A Faraday rotation search for magnetic fields in quasar damped Ly alpha absorption systems
Oren, Abraham L.; Wolfe, Arthur M.
1995-01-01
We present the results of a Faraday rotation survey of 61 radio-bright QSOs conducted at the National Radio Astronomy Observatory (NRAO) Very Large Array (VLA). The Galactic contribution to the Faraday rotation is estimated and subtracted to determine the extragalactic rotation measure (RRM) for each source. Eleven of these QSOs are known to exhibit damped Ly alpha absorption. The rate of incidence of significant Faraday rotation of these 11 sources is compared to the remaining 50 and is found to be higher at the 99.8% confidence level. However, as this is based upon only two detections of Faraday rotation in the damped Ly alpha sample, the result is only tentative. If the two detections in the damped Ly alpha sample are dug to the absorbing systems, then the inferred rotation measure induced by these systems is roughly 250 rad/sq m. The two detections were for the two lowest redshift absorbers in the sample. We find that a rotation measure of 250 rad/sq m would have gone undetected for any other absorber in the damped Ly alpha sample due to the 1/(1 + 2) squared dilution of the observed RRM with redshift. Thus the data are consistent with, but do not prove, the hypothesis that Faraday rotation is a generic property of damped Ly alpha absorbers. We do not confirm the suggestion that the amplitude of RRMs increases with redshift. Rather, the data are consistent with no redshift evolution. We find that the uncertainty in the estimation of the Galactic rotation measure (GRM) is a more serious problem than previously realized for extra-galactic Faraday rotation studies of QSO absorbers. A careful analysis of current methods for estimating GRM indicate that it can be determined to an accuracy of about 15 - 20 rad/sq m. Previous studies underestimated this uncertainty by more than a factor of 2. Due to this uncertainty, rotation measures such as we suspect are associated with damped Ly alpha absorption systems can only be detected at redshifts less than z approximately
HI column density distribution function at z=0 : Connection to damped Ly alpha statistics
Zwaan, Martin; Verheijen, MAW; Briggs, FH
We present a measurement of the HI column density distribution function f(N-HI) at the present epoch for column densities > 10(20) cm(-2). These high column densities compare to those measured in damped Ly alpha lines seen in absorption against background quasars. Although observationally rare, it
The z = 0.8596 damped Ly-alpha absorbing galaxy toward PKS 0454+039
Steidel, Charles C.; Bowen, David V.; Blades, J. Chris; Dickenson, Mark
1995-01-01
We present Hubble Space Telescope (HST) and ground-based data on the Z(sub abs) = 0.8596 metal-line absorption system along the line of sight to PKS 0454+0356. The system is a moderate-redshift damped Ly-alpha system, with N(H I) = (5.7 +/- 0.3) x 10(exp 20)/sq cm as measured from the Faint Object Spectrograph (FOS) spectrum. We also present ground-based images which we use to identify the galaxy which most probably gives rise to the damped system; the most likely candidate is relatively underluminous by QSO absorber standards M(sub B) approximately -19.0 for A(sub 0) = 0.5 and H(sub 0) = 50 km/s/Mpc) and lies approximately 8.5/h kpc in projection from the QSO sight line. Ground-based measurements of Zn II, Cr II, and Fe II absorption lines from this system allow us to infer abundances of (Zn/H) = -1.1, (Cr/H) = -1.2, and (Fe/H) = -1.2 indicating overall metallicity similar to damped systems at z is greater than 2, and that the depletion of Cr and Fe onto dust grains may be even less important than in many of the high-redshift systems of comparable metallicity. Limits previously placed on the 21 cm optical depth in the z = 0.8596 system, together with our new N(H I) measurement, suggest a very high spin temperature for the H I, T(sub s) is greater than 580 K.
Clustering of galaxies near damped Lyman-alpha systems with (z) = 2.6
Wolfe, A. M
1993-01-01
The galaxy two-point correlation function, xi, at (z) = 2.6 is determined by comparing the number of Ly-alpha-emitting galaxies in narrowband CCD fields selected for the presence of damped L-alpha absorption to their number in randomly selected control fields. Comparisons between the presented determination of (xi), a density-weighted volume average of xi, and model predictions for (xi) at large redshifts show that models in which the clustering pattern is fixed in proper coordinates are highly unlikely, while better agreement is obtained if the clustering pattern is fixed in comoving coordinates. Therefore, clustering of Ly-alpha-emitting galaxies around damped Ly-alpha systems at large redshifts is strong. It is concluded that the faint blue galaxies are drawn from a parent population different from normal galaxies, the presumed offspring of damped Ly-alpha systems.
The z=0.0912 and z=0.2212 damped Ly alpha galaxies along the sight line toward the quasar OI 363
Turnshek, DA; Rao, S; Nestor, D; Lane, W; Monier, E; Bergeron, J; Smette, A
2001-01-01
New optical and infrared observations along the sight line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding quasars selectively observed because they were known to be located behind gas-rich galaxies and systems which lack confirming UV spectroscopic observations of the
Ly-alpha polarimeter design for CLASP rocket experiment
Kubo, M.; Watanabe, H.; Narukage, N.; Ishikawa, R.; Bando, T.; Kano, R.; Tsuneta, S.; Kobayashi, K.; Ichimoto, K.; Trujillo Bueno, J.; Song, D.
2011-12-01
A sounding-rocket program called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is proposed to be launched in the Summer of 2014. CLASP will observe the upper solar chromosphere in Ly-alpha (121.567 nm), aiming to detect the linear polarization signal produced by scattering processes and the Hanle effect for the first time. The CLASP needs a rotating half-waveplate and a polarization analyzer working at the Ly-alpha wavelength to measure the linear polarization signal. We select Magnesium Fluoride (MgF2) as a material of the optical components because of its birefringent property and high transparency at UV wavelength. We have confirmed that the reflection at the Brewster's Angle of MgF2 plate is a good polarization analyzer for the Ly-alpha line by deriving its ordinary refractive index and extinction coefficient along the ordinary and extraordinary axes. These optical parameters are calculated with a least-square fitting in such a way that the reflectance and transmittance satisfy the Kramers-Kronig relation. The reflectance and transmittance against oblique incident angles for the s-polarized and the p-polarized light are measured using the synchrotron beamline at the Ultraviolet Synchrotron Orbital Radiation Facility (UVSOR). We have also measured a retardation of a zeroth-order waveplate made of MgF2. The thickness difference of the waveplate is 14.57 um.This waveplate works as a half-waveplate at 121.74 nm. From this measurement, we estimate that a waveplate with the thickness difference of 15.71 um will work as a half-waveplate at the Ly-alpha wavelength. We have developed a rotating waveplate - polarization analyzer system called a prototype of CLASP polarimeter, and input the perfect Stokes Q and U signals. The modulation patterns that are consistent with the theoretical prediction are successfully obtained in both cases.
GAS MOTION STUDY OF Ly{alpha} EMITTERS AT z {approx} 2 USING FUV AND OPTICAL SPECTRAL LINES {sup ,}
Energy Technology Data Exchange (ETDEWEB)
Hashimoto, Takuya; Shimasaku, Kazuhiro; Nakajima, Kimihiko [Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113-0033 (Japan); Ouchi, Masami; Ono, Yoshiaki [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan); Rauch, Michael; Janice Lee [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Okamura, Sadanori, E-mail: thashimoto@astron.s.u-tokyo.ac.jp [Department of Advanced Sciences, Faculty of Science and Engineering, Hosei University, 3-7-2 Kajino-cho, Koganei-shi, Tokyo 184-8584 (Japan)
2013-03-01
We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for five Ly{alpha} emitters (LAEs) at z {approx_equal} 2.2 for which high-resolution FUV spectra from Magellan/MagE are available. We detect nebular emission lines including H{alpha} on the individual basis and low-ionization interstellar (LIS) absorption lines in a stacked FUV spectrum, and measure average offset velocities of the Ly{alpha} line, {Delta}v {sub Ly{alpha}}, and LIS absorption lines, {Delta}v {sub abs}, with respect to the systemic velocity defined by the nebular lines. For a sample of eight z {approx} 2-3 LAEs without active galactic nucleus from our study and the literature, we obtain {Delta}v {sub Ly{alpha}} = 175 {+-} 35 km s{sup -1}, which is significantly smaller than that of Lyman-break Galaxies (LBGs), {Delta}v {sub Ly{alpha}} {approx_equal} 400 km s{sup -1}. The stacked FUV spectrum gives {Delta}v {sub abs} = -179 {+-} 73 km s{sup -1}, comparable to that of LBGs. These positive {Delta}v {sub Ly{alpha}} and negative {Delta}v {sub abs} suggest that LAEs also have outflows. In contrast to LBGs, however, the LAEs' {Delta}v {sub Ly{alpha}} is as small as |{Delta}v {sub abs}|, suggesting low neutral hydrogen column densities. Such a low column density with a small number of resonant scattering may cause the observed strong Ly{alpha} emission of LAEs. We find an anti-correlation between Ly{alpha} equivalent width (EW) and {Delta}v {sub Ly{alpha}} in a compilation of LAE and LBG samples. Although its physical origin is not clear, this anti-correlation result appears to challenge the hypothesis that a strong outflow, by means of a reduced number of resonant scattering, produces a large EW. If LAEs at z > 6 have similarly small {Delta}v {sub Ly{alpha}} values, constraints on the reionization history derived from the Ly{alpha} transmissivity may need to be revised.
A quadruple quasar coincident with a giant Ly-alpha nebula and a protocluster at z=2
Vignali, Cristian
2016-09-01
We propose to observe the only known quadruple AGN system in the Universe, embedded in a giant Ly-alpha nebula at z 2. These active nuclei and the large number of Ly-alpha emitting galaxies at the same redshift are clear indications that this is one of the most overdense protoclusters known z 2. We request a 140 ks Chandra exposure to (a) define the basic X-ray properties of all the AGN and then their bolometric luminosities and Eddington ratios, and compare these with those of "isolated" quasars at similar redshifts/luminosities; (b) detect the hot gas emission in the protocluster. Chandra is unique for this investigation: the close (few arcsec) distance of some of the AGN needs high spatial resolution, and the extended emission requires low background contribution.
A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. II. SPECTROSCOPIC CONFIRMATION
Energy Technology Data Exchange (ETDEWEB)
Prescott, Moire K. M. [Department of Physics, University of California, Broida Hall, Mail Code 9530, Santa Barbara, CA 93106 (United States); Dey, Arjun; Jannuzi, Buell T., E-mail: mkpresco@physics.ucsb.edu [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
2013-01-01
Using a systematic broadband search technique, we have carried out a survey for large Ly{alpha} nebulae (or Ly{alpha} {sup b}lobs{sup )} at 2 {approx}< z {approx}< 3 within 8.5 deg{sup 2} of the NOAO Deep Wide-Field Survey Booetes field, corresponding to a total survey comoving volume of Almost-Equal-To 10{sup 8} h {sup -3} {sub 70} Mpc{sup 3}. Here, we present our spectroscopic observations of candidate giant Ly{alpha} nebulae. Of 26 candidates targeted, 5 were confirmed to have Ly{alpha} emission at 1.7 {approx}< z {approx}< 2.7, 4 of which were new discoveries. The confirmed Ly{alpha} nebulae span a range of Ly{alpha} equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Ly{alpha} nebulae lying within the redshift desert (i.e., 1.2 {approx}< z {approx}< 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Ly{alpha} nebula population across enormous comoving volumes.
The matter power spectrum from the Ly alpha forest : an optical depth estimate
Zaroubi, S; Nusser, A; Haehnelt, M; Kim, TS; Viel, M.
2006-01-01
We measure the matter power spectrum from 31 Ly alpha spectra spanning the redshift range of 1.6-3.6. The optical depth, tau, for Ly alpha absorption of the intergalactic medium is obtained from the flux using the inversion method of Nusser & Haehnelt. The optical depth is converted to density by
CONSTRAINING DUST AND MOLECULAR GAS PROPERTIES IN Ly{alpha} BLOBS AT z {approx} 3
Energy Technology Data Exchange (ETDEWEB)
Yang Yujin; Decarli, Roberto; Walter, Fabian; Leipski, Christian [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, Heidelberg (Germany); Dannerbauer, Helmut; Le Floc' h, Emeric [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d' Astrophysique, CEA-Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex (France); Weiss, Axel; Menten, Karl M. [Max-Planck-Insitut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Dey, Arjun [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Chapman, Scott C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Prescott, Moire K. M. [Department of Physics, Broida Hall, Mail Code 9530, University of California, Santa Barbara, CA 93106 (United States); Neri, Roberto [IRAM-Institut de Radio Astronomie Millimetrique, 300 rue de la Piscine, 38406 Saint-Martin d' Heres (France); Borys, Colin [IPAC, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Matsuda, Yuichi [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Yamada, Toru [Astronomical Institute, Tohoku University, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Hayashino, Tomoki [Research Center for Neutrino Science, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Tapken, Christian [Leibnitz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam (Germany)
2012-01-10
In order to constrain the bolometric luminosities, dust properties, and molecular gas content of giant Ly{alpha} nebulae, the so-called Ly{alpha} blobs, we have carried out a study of dust continuum and CO line emission in two well-studied representatives of this population at z {approx} 3: an Ly{alpha} blob discovered by its strong Spitzer Multiband Infrared Photometer 24 {mu}m detection (LABd05) and the Steidel blob 1 (SSA22-LAB01). We find that the spectral energy distribution of LABd05 is well described by an active-galactic-nucleus-starburst composite template with L{sub FIR} = (4.0 {+-} 0.5) Multiplication-Sign 10{sup 12} L{sub Sun }, comparable to high-z submillimeter galaxies and ultraluminous infrared galaxies. New Large APEX Bolometer Camera 870 {mu}m measurements rule out the reported Submillimeter Common-User Bolometer Array detection of the SSA22-LAB01 (S{sub 850{mu}m} = 16.8 mJy) at the >4{sigma} level. Consistent with this, ultradeep Plateau de Bure Interferometer observations with {approx}2'' spatial resolution also fail to detect any 1.2 mm continuum source down to Almost-Equal-To 0.45 mJy beam{sup -1} (3{sigma}). Combined with the existing (sub)millimeter observations in the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains uncertain. No CO line is detected in either case down to integrated flux limits of S{sub {nu}}{Delta}V {approx}< 0.25-1.0 Jy km s{sup -1}, indicating a modest molecular gas reservoir, M(H{sub 2}) < (1-3) Multiplication-Sign 10{sup 10} M{sub Sun }. The non-detections exclude, with high significance (12{sigma}), the previous tentative detection of a CO J = 4-3 line in the SSA22-LAB01. The increased sensitivity afforded by the Atacama Large Millimeter/submillimeter Array will be critical in studying molecular gas and dust in these interesting systems.
A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. I. SURVEY DESIGN AND CANDIDATE SELECTION
Energy Technology Data Exchange (ETDEWEB)
Prescott, Moire K. M. [Department of Physics, Broida Hall, Mail Code 9530, University of California, Santa Barbara, CA 93106 (United States); Dey, Arjun; Jannuzi, Buell T., E-mail: mkpresco@physics.ucsb.edu [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
2012-04-01
Giant Ly{alpha} nebulae (or Ly{alpha} 'blobs') are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Ly{alpha} nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Ly{alpha} nebulae at 2 {approx}< z {approx}< 3 within deep broadband imaging and have carried out a survey of the 9.4 deg{sup 2} NOAO Deep Wide-Field Survey Booetes field. With a total survey comoving volume of Almost-Equal-To 10{sup 8} h{sup -3}{sub 70} Mpc{sup 3}, this is the largest volume survey for Ly{alpha} nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Ly{alpha} nebula.
International Nuclear Information System (INIS)
Turnshek, D.A.; Wolfe, A.M.; Lanzetta, K.M.; Briggs, F.H.; Cohen, R.D.
1989-01-01
New intermediate-resolution spectroscopy for six members of a sample of 68 moderate- to high-redshift QSOs is presented. Evidence is reported which indicates that seven strong absorption features in the QSO spectra are due to damped Ly-alpha absorption. A standard curve-of-growth analysis on five of the damped systems is performed, and relevant properties are tabulated and discussed. Six of the seven damped Ly-alpha systems have H I column densities of 2 x 10 to the 20th/sq cm or larger, while the remaining system has an H I column density of about 10 to the 20th/sq cm. It is suggested that damped Ly-alpha systems arise when a sight line intercepts a high-redshift protogalaxy disk containing a quiescent cloud component characterized by high column density and low effective velocity dispersion. At the same time, the sight line usually intercepts a broader turbulent component, which is identified as the halo, characterized by much lower column density and higher effective velocity dispersion. 42 refs
POLARIZED EXTENDED Ly{alpha} EMISSION FROM A z = 2.3 RADIO GALAXY
Energy Technology Data Exchange (ETDEWEB)
Humphrey, A. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Vernet, J.; Fosbury, R. A. E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Villar-Martin, M. [Centro de Astrobiologia (INTA-CSIC), Carretera de Ajalvir, km 4, E-28850 Torrejon de Ardoz, Madrid (Spain); Di Serego Alighieri, S. [INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Cimatti, A., E-mail: andrew.humphrey@astro.up.pt [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
2013-05-01
We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly{alpha} emission is low centrally (P < 5%), but rises to P = 16.4% {+-} 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Ly{alpha} photons by H I. Not only is this the first detection of polarized Ly{alpha} around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly{alpha} nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly{alpha} nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.
Constraint on neutrino masses from SDSS-III/BOSS Ly$\\alpha$ forest and other cosmological probes
Palanque-Delabrouille, Nathalie; Lesgourgues, Julien; Rossi, Graziano; Borde, Arnaud; Viel, Matteo; Aubourg, Eric; Kirkby, David; LeGoff, Jean-Marc; Rich, James; Roe, Natalie; Ross, Nicholas P.; Schneider, Donald P.; Weinberg, David
2015-02-27
We present constraints on the parameters of the $\\Lambda$CDM cosmological model in the presence of massive neutrinos, using the one-dimensional Ly$\\alpha$ forest power spectrum obtained with the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS) by Palanque-Delabrouille et al. (2013), complemented by additional cosmological probes. The interpretation of the measured Ly$\\alpha$ spectrum is done using a second-order Taylor expansion of the simulated power spectrum. BOSS Ly$\\alpha$ data alone provide better bounds than previous Ly$\\alpha$ results, but are still poorly constraining, especially for the sum of neutrino masses $\\sum m_\
International Nuclear Information System (INIS)
Anderson, M.J.; Barta, D.A.; Lindquist, M.R.; Renkey, E.J.; Ryan, J.A.
1983-06-01
LMFBR pipe systems typically utilize a thicker insulation package than that used on water plant pipe systems. They are supported with special insulated pipe clamps. Mechanical snubbers are employed to resist seismic loads. Recent laboratory testing has indicated that these features provide significantly more damping than presently allowed by Regulatory Guide 1.61 for water plant pipe systems. This paper presents results of additional in-situ vibration tests conducted on FFTF pipe systems. Pipe damping values obtained at various excitation levels are presented. Effects of filtering data to provide damping values at discrete frequencies and the alternate use of a single equivalent modal damping value are discussed. These tests further confirm that damping in typical LMFBR pipe systems is larger than presently used in pipe design. Although some increase in damping occurred with increased excitation amplitude, the effect was not significant. Recommendations are made to use an increased damping value for both the OBE and DBE seismic events in design of LMFBR pipe systems
Anomalous Temporal Behaviour of Broadband Ly Alpha Observations During Solar Flares from SDO/EVE
Milligan, Ryan O.; Chamberlin, Phillip C.
2016-01-01
Although it is the most prominent emission line in the solar spectrum, there has been a notable lack of studies devoted to variations in Lyman-alpha (Ly-alpha) emission during solar flares in recent years. However, the few examples that do exist have shown Ly-alpha emission to be a substantial radiator of the total energy budget of solar flares (of the order of 10 percent). It is also a known driver of fluctuations in the Earth's ionosphere. The EUV (Extreme Ultra-Violet) Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) now provides broadband, photometric Ly-alpha data at 10-second cadence with its Multiple EUV Grating Spectrograph-Photometer (MEGS-P) component, and has observed scores of solar flares in the 5 years since it was launched. However, the MEGS-P time profiles appear to display a rise time of tens of minutes around the time of the flare onset. This is in stark contrast to the rapid, impulsive increase observed in other intrinsically chromospheric features (H-alpha, Ly-beta, LyC, C III, etc.). Furthermore, the emission detected by MEGS-P peaks around the time of the peak of thermal soft X-ray emission and not during the impulsive phase when energy deposition in the chromosphere (often assumed to be in the form of non-thermal electrons) is greatest. The time derivative of Ly-alpha lightcurves also appears to resemble that of the time derivative of soft X-rays, reminiscent of the Neupert effect. Given that spectrally-resolved Ly-alpha observations during flares from SORCE / SOLSTICE (Solar Radiation and Climate Experiment / Solar Stellar Irradiance Comparison Experiment) peak during the impulsive phase as expected, this suggests that the atypical behaviour of MEGS-P data is a manifestation of the broadband nature of the observations. This could imply that other lines andor continuum emission that becomes enhanced during flares could be contributing to the passband. Users are hereby urged to exercise caution when interpreting
High-Velocity Ly(Alpha) Emission from SMR 1987A
Michael, Eli; McCray, Richard; Borkowski, Kazimierz J.; Pun, Chu S. J.; Sonneborn, George
1998-01-01
The high-velocity Ly(Alpha) emission from SN 1987A observed with the Space Telescope Imaging Spectrograph (STIS) evidently comes from a reverse shock formed where the outer envelope of SN 1987A strikes ionized gas inside the inner circumstellar ring. The observations can be explained by a simple kinematic model, in which the Ly(Alpha) emission comes from hydrogen atoms with radial velocity approximately 15,000 km s(exp -1) crossing a reverse shock in the shape of a slightly prolate ellipsoid with equatorial radius 4.8 x 10(exp 17) cm or approximately 80% of the distance to the inner surface of the inner ring. N v double Lambda 1239, 1243 emission, if present, has a net luminosity approximately less than 30% times that of the Ly(Alpha) emission. Future STIS observations should enable us to predict the time of impact with the inner ring and to determine unambiguously whether or not N v emission is present. These observations will offer a unique opportunity to probe the structure of SN 1987A's circumstellar environment and the hydrodynamics and kinetics of very fast shocks.
Nuclear piping system damping data studies
International Nuclear Information System (INIS)
Ware, A.G.; Arendts, J.G.
1985-01-01
A programm has been conducted at the Idaho National Engineering Laboratory to study structural damping data for nuclear piping systems and to evaluate if changes in allowable damping values for structural seismic analyses are justified. The existing pipe damping data base was examined, from which a conclusion was made that there were several sets of data to support higher allowable values. The parameters which most influence pipe damping were identified and an analytical investigation demonstrated that increased damping would reduce the required number of seismic supports. A series of tests on several laboratory piping systems was used to determine the effect of various parameters such as types of supports, amplitude of vibration, frequency, insulation, and pressure on damping. A multiple regression analysis was used to statistically assess the influence of the various parameters on damping, and an international pipe damping data bank has been formed. (orig.)
Piping system damping data at higher frequencies
International Nuclear Information System (INIS)
Ware, A.G.
1987-01-01
Research has been performed at the Idaho National Engineering Laboratory (INEL) for the United States Nuclear Regulatory Commission (USNRC) to determine best-estimate damping values for dynamic analyses of nuclear piping systems excited in the 20 to 100 Hz frequency range. Vibrations in this frequency range are typical of fluid-induced transients, for which no formal pipe damping guidelines exist. The available data found in the open literature and the USNRC/INEL nuclear piping damping data bank were reviewed, and a series of tests on a straight 3-in. (76-mm) piping system and a 5-in. (127-mm) system with several bends and elbows were conducted as part of this research program. These two systems were supported with typical nuclear piping supports that could be changed from test to test during the series. The resulting damping values were ≥ those of the Pressure Vessel Research Committee (PVRC) proposal for unisulated piping. Extending the PVRC damping curve from 20 to 100 Hz at 3% of critical damping would give a satisfactory representation of the test data. This position has been endorsed by the PVRC Technical Committee on Piping Systems. 14 refs
PHYSICAL PROPERTIES OF Ly{alpha} EMITTERS AT z {approx} 0.3 FROM UV-TO-FIR MEASUREMENTS
Energy Technology Data Exchange (ETDEWEB)
Oteo, I.; Bongiovanni, A.; Perez Garcia, A. M.; Cepa, J.; Pintos-Castro, I. [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Ederoclite, A. [Centro de Estudios de Fisica del Cosmos de Aragon, Plaza San Juan 1, Planta 2, Teruel, 44001 (Spain); Sanchez-Portal, M.; Altieri, B. [Herschel Science Centre (ESAC), Villafranca del Castillo (Spain); Perez-Martinez, R. [XMM/Newton Science Operations Centre (ESAC), Villafranca del Castillo (Spain); Lutz, D.; Berta, S.; Foerster Schreiber, N.; Genzel, R.; Magnelli, B. [Max-Planck-Institut fuer Extraterrestrische Physik (MPE), Postfach 1312, 85741 Garching (Germany); Andreani, P. [ESO, Karl-Schwarzchild-Str. 2, D-85748 Garching (Germany); Aussel, H.; Daddi, E.; Elbaz, D.; Le Floc' h, E. [Commissariat a l' Energie Atomique (CEA-SAp) Saclay (France); Cimatti, A. [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, 40127 Bologna (Italy); and others
2012-06-01
The analysis of the physical properties of low-redshift Ly{alpha} emitters (LAEs) can provide clues in the study of their high-redshift analogs. At z {approx} 0.3, LAEs are bright enough to be detected over almost the entire electromagnetic spectrum and it is possible to carry out a more precise and complete study than at higher redshifts. In this work, we examine the UV and IR emission, dust attenuation, star formation rate (SFR), and morphology of a sample of 23 GALEX-discovered star-forming LAEs at z {approx} 0.3 with direct UV (GALEX), optical (ACS), and FIR (PACS and MIPS) data. Using the same UV and IR limiting luminosities, we find that LAEs at z {approx} 0.3 tend to be less dusty, have slightly higher total SFRs, have bluer UV continuum slopes, and are much smaller than other galaxies that do not exhibit Ly{alpha} emission in their spectrum (non-LAEs). These results suggest that at z {approx} 0.3, Ly{alpha} photons tend to escape from small galaxies with low dust attenuation. Regarding their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and morphology represent the most noticeable difference between LAEs and non-LAEs at z {approx} 0.3. Furthermore, the comparison of our results with those obtained at higher redshifts indicates either that the Ly{alpha} technique picks up different kind of galaxies at different redshifts or that the physical properties of LAEs are evolving with redshift.
Energy Technology Data Exchange (ETDEWEB)
Jiang Linhua; Egami, Eiichi; Walth, Gregory [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Kashikawa, Nobunari [Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Matsuda, Yuichi [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Shimasaku, Kazuhiro [Department of Astronomy, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Nagao, Tohru [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan); Ota, Kazuaki [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Ouchi, Masami [Institute for Cosmic Ray Research, University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 77-8582 (Japan)
2011-12-10
We present Keck spectroscopic observations of z > 6 Lyman-break galaxy (LBG) candidates in the Subaru Deep Field (SDF). The candidates were selected as i'-dropout objects down to z' = 27 AB magnitudes from an ultra-deep SDF z'-band image. With the Keck spectroscopy we identified 19 LBGs with prominent Ly{alpha} emission lines at 6 {<=} z {<=} 6.4. The median value of the Ly{alpha} rest-frame equivalent widths (EWs) is {approx}50 A, with four EWs >100 A. This well-defined spectroscopic sample spans a UV-continuum luminosity range of -21.8 {<=} M{sub UV} {<=} -19.5 (0.6 {approx} 5 L*{sub UV}) and a Ly{alpha} luminosity range of (0.3-3) Multiplication-Sign 10{sup 43} erg s{sup -1} (0.3-3 L*{sub Ly{alpha}}). We derive the UV and Ly{alpha} luminosity functions (LFs) from our sample at (z) {approx} 6.2 after we correct for sample incompleteness. We find that our measurement of the UV LF is consistent with the results of previous studies based on photometric LBG samples at 5 < z < 7. Our Ly{alpha} LF is also generally in agreement with the results of Ly{alpha}-emitter surveys at z {approx} 5.7 and 6.6. This study shows that deep spectroscopic observations of LBGs can provide unique constraints on both the UV and Ly{alpha} LFs at z > 6.
Radiation damping in focusing-dominated systems
International Nuclear Information System (INIS)
Huang, Zhirong; Chen, Pisin; Ruth, R.D.
1995-01-01
A quasi-classical method is developed to calculate the radiation damping of a relativistic particle in a straight, continuous focusing system. In one limiting case where the pitch angle of the particle θ p is much larger than the radiation opening angle 1/γ, the radiation power spectrum is similar to synchrotron radiation and the relative damping rate of the transverse action is proportional to the relative energy loss rate. In the other limiting case where θ p much-lt 1/γ, the radiation is dipole in nature and the relative damping rate of the transverse action is energy-independent and is much faster than the relative energy rate. Quantum excitation to the transverse action is absent in this focusing channel. These results can be extended to bent systems provided that the focusing field dominates over the bending field
Energy Technology Data Exchange (ETDEWEB)
Ono, Yoshiaki; Shimasaku, Kazuhiro; Nakajima, Kimihiko, E-mail: ono@astron.s.u-tokyo.ac.jp [Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo 113-0033 (Japan); Ouchi, Masami [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582 (Japan); Mobasher, Bahram; Nayyeri, Hooshang [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Dickinson, Mark; Kartaltepe, Jeyhan S. [National Optical Astronomical Observatories, Tucson, AZ 85719 (United States); Penner, Kyle [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Weiner, Benjamin J. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Kashikawa, Nobunari [Optical and Infrared Astronomy Division, National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan); Spinrad, Hyron [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)
2012-01-10
We present the results of our ultra-deep Keck/DEIMOS spectroscopy of z-dropout galaxies in the Subaru Deep Field and Great Observatories Origins Deep Survey's northern field. For 3 out of 11 objects, we detect an emission line at {approx}1 {mu}m with a signal-to-noise ratio of {approx}10. The lines show asymmetric profiles with high weighted skewness values, consistent with being Ly{alpha}, yielding redshifts of z = 7.213, 6.965, and 6.844. Specifically, we confirm the z = 7.213 object in two independent DEIMOS runs with different spectroscopic configurations. The z = 6.965 object is a known Ly{alpha} emitter, IOK-1, for which our improved spectrum at a higher resolution yields a robust skewness measurement. The three z-dropouts have Ly{alpha} fluxes of 3 Multiplication-Sign 10{sup -17} erg s{sup -1} cm{sup -2} and rest-frame equivalent widths EW{sup Ly{alpha}}{sub 0} = 33-43 A. Based on the largest spectroscopic sample of 43 z-dropouts, which is the combination of our and previous data, we find that the fraction of Ly{alpha}-emitting galaxies (EW{sup Ly{alpha}}{sub 0} > 25 A) is low at z {approx} 7; 17% {+-} 10% and 24% {+-} 12% for bright (M{sub UV} {approx_equal} -21) and faint (M{sub UV} {approx_equal} -19.5) galaxies, respectively. The fractions of Ly{alpha}-emitting galaxies drop from z {approx} 6 to 7 and the amplitude of the drop is larger for faint galaxies than for bright galaxies. These two pieces of evidence would indicate that the neutral hydrogen fraction of the intergalactic medium increases from z {approx} 6 to 7 and that the reionization proceeds from high- to low-density environments, as suggested by an inside-out reionization model.
INFERENCES ON THE DISTRIBUTION OF Ly{alpha} EMISSION OF z {approx} 7 AND z {approx} 8 GALAXIES
Energy Technology Data Exchange (ETDEWEB)
Treu, Tommaso; Auger, Matthew W. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Trenti, Michele [University of Colorado, Center for Astrophysics and Space Astronomy, 389-UCB, Boulder, CO 80309 (United States); Stiavelli, Massimo; Bradley, Larry D., E-mail: tt@physics.ucsb.edu [Space Telescope Science Institute, 3700 San Martin Dr, Baltimore MD 21218 (United States)
2012-03-01
Spectroscopic confirmation of galaxies at z {approx} 7 and above has been extremely difficult, owing to a drop in intensity of Ly{alpha} emission in comparison with samples at z {approx} 6. This crucial finding could potentially signal the ending of cosmic reionization. However, it is based on small data sets, often incomplete and heterogeneous in nature. We introduce a flexible Bayesian framework, useful to interpret such evidence. Within this framework, we implement two simple phenomenological models: a smooth one where the distribution of Ly{alpha} is attenuated by a factor {epsilon}{sub s} with respect to z {approx} 6 and a patchy one where a fraction {epsilon}{sub p} is absorbed/non-emitted while the rest is unabsorbed. From a compilation of 39 observed z {approx} 7 galaxies, we find {epsilon}{sub s} = 0.69 {+-} 0.12 and {epsilon}{sub p} = 0.66 {+-} 0.16. The models can be used to compute fractions of emitters above any equivalent width W. For W > 25 A, we find X{sup 25}{sub z=7} = 0.37 {+-} 0.11 (0.14 {+-} 0.06) for galaxies fainter (brighter) than M{sub UV} = -20.25 for the patchy model, consistent with previous work, but with smaller uncertainties by virtue of our full use of the data. At z {approx} 8 we combine new deep (5{sigma} flux limit 10{sup -17} erg s{sup -1} cm{sup -2}) Keck/NIRSPEC observations of a bright Y-dropout identified by our Brightest of Reionization Galaxies Survey, with those of three objects from the literature and find that the inference is inconclusive. We compute predictions for future near-infrared spectroscopic surveys and show that it is challenging but feasible to constrain the distribution of Ly{alpha} emitters at z {approx} 8 and distinguish between models.
Damping system immersed in a fluid
International Nuclear Information System (INIS)
1980-01-01
The invention relates to a damping system which is immersed in a fluid and allows slow motion, while opposing fast motion of a mobile or deformable system immersed in a fluid. Nuclear reactors utilize fabricated assemblies immmersed in the spent fuel storage pool to support the fuel elements placed in the pool, e.g., when refueling the reactor. These fabricated assemblies must be held in position, relative to the concrete walls of the pool, so as to allow slow deformation of the assemblies due to thermal expansion, while curbing fast motion, e.g., earthquake-induced motion. Such fast motion due to earthquakes might be the cause of resonance phenomena involving the fuel storage rack structure and the pool walls, should the rack structure and pool walls have the same resonant frequency. In the event of an earthquake, the damping system would provide for fast curbing of structure motion to prevent uncontrolled deformation which might result in breaks and destruction [fr
Energy Technology Data Exchange (ETDEWEB)
Nakajima, Kimihiko; Shimasaku, Kazuhiro; Ono, Yoshiaki; Okamura, Sadanori [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Ouchi, Masami [Institute for the Physics and Mathematics of the Universe (IPMU), TODIAS, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Lee, Janice C.; Ly, Chun [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Foucaud, Sebastien [Department of Earth Sciences, National Taiwan Normal University, No. 88, Tingzhou Road, Sec. 4, Taipei 11677, Taiwan (China); Dale, Daniel A. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY (United States); Salim, Samir [Department of Astronomy, Indiana University, Bloomington, IN (United States); Finn, Rose [Department of Physics, Siena College, Loudonville, NY (United States); Almaini, Omar, E-mail: nakajima@astron.s.u-tokyo.ac.jp [School of Physics and Astronomy, University of Nottingham, Nottingham (United Kingdom)
2012-01-20
We present the average metallicity and star formation rate (SFR) of Ly{alpha} emitters (LAEs) measured from our large-area survey with three narrowband (NB) filters covering the Ly{alpha}, [O II]{lambda}3727, and H{alpha}+[N II] lines of LAEs at z = 2.2. We select 919 z = 2.2 LAEs from Subaru/Suprime-Cam NB data in conjunction with Magellan/IMACS spectroscopy. Of these LAEs, 561 and 105 are observed with KPNO/NEWFIRM near-infrared NB filters whose central wavelengths are matched to redshifted [O II] and H{alpha} nebular lines, respectively. By stacking the near-infrared images of the LAEs, we successfully obtain average nebular-line fluxes of LAEs, the majority of which are too faint to be identified individually by NB imaging or deep spectroscopy. The stacked object has an H{alpha} luminosity of 1.7 Multiplication-Sign 10{sup 42} erg s{sup -1} corresponding to an SFR of 14 M{sub Sun} yr{sup -1}. We place, for the first time, a firm lower limit to the average metallicity of LAEs of Z {approx}> 0.09 Z{sub Sun} (2{sigma}) based on the [O II]/(H{alpha}+[N II]) index together with photoionization models and empirical relations. This lower limit of metallicity rules out the hypothesis that LAEs, so far observed at z {approx} 2, are extremely metal-poor (Z < 2 Multiplication-Sign 10{sup -2} Z{sub Sun }) galaxies at the 4{sigma} level. This limit is higher than a simple extrapolation of the observed mass-metallicity relation of z {approx} 2 UV-selected galaxies toward lower masses (5 Multiplication-Sign 10{sup 8} M{sub Sun }), but roughly consistent with a recently proposed fundamental mass-metallicity relation when the LAEs' relatively low SFR is taken into account. The H{alpha} and Ly{alpha} luminosities of our NB-selected LAEs indicate that the escape fraction of Ly{alpha} photons is {approx}12%-30%, much higher than the values derived for other galaxy populations at z {approx} 2.
System Reduction and Damping of Flexible Structures
DEFF Research Database (Denmark)
Høgsberg, Jan Riess; Krenk, Steen
2007-01-01
An increasing number of flexible structures such as cable-stayed bridges, pedestrian bridges and high-rise buildings are fitted with local dampers to mitigate vibration problems. In principle the effect of local dampers can be analyzed by use of complex modes, e.g. in conjunction with an averaging...... technique for local linearization of the damper characteristics. However, the complex mode shapes and frequencies depend on the magnitude of the damper and therefore are less suitable for design of the damper system. An efficient alternative consists in the use of a two-component representation...... of the damped modes of the structure. The idea is to represent the damped mode as a linear combination of the modes that occur in two distinctly different situations representing extreme conditions: the mode shape of the structure without the damper(s), and the mode shape of the structure, when the damper...
Chen, D
The $\\textbf{DA}$rk $\\textbf{M}$atter $\\textbf{P}$article $\\textbf{E}$xplorer (DAMPE) experiment is a high-energy astroparticle physics satellite mission to search for Dark Matter signatures in space, study the cosmic ray spectrum and composition up to 100 TeV, and perform high-energy gamma astronomy. The launch is planned for end 2015, initially for 3 years, to compliment existing space missions FERMI, AMS and CALET.
Damping Estimation of Friction Systems in Random Vibrations
DEFF Research Database (Denmark)
Friis, Tobias; Katsanos, Evangelos; Amador, Sandro
Friction is one of the most efficient and economical mechanisms to reduce vibrations in structural mechanics. However, the estimation of the equivalent linear damping of the friction damped systems in experimental modal analysis and operational modal analysis can be adversely affected by several...... assumptions regarding the definition of the linear damping and the identification methods or may be lacking a meaningful interpretation of the damping. Along these lines, this project focuses on assessing the potential to estimate efficiently the equivalent linear damping of friction systems in random...
System for damping vibrations in a turbine
Roberts, III, Herbert Chidsey; Johnson, Curtis Alan; Taxacher, Glenn Curtis
2015-11-24
A system for damping vibrations in a turbine includes a first rotating blade having a first ceramic airfoil, a first ceramic platform connected to the first ceramic airfoil, and a first root connected to the first ceramic platform. A second rotating blade adjacent to the first rotating blade includes a second ceramic airfoil, a second ceramic platform connected to the second ceramic airfoil, and a second root connected to the second ceramic platform. A non-metallic platform damper has a first position in simultaneous contact with the first and second ceramic platforms.
Lázaro, Mario
2018-01-01
In this paper, nonviscous, nonproportional, vibrating structures are considered. Nonviscously damped systems are characterized by dissipative mechanisms which depend on the history of the response velocities via hereditary kernel functions. Solutions of the free motion equation lead to a nonlinear eigenvalue problem involving mass, stiffness and damping matrices. Viscoelasticity leads to a frequency dependence of this latter. In this work, a novel closed-form expression to estimate complex eigenvalues is derived. The key point is to consider the damping model as perturbed by a continuous fictitious parameter. Assuming then the eigensolutions as function of this parameter, the computation of the eigenvalues sensitivity leads to an ordinary differential equation, from whose solution arises the proposed analytical formula. The resulting expression explicitly depends on the viscoelasticity (frequency derivatives of the damping function), the nonproportionality (influence of the modal damping matrix off-diagonal terms). Eigenvectors are obtained using existing methods requiring only the corresponding eigenvalue. The method is validated using a numerical example which compares proposed with exact ones and with those determined from the linear first order approximation in terms of the damping matrix. Frequency response functions are also plotted showing that the proposed approach is valid even for moderately or highly damped systems.
Hou, Junfang; jing, Min; Zhang, Weihua; Lu, Yahui; He, Haiwen
2017-12-01
As for the isolation problem of electronic equipments on vehicle, the vibration response characteristics of dry friction damping isolation system under base displacement excitation was analyzed in theory by harmonic balance method, and the displacement response was compared between the isolation systems with dry friction damping and vicious damping separately. The results show that the isolation system with small dry friction damping can’t meet the demands of displacement reduction close to the natural frequency, and it can realize full-frequency vibration isolation by improving dry friction damping when the lock frequency passes beyond the resonance frequency band. The results imply that the damping mechanism of dry friction isolator can’t be described only by dry friction damping, and the composite damping with dry friction and vicious damping is more appropriate.
Rising damp in building walls: the wall base ventilation system
Energy Technology Data Exchange (ETDEWEB)
Guimaraes, A.S.; Delgado, J.M.P.Q.; Freitas, V.P. de [Faculdade de Engenharia da Universidade do Porto, Laboratorio de Fisica das Construcoes (LFC), Departamento de Engenharia Civil, Porto (Portugal)
2012-12-15
This work intends to validate a new system for treating rising damp in historic buildings walls. The results of laboratory experiments show that an efficient way of treating rising damp is by ventilating the wall base, using the HUMIVENT technique. The analytical model presented describes very well the observed features of rising damp in walls, verified by laboratory tests, who contributed for a simple sizing of the wall base ventilation system that will be implemented in historic buildings. (orig.)
Gyroscopic stabilization and indefimite damped systems
DEFF Research Database (Denmark)
Pommer, Christian
a class of feasibel skew-Hermitian matrices A depending on the choise of M. The theory can be applied to dynamical systems of the form x''(t) + ( dD + g G) x'(t) + K x(t) = 0 where G is a skew symmetric gyrocopic matrix, D is a symmetric indefinite damping matrix and K > 0 is a positive definite stiffness......An important issue is how to modify a given unstable matrix in such a way that the resulting matrix is stable. We investigate in general under which condition a matrix M+A is stable,where M is an arbitrary matrix and A is skew-Hermitian. We show that if trace(M) > 0 it is always possible to find...
Magnon damping in two-dimensional Heisenberg ferromagnetic system
International Nuclear Information System (INIS)
Cheng, T.-M.; Li Lin; Ze Xianyu
2006-01-01
A magnon-phonon interaction model is set up for a two-dimensional insulating ferromagnetic system. By using Matsubara function theory we have studied the magnon damping -I m Σ* (1) (k->) and calculated the magnon damping -I m Σ* (1) (k->) curve on the main symmetric point and line in the Brillouin zone for various parameters in the system. It is concluded that at the boundary of Brillouin zone there is a strong magnon damping. However, the magnon damping is very weak on the zone of small wave vector and the magnon damping reaches maximal value at very low temperature. The contributions of longitudinal phonon and transverse phonon on the magnon damping are compared and the influences of various parameters are also discussed
International Nuclear Information System (INIS)
Pradeep, R. Gladwin; Chandrasekar, V. K.; Senthilvelan, M.; Lakshmanan, M.
2009-01-01
In this paper we point out the existence of a remarkable nonlocal transformation between the damped harmonic oscillator and a modified Emden-type nonlinear oscillator equation with linear forcing, xe+αxx+βx 3 +γx=0, which preserves the form of the time independent integral, conservative Hamiltonian, and the equation of motion. Generalizing this transformation we prove the existence of nonstandard conservative Hamiltonian structure for a general class of damped nonlinear oscillators including Lienard-type systems. Further, using the above Hamiltonian structure for a specific example, namely, the generalized modified Emden equation xe+αx q x+βx 2q+1 =0, where α, β, and q are arbitrary parameters, the general solution is obtained through appropriate canonical transformations. We also present the conservative Hamiltonian structure of the damped Mathews-Lakshmanan oscillator equation. The associated Lagrangian description for all the above systems is also briefly discussed.
Dynamic characteristics of a novel damped outrigger system
Tan, Ping; Fang, Chuangjie; Zhou, Fulin
2014-06-01
This paper presents exact analytical solutions for a novel damped outrigger system, in which viscous dampers are vertically installed between perimeter columns and the core of a high-rise building. An improved analytical model is developed by modeling the effect of the damped outrigger as a general rotational spring acting on a Bernoulli-Euler beam. The equivalent rotational spring stiffness incorporating the combined effects of dampers and axial stiffness of perimeter columns is derived. The dynamic stiffness method (DSM) is applied to formulate the governing equation of the damped outrigger system. The accuracy and efficiency are verified in comparison with those obtained from compatibility equations and boundary equations. Parametric analysis of three non-dimensional factors is conducted to evaluate the influences of various factors, such as the stiffness ratio of the core to the beam, position of the damped outrigger, and the installed damping coefficient. Results show that the modal damping ratio is significantly influenced by the stiffness ratio of the core to the column, and is more sensitive to damping than the position of the damped outrigger. The proposed analytical model in combination with DSM can be extended to the study of structures with more outriggers.
Observations of nickel, chromium, and zinc in QSO absorption-line systems
International Nuclear Information System (INIS)
Meyer, D.M.; Roth, K.C.
1990-01-01
New observations of Ni II, Cr II, and Zn II in several damped Ly-alpha QSO absorption-line systems at z about 2 are presented. Using the N(Zn II)/N(H I) ratio as a probe of the metallicity and N(Cr II)/N(Zn II) as a measure of the dust content, it is found that the heavy-element abundances in the z = 1.921 system toward the QSO 2206-199N are 20 percent solar and that the dust-to-gas ratio is 11 percent of the Galactic disk value. The observations of these species in the z = 2.309 system toward PHL 957 yield a more extreme metallicity (4 percent solar) and dust-to-gas ratio (3 percent Galactic). In addition, a depletion of Ni in the z = 2.039 absorber toward PKS 0458 - 020 and an absence of C I absorption in the z about 2 damped systems toward 1215 + 333 and 2359 - 022 are found which are consistent with a lack of dust. Among the four damped systems whose Ni, Cr, and Zn abundances have been examined quantitatively to date, all show convincing evidence of much lower metallicities and dust content than the Galactic disk. The implications of these results with regard to the interpretation of the high-redshift damped Ly-alpha systems as an evolving population of young galaxies are discussed. 41 refs
Self-sustained solitons in systems with nonlinear damping
International Nuclear Information System (INIS)
Gonzalez, J.A.
1993-05-01
The existence and stability of kinks in systems with nonlinear damping are investigated. We discuss the mechanism of a bifurcation after which the kink becomes a non-stationary state. (author). 9 refs
Nonlinear time heteronymous damping in nonlinear parametric planetary systems
Czech Academy of Sciences Publication Activity Database
Hortel, Milan; Škuderová, Alena
2014-01-01
Roč. 225, č. 7 (2014), s. 2059-2073 ISSN 0001-5970 Institutional support: RVO:61388998 Keywords : nonlinear dynamics * planetary systems * heteronymous damping Subject RIV: JT - Propulsion, Motors ; Fuels Impact factor: 1.465, year: 2014
International Nuclear Information System (INIS)
Shibata, H.; Ito, A.; Tanaka, K.; Niino, T.; Gotoh, N.
1981-01-01
Generally, damping phenomena of structures and equipments is caused by very complex energy dissipation. Especially, as piping systems are composed of many components, it is very difficult to evaluate damping characteristics of its system theoretically. On the other hand, the damping value for aseismic design of nuclear power plants is very important design factor to decide seismic response loads of structures, equipments and piping systems. The very extensive studies titled SDREP (Seismic Damping Ratio Evaluation Program) were performed to establish proper damping values for seismic design of piping as a joint work among a university, electric companies and plant makers. In SDREP, various systematic vibration tests were conducted to investigate factors which may contribute to damping characteristics of piping systems and to supplement the data of the pre-operating tests. This study is related to the component damping characteristics tests of that program. The object of this study is to clarify damping characteristics and mechanism of hanger supports used in piping systems, and to establish the evaluation technique of dispersing energy at hanger support points and its effect to the total damping ability of piping system. (orig./WL)
Eddy damping effect of additional conductors in superconducting levitation systems
Energy Technology Data Exchange (ETDEWEB)
Jiang, Zhao-Fei; Gou, Xiao-Fan, E-mail: xfgou@hhu.edu.cn
2015-12-15
Highlights: • In this article, for the eddy current damper attached to the HTSC, we • quantitatively investigated the damping coefficient c, damping ratio, Joule heating of the copper damper, and the vibration frequency of the PM as well. • presented four different arrangements of the copper damper, and comparatively studied their damping effects and Joule heating, and finally proposed the most advisable arrangement. - Abstract: Passive superconducting levitation systems consisting of a high temperature superconductor (HTSC) and a permanent magnet (PM) have demonstrated several fascinating applications such as the maglev system, flywheel energy storage. Generally, for the HTSC–PM levitation system, the HTSC with higher critical current density J{sub c} can obtain larger magnetic force to make the PM levitate over the HTSC (or suspended below the HTSC), however, the process of the vibration of the levitated PM, provides very limited inherent damping (essentially hysteresis). To improve the dynamic stability of the levitated PM, eddy damping of additional conductors can be considered as the most simple and effective approach. In this article, for the HTSC–PM levitation system with an additional copper damper attached to the HTSC, we numerically and comprehensively investigated the damping coefficient c, damping ratio, Joule heating of the copper damper, and the vibration frequency of the PM as well. Furthermore, we comparatively studied four different arrangements of the copper damper, on the comprehensive analyzed the damping effect, efficiency (defined by c/V{sub Cu}, in which V{sub Cu} is the volume of the damper) and Joule heating, and finally presented the most advisable arrangement.
Further considerations for damping in heavily insulated pipe systems
International Nuclear Information System (INIS)
Anderson, M.J.; Lindquist, M.R.; Severud, L.K.
1985-01-01
Over the past several years a body of test data has been accumulated which demonstrates that damping in small diameter heavily insulated pipe systems is much larger than presently recommended by Regulatory Guide 1.61. This data is generally based on pipe systems using a stand-off insulation design with a heater annulus. Additional tests have how been completed on similar pipe systems using a strap-on insulation design without the heater annulus. Results indicate some reduction in damping over the stand-off designs. Test data has also been obtained on a larger sixteen-inch diameter heavily insulated pipe system. Results of these two additional test series are presented. Revised damping values for seismic design of heavily insulated pipe systems are then recommended
Further considerations for damping in heavily insulated pipe systems
International Nuclear Information System (INIS)
Anderson, M.J.; Lindquist, M.R.; Severud, L.K.
1985-01-01
Over the past several years a body of test data has been accumulated which demonstrates that damping in small diameter heavily insulated pipe systems is much larger than presently recommended by Regulatory Code 1.61. This data is generally based on pipe systems using a stand-off insulation design with a heater annulus. Additional tests have now been completed on similar pipe systems using a strap-on insulation design without the heater annulus. Results indicate some reduction in damping over the stand-off designs. Test data has also been obtained on a larger sixteen-inch diameter heavily insulated pipe system. Results of these two additional test series are presented. Revised damping values for seismic design for heavily insulated pipe systems are then recommended
Thiol-ene/methacrylate systems for mechanical damping
McNair, Olivia; Senyurt, Askim; Wei, Huanyu; Gould, Trent; Piland, Scott; Hoyle, Charles; Savin, Daniel
2010-03-01
Ternary thiol-ene-methacrylate (TEMA) networks as materials for mechanical energy damping are unique to the sports world. Using a photoinitiation process, TEMA systems are formed via an initial thiol-ene step-growth mechanism along with traditional radical polymerization of acrylate and ene monomers. Final networks have two-part morphologies: acrylate homopolymer sectors imbedded in a multi-component mesh. Several (TEMA) systems have been synthesized and analyzed via thermal and mechanical probing. Initial studies on these ternary systems have shown excellent properties compared to traditional ethylene vinyl alcohol (EVA) copolymers. For example, PEMA networks exhibit glass transition temperatures 33 K higher than EVA, resulting in improved damping at room temperature. This research will help develop relationships between tan delta, glass transition and their effects on mechanical energy damping for ternary (TEMA) systems.
Eddy damping effect of additional conductors in superconducting levitation systems
Jiang, Zhao-Fei; Gou, Xiao-Fan
2015-12-01
Passive superconducting levitation systems consisting of a high temperature superconductor (HTSC) and a permanent magnet (PM) have demonstrated several fascinating applications such as the maglev system, flywheel energy storage. Generally, for the HTSC-PM levitation system, the HTSC with higher critical current density Jc can obtain larger magnetic force to make the PM levitate over the HTSC (or suspended below the HTSC), however, the process of the vibration of the levitated PM, provides very limited inherent damping (essentially hysteresis). To improve the dynamic stability of the levitated PM, eddy damping of additional conductors can be considered as the most simple and effective approach. In this article, for the HTSC-PM levitation system with an additional copper damper attached to the HTSC, we numerically and comprehensively investigated the damping coefficient c, damping ratio, Joule heating of the copper damper, and the vibration frequency of the PM as well. Furthermore, we comparatively studied four different arrangements of the copper damper, on the comprehensive analyzed the damping effect, efficiency (defined by c/VCu, in which VCu is the volume of the damper) and Joule heating, and finally presented the most advisable arrangement.
Linear time heteronymous damping in nonlinear parametric systems
Czech Academy of Sciences Publication Activity Database
Hortel, Milan; Škuderová, Alena; Houfek, Martin
2016-01-01
Roč. 40, 23-24 (2016), s. 10038-10051 ISSN 0307-904X Institutional support: RVO:61388998 Keywords : nonlinear dynamics of systems * parametric systems * time heteronymous damping * gears Subject RIV: JT - Propulsion, Motors ; Fuels Impact factor: 2.350, year: 2016
Nonlinear damping based semi-active building isolation system
Ho, Carmen; Zhu, Yunpeng; Lang, Zi-Qiang; Billings, Stephen A.; Kohiyama, Masayuki; Wakayama, Shizuka
2018-06-01
Many buildings in Japan currently have a base-isolation system with a low stiffness that is designed to shift the natural frequency of the building below the frequencies of the ground motion due to earthquakes. However, the ground motion observed during the 2011 Tohoku earthquake contained strong long-period waves that lasted for a record length of 3 min. To provide a novel and better solution against the long-period waves while maintaining the performance of the standard isolation range, the exploitation of the characteristics of nonlinear damping is proposed in this paper. This is motivated by previous studies of the authors, which have demonstrated that nonlinear damping can achieve desired performance over both low and high frequency regions and the optimal nonlinear damping force can be realized by closed loop controlled semi-active dampers. Simulation results have shown strong vibration isolation performance on a building model with identified parameters and have indicated that nonlinear damping can achieve low acceleration transmissibilities round the structural natural frequency as well as the higher ground motion frequencies that have been frequently observed during most earthquakes in Japan. In addition, physical building model based laboratory experiments are also conducted, The results demonstrate the advantages of the proposed nonlinear damping technologies over both traditional linear damping and more advanced Linear-Quadratic Gaussian (LQG) feedback control which have been used in practice to address building isolation system design and implementation problems. In comparison with the tuned-mass damper and other active control methods, the proposed solution offers a more pragmatic, low-cost, robust and effective alternative that can be readily installed into the base-isolation system of most buildings.
Stochastic seismic floor response analysis method for various damping systems
International Nuclear Information System (INIS)
Kitada, Y.; Hattori, K.; Ogata, M.; Kanda, J.
