• Structural Engineering and Mechanics
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• 제65권1호
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• pp.53-68
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• 2018

In this paper, an innovative procedure is proposed for the seismic design of reinforced concrete frame structures. The main contribution of the proposed procedure is to minimize the construction cost, considering the uniform damage distribution over the height of structure due to earthquake excitations. As such, this procedure is structured in the framework of an optimization problem, and the initial construction cost is chosen as the objective function. The aim of uniform damage distribution is reached through a design constraint in the optimization problem. Since this aim requires defining allowable degree of damage, a damage pattern based on the concept of global collapse mechanism is presented. To show the efficiency of the proposed procedure, the uniform damage-based optimum seismic design is compared with two other seismic design procedures, which are the strength-based optimum seismic design and the damage-based optimum seismic design. By using the three different seismic design methods, three reinforced concrete frames including six-, nine-, and twelve-story with three bays are designed optimally under a same artificial earthquake. Then, to show the effects of the uniform damage distribution, all three optimized frames are used for seismic damage analysis under a suite of earthquake records. The results show that the uniform damage-based optimum seismic design method renders a design that will suffer less damage under severe earthquakes.

• 한국ITS학회 논문지
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• 제7권3호
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• pp.38-47
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• 2008

비디오 카메라에서 입력된 동영상을 분석하여 교차로에서 교통량을 자동적으로 측정하는 시스템을 설계, 구현하였다. 입력 영상에서 배경과 전경을 분리하기 위하여 3가지 방법을 비교 분석하였으며 이중에서 좋은 결과를 보여주는 Li의 방법을 선택하였다. 전경 영상에서 연결 성분 분석을 이용하여 각각의 블로브들을 분리하였으며 분리된 블로브들은 블로브 추적기를 이용하여 프레임 별로 추적된다. 가장 기본적인 추적기는 블로브의 크기와 위치 정보들을 이용한다. 블로브들 간에 충돌이 있는 경우에는 블로브 안의 컬러 분포를 이용하는 mean shift 알고리즘이 사용되었다. 제안된 시스템은 실제 교차로 동영상을 이용하여 테스트되었으며 휴리스틱을 추가할 경우, 좋은 감지율과 오차율을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권5호
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• pp.2294-2309
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• 2020

In this article, a new Aloha-based tag identification protocol is presented to improve the reading efficiency of the EPC C1 Gen2-based UHF RFID system. Collision detection (CD) plays a vital role in tag identification process which determines the efficiency of anti-collision protocols since most Aloha-based protocols optimize the incoming frame length based on the collisions in current frame. Existing CD methods are ineffective in identifying collision, resulting in a degradation of identification performance. Our proposed algorithm adopts an enhanced CD (ECD) scheme based on the EPC C1 Gen2 standard to optimize identification performance. The ECD method can realize timely and effective CD by detecting the pulse width of the randomly sent by tags. According to the ECD, the reader detects the slot distribution and predicts tag cardinality in every collision slot. The tags involved in each collision slot are identified by independently assigned sub-frames. A large number of numerical results show that the proposed solution is superior to other existing anti-collision protocols in various performance evaluation metrics.

• 한국강구조학회 논문집
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• 제10권3호통권36호
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• pp.463-472
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• 1998

본 논문의 목적은 4각형네트워크 패턴을 가지는 단층래티스돔의 좌굴특성을 실험과 이론을 통하여 검토하고, 나아가 4각형 네트워크 단층돔에 대한 신뢰할 수 있는 이론해석법을 개발하기 위한 기초연구를 하는데 그 목적이 있다. 이론해석은 야마다의 연속체치환법과 유한요소법에 의한 프레임해석법으로 한다. 원주방향에 대한 불균일한 강성과 지붕재료의 강성이 돔전체 좌굴특성에 미치는 영향을 검토한다. 이론과 실험에 의한 결과는 불균일한 강성을 가지거나 또는 강성을 갖는 지붕재료를 사용하는 다양한 종류의 단층래티스돔에 대한 일반적인 이론해석법을 개발하기 위한 기초자료로 활용될 것이다.

