双浮体波浪能装置的振荡和能量转换特性研究（英文）

In this study, we investigated the hydrodynamic and energy conversion performance of a double-float wave energy converter(WEC) based on the linear theory of water waves. The generator power take-off(PTO) system is modeled as a combination of a linear viscous damping and a linear spring. Using the frequency domain method, the optimal damping coefficient of the generator PTO system is derived to achieve the optimal conversion efficiency(capture width ratio).Based on the potential flow theory and the higher-order boundary element method(HOBEM), we constructed a threedimensional model of double-float WEC to study its hydrodynamic performance and response in the time domain. Only the heave motion of the two-body system is considered and a virtual function is introduced to decouple the motions of the floats. The energy conversion character of the double-float WEC is also evaluated. The investigation is carried out over a wide range of incident wave frequency. By analyzing the effects of the incident wave frequency, we derive the PTO's damping coefficient for the double-float WEC's capture width ratio and the relationships between the capture width ratio and the natural frequencies of the lower and upper floats. In addition, it is capable to modify the natural frequencies of the two floats by changing the stiffness coefficients of the PTO and mooring systems. We found that the natural frequencies of the device can directly influence the peak frequency of the capture width, which may provide an important reference for the design of WECs.     

The distribution of the benefits of waterfront reform

In this paper we introduce, for the first time, a methodology from the most recent literature of finance to reveal the duration of shipping cycles and then show the benefit of the use of this information to make more successful shipping loans. This is so as banks are willing to finance, during boom periods, shipping loans for new buildings but by this way ‘create’ oversupply and thus depress the freight market by their own actions. The information about cycles, especially their forecasting, is mostly important as shipping loans are based on project financing/cash flow financing, which means that ship revenue is of utmost importance. The Rescaled Range Analysis is applied here to 379 monthly freight trips—made stationary—between 1971 and 2002 (July), due to Hurst 1 Hurst, HE. 1950. Long-term storage capacity of reservoirs. April1950. pp.770–808. American Society of Civil Engineers. Paper No. 2447 [Google Scholar] and elaborated and popularized by Mandelbrot 2 Mandelbrot, BB. 1975. Stochastic models for the earth's relief, the shape and the fractal dimensions of the coastlines, and the number-area rule for islands. Proceedings of the National Academy of Sciences. 1975, USA 72. pp.3825–3828. [Crossref] , [Google Scholar]. The most important effect, however, is that shipping freight series exhibit non-normality and long-run dependence rendering the use of random walk models such as GARCH (Generalized Autoregressive Conditional Heteroscedasticity) problematic. Thus an adequate literature review is carried out with criticism against the models used. The cycles have been calculated as equal to 4.5 years and 2.25 years. This is almost compatible with the most recent paper of Stopford 3 Stopford, M. 21 September 2001. “Forecasting the dry bulk, tanker and container markets”. In Maritime Cyprus 21 September,  [Google Scholar]. The Hurst exponent was found equal to 0.93, alternating over the periods examined (0.65, 0.73, 0.62, 0.59 and 0.55) and indicating long-term persistence but seriously away from normal/random walk domain. Most studies have said the same using the Jarque--Bera test for normality but provided no alternative.     

“Blue” social capital and work performance: anthropological fieldwork among crew members at four Danish international ships

One outcome of globalization is an increasing number of seafarers, who seldom are members of the same crew two voyages in a row and must cooperate with seafarers from many countries (Progoulaki and Roe WMU J Marit Affairs 10:7–23, 2011). This situation challenges the level of social capital on board, i.e., the resources inherent in network cooperation associated with norms of reciprocity and trust (Putnam 2000: 19). Fragmentized “blue” social capital should, however, be restored, as work performance depends on the quality of cooperation among crew members horizontally, as well as between crew members and the shipping company vertically. Drawing on anthropological fieldwork data from four Danish international ships, the purpose of this paper is to offer a new theoretical framework for analyzing cooperation among crews. Our inductive empirical findings suggest that a balance between three types of social capital—bonding, bridging and linking—is needed to achieve a high-performing work system (Gittell et al. Organ Sci 21(2):490–506, 2010). Hence, the main actors within the shipping sector should take “blue” social capital into account to increase work efficiency and economic performance.     

The rationality of conference pricing and output policies. Part 2

In Part 1 ^{* *}Maritime Studies and Management (1975) Vol 3, No. 2, pp. 103–111. of this article a background to the economics of conference operation was provided, and conference fleet planning and single voyage costs were discussed. This part of the paper will analyse the economic objectives of conferences and will consider the implications of ending the conference princing structure. Some recommendations are also offered.     

