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Articles de revues sur le sujet « Pulsatoria »

Auteur : Grafiati
Publié le 9 mars 2023
Mis à jour le 10 mars 2023

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1

Fryč, J., R. Kukla et J. Los. « Possible use of vacuum controlled pulsators for sheep milking machines ». Research in Agricultural Engineering 50, No. 1 (8 février 2012) : 23–27. http://dx.doi.org/10.17221/4922-rae.

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Comparison measurements and evaluation of the suitability of three pulsators for sheep milking machines were carried out, i.e. a prototype made by the manufacturer of the milking parlour of the pulsator ratio 50% (50:50) and two hydraulic pulsators of the Danish manufacturer S.A. Christensen (SAC), models Unipuls-2 of the pulsator ratios 50% (50:50) and 60% (60:40). The specified pulsation rate was 2.5/s(150/min). It was found that the pulsator prototype made by the milking parlour manufacturer slowly passed air, whereby the vacuum in pulsation chambers did not attain the maximum value. Fig. 2 illustrates the operation of this pulsator. Both SAC pulsators had better parameters and their pulsograms are plotted in Figs. 3 and 4. Also the measurements of a liner deformation in dependence on the vacuum in the teatcup pulsation chamber were made based on which the moment of a real liner opening, i.e. at the vacuum of 35 kPa was determined. The results obtained by the experiments carried out can be summed up as follows: As the change in pulsation rate does not affect the time of transition phases “a” and “c”, the intervals “b” and “d” are shorter if the pulsation rate is increased. Interval “b”, i.e. a full liner opening, shortens with the rising rate and extends with the increased value of the pulsator ratio. For this reason higher pulsator ratios should be used at very high pulsation rates. The teatcup operation depends on the physical-mechanical properties of the liner used. On the milking unit measured considerable differences in time take place between the interval “b” and the liner full opening due to a relatively high resistance power of the liner to deformation. The pulsator prototype designed by the milking parlour producer revealed as fully unsuitable based on its pulsogram. As far as the time of the liner opening is concerned, its parameters were worse than on both SAC pulsators, however, we cannot indicate it as unsuitable.
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Burssens, S., D. M. Bowman, C. Aerts, M. G. Pedersen, E. Moravveji et B. Buysschaert. « New β Cep pulsators discovered with K2 space photometry ». Monthly Notices of the Royal Astronomical Society 489, no 1 (16 août 2019) : 1304–20. http://dx.doi.org/10.1093/mnras/stz2165.

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Abstract We present the discovery of three new β Cep pulsators, three new pulsators with frequency groupings, and frequency patterns in a B3Ib star, all of which show pulsations with frequencies as high as about 17 d−1, with K2 space mission photometry. Based on a Fourier analysis and iterative pre-whitening, we present a classification and evaluate the potential for asteroseismic modelling. We include the lists of pulsation frequencies for three new β Cep pulsators, CD-28 12286, CD-27 10876, LS 3978, and additional pulsation mode frequencies for the known β Cep pulsator HD 164741. In addition, we characterize the regular frequency spacing found in the new pulsator HD 169173, and discuss its origin. We place the newly discovered variables in a colour–magnitude diagram using parallaxes from GaiaDR2 (second data release), showcasing their approximate location in the massive star domain. The identified frequency lists of these multiperiodic pulsators are a good starting point for future forward seismic modelling, after identification of at least one pulsation frequency from high-resolution time-series spectroscopy and/or multicolour photometry.
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Salazar-Vallejo, Sergio I., Patrick Gillet et Victor Surugiu. « How false is Nereis falsa (Annelida, Phyllodocida, Nereididae) ? » Revista de Biología Tropical 65, no 3 (23 mars 2017) : 847. http://dx.doi.org/10.15517/rbt.v65i3.26635.

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There are many taxonomic problems in polychaete species names and solving confusing or inadequate taxonomic procedures is both time-demanding and extremely important. Our objective in this contribution was to analyse what is the current taxonomic situation for Nereis falsa de Quatrefages, 1866; it was based upon Nereis pulsatoria? Rathke, 1837 from the Black Sea, and it is currently regarded as having a very wide distribution. The species has been collected from different benthic substrates and even can be found on floating objects or marine turtles. Nereis falsa has been recorded from the Mediterranean Sea, the Eastern Atlantic along Africa, the Western Atlantic (Gulf of Mexico, Caribbean Sea, Brazil), and the Indian Ocean. However, despite the fact N. falsa was proposed as a species from the Black Sea, it has not yet been found there. How can we explain that a species is able to attain a very wide distribution and yet be missing from its type locality? After a careful study of previous publications and with our understanding of the systematics of nereidid polychaetes, we clarify the current situation by examining several related species and pointed out some nomenclatural issues. Our analysis indicates there is more than one species included under the same name, and in this contribution we propose some means to promote discussion and actions, and suggest some basic research for solving this issue.
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Westwood, J. O. « XV. Observations upon the structural Character of the Death Watch (Atropos pulsatoria), with Description of a new British Genus in the Family to which it belongs ». Transactions of the Royal Entomological Society of London 4, no 1 (24 avril 2009) : 71–72. http://dx.doi.org/10.1111/j.1365-2311.1845.tb01339.x.

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Yatsunskyi, Petro. « THE RESULTS OF RESEARCH PNEUMATIC ELECTROMAGNETIC PULSATOR COMBINED WITH COLLECTOR ». Mokslas - Lietuvos ateitis 14 (1 février 2022) : 1–4. http://dx.doi.org/10.3846/mla.2022.15162.

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This article demonstrates the results of experimental research one of the pulsators. Its main difference from others is a pneumatic electromagnetic pulsator in combination with a collector. Therefore, this article describes in detail the process of studying the pulsator. The planned experiment was carried out on by Factorial experiments with multiple factors. The influence of factors (the ripple frequency n, the milk ejection q and the ratio between strokes t/T) on the vacuum pressure in the inter wall chamber of teat cups was studied. The regression equation of the dependence response criterion on factors is modeled. This dependence is demonstrated graphically. Also there is a contour graph which is for more detailed information.
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Kurtz, D. W., G. Handler, S. A. Rappaport, H. Saio, J. Fuller, T. Jacobs, A. Schmitt et al. « The single-sided pulsator CO Camelopardalis ». Monthly Notices of the Royal Astronomical Society 494, no 4 (13 avril 2020) : 5118–33. http://dx.doi.org/10.1093/mnras/staa989.

