Smart devices capable of harvesting their own energy have advantages over their wired or battery-powered alternatives including improved portability, simplified installation, and reduced maintenance and operating costs. This thesis studies energy harvesting technology through a case study of a solar-powered motorized window shade. An analytical and experimental evaluation of window attenuation found that windows reduced the ability of solar cells to produce photocurrent by 30%-70%. This still allows significant potential to power small electronics so a prototype motorized window blind was designed and assembled. The solar array was mounted to the roller blind's bottom rail and power is conveyed to the control electronics and motor in the unit’s top cylinder through wires embedded in the shade’s fabric. A simple battery system was implemented to ensure the prototype could remain powered in the absence of light. Various forms of powerflow in the prototype were evaluated. Experimental evaluation of joule heating within the conductive textile indicates that a temperature gradient that is less than 10 °C develops, meaning it is safe for use. The prototype was designed with artificial friction to prevent the blinds from slipping when not in use. An experimentally validated motor model was developed and used to determine that the system could use up to 46% less energy if the artificial friction was removed. A pseudo-empirical system model was developed to simulate the interaction between system electronics. Simulation results indicate that the system would remain consistently powered if placed behind a south-facing window that receives a consistent supply of direct sunlight and attenuates that light by less than 75%. These results also indicate that the unit would remain powered in the absence of light for 13 days. Similar methods could be used to evaluate future energy harvesting systems. / Thesis / Master of Applied Science (MASc)

The current methodologies in body scanning diagnostic uses different simultaneous imaging modalities like Ultrasound (US), magnetic resonance imaging (MRI), single photon emission tomography (SPECT) and positron emission tomography (PET). The field requires combination of different modalities for effective use in clinical diagnostics. Such incorporation of different modalities has already been achieved. For example, PET-CT hybrid scanner is designed to acquire align functional and anatomical images and recently US-MRI scanner has successfully shown to improve diagnosis of prostate cancer. The non ionizing radiation hybrid US-MRI is of great interest in health care industry. Further these US and MRI modalities uses different contrast agents like micro-sized gas bubbles (MBs) encapsulated by surfactant for US and superparamagnetic nanoparticles for MRI imaging modalities to further enables new diagnostic opportunities and therapeutic applications. Recently in our 3MiCRON project, we have developed the multimodal contrast agent that could be supported for both US and MRI. This was achieved by coating the magnetic nanoparticles to the poly vinyl alcohol (PVA) surfactant shelled MBs. The nanoparticles in the shell effect the structure can alter the MBs performance as an ultrasound contrast agent. The present thesis is conducted to examine the acoustic and mechanical properties of such multimodal contrast agents. These multimodal contrast agents were prepared by coating the surface of PVA-shelled MBs by two following strategies: (1) The superparamagnetic iron oxide (Fe3O4) nano-particles (SPIONs) were chemically anchored to the surface of poly vinyl alcohol (PVA) shelled MBs namely MBs-chem and (2) in the second strategy the SPIONs were physical entrapped into the PVA shell while formation of PVA surface on the gas bubble were named as MBs-phys. To understand the scattering efficiency and viscoelastic properties of these modified agents, we investigated the backscattering power, attenuation coefficient and phase velocity measurements. Our acoustic experimental results indicate that both the modified MBs and non-modified plain PVA-shelled ultrasound contrast agents have the same echogenic response. The investigation of mechanical properties of modified MBs revealed that the attached SPIONs on the PVA shell has reduced the stiffness of MBs-chem shell, while, the SPIONs inside the shell has increased MBs-phys stiffness. As a result, MBs-chem exhibits soft shell behavior under ultrasound exposure than both MBs-phys. Finally, the images were obtained through the MRI investigations at the department of Radiology, Karolinksa Institute, has demonstrated that both MB types have enough magnetic susceptibility that further provides good detectability in vitro and in vivo. As an outlook, the modified magnetic gas bubbles, i.e. both MBs-chem and MBs-phys can be proposed as a potential contrast agent for both US and MR imaging and can be further utilized in potential therapeutic applications. / <p>QC 20131126</p>

