Наукові вісті

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The International Science and Technology journal was founded in 1997.

State registration certificate: KB № 18963-775 ПР of April 25 2012.

ISSN 1810-0546 (Print)

ISSN 2519-8890 (Online)

CODEN: NVNTB7

LCCN: 2016214741

The journal publishes only the new results of fundamental and applied scientific research on the subjects of the journal, which had not been previously published in other scientific publications in Ukraine or abroad.

The editorial board of the journal accepts overview and original research papers on the following topics: electronics, radio engineering and telecommunications; power engineering and energy generating technologies; Information technologies, system analysis and control; science of materials and mechanical engineering; instrument- making and information-measuring equipment; problems of biotechnology; energy saving problems; problems of chemistry and chemical technology; theoretical and applied problems of physics and mathematics.

According to the order of MES of Ukraine from 07.13.2015 no. 747, from 07.10.2015 no. 1021, and from 09.03.2016 no. 241 the journal specializes in the physical and mathematical, technical, chemical and biological sciences.

The periodicity of the journal is 6 times a year (no. 1, 2, 5, 6 – engineering sciences, no. 3 – chemical and biological sciences and technology, no. 4 – physical and mathematical sciences).

Languages: Ukrainian, Russian, English.

Founder: National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”.

Mailing address of the editorial office: building 1, room 171-3 and 193-Б, Peremohy Str. 37, Kyiv 03056, Ukraine.

E-mail: n.visti@kpi.ua   and  n-visti@kpi.ua

Tel.: +38(044)204-91-23; +38(044)204-94-53

The journal is covered by following indexing services:

Index Copernicus

Адреса URL: http://bulletin.kpi.ua/
Оновлено: 13 годин 54 хв тому

Optimization of Cell Viability Assays for Screening Glioprotective Compounds in Primary Rat Optic Nerve Head Astrocytes

Чтв, 12/28/2017 - 00:00

Background. Optic nerve head astrocytes (ONHAs) are the major glia cell type in the non-myelinated optic nerve head where they contribute to extracellular matrix synthesis. Pathological changes in glaucoma include reactive astrocytosis, a process characterized by altered astrocyte gene and protein expression and extracellular matrix remodeling. ONHAs are highly sensitive to mechanical and oxidative stress resulting in the initiation of axon damage early during pathogenesis. Furthermore, ONHAs are crucial for the maintenance of retinal ganglion cell physiology and function. Therefore, glioprotective strategies with the goal to preserve and/or restore the structural and functional viability of ONHA to slow glaucoma and related pathologies are of high clinical relevance.

Objective. The aim of the paper is the development of standardized methods for the systematic advancement of glioprotective strategies using plate reader-based assays determining cellular viability, plate-reader based proliferation and the intracellular redox state.

Methods. In our work we used primary culture of OHNAs as a model system. The oxidative stress was induced by tBHP. Reactive oxygen species (ROS) were measured by the DCDFA assay. For cell viability tests we used the optimized lactate dehydrogenase (LDH) release assay, as well as the MTT and Calcein-AM uptake assays.

Results. The half-maximal effect (EC50) of tBHP on OHNAs ROS levels in the DCFDA assay was 192.1 ± 15.7 μM. The measurement of cellular viability of OHNAs after tBHP-induced oxidative stress showed EC50 = 156.9 ± 3.8 µM in the Calcein-AM uptake assay. In the MTT assay, the EC50 for tBHP was 138.1 ± 1.4 µM, and shifted to 192.7 ± 2.8 µM with 100 μM Trolox pre-treatment of OHNA. In the LDH release assay, the EC50 for tBHP was 146.9 ± 4.9 µM and 246.3 ± 7.3 µM for the control and Trolox conditions respectively.

Conclusions. Our results provide feasibility data for the plate-reader based screening for novel glioprotectants using primary ONHA culture.

