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231.
我国泛珠三角地区,处于磁赤道异常区的峰值区域,是全球范围内电离层闪烁衰落出现最频繁、影响最严重的区域之一。简单介绍了电离层闪烁基础理论和广州气象卫星地面站的GPS电离层闪烁监测系统,并对其监测数据进行了初步分析,为将来开展针对静止气象卫星通讯链路的电离层闪烁监测研究打基础。  相似文献   
232.
河南地区是中国文明起源的核心区域之一,史前文明璀璨发达,是开展全新世环境考古研究的理想区域。近二十年来,河南地区环境考古研究中,文化演化的环境背景分析成果突出,灾变事件影响及人类对环境变化的响应研究亦有涉及,数字环境考古工作也开始逐渐起步。但在河南地区仍缺少高分辨率古环境重建方面的研究,且已有环境考古研究多关注环境变化对文明演化的影响,而在人类活动对环境变化响应及其环境效应方面研究尚显不足。此外,随着RS、GIS等技术应用的不断深入以及对景观考古的不断关注,考古遗址预测模型以及史前人与自然关系的定量和模拟研究已成为当前国际环境考古研究的热点。  相似文献   
233.
Hani rice terraces system is one of the Globally Important Agricultural Heritage Systems (GIAHS) pilot sites selected by FAO. Soil nutrients are an important symbol of soil fertility, and play an important role in the sustainable utilization of land. Based on geo-statistics and GIS, the spatial variation of pH, organic matter, total nitrogen, alkaline hydrolyzable nitrogen, available phosphorus and available potassium in the soil in Yisa (a town in Honghe County, Yunnan Province) was studied. The results show that the spatial variability of pH, organic matter, total nitrogen, alkaline hydrolyzable nitrogen and available potassium exhibited medium spatial variability, and the coefficients of variation are 12.54%, 40.14%, 40.00%, 34.89%, and 40.00% respectively. Available phosphorus exhibited strong spatial variability, and the coefficient of variation is 102.13%. The spatial variation of pH, organic matter, total nitrogen, alkaline hydrolyzable nitrogen and available potassium fit the index mode, however, the spatial variation of available phosphorus fits the spherical model. Total nitrogen, available phosphorus and available potassium were greatly affected by soil structural factors, while pH, organic matter and alkaline hydrolyzable nitrogen were affected by both structural and random factors. The spatial distribution of soil nutrients in Yisa was intuitively characterized by Kriging interpolation. It is very important to understand the spatial distribution of soil nutrients, which will provide the guidance for adjusting agricultural management measures such as fertilization.  相似文献   
234.
厦门港的中华白海豚Ⅴ.对水生生活的适应   总被引:1,自引:1,他引:0  
1994~1999年,在厦门港20个中华白海豚监视站进行观测,实施了87航次跟踪拍照,对7头幼仔和6头成体标本进行了现场测量和解剖。第二次下水的中华第豚既具备哺乳动物纲最基本的特征,也在运动(游泳)、水下生殖和哺乳、呼吸和感觉(包括声纳)等方面产生了一系列对水环境的适应。  相似文献   
235.
1994~ 1 999年 ,在厦门港 2 0个中华白海豚监视站进行观测 ,实施了87航次跟踪拍照 ,对 7头幼仔和 6头成体标本进行了现场测量和解剖。第二次下水的中华白海豚既具备哺乳动物纲最基本的特征 ,也在运动 (游泳 )、水下生殖和哺乳、呼吸和感觉 (包括声纳 )等方面产生了一系列对水环境的适应。  相似文献   
236.
祁连山气枪主动震源浮台漂移钢索悬吊控制技术   总被引:1,自引:0,他引:1  
针对地下介质动态变化监测研究中的信噪比、震源可重复性和波速精确测量等关键问题,利用大容量气枪作为主动震源,构建了一套高性能的主动源探测技术系统,该系统主要由气枪震源和信号接收部分组成。为了解决浮台偏离设定位置的问题 ,提出了浮台漂移控制技术。实验结果表明,该技术可以有效地解决气枪激发后浮台受到水流冲击作用而偏离设定位置的问题。本研究结果可为一定激发场地情况下的气枪主动震源重复探测工作所借鉴。  相似文献   
237.
