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The paper presents the results of an experimental study of the dielectric and switching characteristics of some initial and annealed alanine-doped crystals of the triglycine sulfate group at room temperature. The results of measurements and calculations of the effective permittivity, switchable polarization, coercive and bias fields, unipolarity coefficient and dielectric loss tangent are presented. It was found that for most samples before and after annealing, the dielectric hysteresis loops are unipolar and shifted along the abscissa axis. This indicates a preferential orientation of domains and the presence of bias fields. As a result of annealing, the values of the coercive field and the unipolarity coefficient of the crystals decrease, and the switchable polarization increases. It is shown that the field dependences of the effective permittivity of the crystals before annealing have extrema lying in the field range of (5-7,5) ∙ 104 V∙m-1 and in the range (5-12) ∙ 104 V∙m-1 after their annealing.

The results of experimental studies of magnetic properties and magnetization reversal processes of a series of alloys Sm-Gd-Zr-Co-Cu-Fe are presented. The studied samples were subjected to prolonged isothermal annealing for 24 hours, which made it possible to achieve the formation of a certain nanostructure that affects the hysteresis properties of the material and allows to achieve a high coercivity state. According to the magnetic measurements data obtained by the method of a vibrating magnetometer, the hysteresis loops are constructed, the dependence of the saturation magnetization, and the coercive force on chemical composition, and the values of the temperature coefficient of magnetization change depending on the relative content of Sm and Gd are determined. It is shown that the substitution of a part of samarium atoms for gadolinium atoms increases the effect of the mechanism of irreversible rotation of the spontaneous magnetization vector on the remagnetization of samples. Application of the studied samples in various devices puts serious demands on the stability of their magnetic properties at high temperatures. Our researches allow us to conclude that compounds with gadolinium concentration x=0,5 have the greatest coercive force, and compounds with gadolinium concentration in the range x=0,5-0,6 have the highest temperature stability.

Background. The information content of the complex for measuring the parameters of the TIR structure can be increased by using a GLIN implemented on the basis of a microcontroller in its configuration. Materials and methods. The method of a "small" signal is used, designed for the analysis of nonlinear electrical systems representing semiconductor structures, and used to model the transfer function and describe the response of such systems at "small" values of the amplitude of the measuring signal supplied to the input of the system. This approach allows us to evaluate the response of a system with a semiconductor, which is a metal-dielectric-semiconductor (MDP) structure, and fix the C-V characteristics of this structure. Results. The addition of a microcontroller to the GLIN makes it possible to implement a universal research complex that can assess in more detail the characteristics of a TIR structure with dielectric layers of various thicknesses, both thin and significantly enlarged. Conclusions. The use of a microcontroller in GLIN, capable, along with the operations of memorization and storage, to perform the computational ones necessary for the final assessment of the charge instability of the TIR structure, not only expands the amount of information received, but also allows us to evaluate the reaction of the investigated TIR structure, located in various energy states, to the external influence of a "small" signal.

The dependence of the properties of elastic sensitive elements made of beryllium bronze on the modes of their heat treatment is studied. It is shown that the duration of aging significantly affects the value of nonlinearity of elastic characteristic, hysteresis, shrinkage of elements and mechanical properties of membrane material (hardness, elastic limit). The relations between submicroscopic structure and properties of elastic elements are established. The greatest nonlinearity of the elastic characteristic, hysteresis and shrinkage belong to elements subjected to short-term aging at 310–350 °С. With increasing duration of aging, the corresponding values of the above parameters decrease. For aging temperatures 310–320 °С, the nonlinearity of elasticity characteristics reaches the minimum values after 4–5 h of aging, and for 340 °С — after 3 h. At 350 °С minimum values of nonlinearity are reached after aging duration of 45–60 min. From the obtained data it follows that from the point of view of obtaining the minimum hysteresis and nonlinearity characteristics of aneroid sensing elements made of bronze of БрБНТ-1,9Мг (BrBNT-1.9Mg) grade, heat treatment of membranes should be carried out according to the regimes of 1 h at 350 °С or 3 h at 340 °С.