1991-01-01
A study using the stochastic seismic response analysis method which is applicable for the estimation of floor response spectra is carried out. It is pointed out as a shortcoming in this stochastic seismic response analysis method, that the method tends to overestimate floor response spectra for low damping systems, e.g. 1% of the critical damping ratio. An investigation on the cause of the shortcoming is carried out and a number of improvements in this method were also made to the original method by taking correlation of successive peaks in a response time history into account. The application of the improved method to a typical BWR reactor building is carried out. The resultant floor response spectra are compared with those obtained by deterministic time history analysis. Floor response spectra estimated by the improved method consistently cover the response spectra obtained by the time history analysis for various damping ratios. (orig.)
Variation of structural damping with response amplitude in piping systems
International Nuclear Information System (INIS)
Ware, A.G.
1986-01-01
From tests conducted over the last several years, it has become apparent that structural damping is not a single number applicable to all piping systems, but is highly dependent on piping system parameters such as supports, response amplitude, and insulation. As a result, there is considerable scatter in the available data. Furthermore, the relationships between the parameters and damping are often highly complex, interrelated, and difficult to predict. From tests of piping supported by various typical methods, two basic types of energy dissipation in the supports can be observed. The first is friction such as between spring hangers and their housings or in the internal mechanisms of constant force hangers. The second is impacting such as occurs in snubbers, rigid struts, and rod hangers. Overall, these effects lead to a wide variety of possibilities that can occur at low vibration levels and can change with only a slight perturbation of vibration amplitude. This can account for much of the scatter in the data at low strain levels. Thus damping is almost impossible to predict at low amplitudes, and extrapolation of this type data to higher amplitudes is cautioned. However, once strain levels rise above 100 to 200 micro in/in, the damping trend becomes easier to characterize. From the 100 to 200 micro in/in to 800 to 1000 micro in/in range the damping is fairly constant and is induced primarily by the supports. At the upper end of this range a threshold is reached in which damping increases with increasing strain amplitude. Data in the high strain (plastic range) is sparse since the test usually renders the pipe unsuitable for further use. 15 refs
MR damping system on Dongting Lake cable-stayed bridge
Chen, Z. Q.; Wang, X. Y.; Ko, J. M.; Ni, Y. Q.; Spencer, Billie F., Jr.; Yang, G.
2003-08-01
The Dongting Lake Bridge is a cable-stayed bridge crossing the Dongting Lake where it meets the Yangtze River in southern central China. After this bridge was completed in 1999, its cables were observed to be sensitive to rain-wind-induced vibration, especially under adverse weather conditions of both rain and wind. To investigate the possibility of using MR damping systems to reduce cable vibration, a joint project between the Central South University of China and the Hong Kong Polytechnic University was conducted. Based on the promising research results, the bridge authority decided to install MR damping systems on the longest 156 stay cables. The installation started in July 2001 and finished in June 2002, making it the world's first application of MR dampers on cable-stayed bridge to suppress the rain-wind-induced cable vibration. As a visible and permanent aspect of bridge, the MR damping system must be aesthetically pleasing, reliable, durable, easy to maintain, as well as effective in vibration mitigation. Substantial work was done to meet these requirements. This paper describes the implementation of MR damping systems for cable vibration reduction.
Beam excitation and damping with the transverse feedback system
International Nuclear Information System (INIS)
Pellegrin, J.L.; Rees, J.R.
1979-08-01
The questions often come up, ''What is the strength if the beam excitation system? How much damping can the transverse feedback provide?'' The design is now advanced enough to answer these questions; also, laboratory tests of some components have been conducted and we know what can be expected of the hardware. This paper discusses these questions
Electric Generator in the System for Damping Oscillations of Vehicles
Serebryakov A.; Kamolins E.; Levin N.
2017-01-01
The control systems for the objects of industry, power generation, transport, etc. are extremely complicated; functional efficiency of these systems determines to a great extent the safe and non-polluting operation as well as convenience of service and repair of such objects. The authors consider the possibility to improve the efficiency of systems for damping oscillations in transport using a combination of electrical (generators of rotational and linear types) and hydraulic means. Better ef...
Rahimi, Z.; Rashahmadi, S.
2017-11-01
The thermo-elastic damping is a dominant source of internal damping in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS). The internal damping cannot neither be controlled nor minimized unless either mechanical or geometrical properties are changed. Therefore, a novel FGMNEM system with a controllable thermo-elastic damping of axial vibration based on Eringen nonlocal theory is considered. The effects of different parameter like the gradient index, nonlocal parameter, length of nanobeam and ambient temperature on the thermo-elastic damping quality factor are presented. It is shown that the thermo-elastic damping can be controlled by changing different parameter.
Damped oscillations of linear systems a mathematical introduction
Veselić, Krešimir
2011-01-01
The theory of linear damped oscillations was originally developed more than hundred years ago and is still of vital research interest to engineers, mathematicians and physicists alike. This theory plays a central role in explaining the stability of mechanical structures in civil engineering, but it also has applications in other fields such as electrical network systems and quantum mechanics. This volume gives an introduction to linear finite dimensional damped systems as they are viewed by an applied mathematician. After a short overview of the physical principles leading to the linear system model, a largely self-contained mathematical theory for this model is presented. This includes the geometry of the underlying indefinite metric space, spectral theory of J-symmetric matrices and the associated quadratic eigenvalue problem. Particular attention is paid to the sensitivity issues which influence numerical computations. Finally, several recent research developments are included, e.g. Lyapunov stability and ...
Power system damping - Structural aspects of controlling active power
Energy Technology Data Exchange (ETDEWEB)
Samuelsson, O.
1997-04-01
Environmental and economical aspects make it difficult to build new power lines and to reinforce existing ones. The continued growth in demand for electric power must therefore to a great extent be met by increased loading of available lines. A consequence is that power system damping is reduced, leading to a risk of poorly damped power oscillations between the generators. This thesis proposes the use of controlled active loads to increase damping of such electro-mechanical oscillations. The focus is on structural aspects of controller interaction and of sensor and actuator placement. On-off control based on machine frequency in a single machine infinite bus system is analysed using energy function analysis and phase plane plots. An on-off controller with estimated machine frequency as input has been implemented. At a field test it damped oscillations of a 0.9 MW hydro power generator by controlling a 20kW load. The linear analysis uses two power system models with three and twenty-three machines respectively. Each damper has active power as output and local bus frequency or machine frequency as input. The power system simulator EUROSTAG is used both for generation of the linearized models and for time simulations. Measures of active power mode controllability and phase angle mode observability are obtained from the eigenvectors of the differential-algebraic models. The geographical variation in the network of these quantities is illustrated using the resemblance to bending modes of flexible mechanical structures. Eigenvalue sensitivities are used to determine suitable damper locations. A spring-mass equivalent to an inter-area mode provides analytical expressions, that together with the concept of impedance matching explain the structural behaviour of the power systems. For large gains this is investigated using root locus plots. 64 refs, 99 figs, 20 tabs
Some Passive Damping Sources on Flooring Systems besides the TMD
DEFF Research Database (Denmark)
Pedersen, Lars
2010-01-01
Impulsive loads and walking loads can generate problematic structural vibrations in flooring-systems. Measures that may be taken to mitigate the problem would often be to consider the implementation of a tuned mass damper or even more advanced vibration control technologies; this in order to add...... damping to the structure. Basically also passive humans on a floor act as a damping source, but it also turns out from doing system identification tests with a floor strip that a quite simple set-up installed on the floor (cheap and readily at hand) might do a good job in terms of reducing vertical floor...... vibrations for some floors. The paper describes the tests with the floor strip, and the results, in terms of dynamic floor behaviour, are compared with what would be expected had the floor instead been equipped with a tuned mass damper....
Swing Damping for Helicopter Slung Load Systems using Delayed Feedback
Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon
2009-01-01
This paper presents the design and verification of a swing reducing controller for helicopter slung load systems usingintentional delayed feedback. It is intended for augmenting a trajectory tracking helicopter controller and thereby improving the slung load handing capabilities for autonomous helicopters. The delayed feedback controller is added to actively reduce oscillations of the slung load by improving the damping of the slung load pendulum modes. Furthermore, it is intended for integra...
Bifurcation characteristics in parametric systems with combined damping
Czech Academy of Sciences Publication Activity Database
Hortel, Milan; Škuderová, Alena
Vol.16, č. 3 (2009), s. 1-9 ISSN 1802-1484 R&D Projects: GA ČR(CZ) GA101/07/0884 Institutional research plan: CEZ:AV0Z20760514 Keywords : non-linear dynamics * parametric systems * impact effects * linear and non-linear damping Subject RIV: BI - Acoustics http://www.im.fme.vutbr.cz/pdf/16_3_221.full.pdf
Design of the APS transverse and longitudinal damping system
International Nuclear Information System (INIS)
Sellyey, W.; Barr, D.; Kahana, E.; Votaw, A.
1994-01-01
The main sources of instabilities in the Advanced Photon Source (APS) storage ring are expected to be higher-order modes (HOMs) of the accelerating cavities and the resistive wall impedance of the small insertion devices beam tubes. Extensive efforts are being made to reduce the Qs of HOMs. The maximum operating current of the ring will be 300 mA. At this current, analysis of measurements on cavity prototypes shows that the transverse growth rates will be less than 500/sec above radiation damping. The longitudinal growth rate due to HOMs is predicted to never exceed the radiation damping of 213/sec. The largest transverse resistive wall growth rate is calculated to be 2720/sec when 54 evenly spaced rigid bunches are used to produce 300 mA. There will be 26 additional unstable modes. The sum of these growth rates is 17,163/sec. Thus, it is clear that an effective transverse damping system will be needed and that the strength of this damper will be dominated by the resistive wall modes. A longitudinal damper system will also be built. This will provide damping about 2/3 times that due to synchrotron radiation. The most serious disturbances which can initiate instabilities will take place at injection. Typically, each bunch in the ring will be accumulated by injecting 115 of the final charge five times. A standard mode of operation is used in this paper in which there will be 54 evenly spaced bunches around the ring. During the ring filling process, the highest growth rates will occur when the last fifth of a bunch is injected into the last bunch. The largest expected vertical excursion of 1/5 of a bunch is about 5 mm. Anything larger will cause the bunch to scrape in the insertion device sections
International Nuclear Information System (INIS)
Ware, A.G.
1985-01-01
Studies are being conducted at the Idaho National Engineering Laboratory to determine whether an increase in the damping values used in seismic structural analyses of nuclear piping systems is justified. Increasing the allowable damping would allow fewer piping supports which could lead to safer, more reliable, and less costly piping systems. Test data from availble literature were examined to determine the important parameters contributing to piping system damping, and each was investigated in separate-effects tests. From the combined results a world pipe damping data bank was established and multiple regression analyses performed to assess the relative contributions of the various parameters. The program is being extended to determine damping applicable to higher frequency (33 to 100 Hz) fluid-induced loadings. The goals of the program are to establish a methodology for predicting piping system damping and to recommend revised guidelines for the damping values to be included in analyses
Conceptual Design of ILC Damping Ring Wiggler Straight Vacuum System
International Nuclear Information System (INIS)
Marks, S.; Kennedy, K.; Plate, D.; Schlueter, R.D.; Zisman, M.
2007-01-01
The positron and electron damping rings for the International Linear Collider will contain long straight sections consisting of twenty wiggler/quadrupole pairs. The wigglers will be based upon the CESR superconducting design. There are a number of challenges associated with the design of the wiggler straight vacuum system, in particular, the absorption of photon power generated by the wigglers. This paper will present the overall conceptual design of the wiggler straight vacuum system developed for the ILC Reference Design Report. Particular emphasis will be placed on photon power load calculations and the absorber design
Indefinite damping in mechanical systems and gyroscopic stabilization
DEFF Research Database (Denmark)
Kliem, Wolfhard; Pommer, Christian
2009-01-01
This paper deals with gyroscopic stabilization of the unstable system Mx + D(x) over dot + K-x = 0, with positive definite mass and stiffness matrices M and K, respectively, and an indefinite damping matrix D. The main question if for which skew-symmetric matrices G the system Mx (D+ G)(x) over dot...... + K-x = 0 can become stable? After investigating special cases we find an appropriat solution of the Lyapunov matrix equation for the general case. Examples show the deviation of the stability limit found by the Lyapunov method from the exact value....
Energy Technology Data Exchange (ETDEWEB)
Nguyen, H; Herman, L [Laboratoire de Recherches Physiques, Faculte des sciences, 9 Quai Saint Bernard, 75 - Paris (France); Drawin, H W [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires
1967-02-15
This report contains numerical data of the line shapes of Ly{alpha}, Ly{beta}, and H{alpha} for the following parameters: 1. 10{sup 2} {<=} H [gauss] {<=} 1.2. 10{sup 5} 1. 10{sup 15}{<=} N [cm{sup -3}] {<=} 1. 10{sup 18} cm{sup -3} 1. 10{sup 4} {<=} T [deg. K] {<=} 4. 10{sup 4} where H = magnetic field strength, K = density of plasma ions, T = electron temperature. (authors) [French] Dans ce rapport, on donne les valeurs numeriques des contours des raies spectrales Ly{alpha}, Ly{beta}, et H{alpha} pour les valeurs suivantes des parametres H, N et T 1. 10{sup 2} {<=} H [gauss] {<=} 1.2. 10{sup 5} 1. 10{sup 15}{<=} N [cm{sup -3}] {<=} 1. 10{sup 18} cm{sup -3} 1. 10{sup 4} {<=} T [deg. K] {<=} 4. 10{sup 4} ou H intensite du champ magnetique, N = densite des ions, T = temperature electronique. (auteurs)
Calculating latent frequencies of systems with local damping
International Nuclear Information System (INIS)
Kolonits, Ferenc
2005-01-01
Modal analysis of damped systems often cannot proceed with common real-eigenvalue techniques. The system of equilibrium equations leads to a matrix with elements being quadratic functions of a parameter λ. The values of that which make the matrix singular are the latent roots, while the solutions of the associated homogenous equation are the latent vectors. They are the (generally complex) characteristic frequencies and the mode shapes of the system, respectively. Although the theory is well developed, the numerical application is open to refinements yet. A reduction to better-known real-domain subtasks deserves attention. With a theorem of Popper and Gaspar, a n x n λ-matrix problem can be cut in two: into n-size asymmetric real matrices having as eigenvalues the n lower and n upper latent roots, ranked by absolute value. This approach may be of use for systems with high number of degrees of freedom while damped by a relatively few concentrated devices. It might fit also an earthquake analysis, where the lower portion of eigenvalues is customarily what counts. The dampers appear in the splitting algorithm as restricted-size modifications, ready for use by the Sherman-Morrison-Woodbury identity. The task is re-traced this way to a more usual real-asymmetric eigenproblem. A requirement of convergence is that the lower and upper n-set of latent values must be distinct. With odd-number degrees of freedom and neither over-damped, i.e. all latent roots being complex, this condition is surely violated. For such cases, a supplemental algorithm is proposed
High resolution upgrade of the ATF damping ring BPM system
International Nuclear Information System (INIS)
Terunuma, N.; Urakawa, J.; Frisch, J.; May, J.; McCormick, D.; Nelson, J.; Seryi, A.; Smith, T.; Woodley, M.; Briegel, C.; Dysert, R.
2008-01-01
A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring has been accomplished in its first stage, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R and D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and digital downconversion techniques, digital signal processing, and also tests a new automatic gain error correction schema. The technical concept and realization, as well as preliminary results of beam studies are presented
System and method for damping vibration in a drill string
Wassell, Mark Ellsworth; Turner, William Evans; Burgess, Daniel E; Perry, Carl Allison
2014-03-04
A system for damping vibration in a drill string can include a valve assembly having a supply of a fluid, a first member, and a second member capable of moving in relation to first member in response to vibration of the drill bit. The first and second members define a first and a second chamber for holding the fluid. Fluid can flow between the first and second chambers in response to the movement of the second member in relation to the first member. The valve assembly can also include a coil or a valve for varying a resistance of the fluid to flow between the first and second chambers.
Islam, Naz Niamul; Hannan, M A; Shareef, Hussain; Mohamed, Azah; Salam, M A
2014-01-01
Power oscillation damping controller is designed in linearized model with heuristic optimization techniques. Selection of the objective function is very crucial for damping controller design by optimization algorithms. In this research, comparative analysis has been carried out to evaluate the effectiveness of popular objective functions used in power system oscillation damping. Two-stage lead-lag damping controller by means of power system stabilizers is optimized using differential search algorithm for different objective functions. Linearized model simulations are performed to compare the dominant mode's performance and then the nonlinear model is continued to evaluate the damping performance over power system oscillations. All the simulations are conducted in two-area four-machine power system to bring a detailed analysis. Investigated results proved that multiobjective D-shaped function is an effective objective function in terms of moving unstable and lightly damped electromechanical modes into stable region. Thus, D-shape function ultimately improves overall system damping and concurrently enhances power system reliability.
International Nuclear Information System (INIS)
Han, Y.H.; Park, B.J.; Jung, S.Y.; Han, S.C.; Lee, W.R.; Bae, Y.C.
2013-01-01
Highlights: ► We made a 35 kWh superconductor flywheel energy storage system. ► The damping coefficient of the superconductor bearing was increased over 3000 N s/m. ► The source of damping was discussed. -- Abstract: A 35 kWh Superconductor Flywheel Energy Storage system (SFES) using hybrid bearing sets, which is composed of a high temperature superconductor (HTS) bearing and an active magnet damper (AMD), has been developed at KEPCO Research Institute (KEPRI). Damping is a source of energy loss but necessary for the stability of the flywheel system. We found that the damping of HTS bearings can be improved by thermal insulating bolts, which play a role of passive type external damper. To investigate the source of the increased damping, damping coefficients were measured with HTS bearings using insulating bolts made of three kinds of polymer materials. The damping coefficient was raised over 3000 N s/m in the case of PEEK bolts. The value was almost a quarter of the AMD. In this study, thermoelastic and Coulomb friction damping mechanisms are discussed. The main damping mechanism was the thermoelastic damping of the bolts themselves. And interfacial gap between the insulating bolt and metal chamber, which increased during the cooling process, was considered to be the cause of the anisotropic damping coefficients. Finally, the effects of the HTS bearings on the first critical speed are shown
Electric Generator in the System for Damping Oscillations of Vehicles
Directory of Open Access Journals (Sweden)
Serebryakov A.
2017-04-01
Full Text Available The control systems for the objects of industry, power generation, transport, etc. are extremely complicated; functional efficiency of these systems determines to a great extent the safe and non-polluting operation as well as convenience of service and repair of such objects. The authors consider the possibility to improve the efficiency of systems for damping oscillations in transport using a combination of electrical (generators of rotational and linear types and hydraulic means. Better efficiency of functioning is achieved through automatic control over the operational conditions of such a system in order to make it adaptive to variations in the road profile and ambient temperature; besides, it is possible to produce additional electric energy.
Electric Generator in the System for Damping Oscillations of Vehicles
Serebryakov, A.; Kamolins, E.; Levin, N.
2017-04-01
The control systems for the objects of industry, power generation, transport, etc. are extremely complicated; functional efficiency of these systems determines to a great extent the safe and non-polluting operation as well as convenience of service and repair of such objects. The authors consider the possibility to improve the efficiency of systems for damping oscillations in transport using a combination of electrical (generators of rotational and linear types) and hydraulic means. Better efficiency of functioning is achieved through automatic control over the operational conditions of such a system in order to make it adaptive to variations in the road profile and ambient temperature; besides, it is possible to produce additional electric energy.
Improvement of Transient Stability of Power System by System Damping Series Resistor (SDSR)
上里, 勝実; 千住, 智信; 当銘, 秀之; 高原, 景滋; Uezato, Katsumi; Senjyu, Tomonobu; Toume, Hideyuki; Takahara, Keiji
1990-01-01
The system damping resistor is one of the method for improving the transient stability of power systems. The main circuit is the simple construction so that is low cost and is few abnormal surge, and is superior in ability of economy, reliability and maintenance. Conventionally, most of all system damping resistors have adopted the paralleled resistor, whereas the series resistor is used little.In this paper, we investigate the characteristics of the series resistor by comparing with the para...
Damped button electrode for B-Factory BPM system
Energy Technology Data Exchange (ETDEWEB)
Shintake, T; Akasaka, N; Obina, T; Chin, Y H [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)
1996-08-01
A new concept of damping of resonances in a button electrode has been proposed and tested in the BPM system for the B-Factory project at KEK (KEKB). Since a very high current beam has to be stored in the machine, even a small resonance in the ring will result in losing a beam due to multi-bunch instabilities. In a conventional button electrode used in BPMs, a TE110 mode resonance can be trapped in the gap between the electrode and the vacuum chamber. In order to damp this mode, the diameter of the electrode has been chosen to be small to increase the resonance frequency and to radiate the power into the beam pipe. In addition, an asymmetric structure is applied to extract the EM energy of the TE110 mode into the coaxial cable as the propagating TEM mode which has no cut-off frequency. Results of the computer simulations and tests with cold models are reported. The quality factor of the TE110 mode was small enough due to the radiation into the beam pipe even in the conventional electrode and the mode coupling effect due to the asymmetric shape was significant on a cavity-like TE111 mode. (author)
International Nuclear Information System (INIS)
Ware, A.G.
1987-01-01
A pipe damping research program is being conducted for the United States Nuclear Regulatory Commission at the Idaho National Engineering Laboratory to establish more realistic, best-estimate damping values for use in dynamic structural analyses of piping systems. As part of this program, tests were conducted on a 5-in. (128 mm ID) laboratory piping system to determine the effects of pressure, support configuration, insulation and response amplitude on damping. The tests were designed to produce a wide range of damping values, from very low damping in lightly excited uninsulated systems with few supports, to higher damping under conditions of either/or insulation, high level excitation, and various support arrangements. The effect of pressure at representative seismic levels was considered to be minimal. The supports influence damping at all excitation levels; damping was highest when a mechanical snubber was present in the system. The addition of insulation produced a large increase in damping for the hydraulic shaker excitation tests, but there was no comparable increase for the snapback excitation tests. Once a response amplitude of approximately one-half yield stress was reached, overall damping increased to relatively high levels (>10% of critical)
Swing Damping for Helicopter Slung Load Systems using Delayed Feedback
DEFF Research Database (Denmark)
Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon
2009-01-01
of swing. The design of the delayed feedback controller is presented as an optimization problem which gives the possibility of an automated design process. Simulations and flight test verifications of the control system on two different autonomous helicopters are presented and it is shown how a significant......This paper presents the design and verification of a swing reducing controller for helicopter slung load systems using intentional delayed feedback. It is intended for augmenting a trajectory tracking helicopter controller and thereby improving the slung load handing capabilities for autonomous...... helicopters. The delayed feedback controller is added to actively reduce oscillations of the slung load by improving the damping of the slung load pendulum modes. Furthermore, it is intended for integration with a feedforward control scheme based on input shaping for concurrent avoidance and dampening...
An Adaptive Damping Network Designed for Strapdown Fiber Optic Gyrocompass System for Ships
Directory of Open Access Journals (Sweden)
Jin Sun
2017-03-01
Full Text Available The strapdown fiber optic gyrocompass (strapdown FOGC system for ships primarily works on external horizontal damping and undamping statuses. When there are large sea condition changes, the system will switch frequently between the external horizontal damping status and the undamping status. This means that the system is always in an adjustment status and influences the dynamic accuracy of the system. Aiming at the limitations of the conventional damping method, a new design idea is proposed, where the adaptive control method is used to design the horizontal damping network of the strapdown FOGC system. According to the size of acceleration, the parameters of the damping network are changed to make the system error caused by the ship’s maneuvering to a minimum. Furthermore, the jump in damping coefficient was transformed into gradual change to make a smooth system status switch. The adaptive damping network was applied for strapdown FOGC under the static and dynamic condition, and its performance was compared with the conventional damping, and undamping means. Experimental results showed that the adaptive damping network was effective in improving the dynamic performance of the strapdown FOGC.
International Nuclear Information System (INIS)
Chiba, T.; Kobayashi, H.; Kitamura, K.; Ando, K.; Koyanagi, R.
1983-01-01
The objectives of this study are 1) to clarify the damping characteristics and the dynamic stiffness of mechanical snubber, 2) to take the damping characteristics of mechanical snubber into the damping evaluation method obtained in SDREP. Therefore, following vibration tests were conducted. 1) Component test: As a first step, mechanical snubbers were excited with sinusoidal wave, and damping ratio and dynamic stiffness were measured at several loading levels. 2) Piping model test: Second, a 8'' diameter x 16 m length 3-dimensional piping model simulating the supporting conditions of actual piping systems was tested. Damping ratio and made shapes of piping model with mechanical snubbers were measured at several supporting conditions and response levels. From the results of these tests, the damping characteristics and the dynamic stiffness of mechanical snubber can be summarized as follows: 1) The damping effect of mechanical snubber is as strong as that of oil snubber. 2) Mechanical snubber contributes effectively to the damping of piping system, and it is indicated that the damping characteristics of mechanical snubber is applicable to the damping evaluation method obtained in SDREP. (orig./HP)
Ultra-low magnetic damping in metallic and half-metallic systems
Shaw, Justin
The phenomenology of magnetic damping is of critical importance to devices which seek to exploit the electronic spin degree of freedom since damping strongly affects the energy required and speed at which a device can operate. However, theory has struggled to quantitatively predict the damping, even in common ferromagnetic materials. This presents a challenge for a broad range of applications in magnonics, spintronics and spin-orbitronics that depend on the ability to precisely control the damping of a material. I will discuss our recent work to precisely measure the intrinsic damping in several metallic and half-metallic material systems and compare experiment with several theoretical models. This investigation uncovered a metallic material composed of Co and Fe that exhibit ultra-low values of damping that approach values found in thin film YIG. Such ultra-low damping is unexpected in a metal since magnon-electron scattering dominates the damping in conductors. However, this system possesses a distinctive feature in the bandstructure that minimizes the density of states at the Fermi energy n(EF). These findings provide the theoretical framework by which such ultra-low damping can be achieved in metallic ferromagnets and may enable a new class of experiments where ultra-low damping can be combined with a charge current. Half-metallic Heusler compounds by definition have a bandgap in one of the spin channels at the Fermi energy. This feature can also lead to exceptionally low values of the damping parameter. Our results show a strong correlation of the damping with the order parameter in Co2MnGe. Finally, I will provide an overview of the recent advances in achieving low damping in thin film Heusler compounds.
An evaluation of damping ratios for HVAC duct systems using vibration test data
International Nuclear Information System (INIS)
Gunyasu, K.; Horimizu, Y.; Kawakami, A.; Iokibe, H.; Yamazaki, T.
1988-01-01
The function of Heating Ventilating Air Conditioning (HVAC) systems must be maintained including HVAC duct systems to keep the operation of safety-related equipment in nuclear power plants during earthquake excitations. Therefore, it is important to carry out seismic design for HVAC duct systems. In the previous aseismic design for HVAC duct systems, the 0.5% damping ratio has been used in Japan. In recent years, vibration tests, held on actual duct systems in nuclear power plants and mockup duct systems were performed in order to investigate damping ratios for HVAC duct systems. Based on the results, it was confirmed that the damping ratio for HVAC duct systems, evaluated from these tests, were much greater than the 0.5% damping ratio used in the previous aseismic design of Japan. The new damping ratio in aseismic design was proposed to be 2.5%. The present paper describes the results of the above mentioned investigation
Equivalent viscous damping procedure for multi-material systems
International Nuclear Information System (INIS)
Ahmed, H.; Ma, D.
1979-01-01
The inclusion of accurate viscous damping effects in the seismic analysis of nuclear power plants is discussed. A procedure to evaluate and use equivalent viscous damping coefficients in conjunction with the substructure method of finite element analysis is outlined in detail
Controllable outrigger damping system for high rise building with MR dampers
Wang, Zhihao; Chang, Chia-Ming; Spencer, Billie F., Jr.; Chen, Zhengqing
2010-04-01
A novel energy dissipation system that can achieve the amplified damping ratio for a frame-core tube structures is explored, where vertical dampers are equipped between the outrigger and perimeter columns. The modal characteristics of the structural system with linear viscous dampers are theoretically analyzed from the simplified finite element model by parametric analysis. The result shows that modal damping ratios of the first several modes can increase a lot with this novel damping system. To improve the control performance of system, the semi-active control devices, magnetorheological (MR) dampers, are adopted to develop a controllable outrigger damping system. The clipped optimal control with the linear-quadratic Gaussian (LQG) acceleration feedback is adopted in this paper. The effectiveness of both passive and semi-active control outrigger damping systems is evaluated through the numerical simulation of a representative tall building subjected to two typical earthquake records.
Directory of Open Access Journals (Sweden)
Ali Nasser Hussain
2016-09-01
Full Text Available The aim of this study is to present a comprehensive comparison and assessment of the damping function improvement of power system oscillation for the multiple damping controllers using the simultaneously coordinated design based on Power System Stabilizer (PSS and Flexible AC Transmission System (FACTS devices. FACTS devices can help in the enhancing the stability of the power system by adding supplementary damping controller to the control channel of the FACTS input to implement the task of Power Oscillation Damping (FACT POD controller. Simultaneous coordination can be performed in different ways. First, the dual coordinated designs between PSS and FACTS POD controller or between different FACTS POD controllers are arranged in a multiple FACTS devices without PSS. Second, the simultaneous coordination has been extended to triple coordinated design among PSS and different FACTS POD controllers. The parameters of the damping controllers have been tuned in the individual controllers and coordinated designs by using a Chaotic Particle Swarm Optimization (CPSO algorithm that optimized the given eigenvalue-based objective function. The simulation results for a multi-machine power system show that the dual coordinated design provide satisfactory damping performance over the individual control responses. Furthermore, the triple coordinated design has been shown to be more effective in damping oscillations than the dual damping controllers.
Nontrivial effects of high-frequency excitation for strongly damped mechanical systems
DEFF Research Database (Denmark)
Fidlin, Alexander; Thomsen, Jon Juel
2008-01-01
Some non-trivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based on a slightly...... modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical optimally...
Nontrivial effects of high-frequency excitation for strongly damped mechanical systems
DEFF Research Database (Denmark)
Fidlin, Alexander; Thomsen, Jon Juel
Some nontrivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial (depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based...... on a slightly modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical...
DEFF Research Database (Denmark)
Yao, Wei; Fang, Jiakun; Zhao, Ping
2013-01-01
the characteristics of the conventional PID, but adjust the parameters of PID controller online using identified Jacobian information from RBFNN. Hence, it has strong adaptability to the variation of the system operating condition. The effectiveness of the proposed controller is tested on a two-machine five-bus power...... system and a four-machine two-area power system under different operating conditions in comparison with the lead-lag damping controller tuned by evolutionary algorithm (EA). Simulation results show that the proposed damping controller achieves good robust performance for damping the low frequency......In this paper, a nonlinear adaptive damping controller based on radial basis function neural network (RBFNN), which can infinitely approximate to nonlinear system, is proposed for thyristor controlled series capacitor (TCSC). The proposed TCSC adaptive damping controller can not only have...
International Nuclear Information System (INIS)
Shibata, H.; Ito, M.; Hayashi, T.; Chiba, T.; Kobayashi, H.; Kitamura, K.; Ando, K.; Koyanagi, R.
1981-01-01
To clarify the damping characteristics and mechanism in nuclear power plant piping systems, the study group was established and conducted to study SDREP (Seismic Damping Ratio Evaluation Program). As the Phase II of this study, vibration tests were conducted to investigate factors which might contribute to damping characteristics of piping systems. These tests are composed of the next three model tests: 1) The component damping characteristics test of thermal insulator 2) The simplified piping model test 3) The scale model test. In these tests, we studied damping characteristics with emphasis on thermal insulator (mainly calcium silicate insulator). The acceleartion level of pipings is the same as that of the actual seismic response. The excitation was by sinusoidal sweep method using the shaking table and by free vibration method using snapback. (orig./RW)
A PSO based unified power flow controller for damping of power system oscillations
Energy Technology Data Exchange (ETDEWEB)
Shayeghi, H. [Technical Engineering Dept., Univ. of Mohaghegh Ardabili, Daneshgah Street, P.O. Box 179, Ardabil (Iran); Shayanfar, H.A. [Center of Excellence for Power Automation and Operation, Electrical Engineering Dept., Iran Univ. of Science and Technology, Tehran (Iran); Jalilzadeh, S.; Safari, A. [Technical Engineering Dept., Zanjan Univ., Zanjan (Iran)
2009-10-15
On the basis of the linearized Phillips-Herffron model of a single-machine power system, we approach the problem of select the best input control signal of the unified power flow controller (UPFC) and design optimal UPFC based damping controller in order to enhance the damping of the power system low frequency oscillations. The potential of the UPFC supplementary controllers to enhance the dynamic stability is evaluated. This controller is tuned to simultaneously shift the undamped electromechanical modes to a prescribed zone in the s-plane. The problem of robustly UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multiobjective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using particle swarm optimization technique (PSO) that has a strong ability to find the most optimistic results. To ensure the robustness of the proposed damping controller, the design process takes into account a wide range of operating conditions and system configurations. The effectiveness of the proposed controller is demonstrated through eigenvalue analysis, nonlinear time-domain simulation and some performance indices studies. The results analysis reveals that the tuned PSO based UPFC controller using the proposed multiobjective function has an excellent capability in damping power system low frequency oscillations and enhance greatly the dynamic stability of the power systems. Moreover, the system performance analysis under different operating conditions show that the {delta}{sub E} based controller is superior to the m{sub B} based controller. (author)
An active feedback system to control synchrotron oscillations in the SLC Damping Rings
International Nuclear Information System (INIS)
Corredoura, P.L.; Pellegrin, J.L.; Schwarz, H.D.; Sheppard, J.C.
1989-03-01
Initially the SLC Damping Rings accomplished Robinson instability damping by operating the RF accelerating cavities slightly detuned. In order to be able to run the cavities tuned and achieve damping for Robinson instability and synchrotron oscillations at injection an active feedback system has been developed. This paper describes the theoretical basis for the feedback system and the development of the hardware. Extensive measurements of the loop response including stored beam were performed. Overall performance of the system is also reported. 3 refs., 6 figs
Non-stationary pre-envelope covariances of non-classically damped systems
Muscolino, G.
1991-08-01
A new formulation is given to evaluate the stationary and non-stationary response of linear non-classically damped systems subjected to multi-correlated non-separable Gaussian input processes. This formulation is based on a new and more suitable definition of the impulse response function matrix for such systems. It is shown that, when using this definition, the stochastic response of non-classically damped systems involves the evaluation of quantities similar to those of classically damped ones. Furthermore, considerations about non-stationary cross-covariances, spectral moments and pre-envelope cross-covariances are presented for a monocorrelated input process.
The Characteristics of Vibration Isolation System with Damping and Stiffness Geometrically Nonlinear
Lu, Ze-Qi; Chen, Li-Qun; Brennan, Michael J.; Li, Jue-Ming; Ding, Hu
2016-09-01
The paper concerns an investigation into the use of both stiffness and damping nonlinearity in the vibration isolator to improve its effectiveness. The nonlinear damping and nonlinear stiffness are both achieved by horizontal damping and stiffness as the way of the geometrical nonlinearity. The harmonic balance method is used to analyze the force transmissibility of such vibration isolation system. It is found that as the horizontal damping increasing, the height of the force transmissibility peak is decreased and the high-frequency force transmissibility is almost the same. The results are also validated by some numerical method. Then the RMS of transmissibility under Gaussian white noise is calculated numerically, the results demonstrate that the beneficial effects of the damping nonlinearity can be achieved under random excitation.
Directory of Open Access Journals (Sweden)
Chaowu Jin
2016-01-01
Full Text Available At present, the stiffness and damping identification for active magnetic bearings (AMBs are still in the stage of theoretical analysis. The theoretical analysis indicates that if the mechanical structure and system parameters are determined, AMBs stiffness and damping are only related to frequency characteristic of control system, ignoring operating condition. More importantly, few verification methods are proposed. Considering the shortcomings of the theoretical identification, this paper obtains these coefficients from the experiment by using the magnetic bearing as a sine exciter. The identification results show that AMBs stiffness and damping have a great relationship with the control system and rotating speed. Specifically, at low rotating speed, the stiffness and damping can be obtained from the rotor static suspension by adding the same excitation frequency. However, at high speed, different from the static suspension situation, the AMBs supporting coefficients are not only related to the frequency characteristics of control system, but also related to the system operating conditions.
Salgotra, Aprajita; Pan, Somnath
2018-05-01
This paper explores a two-level control strategy by blending local controller with centralized controller for the low frequency oscillations in a power system. The proposed control scheme provides stabilization of local modes using a local controller and minimizes the effect of inter-connection of sub-systems performance through a centralized control. For designing the local controllers in the form of proportional-integral power system stabilizer (PI-PSS), a simple and straight forward frequency domain direct synthesis method is considered that works on use of a suitable reference model which is based on the desired requirements. Several examples both on one machine infinite bus and multi-machine systems taken from the literature are illustrated to show the efficacy of the proposed PI-PSS. The effective damping of the systems is found to be increased remarkably which is reflected in the time-responses; even unstable operation has been stabilized with improved damping after applying the proposed controller. The proposed controllers give remarkable improvement in damping the oscillations in all the illustrations considered here and as for example, the value of damping factor has been increased from 0.0217 to 0.666 in Example 1. The simulation results obtained by the proposed control strategy are favourably compared with some controllers prevalent in the literature. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.
Effect of PVRC damping with independent support motion response spectrum analysis of piping systems
International Nuclear Information System (INIS)
Wang, Y.K.; Bezler, P.; Shteyngart, S.
1986-01-01
The Technical Committee for Piping Systems of the Pressure Vessel Research Committee (PVRC) has recommended new damping values to be used in the seismic analyses of piping systems in nuclear power plants. To evaluate the effects of coupling these recommendations with the use of independent support motion analyses methods, two sets of seismic analyses have been carried out for several piping systems. One set based on the use of uniform damping as specified in Regulatory Guide 1.61, the other based on the PVRC recommendations. In each set the analyses were performed using independent support motion time history and response spectrum methods as well as the envelope spectrum method. In the independent response spectrum analyses, 14 response estimates were in fact obtained by considering different combination procedures between the support group contributions and all sequences of combinations between support groups, modes and directions. For each analysis set, the response spectrum results were compared with time history estimates of those results. Comparison tables were then prepared depicting the percentage by which the response spectrum estimates exceeded the time history estimates. By comparing the result tables between both analysis sets, the impact of PVRC damping can be observed. Preliminary results show that the degree of exceedance of the response spectrum estimates based on PVRC damping is less than that based on uniform damping for the same piping problem. Expressed differently the results obtained if ISM methods are coupled with PVRC damping are not as conservative as those obtained using uniform damping
Damped Lyα system toward QSO1854+116: A new type of absorber?
Directory of Open Access Journals (Sweden)
Ćirković M.M.
1999-01-01
Full Text Available A puzzle of the low-redshift damped Lyα absorption system toward QSO 1854+116 is presented. Problems which conventional intepretation of damped Lyα systems encounters in this case are sketched and a possible explanation, based on transience of the phenomenon, is suggested. It is shown that the detailed Hα tomography can observationally resolve the controversy in the very near future.
Suggestions for new transverse oscillations damping systems in large synchrotrons and colliders
International Nuclear Information System (INIS)
Ivanov, I.N.; Melnikov, V.A.
1994-01-01
Due to the high requirements on beam quality, modern synchrotrons and colliders require special systems for transverse oscillation damping (TDS). New system for the correction of injection errors and multibunch instabilities is proposed. The special beam monitor on the basis of the axial-slotted lines is developed for the transverse beam velocity measuring. The special nonlinear regime of damping is suggested to decrease the operating time of TDS. 2 refs., 4 figs., 2 tabs
Spontaneous symmetry breaking in ΡΤ symmetric systems with nonlinear damping
International Nuclear Information System (INIS)
Karthiga, S.; Chandrasekar, V.K.; Senthilvelan, M.; Lakshmanan, M.
2016-01-01
In this talk, we discuss the remarkable role of position dependent damping in determining the parametric regions of symmetry breaking in nonlinear ΡΤ -symmetric systems. We illustrate the nature of ΡΤ-symmetry preservation and breaking with reference to a remarkable integrable scalar nonlinear system. In the two dimensional cases of such position dependent damped systems, we unveil the existence of a class of novel bi-ΡΤ -symmetric systems which have two fold ΡΤ symmetries. We discuss the dynamics of these systems and show how symmetry breaking occurs, that is whether the symmetry breaking of the two ΡΤ symmetries occurs in pair or occurs one by one. The addition of linear damping in these nonlinearly damped systems induces competition between the two types of damping. This competition results in a ΡΤ phase transition in which the ΡΤ symmetry is broken for lower loss/gain strength and is restored by increasing the loss/gain strength. We also show that by properly designing the form of the position dependent damping, we can tailor the ΡΤ-symmetric regions of the system. (author)
DEFF Research Database (Denmark)
Adamczyk, Andrzej Grzegorz; Teodorescu, Remus; Rodriguez, Pedro
2011-01-01
Damping of low frequency power oscillations is one of essential aspects of maintaining power system stability. In literature can be found publications on damping capability of Doubly Fed Induction Generator based wind turbines. This paper extends discussion on Wind Power Plant damping capability...
WAMS Based Damping Control of Inter-area Oscillations Employing Energy Storage System
Directory of Open Access Journals (Sweden)
MA, J.
2012-05-01
Full Text Available This paper presents a systematic design procedure for a wide-area damping controller (WADC employing Energy Storage Systems (ESSs. The WADC is aimed at enhancing the damping of multiple inter-area modes in a large scale power system. Firstly, geometric measures of controllability and obsevability are used to select the control locations for ESSs and most effective stabilizing signals, respectively. Then, the WADC coordinates these signals to achieve multiple-input-multiple-output (MIMO controllers with the least Frobenius norm feedback gain matrix. The simulation results of frequency and time domains verify the effectiveness of the wide-area damping controller for various operating conditions. Furthermore, the robustness of the wide-area damping controller is also tested with respect to time delay and uncertainty of models.
Emergent large mechanical damping in ferroelastic-martensitic systems driven by disorder
Ni, Yan; Zhang, Zhen; Fang, Minxia; Hao, Yanshuang; Ding, Xiangdong; Otsuka, Kazuhiro; Ren, Xiaobing
2018-05-01
Disorders and point defects strongly interplay with the phase transition and alter the properties of ferroelastic-martensitic systems. Unusual static and quasistatic behaviors, such as time-dependent phase transitions, are discovered when disorders are introduced. However, the role of disorders on the ferroelastic system in vibrational environments at moderate frequency is rarely known, investigation of which could further shed light on their application as mechanical damping materials. Here we present the emergence of large damping capacity in ferroelastic-martensitic systems [including both the T i50 -xN i50 +x alloy and (C a1 -xS rx) Ti O3 ceramics] by introducing disorder (i.e., substitutional Ni and Sr, respectively). As the level disorder increases, the damping capacity of both systems raises and eventually reaches a maximum when long-range-ordered martensite tends to vanish. Moreover, near the disorder-induced phase boundary, we observe a large mechanical damping in ferroelastic ceramics (C a1 -xS rx) Ti O3 with a figure of merit ˜2 GP a1 /2 . Microscopic and dynamic investigations indicate that such damping plateau could result from the competing evolution of density and mobility of domain boundaries when disorder is introduced. Our work provides a degree of freedom to develop ferroelastic damping materials and a potential way to tune domain-boundary-mediated functionalities for other ferroic materials.
Modified multiple time scale method for solving strongly nonlinear damped forced vibration systems
Razzak, M. A.; Alam, M. Z.; Sharif, M. N.
2018-03-01
In this paper, modified multiple time scale (MTS) method is employed to solve strongly nonlinear forced vibration systems. The first-order approximation is only considered in order to avoid complexicity. The formulations and the determination of the solution procedure are very easy and straightforward. The classical multiple time scale (MS) and multiple scales Lindstedt-Poincare method (MSLP) do not give desire result for the strongly damped forced vibration systems with strong damping effects. The main aim of this paper is to remove these limitations. Two examples are considered to illustrate the effectiveness and convenience of the present procedure. The approximate external frequencies and the corresponding approximate solutions are determined by the present method. The results give good coincidence with corresponding numerical solution (considered to be exact) and also provide better result than other existing results. For weak nonlinearities with weak damping effect, the absolute relative error measures (first-order approximate external frequency) in this paper is only 0.07% when amplitude A = 1.5 , while the relative error gives MSLP method is surprisingly 28.81%. Furthermore, for strong nonlinearities with strong damping effect, the absolute relative error found in this article is only 0.02%, whereas the relative error obtained by MSLP method is 24.18%. Therefore, the present method is not only valid for weakly nonlinear damped forced systems, but also gives better result for strongly nonlinear systems with both small and strong damping effect.
International Nuclear Information System (INIS)
Noakes, M.W.; Petterson, B.J.; Werner, J.C.
1990-01-01
Transportation of objects using overhead cranes can induce pendulum motion of the object, which usually must be damped or allowed to decay before the next process can take place. Recent work at Sandia National Laboratories (SNL) has shown that oscillation damped transport and swing-free stops are possible by properly programming the acceleration of the transporting crane. This paper reviews the theory associated with oscillation-damped trajectories for simply suspended objects and describes a specific, full-scale implementation of the damped oscillation methods for the Oak Ridge National Laboratory (ORNL) Advanced Integrated Maintenance System (AIMS). Hardware and software requirements and constraints for proper operation are discussed. Finally, test results and lessons learned are presented. 5 refs., 4 figs
International Nuclear Information System (INIS)
Wang, Xueqin; Pei, Yanling; Ma, Yue
2013-01-01
Samples with various interface microstructures between the coating and the substrate were designed and fabricated in this paper. Dynamic mechanical thermal analyzer (DMTA) was utilized to investigate the dynamic mechanical properties of the samples and scanning electron microscopy (SEM) was used to observe the interface microstructure between the substrate and coating. The effect of the interface microstructure on damping was studied, and results indicated that the larger the coating/substrate interface thickness was and the more interface defects were, the higher interface system damping was. When the micro-hardness ratio of substrate to coating was increased, the damping of coating system was enhanced. The effect of the APS and EB-PVD coating on damping capacity was investigated. There was a dramatic increase in the damping value of the APS coating when the strain was higher than 20 ppm, while the damping amplitude effect of the EB-PVD coating was not so obvious, which could mainly be caused by the different energy dissipation mechanisms of the two coatings.
Doubly Fed Induction Generator System Resonance Active Damping through Stator Virtual Impedance
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
(positive capacitor or negative inductor) into the stator branch through stator current feedforward control. The effectiveness of the DFIG system active damping control is verified by a 7.5 kW experimental down-scaled DFIG system, and simulation results of a commercial 2 MW DFIG system is provided as well....... converters/loads. This paper analyzes and explains first the HFR phenomenon between the DFIG system and a parallel compensated weak network (series RL + shunt C). Then on the basis of the DFIG system impedance modeling, an active damping control strategy is introduced by inserting a virtual impedance...... Frequency Resonance (HFR) due to the impedance interaction between the DFIG system and the weak grid network whose impedance is comparative large. Thus, it is important to implement an active damping for the HFR in order to ensure a safe and reliable operation of both the DFIG system and the grid connected...
Operation and performance of the PEP-II prototype longitudinal damping system at ALS
International Nuclear Information System (INIS)
Teytelman, D.; Claus, R.; Fox, J.
1995-05-01
A modular programmable longitudinal feedback system has been developed as a component of the PEP-II R+D program. This system is based on a family of VME and VXI packaged signal processing functions which implement a general purpose digital feedback controller for accelerators with bunch spacings of 2 ns. A complete PEP-II prototype system has been configured and installed for use at the LBL Advanced Light Source. The system configuration used for tests at the ALS is described and results are presented showing the action of the feedback system. Open and closed loop results showing the detection and calculation of feedback signals from bunch motion are presented and the system is shown to damp coupled-bunch instabilities in the ALS. Use of the system for accelerator diagnostics is illustrated via measurement of grow-damp transients which quantify growth rates without feedback, damping rates with feedback, and identify unstable modes
International Nuclear Information System (INIS)
Kitada, Y.; Makiguchi, M.; Komori, A.; Ichiki, T.
1985-01-01
The records of three earthquakes which had induced significant earthquake response to the piping system were obtained with the earthquake observation system. In the present paper, first, the eigenvalue analysis results for the natural piping system based on the piping support (boundary) conditions are described and second, the frequency and the damping factor evaluation results for each vibrational mode are described. In the present study, the Auto Regressive (AR) analysis method is used in the evaluation of natural frequencies and damping factors. The AR analysis applied here has a capability of direct evaluation of natural frequencies and damping factors from earthquake records observed on a piping system without any information on the input motions to the system. (orig./HP)
Directory of Open Access Journals (Sweden)
Stefanov Predrag Č.
2014-01-01
Full Text Available This paper deals with inter-area power oscillations damping enhancement by distributed energy resources contained in typical micro grid. Main idea behind this work is to use distributed generation and distributed storage, such as battery energy storage to mimic conventional power system stabilizer, but with regulating active power output, rather than reactive power, as in standard power system stabilizer realization. The analysis of the small signal stability is established for four-machine, two-area system, with inverter based micro grids in each area. Dynamic simulation results are included in this work and they show that proposed controller provides additional damping effect to this test system.
International Nuclear Information System (INIS)
Kim, In-Ho; Jung, Hyung-Jo; Koo, Jeong-Hoi
2010-01-01
This paper investigates the effectiveness of a self-powered smart damping system consisting of a magnetorheological (MR) damper and an electromagnetic induction (EMI) device in reducing cable vibrations. The proposed smart damping system incorporates an EMI device, which is capable of converting vibration energy into useful electrical energy. Thus, the incorporated EMI device can be used as an alternative power source for the MR damper, making it a self-powering system. The primary goal of this experimental study is to evaluate the performance of the proposed smart damping system using a full-scale, 44.7 m long, high-tension cable. To this end, an EMI part and an MR damper were designed and manufactured. Using a cable test setup in a laboratory setting, a series of tests were performed to evaluate the effectiveness of the self-powered smart damping system in reducing free vibration responses of the cable. The performances of the proposed smart damping system are compared with those of an equivalent passive system. Moreover, the damping characteristics of the smart damping system and the passive system are compared. The experimental results show that the self-powered smart damping system outperforms the passive control cases in reducing the vibrations of the cable. The results also show that the EMI can operate the smart damping system as a sole power source, demonstrating the feasibility of the self-powering capability of the system
Damping by heat conduction in the Timoshenko system: Fourier and Cattaneo are the same
Said-Houari, Belkacem
2013-08-01
We consider the Cauchy problem for the one-dimensional Timoshenko system coupled with heat conduction, wherein the latter is described by either the Cattaneo law or the Fourier law. We prove that heat dissipation alone is sufficient to stabilize the system in both cases, so that additional mechanical damping is unnecessary. However, the decay of solutions without the mechanical damping is found to be slower than that with mechanical damping. Furthermore, in contrast to earlier results of Said-Houari and Kasimov (2012) [10] and Fernández Sare and Racke (2009) [12], we find that the Timoshenko-Fourier and the Timoshenko-Cattaneo systems have the same decay rate. The rate depends on a certain number α (first identified by Santos et al., 2012 [11] in a related study in a bounded domain), which is a function of the parameters of the system. © 2013 Elsevier Inc.
An identification method for damping ratio in rotor systems
Wang, Weimin; Li, Qihang; Gao, Jinji; Yao, Jianfei; Allaire, Paul
2016-02-01
Centrifugal compressor testing with magnetic bearing excitations is the last step to assure the compressor rotordynamic stability in the designed operating conditions. To meet the challenges of stability evaluation, a new method combining the rational polynomials method (RPM) with the weighted instrumental variables (WIV) estimator to fit the directional frequency response function (dFRF) is presented. Numerical simulation results show that the method suggested in this paper can identify the damping ratio of the first forward and backward modes with high accuracy, even in a severe noise environment. Experimental tests were conducted to study the effect of different bearing configurations on the stability of rotor. Furthermore, two example centrifugal compressors (a nine-stage straight-through and a six-stage back-to-back) were employed to verify the feasibility of identification method in industrial configurations as well.
International Nuclear Information System (INIS)
Poterasu, V.F.
1984-01-01
It is presented a method and the phase resonance for damping characteristic identification of non-linear soil-structural interaction. The algorithm can be applied in case of any, not necessarily, damping characteristic of the system examined. For the identification, the system is harmonically excited and are considered the super-harmonic amplitudes for odd and even powers of the x. The response of shear beam system for different levels of base excitation and for different locations of the load is considered. (Author) [pt
International Nuclear Information System (INIS)
Ware, A.G.; Arendts, J.G.
1984-01-01
A program has been developed to assess the available piping damping data, to generate additional data and conduct seperate effects tests, and to establish a plan for reporting and storing future test results into a data bank. This effort is providing some of the basis for developing higher allowable damping values for piping seismic analyses, which will potentially permit removal of a considerable number of piping supports, particularly snubbers. This in turn will lead to more flexible piping systems which will be less susceptible to thermal cracking, will be easier to maintain and inspect, as well as less costly
Particle Damping with Granular Materials for Multi Degree of Freedom System
Directory of Open Access Journals (Sweden)
Masanobu Inoue
2011-01-01
Full Text Available A particle damper consists of a bed of granular materials moving in cavities within a multi degree-of-freedom (MDOF structure. This paper deals with the damping effects on forced vibrations of a MDOF structure provided with the vertical particle dampers. In the analysis, the particle bed is assumed to be a single mass, and the collisions between the granules and the cavities are completely inelastic, i.e., all energy dissipation mechanisms are wrapped into zero coefficient of restitution. To predict the particle damping effect, equations of motion are developed in terms of equivalent single degree-of-freedom (SDOF system and damper mass with use made of modal approach. In this report, the periodic vibration model comprising sustained contact on or separation of the damper mass from vibrating structure is developed. A digital model is also formulated to simulate the damped motion of the physical system, taking account of all vibration modes. Numerical and experimental studies are made of the damping performance of plural dampers located at selected positions throughout a 3MDOF system. The experimental results confirm numerical prediction that collision between granules and structures is completely inelastic as the contributing mechanism of damping in the vertical vibration. It is found that particle dampers with properly selected mass ratios and clearances effectively suppress the resonance peaks over a wide frequency range.
The Frequency and Damping of Soil-Structure Systems with Embedded Foundation
International Nuclear Information System (INIS)
Ghannad, M. Ali; Rahmani, Mohammad T.; Jahankhah, Hossein
2008-01-01
The effect of foundation embedment on fundamental period and damping of buildings has been the title of several researches in three past decades. A review of the literature reveals some discrepancies between proposed formulations for dynamic characteristics of soil-embedded foundation-structure systems that raise the necessity of more investigation on this issue. Here, first a set of approximate polynomial equations for soil impedances, based on numerical data calculated from well known cone models, are presented. Then a simplified approach is suggested to calculate period and damping of the whole system considering soil medium as a viscoelastic half space. The procedure includes both material and radiation damping while frequency dependency of soil impedance functions is not ignored. Results show that soil-structure interaction can highly affect dynamic properties of system. Finally the results are compared with one of the commonly referred researches
Babakhani, B.; de Vries, Theodorus J.A.; van Amerongen, J.
2012-01-01
In this paper, both collocated and noncollocated active vibration control (AVC) of a the vibrations in a motion system are considered. Pole-zero plots of both the AVC loop and the motion-control (MC) loop are used to analyze the effect of the applied active damping on the system dynamics. Using
An Active Damping Technique for Small DC-Link Capacitor Based Drive System
DEFF Research Database (Denmark)
Maheshwari, Ram Krishan; Munk-Nielsen, Stig; Lu, Kaiyuan
2013-01-01
A small dc-link capacitor based drive system shows instability when it is operated with large input line inductance at operating points with high power. This paper presents a simple, new active damping technique that can stabilize effectively the drive system at unstable operating points, offering...
Directory of Open Access Journals (Sweden)
S. Zhu
1998-01-01
Full Text Available Magnetic damping is one of the important parameters that control the response and stability of maglev systems. An experimental study to measure magnetic damping directly is presented. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters, such as conductivity, gap, excitation frequency, and oscillation amplitude, on magnetic damping. The experimental technique is capable of measuring all of the magnetic damping coefficients, some of which cannot be measured indirectly.
