Eigenvalue system for the scattering from rough surfaces – Saving in computation time by a physical approach

2009 ◽  
Vol 282 (18) ◽  
pp. 3820-3826
Author(s):  
R. Dusséaux ◽  
K. Aït Braham ◽  
N. Emad
Keyword(s):  
Rough Surfaces ◽  
Computation Time ◽  
Physical Approach ◽  
Eigenvalue System

A Numerical Three-Dimensional Model for the Contact of Rough Surfaces by Variational Principle

1996 ◽  
Vol 118 (1) ◽  
pp. 33-42 ◽  
Author(s):  
Xuefeng Tian ◽  
Bharat Bhushan
Keyword(s):  
Variational Principle ◽  
Contact Problem ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Computation Time ◽  
Inversion Method ◽  
Three Dimensional Model ◽  
Perfectly Plastic ◽  
Contact Points ◽  
Uniqueness Of The Solution

A new numerical method for the analysis of elastic and elastic-plastic contacts of two rough surfaces has been developed. The method is based on a variational principle in which the real area of contact and contact pressure distribution are those which minimize the total complementary potential energy. The present variational approach guarantees the uniqueness of the solution of the contact problem and significantly reduces the computation time as compared with the conventional matrix inversion method, and thus, makes it feasible to solve 3-D contact problem with large number of contact points. The model is extended to elastic-perfectly plastic contacts. The model is used to predict contact statistics for computer generated surfaces.

A Hybrid Partial Coherence and Geometry Optics Model of Thin Film Optics on Coated Rough Surfaces

2012 ◽  
Author(s):  
Yuan Ting Wu ◽  
Zhi-feng Huang ◽  
Pei-feng Hsu ◽  
Huaichun Zhou
Keyword(s):  
Rough Surfaces ◽  
Scattered Light ◽  
Incident Light ◽  
Fdtd Method ◽  
Computation Time ◽  
Partial Coherence ◽  
Wave Number ◽  
Heating Process ◽  
Coherent Effect ◽  
Coherence Effect

Thermal and optical engineering applications of electromagnetic wave reflectance from rough surfaces include temperature measurement, radiation heating process, etc. Most of the surfaces are random roughness and often with coating material different from the substrate. This paper presented a novel hybrid partial coherence and geometry optics (HPCGO) model to improve the generic geometry optics (GO) method by incorporating a previously developed partial coherence reflectance equation. In this way, HPCGO expands the applicable region of GO model, and largely reduces the computation time of integrating different wavelength results in the regular hybrid model that considers coherence effect only. First, the HPCGO model is validated by more rigorous Maxwell equations solvers, for example, the finite-difference time-domain (FDTD) method and integral equation (IE) method. Then, the HPCGO model is applied to study the coherent effect of directional-hemispherical reflectance from coated rough surfaces. It is found the roughness of coated rough surface can cause partial or non-coherent scattered light even if the incident light source is coherent. It also shows the coherence effect reduces with increased incident wave-number bandwidth.

scholarly journals Multiscale Modeling Applied to the Hydrodynamic Lubrication of Rough Surfaces for Computation Time Reduction

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 83 ◽  
Author(s):  
Noël Brunetière ◽  
Arthur Francisco
Keyword(s):  
Hydrodynamic Lubrication ◽  
Rough Surfaces ◽  
Computation Time ◽  
Coarse Mesh ◽  
Multiscale Finite Element Method ◽  
Lubricating Film ◽  
Flow Balance ◽  
Multiscale Finite Element ◽  
Time Reduction ◽  
Lateral Scale

This paper presents a multiscale finite element method applied to the simulation of a lubricating film flowing between rough surfaces. The objective of this approach is to study flows between large rough surfaces needing very fine meshes while maintaining a reasonable computation time. For this purpose, the domain is split into a number of subdomains (bottom-scale meshes) connected by a coarse mesh (top-scale). The pressure distribution at the top-scale is used as boundary conditions for the bottom-scale problems. This pressure is adjusted to ensure global mass flow balance between the contiguous subdomains. This multiscale method allows for a significant reduction of the number of operations as well as a satisfactory accuracy of the results if the top-scale mesh is properly fitted to the roughness lateral scale. Furthermore the present method is well-suited to parallel computation, leading to much more significant computation time reduction.

