• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.663-668
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• 2003

With the advent of high speed networking technology, computers connected to the high-speed networks tend to consume more of their CPU cycles to process data. So one of the solutions to improve the performance of the computers is to reduce the CPU cycles for processing the data. As the consumption of the CPU cycles is increased in proportion to the number of the packets per second to be processed, reducing the number of the packets per second by increasing the length of the packet is one of the solutions. In order to meet this requirement, two types of jumbo packets such as jumbograms and jumbo frames have already been standardized or being discussed. In case that the jumbograms and general packets are interleaved and scheduled together in a router, the jumbogrms may deteriorate the QoS of the general packets due to the transfer delay. They also frequently exhaust the memory with storing the huge length of the packets. This produces the congestion state easily in the router that results in the loss of the packets. In this paper, we analyze the problems in processing the jumbo packets and suggest a noble solution to overcome the problems.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.311-315
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• 2008

The switching fabric used to make high speed switching for packet transfer between input and output interface in recent internet environments. Without making any changes in order to remain ATM switching fabric, the existing structures should split/reassemble a packet to certain size, set aside cross-point buffer and will put loads on the system. In this paper, we proposed a new switch architecture, which has separated data memory plane and switching plane packet data will be stored on the separate memory structure and simultaneously only the part of the memory address pointers can pass the switching fabric. The small mini packets which have address pointer and basic information would be passed through the switching fabric. It is possible to achieve the remarkable switching performance than other switch fabrics with contending variable length packets.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9B
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• pp.900-907
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• 2009

With the introduction of the concept such as QoS, QoE, and MOS for the multimedia services over the high-speed network the user's concern about the degradation in the perceived quality of service for the conventional data service has become a new problem to the Internet service providers. In this work we propose a method to evaluate the subjective QoE such as MOS for the high-speed Internet service, where the round trip time for the data transfer is taken into account as a performance parameter for the experienced delay. We develop a tool to evaluate an MOS that enables us to investigate the behavior of users for diverse delay times for the web access service, via which we analyze the sensitivity of users with regard to MOS as a function of delay.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.1
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• pp.25-29
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• 1980

For the preliminary estimation of the vertical hull natural frequency, the Schlick's or Schlick-type formulae have been traditional ones and are still in common use today. Some investigators have made their efforts, based on statistical data of ships' system parameters, to extend the applicability of Schlick-type formulae to higher modes, or to utilize the Rayleigh method. For instance, the work done by Dinsenbacher et al.[5] belongs to the former and that of Nagamoto et al.[6] to the latter. In a part of his previous paper[7], the author, investigating the case of a cargo ship of medium size, suggested that provided statistically simplified curves such as trapezoid of system parameter distributions are available in hands, direct utlization of an ordinary computer program can be also an another convenient method by which we can obtain both natural frequencies and normal mode shapes. In this paper, to confirm the feasibility of the above suggestion, four high speed boats are investigated. The system parameters of them are originally given in [5]. The computer program used here is one confiled based on a calculation method derived from Myklestal-Prohl modeling of hull, transfer matrix formulation and an extended Gumbel's initial value method for solving frequency equation. The results of the investigation show that the direct calculation based on statistically oriented and reasonably assumed trapezoidal mean curves of system parameter distributions can give us natural frequencies within about 5% deviation up to several-noded modes and normal mode shapes serviceable at least up to 4- or 5-noded modes in comparision with those based on actual distributions of system parameters. For this simplified method the actual data required for input are only of ship length, displacement, total added mass, bending and shear rigidity at amidship. They are available at the early stage of design. By this method we can also easily trace variations of vibration characteristics in the course of ship design cycles.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.198-204
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• 2009

Inductive peaking using T-coils has been widely used in broadband I/O interfaces. In this paper, we analyze technical effects and limitations of the T-coil, and discuss several methods that can overcome these restrictions and improve the practicality of the T-coil. In particular we also propose and verify a circuit topology which can further extend bandwidth beyond the limit that conventional T-coil can achieve, and transfer 20 Gb/s data without noticeable distortion.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.3 no.2
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• pp.69-80
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• 1999

Recently in telecommunication, BISDN ( Broadband Integrated Service Digital Network ) has received considerable attention for its capability of providing a common interface for future communication needs including voice, data and video. Since all information in BISDN are statistically multiplexed and are transported in high speed by means of discrete units of 53-octet ATM ( asynchronous Transfer Mode ) cells, appropriate traffic control needs. For traffic shaping of voice, the output cell discarding scheme has been proposed. We analyze the scheme with a MMPP/$D_1$, $D_2$/1/B queueing system to obtain performance measures such as loss probability and waiting time distribution.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.854-858
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• 1987

This paper considers impulsive noise which produce burst error in high speed(approx.160Kbps) data transmission like ISDN(Integrated Servise Digital Network) using PSTN(Public Switching Telephone Network). To begin with, we obtains the transfer function of subscriber line to calculate the variation of bandwidth when the gain of receiver is fixed and channel capacity of non-gaussian channel in upper-and lower bound, and evaluates the transmission capability. In this paper compares channel capacity bounds which obtains when probability density function of impulsive noise is Laplacian distribution function with impulsive noise generated by waveform synthesier.

• Journal of Mechanical Science and Technology
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• v.16 no.3
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• pp.376-385
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• 2002

Spray impingement and fuel film formation models with cavitation have been developed and incorporated into the computational fluid dynamics code, STAR-CD. The spray/wall interaction process was modeled by considering the effects of surface temperature conditions and fuel film formation. The behavior of fuel droplets after impingement was divided into rebound, spread and splash using the Weber number and parameter K(equation omitted). The spray impingement model accounts for mass conservation, energy conservation, and heat transfer to the impinging droplets. The fuel film formation model was developed by integrating the continuity, momentum, and energy equations along the direction of fuel film thickness. Zero dimensional cavitation model was adopted in order to consider the cavitation phenomena and to give reasonable initial conditions for spray injection. Numerical simulations of spray tip penetration, spray impingement patterns, and the mass of film-state fuel matched well with the experimental data. The spray impingement and fuel film formation models have been applied to study spray/wall impingement in high-speed direct injection diesel engines.

• Journal of the Semiconductor & Display Technology
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• v.5 no.1 s.14
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• pp.33-38
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• 2006

The ATE driver to test a high speed semiconductor chip is designed by using general logic drivers instead of dedicated pin drivers. We have proposed a structure of general logic drivers using FPCA and assured its correct operation by EDA tool simulation. PCB circuit was implemented and Altera FPGA chip was programmed using DDR I/O library. On the PCB, it is necessary to place two resistors connected output drivers near to the output pin to adjust an impedance matching. We confirmed that the measured results agree with the simulated values within 5% errors at room temperature for the input signals with 800Mbps data transfer rate and 1.8V operating voltage.

• Journal of Power Electronics
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• v.14 no.3
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• pp.572-579
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• 2014

As a non-linear time variant system, the four-quadrant line converter of an electric multiple unit (EMU) was expressed by linear time periodic functions near an operating point and modeled by a steady-state harmonic domain matrix. The components were then combined according to the circuit connection and relations of the feedback control loops to form a complete converter model. The proposed modeling method allows the study of the amplitude of harmonic impedances to explore harmonic coupling. Moreover, the proposed method helps provide a better design for the converter controllers, as well as solves the problem in coordination operation between the EMUs and the AC supply. On-site data from an actual $CRH_2$ high-speed train were used to validate the modeling principles presented in the paper.