• Bulletin of the Korean Chemical Society
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• 제17권4호
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• pp.358-362
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• 1996

The ionic strength dependent binding mode of 9-aminoacridine (9AA), a well-known DNA intercalator, to DNA is studied by flow linear dichroism, circular dichroism, fluorescence techniques and equilibrium dialysis. The DNA-bound 9AA exhibits spectral properties corresponding to the intercalative binding mode disregarding the salt concentrations; the angle between the long-axis transition moment of the 9AA molecule and DNA helix axis is calculated to be about 65°, indicating a significant deviation from the classical intercalation. At low salt concentrations, however, upwards bending curve in Stern-Volmer plot is observed (where 9AA is a fluorophore and DNA a quencher), indicating the coexistence of both static and dynamic quenching mechanisms or the existence of an additional binding site.

• 한국분무공학회지
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• 제27권1호
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• pp.18-25
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• 2022

Hot-firing tests were performed to experimentally confirm the effect of the eigenmode in the fuel-air mixing section on combustion instability by changing mixing section length, inlet mean velocity, equivalence ratio, and swirler geometry. A premixed gas composed of air and ethylene was supplied to the combustion chamber through an mixing section and an axial swirler. As the mixing section length increased, the inlet velocity perturbation decreased, but the combustion instability increased more. It was found that the resonance frequency of the first longitudinal mode in the mixing section shifted to the third longitudinal mode as the length of the mixing section increased. The results implied that the transition of the resonace frquency by changing the length of the mixing section might cause combustion instability.

• 한국분무공학회지
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• 제27권1호
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• pp.36-41
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• 2022

In this study, the combustion instability characteristics according to the change in the hydrogen ratio in the fuel in the single nozzle system of the hydrogen-natural gas mixed gas turbine for power generation was analyzed using a three-dimensional finite element analysis-based Helmholtz solver. This combustor shows the instability characteristics in which mode transition occurs from a mode having a low amplitude near 70 Hz to a mode having a high amplitude of 250 Hz or higher as the hydrogen fraction in the fuel increases. The current modeling results are found to reasonably predict the main characteristics of the change in measured instability frequency and growth rate with the change in fuel composition.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1495-1505
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• 2002

As combining the functions of a 2K-H B type differential gear unit and a V-belt type continuously variable unit(CVU), 16 different mechanisms are presented. Some useful theoretical formula related to speed ratio, power flow and efficiency are derived and analyzed. Continuously variable transmission(CVT) mechanisms are proposed, which can of ffr a backward mode, a geared neutral, an underdrive mode and an overdrive mode. They are not required of a starting device as a torque converter. CVT mechanisms developed here present two distinct operating modes which are a power circulation mode and a power split mode. The transition of two modes takes place at the particular CVU speed ratio. For these CVT mechanisms, performance analysis related to speed ratio, power ratio and theoretical efficiency are executed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.75-79
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• 1993

The Thermally Stimulated Current(TSC) method has been allied to study the influence of the structural change and interface on the electrical properties of epoxy composites. Three DGBA- MeTHPA matrix model samples mixed different ratios arts silica(SiO$_2$) filled sample and silaln treating-filled sample have been studied. Above room temperature, the relaxation mode ${\alpha}$ peak associated with T$\_$g/ has been located at 110$^{\circ}C$. Below glass transition temperature(T$\_$g/), three relaxation modes are observed in all samples : a ${\beta}$ mode situated at 10$^{\circ}C$, a ${\gamma}$ mode located at -40$^{\circ}C$ and a $\delta$mode appeared in -120$^{\circ}C$, which may be due to segmental motion, side chains, substitution and terminal groups. The analysis of its fine structure indicates that constitution of elementary processes is characterized by the activation energy and relaxation time. Also the change of the molecular structure and their thermal motion are compared with the relaxation mode and conduction mechanism in TSC spectra through the dielectric properties and FTIR measurements.

• 한국분무공학회지
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• 제16권2호
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• pp.76-81
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• 2011

A fuel injection system which is operated with a real vehicle driving simulation was developed as an alternative to a vehicle test for the fuel injectors. The sensor signals that are supplied to the ECU were measured and recorded as a data file for a vehicle driven in FTP-75 mode in a chassis dynamometer. The imperative sensor signals of the throttle position, vehicle speed, engine speed, crank position, cam position, intake air flow, and cooling water and intake air temperature were reconstructed using FPGA DAQ boards and a PXI computer. The scanning results showed good agreement with the input signals that were reconstructed. The ECU HILS system operated successfully to drive six fuel injectors, which injected fuel in the same pattern as if they were mounted in the vehicle driven in FTP-75 mode. Also, the fuel injection system developed in this research shows the possibility of application in evaluating the characteristics of fuel injection rate for injectors according to properties of injected fuel with the real driving mode of vehicles.