The article is devoted to the fatigue of bending reinforced concrete beams under reinforcement corrosion. The influence of lugs and rebar notches periodic profile in concrete under repetitive loads, which act as stress concentrators, leading to the appearance of fatigue cracks and to the reduction of fatigue strength, is considered.

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background and Objectives: The van der Pole oscillator with an additional oscillatory circuit represents one of the simplest self-sustained oscillator system with two degrees of freedom. It is characterized by the phenomenon of frequency pulling, caused by the appearance of bistability and hysteresis. The bifurcation mechanism of pulling and bistability was previously identified, and the bifurcation analysis was carried out for the case of weak excitation when the system exhibits quasi-harmonic self-sustained oscillations. However, the question remains open about the influence of anharmonicity, which develops in the system with increasing excitation parameter, on the phenomenon of multistability and on the bifurcation mechanism of its formation. Is the effect of frequency pulling and the corresponding bistable states preserved over a wide range of values of the control parameters? Are new multistable states being formed? What does the bifurcation structure of the control parameter plane look like? In this paper, the above issues are studied using as an example a self-sustained oscillatory system consisting of the Rayleigh oscillator with an additional linear oscillator. Materials and Methods: Numerical simulation and bifurcation analysis of equilibrium states and limit cycles were performed using the XPPAUTO software package. Results: The results of a two-parameter analysis in a wide range of excitation and frequency detuning parameters have been presented, typical modes of self-sustained oscillations and their bifurcations have been described. Conclusion: It has been shown that the classical phenomenon of frequency pulling is observed only at small values of the excitation parameter of the system. The bistability region, where two limit cycles coexist, corresponding to in-phase and anti-phase oscillation modes in coupled oscillators, is bounded by both the detuning parameter and the excitation parameter.

The paper presents the results of a study of hysteresis properties based on analysis of dielectric hysteresis loops and temperature dependences of switchable polarization for solid solutions 24% Pb(In1/2Nb1/2)O3 – 49% Pb(Mg1/3Nb2/3)O3 – 27% PbTiO3 solutions. It follows from the experiment that at T = 293 K and strengths of the repolarizing field E = (140-301)·103 V·m-1, only partial switching of the crystal occurs. Saturated dielectric hysteresis loops of crystals are observed in a field of 271103 Vm-1 in two temperature ranges 373-383 K and 437-440 K. The temperature dependences of the permittivity and switchable polarization have two anomalies, the first of which correspond to the region of the phase transition of the crystal from the ferroelectric rhombohedral phase to the tetragonal one. At a temperature of about 450 K, the crystal passes into the paraelectric state. Electron microscopic studies of the PIN-PMN-PT crystal structure show that various surface areas contain inhomogeneities that differ in the compositional contrast from the matrix represented by chemical elements, the main mass percentage of which is oxygen and lead. The elemental composition of heterogeneities also includes titanium.

The results of an experimental study of magnetization reversal processes of (R,Zr)(Co,Cu,Fe)Z (R = Sm, Gd) alloys taking into account micro- and nanostructure are presented. To create a highly coercive state in the samples, they were isothermally annealed at 800°C for 8-24 hours. The duration of annealing affects the formation of the nanostructure of alloys of this type. Based on magnetic measurements performed using a vibration magnetometer, magnetic hysteresis loops and graphs of the dependence of the coercive force on the chemical composition and duration of heat treatments were obtained, and the range of changes in the temperature coefficient of magnetic induction was determined depending on the relative content of Sm and Gd in the samples. Data on micro- and nanostructure were obtained using optical and scanning probe microscopy. The correlation relationships between the micro- and nanostructure parameters and the magnetic properties of the studied alloys are described. It was found that the highest values of the coercive force are achieved in an alloy in which the value is x = 0,5.

