中并不罕见,多为鳞状细胞癌,且以淋巴结为主要转移性病灶.外阴癌根治术及淋巴结清扫术是临床常见的治疗手段,但术后并发症发生风险较高.因此,早期外阴癌明确诊断,并采取针对性治疗措施,能够提升治疗效果,改善预后.前哨淋巴结是指最先发生恶性肿瘤转移的淋巴结,能够反应整个区域淋巴结区域.淋巴绘图是指在肿瘤原发病灶附近注射某种标志物,进而暴露最先接受标志物引流的淋巴结,降低辨认前哨淋巴结的难度.本文从前哨淋巴结活检、淋巴绘图、早期外阴癌诊疗等方面入手,阐述前哨淋巴结活检及淋巴绘图在早期外阴癌中的应用进展.

摘要： 《解剖学基础》是一门阐述正常人体形态结构,功能位置的科学,也是中职护理专业学生必学的一门专业基础学科,在培养21世纪护理专业人才,提高新时代护理工作人员的综合素质有着重要意义.在中职护理专业教学中,教学效果难以提高的关键因素有三点:一是概念名词繁多,难以记忆理解.刚从中考失败中进入职业教育的她们,本来也是充满求知欲的,也很想在新环境中成就自我,然而,面对如此庞大的名词概念,感觉哪一句都是重点,都要记忆,到头来还联系不到一起解决实际问题,学着学着就茫然了;二是中职护理专业的学生98％以上是女生,学习习惯差、基础差,没有思考问题的习惯,遇到问题不能迎难而上,缺少总结归纳的习惯,少了想象思维,阶段学习中得不到预期的效果就放弃了;三是中职学校的护理教学设施还不全面,都是从过去职业学校的基础上发展到医药卫生类的,缺少人体模型等教学设备,学生的直观认识很难得到满足,兴趣难以提起.

关键词： 机械制图与CAD绘图   识图绘图   UG建模  

摘要： 《机械制图与CAD绘图》是一门专业基础课,主要让学生学会识图绘图,培养学生正确的作图习惯,使其能够精益求精,注重绘图质量.学好制图课,学生才能更好地学习其他课程,才能看懂图形、分析图形.制图课的入门学习对一些缺乏空间思维能力的学生而言,确实是不小的挑战,他们无法根据三维实体绘制正确的二维图,或者无法根据二维图想象出实体模型.而UG具有强大的建模、制图功能,学生可以建立三维模型,从不同角度观察物体,或者对部件进行隐藏,便于观察部件形状,分析相邻表面间的连接关系,从而正确绘制二维图.

关键词： Mass estimation   Pose and thrust estimates   Maneuvering model  

摘要： Autonomous proximity operation missions in the space domain are a multi-faceted, studied problem. Performing such a mission around an uncooperative, unknown target presents many difficulties in estimating the relative pose of the target. If the target executes a controlled or uncontrolled (outgassing from a damaged satellite) low-thrust continuous maneuver, tracking or rendezvousing with the target becomes challenging and potentially dangerous especially in close proximity. A solution to this problem is desired such that the developed algorithm is amenable to onboard implementation, utilizes stereo vision, can estimate relative pose without initial relative information to the target, and can detect and estimate a continuous low-thrust maneuver. The developed algorithm presented in this dissertation utilizes an octree based approach to construct a three-dimensional map of the target while simultaneously estimating the pose in a multiplicative extended Kalman filter. A coarse volume estimate and probabilistic uncertainty mapping are extrapolated from the octree map and used as the initialization of a consider parameter in a consider variable state dimension (VSD) filter following maneuver detection. This framework switches to a thrusting model after the Mahalanobis distance passes a pre-defined threshold initializing the consider parameters and starting an interacting multiple model (IMM) filter. Assuming an evenly-distributed density, eight density models comprising the models in the IMM establish a mechanism for thrust states to be estimated by combining the best amalgamation of density models and the coarse volume estimate. Essentially, an online process is created to indirectly obtain mass information from the octree map without directly estimating it. Since target volume is not completely observable, it is not directly estimated and instead used as a consider parameter with an associated covariance obtained from the octree mapping uncertainty. Despite using coars