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81.
本文介绍了两个系统模型(多输入线性模型MLM和多输入线性扰动模型MLPM)的基本思路,以赵牛河为研究流域,选取1960年~1967年逐日的降水、入流和出流、蒸发的资料,验算了两个模型。同时,结合一些计算结果,探讨了平原地区产汇流的一些特点。  相似文献   
82.
乌鲁木齐遥测地震台网   总被引:1,自引:0,他引:1  
吴新泉  何彦 《内陆地震》1995,9(2):163-170
对乌鲁木齐遥测地震台网的布局、观测项目的配置和技术系统的总体构成等方面进行了全面介绍,突出了系统的特点和先进之处。台网的建成对加强乌鲁木齐和北天山地区的监测预报工作起到了重要的作用,对国内遥测台网的设计建设和技术改进建设和技术改进起到了一定的促进作用。  相似文献   
83.
This paper presents analytical models to predict the pullout capacity and the load–displacement relationship for shallow single vertical helical and plate anchors in sand. The models were developed based on the failure mechanism deduced from laboratory testing and utilize the limit equilibrium technique. Expression was given to estimate the critical depth for a given anchor/soil conditions, which separates deep from shallow anchors. Furthermore, the radius of influence of a individual anchor on the ground surface is established, and accordingly, the spacing between anchors can be determined to avoid anchors interactions between anchors. The proposed theory compared well with the theories and the experimental data available in the literature.
Résumé Cet article présente un model analytique pour prédire la résistance à l’arrachement et la relation charge-diplacement pour les ancrages à vis et plats verticaux superficiels ancrés dans le sable. Le model est basé sur le mécanisme de rupture déduit des essais de laboratoire et utilise la méthode d’analyse à l’équilibre limite. En outre, une expression a été proposé pour éstimer la profondeur critique pour un ancrage donné permettant d’identifier l’ancrage comme superficiel ou profond. Le rayon d’influence d’un ancrage à la surface du sable autour de l’ancrage a été établi, et par conséquent, l’espacement entre ancrages peut être déterminer pour éviter toute interaction. La théorie proposée montre une bonne concordance avec des résultats theoriques et expérimentaux rapports dans la literature.

  相似文献   
84.
为完善框架预应力锚杆柔性支护结构稳定性研究,针对该结构的稳定性分析和设计均未考虑降雨入渗影响的现状,基于GeoStudio软件,分析了黄土地区强降雨条件下的框架预应力锚杆柔性支护结构的整体稳定性影响参数,在分析中考虑了土体含水率变化对摩擦型灌浆锚杆极限抗拔承载力的影响。分析结果表明:降雨持时、降雨强度和地下水位对框架预应力锚杆柔性支护结构的整体稳定性有明显的影响; 土体饱和渗透系数的影响十分显著; 渗透各向异性的影响可以忽略; 降雨条件下框架预应力锚杆柔性支护结构的安全系数变化存在滞后效应:随着降雨持时和土体饱和渗透系数增大,滞后效应逐渐减弱; 降雨强度越大、初始地下水位越高,滞后效应越明显。本文的研究成果能为非饱和黄土地区框架预应力锚杆柔性支护结构考虑降雨影响的设计和施工提供指导。  相似文献   
85.
This paper systematically reviews and synthesizes peer-reviewed, English-language scientific publications (n=212) to identify relevant research about how Ecosystem-Based Adaptation (EBA) is integrated with coastal planning. Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) methodology is applied in this study. Attention was given to studies concerning human-environment interactions as opposed to physical or biological climate change issues alone because the coastal planning and EBA approach addresses the management of human actions in nature. The literature references include the issue of climate change (77%); however, limited evidence of EBA in coastal areas are reported (18%), and it is evident that the issues have become relevant in the scientific literature published in recent years. Broad texts demonstrate that SLR is one of the major long-term impacts (68%), and all of these papers recognize the most affected ecosystems in the tropics would be mangroves. EBA is an emerging option that can offset anticipated ecosystem losses and improve coastal planning to cope with SLR because it provides benefits beyond climate change stressors. There is a need to synthesize a road map for incorporation of mangrove regulations into local planning instruments and for building capacity for their implementation. Application of PRISMA in marine science will enhance future reviews, facilitate the systematic search and adequately document any theme, and also be useful in determining research gaps or information needs.  相似文献   
86.
