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In cooperation with the USDA Forest Service Southern Research Station, an algorithm has been developed to replace the current aerial-photography-derived FIA Phase 1 estimates of forest/non-forest with a Landsat Thematic Mapper-based forest area estimation. Corrected area estimates were obtained using a new hybrid classifier called Iterative Guided Spectral Class Rejection (IGSCR) for portions of three physiographic regions of Virginia. Corrected area estimates were also derived using the Landsat Thematic Mapper-based Multi-Resolution Land Characteristic Interagency Consortium (MRLC) cover maps. Both satellite-based corrected area estimates were tested against the traditional photo-based estimates. Forest area estimates were not significantly different (at the 95% level) between the traditional FIA, IGSCR, and MRLC methods, although the precision of the satellite-based estimates was lower. The estimated percent forest area and the standard error (respectively) of the estimates for each region and method are as follows; Coastal Plain- Phase 1 66.06% and 1.08%, IGSCR 68.88% and 2.93%, MRLC 69.84% and 3.08%. Piedmont- Phase 1 63.87% and 1.91%, IGSCR 65.52% and 3.50%, MRLC 59.19% and 3.83%. Ridge and Valley- Phase 1 69.74% and 1.22%, IGSCR 70.02%, and 2.43%, MRLC 70.53% and 2.52%. Map accuracies were not significantly different (at the 95% level) between the IGSCR method and the MRLC method. Overall accuracies ranged from 80% to 89% using FIA definitions of forest and non-forest land use. Given standardization of the image rectification process and training data properties, the IGSCR methodology is objective and repeatable across users, regions, and time and outperforms the MRLC for FIA applications. / Master of Science

This paper demonstrates the utility of small area estimation (SAE) of poverty methods for researchers that wish to conduct a detailed welfare analysis as part of a larger survey of a small geographic area of interest. Researchers studying context-specific technologies or interventions can incorporate the survey-based SAE of poverty approach to conduct detailed poverty analyzes of their specific area of interest without the expense of collecting household consumption data. This study applies SAE methods as part of an impact assessment of a locally adapted conservation agriculture production system in Uganda's Tororo District. Using SAE, I assess the Tororo District's Foster-Greer-Thorbecke (FGT) rural poverty indices, estimate the effects of per acre farm profit increases to poor households on the district's rural poverty indices, and compare the findings to current estimates of the net returns from conservation agriculture in the Tororo District. The SAE results suggest that increasing the farm profits of the bottom 30% of households by two U.S. dollars per acre per season could reduce the district's rural poverty incidence by one percentage point. The available data on the net returns to conservation agriculture in the Tororo District, however, indicate that these modest increases may only be achievable for adopting households that face high land preparation costs. / Master of Science

The behavior during dissolution of edge and basal surfaces of the mica phlogopite were examined using in situ atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) in an attempt to characterize the reactive surface area during dissolution. Mica minerals are the ideal material for this study because they offer a high degree of structural anisotropy. Therefore surfaces with different structures are easily identified. Dissolution is shown to proceed preferentially by removal of material from {hk0} edges. Dissolution rates were calculated by measuring the volume of material removed from etch pits, and normalizing to either the "reactive" surface area of {hk0} edges exposed at pit walls, or to a total "BET-equivalent" surface area. Rates normalized to total surface area are in the range of dissolution rates reported in the literature. Edge surface normalized rates are about 100 times faster. Long-term in situ AFM observations of phlogopite dissolution reveal that exposed (001) surfaces also display a distinct reactivity, though it operates on a different time scale. The top layer is shown to expand between 39 and 63 hours in contact with pH 2 HCl solution. Subsequent LEED analysis shows that the (001) surface becomes amorphous upon reacting with pH 2 HCl. Compositional characterization of the phlogopite after reaction shows that for pitted phlogopite surfaces, dissolution is characterized by leaching of octahedral cations and polymerization of the silica-enriched residual layer. No chemical changes or polymerization are observed for freshly cleaved unpitted phlogopite after reaction with pH 2 HCl for 24 hours. This suggests a gallery access mechanism is facilitated by edge attack, and is only significant on exposed (001) surfaces after a certain amount of dissolution by edge attack. / Master of Science

