• 한국통신학회논문지
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• 제32권3C호
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• pp.323-330
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• 2007

CDMA 셀룰라 망의 기지국에 이용될 수 있는 선형 스마트 안테나를 이차원으로 확장시켜 성능의 척도인 출력 신호대잡음비(Output SNR: Output Signal to Noise Ratio), 출력신호대간섭비(Output SIR: Output Signal to Interference Ratio), 출력신호대간섭잡음비(Output SINR: Output Signal to Interference plus Noise Ratio)를 도출 하였다 Beam forming algorithm 으로 SCGM(Simplified Conjugate Gradient Algorithm)을 설정하고 입력신호대 잡음비, antenna element 숫자, 간섭신호의 분포 등을 변화시키며 평면 스마트 안테나의 성능을 simulate 하였다. 간섭신호들의 방위각(Azimuth angle)이 -90도 에서 +90도 사이에서 고르게 분포할 때, 평면 스마트 안테나의 성능은 같은 숫자의 element를 갖는 선형 스마트 안테나의 성능에 근접함을 보였다.

• Structural Engineering and Mechanics
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• 제9권4호
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• pp.365-374
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• 2000

The structural behavior of connections between concrete-filled rectangular tubular column (CFRT column) and steel beam has been studied in this paper through sub-assemblage loading tests. It is found that the sub-assemblages exhibit ductile restoring force characteristics under seismic loading. A formula for the prediction of the yield strength of each member in the connection is proposed by using the yield line theory under the assumption of a simple stress transfer mechanism. It is shown that the proposed formula can produce a reasonable prediction while providing a basis for further investigation.

• Coupled systems mechanics
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• 제2권2호
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• pp.127-146
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• 2013

A closed-form solution for a fluid-structure system is presented in this article. The closed-form is used to evaluate the finite element method results through a numeric example with consideration of high frequencies of excitation. In the example, the structure is modeled as a cantilever beam with rectangular cross-section including only shear deformation and the reservoir is assumed semi-infinite rectangular filled with compressible fluid. It is observed that finite element results deviate from the closed-form in relatively higher frequencies which is the case for the near field earthquakes.

• 한국해양공학회지
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• 제23권6호
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• pp.131-135
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• 2009

We present an optimum design method for a rectangular reinforced concrete beam using Genetic Algorithms. The optimum design procedure in this paper employs 2 design cases: i) all of the design variables (b, d, As) of the rectangular reinforced concrete section are used pseudo-continuously, ii) one is pseudo-continuous for the concrete cross section (b, d) and the other is discrete, using an index for the steel area (As). The optimum design in this paper uses Chakrabarty's model. In this paper, the Genetic Algorithms use the method of Elitism and penalty parameters to improve the fitness in the reproduction process, which leads to very practical designs. The optimum design of the steel area in the examples uses ASTM standard reinforcing bars (#3~#11, #14, #18).

• Steel and Composite Structures
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• 제10권6호
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• pp.489-500
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• 2010

The rigid connections of I-beams to Rectangular Hollow Sections (RHS) in steel structures usually behave as semi-rigid connection. This behavior is directly related to the column face deformation. The deformation in the wall of RHS column in the connection zone causes a relative rotation between beam end and column axis, which consequently reduces the rigidity of beam-column connection. In the present paper, the percentages of connection rigidity reduction for serviceability conditions are evaluated by using the finite element analysis. Such percentages for RHS columns without internal stiffeners are considerable, and can be calculated from presented graphs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.526-529
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• 2006

In this paper, flexure behavior of steel fiber reinforcement ultra high performance cementations composites (SFR-UHPCC) has been analyzed by equivalent stress block. Pulling-out tensile force of steel fiber with concrete matrix was induced. An appropriate flexure evaluation formula, i.e. semi-analytical formula, was established based on rectangular cross section beam for comparing with shear capacity and ultimate load of SFR-UHPCC beam. Finally, the semi-analytical formula has been simplified for the convenience of design work. Experimental results and theoretical shear strength are shown to compare with the formula proposed by this paper. The theory formula has a good prediction of failure type of SFR-UHPCC.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.455-458
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• 2002

Design methods are presented for an X-band traveling-wave slot array realized on a rectangular waveguide. An array of 21 longitudinal slots is realized on the broad wall of a rectangular waveguide. The squint of the antenna main beam is adjusted using the element spacing and the waveguide broad wall dimension. The excitation of the array is controlled by the slot offset from the waveguide center line Multiple I-plane steps are placed around last slot elements so that the second-order beam due to tile reflected wave Is minimized A waveguide-to-coaxial adapter Is designed for feeding the array antenna from a coaxial system. Results of the design show an outstanding performance of the antenna 17.1 dB gain. 36"beam 1111, and -21 dB maximum sidelobe level.evel.

• 한국방재학회 논문집
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• 제11권3호
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• pp.9-15
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• 2011

압축강도 100 MPa, 140 MPa 초고강도 섬유보강 콘크리트 직사각형보와 기하하적 조건 및 PS힘이 동일한 160 MPa RPC 직사각형보의 휨거동 비교를 통하여 압축강도가 낮은 초고강도 섬유보강 콘크리트 구조물의 거동 특성을 파악하였다. 직사각형보에 철근은 배근되지 않았으며 실험변수로는 강섬유, 콘크리트 압축강도, 프리스트레스 도입 방식, PS강재비 등이다. 모멘트-곡률관계와 하중-처짐관계를 통하여 압축응력이 작은 UHPC 직사각형보의 거동 특징을 분석하였다. 초고강도 섬유보강 콘크리트에 대한 간단한 형태의 응력-변형률 관계를 제안하였으며 이를 이용하여 UHPC 직사각형보에 대한 모멘트-곡률관계를 산정하였다. 실험에 의한 모멘트-곡률관계를 비교한 결과 상당히 일치함을 알 수 있었다.

• Computers and Concrete
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• 제16권2호
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• pp.245-260
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• 2015

In this study, nominal moment-axial load interaction diagrams, moment-curvature relationships, and ductility of rectangular hybrid beam-column concrete sections are analyzed using the modified Hognestad concrete model. The hybrid columns are primarily reinforced with steel bars with additional Glass Fiber Reinforced Polymer (GFRP) control bars. Parameters investigated include amount, pattern, location, and material properties of concrete, steel, and GFRP. The study was implemented using a user defined comprehensive $MATLAB^{(R)}$ simulation model to find an efficient hybrid section design maximizing strength and ductility. Generating lower bond stresses than steel bars at the concrete interface, auxiliary GFRP bars minimize damage in the concrete core of beam-column sections. Their usage prevents excessive yielding of the core longitudinal bars during frequent moderate cyclic deformations, which leads to significant damage in the foundations of bridges or beam-column spliced sections where repair is difficult and expensive. Analytical results from this study shows that hybrid steel-GFRP composite concrete sections where GFRP is used as auxiliary bars show adequate ductility with a significant increase in strength. Results also compare different design parameters reaching a number of design recommendations for the proposed hybrid section.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 춘계학술대회 논문집
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• pp.13-17
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• 1993

Analytical models for the prediction of the size of hardened zone in laser surface hardening are presented. The models are based on the solutions to the problem of three-dimensional heat flow in plates with infinite thickness. The validity of the model was tested on medium carbon steel for Gaaussian mode of beam. Then the model for rectangular beam was used for the prediction of the size of harened zone on various hardening process parameters. From the calculation results it appeared that the size and shape of the hardened zone are strongly dependent on process parameters suchas beam mode, beam size, and traverse speed.