PSS and TCSC damping controller coordinated design using PSO in multi-machine power system
Energy Technology Data Exchange (ETDEWEB)
Shayeghi, H., E-mail: hshayeghi@gmail.co [Technical Engineering Department, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Safari, A.; Shayanfar, H.A. [Center of Excellence for Power System Automation and Operation, Electrical Engineering Department, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)
2010-12-15
The paper develops a new design procedure for simultaneous coordinated designing of the thyristor controlled series capacitor (TCSC) damping controller and power system stabilizer (PSS) in multi-machine power system. The coordinated design problem of PSS and TCSC damping controllers over a wide range of loading conditions is converted to an optimization problem with the time domain-based objective function that is solved by a particle swarm optimization (PSO) technique which has a strong ability to find the most optimistic results. By minimizing the proposed fitness function in which oscillatory characteristics between areas are included and thus the interactions among the TCSC controller and PSS under transient conditions in the multi-machine power system are improved. To ensure the robustness of the proposed stabilizers, the design process takes a wide range of operating conditions into account. The effectiveness of the proposed controller is demonstrated through the nonlinear time-domain simulation and some performance indices studies. The results of these studies show that the proposed coordinated controllers have an excellent capability in damping power system inter-area oscillations and enhance greatly the dynamic stability of the power system. Moreover, it is superior to both the uncoordinated designed stabilizers of the PSS and the TCSC damping controller.
DEFF Research Database (Denmark)
Chen, Zhe; Pedersen, John Kim; Blaabjerg, Frede
2004-01-01
A hybrid compensation system consisting of an active filter and a group of distributed passive filters has been studied previously. The passive filters are used for each distorting load or Dispersed Generation (DG) unit to remove major harmonics and provide reactive power compensation. The active...... filter is connected in parallel with the distributed passive filters and loads/DGs to correct the system unbalance and remove the remaining harmonic components. The effectiveness of the presented compensation system has also been demonstrated. This paper studies the performance of the hybrid compensation...... demonstrated that the harmonic resonance can be damped effectively. The hybrid filter system is an effective compensation system for dispersed generation systems. In the compensation system, the passive filters are mainly responsible for main harmonic and reactive power compensation of each individual load/ DG...
Hennig, Jan-Simon; Barr, Bryan W.; Bell, Angus S.; Cunningham, William; Danilishin, Stefan L.; Dupej, Peter; Gräf, Christian; Hough, James; Huttner, Sabina H.; Jones, Russell; Leavey, Sean S.; Pascucci, Daniela; Sinclair, Martin; Sorazu, Borja; Spencer, Andrew; Steinlechner, Sebastian; Strain, Kenneth A.; Wright, Jennifer; Zhang, Teng; Hild, Stefan
2017-12-01
Low-mass suspension systems with high-Q pendulum stages are used to enable quantum radiation pressure noise limited experiments. Utilizing multiple pendulum stages with vertical blade springs and materials with high-quality factors provides attenuation of seismic and thermal noise; however, damping of these high-Q pendulum systems in multiple degrees of freedom is essential for practical implementation. Viscous damping such as eddy-current damping can be employed, but it introduces displacement noise from force noise due to thermal fluctuations in the damping system. In this paper we demonstrate a passive damping system with adjustable damping strength as a solution for this problem that can be used for low-mass suspension systems without adding additional displacement noise in science mode. We show a reduction of the damping factor by a factor of 8 on a test suspension and provide a general optimization for this system.
International Nuclear Information System (INIS)
Jung, Byung C.; Lee, Doo Ho; Youn, Byeng D.; Lee, Soo Bum
2011-01-01
The performance of surface damping treatments may vary once the surface is exposed to a wide range of temperatures, because the performance of viscoelastic damping material is highly dependent on operational temperature. In addition, experimental data for dynamic responses of viscoelastic material are inherently random, which makes it difficult to design a robust damping layout. In this paper a statistical modeling procedure with a statistical calibration method is suggested for the variability characterization of viscoelastic damping material in constrained-layer damping structures. First, the viscoelastic material property is decomposed into two sources: (I) a random complex modulus due to operational temperature variability, and (II) experimental/model errors in the complex modulus. Next, the variability in the damping material property is obtained using the statistical calibration method by solving an unconstrained optimization problem with a likelihood function metric. Two case studies are considered to show the influence of the material variability on the acoustic performances in the structural-acoustic systems. It is shown that the variability of the damping material is propagated to that of the acoustic performances in the systems. Finally, robust and reliable damping layout designs of the two case studies are obtained through the reliability-based design optimization (RBDO) amidst severe variability in operational temperature and the damping material
Sun, Xiaoqiang; Yuan, Chaochun; Cai, Yingfeng; Wang, Shaohua; Chen, Long
2017-09-01
This paper presents the hybrid modeling and the model predictive control of an air suspension system with damping multi-mode switching damper. Unlike traditional damper with continuously adjustable damping, in this study, a new damper with four discrete damping modes is applied to vehicle semi-active air suspension. The new damper can achieve different damping modes by just controlling the on-off statuses of two solenoid valves, which makes its damping adjustment more efficient and more reliable. However, since the damping mode switching induces different modes of operation, the air suspension system with the new damper poses challenging hybrid control problem. To model both the continuous/discrete dynamics and the switching between different damping modes, the framework of mixed logical dynamical (MLD) systems is used to establish the system hybrid model. Based on the resulting hybrid dynamical model, the system control problem is recast as a model predictive control (MPC) problem, which allows us to optimize the switching sequences of the damping modes by taking into account the suspension performance requirements. Numerical simulations results demonstrate the efficacy of the proposed control method finally.
ANFIS based UPFC supplementary controller for damping low frequency oscillations in power systems
Directory of Open Access Journals (Sweden)
M. Sobha
2007-12-01
Full Text Available An adaptive neuro- fuzzy inference system (ANFIS based supplementary Unified Power Flow Controller (UPFC to superimpose the damping function on the control signal of UPFC is proposed. By using a hybrid learning procedure, the proposed ANFIS construct an input –output mapping based on stipulated input-output data pairs. The linguistic rules, considering the dependence of the plant output on the controlling signal are used to build the initial fuzzy inference structure. On the basis of linearized Philips-Hefron model of power system installed with UPFC, the damping function of the UPFC with various alternative UPFC control signals are investigated. In the simulations under widely varying operating conditions and system parameters, ANFIS based controller yields improved performance when compared with constant gain controller, based on phase compensation technique. To validate the robustness of the proposed technique, the approach is integrated to a multi-machine power system and the nonlinear simulation results are presented
Direct heuristic dynamic programming for damping oscillations in a large power system.
Lu, Chao; Si, Jennie; Xie, Xiaorong
2008-08-01
This paper applies a neural-network-based approximate dynamic programming method, namely, the direct heuristic dynamic programming (direct HDP), to a large power system stability control problem. The direct HDP is a learning- and approximation-based approach to addressing nonlinear coordinated control under uncertainty. One of the major design parameters, the controller learning objective function, is formulated to directly account for network-wide low-frequency oscillation with the presence of nonlinearity, uncertainty, and coupling effect among system components. Results include a novel learning control structure based on the direct HDP with applications to two power system problems. The first case involves static var compensator supplementary damping control, which is used to provide a comprehensive evaluation of the learning control performance. The second case aims at addressing a difficult complex system challenge by providing a new solution to a large interconnected power network oscillation damping control problem that frequently occurs in the China Southern Power Grid.
The effect of damping on a quantum system containing a Kerr-like medium
Mohamed, A.-B. A.; Sebawe Abdalla, M.; Obada, A.-S. F.
2018-05-01
An analytical description is given for a model which represents the interaction between Su(1,1) and Su(2) quantum systems taking into account Su(1,1)-cavity damping and Kerr medium properties. The analytic solution for the master equation of the density matrix is obtained. The examination of the effects of the damping parameter as well as the Kerr-like medium features is performed. The atomic inversion is discussed where the revivals and collapses phenomenon is realized at the considered period of time. Our study is extended to include the degree of entanglement where the system shows partial entanglement in all cases, however, disentanglement is also observed. The death and rebirth is seen in the system provided one selects the suitable values of the parameters. The correlation function of the system shows non-classical as well as classical behavior.
Analysis of Damped Mass-Spring Systems for Sound Synthesis
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Don Morgan
2009-01-01
Full Text Available There are many ways of synthesizing sound on a computer. The method that we consider, called a mass-spring system, synthesizes sound by simulating the vibrations of a network of interconnected masses, springs, and dampers. Numerical methods are required to approximate the differential equation of a mass-spring system. The standard numerical method used in implementing mass-spring systems for use in sound synthesis is the symplectic Euler method. Implementers and users of mass-spring systems should be aware of the limitations of the numerical methods used; in particular we are interested in the stability and accuracy of the numerical methods used. We present an analysis of the symplectic Euler method that shows the conditions under which the method is stable and the accuracy of the decay rates and frequencies of the sounds produced.
Comparison among nonlinear excitation control strategies used for damping power system oscillations
International Nuclear Information System (INIS)
Leon, A.E.; Solsona, J.A.; Valla, M.I.
2012-01-01
Highlights: ► A description and comparison of nonlinear control strategies for synchronous generators are presented. ► Advantages of using nonlinear controllers are emphasized against the use of classical PSSs. ► We find that a particular selection of IDA gains achieve the same performance that FL controllers. - Abstract: This work is focused on the problem of power system stability. A thorough description of nonlinear control strategies for synchronous generator excitation, which are designed for damping oscillations and improving transient stability on power systems, is presented along with a detailed comparison among these modern strategies and current solutions based on power system stabilizers. The performance related to damping injection in each controller, critical time enhancement, robustness against parametric uncertainties, and control signal energy consumption is analyzed. Several tests are presented to validate discussions on various advantages and disadvantages of each control strategy.
Wide Area Coordinated Control of Multi-FACTS Devices to Damp Power System Oscillations
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Shiyun Xu
2017-12-01
Full Text Available Aiming at damping the inter-area oscillations of power systems, the present study proposes a wide-area decentralized coordinated control framework, where the upper-level controller is designed to coordinate the lower-level multiple FACTS devices. Based on the polytopic differential inclusion method, the derived controller adopts a decentralized structure and it is guaranteed to be robust to meet the demand of operation under multiple operating conditions. Since time delay of wide area signal transmission is inevitable, in what follows, the quantum evolution algorithm (QEA method is introduced to find an optimal solution of the time-delay coordinated controller. In this regard, the stability of the system with a prescribed time delay is guaranteed and the system damping ratio is increased. Effectiveness and applicability of the proposed controller design methods have been demonstrated through numerical simulations.
Finite-dimensional attractor for a composite system of wave/plate equations with localized damping
International Nuclear Information System (INIS)
Bucci, Francesca; Toundykov, Daniel
2010-01-01
The long-term behaviour of solutions to a model for acoustic–structure interactions is addressed; the system consists of coupled semilinear wave (3D) and plate equations with nonlinear damping and critical sources. The questions of interest are the existence of a global attractor for the dynamics generated by this composite system as well as dimensionality and regularity of the attractor. A distinct and challenging feature of the problem is the geometrically restricted dissipation on the wave component of the system. It is shown that the existence of a global attractor of finite fractal dimension—established in a previous work by Bucci et al (2007 Commun. Pure Appl. Anal. 6 113–40) only in the presence of full-interior acoustic damping—holds even in the case of localized dissipation. This nontrivial generalization is inspired by, and consistent with, the recent advances in the study of wave equations with nonlinear localized damping
Apsimon, Robert; Barnes, Mike; Borburgh, Jan; Goddard, Brennan; Papaphilippou, Yannis; Uythoven, Jan
2014-01-01
Linear machines such as CLIC have relatively low rates of collision between bunches compared to their circular counterparts. In order to achieve the required luminosity, a very small spot size is envisaged at the interaction point, thus a low emittance beam is needed. Damping rings are essential for producing the low emittances needed for the CLIC main beam. It is crucial that the beams are injected and extracted from the damping rings in a stable and repeatable fashion to minimise emittance blow-up and beam jitter at the interaction point; both of these effects will deteriorate the luminosity at the interaction point. In this paper, the parameters and constraints of the injection and extraction systems are considered and the design of these systems is optimised within this parameter space. Related machine protection is considered in order to prevent damage from potential failure modes of the injection and extraction systems.
Chaotic Excitation and Tidal Damping in the GJ 876 System
Puranam, Abhijit; Batygin, Konstantin
2018-04-01
The M-dwarf GJ 876 is the closest known star to harbor a multi-planetary system. With three outer planets locked in a chaotic Laplace-type resonance and an appreciably eccentric short-period super-Earth, this system represents a unique exposition of extrasolar planetary dynamics. A key question that concerns the long-term evolution of this system, and the fate of close-in planets in general, is how the significant eccentricity of the inner-most planet is maintained against tidal circularization on timescales comparable to the age of the universe. Here, we employ stochastic secular perturbation theory and N-body simulations to show that the orbit of the inner-most planet is shaped by a delicate balance between extrinsic chaotic forcing and tidal dissipation. As such, the planet’s orbital eccentricity represents an indirect measure of its tidal quality factor. Based on the system’s present-day architecture, we estimate that the extrasolar super-Earth GJ 876 d has a tidal Q ∼ 104–105, a value characteristic of solar system gas giants.
DEFF Research Database (Denmark)
Bak-Jensen, Birgitte; El-Moursi, M. S.; Abdel-Rahman, Mansour Hassan
2010-01-01
This paper addresses implementation issues associated with a novel damping control algorithm for a STATCOM in a series compensated wind park for mitigating SSR (subsynchronous resonance) and damping power system oscillations. The IEEE first benchmark model on subsynchronous resonance is adopted...... the SSR, damping the power system oscillation and enhancing the transient stability margin in response to different SCRs....... in the STATCOM control structure. The performances of the controllers are tested in steady state operation and in response to system contingencies, taking into account the impact of short circuit ratios (SCRs). Simulation results are presented to demonstrate the capability of the controllers for mitigating...
Effects of Damping Plate and Taut Line System on Mooring Stability of Small Wave Energy Converter
Directory of Open Access Journals (Sweden)
Zhen Liu
2015-01-01
Full Text Available Ocean wave energy can be used for electricity supply to ocean data acquisition buoys. A heaving buoy wave energy converter is designed and the damping plate and taut line system are used to provide the mooring stability for better operating conditions. The potential flow assumption is employed for wave generation and fluid structure interactions, which are processed by the commercial software AQWA. Effects of damping plate diameter and taut line linking style with clump and seabed weights on reduction of displacements in 6 degrees of freedom are numerically studied under different operating wave conditions. Tensile forces on taut lines of optimized mooring system are tested to satisfy the national code for wire rope utilization.
Damping of Low Frequency Power System Oscillations with Wind Power Plants
DEFF Research Database (Denmark)
Adamczyk, Andrzej Grzegorz
of wind power plants on power system low frequency oscillations and identify methods and limitations for potential contribution to the damping of such oscillations. Consequently, the first part of the studies focuses on how the increased penetration of wind power into power systems affects their natural...... oscillatory performance. To do so, at first a generic test grid displaying a complex inter-area oscillation pattern is introduced. After the evaluation of the test grid oscillatory profile for various wind power penetration scenarios, it is concluded that full-converter based wind power plant dynamics do......-synchronous power source. The main body of the work is devoted to the damping control design for wind power plants with focus on the impact of such control on the plant operation. It can be expected that the referred impact is directly proportional to the control effort, which for power processing devices should...
International Nuclear Information System (INIS)
XU, J.; DEGRASSI, G.
2000-01-01
A comprehensive benchmark program was developed by Brookhaven National Laboratory (BNL) to perform an evaluation of state-of-the-art methods and computer programs for performing seismic analyses of coupled systems with non-classical damping. The program, which was sponsored by the US Nuclear Regulatory Commission (NRC), was designed to address various aspects of application and limitations of these state-of-the-art analysis methods to typical coupled nuclear power plant (NPP) structures with non-classical damping, and was carried out through analyses of a set of representative benchmark problems. One objective was to examine the applicability of various analysis methods to problems with different dynamic characteristics unique to coupled systems. The examination was performed using parametric variations for three simple benchmark models. This paper presents the comparisons and evaluation of the program participants' results to the BNL exact solutions for the applicable ranges of modeling dynamic characteristic parameters
Comparison of vibration damping of standard and PDCPD housing of the electric power steering system
Płaczek, M.; Wróbel, A.; Baier, A.
2017-08-01
A comparison of two different types of electric power steering system housing is presented. The first considered type of the housing was a standard one that is made of an aluminium alloy. The second one is made of polydicyclopentadiene polymer (PDCPD) and was produced using the RIM technology. Considered elements were analysed in order to verify their properties of vibrations damping. This property is very important taking into account noise generated by elements of a car’s power steering system. During the carried out tests vibrations of analysed power steering housings were measured using Marco Fiber Composite (MFC) piezoelectric transducers. Results obtained for both considered power steering housings in case of the same parameters of vibrations excitations were measured and juxtaposed. Obtained results were analysed in order to verify if the housing made of PDCPD polymer has better properties of vibration damping than the standard one.
Study on A Control Method of PAPF for Resonance Damping and Harmonics Compensation in Power System
DEFF Research Database (Denmark)
Zhou, Fang; Wu, Longhui; Chen, Zhe
2009-01-01
In power system, capacitors are widely used to compensate reactive power, which generally cause resonance problems in harmonic distorted network. In this paper, A method of using a parallel active power filter (PAPF) to damp the resonances is proposed. The proposed method is compound with traditi......In power system, capacitors are widely used to compensate reactive power, which generally cause resonance problems in harmonic distorted network. In this paper, A method of using a parallel active power filter (PAPF) to damp the resonances is proposed. The proposed method is compound...... with traditional method, it shows that whether the capacitor current is included in the detecting current of PAPF or not. Also the PAPF with proposed method has strong ability in harmonic compensation. Finally, the experiment results are presented to verify the analysis....
Dynamics and Collapse in a Power System Model with Voltage Variation: The Damping Effect.
Ma, Jinpeng; Sun, Yong; Yuan, Xiaoming; Kurths, Jürgen; Zhan, Meng
2016-01-01
Complex nonlinear phenomena are investigated in a basic power system model of the single-machine-infinite-bus (SMIB) with a synchronous generator modeled by a classical third-order differential equation including both angle dynamics and voltage dynamics, the so-called flux decay equation. In contrast, for the second-order differential equation considering the angle dynamics only, it is the classical swing equation. Similarities and differences of the dynamics generated between the third-order model and the second-order one are studied. We mainly find that, for positive damping, these two models show quite similar behavior, namely, stable fixed point, stable limit cycle, and their coexistence for different parameters. However, for negative damping, the second-order system can only collapse, whereas for the third-order model, more complicated behavior may happen, such as stable fixed point, limit cycle, quasi-periodicity, and chaos. Interesting partial collapse phenomena for angle instability only and not for voltage instability are also found here, including collapse from quasi-periodicity and from chaos etc. These findings not only provide a basic physical picture for power system dynamics in the third-order model incorporating voltage dynamics, but also enable us a deeper understanding of the complex dynamical behavior and even leading to a design of oscillation damping in electric power systems.
Simulation of the injection damping and resonance correction systems for the HEB of the SSC
Energy Technology Data Exchange (ETDEWEB)
Li, M.; Zhang, P.; Machida, S.
1993-02-01
An injection damping and resonance correction system for the High Energy Booster (HEB) of the Superconducting Super Collider (SSC) was investigated by means of multiparticle tracking. For an injection damping study, the code Simpsons is modified to utilize two Beam Position Monitors (BPM) and two dampers. ne particles of 200 Gev/c, numbered 1024 or more, with Gaussian distribution in 6-D phase space are injected into the HEB with certain injection offsets. The whole bunch of particles is then kicked in proportion to the BPM signals with some upper limit. Tracking these particles up to several hundred turn while the damping system is acting shows the turn-by-turn emittance growth, which is caused by the tune spread due to nonlinearity of the lattice and residual chromaticity with synchrotron oscillations. For a resonance correction study, the operating tune is scanned as a function of time so that a bunch goes through a resonance. The performance of the resonance correction system is demonstrated. We optimize the system parameters which satisfy the emittance budget of the HEB, taking into account the realistic hardware requirement.
Simulation of the injection damping and resonance correction systems for the HEB of the SSC
Energy Technology Data Exchange (ETDEWEB)
Li, M.; Zhang, P.; Machida, S. (Superconducting Super Collider Laboratory, Dallas, Texas 75237 (United States))
1993-12-25
An injection damping and resonance correction system for the High Energy Booster (HEB) of the Superconducting Super Collider (SSC) was investigated by means of multiparticle tracking. For an injection damping study, the code Simpsons is modified to utilize two Beam Position Monitors (BPM) and two dampers. The particles of 200 Gev/c, numbered 1024 or more, with Gaussian distribution in 6-D phase space are injected into the HEB with certain injection offsets. The whole bunch of particles is then kicked in proportion to the BPM signals with some upper limit. Tracking these particles up to several hundred turns while the damping system is acting shows the turn-by-turn emittance growth, which is caused by the tune spread due to nonlinearity of the lattice and residual chromaticity with synchrotron oscillations. For a resonance correction study, the operating tune is scanned as a function of time so that a bunch goes through a resonance. The performance of the resonance correction system is demonstrated. We optimize the system parameters which satisfy the emittance budget of the HEB, taking into account the realistic hardware requirement.
Methods used for the treatment of non-proportionally damped structural systems
International Nuclear Information System (INIS)
Conoscente, J.P.; Maslenikov, O.R.; Johnson, J.J.
1993-05-01
Non-proportional or non-classical damping is defined as a form of viscous damping that introduces coupling between the undamped modal coordinates of motion. Such problems have practical applications in the dynamic analysis of soil-structure systems, structure-equipment systems, and structural systems made of materials with different energy dissipation capacities, which is applicable to seismic analysis of nuclear power plants. Presented in this report is a review of the methods most commonly used in structural analysis for the solution of the dynamic response of systems with non-proportional damping. Both rigorous and approximate methods are described. Since rigorous methods usually require large computational efforts, approximate methods using undamped mode shapes are often preferred. In the study described here, the accuracy of three approximate methods was evaluated for three benchmark problems, with various parametric variations. Results were compared with the exact solution for different combinations of structural properties. Based on these results, conclusions and recommendations are presented for the use of the selected approximate methods
2014-09-01
small geometries and inertial forces are often negligible, so the behavior of fluids is based primarily on the viscous effects.3 Experimental...system modeling. In isolated environments filled with a working fluid that dissipates energy, damping between parallel and sliding plates that are... damper in a second-order differential equation. Fig. 1 Example of the data taken by the data acquisition device The impact table will produce high
Dynamics of vibration isolation system with rubber-cord-pneumatic spring with damping throttle
Burian, Yu A.; Silkov, M. V.
2017-06-01
The study refers to the important area of applied mechanics; it is the theory of vibration isolation of vibroactive facilities. The design and the issues of mathematical modeling of pneumatic spring perspective design made on the basis of rubber-cord shell with additional volume connected with its primary volume by means of throttle passageway are considered in the text. Damping at the overflow of air through the hole limits the amplitude of oscillation at resonance. But in contrast to conventional systems with viscous damping it does not increase transmission ratio at high frequencies. The mathematical model of suspension allowing selecting options to reduce the power transmission ratio on the foundation, especially in the high frequency range is obtained
System and method for damping vibration in a drill string using a magnetorheological damper
Wassell, Mark Ellsworth; Burgess, Daniel E.; Barbely, Jason R.; Thompson, Fred Lamar
2018-05-22
A system for damping vibration in a drill string can include a magnetorheological fluid valve assembly having a supply of a magnetorheological fluid. A remanent magnetic field is induced in the valve during operation that can be used to provide the magnetic field for operating the valve so as to eliminate the need to energize the coils except temporarily when changing the amount of damping required. The current to be supplied to the coil for inducing a desired magnetic field in the valve is determined based on the limiting hysteresis curve of the valve and the history of the magnetization of the value using a binary search methodology. The history of the magnetization of the valve is expressed as a series of sets of current and it resulting magnetization at which the current experienced a reversal compared to prior values of the current.
Nonlinear Damping Identification in Nonlinear Dynamic System Based on Stochastic Inverse Approach
Directory of Open Access Journals (Sweden)
S. L. Han
2012-01-01
Full Text Available The nonlinear model is crucial to prepare, supervise, and analyze mechanical system. In this paper, a new nonparametric and output-only identification procedure for nonlinear damping is studied. By introducing the concept of the stochastic state space, we formulate a stochastic inverse problem for a nonlinear damping. The solution of the stochastic inverse problem is designed as probabilistic expression via the hierarchical Bayesian formulation by considering various uncertainties such as the information insufficiency in parameter of interests or errors in measurement. The probability space is estimated using Markov chain Monte Carlo (MCMC. The applicability of the proposed method is demonstrated through numerical experiment and particular application to a realistic problem related to ship roll motion.
Pressure Feedback in Fluid Power Systems--Active Damping Explained and Exemplified
DEFF Research Database (Denmark)
Pedersen, Henrik Clemmensen; Andersen, Torben O.
2018-01-01
Fluid power systems are inherently nonlinear and typically suffer from very poor damping. Despite these characteristics, it is not uncommon that traditional linear type controllers are applied. This typically results in conservative adjustment of the controllers, or when more advanced controllers...... a given system, and how to adjust the parameters of the pressure feedback to obtain the best results. This is done for both a traditional symmetric cylinder servo system and a system with a differential cylinder using both pressure and nonpressure compensated proportional valves. Based on the presented...
Fay, Temple H.
2012-01-01
Quadratic friction involves a discontinuous damping term in equations of motion in order that the frictional force always opposes the direction of the motion. Perhaps for this reason this topic is usually omitted from beginning texts in differential equations and physics. However, quadratic damping is more realistic than viscous damping in many…
International Nuclear Information System (INIS)
Lee, Jung Pil; Kim, Han Gun
2012-01-01
In this paper, the robust superconductor flywheel energy storage system(SFESS) controller using H control theory was designed to damp low frequency oscillation of power system. The main advantage of the controller is that uncertainties of power system can be included at the stage of controller design. Both disturbance attenuation and robust stability for the power system were treated simultaneously by using mixed sensitivity problem. The robust stability and the performance for uncertainties of power system were represented by frequency weighted transfer function. To verify control performance of proposed SFESS controller using control, the closed loop eigenvalue and the damping ratio in dominant oscillation mode of power system were analyzed and nonlinear simulation for one-machine infinite bus system was performed under disturbance for various operating conditions. The results showed that the proposed SFESS controller was more robust than conventional power system stabilizer (PSS).
Directory of Open Access Journals (Sweden)
Bin Zhao
2014-05-01
Full Text Available This study presents the auxiliary damping control with the reactive power loop on the rotor-side converter of doubly-fed induction generator (DFIG-based wind farms to depress the sub-synchronous resonance oscillations in nearby turbogenerators. These generators are connected to a series capacitive compensation transmission system. First, the damping effect of the reactive power control of the DFIG-based wind farms was theoretically analyzed, and a transfer function between turbogenerator speed and the output reactive power of the wind farms was introduced to derive the analytical expression of the damping coefficient. The phase range to obtain positive damping was determined. Second, the PID phase compensation parameters of the auxiliary damping controller were optimized by a genetic algorithm to obtain the optimum damping in the entire subsynchronous frequency band. Finally, the validity and effectiveness of the proposed auxiliary damping control were demonstrated on a modified version of the IEEE first benchmark model by time domain simulation analysis with the use of DigSILENT/PowerFactory. Theoretical analysis and simulation results show that this derived damping factor expression and the condition of the positive damping can effectively analyze their impact on the system sub-synchronous oscillations, the proposed wind farms reactive power additional damping control strategy can provide the optimal damping effect over the whole sub-synchronous frequency band, and the control effect is better than the active power additional damping control strategy based on the power system stabilizator.
Energy Technology Data Exchange (ETDEWEB)
Shayeghi, H., E-mail: hshayeghi@gmail.co [Technical Engineering Department, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Shayanfar, H.A. [Center of Excellence for Power System Automation and Operation, Electrical Engineering Department, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Jalilzadeh, S.; Safari, A. [Technical Engineering Department, Zanjan University, Zanjan (Iran, Islamic Republic of)
2010-10-15
In this paper, a new approach based on the particle swarm optimization (PSO) technique is proposed to tune the parameters of the thyristor controlled series capacitor (TCSC) power oscillation damping controller. The design problem of the damping controller is converted to an optimization problem with the time-domain-based objective function which is solved by a PSO technique which has a strong ability to find the most optimistic results. To ensure the robustness of the proposed stabilizers, the design process takes a wide range of operating conditions into account. The performance of the newly designed controller is evaluated in a four-machine power system subjected to the different types of disturbances in comparison with the genetic algorithm based damping controller. The effectiveness of the proposed controller is demonstrated through the nonlinear time-domain simulation and some performance indices studies. The results analysis reveals that the tuned PSO based TCSC damping controller using the proposed fitness function has an excellent capability in damping power system inter-area oscillations and enhances greatly the dynamic stability of the power systems. Moreover, it is superior to the genetic algorithm based damping controller.
Lozia, Z.; Zdanowicz, P.
2016-09-01
The paper presents the optimization of damping in the passive suspension system of a motor vehicle moving rectilinearly with a constant speed on a road with rough surface of random irregularities, described according to the ISO classification. Two quarter-car 2DoF models, linear and non-linear, were used; in the latter, nonlinearities of spring characteristics of the suspension system and pneumatic tyres, sliding friction in the suspension system, and wheel lift-off were taken into account. The smoothing properties of vehicle tyres were represented in both models. The calculations were carried out for three roads of different quality, with simulating four vehicle speeds. Statistical measures of vertical vehicle body vibrations and of changes in the vertical tyre/road contact force were used as the criteria of system optimization and model comparison. The design suspension displacement limit was also taken into account. The optimum suspension damping coefficient was determined and the impact of undesirable sliding friction in the suspension system on the calculation results was estimated. The results obtained make it possible to evaluate the impact of the structure and complexity of the model used on the results of the optimization.
Active damping technique for small DC-link capacitor based drive system
DEFF Research Database (Denmark)
Maheshwari, Ram Krishan; Munk-Nielsen, Stig; Henriksen, Bjarne
2010-01-01
A detailed model of Adjustable Speed Drive (ASD) is discussed, which yield a general rule for active damping in a small DC link based drive. A desired value of input LC resonance damping coefficient can be achieved by changing gain parameters. The modified state space matrix due to active damping...
A hybrid active filter for damping of harmonic resonance in industrial power systems
Fujita, Hideaki; Yamasaki, Takahiro; Akagi, Hirofumi
1998-01-01
This paper proposes a hybrid active filter for damping of harmonic resonance in industrial power systems. The hybrid filter consists of a small-rated active filter and a 5th tuned passive filter. The active filter is characterized by detecting the 5th harmonic current flowing into the passive filter. It is controlled in such a way as to behave as a negative or positive resistor by adjusting a feedback gain from a negative to positive value, and vice versa. The negative resistor presented by t...
Operation and performance of a longitudinal damping system using parallel digital signal processing
International Nuclear Information System (INIS)
Fox, J.D.; Hindi, H.; Linscott, I.
1994-06-01
A programmable longitudinal feedback system based on four AT ampersand T 1610 digital signal processors has been developed as a component of the PEP-II R ampersand D program. This Longitudinal Quick Prototype is a proof of concept for the PEP-II system and implements full speed bunch-by-bunch signal processing for storage rings with bunch spacings of 4 ns. The design implements, via software, a general purpose feedback controller which allows the system to be operated at several accelerator facilities. The system configuration used for tests at the LBL Advanced Light Source is described. Open and closed loop results showing the detection and calculation of feedback signals from bunch motion are presented, and the system is shown to damp coupled-bunch instabilities in the ALS. Use of the system for accelerator diagnostics is illustrated via measurement of injection transients and analysis of open loop bunch motion
Characterization of NiTi Shape Memory Damping Elements designed for Automotive Safety Systems
Strittmatter, Joachim; Clipa, Victor; Gheorghita, Viorel; Gümpel, Paul
2014-07-01
Actuator elements made of NiTi shape memory material are more and more known in industry because of their unique properties. Due to the martensitic phase change, they can revert to their original shape by heating when subjected to an appropriate treatment. This thermal shape memory effect (SME) can show a significant shape change combined with a considerable force. Therefore such elements can be used to solve many technical tasks in the field of actuating elements and mechatronics and will play an increasing role in the next years, especially within the automotive technology, energy management, power, and mechanical engineering as well as medical technology. Beside this thermal SME, these materials also show a mechanical SME, characterized by a superelastic plateau with reversible elongations in the range of 8%. This behavior is based on the building of stress-induced martensite of loaded austenite material at constant temperature and facilitates a lot of applications especially in the medical field. Both SMEs are attended by energy dissipation during the martensitic phase change. This paper describes the first results obtained on different actuator and superelastic NiTi wires concerning their use as damping elements in automotive safety systems. In a first step, the damping behavior of small NiTi wires up to 0.5 mm diameter was examined at testing speeds varying between 0.1 and 50 mm/s upon an adapted tensile testing machine. In order to realize higher testing speeds, a drop impact testing machine was designed, which allows testing speeds up to 4000 mm/s. After introducing this new type of testing machine, the first results of vertical-shock tests of superelastic and electrically activated actuator wires are presented. The characterization of these high dynamic phase change parameters represents the basis for new applications for shape memory damping elements, especially in automotive safety systems.
Asymptotical Behavior of the Solution of a SDOF Linear Fractionally Damped Vibration System
Directory of Open Access Journals (Sweden)
Z.H. Wang
2011-01-01
Full Text Available Fractional-order derivative has been shown an adequate tool to the study of so-called "anomalous" social and physical behaviors, in reflecting their non-local, frequency- and history-dependent properties, and it has been used to model practical systems in engineering successfully, including the famous Bagley-Torvik equation modeling forced motion of a rigid plate immersed in Newtonian fluid. The solutions of the initial value problems of linear fractional differential equations are usually expressed in terms of Mittag-Leffler functions or some other kind of power series. Such forms of solutions are not good for engineers not only in understanding the solutions but also in investigation. This paper proves that for the linear SDOF oscillator with a damping described by fractional-order derivative whose order is between 1 and 2, the solution of its initial value problem free of external excitation consists of two parts, the first one is the 'eigenfunction expansion' that is similar to the case without fractional-order derivative, and the second one is a definite integral that is independent of the eigenvalues (or characteristic roots. The integral disappears in the classical linear oscillator and it can be neglected from the solution when stationary solution is addressed. Moreover, the response of the fractionally damped oscillator under harmonic excitation is calculated in a similar way, and it is found that the fractional damping with order between 1 and 2 can be used to produce oscillation with large amplitude as well as to suppress oscillation, depending on the ratio of the excitation frequency and the natural frequency.
Open quantum system and the damping of collective modes in deep inelastic collisions
International Nuclear Information System (INIS)
Sandulescu, A.
1985-01-01
In the framework of the Lindblad theory for open quantum systems the following results are obtained: a generalization of the fundamental constraints on quantum mechanical diffusion coefficients which appear in the corresponding master equations, a generalization of pure state condition and generalized Schrodinger type nonlinear equation for an open system. Also, the Schroedinger, Heisenberfg and Weyl-Wigner-Moyal representations of the Lindblad equation are given explicitly. On the basis of these representations, it is shown that various master equations for the damped quantum oscillator used in the literature for the description of the damped collective modes are particular cases of the Lindblad equation and that the majority of these equations are not satisfying the constraints on quantum mechanical diffusion coefficients. The solutions of the differential equations for the variances are put in a new synthetic for, suggested by a direct computation of the variances from the time dependent Weyl operators. The solution of the Lindblad equation in the Weyl-Wigner-Moyal representation is of Gaussian type if the initial form of the Wigner function is taken to be a Gaussian corresponding to a coherent wave furction
Analysis and damping control of power system low-frequency oscillations
Wang, Haifeng
2016-01-01
This book presents the research and development results on power systems oscillations in three categories of analytical methods. First is damping torque analysis which was proposed in 1960’s, further developed between 1980-1990, and widely used in industry. Second is modal analysis which developed between the 1980’s and 1990’s as the most powerful method. Finally the linearized equal-area criterion analysis that is proposed and developed recently. The book covers three main types of controllers: Power System Stabilizer (PSS), FACTS (Flexible AC Transmission Systems) stabilizer, and ESS (Energy Storage Systems) stabilizer. The book provides a systematic and detailed introduction on the subject as the reference for industry applications and academic research.
Directory of Open Access Journals (Sweden)
Ting-Chia Ou
2017-04-01
Full Text Available This paper endeavors to apply a novel intelligent damping controller (NIDC for the static synchronous compensator (STATCOM to reduce the power fluctuations, voltage support and damping in a hybrid power multi-system. In this paper, we discuss the integration of an offshore wind farm (OWF and a seashore wave power farm (SWPF via a high-voltage, alternating current (HVAC electric power transmission line that connects the STATCOM and the 12-bus hybrid power multi-system. The hybrid multi-system consists of a battery energy storage system (BESS and a micro-turbine generation (MTG. The proposed NIDC consists of a designed proportional–integral–derivative (PID linear controller, an adaptive critic network and a proposed functional link-based novel recurrent fuzzy neural network (FLNRFNN. Test results show that the proposed controller can achieve better damping characteristics and effectively stabilize the network under unstable conditions.
Huang, Weiquan; Fang, Tao; Luo, Li; Zhao, Lin; Che, Fengzhu
2017-07-03
The grid strapdown inertial navigation system (SINS) used in polar navigation also includes three kinds of periodic oscillation errors as common SINS are based on a geographic coordinate system. Aiming ships which have the external information to conduct a system reset regularly, suppressing the Schuler periodic oscillation is an effective way to enhance navigation accuracy. The Kalman filter based on the grid SINS error model which applies to the ship is established in this paper. The errors of grid-level attitude angles can be accurately estimated when the external velocity contains constant error, and then correcting the errors of the grid-level attitude angles through feedback correction can effectively dampen the Schuler periodic oscillation. The simulation results show that with the aid of external reference velocity, the proposed external level damping algorithm based on the Kalman filter can suppress the Schuler periodic oscillation effectively. Compared with the traditional external level damping algorithm based on the damping network, the algorithm proposed in this paper can reduce the overshoot errors when the state of grid SINS is switched from the non-damping state to the damping state, and this effectively improves the navigation accuracy of the system.
Fay, Temple H.
2012-01-01
Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…
Oscillations of a spring-magnet system damped by a conductive plate
Ladera, C. L.; Donoso, G.
2013-09-01
We study the motion of a spring-magnet system that oscillates with very low frequencies above a circular horizontal non-magnetizable conductive plate. The magnet oscillations couple with the plate via the Foucault currents induced therein. We develop a simple theoretical model for this magneto-mechanical oscillator, a model that leads to the equation of a damped harmonic oscillator, whose weak attenuation constant depends upon the system parameters, e.g. the electrical conductivity of the constituent material of the plate and its thickness. We present a set of validating experiments, the results of which are predicted with good accuracy by our analytical model. Additional experiments can be performed with this oscillating system or its variants. This oscillator is simple and low-cost, easy to assemble, and can be used in experiments or project works in physics teaching laboratories at the undergraduate level.
Oscillations of a spring–magnet system damped by a conductive plate
International Nuclear Information System (INIS)
Ladera, C L; Donoso, G
2013-01-01
We study the motion of a spring–magnet system that oscillates with very low frequencies above a circular horizontal non-magnetizable conductive plate. The magnet oscillations couple with the plate via the Foucault currents induced therein. We develop a simple theoretical model for this magneto-mechanical oscillator, a model that leads to the equation of a damped harmonic oscillator, whose weak attenuation constant depends upon the system parameters, e.g. the electrical conductivity of the constituent material of the plate and its thickness. We present a set of validating experiments, the results of which are predicted with good accuracy by our analytical model. Additional experiments can be performed with this oscillating system or its variants. This oscillator is simple and low-cost, easy to assemble, and can be used in experiments or project works in physics teaching laboratories at the undergraduate level. (paper)
Loss of Landau Damping for Inductive Impedance in a Double RF System
Argyropoulos, T; Burov, A
2013-01-01
In this paper the thresholds of the loss of Landau damping due to the presence of inductive impedance in a single and double harmonic RF systems are determined, both from calculations and particle simulations. A high harmonic RF system, operating in bunch lengthening mode is used in many accelerators with space charge or inductive impedance to reduce the peak line density or stabilize the beam. An analytical approach, based on emerging of the discrete Van Kampen modes, shows that improved stability in a double RF system can be achieved only below some critical value of longitudinal emittance. Above this threshold, a phase shift of more than 15 degrees between the two RF components is proven necessary to stabilize the bunch. These results, confirmed also by particle simulations, now are able to explain observations during the pp operation of the SPS. The thresholds in bunch shortening mode as well as in a single RF case are compared with this regime.
On Coulomb and Viscosity damped single-degree-of-freedom vibrating systems
DEFF Research Database (Denmark)
Jakobsen, J.; Sivebæk, Ion Marius
2016-01-01
influence. The amount of analyses of friction damped system is comparatively more limited. The periodic square wave is a frequently occurring type of friction in this type of analyses. This periodic square wave is often named Coulomb friction. It can be resolved in an infinite series of harmonic components...... with frequencies 1, 3, 5, … times the basic frequency of the square wave and with respective amplitudes: (4/π)∗(1, 1/3, 1/5... )∗Fμ(ωt). Fμ(ωt): the square wave amplitude. The governing equation for the sequence of a free vibration with Coulomb friction damping is nonlinear, but is linear within each ½ period....... A complete solution can therefore be made up compounding solutions from ½ periods by inserting end conditions from one ½ period as initial conditions for the following ½ period. – Only spring and Coulomb forces act together. As a Coulomb force is conceivable as an infinite series of harmonic components...
Energy Technology Data Exchange (ETDEWEB)
Martins, N; Pinto, H J.C.P.; Bianco, A [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Macedo, N J.P. [FURNAS, Rio de Janeiro, RJ (Brazil)
1994-12-31
This paper describes control structures and computer methods to enhance the practical use of thyristor controlled series compensation (TCSC) in power systems. The location and controller design of the TCS devices, to damp system oscillations, are based on modal analysis and frequency response techniques, respectively. Results are given for a large practical power system. (author) 15 refs., 18 figs., 5 tabs.
Energy Technology Data Exchange (ETDEWEB)
Lee, Kanghee; Kang, Heungseok; Oh, Dongseok; Yoon, Kyungho; Kim, Hyungkyu; Kim, Jaeyong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-10-15
This paper summary the fuel assembly damping data in air/in still water/under flow, released from foreign fuel vendors, compared our data with the published data. Some technical issues in fuel assembly damping measurement testing are also briefly discussed. Understanding of each fuel assembly damping mechanisms according to the surrounding medium and flow velocity can support the fuel design improvement in fuel assembly dynamics and structural integrity aspect. Because the upgraded requirements of the newly-developed advanced reactor system will demands to minimize fuel design margin in integrity evaluation, reduction in conservatism of fuel assembly damping can contribute to alleviate the fuel design margin for sure. Damping is an energy dissipation mechanism in a vibrating mechanical structure and prevents a resonant structure from having infinite vibration amplitudes. The sources of fuel assembly damping are various from support friction to flow contribution, and it can be increased by the viscosity or drag of surrounding fluid medium or the average velocity of water flowing. Fuel licensing requires fuel design evaluation in transient or accidental condition. Dynamic response analysis of fuel assembly is to show fuel integrity and requires information on assembly-wise damping in dry condition and under wet or water flowing condition. However, damping measurement test for the full-scale fuel assembly prototype is not easy to carry out because of the scale (fuel prototype, test facility), unsteadiness of test data (scattering, random sampling and processing), instrumentation under water flowing (water-proof response measurement), and noise. LWR fuel technology division in KAERI is preparing the infra structure for damping measurement test of full-scale fuel assembly, to support fuel industries and related research activities. Here is a preliminary summary of fuel assembly damping, published in the literature. Some technical issues in fuel assembly damping
International Nuclear Information System (INIS)
Elfrink, R; Renaud, M; Kamel, T M; De Nooijer, C; Jambunathan, M; Goedbloed, M; Hohlfeld, D; Matova, S; Pop, V; Caballero, L; Van Schaijk, R
2010-01-01
This paper describes the characterization of thin-film MEMS vibration energy harvesters based on aluminum nitride as piezoelectric material. A record output power of 85 µW is measured. The parasitic-damping and the energy-harvesting performances of unpackaged and packaged devices are investigated. Vacuum and atmospheric pressure levels are considered for the packaged devices. When dealing with packaged devices, it is found that vacuum packaging is essential for maximizing the output power. Therefore, a wafer-scale vacuum package process is developed. The energy harvesters are used to power a small prototype (1 cm 3 volume) of a wireless autonomous sensor system. The average power consumption of the whole system is less than 10 µW, and it is continuously provided by the vibration energy harvester
Removing damped sinusoidal vibrations in adaptive optics systems using a DFT-based estimation method
Kania, Dariusz
2017-06-01
The problem of a vibrations rejection in adaptive optics systems is still present in publications. These undesirable signals emerge because of shaking the system structure, the tracking process, etc., and they usually are damped sinusoidal signals. There are some mechanical solutions to reduce the signals but they are not very effective. One of software solutions are very popular adaptive methods. An AVC (Adaptive Vibration Cancellation) method has been presented and developed in recent years. The method is based on the estimation of three vibrations parameters and values of frequency, amplitude and phase are essential to produce and adjust a proper signal to reduce or eliminate vibrations signals. This paper presents a fast (below 10 ms) and accurate estimation method of frequency, amplitude and phase of a multifrequency signal that can be used in the AVC method to increase the AO system performance. The method accuracy depends on several parameters: CiR - number of signal periods in a measurement window, N - number of samples in the FFT procedure, H - time window order, SNR, THD, b - number of A/D converter bits in a real time system, γ - the damping ratio of the tested signal, φ - the phase of the tested signal. Systematic errors increase when N, CiR, H decrease and when γ increases. The value of systematic error for γ = 0.1%, CiR = 1.1 and N = 32 is approximately 10^-4 Hz/Hz. This paper focuses on systematic errors of and effect of the signal phase and values of γ on the results.
Directory of Open Access Journals (Sweden)
Mike D.R. Zhang
2001-01-01
Full Text Available In this paper, a method for analyzing the dynamic response of a structural system with variable mass, damping and stiffness is first presented. The dynamic equations of the structural system with variable mass and stiffness are derived according to the whole working process of a bridge bucket unloader. At the end of the paper, an engineering numerical example is given.
Vibration Disturbance Damping System Design to Protect Payload of the Rocket
Directory of Open Access Journals (Sweden)
Sutisno Sutisno
2012-12-01
Full Text Available Rocket motor generates vibrations acting on whole rocket body including its contents. Part of the body which is sensitive to disturbance is the rocket payload. The payload consists of various electronic instruments including: transmitter, various sensors, accelerometer, gyro, the embedded controller system, and others. This paper presents research on rocket vibration influence to the payload and the method to avoid disturbance. Avoiding influence of vibration disturbance can be done using silicone gel material whose typical damping factors are relatively high. The rocket vibration was simulated using electromagnetic motor, and the vibrations were measured using an accelerometer sensor. The measurement results were displayed in the form of curve, indicating the vibration level on some parts of the tested material. Some measurement results can be applied to determine the good material to attenuate vibration disturbance on the instruments of the payload.
Niamul Islam, Naz; Hannan, M A; Mohamed, Azah; Shareef, Hussain
2016-01-01
Power system oscillation is a serious threat to the stability of multimachine power systems. The coordinated control of power system stabilizers (PSS) and thyristor-controlled series compensation (TCSC) damping controllers is a commonly used technique to provide the required damping over different modes of growing oscillations. However, their coordinated design is a complex multimodal optimization problem that is very hard to solve using traditional tuning techniques. In addition, several limitations of traditionally used techniques prevent the optimum design of coordinated controllers. In this paper, an alternate technique for robust damping over oscillation is presented using backtracking search algorithm (BSA). A 5-area 16-machine benchmark power system is considered to evaluate the design efficiency. The complete design process is conducted in a linear time-invariant (LTI) model of a power system. It includes the design formulation into a multi-objective function from the system eigenvalues. Later on, nonlinear time-domain simulations are used to compare the damping performances for different local and inter-area modes of power system oscillations. The performance of the BSA technique is compared against that of the popular particle swarm optimization (PSO) for coordinated design efficiency. Damping performances using different design techniques are compared in term of settling time and overshoot of oscillations. The results obtained verify that the BSA-based design improves the system stability significantly. The stability of the multimachine power system is improved by up to 74.47% and 79.93% for an inter-area mode and a local mode of oscillation, respectively. Thus, the proposed technique for coordinated design has great potential to improve power system stability and to maintain its secure operation.
Directory of Open Access Journals (Sweden)
Naz Niamul Islam
Full Text Available Power system oscillation is a serious threat to the stability of multimachine power systems. The coordinated control of power system stabilizers (PSS and thyristor-controlled series compensation (TCSC damping controllers is a commonly used technique to provide the required damping over different modes of growing oscillations. However, their coordinated design is a complex multimodal optimization problem that is very hard to solve using traditional tuning techniques. In addition, several limitations of traditionally used techniques prevent the optimum design of coordinated controllers. In this paper, an alternate technique for robust damping over oscillation is presented using backtracking search algorithm (BSA. A 5-area 16-machine benchmark power system is considered to evaluate the design efficiency. The complete design process is conducted in a linear time-invariant (LTI model of a power system. It includes the design formulation into a multi-objective function from the system eigenvalues. Later on, nonlinear time-domain simulations are used to compare the damping performances for different local and inter-area modes of power system oscillations. The performance of the BSA technique is compared against that of the popular particle swarm optimization (PSO for coordinated design efficiency. Damping performances using different design techniques are compared in term of settling time and overshoot of oscillations. The results obtained verify that the BSA-based design improves the system stability significantly. The stability of the multimachine power system is improved by up to 74.47% and 79.93% for an inter-area mode and a local mode of oscillation, respectively. Thus, the proposed technique for coordinated design has great potential to improve power system stability and to maintain its secure operation.
Energy Technology Data Exchange (ETDEWEB)
Xiao, Yanwen; Xu, Wei, E-mail: weixu@nwpu.edu.cn; Wang, Liang [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)
2016-03-15
This paper focuses on the study of the stochastic Van der Pol vibro-impact system with fractional derivative damping under Gaussian white noise excitation. The equations of the original system are simplified by non-smooth transformation. For the simplified equation, the stochastic averaging approach is applied to solve it. Then, the fractional derivative damping term is facilitated by a numerical scheme, therewith the fourth-order Runge-Kutta method is used to obtain the numerical results. And the numerical simulation results fit the analytical solutions. Therefore, the proposed analytical means to study this system are proved to be feasible. In this context, the effects on the response stationary probability density functions (PDFs) caused by noise excitation, restitution condition, and fractional derivative damping are considered, in addition the stochastic P-bifurcation is also explored in this paper through varying the value of the coefficient of fractional derivative damping and the restitution coefficient. These system parameters not only influence the response PDFs of this system but also can cause the stochastic P-bifurcation.
Xiao, Yanwen; Xu, Wei; Wang, Liang
2016-03-01
This paper focuses on the study of the stochastic Van der Pol vibro-impact system with fractional derivative damping under Gaussian white noise excitation. The equations of the original system are simplified by non-smooth transformation. For the simplified equation, the stochastic averaging approach is applied to solve it. Then, the fractional derivative damping term is facilitated by a numerical scheme, therewith the fourth-order Runge-Kutta method is used to obtain the numerical results. And the numerical simulation results fit the analytical solutions. Therefore, the proposed analytical means to study this system are proved to be feasible. In this context, the effects on the response stationary probability density functions (PDFs) caused by noise excitation, restitution condition, and fractional derivative damping are considered, in addition the stochastic P-bifurcation is also explored in this paper through varying the value of the coefficient of fractional derivative damping and the restitution coefficient. These system parameters not only influence the response PDFs of this system but also can cause the stochastic P-bifurcation.
The Use of the Artificial Damped Outrigger Systems in Tall R.C Buildings Under Seismic Loading
Directory of Open Access Journals (Sweden)
Abbas Abd Elmajeed Allawi
2016-04-01
Full Text Available This paper studies the combination of fluid viscous dampers in the outrigger system to add supplementary damping into the structure, which purpose to remove the dependability of the structure to lower variable intrinsic damping. This optimizes the accuracy of the dynamic response and by providing higher level of damping, basically minimizes the wanted stiffness of the structure while at the same time optimizing the achievement. The modal considered is a 36 storey square high rise reinforced concrete building. By constructing a discrete lumped mass model and using frequency-based response function, two systems of dampers, parallel and series systems are studied. The maximum lateral load at the top of the building is calculated, and this load will be applied at every floor of the building, giving a conservative solution. For dynamic study Response Spectrum Analysis was conducted and the behavior of the building was determined considering response parameters. MATLAB software, has been used in the dynamic analysis for three modes. For all modes, it is observed that the parallel system of dampers result in lower amplitude of vibration and achieved more efficiently compared to the damper is in series, until the parallel system arrives 100% damping for mode three.
Bapat, V. A.; Prabhu, P.
1980-11-01
The problem of designing an optimum Lanchester damper for a viscously damped single degree of freedom system subjected to inertial harmonic excitation is investigated. Two criteria are used for optimizing the performance of the damper: (i) minimum motion transmissibility; (ii) minimum force transmissibility. Explicit expressions are developed for determining the absorber parameters.
Dirksz, D. A.; Scherpen, J. M. A.; Ortega, R.
2008-01-01
A dynamic extension for position feedback of port-Hamiltonian mechanical systems is studied. First we look at the consequences for the matching equations when applying Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC). Then we look at the possibilities of asymptotically
International Nuclear Information System (INIS)
Noakes, M.W.; Petterson, B.J.; Werner, J.C.
1990-01-01
The transportation of objects using overhead cranes can induce pendular motion of the object, which usually must be damped or allowed to decay before the next process can take place. Recent work at Sandia National Laboratories has shown that oscillation-damped transport and swing-free stops are possible by properly programming the acceleration of the transporting crane. Initial studies have been completed using a CIMCORP XR6100 gantry robot. The Advanced Integrated Maintenance System (AIMS) is an engineering and operations test bed developed for remote maintenance and handling studies within the Consolidated Fuel Reprocessing Program (CFRP) at Oak Ridge National Laboratory. The goal of CFRP has been to advanced the technology of in-cell systems planned for future nuclear fuel cycle facilities. The AIMS provides the capabilities to examine the needs and constraints necessary for hot-cell remote maintenance and includes a force-reflecting master/slave teleoperator and overhead transporter system. The associated control system provides a flexible programming environment conducive to controls experimentation. This paper reviews the theory associated with oscillation-damped trajectories for simply suspended objects and describes a specific implementation of the oscillation damping methods for the AIMS transporter. Hardware and software requirements and constraints for proper operation are discussed
DEFF Research Database (Denmark)
Li, Hui; Liu, Shengquan; Ji, Haiting
2014-01-01
on the power system stabilizer (PSS) control method. Transient simulation on different damping gain coefficients are conducted for justification. Following the OTEF mechanism analysis, an additional fuzzy damping control strategy with the active/reactive power loop is proposed by identifying the oscillation......This study investigates the inter-area low-frequency damping control strategies of a doubly fed induction generator (DFIG)-based wind farm through oscillation transient energy function (OTEF) analysis. Based on the OTEF descent expressions, the feasibility of damping the inter-area low...... oscillation of the wind turbine shaft. The proposed additional fuzzy control strategy with the active/reactive power loop has better damping performance than the presented PSS control, especially for damping the inter-area low-frequency oscillation....
Broadband feedback systems for the damping of coherent beam instabilities in the stretcher ring ELSA
International Nuclear Information System (INIS)
Roth, Andre
2012-12-01
At the Electron Stretcher Facility ELSA an upgrade of the internal beam current up to 200 mA would be desirable in order to increase the intensity of the extracted electron beam for the future experimental hadron physics program. However, such an upgrade is mainly limited by the excitation of coherent beam instabilities in the stretcher ring. As active counteraction, broadband bunch-by-bunch feedback-systems for the longitudinal, as well as for both transverse planes were installed. After detection of the motion of each of the 27 4 stored bunches via beam position monitors, the systems determine independent correction signals for each bunch using digital signal processors. The amplified correction signals are applied to the beam by means of broadband longitudinal and transverse kicker structures. The detailed setup, the commissioning procedure and measurement results of the damping performance of the systems are presented. In addition, the operation of the longitudinal system during the fast energy ramp of 4 GeV/s from 1.2 GeV to 3.2 GeV is investigated.
