Influence Of System Parameters Research Articles

Simulation of two-plane automatic balancing of a rigid rotor

The paper presents analytical and numerical investigations of a two-plane automatic balancing device for equilibration of rigid-rotor unbalance. It includes the derivation of the full system of equations of motion, the stability analysis on the basis of an analytical approximation and results of numerical simulations. The influence of system parameters, such as rotational speed, damping in supports and resistance to the motion of the compensation balls on the operation of device is analysed. The display of the Sommerfeld effect when balls come to move at a speed corresponding to rotor eigenfrequency is demonstrated. The paper contains examples of simulation results and considerations about the optimal values of the regarded parameters.

PERIODIC MOTIONS AND GLOBAL BIFURCATIONS OF A TWO-DEGREE-OF-FREEDOM SYSTEM WITH PLASTIC VIBRO-IMPACT

A two-degree-of-freedom (d.o.f.) impact system with proportional damping is considered. The maximum displacement of one of the masses is limited to a threshold value by a rigid wall, which gives rise to a non-linearity in the system. A limiting case of a dynamical problem arising in the mechanical systems with amplitude constraints is investigated. For the perfectly plastic vibro-impact case, dynamics of a two-degree-of-freedom vibratory system contacting a single stop is represented by a three-dimensional map. Existence and stability of period n single-impact motions are analyzed by analytical and numerical methods. It is shown that the vibro-impact system may exhibit two different types of periodic motions due to the piecewise property of the map. Transitions of two types of period n single-impact motions are demonstrated. The singularities of the Poincaré map, caused by grazing boundary motion of the impact oscillator, are considered. Due to the piecewise discontinuities and singularities of the map, the vibro-impact system is shown to undergo period-doubling bifurcations followed by complex sequence of transitions, in which the period-doubling cascades do not occur and extremely long-periodic and chaotic motions are generated directly with the motions with grazing boundary occurring. Finally, the influence of system parameters on periodic impacts and global bifurcations is discussed.

Stabilization of a Translating Tensioned Beam Through a Pointwise Control Force

A spectral analysis determining asymptotically the distribution of eigenvalues of a constrained, translating, tensioned beam in closed form is the subject of this paper. The constraint is modeled by a spring-mass-dashpot subsystem that is located at any position within the span of the beam. It can represent a feedback controller with a collocated sensor and actuator. The necessary and sufficient condition that ensures a uniform stability margin for all the modes of vibration is determined. Influences of system parameters on the distribution of eigenvalues are identified. The analytical predictions are validated by numerical analyses. The constraint location maximizing the stability margin of the distributed model is predicted through a combined analytical and numerical approach. The implications and utility of the results are illustrated. The methodology developed can be extended to predict stability margins and optimize control parameters for controlled translating beams with other types of boundary conditions and controller structures. [S0022-0434(00)00702-4]

Theoretical analysis of the pressure oscillation phenomena in capillary pumped loop

Based on the physical model of capillary pumped loop (CPL) system, the phenomena of pressure oscillation are simplified and analyzed. From a set of non-linear differential equations, the influence of system parameters on the performance of the CPL is discussed, including the working temperature (the set point), loop resistance, vapor volume etc. From the analysis, some measures were taken to improve the performance of the loop. Meanwhile, the reason why the deprive of the CPL occurs during the operation is given by analyzing the theoretical calculation results.

Uptake of copper and cobalt in a complexing resin: shrinking-core model with two reaction fronts

The kinetics of simultaneous ion exchange of copper and cobalt with iminodiacetic chelating resins has been studied. Microscopic studies of the ion-exchange process clearly show two different reaction fronts allowing the use of shrinking-core type models. The influence of system parameters is studied both theoretically and experimentally. Experimental results obtained at different total ion concentrations for various copper-cobalt ratios and particle diameters are reasonably predicted by the shrinking-core model, allowing diffusivity calculations.

