scholarly journals Modeling the Influence of the Penetration Channel’s Shape on Plasma Parameters When Handling Highly Concentrated Energy Sources

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Dmitriy N. Trushnikov ◽  
Ekaterina S. Salomatova ◽  
Igor I. Bezukladnikov ◽  
Igor L. Sinani ◽  
K. P. Karunakaran
Keyword(s):  
Electron Beam Welding ◽  
Gaussian Function ◽  
Three Dimensional ◽  
Energy Sources ◽  
Plasma Parameters ◽  
Statistical Probability ◽  
Secondary Current ◽  
Thermal Fields ◽  
Sustained Discharge ◽  
A Current

In our work to formulate a scientific justification for process control methods when processing materials using concentrated energy sources, we develop a model that can calculate plasma parameters and the magnitude of the secondary waveform of a current from a non-self-sustained discharge in plasma as a function of the geometry of the penetration channel, thermal fields, and the beam’s position within the penetration channel. We present the method and a numeric implementation whose first stage involves the use of a two-dimensional model to calculate the statistical probability of the secondary electrons’ passage through the penetration channel as a function of the interaction zone’s depth. Then, the discovered relationship is used to numerically calculate how the secondary current changes as a distributed beam moves along a three-dimensional penetration channel. We demonstrate that during oscillating electron beam welding the waveform has the greatest magnitude during interaction with the upper areas of the penetration channel and diminishes with increasing penetration channel depth in a way that depends on the penetration channel’s shape. When the surface of the penetration channel is approximated with a Gaussian function, the waveform decreases nearly exponentially.

scholarly journals Inferring Single-Cell 3D Chromosomal Structures Based on the Lennard-Jones Potential

2021 ◽  
Vol 22 (11) ◽  
pp. 5914
Author(s):  
Mengsheng Zha ◽  
Nan Wang ◽  
Chaoyang Zhang ◽  
Zheng Wang
Keyword(s):  
Single Cell ◽  
Loss Function ◽  
Gaussian Function ◽  
Three Dimensional ◽  
Lennard Jones Potential ◽  
Jones Potential ◽  
Cubic Lattice ◽  
Lennard Jones ◽  
3D Fish ◽  
Well Depth

Reconstructing three-dimensional (3D) chromosomal structures based on single-cell Hi-C data is a challenging scientific problem due to the extreme sparseness of the single-cell Hi-C data. In this research, we used the Lennard-Jones potential to reconstruct both 500 kb and high-resolution 50 kb chromosomal structures based on single-cell Hi-C data. A chromosome was represented by a string of 500 kb or 50 kb DNA beads and put into a 3D cubic lattice for simulations. A 2D Gaussian function was used to impute the sparse single-cell Hi-C contact matrices. We designed a novel loss function based on the Lennard-Jones potential, in which the ε value, i.e., the well depth, was used to indicate how stable the binding of every pair of beads is. For the bead pairs that have single-cell Hi-C contacts and their neighboring bead pairs, the loss function assigns them stronger binding stability. The Metropolis–Hastings algorithm was used to try different locations for the DNA beads, and simulated annealing was used to optimize the loss function. We proved the correctness and validness of the reconstructed 3D structures by evaluating the models according to multiple criteria and comparing the models with 3D-FISH data.

Indentation of a Transversely Isotropic Thermoporoelastic Half-Space by a Rigid Circular Cylindrical Punch

2017 ◽  
Vol 84 (11) ◽  
Author(s):  
Yilan Huang ◽  
Guozhan Xia ◽  
Weiqiu Chen ◽  
Xiangyu Li
Keyword(s):  
Half Space ◽  
Original Problem ◽  
Three Dimensional ◽  
Transversely Isotropic ◽  
The Finite Element Method ◽  
Thermal Fields ◽  
Cylindrical Punch ◽  
The One ◽  
Physical Quantities ◽  
Potential Theory Method

Exact solutions to the three-dimensional (3D) contact problem of a rigid flat-ended circular cylindrical indenter punching onto a transversely isotropic thermoporoelastic half-space are presented. The couplings among the elastic, hydrostatic, and thermal fields are considered, and two different sets of boundary conditions are formulated for two different cases. We use a concise general solution to represent all the field variables in terms of potential functions and transform the original problem to the one that is mathematically expressed by integral (or integro-differential) equations. The potential theory method is extended and applied to exactly solve these integral equations. As a consequence, all the physical quantities of the coupling fields are derived analytically. To validate the analytical solutions, we also simulate the contact behavior by using the finite element method (FEM). An excellent agreement between the analytical predictions and the numerical simulations is obtained. Further attention is also paid to the discussion on the obtained results. The present solutions can be used as a theoretical reference when practically applying microscale image formation techniques such as thermal scanning probe microscopy (SPM) and electrochemical strain microscopy (ESM).

