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1رسالة جامعية
المؤلفون: Miller, Matthew Lowell
مرشدي الرسالة: Geography, Carstensen, Laurence W., Campbell, James B. Jr., Thomas, Valerie A.
مصطلحات موضوعية: visibility, digital elevation model, digital surface model, viewshed, LIDAR
الوصف: The analysis of visibility between two points on the earth's terrain is a common use of GIS software. Most commercial GIS software packages include the ability to generate a viewshed, or a map of terrain surrounding a particular location that would be visible to an observer. Viewsheds are often generated using "bare-earth" Digital Elevation Models (DEMs) derived from the process of photogrammetry. More detailed models, known as Digital Surface Models (DSMs), are often generated using Light Detection and Ranging (LIDAR) which uses an airborne laser to scan the terrain. In addition to having greater accuracy than photogrammetric DEMs, LIDAR DSMs include surface features such as buildings and trees. This project used a visibility algorithm to predict visibility between observer and target locations using both photogrammetric DEMs and LIDAR DSMs of varying resolution. A field survey of the locations was conducted to determine the accuracy of the visibility predictions and to gauge the extent to which the presence of surface features in the DSMs affected the accuracy. The use of different resolution terrain models allowed for the analysis of the relationship between accuracy and optimal grid size. Additionally, a series of visibility predictions were made using Monte Carlo methods to add random error to the terrain elevation to estimate the probability of a target's being visible. Finally, the LIDAR DSMs were used to determine the linear distance of terrain along the lines-of-sight between the observer and targets that were obscured by trees or bushes. A logistic regression was performed between that distance and the visibility of the target to determine the extent to which a greater amount of vegetation along the line-of-sight impacted the target's visibility.
Master of Scienceوصف الملف: application/pdf
العلاقة: Miller_ML_T_2011.pdf
الإتاحة: http://hdl.handle.net/10919/35692Test
http://scholar.lib.vt.edu/theses/available/etd-11132011-142756Test/ -
2رسالة جامعية
المؤلفون: Miller, Matthew Michael
مرشدي الرسالة: Mechanical Engineering, von Spakovsky, Michael R., Nelson, Douglas J., Ellis, Michael W.
مصطلحات موضوعية: Micro Air Vehicle, PEM Fuel Cell, Microtubular Fuel Cell
الوصف: Research and prototyping of a fuel cell stack system for micro aerial vehicles (MAVs) was conducted by Virginia Tech in collaboration with Luna Innovations, Inc, in an effort to replace the lithium battery technology currently powering these devices. Investigation of planar proton exchange membrane (PEM) and direct methanol (DM) fuel cells has shown that these sources of power are viable alternatives to batteries for electronics, computers, and automobiles. However, recent investigation about the use of microtubular fuel cells (MTFCs) suggests that, due to their geometry and active surface areas, they may be more effective as a power source where size is an issue. This research focuses on hydrogen MTFCs and how their size and construction within a stack affects the power output supplied to a MAV, a small unmanned aircraft used by the military for reconnaissance and other purposes. In order to conduct this research effectively, a prototype of a fuel cell stack was constructed given the best cell characteristics investigated, and the overall power generation system to be implemented within the MAV was modeled using a computer simulation program. The results from computer modeling indicate that the MTFC stack system and its balance of system components can eliminate the need for any batteries in the MAV while effectively supplying the power necessary for its operation. The results from the model indicate that a hydrogen storage tank, given that it uses sodium borohydride (NaBH4), can fit inside the fuselage volume of the baseline MAV considered. Results from the computer model also indicate that between 30 and 60 MTFCs are needed to power a MAV for a mission time of one hour to ninety minutes, depending on the operating conditions. In addition, the testing conducted on the MTFCs for the stack prototype has shown power densities of 1.0, an improvement of three orders of magnitude compared to the initial MTFCs fabricated for this project. Thanks to the results of MTFC testing paired with computer modeling and prototype fabrication, a MTFC stack system may be possible for implementation within an MAV in the foreseeable future.
Master of Scienceوصف الملف: application/pdf
الإتاحة: http://hdl.handle.net/10919/76880Test
http://scholar.lib.vt.edu/theses/available/etd-10162009-134257Test/ -
3رسالة جامعية
المؤلفون: Miller, Matthew J.
مرشدي الرسالة: Geography
مصطلحات موضوعية: LD5655.V855 1994.M556, Flour mills, Virginia, Augusta County, Geographic information systems, Grinding wheels
الوصف: Water powered mills were a very important part of life in early America, and Augusta County, Virginia had an abundance of milling activity. Excellent records of milling activity, farm production, and road and farm locations for the period of 1880-1885 allowed a geographic information system (GIS) database to be formed so that spatial patterns could be verified and identified in the Riverheads district of the county. Service areas of 21 mills were identified by using a GIS to calculate the shortest road distance to surrounding farms. It was found that wheat, the main crop, was most likely shipped from the 369 farms to the closest mills. A correlation was also found between wheat production and distance from the mill, thus farmers closer to a mill were more likely to grow wheat. The study also demonstrates the usefulness of GIS analysis and computer cartography in historical, geographic research which has traditionally used theoretical approaches or lacked adequate data for GIS analysis.
Master of Scienceوصف الملف: vii, 76 leaves; BTD; application/pdf
العلاقة: OCLC# 30506020; LD5655.V855_1994.M556.pdf; LD5655.V855_1994.M556_drw01.pdf
الإتاحة: http://hdl.handle.net/10919/44614Test
http://scholar.lib.vt.edu/theses/available/etd-09052009-041037Test/ -
4رسالة جامعية
المساهمون: Agricultural, Leadership, and Community Education
مصطلحات موضوعية: 4-H, ambassador, livestock, youth
الوصف: This project focused on developing a framework for the Virginia 4-H Youth Livestock Ambassador program. A survey tool was developed to distribute to 4-H youth livestock and agricultural ambassador alumni in states with established, active programs, with the purpose of assessing the perceived impacts of participating in the programs. The survey was composed of Likert scale statements. The survey was distributed by program coordinators through their email listservs. Most participants responded favorably to the ambassador program, with most agreeing that by participating, they were positively impacted. Respondents especially thought that participating in the program had helped them feel more confident mentoring younger 4-H members and taught them how to act professionally. Interview questions were developed and asked to program coordinators of 4-H youth livestock or agricultural ambassador programs to gather information on various components of the program, including the application and selection process, ambassador requirements, training, program successes, and improvements to be made. Transcription data from the interview was compiled, trends were identified, and specific components of the programs were highlighted. Information was combined to create a draft guide for the Virginia 4-H Youth Livestock Ambassador program, as well as several key tools for the program, including a draft application and a draft service activities tracking document. Results from this project will be presented to the Virginia 4-H Youth Animal Science Extension Specialist with the goal of creating and implementing a Virginia 4-H Youth Livestock Ambassador program. ; MALS
وصف الملف: application/pdf
