Nanostructured (NS, grain size (d) <100nm) and ultrafine grained (UFG, d<500nm) metals possess superior mechanical and electrical properties over coarse grained (CG, d≫1μm) metals. The strength of metals like copper (Cu) has been shown to be significantly improved when engineered to have fine and ultrafine grain sizes via processes such…
Nanostructured (NS, grain size (d) <100nm) and ultrafine grained (UFG, d<500nm) metals possess superior mechanical and electrical properties over coarse grained (CG, d≫1μm) metals. The strength of metals like copper (Cu) has been shown to be significantly improved when engineered to have fine and ultrafine grain sizes via processes such as cryomilling, Cold Isostatic Pressing (CIP) and Continuous Equal Channel Angular Pressing (C-ECAP). This study investigates the mechanical and electrical properties of laboratory scale copper (Cu) conductors manufactured through several steps including cryomilling followed by cold isostatic pressing and finally C-ECAP and how its strength is affected by a variety of parameters when tested in uniaxial tension. The copper material is fabricated through cryomilling, cold isostatic pressing and (C-ECAP). Mechanical characterization is conducted using uniaxial tensile tests, nanoindentation and hardness tests. Pre and Post fabrication examination of the material with 3D-xray tomography, optical and electron microscope were conducted to gain deeper understanding of the effects of the processing parameters on the material during fabrication and the evolution of the microstructure as the powders go through the manufacturing process. Electrical testing is conducted to evaluate the electrical conductivity of the manufactured copper.
While the material showed improved strength and hardness compared to conventional copper material at room temperature, its ductility decreased. Also, higher ECAP temperatures produced materials with higher electrical and mechanical properties.
Material behavior under high strain rate deformation has always been an interesting topic. Under this extreme impact, possible structure changes such as phase transformation, chemical reaction, and densification occur in materials. It is helpful to develop a fundamental understanding of structure-property relationship, which helps to build a theoretical model and…
Material behavior under high strain rate deformation has always been an interesting topic. Under this extreme impact, possible structure changes such as phase transformation, chemical reaction, and densification occur in materials. It is helpful to develop a fundamental understanding of structure-property relationship, which helps to build a theoretical model and speed up the material design process. Although shock experiment techniques have been widely developed, numerical approaches such as first principle calculations and molecular dynamics simulations have demonstrated their power in predicting shock behavior and revealing structure-property relationship in an economic and feasible manner. In this dissertation, the mechanical properties and shock responses of three materials, polyurea, silicate glass, and erythritol were investigated, among which polyurea and silicate glass are proposed to be protective materials, while erythritol is proposedto be a surrogate of the explosive material pentaerythritol tetranitrate. First principle calculations and classical molecular dynamics were carried out to predict the shock Hugoniot, and other thermomechanical properties. The simulations also explored potential shock-induced phase transformations in these three materials and seek to draw connections between shock-driven transformations and the underlying chemical composition and material structure.
composition and material structure.
Vanadium-dioxide-based devices show great switchability in their optical properties due to its dramatic thermochromic phase transition from insulator to metal, but generally have concerns due to its relatively high transition temperature at 68 °C. Doping the vanadium dioxide with tungsten has been shown to reduce its transition temperature at the…
Vanadium-dioxide-based devices show great switchability in their optical properties due to its dramatic thermochromic phase transition from insulator to metal, but generally have concerns due to its relatively high transition temperature at 68 °C. Doping the vanadium dioxide with tungsten has been shown to reduce its transition temperature at the cost lower optical property differences between its insulating and metallic phases. A recipe is developed through parametric experimentation to fabricate tungsten-doped vanadium dioxide consisting of a novel dual target co-sputtering deposition, a furnace oxidation process, and a post-oxidation annealing process. The transmittance spectra of the resulting films are measured via Fourier-transform infrared spectroscopy at different temperatures to confirm the lowered transition temperature and analyze their thermal-optical hysteresis behavior through the transition temperature range. Afterwards, the optical properties of undoped sputtered vanadium films are modeled and effective medium theory is used to explain the effect of tungsten dopants on the observed transmittance decrease of doped vanadium dioxide. The optical modeling is used to predict the performance of tungsten-doped vanadium dioxide devices, in particular a Fabry-Perot infrared emitter and a nanophotonic infrared transmission filter. Both devices show great promise in their optical properties despite a slight performance decrease from the tungsten doping. These results serve to illustrate the excellent performance of the co-sputtered tungsten-doped vanadium dioxide films.
