• 한국정보처리학회논문지
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• 제4권9호
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• pp.2366-2377
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• 1997

본 논문은 ATM망의 트래픽 제어에서 예방적 기법인 가변 토큰풀(Variable Token Pool : VTP)을 이용한 적응적 사용 파라메터 제어에 관한 메카니즘을 제안한다. 가변 토큰풀 메카니즘은 ON-OFF형 트래픽의 버스트 기간과 침묵 기간을 장기간 감시하여 토큰풀을 가변시킴으로서 최대 비트율 뿐만 아니라 평균 비트율과 버스트 기간 위반을 함께 감시할 수 있다. 또한 제안된 메카니즘은 버스트 기간과 평균 비트율 위반에 대한 민감성을 개선할 수 있고, 위반 사항에 대한 반응이 빨리 나타난다. VTP 크기는 버스트와 침묵 구간마다 계단 형태로 변하고, 하향 간격 (Down_size)과 상향 간격 (Up_size)의 값에 따라 제어된다. 본 논문에서 제안한 메카니즘을 시뮬레이션을 통해 LB와 JW 메카니즘과의 성능을 비교 분석하였다. VTP메카니즘은 기존에 제안된 메카니즘보다 좀더 엄격한 제어 능력을 보였다. VTP 메카니즘의 셀 손실율은 VTP의 파라메터 (Down_size, Up_size)값의 증감에 따라 다르게 나타났으며, 두 파라메터 값이 트래픽 상황에 따라 적당한 값으로 결정되어야 함을 보여주었다.

• 대한산업공학회지
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• 제28권2호
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• pp.139-146
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• 2002

The third generation mobile communication needs to provide multimedia service with increased data rates. Thus an efficient allocation of radio and network resources is very important. This paper models the 'burst switching' as an efficient radio resource allocation scheme and the performance is compared to the circuit and packet switching. In burst switching, radio resource is allocated to a call for the duration of data bursts rather than an entire session or a single packet as in the case of circuit and packet switching. After a stream of data burst, if a packet does not arrive during timer2 value ($\tau_{2}$), the channel of physical layer is released and the call stays in suspended state. Again if a packet does not arrive for timerl value ($\tau_{1}$) in the suspended state, the upper layer is also released. Thus the two timer values to minimize the sum of access delay and queuing delay need to be determined. In this paper, we focus on the decision of $\tau_{2}$ which minimizes the access and queueing delay with the assumption that traffic arrivals follow Poison process. The simulation, however, is performed with Pareto distribution which well describes the bursty traffic. The computational results show that the delay and the packet loss probability by the burst switching is dramatically reduced compared to the packet switching.

• Journal of Astronomy and Space Sciences
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• 제23권3호
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• pp.167-176
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• 2006

We investigate the correlation between the peak energy and the burst duration using available long GRB data with known redshift, whose circumburst medium type has been suggested via afterglow light curve modeling. We find that the peak energy and the burst duration of the observed GRBs are correlated both in the observer frame and in the GRB rest frame. For our total sample we obtain, for instance, the Spearman rank-order correlation values ${\sim}0.75\;and\;{\sim}0.65$ with the chance probabilities $P=1.0{\times}10^{-3}\;and\;P=6.0{\times}10^{-3}$ in the observer frame and in the GRB rest frame, respectively. We note that taking the effects of the expanding universe into account reduces the value a bit. We further attempt to separate our GRB sample into the 'ISM' GRBs and the 'WIND' GRBs according to environment models inferred from the afterglow light curves and apply statistical tests, as one may expect that clues on the progenitor of GRBs can be deduced directly from prompt emission properties other than from the ambient environment surrounding GRBs. We find that two subsamples of GRBs show different correlation coefficients. That is, the Spearman rank-order correlation are ${\sim}0.65\;and\;{\sim}0.57$ for the 'ISM' GRBs and 'WIND' GRBs, respectively, after taking the effects of the expanding universe into account. It is not yet, however, statistically very much significant that the GRBS in two types of circumburst media show statistically characteristic behaviors, from which one may conclude that all the long bursts are not originated from a single progenitor population. A larger size of data is required to increase the statistical significance.

