Littérature scientifique sur le sujet « Converse (Ship) »
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Articles de revues sur le sujet "Converse (Ship)"
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Song, Zijie, Zhiqiang Hu et Jonas W. Ringsberg. « Critical Void Volume Fraction Identification Based on Mesoscopic Damage Model for NVA Shipbuilding Steel ». Journal of Marine Science and Application 18, no 4 (15 octobre 2019) : 444–56. http://dx.doi.org/10.1007/s11804-019-00117-2.
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Abstract NVA mild steel is a commonly used material in the shipbuilding industry. An accurate model for description of this material’s ductile fracture behaviour in numerical simulation is still a challenging task. In this paper, a new method for predicting the critical void volume fraction fc in the Guson-Tvergaard-Needleman (GTN) model is introduced to describe the ductile fracture behaviour of NVA shipbuilding mild steel during ship collision and grounding scenarios. Most of the previous methods for determination of the parameter fc use a converse method, which determines the values of the parameters through comparisons between experimental results and numerical simulation results but with high uncertainty. A new method is proposed based on the Hill, Bressan, and Williams hypothesis, which reduces the uncertainty to a satisfying extent. To accurately describe the stress-strain relationship of materials before and after necking, a combination of the Voce and Swift models is used to describe the material properties of NVA mild steel. A user-defined material subroutine has been developed to enable the application of the new parameter determination method and its implementation in the finite element software LS-DYNA. It is observed that the model can accurately describe structural damage by comparing the numerical simulation results with those of experiments; thus, the results demonstrate the model’s capacity for structural response prediction in ship collision and grounding scenario simulations
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Zhang, Yulian, Lihong Guo, Zengfa Wang, Yang Yu, Xinwei Liu et Fang Xu. « Intelligent Ship Detection in Remote Sensing Images Based on Multi-Layer Convolutional Feature Fusion ». Remote Sensing 12, no 20 (12 octobre 2020) : 3316. http://dx.doi.org/10.3390/rs12203316.
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Intelligent detection and recognition of ships from high-resolution remote sensing images is an extraordinarily useful task in civil and military reconnaissance. It is difficult to detect ships with high precision because various disturbances are present in the sea such as clouds, mist, islands, coastlines, ripples, and so on. To solve this problem, we propose a novel ship detection network based on multi-layer convolutional feature fusion (CFF-SDN). Our ship detection network consists of three parts. Firstly, the convolutional feature extraction network is used to extract ship features of different levels. Residual connection is introduced so that the model can be designed very deeply, and it is easy to train and converge. Secondly, the proposed network fuses fine-grained features from shallow layers with semantic features from deep layers, which is beneficial for detecting ship targets with different sizes. At the same time, it is helpful to improve the localization accuracy and detection accuracy of small objects. Finally, multiple fused feature maps are used for classification and regression, which can adapt to ships of multiple scales. Since the CFF-SDN model uses a pruning strategy, the detection speed is greatly improved. In the experiment, we create a dataset for ship detection in remote sensing images (DSDR), including actual satellite images from Google Earth and aerial images from electro-optical pod. The DSDR dataset contains not only visible light images, but also infrared images. To improve the robustness to various sea scenes, images under different scales, perspectives and illumination are obtained through data augmentation or affine transformation methods. To reduce the influence of atmospheric absorption and scattering, a dark channel prior is adopted to solve atmospheric correction on the sea scenes. Moreover, soft non-maximum suppression (NMS) is introduced to increase the recall rate for densely arranged ships. In addition, better detection performance is observed in comparison with the existing models in terms of precision rate and recall rate. The experimental results show that the proposed detection model can achieve the superior performance of ship detection in optical remote sensing image.
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Khaled, Nassim, et Rami Alkhatib. « Novel Formulation for Line of Sight Guidance and Obstacle Avoidance for Under-actuated Ships ». WSEAS TRANSACTIONS ON CIRCUITS AND SYSTEMS 20 (16 mars 2021) : 1–9. http://dx.doi.org/10.37394/23201.2021.20.1.
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Automatic control of under-actuated ships is a challenging task due to the external factors and limited actuators onboard a ship. It is even more so when the controller needs to seamlessly integrate with a guidance system and obstacle avoidance for the purpose of autonimity. In this paper, line of sight guidance system for marine surface vessels is augmented to include obstacle avoidance. The process of directing the ship movement to avoid a stationary and moving obstacles is tackled by introducing an iterative mathematical formulation for the circle of avoidance algorithm. Unlike learning based guidance system, the proposed formulation has an explicit solution that is updated at each instant in time. Three simulations are conducted to assess the performance of the overall guidance and avoidance system. The developed algorithm is validated through simulation results of a 6-degree of freedom model of a ship. The simulation results prove the effectiveness of the developed technique to converge the ship to the desired trajectory autonomously while avoiding obstacles along the path.
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Han, Xue. « Adaptive Neural Backstepping Sliding Mode Heading Control for Underactuated Ships with Drift Angle and Ship-Bank Interaction ». Computational Intelligence and Neuroscience 2020 (27 septembre 2020) : 1–18. http://dx.doi.org/10.1155/2020/8854055.
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In order to track the desired path under unknown parameters and environmental disturbances, an adaptive backstepping sliding mode control algorithm with a neural estimator is proposed for underactuated ships considering both ship-bank interaction effect and shift angle. Using the features of radial basis function neural network, which can approximate arbitrary function, the unknown parameters of the ship model and environmental disturbances are estimated. The trajectory tracking errors include stabilizing sway and surge velocities errors. Based on the Lyapunov stability theory, the tracking error will converge to zero and the system is asymptotically stable. The controlled trajectory is contractive and asymptotically tends to the desired position and attitude. The results show that compared with the basic sliding mode control algorithm, the overshoot of the adaptive backstepping sliding mode control with neural estimator is smaller and the regulation time of the system is shorter. The ship can adjust itself and quickly reach its desired position under disturbances. This shows that the designed RBF neural network observer can track both the mild level 3 sea state and the bad level 5 sea state, although the wave disturbance has relatively fast time-varying disturbance. The algorithm has good tracking performance and can realize the accurate estimation of wave disturbance, especially in bad sea conditions.