Anthropogenic activities have altered the climate and led to changes in the water cycle. Understanding the climate change and hydrological responses is critical to derive adaptive strategies for sustainable water resources management. In this study, we diagnosed the trends of primary climate elements and hydrological components during the past half century (1960–2009) for the humid Xiangjiang River Basin in central-south China at multiple temporal and spatial scales. The air temperature trend demonstrated an overall warming climate but with a quicker pace in recent years; however, the wind speed reduced significantly in the early period, and this downtrend had largely disappeared after the mid-1990s. Under such a shifting climate, the hydrological responses were not monotonic during the past 50 years: the evapotranspiration behaved in a decreasing trend in the early 35 years (1960–1994), followed by an uptrend in the later period (1995–2009). The stepwise analysis of soil water content and baseflow demonstrated a wetting trend followed by a drying one but with a steeper slope, indicating an accelerated drying trend which may cause a concern in stream water availability especially in the dry season. Spatial trend analysis showed that some areas experienced a downtrend (drying) in the dry season, but most areas had an uptrend (wetting) in the wet season for the whole study period. Overall, the analyses of temporal and spatial changes are useful for decision makers to deal with the continuing changes in climate and hydrology. This study also highlighted the necessity of climate change studies at multiple temporal and spatial scales.  相似文献   
238.
近50年福建省年度极端最低气温统计特征   总被引:12,自引:3,他引:9  
把福建省各台站年度极端最低气温统一订正为1950/1951~1999/2000整50年记录,并对其进行标准化处理和评价,继而对其偏冷年景进行特征分析。近50年福建省年度极端最低气温1954/1955为最冷年,1999/2000为第3冷年;冬季月平均气温正常,仍可出现异常或明显偏冷的低温;全省年度极端最低气温年景评价为异常偏冷,有的台站年景却仍属正常,年景等级相差达4级。全省年度极端最低气温的年景评价为异常或明显偏低,该年度福建省果树、花卉和其它冬季作物必然遭受不同程度的冻害和寒害。  相似文献   
239.
文章利用Landsat8卫星影像数据,结合黔南碳酸盐岩岩性图、黔南构造要素图等地质资料,以石灰岩、白云岩以及石灰岩与白云岩互层三类岩组地层作为切入点,获取并分析了黔南地区碳酸盐岩的空间分布特征及其在遥感影像上的表现特征。结果发现:①石灰岩地层在影像上总体显示为色调单一、地形高差大,基本无水系和建设用地分布;白云岩地层在影像上总体表现为色调丰富、水系发育、建设用地分布多;石灰岩与白云岩互层地层总体影像特征介于二者之间。②分布于不同构造发育区域的碳酸盐岩岩组地层在遥感影像上的表现特征差异较大,即使是同种岩性的地层也会由于受到节理、断层、向斜和背斜等构造的影响形成形态各异的影像。   相似文献   
240.
Zou  Caineng  Yang  Zhi  Sun  Shasha  Zhao  Qun  Bai  Wenhua  Liu  Honglin  Pan  Songqi  Wu  Songtao  Yuan  Yilin 《中国科学:地球科学(英文版)》2020,63(7):934-953
The Sichuan Basin is rich in shale oil and gas resources, with favorable geological conditions that the other shale reservoirs in China cannot match. Thus, the basin is an ideal option for fully "exploring petroleum inside source kitchen" with respect to onshore shale oil and gas in China. This paper analyzes the characteristics of shale oil and gas resources in the United States and China, and points out that maturity plays an important role in controlling shale oil and gas composition. US shale oil and gas exhibit high proportions of light hydrocarbon and wet gas, whereas Chinese marine and transitional shale gas is mainly dry gas and continental shale oil is generally heavy. A comprehensive geological study of shale oil and gas in the Sichuan Basin reveals findings with respect to the following three aspects. First, there are multiple sets of organic-rich shale reservoirs of three types in the basin, such as the Cambrian Qiongzhusi Formation and Ordovician Wufeng Formation-Silurian Longmaxi Formation marine shale, Permian Longtan Formation transitional shale, Triassic Xujiahe Formation lake-swamp shale, and Jurassic lacustrine shale. Marine shale gas enrichment is mainly controlled by four elements: Deep-water shelf facies, moderate thermal evolution, calcium-rich and silicon-rich rock association, and closed roof/floor. Second, the "sweet section" is generally characterized by high total organic carbon, high gas content, large porosity, high brittle minerals content, high formation pressure,and the presence of lamellation/bedding and natural microfractures. Moreover, the "sweet area" is generally characterized by very thick organic-rich shale, moderate thermal evolution, good preservation conditions, and shallow burial depth, which are exemplified by the shale oil and gas in the Wufeng-Longmaxi Formation, Longtan Formation, and Daanzhai Member of the Ziliujing Formation. Third, the marine, transitional, and continental shale oil and gas resources in the Sichuan Basin account for 50%, 25%, and 30% of the respective types of shale oil and gas geological resources in China, with great potential to become the cradle of the shale oil and gas industrial revolution in China. Following the "Conventional Daqing-Oil"(i.e., the Daqing oilfield in the Songliao Basin) and the "Western Daqing-Oil Gas"(i.e., the Changqing oilfield in the Ordos Basin), the Southwest oil and gas field in the Sichuan Basin is expected to be built into a "Sichuan-Chongqing Daqing-Gas" in China.  相似文献   
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