• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7A
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• pp.964-972
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• 1999

In this paper, we proposed a simulation model to which apply the AAL 2 (AAL type 2) between BSC and MSC in the cellular mobile communication systems. We suggested the frame structure of processing the packets of short length and the scheme which multiplex to one or more ATM cell. Also, we analyzed the performance of the APR, transmission delay, and channel transmission efficiency used in the packetized voice traffic and the low bit-rate data traffic such as fax. From the simulation results, the maximum number of users are 47 users without using AAL 2 multiplexing, but the maximum number of users are 70 (Non-Overlapping scheme) users, 110 (Overlapping scheme) users, respectively. Thus, we knew that the Overlapping scheme is more efficient than the Non-Overlapping scheme. Finally, we showed that the optimum transmission buffer size is 4 ATM cells in the cellular communication systems with the bandwidth of 2 Mbps.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.307-312
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• 2000

Asynchronous transfer mode(ATM) is flexible to support the various multimedia communication services such as data, voice, and image by applying asynchronous time-sharing and statistical multiplexing techniques to the existing data communication. ATM service is categorized to CBR, VBR, UBR, and ABR according to characteristics of the traffic and a required service qualities. Among them, ABR service guarantees a minimal bandwidth and can transmit cells at a maximum transmission rate within the available bandwidth. To minimize the cell losses in transmission and switching, a feedback information in ATM network is used to control the traffic. In this paper, predictive control algorithms are proposed for the feedback information. When the feedback information takes a long propagation delay to the backward nodes, ATM switch can experience a congestion situation from the queue length increases, and a high queue length fluctuations in time. The control algorithms proposed in this paper provides predictive control model using slop changes of the queue length function and previous data of the queue lengths. Simulation shows the effectiveness result of the proposed control algorithms.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.41-45
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• 2007

This paper presents transport current non-uniformity in a joint for superconducting multistage cable-in-conduit conductor (CICC) and relaxation in the CICC. The joint is considered to have a current loop linked to an external magnetic field so that it becomes an emf voltage source. It is numerically analyzed using an electrical transmission line model. The inductive current in a resistive joint is compared to that of a non-resistive joint when the ramping field is applied vertically to the joints. Regarding the parameter values of the model. a full scale $Nb_3Sn$ CICC and a strand-to-strand (STS) joint for the toroidal field magnet of the KSTAR (Korea Superconducting Tokamak Advanced Research) device are referenced to. It is found that the resistive joint prevents the current from rising too much and enhances decaying the current when the ramping stops. The 'flattop' current is found to be proportional to the ramp rate of the field (dB/dt). The relaxation length, which is defined as the length within which the maximum induced current falls by 1/e. is found to saturate within 0.27m.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.641-652
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• 2007

In this paper, a half-scaled substructure test was performed to evaluate the buckling and structural safety of an existing transmission tower subjected to wind load. A loading scheme was devised to reproduce the dead and wind loads of a prototype transmission tower, which uses a triangular jig that is mounted on the reduced model to which the similarity law of a half length was applied. As a result of the preliminary numerical analysis carried out to evaluate the stability of a specimen for the design load, is was confirmed that the calculated axial forces of tower leg members were distributed to $80{\sim}90%$ of an admissible buckling load. When the substructured transmission tower was loaded by 270% of its maximum admissible buckling load, it was failed due to the local buckling that is occurred in joints with weak constraints for out-of-plane behavior of leg members. By inspection of load-displacement curves, displacements and strains of members, it is considered that this local buckling was due to additional eccentric force by unbalanced deformation because the time that is reached to yielding stress due to the bending moment is different at each point of a same section.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.31-38
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• 2018

Based on the measured data in the south western sea of Jeju Island during the SAVEX15(Shallow Water Acoustic Variability EXperiment 2015), the effect of internal waves on the PPD (Predictive Probability of Detection) of a sonar system was analyzed. The southern west sea of Jeju Island has complex flows due to internal waves and USC (Underwater Sound Channel). In this paper, sonar performance is predicted by probabilistic approach. The LFM (Linear Frequency Modulation) and MLS (Maximum Length Sequence) signals of 11 kHz - 31 kHz band of SAVEX15 data were processed to calculate the TL (Transmission Loss) and NL (Noise Level) at a distance of approximately 2.8 km from the source and the receiver. The PDF (Probability Density Function) of TL and NL is convoluted to obtain the PDF of the SE (Signal Excess) and the PPD according to the depth of the source and receiver is calculated. Analysis of the changes in the PPD over time when there are internal waves such as soliton packet and internal tide has confirmed that the PPD value is affected by different aspects.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.15-22
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• 2008

