Academic literature on the topic 'Schwinger Pair Production Mechanism'

The chapter is focused on state of the art of materials for adsorptive heat energy conversion basic principles for substantiation of working pair choice. Types of heat storage materials based on heat storage mechanism were compared. Sensible heat mechanism of thermal energy is based on increasing the temperature of the material. Phase-change mechanism of heat energy storage concerns with alternating reversible processes of phase-changing. As a rule, they are mainly melting-crystallization. Thermo-chemical heat energy storage mechanism is based on reversible chemical reactions. Limitations of conventional sensible heat storage are shown to lowest density of heat energy storage determined by sensible heat of materials, which led to large mass storage units and additional needs of large areas and building volumes, calculated according to heat storage density, constant changing the temperature when discharged, the need for a large overheating of heat storage media. The main defects of phase-change materials are instability of properties of heat-accumulating substances in multiple cycles of crystallization – melting, degradation in time, corrosion activity, the need for developed surfaces of heat exchange and environmental danger. Commercilisation of thermal chemical storage materials is strongly limited by high operating temperatures of thermal chemical storage materials, which are unacceptable for systems of district heating and decentralized heat supply due to sanitary regulations, impropriety for multifold cycling because of irreversibility of a wide range of chemical reactions. Perspective of adsorptive heat energy storage and conversion is shown. Interval of operating temperatures and heat storage density of conventional adsorptive materials are shown to be intermediate between phase-change and thermal chemical heat storage materials. Properties of probable adsorptive heat storage materials were analysed according with literary data. Low adsorptive capacity of conventional adsorbents results in low heat of adsorption and heat energy storage density. Salts forming crystalline hydrate occur to exhibit rather high energy storage density of 1.9–2.7 GJ/m3 of crystalline hydrate, but their application is strongly inhibited not only by physical and chemical instability along with the corrosive activity of these salts at high temperatures, but instability in multifold cycling, degradation in time, and an underdeveloped heat exchange surface. As engineering solution, modification of conventional adsorbents with salt can be considered. Composites ‘salt inside porous matrix' is shown to be promising alternative to conventional adsorbents. Main advantages of these materials are low regeneration temperature and high adsorptive capacity. Crucial impediments of industrial introduction of composite adsorbents ‘salt inside porous matrix' is shown to be complex technology of their production based on rather expensive dry and wet impregnation of porous media by crystalline hydrate solutions. As an alternative, sol gel method for obtaining composite adsorbents ‘silica gel – crystalline hydrate' developed by authors is suggested. The adsorption properties of the obtained composite adsorbents ‘silica gel – sodium sulphate' and ‘silica gel – sodium acetate' are shown to be non-linear combinations of characteristics of silica gel and massive salt. The key distinction of kinetics of adsorption of water vapor with massive salts and composites obtained with sol gel method is shown to be difference limitative stage of process. The adsorption of water with massive crystalline hydrates is shown to be complicated by kinetic limitations. For composite adsorbents limiting stage is water transport through the pore system. Composites ‘slilica gel – crystalline hydrate' are shown to be a promising material for adsorptive heat energy storage and conversion.

An experimental study on the production and development of streamwise vortices in a compressor cascade is reported. At four locations inside and one location outside the blade passage, the mean velocity components, three turbulent intensities and three Reynolds stresses were measured with a “x” hot wire probe. The results obtained describe the flow structure in the corner between the end-wall and blade suction surface in detail. Besides a passage vortex within the passage, there exist a shed corner vortex pair and a secondary vortex pair in the corner. The characteristics of two vortex pairs w

Abstract Aircraft being capable of Vertical Take-off and Landing (VTOL) and hover are increasingly emerging in various critical and routine applications. Rescue missions in roads and environmental disasters, observance and monitoring-based carriers, surveillance and payload carriage in environments that require high maneuverability and controllability are just a few examples in which this type of aircraft is essential. Helicopters are the most typical aircraft in this kind, but concerning the thrusting mechanism, several alternatives are yet in hand. The tendency to equip aircraft with cycloid

Abstract Surfactant selection is important for oil recovery in a hydraulically fractured reservoir. Two primary mechanisms, ion-pair coupling (cleaning) between surfactant and hydrocarbon and surfactant adsorption onto the rock surface (coating), were previously suggested to explain how surfactants can alter rock wettability, thus improving oil production. Because of the electrostatic interaction, acidic compounds in the oil tend to be adsorbed onto rock surface that is positively charged; whereas basic compounds are preferentially attracted to rock surface that is negatively charged. It has b

In the U.S., more than 27,000 catastrophic and fatal injuries occur annually in rollover crashes. Due to the incidence and severity of injuries in rollover crashes, a strategy for injury mitigation is dynamic compliance testing with dummy-occupied vehicles and occupant protection requirements, similar to that required for frontal and side impacts. Presently, there are dynamic vehicle rollover test devices like the Controlled Rollover Impact System and the Jordan Rollover System that realistically recreate real-world rollover crash scenarios. However, the Hybrid III dummy, which is considered t