• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.304-313
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• 2016

It is necessary to receive telegrams transmitted by transponder tags installed along the track in order to detect the exact position of a high-speed train. In a high-speed railway environment, telegrams can be corrupted by the electromagnetic interference that comes from onboard electric train power equipment or wayside devices. In this study, we verified the railway environment compatibility of a high-speed transponder system developed as a train position detection system. We installed transponder tags on the Honam high-speed line and measured the number of error-free telegrams received from the transponder tag while the HEMU-430X was running at 268km/h~334km/h. Based on the measurement, we estimated the length of the contact zone formed between the transponder reader and tag. Field test results allow us to estimate how many error-free telegrams can be received when HEMU-430X is at speeds up to 400km/h.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.523-528
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• 2013

In this experiment, we investigated the performance of two types of heat sink, swaged- and extruded-type, used in the inverter of industrial electricity generator. The swaged-type heat sink has 62 fins, and the extruded-type has 38 fins having the same dimension as that of the swaged-type. But the extruded-type heat sink maintains the same heat transfer area by the laterally waved surface which has 1 mm in radius. As a result, the swaged- and extruded-type heat sinks released 70.7% and 63.8% of the heat incoming to the heat sink, respectively. The other incoming heat were naturally convected and radiated to the ambient. In spite of 40% decrease in number of fins, the heat release performance of the extruded-type heat sink was lowered only 6.9% than that of the swaged-type. We believe that, this shows the increment of effective heat transfer area by the laterally waved surface of fins and the better heat transfer property of the extruded-type heat sink.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.86-86
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• 2011

1922년 R. L. Parshall이 고안한 파샬플륨은 현재 사용되고 있는 개수로 유량계로서는 가장 많은 실험자료를 보유하고 있다. 위어에 비해 설치가 어렵고 경제성이 떨어지는 단점도 있지만 설치 후에는 상대적으로 다른 시설보다 토사이동이 원활하다는 장점이 있어 하수 및 폐수 등의 유량측정에 많이 적용되고 있다. 용담저수지의 주요 지천인 금강본류와 구량천 2곳에는 국가가 관리하는 수위관측소가 있다. 설치지점의 지명을 따 동향수위관측소와 천천수위관측소로 운용되고 있으며, 동향수위관측소 약 170 m 하류와 천천수위관측소 약 2.5 km 상류 2곳에 갈수기 유량조사를 위한 파샬플륨이 설치되었다. 동향파샬프륨과 천천파샬플륨은 갈수기 유량을 고려하여 Iso 9826의 파샬플륨 번호 10(Parshall flume No. 10)과 유사한 규격(설치당시 목부(Throat)폭 5ft))으로 설계되었으며, 플륨으로 흐름을 유도하는 유입부(Entrance section) 좌 우 횡단방향에 보를 연결하여 상대적으로 하폭이 넓은 자연하천에 적용하였다. 수년간의 현장운용 결과, 파샬플륨의 가장 큰 장점이었던 원활한 토사이동이 보로 인해 차단되고, 누적된 토사가 흐름을 왜곡시킴으로서 플륨내 수위로부터 환산한 유량값에 비교적 큰 오차를 발생시 킬 수 있음을 알게 되었다. 본 연구는 이러한 문제의 원인이 상류에 누적된 토사에 있음을 규명하고 대처방안을 제시하기위해 동향파샬플륨을 대상으로 수행되었다. 플륨을 통한 유량자료의 신뢰도는 (1) 플륨내 정밀유량측정, (2) 50 m 하류에서의 도섭법에 의한 유량측정 그리고 (3) 130 m 하류에서의 도섭법에 의한 유량측정을 통하여 비교 및 검증하였다. 조사결과 플륨내 수위는 상류에 퇴적된 토사로 인해 일정하지 않으며 이로 인해 유량에 오차가 발생하고 있음이 확인되었다. 또한 본 연구에서는 자연하천에서의 파샬플륨 적용을 위해 토사이동을 고려한 설비의 구조개량을 병행하였다. 새로운 형태의 파샬플륨은 '에코플륨'이라 명명하였으며 원활한 토사이동과 인공구조물에 의한 자연경관 훼손을 방지할 수 있는 두 가지의 효과가 기대된다. 현재 실물모형의 제작이 완료되어 실내실험을 수행하고 있으며, 머지않은 장래에 현장설치가 가능하다고 판단된다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.111-111
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• 2018

ASTM A387-Gr.91 강은 우수한 고온 강도, 크리이프 저항성 그리고 내산화성 등으로 인해 화력 및 바이오매스 발전 시설과 같은 고온 설비의 구조재료로 널리 사용되고 있다. 고온 환경에서 높은 강도는 탄화물과 탄질화물에 의한 석출강화가 주 요인으로 작용한다. 열처리 과정에서 Mo, Cr, Mn, 그리고 Fe는 구-오스테나이트 및 마르텐사이트 라스 입계에 $M_{23}C_6$ 탄화물로 석출되며, V, Nb, 및 N은 조직 내부에 미세한 MX 탄질화물로 석출된다. 따라서 합금의 고온 강도는 조직 내 석출물의 개수밀도와 크기에 크게 의존한다. 그러나 적용 환경의 특성 상 고온 노출에 따른 2차상 석출 및 조대화의 조직열화 현상이 발생하며, 이는 재료의 강도를 저하시킨다. 본 연구에서는 ASTM A387-Gr.91 강의 미세조직 열화에 따른 강도저하 및 파괴 양상을 고찰하는데 그 목적을 두었다. 본 연구에서 사용된 ASTM A387-Gr.91 강의 화학성분(wt, %)은 0.1 C, 0.38 Si, 0.46 Mn, 0.25 Ni, 8.38 Cr, 0.93 Mo, 0.18 V, 0.09 Nb, 그리고 나머지는 Fe 이다. 조직열화 및 기계적 강도저하 특성을 평가하기 위한 등온열화는 $650^{\circ}C$의 대기 환경에서 최대 1000시간동안 실시하였다. 열화된 시험편의 미세조직 및 탄화물에 대한 분석은 SEM과 EDS를 이용하여 실시하였다. 그리고 기계적 강도 평가는 인장실험과 비커스 경도시험을 통해 실시하였다. 또한 열화 시간에 따른 파단양상의 변화를 관찰하기 위해 인장시험편의 파단면을 SEM과 EDS를 이용하여 분석하였다. 그 결과, 열화에 따른 마르텐사이트 라스의 소실, 탄화물의 조대화, 그리고 2차상 석출의 조직 열화현상이 나타났다. 또한 기계적 강도는 조직 열화에 따라 저하되는 경향을 나타냈다.