Optimisation Of The Kinetics Of The Stereoselective Reduction Of Geraniol To Citronellol In A Two Liquid Phase System

Kinetics of the stereoselective reduction of geraniol to citronellol by baker's yeast (Saccharomyces cerevisiae) were studied by examining the influence of system parameters on the reaction rate in an aqueous/organic two phase system. This system was used due to the hydrophobic nature of the reactant and product, and enabled simple and accurate measurement of the kinetics, and hence optimisation. This reaction system provided “pseudo steady state” aqueous conditions in batch experiments over short time periods, and therefore allowed direct determination of the biotransformation rate. The maximum biotransformation activity was determined to be 300 nmol min-1 g biomass-1. Of the parameters tested those which most significantly affected the biocatalytic activity were; biomedium pH, reactant concentration, solvent type, and aeration. The optimum pH was found to be 9.5, and this was associated with increased intra-cellular NADPH concentrations. Slight substrate inhibition with geraniol occurred at concentrations above 0.3 g/l in the aqueous phase. The effect of the solvent phase on biocatalytic activity was in general accordance with previous work: solvents with high log P resulted in greatest activity, and the transition value occurred between 4.5 and 5.6. Finally, maximum biotransformation activity was only exhibited when the bioreactor was aerated, however, the reason for this was not established.

Ignition of Non–Premixed Wall–Bounded Boundary–Layer Flows

Ignition of non–premixed boundary–layer flows over a hot wedge–type porous wall with fuel injection is analyzed mathematically and numerically. The free–stream fluid is a diluted oxidizer such as air. An ignition criterion corresponding to the condition for lower vertical tangency on an S-shaped ignition–extinction response curve is derived by the method of large activation energy asymptotics. This ignition criterion depends on all relevant system parameters such as flow conditions, thermophysical properties (Pr, SCo and Scf) and the overall chemical kinetic mechanism of reactants. The relative sensitivity of system parameters affecting the ignition is investigated. In particular, the influence of system parameters on the transition from the kinetically controlled to the diffusionally controlled ignition mechanism is studied. Numerical calculations are also performed to compare with the asymptotic results. The asymptotic solutions are found to be in good qualitative agreement with numerical solutions.

Numerical simulation of active suppression of rotating stall in axial compression systems

In the present paper, a theoretical model is proposed to analyze the transient behavior of suppression of rotating stall in axial compression systems through the use of an additional disturbance. The governing equations of the model are a set of simultaneous nonlinear first order partial differential equations, and for numerical calculations, a simple explicit time marching method can be used. The influence of system parameters on the suppression effectiveness and the interaction between rotating stall and surge have been discussed initially. The analysis of the influence of system parameters presents that both theB parameter and axisymmetric compressor characteristic have significant effect on the stabilization effectiveness of a control strategy. The effectiveness decreases as the value ofB and the number of stages or stage loading of the compressor increase. It has been found that the onset flow rate of rotating stall and surge in a compression system may be different, and there is a strong interaction between these two kinds of instabilities. The onset flow rate of pure one dimensional surge depends on the value ofB and axisymmetric compressor characteristic, besides the slope of the compressor characteristic. In some cases, when rotating stall which is the natural mode of instability in a compression system is suppressed, one dimensional surge can occur. It often limits the effectiveness of a control strategy to suppress rotating stall. But when surge is initiated by rotating stall, it is also possible to inhibit the occurrence of surge by suppressing rotating stall in a compression system.

Parameter variation methods for cell mapping

In the study of nonlinear dynamic systems, the influence of system parameters on the long term behaviour plays an important role. In this paper, parameter variation methods are presented which can be used when investigating a nonlinear dynamic system by means of simple or interpolated cell mapping. In the case of coexisting attractors, the proposed methods determine the evolution of the basin boundaries when a system parameter is varied. Application of the methods to a modified Duffing equation is performed. It is concluded that the proposed methods are very efficient and accurate.

