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Examining The Training Transfer Practice Of A Financial Institution: An Action Research Study, Maria Lourdes Lourdes Gutierrez Dec 2018

Examining The Training Transfer Practice Of A Financial Institution: An Action Research Study, Maria Lourdes Lourdes Gutierrez

UNLV Theses, Dissertations, Professional Papers, and Capstones

Many organizations rely on training to improve the skills and knowledge of its human resources. The underlying assumption is that employees will use what they learned when they return to the workplace. Although there is evidence that learning occurred it does not always result in transfer (Mosel, 1957). Transfer is an issue of concern for training practitioners. If despite the significant investment no return is realized, then the training is not effective and the investment is wasted. This action research study was conducted in a financial institution in the Southwestern United States. The purpose of this study was to (1) …


Conversational Movement Dynamics And Nonverbal Indicators Of Second Language Development: A Microgenetic Approach, Kristine Marie Bragg Dec 2018

Conversational Movement Dynamics And Nonverbal Indicators Of Second Language Development: A Microgenetic Approach, Kristine Marie Bragg

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation study extends on current understandings of gesture and embodied interaction with the eco-social environment in second language development (SLD) while introducing new aspects of movement analysis through dynamical modeling. To understand the role of embodiment during learning activities, a second language learning task has been selected. Dyads consisting of a non-native English-speaking student and a native English-speaking tutor were video recorded during writing consultations centered on class assignments provided by the student. Cross-recurrence quantification analysis was used to measure interactional movement synchrony between the members of each dyad. Results indicate that students with varied English proficiency levels synchronize …


Uas-Based Object Tracking Via Deep Learning, Marc Dinh Dec 2018

Uas-Based Object Tracking Via Deep Learning, Marc Dinh

UNLV Theses, Dissertations, Professional Papers, and Capstones

Tracking is the task of identifying an object of interest and detect its position over time, and has numerous applications like surveillance, security and traffic control. In present times, unmanned aerial vehicles (UAV) have been more and more common which provides us with a new and less explored domain, with an ideal vantage point for surveillance and monitoring applications.. Aerial tracking is a particularly challenging task as it introduces new environmental variables such as rapid motion in 3D space. We propose a new deep learned tracker architecture catered to aerial tracking.

First, a study of six state-of-the-art deep learned trackers …


A Distributed Real-Time Short-Term Solar Irradiation Forecasting Network For Photovoltaic Systems, Michael Adelbert Gacusan Dec 2018

A Distributed Real-Time Short-Term Solar Irradiation Forecasting Network For Photovoltaic Systems, Michael Adelbert Gacusan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Solar irradiation forecasting is essential for PV connected electrical grids to maintain reliability, stability, and effective matching of real-time demand to power distribution. This research paper develops and evaluates proposed forecasting methods using wireless sensor networks. Each node of the network is capable of monitoring illuminance data and communicate it through RF and/or WiFi. The nodes are calibrated with respect to irradiance data from an industry-standard pyranometer. Power consumption of each node type is also collected at different operating states. The proposed sensor network can estimate a cloud motion vector or a cloud shadow’s speed and direction from the data …


Design, Layout, And Testing Of Sige Apds Fabricated In A Bicmos Process, Dane Laurence Gentry Dec 2018

Design, Layout, And Testing Of Sige Apds Fabricated In A Bicmos Process, Dane Laurence Gentry

UNLV Theses, Dissertations, Professional Papers, and Capstones

This Thesis is concerned with the design, layout, and testing of avalanche photodiodes (APDs). APDs are a type of photodetector and, thus, convert light signals into electrical signals (current or voltage). APDs can be fabricated using silicon (Si). In this Thesis, however, three integrated circuit (IC) chips containing various silicon-germanium (SiGe) APDs with different sizes, structures, and geometries were designed, laid out, and fabricated using the Austriamicrosystems (AMS) 0.35μm SiGe BiCMOS (S35) process. This was done in order to compare SiGe APDs to Si only APDs and investigate the hypothesis that SiGe APDs are capable of detecting longer wavelengths than …


