Physical Sciences and Mathematics Commons^™

Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with …

Electrical Characterization Of Irradiated Semiconducting Amorphous Hydrogenated Boron Carbide, George Glen Peterson

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Semiconducting amorphous partially dehydrogenated boron carbide has been explored as a neutron voltaic for operation in radiation harsh environments, such as on deep space satellites/probes. A neutron voltaic device could also be used as a solid state neutron radiation detector to provide immediate alerts for radiation workers/students, as opposed to the passive dosimetry badges utilized today. Understanding how the irradiation environment effects the electrical properties of semiconducting amorphous partially dehydrogenated boron carbide is important to predicting the stability of these devices in operation. p-n heterojunction diodes were formed from the synthesis of semiconducting amorphous partially dehydrogenated boron carbide on silicon …

Data Extraction From Web Tables: The Devil Is In The Details, George Nagy, Sharad C. Seth, Dongpu Jin, David W. Embley, Spencer Machado, Mukkai Krishnamoorthy

CSE Conference and Workshop Papers

We present a method based on header paths for efficient and complete extraction of labeled data from tables meant for humans. Although many table configurations yield to the proposed syntactic analysis, some require access to semantic knowledge. Clicking on one or two critical cells per table, through a simple interface, is sufficient to resolve most of these problem tables. Header paths, a purely syntactic representation of visual tables, can be transformed (“factored”) into existing representations of structured data such as category trees, relational tables, and RDF triples. From a random sample of 200 web tables from ten large statistical web …

End-To-End Conversion Of Html Tables For Populating A Relational Database, George Nagy, David W. Embley, Sharad C. Seth

CSE Conference and Workshop Papers

Automating the conversion of human-readable HTML tables into machine-readable relational tables will enable end-user query processing of the millions of data tables found on the web. Theoretically sound and experimentally successful methods for index-based segmentation, extraction of category hierarchies, and construction of a canonical table suitable for direct input to a relational database are demonstrated on 200 heterogeneous web tables. The methods are scalable: the program generates the 198 Access compatible CSV files in ~0.1s per table (two tables could not be indexed).

Nanomaterials As Stationary Phases And Supports In Liquid Chromatography: A Review, Sandya Beeram, Elliott Rodriguez, Suresh Doddavenkatanna, Zhao Li, Allegra Pekarek, Darin Peev, Kathryn Goerl, Gianfranco Trovato, Tino Hofmann, David S. Hage

David Hage Publications

The development of various nanomaterials over the last few decades has led to many applications for these materials in liquid chromatography (LC). This review will look at the types of nanomaterials that have been incorporated into LC systems and the applications that have been explored for such systems. A number of carbon-based nanomaterials and inorganic nanomaterials have been considered for use in LC, ranging from carbon nanotubes, fullerenes and nanodiamonds to metal nanoparticles and nanostructures based on silica, alumina, zirconia and titanium dioxide. Many ways have been described for incorporating these nanomaterials into LC systems. These methods have included covalent …

In Situ Electron Microscopy Of Plasmon-Mediated Nanocrystal Synthesis, Peter Sutter, Ying Li, Christos Argyropoulos, Eli A. Sutter

Department of Electrical and Computer Engineering: Faculty Publications

Chemical processes driven by nonthermal energy (e.g., visible light) are attractive for future approaches to energy conversion, synthesis, photocatalysis, and so forth. The growth of anisotropic metal nanostructures mediated by excitation of a localized surface plasmon resonance (LSPR) is a prototype example of such a reaction. Important aspects, notably the growth mechanism and a possible role of plasmonic “hot spots” within the metal nanostructures, remain poorly understood. Here, we use in situ electron microscopy to stimulate and image the plasmon-mediated growth of triangular Ag nanoprisms in solution. The quantification of the time-dependent evolution of the lateral size and thickness of …

Women In It: Be The Change, Marcia L. Dority Baker

Information Technology Services: Publications

The influence of established women in IT — specifically Florence Hudson and Melissa Woo — encouraged a librarian to apply for a position in Information Technology Services at the University of Nebraska–Lincoln.

A hands-on approach to planning the IT Leadership conference developed a strong collaborative network that also helped grow attendance.

Paying attention to the pros and cons of the 2016 conference guided the planners in modifying their approach to the upcoming October 2017 conference and its focus on diversity and inclusion.