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ABSTRACT CO Cam (TIC 160268882) is the second ‘single-sided pulsator’ to be discovered. These are stars where one hemisphere pulsates with a significantly higher amplitude than the other side of the star. CO Cam is a binary star comprised of an Am δ Sct primary star with Teff = 7070 ± 150 K, and a spectroscopically undetected G main-sequence secondary star. The dominant pulsating side of the primary star is centred on the L1 point. We have modelled the spectral energy distribution combined with radial velocities, and independently the TESS light curve combined with radial velocities. Both of these give excellent agreement and robust system parameters for both stars. The δ Sct star is an oblique pulsator with at least four low radial overtone (probably) f modes with the pulsation axis coinciding with the tidal axis of the star, the line of apsides. Preliminary theoretical modelling indicates that the modes must produce much larger flux perturbations near the L1 point, although this is difficult to understand because the pulsating star does not come near to filling its Roche lobe. More detailed models of distorted pulsating stars should be developed. These newly discovered single-sided pulsators offer new opportunities for astrophysical inference from stars that are oblique pulsators in close binary stars.
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Lashlee, Taylor, Adrienne DiFoggio, Pablo Jarrin-Yepez, Heather Schwartz, Margarita Colburn, Andrew Cushing et Tulio Prado. « Breeding soundness examination in a clouded leopard ». Clinical Theriogenology 14, no 2 (1 juin 2022) : 98–101. http://dx.doi.org/10.58292/ct.v14.9284.

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A 3-year male clouded leopard was presented to the University of Tennessee College of Veterinary Medicine Theriogenology servicesfor a breeding soundness examination. On physical examination, the left testis felt abnormally small. On ultrasonography,no abnormalities were observed; testis and prostate were of normal size. Semen was collected with a pulsator electroejaculatorand a ram electroejaculator probe (commonly used to collect semen in small ruminants). The purpose of using this electroejaculatorand probe was to determine if they could be used to collect semen from a clouded leopard. Using manual settings with thisdevice we collected ~ 0.2 - 0.3 ml of semen. Motility and morphology of sperm were acceptable. We concluded that the PulsatorIV electroejaculator and ram probe can be used to collect semen as part of breeding soundness evaluation in a clouded leopard.
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8

Byrne, Conor M., et C. Simon Jeffery. « Pulsation in faint blue stars ». Monthly Notices of the Royal Astronomical Society 492, no 1 (11 décembre 2019) : 232–44. http://dx.doi.org/10.1093/mnras/stz3486.

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ABSTRACT Following the discovery of blue large-amplitude pulsators (BLAPs) by the OGLE survey, additional hot, high-amplitude pulsating stars have been discovered by the Zwicky Transient Facility. It has been proposed that all of these objects are low-mass pre-white dwarfs and that their pulsations are driven by the opacity of iron-group elements. With this expanded population of pulsating objects, it was decided to compute a sequence of post-common-envelope stellar models using the mesa stellar evolution code and to examine the pulsation properties of low-mass pre-white dwarfs using non-adiabatic analysis with the gyre stellar oscillation code. By including the effects of atomic diffusion and radiative levitation, it is shown that a large region of instability exists from effective temperatures of 30 000 K up to temperatures of at least 50 000 K and at a wide range of surface gravities. This encompasses both groups of pulsator observed so far, and confirms that the driving mechanism is through iron group element opacity. We make some conservative estimates about the range of periods, masses, temperatures, and gravities in which further such pulsators might be observed.
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Karczmarek, P. « Contamination of RR Lyrae stars from Binary Evolution Pulsators ». Advances in Astronomy and Space Physics 5, no 1 (2015) : 24–28. http://dx.doi.org/10.17721/2227-1481.5.24-28.

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A Binary Evolution Pulsator (BEP) is a low-mass (0.26 𝔐☉) member of a binary system, which pulsates as a result of a former mass transfer to its companion. The BEP mimics RR Lyrae-type pulsations, but has completely different internal structure and evolution history. Although there is only one known BEP (OGLE-BLG-RRLYR-02792), it has been estimated that approximately 0.2% of objects classified as RR Lyrae stars can be undetected Binary Evolution Pulsators. In the present work, this contamination value is re-evaluated using the population synthesis method. The output falls inside a range of values dependent on tuning the parameters in the StarTrack code, and varies from 0.06% to 0.43%.
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Gaulme, Patrick, et Joyce A. Guzik. « Systematic search for stellar pulsators in the eclipsing binaries observed by Kepler ». Astronomy & ; Astrophysics 630 (27 septembre 2019) : A106. http://dx.doi.org/10.1051/0004-6361/201935821.

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Eclipsing binaries (EBs) are unique targets for measuring precise stellar properties and can be used to constrain stellar evolution models. In particular, it is possible to measure masses and radii of both components of a double-lined spectroscopic EB at the percent level. Since the advent of high-precision photometric space missions (MOST, CoRoT, Kepler, BRITE, TESS), the use of stellar pulsation properties to infer stellar interiors and dynamics constitutes a revolution for studies of low-mass stars. The Kepler mission has led to the discovery of thousands of classical pulsators such as δ Scuti and solar-like oscillators (main sequence and evolved), but also almost 3000 EBs with orbital periods shorter than 1100 days. We report the first systematic search for stellar pulsators in the entire Kepler EB catalog. The focus is mainly aimed at discovering δ Scuti, γ Doradus, red giant, and tidally excited pulsators. We developed a data inspection tool (DIT) that automatically produces a series of plots from the Kepler light curves that allows us to visually identify whether stellar oscillations are present in a given time series. We applied the DIT to the whole Kepler EB database and identified 303 systems whose light curves display oscillations, including 163 new discoveries. A total of 149 stars are flagged as δ Scuti (100 from this paper), 115 as γ Doradus (69 new), 85 as red giants (27 new), and 59 as tidally excited oscillators (29 new). There is some overlap among these groups, as some display several types of oscillations. Despite the likelihood that many of these systems are false positives, for example, when an EB light curve is blended with a pulsator, this catalog gathers a vast sample of systems that are valuable for a better understanding of stellar evolution.
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11

Evans, Nancy Remage. « Recent Results on Binary Cepheids ». International Astronomical Union Colloquium 139 (1993) : 398–405. http://dx.doi.org/10.1017/s0252921100118056.

