• Title/Summary/Keyword: Beam Element

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Performance Analysis of AOA Estimation for Concentric Ring Array Antenna in Beamforming Satellite System (빔형성 위성 시스템의 동심원 배열 안테나에 대한 도래각 추정 성능 분석)

  • Kim, Tae-Yun;Lee, Dongbin;Hwang, Suk-Seung
    • The Journal of the Korea institute of electronic communication sciences
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    • v.15 no.4
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    • pp.643-650
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    • 2020
  • The phased array antenna has an advantage enabling rapid beam aim without the mechanical rotation of the antenna, because it arranges multiple elements in a linear or planer (grid or circular) and electronically controls the phase for each element. The planar array antenna is generally used a grid array and a circular array, and the circular form has the higher resolution comparing to the grid form due to the its structural characteristics. However, a concentric circular array (CCA) or a concentric ring array (CRA) with multiple circular arrays which each has different radius is used in the limited area, because the entire radius should be increased for the circular array with a number of elements. In this paper, we introduce the angle-of-arrival (AOA) estimator for an adaptive beamforming satellite system based on CRA and provide the simulation results for performance evaluation. In addition, simulation results are compared and analyzed to the case for the circular array antenna.

Numerical study on buckling of steel web plates with openings

  • Serror, Mohammed H.;Hamed, Ahmed N.;Mourad, Sherif A.
    • Steel and Composite Structures
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    • v.22 no.6
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    • pp.1417-1443
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    • 2016
  • Cellular and castellated steel beams are used to obtain higher stiffness and bending capacity using the same weight of steel. In addition, the beam openings may be used as a pass for different mechanical fixtures such as ducts and pipes. The aim of this study is to investigate the effect of different parameters on both elastic and inelastic critical buckling stresses of steel web plates with openings. These parameters are plate aspect ratio; opening shape (circular or rectangular); end distance to the first opening; opening spacing; opening size; plate slenderness ratio; steel grade; and initial web imperfection. The web/flange interaction has been simplified by web edge restraints representing simply supported boundary conditions. A numerical parametric study has been performed through linear and nonlinear finite element (FE) models, where the FE results have been verified against both experimental and numerical results in the literature. The web plates are subject to in-plane linearly varying compression with different loading patterns, ranging from uniform compression to pure bending. A buckling stress modification factor (${\beta}$-factor) has been introduced as a ratio of buckling stress of web plate with openings to buckling stress of the corresponding solid web plate. The variation of ${\beta}$-factor against the aforementioned parameters has been reported. Furthermore, the critical plate slenderness ratio separating elastic buckling and yielding has been identified and discussed for two steel grades of DIN-17100, namely: ST-37/2 and ST-52/3. The FE results revealed that the minimum ${\beta}$-factor is 0.9 for web plates under uniform compression and 0.7 for those under both compression and tension.

A Design of the Double Circular Array Patch Antenna Minimized the Side Lobe (부엽준위를 극소화한 이중 원형 배열 패치 안테나의 설계)

  • 진경수;이원석;한정세;박병우;정치현
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.9B
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    • pp.1676-1682
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    • 1999
  • In this paper, the double circular array microstrip patch antenna was designed to minimize the side lobe in which a cooperate feeding network was used to supply the same amplitude and equi-phase to each antenna element. Eight microstirip patch antenna(MPA) elements were arrayed with $45^{\circ}$ interval in the inner circle and the outer circle respectively. The simulation results showed that when the radii of the inner circle and the outer circle were 0.7 $\lambda$0 and 1.45 $\lambda$0, the side lobes of beam pattern were minimized. As the results of the measurements, the return loss of the designed antenna was -14.5[dB] at 11.75[GHz] in the input terminal. When the level of the main lobe was normalized at 0[dB], those of the first and the second side lobe were -18[dB] and -26[dB] respectively. The radiation patterns agree well with the simulated patterns.

