On the dispersion relation of hydroelastic waves in a plate

This paper deals with the dispersion relation of hydroelastic waves in pontoon-type very large floating structures (VLFS) using a simple beam modeling, where the term hydroelastic waves means propagation of deflection vibrations in VLFS. The purpose of this paper is to show the properties of the hydroelastic waves. The dispersion relation of hydroelastic waves propagating in an infinite plate floating on the water is derived based on the linear water wave theory. The effects of the water depth and of the bending rigidity of the floating plate on the wavelength, phase velocity, and group velocity of the hydroelastic waves are shown theoretically or numerically. Then, the dispersion relation of hydroelastic waves in a finite plate floating on shallow water is investigated. It is shown that the wavelength or the phase velocity of the hydroelastic waves varies with the location in the plate. Received for publication on April 7, 1999; accepted on Aug. 20, 1999     

Control system design and performance evaluation of anti-pitching fins

We have investigated the usefulness of active stabilizing fins to reduce ship pitching under varying forward speeds, and in varying wave lengths. A 4-m self-propelled model ship and an electrohydraulically driven stabilizing fin system were used in our experiment. Pitch angles, pitch rates, and ship forward speeds were measured and fed back to a controller to calculate the deflection angle of the stabilizing fin. The effects of fin nonlinearity on achievable pitch reduction performance are discussed. It is shown that the desired pitch response can only be achieved when the fin is operated in the linear region. The overall dynamic response of the ship approaches open-loop behavior when the degree of nonlinearity is high. This simple analysis of the pitch stablizing system provides basic information to ship designers. Experimental results validate these design guidelines. Received for publication on Feb. 12, 1998; accepted on Dec. 8, 1999     

基于统计及形态特征指标的桥梁线形监测评估

为探讨大跨度桥梁线形实时在线监测及安全评估方法,以武汉阳逻长江公路大桥为工程背景,建立了液压差半封闭式连通管线形监测系统,介绍该桥健康监测系统中线形监测的测点布置、采集方案策略,重点研究了以统计及形态特征为指标的桥梁线形监测加权评估方法。研究表明:该系统能够实时在线监测并评定桥梁线形变化特征,且测试精度高、长期稳定性好;统计及形态特征指标集单个测点与全部测点数据评估为一体,可有效运用于大跨度桥梁线形监测的状态评估。     

Much Ado about Nothing? - An analysis of economic impacts and ecologic effects of the EU-emission trading scheme in the aviation industry

From 2012 on, all CO₂ emissions from flights departing from or arriving at airports within the European Union have to be offset. We analyze the economic and ecological impacts that are caused by an inclusion of the aviation industry into the proposed emissions trading scheme (ETS). Building on the now fixed system design we employ a simulation model to estimate the impacts of the scheme. Our results indicate that financial impacts are highly dependant on external settings, such as allowance prices and demand growth. We show that the financial burden on the aviation industry will be rather modest in the first years after the introduction of the system and therefore induce only low competition distortions. Likewise, emission reductions within air transportation will be comparably low. While aviation will induce a decline of emissions in other sectors, significant absolute reductions within air transportation can only be reached by a more restrictive system design.     

系统思考于长隧道防灾之研究

长公路隧道空间潜藏之危险可能造成重大灾害之伤亡及交通运输路网系统功能失效,其空间内之安全防灾系统及防灾应变作业必需经过严谨的考量,以因应其空间之复杂及防灾功能性要求,故于灾害管理信息整合及应用上也更趋重要。救灾工作系与时间在赛跑,对于时间延迟的影响,是整体防灾目标达成之关键因素;然救灾仅以灾害后果之情境来模拟,恐无法展现各系统因果关联与灾害信息滞延之后遗症影响,此外对于救灾工作跨组织协调、应变工作派遣、救援资源、疏散避难等面向,皆无法完整真实反应防救灾系统。有鉴于此,对于长隧道空间之防灾及安全管理应谨慎进行评估。本文系以系统思考为出发点,考量长公路隧道具有空间复杂、跨领域防灾知识及科技研究限制等特性,针对系统内具时间延迟特性进行灾害冲击探讨,藉由各子系统之因果关系,探究灾害防治问题与灾措施,最后结合长隧道空间灾害信息,尝试以系统性结构建立定性分析模型,希冀本文研究内容可强化灾害防治工作与救援策略,并避免灾害带来的后遗症累积,而所提出之灾害管理之系统思考,将有助于未来系统建立动力模式与进行风险管理之基础建立。     

