Form Of Rectangular Parallelepiped Research Articles

EXPERIMENTAL EVALUATION OF THE HOMOGENEITY OF THE OUTPUT STREAMS OF OPTICAL RADIATION OF A RECTANGULAR SHAPE FOR VARIOUS VERSIONS OF THE OUTPUT SECTIONS OF THE LIGHT GUIDE NOZZLES FOR MEDICAL LASER EQUIPMENT

The article presents the results of a study of the homogeneity of rectangular optical radiation fluxes for different versions of the initial sections of the light guide nozzles. When conducting a significant part of laser exposure in medicine, pathological areas of biological tissue or their projections located on the surface of the body are covered with light spots with contours, as a rule, in the form of flat geometric shapes.
 The variability of the implementation of light spots in shape (circle, square, rectangle, triangle, rhombus, etc.) and linear dimensions of the cross section allows you to select the shape and size of the light spot, covering a specific pathological surface with minimal capture of intact tissues. At the same time, regardless of the shape and linear dimensions, the light spots should be as uniform as possible. To date, of particular interest is the provision of optical uniformity of rectangular light spots.
 Firstly, similar forms of spots are widely used under the influence of laser medicine. Secondly, in the original optical stages of laser equipment and the light guides connected to them, first of all, optical fibers of a cylindrical shape with a rounded cross section of the optical flow at the output are used. The purpose of this work is to optimize the parameters of light guide nozzles of medical laser equipment with rectangular output optical radiation fluxes by evaluating the uniformity of the power density distribution for various options for the output sections of the nozzles. In the work, optical flows at the output of three versions of the distal sections of light guides were studied. The light guides were formed by optical fibers, including the use of microlenses at the output ends, and were apertured by channel optical waveguides in the form of rectangular parallelepipeds.
 The experimental results obtained at the stage of physical modeling show the promise of using spherical micro-optical elements at the initial ends of optical fibers in combination with rectangular apertures in the form of channel optical waves to obtain rectangular light spots with a high level of optical homogeneity.

Hydrothermal Synthesis of Silver Sulfide

Silver sulfide powders with submicro- and micrometer particle sizes have been synthesized by the hydrothermal method at temperatures from 373 to 453 K in aqueous and alcoholic solutions of silver nitrate, sodium sulfide and citrate, sulfur, and thiocarbamide. The crystal structures of the synthesized powders, morphology, composition, and particle size of silver sulfide have been analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, and gas adsorption. The powder particles have a similar morphology in the form of rectangular parallelepipeds and cubes with smoothed edges; the size of the powder particles depends on the synthesis conditions and ranges from ~500 to 2000 nm.

INVESTIGATION OF SENSITIVE ELEMENTS OF TEMPERATURE TRANSDUCERS BASED ON THERMOMETRIC MATERIAL Lu1-xScxNiSb

INVESTIGATION OF SENSITIVE ELEMENTS OF TEMPERATURE TRANSDUCERS BASED ON THERMOMETRIC MATERIAL Lu1-xScxNiSb

APPLICATION OF POSITION-SENSITIVE DETECTORS FOR ANALYZING THE ENERGY SPECTRA OF PHOTON RADIATION

Monitoring the spectral composition of photon radiation from generating sources and emitting objects is the most informative way to analyze the radiation fields created by them. However, it is impossible to study the radiation characteristics of radiation fields of ultra short duration and high intensity using direct measurement methods. This work considers a method for reconstructing the spectral distributions of photon radiation from the profile of the secondary radiation fields recorded by a position-sensitive detector. To implement a new method of measurement in the primary beam of radiation is an extended scattering body of homogeneous material. Outside the field of the primary beam, a position-sensitive detector is placed along the generatrix of the scattering body, which records the photons of the secondary radiation and the coordinates of their emission. The spectral composition of the primary radiation beam is restored from the shape of the spatial distribution obtained. To find a quasi-solution describing the energy spectrum of the primary radiation beam, it is proposed to use the maximum likelihood expectation maximization method. The possibility of switching to measurements in secondary radiation fields having a lower intensity is confirmed by the experimental results. To form secondary radiation fields, we used a composite phantom containing three scattering bodies in the form of rectangular parallelepipeds made of graphite, aluminum, and titanium. The secondary radiation fields were recorded by a radiographic sensor. Using an X-ray source operating in a pulsed mode, images were obtained and profiles of the secondary radiation fields were formed. It is experimentally shown that the secondary radiation fields have a gradient structure and can be used to analyze the energy spectra of the radiation beams generating them. The method for reconstructing spectral distributions proposed in this work allows one to measure the energy spectra of photons using position-sensitive detectors and can be used in solving problems of diagnostics of pulsed high-intensity radiation beams.

