WorldWideScience

Sample records for 160-min radial pulsations

  1. An Adaptive Code For Radial Stellar Pulsations

    CERN Document Server

    Buchler, J R; Marom, A; Kollath, Zoltan; Marom, Ariel

    1997-01-01

    We describe an implicit 1--D adaptive mesh hydrodynamics code that is specially tailored for radial stellar pulsations. In the Lagrangean limit the code reduces to the well tested Fraley scheme. The code has the useful feature that unwanted, long lasting transients can be avoided by smoothly switching on the adaptive mesh features starting from the Lagrangean code. Thus, a limit cycle pulsation that can readily be computed with the relaxation method of Stellingwerf will converge in a few tens of pulsation cycles when put into the adaptive mesh code. The code has been checked with two shock problems, viz Noh and Sedov, for which analytical solutions are known, and it has been found to be both accurate and stable. Superior results were obtained through the solution of the total energy (gravitational + kinetic + internal) equation rather than that of the internal energy only.

  2. Convective hydrocodes for radial stellar pulsation. Physical and numerical formulation

    CERN Document Server

    Smolec, R

    2008-01-01

    In this paper we describe our convective hydrocodes for radial stellar pulsation. We adopt the Kuhfuss (1986) model of convection, reformulated for the use in stellar pulsation hydrocodes. Physical as well as numerical assumptions of the code are described in detail. Described tests show, that our models are numerically robust and reproduce basic observational constraints. We discuss the effects of different treatment of some quantities in other pulsation hydrocodes. Our most important finding concerns the treatment of the turbulent source function in convectively stable regions. In our code we allow for negative values of source function in convectively stable zones, which reflects negative buoyancy. However, some authors restrict the source term to non-negative values. We show that this assumption leads to very high turbulent energies in convectively stable regions. The effect looks like overshooting, but it is not, because turbulence is generated by pulsations. Also, turbulent elements do not carry kinetic...

  3. An Adaptive Code for Radial Stellar Model Pulsations

    Science.gov (United States)

    Buchler, J. Robert; Kolláth, Zoltán; Marom, Ariel

    1997-09-01

    We describe an implicit 1-D adaptive mesh hydrodynamics code that is specially tailored for radial stellar pulsations. In the Lagrangian limit the code reduces to the well tested Fraley scheme. The code has the useful feature that unwanted, long lasting transients can be avoided by smoothly switching on the adaptive mesh features starting from the Lagrangean code. Thus, a limit cycle pulsation that can readily be computed with the relaxation method of Stellingwerf will converge in a few tens of pulsation cycles when put into the adaptive mesh code. The code has been checked with two shock problems, viz. Noh and Sedov, for which analytical solutions are known, and it has been found to be both accurate and stable. Superior results were obtained through the solution of the total energy (gravitational + kinetic + internal) equation rather than that of the internal energy only.

  4. On the pulsation and evolutionary properties of helium burning radially pulsating variables

    Science.gov (United States)

    Bono, G.; Pietrinferni, A.; Marconi, M.; Braga, V. F.; Fiorentino, G.; Stetson, P. B.; Buonanno, R.; Castellani, M.; Dall'Ora, M.; Fabrizio, M.; Ferraro, I.; Giuffrida, G.; Iannicola, G.; Marengo, M.; Magurno, D.; Martinez-Vazquez, C. E.; Matsunaga, N.; Monelli, M.; Neeley, J.; Rastello, S.; Salaris, M.; Short, L.; Stellingwerf, R. F.

    2016-05-01

    We discuss pulsation and evolutionary properties of low- (RR Lyrae, Type II Cepheids) and intermediate-mass (Anomalous Cepheids) radial variables. We focus our attention on the topology of the instability strip and the distribution of the quoted variables in the Hertzsprung-Russell diagram. We discuss their evolutionary status and the dependence on the metallicity. Moreover, we address the diagnostics (period derivative, difference in luminosity, stellar mass) that can provide solid constraints on their progenitors and on the role that binarity and environment have in shaping their current pulsation characteristics. Finally, we briefly outline their use as standard candles.

  5. Non-radial Pulsations in the Open Cluster NGC 3766

    CERN Document Server

    Roettenbacher, Rachael M; McSwain, M Virginia

    2009-01-01

    Non-radial pulsations (NRPs) are a proposed mechanism for the formation of decretion disks around Be stars and are important tools to study the internal structure of stars. NGC 3766 has an unusually large fraction of transient Be stars, so it is an excellent location to study the formation mechanism of Be star disks. High resolution spectroscopy can reveal line profile variations from NRPs, allowing measurements of both the degree, l, and azimuthal order, m. However, spectroscopic studies require large amounts of time with large telescopes to achieve the necessary high S/N and time domain coverage. On the other hand, multi-color photometry can be performed more easily with small telescopes to measure l only. Here, we present representative light curves of Be stars and non-emitting B stars in NGC 3766 from the CTIO 0.9m telescope in an effort to study NRPs in this cluster.

  6. Short-period radial velocity variations of alpha Bootis: Evidence for radial pulsations

    Science.gov (United States)

    Hatzes, Aritie P.; Cochran, William D.

    1994-02-01

    Precise radial velocity measurements (sigma approximately 20 m/s) of alpha Boo taken over eight consecutive nights in 1992 June are presented. A periodogram of the data shows significant power at periods of 2.46 days and 3.8 days. A separate analysis, using nonlinear least-squares fitting,reveals an additional period at 8.5 days, but at a very low amplitude (approximately 14 m/s), in addition to 2.46 day and 4.03 day periods. However, the 1.84 day period found by Smith et al. is not in these data. The expected periods of the fundamental and first harmonic modes of radial pulsations were estimated using the radius determination of Di Benedetto & Rabbia, published log(g) values, and the empirical Q(M,R) relationship of Cox, King & Stellingwerf. The 2.46 day period is near that expected for the fundamental or first harmonic radial mode, depending on the choice of stellar mass which is uncertain due to the wide range of surface gravity determinations. For a given mass and radius the 1.84 day period found by Smith et al. coincides with that of the next harmonic. These periods indicate that the short-term variability of alpha Boo may be explained by radial pulsations. Furthermore, it seems that this star has switched pulsation modes to a lower overtone from the time of the Smith et al. measurements. A recent investigation into the excitation of acoustic oscillations in alpha Boo by Balmforth, Gough, & Tout reveals peaks in the growth rates of modes having periods very near those observed in alpha Boo for a stellar model of 0.23 solar mass. This low value of the mass, however, is inconsistent with stellar evolution theory and a recent determination of the surface gravity of this star. It is clear that alpha Boo is multiperiodic and may be changing modes on timescales of a few years. This star may thus be an ideal candidate for the application of pulsation theory to late-type, evolved stars and my provide important tests of stellar evolution theory.

  7. Non-radial pulsations in the extreme helium star HD 160641

    International Nuclear Information System (INIS)

    Mean periods of 0.35 +- 0.01, 0.71 +- 0.05, 1.12 +- 0.13 and 1.77 +-0.34 day are identified from separately analysed photometric observations (obtained in 1979 and 1982) of the extreme helium star HD 160641. Radial velocities were obtained simultaneously with photometry on three nights in 1982. Optical variations are not accompanied by detectable colour changes, and radial velocities are not characteristic of radial pulsation. HD 160641 is therefore regarded as a non-radial pulsator. Radial velocity and light variations are tentatively interpreted as l = 4 mode pulsation, corresponding to a Wesselink radius of 7.9 +- 1.0 solar radii. (author)

  8. Non-radial pulsations in the extreme helium star HD 160641

    Energy Technology Data Exchange (ETDEWEB)

    Lynas-Gray, A.E.; Kilkenny, D.; Skillen, I.; Jeffery, C.S.

    1987-08-15

    Mean periods of 0.35 +- 0.01, 0.71 +- 0.05, 1.12 +- 0.13 and 1.77 +-0.34 day are identified from separately analysed photometric observations (obtained in 1979 and 1982) of the extreme helium star HD 160641. Radial velocities were obtained simultaneously with photometry on three nights in 1982. Optical variations are not accompanied by detectable colour changes, and radial velocities are not characteristic of radial pulsation. HD 160641 is therefore regarded as a non-radial pulsator. Radial velocity and light variations are tentatively interpreted as l = 4 mode pulsation, corresponding to a Wesselink radius of 7.9 +- 1.0 solar radii.

  9. Discovery of non-radial pulsations in the spectroscopic binary Herbig Ae star RS Cha

    CERN Document Server

    Böhm, T; Catala, C; Alecian, E; Pollard, K; Wright, D

    2008-01-01

    In this article we present a first discovery of non radial pulsations in both components of the Herbig Ae spectroscopic binary star RS Cha. The binary was monitored in quasi-continuous observations during 14 observing nights (Jan 2006) at the 1m Mt John (New Zealand) telescope with the Hercules high-resolution echelle spectrograph. The cumulated exposure time on the star was 44 hrs, corresponding to 255 individual high-resolution echelle spectra with $R = 45000$. Least square deconvolved spectra (LSD) were obtained for each spectrum representing the effective photospheric absorption profile modified by pulsations. Difference spectra were calculated by subtracting rotationally broadened artificial profiles; these residual spectra were analysed and non-radial pulsations were detected. A subsequent analysis with two complementary methods, namely Fourier Parameter Fit (FPF) and Fourier 2D (F2D) has been performed and first constraints on the pulsation modes have been derived. In fact, both components of the spect...

  10. Linear theory radial and nonradial pulsations of DA dwarf stars

    Energy Technology Data Exchange (ETDEWEB)

    Starrfield, S.; Cox, A.N.; Hodson, S.; Pesnell, W.D.

    1982-07-28

    The Los Alamos stellar envelope and radial linear non-adiabatic computer code, along with a new Los Alamos non-radial code are used to investigate the total hydrogen mass necessary to produce the non-radial instability of DA dwarfs. (GHT)

  11. Non-radial pulsation in first overtone Cepheids of the Small Magellanic Cloud

    Science.gov (United States)

    Smolec, R.; Śniegowska, M.

    2016-06-01

    We analyse photometry for 138 first overtone Cepheids from the Small Magellanic Cloud, in which Optical Gravitational Lensing Experiment team discovered additional variability with period shorter than first overtone period, and period ratios in the P/P1O ∈ (0.60, 0.65) range. In the Petersen diagram, these stars form three well-separated sequences. The additional variability cannot correspond to other radial mode. This form of pulsation is still puzzling. We find that amplitude of the additional variability is small, typically 2-4 per cent of the first overtone amplitude, which corresponds to 2-5 mmag. In some stars, we find simultaneously two close periodicities corresponding to two sequences in the Petersen diagram. The most important finding is the detection of power excess at half the frequency of the additional variability (at subharmonic) in 35 per cent of the analysed stars. Interestingly, power excess at subharmonic frequency is detected mostly for stars of the middle sequence in the Petersen diagram (74 per cent), incidence rate is much lower for stars of the top sequence (31 per cent), and phenomenon is not detected for stars of the bottom sequence. The amplitude and/or phase of the additional periodicities strongly vary in time. Similar form of pulsation is observed in first overtone RR Lyrae stars. Our results indicate that the nature and cause of this form of pulsation is the same in the two groups of classical pulsators; consequently, a common model explaining this form of pulsation should be searched for. Our results favour the theory of the excitation of non-radial modes of angular degrees 7, 8 and 9, proposed recently by Dziembowski.

  12. Non-radial pulsations in the γ Doradus star HD 195068

    Science.gov (United States)

    Jankov, S.; Mathias, P.; Chapellier, E.; Le Contel, J.-M.; Sareyan, J.-P.

    2006-07-01

    We present high resolution spectroscopic observations of the γ Doradus star HD 195068. About 230 spectra were collected over 2 years. Time series analysis performed on radial velocity data shows a main peak at 1.61 d-1 , a frequency not yet detected in photometry. The Hipparcos photometric 1.25 d-1 frequency is easily recovered as is 1.30 d-1 while the third photometric frequency, 0.97 d-1 , is only marginally present. The good quality of our data, which includes 196 spectra collected over seven consecutive nights, shows that both the 1.61 d-1 and intermediate 1.27 d-1 (mixture of 1.25 and 1.30 d-1 ) frequencies are present in the line profile variations. Using the Fourier-Doppler Imaging (FDI) method, the variability associated with 1.61 d-1 can be successfully modeled by a non-radial pulsation mode ℓ=5± 1, |m|=4± 1. For the intermediate frequency 1.27 d-1 we deduce ℓ=4± 1, |m|=3± 1. Evidence that the star is not pulsating in the radial mode (ℓ=0) rules out a previous classification as an RR Lyrae type star. We investigate the time variability of FDI power spectra concluding that the observed temporal variability of modes can be explained by a beating phenomenon between closely spaced frequencies of two non-radial modes. The distribution of the oscillation power within the line profile indicates that there is a significant tangential velocity component of oscillations characteristic of high radial order gravity modes which are predicted to be observed in γ Doradus type stars.

  13. Development and validation of a radial variable geometry turbine model for transient pulsating flow applications

    International Nuclear Information System (INIS)

    Highlights: • A radial variable geometry turbine model is developed. • A quasi-bidimensional volute model is used to improve high frequency results. • The model is validated against CFD results. • The quasi-bidimensional volute is able to reproduce the evolution of the flow across the volute. - Abstract: This paper presents the development and validation of a one-dimensional radial turbine model able to be used in automotive turbocharger simulations. The model has been validated using results from a numerical 3D CFD simulation of stationary and pulsating flow in a variable geometry radial turbine. As the CFD analysis showed, the main non-quasi-steady behavior of the turbine is due to the volute geometry, so special care was taken in order to properly model it while maintaining low computational costs. The flow in the volute has been decomposed in its radial and azimuthal direction. The azimuthal flow corresponds to the flow moving along the volute, while the radial flow is computed by coupling its flow with a stator model. Although the stator caused fewer accumulation effects than the volute, a small accumulation model has been used for it, which also allows to compute the evolution of the flow inside the turbine with lower costs. The flow in the moving rotor can be considered quasi-steady, so a zero-dimensional model for the rotor has been developed. Several losses models where implemented for both the stator and the rotor. The results show good agreement with the CFD computations

  14. Ion flux oscillations associated with radially polarized transverse Pc 5 magnetic pulsation

    International Nuclear Information System (INIS)

    The AMPTE CCE spacecraft observed a transverse Pc 5 magnetic pulsation (period ∼ 200 s) at 2155-2310 UT on November 20 (day 324), 1985, at a radial distance of 5.7-7.0 RE, at a magnetic latitude of 1.2 degree-1.9 degree, and near 1300 magnetic local time. The magnetic field perturbation was observed primarily in the radial component with an amplitude of 15 nT peak to peak. Ion fluxes (energy > 50 keV) measured by the medium energy particle analyzer (MEPA) on board CCE were also observed to oscillate at the frequency of the magnetic pulsation. The wide range of energy and pitch angle of ions covered by the MEPA allowed the authors to study the ion flux oscillations in great detail. It is found that (1)regardless of energy the oscillation amplitude tends to maximize near the field-aligned directions while it is essentially zero at 90 degree pitch angle, (2)for a given energy and the given location (east or west) of ion guiding centers, flux oscillations at pitch angle α and at its conjugate, 180 degree -α, are 180 degree out of phase, (3)for a given look direction, the oscillation phase changes with energy, and (4)for a given pitch angle and energy, the eastside flux oscillation leads the westside flux oscillation. These observations can be explained by the adiabatic theory of ion flux pulsations with finite Larmor radius effects included if one assumes an antisymmetric standing wave on the field line, westward propagation of the wave, and a large azimuthal wave number |m| ∼ 110. These properties of the wave are consistent with a second-harmonic standing Alfven wave excited in the region where the ring current ions have an inward density gradient

  15. Non-radial pulsation in first overtone Cepheids of the Small Magellanic Cloud

    CERN Document Server

    Smolec, R

    2016-01-01

    We analyse photometry for 138 first overtone Cepheids from the Small Magellanic Cloud, in which Optical Gravitational Lensing Experiment (OGLE) team discovered additional variability with period shorter than first overtone period, and period ratios in the (0.60, 0.65) range. In the Petersen diagram these stars form three well separated sequences. The additional variability cannot correspond to other radial mode. This form of pulsation is still puzzling. We find that amplitude of the additional variability is small, typically 2-4 per cent of the first overtone amplitude, which corresponds to 2-5 mmag. In some stars we find simultaneously two close periodicities corresponding to two sequences in the Petersen diagram. The most important finding is the detection of power excess at half the frequency of the additional variability (at subharmonic) in 35 per cent of the analysed stars. Interestingly, power excess at subharmonic frequency is detected mostly for stars of the middle sequence in the Petersen diagram (74...

  16. Spectroscopic monitoring of the Herbig Ae star HD 104237. II. Non-radial pulsations, mode analysis and fundamental stellar parameters

    CERN Document Server

    Fumel, Aurelie

    2011-01-01

    Herbig Ae/Be stars are intermediate-mass pre-main sequence (PMS) stars showing signs of intense activity and strong stellar winds, whose origin is not yet understood in the frame of current theoretical models of stellar evolution for young stars. The evolutionary tracks of the earlier Herbig Ae stars cross a recently discovered PMS instability strip. Many of these stars exhibit pulsations of delta Scuti type. HD 104237 is a well-known pulsating Herbig Ae star. In this article, we reinvestigated an extensive high-resolution quasi-continuous spectroscopic data set in order to search for very faint indications of non-radial pulsations in the line profile. To do this, we worked on dynamical spectra of equivalent photospheric (LSD) profiles of HD 104237. A 2D Fourier analysis (F2D) was performed of the entire profile and the temporal variation of the central depth of the line was studied with the time-series analysis tools Period04 and SigSpec. We present a mode identification corresponding to the detected dominan...

  17. Rapid Evolution of GSC 03144-595, a New Triple-mode Radially Pulsating High-amplitude δ Scuti

    Science.gov (United States)

    Mow, Benjamin; Reinhart, Erik; Nhim, Samantha; Watkins, Richard

    2016-07-01

    We present the results of a multi-year study of the high-amplitude δ Scuti (HADS) star GSC 03144-595. The star was observed between June and September in 2011 and 2014 for 13 nights and 28 nights, respectively. Based on our results, we argue that GSC 03144-595 is a new triple-mode radially pulsating HADS, only the fifth discovered and only the second that has a fundamental frequency in the traditional δ Scuti regime. While the frequencies and amplitudes of the fundamental and first harmonic were found to be unchanged between 2011 and 2014, we found that the amplitude of the second harmonic increased by 44%, a form of evolution not previously seen. This finding suggests that the second harmonic may be transient, thus explaining the scarcity of triple-mode HADS stars.

  18. Finding binaries from phase modulation of pulsating stars with Kepler - IV. Detection limits and radial velocity verification

    Science.gov (United States)

    Murphy, Simon J.; Shibahashi, Hiromoto; Bedding, Timothy R.

    2016-10-01

    We explore the detection limits of the phase modulation (PM) method of finding binary systems among multiperiodic pulsating stars. The method is an attractive way of finding non-transiting planets in the habitable zones of intermediate-mass stars, whose rapid rotation inhibits detections via the radial velocity (RV) method. While oscillation amplitudes of a few mmag are required to find planets, many δ Scuti stars have these amplitudes. In suboptimal cases where the signal to noise of the oscillations is lower, low-mass brown dwarfs (˜13MJup) are detectable at orbital periods longer than about 1 yr, and the lowest mass main-sequence stars (0.1-0.2 M⊙) are detectable at all orbital periods where the PM method can be applied. We use purpose-written Markov chain Monte Carlo (MCMC) software for the calculation of the PM orbits, which offers robust uncertainties for comparison with RV solutions. Using Kepler data and ground-based RVs, we verify that these two methods are in agreement, even at short orbital periods where the PM method undersamples the orbit. We develop new theory to account for the undersampling of the time delays, which is also necessary for the inclusion of RVs as observational data in the MCMC software. We show that combining RVs with time delays substantially refines the orbits because of the complementarity of working in both the spatial (PM) and velocity (RV) domains simultaneously. Software outputs were tested through an extensive hare-and-hounds exercise, covering a wide range of orbital configurations including binaries containing two pulsators.

  19. Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection - I. Long-period stars with dominant radial fundamental mode

    Science.gov (United States)

    Smolec, R.; Prudil, Z.; Skarka, M.; Bakowska, K.

    2016-09-01

    We present the discovery of a new, peculiar form of double-periodic pulsation in RR Lyrae stars. In four, long-period (P > 0.6 d) stars observed by the Optical Gravitational Lensing Experiment, and classified as fundamental mode pulsators (RRab), we detect additional, low-amplitude variability, with period shorter than fundamental mode period. The period ratios fall in a range similar to double-mode fundamental and first overtone RR Lyrae stars (RRd), with the exception of one star, in which the period ratio is significantly lower and nearly exactly equals 0.7. Although period ratios are fairly different for the four stars, the light-curve shapes corresponding to the dominant, fundamental mode are very similar. The peak-to-peak amplitudes and amplitude ratios (Fourier parameters R21 and R31) are among the highest observed in RRab stars of similar period, while Fourier phases (ϕ21 and ϕ31) are among the lowest observed in RRab stars. If the additional variability is interpreted as due to radial first overtone, then, the four stars are the most extreme RRd variables of the longest pulsation periods known. Indeed, the observed period ratios can be well modelled with high-metallicity pulsation models. However, at such long pulsation periods, first overtone is typically damped. Five other candidates, with weak signature of additional variability, sharing the same characteristics, were also detected and are briefly discussed.

  20. Finding binaries from phase modulation of pulsating stars with Kepler. IV. Detection limits and radial velocity verification

    CERN Document Server

    Murphy, Simon J; Bedding, Timothy R

    2016-01-01

    We explore the detection limits of the phase modulation (PM) method of finding binary systems among multi-periodic pulsating stars. The method is an attractive way of finding non-transiting planets in the habitable zones of intermediate mass stars, whose rapid rotation inhibits detections via the radial velocity (RV) method. While oscillation amplitudes of a few mmag are required to find planets, many $\\delta$ Scuti stars have these amplitudes. In sub-optimal cases where the signal-to-noise of the oscillations is lower, low-mass brown dwarfs ($\\sim$13 M$_{\\rm Jup}$) are detectable at orbital periods longer than about 1 yr, and the lowest mass main-sequence stars (0.1-0.2 M$_{\\odot}$) are detectable at all orbital periods where the PM method can be applied. We use purpose-written Markov chain Monte Carlo (MCMC) software for the calculation of the PM orbits, which offers robust uncertainties for comparison with RV solutions. Using Kepler data and ground-based RVs, we verify that these two methods are in agreeme...

  1. Non-radial pulsations in the Be/X binaries 4U0115+63 and SAXJ2103.5+4545

    CERN Document Server

    Gutiérrez-Soto, J; Fabregat, J; Fox-Machado, L

    2010-01-01

    The discovery of non-radial pulsations (NRP) in the Be/X binaries of the Magellanic Clouds (MC, eg. Fabrycky 2005, Coe et al. 2005, Schmidtke & Cowley 2005) provided a new approach to understand these complex systems, and, at the same time, favoured the synergy between two different fields: stellar pulsations and X-ray binaries. This breakthrough was possible thanks to the MACHO and OGLE surveys. However, in our Galaxy, only two Be/X have been reported to show NRP: GROJ2058+42 (Kiziloglu et al. 2007) and LSI+61 235 (Sarty et al. 2009). Our objective is to study the short-term variability of Galactic Be/X binaries, compare them to the Be/X of the MC and to the isolated Galactic Be observed with CoRoT and Kepler. We present preliminary results of two Be/X stars, namely 4U0115+63 and SAXJ2103.5+4545 showing multiperiodicity and periodicity respectively, most probably produced by non-radial pulsations.

  2. Spectroscopic monitoring of the Herbig Ae star HD 104237. II. Non-radial pulsations, mode analysis and fundamental stellar parameters

    OpenAIRE

    Fumel, Aurelie; Boehm, Torsten

    2011-01-01

    Herbig Ae/Be stars are intermediate-mass pre-main sequence (PMS) stars showing signs of intense activity and strong stellar winds, whose origin is not yet understood in the frame of current theoretical models of stellar evolution for young stars. The evolutionary tracks of the earlier Herbig Ae stars cross a recently discovered PMS instability strip. Many of these stars exhibit pulsations of delta Scuti type. HD 104237 is a well-known pulsating Herbig Ae star. In this article, we reinvestigat...

  3. Nonlinear pulsations of luminous He stars

    International Nuclear Information System (INIS)

    Radial pulsations in models of R Cor Bor stars and BD + 104381 have been studied with a nonlinear hydrodynamic pulsation code. Comparisons are made with previous calculations and with observed light and velocity curves. 13 refs., 2 tabs

  4. The complex case of V445 Lyr observed with Kepler: Two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more

    CERN Document Server

    Guggenberger, E; Nemec, J M; Smolec, R; Benkő, J M; Ngeow, C -C; Cohen, J G; Sesar, B; Szabó, R; Catelan, M; Moskalik, P; Kinemuchi, K; Seader, S E; Smith, J C; Tenenbaum, P; Kjeldsen, H

    2012-01-01

    Rapid and strong changes in the Blazhko modulation of RR Lyrae stars, as they have recently been detected in high precision satellite data, have become a crucial topic in finding an explanation of the long-standing mystery of the Blazhko effect. We present here an analysis of the most extreme case detected so far, the RRab star V445 Lyr (KIC 6186029) which was observed with the Kepler space mission. V445 Lyr shows very strong cycle-to-cycle changes in its Blazhko modulation, which are caused both by a secondary long-term modulation period as well as irregular variations. In addition to the complex Blazhko modulation, V445 Lyr also shows a rich spectrum of additional peaks in the frequency range between the fundamental pulsation and the first harmonic. Among those peaks, the second radial overtone could be identified, which, combined with a metallicity estimate of [Fe/H]=-2.0 dex from spectroscopy, allowed to constrain the mass (0.55-0.65 M_sun) and luminosity (40-50 L_sun) of V445 Lyr through theoretical Pete...

  5. Detection of the 128 day radial velocity variations in the supergiant {\\alpha} Persei. Rotational modulations, pulsations, or a planet?

    CERN Document Server

    Lee, Byeong-Cheol; Park, Myeong-Gu; Kim, Kang-Min; Mkrtichian, David E

    2012-01-01

    Aims. In order to search for and study the nature of the low-amplitude and long-periodic radial velocity (RV) variations of massive stars, we have been carrying out a precise RV survey for supergiants that lie near or inside the Cepheid instability strip. Methods. We have obtained high-resolution spectra of {\\alpha} Per (F5 Ib) from November 2005 to September 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). Results. Our measurements reveal that {\\alpha} Per shows a periodic RV variation of 128 days and a semi-amplitude of 70 m/s. We find no strong correlation between RV variations and bisector velocity span (BVS), but the 128-d peak is indeed present in the BVS variations among several other significant peaks in periodogram. Conclusions. {\\alpha} Per may have an exoplanet, but the combined data spanning over 20 years seem to suggest that the 128-d RV variations have not been stable on long-term scale, which is somewhat difficult to r...

  6. radial

    Directory of Open Access Journals (Sweden)

    JOHN WILLIAM BRANCH

    2007-01-01

    Full Text Available La creación de modelos de objetos reales es una tarea compleja para la cual se ha visto que el uso de técnicas tradicionales de modelamiento tiene restricciones. Para resolver algunos de estos problemas, los sensores de rango basados en láser se usan con frecuencia para muestrear la superficie de un objeto desde varios puntos de vista, lo que resulta en un conjunto de imágenes de rango que son registradas e integradas en un modelo final triangulado. En la práctica, debido a las propiedades reflectivas de la superficie, las oclusiones, y limitaciones de acceso, ciertas áreas de la superficie del objeto usualmente no son muestreadas, dejando huecos que pueden crear efectos indeseables en el modelo integrado. En este trabajo, presentamos un nuevo algoritmo para el llenado de huecos a partir de modelos triangulados. El algoritmo comienza localizando la frontera de las regiones donde están los huecos. Un hueco consiste de un camino cerrado de bordes de los triángulos en la frontera que tienen al menos un borde que no es compartido con ningún otro triangulo. El borde del hueco es entonces adaptado mediante un B-Spline donde la variación promedio de la torsión del la aproximación del B-spline es calculada. Utilizando un simple umbral de la variación promedio a lo largo del borde, se puede clasificar automáticamente, entre huecos reales o generados por intervención humana. Siguiendo este proceso de clasificación, se usa entonces una versión automatizada del interpolador de funciones de base radial para llenar el interior del hueco usando los bordes vecinos.

  7. Non-radial pulsation, rotation and outburst in the Be star omega Orionis from the MuSiCoS 1998 campaign

    Science.gov (United States)

    Neiner, C.; Hubert, A.-M.; Floquet, M.; Jankov, S.; Henrichs, H. F.; Foing, B.; Oliveira, J.; Orlando, S.; Abbott, J.; Baldry, I. K.; Bedding, T. R.; Cami, J.; Cao, H.; Catala, C.; Cheng, K. P.; Domiciano de Souza, A., Jr.; Janot-Pacheco, E.; Hao, J. X.; Kaper, L.; Kaufer, A.; Leister, N. V.; Neff, J. E.; O'Toole, S. J.; Schäfer, D.; Smartt, S. J.; Stahl, O.; Telting, J.; Tubbesing, S.; Zorec, J.

    2002-06-01

    omega Ori (HD 37490, HR 1934) is a Be star known to have presented variations. In order to investigate the nature and origin of its short-term and mid-term variability, a study is performed of several spectral lines (Hα , Hdelta , ion {He}i 4471, 4713, 4921, 5876, 6678, ion {C}{ii} 4267, 6578, 6583, ion {Mg}{ii} 4481, ion {Si}{iii} 4553 and ion {Si}{ii} 6347), based on 249 high signal-to-noise high-resolution spectra taken with 8 telescopes over 22 consecutive nights during the MuSiCoS (Multi SIte COntinuous Spectroscopy) campaign in November-December 1998. The stellar parameters are revisited and the projected rotational velocity (vsin i = 179 km s-1) is redetermined using several methods. With the MuSiCoS 98 dataset, a time series analysis of line-profile variations (LPVs) is performed using the Restricted Local Cleanest (RLC) algorithm and a least squares method. The behaviour of the velocity of the centroid of the lines, the equivalent widths and the apparent vsini for several lines, as well as Violet and Red components of photospheric lines affected by emission (red ion {He}i lines, ion {Si}{ii} 6347, ion {C}{ii} 6578, 6583) are analyzed. The non-radial pulsation (NRP) model is examined using phase diagrams and the Fourier-Doppler Imaging (FDI) method. The LPVs are consistent with a NRP mode with l = 2 or 3, |m| = 2 with frequency 1.03 c d-1. It is shown that an emission line outburst occurred in the middle of the campaign. Two scenarios are proposed to explain the behaviour of a dense cloud, temporarily orbiting around the star with a frequency 0.46 c d-1, in relation to the outburst. Based on observations taken during the MuSiCoS 98 campaign at OHP (France), La Silla (ESO, Chile, ID 62.H-0270), Mount Stromlo (Australia), Xinglong Station (China), Kitt Peak (USA), MCT/LNA (Brazil) and INT (Isaac Newton Group, La Palma Island).

  8. Pulsating stars

    CERN Document Server

    Catelan, M?rcio

    2014-01-01

    The most recent and comprehensive book on pulsating stars which ties the observations to our present understanding of stellar pulsation and evolution theory.  Written by experienced researchers and authors in the field, this book includes the latest observational results and is valuable reading for astronomers, graduate students, nuclear physicists and high energy physicists.

  9. Pulsations in close binaries: challenges and opportunities

    Directory of Open Access Journals (Sweden)

    Maceroni C.

    2015-01-01

    Full Text Available CoRoT and Kepler provided a precious by-product: a number of eclipsing binaries containing variable stars and, among these, non-radial pulsators. This providential occurrence allows combining independent information from two different phenomena whose synergy yields scientific results well beyond those from the single sources. In particular, the analysis of pulsations in eclipsing binary components throws light on the internal structure of the pulsating star, on the system evolution, and on the role of tidal forces in exciting the oscillations. The case study of the Kepler target KIC 3858884 is illustrative of the difficulties of analysis and of the achievements in this rapidly developing field.

  10. Relativistic stellar pulsations in the Cowling approximation

    International Nuclear Information System (INIS)

    Much that is known about the general pulsational properties of non-rotating Newtonian stars is traceable to the fact that in the Cowling approximation, the stellar pulsation equations can be cast in a nearly Sturm-Liouville form. In this paper, the relativistic Cowling approximation is investigated, and it is shown that in this approximation the equations for non-radial relativistic stellar pulsations are also of nearly Sturm-Liouville character. The consequences of this are discussed as a series of theorems regarding the eigenfrequencies and eigenfunctions of g-, f- and p-modes in relativistic stars. (author)

  11. First Kepler results on compact pulsators - II. KIC 010139564, a new pulsating subdwarf B (V361 Hya) star with an additional low-frequency mode

    DEFF Research Database (Denmark)

    Kawaler, Stephen; Reed, M.D.; Quint, A.C.;

    2010-01-01

    We present the discovery of non-radial pulsations in a hot subdwarf B star based on 30.5 d of nearly continuous time series photometry using the Kepler spacecraft. KIC 010139564 is found to be a short-period pulsator of the V361 Hya (EC 14026) class with more than 10 independent pulsation modes...

  12. Long Period Variables: questioning the pulsation paradigm

    CERN Document Server

    Berlioz-Arthaud, Paul

    2016-01-01

    Long period variables, among them Miras, are thought to be pulsating. Under this approach the whole star inflates and deflates along a period that can vary from 100 to 900 days; that pulsation is assumed to produce shock waves on the outer layers of the star that propagate into the atmosphere and could account for the increase in luminosity and the presence of emission lines in the spectra of these stars. However, this paradigm can seriously be questioned from a theoretical point of view. First, in order to maintain a radial pulsation, the spherical symmetry of the star must be preserved: how can it be reconciled with the large convective cells present in these stars? or when close companions are detected? Secondly, how different radial and non-radial pulsation modes of a sphere could be all damped except one radial mode? These problems have no solution and significantly weigh on the pulsation paradigm. Acknowledging this inconsistency, we show that a close companion around these stars could account for the s...

  13. Spectroscopic Mode Identification in Slowly Pulsating Subdwarf-B Stars

    CERN Document Server

    Schoenaers, C

    2008-01-01

    Mode identification is crucial for an asteroseismological study of any significance. Contrarily to spectroscopic techniques, methods such as period-fitting and multi-colour photometry do not provide a full reconstruction of non-radial pulsations. We present a new method of spectroscopic mode identification and test it on time-series of synthetic spectra appropriate for pulsating subdwarf-B stars. We then apply it to the newly discovered slowly pulsating subdwarf-B star HD 4539.

  14. Hybrid Pulsators -- Pulsating Stars with Multiple Identities

    CERN Document Server

    Zhou, A -Y

    2015-01-01

    We have carried out a statistic survey on the pulsating variable stars with multiple identities. These stars were identified to exhibit two types of pulsation or multiple light variability types in the literature, and are usually called hybrid pulsators. We extracted the hybrid information based on the Simbad database. Actually, all the variables with multiple identities are retrieved. The survey covers various pulsating stars across the Hertzsprung-Russell diagram. We aim at giving a clue in selecting interesting targets for further observation. Hybrid pulsators are excellent targets for asteroseismology. An important implication of such stars is their potential in advancing the theories of both stellar evolution and pulsation. By presenting the statistics, we address the open questions and prospects regarding current status of hybrid pulsation studies.

  15. Latitude distribution of nonradial pulsations in rapidly rotating B stars

    Science.gov (United States)

    Jankov, S.; Mathias, P.; Domiciano de Souza, A., Jr.; Uytterhoeven, K.; Aerts, C.

    2004-05-01

    We present a method for the analysis of latitude distribution associated with temperature and/or velocity perturbations of the stellar surface due to non-radial pulsation (NRP) modes in rapidly rotating B stars. The technique is applied together with Fourier Doppler Imaging (FDI) to high resolution and high signal-to-noise ratio spectroscopic observations of ɛ Per. The main advantage of this approach is that it decomposed complex multi-periodic line profile variations into single components, allowing the detailed analysis of each mode seperately. We study the 10.6-d-1 frequency that is particularly important for modal analysis of non-radial pulsations in the star.

  16. A Planet Found by Pulsations

    Science.gov (United States)

    Kohler, Susanna

    2016-10-01

    Searching for planets around very hot stars is much more challenging than looking around cool stars. For this reason, the recent discovery of a planet around a main-sequence A star is an important find both because of its unique position near the stars habitable zone, and because of the way in which the planet was discovered.Challenges in VariabilityIn the past three decades, weve discovered thousands of exoplanets yet most of them have been found around cool stars (like M dwarfs) or moderate stars (like G stars like our Sun). Very few of the planets that weve found orbit hot stars; in fact, weve only discovered ~20 planets orbiting the very hot, main-sequence A stars.The instability strip, indicated on an H-R diagram. Stellar classification types are listed across the bottom of the diagram. Many main-sequence A stars reside in the instability strip. [Rursus]Why is this? We dont expect that main-sequence A stars host fewer planets than cooler stars. Instead, its primarily because the two main techniques that we use to find planets namely, transits and radial velocity cant be used as effectively on the main-sequence A stars that are most likely to host planets, because the luminosities of these stars are often variable.These stars can lie on whats known as the classical instability strip in the Herzsprung-Russell diagram. Such variable stars pulsate due to changes in the ionization state of atoms deep in their interiors, which causes the stars to puff up and then collapse back inward. For variable main-sequence A stars, the periods for these pulsations can be several to several tens of times per day.These very pulsations that make transits and radial-velocity measurements so difficult, however, can potentially be used to detect planets in a different way. Led by Simon Murphy (University of Sydney, Australia and Aarhus University, Denmark), a team of scientists has recently detected the first planet ever to be discovered around a main-sequence A star from the timing

  17. The pulsating extreme helium star BD + 1303224

    International Nuclear Information System (INIS)

    Ultraviolet flux variations are reported for the pulsating extreme helium star BD + 1303224 (V652 Her). Effective temperature and angular radius variations over a cycle are determined from static plane-parallel LTE model atmospheres. When compared with radius changes derived from ground-based spectroscopy, the angular radius variations indicate radial pulsations and correspond to a distance of 1.5 +- 0.1 kpc. BD + 1303224 is thought to be a helium-burning star of 0.7 Msolar masses, which has an envelope contracting as the helium-burning core grows; it is similar to HD 144941 and these two stars may constitute a new sub-class of the hydrogen-deficient stars. (author)

  18. Detection of 160 min solar intensity variations: Sampling effect

    International Nuclear Information System (INIS)

    The hypothesis that the 2h40m period in the Crimean and Stanford global solar velocity oscillation measurements, which is close to a 1/9 of a day, might be produced partly by a 1-day sampling regularity in observations, is checked using the IR center-limb intensity variations measurements. We find: a) The power spectrum of the series of these data does show a peak near the 2 h 40 m period. b) Power spectra of the series with observing windows 'filled' with a constant do not exhibit a significant peak at the 9th harmonic of a day, nor do the power spectra of the set with observing windows 'filled' with randomly generated numbers. Accordingly, we conclude that the analysis performed on the really observed data is not biased by the effect of data windows and a 1-day sampling regularity of observations. (orig.)

  19. White dwarf pulsations

    International Nuclear Information System (INIS)

    The DA white dwarfs are those which show only the Stark-broadened lines of hydrogen in their spectra. They comprise about 80% of the total white dwarf population. A subset of the DA dwarfs, the ZZ Ceti stars, form a highly homogeneous class of nonradially pulsating variable stars. In this paper we shall review the observations from which both the physical properties of the stars and the characteristics of the pulsations have been derived. Data obtained since the last review of these variables (Robinson 1979) is stressed, as these data are forcing a somewhat revised understanding of the ZZ Ceti stars and their relationship to investigations of white dwarfs and to pulsating variable stars, in general. (orig.)

  20. GW Librae: A unique laboratory for pulsations in an accreting white dwarf

    CERN Document Server

    Toloza, O; Hermes, J J; Townsley, D M; Schreiber, M R; Szkody, P; Pala, A; Beuermann, K; Bildsten, L; Breedt, E; Cook, M; Godon, P; Henden, A A; Hubeny, I; Knigge, C; Long, K S; Marsh, T R; de Martino, D; Mukadam, A S; Myers, G; Nelson, P; Oksanen, A; Patterson, J; Sion, E M; Zorotovic, M

    2016-01-01

    Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of HST ultraviolet spectroscopy taken in 2002, 2010 and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in May~2013, we obtained new HST/COS ultraviolet observations that displayed unexpected behaviour: besides showing variability at ~275s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhi...

  1. Theoretical rates of pulsation period change in the Galactic Cepheids

    CERN Document Server

    Fadeyev, Yuri A

    2014-01-01

    Theoretical estimates of the rates of radial pulsation period change in Galactic Cepheids with initial masses 5.5M_\\odot <= Mzams <= 13M_\\odot, chemical composition X=0.7, Z=0.02 and periods 1.5 day <= P <= 100 day are obtained from consistent stellar evolution and nonlinear stellar pulsation computations. Pulsational instability was investigated for three crossings of the instability strip by the evolutionary track in the HR diagram. The first crossing occurs at the post-main sequence helium core gravitational contraction stage which proceeds in the Kelvin--Helmholtz timescale whereas the second and the third crossings take place at the evolutionary stage of thermonuclear core helium burning. During each crossing of the instability strip the period of radial pulsations is a quadratic function of the stellar evolution time. Theoretical rates of the pulsation period change agree with observations but the scatter of observational estimates of dP/dt noticeably exceeds the width of the band (\\delta\\lo...

  2. Interaction Between Convection and Pulsation

    Science.gov (United States)

    Houdek, Günter; Dupret, Marc-Antoine

    2015-12-01

    This article reviews our current understanding of modelling convection dynamics in stars. Several semi-analytical time-dependent convection models have been proposed for pulsating one-dimensional stellar structures with different formulations for how the convective turbulent velocity field couples with the global stellar oscillations. In this review we put emphasis on two, widely used, time-dependent convection formulations for estimating pulsation properties in one-dimensional stellar models. Applications to pulsating stars are presented with results for oscillation properties, such as the effects of convection dynamics on the oscillation frequencies, or the stability of pulsation modes, in classical pulsators and in stars supporting solar-type oscillations.

  3. Atomic diffusion and observations of pulsating A stars

    Science.gov (United States)

    Kurtz, D. W.

    2013-12-01

    Atomic diffusion - important in many contexts in stellar astrophysics and an important thread running through this meeting - is most spectacularly observable in the atmospheres of some A stars. The magnetic Ap stars and the non-magnetic Am stars show directly abundance anomalies caused by gravitational settling and radiative levitation. Over the last decade spectroscopic studies have begun to provide maps of abundance distributions in the magnetic Ap stars in three dimensions. Interestingly, high radial overtone p-mode pulsations in roAp stars have also given three-dimensional views of the stellar atmospheres with studies of rotational and line profile variations of pulsation amplitudes and phases. These detailed looks at the effects of microscopic atmospheric changes in the strongly non-LTE and magnetic upper atmospheric layers of Ap stars provide perhaps the most exciting challenge to atomic diffusion theory in terms of detailed explanation and prediction. Am stars were at one time thought not to pulsate because of gravitational settling of He from the He ii ionization zone that provides the κ-mechanism driving for δ Sct pulsations in A stars. In the last few years we have found with SuperWASP and Kepler observations that many Am stars do pulsate. More than half of all A stars pulsate at Kepler micromagnitude precision, yet there is a subset of A stars that truly do not pulsate at that level. Are these Am stars with the strongest signature of atomic diffusion? Is atomic diffusion the reason for the pulsational stability of these stars? The answers are not yet known.

  4. Gas Pulsation Control Using a Shunt Pulsation Trap

    OpenAIRE

    Huang, Paul Xiubao; Yonkers, Sean; Hokey, David

    2014-01-01

    Gas pulsations commonly exist in HVACR, energy and automotive industry. They are believed to be a major source for system inefficiency, vibrations, noises and fatigue failures. It has been widely accepted that gas pulsations mainly take place at the discharge side of a positive displacement (PD) type compressor such as a screw, scroll or internal combustion engine. The pulsation magnitudes, ranging from a fraction to a few bars, are especially significant at off-design conditions of either un...

  5. On the pulsation modes and masses of RGB OSARGs

    Directory of Open Access Journals (Sweden)

    Saio H.

    2013-03-01

    Full Text Available OSARG (OGLE Small Amplitude Red Giants variables are RGB or AGB stars that show multi-periodic light variations with periods of about 10-100 days. Comparing linear nonadiabatic pulsation periods and period ratios with observed ones, we determined pulsation modes and masses of the RGB OSARG variables in the LMC. We found that pulsations of OSARGs involve radial 1st to 3rd overtones, p4 of l = 1, and p2 of l = 2 modes. The range of mass isfound to be 0.9-1.4M⊙ for RGB OSARGs and their mass-luminosity relation is logL/L⊙ = 0.79 M/M⊙ + 2.2.

  6. Pulsation driving and convection

    Science.gov (United States)

    Antoci, Victoria

    2015-08-01

    Convection in stellar envelopes affects not only the stellar structure, but has a strong impact on different astrophysical processes, such as dynamo-generated magnetic fields, stellar activity and transport of angular momentum. Solar and stellar observations from ground and space have shown that the turbulent convective motion can also drive global oscillations in many type of stars, allowing to study stellar interiors at different evolutionary stages. In this talk I will concentrate on the influence of convection on the driving of stochastic and coherent pulsations across the Hertzsprung-Russell diagram and give an overview of recent studies.

  7. GW Librae: a unique laboratory for pulsations in an accreting white dwarf

    Science.gov (United States)

    Toloza, O.; Gänsicke, B. T.; Hermes, J. J.; Townsley, D. M.; Schreiber, M. R.; Szkody, P.; Pala, A.; Beuermann, K.; Bildsten, L.; Breedt, E.; Cook, M.; Godon, P.; Henden, A. A.; Hubeny, I.; Knigge, C.; Long, K. S.; Marsh, T. R.; de Martino, D.; Mukadam, A. S.; Myers, G.; Nelson, P.; Oksanen, A.; Patterson, J.; Sion, E. M.; Zorotovic, M.

    2016-07-01

    Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of Hubble Space Telescope (HST) ultraviolet spectroscopy taken in 2002, 2010, and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in 2013 May, we obtained new HST/Cosmic Origin Spectrograph ultraviolet observations that displayed unexpected behaviour: besides showing variability at ≃275 s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhibits high-amplitude variability on an ≃4.4 h time-scale. We demonstrate that this variability is produced by an increase of the temperature of a region on white dwarf covering up to ≃30 per cent of the visible white dwarf surface. We argue against a short-lived accretion episode as the explanation of such heating, and discuss this event in the context of non-radial pulsations on a rapidly rotating star.

  8. Damping Pressure Pulsations in a Wave-Powered Desalination System

    OpenAIRE

    Padhye, Nikhil; Torres, James, Ph. D. Massachusetts Institute of Technology.; Thomas, Levon; Ljubicic, Dean M.; Kassner, Mortiz P.; Slocum, Alexander H.; Hopkins, Brandon James; Greenlee, Alison S.

    2014-01-01

    Wave-driven reverse osmosis desalination systems can be a cost-effective option for providing a safe and reliable source of drinking water for large coastal communities. Such systems usually require the stabilization of pulsating pressures for desalination purposes. The key challenge is to convert a fluctuating pressure flow into a constant pressure flow. To address this task, stub-filters, accumulators, and radially elastic-pipes are considered for smoothing the pressure fluctuations in the ...

  9. Asteroseismology of Pulsating Stars

    Indian Academy of Sciences (India)

    Santosh Joshi; Yogesh C. Joshi

    2015-03-01

    The success of helioseismology is due to its capability of measuring -mode oscillations in the Sun. This allows us to extract information on the internal structure and rotation of the Sun from the surface to the core. Similarly, asteroseismology is the study of the internal structure of the stars as derived from stellar oscillations. In this review we highlight the progress in the observational asteroseismology, including some basic theoretical aspects. In particular, we discuss our contributions to asteroseismology through the study of chemically peculiar stars under the 'Nainital-Cape Survey' project being conducted at ARIES, Nainital, since 1999. This survey aims to detect new rapidly-pulsating Ap (roAp) stars in the northern hemisphere. We also discuss the contribution of ARIES towards the asteroseismic study of the compact pulsating variables. We comment on the future prospects of our project in the light of the new optical 3.6-m telescope to be installed at Devasthal (ARIES). Finally, we present a preliminary optical design of the high-speed imaging photometers for this telescope.

  10. Properties of strongly magnetized ultradense matter and their imprints on magnetar pulsations

    CERN Document Server

    Flores, C Vásquez; Lugones, G

    2016-01-01

    We investigate the effect of strong magnetic fields on the adiabatic radial oscillations of hadronic stars. We describe magnetized hadronic matter within the framework of the relativistic nonlinear Walecka model and integrate the equations of relativistic radial oscillations to determine the fundamental pulsation mode. We consider that the magnetic field increases, in a density dependent way, from the surface, where it has a typical magnetar value of $10^{15}$ G, to the interior of the star where it can be as large as $3 \\times 10^{18}$ G. We show that magnetic fields of the order of $10^{18}$ G at the stellar core produce a significant change in the frequency of neutron star pulsations with respect to unmagnetized objects. If radial pulsations are excited in magnetar flares, they can leave an imprint in the flare lightcurves and open a new window for the study of highly magnetized ultradense matter.

  11. Properties of strongly magnetized ultradense matter and its effects on magnetar pulsations

    Science.gov (United States)

    Flores, C. Vásquez; Castro, L. B.; Lugones, G.

    2016-07-01

    We investigate the effect of strong magnetic fields on the adiabatic radial oscillations of hadronic stars. We describe magnetized hadronic matter within the framework of the relativistic nonlinear Walecka model and integrate the equations of relativistic radial oscillations to determine the fundamental pulsation mode. We consider that the magnetic field increases, in a density dependent way, from the surface, where it has a typical magnetar value of 1015G , to the interior of the star, where it can be as large as 3 ×1018G . We show that magnetic fields of the order of 1018G at the stellar core produce a significant change in the frequency of neutron star pulsations with respect to unmagnetized objects. If radial pulsations are excited in magnetar flares, they can leave an imprint in the flare lightcurves and open a new window for the study of highly magnetized ultradense matter.

  12. The evolved pulsating CEMP star HD112869

    CERN Document Server

    Začs, L; Grankina, A; Deveikis, V; Kaminskyi, B; Pavlenko, Y; Musaev, F

    2015-01-01

    Radial velocity measurements, $BVR_C$ photometry, and high-resolution spectroscopy in the wavelength region from blue to near infrared are employed in order to clarify the evolutionary status of the carbon-enhanced metal-poor star HD112869 with unique ratio of carbon isotopes in the atmosphere. An LTE abundance analysis was carried out using the method of spectral synthesis and new self consistent 1D atmospheric models. The radial velocity monitoring confirmed semiregular variations with a peak-to-peak amplitude of about 10 km $s^{-1}$ and a dominating period of about 115 days. The light, color and radial velocity variations are typical of the evolved pulsating stars. The atmosphere of HD112869 appears to be less metal-poor than reported before, [Fe/H] = -2.3 $\\pm$0.2 dex. Carbon to oxygen and carbon isotope ratios are found to be extremely high, C/O $\\simeq$ 12.6 and $^{12}C/^{13}C \\gtrsim$ 1500, respectively. The s-process elements yttrium and barium are not enhanced, but neodymium appears to be overabundan...

  13. Mode selection in pulsating stars

    CERN Document Server

    Smolec, R

    2013-01-01

    In this review we focus on non-linear phenomena in pulsating stars the mode selection and amplitude limitation. Of many linearly excited modes only a fraction is detected in pulsating stars. Which of them and why (the problem of mode selection) and to what amplitude (the problem of amplitude limitation) are intrinsically non-linear and still unsolved problems. Tools for studying these problems are briefly discussed and our understanding of mode selection and amplitude limitation in selected groups of self-excited pulsators is presented. Focus is put on classical pulsators (Cepheids and RR Lyrae stars) and main sequence variables (delta Scuti and beta Cephei stars). Directions of future studies are briefly discussed.

  14. Precise Radial Velocities of Polaris: Detection of Amplitude Growth

    CERN Document Server

    Lee, Byeong-Cheol; Han, Inwoo; Park, Myeong-Gu; Kim, Kang-Min

    2008-01-01

    We present a first results from a long-term program of a radial velocity study of Cepheid Polaris (F7 Ib) aimed to find amplitude and period of pulsations and nature of secondary periodicities. 264 new precise radial velocity measurements were obtained during 2004-2007 with the fiber-fed echelle spectrograph Bohyunsan Observatory Echelle Spectrograph (BOES) of 1.8m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. We find a pulsational radial velocity amplitude and period of Polaris for three seasons of 2005.183, 2006.360, and 2007.349 as 2K = 2.210 +/- 0.048 km/s, 2K = 2.080 +/- 0.042 km/s, and 2K = 2.406 +/- 0.018 km/s respectively, indicating that the pulsational amplitudes of Polaris that had decayed during the last century is now increasing rapidly. The pulsational period was found to be increasing too. This is the first detection of a historical turnaround of pulsational amplitude change in Cepheids. We clearly find the presence of additional radial velocity variations on a time scal...

  15. Method of LSD profile asymmetry for estimating the center of mass velocities of pulsating stars

    Science.gov (United States)

    Britavskiy, N.; Pancino, E.; Tsymbal, V.; Romano, D.; Cacciari, C.; Clementini, C.

    2016-05-01

    We present radial velocity analysis for 20 solar neighborhood RR Lyrae and 3 Population II Cepheids. High-resolution spectra were observed with either TNG/SARG or VLT/UVES over varying phases. To estimate the center of mass (barycentric) velocities of the program stars, we utilized two independent methods. First, the 'classic' method was employed, which is based on RR Lyrae radial velocity curve templates. Second, we provide the new method that used absorption line profile asymmetry to determine both the pulsation and the barycentric velocities even with a low number of high-resolution spectra and in cases where the phase of the observations is uncertain. This new method is based on a least squares deconvolution (LSD) of the line profiles in order to an- alyze line asymmetry that occurs in the spectra of pulsating stars. By applying this method to our sample stars we attain accurate measurements (+- 2 kms^-1) of the pulsation component of the radial velocity. This results in determination of the barycentric velocity to within 5 kms^-1 even with a low number of high- resolution spectra. A detailed investigation of LSD profile asymmetry shows the variable nature of the project factor at different pulsation phases, which should be taken into account in the detailed spectroscopic analysis of pulsating stars.

  16. Discovery of new roAp pulsators in the UVES survey of cool magnetic Ap stars

    CERN Document Server

    Kochukhov, O; Ryabchikova, T; Boyko, S; Cunha, M; Tsymbal, V; Weiss, W

    2013-01-01

    We have carried out a survey of short-period pulsations among a sample of carefully chosen cool Ap stars using time-resolved observations with the UVES spectrometer at the ESO 8-m VLT telescope. Here we report the discovery of pulsations with amplitudes 50-100 m/s and periods 7-12 min in HD132205, HD148593 and HD151860. These objects are therefore established as new rapidly oscillating Ap (roAp) stars. In addition, we independently confirm the presence of pulsations in HD69013, HD96237 and HD143487 and detect, for the first time, radial velocity oscillations in two previously known photometric roAp stars HD119027 and HD185256. At the same time, no pulsation variability is found for HD5823, HD178892 and HD185204. All of the newly discovered roAp stars were previously classified as non-pulsating based on the low-precision ground-based photometric surveys. This shows that such observations cannot be used to reliably distinguish between pulsating and non-pulsating stars and that all cool Ap stars may harbor p-mod...

  17. Recent advances in the theoretical modeling of pulsating low-mass He-core white dwarfs

    CERN Document Server

    Córsico, A H; Calcaferro, L M; Serenelli, A M; Kepler, S O; Jeffery, C S

    2016-01-01

    Many extremely low-mass (ELM) white-dwarf (WD) stars are currently being found in the field of the Milky Way. Some of these stars exhibit long-period nonradial $g$-mode pulsations, and constitute the class of ELMV pulsating WDs. In addition, several low-mass pre-WDs, which could be precursors of ELM WDs, have been observed to show short-period photometric variations likely due to nonradial $p$ modes and radial modes. They could constitute a new class of pulsating low-mass pre-WD stars, the pre-ELMV stars. Here, we present the recent results of a thorough theoretical study of the nonadiabatic pulsation properties of low-mass He-core WDs and pre-WDs on the basis of fully evolutionary models representative of these stars.

  18. Asteroseismology of hybrid $\\delta$ Scuti--$\\gamma$ Doradus pulsating stars

    CERN Document Server

    Arias, J P Sánchez; Althaus, L G

    2016-01-01

    Hybrid $\\delta$ Scuti-$\\gamma$ Doradus pulsating stars show acoustic ($p$) oscillation modes typical of $\\delta$ Scuti variable stars, and gravity ($g$) pulsation modes characteristic of $\\gamma$ Doradus variable stars simultaneously excited. Observations from space missions like MOST, CoRoT, and \\emph{Kepler} have revealed a large number of hybrid $\\delta$ Scuti-$\\gamma$ Doradus pulsators, thus paving the way for a exciting new channel for asteroseismic studies. We perform a detailed asteroseismological modeling of five hybrid $\\delta$ Scuti-$\\gamma$ Doradus stars. We employ a grid-based modeling approach to sound the internal structure of the target stars by employing a huge grid of stellar models from the zero-age main sequence to the terminal-age main sequence, varying parameters like stellar mass, effective temperature, metallicity and core overshooting. We compute their adiabatic radial ($\\ell= 0$) and non-radial ($\\ell= 1, 2, 3$) $p$ and $g$ mode periods. We employ two model-fitting procedures to searc...

  19. Pulsating Star Mystery Solved

    Science.gov (United States)

    2010-11-01

    By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment of the orbits of the two stars in the double star system has allowed a measurement of the Cepheid mass with unprecedented accuracy. Up to now astronomers had two incompatible theoretical predictions of Cepheid masses. The new result shows that the prediction from stellar pulsation theory is spot on, while the prediction from stellar evolution theory is at odds with the new observations. The new results, from a team led by Grzegorz Pietrzyński (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), appear in the 25 November 2010 edition of the journal Nature. Grzegorz Pietrzyński introduces this remarkable result: "By using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile, along with other telescopes, we have measured the mass of a Cepheid with an accuracy far greater than any earlier estimates. This new result allows us to immediately see which of the two competing theories predicting the masses of Cepheids is correct." Classical Cepheid Variables, usually called just Cepheids, are unstable stars that are larger and much brighter than the Sun [1]. They expand and contract in a regular way, taking anything from a few days to months to complete the cycle. The time taken to brighten and grow fainter again is longer for stars that are more luminous and shorter for the dimmer ones. This remarkably precise relationship makes the study of Cepheids one of the most effective ways to measure the distances to nearby galaxies and from there to map out the scale of the whole Universe [2]. Unfortunately, despite their importance, Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20-30% less than predictions from the theory of the

  20. [Bachelard and the mathematical pulsation].

    Science.gov (United States)

    Guitart, René

    2015-01-01

    The working mathematician knows a specific gesture named « mathematical pulsation », a necessary creative moving in diagrams of thoughts and interpretations of mathematical writings. In this perspective the fact of being an object is definitely undecided, and related to the game of relations. The purpose of this paper today is to construct this pulsation, starting from the epistemology of Bachelard, concerning mathematics as well as mathematical physics. On the way, we recover links between ideas of Bachelard and more recent specific propositions by Gilles Ch-let, Charles Alunni, or René Guitart. Also are used authors like Jacques Lacan, Arthur Koestler, Alfred N. Whitehead, Charles S. Peirce. We conclude that the mathematical work consists with pulsative moving in the space of diagrams; we claim that this view is well compatible with the Bachelard's analysis of scientific knowledge: the intellectual or formal mathematical data preceeds the empirical objects, and in some sense these objects result from the pulsative gestures of the thinkers. So we finish with a categorical scheme of the pulsation. PMID:26223414

  1. [Bachelard and the mathematical pulsation].

    Science.gov (United States)

    Guitart, René

    2015-01-01

    The working mathematician knows a specific gesture named « mathematical pulsation », a necessary creative moving in diagrams of thoughts and interpretations of mathematical writings. In this perspective the fact of being an object is definitely undecided, and related to the game of relations. The purpose of this paper today is to construct this pulsation, starting from the epistemology of Bachelard, concerning mathematics as well as mathematical physics. On the way, we recover links between ideas of Bachelard and more recent specific propositions by Gilles Ch-let, Charles Alunni, or René Guitart. Also are used authors like Jacques Lacan, Arthur Koestler, Alfred N. Whitehead, Charles S. Peirce. We conclude that the mathematical work consists with pulsative moving in the space of diagrams; we claim that this view is well compatible with the Bachelard's analysis of scientific knowledge: the intellectual or formal mathematical data preceeds the empirical objects, and in some sense these objects result from the pulsative gestures of the thinkers. So we finish with a categorical scheme of the pulsation.

