scholarly journals Models of bars − II. Exponential profiles

2020 ◽  
Vol 493 (2) ◽  
pp. 2676-2687 ◽  
Author(s):  
D P McGough ◽  
N W Evans ◽  
J L Sanders
Keyword(s):  
Cross Sections ◽  
High Velocity ◽  
Dominant Role ◽  
Gaussian Quadrature ◽  
Major Axis ◽  
Orbital Structure ◽  
Linear Superposition ◽  
Lagrange Points ◽  
Gaussian Potential ◽  
First Time

ABSTRACT We present a new model for galactic bars with exponentially falling major axis luminosity profiles and Gaussian cross-sections. This is based on the linear superposition of Gaussian potential–density pairs with an exponential weight function, using an extension of the method originally introduced by Long & Murali. We compute the density, potential, and forces, using Gaussian quadrature. These quantities are given as explicit functions of position. There are three independent scaled bar parameters that can be varied continuously to produce bespoke bars of a given mass and shape. We categorize the effective potential by splitting a reduced parameter space into six regions. Unusually, we find bars with three stable Lagrange points on the major axis are possible. Our model reveals a variety of unexpected orbital structure, including a bifurcating x1 orbit coexisting with a stable x4 orbit. Propeller orbits are found to play a dominant role in the orbital structure, and we find striking similarities between our bar configuration and the model of Kaufmann & Contopoulos. We find a candidate orbital family, sired from the propeller orbits, that may be responsible for the observed high-velocity peaks in the Milky Way’s bar. As a cross-check, we inspect, for the first time, the proper motions of stars in the high-velocity peaks, which also match our suggested orbital family well. This work adds to the increasing body of evidence that real galactic bars may be supported at least partly by propeller orbits rather than solely by elliptical-like orbits of the x1 family.

State-to-state charge exchange cross sections in high-velocity asymmetric and near-symmetric collisions of 400 MeV Fe26+ions

1983 ◽  
Vol 16 (21) ◽  
pp. 3993-4003 ◽  
Author(s):  
A Chetioui ◽  
K Wohrer ◽  
J P Rozet ◽  
A Jolly ◽  
C Stephan ◽  
...  
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
High Velocity ◽  
State Charge

The Mechanics of the Secondary Flows of Viscoelastic Fluids in Non-Circular Straight Tubes and the Mean Transversal Field in Pulsating Flows

2000 ◽  
Author(s):  
Dennis A. Siginer ◽  
Mario F. Letelier
Keyword(s):  
Secondary Flow ◽  
Cross Sections ◽  
Viscoelastic Fluids ◽  
Secondary Flows ◽  
Novel Approach ◽  
Transversal Field ◽  
Time Domains ◽  
Viscoelastic Liquids ◽  
First Time ◽  
Secondary Flow Field

Abstract A survey of secondary flows of viscoelastic liquids in straight tubes is given including recent work pointing at striking analogies with transversal deformations associated with the simple shearing of solid materials. The importance and implications of secondary flows of viscoelastic fluids in heat transfer enhancement are explored together with the difficulties in detecting weak secondary flows (dilute, weakly viscoelastic solutions) in a laboratory setting. Recent new work by the author and colleagues which explores for the first time the structure of the secondary flow field in the pulsating flow of a constitutively nonlinear simple fluid, whose structure is defined by a series of nested integrals over semi-infinite time domains, in straight tubes of arbitrary cross-sections is summarized. The transversal field arises at the second order of the perturbation of the nonlinear constitutive structure, and is driven by first order terms which define the linearly viscoelastic longitudinal flow in the hierarchy of superposed linear flows stemming from the perturbation of the constitutive structure. Arbitrary conduit contours are obtained through a novel approach to the concept of domain perturbation. Time averaged, mean secondary flow streamline contours are presented for the first time for triangular, square and hexagonal pipes.

A Practical Computing Method for Residual Area of Rebar Cross-Sections under Carbonation Induced Corrosion

2012 ◽  
Vol 166-169 ◽  
pp. 1895-1899
Author(s):  
Xiao Gang Wang ◽  
De Ming Zhong
Keyword(s):  
Cross Sections ◽  
Laser Scanning ◽  
Major Axis ◽  
Structural Deterioration ◽  
Minimum Residual ◽  
Degree Of Confidence ◽  
Conservative Approximation ◽  
Rc Slabs ◽  
Computing Method ◽  
Geometric Measurement

