• Title/Summary/Keyword: Multi-variable system

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Orthogonal variable spreading factor encoded unmanned aerial vehicle-assisted nonorthogonal multiple access system with hybrid physical layer security

  • Omor Faruk;Joarder Jafor Sadiqu;Kanapathippillai Cumanan;Shaikh Enayet Ullah
    • ETRI Journal
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    • v.45 no.2
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    • pp.213-225
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    • 2023
  • Physical layer security (PLS) can improve the security of both terrestrial and nonterrestrial wireless communication networks. This study proposes a simplified framework for nonterrestrial cyclic prefixed orthogonal variable spreading factor (OVSF)-encoded multiple-input and multiple-output nonorthogonal multiple access (NOMA) systems to ensure complete network security. Various useful methods are implemented, where both improved sine map and multiple parameter-weighted-type fractional Fourier transform encryption schemes are combined to investigate the effects of hybrid PLS. In addition, OVSF coding with power domain NOMA for multi-user interference reduction and peak-toaverage power ratio (PAPR) reduction is introduced. The performance of $\frac{1}{2}$-rated convolutional, turbo, and repeat and accumulate channel coding with regularized zero-forcing signal detection for forward error correction and improved bit error rate (BER) are also investigated. Simulation results ratify the pertinence of the proposed system in terms of PLS and BER performance improvement with reasonable PAPR.

Shifting Algorithm and Response Characteristics of Torque Split Multi-Pass CVT (토크 분배방식 다경로 CVT의 변속 알고리듬과 응답특성)

  • 성덕환;김현수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.11
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    • pp.2817-2824
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    • 1994
  • A torque split type multi-pass CVT(MPC) system consiting of CVT and planetary gear train with 4 clutches was suggested to overcome the inherent inferior acceleration performance of CVT. Also, a shifting algorithm of MPC was suggested for the two driving modes : (1) power mode and (2) economy mode. By using the shifting algorithm and the MPC vehicle dynamic model, numerical simulations were performed to estimate the performance of the MPC vehicle. Simulation results showed that comparing the performance of the conventional 4-speed automatic transmission, an improvement in acceleration can be obtained by MPC for the power mode and 31% improvement in fuel economy for the economy mode.

Design and Implementation of the Modified Cubic Interpolator Based on Variable Parameters for Multi-Band OFDM UWB System (Multi-Band OFDM UWB 시스템용 변형된 가변 파라미터를 이용한 큐빅 인터폴레이터의 설계 및 구현)

  • Kim, Sang-Dong;Lee, Jong-Hum;Jung, Woo-Young;Chong, Jong-Wha
    • IEMEK Journal of Embedded Systems and Applications
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    • v.1 no.1
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    • pp.20-23
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    • 2006
  • 본 논문은 MB-OFDM UWB(Multi Band-Orthogonal Frequency Division Multiplexing Ultra Wide Band) 시스템을 위한 변형된 가변 파라미터를 이용한 큐빅 인터폴레이터를 제안한다. MB-OFDM UWB 시스템은 고속의 동작속도가 필요하기 때문에, 기존 가변 파라미터를 이용한 큐빅 인터폴레이터에 병렬 처리 기술과 파이프라인 기법을 동시에 적용한다. 실험 결과, Stratix II 2S60F101020C3 디바이스를 타켓으로 최대지연경로 속도와 최대지연경로 주기가 각각 최대 88.79MHz와 11.262ns가 되었고, 동작속도는 최대 대략 200% 이상 향상되었음을 알 수 있다.

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Response Property of Multi-directional Mount Using Magneto-Rheological Fluid (MR유체를 이용한 다방향 제진형 마운트의 응답특성)

  • 안영공;신동춘;양보석;이일영;김동조
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.7
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    • pp.517-523
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    • 2003
  • This paper presents response property of the squeeze mode type mount using Magneto-Rheological fluid (MR fluid) . The MR mount for the isolation of multi-directional vibrations was constructed in this study. Both the mechanism and shape of the mount are the same as squeeze film dampers for a rotor system. In the present work, the performance of the mount was experimentally Investigated according to the magnetic field strength. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic filed strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents In this study.

Performance of the Flow Distribution and Capacity Modulation of a Multi-Heat Pump System (멀티형 열펌프의 유량분배 및 용량조절 특성)

  • 최종민;김용찬;하진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.5
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    • pp.313-320
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    • 2001
  • In the present study, various experiments were performed to investigate capacity modulation and refrigerant flow distribution of a multi-heat pump using a variable speed compressor and electronic expansion valves(EEVs) in the cooling mode. Based on the experimental results, it was possible to understand the interrelation of dual indoor units which provides some difficulties in capacity control of each indoor unit. The characteristics of capacity modulation of two indoor units were measured by controlling two EEVs with a cooling load of each indoor unit.

