On optimal cloaking-by-mapping transformations

A central ingredient of cloaking-by-mapping is the diffeomorphisn which transforms an annulus with a small hole into an annulus with a finite size hole, while being the identity on the outer boundary of the annulus. The resulting meta-material is anisotropic, which makes it difficult to manufacture. The problem of minimizing anisotropy among radial transformations has been studied in [4]. In this work, as in [4], we formulate the problem of minimizing anisotropy as an energy minimization problem. Our main goal is to provide strong evidence for the conjecture that for cloaks with circular boundaries, non-radial transformations do not lead to lower degree of anisotropy. In the final section, we consider cloaks with non-circular boundaries and show that in this case, non-radial cloaks may be advantageous, when it comes to minimizing anisotropy.

On the Recycling of Water Atomized Powder and the Effects on Properties of L-PBF Processed 4130 Low-Alloy Steel

The microstructure and mechanical properties of a 4130-grade steel processed by L-PBF using a feedstock of low-cost water atomized powder have been investigated considering the effects of powder recycling. Chemical analysis of the recycled powder showed a constant amount of alloying elements with a slight reduction in oxygen content. The as-built microstructure was mainly composed of a martensitic structure separated by a high fraction of low-angle grain boundaries, suggesting the application of a direct tempering treatment starting from the as-built condition as a cost-effective post-process thermal treatment rather than the conventional quench and tempering treatment. Moreover, the degree of anisotropy generated by L-PBF in as-built specimens could be reduced after performing either the direct tempering or the quench and tempering treatments. The possible degradation of powder properties on the steel performance was also investigated. After various powder recycling events, no significant deterioration in tensile properties was measured, indicating that the water atomized powder could be a sustainable feedstock candidate for L-PBF.

Characterization and Spectroscopic Applications of Metal Foams From New Lightweight Materials

Lightweight materials such as metallic foams possess good mechanical, chemical, and physical properties, which make them suitable for a wide range of functional and structural applications. Metal foams have recently gained substantial interest in both industry and academia due to their low cost, thermal conductivity, high working temperature, vibration damping, specific mechanical properties, energy absorption, and heat resistance. The use of metal foams on a large scale and successful applications depend on a detailed understanding of their characteristic properties. Metallic foams are characterized by the morphology of the porous cells (size and shape, open or closed, macro and micro), pore topology, relative density, properties of the pore wall, and the degree of anisotropy. This contribution focuses on x-ray diffraction, Fourier transform infrared (FT-IR), and Raman spectroscopic applications used for the characterization of metal foam, and also a brief of the most important applications, including a significant number of examples given.

Optical properties of semiconductor “anisotropic” quantum dot

The optical properties of an “anisotropic” semiconductor nanodot – a nanoscale object in the form of a rectangular parallelepiped - with sides a ≠ b ≠ c are considered. Such dimensions are closely related to the values of the effective masses of the electron. The analysis of the spectral dependence of the absorption coefficient a(w) under different degrees of "anisotropy" and under different polarizations of the electromagnetic wave is carried out. The cases of the most intense optical transitions, i.e. between electronic states separated by the Fermi level, are analyzed. The obtained results indicate that 1) a(w) is of line structure, and 2) the positions of the peaks of a(w) in identical optical transitions in the isotropic nanodot and in the “anisotropic” ones coincide qualitatively. However, different masses in the “anisotropic” nanodot lead to a shift to the left or right of the peaks relative to identical peaks in the isotropic nanodot with simultaneous splitting of its degenerate peaks. Such shifts and their magnitudes are determined both by the degree of anisotropy (i.e. by the ratio between the effective masses), and by the polarization of light. It is pointed out that modern achievements in the creation of ordered semiconductor materials with nanoobjects of different shapes and sizes in nanostructures allows us to consider polarized electromagnetic wave as an effective factor in achieving the desired physical characteristics.

