Optimal Jammer Placement in UAV-assisted Relay Networks

We consider the relaying application of unmanned aerial vehicles (UAVs), in which UAVs are placed between two transceivers (TRs) to increase the throughput of the system. Instead of studying the placement of UAVs as pursued in existing literature, we focus on investigating the placement of a jammer or a major source of interference on the ground to effectively degrade the performance of the system, which is measured by the maximum achievable data rate of transmission between the TRs. We demonstrate that the optimal placement of the jammer is in general a non-convex optimization problem, for which obtaining the solution directly is intractable. Afterward, using the inherent characteristics of the signal-to-interference ratio (SIR) expressions, we propose a tractable approach to find the optimal position of the jammer. Based on the proposed approach, we investigate the optimal positioning of the jammer in both dual-hop and multi-hop UAV relaying settings. Numerical simulations are provided to evaluate the performance of our proposed method.Comment: 6 pages, 6 figure

Industrial Air Pollution Control

Ambient air contaminants have different adverse effects on human health, environment, and structures. Some pollutions are more toxic and have unfavorable effects on workers’ and public health, for example, cyanide/isocyanide vapor produced in some processes or in burning of polyurethane compounds, which is a toxic gas that can kill or cause harms impossible to reverse. It is so necessary that air pollutants will be controlled and treatment will be provided for the workers and public who are exposed or exhausted to the environment. Industrial ventilation (general ventilation, dilution ventilation, and local exhaust ventilation) is an appropriate system to control indoor air pollutions. Local exhaust ventilation (LEV) has different segments such as hoods, fittings, collectors (air cleaners), stacks, and fans that could collect and treat indoor and outdoor air contaminants. Each well-designed segment of a local exhaust ventilation is a vital subject that can cause an appropriate or inappropriate performance of systems. A well-designed LEV can lead to obtain a high efficiency level of pollution removal and minimum exposure (workers, public, and environment) to pollutants and save costs and energy

Oxygen Exosphere of Mars: Evidence from Pickup Ions Measured by MAVEN

Mars possesses a hot oxygen exosphere that extends out to several Martian radii. The main source for populating this extended exosphere is the dissociative recombination of molecular oxygen ions with electrons in the Mars ionosphere. The dissociative recombination reaction creates two hot oxygen atoms that can gain energies above the escape energy at Mars and escape from the planet. Oxygen loss through this photochemical reaction is thought to be one of the main mechanisms of atmosphere escape at Mars, leading to the disappearance of water on the surface. In this work the hot oxygen exosphere of Mars is modeled using a two-stream/Liouville approach as well as a Monte-Carlo simulation. The modeled exosphere is used in a pickup ion simulation to predict the flux of energetic oxygen pickup ions at Mars. The pickup ions are created via ionization of neutral exospheric oxygen atoms through photo-ionization, charge exchange with solar wind protons, and electron impact ionization. Once ionized, the pickup ions are accelerated by the solar wind motional electric field to high energies, thus detectable by spacecraft instruments. The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft arrived at Mars in September of 2014 and has been taking measurements in the upper atmosphere of Mars, with the goal of determining the drivers and rates of atmospheric escape. In this work comparisons are made between the pickup ion model results and the MAVEN data from the SEP (Solar Energetic Particle) and SWIA (Solar Wind Ion Analyzer) instruments. It is shown that these model-data comparisons can be used to constrain the hot oxygen exospheric densities and the associated escape rates of oxygen from Mars