The Analysis of Thermoelectric Signals in Metallic Sliding

1989 ◽  
Vol 111 (1) ◽  
pp. 114-120 ◽  
Author(s):  
Jui-Hsieh Shen ◽  
C. M. Ettles ◽  
H. A. Scarton
Keyword(s):  
Power Spectrum ◽  
Surface Temperature ◽  
Surface Topography ◽  
Temperature Rise ◽  
Signal Analysis ◽  
Steel Surface ◽  
Power Spectra ◽  
Average Temperature ◽  
Voltage Signal ◽  
Temperature Signal

The thermoelectric signal from an Alumel pin sliding over a steel surface was recorded and analyzed. The load, speed and surface topography were varied and correlations were attempted of the voltage signal against several parameters. The average temperature of the whole contact was found to agree fairly consistently with the surface temperature rise models of Blok and Archard. Of the available methods of signal analysis, the power spectrum of the voltage signal was found to give the best understanding of the micro-mechanisms of sliding, particularly when compared against the power spectra of profilometer signals. The largest component of the temperature signal was found to be caused by wavelength components equal to the extent of the contact. The correlation distance β* of the test surfaces was much less than the contact extent and contributed negligibly to the voltage signal rise.

scholarly journals Milking-related changes of teat temperature caused by various milking machines

2008 ◽  
Vol 53 (No. 4) ◽  
pp. 121-125 ◽  
Author(s):  
J. Vegricht ◽  
A. Machálek ◽  
P. Ambrož ◽  
U. Brehme ◽  
S. Rose
Keyword(s):  
Surface Temperature ◽  
Temperature Rise ◽  
Temperature Fluctuation ◽  
Blood Circulation ◽  
Average Temperature ◽  
Before And After ◽  
Working Quality

The aim of the performed work was to verify the hypothesis that different milking equipments have different influence on the blood circulation in the milk gland during milking. This influence was investigated by measuring the surface temperature of the milk gland using thermography. The influence was monitored of 5 different milking units in total, out of them 2 AMS, on the teat temperature which was scanned and evaluated in the teat tip centre and on the teat base at the same time with the surface temperature of the udder, always at the instant closely preceding the cluster application and then after its removal. It was ascertained that the average temperature of the teat tip after milking was increased in comparison with the temperature before milking practically in all the milking units monitored. At the same time, the average temperature of the teat tip in the milking equipment in parlours increased by about 1.7°C–2.7°C (6.1%–9.0%) as compared to the temperature before milking. At milking in AMS, the temperature rise of the teat tip was smaller and reached only 0.9°C–1.7°C (2.9%–6.0%). At the same time, the temperature of other parts of the milk gland grew commensurately. It was also found that differences exist between different milking units with respect to their influence on the temperature fluctuation of the milk gland. From the monitoring performed up to now and from the results acquired it is possible to apprehend that the monitoring of the teat temperature before and after milking with the help of thermography can become an indicator of the working quality of the milking equipment and its influence on the milk gland. The confirmation of this hypothesis requires, however, further detailed and extensive measuring to be carried out.

Polishing and Lapping Temperatures

1997 ◽  
Vol 119 (1) ◽  
pp. 163-170 ◽  
Author(s):  
Vispi H. Bulsara ◽  
Yoomin Ahn ◽  
Srinivasan Chandrasekar ◽  
Thomas N. Farris
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Temperature Rise ◽  
Abrasive Particle ◽  
Soda Lime ◽  
Soda Lime Glass ◽  
Average Temperature ◽  
Work Surface ◽  
Mechanistic Analysis ◽  
Finishing Process