Water is an integral part of agricultural practices, with agriculture being the largest user of surface water in the United States. Agriculture's reliance on surface water is strengthening as climate change and growing populations are stressing irrigated croplands. This surface water is primarily stored by a complex network of dams, but despite our reliance on surface water for irrigation, we lack a spatially detailed record of irrigation dam command areas. Therefore, we assigned irrigation command areas to the approximately 1,100 large irrigation dams in the continental United States by combining a tiered assignment strategy with field level infrastructure and agricultural data. We showed that these large irrigation dam command areas are responsible for 10.7 million acres of cropland. This translates to approximately 13.3 billion dollars of crops annually that depend on these large irrigation dams for water. The high-resolution, crop specific assignment of these command areas allows for water scarcity assessments that can be used for better water management decisions to address the changing environmental conditions and public demand pressuring the nation's agriculture and water infrastructure. / Master of Science / Agriculture depends heavily on surface water stored by large dams, especially in the face of climate change and population growth. However, the spatial distribution of croplands that rely on these dams is poorly known. We mapped the irrigation command areas of around 1,100 large dams in the continental US using a combination of field-level data and a tiered assignment method. We then traced the agricultural products from these areas to their domestic and international markets. We found that large dams support 10.7 million ares of cropland and 13.3 billion dollars of crop value annually in the US. Our high-resolution mapping of irrigation command areas enables more accurate assessments of water scarcity and reveals the local and distant connections between water infrastructure and its users.

The Soil Taxonomy definition for the brittle, compact subsoil horizons known as fragipans is vague and processes responsible for fragipan formation are poorly understood. Ambiguities in the fragipan definition have resulted in a lack of consistency in the interpretation of fragipan characteristics. These ambiguities may be attributed to difficulties encountered in establishing a precise definition broad enough to encompass the wide range of fragipan soils known to occur. This study approaches the problems of defining and identifying fragipans from a geographic perspective; emphasizing distribution of fragipan soils in the United States, and interpretation of fragipan characteristics across this range. A series of maps based on data gathered from county soil surveys are presented to estimate the areal distribution of fragipan soils in the United States and explore the regional variability of several fragipan characteristics. This study demonstrates that a "universal" definition of fragipans may not be realistic. / Master of Science

Yes / Tranquil spaces can be found and made in the city and their promotion and use by residents and visitors is an important means of building resilience. Studies have shown that spaces that are rated by visitors as tranquil are more likely to produce higher levels of relaxation and less anxiety that should ultimately result in health and well-being benefits. Such spaces can therefore be classed as restorative environments. Tranquil spaces are characterized by a soundscape dominated by natural sounds and low levels of man-made noise. In addition, the presence of vegetation and wild life has been shown to be an important contributory factor. Levels of rated tranquillity can be reliably predicted using a previously developed model TRAPT and then used to design and identify tranquil spaces, improve existing green spaces and develop Tranquillity Trails to encourage usage. Tranquillity Trails are walking routes that have been designed to enable residents and visitors to reflect and recover from stress while receiving the benefits of healthy exercise. This paper describes Tranquillity Trails designed for three contrasting areas. Predictions of the rated tranquillity have been made along these routes and feedback from users was elicited at one site that confirmed the expected benefits. / Bradford Centre for Sustainable Environments in the Faculty of Engineering and Informatics at the University of Bradford.

