广州市蔬菜生产布局与“渡淡”问题探讨

本文分析了广州市蔬菜供应出现淡季的主要原因，指出现行蔬菜生产布局的不合理性，并提出合理调整生产布局，改善淡季蔬菜供应的基本设想。     

内蒙古苏尼特左旗交其尔推覆构造带的发现及其地质意义

内蒙古苏尼特左旗中部交其尔一带发现一条近ＥＷ向延伸的推覆构造带。上元古界－下古生界浅变质岩以低角度向北推覆于晚古生代花岗岩基之上．推覆构造上盘的浅变质岩中发育有一套轴面向南倾的同斜倒转褶皱系，并伴有一系列向南倾的叠瓦状逆冲断面。下盘花岗岩中发育有较宽的糜棱岩带．沿推覆构造带分布有一系列的飞来峰及构造窗。这一构造带的发现，为纬向构造带的存在提供了有力证据，并显示了晚古生代末期以来地壳沿经线方向的强烈缩短。     

从景观生态学构建城市旅游开发与规划的操作模式

本文尝试建立一个关于旅游开发与规划的应用理论模式,以兼顾理论的抽象性和操作性。模式的构建依据地理空间分析方法,同时借用景观生态学斑、廊、基的概念。文中详细论述了该斑廊基网络结构操作模式的基本特点、变换空间分析方法等运行机制,并以不同城市旅游规划、设计实例说明三大操作块的功能和操作意义。     

计算机地形分析中的多边形迭加问题

在计算机地形分析中,研究地形多要素迭加分析的关键是解决多边形的迭加问题。本文通过对多边形迭加的数学方法的研究,提出了适合计算机多要素分析的原理和方法。     

Going Home: The Migration of Puerto Rican-Born Women from the United States to Puerto Rico*

This paper analyzes the migration of Puerto Rican-born women from the United States to Puerto Rico using longitudinal data. We hypothesize that sojourn length in the United States is a function of both structural (macro-level economic and cultural factors) and behavioral (micro-level life-cycle experiences and personal attributes) variables. We test these hypotheses by estimating a proportional hazards model. The parameter estimates of this model indicate that sojourn length in the United States, and thus the decision to return to Puerto Rico, is a function of wage trends and community characteristics on the mainland plus a number of individual attributes that include education, marriage, and childbirth.     

Structural Spatial Interaction*

This paper identifies a concept of structural spatial interaction. Although it is defined differently from its counterpart of structural unemployment in economics, it attempts to define a similar idea. In economics, the focus is on equilibrium in the supply and demand of labor. In this paper structural interaction is that which minimizes aggregate distance travelled, subject to constraints on origins and destinations. The structural interaction model produces an equilibrium, therefore, in the supply and demand of movers, while identifying a spatially efficient trip distribution. It is portrayed as a type of relaxed interaction model and is illustrated using an example of structural migration with Canadian interprovincial migration data.     

Structural pattern in the Precambrian rocks of Sonua-Lotapahar region,North Singhbhum,eastern India

In the western part of the North Singhbhum fold belt near Lotapahar and Sonua the remobilized basement block of Chakradharpur Gneiss is overlain by a metasedimentary assemblage consisting of quartz arenite, conglomerate, slate-phyllite, greywacke with volcanogenic material, volcaniclastic rocks and chert. The rock assemblage suggests an association of volcanism, turbidite deposition and debris flow in the basin. The grade of metamorphism is very low, the common metamorphic minerals being muscovite, chlorite, biotite and stilpnomelane. Three phases of deformation have affected the rocks. The principal D1 structure is a penetrative planar fabric, parallel to or at low angle to bedding. No D1 major fold is observed and the regional importance of this deformation is uncertain. The D2 deformation has given rise to a number of northerly plunging major folds on E-W axial planes. These have nearly reclined geometry and theL ₂lineation is mostly downdip on theS ₂surface, though some variation in pitch is observed. The morphology of D2 planar fabric varies from slaty cleavage/schistosity to crenulation cleavage and solution cleavage. D3 deformation is weak and has given rise to puckers and broad warps on schistosity and bedding. The D2 major folds south of Lotapahar are second order folds in the core of the Ongarbira syncline whose easterly closure is exposed east of the mapped area. Photogeological study suggests that the easterly and westerly closing folds together form a large synclinal sheath fold. There is a continuity of structures from north to south and no mylonite belt is present, though there is attenuation and disruption along the fold limbs. Therefore, the Singhbhum shear zone cannot be extended westwards in the present area. There is no evidence that in this area a discontinuity surface separates two orogenic belts of Archaean and Proterozoic age.     

