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Trait-like Resting-State Brain Oscillations Predict Subsequent Problem-Solving Strategies
Get PDFPeople use different processing strategies to solve problems. Previous research distinguishes between solving problems by analysis, that is, in a conscious, deliberate manner, versus by insight, in which the solution appears abruptly in awareness (the "Aha" phenomenon) after a period of unconscious processing. Prior work provides little evidence whether the tendency to solve problems using one or the other of these strategies constitutes a stable, trait-like cognitive style. We tested this hypothesis by assessing whether individuals evince a consistent preference for a particular solving strategy across days and types of problems and whether these cognitive styles have neural correlates. We recorded participants' resting-state electroencephalograms (EEGs) on 4 occasions, approximately once per week. At the end of the third and fourth sessions, participants attempted to solve a series of short verbal problems (compound remote associates during session 3 and anagrams during session 4). Based on participants' trial-by-trial reports of the manner in which they solved anagram problems, individuals were categorized as predominantly relying on an insight or an analytic solving strategy. The resting-state EEGs of these groups, recorded during previous sessions were compared. Participants in the analytic group showed greater EEG beta power over midline and right inferior-frontal regions compared to insightful participants; participants in the insightful group showed greater beta power over left superior parietal cortex compared to those in the analytic group. Group differences in solving strategy and resting-state EEGs assessed with anagram problems generalized to the compound remote associates problems. Overall, these results demonstrate the behavioral and neural consistency of these cognitive styles over both time and type of problem. The finding that insightful solvers exhibited a lower ratio of frontal to parietal neural activity supports the hypothesis that insightfulness results from chronic relative frontal hypoactivation and concomitant parietal disinhibition whereas analytic solvers exhibit chronic relative frontal hyperactivation and parietal inhibition.Ph.D., Psychology -- Drexel University, 201
Symmetry Breaking in the Correlated Electronic and Lattice Degrees of Freedom in the CuTiSe T-x Phase Diagram
Get PDFIn this thesis I investigate the relationship between the charge density wave (CDW) phase and superconductivity in the T-x phase diagram of CuTiSe. I find that the incommensurate (IC)-CDW is related to the superconducting phase due to the fact that the former effectively isolates the CDW subsystem degrees of freedom. This increases the symmetry of the electronic populations within the IC-CDW band structure and leave them susceptible to internal instabilities, which in turn give rise to the superconducting phase. Because the correlated properties of these solid-state phases of matter are highly dependent on the crystalline quality of our samples, I also detail the growth of pristine single crystals and utilize several characterization techniques to aid in this purpose. In this portion of the thesis the single crystals are deliberately injected with heat and monitored to deduce the formation of defects through selenium migration. I also confirm the existence of chiral symmetry breaking in the bulk commensurate (C)-CDW phase in TiSe brought about by the cooperation of phonon and exciton degrees of freedom, and also observe chiral character in fluctuations above T. These thermal fluctuations were observed up to 80\,K above T via optical signatures of the folded Se-4p band and Raman signatures of the soft L phonon mode. The suppression of the excitonic degree of freedom with Cu intercalation brings about a quantum phase transition into the IC-CDW at x=0.04. Large quantum fluctuations of the folded Se-4p electronic band were observed at the quantum phase transition where measurements of the phonon system show the onset of incommensuration in the CDW super-lattice. Optical measurements demonstrate a large decoupling of the electron-phonon degrees of freedom within the electronic band structure of the IC-CDW subsystem.Ph.D., Physics -- Drexel University, 201
Computer Aided Patent Processing: Natural Language Processing, Machine Learning, and Information Retrieval