Colloidal Characteristics of Water Systems of Rhamnolipid Biocomplex of Strain Pseudomonas sp. PS-17 with Tween-80 and their Prospects for Biotechnology

Срд, 12/27/2017 - 00:00

Background. Efficiency of mixed systems of biogenic and synthetic surfactants, based on their colloidal chemical properties, in environmentally safe technologies.

Objective. The aim of the paper is the study of the aqueous systems’ colloidal characteristics of the rhamnolipid biocomplex with Twееn-80 nonionic surfactant, as well as the study of the obtained mixtures’ action for the emulsion stabilization and for plant growth stimulation.

Methods. The surface tension of RBC, Tween-80, and their mixture solutions was measured by the Du-Nui method (with a platinum ring). The dependence of the surface tension on the surfactant concentration was determined for mixtures with RBC content, %: 0.0; 11.1; 25.0; 42.9; 66.7; 100. The emulsifying activity of the surfactant mixtures was determined on the emulsification index (E24). The surfactant influence on plants was assessed by their morphometric parameters after presowing seed treatment.

Results. It was found that the obtained mixture behavior, regardless of the surfactant concentration, deviates from the ideal mixture – the deviation is negative, which indicates the predominance of RBC in the surface layer. The shapes of the surface tension curves for different surfactant ratios indicate synergistic effects before and after micelle formation. The optimum ratio in the RBC-Tween-80 system for sunflower growth and sunflower oil emulsification is 2:1.

Conclusions. The peculiarities of colloid-chemical characteristics of RBC and Tween-80 systems are determined, the prospects of their use for increasing efficiency of emulsification and sunflower growth stimulation are determined.

Estimation of Filter Bed Efficiency at Biotechnologically Intensified Process of Water Deferrization and Demanganation on Rapid Filters

Срд, 12/27/2017 - 00:00

Background. The results of investigations of various types of filter beds (zeolite, quartz sand, keramzit, activated carbon), which are used as beds for rapid filters at biotechnological intensification for ground water defferization and demanganation, are presented.

Objective. The aim of the paper is to evaluate the effectiveness of different types of filtering materials at biotechnological intensification of processes of water defferization and demanganation on rapid filters, both in terms of microorganism fixation and biomass accumulation in the filter loading, and from the point of view of the possible depth of iron and manganese compound removal.

Methods. The research was carried out on the model installation of filters with different types of loading (single and multilayer), artificially populated with microorganisms of the cultures of Leptothrix and Sphaerotillus. The investigated water was characterized by high level of iron and manganese. After the set biomass rise time, the number of microorganisms per unit volume of filter loading was determined, and the defferization and demanganation effectiveness was evaluated.

Results. The obtained results showed a high ability of activated carbon to accumulate the biomass of bacteria during the filtration (4500 CFU/cm3), but the defferization and demanganation percentage was low (65 % and 60 %, respecti­vely). When water was filtered through other research materials, less biomass accumulation was observed, as well as the overall efficiency of the treatment process. For sand-zeolite-coal loading, the removal efficiency was up to 90 % for iron, and for manganese – up to 71 %.

Conclusions. The obtained results showed the prospects of using three-layer sand-zeolite-coal loading and the need to determine the optimal technological parameters.

Increasing Certainty of Fault Identification in Power Transformers of Power Plants by Setting Parameters for Fuzzy Model

Срд, 12/27/2017 - 00:00

Background. Problem of ensuring reliability and safety operation of thermal, nuclear and hydro power plants is exacerbated under increasing accident in modern electric power systems due to power equipment failures. Therefore, deve­lopment of adequate mathematical models for technical condition determination and risk assessment of power transformer failure in power plants is relevant.

Objective. The aim of the paper is to improve the diagnostic fuzzy model of power transformer technical condition by setting parameters and risk failure assessment under presence damage.

Methods. The mathematical model of power transformer used approaches based on fuzzy sets theory, fuzzy logic and nonlinear optimization methods. Risk assessment of power transformer failure under presence damage was solved based on formed hierarchy factors and parameters of influence on integral risk indicator of power transformer failure.