An Assessment of Integrated Coastal Management Governance and Implementation Using the DPSIR Framework: KwaZulu-Natal,South Africa

Coastal areas are under increasing pressure driven by demands for coastal space, primarily though population growth, in migration and the need for space for socioeconomic activities. The pressures and associated changes to the coastal environment need to be managed to ensure long-term sustainability. South Africa has enacted an Integrated Coastal Management Act (ICM Act) to facilitate dedicated management of its coastal environment. The implementation has been met with a number of challenges, primarily relating to financial and human capacity constraints, particularly at the local government level. Given that the ICM Act devolves powers to local government, it is imperative that implementation challenges be addressed. This paper focuses on KwaZulu-Natal, one of four South African coastal regions, which is a renowned tourist destination and home to 11.1 million people (Statistics South Africa 2015 Statistics South Africa. 2015. Mid-Year Population Estimates. Statistical release P0302. Pretoria, South Africa: Statistics South Africa. [Google Scholar]). This paper considers the state of coastal management, as well as implementation challenges being experienced at a local governance level, and highlights ways to address these. Data were acquired through questionnaire surveys and semistructured interviews. The Drivers-Pressures-State-Impact-Response (DPSIR) framework was used to identify relevant ICM issues and concerns and develop potential actions for improving the implementation of coastal management activities and the ICM Act. In the assessment of the ICM governance and implementation to date, a key concern identified was a general lack of coastal management knowledge among officials. It was specifically identified that knowledgeable management and capacity-building required championing from the provincial government in order to more efficiently and effectively implement the objectives of the ICM Act through an improved understanding of the coastal environment, its functioning and management.     

Groups in DEA based cross-evaluation: An application to Asian container ports

In container port performance evaluation, a group of ports in one country is always significantly different from a group of ports in another country. This is noticed as the heterogeneity of port performance. It is therefore necessary to further investigate the impact of the different groups on efficiency evaluation of ports. The cross-evaluation method is a DEA extension tool to identify best performing DMUs and to rank DMUs using cross efficiency scores linked to all DMUs. A factor that possibly reduces the usefulness of the cross efficiency evaluation method is that cross efficiency scores may not be unique due to the presence of alternative optima. Doyle and Green 1 Doyle, J and Green, R. 1994. Efficiency and cross efficiency in DEA: Derivations, meanings and uses. Journal of the Operational Research Society, 45: 567–578. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar] propose the use of secondary goals to deal with the non-uniqueness issue by the aggressive/benevolent model formulations. This article extends the model of Doyle and Green by considering the groups of DMUs in the determination of final cross efficiency. A new approach based on cross efficiency evaluation method is developed and applied to efficiency analysis of 28 container ports from 12 countries in Asia. A comparative study between traditional and newly proposed methods is conducted.     

深水起重铺管船横摇运动性能分析(英文)

For a large floating vessel in waves,radiation damping is not an accurate prediction of the degree of roll unlike other degrees of freedom motion.Therefore,to get the knowledge of roll motion performance of deepwater pipelay crane vessels and to keep the vessel working safety,the paper presents the relationship between a series of dimensionless roll damping coefficients and the roll response amplitude operator(RAO).By using two kinds of empirical data,the roll damping is estimated in the calculation flow.After getting the roll damping coefficient from the model test,a prediction of roll motion in regular waves is evaluated.According to the wave condition in the working region,short term statistics of roll motion are presented under different wave parameters.Moreover,the relationship between the maximal roll response level to peak spectral wave period and the roll damping coefficient is investigated.Results may provide some reference to design and improve this kind of vessel.     

Experimental study on reflection coefficient of curved perforated plate

A set of experiments is carried out in a towing tank to study the effects of the curvature of perforated plates on the wave reflection coefficient (C _r ). The curvature of a perforated plate can be changed by rotating a reference perforated plate aboutits origin according to the parabolic equation y=?x ². A plunger-type wave maker is used to generate regular waves. The reflection coefficients are calculated using Goda and Suzuki’s (1976) method. The results are compared with those of vertical or sloped passive wave absorbers. The comparison shows that a perforated plate with a curved profile is highly efficient in terms of reducing the wave reflection coefficient. A correlation is established to estimate the reflection coefficient of curved perforated plates as a function of both flow and geometry characteristics.     

