饱和地基上条形弹性基础的摇摆振动

基于Biot动力方程,研究了饱和均质弹性半空间上弹性条形基础的摇摆振动问题。通过Fourier积分变换求解了饱和土的动力控制方程,然后结合基础底部为混合边界的条件得到了弹性条形基础的摇摆振动对偶积分方程,利用正交多项式将对偶积分方程转化为求解一组线性代数方程组,同时利用复合Simpson法则,得到了动力柔度系数的表达式,通过算例得出了不同参数时地基动力柔度系数随无量纲频率的关系曲线。     

Opening up the secret city of Stepnogorsk: biological weapons in the Former Soviet Union

For almost 30 years, the Soviet government hid a large part of its biological weapons programme behind the façade of a network of civilian bio-technology facilities, called the All-Union Production Association Biopreparat, which were established to overcome deficiencies in molecular biology and genetics research. This paper, which is developed from a presentation given during an ESRC-sponsored seminar series, 'Locating Technoscience: The Geographies of Science, Technology and Politics', details the secret geography of one of those Biopreparat facilities located in Stepnogorsk, Kazakhstan. In doing this the paper illustrates how secret geographies can operate simultaneously, and at multiple scales. In the case of the Soviet bio-weapons programme, enacting secrecy at these multiple scales was made possible by the purposeful exploitation of 'dual use' technologies. By recounting a trip made to the Kazak facility, and using personal communications with UK and US experts involved with uncovering the Soviet bio-warfare programme, the author addresses some of the methodological challenges involved with researching secret geographies. This case study therefore looks in several directions – to work on the geographies of scale, research on the geographies of knowledge and work on secrecy in science and technology studies.     

Three‐dimensional vibration control of high‐tech facilities against earthquakes and microvibration using hybrid platform

High‐tech equipments engaged in the production of ultra‐precision products have very stringent vibration criteria for their functionality in normal operation conditions and their safety during an earthquake. Most previous investigations were based on simplified planar models of building structures, despite the fact that real ground motions and structures are always three‐dimensional. This paper hence presents a three‐dimensional analytical study of a hybrid platform on which high‐tech equipments are mounted for their vibration mitigation. The design methodology of the hybrid platform proposed in this study is based on dual‐level performance objectives for high‐tech equipments: safety against seismic hazard and functionality against traffic‐induced microvibration. The passive devices (represented by springs and viscous dampers) and the active actuators are designed, respectively, to meet vibration criteria corresponding to safety level and functionality level. A prototype three‐story building with high‐tech equipments installed on the second floor is selected in the case study to evaluate the effectiveness of the hybrid platform. The optimal location of the platform on the second building floor is determined during the design procedure in terms of the minimal H ₂ cost function of absolute velocity response. The simulation of the coupled actuator‐platform‐building system subjected to three‐dimensional ground motions indicates that the optimally designed hybrid platform can well achieve the dual target performance and effectively mitigate vibration at both ground motion levels. Copyright © 2009 John Wiley & Sons, Ltd.     

一种面向栅格的空间-属性双重约束聚类方法

针对栅格数据,传统聚类方法大都基于专题属性进行聚类,分裂了栅格对象的空间特性与专题属性,而兼顾空间与专题属性的现有空间聚类方法又存在算法复杂、参数设置多等问题,因此本文提出了一种面向栅格的空间-属性双重约束聚类算法（A Raster-oriented Clustering Method with Space-Attribute Constraints, RoCMSAC）。RoCMSAC利用栅格数据空间邻域和空间连通特性,重新定义栅格簇的相似性度量准则,通过属性均质簇生成,空间相邻栅格簇合并和空间邻近栅格簇合并3个步骤对栅格数据进行空间-属性双重约束聚类。利用太平洋海域海表温度栅格数据对算法的可行性以及有效性进行验证,并与现有算法进行对比分析。通过实例验证与对比发现：① RoCMSAC方法能够保证栅格簇空间域的邻近性和属性域的均质性;② RoCMSAC方法可发现复杂形状的栅格簇,且算法时间复杂度低,需输入参数较少。     

基于卡方检验的抗差自适应Kalman滤波在变形监测中的应用

在抗差Kalman滤波的基础上引入双自适应因子,分别对动态模型不准确和观测模型存在粗差进行调节,构建双自适应因子滤波模型。针对抗差自适应Kalman滤波效率较低的缺点,通过构建基于卡方检验的抗差自适应Kalman滤波,先用卡方检验对粗差进行检验,再调用抗差自适应Kalman滤波进行处理。工程实例表明,双自适应因子滤波模型可以很好地抵御粗差,并减弱模型不精确的影响。基于卡方检验的抗差自适应Kalman滤波不仅可以削弱粗差对滤波估值的影响,而且可以提高数据处理的效率。     

