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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Development of a synthetic vision system for general aviation

Wenger, Jason Christopher 01 January 2007 (has links)
Synthetic Vision is an aviation technology that uses databases and position estimation to establish a view of the database which provides an intuitive view that corresponds to the features of the outside world. The Synthetic Flight Bag is a low cost, portable system which implements synthetic vision, moving map, and route planning in a single software and hardware package. Human factors analysis was performed to identify appropriate functional requirements for the development of the system. Preliminary simulator testing identified requirements on screen size and mounting location with a mind to the cramped general aviation cockpit. Hardware survey identified appropriate computing platform targets. Hardware selected was a compact motherboard intended for embedded systems applications and graphics support. It was packaged into a custom-built avionics case, along with supporting power and I/O hardware. An LCD display with touch screen was designed and built, and represents the smallest, yet highest resolution display commercially available at this time. Software development led to a complete system with a primary flight display, multi function display, vertical profile display, and a menu and information system allowing for flight plan editing. A flight test aircraft was instrumented and outfitted with the Synthetic Flight Bag system. A ground simulator was also created for the purpose of training prior to flight test. VFR and IFR pilots participated in the study, and were evaluated on flight technical errors, workload, and eye movement. A flight test was performed, and results indicated that while the Synthetic Flight Bag system improves terrain awareness, it is not in its tested version a complete solution to the problem. The system was found to significantly improve the accuracy of flight, but was also found to increase workload in pilots not yet familiar with its operation. Several future improvements were identified, but the system as designed meets the project needs.
52

A Feasibility Investigation of Modular Portable “Chelson Shelters” Micro-Homes to Alleviate Housing Deficiencies: A Case Study in Mithi, Tharpakar, Pakistan

Ghani, Muhammad Usman 01 July 2017 (has links)
Many people in Mithi, Tharparkar do not have proper housing, face an unhygienic water supply, and have no sanitation facilities. These factors contribute to disease, suffering and the inability to rise above their destitute existence. The idea for building portable houses for the people of Mithi is presented to provide them with better living conditions and where they can feel a sense of security, ownership and sanitation. Research on existing building systems and materials showed that the most feasible structure for the desert environment is modular panels attached to a core unit that contains all the basic plumbing and electrical fixtures. The unit can be expanded based on family needs. Discussion with government officials showed that these could be used for the immediate needs of the people who have been suffering more acutely the last several years due to a drought. They could also be a permanent solution to the housing crisis if the "Chelson Shelter" communities worked well for ten years. The infrastructure in the Tharparker Desert is inadequate to support typical housing. These shelters have low environmental impact, use little water and electricity and would be a good solution to make a community of people that can support each other and provide security.
53

Design of a Chemical Agent Detector Based on Polymer Coated Surface Acoustic Wave (SAW) Resonator Technology

Manoosingh, Lane Leslie 18 June 2004 (has links)
This dissertation presents the design of a unique prototype chemical agent detector which utilizes an array of polymer coated SAW resonators as the sensor elements. The design's particular embodiment is that of a testing platform for evaluating the utility of constructing a portable chemical agent detector, utilizing commercially available SAW resonators. It involves the consolidation of the sub-systems comprising a large laboratory development system, into a portable enclosure. A combination of design techniques, utilized to achieve an overall balance between the physical dimensions of the system and its detection performance, comprises the unique nature of the overall design of this detection system. Such techniques include; sensor power cycling, individually phase-tunable sensor oscillators, single step down conversion and the locality of the sensor's driving circuitry and sensing chamber. A frequency shift model is developed to characterize the device's response to target analytes. Reported here are the results of the preliminary tests of the detector system and the verifications of the device's operation as per the design requirements. Further, an assay of the system noise is undertaken, and the detector's limit of detection (LOD) is reported. The analytes used in this investigation were simulants of nerve and mustard gas as well as the interferent compound diesel. Among others, the following conclusions are reported: 1) that a mass loading model can adequately describe the frequency shifts of the SAW resonators utilized for sorption sensing; 2) that the quality factor of a polymer coated SAW resonator ultimately determines the noise performance of the driving oscillator; 3) that the lowest usable quality factor for the designed oscillator is 2500; 4) that the implementation of individual phase-tuning networks for each sensor in the sensor array can adequately compensate for phase variations among these sensors, and 5) that commercially available SAW resonators coated with chemo-selective polymers provide a reasonably inexpensive and reliable solution to the detection of chemical warfare agents when incorporated into a miniaturized sensing platform.
54

