Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

2019

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 1 - 30 of 1206

Full-Text Articles in Physics

Dimension Reduction Techniques For High Dimensional And Ultra-High Dimensional Data, Subha Datta Dec 2019

Dimension Reduction Techniques For High Dimensional And Ultra-High Dimensional Data, Subha Datta

Dissertations

This dissertation introduces two statistical techniques to tackle high-dimensional data, which is very commonplace nowadays. It consists of two topics which are inter-related by a common link, dimension reduction.

The first topic is a recently introduced classification technique, the weighted principal support vector machine (WPSVM), which is incorporated into a spatial point process framework. The WPSVM possesses an additional parameter, a weight parameter, besides the regularization parameter. Most statistical techniques, including WPSVM, have an inherent assumption of independence, which means the data points are not connected with each other in any manner. But spatial data violates this assumption. Correlation between ...


Magnetic And Structural Transitions In Euag4as2 Studied Using 151eu Mössbauer Spectroscopy, D. H. Ryan, Sergey L. Bud’Ko, Chaowei Hu, N. Ni Dec 2019

Magnetic And Structural Transitions In Euag4as2 Studied Using 151eu Mössbauer Spectroscopy, D. H. Ryan, Sergey L. Bud’Ko, Chaowei Hu, N. Ni

Ames Laboratory Accepted Manuscripts

151Eu Mössbauer spectroscopy confirms that the europium in EuAg4As2 is fully divalent and that the spectrum at 5 K consists of a single, sharp magnetic pattern with a hyperfine field (Bhf) of 27.1(1) T and an isomer shift of −11.04(3) mm/s (relative to EuF3). The temperature dependence of the spectra shows that the ordering of the Eu moments proceeds via an incommensurate sine modulated structure starting at 15 K. The structure squares up below 9 K. A search for charge density or phonon softening signatures at the 120 K ...


Definition Of Extended Structural Defects In Epitaxial Films Of Znteg‘Gaas Grown By Mbe, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov Dec 2019

Definition Of Extended Structural Defects In Epitaxial Films Of Znteg‘Gaas Grown By Mbe, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov

Scientific Bulletin. Physical and Mathematical Research

The last three decades of the development of solid state physics are characterized by the fact that the main objects of research are increasingly not massive crystals, but thin films, multilayer thin-film systems, conducting filaments and crystallites of small size. Epitaxial films are grown on a substrate of a single crystal of the same or another material. In the first case, the epitaxial layer with the correct technology becomes a natural extension of the substrate. Epitaxial film can be doped with various impurities. To introduce an alloying admixture into the epitaxial film, three methods are used. According to the first ...


Sub-Barrier And Above-Barrier Electron Transport Through Multilayer Semiconductors, Vohob R. Rasulov, Rustam Y. Rasulov, Ikbol M. Eshboltaev, Ravshan R. Sultonov Dec 2019

Sub-Barrier And Above-Barrier Electron Transport Through Multilayer Semiconductors, Vohob R. Rasulov, Rustam Y. Rasulov, Ikbol M. Eshboltaev, Ravshan R. Sultonov

Scientific Bulletin. Physical and Mathematical Research

In the article the transparency coefficients of the semiconductor structure, consisting of alternating asymmetric potential barriers and wells, where the Bastard condition is taken into account, are calculated. It is shown that in the structure there should be an oscillation of the transmission coefficient of electrons depending on their energy, which is due to the interference of the de Broglie waves reaching the barrier and reflected from the potential barrier. The electronic states of a multilayer semiconductor structure consisting of alternating potential wells and barriers are analyzed. It has been shown that both in the above-barrier and in the barrier ...


