• Journal of the Korean Data and Information Science Society
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• 제17권3호
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• pp.991-997
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• 2006

Recently, Liu (2005) proposed a special type of weighting function under a given preference index level with the minimal variability similar to the minimal variability OWA operator weights problem proposed by Fuller and Majlender (2003). He solved this problem using a result of classical optimal control theory. In this note, we give a direct elementary proof of this problem without using any known results.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제2권11호
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• pp.739-746
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• 2013

소프트웨어 프로덕트라인에서 가변성은 프로덕트라인의 멤버제품들을 차별화하는 특성으로, 가변성의 기술은 의미가 명확하고 선택이 용이하도록 가시화되어야 하며 관리하기 용이하여야 한다. 가변성 기술은 크게 개발 모델에 통합하는 방법과 개발 모델과는 독립적으로 기술하는 방법으로 나눌 수 있다. OVDL (Orthogonal Variability Description Language)은 독립적 가변성 기술 방법이면서 타 방법들의 가지는 의미의 모호성을 개선하기 위하여 제안된 가변성 표현 언어이다. 이 논문은 독립적 가변성 기술 방법의 기반을 제공한 OVM (Orthogonal Variability Model)으로 기술된 IWF (Inter-Working Function) 프로덕트라인의 가변성이 OVDL로 번역될 수 있는지 확인하는 방식으로 OVDL의 가변성 기술 역량을 검증한다.

• 천문학논총
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• 제30권2호
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• pp.531-533
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• 2015

We have investigated the long term variability of the intensities of the broad-line region emission lines in the UV spectra of Seyfert I galaxy NGC 5548 from 1973-1996. We have obtained the following results: 1) a high level correlation between the intensities of emission lines as well as between intensities of emission lines and continuum fluxes was discovered. With increasing wavelength the correlation in both cases becomes weaker, 2) the relationship between the intensity of emission lines and the flux radiation in the continuum can be expressed by a power law function with coefficients of ${\alpha}{\approx}0.8-1.1$ for different lines. When the difference between the wavelengths of spectral lines and the continuum is increased, the value of the power function decreases, and 3) it was found that the magnitude of the variability of the line intensities are weaker than the range of variability of the continuum fluxes. The magnitude of the variability of the line intensities and the continuum fluxes increase at longer wavelengths.

• 천문학회보
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• 제45권1호
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• pp.60.1-60.1
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• 2020

We present optical variability of nearby luminous active galactic nucleus (AGN). We use the multi-epoch data of 46 AGNs obtained from 2015 to 2019 through SNU AGN Monitoring Project (SAMP), which was carried out for the reverberation mapping of luminous AGNs. We estimated variability amplitudes and time scales using the various types of analytic function, such as structure function and damped random work. We present the comparisons between physical properties of AGNs and optical variability in order to unveil the origin of the variability of AGNs.

• 수산경영론집
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• 제48권2호
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• pp.1-17
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• 2017

This work studies the variability of flatfish sales revenue. The theoretical analysis draws functions for equilibrium price and quantity using expectation hypotheses. The functions include unpredictable phenomenon with dummy variable and GARCH. The equilibrium function, using adaptive expectation hypothesis, contains the independent variables of supply and demand, while the equilibrium function, embodying rational expectation hypothesis, includes only the independent variables of supply side, because the demand side disappears by the information extraction process theoretically, if economic subjects build the expectation rational. The empirical analysis shows: the variability of flatfish production has a spillover effect on the variability of revenue with the adaptive expectation hypothesis. In the case when the model has a rational expectation hypothesis, the variability of flatfish production has a spillover effect on the revenue (the mean equation of GARCH model). This study indicates that there is the variability in flatfish production and sales revenue, and the spillover effect between them. The result can help to build of the rational system for the fishery income stability.

