cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Annealing-induced transition from a (311)A-oriented Ga0.98Mn0.02As alloy to a GaMnAs/MnAs hybrid structure studied by angle-dependent magnetotransport
Creators: name: Elm, M. T.
name: Klar, P. J.
name: Heimbrodt, W.
name: Wurstbauer, Ursula
name: Reinwald, Matthias
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: annealing, gallium arsenide, gallium compounds, III-V semiconductors, magnetic anisotropy, magnetic epitaxial layers, magnetoresistance, manganese compounds, molecular beam epitaxial growth, semiconductor epitaxial layers, semimagnetic semiconductors
subject: 530 Physik
subject: 73.61.Ey; 75.50.Pp; 75.47.Pq; 68.55.A-; # 61.72.Cc; 73.50.Jt

description: The angle-dependent behavior of the magneto-resistance of a series of low-temperature molecular beam epitaxy grown Ga0.98Mn0.02As samples on (311)A-GaAs-substrates is studied. The samples are annealed at different temperatures in a range from 300 °C to 500 °C, which leads to a redistribution of the manganese in the sample and finally to the formation of MnAs clusters. As a consequence, the angle-dependence of the magneto-resistance changes with increasing annealing temperature and vanishes finally at an annealing temperature of 400 °C. The observed anisotropy of the magneto-resistance can be correlated with the magnetic anisotropy of the magnetization. The parameters describing this magnetic anisotropy and their changes due to annealing are extracted from the experimental magneto-resistance data by a fitting procedure. The magnetocrystalline anisotropy of the samples can be described by the sum of cubic and uniaxial contributions. The former are not affected by the annealing whereas the latter change considerably.
Aparadh Vikash Aur SatyanashDaridra Vyaktiyon Kee SamasyayenDr. NEETU SINGH TOMAR, Post Doctoral Fellow, University Grant Commission New Delhi
Creators: name: Tomar, Neetusingh
Publisher: name: figshare
Year: 2021
Subjects: subject: Sociology
subject: FOS: Sociology

description: Aparadh Vikash Aur Satyanash
Investigating the transport properties of the excitonic state in quasi-Corbino electron bilayers
Creators: name: Tiemann, L.
name: Lok, J. G. S.
name: Dietsche, W.
name: Klitzing, Klaus von
name: Muraki, K.
name: Schuh, Dieter
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: Total filling factor 1; Quasi-Corbino; Drag; Electron-bilayer
subject: 530 Physik
subject: 73.43.-f; 71.10.Pm; 71.53.Lk

description: We investigate two closely spaced 2D electron systems in a quasi-Corbino geometry with independent contacts to both layers. Magneto-transport and drag experiments show that at the systems total filling factor 1 the drive current diminishes with increasing interlayer interaction (parameterized by the ratio of layer separation and magnetic length) while voltages of equal magnitude build up over both the drive and the drag layer. The identity of both voltages is resilient to thermal perturbations which contrasts markedly to the behavior observed in Hall bars.
Velocity and velocity bounds in static spherically symmetric metrics
Creators: name: Arraut, I.
name: Batic, D.
name: Nowakowski, M.
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We find simple expressions for velocity of massless particles in dependence of the distance $r$ in Schwarzschild coordinates. For massive particles these expressions put an upper bound for the velocity. Our results apply to static spherically symmetric metrics. We use these results to calculate the velocity for different cases: Schwarzschild, Schwarzschild-de Sitter and Reissner-Nordström with and without the cosmological constant. We emphasize the differences between the behavior of the velocity in the different metrics and find that in cases with naked singularity there exists always a region where the massless particle moves with a velocity bigger than the velocity of light in vacuum. In the case of Reissner-Nordström-de Sitter we completely characterize the radial velocity and the metric in an algebraic way. We contrast the case of classical naked singularities with naked singularities emerging from metric inspired by noncommutative geometry where the radial velocity never exceeds one. Furthermore, we solve the Einstein equations for a constant and polytropic density profile and calculate the radial velocity of a photon moving in spaces with interior metric. The polytropic case of radial velocity displays an unexpected variation bounded by a local minimum and maximum.
description: 20 pages, 5 figures
Broadband electrical detection of spin excitations in Ga0.98Mn0.02As using a photovoltage technique
Creators: name: Wirthmann, André
name: Hui, Xiong
name: Mecking, N.
name: Gui, Y. S.
name: Chakraborty, Tapash
name: Hu, C. M.
name: Reinwald, Matthias
name: Schüller, Christian
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: crystal microstructure, ferromagnetic materials, ferromagnetic resonance, gallium compounds, galvanomagnetic effects, g-factor, magnetic thin films, magnetisation, manganese compounds, photovoltaic effects, semiconductor thin films, spin dynamics
subject: 530 Physik
subject: 75.70.Ak; 73.50.Pz; 73.50.Jt; 75.40.Gb; 76.50.+g; 75.50.Dd;

description: We report on microwave photovoltage and simultaneous magnetotransport measurements in a (Ga, Mn) As film oriented normal to the magnetic field. We detect the ferromagnetic resonance over a broad frequency range of 2–18.5 GHz and determine the spectroscopic g-factor and separate the Gilbert from the inhomogeneous contribution to magnetization relaxation. Temperature dependent measurements below the saturation magnetization indicate that the photovoltage signal can serve as a sensitive tool to study the crystal anisotropy. We demonstrate that the combination of spin dynamics with charge transport is a promising tool to study microstructured ferromagnetic semiconductor samples.
Daridrata Kuchakra Aur ArthvyavasthaDaridra Vyaktiyon Kee SamasyayenDr. NEETU SINGH TOMAR, Post Doctoral Fellow, University Grant Commission New Delhi
Creators: name: Tomar, Neetusingh
Publisher: name: figshare
Year: 2021
Subjects: subject: Sociology
subject: FOS: Sociology

