scholarly journals SPHERICAL STANDING BURNING WAVE WITH EXTERNAL AUTOMATIC REACTIVITY CONTROL

2019 ◽  
pp. 18-24
Author(s):  
Yu.Y. Leleko ◽  
V.V. Gann ◽  
A.V. Gann
Keyword(s):  
Computer Simulation ◽  
Nuclear Reactions ◽  
Neutron Kinetics ◽  
Mcnpx Code ◽  
Burning Wave ◽  
Peripheral Area ◽  
Nuclear Burning ◽  
Kinetics Of ◽  
Theoretical Results ◽  
Rate Comparison

Neutron kinetics of a nuclear burning wave in moving incompressible neutron-multiplying medium in the pres-ence of nuclear reactions is developed. A spherical reactor is considered, where fuel moves with acceleration to the center of the reactor at a velocity V(r)=VR(R/r)2, and the burning wave travels radially from the center to periphery. The fuel that came to the origin was unloaded from the reactor, and U-238 was loaded to the peripheral area at the same rate. Comparison of theoretical results with computer simulation using MCNPX code was performed.

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

On the kinetics of Hadamard-type fractional differential systems

2020 ◽  
Vol 23 (2) ◽  
pp. 553-570 ◽  
Author(s):  
Li Ma
Keyword(s):  
Differential Operator ◽  
Numerical Simulations ◽  
Type Inequality ◽  
The Other ◽  
Differential Systems ◽  
Fractional Differential Systems ◽  
Fractional Differential Operator ◽  
Fractional Differential ◽  
Kinetics Of ◽  
Theoretical Results

AbstractThis paper is devoted to the investigation of the kinetics of Hadamard-type fractional differential systems (HTFDSs) in two aspects. On one hand, the nonexistence of non-trivial periodic solutions for general HTFDSs, which are considered in some functional spaces, is proved and the corresponding eigenfunction of Hadamard-type fractional differential operator is also discussed. On the other hand, by the generalized Gronwall-type inequality, we estimate the bound of the Lyapunov exponents for HTFDSs. In addition, numerical simulations are addressed to verify the obtained theoretical results.

scholarly journals Nuclear burning in collapsar accretion discs

2020 ◽  
Vol 499 (3) ◽  
pp. 4097-4113 ◽  
Author(s):  
Yossef Zenati ◽  
Daniel M Siegel ◽  
Brian D Metzger ◽  
Hagai B Perets
Keyword(s):  
Angular Momentum ◽  
Gamma Ray ◽  
Nuclear Reactions ◽  
Reaction Network ◽  
Accretion Discs ◽  
Late Time ◽  
Rotating Stars ◽  
Stellar Envelope ◽  
Nuclear Burning ◽  
R Process

ABSTRACT The core collapse of massive, rapidly-rotating stars are thought to be the progenitors of long-duration gamma-ray bursts (GRB) and their associated hyperenergetic supernovae (SNe). At early times after the collapse, relatively low angular momentum material from the infalling stellar envelope will circularize into an accretion disc located just outside the black hole horizon, resulting in high accretion rates necessary to power a GRB jet. Temperatures in the disc mid-plane at these small radii are sufficiently high to dissociate nuclei, while outflows from the disc can be neutron-rich and may synthesize r-process nuclei. However, at later times, and for high progenitor angular momentum, the outer layers of the stellar envelope can circularize at larger radii ≳ 107 cm, where nuclear reactions can take place in the disc mid-plane (e.g. 4He + 16O → 20Ne + γ). Here we explore the effects of nuclear burning on collapsar accretion discs and their outflows by means of hydrodynamical α-viscosity torus simulations coupled to a 19-isotope nuclear reaction network, which are designed to mimic the late infall epochs in collapsar evolution when the viscous time of the torus has become comparable to the envelope fall-back time. Our results address several key questions, such as the conditions for quiescent burning and accretion versus detonation and the generation of 56Ni in disc outflows, which we show could contribute significantly to powering GRB SNe. Being located in the slowest, innermost layers of the ejecta, the latter could provide the radioactive heating source necessary to make the spectral signatures of r-process elements visible in late-time GRB-SNe spectra.

Experimental Investigations of the Kinetics of a Catalytic Trapping Reaction in Confined Spaces

1996 ◽  
Vol 464 ◽  
Author(s):  
Mark S. Feldman ◽  
Anna L. Lin ◽  
Raoul Kopelman
Keyword(s):  
Reaction Front ◽  
Rate Coefficient ◽  
Capillary Tube ◽  
One Dimension ◽  
Experimental Investigations ◽  
Confined Spaces ◽  
Diffusion Limited ◽  
Kinetics Of ◽  
Oxidation Of Glucose ◽  
Theoretical Results

AbstractWe investigate the anomalous kinetics in one dimension of a diffusion limited catalytic trapping reaction, A + T → T, by measuring the oxidation of glucose. The reaction is carried out in a thin capillary tube, and the depletion of oxygen in the vicinity of the reaction front is monitored by the fluorescence of a Ru(II) dye. Theoretical results and simulations have predicted an asymptotic t1/2 dependence for the rate coefficient. We observe a depedence on t0.56, with what appears to be an asymptotic behavior approaching t1/2.

