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361.
Justin S. Chang Soo Yon Cho Beom Shin Lee Yonghwan Kim Suk Kang Yun 《Transportation》2012,39(1):33-54
The total economic value for a transportation service consists of use, option, and non-use value. The use benefit is based
on a traveler’s willingness to pay for usual consumption of the service. The optional value, on the other hand, is related
to the possible use of the service for trips not yet anticipated or currently accommodated by other travel modes. The non-use
value, however, is derived from the intrinsic merit of the service, even though a trip-maker never actually or potentially
depends on the mode. A closed-ended contingent valuation method is considered for the quantification of the option and non-use
values. A survey of single- and double-bounded dichotomous choices is conducted with a case study of South Korean bus operations.
A logistic regression model and a survival analysis for the single- and double-bounded approaches, respectively, are applied.
The estimation result is examined according to the statistical property required and the behavioral validity expected. In
particular, three issues from the output are discussed. First, the results help to show the preferable framework between single-
and double-bounded surveys for addressing an individual’s option and non-use values. Second, the differences in the absolute
values of option and non-use values are compared. Thirdly, the relationship between trip-makers’ willingness to pay and the
level of service of their primary travel modes are investigated. In conclusion, the summary of research and the possibilities
for future studies are given. 相似文献
362.
Hwa-Joong KimYoung-Tae Chang Kwang-Tae KimHyo-Jeong Kim 《Transportation Research Part D: Transport and Environment》2012,17(2):97-103
This paper provides an algorithm to minimize the fixed ordering, purchase, and inventory-carrying costs associated with bunker fuel together with ship time costs; and environmental costs associated with greenhouse gas emissions. It determines the optimum ship speed, bunkering ports, and amounts of bunker fuel for a given ship’s route. To solve the problem, we use an epsilon-optimal algorithm by deriving a property. The algorithm is illustrated by applying it to typical sample data obtained and the effects of bunker prices, carbon taxes, and ship time costs on the ship speed are analyzed. The results indicate that the ship speed and CO2 emissions are highly sensitive to the factors considered. 相似文献
363.
This paper studies the springing response of a flexible floating barge under an oblique wave. A time domain Rankine panel
method was used to represent fluid motion surrounding a flexible seagoing vessel, and a finite element method was used for
structural response. For accurate prediction of the structural response under an oblique wave, special attention was given
to the structural model, such as the effect of warping distortion and bending-torsion coupling. The Vlasov assumption was
followed for a deformable beam element to take into account the effect of warping distortion so that the cross section of
the beam deforms out of its original plane without changing its cross-section contour. The coupled equation for both the fluid
and structural domain was solved by using the implicit iterative method. A fixed point iteration with a relaxation scheme
was employed in this study with the aid of the Aitken δ2 process seeking acceleration of solution convergence. Accuracy of a developed computer program was verified through the comparison
with experimental work done by Remy et al. (Experimental and numerical study of the wave response of a flexible barge, Hydroelasticity in Marine Technology, Wuxi, 2006) resulting in good correspondence between the two results. 相似文献
364.
Computational predictions of ship-speed performance 总被引:1,自引:0,他引:1
Jung-Eun Choi Jung-Hun Kim Hong-Gi Lee Bong-Jun Choi Dong-Hyun Lee 《Journal of Marine Science and Technology》2009,14(3):322-333
This paper examines ship-speed performance based on acomputational method. The computations are carried out under identical
model conditions, i.e., resistance and self-propulsion tests, to predict the speed-power relationship. The self-propulsion
point is obtained from the self-propulsive computational results of two propeller rotative speeds. The speed-power relationship
in full scale is obtained through analyzing the computational results in model scale according to the model-ship performance
analysis method of ITTC’78. The object ship is a VLCC. The limiting streamlines and the distribution of the pressure coefficient
on the hull, the wake characteristics on the propeller plane, and the wave characteristics around a model ship are also investigated.
After completing the computations, a series of model tests are conducted to evaluate the accuracy of the predictions by comparing
the computational results with the experimental results. 相似文献
365.
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
366.