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Miller, Cale A., Christina Bonsell, Nathan D. McTigue et Amanda L. Kelley. « The seasonal phases of an Arctic lagoon reveal the discontinuities of pH variability and CO<sub>2</sub> ; flux at the air–sea interface ». Biogeosciences 18, no 3 (16 février 2021) : 1203–21. http://dx.doi.org/10.5194/bg-18-1203-2021.
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Abstract. The western Arctic Ocean, including its shelves and coastal habitats, has become a focus in ocean acidification research over the past decade as the colder waters of the region and the reduction of sea ice appear to promote the uptake of excess atmospheric CO2. Due to seasonal sea ice coverage, high-frequency monitoring of pH or other carbonate chemistry parameters is typically limited to infrequent ship-based transects during ice-free summers. This approach has failed to capture year-round nearshore carbonate chemistry dynamics which is modulated by biological metabolism in response to abundant allochthonous organic matter to the narrow shelf of the Beaufort Sea and adjacent regions. The coastline of the Beaufort Sea comprises a series of lagoons that account for > 50 % of the land–sea interface. The lagoon ecosystems are novel features that cycle between “open” and “closed” phases (i.e., ice-free and ice-covered, respectively). In this study, we collected high-frequency pH, salinity, temperature, and photosynthetically active radiation (PAR) measurements in association with the Beaufort Lagoon Ecosystems – Long Term Ecological Research program – for an entire calendar year in Kaktovik Lagoon, Alaska, USA, capturing two open-water phases and one closed phase. Hourly pH variability during the open-water phases are some of the fastest rates reported, exceeding 0.4 units. Baseline pH varied substantially between the open phase in 2018 and open phase in 2019 from ∼ 7.85 to 8.05, respectively, despite similar hourly rates of change. Salinity–pH relationships were mixed during all three phases, displaying no correlation in the 2018 open phase, a negative correlation in the 2018/19 closed phase, and a positive correlation during the 2019 open phase. The high frequency of pH variability could partially be explained by photosynthesis–respiration cycles as correlation coefficients between daily average pH and PAR were 0.46 and 0.64 for 2018 and 2019 open phases, respectively. The estimated annual daily average CO2 efflux (from sea to atmosphere) was 5.9 ± 19.3 mmolm-2d-1, which is converse to the negative influx of CO2 estimated for the coastal Beaufort Sea despite exhibiting extreme variability. Considering the geomorphic differences such as depth and enclosure in Beaufort Sea lagoons, further investigation is needed to assess whether there are periods of the open phase in which lagoons are sources of carbon to the atmosphere, potentially offsetting the predicted sink capacity of the greater Beaufort Sea.
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Wang, Xingzhong, Xinghua Kou, Jinfeng Huang et Xianchun Tan. « A Collision Avoidance Method for Intelligent Ship Based on the Improved Bacterial Foraging Optimization Algorithm ». Journal of Robotics 2021 (9 février 2021) : 1–10. http://dx.doi.org/10.1155/2021/6661986.
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The bacterial foraging optimization algorithm (BFOA) is an intelligent population optimization algorithm widely used in collision avoidance problems; however, the BFOA is inappropriate for the intelligent ship collision avoidance planning with high safety requirements because BFOA converges slowly, optimizes inaccurately, and has low stability. To fix the above shortcomings of BFOA, an autonomous collision avoidance algorithm based on the improved bacterial foraging optimization algorithm (IBFOA) is demonstrated in this paper. An adaptive diminishing fractal dimension chemotactic step length is designed to replace the fixed step length to achieve the adaptive step length adjustment, an optimal swimming search method is proposed to solve the invalid searching and repeated searching problems of the traditional BFOA, and the adaptive migration probability is developed to take the place of the fixed migration probability to prevent elite individuals from being lost in BOFA. The simulation of benchmark tests shows that the IBFOA has a better convergence speed, optimized accuracy, and higher stability; according to a collision avoidance simulation of intelligent ships which applies the IBFOA, it can realize the autonomous collision avoidance of intelligent ships in dynamic obstacles environment is quick and safe. This research can also be used for intelligent collision avoidance of automatic driving ships.
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Wang, Yun-long, Zhang-pan Wu, Guan Guan et Chao-guang Jin. « Research on Intelligent Design Method of Ship Cabin Layout ». Marine Technology Society Journal 54, no 2 (1 mars 2020) : 79–92. http://dx.doi.org/10.4031/mtsj.54.2.8.
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AbstractThe design of the ship cabin layout is a multi-objective comprehensive optimization problem, which needs to consider the location of the passage, cabin layout, space utilization ratio, functional realization, comfort, safety, and so on. In this paper, an improved tabu-criterion genetic algorithm for the intelligent design of ship cabin layout is proposed. According to the characteristics of ship accommodation cabin layout design, a ship deck layout area model and a multi-objective optimization model including relative location model, absolute location model, and ergonomic constraint model are established. The neighborhood transformation criterion and tabu-criterion of tabu search algorithm are introduced into genetic algorithm to advance the local search ability of a genetic algorithm. At the same time, a new genetic algorithm coding method is proposed to avoid the generation of illegal solutions in cabin layout sequence crossover and mutation operation. The improved genetic algorithm can effectively improve the local search ability of a genetic algorithm and make the algorithm converge to the optimal solution as soon as possible at the later stage of calculation. Finally, the simulation results verify the feasibility and efficiency of the proposed intelligent design method for ship accommodation cabin layout.
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Zhu, Qidan, Junda Ma, Zhilin Liu et Ke Liu. « Containment Control of Underactuated Ships with Environment Disturbances and Parameter Uncertainties ». Mathematical Problems in Engineering 2017 (2017) : 1–19. http://dx.doi.org/10.1155/2017/5086705.
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An implementable robust containment control algorithm is proposed for a group of underactuated ships in the presence of hydrodynamic parameter uncertainties and external disturbances. The control objective is to drive all the followers into the convex hull spanned by the virtual leaders, whose state information is available only to a subset of the followers. For this purpose, the ship model is primarily transformed to a strict-feedback form. In the kinematic design, a virtual containment controller, requiring the state information from its neighbors, is presented based on the results obtained from graph theory. In the dynamic design, a robust containment controller is developed through utilizing upper-to-up sliding mode control. In addition, in order to simplify the implementations of the control law, the command filtered backstepping (CFBP) method is introduced to prevent the analytic differentiations of the virtual law from each design step of the backstepping (BP) method. Subsequently, it is well proven that all the tracking errors could converge to and remain small neighborhoods of the equilibrium point. Finally, several simulation experiments are conducted to demonstrate the performance of the proposed control algorithm.
