Efficient methods of discharge measurements in rivers and streams based on the probability concept     

Chao‐Lin Chiu  Shih‐Meng Hsu  Ning‐Chien Tung 《水文研究》2005,19(20):3935-3946

Regularities exist in fluid flows and can be represented by a set of constants. These constants are functions of the parameter of a probability distribution that exhibits resilience and stability under various flow conditions. Together, these regularities form a network and interact with each other, such that if one is known then the others can be determined from it. The regularities and their network explain the various fluid‐flow phenomena and can be used in analysis of rivers and streams. For example, they can be used as the basis to develop simple and efficient methods of discharge measurements as presented herein, which only require velocity sampling at a single point on a water surface or a few points on a single vertical. Because of their simplicity and the short time requirement, these methods can be easily automated for collecting discharge data in unsteady, high flows that are badly needed for real‐time flow forecasting and design of flood control structures, and for advancing the fundamental, scientific knowledge in hydrology. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Population growth in Bejing: trends and countermeasures     

Zhaoliang Hu  Francis Yee  George Chusheng Lin 《中国地理科学(英文版)》1991,1(3):212-220

Beijing’ population has experienced a dramatic increase eversince the founding of the People’s Republic of China. Population growthin Beijing can be broadly broken down into three major components:natural increase, immigration, and the growth of floating population. Thecontinuous growth of Beijing’s population is closely linked with its centralized multi-function. The comprehensive countermeasures to control Beijing’s population growth are proposed, for example, decentralizing economicfunctions, including developing the suburbs, developing the metropolitan areaand creating counter-magnetic centers, reforming the administrative and economic systems.  相似文献   

油气田裂缝密度定量研究方法   总被引：1，自引：0，他引：1  

魏永佩  张之一 《地球科学与环境学报》1991,(1)

本文首先简要评述了目前研究裂缝方法的优缺点。用实例介绍了裂缝密度的定量估计方法,这种方法能将岩芯资料和地震资料有机地结合起来。应用这种方法不但能预测区域性裂缝及油气分布规律,而且能回答所获得成果的正确程度。  相似文献   

Regional Features of Vapor Transfer and Precipitation Distributed in Northwest China          下载免费PDF全文

TAO Jianhong  WANG Baojian  HUANG Yuxi  WANG Jinsong 《Acta Meteorologica Sinica》2006,20(5):31-39

This article investigates regional distribution features of rainfall and vapor transport in Northwest China during 1961-2002, achieving that: (1) Three climate zones in this vast region differ in trends of annual precipitation, with rainfall in the westerly belt (denoted as zoneWB) exhibiting an increasing trend from the 1970s, rainfall in the East Asian monsoon belt (denoted as zoneMB) displaying a decreasing trend in the study period and the Qinghai Plateau zone (denoted as zoneQP) precipitation fluctuating roughly around the mean; (2) The net vapor fluxes (NVF) in zoneWB and zoneQP show an increasing trend as opposited to zoneMB, for which the reason may lie behind that the NVF increase in zoneWB and zoneQP is attributed to pronounced decrease in deficit of westerly NVF, whereas the decrease in zoneMB NVF is ascribed to the significant drop in meridional vapor transfer; (3) ZoneWB rainfall and atmospheric vapor transport change abrupt in 1990 and 1985, respectively, without such happening in zoneMB and zoneQP; (4) ZoneWB rainfall increase occurs when atmospheric vapor budget/NVF increases, so that the latter has to occur ahead of the former; zoneMB rainfall decrease relates to the decrease in atmospheric vapor budget after the 1990s,leading to (more and even) successive droughts in the east of Northwest China on a synchronous basis except zoneQP of which the precipitation factors include river evaporation, glaciers, and snow cover in addition to atmospheric vapor.  相似文献   

