• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.85-94
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• 1999

Transient aerodynamic response of an airfoil to a moving plane-flap is numerically investigated using two-dimensional Euler equations with conservative Chimera grid method. A body moving relative to a stationary grid is treated by an overset grid bounded by a 'dynamic domain-dividing line' the concept of which is developed in this study. A conservative Chimera grid method with a dynamic domain-dividing line technique is applied and validated by solving the flowfield around circular cylinder moving supersonic speed. The unsteady and transient characteristics of the flow solver is also examined by computations of a oscillating airfoil and a ramp pitching airfoil respectively. The transient aerodynamic behavior of an airfoil with a moving plane-flap is analyzed for various flow conditions such as deflecting rate of flap and free stream Mach number.

• Journal of Power Electronics
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• 제9권2호
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• pp.188-197
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• 2009

This paper presents an adaptive flux observer to estimate stator flux linkage and stator inductances of an interior permanent-magnet synchronous machine considering magnetic saturation. The concept of static and dynamic inductances due to saturation is introduced in the machine model to describe the relationship between current and flux linkage and the relationship between their time derivatives. A flux observer designed in the stationary reference frame with constant inductance is analyzed in the rotor reference frame by a frequency-response characteristic. An adaptive algorithm for an on-line inductance estimation is proposed and a Lyapunov-based analysis is given to discuss its stability. The dynamic inductances are estimated by using Taylor approximation based on the static inductances estimated by the adaptive method. The simulation and experimental results show the feasibility and performance of the proposed technique.

• 방송공학회논문지
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• 제23권5호
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• pp.642-655
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• 2018

빌딩, 집에 설치되어 있는 점유 센서는 사람이 없으면 소등하고, 반대이면 점등한다. 현재는 주요 센서로 PIR(pyroelectric infra-red)이 널리 사용되고 있다. 최근에 비전 카메라 센서를 이용하여 사람 점유를 검출하는 연구가 진행되고 있다. 카메라 센서는 정지된 사람을 검출할 수 없는 PIR의 단점을 극복할 수 있는 장점이 있다. 이동 및 정지된 사람의 추적은 카메라 점유 센서의 주요 기능이다. 본 논문에서는 합성곱 신경망 모델과 자기 조직화 지도를 활용한 온라인 사람 추적 기법을 제안한다. 오프라인에 모델을 학습시키기 위해서는 많은 수의 훈련 샘플이 필요하다. 이러한 문제를 해결하기 위해, 학습되지 않은 모델을 사용하고, 실험 영상으로부터 직접 훈련 샘플을 수집하여 모델을 갱신한다. 오버헤드 카메라로 실내에서 촬영한 영상을 이용하여, 제안 방법이 효과적으로 사람을 추적하고 있음을 실험을 통해 증명하였다.

• Radiation Oncology Journal
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• 제17권3호
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• pp.223-229
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• 1999

목적 : 세포의 성장 상태 즉, 지수적 증식기와 평형기 세포에서 방사선에 의한 c-jun의 발현 양상의 차이를 파악하고, 방사선조사 후 세포주기 분포를 분석하여 이들의 상관 관계를 알아보고자 하였다. 대상 및 방법 : 사람 자궁경부암 세포주인 CaSki를 대상으로 날자 경과에 따른 세포성장곡선을 작성하여 지수적 증식기(제 4일)와 평형기(제 9일) 세포를 정하였다. 방사선조사는 6 MV 선형가속기를 이용해 2 Gy의 선량을 조사하였고, 이때 선량률은 3 Gy/min 이었다. 지수적 증식기와 평형기 세포 각각에 방사선조사 후 시간 경과에 따라 total RNA를 추출하여 northern blot analysis를 시행해 c-jun의 발현 양상을 관찰하였다. 또 방사선조사 후 시간 경과에 따라 세포를 얻어 유세포계측법을 이용해 세포주기 분포를 분석하였다. 결과 : 방사선조사 1 시간 후에 지수적 증식기와 평형기 세포 모두에서 최대의 발현이 관찰되었다. 그러나 이후 6시간까지 지수적 증식기 세포에서는 지속적으로 발현이 증가한 반면, 평형기에서는 점차 발현이 감소되는 양상을 보였다. 방사선에 의한 세포주기의 변화는 지수적 증식기에서 시간 경과에 따라 G0-G1에서 S, G2-M 기로의 이동이 더 활발히 일어났다. 결론 : c-jun 은 방사선조사 후 성장상태에 따른 세포 증식의 조절과 관련 있을 것이다.

