• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.423-435
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• 2022

In this article, we present torsion-bending analysis of a composite FGM beam with an open section, according to the advanced and refined theory of 1D / 3D beams based on the 3D Saint-Venant's solution and taking into account the edge effects. The (initially one-dimensional) model contains a set of three-dimensional (3D) displacement modes of the cross section, reflecting its 3D mechanical behaviour. The modes are taken into account depending on the mechanical characteristics and the geometrical form of the cross-section of the composite FGM beam. The model considered is implemented on the CSB (Cross-Section and Beam Analysis) software package. It is based on the RBT/SV theory (Refined Beam Theory on Saint-Venant principle) of FGM beams. The mechanical and physical characteristics of the FGM beam continuously vary, depending on a power-law distribution, across the thickness of the beam. We compare the numerical results obtained by the three-beam theories, namely: The Classical Beam Theory of Saint-Venant (Classical Beam Theory CBT), the theory of refined beams (Refined Beam Theory RBT), and the theory of refined beams, using the higher (high) modes of distortion of the cross-section (Refined Beam Theory using distorted modes RBTd). The results obtained confirm a clear difference between those obtained by the three models at the level of the supports. Further from the support, the results of RBT and RBTd are of the same order, whereas those of CBT remains far from those of higher-order theories. The 3D stresses, strains and displacements, obtained by the present study, reflect the 3D behaviour of FGM beams well, despite the initially 1D nature of the problem. A validation example also shows a very good agreement of the proposed models with other models (classical or higher-order beam theory) and Carrera Unified Formulation 1D-beam model with Lagrange Expansion functions (CUF-LE).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.196-213
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• 2001

A split beam ultrasonic transducer operating at a frequency of 70 kHz to use in the fish sizing echo sounder was developed and the acoustic radiation characteristics were experimentally analyzed. The amplitude shading method utilizing the properties of the Chebyshev polynomials was used to obtain side lobe levels below -20 dB and to optimize the relationship between main beam width and side lobe level of the transducer, and the amplitude shading coefficient to each of the elements was achieved by changing the amplitude contribution of elements with 4 weighting transformers embodied in the planar array transducer assembly. The planar array split beam transducer assembly was composed of 36 piezoelectric ceramics (NEPEC N-21, Tokin) of rod type of 10 mm in diameter and 18.7 mm in length of 70 kHz arranged in the rectangular configuration, and the 4 electrical inputs were supplied to the beamformer. A series of impedance measurements were conducted to check the uniformity of the individual quadrants, and also in the configurations of reception and transmission, resonant frequency, and the transmitting and receiving characteristics were measured in the water tank and analyzed, respectively. The results obtained are summarized as follows : 1. Average resonant and antiresonant frequencies of electrical impedance for four quadrants of the split beam transducer in water were 69.8 kHz and 83.0 kHz, respectively. Average electrical impedance for each individual transducer quadrant was 49.2$\Omega$ at resonant frequency and 704.7$\Omega$ at antiresonant frequency. 2. The resonance peak in the transmitting voltage response (TVR) for four quadrants of the split beam transducer was observed all at 70.0 kHz and the value of TVR was all about 165.5 dB re 1 $\mu$Pa/V at 1 m at 70.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The resonance peak in the receiving sensitivity (SRT) for four combined quadrants (quad LU+LL, quad RU+RL, quad LU+RU, quad LL+RL) of the split beam transducer was observed all at 75.0 kHz and the value of SRT was all about -177.7 dB re 1 V/$\mu$Pa at 75.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The sum beam transmitting voltage response and receiving senstivity was 175.0 dB re 1$\mu$Pa/V at 1 m at 75.0 kHz with bandwidth of 10.0 kHz, respectively. 3. The sum beam of split beam transducer was approximately circular with a half beam angle of $9.0^\circ$ at -3 dB points all in both axis of the horizontal plane and the vertical plane. The first measured side lobe levels for the sum beam of split beam transducer were -19.7 dB at $22^\circ$ and -19.4 dB at $-26^\circ$ in the horizontal plane, respectively and -20.1 dB at $22^\circ$ and -22.0 dB at $-26^\circ$ in the vertical plane, respectively. 4. The developed split beam transducer was tested to estimate the angular position of the target in the beam through split beam phase measurements, and the beam pattern loss for target strength corrections was measured and analyzed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.4
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• pp.413-422
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• 2011

