• Journal of Korean Society for Quality Management
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• v.25 no.3
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• pp.22-38
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• 1997

In a traditional sequential acceptance sampling plan, it is assumed that the sampled items are independent each other. In this paper, stochastically dependent sequential acceptance sampling plans are dealt when there exists dependency between sampled items. Monte-Calro algorithm is used to find the acceptance and rejection probabilities of a lot. The number of defectives for the test to be accepted and rejected in probability ratio sequential test can be found by using these probabilities. The formula for measures of performance of these sampling plans is developed. Type I and II error probabilities are estimated by simulation. This research can be a, pp.ied to sequential sampling procedures in place of control charts where there is a recognized and necessary dependency during the production processes. Also, dependent multiple acceptance sampling plans can be derived by extending this sequential sampling procedure. As a numerical example, a Markov dependent process model is given, and the characteristics of the sampling plans are examined according to the change of the dependency factor.

• Journal of Sensor Science and Technology
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• v.25 no.4
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• pp.252-256
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• 2016

Epitaxially grown GaN layers have a high surface state density, which typically results in a surface leakage current and a photoresponse in undesirable wavelengths in GaN optoelectronic devices. Surface passivation is, therefore, an important process necessary to prevent performance degradation of GaN UV photodetectors. In this study, we propose oxygen-enhanced thermal treatment as a simple surface passivation process without capping layers. The GaN UV photodetector fabricated using a thermal annealing process exhibits improved electrical and photoresponsive characteristics such as a reduced dark current and an enhanced photoresponsive current and UV-to-visible rejection ratio. The results of this study show that the proposed surface passivation method would be useful to enhance the reliability of GaN-based optoelectronic devices.

• MALSORI
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• no.49
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• pp.145-158
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• 2004

This paper is aiming at implementation of real-time speaker verification system using DSP board. Dialog/4, which is based on microprocessor and DSP processor, is selected to easily control telephone signals and to process audio/voice signals. Speaker verification system performs signal processing and feature extraction after receiving voice and its ID. Then through computing the likelihood ratio of claimed speaker model to the background model, it makes real-time decision on acceptance or rejection. For the verification experiments, total 15 speaker models and 6 background models are adopted. The experimental results show that verification accuracy rates are 99.5% for using telephone speech-based speaker models.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.349-352
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• 1997

The EEG amplifier satisfies high gain, high common mode rejection ratio(CMRR), high input impedance, low thermal drift, low noise and good d.c. performance. The Bipolar amplifier of this paper safisfies above categories and aim at minimization of the ESU(electric surgical unit) interference.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.158.3-158
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• 2001

In this paper, an instrumentation amplifier, which the voltage gain can be electronically adjusted, is proposed. The realization method is based on the use of operational transconductance amplifiers (OTAs) as active circuit elements. The common mode rejection ratio (CMRR) of the proposed scheme is better than 93dB at the frequency of about 70kHz. The temperature effect to the circuit performance is also compensated. Experimental and simulation results demonstrating the characteristics of the proposed scheme are also included.

• Proceedings of the KSPS conference
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• 2005.04a
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• pp.95-98
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• 2005

Many utterance verification (UV) algorithms have been studied to reject out-of-vocabulary (OOV) in speech recognition systems. Most of conventional confidence measures for UV algorithms are mainly based on log likelihood ratio test, but these measures take much time to evaluate the alternative hypothesis or anti-model likelihood. We propose a novel confidence measure which makes use of a momentary best scored state sequence during Viterbi search. Our approach is more efficient than conventional LRT-based algorithms because it does not need to build anti-model or to calculate the alternative hypothesis. The proposed confidence measure shows better performance in additive noise-corrupted speech as well as clean speech.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3E
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• pp.19-23
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• 1997

The goal of postprocessing in automatic speech recognition is to improve recognition performance by utterance verification at the output of recognition stage. It is focused on the effective rejection of out-of vocabulary words based on the confidence score of hypothesized candidate word. We present two methods for computing confidence scores. Both methods are based on the distance between each observation vector and the representative code vector, which is defined by the most likely code vector at each state. While the first method employs simple time normalization, the second one uses a normalization technique based on the concept of on-line garbage mode[1]. According to the speaker independent isolated words recognition experiment with discrete density HMM, the second method outperforms both the first one and conventional likelihood ratio scoring method[2].

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.1
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• pp.14-19
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• 1982

A differential amplifier has been designed and fabricated using aluminum-gate PMOS technology, Only enhaneement-mode MOSFET's are used in the circuit and the dimensions of transistors have been determined using simulation program MSINC. The fabricated integrated circuit with +15V and -l5V power supplies shows an open-loop DC voltage gain of 42 dB, a common mode rejection ratio (CMRR) of 50 dB, and a Power consumption of 20mW.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.867-872
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• 2005

This paper describes the measurement and location method of partial discharges in high voltage CV cables. Coupling capacitors were used to detect partial discharge signal. Impedance characteristic of the coupling circuit and an amplifier with a high Common Mode Rejection Ratio(CMRR) were studied to improve sensitivity of the circuit. From the calibration experiment, the sensitivity of the partial discharge detection circuit was about 100pC. Also, we confirmed that the location of partial discharges in cables can be estimated by calculation of time difference between the first pulse and the second one reflected from the other end of the cable.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.977-984
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• 2012

The cross-correlation technique has been widely used for leakage detection of buried pipes, and this technique can be successfully applied when the leakage signal has a high signal-to-noise ratio. In the case of a power plant, the measured leakage signals obtained from the sensors may contain background noise and mechanical noise generated by adjacent machinery. In such a case, the conventional method using the cross-correlation function may fail to estimate the leakage point. In order to enhance the leakage estimation capability of a buried pipe in a noisy environment, an improved cross-correlation technique is proposed. It uses a noise rejection technique in the frequency domain to effectively eliminate the tonal noise due to rotating machinery. Experiments were carried out to verify the validity of the proposed method. The results show that even in a tonal noisy environment, the proposed method can provide more reliable means for estimating the time delay of the leakage signals.