No full textThe intellectual property economy, and, more narrowly, the patent economy, form an incredibly wide-reaching and important part of the economic activity of the United States, and of the broader world. The patent ecosystem involves a diverse collection of players and interests. Inventors conceive of an idea, then patent agents and attorneys help them author and defend/refine a patent application, interacting with patent examiners at the patent offices who review it, checking for novelty, prior art, and usefulness (or industrial applicability). Once the patent is issued, and even sometimes while it is still in the application phase, middlemen companies may buy and sell it. A company owning a patent may then request that other companies license its use. Standards organizations, such as ETSI 3GPP or IEEE, are also important participants in the lifecycle of many important patents, since often certain patents are required in order to implement standards, and hence license agreement structures, such as the FRAND (fair reasonable and non-discriminatory) agreement, are set up to coordinate their licensing for use. Finally, if a company decides that another company is likely infringing on its patent, it may bring a case, which the federal courts must then hear. Today each of these problems are done by humans with minimal, near non-existent use of any custom software or algorithmic tools designed specifically to help with these tasks. The work carried out in this dissertation is part of a broader intellectual agenda which aims to address this deficiency. In order to maximize novelty, this dissertation selects two problems that are especially overlooked. One is extracting deep meaning from patent claims. The other one is using deep meaning in recommender systems mapping between patents and standards. Furthermore, in order to maximize impact and to kickstart further research in these problems, the work in this dissertation focuses on the creation and curation of datasets germane to these two problems, as well as the creation and evaluation of prototype baseline systems to solve them. In particular, a dataset of grammar annotations of patent claims is firstly curated via Amazon Mechanical Turk. Then a baseline natural language processing system is trained and evaluated for extracting deep meaning from patent claims on this dataset, showing that substantial improvements over existing techniques for extracting this deep meaning are possible by leveraging this new dataset. Next, two ground truth datasets associating patent claims and sections of standards from information provided in intellectual property rights (IPR) disclosures to the European Telecommunications Standards Institute (ETSI) are extracted and curated. Following that, a new machine learning based retrieval system is designed for mapping between patent claims and standards. Finally, the new machine learning based retrieval system is evaluated on both datasets and their subsets and reveals substantial improvements comparing with SVM and retrieval baseline systems.Ph.D., Electrical Engineering -- Drexel University, 201
Factoring Permutations into the Product of Two Involutions: A Probabilistic, Combinatorial, and Analytic Approach
Get PDFAn involution is a permutation that is its own inverse. Given a permutation [sigma] of [n], let N_n([sigma]) denote the number of ways to write [sigma] as a product of two involutions. The random variables N_n are asymptotically lognormal when the symmetric groups S_n are equipped with uniform probability measures, in particular, and more generally, Ewens measures of some fixed parameter [theta] > 0. The proof is based upon the observation that, for most permutations [sigma], the number of involution factorizations N_n([sigma]) can be well-approximated by B_n([sigma]), the product of the cycle lengths of [sigma]. The asymptotic lognormality of N_n can therefore be deduced from Erdős and Turán's theorem that B_n is itself asymptotically lognormal. We then briefly consider fixed-point free involution factorizations. A necessary and sufficient condition for a permutation to be the composition of two fixed-point free involutions is for it to have an even number of k-cycles, k = 1, 2, ... Through a combination of singularity analysis, the method of moments, and an appeal to the Shepp-Lloyd model for random permutations, the asymptotic enumeration and cycle structure of random permutations admitting fixed-point free involution factorizations are calculated.Ph.D., Mathematics -- Drexel University, 201
Solution deposited and modified iron oxide for enhanced solar water splitting
