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Hirotada Hashimoto Naoya Umeda Akihiko Matsuda 《Journal of Marine Science and Technology》2011,16(4):448-461
The new intact stability criteria which are under development at the International Maritime Organization (IMO) are required
to cover a broaching phenomenon, well known as a great threat to high-speed vessels which can lead to capsizing. Some reports
exist which demonstrate that their numerical models can predict a highly nonlinear phenomenon of broaching. However, additional
validation studies are needed for unconventional vessels, in addition to conventional ones, to develop direct stability assessment
methods for the new intact stability criteria. In this research, we selected as the subject ship a wave-piercing tumblehome
vessel with twin screws and twin rudders, a design expected to be one of a new generation of high-speed monohull ships. Firstly,
a series of captive model tests were conducted to measure the resistance, the manoeuvring forces, the wave-exciting forces,
the heel-induced hydrodynamic forces, and the roll restoring variation for the unconventional tumblehome vessel. Secondly,
the existing mathematical model which had been developed for broaching prediction of conventional vessels with a single propeller
and a single rudder was extended to unconventional vessels with twin propellers and twin rudders. Finally, comparisons between
numerical simulations and the existing free running model experiments were conducted. As a result, it was demonstrated that
fair quantitative prediction of broaching is realised when the rudder force variation, the roll restoring variation and the
heel-induced hydrodynamic force for large heel angles are taken into account. 相似文献
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Naoya Umeda Hirotada Hashimoto Shohei Minegaki Akihiko Matsuda 《Journal of Marine Science and Technology》2008,13(1):16-23
The parametric rolling of modern containerships is emerging as a serious problem, to the extent that its effects warrant a
study into its prevention. In light of this, two methods for reduction of parametric rolling are proposed and examined by
physical model experiments. The first is a sponson attached to the side of a ship, the purpose being to decrease the rate
of change of the rollrestoring moment. The second is an antirolling tank to increase roll damping. By conducting free-running
model experiments for a 6600-TEU post-Panamax container ship with sponsons under typical parametric rolling conditions, it
was found that the sponsons could decrease the magnitude of parametric rolling. The antirolling tank could prevent parametric
rolling completely in certain conditions, even in severe head seas. Using the damping coefficients from experimentally derived
data of a model ship with an antiroll tank, a numerical simulation was established. The numerical model was then compared
with the free-running model experiments. The results indicated that the numerical model could qualitatively verify the experimental
results. Finally, an attempt to optimise the size of an antirolling tank for preventing parametric rolling for the subject
post-Panamax container ship in the North Pacific Ocean is presented. 相似文献
5.
During automated driving in urban areas, decisions must be made while recognizing the surrounding environment using sensors such as camera, Light Detection and Ranging (LiDAR), millimeter-wave radar (MWR), and the global navigation satellite system (GNSS). The ability to drive under various environmental conditions is an important issue for automated driving on any road. In order to introduce the automated vehicles into the markets, the ability to evaluate various traffic conditions and navigate safely presents serious challenges. Another important challenge is the development of a robust recognition system can account for adverse weather conditions. Sun glare, rain, fog, and snow are adverse weather conditions that can occur in the driving environment. This paper summarizes research focused on automated driving technologies and discuss challenges to identifying adverse weather and other situations that make driving difficult, thus complicating the introduction of automated vehicles to the market. 相似文献
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ZhuHe(朱和);HashimotoTsuneichi(桥本恒一);KatsuraMasahi(桂昌司);KuriyamaKinya(粟山欣弥)MODULATIONOFγ-AMINOBUTYRICACID(GABA)RELEASEFROMRATCE... 相似文献
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Simulation of the oil spill processes in the Sea of Japan with regional ocean circulation model 总被引:1,自引:0,他引:1
Sergey M. Varlamov Jong-Hwan Yoon Naoki Hirose Hideyuki Kawamura Ken Shiohara 《Journal of Marine Science and Technology》1999,4(3):94-107
A simulation of the movement of spilled oil after the incident of the Russian tanker Nakhodka in the Sea of Japan, in January 1997, was performed by a particle tracking model incorporating advection by currents, random
diffusion, the buoyancy effect, the parameterization of oil evaporation, biodegradation, and beaching. The currents advecting
spilled oil were defined by surface wind drift superposed on the three-dimensional ocean currents obtained by the Geophysical
Fluid Dynamics Laboratory modular ocean model (GFDL MOM), which was forced by the climatological monthly mean meteorological
data, or by the European Center for Medium Range Weather Forecasts (ECMWF) daily meteorological data, and assimilated sea
surface topography detected by satellite altimeter. A number of experiments with different parameters and situations showed
that the wide geographical spread of oil observed is not explained by wind drift alone, and that including the simulated climatological
currents gives better results. The combination of surface wind drift and daily ocean currents shows the best agreement between
the model and observations except in some coastal areas. The daily meteorological effect on the ocean circulation model results
in a stronger variability of currents that closely simulates some features of the nonlinear large-scale horizontal turbulent
diffusion of oil. The effect of different parameterizations for the size distribution of model oil particles is discussed.
