FD-TD calculation with composite materials. Application to C160 aircraft measurements

In a frequency domain in which a material thickness is smaller than the skin depth, a formalism based on the sheet impedance concept was developed and introduced in the FD-TD (finite difference-time domain) code ALICE. The predictive capabilities of the 3D code was evaluated by comparison to analytical and experimental data. The following subject areas are covered: low frequency electromagnetic penetration of loaded apertures; FD-TD modeling; and in-flight experiment modeling

Development of Adaptive Tilt Tracker that Utilizes QUAD-cell Detector to Track Extended Objects

Atmospheric turbulence causes tilt distortion that requires telescopes to track and remove image jitter effects. This research develops an adaptive tilt tracking system to measure and compensate for centroid gain volatility while tracking extended objects. The adaptive tracker counteracts deviations in tilt measurement and correction, due to unintended centroid gain changes. Non-adaptive trackers experience sub-optimal bandwidths and possible instabilities. The adaptive tracker utilizes a quadrant (QUAD) cell tilt detector to measure tilt distortion and its centroid gain relates measured intensity imbalances amongst the four cells to tilt distortion. Additionally, this gain becomes a random variable as it is determined by random image spot characteristics. The tracked LEO object and atmospheric seeing govern spot characteristics. This research develops an innovative methodology that rotates the LEO object\u27s image to create a more favorable intensity distribution for the QUAD-cell. Along with image rotation, an adaptive gain term yields significant improvements in QUAD-cell measurement performance, up to 91% for the simulated tilt processes. Using the image rotation and adaptive gain methodology, this research realizes an adaptive tilt tracker model that dithers the fast steering mirror to detect non-optimal centroid gains. Results show the adaptive tracker effectively counteracts centroid-gain deviations

Plasma density measurements using chirped pulse broad-band Raman amplification

Stimulated Raman backscattering is used as a non-destructive method to determine the density of plasma media at localized positions in space and time. By colliding two counter-propagating, ultra-short laser pulses with a spectral bandwidth larger than twice the plasma frequency, amplification occurs at the Stokes wavelengths, which results in regions of gain and loss separated by twice the plasma frequency, from which the plasma density can be deduced. By varying the relative delay between the laser pulses, and therefore the position and timing of the interaction, the spatio-temporal distribution of the plasma density can be mapped out

Chirped pulse Raman amplification in plasma: high gain measurements

High power short pulse lasers are usually based on chirped pulse amplification (CPA), where a frequency chirped and temporarily stretched ``seed'' pulse is amplified by a broad-bandwidth solid state medium, which is usually pumped by a monochromatic ``pump'' laser. Here, we demonstrate the feasibility of using chirped pulse Raman amplification (CPRA) as a means of amplifying short pulses in plasma. In this scheme, a short seed pulse is amplified by a stretched and chirped pump pulse through Raman backscattering in a plasma channel. Unlike conventional CPA, each spectral component of the seed is amplified at different longitudinal positions determined by the resonance of the seed, pump and plasma wave, which excites a density echelon that acts as a "chirped'" mirror and simultaneously backscatters and compresses the pump. Experimental evidence shows that it has potential as an ultra-broad bandwidth linear amplifier which dispenses with the need for large compressor gratings

Challenges and opportunities of centrifugal microfluidics for extreme point-of-care testing

The advantages offered by centrifugal microfluidic systems have encouraged its rapid adaptation in the fields of in vitro diagnostics, clinical chemistry, immunoassays, and nucleic acid tests. Centrifugal microfluidic devices are currently used in both clinical and point-of-care settings. Recent studies have shown that this new diagnostic platform could be potentially used in extreme point-of-care settings like remote villages in the Indian subcontinent and in Africa. Several technological inventions have decentralized diagnostics in developing countries; however, very few microfluidic technologies have been successful in meeting the demand. By identifying the finest difference between the point-of-care testing and extreme point-of-care infrastructure, this review captures the evolving diagnostic needs of developing countries paired with infrastructural challenges with technological hurdles to healthcare delivery in extreme point-of-care settings. In particular, the requirements for making centrifugal diagnostic devices viable in developing countries are discussed based on a detailed analysis of the demands in different clinical settings including the distinctive needs of extreme point-of-care settings.ope

An investigation into predator-prey systems

This paper looked at how to obtain quantitative information about the behaviour of Predator-Prey models using analytical methods, we look at how to solve the Lotka-Volterra model analytically, analysed the stability and behaviour of the critical points of a bounded Lotka-Volterra model and the Holling-Tanner model and how to look for Hopf bifurcation and limit cycles in the Holling-Tanner model. We have also compared a variety of numerical methods used to solve the predator-prey models. It has also used these results to validate our ndings from our analytical analysis

Characterization of Surface Geology and Hydrogeology in the Upper Ulua River Basin, Honduras

This research includes a hydrogeologic assessment in and around La Union, Honduras to determine the contribution of groundwater to the surface water system and understand the geological control of groundwater storage and movement. Field methods were employed and focused on spring characterization, geochemical signatures, and structural data. Field data was gathered, and locations determined using cellular-integrated GPS signal and the Fulcrum mapping software mobile application. During the summer of 2017, data on 111 geologic points and 34 water points were collected to understand the hydrogeology of the region. Streams and springs were monitored for pH, flow characteristics and conductance as a measure of total-dissolved-solids (TDS). TDS ranged from 22.6 to 485 mg/L with higher values indicating groundwater influx into the surface system. In comparison, lower TDS values are attributed to runoff. Structural information was collected using a Brunton transit compass for strike and dip of lithologic contacts. Structural trends include strikes around 240 degrees, dip direction and approximate magnitudes at 330 and 40 degrees, respectively. Geologic data indicate significant structural deformation, supportive of tectonic activity in the region. For many of the springs in this area, the data can be used to interpret that water is stored in the Jaitique Formation as a perched aquifer controlled by stratigraphy and structure. The groundwater moves down dip through secondary porosity in the Jaitique Formation until it comes into contact with the Lower Valle de Angeles. This Lower Valle de Angeles unit acts as an aquiclude preventing percolation into the ground and resulting in springs at the surface