scholarly journals Formation of cluster crystals in an ultra-soft potential model on a spherical surface

Soft Matter ◽  
2018 ◽  
Vol 14 (43) ◽  
pp. 8724-8739 ◽  
Author(s):  
Stefano Franzini ◽  
Luciano Reatto ◽  
Davide Pini
Keyword(s):  
Point Defects ◽  
Potential Model ◽  
Spherical Surface ◽  
Soft Potential ◽  
Spherical Surfaces ◽  
Soft Particles

DFT and simulations show clustering of soft particles on spherical surfaces, where geometry leads to many different crystals with ineliminable point defects.

Testing the link between mergers and AGN in the Arp 245 system

2020 ◽  
Vol 15 (S359) ◽  
pp. 192-194
Author(s):  
Elismar Lösch ◽  
Daniel Ruschel-Dutra
Keyword(s):  
Star Formation ◽  
Active Galactic Nucleus ◽  
Spherical Surface ◽  
Galaxy Mergers ◽  
Nuclear Activity ◽  
Upper Limit ◽  
Spherical Surfaces ◽  
Galactic Centers ◽  
Merger Event ◽  
Major Merger

AbstractGalaxy mergers are known to drive an inflow of gas towards galactic centers, potentia- lly leading to both star formation and nuclear activity. In this work we aim to study how a major merger event in the ARP 245 system is linked with the triggering of an active galactic nucleus (AGN) in the NGC galaxy 2992. We employed three galaxy collision numerical simulations and calculated the inflow of gas through four different concentric spherical surfaces around the galactic centers, estimating an upper limit for the luminosity of an AGN being fed the amount of gas crossing the innermost spherical surface. We found that these simulations predict reasonable gas inflow rates when compared with the observed AGN luminosity in NGC 2992.

Research on Transition Zones of Spherical Surface Parts in 3D Rolling Process

2014 ◽  
Vol 687-691 ◽  
pp. 3-6
Author(s):  
Da Ming Wang ◽  
Ming Zhe Li ◽  
Zhong Yi Cai
Keyword(s):  
Sheet Metal ◽  
Spherical Surface ◽  
Three Dimensional ◽  
Rolling Process ◽  
Experimental Results ◽  
Transition Zones ◽  
Spherical Surfaces ◽  
Sheet Width ◽  
Forming Precision ◽  
Roll Gap

3D rolling is a novel technology for three-dimensional surface parts. In this process, by controlling the gap between the upper and lower forming rolls, the sheet metal is non-uniformly thinned in thickness direction, and the longitudinal elongation of the sheet metal is different along the transverse direction, which makes the sheet metal generate three-dimensional deformation. In this paper, the transition zones of spherical surface parts in 3D rolling process are investigated. Spherical surface parts with the same widths but different lengths are simulated in condition of the same roll gap, and their experimental results are presented. The forming precision of forming parts and the causes of transition zones in the head and tail regions are analyzed through simulated results. The simulated and experimental results show that the lengths of transition zones of spherical surfaces in the head and tail regions are fixed values in condition of the same sheet width and roll gap.

scholarly journals Simulations of Defect-Interface Interactions in GaN

2000 ◽  
Vol 5 (S1) ◽  
pp. 287-293
Author(s):  
J. A. Chisholm ◽  
P. D. Bristowe
Keyword(s):  
Electronic Structure ◽  
Binding Energy ◽  
Point Defects ◽  
Potential Model ◽  
Pair Potential ◽  
Planar Defects ◽  
Native Defects ◽  
Native Point Defects ◽  
Bulk Gan ◽  
Image Position

We report on the interaction of native point defects with commonly observed planar defects in GaN. Using a pair potential model we find a positive binding energy for all native defects to the three boundary structures investigated indicating a preference for native defects to form in these interfaces. The binding energy is highest for the Ga interstitial and lowest for vacancies. Interstitials, which are not thought to occur in significant concentrations in bulk GaN, should form in the (11 0) IDB and the (10 0) SMB and consequently alter the electronic structure of these boundaries.

Study of The Tool Path Generation Method of an Ultra-Precision Spherical Complex Surface Based on a Five-Axis Machine Tool

2021 ◽  
Author(s):  
Tianji Xing ◽  
Xuesen Zhao ◽  
Zhipeng Cui ◽  
Rongkai Tan ◽  
Tao Sun
Keyword(s):  
Surface Roughness ◽  
Tool Path ◽  
Spherical Surface ◽  
Tool Path Generation ◽  
Path Generation ◽  
Tool Paths ◽  
Spherical Surfaces ◽  
Spherical Complex ◽  
Ultra Precision ◽  
Five Axis

Abstract The improvement of ultra-precision machining technology has significantly boosted the demand for the surface quality and surface accuracy of the workpieces to be machined. However, the geometric shapes of workpiece surfaces cannot be adequately manufactured with simple plane, cylindrical, or spherical surfaces because of their different applications in various fields. In this research, a method was proposed to generate tool paths for the machining of complex spherical surfaces based on an ultra-precise five-axis turning and milling machine with a C-Y-Z-X-B structure. Through the proposed tool path generation method, ultra-precise complex spherical surface machining was achieved. First, the complex spherical surface model was modeled and calculated, and then it was combined with the designed model to generate the tool path. Then the tool paths were generated with a numerically controlled (NC) program. Based on an ultra-precision three-coordinate measuring instrument and a white light interferometer, the machining accuracy of a workpiece surface was characterized, and t[1]he effectiveness of the provided tool path generation method was verified. The surface roughness of the machined workpiece was less than 90 nm. Furthermore, the surface roughness within the spherical region appeared to be less than 30 nm. The presented tool path generation method in this research produced ultra-precision spherical complex surfaces. The method could be applied to complex spherical surfaces with other characteristics.

