古新世—始新世最热事件对地球表层循环的影响及其触发机制

古新世—始新世最热事件（PETM, Paleocene Eocene Thermal Maximum）是发生在古新世—始新世交界时的一次全球性的气候突变事件。它造成了大洋环流模式的突然倒转和海水盐度、大气湿度的迅速上升。海洋表层生态系统和陆地生态系统生产力迅速上升,许多属种的植物、动物、微生物生活范围向高纬区扩大;大洋底栖微生物发生集群灭绝。现代哺乳动物的主要属种（灵长类、奇蹄类及偶蹄类）产生,哺乳动物演化进程发生重大改变。地球表层碳循环系统发生不同程度的碳同位素负偏移,全球碳循环系统发生大规模搅动。对于PETM的触发机制,主流的观点认为是海底天然气水合物突然释放造成巨量甲烷迅速进入表层系统引发的碳循环系统内部反馈。而对于甲烷释放的原因,又存在着减压释放和热释放两种解释;此外还有科学家用岩浆作用和地外星体撞击来解释PETM的发生。     

彩色印刷复制中色差公式加权系数的计算和可接受阈值的评价

对印在有光泽的铜版纸上的9个颜色中心、共216种颜色色样进行了视觉评价和客观测量，得出了每种颜色中心的色差的可接受阈值；然后，应用视觉评价标准确定了可用于CIE94、CMC和CIE2000中的最佳l：c加权系数，并将△E94（l：c）、AEcmc（l：c）、DE2000（l：c）与△Eab进行了比较。     

General sky models for illuminating terrains

Sky models are quantitative representations of natural luminance of the sky under various atmospheric conditions. They have been used extensively in studies of architectural design for nearly a century, and more recently for rendering objects in the field of computer graphics. The objectives of this paper are to (1) describe sky models, (2) demonstrate how map designers can render terrain under various sky models in a typical geographic information system (GIS), (3) illustrate potential enhancements to terrain renderings using sky models, and (4) discuss how sky models, with their well-established standards from a different discipline, might contribute to a virtual geographic environment (VGE).

Current GIS hill-shading tools use the Lambertian assumption which can be related to a simple point light source at an infinite distance to render terrain. General sky models allow the map designer to choose from a gamut of sky models standardized by the International Commission on Illumination (CIE). We present a computer application that allows the map designer to select a general sky model and to use existing GIS tools to illuminate any terrain under that model. The application determines the orientations and weights of many discrete point light sources that, in the aggregate, approximate the illumination provided by the chosen sky model. We discuss specific enhancements to terrains that are shaded and shadowed with these general sky models, including additional detail of secondary landforms with soft shadows and more realistic shading contrasts. We also illustrate how non-directional illumination models result in renderings that lack the perceptual relief effect. Additionally, we argue that this process of creating hill-shaded visualizations of terrain with sky models shows parallels to other geo-simulations, and that basing such work on standards from the computer graphics industry shows potential for its use in VGE.     

A wavelet method for detecting S‐waves in seismic data

Seismic signals consist of several typically short energy bursts, called phases, exhibiting several patterns in terms of dominant frequency, amplitude and polarisation. We present a fast algorithm to detect the so‐called S‐phase in a three‐component seismic signal. This new approach combines traditional S‐phase detection methods and the discrete wavelet transform. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optimization of reinforced soil embankments by genetic algorithm

A Genetic Algorithm (GA) is described, which produces solutions to the cost optimization problem of reinforcement layout for reinforced soil slopes. These solutions incorporate different types of reinforcement within a single slope. The GA described is implemented with the aim of optimizing the cost of materials for the preliminary layout of reinforced soil embankments. The slope design method chosen is the U.K. Department of Transport HA 68/94 ‘Design Methods for the Reinforcement of Highway Slopes by Reinforced Soil and Soil Nailing Techniques’. The results confirm that there is a role for the GA in optimization of reinforced soil design. Copyright © 2000 John Wiley & Sons, Ltd.     