The challenge of climate change in glaciated mountain systems is significant and cannot be met without adaptation actions and research that addresses the interwoven scientific, human, and socio-ecological dimensions of climate change. However, our understanding of the effectiveness of existing efforts in meeting this challenge is lacking, a shortcoming compounded by a lack of consistent and comparable information about adaptation action and research in glaciated mountain systems. This study develops a typology of the challenge of climate change in glaciated mountain systems and uses formal systematic review methods to critically evaluate existing adaptation actions and research in light of this framework. Our results––based on an evaluation of 170 English-language peer-reviewed and grey literature documents––indicate that socially-relevant climate-related changes are already manifesting in glaciated mountain systems, with the most commonly documented stimuli for adaptation being hydrological changes related to the degradation of the high mountain cryosphere. Some degree of adaptation action has occurred in 78% of countries with glaciated mountain ranges, but most adaptations are reactions to experienced climatic stimuli and carried out without guidance from a formal adaptation plan. The study also identified the emergence of explicitly mountain-focused adaptation research, yet studies framed in this way are still relatively scarce and have only been carried out in about half of the countries with glaciated mountain ranges. Although we document several laudable adaptation action and research efforts, few initiatives are adequately addressing the difficulties outlined in our evaluation framework for the challenge of climate change. The study discusses the consequences of observed shortcomings and identifies recommendations for more fully meeting the challenge of climate change in glaciated mountain systems.  相似文献   
87.
Uses for expansive cements and additives have extended well beyond off‐setting the shrinkage characteristics of grout and concrete to include enhancement of rock anchor and pile performance, providing an alternative form of connection for tubular members in off‐shore structures and as an excavation tool in open‐pit mines. In each case, the design rules governing the quantity of expansive additive to be used are based on guesswork or empiricism. This paper presents analytical solutions for estimating the degree of expansion and the level of normal stress developed for a range of different boundary conditions and expansive additive contents. The expansion process is modelled as a thermal expansion and is governed by one parameter that depends on the type of expansive additive and its dosage. Simple laboratory procedures for determining this property are outlined. Predictions from the analytical solutions are compared with laboratory experiments. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   
88.
利用垂直向Pg和Sg波最大振幅比方法,计算得到张家口地区2007—2015年发生的中小地震震源机制解;通过系统聚类分析,研究震源机制分布特征与断裂活动的关系,并采用网格搜索法对张家口地区的现今地壳应力场进行反演,得到了较为精确的张家口地区的构造应力场。结果表明:主压应力轴的走向范围:211°~223°,即NE—SW向;主张应力轴的走向范围:323°~332°,即NNW—SSE向,P轴、T轴都近于水平;两组节面的走向分别为N18°E向和近EW向(N83°E),破裂以水平走滑为主。  相似文献   
89.
Estimation of loads derived from shipping water events in naval and offshore structures is of importance to improve their structural design or to predict changes in their dynamics. For the case of vertical loads on deck of a fixed structure, it is possible to estimate analytically their evolution in time by considering the distribution of shipping water elevations. However, the classical approach to estimate this distribution (i.e., dam-break method) tends to overestimate the amount of water on deck and does not follow the generated decay trends observed experimentally. In the present work, the time evolution of the vertical loads due to shipping water events was studied analytically and experimentally. The validation of the use of a convolution model to estimate the time evolution of vertical loads is presented, aiming to improve the results obtained with classical approaches. A systematic experimental study has been conducted using the wet dam-break method to generate isolated shipping water events, measuring the slow-varying vertical loads on a rectangular fixed structure. A force balance and a high-speed camera have been used at the same sampling rate to monitor the vertical loads and the shipping water evolution on the deck. Results demonstrated that the use of the convolution model improved the representation of the time series of loads compared with the traditional dam-break approach. With this new method, it was possible to capture the peaks and the decay tendencies observed in the experimental data in an approximated way.  相似文献   
90.
1. IntroductionThe Asian summer monsoon circulation is a thermally driven circulation, which arisesprimarily from the temperature differences between the warmer continental areas of theNorthern Hemisphere and the oceans of the Southern Hemisphere. The complex feedback between the flow field and the heating, especially through the interaction between thelarge--scale flow and moist convection, is yet to be well understood. Nevertheless, this facetensures the prominence of the summer monsoon ci…  相似文献   
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