双线偏振多普勒雷达资料质量分析

以中国气象科学研究院灾害天气国家重点实验室的车载C波段双线偏振多普勒雷达（CPDRW）2011年完成升级改造后观测的一次大范围层状云降水过程资料为例,讨论了该设备改造后探测资料质量的改进情况及其对降水粒子的探测性能,同时利用模糊逻辑法结合地物的常规特性和偏振特性,建立了一种运用双线偏振雷达观测资料识别地物及地物与降水混合回波的方法,并利用该雷达的观测资料对识别结果进行了分析检验,最后统计分析了降水回波的差分反射率因子(Z_DR)、零滞后互相关系数(ρ_HV（0）)与信噪比的关系,以及系统初始相位的稳定性及降水资料的一致性。分析结果表明,在常规参量的基础上添加偏振参量并采用模糊逻辑法构建的综合识别模式和常规识别模式都能较好地识别地物,但综合识别模式明显改善了常规识别模式0速度区过度识别的问题,且在地物与降水回波混合的情况下叠加混合回波识别模式具有更加明显的优势。雷达改造前,Z_DR及ρ_HV（0）在信噪比小于25 dB时受噪声影响很大,测量值存在较大误差,资料变得不可信;通过这次的升级改造,其信噪比探测阈值由25 dB降低到15 dB。系统初始相位比改造前更加稳定,随仰角和时间的波动性更小。利用垂直扫描数据进行系统误差订正后的Z_DR资料能较好地反映降水粒子的实际情况,Z_DR随信噪比的变化较之改造前更加平稳,而对差传播相移Φ_DP进行分类处理后拟合的差传播相移率K_DP资料也与实际情况一致。     

1981-2012年辽宁省春播期土壤相对湿度月尺度数据重建

辽宁省现有测站春播期土壤相对湿度数据存在不连续性及长时间序列缺失问题。以海城站为例,分析现有土壤相对湿度（0-20 cm）与气象因子及临近站点土壤相对湿度的相关关系,构建海城春播期土壤相对湿度统计回归模型,模拟缺测时段春播期土壤相对湿度。进而以此方法重建辽宁省20个观测站1981-2012年春播期土壤相对湿度月尺度数据。结果表明：海城土壤相对湿度与降水量和秋季封冻雨关联较大,相关系数分别超过0.60和0.30,与同期临近站点本溪站土壤相对湿度相关性也超过0.40,依据该3要素构建的4月和5月土壤相湿度统计回归模型复相关系数R2分别达0.79和0.77,模拟结果与实测资料平均相对误差为2.6 %,模拟效果较好;对辽宁省其他数据缺失站点构建的回归模型复相关系数均高于0.50,模型拟合精度优于85 %,拟合值和实测值平均相对误差基本控制在15 %以内,较好完成辽宁省20个测站1981-2012年春播期土壤相对湿度月尺度数据重建。     

复杂网络牵制控制概述

本文回顾了十多年来复杂网络牵制控制的研究进展,对复杂网络现有的牵制控制算法进行了归纳分类,然后基于网络拓扑及节点动力学特性讨论了网络牵制控制的一些必要或充分条件.针对牵制控制下的复杂网络,重点论述了牵制节点的选取策略,综合分析了牵制节点个数、耦合强度、牵制控制增益及节点动力学等因素对复杂网络牵制控制的影响,讨论了具有合作竞争关系符号网络牵制控制的进展,并简要介绍了复杂网络牵制控制的一些应用前景.最后,就复杂网络牵制控制将来的研究方向提了一些建议及展望.     

