• Journal of Energy Engineering
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• v.28 no.4
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• pp.35-41
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• 2019

In order to overcome these disadvantages, the halogen light source, which was previously used as a vehicle fog light, has increased power consumption and a short lifetime, and thus, an automobile light source is gradually being replaced with an LED. However, when the vehicle LED fog light is turned on, there is a disadvantage in reducing the life of the fog lamp due to the high heat generated from the LED. The heat generated by the LED inside the fog lamp is mainly emitted by the heatsink, but most of the remaining heat is released to the outside through convection. When cooling efficiency decreases due to convection, thermal energy generates heat to lenses, reflectors, and bezels, which are the main parts of lamps, or generates high temperatures in LED, thereby shortening the life of LED fog lights. In this study, we tried to improve the heat dissipation performance by convection in addition to the heat dissipation method by heat sink, and to determine the installation location of vents that can discharge the internal air or intake the external air of LED fog lamp for vehicle. Thermal fluid analysis was performed to ensure that the optimal data were reflected in the design. The average velocity of air increased in the order of Case3 and Case2 compared to Case1, which is the existing prototype, and the increase rate of Case3 was relatively higher than that of other cases. This is because the vents installed above and below the fog lamps induce the convective phenomena generated according to the temperature difference, and the heat is efficiently discharged with the increase of the air speed.

• Composites Research
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• v.34 no.4
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• pp.241-248
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• 2021

As the electric vehicle market grows, there is an issue of light weight vehicles to increase battery efficiency. Therefore, it is going to replace the battery module cover that protects the battery module of electric vehicles with high strength/high heat-resistant polymer composite material which has lighter weight from existing aluminum materials. It also aims to respond to the early electric vehicle market where technology changes quickly by combining 3D printing technology that is advantageous for small production of multiple varieties without restrictions on complex shapes. Based on the composite material mechanics, the critical length of glass fibers in short glass fiber (GF)/polycarbonate (PC) composite materials manufactured through extruder was derived as 453.87 ㎛, and the side feeding method was adopted to improve the residual fiber length from 365.87 ㎛ and to increase a dispersibility. Thus, the optimal properties of tensile strength 135 MPa and Young's modulus 7.8 MPa were implemented as GF/PC composite materials containing 30 wt% of GF. In addition, the filament extrusion conditions (temperature, extrusion speed) were optimized to meet the commercial filament specification of 1.75 mm thickness and 0.05 mm standard deviation. Through manufactured filaments, 3D printing process conditions (temperature, printing speed) were optimized by multi-optimization that minimize porosity, maximize tensile strength, and printing speed to increase the productivity. Through this procedure, tensile strength and elastic modulus were improved 11%, 56% respectively. Also, by post-processing, tensile strength and Young's modulus were improved 5%, 18% respectively. Lastly, using the FEA (finite element analysis) technique, the structure of the battery module cover was optimized to meet the mechanical shock test criteria of the electric vehicle battery module cover (ISO-12405), and it is satisfied the battery cover mechanical shock test while achieving 37% lighter weight compared to aluminum battery module cover. Based on this research, it is expected that 3D printing technology of polymer composite materials can be used in various fields in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.97-105
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• 1992

The purpose of this study is to provide the cause and countermeasure for track problems in the high speed railways due to the irregularly increasing dynamic wheel loads running over the speed range of 300 km/h. It has long been recognised that the track problems encountered on high speed railways are associated mainly with vertical dynamic loads which are related to the unsprung mass of vehicles and track irregularities. In addition to these parameters for the estimation of the dynamic wheel load variation, however, the dynamic characteristics of track structures are discussed in this paper with reference to mathematical modelling of the tracks and vehicle. From the results of the more detailed analyses, the effects of track stiffness and damping characteristics are considered to be significant for reducing the dynamic wheel loads. To make this point clear and appraise the overall performance of the track components, the theoretical analysis on the dynamic behavior of the tracks and wheel set impact tests on several track structures are performed. The experimental results from different track components are compared with each other. The track stiffness and damping characteristics are also presented quantatively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.623-628
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• 2013

