• Journal of Korean Association for Spatial Structures
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• v.8 no.4
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• pp.81-90
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• 2008

This paper presents a finite element formulation for the three-dimensional hierarchical solid element using Integrals of Legendre polynomials. The proposed hexahedral solid element is composed of four different modes including vertex, edge, face, and internal mode, respectively. The eigenvalue and patch test have been carried out to confirm the zero-energy mode and constant strain condition. In addition to these, a posteriori error estimation has been studied for the p-adaptive finite element analysis that is based on a smoothing technique to compute a post-processed solution from the finite element solution. The uniform p-refinement and non-uniform p-refinement are compared in terms of convergence rate as the number of degree of freedom is increased. The simple cantilever beam is tested to show the performance of the proposed solid element.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.187-195
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• 1996

A finite element formulation based on the CFT(Compression Field Theory), considering the effect of compression softening in cracked concrete, and macro-scopic and rotating crack models etc., was presented for the nonlinear behaviour of structural concrete. Considering the computational efficency and the ability of modelling the post-ultimate behaviour as major concerns, the Incremental displacement solution algorithm involving initial material stiffnesses and the relaxation procedure for fast convergence was adopted and formulated in a type of 8-noded quadrilateral isoparametric elements. The analysis program NASCOM(Non1inear Analysis of Structural Concrete by FEM : Monotonic Loading) developed in this way enables the predictions of strength and deformation capacities in a full range, crack patterns and their corresponding widths, and yield extents of reinforcement. As the verification purpose of NASCOM, the predictions were made for Bhide's Panel(PB21) and Leonhardt's deep beam tests. The predicted results shows somewhat stiff behaviour for the panel test, and vice versa for deep beam tests. More refining process would be necessary hereafter in terms of more accurately simulating the effects of tension-stiffening and compression softening in concrete.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.4
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• pp.28-36
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• 2009

Sequence-Pair(SP) model represents the topological relation between modules. In general, SP model based floorplanners search solutions using Simulated-Annealing(SA) algorithm. Several SA based floorplanning techniques using SP model have been published. To improve the performance of those techniques they tried to improve the speed for evaluation function for SP model, to find better scheduling methods and perturb functions for SA. In this paper we propose a two phase SA based algorithm. In the first phase, white space between modules is reduced by applying compaction technique to the floorplan obtained by an SP. From the compacted floorplan, the corresponding SP is determined. Solution space has been searched by changing the SP in the SA framework. When solutions converge to some threshold value, the first phase of the SA based search stops. Then using the typical SA based algorithm, ie, without using the compaction technique, the second phase of our algorithm continues to find optimal solutions. Experimental results with MCNC benchmark circuits show that how the proposed technique affects to the procedure for SA based floorplainning algorithm and that the results obtained by our technique is better than those obtained by existing SA-based algorithms.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.111-118
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• 2008

In this paper, novel latch-up prevention method that employs power-up sequential switches has been proposed to relieve latch-up problem in liquid crystal display (LCD) driver ICs. These sequential switches are inserted in the 2'nd and 3'rd boosting stages, and are used to short the emitter-base terminals of parasitic p-n-p-n circuit before relevant boosting stages are activated during power-up sequence. To verily the performance of the proposed method, test chips were designed and fabricated in a 0.13-um CMOS process technology. The measurement results indicated that, while the conventional LCD driver If entered latch-up mode at $50^{\circ}C$ accompanying a significant amount of excess current, the driver IC adopting the proposed method showed no latch-up phenomenon up to $100^{\circ}C$ and maintained normal current level of 0.9mA.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.5
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• pp.1-12
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• 2000

In this paper we propose a design method of the adaptive fuzzy controller for autonomous navigation of mobile robots based on the fuzzy theory. We present two improvements. First, unnecessary rules in the fuzzy inference process make data processing time increase. We reduce this data processing time by generating suitable fuzzy inference rules and membership functions according to the current state of a mobile robot. It is implemented with the clustering method using input and output data pairs, and then it is possible for a mobile robot to navigate in shorter processing time with less fuzzy inference rules. Second, existing algorithms used fixed membership functions of input and output variables, hence converged slowly. We improve convergence time via scaling membership functions generated by the clustering method. To evaluate and compare the performance of the proposed method with the existing fuzzy navigation controller, computer simulations and navigation experiments of a mobile robot are Presented.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.6
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• pp.599-607
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• 2001

In Conventional BMA, the motion vector can describe only translational movement and blocking noise is generated. To overcome this defect, motion estimation using triangular mesh has been proposed. The regular mesh is the method of dividing the image area into equal size triangle and haying the same node connection. It has no additional information about mesh structure, but do not reflect the real motion because it represents the regions by equal mesh structure regardless of the amount of motion. In this paper, motion estimation using dynamic regular mesh is proposed, In this method, the mesh structure is varied from the amount of motion and maintain the form of regular mesh. By the simulation, proposed method have better performance in PSNR and is superior to the other method in convergence rate.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.79-84
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• 1996

In this paper, adaptive correlator model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of adaptive correlator uswing backpropagation neural network improved than that of adaptive transversal filter of direct sequence spread spectrum considering of co-channel and narrow-band interference. Bit error ratio of adaptive correlator using backpropagation neural network is reduced about $10^{-1}$ than that of adaptive transversal filter where interference versus signal ratio is 5 dB.

• Journal of Korea Multimedia Society
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• v.12 no.3
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• pp.372-382
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• 2009

When the range of projection angles is limited, tomographic reconstruction suffers from artifacts caused by incomplete data. One can consider a data completion technique, which estimates projection data at unobserved angles using a prior knowledge or mathematical exploration, but the result is often not improved; the improvement by the data completion often undermined by the artifacts by inaccurate estimation, In this paper, we propose an iterative method, which computes projection data at unobserved angles by using the current estimate on the image, links the computed projection data to the observed ones by using the consistence condition of Radon transform, and reconstruct the next estimate on the image by filtered backprojection. The proposed method does not require a prior knowledge on the image, and has much faster approximation rate than the expectation maximization method. The performance of the proposed method was tested through several simulation studies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.431-438
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• 2012

The $CO_2$ capture technology using an aqueous amine solution is studied widely now. The entire process consists of an absorber to remove carbon dioxide selectively and a regenerator to regenerate absorbent and acquire pure carbon dioxide. Because there are the complicated design variables that affect performance of the process, it needs optimization and analysis through modeling to make a commercially reliable process. In this study, the decomposition method was proposed to consider convergence problem and sensitivity analysis was executed for the carbon dioxide capture process variables. Non-equilibrium model was used in the simulation to get more realistic results and we designed optimized process with more than 95% purity and 90% recovery.

• Journal of Satellite, Information and Communications
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• v.11 no.2
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• pp.55-59
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• 2016

Conventional RF energy harvesting systems can harvest energy and decode information from same source as an Hybirid-AP (H-AP). However, harvesting efficiency is seriously dependent on distance between users and H-AP. Therefore, in this paper, we proposed a transmission model for RF harvesting consisting of information and power source separately called Decoupled RF Energy harvesting networks. Main purpose of this paper is to maximize energy efficiency under various constraints of transmit power from H-AP and power beacon (PB), minimum quality of service and quality of harvested power of each users. To measure proposed model's performance, we proposed optimal time scheduling algorithms for energy efficiency (EE) maximization using Lagrangian dual decomposition theory that locally maximizes the EE by obtaining suboptimal values of three arguments : transmit power of H-AP, transmit power of PB, frame splitting factor. Experiment results show that the proposed energy-efficient algorithms converge within a few iterations with its optimality and greatly improve the EE compared to that of baseline schemes.