Results. The necessity of complex simulation of technical condition of power transformer and electric power system modes is substantiated. The fuzzy model of power transformer technical condition evaluation was upgraded by parametrically identifying the optimal function values of fuzzy terms of linguistic variables.

Conclusions. A mathematical model of risk assessment of power transformer failure with presence damage was proposed for emergency risk estimation in electric power systems under electrical equipment failures.

Haar Cascade Face Detector Quality Dependence on Training Dataset Variablity

Срд, 12/27/2017 - 00:00

Background. When training generalized face detectors based on Haar cascades, there is a problem of long learning time of the resulting cascades and their poor quality. Therefore, in practice, frontal and profile face detectors are trained separately. Such approach makes recognition systems more complex.

Objective. The aim of the paper to compare the impact of the training set composition with faces at different inclination angles on the quality of the trained detectors.

Methods. It is proposed to train a series of face detectors on sub-sets that cover different ranges of face angles. All other parameters of training are fixed. As the result, the learning time and the quality of the obtained cascades will be compared.

Results. The quality and the training time of face classifiers are evaluated depending on the composition of the training subsets. Also the quality of the frontal and side face classifiers is compared having the same sizes of training sets. It is shown that the AUC metric has a difference of 0.003 between the frontal and profile face detectors.

Conclusions. It has been shown experimentally that the more variations present in the object’s dataset (the side-view of faces compared to the frontal positions), the longer and harder the Haar cascade learns, given the same amounts of the training samples. Using the proposed approach, the quality of the final classifier can be controlled by selecting the appropriate composition of the training samples.

Assessment Method of Cooling and Heart Rewarming Speed under Cardiopulmonary Bypass

Срд, 12/27/2017 - 00:00

Background. The analysis of the heat propagation rate in the myocardium with hypothermia and hyperthermia of the heart under cardiopulmonary bypass is considered.

Objective. Development of a method for assessing the hypothermia and cardiac hyperthermia rate, which allows quantitatively describe the heat and mass transfer between the liquid medium and the heart muscle tissue.

Methods. The analysis of the heat spread rate in the myocardium during hypothermia and cardiac hyperthermia in conditions of cardiopulmonary bypass allows us to isolate from the temperature distribution on the thermogram the branches of the coronary vessels and their distal segments. The method application provides additional information for increasing the effectiveness of non-invasive heart temperature monitoring under cardiopulmonary bypass. Clinical approbation of a method for assessing the rate of hypothermia and hyperthermia was carried out, and cardiac thermograms were used in conditions of cardiopulmonary bypass, which were obtained using Flir i7 and ThermoCam E300 thermal imagers.

Results. Formulas are derived and a method for estimating the rate of hypothermia and cardiac hyperthermia is developed, it is determined that the temperature acceleration can be estimated as a derivative of the temperature change rate for the maximum and minimum temperature values in the investigated area of the myocardium, and the temperature change rate during the operation is determined by the ratio of the temperature range to the temperature change time period ∆T/t  for the minimum and maximum temperature fluctuations.

Conclusions. The obtained data allow determining the coronary obstruction degree and the degree of narrowing of the coronary arteries, which reduces the probability of ischemic complications after surgery on the open heart.

The Study of 99mTc Production Using Medical Cyclotrons in Ukraine

Срд, 12/27/2017 - 00:00

Background. Tracer production for nuclear medicine.

Objective. The aim of the paper is to consider the possibility of 99mTc tracer production using low-energy medical cyclotrons installed in Ukraine applying enriched 100Мо targets.

Methods. The cross sections of 100Mo(p,2n)99mTc nuclear reactions and reactions, leading to formation of impurities were calculated. The technical aspects of irradiation process were considered. Necessary target thickness and 99mTc tracer yield for the Eclipse RD (Siemens) and PETtrace (GE) cyclotrons were estimated.