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Shen, Zhi Peng, Chen Guo et Yu Ting Wang. « A Hybrid Intelligent Excitation Control for Ship Power Station ». Applied Mechanics and Materials 128-129 (octobre 2011) : 780–83. http://dx.doi.org/10.4028/www.scientific.net/amm.128-129.780.
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Hybrid intelligent control technique is used for ship power station synchronous generator excitation control in this paper. The parameters and structure of the excitation controller are learned and adjusted through a hybrid learning algorithm combining self-organizing learning with BP learning. This algorithm converges much faster than original BP learning. Simulation results show that the synchronous generator excitation controller based on the learning algorithm can significantly stabilize terminal voltage.
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Wang, Hao Duo, Qin Ruo Wang, Luo Yan et Xiao Ze Wu. « A New Robust Adaptive Backstepping for Ship Course-Keeping Control ». Applied Mechanics and Materials 536-537 (avril 2014) : 793–97. http://dx.doi.org/10.4028/www.scientific.net/amm.536-537.793.
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In this paper, we develop a new robust adaptive control scheme for ship steering by introducing alternative smooth function and Nussbaum function into backstepping approaches. And no requirements for the knowledge of control coefficient and the bound of unknown external disturbance, the proposed strategy implements the global stability of the ship course control and guarantees the global uniform boundedness of all signals of the resulting closed-loop system. Theoretical analysis demonstrates that tracking error asymptotically converges within an arbitrary small value pre-described by designer. Simulation results illustrate the effectiveness of the developed adaptive backstepping control law.
Thèses sur le sujet "Converse (Ship)"
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Souhan, Brian E. « Closed loop control of a cascaded multi-level converter to minimize harmonic distortion ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FSouhan.pdf.
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Salerno, Benjamin D. « Controller design, analysis, and prototype for ship service converter module ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA313846.
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Stallings, Brad L. « Design of a ship service converter module for a reduced-scale prototype integrated power system ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.navy.mil/100.2/ADA392078.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, December 2001.Thesis advisor(s): Ciezki, John G. ; Ashton, Robert W. "December 2001." Includes bibliographical references (p. 201-202). Also available in print.
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Borisov, Konstantin A. « Multifunctional voltage source converter for shipboard power systems ». Diss., Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-06042007-142951.
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Nord, Thomas. « Voltage Stability in an Electric Propulsion System for Ships ». Thesis, KTH, Elektriska energisystem, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118932.
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This Master of Science thesis was written based on the shipbuilder Kockums AB feasibility study regarding the development of an All- Electric Ship for the Swedish Navy. The thesis was aiming at addressing voltage stability issues in a dc system fed by PWM rectifiers operating in parallel when supplying constant power loads. A basic computer model was developed for investigating the influence from various parameters on the system. It was shown that the voltage stability is dependent upon the ability to store energy in large capacitors. It was also shown that a voltage droop must be implemented maintaining load sharing within acceptable limits. Different cases of operation were modelled, faults were discussed, and the principal behaviour of the system during a short-circuit was investigated. It was shown that the short-circuit current is much more limited in this type of system in comparison to an ac system. It was concluded that more research and development regarding the components of the system must be performed.
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Nelson, Amy. « Cross-Cultural Conversion Narratives : An American Missionary in Taichung, Taiwan ». Diss., CLICK HERE for online access, 1998. http://patriot.lib.byu.edu/u?/MTNZ,2354.
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Huang, Chun-Chieh, et 黃俊傑. « Design of High Power Bi-directional DC-DC Converter Module for Electric Ships ». Thesis, 2017. http://ndltd.ncl.edu.tw/handle/y7qfbs.
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碩士國立臺灣科技大學
電子工程系
105
In this thesis, a high power bi-directional DC-DC converter module for electric ships is studied and implemented, to be used for energy conversion between battery and DC bus. The module consists of two-stage circuits: a bi-directional buck/boost converter at battery side and a full-bridge series resonant converter at DC bus side. The developed bi-directional DC-DC converter module can be applied to the electric ship power system for charging/ discharging between battery and DC bus and adjusting bidirectional power transfer. In addition to establish a bi-directional DC-DC converter module and to discuss the bi-directional buck/boost converter and the full-bridge series resonant converter, the design criterions have been found. A 15 kW prototype module with circuit specifications of 400 V to 750 V input and output voltages was implemented and tested. A digital signal processor TMS320F28035 is used to realize the digital controller. According to the experimental results, the overall conversion efficiency can be up to 93%.
Livres sur le sujet "Converse (Ship)"
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Nouwen, Henri J. M. Sashinoberareru te : Shin no inori e no mittsu no dankai. Tōkyō : Joshi Pauro Kai, 2002.
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Ships, saints, and mariners : A maritime encyclopedia of Mormon migration, 1830-1890. Salt Lake City : University of Utah Press, 1987.
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Oliver, Jennifer H. Shipwreck in French Renaissance Writing. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198831709.001.0001.
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In the sixteenth century, a period of proliferating transatlantic travel and exploration, and, latterly, religious civil wars in France, the ship is freighted with political and religious, as well as poetic, significance; symbolism that reaches its height when ships – both real and symbolic – are threatened with disaster. The Direful Spectacle argues that, in the French Renaissance, shipwreck functions not only as an emblem or motif within writing, but as a part, or the whole, of a narrative, in which the dynamics of spectatorship and of co-operation are of constant concern. The possibility of ethical distance from shipwreck – imagined through the Lucretian suave mari magno commonplace – is constantly undermined, not least through a sustained focus on the corporeal. This book examines the ways in which the ship and the body are made analogous in Renaissance shipwreck writing; bodies are described and allegorized in nautical terms, and, conversely, ships themselves become animalized and humanized. Secondly, many texts anticipate that the descriptionof shipwreck will have an affect not only on its victims, but on those too of spectators, listeners, and readers. This insistence on the physicality of shipwreck is also reflected in the dynamic of bricolage that informs the production of shipwreck texts in the Renaissance. The dramatic potential of both the disaster and the process of rebuilding is exploited throughout the century, culminating in a shipwreck tragedy. By the late Renaissance, shipwreck is not only the end, but often forms the beginning of a story.
