摘要:

AbstractA simulation procedure for the computation of current wave forms in a system composed by a three-phase in verter driving an induction motor is proposed.The amplitude of the fundamental harmonic of the AC voltage driving the motor is varied by means of a PWM technique: a triangular wave form carrier is modulated by a sinusoidal waveform.The induction motor is described by four differential equations referred to the d-q transformation, with the assumption that the speed does not change during the time interval corresponding to one period of the drive voltage.The input data required by the procedure, which is based on a discrete-time domain analysis,are the ratio between the carrier and the modulation signal frequencies, the speed and the motor parameter sj the outputs are the current wave forms in the motor windings, in the transist or sand in the diodes. The spectra of the resulting currents are also computed.

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759972

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThis paper examines a class of sampled systems where the data collection is disturbed by external reasons and several samples are missing. Common data logging problems such as, instrumentation failure, unpredicted power failure, etc,, can be solved by applying theproposed signal processing algorithms.The technique used is based on modeling the process with an auto regressive moving average (ARMA) filter. Identifying the parameters of the filter and using the filter to estimate the missing observations. Simulation results indicate the applicability of the algorithms in a microcomputer environment, with limited computationa resources. The algorithms give satisfactory results in case of burst missing data.

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759973

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractIn this paper we have developed an econometric model of a major export commodity in a sub national economy .Prince Edward Island, the smallest subnational economy in North America, is a major international exporter of potatoes. The Island economy, being heavily dependent on the potato income, is greatly affected by fluctuations in potato prices and exports. Our model, using impact and long-run multiplier analysis, explores inter relationships between potato sector variables and at tempts to quantify the impact of potato price and export fluctuations on the Island economy .The impact of the weather factor on the Island economy through its influence on the potato sector is also analyzed.

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759974

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractIn this paper a cellular model for the simulation of the lava flow is presented together with the results of a first implementation, considering simple situations with elementary morphologies and viscous magmas.Lava flow is viewed as a local interactions-based dynamic system with discrete time and space where space is divided in parallelepipedal cells. The computation of lava flow-down from the cells describes the evolution the phenomenon.An abstraction of the phenomenon development not in discording with field data was obtained. Cases reported here present classical situation sand compare different lava flows starting phase shaving the same morphology .

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759975

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractOptical communication fibers are pulled at high temperatures from solid quartz rods with radially varying indices of refraction. These solid quartz rods are called preforms and their manufacturere presents the largest portion of the price of the finished fiber. This paper deals with the theoretical and experimental identification of the single most time consuming (and thus expensive) stepsin preform fabrication: the collapse of a quartz tube to a solid rod. It is the result of a coope rative effort with the Nordiske Kabel- og Traadfabrikker A/S (NKT).An optical fiber preform is manufactured from a quartz tube in which a glass dust is deposited. This glass dust has impurities which give the core of the preform the requiredrefractive index profile.Finally the tube is collapsed to a solid rod by slowly passing a high temperature flame a long the tube. The total collapse can consurne as much as 24 hours for some tubes. Moreover for low loss fiber sit is extremely important that the core of the preform is exactly circular. This implies an automatic control which can only be achieved if the dynamics of the process are known.The identification of the collapse process has been carried out using direct physical modelling of a system which involves the solution of the Navier Stokes differential equation in two dimensions. This complicated system has been reduced to an analytical nonlinear state space model. Experiments show that this model describs the collapse process quite weIl. Automatic contra1 will be attempted in the near furture.

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759976

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractTransient responses of linear systems governed by partial dffferential equations (withtime and one spatial coordinate as independent variables), having time-dependent coefficients and non-homogeneous initial conditions,are simulated numerically by a hybrid use of Crump's scheme for the inversion of Laplace transforms and some traditional numerical methods. To handle the time dependency of coefficients, the“stairway”approximation whereby a time-curve is replaced by a series of small steps is incorporated. For each of these steps, the technique of Laplace transforms is applied; with an“initial”condition supplied by the solution at the end of the preceding step. These non-homogeneous“initial”conditions are fitted with high-degree polynomials so that the particular integrals to the ordinary differential equations in the trànsformed domain can be written down explicitly as polynomials. The solutions in the transformed domain can be, then, inverted using a numerical inversion scheme of the new generation (based on a Fourier series expansion). The hybrid method is applied,as an example, to the engineering system of packed-bed energy storage and regeneration where the mass-flow rateof fluid stream is time-dependent, and may change itssign (direction of flow). Numerical results show the method to be fast, robust, easy to implement, and with acceptabledegree of accuracy.

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759977

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe flow field through the vertical axis wind turbineis assumed to be two-dimensional in the mid-plane of the machine. The vorticity shed by the blades is concentrated into vortex blobs, i.e. circular regions with uniform distribution of vorticity. The blob radiiare assumed to grow with time starting from a zero value at the time of their generation, according to√40νt in whichνis kinematic viscosity. The bound vorticity of the blades isconcentrated in their aerodynamic center. The velocity field induced by the vortices is calculated by Biot-Savart integration. The lift-and drag coefficients of the blades are taken from static airfoil data for a profile Reynolds number calculated with the mean relative velocity during one revolution. The vorticity shed by a blade during a time step is taken equal and opposite to the change of circulation on the blade during the same time step in order to keep constant the total amount of vorticity in the flow field. The motionof the free vortices is calculated by Run ge-Kutta integration of four thorder based on the velocity vector in the center of the blobs.Results are presented shewing the vertex streets for one-and three bladed machines forone tip speed ratie. For a one bided machine, a power coefficient versus tip speed ratio characteristic is shown. Fera three-bladed machine, the agreement be t we en the calculated power coefficient obtained by free vortex analysis and obtained by mu ltiple stream tube theory is shown.

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759978

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA recirculation system (RS) with a single input function, heterogeneous subsystems,and a finite capacity is considered. Inside the RS the subsystems are placed in parallel and are accessed randomly.Each subsystem is considered as a GI/M/I/o single server Queueing loss system with renewal input, no waiting room, and negative exponentialIy distributed service times. The single input function is a stationary counting process.Inside the RS, at any cycle the incoming stream of units entering the system, travel inside to reach the routing mechanism. There, they are assigned upon arrival to one of the subsystems. At each subsystem,the units whicn find it full, retry to receive service oy recirculating back to the entrance of the system.There, they merge with the incoming arrival strem to form a new input to the routing mechanism at the next cycle. The units which enter each subsystem after receiving service depart from it. the previous steps are then repeated until the steady state is achieve.An open Queueing network is developed to study the asymptotic performance of the above RS. The flows of units inside the RS are approximated by a two parameter method. The performance of the RS is measured by approximating the congestion inside the RS and evaluating the efficiency of eacn of its subsystms. Finally, an example is introduced and the approximation outcomes are campared against those from a simulation study.

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759979

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

ISSN:0228-6203    

DOI:10.1080/02286203.1986.11759939

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor