• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.514-519
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• 1992

To make an accurate retrieval of the proportion of each category among mixed pixels (Mixel's) of a remotely sensed imagery, a maximum likelihood estimation method of category proportion is proposed. In this method, the observed multispectral vector is considered as probability variables along with the approximation that the supervised data of each category can be characterized by normal distribution. The results show that this method can retrieve accurate proportion of each category among Mixel's. And a index that can estimate the degree of error in each category is proposed. AS one of the application of the proportion estimation, a method for image classification based on category proportion estimation is proposed. In this method all pixel in a remotely sensed imagery are assumed to be Mixel's, and are classified to most dominant category. Among the Mixel's, there exists unconfidential pixels which should be categorized as unclassified pixels. In order to discriminate them, two types of criteria, Chi square and AIC, are proposed for fitness test on pure pixel hypothesis. Experimental result with a simulated dataset show an usefulness of proposed classification criterion compared to the conventional maximum likelihood criterion and applicability of the fitness tests based on Chi square and AIC,

• 한국컴퓨터정보학회논문지
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• 제9권4호
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• pp.85-91
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• 2004

최근 들어 인간의 의지를 컴퓨터에 전달하기 위한 수단으로 컴퓨터 시각기반 방식으로 제스처를 인식하고자 하는 연구가 널리 진행되고 있다. 제스처 인식에서 가장 중요한 이슈는 알고리즘의 단순화와 처리 시간의 감소이다. 이러한 문제를 해결하기 위하여 본 연구에서는 기하학적 집합론에 근거하고 있는 수학적 형태론을 적용하였다. 본 논문에서 제안한 알고리즘의 키 아이디어는 형태론적 형상분해를 적용하여 얻은 원시형상 요소들의 중심점을 연결하는 궤적을 추적하는 것이다. 핸드 제스처 시퀀스의 중심점 궤적은 핸드 제스처의 형상에 관련된 중요한 정보를 내포하고 있다. 이러한 특징에 근거하여 본 연구에서는 원시형상 요소들의 중심점 궤적과 직접적으로 관련되는 체인코드 에지벡터로부터 형상의 특징벡터를 계산하여 핸드 제스처 시퀀스를 인식할 수 있는 알고리즘을 제안하고, 실험을 통하여 그 유용성을 증명하였다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.324-327
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• 2008

Microwave remote sensing has great potential, especially in monsoon Asia, since optical observations are often hampered by cloudy conditions. The radar backscattering characteristics of rice crop were investigated with a ground-based automatic scatterometer system. The system was installed inside a shelter in an experimental paddy field at the National Institute of Agricultural Science and Technology (NIAST) before transplanting. The rice cultivar was a kind of Japonica type, called Chuchung. The scatterometer system consists of X-band antennas, HP8720D vector network analyzer, RF cables, and a personal computer that controls frequency, polarization and data storage. This system automatically measures fully-polarimatric backscattering coefficients of rice crop every 10 minutes, accompanied by a digital camera that takes pictures in a fixed position with the same interval. The backscattering coefficients were calculated by applying a radar equation. Plant variables, such as leaf area index (LAI), biomass, plant height and weather conditions were measured periodically throughout the rice growth season. We have performed polarimetric decomposition of paddy data such as single, double and volume scattering to extract the scattering information effectively. We investigated the relationships between backscattering coefficients and the plant variables.

• 한국전산유체공학회지
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• 제18권3호
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• pp.26-33
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• 2013

In the present study, unsteady flow simulations of a variable geometry nozzle were conducted using a two-dimensional flow solver based on hybrid unstructured meshes. The variable geometry nozzle is used to achieve efficient performances of aircraft engines at various operating conditions. To describe the motion of the variable geometry nozzle, an algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements. A ball-vertex spring analogy was used for inviscid elements. The aerodynamic data were obtained for a range of nozzle pressure ratios, and the validations were made by comparing the present results with available experimental data. The unsteady nozzle flows were simulated with an oscillating diverging section and a converging-diverging section. It was found that the nozzle performances are influenced by the nozzle exit flow characteristics, mass flow rate, as well as unsteady effects. These unsteady effects are shown to behave differently depending on the frequency of the nozzle motion.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권3호
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• pp.494-507
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• 2011

In this paper, we propose two schemes to reduce the complexity of fixed-complexity sphere decoder (FSD) algorithm in the ordering and tree-search stages, respectively, while achieving quasi-ML performance. In the ordering stage, we propose a QR-decomposition-based FSD signal ordering based on the zero-forcing criterion (FSD-ZF-SQRD) that requires only a few number of additional complex flops compared to the unsorted QRD. Also, the proposed ordering algorithm is extended using the minimum mean square error (MMSE) criterion to achieve better performance. In the tree-search stage, we introduce a threshold-based complexity reduction approach for the FSD depending on the reliability of the signal with the largest noise amplification. Numerical results show that in 8 ${\times}$ 8 MIMO system, the proposed FSD-ZF-SQRD and FSD-MMSE-SQRD only require 19.5% and 26.3% of the computational efforts required by Hassibi's scheme, respectively. Moreover, a third threshold vector is outlined which can be used for high order modulation schemes. In 4 ${\times}$ 4 MIMO system using 16-QAM and 64-QAM, simulation results show that when the proposed threshold-based approach is employed, FSD requires only 62.86% and 53.67% of its full complexity, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3010-3025
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• 2016

