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内河船舶避碰决策研究现状及趋势分析 总被引:1,自引:0,他引:1
《世界海运》2015,(3):37-40
本文将船舶避碰研究分为船舶领域、船舶碰撞危险度和船舶避碰决策优化方法三个部分进行综述,通过与船舶避碰整体研究的对比,分析内河船舶避碰研究的现状,得出内河船舶避碰的研究趋势,并得到内河船舶避碰会从二维避碰向三维避碰研究转变、完善船舶领域和碰撞危险度模型及引入先进理论算法等研究趋势。 相似文献
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欠驱动船舶是指只能通过螺旋桨推进器和船舵进行水平面3个自由度运动的船舶,通常,当船舶某些执行器结构出现故障时,船舶此时具有欠驱动特征。欠驱动船舶的航行控制系统是一个典型的非线性系统,研究欠驱动船舶的运动控制不仅可以提高船舶的自动化水平,还对保障船舶的航行安全有重要意义。本文首先介绍了一种粒子群优化算法,并对该优化算法的原理和流程进行研究,然后基于粒子群优化算法对欠驱动船舶的运动控制进行研究,开发了一种基于粒子群算法的欠驱动船舶运动控制器,并进行仿真试验。 相似文献
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对船舶图像进行快速准确识别在军民领域都有广泛应用,随着船舶种类的增多、图像质量的提高,传统的卷积神经网络进行船舶图像识别需耗费大量时间。本文对深度神经网络的原理进行分析,并在此基础上研究基于深度神经网络的船舶图像识别流程,对船舶图像预处理技术进行研究,建立船舶图像训练集和测试集,对YOLOV2、卷积神经网络和本文算法的平均识别时间和识别准确率进行分析,最后研究3种算法的训练次数对识别准确率的影响。本文研究的深度神经网络船舶图像识别算法,在平均识别时间以及识别准确率上具有一定优势。 相似文献
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本文对船舶航行过程进行分析,着重研究船舶在航行过程中的流场理论,并对船舶受到的阻力进行分析,同时给出船舶摩擦阻力和傅汝德数之间的关系;基于计算流体力学对船舶航行过程中的受力情况进行仿真分析,探讨波浪流速对船舶航行过程的影响,同时对波浪抨击下的船体受力情况进行分析。最后,构建出船舶压力监测系统。本文对船体行驶过程中压力监测方法的研究,有助于推动船舶结构安全技术的发展。 相似文献
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船舶制造正在朝向大型化和智能化方向发展,船舶管系建造是船舶制造过程中的重要一环。船舶管系的安装以及焊接过程中会受到材料质量、工人技能、焊接工艺等多方面的影响,因而需要对管系建造进行监督。传统船舶管系建造监管依靠人力,效率很低,本文在对图像处理技术进行充分研究的基础上,对图像去噪、图像增强以及边缘提取等图像预处理技术进行研究,研究图像处理技术在船舶管系识别中的应用。通过对船舶管系颜色和轮廓的识别,可以确定船舶管系的建造和设计图纸之间的差别。提出基于支持向量机和图像处理技术的焊缝分类判定流程,通过少量样本的训练可以完成对船舶管系焊缝焊接质量的基本判定,大幅度提升船舶管系建造监管效率。 相似文献
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In recent years, demands for car transportation by a ship have been increasing with favorable economic conditions in auto
sector, and the need of a pure car carrier (PCC) has grown quickly. A PCC needs huge parking space but smaller displacement
since a car is comparatively light for its volume. As a result, almost all PCCs have wide breadth, shallow draft and huge
structure above the water surface. These features cause some technical issues of a PCC, like lack of stability, effect of
strong winds on its resistance, difficulty of course keeping in rough seas, difficulty of berthing in strong winds, and so
on. To overcome these technical issues, one of the authors has proposed a new concept for a PCC. This is a trimaran PCC which
has very limited transverse bulkheads in the center hull by using two side hulls as fenders. In the present research, wind
forces acting on a scale model of the trimaran PCC were measured in the towing tank with a wind generator at Osaka Prefecture
University. Furthermore, in order to clarify the characteristics of wind pressure on the trimaran, height and width of tunnels
which are between a main hull and side hulls were changed. And then, in order to imitate a real ship, we used wind reduction
technology of corner-cut design for accommodation house of the ship. Moreover, the wind pressure acting on the trimaran was
compared with that on a mono-hull PCC. Using these experimental and theoretical results, an estimation method of wind pressure
acting on the trimaran PCC is deduced. 相似文献
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This paper deals with numerical techniques for computing the viscous flow past a ship hull with and without a free surface
using a Reynolds-averaged Navier-Stokes solver with global conservation. In the first technique, a coarse grid is used to
find an approximate solution to the free surface problem. Interpolation of a fine grid is subsequently carried out, and a
more exact solution, particularly in the boundary layer and wake, is obtained. In the second technique, a modified Baldwin-Lomax
model is introduced to compute the viscous flow with and without a free surface. These numerical techniques are applied to
simulations of the flow around a Series 60 and an SR196C ship model. The results are compared with measurement data, and the
usefulness of the numerical techniques is demonstrated. 相似文献
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This review presents a systematic summary of the state-of-the-art development of technological solutions, modeling, and control strategies of thruster-assisted position mooring (TAPM) systems. The survey serves as a starting point for exploring automatic control and real-time monitoring solutions proposed for TAPM systems. A brief historical background of the mooring systems is given. The kinematics and a simplified kinetic control-design model of a TAPM system are derived in accordance with established control methods, including a quasistatic linearized model for the restoring and damping forces based on low-frequency horizontal motions of the vessel. In addition, another two