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11.
Nancy D. Yamaguchi 《Maritime Policy and Management》1999,26(4):327-336
The 'Asian 'flu' has caused uncertainty about the future of product shipping in Asia. Product shipping is a difficult business, subject to the vagaries of such factors as local and regional supply/demand imbalances, refinery inputs, outputs and utilization rates, storage and terminalling considerations, product quality differences, price differentials, seasonal variations, and port traffic. This paper covers the Asia-Pacific product demand and trade by type in four major submarkets: Australasia, Southeast Asia, South Asia and East Asia. Forecasts are created of product demand by type and country, assessing likely additions to refinery capacities, and conducting computer-modelling exercises that simulate refinery output and product blending. The difference between product output and product demand in any given country is assumed to equate to trade. The analysis suggests that Asian economies will recover during the 2000-2005 period, and that there will be an increase in the petroleum product trade. 相似文献
12.
Chang Kyu Rheem Hajime Yamaguchi Hiroharu Kato 《Journal of Marine Science and Technology》1997,2(2):101-121
A new model, called the distributed mass/discrete floe model, is proposed for performing practical computations of mesoscale
pack ice rheology. This model possesses the advantages of both the continuum and the discrete element models: it can express
the discrete nature of pack ice, for which it is difficult to use a continuum model, and requires a much shorter computation
time than a discrete element model. The pack ice is divided into ice bunches in which the floes, assumed to be distributed
uniformly, are modeled as inelastic disks or rectangles floating on the water. The ice interaction forces are formulated from
the relationship between the impulse on the bunch and the variation of momentum in the bunch. The ocean flow is calculated
simultaneously with the floe movement using a multilayer model. In a circulating water channel, drift tests of physical model
floes were performed in order to investigate the characteristics of their motion and interaction with ocean structure models.
Near the structure, the floe motion depends on the floe shape. Disk floes show a lateral motion in front of the structure.
They flow out around both sides of the structure and the number of floes in front of the structure decreases with the lapse
of time. On the other hand, rectangular floes scarcely flow laterally. The number of floes in front of the structure remains
constant over time. These experiments indicate that when the motion of pack ice around a structure is simulated, it is important
to consider the floe shape. The disk floe motion and the rectangular floe motion can be regarded as extreme cases of pack
ice motion. Actual pack ice motion may be between these two extremes. Computations were carried out using the distributed
mass/discrete floe (DMDF) model. Simulation results were compared with the circulating water channel experiment results and
sea ice motion in the southern part of the Sea of Okhotsk. The DMDF model predicted the circulating water channel drift test
results quite closely. The DMDF model results also compared quite well with the sea ice motion. 相似文献
13.
H. Yamaguchi S.-I. Doi N. Iwama Y. Hayashi 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1993,22(5):299-308
The improvements of ride comfort and vehicle maneuverability in the vehicle design can be achieved by using an active suspension. However, the problems in such a control are the complex control logic because of the control laws incompatible with the improvements of ride comfort and maneuverability, and the cost increase because of various sensors to be attached. Therefore, we examined the control abilities of ride comfort and maneuverability on a unique control law using frequency shaped LQ, and controlled the characteristic of the contact between tire and road without a road displacement sensor 相似文献
14.
Hajime Yamaguchi Hiroharu Kato Kazuyuki Matsuda 《Journal of Marine Science and Technology》1996,1(4):198-208
Sound pressure distribution around a monotone sound source was measured inside a marine propeller cavitation tunnel and compared
with the calculated result by a two-dimensional boundary element method. The measured sound pressure distribution showed some
peaks due to the reflection effect of the tunnel test section boundary. As the frequency increased, the sound pressure distribution
became more complicated, showing more peaks. The tunnel reverberant effect should be taken into account when the noise data
measured in the tunnel are converted into full-scale values. In the boundary element method calculation, the boundary condition
at the acrylic observation window of the tunnel was examined in detail. The calculated sound pressure distribution pattern
in the tunnel transverse section agreed well with the measured distribution when a reasonable boundary condition was adopted.
The boundary element method is an effective method for theoretically predicting the acoustic field inside the cavitation tunnel
if the precise boundary condition is adopted. 相似文献
15.
Akihisa Konno Kazuaki Wakabayashi Hajime Yamaguchi Masatsugu Maeda Norio Ishii Shunji Soejima Koyu Kimura 《Journal of Marine Science and Technology》2002,6(4):181-192
The bursting phenomenon of tip vortex cavitation of a propeller sometimes causes severe high-frequency vibration, but its
mechanism has not yet been elucidated. In this study, we carried out model experiments by changing the propellers, wake distributions,
thrust coefficients, and cavitation numbers parametrically, examined the bursting phenomenon with a high-speed video camera,
and measured the pressure fluctuations caused by the phenomenon. We also measured flow distribution around the tip vortex.
As a result, we found that in the bursting phenomenon, large pressure fluctuations occurred twice, and that they strongly
depended on the wake distribution. Two means were suggested to suppress the bursting phenomenon, other than changing the wake
distribution: stabilizing tip vortex cavitation or reducing the cavity volume.
