基于面向对象的空间数据库引擎模型分析   总被引：5，自引：0，他引：5  

王建涛 宋冰王青山  李林涛 《测绘学院学报》2005,22(2):110-111,115

分析了现有的空间数据库系统SDE的核心技术和面向对象SDE模型的结构。SDE是目前应用比较成功的空间数据库系统，它采用的空间数据库技术在一定程度上能够很好地对空间数据和属性数据进行管理，对设计自己的空间数据管理系统是很好的借鉴。  相似文献   

7个新近发现的与分子外流成协的H_2O脉泽     

向德琳 《天文学报》1995,(1)

本文发表继探测到恒星形成区的１０个新Ｈ２Ｏ脉泽［１］后，再发现和证认的７个银河系星际Ｈ２Ｏ脉泽及其有关参量和谱线图。这些新Ｈ２Ｏ脉泽是与ＣＯ分子外流源［２－５］ＡＦＧＬ５１４２，ＨＨ－３，ＡＦＯＬ５１５７，ＮＧＣ２０２３，ＲＮＯ７３，２０１２６＋４１０４，Ｌ１２５１－Ａ成协的。它们与相应的外向流的中心ＩＲＡＳ点源间的平均位置差为｜△α｜＝２４＇＇．８，｜△δ｜＝２７＇＇。  相似文献   

The effects of demagnetizing fields on thermoremanent magnetization acquired by parallel-sided baked clay blocks     

Philippe Lanos 《Geophysical Journal International》1987,91(3):985-1012

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Coma Morphology And Constraints On The Rotation Of Comet Hale–Bopp (C/1995 O1)     

Samarasinha  Nalin H.  Mueller  Béatrice E. a.  Belton  Michael J. S. 《Earth, Moon, and Planets》1997,77(3):189-198

We present constraints on the spin state of comet Hale-Bopp based on coma morphology. Three cases of rotational states are compatible with near perihelion observations: (1) principal-axis rotation, (2) complex rotational state with a small precessional angle, or (3) complex rotational state with a large ratio between the component periods. For principal axis rotators, images from 1996 (pre-perihelion) are consistent with a rotational angular momentum vector, M, directed at ecliptic longitude and latitude (250°, -5°) while images from late 1997 (post-perihelion) indicate (310°, -40°). This may suggest a change in M. A complex rotational state with small precessional angle requires only a small or no change in M over the active orbital arc. In this case, M is directed near ecliptic longitude and latitude (270°, -20°). A rotationally excited nucleus with a large ratio between component periods requires the nucleus to be nearly spherical. The transformation of dust coma morphology from near-radial jets to bright arcs and then again to near-radial jets is interpreted as a heliocentric and geocentric distance dependent evolutionary sequence. The spiral structures seen in CN filters near perihelion (in contrast to sunward side arcs seen in continuum) can be explained if the precursor of CN molecules (likely sub-micron grains) are emitted from the nucleus at low levels (≈ 10% of the peak daytime emission) during the nighttime. This may be indicative of a nucleus with a CO-rich active area(s). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

关于创建网络经济学的构想     

黄宗捷 《成都信息工程学院学报》2001,16(1):46-51

网络经济的迅猛发展，不仅给全球的社会经济活动注入了新的活力，而且还赋予了经济理论工作者的建网络经济学的重任。实践正在热切地呼唤网络经济学的横空出发；在网络经济这一特研究领域里，客观存在着研究网络经济生产方工的特有矛盾，这为网络经济学的科学创立奠定了坚实的基础；由于网络经济既是一种覆盖全球的经济，又是一半随自身运行而产生若干新价值观念带许多新问题的经济。因此，对网络经济的研究应有其独特的方法。  相似文献   

Variations of some heavy minerals in recent beach sands     

A. B. Vistelius  M. E. Demina 《Mathematical Geology》1982,14(2):161-187

The influence of shape, size, and specific gravity of mineral grains on the variation of the content of these minerals in beach sands has been investigated for fixed conditions of sedimentation on the beaches of the Baltic Sea and Michigan Lake. The coefficient of variation was used as a measure of the variance. Linear models tested by the analysis of variance were applied and revealed that the shape of grains and the combined effect of the size and specific gravity are responsible for the main part of the variation.  相似文献   