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AbstractIUE observations of hot companions of Cepheids have been used to determine the temperatures of the companions. For companions on the ZAMS, the temperatures can be used to determine the luminosity of the Cepheids from the inferred absolute magnitude of the companion. The accuracy of this method is comparable to the accuracy of calibration using Cepheids in clusters. An over-tone pulsator (SU Cas) has been identified by this technique. The luminosity of the double mode pulsator Y Car agrees with that from the PLC, confirming that is a normal Population I Cepheid. The variation of the width of the instability strip (as a function of luminosity) in the HR diagram is confirmed, and overtone and double mode pulsators are shown to be near the blue edge of the instability strip. Comparison between variables and nonvariables in the HR diagram (from IUE and cluster studies) shows very little overlap. The shape of the observed instability region may be determined both by the boundary between the variables and nonvariables and also the location of the tips of the blue loops of evolutionary tracks. Finally, eight Cepheids with hot companions which are evolved beyond the ZAMS have been studied. Half the systems are matched well by evolutionary tracks with little or no core convective overshoot near the main sequence. At least two and possibly four systems, however, cannot be matched by current isochrones.
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Winget, D. E., et C. F. Claver. « Discovery of the sixth DBV Star : CBS 114 ». International Astronomical Union Colloquium 114 (1989) : 290–92. http://dx.doi.org/10.1017/s0252921100099735.

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Though widely spread across the H-R diagram the compact pulsators have much in common. All are multi-periodic, and most have extremely complex light curves. All appear to be pulsating in nonradial g-modes, with temperature variations responsible for the bulk of the light modulations. The g-modes are global in nature and, typically, many are excited in each pulsator, so they are a rich source of seismological information about the interior regions of the white dwarf stars.The pulsating DB white dwarf stars (DBV’s) form one of the three distinct classes of pulsating compact objects currently known. We find these classes nearly uniformly distributed in log Te spanning virtually the whole range of the white dwarf cooling sequence, from the hot DOV stars at log Te ~ 5 to the DAV (ZZ Ceti) stars at log Te ~ 4; the DBV stars, with logTe ~ 4.5, fall in the middle.
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13

Byrne, C. M., E. R. Stanway et J. J. Eldridge. « Binary evolution pathways of blue large-amplitude pulsators ». Monthly Notices of the Royal Astronomical Society 507, no 1 (24 juillet 2021) : 621–31. http://dx.doi.org/10.1093/mnras/stab2115.

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ABSTRACT Blue large-amplitude pulsators (BLAPs) are a recently discovered class of pulsating star, believed to be proto-white dwarfs, produced by mass stripping of a red giant when it has a small helium core. An outstanding question is why the stars in this class of pulsator seem to form two distinct groups by surface gravity, despite predictions that stars in the gap between them should also pulsate. We use a binary population synthesis model to identify potential evolutionary pathways that a star can take to become a BLAP. We find that BLAPs can be produced either through common envelope evolution or through Roche lobe overflow, with a main-sequence star or an evolved compact object being responsible for the envelope stripping. The mass distribution of the inferred population indicates that fewer stars would be expected in the range of masses intermediate to the two known groups of pulsators, suggesting that the lack of observational discoveries in this region may be a result of the underlying population of pre-white dwarf stars. We also consider metallicity variation and find evidence that BLAPs at Z = 0.010 (half-solar) would be pulsationally unstable and may also be more common. Based on this analysis, we expect the Milky Way to host around 12 000 BLAPs and we predict the number density of sources expected in future observations such as the Legacy Survey of Space and Time at the Vera Rubin Observatory.
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Fontaine, G., P. Brassard, P. Bergeron et F. Wesemael. « White Dwarf Seismology at the Université de Montréal ». International Astronomical Union Colloquium 139 (1993) : 120. http://dx.doi.org/10.1017/s0252921100117063.

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Over the last several years, we have developed a comprehensive program aimed at better understanding the properties of pulsating DA white dwarfs (or ZZ Ceti stars). These stars are nonradial pulsators of the g-type, and their study can lead to inferences about their internal structure. For instance, the period spectrum of a white dwarf is most sensitive to its vertical chemical stratification, and one of the major goals of white dwarf seismology is to determine the thickness of the hydrogen layer that sits on top of a star. This can be done, in principle, by comparing in detail theoretical period spectra with the periods of the observed excited modes. Likewise, because the cooling rate of a white dwarf is very sensitive to the specific heat of its core material (and hence to its composition), it is possible to infer the core composition through measurements and interpretations of rates of period change in a pulsator.
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Kudzys, Algirdas. « CRACKING AND BEARING CAPACITY OF REPAIRED REINFORCED CONCRETE WALL-FLOOR JOINTS/SUREMONTUOTŲ MONOLITINIŲ SIENŲ IR PERDANGŲ SANDŪRŲ PLEIŠĖJIMAS IR LAIKOMOJI GALLA ». JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 3, no 11 (30 septembre 1997) : 24–29. http://dx.doi.org/10.3846/13921525.1997.10531349.