Methods for Restricting Maximum Exposure Rate in Computerized Adaptative Testing

Methodology ◽  
2007 ◽  
Vol 3 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Juan Ramon Barrada ◽  
Julio Olea ◽  
Vicente Ponsoda
Keyword(s):  
Measurement Accuracy ◽  
Computerized Adaptive Testing ◽  
Computation Time ◽  
Adaptive Testing ◽  
Exposure Rate ◽  
Control Parameters ◽  
The Impact ◽  
Two Alternatives ◽  
Selection Of ◽  
Maximum Exposure

Abstract. The Sympson-Hetter (1985) method provides a means of controlling maximum exposure rate of items in Computerized Adaptive Testing. Through a series of simulations, control parameters are set that mark the probability of administration of an item on being selected. This method presents two main problems: it requires a long computation time for calculating the parameters and the maximum exposure rate is slightly above the fixed limit. Van der Linden (2003) presented two alternatives which appear to solve both of the problems. The impact of these methods in the measurement accuracy has not been tested yet. We show how these methods over-restrict the exposure of some highly discriminating items and, thus, the accuracy is decreased. It also shown that, when the desired maximum exposure rate is near the minimum possible value, these methods offer an empirical maximum exposure rate clearly above the goal. A new method, based on the initial estimation of the probability of administration and the probability of selection of the items with the restricted method ( Revuelta & Ponsoda, 1998 ), is presented in this paper. It can be used with the Sympson-Hetter method and with the two van der Linden's methods. This option, when used with Sympson-Hetter, speeds the convergence of the control parameters without decreasing the accuracy.

Infrared spectra of carbon monoxide on platinum, iridium and copper ; comparison of flat and rough surfaces

1981 ◽  
Vol 78 ◽  
pp. 927-932 ◽  
Author(s):  
F.J.C.M. Toolenaar ◽  
G.J. van der Poort ◽  
F. Stoop ◽  
V. Ponec
Keyword(s):  
Carbon Monoxide ◽  
Infrared Spectra ◽  
Rough Surfaces

OPTICAL PROPERTIES OF THIN FILMS ON ROUGH SURFACES

1983 ◽  
Vol 44 (C10) ◽  
pp. C10-363-C10-366 ◽  
Author(s):  
J. Vlieger ◽  
M. M. Wind
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Rough Surfaces

A Laboratory Device to Measure the Interfacial Phenomena between Rubber and Rough Surfaces

1999 ◽  
Vol 27 (4) ◽  
pp. 206-226 ◽  
Author(s):  
L. Garro ◽  
G. Gurnari ◽  
G. Nicoletto ◽  
A. Serra
Keyword(s):  
Rough Surfaces ◽  
Computer Software ◽  
Interfacial Phenomena ◽  
New Device ◽  
The Road ◽  
Constant Torque ◽  
Rubber Compounds ◽  
Simple Geometry ◽  
Tangential Forces ◽  
On The Road

Abstract The interfacial phenomena between tread rubber compounds and rough surfaces are responsible for most of the behavior of a tire on the road. A new device was developed for the investigation of these phenomena in the laboratory. The device consists of a fully instrumented road wheel on which a simple geometry specimen is driven. The possibilities offered by this device are to perform tests at constant slip or at constant torque on both wet and dry surfaces, with complex cycles. The machine allows the measurement of slip, tangential forces, and temperature on the specimen, and computer software adds the possibility of applying Fourier analyses on force, road wheel speed, and specimen speed data. Other possibilities offered by the road wheel are to change the road surface, the load on the specimen, and the water rate. The description of a complete experiment is detailed in the paper showing the correlation of data with actual tire performances.

The Markov Model for Alteration of Rough Surfaces during Their Mechanical Interaction

Vestnik MEI ◽  
2017 ◽  
pp. 101-110
Author(s):  
Yuri A. Goritskiy ◽  
◽  
Konstantin V. Gavrilov ◽  
Yulia S. Ismailova ◽  
Olga V. Shevchenko ◽  
...  
Keyword(s):  
Markov Model ◽  
Rough Surfaces ◽  
Mechanical Interaction
Sign in / Sign up

Export Citation Format

Share Document