Influencing Hawai‘I Hotel Patrons To Use Reef-Safe Sunscreens, Rochelle Good Dec 2018

Influencing Hawai‘I Hotel Patrons To Use Reef-Safe Sunscreens, Rochelle Good

UNLV Theses, Dissertations, Professional Papers, and Capstones

The health of Hawaiian coral reefs is threatened by pollution from common sunscreen ingredients such as oxybenzone. Hawai‘i hotel patrons using sunscreens with harmful ingredients contaminate coral reefs when these products wash off while swimming or bathing. Reef-safe sunscreens are alternative sunscreens that provide effective sun protection while averting damage to coral reefs. The purpose of this research was to determine the dominant factors leading to the pro-environmental behavior of using reef-safe sunscreen and identify practices that Hawai‘i hotel operators could implement to influence patrons to engage in this behavior. This research applied an integrative conceptual framework to model pro-environmental …


Mechanisms For The Incorporation And Distribution Of Radionuclides In Near-Surface Fallout, Marc Alan Fitzgerald Dec 2018

Mechanisms For The Incorporation And Distribution Of Radionuclides In Near-Surface Fallout, Marc Alan Fitzgerald

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fallout is the radioactive glass formed from a mixture of vaporized anthropogenic materials with proximate environmental material. These glassy byproducts constitute a compositional record of environmental materials such as soil and vapor precursors that are responsible for chemical heterogeneity in the glasses. The work of this dissertation is to untangle these different sources of compositional heterogeneity, distinguishing low-abundance vaporized anthropogenic-rich material from natural compositions, in order examine soil behavior and chemical evolution during fallout formation. Unfortunately, mixing convolutes the multivariate elemental relationships in these melts due to overlapping element abundances that might distinguish different source materials and chemical behaviors, making …


Calculation Of Access Charge For High Speed Rail Xpresswest Of Nevada, Sameeksha Sapkota Dec 2018

Calculation Of Access Charge For High Speed Rail Xpresswest Of Nevada, Sameeksha Sapkota

UNLV Theses, Dissertations, Professional Papers, and Capstones

XpressWest is a High Speed Rail (HSR) system that plans to connect Las Vegas with California at Palmdale. It will utilize the railway network of the California High Speed Rail (CAHSR) to connect Las Vegas with California destinations that include Los Angeles and San Francisco. For sharing the railway network of CAHSR, XpressWest will pay certain charge known as an access charge. The access charge is the fee paid by the train operator to the infrastructure owner for the addition of trains in a track. There are several access charge systems in the world. However, there is no study that …


Application Of Machine Learning Techniques In Credit Card Fraud Detection, Ronish Shakya Dec 2018

Application Of Machine Learning Techniques In Credit Card Fraud Detection, Ronish Shakya

UNLV Theses, Dissertations, Professional Papers, and Capstones

Credit card fraud is an ever-growing problem in today’s financial market. There has been a rapid increase in the rate of fraudulent activities in recent years causing a substantial financial loss to many organizations, companies, and government agencies. The numbers are expected to increase in the future, because of which, many researchers in this field have focused on detecting fraudulent behaviors early using advanced machine learning techniques. However, the credit card fraud detection is not a straightforward task mainly because of two reasons: (i) the fraudulent behaviors usually differ for each attempt and (ii) the dataset is highly imbalanced, i.e., …


Estimation Of The Parameters In A Spatial Regressive-Autoregressive Model Using Ord's Eigenvalue Method, Sajib Mahmud Mahmud Tonmoy Dec 2018

Estimation Of The Parameters In A Spatial Regressive-Autoregressive Model Using Ord's Eigenvalue Method, Sajib Mahmud Mahmud Tonmoy

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this thesis, we study one of Ord's (1975) global spatial regression models.

