Characterization of the chemical homogeneity of solids affected with periodical concentration fluctuations using the statistics of stochastic processes

1989 ◽  
Vol 97 (3-4) ◽  
pp. 145-158 ◽  
Author(s):  
G�nter Ehrlich ◽  
Werner Kluge
Keyword(s):  
Stochastic Processes ◽  
Concentration Fluctuations ◽  
Chemical Homogeneity

SELF-SIMILARITY OF FREE STOCHASTIC PROCESSES

2006 ◽  
Vol 09 (03) ◽  
pp. 451-469 ◽  
Author(s):  
ZHAOZHI FAN
Keyword(s):  
Stochastic Processes ◽  
Self Similarity ◽  
Strict Stability ◽  
Classical Analogue ◽  
Self Similar

In this paper we study self-similarity of free stochastic processes. We establish the noncommutative counterpart of Lamperti's self-similar processes. We develop the characterization of noncommutative self-similar processes through a modification of Voiculescu transform, the free cumulant transform. We study the connection between free self-similarity, strict ⊞-stability and ⊞-self-decomposability. In particular, we derive the properties of free self-similar processes and their connection to strict ⊞-stability and ⊞-self-decomposability, that turn out to be consistent with their classical analogue.

Representation of Strongly Stationary Stochastic Processes

1993 ◽  
Vol 60 (3) ◽  
pp. 689-694 ◽  
Author(s):  
M. Di Paola
Keyword(s):  
Stochastic Process ◽  
Stochastic Processes ◽  
Linear Systems ◽  
Stationary Processes ◽  
Orthogonality Conditions ◽  
Probabilistic Characterization ◽  
Stationary Stochastic Processes ◽  
Fixed Order ◽  
Strongly Stationary

A generalization of the orthogonality conditions for a stochastic process to represent strongly stationary processes up to a fixed order is presented. The particular case of non-normal delta correlated processes, and the probabilistic characterization of linear systems subjected to strongly stationary stochastic processes are also discussed.

Characterization of Mechanical Deformation of Nanoscale Volumes

2002 ◽  
Vol 740 ◽  
Author(s):  
Christopher R. Perrey ◽  
William M. Mook ◽  
C. Barry Carter ◽  
William W. Gerberich
Keyword(s):  
Mechanical Behavior ◽  
Defect Structure ◽  
Mechanical Deformation ◽  
Chemical Homogeneity ◽  
Preparation Methods ◽  
Material Parameters ◽  
Tem Characterization ◽  
Study Techniques ◽  
Sample Preparation Methods

ABSTRACTThe mechanical properties of nanoscale volumes and their associated defect structure are key to many future applications in nanoengineered products. In this study, techniques of mechanical testing and microscopy have been applied to better understand the mechanical behavior of nanoscale volumes. Nanoindentation has been used to investigate important mechanical material parameters such as the elastic modulus and hardness for single nanoparticles. New sample preparation methods must be developed to allow the necessary TEM characterization of the inherent and induced defect structure of these nanoparticles. Issues of chemical homogeneity, crystallinity, and defect characteristics at the nanoscale are being addressed in this study. This integration of investigative methods will lead to a greater understanding of the mechanical behavior of nanostructured materials and insights into the nature of defects in materials at the nanoscale.

scholarly journals Microscopy characterization of metallurgical production evidences from Vila Nova de São Pedro (Azambuja, Portugal)

2013 ◽  
Vol 19 (S4) ◽  
pp. 149-150
Author(s):  
F. Pereira ◽  
R.J. Silva ◽  
A.M. Monge Soares ◽  
M.F. Araújo
Keyword(s):  
Elemental Composition ◽  
Chemical Elements ◽  
Research Work ◽  
Analytical Techniques ◽  
Microstructural Characterization ◽  
Chemical Homogeneity ◽  
Metallurgical Production ◽  
Microscopy Techniques ◽  
Arsenical Copper

