• International Journal of Automotive Technology
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• v.6 no.3
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• pp.221-227
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• 2005

Aim of this study is to investigate an aerodynamic effect of a drag-reducing device on a heavy-duty truck. The vehicle experiences two different kinds of aerodynamic forces such as drag and uplifting force (or downward force) as it is traveling straight forward at constant speed. The drag force on a vehicle may cause an increase of the rate of fuel consumption and driving instability. The rolling resistance of the vehicle may be increased as result of the negative uplifting or downward force on the vehicle. A device named roof-fairing system has been applied to examine the reduction of aerodynamic drag force on a heavy-duty truck. As for a engineering design information, the drag-reducing system should be studied theoretically and experimentally for the best efficiency of the device. Four different types of roof-fairing model were considered in this study to investigate the aerodynamic effect on a model truck. The drag and downward force generated by vehicle has been obtained from numerical calculation conducted in this study. The forces produced on four fairing models considered in this study has been compared each other to evaluate the best fairing model in terms of aerodynamic performance. The result shows that the roof-fairing mounted truck has bigger negative uplifting or downward force than that of non-mounted truck in all speed ranges, and drag force on roof-fairing mounted truck has smaller than that of non-mounted truck. The drag coefficient $(C_D)$ of the roof-fairing mounted truck (Model-3) is reduced up to $41.3\%$ than that of non-mounted trucks (Model-1). A downward force generated by a roof-fairing mounted on a truck is linearly proportional to the rolling resistance force. Therefore, the negative lifting force on a heavy-duty truck is another important factor in aerodynamic design parameter and should be considered in the design of a drag-reducing device of a tractor-trailer. According to the numerical result obtained from present study, the drag force produced by the model-3 has the smallest of all in all speed ranges and has reasonable downward force. The smaller drag force on model-3 with 2/3h in height may results of smallest thickness of boundary layer generated on the topside of the container and the lowest intensity of turbulent kinetic energy occurs at the rear side of the container.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.2
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• pp.123-130
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• 2013

The responses of a bridge due to a moving vehicle are obtained analytically by modeling a vehicle as a constant point force. From the results it is found that the responses after a vehicle leaves the bridge become very small for some speeds of a vehicle. When a vehicle is modeled as a two dof system for a more accurate analysis, the same phenomenon is observed while the roughness of the surface of the bridge is small. Determining the fundamental frequency of a bridge so that one of the above speeds coincides with a frequent speed of vehicles, the responses of a bridge can be minimized.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.40-45
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• 2009

This article deals with the transient analysis using multi-flexible body dynamics of a trailer vehicle, which is passing a bump on the flat road. In order to investigate the transient dynamic behavior of the trailer, we developed an equivalent finite element model for the trailer and a vehicle dynamic model for the truck using multi-body dynamics. The driving condition considered here is set as the trailer vehicle passes a bump on the flat road in 7km/h. And we investigate the time histories of vertical load and deflections on connecting points between the trailer and truck during the vehicle passes a bump. Due to the dynamic load resulted from the driving condition, additional stress concentrations are found in the trailer and the suspension connecting points between the trailer and rear axles along with kingpin.

• Journal of Auto-vehicle Safety Association
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• v.7 no.2
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• pp.32-38
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• 2015

A sine with dwell test is well known as a test scenario for evaluation of performance of electronic stability control(ESC) on passenger vehicles and heavy commercial vehicles. However, when it comes to ESC for medium commercial vehicles, the test scenario has not been established yet. In this paper, the sine with dwell test was modified considering characteristics of medium commercial vehicles. The three main modifications of the original test scenario are the steering angle level, steering frequency, and loading condition of the vehicle. These modifications are derived from simulation study for different medium commercial vehicles. From simulation study, it was shown that the ESC system for medium commercial vehicle is objectively evaluated by the proposed test scenario. A clear improvement on vehicle stability was seen in the results when ESC system was used.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.825-830
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• 2007

For the design and maintenance of highways and road structures, the statistical data are needed for the vehicle, especially heavy truck crossing. So far, static weighing has been used but it needs fixed station, crews, and it takes a lot of time. Also truck mix and headway distances cannot be obtained. Weigh-In-Motion system uses the sensor as a weighing scale and collects the axle weights, axle distances, vehicle types and etc. without stopping or slowing down the vehicle. Objectives of the study is make a determination of WIM Sensor for Implementation of U-Overloaded Vehicle Regulation System.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.139-147
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• 2007

