• 대한핵의학회지
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• 제38권6호
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• pp.486-491
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• 2004

목적: 요소분석법. 독립성분분석법 등이 PET을 이용하여 심근혈류를 비침습적으로 측정하기 위하여 사용되어 왔다. 이론적으로 뛰어나고 새로운 방법인 앙상블 독려성분분석법을 이용하여 $H_2^{15}O$ 동적 심근 PET데이터의 정량분석방법을 개발하였다. 이 연구에서 사용한 앙상블 독려성분분석법을 이용하여 환자의 혈류를 정량화 하였다. 대상 및 방법: 관동맥질환이 의심되어 관류 SPECT를 시행한 환자 20명을 대상으로 $H_2^{15}O$ 동적 심근 PET을 시행한 후 앙상블 독립성분분석법을 이용하여 심근 독립성분영상을 추출하였으며, 좌심실영역과 심근영역에 대한 영상대조도를 조사하였다. 앙상블 학습은 독립성분과 가중치 행렬에 대한 확률분포를 가정하고 베이지안 이론에 의해서 혼합자료에 대한 확률분포를 추정한다. 이렇게 추정한 혼합자료의 확률분포와 실제 분포간의 차이인 Kullback-Leibler 발산치가 최소가 되도록 독립성분과 가중치 행렬을 순차적으로 변화시켜가며 최종 해를 찾는 방식이다. 이 연구에서 사후확률분포는 동적 핵의학 영상에 적합한 비음성제약조건과 함께 수정된 가우시안 분포를 이용하여 최적화 하였다. 혈류량은 심첨부, 중벽 네 부분, 하벽 네 부분의 9개 영역으로 나누어 측정하였으며, 측정결과에 대해 관류 SPECT 소견과 관동맥조영술의 소견과 비교하였다. 결과: 전체 20명의 휴식기 및 부하기 영상에서 5명을 제외한 15명의 데이터에 대해 심근혈류를 측정할 수 있었다. $H_2^{15}O$ 동적 심근 PET에서 앙상블 독립성분분석법을 이용하여 정량화한 휴식기 혈류량은 $1.2{\pm}0.40$ ml/min/g, 부하기 혈류량은 $1.85{\pm}1.12$ml/min/g이었다. 같은 영역에 대해 두 번 측정했을 때 측정된 심근혈류값의 상관계수는 0.99로 재현성이 높았다. 분리된 독립성분영상에서 영상대조도는 좌심실에 대한 심근영역의 비는 평균 1:2.7이었다. 관동맥 조영술을 시행한 9명에서 협착이 없는 분절과 협착이 있는 분절의 혈류예비능에 유의한 차이가 있었다(P<0.01). 또한, 관동맥조영술에서 협착이 확인된 66분절의 심근관류 SPECT 소견에서 가역적 혈류감소를 보인 분절의 혈류예비능이 더 많이 감소되는 경향을 보였으나 통계적 유의성을 보이지는 않았다. 결론: 앙상블 학습을 이용한 독립성분분석방법을 이용하여 심근혈류가 측정이 되었다. 앙상블 독립성분분석법을 이용한 $H_2^{15}O$ 동적 심근 PET 분석방법이 관상동맥 질환의 분석 및 동적 핵의학 영상 데이터의 연구에 도움이 될 것으로 기대된다.

• 대한기계학회논문집A
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• 제36권3호
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• pp.305-311
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• 2012

보강 원통셸의 기본 고유 진동수를 최적화하기 위해서, 보강재의 개수를 1 개에서 5 개까지 보강된 원통셸에 대한 시뮬레이션을 수행하였다. 고유 진동수에 대한 최적화를 시뮬레이션하기 위해서 ANSYS 11.0 을 사용하였다. 최적화 방법으로 Subproblem Approximation Method 를 이용하였다. 최적화의 설계 함수로는 T-형 링 보강재의 기하형상이며, 제한 함수로는 보강에 따른 추가 부피가 10 % 이내로 제한하였다. 목적함수는 기본 고유진동수를 최대화하는 것이다. 최적 설계에 대한 성능 지표는 비보강 원통셸과 보강원통셸의 고유진동수와 부피의 비로서 정의하였다. 최적 성능 지수는 3 개의 보강재를 사용한 원통셸에서 나타났다.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.345-351
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• 2016

