• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.87-90
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• 2003

본 논문에서는 정현파를 이용한 spread-spectrum watermarking 에서 비가청성을 높이기 위한 방법과 효율적인 threshold 설정 방법을 제안한다. 제안하는 방법에서는 spread-spectrum 기법을 사용할 때 계산량이 많이 요구되는 심리음향모델 계산을 피하면서도 가청잡음을 줄이기 위한 방법을 제시한다. 또한 outlier 를 이용하여 워터마크 검출에서 적절한 threshold 설정방법을 제안한다.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.541-543
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• 1995

We propose the improved threshold current ratio method to determine the reflectivity of coated facets. The carrier recombination time used in the improved threshold current ratio method depends on the value of facet reflectivities. However, the carrier recombination time used in the conventional threshold current ratio method is constant regardless of facet reflectivities. The difference between the results of the two methods increases as the reflectivity of a coated facet decreases.

• Journal of the Korean Data and Information Science Society
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• v.22 no.2
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• pp.353-360
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• 2011

We consider an asymmetric power transformed threshold GARCH(1.1) process and find sufficient conditions for the existence of a strictly stationary solution, geometric ergodicity and ${\beta}$-mixing property. Moments conditions are given. Box-Cox transformed threshold GARCH(1.1) is also considered as a special case.

• Proceedings of the Korea Society for Simulation Conference
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• 1993.10a
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• pp.2-2
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• 1993

Inference for discrete event simulations usually relies on either independent replications or, if each simulation run is expensive, the method of batch means applied to a single replications. We present a new method, threshold bootstrap, which equals or exceeds the performance of independent replications or batch means. The method works by resampling runs of data created when a stationary time series crosses a threshold level, such as the sample mean of series. Computational results show that the threshold bootstrap matches or exceeds the performance of these alternative methods in estimating the standard deviation of the sample mean and producing valid confidence intervals.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.14-17
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• 2003

웨이블릿 변환 영역에서 잡음제거 방법 중 Visushrink 추정에 사용되는 경계값은 측정 데이터 수와 잡음편차에 비례하는 것으로 알려져 있으나 잡음편차가 알려지지 않은 경우 Donoho는 웨이블릿 변환 영역의 최고대역에서 잡음편차 추정 방법을 제시하였다. 본 논문에서는 분산이 데이터 수에 반비례함을 이용하여 threshold 기법을 이용하여 잡음제거 시 계산량을 감소를 목적으로 차 신호를 이용하여 측정데이터 수를 줄인 후 영상신호의 가우시안 잡음을 soft threshold 기법을 적용하고 이 기법의 실용성을 밝혔다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.403-405
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• 2003

Ad Hoc 네트워크에서 Threshold-Tuning을 통한 노드들간의 균형적인 에너지 소모를 위한 알고리즘 (BECT : A Balanced Energy Consumption Algorithm by Threshold-Tuning)을 제안한다. BECT는 노드간 에너지 균형을 맞추어 네트워크의 수명 (Network Lifetime)을 연장한다. 제안한 알고리즘은 DSR (Dynamic Source Routing) 프로토콜을 기반으로 구현하였으며, GloMoSim 2.0을 이용하여 실험을 하였다. 실험 결과 BECT가 실험 토폴로지에 따라 DSR의 에너지 균형을 17-31% 향상시키며, 데이터 전송율이나 제어 패킷 비율에 있어서도 향상된 성능을 보여준다.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.393-396
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• 2003

고압축 영상신호에서 발생된 양자화잡음 제거 효과를 비교하였다. 잡음제거는 Soft-Threshold 기법을 이용하여 각 대역에서 양자화 잡음을 제거하였다. Soft-Threshold 기법에 적용하기 위해 각 대역별 잡음분산을 Monotonic 변환 및 SURE, Visu 방법으로 추정하여 양자화 잡음제거 효과를 PSNR로 비교하였다. 양자화 잡음 제거 결과 영상에 따라 달라지지만 유니폼 양자화 영상에서 약 5～6dB 정도의 영상품질 개선 효과가 있었다.

