Formation Of Optimal Structure Research Articles

Specific Mass Activity and Surface Activity of Platinum Electrically Connected with CNTs in the Oxygen Reduction Reaction.

This paper presents a study of the platinum activity in the ORR in a hydrogen polymer electrolyte membrane fuel cell with electrodes containing multi-walled CNTs in a wide range of compositions and conditions. The data of the comparative analysis of the platinum activity on a fraction of Nafion in the electrode, the composition of the oxidizing agent (oxygen, air), pressure, and temperature are provided. The reasons for the dependence of the platinum surface activity on the component composition of the electrode are considered. Specific mass activity and surface activity of platinum in the ORR in MEA with the electrodes with CNTs depend on the ionomer/platinum ratio. Both dependences have a maximum at the level of the 25% Nafion fraction. The maximum appears as a result of an optimal structure formation, which ensures the fullest use of the platinum surface and minimal concentration overvoltages. Specific mass activity and surface activity of platinum for the sample with 34% CNTs at T = 60 °C and excessive pressure of p = 2 atm amount to 0.46 A/mg and 0.72 mA/cm2, respectively.

Formation of optimal structure and properties of automotive pearlite steel during cold processing

Special requirements for structural and mechanical properties are applied to core fasteners manufactured on cold-forming machines made of automotive pearlitic steel. Mill products come as an original unit to manufacture various fasteners of hot-rolled steel, which can not be used for forming hardware due to the poor quality of the structure and surface layer. Therefore, the calibration rod undergoes intermediate heat treatment before drawing. In addition, products of strength grade 8.8 and higher, obtained from alloy steels on cold-forming machines, are quenched during tempering, which often leads to decarburization, cracking and bending of finished products, which increases the labor intensity, energy intensity and, consequently, the final cost. The article suggests a method for producing rolled products from automotive pearlitic steel 35Cr and 38CrA, including an isothermal process that excludes full annealing, quenching when tempering rod-shaped products and preventing decarburization, risks and curvature. The design, caused by passing through the drawing die, strengthening the surface by reducing and rolling the thread, provides mechanical properties of bolts and studs M8 strength grade 8.8 and 9.8.

STRATEGIC DIRECTIONS OF DEVELOPMENT OF THE AGRICULTURAL MARKET OF UKRAINE IN NOWADAYS INTERNATIONAL TRADE CONDITIONS

Current state of agricultural market of Ukraine is analyzed at these paper. Dependence of this market on state regulation of external economic activity of Ukraine is determined. It is investigated, under what conditions of state regulation, market of agrarian products of Ukraine can develop. Also, it is singled out factors of state regulation of external trade of Ukraine, which adversely affects on development of agrarian market. Strategic directions of development of Ukraine agricultural market is examined in current paper by author. With what problems participants of this market are faced during process of output of their own product to foreign markets, is considered. Also, how the state can regulate the problematic issues in current field, is mentioned in the scientific paper. Directions for improvement of state regulation of external economic activity in the market of agrarian products of Ukraine is proposed by author in this article. Ways of improving export and import policy of Ukraine for agricultural products in modern conditions are presented. In the article directions of formation of optimal structure of foreign trade in the agroindustrial complex of Ukraine are considered. The means of improving the export-import policy for agricultural products are presented.

Influence of thermal treatment on photoluminescent properties of PP/PbS/CdS nanocomposites

This paper deals with an investigation on the photoluminescence (PL) properties of PP+PbS/CdS nanocomposites at different temperatures ([Formula: see text], [Formula: see text] and [Formula: see text]) under vacuum. The optical bandgap was calculated on the basis of the spectra of UV absorption and it was shown that after thermal treatment the nanocomposites optical bandgap changed. The change has been attributed to the modification of the upper molecular structure of the polymer matrix due to the thermal process. The luminescence spectra of nanocomposites before and after thermal treatment at different temperatures ([Formula: see text], [Formula: see text] and [Formula: see text]) under vacuum were also measured and discussed. A very high luminescence intensity was observed after thermal treatment at [Formula: see text] temperature. This was attributed to the luminescent centers’ increase and the optimal structure formation.

