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971.
干旱地区土地合理利用问题研究:——以新疆阜康县为例   总被引:2,自引:2,他引:2  
本文以阜康县为例,对干旱地区土地利用的特点,问题进行了探讨,并提出了合理利用途径。  相似文献   
972.
Summary Dynamic programming is a technique which has been used to design the optimum final surface mining pit limit. In using dynamic programming there is a trade-off: if the geometric constraints are specified too strictly, the pit limit will not be the optimum, but if they are specified more loosely, then the computed pit contours must be smoothed. The smoothing process has usually been manual and is time consuming. In this paper a colour graphics computer routine is presented. This not only facilitates the smoothing but also has the following benefits: open-pit limits can be designed interactively on a personal computer; pit designs that are closer to the economic optimum can be obtained; and the engineer can bring his or her own experience and intuition to bear on the final open-pit design.  相似文献   
973.
Subducted sediments play an important role in crust-mantle interaction and deep mantle processes, especially for subduction zone magmatism and mantle geochemistry. The current rate of Global Subducting Sediments (GLOSS) is 0.5~0.7 km3/a. The GLOSS are composed of terrigenous material(76 wt.%), calcium carbonate(7 wt.%), opal(10 wt.%) and mineral-bound H2O+(7 wt.%). The chemical compositions of GLOSS are similar to those of upper continental crust which is mainly controlled by the terrigenous materials, and yet the materials formed by marine processes will dilute the terrigenous materials. The components of subducted sediments are different among trenches. In the accretionary margin, the components of subducted sediments are similar to those of the upper crust, while in the non-accretionary margin the components are terrigenous materials plus those produced by marine processes. During subduction, subducted sediments will released fluids, melt or supercritical fluid to affect island arc/back-arc basin magmatism by means of aqueous fluid or sediment melt. In addition, a part of subducted sediments, together with underlying altered oceanic crust/lithosphere, recycle into the mantle and contribute to the mantle heterogeneity. Geochemical tracers indicate that subducted sediments play variable contributions to the magmatic processes in different tectonic setting. Thus, subducted sediments play an important role in two relatively independent dynamics systems (plate tectonics and mantle plume), as well as related mantle evolution models. As a result, by accurately calculating the compositions of subduction sediments and using various geochemical indicators, we can further limit the input and output fluxes of various elements or isotopes, and then obtain more accurately residual subducted components, which can provide us some important clues for geodynamic process.  相似文献   
974.
刘宗香  谢自楚 《冰川冻土》1995,17(4):356-359
本选用中国冰川目录数据库中的青藏高原内陆水系冰川粒雪线、中值高度和地理坐标资料,利用计算机绘图方法,绘制出冰川粒支线、中值高度在空间的变化趋势,以便全面认识该地区的冰川发育特征。  相似文献   
975.
山坡风化表层碎石爬行运动是存在于自然界、受多种环境因素影响的一种地表缓慢地质变形现象。本文在介绍有关现场试验测量方法的基础上,通过对测量数据和实地观察结果的分析研究,初步描述了这一自然现象的运动机理和存在的运动形式,并提出了对这一自然现象进行可能的力学、数学模拟研究的初步设想和尝试。  相似文献   
976.
Surface air temperatures recorded over the past three decades at the weather stations located in Lahore (anindustrialized and densely populated city) and Mianwali (a small and sparsely populated city) were analyzed in order tostudy their climatic trend.Lahore,where meteorological data are recorded at two weather stations (city station and air-port station) indicates a cooling trend,of about 0.5℃ per record period of 1953—1992,for the airport station (31°31′N,74°24′E) and a slight warming trend,of about 0.2℃,for the city station (31°33′N,74°20′E) for the record period of 1950—1992.The Mianwali weather station (32°33′N,71°31′E) also shows a slight cooling trend,of about 0.4℃ per recordperiod of 1959—1992.The climatic variability at these stations was studied by computing seasonal and annual tempera-ture anomalies.The results are explained in terms of the local environmental conditions.  相似文献   
977.
In this paper,we use a two-dimensional primary equation model which contains (1) heating ofradiation,(2) heating of condensation,and (3) transfers of sensible and latent heat between air andthe underlying surface.To investigate the causes for the formation of the eastern North Pacific sum-mer monsoon,the data at 110°W are obtained and winds at underlying surface and at 200 hPa aremodified under the conditions (1) removing topography and (2) changing meridional sea surface tem-perature (SST) gradient.In the numerical modification,we find that by removing the topography,the center's location ofthe eastern North Pacific summer monsoon does not change,but the intensity of the summer monsoonis weakened.Also the onset of the summer monsoon is delayed to the end of May.The tropical east-erly jet is weakened obviously,even changes to westerly wind.On the other hand,we find that theSST gradient along 110°W influences the eastern North Pacific summer monsoon distinctly.If theSST gradient is decreased,the center of the southwest wind near 12°N does not exist any more.theintensity of the whole summer monsoon becomes very weak and the circulation pattern of the summermonsoon also changes a lot.Finally,we indicate that both topography and meridional SST gradient play important roles inthe occurrence of the eastern North Pacific summer monsoon.The meridional SST gradient is themost important factor that triggers the summer monsoon and the topography along 110°W influencesthe intensity and the onset time of the summer monsoon there mostly.  相似文献   
978.
研究表明,康滇地轴及其东部地区属均衡补偿平衡区,西部属强烈上升的异常区。上升的原动力为板块碰撞的构造力与均衡调整力的综合。  相似文献   
979.
对北京房山花岗闪长岩体中长石斑晶进行了系统测量,测点密度平均4.37个/km~2,测量标志为长石斑晶长轴长度和长石斑晶线含量等。对测得数据进行了分布统计、有序样品最优分割、和趋势变化分析等处理。揭示了长石斑晶在岩体中的分布规律和数学特征,划分了趋势岩相带,从而提出了较为合理的岩相带划分原则。  相似文献   
980.
The characteristics of simulated air flow over Andaman Islands are studied with a two-dimensional version of the University of Virginia meso scale model (UVMM). Using the observed synoptic data as initial conditions, 24 hr simulations are obtained for a day each in April and November. These days are chosen to study the variations in the simulated flow pattern under different synoptic conditions including precipitation effects. A large scale condensation scheme is employed to consider the effect of latent heat release on the perturbations. The results show that the latent heat released by condensation strengthens the intensity of perturbations and the topography accelerates the arrival of sea breeze by about an hour. The model-simulated results, given in graphical form, are discussed and compared with available observations.  相似文献   
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