scholarly journals Emissivity of Triangular Surfaces Determined by Differential Method: From Homogenization to Validity Limit of Geometrical Optics

2007 ◽  
Vol 4 (3) ◽  
pp. 146-154 ◽  
Author(s):  
Taoufik Ghabara ◽  
Faouzi Ghmari ◽  
M. Salah Sifaoui
Keyword(s):  
Geometrical Optics ◽  
Differential Method ◽  
Validity Limit

scholarly journals Electric Transverse Emissivity of Sinusoidal Surfaces Determined by a Differential Method: Comparison with Approximation of Geometric Optics

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Taoufik Ghabara
Keyword(s):  
Transition Layer ◽  
Numerical Study ◽  
Rough Surfaces ◽  
Method Comparison ◽  
Electromagnetic Theory ◽  
Differential Method ◽  
Homogenization Theory ◽  
Geometric Optics ◽  
Optical Index ◽  
Validity Limit

We present in this paper a numerical study of the validity limit of the optics geometrical approximation in comparison with a differential method which is established according to rigorous formalisms based on the electromagnetic theory. The precedent studies show that this method is adopted to the study of diffraction by periodic rough surfaces. For periods much larger than the wavelength, the mechanism is analog to what happens in a cavity where a ray is trapped and undergoes a large number of reflections. For gratings with a period much smaller than the wavelength, the roughness essentially behaves as a transition layer with a gradient of the optical index. Such a layer reduces the reflection there by increasing the absorption. The code has been implemented for TE polarization. We determine by the two methods such as differential method and the optics geometrical approximation the emissivity of gold and tungsten cylindrical surfaces with a sinusoidal profile, for a wavelength equal to 0.55 microns. The obtained results for a fixed height of the grating allowed us to delimit the validity domain of the optic geometrical approximation for the treated cases. The emissivity calculated by the differential method and that given on the basis of the homogenization theory are satisfactory when the period is much smaller than the wavelength.

Quantitative indicators of air traffic controllers’ attitude to the danger of errors

2020 ◽  
pp. 68-78
Author(s):  
O. M. Reva ◽  
V. V. Kamyshin ◽  
S. P. Borsuk ◽  
V. A. Shulhin ◽  
A. V. Nevynitsyn
Keyword(s):  
Human Factor ◽  
Differential Method ◽  
Air Traffic ◽  
Professional Activity ◽  
Aviation Accidents ◽  
Air Traffic Controllers ◽  
The Difference ◽  
Level Of Significance ◽  
The Individual ◽  
High Level

The negative and persistent impact of the human factor on the statistics of aviation accidents and serious incidents makes proactive studies of the attitude of “front line” aviation operators (air traffic controllers, flight crewmembers) to dangerous actions or professional conditions as a key component of the current paradigm of ICAO safety concept. This “attitude” is determined through the indicators of the influence of the human factor on decision-making, which also include the systems of preferences of air traffic controllers on the indicators and characteristics of professional activity, illustrating both the individual perception of potential risks and dangers, and the peculiarities of generalized group thinking that have developed in a particular society. Preference systems are an ordered (ranked) series of n = 21 errors: from the most dangerous to the least dangerous and characterize only the danger preference of one error over another. The degree of this preference is determined only by the difference in the ranks of the errors and does not answer the question of how much time one error is more dangerous in relation to another. The differential method for identifying the comparative danger of errors, as well as the multistep technology for identifying and filtering out marginal opinions were applied. From the initial sample of m = 37 professional air traffic controllers, two subgroups mB=20 and mG=7 people were identified with statisti-cally significant at a high level of significance within the group consistency of opinions a = 1%. Nonpara-metric optimization of the corresponding group preference systems resulted in Kemeny’s medians, in which the related (middle) ranks were missing. Based on these medians, weighted coefficients of error hazards were determined by the mathematical prioritization method. It is substantiated that with the ac-cepted accuracy of calculations, the results obtained at the second iteration of this method are more ac-ceptable. The values of the error hazard coefficients, together with their ranks established in the preference systems, allow a more complete quantitative and qualitative analysis of the attitude of both individual air traffic controllers and their professional groups to hazardous actions or conditions.

Electromagnetic waves

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Plane Wave ◽  
Electromagnetic Waves ◽  
Maxwell Equations ◽  
Plane Waves ◽  
Geometrical Optics ◽  
Particle Detection ◽  
Spatial Coordinates ◽  
A Charge

This chapter examines solutions to the Maxwell equations in a vacuum: monochromatic plane waves and their polarizations, plane waves, and the motion of a charge in the field of a wave (which is the principle upon which particle detection is based). A plane wave is a solution of the vacuum Maxwell equations which depends on only one of the Cartesian spatial coordinates. The monochromatic plane waves form a basis (in the sense of distributions, because they are not square-integrable) in which any solution of the vacuum Maxwell equations can be expanded. The chapter concludes by giving the conditions for the geometrical optics limit. It also establishes the connection between electromagnetic waves and the kinematic description of light discussed in Book 1.

