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451.
Amin T. Kiggundu 《Transportation》2009,36(3):275-294
Most major cities across the world today are facing an intractable challenge of financing public transport. In Kuala Lumpur
for example, public transport services are somewhat poor in part because of the failure of major operators to secure ample
funding. Previous funding programs implemented in the city have failed to produce a replicable model for financing public
transport. Due to numerous financial problems and the dismal performance of privately owned transport firms, the State has
in the recent past emerged as a key source of funding for the public transport sector in Kuala Lumpur. This article argues
that, despite the insuperable challenges, prospects for the future funding of public transport in Kuala Lumpur appears to
be good. The article also draws lessons from both Tokyo and Hong Kong. In order to address the funding deficit facing the
public transport industry in the city it is crucial that more viable strategies and policies such as value capture and public–private
sector partnerships are adopted by the urban authorities.
相似文献
Amin T. KiggunduEmail: |
452.
Annually, thousands of unprotected pedestrians are killed or suffer serious injuries in accidents with moving vehicles. Numerous
automobile organizations have performed research on pedestrian safety. The European Enhanced Vehicle- Safety Committee (EEVC),
Working Group 17 (WG17) proposed three component subsystem tests to evaluate the friendliness of a vehicle to pedestrians:
the legform to hood test, the upper legform to bonnet leading edge test and the headform to bonnet top test. In assessing
the pedestrian friendliness of a vehicle, the present study adopted the WG17 regulations of the three component subsystem
tests. We herein describe in detail a finite element subsystem model built to analyze the pedestrian friendliness of a vehicle
using LS-DYNA. The first objective of this study was to simulate these three component subsystem impact tests and evaluate
car front aggressiveness. The second objective was to analyze the frontal structures of a vehicle and, based on the simulation
results, identify dangerous areas and provide suggestions for vehicle front design that may decrease pedestrian injuries.
The analysis of these models and the results obtained may be used to help evaluate the pedestrian friendliness of a vehicle
and guide the future development of pedestrian-friendly vehicle technologies. 相似文献
453.
Hydroplaning tires have been frequently simulated using commercial explicit FEM (Finite Element Method) codes. However, these
simulations are slow, and the result of the lift force is so oscillatory that the hydroplaning speed cannot be accurately
determined. Thus, in the author’s previous study, a new methodology using FDM (Finite Difference Method) code and an FE tire
model iteratively was proposed. However, this full iteration method still required a long computation time, especially for
patterned tires. Thus, in this study, the full iteration methodology was modified such that no iteration or only one additional
iteration was needed at each speed. Then, by applying the full iteration method, no iteration method and one iteration method,
the hydroplaning speeds of a straight-grooved tire were determined, and it was noted that the hydroplaning speed obtained
from the one iteration method was almost the same as that obtained from the full iteration method. Moreover, the hydroplaning
speeds of two patterned tires were determined using the one iteration method, and they were compared with the hydroplaning
speeds obtained experimentally. 相似文献
454.
Y. -M. Kim Y. -G. Kim S. -W. Kim C. -K. Park T. -W. Park 《International Journal of Automotive Technology》2010,11(5):673-680
The performance of brakes has become important due to increased train speeds. The brake system of a train must possess a large
brake force to stop the train safely within a limited stopping distance. However, an excessive brake force deteriorates the
ride comfort and causes the train to skid. Therefore, it is necessary to control the brake force within the adhesion force
limit. This paper presents an analytical method to estimate the relationship between the brake and adhesion forces of a disc
brake system. This method has been applied to the actual disc braking control system of the Korea High-Speed Train (HSR350x),
and the adhesion force is estimated in an actual skid condition. 相似文献
455.
T. J. Kim H. Y. Kim B. C. Hwang H. J. Kang C. Kim 《International Journal of Automotive Technology》2009,10(5):611-618
There are three sub-processes associated with the assembly of an automobile transmission: heat fitting, shrink fitting, and
combination fitting. In the heat fitting stage, the gear is heated to a specified temperature and then squeezed towards the
outer diameter of the shaft. The stress of the heat-fitted gear depends on the yield strength of the gear. In the shrink fitting
process, the gear is typically squeezed towards the shaft at room temperature using a press. An alternate method, known as
warm shrink fitting, heats the already warm gear and safely squeezes it toward the shaft. The warm shrink fitting process
for automobile transmission parts is becoming more commonplace, but the additional heating can cause the dimensions of the
assembled parts (shaft/gear) to change with respect to both the outer diameter and the profile of the gear. As a result, there
may be additional noise and vibration between gears. To address these problems, we analyzed the warm shrink fitting process
using the contact pressure caused by fitting interference between the outer diameter of the shaft and the inner diameter of
the gear, fitting temperature, and the profile tolerance of the gear as design parameters. In this study, a closed form equation
for predicting the contact pressure and fitting load is proposed. This equation is used to develop an optimization technique
for the warm shrink fitting process. The reliability of the model was verified using experimental results measured in the
field, and FEM with thermal-structural coupled field analysis. Actual loads measured in the field showed good agreement with
the results obtained by theoretical and finite element analysis, and expansion of the outer diameters of the gears agreed
well with the results. 相似文献
456.
