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There are several approaches to the prediction of global deckhouse vibration where the deckhouse natural frequencies lie close to the blade rate exciting frequencies. This paper discusses several approaches and recommends the eigenvalue analysis procedures as the most useful design tool for the early prediction of deckhouse vibration problems. Three eigenvalue analysis procedures are presented: the Hirowatari method—an empirical approach; the simplistic modeling method—a simple analytical approach; and the finite-element method—a more sophisticated analytical approach. The need for simplicity and accuracy is emphasized. Two example problems are included to demonstrate the merits of the eigenvalue analysis procedures.

A generalized formulation for the analysis of doubly curved shell structures using the finite element method has been described in a previous paper. The results of the eigenvalue analysis performed for an isotropic shell element have been presented to show proper inclusion of six rigid body modes. One paraboloid of revolution shell problem using this formulation has been solved with three different mesh sizes and taking three different values of Poisson's ratio. A comparative study of the results with those of earlier investigators, along with the effects of Poisson's ratio on the values of the shell actions, has been made.

Increasingly, business firms will be disclosing management forecasts in financial reports to investors. Single estimates based on a consensus view (e.g., Delphi estimates) may be used. It seems logical, however, to consider methods that seek formally to derive internally consistent subjective views regarding the sensitivity of assumptions and interacting events on forecasts. The major purpose of this paper is to extend micro-level cross-impact analysis to a macro-level eigenvalue analysis approach that elicits views of the effects of assumptions and interaction events on entire scenarios. Both methods are illustrated and contrasted. They are complementary rather than alternative methods. In particular, each method offers some potential in the development of operational guidelines for elicitation and reporting of management forecasts. In addition, the eigenvalue analysis offers several key advantages that make it potentially useful in preparing entire scenario forecasts.

This paper utilizes the eigenvalue analysis in identifying model parameters and selecting their appropriate values to obtain a stable system response in the production-stock problem of Coyle. The model is first assumed to be in steady-state equilibrium. This obviates the need for the delays in physical flows and the smoothing levels in the information flows, and helps in converting an eight-order model into a second-order model. Applying the eigenvalue analysis to select appropriate parameter values, it is shown that the initial policy set, which was rejected by Coyle because it produced undesirable, explosive oscillations, can result in extremely good model behaviour. The model behaviour so obtained has been found to be superior even to that obtained with the final policy of Coyle.

This paper presents an efficient FEM eigenvalue analysis technique for symmetrically laminated composite plates by using a personal computer. In order to realize the analysis on a personal computer, a 12 d. o. f. ACM element considering the anisotropic behavior of symmetrically laminated composite is formulated and a subspace iteration algorithm is used for the analysis. A shaking test using CFRP symmetrically laminated composite plates is performed to prove the effectiveness of the method. It has been shown from the study that the proposed technique could be of practical use for plates with a wide variety of fiber angle and dynamic coupling between bending and torsion.

A study of the effects of induction motor load on the dynamic stability of power systems is presented in this paper. The power system is modelled as a multivariable system with load dynamics considered in the feedback path. The induction motor is represented by a transfer function matrix relating bus voltage magnitude and frequency to the active power and reactive power of the motor Multivariable Nyquist criterion and eigenvalue analysis are used to investigate the effects of induction motor dynamics on system stability

This paper presents a numerical approach useful for determining the modes of transient response of a synchronous generator. The approach is based upon the Floquet theory of periodic time-variable systems. A computer algorithm for system transition matrix eigenvalue analysis is described and applied to a three-phase synchronous machine.

Frequently in the analysis of the steady state stability of a power system large portions of the system remain unchanged while parameters in one or a few machines and their associated control systems are altered and the effect on the total system examined. The section of the system in which the parameters are to be altered can be designated as the study system while the remainder of the system can be designated as the external system. This paper describes a procedure to form a low order mathematical equivalent of the external system which can be simply linked to a complete model of the study system. Stability can then be determined by an eigenvalue analysis of the resulting lower order system.

