新疆焉耆盆地绿洲景观的空间格局及其变化

通过GIS技术的叠加和提取功能建立了焉耆盆地两个时间段的景观类型转移矩阵。在此基础上,分析了焉耆盆地内部绿洲景观类型的动态演化过程和空间分布特征。结果表明:焉耆盆地经过近40年的土地开垦后,人工绿洲呈现出上升的趋势,农田向自然绿洲和荒漠的扩张在整个研究阶段均可见;农田开垦的对象表现为从草地(含部分沼泽地)→多汁木本盐柴类荒漠→超旱生灌木半灌木荒漠迁移,体现了农田绿洲开垦从易到难,自然绿洲不断缩小,人工绿洲不断扩大的过程;对土地和水资源的不合理利用,导致盆地内湖泊水体、湖泊周边及农田绿洲出现明显的生态退化。焉耆盆地今后的规划和发展必须高度重视人工绿洲生态系统和自然生态之间的平衡,盆地环境治理很大程度决定于水资源的合理利用和合理调节。     

黄河下游游荡段河道平面形态与河热变化趋势预测

黄河下游可道平面形态与河势演变,从２０世纪６０年代起,地貌界就用地图法和航片资料作过不同程度的研究。随着资料的不断积累,该项研究得到逐步的深化。“八五”期间,水利界又对主流线作了深入分析,结果表明：各家所得结论不同,需要作进一步的分析讨论。我们认为：从长远的角度来看,小浪底水库清水下泄期间,黄河下游游荡性可段不对称的河谷形态不会改变;在继承性新构造运动造成的地壳向南掀沉、科氏力和人类活动的综合影响     

基于GIS的自适应三维古海面-地面演变模型研究

本文设计了基于GIS的具有"自适应"功能的三维古海面-地面演变模型.该模型可以动态演绎沿海地区"沧海桑田"的变化景象,并且可以运用历史资料及专家知识,对海面-地面变化模拟结果进行检验,根据检验结果来对模型的一系列控制参数进行自动半自动的修订,然后重新进行海面-地面演变的动态模拟,直到更趋近于真实的历史演变过程,从而实现...     

与国际框架接轨的我国矿产资源/储量分类

回顾了我国现行矿产储量分类分级标准的制订情况,分析了其存在的主要问题。简要介绍了《联合国国际储量／ 资源分类框架》。通过新颁发的《固体矿产资源／ 储量分类》国家标准与我国现行分类及联合国框架的对比,阐述了其主要特点及实施意义。     

The Imperial IRAS-FSC Redshift Catalogue

We present a new catalogue, the Imperial IRAS -FSC Redshift Catalogue (IIFSCz), of 60 303 galaxies selected at 60 μm from the IRAS Faint Source Catalogue (FSC). The IIFSCz consists of accurate position, optical, near-infrared and/or radio identifications, spectroscopic redshift (if available) or photometric redshift (if possible), predicted far-infrared (FIR) and submillimetre (submm) fluxes ranging from 12 to 1380 μm based upon the best-fitting infrared template. About 55 per cent of the galaxies in the IIFSCz have spectroscopic redshifts, and a further 20 per cent have photometric redshifts obtained through either the training set or the template-fitting method. For S(60) > 0.36 Jy, the 90 per cent completeness limit of the FSC, 90 per cent of the sources have either spectroscopic or photometric redshifts. Scientific applications of the IIFSCz include validation of current and forthcoming infrared and submm/mm surveys such as AKARI , Planck and Herschel , follow-up studies of rare source populations, large-scale structure and galaxy bias, local multiwavelength luminosity functions and source counts. The catalogue is publicly available at http://astro.imperial.ac.uk/~mrr/fss/ .     

Short-period Jupiter family comets after Stardust

The NASA Stardust mission has provided for laboratory study an extensive data set of cometary dust of known provenance (from comet 81P/Wild 2) yielding detailed insights into the composition of the comet. Combined with the results of data from other missions to short-period Jupiter family comets (JFC), this has greatly deepened the understanding of such objects. If depressions on the surface of comet 81P/Wild 2 are all taken as evidence of impact cratering, their number suggests a long occupancy in the outer region of the Solar System. The dust from comet 81P/Wild 2 has been shown to be heavily deficient in pre-Solar grains and rich in materials formed at high temperatures in the inner Solar System. Although it is too early to know if this is typical of JFC, it does argue for rapid and thorough mixing of materials in the disk on timescales related to comet formation, and may also suggest outward migration of small icy bodies after their formation. Thus, instead of providing mainly new knowledge of the pre-Solar materials expected to be rich in comets, Stardust and comet 81P/Wild 2 have instead focussed attention on large-scale transport processes during the critical period when cometary parent bodies were forming in the early Solar System.     