Y. Tsutsumi A. Iijima K. Yoshida H. Shoji J. T. Lee 《International Journal of Automotive Technology》2009,10(6):645-652
The Homogeneous Charge Compression Ignition (HCCI) engine has attracted much interest because it can simultaneously achieve
high efficiency and low emissions. However, the ignition timing is difficult to control because this engine has no physical
ignition mechanism. In addition, combustion proceeds very rapidly because the premixed mixture ignites simultaneously at multiple
locations in the cylinder, making it difficult to increase the operating load. In this study, an HCCI engine was operated
using blended test fuels comprised of dimethyl ether (DME) and methane, each of which have different ignition characteristics.
The effects of mixing ratios and absolute quantities of the two types of fuel on the ignition timing and rapidity of combustion
were investigated. Cool flame reaction behavior, which significantly influences the ignition, was also analyzed in detail
on the basis of in-cylinder spectroscopic measurements. The experimental results revealed that within the range of the experimental
conditions used in this study, the quantity of DME supplied substantially influenced the ignition timing, whereas there was
little observed effect from the quantity of methane supplied. Spectroscopic measurements of the behavior of a substance corresponding
to HCHO also indicated that the quantity of DME supplied significantly influenced the cool flame behavior. However, the rapidity
of combustion could not be controlled even by varying the mixing ratios of DME and methane. It was made clear that changes
in the ignition timing substantially influence the rapidity of combustion. 相似文献
457.
Journal of Marine Science and Technology - The rudder force, including interference with a ship hull in large drifting conditions, is investigated in this study by captive model tests using a ship... 相似文献
458.
Vagale Anete Bye Robin T. Oucheikh Rachid Osen Ottar L. Fossen Thor I. 《Journal of Marine Science and Technology》2021,26(4):1307-1323
Journal of Marine Science and Technology - Artificial intelligence is an enabling technology for autonomous surface vehicles, with methods such as evolutionary algorithms, artificial potential... 相似文献
459.
This paper proposes a current sensorless drive method by using the mathematical modeling of a surface-mounted permanent magnet synchronous motor (SPMSM) and a dead-time compensation method to reduce the calculated current error caused by differences between real output voltages and voltage commands. The proposed method is implemented by using only a processor algorithm internally, i.e., without any voltage-sensing circuit hardware, such as filtering circuits and current sensor feedback circuits. To show the effectiveness of the proposed method, MATLAB simulations are carried out with an Electric Power Steering (EPS) System containing an SPMSM, a motor drive system and a mechanical gear system. The result shows the validity of the proposed method. 相似文献
460.
Experiments regarding the modification of the foil geometry and/or active or passive mass injection in the vortex core have been performed to investigate the possibility of inhibiting tip vortex cavitation. The ejection at very low flow rates of drag-reducing polymer solutions at the tip of hydrofoils and propeller blades has demonstrated effectiveness as a tip vortex cavitation inhibitor. This paper reports the results obtained with an elliptical hydrofoil, of 8cm maximum chord and 12cm haif-span, operating at Reynolds numbers, of =106, much larger than those previously reported in the literature. Lift coefficients and critical cavitation numbers were determined for a variety of flow and polymer solution ejection conditions. Tangential and axial components of the mean velocity as well as velocity fluctuations along the vortex path were also measured. At 12.5 m/s free stream velocity and a variety of angles of attack, the ejection of a 500 ppm aqueous solution of a drag-reducing polymer at a flow rate of about 5 cm3/s leads to a decrease of up to 30% in the cavitation number. This occurs without modification of the lift coefficient and, hence, of the midspan bound circulation of the foil. Moreover, water injection does not cause any appreciable change in the cavitation numbers. The tangential velocity profiles along the vortex path during polymer ejection indicate that the potential region remains the same, while the viscous core dimension increases, and the maximum tangential velocity decreases substantially as compared to the no ejection or water ejection experiments. Thus, the pressure coefficients at the vortex axis are smaller than for the no ejection or water ejection cases and cause the reduction of the critical cavitation numbers. It is speculated that this inhibition effect is due only to swelling of the polymer solution when exiting the ejection orifice.List of symbols
a
core radius (distance to the vortex axis for maximum tangential velocity)
-
C
1
lift coefficient
-
c
max
maximum chord
-
Cp
pressure coefficient at the vortex axis
-
Cp
min
minimum pressure coefficient at the vortex axis
-
d
e
diameter of the ejection port
-
m
ejection flow rate
-
P
reference pressure
-
P
v
vapor pressure
-
V
free stream velocity
-
V
a
axial velocity
-
V
t
tangential velocity
-
v
r
radial component of the velocity resulting from jet swelling
-
x
downstream distance from the tip of the foil
-
y, r
distance to the vortex axis
-
angle of attack
- r
difference between the swollen jet and the ejection port radii
-
boundary layer thickness
-
tip vortex intensity
-
d
(
de
)
desinent cavitation number (with ejection)
-
i
(
ie
)
inception cavitation number (with ejection)
-
ii
normal stresses
-
viscosity
-
v
kinematic viscosity
-
p
specific mass 相似文献