Identification Of Inhomogeneities Research Articles

Identification of Inhomogeneities: The Selected Coordinate Descent Method Applied in the Drilling Area

The exploration of inhomogeneities is a crucial factor for industries because of the necessary control of the quality of output products or the check adequacy of the data from the helping information systems. In the energy-conception field, the preliminary study of borehole areas has special importance because it can avoid risks of secure drilling and financial expenses. In this paper, an innovative option of the traditional coordinate descent method called selected coordinate descent, was investigated by collating its fundamentals with other methods used in various industrial branches. A practical application of selected coordinate descent was performed for experimental data of seismic event registration observed in the region of geothermal plants. An explicit formula for the resolution parameter was utilized to distinguish well and poorly resolved anomalies. The inhomogeneities were validated on the basis of a good resolution and comparison with data from other disciplines. The main result of our study is the performance of the algebraic technique application in the reconstruction of large-size structures. The identification of the found seismic inhomogeneities permits us to indicate the sites that are questionable for drilling and to obtain knowledge about the rock types at crucial depths.

Digital holographic imaging of thermal signatures and its use in inhomogeneity identification

Thermal diffusion results in spatiotemporally evolving temperature distribution in material mediums. In dielectric mediums it will also lead to change in local refractive index. Digital holographic interferometry can be used for high contrast quantitative phase imaging of spatially and temporally evolving refractive index variations in dielectric mediums, arising due to temperature changes. Phase retrieved from numerically processed digital holograms recorded at different time instances can be compared to obtain this information. Since the thermal conductivity varies for materials, the thermal diffusion and hence the refractive index across them will also vary. Time varying optical path length distributions of the test sample under thermal stress, obtained from the phase maps retrieved from the recorded holograms, can be used to obtain this information. This leads to detection of regions having different thermal conductivities and hence identification of inhomogeneities in the test sample. Lens less Fourier transform digital holographic interferometry is a perfect tool to quantify optical path length distributions with nanometre accuracy to quantify spatiotemporally evolving refractive index distributions. In this technique, a single Fourier transform of the recorded hologram yields the spatial distribution of object phase, making it ideal for real time imaging and applications. Here we describe our efforts in the development lens less Fourier transform digital holographic interferometric technique for the imaging and quantification of spatiotemporally evolving refractive index distributions in test samples under thermal stress and its application in detection of surface and sub-surface inhomogeneities.

Decoding the precision of historical temperature observations

Historical observations of temperature underpin our ability to monitor Earth's climate. We identify a pervasive issue in archived observations from surface stations, wherein the use of varying conventions for units and precision has led to distorted distributions of the data. Apart from the original precision being generally unknown, the majority of archived temperature data are found to be misaligned with the original measurements because of rounding on a Fahrenheit scale, conversion to Celsius, and re‐rounding. Furthermore, we show that commonly used statistical methods including quantile regression are sensitive to the finite precision and to double‐rounding of the data after unit conversion. To remedy these issues, we present a Hidden Markov Model that uses the differing frequencies of specific recorded values to recover the most likely original precision and units associated with each observation. This precision‐decoding algorithm is used to infer the precision of the 644 million daily surface temperature observations in the Global Historical Climate Network database, providing more accurate values for the 63% of samples found to have been biased by double‐rounding. The average absolute bias correction across the dataset is 0.018 °C, and the average inferred precision is 0.41 °C, even though data are archived at 0.1 °C precision. These results permit better inference of when record temperatures occurred, correction of rounding effects, and identification of inhomogeneities in surface temperature time series, amongst other applications. The precision‐decoding algorithm is generally applicable to rounded observations–including surface pressure, humidity, precipitation, and other temperature data–thereby offering the potential to improve quality‐control procedures for many datasets.

Collimated scanning for large sample neutron activation analysis of inhomogeneous samples

A technique was developed for the identification of inhomogeneities in activity distribution and the correction of their effect on the interpretation of gamma spectrometry data in Large Sample Neutron Activation Analysis. The method was based on collimated gamma scanning using a germanium detector to obtain the activity pattern in the bulk sample and Monte Carlo simulations in order to correct the experimental data for the effect of the inhomogeneous activity distribution. The method was experimentally evaluated in the case of a large cylindrical reference sample of 2 L in volume containing quartz as matrix material and a known source of radioactivity and an excellent agreement was observed. The discussed technique improves the trueness of quantitative analysis of large samples with inhomogeneous activity distribution.