• 천문학논총
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• 제30권2호
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• pp.605-607
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• 2015

The development of time-frequency analysis techniques allow astronomers to successfully deal with the non-stationary time series that originate from unstable physical mechanisms. We applied a recently developed time-frequency analysis method, the Hilbert-Huang transform (HHT), to two non-stationary phenomena: the superorbital modulation in the high-mass X-ray binary SMC X-1 and the quasi-periodic oscillation (QPO) of the AGN RE J1034+396. From the analysis of SMC X-1, we obtained a Hilbert spectrum that shows more detailed information in both the time and frequency domains. Then, a phase-resolved analysis of both the spectra and the orbital profiles was presented. From the spectral analysis, we noticed that the iron line production is dominated by different regions of this binary system in different superorbital phases. Furthermore, a pre-eclipse dip lying at orbital phase ~0:6-0:85 was discovered during the superorbital transition state. We further applied the HHT to analyze the QPO of RE J1034+396. From the Hilbert spectrum and the O-C analysis results, we suggest that it is better to divide the evolution of the QPO into three epochs according to their different periodicities. The correlations between the QPO periods and corresponding fluxes were also different in these three epochs. The change in periodicity and the relationships could be interpreted as the change in oscillation mode based on the diskoseismology model.

• Journal of Communications and Networks
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• 제17권1호
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• pp.1-11
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• 2015

In this paper, the transmission of an improper-complex second-order stationary data sequence is considered over a strictly band-limited frequency-selective channel. It is assumed that the transmitter employs linear modulation and that the channel output is corrupted by additive proper-complex cyclostationary noise. Under the average transmit power constraint, the problem of minimizing the mean-squared error at the output of a widely linear receiver is formulated in the time domain to find the optimal transmit and receive waveforms. The optimization problem is converted into a frequency-domain problem by using the vectorized Fourier transform technique and put into the form of a double minimization. First, the widely linear receiver is optimized that requires, unlike the linear receiver design with only one waveform, the design of two receive waveforms. Then, the optimal transmit waveform for the linear modulator is derived by introducing the notion of the impropriety frequency function of a discrete-time random process and by performing a line search combined with an iterative algorithm. The optimal solution shows that both the periodic spectral correlation due to the cyclostationarity and the symmetric spectral correlation about the origin due to the impropriety are well exploited.

• 천문학회보
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• 제45권1호
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• pp.43.1-43.1
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• 2020

Cassiopeia A (Cas A) is a young supernova remnant (SNR) where we observe the interaction of SNR blast wave with circumstellar medium. From the early optical studies, dense, slowly-moving, N-rich "quasi-stationary flocculi" (QSF) have been known. These are probably dense CNO-processed circumstellar knots that have been engulfed by the SNR blast wave. We have carried out near-infrared, high-resolution (R=45,000) spectroscopic observations of ~40 QSF, and here we present the result on a QSF knot (hereafter 'Knot 24') near the SNR boundary of Cas A. The average [Fe II] 1.644 um spectrum of Knot 24 has a remarkable shape with a narrow (~8 km/s) line superposed on the broad (~200 km/s) line emitted from shocked gas. The spatial morphology and the line parameters indicate that Knot 24 has been partially destroyed by a shock wave and that the narrow line is emitted from the unshocked material heated/ionized by the shock radiation. This is the first detection of the emission from the pristine circumstellar material of the Cas A supernova progenitor. We also detected H Br gamma and other [Fe II] lines corresponding to the narrow [Fe II] 1.644 um line. For the main clump where we can clearly identify the shock emission associated with the unshocked material, we analyze the observed line ratios using a shock model that includes radiative precursor. The analysis indicates that the majority of Fe in the unshocked material is in the gas phase, not depleted onto dust grains as in the general interstellar medium. We discuss the non-depletion of Fe in QSF and its implications on the immediate progenitor of the Cas A supernova.