94/220 GHz星载雷达双波长比对非球形冰晶云参数敏感性分析

利用不同形状冰晶的散射特性,获得了非球形冰晶云的94/220 GHz测云雷达双波长比,探讨了非球形冰晶云的双波长比与云内微物理参数的关系,分析了衰减前后的星载雷达反射率因子及双波长比的垂直廓线。结果表明:（1）双波长比可以反映小到0.1 mm中值尺度的冰粒子,对粒子总数、谱的形状参数不敏感,对粒子大小、形状、云衰减较敏感。（2）雷达灵敏度一定时,星载雷达可测云厚与雷达波长、冰含水量（IWC）的垂直分布、云厚及衰减有关;没有进行衰减订正时,双波长比和衰减有关,冰含水量越大,波长越短,衰减越大,双波长比最大值与可探测云厚有关。两部雷达可探测冰含水量为0.001—0.1 g/m3、厚2 km的冰云;当云厚5 km、冰含水量垂直分布在0.001—0.2 g/m3时,云厚的94%基本可以被220 GHz云雷达探测到。（3）如果两部雷达气象方程中用水的介电因子,测量回波强度应进行介电因子的订正后再计算双波长比。      

Using slitless spectroscopy to study the kinematics of the planetary nebula population in M94

The planetary nebula populations of relatively nearby galaxies can be easily observed and provide both a distance estimate and a tool with which dynamical information can be obtained. Usually the requisite radial velocities are obtained by multi-object spectroscopy once the planetary nebulae have been located by direct imaging. Here we report on a technique for measuring planetary nebula kinematics using the double-beam ISIS spectrograph at the William Herschel Telescope in a novel slitless mode, which enables the detection and radial velocity measurements to be combined into a single step. The results on our first target, the Sab galaxy NGC 4736, allow the velocity dispersion of the stellar population in a disc galaxy to be traced out to four scalelengths for the first time and are consistent with a simple isothermal sheet model.     

中国城市空间反增长联盟的新特征——基于昆明市“94号院”的实证分析

以昆明市“94号院”为案例解构其中城市政体上层建筑,并对各方利益集团的相互关系进行详细分析。结果表明：中国城市政体具有连续性的特点,即增长联盟与反增长联盟之间并不是泾渭分明的关系,而是一个渐变的连续统,增长联盟内部也是连续变化的。同时,中国城市政体亦具有尺度性特征,即地理尺度越大,增长联盟与反增长联盟之间的分歧就越大,二者态度越鲜明,二元论愈显化,反增长联盟更能得到第三方的支持,在双方博弈中的话语权越大;尺度越小,二者态度越模糊,增长联盟具有更多的规则制定优势,更具有主导和优先权;同时,为了在博弈中获得更大话语权,尺度变迁成为双方关注的焦点,反增长联盟力求上推尺度,而增长联盟则尽力下压尺度。     

对非球形冰晶94 GHz云雷达后向散射和衰减的研究

针对94 GHz毫米波云雷达的数据处理,基于离散偶极子近似法(DDA)计算了几种非球形冰晶的后向散射及衰减效率,探讨了不同冰云模型下冰云的雷达反射率因子(Z_e)和衰减系数(k)及冰水含量(IWC,记作W)的关系。结果表明:(1)形状对冰晶的散射及衰减效率与粒子大小有关。(2)在实际的冰云中,将六角形冰晶和椭圆冰晶看做同体积的球形粒子将低估其衰减和后向散射。将聚合物冰晶看做等体积球形,将高估其后向散射及衰减,子弹花冰晶的后向散射与同体积的球形相比有减小也有增大,但是衰减比同体积球形的小。(3)冰云模型对Z_e-k、Z_e-W关系具有较大影响,假设滴谱相同的条件下,得到了具体冰云模型下对应Z_e-k、Z_e-W关系的系数。这些探讨为我国W波段云雷达的数据处理提供了参考。