变质岩构造置换与片层理概念的讨论

构造置换应分成形体置换和方位置换两类。形体置换是在一定尺度内新的透入性构造要素代替了旧的透入性构造要素,使后者不易识别或无法识别的置换作用;方位置换是在一定尺度内旧的透入性构造要素残存着,但其方位被改变,与新的透入性构造要素平行或近于平行的置换作用。片层理是受到不明显的形体置换和强的方位置换的层理,它具有片理的方位,层理的形体,是与片理产状一致的那一部分层理。     

Sedimentational,structural and migmatitic history of the Archaean Dharwar tectonic province,southern India

The earliest decipherable record of the Dharwar tectonic province is left in the 3.3 Ga old gneissic pebbles in some conglomerates of the Dharwar Group, in addition to the 3.3–3.4 Ga old gneisses in some areas. A sialic crust as the basement for Dharwar sedimentation is also indicated by the presence of quartz schists and quartzites throughout the Dharwar succession. Clean quartzites and orthoquartzite-carbonate association in the lower part of the Dharwar sequence point to relatively stable platform and shelf conditions. This is succeeded by sedimentation in a rapidly subsiding trough as indicated by the turbidite-volcanic rock association. Although conglomerates in some places point to an erosional surface at the contact between the gneisses and the Dharwar supracrustal rocks, extensive remobilization of the basement during the deformation of the cover rocks has largely blurred this interface. This has also resulted in accordant style and sequence of structures in the basement and cover rocks in a major part of the Dharwar tectonic province. Isoclinal folds with attendant axial planar schistosity, coaxial open folds, followed in turn by non-coaxial upright folds on axial planes striking nearly N-S, are decipherable both in the “basement” gneisses and the schistose cover rocks. The imprint of this sequence of superposed deformation is registered in some of the charnockitic terranes also, particularly in the Biligirirangan Hills, Shivasamudram and Arakalgud areas. The Closepet Granite, with alignment of feldspar megacrysts parallel to the axial planes of the latest folds in the adjacent schistose rocks, together with discrete veins of Closepet Granite affinity emplaced parallel to the axial planes of late folds in the Peninsular Gneiss enclaves, suggest that this granite is late-tectonic with reference to the last deformation in the Dharwar tectonic province. Enclaves of tonalite and migmatized amphibolite a few metres across, with a fabric athwart to and overprinted by the earliest structures traceable in the supracrustal rocks as well as in a major part of the Peninsular Gneiss, point to at least one deformation, an episode of migmatization and one metamorphic event preceding the first folding in the Dharwar sequence. This record of pre-Dharwar deformation and metamorphism is corroborated also by the pebbles of gneisses and schists in the conglomerates of the Dharwar Group. Volcanic rocks within the Dharwar succession as well as some of the components of the Peninsular Gneiss give ages of about 3.0 Ga. A still younger age of about 2.6 Ga is recorded in some volcanic rocks of the Dharwar sequence, a part of the Peninsular Gneiss, Closepet Granite and some charnockites. These, together with the 3.3 Ga old gneisses and 3.4 Ga old ages of zircons in some charnockites, furnish evidence for three major thermal events during the 700 million year history of the Archaean Dharwar tectonic province.