Application Of Optoelectron Converters Of Reflective Type For Automation Of Liquid And Gas Version Test Measuring Units, Yuriy G. Shipulin, Otabek T. Almataev Dec 2019

Application Of Optoelectron Converters Of Reflective Type For Automation Of Liquid And Gas Version Test Measuring Units, Yuriy G. Shipulin, Otabek T. Almataev

Scientific Bulletin. Physical and Mathematical Research

This work is devoted to the use of reflective optoelectronic converters for the automation of liquid and gas calibration flowmeter installations. Liquid and gas calibration flowmeter devices are widely used for verification and certification of various liquid and gas flowmeters and meters. The analysis of the principles of construction of a reflective optoelectronic converter for calibration devices is carried out and the basic principles of their construction are determined. A functional diagram of an experimental automated programmable calibration test setup of flow meters, liquid meters developed on the basis of ROC is presented. High accuracy requirements are imposed on the ...


Spectral Characteristics Of The Absorption Coefficient And Energy Position Of Defects, Sirojiddin Z. Zaynobidinov, Rustamjon G. Ikramov, Mashhurahon A. Nuriddinova, Khurshid A. Muminov Dec 2019

Spectral Characteristics Of The Absorption Coefficient And Energy Position Of Defects, Sirojiddin Z. Zaynobidinov, Rustamjon G. Ikramov, Mashhurahon A. Nuriddinova, Khurshid A. Muminov

Scientific Bulletin. Physical and Mathematical Research

In this paper, a theoretical method to study the spectral characteristics of the absorption coefficient, namely the area of ​​defective absorption of amorphous hydrogenated silicon according to the Davis-Mott approximation from the Kubo-Greenwood formula. It is shown that using the experimental spectral characteristic of the defect absorption coefficient, one can determine the energy position of defects in the mobility gap. Optical transitions of electrons, in which electronic states participate in defects, indicate that there are three types of optical transitions of electrons: between defects, between defects and tails of allowed zones, and also between defects and allowed zones. It was ...


Features Of The Physical Properties Of The Modified Surface Of The P-Cdte – Znse Film Heterostructure With Deep Impurity Levels, Yuozas Y. Vaytkus, Nodir E. Alimov, Salim M. Otajonov Dec 2019

Features Of The Physical Properties Of The Modified Surface Of The P-Cdte – Znse Film Heterostructure With Deep Impurity Levels, Yuozas Y. Vaytkus, Nodir E. Alimov, Salim M. Otajonov

Scientific Bulletin. Physical and Mathematical Research

This article analyzes the spectrum of the photocurrent in a layered film heterostructure CdTe-ZnSe with deep primesnymi levels. The experimental results demonstrated that the heterostructure CdTe-ZnSe observed a new effect in the measurement of the photoconductivity spectra, depending on the direction of the applied electric field, and the applied field stimulates the emergence of photo-emf. The spectrum of the photocurrent in a layered CdTe- ZnSe heterostructure film with deep impurity levels are considered in the article. It follows from the experimental results that a new effect is observed in the CdTe-ZnSe heterostructure when measuring the photoconductivity spectra depending on the ...


Structure And Electro Physical Properties Of Solid Solution (Si2)1-X(Cds)X (0 £ X £ 0.01), Xurshidjon M. Madaminov Dec 2019

Structure And Electro Physical Properties Of Solid Solution (Si2)1-X(Cds)X (0 £ X £ 0.01), Xurshidjon M. Madaminov

Scientific Bulletin. Physical and Mathematical Research

This paper shows the possibility of obtaining a single-crystal solid solution for the substitution of p-Si-n-(Si2)1-x (CdS)x (0 £ x £ 0.01) on silicon substrates with a diameter of 20 mm and thickness » 400, with a crystallographic orientation (111) n-types of conductivity with a specific resistance of 1 Ω cm, by the method of liquid phase epitaxy from Sn – Si – CdS solution – melt in a hydrogen atmosphere purified by palladium. Perfect epitaxial layers with mirror surfaces and with the best parameters are grown under the following technological conditions: temperatures start crystallization –1150 ОС, speed of forced cooling is ...