Ord considered spatial regressive-autoregressive models to describe the interaction

between location and a response variable in the presence of several covariates. He also

developed a practical estimation method for the parameters of this regression model

using the eigenvalues of a weight matrix that captures the contiguity of locations.

We review the theoretical aspects of his estimation method and implement it in the

statistical package R.

We also implement Ord's methods on the Columbus, Ohio, crime data set from the

year 1980, which involves the crime rate of …


A Case Study: Number Apps In Preschool, Amy Beth Adkins Dec 2018

A Case Study: Number Apps In Preschool, Amy Beth Adkins

UNLV Theses, Dissertations, Professional Papers, and Capstones

iPads are increasingly present in education. This research explores their role developing fundamental mathematics concepts. It investigates preschoolers’ interactions with mathematics apps, and affordances and constraints accessed. It was conducted over fourteen weeks; students played mathematics apps for thirty minutes a week. The qualitative case study design included participants who varied in mathematics and technological skill. Data was collected through assessments, interviews, questionnaires, videotapes, and artifacts. Results determined that students access constraints or affordances based on ability level. Findings indicate iPads are beneficial tools for preschool classrooms. Preschoolers showed an increase in math ability when using iPads.


Efficient And Practical Composition Of Lock-Free Data Structures, Neha Bajracharya Dec 2018

Efficient And Practical Composition Of Lock-Free Data Structures, Neha Bajracharya

UNLV Theses, Dissertations, Professional Papers, and Capstones

A concurrent data object is lock-free if it guarantees that at least one, among all concurrent operations, finishes after a finite number of steps. In other words, a lock free technique guarantees that some thread always makes progress. Lock-free data objects offer several advantages over their blocking counterparts, such as being immune to deadlocks and priority inversion, and typically provide high scalability and performance, especially in shared memory multiprocessor architectures.

Composition of data structures is a powerful approach to combine simple data structures to create more complex ones. It works as a building block for many advanced useful data structures. …


Toward An Understanding Of Grb Prompt Emission Mechanism. Ii. Patterns Of Peak Energy Evolution And Their Connection To Spectral Lags, Z. Lucas Uhm, Bing Zhang, Judith Racusin Dec 2018

Toward An Understanding Of Grb Prompt Emission Mechanism. Ii. Patterns Of Peak Energy Evolution And Their Connection To Spectral Lags, Z. Lucas Uhm, Bing Zhang, Judith Racusin

Physics & Astronomy Faculty Research

The prompt emission phase of gamma-ray bursts (GRBs) exhibits two distinct patterns of the peak energy (E p ) evolution, i.e., time-resolved spectral analyses of νF ν spectra of broad pulses reveal (1) "hard-to-soft" and (2) "flux-tracking" patterns of E p evolution in time, the physical origin of which still remains not well understood. We show here that these two patterns can be successfully reproduced within a simple physical model invoking synchrotron radiation in a bulk-accelerating emission region. We show further that the evolution patterns of the peak energy have, in fact, direct connections to the existence of two different …


First Observation Of P-Odd Gamma Asymmetry In Polarized Neutron Capture On Hydrogen, D. Blyth, J. Fry, N. Fomin, R. Alarcon, L. Alonzi, E. Askanazi, S. Baeßler, S. Balascuta, L. Barrón-Palos, Alex Barzilov, J. D. Bowman, N. Birge, J. R. Calarco, T. E. Chupp, V. Cianciolo, C. E. Coppola, C. B. Crawford, K. Craycraft, D. Evans, C. Fieseler, E. Frlež, I. Garishvili, M. T. W. Gericke, R. C. Gillis, K. B. Grammer, G. L. Greene, J. Hall, J. Hamblen, C. Hayes, E. B. Iverson, M. L. Kabir Dec 2018

