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7月的贝加尔湖畔,天是蓝的,水是蓝的,时而绿油油的森林在苍翠欲滴的草地上蜿蜒起伏,时而莽莽林海中现出盛开鲜花的草甸,群山与湖泊之间,或悬崖峭壁,疾风凛冽,或平坦湿地,绿色,黄色,粉红色,看不见村庄,看不见农田,一切都那样的自自然然,如果没有笔直的柏油马路和来来往往的车辆,没有理由不相信这里是梦幻般的童话世界. 相似文献
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滇西北横断山区的旅游资源及其开发研究--21世纪中国极具开发潜力的旅游区 总被引:1,自引:0,他引:1
滇西北横断山区,由于地质的强烈作用,形成怒江,澜沧江,金沙江三江相间并流的地貌大奇观,有众多峡保和高大雪山群,低纬海拔的冰川。气候多样,生物资源品种繁多,垂直地带性非常明显,集聚了最壮丽的自然风光。藏纳西,白,彝,傈僳,怒,独龙,普米,回等民族聚居,社会发展层次有先有后,有人类社会发展的博物馆之称,民族风情浓郁。 相似文献
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《地域研究与开发》1986,(1)
地球是个水的行星,海洋面积有3.61亿平方公里,约占地球总面积5.1亿平方公里的71%。海洋是生命的摇蓝,风雨的故乡,资源的宝库,友谊的纽带,贸易的坦途,战略的要地.开发海洋,发展海洋事业,已成为世界新产业革命的重要内容,因此,考察、认识、研究、开发、利用和保护海洋,已成为当今世界关注的问题,《大洋洲岛国地理》迎合这一世界趋势而问世,具有重要的现实意义在世界最大的洋,浩瀚的太平洋西部,赤道两侧南北回归线之间的热带、亚热带湛兰海域,散布着大洋洲的美拉尼西亚、密克罗尼西亚、波利尼西亚三大群岛中的一万多个岛屿,其中以夏威夷群岛属火山岛,少数岛屿属大陆岛以外,多数属珊瑚岛,而且气候暖湿,森林茂密,出产椰子、甘蔗、菠萝、香蕉、海鱼、磷、镍、铬、金等物产,其中许多岛屿是联系各大洲海、空航线和海底电缆经过的地方,在国际交 相似文献
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长江流域持续发展的态势、问题及对策研究 总被引:8,自引:2,他引:6
通过研究长江流域经济的持续快速健康发展,上中下游的协调发展,产业结构的优化和产业政策的实施,外向型经济发展,基础产业和基础设施的发展与合理布局,大中小城市协调发展和城乡一体化,自然资源的合理开发利用,生态环境的治理与保护,分析了长江流域持续发展的基本态势,存在的主要问题,并提出对策。 相似文献
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八月,内蒙古高原,天高气清,草木葱茏。八月, 《西部资源》更名已届一年。面对案头一期期杂志,犹如面对精心抚育的孩子,那一行行精彩叠呈的文字,一篇篇厚重睿智的文章,一张张美仑美奂的图片,一幅幅新颖醒目的封面,一页页的精美设计与制作,一则小知识,一个小故事……,汇聚在一起,支撑起一个刊物,记录着各级领导的支持,各界朋 相似文献
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赏石文化作为中华传统文化中的一支奇葩,历史悠久,博大精深,承德载道,天人合一,在漫长的历史长河中以其自身的和谐多姿,向世人展示着自然的奥妙和人生的哲理。观赏石文化到底起源于什么时候,在石界尚没有一个统一的说法。在中国,新石器时代应该说是观赏石文化的萌芽时期,随后经历了魏晋南北朝的兴起时期,唐宋的繁荣时期,明清的鼎盛时期。从春秋战国到清末,涉及观赏石的著作举不胜举, 相似文献
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绿洲边缘地带温湿风的廓线特征及其通量计算 总被引:6,自引:0,他引:6
讨论了绿洲边缘地区的温湿风廓线及日变化特征,用Buisinger模式计算了显热通量,并将结果与波文比法,涡度相关法作了比较。 相似文献
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滇西北三江河谷纵剖面的发育图式与演化规律 总被引:12,自引:1,他引:12
在地壳持续、匀速抬升继以长期稳定的构造条件下,均一流域河谷纵剖面形态是以河口或河源为原点的抛物线(h=Al~N)。抬升期,河流深切侵蚀,纵剖面为上凸抛物线型;稳定期,河流均衡调整,纵剖面为下凹抛物线形;其间过渡阶段,纵剖面为直线型。流域地貌随侵蚀循环而相应演化,最终形成准平原。滇西北金沙江、澜沧江、怒江流域接近理想假设条件,其河谷纵剖面的形态和演化符合上述的图式和规律。 相似文献
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泥石流沟谷演化的不等时距灰色预测* 总被引:4,自引:0,他引:4
泥石流沟谷纵剖面形态系表征泥石流发育的综合地形指标.本文以利子依达沟为例,用不等时距GM(1,1)预测沟谷纵剖面形态指数N值的变化,并改进了预测模型的精度. 相似文献
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Detailed wind tunnel tests were carried out to establish the mean downwind velocity and transport rate of different-sized loose dry sand at different free-stream wind velocities and heights, as well as to investigate the vertical variation in the concentration of blowing sand in a cloud. Particle dynamic analyzer (PDA) technology was used to measure the vertical variation in mean downwind velocity of a sand cloud in a wind tunnel. The results reveal that within the near-surface layer, the decay of blown sand