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OFDM Transmission Method Based on the Beam-Space MIMO System (빔공간 MIMO 시스템에 기반한 OFDM 전송방법)

  • Choi, Jinkyu;An, Changyoung;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.3
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    • pp.425-431
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    • 2015
  • Beamspace Multiple-Input Multiple Output(MIMO) system can transmit multiple data by using Electronically Steerable Parasitic Array Radiator(ESPAR) antenna which has single Radio Frequency(RF)-chain. Beamspace MIMO system can reduce complexity of the system and size of antenna in comparison with the conventional MIMO system because of characteristic of ESPAR antenna using the single antenna and the RF-chain. Heretofore, only the research of transmitting single-carrier has been conducted by the use of beamspace MIMO system. Therefore, in this paper, we propose beamspace MIMO system based on Orthogonal Frequency Division Multiplexing(OFDM) for transmitting the multi-carrier and analysis the performance of this system. We find a proper reactance value which has good performance because proposed system changes the performance by the reactance values of parasitic elements. and we confirm that performance of the proposed system is similar to conventional MIMO system based on OFDM.

Analysis of Light Elements by PIGE (양성자 유발 감마선 발생법에 의한 경원소 분석)

  • Kim, Y.S.;Choi, H.W.;Kim, D.K.;Woo, H.J.;Kim, N.B.;Park, K.S.
    • Analytical Science and Technology
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    • v.13 no.1
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    • pp.12-21
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    • 2000
  • The PIGE (Proton Induced Gamma ray Emission) method was applied for the measurement of light elements Li ~ K. A test measurement has been performed for geological, biological, environmental and material samples by using a standard sample for each element. The measurement was performed for the two proton energies of 2.4 and 3.4 MeV, and 3.4 MeV was found to yield better result for multielemental analysis. The result shows a fair agreement within 15% for all elements with standard values. The detection limits of Li, B, F and Na are less than 100 ppm, while those of the other elements are from a few hundred ppm to a few percents.

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Structural Design and Analysis upon Active Rotor Blade with Trailing-edge Flap (뒷전 플랩을 장착한 지능형 로터 블레이드의 구조 설계 및 해석)

  • Eun, Won-Jong;Natarajan, Balakumaran;Lee, Jae-Hwan;Shin, Sang-Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.6
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    • pp.499-505
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    • 2012
  • Vibratory loads imposed by the rotating blade upon the fuselage has been one of major obstacles in rotorcrafts. A new concept of rotor blade is currently developed to adopt an Active Trailing-edge Flap (ATF) to alleviate such obstacles. The flap is mounted at 65~85% spanwise location from the rotor hub. The nominal rotational speed of the blade is as high as 1,528 RPM, to match the required tip Mach number. Structural integrity is one of the important design aspects to be maintained and monitored in this special type of rotor. This is due to that many detailed components, which drive the flap, are inserted inside the rotating blade. To conduct its structural design and analysis, CAMRAD-II and the one-dimensional beam analysis are used. At the same time, three-dimensional finite element analysis are also used, such as MSC. PATRAN/NASTRAN, in order to analyze the details of the present active blade. As a result, comparable characteristics for the present rotor are predicted by both approaches.

A Study on the Fuel Assembly Stress Analysis for Seismic and Blowdown Events (지진 및 냉각재상실사고시의 핵연료집합체 응력해석에 관한 연구)

  • Kim, Il-Kon
    • Nuclear Engineering and Technology
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    • v.25 no.4
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    • pp.552-560
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    • 1993
  • In this study, the detailed fuel assembly stress analysis model to evaluate the structural integrity for seismic and blowdown accidents is developed. For this purpose, as the first step, the program MAIN which identifies the worst bending mode shaped fuel assembly(FA) in core model is made. And the finite element model for stress calculation of FA components is developed. In the model the fuel rods (FRs) and the guide thimbles are modelled by 3-dimensional beam elements, and the spacer grid spring is modelled by a linear and relational spring. The constraints come from the results of the program MAIN. The stress analysis of the 16$\times$16 type FA under arbitary seismic load is performed using the developed program and modelling technique as an example. The developed stress model is helpful for the stress calculation of FA components for seismic and blowdown loads to evaluate the structural integrity of FA.