The paper presents an initial post buckling analysis for the rotationally symmetric branching of a cylindrical shell with a free edge following the linear eigenvalue analysis of Ashwell. The shell is supposed to be infinitely long and a closed form solution is obtained for the initial curvature of the post buckling path. This curvature is seen to be negative and more severe than that of the corresponding classical solution. The solution is shown to be relevant to the buckling of a cracked concrete shell such as a cooling tower.

Because of the very large matrices arising in dynamic analyses problems treated by the finite element method, approximate methods have to be used for eigenvalue determinations. In this paper a method for obtaining accurate error bounds for eigenvalue analysis by elimination of variables is described. The method is based on theorems of Kato and Temple. It has been applied to a large scale problem: namely a delta wing for which both numerical and experimental analyses are available. The results showed that loss of accuracy for the lower modes was negligible.

Galerkin (spectral) methods for numerical simulation of incompressible flows within simple boundaries are shown to possess many advantages over existing finite-difference methods. In this paper, the accuracy of Galerkin approximations obtained from truncated Fourier expansions is explored. Accuracy of simulation is tested empirically using a simple scalar-convection test problem and the Taylor–Green vortex-decay problem. It is demonstrated empirically that the Galerkin (Fourier) equations involving Np degrees of freedom, where p is the number of space dimensions, give simulations at least as accurate as finite-difference simulations involving (2N)p degrees of freedom. The theoretical basis for the improved accuracy of the Galerkin (Fourier) method is explained. In particular, the nature of aliasing errors is examined in detail. It is shown that ‘aliasing’ errors need not be errors at all, but that aliasing should be avoided in flow simulations. An eigenvalue analysis of schemes for simulation of passive scalar convection supplies the mathematical basis for the improved accuracy of the Galerkin (Fourier) method. A comparison is made of the computational efficiency of Galerkin and finite-difference simulations, and a survey is given of those problems where Galerkin methods are likely to be applied most usefully. We conclude that numerical simulation of many of the flows of current interest is done most efficiently and accurately using the spectral methods advocated here.

In this paper, on the basis of matrix splitting, two preconditioners are proposed and analyzed, for nonsymmetric saddle point problems. The spectral property of the preconditioned matrix is studied in detail. When the iteration parameter becomes small enough, the eigenvalues of the preconditioned matrices will gather into two clusters—one is near (0,0) and the other is near (2,0)—for the PPSS preconditioner no matter whether A is Hermitian or non-Hermitian and for the PHSS preconditioner when A is a Hermitian or real normal matrix. Numerical experiments are given, to illustrate the performances of the two preconditioners.

This study is intended to develop an analytical approach to simulate the coupled vibration of bridges and running vehicles, and to investigate the dynamic characteristics of rationalized curved bridges. In this paper, a curved twin Igirder bridge with general cross-section is adopted for the analysis. As a preliminary step, a general large dump truck with one axis at front and two axes at rear is modeled as a sprung-mass system with 2-degree-of-freedom for the vehicle-bridge interaction analysis. The coupled vibration of the interaction system is formulized and a computer program is developed. Eigenvalue analyses are carried out for different types of bridges to find acceptable torsional stiffness. The coupled vibration of the running vehicle and the bridge is simulated using the developed analytical approach, based on which the dynamic responses of the curved bridge are evaluated.

The ITER pulsed power electrical network (PPEN) supplies the superconducting magnets and the heating and current drive systems. During the experimental pulses, about several hundreds of seconds long, active power consumption of 500 MW and reactive one of 950 Mvar are expected. The ITER power supply system is very large and complex, and a careful design is required to assure a safe operation. Stability of ITER PPEN has been already investigated in recent studies by numerical simulation and analytical methods. Now, a new dynamic analytical model of the ITER power supply system is being developed, based on the state-space theoretical approach, which allows the application of the linear control theory to study the stability of the whole system. For each subsystem of the ITER power supply, a state-space model was developed, and in this paper, the ac/dc converter model is presented and validated for six and twelve pulse operation, and circulating current mode.

This paper presents the deterministic and stochastic model for a linear compartment system with constant coefficients, and it develops expressions for the mean residence times (MRT) and the variances of the residence times (VRT) for the stochastic model. The expressions are relatively simple computationally, involving primarily matrix inversion, and they are elegant mathematically, in avoiding eigenvalue analysis and the complex domain. The MRT and VRT provide a set of new meaningful response measures for pharmacokinetic analysis and they give added insight into the system kinetics. The new analysis is illustrated with an example involving the cholesterol turnover in rats.

