Samples Of Various Shapes Research Articles

Standardization and quantification of backscattered electron imaging in scanning electron microscopy

Backscattered electron (BSE) imaging based on scanning electron microscopy (SEM) has been widely used in scientific and industrial disciplines. However, achieving consistent standards and precise quantification in BSE images has proven to be a long-standing challenge. Previous methods incorporating dedicated calibration processes and Monte Carlo simulations have still posed practical limitations for widespread adoption. Here we introduce a bolometer platform that directly measures the absorbed thermal energy of the sample and demonstrates that it can help to analyze the atomic number (Z) of the investigated samples. The technique, named Atomic Number Electron Microscopy (ZEM), employs the conservation of energy as the foundation of standardization and can serve as a nearly ideal BSE detector. Our approach combines the strengths of both BSE and ZEM detectors, simplifying quantitative analysis for samples of various shapes and sizes. The complementary relation between the ZEM and BSE signals also makes the detection of light elements or compounds more accessible than existing microanalysis techniques.

FRACTAL ANALYSIS OF BRANCHING OF HUMAN CEREBELLAR ARTERIES

Human cerebellum is supplied by three arteries: the superior surface is nourished by the superior cerebellar artery (SCA), while the inferior surface is supplied by the anterior inferior cerebellar artery (AICA) and the posterior inferior cerebellar artery (PICA). Traditionally, the branching pattern of the superfi cial vascular network is subjectively assessed, distinguishing between the trunk, lose or mixed types. Fractal analysis is an objective alternative method.The aim of this study is to investigate the fractal dimension of branching complexity of superfi cial arteries in the human cerebellum and to establish the relationship between the magnitude of the fractal index and the shape of the cerebellum.Material and Methods. A total of 100 cerebellum samples, including the brainstem, were examined. The width, length, and height of the cerebellum were measured. Parameters of cerebellar shape, namely relative width (rW), relative length (rL), and relative height (rH), were determined as the ratios of the square of one linear dimension to the product of the other two. For fractal analysis, 15 cerebellar samples of various shapes (9 from male and 6 from female individuals) were selected. Fractal analysis of digital images of the superior and inferior surfaces of the cerebellum was performed bilaterally using the box-counting method.Results. The range of fractal index values was determined, and intervals corresponding to the mixed (1.54-1.73), trunk (<1.54) and loose (>1.73) branching types were identifi ed. The superior surface predominantly exhibited trunk or mixed branching types, whereas the inferior surface was more characteristic of mixed or loose branching types. The greatest diversity of arterial branching patterns – from the trunk to lose type – is observed in the most numerous group – cerebella of proportional shape, regardless of which shape parameter is analyzed. The branching pattern of superfi cial cerebellar arteries tends towards a loose type in relatively narrow and relatively short cerebella, and conversely towards a trunk type in relatively wide and relatively long cerebella. Conversely, relative height has an opposite eff ect: the branching pattern of superfi cial cerebellar arteries tends towards a loose type as the relative height of the cerebellum increases. Thus, relatively low cerebella typically exhibit a trunk branching pattern (more noticeable on the superior surface), while in relatively high cerebella, the branching pattern tends towards loose (more noticeable on the inferior surface).

A method for correcting self-absorption shown in fluorescence XAFS spectra

X-ray-absorption fine-structure (XAFS) measurement by the fluorescence-yield (FY) method can be applied to samples of various shapes and concentrations. However, it is known that XAFS spectra obtained by the FY method do not precisely reflect the original X-ray absorption of the sample due to the self-absorption effect. We therefore propose a method for correcting the self-absorption by using FY XAFS spectra of original and diluted samples. The proposed self-absorption correction method can be applied to samples with unknown compositions. The effectiveness of the correction method was evaluated by applying it to the FY XAFS spectra of several iron oxides and their mixtures. As a result, the corrected FY XAFS of Fe K-edge spectra were almost identical to the XAFS spectra obtained by the transmission method. The suppressed EXAFS oscillations of the FY XAFS spectra were also recovered. These results validate the effectiveness of the proposed correction method. They also demonstrate that the corrected XANES spectra can be applicable to linear combination fitting analysis.

On the physical meaning of the geometric factor and the effective thickness in the Montgomery method

The Montgomery method is extensively employed to determine the electrical resistance tensor of anisotropic samples. This technique relies on two essential parameters describing an isotropic system: the geometric factor (H1) and the effective thickness (E). The numerical values of these parameters are intricately linked to the dimensions of an isotropic block equivalent to the studied anisotropic specimen. While these parameters hold importance, the physical interpretation of these terms still lacks clarity. In this study, we utilized the finite element method to simulate electrical transport experiments across samples of various shapes. Utilizing the Electric Currents physics interface in the COMSOL program, we were able to provide a comprehensive analysis of the physical meaning of these parameters to accurately determine the electrical properties of thin films and wafers. The presented findings related to the physical interpretation of H1 and E terms make substantial contributions to the field of electrical transport experimental techniques, which are fundamental to design advanced materials for technological applications and understand their physical properties.