• 대한후두음성언어의학회지
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• 제7권1호
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• pp.50-55
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• 1996

Acoustic analysis study was performed on 20 normal subjects by speaking nonsense syllables composed of Korean bilabial stops$(/P, P^{\star}, P^{h}/)$ and their preceding and/or following vowel /a/ (that is, $[pa, p^{\star}a, p^{h}a, apa, ap^{\star}a, ap^{h}a]$) with an ultraminiature pressure, sensor. in their mouths. Speech materials were phonated twice, once with a moderate voice, another time with a loud voice. The acoustic signal and intraoral pressure were recorded simultaneously on computer. By these procedures, we were to measure the intraoral pressure, closure duration and VOT of Korean bilabial stops, and to compare the values one another according to the intensity of phonation and the position of the target consonants. Intraoral pressure was measured by the peak intraoral pressure value of Its wave closure duration by the time interval between the onset of intraoral pressure build-up and the burst meaning the release of closure ; Voice onset time(VOT) on by the time interval between the burst and the onset or glottal vibration. Heavily aspirated bilabial stop consonant /$p^h$/ showed the highest intraoral pressure value, unaspirated /$p^{\star}$/, the second, slightly aspirated /P/, the lowest. The syllable initial bilabial stops showed higher intraoral pressure than word initial stops, and the value of loudly phonated consonants were higher than moderate consonants. The longest closure duration period was that of /$p^{\star}$/ and the shortest, /P/, and the duration was longer in word initial position and in the moderate voice. In VOT, the order of the longest to shortest was $/{p^h}/, /p/, /{p^\star}/$, and the value was shorer when the consonant was in intervocalic position and when it was phonated with a loud voice.

• 대한물리의학회지
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• 제11권2호
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• pp.1-11
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• 2016

PURPOSE: This study was conducted to assess the effects of local vibration on ankle plantarflexion spasticity and clonus in patients with spinal cord injury. METHODS: The subjects were 14 inpatients with complete or incomplete spinal cord injury (SCI) whose scores were higher than 1 on the Modified Ashworth Scale (MAS) and Spinal Cord Assessment Tool for Spastic Reflexes (SCATS) scale of paraplegia. A randomized single-blind cross-over design was used. Vibration treatment involved a single application of vibration for 10 min in the sitting position, and placebo treatment involved the patient remaining in the sitting position for 10 min. One day after treatment, vibration and placebo treatments were crossed over. Spasticity was measured by using the MAS, and resistance force, by using a hand-held dynamometer; clonus was gauged by using the SCATS scale and clonus burst duration. Additionally, the burst maximal frequency and voluntary ankle dorsiflexion angle of the triceps surae were measured. RESULTS: The application of vibration treatment in the sitting position significantly reduced the MAS scores and resistance force, but significantly increased the dorsiflexion angle of the ankle joint (p<0.05). Furthermore, the vibration treatment diminished the clonus burst duration and SCATS score significantly (p<0.05). Although it reduced the burst maximal frequency of the lateral gastrocnemius and medial soleus, this was significant only for the lateral gastrocnemius. The placebo treatment did not significantly affect any of the test parameters. CONCLUSION: Vibration treatment in the sitting position was effective in cases of spasticity and clonus caused by SCI.

• 음성과학
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• 제4권1호
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• pp.47-58
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• 1998

This paper tests whether frication duration plays an important role in perceiving fricatives and affricates. In other words, whether the frication duration is an acoustic cue for distinguishing fricatives from affricates. For this purpose two types of experiments are carried out. In the first experiment two sets of stimuli are created by decreasing the frication duration of fricatives by 10ms, and in the second experiment two steps of stimuli are created by increasing the frication duration of affricates by 10 ms. The results of the present study show that frication duration is the primary acoustic cue in perceiving fricative/affricate distinction in Korean. In addition, the amplitude rise time and burst information appear to play secondary roles in perceiving the distinction by a series of perception tests.

• 대한음성학회:학술대회논문집
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• 대한음성학회 1996년도 10월 학술대회지
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• pp.390-398
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• 1996

Acoustic analysis study was performed on 20 normal subjects by speaking nonsense syllables composed of Korean bilabial stops(/p, $p^{*}$/, ph/) and their Preceding and/or following vowel /a/(that is, [pa, $p^{*}a$, pha, apa, $ap^{*}a$, apha]) with an ultraminiature pressure sensor in their mouths. Speech materials were phonated twice, once with a moderate voice, another time with a loud voice. The acoustic signal and intraoral pressure were recorded simultaneously on computer. By these procedures, we were to measure the intraoral pressure, closure duration and VOT of Korean bilabial stops, and to compare the values one another according to the intensity of phonation and the position of the target consonants. Intraoral pressure was measured by the peak intraoral pressure value of its wave; closure duration by the time interval between the onset of intraoral pressure build-up and the burst meaning the release of closure; Voice onset time(VOT) by the time interval between the burst and the onset of glottal vibration. Heavily aspirated bilabial stop consonant /ph/ showed the highest intraoral pressure value, unaspirated /p$^{*}$/, the second, slightly aspirated /p/, the lowest. The syllable initial bilabial stops showed higher intraoral pressure than word initial stops, and the value of loudly phonated consonants were higher than moderate consonants. The longest closure duration period was that of /$p^{*}$/ and the shortest, /p/, and the duration was longer in word initial position and in the moderate voice. In VOT, the order of the longest to shortest was /ph/, /p/, /$p^{*}$/, and the value was shorter when the consonant was in intervocalic position and when it was phonated with a loud voice.

