陕西北部榆林第四纪地层剖面的粒度分析与讨论

本文根据榆林剖面及其粒度分析结果,讨论了剖面中地层的沉积相、古气候和环境演化.     

人工神经网络在水文水资源中的应用

人工神经网络理论被广泛地应用于水文水资源领域中各种问题的研究,依问题性质不同将其划分为4大类:(1)分类和识别问题;(2)预测预报问题;(3)优化计算问题;(4)基于神经网络的专家系统研制与开发问题,对人工神经网络在水文水资源中的应用现状作了较全面的介绍。还指出了目前应用中存在的主要问题以及今后的研究方向。     

Detailed surface photometry of some galaxies integrated properties,II

Results about the standard photometric parameters of four galaxies are given. The equivalent and the integrated parameters defined according to de Vaucouleurs are listed. Effective values of the abovementioned ingredients, the reduced luminosity profiles and the dimensions defined by the quartiles are also given.     

Characterization of a Malaysian mangrove estuary

The Sungai Merbok estuary, in wet tropical Peninsular Malaysia, borders the Straits of Malacca. Tide, current, and salinity data are used to describe the salient hydrographic features of the mangrove-fringed system. The Sungai Merbok estuary is characterized by a 1.7 m semidiurnal tide with a 0.16 form number, peak currents of 1.3 m s^?1, and mean freshwater discharge of 20 m³ s^?1. The system is classified as 2a/2b estuary (Hansen and Rattray 1966) or 1a/1b during periods of low runoff. Gravitational circulation is highly variable (but coincides with the neap stratification) and vertical stratification varies from 10^?2 to 1. The estuary displays a pronounced fortnightly neap-spring stratification-destratification cycle. The effective longitudinal dispersion coefficient is approximately 100 m² s^?1.     

Changes in the scope for growth of blood cockles (Anadara granosa) exposed to industrial discharge

Blood cockles (Anadara granosa) were placed in plastic cages and deployed at eight locations along a pollution gradient. A control site was chosen a few kilometres away. At 2-week intervals for 8 weeks, the scope for growth of the cockles was determined. A total of 11 environmental parameters were measured during each sampling exercise for correlation with the growth index. Values of scope for growth for all the eight stations, except for stations 7 and 8, were significantly lower than the value for the control site; station 1 (nearest the discharge point) had the lowest value. Strong correlations were found between the scope for growth of the cockles and seven of the environmental parameters. The pattern of the impact of the discharge on the scope for growth of the cockles suggests that longshore currents may play a dominant role in the distribution of the industrial wastes.     

Assessment of seismic hazard of roller compacted concrete dam site in Gilgit-Baltistan of northern Pakistan

The proposed site of the Diamer Bhasha Dam in northern Pakistan is situated in an active tectonic zone with intensive seismicity, which makes it necessary for seismic hazard analysis(SHA). Deterministic and probabilistic approaches have been used for SHA of the dam site. The Main Mantle Thrust(MMT), Main Karakaram Thrust(MKT), Raikot-Sassi Fault(RKSF) and Kohistan Fault(KF) have been considered as major seismic sources, all of which can create maximum ground shaking with maximum potential earthquake(MPE). Deterministically estimated MPE for magnitudes of 7.8, 7.7, 7.6, and 7.1 can be produced from MMT, MKT, RKSF and KF, respectively. The corresponding peak ground accelerations(PGA) of 0.07, 0.11, 0.13 and 0.05 g can also be generated from these earthquakes, respectively. The deterministic analysis predicts a so-called floating earthquake as a MPE of magnitude = 7.1 as close as 10 km away from the site. The corresponding PGA was computed as 0.38 g for a maximum design earthquake at the project site. However, the probabilistic analysis revealed that the PGA with 50% probability of exceedance in 100 years is 0.18 g. Thus, this PGA value related to the operational basis earthquake(OBE) is suggested for the design of this project with shear wave velocity(V_(s30)) equal to 760 m/s under dense soil and soft rock conditions.     

天气现象自动化观测资料可用性分析与应用探讨

通过对北京地区天气现象组网试验资料的可用性分析以及在精细化预报业务中的应用,发现自动观测天气现象资料连续时长多于20 min以上时,数据可信度较高,对预报员有较高的参考价值。自动观测系统对雨、雾、霾现象的识别结果正确率总体较好,其高频次的探测数据对低频次的人工观测起到补充作用。但在天气现象识别算法、质控、雷暴和降水性质识别、现象识别连续性等方面还存在不足,需要进一步改进。     

1991年2月17日青浦练塘3.0级地震概述

1991年2月17日青浦练塘3.0级地震,震级不高,波及甚广,损失轻微,是上海地区解放以来陆域的最大地震,属正常地震活动之一。