The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Naoya Umeda - One of the best experts on this subject based on the ideXlab platform.
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Effectiveness and mechanism of broaching-to prevention using global optimal control with evolution strategy (CMA-ES)
Journal of Marine Science and Technology, 2020Co-Authors: Sreenath Maniyappan, Naoya Umeda, Atsuo Maki, Youhei AkimotoAbstract:This paper demonstrates the effectiveness of using global optimal rudder control with the covariance matrix adaptation evolution strategy, applied to a surge-sway-yaw-roll coupled numerical model, in preventing broaching-to, occurring under conventional PD rudder controls in stern Quartering waves. In particular, the PD control with optimized PD parameters is more efficient than the time history-optimized approach. With the help of stability analysis of surf-riding equilibria, two different mechanisms to successfully prevent broaching-to were identified: one is to tend to a periodic orbit with additional slight rudder actions and the other is to stay in surf-riding on a position of unstable equilibrium in regular waves for a longer duration with a larger differential gain. These outcomes could facilitate real-time prevention of broaching-to in actual seas.
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cfd prediction of wave induced forces on ships running in irregular stern Quartering seas
Ocean Engineering, 2019Co-Authors: Hirotada Hashimoto, Frederick Stern, Akihiko Matsuda, Naoya Umeda, Shota Yoneda, Tomoyuki Omura, Yusuke TaharaAbstract:Abstract Surf-riding/broaching is a dangerous event for high-speed ships running in stern Quartering seas. Theoretical methods for the prediction of wave-induced forces on ships in surf-riding and broaching situations are still of the qualitative level. Therefore, an unsteady Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) solver with overset grids was applied to predict the wave-induced forces on ships in irregular stern Quartering seas. To validate the CFD method, a dedicated model experiment was conducted for slender ships, and the wave-induced forces were measured to be for a direct comparison with CFD predictions using the same irregular waves encountered. The comparison results indicate good agreement between the CFD results and the experimental fluid dynamics (EFD) results except for the wave-induced roll moment.
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water on deck effects on roll motions of an offshore supply vessel in regular stern Quartering waves
Ocean Engineering, 2019Co-Authors: Su Sandy Htun, Akihiko Matsuda, Naoya Umeda, Masahiro Sakai, Daisuke TeradaAbstract:Abstract The applicability of the second generation intact stability criteria for preventing pure loss of stability in astern waves to offshore supply vessels (OSV) is investigated. OSVs show an inconsistency problem in the first and second level criteria. Thus, free-running model experiments of an OSV by changing its length of low weather deck in regular stern Quartering waves were conducted and were compared with numerical simulation used for pure loss of stability so far. As a result, it was confirmed that the effects of water on deck (WOD) on the behaviour of the OSV could prevent the occurrence of typical pure loss of stability for the cases of long low weather deck. One of WOD's effects is the increase of roll damping and the other is the loss of static stability.
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Effect of above-waterline hull shape on broaching-induced roll in irregular stern-Quartering waves
Journal of Marine Science and Technology, 2019Co-Authors: Naoya Umeda, Akihiko Matsuda, Daisuke TeradaAbstract:In this paper, the effect of the above-waterline hull shape on broaching danger in irregular stern-Quartering waves was numerically investigated using the US Office of Naval Research (ONR)-tumblehome and ONR-flare hulls. To indicate the danger of broaching, the probability of a broaching-induced large roll angle of the two vessels was examined along with the probability of broaching. The numerically estimated broaching-induced roll angles were compared with the time histories of the free-running model experiments. Then, the effects of above-waterline hull shape on broaching danger in the North Atlantic were simulated for various speeds, autopilot courses and rudder gains.
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improved maneuvering based mathematical model for free running ship motions in following waves using high fidelity cfd results and system identification technique
2019Co-Authors: Motoki Araki, Naoya Umeda, Hamid Sadathosseini, Yugo Sanada, Frederick SternAbstract:Predicting maneuverability and stability of a free running ship in following and Quartering waves are one of the most important topics to prevent broaching; however current mathematical models show quantitative errors with the experimental data while high-fidelity CFD simulations show quantitative agreement, which provides the opportunity to improve the mathematical models for free running ship dynamics in waves. In this study, both maneuvering coefficients and wave model in the mathematical model are improved utilizing system identification technique and CFD free running outputs. From turning circle and zigzag calm water CFD free running data, the maneuvering coefficients are estimated. The wave correction parameters are introduced to improve the wave model, which are found from a few forced and free running CFD simulations in waves. The mathematical model with the improved parameters shows much better agreement with experiments in both calm water and waves than the original mathematical model. The original mathematical model was based on the maneuvering coefficients estimated from several captive tests and wave forces calculated from linear Froude-Krylov forces and diffraction forces based on a slender ship theory.