Studies Of Tribotechnical Properties Of Composite Polymeric Materials Of Machine Designation, Tojiboy O. Almataev, Nozimbek T. Almataev Dec 2019

Studies Of Tribotechnical Properties Of Composite Polymeric Materials Of Machine Designation, Tojiboy O. Almataev, Nozimbek T. Almataev

Scientific Bulletin. Physical and Mathematical Research

In the given work are experimentally investigated tribotechnical properties as intensity of wear process and factor of a friction composite epoxy the polymeric materials processed by ultrasound. Results of influence of a kind and the maintenance loading on tribotechnical properties composite epoxy polymeric materials depending on modes of ultrasonic processing are received. Correlation dependence of intensity of wear process and factor of a friction composite epoxy coverings from modes of ultrasonic processing is established. It is shown in the work that with an increase in the duration of ultrasonic exposure, the wear rate and the friction coefficient of the coatings ...


Scientific Foundation Of The Rate Of Falling Of Raw Materials On Walnut Breakage Device, Otabek A. Mirzaev, Xolhuzha A. Sobirov, Nusratillo R. Barakaev Dec 2019

Scientific Foundation Of The Rate Of Falling Of Raw Materials On Walnut Breakage Device, Otabek A. Mirzaev, Xolhuzha A. Sobirov, Nusratillo R. Barakaev

Scientific Bulletin. Physical and Mathematical Research

Today, there are many types of fruits that are separated the kernel from the shell: walnuts, almonds, filberts, chestnuts, pistachios and cashews. Nuts have a high calorific value and a rich nutrient composition. The most critical and delicate operation is shell cracking to extract the fragile whole kernel from the shell. Studies on nut rupturing are particularly focused on the following three aspects: the physical characteristics of nuts, the mechanical properties of nut rupturing, and nut rupturing equipment. Determining the velocity of the nut entered into the apparatus will allow the machine to operate normally, but will also increase its ...


Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel Dec 2019

Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel

Mathematics, Physics, and Computer Science Faculty Articles and Research

Out-of-time-ordered correlators (OTOCs) have been proposed as a tool to witness quantum information scrambling in many-body system dynamics. These correlators can be understood as averages over nonclassical multitime quasiprobability distributions (QPDs). These QPDs have more information and their nonclassical features witness quantum information scrambling in a more nuanced way. However, their high dimensionality and nonclassicality make QPDs challenging to measure experimentally. We focus on the topical case of a many-qubit system and show how to obtain such a QPD in the laboratory using circuits with three and four sequential measurements. Averaging distinct values over the same measured distribution reveals either ...


First-Principles Study Of High-Pressure Phase Stability And Superconductivity Of Bi4i4, Shiyu Deng, Xianqi Song, Quan Li, Yu Xie, Changfeng Chen, Yanming Ma Dec 2019

First-Principles Study Of High-Pressure Phase Stability And Superconductivity Of Bi4i4, Shiyu Deng, Xianqi Song, Quan Li, Yu Xie, Changfeng Chen, Yanming Ma

Physics & Astronomy Faculty Publications

Bismuth iodide Bi4I4 exhibits intricate crystal structures and topological insulating states that are highly susceptible to influence by environments, making its physical properties highly tunable by external conditions. In this work, we study the evolution of structural and electronic properties of Bi4I4 at high pressure using an advanced structure search method in conjunction with first-principles calculations. Our results indicate that the most stable ambient-pressure monoclinic α−Bi4I4 phase in C2/m symmetry transforms to a trigonal P31c structure (ɛ−Bi4I4) at 8.4 GPa, then to a tetragonal P4/mmm structure (ζ−Bi4I4) above 16.6 GPa. In contrast to ...


The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky Dec 2019

The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky

Ames Laboratory Accepted Manuscripts

Our 151Eu Mössbauer investigation of Eu2In and Eu2Sn shows that the europium in both materials is fully divalent. We confirm the distinct thermodynamic orders of the magnetic transitions and reveal a remarkable difference between the magnetic environments of the europium atoms in the two compounds. Possible structural and electronic origins for these differences are discussed using DFT calculations.