The infectious disease caused by human immunodeficiency virus type 1 (HIV-1) remains a serious threat to human health. The current approach to HIV-1 treatment is based on the use of highly active antiretroviral therapy, which has side effects and is costly. For clinical practice, it is highly important to create functional cures that can enhance immune control of viral growth and infection of target cells with a subsequent reduction in viral load and restoration of the immune status. HIV-1 control efforts with reliance on immunotherapy remain at a conceptual stage due to the complexity of a set of processes that regulate the dynamics of infection and immune response. For this reason, it is extremely important to use methods of mathematical modeling of HIV-1 infection dynamics for theoretical analysis of possibilities of reducing the viral load by affecting the immune system without the usage of antiviral therapy. The aim of our study is to examine the existence of bi-, multistability and hysteresis properties with a meaningful mathematical model of HIV-1 infection. The model describes the most important blocks of the processes of interaction between viruses and the human body, namely, the spread of infection in productively and latently infected cells, the appearance of viral mutants and the development of the T cell immune response. Furthermore, our analysis aims to study the possibilities of transferring the clinical pattern of the disease from a more severe state to a milder one. We analyze numerically the conditions for the existence of steady states of the mathematical model of HIV-1 infection for the numerical values of model parameters corresponding to phenotypically different variants of the infectious disease course. To this end, original computational methods of bifurcation analysis of mathematical models formulated with systems of ordinary differential equations and delay differential equations are used. The macrophage activation rate constant is considered as a bifurcation parameter. The regions in the model parameter space, in particular, for the rate of activation of innate immune cells (macrophages), in which the properties of bi-, multistability and hysteresis are expressed, have been identified, and the features cha rac terizing transition kinetics between stable equilibrium states have been explored. Overall, the results of bifurcation analysis of the HIV-1 infection model form a theoretical basis for the development of combination immune-based therapeutic approaches to HIV-1 treatment. In particular, the results of the study of the HIV-1 infection model for parameter sets corresponding to different phenotypes of disease dynamics (typical, long-term non-progressing and rapidly progressing courses) indicate that an effective functional treatment (cure) of HIV-1-infected patients requires the development of a personalized approach that takes into account both the properties of the HIV-1 quasispecies population and the patient’s immune status.

The relationship between the change in the structural and mechanical properties of metal materials and structural elements and the modification of their magnetic behaviour under the influence of mechanical stresses, temperature and aggressive environments is established in order to create a methodology for both determining the residual resource and increasing the operational reliability of materials and systems. An express method of microstructure assessment by means of determining the change in the magnetoacoustic response of the material is proposed. [ABSTRACT FROM AUTHOR]

One of the possible ways to obtain silicon with magnetic properties is the introduction of paramagnetic impurities into silicon: Cr, Mn, Fe, Ni, and Co. In our opinion, silicon materials containing magnetic nanosized clusters are most suitable for spintronic devices. The possibility of obtaining silicon with magnetic properties by diffusion doping was studied in this work. To obtain silicon doped with Cr, Mn, Fe and Ni impurity atoms, p-type single-crystal silicon with a specific resistance of ρ = 5 Ohm·cm and ρ = 0.5 Ohm·cm was used, and for doping with Co atoms, n-type silicon with resistivity ρ=10 Ohm·cm was used. The diffusion temperature and time were chosen such that, after diffusion annealing, the samples with impurity Cr, Fe, and Mn atoms remained highly compensated p-type, and when doped with impurity Co atoms, they remained high-resistance n-type. The results of the study showed that with decreasing temperature, the value of the negative magnetoresistance Δρ/ρ in the Si samples increases and reaches its maximum value (about 800%) at T = 240 K, a further decrease in temperature leads to a decrease in the magnetoresistance, and at a temperature T = 170 K, the sign of the magnetoresistance is inverted. In Si samples, with decreasing temperature, the positive magnetoresistance turns into a negative one, the value of which increases with decreasing temperature, and is achieved at T=100 K Δρ/ρ = 45–50%. In Si samples, with decreasing temperature, the value of negative magnetoresistance increases monotonically and at T=100 K its value is Δρ/ρ = (100÷120) %. The study in Si samples showed that with decreasing temperature the value of positive magnetoresistance increases and at Т=100 K it reaches Δρ/ρ = (17÷20) %. The study of magnetoresistance in samples - Si showed that with decreasing temperature the value of positive magnetoresistance increases and at T=100 K it reaches Δρ/ρ = (10÷15) %. When studying the magnetic properties of p-Si samples at low temperatures (below T=30 K), a ferromagnetic state was found, i.e. succeeded in obtaining a magnetic semiconductor material by the method of diffusion of a paramagnetic impurity. In the overcompensated Si (n‑type) samples, no magnetic hysteresis was found. This shows a significant effect on the magnetic properties of the manganese impurity in silicon of its charge and, accordingly, spin state. Based on the results obtained, it can be argued that diffusion doping of silicon with manganese can be used to obtain silicon with magnetic properties.

