A proposed mechanism for storm beach sedimentation     

Julian D. Orford 《地球表面变化过程与地形》1977,2(4):381-400

One of the major problems of shingle beach dynamics is the method by which coarse gravel is transferred from beach face to storm beach, the latter often lying several metres above high spring tidal levels. The mechanism which is usually proposed, cites the action of plunging breakers as being central to this problem of sediment transfer. However, the nature of net residual fluid force of plunging breakers is deemed unsatisfactory for any substantial upbeach (onshore) sediment transport during storm conditions on gravel beaches. A mechanism is proposed by which high still water levels due to high astronomical tides, onshore storm force winds and allied wave surge, promote shoaling characteristics and beach profile changes which are conducive to spilling breaker development at tidal extremities. It is the net onshore fluid force vector of the spilling breaker overtopping the beach crest which may be the cause of extreme sedimentation events on the storm beach. An example of such sediment transfer is given for a known storm beach sedimentation event at Llanrhystyd gravel beach, West Wales, during February 1974. Process variables were monitored on several days allowing the use of an inshore breaker steepness criterion, to indicate positions in the tidal regime where plunging breakers give way to spilling forms. This example serves to suggest that more attention should be given to the nature and characteristics of shoaling waves, especially in respect of breaker type, when examining problems of shingle beach dynamics and sedimentation.  相似文献   

PANDOROS高压发生器Jmax灯亮故障检修     

李国耀  张延武 《CT理论与应用研究》1995,4(4):34-35

本文分析了引发Ｊｍａｘ灯亮的三种原因。即Ｘ线管电流检测回路Ｒ３３电位计故障；ＫＶ参数值产生回路Ｖ２４管击穿故障，以及灯丝初级加热回路Ｖ２管软击穿故障，所以导致的高压发生器低电流保护，Ｊｍａｘ灯亮，不同的是前二项原因使曝光开始即刻Ｊｍａｘ灯亮。  相似文献   

GoodyGIS在电力工程测绘中的应用     

常红斌  张辉 《测绘工程》2014,(8):73-76

在电厂和输电线路的可研和初设阶段中,需要测绘人员向设计专业人员快速地提供小比例尺地形图和线路平（断）面图作为设计依据和参考,而传统的作业模式无法满足上述要求.为此提出运用GoodyGIS软件提供的免费卫星航空影像资源数据来快速获取地形图、平（断）面图的方法和线路路径优化方法以满足设计的需求.结合具体工程实例进行数据比较分析,确认方法在电力工程应用中的可行性和实用性.  相似文献   

An elastoplastic model for the analysis of a driven pile extended with a micropile     

《Computers and Geotechnics》2017

An elastoplastic model for the analysis of a driven pile extended at the bottom with a micropile under axial load is presented. The model is an extension of the integral equation method of Poulos and Davis. The finite-difference scheme used to obtain the pile displacements is reformulated to take into account the discontinuity in the stress distribution at the joint between pile and micropile. The results obtained with the proposed method are compared with the outcomes of a more sophisticated finite element simulation, and also with data from full-scale load tests. Reasonably good agreement is obtained in both cases.  相似文献   

岩石电容:物探"激发极化"的实质 ——对于物探"激发极化"一次和二次电压现象的讨论     

商木元 《地质与资源》2019,28(1):98-108

利用岩石、地质体的电容特性论证“激发激化”（IP）一次和二次电压的形成机理,指出了假说状态的IP理论错误,使得一次和二次电压现象能够科学地应用到地球物理勘探.根据实际的电阻都具有电容的特性以及实际的电容都“漏电”的事实,推定同样是电阻的岩石、地质体具有电容特性.利用岩石、地质体的电阻电容等效电路验证了岩石、地质体充放电过程中产生一次电压和二次电压,且一次和二次电压的和等于充电稳定时的电压的事实;在交流充电中,利用该等效电路同样验证了电流与电压间的相位移及阻抗的减小现象,并得到实测数据证明;利用实测数据,通过综合分析方法推断出等效电路推导的一次和二次电压与实测相符.岩石、地质体具有电容特性,实际上是体现了岩石具有电容这一物性特征.研究结果显示,一次二次电压的形成不存在“激发”因素,IP理论中的“极化率”大小与极化没有关系.研究表明,一次和二次电压的关系可以反映岩石、地质体内金属矿物的含量;利用岩石、地质体的充放电的时间常数、电容特性进行物探,对于识别隐伏地质体,效果会更好.  相似文献   

一种高分辨率温度传感器     

杨晓明  朱小毅  薛兵 《地震》2018,38(3):181-188

介绍一种基于Pt1000惠斯通平衡电桥的高分辨率温度传感器。 实验测试表明, 该温度传感器具有精确、 稳定、 分辨率高的特点, 测试温度的分辨率可以达到1×10^-5℃。 其温度测试范围可调, 从而可以满足不同测试环境温度测试的需要, 具有较广泛的应用范围, 并可同通用数据采集器连接构成精密温度观测系统。  相似文献   

ZnO压敏陶瓷冲击老化的电子陷阱过程研究   总被引：1，自引：0，他引：1       下载免费PDF全文

尹桂来  李建英  尧广  成鹏飞  李盛涛 《海洋学报》2010,32(9):6345-6350

使用8/20 μs脉冲电流发生器对普通商用ZnO陶瓷压敏电阻片进行了最多5000次的冲击试验.测量了冲击前后试样的电气性能和介电特性,分析了冲击后小电流区的U-I特性和损耗角正切值tanδ随脉冲大电流的不断作用而发生的变化.实验发现压敏电压U1mA随冲击次数的增加经历增大—稳定—减小三个过程.认为正反偏Schottky势垒的中性费米能级的变化是影响样品小电流区的最根本原因.本文提出用试样的非线性系数α作为老化特征参数比传统的U  _相似文献