• 대한교통학회지
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• 제30권2호
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• pp.127-136
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• 2012

다중추돌사고의 형태는 연쇄 추돌이라고 불리우는 뒤로부터의 순차적인 추돌과 앞으로부터의 순차적인 추돌, 그리고 순서가 섞여 있는 추돌형태로 구분된다. 다중추돌사고에 대하여 몇가지 효과적인 재구성 해석 방안을 제시한다. 브레이크 다이브 등으로 인한 차량 파손과 승객 부상을 활용하는 전통적인 경험적 수법과 강체역학 범주내에서의 이론적인 해석 결과를 구하여 당장에의 실용적인 적용이 가능하도록 하였다. 국내에 보급이 확산되고 있는 영상사고기록장치를 활용하고 시뮬레이션 프로그램 등을 병행 활용하여 다중추돌사고를 효과적으로 해석하는 방안을 제시하였다. 저장 동영상에 대한 단순 직관적인 조사를 넘어설 수 있도록 동영상 분석 결과에 근거한 시뮬레이션 해석을 수행하여 다중추돌사고에 대한 구체적이고 다양한 정보의 획득을 가능하게 하여 원인 규명 및 책임 소재 등을 명확하게 구분할 수 있도록 하였다.

• 대한기계학회논문집B
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• 제24권9호
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• pp.1264-1276
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• 2000

Light-off catalyst has been used for minimization of cold-start emissions. Improved cold-start performance of light-off catalyst needs the optimal design in terms of flow distribution, geometric surface area, precious metal loading, cell density and space velocity. In this study, these influential factors are numerically investigated using integrated numerical technique by considering not only 3-D fluid flow but also heat and mass transfer with chemical reactions. The present results indicate that uneven catalyst loading of depositing high active catalyst at upstream of monolith is beneficial during warm-up period but its effect is severely deteriorated when the space velocity is above 100,000 $hr^{-1}$ To maximize light-off performance, this study suggests that 1) a light-off catalyst be designed double substrate type; 2) the substrate with high GSA and high PM loading at face be placed at the front monolith; and 3) the cell density of the rear monolith be lower to reduce the pressure drop.

• 대한교통학회지
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• 제12권1호
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• pp.55-73
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• 1994

The objective of this research is to evaluate the pedestrian signal time involving green and flashing green times. The minimum pedestrian green indication should give time for pedestrian to start crossing safely, and the flashing green indication should give time to complete the crossing. An average pedestrian crossing speed of 1.1(m/s) was estimated by analyzing the field data which was slower than the 1.2(m/s) currently used. Furthermore, the study proposed that design speed for the flashing green time should be slow speed for considerations pedestrian safety, not the average speed. The 0.78-1.01(m/s) of pedestrian speed was estimated at the elementary school areas that indicated 0.2(m/s) slower than the other areas. The pedestrian starting time (perception/reaction time) and time headway from front to back of herd was estimated to determine minimum pedestrian green time. the pedestrian starting time was estimated to determine minimum pedestrian green time. The pedestrian starting time was ranged 2.52-4.29 seconds. The time interval between the pedestrian rows was found to be 1.25-1.86 seconds, which declines as the pedestrian rows increases, The equation to calculate the pedestrian signal, which declines as the pedestrian rows increases. The equation to calculate the pedestrian signal time is proposed using the pedestrian starting time, the time interval between the pedestrian rows, and pedestrian crossing speed given area types (commercial, business, mixed, and elementary school areas), number of both-directional pedestrians for a cycle, crosswalk length and width.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.189-189
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• 2016

In this study, the Al-rich AlTiSiN thin films that consisted of TiN/AlSiN nano-multilayers were deposited on the steel substrate by magnetron sputtering, and their high-temperature oxidation behavior was investigated, which has not yet been adequately studied to date. Since the oxidation behavior of the films depends sensitively on the deposition method and deposition parameters which affect their crystallinity, composition, stoichiometry, thickness, surface roughness, grain size and orientation, the oxidation studies under various conditions are imperative. AlTiSiN nano-multilayer thin films were deposited on a tool steel substrate, and their oxidation behavior of was investigated between 600 and $1000^{\circ}C$ in air. Since the amount of Al which had a high affinity for oxygen was the largest in the film, an ${\alpha}-Al_2O_3-rich$ scale formed, which provided good oxidation resistance. The outer surface scale consisted of ${\alpha}-Al_2O_3$ incoporated with a small amount of Ti, Si, and Fe. Below this outer surface scale, a thin ($Al_2O_3$, $TiO_2$, $SiO_2$)-intermixed scale formed by the inwardly diffusing oxygen. The film oxidized slower than the $TiO_2-forming$ kinetics and TiN films, but faster than ${\alpha}-Al_2O_3-forming$ kinetics. During oxidation, oxygen from the atmosphere diffused inwardly toward the reaction front, whereas nitrogen and the substrate element of iron diffused outwardly to a certain extent.