A usability comparison of PDA-based quizzes and paper-and-pencil quizzes

Segall, Noa 17 July 2003 (has links)
In the last few years, many schools and universities have incorporated personal digital assistants (PDAs) into their teaching curricula, in an attempt to enhance students' learning experience and reduce instructors' workload. One of the most common uses of PDAs in the classroom is as a test administrator. This study compared the usability effectiveness, efficiency, and satisfaction of a PDA-based quiz application to that of standard paper-and-pencil quizzes in a university course in order to determine whether it was advisable to invest time and money in PDA-based testing. The effects of computer anxiety, age, gender, and ethnicity on usability were also evaluated, to ascertain that these factors do not discriminate against individuals taking PDA-based tests. Five quizzes were administered to students participating in an engineering introductory course. Of these, students took two PDA-based quizzes and three paper-and-pencil quizzes. One PDA-based quiz and one paper-and-pencil quiz were compared in terms of their effectiveness, measured as students' quiz scores and through a mental workload questionnaire; their efficiency, which was the time it took students to complete each quiz; and their satisfaction, evaluated using a subjective user satisfaction questionnaire. Computer anxiety was also measured, using an additional questionnaire. It was hypothesized that the PDA-based quiz would be more effective and efficient than the paper-and-pencil quiz and that students' satisfaction with the PDA-based quiz would be greater. The study showed the PDA-based quiz to be more efficient, that is, students completed it in less time than they needed to complete the paper-and-pencil quiz. No differences in effectiveness and satisfaction were found between the two quiz types. It was also hypothesized that for PDA-based quizzes, as computer anxiety increased, effectiveness and satisfaction would decrease; for paper-and-pencil quizzes there would be no relationship between computer anxiety and effectiveness and no relationship between computer anxiety and satisfaction. Findings showed an increase in quiz score (increase in effectiveness) and an increase in mental workload (decrease in effectiveness) as computer anxiety increased for both quiz types. No relationship was found between computer anxiety and satisfaction for either paper-and-pencil or PDA-based quizzes. The final hypothesis suggested that user satisfaction would be positively correlated with effectiveness (quiz score and mental workload) for both PDA-based and paper-and-pencil quizzes. No relationship was found between quiz score and satisfaction for either quiz type. User satisfaction was positively correlated with mental workload, regardless of quiz type. The usability comparison of paper-and-pencil and PDA-based quizzes found the latter to be equal, if not superior, to the former. The effort students put into taking the quiz was the same, regardless of administration method, and scores were not affected. In addition, different demographic groups performed almost equally well in both quiz types (white students' PDA-based quiz scores were slightly lower than those of the other ethnic groups). Computer anxiety was not affected by the quiz type. For these reasons, as well as other advantages to both students (e.g. real-time scoring) and teachers (e.g. spending less time on grading), PDAs are an attractive test administration option for schools and universities. / Graduation date: 2004
55

Development and characterization of a high resolution portable gamma spectrometer

Ali, Muhammad 01 April 2012 (has links)
The recent disaster of Fukushima in Japan combined with the high demand to enhance nuclear safety and to minimize personal exposure to radioactive materials has a significant impact on research and development of radiation detection instrumentation. Currently, there is ample effort worldwide in the pursuit of radiation detection to maximize the accuracy and meet international standards in terms of size and specifications to enable radiation protection decision making. Among the requirements is the development of a portable, light-weight gamma-ray isotope identifier to be used by first responders in nuclear accidents as well as for radiation security and identification of illicit material isotopes. From nuclear security perspective, research into advanced screening technologies has become a high priority in all aspects, while for occupational safety, and environmental radiation protection, the regulatory authorities are requiring specific performance of radiation detection and measuring devices. At the applied radiation laboratory of the University of Ontario Institute of Technology, UOIT, the development of a high resolution spectrometer for medium and high energy gamma ray has been conducted. The spectrometer used a newly developed scintillator based on a LaBr3(Ce) crystal. The detector has been modeled using advanced Monte Carlo code (MCNP/X code) for the response function simulation and parameter characterization. The simulation results have been validated by experimental investigations using a wide range of gamma radiation energies. The developed spectrometer has been characterized in terms of resolution and response in different fields. It has also been compared with other crystals such as NaI(TI) and LiI(Eu). / UOIT
56

Needle Trap Device and Solid Phase Microextraction Combined with Portable GC-MS for On-Site Applications