三维可视化填图在晴隆锑矿外围勘查中的应用

三维可视化技术在辅助传统地质方法工作的同时,将复杂地质体形态、地质构造情况以三维的形式表现出来,呈现较丰富的的视觉效果。首次把三维可视化技术应用于贵州晴隆锑矿田找矿,有较好效果。     

浅谈如何编好对外援助项目的工程概算

准确的工程概算和资料搜集对.外项目的顺利实施起着非常重要的作用,分析了编制.外工程概算的内容及方法,提出了做好编制工程概算应注意的问题。     

Top layers charaterization of the Martian surface: Permittivity estimation based on geomorphology analysis

Mars Express spacecraft inserted successfully Martian orbit at the end of 2003. On board this probe, a radar instrument called MARSIS (for Mars Advanced Radar for Surface and Ionosphere Sounding) is looking for water inside the first kilometers of Martian crust. To support MARSIS planning and data inversion, Laboratoire de Planétologie de Grenoble developed a MARSIS signal simulator.We show in this paper that MARSIS can also characterize some surface features, in addition to subsurface water and ionosphere sounding. We study a Martian surface region of special interest: Nilokeras Mensae, inside Acidalia Planitia. We discuss the previous geological studies of this region, and show the geomorphologies analyze of this surface area could lead to a simple terrain model. Then, we present a possible data inversion scheme and applying the MARSIS simulator, we test a first radar data inversion.Finally, we will show that complete dielectric characteristics of surface top layers can be retrieved, at least as often Mars Express flies over some layered terrain (at wavelength scale).     

Photometric calibration of the LASCO-C2 coronagraph for Solar System objects

We present a photometric calibration of the SOHO/LASCO-C2 coronagraph appropriate to Solar System objects based on the extensive analysis of all stars down to magnitude V=8 which transited its field-of-view during the past nine years of operation (1996-2004). An automatic procedure was developed to analyze some 143,000 images, and to detect, locate and measure those stars. Aperture photometry was performed using three different aperture sizes and the zero points of the photometric transformations between the LASCO-C2 magnitudes for its three filters (orange, blue and red) and the standard V magnitudes were determined after introducing a correction for the color of the stars. The calibration coefficients for the surface photometry of extended sources were then derived from the zero points. An analysis of their temporal evolution indicates a slight decrease of the sensitivity of LASCO-C2 at a rate of ∼0.7% per year.     

Gamma–hadron separation methods for the VERITAS array of four imaging atmospheric Cherenkov telescopes

Ground-based arrays of imaging atmospheric Cherenkov telescopes have emerged as the most sensitive γ-ray detectors in the energy range of about 100 GeV and above. The strengths of these arrays are a very large effective collection area on the order of 10⁵ m², combined with excellent single photon angular and energy resolutions. The sensitivity of such detectors is limited by statistical fluctuations in the number of Cosmic-ray initiated air showers that resemble γ-ray air showers in many ways. In this paper, we study the performance of simple event reconstruction methods when applied to simulated data of the Very Energetic Radiation Imaging Telescope Array System (VERITAS) experiment. We review methods for reconstructing the arrival direction and the energy of the primary photons, and examine means to improve on their performance. For a software threshold energy of 300 GeV (100 GeV), the methods achieve point source angular and energy resolutions of σ_63% = 0.1° (0.2°) and σ_68% = 15% (22%), respectively. The main emphasis of the paper is the discussion of γ–hadron separation methods for the VERITAS experiment. We find that the information from several methods can be combined based on a likelihood ratio approach and the resulting algorithm achieves a γ–hadron suppression with a quality factor that is substantially higher than that achieved with the standard methods used so far.     

A fast method for finding bound systems in numerical simulations: Results from the formation of asteroid binaries

We present a new code (companion) that identifies bound systems of particles in O(NlogN) time. Simple binaries consisting of pairs of mutually bound particles and complex hierarchies consisting of collections of mutually bound particles are identifiable with this code. In comparison, brute force binary search methods scale as O(N²) while full hierarchy searches can be as expensive as O(N³), making analysis highly inefficient for multiple data sets with N?¹⁰³. A simple test case is provided to illustrate the method. Timing tests demonstrating O(NlogN) scaling with the new code on real data are presented. We apply our method to data from asteroid satellite simulations [Durda et al., 2004. Icarus 167, 382-396; Erratum: Icarus 170, 242; reprinted article: Icarus 170, 243-257] and note interesting multi-particle configurations. The code is available at http://www.astro.umd.edu/zoe/companion/ and is distributed under the terms and conditions of the GNU Public License.