Evolving Philosophies on Autonomous Obstacle/Collision Avoidance of Unmanned Aerial Vehicles

Much of the benefits of deploying unmanned aerial vehicles can be derived from autonomous missions. For such missions, however, sense-and-avoid capability (i.e., the ability to detect potential collisions and avoid them) is a critical requirement. Collision avoidance can be broadly classified into global and local path-planning algorithms, both of which need to be addressed in a successful mission. Whereas global path planning (which is mainly done offline) broadly lays out a path that reaches the goal point, local collision-avoidance algorithms, which are usually fast, reactive, and carried out online, ensure safety of the vehicle from unexpected and unforeseen obstacles/collisions. Even though many techniques for both global and local collision avoidance have been proposed in the recent literature, there is a great interest around the globe to solve this important problem comprehensively and efficiently and such techniques are still evolving. This paper presents a brief overview of a few promising and evolving ideas on collision avoidance for unmanned aerial vehicles, with a preferential bias toward local collision avoidance.

Toeplitz Operators with Special Symbols on Segal-Bargmann Spaces

We study the boundedness of Toeplitz operators on Segal-Bargmann spaces in various contexts. Using Gutzmer's formula as the main tool we identify symbols for which the Toeplitz operators correspond to Fourier multipliers on the underlying groups. The spaces considered include Fock spaces, Hermite and twisted Bergman spaces and Segal-Bargmann spaces associated to Riemannian symmetric spaces of compact type.

Injection cooling of blunt bodies flying at high Mach numbers

A study of transpiration cooling of blunt bodies such as a hemicylinder is made by solving Navier-Stokes equations. An upwind, implicit time-marching code is developed for this purpose. The study is conducted for both perfect-gas and real-gas (chemical equilibrium) flows. Investigations are carried out for a special wall condition that is referred to as no heat flow into the wall condition. The effects of air injection on wall temperature are analyzed. Analyses are carried out for Mach numbers ranging between 6-10 and Reynolds numbers ranging between 10(6)-10(7). Studies are made for spatially constant as well as spatially varying mass injection rate distributions, White cold air injection reduces the wall temperature substantially, transpiration cooling is relatively less effective when the gas is in chemical equilibrium.

A profile of adenosine triphosphate

An attempt is made to draw a profile of adenosine triphosphate (ATP) and to project its many actions. The amazing versatility of its participation in a number of synthetic reactions lies in the oligophosphate structure. Many proteins that use ATP have conserved binding 'P-loop' but this gives no clue what makes it so special. The energy transducing reactions leading to synthesis of the terminal phosphodiester had at least three strategies. Of these, direct dehydration and transfer of inorganic phosphate using respiratory energy operate through mechano-coupling in a multisubunit protein. This tripartite, knob-stalk-base structure provides a novel mechanism of rotational catalysis and the tiniest molecular motor, All the reactions occur in concert with no sign of energized chemical intermediate. With the new knowledge on the crystal structure of F-1-ATPase, proton translocation needs a relook. An alternative perspective is emerging on energy being received and stored in polypeptide structure by breaking hydrogen bonds. Membrane serves the purpose of mobilizing the constituent proteins and also as a potential energy carrier of proteins with little loss of energy.