Warren, Jamie January 2011 (has links)
Needle trap device (NTD) is a technique that is useful for a wide variety of applications involving the sample preparation of compounds with a wide range of chemico-physico properties, and varying volatilities. A newly designed NTD that improves the performance relative to previous NTD designs is simple to produce is developed. The NTD utilizes a side-hole needle with a modified tip to improve the sealing between the NTD and narrow neck liner of the GC injector, thereby increasing the desorption efficiency. The slurry packing method was applied, evaluated, and NTDs prepared by this method were compared to NTDs prepared using the vacuum aspiration method. NTD geometries including blunt tip with a side-hole needle, tapered tip with side-hole needle, dome tapered tip with side-hole, sliding tip with side-hole and blunt tip with no side-hole needle (expanded desorptive flow) were prepared and evaluated. Sampling performance and desorption efficiency were investigated using automated headspace extraction of benzene, toluene, ethylbenzene, p¬-xylene (BTEX), anthracene and pyrene. The tapered tip and sliding tip NTDs were found to have increased desorption efficiency. SPME and NTDs are valuable sample preparation tools for on-site analysis. Combining both extraction techniques allows for the differentiation of free and particle-bound compounds in a sample matrix. Portable GC/MS instrumentation can achieve fast separation, identification, and quantitation of samples prepared by the above techniques on-site without the need for transport to the laboratory. This minimizes the effects of volatiles lost and sample degradation during storage time. Here, SPME and tapered tip NTDs combined with portable GC/MS are used to investigate free and total emissions of BTEX and select PAHs from gasoline and diesel exhaust. Using the above optimized technologies, cigarette smoke in a smoking area where people were actively smoking and inside a smoker’s car were also investigated. Target contaminants were found in the investigated matrices at ng/mL levels.
57

SAR Reduction on a Portable Device Using Intelligent Metamaterial

Wang, Yi-jen 28 July 2010 (has links)
In this thesis, intelligent metamaterial was designed to reduce the peak specific absorption rate (SAR) value. Intelligent metamaterial means that when the antenna is far away from a human head, the metamaterial behaves like air and it does not affect the antenna performance; when the antenna is close to a human head, however, the metamaterial acts like a single negative (SNG) material. We designed two kinds of intelligent metamaterial structures. One makes use of impedance mismatching, and the other makes use of the frequency band shift property to reduce the peak SAR value at the operating frequency. The former structure is broadband, and it can reduce the peak SAR value by 56.7%. The latter structure has a much smaller size compared to the former one, and it is suitable for cellular phone applications. The peak SAR value can be reduced by 40% using the latter structure. The proposed two kinds of the intelligent metamaterial structures do not affect the antenna performance. Finally, the intelligent metamaterial has been applied to a cellular phone. The dimension of the intelligent metamaterial is only 40 mm ¡Ñ 20 mm ¡Ñ 0.8 mm. The intelligent metamaterial does not affect the antenna performance when the antenna is far away from a human head. When the antenna is close to a human head, the peak SAR is reduced by 41.7%.
58

Studies of Performance Improvement and Stabilization of Passive Portable DMFCs

Cai, Cheng-Zong 28 August 2012 (has links)
Abstract The improvement of performance and the maintenance of stability of a portable air-breathing DMFC are studied in this thesis. The effect of the improvement of the internal structural of carbon fiber bunches on the cell performance is studied firstly. The small channels in the soft end of the carbon fiber bunches can be formed by changing the thickness of the copper plates burry within the gluing zone of the fiber bunches. Then one or two transverse grooves are form in proper location by cutting part of the carbon fibers at the soft end to shorten the airflow path to the area of electrode which is covered by the carbon fiber bunches so that the reaction area can obtained enough oxygen or fuel. Experimental results show that the maximum power density is about 20 mW/cm2 with no structure but it raised to about 24 mW/cm2 with the burry a 0.5mm thick copper plate and the two transverse grooves. It improves about 20% power density. The experiments prove that the improvement of the internal structure of the carbon fiber bunches is helpful in stack performance. In order to reduce the unneeded depletion of fuel, the bare nafion membrane pastes another special membrane to block methanol and water leakage. The strategy to block the leakage improved the rate of fuel utilization about 24%. In order to make the direct methanol fuel cell operating stably, a fuel supplying system by gravitation and diffusion forces is delivering the consumed fuel to maintain the concentration of methanol solution in anode reaction, by adjusting a sliding gate to control the diffusion area and utilizing three cotton threads and hoses to distribute the fuel to proper location. The multi-point type of fuel supplementary system allows the methanol solution to be distributed uniformly, so that the stack can maintain stable operation for a long period. In order to make the stack size to a minimization, the volume of the anode reaction chamber will be minimized as possible; however, the reduced chamber is still able to supply sufficient fuel maintaining operating stably in the high-current condition. The transient phenomena of output voltage under the various volume of the reaction chamber are also studied in this research. Finally, we hope to be able to identify the most appropriate space to meet demand. The above optimization results are able to provide a reference in the future design and production of portable DMFCs.
59