I. Loxton - One of the best experts on this subject based on the ideXlab platform.
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effect of biotin supplementation on meat quality of f1 wagyu black angus feedlot steers of known genotype
Meat Science, 2007Co-Authors: R. J. Lawrence, R. Elliott, B. W. Norton, J Doyle, I. LoxtonAbstract:Biotin (D-biotin) was supplemented to F1 Wagyu/Black Angus steers fed a wheat-based ration to evaluate the effect on meat quality. One hundred and eight steers of known Wagyu sire lines were assigned to three biotin treatments (0, 10 and 20 mg/head/day) with each treatment replicated four times using an unfasted liveweight of 410.5 kg (+/- 24.42 SD). Biotin supplementation had no effect (P > 0.05) on beef marbling standard at either the 5/6th or 10/11th rib Quartering site, 10/11th rib intra-muscular fat percentage, intra-muscular fat fatty acid composition or adipose melting points. Wagyu genotype had an effect (P < 0.05) on beef marbling standard and intra-muscular fat percentage at the 10/11th rib, inter-muscular and intra-muscular melting point and fatty acid composition of intra-muscular fat. A significant (P < 0.001) but poor correlation existed between beef marbling standard and intra-muscular fat percentage (R-2 = 0.198). Total conjugated linoleic acid had a highly significantly (P < 0.0001) positive correlation to intra-muscular fat percentage (R-2 = 0.446). (c) 2007 Published by Elsevier Ltd.
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Effect of biotin supplementation on meat quality of F1 Wagyu/Black Angus feedlot steers of known genotype
Meat science, 2007Co-Authors: R. J. Lawrence, J.c. Doyle, R. Elliott, B. W. Norton, I. LoxtonAbstract:Biotin (D-biotin) was supplemented to F1 Wagyu/Black Angus steers fed a wheat-based ration to evaluate the effect on meat quality. One hundred and eight steers of known Wagyu sire lines were assigned to three biotin treatments (0, 10 and 20 mg/head/day) with each treatment replicated four times using an unfasted liveweight of 410.5 kg (+/- 24.42 SD). Biotin supplementation had no effect (P > 0.05) on beef marbling standard at either the 5/6th or 10/11th rib Quartering site, 10/11th rib intra-muscular fat percentage, intra-muscular fat fatty acid composition or adipose melting points. Wagyu genotype had an effect (P < 0.05) on beef marbling standard and intra-muscular fat percentage at the 10/11th rib, inter-muscular and intra-muscular melting point and fatty acid composition of intra-muscular fat. A significant (P < 0.001) but poor correlation existed between beef marbling standard and intra-muscular fat percentage (R-2 = 0.198). Total conjugated linoleic acid had a highly significantly (P < 0.0001) positive correlation to intra-muscular fat percentage (R-2 = 0.446). (c) 2007 Published by Elsevier Ltd.
Akihiko Matsuda - One of the best experts on this subject based on the ideXlab platform.
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cfd prediction of wave induced forces on ships running in irregular stern Quartering seas
Ocean Engineering, 2019Co-Authors: Hirotada Hashimoto, Frederick Stern, Akihiko Matsuda, Naoya Umeda, Shota Yoneda, Tomoyuki Omura, Yusuke TaharaAbstract:Abstract Surf-riding/broaching is a dangerous event for high-speed ships running in stern Quartering seas. Theoretical methods for the prediction of wave-induced forces on ships in surf-riding and broaching situations are still of the qualitative level. Therefore, an unsteady Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) solver with overset grids was applied to predict the wave-induced forces on ships in irregular stern Quartering seas. To validate the CFD method, a dedicated model experiment was conducted for slender ships, and the wave-induced forces were measured to be for a direct comparison with CFD predictions using the same irregular waves encountered. The comparison results indicate good agreement between the CFD results and the experimental fluid dynamics (EFD) results except for the wave-induced roll moment.
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water on deck effects on roll motions of an offshore supply vessel in regular stern Quartering waves
Ocean Engineering, 2019Co-Authors: Su Sandy Htun, Akihiko Matsuda, Naoya Umeda, Masahiro Sakai, Daisuke TeradaAbstract:Abstract The applicability of the second generation intact stability criteria for preventing pure loss of stability in astern waves to offshore supply vessels (OSV) is investigated. OSVs show an inconsistency problem in the first and second level criteria. Thus, free-running model experiments of an OSV by changing its length of low weather deck in regular stern Quartering waves were conducted and were compared with numerical simulation used for pure loss of stability so far. As a result, it was confirmed that the effects of water on deck (WOD) on the behaviour of the OSV could prevent the occurrence of typical pure loss of stability for the cases of long low weather deck. One of WOD's effects is the increase of roll damping and the other is the loss of static stability.