  2. Pulsations of delta Scuti stars

    International Nuclear Information System (INIS)

    A general review of the pulsating δ Scuti variables is given including the observed light curves and positions of the stars in the Hertzsprung-Russell diagram. Theoretical interpretations from evolution and pulsation calculations give their masses, radii, luminosities, and even their approximate internal compositions. Three models of these stars are discussed and used to study the nonlinear hydrodynamic behavior of these stars. The hydrodynamic equations and the Stellingwerf method for obtaining strictly periodic solutions are outlined. Problems of allowing for time-dependent convection and its great sensitivity to temperature and density are presented. Tentative results to date do not show any tendency for amplitudes to grow to large unobserved amplitudes, in disagreement with an earlier suggestion by Stellingwerf. It is found that the very small growth rates of the pulsations may even be too small to be useful in seeking a periodic solution. 15 refs., 8 figs., 3 tabs

  3. Cepheid distances from the SpectroPhoto-Interferometry of Pulsating Stars (SPIPS) - Application to the prototypes delta Cep and eta Aql

    CERN Document Server

    Merand, Antoine; Breitfelder, Joanne; Gallenne, Alexandre; Foresto, Vincent Coude du; Brummelaar, Theo A ten; McAlister, Harold A; Ridgway, Stephen; Sturmann, Laszlo; Sturmann, Judit; Turner, Nils H

    2015-01-01

    The parallax of pulsation, and its implementations such as the Baade-Wesselink method and the infrared surface bright- ness technique, is an elegant method to determine distances of pulsating stars in a quasi-geometrical way. However, these classical implementations in general only use a subset of the available observational data. Freedman & Madore (2010) suggested a more physical approach in the implementation of the parallax of pulsation in order to treat all available data. We present a global and model-based parallax-of-pulsation method that enables including any type of observational data in a consistent model fit, the SpectroPhoto-Interferometric modeling of Pulsating Stars (SPIPS). We implemented a simple model consisting of a pulsating sphere with a varying effective temperature and a combina- tion of atmospheric model grids to globally fit radial velocities, spectroscopic data, and interferometric angular diameters. We also parametrized (and adjusted) the reddening and the contribution of the cir...

  4. Line-profile variations in pulsating subdwarf-B stars as a pulsation mode diagnostic

    OpenAIRE

    Schoenaers, C.; Lynas-Gray, A. E.

    2005-01-01

    In previous attempts to perform seismic modelling of pulsating subdwarf-B stars, various mode identification techniques are used with uncertain results. We investigated a method so far neglected in sdB stars, but very successful for Main Sequence pulsators, that is, mode identification from the line-profile variations caused by stellar pulsation. We report the calculation of time-resolved synthetic spectra for sdB stars pulsating with various combinations of pulsation modes; these calculation...

  5. Pulsational-Pair Instability Supernovae

    CERN Document Server

    Woosley, S E

    2016-01-01

    The final evolution of stars in the mass range 60 - 150 solar masses is explored. Depending upon their mass loss and rotation rates, many of these stars will end their lives as pulsational pair-instability supernovae. Even a non-rotating 70 solar mass star is pulsationally unstable during oxygen shell burning and can power a sub-luminous supernova. Rotation decreases the limit further. For more massive stars, the pulsations are less frequent, span a longer time, and are more powerful. Violent pulsations eject not only any residual low density envelope, but also that fraction of the helium core mass outside about 35 - 50 solar masses. The remaining core of helium and heavy elements continues to evolve, ultimately forming an iron core of about 2.5 solar masses that probably collapses to a black hole. A variety of observational transients result with total durations ranging from days to 10,000 years, and luminosities from 10$^{41}$ to 10$^{44}$ erg s$^{-1}$. Many transients resemble ordinary Type IIp supernovae,...

  6. Blue straggler masses from pulsation properties. II. Topology of the Instability Strip

    CERN Document Server

    Fiorentino, G; Bono, G; Dalessandro, E; Ferraro, F R; Lanzoni, B; Lovisi, L; Mucciarelli, A

    2015-01-01

    We present a new set of nonlinear, convective radial pulsation models for main sequence stars computed assuming three metallicities: Z=0.0001, 0.001 and 0.008. These chemical compositions bracket the metallicity of stellar systems hosting SX Phoenicis stars (SXPs or pulsating Blue Stragglers), namely Galactic globular clusters and nearby dwarf spheroidals. Stellar masses and luminosities of the pulsation models are based on alpha--enhanced evolutionary tracks from the BASTI website. We are able to define the topology of the instability strip (IS), and in turn the pulsation relations for the first four pulsation modes. We found that third overtones approach a stable nonlinear limit cycle. Predicted and empirical IS agree quite well in the case of 49 SXPs belonging to omega Cen. We used theoretical Period-Luminosity relations in B,V bands to identify their pulsation mode. We assumed Z=0.001 and Z=0.008 as mean metallicities of SXPs in omega Cen. We found respectively 13-15 fundamental, 22-6 first and 9-4 second...

  7. Pulsating Helium Atmosphere White Dwarfs

    Science.gov (United States)

    Provencal, Judith; Montgomery, Michael H.; Bischoff-Kim, Agnes; Shipman, Harry; Nitta, Atsuko; Whole Earth Telescope Collaboration

    2015-08-01

    The overwhelming majority of all stars currently on the main sequence as well as those from earlier generations will or have ended their stellar lives as white dwarf stars. White dwarfs are rich forensic laboratories linking the history and future evolution of our Galaxy. Their structure and atmospheric composition provide evidence of how the progenitors lived, how they evolved, and how they died. This information reveals details of processes governing the behavior of contemporary main sequence stars. Combined with their distribution in luminosity/temperature, white dwarfs strongly constrain models of galactic and cosmological evolution.GD358 is among the brightest (mv =13.7) and best studied of the pulsating white dwarfs. This helium atmoshere pulsator (DBV) has an extensive photometric database spanning 30 years, including nine multisite Whole Earth Telescope campaigns. GD358 exhibits a range of behaviors, from drastic changes in excited pulsation modes to variable multiplet splittings. We use GD358 as a template for an examination of the DBV class, combining photometric results with recent COS spectroscopy. The results present new questions concerning DB formation and evolution.

  8. Why do hot subdwarf stars pulsate?

    CERN Document Server

    Geier, S

    2015-01-01

    Hot subdwarf B stars (sdBs) are the stripped cores of red giants located at the bluest extension of the horizontal branch. Several different kinds of pulsators are found among those stars. The mechanism that drives those pulsations is well known and the theoretically predicted instability regions for both the short-period p-mode and the long-period g-mode pulsators match the observed distributions fairly well. However, it remains unclear why only a fraction of the sdB stars pulsate, while stars with otherwise very similar parameters do not show pulsations. From an observers perspective I review possible candidates for the missing parameter that makes sdB stars pulsate or not.

  9. Time-series Spectroscopy and Photometry of the Pulsating Subdwarf B Star PG 1219+534 (KY UMa)

    CERN Document Server

    Reed, M D; Harms, S L; Telting, J H; Ostensen, R H; O'Toole, S J; Terndrup, D M; Zhou, A Y; Kienenberger, R L; Heber, U

    2008-01-01

    We present observations and analysis of time-series spectroscopy and photometry of the pulsating subdwarf B star PG 1219+534 (KY UMa). Subdwarf B stars are blue horizontal branch stars which have shed most of their hydrogen envelopes. Pulsating subdwarf B stars allow a probe into this interesting phase of evolution. Low resolution spectra were obtained at the Nordic Optical Telescope and Kitt Peak National Observatory, and photometric observations were obtained at MDM and Baker observatories in 2006. We extracted radial velocity and equivalent width variations from several Balmer and He I lines in individual spectra. The pulsation frequencies were separated via phase binning to detect line-profile variations in Balmer and helium lines, which were subsequently matched to atmospheric models to infer effective temperature and gravity changes throughout the pulsation cycle. From the photometry we recovered the four previously observed frequencies and detected a new fifth frequency. From the spectra we directly me...

  10. Pulsating variable stars in the Magellanic Clouds

    OpenAIRE

    Clementini, Gisella

    2009-01-01

    Pulsating variable stars can be powerful tools to study the structure, formation and evolution of galaxies. I discuss the role that the Magellanic Clouds' pulsating variables play in our understanding of the whole Magellanic System, in light of results on pulsating variables produced by extensive observing campaigns like the MACHO and OGLE microlensing surveys. In this context, I also briefly outline the promise of new surveys and astrometric missions which will target the Clouds in the near ...

  11. PULSATION FREQUENCIES AND MODES OF GIANT EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Le Bihan, Bastien [Ecole Polytechnique, Palaiseau, France. (France); Burrows, Adam, E-mail: bastien.le-bihan@polytechnique.edu, E-mail: burrows@astro.princeton.edu [Department of Astrophysical Science, Peyton Hall Princeton University, Princeton, NJ 08544 (United States)

    2013-02-10

    We calculate the eigenfrequencies and eigenfunctions of the acoustic oscillations of giant exoplanets and explore the dependence of the characteristic frequency {nu}{sub 0} and the eigenfrequencies on several parameters: the planet mass, the planet radius, the core mass, and the heavy element mass fraction in the envelope. We provide the eigenvalues for degree l up to 8 and radial order n up to 12. For the selected values of l and n, we find that the pulsation eigenfrequencies depend strongly on the planet mass and radius, especially at high frequency. We quantify this dependence through the calculation of the characteristic frequency {nu}{sub 0} which gives us an estimate of the scale of the eigenvalue spectrum at high frequency. For the mass range 0.5 M{sub J} {<=} M{sub P} {<=} 15 M{sub J} , and fixing the planet radius to the Jovian value, we find that {nu}{sub 0} {approx} 164.0 Multiplication-Sign (M{sub P} /M{sub J} ){sup 0.48}{mu}Hz, where M{sub P} is the planet mass and M{sub J} is Jupiter's mass. For the radius range from 0.9 to 2.0 R{sub J} , and fixing the planet's mass to the Jovian value, we find that {nu}{sub 0} {approx} 164.0 Multiplication-Sign (R{sub P} /R{sub J} ){sup -2.09}{mu}Hz, where R{sub P} is the planet radius and R{sub J} is Jupiter's radius. We explore the influence of the presence of a dense core on the pulsation frequencies and on the characteristic frequency of giant exoplanets. We find that the presence of heavy elements in the envelope affects the eigenvalue distribution in ways similar to the presence of a dense core. Additionally, we apply our formalism to Jupiter and Saturn and find results consistent with both the observational data of Gaulme et al. and previous theoretical work.

  12. Whole Earth Telescope observations of the pulsating subdwarf B star PG 0014+067

    CERN Document Server

    Vuckovic, M; O'Toole, S; Csubry, Z; Baran, A; Zola, S; Moskalik, P; Klumpe, E W; Riddle, R; O'Brien, M S; Mullally, F; Wood, M A; Wilkat, V; Zhou, A Y; Reed, M D; Terndrup, D M; Sullivan, D J; Kim, S L; Chen, W P; Chen, C W; Hsiao, W S; Sanchawala, K; Lee, H T; Jiang, X J; Janulis, R; Siwak, M; Ogloza, W; Paparo, M; Bognár, Z; Sodor, A; Handler, G; Lorenz, D; Steininger, B; Silvotti, R; Vauclair, G; Oreiro, R; Ostensen, R; Bronowska, A; Castanheira, B G; Kepler, S O; Fraga, L; Shipman, H L; Provencal, J L; Childers, D

    2006-01-01

    PG 0014+067 is one of the most promising pulsating subdwarf B stars for seismic analysis, as it has a rich pulsation spectrum. The richness of its pulsations, however, poses a fundamental challenge to understanding the pulsations of these stars, as the mode density is too complex to be explained only with radial and nonradial low degree (l < 3) p-modes without rotational splittings. One proposed solution, for the case of PG 0014+067 in particular, assigns some modes with high degree (l=3). On the other hand, theoretical models of sdB stars suggest that they may retain rapidly rotating cores, and so the high mode density may result from the presence of a few rotationally-split triplet (l=1), quintuplet (l=2) modes, along with radial (l=0) p-modes. To examine alternative theoretical models for these stars, we need better frequency resolution and denser longitude coverage. Therefore, we observed this star with the Whole Earth Telescope for two weeks in October 2004. In this paper we report the results of Whol...

  13. Line-profile variations in pulsating subdwarf-B stars as a pulsation mode diagnostic

    CERN Document Server

    Schoenaers, C

    2005-01-01

    In previous attempts to perform seismic modelling of pulsating subdwarf-B stars, various mode identification techniques are used with uncertain results. We investigated a method so far neglected in sdB stars, but very successful for Main Sequence pulsators, that is, mode identification from the line-profile variations caused by stellar pulsation. We report the calculation of time-resolved synthetic spectra for sdB stars pulsating with various combinations of pulsation modes; these calculations were carried out over appropriate ranges of effective temperature, surface gravity and helium abundances. Preliminary tests using these synthetic line-profile variations demonstrated their potential for mode identification by comparison with observation.

  14. First Kepler results on compact pulsators - I. Survey target selection and the first pulsators

    DEFF Research Database (Denmark)

    Østensen, Roy H.; Silvotti, Roberto; Charpinet, S.;

    2010-01-01

    We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its compilation are described, and spectroscopic observations are presented to separate the objects into...... accurate classes. From the Kepler photometry we clearly identify nine compact pulsators and a number of interesting binary stars. Of the pulsators, one shows the strong, rapid pulsations typical of a V361 Hya-type sdB variable (sdBV); seven show long-period pulsation characteristics of V1093 Her-type sd...

  15. Enhancements of Impinging Flame by Pulsation

    Institute of Scientific and Technical Information of China (English)

    AySu; Ying-ChiehLiu

    2000-01-01

    Experimental investigations on the pulsating jet-impinging diffusion flame were executed.A soleoid valve was aligned upstream of the jet orifice and the methane fuel was controlled in open-closed cycles from 0 Hz to 20Hz.Results show that the open-closed cycles,indeed increase the fluctuations of the methane fuel obviously.The evolutions of pulsating flame therefore develop faster than the continuous impinging flame.The optimized pulating frequencies are near 9 to 11 hz from the Re=170 to 283.The temperature differences between that under optimized pulsating rate and full open condition(no pulsation)are ranging from 100 to 150 degree.The pulsating effect is more singnificant at low Reynolds number.The cross section of continuous impinging flame behaves as elliptic shape with axial ratio equals to 2/3.The tip of the impinging flame obviously crosses at 42mm above the impinging point.ecause of the phenomenon of pulsation flame,the flame sheet or flame front may not be identified clearly in the averaged temperature contours.Results shows that the averaged end-contour of pulsation flame rears at 38mm above the impinging point.By observation and experiment,the pulsating flame behaves more stable and efficient than the continuous impinging flame.

  16. Self-pulsation in Raman fiber amplifiers

    DEFF Research Database (Denmark)

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.......Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated....

  17. Experimental Investigation of the Effect of Radial Gap and Impeller Blade Exit on Flow-Induced Vibration at the Blade-Passing Frequency in a Centrifugal Pump

    OpenAIRE

    Al-Qutub, A.; KHALIFA, A.; Khulief, Y.

    2009-01-01

    It has been recognized that the pressure pulsation excited by rotor-stator interaction in large pumps is strongly influenced by the radial gap between impeller and volute diffusers/tongues and the geometry of impeller blade at exit. This fluid-structure interaction phenomenon, as manifested by the pressure pulsation, is the main cause of flow-induced vibrations at the blade-passing frequency. In the present investigation, the effects of the radial gap and flow rate on pressure fluctuations, v...

  18. A study of the pulsation driving mechanism in pulsating combustors

    Science.gov (United States)

    Goldman, Y.; Timnat, Y. M.

    Experiments performed in a facility consisting of a Schmidt-type pulsating combustor, in which high-speed photographs were taken and pressure, temperature and gas composition measured, showed that the air supply conditions at the inlet and the volume of the combustor strongly influence the oscillation frequency. From the measurements, the existence of two separate regions, one containing cold air and the other containing fuel-rich gas, was found, and a pressure-volume diagram was drawn, showing the effect of chemical energy release and heat supply during the compression stroke and differentiating it from the expansion. A model of the interaction between the cyclic combustion process and the acoustic oscillations of the gas volume within the chamber and the tail-pipe is presented. The conditions for chemical energy release that result in high-pressure amplitude are described.

  19. Tidally Induced Pulsations in Kepler Eclipsing Binary KIC 3230227

    CERN Document Server

    Guo, Zhao; Fuller, Jim

    2016-01-01

    KIC 3230227 is a short period ($P\\approx 7.0$ days) eclipsing binary with a very eccentric orbit ($e=0.6$). From combined analysis of radial velocities and {\\it Kepler} light curves, this system is found to be composed of two A-type stars, with masses of $M_1=1.84\\pm 0.18M_{\\odot}$, $M_2=1.73\\pm 0.17M_{\\odot}$ and radii of $R_1=2.01\\pm 0.09R_{\\odot}$, $R_2=1.68\\pm 0.08 R_{\\odot}$ for the primary and secondary, respectively. In addition to an eclipse, the binary light curve shows a brightening and dimming near periastron, making this a somewhat rare eclipsing heartbeat star system. After removing the binary light curve model, more than ten pulsational frequencies are present in the Fourier spectrum of the residuals, and most of them are integer multiples of the orbital frequency. These pulsations are tidally driven, and both the amplitudes and phases are in agreement with predictions from linear tidal theory for $l=2, m=-2$ prograde modes.

  20. Studies of the Long Secondary Periods in Pulsating Red Giants

    CERN Document Server

    Percy, John R

    2016-01-01

    We have used systematic, sustained visual observations from the AAVSO International Database, and the AAVSO time-series analysis package VSTAR to study the unexplained "long secondary periods" (LSPs) in 27 pulsating red giants. In our sample, the LSPs range from 479 to 2967 days, and are on average 8.1 +/- 1.3 times the pulsation period. There is no evidence for more than one LSP in each star. In stars with both the fundamental and first overtone radial period present, the LSP is more often about 10 times the latter. The visual amplitudes of the LSPs are typically 0.1 magnitude and do not correlate with the LSP. The phase curves tend to be sinusoidal, but at least two are sawtooth. The LSPs are stable, within their errors, over the timespan of our data, which is typically 25,000 days. The amplitudes, however, vary by up to a factor of two or more on a timescale of roughly 20-30 LSPs. There is no obvious difference between the behavior of the carbon (C) stars and the normal oxygen (M) stars. Previous multicolo...

  1. V2653 Ophiuchii with a pulsating component and Ppuls - Porb, Ppuls - g correlations for γ Dor type pulsators

    Science.gov (United States)

    Çakırlı, Ö.; Ibanoglu, C.

    2016-05-01

    We present new spectroscopic observations of the double-lined eclipsing binary V2653 Ophiuchii. The photometric observations obtained by ASAS were analyzed and combined with the analysis of radial velocities for deriving the absolute parameters of the components. Masses and radii were determined for the first time as Mp = 1.537 ± 0.021 M⊙ and Rp = 2.215 ± 0.055 R⊙, Ms = 1.273 ± 0.019 M⊙ and Rs = 2.000 ± 0.056 R⊙ for the components of V2653 Oph. We estimate an interstellar reddening of 0.15 ± 0.08 mag and a distance of 300 ± 50 pc for the system, both supporting the membership of the open cluster Collinder 359. Using the out-of-eclipse photometric data we have made frequency analysis and detected a periodic signal at 1.0029 ± 0.0019 c/d. This frequency and the location of the more massive star on the HR diagram lead to classification of a γ Dor type variable. Up to date only eleven γ Dor type pulsators in the eclipsing binaries have been discovered. For six out of 11 systems, the physical parameters were determined. Although a small sample, we find empirical relations that Ppuls ∝ Porb0.43 and Ppuls ∝ g-0.83. While the pulsation periods increase with longer orbital periods, they decrease with increasing surface gravities of pulsating components and gravitational pull exerted by the companions. We present, briefly, the underlying physics behind the correlations we derived.

  2. Blue Straggler Masses from Pulsation Properties. II. Topology of the Instability Strip

    Science.gov (United States)

    Fiorentino, G.; Marconi, M.; Bono, G.; Dalessandro, E.; Ferraro, F. R.; Lanzoni, B.; Lovisi, L.; Mucciarelli, A.

    2015-09-01

    We present a new set of nonlinear, convective radial pulsation models for main-sequence stars computed assuming three metallicities: Z = 0.0001, 0.001, and 0.008. These chemical compositions bracket the metallicity of stellar systems hosting SX Phoenicis stars (SXPs, or pulsating Blue Stragglers), namely, Galactic globular clusters and nearby dwarf spheroidals. Stellar masses and luminosities of the pulsation models are based on alpha-enhanced evolutionary tracks from the BASTI website. We are able to define the topology of the instability strip (IS) and in turn the pulsation relations for the first four pulsation modes. We found that third overtones approach a stable nonlinear limit cycle. Predicted and empirical ISs agree quite well in the case of 49 SXPs belonging to ω Cen. We used theoretical period-luminosity (PL) relations in B and V bands to identify their pulsation mode. We assumed Z = 0.001 and Z = 0.008 as mean metallicities of SXPs in ω Cen. We found respectively 13-15 fundamental, 22-6 first-overtone, and 9-4 second-overtone modes. Five are unstable in the third-overtone mode only for Z = 0.001. Using the above mode identification and applying the proper mass-dependent PL relations, we found masses ranging from ˜1.0 to 1.2 {M}⊙ ( = 1.12, σ =0.04 {M}⊙ ) and from ˜1.2 to 1.5 {M}⊙ ( = 1.33, σ =0.03 {M}⊙ ) for Z = 0.001 and 0.008, respectively. Our investigation supports the use of evolutionary tracks to estimate SXP masses. We will extend our analysis to higher helium content, which may have an impact on our understanding of the blue straggler stars formation scenario.

  3. Controlling methods of a newly developed extra aortic counter-pulsation device using shape memory alloy fibers.

    Science.gov (United States)

    Hashem, Mohamed O; Yamada, A; Tsuboko, Y; Muira, H; Homma, D; Shiraishi, Y; Yambe, T

    2013-01-01

    Diastolic counter-pulsation has been used to provide circulatory augmentation for short term cardiac support. The success of intra-aortic balloon pump (IABP) therapy has generated interest in long term counter-pulsation strategies to treat heart failure patients. The authors have been developing a totally implantable extra aortic pulsation device for the circulatory support of heart failure patients, using 150 µm Ni-Ti anisotropic shape memory alloy (SMA) fibers. These fibers contract by Joule heating with an electric current supply. The special features of our design are as follow: non blood contacting, extra aortic pulsation function synchronizing with the native heart, a wrapping mechanical structure for the aorta in order to achieve its assistance as the aortomyoplsty and the extra aortic balloon pump. The device consisted of rubber silicone wall plates, serially connected for radial contraction. We examined the contractile function of the device, as well as it controlling methods; the phase delay parameter and the pulse width modulation, in a systemic mock circulatory system, with a pneumatically driven silicone left ventricle model, arterial rubber tubing, a peripheral resistance unit, and a venous reservoir. The device was secured around the aortic tubing with a counter-pulsation mode of 1:4 against the heartbeat. Pressure and flow waveforms were measured at the aortic outflow, as well as its driving condition of the contraction phase width and the phase delay. The device achieved its variable phase control for co-pulsation or counter-pulsation modes by changing the phase delay of the SMA fibers. Peak diastolic pressure significantly augmented, mean flow increased (p<0.05) according to the pulse width modulation. Therefore the newly developed extra aortic counter-pulsation device using SMA fibers, through it controlling methods indicated its promising alternative extra aortic approach for non-blood contacting cardiovascular circulatory support.

  4. Pulsating hot subdwarfs with MS companions or: EO Ceti is an sdO pulsator!

    CERN Document Server

    Østensen, Roy H

    2011-01-01

    About half of the hot subdwarfs are found to have spectra of composite types, indicating a main sequence companion of spectral type F-K, and the pulsators are no exception to this rule. The spectroscopic contamination from the main sequence stars makes it hard to reliably establish physical parameters for the hot component, and also makes pulsations harder to detect as the amplitudes are depressed. The binary fraction of the observed sample of hot subdwarf pulsators is discussed, as are the biases that are affecting it. Spectroscopic evidence is presented that clearly demonstrates that the well known sdB pulsator, EOCeti, is misclassified, and is actually an sdOV star.

  5. Pulsation, Mass Loss and the Upper Mass Limit

    Science.gov (United States)

    Klapp, J.; Corona-Galindo, M. G.

    1990-11-01

    RESUMEN. La existencia de estrellas con masas en exceso de 100 M0 ha sido cuestionada por mucho tiempo. Lfmites superiores para la masa de 100 M0 han sido obtenidos de teorfas de pulsaci6n y formaci6n estelar. En este trabajo nosotros primero investigamos la estabilidad radial de estrellas masivas utilizando la aproximaci6n clasica cuasiadiabatica de Ledoux, la aproximaci6n cuasiadiabatica de Castor y un calculo completamente no-adiabatico. Hemos encontrado que los tres metodos de calculo dan resultados similares siempre y cuando una pequefia regi6n de las capas externas de la estrella sea despreciada para la aproximaci6n clasica. La masa crftica para estabilidad de estrellas masivas ha sido encontrada en acuerdo a trabajos anteriores. Explicamos Ia discrepancia entre este y trabajos anteriores por uno de los autores. Discunmos calculos no-lineales y perdida de masa con respecto a) lfmite superior de masa. The existence of stars with masses in excess of 100 M0 has been questioned for a very long time. Upper mass limits of 100 Me have been obtained from pulsation and star formation theories. In this work we first investigate the radial stability of massive stars using the classical Ledoux's quasiadiabatic approximation. the Castor quasiadiabatic approximation and a fully nonadiabatic calculation. We have found that the three methods of calculation give similar results provided that a small region in outer layers of the star be neglected for the classical approximation. The critical mass for stability of massive stars is found to be in agreement with previous work. We explain the reason for the discrepancy between this and previous work by one of the authors. We discuss non-linear calculations and mass loss with regard to the upper mass limit. Key words: STARS-MASS FUNCTION - STARS-MASS LOSS - STARS-PULSATION

  6. Connections between whistlers and pulsation activity

    OpenAIRE

    Verö, J.; Zieger, B.; Szendröi, J.; Vellante, M.; Střesğtik, J.; Lühr, H.; A. Best; Körmendi, A.; Lichtenberger, J.; Ménesi, T.; P. Bencze; Märcz, F.; V. Wesztergom

    2000-01-01

    Simultaneous whistler records of one station and geomagnetic pulsation (Pc3) records at three stations were compared. In a previous study correlation was found between occurrence and L value of propagation/excitation for the two phenomena. The recently investigated simultaneous records have shown that the correlation is better on longer time scales (days) than on shorter ones (minutes), but the L values of the propagation of whistlers/excitation of pulsat...

  7. A motion picture presentation of magnetic pulsations

    Science.gov (United States)

    Suzuki, A.; Kim, J. S.; Sugura, M.; Nagano, H.

    1981-01-01

    Using the data obtained from the IMS North American magnetometer network stations at high latitudes, a motion picture was made by a computer technique, describing time changes of Pc5 and Pi3 magnetic pulsation vectors. Examples of pulsation characteristics derived from this presentation are regional polarization changes including shifts of polarization demarcation lines, changes in the extent of an active region and its movement with time.

  8. Convective heat transfer characteristics from combined mechanical and supply pulsed radial reattaching jets

    International Nuclear Information System (INIS)

    The heat transfer characteristics of combined mechanically and supply pulsated radial reattaching jets, CPRJR, were documented as a function of nozzle exit angle (0 deg. and 20 deg.), non-dimensional gap height (0.05 and 0.13), non-dimensional flow guide height (0.8 and 1.16), mechanical pulsation rate (5 and 10 Hz), mechanical to supply pulsation rate (1:1, 1:2, 1:3, and 1:4), phase angle (0 deg. and 180 deg.), and Reynolds number (1683 and 2366). Air was forced through a supply pulsation mechanism and then through a pulsated nozzle diverter apparatus. The air impinged on a heated plate where instantaneous heat flux and surface temperature measurements were collected and analyzed on instantaneous, ensemble-averaged, and area-averaged bases. CPRJR heat transfer can be characterized as a frequency interference of mechanical and supply pulsation effects. Significant improvement, up to 72%, over the corresponding mechanical pulsation case was found to occur for a supply-to-mechanical ratio of 3:1 with a phase angle of 0 deg. In general, the increased heat transfer rates were associated with the an increase in surface-directed momentum caused by increased cycle 'on' mass flow rate and corresponding entrainment

  9. A 3-D study of the photosphere of HD99563: I. Pulsation analysis

    CERN Document Server

    Freyhammer, L M; Elkin, V G; Mathys, G; Savanov, I; Zima, W; Shibahashi, H; Sekiguchi, K

    2009-01-01

    We have used high-speed spectroscopy of the rapidly oscillating Ap (roAp) star HD99563 to study the pulsation amplitude and phase behaviour of elements in its stratified atmosphere over one 2.91-d rotation cycle. We identify spectral features related to patches in the surface distribution of chemical elements and study the pulsation amplitudes and phases as the patches move across the stellar disk. The variations are consistent with a distorted nonradial dipole pulsation mode. We measure a 1.6 km/s rotational variation in the mean radial velocities of H-alpha and argue that this is the first observation of H-alpha abundance spots caused by He settling through suppression of convection by the magnetic field on an oblique rotator, in support of a prime theory for the excitation mechanism of roAp star pulsation. We demonstrate that HD99563 is the second roAp star to show aspect dependence of blue-to-red running wave line profile variations in Nd iii spots.

  10. Natural convection in square enclosure induced by inner circular cylinder with time-periodic pulsating temperature

    KAUST Repository

    Huang, Zhu

    2015-03-01

    The periodic unsteady natural convection flow and heat transfer in a square enclosure containing a concentric circular cylinder is numerically studied. The temperature of the inner circular cylinder fluctuates periodically with time at higher averaged value while the temperature of the enclosure keeps lower constant, and the natural convection is driven by the temperature difference. The two-dimensional natural convection is simulated with high accuracy temporal spectral method and local radial basis functions method. The Rayleigh number is studied in the range 103 ≤ Ra ≤ 106, the temperature pulsating period ranges from 0.01 to 100 and the temperature pulsating amplitudes are a = 0.5, 1.0 and 1.5. Numerical results reveal that the fluid flow and heat transfer is strongly dependent on the pulsating temperature of inner cylinder. Comparing with the steady state natural convection, the heat transfer is enhanced generally for the time-periodic unsteady natural convection, and the local maximum heat transfer rate is observed for Ra = 105 and 106. Moreover, the phenomenon of backward heat transfer is discussed quantitatively. Also, the influence of pulsating temperature on the unsteady fluid flow and heat transfer are discussed and analyzed.

  11. Pulsational line profile variation of the roAp star HR 3831

    CERN Document Server

    Kochukhov, O

    2005-01-01

    We report the first comprehensive investigation of the line profile variation caused by non-radial pulsation in a magnetic oscillating chemically peculiar star. Spectrum variation of the well-known roAp star HR 3831 is detected using very high-resolution high signal-to-noise spectroscopic time-series observations and are followed through the whole rotation cycle of the star. We confirm outstanding diversity of pulsational behaviour of different lines in the HR 3831 spectrum and attribute this phenomenon to an interplay between extreme vertical chemical inhomogeneity of the HR 3831 atmosphere and a running pulsation wave, propagating towards the upper photospheric layers with increasing amplitude. Rapid profile variation of the NdIII 6145 A line is characterized by measuring changes of its equivalent width and the first three moments. We demonstrate that rotational modulation of the radial velocity oscillations cannot be fully explained by an oblique axisymmetric dipole (ell=1, m=0) mode, implied by the classi...

  12. Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: II. Nonadiabatic analysis

    CERN Document Server

    Córsico, Alejandro H

    2016-01-01

    Low-mass ($M_{\\star}/M_{\\sun} \\lesssim 0.45$) white dwarfs, including the so called extremely low-mass white dwarfs (ELM, $M_{\\star}/M_{\\sun } \\lesssim 0.18-0.20$), are being currently discovered in the field of our Galaxy through dedicated photometric surveys. The fact that some of them pulsate opens the unparalleled chance for sounding their interiors. We present a detailed nonadiabatic pulsational analysis of such stars based on a new set of He-core white-dwarf models with masses ranging from $0.1554$ to $0.4352 M_{\\sun}$ derived by computing the non-conservative evolution of a binary system consisting of an initially $1 M_{\\sun}$ ZAMS star and a $1.4 M_{\\sun}$ neutron star. We have computed nonadiabatic radial modes and nonradial g and p modes to assess the dependence of the pulsational stability properties of these objects with stellar parameters such as the stellar mass, the effective temperature, and the convective efficiency. We found that a dense spectrum of unstable radial modes and nonradial g and ...

  13. Objective detection of retinal vessel pulsation.

    Directory of Open Access Journals (Sweden)

    William H Morgan

    Full Text Available PURPOSE: Retinal venous pulsation detection is a subjective sign, which varies in elevated intracranial pressure, venous obstruction and glaucoma. To date no method can objectively measure and identify pulsating regions. METHOD: Using high resolution video-recordings of the optic disk and retina we measured fluctuating light absorption by haemoglobin during pulsation. Pulsation amplitude was calculated from all regions of the retinal image video-frames in a raster pattern. Segmented retinal images were formed by objectively selecting regions with amplitudes above a range of threshold values. These were compared to two observers manually drawing an outline of the pulsating areas while viewing video-clips in order to generate receiver operator characteristics. RESULTS: 216,515 image segments were analysed from 26 eyes in 18 research participants. Using data from each eye, the median area under the receiver operator curve (AU-ROC was 0.95. With all data analysed together the AU-ROC was 0.89. We defined the ideal threshold amplitude for detection of any pulsating segment being that with maximal sensitivity and specificity. This was 5 units (95% confidence interval 4.3 to 6.0 compared to 12 units before any regions were missed. A multivariate model demonstrated that ideal threshold amplitude increased with increased variation in video-sequence illumination (p = 0.0119, but between the two observers (p = 0.0919 or other variables. CONCLUSION: This technique demonstrates accurate identification of retinal vessel pulsating regions with no areas identified manually being missed with the objective technique. The amplitude values are derived objectively and may be a significant advance upon subjective ophthalmodynamometric threshold techniques.

  14. Modeling of pulsating heat pipes.

    Energy Technology Data Exchange (ETDEWEB)

    Givler, Richard C.; Martinez, Mario J.

    2009-08-01

    This report summarizes the results of a computer model that describes the behavior of pulsating heat pipes (PHP). The purpose of the project was to develop a highly efficient (as compared to the heat transfer capability of solid copper) thermal groundplane (TGP) using silicon carbide (SiC) as the substrate material and water as the working fluid. The objective of this project is to develop a multi-physics model for this complex phenomenon to assist with an understanding of how PHPs operate and to be able to understand how various parameters (geometry, fill ratio, materials, working fluid, etc.) affect its performance. The physical processes describing a PHP are highly coupled. Understanding its operation is further complicated by the non-equilibrium nature of the interplay between evaporation/condensation, bubble growth and collapse or coalescence, and the coupled response of the multiphase fluid dynamics among the different channels. A comprehensive theory of operation and design tools for PHPs is still an unrealized task. In the following we first analyze, in some detail, a simple model that has been proposed to describe PHP behavior. Although it includes fundamental features of a PHP, it also makes some assumptions to keep the model tractable. In an effort to improve on current modeling practice, we constructed a model for a PHP using some unique features available in FLOW-3D, version 9.2-3 (Flow Science, 2007). We believe that this flow modeling software retains more of the salient features of a PHP and thus, provides a closer representation of its behavior.

  15. Pulsations in Subdwarf B Stars

    Indian Academy of Sciences (India)

    C. Simon Jeffery

    2005-06-01

    Subdwarf B stars play a significant role in close binary evolution and in the hot star content of old stellar populations, in particular in giant elliptical galaxies. While the question of their origin poses several problems for stellar evolution theory, one of their most fascinating properties is the presence of multi-periodic 2–3 minute oscillations. Interpreting these oscillations optimally requires the correct identification of the modes. Partial identifications can be obtained using high-speed observations of radial velocity and colour variations. We review some of the several attempts to make such observations, most recently with the Multi-Site Spectroscopic Telescope campaign and with ULTRACAM.

  16. Connections between whistlers and pulsation activity

    Directory of Open Access Journals (Sweden)

    J. Verö

    Full Text Available Simultaneous whistler records of one station and geomagnetic pulsation (Pc3 records at three stations were compared. In a previous study correlation was found between occurrence and L value of propagation/excitation for the two phenomena. The recently investigated simultaneous records have shown that the correlation is better on longer time scales (days than on shorter ones (minutes, but the L values of the propagation of whistlers/excitation of pulsations are correlated, i.e. if whistlers propagate in higher latitude ducts, pulsations have periods longer than in the case when whistlers propagate in lower latitude ducts.

    Key words: Electromagnetics (wave propagation - Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and instabilities

  17. Recent developments in pulsating aurora studies

    International Nuclear Information System (INIS)

    The field of pulsating aurora studies is reviewed. The paper begins with a short description of the characteristics of pulsating auroras and the theoretical ideas which, in view of existing experimental results, seem most important. A selection of new theoretical results and experimental results from both ground based instruments and instruments on rockets and satellites is then presented. There is now convincing evidence that the luminosity modulation is caused by a modulated flux of electron. The electron flux modulation seems to arise from a modulated resonant interaction between electrons and whistler mode waves in the equatorial plane, but the reason for the modulation is not known. Measurements concerning the drift and location of patches and the creation of Pi1 micropulsations are also deiscussed. Finally some suggestions for future research work are outlined. Optical measurements, especially with low light level TV, have proven to be of great importance in experimental studies of pulsating auroras. (author)

  18. Pulsations of blue supergiants before and after helium core ignition

    OpenAIRE

    Ostrowski, Jakub; Daszyńska-Daszkiewicz

    2013-01-01

    We present results of pulsation analyses of B-type supergiant models with masses of $14 - 18 M_\\odot$, considering evolutionary stages before and after helium core ignition. Using a non-adiabatic pulsation code, we compute instability domains for low degree modes. For selected models in these two evolutionary phases, we compare properties of pulsation modes. Significant differences are found in oscillation spectra and the kinetic energy density of pulsation modes.

  19. Benefit of pulsation in soft corals.

    Science.gov (United States)

    Kremien, Maya; Shavit, Uri; Mass, Tali; Genin, Amatzia

    2013-05-28

    Soft corals of the family Xeniidae exhibit a unique, rhythmic pulsation of their tentacles (Movie S1), first noted by Lamarck nearly 200 y ago. However, the adaptive benefit of this perpetual, energetically costly motion is poorly understood. Using in situ underwater particle image velocimetry, we found that the pulsation motions thrust water upward and enhance mixing across the coral-water boundary layer. The induced upward motion effectively prevents refiltration of water by neighboring polyps, while the intensification of mixing, together with the upward flow, greatly enhances the coral's photosynthesis. A series of controlled laboratory experiments with the common xeniid coral Heteroxenia fuscescens showed that the net photosynthesis rate during pulsation was up to an order of magnitude higher than during the coral's resting, nonpulsating state. This enhancement diminished when the concentration of oxygen in the ambient water was artificially raised, indicating that the enhancement of photosynthesis was due to a greater efflux of oxygen from the coral tissues. By lowering the internal oxygen concentration, pulsation alleviates the problem of reduced affinity of ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) to CO2 under conditions of high oxygen concentrations. The photosynthesis-respiration ratio of the pulsating H. fuscescens was markedly higher than the ratios reported for nonpulsating soft and stony corals. Although pulsation is commonly used for locomotion and filtration in marine mobile animals, its occurrence in sessile (bottom-attached) species is limited to members of the ancient phylum Cnidaria, where it is used to accelerate water and enhance physiological processes.

  20. Pulsating Strings in Lunin-Maldacena Backgrounds

    OpenAIRE

    Giardino, Sergio; Rivelles, Victor

    2011-01-01

    We consider pulsating strings in Lunin-Maldacena backgrounds, specifically in deformed Minkowski spacetime and deformed AdS_5xS^5. We find the relation between the energy and the oscillation number of the pulsating string when the deformation is small. Since the oscillation number is an adiabatic invariant it can be used to explore the regime of highly excited string states. We then quantize the string and look for such a sector. For the deformed Minkowski background we find a precise match w...

  1. Evaluation of Pump Pulsation in Respirable Size-Selective Sampling: Part I. Pulsation Measurements

    OpenAIRE

    Lee, Eun Gyung; Lee, Larry; Möhlmann, Carsten; Flemmer, Michael M.; Kashon, Michael; Harper, Martin

    2013-01-01

    Pulsations generated by personal sampling pumps modulate the airflow through the sampling trains, thereby varying sampling efficiencies, and possibly invalidating collection or monitoring. The purpose of this study was to characterize pulsations generated by personal sampling pumps relative to a nominal flow rate at the inlet of different respirable cyclones. Experiments were conducted using a factorial combination of 13 widely used sampling pumps (11 medium and 2 high volumetric flow rate pu...

  2. Kinetic theory of geomagnetic pulsations 2. Ion flux modulations by transverse waves

    International Nuclear Information System (INIS)

    Ion flux modulations by ultra-low-frequency radially polarized geomagnetic pulsations are examined theoretically based on the gyrokinetic analysis of Chen and Hasegawa. The theoretical results thus contain important effects such as plasma anisotropy and inhomogeneities, finite Larmor radii, realistic magnetic field, magnetic trapping, and wave mode structures. The predicted properties are consistent with the satellite observations [Takahashi et al.] and further support the drift-Alfven ballooning mode as a primary instability candidate. The analysis, furthermore, demonstrates that, in the case of highly energetic ions, it is crucial to include the finite-Larmor-radius effects self-consistently in order to properly analyze and compare with the satellite observations

  3. Auroral pulsations and accompanying VLF emissions

    Directory of Open Access Journals (Sweden)

    V. R. Tagirov

    Full Text Available Results of simultaneous TV observations of pulsating auroral patches and ELF-VLF-emissions in the morning sector carried out in Sodankylä (Finland on February 15, 1991 are presented. Auroral pulsating activity was typical having pulsating patches with characteristic periods of about 7 s. Narrow-band hiss emissions and chorus elements at intervals of 0.3–0.4 s formed the main ELF-VLF activity in the frequency range 1.0–2.5 kHz at the same time. The analysis of auroral images with time resolution of 0.04 s allowed perfectly separate analysis of spatial and temporal variations in the auroral luminosity. Mutual correspondence between the behaviour of the luminous auroral patches and the appearance of ELF noise type hiss emissions and VLF chorus trains was found in two intervals chosen for analysis. While the hiss emissions were associated with the appearance of luminosity inside a limited area close to the zenith, the structured VLF emissions were accompanied by rapid motion of luminosity inside the area. The spatial dimension of the pulsating area was about 45–50 km and luminosity propagated inside it with velocity of about 10–12 kms. We discuss a new approach to explain the 5–15 s auroral pulsation based on the theory of flowing cyclotron maser and relaxation characteristics of ionosphere.

    Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions · Space plasma physics (wave-particle interactions

  4. Digital filter technology and its application to geomagnetic pulsations in Antarctica

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Digital filter technology is an important method in study of geomagnetic pulsations in Antarctica. The signals received by pulsation magnetometer on the ground include various types of magnetic pulsations. Some types of pulsations or some frequency hands of pulsations can be extracted from the signals by means of digital filter technology because types of pulsations are defined according to their frequency range. In this paper usual digital filter technology is provided for study of magnetic pulsations in Antarctica and some examples are introduced.

  5. Interplay between pulsations and mass loss in the blue supergiant 55 Cygnus = HD 198478

    CERN Document Server

    Kraus, M; Cidale, L S; Venero, R O J; Nickeler, D H; Nemeth, P; Niemczura, E; Tomic, S; Aret, A; Kubat, J; Kubatova, B; Oksala, M E; Cure, M; Kaminski, K; Dimitrov, W; Fagas, M; Polinska, M

    2015-01-01

    Blue supergiant stars are known to display photometric and spectroscopic variability that is suggested to be linked to stellar pulsations. Pulsational activity in massive stars strongly depends on the star's evolutionary stage and is assumed to be connected with mass-loss episodes, the appearance of macroturbulent line broadening, and the formation of clumps in the wind. To investigate a possible interplay between pulsations and mass-loss, we carried out an observational campaign of the supergiant 55 Cyg over a period of five years to search for photospheric activity and cyclic mass-loss variability in the stellar wind. We modeled the H, He I, Si II and Si III lines using the nonlocal thermal equilibrium atmosphere code FASTWIND and derived the photospheric and wind parameters. In addition, we searched for variability in the intensity and radial velocity of photospheric lines and performed a moment analysis of the line profiles to derive frequencies and amplitudes of the variations. The Halpha line varies wit...

  6. KIC7668647: a 14 day beaming sdB+WD binary with a pulsating subdwarf

    CERN Document Server

    Telting, J H; Nemeth, P; Ostensen, R H; Kupfer, T; Macfarlane, S; Heber, U; Aerts, C; Geier, S

    2014-01-01

    The recently discovered subdwarf B (sdB) pulsator KIC7668647 is one of the 18 pulsating sdB stars detected in the Kepler field. It features a rich g-mode frequency spectrum, with a few low-amplitude p-modes at short periods. We use new ground-based low-resolution spectroscopy, and the near-continuous 2.88 year Kepler lightcurve, to reveal that KIC7668647 consists of a subdwarf B star with an unseen white-dwarf companion with an orbital period of 14.2d. An orbit with a radial-velocity amplitude of 39km/s is consistently determined from the spectra, from the orbital Doppler beaming seen by Kepler at 163ppm, and from measuring the orbital light-travel delay of 27 by timing of the many pulsations seen in the Kepler lightcurve. The white dwarf has a minimum mass of 0.40 M_sun. We use our high signal-to-noise average spectra to study the atmospheric parameters of the sdB star, and find that nitrogen and iron have abundances close to solar values, while helium, carbon, oxygen and silicon are underabundant relative t...

  7. Properties of daytime long-period pulsations during magnetospheric storm commencement

    Science.gov (United States)

    Klibanova, Yu. Yu.; Mishin, V. V.; Tsegmed, B.; Moiseev, A. V.

    2016-07-01

    Long-period geomagnetic pulsations during the SSC of July 14, 2012, are studied. The prenoon longitudinal sector (09:20-11:30) MLT, from the boundaries of which pulsations propagate azimuthally onto the dawn and dusk sides with an opposite polarization direction and increased amplitude, has been distinguished. The position of this sector relative to noon (a shift to the dawn side) depends on the front azimuthal inclination. It has been found that the polarization direction reverses in going from low (geomagnetic pulsations mainly fluctuate near the f 1 = 2.9 and f 2 = 4.4 mHz frequencies. Fluctuations with frequency f 1, which coincide with the fluctuation frequency of the IMF x component, predominate at the polar cap latitudes (the open field line region) in the form of rapidly attenuating impulses and at low latitudes with a much smaller amplitude. Fluctuations with frequency f 2 are globally registered at all latitudes in the dayside sector below the magnetopause projection as a train of several fluctuations. It is assumed that fluctuations with frequency f 1 penetrate from the solar wind, and fluctuations with frequency f 2 are radial magnetopause oscillations.

  8. A Pulsation Search Among Young Brown Dwarfs and Very Low Mass Stars

    CERN Document Server

    Cody, Ann Marie

    2014-01-01

    In 2005, Palla & Baraffe proposed that brown dwarfs (BDs) and very low mass stars (VLMSs; <0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated periods of 1-4 hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1-15 million year age range. Following up on reports of short-period variability in young clusters, we designed a high-cadence photometric monitoring campaign to search for deuterium-burning pulsation among a sample of 348 BDs and VLMSs in the four young clusters $\\sigma$ Orionis, Chamaeleon I, IC 348, and Upper Scorpius. In the resulting light curves we achieved sensitivity to periodic signals of amplitude several millimagnitudes, on timescales from 15 minutes to two weeks. Despite the exquisite data quality, we failed to detect any periodicities below seven hours. We conclude that D-burning pulsations are not able to grow to obs...

  9. Search for pulsations in M dwarfs in the Kepler short-cadence data base

    Science.gov (United States)

    Rodríguez, E.; Rodríguez-López, C.; López-González, M. J.; Amado, P. J.; Ocando, S.; Berdiñas, Z. M.

    2016-04-01

    The results of a search for stellar pulsations in M dwarf stars in the Kepler short-cadence (SC) data base are presented. This investigation covers all the cool and dwarf stars in the list of Dressing & Charbonneau, which were also observed in SC mode by the Kepler satellite. The sample has been enlarged via selection of stellar parameters (temperature, surface gravity and radius) with available Kepler Input Catalogue values together with JHK and riz photometry. In total, 87 objects observed by the Kepler mission in SC mode were selected and analysed using Fourier techniques. The detection threshold is below 10 μmag for the brightest objects and below 20 μmag for about 40 per cent of the stars in the sample. However, no significant signal in the [˜10,100] cd-1 frequency domain that can be reliably attributable to stellar pulsations has been detected. The periodograms have also been investigated for solar-like oscillations in the >100 cd-1 region, but with unsuccessful results too. Despite these inconclusive photometric results, M dwarfs pulsation amplitudes may still be detected in radial velocity searches. State-of-the-art coming instruments, like CARMENES near-infrared high-precision spectrograph, will play a key role in the possible detection.

  10. Precise radial velocities of giant stars VIII. Testing for the presence of planets with CRIRES Infrared Radial Velocities

    CERN Document Server

    Trifonov, Trifon; Zechmeister, Mathias; Reiners, Ansgar; Quirrenbach, Andreas

    2015-01-01

    We have been monitoring 373 very bright (V < 6 mag) G and K giants with high precision optical Doppler spectroscopy for more than a decade at Lick Observatory. Our goal was to discover planetary companions around those stars and to better understand planet formation and evolution around intermediate-mass stars. However, in principle, long-term, g-mode nonradial stellar pulsations or rotating stellar features, such as spots, could effectively mimic a planetary signal in the radial velocity data. Our goal is to compare optical and infrared radial velocities for those stars with periodic radial velocity patterns and to test for consistency of their fitted radial velocity semiamplitudes. Thereby, we distinguish processes intrinsic to the star from orbiting companions as reason for the radial velocity periodicity observed in the optical. Stellar spectra with high spectral resolution have been taken in the H-band with the CRIRES near-infrared spectrograph at ESO's VLT for 20 stars of our Lick survey. Radial velo...

  11. Noncommutative radial waves

    OpenAIRE

    Acatrinei, Ciprian

    2001-01-01

    We study radial waves in (2+1)-dimensional noncommutative scalar field theory, using operatorial methods. The waves propagate along a discrete radial coordinate and are described by finite series deformations of Bessel-type functions. At radius much larger than the noncommutativity scale $\\sqrt{\\theta}$, one recovers the usual commutative behaviour. At small distances, classical divergences are smoothed out by noncommutativity.

  12. Noncommutative radial waves

    CERN Document Server

    Acatrinei, C S

    2001-01-01

    We study radial waves in (2+1)-dimensional noncommutative scalar field theory, using operatorial methods. The waves propagate along a discrete radial coordinate and are described by finite series deformations of Bessel-type functions. At large radius with respect to the noncomutativity scale $\\theta$, the waves behave like the usual commutative ones.

  13. Study of sdO models. Pulsation Analysis

    CERN Document Server

    Rodríguez-López, C; Garrido, R; MacDonald, J; Oreiro, R; Ulla, A

    2009-01-01

    We have explored the possibility of driving pulsation modes in models of sdO stars in which the effects of element diffusion, gravitational settling and radiative levitation have been neglected so that the distribution of iron-peak elements remains uniform throughout the evolution. The stability of these models was determined using a non-adiabatic oscillations code. We analysed 27 sdO models from 16 different evolutionary sequences and discovered the first ever sdO models capable of driving high-radial order g-modes. In one model, the driving is by a classical kappa-mechanism due to the opacity bump from iron-peak elements at temperature ~200,000 K. In a second model, the driving result from the combined action of kappa-mechanisms operating in three distinct regions of the star: (i) a carbon-oxygen partial ionization zone at temperature ~2 10^6 K, (ii) a deeper region at temperature ~2 10^7 K, which we attribute to ionization of argon, and (iii) at the transition from radiative to conductive opacity in the co...

  14. Quasiperiodic ULF-pulsations in Saturn's magnetosphere

    Directory of Open Access Journals (Sweden)

    G. Kleindienst

    2009-02-01

    Full Text Available Recent magnetic field investigations made onboard the Cassini spacecraft in the magnetosphere of Saturn show the existence of a variety of ultra low frequency plasma waves. Their frequencies suggest that they are presumably not eigenoscillations of the entire magnetospheric system, but excitations confined to selected regions of the magnetosphere. While the main magnetic field of Saturn shows a distinct large scale modulation of approximately 2 nT with a periodicity close to Saturn's rotation period, these ULF pulsations are less obvious superimposed oscillations with an amplitude generally not larger than 3 nT and show a package-like structure. We have analyzed these wave packages and found that they are correlated to a certain extent with the large scale modulation of the main magnetic field. The spatial localization of the ULF wave activity is represented with respect to local time and Kronographic coordinates. For this purpose we introduce a method to correct the Kronographic longitude with respect to a rotation period different from its IAU definition. The observed wave packages occur in all magnetospheric regions independent of local time, elevation, or radial distance. Independent of the longitude correction applied the wave packages do not occur in an accentuated Kronographic longitude range, which implies that the waves are not excited or confined in the same selected longitude ranges at all times or that their lifetime leads to a variable phase with respect to the longitudes where they have been exited.

  15. Variability and pulsations in the Be star 66 Ophiuchi

    Science.gov (United States)

    Floquet, M.; Neiner, C.; Janot-Pacheco, E.; Hubert, A. M.; Jankov, S.; Zorec, J.; Briot, D.; Chauville, J.; Leister, N. V.; Percy, J. R.; Ballereau, D.; Bakos, A. G.

    2002-10-01

    66 Oph is a Be star seen under a moderate inclination angle that shows strong variability from UV to IR wavelengths. A concise review of long-term variability history is given. High resolution, high S/N spectroscopic observations obtained in 1997, 1998 and 2001 and spectropolarimetric observations obtained in 2000 are presented. These observations occurred during a long-term decrease of Hα intensity. Fundamental parameters of the star have been revisited from Barbier-Chalonge-Divan (BCD) calibrations. New V sin i values are obtained using Fourier transforms applied to observed helium lines and a rotational frequency f_rot = 1.29 c d-1 is determined. Time series analysis and Fourier Doppler Imaging (FDI) of He I lines (4713, 4921, 5876 and 6678 Å) lead for the first time to the detection of multi-periodicity in 66 Oph. The two main frequencies found are f = 2.22 c d-1 and f = 4.05 c d-1 . They are attributed to non-radial pulsations and can be associated with mode degree l = 2 and l = 3, respectively. Inspection of Stokes V profiles suggests the presence of a weak Zeeman signature but further observations are needed to confirm the detection of a magnetic field in 66 Oph. Based on observations taken at OHP and Pic du Midi Observatory (France), at MBT/LNA (Brazil) and on Brazilian observing time at La Silla (ESO, Chile).

  16. Stellar Pulsations in Beyond Horndeski Gravity Theories

    CERN Document Server

    Sakstein, Jeremy; Koyama, Kazuya

    2016-01-01

    Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.

  17. Flow induced pulsations in pipe systems

    Science.gov (United States)

    Bruggeman, Jan Cornelis

    1987-12-01

    The aeroacoustic behavior of a low Mach number, high Reynolds number flow through a pipe with closed side branches was investigated. Sound is generated by coherent structures of concentrated vorticity formed periodically in the separated flow in the T-shaped junctions of side branches and the main pipe. The case of moderate pulsation amplitudes was investigated. It appears that the vortical flow in a T-joint is an aeroacoustic source of constant strength when acoustic energy losses due to radiation and friction are small but not negligible. When acoustic energy losses due to radiation and friction are negligible, the nonlinear character of vortex damping is the amplitude limiting mechanism. It is stressed that aeroacoustic sources should not be neglected in studies of the response of a piping lay-out with flow to, e.g., the pulsating output of a compressor.

  18. Pulsating White Dwarf Stars and Precision Asteroseismology

    CERN Document Server

    Winget, D E

    2008-01-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  19. Gas Pulsations: A Shock Tube Mechanism

    OpenAIRE

    Huang, Paul Xiubao

    2012-01-01

    Gas pulsations are defined presently as a macro flow rate and/or pressure fluctuation with relatively low frequency and high amplitude. They commonly exist in HVACR, energy and other processing industries, and are widely accepted to be mainly caused by PD type gas machinery such as reciprocating or rotary compressors, expanders and Roots type blowers. Moreover, they are believed to be responsible for system vibrations, noises and fatigue failures. Naturally, as important a matter as gas pulsa...

  20. Erosion of metals by pulsating water jet

    OpenAIRE

    Foldyna, J.; Klich, J. (Jiří); Hlaváček, P.; M. Zeleňák; Ščučka, J. (Jiří)

    2012-01-01

    The aim of the paper was to determine erosion effects of pulsating water jet impinging the surface of metal sample. The influence of repeated impacts of water pulses and impact velocity (operating pressure) on the erosion of metal surface was investigated. The development of erosion pattern with respect to number of impacts was analysed and discussed. It was found that erosion caused by repeated impacts of water pulses occurs in three stages. The stage of erosion of the surface can be determi...

  1. Nonradial pulsations of hot evolved stars

    International Nuclear Information System (INIS)

    There are three classes of faint blue variable stars: the ZZ Ceti variables (DAV degenerate dwarfs), the DBV variables (DB degenerate dwarfs), and the GW Vir variables (DOV degenerate dwarfs). None of these classes of variable stars were known at the time of the last blue star meeting. Observational and theoretical studies of the ZZ Ceti variables, the DBV variables, and the GW Vir variables have shown them to be pulsating in nonradial g-modes. The cause of the pulsation has been determined for each class of variable star and, in all cases, also involves predictions of the stars envelope composition. The predictions are that the ZZ Ceti variables must have pure hydrogen surface layers, the DBV stars must have pure helium surface layers, and the GW Vir stars must have carbon and oxygen rich surface layers with less than 30% (by mass) of helium. Given these compositions, it is found that pulsation driving occurs as a result of the kappa and gamma effects operating in the partial ionization zones of either hydrogen or helium. In addition, a new driving mechanism, called convection blocking, also occurs in these variables. For the GW Vir variables, it is the kappa and gamma effects in the partial ionization regions of carbon and oxygen. 45 refs

  2. Location of Decimetric Pulsations in Solar Flares

    Science.gov (United States)

    Benz, Arnold O.; Battaglia, Marina; Vilmer, Nicole

    This work investigates the spatial relation between coronal X-ray sources and coherent radio emissions, both generally thought to be signatures of particle acceleration. Two limb events were selected during which the radio emission was well correlated in time with hard X-rays. The radio emissions were of the type of decimetric pulsations as determined from the spectrogram observed by Phoenix-2 of ETH Zurich. The radio positions were measured from observations with the Nançay Radioheliograph between 236 and 432 MHz and compared to the position of the coronal X-ray source imaged with RHESSI. The radio pulsations originated at least 30 - 240 Mm above the coronal hard X-ray source. The altitude of the radio emission increases generally with lower frequency. The average positions at different frequencies are on a line pointing approximately to the coronal hard X-ray source. Thus, the pulsations cannot be caused by electrons trapped in the flare loops, but are consistent with emission from a current sheet above the coronal source.

  3. Location of Decimetric Pulsations in Solar Flares

    CERN Document Server

    Benz, Arnold O; Vilmer, Nicole

    2011-01-01

    This work investigates the spatial relation between coronal X-ray sources and coherent radio emissions, both generally thought to be signatures of particle acceleration. Two limb events were selected during which the radio emission was well correlated in time with hard X-rays. The radio emissions were of the type of decimetric pulsations as determined from the spectrogram observed by Phoenix-2 of ETH Zurich. The radio positions were measured from observations with the Nancay Radioheliograph between 236 and 432 MHz and compared to the position of the coronal X-ray source imaged with RHESSI. The radio pulsations originated at least 30 - 240 Mm above the coronal hard X-ray source. The altitude of the radio emission increases generally with lower frequency. The average positions at different frequencies are on a line pointing approximately to the coronal hard X-ray source. Thus, the pulsations cannot be caused by electrons trapped in the flare loops, but are consistent with emission from a current sheet above the...

  4. SuperWASP observations of pulsating Am stars

    CERN Document Server

    Smalley, B; Smith, A M S; Fossati, L; Anderson, D R; Barros, S C C; Butters, O W; Cameron, A Collier; Christian, D J; Enoch, B; Faedi, F; Haswell, C A; Hellier, C; Holmes, S; Horne, K; Kane, S R; Lister, T A; Maxted, P F L; Norton, A J; Parley, N; Pollacco, D; Simpson, E K; Skillen, I; Southworth, J; Street, R A; West, R G; Wheatley, P J; Wood, P L

    2011-01-01

    We have studied over 1600 Am stars at a photometric precision of 1 mmag with SuperWASP photometric data. Contrary to previous belief, we find that around 200 Am stars are pulsating delta Sct and gamma Dor stars, with low amplitudes that have been missed in previous, less extensive studies. While the amplitudes are generally low, the presence of pulsation in Am stars places a strong constraint on atmospheric convection, and may require the pulsation to be laminar. While some pulsating Am stars have been previously found to be delta Sct stars, the vast majority of Am stars known to pulsate are presented in this paper. They will form the basis of future statistical studies of pulsation in the presence of atomic diffusion.

  5. FAME Radial Velocity Survey

    Science.gov (United States)

    Salim, S.; Gould, A.

    2000-12-01

    Full-Sky Astrometric Mapping Explorer (FAME) belongs to a new generation of astrometry satellites and will probe the surrounding space some 20 times deeper than its predecessor Hipparcos. As a result we will acquire precise knowledge of 5 out of 6 components of phase-space for millions of stars. The remaining coordinate, radial velocity, will remain unknown. In this study, we look at how the knowledge of radial velocity affects the determination of the structure of the Galaxy, and its gravitational potential. We therefore propose a radial velocity survey of FAME stars, and discuss its feasibility and technical requirements.

  6. Radial heat flux transformer

    Science.gov (United States)

    Basiulis, A.; Buzzard, R. J.

    1971-01-01

    Unit moves heat radially from small diameter shell to larger diameter shell, or vice versa, with negligible temperature drop, making device useful wherever heating or cooling of concentrically arranged materials, substances, and structures is desired.