Relative Response to Low-Energy Photons and Determination of Instrument Correction Factors for Portable Radiation Instrumentation

Wagoner, David Andrew 2010 August 1900 (has links)
Practically all portable radiation instruments come from the manufacturer with a graph of photon energy response. However, many of these graphs are in log-log format which can disguise relatively large variations in response, particularly for low-energy photons. Additionally, many only include one specific orientation. Thus, in many cases, it is left up to the user to determine for which orientation and photon energies the instrument will be calibrated and ultimately used in the field. It is known that many instruments can have inconsistent responses below ~300 keV, which may lead to under or over-estimation of exposure rate. However, based on relative response plots, one can derive an instrument correction factor that can be applied to the measured exposure rate to yield a constant response curve and more accurately estimate the exposure rate. Using a combination of irradiator systems, six different types of radiation instrumentation were irradiated with photons with energies from 38 to 1253 keV in various orientations. A calibrated ion chamber, in conjunction with an electrometer, was used to determine the conventionally true exposure rates for various x-ray beam codes and radionuclides contained in the irradiator systems. The conventionally true exposure rates were compared to the measured values for each instrument type and relative response plots were constructed. These plots were used to determine an ideal orientation and correction factors were chosen for responses > ±20 percent. From the relative response plots, instrument correction factors are not necessary for the following; Eberline RO-20, Thermo RadEye B20, and Bicron Micro Rem LE. Correction factors of 0.7 and 1.5 should be applied for photons between 80 – 120 keV for the Eberline Teletector 6112B low and high-range detectors, respectively. A correction factor of 0.8 should be applied for photons below 120 keV for the Eberline RO-7-BM. For the Thermo Mk2 EPD, a correction factor of 1.25 should be applied for photons below 40 keV. The primary causes of under and/or over-responses were found to be window attenuation, varying interaction cross-sections, and the range of secondary electrons. Angular dependence and calibrations for specific applications are also discussed.
60

The Making of a Performance and Low Cost Heterogeneous Composite Bipolar Plate and the Performance analysis of PEMFC with This New Plate

He, Jheng-ru 14 July 2004 (has links)
Abstract Traditional unipolar/bipolar plates, such as the metal and the graphite unipolar/bipolar plates, are expensive, weight heavy and volume large, so that it is hard to be used in the portable application. A high efficiency, low cost and lightweight portable proton exchange membrane fuel cell (called PEMFC or called HFC when using pure hydrogen fuel), which is made with a new heterogeneous composite carbon fiber bipolar plate and a MEA, is developed in our lab. There are many advantages of the new carbon fiber unipolar/bipolar plates, such as low contact resistance, low cost, lightweight and small volume. We hope that the new unipolar/bipolar plate will be able to replace the conventional metal and graphite unipolar/bipolar plates in the future. The characteristics of a portable PEMFC in different operational conditions are studied in this research. From our experimental result, we find that the factors which affect the HFC performance include the gas temperature, humidity ratio, inlet gas pressure in anode, the geometry of inlet ports, the flow channels within cell, and the oxidant flow rate etc. In addition, the contact resistances between different materials within each cell all strongly influence HFC performance. The ribs of the carbon fiber unipolar/bipolar plates is pored structure, and the gas diffusion layer is no deformation because of only slight compression in stack assembly; therefore, the reactive gas can easily flow into the most of active area. In addition, the contact resistance between the carbon fiber unipolar plate and the gas diffusion layer is lower than that between the traditional unipolar plate and the gas diffusion layer, so that the electrons in active layer is easily to exit or enter this region. The experimental result at 1.15 atm and 40 oC displays that the current density with the new unipolar plate is about twice higher than that with the graphite unipolar plate at overpotential 0.6 V. With air as an oxidizer, we find that increasing the fan rotation speed can avoid output-voltage decay in high current density, but the design with fan is unfavorable for portable application. So a front open unipolar plate and air-breathing design is adopted on the cathode. The power density of this design is slightly lower than that with fan, but it still can reach a value 160 mW/cm2 without any heating and humidification in the anode. Because this design needs little supplement device, the application in portable fuel cells of the new design will be wider than that of a traditional design.

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