SOME NEW UNDERSTANDINGS OF LAND-SURFACE PROCESSES IN ARID AREA FROM THE HEIFE^*          下载免费PDF全文

Hu Yinqiao  Gao Youxi 《Acta Meteorologica Sinica》1996,10(2):233-246

The survey for the HEIFE(Atmosphere-Land Surface Processes Experiment at Heihe River Basin,Western China) is given in the paper.The following basic subjects for land-surface processes in arid areas are studied:(1) the general characteristics of the energy budget on ground surface in arid areas;(2) the parameterization of the land surface processes;(3) the interaction between oasis and its desert circumstances,a special phenomenon in arid areas.The analysis shows that the sensible heat flux in the surface energy budget is in the majority,and the latent heat flux may be neglected.The influence of atmospheric stratification stability on the turbulent transfer of energy and substance must be considered in parameterization of land surface processes in arid areas.The "cold island effect" phenomenon in oasis and the "humidity inversion" phenomenon in desert near oasis are the result of the interaction between them.The results would improve the understanding of land surface processes in arid areas.  相似文献   

Energy balance of simple elastodynamic sources     

Václav Vavryčuk 《Pure and Applied Geophysics》1994,143(4):563-586

Complete relations are derived for energy and energy flux of elastic waves generated by an isotropic and double-couple source in a perfectly elastic, homogeneous, isotropic, and unbounded medium. In the energy balance of elastodynamic sources near-field waves play an essential role, transforming static energy into wave energy, andvice versa. For explosive and dislocation sources, the sources surface radiates a positive wave energy that is partially distributed to the medium transforming into static energy. For implosive and antidislocation sources, the source surface generates elastic waves, but it does not necessarily imply that it also radiates a positive wave energy. The energy transported by waves can originate in gradual transformation of the static-to-wave energy during propagation of waves through a stressed medium.On leave from Geophysical Institute, Czech Academy of Sciences, Boní II/1401, 41 31, Praha 4 Czech Republic  相似文献   

Textural segmentation of digital rock images into bedding units using texture energy and cluster labels     

Stefan M. Luthi 《Mathematical Geology》1994,26(2):181-196

The texture of digital rock images, as recorded, for instance, with borehole imaging devices, is shown to reflect different bedding types. Textural segmentation of borehole images, therefore, subdivides the recorded sequence into bedding units. We show that a textural segmentation algorithm based on the concept of texture energy achieves good results when compared with synthetic as well as real data in which petroleum geologists have performed zonations on cores. Texture energy involves filtering of the original image with a set of texture sensitive masks. The filtering is done as a finite convolution over the size of the masks. On the resulting images the variance is computed over a relatively large sliding window, which, in its practical implementation, covers the full width of the image. The resulting nine one-dimensional curves are then clustered hierarchically into a user-determined number of image texture or lithological bedding classes. Principal component analysis previous to clustering can be used to reduce redundancy in the data. A recurring and relatively ill-defined problem in this field are macro-textures, i.e., the cyclic interbedding of two or more bedding types. We show that sliding Fourier transforms and variable mask scale can successfully address the zonation of macro-textures. In general, the method gives best results with mask sizes equivalent to 2–4 centimeters, reflecting the length scale at which the investigated geological bedding seems to have its highest variation.  相似文献   

辽宁避暑旅游气候适宜度评价     

侯亚红  息涛  明惠青  赵淼  关健华 《气象科技》2021,49(6):960-967

利用辽宁省59个国家气象站2008—2017年6—8月逐时地面观测资料，综合考虑夏季气候舒适度和高影响天气对避暑旅游的不利影响，确定辽宁避暑旅游气候适宜度评价方法，分析了辽宁避暑旅游适宜度时空分布，为公众及旅游相关部门了解当地避暑旅游气候资源提供参考。研究表明：①辽宁避暑旅游适宜度由西北到东南逐渐增强， 59个地市（县）中，很适宜避暑的有14个，适宜避暑的有22个，较适宜避暑的有16个。②夏季辽宁大部避暑旅游气候舒适度较好，辽东和辽南气候舒适度优于辽宁中部和西部。辽宁东部的本溪和沿海的丹东、大连、葫芦岛和锦州南部气候舒适度等级最高，避暑气候条件更好。③辽宁夏季暴雨高风险区在东南部的宽甸、丹东和凤城一带。高温高风险区在朝阳大部和锦州西部。大风高风险区在铁岭北部、彰武、锦州、营口和长海。雷暴高风险区在铁岭、抚顺东部、朝阳西部和庄河一带。④6月、8月是辽宁适合避暑旅游的月份，尤其是 6月，避暑旅游适宜度最高，适宜面积最大。8月份次之， 7月避暑旅游适宜度较差。  相似文献   

碳中和目标下关键矿产在清洁能源转型中的作用、供需分析及其建议          下载免费PDF全文

王欢  马冰  贾凌霄  于洋  胡嘉修  王为 《中国地质》2021,48(6):1720-1733

在"碳中和"目标的驱动下，全球能源系统向清洁化、低碳化甚至无碳化发展已是大势所趋。针对向清洁能源转型的需求，采用了统计对比、分类汇总、综合分析等方法，分析研究了关键矿产在电池、电网、低碳发电和氢能等行业中的作用和需求。结合当前关键矿产产量的地理集中度高、项目开发周期长、资源质量下降等矿产供应和投资计划不能满足清洁能源转型的需求等问题，提出确保关键矿产多样性供应，推动价值链各环节的技术创新，扩大回收利用，增强供应链弹性和市场透明度，将更高的环境、社会和治理标准纳入主流程及加强生产者和消费者之间的国际合作等建议。  相似文献   

