• Journal of Communications and Networks
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• 제7권1호
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• pp.65-75
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• 2005

In this paper, we consider a scenario in which the source has been offered QoS guarantees subject to token-bucket regulation. The rate of the source should be controlled such that it conforms to the token-bucket regulation, and also the distortion obtained is the minimum. We have developed an optimal scheduling algorithm for offline (like pre-recorded video) sources with convex distortion function and which can not tolerate any delay. This optimal offline algorithm has been extended for the real-time online source by predicting the number of packets that the source may send in future. The performance of the online scheduler is not substantially degraded as compared to that of the optimal offline scheduler. A sub-optimal offline algorithm has also been developed to reduce the computational complexity and it is shown to perform very well. We later consider the case where the source can tolerate a fixed amount of delay and derive optimal offline algorithm for such traffic source.

• JSTS:Journal of Semiconductor Technology and Science
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• 제8권2호
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• pp.170-177
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• 2008

In the present work a methodology to minimize short channel effects (SCEs) by modulating the effective channel length is proposed to design 25 nm single and double gate-source/drain underlap MOSFETs. The analysis is based on the evaluation of the ratio of effective channel length to natural/ characteristic length. Our results show that for this ratio to be greater than 2, steeper source/drain doping gradients along with wider source/drain roll-off widths will be required for both devices. In order to enhance short channel immunity, the ratio of source/drain roll-off width to lateral straggle should be greater than 2 for a wide range of source/drain doping gradients.

• 대한의용생체공학회:의공학회지
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• 제27권1호
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• pp.30-37
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• 2006

Injecting currents into an electrically conducting subject, we may measure the induced magnetic flux density distributions using an MRI scanner. The measured data are utilized to reconstruct cross-sectional images of internal conductivity and current density distributions in Magnetic Resonance Electrical Impedance Tomography (MREIT). Injection currents are usually provided in a form of mono-polar or bi-polar pulses synchronized with an MR pulse sequence. Given an MRI scanner performing the MR phase imaging to extract the induced magnetic flux density data, the current source becomes one of the key parts determining the signal-to-noise ratio (SNR) of the measured data. Since this SNR is crucial in determining the quality of reconstructed MREIT images, special care must be given in the design and implementation of the current source. This paper describes a current source design for MREIT with features including interleaved current injection, arbitrary current waveform, electrode switching to discharge any stored charge from previous current injections, optical isolation from an MR spectrometer and PC, precise current injection timing control synchronized with any MR pulse sequence, and versatile PC control program. The performance of the current source was verified using a 3T MRI scanner and saline phantoms.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1982년도 추계학술발표회논문집
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• pp.51-55
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• 1982

The analysis of Korean language by the first order markov source is carried out. The calculated entropy of the first order Markov source is also included. The results presented here are new data. The data can be useful in designing the keyboard pattern of terminal and the automatic discrimination of monosyllable in Korean language.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2006년도 춘계 학술대회 발표논문집
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• pp.127-130
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• 2006

This paper suggests an algorithm that can estimate the direction of the sound source with three microphones arranged on a circle. The algorithm is robust to microphones' gains because it uses only the time differences between microphones. To make this possible, a cost function which normalizes the microphone's gains is utilized and a procedure to detect the rough position of the sound source is also proposed. Through our experiments, we obtained significant performance improvement compared with the energy-based localizer.

• Journal of the Optical Society of Korea
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• 제7권4호
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• pp.216-223
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• 2003

We report a technique that improves the spatial resolution of optical coherence tomography (OCT) by utilizing fiber-based spectral filtering. The proposed technique improves the resolution by filtering out the erbium’s characteristic peak from the amplified spontaneous emission (ASE) source spectrum, and reshaping the spectrum to Gaussian-like. We used a long period fiber grating (LPG) and an erbium doped fiber (EDF) absorber for the spectral filtering. An in-house made ASE source as well as a commercial ASE source [ASE-FL7002] was used as the OCT sources to study the proposed technique. The resolution of the OCT based on an in-house made ASE source is enhanced from 200 to 40 ㎛ with an LPG. While, the resolution of the OCT based on a commercial ASE source is enhanced from 25 to 19 ㎛ with the aid of an EDF absorber. However, sidelobes still exist in the interferogram due to imperfect spectral filtering, which limited the resolution. Further enhancement in the spatial resolution of the OCT system using the ASE source is possible with the aid of cascaded LPGs and/or carefully designed EDF absorber.