The Castro de Vila Nova de São Pedro (VNSP) is an emblematic settlement located at Azambuja (Portugal), occupied predominantly during the Chalcolithic period. A large and diversified metallurgical collection was recovered from this settlement which includes artefacts, crucibles and other metallurgical production remains, like slags and droplets. The chemical and microstructural characterization of this metallic collection aims to contribute to a better comprehension of the early copper-based metallurgy on the Portuguese Estremadura, the degree of knowledge of the ancient metallurgists and the role of the metallurgical activities in Chalcolithic societies.A group of 53 selected copper-based fragments of artefacts plus metallurgical production remains (12 crucibles and 20 slags and droplets), all belonging to VNSP, were characterized by using different analytical techniques: EDXRF and micro-EDXRF spectrometry, optical microscopy (OM) and SEM-EDS. The EDXRF and micro-EDXRF spectrometry gives the elemental composition of the artefacts and metallic nodules. The microscopy techniques play a fundamental role in the chemical and microstructural characterization of artefacts and metallurgical remains. The OM allows the identification of different phases, inclusions and thermomechanical processes applied during the shaping of the artefacts. The SEM-EDS plays an important role in the determination of main chemical phases present in the metal alloy and slags, and also in the distribution of chemical elements and minerals in the inclusions. The combination of these two microscopy techniques gives indication of the processes used in the reduction of minerals in order to obtain the metal and also allows the characterization of the operation chain, regarding the production of artefacts.The research that has been carried out by us offer indications concerning the provenance of the arsenic, the technological choices involved in the production of an arsenical copper alloy and how it was recognized by ancient metallurgists. Results obtained on the elemental composition of the metallurgical production remains are consistent with copper and arsenical copper (As > 2 %) artefact production. Crucibles and slags analysed indicate melting and smelting operations (of copper ores or copper/arsenic ores). A statistically significant association was found between copper alloyed with arsenic and artefacts classified as tools/weapons (arrowheads, daggers and knives). In several cases, the presence of arsenic rich phases in the microstructure, resulting from an inverse segregation phenomenon, shows no evidence of chemical homogeneity control during the artefact manufacture. Microstructural analyses also show that the majority of the artefactual group was shaped with forging plus annealing operation cycles and 23 % of the artefacts received a final forging treatment. This final treatment was associated to artefacts presenting higher arsenic contents.This research work has been financed by the Portuguese Science Foundation (FCT-MCTES) through the EarlyMetal project (PTDC/HIS-ARQ/110442/2008) and the PhD Grant SFRH/BD/78107/2011 (FP). The financial support of CENIMAT/I3N through the Strategic Project-LA25-2011-2012 (PEst-C/CTM/LA0025/2011) is also acknowledged.

scholarly journals Sol-Gel Synthesis and Characterization of Cubic Bismuth Zinc Niobium Oxide Nanopowders

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Ganchimeg Perenlei ◽  
Peter C. Talbot ◽  
Wayde N. Martens
Keyword(s):  
Niobium Oxide ◽  
Sol Gel ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
Metal Acetate ◽  
Chemical Homogeneity ◽  
Liquid Suspension ◽  
Crystallite Sizes ◽  
Sol Gel Synthesis

Bismuth zinc niobium oxide (BZN) was successfully synthesized by a diol-based sol-gel reaction utilizing metal acetate and alkoxide precursors. Thermal analysis of a liquid suspension of precursors suggests that the majority of organic precursors decompose at temperatures up to 150°C, and organic free powders form above 350°C. The experimental results indicate that a homogeneous gel is obtained at about 200°C and then converts to a mixture of intermediate oxides at 350–400°C. Finally, single-phased BZN powders are obtained between 500 and 900°C. The degree of chemical homogeneity as determined by X-ray diffraction and EDS mapping is consistent throughout the samples. Elemental analysis indicates that the atomic ratio of metals closely matches a Bi1.5ZnNb1.5O7composition. Crystallite sizes of the BZN powders calculated from the Scherrer equation are about 33–98 nm for the samples prepared at 500–700°C, respectively. The particle and crystallite sizes increase with increased sintering temperature. The estimated band gap of the BZN nanopowders from optical analysis is about 2.60–2.75 eV at 500-600°C. The observed phase formations and measured results in this study were compared with those of previous reports.

Sign in / Sign up

Export Citation Format

Share Document