• Nuclear Engineering and Technology
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• 제38권5호
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• pp.449-454
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• 2006

Neutron imaging technique was used to investigate the water distribution and movement in Polymer Electrolyte Membrane Fuel Cell (PEMFC) at HANARO, KAERI. The Feasibility tests were performed in the first and second exposure rooms at the neutron radiography facility (NRF) at HANARO in order to check the ability of each exposure room, respectively. The feasibility test apparatus was composed of water and pressurized air before making up the actual test apparatus. Due to the low neutron intensity in the second exposure room, the exposure time was too long to investigate the transient phenomena of PEMFC. Although the exposure time was improved to 0.1 sec in the first exposure room, it was difficult to discriminate detail water movement at the channel due to the high noise level. Therefore, the experimental setup must be optimized according to the test conditions. Water discharge characteristics were investigated under different flow field geometries by using feasibility test apparatus and the neutron imaging technique. The water discharge characteristics of a 3-parallel serpentine are superior to those of a 1-parallel serpentine, but water at Membrane Electrode Assembly (MEA) was not removed, regardless of the flow field type.

• 한국해양환경ㆍ에너지학회지
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• 제1권2호
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• pp.40-51
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• 1998

유벽에 의하여 가두어진 오일의 조류중 거동을 회류수조에서 2차원적인 실험설비를 이용하여 살펴보았다. 유벽을 적정 깊이의 수직판으로 대치하고 레이저 광원을 이용하여 오일과 물과의 경계면 변형을 2 종류의 오일 (콩기름과 경유)에 대하여 관찰하였다. 적용된 조건으로 조류의 속도는 10 cm/s - 35 cm/s, 유벽의 깊이는 4 cm 와 8 cm, 그리고 유량은 2 liter - 8 liter 의 변화를 주었다. 다양한 경계면의 거동과 조건에 따른 누유의 손실 방식을 차원해석을 통하여 정리하고 유적누유와 연속누유의 발생 메카니즘을 설명하였다.

• 한국통신학회논문지
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• 제37권8C호
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• pp.655-662
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• 2012

본 연구에서는 다수 레이다신호의 간섭으로 인해 항공기가 데이터통신이 두절될 것을 대비하여 새로운 주파수(채널)을 탐색하기 위해 Cognitive Radio 기술을 활용한 항공인지무선시스템을 제안한다. 항공기의 데이터통신 채널을 확보하기 위해 비행환경하에 레이다의 주파수를 인지하여 지형정보를 통한 유효주파수를 산출하여 빠르게 스펙트럼을 센싱하는 방법을 제안하였다. 기지국은 항공기와 레이더의 위치를 기반으로 자유공간의 경로손실을 이용한 방식으로 유효 주파수를 계산하였고 이동체에 대한 변수를 병행하여 적용하였다. 분석 결과 기존 최대 주파수 탐색시간이 제안된 방법을 활용시 절반으로 단축됨을 입증하였다.

• 대한전자공학회논문지TE
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• 제42권3호
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• pp.1-6
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• 2005

개발된 24 채널 경락 전위측정 시스템의 구성은 마이컴 제어부, 생체신호 아날로그 증폭부, 인터페이스부, 전원장치, personal computer 등 이다. 사용자 인터페이스 프로그램은 이용자를 편리하게 구성하였으며, 측정의 편리성으로 calibration기능 및 자료의 저장 과 검색 기능을 하게 하였다. 경락 전위를 측정하기 위한 프로그램을 구성하여 제어 할 수 있게 하였다. 측정된 생체 전기 신호 자료의 분석을 통하여 각각의 위치에 대한 전위의 상호 분포를 비교하여 결과를 체계적으로 나타낼 수 있게 프로그램 처리 하였다. 다양한 종류의 측정 조건을 변화 할 수 있게 구성하여 경락 전위를 측정을 위한 이용자에게 유리한 측정 환경이 되게 하였다.

• 한국정보처리학회논문지
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• 제6권10호
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• pp.2764-2771
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• 1999

ATM은 높은 처리 능력, 대역 확장, 그리고 다중 서비스 트래픽을 지원할 수 있는 능력 때문에 최근 주목을 받아 왔다 그러나 그 동안 네트워킹 프로토콜이 대부분 비연결형인 것에 반해 ATM은 연결 지향적이다 ATM에서 현재 서비스를 제공하기 위한 대안은 라우탱 기능을 제공하는 스위칭 하드헤어를 적용한 라우터이다 본 논문에서는, 스위치를 이용한 라우터를 설명하고 성능을 시뮬레이션 하였다 시뮬레이션 결과, 라우팅 지연은 플로우 개수에 따라 증가하였다 플로우 채널-유지 시간이 30,000 셀-시간일 때 셀 지연은 가장 적었다. 회선 효율은 플로우 설정 시간이 20 30 셀-시간일 때 급격히 증가하였다. 이 시뮬레이션 결과는 ATM 스위치를 이용한 라우터의 성능을 예측하기 위하여 사용될 수 있다.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.58-65
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• 2005