mooring line models, i.e., the catenary equation and the finite element method model, are presented for the purpose of higher-fidelity simulations. The basic TAPM control strategies are reviewed, including heading control, surge-sway damping, roll–pitch damping (for semisubmersibles), and line break detection and compensation. Details on the concepts of setpoint chasing for optimal positioning of a vessel at the equilibrium position are discussed based on balancing the mooring forces with the environmental loads and avoiding mooring line failure modes. One method for setpoint chasing is the use of a structural reliability index, accounting for both mean mooring line tensions and dynamic effects. Another method is the use of a lowpass filter on the position of the vessel itself, to provide a reference position. The most advanced method seems to be the use of a fault-tolerant control framework that, in addition to direct fault detection and isolation in the mooring system, incorporates minimization of either the low-frequency tensions in the mooring lines or minimization of the reliability indices for the mooring lines to select the optimal directions for the setpoint to move. A hybrid (or supervisory switching) control method is also presented, where a best-fit control law and observer law are automatically selected among a bank of control and observer algorithms based on the supervision of the sea-state and automatic switching logic. 相似文献
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An optimised design of a dynamic umbilical requires an extreme cross-sectional stress to be maintained within an allowable limit and a fatigue life to be guaranteed to be sufficient. It should be noted that a dynamic umbilical is a typical geometric bi-scale structural system. It consists of a local cross-sectional scale and a global configuration scale, which are significantly different in terms of geometric sizes. In this study, we established an approximate model to achieve an optimised design of the dynamic umbilical by considering the parameters of local cross-sections and global configurations simultaneously. The design variables of a dynamic umbilical are independently identified and defined at both local sectional and global configuration scales in the approximate model. Furthermore, we selected the maximum tension strain and the maximum bending moment, for covering local and global properties, as the objectives to be minimised. The approximate model was observed to be effective in integrating the local and global responses into one loop so that the computational efficiency could be significantly increased. We implemented the optimisation framework on a dynamic umbilical with a lazy-wave configuration, which is considered to be a basis for a case study. Furthermore, we verified the feasibility and effectiveness of the integrated optimisation strategy by numerical simulations. Moreover, we compared the optimised dynamic umbilical properties with those without optimisation. It was observed that the fatigue life of the optimised dynamic umbilical was improved significantly, thereby indicating that the integrated optimisation methodology provides a new model and algorithm for an efficient design of the dynamic umbilical. 相似文献
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Naomi Kato 《Journal of Marine Science and Technology》1998,3(3):113-121
The objectives of this study were the development of a new device for maneuvering an underwater vehicle using the mechanism
of a fish swimming, an experimental and theoretical analysis of the hydrodynamic characteristics of the device, and its application
to maneuvering a fish robot. Observations and experimental analysis of the pectoral fins of a black bass (Micropterus salmoides) revealed that the locomotion of the fish, such as swimming forward at low speed, swimming backward, and turning in a horizontal
plane is generated by using a combination of a feathering motion and a lead-lag motion of the pectoral fins. A mechanical
pectoral fin making a feathering motion and a lead-lag motion generates a thrust force in a range of phase differences between
both motions. The unsteady vortex lattice method, including the effect of viscosity, can express fairly well the unsteady
forces acting on the mechanical pectoral fin in the range of phase differences where it exerts the thrust force. The fish
robot, consisting of a model fish body and a pair of mechanical pectoral fins, can not only swim forward and turn in almost
the same position, but can also swim in a lateral direction without changing the yaw angle.
