The pillars of cosmology: a short history and assessment     

Jeff Kanipe 《Astrophysics and Space Science》1995,227(1-2):109-118

Is the big bang model of the universe ascendant and unshakable, or declining and outdated? This paper cursorily explores the state of cosmology today.  相似文献   

Progresses in geology and hazards analysis of Tianchi Volcano     

WEIHai-quan JINBo-lu LIUYong-shun 《东北亚地学研究》2004,7(1):28-35

A number of different lahars have been recognized from a systematic survey of a mapping project. The high setting temporamre feature of the deposits indicates a relationship between the lahar and the Millennium eruption event of Tianchi Volcano. The lahars caused a dramatic disaster. Recognize of the huge avalanche scars and deposits around Tianchi Volcano imply another highly destructive hazard. Three types of different texture of the avalanche deposits have been recognized. There was often magma mixing processes during the Millennium eruption of Tianchi Volcano, indicating a mixing and co-eruption regime of the eruption.  相似文献   

Small-Amplitude Disturbances in a Radiating and Scattering Grey MediumIII. Gravitational Effects on the Solutions of Given Real Wave Number k     

Noboru Kaneko  Kazuhiko Morita 《Astrophysics and Space Science》2006,305(4):349-376

We study the fundamental modes of radiation hydrodynamic linear waves that arise from one-dimensional small-amplitude initial fluctuations with wave number k in a radiating and scattering grey medium by taking into account the gravitational effects. The equation of radiative acoustics is derived from three hydrodynamic equations, Poisson’s equation, and two moment equations of radiation, by assuming a spherical symmetry for the matter and radiation and by using the Eddington approximation. We solve the dispersion relation as a quintic function of angular frequency ω, the wave number k being a real parameter. Numerical results reveal that wave patterns of five solutions are distinguished into three types: the radiation-dominated, type 1, and type 2 matter-dominated cases. In the case of no gravitaional effects (Kaneko et al., 2005), the following wave modes appear: radiation wave, conservative radiation wave, entropy wave, Newtonian-cooling wave, opacity-damped and cooling-damped waves, constant-volume and constant-pressure diffusions, adiabatic sound wave, cooling-damped and drag-force-damped isothermal sound waves, isentropic radiation-acoustic wave, and gap mode. Meanwhile, the gravitaional effects being taken into account, the growing gravo-diffusion mode newly arises from the constant-pressure diffusion at the point that k agrees with Jeans’ wave number specified by the isothermal sound speed. This mode changes to the growing radiation-acoustic gravity mode near the point that k becomes Jeans’ wave number specified by the isentropic radiation-acoustic speed. In step with a transition between them, the isentropic radiation-acoustic wave splits into the damping radiation-acoustic gravity mode and constant-volume diffusion. The constant-volume diffusion emerges twice if the gravitational effects are taken into account. Since analytic solutions are derived for all wave modes, we discuss their physical significance. The critical conditions are given which distinguish between radiation-dominated and type 1 matter-dominated cases, and between type 1 and type 2 matter-dominated cases. Waves in a self-gravitating scattering grey medium are also analyzed, which provides us some hints for the effects of energy and momentum exchange between matter and radiation.  相似文献   

菏泽市地质灾害现状与防治          下载免费PDF全文

张本进  徐淑和  黄文峰  张洪波 《山东国土资源》2003,19(5):26-27,31

菏泽市地质灾害类型主要为地震、地面塌陷、地面沉降、地裂缝、砂土液化、土地盐渍化及地氟病等，其发育与分布受地质构造、水文地质条件的控制以及气象、人类活动等因素的影响。就其分布、危害、致灾原因等做了分析，并提出了防治建议和对策。  相似文献   

Natural radioactivity in sediment of Wei River,China   总被引：1，自引：0，他引：1  

Xinwei Lu  Xiaolan Zhang  Fengling Wang 《Environmental Geology》2008,53(7):1475-1481

The concentrations of natural radionuclides in sediment of Wei River of China were measured using γ-ray spectrometry with the aim of estimating the radiation hazard as establishing a database for radioactivity levels of river sediment of China. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in sediment samples ranged from 10.4 to 39.9 Bq kg⁻¹, 15.3 to 54.8 Bq kg⁻¹ and 514.8 to 1,175.5 Bq kg⁻¹, respectively. The concentrations of these radionuclides were compared with the typical world values and the average activities of Chinese soil and Shaanxi soil. Radium equivalent activity (Ra_eq), external hazard index (H _ex) and representative level index (I _γr) were calculated for the samples to assess the radiation hazards arising due to the use of these sediment samples in the construction of dwellings. All the sediment samples have Ra_eq lower than the limit of 370 Bq kg⁻¹, H _ex less than unity and I _γr close to 1 Bq kg⁻¹. The overall mean outdoor terrestrial gamma dose rate is 64.8 nGy h⁻¹ and the corresponding outdoor annual effective dose is 0.079 mSv. None of the studied location is considered a radiological risk and sediment can be safely used in construction.  相似文献   

