• 대한의용생체공학회:의공학회지
• /
• 제32권3호
• /
• pp.245-250
• /
• 2011

Parallel imaging technique can provide several advantages for a multitude of MRI applications. Especially, in SENSE technique, sensitivity maps were always required in order to determine the reconstruction matrix, therefore, a number of difference approaches using sensitivity information from coils have been demonstrated to improve of image quality. Moreover, many filtering methods were proposed such as adaptive matched filter and nonlinear diffusion technique to optimize the suppression of background noise and to improve of image quality. In this study, we performed SENSE reconstruction using computer simulations to confirm the most suitable method for the feasibility of filtering effect and according to changing order of polynomial fit that were applied on variation of spatial resolution of sensitivity map. The image was obtained at 0.32T(Magfinder II, Genpia, Korea) MRI system using spin-echo pulse sequence(TR/TE = 500/20 ms, FOV = 300 mm, matrix = $128{\times}128$, thickness = 8 mm). For the simulation, obtained image was multiplied with four linear-array coil sensitivities which were formed of 2D-gaussian distribution and the image was complex white gaussian noise was added. Image processing was separated to apply two methods which were polynomial fitting and filtering according to spatial resolution of sensitivity map and each coil image was subsampled corresponding to reduction factor(r-factor) of 2 and 4. The results were compared to mean value of geomety factor(g-factor) and artifact power(AP) according to r-factor 2 and 4. Our results were represented while changing of spatial resolution of sensitivity map and r-factor, polynomial fit methods were represented the better results compared with general filtering methods. Although our result had limitation of computer simulation study instead of applying to experiment and coil geometric array such as linear, our method may be useful for determination of optimal sensitivity map in a linear coil array.

• 한국지능시스템학회논문지
• /
• 제22권6호
• /
• pp.774-779
• /
• 2012

본 논문은 brain-computer interface (BCI)를 통해 움직임 상상 시 측정된 뇌-활동전위신호(EEG)에 내포된 행동의도의 패턴을 보다 정확하게 분류하기 위한 최적 EEG 채널 선택 기법을 제안한다. 기존의 EEG 측정실험에서는 실험 설계자에 의해 대뇌 기능적 피질 분류를 이용하여 인위적으로 선별된 채널을 활용하거나 측정기기가 수용 가능한 전체 채널을 사용해왔으며, 일정 수준의 패턴분류 정확도를 얻을 수 있었지만 다수의 채널로 인해 Common Spatial Pattern (CSP) 등의 패턴특징 추출 시 overfit 및 계산 복잡도 증가의 문제가 발생되었다. 이를 극복하기 위하여 방안으로 본 논문에서는 binary particle swarm optimization (BPSO)을 기반으로 다수의 채널 중 최적 채널을 자동으로 선택하고, 각각의 채널에 대한 impact factor를 부여함으로써 중요 채널 부근의 채널들에 가중치를 부여하는 선택방법을 제안하였으며, Support Vector Machine (SVM)을 이용하여 다수의 채널을 사용 하였을 때의 정확도와 channel impact factor를 고려한 BPSO를 적용시켰을 때의 정확도를 비교, 분석하였다.

• 한국광학회지
• /
• 제10권1호
• /
• pp.32-39
• /
• 1999

본연구에서는 연속적으로 세기 분포를 갖는 CGH 패턴을 두 가지 서로 다른 방법으로 이진화를 하고 그 패턴을 LCSLM(liquid crystal spatial light modulator)에 적용하여 재생 특성을 비교해 보았다. 이진화 방법으로는 에러확산 알고리즘과 직접 얀자화 방법을 사용하였다. 재생 특성 비교에 사용한 인자들은 전체 밝기 평균, 평균 제곱 에러, 그리고 회절 효율이다. 실험에 사용한 LCSLM은 256$\times$256 점들을 가지고 87% fill factor와 15$\mu$m pixel pitch를 가지는 이진의 전기적으로 어드레스되는 반사형 강유전성 액정 공간 광 변조기이다.