An improved split-beam transducer for a 50 kHz fish-sizing echo sounder was developed. The main objective of this study was to minimize the side lobe level in the beam pattern and the distance between acoustic centers for adjacent transducer quadrants in the geometrical arrangement of array elements while maintaining a given number of transducer elements and beam width. To achieve these goals, a 32-element planar array transducer ($6{\times}6$ array with one element in each corner missing) was designed using the Dolph-Chebyshev shading function to suppress side lobes in the array beam pattern and fabricated by arranging the inter-element spacing to be substantially equal to half the wavelength using the transducer element of 0.4 times the wavelength in diameter. The performance characteristics of this split-beam transducer were evaluated in the experimental water tank of $5m{\times}5m{\times}6m$ (length${\times}$height${\times}$width). In this study, the design goal of the beam width and side lobe level for transmitting a beam pattern was initially set at $21^{\circ}$ and -30 dB, respectively. However, the measured beam width at 3 dB was $21^{\circ}$ in both directions with side lobe levels of -24.7 dB in the horizontal plane and -25.6 dB in the vertical plane. The averaged beam width at -3 dB of the receiving beam patterns for four receiving quadrants was $31.4^{\circ}$. The transmitting voltage response was 161.5 dB (re $1{\mu}Pa$/V at 1 m) at 50.23 kHz with a bandwidth of 2.16 kHz, and the averaged receiving sensitivity for four receiving quadrants was -178.13 dB (re 1 V/${\mu}Pa$) at 49.8 kHz with a bandwidth of 2.64 kHz.

• Transactions of Materials Processing
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• v.22 no.7
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• pp.383-388
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• 2013

Metal flow of the beam blank during H-beam rolling was examined in order to correlate the rolling defects with the beam blank configuration. For this purpose, H-beam rolling was performed on the beam blank where stainless steel bolts were inserted as the marker at the web and flange. The positional variation of the marker was monitored at each rolling pass, and the result was compared with the 3D FEM simulation employing the point tracking function. The simulation results were reasonably agreed with the experimental within the error of 0.5~1mm on both web and flange of the H-beam. It is anticipated that the 3D FEM simulation employing the point tracking function provides the guidance information on analyzing the correlation between the rolling defects and the beam blank configuration in H-beam rolling.

• Solar Energy
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• v.11 no.2
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• pp.63-69
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• 1991

A Steady laminar natural convection heat transfer from two isothermal square beams attached to a vertical adiabatic plate has been studied numerically. The results have been obtained for dimensionless beam spacings, $0.5{\le}D/L{\le}3.0$, and for Gr=5000-10000 at ${\phi}_2/{\phi}_1=1.0$. 1. The local Nusselt number from the beam surface is increased with the dimension-less beam spacing D/L. but that of the downward surface of the lower beam is almost same as the D/L increases. And, the local Nusselt number from the upward surface of a lower beam is greatly increased with D/L. 2. The beam spacings of the maximum mean Nusselt number for the downward surface of an upper beam and the upward surface of a lower beam occur at. D/L =2.6 and 2.0 respectively. 3. The beam spacing for the maximum total mean Nusselt number occurs at D/L = 2.6.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.10
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• pp.181-190
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• 2019

In this study, four reinforced concrete coupling beams were subjected to cyclic lateral loading test to evaluate the structural performance of coupling beam according to volume fraction of steel fiber. For this purpose, the volume fraction of steel fiber(0%, 1%, 2%) and transverse reinforcement spacing were determined as the main parameter. According to the test results, the maximum strength of D-40C-s100-0 was 1.15, 1.13, 1.05 times higher than D-40C-s300-0, D-40C-s300-1, D-40C-s300-2, respectively. The maximum strength of coupling beams with mitigated rebar details increases as the volume fraction of steel fiber increases. Although steel fiber 2% reinforced specimen(D-40C-s300-2) did not satisfy the amount of transverse reinforcement required for seismic design of coupling beam, the overall performance including to maximum strength, ductility and energy dissipation capacity was similar to the control specimen(D-40C-s100-0). As a result, the use of steel fiber with 2% reinforcement can partially replace the transverse reinforcement in diagonally reinforced concrete coupling beam.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.934-940
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• 2011