  7. Pulsating extreme helium star BD + 13/sup 0/3224. 2. Ultraviolet fluxes and effective temperature variations

    Energy Technology Data Exchange (ETDEWEB)

    Lynas-Gray, A.E. (University Coll., London (UK). Dept. of Physics and Astronomy; Saint Andrews Univ. (UK). Observatory); Schoenberner, D.; Heber, U. (Kiel Univ. (Germany, F.R.). Inst. fuer Theoretische Physik; Kiel Univ. (Germany, F.R.). Sternwarte); Hill, P.W. (Saint Andrews Univ. (UK). Observatory; Anglo-Australian Observatory, Epping (Australia))

    1984-07-15

    Ultraviolet flux variations are reported for the pulsating extreme helium star BD + 13/sup 0/3224 (V652 Her). Effective temperature and angular radius variations over a cycle are determined from static plane-parallel LTE model atmospheres. When compared with radius changes derived from ground-based spectroscopy, the angular radius variations indicate radial pulsations and correspond to a distance of 1.5 +- 0.1 kpc. BD + 13/sup 0/3224 is thought to be a helium-burning star of 0.7 Msolar masses, which has an envelope contracting as the helium-burning core grows; it is similar to HD 144941 and these two stars may constitute a new sub-class of the hydrogen-deficient stars.

  8. Convective heat transfer characteristics of laminar pulsating pipe air flow

    Science.gov (United States)

    Habib, M. A.; Attya, A. M.; Eid, A. I.; Aly, A. Z.

    Heat transfer characteristics to laminar pulsating pipe flow under different conditions of Reynolds number and pulsation frequency were experimentally investigated. The tube wall of uniform heat flux condition was considered. Reynolds number was varied from 780 to 1987 while the frequency of pulsation ranged from 1 to 29.5Hz. The results showed that the relative mean Nusselt number is strongly affected by pulsation frequency while it is slightly affected by Reynolds number. The results showed enhancements in the relative mean Nusselt number. In the frequency range of 1-4Hz, an enhancement up to 30% (at Reynolds number of 1366 and pulsation frequency of 1.4Hz) was obtained. In the frequency range of 17-25Hz, an enhancement up to 9% (at Reynolds number of 1366 and pulsation frequency of 17.5Hz) was indicated. The rate of enhancement of the relative mean Nusselt number decreased as pulsation frequency increased or as Reynolds number increased. A reduction in relative mean Nusselt number occurred outside these ranges of pulsation frequencies. A reduction in relative mean Nusselt number up to 40% for pulsation frequency range of 4.1-17Hz and a reduction up to 20% for pulsation frequency range of 25-29.5Hz for Reynolds numbers range of 780-1987 were considered. This reduction is directly proportional to the pulsation frequency. Empirical dimensionless equations have been developed for the relative mean Nusselt number that related to Reynolds number (750

  9. Convective heat transfer characteristics of laminar pulsating pipe air flow

    Energy Technology Data Exchange (ETDEWEB)

    Habib, M.A. [King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Attya, A.M.; Eid, A.I.; Aly, A.Z. [Department of Mechanical Engineering, Cairo Univ. (Egypt)

    2002-02-01

    Heat transfer characteristics to laminar pulsating pipe flow under different conditions of Reynolds number and pulsation frequency were experimentally investigated. The tube wall of uniform heat flux condition was considered. Reynolds number was varied from 780 to 1987 while the frequency of pulsation ranged from 1 to 29.5 Hz. The results showed that the relative mean Nusselt number is strongly affected by pulsation frequency while it is slightly affected by Reynolds number. The results showed enhancements in the relative mean Nusselt number. In the frequency range of 1-4 Hz, an enhancement up to 30% (at Reynolds number of 1366 and pulsation frequency of 1.4 Hz) was obtained. In the frequency range of 17-25 Hz, an enhancement up to 9% (at Reynolds number of 1366 and pulsation frequency of 17.5 Hz) was indicated. The rate of enhancement of the relative mean Nusselt number decreased as pulsation frequency increased or as Reynolds number increased. A reduction in relative mean Nusselt number occurred outside these ranges of pulsation frequencies. A reduction in relative mean Nusselt number up to 40% for pulsation frequency range of 4.1-17 Hz and a reduction up to 20% for pulsation frequency range of 25-29.5 Hz for Reynolds numbers range of 780-1987 were considered. This reduction is directly proportional to the pulsation frequency. Empirical dimensionless equations have been developed for the relative mean Nusselt number that related to Reynolds number (750

  10. RY Sgr: pulsation period variations reinterpreted

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, W.A.; Cottrell, P.L.

    1988-04-01

    An analysis of recent observations of RY Sgr has shown that the times of light maxima can no longer be represented by a quadratic solution where the pulsation period decreases linearly with time. A cubic solution gives a better fit to the data, but a series of linear piecewise solutions satisfy the O-C residuals to within the observational uncertainty. We believe that the latter interpretation provides a more astrophysical explanation. Finally, a likely mass for the RCB stars of approx. 0.7 of the solar mass has been derived from observations of the RCB stars in the Large Magellanic Cloud.

  11. Design of a Hydrogen Pulsating Heat Pipe

    Science.gov (United States)

    Liu, Yumeng; Deng, Haoren; Pfotenhauer, John; Gan, Zhihua

    In order to enhance the application of a cryocooler that provides cooling capacity at the cold head location, and effectively spread that cooling over an extended region, one requires an efficient heat transfer method. The pulsating heat pipe affords a highly effective heat transfer component that has been extensively researched at room temperature, but is recently being investigated for cryogenic applications. This paper describes the design. The experimental setup is designed to characterize the thermal performance of the PHP as a function of the applied heat, number of turns, filling ratio, inclination angle, and length of adiabatic section.

  12. Measurement and evaluation of pulsating water jet peening intensity

    OpenAIRE

    Hlaváček, Petr

    2013-01-01

    Pulsating water jet peening is a promising method in surface treatment. It has the potential to induce compressive residual stresses that benefit the fatigue life of components similar to the other peening process. In this paper experimental results obtained by action of pulsating water jet on Almen strips are presented.

  13. Effect of pulsating water jet peening on stainless steel

    OpenAIRE

    Hlaváček, Petr

    2015-01-01

    Effects of action of pulsating water jet on polished surface of the stainless steel AISI 316L are presented. Surface slip bands appeared after this treatment. In the most severe conditions, microcracks were formed. Hardness measurement showed that the affected layer was thinner than 60 μm. Application of the pulsating water jet has beneficial effect on the fatigue life of the material.

  14. Pulsating laminar fully developed channel and pipe flows.

    Science.gov (United States)

    Haddad, Kais; Ertunç, Ozgür; Mishra, Manoranjan; Delgado, Antonio

    2010-01-01

    Analytical investigations are carried out on pulsating laminar incompressible fully developed channel and pipe flows. An analytical solution of the velocity profile for arbitrary time-periodic pulsations is derived by approximating the pulsating flow variables by a Fourier series. The explicit interdependence between pulsations of velocity, mass-flow rate, pressure gradient, and wall shear stress are shown by using the proper dimensionless parameters that govern the flow. Utilizing the analytical results, the scaling laws for dimensionless pulsation amplitudes of the velocity, mass-flow rate, pressure gradient, and wall shear stress are analyzed as functions of the dimensionless pulsation frequency. Special attention has been given to the scaling laws describing the flow reversal phenomenon occurring in pulsating flows, such as the condition for flow reversal, the dependency of the reversal duration, and the amplitude. It is shown that two reversal locations away from the wall can occur in pulsating flows in pipes and channels and the reversed amount of mass per period reaches a maximum at a certain dimensionless frequency for a given amplitude of mass-flow rate fluctuations. These analyses are numerically conducted for pipe and channel flows over a large frequency range in a comparative manner. PMID:20365456

  15. Analysis of low-frequency pulsations in Francis turbines

    Energy Technology Data Exchange (ETDEWEB)

    Fay, A A, E-mail: arpad.fay@t-online.h [Department of Fluid and Heat Engineering, University of Miskolc, Miskolc, H - 3515 (Hungary)

    2010-08-15

    The power pulsations of Francis turbines are discussed which occur regularly at part load but sometimes even at full load. The main tool of the analysis is the torque equation of Francis runners which has been derived from basic mechanics neglecting only very small effects. The various potential pulsation sources are grouped according to their places of origin, namely those occurring (i) in the inlet flow path (rotor-stator interaction) (ii) at the runner (interblade vortices, rotating stall) and (iii) in the draft tube (spiraling vortex flow). Their effects are discussed assuming certain ideal symmetrical velocity distributions. The main theoretical conclusions are: (1) The shaft torque pulsations may be determined from the turbulent velocity field. (2) In case of steady quasi-axisymmetric inflow the main pulsation source does not belong to group (i). (3) Of the pulsation sources (ii) and (iii) one is self-excited while the other is forced. (4) If the discharge is constant and the draft tube vortex rotates uniformly, then (iii) cannot affect the shaft torque. (5) If (iii) is the main source of the torque pulsations then discharge fluctuation must appear. (6) If the discharge pulsation is too small then either (ii) is the main source, or essential interactions of (ii) and (iii) may be expected. Thus, the torque equation is seen as a powerful tool of the analysis, and for future research attention is focused to the discharge pulsation.

  16. [Approaches to radial shaft].

    Science.gov (United States)

    Bartoníček, J; Naňka, O; Tuček, M

    2015-10-01

    In the clinical practice, radial shaft may be exposed via two approaches, namely the posterolateral Thompson and volar (anterior) Henry approaches. A feared complication of both of them is the injury to the deep branch of the radial nerve. No consensus has been reached, yet, as to which of the two approaches is more beneficial for the proximal half of radius. According to our anatomical studies and clinical experience, Thompson approach is safe only in fractures of the middle and distal thirds of the radial shaft, but highly risky in fractures of its proximal third. Henry approach may be used in any fracture of the radial shaft and provides a safe exposure of the entire lateral and anterior surfaces of the radius.The Henry approach has three phases. In the first phase, incision is made along the line connecting the biceps brachii tendon and the styloid process of radius. Care must be taken not to damage the lateral cutaneous nerve of forearm.In the second phase, fascia is incised and the brachioradialis identified by the typical transition from the muscle belly to tendon and the shape of the tendon. On the lateral side, the brachioradialis lines the space with the radial artery and veins and the superficial branch of the radial nerve running at its bottom. On the medial side, the space is defined by the pronator teres in the proximal part and the flexor carpi radialis in the distal part. The superficial branch of the radial nerve is retracted together with the brachioradialis laterally, and the radial artery medially.In the third phase, the attachment of the pronator teres is identified by its typical tendon in the middle of convexity of the lateral surface of the radial shaft. The proximal half of the radius must be exposed very carefully in order not to damage the deep branch of the radial nerve. Dissection starts at the insertion of the pronator teres and proceeds proximally along its lateral border in interval between this muscle and insertion of the supinator

  17. Double-mode radial-non-radial RR Lyrae stars in the OGLE photometry of the Galactic bulge

    CERN Document Server

    Netzel, H; Moskalik, P

    2014-01-01

    Non-radial modes are excited in classical pulsators, both in Cepheids and in RR Lyrae stars. Firm evidence come from the first overtone pulsators, in which additional shorter period mode is detected with characteristic period ratio falling in between 0.60 and 0.65. In the case of first overtone Cepheids three separate sequences populated by nearly 200 stars are formed in the Petersen diagram, i.e. the diagram of period ratio versus longer period. In the case of first overtone RR Lyrae stars (RRc stars) situation is less clear. A dozen or so such stars are known which form a clump in the Petersen diagram without any obvious structure. Interestingly, all first overtone RR Lyrae stars for which precise space-borne photometry is available show the additional mode, which suggests that its excitation is common. Motivated by these results we searched for non-radial modes in the OGLE-III photometry of RRc stars from the Galactic bulge. We report the discovery of 147 stars, members of a new group of double-mode, radia...

  18. Heat transfer characteristics of pulsated turbulent pipe flow

    Science.gov (United States)

    Habib, M. A.; Said, S. A. M.; Al-Farayedhi, A. A.; Al-Dini, S. A.; Asghar, A.; Gbadebo, S. A.

    Heat Transfer characteristics of pulsated turbulent pipe flow under different conditions of pulsation frequency, amplitude and Reynolds number were experimentally investigated. The pipe wall was kept at uniform heat flux. Reynolds number was varied from 5000 to 29 000 while frequency of pulsation ranged from 1 to 8 Hz. The results show an enhancement in the local Nusselt number at the entrance region. The rate of enhancement decreased as Re increased. Reduction of heat transfer coefficient was observed at higher frequencies and the effect of pulsation is found to be significant at high Reynolds number. It can be concluded that the effect of pulsation on the mean Nusselt numbers is insignificant at low values of Reynolds number.

  19. Radial oscillations of neutron stars in strong magnetic fields

    Indian Academy of Sciences (India)

    V K Gupta; Vinita Tuli; S Singh; J D Anand; Ashok Goyal

    2002-09-01

    The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.

  20. SABRE observations of Pi2 pulsations: case studies

    Directory of Open Access Journals (Sweden)

    E. G. Bradshaw

    Full Text Available The characteristics of substorm-associated Pi2 pulsations observed by the SABRE coherent radar system during three separate case studies are presented. The SABRE field of view is well positioned to observe the differences between the auroral zone pulsation signature and that observed at mid-latitudes. During the first case study the SABRE field of view is initially in the eastward electrojet, equatorward and to the west of the substorm-enhanced electrojet current. As the interval progresses, the western, upward field-aligned current of the substorm current wedge moves westward across the longitudes of the radar field of view. The westward motion of the wedge is apparent in the spatial and temporal signatures of the associated Pi2 pulsation spectra and polarisation sense. During the second case study, the complex field-aligned and ionospheric currents associated with the pulsation generation region move equatorward into the SABRE field of view and then poleward out of it again after the third pulsation in the series. The spectral content of the four pulsations during the interval indicate different auroral zone and mid-latitude signatures. The final case study is from a period of low magnetic activity when SABRE observes a Pi2 pulsation signature from regions equatorward of the enhanced substorm currents. There is an apparent mode change between the signature observed by SABRE in the ionosphere and that on the ground by magnetometers at latitudes slightly equatorward of the radar field of view. The observations are discussed in terms of published theories of the generation mechanisms for this type of pulsation. Different signatures are observed by SABRE depending on the level of magnetic activity and the position of the SABRE field of view relative to the pulsation generation region. A twin source model for Pi2 pulsation generation provides the clearest explanation of the signatures observed.

  1. Computational model of miniature pulsating heat pipes.

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Mario J.; Givler, Richard C.

    2013-01-01

    The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

  2. Secular Evolution in Mira Variable Pulsations

    CERN Document Server

    Templeton, M R; Willson, L A

    2005-01-01

    Stellar evolution theory predicts that asymptotic giant branch stars undergo a series of short thermal pulses that significantly change their luminosity and mass on timescales of hundreds to thousands of years. Secular changes in these stars resulting from thermal pulses can be detected as measurable changes in period if the star is undergoing Mira pulsations. The American Association of Variable Star Observers (AAVSO) International Database currently contains visual data for over 1500 Mira variables. Light curves for these stars span nearly a century in some cases, making it possible to study the secular evolution of the pulsation behavior on these timescales. In this paper, we present the results of our study of period change in 547 Mira variables using data from the AAVSO. We find non-zero rates of period change, dlnP/dt, at the 2-sigma significance level in 57 of the 547 stars, at the 3-sigma level in 21 stars, and at the level of 6-sigma or greater in eight of the 547. The latter eight stars have been pr...

  3. Determination of discharge during pulsating flow

    Science.gov (United States)

    Thompson, T.H.

    1968-01-01

    Pulsating flow in an open channel is a manifestation of unstable-flow conditions in which a series of translatory waves of perceptible magnitude develops and moves rapidly downstream. Pulsating flow is a matter of concern in the design and operation of steep-gradient channels. If it should occur at high stages in a channel designed for stable flow, the capacity of the channel may be inadequate at a discharge that is much smaller than that for which the channel was designed. If the overriding translatory wave carries an appreciable part of the total flow, conventional stream-gaging procedures cannot be used to determine the discharge; neither the conventional instrumentation nor conventional methodology is adequate. A method of determining the discharge during pulsating flow was tested in the Santa Anita Wash flood control channel in Arcadia, Calif., April 16, 1965. Observations of the dimensions and velocities of translatory waves were made during a period of controlled reservoir releases of about 100, 200, and 300 cfs (cubic feet per second). The method of computing discharge was based on (1) computation of the discharge in the overriding waves and (2) computation of the discharge in the shallow-depth, or overrun, part of the flow. Satisfactory results were obtained by this method. However, the procedure used-separating the flow into two components and then treating the shallow-depth component as though it were steady--has no theoretical basis. It is simply an expedient for use until laboratory investigation can provide a satisfactory analytical solution to the problem of computing discharge during pulsating flow. Sixteen months prior to the test in Santa Anita Wash, a robot camera had been designed .and programmed to obtain the data needed to compute discharge by the method described above. The photographic equipment had been installed in Haines Creek flood control channel in Los Angeles, Calif., but it had not been completely tested because of the infrequency of

  4. Radial Nerve Tendon Transfers.

    Science.gov (United States)

    Cheah, Andre Eu-Jin; Etcheson, Jennifer; Yao, Jeffrey

    2016-08-01

    Radial nerve palsy typically occurs as a result of trauma or iatrogenic injury and leads to the loss of wrist extension, finger extension, thumb extension, and a reduction in grip strength. In the absence of nerve recovery, reconstruction of motor function involves tendon transfer surgery. The most common donor tendons include the pronator teres, wrist flexors, and finger flexors. The type of tendon transfer is classified based on the donor for the extensor digitorum communis. Good outcomes have been reported for most methods of radial nerve tendon transfers as is typical for positional tendon transfers not requiring significant power. PMID:27387076

  5. Radial Velocity Studies of Close Binary Stars. XV

    CERN Document Server

    Pribulla, T; Blake, R M; Lu, W; Thomson, J R; De Bond, H; Karmo, T; de Ridder, A; Ogloza, W; Stachowski, G; Siwak, M

    2008-01-01

    Radial-velocity measurements and sine-curve fits to the orbital radial velocity variations are presented for the last eight close binary systems analyzed the same way as in the previous papers of this series: QX And, DY Cet, MR Del, HI Dra, DD Mon, V868 Mon, ER Ori, and Y Sex. For another seven systems (TT Cet, AA Cet, CW Lyn, V563 Lyr, CW Sge, LV Vir and MW Vir) phase coverage is insufficient to provide reliable orbits but radial velocities of individual components were measured. Observations of a few complicated systems observed throughout the DDO close-binary program are also presented; among them an especially interesting is the multiple system V857 Her which - in addition to the contact binary - very probably contains one or more sub-dwarf components of much earlier spectral type. All suspected binaries which were found to be most probably pulsating stars are briefly discussed in terms of mean radial velocities and projected rotation velocities (v sin i) as well as spectral type estimates. In two of them...

  6. Pulsating hydraulic fracturing technology in low permeability coal seams

    Institute of Scientific and Technical Information of China (English)

    Wang Wenchao; Li Xianzhong; Lin Baiquan; Zhai Cheng

    2015-01-01

    Based on the difficult situation of gas drainage in a single coal bed of high gas content and low perme-ability, we investigate the technology of pulsating hydraulic pressure relief, the process of crank plunger movement and the mechanism of pulsating pressure formation using theoretical research, mathematical modeling and field testing. We analyze the effect of pulsating pressure on the formation and growth of fractures in coal by using the pulsating hydraulic theory in hydraulics. The research results show that the amplitude of fluctuating pressure tends to increase in the case where the exit is blocked, caused by pulsating pressure reflection and frictional resistance superposition, and it contributes to the growth of fractures in coal. The crack initiation pressure of pulsating hydraulic fracturing is 8 MPa, which is half than that of normal hydraulic fracturing;the pulsating hydraulic fracturing influence radius reaches 8 m. The total amount of gas extraction is increased by 3.6 times, and reaches 50 L/min at the highest point. The extraction flow increases greatly, and is 4 times larger than that of drilling without fracturing and 1.2 times larger than that of normal hydraulic fracturing. The technology provides a technical measure for gas drainage of high gas content and low permeability in the single coal bed.

  7. Introducing CAFein, a New Computational Tool for Stellar Pulsations and Dynamic Tides

    CERN Document Server

    Valsecchi, Francesca; Willems, Bart; Kalogera, Vassiliki

    2013-01-01

    Here we present CAFein, a new computational tool for investigating radiative dissipation of dynamic tides in close binaries and of non-adiabatic, non-radial stellar oscillations in isolated stars in the linear regime. For the latter, CAFein computes the non-adiabatic eigenfrequencies and eigenfunctions of detailed stellar models. The code is based on the so-called Riccati method, a numerical algorithm that has been successfully applied to a variety of stellar pulsators, and which doesn't suffer of the major drawbacks of commonly used shooting and relaxation schemes. Here we present an extension of the Riccati method to investigate dynamic tides in close binaries. We demonstrate CAFein's capabilities as a stellar pulsation code both in the adiabatic and non-adiabatic regime, by reproducing previously published eigenfrequencies of a polytrope, and by successfully identifying the unstable modes of a stellar model in the beta Cephei/SPB region of the Hertzsprung-Russell diagram. Finally, we verify CAFein's behavi...

  8. Spectral Response of the Pulsationally-Induced Shocks in the Atmosphere of BW Vulpeculae

    CERN Document Server

    Smith, M A; Smith, Myron A.

    2003-01-01

    The star BW Vul excites an extremely strong radial pulsation that grows in its envelope and is responsible for visible shock features in the continuum flux and spectral line profiles emerging in the atmosphere At two phases separated by 0.8 cycles. Material propelled upwards in the atmosphere from the shock returns to the lower photosphere where it creates a second shock just before the start of the next cycle. We have obtained three nights of echelle data for this star over about 5 pulsation cycles (P = 0.201 days) in order to evaluate the effects of on a number of important lines in the spectrum, including the HeI 5875A and 6678A lines. These data were supplemented by archival high-dispersion IUE (UV) data from 1994. A comparison of profiles of the two HeI lines during the peak of the infall activity suggests that differences in the development of the blue wing at this time are due to heating and short-lived formations of an optically thin layer above the atmospheric region compressed by the infall. This di...

  9. HD 183648: a Kepler eclipsing binary with anomalous ellipsoidal variations and a pulsating component

    CERN Document Server

    Borkovits, T; Fuller, J; Szabo, Gy M; Pavlovski, K; Csak, B; Dozsa, A; Kovacs, J; Szabo, R; Hambleton, K M; Kinemuchi, K; Kolbas, V; Kurtz, D W; Maloney, F; Prsa, A; Southworth, J; Sztakovics, J; Biro, I B; Jankovics, I

    2014-01-01

    KIC 8560861 (HD 183648) is a marginally eccentric (e=0.05) eclipsing binary with an orbital period of P_orb=31.973d, exhibiting mmag amplitude pulsations on time scales of a few days. We present the results of the complex analysis of high and medium-resolution spectroscopic data and Kepler Q0 -- Q16 long cadence photometry. The iterative combination of spectral disentangling, atmospheric analysis, radial velocity and eclipse timing variation studies, separation of pulsational features of the light curve, and binary light curve analysis led to the accurate determination of the fundamental stellar parameters. We found that the binary is composed of two main sequence stars with an age of 0.9\\+-0.2 Gyr, having masses, radii and temperatures of M_1=1.93+-0.12 M_sun, R_1=3.30+-0.07 R_sun, T_eff1=7650+-100 K for the primary, and M_2=1.06+-0.08 M_sun, R_2=1.11+-0.03 R_sun, T_eff2=6450+-100 K for the secondary. After subtracting the binary model, we found three independent frequencies, two of which are separated by tw...

  10. Evidence of standing waves during a Pi2 pulsation event observed on Cluster

    Directory of Open Access Journals (Sweden)

    A. B. Collier

    2006-10-01

    Full Text Available Observations of Pi2 pulsations at middle and low latitudes have been explained in terms of cavity mode resonances, whereas transients associated with field-aligned currents appear to be responsible for the high latitude Pi2 signature.

    Data from Cluster are used to study a Pi2 event observed at 18:09 UTC on 21 January 2003, when three of the satellites were within the plasmasphere (L=4.7, 4.5 and 4.6 while the fourth was on the plasmapause or in the plasmatrough (L=6.6. Simultaneous pulsations at ground observatories and the injection of particles at geosynchronous orbit corroborate the occurrence of a substorm.

    Evidence of a cavity mode resonance is established by considering the phase relationship between the orthogonal electric and magnetic field components associated with radial and field-aligned standing waves. The relative phase between satellites located on either side of the geomagnetic equator indicates that the field-aligned oscillation is an odd harmonic. Finite azimuthal Poynting flux suggests that the cavity is effectively open ended and the azimuthal wave number is estimated as m~13.5.

  11. White dwarf evolution - Cradle-to-grave constraints via pulsation

    Science.gov (United States)

    Kawaler, Steven D.

    1990-01-01

    White dwarf evolution, particularly in the early phases, is not very strongly constrained by observation. Fortunately, white dwarfs undergo nonradial pulsation in three distinct regions of the H-R diagram. These pulsations provide accurate masses, surface compositional structure and rotation velocities, and help constrain other important physical properties. We demonstrate the application of the tools of stellar seismology to white dwarf evolution using the hot white dwarf star PG 1159-035 and the cool DAV (or ZZ Ceti) stars as examples. From pulsation studies, significant challenges to the theory of white dwarf evolution emerge.

  12. THE PULSATION MODE OF THE CEPHEID POLARIS

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D. G. [Department of Astronomy and Physics, Saint Mary' s University, Halifax NS B3H 3C3 (Canada); Kovtyukh, V. V.; Usenko, I. A. [Astronomical Observatory, Odessa National University, and Isaac Newton Institute of Chile, Odessa Branch, T. G. Shevkenko Park, 65014 Odessa (Ukraine); Gorlova, N. I., E-mail: turner@ap.smu.ca [Institute of Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2013-01-01

    A previously derived photometric parallax of 10.10 {+-} 0.20 mas, d = 99 {+-} 2 pc, is confirmed for Polaris by a spectroscopic parallax derived using line ratios in high dispersion spectra for the Cepheid. The resulting estimates for the mean luminosity of (M{sub V} ) = -3.07 {+-} 0.01 s.e., average effective temperature of (T{sub eff}) = 6025 {+-} 1 K s.e., and intrinsic color of ((B) - (V)){sub 0} = +0.56 {+-} 0.01 s.e., which match values obtained previously from the photometric parallax for a space reddening of E{sub B-V} = 0.02 {+-} 0.01, are consistent with fundamental mode pulsation for Polaris and a first crossing of the instability strip, as also argued by its rapid rate of period increase. The systematically smaller Hipparcos parallax for Polaris appears discrepant by comparison.

  13. The Pulsation Mode of the Cepheid Polaris

    CERN Document Server

    Turner, David G; Usenko, Igor; Gorlova, N

    2012-01-01

    A previously-derived photometric parallax of 10.10+-0.20 mas, d=99+-2 pc, is confirmed for Polaris by a spectroscopic parallax derived using line ratios in high dispersion spectra for the Cepheid. The resulting estimates for the mean luminosity of =-3.07+-0.01 s.e., average effective temperature of =6025+-1 K s.e., and intrinsic color of (-)o=0.56+-0.01 s.e., which match values obtained previously from the photometric parallax for a space reddening of E(B-V)=0.02+-0.01, are consistent with fundamental mode pulsation for Polaris and a first crossing of the instability strip, as also argued by its rapid rate of period increase. The systematically smaller Hipparcos parallax for Polaris appears discrepant by comparison.

  14. Pc3 pulsations during variable IMF conditions

    Directory of Open Access Journals (Sweden)

    U. Villante

    Full Text Available Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes.

    Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions

  15. Radial Halbach Magnetic Bearings

    Science.gov (United States)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2009-01-01

    Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while

  16. Asteroseismic fingerprints of rotation and mixing in the slowly pulsating B8 V star KIC 7760680

    CERN Document Server

    Pápics, P I; Aerts, C; Van Reeth, T; De Smedt, K; Hillen, M; Oestensen, R; Moravveji, E

    2015-01-01

    We present the first detection of a rotationally affected series consisting of 36 consecutive high-order sectoral dipole gravity modes in a slowly pulsating B (SPB) star. The results are based on the analysis of four years of virtually uninterrupted photometric data assembled with the Kepler Mission, and high-resolution spectra acquired using the HERMES spectrograph at the 1.2 meter Mercator Telescope. The spectroscopic measurements place KIC7760680 inside the SPB instability strip, near the cool edge. The photometric analysis reveals the longest unambiguous series of gravity modes of the same degree l with consecutive radial order n, that carries clear signatures of chemical mixing and rotation. With such exceptional observational constraints, this star should be considered as the Rosetta Stone of SPBs for future modelling, and bring us a step closer to the much needed seismic calibration of stellar structure models of massive stars.

  17. KIC 9533489: a genuine gamma Doradus-delta Scuti Kepler hybrid pulsator with transit events

    CERN Document Server

    Bognár, Zs; Frémat, Y; Southworth, J; Sódor, Á; De Cat, P; Isaacson, H T; Marcy, G W; Ciardi, D R; Gilliland, R L; Martín-Fernández, P

    2015-01-01

    Context: Several hundred candidate hybrid pulsators of type A-F have been identified from space-based observations. Their large number allows both statistical analyses and detailed investigations of individual stars. This offers the opportunity to study the full interior of the genuine hybrids, in which both low-radial-order p- and high-order g-modes are self-excited at the same time. However, a few other physical processes can also be responsible for the observed hybrid nature, related to binarity or to surface inhomogeneities. The finding that most delta Scuti stars also show long-period light variations represents a real challenge for theory. Methods: Fourier analysis of all the available Kepler light curves. Investigation of the frequency and period spacings. Determination of the stellar physical parameters from spectroscopic observations. Modelling of the transit events. Results: The Fourier analysis of the Kepler light curves revealed 55 significant frequencies clustered into two groups, which are separ...

  18. Radially inhomogeneous bounded plasmas

    Science.gov (United States)

    Zakeri-Khatir, H.; Aghamir, F. M.

    2016-07-01

    On the basis of kinetic theory along with self-consistent field equations, the expressions for dielectric tensor of radially inhomogeneous magnetized plasma columns are obtained. The study of dielectric tensor characteristics allows the accurate analysis of the inhomogeneous properties, beyond limitations that exist in the conventional method. Through the Bessel–Fourier transformation, the localized form of material equations in a radially inhomogeneous medium are obtained. In order to verify the integrity of the model and reveal the effect of inhomogeneity, a special case of a cylindrical plasma waveguide completely filled with inhomogeneous magnetized cold plasma was considered. The dispersion relation curves for four families of electromagnetic (EH and HE) and electrostatic (SC and C) modes are obtained and compared with the findings of the conventional model. The numerical analysis indicates that the inhomogeneity effect leads to coupling of electromagnetic and electrostatic modes each having different radial eigen numbers. The study also reveals that the electrostatic modes are more sensitive to inhomogeneous effects than the electromagnetic modes.

  19. LARGE EDDY SIMULATION OF PULSATING TURBULENT OPEN CHANNEL FLOW

    Institute of Scientific and Technical Information of China (English)

    ZOU Li-yong; LIU Nan-sheng; LU Xi-yun

    2004-01-01

    Pulsating turbulent open channel flow has been investigated by the use of Large Eddy Simulation (LES) technique coupled with dynamic Sub-Grid-Scale (SGS) model for turbulent SGS stress to closure the governing equations. Three-dimensional filtered Navier-Stokes equations are numerically solved by a fractional-step method. The objective of this study is to deal with the behavior of the pulsating turbulent open channel flow and to examine the reliability of the LES approach for predicting the pulsating turbulent flow. In this study, the Reynolds number (Reτ ) is chosen as 180 based on the friction velocity and the channel depth. The frequency of the driving pressure gradient for the pulsating turbulent flow ranges low, medium and high value. Statistical turbulence quantities as well as the flow structures are analyzed.

  20. Micro-Channel Embedded Pulsating Heat Pipes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — As the need for thermal control technology becomes more demanding Micro-Channel Embedded Pulsating Heat Pipes (ME-PHPs) represents a sophisticated and enabling...

  1. Canards in a rheodynamic model of cardiac pressure pulsations

    Institute of Scientific and Technical Information of China (English)

    Xie Feng; Chen Xian-Feng

    2007-01-01

    This paper reports on the canard phenomenon occurring in a rheodynamic model of cardiac pressure pulsations. By singular perturbation techniques the corresponding parameter value at which canards exist is obtained. The physiological significance of canards in this model is given.

  2. Search of Secondary Pulsation Modes: Globular cluster (NGC 6496)

    CERN Document Server

    Joshi, Gireesh C

    2016-01-01

    The Fourier-discrete-peridogram are used to identify pulsation modes in variables. We have found two pulsation modes in V1 and V2 among 13 new variables as described by Abbas et al.. The five variables V9 to V13 are not shown close to periodic values by analysis of the frequency distribution of multi-band data and also create difficulty to describe their varied nature. The multi-band periodic values of V1 and V6 are matched with known literature values. The scattering of the varied nature of secondary pulsation modes is eliminated by moving average methodology. The phase curve of secondary mode is found to be more smooth compared to a prominent mode of pulsation.

  3. Return of Pulsations in SDSS 0745+4538

    Science.gov (United States)

    Mukadam, Anjum S.; Townsley, D. M.; Szkody, P.; Gänsicke, B. T.; Winget, D. E.; Hermes, J. J.; Howell, Steve B.; Teske, J.; Patterson, Joseph; Kemp, Jonathan; Armstrong, Eve

    2010-11-01

    Nonradial pulsations had ceased in the accreting white dwarf SDSS J074531.92+453829.6 subsequent to its October 2006 outburst. We recently acquired optical high-speed time-series photometry on this cataclysmic variable more than three years after its outburst to find that pulsations have now returned to the primary white dwarf. Moreover, the observed pulsation periods agree with pre-outburst periods within the uncertainties of 1-2 s. This discovery is both remarkable and significant because it indicates that the outburst did not affect the interior stellar structure, which dictates the observed pulsation frequencies. Using this discovery in addition to an HST ultra-violet temperature measurement obtained one year after outburst, we have also been able to constrain the matter accreted during the 2006 outburst.

  4. KIC 7668647: a 14 day beaming sdB+WD binary with a pulsating subdwarf

    Science.gov (United States)

    Telting, J. H.; Baran, A. S.; Nemeth, P.; Østensen, R. H.; Kupfer, T.; Macfarlane, S.; Heber, U.; Aerts, C.; Geier, S.

    2014-10-01

    The recently discovered subdwarf B (sdB) pulsator KIC 7668647 is one of the 18 pulsating sdB stars detected in the Kepler field. It features a rich g-mode frequency spectrum, with a few low-amplitude p-modes at short periods. This makes it a promising target for a seismic study aiming to constrain the internal structure of this star, and of sdB stars in general. We use new ground-based low-resolution spectroscopy, and the near-continuous 2.88 year Kepler light curve, to reveal that KIC 7668647 consists of a subdwarf B star with an unseen white-dwarf companion with an orbital period of 14.2 d. An orbit with a radial-velocity amplitude of 39 km s-1 is consistently determined from the spectra, from the orbital Doppler beaming seen by Kepler at 163 ppm, and from measuring the orbital light-travel delay of 27 s by timing of the many pulsations seen in the Kepler light curve. The white dwarf has a minimum mass of 0.40 M⊙. We use our high signal-to-noise average spectra to study the atmospheric parameters of the sdB star, and find that nitrogen and iron have abundances close to solar values, while helium, carbon, oxygen and silicon are underabundant relative to the solar mixture. We use the full Kepler Q06-Q17 light curve to extract 132 significant pulsation frequencies. Period-spacing relations and multiplet splittings allow us to identify the modal degree ℓ for the majority of the modes. Using theg-mode multiplet splittings we constrain the internal rotation period at the base of the envelope to 46-48 d as a first seismic result for this star. The few p-mode splittings may point at a slightly longer rotation period further out in the envelope of the star. From mode-visibility considerations we derive that the inclination of the rotation axis of the sdB in KIC 7668647 must be around ~60°. Furthermore, we find strong evidence for a few multiplets indicative of degree 3 ≤ ℓ ≤ 8, which is another novelty in sdB-star observations made possible by Kepler. Based on

  5. Perceived radial translation during centrifugation

    NARCIS (Netherlands)

    Bos, J.E.; Correia Grácio, B.J.

    2015-01-01

    BACKGROUND: Linear acceleration generally gives rise to translation perception. Centripetal acceleration during centrifugation, however, has never been reported giving rise to a radial, inward translation perception. OBJECTIVE: To study whether centrifugation can induce a radial translation percepti

  6. Disintegration of Bone Cement by Continuous and Pulsating Water Jet

    OpenAIRE

    S. Hloch; Foldyna, J.; Sitek, L. (Libor); M. Zeleňák; Hlaváček, P.; Hvizdoš, P.; Kloc, J.; Monka, P.; Monková, K.; Kozak, D.; Magurová, D.

    2013-01-01

    The paper deals with the study of using continuous water jet and ultrasonic pulsating water jet for bone cement disintegration. Bone-cement Pallacos R+G (manually mixed) was disintegrated ex-vivo. Mechanical properties of the bone cement were determined by nano-indentation. Factors employed in evaluation were pressure (40, 80, 120) MPa and traverse speed for continuous water jet, pressure (8, 10, 12, 14, 16, 20) MPa and orifice type (flat, circular) for ultrasonic pulsating water jet. Depth p...

  7. Ultrasonic pulsations of pressure in a water jet cutting tool

    OpenAIRE

    Říha, Z. (Zdeněk); Foldyna, J.

    2012-01-01

    Water flow in a tool for water jet cleaning and cutting is evaluated in this paper. There are ultrasonic pulsations of high pressure in the given domain. The efficiency of the amplification of high pressure pulsations in the transitional space between larger and smaller pipes is analysed. Three types of transitional spaces are compared in the paper: step change, conical and radius change of pipe diameters.

  8. 3D Convection-pulsation Simulations with the HERACLES Code

    Science.gov (United States)

    Felix, S.; Audit, E.; Dintrans, B.

    2015-10-01

    We present 3D simulations of the coupling between surface convection and pulsations due to the κ-mechanism in classical Cepheids of the red edge of Hertzsprung-Russell diagram's instability strip. We show that 3D convection is less powerful than 2D convection and does not quench the radiative pulsations, leading to an efficient 3D κ-mechanism. Thus, the 3D instability strip is closer to the observed one than the 1D or 2D were.

  9. Observation and modeling of compressional Pi 3 magnetic pulsations

    Science.gov (United States)

    Matsuoka, Hitoshi; Takahashi, K.; Yumoto, K.; Anderson, B. J.; Sibeck, D. G.

    1995-01-01

    Compressional magnetic pulsations with irregular waveforms and periods longer than 150 s (here termed Pi 3) have been studied by using data from Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE/CCE) and GOES 5 and 6 in the dayside magnetosphere and compared with signatures on the ground at low latitudes by using data from Kakioka station (L = 1.25). On the ground, the pulsations appear in the horizontal component. A study of 17 such concurrent events during a 2-month period in 1986 reveals the following pulsation characteristics. (1) The peak-to-peak amplitudes in space (delta B(sub T)) and on the ground (delta H) are comparable and are in the range of 0.5-7 nT. (2) On the ground the pulsations can be seen at all local times, even at midnight, while at geostationary orbit they are observed only on the dayside with a clear amplitude maximum at noon. (3) The pulsations on the ground lag those observed by CCE near local noon, and the lag increases as the local time separation between CCE and the ground station increases. The time lag is 1-2 min longer when the ground station is on the nightside than when it is on the dayside. (4) The time lag between pulsations observed at geostationary orbit and near noon by CCE varies systematically with local time and is about 2 min per 6 hours of local time separation. These observations indicate that some nightside pulsations in the Pi 3 band have dayside origins. The position dependence of the pulsation amplitude can be explained well by changes in the magnetopause current, which are in turn presumably caused by changes in the solar wind dynamic pressure. The time lags observed in space are consistent with signal propagation in the MHD fast mode, but the variation in space-ground time lags with ground station local time must be attributed to another mechanism.

  10. Radial multiresolution in dimension three.

    NARCIS (Netherlands)

    H. Rauhut; M.M. Rösler

    2005-01-01

    Abstract We present a construction of a wavelet-type orthonormal basis for the space of radial $L^2$-functions in {\\bf R}$^3$ via the concept of a radial multiresolution analysis. The elements of the basis are obtained from a single radial wavelet by usual dilations and generalized translations. Her

  11. First Kepler results on compact pulsators - III. Subdwarf B stars with V1093 Her and hybrid (DW Lyn) type pulsations

    DEFF Research Database (Denmark)

    Reed, M.D.; Kawaler, Stephen D.; Østensen, Roy H.;

    2010-01-01

    -modes with periods of 2-5 min and in addition, these stars exhibit periodicities between both classes from 15 to 45 min. We detect the coolest and longest-period V1093 Her-type pulsator to date, KIC010670103 (Teff≈ 20 900 K, Pmax≈ 4.5 h) as well as a suspected hybrid pulsator, KIC002697388, which is extremely cool...... (Teff≈ 23 900 K) and for the first time hybrid pulsators which have larger g-mode amplitudes than p-mode ones. All of these pulsators are quite rich with many frequencies and we are able to apply asymptotic relationships to associate periodicities with modes for KIC010670103. Kepler data...

  12. Radial Reflection diffraction tomorgraphy

    Science.gov (United States)

    Lehman, Sean K

    2013-11-19

    A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.

  13. Radial reflection diffraction tomography

    Science.gov (United States)

    Lehman, Sean K.

    2012-12-18

    A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.

  14. Radial Rydberg wavepacket maps

    Science.gov (United States)

    Zeibel, J. G.; Jones, R. R.

    2001-04-01

    Picosecond laser pulses have been used to excite radial Rydberg wavepackets in Ca. Time-delayed, unipolar, `half-cycle' electric field pulses are used to probe the evolution of the wavepackets as a continuous function of binding energy. The data provide three-dimensional maps of wavepacket recurrence probability versus binding energy versus time. A rescaling of the energy and time coordinate axes allows the visualization of the distinct difference between the initial oscillations of the wavepacket and those that occur at integer and fractional revivals.

  15. Fine droplet generation using tunable electrohydrodynamic pulsation

    International Nuclear Information System (INIS)

    High-efficiency generation of fine droplets is significant for many microfluidic chips and sensor applications. To produce fine droplets, nozzles with small diameters are needed, which results in a high cost for nozzles and low efficiency of droplet generation. In this paper, a tunable electrohydrodynamic pulsation method which can generate fine droplets with high frequency and controllable size is presented using low conductivity liquids. The effects of flow rates and voltage parameters with respect to deposition frequency and droplet size are investigated. The influence of these parameters on Taylor cone formation time are also discussed and simple scaling laws are proposed to reveal and guide the droplet generation process. Experimental results show that single cycle deposition frequency decreases with increasing voltage frequency, but is only slightly influenced by the flow rates. The droplet size also decreases with voltage frequency, while large flow rates can make this decline gradual allowing better control. Moreover, the Taylor cone formation time may greatly affect the stability of the deposition frequency when the voltage frequency is larger than 30 Hz. Due to the short cycle time of high voltage frequencies, the hydrodynamic behavior in the emission process may be considerably affected by the increase of volume, which is also related to the flow rates. Tunable micropatterns consisting of fine droplets can be achieved by using this method in combination with motion stages. (paper)

  16. Radial cylinder aircraft engines

    OpenAIRE

    Šimíček, Petr

    2015-01-01

    Práce je zaměřena na konstrukční řešení letadlových hvězdicových motorů. Úvod je pojednáním o historii letadlových hvězdicových motorů a jejich vývoji v historickém kontextu. Druhá část je zaměřena na konstrukci letadlových hvězdicových motorů, následně jsou uvedena některá zajímavá konstrukční řešení a porovnání s motorem jiného druhu konstrukce. The bachelor's thesis is focused on design of aircraft radial engines. Home is a treatise on the history of aircraft radial engines and their de...

  17. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    Energy Technology Data Exchange (ETDEWEB)

    Córsico, A.H.; Althaus, L.G. [Grupo de Evolución Estelar y Pulsaciones, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, (1900) La Plata (Argentina); Bertolami, M.M. Miller [Instituto de Astrofísica La Plata, CONICET-UNLP, Paseo del Bosque s/n, (1900) La Plata (Argentina); Kepler, S.O. [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, Porto Alegre 91501-970, RS (Brazil); García-Berro, E., E-mail: acorsico@fcaglp.unlp.edu.ar, E-mail: althaus@fcaglp.unlp.edu.ar, E-mail: marcelo@MPA-Garching.MPG.DE, E-mail: kepler@if.ufrgs.br, E-mail: enrique.garcia-berro@upc.edu [Departament de Física Aplicada, Universitat Politècnica de Catalunya, c/Esteve Terrades 5, 08860, Castelldefels (Spain)

    2014-08-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ{sub ν}) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ{sub ν} ∼< 10{sup -11} μ{sub B}. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.

  18. Time-series spectroscopy of the pulsating eclipsing binary XX Cephei

    CERN Document Server

    Koo, Jae-Rim; Hong, Kyeongsoo; Kim, Seung-Lee; Lee, Chung-Uk

    2016-01-01

    Oscillating Algol-type eclipsing binaries (oEA) are very interesting objects that have three observational features of eclipse, pulsation, and mass transfer. Direct measurement of their masses and radii from the double-lined radial velocity data and photometric light curves would be the most essential for understanding their evolutionary process and for performing the asteroseismological study. We present the physical properties of the oEA star XX Cep from high-resolution time-series spectroscopic data. The effective temperature of the primary star was determined to be 7,946 $\\pm$ 240 K by comparing the observed spectra and the Kurucz models. We detected the absorption lines of the secondary star, which had never been detected in previous studies, and obtained the radial velocities for both components. With the published $BVRI$ light curves, we determined the absolute parameters for the binary via Wilson-Devinney modeling. The masses and radii are $M_{1} = 2.49 \\pm 0.06$ $M_\\odot$, $M_{2} = 0.38 \\pm 0.01$ $M_...

  19. Kepler photometry of RRc stars: peculiar double-mode pulsations and period doubling

    CERN Document Server

    Moskalik, P; Kolenberg, K; Molnár, L; Kurtz, D W; Szabó, R; Benkő, J M; Nemec, J M; Chadid, M; Guggenberger, E; Ngeow, C -C; Jeon, Y -B; Kopacki, G; Kanbur, S M

    2014-01-01

    We present the analysis of four first overtone RR Lyrae stars observed with the Kepler space telescope, based on data obtained over nearly 2.5yr. All four stars are found to be multiperiodic. The strongest secondary mode with frequency f_2 has an amplitude of a few mmag, 20 - 45 times lower than the main radial mode with frequency f_1. The two oscillations have a period ratio of P_2/P_1 = 0.612 - 0.632 that cannot be reproduced by any two radial modes. Thus, the secondary mode is nonradial. Modes yielding similar period ratios have also recently been discovered in other variables of the RRc and RRd types. These objects form a homogenous group and constitute a new class of multimode RR Lyrae pulsators, analogous to a similar class of multimode classical Cepheids in the Magellanic Clouds. Because a secondary mode with P_2/P_1 ~ 0.61 is found in almost every RRc and RRd star observed from space, this form of multiperiodicity must be common. In all four Kepler RRc stars studied, we find subharmonics of f_2 at ~1/...

  20. ISR Radial Field Magnet

    CERN Multimedia

    1983-01-01

    There were 37 (normal) + 3 (special) Radial Field magnets in the ISR to adjust vertically the closed orbit. Gap heights and strengths were 200 mm and .12 Tm in the normal magnets, 220 mm and .18 Tm in the special ones. The core length was 430 mm in both types. Due to their small length as compared to the gap heights the end fringe field errors were very important and had to be compensated by suitably shaping the poles. In order to save on cables, as these magnets were located very far from their power supplies, the coils of the normal type magnets were formed by many turns of solid cpper conductor with some interleaved layers of hollow conductor directly cooled by circulating water

  1. Photometric Survey to Search for Field sdO Pulsators

    CERN Document Server

    Johnson, Christopher B; Wallace, S; O'Malley, C J; Amaya, H; Biddle, L; Fontaine, G

    2013-01-01

    We present the results of a campaign to search for subdwarf O (sdO) star pulsators among bright field stars. The motivation for this project is the recent discovery by Randall et al. (2011), of four rapidly pulsating sdO stars in the globular cluster Omega Cen, with Teff near 50,000 K, 5.4 -0.1 and similar temperatures and gravities. To date, we have found no detectable pulsations at amplitudes above 0.08% (4 times the mean noise level) in any of the 36 field sdO stars that we observed. The presence of pulsations in Omega Cen sdO stars and their apparent absence in seemingly comparable field sdO stars is perplexing. While very suggestive, the significance of this result is difficult to assess more completely right now due to remaining uncertainties about the temperature width and purity of the Omega Cen instability strip and the existence of any sdO pulsators with weaker amplitudes than the current detection limit in globular clusters.

  2. Effects of inflow pulsation on a turbulent coaxial jet

    International Nuclear Information System (INIS)

    The effects of inflow pulsation on the flow characteristics and mixing properties of turbulent confined coaxial jet flows have been studied. Large eddy simulations were performed at Re = 9000 and the mean velocity ratio of the central to annular jet, Ui/Uo, was 0.6. Pulsation was generated in the inflow jet by varying the flow rates. First, inflow pulsation was applied at frequencies in the range 0.1 < St < 0.9 while other parameters were fixed. The pulsation frequency responses were scrutinized by examining the phase- and time-averaged turbulence statistics. The pulsation frequencies St = 0.180 and 0.327 were found to produce the largest enhancement in mixing and the largest reduction in the reattachment length, respectively. The effects of the phase difference between the two inflow jets at these two optimal frequencies were then investigated. The optimal phase difference conditions for mixing enhancement and the reduction in the reattachment length were obtained when the strength of the outer vortices was high. Further, we found that the strength of the inner vortices was reduced by varying the phase difference, and the reattachment length was minimized, and that if the strength of the inner vortices was increased, mixing was enhanced.

  3. Heartbeat Stars and the Ringing of Tidal Pulsations

    Directory of Open Access Journals (Sweden)

    Hambleton Kelly

    2015-01-01

    Full Text Available With the advent of high precision photometry from satellites such as Kepler and CoRoT, a whole new layer of interesting and astounding astronomical objects has been revealed: heartbeat stars are an example of such objects. Heartbeat stars are eccentric ellipsoidal variables that undergo strong tidal interactions when the stars are almost in contact at the time of closest approach. These interactions deform of the stars and cause a notable light curve variation in the form of a tidal pulse. A subset of these objects (~20% show prominent tidally induced pulsations: pulsations forced by the binary orbit. We now have a fully functional code that models binary star features (using PHOEBE and stellar pulsations simultaneously, enabling a complete and accurate heartbeat star model to be determined. In this paper we show the results of our new code, which uses emcee, a variant of mcmc, to generate a full set of stellar parameters. We further highlight the interesting features of KIC 8164262, including its tidally induced pulsations and resonantly locked pulsations.

  4. On the polarization properties of magnetar giant flare pulsating tails

    CERN Document Server

    Yang, Yuan-Pei

    2015-01-01

    Three giant flares have been detected so far from soft gamma-ray repeaters, each characterized by an initial short hard spike and a pulsating tail. The observed pulsating tails are characterized by a duration of $\\sim100\\,\\rm{s}$, an isotropic energy of $\\sim 10^{44}\\,\\rm{erg}$, and a pulse period of a few seconds. The pulsating tail emission likely originates from the residual energy after the intense energy release during the initial spike, which forms a trapped fireball composed of a photon-pair plasma in a closed field line region of the magnetars. Observationally the spectra of pulsating tails can be fitted by the superposition of a thermal component and a power-law component, with the thermal component dominating the emission in the early and late stages of the pulsating tail observations. In this paper, assuming that the trapped fireball is from a closed field line region in the magnetosphere, we calculate the atmosphere structure of the optically-thick trapped fireball and the polarization properties ...

  5. Application of the Baade-Wesselink method to a pulsating cluster Herbig Ae star: H254 in IC348

    CERN Document Server

    Ripepi, V; Marconi, M; Catanzaro, G; Claudi, R; Daszyńska-Daszkiewicz, J; Palla, F; Leccia, S; Bernabei, S

    2013-01-01

    In this paper we present new photometric and radial velocity data for the PMS $\\delta$ Sct star H254, member of the young cluster IC 348. Photometric V,R$_C$,I$_C$ light curves were obtained at the Loiano and Asiago telescopes. The radial velocity data was acquired by means of the SARG@TNG spectrograph. High-resolution spectroscopy allowed us to derive precise stellar parameters and the chemical composition of the star, obtaining: T$_{\\rm eff}$\\,=\\,6750\\,$\\pm$\\,150 K; $\\log g$\\,=\\,4.1\\,$\\pm$\\,0.4 dex; [Fe/H]=-0.07$\\pm$0.12 dex. Photometric and spectroscopic data were used to estimate the total absorption in the $V$ band A$_{\\rm V}$=2.06$\\pm$0.05 mag, in agreement with previous estimates. We adopted the technique of the difference in phase and amplitude between different photometric bands and radial velocities to verify that H254 is (definitely) pulsating in a radial mode. This occurrence allowed us to apply the CORS realization of the Baade--Wesselink method to obtain a value for the linear radius of H254 equ...

  6. Antiproton compression and radial measurements

    CERN Document Server

    Andresen, G B; Bowe, P D; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jorgensen, L V; Kurchaninov, L; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Page R D; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; Van der Werf, D P; Wurtele, J S; Yamazaki, Y

    2008-01-01

    Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, achieved by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile, and its relation to that of the electron plasma. We also measure the outer radial profile by ejecting antiprotons to the trap wall using an octupole magnet.

  7. Finding the Instability Strip for Accreting Pulsating White Dwarfs from HST and Optical Observations

    CERN Document Server

    Szkody, Paula; Gansicke, Boris T; Henden, Arne; Templeton, Matthew; Holtzman, Jon; Montgomery, Michael H; Howell, Steve B; Nitta, Atsuko; Sion, Edward M; Schwartz, Richard D; Dillon, William

    2010-01-01

    Time-resolved low resolution Hubble Space Telescope ultraviolet spectra together with ground-based optical photometry and spectra are used to constrain the temperatures and pulsation properties of six cataclysmic variables containing pulsating white dwarfs. Combining our temperature determinations for the five pulsating white dwarfs that are several years past outburst with past results on six other systems shows that the instability strip for accreting pulsating white dwarfs ranges from 10,500-15,000K, a wider range than evident for ZZ Ceti pulsators. Analysis of the UV/optical pulsation properties reveals some puzzling aspects. While half the systems show high pulsation amplitudes in the UV compared to their optical counterparts, others show UV/optical amplitude ratios that are less than one or no pulsations at either wavelength region.

  8. VizieR Online Data Catalog: Pulsation model data for delta Cep and eta Aql (Merand+, 2015)

    Science.gov (United States)

    Merand, A.; Kervella, P.; Breitfelder, J.; Gallenne, A.; Coude du Foresto, V.; ten Brummelaar, T. A.; McAlister, H. A.; Ridgway, S.; Sturmann, L.; Sturmann, J.; Turner, N. H.

    2015-09-01

    FITS files containing the stars' (delta Cep and eta Aql) data and model presented in the paper. Each fits file has 3 HDU: 1- primary HDU: contains no data apart from the header. The header has the parameters of the model (keywords 'HIERARCH PARAM') as well as some other quantities derived from the modeling (keywords 'HIERARCH MODEL'). These quantities are aimed at people who would like to reproduce or compare their results with us. 2- 'DATA' HDU: this contains the data used for the fit. Each line is a scalar measurement described as follow: col1='MJD' (E) modified Julian date of the observations col2='OBS' (A50) description of the data point: the string before ";" defines the type, after ";" is the source. after | are anciliary data: for diam, UDdiam: [wavelengthum, interfbaseline_m] for mag: photometric band for color: photometric band1 - photometric band2 col3='MEAS' (E) the actual measurements. units are km/s for Vpuls or Vrad (which includes the p-factor correction), and mas (milli-arcseconds) for diameters (diam of UDdiam). col4='ERR' (E) the uncertainty on the measurement. col5='MODEL' (E) corresponding value predicted by the model col6='PHASE' (E) pulsation phase computed from the model ranges from 0 to 1. col7='PERIOD' (E) pulsation period computed from the model in days 3- 'MODEL' HDU: a tabulation of the pulsation model, as a function of pulsation phase. col1='PHASE' (E) phase from 0 to 1. col2='Vpuls' (E) pulsation velocity, in km/s. col3='Vrad' (E) radial velocity, in km/s. It is Vpuls/p-factor + Vgamma. col4='diam' (E) Rosseland angular diameter, in milliarcseconds (mas). col5='Teff' (E) effective temperature, in Kelvin. col6='Lum' (E) Luminosity in solar luminosities. col7='logg' (E) surface gravity, in log_10(cm/s2). col8,9,10='diamK xxxm' (E) biased angular diameters measured by an interferometer at baselines xxx (in m), for xxx=[100, 200, 300]. In milliarcseconds col>=11= 'MAG ...' or 'COLOR ...' (E) reddenned magnitudes or colors in various bands

  9. Prediction of gas pulsation of an industrial compressor

    Institute of Scientific and Technical Information of China (English)

    Heuicheol; Kim; Mi-Gyung; Cho; Jaehong; Park; Cheolho; Bai; Jaesool; Shim

    2013-01-01

    The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field is developed. First, the conventional method for gas pulsation measurement and prediction, which separates the incident and reflected wave of acoustic waves traveling in the frequency domain, is discussed. Then, regression based on our proposed simple model, which is able to predict gas pulsation compared to the conventional method, is introduced for the analysis of a reciprocating compressor(The conventional method requires the value of sound speed in the piping line for the reciprocating compressor). A numerical prediction is made for the regression method. Three power spectrum values along the discharge pipeline are used for analysis, and two values are used for verification. Our results are in a good agreement with the conventional method.

  10. Outbursts in two new cool pulsating DA white dwarfs

    CERN Document Server

    Bell, Keaton J; Montgomery, M H; Fusillo, N P Gentile; Raddi, R; Gaensicke, B T; Winget, D E; Dennihy, E; Gianninas, A; Tremblay, P -E; Chote, P; Winget, K I

    2016-01-01

    The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with T_eff = 10,780 +/- 140 K and log(g) = 7.94 +/- 0.08, shows outbursts recurring on average every 5.0 d, increasing the overall flux by up to 15%. EPIC 229227292, with T_eff = 11,190 +/- 170 K and log(g) = 8.02 +/- 0.05, has outbursts that recur roughly every 2.4 d with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.

  11. Ultra-low-frequency magnetic pulsations in the earth's magnetosphere

    Science.gov (United States)

    Anderson, Brian J.

    1990-01-01

    Spacecraft observations have shown that geomagnetic pulsations originating in magnetospheric processes, in spite of their small amplitude on the ground, have amplitudes in space relative to the local magnetic field of 5-10 percent and occasionally up to about 50 percent. It is noted that by studying geomagnetic pulsations, a detailed comparison can be made between plasma physics theory and observations that are not possible in laboratory experiments. Also geomagnetic pulsations play a role in magnetospheric dynamics and energy transport, and their study forms an integral part of enhancing the knowledge of the magnetosphere. The importance of spacecraft observations are discussed and attention is given to such topics as waves in the magnetosphere, field-line resonances, the quantitative analysis of a dipole field, plasma instabilities, and energy flow.

  12. Finding the First Cosmic Explosions. III. Pair-Pulsational Supernovae

    CERN Document Server

    Whalen, Daniel J; Even, Wesley; Woosley, S E; Heger, Alexander; Stiavelli, Massimo; Fryer, Chris L

    2013-01-01

    Population III supernovae have been the focus of growing attention because of their potential to directly probe the properties of the first stars, particularly the most energetic events that can be seen at the edge of the observable universe. But until now pair-pulsation supernovae, in which explosive thermonuclear burning in massive stars fails to unbind them but can eject their outer layers into space, have been overlooked as cosmic beacons at the earliest redshifts. These shells can later collide and, like Type IIn supernovae, produce superluminous events in the UV at high redshifts that could be detected in the near infrared today. We present numerical simulations of a 110 M$_{\\odot}$ pair-pulsation explosion done with the Los Alamos radiation hydrodynamics code RAGE. We find that collisions between consecutive pair pulsations are visible in the near infrared out to z $\\sim$ 15 - 20 and can probe the earliest stellar populations at cosmic dawn.

  13. Behaviour of Pulsations in Hydrodynamic Models of Massive Stars

    CERN Document Server

    Lovekin, C C

    2014-01-01

    We have calculated the pulsations of massive stars using a nonlinear hydrodynamic code including time-dependent convection. The basic structure models are based on a standard grid published by Meynet et al. (1994). Using the basic structure, we calculated envelope models, which include the outer few percent of the star. These models go down to depths of at least 2 million K. These models, which range from 40 to 85 solar masses, show a range of pulsation behaviours. We find models with very long period pulsations ( $>$ 100 d), resulting in high amplitude changes in the surface properties. We also find a few models that show outburst-like behaviour. The details of this behaviour are discussed, including calculations of the resulting wind mass-loss rates.

  14. Outbursts in Two New Cool Pulsating DA White Dwarfs

    Science.gov (United States)

    Bell, Keaton J.; Hermes, J. J.; Montgomery, M. H.; Gentile Fusillo, N. P.; Raddi, R.; Gänsicke, B. T.; Winget, D. E.; Dennihy, E.; Gianninas, A.; Tremblay, P.-E.; Chote, P.; Winget, K. I.

    2016-10-01

    The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with {T}{eff} = 10,780 ± 140 K and {log} g = 7.94 ± 0.08, shows outbursts recurring on average every 5.0 days, increasing the overall flux by up to 15%. EPIC 229227292, with {T}{eff} = 11,190 ± 170 K and {log} g = 8.02 ± 0.05, has outbursts that recur roughly every 2.4 days with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.

