Suspended sediment transport regime in a debris‐flow gully on Vancouver Island,British Columbia     

Craig J. Nistor  Michael Church 《水文研究》2005,19(4):861-885

In debris‐flow‐prone channels, normal fluvial sediment transport occurs (nearly exclusively in suspended mode) between episodic debris‐flow events. Observations of suspended sediment transport through a winter season in a steepland gully in logged terrain revealed two event types. When flows exceeded a threshold of 270 l s⁻¹, events yielded significant quantities of sediment and suspended sediment concentration increased with flow. Smaller events were strongly ‘supply limited’; sediment concentration decreased as flow increased. Overall, there is no consistent correlation between runoff and sediment yield. Within the season, three subseasons were identified (demarcated by periods of freezing weather) within which a pattern of fine sediment replenishment and evacuation occurred. Finally, a signature of fine sediment mobilization and exhaustion was observed within individual events. Fine sediment transport occurred in discrete pulses within storm periods, most of the yield occurring within 5 to 15% of storm runoff duration, so that it is unlikely that scheduled sampling programs would identify significant transport. Significant events are, however, generally forecastable on the basis of regional heavy rainfall warnings, providing a basis for targeted observations. Radiative snowmelt events and rain‐on‐snow remain difficult to forecast, since the projection of temperatures from the nearest regular weather station yields variable results. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

深井电极交叉供电对自然电位的影响     

赵斐  叶青  张远富 《地震地磁观测与研究》2017,38(3):93-99

通过实验论证平凉地震台深井电阻率观测自然电位畸变由电极交叉供电造成,讨论分析不同电极供电对自然电位的影响。结果表明:对测量极供电,会影响自然电位,不会影响电阻率测值;单极供电对自然电位的影响表现为阶跃突跳,并以指数形态恢复,恢复时间约10 h,干扰峰值与供电电流、供电时间等有关;对观测数据进行校正,取得较好效果。  相似文献   

Disturbance,Trait Similarities,and Trait Advantages Facilitate the Invasion Success of Alternanthera philoxeroides (Mart.) Griseb.     

《洁净——土壤、空气、水》2017,45(9)

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安徽省煤炭资源有效供给能力评价分析   总被引：1，自引：0，他引：1  

朱文伟  孙贵  叶诗忠 《安徽地质》2006,16(4):262-266

后备煤炭资源储量的规模直接决定着宏观煤炭工业的规划和发展“。煤炭资源有效供给能力”是近年来煤炭地质经济研究工作提出的一个新的概念,本文尝试应用煤炭资源有效供给能力概略评价方法,结合我省实际,制订适合我省煤炭资源现状的评价原则和评价办法,评价我省实际有效的煤炭资源供给能力结论为:煤炭资源较丰富,有效供给能力较好。  相似文献   

基于GIS的供水管网管理与服务系统   总被引：3，自引：0，他引：3  

邬群勇  王钦敏  陈涵  刘大维 《测绘科学》2006,31(4):152-154

现有的大多数管网信息系统仅仅局限于管网信息管理或者是管网信息服务,同时管网的三维可视化能力较弱。为了实现管网信息的综合管理和服务,作者提出一个基于C/S与B/S相结合的供水管网管理与服务的计算机应用解决方案,该方案以组件式G IS实现管网信息管理,以W ebG IS实现管网信息服务,同时基于Java3D实现管网信息的三维浏览和信息查询,实现了管网信息的综合管理和服务。本文以某园区供水管网管理与服务系统的建设为例,对系统的结构与功能,数据库设计、空间数据组织以及系统开发与集成模式等方面进行了探讨。该系统从应用角度为城市地下管网的管理和服务提供了一个可行的解决方案。  相似文献   