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Chen, Yiya, Peppina Po-lun Lee et Haihua Pan. Topic and Focus Marking in Chinese. Sous la direction de Caroline Féry et Shinichiro Ishihara. Oxford University Press, 2015. http://dx.doi.org/10.1093/oxfordhb/9780199642670.013.34.
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This chapter reviews how the two important notions of information structure—topic and focus—are encoded in Chinese. It first describes the properties of syntactic constructions (e.g.shi/shi . . . de, lian–dou/ye) and semantic particles (e.g.cai, jiu, dou, and zhi) for focus marking. It then discusses how Chinese, a topic-prominent language, conveys topical information via different structures such as base-generated topics, dangling topics, and moved topics. Finally, it provides an overview of how prosodic structure and prominence cues (e.g. pitch register raising, pitch range expansion, and lengthening) complement and enhance focus and topic marking in a variety of Chinese dialects, and how such prosodic reflexes of information structure are constrained by their characteristic sound structures. Lacunae for the studies of focus and topic in Chinese are also identified as important questions for future research.
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Paiva, Wilson Alves de. A Fontana de Lutécia : Contos Virais. Brazil Publishing, 2021. http://dx.doi.org/10.31012/978-65-5861-566-8.
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A fictional book with five short stories that address the main pandemics in the world. The first story takes place in Ancient Greece, in 428 BC at the time of the Peloponnesian War. Tavros, the main character flees the plague by traveling to Gaul and discovers a mysterious water spring near the village of the Parisii. In AD 166, when Rome, is devasted by the plague, Marcus Aurelius sends out soldiers to the North. One of them, Lucius, arrives in the region of Lutecia and finds the same fountain that Tavros had been to. The water from this spring gives him strength to escape from the persecution of Christians and Jews. In his old age, Lucius becomes a Church elder and writes letters. One of them was read, many centuries later, by a Franciscan Parisian monk during the Middle Ages, who decides to pilgrimage to Jerusalem but is surprised by the Black Death. Back home, he is saved by the water spring, builds an orphanage and has his life converted into a book - which is red by a young journalist who takes the ship Demerara with his fiancée to Brazil in order to avoid the World War I, the Spanish flu and some Russian spies. The last story is about a Brazilian professor, called Lucius Felipe who, in 2019, travels to Paris to develop his postdoctoral studies. Unfortunately he has to return to Brazil due to the COVID-19 pandemic. But not before having visited Lutetia’s fountain and felt its power and the memories it holds.
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Serhan, Randa B. Muslim Immigration to America. Sous la direction de Jane I. Smith et Yvonne Yazbeck Haddad. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199862634.013.021.
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Muslim immigration to America has a protracted history dating back to the first coerced West and North Africans brought on ships as part of the slave trade. Yet, the notion of Muslims as a distinguishable or coherent group arose only in the aftermath of 9/11. The Muslims of the post-9/11 era are defined as fairly recent immigrants from Southeast Asia and the Arab world. Scholarship since 9/11 has implicitly accepted this categorization, whether to make the case that Muslims have been racialized or, conversely, to assess the level of terror threat they may pose. The present chapter views this issue through a longer-range lens and a looser definition of Muslim to allow for the inclusion of the earliest migration flows (coerced and voluntary) and those who are often viewed as contested Muslims, such as the Nation of Islam. In total, six migration flows are analyzed according to Alejandro Portes and Ruben Rumbaut’s conceptualization of immigrant modes of incorporation: namely governmental reception, public reaction toward newcomers, and the preexisting community. By casting this wider net and moving away from the confines of the post-9/11 backlash, this chapter evaluates the place of Islam in the lives of those who identify or are identified as Muslims. Analyzing six major migration flows that include Muslims, it finds that Islam has been secondary to the politics of populations identified as such, whether international or domestic. The Nation of Islam was treated as suspect more because of its black nationalist undertones than its claims to Islam.Palestinians, regardless of religion, were treated as terrorists because of the Arab-Israeli war, and Southeast Asian were viewed as model minorities until 9/11 despite their strong identification with Islam. In other words, the contextual elements, especially governmental reception, have a greater influence on minorities and immigrants than religion. Currently, this has meant that American Muslims have been asked to prove their allegiance to the United States. On a positive note, there are enough educated and civically engaged American Muslims that they are able to contest the imposition of a coherent Muslim identity as alien and dangerous.
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A Song for Nagasaki : The Story of Takashi Nagai - Scientist, Convert, and Survivor of the Atomic Bomb. San Francisco, California, USA : Ignatius Press, 2009.
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Strasser, Ulrike. « Braving the Waves with Francis Xavier ». Dans Missionary Men in the Early Modern World. Nieuwe Prinsengracht 89 1018 VR Amsterdam Nederland : Amsterdam University Press, 2020. http://dx.doi.org/10.5117/9789462986305_ch02.
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This chapter discusses the transoceanic voyage as a rite de passage into missionary manhood. Jesuits defined their brand of masculinity in the social microcosm of the ship, carrying out pastoral work in confinement and danger. If Ignatius was the Society’s inventor and Ur-father, Francis Xavier was its patron of mobility and a model for conduct for generations of missionaries, including many Germans. Hagiographical accounts and paintings of Xavier’s dramatic sea voyages emphasize his exemplary self-governance and ability to convert sinful fears into correct fear of God. The transoceanic ship was a site of embodied conditioning for those who followed in Xavier’s footsteps. When the missionaries reached foreign shores, they felt more ready than ever to convert and regulate indigenous others.
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Kacem, Imed. « Flexible Job-Shop Scheduling Problems ». Dans Encyclopedia of Information Science and Technology, First Edition, 1197–200. IGI Global, 2005. http://dx.doi.org/10.4018/978-1-59140-553-5.ch211.
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Planning and scheduling problems in various industrial environments are combinatorial and very difficult. Generally, it is extremely hard to solve these types of problems in their general form. Scheduling can be formulated as a problem of determining the best sequence to execute a set of tasks on a set of resources, respecting specific constraints like precedence or disjunctive constraints (Carlier & Chrétienne, 1988). They consist generally in a simultaneous optimization of a set of non-homogeneous and conflicting goals. Therefore, the exact algorithms such as branch and bound, dynamic programming, and linear programming are not suitable for such problems and need a lot of time and memory to converge.
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Doshi, Rush. « An Asymmetric Strategy for US-China Competition ». Dans The Long Game, 297–329. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197527917.003.0014.
