• Journal of the Earthquake Engineering Society of Korea
• /
• v.17 no.6
• /
• pp.245-255
• /
• 2013

According to natural frequency of soil, characteristics of earthquake responses of an isolated containment building in nuclear power plants are examined. For this, earthquake response analysis of seismically isolated containment buildings in nuclear power plants is carried out by strictly considering soil-structure interactions. The structure and near-field soil are modeled by the finite element method while far-field soil by consistent transmitting boundary. The equation of motion of a soil-structure interaction system under incident seismic wave is derived. The derived equations of motion are solved to carry out earthquake analysis of a seismically isolated soil-structure system. Generally, the results of this analysis show that seismic isolation significantly reduces the responses of the soil-structure system. However, if the natural frequency of the soil is similar to that of the soil-structure system, the responses of the containment buildings in nuclear power plants rather increases due to interactions in the system.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.18 no.6
• /
• pp.279-289
• /
• 2014

Considering a rigorously fluid-structure interaction, a method for an earthquake response analysis of a floating offshore structure subjected to vertical ground motion from a seaquake is developed. Mass, damping, stiffness, and hydrostatic stiffness matrices of the floating offshore structure are obtained from a finite-element model. The sea water is assumed to be a compressible, nonviscous, ideal fluid. Hydrodynamic pressure, which is applied to the structure, from the sea water is assessed using its finite elements and transmitting boundary. Considering the fluid-structure interaction, added mass and force from the hydrodynamic pressure is obtained, which will be combined with the numerical model for the structure. Hydrodynamic pressure in a free field subjected to vertical ground motion and due to harmonic vibration of a floating massless rigid circular plate are calculated and compared with analytical solutions for verification. Using the developed method, the earthquake responses of a floating offshore structure subjected to a vertical ground motion from the seaquake is obtained. It is concluded that the earthquake responses of a floating offshore structure to vertical ground motion is severely influenced by the compressibility of sea water.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1999.04a
• /
• pp.267-274
• /
• 1999

Since the seismic response of dams can be strongly influenced by the dam-reservior interaction in needs to be taken into account in the seismic design of dams. In general a substructure method is employed to solve the dam-reservoir interaction problem in which the dam body is modeled with finite elements and the infinite region of a reservoir using a transmitting boundary. When the water is modeled as a compressible fluid the equation is formulated in frequency domain. But nonlinear behavior of dam body cannot be studied easily in the frequency domain method. In this study time domain formulation of the dam-reservoir-soil interaction is proposed based onthe lumped parameter modeling of the reservoir region, The frequency dependent dynamic-stiffness coefficients of the reservoir are converted into frequency independent lumped-parameters such as masses dampers and springs. The soil-structure interactionis modeled using lumped parameters in similar way. the ground is assumed as a visco-elastic stratum on the rigid bedrock. The dynamic stiffnesses of the rigid surface foundation are calculated using the hyperelement method and are converted into lumped parameters. The application example demonstrated that the lumped parameter model gives almost identical results with the frequency domain formulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.5B
• /
• pp.443-448
• /
• 2009

A boundary value of the velocity of data gathering node (DGN) and a critical value for training overhead beyond which the scheme will not be feasible for a Multiple Input Multiple Output (MIMO) based cooperative communication for energy-limited wireless sensor networks is proposed in this paper. The performance in terms of energy efficiency and delay for a combination of two transmitting and two receiving antennas is analyzed. The results show that a set of critical value of velocity and training overhead pair is present for the long haul communication from the sensors to the data gathering node. Finally a relation between training overhead and velocity is simulated.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.7
• /
• pp.1229-1236
• /
• 2016

In underwater acoustic multipath channel, a performance of underwater acoustic (UWA) communication systems is affected by dynamic variation of boundary and high temporal and spatial variability of the channel conditions. Time and spatial variations of UWA channel induce a carrier frequency offset (CFO) since a phase and a frequency of received signal mismatch with a transmitting signal. Therefore, a performance of a phase shift keying underwater acoustic communication system is degraded. In this study, we have analyzed a performance of CFO estimation and compensation using a phase code in time and spatial variation channel. A constant amplitude zero autocorrelation (CAZAC) signal is applied as a phase code signal and its performance is evaluated in water tank. The bit error rate of a quadrature phase shift keying (QPSK) system with a phase code is improved about 4 to 10 times better than that without a phase code.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.9
• /
• pp.3011-3018
• /
• 2000

