Computational geometry

Quantum mechanics

Molecular absorption and emission bands dominate the visible, infrared, and submillimeter spectra of most objects with associated gas. These observations reveal a surprisingly rich array of molecular species and attest to a complex chemistry taking place in the harsh environment of the interstellar medium of galaxies. Molecules are truly everywhere and an important component of interstellar gas. This review surveys molecular observations in the various spectral windows and summarizes the chemical and physical processes involved in the formation and evolution of interstellar molecules. The rich organic inventory of space reflects the multitude of chemical processes involved that, on the one hand, build up molecules an atom at a time and, on the other hand, break down large molecules injected by stars to smaller fragments. Both this bottom-up and the trickle-down chemistry are reviewed. The emphasis is on understanding the characteristics of complex polycyclic aromatic hydrocarbon molecules and fullerenes and their role in chemistry as well as the intricate interaction of gas-phase ion-molecule and neutral-neutral reactions and the chemistry taking place on grain surfaces in dense clouds in setting the organic inventory of regions of star and planet formation and their implications for the chemical history of the Solar System. Many aspects of molecular astrophysics are illustrated with recent observations of the HIFI instrument on the Herschel Space Observatory.

https://cab.inta-csic.es/molecular_universe_2011/pressroomNew/tielensInterview.pdf

The molecular universe

Unmanned aerial vehicles (UAVs), or aerial drones, are an emerging technology with significant market potential. UAVs may lead to substantial cost savings in, for instance, monitoring of difficult-to-access infrastructure, spraying fields and performing surveillance in precision agriculture, as well as in deliveries of packages. In some applications, like disaster management, transport of medical supplies, or environmental monitoring, aerial drones may even help save lives. In this article, we provide a literature survey on optimization approaches to civil applications of UAVs. Our goal is to provide a fast point of entry into the topic for interested researchers and operations planning specialists. We describe the most promising aerial drone applications and outline characteristics of aerial drones relevant to operations planning. In this review of more than 200 articles, we provide insights into widespread and emerging modeling approaches. We conclude by suggesting promising directions for future research.

Optimization approaches for civil applications of unmanned aerial vehicles (UAVs) or aerial drones: A survey

Meteorology today : An introduction to weather, Climate, and the environment

Results from the most extensive study of the time-evolving dust structure around the prototype pinwheel nebula WR 104 are presented. Encompassing 11 epochs in three near-infrared filter bandpasses, a homogeneous imaging data set spanning more than 6 yr (or 10 orbits) is presented. Data were obtained from the highly successful Keck Aperture Masking Experiment, which can recover high-fidelity images at extremely high angular resolutions, revealing the geometry of the plume with unprecedented precision. Inferred properties for the (unresolved) underlying binary and wind system are orbital period -->241.5 ? 0.5 days and angular outflow velocity -->0.28 ? 0.02 mas day?1. An optically thin cavity of angular size -->13.3 ? 1.4 mas was found to lie between the central binary and the onset of the spiral dust plume. Rotational motion of the wind system induced by the binary orbit is found to have important ramifications: entanglement of the winds results in strong shock activity far downstream from the nose of the bow shock. The far greater fraction of the winds participating in the collision may play a key role in gas compression and the nucleation of dust at large radii from the central binary and shock stagnation point. Investigation of the effects of radiative braking points toward significant modifications of the simple hydrostatic colliding wind geometry, extending the relevance of this phenomenon to wider binary systems than previously considered. Limits placed on the maximum allowed orbital eccentricity of -->e 0.06 argue strongly for a prehistory of tidal circularization in this system. Finally, we discuss the implications of Earth's polar ( -->i 16?) vantage point onto a system likely to host supernova explosions at future epochs.

https://iopscience.iop.org/article/10.1086/527286/pdf

The Prototype Colliding-Wind Pinwheel WR 104

Soaring is the process of exploiting favorable wind conditions to extend flight duration. This paper presents an approach for simultaneously mapping and using a wind field for soaring with an unpowered aircraft. Previous research by the authors and others has addressed soaring in known wind fields. However, an adequate estimate of the wind field is required in order to generate energy-gain paths. Conversely, the exploration required to generate a useful map estimate requires energy. This work aims to address these problems simultaneously by attempting to maintain and improve a model-free wind map based on observations collected during the flight and to use the currently available map to generate energy-gain paths. Wind estimation is performed using Gaussian process regression. A path planner generates and selects paths based on energy efficiency and field exploration. The method is tested in simulation with wind fields consisting of single and multiple stationary thermal bubbles. The use of soaring flight with consistent improvement in map quality and accuracy is demonstrated in a number of scenarios.

Autonomous Exploration of a Wind Field with a Gliding Aircraft

Soaring is the process of gaining energy from the atmosphere in-flight using an aerodynamic free-flying platform. Dynamic soaring utilizes the energy available in vertical wind gradients and is commonly used by soaring birds. This research aims to develop a guidance and control strategy to utilize dynamic soaring for a fixed-wing gliding UAV. The basic strategies for dynamic soaring in vertical wind shear are explored and a simple piecewise trajectory based controller is developed to identify regions suitable for soaring and attempt traveling energy-neutral trajectories.

A guidance and control strategy for dynamic soaring with a gliding UAV

This paper presents a framework for energy-based path planning for a small xed-wing gliding aircraft. The dynamic equations of motion for a gliding aircraft are derived for a three degree of freedom (3DOF) longitudinal model and a six degree of freedom (6DOF) model. The mechanisms of atmospheric energy gain are explored and formulated as a path planning problem. An energy-based reward function is presented which attempts to maximise energy extracted from the atmosphere. This is tested using a Rapidly Exploring Random Tree-like (RRT-like) path planner which explores reachable states with a limited set of control inputs. The planner is tested with full knowledge of the wind eld for a thermal bubble and a horizontal shear layer. It is capable of generating energy-gain trajectories using both static and dynamic soaring. The method is also tested for a ight through a thermal using only local wind information with a limited planning horizon.

http://enu.kz/repository/2009/AIAA-2009-6112.pdf

Wind Energy Based Path Planning for a Small Gliding Unmanned Aerial Vehicle

An autonomous aircraft capable of utilising soaring flight in a dynamic wind field could considerably extend flight duration by limiting the use of on-board energy for propulsion. While soaring flight is relatively well understood for known wind, an autonomous soaring aircraft would have to generate paths based only on local observations of the wind made during the flight. This paper presents a method to simultaneously map and utilise a wind field using Gaussian process regression to generate a spatio-temporal map of the wind, and a path planning and dynamic target assignment algorithm to generate energy-gain paths from the current wind estimate. The planning architecture is tested in simulation for dynamic wind fields and shows consistent energy gain through exploration and exploitation of the wind environment.

Nicholas R. J. Lawrance

Papers

The Prototype Colliding-Wind Pinwheel WR 104

Autonomous Exploration of a Wind Field with a Gliding Aircraft

A guidance and control strategy for dynamic soaring with a gliding UAV

Wind Energy Based Path Planning for a Small Gliding Unmanned Aerial Vehicle

Path planning for autonomous soaring flight in dynamic wind fields