scholarly journals Model Analysis of 108–76°1

1978 ◽  
Vol 76 ◽  
pp. 354-355
Author(s):  
Bruce Balick ◽  
G.O. Boeshaar
Keyword(s):  
Computer Model ◽  
Galactic Halo ◽  
Line Strength ◽  
Central Star ◽  
Model Analysis ◽  
Homogeneous Sphere ◽  
Plane Parallel ◽  
Atmosphere Model ◽  
Volume Models ◽  
Good Agreement

108–76°1 was discovered by Boeshaar and Bond (1977, Ap. J., 213, 421) to be a member of the galactic halo component. Herein are presente the results of a computer model analysis of these observations and those of Hawley and Miller (this volume). Models producing the 23% of helium in the doubly-ionized state required by the Hell X4686 line strength utilized the 95,000°K, non-gray, spherical atmosphere model of Cassi-nelli (1971, Ap. J., 165, 265) for the central star. Even 100,000°K plane-parallel atmospheres gave less than half the needed He++. The results for model 1 (homogeneous sphere) and model 2 (Gaussian shell) show good agreement with observed fluxes, even for [OH] X3727. The abundance values

Handling of Collimated Irradiation on a Plane-Parallel Participating Medium

2000 ◽  
Author(s):  
Christian Proulx ◽  
Daniel R. Rousse ◽  
Rodolphe Vaillon ◽  
Jean-François Sacadura
Keyword(s):  
Heat Flux ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Radiative Heat ◽  
Radiative Heat Flux ◽  
Scattering Media ◽  
One Dimensional ◽  
Plane Parallel ◽  
Collimated Beam ◽  
Good Agreement

Abstract This article presents selected results of a study comparing two procedures for the treatment of collimated irradiation impinging on one boundary of a participating one-dimensional plane-parallel medium. These procedures are implemented in a CVFEM used to calculate the radiative heat flux and source. Both isotropically and anisotropically scattering media are considered. The results presented show that both procedures provide results in good agreement with those obtained using a Monte Carlo method, when the collimated beam impinges normally.

scholarly journals Characterizing global expansion evolution of the ionized matter in planetary nebulae

2016 ◽  
Vol 12 (S323) ◽  
pp. 352-353
Author(s):  
J. A. López ◽  
M. G. Richer ◽  
M. Pereyra ◽  
M. T. García-Díaz
Keyword(s):  
Galactic Halo ◽  
Evolutionary Rate ◽  
Planetary Nebulae ◽  
Central Star ◽  
Global Expansion ◽  
Kinematic Evolution ◽  
Wide Range ◽  
Model Predictions ◽  
First Time ◽  
Highly Evolved

AbstractBulk outflow or global expansion velocities are presented for a large number of planetary nebulae (PNe) that span a wide range of evolutionary stages and different stellar populations. The sample comprises 133 PNe from the Galactic bulge, 100 mature and highly evolved PNe from the disk, 11 PNe from the Galactic halo and 15 PNe with very low central star masses and low metallicities, for a total of 259 PNe. These results reveal from a statistical perspective the kinematic evolution of the expansion velocities of PNe in relation to changing characteristics of the central star’s wind and ionizing luminosity and as a function of the evolutionary rate determined by the central (CS) mass. The large number of PNe utilized in this work for each group of PNe under study and the homogeneity of the data provide for the first time a solid benchmark form observations for model predictions, as has been described by López et al. (2016).

scholarly journals V471 Tauri and SuWt 2: The Exotic Descendants of Triple Systems?

2002 ◽  
Vol 187 ◽  
pp. 239-243 ◽  
Author(s):  
Howard E. Bond ◽  
M. Sean O’Brien ◽  
Edward M. Sion ◽  
Dermott J. Mullan ◽  
Katrina Exter ◽  
...  
Keyword(s):  
Main Sequence ◽  
Central Star ◽  
High Mass ◽  
Eclipsing Binary ◽  
Triple Systems ◽  
Common Envelope ◽  
Short Period ◽  
Efficiency Parameter ◽  
Hydrodynamical Simulations ◽  
Good Agreement