Lattice reduction (LR) has been used widely in conventional multiple-input multiple-output (MIMO) systems to enhance the performance. However, LR is hard to be applied to the relay systems which are important but more complicated in the wireless communication theory. This paper introduces a new viewpoint for utilizing LR in multiuser MIMO relay systems. The vector precoding (VP) is designed along with zero force (ZF) criterion and minimum mean square error (MMSE) criterion and enhanced by LR algorithm. This implementable precoder design combines nonlinear processing at the base station (BS) and linear processing at the relay. This precoder is capable of avoiding multiuser interference (MUI) at the mobile stations (MSs) and achieving excellent performance. Moreover, it is shown that the amount of feedback information is much less than that of the singular value decomposition (SVD) design. Simulation results show that the proposed scheme using the complex version of the Lenstra--Lenstra--Lovász (LLL) algorithm significantly improves system performance.

• 한국가시화정보학회지
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• 제8권1호
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• pp.31-38
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• 2010

An experimental study to evaluate dynamic structures of flow and turbulence characteristics in bubble-driven liquid flow in a rectangular tank with a varying flow rate of compressed air is conducted. Liquid flow fields are measured by time-resolved particle image velocimetry (PIV) with fluorescent tracer particles to eliminate diffused reflections, and by an image intensifier to acquire enhanced clean particle images. Instantaneous vector fields are investigated by using the two frame cross-correlation function and bad vectors are eliminated by magnitude difference technique. By proper orthogonal decomposition (POD) analysis, the energy distributions of spatial and temporal modes are acquired. When Reynolds number increases, bubble-induced turbulent motion becomes dominant rather than the recirculating flow near the side wall. The total kinetic energy transferred to the liquid from the rising bubbles shows a nonlinear relation regarding the energy input because of the interaction between bubbles and free surface.

• 대한기계학회논문집
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• 제16권12호
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• pp.2298-2305
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• 1992

본 연구에서는 보의 종방향 강성치를 실제보다 훨씬 작은 횡방향 강성치 수준 으로 낮추어 시간 적분을 수행하는 대신, 종방향에 작용하는 힘을 분산시켜서 계산시 종방향 상대 변형을 억제하는 기법을 사용하였다. 또 여러개의 물체가 조인트에서 서로 연결되어 이루어진 다물체 도역학의 해는 운동 방정식과 기구학적 제한조건을 모 두 만족시켜야 하며, 상미분 방정식 해법용 시간 적분을 바로 적용할 수는 없다. 본 논문에서는 참고문헌(13)과 (14)에 소개된 반복계산법 및 계산가속기법에 의하여 Lag- range multiplier를 운동 방정식에서 소거한 후 시간 적분을 수행하는 방법을 사용한 다.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.543-553
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• 2020

This paper examines the effect of COVID-19 pandemic on the Philippine stock exchange, peso-dollar rate and retail price of diesel using robust least squares regression and vector autoregression (VAR). The robust least squares regression using MM-estimation method concluded that COVID-19 daily infection has negative and statistically significant effect on the Philippine stock exchange index, peso-dollar exchange rate and retail pump price of diesel. This is consistent with the results of correlation diagnostics. As for the VAR model, the lag values of the independent variable disclose significance in explaining the Philippine stock exchange index, peso-dollar exchange rate and retail pump price of diesel. Moreover, in the short run, the impulse response function confirmed relative effect of COVID-19 daily infections and the variance decomposition divulge that COVID-19 daily infections have accounted for only minor portion in explaining fluctuations of the Philippine stock exchange index, peso-dollar exchange and retail pump price of diesel. In the long term, the influence levels off. The Granger causality test suggests that COVID-19 daily infections cause changes in the Philippine stock exchange index and peso-dollar exchange rate in the short run. However, COVID-19 infection has no causal link with retail pump price of diesel.

• 전자공학회논문지
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• 제51권7호
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• pp.142-148
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• 2014

3-차원 원통 구조의 공명관에 Krylov-Schur 순환 법을 적용하였다. 균질한 메질에서 공명파의 세기를 기술하는 벡터 Helmholtz 방정식을 FEM을 이용하여 분석하였다. 고유 방정식은 사면 배위 구조 요소의 변-접선 벡터에 기반을 두어 구성하였다. 이 방정식은 Helmholtz 작용자의 curl-curl과 연관된 정방형 행렬들로 이루어져 있다. 고유-값들과 고유-모드들은 이들에 대하여 Krylov-Schur 순환 법을 적용하고, Schur 행렬의 대각 성분들과 변환 행렬들로 부터 구하였다. 결과로써 이들 고유-값과 고유-모드 쌍들을 시각적으로 묘사하였다. 그리고 각각의 경계조건에 따른 고유-쌍들을 서로 비교하였다.