岭澳核电站地震监测系统

介绍岭澳核电站地震监测系统,该系统可实时监测地震加速度随时间的变化过程,自动进行地震检测、事件的识别、数据采集与存储.当检测到地震事件后,立即向主控室发送报警信号,计算加速度响应谱等.     

基于AT89C51的小功率调频调压电源设计

为满足钻井导向系统非接触供电单元开发设计需要,设计一种小功率调压、调频电源.采用智能控制芯片AT89C51作为控制核心部件,自振式反激变换器实现调压模块设计,全桥逆变电路实现调频模块设计,通过IR2110芯片实现驱动.控制芯片产生PWM控制信号,控制开关管的导通并在直流侧加入合适的整流电容使电压平稳输出,经隔离驱动电路实现电能的通断控制,实现电源电压、频率和幅值可调.实验结果表明:该电源具有过电流、过电压保护功能,设计结构合理,成本低廉,控制精度较高,达到设计要求.     

全球气候变化及其影响因素研究进展综述

概述了全球气候变化问题提出的科学背景,总结了引起气候变化的原因,客观分析了引起不同时间尺度气候变化的各种自然因素,透视了人类活动对气候变化的影响程度,讨论了应该如何理解当今全球气候变暖问题。同时,还综述了气候变化研究中的学术分歧和科学困惑。     

Proximate composition of albacore tuna,Thunnus alalunga,from the temperate South Pacific and Tasman Sea

The proximate composition was determined of the white muscle of albacore tuna, Thunnus alalunga, caught by surface trolling along the Subtropical Convergence Zone east of the South Island of New Zealand ("Area 1"), and to the north and west of the North Island ("Area 2"). Fish from Area 1 were 70 ± 10 cm (mean ± s.d.) in fork length, and higher in oil content (4.6 ± 2.9%), than Area 2 fish which measured 55 ± 10 cm and contained 2.8 ±1.7% oil. The ash content of the white muscle of all fish sampled was 1.2 ± 0.1%, and the soluble carbohydrate content 0.36 ± 0.04%. Crude protein contents were calculated at c. 25%. Statistical relationships between moisture and oil contents of both white and red muscle were determined; they can be used to predict oil content from a known moisture content. Oil content was positively correlated with fork length, and negatively correlated with the sea surface temperature at time of capture. Oil levels in the fillet were highest in the muscle layer immediately below the skin and decreased logarithmically with depth. In fish with low white‐muscle oil content (below 5%), the corresponding red‐muscle oil content was higher; above 6% white muscle oil content the corresponding red‐muscle oil content was lower. The proximate composition of whole fish, the head, frame, skin, and viscera is presented.     

基于随机森林的印度洋长鳍金枪鱼渔场预报

为了提高远洋渔场预报水平和满足渔业生产的需要,提出了一种基于随机森林建立印度洋长鳍金枪鱼(Thunnus alalunga)渔场预报模型的方法。选取2002-2009年各个月份印度洋5°×5°格点渔业环境和时空数据(包括海表温度、叶绿素a浓度、表温距平、叶绿素a浓度距平、海表温度梯度强度和海面高度异常等数据)作为预测变量,利用长鳍金枪鱼的CPUE(Catch per unit effort,单位:尾/千钩数)的三分位点将渔区划分为高CPUE、中等CPUE和低CPUE三种类型,作为响应变量,对数据进行训练。结果表明,当随机森林中决策树达到100以上时,袋外数据OOB(out-of-bag)的分类误差率趋于平稳。将训练得到的随机森林用于2010年印度洋长鳍金枪鱼分月渔场的预测,其概率等值面图与实际生产的渔场分布进行叠加比较,显示高CPUE渔场概率分布与实际渔场的位置及范围变化情况符合。通过ROC(Relative Operating Characteristic)分析,高CPUE、中等CPUE和低CPUE的AUC(Area Under ROC Curve)分别达到0.847、0.743和0.803,表明预测精度较高。最后对中等CPUE渔区预测精度相对较低的原因进行了分析。     

浙南沿岸海表面温度分布特征(英文)

文章根据浙南沿岸3个海洋观测站大陈、坎门、南麂站51a(1960～2010年)SST观测资料,进行统计分析,得出SST时空分布特征。结果表明,浙南沿岸的SST总体呈现北低南高的趋势,冬季南北差异最小,夏季南北差异最大;51a年浙南沿岸SST总体呈现上升趋势,上升速率为0.017°C/a;SST变化存在3.5a、5a～6a、2a～7a及11a左右的振荡周期;SST主要由年循环分量决定,谐波拟合效果良好。     

Mass mortality and recolonization of Pyura stolonifera (Heller) on the south coast of South Africa