The paper presents the results of the analysis of experimental dielectric hysteresis loops and field dependens of polarization switching of initial and annealed crystals of triglycine sulfate, doped copper (the concentration range (4,2–8,7) 10-3 wt.%). It has been experimentally established that their dielectric hysteresis loops do not have distortions. It has been found that the relative and effective permittivities and switchable polarization increase with increasing impurity concentration in crystals of TGS:Cu2+. The field dependences of the effective permittivity have extrema: before annealing the samples, the maxima of the εeff(E) curves correspond to a field value of about (20-40)∙103 V∙m-1, and for annealed samples these fields have a value of ~(15-30)∙103V∙m–1. Annealing of the samples increases the mobility of domain walls, which promotes the transformation of lenticular nuclei of domains into lamellae.

When conducting seismic calculations of reinforced concrete buildings and structures, it is quite important to use nonlinear models of structural performance, including those taking into account the overcritical operation in the fracture stage. The application of such models is especially important if the structures have an initial damage from fire or corrosion, as well as mechanical damage caused by force factors. The purpose of this study is to develop an analytical model of the deformation of eccentrically compressed reinforced concrete columns considering the stage of failure, which includes such processes as spelling of the protective layer, loss of stability of compressed reinforcement, and softening of confined concrete after reaching the design resistance. The existing models describing hysteresis behavior of reinforced concrete structures under low-cycle loading have been reviewed. The models have been analyzed in terms of considering the defining monotone curves, which are the boundaries of cyclic deformation. The model proposed in the research is constructed by analyzing the stages of the stress-strain state of a reinforced concrete column. At each stage, formulas are found for determining moment and curvature by solving equations of equilibrium of internal forces. Calculations based on the obtained model for a particular reinforced concrete column are carried out, monotonous diagrams are obtained, and a conclusion about the significant influence of the level of axial load on the character of deformation is made. On the basis of the obtained model, the construction of hysteresis diagrams under low-cycle loading is expected in the future.

The results of laboratory studies to determine the effect of effective stress on the permeability of sandstone are presented. During the test, the samples were subjected to a stepwise increase or decrease of the effective stress (at a constant pore pressure) in a specified step. The values of rock permeability at different values of effective stress were determined, and the influence of the grain size of the reservoir rock matrix on the character of the change in the sandstone permeability coefficient was also established. During the test, a decrease in permeability was observed with an increase in effective stress. It was found that as a result of gradual loading/unloading of the sandstone sample, the original permeability values were not restored, which indicates the beginning of the formation of residual strains in the rock. This effect should be taken into account when modeling field development because in the process of reserves extraction the effective stress acting on the reservoir rock skeleton changes, which results in a significant chang in rock permeability. The results of laboratory studies showed that the deviation of permeability in medium-grained sandstones relative to the initial value was greater than in medium- and fine-grained sandstones. The pressure sensitivity coefficient and constant of material, which are used in empirical relationships between permeability and effective stress, were numerically estimated. At the same time, the constant of material showed no such convergence, which indicates that the values of this parameter are individual for each rock.