AbstractV471 Tauri is a short-period eclipsing binary, and a member of the Hyades. It is composed of a hot DA white dwarf (WD) and a cool main-sequence dK2 companion. HST radial velocities of the WD, in combination with the ground-based spectroscopic orbit of the K star, yield dynamical masses of MWD = 0.84 and MdK = 0.93 M⊙. During the UV observations we serendipitously detected coronal mass ejections from the K star, passing in front of the WD and appearing as sudden, transient metallic absorption. Eclipse timings show that the active dK star is 18% larger than a main-sequence star of the same mass, an apparent consequence of its extensive starspot coverage. The high Teff and high mass of the WD are paradoxical: the WD is the most massive in the Hyades, but also the youngest. A plausible scenario is that the progenitor system was a triple, with a close inner pair that merged after several × 108 yr to produce a single blue straggler. When this star evolved to the AGB phase, it underwent a common-envelope interaction with a distant dK companion, which spiraled down to its present separation and ejected the envelope. The common-envelope efficiency parameter, αCE, was of order 0.3–1.0, in good agreement with recent hydrodynamical simulations.SuWt 2 is a southern-hemisphere planetary nebula (PN) with an unusual ring-shaped morphology. The central star is an eclipsing binary with a period of 4.9 days. Surprisingly, the binary is composed of two main-sequence A-type stars with similar masses of ~ 2.5 M⊙. We discuss scenarios involving a third companion which ejected and ionizes the PN.WeBo 1 is a northern PN with a ring morphology remarkably similar to that of SuWt 2. Although we hoped that its central star would shed light on the nature of SuWt 2, it has proven instead to be a late-type barium star!

scholarly journals LOWER CRITICAL MAGNETIC FIELD OF SUPERCONDUCTING Rb3C60

1992 ◽  
Vol 06 (16n17) ◽  
pp. 1037-1042 ◽  
Author(s):  
V. BUNTAR ◽  
U. ECKERN ◽  
C. POLITIS
Keyword(s):  
Magnetic Field ◽  
Penetration Depth ◽  
High Field ◽  
Model Analysis ◽  
Critical Magnetic Field ◽  
Field Analysis ◽  
Zero Temperature ◽  
Bean Model ◽  
Good Agreement

The lower critical magnetic field Hc1 of superconducting Rb 3 C 60 (Tc=28.5 K ) is estimated by different methods. The zero temperature value is found to be given by Hc1=16.2±1.0 mT, and the penetration depth is λL=215±10 nm . The Bean model analysis leads to threshold fields of 5.3 mT for T=5 K , and 4.0 mT for T=17 K . The big influence of intergranular connections on Hc1 is demonstrated. Good agreement between the low- and the high-field analysis is found.

scholarly journals Some Progress and Problems in the Upper Left of the HR Diagram

1978 ◽  
Vol 80 ◽  
pp. 5-12
Author(s):  
Nolan R. Walborn
Keyword(s):  
Absorption Line ◽  
Spectral Type ◽  
Main Sequence ◽  
Line Strength ◽  
Balmer Line ◽  
Spectral Classification ◽  
Constant Ratio ◽  
Absorption Effect ◽  
Subsequent Work ◽  
Good Agreement

The MK system of spectral classification does not include luminosity classes for types earlier than 09. Subsequent work with higher dispersions has allowed a luminosity classification for early O stars to be proposed. One of the principal criteria at types 09-B0 is the selective, negative luminosity effect in the Hell 4686 Å absorption line; a similar effect was found in the NIII 4634-4640-4642 Å absorption lines at 09-B0. These particular lines weaken markedly with increasing luminosity, while other HeII lines maintain a constant ratio to HeI (by definition), and other NIII lines strengthen considerably. These anomalous lines are the same ones which selectively appear in emission in Of stars, and the derived luminosity classification for earlier types is based upon the hypothesis that the negative absorption effect at 09-B0 is due to emission filling by the same mechanism producing the Of phenomenon, and that hence the latter may also be identified as a luminosity effect (Walborn 1971). One observes strong 4686 Å absorption and often weak 4640 Å emission [denoted ((f))] on the main sequence to the earliest types. As luminosity increases at a given spectral type, the HeII absorption weakens while the NIII emission increases [denoted (f)] and finally the most luminous stars have both 4686 and 4640 Å strongly in emission [denoted f]. A sequence of spectra all with types very near 07, but showing the marked changes with luminosity class in 4686 and 4640 Å, is illustrated by Walborn (1973). These effects show good agreement with other spectroscopic luminosity criteria such as SiIV absorption (Conti and Alschuler 1971) and Balmer-line strength (Crawford 1975, Morrison 1975), which are however less sensitive at the earliest types.

