scholarly journals Stratified NLTE Model Atmospheres for Hot Stars

2003 ◽  
Vol 210 ◽  
pp. 33-43
Author(s):  
Stefan Dreizler ◽  
Sonja L. Schuh
Keyword(s):  
Chemical Composition ◽  
Cross Sections ◽  
Stellar Atmosphere ◽  
Hot Stars ◽  
Gravitational Settling ◽  
Self Consistent ◽  
Chemical Stratification ◽  
The Status ◽  
Homogeneous Chemical ◽  
Radiative Acceleration

In most stellar atmosphere models, a homogeneous chemical composition is assumed, which is a good approximation for many stars. With the absence of convection and mass–loss, however, gravitational settling can produce a chemical stratification gradient. Typical examples are white dwarfs. In hot stars this diffusion process is modified by the radiative acceleration, resulting in levitation of ions with large radiative cross sections. The status of our program for self-consistent stratified non-LTE model atmospheres is presented.

System-wide seismic vulnerability of aging multiple-span multiple-girder bridges in low-to-moderate seismic hazard regions

2021 ◽  
Vol 37 (1_suppl) ◽  
pp. 1626-1651
Author(s):  
John E Lens M.EERI ◽  
Mandar M Dewoolkar ◽  
Eric M Hernandez M.EERI
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Cross Sections ◽  
Seismic Vulnerability ◽  
Time History ◽  
The United States ◽  
National Database ◽  
Eastern United States ◽  
Girder Bridges ◽  
The Status

This article describes the approach, methods, and findings of a quantitative analysis of the seismic vulnerability in low-to-moderate seismic hazard regions of the Central and Eastern United States for system-wide assessment of typical multiple span bridges built in the 1950s through the 1960s. There is no national database on the status of seismic vulnerability of bridges, and thus no means to estimate the system-wide damage and retrofit costs for bridges. The study involved 380 nonlinear analyses using actual time-history records matched to four representative low-to-medium hazard target spectra corresponding with peak ground accelerations from approximately 0.06 to 0.3 g. Ground motions were obtained from soft and stiff site seismic classification locations and applied to models of four typical multiple-girder with concrete bent bridges. Multiple-girder bridges are the largest single category, comprising 55% of all multiple span bridges in the United States. Aging and deterioration effects were accounted for using reduced cross-sections representing fully spalled conditions and compared with pristine condition results. The research results indicate that there is an overall low likelihood of significant seismic damage to these typical bridges in such regions, with the caveat that certain bridge features such as more extensive deterioration, large skews, and varied bent heights require bridge-specific analysis. The analysis also excludes potential damage resulting from liquefaction, flow-spreading, or abutment slumping due to weak foundation or abutment soils.

scholarly journals The circumstellar environment of the B[e] star GG Car: an interferometric modeling

2014 ◽  
Vol 9 (S307) ◽  
pp. 291-292
Author(s):  
A. Domiciano de Souza ◽  
M. Borges Fernandes ◽  
A. C. Carciofi ◽  
O. Chesneau
Keyword(s):  
Binary System ◽  
Primary Component ◽  
Compact Ring ◽  
Hot Stars ◽  
Self Consistent ◽  
Grain Formation ◽  
Formation And Evolution ◽  
Circumstellar Environments ◽  
Consistent Treatment ◽  
Circumstellar Environment

AbstractThe research of stars with the B[e] phenomenon is still in its infancy, with several unanswered questions. Physically realistic models that treat the formation and evolution of their complex circumstellar environments are rare. The code HDUST (developed by A. C. Carciofi and J. Bjorkman) is one of the few existing codes that provides a self-consistent treatment of the radiative transfer in a gaseous and dusty circumstellar environment seen around B[e] supergiant stars. In this work we used the HDUST code to study the circumstellar medium of the binary system GG Car, where the primary component is probably an evolved B[e] supergiant. This system also presents a disk (probably circumbinary), which is responsible for the molecular and dusty signatures seen in GG Car spectra. We obtained VLTI/MIDI data on GG~Car at eight baselines, which allowed to spatially resolve the gaseous and dusty circumstellar environment. From the interferometric visibilities and SED modeling with HDUST, we confirm the presence of a compact ring, where the hot dust lies. We also show that large grains can reproduce the lack of structure in the SED and visibilities across the silicate band. We conclude the dust condensation site is much closer to the star than previously thought. This result provides stringent constraints on future theories of grain formation and growth around hot stars.

