Extending the Capability of the Greenwood Williamson Microcontact Model

2000 ◽  
Vol 122 (3) ◽  
pp. 496-502 ◽  
Author(s):  
John I. McCool
Keyword(s):  
Simulation Model ◽  
Coating Thickness ◽  
Surface Coating ◽  
Relative Effect ◽  
Compliant Coating ◽  
Absolute Effect ◽  
The Mean ◽  
The Absolute

This paper describes a readily implemented simulation model that extends the Greenwood Williamson microcontact model to include skewness in the distribution of surface summit heights and the presence of a surface coating of prescribed thickness and compliance. Parametric runs were made to explore the effect of these factors on the load, area and mean real pressure at the contacting asperities for a fixed separation of the mean planes of the contacting surfaces such as occurs when the surfaces are separated by a stiff elastohydrodynamic film. It was found that the average asperity load increases with coating thickness when the coating is stiffer than the substrate and decreases when the coating is made more compliant. The opposite is true for the average asperity area of contact. Like load, the average asperity pressure increases with coating thickness when the coating is stiffer than the substrate and decreases when the coating is more compliant. For the same rms summit height the mean asperity pressure in the absence of a coating was found to be higher by a factor of 1.6 when the skewness is +1 than when it is −1. The relative effect of skewness on pressure is practically constant as coating thickness increases for the compliant coating while the absolute effect decreases. For the stiff coating the absolute effect is constant while the relative effect diminishes. [S0742-4787(00)02303-1]

scholarly journals Many continuous variables should be analyzed using the relative scale: a case study of β2-agonists for preventing exercise-induced bronchoconstriction

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Harri Hemilä ◽  
Jan O. Friedrich
Keyword(s):  
Meta Analysis ◽  
Relative Effect ◽  
Similar Amount ◽  
Mixed Effect ◽  
Absolute Scale ◽  
Effect Model ◽  
Absolute Effect ◽  
The Absolute ◽  
Relative Scale ◽  
Exercise Induced

Abstract Background The relative scale adjusts for baseline variability and therefore may lead to findings that can be generalized more widely. It is routinely used for the analysis of binary outcomes but only rarely for continuous outcomes. Our objective was to compare relative vs absolute scale pooled outcomes using data from a recently published Cochrane systematic review that reported only absolute effects of inhaled β2-agonists on exercise-induced decline in forced-expiratory volumes in 1 s (FEV1). Methods From the Cochrane review, we selected placebo-controlled cross-over studies that reported individual participant data (IPD). Reversal in FEV1 decline after exercise was modeled as a mean uniform percentage point (pp) change (absolute effect) or average percent change (relative effect) using either intercept-only or slope-only, respectively, linear mixed-effect models. We also calculated the pooled relative effect estimates using standard random-effects, inverse-variance-weighting meta-analysis using study-level mean effects. Results Fourteen studies with 187 participants were identified for the IPD analysis. On the absolute scale, β2-agonists decreased the exercise-induced FEV1 decline by 28 pp., and on the relative scale, they decreased the FEV1 decline by 90%. The fit of the statistical model was significantly better with the relative 90% estimate compared with the absolute 28 pp. estimate. Furthermore, the median residuals (5.8 vs. 10.8 pp) were substantially smaller in the relative effect model than in the absolute effect model. Using standard study-level meta-analysis of the same 14 studies, β2-agonists reduced exercise-induced FEV1 decline on the relative scale by a similar amount: 83% or 90%, depending on the method of calculating the relative effect. Conclusions Compared with the absolute scale, the relative scale captures more effectively the variation in the effects of β2-agonists on exercise-induced FEV1-declines. The absolute scale has been used in the analysis of FEV1 changes and may have led to sub-optimal statistical analysis in some cases. The choice between the absolute and relative scale should be determined based on biological reasoning and empirical testing to identify the scale that leads to lower heterogeneity.

