• Journal of electromagnetic engineering and science
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• 제12권3호
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• pp.203-209
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• 2012

In order to improve sensing performance when the noise variance is not known, this paper considers a so-called blind spectrum sensing technique that is based on eigenvalue models. In this paper, we employed the spiked population models in order to identify the miss detection probability. At first, we try to estimate the unknown noise variance based on the blind measurements at a secondary location. We then investigate the performance of detection, in terms of both theoretical and empirical aspects, after applying this estimated noise variance result. In addition, we study the effects of the number of SUs and the number of samples on the spectrum sensing performance.

• 천문학회보
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• 제36권1호
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• pp.59.2-59.2
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• 2011

Constraining physical (or stellar population) properties - such as stellar mass, star-formation rate, stellar population age, and dust-extinction - of galaxies from observation is crucial in the study of galaxy evolution. This is very challenging especially for high-redshift galaxies, and a widely-used method to estimate physical properties of high-redshift galaxies is to compare their photometric spectral energy distributions (SEDs) to spectral templates from stellar population synthesis models. I will show that the SED-fitting results of high-redshift galaxies are strongly dependent on the assumed forms of star-formation histories. I will also present the results of SED-fitting analysis of observed Lyman-break galaxies which show that parametric models with gradually increasing star-formation histories provide better estimates of physical parameters of high-redshift (z>3) star-forming galaxies than traditionally-used exponentially declining star-formation histories. This result is also consistent with the predictions from the modern galaxy formation models.

• 응용통계연구
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• 제31권5호
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• pp.637-653
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• 2018

빠른 고령화로 고령층의 증가는 인구구조 변화와 인구고령화에 영향을 미친다. 예전부터 선진국은 인구고령화를 주요현안으로 간주하여 고령화로 인한 연금 재정건전성, 건강 및 노인 복지 시스템의 지속 가능성에 집중하고 있다. 이처럼 고령층의 증가로 인구구조 변화와 인구고령화에 미치는 사망률 예측은 어느 때보다도 중요하다. 본 논문은 통계청 1970-2016년 각세별 생명표 자료를 활용하여 사망률 모형 6가지를 비교하였다. 이들 모형은 Lee-Carter(LC) 모형 (Lee and Carter, Journal of the American Statistical Association, 87, 659-671, 1992)에 근원을 두고 있으며, LC 의 가정을 수정하고 개선한 것이다. 이들 개선과정과 가정검토를 모형별로 살펴보고 우리나라에 적합한 사망률 모형을 모색했다. 분석결과 빠른 고령화와 연령별 사망률의 개선 효과를 보이는 우리나라의 경우 기대수명에 큰 변화를 주지 않고 이들 현상을 반영하고 연령별 사망률 패턴을 수정하는 LC-ER 모형 (Li 등, Demography, 50, 2037-2051, 2013)과 Li-Lee 모형과 LC-ER모형을 조합한 LL&LC-ER 모형으로 사망률을 예측하는 것이 바람직하다.

• International Journal of Advanced Culture Technology
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• 제10권3호
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• pp.63-70
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• 2022

This study is to investigate that population change as a result of the decline in population has a correlation with a decrease in crime, with the change in the demographic composition by comparing with two models: model with growth in population and one with the decline in population. We collected demographic data for all cities in Korea from the 2010 Census to 2020 offered by the Korean Statistical Information Service, with crime data comprising serious reported crime events from the Korean Nation Police Agency through requesting data related to the total number of crimes at the same as the period of demographic data. This study can identify the impacts of demographic changes as a result of population change on crime change through a comparative analysis between areas with population growth and ones with population decline. We can confirm that there are differences in determinants of crime between areas with population increase and one with population decrease from the analysis of the impact of demographic change as a result of population change on crime change.

• Communications for Statistical Applications and Methods
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• 제4권3호
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• pp.795-805
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• 1997

In this paper, we consider a Bayesian forecasting method for the analysis of repeated surveys. It is assumed that the parameters of the superpopulation model at each time follow a stochastic model. We propose Bayesian prediction procedures for the finite population total under dynamic generalized linear models. Some numerical studies are provided to illustrate the behavior of the proposed predictors.

• 천문학회지
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• 제22권1호
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• pp.1-24
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• 1989

By applying population synthesis method, stellar populations in the nuclei of M31 and M32 are studied. We obtained five and four models for M31 and M32 respectively, for different main sequence turn-offs and keeping the astrophysical constraints as loose as possible. The best models for M31 and M32 are thought to have G0-5 and F5-8 main sequence trun-offs respectively. These models show that the main sequence stars outnumber the giants, which indicates the dwarf-dominance in external galactic nuclei. Even though there are some computational difficulties because of non-uniqueness in solution, two major points can be pointed out when compared to the previous papers. First, the ultraviolet deficiency expected from the conventional metal rich population models is not detected in our models, Instead ultraviolet radiation turns out to be somewhat higher than that of observation. Second one is the minor contribution from the Super Metal Rich (SMR) K giants to the integrated light of the program galaxies. That is, in our models, the SMR contribution is at best the same level as normal giants contrary to the SMR dominance of previous models. Since the loose astrophysical constraints are the major difference of our study from the previous ones, one should re-examine carefully for their validity further.

• Communications for Statistical Applications and Methods
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• 제10권3호
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• pp.647-654
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• 2003

Bayesian probability models for finite populations are considered assuming so-called the super-population. We find the posterior distribution of population mean by a new approach, using the concept of pivotal quantity for the small sample case. A large sample theory is also treated throught the concept of asymptotically pivotal quantity.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.42.1-42
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• 2002

A model to predict population by sex, age and district over a long-range period is proposed based on fuzzy theories. First, a fuzzy model is described. Second, a method to estimate the social increase by sex and age in each district is proposed based on a fuzzy clustering method for dealing with long-range socioeconomic changes in population migration. By the proposed methods, it became possible to predict the population by sex, age and district over a long-range period. Third, the structure and characteristics of the three models of employment model, time distance model, and land use model constructed to predict various socioeconomic indicators, which are require...

• 한국인구학
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• 제23권1호
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• pp.197-215
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• 2000

이 논문에서는 선형·비선형 성장곡선모형의 종류와 특성을 살펴보고, 이들을 비교·검토하고, 모형선호기준 통계량에 입각하여 추정결과를 비교한다. 또한 최종사용자 환경을 위한 SAS/AF로 구현한 성장곡선모형에 의한 인구예측시스템을 소개한다.

• Spatial Information Research
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• 제18권5호
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• pp.107-117
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• 2010

본 연구는 최근 다수 도시개발사업들이 활발히 진행되고 있는 화성시 동부권을 사례대상지로하여 행정구역 단위 인구데이터를 격자형 인구분포자료로 변환한 후 인구유인을 유발할 것으로 예상되는 주요 도시계획관련 공간변수들을 GIS로 측정 대입하여 제네틱 알고리즘기법과 회귀분석기법 두 가지 방법으로 일종의 도시인구분포모형을 구축하였다. 두 가지 모형의 분석결과를 통해 도시환경 해석에 있어서의 두 기법의 성능상 특장점을 비교해 보았으며, 분석결과 GA기법은 변수 설명력에 관한 변별력에 있어 일반회귀분석보다 우월한 특징이 있음을 알 수 있었고 따라서 회귀분석과 병행할 경우 매우 직관적이며 보완적인 도시분석기법이 될 수 있음을 확인할 수 있었다.