• Journal of Communications and Networks
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• 제12권5호
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• pp.475-479
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• 2010

The clipping value, defined as the log-likelihood ratio (LLR) in the case wherein all the list of candidates have the same binary value, is investigated, and an effective method to estimate it is presented for iterative tree search detection. The basic principle behind the method is that the clipping value of a channel bit is equal to the LLR of the maximum probability of correct decision of the bit to the corresponding probability of erroneous decision. In conjunction with multilevel bit mappings, the clipping value can be calculated with the parameters of the number of transmit antennas, $N_t$; number of bits per constellation point, $M_c$; and variance of the channel noise, $\sigma^2$, per real dimension in the Rayleigh fading channel. Analyses and simulations show that the bit error performance of the proposed method is better than that of the conventional fixed-value method.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.73-78
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• 2003

Ultrasonic measurement is one of important technologies in the lift-time maintenance of nuclear poler plant. Ultrasonic inspection system is consisted of the operator, equipment and procedure. The reliability of ultrasonic inspection system is affected by its ability. The performance demonstration round robin was conducted to quantify the capability of ultrasonic inspection for in-service. The small number of teams who employed procedures that met or exceeded ASME Sec. XI Code requirements detected the piping of nuclear power plant with various cracks to evaluate the capability of detection and sizing. In this paper, the statistical reliability assessment of ultrasonic nondestructive inspection data using Monte Carlo simulation is presented. The results of the probability of detection (POD) analysis using Monte Carlo simulation are compared to these of logistic probability model. In these results, Monte Carlo simulation was found to be very useful to the reliability assessment f3r the small hit/miss data sets.

• Journal of the Korean Statistical Society
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• 제22권1호
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• pp.71-81
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• 1993

Among k independent normal populations with unknown means and a common unknown variance, the problem of detecting the population with the largest absolute value of mean is considered. This problem is formulated in a manner close to the framework of testing hypotheses, and the maximum error probability and the minimum power are considered. The power charts necessary to determine the sample size are provided. The problem of detecting the population with the smallest absolute value of mean is also considered.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.57-59
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• 2006

The purpose of search problem is to maximize the probability of target detection as limited search capability. Especially, as elapsing of time at a point of time of initial information received the target detection rate for searching an expected location due to a moving target such that wrecked ship or submarine decrease in these problems. The algorithm of search problem to a moving target having similar property of above targets should solve the search route as quickly as possible. In existing studies, they have a limit of applying in practice due to increasing computation time required by problem size (i.e., number of search area, search time). In this study, we provide that it takes more reasonable computation time than preceding studies even though extending a problem size practically using an approximate computation of probability.

• Journal of information and communication convergence engineering
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• 제12권2호
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• pp.97-103
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• 2014

In spectrum sensing, there is a tradeoff between the probability of missed detection and the probability of a false alarm according to the value of the sensing threshold. Therefore, it is important to determine the sensing threshold suitable to the environment of cognitive radio networks. In this study, we consider a cognitive radio-based ad hoc network where secondary users directly communicate by using the same frequency band as the primary system and control their transmit power on the basis of the distance between them. First, we investigate a condition in which the primary and the secondary users can share the same frequency band without harmful interference from each other, and then, propose an algorithm that controls the sensing threshold dynamically on the basis of the transmit power of the secondary user. The analysis and simulation results show that the proposed sensing threshold control algorithm has low probabilities of both missed detection and a false alarm and thus, enables optimized spectrum sharing between the primary and the secondary systems.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.246-251
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• 2001

The performance demonstration round robin test was conducted to quantify the capability of ultrasonic inspection for in-service and to address some aspects of reliability for nondestructive evaluation. The fifteen inspection teams who employed procedures that met or exceeded ASME Sec. XI code requirements detected the pinping of nuclear power plant with various cracks to evaluate the capability of detection. With data from PD-RR test, the performance of ultrasonic nondestructive inspection could be assessed using probability of detection and length and depth sizing of cracks.

• 전자공학회논문지SC
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• 제49권1호
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• pp.74-79
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• 2012

위상배열레이더를 이용한 추적의 성능을 지수화하기 위해서 각도예측 오차공분산행렬의 함수를 이용한 정량화 방법에 대해 검토하였다. 특히, 이 오차공분산행렬의 함수로 최대고유값과 대각합을 이용하여 정량화하는 경우에 대해 안테나 빔조향 손실을 반영한 표적탐지확률을 기준으로 정량화의 일관성을 수치실험을 통해 검토하였다. 이를 통해 추적성능을 표적탐지확률로 기준하는 경우, 대각합이 최대고유값 보다 더 일관성을 갖는 정량화 함수임을 확인하였다.

• Journal of Communications and Networks
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• 제5권2호
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• pp.124-134
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• 2003

In this paper, we investigate the error probability performance of noncoherently detected orthogonal modulation combined with Alamouti space-time block coding. We find that there are two types of pair-wise error probabilities that characterize the performance. We employ methods that allow a direct evaluation of exact, closed-form expressions for these error probabilities. Theoretical as well as numerical results show that noncoherent orthogonal modulation combined with space-time block coding (STBC) achieves full spatial diversity. We derive an expression for approximate average bit error probability for-ary orthogonal signaling that allows one to show the tradeoff between increased rate and performance degradation.

• 한국압력기기공학회 논문집
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• 제6권1호
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• pp.43-49
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• 2010

The piping failure probability of the reactor coolant system in Kori unit 1 was evaluated considering stress corrosion cracking. The P-PIE program (Probabilistic Piping Integrity Evaluation Program) developed in this study was used in the analysis. The effect of some variables such as oxygen concentration during start up and steady state operation, and operating temperature, which are related with stress corrosion cracking, on the piping failure probabilities was investigated. The effects of leak detection capability, the size of big leak, piping loops, and reactor types on the piping failure probability were also investigated. The results show that (1) LOCA (loss of coolant accident) probability of Kori unit 1 is extremely low, (2) leak probability is sensitive to oxygen concentration during steady state operation and operating temperature, while not sensitive to the oxygen concentration during start up, and (3) the piping thickness and operating temperature play important roles in the leak probabilities of the cold leg in 4 reactor types having same inner diameter.

• 한국통신학회논문지
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• 제21권7호
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• pp.1803-1813
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• 1996

This paper describes an automatic threshold decision using a maximum mismatched correlation value in the direct sequence spread spectrum (DS-SS) system. For received PN codes with different single-to-noise ratio (SNR), this scheme is able to detect a desired threshold value in the search mode, i.e. a maximum mismstched correlation value, so that value is utilized as a threshold for the verification mode. Performance of the proposed scheme in both the additive white gaussian noise (AWGN) and frequency-selective Rayleigh fading channels is analyzed through the Monte Carlo simulation. And hardware implementation of this scheme using a DSP processor is demonstrated. The proposed acquisition shceme is compared to the conventional constant threshold (CT) scheme, and significant improvement of performance is shown. Analysis of system performance in the verification mode is presented, and key quantities such as the false alarm probability and the detection probability are derived in a AWGN channel.