Recent studies found that culture as part of the socio-cultural lens of human factors has a significant role in aviation safety, not limited to aircraft accident causation. This research aims to employ the Global Leadership and Organizational Behaviour Effectiveness (GLOBE) model to examine the effect of cultural influence on aviation…
Recent studies found that culture as part of the socio-cultural lens of human factors has a significant role in aviation safety, not limited to aircraft accident causation. This research aims to employ the Global Leadership and Organizational Behaviour Effectiveness (GLOBE) model to examine the effect of cultural influence on aviation accident causation analysis, in accordance with the Human Factors Analysis and Classification System (HFACS), with a focus on cases of Indonesian aviation accidents and US aviation accidents. This qualitative research effort evaluated six cases of Indonesian aviation accidents and six cases of US aviation accidents in the period between 2002 through 2022. The analysis used the preliminary HFACS results developed by the author and further analyzed using semi-structured interviews with six Indonesian aviation experts and four US experts to examine the existence of cultural influence on the accidents. Thematic content analysis was utilized to analyze cultural influence on aircraft accident causation cases based on participants’ narration. The result covered the effect of the cultural differences between Indonesia and the US, including the characteristics of power distance, in-group collectivism, and performance orientation on HFACS analysis, which could logically lead to a more comprehensive analysis of issues at the level of unsafe supervision and organizational influences, and could result in a recommendation regarding future enhancement to the HFACS model.
humans are currently facing issues with the high level of carbon emissions that will cause global warming and climate change, which worsens the earth’s
environment. Buildings generate nearly 40% of annual global CO2 emissions, of which
28% is from building operations, and 11% from materials and construction. These
emissions must…
humans are currently facing issues with the high level of carbon emissions that will cause global warming and climate change, which worsens the earth’s
environment. Buildings generate nearly 40% of annual global CO2 emissions, of which
28% is from building operations, and 11% from materials and construction. These
emissions must be decreased to protect from further environmental harm. The good news
is there is a way that carbon emissions can be decreased. The use of thermogalvanic
bricks enables electricity generation by the temperature difference between the enclosure
above the ceiling (i.e., the attic in a single-family home) and the living space below. A
ceiling tile prototype was constructed that can make use of this temperature difference to
generate electricity using an electrochemical system called a thermogalvanic cell.
Furthermore, the application of triply periodic minimal surfaces (TPMS) can increase the
thermal resistance of the ceiling tile, which is important for practical applications. Here,
Schwarz P TPMS structures were 3D-printed from polyvinylidene fluoride (PVDF), and
inserted into the electrolyte solution between the electrodes. Graphite was used as
electrodes on the positive and negative sides of the tile, and Iron (II) and Iron (III)
perchlorate salts were used as electrolytes. The maximum generated power was measured
with different porosities of TPMS structure, and one experiment without a TPMS
structure. The results indicated that as the porosity of the TPMS structure increases, the
maximum power decreases. The experiment with no TPMS structure had the largest
maximum power.
Ethernet based technologies are emerging as the ubiquitous de facto form of communication due to their interoperability, capacity, cost, and reliability. Traditional Ethernet is designed with the goal of delivering best effort services. However, several real time and control applications require more precise deterministic requirements and Ultra Low Latency (ULL),…
Ethernet based technologies are emerging as the ubiquitous de facto form of communication due to their interoperability, capacity, cost, and reliability. Traditional Ethernet is designed with the goal of delivering best effort services. However, several real time and control applications require more precise deterministic requirements and Ultra Low Latency (ULL), that Ethernet cannot be used for. Current Industrial Automation and Control Systems (IACS) applications use semi-proprietary technologies that provide deterministic communication behavior for sporadic and periodic traffic, but can lead to closed systems that do not interoperate effectively. The convergence between the informational and operational technologies in modern industrial control networks cannot be achieved using traditional Ethernet. Time Sensitive Networking (TSN) is a suite of IEEE standards designed by augmenting traditional Ethernet with real time deterministic properties ideal for Digital Signal Processing (DSP) applications. Similarly, Deterministic Networking (DetNet) is a Internet Engineering Task Force (IETF) standardization that enhances the network layer with the required deterministic properties needed for IACS applications. This dissertation provides an in-depth survey and literature review on both standards/research and 5G related material on ULL. Recognizing the limitations of several features of the standards, this dissertation provides an empirical evaluation of these approaches and presents novel enhancements to the shapers and schedulers involved in TSN. More specifically, this dissertation investigates Time Aware Shaper (TAS), Asynchronous Traffic Shaper (ATS), and Cyclic Queuing and Forwarding (CQF) schedulers. Moreover, the IEEE 802.1Qcc, centralized management and control, and the IEEE 802.1Qbv can be used to manage and control scheduled traffic streams with periodic properties along with best-effort traffic on the same network infrastructure. Both the centralized network/distributed user model (hybrid model) and the fully-distributed (decentralized) IEEE 802.1Qcc model are examined on a typical industrial control network with the goal of maximizing scheduled traffic streams. Finally, since industrial applications and cyber-physical systems require timely delivery, any channel or node faults can cause severe disruption to the operational continuity of the application. Therefore, the IEEE 802.1CB, Frame Replication and Elimination for Reliability (FRER), is examined and tested using machine learning models to predict faulty scenarios and issue remedies seamlessly.
