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Stabilized Wide Bandgap MapbbrXI3– X Perovskite By Enhanced Grain Size And Improved Crystallinity, Miao Hu, Cheng Bi, Yongbo Yuan, Yang Bai, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

Methylammonium lead trihalide perovskite (MAPbX₃, where MA is methylammonium, and X is a halide)-based solar cells have been intensively investigated recently, with the demonstrated certified solar power conversion efficiency (PCE) exceeding 20%. To further boost the PCE to beyond the Schockley–Queisser limit, tandem structured solar cells have been investigated based on integrating MAPbX₃ and low bandgap solar cells. However, the efficiency of the two-terminal integrated perovskite-silicon tandem cells is still low. The best reported efficiency of 13.7% for this type of tandem cells is far smaller than the individual cells yet, partially due to the limited performance …

Ultrahigh Sensitivity Of Methylammonium Lead Tribromide Perovskite Single Crystals To Environmental Gases, Hong-Hua Fang, Sampson Adjokatse, Haotong Wei, Jie Yang, Graeme R. Blake, Jinsong Huang, Jacky Even, Maria Antonietta Loi

Department of Mechanical and Materials Engineering: Faculty Publications

One of the limiting factors to high device performance in photovoltaics is the presence of surface traps. Hence, the understanding and control of carrier recombination at the surface of organic-inorganic hybrid perovskite is critical for the design and optimization of devices with this material as the active layer. We demonstrate that the surface recombination rate (or surface trap state density) inmethylammonium lead tribromide (MAPbBr3) single crystals can be fully and reversibly controlled by the physisorption of oxygen and water molecules, leading to a modulation of the photoluminescence intensity by over two orders of magnitude.We report an unusually low surface recombination …

Satellite-Based Global Volcanic So2 Emissions And Sulfate Direct Radiative Forcing During 2005–2012, Cui Ge, Jun Wang, Simon Carn, Kai Yang, Paul Ginoux, Nickolay Krotkov

Department of Earth and Atmospheric Sciences: Faculty Publications

An 8 year volcanic SO₂ emission inventory for 2005–2012 is obtained based on satellite measurements of SO₂ from OMI (Ozone Monitoring Instrument) and ancillary information from the Global Volcanism Program. It includes contributions from global volcanic eruptions and from eight persistently degassing volcanoes in the tropics. It shows significant differences in the estimate of SO₂ amount and injection height for medium to large volcanic eruptions as compared to the counterparts in the existing volcanic SO₂ database. Emissions fromNyamuragira (DR Congo) in November 2006 and Grímsvötn (Iceland) in May 2011 that were not included in the Intergovernmental …

Biomass Burning, Land-Cover Change, And The Hydrological Cycle In Northern Sub-Saharan Africa, Charles Ichoku, Luke T. Ellison, K. Elena Willmot, Toshihisa Matsui, Amin K. Dezfuli, Charles K. Gatebe, Jun Wang, Eric M. Wilcox, Jejung Lee, Jimmy Adegoke, Churchill Okonkwo, John Bolten, Frederick S. Policelli, Shahid Habib

Department of Earth and Atmospheric Sciences: Faculty Publications

The Northern Sub-Saharan African (NSSA) region, which accounts for 20%–25%of the global carbon emissions from biomass burning, also suffers from frequent drought episodes and other disruptions to the hydrological cycle whose adverse societal impacts have been widely reported during the last several decades. This paper presents a conceptual framework of the NSSA regional climate system components that may be linked to biomass burning, as well as detailed analyses of a variety of satellite data for 2001–2014 in conjunction with relevant model-assimilated variables. Satellite fire detections in NSSA show that the vast majority (>75%) occurs in the savanna and woody …

Managing To Clear The Air: Stereotype Threat, Women, And Leadership, Crystal L. Hoyt, Susan E. Murphy

Jepson School of Leadership Studies articles, book chapters and other publications

In this article, we explore the process and implications of stereotype threat for women in leadership, broadly construed. First, we provide a brief background on the phenomenon of stereotype threat generally. Next, we explore stereotype threat for women in leadership by reviewing a model of stereotype threat in leadership contexts that includes cues to stereotype threat, consequences of stereotype threat, and moderators of stereotype threat appraisals and responses. In this review, in addition to considering research focused squarely on leadership, we include the broader categories of research examining stereotype threat effects in the workplace and in tasks and domains relevant …