Get PDFGrowing worldwide energy demand coupled with an increasing awareness of anthropogenic climate change has driven research into carbon-neutral and solar-derived energy sources. One attractive strategy is the storage of solar energy in the bonds of H2 formed by photoelectrochemical (PEC) water splitting. Hematite, an iron oxide, has been widely investigated as a candidate material for PEC water splitting due to its stability, non-toxicity, earth abundance and consequent low cost, and a theoretical 15% solar-to-hydrogen conversion efficiency. However, poor electrical properties and slow rates of the water oxidation reaction have limited its potential as an economical water splitting catalyst. Additionally, the most efficient hematite-based devices are fabricated via expensive, vacuum-phase techniques, limiting scalability to broad integration into the energy supply. In this thesis, I develop a new, solution-based deposition method for high quality, planar hematite thin films using successive ionic layer adsorption and reaction (SILAR). The constant geometry and tight control over layer thickness possible with SILAR makes these films ideal model systems to understand the two key steps of PEC water oxidation: charge separation and interfacial hole transfer. In Chapter 3, I report on facile annealing treatments to dope hematite with Ti and Sn, and I show that these impurity atoms at the hematite/electrolyte interface increase hole transfer efficiency from nearly 0 to above 60%. However, charge separation remains below 15% with these dopants incorporated via solid state diffusion, mainly due to low hole mobility. To overcome this associated small transport length, extremely thin hematite coatings were deposited on Sb:SnO2 monolayer inverse opal scaffolds. With this modified substrate, photocurrent increased proportionately to the surface area of the scaffold. While Chapter 3 discusses incorporation of dopants via solid state diffusion, Chapter 4 examines methods to incorporate Ti via modified SILAR solutions. With this method, hematite films with well-controlled, uniform doping profiles were successfully fabricated. An optimal Ti concentration of 4.2% in the film enabled a charge separation efficiency of >20%, and I show that holes generated within 3 nm of the depletion region are separated with unity efficiency. With the addition of an ultrathin FeOOH overlayer, hole transfer efficiency is increased to 100% as a result of an increased concentration of reactive holes at the hematite/electrolyte interface. These combined effects lead to photocurrents >0.85 mAcm-2 at 1.23 VRHE, which is competitive with champion planar films regardless of fabrication method. Importantly, the methods of fabrication and analysis described in this thesis are applicable to a wide range of materials for a variety of applications. The SILAR method can be applied to many compounds, provided their constituent atoms are soluble in liquid solvents. Additionally, the facile optical and electrochemical measurements used to analyze hematite in Chapters 3 and 4 can be readily adapted to other semiconductor materials with the aim of understanding their charge transport properties.M.S., Materials Science and Engineering -- Drexel University, 201
A Phenomenological Study of Teachers' Perceptions and Interactions of English Language Learners
Get PDFIn the US over the last three decades the use of a language other than English at home has increased by an astounding 148 percent, and by the year 2020 around twenty-three percent of the US population over the age of five will speak a language other than English (Shin & Ortman, 2011). With these staggering increases, it is quite likely that a secondary-level content teacher will have to meet the needs of an English Language Learner (ELL). This hermeneutic phenomenological analysis aims to describe the lived experiences of urban high school teachers who serve this student population by exploring (a) instructional models for ELL students, (b) language acquisition theories, and (c) multiculturalism. This research focuses the central question: What characterizes the experiences of teachers who instruct students in an English Language program in an urban high school? For this research, participants were purposefully selected, and placed into one of three categories (a) monolingual content teachers that are not ESL-certified; (b) multilingual content teachers that are not ESL-certified; and (c) monolingual or multilingual teachers that are ESL-certified. The data for this research was collected through a two-round semi-structured interview process. In order to fully understand the participants' experiences with this phenomena, the data was then bracketed and analyzed for common experiences and themes. The emerging themes, empathy, challenges, preparation, and relationship building are directly related to the participants' experiences while interacting and serving the needs of their English language students. Through these experiences and themes, recommendations for the school are made, which include a series of teacher-led professional developments, providing teachers time and opportunity to meet with their culturally and linguistically diverse students, increase parent involvement, and allowing teachers to deviate from the curriculum in order to become more culturally responsive teachers.Ed.D., Educational Leadership and Management -- Drexel University, 201
Pacific Islander Women of the U.S. Armed Forces: A Narrative Study