• Nuclear Engineering and Technology
• /
• 제55권2호
• /
• pp.749-755
• /
• 2023

A new approximation method was proposed for treating the non-resonant spatial self-shielding effects of double heterogeneous region such as the double heterogeneous effect of VHTR fuel compact in the thermal energy range and that of BP compact with BISO. The method was developed based on the effective homogenization method and a spherical unit cell model with explicit coated layers and a matrix layer. The self-shielding factor was derived from the relation between the collision probabilities for a double heterogeneous compact and the effective cross section for the homogenized compact. First, the collision probabilities and transmission probabilities for all layers of the spherical model were calculated using conventional collision probability solver. Then, the effective cross section for the homogenized sphere cell representing the homogenized compact was obtained from the transmission probability calculated using the probability density function of a chord length. The verification calculations revealed that the proposed method can predict the self-shielding factor with a maximum error of 2.3% and the double heterogeneous effect with a maximum error of 200 pcm in the typical VHTR problems with various packing fractions and BP compact sizes.

• 대한원격탐사학회지
• /
• 제15권2호
• /
• pp.91-105
• /
• 1999

최근 다중 지질정보의 통합적 해석은 GIS의 중요한 응용 분야중 하나로 인식되고 있다. 공간통합을 위하여 지구통계학적 방법들이 개발되어 있지만, 통합결과와 입력 주제도들 사이의 관계에 대한 통계적, 정량적 분석방법론의 개발은 아직까지 체계적으로 정립되어 있지 못한 상황이다. 본 연구에서는 지질도, 지화학자료, 항공지구물리자료, 지형자료 및 원격탐사 영상등 다양한 지질정보등이 보고된 옥동지역을 대상으로 하여 광물 부존 예상도 작성 사례연구를 수행하여 기존에 이용되고 있는 여러 공간 통합 방법중 확실인자 (Certainty Factor: CF) 추정방법과 다변량 통계 분석방법중 하나인 주성분분석을 시험적인 통합방법으로 우선적으로 적용한 뒤, 입력 자료와 통합결과에 대한 정량적인 통계량 정보를 추출하고자 하였다. 입력 주제도와 통합 결과사이의 관계 규명에는 통계 분할표를 이용한 통계처리를 편의 분석에는 잭나이프 방법을 적용하였다. 통합정보에 대한 통계량 분석을 통하여, 통합 결과와 입력자료 사이의 정량적 관계를 추출할 수 있었으며, 부가적으로 입력자료의 상태수준에 대한 판단정보를 얻을 수 있었다. 이러한 결과는 GIS 관점에서 통합결과 해석에 중요한 결정보조자료로 활용될 수 있으며, 복잡한 다중정보를 다루는데 공간 통합문제에서도 입력정보 검증을 위한 일반적일 처리과정으로도 발전할 수 있을 것으로 생각된다.

• 대한지구과학교육학회지
• /
• 제10권3호
• /
• pp.308-322
• /
• 2017

본 연구의 목적은 공간지각능력에 따른 고등학생들의 탄소 순환 개념을 알아보고자 하는 것이다. 이를 위하여 광역시 소재의 평준화 일반계 남녀공학 S고등학교 학생들 중 2학년 1학기에 지구과학 I을 이수한 자연계열 남학생 30명과 여학생 33명을 대상으로 공간지각능력 검사를 실시하고 공간지각능력 상 하 두 집단의 학생들 중에서 본 연구 참여에 동의한 남학생 4명과 여학생 4명을 대상으로 탄소순환 개념 검사를 실시하였다. 본 연구의 결과, 공간지각능력이 높은 학생들은 공간지각능력이 낮은 학생들 보다 단어연상에서 탄소 순환 개념, 상태 변화개념, 과정 개념이 더 많았으며 그림 그리기에서 탄소 순환 개념, 상태 변화와 과정 개념도 더 많은 것으로 나타났다. 시스템적 관점에서 사용된 연결고리는 공간지각능력이 높은 학생들의 인과지도에서 1명이 2개, 1명이 1개, 2명이 0개로 나타났고 그림 그리기에서 3명이 1개, 1명이 0개로 나타났으며 공간지각능력이 낮은 학생들의 인과지도와 그림 그리기에서는 전혀 나타나지 않았다. 공간지각능력이 높은 학생들은 공간지각능력이 낮은 학생들에 비해 지구시스템의 하위영역의 상호작용으로 탄소가 이동하는 것을 이해하고 있었다. 공간지각능력이 높은 3명의 학생들은 낮은 수준의 시스템 사고 개념이 있었으며 공간지각능력이 높은 학생 1명과 공간지각능력이 낮은 학생들 4명은 시스템 사고 개념이 없었다.