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Nagrinėjamos supleišėjusių ar kitaip pažeistų pastatų laikančių jų konstrukcijų bei jų sandūrų atstatymo ir remonto problemos. Jos ypač svarbios dėi tos priežasties, kad realaus pastato suremontuotų konstrukcijų laikomosios galios įvertinimas yra labai sudėtingas. Neardančiais bandymais pakankamai tiksliai galima nustatyti medžiagų fizinesmechanines savybes, tačiau konstrukcijos stiprumo įvertinimas negali būti patikimas, neatlikus laboratorinių eksperimentų su natūralaus dydžio modeliais. Eksperimentinių tyrimų metu buvo išbandyti daugiaaukščių gyvenamųjų namų gelžbetoninių monolitinių sienų ir kompleksinių perdangų (surenkama 60 mm storio gelžbetoninė plokštė monolitinama iš 76 mm diametro plastmasinių vamzdžių suformuojant tuštumas ir betonuojant kartu su sienų elementais) sandūrų modeliai (1 pav.). Pleišėtumo, irimo pobūdžio ir stiprumo analizei buvo naudojami natūralaus dydžio šeši pastato vidinių sienų ir perdangų sandūrų mazgai bei du išorinių sienų ir perdangos bandiniai (2 pav.). Pagrindiniai kintamieji eksperimentų metu buvo sienų ir perdangų armatūros kiekis bei vertikaliosios apkrovos dydis (1 lentelė). Suremontavus sandūrų bandinius (injektavus po spaudimu epoksidinę dervą į pažeistas konstrukcijų zonas) po anksčiau atliktų laikomosios galios nustatymo eksperimentinių tyrimų, jie buvo pakartotinai paveikti kintamosiomis vertikaliosiomis ir horizontaliosiomis apkrovomis. Apkrovimui buvo panaudota speciali įranga su apkrovos pulsatoriais laikantis apkrovimo eiliškumo, koks buvo taikytas bandant naujus bandinius (3 pav.). Horizontalioji apkrova buvo perduodama per reversing pulsatorių kontroliuojant poslinkio R dydį (4 pav.). Bandinių irimo pobūdis, pleišėtumas bei stiprumas buvo palyginti su naujų mazgų bandymo rezultatais (5 pav., 2 lentelė).
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Wołosz, Krzysztof J. « Energy Analysis of an Industrial Nozzle with Variable Outlet Conditions during Compressible and Transient Airflow ». Energies 15, no 3 (24 janvier 2022) : 841. http://dx.doi.org/10.3390/en15030841.

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The nozzle which is applied in industrial pneumatic pulsators is studied. It is a part of the system for unclogging the drains and outlets of silos and hoppers for loose materials. The nozzle is required to achieve the lowest level of energy losses while directing the airflow, which impacts the loose material bed. The energy rate transferred into the bed depends on the temperature and pressure differences between the inlet and outlet of the nozzle. In this study, the available energy is determined assuming compressible and transient airflow through the nozzle, which is a part of the industrial pneumatic pulsator. Numerical simulations are performed using the OpenFOAM CFD toolbox. Energy analysis is carried out by using Reynolds Transport Theorem for specific energy for the variable temperature inside the silo on the basis of CFD results. In fact, the air parameters at the outlet of the nozzle are the ones inside the silo. The study showed that the design of the nozzle is not very sufficient from an energetic point of view.
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Wolosz, Krzysztof J., et Jacek Wernik. « Three-Dimensional Flow Optimization of a Nozzle with a Continuous Adjoint ». International Journal of Nonlinear Sciences and Numerical Simulation 16, no 3-4 (1 juin 2015) : 151–56. http://dx.doi.org/10.1515/ijnsns-2014-0011.

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AbstractThe article presents results of multi-criteria optimization of air nozzle topology. The optimization in the CFD has been recently developed since equations of flow in porous media were applied among others governing equations. Optimization is a seeking for extremum of an objective function with respect to the function constraints. With this definition in mind, the optimization by using a continuous adjoint for the current cases is a finding such channel topology which minimizes for example pressure or energy loss when the constraints of objective function are in the form of flow governing equations of momentum and continuity. This methodology of optimization makes a design process faster comparing to the methods related to Design of Experiments (DoE). However, for the sake of flow governing equations nonlinearity, the continuous adjoint method can be successfully applied only in relatively simply and steady-state cases. The reason is of possibility of finding the global extremum of the objective function only for that kind of cases. The results of optimization of two selected cases are presented in the article and show advantages and limitations of the method applied. The continuous adjoint simulation results indicate the nozzles design directions and can be applied in industry with limited reliability. The object of research reported in the article is the nozzle which is augmented equipment used with a pneumatic pulsator. The pulsators are devices that utilize an air stream to destruct vaults created in loose material structure. The pulsator productivity equipped with a nozzle depends on outlet pressure. Therefore, the optimization problem was stated so that pressure loss is to be as low as possible.
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Wołosz, Krzysztof J., et Jacek Wernik. « ICEEM07 : Three-Dimensional Flow Optimization of a Pneumatic Pulsator Nozzle with a Continuous Adjoint ». International Journal of Nonlinear Sciences and Numerical Simulation 16, no 1 (1 février 2015) : 3–9. http://dx.doi.org/10.1515/ijnsns-2014-0043.

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AbstractThe article presents results of multi-criteria optimization of air nozzle topology. The optimization in the Computational Fluid Dynamics (CFD) has been recently developed since equations of flow in porous media were applied among others governing equations. Optimization is a seeking for extremum of an objective function with respect to the function constraints. With this definition in mind, the optimization by using a continuous adjoint for the current cases is a finding such channel topology which minimizes for example pressure or energy loss when the constraints of objective function are in the form of flow governing equations of momentum and continuity. This methodology of optimization makes a design process faster comparing to the methods related to Design of Experiments (DoE). However, for the sake of flow governing equations nonlinearity, the continuous adjoint method can be successfully applied only in relatively simply and steady-state cases. The method consists in seeking of a global extremum of objective function. This extremum can sometimes be find in only simple and stationary events. The results of optimization of two selected cases are presented in the article and show advantages and limitations of the method applied. The continuous adjoint simulation results indicate the nozzles design directions and can be applied in industry with limited reliability. The object of research reported in the article is the nozzle which is augmented equipment used with a pneumatic pulsator. The pulsators are devices that utilize an air stream to destruct vaults created in loose material structure. The pulsator productivity equipped with a nozzle depends on outlet pressure. Therefore, the optimization problem was stated so that pressure loss is to be as low as possible.
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Charpinet, S., P. Brassard, G. Fontaine, V. Van Grootel, W. Zong, N. Giammichele, U. Heber et al. « TESS first look at evolved compact pulsators ». Astronomy & ; Astrophysics 632 (décembre 2019) : A90. http://dx.doi.org/10.1051/0004-6361/201935395.

