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991.
Water quality assessment for Ulansuhai Lake using fuzzy clustering and pattern recognition 总被引:1,自引:0,他引:1
Water quality assessment of lakes is important to determine functional zones of water use. Considering the fuzziness during the partitioning process for lake water quality in an arid area, a multiplex model of fuzzy clustering with pattern recognition was developed by integrating transitive closure method, ISODATA algorithm in fuzzy clustering and fuzzy pattern recognition. The model was applied to partition the Ulansuhai Lake, a typical shallow lake in arid climate zone in the west part of Inner Mongolia, China and grade the condition of water quality divisions. The results showed that the partition well matched the real conditions of the lake, and the method has been proved accurate in the application. 相似文献
992.
993.
Tropical peatlands of SE-Asia represent a significant terrestrial carbon reservoir of an estimated 65 Gt C. In this paper we present a comprehensive data synthesis of radiocarbon dated peat profiles and 31 basal dates of ombrogenous peat domes from the lowlands of Peninsular Malaysia, Sumatra and Borneo and integrate our peatland data with records of past sea-level and climate change in the region. Based on their developmental features three peat dome regions were distinguished: inland Central Kalimantan (Borneo), Kutai basin (Borneo) and coastal areas across the entire region. With the onset of the Holocene the first peat domes developed in Central Kalimantan as a response to rapid post-glacial sea-level rise over the Sunda Shelf and intensification of the Asian monsoon. Peat accumulation rates in Central Kalimantan strongly declined after 8500 cal BP in close relation to the lowering rate of the sea-level rise and possibly influenced by the regional impact of the 8.2 ka event. Peat growth in Central Kalimantan apparently ceased during the Late Holocene in association with amplified El Niño activity as exemplified by several truncated peat profiles. Peat domes from the Kutai basin are all younger than ~8300 cal BP. Peat formation and rates of peat accumulation were driven by accretion rates of the Mahakam River and seemingly independent of climate. Most coastal peat domes, the largest expanse of SE-Asian peatlands, initiated between 7000 and 4000 cal BP as a consequence of a Holocene maximum in regional rainfall and the stabilisation and subsequent regression of the sea-level. These boundary conditions induced the highest rates of peat accumulation of coastal peat domes. The Late Holocene sea-level regression led to extensive new land availability that allowed for continued coastal peat dome formation until the present. The time weighted mean Holocene peat accumulation rate is 0.54 mm yr?1 for Central Kalimantan, 1.89 mm yr?1 for Kutai and 1.77 mm yr?1 for coastal domes of Sumatra and Borneo. The mean Holocene carbon sequestration rates amount to 31.3 g C m?2 yr?1 for Central Kalimantan and 77.0 g C m?2 yr?1 for coastal sites, which makes coastal peat domes of south-east Asia the spatially most efficient terrestrial ecosystem in terms of long term carbon sequestration. 相似文献
994.
建立了灰色预测模型和整数规划模对对出版社的资源进行优化配置,以期取得最佳经济效益,谋求长远发展战略. 相似文献
995.
996.
The experimental investigation of unidirectional random wave slamming on the three-dimensional structure in the splash zone is presented. The experiment is conducted in the marine environment channel in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The test wave is unidirectional irregular wave. The experiments are carried out with perpendicular random waves (β=0°) and oblique random waves (β=15°, 30°, 45°), the significant wave heights H1/3 ranging from 7.5 to 20 cm with 2.5 cm increment, the peak wave periods Tp ranging from 0.75 to 2.0 s with 0.25 s increment, and the clearance of the model with respect to the significant wave height s/H1/3 ranging from 0.0 to 0.5 with 0.1 increment. The statistical analysis results of different test cases are presented. The statistical distribution characteristics of the perpendicular irregular wave impact pressures are compared with that of the oblique irregular wave on the underside of the structure. The effect of the wave direction β on the wave impact forces on the underside of the structure is determined. The relation between the impact forces and the parameters such as the significant wave height, the relative structure width and the relative clearance of the structure is also discussed. 相似文献
997.
Based on China's observational data in 1951-1990,after minimizing the possible biasescaused by station relocation and urban heat island,the spatial and temporal distributions of trendsfor maximum and minimum temperatures are studied.The results show that increasing trends ofmaximum temperatures are in the areas west to 95°E,and north to the Huanghe(Yellow)River,while decreasing trends exist in eastern China south to the Yellow River.Minimum temperaturesare generally increasing throughout China,with dominant warming trends at the higher latitudes.This resulted in very obvious decreasing trends in diurnal temperature ranges.The periodic cycles are consistent between the maximum and minimum temperatures,butasymmetric trends are very obvious.The significant increase of minimum(nighttime)temperaturesreflects the evidence of enhancement of greenhouse effect.Further analysis shows that the changesof maximum and minimum temperatures are mainly related to sunshine duration and atmosphericwater vapor content. 相似文献
998.
999.
据近年内阿尔金断裂研究的进展阐述了应深入解决的4个科学问题及其研究思路:1)阿尔金大型走滑断裂何时发生?变形年代学研究证明阿尔金断裂初始走滑的年龄在89~97 Ma,即从晚中生代-早新生代才开始出现;2)运动学研究包括隆升与走滑两个方面,需要进行大比例尺度的构造研究和变形组构研究,尤其是断裂两盘错距的确定,必须找准被断裂错移的同一构造-岩相带的界线;3)阿尔金断裂的划分意义,它的延伸和规模及对中国西部以及中亚大陆构造格架的影响;4)阿尔金断裂对两侧盆地沉积-构造演化的控制和影响.解决上述4个科学问题,对于重新认识中国西部大陆构造格架、中国西部成矿带的展布及对中国西部找油的战略评估都具有非常重要的意义. 相似文献
1000.
滑坡灾害空间预测研究 总被引:14,自引:2,他引:14
介绍了滑坡灾害空间预测的常用理论和方法、研究特点和适用范围,指出了区域滑坡空间预测、单体斜坡稳定性预测和滑坡灾害风险研究的发展趋势;以三峡库区巴东县黄土坡区斜坡稳定性区划为例,用神经网络模型和信息量模型两种方法进行了斜坡稳定性预测,取得了满意的效果。 相似文献