Geometry-Coupled Reactive Fluid Transport At The Fracture Scale: Application To Co2 Geologic Storage, S. Kim, J.C. Santamarina

Department of Civil and Environmental Engineering: Faculty Publications

Water acidification follows CO2 injection and leads to reactive fluid transport through pores and rock fractures, with potential implications to reservoirs and wells in CO2 geologic storage and enhanced oil recovery. Kinetic rate laws for dissolution reactions in calcite and anorthite are combined with the Navier-Stokes law and advection–diffusion transport to perform geometry-coupled numerical simulations in order to study the evolution of chemical reactions, species concentration, and fracture morphology. Results are summarized as a function of two dimensionless parame- ters: the Damko€hler number Da which is the ratio between advection and reaction times, and the transverse Peclet number Pe defined …

Enhancement Of Elda Tracker Based On Cnn Features And Adaptive Model Update, Changxin Gao, Huizhang Shi, Jin-Gang Yu, Nong Sang

School of Computing: Faculty Publications

Appearance representation and the observation model are the most important components in designing a robust visual tracking algorithm for video-based sensors. Additionally, the exemplar-based linear discriminant analysis (ELDA) model has shown good performance in object tracking. Based on that, we improve the ELDA tracking algorithm by deep convolutional neural network (CNN) features and adaptive model update. Deep CNN features have been successfully used in various computer vision tasks. Extracting CNN features on all of the candidate windows is time consuming. To address this problem, a two-step CNN feature extraction method is proposed by separately computing convolutional layers and fully-connected layers. …

Modeling Changes In Measured Conductance Of Thin Boron Carbide Semiconducting Films Under Irradiation, George G. Peterson, Yongqiang Wang, Natale J. Ianno, Michael Nastasi

School of Computing: Faculty Publications

Semiconducting, p-type, amorphous partially dehydrogenated boron carbide films (a-B₁₀C_2+x:H_y) were deposited utilizing plasma enhanced chemical vapor deposition (PECVD) onto n-type silicon thus creating a heterojunction diode. A model was developed for the conductance of the device as a function of perturbation frequency (��) that incorporates changes of the electrical properties for both the a-B₁₀C_2+x:H_y film and the silicon substrate when irradiated. The virgin model has 3 independent variables (R1, C1, R3), and 1 dependent variable (��). Samples were then irradiated with 200 keV He⁺ ions, and the conductance …

The Importance Of Computing Education Research, Steve Cooper, Armando Fox, Susanne Hambrusch, Andrew Ko, Beth Simon

School of Computing: Faculty Publications

Interest in computer science is growing. As a result, computer science (CS) and related departments are experiencing an explosive increase in undergraduate enrollments and unprecedented demand from other disciplines for learning computing. According to the 2014 CRA Taulbee Survey, the number of undergraduates declaring a computing major at Ph.D. granting departments in the US has increased 60% from 2011-2014 and the number of degrees granted has increased by 34% from 2008-2013.

The Man-Pocalpyse: Doomsday Preppers And The Rituals Of Apocalyptic Manhood, Casey Ryan Kelly

Department of Communication Studies: Faculty Publications

This essay argues that recent male performances of disaster preparedness in reality television recuperate a preindustrial model of hegemonic masculinity by staging the plausible “real world” conditions under which manly skills appear necessary for collective survival. Representations of masculinity in uncertain times intensify the masculinity-in-crisis motif to cultivate anticipation of an apocalyptic event that promises a final resolution to male alienation. An examination of Nat Geo’s Doomsday Preppers illustrates how these staged performances of everyday life cultivate a dangerous vision of apocalyptic manhood that consummates a fantasy of national virility in the demise of feminine society.

Camp Horror And The Gendered Politics Of Screen Violence: Subverting The Monstrous-Feminine In Teeth (2007), Casey Ryan Kelly

Department of Communication Studies: Faculty Publications

This essay argues that Mitchell Lichtenstein’s film Teeth (2007) is an exemplary appropriation of the femme castratrice, a sadistic and castrating female figure that subverts the patriarchal mythologies undergirding the gendered logics of both screen violence and cultural misogyny. The film chronicles Dawn’s post-sexual assault transformation from a passive defender of women’s purity to an avenging heroine with castrating genitals. First, I illustrate how Teeth intervenes in the gendered politics of spectatorship by cultivating identification with a violent heroine who refuses to abide by the stable binary between masculine violence/feminized victimhood. This subversive iteration of rape-revenge cinema is assisted by …

