• Journal of Energy Engineering
• /
• v.21 no.3
• /
• pp.237-242
• /
• 2012

This study presents numerical solutions of the two-dimensional Navier-Stokes equations for supersonic unsteady flow in a convergent-divergent nozzle with a isolator. The TVD scheme in generalized coordinates is employed in order to calculate the moving shock waves caused by thermal choking. We discuss on transient characteristics, unstart phenomena, fluctuations of specific thrust caused by thermal choking and effects of isolator. The adverse pressure gradient caused by heat addition brings about separation of the wall boundary layers and formation of the oblique shock wave that proceed to upstream. The proceeding speed of the oblique shock wave to upstream direction for the convergent-divergent nozzle with isolator is lower than that for the nozzle without isolator.

• Journal of the Korean Magnetics Society
• /
• v.14 no.3
• /
• pp.109-113
• /
• 2004

GMR isolator was modeled using a Wheatstone bridge which is profitable for transmitting rectangular wave digital data, and the output voltage characteristics in relation to the input current were investigated in time domain. GMR isolator modeling was divided into two parts, namely magnetic and electric parts. The flow chart of the modeling was drawn in which measured MR curve of the spin valves were incorporated to obtain the electrical voltage output. For magnetic modeling, 3-dimensional model of planar coil was analyzed by FEM method to obtain the magnetic field strength corresponding to the input current. For electric modeling, resistance, inductance and capacitance of the planar coil were calculated and magnetic field waveform was obtained corresponding to the coil current waveform in time domain. Finally, MR-H curves of spin valves and the magnetic field waveform at the spin valves were composited to obtain the output voltage waveform of the isolator. Even though the amplitude of the coil current waveform was increased by 100％, decreased by 90％, or delayed by 10％ of the period compared with the input current, similar transmitted output voltage waveform to the input current waveform was obtained due to hysteretic characteristics of the spin valves at the transmission speed of over 400 Mbit/s.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.615-618
• /
• 2006

The broadband power detector for direct- onversion Six-port output circuit was designed and implementaed in this paper. The power detector should linearly operated to produce the linear amplitude and phase signal fer input RF signal in required broadband. So, the power detector should be designed under conditions of matching circuit with low VSWR. The designed power detectors, which were implemented in L-band with 50 ohm matching and Ku-band with matching circuit and isolator, respectively, were evaluated in the performances.

• Proceedings of the KIEE Conference
• /
• 2004.07d
• /
• pp.2495-2497
• /
• 2004

A system, featuring the hybrid isolator for control in the vertical direction, of active microvibration control was proposed. The main components of this system are a stage vibration isolation table with built-in acceleration sensors for detecting microvibration, hybrid isolators and a digital controller with high precision signal converters. The vibration control algorithm is focused on settling-time critical application and feedback/feedforward combination.

• Proceedings of the IEEK Conference
• /
• 2003.07a
• /
• pp.342-345
• /
• 2003

본 논문에서는 90W/sub avg/급 디지털 TV 중계기에 사용되는 140W/sub avg/급 전력증폭기를 설계 및 구현하였다. 중계기 규격의 기반이 되는 미국 FCC(Federal Communications Commission) 의 규격과 KBS(한국방송공사)가 제시하는 사양에 적합한 전력증폭기의 설계 및 구현을 목표로 하였다. 전력증폭기는 4단으로 구성하였으며, 전치증폭기는 A 급, 구동증폭기와 종단증폭기는 AB 급으로 동작시켰다. 구동증폭기에서는 3W/sub avg/의 출력을 얻었으며, 3 개의 전력증폭용 모듈이 병렬 연결된 종단증폭기에서는 140W/sub avg/ 의 출력을 얻을 수 있었다. 사용주파수의 대역을 넓히고 입력 및 출력의 VSWR 을 개선시키기 위하여 발룬과 sage wireline coupler 를 이용하여 전력증폭용 모듈을 설계하였다. 모든 전력증폭용 모듈은 방송용 전력증폭기의 규격사양인 isolator 로 종단 처리하여, 종단 임피던스의 갑작스런 변화시에도 장비가 보호될 수 있도록 설계하였다.

• Journal of Christian Education in Korea
• /
• v.66
• /
• pp.243-272
• /
• 2021

Corona 19 brought about a major shift in the Korean church's pastoral style. Contact and non-contact ministry styles using the Internet and media devices are being held together. The elderly, who have been classified as digital vulnerable, need to see whether they are properly adapting to these changes and they have any difficulties in their religious lives. This study is to organize the current status of Corona 19 related to Korean churches, look at the current state of church programs for Christian elderly people, look at how important the religious life is to their lives, and to suggest educational pastoral methods for their religious lives based on the theory of Maria Harris' educational ministry. First, in terms of Koinonia, it was suggested that the heritage, beliefs, values and ways of life held by the Christian elderly be shared with people inside and outside the church in order to entertain and embrace everyone without alienation. Second, from the perspective of Leiturgia, educational ministry was proposed to expand prayer life from a personal area to a public area to become a life of practicing prayer and justice by providing public prayer content with media that can be used by the elderly to perform spirituality. Third, it was suggested that in terms of Didache, it should be required that the elderly should be educated to be familiar with the changing technologies, that teaching environment should be extended from church to online, and that the educational content of tradition and new forms should be dealt with extensively. Fourth, from the perspective of Kerigma, Christian elderly people who have suffered in various life environments, both personally and socially, should listen to the words again and gain the power to overcome the corona crisis through the God's words, so that they can be melted into the curriculum of koinonia, leiturgia, didache, and diakonia. Fifth, it was suggested that senior citizens should switch their consciousness to become subjects of service, not objects of service, and that digital literacy education should be provided individually at eye level to narrow the digital gap for Diakonia curriculum.