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Chapter 13 outlines a US response to China’s ambitions for displacing the United States from regional and global order. This approach would address the China challenge not through changing China’s internal political structure or reassuring it through a grand bargain, but by limiting China’s ability to convert its power into regional and global order. Given the scale of China’s challenge, the United States needs an asymmetric response, one that strengthens the “forms of control” upon which American order depends while undermining those that Chinese order will soon require. It shows how the United States can avoid competing dollar-for-dollar, ship-for-ship, or loan-for-loan by adopting an asymmetric approach that blunts Chinese advances at lower cost than China expends in generating them, all while reinvesting in the sources of American order that generate disproportionate advantage relative to the costs of maintaining them. The chapter discusses military, political, and economic components of these asymmetric approaches.
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Abou Zahab, Mariam. « ‘It’s Just a Sunni-Shia Thing’ ». Dans Pakistan, 147–62. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780197534595.003.0010.
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This chapter demonstrates that “rising sectarianism” is a direct offshoot of growing Talibanization, which suggests that both schools of thought began to overlap more and more. It talks about the evolution of sectarianism, which translated into mass violence that spilled over to the neighboring region of Orakzai and fostered by socio-economic factors. Sectarianism comes from the belief that the sect which one professes is the only true one and that the followers of other sects should be converted to one's own sect or exterminated. The chapter explains how sectarianism is often seen as the consequence of Zia-ul Haq's Islamization policy in the 1980s, which involved a state monopoly on religion and the dominance of a particular sect. Sectarian consciousness had always existed but it was mostly confined to theological debates and clashes during the month of Muharram.
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« Chapter 8 ». Dans The Diary of a Maritimer, 1816-1901, sous la direction de Nancy Redmayne Ross, 98–111. Liverpool University Press, 1996. http://dx.doi.org/10.5949/liverpool/9780969588597.003.0008.
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This chapter describes important changes in Salter’s life; personal changes include the births of two of his children, Sidney and Bessie, and professional changes include the purchase of a shipyard in Moncton in 1846. Many extracts are devoted to recalling time spent in Liverpool. The chapter conveys the pressures and responsibilities involved in contracting large numbers of ships and vessels and portrays the necessary correspondence, recruitment and transactions of a shipyard manager.
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Fehring, Thomas H., et Terry S. Reynolds. « Energy Production and Conversion ». Dans Chronicles of Mechanical Engineering in the United States, 201–50. ASME, 2021. http://dx.doi.org/10.1115/1.356056_ch6.
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In many ways, energy production and its conversion from one form to another is the heart of mechanical engineering. The history of energy is vast, beginning with efforts to make the energy produced by human muscle more effective through the use of lubricants or the application of the so-called six simple machines in pre-history. By the end of Classical antiquity, inventors and engineers had harnessed the power of wind to move ships and water to grind flour. In the eighteenth century the first practical heat engines opened the era of fossil fuels, utilizing the expansive power of steam to convert thermal energy to mechanical energy.
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McInally, Tom. « The Ḥusaynābādī Scholiasts ». Dans George Strachan of the Mearns, 78–87. Edinburgh University Press, 2020. http://dx.doi.org/10.3366/edinburgh/9781474466226.003.0008.
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The excellence of the teaching that Strachan received while with Feyyād was due to the presence of distinguished exiled Iranian Sunni scholars to whom the emir had given refuge. This chapter outlines the Islamic heritage of Iran and the political and Sunni/Shia sectarian tensions that had led to the scholars’ exile by Shah Abbas. Their renown within the Sunni Islamic world is noted. The chapter also explains how, while gaining intimate knowledge of Islamic doctrine and tradition, Strachan’s discussions with these scholars led them to believe that he fully accepted their arguments and assured Emir Feyyād of his conversion. Strachan had not converted and, despite his comfortable life-style, he saw no option but to flee the emir’s camp and seek refuge in Baghdad.
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Lake, Mark Winter. « MAGICAL Computer Simulation of Mesolithic Foraging ». Dans Dynamics in Human and Primate Societies. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195131673.003.0011.
Texte intégralRésumé :
The MAGICAL (Multi-Agent Geographically Informed Computer AnaLysis) software described in this chapter was designed to integrate two of the most important computational methods used by archaeologists during the last decade: Geographical Information Systems (GIS) (e.g., Allen et al. 1990) and multiagent simulation (e.g., Lake 1995; Mithen 1990). At the outset of model development in 1995, it was recognized that GIS provide archaeologists with a sophisticated means of manipulating spatial data, but offer limited support for modeling change through time. Conversely, multiagent simulation models have allowed archaeologists to study change through time, but have either lacked or had simplistic spatial components. Consequently, the research described here aimed to combine the strengths of GIS and multiagent simulation in one software package so as to better facilitate the quantitative study of spatiotemporal variability in the archaeological record. The MAGICAL software was developed within the broader context of the Southern Hebrides Mesolithic Project (SHMP). This project was established in 1988 by Dr. Steven Mithen (University of Reading) to acquire new data from the Scottish Islands of Islay and Colonsay and, by integrating this with existing data, to develop a regional perspective on the early postglacial settlement of Western Scotland (Mithen and Lake 1996). The construction of a computer simulation model was considered a fundamental part of the postexcavation studies of the SHMP (Lake in press). It was hoped that conceptual models which would otherwise remain largely intuitive could be more rigorously explored by formalizing them into mathematical algorithms, translating those algorithms into computer code, and then running simulation experiments. This chapter describes how the MAGICAL software integrates GIS and multiagent simulation. It does so directly in section one and then by example in sections two, three, and four. Section two discusses the conceptual basis of the SHMP simulation model, and section three describes how this was implemented using the MAGICAL software. Section four presents the results of the SHMP simulations. Note that the SHMP simulation model is discussed primarily as a means of demonstrating the capabilities of the MAGICAL software. Those interested in the wider background to this particular modeling endeavor are urged to consult Mithen (ed., in prep).
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Aso, Michitake. « Managing Disease ». Dans Rubber and the Making of Vietnam, 92–129. University of North Carolina Press, 2018. http://dx.doi.org/10.5149/northcarolina/9781469637150.003.0004.
