ASU Scholarship Showcase

The neural mechanisms that take place during learning and adaptation can be directly probed with brain-machine interfaces (BMIs). We developed a BMI controlled paradigm that enabled us to enforce learning by introducing perturbations which changed the relationship between neural activity and the BMI's output. We introduced a uniform perturbation to the system, through a visuomotor rotation (VMR), and a non-uniform perturbation, through a decorrelation task. The controller in the VMR was essentially unchanged, but produced an output rotated at 30° from the neurally specified output. The controller in the decorrelation trials decoupled the activity of neurons that were highly correlated in the BMI task by selectively forcing the preferred directions of these cell pairs to be orthogonal. We report that movement errors were larger in the decorrelation task, and subjects needed more trials to restore performance back to baseline. During learning, we measured decreasing trends in preferred direction changes and cross-correlation coefficients regardless of task type. Conversely, final adaptations in neural tunings were dependent on the type controller used (VMR or decorrelation). These results hint to the similar process the neural population might engage while adapting to new tasks, and how, through a global process, the neural system can arrive to individual solutions.

Structural health monitoring has been studied by a number of researchers as well as various industries to keep up with the increasing demand for preventive maintenance routines. This work presents a novel method for reconstruct prompt, informed strain/stress responses at the hot spots of the structures based on strain measurements at remote locations. The structural responses measured from usage monitoring system at available locations are decomposed into modal responses using empirical mode decomposition. Transformation equations based on finite element modeling are derived to extrapolate the modal responses from the measured locations to critical locations where direct sensor measurements are not available. Then, two numerical examples (a two-span beam and a 19956-degree of freedom simplified airfoil) are used to demonstrate the overall reconstruction method. Finally, the present work investigates the effectiveness and accuracy of the method through a set of experiments conducted on an aluminium alloy cantilever beam commonly used in air vehicle and spacecraft. The experiments collect the vibration strain signals of the beam via optical fiber sensors. Reconstruction results are compared with theoretical solutions and a detailed error analysis is also provided.

Highly flexible modules using thin 153 cm[superscript 2] silicon crystalline cells and transparent fluoropolymer foil are demonstrated. The modules can be flexed 200 times around a bend radius of 4 cm without change in efficiency. The silicon crystalline heterojunction solar cells are 65±5 μm-thick with efficiencies up to 18.4%. Cracks in the solar cells and interconnections that are induced by mechanical stress during module bending are examined using electroluminescence. Two interconnection solutions are discussed: ribbons affixed to the busbars using a conductive adhesive, and indium coated wires directly bonded to the cell fingers. Modules using wire interconnection are found to be highly flexible with efficiencies greatly exceeding existing commercial flexible modules using thin films and have potential applications in light-weight modules for building integrated and portable photovoltaic power.

The tapered joints of modular hip implants are prone to fretting and crevice-corrosion. This can lead to total failure in under a year, especially for heavier, more active implant recipients. In this study, fractography of a failed Profemur Z implant showed that a life limiting fatigue crack was nucleated on the anterolateral surface of the implant's neck. The fatigue crack nucleation area appeared to have both more fretting damage and a higher corrosion rate than on other surfaces of the neck.

There is mounting evidence to suggest that the urban built form plays a crucial role in household energy consumption, hence planning energy efficient cities requires thoughtful design at multiple scales - from buildings, to neighborhoods, to urban regions. While data on household energy use are essential for examining the energy implications of different built forms, few utilities providing power and gas offer such information at a granular scale. Therefore, researchers have used various estimation techniques to determine household and neighborhood scale energy use. In this study we develop a novel method for estimating household energy demand that can be applied to any urban region in the US with the help of publicly available data. To improve estimates of residential energy this paper describes a methodology that utilizes a matching algorithm to stitch together data from RECS with the Public Use Microdata Sample (PUMS) provided by the Bureau of Census. Our workflow statistically matches households in RECS and PUMS datasets based on the shared variables in both, so that total energy consumption in the RECS dataset can be mapped to the PUMS dataset. Following this mapping procedure, we generate synthetic households using processed PUMS data together with marginal totals from the American Community Survey (ACS) records. By aggregating energy consumptions of synthesized households, small area or neighborhood-based estimates of residential energy use can be obtained.

Although the majority of late-onset Alzheimer's disease (AD) patients are labeled sporadic, multiple genetic risk variants have been identified, the most powerful and prevalent of which is the e4 variant of the Apolipoprotein E (APOE) gene. Here, we generated human induced pluripotent stem cell (hiPSC) lines from the peripheral blood mononuclear cells (PBMCs) of a clinically diagnosed AD patient [ASUi003-A] and a non-demented control (NDC) patient [ASUi004-A] homozygous for the APOE4 risk allele. These hiPSCs maintained their original genotype, expressed pluripotency markers, exhibited a normal karyotype, and retained the ability to differentiate into cells representative of the three germ layers.

The key role of water to obtain high-mobility IO:H (hydrogenated indium oxide) layers has been well documented, but introducing the required tiny amount of water is technologically challenging. We first use simulations to evidence the key role of high mobility for the transparent conductive oxide for high-efficiency crystalline silicon solar cells. Then, we investigate an approach to fabricate high-mobility IO:H that circumvent the introduction of water vapor, relying on water vapor from ambient air. A sputtering tool equipped with a residual gas analyzer allows partial pressure monitoring of hydrogen and water in the system, and to link the gas composition to the properties of the deposited films. To vary the residual water pressure, we varied the pumping time after opening the chamber and before starting the deposition to reach different base pressures (1. 10^-5 mbar to 3. 10^-7 mbar), which are mostly composed of residual water. An optimum base pressure around 3. 10^-6 mbar - and not lower pressures - was found to yield the highest mobility values after annealing. An alternative approach by introducing a small flow of hydrogen together with argon and oxygen is also shown to provide promising results.

Project management has struggled with delivering low performing construction and information technology (IT or ICT) projects. Approximately 60% of construction projects are over budget, over schedule and have low customer satisfaction. The IT industry reports even worse performance for their projects. IT projects seem to be far less defined, leading to increased complexity. Documentation shows that companies do not have a successful methodology to track their performance and thus there is a lack of documented performance information to identify if their project management methodologies are delivering high quality and efficient projects. A literature research was performed on the most used Project Management (PM) methodologies worldwide. These PM methodologies were then compared based upon their characteristics and performance information to identify the most successful methodologies. The analysis of the results revealed that only one methodology had proven performance metrics on over 90% of its projects.

The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed.

Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics, including their significance, from eight flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number that influence droplet concentration. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution.

Cloud droplets were smaller in regions of enhanced particles near shore. However, physically thinner clouds, and not just higher droplet number concentrations from pollution, both contributed to the smaller droplets. Satellite measurements were used to show that cloud albedo was highest 500–1000 km offshore, and actually slightly lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo.

Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

Stereotypical construction of buildings, however convenient, poses its own set of challenges. It affects the sustainable development critically and can give rise to social, economic and environmental problems. In other words, same design of a building if repeated irrationally from one place to another even within an identical climatic region gives rise to some grave problems which can compromise multiple dimensions of sustainability. Mosque architecture has some elements that have gradually become its identity. In this research different elements of repetition i.e. stereotype features in mosque architecture are explored. While using a case study approach this research is used to assess mosque projects in an urban region of Lahore, Pakistan. While considering the case studies the positive and negative effects of stereotype elements on three dimensions of sustainability are investigated.