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Hovering Flight Control for a Model Helicopter using the Minimal-Order LQG/LTR Technique (Minimal Order LQG/LTR 기법에 의한 모형헬리콥터의 정지비행 자세제어)

  • Yang, J.S.;Han, K.H.;Lee, J.S.
    • Proceedings of the KIEE Conference
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    • 1998.11b
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    • pp.457-459
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    • 1998
  • This paper presents a 3-DOF hovering flight controller for a model helicopter using the minimal order LQG/LTR technique. A model helicopter is an unstable multi-input multi-output nonlinear system strongly exposed to disturbances, so a robust multi-variable control theory should be applied to control it. The minimal order LQG/LTR technique which uses a reduced-order observer in the LTR procedure is used to design the controller. Performances for the 3-DOF hovering flight controller are evaluated through computer simulations.

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Multi-objective Topology Optimization of Magneto-Thermal Problem considering Heat Flow Rate (열 유입률을 고려한 자계-열계 다목적 위상최적설계)

  • Shim, Ho-Kyung;Wang, Se-Myung;Moon, Hee-Gon;Hameyer, Kay
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.138-139
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    • 2007
  • This research provides machine designers with some intuition to consider both, magnetic and heat transfer effects. A topological multi-objective function includes magnetic energy and heat inflow rate to the system, which equals to the total heat dissipation by conduction and convection. For the thermal field regarding the heat inflow, introduced as a reaction force, topology design sensitivity is derived by employing discrete equations. The adjoint variable method is used to avoid numerous sensitivity evaluations. As a numerical example, a C-core design excited by winding current demonstrates the strength of the multi-physical approach.

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Optimization of Process Variables of Shape Drawing for Steering Spline Shaft (조향장치용 스플라인 샤프트 이형인발 공정변수 최적화)

  • Lee, S.K.;Kim, S.M.;Lee, S.B.;Kim, B.M.
    • Transactions of Materials Processing
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    • v.19 no.2
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    • pp.132-137
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    • 2010
  • In the multi-pass shape drawing process, the appropriate process design is very important to produce sound products. The reduction ratio, die angle, and the intermediate die shape are very important process variable of the multi-pass shape drawing. The aim of this study is the determination of the reduction ratio, die angle, and the intermediate die shape of the 2 pass shape drawing process for producing steering spline shaft. In this study, FE analysis, Taguchi method, and ANN(artificial neural network) were applied to determine the appropriate reduction ratio, die angle, and intermediate die shape. After the determination of the process variables, FE analysis and drawing experiment were performed to evaluate the effectiveness of the determined process variables. The dimensional accuracy of the final drawn spline shaft was evaluated by using 3D surface profiler and 3D laser digitizing system.

Multiobjective Decision-Making applied to Ship Optimal Design

  • Wang, Li-Zheng;Xi, Rong-Fei;Bao, Cong-Xi
    • Journal of Ship and Ocean Technology
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    • v.5 no.1
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    • pp.30-37
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    • 2001
  • Ship optimal design is a multi-objective decision-making process and its optimal solution does not exit in general. It is a problem in which the decision-maker is very interested that an effective solution is how to be found which has good characteristic and is substituted for optimal solution in a sense. In the previous methods of multi-objective decision-making, the weighting coefficients are decided from the point of view of individuals which have a bit sub-jective an unilateral behavior. in order to fairly and objectively decide the weighting coeffi-cients, which are considered to be optimal in all system of multi-objective decision-making and satisfactory solution to the decision-maker, the pater presents a method of applying the Technology of the Biggest Entropy. It is proved that the method described in the paper is very feasible and effective be means of a practical example of ship optimal design.

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Identification of continuous time-delay systems using the genetic algorithm

  • Hachino, Tomohiro;Yang, Zi-Jiang;Tsuji, Teruo
    • 제어로봇시스템학회:학술대회논문집
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    • 1993.10b
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    • pp.1-6
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    • 1993
  • This report proposes a novel method of identification of continuous time-delay systems from sampled input-output data. By the aid of a digital pre-filter, an approximated discrete-time estimation model is first derived, in which the system parameters remain in their original form and the time delay need not be an integral multiple of th sampling period. Then an identification method combining the common linear least squares(LS) method or the instrumental variable(IV) method with the genetic algorithm(GA) is proposed. That is, the time-delay is selected by the GA, and the system parameters are estimated by the LS or IV method. Furthermore, the proposed method is extended to the case of multi-input multi-output systems where the time-delays in the individual input channels may differ each other. Simulation resutls show that our method yields consistent estimates even in the presence of high measurement noises.

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