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Species Identification of Wooden Elements Used for Daewungjeon Hall in the Woonsoosa Temple, Busan (부산 운수사 대웅전 목부재의 수종 식별)

  • Kim, Ji-Yeong;Lee, Mi-Ok;Park, Won-Kyu
    • Journal of the Korean Wood Science and Technology
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    • v.42 no.3
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    • pp.244-250
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    • 2014
  • This study was conducted to identify wood species of 72 wooden parts (pillar, beam, jangyeo, purlin, judu, soro, bracket, deagong, ceiling panel, etc.) used for Daewungjeon Hall in the Woonsoosa Temple, Busan in Korea. Identified wood species were 67 Pinus spp. (Kesiya group), 4 Carpinus spp. and 1 Quercus spp. (Cerris group). In pillars, 14 red pines and 4 Carpinus and in purlins, 4 red pines and 1 Cerris were found. Other elements were red pines. Carpinus woods, which were used for the lower portions of three pillars (Dongbari), seemed repaired parts. A carved wood used for the stand of Buddhist statues was identified as Alnus spp. This study showed that Daewungjeon Hall of the Woonsoosa Temple was made mostly of red pines.

A Study of Weldability for Pure Titanium by Nd:YAG Laser(II) - Welding Properties of Butt Welding - (순티타늄판의 Nd:YAG 레이저 용접성에 관한 연구(II) - 맞대기 용접 특성 -)

  • Kim, Jong-Do;Kwak, Myung-Sub;Song, Moo-Keun;Park, Seung-Ha
    • Journal of Welding and Joining
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    • v.27 no.6
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    • pp.68-73
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    • 2009
  • Recently, as titanium and titanium alloys are being increasingly used in wide areas, there are on-going researches to obtain high quality weld zone. In particular, growing interest is being drawn to laser welding, which involves low heat input and large aspect ratio in various welding processes and can facilitate shield in atmospheric condition compared with electron beam welding. The first report covered the analysis of embrittlement by the bead color of weld zone through quantitative analysis of oxygen and nitrogen and measurement of hardness as basic experiment to apply laser welding to titanium. Results indicated that the element that affect embrittlement the most was nitrogen, and as embrittlement and oxygenation go on, bead color changed to silver, gold, brown, blue and gray. This study performed butt welding of pure titanium and STS304 by using 1kW CW Nd:YAG laser, and to find out basic physical properties, evaluated welding performance by laser output, welding speed, root gap and misalignment etc, and examined mechanical properties through tensile stress and Erichsen test. The reason particles of pure titanium welded metal and HAZ are greater than STS304 is because they are pure metal and do not include many impure elements that work as nuclei in case of resolidification, thus becoming coarse columnar crystals eventually. In addition, the reason STS304 requires more energy during welding than pure titanium is because the particle size of base metal is smaller.

Behavior of fully- connected and partially-connected multi-story steel plate shear wall structures

  • Azarafrooza, A.;Shekastehband, B.
    • Structural Engineering and Mechanics
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    • v.76 no.3
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    • pp.311-324
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    • 2020
  • Until now, a comparative study on fully and partially-connected steel shear walls leading to enhancing strength and stiffness reduction of partially-connected steel plate shear wall structures has not been reported. In this paper a number of 4-story and 8-story steel plate shear walls, are considered with three different connection details of infill plate to surrounding frame. The specimens are modeled using nonlinear finite element method verified excellently with the experimental results and analyzed under monotonic loading. A comparison between initial stiffness and shear strength of models as well as percentage of shear force by model boundary frame and infill plate are performed. Moreover, a comparison between energy dissipation, ductility factor and distribution of Von-Mises stresses of models are presented. According to the results, the initial stiffness, shear resistance, energy dissipation and ductility of the models with beam-only connected infill plates (SSW-BO) is found to be about 53%, 12%, 15% and 48% on average smaller than those of models with fully-connected infill plates (SPSW), respectively. However, performance characteristics of semi-supported steel shear walls (SSSW) containing secondary columns by simultaneously decreasing boundary frame strength and increasing thickness of infill plates are comparable to those of SPSWs. Results show that by using secondary columns as well as increasing thickness of infill plates, the stress demands on boundary frame decreases substantially by as much as 35%. A significant increase in infill plate share on shear capacity by as much as 95% and 72% progress for the 4-story SSW-BO and 8-story SSSW8, respectively, as compared with non-strengthened counterparts. A similar trend is achieved by strengthening secondary columns of 4-story SSSW leading to an increase of 50% in shear force contribution of infill plate.