  15. Influence of Cylinder Bore Volume on Pressure Pulsations in a Hermetic Reciprocating Compressor

    OpenAIRE

    Novak, Keith Adam

    2014-01-01

    Suction pressure pulsations created when the suction valve opens are caused by unsteady mass flow through the valve exciting acoustic resonances in the suction plenum. These pressure pulsations influence valve dynamics, compressor performance and compressor noise. This paper will show the importance of including the cylinder bore volume in the flow path analysis in order to accurately calculate pressure pulsations. Pressure pulsations will be calculated using Finite Element Method (FEM) calcu...

  16. Observations and asteroseismic analysis of the rapidly pulsating hot B subdwarf PG 0911+456

    Science.gov (United States)

    Randall, S. K.; Green, E. M.; Van Grootel, V.; Fontaine, G.; Charpinet, S.; Lesser, M.; Brassard, P.; Sugimoto, T.; Chayer, P.; Fay, A.; Wroblewski, P.; Daniel, M.; Story, S.; Fitzgerald, T.

    2007-12-01

    Aims:The principal aim of this project is to determine the structural parameters of the rapidly pulsating subdwarf B star PG 0911+456 from asteroseismology. Our work forms part of an ongoing programme to constrain the internal characteristics of hot B subdwarfs with the long-term goal of differentiating between the various formation scenarios proposed for these objects. So far, a detailed asteroseismic interpretation has been carried out for 6 such pulsators, with apparent success. First comparisons with evolutionary theory look promising, however it is clear that more targets are needed for meaningful statistics to be derived. Methods: The observational pulsation periods of PG 0911+456 were extracted from rapid time-series photometry using standard Fourier analysis techniques. Supplemented by spectroscopic estimates of the star's mean atmospheric parameters, they were used as a basis for the “forward modelling” approach in asteroseismology. The latter culminates in the identification of one or more “optimal” models that can accurately reproduce the observed period spectrum. This naturally leads to an identification of the oscillations detected in terms of degree ℓ and radial order k, and infers the structural parameters of the target. Results: The high S/N low- and medium resolution spectroscopy obtained led to a refinement of the atmospheric parameters for PG 0911+456, the derived values being T_eff = 31 940 ± 220 K, log g = 5.767 ± 0.029, and log He/H = -2.548 ± 0.058. From the photometry it was possible to extract 7 independent pulsation periods in the 150-200 s range with amplitudes between 0.05 and 0.8% of the star's mean brightness. There was no indication of fine frequency splitting over the 68-day time baseline, suggesting a very slow rotation rate. An asteroseismic search of parameter space identified several models that matched the observed properties of PG 0911+456 well, one of which was isolated as the “optimal” model on the basis of

  17. Generation of traveling atmospheric disturbances during pulsating geomagnetic storms

    Science.gov (United States)

    Gardner, L. C.; Schunk, R. W.

    2010-08-01

    Traveling atmospheric disturbances (TADs) are effective in transporting momentum and energy deposited at high latitudes to the midlatitude and low-latitude regions of the thermosphere. They also act to transport momentum and energy from the lower thermosphere into the upper thermosphere. Previously, model studies have been conducted to determine the characteristics of isolated, single-pulse TADs, but the generation of multiple TADs excited during pulsating storms have not been considered before. Here a high-resolution global thermosphere-ionosphere model was used to study the basic characteristics of multiple TADs excited during pulsating storms, including idealized weak and strong pulsating storms, and an approximation of the 4 May 1998 pulsating storm. For all three pulsating storm simulations, multiple TADs that propagated away from the auroral oval toward both the poles and the equator at all longitudes, with the maximum amplitudes between midnight and dawn, were excited. The TAD amplitudes were at maximum near the poles and diminished toward the equator and were larger on the nightside than on the dayside. The TADs propagated at a slightly upward angle to the horizontal, with the result that the lower boundary of the TADs increased with decreasing latitude. The TADs crossed the equator and propagated to midlatitudes in the opposite hemisphere, where wave interference occurred for the strong pulsating storm cases. The TAD wavelengths vary from 2500 to 3000 km and the phase speeds vary from 800 to 1000 m/s. The maximum TAD perturbations are 20% for the mass density, 14% for the neutral temperature, and 100 m/s for the winds.

  18. Connections between Quasi-periodicity and Modulation in Pulsating Stars

    CERN Document Server

    Benkő, J M

    2013-01-01

    The observations of the photometric space telescopes CoRoT and Kepler show numerous Blazhko RR Lyrae stars which have non-repetitive modulation cycles. The phenomenon can be explained by multi-periodic, stochastic or chaotic processes. From a mathematical point of view, almost periodic functions describe all of them. We assumed band-limited almost periodic functions either for the light curves of the main pulsation or for the modulation functions. The resulting light curves can generally be described analytically and it can also be examined by numerical simulations. This presentation is a part of our systematic study on the modulation of pulsating stars (Benko et al. 2009, 2011, 2012).

  19. Statistical characteristics of temperature pulsations within post-burnout region

    International Nuclear Information System (INIS)

    The experimental results of studies of statistical characteristics of temperature pulsations in a two-phase flow after dryout in post-burnout region are reported. The following statistical characteristics were investigated: intensity, probability distribution density, auto-correlation function and spectral density. Flow temperature pulsations were measured with microthermocouples. The tube was 10 mm in inner diameter; the pressure used was 137.3 bar for mass velocities of 350,000 and 700 kg/m2s. The maximum of relative flow enthalpy in the experiments did not exceed ΔH/r = 2. (U.S.)

  20. Flame fronts in Supernovae Ia and their pulsational stability

    CERN Document Server

    Glazyrin, S I; Dolgov, A D

    2013-01-01

    The structure of the deflagration burning front in type Ia supernovae is considered. The parameters of the flame are obtained: its normal velocity and thickness. The results are in good agreement with previous work of different authors. After that the question of pulsational instability of the flame subject to plane perturbations is considered. The flame can be unstable if hydrodynamics can be ignored, e.g. in solid-body propellants. However, with account of hydrodynamics we find that the flame in type Ia supernovae is pulsationally stable with realistic parameters of reactions and thermal conduction.

  1. Transformerless photovoltaic inverters with leakage current and pulsating power elimination

    DEFF Research Database (Denmark)

    Tang, Yi; Yao, Wenli; Wang, H.;

    2015-01-01

    This paper presents a transformerless inverter topology, which is capable of simultaneously solving leakage current and pulsating power issues in grid-connected photovoltaic (PV) systems. Without adding any additional components to the system, the leakage current caused by the PV...... that is inherent in single-phase PV systems. By properly injecting CM voltages to the output filter capacitors, the pulsating power can be decoupled from the dc-link. Therefore, it is possible to use long lifetime film capacitors instead of electrolytic capacitors to improve the reliability of the PV system...

  2. Cycles of self-pulsations in a photonic integrated circuit.

    Science.gov (United States)

    Karsaklian Dal Bosco, Andreas; Kanno, Kazutaka; Uchida, Atsushi; Sciamanna, Marc; Harayama, Takahisa; Yoshimura, Kazuyuki

    2015-12-01

    We report experimentally on the bifurcation cascade leading to the appearance of self-pulsation in a photonic integrated circuit in which a laser diode is subjected to delayed optical feedback. We study the evolution of the self-pulsing frequency with the increase of both the feedback strength and the injection current. Experimental observations show good qualitative accordance with numerical results carried out with the Lang-Kobayashi rate equation model. We explain the mechanism underlying the self-pulsations by a phenomenon of beating between successive pairs of external cavity modes and antimodes.

  3. Interactions of adjacent pulsating, erupting and creeping solitons

    Institute of Scientific and Technical Information of China (English)

    Song Li-Jun; Li Lu; Zhou Guo-Sheng

    2007-01-01

    This paper investigates the adjacent interactions of three novel solitons for the quintic complex Ginzburg-Landau equation, which are plain pulsating, erupting and creeping solitons. It is found that different performances are presented for different solitons due to isolated regions of the parameter space where they exist. For example, plain pulsating and erupting solitons exhibit mutual annihilation during collisions with the decrease of total energy, but for creeping soliton,the two adjacent pulses present soliton fusion without any loss of energy. Otherwise, the method for restraining the interactions is also found and it can suppress interacions between these two adjacent pulses effectively.

  4. Search for Optical Pulsations in PSR J0337+1715

    CERN Document Server

    Strader, M J; Meeker, S R; Szypryt, P; Walter, A B; van Eyken, J C; Ulbricht, G; Stoughton, C; Bumble, B; Kaplan, D L; Mazin, B A

    2016-01-01

    We report on a search for optical pulsations from PSR J0337+1715 at its observed radio pulse period. PSR J0337+1715 is a millisecond pulsar (2.7 ms spin period) in a triple hierarchical system with two white dwarfs, and has a known optical counterpart with g-band magnitude 18. The observations were done with the Array Camera for Optical to Near-IR Spectrophotometry (ARCONS) at the 200" Hale telescope at Palomar Observatory. No significant pulsations were found in the range 4000-11000 angstroms, and we can limit pulsed emission in g-band to be fainter than 25 mag.

  5. X-ray Pulsations in the Supersoft X-ray Binary CAL 83

    OpenAIRE

    Schmidtke, P. C.; Cowley, A. P.

    2005-01-01

    X-ray data reveal that the supersoft X-ray binary CAL 83 exhibits 38.4 minute pulsations at some epochs. These X-ray variations are similar to those found in some novae and are likely to be caused by nonradial pulsations the white dwarf. This is the first detection of pulsations in a classical supersoft X-ray binary.

  6. Investigation of the specific mass flow rate distribution in pipes supplied with a pulsating flow

    Energy Technology Data Exchange (ETDEWEB)

    Olczyk, Aleksander [Institute of Turbomachinery, Technical University of Lodz, Wolczanska 219/223, 90-924 Lodz (Poland)], E-mail: aolczyk@p.lodz.pl

    2009-08-15

    A pulsating flow is typical of inlet and exhaust pipes of internal combustion engines and piston compressors. Unsteady flow phenomena are especially important in the case of turbocharged engines, because dynamic effects occurring in the exhaust pipe can affect turbine operation conditions and performance. One of the basic parameters describing the unsteady flow is a transient mass flow rate related to the instantaneous flow velocity, which is usually measured by means of hot-wire anemometers. For the flowing gas, it is more appropriate to analyze the specific mass flow rate {phi}{sub m} = {rho}v, which takes into account also variations in the gas density. In order to minimize the volume occupied by measuring devices in the control section, special double-wire sensors for the specific mass flow rate (CTA) and temperature (CCT) measurement were applied. The article describes procedures of their calibration and measurement. Different forms of calibration curves are analyzed as well in order to match the approximation function to calibration points. Special attention is paid to dynamic phenomena related to the resonance occurring in a pipe for characteristic frequencies depending on the pipe length. One of these phenomena is a reverse flow, which makes it difficult to interpret properly the recorded CTA signal. Procedures of signal correction are described in detail. To verify the measurements, a flow field investigation was carried out by displacing probes radially and determining the profiles of the specific mass flow rate under the conditions of a steady and pulsating flow. The presence and general features of a reverse flow, which was identified experimentally, were confirmed by 1-D unsteady flow calculations.

  7. Radially truncated galactic discs

    CERN Document Server

    De Grijs, R; Wesson, K H; Grijs, Richard de; Kregel, Michiel; Wesson, Karen H.

    2000-01-01

    We present the first results of a systematic analysis of radially truncatedexponential discs for four galaxies of a sample of disc-dominated edge-onspiral galaxies. Edge-on galaxies are very useful for the study of truncatedgalactic discs, since we can follow their light distributions out to largerradii than in less highly inclined galaxies. The origin of these truncationsand their asymmetry and sharpness are helpful to better constrain theories ofgalaxy formation. In general, the discs of our sample galaxies are truncated at similar radiion either side of their centres. With the exception of the disc of ESO 416-G25,it appears that our sample galaxies are closely symmetric, in terms of both thesharpness of their disc truncations and the truncation length. However, thetruncations occur over a larger region and not as abruptly as found by van derKruit & Searle (KS1-4). We show that the truncated luminosity distributions of our sample galaxies,if also present in the mass distributions, comfortably meet the r...

  8. Radial distribution function in polymers

    Science.gov (United States)

    Przygocki, Wladyslaw

    1997-02-01

    Radial distribution function is a very useful tool for determination of the polymer structure. The connection between the scattered X-ray intensity and radial distribution function is presented. Some examples of RDF for polyethylene and for poly(ethylene terephtalate).

  9. Effective temperature and radial velocity of the small-amplitude Cepheid Polaris (alpha UMi) in 2015

    CERN Document Server

    Usenko, I A; Miroshnichenko, A S; Danford, S

    2016-01-01

    We present the results of an analysis of 21 spectra of alpha UMi (Polaris) obtained in September - December 2015. Frequency analysis shows an increase of the pulsation period up to 8.6 min in comparison to the 2007 observational set. The radial velocity amplitude comes to 4.16 km s^-1, and it approximately twice the one found in 2007. The average Teff = 6017 K, and it is close to the value determined for the 2001-2004 set. Therefore Polaris moves to the red edge of the Cepheid instability strip (CIS)

  10. Three ways to solve the orbit of KIC11558725: a 10 day beaming sdB+WD binary with a pulsating subdwarf

    CERN Document Server

    Telting, J H; Baran, A S; Bloemen, S; Reed, M D; Oreiro, R; Farris, L; Ottosen, T A; Aerts, C; Kawaler, S D; Heber, U; Prins, S; Green, E M; Kalomeni, B; O'Toole, S J; Mullally, F; Sanderfer, D T; Smith, J C; Kjeldsen, H

    2012-01-01

    The recently discovered subdwarf B (sdB) pulsator KIC11558725 features a rich g-mode frequency spectrum, with a few low-amplitude p-modes at short periods, and is a promising target for a seismic study aiming to constrain the internal structure of this star, and of sdB stars in general. We have obtained ground-based spectroscopic Balmer-line radial-velocity measurements of KIC11558725, spanning the 2010 and 2011 observing seasons. From these data we have discovered that KIC11558725 is a binary with period P=10.05 d, and that the radial-velocity amplitude of the sdB star is 58 km/s. Consequently the companion of the sdB star has a minimum mass of 0.63 M\\odot, and is therefore most likely an unseen white dwarf. We analyse the near-continuous 2010-2011 Kepler light curve to reveal orbital Doppler-beaming light variations at the 238 ppm level, which is consistent with the observed spectroscopic orbital radial-velocity amplitude of the subdwarf. We use the strongest 70 pulsation frequencies in the Kepler light cur...

  11. First Kepler results on compact pulsators VI. Targets in the final half of the survey phase

    DEFF Research Database (Denmark)

    H. Østensen, R.; Silvotti, R.; Charpinet, S.;

    2011-01-01

    We present results from the final six months of a survey to search for pulsations in white dwarfs and hot subdwarf stars with the Kepler spacecraft. Spectroscopic observations are used to separate the objects into accurate classes, and we explore the physical parameters of the subdwarf B (sd....... No V361 Hya type of short-period pulsating sdB stars were found in this half, leaving us with a total of one single multiperiodic V361 Hya and 13 V1093 Her pulsators for the full survey. Except for the sdB pulsators, no other clearly pulsating hot subdwarfs or white dwarfs were found, although a few...

  12. Pulsating Water Jet - A Tool for the Future?

    OpenAIRE

    Foldyna, J.

    2013-01-01

    Phenomenon arising during the impact of a droplet on the solid surface and its utilization to enhance effects of water jetting is described in the paper. Some examples of superior performance of pulsating water jets over the continuous ones are presented.

  13. Copper and Copper Alloys Disintegration Using Pulsating Water Jet

    OpenAIRE

    Lehocká, D.; Klich, J. (Jiří); Foldyna, J.; S. Hloch; M. Zeleňák; Cárach, J.

    2015-01-01

    Description of the surface topography of copper and coppeer alloys - brass and bronze is the object of investigation. The material was disintegrated using multiple transition of pulsating water jet with changing speed of feed. It is assumed that this ew way of metal eroding can be used in the automotive and engineering industries in the future.

  14. M dwarf search for pulsations within Kepler GO program

    CERN Document Server

    Rodríguez-López, C; MacDonald, J; Amado, P J; Carosso, A

    2014-01-01

    We present the analysis of four M dwarf stars -plus one M giant that seeped past our selection criteria- observed in Cycle 3 of Kepler Guest Observer program (GO3) in a search for intrinsic pulsations. Stellar oscillations in M dwarfs were theoretically predicted by Rodr\\'iguez-L\\'opez et al. (2012) to be in the range ~20-40 min and ~4-8 h, depending on the age and the excitation mechanism. We requested Kepler short cadence observations to have an adequate sampling of the oscillations. The targets were chosen on the basis of detectable rotation in the initial Kepler results, biasing towards youth.The analysis reveals no oscillations attributable to pulsations at a detection limit of several parts per million, showing that either the driving mechanisms are not efficient in developing the oscillations to observable amplitudes, or that if pulsations are driven, the amplitudes are very low. The size of the sample, and the possibility that the instability strip is not pure, allowing the coexistence of pulsators an...

  15. EXOTIME: searching for planets around pulsating subdwarf B stars

    CERN Document Server

    Schuh, Sonja; Lutz, Ronny; Loeptien, Bjoern; Green, Elizabeth M; Ostensen, Roy H; Leccia, Silvio; Kim, Seung-Lee; Fontaine, Gilles; Charpinet, Stephane; Francoeur, Myriam; Randall, Suzanna; Rodriguez-Lopez, Cristina; van Grootel, Valerie; Odell, Andrew P; Paparo, Margit; Bognar, Zsofia; Papics, Peter; Nagel, Thorsten; Beeck, Benjamin; Hundertmark, Markus; Stahn, Thorsten; Dreizler, Stefan; Hessman, Frederic V; Dall'Ora, Massimo; Mancini, Dario; Cortecchia, Fausto; Benatti, Serena; Claudi, Riccardo; Janulis, Rimvydas; 10.1007/s10509-010-0356-4

    2010-01-01

    In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time-scales of several years with two immediate observational goals: 1) determine Pdot of the pulsational periods P 2) search for signatures of substellar companions in O-C residuals due to periodic light travel time variations, which would be tracking the central star's companion-induced wobble around the center of mass. These sets of data should therefore at the same time: on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the Pdot (comparison with "local" evolutionary models), and on the othe...

  16. A statistical method for draft tube pressure pulsation analysis

    Science.gov (United States)

    Doerfler, P. K.; Ruchonnet, N.

    2012-11-01

    Draft tube pressure pulsation (DTPP) in Francis turbines is composed of various components originating from different physical phenomena. These components may be separated because they differ by their spatial relationships and by their propagation mechanism. The first step for such an analysis was to distinguish between so-called synchronous and asynchronous pulsations; only approximately periodic phenomena could be described in this manner. However, less regular pulsations are always present, and these become important when turbines have to operate in the far off-design range, in particular at very low load. The statistical method described here permits to separate the stochastic (random) component from the two traditional 'regular' components. It works in connection with the standard technique of model testing with several pressure signals measured in draft tube cone. The difference between the individual signals and the averaged pressure signal, together with the coherence between the individual pressure signals is used for analysis. An example reveals that a generalized, non-periodic version of the asynchronous pulsation is important at low load.

  17. Articulated pipes conveying fluid pulsating with high frequency

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    1999-01-01

    Stability and nonlinear dynamics of two articulated pipes conveying fluid with a high-frequency pulsating component is investigated. The non-autonomous model equations are converted into autonomous equations by approximating the fast excitation terms with slowly varying terms. The downward hanging...

  18. Pressure pulsations in reciprocating pump piping systems Part 1: Modelling

    CERN Document Server

    Shu, Jian-Jun; Edge, Kevin A

    2014-01-01

    A distributed parameter model of pipeline transmission line behaviour is presented, based on a Galerkin method incorporating frequency-dependent friction. This is readily interfaced to an existing model of the pumping dynamics of a plunger pump to allow time-domain simulations of pipeline pressure pulsations in both suction and delivery lines. A new model for the pump inlet manifold is also proposed.

  19. ON THE POLARIZATION PROPERTIES OF MAGNETAR GIANT FLARE PULSATING TAILS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuan-Pei [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Zhang, Bing, E-mail: yypspore@gmail.com, E-mail: zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

    2015-12-10

    Three giant flares have been detected so far from soft gamma-ray repeaters, each characterized by an initial short hard spike and a pulsating tail. The observed pulsating tails are characterized by a duration of ∼100 s, an isotropic energy of ∼10{sup 44} erg, and a pulse period of a few seconds. The pulsating tail emission likely originates from the residual energy after the intense energy release during the initial spike, which forms a trapped fireball composed of a photon-pair plasma in a closed-field-line region of the magnetars. Observationally the spectra of pulsating tails can be fitted by the superposition of a thermal component and a power-law component, with the thermal component dominating the emission in the early and late stages of the pulsating-tail observations. In this paper, assuming that the trapped fireball is from a closed-field-line region in the magnetosphere, we calculate the atmospheric structure of the optically thick trapped fireball and the polarization properties of the trapped fireball. By properly treating the photon propagation in a hot, highly magnetized, electron–positron pair plasma, we tally photons in two modes (O mode and E mode) at a certain observational angle through Monte Carlo simulations. Our results suggest that the polarization degree depends on the viewing angle with respect to the magnetic axis of the magnetar, and can be as high as Π ≃ 30% in the 1–30 keV band, and Π ≃ 10% in the 30–100 keV band, if the line of sight is perpendicular to the magnetic axis.

  20. The MACHO Project Sample of Galactic Bulge High-Amplitude Scuti Stars: Pulsation Behavior and Stellar Properties

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, D.P.; Cook, K.H.; Freeman, K.C.; Geha, M.; Griest, K.; Lehner, M.J.; Marshall, S.L.; McNamara, B.J.; Minniti, D.; Nelson, C.; Peterson, B.A.; Popowski, P.; Pratt, M.R.; Quinn, P.J.; Rodgers, A.W.; Sutherland, W.; Templeton, M.R.; Vandehei, T.; Welch, D.L.

    1999-11-16

    We have detected 90 objects with periods and lightcurve structure similar to those of field {delta} Scuti stars, using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude {delta} Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground {delta} Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population {delta} Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field {delta} Scuti stars and the {delta} Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude {delta} Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles d{sup -1}) and the observed period ratios of {approx}0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.

  1. The enigmatic He-sdB pulsator LS IV$-$14$^\\circ$116: new insights from the VLT

    CERN Document Server

    Randall, S K; Ziegerer, E; Geier, S; Fontaine, G

    2015-01-01

    The intermediate Helium subdwarf B star LS IV$-$14$^\\circ$116 is a unique object showing extremely peculiar atmospheric abundances as well as long-period pulsations that cannot be explained in terms of the usual opacity mechanism. One hypothesis invoked was that a strong magnetic field may be responsible. We discredit this possibility on the basis of FORS2 spectro-polarimetry, which allows us to rule out a mean longitudinal magnetic field down to 300 G. Using the same data, we derive the atmospheric parameters for LS IV$-$14$^\\circ$116 to be $T_{\\rm eff}$ = 31,150$\\pm$111 K, $\\log{g}$ = 5.88$\\pm$0.02 and $\\log{N(\\rm He)/N(\\rm H)}$ = $-$0.62$\\pm$0.01. The high surface gravity in particular is at odds with the theory that LS IV$-$14$^\\circ$116 has not yet settled onto the Helium Main Sequence, and that the pulsations are excited by an $\\epsilon$ mechanism acting on the Helium-burning shells present after the main Helium flash. Archival UVES spectroscopy reveals LS IV$-$14$^\\circ$116 to have a radial velocity of...

  2. First Kepler results on compact pulsators - V. Slowly pulsating subdwarf B stars in short-period binaries

    DEFF Research Database (Denmark)

    Kawaler, Stephen D.; Reed, Michael D.; Østensen, Roy H.;

    2010-01-01

    of sdB stars with a close M-dwarf companion with orbital periods of less than half a day. Because the orbital period is so short, the stars should be in synchronous rotation, and if so, the rotation period should imprint itself on the multiplet structure of the pulsations. However, we do not find clear...

  3. Understanding the dynamical structure of pulsating stars. HARPS spectroscopy of the delta Scuti stars rho Pup and DX Cet

    CERN Document Server

    Nardetto, N; Rainer, M; Guiglion, G; Scardia, M; Schmid, V S; Mathias, P

    2014-01-01

    High-resolution spectroscopy is a powerful tool to study the dynamical structure of pulsating stars atmosphere. We aim at comparing the line asymmetry and velocity of the two delta Sct stars rho Pup and DX Cet with previous spectroscopic data obtained on classical Cepheids and beta Cep stars. We obtained, analysed and discuss HARPS high-resolution spectra of rho Pup and DX Cet. We derived the same physical quantities as used in previous studies, which are the first-moment radial velocities and the bi-Gaussian spectral line asymmetries. The identification of f=7.098 (1/d) as a fundamental radial mode and the very accurate Hipparcos parallax promote rho Pup as the best standard candle to test the period-luminosity relations of delta Sct stars. The action of small-amplitude nonradial modes can be seen as well-defined cycle-to-cycle variations in the radial velocity measurements of rho Pup. Using the spectral-line asymmetry method, we also found the centre-of-mass velocities of rho Pup and DX Cet, V_gamma = 47.49...

  4. Effects of self-pulsation on the spray characteristics of gas-liquid swirl coaxial injector

    Science.gov (United States)

    Kang, Zhongtao; Li, Qinglian; Cheng, Peng; Zhang, Xinqiao; Wang, Zhen-guo

    2016-10-01

    To understand the influence of self-pulsation on the spray characteristics of gas-liquid swirl coaxial injector, a back-lighting photography technique has been employed to capture the instantaneous self-pulsated spray and stable spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of self-pulsation on the spray pattern, primary breakup, spray angle, diameter and velocity distribution and mass flow rate distribution are analyzed and discussed. The results show that the spray morphology is greatly influenced by self-pulsation. The stable spray has a cone shape, while the self-pulsated spray looks like a Christmas tree. The main difference of these two sprays is the primary breakup. The liquid film of stable spray keeps stable while that of self-pulsated spray oscillates periodically. The film width of self-pulsated spray varies in a large range with 'neck' and 'shoulder' features existing. The liquid film of self-pulsated spray breaks up at the second neck, and then the second shoulder begins to breakup into ligaments. The self-pulsated spray produces droplet clusters periodically, varies horizontal spray width and mass flux periodically. From the point of spatial distribution, self-pulsation is good for the spray, it uniformizes the mass flux along radius and increases the spray angle. However, when self-pulsation occurs, the SMD distribution varies from an inverted V shape to a hollow cone shape, and SMD increases at all the measuring points. Namely, from the point of atomization performance, self-pulsation has negative effects even when the breakup length is smaller. The effects of self-pulsation on the diameter and velocity distributions of the spray are mainly in the center part of the spray. The periphery of stable and self-pulsated spray has similar diameter and velocity distribution.

  5. Dedicated radial ventriculography pigtail catheter

    Energy Technology Data Exchange (ETDEWEB)

    Vidovich, Mladen I., E-mail: miv@uic.edu

    2013-05-15

    A new dedicated cardiac ventriculography catheter was specifically designed for radial and upper arm arterial access approach. Two catheter configurations have been developed to facilitate retrograde crossing of the aortic valve and to conform to various subclavian, ascending aortic and left ventricular anatomies. The “short” dedicated radial ventriculography catheter is suited for horizontal ascending aortas, obese body habitus, short stature and small ventricular cavities. The “long” dedicated radial ventriculography catheter is suited for vertical ascending aortas, thin body habitus, tall stature and larger ventricular cavities. This new design allows for improved performance, faster and simpler insertion in the left ventricle which can reduce procedure time, radiation exposure and propensity for radial artery spasm due to excessive catheter manipulation. Two different catheter configurations allow for optimal catheter selection in a broad range of patient anatomies. The catheter is exceptionally stable during contrast power injection and provides equivalent cavity opacification to traditional femoral ventriculography catheter designs.

  6. CoRoT\\,102699796, the first metal-poor Herbig Ae pulsator: a hybrid $\\delta$ Sct-$\\gamma$ Dor variable?

    CERN Document Server

    Ripepi, V; Di Criscienzo, M; Catanzaro, G; Palla, F; Marconi, M; Ventura, P; Neiner, C; Catala, C; Bernabei, S

    2011-01-01

    We present the analysis of the time series observations of CoRoT\\,102699796 obtained by the CoRoT satellite that show the presence of five independent oscillation frequencies in the range 3.6-5 c/d. Using spectra acquired with FLAMES@VLT, we derive the following stellar parameters: spectral type F1V, T$_{\\rm eff}$=7000$\\pm$200 K, log(g)=$3.8\\pm0.4$, [M/H]=$-1.1\\pm0.2$, $v$sin$i$=$50\\pm5$ km/s, L/L$_{\\odot}$=21$^{+21}_{-11}$. Thus, for the first time we report the existence of a metal poor, intermediate-mass PMS pulsating star. Ground-based and satellite data are used to derive the spectral energy distribution of CoRoT\\,102699796 extending from the optical to mid-infrared wavelengths. The SED shows a significant IR excess at wavelengths greater than $\\sim5 \\mu$. We conclude that CoRoT\\,102699796 is a young Herbig Ae (F1Ve) star with a transitional disk, likely associated to the HII region [FT96]213.1-2.2. The pulsation frequencies have been interpreted in the light of the non-radial pulsation theory, using the...

  7. Pulsating combustion - Combustion characteristics and reduction of emissions

    Energy Technology Data Exchange (ETDEWEB)

    Lindholm, Annika

    1999-11-01

    In the search for high efficiency combustion systems pulsating combustion has been identified as one of the technologies that potentially can meet the objectives of clean combustion and good fuel economy. Pulsating combustion offers low emissions of pollutants, high heat transfer and efficient combustion. Although it is an old technology, the interest in pulsating combustion has been renewed in recent years, due to its unique features. Various applications of pulsating combustion can be found, mainly as drying and heating devices, of which the latter also have had commercial success. It is, however, in the design process of a pulse combustor, difficult to predict the operating frequency, the heat release etc., due to the lack of a well founded theory of the phenomenon. Research concerning control over the combustion process is essential for developing high efficiency pulse combustors with low emissions. Natural gas fired Helmholtz type pulse combustors have been the experimental objects of this study. In order to investigate the interaction between the fluid dynamics and the chemistry in pulse combustors, laser based measuring techniques as well as other conventional measuring techniques have been used. The experimental results shows the possibilities to control the combustion characteristics of pulsating combustion. It is shown that the time scales in the large vortices created at the inlet to the combustion chamber are very important for the operation of the pulse combustor. By increasing/decreasing the time scale for the large scale mixing the timing of the heat release is changed and the operating characteristics of the pulse combustor changes. Three different means for NO{sub x} reduction in Helmholtz type pulse combustors have been investigated. These include exhaust gas recirculation, alteration of air/fuel ratio and changed inlet geometry in the combustion chamber. All used methods achieved less than 10 ppm NO{sub x} emitted (referred to stoichiometric

  8. Nonradial and radial period changes in the Delta Scuti star 4 CVn I. 700+ nights of photometry

    CERN Document Server

    Breger, Michel

    2016-01-01

    The nature of period and amplitude changes in nonradial pulsators is presently unknown. It is therefore important to examine the correlations between these changes in stars with a large number of simultaneously excited pulsation modes. However, the small amplitudes require extensive high-precision photometry covering many years. We present 702 nights of high-precision photometry of the evolved Delta Scuti variable 4 CVn obtained from 2005 - 2012 with a dedicated telescope. We detected 64 frequencies, of which 38 can be identified as combinations and harmonics. The relative amplitudes of the combination frequencies are similar to those found in 44 Tau and show no evidence for resonant mode coupling. Significant period and amplitude changes are detected for the dominant modes. The known prograde and retrograde modes show period changes with opposite signs, while the radial mode exhibits only small, cyclical period changes. For each mode, the period changes are constant over the eight years and range from (1/P)d...

  9. Numerical analysis on convective heat transfer characteristics in a pulsating laminar flow%层流脉动流动对流换热数值分析

    Institute of Scientific and Technical Information of China (English)

    王畅; 高璞珍; 许超

    2011-01-01

    In order to improve the heat transfer equipment design and enhance the heat transfer efficiency, a mathematical model was established to analyze the flow and heat transfer characteristics of a pulsating laminar flow in a circular pipe, and the pipe was heated under a constant heat flux boundary condition. The results show that a phase lag exists between the flow velocity and pressure drop. With an increase in the pulsating frequency, the value of the phase lag tends to be π/2. In addition, the value of radial velocity fluctuation decreases with the increase of frequency , but the annular effect becomes more noticeable. Furthermore, the pulsating amplitude temperature decreases with the increase of frequency and Prandtl number, but increases with the increase of pulsating amplitude veloc-ity.%为了改进换热器设计方法及提高设备换热效率,通过建立恒定热流密度加热的圆管内层流脉动流动数学模型,对流量脉动条件下的流动与传热特性进行了数值分析.研究结果表明,脉动流动时速度与压降发生同周期的变化,但两者之间存在相位差,随着脉动频率增加,相位差逐步趋近于π/2;脉动速度的径向分布在一定频率范围内出现环状效应,频率越大速度脉动幅值越小,但环状效应越明显;温度脉动幅度随脉动频率、普朗特数增加而减小,随速度脉动幅度增加而增加.

  10. Experimental Investigation of the Effect of Radial Gap and Impeller Blade Exit on Flow-Induced Vibration at the Blade-Passing Frequency in a Centrifugal Pump

    Directory of Open Access Journals (Sweden)

    A. Al-Qutub

    2009-01-01

    Full Text Available It has been recognized that the pressure pulsation excited by rotor-stator interaction in large pumps is strongly influenced by the radial gap between impeller and volute diffusers/tongues and the geometry of impeller blade at exit. This fluid-structure interaction phenomenon, as manifested by the pressure pulsation, is the main cause of flow-induced vibrations at the blade-passing frequency. In the present investigation, the effects of the radial gap and flow rate on pressure fluctuations, vibration, and pump performance are investigated experimentally for two different impeller designs. One impeller has a V-shaped cut at the blade's exit, while the second has a straight exit (without the V-cut. The experimental findings showed that the high vibrations at the blade-passing frequency are primarily raised by high pressure pulsation due to improper gap design. The existence of V-cut at blades exit produces lower pressure fluctuations inside the pump while maintaining nearly the same performance. The selection of proper radial gap for a given impeller-volute combination results in an appreciable reduction in vibration levels.

  11. A high-speed bi-polar outflow from the archetypical pulsating star Mira A

    CERN Document Server

    Meaburn, J; Boumis, P; Lloyd, M; Redman, M P

    2009-01-01

    Optical images and high-dispersion spectra have been obtained of the ejected material surrounding the pulsating AGB star Mira A. The two streams of knots on either side of the star, found in far ultra-viollet (FUV) GALEX images, have now been imaged clearly in the light of Halpha. Spatially resolved profiles of the same line reveal that the bulk of these knots form a bi-polar outflow with radial velocity extremes of +- 150 km/s with respect to the central star. The South stream is approaching and the North stream receding from the observer. A displacement away from Mira A between the position of one of the South stream knots in the new Halpha image and its position in the previous Palomar Observatory Sky Survey (POSS I) red plate has been noted. If interpreted as a consequence of expansion proper motions the bipolar outflow is tilted at 69deg +- 2deg to the plane of the sky, has an outflow velocity of 160 +- 10 km/s and is ~1000 y old.

  12. RY Aquarius a Binary System with Pulsating delta-scuti Primary Component

    Science.gov (United States)

    Manzoori, Davood; Salar, Abbasvand

    2016-07-01

    We present simultaneous new BVI light curves along with radial velocity curve analysis of the RY Aqr system, using the PHysics Of Eclipsing BinariEs code. The analysis indicates that while the primary is completely inside its Roche critical surface, the secondary has filled out its Roche surface. In addition, the positions of the system components on M–R, H–R diagrams are specified, which show that the primary is a main-sequence or nearly main-sequence star while the secondary is an evolved subgiant. In addition, analysis of the period and luminosity variations of the system were carried out. Fourier frequency analysis of light variation indicates that the primary is a pulsating, δ-scuti variable star. Moreover, O–C curve analysis shows that the period of the system is secularly decreasing with a rate of dp/dt = 0.074 s yr‑1. This decrease in the orbital period variations was attributed to a mass and angular momentum loss from the system with a rate of 2.57× {10}-10{M}ȯ {{yr}}-1. Apart from the secular period decreases, the orbital period of the system is modulated by a cyclic period of 72.69 year, which was attributed to a third body orbiting around the barycenter of the system.

  13. Three ways to solve the orbit of KIC 11 558 725: a 10-day beaming sdB+WD binary with a pulsating subdwarf

    Science.gov (United States)

    Telting, J. H.; Østensen, R. H.; Baran, A. S.; Bloemen, S.; Reed, M. D.; Oreiro, R.; Farris, L.; Ottosen, T. A.; Aerts, C.; Kawaler, S. D.; Heber, U.; Prins, S.; Green, E. M.; Kalomeni, B.; O'Toole, S. J.; Mullally, F.; Sanderfer, D. T.; Smith, J. C.; Kjeldsen, H.

    2012-08-01

    The recently discovered subdwarf B (sdB) pulsator KIC 11 558 725 is one of the 16 pulsating sdB stars detected in the Kepler field. It features a rich g-mode frequency spectrum, with a few low-amplitude p-modes at short periods. This makes it a promising target for a seismic study aiming to constrain the internal structure of this star, and of sdB stars ingeneral. We have obtained ground-based spectroscopic radial-velocity measurements of KIC 11 558 725 based on low-resolution spectra in the Balmer-line region, spanning the 2010 and 2011 observing seasons. From these data we have discovered that KIC 11 558 725 is a binary with period P = 10.05 d, and that the radial-velocity amplitude of the sdB star is 58 km s-1. Consequently the companion of the sdB star has a minimum mass of 0.63 M⊙, and is therefore most likely an unseen white dwarf. We analyse the near-continuous 2010-2011 Kepler light curve to reveal the orbital Doppler-beaming effect, giving rise to light variations at the 238 ppm level, which is consistent with the observed spectroscopic orbital radial-velocity amplitude of the subdwarf. We use the strongest 70 pulsation frequencies in the Kepler light curve of the subdwarf as clocks to derive a third consistent measurement of the orbital radial-velocity amplitude, from the orbital light-travel delay. The orbital radius asdBsini = 11.5 R⊙ gives rise to a light-travel time delay of 53.6 s, which causes aliasing and lowers the amplitudes of the shortest pulsation frequencies, unless the effect is corrected for. We use our high signal-to-noise average spectra to study the atmospheric parameters of the sdB star, deriving Teff = 27 910 K andlog g = 5.41 dex, and find that carbon, nitrogen and oxygen are underabundant relative to the solar mixture. Furthermore, we analyse the Kepler light curve for its pulsational content and extract more than 160 significant frequencies.We investigate the pulsation frequencies for expected period spacings and rotational

  14. Experimental investigation on a pulsating heat pipe with hydrogen

    Science.gov (United States)

    Deng, H. R.; Liu, Y. M.; Ma, R. F.; Han, D. Y.; Gan, Z. H.; Pfotenhauer, J. M.

    2015-12-01

    The pulsating heat pipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb3Sn and NbTi, MgB2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB2, this paper designs a Hydrogen Pulsating Heat Pipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios.

  15. Experimental research on heat transfer of pulsating heat pipe

    Science.gov (United States)

    Li, Jia; Yan, Li

    2008-06-01

    Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper, and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fill ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.

  16. Pulsations and outbursts in Be stars: Small differences - big impacts

    CERN Document Server

    Baade, D; Pigulski, A; Carciofi, A; Handler, G; Kuschnig, R; Martayan, Ch; Mehner, A; Moffat, A F J; Pablo, H; Popowicz, A; Rucinski, S M; Wade, G A; Weiss, W W; Zwintz, K

    2016-01-01

    New high-cadence observations with BRITE covering many months confirm that coupled pairs of nonradial pulsation modes are widespread among early-type Be stars. With the difference frequency between the parental variations they may form a roughly sinusoidal variability or the amplitude may cyclicly vary. A first - amplified - beat pattern is also found. In all three cases the amplitudes of difference frequencies can exceed the amplitude sum of the base frequencies, and modulations of the star-to-circumstellar-disk mass-transfer rate may be associated with these slow variations. This suggests more strongly than any earlier observations that significant dissipation of pulsational energy in the atmosphere may be a cause of mass ejections from Be stars. A unifying interpretative concept is presented.

  17. Study of the Thermal Pulsation of AGB Stars

    CERN Document Server

    Halabi, Ghina M

    2014-01-01

    A systematic investigation on the third dredge up in a 3M$_{\\odot}$, solar metallicity AGB star will be presented. The model evolves from the main sequence up to the Asymptotic Giant Branch (AGB). Intermediate mass stars are important because they contribute significantly via the slow neutron capture nucleosynthesis. The aim of this work is to gain insight on the behaviour of the AGB star during thermal pulsation. This investigation is based on an extended numerical simulation of the evolutionary phases and full, consistent AGB model calculations. In particular, the convective structure during pulsation will be studied, giving particular emphasis to the analysis of the stability of the Schwarzschild boundary that will eventually determine the occurrence of Third Dredge Up (hereafter referred to as TDUP). We provide a brief description of our updated evolutionary code and focus primarily on the obtaining the TDUP after 14 thermal pulses. We elaborate on the non-standard treatment of convection known as "oversh...

  18. The unique dynamical system underlying RR Lyrae pulsations

    CERN Document Server

    Kolláth, Zoltán

    2016-01-01

    Hydrodynamic models of RR Lyrae pulsation display a very rich behaviour. Contrary to earlier expectations, high order resonances play a crucial role in the nonlinear dynamics representing the interacting modes. Chaotic attractors can be found at different time scales: both in the pulsation itself and in the amplitude equations shaping the possible modulation of the oscillations. Although there is no one-to-one connection between the nonlinear features found in the numerical models and the observed behaviour, the richness of the found phenomena suggests that the interaction of modes should be taken seriously in the study of the still unsolved puzzle of Blazhko effect. One of the main lessons of this complex system is that we should rethink the simple interpretation of the observed effect of resonances.

  19. Quantitative results of stellar evolution and pulsation theories.

    Science.gov (United States)

    Fricke, K.; Stobie, R. S.; Strittmatter, P. A.

    1971-01-01

    The discrepancy between the masses of Cepheid variables deduced from evolution theory and pulsation theory is examined. The effect of input physics on evolutionary tracks is first discussed; in particular, changes in the opacity are considered. The sensitivity of pulsation masses to opacity changes and to the ascribed values of luminosity and effective temperature are then analyzed. The Cepheid mass discrepancy is discussed in the light of the results already obtained. Other astronomical evidence, including the mass-luminosity relation for main sequence stars, the solar neutrino flux, and cluster ages are also considered in an attempt to determine the most likely source of error in the event that substantial mass loss has not occurred.

  20. Experimental research on heat transfer of pulsating heat pipe

    Institute of Scientific and Technical Information of China (English)

    LI Jia; Yan Li

    2008-01-01

    Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper,and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fill ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.

  1. Modelling the effects of cardiac pulsations in arterial spin labelling

    International Nuclear Information System (INIS)

    It has recently been demonstrated experimentally that cardiac pulsations seem significantly to affect the arterial spin labelling (ASL) signal. In this paper, we introduce a new theoretical model to examine this effect. Existing models of ASL do not take such effects into account since they model the transit of the ASL signal assuming uniform plug flow with a single transit delay. In this study, we model cardiac pulsations through the coupling of the Navier-Stokes equations with the three-dimensional mass transport equation. Our results complement the experimental findings and suggest that the ASL signal does depend on the timing of the onset of the cardiac cycle relative to the tagging and imaging locations. However, cardiac pulsatility only appears to have a small effect on the quantification of perfusion estimates.

  2. Pulsating aurora induced by upper atmospheric barium releases

    Science.gov (United States)

    Deehr, C.; Romick, G.

    1977-01-01

    The paper reports the apparent generation of pulsating aurora by explosive releases of barium vapor near 250 km altitude. This effect occurred only when the explosions were in the path of precipitating electrons associated with the visible aurora. Each explosive charge was a standard 1.5 kg thermite mixture of Ba and CuO with an excess of Ba metal which was vaporized and dispersed by the thermite explosion. Traces of Sr, Na, and Li were added to some of the charges, and monitoring was achieved by ground-based spectrophotometric observations. On March 28, 1976, an increase in emission at 5577 A and at 4278 A was observed in association with the first two bursts, these emissions pulsating with roughly a 10 sec period for approximately 60 to 100 sec after the burst.

  3. The First Six Outbursting Cool DA White Dwarf Pulsators

    CERN Document Server

    Bell, Keaton J; Montgomery, M H; Winget, D E; Fusillo, N P Gentile; Raddi, R; Gänsicke, B T

    2016-01-01

    Extensive observations from the Kepler spacecraft have recently revealed a new outburst phenomenon operating in cool pulsating DA (hydrogen atmosphere) white dwarfs (DAVs). With the introduction of two new outbursting DAVs from K2 Fields 7 (EPIC 229228364) and 8 (EPIC 220453225) in these proceedings, we presently know of six total members of this class of object. We present the observational commonalities of the outbursting DAVs: (1) outbursts that increase the mean stellar flux by up to 15%, last many hours, and recur irregularly on timescales of days; (2) effective temperatures that locate them near the cool edge of the DAV instability strip; and (3) rich pulsation spectra with modes that are observed to wander in amplitude/frequency.

  4. Radial lean direct injection burner

    Science.gov (United States)

    Khan, Abdul Rafey; Kraemer, Gilbert Otto; Stevenson, Christian Xavier

    2012-09-04

    A burner for use in a gas turbine engine includes a burner tube having an inlet end and an outlet end; a plurality of air passages extending axially in the burner tube configured to convey air flows from the inlet end to the outlet end; a plurality of fuel passages extending axially along the burner tube and spaced around the plurality of air passage configured to convey fuel from the inlet end to the outlet end; and a radial air swirler provided at the outlet end configured to direct the air flows radially toward the outlet end and impart swirl to the air flows. The radial air swirler includes a plurality of vanes to direct and swirl the air flows and an end plate. The end plate includes a plurality of fuel injection holes to inject the fuel radially into the swirling air flows. A method of mixing air and fuel in a burner of a gas turbine is also provided. The burner includes a burner tube including an inlet end, an outlet end, a plurality of axial air passages, and a plurality of axial fuel passages. The method includes introducing an air flow into the air passages at the inlet end; introducing a fuel into fuel passages; swirling the air flow at the outlet end; and radially injecting the fuel into the swirling air flow.

  5. Preliminary study using pulsating water jet for bone cement demolition

    OpenAIRE

    S. Hloch; Kloc, J.; Foldyna, J.; Pude, F.; Smolko, I.; M. Zeleňák; Sitek, L. (Libor); Hvizdoš, P.; Monka, P.; Monková, K.; Kozak, D.; A. Stoić; A. Sedmak; Milosevic, M; Lehocká, D.

    2015-01-01

    The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of bone cement which creates the interface between femoral stem and trabecular bone tissue. For investigation, commercial bone cements were used. Bone cements were tested by nanoindentation in order to review their mechanical properties. A representative sample Palacos R+G was selected for disintegration of bone cement. Bone cements samples fixed between two plexiglass...

  6. Nonlinear simulations of the convection-pulsation coupling

    OpenAIRE

    Gastine, T.; Dintrans, B.

    2011-01-01

    In cold Cepheids close to the red edge of the classical instability strip, a strong coupling between the stellar pulsations and the surface convective motions occurs. This coupling is by now poorly described by 1-D models of convection, the so-called "time-dependent convection models" (TDC). The intrinsic weakness of such models comes from the large number of unconstrained free parameters entering in the description of turbulent convection. A way to overcome these limits is to compute two-dim...

  7. Mathematical Modelling and Parameter Optimization of Pulsating Heat Pipes

    OpenAIRE

    Yang, Xin-She; Karamanoglu, Mehmet; Luan, Tao; Koziel, Slawomir

    2014-01-01

    Proper heat transfer management is important to key electronic components in microelectronic applications. Pulsating heat pipes (PHP) can be an efficient solution to such heat transfer problems. However, mathematical modelling of a PHP system is still very challenging, due to the complexity and multiphysics nature of the system. In this work, we present a simplified, two-phase heat transfer model, and our analysis shows that it can make good predictions about startup characteristics. Furtherm...

  8. Noise Radiation Of A Strongly Pulsating Tailpipe Exhaust

    Science.gov (United States)

    Peizi, Li; Genhua, Dai; Zhichi, Zhu

    1993-11-01

    The method of characteristics is used to solve the problem of the propagation of a strongly pulsating flow in an exhaust system tailpipe. For a strongly pulsating exhaust, the flow may shock at the pipe's open end at some point in a pulsating where the flow pressure exceeds its critical value. The method fails if one insists on setting the flow pressure equal to the atmospheric pressure as the pipe end boundary condition. To solve the problem, we set the Mach number equal to 1 as the boundary condition when the flow pressure exceeds its critical value. For a strongly pulsating flow, the fluctuations of flow variables may be much higher than their respective time averages. Therefore, the acoustic radiation method would fail in the computation of the noise radiation from the pipe's open end. We simulate the exhaust flow out of the open end as a simple sound source to compute the noise radiation, which has been successfully applied in reference [1]. The simple sound source strength is proportional to the volume acceleration of exhaust gas. Also computed is the noise radiation from the turbulence of the exhaust flow, as was done in reference [1]. Noise from a reciprocating valve simulator has been treated in detail. The radiation efficiency is very low for the pressure range considered and is about 10 -5. The radiation efficiency coefficient increases with the square of the frequency. Computation of the pipe length dependence of the noise radiation and mass flux allows us to design a suitable length for an aerodynamic noise generator or a reciprocating internal combustion engine. For the former, powerful noise radiation is preferable. For the latter, maximum mass flux is desired because a freer exhaust is preferable.

  9. Nonstationary pearl pulsations as a signature of magnetospheric disturbances

    OpenAIRE

    Feygin, F. Z.; Kleimenova, N. G.; O. A. Pokhotelov; M. Parrot; K. Prikner; K. Mursula; J. Kangas; Pikkarainen, T.

    2000-01-01

    We analyse long-lasting (several hours) Pc1 pearl pulsations with decreasing, increasing or constant central frequencies. We show that nonstationary pearl events (those with either decreasing or increasing central frequency) are observed simultaneously with increasing auroral magnetic activity at the nightside magnetosphere while the stationary events (constant central frequency) correspond to quiet magnetic conditions. Events with decreasing central frequency are observed mostly in the late ...

  10. Self-pulsation threshold of Raman amplified Brillouin fiber cavities

    DEFF Research Database (Denmark)

    Ott, Johan Raunkjær; Pedersen, Martin Erland Vestergaard; Rottwitt, Karsten

    2009-01-01

    An implicit equation for the oscillation threshold of stimulated Brillouin scattering from Raman amplified signals in fibers with external feedback is derived under the assumption of no depletion. This is compared to numerical investigations of Raman amplification schemes showing good agreement...... for high reflectivities. For low reflectivities and high attenuation or long fibers, the assumption of no depletion is shown not to be valid. In these cases the effects of the depletion on the self-pulsation is examined....

  11. Pressure Pulsation Signal Analysis for Centrifugal Compressor Blade Crack Determination

    OpenAIRE

    Hongkun Li; Xuefeng Zhang; Xiaowen Zhang; Shuhua Yang; Fujian Xu

    2014-01-01

    Blade is a key piece of component for centrifugal compressor. But blade crack could usually occur as blade suffers from the effect of centrifugal forces, gas pressure, friction force, and so on. It could lead to blade failure and centrifugal compressor closing down. Therefore, it is important for blade crack early warning. It is difficult to determine blade crack as the information is weak. In this research, a pressure pulsation (PP) sensor installed in vicinity to the crack area is used to d...

  12. Decreasing of pulsation intensity levels in X-ray receivers

    CERN Document Server

    Dvoryankin, V F; Kudryashov, A A; Petrov, A G

    2002-01-01

    The low frequency filter is applied in the multichannel receiver on the basis of the GaAs epitaxial structures for decreasing the pulsations level at the signals amplifier outlet. The optimal band of the filter is determined by the transition processes by the detector scanning in the roentgen beams. The X-ray source of radiation with the medium-frequency feeding generator is used for verifying the quality of the obtained X-ray image

  13. Numerical Calculation on Cavitation Pressure Pulsation in Centrifugal Pump

    OpenAIRE

    Weidong Shi; Chuan Wang; Wei Wang; Bing Pei

    2014-01-01

    In order to study the internal flow in centrifugal pump when cavitation occurs, numerical calculation of the unsteady flow field in the WP7 automobile centrifugal pump is conducted based on the Navier-Stokes equations with the RNG k-ε turbulence model and Zwart-Gerber-Belamri cavitation model. The distributions of bubble volume fraction and pressure pulsation laws in the pump are analyzed when cavitation occurs. The conclusions are as follows: the bubble volume fraction is larger on the sucti...

  14. Pulsations powered by hydrogen shell burning in white dwarfs

    CERN Document Server

    Camisassa, María E; Althaus, Leandro G; Shibahashi, Hiromoto

    2016-01-01

    In the absence of a third dredge-up episode during the asymptotic giant branch phase, white dwarf models evolved from low-metallicity progenitors have a thick hydrogen envelope, which makes hydrogen shell burning be the most important energy source. We investigate the pulsational stability of white dwarf models with thick envelopes to see whether nonradial $g$-mode pulsations are triggered by hydrogen burning, with the aim of placing constraints on hydrogen shell burning in cool white dwarfs and on a third dredge-up during the asymptotic giant branch evolution of their progenitor stars. We construct white-dwarf sequences from low-metallicity progenitors by means of full evolutionary calculations, and analyze their pulsation stability for the models in the range of effective temperatures $T_{\\rm eff} \\sim 15\\,000\\,-\\, 8\\,000$ K. We demonstrate that, for white dwarf models with masses $M_{\\star} \\lesssim 0.71\\,\\rm M_{\\sun}$ and effective temperatures $8\\,500 \\lesssim T_{\\rm eff} \\lesssim 11\\,600$ K that evolved...

  15. THE PULSATION MODE AND DISTANCE OF THE CEPHEID FF AQUILAE

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D. G. [Department of Astronomy and Physics, Saint Mary' s University, Halifax, NS B3H 3C3 (Canada); Kovtyukh, V. V. [Astronomical Observatory, Odessa National University, and Isaac Newton Institute of Chile, Odessa Branch, T. G. Shevkenko Park, 65014 Odessa (Ukraine); Luck, R. E. [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215 (United States); Berdnikov, L. N., E-mail: turner@ap.smu.ca, E-mail: val@deneb1.odessa.ua, E-mail: rel2@case.edu, E-mail: leonid.berdnikov@gmail.com [Sternberg Astronomical Institute, Moscow M. V. Lomonosov State University, Moscow 119992 (Russian Federation)

    2013-07-20

    The determination of pulsation mode and distance for field Cepheids is a complicated problem best resolved by a luminosity estimate. For illustration a technique based on spectroscopic luminosity discrimination is applied to the 4.47 day s-Cepheid FF Aql. Line ratios in high dispersion spectra of the variable yield values of (M{sub V} ) = -3.40 {+-} 0.02 s.e. ({+-}0.04 s.d.), average effective temperature T{sub eff} = 6195 {+-} 24 K, and intrinsic color ((B) - (V)){sub 0} = +0.506 {+-} 0.007, corresponding to a reddening of E{sub B-V} = 0.25 {+-} 0.01, or E{sub B-V}(B0) = 0.26 {+-} 0.01. The skewed light curve, intrinsic color, and luminosity of FF Aql are consistent with fundamental mode pulsation for a small-amplitude classical Cepheid on the blue side of the instability strip, not a sinusoidal pulsator. A distance of 413 {+-} 14 pc is estimated from the Cepheid's angular diameter in conjunction with a mean radius of (R) = 39.0 {+-} 0.7 R{sub Sun} inferred from its luminosity and effective temperature. The dust extinction toward FF Aql is described by a ratio of total-to-selective extinction of R{sub V} = A{sub V} /E(B - V) = 3.16 {+-} 0.34 according to the star's apparent distance modulus.

  16. Dark Stars: Improved Models and First Pulsation Results

    Science.gov (United States)

    Rindler-Daller, T.; Montgomery, M. H.; Freese, K.; Winget, D. E.; Paxton, B.

    2015-02-01

    We use the stellar evolution code MESA to study dark stars (DSs). DSs, which are powered by dark matter (DM) self-annihilation rather than by nuclear fusion, may be the first stars to form in the universe. We compute stellar models for accreting DSs with masses up to 106 M ⊙. The heating due to DM annihilation is self-consistently included, assuming extended adiabatic contraction of DM within the minihalos in which DSs form. We find remarkably good overall agreement with previous models, which assumed polytropic interiors. There are some differences in the details, with positive implications for observability. We found that, in the mass range of 104-105 M ⊙, our DSs are hotter by a factor of 1.5 than those in Freese et al., are smaller in radius by a factor of 0.6, denser by a factor of three to four, and more luminous by a factor of two. Our models also confirm previous results, according to which supermassive DSs are very well approximated by (n = 3)-polytropes. We also perform a first study of DS pulsations. Our DS models have pulsation modes with timescales ranging from less than a day to more than two years in their rest frames, at z ~ 15, depending on DM particle mass and overtone number. Such pulsations may someday be used to identify bright, cool objects uniquely as DSs; if properly calibrated, they might, in principle, also supply novel standard candles for cosmological studies.

  17. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    CERN Document Server

    Córsico, Alejandro H; Bertolami, Marcelo M Miller; Kepler, S O; García-Berro, Enrique

    2014-01-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. By comparing the theoretical rate of change of period expected for this star with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment. Our upper limit for the neutrino magnetic dipole moment is somewhat less restrictive than, but still compat...

  18. THE PULSATION MODE AND DISTANCE OF THE CEPHEID FF AQUILAE

    International Nuclear Information System (INIS)

    The determination of pulsation mode and distance for field Cepheids is a complicated problem best resolved by a luminosity estimate. For illustration a technique based on spectroscopic luminosity discrimination is applied to the 4.47 day s-Cepheid FF Aql. Line ratios in high dispersion spectra of the variable yield values of (MV ) = –3.40 ± 0.02 s.e. (±0.04 s.d.), average effective temperature Teff = 6195 ± 24 K, and intrinsic color ((B) – (V))0 = +0.506 ± 0.007, corresponding to a reddening of EB–V = 0.25 ± 0.01, or EB–V(B0) = 0.26 ± 0.01. The skewed light curve, intrinsic color, and luminosity of FF Aql are consistent with fundamental mode pulsation for a small-amplitude classical Cepheid on the blue side of the instability strip, not a sinusoidal pulsator. A distance of 413 ± 14 pc is estimated from the Cepheid's angular diameter in conjunction with a mean radius of (R) = 39.0 ± 0.7 R☉ inferred from its luminosity and effective temperature. The dust extinction toward FF Aql is described by a ratio of total-to-selective extinction of RV = AV /E(B – V) = 3.16 ± 0.34 according to the star's apparent distance modulus

  19. Binaries discovered by the MUCHFUSS project; FBS 0117+396: An sdB+dM binary with a pulsating primary

    CERN Document Server

    Østensen, R H; Schaffenroth, V; Telting, J H; Bloemen, S; Németh, P; Beck, P G; Lombaert, R; Pápics, P I; Tillich, A; Ziegerer, E; Machado, L Fox; Littlefair, S; Dhillon, V; Aerts, C; Heber, U; Maxted, P F L; Gänsicke, B T; Marsh, T R

    2013-01-01

    The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (muchfuss) aims to discover subdwarf-B stars with massive compact companions such as overmassive white dwarfs (M > 1.0 M_sun), neutron stars or black holes. From the 127 subdwarfs with substantial radial-velocity variations discovered in the initial survey, a number of interesting objects have been selected for extensive follow-up. After an initial photometry run with BUSCA revealed that FBS 0117+396 is photometrically variable both on long and short timescales, we chose it as an auxiliary target during a 6-night multi-color photometry run with Ultracam. Spectroscopy was obtained at a number of observatories in order to determine the binary period and obtain a radial-velocity amplitude. After establishing an orbital period of P = 0.252 d, and removing the signal associated with the irradiated hemisphere of the M-dwarf companion, we were able to detect ten pulsation periods in the Fourier spectrum of the light curve. Two pulsation...

  20. An In-Depth Spectroscopic Analysis of RR Lyr Variations over the Pulsation Cycle

    CERN Document Server

    Fossati, L; Shulyak, D V; Elmasli, A; Tsymbal, V; Barnes, T G; Guggenberger, E; Kochukhov, O

    2014-01-01

    The stellar parameters of RR Lyrae stars vary considerably over a pulsation cycle, and their determination is crucial for stellar modelling. We present a detailed spectroscopic analysis of the pulsating star RR Lyr, the prototype of its class, over a complete pulsation cycle, based on high-resolution spectra collected at the 2.7-m telescope of McDonald Observatory. We used simultaneous photometry to determine the accurate pulsation phase of each spectrum and determined the effective temperature, the shape of the depth-dependent microturbulent velocity, and the abundance of several elements, for each phase. The surface gravity was fixed to 2.4. Element abundances resulting from our analysis are stable over the pulsation cycle. However, a variation in ionisation equilibrium is observed around minimum radius. We attribute this mostly to a dynamical acceleration contributing to the surface gravity. Variable turbulent convection on time scales longer than the pulsation cycle has been proposed as a cause for the Bl...

  1. Asteroseismology of the nearby SN II Progenitor Rigel. II. epsilon-mechanism Triggering Gravity-mode Pulsations?

    Science.gov (United States)

    Moravveji, Ehsan; Moya, Andres; Guinan, Edward F.

