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961.
962.
基于多目标遗传算法的土地利用空间结构优化配置 总被引:12,自引:0,他引:12
针对如何将土地利用数量结构落实到具体的地域空间,以实现土地资源的优化配置的土地利用总体规划编制难点,以及常规的叠加法等土地利用配置方法难以根据土地适宜性评价结果,有效地将土地利用数量结构匹配到具体的土地单元问题,该文利用遗传算法的内在并行机制及其全局优化的特性,提出了基于多目标遗传算法的土地利用空间结构优化配置方法。实例分析表明,该方法具有客观性强、灵活性高、操作简便等优点。 相似文献
963.
964.
965.
方解石和白云石溶蚀实验热力学模型及地质意义 总被引:15,自引:0,他引:15
通过碳酸盐(方解石、白云石)溶蚀作用实验室模拟研究,建立了溶蚀作用的热力学模型方程,对埋藏成岩的3种不同温压条件下(348.15K,Mpa ,373.15K,25Mpa,403.15K,30MPa)碳酸盐溶蚀作用进行了定量研究。提出随着温度和压力的升高,碳酸盐溶解反应的吉布春播由能降低,因而溶解反应增强;在相同温度和压力的地质条件下,白云石较方解石更易溶蚀并形成次生孔隙,这为油气生成运移提供了有利的地下空间和通道。 相似文献
966.
Nathaniel W Rutter Dean RokoshMichael E Evans Edward C LittleJiri Chlachula Andrei Velichko 《Quaternary Research》2003,60(1):101-109
Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle. 相似文献
967.
Paleolake sediment, constrained by tephrochronology, from Onepoto basin volcanic crater in Auckland, Northern New Zealand (36° 48′S), provides one of the few uninterrupted records of paleovegetation for marine oxygen isotope stages (MIS) 4 and 3 (76,000–26,000 yr B.P.) in the region. This period was characterized by cool temperate conifer-hardwood forest that lacked some of the warmer taxa typical of the Holocene. The period 64,400–60,500 yr B.P. was marked by opening of forest canopy and expansion of small trees and shrubs, and correlates to the thermal minima of MIS 4. However, the landscape was never as open as the forest-shrubland mosaic of the MIS 2. The beginning of MIS 3 (60,500–50,500 yr B.P.) was marked by the dramatic expansion and then decline of conifer-hardwood forest dominated by Dacrydium cupressinum, a species that prefers wetter conditions. This forest was succeeded by the typically montane Nothofagus at 50,500 yr B.P., corresponding to a thermal decline. Thus, MIS 3 began with an abrupt change to moist cool conditions that lasted about 5000 yr, followed by gradual cooling and dryer conditions. This supports some interpretations from other parts of the southwest Pacific region, that MIS 3 was a period of increased precipitation. The widespread and stratigraphically important Rotoehu tephra, erupted from Okataina Volcanic Centre, has been variously dated at 45,000–65,000 yr B.P. At Onepoto, sedimentation rate and paleovegetation reconstruction imply an age of c. 44,300 yr B.P. The tephra provides a correlation horizon in the marine and terrestrial realms during a period (MIS 3) difficult to date by radiometric methods. 相似文献
968.
向海湿地孢粉记录及其环境意义 总被引:4,自引:2,他引:4
以霍林河下游向海湿地为研究对象,通过对湿地垂直剖面的精细采样,将放射性核素精确计年与孢粉组合特征研究相结合,进行高分辨率剖析。研究结果表明:受沉积环境的影响,不同地表水力梯度与不同地貌单元的孢粉组合特征相差较大。典型剖面孢粉图式、A/C比值与麻黄属花粉丰度分析表明,该区域以草甸草原或草原景观为主,流域大环境以半干旱为特征,局部小环境为水流缓慢或静水沉积环境,并受到风沙的影响。240年以来虽然亦存在短暂的温湿期(1851-1861aA.D.及1890-1920aA.D.),但半干旱的气候特征始终没有改变。对照相邻区域研究成果,本区近代气候具有继承性和相似性。 相似文献
969.
由于中亚优越的地理位置、丰富的能源战略资源,使其成为大国争夺的目标。本文通过阐述中亚能源状况及潜在经济利益,分析美国对中亚能源战略实施的各种手段,预测其发展及影响。 相似文献
970.
Extensive compositional heterogeneity is shown to affect at least twenty four of the doped trace elements in the NIST SRM 610-617 glasses.
Compositional profiling and mapping using laser ablation ICP-MS reveals that all NIST SRM 610-617 wafers examined here contain domains that are significantly depleted in Ag, As, Au, B, Bi, Cd, Cr, Cs, Mo, Pb, Re, (Rh), Sb, Se, Te, Tl and W, and antithetically enriched in Cu (and Pt), with large enrichments in Cd, Fe and Mn also being encountered in some cases. These domains are visible in doubly polished wafers by unaided visual inspection and by transmitted light and schlieren microscopy. They occur in close proximity to the wafer perimeters and also as stretched and complexly folded forms within wafer interiors. The chemical and optical properties of these heterogeneous domains are consistent with those of compositional cords, a phenomenon of glass manufacture where glass bulk composition and physical properties are modified by loss of volatile components from the molten glass surface. The NIST SRM 610-617 glasses may be considered reliable reference materials for microanalysis of only between one half and two thirds of the trace elements with which they were doped, including Be, Mg, Sr, Ba, Sc, Y, REE, V, Zr, Hf, Nb, Ta, Th, U, Ga, In, Sn, Co, Ni and Zn. These elements show no evidence of significant heterogeneity, indicating that the original glass constituents and possible residues remaining in the furnace from preceding glass batch fusions were well homogenised during manufacture. 相似文献
Compositional profiling and mapping using laser ablation ICP-MS reveals that all NIST SRM 610-617 wafers examined here contain domains that are significantly depleted in Ag, As, Au, B, Bi, Cd, Cr, Cs, Mo, Pb, Re, (Rh), Sb, Se, Te, Tl and W, and antithetically enriched in Cu (and Pt), with large enrichments in Cd, Fe and Mn also being encountered in some cases. These domains are visible in doubly polished wafers by unaided visual inspection and by transmitted light and schlieren microscopy. They occur in close proximity to the wafer perimeters and also as stretched and complexly folded forms within wafer interiors. The chemical and optical properties of these heterogeneous domains are consistent with those of compositional cords, a phenomenon of glass manufacture where glass bulk composition and physical properties are modified by loss of volatile components from the molten glass surface. The NIST SRM 610-617 glasses may be considered reliable reference materials for microanalysis of only between one half and two thirds of the trace elements with which they were doped, including Be, Mg, Sr, Ba, Sc, Y, REE, V, Zr, Hf, Nb, Ta, Th, U, Ga, In, Sn, Co, Ni and Zn. These elements show no evidence of significant heterogeneity, indicating that the original glass constituents and possible residues remaining in the furnace from preceding glass batch fusions were well homogenised during manufacture. 相似文献