• Journal of Korean Association for Spatial Structures
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• v.9 no.4
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• pp.73-80
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• 2009

It is very important that predict the inelastic seismic behavior exactly for seismic performance evaluation of a building in the performance based seismic design. But, it is difficulty that predict the building behavior of actual and exact in simplified load-deformation relation of structural material and members. In this study, system ductility and story ductility capacity of building structure used to the Backbone hinge Model are estimated and compared considering the characteristics of load-deformation relation of structural material and members. Analyses results, bilinear hinge model has lower system ductility and story ductility demands than those of backbone hinge model.

• Journal of Broadcast Engineering
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• v.2 no.2
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• pp.194-205
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• 1997

In video compression standards such as MPEG and H.263. rate control is one of the key components for good coding performance. This paper presents a simple adaptive rate control scheme using a piecewise linear approximation model. While conventional buffer control approach is performed by adjusting the quantization parameter linearly according to the buffer fullness. the proposed approach uses a piecewise linear approximation model derived from logarithmic relation between the quantization parameter and bitrate in data compression. In addition. a forward analyzer performed in the spatial domain is used to improve image quality. Simulation results demonstrate that the proposed method provides better performance than the conventional one and reduces the fluctuation of the PSNR per frame while maintaining the quality of the reconstructed frames at a relatively stable level.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.549-555
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• 2001

Ultrasonic is a powerful nondestructive technique for getting the information of flaws and material properties of in-services facilities. We prepared 4 different 1Cr-1Mo-0.25V specimens by Isothermal aging at $630^{\circ}C$. We evaluated material degradation using ultrasonic parameters, velocity, attenuation and harmonic generation. Attenuation and nonlinear parameter derived from harmonic generation efficiency increased as degradation. Especially the second harmonic of the fundamental wave in the 1,820h aging material was observed to exceed 20dB more than that in the un-aged material. But velocity remained virtually the same for all specimens. We concluded that nonlinear parameter and attenuation are sensitive to material degradation, but velocity was not. It'll be a good parameter for evaluating the material degradation.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.6
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• pp.17-24
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• 2002

Dynamic behaviors of a bridge system with several simple spans are evaluated to examine the effects of nonlinear abutment motions upon the seismic responses of the bridge. The idealized mechanical model for the whole bridge system is developed by adopting the multi-degree-of-freedom system, which can consider various influential components. To compare the results, both linear and nonlinear abutment-backfill models are prepared. The linear system has the constant abutment stiffness, and the nonlinear system has the nonlinear stiffness considering the abutment stiffness degradation due to the abutment-soil interaction. From simulation results, the nonlinear abutment motion is found to have an important influence upon the global bridge motions. Maximum relative distances between adjacent vibration units are found to be larger than those found from the linear system. In particular, maximum relative distances at the location with the highest possibility of unseating failure are increased up to about 30% in the nonlinear system. The effects of nonlinear behavior of an abutment on the bridge seismic behaviors are also increased as the number of span increase. Therefore, it can be concluded that the abutment-soil interaction should be considered in the seismic analysis of the bridge system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.373-376
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• 2012

Multiple-Input Multiple-Output (MIMO) 시스템의 복잡도를 감소시키는 방식은 실생활에서 MIMO 시스템을 활용하는 데에 있어 중요한 부분이다. 널리 사용되는 Maximum Likelihood (ML) 복호기의 경우 낮은 에러오율 (BER) 을 보여주지만 복잡도가 높다. 실생활에 활용하기 위하여 ML 복호기의 복잡도를 감소시킬 필요가 있고 이에 Sphere Decoding Algorithm (SDA) 이 제안되었다. 이를 발전시킨 List Sphere Decoding(LSD) 은 여러 종류가 있다. 그 중에 넓이 우선 탐색 방식인 K-Best LSD 알고리즘은 각 레이어에서 리스트의 크기가 복잡도와 밀접한 연관이 있다. 본 논문에서는 기존의 K-Best LSD 알고리즘에 기반하여 초기 반지름 설정 및 선형적으로 리스트 크기를 감소시키는 방식으로 K-Best LSD 알고리즘의 복잡도를 기존 알고리즘에 비해 크게 낮추면서도 비트 오율 성능 열화가 적은 알고리즘을 제안하고 전산 실험을 통해 이를 검증한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.895-902
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• 2012

