RELAXING ASSUMPTIONS OF PERFECT INFORMATION IN PARK VISITATION MODELS*     

Daniel J. Stynes  Daniel M. Spotts  John R. Strunk 《The Professional geographer》1985,37(1):21-28

Variables related to urban park awareness are identified and methods for relaxing assumptions of perfect information in park use models are discussed. Park awareness is related to park characteristics (age and degree of development of the park), population characteristics (race, age, length of residence, recreation participation), and distance. Park attributes are stronger predictors of both park awareness and use than is distance. These findings parallel similar research on the cognitive aspects of shopping decisions.  相似文献   

时空概念中的椭球改正     

夏哲仁 《测绘学报》1991,20(3):190-200

  相似文献   

广西大厂拉么锌铜多金属矿床成岩成矿作用年代学研究   总被引：20，自引：1，他引：19  

李华芹  王登红  梅玉萍  梁婷  陈振宇  郭春丽  应立娟 《地质学报》2008,82(7):912-2008-01-30

本文对广西大厂矿田拉么矿区内出露的酸性侵入岩和矿石进行了精细的年代学研究,分别获得龙箱盖含斑黑云母花岗岩锆石原位SHRIMP UPb和全岩RbSr等时线年龄为94±4Ma（95%可信度）和98.6±1.9Ma（95%可信度）,矽卡岩成矿期锌铜矿石中石英矿物RbSr等时线年龄为98.6±6Ma（95%可信度）。上述测定结果表明,拉么锌铜多金属矿床的成矿年龄与相关岩体的成岩年龄接近,均形成于早白垩世晚期。  相似文献   

舟山国家石油储备基地堆载预压加固效果分析   总被引：5，自引：0，他引：5  

朱向荣  李振  王金昌 《岩土力学》2008,29(4):881-886

介绍了舟山国家石油储备基地试验区软基堆载预压大型现场试验结果,根据现场试验测得的数据,分析了软土地基堆载预压下沉降变化规律、分层沉降变化规律、深层土体位移变化规律、超静孔隙水压力变化规律,进一步探讨了根据应力和应变分析得到的地基固结性状,其中通过应变分析得到适用于储备基地的沉降经验系数m。结果表明,打设塑料排水板结合堆载预压处理软弱地基具有良好的效果。  相似文献   

影响低渗透油藏低速非线性渗流的实验研究     

王正波  岳湘安  韩冬  王金峰 《矿物学报》2008,28(1):48-54

以膨胀性的粘土为主要研究对象,通过粘土浆体的流变性实验和填砂管渗流实验,并使用一种新研制的微流量测量工具,研究了低渗岩心在较低流速下的渗流特性;利用微尺度流动理论,Einstein粘度定律等进行了理论分析,对引起低渗透油藏低速非线性渗流的影响因素进行了初步的探索.结论认为,粘土的膨胀性以及其水化后形成浆体的流变性是引起低速非线性渗流的主要因素之一.  相似文献   

一种计算台风风场的方法     

陈孔沫 《热带海洋学报》1994,(2)

揭示Ｒａｎｋｉｎｅ涡风场模式和Ｊｅｌｅｓｎｉａｎｓｋｉ风场模式之间的联系，并设计了一种台风风场分布模式，它的风速分布曲线落在Ｊｅｌｅｓｎｉａｎｓｋｉ和Ｒａｎｋｉｎｅ涡两个风场模式的风速分布曲线之间，具有一个既优于Ｊｅｌｅｓｎｉａｎｓｋｉ又优于Ｒａｎｋｉｎｅ涡的风速衰减速率，因此它同时克服了Ｒａｎｋｉｎｅ涡模式计算风速偏小和Ｊｅｌｅｓｎｉａｎｓｋｉ模式计算风速偏大的缺点，以一种比较合理的变化趋势向远方衰减，成为一个比较切合实际的台风风场分布模式。同时，文中提出的移行台风风场计算方法对宫崎正卫、上野武夫和Ｊｅｌｅｓｎｉａｎｓｋｉ模式都有一定的改进。  相似文献   

在各类天气系统影响下石臼港沿岸波浪场的分布     

黄爱军  李观金 《海洋预报》1994,11(3):15-25

本文查阅了从１９７３－１９８５，１３年的历史资料，对石臼港沿岸波浪场进行了详细的分类、统计分析和计算，提出了各类较强天气系统影响石（即指石臼港）的极端区域，同时获得了石港沿岸各类天气系统影响下的波浪分布特点以及波高计算式，为保障石港的生产及港口建设为石港的波了提供了有益的分析数据和预报手段。  相似文献   