Constraints On Parton Distribution Functions Imposed By Hadronic Experiments, Boting Wang Dec 2019

Constraints On Parton Distribution Functions Imposed By Hadronic Experiments, Boting Wang

Physics Theses and Dissertations

The theoretical uncertainties of the Large Hadron Collider (LHC) observables are decreasing with the increasing statistics of the LHC experiments, and it is becoming more and more important to reduce the uncertainties in the knowledge of the nucleon structure. The latest LHC high-energy experiments, future experimental proposals, and computational tools are expected to enhance the knowledge of the nucleon structure. However, the global analysis that assesses their impact on Parton Distribution Functions (PDFs) knowledge is computationally expensive due to the corresponding large size of data. I developed a new approach that can make a quick preliminary evaluation to help the ...


Detection Of Whale Acoustic Signals In The Northern Gulf Of Mexico Ladc-Gemm Database, Yingxue Gao Dec 2019

Detection Of Whale Acoustic Signals In The Northern Gulf Of Mexico Ladc-Gemm Database, Yingxue Gao

University of New Orleans Theses and Dissertations

Low-pass Fourier filter, wavelet filter, as well as matched filter detection methods were used to detect baleen whale signals in northern Gulf of Mexico data collected by the Littoral Acoustic Demonstration Center (LADC) consortium. Some potential low frequency signals appeared on the matched filter output figure. The shape of the signals is in line with one of the typical signal shapes of fin whales--vertical down-sweeps with 18s-time interval. Another shape of the signals is in line with one of the call type shapes of Bryde's whales--down-sweeps with 7s-time interval. A high-pass Fourier filter was also used to find toothed ...


Magnetic Structure Of Nd In Ndfeaso Studied By X-Ray Resonant Magnetic Scattering, M. G. Kim, J.-W. Kim, J.-Q. Yan, Alan I. Goldman, Andreas Kreyssig Dec 2019

Magnetic Structure Of Nd In Ndfeaso Studied By X-Ray Resonant Magnetic Scattering, M. G. Kim, J.-W. Kim, J.-Q. Yan, Alan I. Goldman, Andreas Kreyssig

Ames Laboratory Accepted Manuscripts

The magnetic structure of Nd in NdFeAsO compound has been investigated by x-ray resonant magnetic scattering at the Nd L2 edge (E=6.725 keV) at 1.7≤T≤15 K. At T=1.7 K we find that the Nd moments are aligned along the crystallographic c direction with the (1, 0, 0) propagation vector, and are arranged antiferromagnetically along the a direction and ferromagnetically along the b and c directions. At 1.7


Is Contact Nucleation Caused By Pressure Perturbation?, Fan Yang, Will Cantrell, Alexander Kostinski, Raymond Shaw, Andrew M. Vogelmann Dec 2019

Is Contact Nucleation Caused By Pressure Perturbation?, Fan Yang, Will Cantrell, Alexander Kostinski, Raymond Shaw, Andrew M. Vogelmann

Michigan Tech Publications

The reason why ice nucleation is more efficient by contact nucleation than by immersion nucleation has been elusive for over half a century. Six proposed mechanisms are summarized in this study. Among them, the pressure perturbation hypothesis, which arose from recent experiments, can qualitatively explain nearly all existing results relevant to contact nucleation. To explore the plausibility of this hypothesis in a more quantitative fashion and to guide future investigations, this study assessed the magnitude of pressure perturbation needed to cause contact nucleation and the associated spatial scales. The pressure perturbations needed were estimated using measured contact nucleation efficiencies for ...


Exploratory Measurements Of Large Winds And Shears In The Lower Thermosphere And Their Variability Using An Enhanced Sodium Lidar, Tao Yuan Dec 2019

Exploratory Measurements Of Large Winds And Shears In The Lower Thermosphere And Their Variability Using An Enhanced Sodium Lidar, Tao Yuan

Funded Research Records

No abstract provided.


