降水现象仪观测应用评估

利用2017年9月至2018年8月北京20个站降水现象仪采集数据与人工平行观测数据,对降水现象仪进行了对比评估。结果表明:降水现象仪的缺测率为0.01%,空报率为0.6%,捕获率为93.5%,漏报率为27.9%,错报率为10.0%。从统计结果可知,降水现象仪的缺测率、空报率较低,捕获率较高,体现出设备性能良好的一面,漏报率和错报率偏高,表明设备漏识别和错误识别的情况较多,漏报主要发生在弱降水过程中,错报主要出现在毛毛雨的识别上。设备测量和人工观测降水开始时间一致性较好,终止时间一致性偏差;降水现象仪现存问题:在大雨强时易出现雨滴叠加误识别,在小雨强时识别率会降低,在无降水错误输出降水现象方面缺少质控。     

城乡一体化地籍联动变更规则及模型研究

分析了城乡一体化地籍要素的联动变更关系,将联动关系及联动变更关系下的变更操作表示为规则,并给出规则的执行流程,实现规则支持下的地籍变更。通过实例对提出的规则和模型进行验证。结果表明,该模型不仅可以保证地籍变更过程的拓扑和逻辑一致性,还能够提高地籍变更的自动化和智能化程度。     

Fission of a weakly nonlinear interfacial solitary wave at a step

The transformation of a weakly nonlinear interfacial solitary wave in an ideal two-layer flow over a step is studied. In the vicinity of the step the wave transformation is described in the framework of the linear theory of long interfacial waves, and the coefficients of wave reflection and transmission are calculated. A strong transformation arises for propagation into shallower water, but a weak transformation for propagation into deeper water. Far from the step, the wave dynamics is described by the Korteweg-de Vries equation which is fully integrable. In the vicinity of the step, the reflected and transmitted waves have soliton-like shapes, but their parameters do not satisfy the steady-state soliton solutions. Using the inverse scattering technique it is shown that the reflected wave evolves into a single soliton and dispersing radiation if the wave propagates from deep to shallow water, and only dispersing radiation if the wave propagates from shallow to deep water. The dynamics of the transmitted wave is more complicated. In particular, if the coefficient of the nonlinear quadratic term in the Korteweg-de Vries equation is not changed in sign in the region after the step, the transmitted wave evolves into a group of solitons and radiation, a process similar to soliton fission for surface gravity waves at a step. But if the coefficient of the nonlinear term changes sign, the soliton is destroyed completely and transforms into radiation. The effects of cubic nonlinearity are studied in the framework of the extended Korteweg-de Vries (Gardner) equation which is also integrable. The higher-order nonlinear effects influence the amplitudes of the generated solitons if the amplitude of the transformed wave is comparable with the thickness of lower layer, but otherwise the process of soliton fission is qualitatively the same as in the framework of the Korteweg-de Vries equation.     

地理国情要素数据成果的一致性检查方法

本文结合全国地理国情要素数据成果过程质量控制、质量复核工作,以及地理国情要素数据成果自身、与地表覆盖分类数据成果、与外业调查核查数据、与专题资料的一致性要求,通过分析检查中发现的质量问题,提出了地理国情要素数据成果的质量控制方法。该方法为国情要素数据成果的质量控制提供了技术参考,为质检工作提供了方法依据。     

粉质黏土强度指标的水化学敏感性研究

通过对重塑粉质黏土的液、塑限和固结慢速直剪试验,探讨了粉质黏土液限、塑性指数及抗剪强度与不同浓度NaCl孔隙溶液的关系。试验结果表明,随着孔隙溶液浓度增加,液限随之减小,塑性指数表现出粉土的性质;不同竖向正应力下的强度随浓度变化表现出较大的差异,正应力较低时,强度不断减小,而正应力较高时,则强度不断增大,正应力介于二者之间强度则先降后升;内摩擦角随浓度增加而增大,最终趋于稳定;黏聚力先迅速减小后逐渐回升,且均为负值。其性质变化主要是因为扩散双电层、颗粒间作用力以及孔隙比发生了改变。基于Terzaghi的有效应力原理,对饱和粉质黏土固结慢速直剪试验测得的负值黏聚力进行了分析和讨论,认为渗透压力对黏聚力起了非常重要的作用,从而使黏聚力成为负值。     