On ATM networks, ABR services are provided using the remained bandwidth after allocating CBR and VBR traffic. Realtime services such as transmitting audio or video data may be provided using CBR and VBR which have a constrained transmission delay, but in these cases, the communications bandwidth may be wasted. This paper proposes an efficient bandwidth allocation algorithm to transfer real-time data using ABR service. The proposed algorithm guarantees MCR and allocates bandwidth to each connection proportional to its MCR. The proposed algorithm divides the connections in two groups - a satisfied state group and a bottlenecked state group - and enhances bandwidth utilization by allowing the remained bandwidth after allocating the connections in the satisfied state to be allocated to the connections in the bottlenecked state. Our algorithm uses a Queue control function proposed by Ghani[5] to keep the Queue length within some boundary, which makes the transmission delay constant. We simulate and compare the performance of the proposed algorithm with that of the algorithms proposed by ATM Forum[1] and Kalampoukas[2].

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.38 no.4
• /
• pp.307-315
• /
• 1989

In this paper, we have analyzed the temperature variation trend of a slab on between the process of reheating furnace and the termination of roughing mill process during hot rolling process. 1) cooling by radiation and convection current in the air, 2) plastic deformation heat, 3) cooling by descaling water, 4) cooling by contact with rolling rolls and/or transmitting rolls. For the analysis, the factors have been adopted as the problems of the rolling process to be solved such that we have established an application technique in relation to the determination of boundary conditions on the slab surface. We have presented a procedure for an analysis of the cooling phenomenon treated as a problem of two-dimensional transient heat flow using finite difference equation and suggested techniques of implementing sequentialized rolling tasks in correlation with the procedure. From the result of simulation, it is shown that the difference between calculation value and measurement value is within the range of the industrial measurement error. Also, it is proved that the assumptions, conditions, and properties used in the computer simulation is appropriate by showing that the pattern of a drop in temperature at each rolling event is in accord with real circumstances.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.1B
• /
• pp.31-38
• /
• 2012

In this paper, we propose a method to improve cell edge users' performance in HetNet (heterogeneous network) systems by cooperatively transmitting signals using remote radio heads (RRHs) located near coverage boundaries, referred to as edge RRHs. The proposed method locates the edge RRHs in specific locations of the cell boundary and provides an efficient operational strategy by adjusting the duty cycle of the edge RRHs and base stations. The effectiveness of the method is demonstrated by experimental performance based on the system model parameters of the CoMP (coordinated multi-point transmission and reception) scenario, which is discussed in LTE-Advanced (Long Term Evolution - Advanced) standard contributions. When compared with conventional methods, utilization of edge RRHs is especially advantageous for the performance improvement of lower percentile users in terms of average throughput and effectively improves the fairness among users.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.10a
• /
• pp.530-532
• /
• 2018

Digital imaging equipment has been used for a variety of purposes in a wide range of society and has become an important element of the fourth industrial revolution. However, there are various causes of noise in the process of transmitting / receiving data and processing of the equipment, thus affecting the accuracy and reliability of the equipment. In this paper, we propose an image restoration algorithm based on pixel range set by standard deviation to effectively remove Salt and Pepper noise. In the conventional methods, the performance degrades in the edge and high frequency components of the image. However, the proposed method has better noise reduction performance than the conventional method by performing the noise elimination considering the image boundary. It has confirmed that the performance of such PSNR and magnified image, the experimental results showed that the proposed algorithm superior compared to existing methods.

• The KIPS Transactions:PartB
• /
• v.12B no.7 s.103
• /
• pp.755-760
• /
• 2005

To transmit a video bit stream over low bandwith, such as mobile, channels, encoding algorithms for high bit rate like H.263+ are used. In transmitting video bit-streams, packet losses cause severe degradation in image quality. This paper proposes a new algorithm for the recovery of missing or erroneous motion vectors when H.263+ bit-stream is transmitted. Considering that the missing or erroneous motion vectors are closely related with those of neighboring blocks, this paper proposes a temporal-spatial error concealment algorithm. The proposed approach is that missing or erroneous Motion Vectors(MVs) are recovered by clustering the movements of neighboring blocks by their homogeneity. MVs of neighboring blocks we clustered according to ALA(Average Linkage Algorithm) clustering and a representative value for each cluster is determined to obtain the candidate MV set. By computing the distortion of the candidates, a MV with the minimum distortion is selected. Experimental results show that the proposed algorithm exhibits better performance in subjective and objective evaluation than existing methods.