Get PDFThe purpose of this qualitative study was to explore, through their narratives, the cultural, social, and professional experiences of Pacific Islander women who served in the United States Military (both veterans and Active Duty personnel). The researcher delved into the stories Pacific Islander women veterans and Active Duty members shared about their experiences before, during, and after serving in the military. Prior research suggested that Pacific Islander women may be silent about challenges and struggles due to their cultural upbringing (McLaughlin & Braun, 1998). Fifteen Pacific Islander women were invited to participate in this study. Eleven of the 15 participated: six Active Duty and five veterans. Islands represented were Fiji, Guam, Hawaii, Samoa, and Tonga, and branches of service included U.S. Air Force, U.S. Army, U.S. Navy, and the U.S. Marines. Data collected sought to answer three research questions: (a) what stories do Pacific Islander women tell about their cultural and social identity before joining the U.S. Armed Forces? (b) What stories do Pacific Islander women veterans share about being in the U.S. Armed Forces? And (c) What do Pacific Islander women veterans describe about coping with life transitions from military service to civilian education and career opportunities? The findings identified that for Pacific Islander women veterans and Active Duty members, (a) family and church values were integral to their worldviews, (b) encounters led to increasing self-awareness and stronger social identity, (c) building relationships while serving was rewarding, (d) coping with the emotional impacts of deploying, (f) transition from the military difficult, and (g) unprepared for securing civilian professions. More research is needed to bridge the gap in the academic community about Pacific Islander women in the U.S. Armed Forces. Recommendations included to: (a) recruit and retain more Pacific Islander women, both enlisted and officer, into the U.S. Armed Forces; (b) establish a support network for single mothers on Active Duty; (c) provide a sustainable network to assist Pacific Islander women veterans who suffer from PTSD; (d) enhance the Transition Assistance Program-TAP; and (e) focus programs to better support women veterans attending college.Ed.D., Educational Leadership and Management -- Drexel University, 201
The Effect of Grain Boundary Character and Grain Boundary Engineered Microstructures on the Sensitization and Corrosion of 316L
No full textThere is strong evidence showing that the Brandon criterion for misorientation is insufficient determining whether grain boundaries in austenitic stainless steels will resist corrosion. Efforts have been made to use more restrictive criteria, however the prevailing theory is that the grain boundary plane plays a critical role in this phenomena. Understanding how they boundaries resist corrosion, and how they are integrated into the grain boundary engineered (GBE) microstructure, is critical to the successful optimization of these alloys for corrosion resistance. This thesis presents experimental evidence comparing the corrosion performance and microstructural characteristics of GBE microstructures arrived at by cold rolled and tensile strain routes. An iterative process was developed to propagate the Rolled GBE microstructure through the thickness of the specimen by straining by a 5% reduction in area followed by a 1020 degrees Celsius anneal for 2 hours, which was repeated three times. The Tensile GBE used the same iterated processing, but received a 5% tensile extension. The two GBE microstructures were examined using the stereological analysis method and found to have the same level of coherent [sigma]3 grain boundaries as the Annealed microstructure. Measurements of the length fraction of grain boundaries using different misorientation tolerance criteria showed that the Tensile GBE had significantly more highly deviated [sigma]3 grain boundaries than the Rolled GBE. The Rolled GBE possessed more 2-CSL triple junctions, however when only [sigma]3 grain boundaries are considered special, the Tensile GBE possessed more. The Rolled GBE also showed a consistently larger grain size than the Tensile GBE, when considered with [sigma]3, without [sigma] 3, and without [sigma]3, [sigma]9, and [sigma]27 grain boundaries. All of these measures, except the 2-[sigma]3 triple junction metric, suggest that the Rolled GBE should better resist sensitization and corrosion. However, the mass loss testing clearly shows that the Rolled GBE has higher mass loss than the Tensile GBE microstructure in 1, 10, and 100 hour sensitization conditions. The case is further complicated, as the 1000 hour condition shows that the Annealed and Rolled GBE conditions both had lower mass loss due to desensitization but the mass loss of the Tensile GBE continued to increase. Extended exposure