First Observation Of P-Odd Gamma Asymmetry In Polarized Neutron Capture On Hydrogen, D. Blyth, J. Fry, N. Fomin, R. Alarcon, L. Alonzi, E. Askanazi, S. Baeßler, S. Balascuta, L. Barrón-Palos, Alex Barzilov, J. D. Bowman, N. Birge, J. R. Calarco, T. E. Chupp, V. Cianciolo, C. E. Coppola, C. B. Crawford, K. Craycraft, D. Evans, C. Fieseler, E. Frlež, I. Garishvili, M. T. W. Gericke, R. C. Gillis, K. B. Grammer, G. L. Greene, J. Hall, J. Hamblen, C. Hayes, E. B. Iverson, M. L. Kabir

Mechanical Engineering Faculty Research

We report the first observation of the parity-violating gamma-ray asymmetry A(gamma)(np) in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A(gamma)(np) isolates the Delta I = 1, S-3(1)-> P-3(1) component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory… See full text for full abstract.


Rare Helium-Bearing Compound Feo2he Stabilized At Deep-Earth Conditions, Jurong Zhang, Jian Lv, Hefei Li, Xiaolei Feng, Cheng Lu, Simon A. T. Redferm, Hanyu Liu, Changfeng Chen, Yanming Ma Dec 2018

Rare Helium-Bearing Compound Feo2he Stabilized At Deep-Earth Conditions, Jurong Zhang, Jian Lv, Hefei Li, Xiaolei Feng, Cheng Lu, Simon A. T. Redferm, Hanyu Liu, Changfeng Chen, Yanming Ma

Physics & Astronomy Faculty Research

There is compelling geochemical evidence for primordial helium trapped in Earth’s lower mantle, but the origin and nature of the helium source remain elusive due to scarce knowledge on viable helium-bearing compounds that are extremely rare. Here we explore materials physics underlying this prominent challenge. Our structure searches in conjunction with first-principles energetic and thermodynamic calculations uncover a remarkable helium-bearing compound FeO2He at high pressure-temperature conditions relevant to the core-mantle boundary. Calculated sound velocities consistent with seismic data validate FeO2He as a feasible constituent in ultralow velocity zones at the lowermost mantle. These mutually corroborating findings establish the first and …


Inclined Massive Planets In A Protoplanetary Disc: Gap Opening, Disc Breaking, And Observational Signatures, Zhaohuan Zhu Dec 2018

Inclined Massive Planets In A Protoplanetary Disc: Gap Opening, Disc Breaking, And Observational Signatures, Zhaohuan Zhu

Physics & Astronomy Faculty Research

We carry out 3D hydrodynamical simulations to study planet–disc interactions for inclined high-mass planets, focusing on the disc’s secular evolution induced by the planet. We find that, when the planet is massive enough and the induced gap is deep enough, the disc inside the planet’s orbit breaks from the outer disc. The inner and outer discs precess around the system’s total angular momentum vector independently at different precession rates, which causes significant disc misalignment. We derive the analytical formulae, which are also verified numerically, for: (1) the relationship between the planet mass and the depth/width of the induced gap, (2) …


The Circulation Of Climate Change Denial Online: Rhetorical And Networking Strategies On Facebook, Emma Frances Bloomfield, Denise Tillery Dec 2018

The Circulation Of Climate Change Denial Online: Rhetorical And Networking Strategies On Facebook, Emma Frances Bloomfield, Denise Tillery

Communication Studies Faculty Research

This study uses a topical, rhetorical approach to analyze how climate change denial circulates online through the 25 most popular posts on the Watts Up With That and the Global Warming Policy Forum Facebook pages. These groups adopt the appearance of credibility through reposting and hyperlinking, thus establishing a supportive, networked space among other skeptical sites, while distancing readers from original sources of scientific information. Visitors use a variety of rhetorical strategies to echo posts’ main themes and to discredit alternative viewpoints. Differences between the topoi and rhetorical strategies of WUWT and the GWPF show that the climate change denial …


College Of Engineering Senior Design Competition Fall 2018, University Of Nevada, Las Vegas Dec 2018

College Of Engineering Senior Design Competition Fall 2018, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge. The senior design competition helps focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects on …


Review Of: The World Of Scary Video Games: A Study In Videoludic Horror, Approaches To Digital Game Studies, Matthew Murray Dec 2018

Review Of: The World Of Scary Video Games: A Study In Videoludic Horror, Approaches To Digital Game Studies, Matthew Murray

Library Faculty Research

No abstract provided.