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Context. The TESS satellite was launched in 2018 to perform high-precision photometry from space over almost the whole sky in a search for exoplanets orbiting bright stars. This instrument has opened new opportunities to study variable hot subdwarfs, white dwarfs, and related compact objects. Targets of interest include white dwarf and hot subdwarf pulsators, both carrying high potential for asteroseismology. Aims. We present the discovery and detailed asteroseismic analysis of a new g-mode hot B subdwarf (sdB) pulsator, EC 21494−7018 (TIC 278659026), monitored in TESS first sector using 120-s cadence. Methods. The TESS light curve was analyzed with standard prewhitening techniques, followed by forward modeling using our latest generation of sdB models developed for asteroseismic investigations. By simultaneously best-matching all the observed frequencies with those computed from models, we identified the pulsation modes detected and, more importantly, we determined the global parameters and structural configuration of the star. Results. The light curve analysis reveals that EC 21494−7018 is a sdB pulsator counting up to 20 frequencies associated with independent g-modes. The seismic analysis singles out an optimal model solution in full agreement with independent measurements provided by spectroscopy (atmospheric parameters derived from model atmospheres) and astrometry (distance evaluated from Gaia DR2 trigonometric parallax). Several key parameters of the star are derived. Its mass (0.391 ± 0.009 M⊙) is significantly lower than the typical mass of sdB stars and suggests that its progenitor has not undergone the He-core flash; therefore this progenitor could originate from a massive (≳2 M⊙) red giant, which is an alternative channel for the formation of sdBs. Other derived parameters include the H-rich envelope mass (0.0037 ± 0.0010 M⊙), radius (0.1694 ± 0.0081 R⊙), and luminosity (8.2 ± 1.1 L⊙). The optimal model fit has a double-layered He+H composition profile, which we interpret as an incomplete but ongoing process of gravitational settling of helium at the bottom of a thick H-rich envelope. Moreover, the derived properties of the core indicate that EC 21494−7018 has burnt ∼43% (in mass) of its central helium and possesses a relatively large mixed core (Mcore = 0.198 ± 0.010 M⊙), in line with trends already uncovered from other g-mode sdB pulsators analyzed with asteroseismology. Finally, we obtain for the first time an estimate of the amount of oxygen (in mass; X(O)core = 0.16+0.13−0.05) produced at this stage of evolution by an helium-burning core. This result, along with the core-size estimate, is an interesting constraint that may help to narrow down the still uncertain 12C(α, γ)16O nuclear reaction rate.
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Myslinski, Adam, Bazyli Semeniuk et Teresa Kasprzycka-Guttman. « Electrodynamic pulsator ». Industrial & ; Engineering Chemistry Research 32, no 11 (novembre 1993) : 2934–36. http://dx.doi.org/10.1021/ie00023a067.

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Randall, Suzanna, Gilles Fontaine, Pierre Brassard et Stéphane Charpinet. « Modelling compact pulsators ». Journal of Physics : Conference Series 118 (1 octobre 2008) : 012022. http://dx.doi.org/10.1088/1742-6596/118/1/012022.

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Østerås, Olav, Odd Rønningen, Leiv Sandvik et Steinar Waage. « Field studies show associations between pulsator characteristics and udder health ». Journal of Dairy Research 62, no 1 (février 1995) : 1–13. http://dx.doi.org/10.1017/s0022029900033628.

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SummaryFour different field studies including 64, 140, 850 and 180 herds were used to investigate the association between pulsator characteristics and udder health. The results indicate that the best udder health is found in herds with a d phase > 330 ms and a pulsation rate > 55 min-1. A d phase of < 250 ms was associated with significant elevation in bulk milk somatic cell count, a higher incidence of acute clinical mastitis and a higher frequency of cows having mastitis associated with major pathogens (mainly Staphylococcus aureus) as compared with a d phase of > 331 ms. There was also a significant positive association between a shorter d phase and a high incidence of teat lesions needing veterinary treatment. Herds having no such teat lesions had pulsators with significantly longer d phase than herds with teat lesions (300 ms ν. 288 ms). These results strongly suggest that in high-line milking machines the d phase should not be as short as 250 ms and should preferably be ∼ 300 ms, and the pulsation rate should be at least > 55 cycles min-1. There was a strong relationship between the effect of d phase and the rate of pulsation.
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Antoci, V., M. S. Cunha, D. M. Bowman, S. J. Murphy, D. W. Kurtz, T. R. Bedding, C. C. Borre et al. « The first view of δ Scuti and γ Doradus stars with the TESS mission ». Monthly Notices of the Royal Astronomical Society 490, no 3 (7 octobre 2019) : 4040–59. http://dx.doi.org/10.1093/mnras/stz2787.

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ABSTRACT We present the first asteroseismic results for δ Scuti and γ Doradus stars observed in Sectors 1 and 2 of the TESS mission. We utilize the 2-min cadence TESS data for a sample of 117 stars to classify their behaviour regarding variability and place them in the Hertzsprung–Russell diagram using Gaia DR2 data. Included within our sample are the eponymous members of two pulsator classes, γ Doradus and SX Phoenicis. Our sample of pulsating intermediate-mass stars observed by TESS also allows us to confront theoretical models of pulsation driving in the classical instability strip for the first time and show that mixing processes in the outer envelope play an important role. We derive an empirical estimate of 74 per cent for the relative amplitude suppression factor as a result of the redder TESS passband compared to the Kepler mission using a pulsating eclipsing binary system. Furthermore, our sample contains many high-frequency pulsators, allowing us to probe the frequency variability of hot young δ Scuti stars, which were lacking in the Kepler mission data set, and identify promising targets for future asteroseismic modelling. The TESS data also allow us to refine the stellar parameters of SX Phoenicis, which is believed to be a blue straggler.
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Dziembowski, Wojciech A. « The Opacity Driven Pulsators ». Highlights of Astronomy 10 (1995) : 584–85. http://dx.doi.org/10.1017/s1539299600012156.

