3-D density model of the crust of southern and central Finland obtained from joint interpretation of the SVEKALAPKO crustal P-wave velocity models and gravity data   总被引：1，自引：0，他引：1  

E. Kozlovskaya  S. Elo  S.-E. Hjelt  J. Yliniemi  M. Pirttijärvi  SVEKALAPKO Seismic Tomography Working Group 《Geophysical Journal International》2004,158(3):827-848

  相似文献   

山西北部沙棘群落优势种种间关系   总被引：8，自引：2，他引：8  

李晶  上官铁梁 《山地学报》2006,24(2):222-227

用X2检验、Jaccard关联指数及Pearson相关和Spearman秩相关系数对山西北部地区沙棘群落20个优势种群进行种间关系研究。结果表明:1)X2检验共有8个种对为显著正关联,2个种对为显著负关联;Pearson相关系数有10个种对为显著正相关,3个种对为显著负相关;Spearman秩相关系数有14个种对为显著正相关,7个种对为显著负相关。Spearman秩相关检验用于表征种间关联具有较高的灵敏度;2)草本层呈显著和极显著相关的种对最多,灌木与草本间呈显著和极显著相关的种对次之;3)灌木种群间均呈现负相关,表明沙棘群落尚处于动态演替之中。根据Spearman秩相关星座图,将20个优势种划分为4个生态种组,各生态种组内的种具有相似的生态适应性,而组间则表现出明显的差异性;灰栒子、小叶鼠李、灌木铁线莲对特殊生境有较强适应性,呈现独立分布格局。  相似文献   

时空拓扑关系定义及时态拓扑关系描述   总被引：30，自引：6，他引：30  

舒红  陈军 《测绘学报》1997,26(4):299-306

目的，国际上对于作为时空数据模型概念和形式化基础的时空拓扑关系定义和描述还没有一个明确的阐述。本文在分析ＧＩＳ的时空特性后，给出了一个语义层时空拓扑关系定义。同时，提出并证明了完备、唯一的描述时态拓扑关系的４Ｉ框架，列出了时态拓扑关系描述的谓词集，区别了时态拓扑关系和时间方向关系的内涵和谓词描述形式。  相似文献   

A uniform catalog of earthquakes for seismic hazard asesment in Iran   总被引：6，自引：0，他引：6  

高孟谭  陈运泰  王健 《地震学报(英文版)》1997,10(6):713-726

ＡｕｎｉｆｏｒｍｃａｔａｌｏｇｏｆｅａｒｔｈｑｕａｋｅｓｆｏｒｓｅｉｓｍｉｃｈａｚａｒｄａｓｅｓｍｅｎｔｉｎＩｒａｎＮｏｏｒｂａｋｈｓｈＭｉｒｚａｅｉ１，２）ＭＥＮＧ－ＴＡＮＧＡＯ１）（高孟谭）ＹＵＮ－ＴＡＩＣＨＥＮ１）（陈运泰）ＪＩＡＮＷＡＮＧ１...  相似文献   

Regional variation of mechanical and chemical denudation,upper Colorado River Basin,U.S.A.     

Karl-Heinz Schmidt 《地球表面变化过程与地形》1985,10(5):497-508

The variation of mechanical and chemical denudation is investigated using discharge and sediment yield data from the Upper Colorado River System. Annual precipitation ranges from approximately 150 mm to 1500 mm. Mean specific yield ranges from 0-2 1/s km² ( = 6 mm p a) to 151/s km² ( = 475 mm p a). The hydrological-geomorphological system adjusts itself to these varying climatic conditions; in some areas, however, the effects of lithology or land use seem to override the climatic controls. It is demonstrated that the increase in the absolute and particularly the relative amount of suspended sediment is closely related to a decrease in annual runoff and to an increase in the importance of high magnitude/low frequency events. This indicates that in areas of low annual runoff and high runoff variability, soluble rocks are more resistant than in more humid areas. During high magnitude/low frequency events, suspended sediment concentrations and loads are very high in semiarid areas due to sparse vegetation cover and dominance of direct runoff. Events of moderate magnitude and frequency, which in more humid areas transport most of the dissolved load, seldom occur. The trend towards increasing mechanical denudation is even observed in areas of very low runoff (0-221/s km² = 7 mm p a). The peak of sediment yield in dry areas seems to approximate the point of no runoff very closely. Mechanical and chemical denudation are of equal importance at a runoff of about 300 mm per year.  相似文献   

Response to Thrift's “The future of geography”     