Визначення параметрів окремо розташованих породних опор з компенсаційними порожнинами

Purpose: To determine the parameters of detached rock packs with compensating voids. Methodology: Analysis of technologies for the protection of development workings, based on the management of the stress-strain state of rocks around the workings, physical modeling using equivalent materials, numerical modeling by the finite element method, and methods of structural mechanics. Results: In the conditions of soft soil rocks the expediency of application of protection means based on management of a stress-strain condition in a surrounding massif and redirection of extrusion forces from a working has been substantiated. On the basis of analysis of the existing protection measures of the workings behind faces the prospects of use of protection technologies by means of construction of detached rock packs with limiting surfaces between which there are compensatory voids left, have been proved. To determine the parameters of such packs and voids between them in the conditions of soft soil rocks, a set of laboratory and numerical studies has been performed. According to their results, it has been established that to ensure the redirection of extrusion forces from the working it is necessary to build rock packs with limiting surfaces in the form of rectangular parallelepipeds with orientation of their greater side perpendicular to the longitudinal axis of production and trapezoidal prisms with their narrower orientation towards the working. Recommendations on the parameters of these structures and compensatory voids between them in the conditions of soft soil rocks have been formulated. Scientific novelty: On the basis of numerical modeling the regularities of stress distribution in rocks under detached rock packs of different shapes have been investigated, which allowed substantiating the parameters of the last and compensatory voids between them to ensure the stability of workings in the soft soil rocks. Practical significance: The expediency of application of technologies of protection of preparatory workings behind faces in the conditions of soft soil rocks by means of rock packs with limiting surfaces between which there are compensatory voids has been proved, and their parameters have been defined.

The System of Modern University Missions Realization in the Measurement of Three Key Components

Analysis of the choice of potential entrants’ choice of Kyiv National Economic University named after Vadym Hetman (KNEU). We represent key influential factors of choosing KNEU named after Vadym Hetman by entrants: Motivational and Prestigious, Demographic, Geographical, Psychographic, Social. The article presents the key factors, hypotheses confirmation and segment identification of the applicants who choose university. We build up the system of potential factors quantity of choosing KNEU by entrants on the basis of the above-mentioned hypotheses. This structured hierarchical scheme has 5 levels. Construction of the potential factors’ magnitude of choosing KNEU by entrants.For building up the abovementioned potential factors quantity system of choosing KNEU by entrants it was realized the survey by questionnaire for each of the presented factors within KNEU annual survey of first-year students entitled “Motivational factors of university entrants before entering the university”. The results of the survey, which was conducted in 2007, 2011 and 2017 for each item in all levels of the hierarchical scheme, were processed. In the three-dimensional Cartesian coordinate system, it was selected the axes are, which correspond respectively to the values of specific, relevant and potential factors for choosing KNEU by entrants. We presented in geometric interpretation the potential of choosing KNEU by respondents in the form of rectangular parallelepipeds. The modern knowledge economy requires a modern system of proficiency competencies. That’s why the most successful universities focus on instruments of higher education quality, realize educational programs' modernization on the base of student-centred education philosophy and build up a new system of the social network in the direction of social responsibility projects and business partnership with the academic community