Area loss of severely weakened rebar cross sections is a crucial variable in assessment of structural deterioration for corroded concrete structures, which is hard to be measured or estimated precisely in conventional methods. In this paper, rebar samples were taken from naturally corroded RC slabs. Their virtual models were built using 3D laser scanning technique to facilitate geometric measurement. From these models seriously weakened sections were screened out as analyzing samples, and residual areas as well as profiles of the cross-sections were derived and investigated consequently. Shown by the results, corrosion was non-uniformly distributed on rebar surface, and profiles of the residual cross-sections can hardly be formulated efficiently. However, they can be simplified into ellipse with minor axis of minimum residual diameter and major axis of diameter in perpendicular direction. This model has been proved to give an conservative approximation of residual sectional area with 4.27% underestimation and 89.2% degree of confidence.

scholarly journals Performance Evaluation of a Nanomaterial-Based Thermoelectric Generator with Tapered Legs

2020 ◽  
Vol 7 ◽  
pp. 48-54
Author(s):  
Marilyn A. Ebiringa ◽  
John Paul Adimonyemma ◽  
Chika Maduabuchi
Keyword(s):  
Cross Sections ◽  
Thermoelectric Generator ◽  
Bulk Material ◽  
Electrical Energy ◽  
Ansys Software ◽  
Thermoelectric Effects ◽  
Trapezoidal Shape ◽  
Solar Radiation Intensity ◽  
Geometry Configuration ◽  
First Time

A thermoelectric generator (TEG) converts thermal energy to electricity using thermoelectric effects. The amount of electrical energy produced is dependent on the thermoelectric material properties. Researchers have applied nanomaterials to TEG systems to further improve the device’s efficiency. Furthermore, the geometry of the thermoelectric legs has been varied from rectangular to trapezoidal and even X-cross sections to improve TEG’s performance further. However, up to date, a nanomaterial TEG that uses tapered thermoelectric legs has not been developed before. The most efficient nanomaterial TEGs still make use of the conventional rectangular leg geometry. Hence, for the first time since the conception of nanostructured thermoelectrics, we introduce a trapezoidal shape configuration in the device design. The leg geometries were simulated using ANSYS software and the results were post-processed in the MATLAB environment. The results show that the power density of the nanoparticle X-leg TEG was 10 times greater than that of the traditional bulk material semiconductor X-leg TEG. In addition, the optimum leg geometry configuration in a nanomaterial-based TEG is dependent on the operating solar radiation intensity.

scholarly journals CROSS-SECTIONS FOR PHOTONUCLEAR REACTIONS 93Nb(γ,n)92mNb AND 93Nb(γ,n)92tNb IN THE END-POINT BREMSSTRAHLUNG ENERGIES 36...91 MeV

2020 ◽  
pp. 148-153
Author(s):  
A.N. Vodin ◽  
O.S. Deiev ◽  
I.S. Timchenko ◽  
S.N. Olejnik ◽  
A.S. Kachan ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Maximum Energy ◽  
Reaction Cross ◽  
Bremsstrahlung Spectrum ◽  
Photonuclear Reactions ◽  
End Point ◽  
Γ Ray ◽  
First Time ◽  
Good Agreement

The flux-weighted averaged over the energy range of bremsstrahlung spectrum from reaction threshold up to the maximum energy of γ-ray cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb photonuclear reactions were determined by the gamma-activation method within the end-point bremsstrahlung energies Еmax = 36…91 MeV. Activation of 93Nb targets has been done by a bremsstrahlung flux using an electron beam at the linear accelerator LUE-40 at RDC "Accelerator" NSC KIPT. The γ-ray spectra of irradiated targets were registered using the HPGe detector with an energy resolution of 1.8 keV for the 1332 keV line 60Co. To control the bremsstrahlung flux we used natMo witness-targets and a reaction cross-section of 100Mo(γ,n)99Mo. Obtained experimental cross-sections <σ(E)> of the studied reactions are in good agreement with the theoretical values calculated within TALYS 1.9 code and the results of other authors. The averaged cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb reactions in the energy range 35...45 MeV and > 70 MeV were obtained for the first time.

scholarly journals Взаимодействие alpha-частиц keV-энергий с молекулами глицил-лейцина

2021 ◽  
Vol 47 (12) ◽  
pp. 23
Author(s):  
А.А. Басалаев ◽  
А.Г. Бузыкин ◽  
В.В. Кузьмичев ◽  
М.Н. Панов ◽  
А.В. Петров ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Cross Sections ◽  
Density Functional ◽  
Molecular Ions ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Singly Charged ◽  
Doubly Charged ◽  
First Time ◽  
Fragmentation Processes

Radiation damage to isolated glycyl-leucine (C8H16N2O3) molecules caused by interaction with He2+ ions was studied. For the first time, the relative cross sections of the main processes of changes in the charge state of the collision partners and the relative cross sections of the fragmentation processes of singly and doubly charged molecular ions formed during single collisions of glycyl-leucine molecules with ions have been obtained. The optimized geometry of the molecule and singly charged glycyl-leucine ion was calculated using the density functional theory (DFT).