Earlier research has demonstrated that downstream of combustion in a rotating detonation engine, exhaust flow periodically reverses circumferential direction. For small periods, the circumferential flow reaches velocity magnitudes rivaling the bulk flow of exhaust, manifesting as a swirl. The minimization of this swirl is critical to maximizing thrust and engine performance for rocket propulsion. During this study, numerous nozzle contours were iteratively designed and analyzed for losses analytically. Once a nozzle was chosen, further losses were validated through computational fluid dynamics simulations and then tested experimentally. Three different configurations were run with the RDRE: no nozzle, a nozzle without a spike, and a nozzle with a spike. Images of the exhaust quality were recorded using OH* chemiluminescence in high-speed cameras. One camera was used to confirm the existence of a detonation and the frequency of detonation. The second camera is pointed perpendicular to the exhaust flow to capture the quality of exhaust. Quantitative results of the turbulent velocity fluctuations were obtained through particle image velocimetry of the side-imaging frames. All frames in each case were exported and converted to several time-averaged frames whereupon the time-averaged turbulent velocity fluctuation profiles could be compared between cases for swirl attenuation.

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Extreme flooding and excess nutrient pollution have been detrimental to river health under increased environmental stress from human activities (e.g., agriculture, urbanization). Riverine flooding can be detrimental to human life and infrastructure yet provides important habitat and ecosystem services. Traditional flood control approaches (e.g., levees, dams) negatively impact habitat and ecosystem services, and cause flooding elsewhere along the river. Prior studies have shown that stream restoration can enhance flood attenuation, and increased exchange of water between the channel and floodplain can improve water quality. However, the effects of floodplain restoration during small and sub annual recurrence interval storms have not been thoroughly studied, nor have cumulative impacts of floodplain restoration on water quality at watershed scales. We used HEC-RAS to perform 1D unsteady simulations on a 2nd-order generic stream from the Chesapeake Bay Watershed to study flood attenuation under small and sub-annual recurrence interval storms (i.e., 2-year, 1-year, 0.5-year, and monthly). In HEC-RAS we varied percent of channel restored, location of restoration, bank height of restoration, floodplain width, and floodplain Manning's n. Overall, stream restoration reduced peak flow (up to 37%) and decreased time to peak (up to 93%). We found the timing of tributary inflows could obscure the attenuation achieved, and even reverse the trends with certain parameters in the sensitivity analysis. The greatest exchange with the floodplains (greater volume and exchange under more recurrence interval storms) was observed from Stage 0 restoration, which reduces bank height more than other approaches. We also conducted a quantitative literature synthesis of nitrate removal rates from stream restoration projects. We focused on how removal rates varied with properties relevant at watershed scales, such as effects of stream order. The resulting database will aid in determining which stream restoration parameters better reduce nutrient loads and in simulating the effects of stream restoration on water quality at watershed scales. Floodplain restoration practices, and particularly Stage 0 approaches, enhance flood attenuation which can help to counteract urban hydrologic effects. / Master of Science / Extreme flooding and excess nutrient pollution have been detrimental to river health under increased environmental stress from human activities (e.g., agriculture, urbanization). Riverine flooding can be detrimental to human life and infrastructure yet provides important habitat and ecosystem services. Traditional flood control approaches (e.g., levees, dams) negatively impact habitat and ecosystem services, and cause flooding elsewhere along the river. Prior studies have shown that stream restoration can enhance flood attenuation and aid in removal of excess nutrients. Previous studies have shown that stream restoration helps to transport nutrients to highly reactive soils and increases time for reactions. However, the effects of floodplain restoration during small and sub annual recurrence interval storms have not been thoroughly studied, nor have cumulative impacts of floodplain restoration on water quality at watershed scales. To fill these knowledge gaps, increased understanding of stream restoration design parameters and watershed level characteristics (e.g., tributary inflows, nutrient loads, etc.) is necessary. We used HEC-RAS to study flood attenuation via stream restoration under small and sub-annual recurrence interval storms on a generic stream from the Chesapeake Bay Watershed. In HEC-RAS we varied percent of channel restored, location of restoration, bank height of restoration, floodplain width, and floodplain Manning's n (surface roughness). Overall, stream restoration did reduce peak flow and decrease time to peak, which means that restoration can diminish negative flooding effects. The greatest exchange with the floodplains was observed under Stage 0 restoration, which reduces bank height more than other approaches. We also conducted a quantitative literature synthesis to collect nitrate removal rates from stream restoration projects. We focused on how removal rates varied with properties relevant at watershed scales, such as effects of stream order. The resulting database will aid in determining which stream restoration parameters better reduce nutrient loads and in simulating the effects of stream restoration on water quality at watershed scales. These efforts will help to inform practitioners how to construct stream restoration projects that are more efficient for flood control and nutrient reduction. Floodplain restoration practices, particularly Stage 0 approaches, enhance flood attenuation and exchange which can help to counteract urban hydrologic effects.