3D printing of bulk thermoelectric materials: Laser powder bed fusion of N-type silicon germanium

Among Additive Manufacturing (AM) methods, Laser Powder Bed Fusion (L-PBF), also called Selective Laser Melting (SLM), is prevalent to printing complex metal parts in small and medium series. Recent studies in L-PBF processing develops the manufacturing of new materials, including thermoelectric (TE) materials. This study presents manufacturing of an N type Si80Ge20 powder by L-PBF. Silicon germanium alloy is a TE material intended for high temperature applications. It is the first time that this semiconductor material is studied by AM technology. Dense samples of various shapes and sizes were produced, and a first process window was identified. Structural analyses have been performed, highlighting good densification. Unfortunately, mechanical cracking occurs in all samples. TE properties were investigated on as built samples, displaying low values (ZT = 0.11 at 600 °C), due to poor electrical conductivity. Overall, these results show that L-PBF of silicon germanium is possible, which could open up its scope of applications.© 2023 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Materials science in semiconductor processing.

Impact of the mutual direction of Polarizer and Free Layer on the auto-oscillation mode of magnetic tunnel junctions (MTJs) of different geometry

In this work we studied the auto-oscillation mode of structures based on magnetic tunnel junctions. During the experiment we studied how different values and orientation of the magnetic field affect the efficiency of the auto-oscillations regime for samples of various shapes. The auto-oscillation mode in samples was observed near the transition from one state of magnetization of the free layer to another. It was found that the maximum value of the power spectral density and its position relative to the frequency axis can be controlled by changing the magnitude and orientation of the external magnetic field. Keywords: Magnetic tunnel junction (MTJ), auto-oscillations, power spectral density, nanooscillator.

Влияние взаимного направления поляризатора и свободного слоя на автогенерацию магнитных туннельных переходов (МТП) разной геометрии

In this work we studied the auto-oscillation mode of structures based on magnetic tunnel junctions. During the experiment we studied how different values and orientation of the magnetic field affect the efficiency of the self-generation regime for samples of various shapes. The auto-oscillation mode in samples was observed near the transition from one state of magnetization of the free layer to another. It was found that the maximum value of the power spectral density and its position relative to the frequency axis can be controlled by changing the magnitude and orientation of the external magnetic field.

Use of photogrammetry to determine spruce and OSB char bulk density

AbstractThis paper deals with the bulk density determination of char, which is an important input parameter for numerical simulations of pyrolysis. The aim was to develop a time and cost‐effective, non‐destructive, and repeatable method capable to determine the bulk density of highly porous, fragile wood and engineered wood samples of various shapes, namely char of spruce and oriented strand board. Char samples were prepared in a cone calorimeter under various heat flux exposures. Photogrammetry was chosen for this purpose. A detailed photogrammetric measurement procedure consisting of sample preparation, sample measurement and software reconstruction was designed and validated. It was found that the bulk density of char depends on the virgin material and the way char was formed. The spruce and oriented strand board char bulk density value is provided to be used in pyrolysis modeling and compared to literature.

Methods and Equipment for Experimental Evaluation of the Performance of Shell and Hull Structures

Introduction. Pressure-operated thick-walled hull structures are the most common type of high-duty welded structures. When these structures are loaded with internal pressure, a complex biaxial stress field arises in them, which is summed up with the fields of residual welding stresses. Therefore, when selecting a technology for manufacturing critical welded structures, the results obtained during conventional uniaxial tests of samples are insufficient. The variety of factors affecting the performance of structures, and the difficulties of separate assessment of their influence, caused the need to maximize the approximation of experimental conditions to the real working conditions of the structure.Materials and Methods. Testing of full-scale structures has a number of advantages, but they are extremely expensive, and, as a rule, only one, the weakest link, is identified, the bearing capacity of the other structural elements remains unclear. For testing, UDI radiometric installations designed for different sample sizes were used. The presented installations allow testing samples of various shapes, types of welded joints (butt, T-bar), changing the position of welded parts.Results. Without rejecting the results obtained during the testing of full-scale structures in the works of the Bauman Moscow State Technical University, DSTU, NRC «Kurchatov Institute» – CRISM «Prometey», and the authors proposed to conduct the basic scope of the research on individual structural elements that would reflect the characteristic features of loading, manufacturing technology, and operating conditions. The design of the «fitting-sheet» connections was applied, which made it possible to increase the indicators of the failure initiation and propagation to the level of the base metal.Discussion and Conclusions. Schemes of structures for obtaining a biaxial tension or bending field in samples were presented. Samples tested according to the proposed schemes allowed us to draw conclusions about the performance of welded joints under conditions close to the actual operation of the structures under study. The proposed test scheme is used by research laboratories in our country and around the world.

