LOUIS University of Alabama in Huntsville
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British Repatriation of the Parthenon Marbles
Get PDFhttps://louis.uah.edu/honors-399/1011/thumbnail.jp
Creating Instructional Materials for Els: The Impact of Climate Change on the Enviroment
Get PDFhttps://louis.uah.edu/rceu-hcr/1461/thumbnail.jp
Characterization of Single Bounce Ghost Rays in MaGIXS-2 Ground Calibration Using Ray-Tracing Simulation
Get PDFhttps://louis.uah.edu/rceu-hcr/1484/thumbnail.jp
Characterization and analytical prediction of the effective elastic modulus in additively manufactured body-centered cubic lattice structures
Get PDFAdvancements in metal additive manufacturing have enabled the production of metal lattice structures. The customizability of the lattice topology offers the potential to yield lightweight materials with highly tailored thermal and mechanical properties. By building on well-established models of other cellular solids such as metal foams, the intricate structural behavior of these lattices is simplified to effective values for key mechanical properties which are given as a function of the relative density of the lattice as well as certain material and lattice parameters. It is intended that these effective values will be used to represent the lattice at a macroscopic level, vastly reducing the complexity of the models needed to simulate the material for design applications. The study investigates the compressive modulus of lattice structures with a particular emphasis on the impacts of the cell topology and dimensions of the unit cell elements
An Evaluation of Concepts Related to Affordability in Military Domains
Get PDFhttps://louis.uah.edu/research-horizons/1347/thumbnail.jp
Contributions to data compression research for various media formats using particle swarm optimization and neural networks
No full textAdvancement in high resolution devices used to capture images and videos has put strain on data storage and transmission. For their practical usage, efficient data compression techniques becomes essential. In this context, we conducted a study on compression of two media formats, including ROI maps of hyperspectral images, and 3D point clouds. For lossless compression of ROI maps, we proposed novel schemes that can achieve high compression ratios by partitioning the intricate regions of the image into smaller blocks. Our analysis of a linear predictive model applied on the original images showed that the resulting residual images tend to have lower entropy. We then proposed to use the DPSO algorithm that searched for the best combination of scan directions to achieve better compression. Simulation results on various data sets showed that the proposed scheme outperformed JBIG2, the international standard for binary image compression. Our work also advanced the research on lossy attribute compression of 3D point clouds in two aspects. First, we proposed an adaptive scheme based on 3D Sobel filters that can switch between the RAHT and Dyadic RAHT to achieve early termination. We showed that the proposed method was able to achieve noticeable compression gains over the all-dyadic approach. Second, we further improved the adaptive method by training a neural networks so that the switching would no longer depend on a threshold. Compared to the GPCC standardized method that uses only Dyadic transform throughout the point cloud, the proposed scheme can achieve cumulative BR-rate gains on various publicly available datasets
Airborne passive microwave geophysical retrievals and applications in assessing environmental and aerosol impacts on maritime convection
Get PDFImprovements to NASA’s Advanced Microwave Precipitation Radiometer (AMPR) have yielded physically realistic brightness temperatures (Tb) from the Olympic Mountains Experiment / Radar Definition Experiment (OLYMPEX/RADEX) and Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex). Multi-linear regression equations, developed to retrieve integrated cloud liquid water (CLW), water vapor (WV), and 10-m wind speed (WS), were tested using simulations, deconvolved AMPR Tb from OLYMPEX/RADEX, independent retrievals, and in situ data. Simulated retrievals yielded average CLW, WV, and WS root-mean-square deviations (RMSD) of 0.11 kg m-2, 1.28 kg m-2, and 1.11 m s-1, respectively, when compared with modeled atmospheric profiles, with median absolute deviations (MedAD) of 2.26 x 10-2 kg m-2, 0.22 kg m-2, and 0.55 m s-1. Applied to OLYMPEX/RADEX, the CLW, WV, and WS RMSD were 9.95 x 10-2 kg m-2, 2.00 kg m-2, and 2.35 m s-1, respectively, against independent retrievals, and MedAD were 2.88 x 10-2 kg m-2, 1.14 kg m-2, and 1.82 m s-1. Average WV (WS) MedAD against dropsondes were 1.95 kg m-2 (1.34 m s-1), further indicating strong retrieval performances. Expanding to CAMP2Ex involved retrieval improvements, validation, and science applications. CLW retrievals required modification for the maritime tropics, which yielded 1.94 x 10-2 kg m-2 RMSD against simulations. Validation against airborne Ku- and Ka-band radar-derived CLW produced high MedAD around 0.40 kg m-2; however, polarimeter-derived CLW offered MedAD around 8.08 x 10-2 kg m-2. AMPR CLW decreases within polarimeter-derived cloud-top height \u3e 4 km may signify accretion and/or mixed-phase onset. Mean WV (WS) absolute deviation against 144 dropsondes was within target uncertainty at 8.27% (1.76 m s-1). Dropsonde-derived 0°C level height had moderate 0.49 (0.43) correlation with CLW (WS). Bulk correlations between nine dropsonde parameters and three convective metrics from AMPR and airborne radar across CAMP2Ex were relatively weak. Comparisons between five remote-sensing convective metrics and airborne-lidar-derived aerosol concentrations were performed within stratified CAMP2Ex environments in four sensitivity tests, wherein medium to relatively high aerosol concentrations were often directly correlated with convective intensity and frequency within favorable environments. Stratification using environmental lapse rates or K-Index generally yielded the highest correlations between convective metrics and aerosol concentrations
An assessment of actual evapotranspiration and soil moisture functions based on local-scale data in Alabama
Get PDFLarge-scale models and remote technology are widely used for the estimation of the energy budget at a global scale. The interaction of energy fluxes and soil water at the vegetation root zone is the driving force that controls the evapotranspiration process. Although the importance of soil moisture, it can only be measured at a point scale, given the great heterogeneity of soil profile. Large-scale models struggle to capture the spatial heterogeneity of soils, and remote sensing can only observe the surface level soil moisture, omitting the root zone. Studies have shown evapotranspiration estimates (specifically from Remote Sensing) and can provide needed information for characterizing root zone soil moisture, but these studies are mixed, and few have looked at the Southeast United States. To better understand the relationship between soil moisture and evapotranspiration in the humid Southeast environment this study looked at in situ soil moisture and derived soil water balance model evapotranspiration estimates. Findings for this specific region show that, at the transition between evapotranspiration regimes, the critical soil moisture at the root level is lower than soil moisture at the surface level (less than 6 cm depth), particularly in areas with medium to fine soil texture