A search for ultra-high energy counterparts to gamma-ray bursts     

S. P. Plunkett  M. Delaney  B. McBreen  K. J. Hurley  C. T. O'Sullivan 《Astrophysics and Space Science》1995,231(1-2):271-276

A small air shower array operating over many years has been used to search for ultra-high energy (UHE) gamma radiation ( 50 TeV) associated with gamma-ray bursts (GRBs) detected by the BATSE instrument on the Compton Gamma-Ray Observatory (CGRO). Upper limits for a one minute interval after each burst are presented for seven GRBs located with zenith angles < 20°. A 4.3 excess over background was observed between 10 and 20 minutes following the onset of a GRB on 11 May 1991. The confidence level that this is due to a real effect and not a background fluctuation is 99.8%. If this effect is real then cosmological models are excluded for this burst because of absorption of UHE gamma rays by the intergalactic radiation fields.  相似文献   

Impact cratering - a review,with special reference to the economic importance of impact structures and the Southern African impact crater record     

W. U. Reimold 《Earth, Moon, and Planets》1995,70(1-3):21-45

Only since several decades has impact cratering been recognized as an important surface process on all planetary bodies in the Solar System. However, as the process has not yet been effectively introduced into geological curricula, it is necessary to inform a wider public about its importance for (i) planetary formation and (ii) evolution, (iii) the understanding of this process as a geological process, (iv) the terrestrial impact crater record and its limitations, and (v) the recognition criteria for terrestrial impact structures, as well as (vi) the need of improvement of the impact cratering record in the light of the potential danger of an impact catastrophe on this planet. It is, particularly for developing countries, of interest to examine the economic and educational-environmental potential of impact structures. That it is possible to carry out an effective, low-budget geological investigation of impact structures within a Second World environment is demonstrated by the discussion of the progress that has been made in recent years with regard to the Southern African impact crater record. Several recommendations on how to improve, on the one hand, the terrestrial impact crater record and, on the other, their general working situation by activation of workers in Developing Countries are discussed.  相似文献   

Some breakage characteristics of ultra-fine wet grinding with a centrifugal mill     

Heechan Cho  Hoon LeeYeongwoo Lee 《International Journal of Mineral Processing》2006

A centrifugal mill is a high-power intensity media mill that can be used for ultra-fine grinding, employing centrifugal forces generated by gyration of the axis of the mill tube in a circle. The mill charge motion is quite different depending on the ratio of the gyration diameter to the mill diameter (G / D ratio), varying from a motion similar to that of a conventional tumbling media mill to that of a vibration mill. In this study, a centrifugal mill was constructed with an arrangement where the gyration diameter could be readily adjusted. The batch grinding characteristics of three different minerals (limestone, talc and illite) in water with dispersing agent were investigated at various G / D ratios. It was found that the optimum G / D ratio in terms of the specific energy consumption to give a desired fineness of product was different for the three minerals. This was due to their different reactions to the breakage mechanisms provided by the mill charge motion at varying G / D ratios. The size distributions became progressively narrower at increased grinding times, and particles finer than about 0.1 μm were not detected even for prolonged grinding times. Measurement of specific surface areas indicated that this was not due to an artifact of the size measurements by laser diffractometry. This implies that there is a limitation in which particles finer than 0.1 μm are not produced under the conditions tested in this type of mill, but further investigation is needed for experimental verification of this limit of comminution.  相似文献   

On the role of heat flow, lithosphere thickness and lithosphere density on gravitational potential stresses   总被引：1，自引：0，他引：1  

Christophe Pascal   《Tectonophysics》2006,425(1-4):83-99

Gravitational potential stresses (GPSt) are known to play a first-order role in the state of stress of the Earth's lithosphere. Previous studies focussed mainly on crust elevation and structure and little attention has been paid to modelling GPSt using realistic lithospheric structures. The aim of the present contribution is to quantify gravitational potential energies and stresses associated with stable lithospheric domains. In order to model realistic lithosphere structures, a wide variety of data are considered: surface heat flow, chemical depletion of mantle lithosphere, crustal thickness and elevation. A numerical method is presented which involves classical steady-state heat equations to derive lithosphere thickness, geotherm and density distribution, but additionally requires the studied lithosphere to be isostatically compensated at its base. The impact of varying surface and crustal heat flow, topography, Moho depth and crust density on the signs and magnitudes of predicted GPSt is systematically explored. In clear contrast with what is assumed in most previous studies, modelling results show that the density structure of the mantle lithosphere has a significant impact on the value of the predicted GPSt, in particular in the case of thick lithospheres. Using independent information from the literature, the method was applied to get insights in the state of stress of continental domains with contrasting tectono-thermal ages. The modelling results suggest that in the absence of tectonic stresses Phanerozoic and Proterozoic lithospheres are spontaneously submitted to compression whereas Archean lithospheres are in a neutral to slightly tensile stress state. These findings are in general in good agreement with global stress measurements and observed geoid undulations.  相似文献   

Developments in the characterisation of waste materials for environmental impact assessment purposes     

H.A. van der Sloot  J.C.L. Meeussen  A. van Zomeren  D.S. Kosson 《Journal of Geochemical Exploration》2006,88(1-3):72

The characterisation of waste is entering a new phase with the latest developments of characterisation leaching tests and associated modelling capabilities. The currently applied too simple testing approaches lead to poor choices in waste management. With the increased insight in release controlling processes chemical speciation aspects can be addressed even in the most complex and heterogeneous waste materials. From a composition perspective materials may be highly variable, but often materials are far more consistent in their leaching behaviour. This aspect should be exploited more extensively as it holds the key to treat waste materials in such a way that long term solutions are achieved rather than reaching temporary gains.  相似文献