Determination of elastic characteristics of cement stone to predict the fatigue life of concrete

Introduction. The problem of fatigue failure of concrete is one of the least studied in computational practice. The lack of reliable data on the actual processes of accumulation of fatigue damage occurring in the structure of this material during cyclic exposure does not allow us to form a methodology for calculating concrete structures that perceive such loads. To develop the above methodology, it is proposed to use structural simulation modeling. For this purpose, mathematical models of concrete damage under the influence of cyclic loading are considered. The purpose of the study is to determine the elastic and strength characteristics of cement stone for further development of a methodology for predicting the fatigue life of concrete, taking into account the nonlinear kinetics of damage accumulation.
 
 Materials and methods. The strength limits of cement stone during bending and compression were determined by conducting a full-scale experiment on a testing machine and a hydraulic press. Elastic characteristics of cement stone were obtained as a result of static tests of cement stone samples of various shapes on the universal electromechanical system with the joint use of the digital optical system for analysis of deformation and displacement fields and the acoustic emission signal recording system.
 
 Results. During the tests of cement samples for bending and compression, the values of the corresponding bending and compression strength limits were obtained, which made it possible to confirm the design strength class of cement 32.5 N. Inhomogeneous fields of longitudinal and transverse deformations were obtained using a digital optical system to further determine the basic elastic characteristics of the material. Obtaining acoustic emission signals during the experiment made it possible to reflect the dependences of various acoustic emission parameters on time.
 
 Conclusions. The first stage of the proposed methodology for predicting the fatigue life of concrete is performed, taking into account the nonlinear kinetics of damage accumulation, as a result of which the modulus of elasticity and the Poisson’s ratio for cement stone are determined. The obtained data can be used to create a numerical model of the concrete structure, and the use of acoustic emission signals allows us to estimate the kinetics of damage accumulation in the material.

ОШИБКА ИЗМЕРЕНИЯ НАМАГНИЧЕННОСТИ МАГНИТНОЙ ЖИДКОСТИ МЕТОДОМ ЯДЕРНОГО МАГНИТНОГО РЕЗОНАНСА, ВЫЗВАННАЯ НЕОПРЕДЕЛЁННОСТЬЮ КОНСТАНТЫ ЭФФЕКТИВНОГО ПОЛЯ

The magnetic liquid magnetization is usually determined by measuring the magnetic field strength, which linearly depends on the effective field constant of the liquid and the demagnetization coefficient of the sample. The article proposes to measure the magnetic field strength, generated by the same magnetic liquid in the samples of different shapes, and to determine the magnetization relying on the difference in strength, generated by the samples of various shapes, taking advantage of the fact that the effective field constant does not depend on the shape of the sample

Practical methods for the experimental determination of the mechanical characteristics of cement stone under compression

In this work, we propose practical methods for the experimental study of the mechanical characteristics and staging of damage accumulation of cement stone based on the joint use of modern testing equipment and a non-contact optical video system for analyzing displacement and deformation fields, as well as a system for recording acoustic emission signals. In the framework of these practical methods, compression tests of cement stone samples of various shapes and geometrical sizes were carried out. The diagrams of deformation and application of loading have been obtained, the mechanical characteristics have been determined, and the staging of damage accumulation in a cement stone has been analyzed. We have received a conclusion about the optimal shape of samples of cement stone, which can be used to determine the prism strength, elastic modulus and Poisson’s ratio using the proposed practical methods.