    2012-04-01

    The cores of luminous B- and A-type (BA) supergiant stars are the seeds of later core-collapse supernovae. Thus, constraining the near-core conditions in this class of stars can place tighter constraints on the size, mass, and chemical composition of supernova remnants. Asteroseismology of these massive stars is one possible approach into such investigations. Recently, Moravveji et al. in 2012 (hereafter Paper I) extracted 19 significant frequencies from a 6-year radial velocity monitoring of Rigel (β Ori, B8 Ia). The periods they determined broadly range from 1.22 to 74.74 days. Based on our differentially rotating stellar structure and evolution model, Rigel, at its current evolutionary state, is undergoing core He burning and shell H burning. Linear fully non-adiabatic non-radial stability analyses result in the excitation of a dense spectrum of non-radial gravity-dominated mixed modes. The fundamental radial mode (l = 0) and its overtones are all stable. When the hydrogen-burning shell is located even partially in the radiative zone, a favorable condition for destabilization of g-modes through the so-called epsilon-mechanism becomes viable. Only those g-modes that have high relative amplitudes in the hydrogen-burning (radiative) zone can survive the strong radiative damping. From the entire observed range of variability periods of Rigel (found in Paper I), and based on our model, only those modes with periods ranging between 21 and 127 days can be theoretically explained by the epsilon-mechanism. The origin of the short-period variations (found in Paper I) still remains unexplained. Because Rigel is similar to other massive BA supergiants, we believe that the epsilon-mechanism may be able to explain the long-period variations in α Cygni class of pulsating stars.

  2. ASTEROSEISMOLOGY OF THE NEARBY SN II PROGENITOR RIGEL. II. ε-MECHANISM TRIGGERING GRAVITY-MODE PULSATIONS?

    International Nuclear Information System (INIS)

    The cores of luminous B- and A-type (BA) supergiant stars are the seeds of later core-collapse supernovae. Thus, constraining the near-core conditions in this class of stars can place tighter constraints on the size, mass, and chemical composition of supernova remnants. Asteroseismology of these massive stars is one possible approach into such investigations. Recently, Moravveji et al. in 2012 (hereafter Paper I) extracted 19 significant frequencies from a 6-year radial velocity monitoring of Rigel (β Ori, B8 Ia). The periods they determined broadly range from 1.22 to 74.74 days. Based on our differentially rotating stellar structure and evolution model, Rigel, at its current evolutionary state, is undergoing core He burning and shell H burning. Linear fully non-adiabatic non-radial stability analyses result in the excitation of a dense spectrum of non-radial gravity-dominated mixed modes. The fundamental radial mode (l = 0) and its overtones are all stable. When the hydrogen-burning shell is located even partially in the radiative zone, a favorable condition for destabilization of g-modes through the so-called ε-mechanism becomes viable. Only those g-modes that have high relative amplitudes in the hydrogen-burning (radiative) zone can survive the strong radiative damping. From the entire observed range of variability periods of Rigel (found in Paper I), and based on our model, only those modes with periods ranging between 21 and 127 days can be theoretically explained by the ε-mechanism. The origin of the short-period variations (found in Paper I) still remains unexplained. Because Rigel is similar to other massive BA supergiants, we believe that the ε-mechanism may be able to explain the long-period variations in α Cygni class of pulsating stars.

  3. Radial propagators and Wilson loops

    CERN Document Server

    Leupold, S; Leupold, Stefan; Weigert, Heribert

    1996-01-01

    We present a relation which connects the propagator in the radial (Fock-Schwinger) gauge with a gauge invariant Wilson loop. It is closely related to the well-known field strength formula and can be used to calculate the radial gauge propagator. The result is shown to diverge in four-dimensional space even for free fields, its singular nature is however naturally explained using the renormalization properties of Wilson loops with cusps and self-intersections. Using this observation we provide a consistent regularization scheme to facilitate loop calculations. Finally we compare our results with previous approaches to derive a propagator in Fock-Schwinger gauge.

  4. Detonation in supersonic radial outflow

    KAUST Repository

    Kasimov, Aslan R.

    2014-11-07

    We report on the structure and dynamics of gaseous detonation stabilized in a supersonic flow emanating radially from a central source. The steady-state solutions are computed and their range of existence is investigated. Two-dimensional simulations are carried out in order to explore the stability of the steady-state solutions. It is found that both collapsing and expanding two-dimensional cellular detonations exist. The latter can be stabilized by putting several rigid obstacles in the flow downstream of the steady-state sonic locus. The problem of initiation of standing detonation stabilized in the radial flow is also investigated numerically. © 2014 Cambridge University Press.

  5. An experimental investigation of heat transfer to pulsating pipe air flow with different amplitudes

    Science.gov (United States)

    Zohir, A. E.; Habib, M. A.; Attya, A. M.; Eid, A. I.

    2006-05-01

    Heat transfer characteristics to both laminar and turbulent pulsating pipe flows under different conditions of Reynolds number, pulsation frequency, pulsator location and tube diameter were experimentally investigated. The tube wall of uniform heat flux condition was considered for both cases. Reynolds number varied from 750 to 12,320 while the frequency of pulsation ranged from 1 to 10 Hz. With locating the pulsator upstream of the inlet of the test section tube, results showed an increase in heat transfer rate due to pulsation by as much as 30% with flow Reynolds number of 1,643 and pulsation frequency of 1 Hz, depending on the upstream location of the pulsator valve. Closer the valve to the tested section inlet, the better improvement in the heat transfer coefficient is achieved. Upon comparing the heat transfer results of the upstream and the downstream pulsation, at Reynolds number of 1,366 and 1,643, low values of the relative mean Nusselt number were obtained with the upstream pulsation. Comparing the heat transfer results of the two studied test sections tubes for Reynolds number range from 8,000 to 12,000 and pulsation frequency range from 1.0 to 10 Hz showed that more improvement in heat transfer rate was observed with a larger tube diameter. For Reynolds number ranging from 8,000 to 12,000 and pulsation frequency of 10 Hz, an improvement in the relative mean Nusselt number of about 50% was obtained at Reynolds number of 8,000 for the large test section diameter of 50 mm. While, for the small test section diameter of 15 mm, at same conditions of Reynolds number and frequency, a reduction in the relative mean Nusselt number of up to 10% was obtained.

  6. An experimental investigation of heat transfer to pulsating pipe air flow with different amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Zohir, A.E.; Eid, A.I. [Tabbin Institute for Metallurgical Studies-Eltabbin, Helwan (Egypt); Habib, M.A. [King Fahd University of Petroleum and Minerals, Mechanical Engineering Department, Dhahran (Saudi Arabia); Cairo University, Mechanical Engineering Department, Cairo (Egypt); Attya, A.M. [Cairo University, Mechanical Engineering Department, Cairo (Egypt)

    2006-05-15

    Heat transfer characteristics to both laminar and turbulent pulsating pipe flows under different conditions of Reynolds number, pulsation frequency, pulsator location and tube diameter were experimentally investigated. The tube wall of uniform heat flux condition was considered for both cases. Reynolds number varied from 750 to 12,320 while the frequency of pulsation ranged from 1 to 10 Hz. With locating the pulsator upstream of the inlet of the test section tube, results showed an increase in heat transfer rate due to pulsation by as much as 30% with flow Reynolds number of 1,643 and pulsation frequency of 1 Hz, depending on the upstream location of the pulsator valve. Closer the valve to the tested section inlet, the better improvement in the heat transfer coefficient is achieved. Upon comparing the heat transfer results of the upstream and the downstream pulsation, at Reynolds number of 1,366 and 1,643, low values of the relative mean Nusselt number were obtained with the upstream pulsation. Comparing the heat transfer results of the two studied test sections tubes for Reynolds number range from 8,000 to 12,000 and pulsation frequency range from 1.0 to 10 Hz showed that more improvement in heat transfer rate was observed with a larger tube diameter. For Reynolds number ranging from 8,000 to 12,000 and pulsation frequency of 10 Hz, an improvement in the relative mean Nusselt number of about 50% was obtained at Reynolds number of 8,000 for the large test section diameter of 50 mm. While, for the small test section diameter of 15 mm, at same conditions of Reynolds number and frequency, a reduction in the relative mean Nusselt number of up to 10% was obtained. (orig.)

  7. A revised ephemeris for the pulsating hydrogen-deficient star BD + 130 3224 (V652 Her)

    International Nuclear Information System (INIS)

    Additional observations of maxima of the pulsating hydrogen-deficient star, BD + 130 3224 (V652 Her), give an improved ephemeris for the decreasing period of pulsation. A simple quadratic no longer appears sufficient and a cubic solution may be preferable, indicating that the pulsation decrease rate is slowing down as the star contracts. An alternative hypotheses, that the star is a binary is also discussed. (author)

  8. The Separation Performance of the Pulsating High–Gradient Magnetic Separator

    OpenAIRE

    Peng, Yang; Shuyi, Liu; Jin, Chen

    1993-01-01

    In order to develop the pulsating high–gradient magnetic separation technology, a laboratory pulsating high–gradient magnetic separator (PHGMS) has been manufactured.. Experiments on its separation performance were carried out. The results show that PHGMS can significantly increase the grade of the magnetic product and it can eliminate the matrix clogging. The characteristic curve of the pulsating fluid was measured and a formula for estimating the grade of the magnetic product from PHGMS was...

  9. Investigation on the Possible Relationship between Magnetic Pulsations and Earthquakes

    Science.gov (United States)

    Jusoh, M.; Liu, H.; Yumoto, K.; Uozumi, T.; Takla, E. M.; Yousif Suliman, M. E.; Kawano, H.; Yoshikawa, A.; Asillam, M.; Hashim, M.

    2012-12-01

    The sun is the main source of energy to the solar system, and it plays a major role in affecting the ionosphere, atmosphere and the earth surface. The connection between solar wind and the ground magnetic pulsations has been proven empirically by several researchers previously (H. J. Singer et al., 1977, E. W. Greenstadt, 1979, I. A. Ansari 2006 to name a few). In our preliminary statistical analysis on relationship between solar and seismic activities (Jusoh and Yumoto, 2011, Jusoh et al., 2012), we observed a high possibility of solar-terrestrial coupling. We observed high tendency of earthquakes to occur during lower phase solar cycles which significantly related with solar wind parameters (i.e solar wind dynamic pressure, speed and input energy). However a clear coupling mechanism was not established yet. To connect the solar impact on seismicity, we investigate the possibility of ground magnetic pulsations as one of the connecting agent. In our analysis, the recorded ground magnetic pulsations are analyzed at different ranges of ultra low frequency; Pc3 (22-100 mHz), Pc4 (6.7-22 mHz) and Pc5 (1.7-6.7 mHz) with the occurrence of local earthquake events at certain time periods. This analysis focuses at 2 different major seismic regions; north Japan (mid latitude) and north Sumatera, Indonesia (low latitude). Solar wind parameters were obtained from the Goddard Space Flight Center, NASA via the OMNIWeb Data Explorer and the Space Physics Data Facility. Earthquake events were extracted from the Advanced National Seismic System (ANSS) database. The localized Pc3-Pc5 magnetic pulsations data were extracted from Magnetic Data Acquisition System (MAGDAS)/Circum Pan Magnetic Network (CPMN) located at Ashibetsu (Japan); for earthquakes monitored at north Japan and Langkawi (Malaysia); for earthquakes observed at north Sumatera. This magnetometer arrays has established by International Center for Space Weather Science and Education, Kyushu University, Japan. From the

  10. CONGENITAL RADIAL DYSPLASIA: A CASE REPORT

    Directory of Open Access Journals (Sweden)

    Venkatram Reddy

    2015-08-01

    Full Text Available Congenital radial dysplasia, also referred to as radial club hand , means deficiency along the preaxial or radial side of the extremity. It ranges from hypoplasia of the thumb to variou s degrees of radial hypoplasia. We present one such rare case of type 4 congenital unilateral isolated radial dysplasia with carpel anomaly , reported to our department in SVS medical C ollege, Mahabubanagar, Telangana state

  11. Heat transfer characteristics and Nusselt number correlation of turbulent pulsating pipe air flows

    Energy Technology Data Exchange (ETDEWEB)

    Habib, M.A.; Said, S.A.M. [Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Attya, A.M.; Eid, A.I.; Aly, A.Z. [Mechanical Engineering Department, Faculty of Engineering, Cairo University (Egypt)

    2004-02-01

    Heat transfer characteristics to turbulent pulsating pipe flows under a wide range of Reynolds number and pulsation frequency were experimentally investigated under uniform heat flux condition. Reynolds number was varied from 8462 to 48540 while the frequency of pulsation ranged from 1 to 29.5 Hz. The results showed that the relative mean Nusselt number is strongly affected by both pulsation frequency and Reynolds number. Enhancements in mean Nusselt number of up to 50% were obtained at medium pulsation frequency between 4.1 and 13.9 Hz for Reynolds number range of 8462 to 14581. An enhancement of up to 50% in mean Nusselt number was obtained at high pulsation frequency range between 13.9 and 29.5 Hz, specially as Reynolds number is close to 15000, while a reduction was observed at higher Reynolds number more than 21200. This reduction, at high Reynolds number, increased as pulsation frequency increased. Also, there was a reduction in mean Nusselt number of up to 20% that obtained at low pulsation frequency range between 1 and 4.1 Hz for Reynolds number range of 8462 to 48543. A significant reduction in mean Nusselt number of up to 40% was obtained at medium pulsation frequency between 4.1 and 13.9 Hz for Reynolds number range of 21208 to 48543. Empirical equations have been developed for the relative mean Nusselt number that related to Reynolds number and dimensionless frequency with about uncertainty of 10% rms. (orig.)

  12. White Dwarf Period Tables - I. Pulsators with hydrogen-dominated atmospheres

    CERN Document Server

    Bognár, Zs

    2016-01-01

    We aimed at collecting all known white dwarf pulsators with hydrogen-dominated atmospheres and list their main photometric and atmospheric parameters together with their pulsation periods and amplitudes observed at different epochs. For this purpose, we explored the pulsating white dwarf related literature with the systematic use of the SIMBAD and the NASA's Astrophysics Data System (ADS) databases. We summarized our results in four tables listing seven ZZ Ceti stars in detached white dwarf plus main-sequence binaries, seven extremely low-mass DA pulsators, three hot DAVs and 180 ZZ Ceti stars.

  13. On the periodic variations of secondary cosmic rays and the geomagnetic Pc4 pulsations in BMAr

    Directory of Open Access Journals (Sweden)

    I. M. Martin

    Full Text Available In a set of balloon flights in the Brazilian magnetic anomaly region (BMAr short time periodic variations were observed, i.e. pulsation, of secondary charged and neutral particle fluxes, X- and -ray fluxes with amplitudes of about 2–4%. The pulsations are accompanied by the geomagnetic Pc4 pulsations and have similar periodicity. The phenomenon was observed over various local times and in quiet and disturbed magnetospheric conditions. One of the explanations of this effect, i.e. periodic variation of local cut-off rigidity, and following pulsations of primary and secondary cosmic ray intensity is suggested.

  14. Ultrasonic Technology Improves Radial Artery Puncture and Cannulation in Intensive Care Unit (ICU) Shock Patients.

    Science.gov (United States)

    Li, Xiuyan; Fang, Guizhen; Yang, Danhua; Wang, Lanfang; Zheng, Chunmei; Ruan, Longjuan; Wang, Lingcong

    2016-01-01

    BACKGROUND This study observed the efficacy of ultrasonic technique with out-of-plane orientation and in-plane guidance in radial artery puncture and cannulation in intensive care unit (ICU) shock patients to elucidate the effect of this technique on the security of cannulation. MATERIAL AND METHODS A total of 88 ICU shock patients, randomized into a palpation (control) group and an ultrasound (experimental) group, received continuous intravenous sedation and analgesia. The palpation group patients underwent radial artery cannulation using the traditional palpation pulsation approach, and the ultrasound group patients underwent radial artery cannulation under out-of-plane orientation and in-plane guidance using an ultrasonic apparatus. Data were recorded and compared between the 2 groups. RESULTS (1) The success rate of the first puncture in the ultrasound group and the palpation group was 80% and 42%, respectively (Pstoma in the ultrasound group was 2.5% and 5%, respectively, which was significantly lower than that in the palpation group, which was 20% and 32.5%, respectively (P<0.05). (4) Time to achieve the early goal-directed therapy in the ultrasound group and the palpation group was 306.73±39.98 min and 356.75±40.97 min, respectively (P<0.01). CONCLUSIONS Compared with the traditional method, radial artery cannulation with out-of-plane orientation and in-plane guidance is a quick and secure cannulation method and is appropriate for use in clinics. PMID:27397118

  15. Outcomes Following Radial Head Arthroplasty.

    Science.gov (United States)

    Fowler, John R; Henry, Sarah E; Xu, Peter; Goitz, Robert J

    2016-05-01

    Most current series of radial head arthroplasty include small numbers of patients with short- to medium-term follow-up and significant heterogeneity in patients, treatments, and outcome measures. The purpose of this systematic review was to review outcomes for radial head arthroplasty based on injury chronicity, injury pattern, and type of implant used. The authors systematically searched electronic databases for studies containing radial head arthroplasty or radial head replacement and identified 19 studies for inclusion in the analysis. For each included study, a composite mean was obtained for Mayo Elbow Performance Score (MEPS) and range of motion. Outcomes were said to differ significantly if their confidence intervals did not overlap. The MEPS for acute treatment (90) was higher than that for delayed treatment (81). There was no difference in the pooled MEPS between the isolated (89) and complex injury pattern (87) groups or implant material. There was no difference in range of motion between the acute and delayed or isolated and complex groups, but the average degree of pronation was higher in patients treated with titanium implants (76°) compared with cobalt chromium implants (66°). This systematic review suggests that outcomes are improved following acute arthroplasty for treatment of radial head fractures compared with delayed treatment, based on MEPS. The lack of other significant differences detected is likely due to the significant heterogeneity and inadequate power in current studies. Further prospective studies isolating the different variables will be needed to determine their true effect on outcomes. [Orthopedics. 2016; 39(3):153-160.]. PMID:27045484

  16. New systemic radial velocities of suspected RR Lyrae binary stars

    Science.gov (United States)

    Guggenberger, E.; Barnes, T. G.; Kolenberg, K.

    2016-05-01

    Among the tens of thousands of known RR Lyrae stars there are only a handful that show indications of possible binarity. The question why this is the case is still unsolved, and has recently sparked several studies dedicated to the search for additional RR Lyraes in binary systems. Such systems are particularly valuable because they might allow to constrain the stellar mass. Most of the recent studies, however, are based on photometry by finding a light time effect in the timings of maximum light. This approach is a very promising and successful one, but it has a major drawback: by itself, it cannot serve as a definite proof of binarity, because other phenomena such as the Blazhko effect or intrinsic period changes could lead to similar results. Spectroscopic radial velocity measurements, on the other hand, can serve as definite proof of binarity. We have therefore started a project to study spectroscopically RR Lyrae stars that are suspected to be binaries. We have obtained radial velocity (RV) curves with the 2.1m telescope at McDonald observatory. From these we derive systemic RVs which we will compare to previous measurements in order to find changes induced by orbital motions. We also construct templates of the RV curves that can facilitate future studies. We also observed the most promising RR Lyrae binary candidate, TU UMa, as no recent spectroscopic measurements were available. We present a densely covered pulsational RV curve, which will be used to test the predictions of the orbit models that are based on the O - C variations.

  17. Binary Properties from Cepheid Radial Velocities (CRaV)

    CERN Document Server

    Evans, Nancy Remage; Lauer, Jennifer; Morgan, Douglas; Nichols, Joy; Günther, H Moritz; Gorynya, Natalya; Rastorguev, Alexey; Moskalik, Pawel

    2015-01-01

    We have examined high accuracy radial velocities of Cepheids to determine the binary frequency. The data are largely from the CORAVEL spectrophotometer and the Moscow version, with a typical uncertainty of $\\leq1$~km~s$^{-1}$, and a time span from 1 to 20 years. A systemic velocity was obtained by removing the pulsation component using a high order Fourier series. From this data we have developed a list of stars showing no orbital velocity larger than $\\pm1$~km~s$^{-1}$. The binary fraction was analyzed as a function of magnitude, and yields an apparent decrease in this fraction for fainter stars. We interpret this as incompleteness at fainter magnitudes, and derive the preferred binary fraction of $29\\pm8$\\% ( $20\\pm6$\\% per decade of orbital period) from the brightest 40 stars. Comparison of this fraction in this period range (1-20 years) implies a large fraction for the full period range. This is reasonable in that the high accuracy velocities are sensitive to the longer periods and smaller orbital velocit...

  18. Observations and asteroseismological analysis of the rapid subdwarf B pulsator EC 09582-1137

    Science.gov (United States)

    Randall, S. K.; Van Grootel, V.; Fontaine, G.; Charpinet, S.; Brassard, P.

    2009-11-01

    We made photometric and spectroscopic observations of the rapidly pulsating subdwarf B star EC 09582-1137 with the aim of determining the target's fundamental structural parameters from asteroseismology. This analysis forms part of a long-term programme geared towards distinguishing between different proposed formation scenarios for hot B subdwarfs on the basis of their internal characteristics. So far, secure asteroseismic solutions have been computed for 9 of these pulsators, and first comparisons with results from evolutionary calculations look promising. The new data comprise 30 h of fast time-series photometry obtained with SUSI2 at the NTT on La Silla, Chile, as well as 1 h of low-resolution spectroscopy gathered with EMMI, also mounted on the NTT. From the photometry we detected 5 independent harmonic oscillations in the 135-170 s period range with amplitudes up to 0.5% of the mean brightness of the star. In addition, we extracted two periodicities interpreted as components of a rotationally split multiplet that indicate a rotation period of the order of 2-5 days. We also recovered the first harmonic of the dominant pulsation, albeit at an amplitude below the imposed 4σ detection threshold. The spectroscopic observations led to the following estimates of the atmospheric parameters of EC 09582-1137: T_eff = 34 806±233 K, log{g} = 5.80±0.04, and log N(He)/N(H) = -1.68±0.06. Using the observed oscillations as input, we searched in model parameter space for unique solutions that present a good fit to the data. Under the assumption that the two dominant observed periodicities correspond to radial or dipole modes, we were able to isolate a well-constrained optimal model that agrees with the atmospheric parameters derived from spectroscopy. The observed oscillations are identified with low-order acoustic modes with degree indices ℓ = 0, 1, 2, and 4 and match the computed periods with a dispersion of 0.57%. Non-adiabatic calculations reveal all theoretical

  19. DARK STARS: IMPROVED MODELS AND FIRST PULSATION RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Rindler-Daller, T.; Freese, K. [Department of Physics and Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Montgomery, M. H.; Winget, D. E. [Department of Astronomy, McDonald Observatory and Texas Cosmology Center, University of Texas, Austin, TX 78712 (United States); Paxton, B. [Kavli Insitute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)

    2015-02-01

    We use the stellar evolution code MESA to study dark stars (DSs). DSs, which are powered by dark matter (DM) self-annihilation rather than by nuclear fusion, may be the first stars to form in the universe. We compute stellar models for accreting DSs with masses up to 10{sup 6} M {sub ☉}. The heating due to DM annihilation is self-consistently included, assuming extended adiabatic contraction of DM within the minihalos in which DSs form. We find remarkably good overall agreement with previous models, which assumed polytropic interiors. There are some differences in the details, with positive implications for observability. We found that, in the mass range of 10{sup 4}-10{sup 5} M {sub ☉}, our DSs are hotter by a factor of 1.5 than those in Freese et al., are smaller in radius by a factor of 0.6, denser by a factor of three to four, and more luminous by a factor of two. Our models also confirm previous results, according to which supermassive DSs are very well approximated by (n = 3)-polytropes. We also perform a first study of DS pulsations. Our DS models have pulsation modes with timescales ranging from less than a day to more than two years in their rest frames, at z ∼ 15, depending on DM particle mass and overtone number. Such pulsations may someday be used to identify bright, cool objects uniquely as DSs; if properly calibrated, they might, in principle, also supply novel standard candles for cosmological studies.

  20. Appraisal of electromagnetic induction effects on magnetic pulsation studies

    Directory of Open Access Journals (Sweden)

    B. R. Arora

    Full Text Available The quantification of wave polarization characteristics of ULF waves from the geomagnetic field variations is done under ‘a priori’ assumption that fields of internal induced currents are in-phase with the external inducing fields. Such approximation is invalidated in the regions marked by large lateral conductivity variations that perturb the flow pattern of induced currents. The amplitude and phase changes that these perturbations produce, in the resultant fields at the Earth’s surface, make determination of polarization and phase of the oscillating external signals problematic. In this paper, with the help of a classical Pc5 magnetic pulsation event of 24 March 1991, recorded by dense network of magnetometers in the equatorial belt of Brazil, we document the nature and extent of the possible influence of anomalous induction effects in the wave polarization of ULF waves. The presence of anomalous induction effects at selected sites lead to an over estimation of the equatorial enhancement at pulsation period and also suggest changes in the azimuth of ULF waves as they propagate through the equatorial electrojet. Through numerical calculations, it is shown that anomalous horizontal fields, that result from induction in the lateral conductivity distribution in the study region, vary in magnitude and phase with the polarization of external source field. Essentially, the induction response is also a function of the period of external inducing source field. It is further shown that when anomalous induction fields corresponding to the magnitude and polarization of the 24 March 1991 pulsation event are eliminated from observed fields, corrected amplitude in the X and Y horizontal components allows for true characterisation of ULF wave parameters.

    Key words. Geomagnetism and paleomagnetism (geomagnetic induction – Ionosphere (equatorial ionosphere – Magnetospheric physics (magnetosphere-ionosphere interactions

  1. Pi2 pulsations and substorm onsets: A review

    Science.gov (United States)

    Olson, John V.

    1999-08-01

    Pi2 pulsations have been the subject of continuous study since they were recognized to be an integral part of the magnetospheric substorm. With the advent of arrays of ground instruments the nature of the Pi2 has begun to be understood. As adopted by the 13th General Assembly of the International Union of Geodesy and Geophysics in 1963, Pi2 is a designation that includes impulsive pulsations in the period range from 40 to 150 s. The Pi2 signal encompasses a class of pulsations that represents two fundamental processes. The first process is the sudden generation of field-aligned currents in association with the disruption of cross-tail currents in the plasma sheet and their subsequent effects on the ionosphere. The ionosphere appears to be something more than a passive load for this electrodynamic impulse. It responds, sending currents back into a magnetosphere whose topology is changing and, perhaps producing the feedback necessary to cause the explosive growth of the substorm current system. Oscillations of these currents are detected across the nightside of the Earth at onset as the midlatitude and high-latitude portions of Pi2. The second process is the impulse response of the inner magnetosphere to the compressional waves that are generated at substorm onset. Traveling inward, they stimulate field line resonances and surface waves at the plasmapause and excite global oscillations in the inner magnetosphere. The two processes produce wave modes that couple and cross-couple threading energy into the inner magnetosphere and ultimately to the ground. The purpose of this review is to construct a phenomenological overview of the Pi2.

  2. The domains of instability for the pulsating PG1159 stars.

    Energy Technology Data Exchange (ETDEWEB)

    Quirion, P.-O.; Fontaine, Gilles.; Brassard, Pierre; Herwig, F. H. (Falk H.)

    2004-01-01

    The fact that we find pulsating and nonpulsating stars mixed together in the PG 1159 region of the log g - T{sub eff} diagram has been a long standing puzzle. The poor understanding of the driving mechanism in those stars has been the reason why it has taken so long to address properly this problem. Following the work of Saio (1996) and Gautschy (1997) based on the OPAL opacities, Quirion, Fontaine, & Brassard (2004) recently showed that we are now able to understand and reproduce the ranges of observed periods in the pulsating PG 1159 stars in terms of the original {kappa}-mechanism associated with the partial ionization of the K-shell electrons of C and O which, along with He, make up the composition of the envelope of those stars. Contrary to others, those three studies agree in that no composition gradients are needed between the atmospheric layers and the driving region. Furthermore, the cohabitation of pulsating and nonpulsating PG 1159 stars is naturally explained in terms of a dispersion in atmospheric parameters and in terms of a variation in surface composition from star to star. In particular, the most He-rich stars tend to be stable. We go beyond the findings discussed by Quirion et al. (2004) in this paper, and present the results of additional calculations aimed at describing better the role of the chemical composition (in particular the role of metallicity) as well as that of the stellar mass on the boundaries of the instability domain in the log g - T{sub eff} plane.

  3. An Experimental Investigation of Micro Pulsating Heat Pipes

    OpenAIRE

    Kai-Shing Yang; Yu-Chi Cheng; Ming-Shan Jeng; Kuo-Hsiang Chien; Jin-Cherng Shyu

    2014-01-01

    Two Si-based micro pulsating heat pipes (µPHPs) charged using HFE-7100 were either horizontally or vertically oriented and were tested using several heating powers. The width of each channel was 0.8 mm in one µPHP containing uniform channels, and the channel width was 1.0 mm or 0.6 mm in the other µPHP, which did not contain uniform channels. The depth of each channel was 0.25 mm. The overall size of each µPHP was 60 × 10 × 1.25 mm. Visual observation and temperature measurement of the µPHPs ...

  4. Study of sdO models. Pulsation Analysis

    OpenAIRE

    Rodríguez-López, C.; Moya, A.; Garrido, R.; MacDonald, J; Oreiro, R.; Ulla, A.

    2009-01-01

    We have explored the possibility of driving pulsation modes in models of sdO stars in which the effects of element diffusion, gravitational settling and radiative levitation have been neglected so that the distribution of iron-peak elements remains uniform throughout the evolution. The stability of these models was determined using a non-adiabatic oscillations code. We analysed 27 sdO models from 16 different evolutionary sequences and discovered the first ever sdO models capable of driving h...

  5. Stellar Pulsations and Stellar Evolution: Conflict, Cohabitation, or Symbiosis?

    Science.gov (United States)

    Weiss, Achim

    While the analysis of stellar pulsations allows the determination of current properties of a star, stellar evolution models connect it with its previous history. In many cases results from both methods do not agree. In this review some classical and current cases of disagreement are presented. In some cases these conflicts led to an improvement of the theory of stellar evolution, while in others they still remain unsolved. Some well-known problems of stellar physics are pointed out as well, for which it is hoped that seismology—or in general the analysis of stellar pulsations—will help to resolve them. The limits of this symbiosis will be discussed as well.

  6. DYNAMIC STABILITY OF AXIALLY MOVING VISCOELASTIC BEAMS WITH PULSATING SPEED

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-dong; CHEN Li-qun

    2005-01-01

    Parametric vibration of an axially moving, elastic, tensioned beam with pulsating speed was investigated in the vicinity of subharmonic and combination resonance. The method of averaging was used to yield a set of autonomous equations when the parametric excitation frequency is twice or the combination of the natural frequencies. Instability boundaries were presented in the plane of parametric frequency and amplitude. The analytical results were numerically verified. The effects of the viscoelastic damping, steady speed and tension on the instability boundaries were numerically demonstrated. It is found that the viscoelastic damping decreases the instability regions and the steady speed and the tension make the instability region drift along the frequency axis.

  7. Modeling KIC10684673 and KIC12216817 as Single Pulsating Variables

    CERN Document Server

    Turner, Garrison

    2016-01-01

    The raw light curves of both KIC 10684673 and KIC 12216817 show variability. Both are listed in the Kepler Eclipsing Binary Catalog (hereafter KEBC), however both are flagged as uncertain in nature. In the present study we show their light curves can be modeled by considering each target as a single, multi-modal delta Scuti pulsator. While this does not exclude the possibility of eclipsing systems, we argue, while spectroscopy on the systems is still lacking, the delta Scuti model is a simpler explanation and therefore more probable.

  8. Rate of occurrence of dayside Pc 3,4 pulsations: The L-value dependence of the IMF cone angle effect

    International Nuclear Information System (INIS)

    The normalized rate of occurrence of dayside Pc 3,4 pulsations from L = 2.4 to 4.3 has a strong enhancement for low cone angles of the interplanetary magnetic field. When the angle of the IMF to the earth sun line, theta/sub BX/, in 150 or less the occurrence rate is 7-8 times the average rate at L = 2.4 to 2.8 and 2.2 to 3.5 times the average rate at L = 4 to 4.3. These waves disappear when the IMF is nearly at right angles to the sun-earth-line. This absence of pulsations occurs over the widest range of angles at lowest L-values. These observations are consistent with a source originating in the waves upstream of the subsolar bow shock which are transported by convection to the magnetopause where they couple to oscillations of magnetospheric field lines. Since the index of refraction of the magnetospheric plasma decreases with decreasing radial distance, except at the plasmapause, inward propagating waves should be refracted away from the radial direction. Thus, to reach low L-values the waves should couple near the stagnation point and propagate nearly radially inwards. Upstream waves should be convected to the stagnation point for only a limited range of theta/sub BX/. However, to reach higher L-values the coupling may be at later local times where cross streamline propagation can bring waves from a larger range of theta/sub BX/. The streamline geometry and its connection to the foreshock region is illustrated for a variety of IMF orientations using a simple approximation to the magnetosheath flow field

  9. Observation of quasi-periodic pulsations in the solar flare SF 900610

    DEFF Research Database (Denmark)

    Terekhov, O.V.; Shevchenko, A.V.; Kuz'min, A.G.;

    2002-01-01

    A quasi-periodic component was found at the maximum of the X-ray light curve for the June 10, 1990 solar flare detected by the Granat observatory. The pulsation period was 143.2 +/- 0.8 s. The intensity of the pulsing component is not constant; the maximum amplitude of the pulsations is similar t...

  10. Single mode rate equations for two sections self-pulsating DFB laser

    Institute of Scientific and Technical Information of China (English)

    王春林; 伍剑; 林金桐

    2003-01-01

    We propose a set of single mode rate equations for multi-section distributed feedback (DFB) lasers. On the basis of the rate equations, the self-pulsation in the two-section DFB lasers with asymmetrical injection current was explained.It was found that the dynamic distribution of the power in two sections play key role in the self-pulsation running.

  11. Time series and correlation of pulsations observed simultaneously by two aircraft

    International Nuclear Information System (INIS)

    Geomagnetic pulsations are an interesting and ubiquitous component of the geomagnetic field and they have been studied extensively for several decades. Numerous comparisons have been made of pulsations at a variety of sites for various objectives. However, conductivity anomalies introduce a number of complexities into the interpretations of pulsations at ground sites through the action of the primary fields on the electrical properties of the local geologic structure. To avoid the difficulties associated with conductivity irregularities, Ochadlick et al. [1985] described an aeromagnetic approach using two aircraft for studying the relationship between pulsations observed over a deep ocean area. Relative to land regions, a deep sea is presumably a more uniform conductor. Using the dual aeromagnetic results, Ochadlick found that the correlation coefficient of pulsations remained relatively constant for observation points spaced apart from a few to about 150 km. Beyond 150 km the correlation coefficient was found to decrease. This letter summarizes the time series records of pulsations, totaling about 9 h, acquired during several dual aircraft flights performed between 20 May and 15 Aug 1985 and presents the associated correlation coefficient between the dual aircraft data sets. Apparently, those measurements show for the first time that a strong similarity of pulsations weakens quickly at a distance of ∼150 km which is remarkably close to the ionospheric height and is thus suggestive of a strong ionospheric control on the spatial coherence of pulsations

  12. Velocidades radiales en Collinder 121

    Science.gov (United States)

    Arnal, M.; Morrell, N.

    Se han llevado a cabo observaciones espectroscópicas de unas treinta estrellas que son posibles miembros del cúmulo abierto Collinder 121. Las mismas fueron realizadas con el telescopio de 2.15m del Complejo Astronómico El Leoncito (CASLEO). El análisis de las velocidades radiales derivadas del material obtenido, confirma la realidad de Collinder 121, al menos desde el punto de vista cinemático. La velocidad radial baricentral (LSR) del cúmulo es de +17 ± 3 km.s-1. Esta velocidad coincide, dentro de los errores, con la velocidad radial (LSR) de la nebulosa anillo S308, la cual es de ~20 ± 10 km.s-1. Como S308 se encuentra físicamente asociada a la estrella Wolf-Rayet HD~50896, es muy probable que esta última sea un miembro de Collinder 121. Desde un punto de vista cinemático, la supergigante roja HD~50877 (K3Iab) también pertenecería a Collinder 121. Basándonos en la pertenencia de HD~50896 a Collinder 121, y en la interacción encontrada entre el viento de esta estrella y el medio interestelar circundante a la misma, se estima para este cúmulo una distancia del orden de 1 kpc.

  13. Nonradial and radial period changes in the δ Scuti star 4 CVn. I. 700+ nights of photometry

    Science.gov (United States)

    Breger, M.

    2016-08-01

    Context. The nature of period and amplitude changes in nonradial pulsators is presently unknown. Aims: It is therefore important to examine the correlations between these changes in stars with a large number of simultaneously excited pulsation modes. However, the small amplitudes require extensive high-precision photometry covering many years. Methods: We present 702 nights of high-precision photometry of the evolved δ Sct variable 4 CVn obtained from 2005-2012 with a dedicated telescope. Results: We detected 64 frequencies, of which 38 can be identified as combinations and harmonics. The relative amplitudes of the combination frequencies are similar to those found in 44 Tau and show no evidence for resonant mode coupling. Significant period and amplitude changes are detected for the dominant modes. The known prograde and retrograde modes show period changes with opposite signs, while the radial mode exhibits only small, cyclical period changes. For each mode, the period changes are constant over the eight years and range from (1 /P)dP/ dt = -16 × 10-6 to 13 × 10-6. On the other hand, the amplitude variations show no systematic behavior between different pulsation modes. Conclusions: The behavior of the prograde, axisymmetric, and retrograde modes indicate a constant decrease in the rotational splitting over the eight years.

  14. Continuous vs. pulsating flow boiling. Part 2: Statistical comparison using response surface methodology

    DEFF Research Database (Denmark)

    Kærn, Martin Ryhl; Elmegaard, Brian; Meyer, Knud Erik;

    2016-01-01

    -motor expansion valve. Two experimental designs (data point sets) are generated using a modified Central Composite Design for each valve and their response surfaces are compared using the quadratic model. Statistical information on the significant model terms are used to clarify whether the effect of fluid flow......Response surface methodology is used to investigate an active method for flow boiling heat transfer enhancement by means of fluid flow pulsation. The flow pulsations are introduced by a flow modulating expansion device and compared with the baseline continuous flow provided by a stepper...... pulsations is statistically significant in terms of the time-averaged flow boiling heat transfer coefficient. The cycle time range from 1 s to 9 s for the pulsations. The results show that the effect of fluid flow pulsations is statistically significant, disregarding the lowest heat flux measurements...

  15. Nature of Pi1B pulsations as inferred from ground and satellite observations

    Science.gov (United States)

    Lessard, M. R.; Lund, E. J.; Jones, S. L.; Arnoldy, R. L.; Posch, J. L.; Engebretson, M. J.; Hayashi, K.

    2006-07-01

    The occurrence of Pi1B pulsations is well-documented, including the fact that these pulsations can be observed both on the ground and at geosynchronous orbit at substorm onset, although information about their propagation characteristics has been lacking. In this paper, data are presented from FAST, GOES 9 and various ground stations that show the simultaneous observations of Pi1B pulsations in association with an onset. While the data at GOES 9 show that the pulsations are compressional in nature, data from FAST show the presence of shear mode waves, implying that Pi1B mode conversion of some type must take place in the region between geosynchronous orbit and FAST altitudes. An additional point is that Pi1B pulsations apparently propagate through auroral phenomena routinely, begging the question of what role they may play.

  16. High frequency A-type pulsators discovered using SuperWASP

    CERN Document Server

    Holdsworth, Daniel L; Gillon, M; Clubb, K I; Southworth, J; Maxted, P F L; Anderson, D R; Barros, S C C; Cameron, A Collier; Delrez, L; Faedi, F; Haswell, C A; Hellier, C; Horne, K; Jehin, E; Norton, A J; Pollacco, D; Skillen, I; Smith, A M S; West, R G; Wheatley, P J

    2014-01-01

    We present the results of a survey using the WASP archive to search for high frequency pulsations in F-, A- and B-type stars. Over 1.5 million targets have been searched for pulsations with amplitudes greater than 0.5 millimagnitude. We identify over 350 stars which pulsate with periods less than 30 min. Spectroscopic follow-up of selected targets has enabled us to confirm 10 new rapidly oscillating Ap stars, 13 pulsating Am stars and the fastest known $\\delta$ Scuti star. We also observe stars which show pulsations in both the high-frequency domain and in the low-frequency $\\delta$ Scuti range. This work shows the power of the WASP photometric survey to find variable stars with amplitudes well below the nominal photometric precision per observation.

  17. Oscilaciones estelares no-radiales: aplicación a configuraciones politrópicas y modelos de enanas blancas de He

    Science.gov (United States)

    Córsico, A. H.; Benvenuto, O. G.

    Recently in our Observatory we have developed a new Stellar Pulsation Code, independently of other workers. Such program computes eigenvalues (eigenfrequencies) and eigenfunctions of non-radial modes in spherical non-perturbated stellar models. To accomplish this calculations, the four order eigenvalue problem (in the linear adiabatic approach) is solved by means of the well-know technique of Henyey on the finite differences scheme wich replace to the differential equations of the problem. In order to test the Code, we have computed numerous eigenmodes in polytropic configurations for several values of index n. In this comunication we show the excelent agreement of our results and that best available in the literature. Also, we present results of oscillations in models of white dwarf stars with homogeneus chemical composition (pure Helium). This models have been obtained with the Evolution Stellar Code of our Observatory. The calculations outlined above conform a first preliminary step in a major proyect whose main purpose is the study of pulsational properties of DA, DB and DO white dwarfs stars. Detailed investigations have demonstrated that such objets pulsates in non-radial g-modes with eigenperiods in the range 100-2000 sec.

  18. Ventricular dilation and elevated aqueductal pulsations in a new experimental model of communicating hydrocephalus

    Energy Technology Data Exchange (ETDEWEB)

    Wagshul, M.; Smith, S.; Wagshul, M.; McAllister, J.P.; Rashid, S.; Li, J.; Egnor, M.R.; Walker, M.L.; Yu, M.; Smith, S.D.; Zhang, G.; Chen, J.J.; Beneveniste, H.

    2009-03-01

    In communicating hydrocephalus (CH), explanations for the symptoms and clear-cut effective treatments remain elusive. Pulsatile flow through the cerebral aqueduct is often significantly elevated, but a clear link between abnormal pulsations and ventriculomegaly has yet to be identified. We sought to demonstrate measurement of pulsatile aqueductal flow of CSF in the rat, and to characterize the temporal changes in CSF pulsations in a new model of CH. Hydrocephalus was induced by injection of kaolin into the basal cisterns of adult rats (n = 18). Ventricular volume and aqueductal pulsations were measured on a 9.4 T MRI over a one month period. Half of the animals developed ventricular dilation, with increased ventricular volume and pulsations as early as one day post-induction, and marked chronic elevations compared to intact controls (volume: 130.15 {+-} 83.21 {mu}l vs. 15.52 {+-} 2.00 {mu}l; pulsations: 114.51 nl {+-} 106.29 vs. 0.72 {+-} 0.13 nl). Similar to the clinical presentation, the relationship between ventricular size and pulsations was quite variable. However, the pulsation time-course revealed two distinct sub-types of hydrocephalic animals: those with markedly elevated pulsations which persisted over time, and those with mildly elevated pulsations which returned to near normal levels after one week. These groups were associated with severe and mild ventriculomegaly respectively. Thus, aqueductal flow can be measured in the rat using high-field MRI and basal cistern-induced CH is associated with an immediate change in CSF pulsatility. At the same time, our results highlight the complex nature of aqueductal pulsation and its relationship to ventricular dilation.

  19. $\\gamma$ Doradus Pulsations in the Eclipsing Binary Star KIC 6048106

    CERN Document Server

    Lee, Jae Woo

    2016-01-01

    We present the ${\\it Kepler}$ photometry of KIC 6048106 exhibiting O'Connell effect and multiperiodic pulsations. Including a starspot on either of the components, light-curve synthesis indicates that this system is a semi-detached Algol with a mass ratio of 0.211, an orbital inclination of 73.9 deg, and a large temperature difference of 2,534 K. To examine in detail both spot variations and pulsations, we separately analyzed the {\\it Kepler} time-series data at the interval of an orbital period by an iterative way. The results reveal that the variable asymmetries of the light maxima can be interpreted as the changes of a magnetic cool spot on the secondary component with time. Multiple frequency analyses were performed in the outside-eclipse light residuals after removal of the binarity effects from the observed {\\it Kepler} data. We detected 30 frequencies with signal to noise amplitude ratios larger than 4.0, of which six ($f_2$--$f_6$ and $f_{10}$) can be identified as high-order (17 $\\le n \\le$ 25) low-d...

  20. An Experimental Investigation of Micro Pulsating Heat Pipes

    Directory of Open Access Journals (Sweden)

    Kai-Shing Yang

    2014-06-01

    Full Text Available Two Si-based micro pulsating heat pipes (µPHPs charged using HFE-7100 were either horizontally or vertically oriented and were tested using several heating powers. The width of each channel was 0.8 mm in one µPHP containing uniform channels, and the channel width was 1.0 mm or 0.6 mm in the other µPHP, which did not contain uniform channels. The depth of each channel was 0.25 mm. The overall size of each µPHP was 60 × 10 × 1.25 mm. Visual observation and temperature measurement of the µPHPs under various conditions were performed and the results were analyzed. The results indicated that when the µPHPs were operated horizontally at a heating power ranging from 1 to 7 W, the pulsating two-phase flow in the channels of the µPHPs could not begin, except when the µPHP containing nonuniform channels was tested at a heating power of 7 W. With a heating power less than 5 W, the frequency of the sine-like oscillating displacement of the vapor slug increased and the displacement of the vapor slug reduced in either vertically oriented μPHP, as the heating power increased With a heating power higher than 5 W, periodic “start-stop” behaviors were observed in the vertical μPHP containing nonuniform channels.

  1. Closed loop pulsating heat pipes. Part A: parametric experimental investigations

    Energy Technology Data Exchange (ETDEWEB)

    Charoensawan, P.; Terdtoon, P. [Chiang Mai University (Thailand). Department of Mechanical Engineering; Khandekar, S.; Groll, M. [Universitat Stuttgart (Germany). Institut fur Kernenergetik und Energiesysteme

    2003-11-01

    Closed loop pulsating heat pipes (CLPHPs) are complex heat transfer devices having a strong thermo-hydrodynamic coupling governing the thermal performance. In this paper, a wide range of pulsating heat pipes is experimentally studied thereby providing vital information on the parameter dependency of their thermal performance. The influence characterization has been done for the variation of internal diameters, number of turns, working fluid and inclination angle (from vertical bottom heat mode to horizontal orientation mode) of the device. CLPHPs are made of copper tubes of internal diameters 2.0 and 1.0 mm, heated by constant temperature water bath and cooled by constant temperature water-ethylene glycol mixture (50% each by volume). The number of turns in the evaporator is varied from 5 to 23. The working fluids employed are water, ethanol and R-123. The results indicate a strong influence of gravity and number of turns on the performance. The thermophysical properties of working fluids affect the performance which also strongly depends on the boundary conditions of PHP operation. Part B of this paper, which deals with development of semi-empirical correlations to fit the data reported here coupled with some critical visualization results, will appear separately. (author)

  2. Pulsations in Hydrogen Burning Low Mass Helium White Dwarfs

    CERN Document Server

    Steinfadt, Justin D R; Arras, Phil

    2010-01-01

    Helium core white dwarfs (WDs) with mass M < 0.20 M_sun undergo several Gyrs of stable hydrogen burning as they evolve. We show that in a certain range of WD and hydrogen envelope masses, these WDs may exhibit g-mode pulsations similar to their passively cooling, more massive carbon/oxygen core counterparts, the ZZ Cetis. Our models with stably burning hydrogen envelopes on helium cores yield g-mode periods and period spacings longer than the canonical ZZ Cetis by nearly a factor of two. We show that core composition and structure can be probed using seismology since the g-mode eigenfunctions predominantly reside in the helium core. Though we have not carried out a fully nonadiabatic stability analysis, the scaling of the thermal time in the convective zone with surface gravity highlights several low mass helium WDs that should be observed in search of pulsations: NLTT 11748, SDSS J0822+2753, and the companion to PSR J1012+5307. Seismological studies of these He core WDs may prove especially fruitful, as t...

  3. Axions and the pulsation periods of variable white dwarfs revisited

    CERN Document Server

    Isern, J; Althaus, L G; Córsico, A H

    2010-01-01

    Axions are the natural consequence of the introduction of the Peccei-Quinn symmetry to solve the strong CP problem. All the efforts to detect such elusive particles have failed up to now. Nevertheless, it has been recently shown that the luminosity function of white dwarfs is best fitted if axions with a mass of a few meV are included in the evolutionary calculations. Our aim is to show that variable white dwarfs can provide additional and independent evidence about the existence of axions. The evolution of a white dwarf is a slow cooling process that translates into a secular increase of the pulsation periods of some variable white dwarfs, the so-called DAV and DBV types. Since axions can freely escape from such stars, their existence would increase the cooling rate and, consequently, the rate of change of the periods as compared with the standard ones. The present values of the rate of change of the pulsation period of G117-B15A are compatible with the existence of axions with the masses suggested by the lu...

  4. Eclipsing binaries with pulsating components: CoRoT 102918586

    CERN Document Server

    Maceroni, C; Damiani, C; Gandolfi, D; Debosscher, J; Hatzes, A; Guenther, E W; Aerts, C

    2010-01-01

    We present the preliminary results of the study of an interesting target in the first CoRoT exo-planet field (IRa1): CoRoT 102918586. Its light curve presents additional variability on the top of the eclipses, whose pattern suggests multi- frequency pulsations. The high accuracy CoRoT light curve was analyzed by applying an iterative scheme, devised to disentangle the effect of eclipses from the oscillatory pattern. In addition to the CoRoT photometry we obtained low resolution spectroscopy with the AAOmega multi-fiber facility at the Anglo Australian Observatory, which yielded a spectral classification as F0 V and allowed us to infer a value of the primary star effective temperature. The Fourier analysis of the residuals, after subtraction of the binary light curve, gave 35 clear frequencies. The highest amplitude frequency, of 1.22 c/d, is in the expected range for both \\gamma Dor and SPB pulsators, but the spectral classification favors the first hypothesis. Apart from a few multiples of the orbital period...

  5. Numerical simulation of pressure pulsations in Francis turbines

    Science.gov (United States)

    Magnoli, M. V.; Schilling, R.

    2012-11-01

    In the last decades, hydraulic turbines have experienced the increase of their power density and the extension of their operating range, leading the fluid and mechanical dynamic effects to become significantly more pronounced. The understanding of the transient fluid flow and of the associated unsteady effects is essential for the reduction of the pressure pulsation level and improvement of the machine dynamic behaviour. In this study, the instationary fluid flow through the complete turbine was numerically calculated for an existing Francis machine with high specific speed. The hybrid turbulence models DES (detached eddy simulation) and SAS (scale adaptive simulation) allowed the accurate simulation of complex dynamic flow effects, such as the rotor-stator-interaction and the draft tube instabilities. Different operating conditions, as full load, part load, higher part load and deep part load, were successfully simulated and showed very tight agreement with the experimental results from the model tests. The transient pressure field history, obtained from the CFD (computational fluid dynamics) simulation and stored for each time step, was used as input for the full instationary FEA (finite element analysis) of turbine components. The assessment of the machine dynamic motion also offered the possibility to contribute to the understanding of the pressure pulsation effects and to further increase the turbine stability. This research project was developed at the Institute of Fluid Mechanics of the TU München.

  6. Pressure pulsation in roller pumps: a validated lumped parameter model.

    Science.gov (United States)

    Moscato, Francesco; Colacino, Francesco M; Arabia, Maurizio; Danieli, Guido A

    2008-11-01

    During open-heart surgery roller pumps are often used to keep the circulation of blood through the patient body. They present numerous key features, but they suffer from several limitations: (a) they normally deliver uncontrolled pulsatile inlet and outlet pressure; (b) blood damage appears to be more than that encountered with centrifugal pumps. A lumped parameter mathematical model of a roller pump (Sarns 7000, Terumo CVS, Ann Arbor, MI, USA) was developed to dynamically simulate pressures at the pump inlet and outlet in order to clarify the uncontrolled pulsation mechanism. Inlet and outlet pressures obtained by the mathematical model have been compared with those measured in various operating conditions: different rollers' rotating speed, different tube occlusion rates, and different clamping degree at the pump inlet and outlet. Model results agree with measured pressure waveforms, whose oscillations are generated by the tube compression/release mechanism during the rollers' engaging and disengaging phases. Average Euclidean Error (AEE) was 20mmHg and 33mmHg for inlet and outlet pressure estimates, respectively. The normalized AEE never exceeded 0.16. The developed model can be exploited for designing roller pumps with improved performances aimed at reducing the undesired pressure pulsation.

  7. Theoretical fit of Cepheid light an radial velocity curves in the Large Magellanic Cloud cluster NGC 1866

    CERN Document Server

    Marconi, Marcella; Ripepi, Vincenzo; Musella, Ilaria; Brocato, Enzo

    2012-01-01

    We present a theoretical investigation of multifilter (U,B,V, I and K) light and radial velocity curves of five Classical Cepheids in NGC 1866, a young massive cluster of the Large Magellanic Cloud. The best fit models accounting for the luminosity and radial velocity variations of the five selected variables, four pulsating in the fundamental mode and one in the first overtone, provide direct estimates of their intrinsic stellar parameters and individual distances. The resulting stellar properties indicate a slightly brighter Mass Luminosity relation than the canonical one, possibly due to mild overshooting and/or mass loss. As for the inferred distances, the individual values are consistent within the uncertainties. Moreover, their weighted mean value corresponds to a distance modulus of 18.56 + - 0.03 (stat) + - 0.1 (syst) mag, in agreement with several independent results in the literature.

  8. ASTEROSEISMOLOGY OF THE NEARBY SN-II PROGENITOR: RIGEL. I. THE MOST HIGH-PRECISION PHOTOMETRY AND RADIAL VELOCITY MONITORING

    Energy Technology Data Exchange (ETDEWEB)

    Moravveji, Ehsan [Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731 (Iran, Islamic Republic of); Guinan, Edward F. [Department of Astronomy, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085 (United States); Shultz, Matt [Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, ON K7K 4B4 (Canada); Williamson, Michael H. [Center of Excellence in Information Systems, Tennessee State University, Nashville, TN (United States); Moya, Andres, E-mail: moravveji@iasbs.ac.ir [Departamento de Astrofisica, Centro de Astrobiologia (INTA-CSIC), PO BOX 78, 28691 Villanueva de la Canada, Madrid (Spain)

    2012-03-10

    Rigel ({beta} Ori, B8 Ia) is a nearby blue supergiant displaying {alpha} Cyg type variability, and is one of the nearest Type II supernova progenitors. As such it is an excellent test bed to study the internal structure of pre-core-collapse stars. In this study, for the first time, we present 28 days of high-precision MOST photometry and over six years of spectroscopic monitoring. We report 19 significant pulsation modes of signal-to-noise ratio, S/N {approx}> 4.6 from radial velocities, with variability timescales ranging from 1.21 to 74.7 days, which are associated with high-order low-degree gravity modes. While the radial velocity variations show a degree of correlation with the flux changes, there is no clear interplay between the equivalent widths of different metallic and H{alpha} lines.

  9. Validation of Noninvasive MOEMS-Assisted Measurement System Based on CCD Sensor for Radial Pulse Analysis

    Directory of Open Access Journals (Sweden)

    Rolanas Dauksevicius

    2013-04-01

    Full Text Available Examination of wrist radial pulse is a noninvasive diagnostic method, which occupies a very important position in Traditional Chinese Medicine. It is based on manual palpation and therefore relies largely on the practitioner’s subjective technical skills and judgment. Consequently, it lacks reliability and consistency, which limits practical applications in clinical medicine. Thus, quantifiable characterization of the wrist pulse diagnosis method is a prerequisite for its further development and widespread use. This paper reports application of a noninvasive CCD sensor-based hybrid measurement system for radial pulse signal analysis. First, artery wall deformations caused by the blood flow are calibrated with a laser triangulation displacement sensor, following by the measurement of the deformations with projection moiré method. Different input pressures and fluids of various viscosities are used in the assembled artificial blood flow system in order to test the performance of laser triangulation technique with detection sensitivity enhancement through microfabricated retroreflective optical element placed on a synthetic vascular graft. Subsequently, the applicability of double-exposure whole-field projection moiré technique for registration of blood flow pulses is considered: a computational model and representative example are provided, followed by in vitro experiment performed on a vascular graft with artificial skin atop, which validates the suitability of the technique for characterization of skin surface deformations caused by the radial pulsation.

  10. Validation of noninvasive MOEMS-assisted measurement system based on CCD sensor for radial pulse analysis.

    Science.gov (United States)

    Malinauskas, Karolis; Palevicius, Paulius; Ragulskis, Minvydas; Ostasevicius, Vytautas; Dauksevicius, Rolanas

    2013-01-01

    Examination of wrist radial pulse is a noninvasive diagnostic method, which occupies a very important position in Traditional Chinese Medicine. It is based on manual palpation and therefore relies largely on the practitioner's subjective technical skills and judgment. Consequently, it lacks reliability and consistency, which limits practical applications in clinical medicine. Thus, quantifiable characterization of the wrist pulse diagnosis method is a prerequisite for its further development and widespread use. This paper reports application of a noninvasive CCD sensor-based hybrid measurement system for radial pulse signal analysis. First, artery wall deformations caused by the blood flow are calibrated with a laser triangulation displacement sensor, following by the measurement of the deformations with projection moiré method. Different input pressures and fluids of various viscosities are used in the assembled artificial blood flow system in order to test the performance of laser triangulation technique with detection sensitivity enhancement through microfabricated retroreflective optical element placed on a synthetic vascular graft. Subsequently, the applicability of double-exposure whole-field projection moiré technique for registration of blood flow pulses is considered: a computational model and representative example are provided, followed by in vitro experiment performed on a vascular graft with artificial skin atop, which validates the suitability of the technique for characterization of skin surface deformations caused by the radial pulsation. PMID:23609803

  11. PRECISION RADIAL VELOCITIES WITH CSHELL

    International Nuclear Information System (INIS)

    Radial velocity (RV) identification of extrasolar planets has historically been dominated by optical surveys. Interest in expanding exoplanet searches to M dwarfs and young stars, however, has motivated a push to improve the precision of near-infrared RV techniques. We present our methodology for achieving 58 m s-1 precision in the K band on the M0 dwarf GJ 281 using the CSHELL spectrograph at the 3 m NASA Infrared Telescope Facility. We also demonstrate our ability to recover the known 4 MJUP exoplanet Gl 86 b and discuss the implications for success in detecting planets around 1-3 Myr old T Tauri stars.

  12. Radial vibrations of BPS skyrmions

    CERN Document Server

    Adam, C; Romanczukiewicz, T; Wereszczynski, A

    2016-01-01

    We study radial vibrations of spherically symmetric skyrmions in the BPS Skyrme model. Concretely, we numerically solve the linearised field equations for small fluctuations in a skyrmion background, both for linearly stable oscillations and for (unstable) resonances. This is complemented by numerical solutions of the full nonlinear system, which confirm all the results of the linear analysis. In all cases, the resulting fundamental excitation provides a rather accurate value for the Roper resonance, supporting the hypothesis that the BPS Skyrme model already gives a reasonable approximate description of this resonance.

  13. Coupled pulsating and cellular structure in the propagation of globally planar detonations in free space

    Energy Technology Data Exchange (ETDEWEB)

    Han, Wenhu [Center for Combustion Energy, Tsinghua University, Beijing 100084 (China); Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Gao, Yang, E-mail: gaoyang-00@mails.tsinghua.edu.cn [Center for Combustion Energy, Tsinghua University, Beijing 100084 (China); Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Wang, Cheng [Beijing Institute of Technology, Beijing 100081 (China); Law, Chung K. [Center for Combustion Energy, Tsinghua University, Beijing 100084 (China); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

    2015-10-15

    The globally planar detonation in free space is numerically simulated, with particular interest to understand and quantify the emergence and evolution of the one-dimensional pulsating instability and the two-dimensional cellular structure which is inherently also affected by pulsating instability. It is found that the pulsation includes three stages: rapid decay of the overdrive, approach to the Chapman-Jouguet state and emergence of weak pulsations, and the formation of strong pulsations; while evolution of the cellular structure also exhibits distinct behavior at these three stages: no cell formation, formation of small-scale, irregular cells, and formation of regular cells of a larger scale. Furthermore, the average shock pressure in the detonation front consists of fine-scale oscillations reflecting the collision dynamics of the triple-shock structure and large-scale oscillations affected by the global pulsation. The common stages of evolution between the cellular structure and the pulsating behavior, as well as the existence of shock-front pressure oscillation, suggest highly correlated mechanisms between them. Detonations with period doubling, period quadrupling, and chaotic amplitudes were also observed and studied for progressively increasing activation energies.

  14. Spatio-temporal dynamics of sources of hard X-ray pulsations in solar flares

    CERN Document Server

    Kuznetsov, S A; Morgachev, A S; Struminsky, A B

    2016-01-01

    We present systematic analysis of spatio-temporal evolution of sources of hard X-ray (HXR) pulsations in solar flares. We concentrate on disk flares whose impulsive phase are accompanied by a series of more than three peaks (pulsations) of HXR emission detected in the RHESSI 50-100 keV channel with 4-second cadence. 29 such flares observed from February 2002 to June 2015 with time differences between successive peaks of 8-270 s are studied. The main observational result is that sources of HXR pulsations in all flares are not stationary, they demonstrate apparent displacements from pulsation to pulsation. The flares can be subdivided into two groups depending on character of dynamics of HXR sources. The group-1 consists of 16 flares (55%) with systematic dynamics of HXR sources from pulsation to pulsation with respect to a magnetic polarity inversion line (MPIL), which has simple extended trace on the photosphere. The group-2 consists of 13 flares (45%) with more chaotic displacements of HXR sources with respe...