Effects Of Impurities On Calcium Oxalate Crystallization As Measured By Atomic Force Microscopy, Himasha Wijesekara Dec 2019

Effects Of Impurities On Calcium Oxalate Crystallization As Measured By Atomic Force Microscopy, Himasha Wijesekara

Electronic Thesis and Dissertation Repository

Calcium oxalate crystals are found in kidney stones as either calcium oxalate monohydrate (COM) or calcium oxalate dihydrate (COD). COM crystals are the most abundant form as they are thermodynamically more stable than COD crystals under physiological conditions. Certain aspartic acid-rich molecules such as osteopontin (OPN) are known to affect stone formation by inhibiting COM and COD growth. We have studied COM {010} and COD {100} faces in the presence of OPN, poly-aspartic acid (poly-ASP) and synthetic peptides derived from OPN to investigate the inhibitor mechanism.

We observed that poly-ASP preferentially inhibits one particular direction of {010} faces on COM ...


Magnetoelastoresistance In Wte2: Exploring Electronic Structure And Extremely Large Magnetoresistance Under Strain, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’Ko, Paul C. Canfield Dec 2019

Magnetoelastoresistance In Wte2: Exploring Electronic Structure And Extremely Large Magnetoresistance Under Strain, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’Ko, Paul C. Canfield

Physics and Astronomy Publications

Strain describes the deformation of a material as a result of applied stress. It has been widely employed to probe transport properties of materials, ranging from semiconductors to correlated materials. In order to understand, and eventually control, transport behavior under strain, it is important to quantify the effects of strain on the electronic bandstructure, carrier density, and mobility. Here, we demonstrate that much information can be obtained by exploring magnetoelastoresistance (MER), which refers to magnetic field-driven changes of the elastoresistance. We use this powerful approach to study the combined effect of strain and magnetic fields on the semimetallic transition metal ...


Investigation Of Isomer Ratios In The Reactions (Γ, N) And (N, 2N) On Nuclei 76Ge And 82Se, Satimbay Palvanov, Turgunali Akhmadzhanov Dec 2019

Investigation Of Isomer Ratios In The Reactions (Γ, N) And (N, 2N) On Nuclei 76Ge And 82Se, Satimbay Palvanov, Turgunali Akhmadzhanov

Bulletin of National University of Uzbekistan: Mathematics and Natural Sciences

The method of the induced activity measured the isomeric yield ratios and cross-sections ratios of reactions (γ, n) and (n, 2n) on nuclei 76Ge and 82Se. Samples of natural have been irradiated in the bremsstrahlung beam of the betatron SB-50 of National University of Uzbekistan in the energy range of 10-35 MeV with energy step of 1 MeV. For 14 MeV neutron irradiation, we used the NG-150 neutron generator of Institute of Nuclear Physics. The gamma spectra reactions products were measured with a spectroscopic system consisting of HPGe detector CANBERRA with energy resolution of 1.8 keV ...


Cyclotron Resonance In Graphene Heterostructurescyclotron Resonance In Graphene Heterostructures, Billy Jordan Russell Dec 2019

Cyclotron Resonance In Graphene Heterostructurescyclotron Resonance In Graphene Heterostructures, Billy Jordan Russell

Arts & Sciences Electronic Theses and Dissertations

We present observations of cyclotron resonance in graphene Van der Waals heterostructure devices. Such devices provide dramatic improvements in sample quality and allow for ad- vanced electronic control, opening windows on previously inaccessible physics. The design and construction of a dedicated system for the measurement of electronic transport and infrared magnetospectroscopy in microscopic samples of atomically thin materials at cryogenic temperatures is presented. In high-mobility encapsulated monolayer graphene, electron- electron interaction effects are unambiguously observed to impact the interband cyclotron resonance as the Landau level filling factor is varied in a quantizing magnetic field. Additionally, a splitting of transitions involving ...


