Groundwater Irrigation System for Sustainable Agriculture

The aim of this project was to develop a prototype that may be a model to help relieve food insecurity in rural Liberia. This was accomplished by designing a groundwater extraction, recharge, and irrigation system to facilitate year-long crop-growth. The project was in partnership with BRAID Africa and a community in Zwedru, located in east Liberia, near the border of Côte D’Ivoire. During 2010 and 2011, a civil war broke out in Côte D’Ivoire and led to the citizens of the country taking refuge in Liberia (Leaf 2015). Many refugees have decided to stay in Liberia and are struggling to maintain food security as most subsist on rice with not even enough to sell. Currently, villagers in Zwedru only grow the rice in swamps during the rainy season and, with climate change, the rainy season is becoming increasingly unreliable (USAID 2012). The irrigation system that was designed for this project has allowed villagers to grow certain crops, such as cassava, okra, chard, and squash, during the dry season which will help alleviate food insecurity with the goal of providing a source of income for the farmers. This project was designed for a one hectare (2.47 acres) plot, which can be scaled up or down depending on land area and available resources

An Analysis of Optical Contributions to a Photo-Sensor's Ballistic Fingerprints

Lens aberrations have previously been used to determine the provenance of an image. However, this is not necessarily unique to an image sensor, as lens systems are often interchanged. Photo-response non-uniformity noise was proposed in 2005 by Luk\'a\v{s}, Goljan and Fridrich as a stochastic signal which describes a sensor uniquely, akin to a "ballistic" fingerprint. This method, however, did not account for additional sources of bias such as lens artefacts and temperature. In this paper, we propose a new additive signal model to account for artefacts previously thought to have been isolated from the ballistic fingerprint. Our proposed model separates sensor level artefacts from the lens optical system and thus accounts for lens aberrations previously thought to be filtered out. Specifically, we apply standard image processing theory, an understanding of frequency properties relating to the physics of light and temperature response of sensor dark current to classify artefacts. This model enables us to isolate and account for bias from the lens optical system and temperature within the current model.Comment: 16 pages, 9 figures, preprint for journal submission, paper is based on a thesis chapte

Very low inheritance in cosmogenic surface exposure ages of glacial deposits: A field experiment from two Norwegian glacier forelands

Terrestrial cosmogenic nuclide dating has been widely used to estimate the surface exposure age of bedrock and boulder surfaces associated with deglaciation and Holocene glacier variations, but the effect of inherited age has been rarely directly addressed. In this study, small clasts, embedded in flute surfaces on two cirque glacier forelands in Jotunheimen, southern Norway and deposited within the last ~60 years, were used to test whether such clasts have the modern surface exposure age expected in the absence of inheritance. Two different approaches were taken involving dating of (1) a single clast of cobble size from the proglacial area of Austanbotnbreen, and (2) 75 clasts mostly of pebble size from the proglacial area of Storbreen crushed and treated as a single sample. 10Be surface exposure ages were 99 ± 98 and 368 ± 90 years, respectively, with 95% confidence (±2σ). It is concluded that (1) these small glaciers have eroded and deposited rock fragments with a cosmogenic zero or near-zero concentration, (2) the likelihood of inherited cosmogenic nuclide concentrations in similar rock fragments deposited by larger warm-based glaciers and ice sheets should be small, and (3) combining a large number of small rock particles into one sample rather than using single large clasts of boulder size may provide a viable alternative to the commonly perceived need for five or more independent estimates of exposure age per site

Effect of bending rigidity on the knotting of a polymer under tension

A coarse-grained computational model is used to investigate how the bending rigidity of a polymer under tension affects the formation of a trefoil knot. Thermodynamic integration techniques are applied to demonstrate that the free-energy cost of forming a knot has a minimum at non-zero bending rigidity. The position of the minimum exhibits a power-law dependence on the applied tension. For knotted polymers with non-uniform bending rigidity, the knots preferentially localize in the region with a bending rigidity that minimizes the free-energy.Comment: 15 pages, 6 figures. Corrected problem with references to equation