  15. Coupled pulsating and cellular structure in the propagation of globally planar detonations in free space

    International Nuclear Information System (INIS)

    The globally planar detonation in free space is numerically simulated, with particular interest to understand and quantify the emergence and evolution of the one-dimensional pulsating instability and the two-dimensional cellular structure which is inherently also affected by pulsating instability. It is found that the pulsation includes three stages: rapid decay of the overdrive, approach to the Chapman-Jouguet state and emergence of weak pulsations, and the formation of strong pulsations; while evolution of the cellular structure also exhibits distinct behavior at these three stages: no cell formation, formation of small-scale, irregular cells, and formation of regular cells of a larger scale. Furthermore, the average shock pressure in the detonation front consists of fine-scale oscillations reflecting the collision dynamics of the triple-shock structure and large-scale oscillations affected by the global pulsation. The common stages of evolution between the cellular structure and the pulsating behavior, as well as the existence of shock-front pressure oscillation, suggest highly correlated mechanisms between them. Detonations with period doubling, period quadrupling, and chaotic amplitudes were also observed and studied for progressively increasing activation energies

  16. Ultra-fast magnetic resonance encephalography of physiological brain activity - Glymphatic pulsation mechanisms?

    Science.gov (United States)

    Kiviniemi, Vesa; Wang, Xindi; Korhonen, Vesa; Keinänen, Tuija; Tuovinen, Timo; Autio, Joonas; LeVan, Pierre; Keilholz, Shella; Zang, Yu-Feng; Hennig, Jürgen; Nedergaard, Maiken

    2016-06-01

    The theory on the glymphatic convection mechanism of cerebrospinal fluid holds that cardiac pulsations in part pump cerebrospinal fluid from the peri-arterial spaces through the extracellular tissue into the peri-venous spaces facilitated by aquaporin water channels. Since cardiac pulses cannot be the sole mechanism of glymphatic propulsion, we searched for additional cerebrospinal fluid pulsations in the human brain with ultra-fast magnetic resonance encephalography. We detected three types of physiological mechanisms affecting cerebral cerebrospinal fluid pulsations: cardiac, respiratory, and very low frequency pulsations. The cardiac pulsations induce a negative magnetic resonance encephalography signal change in peri-arterial regions that extends centrifugally and covers the brain in ≈1 Hz cycles. The respiratory ≈0.3 Hz pulsations are centripetal periodical pulses that occur dominantly in peri-venous areas. The third type of pulsation was very low frequency (VLF 0.001-0.023 Hz) and low frequency (LF 0.023-0.73 Hz) waves that both propagate with unique spatiotemporal patterns. Our findings using critically sampled magnetic resonance encephalography open a new view into cerebral fluid dynamics. Since glymphatic system failure may precede protein accumulations in diseases such as Alzheimer's dementia, this methodological advance offers a novel approach to image brain fluid dynamics that potentially can enable early detection and intervention in neurodegenerative diseases. PMID:26690495

  17. Propagation and source of Pc5 frequency range pulsation at cusp latitude

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Two induction magnetometers have been installed at Chinese Zhongshan Station and Australia Davis Station, Antarctica respectively. We adopt the cross-spectral analysis technique to analyze the data of the two induction magnetometers, in June, September, December 1996 and March 1997, and to investigate Pc5 frequency range pulsation (150 600 s) occurrence and propagation in cusp latitude. The results are summarized as follows: At Zhongshan-Davis Station, the magnetic pulsations in Pc5 frequency band can occurs over a wide time, but more frequently at pre local magnetic noon and pre local magnetic midnight. The Pc5 pulsations have no significant seasonal variation in the amplitude, occurrence and propagation. The amplitude has a small peak at pre local magnetic noon and large value sometimes at pre local magnetic midnight. In daytime, the Pc5 pulsations propagate westward in morning and eastward in afternoon, and reversal at local magnetic noon. In nighttime, the Pc5 pulsations propagate westward before 20:00 MLT and eastward after 20:00 MLT. Near dusk time, the Pc5 pulsations propagate irregularly. These characteristics indicate that the Pc5 pulsations have different source at different local magnetic time.

  18. Coupled pulsating and cellular structure in the propagation of globally planar detonations in free space

    Science.gov (United States)

    Han, Wenhu; Gao, Yang; Wang, Cheng; Law, Chung K.

    2015-10-01

    The globally planar detonation in free space is numerically simulated, with particular interest to understand and quantify the emergence and evolution of the one-dimensional pulsating instability and the two-dimensional cellular structure which is inherently also affected by pulsating instability. It is found that the pulsation includes three stages: rapid decay of the overdrive, approach to the Chapman-Jouguet state and emergence of weak pulsations, and the formation of strong pulsations; while evolution of the cellular structure also exhibits distinct behavior at these three stages: no cell formation, formation of small-scale, irregular cells, and formation of regular cells of a larger scale. Furthermore, the average shock pressure in the detonation front consists of fine-scale oscillations reflecting the collision dynamics of the triple-shock structure and large-scale oscillations affected by the global pulsation. The common stages of evolution between the cellular structure and the pulsating behavior, as well as the existence of shock-front pressure oscillation, suggest highly correlated mechanisms between them. Detonations with period doubling, period quadrupling, and chaotic amplitudes were also observed and studied for progressively increasing activation energies.

  19. Peculiar variations of white dwarf pulsation frequencies and maestro

    Science.gov (United States)

    Dalessio, James Ruland

    In Part I we report on variations of the normal mode frequencies of the pulsating DB white dwarfs EC 20058-5234 and KIC 8626021 and the pulsating DA white dwarf GD 66. The observations of EC 20058-5234 and KIC 8626021 were motivated by the possibility of measuring the plasmon neutrino production rate of a white dwarf, while the observations of GD 66 were part of a white dwarf pulsation timing based planet search. We announce the discovery of periodic and quasi-periodic variations of multiple normal mode frequencies that cannot be due to the presence of planetary companions. We note the possible signature of a planetary companion to EC 20058-5234 and show that GD 66 cannot have a planet in a several AU orbit down to half a Jupiter mass. We also announce the discovery of secular variations of the normal mode frequencies of all three stars that are inconsistent with cooling alone. Importantly, the rates of period change of several modes of KIC 8626021 are consistent with evolutionary cooling, but are not yet statistically significant. These modes offer the best possibility of measuring the neutrino production rate in a white dwarf. We also observe periodic and secular variations in the frequency of a combination mode that exactly matches the variations predicted by the parent modes, strong observational evidence that combination modes are created by the convection zone and are not normal modes. Periodic variations in the amplitudes of many of these modes is also noted. We hypothesize that these frequency variations are caused by complex variations of the magnetic field strength and geometry, analogous to behavior observed in the Sun. In Part II we describe the MAESTRO software framework and the MAESTRO REDUCE algorithm. MAESTRO is a collection of astronomy specific MatLab software developed by the Whole Earth Telescope. REDUCE is an an algorithm that can extract the brightness of stars on a set of CCD images with minimal configuration and human interaction. The key to

  20. Pulsating flow performance of a turbocharger compressor for automotive application

    International Nuclear Information System (INIS)

    Highlights: • The behavior of a turbocharger for automotive application was studied. • A broad experimental activity was developed under steady and unsteady flow. • Compressor performance was analyzed under unsteady flow. • Compressor unsteady flow performance deviates from the corresponding steady state. • The surge line position proved to be affected by unsteady flow operation. -- Abstract: Downsizing with turbocharging is the most promising way, especially in terms of cost, to get reduced fuel consumption and CO2 emissions particularly in the case of Spark Ignition engines. In automotive applications the turbocharger turbine usually operates under heavy unsteady flow conditions due to the opening and closing of engine valves. However, in the case of extremely downsized engines with a reduced number of cylinders and a small intake circuit volume also the compressor performance can be affected by the unsteady flow generated by the engine intake valves. To make simulation models able to accurately predict engine performance, a better understanding of compressor and turbine pulsating flow performance can be accomplished through measurements performed on specialized test facilities, using suitable measuring equipment. As regards the turbocharger compressor, the surge line position under pulsating flow conditions is another important aspect to be considered. In the paper the results of a broad experimental investigation performed on a small turbocharger compressor matched to a downsized gasoline engine are presented. Measurements were developed on the test facility operating at the University of Genoa, which allows investigations on automotive turbochargers both under steady and unsteady flow conditions. Tested turbocharger compressor was coupled to the automotive engine intake circuit and the pulsating flow was generated by a motor-driven cylinder head fitted with a variable valve actuation system. Different levels of turbocharger rotational speed and

  1. KIC 6220497: a new Algol-type eclipsing binary with multiperiodic pulsations

    Science.gov (United States)

    Lee, Jae Woo; Hong, Kyeongsoo; Kim, Seung-Lee; Koo, Jae-Rim

    2016-08-01

    We present both binarity and pulsation of KIC 6220497 from the Kepler observations. The light curve synthesis shows that the eclipsing system is a semidetached Algol with parameters of q = 0.243 ± 0.001, i = 77.3 ± 0.3 deg, and ΔT = 3372 ± 58 K, in which the detached primary component fills its Roche lobe by ˜87 per cent. A multiple frequency analysis of the eclipse-subtracted light residuals reveals 33 frequencies in the range of 0.75-20.22 d-1 with amplitudes between 0.27 and 4.56 mmag. Among these, four are pulsation frequencies in fundamental (f1, f5) and p (f2, f7) modes, and six are orbital frequency (f8, f31) and its harmonics (f6, f11, f20, f24), which can be attributed to tidally excited modes. For the pulsation frequencies, the pulsation constants of 0.16-0.33 d and the period ratios of Ppul/Porb = 0.042-0.089 indicate that the primary component is a δ Sct pulsating star and, thus, KIC 6220497 is an oscillating eclipsing Algol (oEA) star. The dominant pulsation period of 0.117 4051 ± 0.000 0004 d is significantly longer than that expected from empirical relations that link the pulsation period with the orbital period. The surface gravity of log g1 = 3.78 ± 0.03 is clearly smaller than those of the other oEA stars with similar orbital periods. The pulsation period and the surface gravity of the pulsating primary demonstrate that KIC 6220497 would be the more evolved eclipsing binary, compared with normal oEA stars.

  2. Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: III. The pre-ELM white dwarf instability strip

    CERN Document Server

    Córsico, A H; Serenelli, A M; Kepler, S O; Jeffery, C S; Corti, M A

    2016-01-01

    Two low-mass pre-white dwarfs, which could be precursors of ELM white dwarfs, have been observed to show multiperiodic photometric variations. They could constitute a new class of pulsating low-mass pre-white dwarf stars. We present a detailed nonadiabatic pulsation study of such stars, employing full evolutionary sequences of low-mass He-core pre-white dwarf models. We have considered models in which element diffusion is accounted for and also models in which it is neglected. We confirm and explore in detail a new instability strip in the domain of low gravities and low effective temperatures of the $T_{\\rm eff}-\\log g$ diagram, where low-mass pre-white dwarfs are currently found. The destabilized modes are radial and nonradial $p$ and $g$ modes excited by the $\\kappa-\\gamma$ mechanism acting mainly at the zone of the second partial ionization of He, with non-negligible contributions from the region of the first partial ionization of He and the partial ionization of H. The computations with element diffusion...

  3. A Novel Pre-cooling System for a Cryogenic Pulsating Heat Pipe

    Science.gov (United States)

    Xu, Dong; Liu, Huiming; Gong, Linghui; Xu, Xiangdong; Li, Laifeng

    To reduce the influence of the pipe material on the measurement of effective thermal conductivity, the pipe of a cryogenic pulsating heat pipe is generally made of stainless steel. Because of the low thermal conductivity of stainless steel, the pre-cooling of the evaporator in cryogenic pulsating heat pipe using helium as working fluid at 4.2 K is a problem. We designed a mechanical-thermal switch between the cryocooler and the evaporator, which was on during the pre-cooling process and off during the test process. By using the pre-cooling system, the cool down time of the cryogenic pulsating heat pipe was reduced significantly.

  4. A 'one in a million' case of pulsating thoracoabdominal mass.

    LENUS (Irish Health Repository)

    Tan, Lay Ong

    2012-11-01

    Ectopia cordis is a rare congenital malformation in which the heart is located partially or totally outside the thoracic cavity. It comprises 0.1% of congenital heart diseases. The authors present a case of a male baby born at term by emergency caesarean section due to prolonged fetal bradycardia, who was noted to have a large pulsating mass in the thoracoabdominal area. In view of lower thoracolumbar abdominal defect, ectopic placement of the umbilicus, deficiency of the diaphragmatic pericardium, deficiency of anterior diaphragm and intracardiac abnormalities, a diagnosis of ectopia cordis-Pentalogy of Cantrell was made. He was transferred to a tertiary centre and required oxygen supplement initially. He was sent home after 1 week, on propanolol, with weekly oxygen saturation checks. He is awaiting further surgical intervention pending the required weight gain.

  5. Pulsating instability and self-acceleration of fast turbulent flames

    CERN Document Server

    Poludnenko, A Y

    2015-01-01

    (Abridged) A series of three-dimensional numerical simulations is used to study the intrinsic stability of high-speed turbulent flames. Calculations model the interaction of a fully-resolved premixed flame with a highly subsonic, statistically steady, homogeneous, isotropic turbulence. We consider a wide range of turbulent intensities and system sizes, corresponding to the Damk\\"ohler numbers Da = 0.1-6.0. These calculations show that turbulent flames in the regimes considered are intrinsically unstable. In particular, we find three effects. 1) Turbulent flame speed develops pulsations with the observed peak-to-peak amplitude > 10 and a characteristic time scale close to a large-scale eddy turnover time. Such variability is caused by the interplay between turbulence, which continuously creates the flame surface, and highly intermittent flame collisions, which consume the flame surface. 2) Unstable burning results in the periodic pressure build-up and the formation of pressure waves or shocks, when the flame s...

  6. Improving Sensitivity to Weak Pulsations with Photon Probability Weighting

    CERN Document Server

    Kerr, Matthew

    2011-01-01

    All gamma-ray telescopes suffer from source confusion due to their inability to focus incident high-energy radiation, and the resulting background contamination can obscure the periodic emission from faint pulsars. In the context of the Fermi Large Area Telescope, we outline enhanced statistical tests for pulsation in which each photon is weighted by its probability to have originated from the candidate pulsar. The probabilities are calculated using the instrument response function and a full spectral model, enabling powerful background rejection. With Monte Carlo methods, we demonstrate that the new tests increase the sensitivity to pulsars by more than 50% under a wide range of conditions. This improvement may appreciably increase the completeness of the sample of radio-loud gamma-ray pulsars. Finally, we derive the asymptotic null distribution for the H-test, expanding its domain of validity to arbitrarily complex light curves.

  7. Asteroseismology of pulsating DA white dwarfs with fully evolutionary models

    Directory of Open Access Journals (Sweden)

    Althaus L.G.

    2013-03-01

    Full Text Available We present a new approach for asteroseismology of DA white dwarfs that consists in the employment of a large set of non-static, physically sound, fully evolutionary models representative of these stars. We already have applied this approach with success to pulsating PG1159 stars (GW Vir variables. Our white dwarf models, which cover a wide range of stellar masses, effective temperatures, and envelope thicknesses, are the result of fully evolutionary computations that take into account the complete history of the progenitor stars from the ZAMS. In particular, the models are characterized by self-consistent chemical structures from the centre to the surface, a crucial aspect of white dwarf asteroseismology. We apply this approach to an ensemble of 44 bright DAV (ZZ Ceti stars.

  8. Dynamic response of nuclear fuel assembly excited by pressure pulsations

    Directory of Open Access Journals (Sweden)

    Zeman V.

    2012-12-01

    Full Text Available The paper deals with dynamic load calculation of the hexagonal type nuclear fuel assembly caused by spatial motion of the support plates in the reactor core. The support plate motion is excited by pressure pulsations generated by main circulation pumps in the coolant loops of the primary circuit of the nuclear power plant. Slightly different pumps revolutions generate the beat vibrations which causes an amplification of fuel assembly component dynamic deformations and fuel rods coating abrasion. The cyclic and central symmetry of the fuel assembly makes it possible the system decomposition into six identical revolved fuel rod segments which are linked with central tube and skeleton by several spacer grids in horizontal planes.The modal synthesis method with condensation of the fuel rod segments is used for calculation of the normal and friction forces transmitted between fuel rods and spacer grids cells.

  9. A dynamic film model of the pulsating heat pipe

    International Nuclear Information System (INIS)

    This article deals with the numerical modeling of the pulsating heat pipe (PHP) and is based on the film evaporation/condensation model recently applied to the single-bubble PHP (Das et al., 2010, 'Thermally Induced Two-Phase Oscillating Flow Inside a Capillary Tube', Int. J. Heat Mass Transfer, 53(19-20), pp. 3905-3913). The described numerical code can treat the PHP of an arbitrary number of bubbles and branches. Several phenomena that occur inside the PHP are taken into account: coalescence of liquid plugs, film junction or rupture, etc. The model reproduces some of the experimentally observed regimes of functioning of the PHP such as chaotic or intermittent oscillations of large amplitudes. Some results on the PHP heat transfer are discussed. (author)

  10. Pulsating jet-like structures in magnetized plasma

    Science.gov (United States)

    Goncharov, V. P.; Pavlov, V. I.

    2016-08-01

    The formation of pulsating jet-like structures has been studied in the scope of the nonhydrostatic model of a magnetized plasma with horizontally nonuniform density. We discuss two mechanisms which are capable of stopping the gravitational spreading appearing to grace the Rayleigh-Taylor instability and to lead to the formation of stationary or oscillating localized structures. One of them is caused by the Coriolis effect in the rotating frames, and another is connected with the Lorentz effect for magnetized fluids. Magnetized jets/drops with a positive buoyancy must oscillate in transversal size and can manifest themselves as "radio pulsars." The estimates of their frequencies are made for conditions typical for the neutron star's ocean.

  11. The RCB star RY Sagittarii as a pulsating star

    Science.gov (United States)

    Lloyd Evans, T.

    1986-03-01

    Measurements of CN and C2 bandstrengths in the spectrum of RY Sagittarii in 1969 and 1970, when it was on the latter part of its return to maximum and during its subsequent stay at maximum light after the deep minimum of 1967-68, show that the bands vary in strength in the 38.6-day pulsation period. The variations follow the phasing of the B-V and U-B color curves rather than the V light curve, and must be determined largely by the photospheric temperature as in the case of the carbon-rich Cepheid V553 Centauri. This is supported by a comparison of the ranges in color and in bandstrength, though the bands are stronger at a given color than in typical class Ib supergiants.

  12. Mathematical Modelling and Parameter Optimization of Pulsating Heat Pipes

    CERN Document Server

    Yang, Xin-She; Luan, Tao; Koziel, Slawomir

    2014-01-01

    Proper heat transfer management is important to key electronic components in microelectronic applications. Pulsating heat pipes (PHP) can be an efficient solution to such heat transfer problems. However, mathematical modelling of a PHP system is still very challenging, due to the complexity and multiphysics nature of the system. In this work, we present a simplified, two-phase heat transfer model, and our analysis shows that it can make good predictions about startup characteristics. Furthermore, by considering parameter estimation as a nonlinear constrained optimization problem, we have used the firefly algorithm to find parameter estimates efficiently. We have also demonstrated that it is possible to obtain good estimates of key parameters using very limited experimental data.

  13. Depression of the ULF geomagnetic pulsation related to ionospheric irregularities

    Directory of Open Access Journals (Sweden)

    O. A. Molchanov

    2004-06-01

    Full Text Available We consider a depression in intensity of ULF magnetic pulsations, which is observed on the ground surface due to appearance of the irregularities in the ionosphere. It is supposed that oblique Alfven waves in the ULF frequency range are downgoing from the magnetosphere and the horizontal irregularities of ionospheric conductivity are created by upgoing atmospheric gravity waves from seismic source. Unlike the companion paper by Molchanov et al. (2003, we used a simple model of the ionospheric layer but took into consideration the lateral inhomogeneity of the perturbation region in the ionosphere. It is shown that ULF intensity could be essentially decreased for frequencies f = 0.001-0.1 Hz at nighttime but the change is negligible at daytime in coincidence with observational results.

  14. An application of Bayesian inference for solar-like pulsators

    Science.gov (United States)

    Benomar, O.

    2008-12-01

    As the amount of data collected by space-borne asteroseismic instruments (such as CoRoT and Kepler) increases drastically, it will be useful to have automated processes to extract a maximum of information from these data. The use of a Bayesian approach could be very help- ful for this goal. Only a few attempts have been made in this way (e.g. Brewer et al. 2007). We propose to use Markov Chain Monte Carlo simulations (MCMC) with Metropolis-Hasting (MH) based algorithms to infer the main stellar oscillation parameters from the power spec- trum, in the case of solar-like pulsators. Given a number of modes to be fitted, the algorithm is able to give the best set of parameters (frequency, linewidth, amplitude, rotational split- ting) corresponding to a chosen input model. We illustrate this algorithm with one of the first CoRoT targets: HD 49933.

  15. Zinc electrodeposition from alkaline zincate solution by pulsating overpotentials

    Directory of Open Access Journals (Sweden)

    MILOS V. SIMICIC

    2000-09-01

    Full Text Available It is well known that smooth zinc deposits cannot be obtained from alkaline zincate using constant overpotential and current rate. During prolonged metal deposition, spongy and dendritic deposits are formed. It has been shown that the deposits are less agglomerated in the case of square-wave pulsating overpotentials regime than the ones obtained in case of constant overpotential regime. This is explained in a semiquantitative way by two phenomena: selective anodic dissolution during overpotentials “off” period and decreasing diffusion control. These effects is more pronounced at higher pause-to-pulse ratio. Increasing the pause-to-pulse ratio causes a reduction of the ratio between diffusion and activation overpotential, resulting in a more compact deposit. Confirmation of the proposed semiquantitative mathematical model was obtained by zinc electrodeposition onto a copper wire from a 0.1 M zincate solution in 1.0 M KOH at room temperature.

  16. Relationship of spontaneous retinal vein pulsation with ocular circulatory cycle.

    Directory of Open Access Journals (Sweden)

    Mijin Kim

    Full Text Available PURPOSE: To determine the timing of spontaneous venous pulsation (SVP relative to the ocular circulatory cycle by using the movie tool of confocal scanning laser ophthalmoloscope. METHODS: A video recording of the fundus was obtained using a confocal scanning laser ophthalmoscope (Spectralis HRA, Heidelberg Engineering, Heidelberg, Germany at 8 frames/s in 47 eyes (15 glaucoma patients and 32 glaucoma suspects with visible pulsation of both the central retinal artery (CRA and vein (CRV. The timing of the maximum and minimum diameters of the CRA (CRA(max and CRAmin, respectively and CRV (CRV(max and CRV(min, respectively was identified during four pulse cycles. The interval between CRV(min and CRA(min, and between CRV(max and CRA(max was expressed as the number of frames and as a percentage of the ocular circulatory cycle. RESULTS: The ocular circulatory cycle (from one CRA(max to the next lasted 7.7 ± 1.0 frames (958.8 ± 127.2 ms, mean ± SD, with a mean pulse rate of 62.6 beats/min. The diameter of the CRA was increased for 2.4 ± 0.5 frames (301.9 ± 58.8 ms and decreased for 5.3 ± 0.9 frames (656.9 ± 113.5 ms. CRV(max occurred 1.0 ± 0.2 frames after CRA(max (equivalent to 13.0% of the ocular circulatory cycle, while CRV(min occurred 1.1 ± 0.4 frames after CRA(min (equivalent to 14.6% of the ocular circulatory cycle. CONCLUSIONS: During SVP, the diameter of the CRV began to decrease at early diastole, and the reduction persisted until early systole. This finding supports that CRV collapse occurs during ocular diastole.

  17. Flow and mixing characteristics of an elevated pulsating transverse jet

    Science.gov (United States)

    Huang, Rong F.; Hsu, Ching M.

    2012-01-01

    Flow-evolution processes as well as the penetration, spread, and dispersion characteristics of elevated pulsating transverse jets were studied experimentally in a wind tunnel. Jet pulsations were induced by means of acoustic excitation. Streak pictures of the smoke-flow patterns, illuminated by a laser-light sheet in the median plane, were recorded by a high-speed digital camera. A hot-wire anemometer was used to digitize instantaneous velocities of instabilities in the flow. Penetration height and spread width were obtained through a binary edge identification technique. Tracer-gas concentrations were measured to provide information on jet dispersions and trajectories. Three characteristic flow modes (synchronized flapping jet, transition, and synchronized shear-layer vortices) were identified in the domain of the jet-to-crossflow momentum-flux ratio and the excitation Strouhal number. At low excitation Strouhal numbers, the jet column near the tube exit flapped back-and-forth periodically at the excitation frequency and induced large up-down motions of the deflected jet. The penetration, spread, and dispersion of the jet increased drastically compared with the non-excited jet because the up-down oscillating motions of the deflected jet transformed the axial momentum into oscillating lateral momentum. Forcing the jet into the transition and synchronized shear-layer vortices regimes caused the vortices to appear along the upwind shear layer of the deflected jet. Under these conditions, the penetration, spread, and dispersion of the jet presented insignificant increases because the entrainment effect induced by the shear-layer vortices was not as large as that produced by the jet oscillating motions in the synchronized flapping jet regime.

  18. The Effect of Flow Pulsations on Coriolis Mass Flow Meters

    Science.gov (United States)

    Cheesewright, R.; Clark, C.

    1998-11-01

    It has been reported that the accuracy of Coriolis mass flow meters can be adversely affected by the presence of pulsations (at particular frequencies) in the flow. A full analysis of the transient performance of a commercial Coriolis meter is only possible using finite element techniques. However, this is a transient, nonlinear problem in which the space and time variables are not (strictly) separable and the finite element techniques for tackling such problems make it desirable to have an analytical solution for a simplified meter, against which the finite element solution can be compared. This paper reports such a solution. The solution will also provide guidance for experiments. Existing analytical solutions for the performance of Coriolis meters in steady flow (a complex eigenvalue problem) are not easily extended to the transient flow case. The paper thus begins with the presentation of an alternative solution for steady flow through a simple, straight tube, Coriolis meter and it is notable that this solution gives a simple analytical expression for the experimentally observed small change in the resonant frequency of the meter, with flow rate, as well as an analytical expression for the meter sensitivity. The analysis is extended to the transient case, using classical, forced vibration, modal decomposition techniques. The solution shows that, unlike the steady flow case where the detector signals contain components at the drive frequency and the second mode frequency (Coriolis frequency), for pulsatile flow the detector signals will in general contain components involving at least four frequencies. It is demonstrated that the meter error depends on the algorithm used to estimate the phase difference from the detector signals. The particular flow pulsation frequencies which could possibly lead to large meter errors are identified.

  19. A planet in an 840-d orbit around a Kepler main-sequence A star found from phase modulation of its pulsations

    CERN Document Server

    Murphy, Simon J; Shibahashi, Hiromoto

    2016-01-01

    We have detected a 12 M$_{\\rm Jup}$ planet orbiting in or near the habitable zone of a main-sequence A star via the pulsational phase shifts induced by orbital motion. The planet has an orbital period of $840\\pm20$ d and an eccentricity of 0.15. All known planets orbiting main-sequence A stars have been found via the transit method or by direct imaging. The absence of astrometric or radial-velocity detections of planets around these hosts makes ours the first discovery using the orbital motion. It is also the first A star known to host a planet within 1$\\sigma$ of the habitable zone. We find evidence for planets in a large fraction of the parameter space where we are able to detect them. This supports the idea that A stars harbor high-mass planets in wide orbits.

  20. Radial flow pulse jet mixer

    Science.gov (United States)

    VanOsdol, John G.

    2013-06-25

    The disclosure provides a pulse jet mixing vessel for mixing a plurality of solid particles. The pulse jet mixing vessel is comprised of a sludge basin, a flow surface surrounding the sludge basin, and a downcoming flow annulus between the flow surface and an inner shroud. The pulse jet mixing vessel is additionally comprised of an upper vessel pressurization volume in fluid communication with the downcoming flow annulus, and an inner shroud surge volume separated from the downcoming flow annulus by the inner shroud. When the solid particles are resting on the sludge basin and a fluid such as water is atop the particles and extending into the downcoming flow annulus and the inner shroud surge volume, mixing occurs by pressurization of the upper vessel pressurization volume, generating an inward radial flow over the flow surface and an upwash jet at the center of the sludge basin.

  1. de secador de flujo radial

    Directory of Open Access Journals (Sweden)

    Néstor Durango

    2005-01-01

    Full Text Available En este artículo se presentan los resultados obtenidos en la investigación realizada para establecer la influencia e importancia de las variables cantidad de yuca, relación superficie a volumen del material de los pedazos de yuca, velocidad del ventilador y temperatura del aire de recirculación, en el proceso de secado de yuca en un modelo de secador de flujo radial. La metodología experimental utilizada fue el diseño de experimentos factoriales, la cual, mediante una serie de análisis estadísticos, posibilitó la caracterización del proceso para un tiempo de secado de tres horas y la obtención de un modelo matemático que describe su comportamiento.

  2. Radial smoothing and closed orbit

    International Nuclear Information System (INIS)

    A complete simulation leading to a description of one of the error curves must involve four phases: (1) random drawing of the six set-up points within a normal population having a standard deviation of 1.3 mm; (b) random drawing of the six vertices of the curve in the sextant mode within a normal population having a standard deviation of 1.2 mm. These vertices are to be set with respect to the axis of the error lunes, while this axis has as its origins the positions defined by the preceding drawing; (c) mathematical definition of six parabolic curves and their junctions. These latter may be curves with very slight curvatures, or segments of a straight line passing through the set-up point and having lengths no longer than one LSS. Thus one gets a mean curve for the absolute errors; (d) plotting of the actually observed radial positions with respect to the mean curve (results of smoothing)

  3. A fully relativistic radial fall

    Science.gov (United States)

    Spallicci, Alessandro D. A. M.; Ritter, Patxi

    2014-10-01

    Radial fall has historically played a momentous role. It is one of the most classical problems, the solutions of which represent the level of understanding of gravitation in a given epoch. A gedankenexperiment in a modern frame is given by a small body, like a compact star or a solar mass black hole, captured by a supermassive black hole. The mass of the small body itself and the emission of gravitational radiation cause the departure from the geodesic path due to the back-action, that is the self-force. For radial fall, as any other non-adiabatic motion, the instantaneous identity of the radiated energy and the loss of orbital energy cannot be imposed and provide the perturbed trajectory. In the first part of this paper, we present the effects due to the self-force computed on the geodesic trajectory in the background field. Compared to the latter trajectory, in the Regge-Wheeler, harmonic and all others smoothly related gauges, a far observer concludes that the self-force pushes inward (not outward) the falling body, with a strength proportional to the mass of the small body for a given large mass; further, the same observer notes a higher value of the maximal coordinate velocity, this value being reached earlier during infall. In the second part of this paper, we implement a self-consistent approach for which the trajectory is iteratively corrected by the self-force, this time computed on osculating geodesics. Finally, we compare the motion driven by the self-force without and with self-consistent orbital evolution. Subtle differences are noticeable, even if self-force effects have hardly the time to accumulate in such a short orbit.

  4. A CONSERVATIVE VIEW OF RADIAL KERATOTOMY

    Institute of Scientific and Technical Information of China (English)

    Steven; Olkowski; Walter; J.; Stark; John; D.; Gottsch; Gerri; Goodman; Daniel; Goodman; A.E.; Maumenee; Ivan; Esente

    1991-01-01

    It has been known for almost a century that radial keratotomy (RK) will flatten the cornea and reduce myopia. Since the introduction of radial keratotomy (RK) in the United States by Bores in 1978, there have been many published studies documenting the effects of this procedure. The questions. about radial keratotomy today are not only quantitative but also qualitative in nature. We know this technique can flatten the cornea, but how reliably can the results be predicted? Does the patient benefit suffic...

  5. Hollow Cathode With Multiple Radial Orifices

    Science.gov (United States)

    Brophy, John R.

    1992-01-01

    Improved hollow cathode serving as source of electrons has multiple radial orifices instead of single axial orifice. Distributes ion current more smoothly, over larger area. Prototype of high-current cathodes for ion engines in spacecraft. On Earth, cathodes used in large-diameter ion sources for industrial processing of materials. Radial orientation of orifices in new design causes current to be dispersed radially in vicinity of cathode. Advantageous where desireable to produce plasma more nearly uniform over wider region around cathode.

  6. Numerical analysis of heat transfer in pulsating turbulent flow in a pipe

    Energy Technology Data Exchange (ETDEWEB)

    Xuefang Wang [Nebraska Univ., Lincoln, NE (United States). Dept. of Mechanical Engineering; Nengli Zhang [NASA Glenn Research Center at Lewis Field, Cleveland, OH (United States)

    2005-09-01

    Convection heat transfer in pulsating turbulent flow with large velocity oscillating amplitudes in a pipe at constant wall temperature is numerically studied. A low-Reynolds-number (LRN) k-{epsilon} turbulent model is used in the turbulence modeling. The model analysis indicates that Womersley number is a very important parameter in the study of pulsating flow and heat transfer. Flow and heat transfer in a wide range of process parameters are investigated to reveal the velocity and temperature characteristics of the flow. The numerical calculation results show that in a pulsating turbulent flow there is an optimum Womersley number at which heat transfer is maximally enhanced. Both larger amplitude of velocity oscillation and flow reversal in the pulsating turbulent flow also greatly promote the heat transfer enhancement. (author)

  7. NUMERICAL SIMULATION AND ANALYSIS OF PRESSURE PULSATION IN FRANCIS HYDRAULIC TURBINE WITH AIR ADMISSION

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show: air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.

  8. Relations of field line resonances and upstream waves and the winter attenuation of pulsations

    Directory of Open Access Journals (Sweden)

    J. VerH{o}

    Full Text Available Using data on the occurrence frequency of geomagnetic pulsations of different periods from three observatories in Central Europe, conclusions are drawn about the occurrence of field line resonances and pulsations directly driven by upstream waves at L-values below 3. It was found that both types occur during the interval studied (first 6 months of the year 1991, but both the occurrence frequency of the two types and the characteristic period of the field line resonance change significantly as compared to other intervals. During Northern winter, pulsation activity is severely damped in solar maximum years, including the year 1991. The decrease in the activity of the pulsations is more significant at shorter periods.

  9. The rapidly pulsating sdO star, SDSS J160043.6+074802.9

    CERN Document Server

    Rodríguez-López, C; Kilkenny, D; MacDonald, J; Moya, A; Koen, C; Woudt, P A; Wium, D J; Oruru, B; Zietsman, E

    2009-01-01

    A spectroscopic analysis of SDSS J160043.6+074802.9, a binary system containing a pulsating subdwarf-O (sdO) star with a late-type companion, yields Teff = 70 000 +/- 5000 K and log g = 5.25 +/- 0.30, together with a most likely type of K3V for the secondary star. We compare our results with atmospheric parameters derived by Fontaine et al. (2008) and in the context of existing evolution models for sdO stars. New and more extensive photometry is also presented which recovers most, but not all, frequencies found in an earlier paper. It therefore seems probable that some pulsation modes have variable amplitudes. A non-adiabatic pulsation analysis of uniform metallicity sdO models show those having log g > 5.3 to be more likely to be unstable and capable of driving pulsation in the observed frequency range.

  10. A Novel Multisection Distributed Feedback Laser with Varied Ridge Width for Self-Pulsation Generation

    Institute of Scientific and Technical Information of China (English)

    WAN Qin; SUN Chang-Zheng; XIONG Bing; WANG Jian; LUO Yi

    2006-01-01

    @@ A novel ridge-waveguide multisection (MS) distributed feedback (DFB) laser, which consists of two identical DFB sections but different ridge widths, is proposed to generate beating-type self-pulsations (SPs).

  11. Pulsating stars in NGC 6231 Frequency analysis and photometric mode identification near the main sequence

    CERN Document Server

    Meingast, Stefan; Shobbrook, Robert R

    2013-01-01

    We used Johnson UBV photometric CCD observations to identify pulsating and other variable stars in the young open cluster NGC 6231. The multi-color information was used to classify pulsating variables, perform frequency analysis, and - where possible - to compare observed to theoretical amplitude ratios for mode identification. The data reduction was performed with standard IRAF tools. Differential light curves have been obtained by identifying a set of suitable comparison stars and the frequency analysis was then conducted on the basis of Fourier methods. Our classification of pulsating stars was based on the time scales and amplitudes of the variability with respect to the different filters and stellar parameters as calculated from published Str\\"omgren and Geneva photometry. We identified 32 variable stars in the field of the cluster out of which 21 are confirmed members and twelve are newly detected variable stars. Ten stars were classified as Slowly Pulsating B (SPB) stars in NGC 6231 out of which seven ...

  12. The development of early pulsation theory, or, how Cepheids are like steam engines"

    Science.gov (United States)

    Stanley, Matthew

    2011-05-01

    The pulsation theory of Cepheid variable stars was a major breakthrough of early twentieth-century astrophysics. At the beginning of that century, the basic physics of normal stars was very poorly understood, and variable stars were even more mysterious. Breaking with accepted explanations in terms of eclipsing binaries, Harlow Shapley and A.S. Eddington pioneered novel theories that considered Cepheids as pulsating spheres of gas. These theoretical models relied on highly speculative physics, but nonetheless returned very impressive results despite attacks from figures such as James Jeans. Surprisingly, the pulsation theory not only depended on developments in stellar physics, but also drove many of those developments. In particular, models of stars in radiative balance and theories of stellar energy were heavily inspired and shaped by ideas about variable stars. Further, the success of the pulsation theory helped justify the new approaches to astrophysics being developed before World War II.

  13. The Development of Early Pulsation Theory, or, How Cepheids Are Like Steam Engines

    Science.gov (United States)

    Stanley, M.

    2012-06-01

    The pulsation theory of Cepheid variable stars was a major breakthrough of early twentieth-century astrophysics. At the beginning of that century, the basic physics of normal stars was very poorly understood, and variable stars were even more mysterious. Breaking with accepted explanations in terms of eclipsing binaries, Harlow Shapley and A. S. Eddington pioneered novel theories that considered Cepheids as pulsating spheres of gas. Surprisingly, the pulsation theory not only depended on novel developments in stellar physics, but the theory also drove many of those developments. In particular, models of stars in radiative balance and theories of stellar energy were heavily inspired and shaped by ideas about variable stars. Further, the success of the pulsation theory helped justify the new approaches to astrophysics being developed before World War II.

  14. A Study of Pc4-5 Geomagnetic Pulsations in the Brazilian Sector

    CERN Document Server

    Oliva, David; Papa, Andrés R R

    2014-01-01

    This paper presents a study of Pc4-5 geomagnetic pulsations illustrated by those which were observed after the sudden commencement of May 02 of 2010 at 09 : 08 UT at the Brazilian stations TTB, VSS and SMS. We carry out the spectral analysis of a bivariate data using the Morse wavelets and calculate polarization attributes (ellipticity ratio, tilt angle and phase difference) in the time-frequency domain. The main pulsation wave packets occurred, for the selected day, around noon and a small enhancement of the pulsation amplitude is observed in the TTB station. A change in the pulsation polarization has been found for the TTB station, which we have attributed to effects of the equatorial electrojet.

  15. Nonlinear pulsations of stars with initial mass 3 M_\\odot on the asymptotic giant branch

    CERN Document Server

    Fadeyev, Yuri

    2016-01-01

    Pulsation period changes in Mira type variables are investigated using the stellar evolution and nonlinear stellar pulsation calculations. We considered the evolutionary sequence of stellar models with initial mass 3 Msol and population I composition. Pulsations of stars in the early stage of the asymptotic giant branch are shown to be due to instability of the fundamental mode. In the later stage of evolution when the helium shell source becomes thermally unstable the stellar oscillations arise in either the fundamental mode (for the stellar luminosity L 7e3 Lsol). Excitation of pulsations is due to the kappa-mechanism in the hydrogen ionization zone. Stars with intermediate luminosities 5.4e3 1e-3 per year take place during approx 500 years, that is nearly one hundredth of the interval between helium flashes.

  16. CFD simulation of pulsation noise in a small centrifugal compressor with volute and resonance tube

    Science.gov (United States)

    Wakaki, Daich; Sakuka, Yuta; Inokuchi, Yuzo; Ueda, Kosuke; Yamasaki, Nobuhiko; Yamagata, Akihiro

    2015-02-01

    The rotational frequency tone noise emitted from the automobile turbocharger is called the pulsation noise. The cause of the pulsation noise is not fully understood, but is considered to be due to some manufacturing errors, which is called the mistuning. The effects of the mistuning of the impeller blade on the noise field inside the flow passage of the compressor are numerically investigated. Here, the flow passage includes the volute and duct located downstream of the compressor impeller. Our numerical approach is found to successfully capture the wavelength of the pulsation noise at given rotational speeds by the comparison with the experiments. One of the significant findings is that the noise field of the pulsation noise in the duct is highly one-dimensional although the flow fields are highly three-dimensional.

  17. Continuous vs. pulsating flow boiling. Part 1: Experimental comparison and visualization

    DEFF Research Database (Denmark)

    Kærn, Martin Ryhl; Elmegaard, Brian; Meyer, Knud Erik;

    2016-01-01

    . The fluid pulsations are introduced by a flow modulating expansion device and are compared with continuous flow by a stepper-motor expansion valve in terms of time-averaged heat transfer coefficient. The cycle time ranges from 1 s to 9 s for the pulsations. The time-averaged heat transfer coefficients...... transfer coefficient by as much as 8 % at high heat flux (q ≥ 35 kW/m2) and cycle time (8 s). The latter reduction is adhered to the significant dry-out when the flow modulating expansion valve is closed.......This experimental study investigates an active method for flow boiling heat transfer enhancement by means of fluid flow pulsation. The hypothesis is that pulsations increase the flow boiling heat transfer by means of better bulk fluid mixing, increased wall wetting and flow-regime destabilization...

  18. The post-outburst pulsations of the accreting white dwarf in the cataclysmic variable GW Librae

    CERN Document Server

    Chote, P

    2016-01-01

    We present new time-series photometry of the accreting pulsating white dwarf system GW Librae obtained in 2012 and 2013 at the University of Canterbury Mt John Observatory in New Zealand. Our 2012 data show the return of a $\\sim$19 minute periodicity that was previously detected in 2008. This pulsation mode was a dominant feature of our quality May 2012 data set, which consisted of six contiguous nights; a detailed analysis indicated a degree of frequency variability. We show by comparison with the previously identified pulsation modes that this periodicity is best explained as a new mode, and that the quasi-stability of the periods appears to be a general feature of the pulsations in these systems. We also find a previously unreported 3-hour modulation period, which we believe to be related to the known two and four hour periods of so far unknown origin.

  19. New Pulsating DB White Dwarf Stars from the Sloan Digital Sky Survey

    CERN Document Server

    Nitta, A; Krzesínski, J; Kepler, S O; Metcalfe, T S; Mukadam, Anjum S; Mullally, Fergal; Nather, R E; Sullivan, Denis J; Thompson, Susan E; Winget, D E

    2008-01-01

    We are searching for new He atmosphere white dwarf pulsators (DBVs) based on the newly found white dwarf stars from the spectra obtained by the Sloan Digital Sky Survey. DBVs pulsate at hotter temperature ranges than their better known cousins, the H atmosphere white dwarf pulsators (DAVs or ZZ Ceti stars). Since the evolution of white dwarf stars is characterized by cooling, asteroseismological studies of DBVs give us opportunities to study white dwarf structure at a different evolutionary stage than the DAVs. The hottest DBVs are thought to have neutrino luminosities exceeding their photon luminosities (Winget et al. 2004), a quantity measurable through asteroseismology. Therefore, they can also be used to study neutrino physics in the stellar interior. So far we have discovered nine new DBVs, doubling the number of previously known DBVs. Here we report the new pulsators' lightcurves and power spectra.

  20. Is the Lack of Pulsations in Low Mass X-Ray Binaries due to Comptonizing Coronae?

    CERN Document Server

    Gogus, E; Gilfanov, M; Gogus, Ersin

    2006-01-01

    The spin periods of the neutron stars in most Low Mass X-ray Binary (LMXB) systems still remain undetected. One of the models to explain the absence of coherent pulsations has been the suppression of the beamed signal by Compton scattering of X-ray photons by electrons in a surrounding corona. We point out that simultaneously with wiping out the pulsation signal, such a corona will upscatter (pulsating or not) X-ray emission originating at and/or near the surface of the neutron star leading to appearance of a hard tail of Comptonized radiation in the source spectrum. We analyze the hard X-ray spectra of a selected set of LMXBs and demonstrate that the optical depth of the corona is not likely to be large enough to cause the pulsations to disappear.

  1. An experimental investigation of heat transfer in a spiral-coil tube with pulsating turbulent water flow

    Science.gov (United States)

    Kharvani, H. Ramezani; Doshmanziari, F. Ilami; Zohir, A. E.; Jalali-Vahid, D.

    2016-09-01

    In this study, in order to increase the heat transfer rate in a spiral-coil tube by an active method, a rotating ball valve was mounted downstream/upstream of the spiral-coil tube and used as a pulse generator. Influence of pulsation on heat transfer in the spiral-coil tube was experimentally investigated. Cold water was used as a working fluid inside the spiral-coil that was immersed horizontally in a hot water reservoir tank. The Average temperature of the hot water bath was kept constant at 60 °C to establish a uniform temperature. All experiments for both pulsator locations (upstream and downstream pulsation) were performed at fixed pulsation amplitude. Reynolds number was ranged from 6220 to 16,300 while pulsation frequency was varied from 0 to 20 Hz. It can be clearly observed from heat transfer results that the overall average heat transfer coefficient was enhanced up to 26 % for pulsating flow compared to steady flow without pulsation at all pulsation frequencies. It is also clear that the relative overall average heat transfer coefficient is strongly affected by Reynolds number. Finally, it was obtained that the upstream pulsation heat transfer coefficient has better heat transfer results than the corresponding ones of downstream pulsation in the studied range of Reynolds number.

  2. Spatio-temporal Dynamics of Sources of Hard X-Ray Pulsations in Solar Flares

    Science.gov (United States)

    Kuznetsov, S. A.; Zimovets, I. V.; Morgachev, A. S.; Struminsky, A. B.

    2016-09-01

    We present a systematic analysis of the spatio-temporal evolution of sources of hard X-ray (HXR) pulsations in solar flares. We concentrate on disk flares whose impulsive phases are accompanied by a series of more than three successive peaks (pulsations) of HXR emission detected in the RHESSI 50 - 100 keV energy channel with a four-second time cadence. Twenty-nine such flares observed from February 2002 to June 2015 with characteristic time differences between successive peaks P ≈8 - 270 s are studied. The main observational result of the analysis is that sources of HXR pulsations in all flares are not stationary, they demonstrate apparent movements or displacements in the parent active regions from pulsation to pulsation. The flares can be subdivided into two main groups depending on the character of the dynamics of the HXR sources. Group 1 consists of 16 flares ( 55~%) that show systematic dynamics of the HXR sources from pulsation to pulsation with respect to a magnetic polarity inversion line (MPIL), which has a simple extended trace on the photosphere. Group 2 consists of 13 flares ( 45~%) that show more chaotic displacements of the HXR sources with respect to an MPIL with a more complex structure, and sometimes several MPILs are present in the parent active regions of such flares. Based on the observations, we conclude that the mechanism of the flare HXR pulsations (at least with time differences of the considered range) is related to successive triggering of the flare energy release process in different magnetic loops (or bundles of loops) of the parent active regions. Group 1 flare regions consist of loops stacked into magnetic arcades that are extended along MPILs. Group 2 flare regions have more complex magnetic structures, and the loops are arranged more chaotically and randomly there. We also found that at least 14 ( 88~%) group 1 flares and 11 ( 85~%) group 2 flares are accompanied by coronal mass ejections (CMEs), i.e. the absolute majority of the

  3. Seismic and spectroscopic characterization of the solar-like pulsating CoRoT target HD 49385

    CERN Document Server

    Deheuvels, S; Michel, E; Barban, C; Verner, G; Regulo, C; Mosser, B; Mathur, S; Gaulme, P; Garcia, R A; Boumier, P; Appourchaux, T; Samadi, R; Catala, C; Baudin, F; Baglin, A; Auvergne, M; Roxburgh, I W; Hernandez, F Perez

    2010-01-01

    The star HD 49385 is the first G-type solar-like pulsator observed in the seismology field of the space telescope CoRoT. The satellite collected 137 days of high-precision photometric data on this star, confirming that it presents solar-like oscillations. HD 49385 was also observed in spectroscopy with the NARVAL spectrograph in January 2009. Our goal is to characterize HD 49385 using both spectroscopic and seismic data. The fundamental stellar parameters of HD 49385 are derived with the semi-automatic software VWA, and the projected rotational velocity is estimated by fitting synthetic profiles to isolated lines in the observed spectrum. A maximum likelihood estimation is used to determine the parameters of the observed p modes. We perform a global fit, in which modes are fitted simultaneously over nine radial orders, with degrees ranging from l=0 to l=3 (36 individual modes). Precise estimates of the atmospheric parameters (Teff, [M/H], log g) and of the vsini of HD 49385 are obtained. The seismic analysis ...

  4. Radial head button holing: a cause of irreducible anterior radial head dislocation.

    Science.gov (United States)

    Shin, Su-Mi; Chai, Jee Won; You, Ja Yeon; Park, Jina; Bae, Kee Jeong

    2016-10-01

    "Buttonholing" of the radial head through the anterior joint capsule is a known cause of irreducible anterior radial head dislocation associated with Monteggia injuries in pediatric patients. To the best of our knowledge, no report has described an injury consisting of buttonholing of the radial head through the annular ligament and a simultaneous radial head fracture in an adolescent. In the present case, the radiographic findings were a radial head fracture with anterior dislocation and lack of the anterior fat pad sign. Magnetic resonance imaging (MRI) clearly demonstrated anterior dislocation of the fractured radial head through the torn annular ligament. The anterior joint capsule and proximal portion of the annular ligament were interposed between the radial head and capitellum, preventing closed reduction of the radial head. Familiarity with this condition and imaging findings will aid clinicians to make a proper diagnosis and fast decision to perform an open reduction. PMID:27502623

  5. A second case of outbursts in a pulsating white dwarf observed by Kepler

    CERN Document Server

    Hermes, J J; Bell, Keaton J; Chote, P; Gaensicke, B T; Kawaler, Steven D; Clemens, J C; Dunlap, B H; Winget, D E; Armstrong, D J

    2015-01-01

    We present observations of a new phenomenon in pulsating white dwarf stars: large-amplitude outbursts at timescales much longer than the pulsation periods. The cool (Teff = 11,010 K), hydrogen-atmosphere pulsating white dwarf PG 1149+057 was observed nearly continuously for more than 78.8 d by the extended Kepler mission in K2 Campaign 1. The target showed 10 outburst events, recurring roughly every 8 d and lasting roughly 15 hr, with maximum flux excursions up to 45% in the Kepler bandpass. We demonstrate that the outbursts affect the pulsations and therefore must come from the white dwarf. Additionally, we argue that these events are not magnetic reconnection flares, and are most likely connected to the stellar pulsations and the relatively deep surface convection zone. PG 1149+057 is now the second cool pulsating white dwarf to show this outburst phenomenon, after the first variable white dwarf observed in the Kepler mission, KIC 4552982. Both stars have the same effective temperature, within the uncertain...

  6. Heat transfer from a fully-developed pulsating flow in a curved pipe

    Science.gov (United States)

    Chung, Jae Hwa; Hyun, Jae Min

    1994-01-01

    Numerical studies are made of the flow and heat transfer characteristics of a fully-developed pulsating flow in a strongly curved pipe. Emphasis is placed on delineating the effects of the Reynolds number, and pulsation amplitude and frequency. By using a toroidal coordinate system, the complete, time-dependent incompressible Navier-Stokes equations are formulated. The peripherally-uniform temperature condition is imposed on the pipe wall. Particular attention is given to heat transfer properties over substantially extended parameter ranges of the Reynolds number Re and the Womersley number Wo. Use is made of a well-established numerical solution procedure, with minor amendments. The computed results on the flow field are in close agreement with the existing data in the overlapping parameter ranges. The spatial distributions of axial and secondary flows are depicted. The time variations of flow structure are displayed. The numerical results on the spatial and temporal variations of the thermal field are presented. The circumferential profiles of local Nusselt number are plotted at selected instants. When Wo is small, the time- and space-averaged Nusselt numbers, bar-Nu(sub w), is lower for a pulsating flow than for a corresponding non-pulsating flow. At moderate and high Wo, however, the difference in bar-Nu(sub w) between a pulsating and a non-pulsating flow is insignificant.

  7. Pulsations of red supergiant pair-instability supernova progenitors leading to extreme mass loss

    CERN Document Server

    Moriya, Takashi J

    2014-01-01

    Recent stellar evolution models show consistently that very massive metal-free stars evolve into red supergiants shortly before they explode. We argue that the envelopes of these stars, which will form pair-instability supernovae, become pulsationally unstable, and that this will lead to extreme mass-loss rates even though the metal content of the envelopes is very small. We investigate the pulsational properties of such models, and derive pulsationally induced mass-loss rates which take the damping effects of the mass loss on the pulsations selfconsistently into account. We find that the pulsations may induce mass-loss rates of ~ 1e-4 - 1e-2 Msun/yr shortly before the explosions, which may create a dense circumstellar medium. Our results show that very massive stars with dense circumstellar media may originate from a wider initial mass range than that of pulsational-pair instability supernovae. The extreme mass loss will cease when so much of the hydrogen-rich envelope is lost that the star becomes more comp...

  8. Theoretical and experimental investigations of flow pulsation effects in Coriolis mass flowmeters

    Science.gov (United States)

    Svete, A.; Kutin, J.; Bobovnik, G.; Bajsić, I.

    2015-09-01

    An understanding of the effects of flow pulsations on the dynamic behavior of Coriolis flowmeters is very important for their further development. In order to determine the phase difference between the vibrational signals, which represents the basic measurement effect of Coriolis flowmeters, there are many methods that include the proper filtering of all the signal components, except those with frequencies close to the drive frequency. Therefore, an understanding of the phenomenon of exciting the meter at its first natural frequency is very important. The results of a simple, linear, two-degree-of-freedom, lumped-parameter, dynamic model of a flowmeter show that the flow pulsations can degrade the accuracy of such a flowmeter as a result of indirect excitations of the measuring tube at the first natural frequency through the second-order perturbations by means of the Coriolis forces induced in pulsating flow conditions. In order to experimentally investigate these flow pulsation effects, a prototype of a straight-tube Coriolis mass flowmeter was developed to enable the processing of the response signals logged directly from the flow tube's sensors with the dual quadrature demodulation method, and therefore to provide the information available within the phase-difference data. The experimental results show that the flow pulsations upset the meter at its first natural frequency indirectly, as well as directly at the frequency of the pulsations due to the geometric imperfections of the measuring tube.

  9. Analysis on observational results of Pi2 geomagnetic pulsation in Henan region

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A measurement profile consisted of 5 sites from Xinyang to Tangyin in Henan Province was set up in September of 1996 to carry out simultaneous observation of Pi2 geomagnetic pulsations. Simultaneity of Pi2 geomagnetic pulsation occurrence along the N-S profile was investigated. Results of analysis pointed out that Pi2 geomagnetic pulsations appeared at first at the site of Xinyang at the southern end of the profile, the later the same Pi2 geomagnetic pulsation appeared, the more north the site was at. Apparent propagation speed of Pi2 in N-S direction in the region is about 140 km/s. Because Pi2 geomagnetic pulsation varying with time is of instability, and based on characteristics that basic wavelet can be dilated and localized, we selected proper basic wavelet form and by means of wavelet transform to analyze the changes of periods and amplitudes of main periodic components included in Pi2 pulsations with time. The results show that there existed complex form in periods and amplitudes of wavelet varying with time.

  10. Concepts of radial and angular kinetic energies

    DEFF Research Database (Denmark)

    Dahl, Jens Peder; Schleich, W.P.

    2002-01-01

    We consider a general central-field system in D dimensions and show that the division of the kinetic energy into radial and angular parts proceeds differently in the wave-function picture and the Weyl-Wigner phase-space picture, Thus, the radial and angular kinetic energies are different quantities...

  11. Revised ephemeris for the pulsating hydrogen-deficient star BD + 13/sup 0/ 3224 (V652 Her)

    Energy Technology Data Exchange (ETDEWEB)

    Kilkenny, D.; Lynas-Gray, A.E.

    1984-06-01

    Additional observations of maxima of the pulsating hydrogen-deficient star, BD + 13/sup 0/ 3224 (V652 Her), give an improved ephemeris for the decreasing period of pulsation. A simple quadratic no longer appears sufficient and a cubic solution may be preferable, indicating that the pulsation decrease rate is slowing down as the star contracts. An alternative hypotheses, that the star is a binary is also discussed.

  12. KIC 4552982: outbursts and pulsations in the longest-ever pseudo-continuous light curve of a ZZ Ceti

    Directory of Open Access Journals (Sweden)

    Bell K. J.

    2015-01-01

    Full Text Available KIC 4552982 was the first ZZ Ceti (hydrogen-atmosphere pulsating white dwarf identified to lie in the Kepler field, resulting in the longest pseudo-continuous light curve ever obtained for this type of variable star. In addition to the pulsations, this light curve exhibits stochastic episodes of brightness enhancement unlike any previously studied white dwarf phenomenon. We briefly highlight the basic outburst and pulsation properties in these proceedings.

  13. Heat transfer mechanisms in pulsating heat-pipes with nanofluid

    Science.gov (United States)

    Gonzalez, Miguel; Kelly, Brian; Hayashi, Yoshikazu; Kim, Yoon Jo

    2015-01-01

    In this study, the effect of silver nanofluid on a pulsating heat-pipe (PHP) thermal performance was experimentally investigated to figure out how nanofluid works with PHP. A closed loop PHP was built with 3 mm diameter tubes. Thermocouples and pressure transducers were installed for fluid and surface temperature and pressure measurements. The operating temperature of the PHP varied from 30-100 °C, with power rates of 61 W and 119 W. The fill ratio of 30%, 50%, and 70% were tested. The results showed that the evaporator heat transfer performance was degraded by the addition of nanoparticles due to increased viscosity at high power rate, while the positive effects of high thermal conductivity and enhanced nucleate boiling worked better at low power rate. In the condenser section, owing to the relatively high liquid content, nanofluid more effectively improved the heat transfer performance. However, since the PHP performance was dominantly affected by evaporator heat transfer performance, the overall benefit of enhanced condenser section performance was greatly limited. It was also observed that the poor heat transfer performance with nanofluid at the evaporator section led to lower operating pressure of PHP.

  14. Flow visualization of silicon-based micro pulsating heat pipes

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Two sets of silicon-based micro pulsating heat pipes(SMPHPs) with trapezoidal cross section having hydraulic diameters of 352 μm(#1) and 394 μm(#2) respectively were fabricated for the first time using MEMS technology.With FC-72 as the working fluid,the start-up,steady operation state,as well as flow patterns were investigated using a CCD camera.It was found that the start-up process of these two SMPHPs was rather rapid.At the start-up period,no nucleation was observed,and the vapor plugs at the evaporator U-bends were formed mainly due to the breakup of liquid slugs.At the steady operation state,self-sustained oscillation with large amplitudes dominated the flow behavior when the inclination angle varied from 10° to 90°,but the nucleate boiling and bulk circulation were observed only in SMPHP #2.While bubbly,slug/plug,annular/semi-annular,and wavy-annular flows were observed in both two SMPHPs,the injection flow only appeared in SMPHP #2.

  15. A helium based pulsating heat pipe for superconducting magnets

    Science.gov (United States)

    Fonseca, Luis Diego; Miller, Franklin; Pfotenhauer, John

    2014-01-01

    This study was inspired to investigate an alternative cooling system using a helium-based pulsating heat pipes (PHP), for low temperature superconducting magnets. In addition, the same approach can be used for exploring other low temperature applications. The advantages of PHP for transferring heat and smoothing temperature profiles in various room temperature applications have been explored for the past 20 years. An experimental apparatus has been designed, fabricated and operated and is primarily composed of an evaporator and a condenser; in which both are thermally connected by a closed loop capillary tubing. The main goal is to measure the heat transfer properties of this device using helium as the working fluid. The evaporator end of the PHP is comprised of a copper winding in which heat loads up to 10 watts are generated, while the condenser is isothermal and can reach 4.2 K via a two stage Sumitomo RDK408A2 GM cryocooler. Various experimental design features are highlighted. Additionally, performance results in the form of heat transfer and temperature characteristics are provided as a function of average condenser temperature, PHP fill ratio, and evaporator heat load. Results are summarized in the form of a dimensionless correlation and compared to room temperature systems. Implications for superconducting magnet stability are highlighted.

  16. Pressure Pulsation Signal Analysis for Centrifugal Compressor Blade Crack Determination

    Directory of Open Access Journals (Sweden)

    Hongkun Li

    2014-01-01

    Full Text Available Blade is a key piece of component for centrifugal compressor. But blade crack could usually occur as blade suffers from the effect of centrifugal forces, gas pressure, friction force, and so on. It could lead to blade failure and centrifugal compressor closing down. Therefore, it is important for blade crack early warning. It is difficult to determine blade crack as the information is weak. In this research, a pressure pulsation (PP sensor installed in vicinity to the crack area is used to determine blade crack according to blade vibration transfer process analysis. As it cannot show the blade crack information clearly, signal analysis and empirical mode decomposition (EMD are investigated for feature extraction and early warning. Firstly, signal filter is carried on PP signal around blade passing frequency (BPF based on working process analysis. Then, envelope analysis is carried on to filter the BPF. In the end, EMD is carried on to determine the characteristic frequency (CF for blade crack. Dynamic strain sensor is installed on the blade to determine the crack CF. Simulation and experimental investigation are carried on to verify the effectiveness of this method. The results show that this method can be helpful for blade crack classification for centrifugal compressors.