A novel reconfigurable beam steering antenna using double loops is proposed. The double loop antenna has a superposed beam which is produced by combining the in-phase beam in the inner loop with the out-of-phase beam in the outer loop. Also, the doble loop antenna uses two artificial switches to connect between inner loop and outer loop, and has the beam directions of three separate cases(Case 1, Case 2, Case 3) by changing ON/OFF states of switches. The operation frequency of the antenna is 14.5 GHz, and three maximum beam directions of the antenna are ${\phi}_{max}=0^{\circ}$, ${\theta}_{max}=0^{\circ}$(Case 1), ${\phi}_{max}=230^{\circ}$, ${\theta}_{max}=40^{\circ}$(Case 2) and ${\phi}_{max}=130^{\circ}$, ${\theta}_{max}=40^{\circ}$ (Case 3). The peak gains of each case are 6.5 dBi(Case 1), 7.6 dBi(Case 2) and 7.8 dBi(Case 3). The half power beam width(HPBW) of each case is $86{\sim}104^{\circ}$, and the overall HPBW is $160^{\circ}$.

• Magazine of the Korea Concrete Institute
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• v.7 no.4
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• pp.169-179
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• 1995

The purpose of this study is to spread beam plastic hinging zone of the high-strength($f'_c=700kg/cm^2$) reinforced concrete beam-column joints away from the column face by vertically anchored intermediate reinforcements. The newly proposed intermediate reinforcements which are vertically anchored by interlinking each intermediate rebars are tested to insure the ductile behavior of R /C beam-column joins. Main variable is the shape of intermediate reinforcements. From the test results, the newly proposed intermediate rebar detail can move arid expand the beam plastic hinging zone about 1.Od from column face and can delay the strength decay of the high-strength R /C beam-column joint. Also energy dissipation capacity of specimen IV-1.OD10 which is reinforced by vertically anchored intermediate rebars about 1.0d is 1.6 times as high as the specimen CM-STAN which is designed by ACI318-89.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1061-1070
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• 2009

In this paper, we have designed TDL(True-time Delay Line) for eliminating beam-squint occurring in active phased array antenna with large electrical size operated in wide bandwidth, and have tested its electrical performance. The proposed TDL device is composed of 4-bit microstrip delay line structure and MMIC amplifier for compensation of the delay-line loss. The measured results of gain and phase versus delay state satisfy the electrical requirements, also P1dB output power and noise figure meet the requirement. To verify the performance of fabricated TDL, we have simulated the beam patterns of wide-band active phased array antenna using the measured results and have certified the beam pattern compensation performance. As a result of simulated beam pattern compensation with respect to the 675.8 mm size antenna which is operated in X-band, 800 MHz bandwidth, we have reduced the beam squint error of ${\pm}1^{\circ}$ with ${\pm}0.1^{\circ}$. So this TDL module is able to be applied to active phase array antenna system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4773-4779
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• 2012

In this paper we propose two types of reconfigurable 3-D beam steering antenna for intelligent or smart antenna system. Proposed antennas are composed of triangular(structure1.) or circuler(structure2.) loop structure and bended dipole antenna structure. This antenna can steer beam pattern of 6 direction at xy-plane state (0, 1, 2) and xz-plane state (3, 4, 5) by 4 switch motion with one antenna element. Antenna structure1. is symmetric equilibrium structures based on feeding point. There is no grounding point. As a result, designed antenna's gain is similar to dipole antenna. Also, As unbalanced structure by using CPWG in the form of a semicircular, structure2. is enhanced directivity. The operation frequency of antenna are 2.5 GHz(Structure1.) and 2.55 GHz(Structure2.), maximum gain is 1.04 ~ 2.06 dBi(Structure1. : Omni-directional beam), 1.6 ~ 4 dBi(structure2. : Directional beam). The overall HPBW is about over $160^{\circ}$ in the both of the xy-plane and xz-plane at structure1. and over $125^{\circ}$ at structure2.