Results. Within the framework of proposed concept, 99mTc tracer yield equals 3.7 and 35.5 GBq after 2h of bombardment for Eclipse RD and PETtrace cyclotrons, respectively.

Conclusions. The obtained results showed satisfied 99mTс tracer yields and feasibility of further development of this method, which will significantly improve the efficiency of cyclotron installations.

Flexible Solution of a 2-layer Perceptron Optimization by its Size and Training Set Smooth Distortion Ratio for Classifying Simple-Structured Objects

Срд, 12/27/2017 - 00:00

Background. Two-layer perceptrons are preferred to complex neural network classifiers when objects to be classified have a simple structure. However, even images consisting of a few geometrically primitive elements on a monotonous background are classified poorly with two-layer perceptron if they are badly distorted (shifted, skewed, and scaled). Performance of two-layer perceptron can be bettered much with modifying its training. This is done by deliberately importing distortions like shifting, skewness, and scaling into a training set, but only controlling volumes of the distor­tions with a special ratio. Besides, the performance is improved with optimally sizing the hidden layer.

Objective. The goal is to optimize the two-layer perceptron by its size and the ratio for classifying simple-structured objects.

Methods. The objects are monochrome images of enlarged English alphabet capital letters (the EEACL26 dataset) of a medium size 60-by-80. EEACL26 is an infinite artificial dataset, so mathematical models of distorted images are given. Then two-layer perceptrons having various sizes and training set smooth distortion ratios are trained and tested. The performance is evaluated via ultimate-distortion classification error percentage.

Results. Based on statistical evaluations of classification error percentage at ultimate distortions, it is revealed that, while the best ratio should be between 0.01 and 0.02, and an optimal number of neurons in the hidden layer should be between 361 and 390. Sizes closer to 375 are counted as statistically more reliable, whereas the ratios are selected uni­formly. Such solution is flexible allowing not only further-training with changing the hidden layer size and ratio, but also a smart initial training for the first passes. Nevertheless, even after the first 100 passes, the two-layer perceptron further-trained for extra 1190 passes by 10 times increasing distortion smoothness performs at 8.91 % of errors at ultimate distortions, which is about 45 % better than a previously known result. At the expected practicable distortions, which are far less, the error rate is 0.8 % that is quite tolerable. But here the main benefit of the optimized two-layer perceptron is its fast operation speed, rather than accuracy.

Conclusions. The obtained flexible solution fits other datasets similar to EEACL26. Number of classes can vary between 20 and 30, and number of features can vary between a few hundred and a few thousand. The stated example of achieving high-performance classification with two-layer perceptrons is a part of the common technique of statistical optimization relating to neural network classifiers. For a more sophisticated dataset of objects, this technique is built and executed in a similar way.

Production of Castings with Differentiated Surface Properties

Срд, 12/27/2017 - 00:00

Problems. Surface layers get the most intensive external influences during the operation of molded parts of machines and mechanisms, therefore their structure and properties determine the operability of products as a whole. To achieve high surface strength and durability of parts, various technological processes are used in the industry, but most of them do not make it possible to obtain a surface layer with the desired properties of the required thickness. In this case, more promising can be the technological process of surface alloying (the manufacture of products with differentiated surface properties).

Objective. The aim of the paper is to develop a technological process for the production of castings with specified surface properties.

Methods. Each core was coated with an alloying coating, coated cores were dried in the air during the day, the mold and cores were heated and collected just before pouring them with metal.

Results. It is necessary to use ferromanganese, ferrotitanium and ferrochrome for the manufacture of wear-resistant parts, which allow obtaining on the casting surface an alloyed layer with a thickness up to12 mm and hardness up to 68 NRA. Such process parameters fully meet the operational requirements for products that operate under abrasive or water abrasion wear.