Testing the circumstellar disc hypothesis: a search for H2 outflow signatures from massive young stellar objects with linearly distributed methanol masers

The results of a survey searching for outflows using near-infrared imaging are presented. Targets were chosen from a compiled list of massive young stellar objects associated with methanol masers in linear distributions. Presently, it is a widely held belief that these methanol masers are found in (and delineate) circumstellar accretion discs around massive stars. If this scenario is correct, one way to test the disc hypothesis is to search for outflows perpendicular to the methanol maser distributions. The main objective of the survey was to obtain wide-field near-infrared images of the sites of linearly distributed methanol masers using a narrow-band 2.12-μm filter. This filter is centred on the  H₂ v = 1–0 S(1)  line; a shock diagnostic that has been shown to successfully trace CO outflows from young stellar objects. 28 sources in total were imaged of which 18 sources display H₂ emission. Of these, only two sources showed emission found to be dominantly perpendicular to the methanol maser distribution. Surprisingly, the H₂ emission in these fields is not distributed randomly, but instead the majority of sources are found to have H₂ emission dominantly parallel to their distribution of methanol masers. These results seriously question the hypothesis that methanol masers exist in circumstellar discs. The possibility that linearly distributed methanol masers are instead directly associated with outflows is discussed.     

The dynamics of a channel-fed lava flow on Pico Partido volcano, Lanzarote

A short length of channel on Pico Partido volcano, Lanzarote, provides us the opportunity to examine the dynamics of lava flowing in a channel that extends over a sudden break in slope. The 1–2-m-wide, 0.5–2-m-deep channel was built during the 1730–1736 eruptions on Lanzarote and exhibits a sinuous, well-formed channel over a steep (11° slope) 100-m-long proximal section. Over-flow units comprising smooth pahoehoe sheet flow, as well as evidence on the inner channel walls for multiple (at least 11) flow levels, attest to unsteady flow in the channel. In addition, superelevation is apparent at each of the six bends along the proximal channel section. Superelevation results from banking of the lava as it moves around the bend thus causing preferential construction of the outer bank. As a result, the channel profile at each bend is asymmetric with an outer bank that is higher than the inner bank. Analysis of superelevation indicates flow velocities of ~8 m s^–1. Our analysis of the superelevation features is based on an inertia-gravity balance, which we show is appropriate, even though the down-channel flow is in laminar flow. We use a viscosity-gravity balance model, together with the velocities calculated from superelevation, to obtain viscosities in the range 25–60 Pa s (assuming that the lava behaved as a Newtonian liquid). Estimated volume fluxes are in the range 7–12 m³ s^–1. An apparent down-flow increase in derived volume flux may have resulted from variable supply or bulking up of the flow due to vesiculation. Where the channel moves over a sharp break in slope and onto slopes of ~6°, the channel becomes less well defined and widens considerably. At the break of slope, an elongate ridge extends across the channel. We speculate that this ridge was formed as a result of a reduction in velocity immediately below the break of slope to allow deposition of entrained material or accretion of lava to the channel bed as a result of a change in flow regime or depth.     

Application of horizontal-to-vertical (H/V) Fourier spectral ratio for analysis of site effect on rock (NEHRP-class B) sites in Taiwan

The frequency-dependent amplification for rock (NEHRP-class B) sites was studied using earthquake ground-motion database collected in Taiwan during implementation of the Taiwan Strong Motion Instrumentation Program. The database used includes several hundred records from earthquakes of M_L 4.0–7.3 occurred between 1993 and 2004. The characteristics of amplification were evaluated using the well-known technique of horizontal-to-vertical Fourier spectral ratio (H/V) of the S-wave phase [Lermo J, Chavez-Garcia FJ. Site effect evaluation using spectral ratios with only one station. Bull Seism Soc Am 1993;83:1574–94]. The study allows us to analyze peculiarities of rock sites amplification in Northern and Eastern Taiwan. It was suggested to divide the NEHRP-class B site amplification into four types based on frequency of maximum amplification and the shape of amplification function. The applicability of the technique was also checked for a few stiff and soft soil sites (NEHRP-classes D and E).