The object of this study is to analyze the characteristics of vortex-induced vibration of a slender marine structure with the numerical method. Applying a dynamic analysis method for a slender marine structure based on the 3D finite difference method, we carried out case studies for a tensioned beam model at a constant flow speed. The hydrodynamic forces, in the direction of inline and cross-flow, created by vortex shedding are simultaneously considered based on Morison equation. The frequency of force in the inline direction corresponding to the unstable zone is evaluated. An eigenvalue analysis for different flow speeds of a tensioned beam considering the effect of the tension increase due to the inline and cross-flow drag forces is performed. We found that a revision of the eigenvalue should be considered if the tension along a riser or beam is significantly affected by an environmental or functional load. From a trajectory on the XY plane it was shown that the riser did not move in an exact 8 shape for all flow conditions due to the phase angle difference between inline and cross-flow displacement. It is believed that the phase angles between inline and cross-flow displacements in high modes are different among the nodes. 相似文献
367.
A knowledge-based flow process is presented for large injection-molded body technology (LIMBT). Injection molding of a large body is a difficult technique because of the many factors and their interactions during the molding process. The proposed flow process can support LIMBT through integration of CAE(Computer-Aided Engineering), CAI (Computer-Aided Inspection), and monitoring systems. CAE and DOE (Design of Experiment) are used to construct an optimal mold design in terms of gates and runners and to identify working conditions for the molding process. CAI and monitoring systems with temperature sensors and pressure sensors can be used to inspect the physical molding process and the molded parts. The flow process of a large body is systematically planned and constructed using a knowledge-based flow process with DOE and computer-aided technologies. The proposed flow process is implemented for the molding process of an automobile front bumper fascia. 相似文献
368.
M. H. Lee K. S. Lee H. G. Park Y. C. Cha D. J. Kim B. Kim S. Hong H. H. Chun 《International Journal of Automotive Technology》2012,13(5):801-807
This paper proposes a lateral control system for an unmanned vehicle that is designed to improve the responsiveness of the system with the use of a PD control. The vehicle heading error can be stabilized, and the transient response characteristics can be improved using the proposed controller. A mathematical model of the vehicle dynamics using two degrees of freedom was developed for the controller design. The waypoint tracking method for autonomous navigation was tested with incorporation of the Point-to-Point algorithm with position and heading measurements received from GPS receivers via Kalman filtering. The performance of the designed controller was verified through experiments with a real vehicle. 相似文献
369.
The brake and steering systems in vehicles are the most effective actuators that directly affect the vehicle dynamics. In general, the brake system affects the longitudinal dynamics and the steering system affects the lateral dynamics; however, their effects are coupled when the vehicle is braking on a non-homogenous surface, such as a split-mu road. The yaw moment compensation of the steering control on a split-mu road is one of the basic functions of integrated or coordinated chassis control systems and has been demonstrated by several chassis suppliers. However, the disturbance yaw moment is generally compensated for using the yaw rate feedback or using wheel brake pressure measurement. Access to the wheel brake pressure through physical sensors is not cost effective; therefore, we modeled the hydraulic brake system to avoid using physical sensors and to estimate the brake pressure. The steering angle controller was designed to mitigate the non-symmetric braking force effect and to stabilize the yaw rate dynamics of the vehicle. An H-infinity design synthesis was used to take the system model and the estimation errors into account, and the designed controller was evaluated using vehicle tests. 相似文献
370.
K. -B. Kim K. -W. Choi K. -H. Lee 《International Journal of Automotive Technology》2012,13(3):401-407
A relatively new approach for improving fuel economy and automotive engine performance involves the use of automotive combined
cycle generation technologies. The combined cycle generation, a process widely used in existing power plants, has become a
viable option for automotive applications due to advances in materials science, nanotechnology, and MEMS (Mico-Electro Mechanical
Systems) devices. The waste heat generated from automotive engine exhaust and coolant is a feasible heat source for a combined
cycle generation system, which is basically a Rankine cycle in the context of this study. However, there are still numerous
technical issues that need to be solved before the technology can be implemented in automobiles. A simulation was performed
to examine the amount of waste energy that could be recovered through the use of a combined cycle system. A simulation model
of the Rankine cycle was developed using Cycle-Tempo software. The simulation model was ultimately used to evaluate the rate
of waste heat recovery and the consequential increase in the overall thermal efficiency of the engine with the combined cycle
generation system under typical engine operating conditions. The most effective automotive combined cycle system recovered
68% of the waste heat from the exhaust and coolant, resulting in a 6% improvement in engine efficiency. The results are expected
to be beneficial for evaluating the feasibility of combined cycle generation systems in automotive applications. 相似文献