Geometry of Magnetic Fluctuations near the Sun from the Parker Solar Probe

Solar wind magnetic fluctuations exhibit anisotropy due to the presence of a mean magnetic field in the form of the Parker spiral. Close to the Sun, direct measurements were not available until the recently launched Parker Solar Probe (PSP) mission. The nature of the anisotropy and geometry of the magnetic fluctuations play a fundamental role in dissipation processes and in the transport of energetic particles in space. Using PSP data, we present measurements of the geometry and anisotropy of the inner heliosphere magnetic fluctuations, from fluid to kinetic scales. The results are surprising and different from 1 au observations. We find that fluctuations evolve characteristically with size scale. However, unlike 1 au solar wind, at the outer scale, the fluctuations are dominated by wavevectors quasi-parallel to the local magnetic field. In the inertial range, average wavevectors become less field aligned, but still remain more field aligned than near-Earth solar wind. In the dissipation range, the wavevectors become almost perpendicular to the local magnetic field in the dissipation range, to a much higher degree than those indicated by 1 au observations. We propose that this reduced degree of anisotropy in the outer scale and inertial range is due to the nature of large-scale forcing outside the solar corona.

Concrete anisotropy estimated from ultrasonic signal amplitudes

The anisotropy of concrete is an essential issue in the construction industry. In this study, for the first time, ultrasonic compression and shear wave signals have been investigated for the orthogonal directions of unreinforced concrete by means of fast Fourier transformation (FFT). For this purpose, cubic concrete samples were prepared in 12 designs of different strengths for ultrasound transmission measurements. The characteristic amplitudes at dominant frequencies were determined by the FFT of these signals. The FFT amplitude differences in the compression and the shear wave signals on the orthogonally oriented surfaces provide essential information about the presence and degree of anisotropy. According to linear regression analysis, the FFT amplitude anisotropies and the amplitude ratios of the compression and shear waves decreased significantly according to increasing concrete strength. In addition, it was found that the anisotropy and the ratio of the FFT amplitudes increased proportionally to the water/cement ratio, the porosity and the water content of the various concrete designs.

Anisotropy of turbulent flow behind an asymmetric airfoil

Feature of turbulent flow anisotropy behavior behind an asymmetric NACA 64-618 airfoil investigated in this paper. Experimental studies were performed using a hot-wire anemometery with X-probe at the chord-based Reynolds number $$1.7 \times 10^5$$ 1.7 × 10 5 . The average ensemble velocity and Reynolds stress components are used to determine the wake topology and anisotropy of turbulence. The obtained data allowed to identify the outside wake region, which is characterized by low instability and a high degree of anisotropy of the turbulent flow. This tendency is observed at different angles incident. Further, to gain better insight into the physics of this phenomenon the structure of turbulence have been evaluated. Integral turbulence length and time scales were estimated by the area of the autocorrelation function of velocity fluctuations. Then, using the second-order structural function, we obtained the dissipation characteristics of the flow. In addition, the features of the energy spectrum in the region with high and low degrees of turbulence anisotropy were analyzed.