Texte intégralRésumé :
After World War I, colonial administrative policy, environmental necessity, and economic logic converged to promote Vietnamese migration to meet plantation demands for labor. Peasants from the Tonkin delta travelled by ship and by road to southern plantations, where they sometimes displaced previous inhabitants. These workers helped carry out the deforestation that created the limpid, sunny streams in which mosquito species associated with malaria in the region bred. Malaria, beriberi, and horrible living conditions resulted in the illness and deaths of thousands of plantation workers. These outbreaks, along with the more famous cases of abuse, provided much fodder for opponents of colonialism, French and Vietnamese alike. Even as medical doctors recognized the poor health of plantation workers, they found it more plausible to blame workers’ moral failings and culture rather than the colonial system. By placing the human suffering of laborers in the context of changing disease environments, chapter 3 further investigates the relationships among science, business, and government. Industry played a key role in creating medical institutions and knowledge in Indochina during the colonial period and, partly because of this role, economic concerns trumped humanitarian impulses.
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Taber, Douglass F. « Alkaloid Synthesis : ( S )-Nicotine (Helmchen), (+)-CP-99,994 (Shi),(-)-Adaline (Yu), (-)-Securinine (Bayó n/Figueredo), Alkaloid 223A (Aubé ), (-)-Huperzine A (Fukuyama) 110 ». Dans Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0057.
Texte intégralRésumé :
The recent development of practical methods for the asymmetric preparation of amines has enabled creative approaches to alkaloid construction. Günter Helmchen of the Ruprecht-Karls-Universit ät Heidelberg developed (Synlett 2009, 1413) an iridium catalyst that mediated the enantioselective amination of the allylic carbonate 1 to give 2. Hydroformylation followed by reduction then completed the synthesis of ( S )-nicotine 3. Yian Shi of Colorado State University devised (J. Org. Chem. 2009, 74, 7577) a Pd catalyst for the enantioselective oxidative diamination of terminal alkenes such as 4. The product 6 was readily carried on to (+)-CP-99,994, a potent and selective nonpeptide substance P receptor antagonist. Chan-Mo Yu of Sungkyunkwan University prepared (Synlett 2009, 1498) the alcohol corresponding to the azide 8 by BINOL-catalyzed addition of an allyl stannane to the corresponding aldehyde. Reduction of the azide and subsequent intramolecular condensation with the ketone gave an imine, which was cyclized with Bu3SnF to 9. Oxidative cleavage then delivered (-)-adaline 10. Barry M. Trost of Stanford University developed a family of Pd catalysts for the enantioselective coupling of racemic butadiene monoepoxide 12 with a range of nucleophiles. Pau Bayón and Marta Figueredo of the Universitat Autónoma de Barcelona extended (J. Org. Chem. 2009, 74, 6199) that range to include glutarimide 11 and succinimide. The adduct 13 provided the enantiomerically pure core for a total synthesis of (-)-securinine 14, and others of the Securinega alkaloids. Jeffrey Aubé of the University of Kansas prepared (Organic Lett. 2009, 11, 4140) the enantiomerically enriched ketone 15 by the enantioselective hydroboration of norbornadiene, followed by oxidation and alkylation. Intramolecular Schmidt cyclization following the protocol he had developed converted 15 into 16. He then took advantage of the still substantial ring strain of the expanded norbornene to drive ring-opening metathesis, giving, after hydrogenation, the lactam 17. He was able to selectively convert 17 into either 18 or the diastereomer in which the ethyl groups are cis one to another by varying the acid used in the final reductive work-up.
Actes de conférences sur le sujet "Converse (Ship)"
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Platzer, Max F., Nesrin Sarigul-Klijn, J. Young, M. A. Ashraf et J. C. S. Lai. « Renewable Hydrogen Production Using Sailing Ships ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62311.
Texte intégralRésumé :
Vast ocean areas of planet Earth are exposed year-round to strong wind currents. We suggest that this untapped ocean wind power be exploited by the use of sailing ships. The availability of constantly updated meteorological information makes it possible to operate the ships in ocean areas with optimum wind power so that the propulsive ship power can be converted into electric power by means of ship-mounted hydro-power generators. Their electric power output then is fed into ship-mounted electrolyzers to convert sea water into hydrogen and oxygen. In this paper we estimate the ship size, sail area and generator size to produce a 1.5 MW electrical power output. We describe a new oscillating-wing hydro-power generator and present results of model tests obtained in a towing tank. Navier-Stokes computations are presented to provide an estimate of the power extraction efficiency and drag coefficient of such a generator which depends on a range of parameters such as foil maximum pitch angles, plunge amplitude, phase between pitch and plunge and load. Also, we present a discussion of the feasibility of sea water electrolysis and of the re-conversion of hydrogen and oxygen into electricity by means of shore-based hydrogen-oxygen power plants.
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Vu, T. V., F. Diaz et C. S. Edrington. « Sequence Based Control for Electro-thermal Management of Next Generation Integrated Power Systems ». Dans International Ship Control Systems Symposium. IMarEST, 2018. http://dx.doi.org/10.24868/issn.2631-8741.2018.023.
Texte intégralRésumé :
An individual switching technique for semi-conductor components of power converters presents an individual electrical and thermal output performance. Therefore, understanding the switching patterns or sequence and their effect can significantly improve the overall performance of the power converters. In this paper, a sequence based control methodology for a power converter system to optimize its electrical and thermal performance will be presented, analysed, and discussed. The method includes modelling the converter system with respect to a sequence of switching events, defining and formulating the control objectives into a form of a cost function, and solving the cost function for the optimal electrical performance.
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Ginn III, H. L., J. D. Bakos, Fred Flinstone et A. Benigni. « Fast Coordination of Power Electronic Converters for Energy Routing in Shipboard Power Systems ». Dans International Ship Control Systems Symposium. IMarEST, 2018. http://dx.doi.org/10.24868/issn.2631-8741.2018.024.
