• Title, Summary, Keyword: 적층배열

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On the Damping of A Shock Absorption Device Composed of Disk Spring Stacks (디스크 스프링의 적층 배열에 따른 완충장치의 감쇠에 관한 연구)

  • Choi, Myung-Jin;Ko, Seok-Hoon
    • Journal of the Korean Institute of Gas
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    • v.12 no.4
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    • pp.46-51
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    • 2008
  • The damping of a shock absorption device composed of nonlinear disk spring stacks and rubber rings was investigated. Friction forces of rubber rings and hysteresis of disk springs were obtained experimentally. The hysteresis curves of several types of disk spring stacks were approximated, from which the energy dissipated was estimated. Based upon the friction force and the energy dissipated, 4 damping models were presented and shock responses of the damping models were investigated. The hysteresis of disk spring is more meaningful than the friction of the rubber ring for the damping. For practical use, equivalent viscous damping model for total energy dissipated per cycle was suggested.

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Research of Vibration Analysis and Resonance Avoidance Design of Composite Quadcopter (복합재 쿼드콥터의 진동 특성 분석과 공진 회피에 대한 연구)

  • Kim, Sang-Ryul;Kim, Wie-Dae
    • Composites Research
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    • v.33 no.3
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    • pp.133-139
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    • 2020
  • In this research, the vibration characteristics of composite quadcopter are analyzed, and avoidance design and analysis are performed to avoid resonance. The full platform of a commercial quadcopter with composite rotor arm is analyzed to see the vibration characteristics using FEM program. The manufactured stacking sequences of rotor arm is used for analysis, and the natural frequencies are compared with experimental results and simple analytic model results. It is also confirmed that the natural frequency of the particular mode is included within the operation range of the motor. The resonance avoidance design is carried out by selecting three variables from the existing model: stacking sequence, rotor-arm pipe length, and pipe thickness.

Undamped Dynamic Response of Anisotropic Laminated Composite Plates and Shell Structures using a Higher-order Shear Deformation Theory (비등방성 복합적층판 및 쉘의 고차전단변형을 고려한 비감쇄 동적응답)

  • Yoon, Seok Ho;Han, Seong Cheon;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.9 no.3
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    • pp.333-340
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    • 1997
  • This paper will expand the third-order shear deformation theory by the double-Fourier series and reduce to the solution of a system of ordinary differential equations in time, which are integrated numerically using Newmark's direct integration method and clarify the undamped dynamic responses for the cross-ply and antisymmetric angle-ply laminated composite plates and shells with simply supported boundary condition. Numerical results for deflections are presented showing the effect of side-to-thickness ratio, aspect ratio, material anisotropy, and lamination scheme.

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Nonlinear Transient Heat Transfer Analysis Based on LANCZOS Coordinates (LANCZOS 알고리즘에 기초한 비선형 트랜지언트 열전달 해석)

  • Im, Chang Kyun;Chang, Sung Pil
    • Journal of Korean Society of Steel Construction
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    • v.10 no.2
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    • pp.317-326
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    • 1998
  • This paper describes a reduced finite element formulation for nonlinear transient heat transfer analysis based on Lanczos Algorithm. In the proposed reduced formulation all material nonlinearities of irradiation boundary element are included using the pseudo force method and numerical time integration of the reduced formulation is conducted by Galerkin method. The results of numerical examples demonstrate the applicability and the accuracy of the proposed method for the nonlinear transient heat transfer analysis.

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The Research of Single Fed Broadband Planar Array Antenna with Modified Stacked-Structure using Circular Polarization (변형된 적층구조를 갖는 단일급전방식의 광대역 평판형 배열안테나 연구)

  • 정영배;이영환;문정익;박성욱;하재권
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.6
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    • pp.919-930
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    • 2001
  • This paper presents a wideband technique of impedance and axial-ratio bandwidth which uses the stacked planar array structure through optimum design of sub-polarization generating sections and parasitic patch. So, the effect of the dual-resonance characteristic can contribute to the bandwidth expansion of single fed planar array antenna using circular polarization which doesn\`t hire previous bandwidth expansion technique. The antenna can be used as a dual-band antenna by adjusting the resonance frequencies as well, and then the antenna is designed and fabricated in the frequency band of domestic satellite-TV service. This antenna has the performance of 9.7 % impedance bandwidth and 24 dBi of antenna gain. And it has also 2.8 % and 1.4 % of 3 dB Axial-ratio bandwidth at 11.4 GHz and 11.8 GHz respectively.

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A Study on the Optimization of Ply Angles for Composite Tube using Design of Experiments (실험계획법을 이용한 복합재 경통 적층각의 최적 설계에 관한 연구)

  • Park, Byong-Ug;Seo, Yu-Deok;Kim, Hyun-Jung;Youn, Sung-Kie;Lee, Seung-Hoon;Lee, Deog-Gyu;Lee, Eung-Shik;Chang, Su-Young
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.7
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    • pp.627-633
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    • 2009
  • Composite has become one of the most frequently used material for a tube of satellite camera due to its attractive characteristics. However, laminated composites can be weakened by delamination which comes from interlaminar stress. Such failure mode cause structural instability of the camera as well as degradation of optical quality. Therefore composite tube should be robust in delamination. Also, composite tube should have high stiffness, sufficient high natural frequency and small coefficient of thermal expansion. The design procedures presented in this paper are based on design of experiments. The experiments for mechanical analysis are designed by the tables of orthogonal arrays. In order to manipulate the various mechanical properties systematically, multiple-attribute decision making(MADM) is employed. Through analysis of variance and F-test, the critical design variables which have dominant influences on mechanical performance are determined. Finally improved ply angles for composite tube are determined.