International Nuclear Information System (INIS)
Chao, A.W.; Morton, P.L.; Rees, J.R.
1979-03-01
To describe the horizontal motion of the bunch, we need four coordinates, x and z are the horizontal and longitudinal displacements of the bunch center relative to the ideal trajectory; x' is the angle between the bunch's direction of motion and the ideal trajectory; and δ=ΔE/E is relative energy error of the bunch. Among the four variables, x and z are easy to measure by position monitors, while x' and δ are easy to change by electromagnetic devices. In combination, this suggests four possible types of feedback systems. In the following, we will present a complete analysis of the Type (x, δ) feedback system, using a matrix method. The analyses of other types are similar to that of Type (x, δ) and only the results are included. We then include some comparisons of these types of feedback schemes in terms of power consumptions and the effectiveness in damping the horizontal-betatron and synchrotron oscillations. We will also discuss some effects of position measuring errors on the performance of the feedback system. 2 refs., 3 tabs
International Nuclear Information System (INIS)
Basoglu, B.; Brewer, R.W.; Haught, C.F.; Hollenbach, D.F.; Wilkinson, A.D.; Dodds, H.L.; Pasqua, P.F.
1994-01-01
This paper describes the development of a computer model for predicting the excursion characteristics of a postulated, hypothetical, critically accident involving a homogeneous mixture of low-enriched UO 2 powder and water contained in a cylindrical blender. The model uses point neutronics coupled with simple lumped-parameter thermal-hydraulic feedback. The temperature of the system is calculated using a simple time-dependent energy balance where two extreme conditions for the thermal behavior of the system are considered, which bound the real life situation. Using these extremes, three different models are developed. To evaluate the models, the authors compared the results with the results of the POWDER code, which was developed by the Commissariat a l'Energie Atomique/United Kingdom Atomic Energy Authority (CEA/UKAEA) for damp powder systems. The agreement in these comparisons is satisfactory. Results of the excursion studies in this work show that approximately 10 19 fissions occur as a result of accidental water ingress into powder blenders containing 5,000 kg of low-enriched (5%) UO 2 powder
An enhanced nonlinear damping approach accounting for system constraints in active mass dampers
Venanzi, Ilaria; Ierimonti, Laura; Ubertini, Filippo
2015-11-01
Active mass dampers are a viable solution for mitigating wind-induced vibrations in high-rise buildings and improve occupants' comfort. Such devices suffer particularly when they reach force saturation of the actuators and maximum extension of their stroke, which may occur in case of severe loading conditions (e.g. wind gust and earthquake). Exceeding actuators' physical limits can impair the control performance of the system or even lead to devices damage, with consequent need for repair or substitution of part of the control system. Controllers for active mass dampers should account for their technological limits. Prior work of the authors was devoted to stroke issues and led to the definition of a nonlinear damping approach, very easy to implement in practice. It consisted of a modified skyhook algorithm complemented with a nonlinear braking force to reverse the direction of the mass before reaching the stroke limit. This paper presents an enhanced version of this approach, also accounting for force saturation of the actuator and keeping the simplicity of implementation. This is achieved by modulating the control force by a nonlinear smooth function depending on the ratio between actuator's force and saturation limit. Results of a numerical investigation show that the proposed approach provides similar results to the method of the State Dependent Riccati Equation, a well-established technique for designing optimal controllers for constrained systems, yet very difficult to apply in practice.
International Nuclear Information System (INIS)
Qian, Hong
2014-01-01
We propose a mathematical formulation of the zeroth law of thermodynamics and develop a stochastic dynamical theory, with a consistent irreversible thermodynamics, for systems possessing sustained conservative stationary current in phase space while in equilibrium with a heat bath. The theory generalizes underdamped mechanical equilibrium: dx=gdt+{−D∇ϕdt+√(2D)dB(t)}, with ∇⋅g=0 and {⋯} respectively representing phase-volume preserving dynamics and stochastic damping. The zeroth law implies stationary distribution u ss (x)=e −ϕ(x) . We find an orthogonality ∇ϕ⋅g=0 as a hallmark of the system. Stochastic thermodynamics based on time reversal (t,ϕ,g)→(−t,ϕ,−g) is formulated: entropy production e p # (t)=−dF(t)/dt; generalized “heat” h d # (t)=−dU(t)/dt, U(t)=∫ R n ϕ(x)u(x,t)dx being “internal energy”, and “free energy” F(t)=U(t)+∫ R n u(x,t)lnu(x,t)dx never increases. Entropy follows (dS)/(dt) =e p # −h d # . Our formulation is shown to be consistent with an earlier theory of P. Ao. Its contradistinctions to other theories, potential-flux decomposition, stochastic Hamiltonian system with even and odd variables, Klein–Kramers equation, Freidlin–Wentzell's theory, and GENERIC, are discussed.
Methods of and system for swing damping movement of suspended objects
Jones, J.F.; Petterson, B.J.; Strip, D.R.
1991-03-05
A payload suspended from a gantry is swing damped in accordance with a control algorithm based on the periodic motion of the suspended mass or by servoing on the forces induced by the suspended mass. 13 figures.
Performance analysis of conventional PSS and fuzzy controller for damping power system oscillations
Banna, Hasan UI; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro; Cabrera Tobar, Ana; Ghorbani, Hamidreza; Ying, Shaoqing
2014-01-01
Electro-mechanical oscillations are produced, in the machines of an interconnected power network, followed by a disturbance or due to high power transfer through weak tie lines. These oscillations should be damped as quickly as possible to ensure the reliable and stable operation of the network. To damp these oscillations different controllers, based on local or wide area signals, have been the subject of many papers. This paper presents the analysis of the performance of Conventional Power S...
Energy Technology Data Exchange (ETDEWEB)
Castellanos B., R.; Calderon G., J.G.; Sarmiento U., H. [Instituto de Investigaciones Electricas, IIE,Cuernavaca, Mor. 62580 (Mexico); Olguin S., D. [Instituto Politecnico Nacional, Mexico D.F. 07300 (Mexico); Messina, A.R. [Graduate Program in Electrical Engineering, Cinvestav, P.O. Box 31-438, Plaza La Luna, Guadalajara, Jal. 44550 (Mexico)
2006-01-15
This paper documents research conducted to investigate the use and tuning of power system stabilizers (PSSs) to improve small-signal dynamic performance of the Mexican interconnected system (MIS). The analysis focuses on the control of a critical inter-area mode associated with the interaction between the southeastern and western regions of the system and a critical local mode. Study results include the determination of critical system modes more controllable by existing PSSs and the use of supplementary control actions to damp low-frequency inter-area modes of oscillation. Results for both, small and large perturbations are presented to illustrate the placement and tuning of PSSs at several appropriate locations throughout the system. (author)
International Nuclear Information System (INIS)
Kaesemann, C.-P.; Huart, M.; Mueller, P.; Sigalov, A.
2006-01-01
The electrical power and energy for ASDEX Upgrade (AUG) is provided by three separate pulsed networks based on flywheel generators. Major damages at couplings of the shaft of the synchronous generator EZ4 (220 MVA / 600 MWs) were discovered during a routine check. The damage can only be explained by torsional resonances in the generator shaft which are excited by active power transients from the converter loads. For generator protection, torque sensors were installed near the coupling between the flywheel and the rotor. They cause an early termination of plasma experiments if a predefined torque level is exceeded. These terminations limited the achievable plasma current flattop time of AUG significantly. Since a low natural damping of the torsional resonances was identified as a major cause of the phenomena observed, novel feedback controlled DC circuits were developed providing electromagnetic damping for the generator shafts in case of excitation. Each damping circuit consists of a DC choke, acting as a buffer storage of magnetic energy, fed by a thyristor converter. The current reference for the converter is derived from the torque sensor signals. This enables the choke current to alternate with the measured natural frequency of the shaft assembly. Thus, with proper phasing, torsional resonances in generator shaft systems weighing more than 100 tons can be damped with little additional power. Since April 2003, the damping circuits have been routinely operated during all plasma experiments. Despite the low damping power used, torsional resonances could be reduced to a value that avoids a trip signal from the torque sensors. This paper describes the results from analysing, designing and testing of the feedback controlled buffer storage of magnetic energy, representing an effective and low cost solution for damping torsional resonances in electric power systems. It will present the layout, analyse the results of measurements obtained during commissioning and
Bias of damped Lyman-α systems from their cross-correlation with CMB lensing
Alonso, D.; Colosimo, J.; Font-Ribera, A.; Slosar, A.
2018-04-01
We cross-correlate the positions of damped Lyman-α systems (DLAs) and their parent quasar catalog with a convergence map derived from the Planck cosmic microwave background (CMB) temperature data. We make consistent measurements of the lensing signal of both samples in both Fourier and configuration space. By interpreting the excess signal present in the DLA catalog with respect to the parent quasar catalog as caused by the large scale structure traced by DLAs, we are able to infer the bias of these objects: bDLA=2.6±0.9. These results are consistent with previous measurements made in cross-correlation with the Lyman-α forest, although the current noise in the lensing data and the low number density of DLAs limits the constraining power of this measurement. We discuss the robustness of the analysis with respect to a number different systematic effects and forecast prospects of carrying out this measurement with data from future experiments.
A robust active control system for shimmy damping in the presence of free play and uncertainties
Orlando, Calogero; Alaimo, Andrea
2017-02-01
Shimmy vibration is the oscillatory motion of the fork-wheel assembly about the steering axis. It represents one of the major problem of aircraft landing gear because it can lead to excessive wear, discomfort as well as safety concerns. Based on the nonlinear model of the mechanics of a single wheel nose landing gear (NLG), electromechanical actuator and tire elasticity, a robust active controller capable of damping shimmy vibration is designed and investigated in this study. A novel Decline Population Swarm Optimization (PDSO) procedure is introduced and used to select the optimal parameters for the controller. The PDSO procedure is based on a decline demographic model and shows high global search capability with reduced computational costs. The open and closed loop system behavior is analyzed under different case studies of aeronautical interest and the effects of torsional free play on the nose landing gear response are also studied. Plant parameters probabilistic uncertainties are then taken into account to assess the active controller robustness using a stochastic approach.
International Nuclear Information System (INIS)
Ware, A.G.
1986-01-01
The Idaho National Engineering Laboratory (INEL) is conducting a research program to assist the United States Nuclear Regulatory Commission (USNRC) in determining best-estimate damping values for use in the dynamic analysis of nuclear power plant piping systems. This paper describes four tasks in the program that were undertaken in FY-86. In the first task, tests were conducted on a 5-in. INEL laboratory piping system and data were analyzed from a 6-in. laboratory system at the ANCO Engineers facility to investigate the parameters influencing damping in the seismic frequency range. Further tests were conducted on 3- and 5-in. INEL laboratory piping systems as the second task to determine damping values representative of vibrations in the 33 to 100 Hz range, typical of hydrodynamic transients. In the third task a statistical evaluation of the available damping data was conduted to determine probability distributions suitable for use in probabilistic risk assessments (PRAs), and the final task evaluated damping data at high strain levels
The influence of intraocular pressure on the damping of a coupled speaker–air–eye system
Directory of Open Access Journals (Sweden)
J. Osmers
2018-03-01
Full Text Available Although glaucoma is currently the world's most common cause of irreversible blindness, there is no curative therapy available to date. The major risk factor that can be influenced in order to stop disease progression is the eye pressure (IOP. Therefore early diagnosis of an altered IOP is essential for the goal of preserving vision. A novel IOP measurement principle for a handheld noncontact self-tonometer shall be validated.The measurement principle uses a pressure pulse generated by a loudspeaker to cause vibrations of the eye. In order to reach the required sound pressure, a closed pressure chamber is placed on the human orbit. With a microphone and a displacement sensor the dynamic behavior of the entire system is detected. In this article the abovementioned principle is being analyzed on porcine eyes under laboratory conditions.The combination of the loudspeaker, the pressure chamber, and the eye to be measured can be described as a coupled spring–mass–damper system. It is demonstrated for enucleated porcine eyes that a defined IOP variation leads to a change in the system's damping ratio. Considering only stochastic deviations, the derived standard uncertainty for the determination of the IOP amounts to < 1 mmHg in the physiological range.The in vitro measurements on porcine eyes help the understanding of the underlying physics and demand for further research on the influence of biometric parameters on eye vibrations. However, the laboratory results provide the basis for a gentle noncontact tonometry method with great applicational prospects. Data is currently being collected on human subjects in a clinical trial, to corroborate the measurement principle in vivo.
International Nuclear Information System (INIS)
Xu, J.; DeGrassi, G.; Chokshi, N.
2004-01-01
Under the auspices of the U.S. Nuclear Regulatory Commission (NRC), Brookhaven National Laboratory (BNL) developed a comprehensive program to evaluate state-of-the-art methods and computer programs for seismic analysis of typical coupled nuclear power plant (NPP) systems with non-classical damping. In this program, four benchmark models of coupled building-piping/equipment systems with different damping characteristics were developed and analyzed by BNL for a suite of earthquakes. The BNL analysis was carried out by the Wilson-θ time domain integration method with the system-damping matrix computed using a synthesis formulation as presented in a companion paper [Nucl. Eng. Des. (2002)]. These benchmark problems were subsequently distributed to and analyzed by program participants applying their uniquely developed methods and computer programs. This paper is intended to offer a glimpse at the program, and provide a summary of major findings and principle conclusions with some representative results. The participant's analysis results established using complex modal time history methods showed good comparison with the BNL solutions, while the analyses produced with either complex-mode response spectrum methods or classical normal-mode response spectrum method, in general, produced more conservative results, when averaged over a suite of earthquakes. However, when coupling due to damping is significant, complex-mode response spectrum methods performed better than the classical normal-mode response spectrum method. Furthermore, as part of the program objectives, a parametric assessment is also presented in this paper, aimed at evaluation of the applicability of various analysis methods to problems with different dynamic characteristics unique to coupled NPP systems. It is believed that the findings and insights learned from this program will be useful in developing new acceptance criteria and providing guidance for future regulatory activities involving license
Directory of Open Access Journals (Sweden)
Francisco Palacios-Quiñonero
2014-01-01
Full Text Available We present a new design strategy that makes it possible to synthesize decentralized output-feedback controllers by solving two successive optimization problems with linear matrix inequality (LMI constraints. In the initial LMI optimization problem, two auxiliary elements are computed: a standard state-feedback controller, which can be taken as a reference in the performance assessment, and a matrix that facilitates a proper definition of the main LMI optimization problem. Next, by solving the second optimization problem, the output-feedback controller is obtained. The proposed strategy extends recent results in static output-feedback control and can be applied to design complex passive-damping systems for vibrational control of large structures. More precisely, by taking advantages of the existing link between fully decentralized velocity-feedback controllers and passive linear dampers, advanced active feedback control strategies can be used to design complex passive-damping systems, which combine the simplicity and robustness of passive control systems with the efficiency of active feedback control. To demonstrate the effectiveness of the proposed approach, a passive-damping system for the seismic protection of a five-story building is designed with excellent results.
Yang, C.; Zhang, Y. K.; Liang, X.
2014-12-01
Damping effect of an unsaturated-saturated system on tempospatialvariations of pressurehead and specificflux was investigated. The variance and covariance of both pressure head and specific flux in such a system due to a white noise infiltration were obtained by solving the moment equations of water flow in the system and verified with Monte Carlo simulations. It was found that both the pressure head and specific flux in this case are temporally non-stationary. The variance is zero at early time due to a deterministic initial condition used, then increases with time, and approaches anasymptotic limit at late time.Both pressure head and specific flux arealso non-stationary in space since the variance decreases from source to sink. The unsaturated-saturated systembehavesasa noise filterand it damps both the pressure head and specific flux, i.e., reduces their variations and enhances their correlation. The effect is stronger in upper unsaturated zone than in lower unsaturated zone and saturated zone. As a noise filter, the unsaturated-saturated system is mainly a low pass filter, filtering out the high frequency components in the time series of hydrological variables. The damping effect is much stronger in the saturated zone than in the saturated zone.
International Nuclear Information System (INIS)
Mehai, L.; Paultre, P.; Leger, P.
1992-01-01
In the design of dams to withstand seismic events, recent studies have shown that the dam-foundation and dam-reservoir interactions have a significant influence on the dynamic response of the dam. The hypothesis of proportional damping is not realistic for such structures, in which the mechanisms of energy dissipation present notable differences between their various components. A comparative study is presented of different methods of resolution of linear systems with non-proportional damping, using recent techniques of coordinate reduction. Parametric studies were conducted on a 2-dimensional finite element model of a concrete gravity dam-foundation system. The comparison focuses essentially on the numerical efficiency and precision in the calculation of dynamic parameters (displacements, accelerations, and internal stresses) and in the distribution of damping energy among the components of the system. The evaluation of the energy dissipated in the absorbing boundaries has indicated that the algorithms retained for reducing the coordinates in real and complex space conveniently model the conditions at the limits of the structure. The high degree of numerical stability and the efficiency of the interative procedure of Ibrahimbegovic and Wilson (1989), applied to systems with a large number of degrees of freedom, has been confirmed. 10 refs., 8 figs
Zhileykin, M. M.; Kotiev, G. O.; Nagatsev, M. V.
2018-02-01
In order to meet the growing mobility requirements for the wheeled vehicles on all types of terrain the engineers have to develop a large number of specialized control algorithms for the multi-axle wheeled vehicle (MWV) suspension improving such qualities as ride comfort, handling and stability. The authors have developed an adaptive algorithm of the dynamic damping of the MVW body oscillations. The algorithm provides high ride comfort and high mobility of the vehicle. The article discloses a method for synthesis of an adaptive dynamic continuous algorithm of the MVW body oscillation damping and provides simulation results proving high efficiency of the developed control algorithm.
Amplitude damping for single-qubit system with single-qubit mixed-state environment
International Nuclear Information System (INIS)
Jung, Eylee; Hwang, Mi-Ra; Ju, You Hwan; Park, D K; Kim, Hungsoo; Kim, Min-Soo; Son, Jin-Woo
2008-01-01
We study a generalized amplitude damping channel when environment is initially in the single-qubit mixed state. Representing the affine transformation of the generalized amplitude damping by a three-dimensional volume, we plot explicitly the volume occupied by the channels simulatable by a single-qubit mixed-state environment. As expected, this volume is embedded in the total volume by the channels which is simulated by a two-qubit enviroment. The volume ratio is approximately 0.08 which is much smaller than 3/8, the volume ratio for generalized depolarizing channels
Deep learning of quasar spectra to discover and characterize damped Lyα systems
Parks, David; Prochaska, J. Xavier; Dong, Shawfeng; Cai, Zheng
2018-05-01
We have designed, developed, and applied a convolutional neural network (CNN) architecture using multi-task learning to search for and characterize strong H I Lyα absorption in quasar spectra. Without any explicit modelling of the quasar continuum or application of the predicted line profile for Lyα from quantum mechanics, our algorithm predicts the presence of strong H I absorption and estimates the corresponding redshift zabs and H I column density N_{H I}, with emphasis on damped Lyα systems (DLAs, absorbers with N_{H I}≥ 2 × 10^{20} cm^{-2}). We tuned the CNN model using a custom training set of DLAs injected into DLA-free quasar spectra from the Sloan Digital Sky Survey (SDSS), data release 5 (DR5). Testing on a held-back validation set demonstrates a high incidence of DLAs recovered by the algorithm (97.4 per cent as DLAs and 99 per cent as an H I absorber with N_{H I}> 10^{19.5} cm^{-2}) and excellent estimates for zabs and N_{H I}. Similar results are obtained against a human-generated survey of the SDSS DR5 data set. The algorithm yields a low incidence of false positives and negatives but is challenged by overlapping DLAs and/or very high N_{H I} systems. We have applied this CNN model to the quasar spectra of SDSS DR7 and the Baryon Oscillation Spectroscopic Survey (data release 12) and provide catalogues of 4913 and 50 969 DLAs, respectively (including 1659 and 9230 high-confidence DLAs that were previously unpublished). This work validates the application of deep learning techniques to astronomical spectra for both classification and quantitative measurements.
Energy Technology Data Exchange (ETDEWEB)
Jang, H.K.; Song, D.; Kim, S.B. [Hanyang University, 17 Haengdang-Dong, Seongdong-Gu, Seoul 133-791 (Korea, Republic of); Han, S.C. [Korea Electric Power Research Institute, 103-16 Munji-Ro, Yuseong-Gu, Daejeon 305-380 (Korea, Republic of); Sung, T.H., E-mail: sungth@hanyang.ac.kr [Hanyang University, 17 Haengdang-Dong, Seongdong-Gu, Seoul 133-791 (Korea, Republic of)
2012-05-15
A 5 kWh superconductor flywheel energy storage system (SFES) has advantages in terms of high electrical energy density, environmental affinity and long life. However, the SFES has disadvantage that electromagnetic damper is needed because superconducting bearings do not have enough damping coefficient. The purpose of this experiment is to develop a method of damping the vibration of the SFES. A piezoelectric actuator was attached to a superconducting bearing system for feasibility test in order to make it as a damper of the SFES. For this experiment, a cylindrical permanent magnet (PM) 40 mm in diameter and 10 mm height was used as a rotor, a high-temperature superconductor bulk (HTS bulk) with dimensions 40 mm Multiplication-Sign 40 mm Multiplication-Sign 15 mm was used as a stator, and two vibration exciters (an upper and a lower vibration exciter) and a piezoelectric actuator were used. The PM was fixed on the upper vibration exciter. The HTS bulk was fixed on either the lower vibration exciter to test for damping in the feasibility test, or on the piezoelectric actuator for the actual SFES. The conditions of this experiment included various voltage outputs of a power amplifier to the lower vibration exciter, moving distances of the piezoelectric actuator which are displacements of the HTS bulk, and phase differences between the upper and lower vibration exciter or the piezoelectric actuator. The damping feasibility test was conducted with a 300 {mu}m gap between the PM and HTS bulk with a PM vibration of 30 {mu}m. For the actual SFES test, the gap between the PM and HTS bulk was 1.6 mm and the PM vibration was 25 {mu}m. The following conditions were conducted to optimize: an appropriate voltage input to the lower vibration exciter or a displacement of piezoelectric actuator and an appropriate phase difference. When the piezoelectric actuator was used, the damping effect was greatly improved up to 92.32% which a displacement of damped PM was 1.92 {mu}m.
The Mean Metal-line Absorption Spectrum of Damped Ly α Systems in BOSS
Energy Technology Data Exchange (ETDEWEB)
Mas-Ribas, Lluís [Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029, NO-0315 Oslo (Norway); Miralda-Escudé, Jordi; Pérez-Ràfols, Ignasi; Arinyo-i-Prats, Andreu [Institut de Ciències del Cosmos, Universitat de Barcelona (UB-IEEC), Barcelona E-08028, Catalonia (Spain); Noterdaeme, Pasquier; Petitjean, Patrick [Institut d’Astrophysique de Paris, UPMC and CNRS, UMR7095 98bis Boulevard Arago, F-75014—Paris (France); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); York, Donald G. [Department of Astronomy and Astrophysics and the Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Ge, Jian, E-mail: l.m.ribas@astro.uio.no [Department of Astronomy, University of Florida, Bryant Space Science Center, Gainesville, FL 32611-2055 (United States)
2017-09-01
We study the mean absorption spectrum of the Damped Ly α (DLA) population at z ∼ 2.6 by stacking normalized, rest-frame-shifted spectra of ∼27,000 DLA systems from the DR12 of the Baryon Oscillation Spectroscopic Survey (BOSS)/SDSS-III. We measure the equivalent widths of 50 individual metal absorption lines in five intervals of DLA hydrogen column density, five intervals of DLA redshift, and overall mean equivalent widths for an additional 13 absorption features from groups of strongly blended lines. The mean equivalent width of low-ionization lines increases with N {sub H} {sub i}, whereas for high-ionization lines the increase is much weaker. The mean metal line equivalent widths decrease by a factor ∼1.1–1.5 from z ∼ 2.1 to z ∼ 3.5, with small or no differences between low- and high-ionization species. We develop a theoretical model, inspired by the presence of multiple absorption components observed in high-resolution spectra, to infer mean metal column densities from the equivalent widths of partially saturated metal lines. We apply this model to 14 low-ionization species and to Al iii, S iii, Si iii, C iv, Si iv, N v, and O vi. We use an approximate derivation for separating the equivalent width contributions of several lines to blended absorption features, and infer mean equivalent widths and column densities from lines of the additional species N i, Zn ii, C ii*, Fe iii, and S iv. Several of these mean column densities of metal lines in DLAs are obtained for the first time; their values generally agree with measurements of individual DLAs from high-resolution, high signal-to-noise ratio spectra when they are available.
Eclipsing damped Lyα systems in the Sloan Digital Sky Survey Data Release 12★
Fathivavsari, H.; Petitjean, P.; Jamialahmadi, N.; Khosroshahi, H. G.; Rahmani, H.; Finley, H.; Noterdaeme, P.; Pâris, I.; Srianand, R.
2018-04-01
We present the results of our automatic search for proximate damped Lyα absorption (PDLA) systems in the quasar spectra from the Sloan Digital Sky Survey Data Release 12. We constrain our search to those PDLAs lying within 1500 km s-1 from the quasar to make sure that the broad DLA absorption trough masks most of the strong Lyα emission from the broad line region (BLR) of the quasar. When the Lyα emission from the BLR is blocked by these so-called eclipsing DLAs, narrow Lyα emission from the host galaxy could be revealed as a narrow emission line (NEL) in the DLA trough. We define a statistical sample of 399 eclipsing DLAs with log N(H I) ≥ 21.10. We divide our statistical sample into three subsamples based on the strength of the NEL detected in the DLA trough. By studying the stacked spectra of these subsamples, we found that absorption from high ionization species are stronger in DLAs with stronger NEL in their absorption core. Moreover, absorption from the excited states of species like Si II are also stronger in DLAs with stronger NEL. We also found no correlation between the luminosity of the Lyα NEL and the quasar luminosity. These observations are consistent with a scenario in which the DLAs with stronger NEL are denser and physically closer to the quasar. We propose that these eclipsing DLAs could be the product of the interaction between infalling and outflowing gas. High resolution spectroscopic observation would be needed to shed some light on the nature of these eclipsing DLAs.
Elfrink, R.; Renaud, M.; Kamel, T.M.; Nooijer, C. de; Jambunathan, M.; Goedbloed, M.; Hohlfeld, D.; Matova, S.; Pop, V.; Caballero, L.; Schaijk, R. van
2010-01-01
This paper describes the characterization of thin-film MEMS vibration energy harvesters based on aluminum nitride as piezoelectric material. A record output power of 85 μW is measured. The parasitic-damping and the energy-harvesting performances of unpackaged and packaged devices are investigated.
Active Damping Control Methods for Three-Phase Slim DC-link Drive System
DEFF Research Database (Denmark)
Yang, Feng; Wang, Dong; Blaabjerg, Frede
2017-01-01
for stabilizing such slim dc-link drives together with the benefit of low cost and high flexibility. This paper gives an overview of the state-of-the-art active damping methods for the three-phase slim dc-link drive. The main pros and cons of each method are identified. The theoretical comparison is validated...
Study on optimum aseismic design of complex structure system focusing on damping effect
International Nuclear Information System (INIS)
Takahashi, Yoshitaka; Suzuki, Kohei
1995-01-01
Optimum design technique for the purpose of aseismic design of complex plant structures such as piping and boiler structures is proposed. Particular attention is focused on the evaluation of the optimum damping and stiffness of the structures and components. Pseudo least square algorithm is introduced to determine the optimum design parameters. Under the requirement of certain allowable maximum response to a given earthquake excitation, optimum stiffness and damping values of the structure can be simultaneously calculated by this proposed method. The applicability of the method is demonstrated through three structural models; (1) linear multi-storied building model in which stiffness and damping constant of each floor are optimized; (2) nonlinear multi-storied building model having the isolated floor in which hysteretic energy absorber of the isolator is optimized; (3) combined boiler-supporting structure model connected by the inelastic seismic ties with each other is optimized. In this model, optimum values of damping characteristic of the seismic ties are evaluated. This work is particularly important for the aseismic design of complex plant structures like integrated boiler-supporting structure in thermal power plant and piping-containment vessel structure in nuclear power plant
DEFF Research Database (Denmark)
Sun, Xiaofeng; Zeng, Jian; Chen, Zhe
2013-01-01
, and analyze the harmonic voltage propagation caused by the background harmonic voltage in power systems. Then, a new strategy is proposed for the site selection of resistive active power filter to damp the background harmonic voltage in power systems. Experiments have been performed to verify the theoretical......Series resonance between capacitance and line inductance may magnify background harmonic voltage and worsen the harmonic voltage distortion in power systems. To solve this problem, in this paper, the transmission line theory is used to set up the distributed parameter model of power system feeders...
Hasanvand, Hamed; Mozafari, Babak; Arvan, Mohammad R; Amraee, Turaj
2015-11-01
This paper addresses the application of a static Var compensator (SVC) to improve the damping of interarea oscillations. Optimal location and size of SVC are defined using bifurcation and modal analysis to satisfy its primary application. Furthermore, the best-input signal for damping controller is selected using Hankel singular values and right half plane-zeros. The proposed approach is aimed to design a robust PI controller based on interval plants and Kharitonov's theorem. The objective here is to determine the stability region to attain robust stability, the desired phase margin, gain margin, and bandwidth. The intersection of the resulting stability regions yields the set of kp-ki parameters. In addition, optimal multiobjective design of PI controller using particle swarm optimization (PSO) algorithm is presented. The effectiveness of the suggested controllers in damping of local and interarea oscillation modes of a multimachine power system, over a wide range of loading conditions and system configurations, is confirmed through eigenvalue analysis and nonlinear time domain simulation. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.
Cyranka, Jacek; Mucha, Piotr B.; Titi, Edriss S.; Zgliczyński, Piotr
2018-04-01
The paper studies the issue of stability of solutions to the forced Navier-Stokes and damped Euler systems in periodic boxes. It is shown that for large, but fixed, Grashoff (Reynolds) number the turbulent behavior of all Leray-Hopf weak solutions of the three-dimensional Navier-Stokes equations, in periodic box, is suppressed, when viewed in the right frame of reference, by large enough average flow of the initial data; a phenomenon that is similar in spirit to the Landau damping. Specifically, we consider an initial data which have large enough spatial average, then by means of the Galilean transformation, and thanks to the periodic boundary conditions, the large time independent forcing term changes into a highly oscillatory force; which then allows us to employ some averaging principles to establish our result. Moreover, we also show that under the action of fast oscillatory-in-time external forces all two-dimensional regular solutions of the Navier-Stokes and the damped Euler equations converge to a unique time-periodic solution.
DAMPs, ageing, and cancer: The 'DAMP Hypothesis'.
Huang, Jin; Xie, Yangchun; Sun, Xiaofang; Zeh, Herbert J; Kang, Rui; Lotze, Michael T; Tang, Daolin
2015-11-01
Ageing is a complex and multifactorial process characterized by the accumulation of many forms of damage at the molecular, cellular, and tissue level with advancing age. Ageing increases the risk of the onset of chronic inflammation-associated diseases such as cancer, diabetes, stroke, and neurodegenerative disease. In particular, ageing and cancer share some common origins and hallmarks such as genomic instability, epigenetic alteration, aberrant telomeres, inflammation and immune injury, reprogrammed metabolism, and degradation system impairment (including within the ubiquitin-proteasome system and the autophagic machinery). Recent advances indicate that damage-associated molecular pattern molecules (DAMPs) such as high mobility group box 1, histones, S100, and heat shock proteins play location-dependent roles inside and outside the cell. These provide interaction platforms at molecular levels linked to common hallmarks of ageing and cancer. They can act as inducers, sensors, and mediators of stress through individual plasma membrane receptors, intracellular recognition receptors (e.g., advanced glycosylation end product-specific receptors, AIM2-like receptors, RIG-I-like receptors, and NOD1-like receptors, and toll-like receptors), or following endocytic uptake. Thus, the DAMP Hypothesis is novel and complements other theories that explain the features of ageing. DAMPs represent ideal biomarkers of ageing and provide an attractive target for interventions in ageing and age-associated diseases. Copyright © 2014 Elsevier B.V. All rights reserved.
Development of new damping devices for piping
International Nuclear Information System (INIS)
Kobayashi, Hiroe
1991-01-01
An increase of the damping ratio is known to be very effective for the seismic design of a piping system. Increasing the damping ratio and reducing the seismic response of the piping system, the following three types of damping devices for piping systems are introduced: (1) visco-elastic damper, (2) elasto-plastic damper and (3) compact dynamic damper. The dynamic characteristics of these damping devices were investigated by the component test and the applicability of them to the piping system was confirmed by the vibration test using a three dimensional piping model. These damping devices are more effective than mechanical snubbers to reduce the vibration of the piping system. (author)
Pole-placement Predictive Functional Control for under-damped systems with real numbers algebra.
Zabet, K; Rossiter, J A; Haber, R; Abdullah, M
2017-11-01
This paper presents the new algorithm of PP-PFC (Pole-placement Predictive Functional Control) for stable, linear under-damped higher-order processes. It is shown that while conventional PFC aims to get first-order exponential behavior, this is not always straightforward with significant under-damped modes and hence a pole-placement PFC algorithm is proposed which can be tuned more precisely to achieve the desired dynamics, but exploits complex number algebra and linear combinations in order to deliver guarantees of stability and performance. Nevertheless, practical implementation is easier by avoiding complex number algebra and hence a modified formulation of the PP-PFC algorithm is also presented which utilises just real numbers while retaining the key attributes of simple algebra, coding and tuning. The potential advantages are demonstrated with numerical examples and real-time control of a laboratory plant. Copyright © 2017 ISA. All rights reserved.
D.V.N. Ananth; G.V. Nagesh Kumar
2017-01-01
During grid fault, transmission lines reach its thermal limit and lose its capability to transfer. If this fault current enters generator terminals, it will lead to dip in stator voltage and consequently produces torque and real power oscillations. This further affects in the form of internal heat in rotor windings and finally damages the generator. A new control strategy is proposed to limit fault current using dual STATCOM, which will damp power oscillations and mitigate the voltage dip due...
Wall-plug efficiency analysis of semi-active piezoelectric shunt damping systems
Czech Academy of Sciences Publication Activity Database
Václavík, Jan; Kodejška, M.; Mokrý, Pavel
2014-01-01
Roč. 20, September (2014), 1077546314548910 ISSN 1077-5463 R&D Projects: GA MŠk(CZ) LO1206; GA ČR GA13-10365S Institutional support: RVO:61389021 Keywords : Piezoelectric shunt damping * vibration isolation * negative capacitor * wall-plug efficiency * mechanical power measurement * power supply optimization Subject RIV: BI - Acoustics Impact factor: 4.355, year: 2013 http://jvc.sagepub.com/content/early/2014/09/17/1077546314548910
Wall-plug efficiency analysis of semi-active piezoelectric shunt damping systems
Czech Academy of Sciences Publication Activity Database
Václavík, Jan; Kodejška, M.; Mokrý, Pavel
2016-01-01
Roč. 22, č. 11 (2016), s. 2582-2590 ISSN 1077-5463 R&D Projects: GA MŠk(CZ) LO1206; GA ČR GA13-10365S Institutional support: RVO:61389021 Keywords : Piezoelectric shunt damping * vibration isolation * negative capacitor * wall-plug efficiency * mechanical power measurement * power supply optimization Subject RIV: BI - Acoustics Impact factor: 2.101, year: 2016 http://journals.sagepub.com/doi/abs/10.1177/1077546314548910
International Nuclear Information System (INIS)
Turner, Sam
2011-01-01
The phenomenon of process damping as a stabilising effect in milling has been encountered by machinists since milling and turning began. It is of great importance when milling aerospace alloys where maximum surface speed is limited by excessive tool wear and high speed stability lobes cannot be attained. Much of the established research into regenerative chatter and chatter avoidance has focussed on stability lobe theory with different analytical and time domain models developed to expand on the theory first developed by Trusty and Tobias. Process damping is a stabilising effect that occurs when the surface speed is low relative to the dominant natural frequency of the system and has been less successfully modelled and understood. Process damping is believed to be influenced by the interference of the relief face of the cutting tool with the waveform traced on the cut surface, with material properties and the relief geometry of the tool believed to be key factors governing performance. This study combines experimental trials with Finite Element (FE) simulation in an attempt to identify and understand the key factors influencing process damping performance in titanium milling. Rake angle, relief angle and chip thickness are the variables considered experimentally with the FE study looking at average radial and tangential forces and surface compressive stress. For the experimental study a technique is developed to identify the critical process damping wavelength as a means of measuring process damping performance. For the range of parameters studied, chip thickness is found to be the dominant factor with maximum stable parameters increased by a factor of 17 in the best case. Within the range studied, relief angle was found to have a lesser effect than expected whilst rake angle had an influence.
Directory of Open Access Journals (Sweden)
Abbas AbdulMajeed Allawi
2016-06-01
Full Text Available This paper studies the combination fluid viscous dampers in the outrigger system to add supplementary damping into the structure, which purpose to remove the dependability of the structure to lower variable intrinsic damping. It works by connecting the central core, comprising either shear walls or braced frames, to the outer perimeter columns. The modal considered is a 36 storey square high rise reinforced concrete building. By constructing a discrete lumped mass model, and using frequency-based response function, two systems of dampers, parallel and series systems are studied. The maximum lateral load at the top of the building is calculated, and this load will be applied at every floor of the building, giving a conservative solution. For static study Equivalent Lateral Force (ELF was conducted. MATLAB software, has been used in this study. From analysis data, it is observed that the parallel system of dampers result lower amplitude of vibration and achieved more efficiently compared to the series system, and the horizontal displacement for each configurations by using MATLAB software is less than the analytical solution using a uniformly distributed load of 36 nodal point forces that divided the total height.
Influence of solitons in the initial state on chaos in the driven damped sine-Gordon system
Energy Technology Data Exchange (ETDEWEB)
Bishop, A R; Fesser, K; Lomdahl, P S; Trullinger, S E
1983-01-01
The appearance of chaos in the a.c. driven, damped sine-Gordon equation is studied numerically. Several transitions from periodic to chaotic behavior are investigated in detail for flat initial conditions. Spatial structures (breather, kink) in the initial conditions smooth out many of these transitions and give rise to an interesting symbiosis of time and spatial intermittency. This symbiosis appears to be due to the competition between the background tendency towards chaos and the system's preference to maintain a spatial pattern. The way that this competition is relieved is also found to depend very strongly on symmetry in the initial conditions.
Integration of Shape Memory Alloys into Low-Damped Rotor-Bearing Systems
DEFF Research Database (Denmark)
Enemark, Søren
2015-01-01
to use passive adaptive control through smart materials. Shape Memory Alloys (SMAs) are interesting candidates in that relation, because of their highly temperature sensitive stiffness and mechanical hysteresis, which can be used for damping purposes. The thesis focuses on three main aspects related...... and identifiability, and to call attention to the inherent uncertainties of model predictions. The second aspect concerns design and modelling of machine elements made from SMAs. Different actuation principles of SMAs are covered, and pseudoelastic elements in pre-tension are found to have the most promising...
International Nuclear Information System (INIS)
Bullock, J.C.; Kelley, B.E.
1977-01-01
A valve for damping out flow surges in a vacuum system is described. The surge-damping mechanism consists of a slotted, spring-loaded disk adjacent to the valve's vacuum port (the flow passage to the vacuum roughing pump). Under flow surge conditions, the differential pressure forces the disk into a sealing engagement with the vacuum port, thereby restricting the gas flow path to narrow slots in the disk's periphery. The increased flow damps out the flow surge. When pressure is equalized on both sides of the valve, the spring load moves the disk away from the port to restore full flow conductance through the valve
Damping of Coherent oscillations
Vos, L
1996-01-01
Damping of coherent oscillations by feedback is straightforward in principle. It has been a vital ingredient for the safe operation of accelerators since a long time. The increasing dimensions and beam intensities of the new generation of hadron colliders impose unprecedented demands on the performance of future systems. The arguments leading to the specification of a transverse feedback system for the CERN SPS in its role as LHC injector and the LHC collider itself are developped to illustrate this. The preservation of the transverse emittance is the guiding principle during this exercise keeping in mind the hostile environment which comprises: transverse impedance bent on developping coupled bunch instabilities, injection errors, unwanted transverse excitation, unavoidable tune spreads and noise in the damping loop.
Modelling of Dampers and Damping in Structures
DEFF Research Database (Denmark)
Høgsberg, Jan Riess
2006-01-01
and the maximum attainable damping are found by maximizing the expression for the damping ratio. The theory is formulated for linear damper models, but may also be applied for non-linear dampers in terms of equivalent linear parameters for stiffness and damping, respectively. The format of the expressions......, and thereby the damping, of flexible structures are generally described in terms of the dominant vibration modes. A system reduction technique, where the damped vibration mode is constructed as a linear combination of the undamped mode shape and the mode shape obtained by locking the damper, is applied....... This two-component representation leads to a simple solution for the modal damping representing the natural frequency and the associated damping ratio. It appears from numerical examples that this system reduction technique provides very accurate results. % Analytical expressions for the optimal tuning...
Damped nonlinear Schrodinger equation
International Nuclear Information System (INIS)
Nicholson, D.R.; Goldman, M.V.
1976-01-01
High frequency electrostatic plasma oscillations described by the nonlinear Schrodinger equation in the presence of damping, collisional or Landau, are considered. At early times, Landau damping of an initial soliton profile results in a broader, but smaller amplitude soliton, while collisional damping reduces the soliton size everywhere; soliton speeds at early times are unchanged by either kind of damping. For collisional damping, soliton speeds are unchanged for all time
Jowett, John M; Zimmermann, Frank; Owen, H
2001-01-01
The Compact Linear Colider (CLIC) is designed to operate at 3 TeV centre-of-mass energy with a total luminosity of 10^35 cm^-2 s^-1. The overall system design leads to extremely demanding requirements on the bunch trains injected into the main libac at frequency of 100 Hz. In particular, the emittances of the intense bunches have to be about an order of magnitude smaller than presently achieved. We describe our approach to finding a damping ring design capable of meeting these requirements. Besides lattice design, emittance and damping rate considerations, a number of scattering and instability effects have to be incorporated into the optimisation of parameters. Among these, intra-bem scattering and the electron cloud effect are two of the most significant.
A METALLICITY-SPIN TEMPERATURE RELATION IN DAMPED Lyα SYSTEMS
International Nuclear Information System (INIS)
Kanekar, Nissim; Smette, Alain; Briggs, Frank H.; Chengalur, Jayaram N.
2009-01-01
We report evidence for an anti-correlation between spin temperature T s and metallicity [Z/H], detected at 3.6σ significance in a sample of 26 damped Lyα absorbers (DLAs) at redshifts 0.09 s = (-0.68 ± 0.17) x [Z/H] + (2.13 ± 0.21) from a linear regression analysis. Our results indicate that the high T s values found in DLAs do not arise from differences between the optical and radio sightlines, but are likely to reflect the underlying gas temperature distribution. The trend between T s and [Z/H] can be explained by the larger number of radiation pathways for gas cooling in galaxies with high metal abundances, resulting in a high cold gas fraction, and hence, a low spin temperature. Conversely, low-metallicity galaxies have fewer cooling routes, yielding a larger warm gas fraction and a high T s . Most DLAs at z > 1.7 have low metallicities, [Z/H] s and [Z/H] is consistent with the presence of a mass-metallicity relation in DLAs, suggested by the tight correlation between DLA metallicity and the kinematic widths of metal lines. Most high-z DLAs are likely to arise in galaxies with low masses (M vir 10.5 M sun ), low metallicities ([Z/H] <-1), and low cold gas fractions.
Entanglement near the optical instability point in damped four wave mixing systems
Chiangga, S.; Temnuch, W.; Frank, T. D.
2018-06-01
Entanglement of electromagnetic field modes of signal and idler photons generated by four-wave mixing (FWM) devices is a quantum phenomenon that has been examined in various experimental and theoretical studies. The focus of this theoretical study is on two aspects of this phenomenon: the emergence of signal and idler photons due to an optical instability and the entanglement of the signal and idler modes above the instability threshold. For simple FWM devices that are subjected to damping it is shown that the signal and idler modes are entangled close to the point of optical instability at which the signal and idler photons emerges. The degree of entanglement as measured by a particular entanglement function proposed earlier in the literature assumes at the point of optical instability a unique value that is independent of the model parameters of the devices. The value is slightly higher than the value reported in a FWM experiment by Boyer et al (2008 Science 321 544). Numerical simulations suggest that the aforementioned entanglement function is U-shaped such that the degree of entanglement at the instability point is the maximal possible one and represents the optimal value. A similar U-shaped pattern was observed in an FWM experiment conducted by Lawrie et al (2016 Appl. Phys. Lett. 108 151107). Our semi-analytical findings are derived within the framework of the positive P representation of quantum optical processes and are compared with the aforementioned experimental observations by Boyer et al and Lawrie et al.
Wilches-Bernal, Felipe
Power systems around the world are experiencing a continued increase in wind generation as part of their energy mix. Because of its power electronics interface, wind energy conversion systems interact differently with the grid than conventional generation. These facts are changing the traditional dynamics that regulate power system behavior and call for a re-examination of traditional problems encountered in power systems like frequency response, inter-area oscillations and parameter identification. To address this need, realistic models for wind generation are necessary. The dissertation implements such models in a MATLAB-based flexible environment suited for power system research. The dissertation continues with an analysis of the frequency response of a test power system dependent mainly on a mode referred to as the frequency regulation mode. Using this test system it is shown that its frequency regulation capability is reduced with wind penetration levels of 25% and above. A controller for wind generation to restore the frequency response of the system is then presented. The proposed controller requires the WTG to operate in a deloaded mode, a condition that is obtained through pitching the wind turbine blades. Time simulations at wind penetration levels of 25% and 50% are performed to demonstrate the effectiveness of the proposed controller. Next, the dissertation evaluates how the inter-area oscillation of a two-machine power system is affected by wind integration. The assessment is performed based on the positioning of the WTG, the level of wind penetration, and the loading condition of the system. It is determined that integrating wind reduces the damping of the inter-area mode of the system when performed in an area that imports power. For this worst-case scenario, the dissertation proposes two controllers for wind generation to improve the damping of the inter-area mode. The first controller uses frequency as feedback signal for the active power control
Directory of Open Access Journals (Sweden)
Jian Zuo
2017-04-01
Full Text Available The potential of utilizing doubly-fed induction generator (DFIG-based wind farms to improve power system damping performance and to enhance small signal stability has been proposed by many researchers. However, the simultaneous coordinated tuning of a DFIG power oscillation damper (POD with other damping controllers is rarely involved. A simultaneous robust coordinated multiple damping controller design strategy for a power system incorporating power system stabilizer (PSS, static var compensator (SVC POD and DFIG POD is presented in this paper. This coordinated damping control design strategy is addressed as an eigenvalue-based optimization problem to increase the damping ratios of oscillation modes. Both local and inter-area electromechanical oscillation modes are intended in the optimization design process. Wide-area phasor measurement unit (PMU signals, selected by the joint modal controllability/ observability index, are utilized as SVC and DFIG POD feedback modulation signals to suppress inter-area oscillation modes. The robustness of the proposed coordinated design strategy is achieved by simultaneously considering multiple power flow situations and operating conditions. The recently proposed Grey Wolf optimizer (GWO algorithm is adopted to efficiently optimize the parameter values of multiple damping controllers. The feasibility and effectiveness of the proposed coordinated design strategy are demonstrated through frequency-domain eigenvalue analysis and nonlinear time-domain simulation studies in two modified benchmark test systems. Moreover, the dynamic response simulation results also validate the robustness of the recommended coordinated multiple damping controllers under various system operating conditions.
A z = 3 Lyα BLOB ASSOCIATED WITH A DAMPED Lyα SYSTEM PROXIMATE TO ITS BACKGROUND QUASAR
International Nuclear Information System (INIS)
Hennawi, Joseph F.; Prochaska, J. Xavier; Kollmeier, Juna; Zheng Zheng
2009-01-01
We report on the discovery of a bright Lyα blob associated with the z = 3 quasar SDSS J124020.91+145535.6 which is also coincident with strong damped Lyα absorption from a foreground galaxy (a so-called proximate damped Lyα (PDLA) system). The one-dimensional spectrum acquired by the Sloan Digital Sky Survey (SDSS) shows a broad Lyα emission line with a FWHM ≅500 km s -1 and a luminosity of L Lyα = 3.9 x 10 43 erg s -1 superposed on the trough of the PDLA. Follow-up observations using the Keck/LRIS spectrometer confirm that this source has a Lyα nebula with spatial extent exceeding 5'', corresponding to a proper size >39 kpc. Mechanisms for powering the large Lyα luminosity in this nebula are discussed. We use a Monte Carlo radiative transfer simulation to investigate the possibility that the line emission is fluorescent recombination radiation from a kpc-scale PDLA galaxy powered by the ionizing flux of the quasar, but find that the predicted Lyα flux is several orders of magnitude lower than observed. We conclude that the Lyα emission is not associated with the PDLA galaxy at all, but instead is intrinsic to the quasar's host and similar to the extended Lyα f uzzwhich is detected around many active galactic nuclei. PDLAs are natural coronagraphs that block their background quasar at Lyα and we discuss how systems similar to SDSS J124020.91+145535.6 might be used to image the neutral hydrogen in the PDLA galaxy in silhouette against the screen of extended Lyα emission from the background quasar.
Macdermid, Paul W; Miller, Matthew C; Fink, Philip W; Stannard, Stephen R
2017-11-01
Cross-country mountain bike suspension reportedly enhances comfort and performance through reduced vibration and impact exposure. This study analysed the effectiveness of three different front fork systems at damping accelerations during the crossing of three isolated obstacles (stairs, drop, and root). One participant completed three trials on six separate occasions in a randomised order using rigid, air-sprung, and carbon leaf-sprung forks. Performance was determined by time to cross obstacles, while triaxial accelerometers quantified impact exposure and damping response. Results identified significant main effect of fork type for performance time (p < 0.05). The air-sprung and leaf-sprung forks were significantly slower than the rigid forks for the stairs (p < 0.05), while air-sprung suspension was slower than the rigid for the root protocol (p < 0.05). There were no differences for the drop protocol (p < 0.05). Rigid forks reduced overall exposure (p < 0.05), specifically at the handlebars for the stairs and drop trials. More detailed analysis presented smaller vertical accelerations at the handlebar for air-sprung and leaf-sprung forks on the stairs (p < 0.05), and drop (p < 0.05) but not the root. As such, it appears that the suspension systems tested were ineffective at reducing overall impact exposure at the handlebar during isolated aspects of cross-country terrain features which may be influenced to a larger extent by rider technique.
Overview on methods for formulating explicit damping matrices for non-classically damped structures
International Nuclear Information System (INIS)
Xu, J.
1998-04-01
In computing the dynamic response of a connected system with multiple components having dissimilar damping characteristics, which is often referred to as nonclassically damped system such as nuclear power plant piping systems supported by stiff structures, one needs to define the system-level damping based upon the damping information of components. This is frequently done in practice using approximate methods expressed as composite modal damping with weighting functions. However, when the difference in damping among components is substantial, the composite modal damping may become inappropriate in the characterization of the damping behavior of such systems. In recent years, several new methods have emerged with the expectation that they could produce more exact system-level damping for a group of nonclassically damped structures which are comprised of components that possess classical modal damping. In this paper, an overview is presented to examine these methods in the light of their theoretical basis, the technical merits, and practical applications. To this end, a synthesis method is described, which was shown to reduce to the other methods in the literature
Dang Xuan Truong; Tran Duc Chinh
2014-01-01
The report presents a methodology to determine the directions of the stiffness principal axis (in this case subject to the linear displacement and forced rotation angle) of a solid object interact with the surrounding environment by resilient bearing supports. The results also show that determining the coordinates of the stiffness center in the vibrating system with damping factors is necessary in our research.
Power oscillation damping controller
DEFF Research Database (Denmark)
2012-01-01
A power oscillation damping controller is provided for a power generation device such as a wind turbine device. The power oscillation damping controller receives an oscillation indicating signal indicative of a power oscillation in an electricity network and provides an oscillation damping control...
An Empirical Method for Particle Damping Design
Directory of Open Access Journals (Sweden)
Zhi Wei Xu
2004-01-01
Full Text Available Particle damping is an effective vibration suppression method. The purpose of this paper is to develop an empirical method for particle damping design based on extensive experiments on three structural objects – steel beam, bond arm and bond head stand. The relationships among several key parameters of structure/particles are obtained. Then the procedures with the use of particle damping are proposed to provide guidelines for practical applications. It is believed that the results presented in this paper would be helpful to effectively implement the particle damping for various structural systems for the purpose of vibration suppression.
International Nuclear Information System (INIS)
Banks, E.L. Jr.; Dowell, T.P.
1976-01-01
The description is given of a damper which includes a pair of telescopic components interconnected by relative linear movement one in relation to the other, by a screw and ball nut device, with a braking surface on one of the components, a brake engaging the braking surface, an inertia mass entrained by the other components, non-deformable and distinct brake actuating gear, independently mobile in relation to the other braking system and fixed and controlled by the inertia mass, positively to engage the braking surface. This damper is for retaining the parts of a nuclear power station so that can withstand earthquakes [fr
Energy Technology Data Exchange (ETDEWEB)
Roy, Nirupam [Department of Physics and Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721302 (India); Frank, Stephan; Mathur, Smita [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); Carilli, Christopher L. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Menten, Karl M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Wolfe, Arthur M., E-mail: nroy@physics.iisc.ernet.in [Department of Physics and Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States)
2017-01-10
The far-infrared [C ii] 158 μ m fine structure transition is considered to be a dominant coolant in the interstellar medium (ISM). For this reason, under the assumption of a thermal steady state, it may be used to infer the heating rate and, in turn, the star formation rate (SFR) in local as well as in high redshift systems. In this work, radio and ultraviolet observations of the Galactic ISM are used to understand whether C ii is indeed a good tracer of the SFR. For a sample of high Galactic latitude sightlines, direct measurements of the temperature indicate the presence of C ii in both the cold and the warm phases of the diffuse interstellar gas. The cold gas fraction (∼10%–50% of the total neutral gas column density) is not negligible even at high Galactic latitude. It is shown that to correctly estimate the SFR, C ii cooling in both phases should hence be considered. The simple assumption, that the [C ii] line originates only from either the cold or the warm phase, significantly underpredicts or overpredicts the SFR, respectively. These results are particularly important in the context of Damped Ly α systems for which a similar method is often used to estimate the SFR. The derived SFRs in such cases may not be reliable if the temperature of the gas under consideration is not constrained independently.
Metal Abundances at z<1.5: Fresh Clues to the Chemical Enrichment History of Damped Lyα Systems
Pettini, Max; Ellison, Sara L.; Steidel, Charles C.; Bowen, David V.