scholarly journals Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)

2015 ◽  
Vol 11 (8) ◽  
pp. 1097-1105 ◽  
Author(s):  
R. V. Kochanov ◽  
I. E. Gordon ◽  
L. S. Rothman ◽  
S. W. Sharpe ◽  
T. J. Johnson ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Cross Sections ◽  
Spectral Region ◽  
Radiative Forcing ◽  
Recent Article ◽  
The Other ◽  
Radiative Forcings ◽  
The Status ◽  
Moderate Resolution ◽  
Spectroscopic Database

Abstract. In the recent article by Byrne and Goldblatt, "Radiative forcing for 28 potential Archean greenhouse gases", Clim. Past. 10, 1779–1801 (2014), the authors employ the HITRAN2012 spectroscopic database to evaluate the radiative forcing of 28 Archean gases. As part of the evaluation of the status of the spectroscopy of these gases in the selected spectral region (50–1800 cm−1), the cross sections generated from the HITRAN line-by-line parameters were compared with those of the PNNL database of experimental cross sections recorded at moderate resolution. The authors claimed that for NO2, HNO3, H2CO, H2O2, HCOOH, C2H4, CH3OH and CH3Br there exist large or sometimes severe disagreements between the databases. In this work we show that for only three of these eight gases a modest discrepancy does exist between the two databases and we explain the origin of the differences. For the other five gases, the disagreements are not nearly at the scale suggested by the authors, while we explain some of the differences that do exist. In summary, the agreement between the HITRAN and PNNL databases is very good, although not perfect. Typically differences do not exceed 10 %, provided that HITRAN data exist for the bands/wavelengths of interest. It appears that a molecule-dependent combination of errors has affected the conclusions of the authors. In at least one case it appears that they did not take the correct file from PNNL (N2O4 (dimer)+ NO2 was used in place of the monomer). Finally, cross sections of HO2 from HITRAN (which do not have a PNNL counterpart) were not calculated correctly in BG, while in the case of HF misleading discussion was presented there based on the confusion by foreign or noise features in the experimental PNNL spectra.

scholarly journals Self-consistent rising cross-sections

1971 ◽  
Vol 34 (7) ◽  
pp. 631-634 ◽  
Author(s):  
J. Finkelstein ◽  
F. Zachriasen
Keyword(s):  
Cross Sections ◽  
Self Consistent

scholarly journals Analysis of Chemical Composition Homogeneity in the Cross-section of the Rods Produced from Alloys of 6xxx Group

2020 ◽  
Vol 66 (3) ◽  
pp. 139-148
Author(s):  
Maja Vončina ◽  
Peter Cvahte ◽  
Ana Kračun ◽  
Tilen Balaško ◽  
Jožef Medved
Keyword(s):  
Corrosion Resistance ◽  
Chemical Composition ◽  
Cross Section ◽  
Cross Sections ◽  
Intermetallic Phases ◽  
Scanning Calorimetry ◽  
Good Corrosion Resistance ◽  
Energy Dispersion Spectrometer ◽  
High Casting Speed ◽  
The Cross

AbstractThe alloys from Al–Mg–Si system provide an excellent combination of mechanical properties, heat treatment at extrusion temperature, good weldability, good corrosion resistance and formability. Owing to the high casting speed of rods or slabs, the solidification is rather non-equilibrium, resulting in defects in the material, such as crystalline segregations, the formation of low-melting eutectics, the unfavourable shape of intermetallic phases and the non-homogeneously distributed alloying elements in the cross-section of the rods or slabs and in the entire microstructure. The inhomogeneity of the chemical composition and the solid solution negatively affects the strength, the formability in the warm and the corrosion resistance, and can lead to the formation of undesired phases due to segregation in the material. In this experimental investigation, the cross-sections of the rods from two different alloys of the 6xxx group were investigated. From the cross-sections of the rods, samples for differential scanning calorimetry (DSC) at three different positions (edge, D/4 and middle) were taken to determine the influence of inhomogeneity on the course of DSC curve. Metallographic sample preparation was used for microstructure analysis, whereas the actual chemical composition was analysed using a scanning electron microscope (SEM) and an energy dispersion spectrometer (EDS).

scholarly journals A novel scheme for Dark Matter Annihilation Feedback in cosmological simulations