Fundamental Study on Diamond Spherical Shell Film for Polishing of Concave Spherical Surface

2008 ◽  
Vol 375-376 ◽  
pp. 380-384
Author(s):  
Duo Sheng Li ◽  
Dun Wen Zuo ◽  
Rong Fa Chen ◽  
Yu Li Sun ◽  
Bing Kun Xiang ◽  
...  
Keyword(s):  
Spherical Shell ◽  
Spherical Surface ◽  
High Surface ◽  
Chemical Vapor ◽  
High Hardness ◽  
Internal Quality ◽  
Curvature Radius ◽  
Fundamental Study ◽  
Force Microscopy ◽  
Spherical Surfaces

In this paper, a new polishing technique was proposed to polish concave spherical surface by diamond spherical shell deposited by DC-Plasma Jet CVD(chemical vapor deposition), and preparation was studied from both experiment and theory. The deposited films were investigated by some techniques including: scanning electron microscopy (SEM), atom force microscopy (AFM), Raman spectroscopy, and roughness-profile-meter, which were used to analyze surface phase, microstructure, internal quality and surface roughness. The results show that the deposited diamond spherical shell film has some remarkable properties, such as high surface density, high hardness. Compared to traditional polishing techniques, it will have some potential advantages as convenient, flexible, efficient and precious. To adjust some important parameters as methane concentration, depositing time, and it can deposit the different size grain diamond spherical shell films, which are used to polish different precision degree concave spherical surfaces. Meantime, to change curvature of diamond spherical shell, it can adapt to polish various curvature radius concave spherical surfaces.

scholarly journals CAPACITANCE MEASUREMENTS AND ELECTROSTATIC CALIBRATIONS IN EXPERIMENTS MEASURING THE CASIMIR FORCE

2011 ◽  
Vol 03 ◽  
pp. 527-540 ◽  
Author(s):  
R. S. DECCA ◽  
E. FISCHBACH ◽  
G. L. KLIMCHITSKAYA ◽  
D. E. KRAUSE ◽  
D. LÓPEZ ◽  
...  
Keyword(s):  
Casimir Force ◽  
Spherical Surface ◽  
Scaling Law ◽  
Anomalous Scaling ◽  
Capacitance Measurements ◽  
Spherical Surfaces ◽  
Theoretical Predictions ◽  
Coated Surfaces ◽  
Micrometer Size

We discuss the possibility of determining the properties and quality of spherical surfaces used in precise experiments with the help of capacitance measurements. The results of this kind measurements for the lens-plane and sphere-plane, Au coated surfaces are compared with theoretical predictions from various models of perfect and broken sphericity. It is shown that capacitance measurements are incapable of discriminating between models of perfect and modified centimeter-size spherical surfaces in an experiment demonstrating the anomalous scaling law for the electric force. Claims to the contrary in the recent literature are explained by the use of improper comparison. The data from capacitance measurements in an experiment measuring the Casimir force by means of a micromechanical torsional oscillator employing micrometer-size spheres are shown to be in excellent agreement with theoretical predictions using the model of a perfect spherical surface.

Experimental Study on Ultra-Precision ELID Grinding for Concave Spherical Surface of Carbide

2009 ◽  
Vol 416 ◽  
pp. 18-22
Author(s):  
Fu Qiang Tong ◽  
Yong Zhang ◽  
Fei Hu Zhang
Keyword(s):  
Surface Roughness ◽  
Spherical Surface ◽  
Diamond Powder ◽  
Workpiece Material ◽  
Elid Grinding ◽  
Grinding Method ◽  
Generating Method ◽  
Spherical Surfaces ◽  
Negative Effect ◽  
Ultra Precision

This paper describes the current situation of spherical grinding for carbide material. The experiment of Concave spherical ELID grinding of generating method for carbide is conducted. Because dressing electrode can’t be installed in limited space due to the small space of concave spherical surfaces and carbide material has good conductivity, the workpiece material was used as dressing electrode in the ELID grinding experiment. According to negative effect of spark discharge in the process of grinding to surface roughness, two methods "ELIDⅡ" and "ELID Ⅲ" were designed. Comparing and analyzing the experimental results, it is confirmed preliminary that the spherical error and surface roughness of the workpiece after "ELIDⅡ" grinding were better than those after the "ELID Ⅲ" grinding. The ELID grinding method using micro diamond powder wheel and using carbide workpiece as dressing electrode is an effective way for spherical ultra-precision grinding for carbide.

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