Designing Coastal Management Strategies for Populations with Distinct Needs: The Case of Learning Disabilities

The Disability Discrimination Act (1995, amended 2005), Equality Act (2010 Equality Act. 2010. Equality Act. http://www.legislation.gov.uk/ukpga/2010/15/contents#openingWholeMod (accessed May 17, 2012) [Google Scholar]), EU Disability Action Plan (2003 –2010), and EU Disability Strategy (2010–2020) were designed to make equal opportunities a “reality.” As 16% of the EU population, is statutorily disabled there are considerable implications for beach management. Research examples of beach users include swimmers, anglers, etc. - but rarely people with learning disabilities (LD). This paper considered beach users with LD and their appreciation of three different coastal classifications in South Wales. Because of their disabilities, the research applied a participatory photo interpretation methodology (photovoice). A comparison of the LD ranking of beach issues was made with rankings provided by the general public at the same beaches. Results demonstrated some similarities between LD and general public coastal needs, but identified the need for specific considerations to be made by beach managers for LD users, including informed self-advocacy, use/application of signage, instructive access and a requirement for baseline information gathering. The research proposes an integrated coastal access model from which coastal management/gatekeepers can consider LD needs within coastal strategies. Finally, findings highlight the use of photovoice in coastal research projects and the need for innovative methodological considerations when researching certain groups.     

Robust aspects in dependable filter design for alignment of a submarine inertial navigation system

The strapdown inertial navigation system (SINS) is able to provide continuous estimates of a vehicle??s velocity, position and attitude. As a rule, the SIMS component known as a high accuracy strapdown inertial measurement unit (SIMU) is an exceptionally expensive system. Less expensive SIMUs comprised of low cost sensors suffer from degraded performance, but this can be compensated for, in part, by addition of a velocity data recorder (VDR) to accompany the SINS. In this configuration, the need frequently arises to align the SINS of a submarine to in order to avoid a long run-up of the inertial system before a start command is issued. This in-motion alignment (IMA) can be accomplished by integrating SINS data with some external aiding source, such as the VDR, by using some form of measurement matching method. Accordingly, this paper demonstrates a consistent IMA scheme for a low-cost SIMU using a robust Kalman/ $ H_{\infty } $ filter structure. An error model of the SINS is derived in which the state vector includes attitude, velocity, position and sensor errors. Velocity information from the VDR is used as a measurement to the proposed filter. All significant equations concerning navigation are presented in conjunction with argument. Results show the advantages of the approach and emphasize diverse aspects of the SINS.     

An experimental/numerical approach for evaluating skin friction on full-scale ships with surface roughness

For an accurate evaluation of the increase in skin friction due to various surface topographies on ships, i.e. plate roughness, coatings, or bio fouling, both experimental measurements and a numerical evaluation of those measurements are necessary. The measurements are necessary as no other practical method exists to evaluate the skin friction coefficient on most surface topographies, and numerical evaluation is required to compute the roughness effects of varying ship types and speeds. Therefore, a method for measuring the skin friction coefficient for bio-fouled and structured surfaces at full-scale friction velocity is presented, and a validation of the design and measuring procedures is given. For the ship frictional resistance calculations, the Computational Fluid Dynamics (CFD) code ShipFlow has been modified to take the added friction into account.     

考虑定常兴波影响的辐射问题去奇Rankine源方法数值计算

随着中高速船舶在海洋资源开发中的广泛应用,航速对船舶在波浪中摇荡运动的影响受到重视。本文基于势流理论,采用非均匀有理B样条(NURBS)表达物面,应用去奇Rankine源方法求解流场速度势;推导了兴波问题的二阶近似非线性自由面边界条件,以及考虑二阶近似非线性兴波影响的辐射速度势的线性自由面和物面边界条件。本文编程首先数值计算了Wigley船型的近似非线性兴波问题,将计算的线性和非线性兴波阻力系数与文献结果做了比较;然后数值计算了计及线性定常兴波影响的下潜圆球有航速辐射问题,将计算的附加质量和阻尼系数与文献结果比较。本文计算结果与文献结果吻合程度较好,验证了本文数值计算方法的有效性。文中还给出了兴波波形和辐射波形。     

Sustainability Challenges in the Geoduck Clam Fishery of British Columbia: Policy Perspectives