flux with height can be expressed using an exponential function. In general, the mean downwind velocity increases with height and free-stream wind velocity, but decreases with grain size. The vertical variation in mean downwind velocity can be expressed by a power function. The concentration profile of sand within the saltation layer, calculated according to its flux profile and mean downwind profile, can be expressed using the exponential function: cz=ae−bz, where cz is the blown sand concentration at height z, and a and bare parameters changing regularly with wind velocity and sand size. The concentration profiles are converted to rays of straight lines by plotting logarithmic concentration values against height. The slope of the straight lines, representing the relative decay rate of concentration with height, decreases with an increase in free-stream wind velocity and grain size, implying that more blown sand is transported to greater heights as grain size and wind speed increase. 相似文献
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The vertical wind-velocity profile within the saltation layer is investigated theoretically. New equations for the fluid shear stress distribution in the saltation layer and the velocity profile affected by saltation are derived. The dependence of the velocity profile on the threshold shear velocity, the vertical variations of sand grain velocity, the vertical sand-mass-flux distribution, and the fluid shear stress within the saltation are demonstrated. Velocity profiles with or without Bagnold's focus are predicted. These velocity profiles are not very sensitive to the vertical distribution of sand-mass flux. Predicted velocity profiles are compared with profiles measured in the wind tunnel, and satisfactory agreement has been achieved. 相似文献
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赣北芙蓉―周溪断面下蜀黄土粒度特征及其指示意义 总被引:1,自引:0,他引:1
赣北鄱阳湖地区沙山南部近南北向的芙蓉―周溪断面上,分布由FZ-01、FZ-02~FZ-05和FZ-06~FZ-12三部分组成的下蜀土剖面,粒度分析结果表明:1)下蜀黄土砂粒组分自北往南变化为27.29%、1.94%~7.23%和0.45%~7.27%;粉砂组分质量分数大,且存在差异变化,分别为68.23%、81.71%~87.20%和66.9%~79.39%;黏土组分自北向南质量分数增加,变化为4.48%、8.46%~16.35%和18.13%~32.07%,总体表现为砂黄土―黄土―黏黄土等相态的逐渐过渡;2)粒度三组分、粒度参数散点图等均表现为从北而南的阶段性系统渐变特征;3)各种粒度参数与距长江的远近,均服从对数函数变化关系。这些特征初步揭示研究区的下蜀黄土是风成的,并可能与同样是风成堆积的沙山的形成存在某种联系,属于区域性风沙-风尘堆积体系。 相似文献
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Longitudinal profiles of bedrock streams in central Kentucky, and of coastal plain streams in southeast Texas, were analyzed to determine the extent to which they exhibit smoothly concave profiles and to relate profile convexities to environmental controls. None of the Kentucky streams have smoothly concave profiles. Because all observed knickpoints are associated with vertical joints, if they are migrating it either occurs rapidly between