2019 ◽  
Vol 489 (3) ◽  
pp. 4217-4232 ◽  
Author(s):  
Florian List ◽  
Nikolas Iwanus ◽  
Pascal J Elahi ◽  
Geraint F Lewis
Keyword(s):  
Dark Matter ◽  
Blast Wave ◽  
Cross Sections ◽  
Injection Velocity ◽  
Local Energy ◽  
Time Step ◽  
Dark Matter Annihilation ◽  
Self Consistent ◽  
Consistent Method ◽  
Non Local

ABSTRACT We present a new self-consistent method for incorporating Dark Matter Annihilation Feedback (DMAF) in cosmological N-body simulations. The power generated by DMAF is evaluated at each dark matter (DM) particle which allows for flexible energy injection into the surrounding gas based on the specific DM annihilation model under consideration. Adaptive, individual time-steps for gas and DM particles are supported and a new time-step limiter, derived from the propagation of a Sedov–Taylor blast wave, is introduced. We compare this donor-based approach with a receiver-based approach used in recent studies and illustrate the differences by means of a toy example. Furthermore, we consider an isolated halo and a cosmological simulation and show that for these realistic cases, both methods agree well with each other. The extension of our implementation to scenarios such as non-local energy injection, velocity-dependent annihilation cross-sections, and DM decay is straightforward.

scholarly journals Flattening the inflaton potential beyond minimal gravity

2018 ◽  
Vol 168 ◽  
pp. 06001 ◽  
Author(s):  
Hyun Min Lee
Keyword(s):  
Standard Model ◽  
Higgs Field ◽  
Gravity Models ◽  
Induced Gravity ◽  
Consistent Description ◽  
The Standard Model ◽  
Self Consistent ◽  
The Status

We review the status of the Starobinsky-like models for inflation beyond minimal gravity and discuss the unitarity problem due to the presence of a large non-minimal gravity coupling. We show that the induced gravity models allow for a self-consistent description of inflation and discuss the implications of the inflaton couplings to the Higgs field in the Standard Model.

On the superfamily Darwinuloidacea, the type species of Darwinuloidea Mandelstam, 1956, and on the status of Cheikella Sohn and Morris, 1963 (Ostracoda)

1999 ◽  
Vol 73 (1) ◽  
pp. 159-160 ◽  
Author(s):  
I. G. Sohn ◽  
F. M. Swain
Keyword(s):  
Cross Sections ◽  
Type Species ◽  
Adductor Muscle ◽  
Muscle Attachment ◽  
The Family ◽  
The Status

Molostovskaja (1979, p. 54) described without illustrations the family Darwinuloididae Molostovskaja, 1979. The following year, Molostovskaja (1980, p. 33) described the family again as new [Darwinuloididae fam. nov.]. She included the genus Whipplella Holland, 1934, in the family and illustrated Darwinuloides svijazhicus (Sharapova 1948) (Molostovskaja, 1980, p. 28, figs. 5a, b, 8). Schneider (1948, p. 29, pl. 2, figs, 1a, b) originally described and illustrated this species as “Darwinula svijazhicus Sharapova n. mns.” Two years later, Molostovskaja (1982, p. 158) illustrated cross-sections of the adductor muscle attachment scar patterns in the families of the Darwinulacea Brady and Norman, 1889. Later Molostovskaja (1990, p. 166) erected the superfamily Darwinuloidacea Molostovskaja, 1979 to include Whipplella Holland, 1934, Vymella Kalis and Mischina in Mischina and Kalis, 1975, and questionably Pruvostina Scott and Summerson, 1943. In the same paper, she illustrated Whipplella sp. (pl. 72, figs. 6a, b) [from Sohn, 1977], Vymella dobrinini (Kashevarova, 1961) (pl. 72, figs. 7a-c), Darwinuloides sentjakensis (Sharapova in Schneider, 1948) (pl. 73, figs. 5, 6), and D. svijazhicus (Sharapova in Schneider, 1948) (pl. 74, figs. 14a, b).

QuasielasticCa40(e,e’p) cross sections in a many-particle self-consistent Hartree model

1993 ◽  
Vol 47 (5) ◽  
pp. 2024-2029 ◽  
Author(s):  
Yanhe Jin ◽  
J. K. Zhang ◽  
D. S. Onley ◽  
L. E. Wright
Keyword(s):  
Cross Sections ◽  
Self Consistent
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