Engineeringhttp://hdl.handle.net/1773/196532024-03-28T09:52:46Z2024-03-28T09:52:46ZResistive Switching Effects of Vanadium Pentoxide Thin FilmWan, Zhennihttp://hdl.handle.net/1773/417112018-04-25T11:05:13ZResistive Switching Effects of Vanadium Pentoxide Thin Film
Wan, Zhenni
In this Ph.D. work, the resistive switching effects of vanadium pentoxide (V2O5) thin films are extensively explored and investigated. Contrary to conventional Flash memory devices where the information is stored by the electrons in the floating gate (FG), emerging memory devices employs the resistive switching effects of metal-insulator-metal (MIM) devices in which the information is stored in the location of atoms, which determines the high or low resistance state. Both reversible and irreversible resistive switching are discovered for the first time in V2O5 based MIM devices and the switching effects are studied as a function of metal contacts and environment, which play an important role in determining the device characteristics. Two conductor materials, chromium and indium tin oxide (ITO), are mainly investigated and the mechanisms for both irreversible and reversible switching are addressed. The dependence of switching effects on testing environment is enabled by building a vacuum test chamber. The devices are tested in a variety of gases environment and the role of intercalated H2O molecules in enabling the resistive switching is established. Resistance change is attributed to reduction of valence states of vanadium at electrode/V2O5 interface resulting from the electrochemical reactions when a voltage bias is applied. Reversibility of the switching is determined by whether the electrode material has the capability of temporarily storing oxygen ions. V2O5 xerogel film synthesized by sol-gel process experiences drastic atomic structural change during post annealing process, resulting in significant impact on resistive switching characteristics. X-ray diffraction analysis reveals that -phase V2O5 forms at bottom V2O5/ITO interface while -phase V2O5 forms at top V2O5/ITO interface. The presence of intercalated H2O molecules is essential for the reversible switching to occur. Ab initio calculations prove that the enlarged interlayer spacing in V2O5 xerogel significantly reduces the formation energies of oxygen vacancies, thus enabling the creation of mobile oxygen ions. In order to make the synthesis of V¬2O5 thin film more compatible with modern IC fabrication processes, thermal evaporation is employed for V2O5 deposition. Reversible bipolar switching is preserved and the stability of I-V characteristics over annealing temperature has been improved. DFT calculations are performed to simulate the amorphous V2O5 structure generated by melt-quench process using ab initio molecular dynamics technique. Formation energies of oxygen vacancy is also reduced in amorphous V2O5. Degradation of V2O5 film due to spontaneous reduction of vanadium oxide with presence of intercalated water molecules has been suppressed.
Thesis (Ph.D.)--University of Washington, 2018
Real-Time Prediction of Lean Blowout using Chemical Reactor NetworkKaluri, Abhishekhttp://hdl.handle.net/1773/417102018-04-25T11:05:11ZReal-Time Prediction of Lean Blowout using Chemical Reactor Network
Kaluri, Abhishek
The lean blow-out (LBO) of gas turbine combustors is a concern that can limit the rate of descent for an aircraft, the maneuverability of military jets, and cause a costly and time-intensive reignition of land-based gas turbines. This work explores the feasibility of a model-based combustor monitoring for the real-time prediction of combustion system proximity to LBO. The approach makes use of (1) real-time temperature measurements in the reactor, coupled with (2) the use of a real-time chemical reactor network (CRN) model to interpret the data as it is collected. The approach is tested using a laboratory jet-stirred reactor (JSR), operating on methane at near atmospheric pressure. The CRN represents the reactor as three perfectly stirred reactors (PSRs) in series with a recirculation pathway, the model inputs include real-time reactor temperature measurements and mass flows of fuel and air. The goal of the CRN is to provide a computationally fast means of interpreting measurements in real time with regard to blowout proximity. The free radical concentrations and their trends and ratios are studied in each reactor zone. The results indicate that the hydroxyl radical maximum concentration moves downstream as the reactor approaches LBO. The ratio of hydroxyl radical concentrations in the jet region versus the recirculation region is proposed as a criterion for the LBO proximity. This real-time, model-based monitoring methodology sheds insight into combustion processes in aerodynamically stabilized combustors as they approach LBO.
Thesis (Master's)--University of Washington, 2018
High Accuracy Mobile 3D Scanning Using Structured Laser Beam PatterningMakhsous, Sepehrhttp://hdl.handle.net/1773/380372017-02-15T11:56:14ZHigh Accuracy Mobile 3D Scanning Using Structured Laser Beam Patterning
Makhsous, Sepehr
A person's diet affects their weight, lifespan, and chances of occurrence of such medical problems as diabetes, obesity, and cancer, to name a few. Enhanced dietary assessment techniques are critical for epidemiological studies that target diet-related problems. Currently, nutritional research is considerably hindered by the low accuracy in estimating individual dietary intake, and, more specifically, portion size. Dietary assessment plays an increasingly significant role in modern medical research. While inadequate diets can increase the risk of diabetes, obesity, and cancer. It is essential to design accurate, cost-effective tools that measure dietary data to advance nutritional research. This dissertation describes a low-cost and efficient method of calculating nutritional information by using 3D reconstruction and image processing. This system is called Dietary Data Recorder System (DDRS), which consists of a smartphone, a laser projector, and the main algorithm, which extracts the data from the DDRS for volume and nutritional calculations. The DDRS software consists of four main algorithms: Automatic Laser Detection algorithm, Segmentation algorithm, 3D Mapping algorithm, and Nutritional Estimation algorithm. In particular, this dissertation focuses on the first two functions: Automatic Laser Detection algorithm and Segmentation algorithm.
Thesis (Master's)--University of Washington, 2016-12