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Improvement of Noise Characteristics by Analyzing Power Integrity and Signal Integrity Design for Satellite On-board Electronics (위성용 전장품 탑재보드의 Power Integrity 및 Signal Integrity 설계 분석을 통한 노이즈 성능 개선)

  • Cho, Young-Jun;Kim, Choul-Young
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.1
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    • pp.63-72
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    • 2020
  • As the design complexity and performances are increased in satellite electronic board, noise related problems are also increased. To minimize the noise issues, various design improvements are performed by power integrity and signal integrity analysis in this research. Static power and dynamic power design are reviewed and improved by DC IR drop and power impedance analysis. Signal integrity design is reviewed and improved by time domain signal wave analysis and PCB(Printed Circuit Board) design modifications. And also power planes resonance modes are checked and mitigation measures are verified by simulation. Finally, it is checked that radiated noise is reduced after design improvements by EMC(Electro Magnetic Compatibility) RE(Radiated Emission) measurement results.

Performance Assessment of Precast Concrete Segmental Bridge Columns with Shear Resistance Connecting Structure (전단저항 연결체를 갖는 프리캐스트 세그먼트 교각의 성능평가)

  • Kim, Tae-Hoon;Kim, Young-Jin;Kim, Seong-Woon;Shin, Hyun-Mock
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.4A
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    • pp.591-601
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    • 2008
  • The purpose of this study was to investigate the performance of precast concrete segmental bridge columns with shear resistance connecting structure. The system can reduce work at a construction site and makes construction periods shorter. A model of precast concrete segmental bridge columns with shear resistance connecting structure was tested under a constant axial load and a cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. An bonded or unbonded tendon element based on the finite element method, that can represent the interaction between tendon and concrete of prestressed concrete member, is used. A joint element is newly modified to predict the inelastic behaviors of segmental joints. The proposed numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated.

Enhancement of SNUF Active Trailing-edge Flap Blade Mechanism Design (SNUF뒷전 플랩 블레이드 메커니즘의 설계 개선)

  • Natarajan, Balakumaran;Eun, WonJong;Shin, SangJoon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.7
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    • pp.645-653
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    • 2013
  • Seoul National University flap(SNUF) blade is a small-scale rotor blade incorporating a small trailing-edge flap control surface driven by piezoelectric actuators at higher harmonics for vibration attenuation. Initially, the blade was designed using two-dimensional cross-section analysis and geometrically exact one-dimensional beam analysis, and its material configuration was finalized. A flap-deflection angle of ±4 was established as the criterion for enhanced vibration reduction based on an earlier simulation. The flap-linkage mechanism was designed and static bench tests were conducted for verifying the performance of the flap-actuation mechanism. Different versions of test beds were developed and tested with the designed flap and the selected APA 200M piezoelectric actuators. Through significant improvements, a maximum deflection of ±3.7 was achieved. High-frequency experiments were conducted for evaluating the performance, and the transfer function of the test bed was determined experimentally. With the static tests almost complete, the rotor power required for testing the blade in a whirl tower (centrifugal environment) was calculated, and further preparations are underway.

Numerical Simulation for the Quasi-static Behavior of Superelastic Nitinol Shape Memory Alloys (SMAs) (초탄성 니티놀 형상기억합금의 준정적 거동에 대한 수치해석적 재현)

  • Hu, Jong Wan
    • Journal of Korean Society of Steel Construction
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    • v.27 no.6
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    • pp.493-501
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    • 2015
  • Superelastic shape memory alloys (SMAs) are metallic materials that can automatically recover to their original condition without heat treatment only after the removal of the applied load. These smart materials have been wildly applied instead of steel materials to the place where large deformation is likely to concentrate. In spite of many advantages, superelastic SMA materials have been limited to use in the construction filed because there is lack of effort and research involved with the development of the material model, which is required to reproduce the behavior of superelastic SMA materials. Therefore, constitutive material models as well as algorithm codes are mainly treated in this study for the purpose of simulating their hysteretic behavior through numerical analyses. The simulated curves are compared and calibrated to the experimental test results with an aim to verify the adequacy of material modeling. Furthermore, structural analyses incorporating the material property of the superelastic SMAs are conducted on simple and cantilever beam models. It can be shown that constitutive material models presented herein are adequate to reliably predict the behavior of superelastic SMA materials under cyclic loadings.

New Development of Hybrid Concrete Support Structure with Driven Piles for Offshore Wind Turbines (하이브리드 해상풍력 파일 기초 콘크리트 지지구조(MCF) 개발)

  • Kim, Hyun Gi;Kim, Bum Jun;Kim, Ki Du
    • Journal of Korean Society of Steel Construction
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    • v.25 no.3
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    • pp.307-320
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    • 2013
  • This paper proposes a new hybrid support structure by the driven piles which removes disadvantages of the existing type of support structure for offshore wind turbines. The hybrid type of support structure is combined with concrete cone and steel shaft, and is supported not only by gravity type foundations but also by driven piles. For three dimensional analysis of the huge and thick concrete structure, a solid-shell element that is capable of exact modeling and node interpolations of stresses is developed. By applying wave theory of stream function and solid-shell element in XSEA simulation software for fixed offshore wind turbines, a quasi-static analysis and natural frequency analysis of proposed support structure are performed with the environmental condition on Southwest Coast in Korea. In the result, lateral displacement is not exceed allowable displacement and a superiority of dynamic behavior of new hybrid support structure is validated by natural frequency analysis. Consequently, the hybrid support structure presented in this study has a structural stability enough to be applied on real-site condition in Korea. The optimized structures based on the preliminary design concept resulted in an efficient structure, which reasonably reduces fabrication costs.