• 대한원격탐사학회지
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• 제17권2호
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• pp.111-119
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• 2001

This study analyzes time variability of the normalized difference vegetation index (NDVI), the leaf area index (LAI) and surface temperature (Ts) estimated from AVHRR data collected from across the Korean peninsula from 1981 to 1994. In the present study, LAI defined as vegetation density, as a function of NDVI applied for the vegetation types and Ts defined by the split-window formulation of Becker and Li (1990) with emissivity of a function of NDVI, are used. Results of the inter-annual, intra-annual and intra-seasonal variabilities in Korea show: (1) Inter-annual variability of NDVI is generally larger in the southem and eastern parts of the peninsula than in the western part. This large variability results from the significant mean variation. (2) Inter-annual variability of Ts is larger in the areas of smaller NDVI. This result shows that the NDVI play a small role in emissivity. (3) Inter-annual variability of LAI is larger in the regions of higher elevation and urban areas. Changes in LAI are unlikely to be associated with NDVI changes. (4) Changes in NDVI and Ts are likely dominant in July and are relatively small in spring and fall. (5) Urban effect would be obvious on the time-varying properties of NDVI and Ts in Seoul and the northern part of Taejon, where NDVI decreases and Ts increases with a significant magnitude.

• 한국시뮬레이션학회논문지
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• 제20권2호
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• pp.1-10
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• 2011

본 연구에서는 대기행렬네트워크 성과측정 방법 중의 한 가지로서 널리 이용되는 분해법의 구성요소로 제안된 변동성 함수 의 이론적 근거를 살펴보고 성과척도 측정의 정확도 제고를 위하여 회귀분석을 통한 변동성 함수의 모수추정 개선방안을 제안하고자 한다. 이를 위하여 변동성이 높은 도착과정과 서비스 과정이 포함된 직렬 대기행렬 네트워크에서의 이탈과정의 자동상관계수 함수를 추정하여 분해법에 사용할 수 있는 방안을 알아본다.

• 정신신체의학
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• 제12권1호
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• pp.3-14
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• 2004

신경심장학의 발전으로 중추신경 활성이 심장의 전기적 활동도에 미치는 영향이 밝혀지고 있고, 심박동수변이(Heart rate variability, HRV)가 정신적 스트레스와 심혈관질환의 기계적 연관성을 나타내는 중요한 지표로 제기되고 있다. HRV란 자율신경계의 정상적 상호작용에 의해 나타나는 생리적인 심박수 변동을 타나내며, 자율신경 기능을 정량화하여 측정할 수 있는 방법론이다. 분석 방법은 시간 영역 분석과 주파수 영역 분석으로 나눌 수 있으며, 측정 시간대에 따라 단기간 측정과 24시간 측정 등의 방법이 확립되어 있다. 임상적으로는 변이 정도, 교감신경과 부교감신경의 활성과 균형도를 파악하여 다양한 질환과 스트레스 등의 진단과 치료 및 예후 판정에 활용되고 있다. HRV를 이용한 바이오피드백도 최근 자율신경 관련 질환의 치료에 활용되고 있다. 향후 다양한 프로토콜의 개발과 임상적 적용이 필요할 것으로 보인다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 가을 학술발표회논문집
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• pp.207-215
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• 1993

With the aid of finite element method, this paper deals with the problem of structural response variability of transmission tower subjected to the spatial variability of material properties, Young's modulus herein. The spatial variability of material property are modeled as two-dimensional stochastic field which has an isotropic auto-correlation function. Response variability has been computed based on two numerical techniques, such as the Neumann expansion method in conjunction with the Monte Carlo simulation method. The results by these numerical methods are compared with those by the deterministic approach.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.857-864
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• 2006

Due to the difficulties in numerical generation of random fields that satisfy not only the probabilistic distribution but the spectral characteristics as well. it is relatively hard to find an exact response variability of a structural response with a specific random field which has its features in the spatial and spectral domains. In this study. focusing on the fact that the random field assumes a constant over the domain under consideration when the correlation distance tends to infinity, a semi-theoretical solution of response variability is proposed for in-plane and plate bending structures. In this procedure, the probability density function is used directly resulting in a semi-exact solution for the random field in the state of random variable. It is particularly noteworthy that the proposed methodology provides response variability for virtually any type of probability density functions.