The geoduck clam fishery, worth approximately CDN $40 million ¹ US $ equivalence: 35 million (Bank of Canada exchange rate on February 1, 2006). in annual landed value, is British Columbia's most valuable invertebrate fishery. This fishery has been co-managed by the Department of Fisheries and Oceans (DFO) and the Underwater Harvesters Association (UHA) since 1989. Earlier input control measures such as effort regulation, seasonal closures, and licenses failed to work effectively for more than ten years, resulting in excess fishing capacity, over harvesting, poor economic returns, and unsafe fishing practices. Output control measures such as the individual vessel quota system (IVQ) have, to some extent, proven successful in improving revenues, controlling excess fishing capacity, gaining compliance with regulations, and involving fishers in the joint decision-making processes. However, there are public concerns about a common property resource at risk of being dominated by a few UHA license holders. Additionally, there are concerns about the job losses resulting from IVQ implementation, as well as distribution and equity issues. This article traces and examines the policy context for fisheries management in the British Columbia (BC) geoduck fishery, discusses the major concerns surrounding the exploitation of long lived Methuselah's clams and concludes with areas for further research in sustaining this lucrative fishery.     

无航速三体浮驳水动力特性频域分析

为了研究不同工作条件下无航速三体浮驳的水动力特性的变化规律,根据势流理论和波浪的辐射/衍射理论对无航速三体浮驳的水动力特性进行了分析,并以某三体浮驳为例应用水动力计算软件AQWA对其在不同工况下进行了水动力计算。分别求得了该三体浮驳在不同水深、不同吃水深度时的附加质量、附加阻尼、不同波向下的波浪激励力和幅值响应算子随波频的变化曲线,并对其进行了对比分析。结果表明,水深对三体浮驳附加质量、附加阻尼、波浪激励力和幅值响应算子均有较大的影响,特别是在低波频时影响较为显著;水深大于20倍吃水深度后三体浮驳的水动力系数可按照无限水深进行近似计算。吃水深度对三体浮驳纵荡和横荡幅值响应算子几乎无影响,对垂荡和纵摇幅值响应算子的影响较小,对横摇和艏摇幅值响应算子的影响较大。     

波能转换型浮式防波堤的水动力性能研究（英文）

The integration of wave energy converters(WECs) with floating breakwaters has become common recently due to the benefits of both cost-sharing and providing offshore power supply. In this study, based on viscous computational fluid dynamics(CFD) theory, we investigated the hydrodynamic performances of the floating box and Berkeley Wedge breakwaters, both of which can also serve as WECs. A numerical wave flume model is constructed using Star-CCM+software and applied to investigate the interaction between waves and wave energy converters while completing the verification of the convergence study of time and space steps. The effects of wave length on motion response and transmission coefficient of the floating box breakwater model are studied. Comparisons of our numerical results and published experimental data indicate that Star-CCM+ is very capable of accurately modeling the nonlinear wave interaction of floating structures, while the analytical potential theory overrates the results especially around the resonant frequency. Optimal damping can be readily predicted using potential flow theory and can then be verified by CFD numerical results. Next, we investigated the relationship between wave frequencies and various coefficients using the CFD model under optimal damping, including the motion response, transmission coefficient, reflection coefficient,dissipation coefficient, and wave energy conversion efficiency. We then compared the power generation efficiencies and wave dissipation performances of the floating box and Berkeley Wedge breakwaters. The results show that the power generation efficiency of the Berkeley Wedge breakwater is always much higher than that of the floating box breakwater. Besides, the wave dissipation performance of the Berkeley Wedge breakwater is much better than that of the floating box breakwater at lower frequency.     

浸水矩形板的声辐射阻尼研究

对空气中简支边界矩形板在点简谐力激励下的振速响应公式从附加质量和声辐射阻尼的角度进行修正,得到了浸水矩形板的振速响应公式。从浸水矩形板振速公式出发,结合声辐射阻尼的定义,从能量的角度推导了矩形板声辐射阻尼的表达式,给出了其与模态辐射效率之间的关系,文中推论与已发表有关文献相比较一致性良好。研究表明：辐射阻尼随着波数比的变化而变化;在中高频段,单面临水矩形板的辐射阻尼远高于其在空气中时的辐射阻尼;板越厚,其声辐射阻尼越小。     

