海水光衰减变化与颗粒有机碳估算——以菲律宾海为例   总被引：1，自引：0，他引：1  

魏建伟  方习生  石学法  杨刚  李朝新 《海洋科学进展》2007,25(4):460-467

2004年夏季在菲律宾海进行了上层水体光衰减(660 nm)剖面测量和海水取样分析,提出了海区悬浮颗粒有机碳的光学统计模型。根据大量的现场观测资料,得到了菲律宾海上层水体高分辨率颗粒有机碳断面,对颗粒有机碳分布与变化特征进行了探讨。研究表明,菲律宾海上层水体颗粒有机碳和叶绿素a的比值约为400~2000,浮游植物现存量与颗粒有机碳现存量变化趋势一致。  相似文献   

Stability of breakwater defenced by a seaward submerged reef     

Kiran G. Shirlal  Subba Rao  Venkata Ganesh  Manu 《Ocean Engineering》2006,33(5-6):829-846

The stability of a uniformly sloped conventional rubble mound breakwater defenced by a seaward submerged reef is investigated using physical model studies. Regular waves of wide ranging heights and periods are used. Tests are carried out for different spacings between two rubble mound structures (X/d=2.5–13.33) and for different relative heights (h/d=0.625–0.833) and relative widths (B/d=0.25–1.33) of the reef. It is observed that a reef of width (B/d) of 0.6–0.75 constructed at a seaward distance (X/d) of 6.25–8.33 breaks all the incoming waves and dissipates energy and protects the breakwater optimally.  相似文献   

Factors affecting rule compliance with mesh size regulations in the Baltic cod trawl fishery   总被引：1，自引：0，他引：1  

Suuronen  Petri; Tschernij  Vesa; Jounela  Pekka; Valentinsson  Daniel; Larsson  P-O. 《ICES Journal of Marine Science》2007,64(8):1603-1606

  相似文献   

杭州湾粉质土动强度特性研究   总被引：8，自引：0，他引：8       下载免费PDF全文

叶银灿  来向华 《海洋科学》2003,27(2):56-59

通过对杭州湾海底浅层粉土动强度的研究 ,发现动强度指标内摩擦角Cd 为静强度的39.7 %左右 ,同时动强度与固结比Kc、振动频率 f关系密切。当Kc 较小时 ,动强度随Kc 的增大而增大 ,但Kc>1.5后 ,动强度曲线平缓且有降低的趋势 ;在振动次数较小 (<22次 )时 ,f=0.2Hz的粉土表现出较高的动强度 ,振动次数较大后 ,曲线变化复杂 ,这可能与试样两端的透水石发生共振有关 ,但均在30～50次振动范围内出现峰值后破坏。  相似文献   

Improved thermodynamic calculations for concentrated mixed electrolyte systems including ion pairing (or the absence of it)     

Peter M. May   《Marine Chemistry》2006,99(1-4):62

Knowledge of the activity coefficients of solutes under temperature and pressure ranges of interest is generally required for calculations of the physicochemical properties of aqueous multicomponent electrolyte solutions such as seawater. Whilst these activity coefficients are well characterized for the predominant salts individually, fewer data are available for minor components under a sufficiently wide range of conditions and there are significant interactions between some of the chemical species involved which can substantially alter the required activity coefficients in mixtures.For these reasons, accurate thermodynamic predictions for seawater and other multi-electrolyte solutions in moderate or high concentration are more difficult than is often supposed. In particular, progress in this area has been slowed by uncertainty regarding the nature and extent of ion pairing in concentrated strong electrolyte solutions, a problem that has been debated for decades. Zdanovskii's rule, described originally almost a century ago but widely neglected, provides a fundamentally sound method for calculating the properties of mixed electrolyte solutions. Modelling developments are described, which accord with various types of experiment, from our laboratory and from the chemical literature. It has become clear that, when treated in an appropriate way based on solvent activity, linear mixing behaviour of strong electrolyte solutions can be considered the norm. This is an inevitable consequence, first recognized by Guggenheim, of the cancellation of ion pairing and other interactions as, conceptually, one ion replaces another. Stronger solute–solute interactions, described by equilibrium constants, can then easily be coupled in a thermodynamically consistent manner.  相似文献   