基于多源数据的夜间经济时空分布格局研究方法     

曾磊鑫  刘涛  杜萍 《地球信息科学学报》2022,24(1):38-49

夜间经济是一个城市经济发展和消费水平的重要表征。目前国内外研究者对夜间经济的研究多停留在理论层面,或基于市场调研和问卷调查的小范围精细化研究。本文融合多源数据为夜间经济提供了新的视角,相较于传统的调查数据,具有更加快速、高效、广泛的特点,适合于夜间经济大范围研究。本文基于夜间灯光、POI、OD流等多源数据,采用DBSCAN、K-Means++等空间聚类算法和研究供需关系的盈亏法,分别从消费者角度和商户角度识别厦门市夜间活动热点区域和夜间服务设施分布区域,分析厦门市夜间经济时空分布格局及相关性。研究表明:① 厦门市夜间活动在空间上呈多环状分布并向四周递减,夜间活动热点区域分布受假期的影响因地而异;② 厦门市部分区域已有服务设施未能很好地服务于夜间经济,现有的照明、夜景等夜间灯光基础设施存在供给不足之处;③ 居住人口密度与夜间活动密度呈中度正相关,研究结果具有有效性,夜间服务设施盈亏值及数量、夜间灯光与夜间活动密度呈中、弱度相关,并且餐饮设施更加依赖于夜间灯光。最后,为厦门市未来夜间经济建设提出了根据不同的消费人群和心理提供不同的夜间服务、加强夜间灯光基础设施建设以及市场扶持的举措。研究结论对促进社会就业、增强基础设施使用率有积极意义,同时也能够为城市夜间经济发展和政策制定提供参考。  相似文献   

French marine technology policy : Industrializing ocean depths     

Daniel Spagni  Luke Georghiou  Michael Gibbons 《Marine Policy》1985,9(4):280-291

This paper outlines the structure of the institutions involved in scientific and technological development in France. It points to new trends in French marine policy, and gives details of the country's offshore petroleum technology and nodule mining.  相似文献   

黄海太平洋褶柔鱼资源现状与开发   总被引：2，自引：0，他引：2  

董正之 《海洋科学》1996,20(6):34-38

太平洋褶柔鱼是我国近年在黄海开发的重要渔业资源。首先概括了本种柔鱼的基本属性，阐述了资源开发现状，块状分布，种群，渔获量和资源量，对块状分布的形成作了理论分析；最后探讨了黄海柔鱼资源的开发与保护问题。  相似文献   

Inter-annual variability in larval supply to populations of three invertebrate taxa in the northern California Current     

Stephen R. Wing  Louis W. Botsford  Lance E. Morgan  Jennifer M. Diehl  Carolyn J. Lundquist 《Estuarine, Coastal and Shelf Science》2003,57(5-6):859-872

We investigated sources of inter-annual variability in larval supply to crab and sea urchin populations at Bodega Head and Point Reyes in northern California. During the spring and summer upwelling seasons of the years 1992 through 1997 we monitored the weekly settlement rates of nine species of crabs and two species of sea urchins. As observed in previous studies, daily values of alongshore windstress, temperature and salinity provided evidence for the poleward flow of relatively warm, low salinity water from south of Point Reyes, an apparent retention zone, during upwelling relaxation events. In years dominated by these events (1992, 1993, 1995 and 1996) we observed that alongshore windstress, temperature and salinity were coherent and temperature was significantly correlated with cancrid crab settlement. During these years the magnitude of cancrid crab settlement and the fraction of cancrid crabs relative to other crab species settling were high. Over four years of concurrent sampling there was consistently greater cancrid crab settlement at the Point Reyes site, within the retention zone, than at Bodega Head. Settlement of non-cancrid crabs (porcellanids, grapsids, pagurids and majids) was not as closely linked to intra-annual patterns of upwelling and relaxation, possibly due to the shorter seasonal availability of larvae allowing for the influence of fewer relaxation events. Settlement of this group among years was positively correlated with environmental indicators of strong seasonal upwelling; high salinity, Bakun upwelling index and low temperature. Sea urchin settlement events were observed in June and July of 1992, 1994 and 1997 during warming periods when salinity and temperature were increasing and alongshore windstress was low. Across the six years of the study, we found that cancrid crab larvae had a more even seasonal availability than larvae of non-cancrid species, which settled in greatest numbers during the early portion of the upwelling season. Sea urchins settled in greatest numbers during the later part of the upwelling season. Together these patterns demonstrate the taxon-specific way that inter-annual variability in larval supply is forced by the coincidence of larval availability with favorable physical transport mechanisms.  相似文献   

北方集中供热系统气象风险评估初探   总被引：1，自引：0，他引：1  

陈莉  李帅 《冰川冻土》2018,40(6):1285-1290

供热管网爆裂、跑冒滴漏是北方集中供热城市面临的常见问题,供热管网出现大型故障往往是在室外寒冷的隆冬时节,如果间断或限额供热时间过长,将会造成严重的社会和经济影响。同时在极端低温情况下,可能会造成热源供应不足,出现限额供热现象,不能保证室内舒适度,影响人们的正常生活。本文提出了能源供应气象风险评估和热网维修寒冷风险评估方法,并进行了案例评估,以期为未来进行相关风险评估提供参考。  相似文献