Electric Power Sources Based on the Seebeck Effect of Manganese Sulfides with Rare Earth Substitution

The thermoelectric properties of compounds with variable valence Mn1-ХReХS (0 ≤ X ≤ 0.2) in the temperature range of (80 – 1100) K are studied. The maxima on the temperature dependences of the Seebeck coefficient (thermal EMF) for all substitution concentrations and the change of the sign of the Seebeck coefficient from positive to negative with an increase in the substitution concentration in Mn1-XYbXS are determined. A model of impurity donor 4f-states is proposed and a satisfactory agreement with the data on the thermal EMF is obtained.

SHIP-SHIP HYDRODYNAMIC INTERACTION IN CONFINED WATERS WITH COMPLEX BOUNDARIES BY A PANELLED MOVING PATCH METHOD

This paper presents a potential flow solution for online estimation of hydrodynamic interaction between ships moving in restricted waters with complex boundaries. Each ship in concern is linked with a moving patch representing the arbitrary bathymetry beneath it. The wetted surfaces of ship hulls are meshed and loaded prior to the simulation, while the moving patches are dynamically discretized by a fast and robust mesh generator. The proposed method is validated for the ship- ship interaction case in the shallow water case with a flat and horizontal seabed where the mirror image technique is applicable, and satisfactory agreement is obtained. The method is further applied to simulate two interaction scenarios involving arbitrary seabed topography, and the numerical results are obtained and discussed.

General principles for describing electronic and proton multiple scattering processes in solids

Analytical solution for the reflected light ions Pass Length Distribution Function (PLDF) equation is obtained. Reflected ions energy spectra calculated on the basis of the developed method shows satisfactory agreement with experimental data. The effectiveness of the developed methodology in the procedure for verifying the stopping power value is indicated.

Characteristics of the circular subsonic laminar jets flow with an initial Poiseuille profile

In this work, the experimental data are compared with the version of the “strong” jet (Re ≫ 1) of the exact Landau-Squire solution. The experiments were performed for a submerged air jet flowing out of a tube with a diameter of D = 3.2 mm and a length of more than 100D at a Reynolds number equal to Re = 436. The initial conditions in the jet are the Poiseuille velocity profile, the level of velocity pulsations is less than 1%. Measurements were carried out using a hot-wire anemometer. It is shown that satisfactory agreement with theory is achieved at distances from the tube starting from x/D = 5.6 and up to the zone of transition to turbulence (x/D > 35). Turbulence along the jet axis will increase from 1% to 2.5%, while in the mixing layers it increases to 4.7%.

MEASURING THE PRE-HEATING TEMPERATURE OF THE PLATES SURFACE WITH IMPACT GAS IN THE WELDING GAP DURING EXPLOSION WELDING

A technique for measuring the heat flux from the shock-compressed gas in front of the point of contact to the surface of the colliding plates has been developed. The experimental values of the heat flux are obtained, which are in satisfactory agreement with theoretical calculations. For the first time experimentally proved a significant effect of preheating of plates before collision for various materials. The effect consists in heating the surface of the plates, depending on their dimensions and properties, up to 1000 ° C and above.

Comparing the Köppen-Geiger, Feddema, and UNEP Climate Classifications: An Application to Iran

This study introduces the climates of Iran defined by Köppen-Geiger, Feddema’s, and UNPEP classifications that applied to a high-resolution ground-based gridded data set relative to the 1985–2017 period. Ten Köppen-Geiger climate types were found for Iran, from which Bwh, Bsk, Csa, Bsh, and Bwk cumulatively account for more than 98% of the territory. Likewise, from 36 possible Feddema’s climate types, Iran possesses fifteen climate types from which the Dry Cool, Semiarid Torrid, Semiarid Hot, Semiarid Warm, Dry warm, Semiarid Cool, and Moist Cool climates collectively occupied approximately 93% of the country. Similarly, arid, semi-arid, humid, and sub-humid UNEP climate types characterized more than 98% of Iran. A few other vertically stratified climates appeared at the highlands of Iran just because of changes in elevation and slope aspects of the mountains. The combined effect of topography and vicinity to sea also creates very distinct climate types in northern Iran. The climate maps of the three used methods reflect the joint effects of topography, latitudinal variation, and land/sea surface contrast on the climate of Iran. A pairwise comparison made between the three classifications showed a satisfactory agreement between the three schemes in representing the main climate types of Iran.