• Journal of Electrical Engineering and information Science
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• v.1 no.2
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• pp.87-95
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• 1996

This paper presents a (k,n) threshold digital signature scheme with no trusted dealer. Our idea is to use the EIGamal signature scheme modified for group use. Among many digital signature schemes, our modification has a nice property for our purpose. We also show a (k.n) threshold fail stop signature scheme and two (k.n) threshold undeniable signature schemes. We use [10] as the original fail stop signature scheme, and use [3] and [2] as the original undeniable signature schemes. Since all these schemes are based on the discrete log problem, we can use the same technique.

• Journal of IKEEE
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• v.9 no.2 s.17
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• pp.123-135
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• 2005

3GPP RLC protocol specification adopted a window-controlled selective-repeat ARQ scheme for provisioning reliable data transmission. Inevitably, the re-ordering issue arises in the 3GPP's ARQ since it belongs to the selective-repeat ARQ clan. A long re-ordering time results in the degradation of throughput and delay performance, and may invoke the overflow of the re-ordering buffer. Also, the re-ordering time must be regulated to meet the requirements of some services which are both loss-sensitive and delay-sensitive. In the 3GPP's ARQ, we may deflate the occupancy of the re-ordering buffer by reducing the window size and/or length of the status report period. Such a decrease, however, deteriorates the throughput and delay performance and encroaches the resource of the reverse channel. Aiming at reducing the occupancy at the re-ordering buffer while suppressing the degradation of throughput and delay performance, we propose threshold-dependent occupancy control schemes, identified as post-threshold and pre-threshold schemes, as supplements to the 3GPP's ARQ. For judging the effectiveness of the proposed schemes, we investigate peak occupancy, maximum throughput and average delay in the practical environment involving fading channels. From the simulation results, we observe that the proposed schemes invoke the performance trade-off between occupancy and throughput in general. Also, we reveal that the post-threshold scheme is able to improve the throughput and delay performance of the ordinary 3GPP's ARQ without inflating the occupancy of the re-ordering buffer.

• Journal of Preventive Medicine and Public Health
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• v.32 no.1
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• pp.17-29
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• 1999

Objectives. This study was carried out to analyze the hearingthreshold levels and relating factors of 1,048 workers with noiseinduced hearing loss$(D_1)$. Methods. We analyzed the hearing-threshold levels and relating factors of 1,048 workers with noise-induced hearing loss$(D_1)$ examined by the summary reports of specific health examination results of industries and personal reports of specific health examination results reported by 58 specific health examination institutes and 8 secondary pneumoconiosis examination institutes in 1996. Results. Among 1,048 workers at 510 workplaces, male workers were 1,009 (96.3%) and female workers were 39 (3.7%). The mean ages of workers initially exposed to noise and at present were 28.7 and 47.2, respectively. The duration of total exposure was 16.5 years. Average hearing-threshold levels analyzed by three-divided classification of the study subjects were 43.7dB(Lt) and 42.6dB(Rt). Those analyzed by six-divided classification were 50.5dB(Lt) and 48.6d8(Rt). Among workers with noise-induced shearing loss$(D_1)$, 16.3% was unilateral hearing loss and 84.6% was classified to compensation case. 8.8%(Rt) and 10.2%(Lt) of them were suspected to be conductive hearing loss by differences of air-bone hearing-threshold levels. Hearing-threshold levels of workers in manufacturing industry were significantly increased during the short exposure compared with the levels in mining industry. Among manufacturing industries, hearing-threshold levels of workers in trailer and other transportation equipment manufacturing industry were significantly increased. Age and duration of total noise exposure were not significantly related to the average hearing-threshold levels analyzed by three-divided classification. Hearing-threshold levels of female workers were significantly increased during the short exposure compared with those of male workers. Hearing-threshold levels of workers at the high risk group, ages of 20s, 30s and total exposure duration of less than 10 years, were not significantly increased compared with those of the other groups. However, they were exposed at young ages. The 3 leading industries of workers at high risk group were trailer and other transportation equipment manufacturing, automobile manufacturing and assemble-metal manufacturing industries. Conclusions. This study was the first nationwide analysis of the hearing-threshold levels and relating factors of workers with noise. induced hearing loss$(D_1)$. We found the differences of the real number by the statistics of the department of labour and the expected number of worker' s compensations for occupationally-induced hearing loss estimated by this study. According to the results of this study, we should carefully examine the methods to narrow this difference.