Cubic Spline Interpolation Reveals Different Evolutionary Trends Of Various Species, Zhiqiang Li, Peter Z. Revesz

School of Computing: Faculty Publications

Instead of being uniform in each branch of the biological evolutionary tree, the speed of evolution, measured in the number of mutations over a fixed number of years, seems to be much faster or much slower than average in some branches of the evolutionary tree. This paper describes an evolutionary trend discovery algorithm that uses cubic spline interpolation for various branches of the evolutionary tree. As shown in an example, within the vertebrate evolutionary tree, human evolution seems to be currently speeding up while the evolution of chickens is slowing down. The new algorithm can automatically identify those branches and …

Unraveling The Hidden Function Of A Stabilizer In A Precursor In Improving Hybrid Perovskite Film Morphology For High Efficiency Solar Cells, Zhengguo Xiao, Dong Wang, Qingfeng Dong, Qi Wang, Wei Wei, Jun Dai, Xiwei Zheng, Jinsong Huang

Xiao Cheng Zeng Publications

The morphology of the organometal trihalide perovskite (OTP) plays a critical role in the performance of solar cell devices. Nevertheless it has been frequently reported that the morphology of OTP films tends to be different in different laboratories even with the same film preparation procedure, which makes it very difficult to compare and understand the material and device physics. Here, we unravel a critical role of the H₃PO₂ stabilizer in HI, which has been largely ignored, in controlling the morphology of the perovskite films. The H₃PO₂ stabilizer in HI solution introduces MAH₂PO …

Tuning The Electronic Properties Of Monolayer And Bilayer Ptse2 Via Strain Engineering, Pengfei Li, Lei Li, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

The recently synthesized monolayer PtSe₂ belongs to the class of two-dimensional transition metal dichalcogenide (TMDC) materials (Nano Lett., 2015, 15, 4013). Based on first-principles calculations, we show that the band gaps of monolayer and bilayer PtSe₂ can be tuned over a wide range via strain engineering. Both isotropic and uniaxial strains are investigated. For bilayer PtSe₂, the vertical out-of-plane strain is also considered. In most cases, the strain can reduce the band gap except for the bilayer PtSe₂ under the isotropic strain (Ɛ≤ 4%) for which the band gap can be slightly enlarged. Importantly, the …

Resolving The Hono Formation Mechanism In The Ionosphere Via Ab Initio Molecular Dynamic Simulations, Rongxing He, Lei Li, Jie Zhong, Chongqin Zhu, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Solar emission produces copious nitrosonium ions (NO⁺) in the D layer of the ionosphere, 60 to 90 km above the Earth’s surface. NO⁺ is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200–220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates—tetrahydrate NO⁺(H₂O)₄ and pentahydrate NO⁺(H₂O)_{5 …}

Polyurethane Foam (Puf) Passive Samplers For Monitoring Phenanthrene In Stormwater, Yueqin Dou, Tian C. Zhang, Jing Zeng, John S. Stansbury, Massom Moussavi, Dana L. Richter-Egger, Mitchell R Klein

Department of Civil and Environmental Engineering: Faculty Publications

Pollution from highway stormwater runoff has been an increasing area of concern. Many structural Best Management Practices (BMPs) have been implemented for stormwater treatment and management. One challenge for these BMPs is to sample stormwater and monitor BMP performance. The main objective of this study was to evaluate the feasibility of using polyurethane foam (PUF) passive samplers (PSs) for sampling phenanthrene (PHE) in highway stormwater runoff and BMPs. Tests were conducted using batch reactors, glass-tube columns, and laboratory-scale BMPs (bioretention cells). Results indicate that sorption for PHE by PUF is mainly linearly relative to time, and the high sorption capacity …

Expedient Airfield Runway Repair Using Folded Fiberglass Mat, Christopher Y. Tuan, Willaim C. Dass

Department of Civil and Environmental Engineering: Faculty Publications

For expedient airfield runway repair, the US Air Force has developed a folded fiberglass mat to cover craters repaired with a well-compacted granular base material. The objective of this study was to evaluate the adequacy of using polymer plugs to anchor the mat to a repaired asphalt pavement for heavy aircraft operations. The effort consisted of materials testing, field experiments and analytical modeling. An 89,800-kg (198,000-pound) load cart having the footprint of a single C-5 main gear was pulled on a mat with wheels locked to simulate full braking forces. Anchor bushings were instrumented to measure anchor loads. A simplified …

