DETERMINATION OF THE AVERAGE WALL TEMPERATURE OF THE PLATE IN A RECUPERATIVE HEAT EXCHANGER WITH A CORRUGATED MESH INSERT

This article discusses the issue of determining the value the average wall temperature of the plate of a recuperative heat exchanger type “air-to-air” with a corrugated mesh insert based on the results processing the data of a physical experiment to determine the thermohydraulic characteristics such heat exchange surfaces. It has been established that the temperature fi eld of heat exchange surfaces of this type is nonuniform, depends on the conditions of heat exchange and hydraulic regimes of air fl ow. Therefore, the adoption of the arithmetic means value of the measured surface temperatures as the calculated average temperature of the heat exchanger wall entails signifi cant errors in the subsequent processing of experimental data and fi nal the values of the heat transfer coeffi cients, the values the Nusselt criterion and the criterion equations of heat transfer. It is proposed to determine the average value the wall temperature of the heat exchanger based on the results of measurements the wall’s temperatures, the estimate of the coordinates the center of distribution the results of measurements the wall temperatures, the equations of heat balance and heat transfer.

Transfer and Friction Characteristics of Sports Socks Fabrics Made of Synthetic Fibres in Different Structures

Sports socks fabrics produced from polyester, polypropylene, their modified forms Thermocool®, Polycolon®, in three different structures (single jersey, piquet, terry) were investigated for their skin-fabric friction, permeability (air and water vapour), liquid absorption and transfer (absorbency, immersion, absorption capacity, wetback and drying) properties. According to the results, the effect of structure is dominant for frictional characteristics but focusing on the material, polypropylene created a bulkier and lighter structure with lower friction coeffi¬cients, an advantage for sports socks. The effect of structure is greater than the material also for some thermal comfort parameters, e.g. air permeability and absorbency. Focusing on materials, besides their better liquid transfer characteristics, modified forms of both fibres had worse performances for air permeability and absor¬bency compared to their standard forms. Absorption capacity, wetback and drying performances were related to fabric density besides the polyester’s higher regain capacity. While Polycolon® had superiority for wetback performance against standard polypropylene, this was not the case for Thermocool®; however, both modified materials showed apparent superiority for drying periods. Piquet structures were advantageous for absorption capacity and wetback performances for polypropylene. For sports socks parts, specific needs can be met by changing the fabric structure. Considering the materials, polypropylene and Polycolon® can be recommended for both thermal and tactile aspects.

Thermal radiation of extended particles with subwavelength transverse dimensions

The paper proposes a new method for calculating the integral and spectral radiation coeffi-cients of extended subwavelength particles (ESPs), which include micro and nanocylinders and parallelepipeds. Comparison of the results of calculations by the proposed method with the calculated and experimental data found in the literature is carried out. It is shown that with decrease in only the transverse dimensions of the ESP (from values much larger than λmax to values much smaller than max) from the radiation spectrum, which was originally de-scribed by Planck's law and contained modes with both polarization directed along the axis and with polarization directed perpendicular to the axis , modes with wavelengths exceeding λcutoff (λcutoff is the cutoff wavelength) and having polarization perpendicular to the longi-tudinal axis of the ESP will be gradually eliminated, while modes with wavelengths polarized along the ESP axis will always be present in the radiation spectrum of the ESP. When the transverse dimensions of the ESP become much less than λmax, then all modes with polariza-tion perpendicular to the axis will disappear from the emission spectrum of this ESP, and on-ly modes with longitudinal polarization will remain. This is a fundamental difference from the SPs considered earlier in [16, 17], where methods for calculating SPs as disks, spheres, cubes were proposed. All the proposed calculation methods use the formalism of the decom-position of radiation fluxes into spectral-spatial modes.

Performance of ANN in Predicting Internal Bonding of Cement Particleboard Manufactured from Giant Reed and Bagasse

The present article investigates the microstructure of the cement matrices and the products of cement hydration by means of scanning electron microscopy, Fourier transform infrared spectroscopy and X-Ray diffraction. Then, the internal bonding strength (IB) is measured for the mixtures containing various amounts of nanosilica (NS), reed and bagasse particles. Finally, an Artificial Neural Network (ANN) is trained to reproduce these experimental results. The results show that the hardened cement paste including NS features the highest level of C-S-H. However, it has a lower level of C-S-H polymerization if reed or bagasse particles are applied. A relatively new dense microstructural degree is considered in the cement pastes containing NS, and a lower agglomeration is observed in the samples including reed or bagasse particles with NS. According to the microstructural analysis, the addition of NS to the samples containing reed or bagasse particles increases the unhydrated amount of C2S and C3S in the cement paste due to the decrease in the water needed for fully hydrated cement grains through portlandite (Ca(OH)2), C-S-H and ettringite increase. Besides, it is shown that the ANN prediction model is a useful, reliable and quite effective tool for modeling IB of cement-bonded particleboard (CBPB). It is indicated that the mean absolute percentage errors (MAPE) are 1.98 % and 1.45 % in the prediction of the IB values for the training and testing datasets, respectively. The determination coeffi cients (R2) of the training and testing data sets are 0.972 and 0.997 in the prediction of the bonding strength by ANN, respectively.

Discriminant Analysis of the Coordinated Work Indicators of the Heart and Blood Vessels in Health and Disease

A discriminant method was proposed for modeling and quantifying the consistency of regulatory mechanisms in the cardiovascular system (CVS) of apparently healthy volunteers and those suffering from circulatory disorders associated with cervical spine osteochondrosis (OCS) and somatoform autonomic dysfunction (SAD). The congruence of the parameters of ECG intervalometry (DCI) and pulse wave duration (PWD) according to the volunteers’ photoplethysmograms (PPG) was established by calculating the disparity measure and deviations from the mean values using the coeffi cients of displacement, slope of the approximating straight line, as well as by comparing the reliability and correlation of the trend model with the initial data. We discovered gross violations of congruence in the work of efferent and afferent regulatory CVS mechanisms, mismatch and decrease in comparison with the norm of DCI and PWD, a signifi cant decrease in their approximation in the SAD volunteers. In volunteers with OCS, deviations in DCI and PWD from their mean values are much lower than in those with SAD, being inferior compared to healthy volunteers. Similar to SAD, these patients are inferior to healthy volunteers in terms of the disparity measure.