Gain Enhancement of a Circularly-Polarized Patch Antenna with a Double-Layered Superstrate for Wireless LAN (무선 LAN용 원형편파 패치안테나에 이중 적층 상부덮개를 적용한 이득 향상)

  • Lee, Sangrok
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.12
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    • pp.2427-2433
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    • 2015
  • A high-gain circularly-polarized patch antenna with a double-layered superstrate is proposed operating at a wireless LAN frequency. A superstrate has an array of metallic periodic unit cells and is located above the patch antenna with an air-gap. The designed antenna has a high gain of over 9.59dBi, which is the gain enhancement of 6.48dB compared to the patch antenna without superstrate. And it has a low axial ratio of under 3dB, so that it maintains the circular polarization of the patch antenna. The optimum air-gap height at the superstrate of $4{\times}4$ arrays is 25mm, which is equivalent to about $0.2{\lambda}$ at the frequency of 2.45GHz. We confirmed that the double-layered stacking of a superstrate increases the effective aperture size and hence it leads to enhance a gain of the patch antenna.

Wide Bandwidth Circularly Polarized Aperture Coupled Microstrip Antenna using Cross-slot (십자 슬롯을 이용한 광대역 원형편파 적층 개구결합 마이크로스트립 안테나)

  • 양태식;이범선
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.5
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    • pp.748-754
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    • 2000
  • A novel single feed wide band CP stacked microstrip antenna using crossed slots has been designed, fabricated and measured. For the single rediating element the designed 10dB return loss bandwidth is 34.5%99.45~13.54 GHz), 3dB axial ratio bandwidth is 18.7%(11.17~13.39GHz), and 6 dB gain bandwidth is 29%(10.21~13.64GHz). For the 2$\times$2 array designed using a sequential rotation method, the 10dB return loss bandwidth is 35.9%(9.69~13.94GHz), 3dB axial ratio bandwidth is 34.6GHz (9.93~14.03GHz), and 6dB gain bandwidth is 27.4%(10.35~13.6GHz). For the fabricated 8$\times$8 array antenna, the 10dB return loss bandwidth is 27.3%(10.17~13.41GHz), 3dB axial ratio bandwidth is 27.9GHz(10.1~13.4GHz), and the radiation pattern is good agreement with theory. This antenna can be used for broadband applications for communications or broadcasting in Ku band.

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Design and Analysis of 45°-Inclined Linearly Polarized Substrate Integrated Waveguide(SIW) Slot Sub-Array Antenna for 35 GHz (45도 선형 편파 발생용 SIW 슬롯 Sub-Array 안테나 설계 및 해석)

  • Kim, Dong-Yeon;Nam, Sangwook
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.4
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    • pp.357-365
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    • 2013
  • The 4 by 4 series slot sub-array antenna is proposed using substrate integrated waveguide(SIW) technology for 35 GHz of Ka band application. The proposed antenna is realized with multi-layered structure for compact size and easy integration features. 4 by 4 radiating slots are arrayed on top PCB with equal spacing and the feeding SIWs are arranged on middle and bottom PCBs for uniform power distribution. The multi-layered antenna is realized using RT/Duroid 5880 that has dielectric constant of 2.2 and the total antenna size is $750.76mm^2$. The individual parts such as radiators and feeding networks are simulated using full-wave simulator CST MWS. Furthermore, the total sub-array antenna also fabricated and measured the electrical performances such as impedance bandwidth under the criteria of -10 dB(490 MHz), maximum gain(18.02 dBi), sidelobe level(SLL)(-11.0 dB), and cross polarization discrimination (XPD)(-20.16 dB).

Effect of the Whisker Amount and Orientation on Mechanical Properties of the Si$_3$N$_4$ based Composites (Si$_3$N$_4$ Whisker의 첨가량과 배열방향이 Si$_3$N$_4$ 복합 소결체의 기계적 특성에 미치는 영향)

  • Kim, Chang-Won;Park, Dong-Soo;Park, Chan
    • Journal of the Korean Ceramic Society
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    • v.36 no.1
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    • pp.43-49
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    • 1999
  • Gas pressure sintered silicon nitride based composites with 0~5wt% $\beta$-Si3N4 whiskers were prepared. The whiskers were unidirectionally oriented by a modified tape casting technqiue and green bodies with various microstructure were formed by changing stacking sequences of sheets cut from the tape. Orientations of the large elongated grains of the sample after gas pressure sintering were the same as the those of the whiskers of green body, and the sintering shrinkage and mechanical properties of sintered sample were consistent with the microstructural characteristics. In case of unidirectional samples, the sintering shrinkage normal to whisker alignment direction was larger than that parallel to the direction. The shrinkage difference inceaed as the whiskercontent increaed. As whisker content increaed, the crack length normal to and parallel to tape casting direction became shorter and larger, respectively. Although the grain size increased by th whisker addition, the flexural strength of unidirectional samples was not lower than that of smaple without the whisker. In case of crossplied and 45$^{\circ}$rotated samples, the anisotropy of mechanical preoperties disappeared.

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