Pressure Driven Electronic Band Gap Engineering In Tin(Iv)-O,N Compounds, Daniel Thomas Sneed Dec 2019

Pressure Driven Electronic Band Gap Engineering In Tin(Iv)-O,N Compounds, Daniel Thomas Sneed

UNLV Theses, Dissertations, Professional Papers, and Capstones

The intrinsic link between long-range order, coordination geometry, and the electronic properties of a system must be understood in order to tailor function-specific materials. Although material properties are typically tailored using chemical dopants, such methods can cause irreversible changes to the structure, limiting the range of functionality. The application of high pressure may provide an alternative “clean” method to tune the electronic properties of semiconducting materials by tailoring their defect density and structure.

We have explored a number of optoelectronic relevant materials with promising characteristics, specifically Sn-(O,N) compounds which have been predicted to undergo pressure-mediated opening of their ...


Development Of High-Speed Photoacoustic Imaging Technology And Its Applications In Biomedical Research, Yun He Dec 2019

Development Of High-Speed Photoacoustic Imaging Technology And Its Applications In Biomedical Research, Yun He

Engineering and Applied Science Theses & Dissertations

Photoacoustic (PA) tomography (PAT) is a novel imaging modality that combines the fine lateral resolution from optical imaging and the deep penetration from ultrasonic imaging, and provides rich optical-absorption–based images. PAT has been widely used in extracting structural and functional information from both ex vivo tissue samples to in vivo animals and humans with different length scales by imaging various endogenous and exogenous contrasts at the ultraviolet to infrared spectrum. For example, hemoglobin in red blood cells is of particular interest in PAT since it is one of the dominant absorbers in tissue at the visible wavelength.The main ...


Contemporary Problems In Aerosol Aggregation And Gelation, Pai Liu Dec 2019

Contemporary Problems In Aerosol Aggregation And Gelation, Pai Liu

Engineering and Applied Science Theses & Dissertations

Aggregation of nanoparticles in aerosols is a fundamental phenomenon with important implications to diverse fields ranging from material synthesis to pollutant control. The past few decades have witnessed extensive research on investigating the structure and growth mechanism of aerosol aggregates with sizes spanning across several orders of magnitude. This dissertation focuses on some contemporary problems that remain unaddressed in this topical area. Aerosol aggregates in sub-micron regimes, which are formed via the irreversible collision and aggregation of solid nanoparticle monomers, are fractal-like in their morphology. A mathematical description of this seemingly random structure dates to the seminal works by Forest ...


Direct Observation Of Atomic Exchange During Surface Self-Diffusion, Matthew Aaron Koppa Dec 2019

Direct Observation Of Atomic Exchange During Surface Self-Diffusion, Matthew Aaron Koppa

Physics & Astronomy ETDs

The diffusion of adatoms across the (100) plane of iridium has been previously inferred to occur by an exchange mechanism based on site mapping. This study provides the first direct observation that surface self-diffusion can occur by exchange. Iridium enriched to ≥93% 191Ir was deposited onto an atomically clean and smooth Ir(100) plane as observed in an atom probe field ion microscope. Following thermally activated surface self-diffusion the adatom was field desorbed and mass analyzed. Observation of the 193Ir isotope in one-half of the cases demonstrates conclusively that atomic exchange can occur during surface self-diffusion.


Numerical And Semi-Analytical Estimation Of Convective Heat Transfer Coefficient For Buildings In An Urban-Like Setting, Anwar Demsis Awol Dec 2019

Numerical And Semi-Analytical Estimation Of Convective Heat Transfer Coefficient For Buildings In An Urban-Like Setting, Anwar Demsis Awol

Electronic Thesis and Dissertation Repository

Urban building arrangements such as packing density, orientation and size are known to influence the microclimate surrounding each building. Studies on the impact of urban microclimatic changes on convective heat transfer coefficient (CHTC) from a stock of buildings, however, have been rare in surveyed literature. The present study focuses on numerical and analytical investigation of CHTC from building-like models with homogeneous set of equal and unequal planar and frontal densities. Consequently, the study discusses the CHTC response in relation to broader changes in the urban surface form. Part of the process involves the development of a simplified one-dimensional semi-analytical CHTC ...