B. L. Turner II 《Geoforum》2002,33(4):427-429

Reviews and observations about the status of the discipline of geography, no matter how positive, invariably raise programmatic concerns. These concerns have a long history that arise from geography's struggles to find an identity that embraces its many parts and yet are consistent with the logic by which the academy partitions knowledge. Pedagogy and research historically claimed by geography is currently being reinvented and relabeled under such headings as “integrated environmental science” and “spatial science”, and these developments have the potential to change the breadth of the “geographic imagination”. Several observations about dominant explanatory perspectives and substantive domains of geographic enquiry are also provided.  相似文献   

Practicing Sociogeomorphology: Relationships and Dialog in River Research and Management     

Simon A. Mould  Kirstie Fryirs  Richie Howitt 《社会与自然资源》2018,31(1):106-120

Sustainable river management requires strong participation from technical and nontechnical experts. However, in many cases, the nontechnical element is lacking. This paper explores possibilities for participation that can emerge from a reorientation toward dialog. This reorientation is supported by a sociogeomorphological approach, which encourages recognition of the physical and social coproduction of a fluvial landscape, including a history of colonization and landscape degradation. Recognition of this sociogeomorphic context invited dialog with stakeholders involved in river management, which revealed opportunities for improving relationships in river management. The paper argues that dialog supports building interpersonal relationships as a basis for river management, where relationships could replace “stakes” as a structure for participation. Following reorientation, relationship development and maintenance, through dialog, emerges as a key activity of environmental management. Because dialog happens at the interpersonal scale, a relational approach has potential implications for researchers, practitioners, and stakeholders in many fields of environmental management.  相似文献   

伊利石结晶度Kbler,Weaver和Weber指数关系式常数的确定与应用     

王河锦  陶晓风  Rahn Meinert 《高校地质学报》2007,(3)

根据衍射峰具有的不同分布特点推导出了14个伊利石结晶度Kbler指数,Weaver指数和Weber指数关系式中常数项C1-C14的数值,提出了PearsonVII分布中形态参数μ与C5,C6,C11,C12的4个定量方程。由此,14个伊利石结晶度指数关系式可直接用于实际计算。根据阿尔卑斯复理石伊利石形态特征Sc=0.731,由这些关系式进行近变质带上下界线的转换得出与Kbler指数0.42～0.25。△2θ界线对应的Weaver指数和Weber指数的界线值分别为5.8～17.6和300～179。讨论了在自然干燥状态下直接进行伊蒙混层鉴定的基本原理。  相似文献   

SHEBA flux–profile relationships in the stable atmospheric boundary layer     

Andrey A. Grachev  Edgar L Andreas  Christopher W. Fairall  Peter S. Guest  P. Ola G. Persson 《Boundary-Layer Meteorology》2007,124(3):315-333

Measurements of atmospheric turbulence made during the Surface Heat Budget of the Arctic Ocean Experiment (SHEBA) are used to examine the profile stability functions of momentum, φ _m , and sensible heat, φ _h , in the stably stratified boundary layer over the Arctic pack ice. Turbulent fluxes and mean meteorological data that cover different surface conditions and a wide range of stability conditions were continuously measured and reported hourly at five levels on a 20-m main tower for 11 months. The comprehensive dataset collected during SHEBA allows studying φ _m and φ _h in detail and includes ample data for the very stable case. New parameterizations for φ _m (ζ) and φ _h (ζ) in stable conditions are proposed to describe the SHEBA data; these cover the entire range of the stability parameter ζ = z/L from neutral to very stable conditions, where L is the Obukhov length and z is the measurement height. In the limit of very strong stability, φ _m follows a ζ ^1/3 dependence, whereas φ _h initially increases with increasing ζ, reaches a maximum at ζ ≈ 10, and then tends to level off with increasing ζ. The effects of self-correlation, which occur in plots of φ _m and φ _h versus ζ, are reduced by using an independent bin-averaging method instead of conventional averaging.  相似文献   

High density neighborhoods: Who enjoys them?     

Michal?MitranyEmail author 《GeoJournal》2005,64(2):131-140

To date, research into the subjective aspects of high density has focused mainly on the negative consequences of overcrowding. This study, in contrast, outlines some of the positive aspects of high density in neighborhoods, exploring the physical–spatial environment of two neighborhoods in the city of Haifa, Israel. It was found that while the relatively high residential density was similar in both neighborhoods (40 housing units per acre), this was more positively evaluated in one neighborhood as compared to the other. This can be attributed to some specific environmental and planning features. In particular, where physical planning enabled the potential advantages of high density to be realized, this was positively perceived and evaluated by local residents. Such advantages mainly comprised accessibility to a variety of services, more frequent public transportation, and access to open spaces within walking distance. Particularly advantageous were the increased opportunities for social gathering. At the same time, however, high density did not foster social relationships on the neighborhood level. The study further identified the gender and age groups that benefited most from the high density. Thus, women evaluated high density more positively than men. Young families with children and senior citizens (over 65) were also more likely to benefit, and to evaluate the high density environment more positively than other social groups.  相似文献