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The opacity mechanism is the only well understood excitation mechanism of observed stellar oscillations. The driving effect arises due the a specific form of the opacity perturbation which leads to a conversion of the radiative flux energy into kinetic energy of oscillations. In 1963 Baker and Kippenhan demonstrated that the opacity mechanism acting in the Hell ionization zone is the cause of the Cepheid pulsations. Subsequently it has been shown that the same mechanism works in a large variety of stars. There are three opacity bumps that play a role in pulsation excitation in various types of objects - one connected with the H ionization, one connected with He II ionization zone - and one, discovered quite recently by Iglesias, Rogers & Wilson (1988), caused by a large agglomeration of metal element (mostly Fe) lines.
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Bednarek, Stanisław. « Sterowany elektromagnetycznie pulsator akustyczny ». PRZEGLĄD ELEKTROTECHNICZNY 1, no 10 (3 octobre 2022) : 314–19. http://dx.doi.org/10.15199/48.2022.10.69.

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Handler, G. « ”Hybrid” pulsators – fact or fiction ? » Communications in Asteroseismology 159 (2009) : 42–44. http://dx.doi.org/10.1553/cia159s42.

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Dziembowski, W. A. « Asteroseismology of rapidly rotating pulsators ». Proceedings of the International Astronomical Union 5, H15 (novembre 2009) : 360–61. http://dx.doi.org/10.1017/s1743921310009804.

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AbstractOscillation frequencies were determined for a number of rapidly rotating main sequence stars. However, real seismic probing is still ahead of us. I review here tools that we have for modeling pulsation in rotating stars and their potential application to seismic sounding.
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Østensen, R., U. Heber, R. Silvotti, J. E. Solheim, S. Dreizler et H. Edelmann. « Four new subdwarf B pulsators ». Astronomy & ; Astrophysics 378, no 2 (novembre 2001) : 466–76. http://dx.doi.org/10.1051/0004-6361:20011218.

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Mantegazza, L., et E. Poretti. « First overtone pulsators among Cepheids ». International Astronomical Union Colloquium 139 (1993) : 370. http://dx.doi.org/10.1017/s0252921100117877.

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The Fourier decomposition has been successfully applied to several classes of pulsating variables. Antonello and Poretti (1986) and Antonello et al. (1990a) applied it to the Cepheids with P < 8 d. The latter authors redefined the s – Cepheids a Population I Cepheids that do not follow the Hertzsprung progression, but have progression of their own. The same authors proposed a new denomination (Antonell et al., 1990b): C-a stars to indicate the Classical Cepheids and C-b stars to indicate the redefined s–Cepheids.The new photometric data obtained at La Silla and Merate Observatories (Mantegazza and Poretti, 1992) increase the evidence of a separation of Cepheids into two well defined subclasses on the basis of the Fourier parameters of their light curves.In the ϕ21 – P plane, the s– and Classical Cepheids are characterized by two sequences well separated for P<5.5 d.
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Kovács, G. « Nonradial Pulsations in Classical Pulsators ». International Astronomical Union Colloquium 185 (2002) : 396–403. http://dx.doi.org/10.1017/s0252921100016614.

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AbstractRecent analyses of photometric data on globular clusters and galaxies enabled us to study more closely the long-periodic amplitude/phase modulation (Blazhko effect) in classical variables. In the frequency spectra of these stars we see either a doublet or an equally-spaced triplet with a very small frequency separation close to the main component. None of the available theoretical models are able to explain this behavior without invoking some form of nonradial pulsation. In this review we describe the observational status of the Blazhko variables, and discuss the limits of the applicability of the current models to these stars.
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Randall, S. K., G. Fontaine, S. Charpinet, V. Van Grootel et P. Brassard. « Origin and pulsation of hot subdwarfs ». Proceedings of the International Astronomical Union 9, S301 (août 2013) : 289–96. http://dx.doi.org/10.1017/s1743921313014476.

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AbstractWe briefly introduce hot subdwarfs and their evolutionary status before discussing the different types of known pulsators in more detail. Currently, at least six apparently distinct types of variable are known among hot subdwarfs, encompassing p- as well as g-mode pulsators and objects in the Galactic field as well as in globular clusters. Most of the oscillations detected can be explained in terms of an iron opacity mechanism, and quantitative asteroseismology has been very successful for some of the pulsators. In addition to helping constrain possible evolutionary scenarios, studies focussing on stellar pulsations have also been used to infer planets and characterize the rotation of the host star.
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Østensen, R. H., R. Silvotti, S. Charpinet, R. Oreiro, G. Handler, E. M. Green, S. Bloemen et al. « First Kepler results on compact pulsators - I. Survey target selection and the first pulsators ». Monthly Notices of the Royal Astronomical Society 409, no 4 (4 novembre 2010) : 1470–86. http://dx.doi.org/10.1111/j.1365-2966.2010.17366.x.

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Przybilla, Norbert, et Maria-Fernanda Nieva. « The chemical composition of β Cephei and hybrid pulsators in the solar neighbourhood ». Proceedings of the International Astronomical Union 11, A29B (août 2015) : 485–88. http://dx.doi.org/10.1017/s1743921316005949.

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Abstractβ Cephei variables are the most prominent pulsators among the massive stars on the upper main sequence, extending into the class of the rare hybrid β Cephei-SPB pulsators in the overlap region with the instability strip of the Slowly Pulsating B-stars. While the κ-mechanism has been identified as the driver of the pulsations, a comprehensive explanation of the excitation of the observed p- and g-modes is still lacking. In particular, the instability regions for these main-sequence B-type pulsators are still not fully consistent with any current opacity calculations. We have determined tight observational constraints on the chemical composition of a sample of β Cephei and hybrid pulsators in the solar neighbourhood, covering all elements with abundances log (X/H) + 12 > 7.3. The star sample turns out to be chemically homogeneous, with a metallicity Z ≈ 0.014 and a non-solar abundance mix. The availability of accurate and precise abundances eliminates one of the two variables in the opacity calculations for asteroseismic applications, allowing to focus on (missing) atomic data.
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Beaulieu, J. P. « EROS : Short Period Cepheids in the Bar of the LMC ». International Astronomical Union Colloquium 155 (1995) : 260–69. http://dx.doi.org/10.1017/s0252921100037088.