Fade and inter-fade duration data obtained from the three beacons at 12, 20, and 30 GHz aboard the OLYMPUS satellite were analyzed. The different types of signal impairments and their causes were highlighted and a literature survey conducted. Twelve months of fade and inter-fade data were analyzed and the results of these statistics are presented in the form of tables and figures. The analysis was done on both the monthly and annual data. These tables and figures show that at the higher fade levels, the number of fade events and the fade time is smaller than at the lower thresholds. For the same fade level the number of fade events and the fade time goes down as the fade duration which it exceeds is increased. Inter-fade durations also showed similar results. The fades exhibited seasonal dependencies. The number of fades (and consequently the fade time) were much higher for the months of May through August and for the months of March and December. The other months showed very little fade activity. A model was also constructed that can predict the fade time as a function of frequency, attenuation level, and fade duration interval. The predicted fade times agree well with the measured fade duration data. An alternate simplified version of the model is also presented. / Master of Science

Frequency scaling of attenuation is the prediction of attenuation at a desired frequency from attenuation values at a base frequency. The attenuation at the base frequency is often known from prior measurements. Frequency scaling of attenuation is of interest because of the eventual need to exploit higher frequency bands. Most satellite communications traffic now use C-band (4-8 GHz) and Ku-band (12-18 GHz). The next approved, yet largely unused, frequency allocation for domestic use is in the K-band (18-27 GHz) to Ka-band (27-40 GHz). At these higher frequencies, however, earth-space radio links suffer atmospherically induced impairments as frequency increases. In particular, rain causes severe fading. Consequently, satellite systems in these higher bands are very susceptible to outages due to rain-induced fades. Reliable frequency scaling models are needed in system design to estimate the effect of these rain-induced fades. Between August 1990 and August 1992, V.P.I. & S.U.'s SATCOM Group performed extensive measurements of slant path attenuation using the 12, 20, and 30 GHz beacon signals (in the Ku/Ka-bands) of the European OLYMPUS experimental satellite. The experimental results are used to evaluate the usefulness of scaling models proposed by other researchers, both for instantaneous and statistical purposes. New models are presented for accurate scaling of attenuation within the Ku/Ka-bands. / Master of Science

This thesis reports the results of a thorough study into the effects of rain and ice on the polarization reuse technique for earth-space communications. Precipitation in the form of rain and ice leads to significant depolarization and attenuation of dual polarized signals above about 10 GHz. The depolarization versus attenuation relationship is examined in depth using a rigorous multiple scattering model. This relationship for rain is expressed in the form of a simple function similar to that used by the CCIR. Prediction accuracy using this simple model is quantified by comparisons to measured data and other model values. The impact of depolarization effects on the carrier-to-noise ratio for digital PSK systems is also addressed. Preliminary results for ice layer effects are presented. / Master of Science

This thesis investigates the impedance of acoustic liners, to attenuate noise originating from jet engines and enable compliance with international standards and regulations regarding noise from airplane jet engines. Experimental tests of two supplied liners were conducted in an impedance tube; one liner with known and predictable properties, and one liner with unknown properties. The tests included tonal excitations in the formats of stepped sine and random noise with frequencies within set boundaries. After post-processing of the captured data, the desired impedance could be analysed in terms of excitated frequencies and sound pressure levels. The conclusions from this project are that both of the liners deviated from their expected behavior, which was that liner 1 should have been unaffected by the alternated sound pressure levels, and liner 3 should have shown bigger affection due to the changed sound pressure level. Since the results were different than expected, there might have been minor sources of error during the measurements. It could be investigated if there is leakage from the mounting of the liners, or if the 3D printing resolution is sufficient. Because of limitations in time, there is more left in this project to investigate. Therefore, conducting similar studies where more frequencies, sound pressure levels, and multi-tonal measurements can be included, is suggested as future work.