Texte intégralRésumé :
A long-term goal of future naval shipboard power systems is the ability to manage energy flow with sufficient flexibility to accommodate future platform requirements such as, better survivability, continuity, and support of pulsed and other demanding loads. To attain this vision of shipboard energy management, shipboard power and energy management systems must coordinate operation of all major components in real-time. The primary components of a shipboard power system are the generators, energy storage modules, and increasingly power electronics that interface those sources and main load centers to the system. Flexible management of energy flow throughout shipboard distribution systems can be realized by automated coordination of multiple power electronic converters along with storage and generation systems. Use of power converters in power distribution systems has continuously increased due to continued development of the power electronics building blocks (PEBB) concept which reduces cost and increasing reliability of converters. Recent developments in SiC power devices are yielding PEBBs with far greater switching frequencies than Si based devices resulting in an order of magnitude reduction of the time scales as compared to converter systems utilizing conventional IGBT based PEBBs. In addition there have also been advancements in highly modularized converter systems with hundreds of PEBBs such as the Modular Multilevel Converter. Both of those trends have resulted in the continued evolution of the Universal Controller Architecture which attempts to standardize control interfaces for modular power electronic systems. Further development of interface definitions and increasing communication and computational capabilities of new FPGA based controllers provides opportunities beyond simply supporting SiC PEBBs. Fast control coordination across the system using an appropriate communication architecture provides a degree of energy management not previously realizable in shipboard power systems. The paper will present recent research results in networked control architectures for power electronic converter coordination and control. It will demonstrate that current FPGA and gigabit speed serial communication technologies allow for a very high degree of energy flow control.
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Gilloteaux, Jean-Christophe, et Aurélien Babarit. « Preliminary Design of a Wind Driven Vessel Dedicated to Hydrogen Production ». Dans ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61408.
Texte intégralRésumé :
An innovative concept of harnessing wind energy is presented. The concept consists of a wind driven ship equipped with a hydro-generator that converts the kinetic energy of the water flow into electricity. The electricity is then converted into hydrogen by electrolysis. In the present study the use of a Flettner rotor is considered to propel the ship. A mathematical model of the hydrogen producing ship is developed based on existing data for high performance ship hulls and aerodynamic coefficients of existing Flettner rotors. The design is optimized with respect to the axial induction velocity through the water turbine disk. Results indicate that a 22m long vessel could produce 200 kW while a 80 m long vessel is able to generate 1 MW of mechanical power both for a true wind speed of 8 m/s.
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de Menezes, Fabio Gouveia Telles, Breno Pinheiro Jacob, Carl Horst Albrecht et Fabrício Nogueira Corrêa. « Application of Parametric Surfaces in Contact Assessment Between Two Floaters in Side by Side Operations ». Dans ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-84233.
Texte intégralRésumé :
In front of the growing demand for natural gas, alternative solutions have been adopted to export the production to the several available markets. Conventional gas carriers have been converted to regasification units to operate close to the shore, treating the gas and delivering it to carriers which take the product to the shore. Side by side configurations for the gas transference by loading arms are common, and the reduce distance between the ships is the main challenge. For such application a time domain simulation is demanded. Due to the close proximity between the ships, at each time step, their distance has to be calculated in order to predict eventual ship to ship or ship to fenders collisions. When the ships are modeled by conventional meshes the interference analysis every time step is excessively time consuming, the use of parametric surfaces reduces the number of elements to be checked against each other and saves computational cost. The precision is also improved since the hull shapes are fully represented in comparison to the panel approximation provided by the meshing approach. The contact verification plays a fundamental role for that type of analysis and the gains obtained by the parametric surfaces appliance are significant.
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Clauss, Gu¨nther F., Daniel Testa, Sascha Kosleck et Robert Stu¨ck. « Forecast of Critical Wave Groups From Surface Elevation Snapshots ». Dans ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29090.
Texte intégralRésumé :
Reports on damages of ships, cargo and structures during heavy seas have been increasing within the last years. The impact of single extreme waves or wave groups on marine structures and ships causes enormous forces often leading to critical situations or even loss of crew, ship and cargo. Dangerous situations can be predicted by a forecast of encountering wave trains and the identification of critical wave groups. The paper presents a method to calculate the wave train a ship will encounter from surface elevation snapshots of the surrounding sea, taken by the ship radar. The time-dependent surface elevation snapshot far ahead of the ship is transferred into frequency domain by the use of Fast Fourier Transformation (FFT). The resulting complex Fourier spectrum given over the inverse wave length 1/L is converted into an amplitude spectrum and a phase spectrum. By shifting the phase spectrum to the position of the cruising ship the encountering waves can in turn be calculated in advance — depending on speed. The permanent processing of incoming snapshots delivers a continuous prediction of the water surface elevation at the position of the cruising ship. Based on these data the expected ship motion behaviour can be calculated continuously in time domain. In addition the response spectra, resulting from the wave spectrum and the relevant RAOs, are also evaluated. As wave data far ahead of the ship are used, it allows a forward glance, and dangerous situations, particularly resonance and parametric resonance are detectable before the ship is encountering this wave train. Consequently, the procedure can be used by the master as an assistance support system.
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Driscol, Blake P., Andrew Gish et Ryan G. Coe. « Wave-Powered AUV Recharging : A Feasibility Study ». Dans ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95383.
Texte intégralRésumé :
Abstract The aim of this study is to determine whether multiple U.S. Navy autonomous underwater vehicles (AUVs) could be supported using a small, heaving wave energy converter (WEC). The U.S. Navy operates numerous AUVs that need to be charged periodically onshore or onboard a support ship. Ocean waves provide a vast source of energy that can be converted into electricity using a wave energy converter and stored using a conventional battery. The Navy would benefit from the development of a wave energy converter that could store electrical power and autonomously charge its AUVs offshore. A feasibility analysis is required to ensure that the WEC could support the energy needs of multiple AUVs, remain covert, and offer a strategic military advantage. This paper investigates the Navy’s power demands for AUVs and decides whether or not these demands could be met utilizing various measures of WEC efficiency. Wave data from a potential geographic region is analyzed to determine optimal locations for the converter in order to meet the Navy’s power demands and mission set.
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Yuksek, Errol L., et Parsa Mirmobin. « Electricity Generation From Large Marine Vessel Engine Jacket Water Heat ». Dans ASME 2015 9th International Conference on Energy Sustainability collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/es2015-49226.
