• 대한의용생체공학회:의공학회지
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• 제36권4호
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• pp.135-142
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• 2015

Outflow cannulation site of left ventricular assist device(LVAD) chosen by considering anatomical structure of thoracic cavity and vascular system. Though outflow cannulation site influences blood perfusion at each branch, there is no standard rule or quantitative data. In this study, we computed the amount of blood perfusion at each arterial branch numerically according to outflow cannulation sites(ascending aorta, aortic arch, descending aorta). We generated computational meshes to the three-dimensionally reconstructed arterial system. Clinically measured arterial pressure were used for inlet boundary condition, porous media were applied to mimic blood flow resistance. Blood perfusion through left common carotid artery was 2.5 times higher than other cases, and that through right common carotid artery was 1.1 times higher than other branches. Although this is simulation study, will be useful reference data for the clinical study of LVAD which considers blood perfusion efficiency.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.9-16
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• 2011

Research on ISA(Integrated Starter/Alternator) receives wide attention as system voltage is increased to 42V Based on requirement of starter and alternator for the conventional vehicle, system requirement and specification are determined. Also to control proposed system, suitable control methods are proposed. Main control issues with ISA are whether torque assist is required and if so how much torque is needed. In this paper, vehicle performance with various control methods and capacity are simulated and simulation results are analyzed. Vehicle performance is analyzed with vehicle simulator. For the simulation, suitable ISA model is also developed.

• 한국컴퓨터정보학회논문지
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• 제20권11호
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• pp.39-46
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• 2015

In this paper, we propose a performance-aware workload model for efficient implementation of control systems. When implementing a control algorithm as an embedded computer system, the control code executes periodically. For such systems, its control performance depends on not only the accuracy of the control algorithm itself but also temporal parameters such as control period and sensing to actuation delay. In this regard, this paper studies the relation between control period and delay by measuring and analyzing the control performance of LKAS (Lane Keeping Assist System) with varying period and delay combinations. Through this experimental study, this paper shows that the two timing parameters, i.e.,control period and delay, has a tradeoff relation in terms of control performance.

• Journal of Welding and Joining
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• 제28권5호
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• pp.75-79
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• 2010

The Remote welding system(RWS) using $CO_2$ laser equipment has focusable distance of laser beam longer than 800 mm from workpiece and can deflect the laser beam by the scanner mirrors very rapidly. In the case of normal welding system based on robot, there is a limit to move the shortest path in short time and this causes interference between robot and workpiece. On the other hand, RWS is the optimized equipment to get big merits with advanced sequence of welding and short cycle time. However, there is still a pending task such as the control of plasma in the welding process of thick sheets therefore, it requires high power laser beam because of the absence of assist gas equipment in itself. In this study, high-tensile steel plates were overlap welded with $CO_2$ RWS for the production of car body and the influence of penetration depth according to the existence of assist gas was analyzed. Excellent tensile strength with enough width of molten zone independent to penetration depth was observed under welding condition with 3.6 kW laser power and 2.8 m/min welding speed without assist gas. Finally, the proto-type automotive parts were produced by applying the deduced optimal welding condition.

• 대한기계학회논문집B
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• 제36권3호
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• pp.233-240
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• 2012

레이저 절단가공에서 사용되는 보조가스의 충돌특성을 개선하기 위한 실험적 연구가 진행되었다. 보조가스의 압력, 노즐의 위치 및 각도 등 다양한 관계변수의 변화에 대하여, 초음속 사각노즐에서 분출되는 보조가스의 절단면 충돌특성이 기존의 원형노즐 경우와 비교 관찰되었다. 이를 위하여 쉴러린 유동가시화 및 절단면 하단에서의 피토압 측정이 진행되었다. 본 연구에서 응용된 사각노즐은 절단면 모서리에서 발생하는 마하디스크의 강도를 줄이고, 이를 통하여 기존의 원형노즐에 비하여 절단면을 따라 흐르는 보조가스의 박리현상을 약화시키고 보조가스 후방의 피토압력을 증가시킬 수 있음이 확인되었다.

• 전기학회논문지
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• 제66권1호
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• pp.89-99
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• 2017

Many works have attempted to solve the scalability, the availability, and the low-latency problems of peer-to-peer (P2P) live video streaming; yet, the problems still remain. While tree-based systems are vulnerable to churn, the mesh-based systems suffer from high delay and overhead. The DHT-aided chunk-driven overlay (DCO) [1] tried to tackle these problems by using the distributed hash table (DHT), which structures into a mesh-based overlay to efficiently share the video segment. However, DCO fully depends on the capacity of the users' device which is small and unstable, i.e., the users' device may leave and join the network anytime, and the video server's bandwidth can be insufficient when the number of users joining the network suddenly increases. Therefore, cloud assist is introduced to overcome those problems. Cloud assist can be used to enhance the availability, the low-latency, and the scalability of the system. In this paper, the DHT is used to maintain the location of the streaming segments in a distributed manner, and the cloud server is used to assist other peers when the bandwidth which required for sharing the video segment is insufficient. The simulation results show that by using the threshold and cloud assist, the availability and the low-latency of the video segments, and the scalability of the network are greatly improved.

