• Title/Summary/Keyword: Delay Angle

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Performance Improvement of MIMO-OFDMA system with beamformer

  • Kim, Chan Kyu
    • International Journal of Internet, Broadcasting and Communication
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    • v.11 no.1
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    • pp.60-68
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    • 2019
  • In this paper, we propose the adaptive beamforming algorithm for the MIMO (Multi-Input Multi-Out)-OFDMA(Orthogonal Frequency Division Multiplexing Access)system to improve the performance. The performance of MIMO-OFDMA systems is greatly decreased in the wireless channel environment with multiusers, because the received signals are much distorted by a cochannel interference (CCI) during the space-time decoding. The proposed approach can track the DOA of each signal from the multiple antennas of the desired user without being greatly dependent on the impinging angle. And beams are directed toward the multiple transmitters of the desired user while null beams are directed toward interference directions. Therefore, we can can effectively cancel CCI and mitigate the impairment of delay spread while preserving the STC(space time code) diversity. BER performance improvement is investigated through computer simulation by applying the proposed approach to MIMO-OFDMA system in a multipath fading channel with CCI.

Implementation of Low Loss Radome with Hexa mesh for Ku-Band

  • Seo, Kang;JeongJin, Kang
    • International Journal of Advanced Culture Technology
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    • v.10 no.4
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    • pp.555-560
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    • 2022
  • In this study, the insertion loss and phase delay according to the multi-layer structure radome parameters were analyzed using the boundary value solution approach, and the multi-layer structure and hexa mesh structures with low-loss electrical characteristics for the Ku-band transmission/reception frequency of 10.7 ~ 14.5 GHz were designed and manufactured. A hexa mesh was applied to minimize radio wave transmission and scattering, which lowered the transmittance refractive index according to the radio incident angle and minimized dielectric loss through high-density foam. Similar to the simulation result, the transmission loss obtained the gain in a specific receiving frequency band, and in the transmission frequency band, an excellent low loss characteristic was obtained with an insertion loss of 0.8dB or less. The results of this study can be used in radio transmission radomes of low-weight, low-cost end-system protection devices.

Experimental modeling and Robust Control of an Industrial Overhead Crane

  • Park, B.S.;T.G. Song;Lee, J.Y.;D.H. Hong;J.S. Yoon;E.S. Kang
    • 제어로봇시스템학회:학술대회논문집
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    • 2001.10a
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    • pp.45.2-45
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    • 2001
  • In case that the perfect model following conditions are not satisfied in the system, a perfect model-following controller is difficult to apply to the system. To deal with this problem, in this paper, a robust imperfect stable model-following controller is designed by combining time delay controller and sliding mode controller based on the concept of two degrees of freedom(2-DOF) controller design method. The experimental dynamic modeling of the commercial overhead crane with capacity of two tons is carried out. To remove the noise of the measuring signals from the swing angle measurement device and estimate the state of the swing angles of the transported object at each time instant, realtime tracker is designed using Kalman filter. The performance of the designed robust controller is tested through the commercial overhead. The experimental results show that the designed controller is robust and applicable to real systems.

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Electromyography Triggered Training System for Wrist Rehabilitation (근전도 트리거 손목 재활 훈련 시스템 개발)

  • Kim, Younghoon;Le, DuyKhoa;Chee, Youngjoon;Ahn, Kyoungkwan;Hwang, Changho
    • Journal of Biomedical Engineering Research
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    • v.34 no.3
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    • pp.148-155
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    • 2013
  • This study is about the development of the wrist rehabilitation system for the patient who has limited capability of movement after stroke. Electromyography triggered training system (ETTS) can play the role between complete passive training and patient activating training system. Surface EMG was measured on pronator teres muscle and biceps brachii muscle for wrist pronation and supination. Our system detects whether the subject makes muscular effort for pronation or supination or nothing in every 50 ms. When the effort level exceeds the preset percentage of maximal voluntary contraction, the motor rotates according to the direction of the intention of the subject. EMG triggers the motor rotation for the wrist rehabilitation training until the preset angle. To evaluate its performance, the maximum voluntary contraction level was measured for 4 subjects at first. With the audio-visual instruction to rotate the wrist (pronation or supination) the subjects made effort to follow the instruction. After calculating root mean square (RMS) for 50 ms, the controller determines whether there was muscular effort to rotate while holding the motor. When there was an effort to rotate, the controller rotates the motor 0.8 degree. By comparing the RMS values from two channels of EMG, the controller determines the rotational direction. The onset delay is $0.76{\pm}0.24$ s and offset delay is $0.65{\pm}0.22$ s for pronation. For supination the onset delay is $1.24{\pm}0.41$ s and offset delay is $0.77{\pm}0.22$ s. The system responded fast enough to be used for rehabilitation training. The controller perceived the direction of rotation 100% correctly for the pronation and 97.5% correctly for supination. ETTS was developed and the fundamental functions were validated for normal subjects. The clinical validation should be done with patients for real world application. With ETTS, the subjects can train voluntarily over the limitation of the range of motion which increases the effectiveness of the rehabilitation training.