This study was carried out to determine an optimal lean $NO_x$ trap (LNT) regeneration condition based on a $NO_x$ storage fraction. The LNT regeneration was performed by an in-cylinder post fuel injection method. A $NO_x$ storage fraction is defined by the ratio of current cumulated $NO_x$ amount in the LNT to the $NO_x$ storage capacity: 0 means empty and 1 fully loaded. In this study five engine operating conditions were chosen to represent the New European Driving Cycle. With various $NO_x$ storage fractions each engine operating condition, the LNT regeneration was executed and then $NO_x$ conversion efficiency, additional fuel consumption, CO and THC slip, peak catalyst temperature were measured. The results showed that there exist an optimal condition to regenerate the LNT, eg. 1500 rpm 6 bar BMEP with below 0.7 $NO_x$ storage fraction in this experimental constraint.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.236-241
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• 1998

The NOAA AVHRR remote sense SST data, collected by the National Fisheries Research and Development Institute (NFRDI), are analyzed in order to understand the spatial and temporal distributions of SST in the seas adjacent to Korea. Our study is based on 10-day SST images during last 7 years (1991-1997). For a time series analysis of multiple 557 images, all of images must be aligned exactly at the same position by adjusting the scales and positions of each SST image. We devised an algorithm which yields automatic detections of cloud pixels from multiple SST images. The cloud detection algorithm is based on a physical constraint that SST anomalies in the ocean do not exceed certain limits (we used $\pm$ 3$^{\circ}C$ as a criterion of SST anomalies). The remote sense SST data are tuned by comparing remote sense data with observed SST at coastal stations. Seasonal variations of SST are studied by harmonic fit of SST normals at each pixel. The SST anomalies are studied by statistical method. We found that the SST anomalies are rather persistent with time scales between 1 and 2 months. Utilizing the persistency of SST anomalies, we devised an algorithm for a prediction of future SST Model fit of SST anomalies to the Markov process model yields that autoregression coefficients of SST anomalies during a time elapse of 10 days are between 0.5 and 0.7. We plan to improve our algorithms of automatic cloud pixel detection and prediction of future SST. Our algorithm is expected to be incorporated to the operational real time service of SST around Korea.

• 천문학회지
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• 제48권6호
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• pp.381-398
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• 2015

Dynamical analysis of compact groups provides important tests of models of compact group formation and evolution. By compiling 2066 redshifts from FLWO/FAST, from the literature, and from SDSS DR12 in the fields of compact groups in , we construct the largest sample of compact groups with complete spectroscopic redshifts in the redshift range 0.01 < z < 0.22. This large redshift sample shows that the interloper fraction in the compact group candidates is ~ 42%. A secure sample of 332 compact groups includes 192 groups with four or more member galaxies and 140 groups with three members. The fraction of early-type galaxies in these compact groups is 62%, higher than for the original Hickson compact groups. The velocity dispersions of early-and late-type galaxies in compact groups change little with groupcentric radius; the radii sampled are less than 100 h⁻¹ kpc, smaller than the radii typically sampled by members of massive clusters of galaxies. The physical properties of our sample compact groups include size, number density, velocity dispersion, and local environment; these properties slightly differ from those derived for the original Hickson compact groups and for the DPOSS II compact groups. Differences result from subtle differences in the way the group candidates were originally selected. The abundance of the compact groups changes little with redshift over the range covered by this sample. The approximate constancy of the abundance for this sample is a potential constraint on the evolution of compact groups on a few Gigayear timescale.

• Progress in Superconductivity
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• 제8권1호
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• pp.113-118
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• 2006

The design of superconducting magnets for a 600 kJ SEMS was discussed. The basic constraint conditions in the design of a 600 kJ SMES magnet were V-I loss(<1 W), inductance of magnet(<24 H), the number of Double Pancake Coils(DPC about 10), the number of turns of DPC(<300), outer diameter of DPC(close to 800 mm) and total length of HTS wire in a DPC(<500 m). As a result of optimum design, we obtained design parameters of the 600 kJ SMES magnet with two operating currents, 360 A and 370 A, which are in the limited conditions without V-I loss. V-I loss of each operating current was calculated with design parameters and V-I characteristic of the HTS wire. As a result of calculations, V-I losses with operating currents of 360 A and 370 A were 0.6 W and 1.86 W, respectively. Even though all design parameters of the SMES magnet in case of operating current of 360 A were in the restricted conditions, V-I loss of SMES magnet showed a tendency to generate at local DPCs, which are located on the top and the bottom of the SMES magnet more than that of the other DPCs.