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AbstractWe present Fourier analysis at 490 nm for 87 Cepheid light curves in the bar of the Large Magellanic Cloud. The photometry has been obtained through the EROS project whose main purpose is the search for baryonic dark matter in the Galactic halo. The very high quality of the photometry and the good phase coverage enable us to obtain accurate Fourier decomposition of the light curves. As a consequence we confirm that the so-called s-Cepheids are overtone pulsators and represent about 30 % of our sample, whereas the Classical Cepheids are fundamental pulsators. We have identified a number of features in plots of amplitude ratios and phase differences versus period. These features are usually related to resonances between different pulsation modes. If we accept that Fourier decomposition techniques applied to light curves yield positions for the centres of resonances, then it seems that resonances occur in LMC Cepheids at the same period as in Galactic Cepheids for fundamental pulsators, whereas they appear to be at shorter periods for overtone pulsators.
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Wernik, Jacek, et Krzysztof J. Wołosz. « Study of Heat Transfer in Pneumatic Pulsator ». Applied Mechanics and Materials 797 (novembre 2015) : 320–26. http://dx.doi.org/10.4028/www.scientific.net/amm.797.320.

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The article presents selected results of research work aimed to rationalize and optimize the design of the pneumatic pulsator due to thermal conditions. Pneumatic pulsator is a device used in industry storing bulk and loose materials. It is attached to the silo, allowing their correct operation. The air friction against the inner wall of the pulsator causes the release of heat. In order to investigate the conditions of heat transfer, thermal calculations were made and then numerical simulations using Computational Fluid Dynamics (CFD) were conducted. Various fins options were examined. The objective was to maximize the heat flux discharged from the device. Temperature distribution on the surface of the fins designated by CFD corresponds to the distribution designated analytically. The results were confirmed by industrial tests. Numerical simulations mapping the heat exchange processes in a pneumatic pulsator have not yet been carried out.
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Bigot, L., et W. A. Dziembowski. « The oblique pulsator model revisited ». Astronomy & ; Astrophysics 391, no 1 (29 juillet 2002) : 235–45. http://dx.doi.org/10.1051/0004-6361:20020824.

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Rodríguez, Eloy, Angel Rolland et Pilar López de Coca. « ρ Pup : A Monoperiodic Radially Pulsating δ Set Star ». International Astronomical Union Colloquium 139 (1993) : 430. http://dx.doi.org/10.1017/s0252921100118202.

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Abstractρ Pup is a δ Scuti type pulsator with relatively low amplitude (ΔV∼0.m09). Analysis of the data from different sources, using the Fourier Transform method, establishes ρ Pup as a monoperiodic pulsator. Using the classical O-C method, it is found that the pulsation of this star can be well described by means of a linear ephemeris with a period of P=0.d140881372 over more than eighty years. The nature of radial or nonradial pulsation is discussed on the basis on the derived phase shifts and amplitude ratios between different colours. The results indicate that ρ Pup is a radial pulsator.
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Charpinet, S., V. Van Grootel, S. K. Randall, E. M. Green, G. Fontaine, P. Brassard et P. Chayer. « New advances in asteroseismology of pulsating hot subdwarf stars ». Proceedings of the International Astronomical Union 5, H15 (novembre 2009) : 357. http://dx.doi.org/10.1017/s1743921310009774.

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AbstractHot subdwarf stars (of the sdB and sdO type) host three known classes of nonradial pulsators. Two of them feature short period (P ~ 60 - 600 s) accoustic mode oscillations, while the third group is characterized by slow g-mode deformations with periods of ~ 1 - 2h. These pulsations offer favorable grounds to infer some of the internal properties of these objects through asteroseismology. This has been exploited for the rapid p-mode sdB pulsators and the present contribution reviews some of the recent advances in this field. The long period g-mode pulsators, whose vibrations probe much deeper inside the star, are also of high interest. With the advent of space observations using CoRoT and KEPLER, the asteroseismology of these slower oscillators will also become a possibility, and likely contribute to significant breakthroughs in our understanding of these hot and compact stars.
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KAPITANIAK, Tomasz. « Vibration of the Pulsatory Braking Vehicle ». Vehicle System Dynamics 16, no 1 (janvier 1987) : 27–35. http://dx.doi.org/10.1080/00423118708968865.

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Avelino, P. P., M. S. Cunha et W. J. Chaplin. « Modelling stochastic signatures in classical pulsators ». Monthly Notices of the Royal Astronomical Society 492, no 3 (15 janvier 2020) : 4477–83. http://dx.doi.org/10.1093/mnras/staa125.

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ABSTRACT We consider the impact of stochastic perturbations on otherwise coherent oscillations of classical pulsators. The resulting dynamics are modelled by a driven damped harmonic oscillator subject to either an external or an internal forcing and white noise velocity perturbations. We characterize the phase and relative amplitude variations using analytical and numerical tools. When the forcing is internal the phase variation displays a random walk behaviour and a red noise power spectrum with a ragged erratic appearance. We determine the dependence of the root mean square phase and relative amplitude variations (σΔφ and σΔA/A, respectively) on the amplitude of the stochastic perturbations, the damping constant η, and the total observation time tobs for this case, under the assumption that the relative amplitude variations remain small, showing that σΔφ increases with $t_{\rm obs}^{1/2}$ becoming much larger than σΔA/A for tobs ≫ η−1. In the case of an external forcing the phase and relative amplitude variations remain of the same order, independent of the observing time. In the case of an internal forcing, we find that σΔφ does not depend on η. Hence, the damping time cannot be inferred from fitting the power of the signal, as done for solar-like pulsators, but the amplitude of the stochastic perturbations may be constrained from the observations. Our results imply that, given sufficient time, the variation of the phase associated with the stochastic perturbations in internally driven classical pulsators will become sufficiently large to be probed observationally.
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Buysschaert, B., C. Neiner et C. Aerts. « Magneto-asteroseismology of massive magnetic pulsators ». Proceedings of the International Astronomical Union 12, S329 (novembre 2016) : 146–50. http://dx.doi.org/10.1017/s1743921317002459.