Conclusions. To increase the hardness of the working surfaces, certain chemical elements, ferroalloys and chemical compounds such as carbides, borides and nitrides can be used as fillers of alloying coatings.

Application of External Electromagnetic Forces for Resistance Spot Welding of Р6М5 Instrumental Steel Parts

Срд, 12/27/2017 - 00:00

BackgroundJoining of working part of the instrument using mechanical methods or brazing doesn’t ensure its good fixation and isn’t technologically reasonable for mass production purposes. This problem can be solved by application of electromagnetic forces for resistance welding methods based on physical effect on joint formation process.

Objective. The aim of the paper is estimation of technological possibilities of resistance spot welding with electromagnetic stirring for joining of instrumental steels.

MethodsTransversal opposite-symmetric magnetic field is generated in the working zone. It has equal value but opposite direction of magnetic induction relative to contact plane of parts to be joined for stirring of molten metal with ponderomotive forces.

ResultsPositive changes of parameters of joint formation were detected. They define mechanical properties of joints. Control of molten metal hydrodynamics resulted in decreasing of sponginess-type imperfections in the central area of the nut. It was shown that changes in thermal processes, leading to decreasing of cooling speed, result in decrease of hardened structures in the moulded zone which, in turn, results in decreasing of microhardness of structure elements.

Conclusions. Reasonability and effectiveness of application of electromagnetic forces for resistance spot welding of instrumental steels was proven.

Effect of Form Factors and Magnetic Properties of Thin-Walled Metals on the Induction Heating Processes

Срд, 12/27/2017 - 00:00

Background. The use of induction heating in the technologies of contactless processing of sheet metals is an actual solution, which allows increasing the effectiveness of performed operations. The most of the induction heating systems applied, due to the high level of power used, operate in the modes of deep saturation of the metal. The issue of the electrodynamic processes occurred in the region of the non-constant index of the magnetic permeability of the metal is relevant.

Objective. The aim of the paper is conducting analysis of the peculiarities of electromagnetic processes in a ferromagnetic sheet metal located in the alternating magnetic field of the external inductor to determine the optimal characteristics of the system.

Methods. The adaptation for Maxwell's equations solution in accordance with accepted assumptions of the physical-mathematical model for obtaining numerical estimates.

Results. The analytical dependences obtained, which are the solution of the physical and mathematical problem within the framework of the adopted model, were analyzed with the corresponding numerical estimates.

Conclusions. Numerical estimates have shown that the variation of the metal permeability parameter of the object, as well as the degree of its saturation in the course of vortex currents, has a significant effect on the heating time of the metal. The saturation state avoiding will increase the efficiency of the heating process.

Influence of Geometrical Parameters of Reduction on the Deformation of Working Surface of the Axisymmetric Mirrors

Срд, 12/27/2017 - 00:00

Background. Weight reduction of mirrors is an important issue in the development of space-based optical systems. However, the study of the weight reduction influence on the mirror surface deformation of the axially symmetric mirrors is given little attention.

Objective. The aim of the paper is the analysis of the possibilities of axisymmetric mirror weight reduction by studying the geometrical parameters’ influence of reduction and fastening on the deformation of their working surfaces under the gravity influence.

Methods. The influence of various variants of the axisymmetric mirrors’ construction on their working surface deformation has been carried out by simulation in finite-element and optical analysis programs.

Results. The influence of design values, geometrical dimensions of reduction and fastening on the working surface deformation of axisymmetric mirrors is analyzed, and the recommendations for the application of various types of reduction are given. It is determined that hexagon holes should be used for less deformation, and for the greatest reduction of weight it is necessary to use circular cuts. Particular attention when designing reduction should be drawn to the mechanical part of the mount, as the deformation of the mirror very much depends on it.

Conclusions. In the process, the effect of geometrical parameters of reduction on the working surface deformation of axisymmetric mirrors was carried out. Using the obtained data it is possible to optimize the design of relief and fastening to obtain the minimum weight and deformation of the mirror working surface on the ground.

