• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.34-36
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• 1998

In these days the hybrid interrupters are widely used for medium voltage class circuit breakers. In the design of the hybrid interrupter, the shape of the short-circuit ring is one of the most important design parameters. Recently the investigation into the phase difference between arc current and magnetic field due to the shape variation of the short circuit ring has been conducted. In this paper, the results of eddy current analyses in the hybrid interrupter and test result are presented.

• 한국콘텐츠학회논문지
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• 제11권12호
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• pp.357-363
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• 2011

본 연구는 유리 선량계를 이용한 진단용 X선 장치 선량 및 선질의 입사표면선량 값과 선질 계수에 의한 계산 측정법을 바탕으로 비교 평가하여 의료 피폭 선량에 대해 연구하였다. 실제 측정에 의한 ESDs 값이 Mori에 의한 NDD-M 법에서 가장 큰 차이를 보였으며, Edmonds에 의한 계산법이 가장 적은 차이를 보였다. 또한 정류 방식에 따른 실 측정과 선량 계산법 차이는 삼상 정류 방식, 단상 정류 방식, 인버터 방식으로 차이가 적게 나타났다. 본 연구 결과는 향후 진단용 X-선 촬영 장치의 사용에 있어 환자의 피폭 선량을 예측하고 검사 조건을 조절하여 의료 피폭 선량을 절감할 수 있을 것이다.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.275-281
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• 2007

GTL (Gas To Liquid) has the potential to be used in diesel engines as a clean alternative fuel due to advantages in emission reduction, particularly soot reduction. Since the physical properties of GTL fuel differ from those of diesel fuel to some extent, studying how this difference in characteristics of GTL and diesel fuels affects spray and combustion in diesel engines is important. In this study, visual investigation of sprays and flames from GTL and diesel fuels in a vessel simulating diesel combustion was implemented. The effects of various parameters and conditions, such as injection pressure, chamber temperature and pilot injection on liquid-phase fuel length and auto-ignition delay were investigated. It was determined that GTL has a somewhat shorter liquid-phase fuel length, which explains why there is less contact between the fuel liquid-phase and flame for GTL fuel compared to diesel fuel.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1099-1102
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• 1996

In this paper, roll/yaw attitude control of spacecraft using a double gimbaled wheel is discussed with two feedback controllers designed. One is a PD controller with no phase difference between roll and yaw control input. The other is a PD controller with a phase lag compensator about the yaw control input. The phase lag compensator is designed as a first order system and a lag parameter is designed for the yaw angle control. There are two case simulations for each controller ; constant disturbance torques and initial errors of nutation at motion. We obtain the results through simulations that steady-state error and rising time of yaw angle are determined by the compensator. Simulation parameters used in this study are the values of KOREASAT F1.

• Journal of information and communication convergence engineering
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• 제7권3호
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• pp.372-376
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• 2009

In this paper, new and simple optical transmission link with fixed dispersion management (DM) scheme, i.e., pre(post) compensation and residual dispersion per span (RDPS) are fixed to net residual dispersion (NRD) = 0 ps/nm, and optical phase conjugator (OPC) having optimal position depending on launch power in WDM transmission system is proposed. Also, effective launch power range of WDM channels resulting 1 dB eye opening penalty (EOP) is induced as a function of OPC position. First, it is confirmed that, for applying DM into WDM transmission link fixed pre(post)compensation and RDPS, which are independence on exact system parameters except launch power, sufficiently are used in WDM links, but OPC with optimal position is needed for effective compensating impairments of WDM channels. And, it is confirmed that effective launch power is broader in case of RDPS = 100 ps/nm than in RDPS = 50 ps/nm. But, it is shown that the best OPC position offset is -0.6 km from a point of view of power window, which is defined as difference between maximum and minimum effective launch power.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1122-1127
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• 2004

an isolated droplet combustion exposed to pressure perturbations in stagnant gaseous environment is numerically conducted. Governing equations are solved for flow parameters at gas and liquid phases separately and thermodynamic parameters at the interfacial boundary are matched for problem closure. For high-pressure effects, vapor-liquid interfacial thermodynamics is rigorously treated. A series of parametric calculations in terms of mean pressure level and wave frequencies are carried out employing a n-pentane droplet in stagnant gaseous air. Results show that the operating pressure and driving frequency have an important role in determining the amplitude and phase lag of a combustion response. Mass evaporation rate responding to pressure waves is amplified with increase in pressure due to substantial reduction in latent heat of vaporization. Phase difference between pressure and evaporation rate decreases due to the reduced thermal inertia at high pressure. In addition to this, augmentation of perturbation frequency also enhances amplification of vaporization rate because the time period for the pressure oscillation is much smaller than the liquid thermal inertia time. The phase of evaporation rate shifts backward due to the elevated thermal inertia at high acoustic frequency.