The retrodirective array antenna system is operated faster than existing techniques of beamforming due to its less complexity. Therefore, it is effective for beam tracking in the environment of fast vehicle. On the other hand, it also has difficulty in estimating AOA according to multipath environment or multiuser signals. To improve the certainty of estimating AOA), this article proposes hybrid digital retrodirective array antenna systme combined with MUSIC algorithm. In this paper, the digital retrodirective array antenna system is designed according to the number of antenna array by using only one digital PLL which finds angle of delayed phase. And we evaluate the performance of the digital retrodirective array antenna for the high speed tracking application. Performance is studied by simulink when the speed of mobile is 300km/h and the distance between transmitter and receiver is 100m and then we have to confirm the performance of the system in multi path environment. As a result, the mean of AOA (Angle Of Arrival) error is $4.2^{\circ}$ when SNR is 10dB and it is $1.3^{\circ}$ when SNR is 20dB. Consequently, the digital RDA shows very good performance for high speed tracking due to the simple calculation and realization.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.251-259
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• 2014

The transition zone between an earthwork and a bridge effect to the vehicle's running stability because support stiffness of the roadbed is suddenly changed. The design criteria for the transition structure on ballast track were not particular in the past. However with the introduction of concrete track is introduced, it requires there is a higher performance level required because of maintenance and running stability. In this present paper, a transition structure reinforced with geosynthetics is suggested to improve the performance of existing bridge-earthwork transition structures. The suggested transition structure, in which there is reinforcing of the approach block using high-tension geosynthetics, has a structure similar to that of earth reinforced abutments. The utilized backfill materials are cement treated soil and gravel. These materials are used to reduce water intrusion into the approach block and to increase the recycling of surplus earth materials. An experiment was performed under the same conditions in order to allow a comparison of this new structure with the existing transition structure. Evaluation items are elastic displacement, cumulative settlement, and earth pressure. As for the results of the real-scale accelerated testing, the suggested transition structure has excellent performance for the reduction of earth pressure and settlement. Above all, it has high resistance the variation of the water content.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4D
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• pp.469-476
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• 2008

Recently, TOD gains popularity as a traffic solution measure of high density urban regeneration projects. The purpose of this study is to investigate traffic impacts of high density TOD projects, and to identify the issues to be resolved. For a case study, it chooses Gangnamgucheong station in Gangnam area served by two subway lines, and designates 400m radius from the station as a site for high-density development. The MOEs chosen for this study is traffic volume, time, distance, speed, and mode share. The SECOM model is adopted for traffic simulation. The analysis results show that high-density TOD is an effective tool for traffic improvement even with only one station area being implemented. It is found that the traffic volume increases near the station in nature where high-density development occurs, but it declines overall in the rest of Gangam area. The total travel time and distance of passenger vehicles decline, meaning that the traffic condition becomes better than before. With regulation on parking supply, the improvement becomes more vivid. In terms of the changes of traffic speed, both alternatives show 4.1% increase in speed, but the difference between alternatives is not quite noticeable because of the induced vehicle demand driven to the streets with improved traffic condition. The mode share changes occur for the benefit of subway ridership, because the study station is equipped with two subway line services. When mixed with parking supply restriction, the impact becomes clearer.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.2
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• pp.71-78
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• 2012

The digital tachograph is a device that automatically records speed and distance of a vehicle, together with the driver's activity and vehicle status at an accident. It records vehicle speed, break status, acceleration, engine RPM, longitude and latitude of GPS, accumulated distance, and so on. European Commission regulation made digital tachographs mandatory for all trucks from 2005. Republic of Korea made digital tachographs mandatory for all new business vehicles from 2011 and is widening the range of vehicles that must install digital tachographs year by year. This device is used to analyze driver's daily driving information and car accidents. Under a car accident that makes the device reliability unpredictable, it is very important to store driving information with maximum reliability for its original mission. We designed and implemented a practical digital tachograph. This paper presents a storage scheme that consists of a first storage device with small capacity at a high reliability and a second storage device with large capacity at a low cost in order to reliably records data with a hardware at a low cost. The first storage device records data in a SLC NAND flash memory in a log-structured style. We present a reverse partial scan that overcomes the slow scan time of log-structured storages at the boot stage. The scheme reduced the scan time of the first storage device by 1/50. In addition, our design includes a scheme that fast stores data at a moment of accident by 1/20 of data transfer time of a normal method.

