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121.
Qu JianJun Zhang KeCun Sun Bo Jiang ShengXiang Dong GuangRong Zu RuiPing Fang HaiYan 《中国科学D辑(英文版)》2007,50(9):1351-1358
The sound-producing mechanism of booming sand has long been a pending problem in the blown sand physics. Based on the earlier researches, the authors collected some silent sand samples from Teng- ger Desert, Australian Desert, Kuwait Desert, beaches of Hainan Island and Japanese coast as well as the soundless booming sand samples from the Mingsha Mountain in Dunhuang to make washing ex- periments. In the meantime the chemical corrosion experiment of glass micro-spheres, surface coating experiment and SEM examination were also conducted. The experimental results show that the sound production of booming sand seems to have nothing to do with the presence of SiO2 gel on the surface of sand grains and unrelated to the surface chemical composition of sand grains but is related to the resonance cavities formed by porous (pit-like) physical structure resulting from a number of factors such as wind erosion, water erosion, chemical corrosion and SiO2 gel deposition, etc. Its resonance mechanism is similar to that of Hemholz resonance cavity. Under the action of external forces, nu- merous spherical and sand grains with smooth surface and porous surface are set in motion and rub with each other to produce extremely weak vibration sound and then become audible sound by human ears through the magnification of surface cavity resonance. However the booming sands may lose their resonance mechanism and become silent sand due to the damping action caused by the invasion of finer particles such as dust and clay into surface holes of sand grains. Therefore, clearing away fine pollutants on the quartz grain surface is an effective way to make silent sand emit audible sound. 相似文献
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萨拉乌苏河流域150 ka BP以来的粒度旋回 总被引:18,自引:1,他引:18
萨拉乌苏河流域米浪沟湾地层剖面150kaBP以来古流动砂丘砂与河湖相和古土壤在粒度上具有多次显著的粗细韵律交替变化,粒度参数-Mz、σ、Sk、Kg和SC/D亦随之响应为多波动峰谷交替的态势,同时,粒度特征值-φ5、φ16φ、φ25、φ50、φ84、φ9相应地表现为非常有节奏地跳动,据此,将米浪沟湾剖面划分为27个粒度粗细沉积旋回,并认为其是150kaBP以来在东亚冬夏古代季风交替影响下沙漠演变的一个颇为完整的气候-地质过程记录。 相似文献
125.
滇黔桂微细粒金矿床开发利用问题讨论 总被引:1,自引:0,他引:1
根据矿石加工技术性能,可把微细粒金矿分为原生矿和氧化矿。原生矿难选,成本高,尚未有效开发利用,氧化矿易选冶,成本低,是目前主要开采对象,也是今后勘查重点,根据产出特征可把氧化矿分为原地,残积,塌积氧化矿,其中塌积氧化矿毫无例外地产出碳酸盐岩喀斯特洼地第四系风化土中,习称“红土型”金矿,经深入研究后认为是以碳酸盐岩为底板的整合原生矿,因岩溶塌陷而形成的塌积氧化矿,其成因与国外典型红土型金矿不同,不宜称为红土型金矿,因其首先发现于大厂地区,可称之为“大厂型”金矿,矿床规模一般为小型,个别可达中型,产出形态受控于下伏微喀斯特起伏面,复杂多变,只宜边探边采。 相似文献
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县内土地面积36.49万hm2,坡耕地面积3.44万hm2.坡耕地粮食年产4500-6500kg/km2.低产原因是土层瘠薄,缺土水肥.采取的综合治理措施有:建设农田基础设施,实行生物-工程措施,推行分带轮作三熟制等.由此粮食年产达11000—12500kg/hm2. 相似文献
129.
壳粒磷块岩及其成矿规律 总被引:4,自引:0,他引:4
壳粒磷块岩被作为一种独立的重要类型划分出来。壳粒磷块岩的性质从极重要的方面揭示了海相磷块岩的本质特征。本文以生物成矿论为指导,研究了扬子地块晚震旦世陡山沱期磷块岩形成的古地理,并阐述了磷块岩成矿与富集规律。 相似文献
130.
Judy Ehlen 《地球表面变化过程与地形》1992,17(1):53-67
The granite tors of Dartmoor are characterized by using the regional spatial patterns of 21 geomorphic, petrographic, and structural variables. The data were derived from topographic maps, field measurement, and laboratory analysis of rock samples collected in the field. Identification of spatial patterns and comparison of patterns between variables were made on contour maps generated from the data using ARC/INFO. Three tor types—summit tors, valleyside tors, and spur tors—are semiquantitatively characterized using these data and procedures. The three types of tors are distinguished with respect to variations in relative relief, joint spacing and joint type, rock texture, grain size, and composition. Summit tors have the highest relative relief (mean: 125·7 m), contain the most potassium feldspar (>30 per cent), and have the most widely-spaced primary vertical (>300 cm) and secondary horizontal joints (> 10 cm). The rocks are the most megacrystic (> 15 per cent) and the coarsest grained. Plagioclase is also abundant in summit tors. Valleyside tors have the lowest relative relief (mean: 72·9 m) and the most widely-spaced horizontal joints (primary, 60-200 cm; secondary, > 10 cm). Grain size, vertical joint spacing, and quartz and potassium feldspar abundances are intermediate. The shapes of valleyside tors are controlled by horizontal joints and the rocks are either very feebly magcrystic or equigranular in texture. Spur tors have intermediate relative relief (mean: 115·4 m), the narrowest joint spacing (vertical joints, < 200 cm, 50-75 cm; horizontal joints <60 cm, < 10 cm) and the finest grain. In addition, the rocks are feebly magacrystic. 相似文献