Cm-Wavelength Obserations Of Mwc 758: Resolved Dust Trapping In A Vortex, Simon Casassus, Sebastián Marino, Wladimir Lyra, Clément Baruteau, Matías Vidal, Alwyn Wootten, Sebastián Pérez, Felipe Alarcon, Marcelo Barraza, Miguel Cárcamo, Ruobing Dong, Anibal Sierra, Zhaohuan Zhu, Luca Ricci, Valentin Christiaens, Lucas Cieza Nov 2018

Cm-Wavelength Obserations Of Mwc 758: Resolved Dust Trapping In A Vortex, Simon Casassus, Sebastián Marino, Wladimir Lyra, Clément Baruteau, Matías Vidal, Alwyn Wootten, Sebastián Pérez, Felipe Alarcon, Marcelo Barraza, Miguel Cárcamo, Ruobing Dong, Anibal Sierra, Zhaohuan Zhu, Luca Ricci, Valentin Christiaens, Lucas Cieza

Physics & Astronomy Faculty Research

The large crescents imaged by ALMA in transition discs suggest that azimuthal dust trapping concentrates the larger grains, but centimetre–wavelengths continuum observations are required to map the distribution of the largest observable grains. A previous detection at ∼1 cm of an unresolved clump along the outer ring of MWC 758 (Clump 1), and buried inside more extended sub-mm continuum, motivates followup VLA observations. Deep multiconfiguration integrations reveal the morphology of Clump 1 and additional cm-wave components that we characterize via comparison with a deconvolution of recent 342 GHz data (∼1 mm). ... See full text for complete abstract.


A Conceptual Framework For Integration Development Of Gsflow Model: Concerns And Issues Identified And Addressed For Model Development Efficiency, Chao Chen, Sajjad Ahmad, Ajay Kalra Nov 2018

A Conceptual Framework For Integration Development Of Gsflow Model: Concerns And Issues Identified And Addressed For Model Development Efficiency, Chao Chen, Sajjad Ahmad, Ajay Kalra

Civil and Environmental Engineering and Construction Faculty Research

In Coupled Groundwater and Surface-Water Flow (GSFLOW) model, the three-dimensional finite-difference groundwater model (MODFLOW) plays a critical role of groundwater flow simulation, together with which the Precipitation-Runoff Modeling System (PRMS) simulates the surface hydrologic processes. While the model development of each individual PRMS and MODFLOW model requires tremendous time and efforts, further integration development of these two models exerts additional concerns and issues due to different simulation realm, data communication, and computation algorithms. To address these concerns and issues in GSFLOW, the present paper proposes a conceptual framework from perspectives of: Model Conceptualization, Data Linkages and Transference, Model Calibration, and …


Volunteering At Hyde Park Middle School, Justice Williams Nov 2018

Volunteering At Hyde Park Middle School, Justice Williams

First-Year Seminar Posters (COE 102/103)

The main social issue addressed at Hyde Park Middle School is education. The students attend school to get an education and learn, and the teachers went to college so they would be qualified to teach. However, when students other needs are not meet, they will not focus on their education. This is why the school does what they can to address other issues that the students may be experiencing. They provide free and reduced breakfast and lunches for students who cannot necessarily afford to eat otherwise. This makes it so they can focus on the lessons rather than their hunger. …


Modeling Us Historical Time-Series Prices And Inflation Using Alternative Long-Memory Approaches, Giorgio Canarella, Luis A. Gil-Alana, Rangan Gupta, Stephen M. Miller Nov 2018