基于Star-CCM+的摆式波浪能装置水动力性能研究（英文）

A two-dimensional numerical Computational Fluid Dynamics(CFD) model is established on the basis of viscous CFD theory to investigate the motion response and power absorption performance of a bottom-hinged flap-type wave energy converter(WEC)under regular wave conditions. The convergence study of mesh size and time step is performed to ensure that wave height and motion response are sufficiently accurate. Wave height results reveal that the attenuation of wave height along the wave tank is less than 5% only if the suitable mesh size and time step are selected. The model proposed in this work is verified against published experimental and numerical models. The effects of mechanical damping, wave height, wave frequency, and water depth on the motion response, power generation, and energy conversion efficiency of the flap-type WEC are investigated. The selection of the appropriate mechanical damping of the WEC is crucial for the optimal extraction of wave power. The optimal mechanical damping can be readily predicted by using potential flow theory. It can then be verified by applying CFD numerical results. In addition, the motion response and the energy conversion efficiency of the WEC decrease as the incident wave height increases because the strengthened nonlinear effect of waves intensifies energy loss. Moreover, the energy conversion efficiency of the WEC decreases with increasing water depth and remains constant as the water depth reaches a critical value. Therefore, the selection of the optimal parameters during the design process is necessary to ensure that the WEC exhibits the maximum energy conversion efficiency.     

Influence of Short Time-Scale Water-Column Temperature Fluctuations on Broadband Signal Angular Beam Spreading

Temporal fluctuations in vertical thermocline structure and depth span (on a time scale of 30 to 40 min) are shown to affect the arrival angle, and focusing of measured broadband (22–28 kHz) non-surface-interacting acoustic signals at a depth of ~100 m. Measurements were taken in the Pacific Missile Range Facility near Kauai island, Hawaii, for a source-receiver range of 1.0 km. The arrival time and angular spread of acoustic beams are obtained for measured signals using a plane wave beamformer with a-prior gaussian weighting. The weighting process reduces ambiguity in angular measurements due to spatial aliasing from a vertical array with element spacing d much greater than half the acoustic wavelength \( \left(\frac{\lambda_{\mathrm{a}}}{2}\right) \) of the highest frequency in the broadband signal. Over two full periods of thermocline oscillation, 2 times of high and 2 times of low isotherm depth are selected to show fluctuations in angular beam spreading, focusing, and the robustness of the weighted beamformer routine. To benchmark the performance of the weighted beamformer, a two-dimensional (2D) Parabolic Equation (PE) model calculates the angular signal spread and focusing using parameters to satisfy spatial sampling requirements for broadband beamforming. In the absence of spatial aliasing, beamforming the output of the 2D PE can be conducted without weighting. Comparison of measured and modeled results shows less than a degree of difference in the angular beam spread of direct, bottom reflected, and refracted paths. It is shown that a vertical array with \( d\gg \left(\frac{\lambda_{\mathrm{a}}}{2}\right) \) and gaussian weighting can resolve changes in angular spread and beam focusing as a function of vertical isotherm displacement.     

基于波传播分析的水下粘弹性复合圆柱壳振动功率流研究

采用波传播分析方法,讨论了外部敷设粘弹性自由阻尼材料的无限长圆柱壳在流场中受径向简谐激励的振动功率流.用复模量形式计及粘弹性阻尼的损耗因子,研究了自由阻尼圆柱壳在外激励作用下的输入功率流和沿壳体传播的功率流.结果表明粘弹性阻尼层可以明显降低激振力输入壳体的功率流,加快振动波在结构内的衰减,为潜艇结构和水下各种管道的减振降噪提供了一定的理论参考.     

Coping with Captivity in a maritime hijacking situation

Piracy has unfortunately become a health and safety risk for seafarers in the maritime industry today. However, little do we know about the impact of a pirate hijacking situation and how seafarers cope. Focusing on negotiation communication, the analysis debouches in a discussion of the dynamics of coping strategies, by investigating 173 authentic audio recordings of communication sequences recorded during a pirate hijacking situation that were donated voluntarily by a shipping company. The Captain assessed and reflected on the course of events in the situation, to which the negotiator responded appropriately, with acknowledging brief responses or psychological aid. This is similar to other highly dynamic decision-making settings, where decision-makers tend to continuously reflect and revise their view of the situation (Eraut 2000). The data is also consistent with the “reflection-in-action” concept by Schön (1983) used by van den Heuvel et al. (Cogn Technol Work 16: 25–45, 2014) in their investigation of communication of police officers in hostage situations. However, the coping dynamics changed when the negotiator’s responses became too minimal. This shows how the context and the individual’s cognitive appraisal of the encounter co-shapes the coping dynamics in the situation. It is urged that pre-piracy care and seafarer training involves practical examples and information about roles and coping dynamics in negotiation communication as part of an orchestrated approach to the scourge of piracy.