1999-01-01
We explore the redshift evolution of the metal content of damped Lyα systems (DLAs) with new observations of four absorbers at zintermediate redshifts for which the abundance of Zn has been measured. The main conclusion is that the column density-weighted mean metallicity, []=-1.03+/-0.23 (on a logarithmic scale), is not significantly higher at zaccounted for, leaves no room for the enhancement of the α elements over iron seen in metal-poor stars in the Milky Way. This is contrary to previous assertions that DLAs have been enriched solely by Type II supernovae, but it can be understood if the rate of star formation in the systems studied proceeded more slowly than in the early history of our Galaxy. These results add to a growing body of data pointing to the conclusion that known DLAs do not trace the galaxy population responsible for the bulk of star formation. Possible reasons are that sight lines through metal-rich gas are systematically underrepresented, because the background QSOs are reddened, and that the most actively star-forming galaxies are also the most compact, presenting too small a cross-section to have been probed yet with the limited statistics of current samples. Most of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among Caltech, the University of California, and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Directory of Open Access Journals (Sweden)
Javad Morsali
2017-02-01
Full Text Available In this paper, fractional order proportional-integral-differential (FOPID controller is employed in the design of thyristor controlled series capacitor (TCSC-based damping controller in coordination with the secondary integral controller as automatic generation control (AGC loop. In doing so, the contribution of the TCSC in tie-line power exchange is extracted mathematically for small load disturbance. Adjustable parameters of the proposed FOPID-based TCSC damping controller and the AGC loop are optimized concurrently via an improved particle swarm optimization (IPSO algorithm which is reinforced by chaotic parameter and crossover operator to obtain a globally optimal solution. The powerful FOMCON toolbox is used along with MATLAB for handling fractional order modeling and control. An interconnected multi-source power system is simulated regarding the physical constraints of generation rate constraint (GRC nonlinearity and governor dead band (GDB effect. Simulation results using FOMCON toolbox demonstrate that the proposed FOPID-based TCSC damping controller achieves the greatest dynamic performance under different load perturbation patterns in comparison with phase lead-lag and classical PID-based TCSC damping controllers, all in coordination with the integral AGC. Moreover, sensitivity analyses are performed to show the robustness of the proposed controller under various uncertainty scenarios.
The damped wave equation with unbounded damping
Czech Academy of Sciences Publication Activity Database
Freitas, P.; Siegl, Petr; Tretter, C.
2018-01-01
Roč. 264, č. 12 (2018), s. 7023-7054 ISSN 0022-0396 Institutional support: RVO:61389005 Keywords : damped wave equation * unbounded damping * essential spectrum * quadratic operator funciton with unbounded coefficients * Schrodinger operators with complex potentials Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 1.988, year: 2016
Assessment of remedial control schemes for damping transient oscillations in the Mexican system
Energy Technology Data Exchange (ETDEWEB)
Castellanos, R.B.; Sarmiento, H.U.; Pampin, G. [Inst.de Investigaciones Electricas, Morelos (Mexico); Messina, A.R. [Cinvestav, San Pedro Zacatenco (Mexico)
2008-07-01
In order to enhance voltage control and power system dynamic performance, special protection systems (SPS) are increasingly being used in the Mexican Interconnected System (MIS). These include extensive use of direct load shedding schemes, generator tripping schemes, controlled disconnection of lines, and automatic generation rejection and single phase reclosing schemes. Generator tripping based on local detection of severe disturbance is of particular importance and has been used to enhance transient stability. In addition, the onset of system instability has become more complex, often involving interactions between major system modes. Post-fault transient oscillations have become more common following the loss of major system elements and may result in uncontrolled system separation. This has motivated the need to develop system-wide special protection systems. This paper explored the possible benefits and feasibility of employing SPSs to mitigate wide-area inter-area oscillations in the MIS. The paper described the exploratory studies such as the coordinated application of automatic generation tripping schemes and automatic load shedding to enhance system dynamic performance. The paper also explained sensitivity studies that were conducted to determine the amount and location of generation (load) to be shed and suggested extensions to the basic security criteria to maintain network stability. The proposed techniques were developed and tested on a large-scale representation of the Mexican system that included the operation of several FACTS controllers. It was concluded that automatic generation shedding and automatic loading shedding were efficient alternatives to improve generation and transmission use, reliability and flexibility. 7 refs., 1 tab., 3 figs.
High Frequency Resonance Damping of DFIG based Wind Power System under Weak Network
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
When operating in a micro or weak grid which has a relatively large network impedance, the Doubly Fed Induction Generator (DFIG) based wind power generation system is prone to suffer high frequency resonance due to the impedance interaction between DFIG system and the parallel compensated network...
Gysen, B.L.J.; Paulides, J.J.H.; Lomonova, E.
2011-01-01
A direct-drive electromagnetic active suspension system is considered which consists of a tubular permanent magnet actuator in parallel with a coil spring. This system has the ability of improving the ride comfort while maintaining optimum handling and stability. Since safety is of major concern,
Control by damping Injection of Electrodynamic Tether System in an Inclined Orbit
DEFF Research Database (Denmark)
Larsen, Martin Birkelund; Blanke, Mogens
2009-01-01
dynamical system. Based on this model, a nonlinear controller is designed that will make the system asymptotically stable around its open-loop equilibrium. The control scheme handles the time-varying nature of the system in a suitable manner resulting in a large operational region. The performance...... of the closed loop system is treated using Floquet theory, investigating the closed loop properties for their dependency of the controller gain and orbit inclination.......Control of a satellite system with an electrodynamic tether as actuator is a time-periodic and underactuated control problem. This paper considers the tethered satellite in a Hamiltonian framework and determines a port-controlled Hamiltonian formulation that adequately describes the nonlinear...
Curran, S. J.
2017-09-01
We present a comprehensive analysis of the spin temperature/covering factor degeneracy, Tspin/f, in damped Lyman α absorption systems. By normalizing the upper limits and including these via a survival analysis, there is, as previously claimed, an apparent increase in Tspin/f with redshift at zabs ≳ 1. However, when we account for the geometry effects of an expanding Universe, neglected by the previous studies, this increase in Tspin at zabs ≳ 1 is preceded by a decrease at zabs ≲ 1. Using high resolution radio images of the background continuum sources, we can transform the Tspin/f degeneracy to T_spin/d_abs^{ 2}, where dabs is the projected linear size of the absorber. Again, there is no overall increase with redshift, although a dip at zabs ≈ 2 persists. Furthermore, we find d_abs^{ 2}/T_spin to follow a similar variation with redshift as the star formation rate, ψ*. This suggests that, although the total hydrogen column density, N_{H I}, shows little relation to ψ*, the fraction of the cold neutral medium, \\int τ_obs dv/N_{H I}, may. Therefore, further efforts to link the neutral gas with the star formation history should also consider the cool component of the gas.
Damping by heat conduction in the Timoshenko system: Fourier and Cattaneo are the same
Said-Houari, Belkacem; Kasimov, Aslan R.
2013-01-01
We consider the Cauchy problem for the one-dimensional Timoshenko system coupled with heat conduction, wherein the latter is described by either the Cattaneo law or the Fourier law. We prove that heat dissipation alone is sufficient to stabilize
Information Geometry of Non-Equilibrium Processes in a Bistable System with a Cubic Damping
Directory of Open Access Journals (Sweden)
Rainer Hollerbach
2017-06-01
Full Text Available A probabilistic description is essential for understanding the dynamics of stochastic systems far from equilibrium, given uncertainty inherent in the systems. To compare different Probability Density Functions (PDFs, it is extremely useful to quantify the difference among different PDFs by assigning an appropriate metric to probability such that the distance increases with the difference between the two PDFs. This metric structure then provides a key link between stochastic systems and information geometry. For a non-equilibrium process, we define an infinitesimal distance at any time by comparing two PDFs at times infinitesimally apart and sum these distances in time. The total distance along the trajectory of the system quantifies the total number of different states that the system undergoes in time and is called the information length. By using this concept, we investigate the information geometry of non-equilibrium processes involved in disorder-order transitions between the critical and subcritical states in a bistable system. Specifically, we compute time-dependent PDFs, information length, the rate of change in information length, entropy change and Fisher information in disorder-to-order and order-to-disorder transitions and discuss similarities and disparities between the two transitions. In particular, we show that the total information length in order-to-disorder transition is much larger than that in disorder-to-order transition and elucidate the link to the drastically different evolution of entropy in both transitions. We also provide the comparison of the results with those in the case of the transition between the subcritical and supercritical states and discuss implications for fitness.
Damping in heat exchanger tube bundles. A review
International Nuclear Information System (INIS)
Iqbal, Qamar; Khushnood, Shahab; Ghalban, Ali Roheim El; Sheikh, Nadeem Ahmed; Malik, Muhammad Afzaal; Arastu, Asif
2007-01-01
Damping is a major concern in the design and operation of tube bundles with loosely supported tubes in baffles for process shell and tube heat exchangers and steam generators which are used in nuclear, process and power generation industries. System damping has a strong influence on the amplitude of vibration. Damping depends upon the mechanical properties of the tube material, geometry of intermediate supports and the physical properties of shell-side fluid. Type of tube motion, number of supports, tube frequency, vibration amplitude, tube mass or diameter, side loads, support thickness, higher modes, shell-side temperature etc., affect damping in tube bundles. The importance of damping is further highlighted due to current trend of larger exchangers with increased shell-side velocities in modern units. Various damping mechanisms have been identified (Friction damping, Viscous damping, Squeeze film damping, Support damping. Two-Phase damping, and very recent-Thermal damping), which affect the performance of process exchangers and steam generators with respect to flow induced vibration design, including standard design guidelines. Damping in two-phase flow is very complex and highly void fraction, and flow-regime dependent. The current paper focuses on the various known damping mechanisms subjected to both single and two-phase cross-flow in process heat exchangers and steam generators and formulates the design guidelines for safer design. (author)
Stabilization of periodic solutions in a tethered satellite system by damping injection
DEFF Research Database (Denmark)
Larsen, Martin Birkelund; Blanke, Mogens
2009-01-01
presents a control design for stabilizing these periodic solutions. The design consists of a control law for stabilizing the open-loop equilibrium and a bias term which forces the system trajectory away from the equilibrium. The tether needs to be positioned away from open-loop equilibrium for the tether...... to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...
Analysis of voltage modulation based active damping techniques for small DC-link drive system
DEFF Research Database (Denmark)
Wang, Dong; Lu, Kaiyuan; Rasmussen, Peter Omand
2015-01-01
Small DC-link drive system, built with film capacitor in the DC link, may have the advantages of longer lifetime and the possibility to achieve a more compact design of capacitor bank at medium and high power rates. However, it exhibits instability problem, especially when it is fed by a soft grid...
Preliminary design of the pulse generator for the CLIC damping ring extraction system
Holma, Janne; Ovaska, Seppo
2011-01-01
The spent drive beam must be cleanly extracted and bent away from the decelerator axis at the end of each CLIC decelerator in order to leave space for injecting a fresh beam train in the next sector. Then the spent beam must be safely absorbed. A compact extraction system made of a single dipole is proposed. The spent beam is driven to a water dump located at 20m downstream of the extraction point and transversely 6m away of the axis of the main linac. An adequate spread of the beam impact map on the dump offers small temperature excursions in both the dump and its entrance window, allowing for reliable operation and a long lifetime of the system.
Active Vibration damping of Smart composite beams based on system identification technique
Bendine, Kouider; Satla, Zouaoui; Boukhoulda, Farouk Benallel; Nouari, Mohammed
2018-03-01
In the present paper, the active vibration control of a composite beam using piezoelectric actuator is investigated. The space state equation is determined using system identification technique based on the structure input output response provided by ANSYS APDL finite element package. The Linear Quadratic (LQG) control law is designed and integrated into ANSYS APDL to perform closed loop simulations. Numerical examples for different types of excitation loads are presented to test the efficiency and the accuracy of the proposed model.
Labonnote, Nathalie
2012-01-01
Key point to development of environmentally friendly timber structures, appropriate to urban ways of living, is the development of high-rise timber buildings. Comfort properties are nowadays one of the main limitations to tall timber buildings, and an enhanced knowledge on damping phenomena is therefore required, as well as improved prediction models for damping. The aim of this work has consequently been to estimate various damping quantities in timber structures. In particular, models h...
Reshaping-induced spatiotemporal chaos in driven, damped sine-Gordon systems
International Nuclear Information System (INIS)
Chacon, R.
2007-01-01
Spatiotemporal chaos arising from the competition between sine-Gordon-breather and kink-antikink-pair solitons by reshaping an ac force is demonstrated. After introducing soliton collective coordinates, Melnikov's method is applied to the resulting effective equation of motion to estimate the parameter-space regions of the ac force where homoclinic bifurcations are induced. The analysis reveals that the chaos-order threshold exhibits sensitivity to small changes in the force shape. Computer simulations of the sine-Gordon system show good agreement with these theoretical predictions
Reshaping-induced spatiotemporal chaos in driven, damped sine-Gordon systems
Energy Technology Data Exchange (ETDEWEB)
Chacon, R. [Departamento de Electronica e Ingenieria Electromecanica, Escuela de Ingenierias Industriales, Universidad de Extremadura, E-06071 Badajoz (Spain)]. E-mail: rchacon@unex.es
2007-03-15
Spatiotemporal chaos arising from the competition between sine-Gordon-breather and kink-antikink-pair solitons by reshaping an ac force is demonstrated. After introducing soliton collective coordinates, Melnikov's method is applied to the resulting effective equation of motion to estimate the parameter-space regions of the ac force where homoclinic bifurcations are induced. The analysis reveals that the chaos-order threshold exhibits sensitivity to small changes in the force shape. Computer simulations of the sine-Gordon system show good agreement with these theoretical predictions.
Directory of Open Access Journals (Sweden)
Dang Xuan Truong
2014-12-01
Full Text Available The report presents a methodology to determine the directions of the stiffness principal axis (in this case subject to the linear displacement and forced rotation angle of a solid object interact with the surrounding environment by resilient bearing supports. The results also show that determining the coordinates of the stiffness center in the vibrating system with damping factors is necessary in our research.
The damped wave equation with unbounded damping
Freitas, Pedro; Siegl, Petr; Tretter, Christiane
2018-06-01
We analyze new phenomena arising in linear damped wave equations on unbounded domains when the damping is allowed to become unbounded at infinity. We prove the generation of a contraction semigroup, study the relation between the spectra of the semigroup generator and the associated quadratic operator function, the convergence of non-real eigenvalues in the asymptotic regime of diverging damping on a subdomain, and we investigate the appearance of essential spectrum on the negative real axis. We further show that the presence of the latter prevents exponential estimates for the semigroup and turns out to be a robust effect that cannot be easily canceled by adding a positive potential. These analytic results are illustrated by examples.
Decoherence and Landau-Damping
Energy Technology Data Exchange (ETDEWEB)
Ng, K.Y.; /Fermilab
2005-12-01
The terminologies, decoherence and Landau damping, are often used concerning the damping of a collective instability. This article revisits the difference and relation between decoherence and Landau damping. A model is given to demonstrate how Landau damping affects the rate of damping coming from decoherence.
THE MOST METAL-POOR DAMPED Lyα SYSTEMS: AN INSIGHT INTO DWARF GALAXIES AT HIGH-REDSHIFT
International Nuclear Information System (INIS)
Cooke, Ryan J.; Pettini, Max; Jorgenson, Regina A.
2015-01-01
In this paper we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped Lyα systems (DLAs), to uncover their links to modern-day galaxies. We present evidence that the DLA population as a whole exhibits a ''knee'' in the relative abundances of the α-capture and Fe-peak elements when the metallicity is [Fe/H] ≅ –2.0, assuming that Zn traces the buildup of Fe-peak elements. In this respect, the chemical evolution of DLAs is clearly different from that experienced by Milky Way halo stars, but resembles that of dwarf spheroidal galaxies in the Local Group. We also find a close correspondence between the kinematics of Local Group dwarf galaxies and of high-redshift metal-poor DLAs, which further strengthens this connection. On the basis of such similarities, we propose that the most metal-poor DLAs provide us with a unique opportunity to directly study the dwarf galaxy population more than ten billion years in the past, at a time when many dwarf galaxies were forming the bulk of their stars. To this end, we have measured some of the key physical properties of the DLA gas, including their neutral gas mass, size, kinetic temperature, density, and turbulence. We find that metal-poor DLAs contain a warm neutral medium with T gas ≅ 9600 K predominantly held up by thermal pressure. Furthermore, all of the DLAs in our sample exhibit a subsonic turbulent Mach number, implying that the gas distribution is largely smooth. These results are among the first empirical descriptions of the environments where the first few generations of stars may have formed in the universe
Swing damped movement of suspended objects
International Nuclear Information System (INIS)
Jones, J.F.; Petterson, B.J.; Werner, J.C.
1990-01-01
Transportation of large objects such as nuclear waste shipping casks using overhead cranes can induce pendular motion of the object. Residual oscillation from transportation typically must be damped or allowed to decay before the next process can take place. By properly programming the acceleration of the transporting device (e.g., crane) an oscillation damped transport and swing free stop are obtainable. This report reviews the theory associated with formulating such oscillation damped trajectories for a simply suspended object (e.g., simple pendulum). In addition, the use of force servo damping to eliminate initial oscillation of simply suspended objects is discussed. This is often needed to provide a well defined initial state for the system prior to executing an oscillation damped move. Also included are descriptions of experiments using a CIMCORP XR6100 gantry robot and results from these experiments. Finally, sources of error resulting in small residual oscillations are identified and possible solutions presented
THE NATURE OF DAMPED Lyα SYSTEMS AND THEIR HOSTS IN THE STANDARD COLD DARK MATTER UNIVERSE
International Nuclear Information System (INIS)
Cen Renyue
2012-01-01
Using adaptive mesh refinement cosmological hydrodynamic simulations with a physically motivated supernova feedback prescription, we show that the standard cold dark matter model can account for extant observed properties of damped Lyα systems (DLAs). With detailed examination of DLAs identified for each redshift snapshot through ray tracing through the simulation volumes containing thousands of galaxies, we find the following: (1) While DLA hosts roughly trace the overall population of galaxies at all redshifts, they are always gas-rich and have tendencies of being slightly smaller and bluer. (2) The history of DLA evolution is cosmological in nature and reflects primarily the evolution of the underlying cosmic density, galaxy size, and galaxy interactions. With higher density and more interactions at high redshift the size of DLAs is a larger fraction of their virial radius. (3) The variety of DLAs at high redshift is richer with a large contribution coming from galactic aqueducts, created through close galaxy interactions. The portion of gaseous disks of galaxies where most stars reside makes a relatively small contribution to DLA incidence at z = 3-4. (4) The majority of DLAs arise in halos of mass M h = 10 10 -10 12 M ☉ at z = 1.6-4, as these galaxies dominate the overall population of galaxies then. At z = 3-4, 20%-30% of DLA hosts are Lyman break galaxies (LBGs), 10%-20% are due to galaxies more massive than LBGs, and 50%-70% are from smaller galaxies. (5) Galactic winds play an indispensable role in shaping the kinematic properties of DLAs. Specifically, the high velocity width DLAs are a mixture of those arising in high-mass, high velocity dispersion halos and those arising in smaller mass systems where cold gas clouds are entrained to high velocities by galactic winds. (6) In agreement with observations, we see a weak but noticeable evolution in DLA metallicity. The metallicity distribution centers at [Z/H] = –1.5 to –1 and spans more than three
Directory of Open Access Journals (Sweden)
A. Khoshsaadat
2014-09-01
Full Text Available Static Synchronous Series Compensator (SSSC is a series compensating Flexible AC Transmission System (FACTS controller for maintaining to the power flow control on a transmission line by injecting a voltage in quadrature with the line current and in series mode with the line. In this work, an Adaptive Network-based Fuzzy Inference System controller (ANFISC has been proposed for controlling of the SSSC-based damping system and applied to a Single Machine Infinite Bus (SMIB power system. For implementation of the learning process in this controller, we use of the one approach of the learning ability that named as Forward Signal and Backward Error Back-Propagation (FSBEBP method for improving of the system efficiency. This artificial intelligence-based control model leads to a controller with adaptive structure, improved correctness, high damping ability and dynamic performance. System implementation is easy and it requires 49 fuzzy rules for inference engine of the system. As compared with the other complex neuro-fuzzy systems, this controller has medium number of the fuzzy rules and low number of layers, but it has high accuracy. In order to demonstrate of the proposed controller ability, it is simulated and its output compared with that of classic Lead-Lag-based Controller (LLC and PI controller.
Bach, D; Schmich, F; Masselter, T; Speck, T
2015-09-03
The active transport of fluids by pumps plays an essential role in engineering and biology. Due to increasing energy costs and environmental issues, topics like noise reduction, increase of efficiency and enhanced robustness are of high importance in the development of pumps in engineering. The study compares pumps in biology and engineering and assesses biomimetic potentials for improving man-made pumping systems. To this aim, examples of common challenges, applications and current biomimetic research for state-of-the art pumps are presented. The biomimetic research is helped by the similar configuration of many positive displacement pumping systems in biology and engineering. In contrast, the configuration and underlying pumping principles for fluid dynamic pumps (FDPs) differ to a greater extent in biology and engineering. However, progress has been made for positive displacement as well as for FDPs by developing biomimetic devices with artificial muscles and cilia that improve energetic efficiency and fail-safe operation or reduce noise. The circulatory system of vertebrates holds a high biomimetic potential for the damping of pressure pulsations, a common challenge in engineering. Damping of blood pressure pulsation results from a nonlinear viscoelastic behavior of the artery walls which represent a complex composite material. The transfer of the underlying functional principle could lead to an improvement of existing technical solutions and be used to develop novel biomimetic damping solutions. To enhance efficiency or thrust of man-made fluid transportation systems, research on jet propulsion in biology has shown that a pulsed jet can be tuned to either maximize thrust or efficiency. The underlying principle has already been transferred into biomimetic applications in open channel water systems. Overall there is a high potential to learn from nature in order to improve pumping systems for challenges like the reduction of pressure pulsations, increase of jet
Directory of Open Access Journals (Sweden)
M. Mallika Arjunan
2014-01-01
Full Text Available In this paper, we investigate the existence and controllability of mild solutions for a damped second order impulsive functional differential equation with state-dependent delay in Banach spaces. The results are obtained by using Sadovskii's fixed point theorem combined with the theories of a strongly continuous cosine family of bounded linear operators. Finally, an example is provided to illustrate the main results.
International Nuclear Information System (INIS)
Rees, John; Chao, Alexander
2008-01-01
Landau damping, as the term is used in accelerator science, is a physical process in which an ensemble of harmonic oscillators--an accelerator beam, for example--that would otherwise be unstable is stabilized by a spread in the natural frequencies of the oscillators. This is a study of the most basic aspects of that process. It has two main goals: to gain a deeper insight into the mechanism of Landau damping and to find the coherent motion of the ensemble and thus the dependence of the total damping rate on the frequency spread
Numerical studies of shear damped composite beams using a constrained damping layer
DEFF Research Database (Denmark)
Kristensen, R.F.; Nielsen, Kim Lau; Mikkelsen, Lars Pilgaard
2008-01-01
Composite beams containing one or more damping layers are studied numerically. The work is based on a semi-analytical model using a Timoshenko beam theory and a full 2D finite element model. The material system analysed, is inspired by a train wagon suspension system used in a EUREKA project Sigma......!1841. For the material system, the study shows that the effect of the damping layer is strongly influenced by the presence of a stiff constraining layer, that enforces large shear strain amplitudes. The thickness of the damping rubber layer itself has only a minor influence on the overall damping....... In addition, a large influence of ill positioned cuts in the damping layer is observed....
Significance of non-classical damping in seismic qualification of equipment and piping
Energy Technology Data Exchange (ETDEWEB)
Gupta, Abhinav, E-mail: agupta1@ncsu.edu; Bose, Mrinal K.
2017-06-15
Highlights: • Damping in coupled building-piping or building-equipment systems is nonlclassical. • Significance of nonclassical damping is illustrated. • Classical damping assumption can over predict or under predict response. • Significance of nonclassical damping increases for very light secondary systems. • Composite modal damping is another form of classical damping. - Abstract: This paper presents a discussion on the significance of non-classical damping in coupled primary-secondary systems such as building-equipment or building-piping. Closed-form expressions are used to illustrate that the effect of non-classical damping is significant in systems with tuned or nearly tuned uncoupled modes when the mass-interaction is sufficiently small. Further, simple primary-secondary systems are used to illustrate that composite modal damping is another form of classical damping for which the transformed damping matrix, obtained after pre- and post-multiplication of the damping matrix with the modal matrix, contains only diagonal terms. Both the composite and the classical damping give almost identical results that can be much different from the corresponding results for non-classical damping. Finally, it is shown that consideration of classical damping (ignoring the off-diagonal terms) can give excessively conservative results in nearly tuned primary-secondary systems. For perfectly tuned primary-secondary systems, however, classical damping can give responses that are much lower than what they should be.
Offline software for the DAMPE experiment
Wang, Chi; Liu, Dong; Wei, Yifeng; Zhang, Zhiyong; Zhang, Yunlong; Wang, Xiaolian; Xu, Zizong; Huang, Guangshun; Tykhonov, Andrii; Wu, Xin; Zang, Jingjing; Liu, Yang; Jiang, Wei; Wen, Sicheng; Wu, Jian; Chang, Jin
2017-10-01
A software system has been developed for the DArk Matter Particle Explorer (DAMPE) mission, a satellite-based experiment. The DAMPE software is mainly written in C++ and steered using a Python script. This article presents an overview of the DAMPE offline software, including the major architecture design and specific implementation for simulation, calibration and reconstruction. The whole system has been successfully applied to DAMPE data analysis. Some results obtained using the system, from simulation and beam test experiments, are presented. Supported by Chinese 973 Program (2010CB833002), the Strategic Priority Research Program on Space Science of the Chinese Academy of Science (CAS) (XDA04040202-4), the Joint Research Fund in Astronomy under cooperative agreement between the National Natural Science Foundation of China (NSFC) and CAS (U1531126) and 100 Talents Program of the Chinese Academy of Science
Extended Rayleigh Damping Model
Directory of Open Access Journals (Sweden)
Naohiro Nakamura
2016-07-01
Full Text Available In dynamic analysis, frequency domain analysis can be used if the entire structure is linear. However, time history analysis is generally used if nonlinear elements are present. Rayleigh damping has been widely used in time history response analysis. Many articles have reported the problems associated with this damping and suggested remedies. A basic problem is that the frequency area across which the damping ratio is almost constant is too narrow. If the area could be expanded while incurring only a small increase in computational cost, this would provide an appropriate remedy for this problem. In this study, a novel damping model capable of expanding the constant frequency area by more than five times was proposed based on the study of a causal damping model. This model was constructed by adding two terms to the Rayleigh damping model and can be applied to the linear elements in the time history analysis of a nonlinear structure. The accuracy and efficiency of the model were confirmed using example analyses.
Energy Technology Data Exchange (ETDEWEB)
Roth, Andre
2012-12-15
At the Electron Stretcher Facility ELSA an upgrade of the internal beam current up to 200 mA would be desirable in order to increase the intensity of the extracted electron beam for the future experimental hadron physics program. However, such an upgrade is mainly limited by the excitation of coherent beam instabilities in the stretcher ring. As active counteraction, broadband bunch-by-bunch feedback-systems for the longitudinal, as well as for both transverse planes were installed. After detection of the motion of each of the 27 4 stored bunches via beam position monitors, the systems determine independent correction signals for each bunch using digital signal processors. The amplified correction signals are applied to the beam by means of broadband longitudinal and transverse kicker structures. The detailed setup, the commissioning procedure and measurement results of the damping performance of the systems are presented. In addition, the operation of the longitudinal system during the fast energy ramp of 4 GeV/s from 1.2 GeV to 3.2 GeV is investigated.
Special class of nonlinear damping models in flexible space structures
Hu, Anren; Singh, Ramendra P.; Taylor, Lawrence W.
1991-01-01
A special class of nonlinear damping models is investigated in which the damping force is proportional to the product of positive integer or the fractional power of the absolute values of displacement and velocity. For a one-degree-of-freedom system, the classical Krylov-Bogoliubov 'averaging' method is used, whereas for a distributed system, both an ad hoc perturbation technique and the finite difference method are employed to study the effects of nonlinear damping. The results are compared with linear viscous damping models. The amplitude decrement of free vibration for a single mode system with nonlinear models depends not only on the damping ratio but also on the initial amplitude, the time to measure the response, the frequency of the system, and the powers of displacement and velocity. For the distributed system, the action of nonlinear damping is found to reduce the energy of the system and to pass energy to lower modes.
Quantum damped oscillator I: Dissipation and resonances
International Nuclear Information System (INIS)
Chruscinski, Dariusz; Jurkowski, Jacek
2006-01-01
Quantization of a damped harmonic oscillator leads to so called Bateman's dual system. The corresponding Bateman's Hamiltonian, being a self-adjoint operator, displays the discrete family of complex eigenvalues. We show that they correspond to the poles of energy eigenvectors and the corresponding resolvent operator when continued to the complex energy plane. Therefore, the corresponding generalized eigenvectors may be interpreted as resonant states which are responsible for the irreversible quantum dynamics of a damped harmonic oscillator
Digital notch filter based active damping for LCL filters
DEFF Research Database (Denmark)
Yao, Wenli; Yang, Yongheng; Zhang, Xiaobin
2015-01-01
. In contrast, the active damping does not require any dissipation elements, and thus has become of increasing interest. As a result, a vast of active damping solutions have been reported, among which multi-loop control systems and additional sensors are necessary, leading to increased cost and complexity....... In this paper, a notch filter based active damping without the requirement of additional sensors is proposed, where the inverter current is employed as the feedback variable. Firstly, a design method of the notch filter for active damping is presented. The entire system stability has then been investigated...... in the z-domain. Simulations and experiments are carried out to verify the proposed active damping method. Both results have confirmed that the notch filter based active damping can ensure the entire system stability in the case of resonances with a good system performance....
An experimental study on damping characteristics of thermal insulation
International Nuclear Information System (INIS)
Chiba, Toshio; Kobayashi, Hiroe; Aida, Shigekazu; Wada, Hidetoshi
1984-01-01
The damping ratio is one of the most important parameters in seismic analysis of piping systems in a nuclear power plant. Thermal insulation is considered contributing to the damping characteristics of piping systems. At the 6th SMiRT and 1983 ASME PVP conferences, the damping effect and damping estimating formula were presented as a result of regression analysis using the component test data for 2,4 and 8B diameter piping and the proof model test for 1,2 and 4B piping system. In this study, in order to clarify the damping characteristics of a larger diameter piping than 8B,the component test of 12 and 20B diameter piping with insulation was performed. From the results of these tests and the data survey of the previous papers, it was found that the damping ratio of anactual piping system with thermal insulation is at minimum 1% for all size diameter piping. (author)
An experimental study on damping characteristics of thermal insulation
International Nuclear Information System (INIS)
Chiba, T.; Kobayashi, H.
1985-01-01
The damping ratio is one of the most important parameters in seismic analysis of nuclear power plant piping systems. Thermal Insulation is considered to contribute to the damping characteristics of piping systems. In the 6th SMiRT conference and 1983 ASME PVP, the damping effect and damping estimating formula was presented as a result of regression analysis from the component tests of 2'' , 4'', and 8'' diameter piping and the proof model test of 1'', 2'' and 4'' piping. In this study, in order to clarify the damping characteristics of larger diameter piping than 8'', the component test of 12'' and 20'' diameter piping with insulation was performed. From the results of these tests and the data survey of the previous papers it was found that the damping ratio of actual piping system with thermal insulation is at least 1% for all size diameter piping
Damping in building structures during earthquakes: test data and modeling
International Nuclear Information System (INIS)
Coats, D.W. Jr.
1982-01-01
A review and evaluation of the state-of-the-art of damping in building structures during earthquakes is presented. The primary emphasis is in the following areas: 1) the evaluation of commonly used mathematical techniques for incorporating damping effects in both simple and complex systems; 2) a compilation and interpretation of damping test data; and 3) an evaluation of structure testing methods, building instrumentation practices, and an investigation of rigid-body rotation effects on damping values from test data. A literature review provided the basis for evaluating mathematical techiques used to incorporate earthquake induced damping effects in simple and complex systems. A discussion on the effectiveness of damping, as a function of excitation type, is also included. Test data, from a wide range of sources, has been compiled and interpreted for buidings, nuclear power plant structures, piping, equipment, and isolated structural elements. Test methods used to determine damping and frequency parameters are discussed. In particular, the advantages and disadvantages associated with the normal mode and transfer function approaches are evaluated. Additionally, the effect of rigid-body rotations on damping values deduced from strong-motion building response records is investigated. A discussion of identification techniques typically used to determine building parameters (frequency and damping) from strong motion records is included. Finally, an analytical demonstration problem is presented to quantify the potential error in predicting fixed-base structural frequency and damping values from strong motion records, when rigid-body rotations are not properly accounted for
Structural Damping with Friction Beams
Directory of Open Access Journals (Sweden)
L. Gaul
2008-01-01
Full Text Available In the last several years, there has been increasing interest in the use of friction joints for enhancing damping in structures. The joints themselves are responsible for the major part of the energy dissipation in assembled structures. The dissipated work in a joint depends on both the applied normal force and the excitation force. For the case of a constant amplitude excitation force, there is an optimal normal force which maximizes the damping. A ‘passive’ approach would be employed in this instance. In most cases however, the excitation force, as well as the interface parameters such as the friction coefficient, normal pressure distribution, etc., are not constant. In these cases, a ‘semi-active’ approach, which implements an active varying normal force, is necessary. For the ‘passive’ and ‘semi-active’ approaches, the normal force has to be measured. Interestingly, since the normal force in a friction joint influences the local stiffness, the natural frequencies of the assembled structure can be tuned by adjusting the normal force. Experiments and simulations are performed for a simple laboratory structure consisting of two superposed beams with friction in the interface. Numerical simulation of the friction interface requires non-linear models. The response of the double beam system is simulated using a numerical algorithm programmed in MATLAB which models point-to-point friction with the Masing friction model. Numerical predictions and measurements of the double beam free vibration response are compared. A practical application is then described, in which a friction beam is used to damp the vibrations of the work piece table on a milling machine. The increased damping of the table reduces vibration amplitudes, which in turn results in enhanced surface quality of the machined parts, reduction in machine tool wear, and potentially higher feed rates. Optimal positioning of the friction beams is based on knowledge of the mode
Complex modes and frequencies in damped structural vibrations
DEFF Research Database (Denmark)
Krenk, Steen
2004-01-01
It is demonstrated that the state space formulation of the equation of motion of damped structural elements like cables and beams leads to a symmetric eigenvalue problem if the stiffness and damping operators are self-adjoint, and that this is typically the case in the absence of gyroscopic forces....... The corresponding theory of complex modal analysis of continuous systems is developed and illustrated in relation to optimal damping and impulse response of cables and beams with discrete dampers....
Nuclear power plant piping damping parametric effects
International Nuclear Information System (INIS)
Ware, A.G.
1983-01-01
The NRC and EG and G Idaho are engaged in programs to evaluate piping-system damping, in order to provide realistic and less conservative values to be used in seismic analyses. To generate revised guidelines, solidly based on technical data, new experimental data need to be generated and assessed, and the parameters which influence piping-system damping need to be quantitatively identified. This paper presents the current state-of-the-art knowledge in the United States on parameters which influence piping-system damping. Examples of inconsistencies in the data and areas of uncertainty are explained. A discussion of programs by EG and G Idaho and other organizations to evaluate various effects are included, and both short-and long-range goals of the program are outlined
Controlled damping of a physical pendulum: experiments near critical conditions
International Nuclear Information System (INIS)
Gonzalez, Manuel I; Bol, Alfredo
2006-01-01
This paper presents an experimental device for the study of damped oscillatory motion along with three associated experiments. Special emphasis is given on both didactic aspects and the interactivity of the experimental set-up, in order to assist students in understanding fundamental aspects of damped oscillatory motion and allow them to directly compare their experimental results with the well-known theory they can find in textbooks. With this in mind, a physical pendulum was selected with an eddy-current damping system that allows the damping conditions to be controlled with great precision. The three experiments examine accurate control of damping, frequency shift near critical damping and the transition from underdamped to overdamped conditions
Unified Power Flow Controller Placement to Improve Damping of Power Oscillations
M. Salehi; A. A. Motie Birjandi; F. Namdari
2015-01-01
Weak damping of low frequency oscillations is a frequent phenomenon in electrical power systems. These frequencies can be damped by power system stabilizers. Unified power flow controller (UPFC), as one of the most important FACTS devices, can be applied to increase the damping of power system oscillations and the more effect of this controller on increasing the damping of oscillations depends on its proper placement in power systems. In this paper, a technique based on controllability is pro...
Structural dynamic analysis with generalized damping models analysis
Adhikari , Sondipon
2013-01-01
Since Lord Rayleigh introduced the idea of viscous damping in his classic work ""The Theory of Sound"" in 1877, it has become standard practice to use this approach in dynamics, covering a wide range of applications from aerospace to civil engineering. However, in the majority of practical cases this approach is adopted more for mathematical convenience than for modeling the physics of vibration damping. Over the past decade, extensive research has been undertaken on more general ""non-viscous"" damping models and vibration of non-viscously damped systems. This book, along with a related book
Dislocation damping during irradiation
International Nuclear Information System (INIS)
Burdett, C.F.; Rahmatalla, H.
1977-01-01
The results of Simpson et al (Simpson, H.M., Sosin, A., Johnston, D.F., Phys.Rev. B, 5:1393 (1972)) on the damping produced during electron irradiation of copper are re-examined and it is shown that they can be explained in terms of the model of Granato and Lucke (Granato, A., Lucke, K., J.Appl.Phys., 27:583,789 (1958)). (author)
Mouhot, Clément
2011-09-01
Going beyond the linearized study has been a longstanding problem in the theory of Landau damping. In this paper we establish exponential Landau damping in analytic regularity. The damping phenomenon is reinterpreted in terms of transfer of regularity between kinetic and spatial variables, rather than exchanges of energy; phase mixing is the driving mechanism. The analysis involves new families of analytic norms, measuring regularity by comparison with solutions of the free transport equation; new functional inequalities; a control of non-linear echoes; sharp "deflection" estimates; and a Newton approximation scheme. Our results hold for any potential no more singular than Coulomb or Newton interaction; the limit cases are included with specific technical effort. As a side result, the stability of homogeneous equilibria of the non-linear Vlasov equation is established under sharp assumptions. We point out the strong analogy with the KAM theory, and discuss physical implications. Finally, we extend these results to some Gevrey (non-analytic) distribution functions. © 2011 Institut Mittag-Leffler.
Sun, Miaoping; Nian, Xiaohong; Dai, Liqiong; Guo, Hua
2017-05-01
In this paper, the delay-dependent wide-area dynamic output feedback controller (DOFC) with prescribed degree of stability is proposed for interconnected power system to damp inter-area low-frequency oscillations. Here, the prescribed degree of stability α is used to maintain all the poles on the left of s=-α in the s-plane. Firstly, residue approach is adopted to select input-output control signals and the schur balanced truncation model reduction method is utilized to obtain the reduced power system model. Secondly, based on Lyapunov stability theory and transformation operation in complex plane, the sufficient condition of asymptotic stability for closed-loop power system with prescribed degree of stability α is derived. Then, a novel method based on linear matrix inequalities (LMIs) is presented to obtain the parameters of DOFC and calculate delay margin of the closed-loop system considering the prescribed degree of stability α. Finally, case studies are carried out on the two-area four-machine system, which is controlled by classical wide-area power system stabilizer (WAPSS) in reported reference and our proposed DOFC respectively. The effectiveness and advantages of the proposed method are verified by the simulation results under different operating conditions. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Minimum wakefield achievable by waveguide damped cavity
International Nuclear Information System (INIS)
Lin, X.E.; Kroll, N.M.
1995-01-01
The authors use an equivalent circuit to model a waveguide damped cavity. Both exponentially damped and persistent (decay t -3/2 ) components of the wakefield are derived from this model. The result shows that for a cavity with resonant frequency a fixed interval above waveguide cutoff, the persistent wakefield amplitude is inversely proportional to the external Q value of the damped mode. The competition of the two terms results in an optimal Q value, which gives a minimum wakefield as a function of the distance behind the source particle. The minimum wakefield increases when the resonant frequency approaches the waveguide cutoff. The results agree very well with computer simulation on a real cavity-waveguide system
Dynamic response analysis of a 24-story damped steel structure
Feng, Demin; Miyama, Takafumi
2017-10-01
In Japanese and Chinese building codes, a two-stage design philosophy, damage limitation (small earthquake, Level 1) and life safety (extreme large earthquake, Level 2), is adopted. It is very interesting to compare the design method of a damped structure based on the two building codes. In the Chinese code, in order to be consistent with the conventional seismic design method, the damped structure is also designed at the small earthquake level. The effect of damper systems is considered by the additional damping ratio concept. The design force will be obtained from the damped design spectrum considering the reduction due to the additional damping ratio. The additional damping ratio by the damper system is usually calculated by a time history analysis method at the small earthquake level. The velocity dependent type dampers such as viscous dampers can function well even in the small earthquake level. But, if steel damper is used, which usually remains elastic in the small earthquake, there will be no additional damping ratio achieved. On the other hand, a time history analysis is used in Japan both for small earthquake and extreme large earthquake level. The characteristics of damper system and ductility of the structure can be modelled well. An existing 24-story steel frame is modified to demonstrate the design process of the damped structure based on the two building codes. Viscous wall type damper and low yield steel panel dampers are studied as the damper system.
Quantization of the damped harmonic oscillator revisited
Energy Technology Data Exchange (ETDEWEB)
Baldiotti, M.C., E-mail: baldiott@fma.if.usp.b [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318-CEP, 05315-970 Sao Paulo, S.P. (Brazil); Fresneda, R., E-mail: fresneda@gmail.co [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318-CEP, 05315-970 Sao Paulo, S.P. (Brazil); Gitman, D.M., E-mail: gitman@dfn.if.usp.b [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318-CEP, 05315-970 Sao Paulo, S.P. (Brazil)
2011-04-11
We return to the description of the damped harmonic oscillator with an assessment of previous works, in particular the Bateman-Caldirola-Kanai model and a new model proposed by one of the authors. We argue the latter has better high energy behavior and is connected to existing open-systems approaches. - Highlights: We prove the local equivalence of two damped harmonic oscillator models. We find different high energy behaviors between the two models. Based on the local equivalence, we make a simple construction of the coherent states.
Quantization of the damped harmonic oscillator revisited
International Nuclear Information System (INIS)
Baldiotti, M.C.; Fresneda, R.; Gitman, D.M.
2011-01-01
We return to the description of the damped harmonic oscillator with an assessment of previous works, in particular the Bateman-Caldirola-Kanai model and a new model proposed by one of the authors. We argue the latter has better high energy behavior and is connected to existing open-systems approaches. - Highlights: → We prove the local equivalence of two damped harmonic oscillator models. → We find different high energy behaviors between the two models. → Based on the local equivalence, we make a simple construction of the coherent states.
Damping in accelerators due to classical radiation
International Nuclear Information System (INIS)
Mills, F.E.
1962-01-01
The rates of change of the magnitudes of the adiabatic invariants is calculated in the case of a Hamiltonian system subjected to generalized non conservative forces. These results are applied to the case of the classical radiation of electrons in an accelerator or storage ring. The resulting expressions for the damping rates of three independent oscillation modes suggest structures which are damping in all three modes, while at the same time allowing 'strong focussing' and the attendant strong momentum compaction. (author)
Damping measurements in flowing water
Coutu, A.; Seeley, C.; Monette, C.; Nennemann, B.; Marmont, H.
2012-11-01
Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Water added mass and damping are both critical quantities in evaluating the dynamic response of the turbine component. Although the effect of fluid added mass is well documented, fluid damping, a critical quantity to limit vibration amplitudes during service, and therefore to help avoiding possible failure of the turbines, has received much less attention in the literature. This paper presents an experimental investigation of damping due to FSI. The experimental setup, designed to create dynamic characteristics similar to the ones of Francis turbine blades is discussed, together with the experimental protocol and examples of measurements obtained. The paper concludes with the calculated damping values and a discussion on the impact of the observed damping behaviour on the response of hydraulic turbine blades to FSI.
Damping measurements in flowing water
International Nuclear Information System (INIS)
Coutu, A; Monette, C; Nennemann, B; Marmont, H; Seeley, C
2012-01-01
Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Water added mass and damping are both critical quantities in evaluating the dynamic response of the turbine component. Although the effect of fluid added mass is well documented, fluid damping, a critical quantity to limit vibration amplitudes during service, and therefore to help avoiding possible failure of the turbines, has received much less attention in the literature. This paper presents an experimental investigation of damping due to FSI. The experimental setup, designed to create dynamic characteristics similar to the ones of Francis turbine blades is discussed, together with the experimental protocol and examples of measurements obtained. The paper concludes with the calculated damping values and a discussion on the impact of the observed damping behaviour on the response of hydraulic turbine blades to FSI.
International Nuclear Information System (INIS)
Neumann, U.; Puzalowski, R.; Grimm, I.
1985-01-01
Numerical valve models for simulation of selfactuating safety valves and damped check valves are introduced for the computer programs TRAC-PF1 and ROLAST. As examples of application post-test calculations and stability analysis are given. (orig.)
Stiffness and damping in mechanical design
National Research Council Canada - National Science Library
Rivin, Eugene I
1999-01-01
... important conceptual issues are stiffness of mechanical structures and their components and damping in mechanical systems sensitive to and/or generating vibrations. Stiffness and strength are the most important criteria for many mechanical designs. However, although there are hundreds of books on various aspects of strength, and strength issues ar...
Nuclear power plant piping damping parametric effects
International Nuclear Information System (INIS)
Ware, A.G.
1983-01-01
The present NRC guidelines for structural damping to be used in the dynamic stress analyses of nuclear power plant piping systems are generally considered to be overly conservative. As a result, plant designers have in many instances used a considerable number of seismic supports to keep stresses calculated by large scale piping computer codes below the allowable limits. In response to this problem, the NRC and EG and G Idaho are engaged in programs to evaluate piping system damping, in order to provide more realistic and less conservative values to be used in seismic analyses. To generate revised guidelines, solidly based on technical data, new experimental data need to be generated and assessed, and the parameters which influence piping system damping need to be quantitatively identified. This paper presents the current state-of-the-art knowledge in the United States on parameters which influence piping system damping. Examples of inconsistencies in the data and areas of uncertainty are explained. A discussion of programs by EG and G Idaho and other organizations to evaluate various effects is included, and both short and long range goals of the program are outlined
Structural dynamic modification using additive damping
Indian Academy of Sciences (India)
elements, FEM and perturbation methods for reanalysis or structural dynamic modification ... to a system changes its mass, stiffness and damping. Thus ... due to the phase difference between stress ' and strain or 'a И E1 З iE2 for direct strain.
Impact of Damping Uncertainty on SEA Model Response Variance
Schiller, Noah; Cabell, Randolph; Grosveld, Ferdinand
2010-01-01
Statistical Energy Analysis (SEA) is commonly used to predict high-frequency vibroacoustic levels. This statistical approach provides the mean response over an ensemble of random subsystems that share the same gross system properties such as density, size, and damping. Recently, techniques have been developed to predict the ensemble variance as well as the mean response. However these techniques do not account for uncertainties in the system properties. In the present paper uncertainty in the damping loss factor is propagated through SEA to obtain more realistic prediction bounds that account for both ensemble and damping variance. The analysis is performed on a floor-equipped cylindrical test article that resembles an aircraft fuselage. Realistic bounds on the damping loss factor are determined from measurements acquired on the sidewall of the test article. The analysis demonstrates that uncertainties in damping have the potential to significantly impact the mean and variance of the predicted response.
DEFF Research Database (Denmark)
Cooke, Ryan; Pettini, Max; Steidel, Charles C.
2011-01-01
We present a high spectral resolution survey of the most metal-poor damped Lyα absorption systems (DLAs) aimed at probing the nature and nucleosynthesis of the earliest generations of stars. Our survey comprises 22 systems with iron abundance less than 1/100 solar; observations of seven...... agreement with the values measured in Galactic halo stars when the oxygen abundance is measured from the [O i] λ6300 line. We speculate that such good agreement in the observed abundance trends points to a universal origin for these metals. In view of this agreement, we construct the abundance pattern...... the near-solar values of C/O in DLAs at the lowest metallicities probed, and find that their distribution is in agreement with that seen in Galactic halo stars. We find that the O/Fe ratio in VMP DLAs is essentially constant, and shows very little dispersion, with a mean [〈O/Fe〉]=+0.39 ± 0.12, in good...
Bounce-harmonic Landau Damping of Plasma Waves
Anderegg, Francois
2015-11-01
We present measurement of plasma wave damping, spanning the temperature regimes of direct Landau damping, bounce-harmonic Landau damping, inter-species drag damping, and viscous damping. Direct Landau damping is dominant at high temperatures, but becomes negligible as v vph / 5 . The measurements are conducted in trapped pure ion plasmas contained in Penning-Malmberg trap, with wave-coherent LIF diagnostics of particle velocities. Our focus is on bounce harmonics damping, controlled by an applied ``squeeze'' potential, which generates harmonics in the wave potential and in the particle dynamics. A particle moving in z experiences a non-sinusoidal mode potential caused by the squeeze, producing high spatial harmonics with lower phase velocity. These harmonics are Landau damped even when the mode phase velocity vph is large compared to the thermal velocity v , since the nth harmonic is resonant with a particle bouncing at velocity vb =vph / n . Here we increase the bounce harmonics through applied squeeze potential; but some harmonics are always present in finite length systems. For our centered squeeze geometry, theory shows that only odd harmonics are generated, and predicts the Landau damping rate from vph / n . Experimentally, the squeeze potential increases the wave damping and reduces its frequency. The frequency shift occurs because the squeeze potential reduces the number of particle where the mode velocity is the largest, therefore reducing the mode frequency. We observe an increase in the damping proportional to Vs2,and a frequency reduction proportional to Vs , in quantitative agreement with theory. Wave-coherent laser induced fluorescence allows direct observation of bounce resonances on the particle distribution, here predominantly at vph / 3 . A clear increase of the bounce harmonics is visible on the particle distribution when the squeeze potential is applied. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451 and DE-SC0008693.
Directory of Open Access Journals (Sweden)
Filip-Vacarescu Norin
2016-03-01
Full Text Available This paper discusses the concept of a hybrid damper made from a combination of two dissipative devices. A passive hysteretic device like steel Buckling Restrained Brace (BRB can be combined with a magneto-rheological (MR Fluid Damper in order to obtain a hybrid dissipative system. This system can work either as a semi-active system, if the control unit is available, or as a passive system, tuned for working according to performance based seismic engineering (PBSE scale of reference parameters (i.e. interstory drift.
Natural vibration frequency and damping of slender structures founded on monopiles
DEFF Research Database (Denmark)
Zania, Varvara
2014-01-01
of the modified SSI eigenfrequency and damping is presented, which accounts for the cross coupling stiffness and damping terms of the soil–pile system and is applicable but not restrictive to OWTs. A parametric study was performed to illustrate the sensitivity of the eigenfrequency and damping on the foundation...
DAMPING OF SUBSYNCHRONOUS MODES OF OSCILLATIONS
Directory of Open Access Journals (Sweden)
JAGADEESH PASUPULETI
2006-06-01
Full Text Available The IEEE bench mark model 2 series compensated system is considered for analysis. It consists of single machine supplying power to infinite bus through two parallel lines one of which is series compensated. The mechanical system considered consists of six mass, viz, high pressure turbine, intermediate pressure turbine, two low pressure turbines, generator and an exciter. The excitation system considered is IEEE type 1 with saturation. The auxiliary controls considered to damp the unstable subsynchronous modes of oscillations are Power System Stabilizer (PSS and Static var Compensator (SVC. The different cases of power system stabilizer and reactive power controls are adapted to study the effectiveness of damping these unstable subsynchronous modes of oscillations.
INEL/USNRC pipe damping experiments and studies
International Nuclear Information System (INIS)
Ware, A.G.
1987-08-01
Since the previous paper on this subject presented at the 8th SMiRT Conference, the Idaho National Engineering Laboratory (INEL) has conducted further research on piping system damping for the United States Nuclear Regulatory Commission (USNRC). These efforts have included vibration tests on two laboratory piping systems at response frequencies up to 100 Hz, and damping data calculations from both of these two systems and from a third laboratory piping system test series. In addition, a statistical analysis was performed on piping system damping data from tests representative of seismic and hydrodynamic events of greater than minimal excitation. The results of this program will be used to assist regulators in establishing suitable damping values for use in dynamic analyses of nuclear piping systems, and in revising USNRC Regulatory Guide (RG) 1.61
Isar, Aurelian
1995-01-01
The harmonic oscillator with dissipation is studied within the framework of the Lindblad theory for open quantum systems. By using the Wang-Uhlenbeck method, the Fokker-Planck equation, obtained from the master equation for the density operator, is solved for the Wigner distribution function, subject to either the Gaussian type or the delta-function type of initial conditions. The obtained Wigner functions are two-dimensional Gaussians with different widths. Then a closed expression for the density operator is extracted. The entropy of the system is subsequently calculated and its temporal behavior shows that this quantity relaxes to its equilibrium value.
Energy Technology Data Exchange (ETDEWEB)
Font-Ribera, Andreu [Institute of Theoretical Physics, University of Zurich, 8057 Zurich (Switzerland); Miralda-Escudé, Jordi [Institució Catalana de Recerca i Estudis Avançats, Barcelona, Catalonia (Spain); Arnau, Eduard [Institut de Ciències del Cosmos (IEEC/UB), Barcelona, Catalonia (Spain); Carithers, Bill; Ross, Nicholas P.; White, Martin [Lawrence Berkeley National Laboratory, University of California Berkeley, Berkeley, California 94720 (United States); Lee, Khee-Gan [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Noterdaeme, Pasquier; Pâris, Isabelle; Petitjean, Patrick; Rollinde, Emmanuel [Institut d' Astrophysique de Paris, Université Paris 6 et CNRS, 98bis blvd. Arago, 75014 Paris (France); Rich, James [CEA, Centre de Saclay, IRFU, 91191 Gif-sur-Yvette (France); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); York, Donald G., E-mail: font@physik.uzh.ch, E-mail: miralda@icc.ub.edu [Department of Astronomy and Astrophysics and The Fermi Institute, Chicago University, 5640 So. Ellis Ave., Chicago, IL 60637 (United States)
2012-11-01
We present the first measurement of the large-scale cross-correlation of Lyα forest absorption and Damped Lyman α systems (DLA), using the 9th Data Release of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is clearly detected on scales up to 40h{sup −1}Mpc and is well fitted by the linear theory prediction of the standard Cold Dark Matter model of structure formation with the expected redshift distortions, confirming its origin in the gravitational evolution of structure. The amplitude of the DLA-Lyα cross-correlation depends on only one free parameter, the bias factor of the DLA systems, once the Lyα forest bias factors are known from independent Lyα forest correlation measurements. We measure the DLA bias factor to be b{sub D} = (2.17±0.20)β{sub F}{sup 0.22}, where the Lyα forest redshift distortion parameter β{sub F} is expected to be above unity. This bias factor implies a typical host halo mass for DLAs that is much larger than expected in present DLA models, and is reproduced if the DLA cross section scales with halo mass as M{sub h}{sup α}, with α = 1.1±0.1 for β{sub F} = 1. Matching the observed DLA bias factor and rate of incidence requires that atomic gas remains extended in massive halos over larger areas than predicted in present simulations of galaxy formation, with typical DLA proper sizes larger than 20 kpc in host halos of masses ∼ 10{sup 12}M{sub ☉}. We infer that typical galaxies at z ≅ 2 to 3 are surrounded by systems of atomic clouds that are much more extended than the luminous parts of galaxies and contain ∼ 10% of the baryons in the host halo.
Damping of liquid sloshing by foams
Sauret, A.; Boulogne, F.; Cappello, J.; Dressaire, E.; Stone, H. A.
2015-02-01
When a container is set in motion, the free surface of the liquid starts to oscillate or slosh. Such effects can be observed when a glass of water is handled carelessly and the fluid sloshes or even spills over the rims of the container. However, beer does not slosh as readily as water, which suggests that foam could be used to damp sloshing. In this work, we study experimentally the effect on sloshing of a liquid foam placed on top of a liquid bath. We generate a monodisperse two-dimensional liquid foam in a rectangular container and track the motion of the foam. The influence of the foam on the sloshing dynamics is experimentally characterized: only a few layers of bubbles are sufficient to significantly damp the oscillations. We rationalize our experimental findings with a model that describes the foam contribution to the damping coefficient through viscous dissipation on the walls of the container. Then we extend our study to confined three-dimensional liquid foam and observe that the behavior of 2D and confined 3D systems are very similar. Thus, we conclude that only the bubbles close to the walls have a significant impact on the dissipation of energy. The possibility to damp liquid sloshing using foam is promising in numerous industrial applications such as the transport of liquefied gas in tankers or for propellants in rocket engines.
