Viscous dark energy accretion activities : sonic speed, angular momentum and Mach number studies

In this present article, we study different accretion properties regarding viscous accretion of dark energy. Modified Chaplygin gas is chosen as the dark energy candidate. Viscosity is encountered with the help of Shakura–Sunyaev viscosity parameter. We study sonic speed vs radial distance curves. We compare between adiabatic and dark energy dominated cases and follow that sonic speed falls as we go nearer to the central gravitating object. As viscosity is imposed, a threshold drop in accretion sonic speed is followed. Average rate of fall in accretion sonic speed is increased with black hole’s spin. This is signifying that this kind of accretion is weakening the overall matter/energy infall. Specific angular momentum to Keplerian angular momentum ratio is found to fall as we go far from the black hole. Accretion Mach number turns high as we go towards the inner region and high wind Mach number is not allowed as we are going out. Combining, we conclude that the system weakens the feeding process of accretion.

Numerical Study on Thermal Choke Behaviors Driven by Various Rocket Operations in an RBCC Engine in Ramjet Mode

Thermal choke is commonly employed in a fixed geometry RBCC combustor to eliminate the need for physically variable exit geometry. This paper proposed detailed numerical studies based on a two-dimensional integration model to characterize thermal choke behaviors driven by various embedded rocket operations in an RBCC engine at Mach 4 in ramjet mode. The influences of different embedded rocket operations as well as the corresponding secondary fuel injection adjustment on thermal choke generation process, the related thermal throat feature, and the engine performance are analyzed. Operations of embedded rocket bring significant effects on the thermal choke behaviors: (1) the thermal throat feature becomes much more irregular influenced by the rocket plume; (2) the occupancy range in the combustor is significantly lengthened; (3) the asynchrony of the flow in different regions accelerating to sonic speed becomes much more significant; (4) as the rocket throttling ratio decreases, the thermal choke position constantly moves upstream integrally, and the heated flow in the top region that is directly affected by the rocket plume reaches sonic speed more rapidly. Finally, we can conclude that appropriate secondary fuel injection adjustment can provide a higher integration thrust for the RBCC engine with the embedded rocket operating, while the thermal choke is stably controlled, and the increased heat release and combustion pressure are well balanced by the variations of pre-combustion shocks in the inlet isolator.

Dynamic Intelligent Systems Based on High-Speed Vision

This paper presents an overview of the high-speed vision system that the authors have been developing, and its applications. First, examples of high-speed vision are presented, and image-related technologies are described. Next, we describe the use of vision systems to track flying objects at sonic speed. Finally, we present high-speed robotic systems that use high-speed vision for robotic control. Descriptions of the tasks that employ high-speed robots center on manipulation, bipedal running, and human-robot cooperation.