of the 100 hour condition shows that the mass loss rate has not reached steady state yet, and may approach that of the Annealed microstructure when it is finished. U-bend testing shows that the high nickel alloy used in this work is immune to stress corrosion cracking under normal testing conditions, cracking only during the aggressive ASTM G36 test. A method was developed to use ACOM to calculate the local crystallographic faces in TEM specimens. This was used to evaluate grain boundaries which proved to be corrosion resistant. The [sigma]9 grain boundary that resisted corrosion was found to have a (111) grain boundary crystal plane on one side, and a continuous array of nanotwins on the other, while the [sigma]9 that did corrode did not have a low index crystallographic plane. Neither [sigma]3 grain boundaries which corroded had a (111) grain boundary, and one that appeared curved in SEM was found to have nanoscale facets. A pair of [sigma]7 grain boundaries are examined, one of which corroded and the other did not, and neither had a low index crystallographic plane at the grain boundaries. All examined grain boundaries except the coherent [sigma]3s are enriched in Cr and depleted in Fe, Ni or both. This shows that in the 1 hour sensitization condition, the grain boundaries are not sensitized in the classic sense, suggesting that the corrosion is related to an inherent feature of the grain boundary structures in this case.Ph.D., Materials Science and Engineering -- Drexel University, 201
Engineering Freestanding, Binder-free Electrospun Nanofiber Cathodes and Use of In-Situ Infrared Spectroelectrochemistry for Lithium-Sulfur Batteries
No full textAs energy demands increase, development of energy storage and conversion systems becomes critical to meet the needs of society. The performance and lifetime of energy devices are highly dependent on the material chemistry, processing, and nanostructure. 1D nanomaterials show great promise for advanced energy materials owing to their high aspect ratios, mechanical flexibility, among other unique properties. Electrospun nanofibers are particularly advantageous owing to the versatility, in which control of the nanoarchitecture and composition is easily achievable. Electrospinning is a relatively simple fiber formation technique that uses a strong electric field to rapidly stretch and elongate a polymer-based solution or melt jet, creating ultrathin fibers with diameters on the order of 50 – 500 nm. The nanofibers form continuous into a non-woven fiber mat that is inherently free-standing which allows for direct usage without additional processing with insulating, inactive binder materials. My dissertation will focus on the synthesis and characterization of electrospun nanofibers materials and will establish key process-structure-property relationships for creating simple materials for organic photovoltaics and lithium-sulfur batteries. The nanomaterials for these systems have very different requirements, thus, these studies focused on the challenges associated with each application such that the nanofiber synthesis and types of characterization techniques were tailored to each application. The lithium-sulfur (Li-S) rechargeable battery is an emerging, close-to-market chemistry with several key advantages over lithium-ion: high energy density ~5 times greater than lithium-ion, high theoretical capacity of 1,675 mA h g-1 (vs 8 hours) and slurry processing with insulating binders, toxic solvents, and heavy current collectors which can make up 30-50% of the electrode weight. While cathodes are critical in confining polysulfides to prevent shuttling, the electrolyte plays an equally important role in redox chemistry and overall battery performance and understanding fundamental interactions between intermediate redox species and electrolyte is critical for rational design of electrolyte/cathode systems for Li-S batteries. New electrolyte additives are under development with the aim of suppressing polysulfide shuttling. Although better performance is observed, there is a lack in fundamental evidence of physical and chemical interactions to understand the underlying mechanism of the additive. The freestanding, binder-free sulfur cathodes developed in our previous work facilitated this electrolyte study through in situ infrared spectro-electrochemistry. Owing to the free-standing nature of the cathode, the lack of current collector in this cathode simplified the optical physics in FT-IR with attenuated total reflection (ATR), such that an in situ cell could be developed that closely replicated a coin cell without altering the key battery components, such as electrolyte volume, cathode, sulfur loading, etc., which was made possible with the ATR accessory. In this work, we demonstrate in situ ATR FT-IR to monitor both polysulfide speciation (Sx2-, 2 ≤ x ≤ 8) and triflate