• Steel and Composite Structures
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• 제31권1호
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• pp.13-25
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• 2019

Reactive powder concrete (RPC) is a type of ultra-high strength concrete that has a relatively high brittleness. However, its ductility can be improved by confinement, and the use of RPC in composite RPC filled steel tube columns has become an important subject of research in recent years. This paper aims to present an experimental study of axial capacity calculation of RPC filled circular steel tube columns. Twenty short columns under axial compression were tested and information on their failure patterns, deformation performance, confinement mechanism and load capacity were presented. The effects of load conditions, diameter-thickness ratio and compressive strength of RPC on the axial behavior were further discussed. The experimental results show that: (1) specimens display drum-shaped failure or shear failure respectively with different confinement coefficients, and the load capacity of most specimens increases after the peak load; (2) the steel tube only provides lateral confinement in the elastic-plastic stage for fully loaded specimens, while the confinement effect from steel tube initials at the set of loading for partially loaded specimens; (3) confinement increases the load capacity of specimens by 3% to 38%, and this increase is more pronounced as the confinement coefficient becomes larger; (4) the residual capacity-to-ultimate capacity ratio is larger than 0.75 for test specimens, thus identifying the composite columns have good ductility. The working mechanism and force model of the composite columns were analyzed, and based on the twin-shear unified strength theory, calculation methods of axial capacity for columns with two load conditions were established.

• International Journal of Computer Science & Network Security
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• 제24권2호
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• pp.53-58
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• 2024

This paper presents a novel miniaturized 3-D cubic antenna for use in wireless sensor network (WSN) application. The geometry of this antenna is designed as a cube including a meander dipole antenna. A truly omnidirectional pattern is produced by this antenna in both E-plane and H-plane, which allows for non-intermittent communication that is orientation independent. The operating frequency lies in the ISM band (centered in 2.45 GHz). The dimensions of this ultra-compact cubic antenna are 1.25*1.12*1cm3 which features a length dimension λ/11. The coefficient which presents the overall antenna structure is Ka=0.44. The cubic shape of the antenna is allowing for smart packaging, as sensor equipment may be easily integrated into the cube hallow interior. The major constraint of WSN is the energy consumption. The power consumption of radio communication unit is relatively high. So it is necessary to design an antenna which improves the energy efficiency. The parameters considered in this work are the resonant frequency, return loss, efficiency, bandwidth, radiation pattern, gain and the electromagnetic field of the proposed antenna. The specificity of this geometry is that its size is relatively small with an excellent gain and efficiency compared to previously structures (reported in the literature). All results of the simulations were performed by CST Microwave Studio simulation software and validated with HFSS. We used Advanced Design System (ADS) to validate the equivalent scheme of our conception. Input here the part of summary.

• 대한기관윤리심의기구협의회지
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• 제3권1호
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• pp.11-18
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• 2021