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Effect of above-waterline hull shape on broaching-induced roll in irregular stern-Quartering waves
Journal of Marine Science and Technology, 2019Co-Authors: Naoya Umeda, Akihiko Matsuda, Daisuke TeradaAbstract:In this paper, the effect of the above-waterline hull shape on broaching danger in irregular stern-Quartering waves was numerically investigated using the US Office of Naval Research (ONR)-tumblehome and ONR-flare hulls. To indicate the danger of broaching, the probability of a broaching-induced large roll angle of the two vessels was examined along with the probability of broaching. The numerically estimated broaching-induced roll angles were compared with the time histories of the free-running model experiments. Then, the effects of above-waterline hull shape on broaching danger in the North Atlantic were simulated for various speeds, autopilot courses and rudder gains.
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Broaching probability for a ship in irregular stern-Quartering waves: theoretical prediction and experimental validation
Journal of Marine Science and Technology, 2016Co-Authors: Naoya Umeda, Kentaro Mizumoto, Satoshi Usada, Akihiko MatsudaAbstract:To avoid stability failure due to the broaching associated with surf riding, the International Maritime Organization (IMO) has begun to develop multilayered intact stability criteria. A theoretical model using deterministic ship dynamics and stochastic wave theory is a candidate for the highest layer of this scheme. To complete the project, experimental validation of the theoretical method for estimating broaching probability in irregular waves is indispensable. We therefore conducted free-running model experiments using a typical twin-propeller and twin-rudder ship in irregular waves. A simulation model of coupled surge–sway–yaw–roll motion was simultaneously refined. The broaching probability calculated by the theoretical method was within the 95 % confidence interval of that obtained from the experimental data. This could be an example of experimental validation of the theoretical method for estimating the broaching probability when a ship meets a wave.
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importance of several nonlinear factors on broaching prediction
Journal of Marine Science and Technology, 2004Co-Authors: Hirotada Hashimoto, Naoya Umeda, Akihiko MatsudaAbstract:In order to realize a more quantitative prediction of broaching and capsizing in following and Quartering seas, existing mathematical modelling techniques should be upgraded. Therefore, it is necessary to systematically examine all factors relevant to capsizing in following and Quartering seas. To this end, we first attempted to examine the prediction accuracy of wave-induced forces by comparing calculations with captive model experiments. As a result, we found that a wave-induced surge force has a certain nonlinearitiy with respect to wave steepness. The nonlinearity of sway–roll coupling with respect to sway velocity was also found, and our numerical result with these nonlinearities improves the prediction accuracy of the critical ship speed of capsizing in following and Quartering seas. The importance of the wave effect on propeller thrust was also examined. We found that this effect is not negligibly small and could improve capsizing predictions in heavy following and Quartering seas. Finally, we attempted to investigate the importance of nonlinear heel-induced hydrodynamic forces on numerical predictions of capsizing due to broaching. Here, we propose a new procedure for captive model experiments to obtain hydrodynamic forces with various heel angles up to 90°, and data on heel-induced hydrodynamic forces with respect to heel angle in calm water are provided. We then compare the numerical simulations with the nonlinear heel-induced hydrodynamic forces and without them. These time series comparisons show that the effect of nonlinear heel-induced hydrodynamic forces in calm water is not negligibly small for the case of ship capsizing due to broaching.
R. J. Lawrence - One of the best experts on this subject based on the ideXlab platform.
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effect of biotin supplementation on meat quality of f1 wagyu black angus feedlot steers of known genotype
Meat Science, 2007Co-Authors: R. J. Lawrence, R. Elliott, B. W. Norton, J Doyle, I. LoxtonAbstract:Biotin (D-biotin) was supplemented to F1 Wagyu/Black Angus steers fed a wheat-based ration to evaluate the effect on meat quality. One hundred and eight steers of known Wagyu sire lines were assigned to three biotin treatments (0, 10 and 20 mg/head/day) with each treatment replicated four times using an unfasted liveweight of 410.5 kg (+/- 24.42 SD). Biotin supplementation had no effect (P > 0.05) on beef marbling standard at either the 5/6th or 10/11th rib Quartering site, 10/11th rib intra-muscular fat percentage, intra-muscular fat fatty acid composition or adipose melting points. Wagyu genotype had an effect (P < 0.05) on beef marbling standard and intra-muscular fat percentage at the 10/11th rib, inter-muscular and intra-muscular melting point and fatty acid composition of intra-muscular fat. A significant (P < 0.001) but poor correlation existed between beef marbling standard and intra-muscular fat percentage (R-2 = 0.198). Total conjugated linoleic acid had a highly significantly (P < 0.0001) positive correlation to intra-muscular fat percentage (R-2 = 0.446). (c) 2007 Published by Elsevier Ltd.
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Effect of biotin supplementation on meat quality of F1 Wagyu/Black Angus feedlot steers of known genotype
Meat science, 2007Co-Authors: R. J. Lawrence, J.c. Doyle, R. Elliott, B. W. Norton, I. LoxtonAbstract:Biotin (D-biotin) was supplemented to F1 Wagyu/Black Angus steers fed a wheat-based ration to evaluate the effect on meat quality. One hundred and eight steers of known Wagyu sire lines were assigned to three biotin treatments (0, 10 and 20 mg/head/day) with each treatment replicated four times using an unfasted liveweight of 410.5 kg (+/- 24.42 SD). Biotin supplementation had no effect (P > 0.05) on beef marbling standard at either the 5/6th or 10/11th rib Quartering site, 10/11th rib intra-muscular fat percentage, intra-muscular fat fatty acid composition or adipose melting points. Wagyu genotype had an effect (P < 0.05) on beef marbling standard and intra-muscular fat percentage at the 10/11th rib, inter-muscular and intra-muscular melting point and fatty acid composition of intra-muscular fat. A significant (P < 0.001) but poor correlation existed between beef marbling standard and intra-muscular fat percentage (R-2 = 0.198). Total conjugated linoleic acid had a highly significantly (P < 0.0001) positive correlation to intra-muscular fat percentage (R-2 = 0.446). (c) 2007 Published by Elsevier Ltd.
Bradley Rink - One of the best experts on this subject based on the ideXlab platform.
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Enclaves and Quartering in Urban South Africa
Urban Geography in South Africa, 2019Co-Authors: Bradley RinkAbstract:Comprehending the South African city—and cities beyond—requires an understanding of the form and functioning of the urban environment, in addition to the ways in which urban dwellers shape city spaces into places of meaning, intention and belonging. This chapter introduces readers to the processes and outcomes of shaping urban space in the form of enclaves and urban quarters. Beginning with a discussion of the history of enclave development and the process of ‘Quartering’ urban space, this chapter explores three typologies of enclave and quartered development in the context of South Africa, namely: ethnic/racial; residential; and creative/cultural. While apartheid spatial planning serves as a precursor to enclave development in cities, this chapter traces the continuing deployment of enclaves and urban quarters as a means of materially and discursively shaping urban space and the experience of cities. Using a case study of the urban enclave of De Waterkant, Cape Town, this chapter explores the development and outcomes of enclaves and quarters, while it also provides a conceptual lens through which neighbourhood change more broadly can be understood. At the same time, this chapter provides a framework for investigating and understanding the relationships that urban dwellers create with such structures. In the 21st century, urban quarters constitute an important catalyst in the regeneration and commodification of urban space, while the resulting enclaves and quarters reflect the shifting identities of the city while also embodying new forms of regeneration, inclusion and exclusion that characterise cities in the era of globalisation. Understood in recent literature through a lens of leisure and consumption, a more nuanced analysis of urban enclaves and quarters offers multiple representations of South African and other cities.
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Quartering the City in Discourse and Bricks: Articulating Urban Change in a South African Enclave
Urban Forum, 2016Co-Authors: Bradley RinkAbstract:Focusing on the urban enclave in Cape Town known as De Waterkant, this paper examines the product and process of ‘Quartering’ urban space—shaping urban space as the locus for the symbolic framing of culture. This paper advances recent studies of De Waterkant by applying the concept of Quartering to understand urban change in an African context. Complicating existing research on De Waterkant, the findings show that the area has witnessed four distinct quartered identities including an ethnic Quartering which was dismantled under apartheid , a Bohemian Quartering that changed racial dynamics and improved housing stock, a ‘gay village’ Quartering that engaged sexual identity performance as a strategy for place making and most recently a consumer lifestyle Quartering that exhibited new notions of citizenship and consumption. This paper advances theorisation of how Quartering as a process is articulated through the application of discursive and material tropes to the urban fabric of the city.