Currently, transformer manufacturers are tasked with creating energy-efficient devices with a reduction of steel losses of up to 44 %. Appropriate theoretical developments are needed for its implementation. With a reduction of eddy-current losses, caused, for example, by reduction of decrease in the thickness of the magnetic conductor sheets, hysteresis losses simultaneously increase. A similar effect is caused by changing the size of the crystal grain of steel, thermomagnetic treatment and other technological impacts. In this regard, the exact determination of the components of total losses in steel is an urgent problem, the solution of which would minimize total losses. The article analyzes the expressions that determine the specific losses for eddy currents and hysteresis through the parameters of the magnetic circuit, and states that this technique is too complicated for engineering calculations. Since eddy current losses are proportional to the square of the frequency, and hysteresis losses are proportional to the frequency in the first degree, simple calculated expressions of eddy current and hysteresis losses have been obtained using the wattmetric method. Based on the fact that the dependence of the magnetization loss on the thickness of the magnetic conductor plates is a decreasing linear function, and the eddy current loss is an ascending parabolic function, an expression of the optimal thickness of the plates has been found, the implementation of which makes the losses of steel minimal. This information will make it possible to minimize total steel losses more effectively by varying the design parameters and the material of the magnetic conductor. It is shown that the charted idling losses of transformers manufactured by different manufacturers differ by more than 30 % and can be rounded and underestimated; therefore it is advisable to obtain this parameter as a result of an experiment (idling experiment).

The article describes a method for experimental evaluation of the stiffness of an elastic damper ring. A thin-walled low-stiffness ring with uniformly distributed smooth protrusions on the inner and outer surfaces acts as a damper ring. Despite the widespread use of such a design in domestic and foreign mechanical engineering, control of the characteristics of this element and, accordingly, of the support as a whole remains quite difficult. A numerical model was developed, the reliability of which is confirmed by analytical calculations. To check the data obtained by numerical calculations, a special device was designed, which was installed on the galdabini tensile testing machine, where a series of measurements was carried out. Analysis of the data obtained showed a significant difference between the numerical, analytical and experimental data, which can be explained by the discrepancy between the equipment used and the boundary conditions of the theoretical model. The parameters of the device were selected in such a way that its rigidity was much higher than the rigidity of the elastic ring under study. The paper describes the improvement of both the design of the device and the method for determining the stiffness of the elastic ring of the damper using the specified measuring equipment. After making corrections, the obtained data on the scatter of the stiffness of the elastic ring are in good agreement with the analytical and numerical dependence, which makes it possible to use the data of the latter to refine the analytical methods in the future

As amaranth flour is gluten-free, it can be used only as a partial replacement of wheat flour for making yeast bread. Baking qualities of composite wheat-amaranth flour significantly depend on both the grin processing and the varietal characteristics of used amaranth grains. Studies on the baking properties of composite mixtures of wheat and amaranth flours are limited, and the effect of such flour on the bread freshness during storage is still unexplored. The research aim was to determine the impact of application of amaranth flour made of partially defatted amaranth grain on the bread quality, staleness, and the change of the structural and mechanical properties of bread crumbs during storage in particular. As a result of the study of structural and mechanical properties of fresh bread, change elasticity force of fresh bread F (t) from time t and tension of fresh bread σ (ε) from its relative deformation ε for various content of amaranth flour α were received. The dependence of the tension of fresh bread σ (ε) on its relative deformation ε was represented as elastic hysteresis. It was found that with increasing the content of amaranth flour, α the area of hysteresis decreases, namely, the static elastic hysteresis index. Consequently, the studies of changes in structural and mechanical properties of bread products with different amaranth content after 2 days, it was found that the tension of bread crumb at 25% strain σ (25%) and the modulus of elasticity E can increase 1.8-1.9 times, while the static elastic hysteresis S - 1.9-2.0 times. [ABSTRACT FROM AUTHOR]

The relevance of the paper is related to the search for new efficient technical solutions in the sphere of electric drives for oil pipeline valves based on using the hysteresis principle of electromechanical energy conversion and new hard magnetic materials. The main aim of the research is to reveal with the analysis of the hysteresis layer magnetization the teeth zone optimal geometry of the electromagnetic hysteresis clutch based on the Fe-Cr-Co alloy to obtain the maximum torque. The methods: experimental methods for studying the magnetic characteristics of magnetically hard materials using the original laboratory installations; simulation in the ANSYS MAXWELL, the theoretical methods of electromagnetic field analysis. The results. The authors have obtained and investigated torque dependences on the teeth zone geometric parameters for the clutches based on Fe-Cr-Co 22X15KA alloy. To value the hysteresis material efficiency, the authors introduced the hysteresis layer use coefficient according to the magnetic field tangential component. The model of the electromagnetic hysteresis clutch with fixed control winding, taking into account the parameters of the alloy of Fe-Cr-Co 22X15KA was developed in the ANSYS MAXWELL program. To obtain the maximum torque at the limited clutch sizes and mass the optimal teeth zone geometric dimensions were determined. It is concluded, that the pipeline shut-off valves electric drive with hysteresis clutch and induction motor due to the ease of implementation, the possibility of regulating and limiting the torque in the wide temperatures and rotation speeds range, can be considered as a promising alternative to electric drives with frequency control and thyristor regulators.