• 한국멀티미디어학회논문지
• /
• 제25권4호
• /
• pp.649-659
• /
• 2022

The most important factor in pre-school children's psychological perception is ease of learning, and the closest measure is "natural" interaction. This study aims to explore the potential of tangible user interfaces (TUI) for AR collaboration for children's cognitive development. The conceptual model is constructed by analyzing physical interaction, spatial perception and social collaboration on the usability of TUI, to explore the role of TUI in pre-school children's cognition. In the empirical study, children aged 3-6 were taken as research objects. The experimental tool is "Plugo" education application. Parents answered questionnaires after observing their children's use. Research shows that physical interaction are the most critical factor in TUI. TUI is beneficial to the cultivation of spatial ability. The results are as follows: 1. Cronbach's Alpha and KMO were 0.921 and 0.965, which were significant and passed the reliability and validity test. 2. Through confirmatory factor analysis (model fit index, combinatorial validity), we found that physical interaction were closely related to usability. 3. The path analysis of the relationship proves that usability has a significant impact on the cultivation of pre-school children's spatial ability.

• Geomechanics and Engineering
• /
• 제36권6호
• /
• pp.631-640
• /
• 2024

In the traditional slope stability analysis, ignoring the spatial variability of slope soil will lead to inaccurate analysis. In this paper, the K-L series expansion method is adopted to simulate random field of soil strength parameters. Based on Random Limit Equilibrium Method (RLEM), the influence of variation coefficient and fluctuation range on reliability of soil slope supported by micro-pile is investigated. The results show that the fluctuation ranges and the variation coefficients significantly influence the failure probability of soil slope supported by micro-pile. With the increase of fluctuation range of soil strength parameters, the mean safety factor of the slope increases slightly. The failure probability of the soil slope increases with the increase of fluctuation range when the mean safety factor of the slope is greater than 1. The failure probability of the slope increases by nearly 8.5% when the fluctuation range is increased from δ_v=2 m to δ_v =8 m. With the increase of the variation coefficient of soil strength parameters, the mean safety factor of the slope decreases slightly, and the probability of failure of soil slope increases accordingly. The failure probability of the slope increases by nearly 31% when the variation coefficient increases from COV_c=0.2, COV_φ=0.05 to COV_c=0.5, COV_φ=0.2.

• 한국대기환경학회지
• /
• 제28권3호
• /
• pp.294-305
• /
• 2012

The objective of this study is to estimate the chemical compositions and to identify qualitative sources of fall-out particles in study area. Also, this study used a spatial analysis to estimate spatial distributions and average deposition flux. In this study, the chemical compositions of fall-out particle samples collected at Muncheon lake from May 2010 to January 2011 were analyzed by ICP and IC. The monthly trend of deposition fluxes for fall-out particles showed highest in June ($107.61kg/km^2/day$) and lowest in October ($22.22kg/km^2/day$). The average fluxes of Fe, Si, Al, Zn and Ba are 0.44, 0.24, 0.20, 0.17, $0.09kg/km^2/day$, respectively. Also, the average fluxes of $NO_3^-$, $SO_4^{2-}$, $NH_4^+$, $Ca^{2+}$, and $Na^+$ are 6.48, 5.01, 4.96, 1.75, $1.37kg/km^2/day$, respectively. A Factor analysis identified four sources such as 1) nonferrous metal, motor vehicle, and agriculture, 2) soil, 3) field burning, incineration, and 4) road dust and oil burning. The IDW (inverse distance weighting) spatial analysis method was used to estimate spatial distribution and average deposition flux for fall-out particles. A total average deposition fluxes estimated in Muncheon lake were 936.15 kg/month. The spatial distribution trend of deposition flux showed higher at site 1 and 2 than at site 3, 4 because local road is adjacent to the site 1 and 2.

• ETRI Journal
• /
• 제39권2호
• /
• pp.255-263
• /
• 2017

This paper proposes a graph-theatrical approach to optimize spatial reuse by adopting a technique that quantizes the channel information into single bit sub-messages. First, we introduce an interference graph to model the network topology. Based on the interference graph, the computational requirements of the algorithm that computes the optimal spatial reuse factor of each user are reduced to quasilinear time complexity, ideal for practical implementation. We perform a resource allocation procedure that can maximize the efficiency of spatial reuse. The proposed spatial reuse scheme provides advantages in beamforming systems, where in the interference with neighbor nodes can be mitigated by using directional beams. Based on results of system level measurements performed to illustrate the physical interference from practical millimeter wave wireless links, we conclude that the potential of the proposed algorithm is both feasible and promising.