共查询到20条相似文献，搜索用时 23 毫秒
1.
Donghoon Kang Vishwanath Nagarajan Yoshiaki Gonno Kazuhiko Hasegawa 《Ocean Engineering》2011,38(10):1184-1196
The inflow characteristics to each one of the rudders of single-propeller twin-rudder system are investigated. It is shown that this inflow is not parallel to ship's centerline. This may result in asymmetric maneuvering characteristic of the ship thereby reducing ship's maneuvering performance. For this purpose, a method of installing single-propeller twin-rudder system is proposed. This method is called “virtual zero rudder angle” arrangement. Here, each one of the twin-rudder is set at an angle corresponding to the inflow to the rudder. The improvement in ship's maneuvering characteristics with “virtual zero rudder angle” arrangement is investigated using experiments and numerical simulations for different ship types. It is shown that this arrangement may also improve ship's propulsion performance. 相似文献
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Towed-array history, 1917-2003 总被引：1，自引：0，他引：1
《Oceanic Engineering, IEEE Journal of》2004,29(2):365-373
Towed-array research and development over 86 years is examined from the inventions of Dr. H. C. Hayes during World War I to multiple arrays towed by oil exploration ships in 2003. Time lines of the effort over the years are presented for array applications to military surface ships, submarines, and for oil exploration efforts. Military surface ship towed-array systems from the Hayes electric eel effort to the SQR-14, SURTASS, ETASS, and APL/Johns Hopkins dual towed arrays are reviewed. Submarine towed-array programs from the early 1960s to today are described and a prediction of future towed-array development is presented. 相似文献
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As the number of ships for marine transportation increases with the globalisation of the world economy, waterways are becoming more congested than before. This situation will raise the risk of collision of the ships; hence, an automatic collision avoidance system needs to be developed. In this paper, a novel approach based on deep reinforcement learning (DRL) is proposed for automatic collision avoidance of multiple ships particularly in restricted waters. A training method and algorithms for collision avoidance of ships, incorporating ship manoeuvrability, human experience and navigation rules, are presented in detail. The proposed approach is investigated not only by numerical simulations but also by model experiments using three self-propelled ships. Through the systematic numerical and experimental validation, it is demonstrated the developed approach based on the DRL has great possibility for realising automatic collision avoidance of ships in highly complicated navigational situations. 相似文献
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Ice, harsh weather, severe cold, and remoteness increase the risks of navigating the Arctic. Robust ships and shipboard systems to support routine operations and effectively respond to accidents and emergency situations are necessary. In spite of these challenges, the cruise ship industry is reportedly preparing to expand its passenger capacity, destinations, and operating season in the Arctic. An examination of the Arctic cruise ship fleet shows that the most capable ships are approaching the end of their service lives and may be replaced during the next decade. A window of opportunity is open for the international community to act on concerns about the safety of cruise ships in Polar Regions by codifying and making mandatory the International Maritime Organization's Guidelines for ships operating in Polar waters. A mandatory code would provide regulatory guidance to ship-builders at a critical point in the process of procuring new Arctic cruise ships and ensure that suitably constructed and outfitted ships would serve Arctic cruisers. 相似文献
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UK shipping companies increasingly flagged out their ships from the 1970s to the late 1990s. This study used Lloyd's casualty records from 1970 to 2005 to investigate and compare shipping casualties and crew fatalities in UK shipping, UK second registers (Bermuda, Cayman Islands, Gibraltar, Hong Kong and the Isle of Man) and six foreign flags (Bahamas, Belize, Cyprus, Malta, St. Vincent and Vanuatu) used frequently by UK shipping companies. The study also assessed how 12 shipping factors may affect ships foundering and crew fatalities. Shipping casualty and crew fatality rates fell over time in UK shipping, in UK second registers and in older flags of conveniences, rather than in newer flags of convenience such as Belize and St. Vincent. Cargo, trade and weather most strongly affected ships foundering and crew fatalities. The findings indicate that shipping casualties and crew fatalities should be monitored in new and rapidly expanding flags of convenience. 相似文献