Numerical fluid simulations around a propeller in noncavitating, unsteady conditions were also conducted, and the strength
of the tip vortex along the circumference and its derivative were examined. As a result, the phenomena were parameterized
by the time derivative of the strength of the tip vortex, and if it was higher than a threshold value, the tip vortex cavitation
burst. Therefore, it is possible to predict the occurrence of the bursting phenomenon by numerical analysis.
Received: November 6, 2001 / Accepted: January 24, 2002 相似文献
16.
Katsuhiro Niiro 《Transportation》1989,16(4):279-295
The number of bus passenger has been decreasing in Japan since 1969. The increase in car ownership and development in urban rapid rail network has deprived bus service of passengers. The bus industry has suffered from depression for the last twenty years. However, many bus routes are still operated commercially. The amount of external subsidies is not large. The industry is under strict regulation. The common way for bus operators has been to increase fares rapidly in order to keep their break even condition. The first half of the paper describes present circumstances of the bus industry in more details. Then the second half of the paper treats the estimation of the effect of each factor on bus demand by using pooled data in Japanese medium sized cities. The results suggest that the increase in car ownership has had a crucial effect on local public transport demand and is likely to continue to do so. 相似文献
17.
Dan Walker Neil Bose Hajime Yamaguchi Stephen J. Jones 《Journal of Marine Science and Technology》1997,2(1):12-20
Hydrodynamic loads on a propeller blocked with simulated ice were studied using a cavitation tunnel. Comparative predictions were made using a panel method. The propeller was a model of the Canadian Coast Guard's R-class icebreake propeller, and the ice block was simulated using a solid blockage. Experimental results show the open water performance of the propeller, its performance behind a blockage, and the effects of cavitation in these conditions, as well as the loading on the simulated ice block. Panel method predictions were made of the time series propeller performance in the blocked flow. Cavitation during propellerice interaction resulted in a reduction of mean suction load on the ice block. Block load measurements indicated an increase in the oscillation about the mean value of the loads, with a variation in the phase of the loading with respect to blade position as compared with the non-cavitating results. Comparisons of panel method results with the measured block loads support the reliability of the dynamic measurements.List of symbols
D
propeller diameter
-
F
block drag load
-
K
T
thrust coefficient,T/(n
2
D
4)
-
K
B
block load coefficient,F/(n
2
D
4)
-
K
Q
torque coefficient,Q/(n
2
D
5)
-
Q
propeller torque
-
T
propeller thrust
-
n
propeller rotational speed
-
J
propeller advance coefficientV
A/(nD)
-
P
A
ambient pressure at propeller
-
P
ATM
atmospheric pressure
-
P
V
vapour pressure of water
-
V
A
propeller advance speed
-
dissolved gas content
-
s
saturated dissolved gas content at atmospheric pressure
-
o
open water propeller efficiency
-
cavitation number, (P
A
–P
V
)/(0.5(nD)2)
-
density of water 相似文献
18.
Tadanori Yamaguchi 《国际交通安全学会研究报告》2018,42(4):190-196
In Cambodia, a rider's license is not required for motorcycles below 125?cc. and 73% of traffic accident fatalities among persons aged 15–19?years involve unlicensed riders. Motorcycle riding differs from automobile driving in that motorcycle riding reflects the rider's skill to a much greater degree, so unskilled riding is much more highly correlated with accidents. Going forward, in addition to gaining knowledge from traffic safety education, motorcycle riders should also learn basic specific motorcycle techniques. In particular, having riders learn and practice the three key tasks in motorcycle riding (breaking, leaning, and exiting) is effective at curbing the number of motorcycle accidents. In a new initiative aimed at improving riding skill, university students, instructors, and police officers were given practical riding instruction on a course using pylons. Program participants were able to learn riding techniques in an enjoyable setting, while seeing the potential for becoming motorcycle riding role models. 相似文献
19.
Masuru Sugai Hiroyuki Yamaguchi Masanori Miyashita Takaji Umeno Katsuhiro Asano 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1999,32(4):299-312
In this paper, we propose a new control strategy for an antilock braking system (ABS) to maintain the braking force at maximum. The popularization of the ABS that prevents the wheels from locking has resulted in an improvement of the vehicle stability and shortening of the braking distance. Further improvement is anticipated if the maximization of the braking force is realized. We found an interesting phenomenon in which the characteristics of the resonance system composed of the vehicle body and the wheel and road surface reflects the slip condition of the road surface. Using this phenomenon, we realized a control method for maintaining the maximum value of the braking force. 相似文献
20.
Yoshihisa Takekoshi Takafumi Kawamura Hajime Yamaguchi Masatsugu Maeda Norio Ishii Koyu Kimura Tadashi Taketani Akihiko Fujii 《Journal of Marine Science and Technology》2005,10(2):70-81
A new method for designing propeller blade sections is presented. A vortex lattice method is used to evaluate the performance and the time-dependent pressure distribution on the blade surface in a non-uniform flow, while efficient optimization algorithms are used to modify the blade sections. Two different designs were carried out in this study. The first was a design to realize a target pressure distribution in a rotating three-dimensional flow. A two-dimensional wing theory was used to obtain the target pressure distribution. The predicted increase in efficiency and the reduction in the cavity volume were confirmed by model experiments. The second was a design to maximize the propeller efficiency. By this method, the propeller efficiency was improved by 1.2% under the constrains of constant thrust and a prescribed margin for face cavitation. 相似文献