In this paper, we propose a numerical analysis on reversed current of distributed amplifier based on transmission line theory and proposed a theory to obtain optimum transmission line length to minimize the reversed currents by cancelling those components. The reversed current is analyzed as being simply absorbed into the terminal resistance in the conventional analysis. In the proposed analysis, however, they are designed to be cancelled by each other with opposite phase by the optimal length of the transmission lint Circuit simulation and implementation using pHEMT transistor were performed to validate the proposed theory with the cutoff frequency of 3.6 GHz. From the measurement, maximum gain of 14.5dB and minimum gain of 12.3dB were achieved In the operation band. Moreover, measured efficiency of the proposed distributed amplifier is 25.6% at 3 GHz, which is 7.6%, higher than the conventional distributed amplifier. Measured output power Is about 10.9dBm, achieving 1.7dB higher output power than the conventional one. Those improvement is thought to be based on the cancellation of refersed current.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.598-604
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• 2010

The drilled pier foundation is widely used to support transmission line structures due to its simplicity of construction. When this foundation type is used in conjunction with a single shaft or H-frame structure, it is subjected to a high overturning moment, combined with modest vertical and shear loads. Since the length and diameter of drilled piers are often governed by a maximum permissible deflection, many drilled piers being installed today are very conservatively designed. In this study, Nine prototype field-tests (1/8 scale) have been conducted in order to determine the vertical and lateral resistance of drilled pier foundation for single pole structures. These test results reveal the test piers behaved essentially as rigid bodies in soil (6D) and the center of rotation of the pier were typically 0.6~0.4 of the pier depth below ground surface. Test results also show the relationship between the applied load and the deflection at the top of the pier is highly nonlinear.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1087-1094
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• 2008

The drilled pier foundation is widely used to support transmission line structures due to its simplicity of construction. When this foundation type is used in conjunction with a single shaft or H-frame structure, it is subjected to a high overturning moment, combined with modest vertical and shear loads. Since the length and diameter of drilled piers are often governed by a maximum permissible deflection, many drilled piers being installed today are very conservatively designed. In this study, Five prototype field-tests (1/8 scale) have been conducted in order to determine the lateral resistance of drilled pier foundation for single pole structures. These test results reveal the test piers behaved essentially as rigid bodies in soil (6D) and the center of rotation of the pier were typically 0.6~0.4 of the pier depth below ground surface. Test results also show the relationship between the applied load and the deflection at the top of the pier is highly nonlinear.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.127-134
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• 2009

In this study, possibility of the laser eavesdropping is investigated on the window glasses with various thicknesses, Glass windows are excited by maximum length sequency (MLS) signal and the vibration sound is detected by a laser doppler vibrometer. From the detected sound, speech intelligibility is objectively estimated. Speech transmission index (STI), which is based on the modulation transfer function (MTF). is calculated for the estimation. Finally, disturbing wave effect on the speech intelligibility is analysed by using an outside speaker and a window shaker attached on the glass window. The purpose of the study is to estimate the possibility of remote eavesdropping by the laser sensor and to evaluate the performance of the homemade window shaker to protect from the remote eavesdropping.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1939-1947
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• 1999

This paper proposes new line code BIM (Bit Insertion and Manipulation) that is designed to overcome the problems of existing line codes. The block code, one of typical existing line code, has good transmission performance but difficulty in implementation. The other typical existing line code, bit insertion code, is easy to implementation but has bad transmission performance. BIM code in this paper could provide not only good performance but also provides simplicity in the implementation by combining the good points of block code into it of bit insertion code properly. In this paper, 5B6B type BIM code is designed. Designed 5B6B BIM code shows good transmission performance such $\pm$2 DSV, 0 RSD, 7 maximum run length and also it can be implemented under 2000 gates and need only 1 bit redundancy.