• Journal of the Korea Computer Industry Society
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• 제3권9호
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• pp.1251-1260
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• 2002

Real-time application programs have synchronization constraints which need to be met between media-data. Synchronization method represents feedback method including virtual client-side buffer. This buffer is used in buffer level method. It is client-leading synchronization that is absorbing variable transmission delay time and that is synchronizing by feedback control. It is the important factor for playback rate and QoS if the buffer level is normal or not. To solve the problems, we can control the start of transmission in multimedia server by appling filtering, control and network evaluation function. Synchronization method is processing for smooth presentation without cut-off while media is playing out. When audio frame which is master media is in high threshold buffer level we decrease play out time gradually, otherwise we increase it slowly.

• Journal of the Institute of Electronics Engineers of Korea TC
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• 제38권10호
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• pp.24-33
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• 2001

Delay, delay variation and packet loss rate are principal QoS(Quality of Service) elements of packet communication. This paper proposes a new buffer allocation mechanism to improve the packet loss performance in such a situation that multiple logical buffers share a single physical memory buffer. In the proposed buffer allocation mechanism, the movement of dynamic threshold follows a curved track instead of a straight line which is used in the DT(dynamic threshold) mechanism. In order evaluate the effectiveness of the proposed mechanism, it is compared with the existing previously proposed mechanisms in several aspects including NC(no control), ST(Static Threshold) and DT mechanisms.

• Journal of Power System Engineering
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• 제11권1호
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• pp.76-81
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• 2007

The objective of this study is to find the optimum design of a snubber using CFD analysis. Several dimensions such as snubber height(H), snubber diameter(D), buffer width and buffer angle are considered in this study. The present study shows that the CFD can be applied to study the pressure characteristics inside the snubber. The objective of the snubber design optimization are to minimize a pressure loss and the pulsation ratio. Numerical results such as particle track, pressure distribution and turbulent kinetic energy are used to analyze the critical area and pressure behavior inside the snubber. As a result, snubber model with H/D ratio of 3.23 and buffer angle of $40^{\circ}$ has a minimum pressure loss. On the other hand, snubber model with H/D ratio 4.41 and buffer angle $10^{\circ}$ has a minimum pulsation ratio.

• Nuclear Engineering and Technology
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• 제34권3호
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• pp.218-231
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• 2002

Using a three-dimensional numerical code, B3R developed for nuclide transport of an arbitrary length of decay chain in the buffer between the canister and adjacent rock in a high- level radioactive waste repository by adopting a finite difference method utilizing the control- volume scheme, some illustrative calculations have been done. A linear sorption isotherm, nuclide transport due to diffusion in the buffer and the rock matrix, and advection and dispersion along thin rigid parallel fractures existing in a saturated porous rock matrix as well as diffusion through the fracture wall into the matrix is assumed. In such kind of repository, buffer and rock matrix are known to be important physico-chemical harriers in nuclide retardation. To show effects of buffer and rock matrix on nuclide transport in HLW repository and also to demonstrate usefulness of B3R, several cases of breakthrough curves as well as three- dimensional plots of concentration isopleths associated with these two barriers are introduced for a typical case of decay chain of $^{234}$ Ulongrightarrow$^{230}$ Thlongrightarrow$^{226}$ Ra, which is the most important chain as far as the human environment is concerned.

• Mass Spectrometry Letters
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• 제6권4호
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• pp.112-115
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• 2015

In this article, we examine the influences of Ne and He buffer gases under confined Ar⁺ ion cloud in a homemade Paul ion trap in various pressures and confinement times. The trap is of small size (r₀ = 1 cm) operating in a radio frequency (rf) voltage only mode, and has limited accuracy of 13 V. The electron impact and ionization process take place inside the trap and a Faraday cup has been used for the detection. Although the experimental results show that the Ar⁺ ion FWHM with Ne buffer gas is wider than the He buffer gas at the same pressure (1×10^-1 mbar) and confinement time is about 1000 μs, nevertheless, a faster cooling was found with He buffer gas with 500 μs. ultimetly, the obtanied results performed an average cloud tempertures reduced from 1777 K to 448.3 K for Ne (1000 μs) and from 1787.9 K to 469.4 K for He (500 μs)

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.455-461
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• 2007