Polishing is a finishing process in which a smooth work surface is produced by rubbing it against a polishing block with an abrasive slurry interspersed between them. A model has been developed to estimate the temperature rise of the work surface in polishing. In this model, the forces acting on an abrasive particle are derived from a mechanistic analysis of abrasive-workpiece contacts. The heat generated at a contact is taken as the product of the friction force and the relative sliding velocity between the abrasive and the work surface. For calculating the heat flux transferred into the workpiece, each of the abrasive-workpiece contacts is modeled as a hardness indentation of the work material by a conical indenter. The moving heat source analyses of Jaeger and Blok are then applied to estimate the fraction of the heat flux flowing into the workpiece, and the maximum and average temperature rise of the work surface. Calculations of the work surface temperature rise are made for the polishing of steel, soda-lime glass, and ceramics. These show that the work surface temperature rise in polishing is quite small, typically much less than 200°C, and substantially less than in grinding. The low values calculated for the work surface temperature rise are shown to be consistent with many observations pertaining to the mechanical state of polished surfaces. The effect of polishing process variables on the work surface temperature rise is analyzed.

Log-log scale roughness spectroscopy of surfaces

1993 ◽  
Vol 51 ◽  
pp. 224-225
Author(s):  
P. Fraundorf ◽  
B. Armbruster
Keyword(s):  
Power Spectrum ◽  
Autocorrelation Function ◽  
Power Spectra ◽  
Scanning Force Microscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Scanning Force ◽  
Lateral Structure ◽  
Scale Roughness

Optical interferometry, confocal light microscopy, stereopair scanning electron microscopy, scanning tunneling microscopy, and scanning force microscopy, can produce topographic images of surfaces on size scales reaching from centimeters to Angstroms. Second moment (height variance) statistics of surface topography can be very helpful in quantifying “visually suggested” differences from one surface to the next. The two most common methods for displaying this information are the Fourier power spectrum and its direct space transform, the autocorrelation function or interferogram. Unfortunately, for a surface exhibiting lateral structure over several orders of magnitude in size, both the power spectrum and the autocorrelation function will find most of the information they contain pressed into the plot’s origin. This suggests that we plot power in units of LOG(frequency)≡-LOG(period), but rather than add this logarithmic constraint as another element of abstraction to the analysis of power spectra, we further recommend a shift in paradigm.

scholarly journals The anisotropy of the power spectrum in periodic cosmological simulations

2021 ◽  
Vol 503 (4) ◽  
pp. 5638-5645
Author(s):  
Gábor Rácz ◽  
István Szapudi ◽  
István Csabai ◽  
László Dobos
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Cosmological Simulations ◽  
Spherical Collapse ◽  
Lower Amplitude ◽  
Hydrodynamical Simulations

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

scholarly journals Demonstrating the Tapered Gridded Estimator (TGE) for the Cosmological HI 21-cm Power Spectrum using 150 MHz GMRT observations

2020 ◽  
Author(s):  
Srijita Pal ◽  
Somnath Bharadwaj ◽  
Abhik Ghosh ◽  
Samir Choudhuri
Keyword(s):  
Power Spectrum ◽  
Unbiased Estimate ◽  
Power Spectra ◽  
Neutral Hydrogen ◽  
Statistical Error ◽  
Temperature Fluctuations ◽  
Radio Frequency Interference ◽  
Rectangular Region ◽  
Angular Power Spectrum ◽  
The Mean

Abstract We apply the Tapered Gridded Estimator (TGE) for estimating the cosmological 21-cm power spectrum from 150 MHz GMRT observations which corresponds to the neutral hydrogen (HI) at redshift z = 8.28. Here TGE is used to measure the Multi-frequency Angular Power Spectrum (MAPS) Cℓ(Δν) first, from which we estimate the 21-cm power spectrum P(k⊥, k∥). The data here are much too small for a detection, and the aim is to demonstrate the capabilities of the estimator. We find that the estimated power spectrum is consistent with the expected foreground and noise behaviour. This demonstrates that this estimator correctly estimates the noise bias and subtracts this out to yield an unbiased estimate of the power spectrum. More than $47\%$ of the frequency channels had to be discarded from the data owing to radio-frequency interference, however the estimated power spectrum does not show any artifacts due to missing channels. Finally, we show that it is possible to suppress the foreground contribution by tapering the sky response at large angular separations from the phase center. We combine the k modes within a rectangular region in the ‘EoR window’ to obtain the spherically binned averaged dimensionless power spectra Δ2(k) along with the statistical error σ associated with the measured Δ2(k). The lowest k-bin yields Δ2(k) = (61.47)2 K2 at k = 1.59 Mpc−1, with σ = (27.40)2 K2. We obtain a 2 σ upper limit of (72.66)2 K2 on the mean squared HI 21-cm brightness temperature fluctuations at k = 1.59 Mpc−1.