钢支撑及框架-中心支撑双重抗侧力体系研究现状、不足及改进

本文在总结钢支撑滞回性能及高层双重抗侧力体系研究现状的基础上，分析了现象学、物理学及有限元3种钢支撑模拟方法的优缺点，并针对现有支撑模拟方法及支撑疲劳累积损伤研究的不足提出了可行的改进方法。分析了框架一中心支撑双重体系研究中若干关键性问题之后，指出了我国《高层民用建筑钢结构技术规程》(JGJ99-98)等有关规范中关于双重体系设计相关条款存在的分歧及不足，并提出了通过双重结构体系在罕遇地震下的反应特性模拟分析来统一认识的建议。     

双星敏感器在轨相对热变形分析及修正

为了获取高质量的对地观测遥感图像,除了有效载荷成像的高分辨率外,还需要卫星平台姿态具有高精度。在双星敏联合姿态确定时,星敏感器之间的相对热变形会对姿态确定带来不利影响,需对热变形误差进行辨识与修正。通过对某遥感卫星在轨遥测数据进行分析,建立了星敏感器在轨结构热变形模型,并对星敏感器热变形进行了在轨修正。采用辨识得到的傅里叶级数的热变形模型参数,对星敏热变形进行在轨修正后,提高了星敏感器的测量精度,减小了星敏感器之间的热变形误差对姿态确定精度的影响,对得到高质量的对地观测遥感图像具有很大的工程应用价值。     

利用卷积神经网络开展偏振雷达定量降水估测研究

利用偏振升级改造后的广州新一代天气雷达（CINRAD/SAD）水平反射率ZH、差分传播相移率KDP、差分反射率因子ZDR和广东佛山219个地面气象自动站雨量数据,形成不同偏振量组合的8个数据集。基于卷积神经网络（CNN）,建立雷达定量降水估测网络架构QPEnet, 并将该架构用于雷达定量降水估测（QPE）,评估结果表明：数据集通道数N的增加可降低QPEnet的定量降雨估测的均方根误差（RMSE）,并提高相关系数（CORR）;对于由ZH形成的数据集Z、Z_1~3 km和Z_6 min,随着通道数N的增加,数据集Z、Z_1~3 km和Z_6 min的性能逐步得到提高,数据集Z_1~3 km和Z_6 min的均方根误差（RMSE）分别是4.71和3.78,比数值集Z分别降低了1.3%和18.7%;数据集Z_1~3 km和Z_6 min的CORR分别是0.82和0.88,比数据集Z分别提高了2.5%和10.0%;对于ZH、KDP和ZDR偏振量组成的数据集里面,数据集Z_ZDR_KDP的拟合性能最好,RMSE为3.97,比数据集Z的RMSE降低了14.6%,CORR是0.86,比数据集Z提高了7.5%;分别对0.6～5 mm、5～10 mm、10～20 mm、20～30 mm、30～40 mm、40～50 mm和50 mm以上的7个降水量级的均方根误差（RMSE）、平均偏差比（MBR）、平均误差（AE）和相对误差（RE）等的统计结果表明,数据集Z_6 min降雨精度最高。     

“双循环”新格局与京津冀高质量协同发展——基于价值链分工和要素流动视角

京津冀地区经历了从竞争、合作到迈向高质量协同发展的过程,在“双循环”新发展格局下,京津冀协同发展面临着新挑战和新目标,亟需实现创新驱动经济转型。本文从价值链分工和要素流动等方面入手,系统梳理了京津冀在“外循环”和“国内大循环”中的价值链地位和辐射能力,以及以“京津冀小循环”为表现的京津冀协同发展现状。结果发现,京津冀在“外循环”中没有形成世界级城市群相对应的技术分工和知识生产能力,处于价值链较低附加值环节;在“国内大循环”中,京津冀占据价值链高附加值环节,并向外输出技术和资本,但吸引和辐射力有限。进一步探究发现,京津冀在“外循环”中相对边缘化的重要原因之一是“京津冀小循环”尚未打通,创新成果难以在城市群内部转化,从而未能实现“创新驱动经济增长新引擎”的城市群定位目标。下一阶段京津冀城市群应以水平知识链、梯度创新链为驱动,构建城市群垂直产业链。具体来说,“内循环”中应着力打造“北京研发—天津高端制造—河北物流服务”协同格局,“外循环”中构建以知识转移和市场突破为核心的“北京创新集聚溢出—河北综合制造—天津研发、航运”分工模式,逐步实现“内循环”反哺“外循环”。     

一种适用于多制式移动通信的双阻双频段天线

为了满足现代多制式移动通信频段的需求,设计一种可覆盖大部分移动通信频段的超宽带天线。同时为了抑制与其他通信设备的干扰,在天线馈线旁加载两个U型谐振环用来获得双阻带特性。天线总尺寸为200mm×150 mm×3 mm。通过调整U型环可以获得不同的阻带特性。设计结果表明:天线工作在750~1150MHz和1650~2450MHz。该天线成本低、易集成,同时具有全向辐射特性,适用于现代移动通信需要。