长松藻ITS序列特征及其系统进化分析

采用PCR扩增的方法获得了第一个松藻目物种长松藻(Codium cylindricum)的ITS序列,长松藻ITS全长515bp,其中ITS1的长度为74bp,5.8S序列长163bp,ITS2的长度为278bp.与已知的绿藻门其它5个目8个属物种的ITS序列的系统发育分析结果表明,绿藻门物种分为三大支,其中团藻目藻类为一支,松藻目和刚毛藻目藻类为一支,石莼目、顶管藻目和丝藻目藻类构成一大支;长松藻与刚毛藻目的刚毛藻属和硬毛藻属物种同为多核藻体,在系统发生上表现出更近的亲缘关系;不同绿藻目海藻的聚类关系表明,其能够准确地反映出其在单核与多核、单细胞与多细胞等生物结构特性方面的差异与水平.     

基于震动台试验的数字强震动仪一致性研究

中国数字强震动台网作为"十五"重大项目中国数字地震观测网络的重要组成部分之一,是迄今为止我国投资最多、规模最大的强震动观测台网。由于台网采用了多种数字强震动仪,不同型号数字强震动仪的一致性程度直接影响到台网的观测质量。通过对台网所用5种数字强震动仪的振动台试验和结果分析,表明这5种数字强震动仪的一致性良好,能够满足中国数字强震动台网建设要求。     

Evaluation of the exact conditional spectrum and generalized conditional intensity measure methods for ground motion selection

Two existing, contemporary ground motion selection and modification procedures – (i) exact conditional spectrum (CS‐exact) and (ii) generalized conditional intensity measure (GCIM) – are evaluated in their ability to accurately estimate seismic demand hazard curves (SDHCs) of a given structure at a specified site. The amount of effort involved in implementing these procedures to compute a single SDHC is studied, and a case study is chosen where rigorous benchmark SDHCs can be determined for evaluation purposes. By comparing estimates from ground motion selection and modification procedures with the benchmark, we conclude that estimates from CS‐exact are unbiased in many of the cases considered. The estimates from GCIM are even more accurate, as they are unbiased for most – but not all – of the cases where estimates from CS‐exact are biased. We find that it is possible to obtain biased SDHCs from GCIM, even after employing a very diverse collection of intensity measures to select ground motions and implementing its bias‐checking feature, because it is usually difficult to identify intensity measures that are truly ‘sufficient’ for the response of a complex, multi‐degree‐of‐freedom system. Copyright © 2015 John Wiley & Sons, Ltd.     

A method to estimate the forces exerted by internal solitons on cylindrical piles

Internal soliton is the large amplitude wave existing in the pycnocline, induced by internal tide in the condition of special bottom topography. During its propagation process, the induced disturbance can bring about strong convergence of sea water and sudden strong current (wave-induced-current), which can cause severe threat to the ocean engineering structures, such as oil drilling platform and pipeline. In this paper, Morison’s empirical method, modal separation and regression analyses are introduced to estimate the forces and torques exerted by internal soliton on cylindrical piles. As an example, a limited set of observational data recording a passage of the internal soliton near Dongsha Islands is used to estimate the horizontal velocity and its acceleration in a vertical section for computing the force and torque on a supposed pile, and the estimation results are reasonable. It is shown that, the higher number of the modes retained in the calculation, the better the estimation of velocity profile fits the observational one. A better overall approximation to the real solution can be reached if there are more observational current data acquired in a whole vertical profile.     

Internal tides and waves near the continental shelf edge

Abstract

The subject is reviewed from the viewpoints of theory, internal tide and wave structure and their implications.

A wider theoretical context suggests scope for further investigation of natural or nearly-trapped forms above the inertial frequency.

Although internal tides in many locations are observed to have first-mode vertical structure, higher modes are seen offshore from shallow shelf-break forcing and for particular Froude numbers, and may be expected locally near generation. Bottom intensification is often observed where the sea floor matches the characteristic slope. Solitons form from internal tides of large amplitude or at large changes of depth.

Internal tides and solitons are observed also at many sills and in straits, and to intensify in canyons.

Non-linear effects of the waves, especially solitons, include the conveyance of water, nutrients, ‘‘mixing potential'’ etc. away from their source to other locations, and the generation of mean currents. The waves transfer energy and possibly heat between the ocean and shelf, may be a source of medium frequency waves on the shelf (periods of minutes) and can contribute to interior mixing and overturning, bottom stirring and sediment movement.