In the paper, the biological neural network models are analyzed with a purpose to solve the problems of segmentation and pattern recognition when applied to the bio-liquid facies obtained by the cuneiform dehydration method. The peculiarities of the facies’ patterns and the key steps of their digital processing are specified in the frame of the pattern recognition. Feasibility of neural network techniques for the different image data level digital processing is reviewed as well as for image segmentation. The real-life biological neural network architecture concept is described using the mechanisms of the electrical input-output membrane voltage and both induced and endogenic (spontaneous) activities of the neural clusters when spiking. The mechanism of spike initiation is described for metabotropic and ionotropic receptive clusters with the nature of environmental exciting impact specified. Also, the mathematical models of biological neural networks that comprise ot only functional nonlinearities but the hysteretic ones are analyzed and the reasons are given for preference of the mathematical model with delay differential equations is chosen providing its applicability for modeling a single neuron and neural network as well.

For the description of the hysteresis behavior of ferroelectrics/ferroelastics under complex multiaxial combined electrical and/or mechanical loading, a thermodynamically consistent microstructural model of a ferroelectroelastic material is proposed taking into account the presence and evolution of polar point defects. The model also takes into account multiphase composition (tetragonal, rhombohedral and orthorhombic phases and their mixtures), anisotropy of properties, domain structure, and dissipative motion of domain walls. The linear theory of the evolution of charged point defects is proposed based on the free energy of defects in the form of a quadratic form of the polarization vector and strain tensor of defects. The evolution equations of which are obtained on the base of the dissipation inequality. The cases of changing and unchanging (frozen) defects are considered. Their influence on switching processes is investigated. The dependence of the hysteresis loop shift (due intern bias field) on the parameters of the free energy of defects is shown. The mutual influence of crystallites in a polycrystal is taken into account by using the method of two-level finite element homogenization. Comparison of the computation results with experimental curves of dielectric, mechanical, and electromechanical hysteresis for polycrystalline piezoelectric PZT PIC-151, polycrystalline BaTiO3, single-crystal PMN-PZT and KTS doped with acceptor additives, showed a showed good agreement.

In order to study the effect of temperature changes on the dissipative properties of soils, a certain temperature function is introduced under the integral sign in the equation of the theory of heredity and at the same time takes into account the dependence of the elastic modulus on temperature. As a result, on the basis of experimental data on the thermal creep of soils, an expression was obtained for determining the hysteresis energy losses with periodic voltage changes depending on the temperature change. [ABSTRACT FROM AUTHOR]

In the article, an equipment and practical application of an automatic system (created by the authors) for measuring the ferroelectric hysteresis loops using the Atmega328 microcontroller have been considered. The modern approaches to the classical Sawyer – Tower circuit's application was analyzed, and practical need for such development was proven. The schematic diagram and description of the main device’s components were given. Test results on measuring the hysteresis loops in a barium titanate single crystal were presented, and they were compared with the data published earlier. Moreover, the results on measuring the ferroelectric hysteresis loops of an [110]-oriented 0.8Pb(Mb1/3Nb2/3)O3–0.2PbTiO3 single crystal in a temperature range of 120 –300 K at frequencies from 2 to 50 Hz were presented.

Copyright of Technical Diagnostics & Nondestructive Testing / Tekhnicheskaya Diagnostika I Nerazrushayushchiy Kontrol is the property of International Association Welding (Paton Publishing House) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Results of experimental determination of aerodynamic characteristics of different bodies at transonic Mach numbers of forward flows in conditions of oscillatory mode of motion with multiple amplitudes and frequencies f are given.

