• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.285-291
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• 1991

A two-stage slit type virtual impactor based on the concept of the single stage virtual impactor has been designed, fabricated, and evaluated for the purpose of concentrating the suspended particles in the air with the size range of 1.8-4.5 .mu.m and handling large flow volume. Monodisperse methylene blue particles have been generated with vibrating orifice aerosol generator (VOAG). The separation efficiency and concentration efficiency have been measured by the UV-visible absorption spectrometry. Previous study for a single stage virtual impactor were used to determine the design parameters such as 50% cut-off sizes and dimensions of the two stage virtual impactor. The separation efficiency curve and 50% cut-off Stokes number(cut-off sizes) are not sensitive to the nozzle Reynolds number, but sensitive to the ratio between the minor flow rate and the total flow rate, The measured concentration efficiency was compared with the maximum concentration efficiency determined by the separation efficiencies of the first and the second stages. The differences between the measured and the maximum concentration efficiencies result from the wall loss due to the deposited particles on the internal walls inside the impactor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.33-39
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• 2006

In this paper, the collision avoidance of Unmanned Aerial Vehicles(UAVs) by applying the Traffic alert and Collision Avoidance System II(TCAS-II) is introduced. The performances of two UAVs whose maximum vertical rates are different each other are compared and analysed by not only converting many TCAS-II commands into an autopilot input but also implementing a computer program based on the Minimum Operational Performance Standards for TCAS-II. As the alternative to a possible Near Mid-Air Collision for UAVs whose maximum vertical rates are low, we have proposed a modified algorithm considering the maximum vertical rate and altitude. The modified algorithm is available on the assumption that a wider surveillance range is provided by a ADS-B system.

• Journal of the Korean Society for Railway
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• v.14 no.4
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• pp.333-340
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• 2011

The purpose of this paper is to develop two kinds of finite element models for the heavy deformable obstacle defined in grade crossing collision scenario of the Europe TSI and the Korean rolling stock safety regulations and to apply the crashworthiness evaluation for the Korean high-speed EMU with the FE model. The numerical models of the heavy obstacle were changed from a past rigid one to a current deformable one whose stiffness requirement should be verified by a collision simulation defined in the regulations. Through several trial simulations, two types of numerical models for the heavy obstacle were developed, which satisfied physical properties specifies in the regulations. One is a solid-type obstacle with uniform density and the other is a shell-type. With the obstacles developed in this study, the grade crossing collision scenario for Korean high-speed EMU was simulated and evaluated for the two-type obstacle models. From the simulation results, the shell and solid-type obstacles showed quite different behaviors after collision, and the shell type model gave more severe results.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.3
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• pp.68-83
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• 2019

The number of pedestrian traffic accident fatalities is three times the number of car accidents in South Korea. Serious accidents are caused especially at intersections when the vehicle turns to their right. Various pedestrian collision warning services have been developed, but they are insufficient to prevent dangerous pedestrians. In this study, P2CWS is developed to warn approaching vehicles based on the pedestrians' characteristics. In order to evaluate the performance of the service, actual pedestrian data were collected at the intersection of Daejeon, and comparative analysis was carried out according to pedestrian characteristics. As a result, the performance analysis showed a higher accordance when the characteristics of the pedestrian is considered. Accordingly, we can conclude that identifying pedestrian characteristics in predicting the pedestrian crossing is important.

• 한국도로학회지:도로
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• v.19 no.2
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• pp.80-86
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• 2017

• 도로교통
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• s.95
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• pp.40-51
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• 2004

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.765-768
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• 2001

A universal shipborne automatic identification system(AIS) uses self-organised time division multiple access(SOTDMA). The performance evaluation system of the SOTDMA algorithm for AIS is needed to implement it efficiently. This paper shows the method of designing it. Real ships access the VHF maritime mobile band but in this performance system, several ship objects access the shared memory. Real ships are designed as the object and the wireless communication channel is designed as the shared memory. This system shows several stations are assigned the transmission slot by the SOTDMA algorithm

• Proceedings of the Korean Society of Disaster Information Conference
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• 2017.11a
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• pp.331-332
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• 2017

본 논문에서는 선박간의 충돌이나, 항구시설과의 충돌 등으로 선체에 파공이 발생하여 선박내부에 저장되어 있던 해수 및 오염물질이 해양으로 유출되는 해양 재난상황에서 원격제어 방식으로 파공봉쇄장치가 선체 외벽에 부착 이동을 통해 파공부에 접근하여 파공을 봉쇄할 수 있는 장치를 개발하고 성능을 실험적으로 연구 하였다. 이러한 장치는 인력투입이 불가능한 상황에 신속한 초동 조치를 취할 수 있으며 인력으로 불가능한 압력으로 유출되는 상황에서도 봉쇄가 가능한 장치로 개발하였다. 본 연구를 통해 파공부를 직접적으로 봉쇄하는 장치인 봉쇄 패드의 성능시험의 결과 직경 150mm 파공에서 유출압 0.1~0.75bar의 상황에서 안정적인 봉쇄성능을 실험적으로 검증하였다. 또한 봉쇄패드가 결합된 통합방재로봇인 외부 투입형 선박파공 봉쇄 장치를 원격제어하여 0.1 bar의 압력에서 봉쇄 성능 시험을 성공하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.430-439
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• 2019

In this study, a nonlinear impact analysis was performed to evaluate the safety and damage of an eco-pillar debris barrier with a hollow cross-section, which was proposed to improve constructability and economic efficiency. The construction of concrete eco-pillar debris barriers has increased recently. However, there are no design standards concerning debris barriers in Korea, and it is difficult to find a study on performance evaluations in extreme environments. Thus, an analysis of an eco-pillar debris barrier was done using the rock impact speed, which was estimated from the debris flow velocity. The diameters of rocks were determined by ETAG 27. The impact position, angles, and rock diameter were considered as variables. A concrete nonlinear material model was applied, and the estimation of damage was done by ABAQUS software. As a result, the damage ratio was found to be less than 1.0 at rock diameters of 0.3 m and 0.5 m, but it was 1.39 when the diameter was 0.7 m. This study could be used as basic data on impact force in the design of the cross section of an eco-pillar debris barrier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.42-48
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• 2002

In broadband wireless networks, the effective meeting of the QoS guarantees may strongly depend on the Contention Resolution Algorithm used in the uplink contention period. The time it takes a station to transmit a successful request to the base station, or request delay, must be kept low even during periods of high contention. If a request suffers many collisions, it cannot rely on the preemptive scheduler to receive low access delays. However, the conventional collision resolution algorithm has a problem that all collided stations are treated equally regardless of their delay from previous contention periods. Some requests may have very long request delay caused by continuous collisions. In this paper, we propose an adaptive collision resolution algorithm for fast random access in broadband wireless networks. The design goal is to provide quick access to the request with a high number of collisions. To do this, the proposed algorithm separates the whole contention region into multiple sub regions and permits access through each sub region only to the requests with equal number of collisions. The sub region is adaptively created according to the feedback information of previous random access. By simulation, the proposed algorithm can improve the performance in terms of throughput, random delay and complementary distribution of random delay by its ability to isolate higher priorities from lower ones. We can notice the algorithm provides efficiency and random access delay in random access environment.