Damage identification in a ship’s structure using neural networks

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.     

非线性随机系统的参数辨识及动态预报

鉴于含有加性噪声的指数模型描述了一类重要的非线性随机系统。本文给出这类系统的参数递推辨识算法，克服了迭代算法不能在线运行、需反复矩阵求逆的不足。当系统时变时，还采用了虚拟噪声技术来补偿因参数时变引起的建模误差，从而改善动态预报器的性能。应用这种方法，对油田采油井、注水井的套管损坏情况进行了多步动态预报，其精度令人满意     

Site-specific effects on productivity of an upper trophic-level marine predator: Bottom-up, top-down, and mismatch effects on reproduction in a colonial seabird

We investigated the relative roles of bottom-up and top-down factors in limiting productivity of an upper trophic level marine predator. Our primary working hypothesis was that the reproductive success of black-legged kittiwakes (Rissa tridactyla) a piscivorous, colonial-nesting seabird, was most limited by the abundance, distribution, and species composition of surface-schooling forage fishes. A secondary working hypothesis was that reproductive loss to kittiwake nest predators was greatest during years of reduced prey availability. We report on a broad-scale, integrated study of kittiwakes and their prey in Prince William Sound, Alaska. Our study spanned five breeding seasons (1995–1999) and focused on three colonies that differed in size (ranging from ca. 220 to ca. 7000 breeding pairs) and proximity to each other (50–135 km apart). Kittiwakes in PWS encountered a variety of aquatic habitats, creating a complex foraging environment for breeding birds. We measured kittiwake reproductive success and foraging activities, while simultaneously measuring the abundance of surface schooling forage fishes throughout the foraging range of breeding kittiwakes. The abundance of primary prey species for kittiwakes (Pacific herring Clupea pallasi, Pacific sand lance Ammodytes hexapterus, and capelin Mallotus villosus) varied both annually and regionally, with no one region consistently having the greatest abundance of prey. Likewise, kittiwake reproductive success varied considerably among colonies and years.We found that bottom-up, top-down, timing mismatch, and colony-specific effects were all important to kittiwake productivity. Although bottom-up effects appeared to be strongest, they were not evident in some cases until other effects, such as geographic location (proximity of colony to prey concentrations) and top-down predation, were considered. Important bottom-up effects on kittiwake reproductive success were not only total prey abundance and distribution, but also species, age composition, and chronology of prey occurrence (match/mismatch of timing with critical brood-rearing periods); these effects varied by colony.Top-down effects of predation on kittiwake nest contents (independent of prey abundance) confounded seabird-forage fish relationships. Ultimately, when confounding factors were minimized, non-linear asymptotic relationships were identified between kittiwakes and their prey, with an asymptotic threshold of fish school surface area density of ca. 5 m²/km², beyond which top-down, physiological, or phylogenetic constraints likely restrict further reproductive output. The integrated approach of our investigations provided a more thorough understanding of the mechanisms underlying predator–prey relationships in the complex marine environment. However, such mechanistic theories can only be tested and refined through long-term research and monitoring of much greater duration than the 5-year study reported herein.     

天然气水合物的测井识别和评价

地球物理测井作为传统的资源评价方法，在天然气水合物勘探中是有效评价手段。从国内外对天然气水合物的研究现状出发，简要地总结了天然气水合物的地球物理特征，介绍了利用电阻率测井和声波速度测井识别含天然气水合物储集层的方法和对天然气水合物进行评价，对现有的测井评价模型进行了讨论，指出了对天然气水合物储集层的地球物理测井评价模型还有待于进一步探讨。     

金焰笛鲷与金带笛鲷的RAPD分析

应用RAPD技术，对笛鲷属的金焰笛鲷(Lutjanus fulviflamma)、金带笛鲷(Lutjanus vaigiensis)进行种群内及种群间遗传学分析。结果表明两种鱼的种内遗传多样性指数(H)分别为：金带笛鲷0．1107；金焰笛鲷0．1673。二者的多态位点比例(P)分别为47．8％和59．0％。2种笛鲷种间平均遗传相似系数为0．4640，遗传距离Dpd为0．5360。2种鱼共检出6个可作为种的特异性鉴定的条带。     

物联网在城市精细化管理中的应用

针对目前"数字城市"向"智慧城市"迈进中物联网技术蓬勃发展,而原有数字化城市管理的方法和技术手段在许多方面都有待进一步完善的现状,该文探索利用物联网等高新科技手段,以全新的管理理念和管理模式来提升城市精细化管理水平。该文重点论述了如何综合运用物联网智能感知、无线传输、数据挖掘等技术,在车载感知定位技术及应用、城市安全传感器应用、水雨雪情实时监测及防汛应急、交通运行多源监测数据分析以及基于二维码的公众参与式城市管理等的典型应用实例。这些典型应用有效地解决城市运行管理中的实际问题,满足了物联网理念在城市管理中的拓展以及管理方式继续深入的需要,提升了城市运行管理的科学化、智能化水平。     

控制点识别的全自动相机标定算法研究

针对现有相机标定环节中控制点需要手动选取,标定自动化程度不高,效率较低的问题。该文在圆心投影点精确定位研究成果的基础上,提出了一种基于角距的控制点自动识别算法,解决了三维高精度控制场下全自动相机标定的关键环节。初步实验表明,在同等条件下,基于该方法的全自动标定精度、效率和稳定性均优于传统人工选取控制点的标定方法。