Damage identification in a ship’s structure using neural networks     

A. Zubaydi  M. R. Haddara  A. S. J. Swamidas 《Ocean Engineering》2002,29(10):2356-1200

Visual inspection of large and complex structures such as a ship is difficult and costly due to problems of accessibility. In this paper, a neural network technique is developed for identifying the damage occurrence in the side shell of a ship’s structure. The side shell is modeled as a stiffened plate. The input to the network is the autocorrelation function of the vibration response of the structure. The response was obtained using a finite element model of the structure. The output is a single function , which was formed by adding together the damping and a part of the restoring forces. The function is used to identify not only the damage occurrence in the model but also its extent and location. The results show that the method presented in this work is successful in identifying the occurrence of damage. The detection of the extent and location of damage is promising, however, more work has to be done in this area.  相似文献   

海底底质声学性质原位测量技术研究   总被引：4，自引：0，他引：4  

郭常升  窦玉坛  谷明峰 《海洋科学》2007,31(8):6-10

系统介绍了海底底质声学性质原位测量技术，提出了新的原位测量方法，并根据这一测量方法，初步设计制作了相应的海底原位测量仪器。利用初步制作的测量仪器在实验室内对砂质沉积物进行了模拟测量试验，仪器测量得到的沉积物声速与直接透射法测量获得的声速基本一致。在宁波近海海域进行了海上实际测量试验，获得了该测量区域海底底质的声速，验证了此测量技术的可行性，为进一步研发先进的海底原位测量仪器奠定了基础。  相似文献   

一种北京城区避难场所可达性评价方法   总被引：2，自引：0，他引：2  

周爱华  张景秋  杜姗姗  何丹  付晓 《测绘科学》2017,42(1)

针对传统两步移动搜寻法应用于避难场所可达性研究中存在的中心供给、统一阈值及无距离衰减的问题,提出了"入口供给、分段阈值、高斯距离衰减"的优化方案。入口供给更符合人类的认知规律,分段阈值则充分考虑了避难场所的面积因素,高斯距离衰减符合可达性随距离递减的规律。改良两步移动搜寻法能够较好地揭示城市应急避难场所与人口相互作用的规律。基于ArcGIS平台,将改良两步移动搜寻法应用于北京城区应急避难场所的可达性研究,获得更加真实、可靠的评价结果,展现了改良两步移动搜寻法在公共服务空间可达性评价方面的重要作用。  相似文献   

基于Cityengine平台的CGA规则室内三维建模方法研究     

洪洲 《测绘与空间地理信息》2017,40(9)

随着三维数字城市建设的兴起和不断发展,3D GIS技术逐渐被人们所重视,多种三维建模软件也已被大量应用在三维数字城市的设计和创建中。首先通过与传统建模软件的对比,分析了Cityengine城市引擎软件在快速批量建模和与GIS软件数据交互方面的优点,同时也指出了Cityengine在建筑物室内场景方面缺乏对建模规则的研究。因此本文利用二维GIS几何数据作为模型的底面基础数据,借助Cityengine软件特有的CGA语法编写规则文件,对Cityengine平台下创建建筑物室内三维场景的方法进行了初步探究。通过对该方法的研究旨在使三维室内外场景形成良好的整体,弥补之前Cityengine只能对大场景进行外部批量建模而缺乏对内部模型研究的不足,扩展Cityengine在三维建模领域的应用范围,为智慧城市的创建设计以及可视化分析提供了新的手段。  相似文献   

结合风廓线雷达的毫米波衰减特性初步研究          下载免费PDF全文

钟正宇  马舒庆  杨玲  黄书荣  唐英杰 《应用气象学报》2018,29(4):496-504

使用中国气象局大气探测综合试验基地35 GHz毫米波云雷达和L波段风廓线雷达2016年5月1日-7月31日在降水条件下的观测数据,根据不同观测模式下两部雷达得到的数据,计算在一定高度区间内不同下落速度的降水粒子反射率因子变化量,初步分析不同下落速度的降水粒子对毫米波衰减的影响。结果表明:在持续时间较长的层状云降水且降水粒子在雷达观测范围内均匀分布条件下,毫米波衰减与降水粒子下落速度呈近似线性关系,且毫米波经过的路径长度越长,衰减越大;毫米波在经过1110~2430 m,1110~3510 m的高度区间时,下落速度处于3.5~7.5 m·s-1之间的降水粒子对毫米波的衰减作用导致毫米波云雷达所测的等效反射率因子分别减小约1~7 dB和2~11 dB。  相似文献