• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.85-92
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• 2023

In this study, we present experimental results of cavitating flow around a vortex generator which is used to improve the flow in the wake of ships and enhance propulsion efficiency. We conducted experiments at the CNU cavitation tunnel on a total of six vortex generators, two different aspect ratios and three taper ratios. We recorded cavity patterns using a high-speed camera and quantitatively evaluated cavity fraction using OpenCV. The most important finding of this study is that the vortex cavity generated at a root leading edge of the vortex generator develops at a specific angle.

• Journal of Korean Society of Transportation
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• v.29 no.3
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• pp.73-82
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• 2011

Recent advancement in traffic surveillance systems has allowed the researchers to obtain more detailed vehicular movement such as individual vehicle trajectory data. Understanding the characteristics of interactions between leading and following vehicles in the traffic flow stream is a backbone for designing and evaluating more sophisticated traffic and vehicle control strategies. This study proposes a methodology for estimating rear-end crash potential, as a probabilistic measure, in real-time based on the analysis of vehicular movements. The methodology presented in this study consists of three components. The first predicts vehicle position and speed every second using a Kalman filtering technique. The second estimates the probability for the vehicle's trajectory to belong to either 'changing lane' or 'going straight'. A binary logistic regression (BLR) is used to model the lane-changing decision of the subject vehicle. The other component calculates crash probability by employing an exponential decay function that uses time-to-collision (TTC) between the subject vehicle and the front vehicle. The result of this study is expected to be adapted in developing traffic control and information systems, in particular, for crash prevention.

• Journal of the Korean Society of Safety
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• v.23 no.2
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• pp.45-50
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• 2008

The purpose of the present study was to investigate the age difference in driving behavior(more specifically, left-turn). The participants were instructed to report whether they can turn left their car in the T-shape road(road and other vehicles' behavior relating to driver's tasks were recorded in advance and projected the simulation screen) after the leading vehicle passed them(i.e., before the target vehicle arrived). The participants' judgment accuracy and response bias were analyzed by using signal detection theory. The results showed that the old group tended to be less sensitive but more confident in their judgement of turning left their car. In particular, both age groups appeared to more depend on the distance from observation location to approaching vehicle rather than arrival times or driving speeds of the approaching vehicle.

• Journal of Auto-vehicle Safety Association
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• v.5 no.2
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• pp.39-44
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• 2013

Motor vehicle crashes are the leading cause (70%) of children injury and fatality. 98% of Children under the age of 9 who came to emergency room with a traffic accident are not seated in CRS. Reduction in mortality when using CRS (NHTSA study), 71% for infants of 1-2 years old, 54% for 3-6 years old and 7-12 years old. It is very important and essential to use CRS for child passenger safety. But in Korean market, the CRS fitment rate is relatively low (20~40%). For European market, at the start of 2013, Euro NCAP started to check how easy it is to install the most common seats. And US market, NHTSA is planning a new consumer information program of CRS fitment for near future. This study examines CRS installation performance of 3 vehicles which are produced by GM Korea and 21 CRS which are based on sales volume in Korean market. Purpose of this study is to identify both vehicle and CRS design that causes bad interaction for CRS installation.

• Journal of Auto-vehicle Safety Association
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• v.12 no.2
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• pp.47-55
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• 2020

In this case study, the brake line failure of air over hydraulic(AOH) brake system is described. AOH brake system is applied to commercial vehicles between 5 to 8 tons. It consists of a hydraulic system using compressed air and operates the air master to form hydraulic pressure to transfer braking power to the wheels. When the brake lines of the system applied to vehicles with high load capacity are damaged, the braking force of one shaft is lost, and the braking distance increases rapidly, leading to a big accident. Failure of the brake line occurs due to various causes such as road surface fragmentation, corrosion of the line, and aged deterioration of air brake hose. The braking force could be decreased even when a very small break in the form of a pin-hole occurs. However, it is difficult to find a part where the thickness of the line is thin due to stone pecking or corrosion generated in the pin-hole formed on the brake line located under the lower part of the vehicle by the sensory evaluation or the conventional braking force test. Accordingly, it is necessary to analyze the condition and cause of the failure of the brake line more precisely when the accident investigation of the heavy vehicles, and also to examine the necessity of the advanced test for the aged brake line.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.8
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• pp.711-719
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• 2016