Time-variant ultimate longitudinal strength of corroded bulk carriers

Many bulk carrier losses have been reported of late, and one of the possible causes of such casualties is thought to be the structural failure of aging hulls in rough weather. In aging ships, corrosion and fatigue cracks are the two most important factors affecting structural safety and integrity. This paper uses a set of the time-dependent corrosion wastage models for 23 different member locations/categories of bulk carriers previously developed by the authors, based on the available corrosion measurements for existing large bulk carrier structures. Differences due to the location and corrosion severity of every member type are taken into account. The nominal design corrosion values for the primary members are suggested based on the annualized corrosion rates obtained in the present study. The effect of time-variant corrosion wastage on the ultimate hull girder strength as well as the section moduli is studied. The criteria for repair and maintenance of heavily corroded structural members so as to keep the ultimate longitudinal strength at an acceptable level are discussed. Important insights and conclusions developed are summarized.     

DIAGNOSTIC VALUE OF NERVE ROOT STIMULATION METHOD IN CERVICAL RADICULOPATHY

Diagnosisofcervicalradiculopathygenerallyusesc0mputedtomography(CT),myelogram,magneticresonanceimaging(MRI)andelectromy0gram(EMG)examinati0n.However,c0nduc-tionvelocity0fperipheralnerveinEMGexaminationisusuallyn0rm0lt1i;denerva-rioninparaspinalortheappropriateupper.imbmusclesisastrongevidencefordiag-iosisofcervicalradiculopathy,butasre-ienerationoccursquiteearly,ab0ut5O%>fthepatientshaveals0normalEMG;tudies[2'33.Asconducti0nsl0w0rblockviaybetheonlyabnormalexpressi0ndur-.ngnerveimpairment…     

铁路沿线风吹雪灾害及其防治研究

新疆精—伊铁路经过的风吹雪灾害多发区最大风速平均值为14 0m·s-1,30年一遇的最大风速与最大积雪深度分别为20 3m·s-1和160cm,平均冬季降水量153 2mm。在风吹雪多发区,铁路风吹雪灾害的主要类型是路堑型风吹雪沉积,其次是低填路堤型风吹雪沉积。路堤低、路堤边坡平缓,路面上易发生风吹雪沉积;路堑边坡的角度越小、路堑越深、路堑走向与主导风向的夹角越小,风吹雪沉积越不易发生。在风吹雪害多发区,铁路路堤设计的适宜高度为200～1500cm。风吹雪的防治应以设防风吹雪走廊和下导风板为主,并辅以侧导板和挡雪墙等。     

防雪栅栏对公路风吹雪灾害的防治技术研究

提出了利用防雪栅栏防治公路风吹雪灾害技术，并就防雪栅栏的类型、作用机理、影响因素，以及防雪栅栏的设置等进行了阐述。     

西藏墨脱高等级公路工程地质遥感勘察及GIS应用

运用遥感及地理信息技术能有效地从图像光谱特征、空间特征、影像纹理、微地貌、景观等诸多方面,对岩石、构造、地形地貌、地质灾害等进行识别与划分,从遥感影像中提取公路工程地质信息.结合ENVI和ARC/INFO软件进行数据采集和专题制图,利用GIS的空间分析功能,能快速、准确地对公路工程地质条件进行定量分析和综合评价.