• Journal of Korea Water Resources Association
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• v.55 no.12
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• pp.1091-1104
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• 2022

Climate change is predicted to increase the frequency and intensity of rainfall worldwide, and the pattern is changing due to inundation damage in urban areas due to rapid urbanization and industrialization. Accordingly, the impact assessment of climate change is mentioned as a very important factor in urban planning, and the World Meteorological Organization (WMO) is emphasizing the need for an impact forecast that considers the social and economic impacts that may arise from meteorological phenomena. In particular, in terms of traffic, the degradation of transport systems due to urban flooding is the most detrimental factor to society and is estimated to be around £100k per hour per major road affected. However, in the case of Korea, even if accurate forecasts and special warnings on the occurrence of meteorological disasters are currently provided, the effects are not properly conveyed. Therefore, in this study, high-resolution analysis and hydrological factors of each area are reflected in order to suggest the depth of flooding of urban floods and to cope with the damage that may affect vehicles, and the degree of flooding caused by rainfall and its effect on vehicle operation are investigated. decided it was necessary. Therefore, the calculation formula of rainfall-immersion depth-vehicle speed is presented using various machine learning techniques rather than simple linear regression. In addition, by applying the climate change scenario to the rainfall-inundation depth-vehicle speed calculation formula, it predicts the flooding of urban rivers during heavy rain, and evaluates possible traffic network disturbances due to road inundation considering the impact of future climate change. We want to develop technology for use in traffic flow planning.

• Journal of Korean Society of Transportation
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• v.20 no.3
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• pp.115-128
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• 2002

Dislike the tangent sections, the horizontal curve sections of roads should be designed, considering several factors : one of such factors is widening. In other words, since widening results from that when a vehicle runs on the horizontal curve sections, the rear wheels of the vehicle run not along with tracks of the front wheels but out of that, such offtracking should be exactly investigated and reflected in design of the curve sections. Especially in the case of industrial roads which semi-trailers and large trucks run frequently or arterial roads with small curve radiuses in mountainous regions. serious offtracking Phenomenons result in increasing the risk of accidents. decreasing the capacities and jeopardizing pedestrians' safety on the curve sections. For the offtracking, widening amounts of roads has been determined under the traditional presumption that vehicles run at a low speed and there is no superelevation. In fact, however, since the vehicles run at a high speed as well as at a low speed and the superelevation is installed on the horizontal curve sections in the structural aspect of roads, the existing standards for installing widening have a limitation to reflect exactly actual Phenomenons. In particular, for articulated wheel axles of a tractor and a trailer and long articulated vehicles, not only the offtracking degree is very high but also the interpretation shows different aspects from one of single axles. Comparing and reviewing the results of Korean and foreign studies related to the trailer offtracking model theory and the standards for installing widening, this study developed a realistic dynamic offtracking model which considers geometric structures of roads and speeds of vehicles, suggested how to measure widening with this model and examined applicability of the model. The findings of this study are as follows ; First. a dynamic offtracking model. which considers dynamic movements of a tractor and a trailer and the superelevation, was developed. Second, a new method to measure widening with the developed dynamic offtracking model was developed and a method to measure widening with swept path width was suggested as well. Finally, validity of the current standards for installing widening was examined by determining actual offtracking and widening amounts with the developed model and the applicability was investigated through the case studies. Compared with the existing offtracking models, the dynamic offtracking model developed in this study can reflect practically vehicle speed. dimension and geometric structural aspects of roads. In conclusion, the meaning of this study is that it reviews validity of the current standards for installing widening and provides a base to establish such standards by suggesting new methods to measure the widening with this dynamic offtracking model.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.6
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• pp.452-460
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• 2021

As the global electric vehicle (EV) market expands, eco-friendly EV that complement performance and safety problems continue to be released and the market is growing. However, in the case of EVs, the inconvenience of charging, safety problems such as electric shock, and electromagnetic interference (EMI) problems caused by the interlocking of various electronic components are problems that must be solved in EVs. The use of wireless power transmission technology can solve the problem of safety by not dealing with high current and high voltage directly and solving the inconvenience of charging EVs. In this paper, in order to reduce EMI a wireless charging control module, which is a key electronic component of WPT of EV. EMI reduction was designed through simulation of problems such as resonance and impedance that may occur in the power supply and signal distortion between high-speed communication that may occur in the signal part. Therefore, through the EMI reduction design with power integrity and signal integrity, the WPT wireless charging control module for electric vehicles reduces 10 dBu V/m and 15 dBu V/m, respectively, in 800 MHz to 1 GHz bands and 1.5 GHz bnad.