Purpose: The purpose of this study is to investigate a satisfaction survey of untact education and platforms that can be used for untact education to provide recommendations on future development of Education of Persons Conducting Clinical Trials. Methods: Online survey was distributed among students who have taken Untact Education of Persons Conducting Clinical Trials. The result was separated according to topic and descriptive statistics was used for analysis. The satisfaction survey used 10-point scale. Results: Of the 1,720 students who received the survey, 1,347 (78.3%) responded to the lecture satisfaction survey. The satisfaction level for broadcasting program (Kakao TV), an untact educational platform for the education of clinical trial workers at Kyung Hee University Medical Center, was relatively high with 8.09±1.99 points. Average score respondents recommending Kyung Hee University Untact Education of Persons Conducting Clinical Trials was 8.03±1.83 and customer recommendation score (Net Promotor Score) was 27.1%. Satisfaction level of the preferred training time was divided into weekday-morning (8-11 AM) (8.16±1.75), weekday-afternoon (12-4 PM) (7.73±2.07), weekday-evening (5-9 PM) (7.78±2.22), and weekend-morning (9-11 AM) real-time untact education (8.48±1.76) and analyzed. There was a noticeable difference between weekend-morning and weekday-afternoon (p<0.0001) and weekend-morning and weekday-evening (p=0.0001) real-time untact education. When asked about conducting education after COVID-19 pandemic ends, 79.2% (1,012 of 1,279) of the respondents answered that they prefer real-time untact education while 20.8 % (266 of 1,279) preferred face-to-face education. Conclusion: Online education, without time and space constraint, is expected to be the mainstream market in Korea for Education of Persons Conducting Clinical. Kyung Hee University Untact Education of Persons Conducting Clinical has achieved above average satisfaction using Kakao TV. Kyung Hee University Real-time Untact Education of Persons Conducting Clinical Net Promotor Score is 27.1%, which is above industry average, communication with trainees should be considered to improve Net Promotor Score.

• Journal of Preventive Medicine and Public Health
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• 제18권1호
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• pp.25-39
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• 1985

도시 영세지역 주민의 이환 및 의료이용 양상을 파악하기 위하여 1984년 7월 한 달 동안에 대구시 중구 남산 4동 영세지역 468가구의 가구원 2,002명과 대조지역 374가구의 가구원 1,709명을 대상으로 가구원의 일반적 특성, 질병이환 및 의료이용 양상 등을 면담조사 하였다. 영세지역과 대조지역의 성별, 연령별 분포는 비슷하였으나, 경제수준, 교육수준, 주거밀집도, 의료보장 종류별 분포는 유의한 차이를 보였다. 15일간의 상병 이환율은 영세지역이 1,000명당 131로 대조지역의 71보다 유의하게 높았고, 연령이 증가함에 따라 이환율도 증가하는 경향을 보였으나 65세이상의 노인층에서는 오히려 감소하였다. 년간 만성병 이환율도 영세지역이 1,000명당 134로 대조지역의 89보다 유의하게 높았고 나이가 증가함에 따라 이환율이 증가하였다. 15일간의 상병은 영세지역과 대조지역 모두 호흡기계 질환이 각각 24.0%, 29.8%로 가장 많았고 그 다음은 소화기계 질환으로 21.0%, 20.6%였으며 손상 및 중독은 영세지역이 10.3%인데 비해 대조지역은 3.3%였다. 만성병은 영세지역과 대조지역 모두 소화기계질환이 22.1%, 21.7%로 가장 많았고 그 다음으로 영세지역은 근골격계 질환으로 12.3%, 대조지역은 신경통으로 14.5%였으며, 순환기계 질환은 대조지역이 11.8%로 영세지역의 5.6% 보다 더 많은데 비해 손상 및 중독은 영세지역이 10.8%로 대조지역의 4.6%보다 더 많았다. 15일간의 상병으로 활동제한을 받은 일수는 영세지역이 평균 4.0일로 대조지역의 평균 2.2일보다 유의하게 높았다. 15일간의 상병이나 만성병을 치료받기 위해 영세지역은 약국을 더 많이 이용하고 대조지역은 병의원 외래를 더 많이 이용하였으며, 특히 의료보장 종류별로는 의료보험 가입자는 병의원 외래를, 그리고 일반환자는 약국을 더 많이 이용하였으며, 미치료율은 의료보장 종류에 관계없이 15일 이환의 경우 영세지역이 17.9%, 대조지역은 11.6%, 그리고 만성병은 영세지역이 15.2%, 대조지역은 9.2%로 영세지역의 미치료율이 대조지역보다 더 높았다. 15일간의 상병이나 만성병 모두 경제적인 이유로 치료받지 않은 경우가 가장 많았다. 영세지역의 이환율이 대조지역보다 높은 것은 경제수준, 교육정도, 주거밀집도 등 여러가지 사회 경제적인 요소가 관련된 것으로 나타났으므로, 영세민을 위한 보건사업 계획에는 이러한 사회 경제적인 요소들을 개선하는 노력을 병행해야 효과적인 보건사업이 추진될 것으로 생각된다.