Performance Calculation of a TBD234V12 Diesel Engine with STC

2012 ◽  
Vol 157-158 ◽  
pp. 1075-1078
Author(s):  
Yang Wang ◽  
Yin Yan Wang ◽  
Fan Shi ◽  
Xin Guang Li
Keyword(s):  
Experimental Data ◽  
Diesel Engine ◽  
Computer Model ◽  
High Speed ◽  
Marine Diesel Engine ◽  
High Speed Diesel ◽  
Turbocharging System ◽  
Marine Diesel ◽  
Performance Calculation ◽  
Good Agreement

A computer model for a TBD234V12 marine high-speed diesel engine with 2 turbocharger(2TC) is built on GT-POWER. For validating the computer model, a calculation to the conventional turbocharging system has been done firstly, and the results show good agreement with experimental data. The computer model has then been used for predictive studies of the diesel engine with the proposed STC system on the mapping characteristics. From these results, it can be seen that the STC system can not only improve the part load performance of the diesel engine obviously, but also enlarge the operating range of the marine diesel engine.

Towards Measuring Young’s Modulus by Electronic Probing

2012 ◽  
Author(s):  
Aarti Chigullapalli ◽  
Jason V. Clark
Keyword(s):  
Young’S Modulus ◽  
Computer Model ◽  
Young's Modulus ◽  
Dynamic Performance ◽  
Comb Drive ◽  
Comb Drives ◽  
Electronic Measurement ◽  
On Chip ◽  
True Experiment ◽  
Good Agreement

We propose an accurate and precise method for measuring the Young’s modulus of MEMS with comb drives by electronic probing of capacitance. The electronic measurement can be performed off-chip for quality control or on-chip after packaging for self-calibration. Young’s modulus is an important material property that affects the static or dynamic performance of MEMS. Electrically-probed measurements of Young’s modulus may also be useful for industrial scale automation. Conventional methods for measuring Young’s modulus include analyzing stress-strain curves, which is typically destructive, or include analyzing a large array of test structures of varying dimensions, which requires a large amount of chip real estate. Our method measures Young’s modulus by uniquely eliminating unknowns and extracting the fabricated geometry, displacement, comb drive force, and stiffness. Since Young’s modulus is related to geometry and stiffness that we find using electronic measurands, we are able to express Young’s modulus as a function of electronic measurands. We verify our method by using it to predict the Young’s modulus of a computer model. We treat the computer model as we would treat a true experiment by depending only on its electronic measurands. We find good agreement in predicting the exactly known Young’s modulus in a computer model within 0.1%.

scholarly journals A search for red giant solar-like oscillations in all Kepler data

2019 ◽  
Vol 485 (4) ◽  
pp. 5616-5630 ◽  
Author(s):  
Marc Hon ◽  
Dennis Stello ◽  
Rafael A García ◽  
Savita Mathur ◽  
Sanjib Sharma ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Halo ◽  
Red Giants ◽  
Simulated Model ◽  
Processing Pipeline ◽  
Kepler Mission ◽  
Data Release ◽  
Red Giant ◽  
Subgiant Stars ◽  
Good Agreement

ABSTRACT The recently published Kepler mission Data Release 25 (DR25) reported on ∼197 000 targets observed during the mission. Despite this, no wide search for red giants showing solar-like oscillations have been made across all stars observed in Kepler’s long-cadence mode. In this work, we perform this task using custom apertures on the Kepler pixel files and detect oscillations in 21 914 stars, representing the largest sample of solar-like oscillating stars to date. We measure their frequency at maximum power, νmax, down to $\nu _{\mathrm{max}}\simeq 4\, \mu$Hz and obtain log (g) estimates with a typical uncertainty below 0.05 dex, which is superior to typical measurements from spectroscopy. Additionally, the νmax distribution of our detections show good agreement with results from a simulated model of the Milky Way, with a ratio of observed to predicted stars of 0.992 for stars with $10 \lt \nu _{\mathrm{max}}\lt 270\, \mu$Hz. Among our red giant detections, we find 909 to be dwarf/subgiant stars whose flux signal is polluted by a neighbouring giant as a result of using larger photometric apertures than those used by the NASA Kepler science processing pipeline. We further find that only 293 of the polluting giants are known Kepler targets. The remainder comprises over 600 newly identified oscillating red giants, with many expected to belong to the Galactic halo, serendipitously falling within the Kepler pixel files of targeted stars.

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