Review of the Secondary Flows of Complex Fluids

2003 ◽  
Author(s):  
Dennis A. Siginer
Keyword(s):  
Secondary Flow ◽  
Cross Sections ◽  
Secondary Flows ◽  
Laboratory Setting ◽  
Transfer Enhancement ◽  
Domain Perturbation ◽  
Novel Approach ◽  
Viscoelastic Liquids ◽  
First Time ◽  
Secondary Flow Field

A survey of secondary flows of viscoelastic liquids in straight tubes is given including recent work pointing at striking analogies with transversal deformations associated with the simple shearing of solid materials. The importance and implications of secondary flows of viscoelastic fluids in heat transfer enhancement are explored together with the difficulties in detecting weak secondary flows (dilute, weakly viscoelastic solutions) in a laboratory setting. Recent new work by the author and colleagues which explores for the first time the structure of the secondary flow field in the pulsating flow of a constitutively nonlinear simple fluid in straight tubes of arbitrary cross-sections is summarized. Arbitrary conduit contours are obtained through a novel approach to the concept of domain perturbation. Time averaged, mean secondary flow streamline contours are presented for the first time for triangular, square and hexagonal pipes.

Target electron removal in C5+ + H collision

2021 ◽  
Author(s):  
Saed J Al Atawneh ◽  
Karoly Tokesi
Keyword(s):  
Monte Carlo ◽  
Cross Sections ◽  
Dominant Role ◽  
Correction Term ◽  
Theoretical Data ◽  
Model Potential ◽  
Classical Trajectory ◽  
Projectile Energy ◽  
Collision Dynamics ◽  
The Cross

Abstract We present target ionization and charge exchange cross sections in a collision between C5+ ion and H atom. We treat the collision dynamics classically using a four-body classical trajectory Monte Carlo (CTMC) and a four-body quasi-classical Monte Carlo (QCTMC) model when the Heisenberg correction term is added to the standard CTMC model via model potential. The calculations were performed in the projectile energy range between 1.0 keV/amu and 10 MeV/amu. We found that the cross sections obtained by the QCTMC model are higher than that of the cross sections calculated by the standard CTMC model and these cross sections are closer to the previous experimental and theoretical data. Moreover, for the case of ionization, we show that the interaction between the projectile and the target electrons plays a dominant role in the enhancement of the cross sections at lower energies.

scholarly journals Charge Exchange Cross Sections for Noble Gas Ions and N2 between 0.2 and 5.0 keV

Atoms ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 96
Author(s):  
Steven Bromley ◽  
Corey Ahl ◽  
Chad Sosolik ◽  
Joan Marler
Keyword(s):  
Charge Exchange ◽  
Cross Sections ◽  
Neutral Atom ◽  
Mechanical Design ◽  
Noble Gas ◽  
Dominant Role ◽  
Intermediate Energy ◽  
Fundamental Interaction ◽  
Gas Cell ◽  
Astrophysical Plasmas

Charge transfer of an electron from a neutral atom to an ion is a fundamental interaction that plays a dominant role in the energy balance of atmospheric and astrophysical plasmas. The present investigation measured the charge exchange cross sections of noble gas ions (He + , Ne + , Ar + , Kr + ) with N 2 in the intermediate energy range 0.2–5.0 keV. The systems were chosen because there remains a lack of consensus amongst previous measurements and regions where there were no previous measurements. A description of the mechanical design for an electrically floated gas cell is described herein.

scholarly journals The Molecular Outflow and CO Bullets in HH111

1997 ◽  
Vol 182 ◽  
pp. 141-152 ◽  
Author(s):  
J. Cernicharo ◽  
R. Neri ◽  
Bo Reipurth
Keyword(s):  
High Velocity ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Low Velocity ◽  
Molecular Outflow ◽  
Hh Objects ◽  
Physical Phenomena ◽  
First Time

We present high angular resolution observations of the molecular outflow associated with the optical jet and HH objects of the HH111 system. Interferometric observations in the CO J =2–1 and J =1–0 lines of the high velocity bullets associated with HH111 are presented for the first time. The molecular gas in these high velocity clumps has a moderate kinetic temperature and a mass of a few 10–4 M⊙ per bullet. We favor the view that HH jets and CO bullets, which represent different manifestations of the same physical phenomena, are driving the low-velocity molecular outflow.

Sign in / Sign up

Export Citation Format

Share Document