MONITORING OF MALIGNANT GROWTH DYNAMICS BY STRUCTURAL ANALYSIS OF NON-CELLULAR TISSUE

The authors examined the composition of biocrystalline structures (anisomorphones) of blood serum in patients with laryngeal cancer. Such structures are formed when blood serum becomes solid, i.e. during its marginal dehydration. The revealed anisomorphones represent three types of marker structures: a marker of a malignant tumor active growth (the aggregation of macroferolite and granular microspherolite with the same degree of anisotropy); a marker of a degenerative-dystrophic process (the aggregation of a macrospherolite with a low degree of anisotropy and microspherolite with a high degree of anisotropy); a marker of a malignant growth progression (a wavy microspherolite without aggregation). The aim of the study is to identify diagnostic markers of the malignant process activity in the solid phase structures of the blood serum in patients with laryngeal cancer and to assess their importance for choosing an effective therapy. Materials and Methods. Marginal dehydration of blood serum was used as the main research method. It is a part of the "Litos-system" diagnostic technology (Marketing authorization FS No. 155, of 2009). Results. It has been shown that the developmental phase of laryngeal cancer (active growth or degenerative-dystrophic process) is an important criterion for choosing treatment options. Surgical treatment is the most effective during the degenerative-dystrophic tumor process, while radiation therapy is preferable during the active phase of malignant growth. Key words: laryngeal cancer, blood serum, marginal dehydration of biological fluids, markers of tumor growth activity. Исследован состав биокристаллических структур (анизоморфонов) сыворотки крови больных раком гортани, которые формируются при переходе сыворотки крови в твердую фазу в процессе ее краевой дегидратации. Выявленные анизоморфоны представляют собой три вида маркерных структур: маркер активного роста злокачественной опухоли – агрегация макросферолита и зернистого микросферолита с одинаковой степенью анизотропии; маркер дегенеративно-дистрофического процесса – агрегация макросферолита с низкой степенью анизотропии и микросферолита с высокой степенью анизотропии; маркер прогрессии злокачественного роста – волнистый микросферолит вне агрегации. Цель – выявить диагностические маркеры активности злокачественного процесса в структурах твердой фазы сыворотки крови больных раком гортани и оценить их значение для выбора эффективного вида лечения. Материалы и методы. В качестве основного метода исследования использован метод краевой дегидратации сыворотки крови, являющийся разделом диагностической технологии «Литос-система» (Разрешение ФС № 155 от 2009 г. на применение в клинической практике). Результаты. Показано, что фаза развития рака гортани (активный рост или дегенеративно-дистрофический процесс) служит важным критерием выбора вида лечения: в фазу дегенеративно-дистрофического процесса опухоли наиболее благоприятный эффект дает хирургическое лечение, а в период активной фазы злокачественного роста – лучевая терапия. Ключевые слова: рак гортани, сыворотка крови, краевая дегидратация биологических жидкостей, маркеры фазы активности опухолевого роста.

Extension of the kinematic approximations to the multilayered elastic orthorhombic medium

Understanding the kinematics of horizontally-layered reservoir rocks is important to their proper characterization and to accomplish this it is necessary to specify the explicit model for these kinematic properties. The accurate approximations for traveltime and relative geometrical spreading in an elastic homogeneous orthorhombic (ORT) have been investigated with different forms: Shifted Hyperbola Form (SHF), Taylor Series (TS) and the Rational Form (RF). This paper extends these approximations to the multi-layered ORT model by adopting composite coefficients and effective model parameters. The multi-layered model is characterized without and with the azimuthal variation among layers. There is an overdetermined problem when the azimuthal variation exists; and to address that case, the Least Squares Method (LSM) is adopted. To check the feasibility of the expansion, we select the SHF (Shifted Hyperbola Form) approximation specified in the homogeneous elastic ORT model for the calculation in the numerical example. Four groups of examples are analyzed to investigate the influence on the accuracy of the approximation with the change in rotation angle, degree of anisotropy, and the direction of the orientation. The results indicate that, for the multi-layer, the accuracy of the approximation is proportional to the degree of anisotropy and the value of the angle of rotation. The relative errors in travel time and relative geometrical spreading in this multi-layered extension are very small and can be implemented in practical applications

Highly Nonlinear Solitary Waves to Estimate Orientation and Degree of Anisotropy in Rocks

This paper delves into the use of highly nonlinear solitary waves for the nondestructive identification and characterization of anisotropy in rocks. The nondestructive testing approach proposed expands upon a technique developed recently by some of the authors for the nondestructive characterization of engineering materials and structures. The technique uses the characteristics of solitary waves propagating in a periodic array of spherical particles in contact with the rock to be characterized. The features of the waves that bounce off the chain rock interface are used to infer some properties of the geomaterial under consideration. Numerical models and experimental validation were conducted to explore the feasibility of the method and to standardize the methodology for future widespread applications.