Seasonal export fluxes of particulate organic carbon from <Superscript>234</Superscript>Th/<Superscript>238</Superscript>U disequilibrium measurements in the Ulleung Basin<Superscript>1</Superscript> (Tsushima Basin) of the East Sea<Superscript>1</Superscript> (Sea of Japan)

Export fluxes of particulate organic carbon (POC) were estimated from the ²³⁴Th/²³⁸U disequilibrium in the Ulleung Basin¹ (UB) of the East/Japan Sea¹ (EJS) over four seasons. The fluxes were calculated by multiplying the average POC/²³⁴Th ratio of sinking particles larger than 0.7 μm at 100- and 200-m water depths to ²³⁴Th fluxes by the integrated ²³⁴Th/²³⁸U disequilibrium from the surface to 100-m water depth. In spring, the ²³⁴Th profiles changed dramatically with sampling time, and hence a non-steady-state ²³⁴Th model was used to estimate the ²³⁴Th fluxes. The ²³⁴Th flux estimated from the non-steady-state model was an order of magnitude higher than that estimated from the steady-state model. The ²³⁴Th fluxes estimated using the steady-state model showed distinct seasonal variation, with high values in summer and winter and low values in autumn. In spring, the phytoplankton biomass had the highest value, and primary production was higher than in summer and autumn, but the ²³⁴Th fluxes were moderate. However, these values might have been significantly underestimated, as the ²³⁴Th fluxes were estimated using the steady-state model. The POC export fluxes estimated in autumn were about four times lower than those in other seasons when they were rather similar. The annually averaged POC flux was estimated to be 161 ± 76 mgC m⁻² day⁻¹, which was somewhat lower than that in highly productive coastal areas, and higher than that in oligotrophic regions. The export/primary production (ThE) ratios ranged from 7.0 to 56.1%, with higher values in spring and summer and lower values in autumn and winter. In summer, a high ThE ratio of 48.4 ± 7.0% was measured. This may be attributed to the mass diatom sinking event following nitrate depletion. In the UB¹, the annually averaged ThE ratio was estimated to be 34.4 ± 12.9%, much higher than that in oligotrophic oceans. The high ThE ratio may have contributed to the high organic carbon accumulation in the UB¹.     

黄河柴家峡水电站坝址区地震动参数研究

本文结合柴家峡水电站坝址区的地震地质环境、历史地震特征以及场地条件，采用考虑地震分布时空不均匀性的综合概率法，对场区进行了地震危险性分析，在此基础上给出了坝址区５０年超越概率６３．２％、１０％、２％三个概率水准的设计地震动参数，为大坝的抗震设计和安全运营提供了依据。     

陈村水电站坝基丙凝加强帷幕的防渗时效分析

丙凝是一种曾流行过的化灌材料，形成帷幕体的防渗时效如何过去还很少有报道和研究。本文以陈村水电站为例，根据多年的观测资料、现场调查及室内测试等成果，经过综合分析，指出第７－１７坝段丙凝加强帷幕的总体防渗减压效果是显著的且较稳定的。但局部的防渗效果是在衰减。今后，对这种异常部位应加强观测，以确保大坝的安全运行。     

矿床中元素富集系数序列在找矿中的作用

本文介绍了确定矿床中元素K值(即富集系数)序列的方法;揭示了成矿元素、伴生元素和岩石组合元素具有明显不同的K值特征;阐明了K值序列在预测基本构造单元内的矿产类型,矿源层和成矿机理探讨中的应用及各种介质地球化学异常评价中的作用。     

Feeding broodstocks different starfish diets affect growth and survival of larvae of trumpet shell (<Emphasis Type="Italic">Charonia lampas sauliae</Emphasis> Reeve 1844)

Trumpet shell (Charonia lampas sauliae) (Mollusca, Heterogastropoda, Cymatidae) has extensive economic value. Studies on the artificial larval development of C. lampas sauliae for aquaculture utilization have become especially important due to the finite natural resources. In the present study, the growth and survival rate of the larvae of C. lampas sauliae broodstocks fed three types of starfish diets, Asterina pectinifera Müller & Troschel 1842, A. amurensis Lütken 1871 and their mixture were compared. The larval size increased gradually between day 10 and day 20 after hatching at 15°C and 20°C. No difference was found in body size and specific growth rate (SGR) (two-way ANOVA; P > 0.05). However, during transition from trochophore to veliger stage 20 days after hatching, significant increases in larval survival and growth rates were observed. The maximum survival rate was observed on day 10. The mean survival rate was 0.463, 0.730 and 0.515 at 15°C, and 0.369, 0.713 and 0.444 at 20°C when A. pectinifera, A. amurensis and their mixture were fed, respectively. The SGR and survival rate of the larvae were definitely influenced by the diets (P < 0.05), and the effect of A. amurensis alone was higher than that of A. pectinifera alone and their mixture.     

Total Microbial Activity and Sulfur Cycling Microbe Changes in Response to the Development of Hypoxia in a Shallow Estuary

—We examined the effects of changing from oxic to anoxic conditions on microbial communities using both biogeochemical and molecular approaches in a     

A simple model to predict the effect of volume fraction,diameter, and length of fibres on strength of fibre reinforced brittle matrix composites

A simplified model is presented to predict the strength variations of brittle matrix composites, reinforced by steel fibres, with the variations of fibre parameters—length, diameter and volume fraction. This model predicts that its tensile and flexural strength increase non‐linearly with the fibre volume fraction. It also predicts that similar non‐linear behaviour should be observed with the reduction of the fibre diameter when other parameters are kept constant. The experimental results support both these theoretical predictions. It is also explained why an increase in the fibre length does not always significantly increase the fracture toughness. The objective of this paper is not to explain and understand in great detail the science of all phenomena responsible for the strength increase of fibre reinforced brittle matrix composites, but to provide a simple engineering explanation as to why its strength increases with the fibre addition, and how this increase can be quantitatively related to the variations in fibre parameters—fibre volume fraction, fibre length and diameter. These simplifying steps are needed to provide a tool that the practicing engineers can use to predict the brittle matrix strength variation with the fibre parameters. In the area of geomechanics, the results presented here can be used to assess and predict the behaviour of fibre‐reinforced earth. Copyright © 2000 John Wiley & Sons, Ltd.     

基于扩频通信的深海水声定位技术研究

深海空间站在母船伴随保障时面对恶劣天气存在安全风险及水下多平台作业低效的问题,传统的单一的保障船模式仅依靠超短基线等水下定位方法,水下平台定位速度慢、误差大、相互感知协作困难,已无法满足要求.提出了一种基于通信信标的深海水声定位方法,采用宽带扩频通信进行时延估计,然后利用已建立的等效声速表查找等效声速,完成声线修正,从...