• 한국전자파학회논문지
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• 제9권1호
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• pp.72-86
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• 1998

본 논문은 불특정의 유성 버스트 통신 경로의 버스트 신호 발생빈도와 그 평균 지속 시간을 예측하는데 있어서 기존의 경로를 참조 경로로 하여 각 정수를 서로 비교 계산하므로서 간편, 정확하게 산출할 수 있음을 소개하는 것이다. 이 논문에서는 유성 경로의 발생빈도와 지속시간을 그 경로의 거리, 주파수, 안테나 이득, 송신 출력 그리고 수신기의 문턱치를 기존 경로와 비교 계산하여 산출할 수 있음을 해석적으로 증명하고 이것을 확인하기 위하여 한국 경산으로부터 일본 hamamatu 및 Hatinohe간의 750 km와 1,200 km의 두가지 경로에 관하여 각각 실험을 실시한 결과를 보고하고 있다. 그 결과 실험으로 얻어진 버스트 발생 빈도와 평균지속 시간은 해석 결과와 잘 일치하고 있음을 확인하였다.

• 한국재료학회지
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• 제21권11호
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• pp.623-627
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• 2011

This is a study on the distribution of acoustic emission parameters during a burst test for a type-II CNG vehicle fuel tank. A resonant AE sensor with a central frequency of 150 kHz was attached to the composite materials in the center of the fuel tank. The pressure was increased from 30 to 100% of the expected burst pressure and was maintained for 10 minutes at each level. Damage at 70% of expected burst pressure occurred by various damage mechanisms including fiber breakage and delamination, while that of below 60% only occurred by matrix crack initiation and growth. The count, duration and rise time of the AE signal at 60% of the expected burst pressure are distributed below 500, 5000 ${\mu}s$ and 300 ${\mu}s$, respectively. Then, at above 70% they increased with pressure by superimposing of individual AE signal generated at a nearby place. These results confirmed that the analysis of the distribution of AE parameters is an effective tool for estimating damage of a CNG fuel tank.

• 한국정보과학회논문지:정보통신
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• 제35권2호
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• pp.99-111
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• 2008

최근 무선 랜은 SOHO (Small Office Home Office) 및 Hot Spot과 같은 환경에서 공간의 제약에 구애받지 않고, 인터넷에 접속할 수 있는 기술로서 사용자의 요구가 크게 증가하였다. 하지만, 무선 랜 환경에서의 통신은 유선망과 달리 불안정한 무선 채널의 특성으로 인해 연집적인 패킷 손실이 발생하여 통신상의 제약이 많은 특징을 가진다. 연집적인 패킷 손실은 AP(Access Point) 와 무선 단말의 거리가 증가하거나, AP와 무선 단말사이에 장애물 등이 일시적으로 지나갈 때 주로 발생하는 현상이다 결국, 현재 인터넷상에서 가장 광범위하게 사용되고 있는 무선 랜 기술인 IEEE 802.11은 이러한 특성으로 인해 사용자의 요구에 만족할만한 전송 성능을 나타내지 못하며, 특히 전송 계층에 TCP가 사용될 경우 불필요한 혼잡 제어 기법을 사용하게 함으로써 심각한 성능저하를 야기한다. 이러한 무선 랜 환경의 문제점을 해결하기 위해 MAC-layer LDA(Loss Differentiation Algorithm)가 제안되었다. MAC-layer LDA는 MAC 계풍의 Retry limit을 기반으로 CRD(Consecutive Retry Duration)를 무선 구간의 연집된 패킷손실 기간 이상 증가시켜, TCP의 불필요한 Timeout 발생 이전에 손실된 패킷을 효율적으로 복구하는 기법이다. 하지만, MAC-layer LDA 기법은 한정된 Retry limit의 증가로 인해 CRD가 연집된 패킷 손실 구간 보다 적은 경우가 발생하여 심각한 전송성능 저하를 가져온다. 또한, CRD의 증가는 무선 구간의 패킷 처리 시간을 증가시켜 대역폭과 무선 단말의 한정된 에너지 자원을 불필요하게 낭비하는 문제를 초래한다. 본 논문에서는 이러한 문제점을 개선하기 위해 Cross-layer 기법을 적용한 재전송 기법인 BLD(Burst Loss Detection) 모듈을 제안한다. BLD 모듈의 알고리즘은 현재 무선 랜 환경에서 가장 널리 사용되는 IEEE 802.11 MAC 프로토콜 기반의 재전송 기법으로서, MAC 계층과 TCP에서 사용되는 재전송 기법의 효율적인 연동을 통해 손실된 패킷을 복구한다. ns-2(Network Simulator) 시뮬레이터를 이용한 실험을 통해 BLD 모듈은 무선 구간의 연집적인 패킷 손실에 대해 효율적인 보상을 수행하여 전송 성능과 에너지 효율성을 향상시킬 수 있음을 확인하였다.