Optimization of polling systems with Bernoulli schedules

Many computer-communication networks in which the transmission right is circulated among the nodes have been modeled as polling systems. This paper concerns optimization of cyclic polling systems with respect to the service disciplines at the nodes. The service disciplines are chosen to be Bernoulli schedules. Because the optimization problem is not analytically tractable, a numerical approach to determine the optimal schedule, based on the power-series algorithm, is discussed. Light- and heavy-traffic asymptotes of the optimal schedule are presented; they are based on light-traffic asymptotes of the mean waiting times and the stability condition, respectively. A partial solution of the optimization problem is given; this follows directly from the μc-rule for priority systems. The influence of system parameters on the optimal Bernoulli schedule is examined. Finally, a fast approach to approximate the optimal schedule is presented and tested.

A non-stationary stochastic model for periodic excitation with random phase modulation

The paper presents a non-stationary stochastic model for periodic excitation with random phase modulation, where the phase modulation is modeled as a modulated stationary. Gaussian process. Applications of the model are demonstrated by analysis of response of a single-degree-of-freedom (SDOF) system under such an excitation. The response is, in general, non-Gaussian. Cases of step, rectangular, and exponential envelopes are considered in the present study. The nonstationary second and fourth order moments are calculated by numerically solving the transient moment equations. Non-Gaussianity of the response is studied in terms of the non-stationary excess factor. Some numerical results are presented. The influences of system parameters, build-up and decay rates as well as duration of random phase modulation on the moment response of the SDOF system are discussed.

Steady-State Response of the System which Consists of Shear Loading Rubber Isolators and a Mass

In order to find the mechanism of the steady-state response of a system which consists of shear loading rubber isolators and a mass, experiments for the steady-state frequency response of the system and dynamic tests for the rubber vibration isolators are conducted under the various conditions of ambient temperature and strain amplitude, and the results are considered and discussed. As a result, it is found that the amplitude and temperature response of the system interact via the temperature-dependent dynamic properties and the internal heat-generation rate of the vibrating rubber isolator. On the basis of this result, a new method for the analysis of the steady-state response of the system is presented. Using this method, the influence of system parameters on the response is also discussed.

A Finite Element Model of Railway Track and its Application to the Wheel Flat Problem

To study the dynamic interactions between the railway vehicle and track, a finite element model of infinitely long track is developed. The track is represented by a Timoshenko beam on discrete pad-tie-ballast supports. The non-linear factors such as loss of wheel-rail contact, rail lift-off from the tie and tie lift-off from the ballast are taken into account. A multi-point wheel-rail contact model is also proposed. The dynamic forces on the track and the strains on the rail are directly calculated from the model. The vehicle could travel on the track forever with an arbitrary time-dependent speed. The steady-state response of a vehicle-track system for a perfect wheel carrying a constant load and travelling at a constant speed over a track with no irregularities is studied using the finite element model and is presented. The impact loads due to wheel flats are also studied with this model. The results show a good correlation with the experimental data available in the literature. Influences of system parameters on the impact loads due to a wheel flat are also investigated. T***he results show that the axle load and vehicle speed are the important factors affecting the wheel-rail impact loads. The impact forces transferred from the rail to the tie are strongly affected by the pad stiffness and tie mass.

CPFSK Spectrum in a Heterodyne Receiver with Delay Demodulation

The power spectral density of a continuous phase FSK signal, including additive and phase noise, is derived in a systematical way for a heterodyne receiver with delay demodulation. The power spectrum is given at two important points in the receiver: before and after the delay demodulator. The mathematical model can be used to investigate the influence of system parameters on the power spectrum. As examples are chosen the laser phase and the demodulator delay time

Bifurcation theory and its application to nonlinear dynamical phenomena in an electrical power system