Translation of an article that appeared in the Journal of The Society of Naval Architects of Japan, vol. 182 (1997): The original
article won the SNAJ prize, which is awarded annually to the best papers selected from the SNAJ Journal, JMST, or other quality
journals in the field of naval architecture and ocean engineering. 相似文献
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Mark B. Orams 《Coastal management》2013,41(4):361-380
The growth of whale-watching internationally has been spectacular. It now occurs in almost 100 countries and is estimated to be worth in excess of U.S.$1 billion each year in revenue. Thus, whales have become valuable as a resource for tourism. The Vava'u island group in the northern part of the Kingdom of Tonga in the South Pacific is an area with a growing reputation as a whale-watching destination. However, the industry is relatively new there and the impacts of whale-based tourism in these islands is, as yet, unknown. In addition, there has been a recent consideration of a return to hunting whales in Tonga. As a result, concerns regarding the value of these animals for tourism and the potential impact of a return to hunting have arisen. Consequently, a study was designed to provide a preliminary assessment of the economic impacts of these animals for the island community. This study estimates that humpback whales may be worth in excess of U.S.$700,000 annually as a tourism attraction and that there is significant potential for future growth. Furthermore, the study shows that current visitors are opposed to any resumption of whaling practices in the islands and that such a move would likely displace large numbers of tourists from Tonga. Thus, it is concluded that a resumption of whaling in Tonga would likely have a significant opportunity cost in terms of lost tourism revenues. 相似文献
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An alternative option to the traditional grouted joint for wind turbines is a direct steel-to-steel connection, also known as slip joint. In a recently published work, a proof of concept of a vibration-assisted installation and decommissioning technique of a slip joint was illustrated. Leveraging on the obtained results, the current study shows for the first time a decommissioning campaign carried out using a vibration-assisted technique applied on a prototype hydraulic wind turbine tower located in the North Sea, and connected to the monopile through a slip joint. The key aspect of the dismounting procedure is a priori knowledge of the resonance frequency clusters corresponding to the slip joint’s cross-sectional modes. Therefore, field hammer tests and experimental modal analysis were carried out inside the wind turbine tower. The identified frequencies and mode shapes were then compared with numerical ones estimated by a finite element model of the investigated structure. The comparison showed that a set of frequency clusters can be directly selected from a detailed numerical model. The preparatory work of the slip joint decommissioning was then executed by installing electric shaker devices, based on the dynamic identification results, and hydraulic jacks mounted inside the wind turbine tower. A first decommissioning trial was carried out in May 2019, while the final decommissioning was performed in August 2019. After analysing the measurements of the hydraulic pressures, displacements and excitation frequencies during the decommissioning campaigns, the results showed that it is possible to disconnect the slip joint if, in combination to a vertical static force, one of the identified cross-sectional mode shapes is excited. The vibration-assisted decommissioning proved to be a successful technique to dismount the connection in a controlled and straightforward manner. 相似文献
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针对长甲板室纵向围壁端部与主船体露天甲板交界处的应力集中问题,采用结构有限元数值分析方法,探讨在空间布置受到限制的条件下,应力集中交界处圆弧型肘板臂长、圆弧半径等参数变化对应力分布和大小的影响,并得到降低应力集中系数的圆弧型肘板参数的最佳值。文中根据研究结果,对某艘实船的长甲板室纵向围壁端部与主船体露天甲板交界处圆弧型肘板进行优选设计,有效地降低了该处的应力集中水平。 相似文献
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Evangelia N. KaselimiAuthor Vitae Theo E. NotteboomAuthor Vitae Athanasios A. PallisAuthor Vitae Sheila FarrellAuthor Vitae 《Research in Transportation Economics》2011,32(1):71-80
The decision on the scale of a port terminal affects the terminal’s managerial, operational and competitive position in all the phases of its life. It also affects competition structures in the port in which the terminal is operating, and has a potential impact on other terminals. Port authorities and terminal operators need to know the scale of the terminal when engaging in concession agreements. In economic theory the scale of a plant/firm is typically defined in relation to the Minimum Efficient Scale (MES), the long-run output where the internal economies of scale are fully exploited. However, there are a number of theoretical and empirical indications that in ports the scale of a terminal is commonly guided by a combination of the MES and other determining factors. The “preferred” scale is the result of a complex interaction between the MES, the port governance framework and objectives, the market size and structure, technological change and operational considerations, physical and geographical limitations, and the business patterns of shipping lines. This study analyses the factors resulting in a preferred container terminal scale that in most of the times is different from the MES. The analysis of the technical, market-related and governance-related factors is supported by theoretical and empirical insights that illustrate the presence of a range of actual ”preferred” scales of terminal concessions that usually are different, below or above, MES. 相似文献
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海上极端波因其巨大的波高常常导致船体的极限破坏。该文提出了一个二维的修正水弹性方法来研究一个集装箱船船体梁在极端波中的动态前极限强度。传统的极限强度评估基于准静态方法,没有动态效应被考虑。而船体在波浪下的动态结构响应是基于水弹性方法,传统的水弹性方法并不能计算船体梁的动态非线性强度。该二维修正的水弹性方法考虑时域波浪和非线性船体梁之间的耦合,将水弹性方法和Smith方法结合,用Smith方法计算船体梁的刚度,而其刚度与船体梁的强度和变形曲率有关。所以该时域的非线性刚度被用于修改水弹性方法里的常数项的结构梁刚度。几组极端波模型被用以产生船体梁的大变形和非线性动态垂向弯矩。文中分别采用修正水弹性方法和普通水弹性方法,通过改变四个重要的极端波参数如极端波最大波高、规则波的波高、波速和波长等来研究其对船体梁船中处的大变形转角和非线性垂向弯矩的影响,通过采用修正的水弹性方法计算得来的结果与水弹性方法计算得来的结果相比较,得到了一些差异和结论。 相似文献