Texte intégralRésumé :
As world trade grows, fuel prices increase, and International Maritime Organization (IMO) emissions requirements tighten, there is more demand for the marine industry to employ innovative means of reducing the fuel consumption and emissions of shipping vessels. The main engines of large shipping vessels produce a large quantity of low temperature heat, but this valuable heat energy is transferred to cooling systems and rejected to the oceans as waste. At the same time, the electrical needs of shipping vessels are sustained by burning diesel fuel to run generators. Calnetix Technologies, in partnership with Mitsubishi Heavy Industries, has developed the Hydrocurrent™ 125EJW Organic Rankine Cycle (ORC), a modularized system capable of absorbing the waste heat of main engine jacket water and converting it into grid-quality electric power. By combining this renewable source with the existing non-renewable source (engine gensets) a unique renewable-non-renewable hybrid power system is realized with minimal changes to overall ship power train. This novel hybrid system can be applied to all new and existing ships and allow for further integration into ship systems with available waste heat. Shipping vessels such as tankers, bulk carriers, and container vessels are typically equipped with a category 3 marine diesel engine for main propulsion. A 30 MW engine, a most common engine size, utilizes 200–300 m3/hr of jacket water regulated to a heated temperature of 80–95 C. When integrated into the jacket water and sea water loops, the ORC can produce up to 125 kW of gross grid-quality electric power. This adds an immense benefit to the ship. To produce the same amount of power, a diesel generator consumes as much as 250 metric tons of diesel fuel per year, generates emissions, and requires significant maintenance. Calnetix Technologies has leveraged its core technologies to develop the ORC into a reliable, high efficiency, compact and modular design. The turbo-generator or Integrated Power Module (IPM) is a hermetically sealed, high speed radial turbine coupled to a permanent magnet generator supported by magnetic bearings. Power from the IPM is converted by a high efficiency power converter supplying the ship with reliable power. The integrated design of the ORC along with the sophistication of its controls systems ensures essential ship functions are undisturbed under all conditions. The ORC is designed to comply with Nippon Kaiji Kyokai and Lloyd’s Register marine regulations and sea trials are anticipated to take place in 2015.
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Storhaug, Gaute, Erlend Moe, Ricardo Barreto Portella, Tomazo Garzia Neto, Nelson Luiz Coelho Alves, Sun Gun Park, Dong-Kwon Lee et Yooil Kim. « First Ocean Going Ships With Springing and Whipping Included in the Ship Design ». Dans ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49366.
Texte intégralRésumé :
It is well known that ships vibrate due to waves. The wave induced vibrations of the hull girder are referred to as springing (resonance) and whipping (transient vibration from impacts). These vibrations contribute to the fatigue damage of fatigue sensitive details. An Ore Carrier of 400 000 dwt is currently being built by DSME, and at time of delivery, it will be the world’s largest bulk (ore) carrier. The scantlings of large ships must be carefully designed with respect to global loading, and when extending the design beyond experience, it is also wise to consider all aspects that may affect operation and the life time costs. The vessel will also enter a long term contract and is therefore to be evaluated for 30 year Brazil-China operation. In order to minimize the risk of fatigue damage, the vessel is designed according to DNV’s class notation CSA-2 requiring direct calculations of the loading and strength. Further it has been requested to include the effect of springing and whipping in the design. Reliable numerical tools for assessing the additional fatigue effect of vibrations are non-existing. DNV has, however, developed an empirical guidance on how the additional effect may be taken into account based on previous development projects related to the effect of vibrations on large ore carriers Due to the size and route of operation of the new design, it has, however, been required by the owner to carry out model tests in both ballast and cargo condition in order to quantify the contribution from vibration. The results from this project have been used for verification and further calibration of DNV’s existing empirical guidance. A test program has been designed for the purpose of evaluating the consequence in head seas for the Brazil to China trade. Full scale measurements from previous development projects of ore carriers and model tests have been utilized to convert the current model tests results into estimated full scale results for the 400 000 dwt vessels. It is further important to carefully consider how the vibrations are to be included in the design verification, and to develop a procedure for taking into account the vibrations which results in reasonable scantlings based on in-service experience with similar designs and trades. This procedure has been developed, and a structural verification has been carried out for the design. The final outcome of the model test was in line with previous experience and in overall agreement with DNV’s empirical guidance, showing a significant contribution from vibrations to the fatigue damage. The springing/whipping vibrations more than doubled the fatigue damage compared to fatigue evaluation of the isolated wave induced loading. The cargo condition vibrated relatively more than experienced on smaller vessels. Various sources to establish the wave conditions for the Brazil to China ore trade were used, and the different sources resulted in significant differences in the predicted fatigue life of the design.
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Rodri´guez-Sa´nchez, J. Efrai´n, Alejandro Rodri´guez-Castellanos, Manuel F. Carbajal-Romero et Efre´n Ayala-Uraga. « Controlled Weld Toe Profiles for Fatigue Life Extension in FSO’s and FPSO’s ». Dans ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29220.
Texte intégralRésumé :
Application of controlled weld toe profiles can be considered an option to extend the fatigue life of welded connections when ongoing tankers are converted in dry docks to serve like offshore ships (FPSOs and FSOs). Very slim chances to implement such fatigue improvement will arise when these vessels are in service, since a converted ship is designed to be inspected, maintained and repaired in situ and not in dry dock as it is uneconomical to interrupt production. Codes recognize fatigue life extension by means of a controlled weld toe profile, e.g. [1]. Application of a controlled weld toe profile during conversion in selected areas previously identified by stress analysis of the hull structure can lead to extend the converted vessel fatigue life to comply with an expected field life. The American Bureau of Shipping S-N curves allow a credit of 2.2 on fatigue life when suitable toe grinding and NDE are provided. A controlled weld toe profile can be applied in fatigue crack repaired welds during ship conversion or even on those that during ship conversion are found in a non-cracked condition but were identified prone to fatigue cracking in a stress assessment analysis under in-service conditions. Credit on fatigue life in various codes and results from experimental data obtained from fatigue tested specimens with a controlled weld toe profile are given. Comments on the design of a controlled weld toe profiles and recommendations based on experimental experience for the implementation of equipment to perform a controlled weld toe profile are also given. A Fracture Mechanics approach for the assessment of controlled weld toe profiles for fatigue life extension purposes is described. Initially, a comparison of SCFs for a typical ship hull plate connection with and without weld toe profile control determined by Finite Element Analysis (FEA) is presented. Then, results obtained from the FEA connection such as through plate stress distribution are used in a Fracture Mechanics Analysis to compare the fatigue crack growth curve in as-welded condition to that with controlled weld toe profile.
Rapports d'organisations sur le sujet "Converse (Ship)"
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Ciezki, John G., et Robert W. Ashton. Analysis of a PWM Resonant Buck Chopper for Use as a Ship Service Converter Module. Fort Belvoir, VA : Defense Technical Information Center, janvier 1999. http://dx.doi.org/10.21236/ada361136.
Texte intégral