Finite element (GFEM) simulations on the effect of microwave heating for lossy dielectric samples with various shapes (circle, square and triangle)

Purpose This paper aims to investigate the thermal performance involving larger heating rate, targeted heating, heating with least non-uniformity of the spatial distribution of temperature and larger penetration of heating within samples vs shapes of samples (circle, square and triangular). Design/methodology/approach Galerkin finite element method (GFEM) with adaptive meshing in a composite domain (free space and sample) is used in an in-house computer code. The finite element meshing is done in a composite domain involving triangle embedded within a semicircular hypothetical domain. The comparison of heating pattern is done for various shapes of samples involving identical cross-sectional area. Test cases reveal that triangular samples can induce larger penetration of heat and multiple heating fronts. A representative material (beef) with high dielectric loss corresponding to larger microwave power or heat absorption in contrast to low lossy samples is considered for the current study. The average power absorption within lossy samples has been computed using the spatial distribution and finite element basis sets. Four regimes have been selected based on various local maxima of the average power for detailed investigation. These regimes are selected based on thin, thick and intermediate limits of the sample size corresponding to the constant area of cross section, Ac involving circle or square or triangle. Findings The thin sample limit (Regime 1) corresponds to samples with spatially invariant power absorption, whereas power absorption attenuates from exposed to unexposed faces for thick samples (Regime 4). In Regimes 2 and 3, the average power absorption non-monotonically varies with sample size or area of cross section (Ac) and a few maxima of average power occur for fixed values of Ac involving various shapes. The spatial characteristics of power and temperature have been critically analyzed for all cross sections at each regime for lossy samples. Triangular samples are found to exhibit occurrence of multiple heating fronts for large samples (Regimes 3 and 4). Practical implications Length scales of samples of various shapes (circle, square and triangle) can be represented via Regimes 1-4. Regime 1 exhibits the identical heating rate for lateral and radial irradiations for any shapes of lossy samples. Regime 2 depicts that a larger heating rate with larger temperature non-uniformity can occur for square and triangular-Type 1 lossy sample during lateral irradiation. Regime 3 depicts that the penetration of heat at the core is larger for triangular samples compared to circle or square samples for lateral or radial irradiation. Regime 4 depicts that the penetration of heat is still larger for triangular samples compared to circular or square samples. Regimes 3 and 4 depict the occurrence of multiple heating fronts in triangular samples. In general, current analysis recommends the triangular samples which is also associated with larger values of temperature variation within samples. Originality/value GFEM with generalized mesh generation for all geometries has been implemented. The dielectric samples of any shape are surrounded by the circular shaped air medium. The unified mesh generation within the sample connected with circular air medium has been demonstrated. The algorithm also demonstrates the implementation of various complex boundary conditions in residuals. The numerical results compare the heating patterns for all geometries involving identical areas. The thermal characteristics are shown with a few generalized trends on enhanced heating or targeted heating. The circle or square or triangle (Type 1 or Type 2) can be selected based on specific heating objectives for length scales within various regimes.

Method for Determining the Complete Set of Constants of the Polarized Piezoceramics for a Single Ring-Shaped Sample

Using the ANSYS finite element modeling software package, Russian and foreign methods for determining the constants (modules) of piezoceramics presented in regulatory documents are analyzed. A machine experiment was conducted in which the constants of piezoceramics are entered into a program where the boundary-value problem for an element of the selected size is solved and the resonant and antiresonance frequencies are determined numerically. A method for determining the complete set of ten compatible piezoceramic modules has been developed and theoretically justified. In the presented method, only one sample of piezoceramics in the form of a ring with various electrodes is involved. A scheme for determining the complete set of compatible constants of piezoceramics is described. The proposed method is based on the theoretical foundations of electrical engineering and the solution of electroelasticity problems. It is shown that the use of only one sample instead of four to determine the complete set of compatible constants of piezoceramics increases the accuracy of measuring elastic moduli, since there are no errors caused by the dispersion of the properties of samples of various shapes in sintering and polarization processes, and measurements are simplified.

Study of The Regularities of Postcritical Behavior and Failure of Specimens in the Tests of Composite Materials

New experimental data on the regularities of deformation and fracture of layered GFRP and CFRP composites with various reinforcement schemes were obtained. Particular attention is paid to the manifestation of the postcritical behavior of composites, which is characterized by a decrease in the load that the sample is able to perceive, with a monotonous increase in displacements. In this case, the postcritical deformation stage is associated with the development of damage accumulated during the loading process, interaction of defects and subsequent partial destruction of the structural elements of the composite material. The tests were carried out on the samples of various shapes under three-point bending in a wide range of temperatures. The influence of temperature on the regularities of deformation and fracture of polymer composites and the realization degree of the postcritical deformation stage has been estimated. Methodical issues of experimental study of the effect of the rigidity of the loading system on the postcritical deformation and destruction of polymer composites under three-point bending and interlayer shear (short beam method) are considered when using various combinations of disc springs in the loading circuit. Experimental data on the effect of the rigidity of the loading system on the realization of the equilibrium stage of postcritical deformation during the destruction of composite materials during the interlayer shear are obtained. The structure of the destroyed prototypes was analyzed.