• 한국광물학회지
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• 제10권2호
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• pp.97-104
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• 1997

Based on the method of determination for relative stability of each phase from the difference among the interaction parameters of the phases consisting the mixed layer, the types of interactions between layers were specified and interaction parameter between layers in ordered domain was analytically derived as a function parameter between layers in ordered domain was analytically derived as a function of not only temperature and mole fraction of layers but also ordering parameter. Interaction parameter between the different layers in ordered phase, L is as follows:{{{{ {L }_{1 } (X,Q,T)= { C} over { Q} -4(1-2Q) { L}^{2 } - { RT} over {2} ln { 1} over {2 } - { 2RT} over { { X}_{ s} } ln { { 4QX}`_{s } ^{2 } } over {(1- { X}_{s }- { QX}_{s })( { X}_{s }- {QX }_{s } ) } }}}}L2 is the interaction parameter between ordered and disordered phase in domain and is the mole fraction of the domain which represent the infinite length of mixed layer mineral and Q and C are the reaction progress parameter and arbitrary constant, respectively. This equation was used for the I/S mixed layer clay minerals to infer the relative stability of R1 type I/S mixed layer in the temperature range from 373K to 450K. The result of calculation suggest that, owing to the decrease in interaction parameter with increasing temperature. The interaction parameter decreases more rapidly with decreasing mole fraction of smectite in domain, which is consistent with the fact that the probability of finding the series smectite layer is lo in the domain with small mole fraction of smectite layers in natural system.

• ETRI Journal
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• 제46권2호
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• pp.333-346
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• 2024

Various techniques for noninvasively focus microwave energy on lesions have been proposed for thermotherapy. To focus the microwave energy on the lesion, a focusing parameter, which is referred to as the magnitude and phase of microwaves radiated from an external array antenna, is very important. Although the finite-difference time-domain (FDTD)-based time-reversal (TR) focusing algorithm is widely used, it has a long processing time if the focusing target position changes or if optimization is needed. We propose a technique to obtain multistatic data (MSD) based on Green's function and use it to derive the focusing parameters. Computer simulations were used to evaluate the electric fields inside the object using the FDTD method and Green's function as well as to compare the focusing parameters using FDTD- and MSD-based TR focusing algorithms. Regardless of the use of Green's function, the processing time of MSD-based TR focusing algorithms reduces to approximately 1/2 or 1/590 compared with the FDTD-based algorithm. In addition, we optimize the focusing parameters to eliminate hotspots, which are unnecessary focusing positions, by adding phase-reversed electric fields and confirm hotspot suppression through simulations.

• Bulletin of the Korean Chemical Society
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• 제15권12호
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• pp.1098-1103
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• 1994

Atomic force microscopy (AFM) images of two conducting layered transition-metal ditellurides, $TaTe_2$ and $Ta_{0.5}$$V_{0.5}$$Te_2$, were examined and their surface and bulk structural features were compared. All the measured unit cell parameters from AFM image were consistent and in complete agreement with the results of the X-ray diffraction. The microscopic structures of corrugated surface tellurium sheets were strongly affected by the modification of metal double zig-zag chains underneath Te surface. Large difference in the height amplitudes of AFM images in $TaTe_2$ and $Ta_{0.5}$$V_{0.5}$$Te_2$ phases was observed and this reflects large difference in the surface electron densities of two phases. On surface, the shorter intralayer Te…Te contacts in $TaTe_2$ induce more electron transfer from Te p-block bands to Ta d-block bands, thus electron density on surface observed in $TaTe_2$ is much lower than that of $Ta_{0.5}$$V_{0.5}$$Te_2$. However, in bulk, interlayer Te…Te contacts in V substituted phase are shorter than those in $TaTe_2$ phase, thus tellurium-to-metal electron transfer occurs more easily in $Ta_{0.5}$$V_{0.5}$$Te_2$ phase.

• Composites Research
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• 제31권6호
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• pp.365-370
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• 2018

One of the critical parameters to improve the output power for triboelectric nanogenerators (TENGs) is the surface charge density. In this work, we modify the tribo-material of TENG by introducing the $TiO_x$ embedded Polydimethylsiloxane (PDMS) in anatase and rutile phase. The effect of dielectric constant and electronic structure of the $TiO_x$ on the capacitance of TENG and the output power as well are discussed. The surface charge density is increased as the control of the dielectric constant in difference weight percent of $TiO_x$ and PDMS. As the results of that, the 5% $TiO_x$ rutile phase and 7% $TiO_x$ anatase phase embedded PDMS exhibit the highest TENG output. The peak value of voltage/current obtained from $TiO_x$ rutile and anatase phase are ${\sim}180V/8.2{\mu}A$ and $211.6V/8.7{\mu}A$, respectively, at the external force of 5 N and working frequency of 5 Hz, which gives over 12-fold and 15-fold power enhancement compared with the TENG based on the pristine PDMS film. This study provides a better understanding for TENG performance enhancement from the materials view.