• Journal of the Korean Society for Railway
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• v.18 no.4
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• pp.301-308
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• 2015

To reduce the weight of a railroad vehicle, a bogie frame skin is considered for manufacture using an RTM process and composite material. Compared to other processes, RTM has merits in that it demands only simple manufacturing facilities and can produce a large and complex structure in a short cycle time. On the other hand, it is important to determine the proper number and locations of gates and vents to prevent void formation inside a structure. In this study, we numerically predicted the flow pattern in a bogie frame skin during the RTM process by distinguishing the permeability of a fiber mat as isotropic or anisotropic. Using the results, we analyzed the RTM process conditions of the bogie frame to predict skin void formation, mold filling time, and optimum location of vents depending on the permeability conditions.

• Journal of the Korean Institute of Gas
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• v.16 no.2
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• pp.52-59
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• 2012

The sprinkler system is regarded as the most effective fire extinguishing system. In this study, we proposed a sprinkler layout optimization framework based on fire simulation and mathematical programming. As a case study, the target space in the form of ordinary residence was set up with the size of $5.2m(L){\times}5.4m(W){\times}2.4m(H)$, and we constructed the fire scenario that polyurethane couch was ignited through carelessness. And we simulated and analyzed fire speed, temperature change and heat release rate according to the type and number of sprinklers installed. Through the formulation of installation and damage costs depending on sprinklers, the sprinkler layout showing optimal performance was resulted from mathematical programming.

• Journal of Navigation and Port Research
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• v.35 no.6
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• pp.515-522
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• 2011

This research is intended to suggest some reference materials for the future planning of floating hotel, by reviewing the concept of floating hotel and analyzing the realized and planned ones through the search of related documents and homepages. Floating hotel can be defined as a building for living/recreation/work/entertainment with floating system on water, but without navigation tool. In terms of sequence, the River Kawi Jungle Rafts Resort was built in 1976, Four Seasons Hotel in 1988, and Salt & Sill in 2008. Floating hotels are various in scale(height) and size(room numbers), and have basic, cultural, health & marina facilities. Architectural characteristics of sample facilities can be summarized as self-supporting of the facilities, environmentally friendly architectural planning, utilization of renewable energy, introduction of new plastic composite material, and provision of same view from all bedrooms by rotating the building.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1234-1239
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• 2019

This paper proposes a method for measuring fine dust concentration through digital processing of images captured by only existing CCTVs without additional equipment. This image processing algorithm consists of noise reduction, edge sharpening, ROI setting, edge strength calculation, and correction through HSV conversion. This algorithm is implemented using the C ++ OpenCV library. The algorithm was applied to CCTV images captured over a month. The edge strength values calculated for the ROI region are found to be closely related to the fine dust concentration data. To infer the correlation between the two types fo data, a trend line in the form of a power equation is established using MATLAB. The number of data points deviating from the trend line accounts for around 12.5%. Therefore, the overall accuracy is about 87.5%.

• Journal of Advanced Navigation Technology
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• v.27 no.3
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• pp.287-292
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• 2023

In the case of fixed CCTV, there is a problem in that a shadow area occurs, even if the visible range is maximized by utilizing the pan-tilt and zoom functions. The representative solution for that problem is that a plurality of fixed CCTVs are used. This requires a large amount of additional equipment (e.g., wires, facilities, monitors, etc.) proportional to the number of the CCTVs. Another solution is to use drones that are equipped with cameras and fly. However, Drone's operation time is much short. In order to extend the time, we can use multiple drones and can fly one by one. In this case, drones that need to recharge their batteries re-enter into a ready state at the drone port for next operation. In this paper, we propose a system for precised positioning and stable landing on the drone port by utilizing a small drone equipped with a fixed forward-facing monocular camera. For our conclusion, we implement our proposed system, operate, and finally verify our feasibility.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.361-367
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• 2024

Ultrasound in the air is widely used in industry as a measurement technique to prevent abnormalities in the machinery. Recently, the use of airborne ultrasound imaging techniques, which can find the location of abnormalities using an array transducers, is increasing. A beamforming method that uses the phase difference for each sensor is used to visualize the location of the ultrasonic sound source. We exploit a random sparse ultrasonic array and obtain beamforming power distribution on the source in a certain distance away from the array. Conventional beamforming methods inevitably have limited spatial resolution depending on the number of sensors used and the aperture size. A high-resolution ultrasound imaging technique was implemented by applying functional beamforming as a method to overcome the geometric constraints of the array. The functional beamforming method can be expressed as a generalized beam forming method mathematically, and has the advantage of being able to obtain high-resolution imaging by reducing main-lobe width and side lobes. As a result of observation through computer simulation, it was verified that the resolution of the ultrasonic source in the air was successfully increased by functional beamforming using the ultrasonic sparse array.