ADSORPTION OF OBSOLETE SLUDGE, PEAT, BUCKWHEAT HUSKS AND COMPOSITIONS FROM THEM

The problem of accumulation of obsolete silt deposits at aeration stations is relevant for the whole territory of Ukraine. This can lead to environmental hazards. Therefore, the task of processing silt deposits with the creation of granules based on them with the addition of peat and buckwheat husks. Van Bamelen's tensometric (static) method was used to determine the equilibrium humidity of the experimental samples depending on the relative humidity . As a result of researches kinetic curves of adsorption over obsolete silt deposits, peat, buckwheat husk and the three-component composition created on their basis are received. Kinetic adsorption curves indicate a slow process. The adsorption curves of the three-component composition have the character of curves of obsolete sludge, which have a non-uniform character. The obtained equilibrium humidity does not exceed the standard humidity for fuel pellets. The adsorption isotrams of the three-component composition and its components are determined, from which the equations of experimental and linearized isotrams are obtained. The analysis of experimental isotherms allows to relate them relatively to the isotherms of adsorption IV, which are observed in inorganic oxides and in other porous bodies. For the first time, the adsorption properties of three-component compositions based on peat, sludge and buckwheat husk were studied. The obtained equilibrium humidity of the compositions does not exceed the standard humidity for fuel pellets (is 20%) and is 6 - 7%. Therefore, they can be used for combustion in biomass boilers. The resulting ash can be used for the production of bricks, cement and other building materials. During storage of composite granules in order to prevent loss of their technological properties, it is recommended to maintain humidity at the level of 60 - 70%.

Characterization of milkweed-seed gust response

Inspired by the reproductive success of plant species that employ bristled seeds for wind-borne dispersal, this study investigates the gust response of milkweed seeds, selected for their near-spherical shape. Gust-response experiments are performed to determine whether these porous bodies offer unique aerodynamic properties. Optical motion-tracking and particle image velocimetry (PIV) are used to characterize the dynamics of milkweed seed samples as they freely respond to a flow perturbation produced in an unsteady, gust wind tunnel. The observed seed acceleration ratio was found to agree with that of similar-sized soap bubbles as well as theoretical predictions, suggesting that aerodynamic performance does not degrade with porosity. Observations of high-velocity and high-vorticity fluid deflected around the body, obtained via time-resolved PIV measurements, suggest that there is minimal flow through the porous sphere. Therefore, despite the seed’s porosity, the formation of a region of fluid shear, accompanied by vorticity roll-up around the body and in its wake, is not suppressed, as would normally be expected for porous bodies. Thus, the seeds achieve instantaneous drag exceeding that of a solid sphere (e.g. bubble) over the first eight convective times of the perturbation. Therefore, while the steady-state drag produced by porous bodies is typically lower than that of a solid counterpart, an enhanced drag response is generated during the initial flow acceleration period.

Eyes in cheese: reasons for formation and methods of assessment

The results of scientific research of the process of eyes formation in cheeses depending on the molding method and modes of pressing the cheese mass; the type of gassing microorganisms that make up the starter culture; rheological properties of curd; the presence in the cheese mass of “germs” — the centers of the formation of eyes — are considered. It is noted that the most studied in terms of the formation of the pattern are large cheeses of the Emmental or Swiss type with eyes up to 3 cm in diameter, which can be easily estimated by calculating their quantity and volume. For this, there are methods for visualizing eyes in the volume of cheese: X-ray, computed and magnetic resonance imaging, ultrasound and acoustic sounding. The least studied is the process of pattern formation in cheeses like Tilsiter and Russian, molded in bulk, with a large number of irregular, angular eyes. In connection with the observed tendency to the loss of the distinctive features of this type of cheese (rare, insufficiently pronounced eyes), great importance is attached to objective methods for assessing the pattern in these cheeses as one of the most important indicators of the product quality. Since computed tomography, X-ray and magnetic resonance imaging are methods that require expensive equipment, the need for a simpler procedure, suitable for production laboratories of cheesemaking enterprises, is justified for use in routine examinations. Based on the assumption that cheeses with a frequent pattern of angular, irregular shape can be considered as porous bodies, an assumption was made about the advisability of developing a method for measuring the porosity coefficient, which could supplement the organoleptic assessment of the pattern with an objective indicator that would allow the rejection of cheeses on this basis.

Existence and uniqueness of a finite energy solution for the mixed value problem of porous thermoelastic bodies

We consider the mixed problem with boundary and initial data in thermoelasticity of porous bodies with dipolar structure. By generalizing some known results developed by Dafermos in a more simple case of the classical theory of elasticity, we prove new theorems in which we address the issues regarding the uniqueness and existence of a solution with finite energy of the respective problem after we define this type of solution.

Modeling a Free Burnishing of a Powder Hollow Cylinder

The paper presents the results of the computer modelling of the stressed state and relative density when burnishing a porous hollow cylinder, made from copper sintered powder material. The mathematical model, based on the theory of porous bodies’ plasticity, is used for the analysis. The paper researches the impact of the initial porosity of the material on the effective stresses distribution, relative density and force change when free burnishing of hollow cylinders. It is ascertained that with the decrease of the initial porosity of the sintered material there is the increase of the burnishing force, stresses rate and relative density on the inner sur-face of a hollow cylinder. For porous materials at a certain stage of burnishing, the deformation zone is transformed into the compaction zone with a high relative density which de-creases while moving away from the inner surface of hollow cylinders. The maximum value of the relative density is implemented directly on the inner surface of hollow cylinders; along with this the density value is evenly distributed on the inner wall.