In military transportation, the use of wide trailer for transporting the large and heavy weight equipments such as tank, armoured vehicle, and mobile gunnery is quite common. So, the vulnerability of causing traffic accidents for these wide military trailer to bump or collide with another car in adjacent lane is very high due to its broad width in excess of its own lane's width. Also, the possibility of these strayed accidents can be increased especially by the careless driver. In this paper, the recognition system of lane and vehicle headway direction is developed to detect the possible collision and warn the driver to prevent the fatal accident. In the system development, Kalman filtering is used first to extract the border of driving lane from the video images supplied by the CCD camera attached to the vehicle and the driving lane detection is completed with regression analysis. Next, the vehicle headway direction is recognized by using neural network scheme with the extracted parameters of the detected driving lane feature. The practical experiments for the developed system are also carried out in the real traffic road of Seoul city area and the results show us the more than 90% accuracy in recognizing the driving lane and vehicle headway direction.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.101-112
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• 2021

SpaceX shows various strategies such as constructing various payload portfolio through the reuse of Falcon 9 and Falcon Heavy, constructing the launch vehicles using one type of engine, the transition from kerosene engine to methane engine, and the use of 3D printing. In this study, launch vehicle proposals that can cover a variety of payloads and trajectories from KOMPSAT to GEO-KOMPSAT were constructed, and ten launch vehicles using kerosene gas generator cycle engine, kerosene staged-combustion cycle engine, and methane staged-combustion cycle engine were reviewed. Of the ten launch vehicles, the reusable launch vehicle using a 35-ton methane engine was rated as the best in terms of development potential.

• Coupled systems mechanics
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• v.3 no.2
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• pp.147-170
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• 2014

In the recent times, dimensions of heavy load carrying vehicle have changed significantly incorporating structural flexibility in vehicle body. The present paper outlines a procedure for the estimation of bridge response statistics considering structural bending modes of the vehicle. Bridge deck roughness has been considered to be non homogeneous random process in space. Influence of pre cambering of bridge surface and settlement of approach slab on the dynamic behavior of the bridge has been studied. A parametric study considering vehicle axle spacing, mass, speed, vehicle flexibility, deck unevenness and eccentricity of vehicle path have been conducted. Dynamic amplification factor (DAF) of the bridge response has been obtained for several of combination of bridge-vehicle parameters. The present study reveals that flexible modes of vehicle can reduce dynamic response of the bridge to the extent of 30-37% of that caused by rigid vehicle model. However, sudden change in the bridge surface profile leads to significant amount of increment in the bridge dynamic response even if flexible bending modes remain active. The eccentricity of vehicle path and flexural/torsional rigidity ratios plays a significant role in dynamic amplification of bridge response.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1293-1303
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• 2006

This paper represents a comparison the difference between existence and nonexistence of soundproof trees for road traffic noise. Also we suggested that the simple equation has been derived using a single regression analysis for predicting levels of $Leq_{th}$ at a given distance from a road in terms of the flow rate, the mean speed of the traffic, and the percentage of the type vehicles in the existence and nonexistence of soundproof trees. We classified a vehicle into four and analyzed contribution rate to traffic volume. As a result, the order showed as followed: light vehicle>medium vehicle>heavy vehicle>motorcycle. However, the results of analyzing contribution rate with between traffic volume and traffic noise by the each type showed as followed; Motorcycle>Light vehicle>Medium vehicle>Heavy vehicle. This study showed that the most a lof of traffic volumes of the three vehicles(light vehicle, medium vehicle and motorcycle) and heavy vehicle were existed in 67 km/h and 61 km/h of car speed, respectively. The total traffic noise to the mean car speed decreased because of the inflow a lot of traffic volumes between 2016 and 2388 in the range of 67 km/h of light vehicle speed, in traffic composition of 4.75% heavy vehicles, and 1.11% motorcycle. the final result for this study showed that statistical paired t-test for between existence and nonexistence of soundproof trees was significant(p<0.05) and the difference between daytime and night in the location of the nonexistence of plant communities with the independent sample T-test was significant(p<0.05). However, the independent sample T-test for analyzing the variance of traffic noise between daytime and night was not significant(p>0.05).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.77-86
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• 1993

Recently it is reported in many countries that highway bridges are seriously damaged due to increasing volume of overloaded heavy vehicles. The safety of bridges are highly related to the design load level and the characteristics of extreme load effect induced by traffic loads during its lifetime. The maximum structural load effect during lifetime may be produced by simultaneous loading of trucks with moderate weights on a bridge rather than by single loading of extremely heavy trucks. In this study, a simulation technique to estimate extreme load effect due to traffic loadings has been developed, in which important characteristics of traffic loadings, such as heavy vehicle proportion, traffic mode, vehicle weights, headway distribution. daily traffic volume, etc., should be properly considered. In addition. sensitivity analysis on those factors have been performed.