Effective Demagnetizing Factors of Diamagnetic Samples of Various Shapes

Effective demagnetizing factors that connect the sample magnetic moment with the applied magnetic field are calculated numerically for perfectly diamagnetic samples of various non-ellipsoidal shapes. The procedure is based on calculating total magnetic moment by integrating the magnetic induction obtained from a full three dimensional solution of the Maxwell equations using adaptive mesh. The results are relevant for superconductors (and conductors in AC fields) when the London penetration depth (or the skin depth) is much smaller than the sample size. Simple but reasonably accurate approximate formulas are given for practical shapes including rectangular cuboids, finite cylinders in axial and transverse field as well as infinite rectangular and elliptical cross-section strips.

Failure of structural elements made of polymer supported composite materials during the multiyear natural aging

Modern high-rise construction introduces a number of limitations and tasks. In addition to durability, comfort and profitability, projects should take into account energy efficiency and environmental problems. Polymer building materials are used as substitutes for materials such as brick, concrete, metal, wood and glass, and in addition to traditional materials. Plastic materials are light, can be formed into complex shapes, durable and low, and also possess a wide range of properties. Plastic materials are available in various forms, colors and textures and require minimal or no color. They are resistant to heat transfer and diffusion of moisture and do not suffer from metal corrosion or microbial attack. Polymeric materials, including thermoplastics, thermoset materials and wood-polymer composites, have many structural and non-structural applications in the construction industry. They provide unique and innovative solutions at a low cost, and their use is likely to grow in the future. A number of polymer composite materials form complex material compositions, which are applied in the construction in order to analyze the processes of damage accumulation under the conditions of complex nonstationary loading modes, and to determine the life of structural elements considering the material aging. This paper present the results of tests on short-term compression loading with a deformation rate of v = 2 mm/min using composite samples of various shapes and sizes.

A synthesis of geometry effect on brittle fracture

There are numerous analytical solutions in order to take into account the geometry effect on the fracture toughness and the fracture load of the cracked specimens. However, due to the complexities of the mentioned criteria it is practical to have an engineering method which can be used for fracture prediction in cracked samples of various shapes and loading conditions. In this paper, the fracture behaviors of five different testing samples made of various brittle and quasi-brittle materials have been studied using an energy based criterion namely the Average Strain Energy Density (ASED) criterion. According to the formulation of the ASED criterion, all the stress terms around the crack tip were taken into account and the brittle fracture of different samples with various geometry constraints were well predicted.

Magnetization Reversal Processes in Pr-Fe-B-type Nanocrystalline Magnets

The magnetization reversal processes in magnets derived from rapidly solidi ed Pr9Fe52Co13Zr1Nb4B21 alloy samples were studied by analysis of minor hysteresis loops and recoil curves. The studies were carried out on suction-cast 1 mm diameter rod, 1 mm thick plate, 3 mm outer diameter (o.d.) tube and melt-spun ribbon samples subjected to annealing at 983 K for 5 min. The X-ray di raction analysis has shown multiphase constitution of the samples. Structural and magnetic studies indicated that the initial state of microstructure and phase composition a ects the magnetization reversal processes in annealed samples due to a variation of microstructure in samples of various shapes. Magnetic studies allowed estimation of the mean values of nucleation and pinning elds that control the magnetization reversal processes.

A new technique using FT-IR micro-reflectance spectroscopy for measurement of water concentrations in melt inclusions

This paper presents a new technique to measure water concentrations in small volcanic glasses such as melt inclusions. The technique uses Fourier transform infrared (FT-IR) micro-reflectance spectroscopy, and thus does not require a doubly polished sample. To enhance the signal-to-noise (S/N) ratio, a vacuum pump and a narrow-band mercury-cadmium-telluride (MCT) detector were introduced into the FT-IR spectrometer. The pump reduced noise caused by atmospheric water vapor and carbon dioxide, and the detector enhanced the signal, which resulted in significant improvement of the S/N ratio. For standards, we synthesized 32 glasses with different water concentrations ranging from basaltic to rhyolitic composition. An empirical relationship was established between total water content and the negative peak height normalized by the baseline extrapolated from the neighboring region (ΔR/Rbaseline); for example, H2O wt.% = 49.76 × ΔR/Rbaseline − 0.08 for basaltic composition. The regression error corresponded to approximately 0.29 wt.% water (2σ) with an aperture of 20 μm × 20 μm and 2,048 scans. To apply the technique to natural samples of various shapes, we developed a method to correct the spectrum of melt inclusion contaminated with host minerals. This method calculates the overlapping volume of the host crystal using the reflectance spectra at 800 to 1,300 cm−1 and is applicable to melt inclusions hosted by olivine, orthopyroxene, and plagioclase.