• Journal of Power Electronics
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• 제19권1호
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• 한국통신학회논문지
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• 제21권5호
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• pp.1096-1108
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• 1996

In this paper, we propose a temporal adaptive tranform 3D SBC coder with motion compensation, exploiting redundancy in the temporal domain. We propose a temporal adaptivity measure, by which the R-D optimal temporal transform can be chaosen. The base temporal subband frame is coded using H.261-like MC-DCT coder, while the higher temporal subband frames are coded using the 2D adaptive wavelet packet bases, considering the various energy distribution which results from the temporal variation. In encoding the subbands, we employ adaptive scanning methods, uniform step-size quantization with VLC, and coded/not-coded flag reduction technique using the quadtree structure. From the simulation results, the proposed adaptive 3D subband coder shows about 0.29~3.14 dB gain over the H.261 and the fixed 3D subband coder techniques.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.369-374
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• 2007

For a stability design of steel frames, AISC-LRFD specification recommend to use Alignment Chart and story-based methods in order to determine an effective budding length. Recently, elastic buckling analysis, which is the method that calculate the effective length of members using eigenvalue of the overall structure, has been widely used in practical design of steel frames because this method can be performed effectively and automatically by computers. However, it can in some cases lead to unexpectedly large effective length in column having small axial forces. Therefore, this paper propose a method using elastic buckling analysis, which estimate a proper effective buckling length for all members having a small axial force. For verification of proposed method, it is compared with system based approach and stiffness distribution factor method. As a result, proposed method can rationally solve a problem in some case of column having small axial force. Also, adoption range for proposed method is established.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.189-199
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• 2020

Researchers have elaborated several accurate methods to calculate member-end rotations or moments, directly, for bridge-type structures. Recently, the concept of rotation and moment propagation (RMP) has been presented considering bending flexibility, only. Through which, in spite of moment distribution method, all joints are free resulting in rotation and moment emit throughout the structure similar to wave motion. This paper proposes a new set of closed-form equations to calculate member-end rotation or moment, directly, comprising both shear and bending flexibility. Furthermore, the authors program the algorithm of Timoshenko beam theory cooperated with the finite element. Several numerical examples, conducted on the procedures, show that the method is superior in not only the dominant algorithm but also the preciseness of results.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1236-1245
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• 2004

In this study, an optical imaging method was developed for the measurements of the sizes and velocities of droplets in sprays. Double-exposure single-frame spray images were captured by the imaging system. An image processing program was developed for the measurements of the sizes and positions of individual particles including separation of the overlapped particles and particle tracking and pairing at two time instants. To recognize and separate overlapping particles, the morphological method based on watershed segmentation as well as separation using the perimeter and convex hull of image was used consecutively. Better results in separation were obtained by utilization of both methods especially for the multiple or heavily-overlapped particles. The match probability method was adopted for particle tracking and pairing after identifying the positions of individual particles and it produced good matching results even for large particles like droplets in sprays. Therefore, the developed optical imaging method could provide a reliable way of analyzing the motion and size distribution of droplets produced by various sprays and atomization devices.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2003년도 봄 학술발표논문집 Vol.30 No.1 (C)
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• pp.25-27
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• 2003

본 논문은 10GbE로의 망 전개에 따라 구현될 l0Gb 스위치에 필요한 계층2 부가서비스들 중에서 여러개의 물리적인 링크를 하나의 논리적인 링크로 집합하여 대역폭의 증가를 가져오는 링크 집합(Link Aggregation) 기술에 필요한 프레임 분배방식에 대한 것이다. 링크 집합 기술은 분배 알고리즘의 설계에 따라 스위치에서 성능의 차이를 가져오므로 링크 집합의 장정을 살리려면 종은 성능을 가지는 분배 알고리즘이 필요하다. 우선 링크 집합의 간단한 구현 방법을 살펴보고 기존에 제시된 스위치와 스위치 사이에서의 프레임 분배방식인 정적/동적 프레임 분배 방식과 우리가 새로이 제안한 패딩을 이용한 분배방식을 비교한 후, 정적/동적 프레임 분배 방식과 패딩을 이용한 분배방식을 컴퓨터 시뮬레이션을 통해 성능을 비교하였다.