Model of the Active Surface Structure of the Abstract Biotechnical Object

Срд, 12/27/2017 - 00:00

Background. The article deals with the current problem of monitoring the metrological parameters of technological equipment with computer numerical control through the development of methods and means of express certification of the technological equipment coordinate system, which, in contrast to the existing, will be more economical and not inferior to the accuracy of the laboratory.

Objective. The aim of the paper is to create a method of compensation for the detected errors, which requires models of elementary forms that determine the formation of various types of the object surface structure regularity, in par­ti­cular, modeling the object active surface formation in interaction with other objects.

Methods. The elementary volume form model of any abstract object and the energy processes that occur in it is pro­po­sed. It’s proposed to choose to such extent the thickness of the surface layer, which determines the active properties of the surface.

Results. It was shown that the depth of the active surface determines the real size of the area and the minimum active volume of the abstract object active area. In considering all these processes, the difference between fluid deterioration and current destruction under the influence of external forces (environment) is determined. The interaction between the environment flow and the abstract object is quite a relative situation.

Conclusions. The primary classification of abstract biotechnical object surface elementary structures was created. A mo­del of surface structure based on elementary forms that form the biotechnical object active area is proposed. This appro­ach provides the opportunity to create the most sensitive area of object interaction.

Method for Obtaining Nanodispersion of Silver under the Influence of Plasma Discharge in the Presence of Water-Soluble Polymers

Срд, 12/27/2017 - 00:00

Background. Weight reduction of mirrors is an important issue in the development of space-based optical systems. However, the study of the weight reduction influence on the mirror surface deformation of the axially symmetric mirrors is given little attention.

Objective. The aim of the paper is the analysis of the possibilities of axisymmetric mirror weight reduction by studying the geometrical parameters’ influence of reduction and fastening on the deformation of their working surfaces under the gravity influence.

Methods. The influence of various variants of the axisymmetric mirrors’ construction on their working surface deformation has been carried out by simulation in finite-element and optical analysis programs.

Results. The influence of design values, geometrical dimensions of reduction and fastening on the working surface deformation of axisymmetric mirrors is analyzed, and the recommendations for the application of various types of reduction are given. It is determined that hexagon holes should be used for less deformation, and for the greatest reduction of weight it is necessary to use circular cuts. Particular attention when designing reduction should be drawn to the mechanical part of the mount, as the deformation of the mirror very much depends on it.

Conclusions. In the process, the effect of geometrical parameters of reduction on the working surface deformation of axisymmetric mirrors was carried out. Using the obtained data it is possible to optimize the design of relief and fastening to obtain the minimum weight and deformation of the mirror working surface on the ground.

Thermomechanical and Deformation Properties of Composites Based on the System of Dimethacrylate–Tetraethoxysilane

Срд, 12/27/2017 - 00:00

Background. The appearance of interphase interaction, the geometric limitations of the polymer polymerization space, the polymer free volume growth upon the addition of an inorganic component all affect the physicochemical and mechanical properties of the composites. However, the interrelation of the initial components with the composite properties is of an individual nature and requires experimental study.

Objective. The aim of the paper is the investigation of the effect of the composition of hybrid organo-inorganic composites (HOIC) based on the a,w-dimethacryloyl (tridietilenoksidtereftalat) (MGF-9) – tetraethoxysilane (TEOS) system on their thermomechanical and deformation properties and molecular structure.

Methods. Polymer-silica composites were prepared by the method of photoinitiated polymerization in the block using the laser interferometer and the sol-gel method. Thermomechanical analysis was performed on the device for determining the heat resistance of polymeric materials "Heckert" and the values of the characteristic parameters of the investigated composites of the MGF-9–TEOS system were calculated. The deformation properties of the composites were determined on the Heppler consistometer, calculating the parameter of the surface microhardness (conical point of fluidity).

