• Korean Journal of Materials Research
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• v.4 no.6
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• pp.704-709
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• 1994

The $(LaS)_xCrS_2(x \approx 1.20$) of the incommensurate misfit layer was systhesized from reactant mixture of$La_S_3$,Cr and S at 1273K. Powder X-ray diffration of $(LaS)_xCrS_2(x \approx 1.20$) was indexed as a complex structure consisted with a monoclinic LaS-sublattice, a triclinic $CrS_{2}$-sublattice and their superlattice. The temperature dependence of sublattice dimension was investigated by the X-ray diffraction analysis at low temperature. The magnetic susceptibility of $(LaS)_xCrS_2(x \approx 1.20$) was measured between 77K and room temperature using a Faraday balance method. $(LaS)_xCrS_2(x \approx 1.20$) was paramagnetic on a $\sigma$-H plot at room temperature. The observed effective magnetic moment( p dr) was in fair agreement with the value calculated by spin-only contribution for $Cr^{3+}$ and spin and orbital contribution for $La^{3+}$.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.4
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• pp.473-478
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• 2011

The extent of a rectangular conducting plane for measuring electromagnetic interference is discussed. Mutual coupling between the transmit and receive antennas is negligible, the effects of the ground plane on the normalized site attenuation(NSA) are considered by applying GTD(Geometric theory of diffraction). The calculation was done for the case that measuring distance(d) was 3 m for both horizontal and vertical polarizations. As the result, the size of the rectangular ground plane almost never affects upon NSA for horizontal polarization, but for vertical case, when both width and length of the rectangular plane are several times as long as distance, the effects of the edges are reduced under 1 dB.

• Journal of Environmental Science International
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• v.6 no.5
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• pp.541-550
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• 1997

A least-square regression analysis is applied for the estimation of velocity streamfunction field based on discretely sampled current meter data. The coefficients of a streamfuunction that is expanded in terms of trigonometric basis function are obtained by enforcing the horizontal non-divergence of two-dimensional flow field. This method avoids Interpolation and gives a root-mean-square (rms) residual of fit which Includes the divergent part and noisiness of oceanic data. The Implementation of the method Is done by employing a boundary-fitted, curvilinear orthogonal coordinate which facilitates the specification of boundary conditions. An application is successfully made to the Texas-Louisiana shelf using the 32 months current meter data (31 moorings) observed as a part of the Texas-Louisiana Shelf and Transport Processes Study (LATEX). The rms residual of the fitting is relatively small for the shelf, which indicates the field Is Ivell represented by the streamnfunction.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.2
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• pp.41-50
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• 1993

This paper describes an effort to develop a microcomputer-based parameter identification system for three phase and two phase brushless DC motor. Back EMF equation is derived from back EMF waveform of three phase and two phase brushless DC motor. In this paper, a new identification algorithm for the brushless DC motor parameters by Pasek's technique is developed. It is found that Pasek's equation is valid for the brushless DC motor, too. The results obtained clearly shows that it is possible to implement the identification system for the determination of the brushless DC motor parameters. To minimize errors due to the ripple component in the measured armature current, digital averaging firis employed. The whole identification process of signal generation, measuring, parameter determination is fully automated. The use of the propod method in the parameter identifition system shows that the averaged current curve is in excellent agreement with the estimated current curve. Therefore, this close agreement confirms the validity of this technique.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.179-186
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• 2004