  17. PULSATION PERIOD VARIATIONS IN THE RRc LYRAE STAR KIC 5520878

    International Nuclear Information System (INIS)

    Learned et al. proposed that a sufficiently advanced extra-terrestrial civilization may tickle Cepheid and RR Lyrae variable stars with a neutrino beam at the right time, thus causing them to trigger early and jogging the otherwise very regular phase of their expansion and contraction. This would turn these stars into beacons to transmit information throughout the galaxy and beyond. The idea is to search for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional, omnidirectional signaling. We have performed such a search among variable stars using photometric data from the Kepler space telescope. In the RRc Lyrae star KIC 5520878, we have found two such regimes of long and short pulse durations. The sequence of period lengths, expressed as time series data, is strongly autocorrelated, with correlation coefficients of prime numbers being significantly higher (p = 99.8%). Our analysis of this candidate star shows that the prime number oddity originates from two simultaneous pulsation periods and is likely of natural origin. Simple physical models elucidate the frequency content and asymmetries of the KIC 5520878 light curve. Despite this SETI null result, we encourage testing of other archival and future time-series photometry for signs of modulated stars. This can be done as a by-product to the standard analysis, and can even be partly automated

  18. Interpretation of electron spectra in morningside pulsating aurorae

    International Nuclear Information System (INIS)

    Energy spectra of precipitating electrons in morningside aurorae were obtained with instruments on the NOAA 6 satellite during several passes through the southern auroral zone in 1982. It is substantiated with the aid of coordinated data from particle detectors and a photometer in the Simulated Emission of Energetic Particles experiment payload on satellite S81-1 that the precipitation obserbed by NOAA 6 was probably in a region of pulsating aurorae. The particle detectors and forward/downward looking quadrant photometer onboard S81-1 all exhibited regular modulations at a period of about 5--15 s. The particle detectors on NOAA 6 showed fluctuating electron intensities over an energy range from several kiloelectronvolts to many tens of kiloelectronvolts, superimposed on a steady background component extending down to energies less than 1 keV. The NOAA 6 electron observations are in qualitative agreement with a time-dependent precipitation model that includes the production of backscattered and secondary electrons from the atmosphere. In this model the time variations imposed on the precipitation are restricted to the energetic portion of the electron spectrum, while the integrating effects inherent in the production of backscattered and secondary electrons, together with phase mixing introduced as those electrons transit between conjugate hemispheres, insure the existence of a nearly time independent population of low-energy electrons. A steady background precipitation is thereby created as a natural consequence of a time-variable primary precipitation. copyright American Geophysical Union 1987

  19. PULSATION PERIOD VARIATIONS IN THE RRc LYRAE STAR KIC 5520878

    Energy Technology Data Exchange (ETDEWEB)

    Hippke, Michael [Institute for Data Analysis, Luiter Str. 21b, D-47506 Neukirchen-Vluyn (Germany); Learned, John G. [High Energy Physics Group, Department of Physics and Astronomy, University of Hawaii, Manoa 327 Watanabe Hall, 2505 Correa Road, Honolulu, HI 96822 (United States); Zee, A. [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Edmondson, William H. [School of Computer Science, University of Birmingham, Birmingham B15 2TT (United Kingdom); Lindner, John F. [Physics Department, The College of Wooster, Wooster, OH 44691 (United States); Kia, Behnam; Ditto, William L. [Department of Physics and Astronomy, University of Hawai' i at Mānoa, Honolulu, HI 96822 (United States); Stevens, Ian R., E-mail: hippke@ifda.eu, E-mail: jgl@phys.hawaii.edu, E-mail: zee@kitp.ucsb.edu, E-mail: w.h.edmondson@bham.ac.uk, E-mail: jlindner@wooster.edu, E-mail: wditto@hawaii.edu, E-mail: behnam@hawaii.edu, E-mail: irs@star.sr.bham.ac.uk [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom)

    2015-01-01

    Learned et al. proposed that a sufficiently advanced extra-terrestrial civilization may tickle Cepheid and RR Lyrae variable stars with a neutrino beam at the right time, thus causing them to trigger early and jogging the otherwise very regular phase of their expansion and contraction. This would turn these stars into beacons to transmit information throughout the galaxy and beyond. The idea is to search for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional, omnidirectional signaling. We have performed such a search among variable stars using photometric data from the Kepler space telescope. In the RRc Lyrae star KIC 5520878, we have found two such regimes of long and short pulse durations. The sequence of period lengths, expressed as time series data, is strongly autocorrelated, with correlation coefficients of prime numbers being significantly higher (p = 99.8%). Our analysis of this candidate star shows that the prime number oddity originates from two simultaneous pulsation periods and is likely of natural origin. Simple physical models elucidate the frequency content and asymmetries of the KIC 5520878 light curve. Despite this SETI null result, we encourage testing of other archival and future time-series photometry for signs of modulated stars. This can be done as a by-product to the standard analysis, and can even be partly automated.

  20. Planets around stars in young nearby associations *** radial Velocity searches: a feasibility study, and first results

    CERN Document Server

    Lagrange, A -M; Chauvin, G; Sterzik, M; Galland, F; Curto, G Lo; Rameau, J; Sosnowska, D

    2013-01-01

    Stars in young nearby associations are the only targets allowing giant planet searches at all separations in the near future, by coupling indirect techniques such as radial velocity and deep imaging. These stars are first priorities targets for the forthcoming planets imagers on 10-m class telescopes. Young stars rotate more rapidly and are more active than their older counterparts. Both effects can limit the capability to detect planets using RV. We wish to explore the planet detection capabilities of a representative sample of stars in close and young associations with radial velocity data and explore the complementarity between this technique and direct imaging. We observed 26 such targets with spectral types from A to K and ages from 8 to 300 Myr with HARPS. We compute the detection limits. We also attempt to improve the detection limits in a few cases by correcting for the stellar activity. Our A-type stars RV show high frequency variations due to pulsations, while our F-K stars clearly show activity wit...

  1. The Nainital-Cape Survey. IV. A search for pulsational variability in 108 chemically peculiar stars

    Science.gov (United States)

    Joshi, S.; Martinez, P.; Chowdhury, S.; Chakradhari, N. K.; Joshi, Y. C.; van Heerden, P.; Medupe, T.; Kumar, Y. B.; Kuhn, R. B.

    2016-05-01

    Context. The Nainital-Cape Survey is a dedicated ongoing survey program to search for and study pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution. Aims: The main aims of this survey are to find new pulsating Ap and Am stars in the northern and southern hemisphere and to perform asteroseismic studies of these new pulsators. Methods: The survey is conducted using high-speed photometry. The candidate stars were selected on the basis of having Strömgren photometric indices similar to those of known pulsating CP stars. Results: Over the last decade a total of 337 candidate pulsating CP stars were observed for the Nainital-Cape Survey, making it one of the longest ground-based surveys for pulsation in CP stars in terms of time span and sample size. The previous papers of this series presented seven new pulsating variables and 229 null results. In this paper we present the light curves, frequency spectra and various astrophysical parameters of the 108 additional CP stars observed since the last reported results. We also tabulated the basic physical parameters of the known roAp stars. As a part of establishing the detection limits in the Nainital-Cape Survey, we investigated the scintillation noise level at the two observing sites used in this survey, Sutherland and Nainital, by comparing the combined frequency spectra stars observed from each location. Our analysis shows that both the sites permit the detection of variations of the order of 0.6 milli-magnitude (mmag) in the frequency range 1-4 mHz, Sutherland is on average marginally better. The dataset is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A116

  2. CME on March 16, 2001, electron pulsation event and solar-terrestrial phenomena related with CMEs

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Guiqing(张桂清)

    2002-01-01

    The electron pulsation event is defined in the paper. Firstly, a slow Halo CME on March 16, 2001 that led to low-energetic solar proton event, electron pulsation event and major geomagnetic storm was analyzed. And then, dozens of events are collected. The interrelations among the solar flare, CME, solar proton event, electron pulsation event and geomagnetic storm are studied. The results show that: (ⅰ) Solar proton events can be regarded as the indication that CMEs get to the earth and the electron pulsation events can be regarded as the indication of solar proton flux. (ⅱ) Not only can fast CMEs strongly influence the earth, but also slow CMEs can influence the earth, and its influences are more frequent and cannot be neglected. (ⅲ) Most of high-energetic solar proton events with E≥10 MeV can lead to geomagnetic storms, but most of the medium and weak geomagnetic storms result from low-energetic solar proton events that are caused by CMEs. (ⅳ) Both the electron pulsation events and geomagnetic storms are the link effects of high- and low-energetic solar proton events, but the occurrence of electron pulsation event are generally prior to the geomagnetic storm. So in the circumstance where the near real-time observing data of the low-energetic solar proton event cannot be obtained, we can regard electron pulsation event as the indication of the low-energetic solar proton flux reaching the earth, which can be used as one of the important 参考文献 of short-term prediction and alert of the geomagnetic storm.

  3. [Primary radial head arthroplasty in trauma : Complications].

    Science.gov (United States)

    Schmidt-Horlohé, K; Buschbeck, S; Wincheringer, D; Weißenberger, M; Hoffmann, R

    2016-10-01

    Radial head fractures are common injuries in elbow trauma. Non-displaced fractures are best treated conservatively. Simple but displaced fractures require anatomic reduction and fixation, typically using screws. The treatment course for complex fractures with multiple fragments is still being debated, as results are less predictable. Radial head resection is not advised if concomitant injuries of the coronoid process or the collateral ligaments with instability are present. Favorable outcomes following open reduction and fixation using plates were reported recently. However, complication rates are very high. Radial head replacement is a valuable tool in treating complex fractures of the radial head with predominantly good and excellent results. Patients who suffer radial head fractures are typically of a younger age, resulting in high functional demands. Certainly, unspecific and specific complications related to radial head arthroplasty were reported in up to 40 % of cases in an acute fracture setting. This article highlights common complications in radial head arthroplasty and aims to present strategies to avoid them. PMID:27600571

  4. Radial electric fields for improved tokamak performance

    International Nuclear Information System (INIS)

    The influence of externally-imposed radial electric fields on the fusion energy output, energy multiplication, and alpha-particle ash build-up in a TFTR-sized, fusing tokamak plasma is explored. In an idealized tokamak plasma, an externally-imposed radial electric field leads to plasma rotation, but no charge current flows across the magnetic fields. However, a realistically-low neutral density profile generates a non-zero cross-field conductivity and the species dependence of this conductivity allows the electric field to selectively alter radial particle transport

  5. Quasi-periodic Pulsations during the Impulsive and Decay phases of an X-class Flare

    Science.gov (United States)

    Hayes, L. A.; Gallagher, P. T.; Dennis, B. R.; Ireland, J.; Inglis, A. R.; Ryan, D. F.

    2016-08-01

    Quasi-periodic pulsations (QPPs) are often observed in X-ray emission from solar flares. To date, it is unclear what their physical origins are. Here, we present a multi-instrument investigation of the nature of QPP during the impulsive and decay phases of the X1.0 flare of 2013 October 28. We focus on the character of the fine structure pulsations evident in the soft X-ray (SXR) time derivatives and compare this variability with structure across multiple wavelengths including hard X-ray and microwave emission. We find that during the impulsive phase of the flare, high correlations between pulsations in the thermal and non-thermal emissions are seen. A characteristic timescale of ∼20 s is observed in all channels and a second timescale of ∼55 s is observed in the non-thermal emissions. SXR pulsations are seen to persist into the decay phase of this flare, up to 20 minutes after the non-thermal emission has ceased. We find that these decay phase thermal pulsations have very small amplitude and show an increase in characteristic timescale from ∼40 s up to ∼70 s. We interpret the bursty nature of the co-existing multi-wavelength QPPs during the impulsive phase in terms of episodic particle acceleration and plasma heating. The persistent thermal decay phase QPPs are most likely connected with compressive magnetohydrodynamic processes in the post-flare loops such as the fast sausage mode or the vertical kink mode.

  6. HST/STIS observations of sdBV stars: testing diffusion and pulsation theory

    CERN Document Server

    O'Toole, S J; Chayer, P; Fontaine, G; O'Donoghue, D; Charpinet, S

    2003-01-01

    We present the initial results of an abundance analysis of echelle UV spectra of 5 hot subdwarf B (sdB) stars. These stars have been identified as core helium burning objects on the extreme Horizontal Branch. Around 5% of sdBs show short-period acoustic mode oscillations. Models predict that these oscillations are due to an opacity bump caused by the ionisation of iron group elements. The necessary metal abundance has to be maintained by diffusive equilibrium between gravitational settling and radiative levitation. However, analyses of high resolution optical spectra has revealed that we cannot discriminate between pulsating and non-pulsating sdBs on the basis of the surface iron abundance. We have therefore obtained HST/STIS observations of 3 pulsators and 2 non-pulsators in the near and far UV to measure the surface abundance of elements that are unobservable from the ground. The overall aim of our study is to test diffusion and pulsation calculations by searching for significant differences between these s...

  7. STRAIN ELASTOGRAPHY USING DOBUTAMINE-INDUCED CAROTID ARTERY PULSATION IN CANINE THYROID GLAND.

    Science.gov (United States)

    Lee, Gahyun; Jeon, Sunghoon; Lee, Sang-Kwon; Kim, Hyunwoo; Yu, Dohyeon; Choi, Jihye

    2015-01-01

    Thyroid disease is common in dogs and conventional ultrasonography is a standard diagnostic test for diagnosis and treatment planning. Strain elastography can provide additional information about tissue stiffness noninvasively after applying external or internal compression. However, natural carotid artery pulsations in the canine thyroid gland are too weak to maintain sufficient internal compression force. The objective of the present study was to describe the feasibility of strain elastography for evaluating the canine thyroid gland and the repeatability of dobutamine-induced carotid artery pulsation as an internal compression method. In seven healthy Beagle dogs, strain on each thyroid lobe was induced by external compression using the ultrasound probe and internal compression using carotid artery pulsation after dobutamine infusion. The thyroid appeared homogeneously green and the subcutaneous fat superficial to the thyroid lobe appeared blue. Strain values and strain ratios did not differ among dogs or between the left and right lobes. Interobserver repeatability was excellent for both compression methods. Intraobserver repeatability of the strain ratio measured using the carotid artery pulsation method (intraclass coefficient correlation = 0.933) was higher than that measured using the external compression method (0.760). Mean strain values of thyroid lobes for the external compression method (142.93 ± 6.67) differed from the internal method (147.31 ± 8.24; P thyroid stiffness in dogs. Carotid artery pulsation induced by dobutamine infusion can be used for canine thyroid strain elastography with excellent repeatability.

  8. Discovery of Three Pulsating, Mixed-atmosphere, Extremely Low-mass White Dwarf Precursors

    Science.gov (United States)

    Gianninas, A.; Curd, Brandon; Fontaine, G.; Brown, Warren R.; Kilic, Mukremin

    2016-05-01

    We report the discovery of pulsations in three mixed-atmosphere, extremely low-mass white dwarf (ELM WD, M ≤slant 0.3 M ⊙) precursors. Following the recent discoveries of pulsations in both ELM and pre-ELM WDs, we targeted pre-ELM WDs with mixed H/He atmospheres with high-speed photometry. We find significant optical variability in all three observed targets with periods in the range 320-590 s, consistent in timescale with theoretical predictions of p-mode pulsations in mixed-atmosphere ≈0.18 M ⊙ He-core pre-ELM WDs. This represents the first empirical evidence that pulsations in pre-ELM WDs can only occur if a significant amount of He is present in the atmosphere. Future, more extensive, timeseries photometry of the brightest of the three new pulsators offers an excellent opportunity to constrain the thickness of the surface H layer, which regulates the cooling timescales for ELM WDs. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

  9. Development of Pulsating Twin Jets Mechanism for Mixing Flow Heat Transfer Analysis

    Directory of Open Access Journals (Sweden)

    Ali Ahmed Gitan

    2014-01-01

    Full Text Available Pulsating twin jets mechanism (PTJM was developed in the present work to study the effect of pulsating twin jets mixing region on the enhancement of heat transfer. Controllable characteristics twin pulsed jets were the main objective of our design. The variable nozzle-nozzle distance was considered to study the effect of two jets interaction at the mixing region. Also, the phase change between the frequencies of twin jets was taken into account to develop PTJM. All of these factors in addition to the ability of producing high velocity pulsed jet led to more appropriate design for a comprehensive study of multijet impingement heat transfer problems. The performance of PTJM was verified by measuring the pulse profile at frequency of 20 Hz, where equal velocity peak of around 64 m/s for both jets was obtained. Moreover, the jet velocity profile at different pulsation frequencies was tested to verify system performance, so the results revealed reasonable velocity profile configuration. Furthermore, the effect of pulsation frequency on surface temperature of flat hot plate in the midpoint between twin jets was studied experimentally. Noticeable enhancement in heat transfer was obtained with the increasing of pulsation frequency.

  10. Discovery of Three Pulsating, Mixed Atmosphere, Extremely Low-Mass White Dwarf Precursors

    CERN Document Server

    Gianninas, A; Fontaine, G; Browm, Warren R; Kilic, Mukremin

    2016-01-01

    We report the discovery of pulsations in three mixed atmosphere, extremely low-mass white dwarf (ELM WD, M $<$ 0.3 M$_{\\odot}$) precursors. Following the recent discoveries of pulsations in both ELM and pre-ELM WDs, we targeted pre-ELM WDs with mixed H/He atmospheres with high-speed photometry. We find significant optical variability in all three observed targets with periods in the range 320--590 s, consistent in time-scale with theoretical predictions of p-mode pulsations in mixed-atmosphere $\\approx$ 0.18 M$_{\\odot}$ He-core pre-ELM WDs. This represents the first empirical evidence that pulsations in pre-ELM WDs can only occur if a significant amount of He is present in the atmosphere. Future, more extensive, time-series photometry of the brightest of the three new pulsators offers an excellent opportunity to constrain the thickness of the surface H layer which regulates the cooling timescales for ELM WDs.

  11. KIC 6220497: A New Algol-type Eclipsing Binary with Multiperiodic Pulsations

    CERN Document Server

    Lee, Jae Woo; Kim, Seung-Lee; Koo, Jae-Rim

    2016-01-01

    We present both binarity and pulsation of KIC 6220497 from the {\\it Kepler} observations. The light curve synthesis shows that the eclipsing system is a semi-detached Algol with parameters of $q$ = 0.243$\\pm$0.001, $i$ = 77.3$\\pm$0.3 deg, and $\\Delta T$ = 3,372$\\pm$58 K, in which the detached primary component fills its Roche lobe by $\\sim$87\\%. A multiple frequency analysis of the eclipse-subtracted light residuals reveals 33 frequencies in the range of 0.75$-$20.22 d$^{-1}$ with amplitudes between 0.27 and 4.56 mmag. Among these, four are pulsation frequencies in fundamental ($f_1$, $f_5$) and $p$ ($f_2$, $f_7$) modes, and six are orbital frequency ($f_8$, $f_{31}$) and its harmonics ($f_6$, $f_{11}$, $f_{20}$, $f_{24}$), which can be attributed to tidally excited modes. For the pulsation frequencies, the pulsation constants of 0.16$-$0.33 d and the period ratios of $P_{\\rm pul}/P_{\\rm orb}$ = 0.042$-$0.089 indicate that the primary component is a $\\delta$ Sct pulsating star and, thus, KIC 6220497 is an osc...

  12. Pressure pulsations in piping system excited by a centrifugal turbomachinery taking the damping characteristics into consideration

    Science.gov (United States)

    Hayashi, I.; Kaneko, S.

    2014-02-01

    Pressure pulsations excited by a centrifugal turbomachinery such as compressor, fan or pump at the blade passing frequency may cause severe noise and vibrations in piping system. Therefore, the practical evaluation method of pressure pulsations is strongly recommended. In particular, the maximum pressure amplitude under the resonant conditions should be appropriately evaluated. In this study, a one-dimensional excitation source model for a compressor or pump is introduced based on the equation of motion, so as to incorporate the non-linear damping proportional to velocity squared in the total piping system including the compressor or pump. The damping characteristics of the compressor or pump are investigated by using the semi-empirical model. It is shown that the resistance coefficient of the compressor or pump depends on the Reynolds number that is defined using the equivalent velocity of the pulsating flow. The frequency response of the pressure amplitude and the pressure distribution in the piping system can be evaluated by introducing the equivalent resistance of the compressor or pump and that of piping system. In particular, the relation of the maximum pressure amplitude in piping system to the location of the excitation source under resonant conditions can be evaluated. Finally, the reduction of the pressure pulsations by use of an orifice plate is discussed in terms of the pulsation energy loss.

  13. Development of pulsating twin jets mechanism for mixing flow heat transfer analysis.

    Science.gov (United States)

    Gitan, Ali Ahmed; Zulkifli, Rozli; Abdullah, Shahrir; Sopian, Kamaruzzaman

    2014-01-01

    Pulsating twin jets mechanism (PTJM) was developed in the present work to study the effect of pulsating twin jets mixing region on the enhancement of heat transfer. Controllable characteristics twin pulsed jets were the main objective of our design. The variable nozzle-nozzle distance was considered to study the effect of two jets interaction at the mixing region. Also, the phase change between the frequencies of twin jets was taken into account to develop PTJM. All of these factors in addition to the ability of producing high velocity pulsed jet led to more appropriate design for a comprehensive study of multijet impingement heat transfer problems. The performance of PTJM was verified by measuring the pulse profile at frequency of 20 Hz, where equal velocity peak of around 64 m/s for both jets was obtained. Moreover, the jet velocity profile at different pulsation frequencies was tested to verify system performance, so the results revealed reasonable velocity profile configuration. Furthermore, the effect of pulsation frequency on surface temperature of flat hot plate in the midpoint between twin jets was studied experimentally. Noticeable enhancement in heat transfer was obtained with the increasing of pulsation frequency.

  14. The Music of the Stars : Spectroscopy of Pulsations in gamma Doradus Stars

    Science.gov (United States)

    Brunsden, Emily

    2013-05-01

    p>The mysteries of the interior structures of stars are being tackled with asteroseismology. The observable parameters of the surface pulsations of stars inform us of the interior characteristics of numerous classes of stars. The main-sequence gamma Doradus stars, just a little hotter than the Sun, offer the potential of determining stellar structure right down to the core. To determine the structural profile of a star, the observed frequencies and a full geometric description must be determined. This is only possible with long-term spectroscopic monitoring and careful analysis of the pulsation signature in spectral lines. This work seeks to identify the pulsational geometry of several gamma Doradus stars and to identify areas of improvement for current observation, analysis and modelling techniques. More than 4500 spectra were gathered on five stars for this purpose. For three stars a successful multi-frequency and mode identification solution was determined and significant progress has been made towards the understanding of a binary system involving a gamma Doradus star. A hybrid gamma Doradus/nbsp;delta Scuti pulsator was also intensely monitored and results from this work raise important questions about the classification of this type of star. Current analysis techniques were found to be fit-for-purpose for pure gamma Doradus stars, but stars with complexities such as hybrid pulsations and/or fast rotation require future development of the current models./p>

  15. On the effect of pulsating flow on surge margin of small centrifugal compressors for automotive engines

    Energy Technology Data Exchange (ETDEWEB)

    Galindo, J.; Climent, H.; Guardiola, C.; Tiseira, A. [CMT-Motores Termicos, Universidad Politecnica de Valencia (Spain); Camino de Vera s/n, E 46022, Valencia (Spain)

    2009-11-15

    Surge is becoming a limiting factor in the design of boosting systems of downsized diesel engines. Although standard compressor flowcharts are used for the selection of those machines for a given application, on-engine conditions widely differ from steady flow conditions, thus affecting compressor behaviour and consequently surge phenomenon. In this paper the effect of pulsating flow is investigated by means of a steady gas-stand that has been modified to produce engine-like pulsating flow. The effect of pressure pulses' amplitude and frequency on the compressor surge line location has been checked. Results show that pulsating flow in the 40-67 Hz range (corresponding to characteristic pulsation when boosting an internal combustion engine) increases surge margin. This increased margin is similar for all the tested frequencies but depends on pulsation amplitude. In a further step, a non-steady compressor model is used for modelling the tests, thus allowing a deeper analysis of the involved phenomena. Model results widely agree with experimental results. (author)

  16. Pulsation-triggered mass loss from AGB stars: the 60-day critical period

    CERN Document Server

    McDonald, Iain

    2016-01-01

    Low- and intermediate-mass stars eject much of their mass during the late, red giant branch (RGB) phase of evolution. The physics of their strong stellar winds is still poorly understood. In the standard model, stellar pulsations extend the atmosphere, allowing a wind to be driven through radiation pressure on condensing dust particles. Here we investigate the onset of the wind, using nearby RGB stars drawn from the Hipparcos catalogue. We find a sharp onset of dust production when the star first reaches a pulsation period of 60 days. This approximately co-incides with the point where the star transitions to the first overtone pulsation mode. Models of the spectral energy distributions show stellar mass-loss rate suddenly increases at this point, by a factor of ~10 over the existing (chromospherically driven) wind. The dust emission is strongly correlated with both pulsation period and amplitude, indicating stellar pulsation is the main trigger for the strong mass loss, and determines the mass-loss rate. Dust...

  17. Quasi-Periodic Pulsations during the Impulsive and Decay phases of an X-class Flare

    CERN Document Server

    Hayes, Laura A; Dennis, Brian R; Ireland, Jack; Inglis, Andrew R; Ryan, Daniel F

    2016-01-01

    Quasi-periodic pulsations (QPP) are often observed in X-ray emission from solar flares. To date, it is unclear what their physical origins are. Here, we present a multi-instrument investigation of the nature of QPP during the impulsive and decay phases of the X1.0 flare of 28 October 2013. We focus on the character of the fine structure pulsations evident in the soft X-ray time derivatives and compare this variability with structure across multiple wavelengths including hard X-ray and microwave emission. We find that during the impulsive phase of the flare, high correlations between pulsations in the thermal and non-thermal emissions are seen. A characteristic timescale of ~20s is observed in all channels and a second timescale of ~55s is observed in the non-thermal emissions. Soft X-ray pulsations are seen to persist into the decay phase of this flare, up to 20 minutes after the non-thermal emission has ceased. We find that these decay phase thermal pulsations have very small amplitude and show an increase i...

  18. Study on the Pressure Pulsation inside Runner with Splitter Blades in Ultra-High Head Turbine

    Science.gov (United States)

    Meng, L.; Zhang, S. P.; Zhou, L. J.; Wang, Z. W.

    2014-03-01

    Runners with splitter blades were used widely for the high efficiency and stability. In this paper, the unsteady simulation of an ultra-high head turbine at the best efficiency point, 50% and 75% discharge points were established, to analyze the pressure pulsation in the vaneless space, rotating domain and the draft tube. First of all, runners with different length splitter blades and without splitter blades were compared to learn the efficiency and the pressure distribution on the blade surface. And then the amplitude of the pressure pulsation was analysed. The peak efficiency of the runner with splitter blades is remarkably higher than that of the corresponding impeller without splitter blades. And the efficiency of the turbine is the highest when the length ratio of the splitter blades is 0.75 times the main blades. The pressure pulsation characteristics were also influenced, because the amplitudes of the pulsation induced by the RSI phenomenon were changed as a result of more blades. At last, the best design plan of the length of the splitter blades (length ratio=0.825) was obtained, which improved the pressure pulsation characteristics without significant prejudice to the efficiency.

  19. Asteroseismology of the Beta Cephei star Nu Eridani: photometric observations and pulsational frequency analysis

    CERN Document Server

    Handler, G; Jerzykiewicz, M; Krisciunas, K; Tshenye, T; Rodríguez, E; Costa, V; Zhou, A Y; Medupe, R; Phorah, W M; Garrido, R; Amado, P J; Paparo, M; Zsuffa, D; Ramokgali, L; Crowe, R; Purves, N; Avila, R; Knight, R; Brassfield, E; Kilmartin, P M; Cottrell, P L

    2004-01-01

    We undertook a multisite photometric campaign for the Beta Cephei star Nu Eridani. More than 600 hours of differential photoelectric uvyV photometry were obtained with 11 telescopes during 148 clear nights. The frequency analysis of our measurements shows that the variability of Nu Eri can be decomposed into 23 sinusoidal components, eight of which correspond to independent pulsation frequencies between 5 - 8 c/d. Some of these are arranged in multiplets, which suggests rotational m-mode splitting of nonradial pulsation modes as the cause. If so, the rotation period of the star must be between 30 - 60 d. One of the signals in the light curves of Nu Eri has a very low frequency of 0.432 c/d. It can be a high-order combination frequency or, more likely, an independent pulsation mode. In the latter case Nu Eri would be both a Beta Cephei star and a slowly pulsating B (SPB) star. The photometric amplitudes of the individual pulsation modes of Nu Eri appear to have increased by about 20 per cent over the last 40 y...

  20. Classical Cepheid pulsation models --- VI. The Hertzsprung progression

    Science.gov (United States)

    Bono, G.; Marconi, M.; Stellingwerf, R. F.

    2000-08-01

    We present the results of an extensive theoretical investigation on the pulsation behavior of Bump Cepheids. We constructed several sequences of full amplitude, nonlinear, convective models by adopting a chemical composition typical of Large Magellanic Cloud (LMC) Cepheids (Y=0.25, Z=0.008) and stellar masses ranging from M/M⊙ =6.55 to 7.45. We find that theoretical light and velocity curves reproduce the HP, and indeed close to the blue edge the bump is located along the descending branch, toward longer periods it crosses at first the luminosity/velocity maximum and then it appears along the rising branch. In particular, we find that the predicted period at the HP center is PHP = 11.24∓0.46 d and that such a value is in very good agreement with the empirical value estimated by adopting the Fourier parameters of LMC Cepheid light curves i.e. PHP = 11.2 ∓ 0.8 d (Welch et al. 1997). Moreover, light and velocity amplitudes present a "double-peaked" distribution which is in good qualitative agreement with observational evidence on Bump Cepheids. It turns out that both the skewness and the acuteness typically show a well-defined minimum at the HP center and the periods range from PHP = 10.73 ∓ 0.97 d to PHP = 11.29 ∓ 0.53 d which are in good agreement with empirical estimates. We also find that the models at the HP center are located within the resonance region but not on the 2:1 resonance line (P2/P0 = 0.5), and indeed the P2/P0 ratios roughly range from 0.51 (cool models) to 0.52 (hot models). Interestingly enough, the predicted Bump Cepheid masses, based on a Mass-Luminosity (ML) relation which neglects the convective core overshooting, are in good agreement with the empirical masses of Galactic Cepheids estimated by adopting the Baade-Wesselink method (Gieren 1989). As a matter of fact, the observed mass at the HP center -P ≍ 11.2 d- is 6.9 ∓ 0.9 M⊙, while the predicted mass is 7.0 ∓ 0.45 M⊙. Even by accounting for the metallicity difference

  1. Radial pseudoaneurysm following diagnostic coronary angiography

    Directory of Open Access Journals (Sweden)

    Shankar Laudari

    2015-06-01

    Full Text Available The radial artery access has gained popularity as a method of diagnostic coronary catheterization compared to femoral artery puncture in terms of vascular complications and early ambulation. However, very rare complication like radial artery pseudoaneurysm may occur following cardiac catheterization which may give rise to serious consequences. Here, we report a patient with radial pseudoaneurysm following diagnostic coronary angiography. Adequate and correct methodology of compression of radial artery following puncture for maintaining hemostasis is the key to prevention.DOI: http://dx.doi.org/10.3126/jcmsn.v10i3.12776 Journal of College of Medical Sciences-Nepal, 2014, Vol-10, No-3, 48-50

  2. INDICATIONS AND PATIENTS' SELECTION FOR RADIAL KERATOTOMY

    Institute of Scientific and Technical Information of China (English)

    P.SivaReddy

    1991-01-01

    This paper sums up the indications and patients selection for Radial Keratotomy, including necessary presurgery examination, the age for surgery in myopia and predictability. It benefits the recognization for developing this surgery.

  3. Solutions of relativistic radial quasipotential equations

    Energy Technology Data Exchange (ETDEWEB)

    Minh, V.X.; Kadyshevskii, V.G.; Zhidkov, E.P.

    1985-11-01

    A systematic approach to the investigation of relativistic radial quasipotential equations is developed. The quasipotential equations can be interpreted either as linear equations in finite differences of fourth and second orders, respectively, or as differential equations of infinite order.

  4. Radial interchange motions of plasma filaments

    DEFF Research Database (Denmark)

    Garcia, O.E.; Bian, N.H.; Fundamenski, W.

    2006-01-01

    Radial convection of isolated filamentary structures due to interchange motions in magnetized plasmas is investigated. Following a basic discussion of vorticity generation, ballooning, and the role of sheaths, a two-field interchange model is studied by means of numerical simulations on a...... biperiodic domain perpendicular to the magnetic field. It is demonstrated that a blob-like plasma structure develops dipolar vorticity and electrostatic potential fields, resulting in rapid radial acceleration and formation of a steep front and a trailing wake. While the dynamical evolution strongly depends...... on the amount of collisional diffusion and viscosity, the structure travels a radial distance many times its initial size in all parameter regimes in the absence of sheath dissipation. In the ideal limit, there is an inertial scaling for the maximum radial velocity of isolated filaments. This...

  5. Radial Velocity Fluctuations of RZ Psc

    Science.gov (United States)

    Potravnov, I. S.; Gorynya, N. A.; Grinin, V. P.; Minikulov, N. Kh.

    2014-12-01

    The behavior of the radial velocity of the UX Ori type star RZ Psc is studied. The existence of an inner cavity with a radius of about 0.7 a.u. in the circumstellar disk of this star allows to suggest the presence of a companion. A study of the radial velocity of RZ Psc based on our own measurements and published data yields no periodic component in its variability. The two most accurate measurements of V r , based on high resolution spectra obtained over a period of three months, show that the radial velocity is constant over this time interval to within 0.5 km/s. This imposes a limit of M p ≤10 M Jup on the mass of the hypothetical companion. Possible reasons for the observed strong fluctuations in the radial velocity of this star are discussed.

  6. Design and Operation of a Cryogenic Nitrogen Pulsating Heat Pipe

    Science.gov (United States)

    Diego Fonseca, Luis; Miller, Franklin; Pfotenhauer, John

    2015-12-01

    We report the design, experimental setup and successful test results using an innovative passive cooling system called a “Pulsating Heat Pipe” (PHP) operating at temperatures ranging from 77 K to 80 K and using nitrogen as the working fluid. PHPs, which transfer heat by two phase flow mechanisms through a closed loop tubing have the advantage that no electrical pumps are needed to drive the fluid flow. In addition, PHPs have an advantage over copper straps and thermal conductors since they are lighter in weight, exhibit lower temperature gradients and have higher heat transfer rates. PHPs consist of an evaporator section, thermally anchored to a solid, where heat is received at the saturation temperature where the liquid portion of the two-phase flow evaporates, and a condenser where heat is rejected at the saturation temperature where the vapor is condensed. The condenser section in our experiment has been thermally interfaced to a CT cryocooler from SunPower that has a cooling capacity of 10 W at 77 K. Alternating regions of liquid slugs and small vapor plugs fill the capillary tubing, with the vapor regions contracting in the condenser section and expanding in the evaporator section due to an electric heater that will generate heat loads up to 10 W. This volumetric expansion and contraction provides the oscillatory flow of the fluid throughout the capillary tubing thereby transferring heat from one end to the other. The thermal performance and temperature characteristics of the PHP will be correlated as a function of average condenser temperature, PHP fill liquid ratio, and evaporator heat load. The experimental data show that the heat transfer between the evaporator and condenser sections can produce an effective thermal conductivity up to 35000 W/m-K at a 3.5 W heat load.

  7. PULSATING VARIABLE STARS IN THE COMA BERENICES DWARF SPHEROIDAL GALAXY

    International Nuclear Information System (INIS)

    We present B, V, I time-series photometry of the Coma Berenices dwarf spheroidal galaxy, a faint Milky Way (MW) satellite, recently discovered by the Sloan Digital Sky Survey. We have obtained V, B - V and V, V - I color-magnitude diagrams that reach V ∼ 23.0-23.2 mag showing the galaxy turnoff at V ∼ 21.7 mag, and have performed the first study of the variable star population of this new MW companion. Two RR Lyrae stars (a fundamental-mode, RRab, and a first overtone, RRc, pulsator) and a short period variable with period P = 0.12468 days were identified in the galaxy. The RRab star has a rather long period of P ab = 0.66971 days and is about 0.2 mag brighter than the RRc variable and other nonvariable stars on the galaxy horizontal branch (HB). In the period-amplitude diagram, the RRab variable falls closer to the loci of Oosterhoff type-II systems and evolved fundamental-mode RR Lyrae stars in the Galactic globular cluster M3. The average apparent magnitude of the galaxy HB, (V HB) = 18.64 ± 0.04 mag, leads to a distance modulus for the Coma dSph μ0 = 18.13 ± 0.08 mag, corresponding to a distance d = 42+2-1 kpc, by adopting a reddening E(B - V) = 0.045 ± 0.015 mag and a metallicity [Fe/H] =-2.53 ± 0.05 dex.

  8. Guidance cue for cortical radial migration discovered

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ The regulatory mechanism for neuronal migration in the developing cortex is a major unsolved problem in developmental neurobiology. It is generally accepted that the migration of newborn pyramidal neurons from the ventricular zone toward upper cortical layers is guided by radial glial fibers in the developing cortex, and that the laminar structure of the cortex is formed through regulated attachment and detachment of migrating neurons with radial glial fibers.

  9. Radial transport with perturbed magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Hazeltine, R. D. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-05-15

    It is pointed out that the viscosity coefficient describing radial transport of toroidal angular momentum is proportional to the second power of the gyro-radius—like the corresponding coefficients for particle and heat transport—regardless of any geometrical symmetry. The observation is widely appreciated, but worth emphasizing because some literature gives the misleading impression that asymmetry can allow radial moment transport in first-order.

  10. Elbow dislocation with irreparable fracture radial head

    Directory of Open Access Journals (Sweden)

    Dilip Tanna

    2013-01-01

    Full Text Available Background: Treatment of elbow dislocation with irreparable radial head fracture needs replacement of radial head to achieve stability of elbow. An alternate method in cases of elbow dislocation with radial head fracture can be resection of radial head with repair of medial collateral ligament. We report a retrospective analysis of cases of elbow dislocation with irreparable radial head treated by excision head of radius and repair of MCL. Materials and Methods: Nine patients of elbow dislocation with associated irreparable fractures of the head of the radius were included in this analysis (6 F:3 M, Age: 35-47 years. Radial head excision was done through the lateral approach and MCL was sutured using no 3 Ethibond using medial approach. Above elbow plaster was given for 6 weeks and gradual mobilization was done thereafter. All patients were assessed at final followup using Mayo elbow performance score (MEPS. Results: Mean followup was 19.55 ± 7.12 months (range 14-36 months. There was no extension deficit when compared to opposite side with mean range of flexion of 138.8° ± 6.97° (range 130 -145°. Mean pronation was 87.7° ± 4.4° (range 80-90° and mean supination was 87.7 ± 4.62° (range 80-90°. The mean MEPS was 98.8 ± 3.33 (range 90-100. No patient had pain, sensory complaints, subluxation or redislocation. All were able to carry out their daily activities without disability. Conclusion: Radial head excision with MCL repair is an acceptable option for treatment of patients with elbow dislocation and irreparable radial head fracture.

  11. Metal Abundances, Radial Velocities and other Physical Characteristics for the RR Lyrae Stars in the Kepler Field

    CERN Document Server

    Nemec, James M; Ripepi, Vincenzo; Derekas, Aliz; Moskalik, Pawel; Sesar, Branimir; Chadid, Merieme; Bruntt, Hans

    2013-01-01

    Spectroscopic iron-to-hydrogen ratios, radial velocities, atmospheric parameters, and new photometric analyses are presented for 41 RR Lyrae stars (and one probable high-amplitude delta Scuti star) located in the field-of-view of the Kepler space telescope. Thirty-seven of the RR Lyrae stars are fundamental-mode pulsators (i.e., RRab stars) of which 16 exhibit the Blazhko effect. Four of the stars are multiperiodic RRc pulsators oscillating primarily in the first-overtone mode. Spectroscopic [Fe/H] values for the 34 stars for which we were able to derive estimates range from -2.54 +/- 0.13 (NR Lyr) to -0.05 +/- 0.13 dex (V784 Cyg), and for the 19 Kepler-field non-Blazhko stars studied by Nemec et al.(2011) the abundances agree will with their photometric [Fe/H] values. Four non-Blazhko RR Lyrae stars that they identified as metal-rich (KIC 6100702, V2470 Cyg, V782 Cyg and V784 Cyg) are confirmed as such, and four additional stars (V839 Cyg, KIC 5520878, KIC 8832417, KIC 3868420) are also shown here to be meta...

  12. Micromachining with femtosecond laser written radial polarization converter

    OpenAIRE

    Beresna, M.; Gecevičius, M.; Kazansky, P. G.; Bellouard, Y.; Champion, A.

    2012-01-01

    Structures for microfluidics are fabricated with radially polarized femtosecond laser beam. Radial polarization is produced using birefringent optical element. Omnidirectional etching can be achieved using cylindrically symmetric polarization.

  13. Experimental study on rack cooling system based on a pulsating heat pipe

    Science.gov (United States)

    Lu, Qianyi; Jia, Li

    2016-02-01

    A rack cooling system based on a large scale flat plate pulsating heat pipe is proposed. The heat generated from IT equipment in a closed rack is transferred by the rear door pulsating heat pipe to the chilled air passage and is avoided to release into the room. The influence of the start-up performance of the heat pipe, the load of the rack and the load dissipation to the temperature and the velocity distribution in the rack are discussed. It is found that the temperature would be lower and the temperature distribution would be more uniform in the rack when the pulsating heat pipe is in operation. Also, the effect of rack electricity load on temperature distribution is analyzed. It is indicated that higher velocity of chilled air will improve heat transfer of the rack.

  14. Analysis of liquid-vapor pulsating flow in a U-shaped miniature tube

    Energy Technology Data Exchange (ETDEWEB)

    Yuwen Zhang [New Mexico State University, Las Cruces, NM (United States). Dept. of Mechanical Engineering; Faghri, A.; Shafii, M.B. [University of Connecticut, Storrs, CT (United States). Dept. of Mechanical Engineering

    2002-06-01

    Liquid-vapour pulsating flow in a vertically placed U-shaped miniature tube is investigated numerically. The two sealed ends of the U-shaped tube are the evaporator sections and the condenser section is located in the middle of the tube. The governing equations, obtained by analyzing the conservation of mass, momentum, and energy of the liquid and vapor plugs, are normalized and the pulsating flow is described by five nondimensional parameters. The numerical solution is obtained by employing an implicit scheme. The effects of various nondimensional parameters on the performance of the pulsating heat pipe were investigated. The empirical correlations of the amplitude and circular frequency of oscillation were obtained. (author)

  15. Moment of Inertia Dependence of Vertical Axis Wind Turbines in Pulsating Winds

    Directory of Open Access Journals (Sweden)

    Yutaka Hara

    2012-01-01

    Full Text Available Vertical Axis Wind Turbines (VAWTs are unaffected by changes in wind direction, and they have a simple structure and the potential for high efficiency due to their lift driving force. However, VAWTs are affected by changes in wind speed, owing to effects originating from the moment of inertia. In this study, changes in the rotational speed of a small VAWT in pulsating wind, generated by an unsteady wind tunnel, are investigated by varying the wind cycle and amplitude parameters. It is shown that the responses observed experimentally agree with simulations based on torque characteristics obtained under steady rotational conditions. Additionally, a simple equation expressing the relationship between the rotational change width and amplitude of the pulsating wind is presented. The energy efficiency in a pulsating wind remains constant with changes in both the moment of inertia and the wind cycle; however, the energy efficiency decreases when the wind amplitude is large.

  16. Structure and properties of welded joints produced by pulsating and stationary arcs

    International Nuclear Information System (INIS)

    Comparison studies of the structure and properties of welded joints were carried out for the 245x45 mm pipeline made of the 15Kh1M1F steel and produced by manual welding with pulsating and stationary arcs. Service behaviour of welded joints was evaluated from the metal structure, cold resistance, fracture toughness and heat resistance. The manual welding by pulsating arc is shown to provide formation of 15Kh1M1F steel tube joints with more favourable structure and properties and also with higher cold resistance, deformability and heat resistance. High tempering (710-740 deg C, 3 h) is required for the welded joints produced both by pulsating and stationary arcs

  17. A New Timescale for Period Change in the Pulsating DA White Dwarf WD 0111+0018

    CERN Document Server

    Hermes, J J; Mullally, Fergal; Winget, D E; Bischoff-Kim, A

    2013-01-01

    We report the most rapid rate of period change measured to date for a pulsating DA (hydrogen atmosphere) white dwarf (WD), observed in the 292.9 s mode of WD 0111+0018. The observed period change, faster than 10^{-12} s/s, exceeds by more than two orders of magnitude the expected rate from cooling alone for this class of slow and simply evolving pulsating WDs. This result indicates the presence of an additional timescale for period evolution in these pulsating objects. We also measure the rates of period change of nonlinear combination frequencies and show that they share the evolutionary characteristics of their parent modes, confirming that these combination frequencies are not independent modes but rather artifacts of some nonlinear distortion in the outer layers of the star.

  18. Simulation of laminar pulsations in a rectangular duct containing a rod

    International Nuclear Information System (INIS)

    Flow pulsations in subchannel geometries are important in the homogenization of fluid temperatures within a fuel rod bundle cross-section. Recent experimental work by Gosset and Tavoularis has indicated that flow pulsations can occur under laminar conditions. This paper presents the results of computational fluid dynamics investigation of laminar flow pulsations in a single rod geometry matching the experimental geometry and conditions of Gosset and Tavoularis. A gap height to rod diameter ratio of 0.3 and Reynolds numbers of 718 and 900 were considered. Rough agreement between the simulations and the experimental results was obtained for the measured frequency, and the simulations revealed highly complex flow patterns throughout the duct cross-section. (author)

  19. The challenge of measuring magnetic fields in strongly pulsating stars: the case of HD 96446

    CERN Document Server

    Järvinen, S P; Ilyin, I; Schöller, M; Briquet, M

    2016-01-01

    Among the early B-type stars, He-rich Bp stars exhibit the strongest large-scale organized magnetic fields with a predominant dipole contribution. The presence of $\\beta$ Cep-like pulsations in the typical magnetic early Bp-type star HD 96446 was announced a few years ago, but the analysis of the magnetic field geometry was hampered by the absence of a reliable rotation period and a sophisticated procedure for accounting for the impact of pulsations on the magnetic field measurements. Using new spectropolarimetric observations and a recently determined rotation period based on an extensive spectroscopic time series, we investigate the magnetic field model parameters of this star under more detailed considerations of the pulsation behaviour of the line profiles.

  20. Synthetic photometry for carbon-rich giants II. The effects of pulsation and circumstellar dust

    CERN Document Server

    Nowotny, Walter; Höfner, Susanne; Lederer, Michael T

    2011-01-01

    By using self-consistent dynamic model atmospheres which simulate pulsation-enhanced dust-driven winds of AGB stars we studied in detail the influence of (i) pulsations of the stellar interiors, and (ii) the development of dusty stellar winds on the spectral appearance of long period variables with carbon-rich atmospheric chemistry. While the pulsations lead to large-amplitude photometric variability, the dusty envelopes cause pronounced circumstellar reddening. Based on one selected dynamical model which is representative of C-type Mira variables with intermediate mass loss rates, we calculated synthetic spectra and photometry for standard broad-band filters from the visual to the near-infrared. Our modelling allows to investigate in detail the substantial effect of circumstellar dust on the resultant photometry. The pronounced absorption of amorphous carbon dust grains leads to colour indices which are significantly redder than the corresponding ones based on hydrostatic dust-free models. Only if we account...

  1. Experimental study on heat transfer performance of pulsating heat pipe with refrigerants

    Science.gov (United States)

    Wang, Xingyu; Jia, Li

    2016-10-01

    The effects of different refrigerants on heat transfer performance of pulsating heat pipe (PHP) are investigated experimentally. The working temperature of pulsating heat pipe is kept in the range of 20°C-50°C. The startup time of the pulsating heat pipe with refrigerants can be shorter than 4 min, when heating power is in the range of 10W?100W. The startup time decreases with heating power. Thermal resistances of PHP with filling ratio 20.55% were obviously larger than those with other filling ratios. Thermal resistance of the PHP with R134a is much smaller than that with R404A and R600a. It indicates that the heat transfer ability of R134a is better. In addition, a correlation to predict thermal resistance of PHP with refrigerants was suggested.

  2. On the Field of a Spherical Charged Pulsating Distribution of Matter

    Directory of Open Access Journals (Sweden)

    Stavroulakis N.

    2010-10-01

    Full Text Available In the theory of the gravitational field generated by an isotropic spherical mass, the spheres centered at the origin of $R^3$ are non-Euclidean objects, so that each of them possesses a curvature radius distinct from its Euclidean radius. The classical theory suppresses this distinction and consequently leads to inadmissible errors. Specifically, it leads to the false idea that the field of a pulsating source is static. In a number of our previous publications (see references, we have exposed the inevitable role that the curvature radius plays and demonstrated that the field generated by a pulsating not charged spherical course is dynamical. In the present paper we prove that the curvature radius plays also the main role in the description of the gravitational field generated by a charged pulsating source.

  3. On the influence of stochastic pulsations of a bubble on its translational motion

    Science.gov (United States)

    Melnikov, N. P.

    2016-06-01

    This communication is devoted to theoretical analysis of the dynamics of a solitary cavitation bubble pulsating in a compressible viscous liquid under the action of a nonuniform acoustic field. The system of two nonlinear ordinary second-order differential equations is integrated numerically. In the range of acoustic field parameters corresponding to the principal resonance region, the bubble performs large-scale spatial oscillations. It is shown that in a very small range of initial radii, the bubble stops its oscillatory motion due to stochastic pulsations and is expelled into the region of the acoustic-pressure block. Therefore, stochastic pulsations of the bubble radically change the form of the solution to the system of the above-mentioned equations.

  4. Non-linear axisymmetric pulsations of rotating relativistic stars in the conformal flatness approximation

    CERN Document Server

    Dimmelmeier, H; Font, J A; Dimmelmeier, Harald; Stergioulas, Nikolaos; Font, Jose A.

    2005-01-01

    We study non-linear axisymmetric pulsations of rotating relativistic stars using a general relativistic hydrodynamics code under the assumption of a conformal flatness. We compare our results to previous simulations where the spacetime dynamics was neglected. The pulsations are studied along various sequences of both uniformly and differentially rotating relativistic polytropes with index N = 1. We identify several modes, including the lowest-order l = 0, 2, and 4 axisymmetric modes, as well as several axisymmetric inertial modes. Differential rotation significantly lowers mode frequencies, increasing prospects for detection by current gravitational wave interferometers. We observe an extended avoided crossing between the l = 0 and l = 4 first overtones, which is important for correctly identifying mode frequencies in case of detection. For uniformly rotating stars near the mass-shedding limit, we confirm the existence of the mass-shedding-induced damping of pulsations, though the effect is not as strong as i...

  5. The first evidence for multiple pulsation axes: a new rapidly oscillating Ap star in the Kepler field, KIC 10195926

    DEFF Research Database (Denmark)

    Kurtz, Donald W.; Cunha, Margarida S.; Saio, H.;

    2011-01-01

    to these values that reproduces the rotational variations of the two obliquely pulsating modes with different pulsation axes. The star shows overabundances of the rare earth elements, but these are not as extreme as most other roAp stars. The spectrum is variable with rotation, indicating surface abundance...

  6. A search for non-pulsating, chemically normal stars in the δ Scuti instability strip using Kepler data

    DEFF Research Database (Denmark)

    Murphy, Simon J.; Bedding, Timothy R.; Niemczura, Ewa;

    2015-01-01

    is a challenge to pulsation theory. However, its existence as the only known star of its kind indicates that such stars are rare. We conclude that the delta Sct instability strip is pure, unless pulsation is shut down by diffusion or another mechanism, which could be interaction with a binary companion....

  7. Topical drug delivery in chronic rhinosinusitis patients before and after sinus surgery using pulsating aerosols.

    Directory of Open Access Journals (Sweden)

    Winfried Möller

    Full Text Available OBJECTIVES: Chronic rhinosinusitis (CRS is a common chronic disease of the upper airways and has considerable impact on quality of life. Topical delivery of drugs to the paranasal sinuses is challenging, therefore the rate of surgery is high. This study investigates the delivery efficiency of a pulsating aerosol in comparison to a nasal pump spray to the sinuses and the nose in healthy volunteers and in CRS patients before and after sinus surgery. METHODS: (99mTc-DTPA pulsating aerosols were applied in eleven CRSsNP patients without nasal polyps before and after sinus surgery. In addition, pulsating aerosols were studied in comparison to nasal pump sprays in eleven healthy volunteers. Total nasal and frontal, maxillary and sphenoidal sinus aerosol deposition and lung penetration were assessed by anterior and lateral planar gamma camera imaging. RESULTS: In healthy volunteers nasal pump sprays resulted in 100% nasal, non-significant sinus and lung deposition, while pulsating aerosols resulted 61.3+/-8.6% nasal deposition and 38.7% exit the other nostril. 9.7+/-2.0 % of the nasal dose penetrated into maxillary and sphenoidal sinuses. In CRS patients, total nasal deposition was 56.7+/-13.3% and 46.7+/-12.7% before and after sinus surgery, respectively (p<0.01. Accordingly, maxillary and sphenoidal sinus deposition was 4.8+/-2.2% and 8.2+/-3.8% of the nasal dose (p<0.01. Neither in healthy volunteers nor in CRS patients there was significant dose in the frontal sinuses. CONCLUSION: In contrast to nasal pump sprays, pulsating aerosols can deliver significant doses into posterior nasal spaces and paranasal sinuses, providing alternative therapy options before and after sinus surgery. Patients with chronic lung diseases based on clearance dysfunction may also benefit from pulsating aerosols, since these diseases also manifest in the upper airways.

  8. First axion bounds from a pulsating helium-rich white dwarf star

    Science.gov (United States)

    Battich, T.; Córsico, A. H.; Althaus, L. G.; Miller Bertolami, M. M.

    2016-08-01

    The Peccei-Quinn mechanism proposed to solve the CP problem of Quantum Chromodynamics has as consequence the existence of axions, hypothetical weakly interacting particles whose mass is constrained to be on the sub-eV range. If these particles exist and interact with electrons, they would be emitted from the dense interior of white dwarfs, becoming an important energy sink for the star. Due to their well known physics, white dwarfs are good laboratories to study the properties of fundamental particles such as the axions. We study the general effect of axion emission on the evolution of helium-rich white dwarfs and on their pulsational properties. To this aim, we calculate evolutionary helium-rich white dwarf models with axion emission, and assess the pulsational properties of this models. Our results indicate that the rates of change of pulsation periods are significantly affected by the existence of axions. We are able for the first time to independently constrain the mass of the axion from the study of pulsating helium-rich white dwarfs. To do this, we use an estimation of the rate of change of period of the pulsating white dwarf PG 1351+489 corresponding to the dominant pulsation period. From an asteroseismological model of PG 1351+489 we obtain gae < 3.3 × 10-13 for the axion-electron coupling constant, or macos2β lesssim 11.5 meV for the axion mass. This constraint is relaxed to gae < 5.5 × 10-13 (macos2β lesssim 19.5 meV), when no detailed asteroseismological model is adopted for the comparison with observations.

  9. Optical spectroscopy of RU Cam, a pulsating carbon star

    CERN Document Server

    Kipper, Tonu

    2007-01-01

    We analysed the high resolution spectra of a RU Cam, classified as W Vir type star. The atmospheric parameters of RU Cam were estimated Teff=5250K and log g=1.0. The hydrogen deficiency of RU Cam was not confirmed. The iron abundance, [Fe/H]=-0.37, is close to the solar one. Abundances of most other elements are also close to normal. We found considerable excesses of carbon and nitrogen: [C/Fe]=+0.98, [N/Fe]=+0.60. The carbon to oxygen ratio is C/O$\\ge$1. The carbon isotopic abundance ratio is equal to C^12/C^13=4.5. For sodium a moderate overabundance Na/Fe=+0.55 was obtained. For two moments of observations we found close heliocentric velocity values, Vr=-21.7+/-0.8 and -23.1+/-1.0 km/s. Both spectra contain a peculiar feature - an emission component of NaI doublet which location agrees with the radial velocity from the bulk of metallic lines. For our two observing moments we found no dependence of radial velocities on the formation depth or on excitation energy for metallic lines.

  10. Double-mode radial-non-radial RR Lyrae stars. OGLE-IV photometry of two high cadence fields in the Galactic bulge

    CERN Document Server

    Netzel, H; Moskalik, P

    2015-01-01

    We analyse the OGLE-IV photometry of the first overtone and double-mode RR Lyrae stars (RRc/RRd) in the two fields towards the Galactic bulge observed with high cadence. In 27 per cent of RRc stars we find additional non-radial mode, with characteristic period ratio, P x /P 1O \\in (0.6, 0.64). It strongly corroborates the conclusion arising from the analysis of space photometry of RRc stars, that this form of pulsation must be common. In the Petersen diagram the stars form three sequences. In 20 stars we find two or three close secondary modes simultaneously. The additional modes are clearly non-stationary. Their amplitude and/or phase vary in time. As a result, the patterns observed in the frequency spectra of these stars may be very complex. In some stars the additional modes split into doublets, triplets or appear as a more complex bands of increased power. Subharmonics of additional modes are detected in 20 per cent of stars. They also display a complex structure. Including our previous study of the OGLE-...

  11. Instability in Self-Pulsation in Laser Diodes and its Effect on All-Optical Synchonization

    OpenAIRE

    Hyland, Jonathan; Farrell, Gerald

    1994-01-01

    The effect of short- and long-term frequency instability in self pulsation on all-optical synchronization using a twin-section laser diode is experimentally investigated. Short-term frequency instability broadens the unlocked full width at half maximum (FWHM) of the fundamental of the rf spectrum of the self-pulsating laser diode. We show experimentally that the value of the unlocked FWHM, and thus the level of short-term instability, has a direct effect on the optical power required to maint...

  12. Pulsations as a mass-loss trigger in evolved hot stars

    CERN Document Server

    Kraus, Michaela; Haucke, Maximiliano; Cidale, Lydia; Venero, Roberto; Fernandes, Marcelo Borges; Tomic, Sanja; Cure, Michel

    2013-01-01

    During the post-main sequence evolution massive stars pass through several short-lived phases, in which they experience enhanced mass loss in the form of clumped winds and mass ejection events of unclear origin. The discovery that stars populating the blue, luminous part of the Hertzsprung-Russell diagram can pulsate hence suggests that stellar pulsations might influence or trigger enhanced mass loss and eruptions. We present recent results for two objects in different phases: a B[e] star at the end of the main sequence and a B-type supergiant.

  13. On the period of the pulsating hydrogen-deficient star BD + 1303224

    International Nuclear Information System (INIS)

    Recent observations of maxima of the pulsating early-type hydrogen-deficient star BD + 1303224 indicate a decrease in period since the discovery observations. The data are best fitted by a decrease rate of 46 x 10-10 day cycle, a value which is comparable with the rate derived from a theoretical study of the fast evolutionary phase of a post-giant helium star. Four-colour data are averaged to give mean colours at 0.1 phase intervals around the pulsation cycle. (author)

  14. Period of the pulsating hydrogen-deficient star BD + 13/sup 0/3224

    Energy Technology Data Exchange (ETDEWEB)

    Kilkenny, D. (Council for Scientific and Industrial Research, Cape Town (South Africa). South African Astronomical Observatory); Lynas-Gray, A.E. (University Coll., London (UK); Saint Andrews Univ. (UK). Observatory)

    1982-03-01

    Recent observations of maxima of the pulsating early-type hydrogen-deficient star BD + 13/sup 0/3224 indicate a decrease in period since the discovery observations. The data are best fitted by a decrease rate of 46 x 10/sup -10/ day cycle, a value which is comparable with the rate derived from a theoretical study of the fast evolutionary phase of a post-giant helium star. Four-colour data are averaged to give mean colours at 0.1 phase intervals around the pulsation cycle.

  15. Whether the Classical O-C Diagram can be used to Multi-mode Pulsators

    CERN Document Server

    Niu, Jia-Shu; Fu, Jian-Ning; Xue, Hui-Fang

    2015-01-01

    O-C diagram is a useful technique to analyse the period changes of a pulsator by using the maximum (or minimum) value points which have been obtained from the historical data. But if an object is a double-mode or multi-mode pulsator, the extreme value points are the results of all the modes other than just the fundamental mode. We discussed these situations and give out some criteria to judge whether the O-C diagram can be used in these situations.

  16. Highly Reliable Transformerless Photovoltaic Inverters With Leakage Current and Pulsating Power Elimination

    DEFF Research Database (Denmark)

    Tang, Yi; Yao, Wenli; Loh, Poh Chiang;

    2016-01-01

    This paper presents a transformerless inverter topology, which is capable of simultaneously solving leakage current and pulsating power issues in grid-connected photovoltaic (PV) systems. Without adding any additional components to the system, the leakage current caused by the PV-to-ground...... parasitic capacitance can be bypassed by introducing a common-mode (CM) conducting path to the inverter. The resulting ground leakage current is therefore well controlled to be below the regulation limit. Furthermore, the proposed inverter can also eliminate the well-known double-line-frequency pulsating...... excellent performance of the proposed PV inverter....