Wireless local area networks (WLANs) have experienced tremendous growth with the proliferation of IEEE 802.11 devices in past two decades. Wireless operators are embracing WLAN for cellular offloading in every smartphone nowadays [1]. The traffic over WLAN requires significant improvement of both WLAN throughput and efficiency. To increase throughput, multiple-input and multiple-output (MU-MIMO) has been adopted in the new generation of WLAN, such as IEEE 802.11ac. MU-MIMO systems exploit the spatial separation of users to increase the network throughput. In an MU-MIMO system, efficient channel sounding is essential for achieving optimal throughput. We propose a dynamic sounding approach for MU-MIMO systems in WLANs. We analyse and show that the optimal sounding intervals exist for single user transmit beamforming (SU-TxBF) and MU-MIMO for given channel conditions. We design a low-complexity dynamic sounding approach that adjusts the sounding interval adaptively in real-time. Through our collected over-the-air channel measurements, we demonstrate significant throughput improvements using our proposed dynamic sounding algorithm while being compliant with IEEE 802.11ac standard. Subsequently, we investigate the user grouping problem of downlink WLANs with MU-MIMO. Particularly, we focus on the problem of whether SU-TxBF or MU-MIMO should be utilized, and how many and which users should be in a multi-user (MU) group. We formulate this problem for maximizing the system throughput subject to the multi-user air time fairness (MU-ATF) criterion. We show that hypergraphs provide a suitable mathematical model and effective tool for finding the optimal or close to optimal solution. We show that the optimal grouping problem can be solved efficiently for the case where only SU-TxBF and 2-user MU groups are allowed in the system. For the general case, where any number of users can be assigned to groups of different sizes, we develop an efficient graph matching algorithm (GMA) based on graph theory principles with near-optimal performance. We evaluate the proposed algorithm in terms of system throughput using an 802.11ac emulator using collected channel measurements from an indoor environment and simulated channel samples for outdoor scenarios. We show that the approximate solution, GMA, achieves at least 93% of the optimal system throughput in all considered test cases. A complementary technique for MU-MIMO is orthogonal frequency-division multiple access (OFDMA), which will be the key enabler to maximize spectrum utilization in the next generation of WLAN, IEEE 802.11ax. An unsolved problem for 802.11ax is maximizing the number of satisfied users in the OFDMA system while accommodating the different Quality of Service (QoS) levels. We evaluate the possibility of regulating QoS through prioritizing the users in OFDMA-based WLAN. We define a User Priority Scheduling (UPS) criterion that strictly guarantees service requests of the spectrum and time resources for the users with higher priorities before guaranteeing resources to those of lower priority. We develop an optimization framework to maximize the overall number of satisfied users under this strict priority constraint. A mathematical expression for user satisfaction under prioritization constraints (scheduler) is formulated first and then linearized as a mixed integer linear program that can be efficiently solved using known optimization routine. We also propose a low-complexity scheduler having comparable performance to the optimal solution in most scenarios. Simulation results show that the proposed resource allocation strategy guarantees efficient resource allocation with the user priority constraints in a dense wireless environment. In particular, we show by system simulation that the proposed low-complexity scheduler is an efficient solution in terms of (1) total throughput and network satisfaction rate (less than 10% from the upper bound), and (2) algorithm complexity (within the same magnitude order of conventional scheduling strategy. / Ph. D. / We are now living in a world with seamlessly wireless connections. Our smart phones, tablets, personal computers, etc., enable us to hear, see and communicate with family members, friends and colleagues who could be on the other side of the earth that is thousands of miles away from us. Sharing travel photos, learning breaking news and syncing work documents, etc., can be done immediately by simply touching the screen of our mobile devices. Today’s dedicated wireless infrastructures extensively broaden our view of imagining what the future world for our daily life would be. Among all the wireless infrastructure, Wi-Fi continues to become the one that carries the most amount of digital data transmission. Because of the technology advances and Wi-Fi standardization, we have seen a dramatic reduction of the Wi-Fi device cost and increased deployment of Wi-Fi technology to cover almost every home and office as well as public areas, such as hotel, airport, and hospital. The increased diversity of devices such as smartphones, tablet, laptops, set-top boxes, media centers, televisions, and wireless display adapters requires significant improvement of both throughput and efficiency for new Wi-Fi systems. In this dissertation, we aim to investigate the theoretical foundations and practical algorithms for the advanced wireless technologies, and take Wi-Fi as an example to demonstrate the data rate and user experience improvement. The theoretical study is critical as it can be used as a guideline for system design, and the wireless algorithms are valuable for the deployment by the commercial wireless network system.

One of the local area network medium access control standards created by the Institute of Electrical and Electronic Engineers in IEEE Project 802 is the carrier sense multiple access with collision detection (CSMA/CD) medium access control. Numerous studies have been reported in the literature on the performance of CSMA/CD. These studies show that CSMA/CD performs well under light network load but not well at heavy load. To improve the performance of CSMA/CD under heavy load, a new concept called network partitioning is presented. Network partitioning allows the network to be partitioned into segments when under heavy load. Partition stations then act as bridges between the segments. The impact of network partitioning on network performance was tested using a simulation model of an Ethernet local area network (an implementation of the CSMA/CD medium access control). The simulation results show that network partitioning can improve the performance of CSMA/CD under heavy load.

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