两层流体中水波与垂直圆柱浮体的相互作用

基于特征函数匹配理论,导出了作用在垂直圆柱浮体上波浪力的计算公式.对于两层流体,除了表面波模态的波浪力外,还有内波模态的波浪力,这与单层流体的情况是不同的.对所建立的求解模型进行了数值计算分析.结果表明,在某个频率范围内,流体的分层效应对垂直圆柱浮体的波浪力有一定影响.     

腐蚀损伤的激光超声可视化成像检测

腐蚀损伤广泛存在于国防科技、交通运输等工业领域,严重威胁了结构的安全性和可靠性,因此对腐蚀损伤的安全检测具有重要意义。依据激光超声的基本理论,采用自主设计的全自动激光超声扫描实验系统,通过对铝板中的腐蚀损伤进行激光扫描实验,分析了Lamb波能量、幅值和腐蚀之间的关系,并依据“弹性波能流法”的原理,利用幅值最大值完成了损伤区域的可视化;提出了一种评估铝板腐蚀程度的方法——能量比较法,完成了对不同腐蚀程度的铝板的评估分析。该研究可实现腐蚀缺陷的快速检测与评估,并且检测结果直观可视,展现了巨大的应用前景。     

左手介质组成的完美透镜的两种不同的理论分析

在分析了两种不同的左手介质组成的基础上,根据电磁理论,从传统透镜的理论缺陷入手,利用传统光学性质和传输线理论两种不同的方法来分析,利用倏逝波在左手介质中被放大的性质,解析地研究由左手介质组成的完美透镜以及完美透镜成像的原理．     

直流输电线路行波故障测距系统

介绍了一种采用现代行波故障测距技术的直流输电线路故障测距系统的工作原理、系统结构及其实际运行经验.该系统集成了现代D型和A型2种行波故障测距原理,并且包含3个不同的组成部分:行波采集与处理系统、通信网络和PC主站.现场运行经验表明,该系统具有很高的可靠性和准确性,其测距误差不超过3 km.     

海洋渔业与生态文明

中国是海洋大国,也是海洋水产品消费大国,海洋渔业在中国经济社会和人们日常生活中占有重要地位。随着人们对海洋水产品的需求日益增强,海洋生态系统压力不断增大。如何解决全球渔业资源减少与对水产品需求增长之间的矛盾、海洋食物持续产出与海洋环境恶化之间的矛盾、建立海洋渔业发展新模式,是一个全球性的挑战。海洋牧场作为一个新生事物,已经引起政府、社会、特别是科技界的广泛关注与讨论。从海洋渔业的可持续发展角度,探讨了为什么要建海洋牧场、在哪里建和如何建等方面的问题,涉及对海洋牧场内涵的理解、海洋生态系统食物网关系、海洋鱼类的生活习性与海洋牧场构建之间的关系等科学问题。     

船舶航向H∞鲁棒控制

为有效抑制参数不确定性和干扰随机性对船舶航向的影响,设计了船舶航向鲁棒控制器.针对船舶海浪的遭遇谱能量集中频段随遭遇角的变化而变化,对不同的遭遇角选择不同的权函数进行设计.采用双线性变换对标称模型位于虚轴上的极点进行处理,并利用"2-Riccati"方程法求解控制器方程.仿真结果表明,与PID控制相比,该控制器航向控制精度较高,并具有较好的鲁棒性能.     

超声波和赤霉素处理促进唐古特大黄种子萌发

采用饱和D最优设计方法,研究了超声波作用时间和赤霉素浓度二因素对唐古特大黄种子萌发能力的影响。结果表明:采用超声波和赤霉素处理对唐古特大黄种子的萌发具有一定的促进作用,超声波是促进种子萌发的主要因素;优化综合农艺措施为:超声波作用时间21.6~43.1 min,赤霉素浓度38.2~58.9 mg/kg。     

Novel records and observations of the barnacle Stephanolepas muricata (Cirripedia: Balanomorpha: Coronuloidea); including a case for chemical mediation in turtle and whale barnacles

We report new distribution and host records of the turtle barnacle Stephanolepas muricata Fischer. Ours is the first study to document this species' occurrence in Mexico and in the Atlantic Ocean (North Carolina, Georgia and Florida: USA). We also present the first record of S. muricata from olive ridley sea turtles, Lepidochelys olivacea (Eschscholtz). We discuss the physical and ecological characteristics associated with the specimens collected and present evidence suggesting the likelihood of chemical mediation between embedding coronuloid barnacles like S. muricata and host turtles. We provide the first data on the diet and fecundity of S. muricata.     

Spatial and temporal distributions of juvenile horseshoe crabs (Arthropoda: Chelicerata) approaching extirpation along the northwestern shoreline of the New Territories of Hong Kong SAR,China

Juvenile horseshoe crabs, Tachypleus tridentatus and Carcinoscorpius rotundicauda, with prosomal widths of between 11.5 and 102.5 mm, occur along Hong Kong's northwestern shoreline abutting Deep Bay where dissolved oxygen (DO) has been identified as the principal factor determining distribution and survival. Unreported upon hitherto, however, Tachypleus tridentatus occurred consistently in association with sea-grass (Halophila beccarii) beds, with DO concentrations of 8–14 mg·L^?1, a median grain size of >180 μm, interstitial water contents of <36% (sediment wet weight) and organic contents of <3.2% (sediment dry weight). Most individuals occurred between 60 and 120 m down from the shoreline although there appeared to be a trend of down-shore migration in summer, possibly to alleviate thermal stress. No individuals were found at sediment temperatures ≤20°C, i.e. in sub-tropical Hong Kong's winter, when they adopt buried repose. Abundances of emerged T. tridentatus, peaking in November, were synchronized with interstitial salinities of 22–26‰ and averaged 1–2 individuals per 100 m². Mean population density of T. tridentatus was 4–9 individuals per 100 m². Only four individuals of C. rotundicauda were found in August and September, suggesting a recent dramatic decline in numbers. The natal crèche environment for juvenile horseshoe crabs in Hong Kong is deteriorating and threatening their survival.     

Sipunculans and echiurans from the deep Angola Basin

Sipunculans and echiurans collected by the “DIVA 1” expedition by RV Meteor (Cruise M48/1) to the deep‐sea bottom of the Angola Basin are recorded. Seven species from five genera and two separate phyla are recognized; only the echiuran Pseudoikedella achaeta has not been recorded hitherto in the southern sector of the Atlantic Ocean. A gradient analysis using redundancy analysis (RDA) under the CANOCO package indicates the existence of a neat latitudinal gradient of sipunculans along the Angola Basin from the southernmost stations towards the northern ones. The local abundance of abandoned horny tubes of polychaetes at some of the sampling sites of the northernmost stations explains the dense aggregations of Nephasoma diaphanes. This species exhibits an opportunistic lifestyle inside empty polychaete tubes on the abyssal plains of the Angola Basin.