5,457 research outputs found
AN OBSERVER DESIGN FOR TIME-DELAY CONTROL AND ITS APPLICATION TO DC SERVO MOTOR
No full textThis paper addresses the estimation problem of states and their derivatives for the Time Delay Control (TDC), a robust control technique for nonlinear systems. To this end, an observer design method is presented. Then, in simulations, the controller/observer has been applied to a nonlinear plant, with satisfactory results. Finally, experiments were undertaken on a DC servo motor subject to substantial inertia variations and external disturbances. The results showed that the controller/observer performs quite robustly under those variations and disturbances, and is much less sensitive to sensor noise than the controller using numerical differentiations
Adaptive channel reservation scheme for soft handoff in DS-CDMA cellular systems
No full textSoft handoff techniques in direct-sequence code division multiple-access (DS-CDMA) systems provide mobile calls with seamless connections between adjacent cells. Channel reservation schemes are used to give high priority to more important soft handoff attempts over new call attempts. However, since the number of soft handoff attempts varies according to environmental conditions, fixed reservation schemes for handoff attempts can be inefficient, An adaptive channel reservation scheme is herein proposed to control the size of reservation capacity according to varying the number of soft handoff attempts. The proposed scheme also includes a balancing procedure between soft handoff failure and new call blocking to maximize the system capacity. To evaluate the performance of the proposed scheme, a Markovian model is developed that considers the interference-limited capacity effect of DS-CDMA systems. Analytical result shows that the proposed scheme yields a considerable enhancement in terms of new call blocking and soft handoff failure probabilities when compared with the conventional fixed channel reservation scheme
Wavelength interleaved bidirectional add/drop amplifier module
No full textWe propose a bidirectional add/drop amplifier (BADA) module with an N x N arrayed waveguide grating multiplexer. The relative intensity noise that degrades bidirectional transmission system severely is suppressed by interleaved wavelength allocation. with two proposed BADA modules, we demonstrate bidirectional transmission and add/drop multiplexing of 8 x 2.5 Gb/s WDM signal over 120-km conventional single mode fiber with less than 0.6 dB power penalty in the receiver sensitivity.This work
was supported in part by Samsung and KOSEF under Project 97-0100-0301-3
Molecular-dynamics simulations for the shock Hugoniot meltings of Cu, Pd and Pt
No full textWe perform molecular-dynamics simulations to study the shock melting of transition metals such as Cu, Pd and Pt on the basis of an embedded-atom method. Using the coupling-constant integration method, the Gibbs free energies of the crystalline and liquid phases are calculated as a function of pressure and temperature, so that the melting curves are obtained, up to 3-4 Mbar. We find the melting properties near zero pressure to be in good agreement with experiments. For each metal, we compare the melting curve with the Hugoniot equations of state for the solid and liquid phases and determine the melting region of the shock Hugoniot. The Hugoniot melting of Cu is found to begin at 1.9 Mbar and to end at 2.25 Mbar, in good agreement with experimental data. During the shock compression, we find that the pressure region where the Hugoniot melting occurs increases almost linearly with increase of the ionic mass
Effect of Queueing Soft Handoff Attempts on the Reverse Link Capacity in DS-CDMA Cellular Systems
No full textMeasurement-Based Admission Control for soft handoff Call Requests in DS-CDMA Cellular Systems
No full textNovel Admission Control Scheme in DS-CDMA Cellular Systems Supporting Voice and Stream-Type Data Services
No full text
Molecular dynamics simulations of high pressure and high temperature properties of Cu, Pd, and Pt
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