A tutorial introduction in bifurcation theory is given, and the applicability of this theory to study nonlinear dynamical phenomena in a power system network is explored. The predicted behavior is verified through time simulation. Systematic application of the theory revealed the existence of stable and unstable periodic solutions as well as voltage collapse. A particular response depends on the value of the parameter under consideration. It is shown that voltage collapse is a subset of the overall bifurcation phenomena that a system may experience under the influence of system parameters. A low-dimensional center manifold reduction is applied to capture the relevant dynamics involved in the voltage collapse process. The need for the consideration of nonlinearity, especially when the system is highly stressed, is emphasized. >

SOLUTIONS INCORPORATING MAGNETIC HYSTERESIS TO THE SUBHARMONIC PROBLEM IN POWER SYSTEMS

ABSTRACT One possibility of taking care of the subharmonics in high speed protection is to filter the fundamental frequency components from the fault transients and use them for fault detection and discrimination. This is correct only if the phases and amplitudes of fundamental components during and post-subharmonic periods remain the same in transient waveforms. An attempt is therefore made to establish this aspect by a detailed study of a typical electrical network presenting subharmonics. The Dual Input Describing Function is adopted to show the subharmonic boundaries and the influence of system parameters on subharmonic oscillations. Magnetic hysteresis is incorporated in the analysis. A fifth order nonlinearity and one-third subharmonic are assumed. The theory could be easily extended to any order of nonlinearity and to any subharmonic frequency and also to a combination of subharmonics. The analysis gives a set of nonlinear algebraic equations. These equations are solved by Newton's technique using ...

Application of flow injection potentiometry to the determination of chloride in various matrices

The preparation and performance of a tubular chloride ion selective electrode for flow injection potentiometry is presented. The influence of system parameters on sensitivity, detection limit, response time and sample throughput are investigated. It is shown that 60–200 samples can be processed per hour within the concentration range 0.1–10,000 mg/l. The precision is generally better than 1% r.s.d. over the entire range. Application of the proposed method to analysis of tap and mineral water, emission control of hydrogen chloride and the determination of chloride in pure silicon nitride is shown to give results very well comparable to other methods.

Sensitivity Analysis of Vehicle Design Attributes in Frequency Domain

SUMMARY This paper presents a procedure for determining the sensitivity matrices of a vehicle dynamic system in the frequency domain as derivatives of the transfer function matrix with respect to system parameters. First and second order logarithmic sensitivity functions which possess normalized coefficients have been introduced to enhance analysis. The sensitivity analysis of amplitude-frequency characteristics on changes of selected parameters of a 3 degree-of-freedom vehicle handling model has been performed. It has been demonstrated that the general sensitivity measure proposed can be used to determine the combined influence of system parameters divided into groups such as design, environmental, driver, kinematic, etc., on the multi-parameter system response, prior to determining their order of influence within the groups.

Basic Characteristics of Cycloconverter for Linking Commercial and High-Frequency Distribution Lines

A new method to improve the power factor and current waveform on the commercial ac system is proposed. The frequency of a local distribution line in a factory or a chemical plant is made high, up to about 500 Hz. The local distribution line is linked directly to the commercial line by using a cycloconverter operating in circulating current mode. Quasi-sinusoidal current with unity displacement factor is realized on the commercial line side regardless of the consumed power by loads. The system configuration and the basic principle of operation of the cycloconverter for linking both lines are described. The influence of system parameters on the operation limit is investigated based on the power equilibrium constraints. Experimental results obtained in the 5.2KVA laboratory system show the validity of the proposed system.

Mass transfer in pure lithium and lithium-lead dynamic environments: Influence of system parameters

Test campaigns have been performed in forced and thermal convection loops filled with pure lithium or the Li17Pb83 eutectic alloy. Mass transfer rates and microstructural changes observed for structural materials exposed to these environments have been rationalized in terms of the loop geometries, operation conditions and purification systems. Variation of these parameters have been found to have a larger effect on the corrosion damage development than more traditional parameters such as the hot leg temperature or the temperature difference between the hot and cold legs of the test loop.