Received for publication on July 26, 1999; accepted on Nov. 17, 1999 相似文献
8.
Kana Kuroda Yuu Akiyama Yuichiro Keno Naoki Nakatani Koji Otsuka 《Journal of Marine Science and Technology》2014,19(3):280-291
Marine biomass such as seaweed and fishery waste is a potential energy source although it has not yet been practically utilized. This work focuses on renewable energy technologies, particularly anaerobic digestion, for the utilization of various organic wastes as energy resources. Primarily fundamental data for the efficient operation of an anaerobic digestion plant with marine biomass was obtained and a practical operation method was proposed using a simple model based on the carbon mass balance. Batch-processing experiments for seaweed, fishery waste and vegetable waste were carried out and each digestion characteristic was presented. The results indicate that fishery waste is the most efficient even though the accumulation of ammonium ions may inhibit methane production. Seaweeds are not efficient in either the production rate or the yield of methane gas. We investigated the efficient continuous operation for 6 biomass input scenarios with the proposed model. The results show that seaweed can be a useful supplement for the efficient operation. 相似文献
9.
Naoya Umeda Hirotada Hashimoto Akihiko Matsuda 《Journal of Marine Science and Technology》2003,7(3):145-155
We have attempted to develop a more consistent mathematical model for capsizing associated with surf-riding in following
and quartering waves by taking most of the second-order terms of the waves into account. The wave effects on the hull maneuvring
coefficients were estimated, together with the hydrodynamic lift due to wave fluid velocity, and the change in added mass
due to relative wave elevations. The wave effects on the hydrodynamic derivatives with respect to rudder angles were estimated
by using the Mathematical Modelling Group (MMG) model. Then captive ship model experiments were conducted, and these showed
reasonably good agreements between the experiments and the calculations for the wave effects on the hull and the rudder maneuvring
forces. It was also found that the wave effects on restoring moments are much smaller than the Froude–Krylov prediction, and
the minimum restoring arm appears on a wave downslope but not on a wave crest amidship. Thus, an experimental formula of the
lift force due to the heel angle of the ship is provided for numerical modelling. Numerical simulations were then carried
out with these second-order terms of waves, and the results were compared with the results of free-running model experiments.
An improved prediction accuracy for ship motions in following and quartering seas was demonstrated. Although the boundaries
of the ship motion modes were also obtained with both the original model and the present one, the second-order terms for waves
are not so crucial for predicting the capsizing boundaries themselves.
Received: June 20, 2002 / Accepted: October 10, 2002
Acknowledgments. This research was supported by a Grant-in-Aid for Scientific Research of the Ministry of Education, Culture, Sports, Science
and Technology of Japan (No. 13555270). The authors thank Prof. N. Rakhmanin of the Krylov Ship Research Institute for providing
the Russian literature, as well as Mr. H. Murata of NHK (Japan Broadcasting Corporation) for translating it into Japanese.
Address correspondence to: N. Umeda (e-mail: umeda@naoe.eng.osaka-u.ac.jp) 相似文献
10.
This study evaluates an existing bus network from the perspectives of passengers, operators, and overall system efficiency
using the output of a previously developed transportation network optimisation model. This model is formulated as a bi-level
optimisation problem with a transit assignment model as the lower problem. The upper problem is also formulated as bi-level
optimisation problem to minimise costs for both passengers and operators, making it possible to evaluate the effects of reducing
operator cost against passenger cost. A case study based on demand data for Hiroshima City confirms that the current bus network
is close to the Pareto front, if the total costs to both passengers and operators are adopted as objective functions. However,
the sensitivity analysis with regard to the OD pattern fluctuation indicates that passenger and operator costs in the current
network are not always close to the Pareto front. Finally, the results suggests that, regardless of OD pattern fluctuation,
reducing operator costs will increase passenger cost and increase inequity in service levels among passengers. 相似文献