Local Oscillator Distribution Using A Geostationary Satellite     

J. Bardin  S. Weinreb  D. Bagri 《Experimental Astronomy》2004,17(1-3):193-199

A satellite communication system suitable for distribution of local oscillator reference signals for a widely spaced microwave array has been developed and tested experimentally. The system uses a round-trip correction method to remove effects of atmospheric fluctuations and radial motion of the satellite. This experiment was carried out using Telstar-5, a commercial Ku-band geostationary satellite. A typical Ku-band satellite has uplink and downlink capacity at 14–14.5 GHz and 11.7–12.2 GHz, respectively. For this initial experiment, both earth stations were located at the same site to facilitate direct comparison of the received signals. The local oscillator reference frequency was chosen to be 300 MHz and was sent as the difference between two Ku-band tones. The residual error after applying the round trip correction has been measured to be better than 3 ps for integration times ranging from 1 to 2000 s. For integration times greater than 500 s, the system outperforms a pair of hydrogen masers with the limitation believed to be ground-based equipment phase stability. The idea of distributing local oscillators using a geostationary satellite is not new; several researchers experimented with this technique in the eighties, but the achieved accuracy was 3 to 100 times worse than the present results. Since then, the cost of both leased satellite bandwidth and the Ku-band ground equipment has dropped substantially and the performance of various components has improved. An important factor is the availability of narrow bands which can be leased on a communications satellite. We lease three 100 kHz bands at approximately one hundredth the cost of a full 36 MHz-wide transponder. Further tests of the system using terminals separated by large distances and comparison tests with two hydrogen masers and radio interferometry of astronomical objects are needed.  相似文献   

The method of a two-point conditional column density for estimating the fractal dimension of the distribution of galaxies     

Yu. V. Baryshev  Yu. L. Bukhmastova 《Astronomy Letters》2004,30(7):444-450

We suggest a new method for estimating the fractal dimension of the spatial distribution of galaxies: the method of selected cylinders. We show the capabilities of this method by constructing a two-point conditional column density for galaxies with known redshifts from the LEDA database. The fractal dimension of a sample of LEDA and EDR SDSS galaxies has been estimated to be 2.1±0.1 for cylinder lengths of 200 Mpc. A major advantage of the suggested method is that it allows scales comparable to the catalog depth to be analyzed for galaxy surveys in the form of conical sectors and small fields in the sky.  相似文献   

北半球平流层臭氧的时空分布特征   总被引：3，自引：0，他引：3  

黄仪方  郭世昌  陈辉  秦瑜  吴涧 《成都信息工程学院学报》2001,16(1):8-11

利用1963－1985年北半球的平流层臭氧观测资料，采用自然平交分解方法，初步分析了北半球、特别是东亚地区大气臭氧层的时空分布特征。结果表明：（1）北半球大气臭氧的空分间分布可能与下垫面的性能有关；（2）东亚地区大气臭氧的时间分布主要具有2年和11年变化的周期特征，这与太阳黑子的准2年和准11年变化有一定的对应关系；（3）北美地区的臭氧变化则主要包含4年和7年的周期变经成分。  相似文献   

SOFTWARE REVIEWS     

《The Professional geographer》1991,43(3):362-363

ATLAS*GIS , Version 1.0. ATLAS*MapMaker , Version 4.0. FIVFIV-SINSIN , Release 9.0. Geo-EAS , Version 1.2.1. Evan Englund Sim City , Version 1.0 Statistix , Version 3.1.  相似文献   

Distribution of free electrons in the galactic plane     

R. R. Andreasyan  S. K. Balayan  V. H. Movsisyan 《Astrophysics》2006,49(2):240-247

A method is proposed for constructing a map of the electron density distribution in the galactic plane. Data on the dispersion measures DM of more than 1500 pulsars and their distances, found by an independent method, are used. The independent distances of the pulsars are estimated using an empirical relation of the form L=γP ^α Ṗ ^β W ^δ between the radio luminosity L of the pulsars and their periods P, the rate of change Ṗ. of their periods, and the half width W of their pulses. A map of the electron density distribution in the galactic plane within a ±400 pc layer is provided. __________ Translated from Astrofizika, Vol. 49, No. 2, pp. 277–287 (May 2006).  相似文献   

A revised DDO abundance calibration for population I red giants     

A. E. Piatti  J. J. Clariá  D. Minniti 《Journal of Astrophysics and Astronomy》1993,14(3-4):145-165

Several arguments that justify establishing a revised abundance calibration for DDO photometry of population I red giants are presented. The components of the blanketing vector in the DDOC(45–48) vsC(42–45) diagram are determined for late-type dwarfs and giants. We have redefined the DDO cyanogen anomaly and calibrated it against metallicity. The sample of field giants now available with abundances derived from high dispersion spectroscopy is substantially larger than previously available, leading to a more accurate abundance calibration. Iso-abundance lines in theC(41–42) vsC(42–45) diagram have been determined for population IG and K giants and an iterative method for deriving abundances of these stars is described. We show that the new DDO abundances are in very good agreement with those derived from high dispersion spectroscopy. The new method improves by about 0.1 dex the DDO abundances derived for early G and/or late K giants, with respect to the δCN method of Janes (1975).  相似文献