scholarly journals Diffusion coefficient, correlation function, and power spectral density of velocity fluctuations in monolayer graphene

2013 ◽  
Vol 114 (14) ◽  
pp. 143702 ◽  
Author(s):  
R. Rengel ◽  
M. J. Martín
Keyword(s):  
Diffusion Coefficient ◽  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Monolayer Graphene ◽  
Velocity Fluctuations ◽  
Power Spectral ◽  
Coefficient Corrélation

scholarly journals Research on forest terrain roughness as a source of dynamic action on the vehicle

2017 ◽  
Vol 63 (No. 8) ◽  
pp. 363-369
Author(s):  
Mikleš Milan ◽  
Helexa Milan ◽  
Mikleš Juraj
Keyword(s):  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Ground Surface ◽  
Operating Conditions ◽  
Mobile Object ◽  
Object A ◽  
Power Spectral ◽  
Gneiss Granite ◽  
Ground Conditions

The issue of terrain conditions is very complex and its description is approached from different perspectives and with different objectives. Because it consists of the gathering of basic information for a mobile object, a wheeled forestry tractor, the terrain-vehicle approach was taken as the basis. Ground conditions are part of the operating conditions of wheeled forestry tractors. Uneven ground can be regarded as a source of vibration in the vehicle – towing truck. In this respect, given the random shape of the surface roughness, the solution to vibrations leads to a terrain correlation analysis in order to obtain a correlation function and power spectral density of the ground surface. Scanning of the ground micro-profile was performed using a device for quick terrain scanning, which from the mechanical aspect consists of a towing vehicle and a measuring carriage. Correlation function and power spectral density are the evaluation based on ground micro-profile measurements and the results of calculations. Measurements of forest terrain (road) micro-profile were done in the area of Little Fatra and Little Carpathians in Slovakia. In geological terms, the measurements were done in an area with the occurrence of gneiss, granite, limestone and flysch. No measurements were performed in a sandy area.

Power Spectral Density and Cross Correlation Function Analysis of Finished Surface by Abrasive Jet with Grinding Wheel as Restraint

2009 ◽  
Vol 416 ◽  
pp. 300-305 ◽  
Author(s):  
Chang He Li ◽  
Ya Li Hou ◽  
Yu Cheng Ding ◽  
Bing Heng Lu
Keyword(s):  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Function Analysis ◽  
Grinding Wheel ◽  
Work Surface ◽  
Power Spectral ◽  
Finishing Process ◽  
Finished Surface ◽  
Precision Finishing

The abrasive jet finishing process with wheel as restraint is a kind of compound precision finishing process that combined grinding with abrasive jet machining, in which inject slurry of abrasive and liquid solvent to grinding zone between grinding wheel and work surface under no radial feed condition when workpiece grinding were accomplished. The abrasive particles are driven and energized by the rotating grinding wheel and liquid hydrodynamic pressure and increased slurry speed between grinding wheel and work surface to achieve micro removal finishing.In the paper,the finished surface morphology was studied using Scanning Electron Microscope (SEM) and microscope and microcosmic geometry parameters were measured with TALYSURF5 instrument respectively. According to the metrical results, the surface topographical characteristics were evaluated with correlation function and PSD (Power Spectral Density) of random process about machined surface before and after finishing. The results show that longitudinal geometry parameter values of finishing machining surface were diminished comparing with ground surface,and the mean ripple distance was decreased and, ripple and peak density were increased. Furthermore, the finished surface has little comparability compared to grinding machining surface.The isotropy surface and uniformity veins at parallel and perpendicular machining direction were attained by abrasive jet precision finishing with grinding wheel as restraint and the surface quality is improved obviously.

scholarly journals Theoretical Comparison between the Flicker Noise Behavior of Graphene and of Ordinary Semiconductors

2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Massimo Macucci ◽  
Paolo Marconcini
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Flicker Noise ◽  
Mass Action ◽  
Monolayer Graphene ◽  
Noise Power ◽  
Charge Carrier Density ◽  
Charge Neutrality ◽  
Power Spectral ◽  
Neutrality Point

Graphene is a material of particular interest for the implementation of sensors, and the ultimate performance of devices based on such a material is often determined by its flicker noise properties. Indeed, graphene exhibits, with respect to the vast majority of ordinary semiconductors, a peculiar behavior of the flicker noise power spectral density as a function of the charge carrier density. While in most materials flicker noise obeys the empirical Hooge law, with a power spectral density inversely proportional to the number of free charge carriers, in bilayer, and sometimes monolayer, graphene a counterintuitive behavior, with a minimum of flicker noise at the charge neutrality point, has been observed. We present an explanation for this stark difference, exploiting a model in which we enforce both the mass action law and the neutrality condition on the charge fluctuations deriving from trapping/detrapping phenomena. Here, in particular, we focus on the comparison between graphene and other semiconducting materials, concluding that a minimum of flicker noise at the charge neutrality point can appear only in the presence of a symmetric electron-hole behavior, a condition characteristic of graphene, but which is not found in the other commonly used semiconductors.

scholarly journals Estimation of Evolutionary Spectra of Monitored Seismic Ground Motions by Transformation of Correlation Functions

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Zhifeng Xu ◽  
Li Li ◽  
Liang Hu
Keyword(s):  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Correlation Functions ◽  
Ground Motions ◽  
Engineering Structures ◽  
Power Spectral ◽  
Time Histories ◽  
Evolutionary Spectra ◽  
Sample Time

Spatially varying seismic ground motions recorded by distributed structural health monitoring systems (SHMS) can be used to improve the performances of civil engineering structures, necessitating estimation of the evolutionary power spectral density as an indispensable procedure for utilizing records of SHMS. This paper proposes a method for the estimation of evolutionary power spectral density of a nonstationary process by transforming the correlation functions of its sample time histories. First, the background of the theory of evolutionary power spectral density is reviewed in detail. Relationship between the EPSD and the correlation function of a reference stationary process is then established. Formulas are derived for estimating this correlation function directly from nonstationary sample time histories so that the EPSD can be obtained. The implementation procedure of the proposed method is also detailed. Finally, a numerical example is presented, which validates the proposed method, demonstrates its application for SHMS, and displays its capabilities by comparison with the traditional method.

Fuzzy Modeling of Multi-Degree-of-Freedom Power Spectral Density Systems

2009 ◽  
Vol 2 (1) ◽  
pp. 40-47
Author(s):  
Montasser Tahat ◽  
Hussien Al-Wedyan ◽  
Kudret Demirli ◽  
Saad Mutasher
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Fuzzy Modeling ◽  
Degree Of Freedom ◽  
Power Spectral
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