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김형문,Kim, Hyung-Moon 한국군사과학기술학회 2007 한국군사과학기술학회지 Vol.10 No.2
The ubiquitous embedded computers are firmly established as the basic electronic component of design that control military systems. Such applications can be found everywhere in the field of military system. A embedded computer is required to redesign when system needs performance upgrade or production-state of processor is NRND or EOL. This paper describes a scheme about impact analysis of designing processor alteration on embedded computer. In this case, hardware architecture and interrupt source of target system must be considered. Also, performance and throughput of that must be analyzed.
Optimal classifier for multivariate rectangle-screened normal data classification
김형문,윤영주,김혜중 한국통계학회 2015 Journal of the Korean Statistical Society Vol.44 No.4
This paper discusses the classification procedures which make provision for the case where the interest of an investigator is to classify a multidimensional screened normal observation into one of two or more populations. A number of problems are thoroughly investigated in order to render the procedures optimal. These include multidimensional screened normal models that describe the evolutions of the screened observations from different populations, derivation of an optimal classification rule and its linear approximation, and estimation of the rules via the expectation–maximization algorithm with a sequence of conditional maximization steps. The efficiency of the classification rules is examined by using simulation studies. Using real data of bank employee’s salary from the IBM SPSS Statistics 19, we illustrate the empirical relevance of the screened classification.
Moments of Variogram Estimator for a Generalized Skew t Distribution
김형문 한국통계학회 2005 Journal of the Korean Statistical Society Vol.34 No.2
Variogram estimation is an important step of spatial statistics since it determines the kriging weights. Matheron’s variogram estimator can be written as a quadratic form of the observed data. In this paper, we extend a skew t distribution to a generalized skew t distribution and moments of the variogram estimator for a generalized skew t distribution are derived in closed forms. After calculating the correlation structure of the variogram estimator, variogram fitting by generalized least squares is discussed.
New closed-form estimators for weighted Lindley distribution
김형문,장유형 한국통계학회 2021 Journal of the Korean Statistical Society Vol.50 No.2
We propose new closed-form estimators for two-parameter weighted Lindley (WL) distribution. These new estimators are derived from likelihood equations of power transformed WL distribution. They behave very similarly to maximum likelihood estimators (MLEs) and achieve consistency and asymptotic normality. Numerical results show that, unlike existing closed-form estimators, the new estimators are uniformly comparable to MLEs. In addition, to reduce biases of the new estimators in the case of small samples, we apply a bias-correction method to the new estimators, based on the approximate Cox-Snell formula. Our simulation studies indicate that this bias-correction method is effective in enhancing small-sample performance. Finally, we present three real data examples.
장거리 수중 음향 통신 신호에 의한 수중 운동체 피탐지 성능 분석
김형문,안종민,김인수,김완진 한국시뮬레이션학회 2022 한국시뮬레이션학회 논문지 Vol.31 No.4
Unlike a short-range, a long-range underwater acoustic communication(UWAC) uses low frequency signal and deep sound channel to minimize propagation loss. In this case, even though communication signals are modulated using a covert transmission technique such as spread spectrum, it is hard to conceal the existence of the signals. The unconcealed communication signal can be utilized as active sonar signal by enemy and presence of underwater vehicles may be exposed to the interceptor. Since it is very important to maintain stealthiness for underwater vehicles, the detection probability of friendly underwater vehicles should be considered when interceptor utilizes our long- range UWAC signal. In this paper, we modeled a long-range UWAC environment for analyzing the detection performance of underwater vehicles and proposed the region of interest(ROI) setup method and the measurement of detection performance. By computer simulations, we yielded parameters, analyzed the detection probability and the detection performance in ROI. The analysis results showed that the proposed detection performance analysis method for underwater vehicles could play an important role in the operation of long-range UWAC equipment. 단거리와 달리 장거리 수중 음향 통신에서는 전파 손실을 최소화하기 위해 저주파 신호와 심해 음파 채널을 사용한다. 이 경우 대역 확산과 같은 은밀 통신 기법을 이용하더라도 통신 사실을 숨기기 어려우며, 통신 신호가 탐지 신호처럼 작용하므로 감청기에 수중 운동체의 존재가 노출될 수 있다. 수중 운동체의 경우 은밀성 유지가 매우 중요하므로, 감청기가 통신 신호를 이용하여 아군 수중 운동체를 탐지할 가능성을 반드시 고려해야 한다. 본 논문에서는 수중 운동체의 피탐지 성능 분석을 위한 장거리 수중 음향 통신 환경을 모델링하고, 피탐지 성능 분석을 위한 관심영역 설정 방법과 평가 척도를 제안하였다. 전산 모의 실험을 통해 파라미터를 산출하고, 관심영역에서 피탐지 확률 분석 및 피탐지 성능 분석을 수행하였다. 분석 결과는 제안된 수중 운동체의 피탐지 성능 분석 방법이 장거리 수중 통신 장비의 운용에 있어 중요한 역할을 할 수 있음을 보였다.