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AbstractSimultaneously and coherently studying the large-scale magnetic field and the stellar pulsations of a massive star provides strong complementary diagnostics suitable for detailed stellar modelling. This hybrid method is called magneto-asteroseismology and permits the determination of the internal structure and conditions within magnetic massive pulsators, for example the effect of magnetism on non-standard mixing processes. Here, we overview this technique, its requirements, and list the currently known suitable stars to apply the method.
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Tucker, Michael A., Scott W. Fleming, Ingrid Pelisoli, Alejandra Romero, Keaton J. Bell, S. O. Kepler, Daniel B. Caton et al. « White dwarf variability with gPhoton : pulsators ». Monthly Notices of the Royal Astronomical Society 475, no 4 (22 décembre 2017) : 4768–80. http://dx.doi.org/10.1093/mnras/stx3297.

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Nitta, Atsuko, A. Mukadam, D. E. Winget, A. Kanaan, S. J. Kleinman, S. O. Kepler et M. H. Montgomery. « Search For Cool White Dwarf Pulsators ». International Astronomical Union Colloquium 176 (2000) : 525–26. http://dx.doi.org/10.1017/s0252921100058735.

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AbstractWe are searching for pulsations in cool (< 6000 K) white dwarfs (WDs), hoping to apply asteroseismological techniques to improve our understanding of their structure and the physical processes inside them. This information is important as we use cool WDs to estimate the lower limit of the age of the Galactic disk. Within a spectroscopic and photometric survey of 110 cool WDs by Bergeron, Ruiz, & Legget, we find 28 candidates with appropriate effective temperatures, masses, and chemical compositions for possible pulsations in nonradial g modes with periods similar to those we observe in DAVs. So far, we have observed 4 candidates, but have found no evidence of large variation.
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Popescu, Dumitru, et Alin Gabriel Popescu. « The working of a pulsatory liposome ». Journal of Theoretical Biology 254, no 3 (octobre 2008) : 515–19. http://dx.doi.org/10.1016/j.jtbi.2008.07.009.

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Dziembowski, W. A. « B Star Pulsation - Theory and Seismological Prospects ». Symposium - International Astronomical Union 185 (1998) : 355–60. http://dx.doi.org/10.1017/s007418090023893x.

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Progress in understanding B-type pulsators has been reviewed at several recent meetings (e.g. Dziembowski, 1993, 1995; Moskalik, 1995). Not much happened afterwards. Owing to further improvement in the stellar opacity calculations (Iglesias and Rogers 1996), the theoretical pulsation-instability domain in the upper Main Sequence is now more precisely determined. In the next section I will compare the predicted domain with the positions of various B-type pulsators in the H-R diagram.
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Szabados, L. « Interrelation of Modal Amplitudes of Double-Mode Pulsators ». International Astronomical Union Colloquium 185 (2002) : 418–19. http://dx.doi.org/10.1017/s0252921100016687.

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AbstractDuring the study of the factors governing the modal amplitudes of the double-mode radial pulsators, it has been found that the R21 Fourier parameter deduced from the light curves is in a relationship with the ratio of the modal amplitudes, for beat Cepheids and RR Lyrae variables, as well. The form of this relation gives a natural explanation for the fact that double-mode pulsators with slightly excited second modes do not exist.
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Sahoo, S. K., A. S. Baran, S. Sanjayan et J. Ostrowski. « A search for variable subdwarf B stars in TESS full frame images – I. Variable objects in the southern ecliptic hemisphere ». Monthly Notices of the Royal Astronomical Society 499, no 4 (6 octobre 2020) : 5508–26. http://dx.doi.org/10.1093/mnras/staa2991.

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ABSTRACT We report the results of our search for pulsating subdwarf B stars in full frame images, sampled at 30 min cadence and collected during Year 1 of the TESS mission. Year 1 covers most of the southern ecliptic hemisphere. The sample of objects we checked for pulsations was selected from a subdwarf B stars data base available to public. Only two positive detections have been achieved, however, as a by-product of our search we found 1807 variable objects, most of them not classified, hence their specific variability class cannot be confirmed at this stage. Our preliminary discoveries include: 2 new subdwarf B (sdB) pulsators, 26 variables with known sdB spectra, 83 non-classified pulsating stars, 83 eclipsing binaries (detached and semidetached), a mix of 1535 pulsators and non-eclipsing binaries, two novae, and 77 variables with known (non-sdB) spectral classification. Among eclipsing binaries we identified two known HW Vir systems and four new candidates. The amplitude spectra of the two sdB pulsators are not rich in modes, but we derive estimates of the modal degree for one of them. In addition, we selected five sdBV candidates for mode identification among 83 pulsators and describe our results based on this preliminary analysis. Further progress will require spectral classification of the newly discovered variable stars, which hopefully include more subdwarf B stars.
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Rodríguez, E., et M. Breger. « δ Scuti Variables with Periods Longer than 0.25 Days ». International Astronomical Union Colloquium 185 (2002) : 328–29. http://dx.doi.org/10.1017/s0252921100016377.

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AbstractVariables listed as δ Scuti-type pulsators in the R00 catalogue (Rodriguez et al., 2000) with periods longer than 0.d25 are examined on a star-by-star basis, in order to discriminate their true nature (δ Scuti, RR Lyr or γ Dor-type). From this study, it seems that three stars (DH Peg, UY Cam and YZ Cap) are RR Lyr pulsators rather than δ Scuti variables. Moreover, two variables (AD Ari and DE Oct) seem to be γ Dor variables with the shortest periods known to date (0.d2699 and 0.d2778, respectively).
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B. J. Boman, R. C. Bullock et M. L. Parsons. « Ant Damage to Microsprinkler Pulsator Assemblies ». Applied Engineering in Agriculture 11, no 6 (1995) : 835–37. http://dx.doi.org/10.13031/2013.25810.

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Goodwin, Richard M. « The economy as an evolutionary pulsator ». Journal of Economic Behavior & ; Organization 7, no 4 (décembre 1986) : 341–49. http://dx.doi.org/10.1016/0167-2681(86)90010-7.

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