Experimental and Numerical Studies on Composite Tubes for the Energy Absorber of High-speed Train (복합재 튜브를 이용한 고속 열차의 에너지 흡수장치에 대한 실험 및 수치해석 연구)

  • Nguyen, Cao-Son;Jang, Hong-Kyu;Shin, Jae-Hwan;Son, Yu-Na;Kim, Chun-Gon
    • Composites Research
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    • v.24 no.1
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    • pp.1-9
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    • 2011
  • This paper presents an experimental and numerical study on composite tubes for the energy absorber of the high-speed train. The purpose of the experimental study is to find out which lay-up is the best lay-up for the energy absorber. Four lay-ups were tested using quasi static method: [0/45/90/45]4, [0]16, [0/90]8, [0/30/30]5. Two triggering methods were used to create initial damage and guarantee the progressive collapse mode: bevel edge and notch edge. As a result, [0/45/90/45]4 lay-up was find out the best lay-up among the laminates being tested. In the numerical study, a parametric analysis was done to find out the most proper way to simulate the quasi static test of a composite tube using LS-DYNA program. A single composite tube was modeled to be crashed by a moving wall. Comparison between simulation and experiment was done. Reasonable agreement between experiment and analysis was obtained. Dealing with parameter TFAIL and the mass scaling factor, this parametric study shows the ability and the limitation of LS-DYNA in modeling the quasi static test for the composite tube.

Strain Analysis of Longitudinal Reinforcing Steels of RC Bridge Piers Under Shaking Test (진동대 실험에 의한 RC교각의 주철근 변형률 분석)

  • Hong, Hyun-Ki;Yang, Dong-Wook;Chung, Young-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.93-96
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    • 2008
  • The near fault ground motion(NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Turkey Izmit (1999), Japan Kobe(1995), Northridge(1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the far fault ground motion(FFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on RC bridge piers without lap-spliced longitudinal reinforcing steels. The seismic performance of two RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, Two of four identical RC bridge piers were tested under a quasi-static load, and the others were under a pseudo-dynamic load. The respectively two RC bridge pier is comparatively subjected to Pseudo-dynamic loadings and Quasi-Static loadings. This paper indicated that more gives bigger ultimate strain of longitudinal steels to be fractured at bigger PGA motion.

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Quasi-Static Structural Optimization Technique Using Equivalent Static Loads Calculated at Every Time Step as a Multiple Loading Condition (매 시간단계의 등가정하중을 다중하중조건으로 이용한 준정적 구조최적화 방법)

  • Choe, U-Seok;Park, Gyeong-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.10 s.181
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    • pp.2568-2580
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    • 2000
  • This paper presents a quasi-static optimization technique for elastic structures under dynamic loads. An equivalent static load (ESL) set is defined as a static load set which generates the same displacement field as that from a dynamic load at a certain time. Multiple ESL sets calculated at every time step are employed to represent the various states of the structure under the dynamic load. They can cover every critical state that might happen at an arbitrary time. Continuous characteristics of dynamic load are simulated by multiple discontinuous ones of static loads. The calculated sets of ESLs are applied as a multiple loading condition in the optimization process. A design cycle is defined as a circulated process between an analysis domain and a design domain. Design cycles are repeated until a design converges. The analysis domain gives a loading condition necessary for the design domain. The design domain gives a new updated design to be verified by the analysis domain in the next design cycle. This iterative process is quite similar to that of the multidisciplinary optimization technique. Even though the global convergence cannot be guaranteed, the proposed technique makes it possible to optimize the structures under dynamic loads. It has also applicability, flexibility, and reliability.

A Comparative Study on Interrelation between FDTD Source Models for Coaxial-Probe Feeding Structures (동축 프로브 급전구조에 대한 FDTD 전원 모델들의 상호 관계에 관한 비교 연구)

  • Hyun, Seung-Yeup
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.1
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    • pp.114-122
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    • 2014
  • For an efficient finite-difference time-domain(FDTD) analysis of coaxial-probe feeding structures in radio frequency(RF) and microwave bands, an interrelation between equivalent source modeling techniques is investigated. In existing literature, equivalent source models with delta-gap or magnetic-frill concepts have been developed by many researchers. It is well known that FDTD implementation and computational accuracy of these source models are slightly different. In this paper, the interrelation between FDTD equivalent source models for coaxial feeding structures under the quasi-static approximation(QSA) is presented. As a function of FDTD equivalent source models, time-domain and frequency-domain responses of a coaxial-probe fed conical monopole antenna are calculated numerically. And comparison results of computational accuracy and efficiency are provided.

On the Grounding Damage of Ship Bottom Stiffened Platings(Part II : Damage Prediction Formula) (좌초시 선저보강판의 손상에 관한 연구(제2보 : 손상추정식))

  • Jeom-Kee Paik;Tak-Kee Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.4
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    • pp.119-129
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    • 1994
  • The aim of the present study is to derive an empirical formula relating the absorbed energy and the cutting length for longitudinally stiffened steel palates which are cut by a wedge, idealizing the ship bottom stiffened platings in groundings. This study is based on the test results and the investigations of some parameters affecting the cutting response, described in Part I. By dimensionless ana1ysis of the test results obtained in a quasi-static loading condition, the energy absorbed while a longitudinally stiffened plate is cut by a wedge is expressed as functions of the cutting length, the yield stress, the equivalent plate thickness and the wedge angle. Also, the dynamic effects are incorporated into the static formula such that the proposed formula can be applied to the impact loading situations. The validity of the proposed formula is checked by comparing with the results obtained by the other existing formulas or by the drop-hammer tests.

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