  17. Complex asteroseismology of the hybrid B-type pulsator $\\gamma$ Pegasi: a test of stellar opacities

    CERN Document Server

    Walczak, Przemysław

    2010-01-01

    Using the updated oscillation spectrum of $\\gamma$ Pegasi, we construct a set of seismic models which reproduce two pulsational frequencies corresponding to the $\\ell=0$, p$_1$ and $\\ell=1$, g$_1$ modes. Then, we single out models which reproduce other well identified modes. Finally, we extend our seismic modelling by a requirement of fitting also values of the complex, nonadiabatic parameter $f$ associated to each mode frequency. Such complex asteroseismology of the B-type pulsators provides a unique test of stellar metallicity and opacities. In contrast to our previous studies, results for $\\gamma$ Peg indicate that both opacity tables, OPAL and OP, are equally preferred.

  18. Can pulsating PG1159 stars place constraints on the occurrence of core overshooting?

    OpenAIRE

    A. H. Córsico; Althaus, L.G.

    2005-01-01

    The present letter is aimed at exploring the influence of overshooting during the central helium burning in pre-white dwarf progenitors on the pulsational properties of PG1159 stars. To this end we follow the complete evolution an intermediate-mass white dwarf progenitor from the zero age main sequence through the thermally pulsing and born-again phases to the domain of the PG1159 stars. Our results suggest that the presence of mode-trapping features in the period spacings of these hot pulsat...

  19. Using nonradial pulsations to determine the envelope composition of very evolved stars

    International Nuclear Information System (INIS)

    Recent observational and theoretical studies of the ZZ Ceti variables (DA degenerate dwarfs), the DBV variables (DB degenerate dwarfs), and the GW Vir variables (DO degenerate dwarfs) have shown them to be pulsating in nonradial g+-modes. The pulsation mechanism has been identified for each class of variable star and, in all cases, involves predictions of the stars envelope composition. The ZZ Ceti variables must have pure hydrogen surface layers, the DBV stars must have pure helium surface layers, and the GW Vir stars must have carbon and oxygen rich surface layers. 44 refs

  20. Draft tube pressure pulsation predictions in Francis turbines with transient Computational Fluid Dynamics methodology

    Science.gov (United States)

    Melot, M.; Nennemann, B.; Désy, N.

    2014-03-01

    An automatic Computational Fluid Dynamics (CFD) procedure that aims at predicting Draft Tube Pressure Pulsations (DTPP) at part load is presented. After a brief review of the physics involved, a description of the transient numerical setup is given. Next, the paper describes a post processing technique, namely the separation of pressure signals into synchronous, asynchronous and random pulsations. Combining the CFD calculation with the post-processing technique allows the quantification of the potential excitation of the mechanical system during the design phase. Consequently it provides the hydraulic designer with a tool to specifically target DTPP and thus helps in the development of more robust designs for part load operation of turbines.

  1. A new way to study the stellar pulsation; First Polar mission PAIX

    Science.gov (United States)

    Chadid, M.

    2015-12-01

    In the context of long and continuous time-series photometry and after the MOST, CoRoT, KEPLER space missions and large geographic longitude ground--based networks, a new way is offered by the polar location helping to cope with the problem associated with the Earth day--night cycle. In this paper, we present the first long time-series photometry from the heart of Antarctica -Dome Charlie- and we discuss briefly our new results and perspectives on the pulsating stars from Antarctica, especially the connection between temporal hydrodynamic phenomena and cyclic modulations. Finally, we highlight the impact of PAIX -the robotic Antarctica photometer- on the stellar pulsation study.

  2. Flow effects due to pulsation in an internal combustion engine exhaust port

    International Nuclear Information System (INIS)

    Highlights: • Using POD analysis to identify large coherent flow structures in a complex geometry. • Flow field alters significant for constant and pulsating boundary conditions. • The discharge coefficient of the exhaust port decreases 2% with flow pulsation. • Pulsation causes a pumping mechanism due to a phase shift of pressure and momentum. - Abstract: In an internal combustion engine, the residual energy remaining after combustion in the exhaust gasses can be partially recovered by a downstream arranged device. The exhaust port represents the passage guiding the exhaust gasses from the combustion chamber to the energy recovering device, e.g. a turbocharger. Thus, energy losses in the course of transmission shall be reduced as much as possible. However, in one-dimensional engine models used for engine design, the exhaust port is reduced to its discharge coefficient, which is commonly measured under constant inflow conditions neglecting engine-like flow pulsation. In this present study, the influence of different boundary conditions on the energy losses and flow development during the exhaust stroke are analyzed numerically regarding two cases, i.e. using simple constant and pulsating boundary conditions. The compressible flow in an exhaust port geometry of a truck engine is investigated using three-dimensional Large Eddy Simulations (LES). The results contrast the importance of applying engine-like boundary conditions in order to estimate accurately the flow induced losses and the discharge coefficient of the exhaust port. The instantaneous flow field alters significantly when pulsating boundary conditions are applied. Thus, the induced losses by the unsteady flow motion and the secondary flow motion are increased with inflow pulsations. The discharge coefficient decreased about 2% with flow pulsation. A modal flow decomposition method, i.e. Proper Orthogonal Decomposition (POD), is used to analyze the coherent structures induced with the particular

  3. Intraoperative hemodynamic evaluation of the radial and ulnar arteries during free radial forearm flap procedure.

    Science.gov (United States)

    Lorenzetti, Fulvio; Giordano, Salvatore; Suominen, Erkki; Asko-Seljavaara, Sirpa; Suominen, Sinikka

    2010-02-01

    The purpose of this prospective study was to assess the blood flow of the radial and ulnar arteries before and after radial forearm flap raising. Twenty-two patients underwent radial forearm microvascular reconstruction for leg soft tissue defects. Blood flow of the radial, ulnar, and recipient arteries was measured intraoperatively by transit-time and ultrasonic flowmeter. In the in situ radial artery, the mean blood flow was 60.5 +/- 47.7 mL/min before, 6.7 +/- 4.1 mL/min after raising the flap, and 5.8 +/- 2.0 mL/min after end-to-end anastomosis to the recipient artery. In the ulnar artery, the mean blood flow was 60.5 +/- 43.3 mL/min before harvesting the radial forearm flap and significantly increased to 85.7 +/- 57.9 mL/min after radial artery sacrifice. A significant difference was also found between this value and the value of blood flow in the ulnar and radial arteries pooled together ( P < 0.05). The vascular resistance in the ulnar artery decreased significantly after the radial artery flap raising (from 2.7 +/- 3.1 to 1.9 +/- 2.2 peripheral resistance units, P = 0.010). The forearm has a conspicuous arterial vascularization not only through the radial and ulnar arteries but also through the interosseous system. The raising of the radial forearm flap increases blood flow and decreases vascular resistance in the ulnar artery. PMID:19902406

  4. Radial Tunnel Syndrome, Diagnostic and Treatment Dilemma

    Directory of Open Access Journals (Sweden)

    Ali Moradi

    2015-07-01

    Full Text Available Radial tunnel syndrome is a disease which we should consider it in elbow and forearm pains. It is diagnosed with lateral elbow and dorsal forearm pain may radiate to the wrist and dorsum of the fingers. The disease is more prevalent in women with the age of 30 to 50 years old. It occurs by intermittent compression on the radial nerve from the radial head to the inferior border of the supinator muscle, without obvious extensor muscle weakness. Compression could happen in five different sites but the arcade of Frose is the most common area that radial nerve is compressed. To diagnosis radial tunnel syndrome, clinical examination is more important than paraclinic tests such as electrodiagnsic test and imaging studies. The exact site of the pain which can more specified by rule of nine test and weakness of the third finger and wrist extension are valuable physical exams to diagnosis. MRI studies my show muscle edema or atrophy along the distribution of the posterior interosseous nerve. Although non-surgical treatments such as rest, NSAIDs, injections and physiotherapy do not believe to have permanent relief, but it is justify undergoing them before surgery. Surgery could diminish pain and symptoms in 67 to 93 percents of patients completely.

  5. Radial spoke proteins of Chlamydomonas flagella

    Science.gov (United States)

    Yang, Pinfen; Diener, Dennis R.; Yang, Chun; Kohno, Takahiro; Pazour, Gregory J.; Dienes, Jennifer M.; Agrin, Nathan S.; King, Stephen M.; Sale, Winfield S.; Kamiya, Ritsu; Rosenbaum, Joel L.; Witman, George B.

    2007-01-01

    Summary The radial spoke is a ubiquitous component of ‘9+2’ cilia and flagella, and plays an essential role in the control of dynein arm activity by relaying signals from the central pair of microtubules to the arms. The Chlamydomonas reinhardtii radial spoke contains at least 23 proteins, only 8 of which have been characterized at the molecular level. Here, we use mass spectrometry to identify 10 additional radial spoke proteins. Many of the newly identified proteins in the spoke stalk are predicted to contain domains associated with signal transduction, including Ca2+-, AKAP- and nucleotide-binding domains. This suggests that the spoke stalk is both a scaffold for signaling molecules and itself a transducer of signals. Moreover, in addition to the recently described HSP40 family member, a second spoke stalk protein is predicted to be a molecular chaperone, implying that there is a sophisticated mechanism for the assembly of this large complex. Among the 18 spoke proteins identified to date, at least 12 have apparent homologs in humans, indicating that the radial spoke has been conserved throughout evolution. The human genes encoding these proteins are candidates for causing primary ciliary dyskinesia, a severe inherited disease involving missing or defective axonemal structures, including the radial spokes. PMID:16507594

  6. Chandra Discovers Eruption and Pulsation in Nova Outburst

    Science.gov (United States)

    2001-09-01

    NASA's Chandra X-ray Observatory has discovered a giant outburst of X-rays and unusual cyclical pulsing from a white dwarf star that is closely orbiting another star -- the first time either of these phenomena has been seen in X-rays. The observations are helping scientists better understand the thermonuclear explosions that occur in certain binary star systems. The observations of Nova Aquilae were reported today at the "Two Years of Science with Chandra" symposium by an international team led by Sumner Starrfield of Arizona State University. "We found two important results in our Chandra observations. The first was an underlying pulsation every 40 minutes in the X-ray brightness, which we believe comes from the cyclical expansion and contraction of the outer layers of the white dwarf," said Starrfield. "The other result was an enormous flare of X-rays that lasted for 15 minutes. Nothing like this has been seen before from a nova, and we don't know how to explain it." Novas occur on a white dwarf (a star which used up all its nuclear fuel and shrank to roughly the size of the Earth) that is orbiting a normal size star. Strong gravity tides drag hydrogen gas off the normal star and onto the white dwarf, where it can take more than 100,000 years for enough hydrogen to accumulate to ignite nuclear fusion reactions. Gradually, these reactions intensify until a cosmic-sized hydrogen bomb blast results. The outer layers of the white dwarf are then blown away, producing a nova outburst that can be observed for a period of months to years as the material expands into space. "Chandra has allowed us to see deep into the gases ejected by this giant explosion and extract unparalleled information on the evolution of the white dwarf whose surface is exploding," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics. The brightening of Nova Aquilae was first detected by optical astronomers in December 1999. "Although this star is at a distance of more than 6

  7. On magnetopause inflation under radial IMF

    Science.gov (United States)

    Suvorova, A. V.; Dmitriev, A. V.

    2016-07-01

    Full understanding of the magnetosphere interaction with radial IMF structures embedded in the solar wind flow is far from completeness. In order to analyze the effects of radial IMF, we use THEMIS observations of the magnetopause and magnetosheath together with upstream data acquired from ACE and Wind monitors as well as from the OMNI data base. We demonstrate a prominent magnetopause inflation and low pressure magnetosheath (LPM) mode under long-lasting radial IMF. We propose that these phenomena result from a kinetic effect of energetic ions taking the energy away from the pressure balance at the magnetopause. We show that strict quantitative determination of the inflation and LPM mode as a function of the cone angle is difficult because of the problems with reliable determination of the upstream and magnetosheath conditions. The shortcomings are caused by such effects as ambiguous time delay for the solar wind propagation, THEMIS orbital bias and model-dependent estimations of the magnetopause inflation.

  8. Dispersion-free radial transmission lines

    Science.gov (United States)

    Caporaso, George J.; Nelson, Scott D.

    2011-04-12

    A dispersion-free radial transmission line ("DFRTL") preferably for linear accelerators, having two plane conductors each with a central hole, and an electromagnetically permeable material ("EPM") between the two conductors and surrounding a channel connecting the two holes. At least one of the material parameters of relative magnetic permeability, relative dielectric permittivity, and axial width of the EPM is varied as a function of radius, so that the characteristic impedance of the DFRTL is held substantially constant, and pulse transmission therethrough is substantially dispersion-free. Preferably, the EPM is divided into concentric radial sections, with the varied material parameters held constant in each respective section but stepwise varied between sections as a step function of the radius. The radial widths of the concentric sections are selected so that pulse traversal time across each section is the same, and the varied material parameters of the concentric sections are selected to minimize traversal error.

  9. Precise Near-Infrared Radial Velocities

    CERN Document Server

    Plavchan, Peter; Gagne, Jonathan; Furlan, Elise; Brinkworth, Carolyn; Bottom, Michael; Tanner, Angelle; Anglada-Escude, Guillem; White, Russel; Davison, Cassy; Mills, Sean; Beichman, Chas; Johnson, John Asher; Ciardi, David; Wallace, Kent; Mennesson, Bertrand; Vasisht, Gautam; Prato, Lisa; Kane, Stephen; Crawford, Sam; Crawford, Tim; Sung, Keeyoon; Drouin, Brian; Lin, Sean; Leifer, Stephanie; Catanzarite, Joe; Henry, Todd; von Braun, Kaspar; Walp, Bernie; Geneser, Claire; Ogden, Nick; Stufflebeam, Andrew; Pohl, Garrett; Regan, Joe

    2016-01-01

    We present the results of two 2.3 micron near-infrared radial velocity surveys to detect exoplanets around 36 nearby and young M dwarfs. We use the CSHELL spectrograph (R ~46,000) at the NASA InfraRed Telescope Facility, combined with an isotopic methane absorption gas cell for common optical path relative wavelength calibration. We have developed a sophisticated RV forward modeling code that accounts for fringing and other instrumental artifacts present in the spectra. With a spectral grasp of only 5 nm, we are able to reach long-term radial velocity dispersions of ~20-30 m/s on our survey targets.

  10. Radial velocity observations of VB10

    Directory of Open Access Journals (Sweden)

    Rodler F.

    2011-07-01

    Full Text Available VB 10 is the smallest star known to harbor a planet according to the recent astrometric study of Pravdo & Shaklan [1]. Here we present near-infrared (J-band radial velocity of VB 10 performed from high resolution (R~20,000 spectroscopy (NIRSPEC/KECK II. Our results [2] suggest radial velocity variability with amplitude of ~1 km/s, a result that is consistent with the presence of a massive planet companion around VB10 as found via long-term astrometric monitoring of the star by Pravdo & Shaklan. Employing an entirely different technique we verify the results of Pravdo & Shaklan.

  11. Five Lectures on Radial Basis Functions

    DEFF Research Database (Denmark)

    Powell, Mike J.D.

    2005-01-01

    Professor Mike J. D. Powell spent three weeks at IMM in November - December 2004. During the visit he gave five lectures on radial basis functions. These notes are a TeXified version of his hand-outs, made by Hans Bruun Nielsen, IMM.......Professor Mike J. D. Powell spent three weeks at IMM in November - December 2004. During the visit he gave five lectures on radial basis functions. These notes are a TeXified version of his hand-outs, made by Hans Bruun Nielsen, IMM....

  12. Two new pulsating low-mass pre-white dwarfs or SX Phenix stars?*

    CERN Document Server

    Corti, M A; Córsico, A H; Kepler, S O; Althaus, L G; Koester, D; Arias, J P Sánchez

    2016-01-01

    Context. The discovery of pulsations in low-mass stars opens an opportunity for probing their interiors and to determine their evolution, by employing the tools of asteroseismology. Aims. We aim to analyze high-speed photometry of SDSSJ145847.02$+$070754.46 and SDSSJ173001.94$+$070600.25 and discover brightness variabilities. In order to locate these stars in the $T_{\\rm eff} - \\log g$ diagram we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods. To carry out this study, we used the photometric data obtained by us for these stars with the 2.15m telescope at CASLEO, Argentina. We analyzed their light curves and we apply the Discrete Fourier Transform to determine the pulsation frequencies. Finally, we compare both stars in the $T_{\\rm eff} - \\log g$ diagram, with known two pre-white dwarfs, seven pulsating pre-ELM white dwarf stars, $\\delta$ Scuti and SX Phe stars. Results. We report the discovery of pulsations in SDSSJ145847.02$+$070754.46 and SDSSJ173001.9...

  13. Mass ejection by pulsational pair-instability in very massive stars and implications for luminous supernovae

    CERN Document Server

    Yoshida, Takashi; Maeda, Keiichi; Ishii, Tatsuo

    2015-01-01

    Massive stars having a CO core of $\\sim 40 - 60$ M$_\\odot$ experience pulsational pair-instability (PPI) after carbon-burning. This instability induces strong pulsations of the whole star and a part of outer envelope is ejected. We investigate the evolution and mass ejection of metal-poor very massive stars which experience PPI. We use stellar models with initial masses of 140, 200, and 250 M$_\\odot$ and the metallicity Z=0.004. Their masses decrease to 54.09, 58.65, and 61.03 M$_\\odot$ before the neon-burning owing to mass loss and He mass fraction at the surface becomes about 20%. During the PPI period of $\\sim 1 - 2000$ years, they experience six, four, and three pulsations, respectively. The larger CO-core model has the longer PPI period and ejects the larger amount of mass. Since almost all surface He has been lost by the pulsations, these stars become type Ic supernovae if they explode. Light curves during the PPI stage and supernovae are investigated and are implicated in luminous supernovae. The lumin...

  14. PSR J1738+0333: The First Millisecond Pulsar + Pulsating White Dwarf Binary

    CERN Document Server

    Kilic, Mukremin; Gianninas, A; Brown, Warren R

    2014-01-01

    We report the discovery of the first millisecond pulsar with a pulsating white dwarf companion. Following the recent discoveries of pulsations in extremely low-mass (ELM, <0.3 Msol) white dwarfs (WDs), we targeted ELM WD companions to two millisecond pulsars with high-speed Gemini photometry. We find significant optical variability in PSR J1738+0333 with periods between roughly 1790-3060 s, consistent in timescale with theoretical and empirical observations of pulsations in 0.17 Msol He-core ELM WDs. We additionally put stringent limits on a lack of variability in PSR J1909-3744, showing this ELM WD is not variable to <0.1 per cent amplitude. Thanks to the accurate distance and radius estimates from radio timing measurements, PSR J1738+0333 becomes a benchmark for low-mass, pulsating WDs. Future, more extensive time-series photometry of this system offers an unprecedented opportunity to constrain the physical parameters (including the cooling age) and interior structure of this ELM WD, and in turn, the ...

  15. Experimental study on the start up performance of flat plate pulsating heat pipe

    Science.gov (United States)

    Hu, Chaofa; Jia, Li

    2011-06-01

    An experimental system of flat plate pulsating heat pipe was established and experimental research was carried out in this system to know the mechanism of heat transfer, start-up and operating characteristics. The factors, such as filling rate, heating power, heating method etc, which have great influence on the thermal performance of the plate pulsating heat pipe were discussed. The results indicate that heating power and filling rate are the important factors for the start-up of the plate pulsating heat pipe. The different start-up power is needed with different filling rate, and the start-up of the heat pipe in case of bottom heated is much easier than that of top heated. Increasing the heating power and enlarging the heating area can make the start-up easier. Heating power can also affect the start-up time of heat pipe under the condition of bottom heated, while it does not have some influence to the heat pipe of top heated. The thermal resistance of plate pulsating heat pipe is related with the heating power, and the higher the heating power is, the smaller the thermal resistance is. But the best filling rate which the heat pipe needs is different with different heating methods, and the performance of the heat pipe in the case of bottom heated is better than the others.

  16. Experimental Identification of the Transmittance Matrix for any Element of the Pulsating Gas Manifold

    Science.gov (United States)

    CYKLIS, P.

    2001-07-01

    In positive-displacement compressor manifolds there are pressure pulsations due to their cyclic operation. The analysis of pressure pulsations in the compressor manifolds is important for various reasons: they directly affect the quantity of energy required for medium compression due to dynamic pressure charging, or inversely, dynamic suppression of suction and discharge processes; they cause mechanical vibrations of compressed gas piping network, they cause aerodynamic and mechanical noise; they affect the dynamics of working valves in valve compressors, they intensify the process of heat convection in heat exchangers in the gas network. The Helmholtz model used so far, which is the basis for users, who deal with pressure pulsation damping, contains many simplifying assumptions. This is because; a straight pipe segment substitutes each element of the piping system. In many cases this model is insufficient. An attempt of the analysis of other shapes was presented in references [1-3] but only simple geometry elements were considered. In other papers [4-8] the influence of the mean flow velocity caused problems. In the presented method, on the basis of pressure pulsation measurement results, firstly a division into the forward and backward going wave is determined, then the elements of the scattering (transmittance) matrix are calculated defining the installation element. This allows introducing the correction for gas mean velocity. The results of the method using correction for the gas mean velocity have been compared with the results without correction and Helmholtz model showing better accuracy.

  17. Characteristics pertinent to propagation of pulsating pressure in the channels of turbine machines

    Science.gov (United States)

    Liu, Hong; Chen, Zuoyi

    2007-01-01

    A new model describing the propagation of the pressure pulsations in the intricately shaped channels of turbine machines is presented. The proposed model was successfully used to analyze two emergency events: a failure of a steam turbine’s cast diaphragm and a failure of a rocket engine’s oxygen pump booster stage.

  18. The Araucaria Project : the Baade-Wesselink projection factor of pulsating stars

    CERN Document Server

    Nardetto, N; Gieren, W; Pietrzynski, G; Poretti, E

    2013-01-01

    The projection factor used in the Baade-Wesselink methods of determining the distance of Cepheids makes the link between the stellar physics and the cosmological distance scale. A coherent picture of this physical quantity is now provided based on several approaches. We present the lastest news on the expected projection factor for different kinds of pulsating stars in the Hertzsprung-Russell diagram.

  19. Magnetic observations of pulsating B and Be stars with ESPaDOnS and Narval

    NARCIS (Netherlands)

    J. Silvester; C. Neiner; H.F. Henrichs; G.A. Wade; E. Alecian; V. Petit

    2008-01-01

    Discoveries of magnetic fields in pulsating B and Be stars have been claimed from low-resolution spectropolarimetric observations with FORS1 at VLT. We used the new generation of high-resolution spectropolarimeters, ESPaDOnS at CFHT and NARVAL at TBL, to check for the existence of these fields. We f

  20. Large Variety of New Pulsating Stars in the OGLE-III Galactic Disk Fields

    CERN Document Server

    Pietrukowicz, P; Mroz, P; Soszynski, I; Udalski, A; Poleski, R; Szymanski, M K; Kubiak, M; Pietrzynski, G; Wyrzykowski, L; Ulaczyk, K; Kozlowski, S; Skowron, J

    2013-01-01

    We present the results of a search for pulsating stars in the 7.12 deg^2 OGLE-III Galactic disk area in the direction tangent to the Centaurus Arm. We report the identification of 20 Classical Cepheids, 45 RR Lyr type stars, 14 Long-Period Variables, such as Miras and Semi-Regular Variables, and 56 very likely delta Sct type stars. Based on asteroseismic models constructed for one quadruple-mode and six triple-mode delta Sct type pulsators, we estimated masses, metallicities, ages, and distance moduli to these objects. The modeled stars have masses in the range 0.9-2.5 M_sun and are located at distances between 2.5 kpc and 6.2 kpc. Two triple-mode and one double-mode pulsators seem to be Population II stars of the SX Phe type, probably from the Galactic halo. All reported pulsating variables but one object are new discoveries. They are included in the OGLE-III Catalog of Variable Stars. Finally, we introduce the on-going OGLE-IV Galactic Disk Survey, which covers half of the Galactic plane. For the purposes o...

  1. Numerical simulation of the pulsating catheter pump : A left ventricular assist device

    NARCIS (Netherlands)

    Verkerke, GJ; Mihaylov, D; Geertsema, AA; Lubbers, J; Rakhorst, G

    1999-01-01

    The pulsating catheter (PUCA) pump, a left ventricular assist device, consists of a hydraulically or pneumatically driven membrane pump, extracorporeally placed and mounted to a valved catheter. The catheter is introduced into an easily accessible artery and positioned with its distal tip in the lef

  2. Analysis of the occurrence of flow-induced pulsations in a gas control station

    NARCIS (Netherlands)

    Peters, M.C.A.M.; Riezebos, H.J.

    2001-01-01

    Strong flow-induced pulsations were observed at some measurement and control stations of the major gas transport company in the Netherlands, Gasunie. These resonances occur when the gas flow is passing closed side branches in the system at a sufficiently high velocity. Unsteady vortex shedding at th

  3. Pulsational variability in proto-planetary nebulae and other post-AGB objects

    Science.gov (United States)

    Hrivnak, Bruce J.

    2016-07-01

    Light and velocity curves of several classes of pulsating stars have been successfully modeled to determine physical properties of the stars. In this observational study, we review briefly the pulsational variability of the main classes of post-AGB stars. Our attention is focused in particular on proto-planetary nebulae (PPNe), those in the short-lived phase from AGB stars to the planetary nebulae. New light curves and period analyses have been used to determine the following general properties of the PPNe variability: (a) periods range from 35 to 160 days for those of F—G spectral types, with much shorter periods (day) found for those of early-B spectral type; (b) there is a correlation between the pulsation period, maximum amplitude, and temperature of the star, with cooler stars pulsating with longer periods and larger amplitudes; (c) similar correlations are found for carbon-rich, oxygen-rich, and lower-metalicity PPNe; and (d) multiple periods are found for all of them, with P2/P1 = 1.0±0.1. New models are needed to exploit these results.

  4. Forty Cases of Insomnia Treated by Multi-output Electric Pulsation and Auricular Plaster Therapy

    Institute of Scientific and Technical Information of China (English)

    Liu Weizhe

    2007-01-01

    @@ The writer has treated 40 cases of insomnia by the method of multi-output electric pulsation in combination with auricular plaster therapy (with a seed of Vaccariae segetalis 王不留行 taped tightly to a particular ear point and pressed) and received satisfactory therapeutic effects. A report follows.

  5. Damage Accumulation in Vertical Breakwaters due to Combined Impact Loading and Pulsating Wave Loads

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Nielsen, Søren R. K.

    1999-01-01

    elasto-plastic oscillator. The pulsating part of the wave loading is modelled as a filtered white noise process, and the impact load is modelled by a filtered Poisson process. It is shown how a distribution function for the accumulated permanent deformations can be obtained. Finally, an illustrative...

  6. On the pulsation mode identification of short-period Galactic Cepheids

    CERN Document Server

    Bono, G; Marconi, M; Fouqué, P

    2001-01-01

    We present new theoretical Period-Radius (PR) relations for first overtone Galactic Cepheids. Current predictions are based on several sequences of nonlinear, convective pulsation models at solar chemical composition (Y=0.28, Z=0.02) and stellar masses ranging from 3.0 to 5.5 Mo. The comparison between predicted and empirical radii of four short-period Galactic Cepheids suggests that QZ Nor and EV Sct are pulsating in the fundamental mode, whereas Polaris and SZ Tau pulsate in the first overtone. This finding supports the mode identifications that rely on the comparison between direct and Period-Luminosity (PL) based distance determinations but it is somewhat at variance with the mode identification based on Fourier parameters. In fact, we find from our models that fundamental and first overtone pulsators attain, for periods ranging from 2.7 to 4 d, quite similar phi_21 values, making mode discrimination from this parameter difficult. The present mode identifications for our sample of Cepheids are strengthene...

  7. The puzzling new class of variable stars in NGC 3766 : old friend pulsators?

    CERN Document Server

    Salmon, S J A J; Reese, D R; Dupret, M -A; Eggenberger, P

    2014-01-01

    The recent variability survey of the NGC 3766 cluster revealed a considerable number of periodic variable stars in a region of the H-R diagram where no pulsation is expected. This region lies between the instability strips of the delta Scuti and SPB stars. Moreover the periods of the new phenomenon, P~0.1-0.7 d, do not allow to associate it a priori to either of these two types of pulsations. Stars in the NGC 3766 cluster are known as fast rotators with rotational velocities typically larger than half of their critical velocity. Rotation can affect both the geometrical properties and period domain of pulsations. It also alters the apparent stellar luminosity through gravity darkening, effect seldom taken considered in theoretical studies of the rotation-pulsation interaction. We explore if both of these effects are able to deliver a consistent interpretation for the observed properties of the "new variables" in NGC 3766: explaining their presence outside the known instability strips and their variability peri...

  8. Search for sdB/WD pulsators in the Kepler FOV

    CERN Document Server

    Silvotti, R; Schuh, S; Castanheira, B; Kjeldsen, H

    2009-01-01

    In this article we present the preliminary results of an observational search for subdwarf B and white dwarf pulsators in the Kepler field of view, performed using the DOLORES camera attached to the 3.6m Telescopio Nazionale Galileo (TNG).

  9. An experimental study of pressure losses in pulsatile flows through rigid and pulsating stenosis.

    Science.gov (United States)

    Rabinovitz, R; Degani, D; Gutfinger, C; Milo, S

    1984-11-01

    The time-dependent pressure curves of a pulsatile flow across rigid and pulsating stenoses were investigated experimentally in a laboratory simulator of the outflow tract of the heart right ventricle. The experiments were performed within the range of physiological conditions of frequency and flow rate. The experimental setup consisted of a closed flow system which was operated by a pulsatile pump, and a test chamber which enabled checking different modes of stenosis. Rigid constrictions were simulated by means of axisymmetric blunt-ended annular plugs with moderate-to-severe area reductions. The pulsating stenosis consisted of a short starling resistor device operated by a pulsating external pressure which was synchronized by the pulsatile flow. It was found that the shape of the time-dependent pressure curve upstream of the stenosis was different in the case of rigid stenosis than in the pulsating one. Potential clinical applications of the work may relate to diagnosis of the type of stenosis in the congenital heart disease known as Tetralogy of Fallot. PMID:6513525

  10. Investigation on Characterizing Heated Pulsating Flows with Hot Wire Anemometers - A Hands-On Approach

    Directory of Open Access Journals (Sweden)

    Marius Alexandru PANAIT

    2014-06-01

    Full Text Available The pulsating heated flows are traditionally a difficult subject to treat with conventional hot wire or film methods. Special factors that complicate matters are flow reversal and non linear flow effects of vortices and wire probe wake disturbances on the heat transfer to the hot film or wire sensor in heated pulsating flows. The presence of these strongly nonlinear and unknown terms leads to great difficulties in calibration of hot film probes in this particular regime. The paper analyses the current state of matters in the field and reports a series of solutions that have been practically tested in a case of a high speed pulsated heated flow. Normally such measurements are made in a non-contact fashion using a LDV system or various visualization techniques but there have been recent attempts to use a constant temperature hot wire anemometer system (CTA.To obtain meaningful calibration for hot wire films in hot pulsating flows, a comparison system on other principles (LDV was used, as well as a specially designed nozzle to replace the calibrator unit that could not be operated with heated fluid due to structural integrity reasons. The method as described below works well for the expected speed range that could be generated using the special nozzle.

  11. HD183648: a Kepler eclipsing binary with anomalous ellipsoidal variations and a pulsating component

    Directory of Open Access Journals (Sweden)

    Derekas A.

    2015-01-01

    Full Text Available KIC 8560861 (HD 183648 is a marginally eccentric (e = 0.05 eclipsing binary with an orbital period of Porb = 31.973 d, exhibiting mmag amplitude pulsations on time scales of a few days. We present the results of the complex analysis of high and medium-resolution spectroscopic data and Kepler Q0 – Q16 long cadence photometry.

  12. Rotation and oblique pulsation in Kepler observations of the roAp star KIC 10483436

    DEFF Research Database (Denmark)

    Balona, L. A.; Cunha, M. S.; Gruberbauer, M.;

    2011-01-01

    Photometry of KIC 10483436 was obtained continuously with 1-min exposures over a 27-d period from the Kepler satellite. The light curve shows rotational variations from surface spots with a period of 4.303 ± 0.002 d, an amplitude of about 6 mmag and eight pulsation frequencies typical of roAp stars...

  13. Evolution and pulsation period change in the Large Magellanic Cloud Cepheids

    CERN Document Server

    Fadeyev, Yuri A

    2013-01-01

    Theoretical estimates of the pulsation period change rates in LMC Cepheids are obtained from consistent calculation of stellar evolution and nonlinear stellar pulsation for stars with initial chemical composition X=0.7, Z=0.008, initial masses 5M_\\odot = 7M_\\odot pulsate in the fundamental mode and the period change rate \\dot\\Pi varies nearly by a factor of two for both crossings of the instability strip. In the period -- period change rate diagram the values of the period and \\dot\\Pi concentrate within the strips, their slope and half--width depending on both the direction of the movement in the HR--diagram and the pulsation mode. For oscillations in the fundamental mode the half-widths of the strip are \\delta\\log\\dot\\Pi = 0.35 and \\delta\\log\\dot\\Pi = 0.2 for the first and the second crossings of the instability strip, respectively. Results of computations are compared with observations of nearly 700 LMC Cepheids. Within existing observational uncertainties of \\dot\\Pi the theoretical dependences of the perio...

  14. Analysis of self-pulsating DBR lasing dynamics with a novel formulation

    DEFF Research Database (Denmark)

    Bardella, Paolo; Detoma, Enrico; Tromborg, Bjarne;

    2005-01-01

    The self-pulsation lasing dynamic of a long cavity integrated BDR laser or of an equivalent external cavity laser (ECL) with strong grating-filtered feedback is studied with a novel time domain integral equation for the electric field. The complex frequency diagram obtained from mode stability an...

  15. Pulsating aurora observed on the ground and in-situ by the Van Allen Probes

    Science.gov (United States)

    Lessard, M.; Cohen, I. J.; Denton, R. E.; Engebretson, M. J.; Kletzing, C.; Wygant, J. R.; Bounds, S. R.; Smith, C. W.; MacDowall, R. J.; Kurth, W. S.

    2013-12-01

    Early observations and theory related to pulsating aurora suggested that the electrons that drive this aurora originate from the equatorial region of the magnetosphere and that a likely process that can scatter these electrons would involve chorus waves. Recent satellite observations during pulsating auroral events have provided important "firsts", including evidence of strong correlations between pulsating auroral patches and in-situ lower-band chorus (THEMIS), as well as correlations with energetic electron precipitation in the vicinity of geosynchronous orbit (GOES). These results provide important information regarding particle dynamics, leading to a question about how the chorus might be driven. We present observations of the Van Allen Probes in conjunction with a pulsating aurora event, as confirmed by observations on the ground. The in-situ data again show the presence of lower-band chorus. However, magnetic and electric field data also show that the wave bursts coincide with an apparent poloidal field-line resonance, begging the question of whether the resonance might be responsible for driving the VLF waves.

  16. Kepler detection of a new extreme planetary system orbiting the subdwarf-B pulsator KIC10001893

    CERN Document Server

    Silvotti, R; Green, E; Fontaine, G; Telting, J H; Ostensen, R H; Van Grootel, V; Baran, A S; Schuh, S; Machado, L Fox

    2014-01-01

    KIC10001893 is one out of 19 subdwarf-B (sdB) pulsators observed by the Kepler spacecraft in its primary mission. In addition to tens of pulsation frequencies in the g-mode domain, its Fourier spectrum shows three weak peaks at very low frequencies, which is too low to be explained in terms of g modes. The most convincing explanation is that we are seeing the orbital modulation of three Earth-size planets (or planetary remnants) in very tight orbits, which are illuminated by the strong stellar radiation. The orbital periods are P1=5.273, P2=7.807, and P3=19.48 hours, and the period ratios P2/P1=1.481 and P3/P2=2.495 are very close to the 3:2 and 5:2 resonances, respectively. One of the main pulsation modes of the star at 210.68 {\\mu}Hz corresponds to the third harmonic of the orbital frequency of the inner planet, suggesting that we see, for the first time in an sdB star, g-mode pulsations tidally excited by a planetary companion. The extreme planetary system that emerges from the Kepler data is very similar ...

  17. EROS differential studies of Cepheids in the Magellanic Clouds : Stellar pulsation, stellar evolution and distance scale

    NARCIS (Netherlands)

    Beaulieu, J. P.; Sasselov, D. D.

    1996-01-01

    Abstract: We present a differential study of 500 Magellanic Cepheids with 3 million measurements obtained as a by-product of the EROS microlensing survey. The data-set is unbiased and provides an excellent basis for a differential analysis between LMC and SMC. We investigate the pulsational properti

  18. Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13

    CERN Document Server

    Fuerst, F; Harrison, F A; Stern, D; Barret, D; Brightman, M; Fabian, A C; Madsen, K K; Middleton, M J; Miller, J M; Pottschmidt, K; Ptak, A; Rana, V

    2016-01-01

    We report the detection of coherent pulsations from the ultraluminous X-ray source NGC 7793 P13. The ~0.42s nearly sinusoidal pulsations were initially discovered in broadband X-ray observations using XMM-Newton and NuSTAR taken in 2016. We subsequently also found pulsations in archival XMM-Newton data taken in 2013 and 2014. The significant (>>5 sigma) detection of coherent pulsations demonstrates that the compact object in P13 is a neutron star with an observed peak luminosity of ~1e40 erg/s, well above the Eddington limit for a 1.4 M_sun accretor. This makes P13 the second ultraluminous X-ray source known to be powered by an accreting neutron star. The pulse period varies between epochs, with a slow but persistent spin up over the 2013-2016 period. This spin-up indicates a magnetic field of B ~ 1.5e12 G, typical of many accreting pulsars. The most likely explanation for the extreme luminosity is a high degree of beaming, however this is difficult to reconcile with the sinusoidal pulse profile.

  19. Two new pulsating low-mass pre-white dwarfs or SX Phoenicis stars?

    Science.gov (United States)

    Corti, M. A.; Kanaan, A.; Córsico, A. H.; Kepler, S. O.; Althaus, L. G.; Koester, D.; Sánchez Arias, J. P.

    2016-03-01

    Context. The discovery of pulsations in low-mass stars opens an opportunity to probe their interiors and determine their evolution by employing the tools of asteroseismology. Aims: We aim to analyse high-speed photometry of SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25 and discover brightness variabilities. In order to locate these stars in the Teff - log g diagram, we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods: To carry out this study, we used the photometric data we obtained for these stars with the 2.15 m telescope at CASLEO, Argentina. We analysed their light curves and applied the discrete Fourier transform (FT) to determine the pulsation frequencies. Finally, we compare both stars in the Teff - log g diagram, with two known pre-white dwarfs and seven pulsating pre-ELM white dwarf stars, δ Scuti, and SX Phe stars Results: We report the discovery of pulsations in SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25. We determine their effective temperature and surface gravity to be Teff = 7972 ± 200 K, log g = 4.25 ± 0.5 and Teff = 7925 ± 200 K, log g = 4.25 ± 0.5, respectively. With these parameters, these new pulsating low-mass stars can be identified with either ELM white dwarfs (with ~0.17 M⊙) or more massive SX Phe stars. We identified pulsation periods of 3278.7 and 1633.9 s for SDSS J145847.02+070754.46 and a pulsation period of 3367.1 s for SDSS J173001.94+070600.25. These two new objects, together with those of Maxted et al. (2013, 2014), indicate the possible existence of a new instability domain towards the late stages of evolution of low-mass white dwarf stars, although their identification with SX Phe stars cannot be discarded. Visiting Astronomer, Complejo Astronómico El Leoncito operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

  20. A survey for pulsations in A-type stars using SuperWASP

    Science.gov (United States)

    Holdsworth, Daniel L.

    2015-12-01

    "It is sound judgement to hope that in the not too distant future we shall be competent to understand so simple a thing as a star." - Sir Arthur Stanley Eddington, The Internal Constitution of Stars, 1926 A survey of A-type stars is conducted with the SuperWASP archive in the search for pulsationally variable stars. Over 1.5 million stars are selected based on their (J-H) colour. Periodograms are calculated for light curves which have been extracted from the archive and cleaned of spurious points. Peaks which have amplitudes greater than 0.5 millimagnitude are identified in the periodograms. In total, 202 656 stars are identified to show variability in the range 5-300 c/d. Spectroscopic follow-up was obtained for 38 stars which showed high-frequency pulsations between 60 and 235 c/d, and a further object with variability at 636 c/d. In this sample, 13 were identified to be normal A-type δ Sct stars, 14 to be pulsating metallic-lined Am stars, 11 to be rapidly oscillating Ap (roAp) stars, and one to be a subdwarf B variable star. The spectra were used not only to classify the stars, but to determine an effective temperature through Balmer line fitting. Hybrid stars have been identified in this study, which show pulsations in both the high- and low-overtone domains; an observation not predicted by theory. These stars are prime targets to perform follow-up observations, as a confirmed detection of this phenomenon will have significant impact on the theory of pulsations in A-type stars. The detected number of roAp stars has expanded the known number of this pulsator class by 22 per cent. Within these results both the hottest and coolest roAp star have been identified. Further to this, one object, KIC 7582608, was observed by the Kepler telescope for 4 yr, enabling a detailed frequency analysis. This analysis has identified significant frequency variations in this star, leading to the hypothesis that this is the first close binary star of its type. The observational

  1. Influence of speed and frequency towards the automotive turbocharger turbine performance under pulsating flow conditions

    International Nuclear Information System (INIS)

    Highlights: • 3D CFD modeling of a turbocharger turbine with pulsating flow. • Characterization based on turbine speed and frequency. • Speed has higher influence on turbine performance compared to frequency. • Detailed localized flow behavior are shown for better understanding. - Abstract: The ever-increasing demand for low carbon applications in automotive industry has intensified the development of highly efficient engines and energy recovery devices. Even though there are significant developments in the alternative powertrains such as full electric, their full deployment is hindered by high costing and unattractive life-cycle energy and emission balance. Thus powertrain based on highly efficient internal combustion engines are still considered to be the mainstream for years to come. Traditionally, turbocharger has been an essential tool to boost the engine power, however in recent years it is seen as an enabling technology for engine downsizing. It is a well-known fact that a turbocharger turbine in an internal combustion engine operates in a highly pulsating exhaust flow. There are numerous studies looking into the complex interaction of the pulsating exhaust gas within the turbocharger turbine, however the phenomena is still not fully integrated into the design stage. Industry practice is still to design and match the turbine to an engine based on steady performance maps. The current work is undertaken with the mind to move one step closer towards fully integrating the pulsating flow performance into the turbocharger turbine design. This paper presents the development efforts and results from a full 3-D CFD model of a turbocharger turbine stage. The simulations were conducted at 30,000 rpm and 48,000 rpm (50% and 80% design speed respectively) for both 20 Hz and 80 Hz pulsating flow inlet conditions. Complete validation procedure using cold-flow experimental data is also described. The temporal and spatial resolutions of the incidence angle at the

  2. Russian Pulsating Mixer Pump Deployment in the Gunite and Associated Tanks at ORNL

    Energy Technology Data Exchange (ETDEWEB)

    Hatchell, Brian K.; Lewis, Ben; Johnson, Marshall A.; Randolph, J. G.

    2001-03-01

    In FY 1998, Pulsating Mixer Pump (PMP) technology, consisting of a jet mixer powered by a reciprocating air supply, was selected for deployment in one of the Gunite and Associated Tanks at Oak Ridge National Laboratory (ORNL) to mobilize settled solids. The pulsating mixer pump technology was identified during FY 1996 and FY 1997 technical exchanges between the U.S. Department of Energy (DOE) Tanks Focus Area Retrieval and Closure program, the DOE Environmental Management International Programs, and delegates from Russia as a promising technology that could be implemented in the DOE complex. During FY 1997, the pulsating mixer pump technology, provided by the Russian Integrated Mining Chemical Company, was tested at Pacific Northwest National Laboratory (PNNL) to observe its ability to suspend settled solids. Based on the results of this demonstration, ORNL and DOE staff determined that a modified pulsating mixer pump would meet project needs for remote sludge mobilization of Gunite tank sludge and reduce the cost of operation and maintenance of more expensive mixing systems. The functions and requirements of the system were developed by combining the results and recommendations from the pulsating mixer pump demonstration at PNNL with the requirements identified by staff at ORNL involved with the remediation of the Gunite and Associated Tanks. The PMP is comprised of a pump chamber, check valve, a working gas supply pipe, a discharge manifold, and four jet nozzles. The pump uses two distinct cycles, fill and discharge, to perform its mixing action. During the fill cycle, vacuum is applied to the pump chamber by an eductor, which draws liquid into the pump. When the liquid level inside the chamber reaches a certain level, the chamber is pressurized with compressed air to discharge the liquid through the jet nozzles and back into the tank to mobilize sludge and settled solids.

  3. Influence of high-latitude geomagnetic pulsations on recordings of broadband force-balanced seismic sensors

    Directory of Open Access Journals (Sweden)

    E. Kozlovskaya

    2012-08-01

    Full Text Available Seismic broadband sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude, where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (GMLAT between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003. The problem may be treated, however, if combined analysis of recordings of co-located seismic and magnetic instruments is used.

  4. Experimental investigation of pulsating heat pipe performance with regard to fuel cell cooling application

    International Nuclear Information System (INIS)

    A pulsating heat pipe (PHP) is a closed loop, passive heat transfer device. Its operation depends on the phase change of a working fluid within the loop. Design and performance testing of a pulsating heat pipe was conducted under conditions to simulate heat dissipation requirements of a proton exchange membrane (PEM) fuel cell stack. Integration of pulsating heat pipes within bipolar plates of the stack would eliminate the need for ancillary cooling equipment, thus also reducing parasitic losses and increasing energy output. The PHP under investigation, having dimensions of 46.80 cm long and 14.70 cm wide, was constructed from 0.3175 cm copper tube. Heat pipes effectiveness was found to be dependent upon several factors such as energy input, types of working fluid and its filling ratio. Power inputs to the evaporator side of the pulsating heat pipe varied from 80 to 180 W. Working fluids tested included acetone, methanol, and deionized water. Filling ratios between 30 and 70 percent of the total working volume were also examined. Methanol outperformed other fluids tested; with a 45 percent fluid fill ratio and a 120 W power input, the apparatus took the shortest time to reach steady state and had one of the smallest steady state temperature differences. The various conditions studied were chosen to assess the heat pipe's potential as cooling media for PEM fuel cells. - Highlights: ► Methanol as a working fluid outperformed both acetone and water in a pulsating heat pipe. ► Performance for the PHP peaked with methanol and a fill ratio of 45 percent fluid to total volume. ► A smaller resistance was associated with a higher power input to the system.

  5. Detection of Geomagnetic Pulsations of the Earth Using GPS-TEC Data

    Science.gov (United States)

    Koroglu, Ozan; Arikan, Feza; Köroǧlu, Meltem; Sabri Ozkazanc, Yakup

    2016-07-01

    The magnetosphere of the Earth is made up of both magnetic fields and plasma. In this layer, plasma waves propagate as Ultra Low Frequency (ULF) waves having mHz scale frequencies. ULF waves are produced due to complicated solar-geomagnetic interactions. In the literature, these ULF waves are defined as pulsations. The geomagnetic pulsations are classified into main two groups as continuous pulsations (Pc) and irregular pulsations (Pi). These pulsations can be determined by ionospheric parameters due to the complex lithosphere-ionosphere-magnetosphere coupling processes. Total Electron Content (TEC) is one of the most important parameters for investigating the variability of ionosphere. Global Positioning System (GPS) provides a cost-effective means for estimating TEC from GPS satellite orbital height of 20,000 km to the ground based receivers. Therefore, the time series of GPS-TEC inherently contains the above mentioned ULF waves. In this study, time series analysis of GPS-TEC is carried out by applying periodogram method to the mid-latitude annual TEC data. After the analysis of GPS-TEC data obtained for GPS stations located in Central Europe and Turkey for 2011, it is observed that some of the fundamental frequencies that are indicators of Pc waves, diurnal and semi-diurnal periodicity and earth-free oscillations can be identified. These results will be used in determination of low frequency trend structure of magnetosphere and ionosphere. Further investigation of remaining relatively low magnitude frequencies, all Pi and Pc can be identified by using time and frequency domain techniques such as wavelet analysis. This study is supported by the joint TUBITAK 115E915 and joint TUBITAK114E092 and AS CR 14/001 projects.

  6. Functional Changes of Diaphragm Type Shunt Valves Induced by Pressure Pulsation

    Science.gov (United States)

    Lee, Chong-Sun; Suh, Chang-Min; Ra, Young-Shin

    Shunt valves used to treat patients with hydrocephalus were tested to investigate influence of pressure pulsation on their flow control characteristics. Our focus was on flow dynamic and functional changes of the small and thin diaphragms in the valves that serve as the main flow control mechanism and are made from silicone elastomer. Firstly, pressure-flow control curves were compared under pulsed and steady flow (without pulsation) conditions. Secondly, functional changes of the valves were tested after a long-term continuous pulsation with a peristaltic pump. Thirdly, flushing procedures selectively conducted by neurosurgeons were simulated with a fingertip pressed on the dome of the valves. As 20cc/hr of flow rate was adjusted at a constant pressure, application of 40mmH2O of pressure pulse increased flow rate through shunt valves more than 60%. As a 90cm length silicone catheter was connected to the valve outlet, increase in the flow rate was substantially reduced to 17.5%. Pressure-flow control characteristics of some valves showed significant changes after twenty-eight days of pressure pulsation at 1.0 Hz under 50.0cc/hr of flow rate. Flushing simulation resulted in temporary decrease in the pressure level. It took three hours to fully recover the normal pressure-flow control characteristics after the flushing. Our results suggest that shunt valves with a thin elastic diaphragm as the main flow control mechanism are sensitive to intracranial pressure pulsation or pressure spikes enough to change their pressure-flow control characteristics.

  7. The Early Outcomes with Titanium Radial Head Implants in the Treatment of Radial Head Comminuted Fractures

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jijun; YANG Shuhua; HU Yong

    2007-01-01

    The study assessed the early functional outcomes with cemented titanium implants of ra- dius in the treatment of comminuted fractures of radial heads. The functional outcomes of arthro- plasty with cemented titanium implants of radius in the treatment of radial head fractures (Mason Type Ⅲ: 6; Mason Type Ⅳ: 4) in l0 consecutive patients (mean age, 38 years) were evaluated over a mean time of 23.7 months (18-31 months). The patients were assessed on the basis of physical ex- amination, functional rating (Mayo) and radiographic findings. The parameters evaluated included motion, stability, pain, and grip strength. Five patients were considered to have excellent results, 4 patients had good results and 1 patient had fairly good results. There were no cases of infection, prosthetic failure, heterotopic ossification or dislocation. When medial collateral ligament was injured, radial head became the main stabilizing structure of the elbow. Titanium radial head implant may provide the stability similar to that of native radial head. We believe that titanium radial head im- plants may be indicated for the Mason Type Ⅲ and Mason Type Ⅳ radial head fractures.

  8. One-year results of cemented bipolar radial head prostheses for comminuted radial head fractures

    Directory of Open Access Journals (Sweden)

    Laun, Reinhold

    2015-12-01

    Full Text Available Introduction: Comminuted radial head fractures (Mason type III continue to pose a challenge to orthopedic surgeons. When internal fixation is not possible, radial head arthroplasty has been advocated as the treatment of choice. The purpose of this retrospective study was to evaluate clinical and radiological short-term results of patients with Mason type III radial head fractures treated with a cemented bipolar radial prosthesis. Methods: Twelve patients received cemented bipolar radial head hemiarthroplasty for comminuted radial head fractures. In all patients a CT scan was obtained prior to surgical treatment to assess all associated injuries. Postoperatively an early motion protocol was applied. All patients were evaluated clinically and radiologically at an average of 12.7 months.Results: According to the Mayo Modified Wrist Score, the Mayo Elbow Performance Score, the functional rating index of Broberg and Morrey, and the DASH Score good to excellent results were obtained. Grip strength and range of motion were almost at the level of the unaffected contralateral side. Patient satisfaction was high, no instability or signs of loosening of the implant, and only mild signs of osteoarthritis were seen.Conclusion: Overall good to excellent short-term results for primary arthroplasty for comminuted radial head fractures were observed. These encouraging results warrant the conduction of further studies with long-term follow-up and more cases to see if these short-term results can be maintained over time.

  9. Phased array antenna on a radial waveguide

    OpenAIRE

    Voronin, E. N.; Emel'chenkov, F. I.; Kotov, Yu. V.; Luk'yanov, A. S.

    2003-01-01

    Numerical and research results of investigation and optimization of the distributive system of the monopulse phased array antenna (PAA) with circular aperture based on the radial waveguide are presented. The research was carried out with decomposition technique using a one term approximation of the induced EMF.

  10. Determining Enzyme Activity by Radial Diffusion

    Science.gov (United States)

    Davis, Bill D.

    1977-01-01

    Discusses advantages of radial diffusion assay in determining presence of enzyme and/or rough approximation of amount of enzyme activities. Procedures are included for the preparation of starch-agar plates, and the application and determination of enzyme. Techniques using plant materials (homogenates, tissues, ungerminated embryos, and seedlings)…

  11. Radial velocities of Planetary Nebulae revisited

    Science.gov (United States)

    Vázquez, Roberto; Ayala, Sandra A.; Wendolyn Blanco Cárdenas, Mónica; Contreras, María E.; Gómez-Muñoz, Marco Antonio; Guillén, Pedro F.; Olguín, Lorenzo; Ramos-Larios, Gerardo; Sabin, Laurence; Zavala, Saúl A.

    2015-08-01

    We present a new determination of radial velocities of a sample of Galactic Planetary Nebulae (PNe) using a systematic method and the same instrumental setting: the long-slit high-dispersion Manchester Echelle Spectrograph (MES) on the 2.1-m telescope at the San Pedro Mártir Observatory (OAN-SPM; Mexico). This project was inspired by the work of Schneider et al. (1983, A&AS, 52, 399), which has been an important reference during the last decades. Radial velocities of gaseous nebulae can be obtained using the central wavelength of a Gaussian fit, even when there is an expansion velocity, as expected in PNe, but with not enough resolution to see a spectral line splitting. We have used the software SHAPE, a morpho-kinematic modeling and reconstruction tool for astrophysical objects (Steffen et al. 2011, IEEE Trans. Vis. Comput. Graphics, 17, 454), to prove that non-uniform density or brightness, on an expanding shell, can lead to mistaken conclusions about the radial velocity. To determine radial velocities, we only use the spectral data in which a spectral line-splitting is seen, avoiding thus the problem of the possible biased one-Gaussian fit. Cases when this method is not recommended are discussed.This project has been supported by grant PAPIIT-DGAPA-UNAM IN107914. MWB is in grateful receipt of a DGAPA-UNAM postdoctoral scholarship. MAG acknowledges CONACYT for his graduate scholarship.

  12. Measurement of wear in radial journal bearings

    NARCIS (Netherlands)

    Ligterink, D.J.; Gee, de A.W.J.

    1996-01-01

    this article, the measurement of wear in radial journal bearings is discussed, where a distinction is made between stationary and non-stationary contact conditions. Starting with Holm/Archard's wear law, equations are derived for the calculation of the specific wear rate k of the bearing material as

  13. Dynamic programming using radial basis functions

    OpenAIRE

    Junge, Oliver; Schreiber, Alex

    2014-01-01

    We propose a discretization of the optimality principle in dynamic programming based on radial basis functions and Shepard's moving least squares approximation method. We prove convergence of the approximate optimal value function to the true one and present several numerical experiments.

  14. Discovery of a magnetic field in the CoRoT hybrid B-type pulsator HD 43317

    OpenAIRE

    Briquet, M.; Neiner, C.; Leroy, B; Pápics, P. I.

    2013-01-01

    Context. A promising way of testing the impact of a magnetic field on internal mixing (core overshooting, internal rotation) in main-sequence B-type stars is to perform asteroseismic studies of a sample of magnetic pulsators. Aims: The CoRoT satellite revealed that the B3IV star HD 43317 is a hybrid SPB/β Cep-type pulsator that has a wealth of pulsational constraints on which one can perform a seismic modelling, in particular, probing the extent of its convective core and mixing processes. M...

  15. Variations in the usage and composition of a radial cocktail during radial access coronary angiography procedures.

    LENUS (Irish Health Repository)

    Pate, G

    2011-10-01

    A survey was conducted of medication administered during radial artery cannulation for coronary angiography in 2009 in Ireland; responses were obtained for 15 of 20 centres, in 5 of which no radial access procedures were undertaken. All 10 (100%) centres which provided data used heparin and one or more anti-spasmodics; verapamil in 9 (90%), nitrate in 1 (10%), both in 2 (20%). There were significant variations in the doses used. Further work needs to be done to determine the optimum cocktail to prevent radial artery injury following coronary angiography.

  16. 叶片圆盘泵压力脉动及叶轮径向力特性分析%Numerical Analysis on Pressure Fluctuation and Radial Force of Disc Pump with Straight Blade

    Institute of Scientific and Technical Information of China (English)

    解永超; 陈国明; 张叶; 孙政委; 张建宾

    2015-01-01

    开展叶片圆盘泵压力脉动相关研究对于了解其瞬态特性,提高其运行稳定性具有重要意义。应用Fluent软件对叶片圆盘泵内部流场进行了三维非定常数值模拟,在外特性试验验证的基础上,分析了设计工况下叶轮内压力、蜗壳内压力、扬程脉动情况以及叶轮径向力变化规律和影响因素。分析结果表明,泵内监测点压力脉动周期取决于叶轮叶片数目,且前、后盖板有叶区内监测点压力脉动规律基本相同,无叶区压力脉动幅值小于有叶区压力脉动幅值,隔舌附近压力脉动幅值最大,且蜗壳入口侧大于出口侧;扬程脉动周期与监测点压力脉动周期相同,当叶片转至隔舌时扬程为极小值,隔舌处于相邻2叶片中间位置时扬程为极大值。叶轮所受径向力变化周期与叶轮转动周期相同,径向力2垂直分量呈正弦规律变化。%Study on pressure fluctuation of disc pump with radial straight blade has a great significance on un⁃derstanding the pump transient characteristics and improving its operating stability�Three⁃dimensional unsteady nu⁃merical simulation has been conducted on the inner flow field of the pump by using Fluent software�Pressure fluctu⁃ations in the impeller and the volute and the pump head pressure fluctuation, as well as the impeller radial force changing law and the influencing factors have been analyzed based on the validation of outer characteristic test�The results show that the pressure pulsation period of the monitoring point within the pump depends on the number of impeller blades�The pressure pulsation at the monitoring points in the front and back cover area with blades is basi⁃cally the same�The pressure pulsation amplitude in the non⁃blade area is smaller�The maximum pressure pulsation amplitude occurs near the volute tongue�The volute inlet side has larger pressure pulsation amplitude than the outlet side

  17. Radial forces analysis and rotational speed test of radial permanent magnetic bearing for horizontal axis wind turbine applications

    Science.gov (United States)

    Kriswanto, Jamari

    2016-04-01

    Permanent magnet bearings (PMB) are contact free bearings which utilize the forces generated by the magnets. PMB in this work is a type of radial PMB, which functions as the radial bearings of the Horizontal Axis Wind Turbine (HAWT) rotor shaft. Radial PMB should have a greater radial force than the radial force HAWT rotor shaft (bearing load). This paper presents a modeling and experiments to calculate the radial force of the radial PMB. This paper also presents rotational speed test of the radial PMB compared to conventional bearings for HAWT applications. Modeling using COMSOL Multiphysics 4.3b with the magnetic fields physics models. Experiments were conducted by measuring the displacement of the rotor to the stator for a given load variation. Results of the two methods showed that the large displacement then the radial force would be greater. Radial forces of radial PMB is greater than radial forces of HAWT rotor shaft. The rotational speed test results of HAWT that used radial PMB produced higher rotary than conventional bearings with an average increase of 87.4%. Increasing rotational speed occured because radial PMB had no friction. HAWT that used radial PMB rotated at very low wind speeds are 1.4 m/s with a torque of 0.043 Nm, while the HAWT which uses conventional bearing started rotating at a wind speed of 4.4 m/s and required higher torque of 0.104 N.

  18. Radial velocity eclipse mapping of exoplanets

    CERN Document Server

    Nikolov, Nikolay

    2015-01-01

    Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter-McLauglin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blue-shifted) or receding (red-shifted) parts of the planet causes a temporal distortion in the planet's spectral line profiles resulting in an anomaly in the planet's radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt and impact factor (i.e. sky-projected planet spin-orbital alignment). In addition, line asymmetrie...

  19. RFQ radial matching sections and fringe fields

    International Nuclear Information System (INIS)

    The entrance radial matching section is an extremely important part of any radio-frequency quadrupole (RFQ) linac. It allows a beam having time-independent characteristics to become adapted to the time-dependent focusing in the RFQ. The matching sections proposed in this paper are defined by a four-term potential function and are very effective over lengths of 3 β lambda or longer. The fringe field at the RFQ exit is mainly of interest because of the time-varying on-axis potential. The beam can either lose or gain energy, depending on the shape of the fringe field. The same four-term potential function can be used for shaping the vanes at the exit so that the fringe fields can be controlled. This formulation also applies to exit radial matching sections, which would be useful if the beam is to enter another RFQ operated at a higher frequency. 4 references, 4 figures

  20. Magnetohydrodynamic stability of plasmas with radial motion

    International Nuclear Information System (INIS)

    The stability of a screw-pinch plasma with radial motion is explored. The linear theory of ideal magnetohydrodynamic (NHD) stability for stationary equilibrium has been generalized to include radial motion. This generalization results in the force operator, F, being non-self-adjoint and the widely used energy principle being no longer useful in this case. Because of this, a set of seven complex, first-order, simultaneous ordinary differential equations needs to be solved to determine the stability. The equations are solved subject to appropriate boundary conditions using the Runge-Kutta-Fehlberg. The eigenvalues for the set of equations are also complex, with the imaginary part of the eigenvalue corresponding to the exponential growth or decay of the instability. While the method derived can be used for any cylindrical equilibrium profiles, the results will be presented for imploding screw-pinch plasmas