• Title/Summary/Keyword: link beam

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Data-link antenna for mounting low-RCS Unmanned Aerial Vehicles(UAV) (저피탐 무인기 탑재를 위한 데이터링크용 안테나에 관한 연구)

  • Park, Jin-Woo;Jung, Eun-Tae;Park, Il-Hyun;Seo, Jong-Woo;Jung, Jae-Soo;Yu, Byung-Gil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.25 no.8
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    • pp.1110-1116
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    • 2021
  • In this paper, we propose a conformal Ku-band data link antenna to ensure low RCS of stealth UAV. As a phased array antenna with electrical beam steering function, a transmitter and a receiver were designed and manufactured for FDD communication, respectively. Each antenna is designed as a 12*12 planar array antenna and has a function to form a uni-directional pattern and a bi-directional pattern through phase control of unit elements. The beam steering range is designed to be able to steer up to 60 degrees in theta direction and 360 degrees in the phi direction. As a result of manufacturing and measurement, the conformal type radome has low transmission loss and meets the required specifications including system performance. The feasibility of mounting the stealth UAV has been confirmed, and future research directions such as interworking of baseband devices and conversion to digital beam steering function are suggested.

A Study on the Position Control of Flexible Robot Beam Using Neural Networks (신경회로망을 이용한 유연한 로보트 빔의 위치제어에 관한 연구)

  • 탁한호;이상배
    • Journal of the Korean Institute of Navigation
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    • v.21 no.1
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    • pp.109-118
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    • 1997
  • In this paper, applications of multilayer neural networks to control of flexible robot beam are considered. The multilayer nerual networks can be used to approximate any continuous function to a desired degree of accuracy and the weights are updated by Gradient Method. When a flexible beam is rotated by a motor through the fixed end, transverse vibration may occur. The motor torque should be controlled insuch a way that the motor rotates by a specified angle, while simultaneously stabilizing vibration of the flexible manipulators so that is arrested as soon as possbile at the end of rotation. Accurate control of lightweight beam during the large changes in configuration common to robotic tasks requires dynamic models that describe both rigid body motions, as well as the flexural vibrations. Therefore, a linear dynamic state-space model of for a single link flexible robot beam is derived and PD controller, LQP controller, and inverse dynamical neural networks controller are composed. The effectiveness the proposed control system is confirmed by computer simulation.

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Energy dissipation system for earthquake protection of cable-stayed bridge towers

  • Abdel Raheem, Shehata E.;Hayashikawa, Toshiro
    • Earthquakes and Structures
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    • v.5 no.6
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    • pp.657-678
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    • 2013
  • For economical earthquake resistant design of cable-stayed bridge tower, the use of energy dissipation systems for the earthquake protection of steel structures represents an alternative seismic design method where the tower structure could be constructed to dissipate a large amount of earthquake input energy through inelastic deformations in certain positions, which could be easily retrofitted after damage. The design of energy dissipation systems for bridges could be achieved as the result of two conflicting requirements: no damage under serviceability limit state load condition and maximum dissipation under ultimate limit state load condition. A new concept for cable-stayed bridge tower seismic design that incorporates sacrificial link scheme of low yield point steel horizontal beam is introduced to enable the tower frame structure to remain elastic under large seismic excitation. A nonlinear dynamic analysis for the tower model with the proposed energy dissipation systems is carried out and compared to the response obtained for the tower with its original configuration. The improvement in seismic performance of the tower with supplemental passive energy dissipation system has been measured in terms of the reduction achieved in different response quantities. Obtained results show that the proposed energy dissipation system of low yield point steel seismic link could strongly enhance the seismic performance of the tower structure where the tower and the overall bridge demands are significantly reduced. Low yield point steel seismic link effectively reduces the damage of main structural members under earthquake loading as seismic link yield level decreases due their exceptional behavior as well as its ability to undergo early plastic deformations achieving the concentration of inelastic deformation at tower horizontal beam.

The Control of Flexible Robot Arm using Adaptive Control Theory (적응제어 이론을 이용한 유연한 로봇팔의 제어)

  • Han, Jong-Kil
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.5
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    • pp.1139-1144
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    • 2012
  • The ration of payload to weight of industrial robot amounts form 1:10 to 1:30. Compared with man who have a ration of 3:1, it is very low. One of the goals for the next generation of robots will be a ration. This might be possible only by developing lightweight robots. When two-link flexible arm is rotated about an joint axis, transverse vibration may occur. In this paper, vibration dynamics of flexible arm is modeled by using Bernoulli-Euler beam theory and Lagrange equation. Using the fact that matrix $\dot{D}-2C$ is skew symmetric, new controllers which have a simplified structure with less computational burden is proposed by using Lyapunov stability theory. We propose deterministic and adaptive control laws for two link flexible arm, and the validity of the proposed control scheme is shown in computer simulation for two-link flexible arm.

Experimental Study of High Strength Concrete Beam-Column-Slab Connections subjected to cyclic loading (고강도 콘크리트 보-기둥-슬래브 접합부의 반복하중 실험)

  • 오영훈;오정근;장극관;김윤일
    • Proceedings of the Korea Concrete Institute Conference
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    • 1995.04a
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    • pp.339-344
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    • 1995
  • In the design of ductile moment-resisting frames (DMRFs) following the strong column-weak beam dsign philosophy, it is desirable that the joint and column remain essentially elastic in order to insure proper energy dissipation and lateral stability of the structure. The joint has been identified as the "weak link" in DMRFs because any stiffness or strength deterioration in this region can lead to substantial drifts and the possibility of collapse due to P-delta effects. Moreover, the engineer is faced with the difficult task of detailing an element whose size is determined by the framing members, but which must resist a set of loads very different from those used in the design of the beams and columns. Four 2/3-scale beam-column-slab joint assemblies were designed according to existing code requirements of ACI 318-89, representing interior joints of DMRFs with reinforced high strength concrete. The influence on aseismic behavior of beam-column joints due to monolithic slab, has been investigated.estigated.