Marine Ecology - A Century of Changes     

Rupert  Riedl 《Marine Ecology》1980,1(1):3-46

Abstract. The major changes within the concepts of marine ecology are investigated, with the aim to design this new journal's scientific format. Four phases of marine sciences are distinguished: the phase of seafarers, of oceanographic expeditions, of marine stations, and of field research. The changes in the latter two are discussed in detail. The changes are described as occurring along three axes. First, as a movement towards the object; accomplished by fieldwork, scientific diving, remote controlled equipment, and by underwater experimentation. Second, the cooperation between several disciplines that led towards bridging gaps. And lastly, how the discovery of unifying principles in ecology (the development of an ecological theory) led the approach in marine ecology towards increasing complexity.  相似文献   

海水中234Th的超低水平液闪谱仪测定   总被引：2，自引：1，他引：2  

李鸿宾  黄奕普  陈敏  刘广山  邱雨生 《台湾海峡》2004,23(2):199-207

本文提出了利用超低水平液闪谱仪测定海水中234Th的方法.海水经氢氧化铁吸附共沉淀富集后,接着用阴离子交换和TBP/煤油萃取进行Th同位素的分离与纯化.对一系列测定条件进行了详细的研究,提出了测定海水中234Th的适宜程序,即在含有234Th和产额示踪剂230Th的纯化后的5mol/dm3HNO3溶液中加入TBP/煤油进行萃取,然后用0.1mol/dm3HNO3反萃取,后者是先用契伦柯夫计数法测量234Th(通过234mPa),后加入闪烁液Hisafe 3用α/β模式测量α放射体230Th.对于α和β放射体液闪谱仪的计数效率分别为100%和55.7%±2.7%.234Th的化学回收率和总探测效率分别为70%～80%和30%～45%.该法测定海水中的234Th快速、简便和高效.  相似文献   

Rifting to Spreading Process along the Northern Continental Margin of the South China Sea   总被引：7，自引：0，他引：7  

Kido  Yukari  Suyehiro  Kiyoshi  Kinoshita  Hajimu 《Marine Geophysical Researches》2001,22(1):1-15

Understanding the development from syn-rift to spreading in the South China Sea (SCS) is important in elucidating the western Pacific's tectonic evolution because the SCS is a major tectonic constituent of the many marginal seas in the region. This paper describes research examining the transition from rifting to spreading along the northern margin of the SCS, made possible by the amalgamation of newly acquired and existing geophysical data. The northernmost SCS was surveyed as part of a joint Japan-China cooperative project (JCCP) in two phases in 1993 and 1994. The purpose of the investigation was to reveal seismic and magnetic characteristics of the transitional zone between continental crust and the abyssal basin. Compilation of marine gravity and geomagnetic data of the South China Sea clarify structural characteristics of its rifted continental and convergent margins, both past and present. Total and three component magnetic data clearly indicate the magnetic lineations of the oceanic basin and the magnetic characteristics of its varied margins. The analyses of magnetic, gravity and seismic data and other geophysical and geological information from the SCS led up to the following results: (1) N-S direction seafloor spreading started from early Eocene. There were at least four separate evolutional stages. Directions and rates of the spreading are fluctuating and unstable and spreading continued from 32 to 17 Ma. (2) The apparent difference in the present tectonism of the eastern and western parts of Continent Ocean Boundary (COB) implies that in the east of the continental breakup is governed by a strike slip faulting. (3) The seismic high velocity layer in the lower crust seems to be underplated beneath the stretched continental crust. (4) Magnetic anomaly of the continental margin area seems to be rooted in the uppermost sediment and upper part of lower crust based on the tertiary volcanism. (5) Magnetic quiet zone (MQZ) anomaly in the continental margin area coincides with COB. (6) The non-magnetic or very weakly magnetized layer is probably responsible for MQZ. One of the causes of demagnetization of the layer is due to hydrothermal alteration while high temperature mantle materials being underplated. Another explanation is that horizontal sequences of basalt each with flip-flop magnetization polarity cancel out to the resultant magnetic field on the surface. We are currently developing a synthetic database system containing datasets of seismicity, potential field data, crustal and thermal structures, and other geophysical data to facilitate the study of past, contemporary and future changes in the deep sea environment around Japan; i.e. trench, trough, subduction zones, marginal basins and island arcs. Several special characteristics are an object-oriented approach to the collection and multi-faceted studies of global data from a variety of sources.  相似文献