vertical joints, or migrating knickpoints become stalled at structural features. These streams have been adjusting to downcutting of the Kentucky River for at least 1.3 Ma, suggesting that the time required to produce a concave profile is long compared to the typical timescale of environmental change. A graded concave longitudinal profile is not a reasonable prediction or benchmark condition for these streams. The characteristic profile forms of the Kentucky River gorge area are contingent on a particular combination of lithology, structure, hydrologic regime, and geomorphic history, and therefore do not represent any general type of equilibrium state. Few stream profiles in SE Texas conform to the ideal of the smoothly, strongly concave profile. Major convexities are caused by inherited topography, geologic controls, recent and contemporary geomorphic processes, and anthropic effects. Both the legacy of Quaternary environmental change and ongoing changes make it unlikely that consistent boundary conditions will exist for long. Further, the few exceptions within the study area–i.e., strongly and smoothly concave longitudinal profiles–suggest that ample time has occurred for strongly concave profiles to develop and that such profiles do not necessarily represent any mutual adjustments between slope, transport capacity, and sediment supply. The simplest explanation of any tendency toward concavity is related to basic constraints on channel steepness associated with geomechanical stability and minimum slopes necessary to convey flow. This constrained gradient concept (CGC) can explain the general tendency toward concavity in channels of sufficient size, with minimal lithological constraints and with sufficient time for adjustment. Unlike grade- or equilibrium-based theories, the CGC results in interpretations of convex or low-concavity profiles or reaches in terms of local environmental constraints and geomorphic histories rather than as “disequilibrium” features. 相似文献
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粗糙床面风廓线的转折特征及其物理意义 总被引:4,自引:3,他引:1
为了进一步认识粗糙床面空气动力学粗糙度的物理意义,理解空气动力学粗糙度对动量传递和跃移起动的影响机制,从风洞试验测定的粗糙床面风廓线转折特征入手,分析了粗糙床面的空气动力学性质并提出了内边界层动量传递及近壁区沙粒起动的可能机制。结果表明,细高粗糙元(方向比率在4~20之间)和孔隙粗糙元(孔隙度在0.15~0.75)风廓线呈现4个转折段,对应的湍流垂直分层为近壁区-尾涡层(Z≤0.15H~0.5H)、内边界层-尾涡层过渡层(0.15H≤Z≤0.75H)、内边界层(0.3H~0.75H≤Z≤1.2H~6H)和内边界层与外边界层过渡层等。粗矮粗糙元(粗糙元的方向比率在0.4~1.25之间)风廓线存在几个转折段,对应气流垂直分层为近壁区-尾涡层(Z≤1H~1.5H)和内边界层(1H~1.5H≤Z≤7H~35H)等。细高粗糙元和孔隙粗糙元覆盖21组床面(侧影盖度在0.007~0.50,粗糙元的高度在10~100 mm)的内边界层内空气动力学粗糙度在0.07~30.74 mm之间,比内边界层以上或以下过渡层的空气动力学粗糙度高几个数量级到数倍;内边界层摩阻风速的0.50~1.66 m\5s-1之间,是内边界层以下过渡层的1.5~10倍、内边界层以上过渡层的摩阻风速的1.1~2.8倍。内边界层的空气动力学粗糙度和摩阻风速分别代表了粗糙床面对气流阻力特征和湍流切应力。内边界层以下过渡层湍流切应力与粗糙元之间光滑地表所受切应力关系不大,而近壁层切应力与光滑地表所受切应力直接相关。近壁层猝发过程上抛运动和内边界层湍流猝发过程下扫运动耦合关系是内边界层的一部分动量传递到近壁区并导致沙粒起动的可能机制。 相似文献