Development of Ultrasonic Sensors for Simultaneous Measurement of Longitudinal and Shear Waves (종-횡파 동시 측정용 초음파 센서의 개발)

  • Kim, Yeon-Bo;Rho, Yong-Rae
    • Journal of Sensor Science and Technology
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    • v.8 no.1
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    • pp.1-9
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    • 1999
  • A study has been made on the fabrication of a dual mode(a longitudinal and shear mode) ultrasonic sensor using a single PZT piezoelectric ceramic element. We investigated the mechanism of the dual mode sensor that generated both of the longitudinal and the shear waves simultaneously with the single PZT element. Through the analysis of analytic wave propagation equations, all the possible crystal cuts have been examined to determine appropriate Euler transformation angles for efficient excitations of the dual modes. We studied the performance of a PZT element as a function of its rotation angle so that its efficiency is optimized to excite the two waves of equal strength. Experimental examination of the waveform on a delay line(STS303) setup confirms that the ultrasonic sensor can transmit and detect both longitudinal and shear waves simultaneously.

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A Study on the Injection Characteristics of Swirl Nozzle Injector in Common-rail System for High Pressure Fuel Injection (커먼 레일 시스템 고압 연료 분사용 스월 노즐 인젝터의 분사 특성에 관한 연구)

  • Sin, Yunsub;Lee, Geesoo;Kim, Hyunchul;Kwak, Sangshin;Shin, Suk Shin;Suh, Hyun Kyu
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.4
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    • pp.89-95
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    • 2013
  • In this work, the evaluation of swirl nozzle injector performance was conducted by investigating effective area ($A_{eff}$), injection mass ($m_{inj}$), injection rate ($Q_{inj}$), and injection delay ($t_{delay}$) under various test conditions. To achieve these, fuel injection analysis system which was composed of fuel supply system, injection system, and control system was installed. At the same time, the swirl nozzle that had 12 orifice hole with $120^{\circ}$ injection angle was used in this work. It was revealed that the difference of injection mass ($m_{inj}$) between base and swirl nozzle injector increased as the injection pressure ($P_{inj}$) and energizing duration ($t_{eng}$) decreased under the same test conditions. The maximum injection rate ($Q_{inj}$) of swirl nozzle injector was higher than base nozzle injector about 2~5%. The injection performance of swirl nozzle was better than base nozzle at low injection pressure ($P_{inj}$) and short energizing duration ($t_{eng}$) conditions.

Calculation of the Peak-delay Force Reduction Parameter of Multi-Directional Random Waves Acting on a Long Caisson Breakwater (장대 케이슨 방파제에 작용하는 다방향 불규칙파랑의 파력감소계수 산정)

  • Jung, Jae-Sang;Kim, Bum-Hyung;Kim, Hyung-Jun;Cho, Yong-Sik
    • Journal of Korea Water Resources Association
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    • v.43 no.10
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    • pp.843-850
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    • 2010
  • By employing multi-directional random waves, a parameter controlling the force acting on a long caisson breakwater is investigated in detail. Both JONSWAP (Joint North Sea Wave Project) and asymmetric directional spectra are adopted for frequency and directional spectra. It is found that the parameter decreases as the length of caisson and the angle of main direction of incident waves increase. Furthermore, the parameter is much similar to that of regular waves as the maximum spreading parameter $s_{max}$ increases. The parameter, however, decreases as asymmetry parameter ${\mu}$ increases when the main direction of incident waves is oblique to the breakwater.