Математична модель функціонування бункера шнекового транспортера-подрібнювача

Шнекові транспортери широко застосовуються в аграрній сфері виробництва для переміщення, змішування, дозування продуктів тощо. Удосконалення існуючих конструкцій шнекових транспортерів і обгрунтування їх раціональних параметрів і режимів роботи дозволяє розширити функціональні можливості технологічних операцій і підвищити продуктивність роботи механізмів загалом. На основі аналізу існуючих гвинтових механізмів запропоновано шнековий транспортер-подрібнювач коренеплодів з комбінованим робочим органом. Він виконаний у вигляді шнекового конвеєра, який встановлено в напрямній трубі, яка має завантажувальний бункер. На внутрішній стороні витків шнека закріплено ножі-подрібнювачі. Наведено результати аналітичних досліджень технологічного процесу переміщення коренеплодів в об’ємному просторі бункера. Розроблено математичну модель функціонального процесу роботи бункера залежно від вхідних і вихідних потоків коренеплодів. Результати досліджень є подальшим кроком з розробки методики обгрунтування параметрів шнекових механізмів. Ключові слова: коренеплоди, завантажувальна горловина, запас коренеплодів, вивантажувальна горловина, споживання запасу, маса коренеплодів

Up-conversion in an Er-containing nanocomposite and microlasers based on it

The results of an investigation of three-dimensional polymer microcavities doped with inorganic luminescent particles are presented. Microlasers in the form of rectangular parallelepipeds were fabricated based on the SU8 2025 photoresist by means of compact UV lithography. Luminescent particles containing erbium oxide were obtained by low-temperature synthesis of the corresponding chlorides in a nonaqueous medium. The obtained spectra confirm the presence of a narrowband laser radiation exhibiting a Stokes shift.

The inverse stationary heat conduction problem for a cuboid

The heat conductivity coefficient is important characteristic which is used in various spheres. The original methodic for conductivity coefficient determination was proposed for samples in form of rectangular parallelepiped. The results of numerical solution of nonlinear heat conduction problem in heat conduction coefficient value range 0.04-5 W/(m K) with different sample relative size were presented.

Four-probe methods for measuring the resistivity of samples in the form of rectangular parallelepipeds

The problem of measuring the resistivity of isotropic samples of finite dimensions in the form of rectangular parallelepipeds using the four-probe technique was considered. Two variants of contact arrangements were studied: (1) four collinear probes are positioned on one side of a sample symmetrically with respect to the other sides, and (2) two probes on one side of a sample and two on the opposite side are placed precisely in opposite positions and symmetrically with respect to the other sides of the sample (the Schnabel method). Solutions of the problem of the electric field potential distribution in a sample for different positions of the current contacts were found. The solutions were obtained in the form of double series and methods of their summation are presented. The obtained results are extended to the case of measuring the resistivity of anisotropic samples when the resistivity tensor has two independent components. The results of using the developed technique for measuring the resistivity of such a highly anisotropic material as highly oriented pyrolitic graphite using the Schnabel method are presented.

Light scattering in langasite (La3Ga5SiO14) crystals

A way to plot the light-scattering indicatrix for crystals in the form of rectangular parallelepipeds of different crystallophysical orientations has been proposed. The experimental setup, which makes it possible to record the intensity of light scattered in these samples in the plane oriented perpendicular to the input face, has been designed. The light-scattering indicatrices for langasite crystals have been plotted in the XY and YZ planes. The reflectance and transmittance of the samples under the normal incidence of light have been estimated. The maximum angle at which the light scattered within the crystal bulk emerges from it without total internal reflection has been found. The angle by which langasite crystal should be rotated to record the scattered-light intensity by a photodetector has been experimentally determined.

Twinning and de-twinning in beryllium during strain path changes

Rolled beryllium samples in the form of rectangular parallelepipeds were deformed at strain rates of 0.001/s and 5/s through multiple strain paths. Samples were initially deformed in-plane nominally −0.22 in compression at a rate of 5/s to populate the microstructure with twins and then reoriented and deformed a second time either in the through-thickness direction or the other in-plane direction. The microstructure (texture and internal strain) were monitored through in-situ and ex-situ diffraction measurements using neutron diffraction on the HIPPO diffractometer at LANSCE, and high energy X-ray diffraction on the 1-ID-C beamline at the APS. Twin reversal is observed when the sample is reoriented and deformed a second time in the TT direction. The twin reversal is strain rate independent in contrast to the strong strain rate dependence observed during twinning in beryllium. Deformation twinning is also observed during secondary compression in the second in-plane direction, but from the current data set we cannot determine with certainty if these twins originate from the parent orientation or the twins formed during primary in-plane compression. As a whole, this data set creates a very demanding test for the development of polycrystalline plasticity models of deformation in hexagonal metals.