Trend analysis of rainfall-runoff regimes in selected headwater areas of the Czech Republic

The main aim of this work is to evaluate the development of rainfall-runoff regime in selected river basins of the Sumava Mountains (Bohemian Forest), the Jeseniky Mountains and the Krusne Mountains (Ore Mountains) in the last 50 years. Besides the identification of inhomogeneity in time series of mean discharges, rainfall amounts, temperature and snow cover data, the work deals with an analysis of trends using annual and monthly data. Different methodological tools for identification of changes and trends in hydro-climatic time series have been introduced in this study, especially different methods of statistic testing and an application of Mann-Kendall seasonal test. The results have been compared not only from the point of view of the methods applied here, but as well from the viewpoint of geographical difference of the mentioned areas. KEY WORDS: Statistics, Trends, Rainfall-Runoff Regime, Air Temperature, Snow Parameters, Headwaters Areas, Czech Republic. Zdeněk Kliment, Milada Matouskova, Ondřej Ledvinka, Vaclav Kralovec: ANALÝZA TRENDŮ SRAŽKO-ODTOKOVEHO REŽIMU VE VYBRANÝCH PRAMENNÝCH OBLASTECH CESKE REPUBLIKY. J. Hydrol. Hydromech.,

Application of EDS microanalysis in the identification of inhomogeneities in surface protective layers on ductile cast iron parts

In this study, the results of the application of both scanning electron microscopy and EDS microanalysis in investigations of the process of the protective layer formation on the surface of ductile cast iron (the substrate material) turbine blades are presented. The turbine blades, designated for operation in an aggressive environment, were coated with protective chromium carbide layers using plasma spraying methods. The first turbine blade was coated using a standard plasma spraying technique, followed by superficial remelting treatment, while the second one was coated using a modified plasma technology, i.e., HVOF (High Velocity Oxy Fuel) spraying technique.

Numerical calculations of scattering characteristics of inhomogeneities in biological tissue

Identification of inhomogeneities is one of the main problems in medical diagnosis, particularly in tissue characterization. Often the backscatter signal does not permit discrimination between inhomogeneities in the tissue. Despite high effectiveness of the B-mode diagnostic systems, at the present time ultrasonography does not provide a sufficient degree of diagnostic confidence in identification of pathology. Diffraction tomography promises to extend these observations quantitatively and provide information about tissue properties. The main goal of this work is to present a theoretical basis of the scattering process on inhomogeneities and provide some preliminary experimental results confirming theoretical investigations and numerical simulations. The method of integral equations for solving forward and inverse scattering problems is used, and scattering diagrams are presented. Experimental setup is based on one transmitting and seven receiving elements. Presented experimental resuls support numerical simulations.

Scattering from a sphere of small radius embedded into a dielectric one

In this paper, the scattering of a plane electromagnetic wave from a metallic or dielectric sphere of electrically small radius, embedded into a dielectric one, is considered. The classical method of separation of variables is used, combined with translational addition theorems for spherical vector wave functions. Analytical expressions are obtained for the scattered field and the various scattering cross-sections, in the case of an inner sphere with electrically small radius. Numerical results are given for various values of the parameters and for metallic and dielectric inner sphere. Some remarks are made about the possibility of detection or identification of inhomogeneities or nonsymmetries.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Scattering from an eccentrically stratified dielectric sphere

In this paper the scattering from eccentrically stratified spheres is considered. For the case of a spherical inhomogeneity embedded inside a dielectric sphere, the method of separation of variables is used in conjunction with translational addition theorems for spherical vector waves. Analytical results are obtained when the difference in the dielectric constants of the two spheres is small by employing a special perturbation technique. Scattering properties such as distortion of the scattering patterns, variation of total and backscattering cross sections, and depolarization for randomly oriented scatterers are investigated. Methods of detection and identification of inhomogeneities are discussed.