scholarly journals Application of Computer Simulation to Study the Features of the Austenite Isothermal Transformation in Steels

2019 ◽  
Vol 1 (1) ◽  
pp. 1
Author(s):  
Yu.V. Yudin ◽  
M.V. Maisuradze ◽  
A.A. Kuklina ◽  
P.D. Lebedev
Keyword(s):  
Phase Transition ◽  
Computer Simulation ◽  
Solid State ◽  
Isothermal Transformation ◽  
Avrami Equation ◽  
Kinetic Curves ◽  
Simulation Results ◽  
Experimental Kinetics ◽  
Kinetics Of ◽  
New Phase

An algorithm was developed for the simulation of a phase transition in solid state whichmakes it possible to obtain the kinetic curves of transformation under different initialconditions (the number and arrangement of new phase nuclei, the distance betweenthe nearest nuclei). The simulation results were analyzed using the Kolmogorov-Johnson-Mehl-Avrami equation and the corresponding coefficients were determined.The correlation between the simulation results and the experimental kinetics of theaustenite isothermal transformation in alloyed steels was shown.

The Developments and its Applicaton Examples of Computer Simulation Code on Heat Treatment Process

2013 ◽  
Vol 651 ◽  
pp. 589-594
Author(s):  
Dong Ying Ju ◽  
Li Ping Cao
Keyword(s):  
Heat Treatment ◽  
Computer Simulation ◽  
Induction Heat ◽  
Simulation Code ◽  
Induction Heat Treatment ◽  
Coupled Equations ◽  
Field Diffusion ◽  
Material Process ◽  
And Function ◽  
Kinetics Of

Strategy and function of a new developed FEM code COSMAP(COmputer Simulation of MAterial Process) for surface hardening during of thermo-mechanical processing, including heat treatment, carbonizing and nitriding and induction heat treatment, is briefly introduced in this paper. The simulation code is developed based on the metallo-thermo-mechanical theory considering the coupled equations of magnetic or electrical field, diffusion, heat conduction, inelastic stresses and kinetics of phase transformation. Some examples of simulation and the experimental verification for induction heat treatment, carbonized quenching, carbonized- nitrided-quenching process of a cylinder and ring as well as a gear are illustrated, and comparison of the simulated values of distortion, residual stresses and profile of induced phases with the experimental data is made with some discussions.

Thermodynamics and kinetics of homogeneous crystal nucleation studied by computer simulation

2000 ◽  
Vol 62 (22) ◽  
pp. 14690-14702 ◽  
Author(s):  
H. E. A. Huitema ◽  
J. P. van der Eerden ◽  
J. J. M. Janssen ◽  
H. Human
Keyword(s):  
Computer Simulation ◽  
Crystal Nucleation ◽  
Thermodynamics And Kinetics ◽  
Homogeneous Crystal ◽  
Kinetics Of

Influence of the radial neutron reflector efficiency on the power of fast nuclear-burning-wave reactor

2020 ◽  
Vol 148 ◽  
pp. 107699
Author(s):  
S.P. Fomin ◽  
A.I. Kirdin ◽  
M.S. Malovytsia ◽  
V.V. Pilipenko ◽  
N.F. Shul’ga
Keyword(s):  
Burning Wave ◽  
Nuclear Burning

Level density model effects on the production cross-section calculations of some medical isotopes via (α, xn) reactions where x = 1–3

2020 ◽  
Vol 35 (24) ◽  
pp. 2050202
Author(s):  
Mert Şekerci ◽  
Hasan Özdoğan ◽  
Abdullah Kaplan
Keyword(s):  
Cross Section ◽  
Production Cross Section ◽  
Nuclear Reactions ◽  
Theoretical Calculations ◽  
Production Cross ◽  
Level Density ◽  
Medical Application ◽  
Density Model ◽  
Level Density Models ◽  
Theoretical Results

Level density models have an undeniable importance for a better perception on the nature of nuclear reactions, which influences our life via various ways. Many novel and advanced medical application use radioisotopes, which are produced with nuclear reactions. By considering the connection between the level density models and the importance of theoretical calculations for the production routes of medically important isotopes, this study is performed to investigate the level density model effects on the production cross-section calculations of [Formula: see text]Zn, [Formula: see text]Ga, [Formula: see text]Kr, [Formula: see text]Pd, [Formula: see text]In, [Formula: see text]I and [Formula: see text]At radioisotopes via some alpha particle induced and neutron emitting reactions. For theoretical calculations; frequently used computation tools, such as TALYS and EMPIRE codes, are applied. Obtained theoretical results are then compared with the experimental data, taken from Experimental Nuclear Reaction Data (EXFOR) library. For a better interpretation of the results, a mean weighted deviation calculation for each investigated reaction is performed in addition to a visual comparison of the graphical representations of the outcomes.

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