一种基于知识的航空影像中道路半自动提取方法

利用线特征算子和多种线状地物跟踪方法建立了一种基于知识的航空影像中道路半自动提取方法。该算法计算量小 ,判断速度快 ,准确率较高 ,并且有较好的适应性。试验表明这是一种良好的道路提取方法。     

Giant HVC’s and the Rotation Curves of the Milky Way and M31

We have modelled, for the cases of Milky Way and M31, the effects on the galactic discs, of the arrival at high velocity (≥150 km s⁻¹) of giant HI clouds, with masses of up to 10⁸M⊙. Predictions are compared with the detailed structure of the observed rotation curves for these two galaxies. The model explains the rises and falls observed at large distances from the centre of each galaxy, distributed with a degree of regularity in radius, in terms of a specific type of perturbations driven by the infall of the high velocity clouds (HVC's) arriving from the intracluster medium of the Local Group. The underlying rotation curve is explained conventionally via the distribution of the baryonic and dark matter components of the galaxy in question. This scenario, though tested here on the two major Local Group objects, is in principle applicable to galaxies undergoing minor mergers with subgalactic mass gas clouds.     

Dark matter in dwarf spheroidals – II. Observations and modelling of Draco

We present stellar radial velocity data for the Draco dwarf spheroidal (dSph) galaxy obtained using the AF2/WYFFOS instrument combination on the William Herschel Telescope. Our data set consists of 186 member stars, 159 of which have good quality velocities, extending to a magnitude   V ≈19.5  with a mean velocity precision of ≈2 km s⁻¹. As this survey is based on a high-precision photometric target list, it contains many more Draco members at large radii. For the first time, this allows a robust determination of the radial behaviour of the velocity dispersion in a dSph.
We find statistically strong evidence of a rising velocity dispersion consistent with a dark matter halo that has a gently rising rotation curve. There is a <2 σ signature of rotation about the long axis, inconsistent with tidal disruption as the source of the rising dispersion. By comparing our data set with earlier velocities, we find that Draco probably has a binary distribution and fraction comparable to those in the solar neighbourhood.
We apply a novel maximum likelihood algorithm and fit the velocity data to a two parameter spherical model with an adjustable dark matter content and velocity anisotropy. Draco is best fit by a weakly tangentially anisotropic distribution of stellar orbits in a dark matter halo with a very slowly rising rotation law  ( v _circ∝ r ^0.17)  . We are able to rule out both a mass-follows-light distribution and an extended halo with a harmonic core at the 2.5 to 3 σ significance level, depending on the details of our assumptions about Draco's stellar binary population. Our modelling lends support to the idea that the dark matter in dwarf spheroidals is distributed in the form of massive, nearly isothermal haloes.     

强随机噪声条件下时窗类型局部线性化对TFPF技术的影响

为了更广泛地应用时频峰值滤波方法消减地震勘探记录中强随机噪声,本文比较详细地探讨了该方法在应用时需要处理的时窗选取、一个时窗内局部线性化等主要基础技术问题.经过时变时窗的仿真计算,运用多项指标比较,包括整体背景强弱、振幅谱、信噪比、均方误差、有效子波波峰波谷幅值、畸变程度,综合评价出（L0+Lx）时窗滤波的效果较理想.对于三角波这类简单类型的周期波,其时频峰值滤波效果与边线段平均曲率变化、时窗长度等条件有关,即三角波边线段平均曲率越大,滤波结果的均方误差越大;另外,边线段平均曲率增大时,选取的时窗长度有变小的趋势.总之,在地震勘探中应用时频峰值滤波方法消减强随机噪声时,一方面要合理地选取时窗参数,另一方面时窗参数又不能变化过大,以避免对有效子波波形产生畸变影响.     

我国市县地球物理监测资源评估

我国地球物理监测站网主要由GNSS、定点形变、重力、地电、地磁、地下流体六大观测站网组成,由国家站、省级站和市县站构成基本监测单元。市县站观测手段多、站点数量庞大,是地球物理监测站网的重要组成部分。为摸清市县站监测资源底数、统筹利用市县监测数据,中国地震局历时2年完成了我国市县地震监测资源评估工作。基于此项工作,本文从观测环境、观测系统、数据质量和预报应用四个方面对我国市县地球物理监测资源进行简要分析,评估结果显示: 37.8%的测项评估为合格,可直接纳入国家地球物理数据库管理,47.9%的测项评估为基本合格,可纳入国家市县数据库管理,14.3%的测项评估为不合格,需要停测或者优化改造。针对评估结果,简要分析了市县监测运维工作存在的主要问题并提出具体可行的解决建议,为提升市县站监测质量提供参考。     