Modeling Us Historical Time-Series Prices And Inflation Using Alternative Long-Memory Approaches, Giorgio Canarella, Luis A. Gil-Alana, Rangan Gupta, Stephen M. Miller

Molasky Family Department of Economics and Real Estate Faculty Research

We consider two important features of the historical US price data (1774–2015), namely the data’s persistence and cyclical structure. We first consider the persistence of the series and focus on standard long-memory models that incorporate a peak at the zero frequency. We examine different models with respect to the deterministic terms, including nonlinear deterministic trends of the Chebyshev form. Then, we investigate a more general model that includes both persistence and cyclicality of the series and, thus, includes two fractional integration parameters, one at the zero (long-run) frequency and the other at the nonzero (cyclical) frequency. We model the cyclical …


Probabilistic Interpretation Of Solutions Of Linear Ultraparabolic Equations, Michael D. Marcozzi Nov 2018

Probabilistic Interpretation Of Solutions Of Linear Ultraparabolic Equations, Michael D. Marcozzi

Mathematical Sciences Faculty Research

We demonstrate the existence, uniqueness and Galerkin approximatation of linear ultraparabolic terminal value/infinite-horizon problems on unbounded spatial domains. Furthermore, we provide a probabilistic interpretation of the solution in terms of the expectation of an associated ultradiffusion process.


Photospheric Radius Evolution Of Homologous Explosions, Liang-Duan Liu, Bing Zhang, Ling-Jun Wang, Zi-Gao Dai Nov 2018

Photospheric Radius Evolution Of Homologous Explosions, Liang-Duan Liu, Bing Zhang, Ling-Jun Wang, Zi-Gao Dai

Physics & Astronomy Faculty Research

Recent wide-field surveys discovered new types of peculiar optical transients that showed diverse behaviors of the evolution of photospheric properties. We develop a general theory of homologous explosions with constant opacity, paying special attention to the evolution of the photospheric radius R ph. We find that regardless of the density distribution profile, R ph always increases early on and decreases at late times. This result does not depend on the radiation and cooling processes inside the ejecta. The general rising/falling behavior of R ph can be used to quickly diagnose whether the source originates from a supernova-like explosion. The shape …


Boron Oxides Under Pressure: Prediction Of The Hardest Oxides, Huafeng Dong, Artem R. Oganov, Vadim V. Brazhkin, Qinggao Wang, Jin Zhang, M. Mahdi Davari Esfahani, Xiang-Feng Zhou, Fugen Wu, Qiang Zhu Nov 2018

Boron Oxides Under Pressure: Prediction Of The Hardest Oxides, Huafeng Dong, Artem R. Oganov, Vadim V. Brazhkin, Qinggao Wang, Jin Zhang, M. Mahdi Davari Esfahani, Xiang-Feng Zhou, Fugen Wu, Qiang Zhu

Physics & Astronomy Faculty Research

We search for stable compounds of boron and oxygen at pressures from 0 to 500 GPa using the ab initio evolutionary algorithm uspex. Only two stable stoichiometries of boron oxides, namely, B6O and B2O3, are found to be stable, in good agreement with experiment. A hitherto unknown phase of B6O at ambient pressure, Cmcm−B6O, has recently been predicted by us and observed experimentally. For B2O3, we predict three previously unknown stable high-pressure phases—two of these (Cmc21 and P212121) are dynamically and mechanically stable at ambient pressure, and should be quenchable to ambient conditions. Their predicted hardnesses, reaching 33–35 GPa, make …


Diffusion And Concentration Of Solids In The Dead Zone Of A Protoplanetary Disk, Chao-Chin Yang, Mordecai-Mark Mac Low, Anders Johansen Nov 2018

Diffusion And Concentration Of Solids In The Dead Zone Of A Protoplanetary Disk, Chao-Chin Yang, Mordecai-Mark Mac Low, Anders Johansen