<Superscript>226</Superscript>Ra, <Superscript>232</Superscript>Th and <Superscript>40</Superscript>K activities in soils of Cuihua Mountain National Geological Park,China     

Xinwei Lu  Xiaolan Zhang 《Environmental Geology》2008,56(2):353-357

Gamma activity from the naturally occurring radionuclides namely, ²²⁶Ra, ²³²Th, the primordial radionuclide ⁴⁰K was measured in the soil of Cuihua Mountain National Geological Park, China using γ-ray spectrometry technique. The mean activity of ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 27.2 ± 6.5, 43.9 ± 6.2 and 653.1 ± 127.6 Bq kg⁻¹, respectively. The concentrations of these radionuclides were compared with the typical world values and the average activities of Chinese soil. The radium equivalent activity, the air absorbed dose rate, the annual effective dose rate, and the external hazard index were evaluated and compared with the internationally approved values. All the soil samples have Ra_eq lower than the limit of 370 Bq kg⁻¹ and H _ex less than unity. The overall mean outdoor terrestrial gamma dose rate is 66.3 nGy h⁻¹ and the corresponding outdoor annual effective dose is 0.081 mSv.  相似文献   

Rain-induced debris and mudflow triggering factors assessment in the Santiago cordilleran foothills,Central Chile   总被引：1，自引：1，他引：0  

Sergio A. Sepúlveda  Cristóbal Padilla 《Natural Hazards》2008,47(2):201-215

Debris and mudflows are some of the main geological hazards in the mountain foothills of the Chilean capital city of Santiago. There, the risk of flows triggered in the basins of ravines that drain the range into the city increases with time due to the city growth. A multivariate statistical study based on the logistic regression method is presented. The model provides equations that allow the computation of combined meteorological triggering factors associated with a probability of rain-induced flow occurrence. Daily rainfall, accumulated rainfall and the snowfall level, traditionally considered as the relevant factors, are analysed for a 25-year period. The results show a strong relevance of the rainfall on the day of the flow event over the other factors. However, the relatively low probabilities returned for some real flow events suggest that the model does not capture all the significant variables and the problem is more complex than as it has been traditionally assumed, and further investigations are needed to develop predictive models of flow triggering.  相似文献   

汶川地震山地灾害遥感快速提取及其分布特点分析   总被引：12，自引：0，他引：12  

苏凤环  刘洪江  韩用顺 《遥感学报》2008,12(6)

针对泥石流滑坡灾害体特有的物质组成与活动特点,通过比较分析其在不同遥感影像的光谱特征差异,选择ETM+影像作为主要数据源,提取湿度指数与绿度指数,利用ETM+的穗帽变换、影像差值增强、密度分割和掩膜技术建立了泥石流滑坡山地灾害快速提取模型,并用于汶川地震.通过灾害体的提取,分析了本次地震山地次生灾害的分布规律,利用空间叠加进行了成因的分析.本次地震山地灾害具有如下特点:(1)沿主要地表破裂带分布;(2)山地灾害主要出现在8度-9度地震烈度区,随着烈度的降低,山地灾害的总面积也相应的减少;(3)山地灾害主要发生在海拔高度1000-2500m的地带;(4)主要发生在坡度20°-50°之间的边坡上;(5)地震及余震期间以崩塌滑坡滚石为主,后期以泥石流滑坡为主;(6)具有河流左右两岸呈不对称分布等特点.结果表明,利用ETM+影像建立基于湿度指数与绿度指数的快速提取模型,对于大规模泥石流滑坡提取效果较好,进行大区域山地灾害的遥感快速提取是可行的.  相似文献   

河西走廊疏勒河流域地质灾害危险性现状评估方法的应用——以甘肃省河西走廊(疏勒河)农业灌溉暨移民安置综合开发建设项目8个移民社区及配套工程建设为例          下载免费PDF全文

王永斌  崔艳荣 《甘肃地质》2008,(4):67-71

依据“建设用地地质灾害危险性评估技术要求”、利用野外踏勘及相关资料,对“甘肃省河西走廊（疏勒河）农业灌溉暨移民安置综合开发建设项目8个移民社区及配套工程”进行地质灾害危险性现状评估。结果认为：评估区发育和分布的地质灾害类型有土壤盐渍化、风蚀沙埋和洪水冲蚀。现状评估结果：土壤盐渍化和洪水冲蚀危险性均小;风蚀沙埋有1处危险性中等,其它危险性小。  相似文献   

基于WiMAX的地质灾害应急无线通信系统探索     

达格  张丽君 《国土资源信息化》2008,(4):15-19

基于OFDM核心技术的WiMAX(全球微波接入互操作性)具有4G技术的特点。与3G和WiFi无线通讯技术相比具有明显的高速率、大容量数据传输优势。本文就基于WiMAX的地质灾害应急通讯系统的几种技术方案加以详细论述,说明WiMAX在地质灾害应急指挥中具有广阔前景。  相似文献