Impact of nuclear inertia momenta on fission observables

Fission is probably the nuclear process the less accurately described with current models because it involves dynamics of nuclear matter with strongly coupled manybody interactions. It is thus diffcult to find models that are strongly rooted in good physics, accurate enough to reproduce target observables and that can describe many of the nuclear fission observables in a consistent way. One of the most comprehensive current modeling of the fission process relies on the fission sampling and Monte-Carlo de-excitation of the fission fragments. This model is implemented for instance in the FIFRELIN code. In this model fission fragments and their state are first sampled from pre-neutron fission yields, angular momentum distribution and excitation energy repartition law then the decay of both initial fragments is simulated. This modeling provides many observables: prompt neutron and gamma fission spectra, multiplicities and also fine decompositions: number of neutrons emitted as a function of the fragment mass, spectra per fragments, etc. This model relies on nuclear structure databases and on several basic nuclear models describing for instance gamma strength functions or level densities. Additionally some free parameters are still to be determined, namely two parameters describing the excitation energy repartition law, the spin cutoff of the heavy and light fragments and a rescaling parameter for the rotational inertia momentum of the fragments with respect of the rigid-body model. In the present work we investigate the impact of this latter parameter. For this we mainly substitute the corrected rigid-body value by a quantity obtained from a microscopic description of the fission fragment. The independent-particle model recently implemented in the CONRAD code is used to provide nucleonic wave functions that are required to compute inertia momenta with an Inglis-Belyaev cranking model. The impact of this substitution is analyzed on different fission observables provided by the FIFRELIN code.

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Research on Dynamic Modelling and Simulation of Erection System of Mobile Equipment in Absolute Coordinates

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.66-68.2034 ◽

2011 ◽

Vol 66-68 ◽

pp. 2034-2040

Author(s):

Qin He Gao ◽

Xiang Yang Li

Keyword(s):

Rigid Body ◽

Dynamic Models ◽

Dynamic Modelling ◽

Hydraulic Cylinder ◽

Correction Method ◽

Integration Time ◽

Multi Stage ◽

Rigid Body Model ◽

Absolute Coordinates ◽

The Impact

This paper employed the theories of multibody system dynamics to analyze the multi-rigid-body model of erection system and build the general dynamic models in absolute coordinates. The impact theory of contact mechanics and nonlinear spring-damper force function were used to model the impact problems between rods of multi-stage hydraulic cylinder of erection system and educe the dynamic models of multi-rigid-body erection system with impact. An automatic violation correction method according to the step of integration time was given to solve the violation which is an incident problem in numerical integration of dynamic models in absolute coordinates. Simulation results show that these dynamic models are effective.

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The 4-dimensional Langevin approach to low energy nuclear fission

EPJ Web of Conferences ◽

10.1051/epjconf/201816900005 ◽

2018 ◽

Vol 169 ◽

pp. 00005

Author(s):

F.A. Ivanyuk ◽

C. Ishizuka ◽

M.D. Usang ◽

S. Chiba

Keyword(s):

Excitation Energy ◽

Mass Number ◽

Nuclear Fission ◽

Deformation Energy ◽

Low Energy ◽

Tooth Structure ◽

Fission Fragments ◽

Langevin Approach ◽

Intrinsic Excitation ◽

Mother Nucleus

We applied the four-dimensional Langevin approach to the description of fission of 235U by neutrons and calculated the dependence of the excitation energy of fission fragments on their mass number. For this we have fitted the compact just-before-scission configuration obtained by the Langevin calculations by the two separated fragments and calculated the intrinsic excitation and the deformation energy of each fragment accurately taking into account the shell and pairing effects and their dependence on the temperature and mass of the fragments. For the sharing of energy between the fission fragments we have used the simplest and most reliable assumption - the temperature of each fragment immediately after the neck rupture is the same as the temperature of mother nucleus just before scission. The calculated excitation energy of fission fragments clearly demonstrates the saw-tooth structure in the dependence on fragment mass number.

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Three-Dimensional Frictional Rigid-Body Impact

Journal of Applied Mechanics ◽

10.1115/1.2896017 ◽

1995 ◽

Vol 62 (4) ◽

pp. 893-898 ◽

Cited By ~ 32

Author(s):

V. Bhatt ◽

Jeff Koechling

Keyword(s):

Differential Equations ◽

Rigid Body ◽

Initial Conditions ◽

Three Dimensional ◽

Local Analysis ◽

Integration Scheme ◽

Numerical Integration Scheme ◽

Rigid Body Model ◽

Global Nature ◽

The Impact

We present an analysis of the rigid-body model for frictional three-dimensional impacts, which was originally studied by Routh. Using Coulomb’s law for friction, a set of differential equations describing the progress and outcome of the impact process for general bodies can be obtained. The differential equations induce a flow in the tangent velocity space for which the trajectories cannot be solved for in a closed form, and a numerical integration scheme is required. At the point of sticking, the numerical problem becomes ill-conditioned and we have to analyze the flow at the singularity to determine the rest of the process. A local analysis at the point of sticking provides enough information about the global nature of the flow to let us enumerate all the possible dynamic scenarios for the sliding behavior during impact. The friction coefficient, and the mass parameters at the point of contact, determine the particular sliding behavior that would occur for a given problem. Once the initial conditions are specified, the possible outcome of the impact can then be easily determined.

