IN THE SEISMIC ACTIVITI OF THE AREA CHIRKEYIRGANAYSKAVA NODE SULAK CASCADE OF HPS

Показано, что заполнение и эксплуатация водохранилища Ирганайской ГЭС существенно не влияет на сейсмический режим исследуемой территории. В результате длительной эксплуатации водохранилища Чиркейской ГЭС (более 40 лет) изменились реологические свойства геологической среды и, соответственно, сейсмический режим, прилегающей к водохранилищу территории, что отразилось на величине угла наклона графика повторяемости It is shown that the filling and operation of reservoirs Irgnayskaya HPS does not significantly affect the seismic regime of the study area. As a result of prolonged operation of the reservoir Chirkeisk HPS (over 40 years) has changed theological properties of the geological environment and, accordingly, seismic regime adjacent to the reservoir site, which is reflected in the angle of the slope of the recurrence graph.

A numerical study of the rheological properties of suspensions of rigid, non-Brownian fibres

Using techniques developed in our previous publication (Mackaplow et al. 1994), we complete a comprehensive set of numerical simulations of the volume-averaged stress tensor in a suspension of rigid, non-Brownian slender fibres at zero Reynolds number. In our problem formulation, we use slender-body theory to develop a set of integral equations to describe the interfibre hydrodynamic interactions at all orders. These integral equations are solved for a large number of interacting fibres in a periodically extended box. The simulations thus developed are an accurate representation of the suspensions at concentrations up to and including the semidilute regime. Thus, large changes in the suspensions properties can be obtained. The Theological properties of suspensions with concentrations ranging from the dilute regime, through the dilute/semi-dilute transition, and into the semi-dilute regime, are surprisingly well predicted by a dilute theory that takes into account two-body interactions. The accuracy of our simulations is verified by their ability to reproduce published suspension extensional and shear viscosity data for a variety of fibre aspect ratios and orientation distributions, as well as a wide range of suspension concentrations.

Simulated Non-Newtonian Lubricant Behaviour under Extreme Conditions

Equilibrium and non-equilibrium molecular dynamics techniques are used to simulate a molecular liquid (n-hexadecane) at extreme physical conditions (high temperatures, pressures and shear rates), typical of those encountered in many elastohydrodynamic lubrication applications, and to study the effects of pressure and temperature on the calculated theological properties. Pressure and temperature effects are found to be more pronounced at low shear rates than at high shear rates, where the non-Newtonian behaviour is dominated by the strong external kinematic effects. The observed non-Newtonian behaviour of the pressure and temperature coefficients of viscosity and the variation of certain molecular geometric functions calculated to assist the microscopic understanding are combined to provide a possible explanation for the phenomenon of limiting shear stress under elastohydrodynamic lubrication conditions. Further implications for the behaviour of lubricant-like molecules in practical applications are also discussed.

Novel Ultrasonic Technology for Devulcanization of Waste Rubbers

A novel patented process and several reactors have been developed for devulcanization of waste rubbers. The technology is based on the use of the high power ultrasonics. The ultrasonic waves of certain levels in the presence of pressure and heat rapidly break up the three-dimensional network in crosslinked rubbers. The devulcanized rubber can be reprocessed, shaped and revulcanized in much the same way as a virgin rubber. The first laboratory reactor has been scaled up to pilot-plant level by the National Feedscrew and Machining, Inc. Various devulcanization experiments were carried out with model styrene-butadiene rubber (SBR) and with ground rubber tire (GRT). Curing behavior, Theological properties, and structural characteristics of rubbers devulcanized at various processing conditions were studied, as well as mechanical properties of revulcanized rubber samples. A possible mechanism of the devulcanization is discussed. The performed measurements indicate that the rubbers are partially devulcanized, and the devulcanization process is accompanied by certain degradation of the macromolecular chains. In spite of these observations, the processing conditions are identified at which the retention of the mechanical properties is found to be good. A further work is in progress to find the optimal conditions of devulcanization and to improve the selectivity of the process towards breaking up the chemical network only.

