• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.6
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• pp.630-639
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• 2001

This study proposes a new calculation method for generating real nighttime lamp-lit images. In order to improve the color appearance in the prediction of a nighttime lamp-lighted scene, the lamp-lit image is synthesized based on spectral distribution using the estimated local spectral distribution of the headlamps and the surface reflectance of every object. The Principal component analysis method is introduced to estimate the surface color of an object, and the local spectral distribution of the headlamps is calculated based on the illuminance data and spectral distribution of the illuminating headlamps. HID and halogen lamps are utilized to create beam patterns and captured road scenes are used as background images to simulate actual headlamp-lit images on a monitor. As a result, the reproduced images presented a color appearance that was very close to a real nighttime road image illuminated by single and multiple headlamps compared to the conventional graphic-based algorithm.

• Journal of the Korean Society for Railway
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• v.19 no.1
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• pp.46-53
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• 2016

LED light sources have been known to have a long life and good energy efficiency compared to traditional light sources. Recently, headlamps using LED light sources have ensured the forward visibility and safe operation of high-speed rolling stock. However, assessing the lifespan of LED headlamps based on real test data is not easy because it depends on the multiple stress factors such as a fixed driving current, junction temperature, vibration and so on. Generally, LED headlamps have failed before their advertised life span mainly due to temperature. Thus, the performance assessment of a temperature control unit should be done before a life cycle test of LED headlamps. This study attempted to develop a prototype temperature control module for a lifecycle test system using a commercial LED headlight and verified the system through experiments.

• Journal of the Korean Society for Railway
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• v.18 no.2
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• pp.111-116
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• 2015

LED luminaires as a lighting system have attracted much research attention due to their high efficiency and long lifetimes. However, disappointing outcomes have been noted in terms of performance levels and lifetimes as compared to desired system requirements in practice due to certain electrical and thermal characteristics of LEDs. LM-80 and TM-21 established by IESNA are the best known standards for lifetime test procedures and estimation techniques. However, they only handle LED light sources without guaranteeing the LED luminaire in a reliability test. They also operate for more than 6,000 hours and undergo various stresses, such as the operating current and temperature. Therefore, a lifetime standard for LED luminaires has not yet been established. This paper proposes a conceptual design of a lifetime test system for LED headlamps depending on the operating environment. Eventually, this method can assist with evaluations of the validity of lifetime standard tests of LED headlamps.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.120-124
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• 2006

In this study, psychological assessment was carried out to investigate the driver's psychological characteristics by the change of the headlight. The participants were 20 men and 20 women in their 20s and thirty-two different conditions in combinations of waveform of light, voltage, and alteration time were used. The questionnaire for the assessment was evaluated by 8 subjective items and 5-point SD criteria of 19 pair's adjective. The results were as follows. 1. The assessment results from SD method indicated 3 factors by factor analysis, and it was shown that A waveform had significances in a sense of security and impetus and B waveform had a significance in a sense of security The levels of the limitations for the voltage change were 12V in the factor of a sense of security and 11V in the factor of a sense of impetus for A waveform, 12.6V in the factor of a sense of security for B waveform. 2. The results of the subjective assessment showed that the limitation of A waveform's brightness change was 12V. Moreover, the limitations of voltage changes were 12.6V for B waveform brightness change, 12V for discomfort, 12.6V for darkness. And the limitation of C waveform's brightness change was 12V.

• Tribology and Lubricants
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• v.35 no.1
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• pp.65-70
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• 2019

Self-loosening of bolts owing to external forces occurs in several machines that are clamped by bolts and nuts. This study focuses on the self-loosening of the aiming bolt of the head lamp in a vehicle. It is important to prevent the aiming bolt from self-loosening as it has a decisive effect on the angle of the head lamp. A nut clamped with a bolt, known as a retainer, is made of plastic and has a partial screw thread. In addition, a transverse load has a considerable impact on the self-loosening of a bolt. We concentrate on the self-loosening of a bolt by a transverse load. The aim of this study is to define the limits of the external force that loosen the bolt. Based on the above conditions, we derive a theoretical equation and develop a numerical analysis program that can calculate the limiting forces for self-loosening. To verify the developed program, we design a test device that can measure the self-loosening by applying sliding forces to the aiming bolt. Using this method, we can draw the following conclusions. First, the developed testing device is suitable to prove the theory for calculating the self-loosening force. Second, the equation confirms the relationship of bolt self-loosening between resistance torque and shear force. Finally, the equation obtains the minimum value of the resistance torque required to decrease the change in the angle of the head lamp, thereby improving the possibility of increasing the stability of the head lamp.

• Journal of Korea Multimedia Society
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• v.14 no.6
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• pp.752-758
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• 2011

In this paper, we perform a research on a message delivery link based on visible light communication using illumination light-emitting diodes (LEDs) for car-to-car communications and the link transmission success probability is analyzed for the link. The message delivery system is modeled and the signal-to-noise ratio is calculated from the received optical power. Then, the link transmission probability is estimated from the calculated bit error rates (BERs). The message delivery system has optical links from an LED transmitter near the rear lamp of a car ahead to a receiver near the headlamp of a car behind, whose positions are assumed to follow the normal Gaussian distribution. The link transmission success probability is calculated considering the physical characteristics of the optical link. The car positions are generated according to the normal distribution and the bit error rates are calculated for all links. The link transmission success probability is defined. For the unoptimized optical car-to-car message delivery links, it is shown that the link transmission success probability is larger than 0.9 with the transmitted optical power of 400 mW and the semi-angle at half power of 30 degree.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.224-236
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• 2017

This study analyzed the characteristics of traffic accidents among elderly drivers according to area type in Gyeonggido(urban areas, urban-rural complex areas, and rural areas). Traffic accidents caused by unsafe driving are common in all three types of areas. In urban areas and urban-rural complex areas, traffic accidents were more frequent due to traffic violations and intersection accidents, while rural areas were more affected by central lines. Urban areas and urban-rural complex areas require simpler signal exposures, such as a simple straight line, left turn, or straight line and left turn signal rather than complex signal operations, such as overlaps in a signal operation. Improvement of non-signal intersections and unprotected traffic signal processing is also needed. In order to prevent the intrusion of the central line in rural areas, the center line guard rail should be prevented from penetrating the center line, and the influence of the vehicle headlamp should be reduced in the opposite direction. It is necessary to improve the visibility by using fluorescent letters to enlarge the font size of traffic signs and road signs, particularly to increase visibility at night and prevent traffic accidents at sunset. Minimal, simplified should be provided rather than complex phrases and information.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.19-26
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• 2006

In this study, psychological assessment was carried out to investigate the driver's psychological characteristics by the change of the headlight. The participants were 20 men and 20 women in their 20s and thirty-two different conditions in combinations of waveform of light, voltage, and alteration time were used. The questionnaire for the assessment was evaluated by 8 subjective item and 5-point SD criteria of 19 pair's adjective. The results were as follows : 1. The assessment results from SD method indicated 4 factors by factor analysis, and it was shown that A waveform had significances in a sense of security and impetus and B waveform had a significance in a sense of security. The levels of the limitations for the voltage change were 12[V] in the factor of a sense of security and 11[V] in the factor of a sense of impetus for A waveform, 12.6[V] in the factor of a sense of security for B waveform. 2. The results of the subjective assessment showed that the limitation of A waveform's brightness change was 12[V]. Moreover, the limitations of voltage changes were 12.67[V] for B waveform brightness change, 12.12[V] for discomfort, 12.71[V] for darkness. And the limitation of C waveform's brightness change was 12[V].