Results. The dependence of the deformation and thermomechanical properties of composites on the ratio of the organic and inorganic components of the system was confirmed.

Conclusions. It is shown that the introduction of an inorganic filler into the polymer matrix improves the thermomechanical and deformation properties of the composites. It was established that the maximum thermomechanical stability and strength has the composition of MGF-9:TEOS = 90:10 % vol.

The Optimization of the Data Packet Length in Adaptive Radio Networks

Втр, 10/31/2017 - 00:00

Background. Development of methods and means of the adaptive management of the radio networks bandwidth with competitive access to the radio channel.

Objective. The aim of the paper is to determine the packet length effect on the effective radio networks transmission rate with taking into account the parameters, formats, and procedures of the physical and link levels at using the MAC protocol with a rigid strategy of competitive access to the radio channel.

Methods. The goal is achieved by creating and analyzing the mathematical model of the effective transmission rate in radio networks. The model is described by the equation for the effective transmission rate, which is the function of both the probability of the conflict-free transmission of the MAC protocol and the coefficient of the data packet size deviation from the optimal for LLC protocol.

Results. It is proved that there is the optimal deviation of the data packet length for each MAC protocol traffic intensity value, which provides the most effective transfer rate. This makes the possibility for adaptive management of the radio bandwidth by applying a pre-calculated deviation of the data packet size in dependence on the traffic intensity.

Conclusions. The proposed mathematical model is the tool for calculation of both the radio bandwidth network capacity and the optimal deviation of the data packet length at adaptive management of competitive access to a radio channel with a rigid strategy at conditions of the significant fluctuation in traffic intensity.

Technology of Rock Destruction by Combined Explosion-Mechanical Load

Втр, 10/31/2017 - 00:00

Background. Rock drilling is characterized by an energy capacity of more than 120 kWh/m3. This is due to the fact that about 90 % of the energy is expended on the “preparation” of rocks for destruction. This study proposes to combine explosive and mechanical loads to reduce specific energy consumption of rock destruction.

Objective. The aim of the paper is energy effective technology development for rock destruction by combined explosive-mechanical loads.

Methods. Analytical studies; regression analysis; math modeling; experimental research; technical and economic analysis.

Results. Specific energy decreasing for explosive-mechanical rock drilling by 4–16 % was experimentally proved.

Conclusions. As a result of the implementation of explosive-mechanical rock drilling on the created full-sized experimental device, the efficiency coefficient increased from 77 to 80 %.

Statistics Based Models for the Dynamics of Chernivtsi Children Disease

Втр, 10/31/2017 - 00:00

Background. Simple mathematical models of contamination and SIR-model of spreading an infection were used to simulate the time dynamics of the unknown before children disease, which occurred in Chernivtsi (Ukraine). The cause of many cases of alopecia, which began in this city in August 1988 is still not fully clarified. According to the official report of the governmental commission, the last new cases occurred in the middle of November 1988, and the reason of the illness was reported as chemical exogenous intoxication. Later this illness became the name “Chernivtsi chemical disease”. Nevertheless, the significantly increased number of new cases of the local alopecia was registered almost three years and is still not clarified.

Objective. The comparison of two different versions of the disease: chemical exogenous intoxication and infection. Identification of the parameters of mathematical models and prediction of the disease development.

Methods. Analytical solutions of the contamination models and SIR-model for an epidemic are obtained. The optimal values of parameters with the use of linear regression were found.

Results. The optimal values of the models parameters with the use of statistical approach were identified. The calculations showed that the infectious version of the disease is more reliable in comparison with the popular contamination one. The possible date of the epidemic beginning was estimated.

Conclusions. The optimal parameters of SIR-model allow calculating the realistic number of victims and other characteristics of possible epidemic. They also show that increased number of cases of local alopecia could be a part of the same epidemic as “Chernivtsi chemical disease”.

