两种水稻种植面积遥感提取方案的分析   总被引：13，自引：0，他引：13  

方红亮 《地理学报》1998,53(1):58-65,T001

文章以湖北省江陵县水稻面积提取为例,对这两种方案（分别称之为Ａ方案和Ｂ方案）进行了非监督分类试验,结果表明,在非监督分类过程中Ｂ方案明显优于Ａ方案,所提取的水稻面积精度也在８４％以上。  相似文献   

闽东南区域甘蔗生产变化与适度规模问题     

凌起  曾尊固 《热带地理》1998,18(1):53-58

闽乐南区域是中国主要蔗糖产区之一,１９８６年其甘蔗种植面积为７．３３×１０＾４ｈｍ＾２,蔗糖产量为５１．２×１０＾４ｔ,之后连年滑坡,１９９５年其甘蔗种植面积仅为３．１５×１０＾４ｍｈ＾２,蔗糖产量１６．２×１０＾４ｔ。调查分析了闽乐南区域甘蔗生产的历史及现状,认为其连年滑坡是由多种因素造成的,包括粮食和甘蔗争地矛盾、甘蔗生产和收购政策变化、种蔗收入比其他现金作物低、农户生产规模小而分散等。根据消  相似文献   

四川省若干治水方案的分析和讨论     

魏涛  卢敬华 《成都信息工程学院学报》1998,(1)

归纳了四川省治理干旱的４种方法：工程治水、生态治水、环境治水和农业治水,并对其进行了评价分析。最后,提出了治水的综合建议。  相似文献   

大型关系数据库与城市地质信息系统     

樊钧 《水文地质工程地质》1997,24(6):48-49

随着城市建设的迅速发展，勘测单位计算机应用已从孤立地处理单项工程走向管理和决策，以大型关系数据库为核心的信息管理和决策支持已经成为大型勘测单位设计地质信息系统的新命题。本文介绍了地质信息系统的特点及大型关系数据库在城市地质信息系统中的地位和作用。  相似文献   

大型板状交错层理内部沉积物的分异   总被引：2，自引：0，他引：2  

王泽中 《矿物岩石》1997,17(1):71-76

本文对取自长江上荆江三八滩大型板状交错层理内部同一细层不同部位的５个样品进行了粒度分析和矿物鉴定，结果表明，在同一细层内沉积物有明显的分异作用。细层中上部以中等粒径、低密度的颗粒为主，分选好。细层的下部和底部主要聚集沉积物的粗尾和细尾部分，因而分选较差。此外，密度较大的矿物亦趋于聚集在细层的底部。沉积物的这种分异主要是因为在沙波运移过程中矿物沿背流面发生重力分异且在背流面附近存在回流所致。大型板状交错层理内部沉积物的这种分异作用对认识其储集性能的层内非均质性有重要的意义  相似文献   

地壳内上升气流对物质的迁移及地气测量原理   总被引：21，自引：0，他引：21  

单纯菡  李巨初 《矿物岩石》1997,17(3):83-88

对地气采样片上地气物质状态观测，上升气流模拟模型以及扩散模型实验初步证明，地气物质是以纳米级微粒形式迁移；上升气流对物质的过移作用比物质扩散作用要强得多。结合对８个地区已知金矿地气测量成果，讨论了地气测量原理，认为是地壳内上升气流携带纳米级成矿物质至地表，在矿化体垂向投影的地表位置形成矿致地气异常。  相似文献   

ON THE BAROTROPIC INSTABILITY OF LARGE SCALE VORTICES^*     

Luo Zhexian 《Acta Meteorologica Sinica》1996,10(1):13-21

By using the linearized barotropic vorticity equation in polar coordinates the stability of perturbations on a large scale circular basic flow is transformed into a generalized eigenvalue problem,yielding the relationship between the growth rate of the amplitude of perturbations and the azimuthal wave number. Then, numerical experiments whose integration time is 60 model hours are performed in terms of a quasi-geostrophic barotropic model in Cartesian coordinates using the perturbation stream function field of unstable mode superimposed on a strong and weak circular basic flows as the initial fields. The experimental results reveal that the amplitudes of the initial perturbations in the model atmosphere grow with time. The amplitude of the perturbations superimposedon the strong circular basic flow grows quicker and forms a spiral-band-like structure.  相似文献   

Gravity potential at the Major Vertical Datum as primary geodetic constant     

Mariya I. Yurkina 《Studia Geophysica et Geodaetica》1996,40(1):9-13

Summary On the basis of the fundamental relations of the Molodensky's Earth's figure theory (1945), admitting the inequality of the gravity potentials at the Major Vertical Datum W₀ and on the surface of the reference level ellipsoid U₀, and taken into account that potential W₀ enters into equations directly, it is recomended, W₀ should be adopted as a primary geodetic constant. Parameters of the best fitting ellipsoid are not needed for the solution of geodetic problems and for the investigation of the Earth's gravity field. The reason for requiring the reference and actual fields be close is only that the boundary-value problem can be solved in the linear approximation. Dedicated to the Memory of M.S. Molodensky Contribution to the I.A.G. Special Commission SC3 Fundamental Constants (SCFC).  相似文献   

洛川黄土序列时间标尺的初步建立   总被引：10，自引：0，他引：10  

鹿化煜  安芷生 《高校地质学报》1996,2(2):230-236

对厚１４０ｍ的洛川坡头黄土剖面黄土层以５ｃｍ，古土壤层以３ｃｍ系统采样，全部样品进行了室内磁化率测量。以黄土序列磁化率变化作为古季风气候变化的代用指标，根据第四纪冰期的Ｍｉｌａｎｋｏｖｉｔｃｈ理论，利用轨道调缠绵的方法初步建立了洛川黄支的时间标尺。通过古地磁场倒转时间的检验以及与宝鸡黄土序列时间标尺对比，表明本文所论述的时间标尺适用于该地区古环境演化的研究。  相似文献   

Endogenous technological change and pollution abatement     

C. S. Kim  N. D. Uri  C. Sandretto  I. W. Parry 《Environmental Geology》1996,27(3):191-197

Nonpoint source pollution control is a more complicated process than traditional analysis suggests. Whether a new pollution abatement technology is developed exogenously or endogenously and the per unit reduction in the rate at which a pollutant associated with the use of a factor of production needed to produce an agricultural commodity due to this technology enters the environment are critical factors in the determination of the effects of agricultural production on the pollutant stock. These are the issues addressed here. The optimal current period research and development expenditures on an endogenously induced abatement technology associated with the use of a factor of production giving rise to environmental externalities are shown to be a function of, among other things, the cumulation of all research and development expenditures, the probability of an abatement technology being developed, the level of use of the factor of production, the unit pollution tax on the factor, the rate of time preference (discount rate), the rate at which the pollutant associated with the factor enters the environment, the rate of discharge of the pollutant stock, and so forth. Finally, the analysis demonstrates that a reduction in pollution by the adoption of an abatement technology may lead to an increase in the pollutant stock as a result of endogenous technological change associated with the pollution abatement. When the rate of pollution reduction is greater than a threshold, however, the adoption of an endogenously determined abatement technology will unequivocally lead to a reduction in the pollutant stock.The views expressed are those of the authors and do not necessarily represent the policies of the US Department of Agriculture or the views of other US Department of Agriculture staff members.  相似文献