Study on the New Methods of Ship Object Detection Based on GNSS Reflection     

Yong Lu  Dongkai Yang  Weiqiang Li  Jichen Ding  Ziwei Li 《Marine Geodesy》2013,36(1):22-30

This paper presents a study on the new methods of ship object detection based on GPS-R correlation power spectra. Both the principle and the algorithms for recognition are given in detail. The architecture of Doppler Delay Mapping Receiver (DDMR), signal-processing chain, and correlation power spectra discriminant of the reflected signals from the ship object are discussed. Real-time data collection campaigns were done near the sea at Sanya with the Doppler delay mapping receiver mounted on an airplane. Some preliminary experiment results show that the DDMR could work well and can be used in ship object detecting.  相似文献   

Harbour entrance morphology and sediments at a river mouth port,Westport, New Zealand     

R. M. Kirk  W. J. Hastie  J. L. Lumsden 《新西兰海洋与淡水研究杂志》2013,47(4):689-697

Entrance morphologies and sediment characteristics were studied at Westport Harbour, a river mouth port located on the Buller River, New Zealand. The most frequent morphology found was that in which two submarine bars were present off the river mouth. When present, these bars were separated by a transverse channel running east from Carters Beach and terminating in the principal inlet channel. Sediment samples were collected and analysed for grain size, reliability (grain shape), and, in a few instances, mineralogy. The data collected suggested that longshore sediment transport is predominantly west to east and that river derived sediment is deflected to the east. The inner bar is predominantly a littoral drift related event whereas the outer bar, which is composed mainly of littoral drifted sediment, forms as a submarine extension of Carters Beach. Both bars can be modified by floods in the river, although modification of the outer bar is much less frequent because of the very high river flows required. Sediment can bypass directly across the river mouth only when the inner bar is present. On other occasions bypassing can only occur by transport through the transverse channel or over the outer bar, into the river channel and then onshore.  相似文献   

Shape from shading—a method of integration of sonar images and bathymetric data for ocean mapping     

Rongxing Li 《Marine Geodesy》2013,36(2-3):115-127

Shape from shading is one of the methods that derive geometric information of objects from analysis of monocular images. Application of this technique to underwater sonar images enables the conversion of imposed reflectance characteristics in sonar images to shape information, namely, slopes, about the seafloor surface. A combination of this shape information and available sparse distributed depth points results in improved dense bathymetric data.

The reconstruction of shape models of seafloor surfaces from sonar images is treated as an inverse problem and is solved by the regularization theory. Sparse gridded points are used for boundary constraints. The regularization is implemented as a relaxation procedure with a hierarchical structure of multiresolution grids.  相似文献   

扇三角洲砂体几何形态沉积数值模拟方法研究          下载免费PDF全文

陈戈  斯春松  张惠良 《江苏地质》2013,37(2):178-182

扇三角洲是陆相碎屑岩重要的沉积类型之一.利用砂体沉积过程数值模拟方法可以预测扇三角洲砂体的几何形态.在利用泥沙冲淤动力学模式建立扇三角洲沉积过程的数学方程后,根据现代三角洲沉积特征,设计了其沉积过程的模拟条件,计算域长100 km、宽50 km,流量按50年一遇洪水设计,模拟过程到2 000年时,扇三角洲沉积过程基本达到平衡状态,此时前缘复合砂体最大厚度约39 m.通过对扇三角洲前缘砂体几何形态的模拟研究,总结出扇三角洲沉积体储层建筑结构的模拟与预测方法.计算过程中可识别出4种沉积砂体,包括水下分流河道(砂体的平均长宽比为2.68,平均宽厚比为79.8)、河口砂坝(平均长宽比为2.02,平均宽厚比为68.2)、远砂坝(平均长宽比为1.65,平均宽厚比为58.3)、水下溢岸沉积.主要沉积单元砂体几何参数之间的相关关系较好.实验结果表明,利用泥沙冲淤动力模式可以较好地揭示扇三角洲发育过程,进而可以预测扇三角洲砂体的几何形态.  相似文献