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Failure mechanisms in coupled poro-plastic medium

  • Hadzalic, Emina;Ibrahimbegovic, Adnan;Nikolic, Mijo
    • Coupled systems mechanics
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    • v.7 no.1
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    • pp.43-59
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    • 2018
  • The presence of the pore fluid strongly influences the reponse of the soil subjected to external loading and in many cases increases the risk of final failure. In this paper, we propose the use of a discrete beam lattice model with the aim to investigate the coupling effects of the solid and fluid phase on the response and failure mechanisms in the saturated soil. The discrete cohesive link lattice model used in this paper, is based on inelastic Timoshenko beam finite elements with enhanced kinematics in axial and transverse direction. The coupling equations for the soil-pore fluid interaction are derived from Terzaghi's principle of effective stresses, Biot's porous media theory and Darcy's law for fluid flow through porous media. The application of the model in soil mechanics is illustrated through several numerical simulations.

Design procedure for seismic retrofit of RC beam-column joint using single diagonal haunch

  • Zabihi, Alireza;Tsang, Hing-Ho;Gad, Emad F.;Wilson, John L.
    • Structural Engineering and Mechanics
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    • v.71 no.4
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    • pp.341-350
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    • 2019
  • Exterior beam-column joint is typically the weakest link in a limited-ductile reinforced concrete (RC) frame structure. The use of diagonal haunch element has been considered as a desirable seismic retrofit option for reducing the seismic demand at the joint. Previous research globally has focused on implementing double haunches, while the use of single haunch element as a less-invasive and more architecturally favorable retrofit option has not been investigated. In this paper, the key formulations and a design procedure for the single haunch system for retrofitting RC exterior beam-column joint are developed. An application of the proposed design procedure is then illustrated through a case study.

3D Finite Element Analysis of Lateral Loaded Pile using Beam and Rigid Link (빔요소와 Rigid 링크를 이용한 수평하중에 대한 말뚝 거동 3차원 유한요소해석)

  • Park, Du-Hee;Park, Jong-Bae;Kim, Sang-Yeon;Park, Yong-Boo
    • Land and Housing Review
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    • v.4 no.3
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    • pp.271-277
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    • 2013
  • The BNWF (Beam on Nonlinear Winkler Foundation) model is one of the simplest idealizations for a pile embedded in soil as it ignores the continuity of the soil. This method is difficult to model the behavior of pile group foundation subjected to lateral loading. The limitation can be overcome with the utilization of the finite element method (FEM) or finite different method (FDM) to represent a pile element embedded in a soil medium. Both the ground and piles are modeled with soild elements. The solid elements, which do not have rotational degree of freedom, is not appropriate for modeling piles. It can be overcome by substantially increasing the number of elements, which can be prohibitive for 3D modeling. This paper used the beam element and rigid link incorporated in the OpenSees to model the pile. The accuracy of the model is validated through comparison with lateral load test and BNWF analysis. It is shown that the method can capture the measured behavior accurately. It is therefore recommended to be used in group pile analyses.

The optimum design of optical transmitting antenna versus elevation angle on the optical satellite communication up-link for B-ISDN (B-ISDN용 광위성 통신 업링크의 앙각에 따른 송신안테나 최적설계에 관한 연구)

  • 한종석;이준구;정진호;김영권
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.10
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    • pp.64-72
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    • 1995
  • In this paper, atmospheric turbulence and absorption under clear weather condition, which affect the optical satellite up-link communication between geo-satellites and earth station, were studied. In case of the up-link communication, the received optical power is weakened by pointing loss caused by beam tilt which is the main effect of turbulent atmosphere. This pointing loss directly has relation to the diameter of optical transmitting antenna. From the inverse proportion of the pointing and spaced loss, it is the regions where the diameter of transmitting antenna increases abruptly and the efficient design of transmitting antenna is impossible. In case of using channel coding, it was shown that the peak value of diameter moved to the lower regions of elevation angle with increasing the coding gain and its width was also decreased. In case of considering both coding gain and transmission rate on the design of transmitting antenna, it was known that more coding gain was necessary as transmission rate was increased.

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Simulation of corroded RC structures using a three-dimensional irregular lattice model

  • Kim, Kunhwi;Bolander, John E.;Lim, Yun Mook
    • Structural Engineering and Mechanics
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    • v.41 no.5
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    • pp.645-662
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    • 2012
  • Deteriorative effects of steel corrosion on the structural response of reinforced concrete are simulated for varying degrees of corrosion. The simulation approach is based on a three-dimensional irregular lattice model of the bulk concrete, in which fracture is modeled using a crack band approach that conserves fracture energy. Frame elements and bond link elements represent the reinforcing steel and its interface with the concrete, respectively. Polylinear stress-slip properties of the link elements are determined, for several degrees of corrosion, through comparisons with direct pullout tests reported in the literature. The link properties are then used for the lattice modeling of reinforced concrete beams with similar degrees of corrosion of the main reinforcing steel. The model is successful in simulating several important effects of steel corrosion, including increased deflections, changes in flexural cracking behavior, and reduced yield load of the beam specimens.