The Race for Online Reputation: Implications for Platforms, Firms, and Consumers

2021 ◽  
Author(s):  
Mingwen Yang ◽  
Zhiqiang (Eric) Zheng ◽  
Vijay Mookerjee
Keyword(s):  
Adverse Event ◽  
Marketing Mix ◽  
Digital Economy ◽  
The Other ◽  
The Mean ◽  
The Absolute ◽  
The Cost ◽  
Online Reputation ◽  
Better Than

Online reputation has become a key marketing-mix variable in the digital economy. Our study helps managers decide on the effort they should use to manage online reputation. We consider an online reputation race in which it is important not just to manage the absolute reputation, but also the relative rating. That is, to stay ahead, a firm should try to have ratings that are better than those of its competitors. Our findings are particularly significant for platform owners (such as Expedia or Yelp) to strategically grow their base of participating firms: growing the middle of the market (firms with average ratings) is the best option considering the goals of the platform and the other stakeholders, namely incumbents and consumers. For firms, we find that they should increase their effort when the mean market rating increases. Another key insight for firms is that, sometimes, adversity can come disguised as an opportunity. When an adverse event strikes the industry (such as a reduction in sales margin or an increase in the cost of effort), a firm’s profit can increase if it can manage this event better than its competitors.

scholarly journals A First Application of Thermographic Phosphors in a Marine Two-Stroke Diesel Engine for Surface Temperature Measurement

2014 ◽  
Author(s):  
Fahd Abou Nada ◽  
Johan Hult ◽  
Christoph Knappe ◽  
Mattias Richter ◽  
Stefan Mayer ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Coating Thickness ◽  
Surface Coating ◽  
Cylinder Wall ◽  
Load Range ◽  
Marine Research ◽  
Surface Temperature Measurement ◽  
Thermographic Phosphors ◽  
Phosphor Thermometry ◽  
First Time

Phosphor thermometry is applied for the first time in a large-bore two-stroke diesel engine. The work proves the practicality of phosphor thermometry in large-bore engines. The experiments were conducted on the MAN 4T50ME-X marine research engine equipped with an optical cylinder head. By employing a thin surface coating of CdWO4 phosphor, cycle resolved temperature measurements of the cylinder wall were obtained. Motored and fired engine operations were tested at engine loads covering the low and medium engine load range. Phosphor thermometry proved to be successful in retrieving the temperature with standard deviations ranging around 1–8 K. Experimental considerations like detector linearity, coating thickness and an automated phosphor calibration routine will be addressed.

scholarly journals The Luminosity Determination

1995 ◽  
Vol 10 ◽  
pp. 399-402
Author(s):  
A.E. Gómez ◽  
C. Turon
Keyword(s):  
Main Sequence ◽  
Small Volume ◽  
Absolute Magnitude ◽  
Fitting Procedure ◽  
Trigonometric Parallaxes ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Kinematical Data ◽  
Magnitude Determination

The Hertzprung-Russel (HR) diagram luminosity calibration relies basically on three kinds of data: trigonometric parallaxes, kinematical data (proper motions and radial velocities) and cluster distances obtained by the zero-age main sequence fitting procedure. The most fundamental method to calculate the absolute magnitude is the use of trigonometric parallaxes, but up to now, accurate data only exist for stars contained in a small volume around the sun. Individual absolute magnitudes are obtained using trigonometric parallaxes or photometric and spectroscopic calibrations. In these calibrations the accuracy on the absolute magnitude determination ranges from ±0.m2 in the main sequence to ±0m5 in the giant branch. On the other hand, trigonometric parallaxes, kinematical data or cluster distances have been used to make statistical calibrations of the absolute magnitude. The standard error on the mean absolute magnitude calibrations ranges from ±0m3 to ±0m6 on the mean sequence, from ±0m5 to ±0m7 on thegiant branch and is of about 1mfor supergiants.Future improvements in the absolute magnitude determination will depend on the improvement of the basic data from the ground and space. A brief overview of the new available data is presented. In particular, the analysis of the first 30 months data of the Hipparcos mission (H30) (from the 37 months data of the whole mission) allows to perform a statistical evaluation of the improvements expected in the luminosity determination.

4. Results of Makerstoun Observations, No. III. On the Solar and Lunar periods of the Magnetic Declination.

1851 ◽  
Vol 2 ◽  
pp. 144-145
Author(s):  
J. A. Broun
Keyword(s):  
The North ◽  
Magnetic Declination ◽  
The Mean ◽  
The Absolute ◽  
Annual Period ◽  
North End

The absolute westerly declination at Makerstoun, for the mean epoch, June 1844 = 25° 17′·12.The annual motion of the north end of the needle towards the east = 5′·67.The annual periodof magnetic declination consists of a double oscillation, having nearly the following epochs of maxima and minima.

