scholarly journals Estimating Participation Factors and Mode Shapes for Electromechanical Oscillations in Ambient Conditions

2018 ◽  
Author(s):  
Xiaozhe Wang ◽  
Ilias Zenelis
Keyword(s):  
Mode Shapes ◽  
Ambient Conditions ◽  
Electromechanical Oscillations

Application of partial eigenvalue assignment techniques to dampen electromechanical oscillations in multi-machine power systems

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Erick Baleeiro da Silva ◽  
José Mário Araújo
Keyword(s):  
Power Systems ◽  
The Other ◽  
Mode Shapes ◽  
Eigenstructure Assignment ◽  
Power System Stabilizers ◽  
Control Effort ◽  
Electromechanical Oscillations ◽  
Oscillation Modes ◽  
Partial Controllability

AbstractIn this study, a methodology for partial eigenstructure assignment (PEVA) is applied to dampen electromechanical oscillations in electrical multi-machine power systems. The approach is anchored in allocating a small number of undesirable eigenvalues, for example, which are poorly damped, preserving the other eigenvalues in the system - the so-called no-spillover spectrum. The new position of the selected eigenvalues is carried out based on the partial controllability analysis of the system, in order to minimize the control effort. Simulation examples using a system with 68 buses, 16 generators and five areas showed that the presented methodology is efficient in dampening the local and inter-area oscillation modes when compared to the classic power system stabilizers (PSS). The quality of the solution is illustrated through computer simulations, eigenvalues tables and mode-shapes.

Role of Dynamic Testing in Assessment of Bridges

1997 ◽  
Vol 1594 (1) ◽  
pp. 115-124 ◽  
Author(s):  
P. C. Das ◽  
J. S. Owen ◽  
B. J. Eccles ◽  
M. A. Woodings ◽  
B. S. Choo
Keyword(s):  
Reinforced Concrete ◽  
Natural Frequencies ◽  
Concrete Beams ◽  
Dynamic Testing ◽  
Reinforced Concrete Beams ◽  
Mode Shapes ◽  
Ambient Conditions ◽  
Frequency Changes ◽  
Frequency Ratios

Six reinforced concrete beams were loaded incrementally up to failure. After each increment the load was removed and measurements of the modal properties of the beams were made by impulse testing. The variation of the natural frequencies, frequency ratios, mode shapes, and the level of damage were investigated. It was found that on completion of the tests the natural frequencies of the beams had been reduced by an average of 25 percent in each mode. However, changes in mode shape were very small, and appreciable differences were only observed when the damage was highly localized. Modeling of the beam by using finite elements predicted trends that compared well with experimental observations. It is concluded that if dynamic testing were used in monitoring reinforced concrete structures, then the changes in frequency due to initial concrete cracking or yield of the reinforcement could be detected. More useful information associated with the spread and type of cracking through a structure may be detectable, although the level of the frequency changes is of the same order as those due to changes in ambient conditions.

Sensitivity Study on Damage Indexes of Cable-Stayed Bridges

2011 ◽  
Vol 243-249 ◽  
pp. 1573-1577 ◽  
Author(s):  
Wei Peng ◽  
Zhi Xiang Zha
Keyword(s):  
Structural Parameters ◽  
Sensitivity Study ◽  
Mode Shapes ◽  
Ambient Conditions ◽  
Engineering Project ◽  
Modal Damping ◽  
Stress Energy ◽  
Modal Curvature ◽  
Bridge Damage ◽  
Cable Stayed Bridges

Damages in a structure alter its static and dynamic characteristics. These changes occur in some structural parameters such as the mass, the stiffness, the flexibility and the damping matrices of the structure and can be characterized by changes in the modal parameters, i.e., modal frequencies, modal damping values and mode shapes, and their derivatives, such as the modal curvature and modal stress energy. According to the properties of cable-stayed bridges, various damage indexes of static and dynamic are constructed to indicate damage of cable, tower and girder respectively. A comprehensive index accounting for their interaction and the whole bridge damage is presented which is robust to measurement noises and uncertainties in ambient conditions. The sensitivities of these damage indexes are illustrated by numerical studies. The effectiveness of the proposed damage detection method of cable-stayed bridges is demonstrated through an engineering project.