• 한국환경보건학회지
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• 제32권5호
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• pp.506-514
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• 2006

The objectives of this study were to evaluate personal exposure estimated using a time activity pattern and microenvironmental model. The study was carried out for 44 children attending a primary school nearby the lines (school A) and 125 children attending a school away from 154 kV power lines (school B). For children attending school A, the estimated personal level was a little weak correlated with the measured level($Pearson\;r\;=0.34{\sim}0.35$). For children attending school B, the correlation was very low ($Pearson\;r\;=\;0.09{\sim}0.16$) using the TW A Model II, otherwise, TWA Model II-I which considered the average residential MF level according to the distance from the power line and home explained $39{\sim}53%$ of the correlation in MF personal exposures. The estimated personal exposure level was very well represented by the measured exposure level using TWA Model II-2 which consisted on spot and 24 h stationary measurements at subject's home ($Pearson\;r\;=\;0.65{\sim}0.85$). In conclusion, personal magnetic field expsoure estimated using a TWA Model II-2 should be provided for a reasonable estimate of measured exposure in schoolchildren living near the power line.

• Wind and Structures
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• 제23권3호
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• pp.211-229
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• 2016

In recent years, the frequency and duration of supply interruption in electric power transmission system due to flashover increase yearly in China. Flashover is usually associated with inadequate electric clearance and often takes place in extreme weathers, such as downbursts, typhoons and hurricanes. The present study focuses on the wind-induced oscillation of conductor during the process when a downburst is passing by or across a specified transmission line. Based on a revised analytical model recently developed for stationary downburst, transient three-dimensional wind fields of moving downbursts are successfully simulated. In the simulations, the downbursts travel along various motion paths according to the certain initial locations and directions of motion assumed in advance. Then, an eight-span section, extracted from a practical 500 kV ultra-high-voltage transmission line, is chosen. After performing a non-linear transient analysis, the transient displacements of the conductors could be obtained. Also, an extensive study on suspension insulator strings' rotation angles is conducted, and the electric clearances at different strings could be compared directly. The results show that both the variation trends of the transient responses and the corresponding peak values vary seriously with the motion paths of downburst. Accordingly, the location of the specified string, which is in the most disadvantageous situation along the studied line section, is picked out. And a representative motion path is concluded for reference in the calculation of each string's oscillation for the precaution of wind-induced flashover under downburst.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권3호
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• pp.178-184
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• 2002

High-throughput screening has become a popular method used to identify new “leads”for potentially therapeutic compounds. Further screening of these lead compounds is typically done with secondary assays which may utilize living, functioning cells as screening tools. A problem (or benefit) with these cell-based assays is that living cells are very sensitive to their environment. We have been interested in the process of stem cell migration and how it relates to the cellular therapy of bone marrow transplantation. In this study we describe a secondary, cell-based assay for screening the effects of various in-vitro conditions on Immature Hematopoietic Cell (IHC) migration. Our results have revealed many subtle factors, such as the cell's adhesive characteristics, or the effect of a culture's growth phase, that need to be accounted for in a screening protocol. Finally, we show that exponentially glowing KG1a cells (a human IHC cell line) were 10 times more motile than those in the lag or stationary phases. These data strongly suggest that KG1a cells secrete a chemokinetic factor during the exponential growth phase of a culture.