In this paper the problem of designing structure and parameter of power system controllers is discussed. Appropriate Computers-Aided engineering tools are presented. The effectiveness of the design procedure is illustrated by the example of damping control design in compound ac/hvdc-power systems. Eigenvalue analysis of the linearized power system model lead to a decentralized control structure but it showed that both, active and reactive damping control loops, have to be considered during parameter optimization.

This paper focuses on the problem of stability in homogeneous systems with dilation. First, we propose an ‘homogeneous eigenvalue’ for homogeneous systems. Next, we analyze the stability of homogeneous systems using homgeneous eigenvalues, and we show that the use of positive real homogeneous eigenvalues implies instability. Finally, we show the effectiveness of the proposed method through an example.

Nowadays, there is a huge potential for power generation from offshore wind farms, with the North Sea constituting the central point for offshore wind power deployment. In order to integrate the latter into the mainland transmission system, DC interconnection forming multi-terminal HVDC (MTDC) transmission systems can be used. Currently, only PtP HVDC links are in operation, including BorWin, DolWin, HelWin and SylWin projects. However, MTDC transmission systems are expected to be built in the near future. As an example, COBRAcable between Denmark and the Netherlands is planned to become an MTDC system, where a possible expansion can be realized with the addition of an offshore converter along its cable. The expansion introduces challenges in the operation of the three-terminal system, including its control strategies. As explained in CIGRE WG D2.35, HVDC systems can work together with the control function of Power Oscillation Damping (POD), which consists in modulating the transferred power through the HVDC link in order to provide damping to low frequency power oscillations within either or both of interconnected AC systems.Although the POD control is well established for PtP schemes, there is room for further research regarding its application in MTDC systems, which create challenges in the design and tuning of the POD function. For example, when a PtP system is to be connected to an offshore wind terminal, the effect of the wind farm output power profile on the power oscillation damping capability has to be investigated and the POD function has to be adapted in order to provide adequate damping for the three-terminal system. This paper initially presents the design and application of a POD controller to a PtP system. Afterwards, the aforementioned issues are adressed: An AC two-area test system is used to introduce a three-phase fault and a PtP HVDC link is connected in parallel in order to damp its oscillations. An offshore wind farm is connected to it and the influence of the various wind turbine output profiles on the POD performance is analyzed for two control modes of the onshore converters, i.e. master-slave and DC voltage droop. The POD controller is shown to provide larger damping for operation in master-slave mode. It is observed that the decreased production of the traditional generators involved in the interarea power exchange results in increased damping. In addition, it is shown that the rate of change of the wind power output has negligible effect on the controller’s damping performance, which is proved to reduce when the existing controller is applied to the system operated in droop control mode. Thus, a modification in its tuning is proposed in order to damp the oscillations effectively. The results show that the damping performance is improved, opening more possibilities for use of MTDC-HVDC links during emergency operation.

The paper traces the background, conditions and system study work leading to the development of analytical techniques currently in use for system damping evaluation in England and Wales. The early study work, providing indications of possible low-frequency electromechanical oscillations, is examined together with the early simplified models used for eigenvalue analysis evaluating the damping behaviour of the system during such oscillations. The mechanism producing negative damping of such low frequency electromechanical oscillations is analysed. The development of the detailed eigenvalue analysis program package PRASM currently in use by the CEGB is described in detail. Finally, sample results from the extensive analysis carried out on the CEGB/SSEB oscillation incidents of December 1978-January 1979, utilising the PRASM program package, are given with commentary on likely future developments.

The justification for the installation of power system stabilisers at selected Scottish power stations is outlined. The selection process, specification and design criteria for these stabilisers are detailed and the eigenvalue analysis to achieve optimum gain settings and margins is explained. The paper proceeds to illustrate the theoretical improvement in interarea damping and to explore the errors which can be introduced by modelling a multiplicity of identical sets by a single equivalent machine. Finally, the studies where three generating sites have stabilisers in service indicate scope for further co-ordination to optimise the improvement.