Development Of Adsorptive Membranes By Confinement Of Activated Biochar Into Electrospun Nanofibers, Mehrdad Taheran, Mitra Naghdi, Satinder K. Brar, Emile Knystautas, Mausam Verma, Rao Y. Surampalli, Jose R. Valero

Department of Civil and Environmental Engineering: Faculty Publications

Adsorptive membranes have many applications in removal of contaminants, such as heavy metals and organic contaminants from water. Recently, increasing concentrations of pharmaceutically active compounds, especially antibiotics, such as chlortetracycline in water and wastewater sources has raised concerns about their potentially adverse impacts on environment and human health. In this study, a series of polyacrylonitrile (PAN)/activated biochar nanofibrous membranes (NFMs) with different loadings of biochar (0–2%, w/w) were fabricated using electrospinning. The morphology and structure of fabricated membranes was investigated by scanning electron microscopy, Fourier transform infrared and thermogravimetric analysis. The results showed that at 1.5% of biochar loading, the …

Evaluation Of The Midwest Guardrail System Stiffness Transition With Curb, Jennifer D. Schmidt, Scott K. Rosenbaugh, Ronald K. Faller

Department of Civil and Environmental Engineering: Faculty Publications

A W-beam to thrie beam stiffness transition with a 102-mm (4- in.) tall concrete curb was developed to connect 787-mm (31-in.) tall W-beam guardrail, commonly known as the Midwest Guardrail System (MGS), to a previously developed thrie beam approach guardrail transition system. This upstream stiffness transition was configured with standard steel posts that are commonly used by several state departments of transportation. The toe of a 102-mm (4-in.) tall sloped concrete curb was placed flush with the backside face of the guardrail and extended the length of the transition region. Three full-scale crash tests were conducted according to the Test …

Pulses In The Sand: Impulse Response Analysis Of Wireless Underground Channel, Abdul Salam, Mehmet C. Vuran, Suat Irmak

School of Computing: Conference and Workshop Papers

Wireless underground sensor networks (WUSNs) are becoming ubiquitous in many areas and designing robust systems requires extensive understanding of the underground (UG) channel characteristics. In this paper, UG channel impulse response is modeled and validated via extensive experiments in indoor and field testbed settings. Three distinct types of soils are selected with sand and clay contents ranging from 13% to 86% and 3% to 32%, respectively. Impacts of changes in soil texture and soil moisture are investigated with more than 1,200 measurements in a novel UG testbed that allows flexibility in soil moisture control. Time domain characteristics of channel such …

Table Headers: An Entrance To The Data Mine, George Nagy, Sharad C. Seth

School of Computing: Conference and Workshop Papers

Algorithmic methods are demonstrated for information extraction from table header elements, including data categories and data hierarchies. The table headers are found with the Minimum Index Point Search algorithm. The header-path alignment and header completion algorithms yield database-ready table content and configuration statistics on a random sample of 400 diverse tables with ground truth and 1120 tables without ground truth from international statistical data sites.

The Effectiveness Of A Computer-Based Program On The Reading Performance Of Fourth-Grade Students, Latonya L. Cooper

Theses and Dissertations

The intent of this applied dissertation was to determine whether a reading intervention of a computer-based program would increase the reading comprehension and vocabulary skills of students in fourth grade in a Title I elementary school. Although the No Child Left Behind Act (NCLB) covers various federal education programs, the law’s requirements for testing, accountability, and school improvement receive the most attention. NCLB requires states to test students in reading and mathematics annually in Grades 3-8 and once in Grades 10-12. Schools must test students in science once in Grades 3-5, 6-8, and 10-12. Individual schools, school districts, and states …

Constructing Stability Landscapes To Identify Alternative States In Coupled Social-Ecological Agent-Based Models, Patrick Bitterman, David A. Bennett

Geography Program: Faculty Publications

The resilience of a social-ecological system is measured by its ability to retain core functionality when subjected to perturbation. Resilience is contextually dependent on the state of system components, the complex interactions among these components, and the timing, location, and magnitude of perturbations. The stability landscape concept provides a useful framework for considering resilience within the specified context of a particular social-ecological system but has proven difficult to operationalize. This difficulty stems largely from the complex, multidimensional nature of the systems of interest and uncertainty in system response. Agent-based models are an effective methodology for understanding how cross-scale processes within …

False Rubicons, Moral Panic & Conceptual Cul-De-Sacs: Critiquing & Reframing The Call To Ban Lethal Autonomous Weapons, Chris Jenks

Faculty Journal Articles and Book Chapters

Casting into the indeterminate future and projecting visions of so-called killer robots, The Campaign to Stop Killer Robots (The Campaign) has incited moral panic in an attempt to stimulate a discussion and ultimately a ban on lethal autonomous weapons (LAWS). Their efforts have been superficially successful but come at a self-defeating substantive cost. In the hope of shifting the dialogue from the hyperbolic to a constructive dialogue on the interaction between human and machine abilities in both current and future weapon systems, this article explores the conceptual paradox implicit in The Campaign and proposes an alternative.