We develop and analyze the generalized version of the shallow lake economics model, built upon the initial version of the model as described in a seminal paper by Mäler et al. (2003). The model is able to simulate the coupled economic-ecological dynamics under conditions of the pronounced nonlinearity of the ecological (lake) module leading to hysteresis effects and irreversibility for certain values of model parameters. The decision making in the area of lake water management is parameterized by the social welfare function consisting of two terms: the utility originating from the economic activity in the surroundings of the lake (increasing with the anthropogenic loading on the lake), and the disutility originating from the pollution of the lake (increasing with the pollution level). From economic side, the problem is therefore to find a tradeoff between the level of economic activity in the surroundings of the lake and the pollution level. In the basic version of the model, the disutility related to pollution is quadratic in phosphorous concentration. We replace this quadratic disutility with a more general power low, and explore the sensitivity of the generalized model to its exponent. The numerical analysis performed suggests that the generalized model is quantitatively sensitive to varying the value of the exponent, yet structurally robust.

The relevance of the work is in need to obtain new data on the impact of dispersion medium composition on structural and mechanical properties of the wax-systems, treated in ultrasonic field. This will determine the optimal conditions for exposure to wax disperse systems, including oil, to reduce the viscosity-temperature characteristics and inhibiting process of sedimentation. The aim of the work is to determine the effect of dispersion medium composition on structural and mechanical properties and sedimentation of wax-model systems after ultrasonic treatment. The methods: rotary viscosimetry, pour point, liquid-adsorption chromatography, method of «cold finger», wax deposit, FT-IR spectroscopy, GC-MS. The results. The authors have studied the structural and mechanical properties and sedimentation of petroleum wax solutions in the decane and aviation kerosene TS-1 treated in the acoustic field. Viscosity, pour point, and energetic parameters of the petroleum wax solutions in decane increase at ultrasonic exposure. High alifacity of dispersion medium, which is characteristic for petroleum wax solution in decane, causes a reduction of aggregate and sedimentation stability and intensification of precipitation in high-paraffin crude oil systems after sonication. In composition of sediments allocated from the petroleum wax solutions, the content of n-alkanes C27-C32 increases. The aromatic compounds in the dispersion medium of the petroleum wax solution in TC-1 retard crystallization of paraffin hydrocarbons and decrease the amount of sediments, allocated from treated samples. In composition of these sediments the aromatic and naphthenic hydrocarbons, captured by paraffins during formation of disperse phase are concentrated. The experimental data show that the use of the petroleum wax solutions can adequately describe the behavior of high-paraffin crude oils in the acoustic field. Results. We defined the main complicating factors which influence the efficiency of rod pump operation. The analysis of the rod screw pumps repair causes shown that low quality of polished rods produced by the manufacturer, rod deviation from geometric parameters of different structures, hardness, chemical composition of rods (factory defect) are often the causes of breaks. Open threaded rod or polished rod was primarily due to insufficient torque screwing the threaded connection or a bend in the rod head. The breackage of polished rods mainly occur in the oil seal and due to fatigue voltage. The fatigue fracture occurs as a result of permanent deformation forces and temperature action. One of the main causes of the elastomer swelling is the maintenance with pressure at the reception of rod screw pumps below the saturation pressure. It leads to saturation of elastomer material with gases and rotor jamming in the stator which can turn into breakages of the rod string and polished rod.

The paper tackles functioning aspects of elastomeric center-coupler draft gears. For the time being such draft gears are the only shock absorbers responsible for safe and secure transportation of hazardous materials and high-value car-goes. The predecessor research works dealing with force pattern intrinsic to impact and compression failed to present the clean-cut description of pressure field structure within the draft gear chambers, thus making difficult mathematical modeling of such a complicated device. The authors of the described research managed to fill the indicated gap through use of up-to-date high-quality sensors capable of tracing pressure values up to 300 MPa. The center-coupler draft gear EPA-110 with crucial component in the form of double-chamber plunger assembly with a partition piston group was selected as a full-scale object of research. There are presented outcomes produced by experimental research and computations of the pressure values in the draft gear chambers in terms of different patterns of orifice holes used for quasi-static and dynamic testing. Also there are introduced new dependences to be used in calculations of force acting upon the draft gear and are provided rec-ommendations concerning introduction of amendments to the draft gear design and modification of its mathematical model.