Dehumidifiers are ubiquitous and essential household appliances in many parts of the world. They are used extensively in tropical and sub-tropical environments to lower humidity in living spaces, where high ambient humidity can lead to numerous negative health effects from mild physical discomfort to more serious conditions such as mold…
Dehumidifiers are ubiquitous and essential household appliances in many parts of the world. They are used extensively in tropical and sub-tropical environments to lower humidity in living spaces, where high ambient humidity can lead to numerous negative health effects from mild physical discomfort to more serious conditions such as mold build up in structures and dangerous illnesses in humans. Most common dehumidifiers are based on conventional mechanical refrigeration cycles, where the effects of condensation heat transfer play a critical role in their effectiveness. In these devices, humid ambient air flows over a cold evaporator, which lowers the temperature of the humid ambient air below its dew point temperature and therefore decreases its water content by causing liquid water condensation on the evaporator surface. The rate at which humidity can be extracted from the ambient air is governed in part by how quickly the evaporator can shed the condensed droplets. Recent advances in soft, stretchable, thermally enhanced (through the addition of liquid metals) silicone tubing offer the potential to use these stretchable tubes in place of conventional copper pipe for applications such as dehumidification. Copper is a common material choice for dehumidifier evaporator tubing owing to its ubiquity and its high thermal conductivity, but it has several thermal downsides. Specifically, copper tubes remain static and typically rely on gravity alone to remove water droplets when they reach a sufficient mass. Additionally, copper’s naturally hydrophilic surface promotes film-wise condensation, which is substantially less effective than dropwise condensation. In contrast to copper, thermally enhanced soft stretchable tubes have naturally hydrophobic surfaces that promote the more effective dropwise condensation mode and a soft surface that offers higher nucleation density. However, soft surfaces also increase droplet pinning, which inhibits their departure. This work experimentally explores the effects of periodic axial stretching and retraction of soft tubing internally cooled with water on droplet condensation dynamics on its exterior surface. Results are discussed in terms of overall system thermal performance and real-time condensation imaging. An overall null result is discovered, and recommendations for future experiments are made.
Realtime understanding of one’s complete metabolic state is crucial to controlling weight and managing chronic illnesses, such as diabetes. This project represents the development of a novel breath acetone sensor within the Biodesign Institute’s Center for Bioelectronics and Biosensors. The purpose is to determine if a sensor can be manufactured…
Realtime understanding of one’s complete metabolic state is crucial to controlling weight and managing chronic illnesses, such as diabetes. This project represents the development of a novel breath acetone sensor within the Biodesign Institute’s Center for Bioelectronics and Biosensors. The purpose is to determine if a sensor can be manufactured with the capacity to measure breath acetone concentrations typical of various levels of metabolic activity. For this purpose, a solution that selectively interacts with acetone was embedded in a sensor cartridge that is permeable to volatile organic compounds. After 30 minutes of exposure to a range of acetone concentrations, a color change response was observed in the sensors. Requiring only exposure to a breath, these novel sensor configurations may offer non-trivial improvements to clinical and at-home measurement of lipid metabolic rate.
Two of the most fundamental barriers to the exploration of the solar system are the cost of transporting material to space and the time it takes to get to destinations beyond Earth’s sphere of influence. Space elevators can solve this problem by enabling extremely fast and propellant free transit to…
Two of the most fundamental barriers to the exploration of the solar system are the cost of transporting material to space and the time it takes to get to destinations beyond Earth’s sphere of influence. Space elevators can solve this problem by enabling extremely fast and propellant free transit to nearly any destination in the solar system. A space elevator is a structure that consists of an anchor on the Earth’s surface, a tether connected from the surface to a point well above geostationary orbit, and an apex counterweight anchor. Since the entire structure rotates at the same rate as the Earth regardless of altitude, gravity is the dominant force on structures below GEO while centripetal force is dominant above, allowing climber vehicles to accelerate from GEO along the tether and launch off from the apex with large velocities. The outcome of this project is the development of a MATLAB script that can design and analyze a space elevator tether and climber vehicle. The elevator itself is designed to require the minimum amount of material necessary to support a given climber mass based on provided material properties, while the climber is simulated separately. The climber and tether models are then combined to determine how the force applied by the climber vehicle changes the stress distribution inside the tether.
Arizona has been rapidly expanding in both population and construction over the last 20 years, and with the hot summer climate, many homeowners experience a significant increase in their utility bills. The cost to reduce these energy bills with home renovations can become expensive. This has become increasingly apparent over…
Arizona has been rapidly expanding in both population and construction over the last 20 years, and with the hot summer climate, many homeowners experience a significant increase in their utility bills. The cost to reduce these energy bills with home renovations can become expensive. This has become increasingly apparent over the last few years with the impact that covid had on the global supply chain. Prices of materials and labor have never been higher, and with this, the price of energy continues to increase. Therefore, it is important to explore methods to make homes more energy-efficient without the price tag. In addition to benefitting the homeowner by decreasing the cost of their monthly utility bills, making homes more energy efficient will aid in the overall goal of reducing carbon emissions.