anion (electrolyte) coordination states while simultaneously running cyclic voltammetry (CV). Polysulfide evolution was monitored with IR via the S-S vibrational frequency around ~500 cm-1, which shifts with polysulfide order (chain length). While most in situ techniques only monitor polysulfide s, we found molecular-level changes occurred in the salt anion in response to polysulfide speciation. During CV, polysulfide dissolution increases total solute concentration, inducing anion interactions between low coordination state complexes– ion-pairs and free ions– to form aggregate complexes. Under fast CV sweep, less progressive formation of all polysulfides, due to diffusion limitations, resulting in higher concentrations of aggregates and polysulfide even upon completion of discharge. This new application of in situ FT-IR offers direct insight on dynamic interactions between electrolyte salt and polysulfide fundamental in developing Li-S systems and would be particularly useful to study electrolytes, additives, and new systems. With the development of energy technologies, green and renewable resources provide attractive alternatives to depleting fossil fuel supplies. Organic photovoltaics (OPV) offer several advantages over conventional inorganic PV: low weight, flexibility, semi-transparency, simple integration into other products, significantly lower manufacturing costs, short energy payback time, low environmental impact processing, as well as the potential for new markets, such as wearable PV. However, significantly lower efficiencies, due to poor separation and transport of free charge carriers in the photoactive layer, hinder widespread use of OPV technology. The photoactive layer consists of a spin-coated film of electron donor and acceptor materials, typically poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), respectively, with tortuous, discontinuous donor/acceptor phases. Alternatively, methods that control phase separation on the order of the exciton (photo-generated electron-hole pair) diffuse length scale (~10-20 nm) with continuous, ordered donor and acceptor pathways are desirable because these design elements will lead to a highly probability of separation of free carriers at donor/acceptor interface as well as limited recombination while charges transport through each phase to be collected. We development a single-step monoaxial electrospinning of P3HT/PCBM to understand impact of extensional flow on controlling the nanostructure. This conventional method of spinning has yet to be applicable to this blend owing to the rigidity of the P3HT rod-like polymer, which hinders polymer chain-entanglements needed for electrospinning; therefore, coaxial spinning and auxiliary polymer methods have been employed in literature. Nevertheless, a specific solution concentration was determined to successfully fabricate pure P3HT/PCBM nanofibers, without the need to remove auxiliary polymer or shell material, possible by PCBM molecules or aggregates serving as nodes for temporary networks between P3HT chains to enhance the material elasticity. Nanofibers were directly compared to films (as made and annealed) to reveal that the elongational flow during electrospinning improved crystallinity and reduced length scale of co-continuous P3HT and PCBM phases. These morphological characteristics are necessary for designing OPV materials and electrospinning offers a facile route to controlling the photoactive layer at the nanoscale.Ph.D., Chemical Engineering -- Drexel University, 201
Fostering Campus Diversity Through Arts Programming: A Case Study of Culture and the Arts at West Chester University
No full textWith diversity on the rise in society, colleges and universities are tasked with finding methods of integrating multiculturalism on campus. My study investigates the effectiveness of the arts and culture programs at West Chester University (WCU), a public university in West Chester, Pennsylvania. In my preliminary research, I discover the benefits of diverse interactions among college students, the importance of educating the community on cultural acceptance, and various ways that the arts can be used to teach and present cultural differences in a positive way. Through one-on-one conversations with arts, culture, and diversity leaders at WCU, I learn that despite cultural challenges and institutional limitations, WCU’s leaders have been successful at increasing the multicultural presence and serving diverse communities in and around West Chester between the years of 1993 and 2016. There are many missed opportunities, however, for collaboration, partnerships, and research practices that could improve services overall. There are also some missing links between diversity and the arts, as well as minimal communication between the individual arts programs.M.S., Arts Administration -- Drexel University, 201