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Ships experience roll motion due to waves in a seaway. Therefore, fin stabilizers are installed to stabilize such roll motion. A fin stabilizer is effective at reducing the roll motion at moderate speeds but not at low speeds. Recently, pod propellers have been used with fin stabilizers for roll stabilization. In the paper, a MIMO (multi-input multi-output) optimal control system that has two control inputs such as fin stabilizers and pod propellers is designed. The LQR (linear quadratic regulator) control algorithm is applied to reduce the roll motion of cruise ships in regular waves. Also, the nominal plant and the frequency-weighted LQR are applied to reduce the roll motion in irregular waves. The roll motion of cruise ships is effectively reduced when the fin and pod propeller are used as the control actuators at low speeds. The optimal control gain is easily found when the frequency-weighted LQR is applied. 相似文献
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The article presents initial ideas towards a network-based approach for sea state estimation used for marine operations and other maritime applications. In principle, all available means, ranging from in situ buoys, fleet of ships to remote sensing by satellite and aircraft, could be considered, emphasising that each means and any combinations among may act simultaneously. This study focuses on just one of the means; the use of ships as sailing wave buoys. The article introduces the wave buoy analogy, i.e. ship-as-a-wave-buoy, and it makes a proposal on how to impose (different) weights to the single ship-specific wave spectrum estimates obtained from multiple ships. Moreover, the work includes a discussion about the importance to associate a measure to reflect the (un)certainty of the wave spectrum estimate. The article presents a numerical case study, where multiple ships act simultaneously as wave spectrum-estimators. The case study relies on numerical motion simulations, as appropriate full-scale data is not yet available. In the analysis, it is shown that the use of simultaneous data from multiple ships leads to more accurate wave spectrum estimations. 相似文献
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为解决无人船适用海商法存在的问题,促进我国无人船海上运输产业的健康可持续发展,文章从法理的角度阐释国际海事委员会无人船调查问卷中无人船的法律地位、船长和船员的认定以及无人船的碰撞责任,提出无人船适用海商法存在不确定性风险;在海商法领域,无人船的法律地位认定、船长和船员的识别以及船舶碰撞责任的适用仍存在问题,解决上述问题的有效路径是明确无人船的法律地位、将岸基控制人员识别为船员、采用过错责任原则认定无人船的碰撞责任以及合理分配船东与生产者之间的碰撞责任,以合理规避无人船的风险。 相似文献
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《Marine Policy》2013
This paper investigates the effects of fuel subsidies and value added tax refunds on the operation of two types of firms associated with the jumbo squid (Dosidicus gigas) fishery in Mexico: (a) firms with ships that catch shrimp and squid in different periods of the year and (b) firms that deploy outboard-motor boats to catch squid year-round. The cost-benefit ratios of the policies are analyzed for 2008–2015, both with and without subsidy-related income. Additionally, the net cash surplus is calculated. The elimination of subsidies may affect jobs related to vessel operations in the squid fishery and may also encourage the voluntary retirement of shrimp ships. This effect is less evident in the case of the smaller boats. Strategies aimed at improving the landed squid prices are nonetheless suggested. 相似文献
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The composition and frequency of antibiotic resistance of pathogenic bacteria, the abundance of heterotrophic aerobic bacteria (HPC) and possible in-situ use of chromogenic agar were investigated in the ships' ballast water coming from different regions of the world to the Sea of Marmara, Turkey for the first time. The samples that were taken from 21 unit ships coming from various marine environments of the Southern China Sea, the Atlantic Ocean, the Mediterranean and the Black Sea to the Sea of Marmara, Turkey in 2009 and 2010 were tested. 38 bacteria species, 27 of them pathogenic bacteria belonging to 17 familia, were detected. Vibrio cholera was not detected in the samples. However, the presence of a high number of HPC, including a cocktail of pathogenic bacteria showed that the ships carry a potential risk for the Sea of Marmara. 相似文献
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Seakeeping of two ships in close proximity 总被引：1，自引：0，他引：1