Efecto de la Temperatura y Tiempo de Fritura sobre las Características Sensoriales del Ñame (Dioscorea alata)

The influence of frying parameters (time and temperature) on the sensory characteristics of yam (Dioscorea alata) was studied. Name was washed and cut in the form of rectangular parallelepiped and soybean oil was used as heating media. The frying process was evaluated at three temperatures (140, 160 and 180 ° C) and five heating times (1, 3, 5, 7 and 9 min). The sensory analysis was performed by 5 judges and color, hardness and fat were evaluated. Hexagonal factorial design and surface response methodology were used. The best combination resulted to be 5 minutes and 160 0 C for which the most appropriate characteristics of color, hardness and fat were

Numerical investigation of air free convection in a room with heat source

Mathematical modelling of three-dimensional steady free convective incompressible viscous gas flows in the rooms with a heat source is carried out within the framework of the Navier — Stokes equations with the effective viscosity determined on the basis of the κ-ɛ turbulence model. The investigation is carried out for the case of model rooms and heat sources having the form of rectangular parallelepipeds with square bases. The influence of the heat source power and the sizes of the room base on local and averaged values of the air velocity and temperature in the rooms is analysed. The flow pattern in the room is shown to have a torus-like shape. It is found that the variation of sizes of the room base rather than the capacity variation of the heat source is of determining importance for the gas motion character in a closed volume.

Molecular Dynamic Simulation of High Speed Deformation Effect on Microstructure Change in Thermal Heated Metals

In the present paper computer simulation of high-speed deformation (shock wave propagation) by molecular dynamic method is performed in thin copper sample, having the form of rectangular parallelepiped (10 a ‐ 10 a ‐ 20 a , where a is the lattice constant) with 8000 atoms. On the surfaces Z 0 =0 and Z max =20 a the mirror boundary conditions with rigid walls and the periodic boundary conditions along X and Y directions corresponding to short sides of deformed crystal are used, which allows to investigate the reflection of shock wave from the surfaces in Z direction. The changes of microstructure have been investigated up to 12 ps. The numerical calculations of microstructure changes have been performed here taking into account the effect of thermal heating of crystal lattice before shock wave front. The numerical results show that comparing with the propagation of shock waves under room temperature in thermal heated structure additional displaced atoms (vacancies and interstitials) are produced. The obtained results show that the production of point defects during high-speed deformation is determined by the thermal softening of microstructure and generation rate of point defects very strong increases with an increasing of high speed deformation rate. The peculiarities of microstructure changes in deformed copper are analyzed here at the different initial temperatures and various high-speed deformations (average ion velocities behind shock wave).

An evaluation of critical strain for internal crack formation in continuously cast slabs.

An in-situ melt-bending test method has been developed, which permits the simple evaluation of the critical strain for the internal crack initiation in continuously cast slabs. In this testing method, the center of the top surface of a specimen in the form of rectangular parallelepiped is melted by high-frequency induction heating and the heating current is then lowered to form a solidified layer about 20mm in thickness. The specimen under this condition is deformed by bending. The amount of strain applied to the solid-liquid interface is changed by changing the amount of bending. This test is conducted in an argon gas atmosphere. After the test, the internal cracking in the specimen is investigated and the critical strain for the internal crack initiation is determined by comparing the cracking condition with the amount of the strain applied. The critical strain was measured in six carbon steels by the above-mentioned method. It has been found that the difference in the critical strain among the steel grades is correlated to the difference between the calculated liquidus temperature and the calculated solidus temperature and that the greater the difference, the smaller the critical strain will be. It is also revealed that the critical strain values obtained by the other researchers show the same tendency.