• 한국운동역학회지
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• 제20권1호
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• pp.57-65
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• 2010

Korean traditional martial arts Taekkyon has a unique stepping method, Poombalbki. The purpose of this study was to investigate kinematic factors and ground reaction forces on two types of Poombalbki, one of which use knee bending and the other use chiefly hip bending. Six male taekkyoners who are the students of Y University participated in this study. Positions and velocities of CoM, the elapsed times of each phase, angles and angular velocities of low limb joints, and GRFs were analyzed for this study. The results were as follows; CoMs of whole body, trunk, and head were more posteriorly positioned in performing hip bending Poombalbki than knee bending one. Horizontal velocities of those were slower in performing hip bending Poombalbki. A player stayed more shortly within range of his opponent in performing hip bending Poombalbki. The vertical and horizontal components of GRF of forward-stepping foot were smaller in performing hip bending Poombalbki(p<.05). In conclusion hip bending is useful strategy, because A player is farther from his opponent, he stayed more shortly within range of his opponent, and the smaller weight is loaded on his front foot in performing hip bending Poombalbki than knee bending one.

• 한국전기전자재료학회논문지
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• 제26권6호
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• pp.446-450
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• 2013

Growth mechanism of GS-MBE(Gas source-Molecular Beam Epitaxy) has been investigated. We observed that the growth rate of GaN films is changing from 520 nm/h to 440 nm/h by the variation of V/III ratio under nitrogen-rich growth condition. It was explained that the amount of hydrogen on the growth front varies by the ammonia flow, and gallium hydrides are generated on the surface by a reaction of hydrogen and gallium, resultantly the amount of gallium supplying is changing along with the $NH_3$ flow. Reflection high energy electron diffraction (RHEED) observation was used to confirm the N-rich condition. The crystal quality of GaN was estimated by photoluminescence (PL) and X-ray diffraction (XRD).

• Journal of Biosystems Engineering
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• 제16권2호
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• pp.118-123
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• 1991

This study was conducted to investigate the influences of virtual hitch point (VHP) positions of a three-point hitch on the steering stability of agricultural tractors. The VHP locations were determined analytically from the linkage geometry and implement posture during the normal tillage operations. The maximum force applicable to the VHP was also determined under the given soil and power constraints. From these possible ranges of the VHP locations, a safe region for steering control was determined theoretically by using maximum applicable forces for the given tractor and implement combinations. With VHP positions within the safe region, tractor can maintain the minimum soil reaction forces, assumed 20% of the total tractor weight in this study, at the front wheels which is required for the steering control under the maximum traction conditions. This paper mainly concerns with mathematical developments for the determination of VHP locations and maximum forces applicable to the VHP for steering control. Experimental validation of the theory developed here follows as the second part of this study.

• 전기학회논문지
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• 제56권1호
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• pp.151-155
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• 2007

A compact discharge plasma system with a photocatalyst has been proposed and investigated experimentally for application to air conditioners. It was found that there was intense ultra violet radiation with high energy of 3.2 eV from the corona discharge due to the DC-biased pulse voltage applied on a wire. An electrophotochemical reaction took place apparently on the surfaces of the photocatalyst of $TiO_2$ irradiated ultra violet front the discharge plasma in the proposed plasma system. The proposed discharge plasma system with the photocatalyst of $TiO_2$ showed very high removal efficiency of VOCs by tile additional electrophotochemical reactions on the photocatalyst. The proposed discharge plasma system also showed very high removal efficiency of particles such as smokes, suspended bacteria, and pollen and mite allergens by the electrostatic precipitation part. This type of corona discharge plasma system with a photocatalyst can be used as an effective means of removing both indoor pollutant gases and particles including suspended allergens.

• Journal of Biosystems Engineering
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• 제26권6호
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• pp.517-524
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• 2001

Steep and narrow ramp installed in the paddy field makes it difficult and sometimes dangerous to drive agricultural machines on it. Because agricultural machinery become larger and heavier, it is necessary to revise design standard for ramp to provide safe travel. This study was conducted to revise the design standard fur paddy field ramp, especially for its width and slope. A mathematical model predicting travelling path of a tractor on paddy field ramp and farm road was developed and simulated. To verify this model, field tests were carried out. The model could predict trvelling path with RMS Error of 12.5cm and 8.2cm, which were judged to be adoptable fur determining the width of paddy field ramp. By applying this model to 110ps tractor, which was assumed to be the largest tractor in Korea, width of paddy field ramp was determined as over 3.6m. The slope of paddy field ramp, which provided tractor with 10% of the total weight of the tractor and the mounted implement as reaction force at front wheel against ground was analyzed by considering weight transfer effect on a ramp. The result showed that adequate slope of paddy field ramp was 14°.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.13-21
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• 2005

이 논문은 발열 반응에서 상이 변화하는 물질의 연속 방정식에서 유도되는 안정된 파면의 구조를 고려했다. 특별히 액체와 기체, 고체와 액체 사이의 동적인 파면 구조를 수치적으로 연구하였다. 1차원 충격파 구조 분석에 근거한 본 연구에 의하면 연소 시 나노 사이즈의 파면이 존재한다고 추정한다. 설명을 위해, 증발과 응축에는 n-heptane이 사용되었고, 용해와 응고에는 HMX를 사용하였다. 이 개념의 확장은 로켓 추진제와 같이 액체, 고체 연료의 넓은 범위 모두를 포함한다.