Thermodynamic Mixing Properties of Li–Mg Binary Alloy

Theoretical calculations of thermodynamic mixing properties viz., Gibbs’ free energy of mixing GM , heat of mixing HM , entropy of mixing SM , as well as the activity and its coeffi cients, are performed using the Bhatia–Hargrove complex formation model. The mixture is assumed to be pseudobinary. The components exhibit a negative deviation from Raoult’s behavior, and the system is weakly interacting in nature.

CALCULATION OF THE DEFLECTION OF A PINCHED ROUND PLATE

A method for calculating the deflection of a round flat steel plate pinched along the edge, bearing an axisymmetric load, is considered. For practical calculations, dimensionless coeffi cients of deflection in the center and in the area of fixing a round flat plate pinched along the edge are applied, the stress coefficient and the accompanying function, which depends on the deflection of the plate and the pressure force on it, are taken into account

Assortment policy of retailers in the «Sugar» product subcategory

The article considers the results of the study of the commercial assortment of the subcategory «Sugar», which is included in the category «Groceries» in the stores of three retail chains in Moscow. It was found that in all stores there is a detailed assortment, represented by 6 to 10 types, 25 trademarks and their 70 modifi cations. The assortment of sugar under study is characterized by high coeffi cients of completeness, depth and stability, as well as an average degree of novelty and moderate rationality. The analysis of the assortment indicators revealed that in the assortment policy of all surveyed stores, the main directions are assortment stabilization and, as an additional direction, renewal. Along with this, it is recommended to apply the directions for improving the assortment when forming the assortment of sugar.

The use of organic sources of chromium in the feeding of laying hens

The purpose of the research was to study the eff ect of the mineral complex “Availa Chrome 1000”, which used in the feeding of laying hens of the highly productive cross Highsex Brown under the conditions of the Research Center for the Safety and Eff ectiveness of Feed and Additives of the Volgograd State Agrarian University. For the experiment two groups of laying hens (control and experimental) have been formed with 70 heads in each. The diff erence between the groups was that the laying hens of the control group received a complete farm diet, and into the diet of the laying hens of the experimental group the feed additive “Availa Chrome 100” in the amount of 300 g/t of compound feed was introduced. It has been found during the study of the coeffi cients of digestibility of nutrients of the diet in the experimental poultry that the best digestibility diff ered laying hens of the experimental group where the additive “Avila Chrome 1000” in the amount of 300 g/t of compound feed has been put into the basic diet. It has been found as a result that the tested mineral additive increases the digestibility of dry matter by 3,09 %, organic matter by 2,59 %, crude protein by 1,35 %, crude fat by 2,16 %, crude fi ber by 0,63 %. The studied feed additive had a stimulating eff ect on the formation of red blood cells the level of which increased in the blood of poultry of the experimental group by 2,87 %. It has been found that in laying hens of the experimental group the level of hemoglobin was higher by 6,25 %. The use of the mineral complex allowed to improve the egg productivity of poultry by 3,3 % and increase the egg mass by 2,66 %. The inter-group economic eff ect for the period of experiment reached 573,43 rubles, so we believe that the use of organic chromium additives is economically feasible.

THE ASESSMENT OF THE SPATIAL AND TEMPORAL DYNAMICS OF AIR TEMPERATURE OF AIR TEMPERATURE IN THE URALS AND WESTERN SIBERIA IN THE SECOND HALF OF THE 20TH-EARLY 21TH CENTURIES WITH THE USE OF REANALYSIS

Проведен анализ пространственно-временной динамики приземной среднегодовой температуры воздуха на территории Урала и Западной Сибири по данным 92 метеостанций и реанализов ERA-20С и CERA-20С за период с 1961 по 2010 гг. Установлено, что значения коэффициента корреляции за исследуемый временной промежуток между данными инструментальных метеонаблюдений и данными реанализов ERA-20С и CERA-20С лежат в интервалах 0,81–0,97 и 0,86–0,98 соответственно. Данные по температуре воздуха реанализа CERA-20С лучше согласуются со значениями температуры, полученными на метеостанциях, по сравнению с данными реанализа ERA-20C. В южной части района исследований коэффициенты корреляции ниже, чем в регионах, расположенных севернее. В целом данные реанализа CERA-20C целесообразно использовать при проведении исследований, связанных с климатической изменчивостью и региональным изменением климата Урала и Западной Сибири на участках, находящихся на удалении от метеостанций. The analysis of the spatio-temporal dynamics of the mean annual air temperature in the Urals and Western Siberia on the basis of data of 92 weather stations and reanalysis ERA-20C and CERA-20C for the period from 1961 to 2010 was implemented. It was found that the values of the correlation coeffi cients for the studied time interval between the meteorological data and the data of reanalysis ERA-20C and CERA-20C lie in the intervals of 0,81–0,97 and 0,86–0,98, respectively. The reanalysis of CERA20C is in better agreement with the data obtained at weather stations compared to the reanalysis of ERA20C. In the southern part of the research area, the correlation coeffi cients are lower than in the regions located to the North. In general, data of the CERA-20C. Reanalysis should be used for studies related to climate variability and regional climate change in the Urals and Western Siberia at sites located at a signifi cant distance from weather stations.