Power Oscillations Damping in DC Microgrids
DEFF Research Database (Denmark)
Hamzeh, Mohsen; Ghafouri, Mohsen; Karimi, Houshang
2016-01-01
This paper proposes a new control strategy for damping of power oscillations in a multi-source dc microgrid. A parallel combination of a fuel cell (FC), a photovoltaic (PV) system and a supercapacitor (SC) are used as a hybrid power conversion system (HPCS). The SC compensates for the slow transi...... of the proposed control scheme is verified using hardware-in-the-loop (HIL) simulations carried out in OPAL-RT technologies....
Multibunch resistive wall instability damping with feedback
International Nuclear Information System (INIS)
Zhabitskij, V.M.; Korenev, I.L.; Yudin, L.A.
1992-01-01
The theory of multibunch transverse resistive wall instability damping with feedback is development. The system of coupling equations is obtained for description of bunched beam motion. The general solution and eigen frequencies are found. But for two bunches or multi bunches the tune splitting is found. The band of the tune splitting is calculated. The influence of the tune splitting on the damper system stability is discussed. 14 refs
International Nuclear Information System (INIS)
Wang, Donghua; Huang, Jianzhe
2017-01-01
In this paper, the complex motions for a moving piston in a closed gas cylinder will be analyzed using the discrete implicit maps method. The strong nonlinearity of such system will be observed due to the large quadratic and cubic stiffness. Period-1 motions which contain high order of harmonic components will be presented. The periodic motions will be discretized into multiple continuous mappings, and such mapping can be analyzed via Newton–Raphson iteration. The stability analysis will be given and the analytic conditions for the saddle-node and period-doubling bifurcation will be determined. From the semi-analytic solution route, the possible motions without considering the impact of the piston with the end wall of the cylinder will be obtained analytically. The scheme to reduce the vibration of the piston can be obtained through the parameter studies.
Highly Damping Hard Coatings for Protection of Titanium Blades
National Research Council Canada - National Science Library
Movchan, Boris A; Ustinov, Anatolii I
2005-01-01
Sn-Cr-MgO system is used as an example to show the basic capability to produce by EBPVD protective metal-ceramic coatings with a high adhesion strength, high values of hardness and damping capacity...
Damping layout optimization for ship's cabin noise reduction based on statistical energy analysis
Directory of Open Access Journals (Sweden)
WU Weiguo
2017-08-01
Full Text Available An optimization analysis study concerning the damping control of ship's cabin noise was carried out in order to improve the effect and reduce the weight of damping. Based on the Statistical Energy Analysis (SEA method, a theoretical deduction and numerical analysis of the first-order sensitivity analysis of the A-weighted sound pressure level concerning the damping loss factor of the subsystem were carried out. On this basis, a mathematical optimization model was proposed and an optimization program developed. Next, the secondary development of VA One software was implemented through the use of MATLAB, while the cabin noise damping control layout optimization system was established. Finally, the optimization model of the ship was constructed and numerical experiments of damping control optimization conducted. The damping installation region was divided into five parts with different damping thicknesses. The total weight of damping was set as an objective function and the A-weighted sound pressure level of the target cabin was set as a constraint condition. The best damping thickness was obtained through the optimization program, and the total damping weight was reduced by 60.4%. The results show that the damping noise reduction effect of unit weight is significantly improved through the optimization method. This research successfully solves the installation position and thickness selection problems in the acoustic design of damping control, providing a reliable analysis method and guidance for the design.
DEFF Research Database (Denmark)
Zhao, Bin; Li, Hui; Wang, Mingyu
2014-01-01
This study presents the auxiliary damping control with the reactive power loop on the rotor-side converter of doubly-fed induction generator (DFIG)-based wind farms to depress the sub-synchronous resonance oscillations in nearby turbogenerators. These generators are connected to a series capaciti...
Directory of Open Access Journals (Sweden)
Alexander G. Tyapin
2018-03-01
Full Text Available Development of linear equations of motion for seismic analysis is discussed in the paper. The paper continues the discussion: the author does not agree with colleagues putting damping matrix into the right-hand part of the equation of motion describing dynamic loads. This disagreement refers to the most popular case of “rigid” motion of multiple supports. In this paper the author follows the logic of general “non-rigid” support motion and points out a step in the equation development when the transition to “rigid” support motion (as a particular case of “non-rigid” motion is spoiled by the opponents. In the author’s opinion, the mistake is in the implementation of the Rayleigh damping model for the right-hand part of the equation. This is in the contradiction with physical logic, as damping in the Rayleigh model is not really “internal”: due to the participation of mass matrix it works on rigid displacements, which is impossible for internal damping.
Xie, Xiaoyi; Zhou, Hongyan; Pan, Xiang; Jiang, Peng; Shi, Xiheng; Ji, Tuo; Zhang, Shaohua; Wu, Shengmiao; Zhong, Zhihao
2018-05-01
In this paper, we present an intercomparison study of two quasars, SDSS J145618.32+340037.2 and SDSS J215331.50–025514.1, which have proximate damped Lyα systems (PDLAs) with residual flux upon the Lyα absorption trough. Though they both have residual flux as luminous as 1043 erg s‑1, their PDLAs are quite different in, e.g., neutral hydrogen column density, metal line absorption strength, high-ionization absorption lines as well as residual flux strength. For J1456+3400, the H I column density is log(N H I /cm–2) = 20.6 ± 0.2, with z abs = 2.3138, nearly identical to the quasar redshift (z = 2.3142) determined from the [O III] emission line. The metallicity of this system is typical of DLAs and there is high ionization therein, suggesting that the PDLA system is multiphase, putting it in the quasar environment. For J2153–0255, we measure the H I column density to be log(N H I /cm–2) = 21.5 ± 0.1 at z abs = 3.511, slightly redshifted with respect to the quasar (z = 3.490) measured from C III]. The metallicity of this system is quite low and there is a lack of significant high-ionization absorption lines therein, suggesting that the system is beyond the quasar host galaxy. The residual flux is wide (∼1000 km s‑1) in J1456, with a significance of ∼8σ, while also wide (∼1500 km s‑1) but with a smaller significance of ∼3σ in J2153. Among many explanations, we find that Lyα fuzz or resonant scattering can be used to explain the residual flux in the two sources while partial coverage cannot be excluded for J1456. By comparing these two cases, together with a similar case reported previously, we suggest that the strength of the residual flux is related to properties such as metallicity and high-ionization absorption lines of PDLAs. The residual flux recorded upon the PDLA absorption trough opens a window for us to see the physical conditions and processes of the quasar environment, and their profile and strength further remind us of their
Experimental validation of solid rocket motor damping models
Riso, Cristina; Fransen, Sebastiaan; Mastroddi, Franco; Coppotelli, Giuliano; Trequattrini, Francesco; De Vivo, Alessio
2017-12-01
In design and certification of spacecraft, payload/launcher coupled load analyses are performed to simulate the satellite dynamic environment. To obtain accurate predictions, the system damping properties must be properly taken into account in the finite element model used for coupled load analysis. This is typically done using a structural damping characterization in the frequency domain, which is not applicable in the time domain. Therefore, the structural damping matrix of the system must be converted into an equivalent viscous damping matrix when a transient coupled load analysis is performed. This paper focuses on the validation of equivalent viscous damping methods for dynamically condensed finite element models via correlation with experimental data for a realistic structure representative of a slender launch vehicle with solid rocket motors. A second scope of the paper is to investigate how to conveniently choose a single combination of Young's modulus and structural damping coefficient—complex Young's modulus—to approximate the viscoelastic behavior of a solid propellant material in the frequency band of interest for coupled load analysis. A scaled-down test article inspired to the Z9-ignition Vega launcher configuration is designed, manufactured, and experimentally tested to obtain data for validation of the equivalent viscous damping methods. The Z9-like component of the test article is filled with a viscoelastic material representative of the Z9 solid propellant that is also preliminarily tested to investigate the dependency of the complex Young's modulus on the excitation frequency and provide data for the test article finite element model. Experimental results from seismic and shock tests performed on the test configuration are correlated with numerical results from frequency and time domain analyses carried out on its dynamically condensed finite element model to assess the applicability of different equivalent viscous damping methods to describe
Experimental validation of solid rocket motor damping models
Riso, Cristina; Fransen, Sebastiaan; Mastroddi, Franco; Coppotelli, Giuliano; Trequattrini, Francesco; De Vivo, Alessio
2018-06-01
In design and certification of spacecraft, payload/launcher coupled load analyses are performed to simulate the satellite dynamic environment. To obtain accurate predictions, the system damping properties must be properly taken into account in the finite element model used for coupled load analysis. This is typically done using a structural damping characterization in the frequency domain, which is not applicable in the time domain. Therefore, the structural damping matrix of the system must be converted into an equivalent viscous damping matrix when a transient coupled load analysis is performed. This paper focuses on the validation of equivalent viscous damping methods for dynamically condensed finite element models via correlation with experimental data for a realistic structure representative of a slender launch vehicle with solid rocket motors. A second scope of the paper is to investigate how to conveniently choose a single combination of Young's modulus and structural damping coefficient—complex Young's modulus—to approximate the viscoelastic behavior of a solid propellant material in the frequency band of interest for coupled load analysis. A scaled-down test article inspired to the Z9-ignition Vega launcher configuration is designed, manufactured, and experimentally tested to obtain data for validation of the equivalent viscous damping methods. The Z9-like component of the test article is filled with a viscoelastic material representative of the Z9 solid propellant that is also preliminarily tested to investigate the dependency of the complex Young's modulus on the excitation frequency and provide data for the test article finite element model. Experimental results from seismic and shock tests performed on the test configuration are correlated with numerical results from frequency and time domain analyses carried out on its dynamically condensed finite element model to assess the applicability of different equivalent viscous damping methods to describe
Damping of Crank–Nicolson error oscillations
DEFF Research Database (Denmark)
Britz, Dieter; Østerby, Ole; Strutwolf, J.
2003-01-01
The Crank–Nicolson (CN) simulation method has an oscillatory response to sharp initial transients. The technique is convenient but the oscillations make it less popular. Several ways of damping the oscillations in two types of electrochemical computations are investigated. For a simple one......-dimensional system with an initial singularity, subdivision of the first time interval into a number of equal subintervals (the Pearson method) works rather well, and so does division with exponentially increasing subintervals, where however an optimum expansion parameter must be found. This method can...... be computationally more expensive with some systems. The simple device of starting with one backward implicit (BI, or Laasonen) step does damp the oscillations, but not always sufficiently. For electrochemical microdisk simulations which are two-dimensional in space and using CN, the use of a first BI step is much...
The Duffing oscillator with damping
DEFF Research Database (Denmark)
Johannessen, Kim
2015-01-01
An analytical solution to the differential equation describing the Duffing oscillator with damping is presented. The damping term of the differential equation and the initial conditions satisfy an algebraic equation, and thus the solution is specific for this type of damping. The nonlinear term...... of the differential equation is allowed to be considerable compared to the linear term. The solution is expressed in terms of the Jacobi elliptic functions by including a parameter-dependent elliptic modulus. The analytical solution is compared to the numerical solution, and the agreement is found to be very good....... It is established that the period of oscillation is shorter compared to that of a linearized model but increasing with time and asymptotically approaching the period of oscillation of the linear damped model. An explicit expression for the period of oscillation has been derived, and it is found to be very accurate....
Damping in aerospace composite materials
Agneni, A.; Balis Crema, L.; Castellani, A.
Experimental results are presented on specimens of carbon and Kevlar fibers in epoxy resin, materials used in many aerospace structures (control surfaces and wings in aircraft, large antennas in spacecraft, etc.). Some experimental methods of estimating damping ratios are first reviewed, either in the time domain or in the frequency domain. Some damping factor estimates from experimental tests are then shown; in order to evaluate the effects of the aerospace environment, damping factors have been obtained in a typical range of temperature, namely between +120 C and -120 C, and in the pressure range from room pressure to 10 exp -6 torr. Finally, a theoretical approach for predicting the bounds of the damping coefficients is shown, and prediction data are compared with experimental results.
Amplitude damping of vortex modes
CSIR Research Space (South Africa)
Dudley, Angela L
2010-09-01
Full Text Available An interferometer, mimicking an amplitude damping channel for vortex modes, is presented. Experimentally the action of the channel is in good agreement with that predicted theoretically. Since we can characterize the action of the channel on orbital...
Emittance damping considerations for TESLA
International Nuclear Information System (INIS)
Floettmann, K.; Rossbach, J.
1993-03-01
Two schemes are considered to avoid very large damping rings for TESLA. The first (by K.F.) makes use of the linac tunnel to accomodate most of the damping 'ring' structure, which is, in fact, not a ring any more but a long linear structure with two small bends at each of its ends ('dog-bone'). The other scheme (by J.R.) is based on a positron (or electron, respectively) recycling scheme. It makes use of the specific TESLA property, that the full bunch train is much longer (240 km) than the linac length. The spent beams are recycled seven times after interaction, thus reducing the number of bunches to be stored in the damping ring by a factor of eight. Ultimately, this scheme can be used to operate TESLA in a storage ring mode ('storage linac'), with no damping ring at all. Finally, a combination of both schemes is considered. (orig.)
Vibration damping method and apparatus
Redmond, James M.; Barney, Patrick S.; Parker, Gordon G.; Smith, David A.
1999-01-01
The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof.
Damping Measurements of Plasma Modes
Anderegg, F.; Affolter, M.; Driscoll, C. F.
2010-11-01
For azimuthally symmetric plasma modes in a magnesium ion plasma, confined in a 3 Tesla Penning-Malmberg trap with a density of n ˜10^7cm-3, we measure a damping rate of 2s-1plasma column, alters the frequency of the mode from 16 KHz to 192 KHz. The oscillatory fluid displacement is small compared to the wavelength of the mode; in contrast, the fluid velocity, δvf, can be large compared to v. The real part of the frequency satisfies a linear dispersion relation. In long thin plasmas (α> 10) these modes are Trivelpiece-Gould (TG) modes, and for smaller values of α they are Dubin spheroidal modes. However the damping appears to be non-linear; initially large waves have weaker exponential damping, which is not yet understood. Recent theoryootnotetextM.W. Anderson and T.M. O'Neil, Phys. Plasmas 14, 112110 (2007). calculates the damping of TG modes expected from viscosity due to ion-ion collisions; but the measured damping, while having a similar temperature and density dependence, is about 40 times larger than calculated. This discrepancy might be due to an external damping mechanism.
Validation of Analytical Damping Ratio by Fatigue Stress Limit
Foong, Faruq Muhammad; Chung Ket, Thein; Beng Lee, Ooi; Aziz, Abdul Rashid Abdul
2018-03-01
The optimisation process of a vibration energy harvester is usually restricted to experimental approaches due to the lack of an analytical equation to describe the damping of a system. This study derives an analytical equation, which describes the first mode damping ratio of a clamp-free cantilever beam under harmonic base excitation by combining the transverse equation of motion of the beam with the damping-stress equation. This equation, as opposed to other common damping determination methods, is independent of experimental inputs or finite element simulations and can be solved using a simple iterative convergence method. The derived equation was determined to be correct for cases when the maximum bending stress in the beam is below the fatigue limit stress of the beam. However, an increasing trend in the error between the experiment and the analytical results were observed at high stress levels. Hence, the fatigue limit stress was used as a parameter to define the validity of the analytical equation.
Limitations of modal analysis of damped structures
International Nuclear Information System (INIS)
Krapf, K.G.; Woelfel, H.
1983-01-01
Quite recently discrete spring-damper elements are increasingly used for the low-tuned supports of nuclear power-plant buildings and equipment (reactor building, turbine-fundaments etc.) to reduce the vibration response due to the dynamic load cases earthquake and airplane crash. Because of this development, it is to be investigated whether the usual modal analysis method is applicable within the design process or should be changed respectively replaced in special cases. The paper contributes to this discussion by demonstrating and valuing the discrepancies in the different ways for the implementation of damping. Different methods for uncoupling (energy weighting, reduction to Rayleigh-damping) are compared with the solution of the coupled equations of motion. In particular vertical vibrations of a spring-damper-supported building on foundation (including ground springs) are examined using a two-degree-of-freedom-system. The results of coupled and (by force) uncoupled methods are interpreted concerning free vibration by comparison of the damping of natural vibrations, natural frequencies and natural mode shapes. The effect on the forced vibrations is shown by floor response spectra to an earthquake accelerogram. (orig./HP)
DAMPs and influenza virus infection in ageing.
Samy, Ramar Perumal; Lim, Lina H K
2015-11-01
Influenza A virus (IAV) is a serious global health problem worldwide due to frequent and severe outbreaks. IAV causes significant morbidity and mortality in the elderly population, due to the ineffectiveness of the vaccine and the alteration of T cell immunity with ageing. The cellular and molecular link between ageing and virus infection is unclear and it is possible that damage associated molecular patterns (DAMPs) may play a role in the raised severity and susceptibility of virus infections in the elderly. DAMPs which are released from damaged cells following activation, injury or cell death can activate the immune response through the stimulation of the inflammasome through several types of receptors found on the plasma membrane, inside endosomes after endocytosis as well as in the cytosol. In this review, the detriment in the immune system during ageing and the links between influenza virus infection and ageing will be discussed. In addition, the role of DAMPs such as HMGB1 and S100/Annexin in ageing, and the enhanced morbidity and mortality to severe influenza infection in ageing will be highlighted. Copyright © 2015 Elsevier B.V. All rights reserved.
Estimating the Effects of Damping Treatments on the Vibration of Complex Structures
2012-09-26
26 4.3 Literature review 26 4.3.1 CLD Theory 26 4.3.2 Temperature Profiling 28 4.4 Constrained Layer Damping Analysis 29 4.5 Results 35...Coordinate systems and length scales are noted. Constraining layer, viscoelastic layer and base layer pertain to the nomenclature used through CLD ...for vibrational damping 4.1 Introduction Constrained layer damping ( CLD ) treatment systems are widely used in complex structures to dissipate
Robust Rudder Roll Damping Control
DEFF Research Database (Denmark)
Yang, C.
The results of a systematic research to solve a specific ship motion control problem, simultaneous roll damping and course keeping using the rudder are presented in this thesis. The fundamental knowledge a priori is that rudder roll damping is highly sensitive to the model uncertainty, therefore H-infinity...... theory is used to deal with the problem. The necessary mathematical tools and the H-Infinity theory as the basis of controller design are presented in Chapter 2 and 3. The mu synthesis and the D-K iteration are introduced in Chapter 3. The ship dynamics and modeling technology are discussed in Chapter 4...
Damping ring designs and issues
International Nuclear Information System (INIS)
Wolski, Andrzej; Decking, Winfried
2003-01-01
The luminosity performance of a future linear collider (LC) will depend critically on the performance of the damping rings. The design luminosities of the current LC proposals require rings with very short damping times, large acceptance, low equilibrium emittance and high beam intensity. We discuss the design strategies for lattices achieving the goals of dynamical stability, examine the challenges for alignment and coupling correction, and consider a variety of collective effects that threaten to limit beam quality. We put the design goals in context by referring to the experience of operating facilities, and outline the further research and development that is needed
The Microstructural Basis of Damping in High Damping Alloys
1989-09-01
This transformation is diffusionless and is characterized by the cooperative movement of atoms in a given section of crystal. Removal of the stress...martensites. The cooperative movement of atoms causes large internal friction and high damping. The temperature range in which this transformation can
Energy Technology Data Exchange (ETDEWEB)
Bulos, Fatin [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tomlin, Bill T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Weaver, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States)
2014-03-04
The principle of the design of these magnets was discussed in CN-72. Fig. 1 shows what the total system looks like. Such a system was completed last January and since then we have been evaluating its performance.
Power Oscillations Damping in DC Microgrids
Hamzeh, Mohsen; Ghafouri, Mohsen; Karimi, Houshang; Sheshyekani, Keyhan; Guerrero, Josep M.
2016-01-01
This paper proposes a new control strategy for damping of power oscillations in a multi-source dc microgrid. A parallel combination of a fuel cell (FC), a photovoltaic (PV) system and a supercapacitor (SC) are used as a hybrid power conversion system (HPCS). The SC compensates for the slow transient response of the FC stack. The HPCS controller comprises a multi-loop voltage controller and a virtual impedance loop for power management. The virtual impedance loop uses a dynamic droop gain to a...
Rotational damping motion in nuclei
International Nuclear Information System (INIS)
Egido, J.L.; Faessler, A.
1991-01-01
The recently proposed model to explain the mechanism of the rotational motion damping in nuclei is exactly solved. When compared with the earlier approximative solution, we find significative differences in the low excitation energy limit (i.e. Γ μ 0 ). For the strength functions we find distributions going from the Wigner semicircle through gaussians to Breit-Wigner shapes. (orig.)
Dampness in buildings and health
DEFF Research Database (Denmark)
Bornehag, Carl-Gustaf; Blomquist, G.; Gyntelberg, F.
2001-01-01
Several epidemiological investigations concerning indoor environments have indicated that "dampness" in buildings is associated to health effects such as respiratory symptoms, asthma and allergy The aim of the present interdisciplinary review is to evaluate this association as shown in the epidem...
Nonlocal quasilinear damped differential inclusions
Directory of Open Access Journals (Sweden)
Mouffak Benchohra
2002-01-01
Full Text Available In this paper we investigate the existence of mild solutions to second order initial value problems for a class of damped differential inclusions with nonlocal conditions. By using suitable fixed point theorems, we study the case when the multivalued map has convex and nonconvex values.
Energy Technology Data Exchange (ETDEWEB)
Rubin, David L. [Cornell Univ., Ithaca, NY (United States). Dept. of Physics
2015-01-23
, and that an instability associated with residual gas in the beam pipe would limit the intensity of the electron ring. It was also not clear whether the required very small beam size could be achieved. The results of this study are important contributions to the design of both the electron and positron damping rings in which all of those challenges are addressed and overcome. Our findings are documented in the ILC Technical Design Report, a document that represents the work of an international collaboration of scientists. Our contributions include design of the beam magnetic optics for the 3 km circumference damping rings, the vacuum system and surface treatments for electron cloud mitigation, the design of the guide field magnets, design of the superconducting damping wigglers, and new detectors for precision measurement of beam properties. Our study informed the specification of the basic design parameters for the damping rings, including alignment tolerances, magnetic field errors, and instrumentation. We developed electron cloud modelling tools and simulations to aid in the interpretation of the measurements that we carried out in the Cornell Electron-positron Storage Ring (CESR). The simulations provide a means for systematic extrapolation of our measurements at CESR to the proposed ILC damping rings, and ultimately to specify how the beam pipes should be fabricated in order to minimize the effects of the electron cloud. With the conclusion of this study, the design of the essential components of the damping rings is complete, including the development and characterization (with computer simulations) of the beam optics, specification of techniques for minimizing beam size, design of damping ring instrumentation, R&D into electron cloud suppression methods, tests of long term durability of electron cloud coatings, and design of damping ring vacuum system components.
Marhauser, Frank
2017-06-01
Research and development for superconducting radio-frequency cavities has made enormous progress over the last decades from the understanding of theoretical limitations to the industrial mass fabrication of cavities for large-scale particle accelerators. Key technologies remain hot topics due to continuously growing demands on cavity performance, particularly when in pursuit of high quality beams at higher beam currents or higher luminosities than currently achievable. This relates to higher order mode (HOM) damping requirements. Meeting the desired beam properties implies avoiding coupled multi-bunch or beam break-up instabilities depending on the machine and beam parameters that will set the acceptable cavity impedance thresholds. The use of cavity HOM-dampers is crucial to absorb the wakefields, comprised by all beam-induced cavity Eigenmodes, to beam-dynamically safe levels and to reduce the heat load at cryogenic temperature. Cavity damping concepts may vary, but are principally based on coaxial and waveguide couplers as well as beam line absorbers or any combination. Next generation energy recovery linacs and circular colliders call for cavities with strong HOM-damping that can exceed the state-of-the-art, while the operating mode efficiency shall not be significantly compromised concurrently. This imposes major challenges given the rather limited damping concepts. A detailed survey of established cavities is provided scrutinizing the achieved damping performance, shortcomings, and potential improvements. The scaling of the highest passband mode impedances is numerically evaluated in dependence on the number of cells for a single-cell up to a nine-cell cavity, which reveals the increased probability of trapped modes. This is followed by simulations for single-cell and five-cell cavities, which incorporate multiple damping schemes to assess the most efficient concepts. The usage and viability of on-cell dampers is elucidated for the single-cell cavity since it
Damped Oscillator with Delta-Kicked Frequency
Manko, O. V.
1996-01-01
Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.
Damping characteristics of reinforced concrete structures
International Nuclear Information System (INIS)
Hisano, M.; Nagashima, I.; Kawamura, S.
1987-01-01
Reinforced concrete structures in a nuclear power plant are not permitted to go far into the inelasticity generally, even when subjected to strong ground motion. Therefore it is important to evaluate the damping appropriately in linear and after cracking stage before yielding in the dynamic response analysis. Next three dampings are considered of reinforced concrete structures. 1) Internal damping in linear range material damping of concrete without cracks;2) Hysteretic damping in inelastic range material hysteretic damping of concrete due to cracking and yielding;3) Damping due to the energy dissipation into the ground. Among these damping material damping affects dynamic response of a nuclear power plant on hard rock site where damping due to energy dissipation into the ground is scarcely expected. However material damping in linear and slightly nonlinear range have only been assumed without enough experimental data. In this paper such damping is investigated experimentally by the shaking table tests of reinforced concrete box-walls which modeled roughly the outer wall structure of a P.W.R. type nuclear power plant
Squeeze-Film Air Damping of a Five-Axis Electrostatic Bearing for Rotary Micromotors.
Wang, Shunyue; Han, Fengtian; Sun, Boqian; Li, Haixia
2017-05-13
Air-film damping, which dominates over other losses, plays a significant role in the dynamic response of many micro-fabricated devices with a movable mass suspended by various bearing mechanisms. Modeling the damping characteristics accurately will be greatly helpful to the bearing design, control, and test in various micromotor devices. This paper presents the simulated and experimental squeeze-film air damping results of an electrostatic bearing for use in a rotary high-speed micromotor. It is shown that the boundary condition to solve the three-dimensional Reynolds equation, which governs the squeeze-film damping in the air gap between the rotor and its surrounding stator sealed in a three-layer evacuated cavity, behaves with strong cross-axis coupling characteristics. To accurately characterize the damping effect, a set of multiphysics finite-element simulations are performed by computing both the rotor velocity and the distribution of the viscous damping force acting on the rotor. The damping characteristics varying with several key structure parameters are simulated and discussed to optimize the device structure for desirable rotor dynamics. An electrical measurement method is also proposed and applied to validate the numerical results of the damping coefficients experimentally. Given that the frequency response of the electric bearing is critically dependent on the damping coefficients at atmospheric pressure, a solution to the air-film damping measurement problem is presented by taking approximate curve fitting of multi-axis experimental frequency responses. The measured squeeze-film damping coefficients for the five-axis electric bearing agrees well with the numerical solutions. This indicates that numerical multiphysics simulation is an effective method to accurately examine the air-film damping effect for complex device geometry and arbitrary boundary condition. The accurate damping coefficients obtained by FEM simulation will greatly simplify the design
Thermal equilibrium in strongly damped collisions
International Nuclear Information System (INIS)
Samaddar, S.K.; De, J.N.; Krishan, K.
1985-01-01
Energy division between colliding nuclei in damped collisions is studied in the statistical nucleon exchange model. The reactions 56 Fe+ 165 Ho and 56 Fe+ 238 U at incident energy of 465 MeV are considered for this purpose. It is found that the excitation energy is approximately equally shared between the nuclei for the peripheral collisions and the systems slowly approach equilibrium for more central collisions. This is in conformity with the recent experimental observations. The calculated variances of the charge distributions are found to depend appreciably on the temperature and are in very good agreement with the experimental data
Transit-Time Damping, Landau Damping, and Perturbed Orbits
Simon, A.; Short, R. W.
1997-11-01
Transit-time damping(G.J. Morales and Y.C. Lee, Phys. Rev. Lett. 33), 1534 (1974).*^,*(P.A. Robinson, Phys. Fluids B 3), 545 (1991).** has traditionally been obtained by calculating the net energy gain of transiting electrons, of velocity v, to order E^2* in the amplitude of a localized electric field. This necessarily requires inclusion of the perturbed orbits in the equation of motion. A similar method has been used by others(D.R. Nicholson, Introduction to Plasma Theory) (Wiley, 1983).*^,*(E.M. Lifshitz and L.P. Pitaevskifi, Physical Kinetics) (Pergamon, 1981).** to obtain a ``physical'' picture of Landau damping in a nonlocalized field. The use of perturbed orbits seems odd since the original derivation of Landau (and that of Dawson) never went beyond a linear picture of the dynamics. We introduce a novel method that takes advantage of the time-reversal invariance of the Vlasov equation and requires only the unperturbed orbits to obtain the result. Obviously, there is much reduction in complexity. Application to finite slab geometry yields a simple expression for the damping rate. Equivalence to much more complicated results^2* is demonstrated. This method allows us to calculate damping in more complicated geometries and more complex electric fields, such as occur in SRS in filaments. See accompanying talk.(R.W. Short and A. Simon, this conference.) This work was supported by the U.S. DOE Office of Inertial Confinement Fusion under Co-op Agreement No. DE-FC03-92SF19460.
DEFF Research Database (Denmark)
Perez, Tristan; Blanke, Mogens
2012-01-01
limitations and large variations of the spectral characteristics of wave-induced roll motion. This tutorial paper presents an account of the development of various ship roll motion control systems together with the challenges associated with their design. It discusses the assessment of performance...
DEFF Research Database (Denmark)
Pedersen, Lars
2012-01-01
system and change its dynamic behavior and its dynamic characteristics. When predicting structural vibrations it is not common to account for the passive crowd, but the paper will illustrate effects of the presence of a passive croud on structural behavior. Numerical and experimental results...
Damping of Inter-Area Low Frequency Oscillation Using an Adaptive Wide-Area Damping Controller
DEFF Research Database (Denmark)
Yao, Wei; Jiang, L.; Fang, Jiakun
2013-01-01
This paper presents an adaptive wide-area damping controller (WADC) based on generalized predictive control (GPC) and model identification for damping the inter-area low frequency oscillations in large-scale inter-connected power system. A recursive least-squares algorithm (RLSA) with a varying...... forgetting factor is applied to identify online the reduced-order linearlized model which contains dominant inter-area low frequency oscillations. Based on this linearlized model, the generalized predictive control scheme considering control output constraints is employed to obtain the optimal control signal...... conditions and different disturbances, but also has better robustness against to the time delay existing in the remote signals. The comparison studies with the conventional lead-lag WADC are also provided....
Route Flap Damping Made Usable
Pelsser, Cristel; Maennel, Olaf; Mohapatra, Pradosh; Bush, Randy; Patel, Keyur
The Border Gateway Protocol (BGP), the de facto inter-domain routing protocol of the Internet, is known to be noisy. The protocol has two main mechanisms to ameliorate this, MinRouteAdvertisementInterval (MRAI), and Route Flap Damping (RFD). MRAI deals with very short bursts on the order of a few to 30 seconds. RFD deals with longer bursts, minutes to hours. Unfortunately, RFD was found to severely penalize sites for being well-connected because topological richness amplifies the number of update messages exchanged. So most operators have disabled it. Through measurement, this paper explores the avenue of absolutely minimal change to code, and shows that a few RFD algorithmic constants and limits can be trivially modified, with the result being damping a non-trivial amount of long term churn without penalizing well-behaved prefixes' normal convergence process.
Design of passive piezoelectric damping for space structures. Final Report Ph.D. Thesis
Hagood, Nesbitt W., IV; Aldrich, Jack B.; Vonflotow, Andreas H.
1994-01-01
Passive damping of structural dynamics using piezoceramic electromechanical energy conversion and passive electrical networks is a relatively recent concept with little implementation experience base. This report describes an implementation case study, starting from conceptual design and technique selection, through detailed component design and testing to simulation on the structure to be damped. About 0.5kg. of piezoelectric material was employed to damp the ASTREX testbed, a 500kg structure. Emphasis was placed upon designing the damping to enable high bandwidth robust feedback control. Resistive piezoelectric shunting provided the necessary broadband damping. The piezoelectric element was incorporated into a mechanically-tuned vibration absorber in order to concentrate damping into the 30 to 40 Hz frequency modes at the rolloff region of the proposed compensator. A prototype of a steel flex-tensional motion amplification device was built and tested. The effective stiffness and damping of the flex-tensional device was experimentally verified. When six of these effective springs are placed in an orthogonal configuration, strain energy is absorbed from all six degrees of freedom of a 90kg. mass. A NASTRAN finite element model of the testbed was modified to include the six-spring damping system. An analytical model was developed for the spring in order to see how the flex-tensional device and piezoelectric dimensions effect the critical stress and strain energy distribution throughout the component. Simulation of the testbed demonstrated the damping levels achievable in the completed system.
Multiparticle phenomena and Landau damping
International Nuclear Information System (INIS)
Talman, R.
1987-01-01
The purpose of this paper is to survey various methods of studying multiparticle phenomena in accelerators. Both experimental and theoretical methods are described. An effort has been made to emphasize the intuitive and qualitative aspects rather than the detailed mathematics. Some of the terms or concepts to be explained are coherent and incoherent tunes, normal modes, Landau damping, beam-transfer functions, and feedback. These are all of daily importance in the interpretation of colliding-beam observations and the control of performance
Sheath waves, non collisional dampings
International Nuclear Information System (INIS)
Marec, Jean Lucien Ernest
1974-01-01
When a metallic conductor is inserted into an ionised gas, an area of electron depletion is formed between the conductor and the plasma: the ionic sheath. Moreover, if the conductor is excited by an electric field, this ionic sheath plays an important role with respect to microwave properties. In this research thesis, the author addresses the range of frequencies smaller than the plasma frequency, and reports the study of resonance phenomena. After a presentation of the problem through a bibliographical study, the author recalls general characteristics of sheath wave propagation and of sheath resonances, and discusses the validity of different hypotheses (for example and among others, electrostatic approximations, cold plasma). Then, the author more particularly addresses theoretical problems related to non collisional dampings: brief bibliographical study, detailed presentation and description of the theoretical model, damping calculation methods. The author then justifies the design and performance of an experiment, indicates measurement methods used to determine plasma characteristics as well as other magnitudes which allow the description of mechanisms of propagation and damping of sheath waves. Experimental results are finally presented with respect to various parameters. The author discusses to which extent the chosen theoretical model is satisfying [fr
The DAMPE silicon tungsten tracker
Gallo, Valentina; Asfandiyarov, R; Azzarello, P; Bernardini, P; Bertucci, B; Bolognini, A; Cadoux, F; Caprai, M; Domenjoz, M; Dong, Y; Duranti, M; Fan, R; Franco, M; Fusco, P; Gargano, F; Gong, K; Guo, D; Husi, C; Ionica, M; Lacalamita, N; Loparco, F; Marsella, G; Mazziotta, M N; Mongelli, M; Nardinocchi, A; Nicola, L; Pelleriti, G; Peng, W; Pohl, M; Postolache, V; Qiao, R; Surdo, A; Tykhonov, A; Vitillo, S; Wang, H; Weber, M; Wu, D; Wu, X; Zhang, F; De Mitri, I; La Marra, D
2017-01-01
The DArk Matter Particle Explorer (DAMPE) satellite has been successfully launched on the 17th December 2015. It is a powerful space detector designed for the identification of possible Dark Matter signatures thanks to its capability to detect electrons and photons with an unprecedented energy resolution in an energy range going from few GeV up to 10 TeV. Moreover, the DAMPE satellite will contribute to a better understanding of the propagation mechanisms of high energy cosmic rays measuring the nuclei flux up to 100 TeV. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon-tungsten tracker-converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is made of twelve layers of single-sided AC-coupled silicon micro-strip detectors for a total silicon area of about 7 $m^2$ . To promote the conversion of incident photons into electron-positron pairs, tungsten foils are inserted into the supporting structure. In this document, a detailed description of the STK constructi...
A Look at Damped Harmonic Oscillators through the Phase Plane
Daneshbod, Yousef; Latulippe, Joe
2011-01-01
Damped harmonic oscillations appear naturally in many applications involving mechanical and electrical systems as well as in biological systems. Most students are introduced to harmonic motion in an elementary ordinary differential equation (ODE) course. Solutions to ODEs that describe simple harmonic motion are usually found by investigating the…
Prognostic and predictive value of DAMPs and DAMP-associated processes in cancer
Directory of Open Access Journals (Sweden)
Jitka eFucikova
2015-08-01
Full Text Available It is now clear that human neoplasms form, progress and respond to therapy in the context of an intimate crosstalk with the host immune system. In particular, accumulating evidence demonstrates that the efficacy of most, if not all, chemo- and radiotherapeutic agents commonly employed in the clinic critically depends on the (reactivation of tumor-targeting immune response. One of the mechanisms whereby conventional chemotherapeutics, targeted anticancer agents and radiotherapy can provoke a therapeutically relevant, adaptive immune response against malignant cells is commonly known as „immunogenic cell death (ICD. Importantly, dying cancer cells are perceived as immunogenic only when they emit a set of immunostimulatory signals upon the activation of intracellular stress response pathways. The emission of these signals, which are generally referred to as „damage-associated molecular patterns (DAMPs, may therefore predict whether patients will respond to chemotherapy or not, at least in some settings. Here, we review clinical data indicating that DAMPs and DAMP-associated stress responses might have prognostic or predictive value for cancer patients.
Study of damping characteristics of fibre reinforced composite aerospace structure
International Nuclear Information System (INIS)
Khan, M.Z.; Saleh, S.; Munir, A.
2006-01-01
Composite materials are used in a variety of high demanding structural applications. Apart from their other preferable properties, they have high-energy dissipation characteristics, which is important aspect when we repeatedly wiggle the system back and forth. It is important to have thorough understanding of material damping behavior; in general materials damping tends to be complex nonlinear function of vibration amplitude, frequency of loading and material formulation. There are number of mathematical models available in literature to obtain hysteresis curves. One approach for identifying damping characteristics used mechanical hysteresis curves. In present work, a phenomenon was observed during testing of fibre reinforced composite beam of an aerospace structure, that for increase load in structure, the path of Force vs. Displacement curve is different than the path of unloading. A plot is generated which indicate the hysteresis loop representing the steady state dynamic behavior of material. The area enclosed by such curves is proportional to energy dissipation per cycle. However, the specific shape of the curve also has important implications for characterizing the specific functional form of the damping. Therefore, it is important to develop methods for accurately accounting for such effects. The current work explores the damping characteristics both theoretically and experimentally. (author)
Galaxy at a redshift of 3.215 - further studies of the PKS 1614+051 system
International Nuclear Information System (INIS)
Djorgovski, S.; Strauss, M.A.; Spinrad, H.; Mccarthy, P.; Perley, R.A.; California Univ., Berkeley; National Radio Astronomy Observatory, Charlottesville, VA)
1987-01-01
A narrow-emission-line companion of the quasar PKS 1614+051 was reported earlier as a probable galaxy at a redshift of 3.218, which would have made it by far the most distant galaxy known at the time. New radio and optical imaging, and optical and near-IR spectroscopy of the PKS 1614+051 system is reported here. It is argued that the data support and reinforce the original interpretation of the companion object as a mildly active galaxy, possibly a marginal Seyfert 2. The object has a detectable and marginally resolved optical continuum, but was not detected at radio wavelengths. The ionization state is low, and the emission lines are fairly narrow. The improved redshift for the companion, based on the Ly-alpha line alone, is 3.215 + or - 0.002. New Ly-alpha images show interesting morphology of extended emission-line gas, suggestive of a possible tidal interaction with the neighboring QSO. 24 references
Structural damping results from vibration tests of straight piping sections
International Nuclear Information System (INIS)
Ware, A.G.; Thinnes, G.L.
1984-01-01
EG and G Idaho is assisting the USNRC and the Pressure Vessel Research Committee in supporting a final position on revised damping values for structural analyses of nuclear piping systems. As part of this program, a series of vibrational tests on 76-mm and 203-mm (3-in. amd 8-in.) Schedule 40 carbon steel piping was conducted to determine the changes in structural damping due to various parametric effects. The 10-m (33-ft) straight sections of piping were rigidly supported at the ends. Spring, rod, and constant force hangers, as well as a sway brace and snubbers were included as intermediate supports. Excitation was provided by low-force level hammer inpacts, a hydraulic shaker, and a 445-kN (50-ton) overhead crane. Data was recorded using acceleration, strain, and displacement time histories. This paper presents results from the testing showing the effect of stress level and type of supports on structural damping in piping
Dynamic soil-pile-interaction effects on eigenfrequency and damping of slender structures
DEFF Research Database (Denmark)
Zania, Varvara
2014-01-01
after a rigorous solution of horizontal soil – pile vibration, while the modified SSI eigenperiod and damping are calculated accounting for the cross coupling stiffness and damping terms of the soil – pile system. Disregarding the off diagonal terms is considered inappropriate since it results to non...
Satellite Dynamic Damping via Active Force Control Augmentation
Varatharajoo, Renuganth
2012-07-01
An approach that incorporates the Active Force Control (AFC) technique into a conventional Proportional-Derivative (PD) controller is proposed for a satellite active dynamic damping towards a full attitude control. The AFC method has been established to facilitate a robust motion control of dynamical systems in the presence of disturbances, parametric uncertainties and changes that are commonly prevalent in the real-world environment. The usefulness of the method can be extended by introducing intelligent mechanisms to approximate the mass or inertia matrix of the dynamic system to trigger the compensation effect of the controller. AFC is a technique that relies on the appropriate estimation of the inertial or mass parameters of the dynamic system and the measurements of the acceleration and force signals induced by the system if practical implementation is ever considered. In AFC, it is shown that the system subjected to a number of disturbances remains stable and robust via the compensating action of the control strategy. We demonstrate that it is possible to design a spacecraft attitude feedback controller that will ensure the system dynamics set point remains unchanged even in the presence of the disturbances provided that the actual disturbances can be modeled effectively. In order to further facilitate this analysis, a combined energy and attitude control system (CEACS) is proposed as a model satellite attitude control actuator. All the governing equations are established and the proposed satellite attitude control architecture is made amenable to numerical treatments. The results show that the PD-AFC attitude damping performances are superiorly better than that of the solely PD type. It is also shown that the tunings of the AFC system gains are crucial to ensure a better attitude damping performance and this process is mandatory for AFC systems. Finally, the results demonstrate an important satellite dynamic damping enhancement capability using the AFC
Bunch length measurements in the SLC damping ring
International Nuclear Information System (INIS)
Decker, F.J.; Limberg, T.; Minty, M.; Ross, M.
1993-05-01
The synchrotron light of the SLC damping ring was used to measure the bunch length with a streak camera at different times in the damping cycle. There are bunch length oscillations after injection, different equilibrium length during the cycle due to rf manipulations to avoid microwave instability oscillations, and just before extraction there is a longitudinal phase space rotation (bunch muncher) to shorten the bunch length. Measurements under these different conditions are presented and compared with BPM pulse height signals. Calibration and adjustment issues and the connection of the streak camera to the SLC control system are also discussed
Evaluation of Damping Using Time Domain OMA Techniques
DEFF Research Database (Denmark)
Bajric, Anela; Brincker, Rune; Georgakis, Christos T.
2014-01-01
. In this paper a comparison is made of the effectiveness of three existing OMA techniques in providing accurate damping estimates for varying loadings, levels of noise, number of added measurement channels and structural damping. The evaluated techniques are derived in the time domain and are namely the Ibrahim...... Time Domain (ITD), Eigenvalue Realization Algorithm (ERA) and the Polyreference Time Domain (PTD). The response of a two degree-of-freedom (2DOF) system is numerically established from specified modal parameters with well separated and closely spaced modes. Two types of response are considered, free...
Weakly damped modes in star clusters and galaxies
Weinberg, Martin D.
1994-01-01
A perturber may excite a coherent mode in a star cluster or galaxy. If the stellar system is stable, it is commonly assumed that such a mode will be strongly damped and therefore of little practical consequence other than redistributing momentum and energy deposited by the perturber. This paper demonstrates that this assumption is false; weakly damped modes exist and may persist long enough to have observable consequences. To do this, a method for investigating the dispersion relation for spherical stellar systems and for locating weakly damped modes in particular is developed and applied to King models of varying concentration. This leads to a following remarkable result: King models exhibit very weakly damped m = 1 modes over a wide range of concentration (0.67 less than or equal to c less than or equal to 1.5 have been examined). The predicted damping time is tens of hundreds of crossing times. This mode causes the peak density to shift from and slowly revolve about the initial center. The existence of the mode is supported by n-body simulation. Higher order modes and possible astronomical consequences are discussed. Weakly damped modes, for example, may provide a neutral explanation for observed discrepancies between density and kinematic centers in galaxies, off-center nuclei, the location of velocity cusps due to massive black holes, and both m = 1 and barlike disturbances of disks enbedded in massive halos or spheroids. Gravitational shocking may excite the m = 1 mode in globular clusters, which could modify their subsequent evolution and displace the positions of exotic remnants.
Damping rates of the SRRC storage ring
International Nuclear Information System (INIS)
Hsu, K.T.; Kuo, C.C.; Lau, W.K.; Weng, W.T.
1995-01-01
The SRRC storage ring is a low emittance synchrotron radiation machine with nominal operation energy 1.3 GeV. The design damping time due to synchrotron radiation is 10.7, 14.4, 8.7 ms for the horizontal, vertical and longitudinal plane, respectively. The authors measured the real machine damping time as a function of bunch current, chromaticity, etc. To damp the transverse beam instability, especially in the vertical plane, they need to increase chromaticity to large positive value. The damping rates are much larger than the design values. Landau damping contribution in the longitudinal plane is quite large, especially in the multibunch mode. The estimated synchrotron tune spread from the Landau damping is in agreement with the measured coherent longitudinal coupled bunch oscillation amplitude
Anisotropic damping of Timoshenko beam elements
Energy Technology Data Exchange (ETDEWEB)
Hansen, M.H.
2001-05-01
This report contains a description of a structural damping model for Timoshenko beam elements used in the aeroelastic code HawC developed at Risoe for modeling wind turbines. The model has been developed to enable modeling of turbine blades which often have different damping characteristics for flapwise, edgewise and torsional vibrations. The structural damping forces acting on the beam element are modeled by viscous damping described by an element damping matrix. The composition of this matrix is based on the element mass and stiffness matrices. It is shown how the coefficients for the mass and stiffness contributions can be calibrated to give the desired modal damping in the complete model of a blade. (au)
Asymptotic behavior of tidal damping in alluvial estuaries
Cai, H.; Savenije, H.H.G.
2013-01-01
Tidal wave propagation can be described analytically by a set of four implicit equations, i.e., the phase lag equation, the scaling equation, the damping equation, and the celerity equation. It is demonstrated that this system of equations has an asymptotic solution for an infinite channel,
Nonlinear piping damping and response predictions
International Nuclear Information System (INIS)
Severud, L.K.; Weiner, E.O.; Lindquist, M.R.; Anderson, M.J.; Wagner, S.E.
1986-10-01
The high level dynamic testing of four prototypic piping systems, used to provide benchmarks for analytical prediction comparisons, is overviewed. The size of pipe tested ranged from one-inch to six-inches in diameter and consisted of carbon steel or stainless steel material. Failure of the tested systems included progressive gross deformation or some combination of ratchetting-fatigue. Pretest failure predictions and post test comparisons using simplified elastic and elasto-plastic methods are presented. Detailed non-linear inelastic analyses are also shown, along with a typical ratchet-fatigue failure calculation. A simplified method for calculating modal equivalent viscous damping for snubbers and plastic hinges is also described. Conclusions are made regarding the applicability of the various analytical failure predictive methods and recommendations are made for future analytic and test efforts
Phenomenology of chiral damping in noncentrosymmetric magnets
Akosa, Collins Ashu; Miron, Ioan Mihai; Gaudin, Gilles; Manchon, Aurelien
2016-01-01
A phenomenology of magnetic chiral damping is proposed in the context of magnetic materials lacking inversion symmetry. We show that the magnetic damping tensor acquires a component linear in magnetization gradient in the form of Lifshitz invariants. We propose different microscopic mechanisms that can produce such a damping in ferromagnetic metals, among which local spin pumping in the presence of an anomalous Hall effect and an effective “s-d” Dzyaloshinskii-Moriya antisymmetric exchange. The implication of this chiral damping in terms of domain-wall motion is investigated in the flow and creep regimes.
Parametric Landau damping of space charge modes
Energy Technology Data Exchange (ETDEWEB)
Macridin, Alexandru [Fermilab; Burov, Alexey [Fermilab; Stern, Eric [Fermilab; Amundson, James [Fermilab; Spentzouris, Panagiotis [Fermilab
2016-09-23
Landau damping is the mechanism of plasma and beam stabilization; it arises through energy transfer from collective modes to the incoherent motion of resonant particles. Normally this resonance requires the resonant particle's frequency to match the collective mode frequency. We have identified an important new damping mechanism, parametric Landau damping, which is driven by the modulation of the mode-particle interaction. This opens new possibilities for stability control through manipulation of both particle and mode-particle coupling spectra. We demonstrate the existence of parametric Landau damping in a simulation of transverse coherent modes of bunched accelerator beams with space charge.
Phenomenology of chiral damping in noncentrosymmetric magnets
Akosa, Collins Ashu
2016-06-21
A phenomenology of magnetic chiral damping is proposed in the context of magnetic materials lacking inversion symmetry. We show that the magnetic damping tensor acquires a component linear in magnetization gradient in the form of Lifshitz invariants. We propose different microscopic mechanisms that can produce such a damping in ferromagnetic metals, among which local spin pumping in the presence of an anomalous Hall effect and an effective “s-d” Dzyaloshinskii-Moriya antisymmetric exchange. The implication of this chiral damping in terms of domain-wall motion is investigated in the flow and creep regimes.
Vibration isolation and damping in high precision equipment
Bukkems, B.; Ruijl, T.; Simons, J.
2017-06-01
All systems located in a laboratory environment or factory are subject to disturbances. These disturbances can either come from the surroundings, e.g. floor-induced vibrations, or from the system itself, e.g. stage-induced vibrations. In many cases it is needed to minimize the effect of these disturbances. This can either be done by isolating the system from its disturbance source or by applying damping to the system. In this paper we present various cases in which we have effectively reduced the impact of disturbances on the system's performance, either by improving its isolation system, by minimizing the impact of stage reaction forces, or by designing polymer damping into the system.
Design of multi-objective damping controller for gate-controlled ...
Indian Academy of Sciences (India)
augment the modulated damping torque of the GCSC against the system uncertainties and non- .... all of the simulation processes from mathematical modelling from current ... system, are performed in the MATLAB/SIMULINK environment.
Parameter identification in a generalized time-harmonic Rayleigh damping model for elastography.
Directory of Open Access Journals (Sweden)
Elijah E W Van Houten
Full Text Available The identifiability of the two damping components of a Generalized Rayleigh Damping model is investigated through analysis of the continuum equilibrium equations as well as a simple spring-mass system. Generalized Rayleigh Damping provides a more diversified attenuation model than pure Viscoelasticity, with two parameters to describe attenuation effects and account for the complex damping behavior found in biological tissue. For heterogeneous Rayleigh Damped materials, there is no equivalent Viscoelastic system to describe the observed motions. For homogeneous systems, the inverse problem to determine the two Rayleigh Damping components is seen to be uniquely posed, in the sense that the inverse matrix for parameter identification is full rank, with certain conditions: when either multi-frequency data is available or when both shear and dilatational wave propagation is taken into account. For the multi-frequency case, the frequency dependency of the elastic parameters adds a level of complexity to the reconstruction problem that must be addressed for reasonable solutions. For the dilatational wave case, the accuracy of compressional wave measurement in fluid saturated soft tissues becomes an issue for qualitative parameter identification. These issues can be addressed with reasonable assumptions on the negligible damping levels of dilatational waves in soft tissue. In general, the parameters of a Generalized Rayleigh Damping model are identifiable for the elastography inverse problem, although with more complex conditions than the simpler Viscoelastic damping model. The value of this approach is the additional structural information provided by the Generalized Rayleigh Damping model, which can be linked to tissue composition as well as rheological interpretations.
Directory of Open Access Journals (Sweden)
Irene Y. H. Gu
2007-01-01
Full Text Available This paper describes an efficient yet accurate methodology for estimating system damping. The proposed technique is based on linear dynamic system theory and the Hilbert damping analysis. The proposed technique requires capacitor switching waveforms only. The detected envelope of the intrinsic transient portion of the voltage waveform after capacitor bank energizing and its decay rate along with the damped resonant frequency are used to quantify effective X/R ratio of a system. Thus, the proposed method provides complete knowledge of system impedance characteristics. The estimated system damping can also be used to evaluate the system vulnerability to various PQ disturbances, particularly resonance phenomena, so that a utility may take preventive measures and improve PQ of the system.
de Goeje, Marius; van Overbeek, Michiel Wilbert R.M.; van der Waal, Adri; Berkhoff, Arthur P.; Nederveen, Peter J.
2005-01-01
A semimanufacture intended to be mounted on a vibrating wall or a vibrating panel for actively damping the vibrations in the wall or the panel with frequencies which are at least partly audible, wherein the semimanufacture is provided with a plate wherein the plate is integrated with: at least one
Charged-particle incoherent-motion damping in storage rings by means of dissipative elements
International Nuclear Information System (INIS)
Derbenev, Ya.S.; Khejfets, S.A.
1979-01-01
In consecutive order a possibility of damping of beam incoherent oscillations in a storage ring was studied by means of an external dissipative system in a sufficient common case. It is shown, that a useful effect, as for the case of electron cooling, is one-particle effect of particle oscillations damping due to nonconservatism of its interaction with an external system. Each other mutual influence through the external system becomes significant with increasing beam density and results in the limitation to achievable damping decrements
Tachyonic ionization cross sections of hydrogenic systems
Energy Technology Data Exchange (ETDEWEB)
Tomaschitz, Roman [Department of Physics, Hiroshima University, 1-3-1 Kagami-yama, Higashi-Hiroshima 739-8526 (Japan)
2005-03-11
Transition rates for induced and spontaneous tachyon radiation in hydrogenic systems as well as the transversal and longitudinal ionization cross sections are derived. We investigate the interaction of the superluminal radiation field with matter in atomic bound-bound and bound-free transitions. Estimates are given for Ly-{alpha} transitions effected by superluminal quanta in hydrogen-like ions. The tachyonic photoelectric effect is scrutinized, in the Born approximation and at the ionization threshold. The angular maxima occur at different scattering angles in the transversal and longitudinal cross sections, which can be used to sift out longitudinal tachyonic quanta in a photon flux. We calculate the tachyonic ionization and recombination cross sections for Rydberg states and study their asymptotic scaling with respect to the principal quantum number. At the ionization threshold of highly excited states of order n {approx} 10{sup 4}, the longitudinal cross section starts to compete with photoionization, in recombination even at lower levels.
Damping-off in forest nurseries
Carl Hartley
1921-01-01
Damping-off is the commonest English name for a symptomatic group of diseases affecting great numbers of plant species of widely separated phylogenetic groups. It is commonly used for any disease which results in the rapid decay of young succulent seedlings or soft cuttings. Young shoots from underground rootstocks may also be damped-off before they break through the...
Beam dynamic issues in TESLA damping ring
International Nuclear Information System (INIS)
Shiltsev, V.
1996-05-01
In this paper we study general requirements on impedances of the linear collider TESLA damping ring design. Quantitative consideration is performed for 17-km long ''dog-bone'' ring. Beam dynamics in alternative options of 6.3 and 2.3-km long damping rings is briefly discussed. 5 refs., 2 tabs
On Collisionless Damping of Ion Acoustic Waves
DEFF Research Database (Denmark)
Jensen, Vagn Orla; Petersen, P.I.
1973-01-01
Exact theoretical treatments show that the damping of ion acoustic waves in collisionless plasmas does not vanish when the derivative of the undisturbed distribution function at the phase velocity equals zero.......Exact theoretical treatments show that the damping of ion acoustic waves in collisionless plasmas does not vanish when the derivative of the undisturbed distribution function at the phase velocity equals zero....
