Application of Modified Bloch Waves to Image Analysis of Extended Linear Defects

1974 ◽  
Vol 32 ◽  
pp. 402-403
Author(s):  
S. Nakahara ◽  
D. M. Maher
Keyword(s):  
Image Analysis ◽  
Computational Approach ◽  
Dislocation Loops ◽  
Plane Wave Expansion ◽  
Dynamical Equations ◽  
Bloch Waves ◽  
Linear Defects ◽  
Imperfect Crystal ◽  
Localized Defects ◽  
Defective Crystals

Since Head first demonstrated the advantages of computer displayed theoretical intensities from defective crystals, computer display techniques have become important in image analysis. However the computational methods employed resort largely to numerical integration of the dynamical equations of electron diffraction. As a consequence, the interpretation of the results in terms of the defect displacement field and diffracting variables is difficult to follow in detail. In contrast to this type of computational approach which is based on a plane-wave expansion of the excited waves within the crystal (i.e. Darwin representation ), Wilkens assumed scattering of modified Bloch waves by an imperfect crystal. For localized defects, the wave amplitudes can be described analytically and this formulation has been used successfully to predict the black-white symmetry of images arising from small dislocation loops.

Image Simulation of Dislocation Loops

1976 ◽  
Vol 34 ◽  
pp. 474-475
Author(s):  
S. M. Ohr
Keyword(s):  
Numerical Scheme ◽  
Computer Time ◽  
Bottom Surface ◽  
Image Simulation ◽  
Dislocation Loops ◽  
Final Solution ◽  
Step Size ◽  
Dynamical Equations ◽  
Runge Kutta Method ◽  
Simulated Images

Computer simulation of image contrast is a useful tool in the identification of lattice defects observed in the electron microscope. In order to obtain high quality simulated micrographs, it is necessary either to consume a considerable amount of computer time or to have the micrographs processed through special photographic devices. In this paper, we describe a numerical scheme by which half-tone simulated images of dislocation loops can be constructed with efficient use of computer time and without special photographic handling.We have solved the Howie-Whelan two-beam dynamical equations by the extrapolation method of Bulirsch and Stoer which has been shown to be about six times faster than the Runge-Kutta method. The method evaluates the transmitted and diffracted intensities at the bottom surface of the foil as a function of step size. The final solution is obtained by forcing the convergence of this sequence of solutions to the limit.

Diffraction Contrast Image Analysis on the Facet Defects of the Laser Diodes Caused by ECR Cleaning Process

2003 ◽  
Vol 792 ◽  
Author(s):  
S.C. Cheng ◽  
M.X. Ouyang
Keyword(s):  
Image Analysis ◽  
Ion Beam ◽  
Crystal Defects ◽  
Cleaning Process ◽  
Dislocation Loops ◽  
Tem Analysis ◽  
Plan View ◽  
Diffraction Contrast ◽  
Operation Conditions ◽  
Contrast Image

ABSTRACTCross-sectional and plan-view TEM techniques were used to study the ion beam passivation of 980 nm laser pump diodes. It is found that under certain operation conditions, the ECR cleaning process produces crystal defects in the facets region of the diodes. By TEM diffraction contrast image analysis, the crystal defects are determined as Frank dislocation loops at the {111} planes of the GaAs crystal. The details of the TEM analysis procedures are described in the paper. In order to obtain high quality passivation of the diodes, the parameters of the ECR cleaning process have to be optimized to eliminate the induced defects.

Some Principles of Many-Beam Image Computations for Defective Crystals

1974 ◽  
Vol 32 ◽  
pp. 346-347
Author(s):  
S. Nakahara ◽  
D. M. Maher ◽  
L. E. Thomas ◽  
R. M. Fisher
Keyword(s):  
Cross Section ◽  
Plane Stress ◽  
Stacking Faults ◽  
Infinite Medium ◽  
Computational Techniques ◽  
Dynamical Equations ◽  
Important Principle ◽  
Beam Image ◽  
General Defect ◽  
Defective Crystals

Rapid computational techniques for obtaining two-beam, computer displayed images of inclined straight dislocations and stacking faults have been given, respectively, by Head and Humble. Their computational techniques are based on two principles, namely, the generalized cross section (GCS) and linear combination (LC) of wave amplitudes. The first of these principles is a consequence of the plane stress and/or plane strain nature of the defects they considered whereas the second principle follows directly from linearity of the two-beam dynamical equations assuming the validity of the column approximation. in this paper the concept of an expanded column (EC) is introduced and it is shown that if the column approximation is assumed then the LC of wave amplitudes is a valid and important principle when calculating many-beam, image intensities for a general defect in an infinite medium.

scholarly journals Defect Structures of Magnetic Nanoparticles in Smectic A Liquid Crystals

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5717
Author(s):  
Vladimíra Novotná ◽  
Lubor Lejček ◽  
Věra Hamplová ◽  
Jana Vejpravová
Keyword(s):  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Hybrid System ◽  
Topological Defects ◽  
Elastic Interaction ◽  
Critical Dimension ◽  
Smectic Layer ◽  
Dislocation Loops ◽  
Smectic A ◽  
Linear Defects

Topological defects in anisotropic fluids like liquid crystals serve as a playground for the research of various effects. In this study, we concentrated on a hybrid system of chiral rod-like molecules doped by magnetic nanoparticles. In textures of the smectic A phase, we observed linear defects and found that clusters of nanoparticles promote nucleation of smectic layer defects just at the phase transition from the isotropic to the smectic A (SmA) phase. In different geometries, we studied and analysed creation of defects which can be explained by attractive elastic forces between nanoparticles in the SmA phase. On cooling the studied hybrid system, clusters grow up to the critical dimension, and the smectic texture is stabilised. The presented effects are theoretically described and explained if we consider the elastic interaction of two point defects and stabilisation of prismatic dislocation loops due to the presence of nanoparticles.

Automated Image Analysis Of Nuclear And Cytoplasmic Changes In Exfoliated Cells From Tracheas Treated With Carcinogen

1977 ◽  
Vol 35 ◽  
pp. 220-221
Author(s):  
S.F. Stinson ◽  
J.C. Lilga ◽  
M.B. Sporn
Keyword(s):  
Image Analysis ◽  
Pattern Analysis ◽  
Relative Proportion ◽  
Automated Image Analysis ◽  
Image Analyzer ◽  
Cross Sectional ◽  
Exfoliated Cells ◽  
Neoplastic Lesions ◽  
Analysis System ◽  
Morphologic Criterion

Increased nuclear size, resulting in an increase in the relative proportion of nuclear to cytoplasmic sizes, is an important morphologic criterion for the evaluation of neoplastic and pre-neoplastic cells. This paper describes investigations into the suitability of automated image analysis for quantitating changes in nuclear and cytoplasmic cross-sectional areas in exfoliated cells from tracheas treated with carcinogen.Neoplastic and pre-neoplastic lesions were induced in the tracheas of Syrian hamsters with the carcinogen N-methyl-N-nitrosourea. Cytology samples were collected intra-tracheally with a specially designed catheter (1) and stained by a modified Papanicolaou technique. Three cytology specimens were selected from animals with normal tracheas, 3 from animals with dysplastic changes, and 3 from animals with epidermoid carcinoma. One hundred randomly selected cells on each slide were analyzed with a Bausch and Lomb Pattern Analysis System automated image analyzer.

Sign in / Sign up

Export Citation Format

Share Document