The Distribution Of Ultra-Diffuse And Ultra-Compact Galaxies In The Frontier Fields, Steven Janssens, Roberto Abraham, Jean Brodie, Duncan Forbes, Aaron Romanowsky Dec 2019

The Distribution Of Ultra-Diffuse And Ultra-Compact Galaxies In The Frontier Fields, Steven Janssens, Roberto Abraham, Jean Brodie, Duncan Forbes, Aaron Romanowsky

Faculty Publications

Large low-surface-brightness galaxies have recently been found to be abundant in nearby galaxy clusters. In this paper, we investigate these ultra-diffuse galaxies (UDGs) in the six Hubble Frontier Fields galaxy clusters: A2744, MACS J0416.1−2403, MACS J0717.5+3745, MACS J1149.5+2223, AS1063, and A370. These are the most massive (1–3 × 1015 M ⊙) and distant (0.308 < z < 0.545) systems in which this class of galaxy has yet been discovered. We estimate that the clusters host of the order of ~200–1400 UDGs inside the virial radius (R 200), consistent with the UDG abundance–halo-mass relation found in the local universe, and suggest that UDGs may be formed in clusters. Within each cluster, however, we find that UDGs are not evenly distributed. Instead their projected spatial distributions are lopsided, and they are deficient in the regions of highest mass density as traced by gravitational lensing. While the deficiency of UDGs in central regions is not surprising, the lopsidedness is puzzling. The UDGs, and their lopsided spatial distributions, may be associated with known substructures late in their infall into the clusters, meaning that we find evidence both for formation of UDGs in clusters and for UDGs falling into clusters. We also investigate the ultra-compact dwarfs (UCDs) residing in the clusters, and find that the spatial distributions of UDGs and UCDs appear anticorrelated. Around 15% of UDGs exhibit either compact nuclei or nearby point sources. Taken together, these observations provide additional evidence for a picture in which at least some UDGs are destroyed in dense cluster environments and leave behind a residue of UCDs.


Comparison Of Charge Storage Properties Of Prussian Blue Analogues Containing Cobalt And Copper, Amanda Rensmo, Jennifer R. Hampton Dec 2019

Comparison Of Charge Storage Properties Of Prussian Blue Analogues Containing Cobalt And Copper, Amanda Rensmo, Jennifer R. Hampton

Faculty Publications

Prussian blue analogues are of great interest as alternative battery materials because of their long life cycle and potential use of earth-abundant elements. In this work, thin film mixed-metal hexacyanoferrates (HCFs) based on NiCo and NiCu alloys were fabricated in an all electrochemical process. The structure and composition of the samples were characterized, along with the charge storage capacity and kinetics of the charge transfer reaction. For both NiCo-HCF and NiCu-HCF samples, the total charge capacity increased with the substitution of Ni with more Co or Cu, and the increase was larger for Cu samples than for Co samples. On ...


Design Of Reinforced Concrete Deep Beams Using Particle Swarm Optimization Technique, Qais F. Hasan, Dler A. Al-Mamany, Omer K. Fayadh Dec 2019

Design Of Reinforced Concrete Deep Beams Using Particle Swarm Optimization Technique, Qais F. Hasan, Dler A. Al-Mamany, Omer K. Fayadh

Karbala International Journal of Modern Science

Researches available in literature interrelating neural networks to civil engineering design problems, especially for beep beams, are very rare. Therefore, an optimization algorithm is developed and verified in this study and coded using MATLAB functions to determine the optimum cost design of reinforced concrete deep beams. ACI 318-14 code method is used benefiting from iterative particle swarm optimization technique due to its efficiency and reliability. Minimizing total cost is used as the objective function in terms of four decision variables. Self-adaptive penalty function technique is used to handle constraints for each of the 300 randomly selected particles, and in each ...