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1.
Katsuya Tanifuji Tsukasa Sato Roger Goodall 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,39(4):309-327
Summary This paper deals with a basic study on the actively steered rail vehicle with two-axle bogie trucks, which employs a control law based on the self-steering ability of wheelset. However, this control law not only helps the steering performance, but also tends to lower the running stability. Two methods are proposed to improve the stability. The first method is to add a feedback of wheelset lateral velocity, the second one is to give some time lag to the control force, and both are proved to be affective. Here, the latter is more practical method and the delay of control due to the time lag does not deteriorate the steering performance. 相似文献
2.
Naoya Umeda Akihiko Matsuda Masami Hamamoto Shiro Suzuki 《Journal of Marine Science and Technology》1999,4(2):45-57
A systematic method for assessing intact ship stability with a free-running model in a seakeeping and maneuvering basin is
proposed in this paper. Model experiments were carried out in extremely steep regular waves for a model drifting, running
in head seas, and quartering seas. This method was applied to two purse seiners, and efficiently identified thresholds in
metacentric heights for capsizing of these ships. These capsizing thresholds are compared with requirements of the IMO Code
on Intact Stability. This series of model experiments also confirms that capsizing at the threshold occurs only in quartering
seas, and shows that capsizing is caused by broaching, loss of stability on a wave crest, or bow diving.
Received for publication on Jan. 20, 1999; accepted on July 6, 1999 相似文献
3.
Structural pipe-in-pipe cross sections have significant potential for application in offshore oil and gas production systems
because they combine thermal insulation performance with structural strength and self weight in an integrated way. Such cross
sections comprise inner and outer thin-walled pipes with the annulus between them fully filled by a selectable filler material
to impart an appropriate combination of properties. Structural pipe-in-pipe cross sections can exhibit several different collapse
mechanisms, and the basis of the preferential occurrence of one over the others is of interest. This article presents an exact
analysis for predicting the elastic buckling behaviours of a structural pipe-in-pipe cross section when subjected to external
hydrostatic pressure. Simplified approximations are also investigated for elastic buckling pressure and mode when the outer
pipe and its contact with the filler material is considered as a pipe on an elastic foundation. Results are presented to show
the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler
thickness, and the thicknesses of the inner and outer pipes. Case studies based on realistic application scenarios are used
to show that the simplified approximations are sufficiently accurate for practical structural design purposes. 相似文献
4.
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
5.
A series of elastoplastic large deflection FEM analyses has been performed on hatch covers of bulk carriers subjected to lateral load. Two types of hatch covers are considered which are the folding type and the side-sliding type. For the folding-type cover, one size is considered which is for Handy size bulk carrier, whilst for the side-sliding-type cover, two sizes are considered which are for Panamax and Cape size bulk carriers. For each type, two hatch covers are selected which are designed in accordance with the old ICLL rule and new IACS rule, respectively. Calculated collapse strengths are compared with individual design loads, and a strength assessment is performed. On the basis of collapse behaviour observed in FEM analyses, a simple method is proposed to evaluate the collapse strength of a hatch cover subjected to lateral load. It is confirmed that the collapse strength is accurately predicted by the proposed method. 相似文献
6.
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
7.
A free-fall microstructure profiler (TurboMAP) reveals highly intermittent features in the fluorescence field. Conventional CTDs that mount a fluorometer are usually deployed with a tethered cable, and the data are averaged or smoothed over a given time or water depth. Because of the nature of the operation and the data processing involved, intermittent features of fluorescence fields are masked. We have developed a statistical technique to extrapolate the intermittency using a lognormal mixture probability density function (mixture pdf). The statistics obtained from the mixture pdf are consistent with microstructure data, thus the conventional CTD can provide statistics appropriate to a micro-scale fluorescence field. 相似文献
8.
CFD simulation of 3-dimensional motion of a ship in waves: application to an advancing ship in regular heading waves 总被引:1,自引:0,他引:1
A new computational fluid dynamics simulation method has been developed for the unsteady motion of a ship advancing in waves.
The objective is to evaluate the added resistance and predict the performance of a ship in waves. In this study, a finite
volume method, in the framework of a boundary-fitted grid system, is employed. The motion of the ship is solved with six degrees
of freedom by using the hydrodynamic forces and moments obtained from the solution of the simulation method. The marker–density–function
method is employed to calculate the nonlinear free surface. This method is applied to the coupled motion problem of heaving
and pitching.
Received for publication on Nov. 15, 1999; accepted on Nov. 18, 1999 相似文献
9.
介绍了在新干线700系车组的开发中,为降低空气动力噪声,对车体外形、受电弓、超压母线所进行的改进。 相似文献
10.
Timothy Lilienthal Akihiko Matsuda Giles Thomas 《Journal of Marine Science and Technology》2007,12(2):111-118
This article presents work based on the development of a performance-based stability assessment method. It describes a numerical
method used to determine the survival limit for a dynamic intact stability assessment procedure. The numerical method utilises
a time-domain vessel motion program to assess the limit for a range of vertical centres of gravity (KG). The appropriateness
of the numerical predictions was examined through comparison with model experiment results. Free-running model tests were
conducted in regular following waves at discrete KGs. A comparison between the survival limits determined through the numerical
and experimental methods is presented. The current International Maritime Organisation (IMO) stability criteria are also evaluated
against the numerical and experimental dynamic performance-based stability assessment methods. 相似文献