본 연구의 목적은 숙련된 골프선수들의 골프 스윙동작 시 상이한 무게중심 변환 형태가 존재하는지 그리고 만약 이 상이한 무게중심 변환 형태가 존재한다면 어떤 형태로 나타나는지를 알아보고자 하였다. 본 실험을 위해 13명의 남자 대학 엘리트 골프 선수들을 대상으로 드라이버를 이용한 스윙을 실시하게 하였다. 수직 지면 반력과 압력중심 이동 패턴을 측정하기 위해 지면반력기 2대와 스윙 동작 시 critical event 설정을 위해 1대의 고감도 비디오 카메라를 사용하였다. 또한 스윙 결과로 나타나는 비거리, 클럽헤드 속도를 측정하기 위해 스윙 분석기를 이용하였다. 피험자 간 상호 비교를 위해 측정된 수직 지면반력 성분은 몸무게를 이용하여 표준화하였고 압력중심은 어드레스시의 압력중심을 원점으로 재 계산하였다. 또한 임팩트 시 측정된 좌우 수직 지면반력 성분을 이용하여 두 가지의 상이한 스윙 스타일로 구분하였다. 연구결과 8명(62%)의 피험자에게서 좌측 수직력 성분이 상대적으로 높은 전족(FFS) 스타일임이 밝혀졌고 5명(38%)은 그 반대인 리버스(RFS) 스타일임이 밝혀졌다. 이 전족 스타일은 대부분의 골퍼들이 선호하고 또 그렇게 하여야만 한다고 믿고 있는 스윙방식이다. 이와 반대인 리버스 스타일은 코치들이 금기시 하는 스윙의 형태로서 초보자, 즉 비숙련 자에게만 나타나는 전형적인 스윙형태라고 인지되고 있다. 하지만 이 두 가지 스윙 스타일이 초보자가 아닌 숙련된 골프 선수들에게서도 실제 존재한다는 것이 본 실험 결과로 나타났다. 평균 압력중심 이동 패턴은 전후축 방향의 경우 RFS 스타일 그룹이 RFS 스타일 그룹에 비해 압력중심 이동이 크게 나타났고 좌우축의 경우에도 RFS 그룹이 FFS 그룹에 비해 압력중심 이동이 크게 나타났다. 특히 임팩트 시 압력중심의 위치가 FFS 그룹은 전족 근처에 있는 반면 RFS 그룹은 후족(rear foot)에 위치하여 두 스윙 스타일의 차이점을 분명하게 보여주었다. 따라서 비록 이 RFS 스타일이 대부분의 코칭 이론과는 상반되는 무게중심 이동 패턴을 보여주었지만 이 스윙 스타일이 잘못된 것이 아닌 실제 존재하는 하나의 스윙 스타일로 인식하여 스윙 지도 시 이에 알맞은 적절한 교습법을 마련해야 할 것이다.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.18-24
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• 2017

We performed seismic imaging based on relative S-wave travel times to examine S-wave velocity of upper mantle structure beneath East Asia. We used teleseismic events recorded at 129 broadband stations of the Korea Institute of Geoscience and Mineral Resources (KIGAM), Korea Meteorological Administration (KMA), and National Research Institute for Earth Science and Disaster Prevention (NIED). Relative travel time residuals were obtained by a multi-channel cross-correlation method designed to automatically determine accurate relative phase arrival times. The resulting images show high-velocity anomalies along plate boundaries around the Japanese islands region. These anomalies may indicate subducting Pacific and Philippine Sea plates. On the other hand, a low-velocity anomaly is revealed beneath east of the Korean peninsula down to around 300 km depth, which is thought to be related to the formation of the Ulleung basin and the Ulleung island. Low-velocity anomalies revealed beneath the Jeju island may imply that the formation and volcanism of the Jeju island have been caused by magmatic sources from the deep mantle.

• Journal of the Korea Society of Computer and Information
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• v.25 no.7
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• pp.27-37
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• 2020

In this paper, we propose the methodology based on data-driven approach using Natural Language Processing and Machine Learning for classifying requirements into functional requirements and non-functional requirements. Through the analysis of the results of the requirements classification, we have learned that the trained models derived from requirements classification with data-preprocessing and classification algorithm based on the characteristics and information of existing requirements that used term weights based on TF and IDF outperformed the results that used stemming and stop words to classify the requirements into functional and non-functional requirements. This observation also shows that the term weight calculated without removal of the stemming and stop words influenced the results positively. Furthermore, we investigate an optimized method for the study of classifying software requirements into functional and non-functional requirements.

