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371.
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
372.
J. Kim N. Kim S. Hwang Y. Hori H. Kim 《International Journal of Automotive Technology》2009,10(6):733-742
A motor control strategy for an input-split hybrid electric vehicle (HEV) is proposed. From a power characteristic analysis,
it is found that the powertrain efficiency decreases for speed ratios at which power circulation occurs. Using dynamic models
of an input-split HEV powertrain, a motor-generator control algorithm for obtaining high system efficiency is designed by
inversion-based control. The performance of the control algorithm is evaluated by the simulator which is developed based on
PSAT, and simulation results are compared with the test results. It is found that, even if the engine thermal efficiency is
sacrificed by moving the engine operation point from the OOL for the control strategy, improved overall powertrain system
efficiency can be achieved by the engine operation that gives a relatively high efficiency from the viewpoint of the overall
powertrain efficiency. The control algorithm developed can be used in design of future electric vehicles. 相似文献
373.
H. G. Jung Y. H. Lee H. J. Kang J. Kim 《International Journal of Automotive Technology》2009,10(2):219-228
This paper discusses the market trends and advantages of a safety system integrating LKS (Lane Keeping System) and ACC (Adaptive
Cruise Control), referred to as the LKS+ACC system, and proposes a method utilizing the range data from ACC for the sake of
lane detection. The overall structure of lane detection is the same as the conventional method using monocular vision: EDF
(Edge Distribution Function)-based initialization, sub-ROI (Region Of Interest) for left/right and distance-based layers,
steerable filter-based feature extraction, and model fitting in each sub-ROI. The proposed method adds only the system for
confining lane detection ROI to free space that is established by range data. Experimental results indicate that such a simple
adaptive ROI can overcome occlusion of lane markings and disturbance of neighboring vehicles. 相似文献
374.
375.
Jong-Chun Park Moo-Hyun Kim Hideaki Miyata 《Journal of Marine Science and Technology》2001,6(2):70-82
A finite-difference scheme and a marker-and-cell (MAC) method are used for numerical wave tank (NWT) simulations to investigate
the characteristics of nonlinear wave motions and their interactions with a stationary three-dimensional body in the presence
of steady uniform currents. The Navier–Stokes (NS) equation is solved in the computational domain, and the boundary values
are updated at each time-step by a finite-difference time-marching scheme in the frame of a rectangular coordinate system.
The fully nonlinear kinematic free-surface condition is satisfied by the marker–density function technique developed for two
fluid layers. The incident waves are generated from the inflow boundary by prescribing a velocity profile resembling the motions
of a flexible flap wavemaker, and the outgoing waves are numerically dissipated inside an artificial damping zone located
at the end of the tank. Using the NS–MAC NWT, nonlinear wave and current interactions around a stationary vertical truncated
circular cylinder are studied, and the results are compared with the experimental results of Mercier and Niedzwecki, a time-domain
NWT based on linear potential theory, a fully nonlinear NWT, and a second-order diffraction computation.
Received: July 3, 2001 / Accepted: September 25, 2001 相似文献
376.
Identifying accurate origin-destination (O-D) travel demand is one of the most important and challenging tasks in the transportation planning field. Recently, a wide range of traffic data has been made available. This paper proposes an O-D estimation model using multiple field data. This study takes advantage of emerging technologies – car navigation systems, highway toll collecting systems and link traffic counts – to determine O-D demand. The proposed method is unique since these multiple data are combined to improve the accuracy of O-D estimation for an entire network. We tested our model on a sample network and found great potential for using multiple data as a means of O-D estimation. The errors of a single input data source do not critically affect the model’s overall accuracy, meaning that combining multiple data provides resilience to these errors. It is suggested that the model is a feasible means for more reliable O-D estimation. 相似文献
377.
The adequate provision of charging infrastructure is critical for the effective deployment of electric taxis. This study attempts to locate charging stations for electric taxis reflecting real-world taxi travel patterns identified from taxis equipped with digital tachographs. Data for one week are processed in order to estimate their charge demand. The estimated temporal distribution of charge demand indicates that it varies day-by-day and hour-by-hour. The maximum set covering model is applied for determining the locations of charging stations. The results show that the pre-specified service distance and service coverage rate (defined by the proportion of total demand served) can be critical factors for determining the number and location of charging stations. These factors should be carefully specified by considering the tradeoff between operational efficiency of charging facilities and user convenience. 相似文献
378.
Valuable mineral resources are widely distributed throughout the seabed. autonomous underwater vehicles (AUVs) are preferable
to remotely-operated vehicles (ROVs) when probing for such mineral resources as the extensive exploration area makes it difficult
to maintain contact with operators. AUVs depend on batteries, so their power consumption should be reduced to extend exploration
time. Power for conventional marine instrument systems is incorporated in their waterproof sealing. External intermittent
control of this power source until termination of exploration is challenging due to limitations imposed by the underwater
environment. Thus, the AUV must have a power control system that can improve performance and maximize use of battery capacity.
The authors developed such a power control system with a three-step algorithm. It automatically detects underwater operational
states and can limit power, effectively decreasing power consumption by about 15%. 相似文献
379.
Spatial and temporal variability in the pelagic ecosystem of the East Sea (Sea of Japan): A review 总被引:1,自引:0,他引:1
Jae-Young Lee Dong-Jin Kang Il-Nam Kim Taekeun Rho Tongsup Lee Chang-Keun Kang Kyung-Ryul Kim 《Journal of Marine Systems》2009,78(2):288
The East Sea (Sea of Japan) is a unique marginal sea because it exhibits features of oceanic dynamics of much larger ocean basins. This semi-enclosed basin may be considered as a model or microcosm for understanding of how biological processes and distributions in pelagic ecosystem are interacting with physical processes in highly dynamic ocean regions. This overview summarizes the recent progresses concerning spatial and temporal variability of pelagic ecosystem components form an interdisciplinary point of view. Spatial characteristics of physical environments and biogeography in the region are distinguished mainly by the subpolar front. It was also found that long-term changes in biomass and community structure as well as those in the physical and biological environments are associated with climate variability in the region. We conclude by identifying main needs for the information and researches, particularly regular and long-term sampling, and permanent monitoring if possible. 相似文献
380.
Yoo-Chul Kim Tae-Wan Kim Sangwoo Pyo Jung-Chun Suh 《Journal of Marine Science and Technology》2009,14(2):161-170
We refine the geometry of a propeller by modifying the blade sections to align them with surface streamlines, obtained by
the panel method. Redefinition of the blade sections aligned with the streamlines is provided together with surface modeling
scheme by which model propellers were built. Numerical simulations and open-water tests on models suggest a possible increase
of 1% in propeller efficiency. 相似文献