Physics & Astronomy Faculty Research

The streaming instability is a promising mechanism to drive the formation of planetesimals in protoplanetary disks. To trigger this process, it has been argued that sedimentation of solids onto the mid-plane needs to be efficient, and therefore that a quiescent gaseous environment is required. It is often suggested that dead-zone or disk-wind structure created by non-ideal magnetohydrodynamical (MHD) effects meets this requirement. However, simulations have shown that the mid-plane of a dead zone is not completely quiescent. In order to examine the concentration of solids in such an environment, we use the local-shearing-box approximation to simulate a particlegas system with …


First-Principles Structural, Mechanical, And Thermodynamic Calculations Of The Negative Thermal Expansion Compound Zr2(Wo4)(Po4)2, Philippe F. Weck, Eunja Kim, Margaret E. Gordon, Jeffrey A. Greathouse, Remi Dingreville, Charles R. Bryan Nov 2018

First-Principles Structural, Mechanical, And Thermodynamic Calculations Of The Negative Thermal Expansion Compound Zr2(Wo4)(Po4)2, Philippe F. Weck, Eunja Kim, Margaret E. Gordon, Jeffrey A. Greathouse, Remi Dingreville, Charles R. Bryan

Physics & Astronomy Faculty Research

The negative thermal expansion (NTE) material Zr2(WO4)(PO4)2 has been investigated for the first time within the framework of the density functional perturbation theory (DFPT). The structural, mechanical, and thermodynamic properties of this material have been predicted using the Perdew, Burke and Ernzerhof for solid (PBEsol) exchange–correlation functional, which showed superior accuracy over standard functionals in previous computational studies of the NTE material α-ZrW2O8. The bulk modulus calculated for Zr2(WO4)(PO4)2 using the Vinet equation of state at room temperature is K0 = 63.6 GPa, which is in close agreement with the experimental estimate of 61.3(8) at T = 296 K. The …


Bunching Coherent Curvature Radiation In Three-Dimensional Magnetic Field Geometry: Application To Pulsars And Fast Radio Bursts, Yuan-Pei Yang, Bing Zhang Nov 2018

Bunching Coherent Curvature Radiation In Three-Dimensional Magnetic Field Geometry: Application To Pulsars And Fast Radio Bursts, Yuan-Pei Yang, Bing Zhang

Physics & Astronomy Faculty Research

The extremely high brightness temperatures of pulsars and fast radio bursts (FRBs) require their radiation mechanisms to be coherent. Coherent curvature radiation from bunches has been long discussed as the mechanism for radio pulsars and recently for FRBs. Assuming that bunches are already generated in pulsar magnetospheres, we calculate the spectrum of coherent curvature radiation under a three-dimensional magnetic field geometry. Different from previous works assuming parallel trajectories and a monoenergetic energy distribution of electrons, we consider a bunch characterized by its length, curvature radius of the trajectory family, bunch opening angle, and electron energy distribution. We find that the …


A Long-Lived Neutron Star Merger Remnant In Gw170817: Constraints And Clues From X-Ray Observations, L Piro, E Troja, Bing Zhang, G Ryan, H Van Eerten, R Ricci, M H. Wieringa, A Tiengo, N R. Butler, S B. Cenko, O D. Fox, H G. Khandrika, G Novara, A Rossi, T Sakamoto Nov 2018

A Long-Lived Neutron Star Merger Remnant In Gw170817: Constraints And Clues From X-Ray Observations, L Piro, E Troja, Bing Zhang, G Ryan, H Van Eerten, R Ricci, M H. Wieringa, A Tiengo, N R. Butler, S B. Cenko, O D. Fox, H G. Khandrika, G Novara, A Rossi, T Sakamoto

Physics & Astronomy Faculty Research

Multimessenger observations of GW170817 have not conclusively established whether the merger remnant is a black hole (BH) or a neutron star (NS). We show that a long-lived magnetized NS with a poloidal field B ≈ 1012 G is fully consistent with the electromagnetic dataset, when spin-down losses are dominated by gravitational wave (GW) emission. ... See full text for complete abstract.