Study for ILC Damping Ring at KEKB
Energy Technology Data Exchange (ETDEWEB)
Flanagan, J.W.; Fukuma, H.; Kanazawa, K.I.; Koiso, H.; Masuzawa, M.; Ohmi, Kazuhito; Ohnishi, Y.; Oide, Katsunobu; Suetsugu, Y.; Tobiyama, M.; /KEK, Tsukuba; Pivi, M.; /SLAC
2011-11-04
ILC damping ring consists of very low emittance electron and positron storage rings. It is necessary for ILC damping ring to study electron cloud effects in such low emittance positron ring. We propose a low emittance operation of KEKB to study the effects.
Damping Effects of Drogue Parachutes on Orion Crew Module Dynamics
Aubuchon, Vanessa V.; Owens, D. Bruce
2016-01-01
Because simulations of the Orion Crew Module (CM) dynamics with drogue parachutes deployed were under-predicting the amount of damping seen in free-flight tests, an attach-point damping model was applied to the Orion system. A key hypothesis in this model is that the drogue parachutes' net load vector aligns with the CM drogue attachment point velocity vector. This assumption seems reasonable and has historically produced good results, but has never been experimentally verified. The wake of the CM influences the drogue parachutes, which makes performance predictions of the parachutes difficult. Many of these effects are not currently modeled in the simulations. A forced oscillation test of the CM with parachutes was conducted in the NASA LaRC 20-Ft Vertical Spin Tunnel (VST) to gather additional data to validate and refine the attach-point damping model. A second loads balance was added to the original Orion VST model to measure the drogue parachute loads independently of the CM. The objective of the test was to identify the contribution of the drogues to CM damping and provide additional information to quantify wake effects and the interactions between the CM and parachutes. The drogue parachute force vector was shown to be highly dependent on the CM wake characteristics. Based on these wind tunnel test data, the attach-point damping model was determined to be a sufficient approximation of the parachute dynamics in relationship to the CM dynamics for preliminary entry vehicle system design. More wake effects should be included to better model the system.
Evaluation of radiation damping using 3-D finite element models
International Nuclear Information System (INIS)
Vaughan, D.K.; Isenberg, J.
1983-01-01
The paper presents an analytic approach which is being used to quantify the contribution of radiation damping to overall system damping. The approach uses three-dimensional finite element techniques and can easily include details of site geology, foundation shape, and embedment depth. The approach involves performing free vibration response analyses for each soil-structure interaction (SSI) mode of interest. The structural model is specified without damping and, consequently, amplitude decay of the structure's free vibration response is a measure of the radiation damping characteristics of the soil-structure system for the particular deformational mode being investigated. The computational approach developed is highly efficient in order to minimize the impact of including three-dimensional geometry within the model. A new finite element code, FLEX, has been developed to represent the soil continuum. FLEX uses a highly optimized explicit time integration algorithm which takes advantage of parallel processing on vector machines, such as the CRAY 1 computer. A modal representation of the superstructure is used in combination with a substructuring approach to solve for the coupled response of the soil-structure system. This requires solving for numerical Green's functions for each degree-of-freedom of the foundation (assumed rigid). Once computed for a particular site and foundation, these Green's functions may be used within a convolution integral to represent the continuum forces on the foundation for any free vibration SSI response computation of any superstructure model. This analytic approach is applied to an investigation of the radiation damping coefficients for the first two fundamental SSI modes of the HDR containment structure. (orig./HP)
Identification of Damping from Structural Vibrations
DEFF Research Database (Denmark)
Bajric, Anela
Reliable predictions of the dynamic loads and the lifetime of structures are inﬂuenced by the limited accuracy concerning the level of structural damping. The mechanisms of damping cannot be derived analytically from ﬁrst principles, and in the design of structures the damping is therefore based...... on experience or estimated from measurements. This thesis consists of an extended summary and three papers which focus on enhanced methods for identiﬁcation of damping from random struc-tural vibrations. The developed methods are validated by stochastic simulations, experimental data and full-scale measurements...... which are representative of the vibrations in small and large-scale structures. The ﬁrst part of the thesis presents an automated procedure which is suitable for estimation of the natural frequencies and the modal damping ratios from random response of structures. The method can be incorporated within...
Discovery of Scattering Polarization in the Hydrogen Ly alpha Line of the Solar Disk Radiation
Czech Academy of Sciences Publication Activity Database
Kano, R.; Trujillo Bueno, J.; Winebarger, A.; Auchere, F.; Narukage, N.; Ishikawa, R.; Kobayashi, K.; Bando, T.; Katsukawa, Y.; Kubo, M.; Ishikawa, S.; Giono, G.; Hara, H.; Suematsu, Y.; Shimizu, T.; Sakao, T.; Tsuneta, S.; Ichimoto, K.; Goto, M.; Belluzzi, L.; Štěpán, Jiří; Asensio Ramos, A.; Sainz, R.M.; Champey, P.; Cirtain, J.; de Pontieu, B.; Casini, R.; Carlsson, M.
2017-01-01
Roč. 839, č. 1 (2017), L10/1-L10/6 ISSN 2041-8205 Institutional support: RVO:67985815 Keywords : vacuum-ultraviolet spectropolarimeter * transition region * chromosphere Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.522, year: 2016
The Ly Alpha Reference Sample. I. Survey Outline and First Results for Markarian 259
Czech Academy of Sciences Publication Activity Database
Ostlin, G.; Hayes, M.; Duval, F.; Sandberg, A.; Rivera-Thorsen, T.; Marquart, T.; Orlitová, Ivana; Adamo, A.; Melinder, J.; Guaita, L.; Atek, H.; Cannon, J.M.; Gruyters, P.; Herenz, E.Ch.; Kunth, D.; Laursen, P.; Más-Hesse, J. M.; Micheva, G.; Oti-Floranes, H.; Pardy, S.; Roth, M.; Schaerer, D.; Verhamme, A.
2014-01-01
Roč. 797, č. 1 (2014), 11/1-11/23 ISSN 0004-637X R&D Projects: GA ČR(CZ) GP14-20666P Institutional support: RVO:67985815 Keywords : cosmology: observations * galaxies: evolution * galaxies: individual: Mrk 259 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.993, year: 2014
Deep Ly alpha imaging of two z=2.04 GRB host galaxy fields
DEFF Research Database (Denmark)
Fynbo, J.P.U.; Møller, Per; Thomsen, Bente
2002-01-01
We report on the results of deep narrow-band Lyalpha and broad-band U and I imaging of the fields of two Gamma-Ray bursts at redshift z = 2.04 (GRB 000301C and GRB 000926). We find that the host galaxy of GRB 000926 is an extended (more than 2 arcsec), strong Lyalpha emitter with a rest-frame equ......We report on the results of deep narrow-band Lyalpha and broad-band U and I imaging of the fields of two Gamma-Ray bursts at redshift z = 2.04 (GRB 000301C and GRB 000926). We find that the host galaxy of GRB 000926 is an extended (more than 2 arcsec), strong Lyalpha emitter with a rest...... - I colour than the eastern component, suggesting the presence of at least some dust. We do not detect the host galaxy of GRB 000301C in neither Lyalpha emission nor in U and I broad-band images. The strongest limit comes from combining the narrow and U-band imaging where we infer a limit of U...
Frequency and temperature dependence of high damping elastomers
International Nuclear Information System (INIS)
Kulak, R.F.; Hughes, T.H.
1993-01-01
High damping steel-laminated elastomeric seismic isolation bearings are one of the preferred devices for isolating large buildings and structures. In the US, the current reference design for the Advanced Liquid Metal Reactor (ALMR) uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of high damping rubber and steel plates. They are typically designed for shear strains between 50 and 100% and are expected to sustain two to three times these levels for beyond design basis loading conditions. Elastomeric bearings are currently designed to provide a system frequency between 0.4 and 0.8 Hz and expected to operate between -20 and 40 degrees Centigrade. To assure proper performance of isolation bearings, it is necessary to characterize the elastomer's response under expected variations of frequency and temperature. The dynamic response of the elastomer must be characterized within the frequency range that spans the bearing acceptance test frequency, which may be as low as 0.005 Hz, and the design frequency. Similarly, the variation in mechanical characteristics of the elastomer must be determined over the design temperature range, which is between -20 and 40 degrees Centigrade. This paper reports on (1) the capabilities of a testing facility at ANL for testing candidate elastomers, (2) the variation with frequency and temperature of the stiffness and damping of one candidate elastomer, and (3) the effect of these variations on bearing acceptance testing criteria and on the choice of bearing design values for stiffness and damping
Analytical Solution and Physics of a Propellant Damping Device
Yang, H. Q.; Peugeot, John
2011-01-01
NASA design teams have been investigating options for "detuning" Ares I to prevent oscillations originating in the vehicle solid-rocket main stage from synching up with the natural resonance of the rest of the vehicle. An experimental work started at NASA MSFC center in 2008 using a damping device showed great promise in damping the vibration level of an 8 resonant tank. However, the mechanisms of the vibration damping were not well understood and there were many unknowns such as the physics, scalability, technology readiness level (TRL), and applicability for the Ares I vehicle. The objectives of this study are to understand the physics of intriguing slosh damping observed in the experiments, to further validate a Computational Fluid Dynamics (CFD) software in propellant sloshing against experiments with water, and to study the applicability and efficiency of the slosh damper to a full scale propellant tank and to cryogenic fluids. First a 2D fluid-structure interaction model is built to model the system resonance of liquid sloshing and structure vibration. A damper is then added into the above model to simulate experimentally observed system damping phenomena. Qualitative agreement is found. An analytical solution is then derived from the Newtonian dynamics for the thrust oscillation damper frequency, and a slave mass concept is introduced in deriving the damper and tank interaction dynamics. The paper will elucidate the fundamental physics behind the LOX damper success from the derivation of the above analytical equation of the lumped Newtonian dynamics. Discussion of simulation results using high fidelity multi-phase, multi-physics, fully coupled CFD structure interaction model will show why the LOX damper is unique and superior compared to other proposed mitigation techniques.
Air Damping in a Fan-Shaped Rotational Resonator with Comb Electrodes
Uchida, Yuki; Sugano, Koji; Tsuchiya, Toshiyuki; Tabata, Osamu; Ikehara, Tsuyoshi
We theoretically and experimentally evaluated the damping effect in a rotational resonator with a comb-drive actuator and sensor. The resonator was fabricated from an SOI wafer and has a fan-shaped mass. The underlying substrate was removed using back side deep reactive ion etching. One set of comb electrodes was attached to each side of the mass: one for electrostatic driving and the other for capacitive detection. In our theoretical analysis, the dynamics of the resonator were simplified so that they could be represented by a lumped system. In this lumped system, the damping coefficient was estimated by assuming the damping to be slide film damping and the air flow to be a Stokes flow. The phase shift due to the slide film damping of thick air layers was included in the lumped system. In the experimental evaluation, one side of the rotational combs was removed step-by-step and a half of the mass using a laser trimming tool so that the individual damping effects caused by the comb electrodes and mass could be determined quantitatively. We compared the experimental results with the results of the theoretical analysis and found that the difference in the damping coefficients between the experimental results and results of the theoretical analysis was less than 40%.
Sub-synchronous resonance damping using high penetration PV plant
Khayyatzadeh, M.; Kazemzadeh, R.
2017-02-01
The growing need to the clean and renewable energy has led to the fast development of transmission voltage-level photovoltaic (PV) plants all over the world. These large scale PV plants are going to be connected to power systems and one of the important subjects that should be investigated is the impact of these plants on the power system stability. Can large scale PV plants help to damp sub-synchronous resonance (SSR) and how? In this paper, this capability of a large scale PV plant is investigated. The IEEE Second Benchmark Model aggregated with a PV plant is utilized as the case study. A Wide Area Measurement System (WAMS) based conventional damping controller is designed and added to the main control loop of PV plant in order to damp the SSR and also investigation of the destructive effect of time delay in remote feedback signal. A new optimization algorithm called teaching-learning-based-optimization (TLBO) algorithm has been used for managing the optimization problems. Fast Furrier Transformer (FFT) analysis and also transient simulations of detailed nonlinear system are considered to investigate the performance of the controller. Robustness of the proposed system has been analyzed by facing the system with disturbances leading to significant changes in generator and power system operating point, fault duration time and PV plant generated power. All the simulations are carried out in MATLAB/SIMULINK environment.
Symmetries of the quantum damped harmonic oscillator
International Nuclear Information System (INIS)
Guerrero, J; López-Ruiz, F F; Aldaya, V; Cossío, F
2012-01-01
For the non-conservative Caldirola–Kanai system, describing a quantum damped harmonic oscillator, a couple of constant-of-motion operators generating the Heisenberg–Weyl algebra can be found. The inclusion of the standard time evolution generator (which is not a symmetry) as a symmetry in this algebra, in a unitary manner, requires a non-trivial extension of this basic algebra and hence of the physical system itself. Surprisingly, this extension leads directly to the so-called Bateman dual system, which now includes a new particle acting as an energy reservoir. In addition, the Caldirola–Kanai dissipative system can be retrieved by imposing constraints. The algebra of symmetries of the dual system is presented, as well as a quantization that implies, in particular, a first-order Schrödinger equation. As opposed to other approaches, where it is claimed that the spectrum of the Bateman Hamiltonian is complex and discrete, we obtain that it is real and continuous, with infinite degeneracy in all regimes. (paper)
Shape memory alloys as damping materials
International Nuclear Information System (INIS)
Humbeeck, J. van
2000-01-01
Shape memory alloys are gaining an increased interest as passive as well as active damping materials. This damping ability when applied in structural elements can lead to a better noise control, improved life time and even better performance of the envisaged tools. By passive damping, it is understood that the material converts a significant part of unwanted mechanical energy into heat. This mechanical energy can be a (resonance) vibration, impact loading or shock waves. This high damping capacity finds its origin in the thermoelastic martensitic phase due to the hysteretic mobility of martensite-variants or different phase interfaces. The damping capacity increases with increasing amplitude of the applied vibration or impact and is almost frequency independent. Special interest exists moreover for damping extreme large displacements by applying the mechanical hysteresis performed during pseudoelastic loading. This aspect is nowadays very strongly studied as a tool for protecting buildings against earthquakes in seismic active regions. Active damping can be obtained in hybrid composites by controlling the recovery stresses or strains of embedded shape memory alloy wires. This controls the internal energy fo a structure which allows controlled modal modification and tuning of the dynamical properties of structural elements. But also impact damage, acoustic radiation, dynamic shape control can be actively controlled. As a consequence improved fatigue-resistance, better performance and a longer lifetime of the structural elements can be obtained. (orig.)
Resistive Wall Instability in the NLC Main Damping Rings
International Nuclear Information System (INIS)
Wolski, Andrzej
2004-01-01
We study transverse coupled-bunch instabilities driven by the resistive-wall impedance in the NLC Main Damping Rings. We compare the growth rates of the different modes predicted by a simple theory using a simplified lattice model with the results of a detailed simulation that includes variation of the beta functions and the actual fill structure of the machine. We find that the results of the analytical calculations are in reasonable agreement with the simulations. We include a simple model of a bunch-by-bunch feedback system in the simulation to show that the instabilities can be damped by a feedback system having parameters that are realistic, and possibly conservative. The noise level on the feedback system pick-up must be low, to avoid driving random bunch-to-bunch jitter above the specified limit of 10 percent of the vertical beam size
Optimization of SMA layers in composite structures to enhance damping
Haghdoust, P.; Cinquemani, S.; Lecis, N.; Bassani, P.
2016-04-01
The performance of lightweight structures can be severely affected by vibration. New design concepts leading to lightweight, slender structural components can increase the vulnerability of the components to failure due to excessive vibration. The intelligent approach to address the problem would be the use of materials which are more capable in dissipating the energy due to their high value of loss factor. Among the different materials available to achieve damping, much attention has been attached to the use of shape memory alloys (SMAs) because of their unique microstructure, leading to good damping capacity. This work describes the design and optimization of a hybrid layered composite structure for the passive suppression of flexural vibrations in slender and light structures. Embedding the SMA layers in composite structure allows to combine different properties: the lightness of the base composite (e.g. fiber glass), the mechanical strength of the insert of metallic material and the relevant damping properties of SMA, in the martensitic phase. In particular, we put our attention on embedding the CuZnAl in the form of thin sheet in a layered composite made by glass fiber reinforced epoxy. By appropriately positioning of the SMA sheets so that they are subjected to the maximum curvature, the damping of the hybrid system can be considerably enhanced. Accordingly analytical method for evaluating the energy dissipation of the thin sheets with different shapes and patterns is developed and is followed by a shape optimization based on genetic algorithm. Eventually different configurations of the hybrid beam structure with different patterns of SMA layer are proposed and compared in the term of damping capacity.
Structural damping values as a function of dynamic response stress and deformation levels
International Nuclear Information System (INIS)
Stevenson, J.D.
1980-01-01
Damping as it is normally defined is the means by which the response motion of a structural system is reduced as the result of energy losses. However, as used in the context of nuclear plant design, the effects of changes in structural stiffness, geometry, support configuration, and modulus of elasticity are also usually lumped under the general heading of damping in current design methods. For convenience in structural design, damping in usually assumed as viscous in nature and in recognition of its use in modal response spectrum dynamic analysis is normally expressed as a percent of critical. In general, it should be understood that damping as used in design or analysis of nuclear plants is an experimentally determined factor which is used to make the results of linear elasticity analysis of dynamic systems agree reasonably well with observed experimental results. In this paper, damping data existing in the open literature applicable to nuclear power plant structures and equipment is summarized and statistically analyzed. Results of this analysis are used to develop damping trend curves which predict applicable damping values to be used in design at various levels of stress or deformation. (orig.)
Lifetime measurement of ATF damping ring
International Nuclear Information System (INIS)
Okugi, T.; Hayano, H.; Kubo, K.; Naito, T.; Terunuma, N.; Urakawa, J.; Zimmermann, F.
1998-06-01
The purpose of the ATF damping ring is the development of technologies for producing a low emittance beam required in future linear colliders such as JLC. The lifetime of the damping ring is very short (typically a few minutes). It is limited by elastic beam-gas scattering along with a small dynamic aperture, and by single intra-beam scattering (Touschek effect). The Touschek lifetime strongly depends upon the charge density of the beam, especially, the size of the vertical emittance. In this paper, the authors report the results of beam lifetime measurements in the ATF damping ring and the estimation of the vertical emittance from these measurements
A Resonant Damping Study Using Piezoelectric Materials
Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.
2008-01-01
Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.
Min, James B.; Harris, Donald L.; Ting, J. M.
2011-01-01
For advanced aerospace propulsion systems, development of ceramic matrix composite integrally-bladed turbine disk technology is attractive for a number of reasons. The high strength-to-weight ratio of ceramic composites helps to reduce engine weight and the one-piece construction of a blisk will result in fewer parts count, which should translate into reduced operational costs. One shortcoming with blisk construction, however, is that blisks may be prone to high cycle fatigue due to their structural response to high vibration environments. Use of ceramic composites is expected to provide some internal damping to reduce the vibratory stresses encountered due to unsteady flow loads through the bladed turbine regions. A goal of our research was to characterize the vibration viscous damping behavior of C/SiC composites. The vibration damping properties were measured and calculated. Damping appeared to decrease with an increase in the natural frequency. While the critical damping amount of approximately 2% is required for typical aerospace turbomachinery engines, the C/SiC damping at high frequencies was less than 0.2% from our study. The advanced high-performance aerospace propulsion systems almost certainly will require even more damping than what current vehicles require. A purpose of this paper is to review some work on C/SiC vibration damping by the authors for the NASA CMC turbine blisk development program and address an importance of the further investigation of the blade vibration damping characteristics on candidate CMC materials for the NASA s advanced aerospace turbomachinery engine systems.
Determination of the acoustic damping characteristics of an annular tail pipe
Boonen, Rene; Sas, Paul; Van den Bulck, Eric
2010-01-01
A damping device, consisting of an annular tail-pipe, has been developed. It is applicable in situations wherein acoustic damping is required in combination with low flow resistance. Examples are ventilation systems, turbo- engines, intake and exhaust systems for internal combustion engines. The device consists of a central tube surrounded by a narrow slit. The central tube has an acoustic mass which impedance increases with frequency. When the frequency has been increased sufficiently, a con...
Directory of Open Access Journals (Sweden)
Saleh M. Bamasak
2017-09-01
Full Text Available Wide Area Measurement System (WAMS can extend and effectively improve the power system stabilizers (PSS capability in damping the inter-area low frequency oscillations in interconnected bulk power systems. This paper proposes the implementation of Weighted Wide Area Damping Controller (WWADC in which weighted factors are introduced for each remote feedback signals. Modal analysis approach is implemented for the purpose of identifying the optimal location as well as the input signals’ optimal combination of WWADC. Based on the linearized model, Differential Evolution (DE algorithm is applied to search for optimal controller parameters and optimal weighted factors. The successful application of the proposed approach is achieved in two power networks; the two-area 4-machine system and the IEEE-39 bus 10-machine system. The analysis of the eigenvalue and non-linear time domain simulations indicate that damping the inter-area oscillations and improving the system stability irrespective of the severity and the location of the disturbances can be effectively achieved by WADC
Wind/PV Generation for Frequency Regulation and Oscillation Damping in the Eastern Interconnection
Energy Technology Data Exchange (ETDEWEB)
Liu, Yong [Univ. of Tennessee, Knoxville, TN (United States); Gracia, Jose R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hadley, Stanton W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Yilu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2013-12-01
This report presents the control of renewable energy sources, including the variable-speed wind generators and solar photovoltaic (PV) generators, for frequency regulation and inter-area oscillation damping in the U.S. Eastern Interconnection (EI). In this report, based on the user-defined wind/PV generator electrical control model and the 16,000-bus Eastern Interconnection dynamic model, the additional controllers for frequency regulation and inter-area oscillation damping are developed and incorporated and the potential contributions of renewable energy sources to the EI system frequency regulation and inter-area oscillation damping are evaluated.
Quantum chaos in nuclear single-particle motion and damping of giant resonances
International Nuclear Information System (INIS)
Pal, Santanu; Mukhopadhyay, Tapan
1995-01-01
The spectral statistics of single particle motion in deformed cavities with axial symmetry are presented. The single particle motion in the cavities considered are non-integrable and the systematics of the fluctuation measures of the spectra reveal a transition from regular to chaotic regime in the corresponding classical systems. Quantitative estimate of the degree of chaos enables us to introduce a correction factor to the one-body wall formula for the damping widths of isoscalar giant resonances. The damping widths calculated with this correction factor give much better agreement with experimental values than earlier calculations of one-body damping widths. (author). 21 refs., 5 figs
Nonlinear damping for vibration isolation of microsystems using shear thickening fluid
Iyer, S. S.; Vedad-Ghavami, R.; Lee, H.; Liger, M.; Kavehpour, H. P.; Candler, R. N.
2013-06-01
This work reports the measurement and analysis of nonlinear damping of micro-scale actuators immersed in shear thickening fluids (STFs). A power-law damping term is added to the linear second-order model to account for the shear-dependent viscosity of the fluid. This nonlinear model is substantiated by measurements of oscillatory motion of a torsional microactuator. At high actuation forces, the vibration velocity amplitude saturates. The model accurately predicts the nonlinear damping characteristics of the STF using a power-law index extracted from independent rheology experiments. This result reveals the potential to use STFs as adaptive, passive dampers for vibration isolation of microelectromechanical systems.
Tuning of damping controller for UPFC using quantum particle swarm optimizer
Energy Technology Data Exchange (ETDEWEB)
Shayeghi, H., E-mail: hshayeghi@gmail.co [Technical Engineering Department, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Shayanfar, H.A. [Center of Excellence for Power System Automation and Operation, Electrical Engineering Department, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Jalilzadeh, S.; Safari, A. [Technical Engineering Department, Zanjan University, Zanjan (Iran, Islamic Republic of)
2010-11-15
On the basis of the linearized Phillips-Herffron model of a single machine power system, we design optimally the unified power flow controller (UPFC) based damping controller in order to enhance power system low frequency oscillations. The problem of robustly UPFC based damping controller is formulated as an optimization problem according to the time domain-based objective function which is solved using quantum-behaved particle swarm optimization (QPSO) technique that has fewer parameters and stronger search capability than the particle swarm optimization (PSO), as well as is easy to implement. To ensure the robustness of the proposed damping controller, the design process takes into account a wide range of operating conditions and system configurations. The effectiveness of the proposed controller is demonstrated through non-linear time-domain simulation and some performance indices studies under various disturbance conditions of over a wide range of loading conditions. The results analysis reveals that the designed QPSO based UPFC controller has an excellent capability in damping power system low frequency oscillations in comparison with the designed classical PSO (CPSO) based UPFC controller and enhance greatly the dynamic stability of the power systems. Moreover, the system performance analysis under different operating conditions show that the {delta}{sub E} based damping controller is superior to the m{sub B} based damping controller.
Landau damping in bi-dust ion-acoustic waves
International Nuclear Information System (INIS)
Castro, E.; Puerta, J.; Martin, P.; Cereceda, C.
2006-01-01
Ion acoustic dust waves in a bi-dust plasma are analyzed in this paper. In order to model this system, we assume the existence of two different kinds of grains, each characterized by a different radius. Relative velocities between grains and charge fluctuations are neglected. In order to derive the dispersion relation of this system, we use the well known hybrid fluid-kinetic model, in which ions are treated kinetically and other species as fluids. In this plasma, waves with non-relative velocities between species leads to damped waves with frequency modes, defined by the grain radius. The induced damping ratio is studied as a function of the grain and ion densities. (Author)
Resonant Electromagnetic Shunt Damping of Flexible Structures
DEFF Research Database (Denmark)
Høgsberg, Jan Becker
2016-01-01
Electromagnetic transducers convert mechanical energy to electrical energy and vice versa. Effective passive vibration damping of flexible structures can therefore be introduced by shunting with an accurately calibrated resonant electrical network thatcontains a capacitor to create the desired...
Simplified Model of Nonlinear Landau Damping
International Nuclear Information System (INIS)
Yampolsky, N.A.; Fisch, N.J.
2009-01-01
The nonlinear interaction of a plasma wave with resonant electrons results in a plateau in the electron distribution function close to the phase velocity of the plasma wave. As a result, Landau damping of the plasma wave vanishes and the resonant frequency of the plasma wave downshifts. However, this simple picture is invalid when the external driving force changes the plasma wave fast enough so that the plateau cannot be fully developed. A new model to describe amplification of the plasma wave including the saturation of Landau damping and the nonlinear frequency shift is proposed. The proposed model takes into account the change of the plasma wave amplitude and describes saturation of the Landau damping rate in terms of a single fluid equation, which simplifies the description of the inherently kinetic nature of Landau damping. A proposed fluid model, incorporating these simplifications, is verified numerically using a kinetic Vlasov code.
Electron beam depolarization in a damping ring
International Nuclear Information System (INIS)
Minty, M.
1993-04-01
Depolarization of a polarized electron beam injected into a damping ring is analyzed by extending calculations conventionally applied to proton synchrotrons. Synchrotron radiation in an electron ring gives rise to both polarizing and depolarizing effects. In a damping ring, the beam is stored for a time much less than the time for self polarization. Spin flip radiation may therefore be neglected. Synchrotron radiation without spin flips, however, must be considered as the resonance strength depends on the vertical betatron oscillation amplitude which changes as the electron beam is radiation damped. An expression for the beam polarization at extraction is derived which takes into account radiation damping. The results are applied to the electron ring at the Stanford Linear Collider and are compared with numerical matrix formalisms
Damping Wiggler Study at KEK-ATF
Naito, Takashi; Honda, Yosuke; Korostelev, Maxim S; Kubo, Kiyoshi; Kuriki, Masao; Kuroda, Shigeru; Muto, Toshiya; Nakamura, Norio; Ross, Marc; Sakai, Hiroshi; Terunuma, Nobuhiro; Urakawa, Junji; Zimmermann, Frank
2005-01-01
The effects by damping wiggler magnets have been studied at KEK-ATF. The damping ring of the KEK-ATF is a 1.3 GeV storage ring capable of producing ultra-low emittance electron beams. It is significant issue to realize fast damping in the damping ring. The tuning method with 4 sets of wiggler was investigated for the ultra-low emittance beam. The performance on the beam quality, which is related to the transverse (x and y) and the longitudinal (z and dp/p), has been measured by the SR monitor, the laser wire, the streak camera and the energy spread monitor at the extraction line. We report on the operation condition and the measurement results.
Damping of type III solar radio bursts
International Nuclear Information System (INIS)
Levin, B.N.
1982-01-01
The meter- and decameter-wavelength damping of type III bursts may be attributable to stabilization of the Langmuir-wave instability of the fast-electron streams through excitation of cyclotron-branch plasma waves
Xie, Longhan; Li, Jiehong; Li, Xiaodong; Huang, Ledeng; Cai, Siqi
2018-01-01
Hydraulic dampers are used to decrease the vibration of a vehicle, where vibration energy is dissipated as heat. In addition to resulting in energy waste, the damping coefficient in hydraulic dampers cannot be changed during operation. In this paper, an energy-harvesting vehicle damper was proposed to replace traditional hydraulic dampers. The goal is not only to recover kinetic energy from suspension vibration but also to change the damping coefficient during operation according to road conditions. The energy-harvesting damper consists of multiple generators that are independently controlled by switches. One of these generators connects to a tunable resistor for fine tuning the damping coefficient, while the other generators are connected to a control and rectifying circuit, each of which both regenerates electricity and provides a constant damping coefficient. A mathematical model was built to investigate the performance of the energy-harvesting damper. By controlling the number of switched-on generators and adjusting the value of the external tunable resistor, the damping can be fine tuned according to the requirement. In addition to the capability of damping tuning, the multiple controlled generators can output a significant amount of electricity. A prototype was built to test the energy-harvesting damper design. Experiments on an MTS testing system were conducted, with results that validated the theoretical analysis. Experiments show that changing the number of switched-on generators can obviously tune the damping coefficient of the damper and simultaneously produce considerable electricity.
On the experimental prediction of the stability threshold speed caused by rotating damping
Vervisch, B.; Derammelaere, S.; Stockman, K.; De Baets, P.; Loccufier, M.
2016-08-01
An ever increasing demand for lighter rotating machinery and higher operating speeds results in a raised probability of instabilities. Rotating damping is one of the reasons, instability occurs. Rotating damping, or rotor internal damping, is the damping related to all rotating parts while non-rotating damping appearing in the non-rotating parts. The present study describes a rotating setup, designed to investigate rotating damping experimentally. An efficient experimental procedure is presented to predict the stability threshold of a rotating machine. The setup consists of a long thin shaft with a disk in the middle and clamped boundary conditions. The goal is to extract the system poles as a function of the rotating speed. The real parts of these poles are used to construct the decay rate plot, which is an indication for the stability. The efficiency of the experimental procedure relies on the model chosen for the rotating shaft. It is shown that the shaft behavior can be approximated by a single degree of freedom model that incorporates a speed dependent damping. As such low measurement effort and only one randomly chosen measurement location are needed to construct the decay rate plot. As an excitation, an automated impact hammer is used and the response is measured by eddy current probes. The proposed method yields a reliable prediction of the stability threshold speed which is validated through measurements.
Proceedings of Damping Volume 1 of 3
1993-06-01
paper. This work will present a passive piezoelectric damping implementation on ASTREX, a large space structure. The motivation behind this research is...Presented at Damping San Francisco, CA February 24-26, 1993 Motivation "• Accurate design of precision structures "* Computer modelling - Design...14) (KI f(0)/Fl,.) FRom equations (3) and (6), Young’s modulus of rubber specimen is written as; L Ea-K (15) A E - EJ(I+ PS4 ) (16) NONRESONANT TEST
International Nuclear Information System (INIS)
Edme, R.
1983-01-01
If a dynamic response analysis (harmonic excitation) is carried out with the modal method, the modal damping coefficients must be approximated to match the structural damping. The program ASKA-Damping, which also supplies an error assessment of the approximation, was developed for this purpose. The modal method and the direct method are applied to a test example and their results compared. It is suggested that the ASKA manufacturers extend the spectral earthquake response analysis to take these modal damping coefficients into account so that the results become less conservative. (orig.) [de
Blade couple connected by damping element with dry friction contacts
Czech Academy of Sciences Publication Activity Database
Pešek, Luděk; Půst, Ladislav
2014-01-01
Roč. 52, č. 3 (2014), s. 815-826 ISSN 1429-2955 R&D Projects: GA ČR GA101/09/1166 Institutional support: RVO:61388998 Keywords : dry friction * three masses system * damping of vibrations * irregular vibrations Subject RIV: BI - Acoustics Impact factor: 0.636, year: 2014 http://www.ptmts.org.pl/article.xsl?vol=52&no=3&page=815
Optimal Damping of Perturbations of Moving Thermoelastic Panel
Banichuk, N. V.; Ivanova, S. Yu.
2018-01-01
The translational motion of a thermoelastic web subject to transverse vibrations caused by initial perturbations is considered. It is assumed that a web moving with a constant translational velocity is described by the model of a thermoelastic panel simply supported at its ends. The problem of optimal damping of vibrations when applying active transverse actions is formulated. For solving the optimization problem, modern methods developed in control theory for systems with distributed parameters described by partial differential equations are used.
Human-in-the-loop evaluation of RMS Active Damping Augmentation
Demeo, Martha E.; Gilbert, Michael G.; Scott, Michael A.; Lepanto, Janet A.; Bains, Elizabeth M.; Jensen, Mary C.
1993-01-01
Active Damping Augmentation is the insertion of Controls-Structures Integration Technology to benefit the on-orbit performance of the Space Shuttle Remote Manipulator System. The goal is to reduce the vibration decay time of the Remote Manipulator System following normal payload maneuvers and operations. Simulation of Active Damping Augmentation was conducted in the realtime human-in-the-loop Systems Engineering Simulator at the NASA Johnson Space Center. The objective of this study was to obtain a qualitative measure of operational performance improvement from astronaut operators and to obtain supporting quantitative performance data. Sensing of vibratory motions was simulated using a three-axis accelerometer mounted at the end of the lower boom of the Remote Manipulator System. The sensed motions were used in a feedback control law to generate commands to the joint servo mechanisms which reduced the unwanted oscillations. Active damping of the Remote Manipulator System with an attached 3990 lb. payload was successfully demonstrated. Six astronaut operators examined the performance of an Active Damping Augmentation control law following single-joint and coordinated six-joint translational and rotational maneuvers. Active Damping Augmentation disturbance rejection of Orbiter thruster firings was also evaluated. Significant reductions in the dynamic response of the 3990 lb. payload were observed. Astronaut operators recommended investigation of Active Damping Augmentation benefits to heavier payloads where oscillations are a bigger problem (e.g. Space Station Freedom assembly operators).
Electromagnetic damping of neutron star oscillations
International Nuclear Information System (INIS)
McDermott, P.N.; Savedoff, M.P.; Van Horn, H.M.; Zweibel, E.G.; Hansen, C.J.
1984-01-01
Nonradial pulsations of a neutron star with a strong dipole magnetic field cause emission of electromagnetic radiation. Here we compute the power radiated to vacuum by neutron star g-mode pulsations and by torsional oscillations of the neutron star crust. For the low-order quadrupole fluid g-modes we have considered, we find electromagnetic damping to be considerably more effective than gravitational radiation. For example, a 0.5 M/sub sun/ neutron star with a core temperature approx.10 7 K has a g 1 -mode period of 371 ms; for this mode were find the electromagnetic damping time to be tau/sub FM/approx.0.3 s, assuming the surface magnetic field strength of the neutron star to be B 0 approx.10 12 gauss. This is considerably less than the corresponding gravitational radiation time tau/sub GR/approx.3 x 10 17 yr. For dipole g-mode oscillations, there is no gravitational radiation, but electromagnetic damping and ohmic dissipation are efficient damping mechanisms. For dipole torsional oscillations, we find that electromagnetic damping again dominates, with tau/sub EM/approx.5 yr. Among the cases we have studied, quadrupole torsional oscillations appear to be dominated by gravitational radiation damping, with tau/sub GR/approx.10 4 yr, as compared with tau/sub EM/approx.2 x 10 7 yr
Bryan's effect and anisotropic nonlinear damping
Joubert, Stephan V.; Shatalov, Michael Y.; Fay, Temple H.; Manzhirov, Alexander V.
2018-03-01
In 1890, G. H. Bryan discovered the following: "The vibration pattern of a revolving cylinder or bell revolves at a rate proportional to the inertial rotation rate of the cylinder or bell." We call this phenomenon Bryan's law or Bryan's effect. It is well known that any imperfections in a vibratory gyroscope (VG) affect Bryan's law and this affects the accuracy of the VG. Consequently, in this paper, we assume that all such imperfections are either minimised or eliminated by some known control method and that only damping is present within the VG. If the damping is isotropic (linear or nonlinear), then it has been recently demonstrated in this journal, using symbolic analysis, that Bryan's law remains invariant. However, it is known that linear anisotropic damping does affect Bryan's law. In this paper, we generalise Rayleigh's dissipation function so that anisotropic nonlinear damping may be introduced into the equations of motion. Using a mixture of numeric and symbolic analysis on the ODEs of motion of the VG, for anisotropic light nonlinear damping, we demonstrate (up to an approximate average), that Bryan's law is affected by any form of such damping, causing pattern drift, compromising the accuracy of the VG.
Equivalent Representation Form of Oscillators with Elastic and Damping Nonlinear Terms
Directory of Open Access Journals (Sweden)
Alex Elías-Zúñiga
2013-01-01
Full Text Available In this work we consider the nonlinear equivalent representation form of oscillators that exhibit nonlinearities in both the elastic and the damping terms. The nonlinear damping effects are considered to be described by fractional power velocity terms which provide better predictions of the dissipative effects observed in some physical systems. It is shown that their effects on the system dynamics response are equivalent to a shift in the coefficient of the linear damping term of a Duffing oscillator. Then, its numerical integration predictions, based on its equivalent representation form given by the well-known forced, damped Duffing equation, are compared to the numerical integration values of its original equations of motion. The applicability of the proposed procedure is evaluated by studying the dynamics response of four nonlinear oscillators that arise in some engineering applications such as nanoresonators, microresonators, human wrist movements, structural engineering design, and chain dynamics of polymeric materials at high extensibility, among others.
DEFF Research Database (Denmark)
Enemark, Søren; Santos, Ilmar F.
2016-01-01
nonlinear coupled dynamics of the rotor-bearing system. The nonlinear forces from the thermomechanical shape memory alloy springs and from the passive magnetic bearings are coupled to the rotor and bearing housing dynamics. The equations of motion describing rotor tilt and bearing housing lateral motion......Helical pseudoelastic shape memory alloy (SMA) springs are integrated into a dynamic system consisting of a rigid rotor supported by passive magnetic bearings. The aim is to determine the utility of SMAs for vibration attenuation via their mechanical hysteresis, and for adaptation of the dynamic...
International Nuclear Information System (INIS)
Severud, L.K.
1987-01-01
Simplified methods for predicting equivalent viscous damping are used to assess damping contributions due to piping inelastic plastic hinge action and support snubbers. These increments are compared to experimental findings from shake and snap-back tests of several pipe systems. Good correlations were found confirming the usefulness of the simplified methods
SOGI-based capacitor voltage feedback active damping in LCL-filtered grid converters
DEFF Research Database (Denmark)
Xin, Zhen; Wang, Xiongfei; Loh, Poh Chiang
2015-01-01
The capacitor voltage feedback active damping control is an attractive way to suppress LCL-filter resonance especially for the systems where the capacitor voltage is used for grid synchronization, since no extra sensors are added. The derivative is the core of the capacitor voltage feedback active...... derivative is more suited for capacitor voltage feedback active damping control. Experimental results validate the effectiveness of the proposed method....
Damping parameter study of a perforated plate with bias flow
Mazdeh, Alireza
One of the main impediments to successful operation of combustion systems in industrial and aerospace applications including gas turbines, ramjets, rocket motors, afterburners (augmenters) and even large heaters/boilers is the dynamic instability also known as thermo-acoustic instability. Concerns with this ongoing problem have grown with the introduction of Lean Premixed Combustion (LPC) systems developed to address the environmental concerns associated with the conventional combustion systems. The most common way to mitigate thermo-acoustic instability is adding acoustic damping to the combustor using acoustic liners. Recently damping properties of bias flow initially introduced to liners only for cooling purposes have been recognized and proven to be an asset in enhancing the damping effectiveness of liners. Acoustic liners are currently being designed using empirical design rules followed by build-test-improve steps; basically by trial and error. There is growing concerns on the lack of reliability associated with the experimental evaluation of the acoustic liners with small size apertures. The development of physics-based tools in assisting the design of such liners has become of great interest to practitioners recently. This dissertation focuses primarily on how Large-Eddy Simulations (LES) or similar techniques such as Scaled Adaptive Simulation (SAS) can be used to characterize damping properties of bias flow. The dissertation also reviews assumptions made in the existing analytical, semi-empirical, and numerical models, provides a criteria to rank order the existing models, and identifies the best existing theoretical model. Flow field calculations by LES provide good insight into the mechanisms that led to acoustic damping. Comparison of simulation results with empirical and analytical studies shows that LES simulation is a viable alternative to the empirical and analytical methods and can accurately predict the damping behavior of liners. Currently the
Investigation of superstructure damping identification for the HDR containment building
International Nuclear Information System (INIS)
Hsieh, B.J.; Kot, C.A.; Srinivasan, M.G.
1985-01-01
A method for the estimation of first mode structural damping, developed by other investigators, was applied to shaker test data of the HDR containment building. Due to inadequate precision in the experimental phase measurements no valid results could be obtained. Based on modal analysis it was also noted that for systems such as the HDR building, contributions of higher modes are not negligible as was assumed in the original approach. Therefore, the procedure for the determination of superstructure damping using experimental data was extended to include the effects of higher modes. The extended method does not lead to any higher order nonlinear equations than the first mode approximation and was found to be as simple to apply as the original approach
López-Ruiz, F. F.; Guerrero, J.; Aldaya, V.; Cossío, F.
2012-08-01
Using a quantum version of the Arnold transformation of classical mechanics, all quantum dynamical systems whose classical equations of motion are non-homogeneous linear second-order ordinary differential equations (LSODE), including systems with friction linear in velocity such as the damped harmonic oscillator, can be related to the quantum free-particle dynamical system. This implies that symmetries and simple computations in the free particle can be exported to the LSODE-system. The quantum Arnold transformation is given explicitly for the damped harmonic oscillator, and an algebraic connection between the Caldirola-Kanai model for the damped harmonic oscillator and the Bateman system will be sketched out.
International Nuclear Information System (INIS)
López-Ruiz, F F; Guerrero, J; Aldaya, V; Cossío, F
2012-01-01
Using a quantum version of the Arnold transformation of classical mechanics, all quantum dynamical systems whose classical equations of motion are non-homogeneous linear second-order ordinary differential equations (LSODE), including systems with friction linear in velocity such as the damped harmonic oscillator, can be related to the quantum free-particle dynamical system. This implies that symmetries and simple computations in the free particle can be exported to the LSODE-system. The quantum Arnold transformation is given explicitly for the damped harmonic oscillator, and an algebraic connection between the Caldirola-Kanai model for the damped harmonic oscillator and the Bateman system will be sketched out.
Design and Analysis of Robust Active Damping for LCL Filters using Digital Notch Filters
DEFF Research Database (Denmark)
Yao, Wenli; Yang, Yongheng; Zhang, Xiaobin
2017-01-01
Resonant poles of LCL filters may challenge the entire system stability especially in digital-controlled Pulse Width Modulation (PWM) inverters. In order to tackle the resonance issues, many active damping solutions have been reported. For instance, a notch filter can be employed to damp the reso......Resonant poles of LCL filters may challenge the entire system stability especially in digital-controlled Pulse Width Modulation (PWM) inverters. In order to tackle the resonance issues, many active damping solutions have been reported. For instance, a notch filter can be employed to damp...... the resonance, where the notch frequency should be aligned exactly to the resonant frequency of the LCL filter. However, parameter variations of the LCL filter as well as the time delay appearing in digital control systems will induce resonance drifting, and thus break this alignment, possibly deteriorating...... the original damping. In this paper, the effectiveness of the notch filter based active damping is firstly explored, considering the drifts of the resonant frequency. It is revealed that, when the resonant frequency drifts away from its nominal value, the phase lead or lag introduced by the notch filter may...
Radiation damping and decoherence in quantum electrodynamics
International Nuclear Information System (INIS)
Breuer, H.P.
2000-01-01
The processes of radiation damping and decoherence in quantum electrodynamics are studied from an open system's point of view. Employing functional techniques of field theory, the degrees of freedom of the radiation field are eliminated to obtain the influence phase functional which describes the reduced dynamics of the matter variables. The general theory is applied to the dynamics of a single electron in the radiation field. From a study of the wave packet dynamics a quantitative measure for the degree of decoherence, the decoherence function, is deduced. The latter is shown to describe the emergence of decoherence through the emission of bremsstrahlung caused by the relative motion of interfering wave packets. It is argued that this mechanism is the most fundamental process in quantum electrodynamics leading to the destruction of coherence, since it dominates for short times and because it is at work even in the electromagnetic field vacuum at zero temperature. It turns out that decoherence trough bremsstrahlung is very small for single electrons but extremely large for superpositions of many-particle states. (orig.)
Demountable damped cavity for HOM-damping in ILC superconducting accelerating cavities
Energy Technology Data Exchange (ETDEWEB)
Konomi, T., E-mail: konomi@ims.ac.jp [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Yasuda, F. [University of Tokyo, Bunkyo-ku, Tokyo 113-8654 (Japan); Furuta, F. [Laboratory for Elementary-Particle Physics, Cornell University, Ithaca, NY 14853 (United States); Saito, K. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)
2014-01-11
We have designed a new higher-order-mode (HOM) damper called a demountable damped cavity (DDC) as part of the R and D efforts for the superconducting cavity of the International Linear Collider (ILC). The DDC has two design concepts. The first is an axially symmetrical layout to obtain high damping efficiency. The DDC has a coaxial structure along the beam axis to realize strong coupling with HOMs. HOMs are damped by an RF absorber at the end of the coaxial waveguide and the accelerating mode is reflected by a choke filter mounted at the entrance of the coaxial waveguide. The second design concept is a demountable structure to facilitate cleaning, in order to suppress the Q-slope problem in a high field. A single-cell cavity with the DDC was fabricated to test four performance parameters. The first was frequency matching between the accelerating cavity and the choke filter. Since the bandwidth of the resonance frequency in a superconducting cavity is very narrow, there is a possibility that the accelerating field will leak to the RF absorber because of thermal shrinkage. The design bandwidth of the choke filter is 25 kHz. It was demonstrated that frequency matching adjusted at room temperature could be successfully maintained at 2 K. The second parameter was the performance of the demountable structure. At the joint, the magnetic field is 1/6 of the maximum field in the accelerating cavity. Ultimately, the accelerating field reached 19 MV/m and Q{sub 0} was 1.5×10{sup 10} with a knife-edge shape. The third parameter was field emission and multipacting. Although the choke structure has numerous parallel surfaces that are susceptible to the multipacting problem, it was found that neither field emission nor multipacting presented problems in both an experiment and simulation. The final parameter was the Q values of the HOM. The RF absorber adopted in the system is a Ni–Zn ferrite type. The RF absorber shape was designed based on the measurement data of permittivity
Demountable damped cavity for HOM-damping in ILC superconducting accelerating cavities
International Nuclear Information System (INIS)
Konomi, T.; Yasuda, F.; Furuta, F.; Saito, K.
2014-01-01
We have designed a new higher-order-mode (HOM) damper called a demountable damped cavity (DDC) as part of the R and D efforts for the superconducting cavity of the International Linear Collider (ILC). The DDC has two design concepts. The first is an axially symmetrical layout to obtain high damping efficiency. The DDC has a coaxial structure along the beam axis to realize strong coupling with HOMs. HOMs are damped by an RF absorber at the end of the coaxial waveguide and the accelerating mode is reflected by a choke filter mounted at the entrance of the coaxial waveguide. The second design concept is a demountable structure to facilitate cleaning, in order to suppress the Q-slope problem in a high field. A single-cell cavity with the DDC was fabricated to test four performance parameters. The first was frequency matching between the accelerating cavity and the choke filter. Since the bandwidth of the resonance frequency in a superconducting cavity is very narrow, there is a possibility that the accelerating field will leak to the RF absorber because of thermal shrinkage. The design bandwidth of the choke filter is 25 kHz. It was demonstrated that frequency matching adjusted at room temperature could be successfully maintained at 2 K. The second parameter was the performance of the demountable structure. At the joint, the magnetic field is 1/6 of the maximum field in the accelerating cavity. Ultimately, the accelerating field reached 19 MV/m and Q 0 was 1.5×10 10 with a knife-edge shape. The third parameter was field emission and multipacting. Although the choke structure has numerous parallel surfaces that are susceptible to the multipacting problem, it was found that neither field emission nor multipacting presented problems in both an experiment and simulation. The final parameter was the Q values of the HOM. The RF absorber adopted in the system is a Ni–Zn ferrite type. The RF absorber shape was designed based on the measurement data of permittivity and
DEFF Research Database (Denmark)
Hagerhed, L.; Bornehag, Carl-Gustaf; Sundell, Jan
2002-01-01
Questionnaire data on 8681 dwellings included in the Swedish study "Dampness in Buildings and Health" have been analysed for associations between dampness indicators, perceptions of indoor air quality and building characteristics such as time of construction, type of ventilation and type of found......Questionnaire data on 8681 dwellings included in the Swedish study "Dampness in Buildings and Health" have been analysed for associations between dampness indicators, perceptions of indoor air quality and building characteristics such as time of construction, type of ventilation and type...... of "Dry air" in 17.3 and 33.7% respectively. Older buildings and the use of natural ventilation were associated with increased frequency of dampness indicators as well as to increased frequencies of complaints on bad indoor air quality....
Power Oscillation Damping from VSC-HVDC Connected Offshore Wind Power Plants
DEFF Research Database (Denmark)
Zeni, Lorenzo; Eriksson, Robert; Goumalatsos, Spyridon
2016-01-01
The implementation of power oscillation damping service on offshore wind power plants connected to onshore grids by voltage-source-converter-based high voltage direct current transmission is discussed. Novel design guidelines for damping controllers on voltage-source converters and wind power plant...... regarding real wind power plants are discussed: 1) robustness against control/communication delays; 2) limitations due to mechanical resonances in wind turbine generators; 3) actual capability of wind power plants to provide damping without curtailing production; and 4) power-ramp rate limiters....... controllers are derived, using phasor diagrams and a test network model and are then verified on a generic power system model. The effect of voltage regulators is analyzed, which is important for selecting the most robust damping strategy. Furthermore, other often disregarded practical implementation aspects...
Symbolic-Numerical Modeling of the Influence of Damping Moments on Satellite Dynamics
Gutnik, Sergey A.; Sarychev, Vasily A.
2018-02-01
The dynamics of a satellite on a circular orbit under the influence of gravitational and active damping torques, which are proportional to the projections of the angular velocity of the satellite, is investigated. Computer algebra Gröbner basis methods for the determination of all equilibrium orientations of the satellite in the orbital coordinate system with given damping torque and given principal central moments of inertia were used. The conditions of the equilibria existence depending on three damping parameters were obtained from the analysis of the real roots of the algebraic equations spanned by the constructed Gröbner basis. Conditions of asymptotic stability of the satellite equilibria and the transition decay processes of the spatial oscillations of the satellite at different damping parameters have also been obtained.
Coupled oscillators in identification of nonlinear damping of a real parametric pendulum
Olejnik, Paweł; Awrejcewicz, Jan
2018-01-01
A damped parametric pendulum with friction is identified twice by means of its precise and imprecise mathematical model. A laboratory test stand designed for experimental investigations of nonlinear effects determined by a viscous resistance and the stick-slip phenomenon serves as the model mechanical system. An influence of accurateness of mathematical modeling on the time variability of the nonlinear damping coefficient of the oscillator is proved. A free decay response of a precisely and imprecisely modeled physical pendulum is dependent on two different time-varying coefficients of damping. The coefficients of the analyzed parametric oscillator are identified with the use of a new semi-empirical method based on a coupled oscillators approach, utilizing the fractional order derivative of the discrete measurement series treated as an input to the numerical model. Results of application of the proposed method of identification of the nonlinear coefficients of the damped parametric oscillator have been illustrated and extensively discussed.
Unwrapped phase inversion with an exponential damping
Choi, Yun Seok
2015-07-28
Full-waveform inversion (FWI) suffers from the phase wrapping (cycle skipping) problem when the frequency of data is not low enough. Unless we obtain a good initial velocity model, the phase wrapping problem in FWI causes a result corresponding to a local minimum, usually far away from the true solution, especially at depth. Thus, we have developed an inversion algorithm based on a space-domain unwrapped phase, and we also used exponential damping to mitigate the nonlinearity associated with the reflections. We construct the 2D phase residual map, which usually contains the wrapping discontinuities, especially if the model is complex and the frequency is high. We then unwrap the phase map and remove these cycle-based jumps. However, if the phase map has several residues, the unwrapping process becomes very complicated. We apply a strong exponential damping to the wavefield to eliminate much of the residues in the phase map, thus making the unwrapping process simple. We finally invert the unwrapped phases using the back-propagation algorithm to calculate the gradient. We progressively reduce the damping factor to obtain a high-resolution image. Numerical examples determined that the unwrapped phase inversion with a strong exponential damping generated convergent long-wavelength updates without low-frequency information. This model can be used as a good starting model for a subsequent inversion with a reduced damping, eventually leading to conventional waveform inversion.
Damping of Quasi-stationary Waves Between Two Miscible Liquids
Duval, Walter M. B.
2002-01-01
Two viscous miscible liquids with an initially sharp interface oriented vertically inside a cavity become unstable against oscillatory external forcing due to Kelvin-Helmholtz instability. The instability causes growth of quasi-stationary (q-s) waves at the interface between the two liquids. We examine computationally the dynamics of a four-mode q-s wave, for a fixed energy input, when one of the components of the external forcing is suddenly ceased. The external forcing consists of a steady and oscillatory component as realizable in a microgravity environment. Results show that when there is a jump discontinuity in the oscillatory excitation that produced the four-mode q-s wave, the interface does not return to its equilibrium position, the structure of the q-s wave remains imbedded between the two fluids over a long time scale. The damping characteristics of the q-s wave from the time history of the velocity field show overdamped and critically damped response; there is no underdamped oscillation as the flow field approaches steady state. Viscous effects serve as a dissipative mechanism to effectively damp the system. The stability of the four-mode q-s wave is dependent on both a geometric length scale as well as the level of background steady acceleration.
Thermal Degradation and Damping Characteristic of UV Irradiated Biopolymer
Directory of Open Access Journals (Sweden)
Anika Zafiah M. Rus
2015-01-01
Full Text Available Biopolymer made from renewable material is one of the most important groups of polymer because of its versatility in application. In this study, biopolymers based on waste vegetable oil were synthesized and cross-link with commercial polymethane polyphenyl isocyanate (known as BF. The BF was compressed by using hot compression moulding technique at 90°C based on the evaporation of volatile matter, known as compress biopolymer (CB. Treatment with titanium dioxide (TiO2 was found to affect the physical property of compressed biopolymer composite (CBC. The characterization of thermal degradation, activation energy, morphology structure, density, vibration, and damping of CB were determined after UV irradiation exposure. This is to evaluate the photo- and thermal stability of the treated CB or CBC. The vibration and damping characteristic of CBC samples is significantly increased with the increasing of UV irradiation time, lowest thickness, and percentages of TiO2 loading at the frequency range of 15–25 Hz due to the potential of the sample to dissipate energy during the oscillation harmonic system. The damping property of CBC was improved markedly upon prolonged exposure to UV irradiation.
Damping of wind turbine tower vibrations
DEFF Research Database (Denmark)
Brodersen, Mark Laier; Pedersen, Mikkel Melters
Damping of wind turbine vibrations by supplemental dampers is a key ingredient for the continuous use of monopiles as support for offshore wind turbines. The present thesis consists of an extended summary with four parts and appended papers [P1-P4] concerning novel strategies for damping of tower...... dominated vibrations.The first part of the thesis presents the theoretical framework for implementation of supplemental dampers in wind turbines. It is demonstrated that the feasibility of installing dampers at the bottom of the tower is significantly increased when placing passive or semiactive dampers...... in a stroke amplifying brace, which amplifies the displacement across the damper and thus reduces the desired level of damper force. For optimal damping of the two lowest tower modes, a novel toggle-brace concept for amplifying the bending deformation of the tower is presented. Numerical examples illustrate...