A spherical surface coating thickness model for a robotized thermal spray system

2019 ◽  
Vol 59 ◽  
pp. 297-304 ◽  
Author(s):  
Yanjun Zhang ◽  
Wenbo Li ◽  
Chao Zhang ◽  
Hanlin Liao ◽  
Yicha Zhang ◽  
...  
Keyword(s):  
Thermal Spray ◽  
Coating Thickness ◽  
Surface Coating ◽  
Spherical Surface ◽  
Spray System

scholarly journals The Parallaxes of U Gem Variables

1979 ◽  
Vol 53 ◽  
pp. 494-494
Author(s):  
Karl W. Kamper
Keyword(s):  
Confidence Level ◽  
Absolute Magnitude ◽  
Weighted Mean ◽  
Quiescent Phase ◽  
A Value ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes

An Allegheny parallax series of SS Cyg, consisting of 52 exposures obtained on 15 nights, was recently measured on the PDS microphotometer at the David Dunlap Observatory, and a value of (m.e.) derived for the absolute parallax. This is close to the mean of the two previous discordant measures for this star given in the table below. The weighted mean of the three determinations implies that the absolute magnitude, at quiescent phase, of the star is between 7.0 and 9.0 formally at a 90% confidence level. Recent parallax determinations made at Lick by Vasilevskls et al. (1975) for three other stars, listed below along with the Mt. Wilson value for U Gem, imply even fainter absolute magnitudes.

scholarly journals Analysis of the FK5 System in the Equatorial Zone

1995 ◽  
Vol 166 ◽  
pp. 382-382
Author(s):  
Yu.B. Kolesnik
Keyword(s):  
Equatorial Zone ◽  
Motion System ◽  
Area Distribution ◽  
The Sixties ◽  
Hipparcos Catalogue ◽  
The Mean ◽  
The Absolute ◽  
The Individual ◽  
Right Ascension ◽  
Selection Of

15 catalogues produced in the eighties and 12 catalogues of the sixties-seventies have been used to assess the consistency of the FK5 system with observations in the declination zone from −30° to 30°. Positions of the FK4-based catalogues have been transformed at the equinox and equator J2000.0. Classical δ-dependent and α-dependent systematic differences (Cat-FK5) have been formed for individual instrumental systems of the catalogues by a method close to the classical Numerical Method. The weighted mean instrumental systems for the two subsets of catalogues centered at the epochs 1970 (MIS 60–70) and 1987 (MIS 80) and for all types of systematic differences have been constructed. The mean errors of the total systematic differences in α and δ have been estimated as 14 mas and 21 mas, respectively, for the catalogues of the 60-70ies, and 10 mas in both α and δ for the catalogues of the 80ies.It has been found that the mutual consistency of individual instrumental systems of catalogues of the 80ies with respect to δ-dependent systematic differences is superior by the factor 1.5 comparing with the catalogues of 60-70ies, while the consistency of both catalogue selections with respect to α-dependent systematic differences is comparable. Random accuracy of the FK5 positions and proper motions at the epochs under analysis has been assessed as close to expected from the formal considerations. Actual systematic discrepancies of the FK5 with observations at the respective epochs have been detected. For systematic differences δαδ cosδ and δδδ, the absolute deviations of the MIS 80 are, in general, within 40 mas, those of the MIS 60-70 are within 30 mas. For systematic differences δαα cosδ and δδα, the absolute deviations reach 30-40 mas for both MIS. For total systematic differences, local deformations of the FK5 system in the equatorial zone in both right ascension and declination has been found exceeding expected ones from the formal errors of the FK5 system by a factor about 1.5 for the MIS 60-70, and by a factor about 2 for the MIS 80. Consistency in area distribution between both MIS for the total systematic differences δαcosδ has been detected. Quick degradation of the FK5 system with time due to optimistic estimation of the errors of its proper motion system is supposed to be one of the main causes of its discrepancies with observations. The results in declination are recognized to be less reliable due to larger inconsistency of the individual instrumental systems.Before the next space astrometric mission will be realized, ground-based observations will continue to be the only available check of an external systematic accuracy of the HIPPARCOS catalogue. Evidently, random and, possibly, systematic accuracy of each individual catalogue observed from the Earth surface would be inferior to that of the HIPPARCOS catalogue. Taken as an ensemble, however, a certain selection of catalogues might give a rather definite idea about the actual distortions of the HIPPARCOS system. This study shows to which level of accuracy such ensembles of different selections of catalogues might check the HIPPARCOS system in the equatorial zone. The analysis of the FK5 gives also an idea about levels of random and systematic discrepancies which may be expected in the equatorial zone when the HIPPARCOS catalogue will be compared with the FK5 at different epochs.

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