Finding an Optimal Decisions’ Subset by Minimaximax Regret Criterion Regarding Instability of the Decision Function

Втр, 10/31/2017 - 00:00

Background. A generalization of the minimax regret criterion is represented as even the best-assurance minimax regret criterion comes inconsistent under instable evaluations of decision situations.

Objective. The goal is to formulate the minimaximax regret criterion.

Methods. Unlike the classic one, the generalized regret criterion is minimaximax which operates over generalized regrets. These regrets are found from a generalized decision function which is defined on a Cartesian product of a decisions’ set, a set of states, and a set of metastates. Metastate describes instability of the decision function whose values change through a set of metastates. The instability destroys assurance of minimaxed regrets found classically, so regrets are found over a generalized decision function. For this, utility evaluations are subtracted from the utility maximized across a decision set, or the loss/risk minimized across a decision set is subtracted from loss/risk evaluations. Then regrets are minimized under uncertainty across two dimensions of states and metastates, that is they are minimaximaxed.

Results. The suggested minimaximax regret criterion allows finding an optimal decisions’ subset with not only regarding instability of the decision function, but also with reducing the initial decisions’ set more, unlike the ultimate pes-simism criterion without regrets (minimaximax/maximinimin). This especially concerns nonnegative utility matrices with many zeros.

Conclusions. A ratio of a number of optimal decisions by the without-regret maximinimin/minimaximax to a number of optimal decisions by the minimaximax regret criterion decreased by 1 can be interpreted as a gain of applying the represented minimax regret criterion generalization. This gain fundamentally depends on whether sets of decisions, states, and metastates are finite or not. If they all are finite, then the gain depends on values in a three-dimensional regret matrix and its dimensions. It is surprising but the gain may be negative, that is finding regrets may come non-effective.

Effect of Fluid Viscosity on Noise of Bileaflet Prosthetic Heart Valve

Втр, 10/31/2017 - 00:00

Background. Numerical simulation and experimental research have been used as powerful tools to understand and predict the behavior and mechanics of the operation of natural heart valves and their prostheses in natural and patho­logical conditions. Such studies help to evaluate the effectiveness of the valves, their design and the results of surgical procedures, to diagnose healthy and impaired function of the heart valves. There is an actual problem in creating more reliable methods and tools for the operation diagnostics of mechanical heart valves.

Objective. The aim of the research is to investigate the effect of fluid viscosity on the hydroacoustic characteristics of jets that flow from a semi-closed and open mechanical bileaflet heart valve. To study the possibility of using hydro­acoustic measuring instruments as diagnostic equipment for determining the working conditions of the bileaflet pro­sthe­tic heart valve.

Methods. The experimental research was carried out by means of hydroacoustic measurements of the hydrodynamic noise in the near wake of the side and central jets of the glycerin solution and the pure water flow downstream of the prosthetic bileaflet heart valve.

Results. The effect of fluid viscosity on the hydroacoustic characteristics of the jets that flow from a semi-closed and open mechanical bileaflet heart valve has been experimentally determined. Integral and spectral characteristics of the hydrodynamic noise of jets of the glycerin solution and the pure water flow downstream of the bileaflet mitral heart valve for different fluid rate were detected.

Conclusions. In the stream conditions of pure water, the integral characteristics of the pressure field are lower than in stream conditions of the aqueous glycerin solution. As the glycerin concentration in the solution increases, increase average pressures and especially RMS pressure fluctuations. The spectral levels of the hydrodynamic noise in the near wake of the side jet of the glycerin solution are lower than for water flow in the frequency ranges from 1 to 7-8 Hz and from 100 to 1000 Hz for fluid rate 5 l/min. For higher fluid rates, the spectral components of the hydrodynamic noise in the near wake of the side jet of the glycerin solution of the semi-closed mitral valve are higher than that for the pure water. The greatest difference (1.5–1.8 times) in the spectral levels is observed in the frequency range from 10 to 100 Hz for the fluid rate 15 l/min.

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