A main goal for future IT Leadership conferences focusing on women and diversity in IT is providing attendees …

Band-To-Band Transitions, Selection Rules, Effective Mass, And Excitonic Contributions In Monoclinic Β-Ga2o3, Alyssa Mock, Rafal Korlacki, Chad Briley, Vanya Darakchieva, Bo Monemar, Yoshinao Kumagai, Ken Goto, Masataka Higashiwaki, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

We employ an eigenpolarization model including the description of direction dependent excitonic effects for rendering critical point structures within the dielectric function tensor of monoclinic β-Ga₂O₃ yielding a comprehensive analysis of generalized ellipsometry data obtained from 0.75–9 eV. The eigenpolarization model permits complete description of the dielectric response. We obtain, for single-electron and excitonic band-to-band transitions, anisotropic critical point model parameters including their polarization vectors within the monoclinic lattice. We compare our experimental analysis with results from density functional theory calculations performed using the Gaussian-attenuation-Perdew-Burke-Ernzerhof hybrid density functional. We present and discuss the order of the …

Anisotropy, Phonon Modes, And Lattice Anharmonicity From Dielectric Function Tensor Analysis Of Monoclinic Cadmium Tungstate, Alyssa Mock, Rafal Korlacki, Sean Knight, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

We determine the frequency dependence of four independent Cartesian tensor elements of the dielectric function for CdWO₄ using generalized spectroscopic ellipsometry within mid-infrared and far-infrared spectral regions. Different single crystal cuts, (010) and (001), are investigated. From the spectral dependencies of the dielectric function tensor and its inverse we determine all long-wavelength active transverse and longitudinal optic phonon modes with A_u and B_u symmetry as well as their eigenvectors within the monoclinic lattice. We thereby demonstrate that such information can be obtained completely without physical model line-shape analysis in materials with monoclinic symmetry. We then augment the …

Smart Underground Antenna Arrays: A Soil Moisture Adaptive Beamforming Approach, Abdul Salam, Mehmet C. Vuran

CSE Technical Reports

In this paper, a novel framework for underground beamforming using adaptive antenna arrays is presented. Based on the analysis of propagation in wireless underground channel, a theoretical model is developed which uses soil moisture information and feedback mechanism to improve performance wireless underground communications. Array element in soil has been analyzed empirically and impacts of soil type and soil moisture on return loss and resonant frequency are investigated. Beam patterns are investigated to communicate with both underground and above ground devices. Depending on the incident angle, refraction from soil-air interface has the adverse effects in the UG communications. It is …

Wireless Underground Channel Diversity Reception With Multiple Antennas For Internet Of Underground Things, Abdul Salam, Mehmet C. Vuran

CSE Conference and Workshop Papers

Internet of underground things (IOUT) is an emerging paradigm which consists of sensors and communication devices, partly or completely buried underground for real-time soil sensing and monitoring. In this paper, the performance of different modulation schemes in IOUT communications is studied through simulations and experiments. The spatial modularity of direct, lateral, and reflected components of the UG channel is exploited by using multiple antennas. First, it has been shown that bit error rates of $10^{-3}$ can be achieved with normalized delay spreads ($\tau_d$) lower than $0.05$. Evaluations are conducted through the first software-defined radio-based field experiments for UG channel. Moreover, …

Towards Internet Of Underground Things In Smart Lighting: A Statistical Model Of Wireless Underground Channel, Abdul Salam, Mehmet C. Vuran, Suat Irmak

CSE Conference and Workshop Papers

The Internet of Underground Things (IOUT) has many applications in the area of smart lighting. IOUT enables communications in smart lighting through underground (UG) and aboveground (AG) communication channels. In IOUT communications, an in-depth analysis of the wireless underground channel is important to design smart lighting solutions. In this paper, based on the empirical and the statistical analysis, a statistical channel model for the UG channel has been developed. The parameters for the statistical tapped-delay-line model are extracted from the measured power delay profiles (PDP). The PDP of the UG channel is represented by the exponential decay of the lateral, …

Smart Underground Antenna Arrays: A Soil Moisture Adaptive Beamforming Approach, Abdul Salam, Mehmet C. Vuran

CSE Conference and Workshop Papers

Current wireless underground (UG) communication techniques are limited by their achievable distance. In this paper, a novel framework for underground beamforming using adaptive antenna arrays is presented to extend communication distances for practical applications. Based on the analysis of propagation in wireless underground channel, a theoretical model is developed which uses soil moisture information to improve wireless underground communications performance. Array element in soil is analyzed empirically and impacts of soil type and soil moisture on return loss (RL) and resonant frequency are investigated. Accordingly, beam patterns are analyzed to communicate with underground and above ground devices. Depending on the …

Biosimp: Using Software Testing Techniques For Sampling And Inference In Biological Organisms, Mikaela Cashman, Jennie L. Catlett, Myra B. Cohen, Nicole R. Buan, Zahmeeth Sakkaff, Massimiliano Pierobon, Christine A. Kelley

CSE Conference and Workshop Papers

Years of research in software engineering have given us novel ways to reason about, test, and predict the behavior of complex software systems that contain hundreds of thousands of lines of code. Many of these techniques have been inspired by nature such as genetic algorithms, swarm intelligence, and ant colony optimization. In this paper we reverse the direction and present BioSIMP, a process that models and predicts the behavior of biological organisms to aid in the emerging field of systems biology. It utilizes techniques from testing and modeling of highly-configurable software systems. Using both experimental and simulation data we show …