A method measuring angular speed and estimating angular acceleration of an automotive wind shield wiper pivot with limited resources has been proposed. Limited resources refer to the fact that processes cannot be operated in real-time with a regular notebook running a Microsoft Windows. Also, they refer to the fact that data acquisition cards have only two general purpose counters as many generic cards do. An optical incremental encoder has been employed for measuring angular motion. To measure the angular speed of the pivot, periods for the encoder's output pulses have been measured as the speed is related to the reciprocal of the period. Since only information acquired from one counter channel is the magnitude of the angular speed, sign correction is necessary. Also the information for the exact time when a pivot passes left and right dead points is also missing and the situation is inherent to the hardware setup. To find out the zero-crossing time of the angular speed, a linear interpolation technique has been employed. Lastly, to overcome the imperfection of the mechanical encoders, the angular speed has been curve fitted to a spline. Angular acceleration can be obtained by a differentiation of the angular speed.

• 대한기계학회논문집B
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• 제30권5호
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• pp.489-495
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• 2006

Proton exchange membrane (PEM) should be sufficiently hydrated with a careful consideration of heat and water management. Water management has been a critical operation issue for better understanding the operation and optimizing the performance of a PEM fuel cell. The flooding on cathode side resulting from excess water can limit the fuel cell performance. In this study, the visual cell was designed and fabricated fur the visualization of liquid water droplet dynamics related to cathode flooding in flow channels. The experiment was carried out to observe the formation, growth and removal of water droplets using CCD imaging system. Effects of operating conditions such as cell temperature, air flow rate and air relative humidity on cathode flooding characteristics were mainly investigated. Based on this study, we can get the basic insight into flooding phenomena and its two-phase flow nature. It is expected that data obtained can be effectively used fur the setup and validation of two-phase PEM fuel cell models considering cathode flooding.

• Nuclear Engineering and Technology
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• 제51권7호
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• pp.1853-1859
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• 2019

The two-thermocouple method was investigated experimentally to evaluate its accuracy for the measurement of local wall temperature and heat flux on a heat transfer tube with an electric heater rod installed in an annulus channel. This work revealed that a thermocouple flush-mounted in a surface groove serves as a good reference method for the accurate measurement of the wall temperature, whereas two thermocouples installed at different depths in the tube wall yield large bias errors in the calculation of local heat flux and wall temperature. These errors result from conductive and convective changes due to the fin effect of the thermocouple sheath. To eliminate the bias errors, we proposed a calibration method based on both the local heat flux and Reynolds number of the cooling water. The calibration method was validated with the measurement of local heat flux and wall temperature against experimental data obtained for single-phase convection and two-phase condensation flows inside the tube. In the manuscript, Section 1 introduces the importance of local heat flux and wall temperature measurement, Section 2 explains the experimental setup, and Section 3 provides the measured data, causes of measurement errors, and the developed calibration method.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.274-284
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• 2019

The control architectures of Chuan Suo (CS) deep submergence rescue vehicle are introduced. The hardware and software architectures are also discussed. The hardware part adopts a distributed control system composed of surface and underwater nodes. A computer is used as a surface control machine. Underwater equipment is based on a multi-board-embedded industrial computer with PC104 BUS, which contains IO, A/D, D/A, eight-channel serial, and power boards. The hardware and software parts complete data transmission through optical fibers. The software part involves an IPC of embedded Vxworks real-time operating system, upon which the operation of I/O, A/D, and D/A boards and serial ports is based on; this setup improves the real-time manipulation. The information flow is controlled by the software part, and the thrust distribution is introduced. A submergence vehicle heeling control method based on ballast water tank regulation is introduced to meet the special heeling requirements of the submergence rescue vehicle during docking. Finally, the feasibility and reliability of the entire system are verified by a pool test.

• International Journal of Computer Science & Network Security
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• 제22권2호
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• pp.209-213
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• 2022

Key exchange protocol (KEP) is an essential setup to secure authenticates transmission among two or more users in cyberspace. Digital files protected and transmitted by the encryption of the files over public channels, a single key communal concerning the channel parties and utilized for both to encrypt the files as well as decrypt the files. If entirely done, this impedes unauthorized third parties from imposing a key optimal on the authorized parties. In this article, we have suggested a new KEP term as isokey interchange protocol based on generalization of modern mathematics term as isomathematics by utilizing isonumbers for corresponding isounits over the Block Upper Triangular Isomatrices (BUTI) which is secure, feasible and extensible. We also were utilizing arithmetic operations like Isoaddition, isosubtraction, isomultiplication and isodivision from isomathematics to build iso-key interchange protocol for network communication. The execution of our protocol is for two isointegers corresponding two elements of the group of isomatrices and cryptographic performance of products eachother. We demonstrate the protection of suggested isokey interchange protocol against Brute force attacks, Menezes et al. algorithm and Climent et al. algorithm.