Influence of Fe component from milling yield on characteristics of perlite based geopolymers

The mineral and chemical composition of aluminosilicates used in geopolymer systems is critical for optimal structure formation and the overall performance of the geopolymer products. The composition of alumosilicates can be altered during the technological processing, especially, at the stage of fine milling. This study investigated the effect of aluminosilicate contamination with Fe from milling yield, the characteristics of the aluminosilicates with a metal lining, structure formation, and hardened properties of geopolymers based on different natural and technogenic persilicic aluminosilicates. The formation of Fe-phases due to milling yield was detected by the XRF analysis and the XRD investigation revealed the formation of nanosized ferrous hydroxide or bernalite Fe(OH)3(H2O)0.25. The volume of an elemental cell of the nanosized bernalite per Fe atom is 4.5 times larger than that of the metallic iron. This results in the disintegration of the matrix, which was observed by SEM and then confirmed by reduced strength performance of geopolymer composites. Based on this study, the negative effect of Fe-phases from milling and nanosized ferrous hydroxide on structural characteristics and service performance of geopolymer composites based on natural and technogenic raw materials was concluded.

Formation of optimal structure of cellular concrete

The paper presents the results of experimental studies on the effect of silica-containing components on the structure and properties of cellular concrete. It is shown that the creation of the optimal pore structure of concrete and the structure of the interporous frame, the intensification of hydration and crystallization processes in hydrothermal treatment can improve the physical and mechanical characteristics of cellular concrete. At the level of modern knowledge about the structure and properties of cellular concrete, the potential for increasing its strength characteristics has been studied. Through the effective use of the energy potentials of the multicomponent binder, including Portland cement, calcium lime and activated silica components, the nanopore structure of the matrix stone is formed.

EXPLORING OF THE PROBLEMS OF THE CHOICE AND FORMATION OF THE OPTIMAL TRAJECTORY OF ECONOMIC DEVELOPMENT OF STATES IN THE CONDITIONS OF FINANCIAL AND TRADE OPENNESS

The article analyzes scientific achievements, research results of the exploring the optimal trajectory of economic development in the conditions of significant financial and trade openness that had been done at the Department of International Economic Analysis and Finance, Ivan Franko National University. The economic strategies related to the export orientation of the countries, formation of optimal structure of production and foreign trade, investment policy and capital accumulation, economic efficiency, energy efficiency and implementation of effective macroeconomic policy in the monetary, currency and fiscal areas, and formation of a high-quality institutional environment are considered/ Key words: international economic analysis; classical paradigms; modern paradigms; international trade; financial globalization; economic development; economic growth; countries of Central and Eastern Europe.

THE STUDY OF DEFORMATION CHARACTERISTICS OF SOIL MATERIALS WITH THE USAGE OF WASTES

Purpose. More often the qualified building materials are replaced by the industrial wastes for environmental improvement. This refers to both metallurgical slags and biological solids of water treatment plants. In order to understand the possibilities of their usage it needs studying deformation properties of composite soil materials with industrial wastes addition. Methodology. The soil of real buildings and structures foundation is in the complicated conditions and the stress-strained state. While studying this state the total deformation modulus Е 0 is used as the deformation characteristic. This one is determined according to the results of sample soil testing in the compression instrument (odometer). This instrument prevents the possibility of lateral expansion of sample soil under the vertical load. Findings. As a result of the testing the compression curves are plotted as the dependence of the porosity coefficient on pressure. These data allow determining the compressibility coefficient and the strain modulus. It is found that a biological solids addition increases the compressibility coefficient four times compared to the clay. The two types of samples are compared. The first type contains 50% of biological solids. The second type contains 50% of biological solids and 50% of slag. The comparison shows that the second type is compressed twelve times less. An addition into the clay of biological solids increases the strain modulus from 7 . 8 to 20 . 3 MPa. The slag increases the strain modulus to 52 . 7 MPa. Originality. While making the composition based clay materials the functional groups of biological solids interact with hydroxyl groups which are placed on the surface of clay particles and form a spatial structure. Besides an addition of biological solids contributes to peptization, soil aggregates destroy themselves, and form contacts between separate particles. It causes the decrease of soil compressibility due to the total porosity decrease. An addition of slag results in formation of optimal structure where particles of less sizes are placed in layers between bigger particles. Practical value. An application of biological solids and slag provides the increased load-carrying capacity of soil, extending of raw material sources while improving the environmental situation in the cities. Also it provides the recycling of reinforced soil.