scholarly journals Geometrical Optics Restricted Eavesdropping Analysis of Satellite-to-Satellite Secret Key Distillation

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 950
Author(s):  
Ziwen Pan ◽  
Ivan B. Djordjevic
Keyword(s):  
Free Space ◽  
Quantum Key Distribution ◽  
Security Analysis ◽  
Key Distribution ◽  
Geometrical Optics ◽  
Secret Key ◽  
Satellite Applications

Traditionally, the study of quantum key distribution (QKD) assumes an omnipotent eavesdropper that is only limited by the laws of physics. However, this is not the case for specific application scenarios such as the QKD over a free-space link. In this invited paper, we introduce the geometrical optics restricted eavesdropping model for secret key distillation security analysis and apply to a few scenarios common in satellite-to-satellite applications.

scholarly journals Annoyance evaluation of noise emitted by urban substation

2021 ◽  
pp. 146134842110143
Author(s):  
Li Jun ◽  
Li Li ◽  
Zhang Yongxiang ◽  
Chu Zhigang ◽  
Fan Xiaopeng
Keyword(s):  
Regression Model ◽  
Urban Areas ◽  
Subjective Evaluation ◽  
Noise Pollution ◽  
Objective Evaluation ◽  
Semantic Differential ◽  
Differential Method ◽  
Practical Application ◽  
Noise Evaluation ◽  
Objective And Subjective Evaluation

In China, noise pollution from substations in urban areas is becoming more and more serious. An annoyance evaluation of the noise emitted by urban substations is presented. First, the subjective evaluation is conducted on the noise samples from urban substations via the semantic differential method. Subsequently, according to the typical characteristics of urban substation noise, 14 acoustical metrics are used to describe the noise samples for objective evaluation. Then the correlation analysis and regression analysis between the objective and subjective evaluation results are carried out. Finally, a regression model for urban substation noise evaluation is established. Practical application shows that the regression model can correctly predict the subjective annoyance of urban substation noise.

scholarly journals Evaluating Stress Relief from Architecture: A Case Study Based on Buildings in Taiwan, China and Japan

2021 ◽  
Vol 13 (14) ◽  
pp. 7899
Author(s):  
Ming-Chyuan Ho ◽  
Yung-Chia Chiu
Keyword(s):  
Urban Landscape ◽  
Stress Relief ◽  
Future Trend ◽  
Differential Method ◽  
City Image ◽  
Structured Interviews ◽  
Architectural Styles ◽  
Stress Relieving ◽  
Study Results ◽  
Image Identity

The urban landscape can be improved to reduce the stress experienced by citizens. Therefore, stress-relieving buildings constitute a crucial topic and a future trend in architecture and design. In this study, different architectural styles were investigated to explore design methods for and characteristics of stress-relieving building shapes and to identify indicators for measuring participant stress relief while viewing buildings. To understand stress relief from architecture, we performed semi-structured interviews with 60 participants who viewed images of 30 buildings. The semantic differential method with a 7-point image scale was used to rate stress relief from different architectural styles. The study results revealed that the participants perceived curvilinear buildings as interesting but do not relieve stress. The participants identified as feeling high pressure considering rectilinear patterns to relieve more stress. To support this observation, we identified three principles—city image, identity, and spiritual atmosphere—as fundamental loci of designing cities for livability. We illustrate the three principles with several cases that facilitate a detailed understanding of their applicability in biodesign practices.

scholarly journals Plastic forming processes of transverse non-homogeneous composite metallic sheets

2021 ◽  
Vol 11 (1) ◽  
pp. 294-302
Author(s):  
Gal Davidi
Keyword(s):  
Inner Core ◽  
Plastic Material ◽  
Radial Solution ◽  
Algebraic Differential Equation ◽  
Forming Process ◽  
Perfectly Plastic ◽  
Plastic Forming ◽  
Validity Limit ◽  
Significant Achievement

Abstract In this work an analysis of the radial stress and velocity fields is performed according to the J 2 flow theory for a rigid/perfectly plastic material. The flow field is used to simulate the forming processes of sheets. The significant achievement of this paper is the generalization of the work by Nadai & Hill for homogenous material in the sense of its yield stress, to a material with general transverse non-homogeneity. In Addition, a special un-coupled form of the system of equations is obtained where the task of solving it reduces to the solution of a single non-linear algebraic differential equation for the shear stress. A semi-analytical solution is attained solving numerically this equation and the rest of the stresses term together with the velocity field is calculated analytically. As a case study a tri-layered symmetrical sheet is chosen for two configurations: soft inner core and hard coating, hard inner core and soft coating. The main practical outcome of this work is the derivation of the validity limit for radial solution by mapping the “state space” that encompasses all possible configurations of the forming process. This configuration mapping defines the “safe” range of configurations parameters in which flawless processes can be achieved. Several aspects are researched: the ratio of material's properties of two adjacent layers, the location of layers interface and friction coefficient with the walls of the dies.

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