• 재활복지공학회논문지
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• 제8권2호
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• pp.79-88
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• 2014

국내에서 전기적 자극방식 삼킴 보조 치료기는 높은 보급률과 사용빈도를 가진 전문 의료기기임에도 불구하고 기기에 대한 관리체계가 전무하여 유지 보수의 측면에 있어서도 매우 큰 취약성을 노출해 왔다. 이에 본 연구는 전기적 자극방식 삼킴 보조 치료기의 장비관리 및 안전진단 매뉴얼 개발에 목적을 두고 프로그램을 개발하였다. 이를 위하여 국제전기기술위원회(International Electrotechnical Commission, IEC)등의 기관에서 공시한 표준화된 프로그램 수집과 문헌고찰을 통해 매뉴얼 개발의 근거를 마련하고, 프로토콜을 개발하여 제시하였다. 완성된 알고리즘과 프로토콜, 지표 등의 자료를 전문가 및 현장 실무자의 자문을 통하여 수정 및 보완하고 유지보수 워크시트(Maintenance Worksheet)의 5지표 18항목, 삼킴 보조 전자 의료기기 장비관리/안전진단 절차 매뉴얼(Equipment Procedure Manual)에서 4개 지표 32항목으로 구성된 점검 매뉴얼을 최종적으로 완성하였다. 완성된 지표는 장비의 고장률을 줄이고 의료기록 문서화의 체계성 제고에 도움을 줄 것이며, 의료서비스의 효율성, 적절성을 유지하는데 기여할 수 있을 것이라 생각된다.

• Journal of Chest Surgery
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• 제53권6호
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• pp.368-374
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• 2020

Background: The extracorporeal ventricular assist device (e-VAD) system is designed for left ventricular support using a permanent life support console. This study aimed to determine the impact of temporary e-VAD implantation bridging on posttransplant outcomes. Methods: We reviewed the clinical records of 6 patients with the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) profile 1, awaiting heart transplantation, who were provided with temporary e-VAD from 2018 to 2019. The circuit comprised a single centrifugal pump without an oxygenator. The e-VAD inflow cannula was inserted into the apex of the left ventricle, and the outflow cannula was positioned in the ascending aorta. The median follow-up duration was 8.4±6.9 months. Results: After e-VAD implantation, lactate dehydrogenase levels significantly decreased, and Sequential Organ Failure Assessment scores significantly improved. Bedside rehabilitation was possible in 5 patients. After a mean e-VAD support duration of 14.5±17.3 days, all patients were successfully bridged to transplantation. After transplantation, 5 patients survived for at least 6 months. Conclusion: e-VAD may reverse end-organ dysfunction and improve outcomes in INTERMACS I heart transplant patients.

• 대한임베디드공학회논문지
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• 제15권2호
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• pp.71-78
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• 2020

This paper proposes vision sensors and deep learning-based around view monitoring system for ship berthing. Ship berthing to the port requires precise relative position and relative speed information between the mooring facility and the ship. For ships of Handysize or higher, the vesselships must be docked with the help of pilots and tugboats. In the case of ships handling dangerous cargo, tug boats push the ship and dock it in the port, using the distance and velocity information receiving from the berthing aid system (BAS). However, the existing BAS is very expensive and there is a limit on the size of the vessel that can be measured. Also, there is a limitation that it is difficult to measure distance and speed when there are obstacles near the port. This paper proposes a relative distance and speed estimation system that can be used as a ship berthing assist system. The proposed system is verified by comparing the performance with the existing laser-based distance and speed measurement system through the field tests at the actual port.

• 한국산학기술학회논문지
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• 제21권3호
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• pp.57-64
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• 2020

첨단 운전자 보조시스템(ADAS, Advanced Driver Assist System)의 주요 기술에는 적응형 순항 제어(ACC, Advanced Cruise Control), 주행 조향보조 시스템(LKAS, Lane Keeping Assist System), 자동 긴급제동 시스템(AEB, Autonomous Emergency Braking) 등이 있다. ADAS 중 LKAS는 카메라(camera)와 적외선 센서(sensor)를 사용하여 운전자가 의도하지 않은 차선이탈이 발생하였을 때, 조향 보조장치를 제어하여 주행 차선으로 복귀하는 시스템이다. 이러한 시스템의 안전성 평가와 검증을 위해 실차시험을 진행한다. 그러나 LKAS 동작 후 임의의 추가 조향각이 인가될 경우에 대한 연구는 미흡하다. 본 논문에서는 선행연구에서 제안한 시나리오에 대해 Prescan을 이용하여 추가 조향각 인가 모델링(modeling)기법을 개발하고 시뮬레이션(simulation) 하고, 실차시험을 통해 취득한 데이터(data)와의 비교분석으로 모델링 기법의 타당성을 검증하였다. 앞바퀴부터 차선까지 최대 거리오차는 0.56 m이며, 시뮬레이션과 실차시험의 차선 복귀 속도의 차이로 인해 발생하였다. 시뮬레이션과 달리 실차시험은 주행 차선으로 복귀 속도가 느려 이탈하는 차의 횡방향 변화가 상대적으로 적어 시뮬레이션과 오차가 발생한 것으로 판단된다. 시뮬레이션과 실차시험 값의 비교분석 결과 차선복귀 속도 차이는 있지만 앞바퀴부터 차선까지 거리가 약 0.5m로 수렴하는 경향성을 나타내어 신뢰성을 확인할 수 있었다.