• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.90-94
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• 2000

In this paper, we propose an efficient method of estimating a critical threshold which is used to reject unreliable patterns in a HMM based recognition system. The rejection methods based on the anti-models which are formulated as the statistical hypothesis determine whether or not to accept an input pattern by comparing the likelihood ratio of HMM and anti-models to a critical threshold. It is quite difficult to fix a threshold for the probability of a HMM because the range of such probabilities varies severely depending on the chosen class model. We estimate the critical threshold, which is very class-dependent, using the likelihood scores for the training database. In our experiments, we applied the proposed estimating method of the threshold to the HMM based 3D hand gesture recognition system. We found that this method can be used successfully for rejecting unreliable input gestures regardless of the types of anti-models.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.4
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• pp.213-219
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• 2021

The submarine's intercept pulse detection detects pulses radiated from enemy surface ships, submarines, and torpedoes, and performs an important function of providing maneuverability and survivability of submarine. Whether or not the intercept pulse is detected is determined by comparing the size of the received pulse with the threshold value by the operator. In the case of intercept pulses, the intensity of the pulses is frequently reduced under the influence of various environmental factors. In the situation, if detection is performed with a fixed threshold, a non-detection problem occurs and persists until the operator sets a low threshold. In this paper, we proposed method for automatically adjusting threshold to reduce the non-detection problem caused by a fixed threshold. Simulation were preformed on 4 cases with different pulse level fluctuation widths, and it was confirmed that the detection performance was improved by increasing the number of detections when a method for automatically adjusting threshold was applied to all cases. Through the proposed method, it is expected that the intercept pulse detection performance will be improved in the marine environment the large fluctuations in pulse level in the future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10C
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• pp.999-1006
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• 2005

The difference threshold test (DTT) declares erasures whenever the difference between the largest and second largest energy detector outputs does not exceed a given threshold. we show that the DTT outperforms the ratio threshold test (RTT) for finite modulation size and diversity order in the detection of M-FSK signals. The asymptotic performance for infinite modulation size and diversity order is then investigated. It is shown that the minimum signal-to-noise ratio required to achieve error-free communication for the DTT is the same as that for the RTT.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2071_2072
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• 2009

본 연구에서는 소형 유도전동기의 회전자 바 고장을 자동 진단을 함에 있어, 회전속도 변화에 따라 변동하는 문턱값을 적용하는 방법을 제안하였다. 유도전동기 회전자 바 고장 시 부하의 감소에 따라 회전자 바 고장 특징 주파수 진폭의 크기는 작아진다. 따라서 부하의 감소에 따라 문턱값 또한 작아지는 것이 정확한 회전자 바 고장 진단에 유리하다. 유도전동기 회전속도의 증가는 부하의 감소를 의미하므로 회전속도 증가에 따라 문턱값의 크기를 감소시켜주는 변동 문턱값을 적용하여 진단함으로써 유도전동기 회전자 바 고장 진단의 정확도를 높였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.8
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• pp.1475-1484
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• 1994

In this paper, a priority scheduling algorithm with double threshold and a traffic control mechanism with hysteresis effect are proposed. The double threshold priority scheduling is studied based on HOL and QLT. The hysteresis effect traffic control is specified by hysteresis effect QLT and traffic rate control. According to the simulation results, it can be shown that the proposed dynamic priority scheduling brings better processing performance than the existing QLT algorithm. And the results demonstrate that QLT and traffic rate control with hysteresis effect enhance the performance in comparison with those of single threshold.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.1-8
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• 2000

In this paper, we formulate an optimal control problem to obtain the optimal signal strength and detection threshold for tracking with NN filter, First, we predict the tracking performance of NN filter by using the HYCA method. Based on this method, the predicted tracking performance is represented with respect to signal strength and detection threshold. Using this relation, we find the optimal parameters for following three examples： 1) the sequence of optimal detection threshold which minimizes sum of position estimation error； 2) the sequence of optimal detection threshold which minimizes sum of validation gate volume； and 3) the sequence of optimal signal strength and detection threshold which minimizes sum of signal strength.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.2
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• pp.176-181
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• 2002

In this paper, we consider the optimal control of detection threshold to minimize the conditional expectation of mean-square state estimation error for a probabilistic data association (PDA) filter. Earlier works on this problem involved the cumbersome graphical optimization algorithm or time-consuming numerical optimization algorithm. Using the numerical approximation of information reduction factor, we obtained the suboptimal detection threshold in a closed-form. This results are very useful for real- time implementation.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.259-261
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• 1999

본 논문에서는 IMT-2000 시스템에서 공용 채널과 전용 채널을 동시에 사용하는 이중 모드 패킷 전송 방식의 성능을 분석하였다. 공용 채널을 통한 패킷 전송은 랜덤 액세스 방식을 사용한다. 이중 모드 패킷 전송 방식은 전송할 패킷의 길이와 발생 빈도에 따라 공용 채널과 전용 채널을 동시에 사용함으로써 높은 전송 효율을 보장하는 전송 방식이다. 이중 모드 패킷 전송 방식은 전송할 패킷의 크기가 스위칭 문턱값 보다 클 경우 전용 채널을 통해 전송하며 그렇지 않을 경우 공용 채널을 통해 전송을 시도하게 된다. 이중 모드 패킷 전송에서 높은 전송 효율을 보장하기 위해서는 스위칭 문턱값을 적절히 설정하여야 하며 최적의 스위칭 문턱값은 전용 채널을 요청한 후 할당받는데 걸리는 지연 시간, 공용 채널에서 패킷을 전송한 후 ACK를 받는데 걸리는 지연 시간, 전용 채널과 공용 채널의 오류율, 전용 채널과 공용 채널의 수 그리고 발생되는 평균 패킷 길이에 의해 영향을 받는다. 본 논문에서는 이중 모드 패킷 전송 방식에서 트래픽 형태에 따른 최적의 스위칭 문턱값을 시뮬레이션을 통해서 분석하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.6
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• pp.213-224
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• 2003

The proposed algorithm can always set up the optimal threshold value regardless of channel characteristics using an adaptive threshold establishment method that determines the threshold level according to channel noise power, and then it uses the specially designed training symbols that can make the algorithm's estimation performance be less sensitive to power delay profile variation in a multipath channel. In result, the estimation performance of the proposed technique is less affected by channel characteristic variation.

• Journal of Broadcast Engineering
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• v.17 no.6
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• pp.1061-1068
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• 2012

This paper deals with a noise reduction algorithm which uses the binary masking approach in the time-frequency domain to improve speech intelligibility. In the binary masking approach, the noise-corrupted speech is decomposed into time-frequency units. Noise-dominant time-frequency units are removed by setting the corresponding binary masks as "0"s and target-dominant units are retained untouched by assigning mask "1"s. We propose a binary mask estimation by comparing the local signal-to-noise ratio (SNR) to a threshold. The local SNR is estimated by a training-based approach. An optimal threshold is proposed, which is obtained from observing the distribution of the training database. The proposed method is evaluated by normal-hearing subjects and the intelligibility scores are computed by counting the number of words correctly recognized.