The fauna and flora of two sublittoral communities situated in close proximity on the west coast of South Africa are described and shown to be radically different, despite the fact that both experience similar physical conditions. One of these communities, at Marcus Island, has prolific beds of the black mussel Choromytilus meridionalis (35 954 g wet weight·m^?2) accompanied by a large number of other species, notably sea urchins, holothurians, brittle stars, whelks and barnacles. In contrast, the other site, Malgas Island, is dominated by a large population of rock lobsters Jasus lalandii together with a dense seaweed flora (3 866 and 4 402 g wet weight·m^?2 respectively). The numbers of species are similar at both sites (102 at Malgas Island and 107 at Marcus Island) but only 34 per cent are common to both localities. Although preliminary research indicates that the two sites have fairly similar physical conditions and bottom topography, they maintained their contrasting communities for the whole research period (1983–1986) and have probably done so for at least nine years, suggesting that they represent two stable alternative states of the same ecosystem. In the absence of rock lobsters at Marcus Island, wave action and inter/intraspecific competition are the main forces structuring the benthic community. Stability is maintained here by the resilience and rapid recovery of the mussel population after disturbance by storms. Where rock lobsters are abundant, as at Malgas Island, intense predation pressure is the main force controlling the structure of the benthos, and it is continually maintained because the rock lobsters are resistant to the effect of storms. Therefore, the presence or absence of high densities of rock lobsters is fundamental to the maintenance of these two contrasting communities.     

Reviewing evidence of marine ecosystem change off South Africa

Recent changes have been observed in South African marine ecosystems. The main pressures on these ecosystems are fishing, climate change, pollution, ocean acidification and mining. The best long-term datasets are for trends in fishing pressures but there are many gaps, especially for non-commercial species. Fishing pressures have varied over time, depending on the species being caught. Little information exists for trends in other anthropogenic pressures. Field observations of environmental variables are limited in time and space. Remotely sensed satellite data have improved spatial and temporal coverage but the time-series are still too short to distinguish long-term trends from interannual and decadal variability. There are indications of recent cooling on the West and South coasts and warming on the East Coast over a period of 20–30 years. Oxygen concentrations on the West Coast have decreased over this period. Observed changes in offshore marine communities include southward and eastward changes in species distributions, changes in abundance of species, and probable alterations in foodweb dynamics. Causes of observed changes are difficult to attribute. Full understanding of marine ecosystem change requires ongoing and effective data collection, management and archiving, and coordination in carrying out ecosystem research.     

Assessment of South African Umbrina robinsoni based on per-recruit models

Slender baardman Umbrina robinsoni are an important component of recreational shore-angler and spearfisher catches along the eastern seaboard of South Africa. Stocks of U. robinsoni at three sites—False Bay, Stil Bay and the KwaZulu-Natal (KZN) coast—were modelled using a per-recruit approach. Total (Z) and fishing (F) mortality rates were estimated by catch-curve analyses using measures of individual size (length or weight) recorded by researchers, divers (log books) or during spearfishing competitions. Based on estimates of F during the period 2001–2003, spawner biomass per-recruit ratios were estimated to be either at or below the 25% threshold (False Bay SB/R = 21% SB/R_{F = 0}, Stil Bay SB/R = 25% SB/R_{F = 0}, and KZN SB/R = 21% SB/R_{F = 0}), suggesting that rates of F were too high. Reductions in F necessary to achieve target fishing mortality levels (F _{F = 0}) at the current minimum size limit (l 40 cm total length) were 51% for Stil Bay and the KZN coast and 57% for False Bay. Based on the bag frequencies from 927 diver outings in KZN (1989–2003), a reduction in bag limit from the current five to two fish is predicted to reduce F in this region by approximately 25%. Increasing the l to 50 cm is predicted to increase SB/R ratios to 36% SB/R_{F = 0} in False Bay, 43% SB/R_{F = 0} in KZN and 52% SB/R_{F = 0} in Stil Bay, at current levels of F. Owing to the philopatric nature of U. robinsoni and the consequent existence of temporary refugia, catch curves are likely to underestimate fishing mortality. The reductions in F estimated to attain the target reference points are therefore probably conservative.     

Can long-term content analysis of print media be used to examine species composition,population demography and changes in distributional range of recreational fishery species?

Although marine recreational fisheries are socially and economically important, there is often limited funding for their monitoring and assessment. With South African anglers reporting catch declines for almost all targeted species and little long-term monitoring data available, novel methods need to be explored to provide managers with additional information. This study aimed to evaluate the efficacy of content analysis of print-media records for detecting long-term trends in species composition, size composition and distribution of selected recreational fishery species. Information for eight fishes captured in the marine shore-based fishery was collected from South Africa’s most popular recreational fishery magazine, between 1960 and 2009. During the five decades, there were shifts in the catch composition, from being dominated by slow-growing, large predators to faster-growing, large predators and lower-trophic-level species. There were no significant trends in the mean and maximum sizes of the dominant species, except for dusky kob Argyrosomus japonicus, which increased significantly in the maximum size reported during the study period. The distributional range of A. japonicus and leervis Lichia amia significantly increased, and that of galjoen Dichistius capensis significantly decreased. However, it was uncertain whether these trends could be attributed to population changes, changes in angler technology and/or behaviour, or climate signals. Overall, this type of content analysis may provide a cost-effective method to examine changes in species composition and fish distributions over time, but, without detailed knowledge of shifts in angler behavioural patterns, it may not be as useful for understanding changes in the population dynamics of recreational fishery species. It is suggested that fishery-independent monitoring programmes are most suited for this type of complex fishery.