Distributed collision avoidance for autonomous vehicles: World automata representation

The automatic control of interacting autonomous vehicles (AVs) is one of the problems that engineers are currently trying to solve. The present paper deals with the design of local control laws governing the movement and collision avoidance of such groups of AVs, enforcing the safeness of the operations as well as task completions. This problem is inspired by the automation of a container terminal where each AV executes tasks assigned by a supervisor. A task involves moving an AV from an assigned origin to an assigned destination by a given deadline. The constraints imposed by the bounded workspace (a long and narrow quay in the container terminal example), the deadlines assigned to each task, and the uncertainty in the detection and communication make the problem difficult to solve in a centralized way. Therefore a distributed control approach is preferred with a local control agent in each AV adjusting its trajectory, so that its task is completed without collisions. By applying a fixed set of priority rules the computational complexity for each agent is reduced compared to the centralized case. Whenever an AV detects a possible conflict, i.e. the estimated position of another AV within the detection range, it must adjust its own speed and trajectory in order to avoid a future collision, reducing the number of cases where a supervisor has to intervene in order to resolve conflicts that degenerate in dead-locks. The modelling and validation of the system is performed by using the world automata theory

Texture Formation in Polycrystalline Thin Films of All Inorganic Lead Halide Perovskite

Controlling grain orientations within polycrystalline all inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits; however, the forces governing texture formation are ambiguous. Using synchrotron X ray diffraction, mesostructure formation within polycrystalline CsPbI2.85Br0.15 powders as they cool from a high temperature cubic perovskite alpha phase is reported. Tetragonal distortions beta phase trigger preferential crystallographic alignment within polycrystalline ensembles, a feature that is suggested here to be coordinated across multiple neighboring grains via interfacial forces that select for certain lattice distortions over others. External anisotropy is then imposed on polycrystalline thin films of orthorhombic gamma phase CsPbI3 xBrx perovskite via substrate clamping, revealing two fundamental uniaxial texture formations; i I rich films possess orthorhombic like texture lt;100 gt; out of plane; lt;010 gt; and lt;001 gt; in plane , while ii Br rich films form tetragonal like texture lt;110 gt; out of plane; lt;110 gt; and lt;001 gt; in plane . In contrast to relatively uninfluential factors like the choice of substrate, film thickness, and annealing temperature, Br incorporation modifies the gamma CsPbI3 xBrx crystal structure by reducing the orthorhombic lattice distortion making it more tetragonal like and governs the formation of the different, energetically favored textures within polycrystalline thin film

Drain current modulation in a nanoscale field-effect-transistor channel by single dopant implantation

We demonstrate single dopant implantation into the channel of a silicon nanoscale metal-oxide-semiconductor field-effect-transistor. This is achieved by monitoring the drain current modulation during ion irradiation. Deterministic doping is crucial for overcoming dopant number variability in present nanoscale devices and for exploiting single atom degrees of freedom. The two main ion stopping processes that induce drain current modulation are examined. We employ 500 keV He ions, in which electronic stopping is dominant, leading to discrete increases in drain current and 14 keV P dopants for which nuclear stopping is dominant leading to discrete decreases in drain current.Kavli Institute of NanoscienceApplied Science

Single Ion Implantation into Si-Based Devices

Deterministic doping is crucial for overcoming dopant number variability in present nano-scale devices and for exploiting single atom degrees of freedom. The development of determinisitic doping schemes is required. Here, two approaches to the detection of single ion impact events in Si-based devices are reviewed. The first is via specialized PiN structures where ions are directed onto a target area around which a field effect transistor can be formed. The second approach involves monitoring the drain current modulation during ion irradiation. We investigate the detection of both high energy He+ and 14 keV P+ dopants. The stopping of these ions is dominated by ionization and nuclear collisions, respectively. The optimization of the implant energy for a particular device and post-implantation processing are also briefly considered.QN/Quantum NanoscienceApplied Science