Efficiency of technology of grain harvesting by means of combine stripping

Grain harvesting on most farms in Russia lasts up to 25-30 days, because of the deficit of combines; that results to 30% harvest losses. With introduction of technology of grain harvesting by means of combine stripping, the performance of harvesting units is increased by 1.5-2 times, which allows to cut down the harvesting duration and to reduce the fuel consumption by 35-45%. But grain losses after passing of harvesting units are increased and the haulm stand appears on field, which stimulates moisture accumulation. Additional operation for haulm stand treatment is required, such as disk harrowing or chopping and spreading on field. According to the state standard no. 53056-2008, the efficiency of mechanized technologies and machine complexes is defined during formation of optimal structure of machine and tractor fleet for a typical farm, on the criteria of minimum of total costs. The paper deals with efficiency evaluation of technology of grain harvesting by means of combine stripping and of a traditional technology through comparing the total costs of work performance by means of optimal machine and tractor fleets of a typical farm. For that, earlier designed mathematical model and algorithm-program complex are improved. Investigations are performed on the example of a typical farm of the south of Rostov region with 5000 hectares of cultivated area. According to their results, it is found that for such farm the total costs are 31 499 thousands rubles in case of grain harvesting by means of stripping with duration of 10 days, and 35 325 thousands rubles in case of traditional technology with duration of 13 days.

Structuring in Systems on the Basis of Calcium Sulfate Dihydrate

A model of the process of gypsum optimal structure formation has been designed with the application of computer simulation methods. An optimal raw mix speciation and gypsum specimen strength top values corresponding to the model were experimentally obtained and recorded.

Application of Mathematical and Computer Modeling Methods to Manufacture High-Strength Unfired Gypsum Materials

A mathematical model of the process of gypsum optimal structure formation has been designed with the application of computer simulation methods. An optimal raw mix speciation and gypsum specimen strength top values corresponding to the model were experimentally obtained and recorded.

Alloying and heat treatment of high-strength structural titanium β alloys

The influence of alloying elements on the mechanical properties of titanium β alloys is investigated. Optimal structure formation is considered as a function of heat-treatment conditions. The basic principles are formulated for complex alloying, microalloying, and the selection of the optimal β alloy.

Optimal structure formation using a chaotic self-organisational algorithm

Optimal engineering shape design is becoming increasingly important as the efficient utilisation of material can account for significant cost savings during production. Traditional optimisation techniques based on finite element analysis using functional or variational calculus find this task difficult, as the design landscape is one in which the optimisation problem can be non-convex and hence the solution may have many local optima. The approach adopted in this work is based on a self-organisational system governed by a local state operator that defines the state of each element in the finite element mesh at each time step. This operator has the form of a nonlinear differential equation based on the use of strain energy density and is an extension of an expression originally developed for predicting morphogenetic density distributions in natural human bone.

Origin of J/sub c/ lateral spatial distribution in Ag-sheathed Bi-2212 HTSC tapes

Critical current density (J/sub c/) spatial distribution in the superconducting core of the Ag-sheathed Bi-2212 tapes prepared by powder in tube technique has been measured by means of tape cutting along the rolling direction to a few narrow strips and separate J/sub c/ measurements each of them. The J/sub c/ value on the edges of tapes has been found to be higher by a factor of about 3 in comparison with the central area. Unexpectedly, the measured oxide core density is shown to be in contrary the lowest in the edge regions. The thin interface layer (about 10 /spl mu/m thick) with no secondary phase has been observed by SEM on the whole circumference of Ag-sheath/core boundary. This interface layer is assumed to be responsible for the dominant contribution to the supercurrent-carrying ability of a tape. However, in fact the J/sub c/-values on the very edge of the core still are twice as high as J/sub c/ in the central region (3.6/spl times/10/sup 4/ against 1.8/spl times/10/sup 4/ A/cm/sup 2/). Thus, an optimal structure formation can be promoted by the core edge geometry.