Having provoked the international …

How Cheap Is Corporate Talk? Comparing Companies' Comments On Regulations With Their Securities Disclosures, James W. Coleman

Faculty Journal Articles and Book Chapters

When companies face adverse proposed rules, they may want to convince regulators that the proposed rules are unworkable and should be changed while, at the same time, reassuring investors that the rules will be manageable. These conflicting incentives may lead to inconsistent messages in regulatory comments and securities disclosures, fueling a perception that corporate submissions to regulators are cheap talk. Despite this perception, there has been no empirical study comparing statements to these two audiences. This project performs such a study, taking the example of comments submitted on the Environmental Protection Agency's Renewable Fuel Standard. This standard provides an ideal …

Effects Of A Music Literacy Integration Intervention On Teachers’ Self-Efficacy And Proactive Attitudes Toward Music Integration In Classroom Instruction, Mary Louise Keyloun Cruz

Theses and Dissertations

With the adoption of the common core state standards, pressure to raise the achievement of young learners was intense. Classroom teachers were scrutinized to teach lessons with high levels of thinking and rigor. Teachers were inclined to eliminate or ignore artsenriched lessons that would benefit students. The reason for this action was associated with the efficacy of the classroom teacher toward music integration in literacy curriculum. The purpose of the study was to examine the effects of the Music Literacy Integration Intervention (MLII) on the self-efficacy and proactiveness of teachers at a small elementary school in Florida toward integration of …

Universal Communications Hub, Ian Robins, Christopher Pangalos, Cargill Chan

Electrical Engineering and Computer Science Student Publications

To design a mobile communications system capable of maintaining a data and communications link in scenarios where traditional communications have been lost or are unavailable. In a practical scenario, this type of hub would be mounted to several UAVs and deployed in a matter of minutes to create a mesh network which facilitates emergency communications over a variety of methods.

Light Exoskeleton Gear (L.E.G.), Andy Myers, Ali Al Matouq, Kelsey Dejesus-Banos, Jessica Vidmark

Electrical Engineering and Computer Science Student Publications

The L.E.G. combines the inherent mechanical support of a knee brace with extra assistance provided in a similar way as a robotic leg. Surface Electromyography (SEMG) sensors are connected to the user’s leg to assess in what direction the brace should assist the user. In addition to providing assistive and resistive features for the user’s physical benefit, there is an option for the user to send the voltage data of the L.E.G. to a computer via Bluetooth and display the results in a VI executable.

Omnisphere, Chris Ballentine, Gerardo Dudamel, James Frisbie, Macdonald Taylor

Electrical Engineering and Computer Science Student Publications

Our Omnisphere robot is a user-friendly controlled platform with three spheres for wheels. A friction-based drive system rotates each sphere with 360 degrees of full planar freedom. This system eliminates the restrictive motions associated with common cylindrical-wheel systems and utilizes previously unattainable motions.

Evidence Of Magnetic Field Decay In Massive Main-Sequence Stars, Luca Fossati, Fabian R.N. Schneider, Norberto Castro, Norbert Langer, Sergio Simón-Díaz, André Luís Müller, Alex De Koter, Thierry Morel, Véronique Petit, Hugues Sana, Gregg A. Wade

Aerospace, Physics, and Space Science Faculty Publications

A significant fraction of massive main-sequence stars show strong, large-scale magnetic fields. The origin of these fields, their lifetimes, and their role in shaping the characteristics and evolution of massive stars are currently not well understood. We compile a catalogue of 389 massive main-sequence stars, 61 of which are magnetic, and derive their fundamental parameters and ages. The two samples contain stars brighter than magnitude 9 in the V-band and range in mass between 5 and 100 M⊙. We find that the fractional main-sequence age distribution of all considered stars follows what is expected for a magnitude limited sample, while …