Picture iteration theorems for regular, linear, and context-free languages are presented. These theorems serve as picture-counterparts of the well-known string iteration theorems and suggest that regular, linear, and ...
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Picture iteration theorems for regular, linear, and context-free languages are presented. These theorems serve as picture-counterparts of the well-known string iteration theorems and suggest that regular, linear, and context-free languages describe large pictures by iterating small picture primitives. It is also shown that the picture ambiguity problem is undecidable for regular languages and for linear languages which describe three-way stripe picture languages.
Real-time communication with performance guarantees is expected to become an important and necessary feature of future computer networks. In this paper, we present a scheme which can provide real-time communication se...
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Real-time communication with performance guarantees is expected to become an important and necessary feature of future computer networks. In this paper, we present a scheme which can provide real-time communication services with both absolute and statistical performance guarantees on multiaccess bus networks for given input traffic characteristics and performance requirements. The proposed scheme reserves network bandwidth for real-time connections according to their needs. It also allows for independent addition and deletion of real-time connections while preserving existing guarantees. Our extensive simulation results for motion video communication have shown the proposed scheme to outperform the other well-known schemes.
The classic technology of the saturable core may be combined with the microcomputer to yield an improved version of the magnetic flux-gate compass. General description and fundamental principles are discussed with app...
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The classic technology of the saturable core may be combined with the microcomputer to yield an improved version of the magnetic flux-gate compass. General description and fundamental principles are discussed with application to mass-produced automobiles. A transfer function between the earth's magnetic field and the fluxgate output voltages is developed. The introduction of the microcomputer allows a faster calibration which does not require any type of nulling or feedback circuit.
Using a set of characteristic curves derived from the stateplane analysis, a novel approach to the design of the parallel resonant convertor (PRC) is presented. It will be shown that the steady-state response of the c...
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Using a set of characteristic curves derived from the stateplane analysis, a novel approach to the design of the parallel resonant convertor (PRC) is presented. It will be shown that the steady-state response of the convertor can also be obtained from these characteristic curves
The question of attitude control and elastic mode stabilization of a spacecraft (orbiter) with beam-tip-mass-type payloads is considered. A three-axis moment control law is derived to control the attitude of the space...
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The question of attitude control and elastic mode stabilization of a spacecraft (orbiter) with beam-tip-mass-type payloads is considered. A three-axis moment control law is derived to control the attitude of the spacecraft. The derivation of the control moments acting on the spacecraft does not require any information on the system dynamics. The control law includes a reference model and a dynamic compensator in the feedback path. For damping out the elastic motion excited by the slewing maneuver, an elastic mode stabilizer is designed. The stabilization is achieved by modal velocity feedback using force and torque actuators located at the payload end of the elastic beam. Collocated actuators and sensors provide robust stabilization. Simulation results are presented to show that rotational maneuvers and vibration stabilization can be accomplished in the closed-loop systems despite the presence of model uncertainty and disturbance torque in the system.
This paper presents an iterative procedure called the relaxation of autocorrelation equations (RAE) for solving the phase retrieval problem for nonnegative signals. First, the phase retrieval problem is formulated in ...
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This paper presents an iterative procedure called the relaxation of autocorrelation equations (RAE) for solving the phase retrieval problem for nonnegative signals. First, the phase retrieval problem is formulated in the spatial domain as a set of polynomial equations with autocorrelations as known data and signal values as unknowns. Then, the RAE procedure solves these equations by recognizing one unknown at a time. While other unknowns are held constant at previously estimated values, a single unknown is varied inside the nonnegative region to globally minimize the sum of squared residuals of the equations with respect to the unknown. In every iteration, this procedure is repeated for each signal value. Since the sum of squared residuals is nonincreasing, the algorithm will either converge to a solution or stagnate;ways to overcome stagnation are suggested. The key feature of the RAE procedure is that unlike iterative transform algorithms, it allows direct control over bounding values df the signal at all times. Several numerical examples illustrate the RAE procedure.
In this paper a new algorithm is presented for determining etch rate from single or multiple wavelength reflectometry data, This algorithm is based on techniques from recursive nonlinear estimation theory-Extended Kal...
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In this paper a new algorithm is presented for determining etch rate from single or multiple wavelength reflectometry data, This algorithm is based on techniques from recursive nonlinear estimation theory-Extended Kalman Filtering, A major advantage of our algorithm is extremely high speed, with computation time less than 1 ms on a Pentium PC, Consequently, it can be used in real-time feedback control applications. The speed advantage also makes it a suitable candidate for full wafer (or multi-point) high-speed etch rate measurement.
Multiple-unit computer systems which are to be tolerant of intermittently faulty units or transiently upset units are considered in this paper. Designs for such systems, which exploit a new so-called greedy diagnosis ...
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Multiple-unit computer systems which are to be tolerant of intermittently faulty units or transiently upset units are considered in this paper. Designs for such systems, which exploit a new so-called greedy diagnosis theory, are developed. Using greedy diagnosis, assessments on the condition of a unit (intermittent-fault case) or the integrity of data (transient-upset case) can be made on the basis of syndromes formed from comparisons of the results of jobs performed by pairs of units. Greedy diagnosis avoids the requirement that for such syndromes to be useful, they must be interpretable from a permanent-fault/continuous-upset perspective.
In SIMD MIMD functionally reconfigurable multimicroprocessor systems /MMPS/ some of the microprocessor modules /MPM/ can execute a common program /SIMD mode/ while the rest of the MPMs are executing their own programs...
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In SIMD MIMD functionally reconfigurable multimicroprocessor systems /MMPS/ some of the microprocessor modules /MPM/ can execute a common program /SIMD mode/ while the rest of the MPMs are executing their own programs /MIMD mode/. Every MPM at any moment can be reconfigured functionally from one to another mode. In this paper the problems of designing such MMPSs are discussed as well as some realisations of a data exchange module as a register module and some algorithms for parallel data exchange between the MPMs. A hierarchically structed MMPS are developed.
Very-low threshold currents are expected to be achieved in quantum-wire lasers owing to the singularity in the density of states occurring at the bandedge. On the other hand, the high-speed modulation of quantum-wire ...
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Very-low threshold currents are expected to be achieved in quantum-wire lasers owing to the singularity in the density of states occurring at the bandedge. On the other hand, the high-speed modulation of quantum-wire lasers may be limited by carrier relaxation processes that are greatly affected by the reduction in the momentum space. In this paper, we calculate the electron relaxation times for GaAs/AlGaAs wires of various cross sections assuming that electrons are injected in a thermal distribution at the edge of the potential well formed by the barrier. The relaxation times are extracted from the time evolution of the carrier distribution as the electrons come to thermal equilibrium with the lattice. The Monte Carlo method is used to simulate the details of the relaxation process with the inclusion of electron-bulklike phonon, electron-electron and electron-hole interactions. We find that the electron relaxation times range from 120 ps for the 100 x 100 angstrom wire to 30 ps for the 200 x 200 angstrom wire for a carrier density of 10(18) cm-3. When the electron-hole interaction is included into the calculations, the equilibration time for the 100 x 100 angstrom wire is reduced to almost-equal-to 50 ps. Screening effects are incorporated using the Thomas-Fermi formalism. At a carrier concentration of 10(16) cm-1, the equilibration times for the corresponding wire sizes are 20 and 5 ps. Thus, the relaxation time calculated within the limits of our model decreases with an increased wire cross section. This trend indicates the presence of a trade-off between speed and efficiency in quantum-wire lasers considering that the threshold current is decreased by reducing the wire cross section.
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