天津局地暴雨特征及落区预报分析

利用常规观测资料分析2009-2011年天津地区33次局地暴雨天气过程的影响系统。对局地暴雨天气发生前的大气环境物理参数进行统计,对比不同影响系统下预报着眼点的差异。结果表明：天津局地暴雨主要发生在蒙古冷涡、东北冷涡、高空槽前以及高空槽后四种天气系统的影响下。蒙古冷涡系统下应以整层良好的水汽和涡旋系统东南象限深厚的辐合上升运动为着眼点;而东北冷涡系统下则需关注低层水汽条件充沛和中层强烈的辐合抬升;高空槽系统下在动力、水汽以及能量条件配合较为均衡;而槽后型系统影响下若发生局地暴雨,各种强对流参数特征则最为显著。在此基础上,通过典型局地暴雨过程对强降水落区进行诊断表明,天津构造加密探空由于充分考虑了近地面的温湿风特征,计算所得的可降水量、对流有效位能以及地面至3km高度的垂直风切变对局地暴雨落区具有良好的指示性。同时,个例研究也表明TJ-WRF对局地暴雨天气过程有较好的预报能力,综合应用模式物理量结果能较好地预报局地暴雨落区。     

Masses of the local group and of the M81 group estimated from distortions in the local velocity field

Based on high precision measurements of the distances to nearby galaxies with the Hubble telescope, we have determined the radii of the zero velocity spheres for the local group, R₀ = 0.96±0.03Mpc, and for the group of galaxies around M 81/M 82, 0.89±0.05Mpc. These yield estimates of M_T = (1.29±0.14)· 10¹² M_⊙ and (1.03±0.17)· 10¹² M_⊙, respectively, for the total masses of these groups. The R₀ method allows us to determine the mass ratios for the two brightest members in both groups, as well. By varying the position of the center of mass between the two principal members of a group to obtain minimal scatter in the galaxies on a Hubble diagram, we find mass ratios of 0.8:1.0 for our galaxy and Andromeda and 0.54:1.00 for the M82 and M81 galaxies, in good agreement with the observed ratios of the luminosities of these galaxies. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 5–22 (February 2006).     

State and Development： Changes in Livelihood Strategies in Garhwal with Special Reference to Ecotourism in the Gangotri Region

The object of the paper is to provide an insight into the changes in livelihood strategies of the people in the Garhwal Himalayas over time. From sustaining an economy based on transit trade and subsistence agriculture, there has been a shift towards tourism in recent times. This shift has been due to the tradition of pilgrimage to the higher reaches and also due to promotion by the state by developing infrastructure and providing incentives. The paper is divided into four parts. In the first part, the policies of the colonial state and the events leading to the destruction of forests and the impoverishment of the self-sustaining semi-pastoral economy in the Garhwal Himalayas are outlined. It is argued that the destruction of forests and subsequently, the economy of the Himalayas were directly responsible for the large-scale migration to the plains. This also led to further exploitation of forests by the people who were unfamiliar with any other form of livelihood. The paper also discusses the policies of the newly independent Indian state and sees them as an extension of the British policy of large-scale exploitation of Himalayan forests for the purpose of development and economic growth. In the third section, the growth of ecotourism as a direct outcome of the orocess of deforestation and as resulting from the need of society to conserve and yet to earn a livelihood is discussed. The case study of the Gangotrir egion examines the dilemma faced by the people of Garhwal in sustaining their livelihood, income or the development in the area. In addition, tourism has fostered monopolies of groups external to the region thereby contributing neither to the income or the development in the area. In addition, there is an added threat to the environment-deforestation, and erosion-a direct outcome of increased and unplanned tourism. Such problems demand state intervention and management of t.ourism. The conclusion to the paper asserts that in order that the requirements of the society to progress and to sustain itself in its natural habitat are not compromised, it is essential to increase the process of democratization by strengthening local structures and by vesting the community with the autonomy to determine its future. The paper therefore argues that ecotourism in the Himalayas undertaken without local involvement is not desirable. The constant need for local monitoring of external agencies or even of the State‘s participation and the need for re-evaluation of environmental standards are cumbersome details that add to the costs of promoting low-impact tourism. To be viable, ecotourism should be community based and the needs of the community, their ideas of conservation should be given prime importance and local community must be encouraged to review the standards governing conservation. Local structures should thus receive patronage and promotion, so that ecotourism becomes a dynamic facet of economic development.