International Nuclear Information System (INIS)
Jeon, Jin Young
2009-01-01
This paper presents a new acoustic radiation optimization method for a vibrating panel-like structure with a passive piezoelectric shunt damping system in order to minimize well-radiating modes generated from the panel. The optimization method is based on an idea of using the p-version finite element method(p-version FEM), the boundary element method(BEM), and the particle swarm optimization algorithm(PSOA). Optimum embossment design for the vibrating panel using the PSOA is first investigated in order to minimize noise radiation over a frequency range of interest. The optimum embossment design works as a kind of stiffener so that well-radiating natural modes are shifted up with some degrees. The optimized panel, however, may still require additional damping for attenuating the peak acoustic amplitudes. A passive shunt damping system is thus employed to additionally damp the well-radiating modes from the optimized panel. To numerically evaluate the acoustic multiple-mode damping capability by a shunt damping system, the integrated p-version FEM/BEM for the panel with the shunt damping system is modeled and developed by MATLAB. Using the PSOA, the optimization technique for the optimal multiple-mode shunt damper is investigated in order to achieve the optimum damping performance for the well-radiating modes simultaneously. Also, the acoustic damping performance of the shunt damping circuit in the acoustic environment is demonstrated numerically and experimentally with respect to the realistically sized panel. The simulated result shows a good agreement with that of the experimental result
Directory of Open Access Journals (Sweden)
Walter G. Land
2015-05-01
Full Text Available This article is the second part of a review that addresses the role of damage-associated molecular patterns (DAMPs in human diseases by presenting examples of traumatic (systemic inflammatory response syndrome, cardiovascular (myocardial infarction, metabolic (type 2 diabetes mellitus, neurodegenerative (Alzheimer’s disease, malignant and infectious diseases. Various DAMPs are involved in the pathogenesis of all these diseases as they activate innate immune machineries including the unfolded protein response and inflammasomes. These subsequently promote sterile autoinflammation accompanied, at least in part, by subsequent adaptive autoimmune processes. This review article discusses the future role of DAMPs in routine practical medicine by highlighting the possibility of harnessing and deploying DAMPs either as biomarkers for the appropriate diagnosis and prognosis of diseases, as therapeutics in the treatment of tumours or as vaccine adjuncts for the prophylaxis of infections. In addition, this article examines the potential for developing strategies aimed at mitigating DAMPs-mediated hyperinflammatory responses, such as those seen in systemic inflammatory response syndrome associated with multiple organ failure.
Single isotope fractionation of (16)O(-) implications for early history of solar system
Arrhenius, G.
1980-01-01
Chemical fractionation processes are investigated with emphasis on selective single isotope fractionation in polyisotopic systems, particularly in oxygen. The related temperature parameters of meteoritic condensates and of their source medium are investigated by a thermometric method that is independent of assumptions regarding temperatures and pressures in the solar nebula. The crucial nonlinear chemical fractionation of O-16 was demonstrated experimentally. The effect was achieved in condensed CO2 formed from CO with C-12 O-16 selectively excited by H Ly alpha. The effect was verified by mass spectrometric measurements. The meteorite paleotemperature estimates were advanced from defining only thermal exposure to evaluating time and temperature independently. Grain temperatures at condensation of refractory inclusion materials are indicated to be less than 900 K in agreement with radiation temperature considerations and observations in circumstellar dust shells.
Directory of Open Access Journals (Sweden)
Yanfeng Ma
2018-05-01
Full Text Available Large-scale wind power interfacing to the power grid has an impact on the stability of the power system. However, with an additional damping controller of the wind generator, new ways for improving system damping and suppressing the low frequency oscillation (LFO of power systems can be put forward. In this paper, an active-reactive power additional damping controller based on active disturbance rejection control (ADRC is proposed. In order to improve the precision of the controller, the theory of data driven control is adopted, using the numerical algorithms for subspace state space system identification (N4SID to obtain the two order model of the ADRC controlled object. Based on the identification model, the ADRC additional damping controller is designed. Taking a 2-area 4-machine system containing the doubly fed induction generator (DFIG wind farm as an example, it is verified that the active-reactive additional damping controller designed in this paper performs well in suppressing negative-damping LFO and forced power oscillation. When the operation state of the power system changes, it can still restrain the LFO effectively, showing stronger robustness and better effectiveness compared to the traditional proportional–integral–derivative (PID additional damping controller.
Variable stiffness and damping MR isolator
Energy Technology Data Exchange (ETDEWEB)
Zhang, X Z; Wang, X Y; Li, W H; Kostidis, K [University of Wollongong, School of Mechanical, Materials and Mechatronic Engineering, NSW 2522 (Australia)], E-mail: weihuali@uow.edu.au
2009-02-01
This paper presents the development of a magnetorheological (MR) fluid-based variable stiffness and damping isolator for vibration suppressions. The MR fluid isolator used a sole MR control unit to achieve the variable stiffness and damping in stepless and relative large scope. A mathematical model of the isolator was derived, and a prototype of the MR fluid isolator was fabricated and its dynamic behavior was measured in vibration under various applied magnetic fields. The parameters of the model under various magnetic fields were identified and the dynamic performances of isolator were evaluated.
Modulated Langmuir waves and nonlinear Landau damping
International Nuclear Information System (INIS)
Yajima, Nobuo; Oikawa, Masayuki; Satsuma, Junkichi; Namba, Chusei.
1975-01-01
The nonlinear Schroedinger euqation with an integral term, iusub(t)+P/2.usub(xx)+Q/u/ 2 u+RP∫sub(-infinity)sup(infinity)[/u(x',t)/ 2 /(x-x')]dx'u=0, which describes modulated Langmuir waves with the nonlinear Landau damping effect, is solved by numerical calculations. Especially, the effects of nonlinear Landau damping on solitary wave solutions are studied. For both cases, PQ>0 and PQ<0, the results show that the solitary waves deform in an asymmetric way changing its velocity. (auth.)
Damping of multispan heat exchanger tubes. Pt. 1: in gases
International Nuclear Information System (INIS)
Pettigrew, M.J.; Goyder, H.G.D.; Qiao, Z.L.; Axisa, F.
1986-07-01
Flow-induced vibration analyses of heat exchanger tubes require the knowledge of damping. This paper treats the question of damping on multispan heat exchanger tubes in air and gases. The different energy dissipation mechanisms that contribute to tube damping are discussed. The available experimental data are reviewed and analysed. We find that the main damping mechanism in gases is friction between tube and tube-supports. Damping is strongly related to tube-support thickness. Damping values are recommended for design purposes. This study is interesting in the nuclear industry for it often uses heat exchangers
Spectral damping scaling factors for shallow crustal earthquakes in active tectonic regions
Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Campbell, Kenneth; Abrahamson, Norman; Silva, Walter
2012-01-01
Ground motion prediction equations (GMPEs) for elastic response spectra, including the Next Generation Attenuation (NGA) models, are typically developed at a 5% viscous damping ratio. In reality, however, structural and non-structural systems can have damping ratios other than 5%, depending on various factors such as structural types, construction materials, level of ground motion excitations, among others. This report provides the findings of a comprehensive study to develop a new model for a Damping Scaling Factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE to spectral ordinates with damping ratios between 0.5 to 30%. Using the updated, 2011 version of the NGA database of ground motions recorded in worldwide shallow crustal earthquakes in active tectonic regions (i.e., the NGA-West2 database), dependencies of the DSF on variables including damping ratio, spectral period, moment magnitude, source-to-site distance, duration, and local site conditions are examined. The strong influence of duration is captured by inclusion of both magnitude and distance in the DSF model. Site conditions are found to have less significant influence on DSF and are not included in the model. The proposed model for DSF provides functional forms for the median value and the logarithmic standard deviation of DSF. This model is heteroscedastic, where the variance is a function of the damping ratio. Damping Scaling Factor models are developed for the “average” horizontal ground motion components, i.e., RotD50 and GMRotI50, as well as the vertical component of ground motion.
Pipe damping: experimental results from laboratory tests in the seismic frequency range
International Nuclear Information System (INIS)
Ware, A.G.; Arendts, J.G.
1986-06-01
The Idaho National Engineering Laboratory (INEL) has been conducting a research program to assist the United States Nuclear Regulatory Commission (USNRC) in determining best-estimate damping values for the seismic analysis of nuclear piping systems. As part of this program, a 5-in. piping system was tested by the INEL, and data from USNRC/EPRI piping vibration tests at the ANCO Engineers facility were evaluated. These systems were subjected to various types of excitation methods and magnitudes, the support configurations were varied, and the effects of pipe insulation and internal pressure were investigated on the INEL system. The INEL has used several different methods to reduce the data to determine the damping in both these piping systems under the various test conditions. It was concluded that at representative seismic excitation levels, pressure was not a contributing factor, but the supports, insulation, and magnitude of response all were major influences contributing to damping. These tests are part of the ongoing program to determine how various parameters and data reduction methods affect piping system damping. The evaluation of all relevant test results, including these two series, will potentially lead to revised damping guidelines for the seismic analysis of nuclear plants, making them safer, less costly, and easier to inspect and maintain. The test results as well as accompanying evaluations and recommendations are presented in this report. 27 refs., 72 figs., 13 tabs
Directory of Open Access Journals (Sweden)
Dmitrii A. Oshmarin
2016-09-01
Full Text Available In technical applications it takes place the problem of vibration damping in certain regions of the structure, at the location of optical sensors for instance, at any external dynamic excitations with no mass increase and no changes in spectral portrait. In order to solve these problems it is widespread the use of special damping devices: piezoelectric elements connected to external electric circuits and attached to the structure. It became possible due to piezoelectric effect, which provides transformation of part of energy of vibrations into electric one, which is dissipated in external electric circuit. So that by using appropriate electric circuits one may dissipate internal energy and therefore reduce structural vibrations in definite frequency range. As a rule, external circuit of single branch, which shunts single piezoelectric element, allows vibration damping on one certain frequency. Due to the fact, that practical applications usually include requirements of damping of several modes by one and the same technical devices, the problem of multimodal vibration damping in smart-structures is rather acute. The objective of this paper is the study of possibility of vibration damping on several modes by using single external series RL-circuit, connected to electrodes of single piezoelectric element on the basis of solution of problems on natural and forced steady-state vibrations of electroelastic systems with external electric circuits.
Damping and fluidelastic instability in two-phase cross-flow heat exchanger tube arrays
Moran, Joaquin E.
flux, and its dependency is a function of void fraction. A dimensional analysis was carried out to investigate the relationship between damping and two-phase flow related parameters. As a result, the inclusion of surface tension in the form of the Capillary number appears to be useful when combined with the two-phase component of the damping ratio (interfacial damping). A strong dependence of damping on flow regime was observed when plotting the interfacial damping versus the void fraction, introducing an improvement over the previous result obtained by normalizing the two-phase damping, which does not exhibit this behaviour. The interfacial velocity model was selected to represent the fluidelastic data in two-phase experiments, due to the inclusion of the tube array geometry and density ratio effects, which does not exist for the pitch velocity approach. An essential component in reliably establishing the velocity threshold for fluidelastic instability, is a measure of the energy dissipation available in the system to balance the energy input from the flow. The present analysis argues that the damping in-flow is not an appropriate measure and demonstrates that the use of quiescent fluid damping provides a better measure of the energy dissipation, which produces a much more logical trend in the stability behaviour. This value of damping, combined with the RAD density and the interfacial velocity, collapses the available data well and provides the expected trend of two-phase flow stability data over the void fraction range from liquid to gas flows. The resulting stability maps represent a significant improvement over existing maps for predicting fluidelastic instability of tube bundles in two-phase flows. This result also tends to confirm the hypothesis that the basic mechanism of fluidelastic instability is the same for single and two-phase flows.
Evaluating damping elements for two-stage suspension vehicles
Directory of Open Access Journals (Sweden)
Ronald M. Martinod R.
2012-01-01
Full Text Available The technical state of the damping elements for a vehicle having two-stage suspension was evaluated by using numerical models based on the multi-body system theory; a set of virtual tests used the eigenproblem mathematical method. A test was developed based on experimental modal analysis (EMA applied to a physical system as the basis for validating the numerical models. The study focused on evaluating vehicle dynamics to determine the influence of the dampers’ technical state in each suspension state.
Use of electro-magnetic damping for vibration control
DEFF Research Database (Denmark)
Stein, George Juraj; Darula, Radoslav; Sorokin, Sergey
2012-01-01
to introduce additional electromagnetic damping into vibrating mechanical system. The hysteretic losses and eddy currents are included in the model, to take into account more realistic dynamic behaviour of the system. The mathematical model of the controller is derived using lumped parameter approach......Vibration of machines is an unwanted phenomenon, and it is usually of interest to eliminate it. There are various means to be used in order to reach the goal, where the utilization of the electromagnet augmented by an external shunt circuit is analyzed in the paper. The magnetic force is used...
Damping Inter-area Oscillations using Static Synchronous Series Compensator (SSSC)
DEFF Research Database (Denmark)
Su, Chi; Chen, Zhe
2011-01-01
Static synchronous series compensator (SSSC) has the ability to emulate a reactance in series with the connected transmission line. When fed with some supplementary signals from the connected system, SSSC is able to participate in the power system inter-area oscillation damping by changing...... the compensated reactance. This paper analyses the influence of SSSC on power system small signal stability. A SSSC damping controller scheme is presented and discussed. In DIgSILENT PowerFactory software, modal analysis and time-domain simulation are conducted in a single-machine infinite bus system model...... and a four-machine two-area test system model to verify and improve the damping controller scheme....
Dry friction damping couple at high frequencies
Czech Academy of Sciences Publication Activity Database
Půst, Ladislav; Pešek, Luděk; Košina, Jan; Radolfová, Alena
2014-01-01
Roč. 8, č. 1 (2014), s. 91-100 ISSN 1802-680X Institutional support: RVO:61388998 Keywords : dry friction * damping * high frequencies Subject RIV: BI - Acoustics http://www.kme.zcu.cz/acm/acm/article/view/239/265
Chiral damping of magnetic domain walls
Jué , Emilie; Safeer, C. K.; Drouard, Marc; Lopez, Alexandre; Balint, Paul; Buda-Prejbeanu, Liliana; Boulle, Olivier; Auffret, Stephane; Schuhl, Alain; Manchon, Aurelien; Miron, Ioan Mihai; Gaudin, Gilles
2015-01-01
Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics1, current-induced spin–orbit torques2, 3, 4, 5, 6, 7 and some topological magnetic structures8, 9, 10, 11, 12. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii–Moriya interaction (DMI) exhibit identical spatial symmetry13, 14, 15, 16, 17, 18, 19. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. 20).
Piezoelectric RL shunt damping of flexible structures
DEFF Research Database (Denmark)
Høgsberg, Jan Becker; Krenk, Steen
2015-01-01
in the present analysis is based on equal damping of the two modes associated with the resonant vibration form of the structure. An important result of the presented calibration procedure is the explicit inclusion of a quasi-static contribution from the non-resonant vibration modes of the structure via a single...
Chiral damping of magnetic domain walls
Jué, Emilie
2015-12-21
Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics1, current-induced spin–orbit torques2, 3, 4, 5, 6, 7 and some topological magnetic structures8, 9, 10, 11, 12. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii–Moriya interaction (DMI) exhibit identical spatial symmetry13, 14, 15, 16, 17, 18, 19. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. 20).
Active damping based on decoupled collocated control
Holterman, J.; de Vries, Theodorus J.A.; Auer, Frank; Gardonio, P.; Rafaely, B.
2002-01-01
High-precision machines typically suffer from small but persistent vibrations. As it is difficult to damp these vibrations by passive means, research at the Drebbel Institute at the University of Twente is aimed at the development of an active structural element that can be used for vibration
BNS damping of beam breakup instability
International Nuclear Information System (INIS)
Stupakov, G.V.
1997-08-01
The author studies BNS damping of the beam breakup instability in a simple model assuming a constant beam energy, flat bunch distribution, and a smooth transverse focusing. The model allows an analytic solution for a constant and linear wake functions. Scaling dimensionless parameters are derived and the beam dynamics is illustrated for the range of parameters relevant to the Stanford Linear Collider
The DAMPE silicon–tungsten tracker
Energy Technology Data Exchange (ETDEWEB)
Azzarello, P., E-mail: philipp.azzarello@unige.ch [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Ambrosi, G. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Asfandiyarov, R. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Bernardini, P. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare Sezione di Lecce, Lecce (Italy); Bertucci, B.; Bolognini, A. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Cadoux, F. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Caprai, M. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); De Mitri, I. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento, Lecce (Italy); Istituto Nazionale di Fisica Nucleare Sezione di Lecce, Lecce (Italy); Domenjoz, M. [Département de Physique Nucléaire et Corpusculaire, University of Geneva, Geneva (Switzerland); Dong, Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China); Duranti, M. [Istituto Nazionale di Fisica Nucleare Sezione di Perugia, Perugia (Italy); Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Fan, R. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China); and others
2016-09-21
The DArk Matter Particle Explorer (DAMPE) is a spaceborne astroparticle physics experiment, launched on 17 December 2015. DAMPE will identify possible dark matter signatures by detecting electrons and photons in the 5 GeV–10 TeV energy range. It will also measure the flux of nuclei up to 100 TeV, for the study of the high energy cosmic ray origin and propagation mechanisms. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon–tungsten tracker–converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is composed of six tracking planes of 2 orthogonal layers of single-sided micro-strip detectors, for a total detector surface of ca. 7 m{sup 2}. The STK has been extensively tested for space qualification. Also, numerous beam tests at CERN have been done to study particle detection at silicon module level, and at full detector level. After description of the DAMPE payload and its scientific mission, we will describe the STK characteristics and assembly. We will then focus on some results of single ladder performance tests done with particle beams at CERN.
Kicker for the SLC electron damping ring
International Nuclear Information System (INIS)
Bartelson, L.; Crawford, C.; Dinkel, J.; Kerns, Q.; Howell, J.; Snowdon, S.; Walton, J.
1987-01-01
The SLC electron damping ring requires two kickers each providing a 5 mr kick at 1.2 GEV to pairs of electron bunches spaced 61.63 nsec apart. The exact shape of the kick is unimportant, but the specification applies to the field the bunches see
Factors controlling superelastic damping capacity of SMAs
Czech Academy of Sciences Publication Activity Database
Heller, Luděk; Šittner, Petr; Pilch, Jan; Landa, Michal
2009-01-01
Roč. 18, 5-6 (2009), 603-611 ISSN 1059-9495 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20760514 Keywords : shape memory alloys * superelastic damping * thermomechanical testing Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.592, year: 2009
Spatial Damping of Linear Compressional Magnetoacoustic Waves ...
Indian Academy of Sciences (India)
The uncertainty in the radiative relaxation time, how- ever, does .... For spatial damping, we take ω to be real and k to be complex as kR +ikI . The disper- ... bances may travel up in the solar atmosphere through the magnetic field lines that are.
Moderate resolution spectrophotometry of high redshift quasars
Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.
1991-01-01
A uniform set of photometry and high signal-to-noise moderate resolution spectroscopy of 33 quasars with redshifts larger than 3.1 is presented. The sample consists of 17 newly discovered quasars (two with redshifts in excess of 4.4) and 16 sources drawn from the literature. The objects in this sample have r magnitudes between 17.4 and 21.4; their luminosities range from -28.8 to -24.9. Three of the 33 objects are broad absorption line quasars. A number of possible high redshift damped Ly-alpha systems were found.
A review of experimental soil-structure interaction damping
International Nuclear Information System (INIS)
Tsai, N.C.
1981-01-01
In soil-structure interaction analysis, the foundation soil is usually represented by impedance springs and dampers. The impedance damping includes the effect of both the material damping and the radiation damping. Because the impedance theory normally assumes a rigid structural base and an elastic bond between the soil and structure, it is generally held that the radiation damping has been overestimated by the theory. There are some published information on the dynamic tests of footings and structures that allow direct or indirect assessments of the validity of the analytical radiation damping. An overview of such information is presented here. Based on these limited test data, it is concluded that for horizontal soil-structure interaction analysis the analytical radiation damping alone is sufficient to represent the combined material and radiation damping in the field. On the other hand, for vertical analysis it appears that the theory may have overestimated the radiation damping and certain reduction is recommended. (orig.)
Damped time advance methods for particles and EM fields
International Nuclear Information System (INIS)
Friedman, A.; Ambrosiano, J.J.; Boyd, J.K.; Brandon, S.T.; Nielsen, D.E. Jr.; Rambo, P.W.
1990-01-01
Recent developments in the application of damped time advance methods to plasma simulations include the synthesis of implicit and explicit ''adjustably damped'' second order accurate methods for particle motion and electromagnetic field propagation. This paper discusses this method
Exponential decay for solutions to semilinear damped wave equation
Gerbi, Sté phane; Said-Houari, Belkacem
2011-01-01
This paper is concerned with decay estimate of solutions to the semilinear wave equation with strong damping in a bounded domain. Intro- ducing an appropriate Lyapunov function, we prove that when the damping is linear, we can find initial data
Identification of weak nonlinearities on damping and stiffness by the continuous wavelet transform
Ta, Minh-Nghi; Lardiès, Joseph
2006-05-01
We consider the free response of a nonlinear vibrating system. Using the ridges and skeletons of the continuous wavelet transform, we identify weak nonlinearities on damping and stiffness and estimate their physical parameters. The crucial choice of the son wavelet function is obtained using an optimization technique based on the entropy of the continuous wavelet transform. The method is applied to simulated single-degree-of-freedom systems and multi-degree-of-freedom systems with nonlinearities on damping and stiffness. Experimental validation of the nonlinear identification and parameter estimation method is presented. The experimental system is a clamped beam with nonlinearities on damping and stiffness and these nonlinearities are identified and quantified from a displacement sensor.
Two methods for damping torsional vibrations in DFIG-based wind generators using power converters
Zhao, Zuyi; Lu, Yupu; Xie, Da; Yu, Songtao; Wu, Wangping
2017-01-01
This paper proposes novel damping control algorithms by using static synchronous compensator (STATCOM) and energy storage system (ESS) to damp torsional vibrations in doubly fed induction generator (DFIG) based wind turbine systems. It first analyses the operating characteristics of STATCOM and ESS for regulating power variations to increase grid voltage stability. Then, new control strategies for STATCOM and ESS are introduced to damp the vibrations. It is followed by illustration of their effectiveness to damp the drive train torsional vibrations of wind turbines, which can be caused by grid disturbances, such as voltage sags and frequency fluctuations. Results suggest that STATCOM is a promising technology to mitigate the torsional vibrations caused by grid voltage sags. By contrast, the ESS connected to the point of common coupling (PCC) of wind turbine systems shows even obvious advantages because of its capability of absorbing/releasing both active and reactive power. It can thus be concluded that STATCOM is useful for stabilizing power system voltage fluctuations, and ESS is more effective both in regulating PCC voltage fluctuations and damping torsional vibrations caused by grid voltage frequency fluctuations.
Onset of chaos in Josephson junctions with intermediate damping
International Nuclear Information System (INIS)
Yao, X.; Wu, J.Z.; Ting, C.S.
1990-01-01
By use of the analytical solution of the Stewart-McCumber equation including quadratic damping and dc bias, the Melnikov method has been extended to the parameter regions of intermediate damping and dc bias for the Josephson junctions with quadratic damping and with linear damping and cosφ term. The comparison between the thresholds predicted by the Melnikov method and that derived from numerical simulation has been studied. In addition, the validity conditions for the Melnikov threshold are also discussed
DEFF Research Database (Denmark)
Wu, Weimin; Liu, Yuan; He, Yuanbin
2017-01-01
Grid-tied voltage source inverters using LCL filter have been widely adopted in distributed power generation systems (DPGSs). As high-order LCL filters contain multiple resonant frequencies, switching harmonics generated by the inverter and current harmonics generated by the active/passive loads...... innovative damping methods have been proposed. A comprehensive overview on those contributions and their classification on the inverter- and grid-side damping measures are presented. Based on the concept of the impedance-based stability analysis, all damping methods can ensure the system stability...
Preliminary Study on the Damping Effect of a Lateral Damping Buffer under a Debris Flow Load
Directory of Open Access Journals (Sweden)
Zheng Lu
2017-02-01
Full Text Available Simulating the impact of debris flows on structures and exploring the feasibility of applying energy dissipation devices or shock isolators to reduce the damage caused by debris flows can make great contribution to the design of disaster prevention structures. In this paper, we propose a new type of device, a lateral damping buffer, to reduce the vulnerability of building structures to debris flows. This lateral damping buffer has two mechanisms of damage mitigation: when debris flows impact on a building, it acts as a buffer, and when the structure vibrates due to the impact, it acts as a shock absorber, which can reduce the maximum acceleration response and subsequent vibration respectively. To study the effectiveness of such a lateral damping buffer, an impact test is conducted, which mainly involves a lateral damping buffer attached to a two-degree-of-freedom structure under a simulated debris flow load. To enable the numerical study, the equation of motion of the structure along with the lateral damping buffer is derived. A subsequent parametric study is performed to optimize the lateral damping buffer. Finally, a practical design procedure is also provided.
Directory of Open Access Journals (Sweden)
Tai-Hong Cheng
2015-01-01
Full Text Available Composite materials are increasingly used in wind blade because of their superior mechanical properties such as high strength-to-weight and stiffness-to-weight ratio. This paper presents vibration and damping analysis of fiberreinforced composite wind turbine blade with viscoelastic damping treatment. The finite element method based on full layerwise displacement theory was employed to analyze the damping, natural frequency, and modal loss factor of composite shell structure. The lamination angle was considered in mathematical modeling. The curved geometry, transverse shear, and normal strains were exactly considered in present layerwise shell model, which can depict the zig-zag in-plane and out-of-plane displacements. The frequency response functions of curved composite shell structure and wind blade were calculated. The results show that the damping ratio of viscoelastic layer is found to be very sensitive to determination of magnitude of composite structures. The frequency response functions with variety of thickness of damping layer were investigated. Moreover, the natural frequency, modal loss factor, and mode shapes of composite fiber reinforced wind blade with viscoelastic damping control were calculated.
Active and passive damping based on piezoelectric elements -controllability issues-
Holterman, J.; de Vries, Theodorus J.A.; van Amerongen, J.; Jonker, Jan B.; Jonker, J.B.
2001-01-01
Piezoelectric elements are widely used for damping micro-vibrations in mechanical structures. Active damping can be realised robustly by means of collocated actuator-sensor-pairs, controlled so as to extract vibration energy. Excellent damping performance is possible as long as sufficient
Damping of resistive instability in UNK-1 with digital electronics in feedback
International Nuclear Information System (INIS)
Zhabitskij, V.M.; Ivanov, I.N.; Korenev, I.L.; Yudin, L.A.
1991-01-01
The basis of resistive instability damper system for the UNK-1 is obtained. The system for each of two directions of beam transverse oscillations includes two pairs of pick-up electrodes and damping kickers connected by delayed negative feedback with digital electronics. The requirements for digital electronics in feedback are discussed. The influence of a notch filter is under consideration. In turns out that a 0.8 MHz feedback system damps the resistive instability in the UNK-1 with increment of 0.7 revolution frequency (for low frequencies). 7 refs.; 8 figs
Fast relaxation transients in a kicked damped oscillator
Energy Technology Data Exchange (ETDEWEB)
Urquizu, Merce [Laboratori d' Estudis Geofisics ' Eduard Fontsere' , IEC, Barcelona (Spain); Correig, Antoni M. [Departament d' Astronomical i Meteorologia, Laboratori d' Estudis Geofisics Eduard Fontsere, UB Marti Franques 1, E-08028 Barcelona (Spain) and Laboratori d' Estudis Geofisics ' Eduard Fontsere' , IEC, Barcelona (Spain)]. E-mail: ton.correig@am.ub.es
2007-08-15
Although nonlinear relaxation transients are very common in nature, very few studies are devoted to its characterization, mainly due to its short time duration. In this paper, we present a study about the nature of relaxation transients in a kicked damped oscillator, in which transients are generated in terms of continuous fast changes in the parameters of the system. We have found that transient dynamics can be described, rather than in terms of bifurcation dynamics, in terms of instantaneous stretching factors, which are related to the stability of fixed points of the corresponding stroboscopic maps.
Characterization of Slosh Damping for Ortho-Grid and Iso-Grid Internal Tank Structures
Westra, Douglas G.; Sansone, Marco D.; Eberhart, Chad J.; West, Jeffrey S.
2016-01-01
Grid stiffened tank structures such as Ortho-Grid and Iso-Grid are widely used in cryogenic tanks for providing stiffening to the tank while reducing mass, compared to tank walls of constant cross-section. If the structure is internal to the tank, it will positively affect the fluid dynamic behavior of the liquid propellant, in regard to fluid slosh damping. As NASA and commercial companies endeavor to explore the solar system, vehicles will by necessity become more mass efficient, and design margin will be reduced where possible. Therefore, if the damping characteristics of the Ortho-Grid and Iso-Grid structure is understood, their positive damping effect can be taken into account in the systems design process. Historically, damping by internal structures has been characterized by rules of thumb and for Ortho-Grid, empirical design tools intended for slosh baffles of much larger cross-section have been used. There is little or no information available to characterize the slosh behavior of Iso-Grid internal structure. Therefore, to take advantage of these structures for their positive damping effects, there is much need for obtaining additional data and tools to characterize them. Recently, the NASA Marshall Space Flight Center conducted both sub-scale testing and computational fluid dynamics (CFD) simulations of slosh damping for Ortho-Grid and Iso-Grid tanks for cylindrical tanks containing water. Enhanced grid meshing techniques were applied to the geometrically detailed and complex Ortho-Grid and Iso-Grid structures. The Loci-STREAM CFD program with the Volume of Fluid Method module for tracking and locating the water-air fluid interface was used to conduct the simulations. The CFD simulations were validated with the test data and new empirical models for predicting damping and frequency of Ortho-Grid and Iso-Grid structures were generated.
International Nuclear Information System (INIS)
Challa, Vinod R; Prasad, M G; Fisher, Frank T
2009-01-01
Vibration energy harvesting is being pursued as a means to power wireless sensors and ultra-low power autonomous devices. From a design standpoint, matching the electrical damping induced by the energy harvesting mechanism to the mechanical damping in the system is necessary for maximum efficiency. In this work two independent energy harvesting techniques are coupled to provide higher electrical damping within the system. Here the coupled energy harvesting device consists of a primary piezoelectric energy harvesting device to which an electromagnetic component is added to better match the total electrical damping to the mechanical damping in the system. The first coupled device has a resonance frequency of 21.6 Hz and generates a peak power output of ∼332 µW, compared to 257 and 244 µW obtained from the optimized, stand-alone piezoelectric and electromagnetic energy harvesting devices, respectively, resulting in a 30% increase in power output. A theoretical model has been developed which closely agrees with the experimental results. A second coupled device, which utilizes the d 33 piezoelectric mode, shows a 65% increase in power output in comparison to the corresponding stand-alone, single harvesting mode devices. This work illustrates the design considerations and limitations that one must consider to enhance device performance through the coupling of multiple harvesting mechanisms within a single energy harvesting device
An efficient delivery of DAMPs on the cell surface by the unconventional secretion pathway
International Nuclear Information System (INIS)
Zhu, Haiyan; Wang, Lan; Ruan, Yuanyuan; Zhou, Lei; Zhang, Dongmei; Min, Zhihui; Xie, Jianhui; Yu, Min; Gu, Jianxin
2011-01-01
Research highlights: → Hsp60 transported to cell surface through the classical secretory pathway was modified with N-glycosylation. → HSAPB-N18 could efficiently deliver Hsp60 to the cell surface via the unconventional secretory pathway. → Cell surface Hsp60 delivered by HASPB-N18 has a proper conformation. → HASPB-N18 is an efficient delivery signal for other DAMP molecules such as Hsp70 and HMGB1. -- Abstract: Damage-associated molecular patterns (DAMPs) are signals released from dying cells evoking the immune system response in several inflammatory disorders. In normal situations, many of DAMPs are nuclear or cytosolic proteins with defined intracellular function, but they could be found on the cell surface following tissue injury. The biological function of the translocated DAMPs is still not well known and an efficient delivery of these molecules on the cell surface is required to clarify their biological effects. In this study, we demonstrated that an unclassical secretory signal peptide, N-terminal 18 amino acids of HASPB (HASPB-N18), could efficiently deliver Hsp60, Hsp70, and HMGB1 on the cell surface. Furthermore, the delivery of these molecules on the cell surface by HASPB-N18 is not limited to a special cell line because several cell lines could use this delivery signal to deliver these molecules on the cell surface. Moreover, we demonstrated that Hsp60 on the cell surface delivered by HASPB-N18 could be recognized by a soluble form of LOX-1, which implies that DAMPs on the cell surface delivered by HASPB-N18 have a proper conformation during transport. Therefore, delivery of DAMPs by HASPB-N18 is a reliable model to further understand the biological significance of DAMPs on the cell surface.
Relativity damps OPEP in nuclear matter
International Nuclear Information System (INIS)
Banerjee, M.K.
1998-06-01
Using a relativistic Dirac-Brueckner analysis the OPEP contribution to the ground state energy of nuclear matter is studied. In the study the pion is derivative-coupled. The author finds that the role of the tensor force in the saturation mechanism is substantially reduced compared to its dominant role in a usual nonrelativistic treatment. He shows that the damping of derivative-coupled OPEP is actually due to the decrease of M * /M with increasing density. He points out that if derivative-coupled OPEP is the preferred form of nuclear effective lagrangian nonrelativistic treatment of nuclear matter is in trouble. Lacking the notion of M * it cannot replicate the damping. He suggests an examination of the feasibility of using pseudoscalar coupled πN interaction before reaching a final conclusion about nonrelativistic treatment of nuclear matter
Barotropic FRW cosmologies with Chiellini damping
Energy Technology Data Exchange (ETDEWEB)
Rosu, Haret C., E-mail: hcr@ipicyt.edu.mx [IPICyT, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San José 2055, Col. Lomas 4a Sección, 78216 San Luis Potosí, SLP (Mexico); Mancas, Stefan C., E-mail: stefan.mancas@erau.edu [Department of Mathematics, Embry–Riddle Aeronautical University, Daytona Beach, FL 32114-3900 (United States); Chen, Pisin, E-mail: pisinchen@phys.ntu.edu.tw [Leung Center for Cosmology and Particle Astrophysics (LeCosPA) and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)
2015-05-08
It is known that barotropic FRW equations written in the conformal time variable can be reduced to simple linear equations for an exponential function involving the conformal Hubble rate. Here, we show that an interesting class of barotropic universes can be obtained in the linear limit of a special type of nonlinear dissipative Ermakov–Pinney equations with the nonlinear dissipation built from Chiellini's integrability condition. These cosmologies, which evolutionary are similar to the standard ones, correspond to barotropic fluids with adiabatic indices rescaled by a particular factor and have amplitudes of the scale factors inverse proportional to the adiabatic index. - Highlights: • Chiellini-damped Ermakov–Pinney equations are used in barotropic FRW cosmological context. • Chiellini-damped scale factors of the barotropic FRW universes are introduced. • These scale factors are similar to the undamped ones.
WAKEFIELD DAMPING FOR THE CLIC CRAB CAVITY
Ambattu, P; Dexter, A; Carter, R; Khan, V; Jones, R; Dolgashev, V
2009-01-01
A crab cavity is required in the CLIC to allow effective head-on collision of bunches at the IP. A high operating frequency is preferred as the deflection voltage required for a given rotation angle and the RF phase tolerance for a crab cavity are inversely proportional to the operating frequency. The short bunch spacing of the CLIC scheme and the high sensitivity of the crab cavity to dipole kicks demand very high damping of the inter-bunch wakes, the major contributor to the luminosity loss of colliding bunches. This paper investigates the nature of the wakefields in the CLIC crab cavity and the possibility of using various damping schemes to suppress them effectively.
Damping values for nuclear power plant piping during seismic events and fluid-induced transients
International Nuclear Information System (INIS)
Ware, A.G.
1986-01-01
For several years the Idaho National Engineering Laboratory (INEL) has been assisting the United States Nuclear Regulatory Commission (USNRC) in efforts to establish best-estimate damping values for use in the dynamic analysis of nuclear power plant piping systems. Data from a number of piping vibration tests conducted at facilities worldwide (including the INEL) have been collected, evaluated, reported, and placed in a nuclear piping data bank at the INEL. These data are being used to justify changes in allowable damping values for use in nuclear piping design, thus making piping systems safer, less costly, and easier to inspect and maintain
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang
2014-01-01
This paper investigates the active damping of LCL-filter resonance within single-loop grid current control of grid-connected voltage source converters. First, the basic analysis in the continuous s-domain reveals that the grid-current-feedback active damping forms a virtual impedance across...... in a digital control system. The instability induced by the negative virtual resistance, which is commonly experienced in the feedback-type active damping, can thus be avoided. A systematic design method of the highpass filter is also proposed by the help of root locus analysis in the discrete z-domain. Lastly...
Size effect related to damping caused by water submersion
International Nuclear Information System (INIS)
Dong, R.G.
1981-01-01
An important effect of water submersion on the dynamic response of a structure is the increase in effective damping. The dynamic response of submerged structures is of interest in the nuclear power industry for reasons of operational safety during seismic and other dynamic excitations. In this paper, the added damping contribution that results from the viscosity of water and the dependence of the contribution on structural size are examined. Other factors considered are the applicable range of viscous damping with respect to displacement amplitude and, as far as damping is concerned, how far neighboring members must be from each other to respond as if in open water. An expression is derived for relating the damping value to structural size. Estimated added-damping values for representative fuel elements, fuel bundles, and main steam-pressure-relief-valve lines are given based on our derived expression for added damping
Tuned mass absorbers on damped structures under random load
DEFF Research Database (Denmark)
Krenk, Steen; Høgsberg, Jan Becker
2008-01-01
the mass ratio alone, and the damping can be determined subsequently. Only approximate results are available for the influence of damping in the original structure, typically in the form of series expansions. In the present paper it is demonstrated that for typical mass ratios in the order of a few percent......A substantial literature exists on the optimal choice of parameters of a tuned mass absorber on a structure excited by a force or by ground acceleration with random characteristics in the form of white noise. In the absence of structural damping the optimal frequency tuning is determined from...... for the response variance of a structure with initial damping in terms of the mass ratio and both damping ratios. Within this format the optimal tuning of the absorber turns out to be independent of the structural damping, and a simple explicit expression is obtained for the equivalent total damping....
Single bunch beam breakup in linacs and BNS damping
International Nuclear Information System (INIS)
Toyomasu, Takanori
1991-12-01
We study a single-bunch beam breakup (BBU) problem by a macro-particle model. We consider both the BBU solution and the Landau damping solution which includes the Balakin-Novokhatsky-Smirnov (BNS) damping. In the BBU solution, we get an analytic solution which includes both the Chao-Richter-Yao solution and the two-particle model solution and which agrees well with simulation. The solution can also be used in a multi-bunch case. In the Landau damping solution, we can be see the mechanism of Landau damping formally and can get some insights into BNS damping. We confirm that a two-particle model criterion for BNS damping is a good one. We expect that the two-particle model criterion is represented by the first order interaction in Landau damping solution of a macro-particle model. (author)
A review of damping of two-phase flows
International Nuclear Information System (INIS)
Hara, Fumio
1993-01-01
Damping of two-phase flows has been recognized as one of the most unknown parameters in analyzing vibrational characteristics of structures subjected to two-phase flows since it seems to be influenced by many physical parameters involved in the physics of dynamic energy dissipation of a vibrating structure, for example, liquid viscosity, surface tension, flow velocity, mass ratio, frequency, void fraction, flow regime and so forth. This paper deals with a review of scientific works done to date on the damping of two phase flows and discussions about what has been clarified and what has not been known to us, or what kinds of research are needed about two-phase flow damping. The emphasis is put on the definition of two-phase fluid damping, damping measurement techniques, damping characteristics in relation to two phase flow configurations, and damping generation mechanisms
Controllable damping of high-Q violin modes in fused silica suspension fibers
Energy Technology Data Exchange (ETDEWEB)
Dmitriev, A V; Mescheriakov, S D; Mitrofanov, V P [Faculty of Physics, Moscow State University, Moscow 119991 (Russian Federation); Tokmakov, K V, E-mail: dmitriev@hbar.phys.msu.r, E-mail: mitr@hbar.phys.msu.r [Present address: Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)
2010-01-21
Fused silica fiber suspension of the test masses will be used in the interferometric gravitational wave detectors of the next generation. This allows a significant reduction of losses in the suspension and thermal noise associated with the suspension. Unfortunately, unwanted violin modes may be accidentally excited in the suspension fibers. The Q-factor of the violin modes also exceeds 10{sup 8}. They have a ring-down time that is too long and may complicate the stable control of the interferometer. Results of the investigation of a violin mode active damping system are described. An original sensor and actuator were especially developed to realize the effective coupling of a thin, optically transparent, non-conducting fused silica fiber with an electric circuit. The damping system allowed the changing of the violin mode's damping rate over a wide range.
Controllable damping of high-Q violin modes in fused silica suspension fibers
Dmitriev, A. V.; Mescheriakov, S. D.; Tokmakov, K. V.; Mitrofanov, V. P.
2010-01-01
Fused silica fiber suspension of the test masses will be used in the interferometric gravitational wave detectors of the next generation. This allows a significant reduction of losses in the suspension and thermal noise associated with the suspension. Unfortunately, unwanted violin modes may be accidentally excited in the suspension fibers. The Q-factor of the violin modes also exceeds 108. They have a ring-down time that is too long and may complicate the stable control of the interferometer. Results of the investigation of a violin mode active damping system are described. An original sensor and actuator were especially developed to realize the effective coupling of a thin, optically transparent, non-conducting fused silica fiber with an electric circuit. The damping system allowed the changing of the violin mode's damping rate over a wide range.
Controllable damping of high-Q violin modes in fused silica suspension fibers
International Nuclear Information System (INIS)
Dmitriev, A V; Mescheriakov, S D; Mitrofanov, V P; Tokmakov, K V
2010-01-01
Fused silica fiber suspension of the test masses will be used in the interferometric gravitational wave detectors of the next generation. This allows a significant reduction of losses in the suspension and thermal noise associated with the suspension. Unfortunately, unwanted violin modes may be accidentally excited in the suspension fibers. The Q-factor of the violin modes also exceeds 10 8 . They have a ring-down time that is too long and may complicate the stable control of the interferometer. Results of the investigation of a violin mode active damping system are described. An original sensor and actuator were especially developed to realize the effective coupling of a thin, optically transparent, non-conducting fused silica fiber with an electric circuit. The damping system allowed the changing of the violin mode's damping rate over a wide range.
Approximate damped oscillatory solutions and error estimates for the perturbed Klein–Gordon equation
International Nuclear Information System (INIS)
Ye, Caier; Zhang, Weiguo
2015-01-01
Highlights: • Analyze the dynamical behavior of the planar dynamical system corresponding to the perturbed Klein–Gordon equation. • Present the relations between the properties of traveling wave solutions and the perturbation coefficient. • Obtain all explicit expressions of approximate damped oscillatory solutions. • Investigate error estimates between exact damped oscillatory solutions and the approximate solutions and give some numerical simulations. - Abstract: The influence of perturbation on traveling wave solutions of the perturbed Klein–Gordon equation is studied by applying the bifurcation method and qualitative theory of dynamical systems. All possible approximate damped oscillatory solutions for this equation are obtained by using undetermined coefficient method. Error estimates indicate that the approximate solutions are meaningful. The results of numerical simulations also establish our analysis
Research on low strain magnetic mechanical hysteresis damping performance of Fe-15Cr-3Mo-0.5Si alloy
International Nuclear Information System (INIS)
Wang, Hui; Huang, Huawei; Hong, Xiaofeng; Yin, Changgeng; Huang, Zhaohua; Chen, Le
2015-01-01
Highlights: • Heat treatment system has a great effect on the alloy damping performance. • Damping performance does not improve monotonously with temperature. • Furnace cooling is higher than that of alloy after air cooling. • There is an optimum annealing temperature and grain size to obtain high damping. - Abstract: This paper studies the preparation of Fe-15Cr-3Mo-0.5Si alloy by using vacuum induction melting furnace and vacuum annealing furnace, the damping performance of which in different heat treatment states is tested with dynamic mechanical thermal analyzer (DMA). Through microstructure observation with metallographic microscope (OM), grain boundary observation with scanning electron microscopy (SEM), phase structure analysis with X-ray diffraction (XRD) and internal stress of S-B model analysis, the effect law of annealing temperature, types of cooling, holding time and grain sizes on the damping performance of alloy and the related mechanism can be concluded as follows. The annealing temperature and grain sizes have a significant impact on the damping strain amplitude as well as the magnetic and mechanical damping performance of this ferromagnetic alloy. Proper annealing temperature and grain size is the necessary condition to get high damping performance of the alloy. It is not conducive to improvement of the damping performance if the annealing temperature is too high or too low and the grain size is too small or too large. For Fe-15Cr-3Mo-0.5Si alloy, within the range of the low strain amplitude, alloy damping performance does not improve monotonously with the increase of the annealing temperature and grain size. The maximum value appears at the annealing temperature of 1100 °C/1 h with the grain size of about 300 μm. At high annealing temperature of 1100 °C, the damping performance of alloy in the slow cooling furnace is higher than that with air cooling treatment. The extension or shortening of the holding time, to a certain extent
Research on low strain magnetic mechanical hysteresis damping performance of Fe-15Cr-3Mo-0.5Si alloy
Energy Technology Data Exchange (ETDEWEB)
Wang, Hui, E-mail: qinghe5525@163.com; Huang, Huawei; Hong, Xiaofeng; Yin, Changgeng; Huang, Zhaohua; Chen, Le
2015-02-15
Highlights: • Heat treatment system has a great effect on the alloy damping performance. • Damping performance does not improve monotonously with temperature. • Furnace cooling is higher than that of alloy after air cooling. • There is an optimum annealing temperature and grain size to obtain high damping. - Abstract: This paper studies the preparation of Fe-15Cr-3Mo-0.5Si alloy by using vacuum induction melting furnace and vacuum annealing furnace, the damping performance of which in different heat treatment states is tested with dynamic mechanical thermal analyzer (DMA). Through microstructure observation with metallographic microscope (OM), grain boundary observation with scanning electron microscopy (SEM), phase structure analysis with X-ray diffraction (XRD) and internal stress of S-B model analysis, the effect law of annealing temperature, types of cooling, holding time and grain sizes on the damping performance of alloy and the related mechanism can be concluded as follows. The annealing temperature and grain sizes have a significant impact on the damping strain amplitude as well as the magnetic and mechanical damping performance of this ferromagnetic alloy. Proper annealing temperature and grain size is the necessary condition to get high damping performance of the alloy. It is not conducive to improvement of the damping performance if the annealing temperature is too high or too low and the grain size is too small or too large. For Fe-15Cr-3Mo-0.5Si alloy, within the range of the low strain amplitude, alloy damping performance does not improve monotonously with the increase of the annealing temperature and grain size. The maximum value appears at the annealing temperature of 1100 °C/1 h with the grain size of about 300 μm. At high annealing temperature of 1100 °C, the damping performance of alloy in the slow cooling furnace is higher than that with air cooling treatment. The extension or shortening of the holding time, to a certain extent
Metallic materials for mechanical damping capacity applications
Crăciun, R. C.; Stanciu, S.; Cimpoeșu, R.; (Dragoș Ursanu, A. I.; Manole, V.; Paraschiv, P.; Chicet, D. L.
2016-08-01
Some metallic materials exhibit good damping capacity of mechanical energy into thermal energy. This property along with the others metallic characteristics make this materials interesting for a big number of applications. These materials can be used as bumpers in different applications including automotive field. Beside grey cast iron and shape memory alloys few new metallic materials are presented for the supposition of high damping capacity. We analyze the causes that increase the internal friction of some metallic materials and possibilities to enhance this property through different mechanical, physical or chemical methods. Shape memory alloys, especially those based on copper, present a different damping capacity on martensite, austenite or transition state. In the transformation range M ↔A, which in case of copper base shape memory alloys is quite large, the metallic intelligent materials present a high internal friction, almost comparable with natural rubber behavior that can transform mechanical energy into thermal energy till a certain value of the external solicitation. These materials can be used as noise or small vibrations bumpers or even as shock absorbers in automotive industry.
Collisional damping rates for plasma waves
Energy Technology Data Exchange (ETDEWEB)
Tigik, S. F., E-mail: sabrina.tigik@ufrgs.br; Ziebell, L. F., E-mail: luiz.ziebell@ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, Rio Grande do Sul (Brazil); Yoon, P. H., E-mail: yoonp@umd.edu [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of)
2016-06-15
The distinction between the plasma dynamics dominated by collisional transport versus collective processes has never been rigorously addressed until recently. A recent paper [P. H. Yoon et al., Phys. Rev. E 93, 033203 (2016)] formulates for the first time, a unified kinetic theory in which collective processes and collisional dynamics are systematically incorporated from first principles. One of the outcomes of such a formalism is the rigorous derivation of collisional damping rates for Langmuir and ion-acoustic waves, which can be contrasted to the heuristic customary approach. However, the results are given only in formal mathematical expressions. The present brief communication numerically evaluates the rigorous collisional damping rates by considering the case of plasma particles with Maxwellian velocity distribution function so as to assess the consequence of the rigorous formalism in a quantitative manner. Comparison with the heuristic (“Spitzer”) formula shows that the accurate damping rates are much lower in magnitude than the conventional expression, which implies that the traditional approach over-estimates the importance of attenuation of plasma waves by collisional relaxation process. Such a finding may have a wide applicability ranging from laboratory to space and astrophysical plasmas.
Landau damping in trapped Bose condensed gases
Energy Technology Data Exchange (ETDEWEB)
Jackson, B; Zaremba, E [Department of Physics, Queen' s University, Kingston, ON K7L 3N6 (Canada)
2003-07-01
We study Landau damping in dilute Bose-Einstein condensed gases in both spherical and prolate ellipsoidal harmonic traps. We solve the Bogoliubov equations for the mode spectrum in both of these cases, and calculate the damping by summing over transitions between excited quasiparticle states. The results for the spherical case are compared to those obtained in the Hartree-Fock (HF) approximation, where the excitations take on a single-particle character, and excellent agreement between the two approaches is found. We have also taken the semiclassical limit of the HF approximation and obtain a novel expression for the Landau damping rate involving the time-dependent self-diffusion function of the thermal cloud. As a final approach, we study the decay of a condensate mode by making use of dynamical simulations in which both the condensate and thermal cloud are evolved explicitly as a function of time. A detailed comparison of all these methods over a wide range of sample sizes and trap geometries is presented.
First Results from the DAMPE Mission
CERN. Geneva
2018-01-01
DAMPE (DArk Matter Particle Explorer) is a satellite mission of the Chinese Academy of Sciences (CAS) dedicated to high energy cosmic ray detections. Since its successful launch on December 17th, 2015 a large amount of cosmic ray data has been collected. With relatively large acceptance, DAMPE is designed to detect electrons (and positrons) up to 10 TeV with unprecedented energy resolution to search for new features in the cosmic ray electron plus positron (CRE) spectrum. It will also study cosmic ray nuclei up to 100 TeV with good precision, which will bring new input to the study of their still unknown origin and their propagation through the Galaxy. In this talk, the DAMPE mission will be introduced, together with some details of the construction and on-ground calibration of the detector subsystems. The in-orbit detector commissioning, calibration and operation will be described. First data analysis results, including the recently published CRE spectrum from 25 GeV to 4.6 TeV based on the data collected i...
Etiology of root parsley damping-off
Directory of Open Access Journals (Sweden)
Bogdan Nowicki
2013-12-01
Full Text Available The investigations were done between 1990-1994. Seedlings collected from 120 plantations were evaluated. The fungi responsible for seedling damping-off occurrening most often were Alternariu spp., Fusarium spp. and Pythium spp. isolated from 46,3, 32,2 and 16,6% of infected plants, respectively. The most important pathogens were A.petroselini which infected 33% of seedlings and A.radicina - 11%„ Among Fusarium species the most common was F.avenaceum, comprising 61% of total Fusarium isolates. The next were following: F.culmorum - 21%, F.solani - 12,6% and 3% for both F.equiseti and F.oxysporum. Damping-off of se,edlings was also caused by the other fungi but they were noted in low intensity. Among them were following: Phoma spp., A.alternata and Rhizoctonia solani on 2,8; 2,3 and 1,2% of tested seedlings. respectively. The species: Sclerotinia sclerotiorum, Botrytis cinerea, Bipolaris sorokinianu and Septoria petroselini were isolated in total from 0,9% of seedlings. Drechslera biseptata and Stemphylium botryosum caused seedling damping-off sporadically.
Possibility of Landau damping of gravitational waves
International Nuclear Information System (INIS)
Gayer, S.; Kennel, C.F.
1979-01-01
There is considerable uncertainty in the literature concerning whether or not transverse traceless gravitational waves can Landau damp. Physically, the issue is whether particles of nonzero mass can comove with surfaces of constant wave phase, and therefore, loosely, whether gravitational waves can have phase speeds less than that of light. We approach the question of Landau damping in various ways. We consider first the propagation of small-amplitude gravitational waves in an ideal fluid-filled Robertson-Walker universe of zero spatial curvature. We argue that the principle of equivalence requires those modes to be lightlike. We show that a freely moving particle interacting only with the collective fields cannot comove with such waves if it has nonzero mass. The equation for gravitational waves in collisionless kinetic gases differs from that for fluid media only by terms so small that deviations from lightlike propagation are unmeasurable. Thus, we conclude that Landau damping of small-amplitude, transverse traceless gravitational waves is not possible
Radiative damping in plasma-based accelerators
Directory of Open Access Journals (Sweden)
I. Yu. Kostyukov
2012-11-01
Full Text Available The electrons accelerated in a plasma-based accelerator undergo betatron oscillations and emit synchrotron radiation. The energy loss to synchrotron radiation may seriously affect electron acceleration. The electron dynamics under combined influence of the constant accelerating force and the classical radiation reaction force is studied. It is shown that electron acceleration cannot be limited by radiation reaction. If initially the accelerating force was stronger than the radiation reaction force, then the electron acceleration is unlimited. Otherwise the electron is decelerated by radiative damping up to a certain instant of time and then accelerated without limits. It is shown that regardless of the initial conditions the infinite-time asymptotic behavior of an electron is governed by a self-similar solution providing that the radiative damping becomes exactly equal to 2/3 of the accelerating force. The relative energy spread induced by the radiative damping decreases with time in the infinite-time limit. The multistage schemes operating in the asymptotic acceleration regime when electron dynamics is determined by the radiation reaction are discussed.
Experimental damping assessment of a full scale offshore mono bucket foundation
DEFF Research Database (Denmark)
Gres, Szymon; Fejerskov, Morten; Ibsen, Lars Bo
2016-01-01
This paper quantifies the system damping of a offshore meteorological mast supported by a Mono Bucket foundation based on a long-term experimental campaign. The structure is located at Dogger Bank west, North Sea, and equipped with a measurement system monitoring acceleration, strain, inclination...
Temperature-dependent Gilbert damping of Co2FeAl thin films with different degree of atomic order
Kumar, Ankit; Pan, Fan; Husain, Sajid; Akansel, Serkan; Brucas, Rimantas; Bergqvist, Lars; Chaudhary, Sujeet; Svedlindh, Peter
2017-12-01
Half-metallicity and low magnetic damping are perpetually sought for spintronics materials, and full Heusler compounds in this respect provide outstanding properties. However, it is challenging to obtain the well-ordered half-metallic phase in as-deposited full Heusler compound thin films, and theory has struggled to establish a fundamental understanding of the temperature-dependent Gilbert damping in these systems. Here we present a study of the temperature-dependent Gilbert damping of differently ordered as-deposited Co2FeAl full Heusler compound thin films. The sum of inter- and intraband electron scattering in conjunction with the finite electron lifetime in Bloch states governs the Gilbert damping for the well-ordered phase, in contrast to the damping of partially ordered and disordered phases which is governed by interband electronic scattering alone. These results, especially the ultralow room-temperature intrinsic damping observed for the well-ordered phase, provide fundamental insights into the physical origin of the Gilbert damping in full Heusler compound thin films.