Despite the fact that the eye represents a challenge for biomechanical research due to its size, over the last two decades, much data on ocular biomechanics were accumulated. Scleral and lamina cribrosa biomechanics contribute to our understanding of myopia and open-angle glaucoma; iris and trabecular meshwork biomechanics to that of angle-closure glaucoma; vitreous biomechanics to that of retinal detachment and ocular drug delivery; corneal biomechanics to that of keratoconus; and lens capsule biomechanics to that of cataract. This paper offers a general overview of recent advances in corneal, scleral, crystalline lens, and lamina cribrosa biomechanics and summarizes the results of experimental and clinical studies. Ocular biomechanics abnormalities affect etiology of many eye diseases. Ocular biomechanics plays an important role in the development of novel diagnostic methods, therapeutic and surgical procedures. Corneal biomechanics impacts etiology and pathogenesis of keratoconus as well as tonometry accuracy and explains corneal refractive surgery effect. Scleral biomechanics is associated with IOP and progressive myopia. Accommodative apparatus (ciliary body and crystalline lens) is an important anatomic physiological structure. Recent studies uncovered the causes of agerelated loss of accommodation as a result of lens involution. Optic nerve head abnormalities due to IOP fluctuations are the key factor of glaucomatous neuropathy. They are directly associated with ocular biomechanics as well.

Theoretical studies of the dynamics of a nonlinear oscillator with cubic and quadratic nonlinearities simultaneously excited by low- and high-frequency external forcing are presented. A new mechanism of the appearance of bistability and hysteresis due to such an interaction is discovered. This mechanism manifests as the bistability and hysteresis of tori formed in the oscillator phase space. A comparative analysis of the oscillator behavior under the resonant harmonic excitation and under the dual frequency excitation is made.

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper analyzes the impact of non-linear elements with characteristics with hysteresis on the stability of the closed systems, explains the causes of oscillations in a closed system in which no non-linear elements with hysteresis oscillation does not occur.

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Problems of Friction & Wear is the property of National Aviation University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The results of the experimental studies of the structural and phase state, magnetic and magnetoresistive properties of thin films of Ni-Fe-Co alloy with the initial concentration of components ?Ni = 40, ?Fe = 10, and ?Co = 50 at.% in the annealing temperature range of Δ?a = 300-1000 K are presented. It is shown that as-deposited alloy films have a two-phase structure fcc-Ni3Fe + hcp-Co. The fcc-phase with the lattice parameter of 0,354 nm, which corresponds to Ni-Fe-Co solid solution, is observed after heat treatment at 900 K. Thin films based on Ni-Fe and Co exhibit anisotropic magnetoresistance with the highest value (0,35%) observed in the perpendicular measurement geometry. The value of magnetoresistance tends to rise with increasing annealing temperature. The results of the magnetic and magnetoresistive measurements indicate the presence of the easy axis of magnetization in plane of the sample. [ABSTRACT FROM AUTHOR]

A vector hysteresis model for the symmetric magnetization cycle, based on a combination of fractional rational functions was proposed. The model explicitly expresses dependences of field strength from induction. The model is intended to be used with finite element method and represents the influence of the saturation of ferromagnetic on the magnitude of the magnetic field and its wave form in two orthogonal directions. The dependence of losses on the magnetic induction under condition of rotational magnetization is in good agreement with known experimental data. References 17, figures 5. [ABSTRACT FROM AUTHOR]

Principles of electric power generation by power supply systems based on self-excited electrical machines are presented in this paper. Functioning conditions of aircraft power supply systems were analyzed. Advantages and disadvantages of permanent magnet synchronous generators were revealed. Similarity of self-exciting processes in DC electrical machines -- induction and hysteresis synchronous ones -- is revealed. Block diagrams that show similarity of self-exciting processes in DC generator -- induction and hysteresis synchronous ones -- from the automatic control theory point of view are provided. It is shown that the controlled generation systems contained semiconductor converters are possible to be constructed. [ABSTRACT FROM AUTHOR]