Proportions influence of simple shape orbital objects on their aerodynamic characteristics

When developing modern and promising aerospace technology models, the relevance of simulation of the flow around apparatuses (spacecraft) of various geometric shapes in a transitional mode corresponding to the flight in the region of the upper layers of the atmosphere and near space is growing. Solving the Boltzmann equation, which most adequately describes this process in the framework of kinetic theory, still remains a difficult task. To solve this equation, the Monte Carlo statistical methods are used quite successfully. An example of such a method is the direct statistical simulation, or, less common but also well-established in rarefied gas dynamics, the test particles method (TPM). The aim of this work is to study the effect of geometric proportions of simply-shaped orbiting objects during uncontrolled descent to dense layers of the atmosphere on their drag coefficients. Such objects may be elements of space debris or spacecraft of appropriate shapes and proportions. The studies were based on the results obtained by numerical simulation of TPMs on uniform rectangular grids. The shape of the orbital objects was set in the form of a circular cone, cylinder, rectangular parallelepiped of various elongations, and spheres. The calculations were carried out in a wide range of attack angles. The characteristic dimensions of the body class in question varied from 2 to 12 meters. According to the standard atmosphere for such characteristic dimensions, the transitional flow regime is realized at altitudes from 90 km to 180 km. It was found that the calculated values of the drag coefficients in the transition regime are in satisfactory agreement with the experimental data and calculations on the theory of local interaction, and at an altitude of 300 km, they correspond to the control free molecular values obtained by analytical formulas. The dependence of the drag coefficients of the bodies of the considered shapes on the angle of attack and flight altitude was studied. The influence of the choice of the characteristic area on the range of values of the calculation results is shown. The drag coefficient of the considered class of bodies at the entrance to the dense layers of the atmosphere using the TPM was calculated for the first time. Satisfactory agreement of the obtained results with the available experimental and calculated data confirms the effectiveness of the applied method in transition mode. This makes it possible to use it in practical calculations of the parameters of the external environment effect on the spacecraft in the most difficult to study altitude ranges corresponding to the transitional flow regime.

Контроль одноосных напряжений в сталях с учетом их магнитоупругой чувствительности

The magnetoelastic demagnetization of a number of steels in the state of delivery under longitudinal elastic tension, transverse compression and impact has been investigated. The estimation of the magnetoelastic sensitivity of the studied steel grades in the linear approximation is given. The possibility of determining the tensile and compressive stress in the mode of magnetoelastic memory is considered, taking into account the magnetoelastic sensitivity of the selected section of steel, and a method for its determination using dosed loading (impact or compression) is proposed. It is shown that the regression equation in the form of a polynomial is in satisfactory agreement with the experimental results.

Experimental and modelling study of the grain refinement of Fe-30wt%Ni-Nb austenite model alloy subjected to severe plastic deformation process

This study addresses some aspects regarding a computer modelling based on three-dimensional Frontal Cellular Automata (FCA) for the simulation of ultrafine-grained (UFG) microstructure development in purpose-designed microalloyed austenite model alloy i.e. FCC structure. Proposed in the present study model is a step forward towards understanding the deformation and microstructure development mechanisms occurring during severe plastic deformation (SPD) processes with high accumulation of the plastic deformation effects in FCC structures. The analysed microalloyed austenite microstructures were developed due to SPD effects. Using the proposed computer model, based on three-dimensional FCA it has been shown that it is possible to predict some characteristics of the FCC microstructures such as the grain size and the distribution of the boundaries misorientation angle. These abilities were proved by the qualitative and quantitative comparisons of the modelling and SEM/EBSD results. The capabilities of the proposed model were tested using experimental results of the wire drawing processes. The paper presents the new original results of experimental studies of multi-staged MaxStrain technology with the microscopic investigation. Basing on data obtained from these studies, the dependencies of the evolution of grain structure and misorientation angle on the accumulative strain and cycle number were obtained in a form of approximation equations. The equations were implemented into the CA model, and MaxStrain technology was simulated. Comparison of the results obtained in experimental studies and simulations shows a satisfactory agreement. Industrial verification of the developed model as well shows a satisfactory agreement.

Оптимизация измерений вектора силы взаимодействия в атомно-силовой микроскопии

The issue of optimization of measurements of three spatial components of the probe-sample interaction force and the corresponding displacement vector of the "ideal cantilever" is considered. To determine these components in an atomic force microscope with an optical beam deflection scheme, it is necessary to register the bending angles at least at two points on the rectangular cantilever and the torsion angle at any of them. It has been proven analytically that one optimal point is the intersection of the probe axis with the console plane. A method to calculate the position of another optimal point has been developed. An experiment was carried out to map the force and displacement vector, and satisfactory agreement with the theory was obtained.