Microstructure and Flow Behaviior of Fresh Cement Paste

Characteristics of aqueous cement suspensions and the packing nature during setting were investigated as keys controlling the microstructure and density of a cement paste. The theological properties of the paste were studied as functions of hydration and setting; these properties are influenced by a variety of external factors, which are discussed. The objective of this paper is to sketch a new atomistic approach to a group of rheological phenomena which are as interesting from a scientific viewpoint as they are important for technology. The experiments were carried out by a HAAKE rheometer and an acoustic ultrasonic system. At different flow state, the acoustic emission signal generated from micro-structure is transformed due to wave propagation and due to the transducer response. The scientific information obtained through this study is expected to contribute the establishment of concept of setting processing. The measurements of flow properties relating to flocculation and coagulation were evaluated with respect to the effects of processing conditions on structure development in cement paste.

Rotation of small fluorophores in cell cytoplasm measured by confocal anisotropy imaging and picosecond microfluorimetry

The Theological properties of cell cytoplasm are of importance for a number of intracellular processes including diffusion-limited enzyme reactions, intracellular vesicle trafficking, solute transport and cell motility. A wide range of cytoplasmic viscosities have been reported from fluorescence anisotropy, photobleaching recovery, tracer diffusion and electron spin resonance methods. To examine the viscosity of the fluid space between macromolecules and cytoskeletal structures in intact cells, the time-resolved picosecond motion of small fluorophores was measured. Unlike previous methods, measurements of time-resolved fluorophore motion are not confounded by probe binding to and restriction by intracellular structures.Picosecond anisotropy decay was measured by multi-harmonic phase modulation microfluorimetry. The excitation source was a 9 watt argon laser which was impulse modulated by a Pockel's cell. Light was polarized and focused onto a < 1 μ spot on a fluorescently labelled cell. Emitted light was filtered and detected by a phase sensitive photomultiplier through a rotatable analyzing polarizer. Thirty to forty pairs of differential modulation amplitudes and phase angles were collected in parallel over the frequency range 5 to 250 MHz.

Polyolefin Thermoplastic Elastomer Blends

Thermoplastic elastomers based on blends of polyolefins are an important family of engineering materials. Their importance arises from a combination of rubbery properties along with their thermoplastic nature in contrast to thermoset elastomers. The development of polyolefin thermoplastic elastomer blends follows somewhat that of thermoplastic elastomers based on block copolymers such as styrene-butadiene-styrene triblock copolymer and multisegmented polyurethane thermoplastic elastomers which were instrumental in showing the utility of thermoplastic processing methods. Polyoleflns are based on coordination catalysts that do not easily lend themselves to block or multisegmented copolymer synthesis. However, since polyolefins have many important attributes favorable to useful elastomeric systems, there was considerable incentive to produce thermoplastic elastomers based on simple α-olefins by some means. Low density, chemical stability, weather resistance, and ability to accept compounding ingredients without compromising physical properties are highly desirable. These considerations led to the development of polyolefin thermoplastic elastomer blends, and two types are now widely used: blends of ethylene-propylene rubber (EPM) with polypropylene (PP) and blends of EPDM and PP in which the rubber phase is highly crosslinked. This article reviews the nature of these blends. Both physical and Theological properties are very dependent on the morphology and crosslink density of the blend system. Moreover, the usefulness of practical systems depends extensively on compounding technology based on added plasticizers and fillers.

Recent Advances in the Molecular Aspects of Polymer Viscoelasticity

Polymers are materials worthy of study both because of their unique properties and because of their common occurrence in industrial products and in biological systems. The attention focused on them has been rewarded by an increased amount of success in establishing the relationships between their complex physical properties and their molecular structure. This article is concerned with a particular aspect of these investigations, the Theological properties of polymers in the liquid state. There has been an increase of activity in this field during the last fifteen years, which is the period covered by this review. The interested reader is directed to earlier reviews and articles that discuss related subject material. We begin with a qualitative description of a rheological experiment which demonstrates the mechanical response of polymers as well as introduces some of the essential phenomena which need to be explained. When a small shearing force is applied to a high-molecular-weight polymer liquid, it deforms rapidly. At first, the material acts like a rubbery solid and, if the stress is quickly removed, it essentially recovers its original shape. The constant relating the applied stress, σ, and the initial deformation or strain, γ, is the elastic modulus, GN, often referred to as the plateau modulus.