The electric current of a flow injection type enzyme-sensor was measured to confirm the stable operating conditions of the sensor. The current of the sensor was decreased as the buffer solution velocity increased. Under the limitation of the cycle time to be below 10 minutes, the effective ranges of the buffer solution velocity were suggested $0.10{\sim}0.26$, $0.12{\sim}0.24$, $0.1{\sim}0.25$ and $0.05{\sim}0.10\;cm/s$ of 1.0, 1.4, 2.4 and 3.4 mm of the electrode diameters, respectively. As the reaction time of the enzyme and the substrate was increased, the current was decreased because of the dilution between the sample and buffer solution. Therefore, it could be recommended that the reaction time was able to be selected as shortly as possible in consideration of the total cycle time. As the result of the experiments using a different volume ratio of the enzyme to substrate, it was concluded that the substrate had to be mixed with the same amount of the enzyme. The current have increased remarkably in proportion to the electrode diameter under 0.1 cm/s of the buffer solution velocity but there was no difference over 0.1 cm/s of the buffer solution velocity. The cross type arrangement of the electrode was highly suggested for application and machining of the sensor.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제30권8B호
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• pp.535-540
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• 2005

This paper presents a scalable caching algorithm of proxy server with the finite storage size minimizing client's buffer size and constant-bit-rate channel bandwidth. Under the general video traffic condition, it is observed that the amount of decreased client's buffer size and channel bandwidth after caching a video frame depends on the relative frame position in the time axis as the frame size. Based on this fact, we propose an effective caching algorithm to select the cached frames by using the normalized buffer size. Finally, experimental results are provided to show the superior performance of the proposed alghrithm.

• The KIPS Transactions:PartC
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• 제17C권3호
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• pp.299-306
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• 2010

IPTV and VoIP services are considered as killer applications over Mobile WiMAX network, which provideshigh mobility and data rate. Among those which affect the quality of voice in those services, the jitter buffer or playout buffer can compensate the poor voice quality caused by the packet drop due to frequent route change or differences among routes between service endpoints. In this paper, we analyze the correlation between the sleep interval length and jitter buffer size in order to guarantee a predefined level of voice quality. For this purpose, we present an end-to-end delay model considering additional delay incurred by the WiMAX PSC-II sleep mode and a VoIP service quality requirement based on the delay constraints. Through extensive simulation experiments, we also show that the increase of jitter buffer size may degrade the voice quality since it can introduce additional packet drop in the jitter buffer under WiMAX power saving mode.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.302-305
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• 2003

3GPP RLC protocol specification adopted an error control scheme based on selective repeat ARQ. In the 3GPP ARQ, distinctive windows are provided at transmitting and receiving stations so that those stations are prohibited to send or receive data PDU's out of window. An increase in window size enhances delay performance. Such an increase, however, raises the occupancy at re-ordering buffer, which results in a long re-ordering time. Aiming at suppressing the occupancy at re-ordering buffer, we propose partial go back N scheme in this paper In the partial go back N scheme, the receiving station regards all data PDU's between the first (lowest sequence numbered) error-detected PDU and last (highest sequence numbered) error-detected PDU. By the employment of the partial go back N scheme, the occupancy at the re-ordering buffer is apparently reduced, while the delay and throughput performance may be degraded due to the remaining properties of go back N. We thus consider peak occupancy of re-ordering buffer, mean sojourn time at re-ordering buffer, mean delay time, and maximum throughput as measures to evaluate tile proposed scheme and investigate such performance by using a simulation method. From numerical examples, we observe a trade-off among performance measures and conclude that the partial go back N scheme is able to effectively reduce the occupancy of re-ordering buffer.

• Journal of the Korean Institute of Telematics and Electronics A
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• 제31A권12호
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• pp.38-43
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• 1994

GaAs and AlGaAs layers were grown by Molecular Beam Epitaxy (MBE) to fabricate hith performance GaAs MESFETs. Optimum growth temperatures were found to be 600$^{\circ}C$ from their Hall measurement data. MESFETs with the gate legth of 1${\mu}$m and the gate width of 100.mu.m were fabricated on the MBE-grown GaAs layters which has i-GaAs buffer layer and characterized. Knee volgate and mazimum transconductance of the devices were 1V, 224mS/mm, respectively. Cut-off frequency at on-wafer measuring pattern was measured to be 18 GHz. The MESFET with the 1${\mu}$m -thick i-Al$_{0.3}Ga_{0.7}$As buffer layer between nactive and i-GaAs was fabricated on order to reduce the leakage current which flows through the i-GaAs buffer layer. Its output resistance was 2.26 k${\Omega}$.mm which increased by a factor of 15 compared with the MESFET without i-Al$_{0.3}Ga_{0.7}$As buffer layer.