• Geophysics and Geophysical Exploration
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• v.20 no.3
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• pp.129-136
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• 2017

3D seismic data processing methods such as full waveform inversion or reverse-time migration require 3D wave propagation modeling and heavy calculations. We compared efficiency and accuracy of a Xeon Phi coprocessor to those of a high-end server CPU using 3D frequency-domain wave propagation modeling. We adopted the OpenMP parallel programming to the time-domain finite difference algorithm by considering the characteristics of the Xeon Phi coprocessors. We applied the Fourier transform using a running-integration to obtain the frequency-domain wavefield. A numerical test on frequency-domain wavefield modeling was performed using the 3D SEG/EAGE salt velocity model. Consequently, we could obtain an accurate frequency-domain wavefield and attain a 1.44x speedup using the Xeon Phi coprocessor compared to the CPU.

• Journal of Korea Multimedia Society
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• v.15 no.7
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• pp.847-858
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• 2012

In this paper, we propose a mobile watermarking based on the distortion analysis of display-capture image in a smart phone. We compose a random sequence by utilizing the property of frequency band in the wavelet domain. Then we calculate the CCS (Coefficients Comparative Sum) using the block wavelet coefficients of selected subbands after the wavelet transformation and the random sequence and repeatedly embed a watermark using an insertion threshold for the watermark robustness. For correcting a distortion caused by the display-capture process, we adopt a frame at the outside of watermarked image, then we can equate a watermark synchronization by detecting the frame. And we can improve frame detection ratio by using an iteratively adaptive threshold. A proposed scheme embedded information of 206 bits into standard digital images and it shows an average about 41.42 dB in PSNR. In watermark extract experiments, a proposed scheme accurately recognizes the frame more than 97% in total captured images. Also in BER (Bit Error Ratio) of captured images, it shows about 3.73%, then it was improved more than 70%, compared with the Pramila's method.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.271-271
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• 2011

최근의 유출해석은 지리정보체계(GIS, Geographic Information System) 및 지형자료(DEM, Digital Elevation Model 등) 구축의 발달로 대부분 격자 기반의 분포형 강우-유출 모형을 통해 이루어지고 있으며, Rodriguez-Iturbe and Valdes (1979)에 의해 소개된 통계물리학적 접근방법인 지형학적 순간단위도(GIUH)모형 역시 DEM을 기반으로 한 연구가 꾸준히 진행되어 온 실정이다(Maidment, 1993; D'odorico and Rigon, 2003; Di Lazzaro, 2010). 이러한 격자 기반 모형들은 대부분 8방향 최급경사에 기초한 흐름방향도를 기반으로 물의 유동을 표현한다. 8방향법에 의해 결정된 흐름방향도를 이용할 경우 각 격자 중심에서 유역출구 까지의 배수로경로길이를 비교적 쉽고, 빠르게 계산할 수 있다는 장점을 가지나, 공간해상도(격자 규모)에 따라 상이한 결과를 나타내는 것을 예상할 수 있다. 따라서 본 연구에서는 DEM의 공간해상도에 따른 배수경로길이의 통계적 변화양상을 살펴보고, 이로부터 실제 수문사상의 통계적 특성과 Di Lazzaro(2010)의 특성유속산정 공식을 이용해 지표면과 하천의 특성유속을 산정하였다. 산정된 특성유속들을 D'odorico and Rigon(2003)이 제시한 값과 비교함으로써 격자 기반의 GIUH 모형의 적용에 있어서 적정 공간해상도를 찾고자 하였다. 대상유역으로는 국제수문개발계획(IHP, International Hydrological Project)의 금강수계 보청천 유역 중 이평수위국을 출구로하는 소유역을 선정하였으며, DEM의 공간해상도는 수치지형도의 축척을 고려하여 1: 5,000의 경우 5, 10, 15, 20m를, 1: 25,000의 경우 20, 30, 50, 100, 150, 200m로 결정하였다. 분석 결과 격자 형태 GIUH의 특성유속을 산정을 위한 적정 공간해상도는 1:5,000의 경우 5m를, 1:25,000의 경우에는 20～50m의 범위를 적용하는 것이 타당할 것으로 판단된다.