Underway replenishment is an essential component of long-term naval operations. During underway replenishment, two ships travel in close proximity at moderate forward speed. This paper examines the hydrodynamic interactions that can influence seakeeping during such operations. Presented numerical predictions include the influence of interaction effects on hydrodynamic forces for two ships in waves. A scarcity of validation material for numerical predictions prompted new towing tank experiments for two ships in waves. The experiments used semi-captive models, and the numerical code was modified to include restraining forces for specified modes. The numerical predictions and experiments show that the presence of a larger ship can significantly influence the motions of a smaller ship in close proximity. 相似文献
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《Marine Policy》2017
The air pollutant emissions of the ships at port represent a small percentage of the overall emissions from shipping however they are concentrated in a small area. In Mytilene, Lesvos, the port is located within the city limits, resulting in air pollution, congestion and noise, especially during the tourist season. The aim of this study is to estimate the quantities of particulate matter and CO2 emitted by ships in the port of Mytilene and to explore the potential of shore side electricity to reduce the emissions. The emissions were estimated using the bottom–up methodology, based on the activity of the ships in the port (berthing, maneuvering). Simulation of renewable energy sources was made using Homer Energy microgrid simulation software. The results showed that between the 10th and 20th of August 2012, there were 40 calls of passenger ships, tankers and bulk carriers in the port of Mytilene, emitting 441 kg of PM10 and 282 metric tonnes of CO2. About 63% of PM10 and 77% of CO2 were emitted at the berthing phase and the remaining during the maneuvering. These emissions could be reduced by providing electricity to the ships from a hybrid renewable energy system with wind turbines and photovoltaics, connected to the grid. Simulations showed that the total energy requirements of the ships in the port of Mytilene could be covered by four 1.5 MW wind turbines combined with a 5 MW photovoltaics. With this configuration, renewable energy will exceed the ships' electricity needs for most of the time in order not to increase the power station's load. The excess energy could be fed to the islands' grid, so a costly battery storage system is not necessary to handle the variations of alternative energy. In this way, a considerable reduction of the CO2 and PM10 emissions by the ships in the port occurs, providing a viable solution for a cleaner and healthier environment. 相似文献
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随人工智能技术发展，智能船舶因其无人化、智能化的特点而与传统国际法律制度产生碰撞。当前，国际海事组织将制定“海上自主水面船舶规则”工作提上日程，航行安全问题作为其中的高度优先事项，受到各国广泛关注。船舶适航作为承运人的主要义务之一，是保障航行安全的先决条件。但智能船舶是否需要符合适航标准，如果适用会产生哪些法律障碍并如何解决等诸多问题亟待研究。对此，应修订《国际海上避碰规则》并明确智能船舶适船技术标准，明确岸基操作人员的法律地位并制定其资格取得、培训、值班标准，明确安全配员标准及需船员在船承担的职责的履行方式。 相似文献
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Osman Turan Zafer Ayaz Seref Aksu Jan Kanar Antoni Bednarek 《Ocean Engineering》2008,35(13):1339-1356
The study investigates the experimental and numerical analysis of the occurrence of auto-parametric rolling for large, high-speed pod-driven ships in waves. Considering unique design and performance targets, the aim here is to exploit susceptibility to auto-parametric rolling behaviour and to identify probable design and operational precautions. In order to achieve this aim, an existing non-linear time-domain software to simulate capsizing and other critical manoeuvring behaviours of slow- to medium-speed conventional and podded ships in waves is being enhanced for fast pod-driven vessels and then compared against the dedicated model test conducted in long-crested regular and random waves for a large, pod-driven containership model. This paper includes the presentation of current numerical modifications for pod-driven ships and the verification analysis. 相似文献
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《Marine Policy》2016
Ocean noise levels are thought to be increasing as a result of major growth in global shipping activity, but data quantifying those changes are limited in space and time. As an alternative approach, this study examines the current and future maximum noise capacity of three segments of the global commercial shipping fleet: container ships, oil tankers, and bulk carriers. It shows that continued growth in the number of ships, the quantity of goods carried and the distances traveled could increase the maximum noise capacity of the global shipping fleet by up to a factor of 1.9 by 2030, with major growth in particular in the container and bulk carrier segments. Thus, in the absence of operational or manufacturing changes to such ships, the contribution of commercial shipping to ambient ocean noise levels can be expected to dramatically increase. 相似文献
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不规则波作用下的船舶撞击作用 总被引：2，自引：1，他引：2
随着波谱理论研究的发展,各种海工结构及船舶的荷载及其内力分析也日趋应用不规则波的计算方法。目前对于外海码头在波浪作用下的船舶撞击荷载还应用规则波的研究方法,对其应用不规则波分析方法的途径以及在考虑波谱作用后会有怎样的结果等问题目前还较少研究。本文试图对此问题进行初步的分析。 相似文献