scholarly journals Sufficiency of a Gaussian power spectrum likelihood for accurate cosmology from upcoming weak lensing surveys

2021 ◽  
Author(s):  
Robin E Upham ◽  
Michael L Brown ◽  
Lee Whittaker
Keyword(s):  
Power Spectrum ◽  
Random Noise ◽  
Power Spectra ◽  
Stage Iv ◽  
Wishart Distribution ◽  
Weak Lensing ◽  
Dependence Structure ◽  
Gaussian Fields ◽  
Non Gaussian ◽  
Parameter Constraints

Abstract We investigate whether a Gaussian likelihood is sufficient to obtain accurate parameter constraints from a Euclid-like combined tomographic power spectrum analysis of weak lensing, galaxy clustering and their cross-correlation. Testing its performance on the full sky against the Wishart distribution, which is the exact likelihood under the assumption of Gaussian fields, we find that the Gaussian likelihood returns accurate parameter constraints. This accuracy is robust to the choices made in the likelihood analysis, including the choice of fiducial cosmology, the range of scales included, and the random noise level. We extend our results to the cut sky by evaluating the additional non-Gaussianity of the joint cut-sky likelihood in both its marginal distributions and dependence structure. We find that the cut-sky likelihood is more non-Gaussian than the full-sky likelihood, but at a level insufficient to introduce significant inaccuracy into parameter constraints obtained using the Gaussian likelihood. Our results should not be affected by the assumption of Gaussian fields, as this approximation only becomes inaccurate on small scales, which in turn corresponds to the limit in which any non-Gaussianity of the likelihood becomes negligible. We nevertheless compare against N-body weak lensing simulations and find no evidence of significant additional non-Gaussianity in the likelihood. Our results indicate that a Gaussian likelihood will be sufficient for robust parameter constraints with power spectra from Stage IV weak lensing surveys.

scholarly journals Study on the effect of Weber Number to heat transfer of multiple droplets on hot stainless steel surface

2018 ◽  
Vol 154 ◽  
pp. 01114 ◽  
Author(s):  
Aria Riswanda ◽  
Indro Pranoto ◽  
Deendarlianto ◽  
Indarto ◽  
Teguh Wibowo
Keyword(s):  
Stainless Steel ◽  
Surface Temperature ◽  
Weber Number ◽  
Steel Surface ◽  
Cooling System ◽  
Spray Cooling ◽  
Stainless Steel Surface ◽  
Temperature Decrease ◽  
Evaporation Time ◽  
Decrease Rate

Multiple droplets are drops of water that continuously dropped onto a surface. Spray cooling is an application of the use of droplet on a cooling system. Spray cooling is usually used in a cooling system of electronic devices, and material quenching. In this study, correlations between Weber number and surface temperature decrease rate during multiple droplets impingement are investigated and analyzed. Visualization process is used to help determine the evaporation time of droplets impingement by using high speed camera. Induction stove is used to maintain a stainless steel surface temperature at 120°C, 140°C, and 160°C. The Weber number was varied at 15, and 52.5 to simulate low and medium Weber number. The result of this study shows that increase in Weber number does not increase the temperature decrease rate noticeably. Whereas the Weber number decrease the time required for surface temperature to reach its lowest surface temperature. It was also found that for low and medium Weber number, Weber number affect the evaporation time of multiple droplets after impingement.

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