In this study, we derived an theoretical equation, using a simplified spring-mass model for the rolling stock, to obtain the overriding behavior of a leading vehicle, which is considered as the main factor in train accidents. To verify the derived equation, we created a simple 2D model based on the theoretical model, and a simple 3D model considering the characteristics of the power bogie. We then compared the theoretical results with the simulation results obtained using LS-DYNA. The maximum relative derivations in the vertical displacements at the first end-buffer, which is the most important point in overriding, were 3.5 [%] and 1.7 [%] between the two results. Further, we evaluated collision-induced overriding displacements using the theoretical equation for a rubber draft gear, a hydraulic buffer under various collision conditions. We have suggested a theoretical approach for the realization of overriding collision accidents or the energy absorption design of the front end of trains.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.739-743
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• 2009

Japan is leading standards for the hydrogen fuel quality on the PEMFC(Proton Exchange Membrane Fuel Cell) vehicle at ISO/TC197/WG12. However, it has many problems to solve the standard of measurement and the test method. because the standard of measurement which was proposed in Japan is too high to reach the technique for many countries. it might not control standards for the hydrogen fuel quality on the PEMFC vehicle in Korea. So we need to develop the study of standards and the technique of measurement continuously for the International Standards Meeting.

• Geomechanics and Engineering
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• v.3 no.1
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• pp.45-59
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• 2011

Scaled centrifuge modelling techniques were used to study the soil-structure interactions and performance of a jointed rollable aluminium roadway (or trackway) system on soft clay under light truck tyre loads. The measured performance and subsequent analyses highlighted that the articulated connections significantly reduced the overall longitudinal flexural stiffness of the roadway leading to stress concentrations in the soil below the joints under tyred vehicle loadings. This resulted in rapid localised failure of the supporting soil that in turn led to excessive transverse flexure of the roadway and ultimately plastic deformations. It is shown that the performance of rollable roadway systems under tyred vehicle trafficking will be improved by eliminating joint rotation to increase longitudinal stiffness.

• Journal of Auto-vehicle Safety Association
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• v.6 no.1
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• pp.16-21
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• 2014

Recently Korea and many countries are legislated for pedestrian protection as following the GTR(Global Technical Regulation). Most NCAP organization have been applying pedestrian protection results in their own rating system in individual or overall rating. Euro NCAP agency has been introduced it first. From the beginning, Euro NCAP had assessed occupant and pedestrian protection. It has become to strengthen a pedestrian protection protocol every time published. Korea NCAP also has been rating pedestrian protection with overall rating system. This paper proposed to study new pedestrian protection protocol especially upper leg in order to find injury response based on physical test. On Euro NCAP, the upper leg injury are assessed two kind of value which are bending moment and force.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1059-1060
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• 2011

녹색 성장을 위한 전기 자동차 실용화에 대한 다양한 방법들이 제시되고 있다. 이를 효과적으로 운영 관리 하기 위한 시스템들이 개발되고 있다. 기존 연구는 무선 급집전 전기 자동차와 인프라의 특성을 반영하고 접근 편의성에 어려움이 있다. 본 연구에서는 한국과학기술원에서 연구개발 중인 OLEV 시스템을 근거리에서 운영관리 하기 위한 설계를 제안한다. 무선 인트라넷 환경을 구축함을 통해 이동하는 차 안에서 차량의 상태와 동작 중인 충전 인프라의 상태를 함께 관제할 수 있도록 하였다. 이동성과 개인 사용성을 위해 모바일 기기를 이용하여 관리의 유용성과 일반인들의 전기 자동차에 대한 이해를 향상시켰다. 시스템의 유용성을 입증하기 위해 서울대공원 코끼리 전기열차와 한국과학기술원 문지 캠퍼스에서 주행 실험을 수행하였다.