Thermal Analysis of Solids at High Peclet Numbers Subjected to Moving Heat Sources

1999 ◽  
Vol 121 (1) ◽  
pp. 182-186 ◽  
Author(s):  
O. Manca ◽  
B. Morrone ◽  
S. Nardini
Keyword(s):  
Thermal Field ◽  
Three Dimensional ◽  
Heat Losses ◽  
Transfer Model ◽  
Heat Sources ◽  
Moving Heat Source ◽  
Motion Direction ◽  
Thermal Fields ◽  
Diffusion Component ◽  
Conductive Thermal Field

A three-dimensional heat transfer model has been developed to obtain the conductive thermal field inside a brick-type solid under a moving heat source with different beam profiles. The problem in quasi-steady state has been approximated by neglecting the axial diffusion component; thus, for Peclet numbers greater than 5, the elliptic differential equation becomes a parabolic one along the motion direction. The dependence of the solution on the radiative and convective heat losses has been highlighted. Thermal fields are strongly dependent on different spot shapes and on the impinging jet; this situation allows control of the parameters involved in the technological process.

A current assessment of photosystem II structure

1996 ◽  
Vol 16 (2) ◽  
pp. 159-187 ◽  
Author(s):  
William V. Nicholson ◽  
Robert C. Ford ◽  
Andreas Holzenburg
Keyword(s):  
Photosystem Ii ◽  
Structural Information ◽  
Three Dimensional ◽  
Structural Data ◽  
X Ray Diffraction ◽  
Membrane Protein Complex ◽  
Fast Absorption ◽  
Current Assessment ◽  
Electron Microscopical ◽  
A Current

This review covers the recent progress in the elucidation of the structure of photosystem II (PSII). Because much of the structural information for this membrane protein complex has been revealed by electron microscopy (EM), the review will also consider the specific technical and interpretation problems that arise with EM where they are of particular relevance to the structural data. Most recent reviews of photosystem II structure have concentrated on molecular studies of the PSII genes and on the likely roles of the subunits that they encode or they were mainly concerned with the biophysical data and fast absorption spectroscopy largely relating to electron transfer in various purified PSII preparations. In this review, we will focus on the approaches to the three-dimensional architecture of the complex and the lipid bilayer in which it is located (the thylakoid membrane) with special emphasis placed upon electron microscopical studies of PSII-containing thylakoid membranes. There are a few reports of 3D crystals of PSII and of associated X-ray diffraction measurements and although little structural information has so far been obtained from such studies (because of the lack of 3D crystals of sufficient quality), the prospects for such studies are also assessed.

Residual Stresses in Steel and Zirconium Weldments

1997 ◽  
Vol 119 (2) ◽  
pp. 137-141 ◽  
Author(s):  
J. H. Root ◽  
C. E. Coleman ◽  
J. W. Bowden ◽  
M. Hayashi
Keyword(s):  
Residual Stress ◽  
Electron Beam ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Prolonged Exposure ◽  
Electron Beam Welding ◽  
Three Dimensional ◽  
Diffraction Method ◽  
Outer Diameter ◽  
Stress Relieving

Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5Nb plate have shown that heat treatment at 530°C for 1 h reduces the longitudinal residual strain by 60 percent. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclear reactor.

scholarly journals 3D turbulent reconnection driven current-sheet dynamics: solar applications

2010 ◽  
Vol 6 (S274) ◽  
pp. 458-460
Author(s):  
Lapo Bettarini ◽  
Giovanni Lapenta
Keyword(s):  
Current Sheet ◽  
Characteristic Time ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Anomalous Effect ◽  
Instability Modes ◽  
Diffusive Dynamics ◽  
Three Dimensional Configuration ◽  
A Current ◽  
Dimensional Picture

AbstractWe provide a complete three-dimensional picture of the reconnecting dynamics of a current-sheet. Recently, a two-dimensional non-steady reconnection dynamics has been proved to occur without the presence of any anomalous effect (Lapenta, 2008, Skender & Lapenta, 2010, Bettarini & Lapenta, 2010) but such a picture must be confirmed in a full three-dimensional configuration wherein all instability modes are allowed to drive the evolution of the system, i.e. to sustain a reconnection dynamics or to push the system along a different instability path. Here we propose a full-space analysis allowing us to determine the longitudinal and, possibly, the transversal modes driving the different current-sheet disruption regimes, the corresponding characteristic time-scales and to study system's instability space- parameter (plasma beta, Lundquist and Reynolds numbers, system's aspect ratio). The conditions leading to an explosive evolution rather then to a diffusive dynamics as well as the details of the reconnection inflow/outflow regime at the disruption phase are determined. Such system embedded in a solar-like environment and undergoing a non-steady reconnection evolution may determine the formation both of jets and waves influencing the dynamics and energetic of the upper layers and of characteristic down-flows as observed in the low solar atmosphere.

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