• 정보보호학회논문지
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• 제30권4호
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• pp.657-667
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• 2020

안드로이드 프레임워크는 단 한번의 권한 허용을 통해 앱이 사용자의 정보를 자유롭게 이용할 수 있으며, 유출되는 데이터가 개인정보임을 식별하기 어렵다는 문제가 있다. 따라서 본 논문에서는 어플리케이션을 통해 유출되는 데이터를 분석하여, 해당 데이터가 실제로 개인정보에 해당하는 것인지를 파악하는 기준을 제시한다. 이를 위해 우리는 제어 흐름 그래프를 기반으로 소스와 싱크를 추출하며, 소스에서 싱크까지의 흐름이 존재하는 경우 사용자의 개인정보를 유출하는지 확인한다. 이 과정에서 우리는 구글에서 제공하는 위험한 권한 정보를 기준으로 개인정보와 직결되는 소스와 싱크를 선별하며, 동적분석 툴을 통해 각 API에 대한 정보를 후킹한다. 후킹되는 데이터를 통해 사용자는 해당 어플리케이션이 실제로 개인정보를 유출한다면 어떤 개인정보를 유출하는지 여부를 파악할 수 있다. 우리는 툴을 최신 버전의 API에 적용하기 위해 머신러닝을 통해 최신 버전의 안드로이드의 소스와 싱크를 분류하였으며, 이를 통해 86%의 정확도로 최신 배포 버전인 9.0 안드로이드의 API를 분류하였다. 또한 툴은 2,802개의 APK를 통해 평가되었으며, 개인정보를 유출하는 850개의 APK를 탐지하였다.

• 패션비즈니스
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• 제26권4호
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• pp.52-63
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• 2022

As live commerce, mobile sales platforms based on real-time content and text are drawing attention as a new marketing channel. In particular, the fashion industry also using live commerce as a new fashion distribution channel, requiring marketing strategies to utilize it efficiently. This study attempted to verify the effect of information source, sales promotion, and impulse buying tendency characteristics on fashion live commerce purchase intention. The experimental design of this study was 2(characteristics of information source: expertise vs attractiveness) × 2(sales promotion type: value-added vs price discount) × 2(impulse buying tendency: high vs low) three-way mixed analysis of variance(ANOVA). A convenience sampling of 264 women in their 20s and 50s living in Seoul and the Gyeonggi area who had purchased products through Live Commerce was conducted. For the final analysis, 240 questionnaires were used. Data were analyzed by the SPSS 26 program and three-way ANOVA. Simple main effects analysis was conducted. The results of this study follow. First, there were statistically significant differences in purchase intention according to consumers' impulse buying tendencies and sales promotions. Second, information source and sales promotion showed statistically significant interaction effects on purchase intention. Lastly, information source, sales promotion, and impulse buying tendency showed significant three-way interaction effects on fashion live commerce purchase intention. Therefore, conducting appropriate marketing analysis can result in positive attitudes regarding live commerce products and substantive increases in sales.

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.158-163
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• 2013

In this paper, thermal analysis of heatsink for 30 W class Chip-on-Board (COB) LED light source is performed by using SolidWorks Flow Simulation package. In order to increase the convection heat transfer, number of fin and shape of the heatsink is optimized. Furthermore, a copper spread is applied between the COB LED light source and the heatsink to mitigate the heat concentration on the heatsink. With the copper spread, the junction temperature between the COB LED light source and the heatsink is $50.9^{\circ}C$, which is $5.4^{\circ}C$ lower than the heatsink without the copper spread. Due to the improvement of the junction temperature, the light output is improved by 5.8% when the LED light source is stabilized. The temperature difference between the simulation and measured result of the heatsink with the copper spread is within $2^{\circ}C$, which verifies the validity of the thermal design method using a simulation package.

• Journal of Communications and Networks
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• 제17권5호
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• pp.499-505
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• 2015

We analyze the performance of multistage cooperation in decode-and-forward relay networks where the transmission between source and destination takes place in $T{\geq}2$ equal duration and orthogonal time phases with the help of relays. The source transmits only in the first time phase. All relays that can decode the source's transmission forward the source's message to the destination in the second time phase, using a space-time code. During subsequent time phases, the relays that have successfully decoded the source message using information from all previous transmitting relays, transmit the space-time coded symbols for the source's message. The non-decoding relays keep accumulating information and transmit in the later stages when they are able to decode. This process continues for T cooperation phases. We develop and analyze the outage probability of multistage cooperation protocol under orthogonal relaying. Through analytical results, we obtain the near-optimal placement strategy for relays that gives the best performance when compared with most other candidate relay location strategies of interest. For different relay network topologies, we also investigate an interesting tradeoff between an increased SNR and decreased spectral efficiency as the number of cooperation stages is increased. It is also shown that the largest multistage cooperation gain is obtained in the low and moderate SNR regime.