Free-surface evolution and wave kinematics for nonlinear uni-directional focused wave groups

This paper concerns the propagation of transient wave groups, focused at a point in time and space to produce locally large waves having a range of steepness. The experimental study was carried out in a wave flume at Dalian University of Technology. The numerical simulations were based on a nonlinear boundary integral equation solved by a higher-order boundary element method (HOBEM). Rather than simulate the whole experimental tank, local surface elevation measurements were used to drive the numerical solution from a point less than two wavelengths upstream of the focus position, leading to significant savings in computational time. Excellent agreement is achieved between the water surface elevations and the water particle kinematics measured in the experiments and those predicted numerically at wave group focus, even for near-breaking waves up to a steepness of kA=0.405 for which even locally matched 2nd-order theory is inadequate. Results based on the linear and 2nd-order theory are also presented in the comparisons. When compared with the first- and 2nd-order solutions, the fully nonlinear wave–wave interactions produce a steeper wave envelope in which the central wave crest is higher and narrower, while the adjacent wave troughs are broader and less deep.     

沉积白云石形成条件的试验研究

经过大量试验研究工作，总结出在常温常压条件下，全成碳酸盐矿物的控制因素和形成条件，合成出原白云石（无序白云）等一系列碳酸盐矿物.原白云石经加温加压，在100℃或150℃转化为白云石（有序白云石）.     

基于时序InSAR技术监测大桥历史形变

2019-06-14,河源市源城区东江大桥第三跨第二桥墩以及第四跨第三桥墩出现了垮塌,此次事故造成了人员伤亡和重大经济损失.为了分析此次灾害事故发生发展的成因,本研究获取了Sentinel-1A雷达卫星2018年12月至2019年6月的历史影像数据,基于时序InSAR技术手段处理得到了该监测时间段内的历史形变信息.研究...     

海产腹足类有机锡化合物的检测方法

三丁基锡(TBT)等有机锡化合物因其毒性及结构上的特点被广泛应用于船舶、网箱渔排等的防污涂料中.它的主要作用是在水体中持久地释放出可以有效杀死海洋污损生物的毒性物质,从而达到防护船舶、渔排等体表的目的[1],然而进入海洋环境的有机锡化合物在防污的同时也会影响到许多非靶生物,并对海洋生态系统的结构与功能产生严重的危害,被认为是迄今为止人为引入海洋环境毒性最大的物质之一[2～4].因此,检测海洋生物体内的有机锡含量成为对有机锡污染生态效应调查与研究不可缺少的手段[5～7].     

浙江省山区综合开发的探讨

山区综合开发必须调整偏农型产业结构,实行合理利用自然资源和旨在使山区人口向山下流动的积极的社会经济政策,摆脱与分散性密切相关的自给自足观念。由于山区物质、信息流动阻力大,城镇发展宜取多核分散型,要注意交通等基础设施的超前建设,改善山区环境。     

岩性反演技术在煤田三维地震勘探中的应用

以开滦集团范各庄矿某采区岩性勘探为例,介绍利用地震反演技术解决煤层顶底板岩性问题。该项技术是以测井资料作为约束条件,对地震资料进行反演,推算出波阻抗资料,进而计算煤层厚度,并对顶底板岩性作出推断。通过对部分资料验证,采用岩性反演技术解释的该采区5煤、7煤、9煤、12煤的深度、厚度及其顶底板岩性,与实际情况基本相符。     

Effect of brittle fracture on the rheological structure of the lithosphere and its application in the Ordos

An empirical formula for the fracture strength of the principal rock type in the lithosphere is obtained based on the experimental data from previous studies, in which the effects of the confining pressure, size of the rock sample, temperature, strain rate and the pore pressure are taken into account, the empirical formulae for the effects of them are also presented. By comparing the frictional strength to the fracture strength calculated using the new empirical formula, it is shown that frictional sliding is dominant in the upper crust but brittle fracture is dominant in the lower part of the crust and the lithosphere beneath the crust. Therefore the fracture mechanism must be taken into account in the study of the rheological structure of the lithosphere. The empirical formula for the fracture strength is applied to study the rheological structure of the lithosphere in the Ordos block. Brittle regime in the rheological structure can be divided into two sub-regions, in one of which brittle fracture and in the other frictional sliding are dominant, respectively, unlike previous conventional studies in which frictional sliding is assumed to be the only factor; the magnitude of the rheological strength of the lithosphere calculated by the empirical formula is also lower than that obtained in previous conventional studies.     

雨涝灾害对舞钢市棉花生产的影响

通过田间调查,对2004-2006年棉花不同阶段雨涝情况对棉花生育及产量构成的影响进行了比较分析,并提出了相应的抗灾减灾对策。     

THE LANDSCAPE ECOLOGICAL ，ASSESSMENT AND PLANNING IN THE CONTOL WATERSHED BY RESERVOIR OF ERLKONG MOUNTAIN

Based on the theories of landscape ecology,landscape eco-environment in the coutrol watershed by reser-voir of Erlong Mountain in Heilogjiang Province was analyzed and assessed by using GIS technique and statistical model of Principal Component Analysis and Spatial Cluster Analysis.It is found that 100.08km^2(36%) of the total area is in the state of kilter,85.73km^2(31%) of the total area is in the state of general,and 47.26km^2(17%) and 15.48km^2(16%) is in the relatively poor state and ideal state.According to landscape ecological structure,there are three land-scape function areas being planned and designed.1) Agricultural landscape function area:its developmental direction is tour agriculture and high-benefit agriculture.2)Eco-environment protected function area:the direction of development and utilization of this region is to develop vigorously forest for soil and water conservation ,and try to increase the rate of vegetation cover.3)Forest landscape function area:rational cut and utilization of forest resources,space optimization disposal of category of forest ,foster of forest and protection of wildwood will become the main development directions for this region.This study trys to provide scientific foundation for ecological restoration of the whole valley and its sustain-able development.     

Method of Separating Cosmic-Ray Positrons from Electrons in the DAMPE Experiment

A method of identifying positron/electron species from the cosmic rays was studied in the DArk Matter Particle Explorer(DAMPE)experiment.As there is no onboard ...