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The description of the excitation energy sharing in nuclear fission within the Langevin approach

EPJ Web of Conferences ◽

10.1051/epjconf/202125600007 ◽

2021 ◽

Vol 256 ◽

pp. 00007

Author(s):

F.A. Ivanyuk ◽

S. Chiba

Keyword(s):

Excitation Energy ◽

Mass Number ◽

Nuclear Fission ◽

Deformation Energy ◽

Langevin Equations ◽

Excitation Energies ◽

Tooth Structure ◽

Fission Fragments ◽

Langevin Approach ◽

Energy Sharing

We apply the four-dimensional Langevin approach to the description of fission of 235U by neutrons and calculate the dependence of the excitation energy of fission fragments on their mass number. For this we run the Langevin equations until the compound nucleus splits into two separated fragments. This is possible since the we used in this work two-center shell model shape parametrization that describes well both compact and separated shapes. The excitation energies of each fragment are calculated assuming that the temperatures of both fragments are the same. The deformation energy of the fragment immediately after scission is added to its excitation energy. The saw-tooth structure of the dependence neutron multiplicity on the fragment’s mass number in reaction 235U + n at En = 5 Mev is qualitatively reproduced.

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PERFORMANCE ASSESSMENT OF AN ELECTRIC REMOTELY PILOTED AIRCRAFT EMPLOYING RIGID BODY MODEL

10.26678/abcm.cobem2019.cob2019-0466 ◽

2019 ◽

Author(s):

Vinícius Santos Pereira ◽

Pedro Paglione ◽

Andre Luis da Silva

Keyword(s):

Rigid Body ◽

Performance Assessment ◽

Body Model ◽

Rigid Body Model ◽

Remotely Piloted Aircraft

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Impact of Scene Content on High Resolution Video Quality

Sensors ◽

10.3390/s21082872 ◽

2021 ◽

Vol 21 (8) ◽

pp. 2872

Author(s):

Miroslav Uhrina ◽

Anna Holesova ◽

Juraj Bienik ◽

Lukas Sevcik

Keyword(s):

Video Compression ◽

Spatial Information ◽

Video Quality ◽

Video Sequences ◽

Compression Efficiency ◽

Opinion Score ◽

Scene Description ◽

Two Parameters ◽

The University ◽

The Impact

This paper deals with the impact of content on the perceived video quality evaluated using the subjective Absolute Category Rating (ACR) method. The assessment was conducted on eight types of video sequences with diverse content obtained from the SJTU dataset. The sequences were encoded at 5 different constant bitrates in two widely video compression standards H.264/AVC and H.265/HEVC at Full HD and Ultra HD resolutions, which means 160 annotated video sequences were created. The length of Group of Pictures (GOP) was set to half the framerate value, as is typical for video intended for transmission over a noisy communication channel. The evaluation was performed in two laboratories: one situated at the University of Zilina, and the second at the VSB—Technical University in Ostrava. The results acquired in both laboratories reached/showed a high correlation. Notwithstanding the fact that the sequences with low Spatial Information (SI) and Temporal Information (TI) values reached better Mean Opinion Score (MOS) score than the sequences with higher SI and TI values, these two parameters are not sufficient for scene description, and this domain should be the subject of further research. The evaluation results led us to the conclusion that it is unnecessary to use the H.265/HEVC codec for compression of Full HD sequences and the compression efficiency of the H.265 codec by the Ultra HD resolution reaches the compression efficiency of both codecs by the Full HD resolution. This paper also includes the recommendations for minimum bitrate thresholds at which the video sequences at both resolutions retain good and fair subjectively perceived quality.

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Coastal Mangrove Response to Marine Erosion: Evaluating the Impacts of Spatial Distribution and Vegetation Growth in Bangkok Bay from 1987 to 2017

Remote Sensing ◽

10.3390/rs12020220 ◽

2020 ◽

Vol 12 (2) ◽

pp. 220 ◽

Cited By ~ 2

Author(s):

Han Xiao ◽

Fenzhen Su ◽

Dongjie Fu ◽

Qi Wang ◽

Chong Huang

Keyword(s):

Spatial Distribution ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Mangrove Ecosystem ◽

Early Growth ◽

Growth Stages ◽

Human Disturbances ◽

Vegetation Growth ◽

Two Parameters ◽

The Impact

Long time-series monitoring of mangroves to marine erosion in the Bay of Bangkok, using Landsat data from 1987 to 2017, shows responses including landward retreat and seaward extension. Quantitative assessment of these responses with respect to spatial distribution and vegetation growth shows differing relationships depending on mangrove growth stage. Using transects perpendicular to the shoreline, we calculated the cross-shore mangrove extent (width) to represent spatial distribution, and the normalized difference vegetation index (NDVI) was used to represent vegetation growth. Correlations were then compared between mangrove seaside changes and the two parameters—mangrove width and NDVI—at yearly and 10-year scales. Both spatial distribution and vegetation growth display positive impacts on mangrove ecosystem stability: At early growth stages, mangrove stability is positively related to spatial distribution, whereas at mature growth the impact of vegetation growth is greater. Thus, we conclude that at early growth stages, planting width and area are more critical for stability, whereas for mature mangroves, management activities should focus on sustaining vegetation health and density. This study provides new rapid insights into monitoring and managing mangroves, based on analyses of parameters from historical satellite-derived information, which succinctly capture the net effect of complex environmental and human disturbances.

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