Hydrogen bonding in liquid methanol at ambient conditions and at high pressure

2000 ◽  
Vol 98 (3) ◽  
pp. 125-134 ◽  
Author(s):  
T. Weitkamp, J. Neuefeind, H. E. Fisch
Keyword(s):  
High Pressure ◽  
Hydrogen Bonding ◽  
Ambient Conditions

Hybrid Micro-Optical Sensors via Sol-Gel Soft Lithography

2000 ◽  
Vol 628 ◽  
Author(s):  
Mark A. Clarner ◽  
Michael J. Lochhead
Keyword(s):  
Optical Sensors ◽  
Soft Lithography ◽  
Sol Gel ◽  
Silica Gels ◽  
Ph Sensing ◽  
Ambient Conditions ◽  
Sensor Applications ◽  
Patterned Structures ◽  
Biological Functionality ◽  
Indicator Dyes

ABSTRACTOrganically modified silica gels and dye-doped silica gels have been patterned into micrometer-scale structures on a substrate using micro molding in capillaries (MIMIC). This approach is from a class of elastomeric stamping and molding techniques collectively known as soft lithography. Soft lithography and sol-gel processing share attractive features in that they are relatively benign processes performed at ambient conditions, which makes both techniques compatible with a wide variety of organic molecules, molecular assemblies, and biomolecules. The combination of sol-gel and soft lithography, therefore, holds enormous promise as a tool for microfabrication of materials with optical, chemical, or biological functionality that are not readily patterned with conventional methods. This paper describes our investigation of micro-patterned organic-inorganic hybrid materials containing indicator dyes for microfluidic sensor applications. Reversible colorimetric pH sensing via entrapped reagents is demonstrated in a prototype microfluidic sensor element. Patterned structures range from one to tens of micrometers in cross-section and are up to centimeters in length. Fundamental chemical processing issues associated with mold filling, cracking and sensor stability are discussed.

Tire Vibrations

1977 ◽  
Vol 5 (4) ◽  
pp. 202-225 ◽  
Author(s):  
G. R. Potts ◽  
C. A. Bell ◽  
L. T. Charek ◽  
T. K. Roy
Keyword(s):  
Natural Frequencies ◽  
Standing Waves ◽  
Resonant Mode ◽  
Mode Shapes ◽  
Resonant Vibrations ◽  
Resonant Frequencies ◽  
Radial Tire ◽  
Analysis Techniques ◽  
Thin Ring ◽  
Good Agreement

Abstract Natural frequencies and vibrating motions are determined in terms of the material and geometric properties of a radial tire modeled as a thin ring on an elastic foundation. Experimental checks of resonant frequencies show good agreement. Forced vibration solutions obtained are shown to consist of a superposition of resonant vibrations, each rotating around the tire at a rate depending on the mode number and the tire rotational speed. Theoretical rolling speeds that are upper bounds at which standing waves occur are determined and checked experimentally. Digital Fourier transform, transfer function, and modal analysis techniques used to determine the resonant mode shapes of a radial tire reveal that antiresonances are the primary transmitters of vibration to the tire axle.

Effect of Bass Bar Tension on Modal Parameters of a Violin's Top Plate

2015 ◽  
Vol 39 (1) ◽  
pp. 145-149 ◽  
Author(s):  
Ewa B. Skrodzka ◽  
Bogumił B.J. Linde ◽  
Antoni Krupa
Keyword(s):  
Modal Analysis ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Normal Value ◽  
Modal Damping

Abstract Experimental modal analysis of a violin with three different tensions of a bass bar has been performed. The bass bar tension is the only intentionally introduced modification of the instrument. The aim of the study was to find differences and similarities between top plate modal parameters determined by a bass bar perfectly fitting the shape of the top plate, the bass bar with a tension usually applied by luthiers (normal), and the tension higher than the normal value. In the modal analysis four signature modes are taken into account. Bass bar tension does not change the sequence of mode shapes. Changes in modal damping are insignificant. An increase in bass bar tension causes an increase in modal frequencies A0 and B(1+) and does not change the frequencies of modes CBR and B(1-).

Fluorescence of BODIPY Dyes in Gas Phase at near Ambient Conditions

2020 ◽  
Author(s):  
Kseniya A. Mariewskaya ◽  
Denis Larkin ◽  
Yuri Samoilichenko ◽  
Vladimir Korshun ◽  
Alex Ustinov
Keyword(s):  
Gas Phase ◽  
Molecular Interactions ◽  
Atmospheric Pressure ◽  
Fluorescence Spectra ◽  
Visible Range ◽  
Intrinsic Properties ◽  
Ambient Conditions ◽  
Ideal Model ◽  
Molecular Fluorescence ◽  
Tesla Coil

Molecular fluorescence is a phenomenon that is usually observed in condensed phase. It is strongly affected by molecular interactions. The study of fluorescence spectra in the gas phase can provide a nearly-ideal model for the evaluation of intrinsic properties of the fluorophores. Unfortunately, most conventional fluorophores are not volatile enough to allow study of their fluorescence in the gas phase. Here we report very bright gas phase fluorescence of simple BODIPY dyes that can be readily observed at atmospheric pressure using conventional fluorescence instrumentation. To our knowledge, this is the first example of visible range gas phase fluorescence at near ambient conditions. Evaporation of the dye in vacuum allowed us to demonstrate organic molecular electroluminescence in gas discharge excited by electric field produced by a Tesla coil.

Sign in / Sign up

Export Citation Format

Share Document