In this paper, we propose a novel equalizer to compensate for the group delay including AM/PM nonlinear distortion characteristics by the nonlinear power amplifier (PA). The group delay characteristic is a nonlinear non-constant time delay that appears differently depending on each frequency component. The phase distortion by AM/PM characteristics arising from the power amplifier is a major factor to increase group delay. By the group delay distortion, the signal in the constellation expands and is rotated. Considering the problem mentioned above, the nonlinear time delay that appears differently depending on each frequency component is classified as a static group delay and AM/PM characteristic of PA, the different phase transitions depending on the size of input signal as a dynamic group delay. Static group delay estimates and compensate for phase distortions in the frequency domain with type-based method and dynamic group delay compensates for phase rotation in the time domain. We confirmed that the group delay compensation techniques were enough to compensate the group delay characteristics including AM/PM characteristics of the power amplifier.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.190-196
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• 2013

Curved integral imaging is a simple method to display 3D images in space using lens array and provides wide viewing angle. In this paper, we propose a nonlinear 3D correlator based on the direct pixel-mapping (DPM) method in order to improve the recognition performance of 3D target object in curving-effective integral imaging. With this scheme, the elemental image array (EIA) originally picked up from a partially occluded 3-D target object can be converted into a resolution enhanced new EIA by using DPM method. Then, through nonlinear cross-correlations between the reconstructed reference and the target plane images, the improved pattern recognition can be performed from the correlation outputs. To show the feasibility of the proposed method, some preliminary experiments are carried out and results are presented by comparing the conventional method.

• Journal of IKEEE
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• v.17 no.1
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• pp.83-88
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• 2013

This paper presents the output feedback control design for feedforward nonlinear systems with input and output delay. The proposed output feedback controller is composed of a linear observer and a linear controller. It is shown that by using Lyapunov-Krasovskii theorem, the proposed controller ensures a global asymptotic stability for arbitrarily large delay. Finally, an illustrative example is given in order to show the effectiveness of our design method.

• The Journal of the Acoustical Society of Korea
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• v.17 no.2
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• pp.32-42
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• 1998

본 논문은 비균일 분포 수동형 견인 배열 센서를 사용하여 입사각 추정은 물론, 도 플러 주파수를 동시에 추정해내기 위한 기법을 제안한다. 균일 선형 센서 배열을 사용하는 전통적인 수동형 견인 센서 배열 처리기법은 센서간의 등 간격 구조 및 단순한 표본 과정에 기인하여 활용 분야의 한계성을 가지며, 주된 응용 분야가 방사된 음향신호의 입사각을 추 정하는데만 국한되어 사용될 수 있다는 문제점을 내포하고 있다. 이러한 사실 때문에, 수중 천해 환경 하에서 견인함의 등속 이동에 의해 발생하는 도플러 주파수들에 대한 정보는 목 표물에 대한 식별이나 음향신호 전달 경로의 모델링에 중요한 매개변수로 작용하며, 일반적 인 수동형 견인 센서 배열의 사용에 의한 처리 방식으로는 이러한 매개변수의 추출이 불가 능하게 된다. 본 논문은 이러한 제한성을 극복하고 방사 신호들의 개별적인 입사각 및 도플 러 주파수의 동시 추정을 가능케하도록 비균일 분포의 선형 센서 배열과 Sample Skipping 기법(Sample Skipping Technique;SST)을 적용한 새로운 형태의 수동형 견인 배열 센서 처 리 기법을 제안한다.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.135-144
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• 2004

Since Modern bridges have a tendency to make the spans continuous and longer, the effect of concrete shrinkage and creep is very important and must be evaluated appropriately for the durability and safety of steel-concrete composite bridges. However, highway design specification in current use prescribes $180^{1\;2}$ as the final shrinkage strain. which is for less value than one resulted from many experimental researches and cause some problems in the construction of composite bridges due to the understimation of shrinkage strain. Thus, in this paper nonlinear analysis with time-steps applying the CEB-FIP(90) provision have been conducted for plate girder bridge, box girder bridge and Preflex beam bridge and the linear equivalent shrinkage strain for the design of composite bridges. which produces the stress equal to the values from the nonlinear analysis, has been calculated by comparing the results with the values following highway design specification. The results yield appropriately double values than $180^{1\;2}$ which highway design specification prescribes.