• Journal of Communications and Networks
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• 제11권3호
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• pp.279-286
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• 2009

This paper proposes an adaptive mode switching algorithm between two strategies in multiple antenna cellular networks:A single-user mode and a multi-user mode for the broadcast channel. If full channel state information is available at the base station, it is known that a multi user transmission strategy would outperform all single-user transmission strategies. In the absence of full side information, it is unclear what the capacity achieving method is, and thus there are few criteria to decide which of the myriad possible methods performs best given a system configuration. We compare a single user transmission and a multi user transmission with linear receivers in this paper where the transmitter and the receivers have multiple antennas, and find that neither strategy dom inates the other. There is instead a transition point between the two strategies. Then, the mode switching point is determined both ana lytically and numerically for a multiple antenna cellular downlink with correlation between transmit antennas.

• 한국재료학회지
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• 제8권5호
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• pp.383-393
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• 1998

고효율 박막형 태양전지 제조를 위해 근접승화법에 의한 CdTe박막의 성장을 연구하였다. 내부압력의 변화, 기판과 소스 사이의 거리, 기판과 소스의 온도 등의 변수가 성장속도와 미세구조에 미치는 영향을 관찰했다. 내부압력의 변화에 따라 성장과정이 diffusion limited transport와 sublimation limited transport로 나뉘어지며, 이 두가지 성장방식의 분기점은 기체분자의 평균자유행정거리에 의해 결정되었다. 소스의 형태에 따라서 박막의 성장속도와 미세구조는 큰 차이를 보였으며, 실험을 통해 이러한 차이가 증발표면의 온도강하에 의한 현상임을 규명하였다. 기판과 소스사이의 간격에 따른 성장속도를 해석하기 위해 일방향열해석을 통해 기판과 소스표면의 온도를 계산하였다. X선 회절분석과 표면형상의 관찰을 통해 성장속도가 박막의 미세구조에 영향을 줌을 알았다. 기판의 온도가 증가하면서 박막성장시 (111)로의 우선성장방위가 관찰되었지만 고온이 되면서 다시 random orientation의 경향을 나타냈다.

• 전자공학회논문지
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• 제53권10호
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• pp.40-47
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• 2016

본 논문에서는 휴대기기에 적합한 모드 전환 제어 가능한 듀얼 모드 벅 변환기를 제안한다. 기존의 모드 제어 회로는 부하의 변동이 급격하거나 천천히 변동하거나 둘 중 하나의 조건에서만 모드 전환이 이루어지는 문제점을 슬로우 클럭을 이용한 모드 제어 회로 기법으로 해결하였다. 그리고 PFM(Pulse Frequency Modulation) 모드에서 PWM(Pulse Width Modulation) 벅 변환기로 전환할 때에도 카운터를 사용하여 고부하를 감지할 수 있도록 하였으며 3비트의 디지털 신호로 20mA~90mA내에서 모드 전환 시점을 선택할 수 있도록 설계하였다. 이 회로는 BCDMOS 0.18um 2-poly 3-metal 공정으로 제작되었으며, 측정 결과 입력전압 3.7V, 출력전압 1.2V 부하 전류 10uA~500mA 범위에서 32mV 이하의 출력 전압 리플을 가지며 86%의 최대 전력 변환 효율을 나타내었다.

• 한국항공우주학회지
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• 제36권5호
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• pp.407-419
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• 2008

본 연구에서는 축 대칭 원뿔 형상 위의 압축성 경계층의 천이 지점을 선형 안정성 이론과 -method를 이용하여 예측하였다. 축 대칭 좌표계에서의 압축성 유동 지배 방정식으로부터 압축성 원뿔 경계층의 선형 안정성 방정식을 얻었으며 안정성 방정식을 2차 정확도의 유한 차분법을 이용하여 계산하는 수치 프로그램을 개발하였다. 개발 된 코드로 원뿔 경계층의 안정성 특성 및 2차원 교란의 증폭률을 계산하고 실험결과와의 비교를 통해 검증을 수행하였다. 얻어진 교란의 증폭률을 활용하여 -method를 통해 천이지점 예측을 수행하였다. 풍동 시험 및 비행 시험 결과와의 비교를 통해 비행 조건에 있는 마하수 4와 8사이의 원뿔 경계층에 대한 본 연구의 천이지점의 예측 능력을 확인하였다. 또한 벽면 냉각이 경계층 내부 교란의 안정성 및 천이 지점에 미치는 영향을 분석하였다.