Development of "ZIGTECHnology" Apparel for Body Shape Renovation of New Senior Life Generation

  • Cha, Su-Joung
    • Journal of the Korea Society of Computer and Information
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    • v.25 no.11
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    • pp.157-166
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    • 2020
  • In this study, I tried to develop ZIGTECHnology clothing for renovation that can correct the body shape of elderly women according to aging and delay the change of body shape. Develop and suggest corrective clothing for elderly women with easy movement that can alleviate symptoms and delay changes in body shape by analyzing body types for each symptom, such as bending of shoulders, back and waist caused by aging and diseases such as spinal curvature. As a result of the wear evaluation of the developed ZIGTECHnology clothing designs 1, 2, and 3, in terms of functionality, Design 1 was evaluated as excellent by reducing the back angle by 3.17°, but design 3 was evaluated as the most excellent considering the fit. In the clothing of elderly women, the need for clothing that complements physical shortcomings increases, so it is thought that continuous development of body shape relief devices should be made.

Comparison of EMG and Muscle Reaction Force to Detect Exercise Intention (운동의도 검출을 위한 근육반력과 근전도의 비교)

  • Heo, J.H.;Kim, J.W.;Kwon, Y.R.;Eom, Gwang-Moon;Jeong, K.Y.;Kwon, D.K.
    • Journal of Biomedical Engineering Research
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    • v.34 no.2
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    • pp.63-68
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    • 2013
  • Activeness of exercise is critical for stroke rehabilitation so that application of stimulation in response to patient's intention would be effective in FES cycling. The purpose of this study was to investigate the relationship between muscle reaction force (MRF) and electromyogram (EMG) during cycling exercise, for the future usage of MRF as patients' intention signal. Seven young men ($24{\pm}1.63$ yrs) participated in this study. Cycling speed was set to 20 RPM and 60 RPM. MRF and EMG were measured in the vastus lateralis muscle of right leg. Active cycling was performed at the maximal load (16 Nm) of an ergometer. Angle dependent artifact in MRF was measured from passive cycling and was subtracted from the MRF of active cycling. The delay of MRF with respect to EMG envelope and their correlation coefficients were derived from the best of cross correlation. MRF was significantly correlated with EMG amplitude in all subjects (p<0.01). Their mean correlations were 0.84 and 0.91 for 20 RPM and 60 RPM, respectively. Mean delay in MRF was 59.14 ms and 53.14 ms for 20 RPM and 60 RPM, respectively. The result suggests that MRF can be used to assess patient's intention for exercise as a substitute to EMG. The method may be applied to FES cycling to encourage patient's effort which is critical for stroke rehabilitation.

Effect of trailing-edge modification over aerodynamic characteristics of NACA 0020 airfoil

  • Ethiraj, Livya;Pillai, Subramania Nadaraja
    • Wind and Structures
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    • v.33 no.6
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    • pp.463-470
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    • 2021
  • This study investigates the aerodynamic characteristics of NACA series airfoil by altering the trailing edge in the form of extended and serrated sections. This contemporary advent examined NACA 0020 airfoil experimentally at the angle of attack ranging from 0° to 45° and for the Reynolds number of 2.46 × 105. To figure out the flow behaviour, the standard average pressure distribution over the airfoil surface is estimated with 50 pressure taps. The time series surface pressure is recorded for 700 Hz of sampling frequency. The extended trailing edge of 0.1 c, 0.2 c and 0.3 c are attached to the base airfoil. Further, the triangular serration is introduced with the base length of 2 cm, 4 cm and 6 cm. Each base length with three different amplitudes of 0.1 c, 0.2 c and 0.3 c were designed and equipped with the baseline case at the trailing edge and tested. The aerodynamic force coefficient, as well as pressure coefficient are presented. The obtained data advises that modification in the trailing edge will reflect the aerodynamic characteristics and the flow behaviour over the section of a wing. Resultantly, the extended trailing edge as a thin elongated surface attached to a base airfoil without revising the main airfoil favors good lift increment. The serrated trailing edge acts as a flow control device by altering the flow pattern results to delay the stall phenomenon. Besides it, improves lift co-efficient with less amount of additional drag. This extended and serrated trailing edge approach can support for designing the future smart airfoil.