Recently Abramowicz and Bajtlik (arXiv:0905.2428 (2009)) have studied the twin paradox in Schwarzschild spacetime. Considering circular motion they showed that the twin with a non-vanishing 4-acceleration is older than his brother at the reunion and argued that, in spaces that are asymptotically Minkowskian, there exists an absolute standard of rest determining which twin is the oldest at the r...

Co-rotating twin-screw extruders are widely used by polymer materials producers and compounders due to a number of interesting constructive and functional features. In fact, a broad range of polymer systems can be prepared / processed by adjusting adequately the operating conditions (output, screw speed and barrel temperature profile) and the screws geometry/configuration. This work presents a ...

This work aims at selecting the operating conditions and designing screws that optimize the performance of single-screw and co-rotating twin-screw extruders, which are machines widely used by the polymer processing industry. A special MOEA, denoted as Reduced Pareto Set Genetic Algorithm, RPSGAe, is presented and used to solve these multiobjective combinatorial problems. Twin screw design is fo...

This paper investigates the thermal fluid-flow transport phenomena in an axially rotating passage in which twin concentric orifices of different radii are installed. Emphasis is placed on the effects of pipe rotation and orifice configuration on the flow and thermal fields, i.e. both the formation of vena contracta and the heattransfer performance behind each orifice. The governing equations ar...

Centrifugal compressors are widely used in many industrial applications because of their advantages. However, these turbomachines suffer at a low-flow rate from instabilities, such as rotating stall and surge. That leads to operational failure, pressure fluctuations vibrations the thorough system. Many mechanical solutions minimize instabilities expand operating range towards rates like active ...

the effect of impact modifier on creep behavior of wood flour- recycled polypropylene composites has been evaluated in this work. for this purpose, impact modifier (ethylene vinyl acetate) and recycled polypropylene were mixed with wood flour (50/50% w/w) as well as the impact modifier (0, 3%, 6% and 9%) by a counter-rotating twin-screw extruder to manufacture the wood flour- recycled polypropy...

Abstract To improve the utilization rate of tidal current energy, Twin Half-rotating Impeller Tidal Turbine(THITT), a new type turbine was proposed based on half-rotating impeller(HRI) which lift-resistance compound impeller, and its virtual prototype established. By changing way impeller rotated, two kinds CFD models were established taken into Xflow to calculate. The differences in their velo...

Simulation results for mixing of two different polymers in a co-rotating twin-screw extruder are presented. Velocity distribution predicted by a threedimensional simulation of the flow is used to predict the change in the spatial distribution of initially segregated particles as well as the reduction in radius due to erosion. The predicted particle distribution is used to estimate the increase ...