description: Daridrata Kuchakra Aur Arthvyavastha
The African Storybook and teacher identity
Creators: name: Stranger-Johannessen, Espen
Publisher: name: University of British Columbia
Year: 2018

description: The African Storybook (ASb) is a digital initiative that promotes multilingual literacy for African children by providing openly licenced children’s stories in multiple African languages, as well as English, French, and Portuguese. One of the ASb pilot sites, a primary school in Uganda, served as the focal case in this research, while two other schools and libraries were also included. Data was collected from June to December 2014 in the form of field notes, classroom observations, interview transcripts, and questionnaires, which were coded using retroductive coding. Based on Darvin and Norton’s (2015) model of identity and investment, and drawing on the Douglas Fir Group’s (2016) framework for second language acquisition, this study investigates Ugandan primary school teachers’ investment in the ASb and how their identities change through the process of using the stories and technology provided by the ASb. The findings indicate that the use of stories expands the repertoire of teaching methods and topics, and that this use is influenced by teachers’ social capital as well as financial factors and policies. Through the ASb initiative and its stories, the teachers began to imagine themselves as writers and translators; change agents; multimodal, multiliterate educators; and digital educators, reframing what it means to be a reading teacher. Teachers’ shifts of identity were indexical of their enhanced social and cultural capital as they engaged with the ASb, notwithstanding ideological constraints associated with mother tongue usage, assessment practices, and teacher supervision. This exploration of teachers’ resourcefulness, needs, and realities provides a foundation for enhancing existing practices.
Investigations on unconventional aspects in the quantum Hall regime of narrow gate defined channels
Creators: name: Horas, J.
name: Siddiki, A.
name: Moser, Jürgen
name: Wegscheider, Werner
name: Ludwig, S.
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: Edge states; Quantum Hall effect; Screening
subject: 530 Physik
subject: 73.20.Dx; 73.40.Hm; 73.50.−h; 73.61.−r

description: We report on theoretical and experimental investigations of the integer quantized Hall effect in narrow channels at various mobilities. The Hall bars are defined electrostatically in two-dimensional electron systems by biasing metal gates on the surfaces of GaAs/AlGaAs heterostructures. In the low mobility regime the classical Hall resistance line is proportional to the magnetic field as measured in the high temperature limit and cuts through the center of each Hall plateau. For high mobility samples we observe in linear response measurements that this symmetry is broken and the classical Hall line cuts the plateaus not at the center but higher B field edges of the plateaus. These experimental results confirm the unconventional predictions of a model for the quantum Hall effect taking into account mutual screening of charge carriers within the Hall bar. The theory is based on solving the Poisson and Schrödinger equations in a self-consistent manner.
Large in-plane spin-dephasing anisotropy in a [0 0 1]-grown two-dimensional electron system
Creators: name: Korn, Tobias
name: Stich, Dominik
name: Schulz, Robert
name: Schuh, Dieter
name: Wegscheider, Werner
name: Schüller, Christian
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: Heterostructures; 2D electron system; Spin dephasing; Anisotropy
subject: 530 Physik
subject: 39.30.+w; 73.20.−r; 85.75.−d; 71.70.E

description: A large anisotropy in the spin dephasing times for the different in-plane directions of [0 0 1] quantum wells has been predicted in calculations by Averkiev and Golub [Phys. Rev. B 60 (1999) 15582] for systems with both Rashba and Dresselhaus spin-orbit fields. Here, we present time-resolved Faraday rotation measurements performed in the Voigt geometry on a high-mobility 2D electron system grown on a [0 0 1] substrate. An out-of-plane spin polarization is created in the sample by a circularly polarized pump pulse. The magnetic field applied in the sample plane forces the spins to precess perpendicular to it. For a magnetic field applied along [1 1 0], the spins precess into the View the MathML source direction, which is in the sample plane, for a magnetic field along View the MathML source, the spins precess into the [1 1 0] direction. The experimentally determined spin dephasing times for these two different cases differ by about 60%, demonstrating that the predicted anisotropy is present in our sample.
title: Validation of the HIC rain gauges data: year 2022
Creators: name: Journée, M.
name: Deschamps, Maarten
Publisher: name: Flanders Hydraulics
Year: 2023

description: This report summarizes the results of the validation of the data recorded during the year 2022 by 19 rain gauges operated by HIC. This validation is made by RMI and integrates two aspects. First, a human operator routinely monitors the data on successive periods of 24 hours. Issues detected on that daily timeframe are directly corrected. Second, monthly and annual values from the validated HIC data are compared against neighboring stations data as well as radar-derived rainfall estimates. Both validation aspects are treated in this report.
description: Title : FH reports. Flanders Hydraulics: Antwerp.
Volume : PA027_28
Issue :
Pagination : III, 36
Khadya Adhikar Ki Suraksha Aur Vitran PranalyDaridra Vyaktiyon Kee Samasyayen
Creators: name: Tomar, Neetusingh
Publisher: name: figshare
Year: 2019
Subjects: subject: Sociology
subject: FOS: Sociology

description: Khadya Adhikar Ki Suraksha Aur Vitran Pranaly
Spin-momentum correlation in relativistic single particle quantum states
Creators: name: Jafarizadeha, M. A.
name: Mahdian, M.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: This paper was concerned with the spin-momentum correlation in single-particle quantum states, which is described by the mixed states under Lorentz transformations. For convenience, instead of using the superposition of momenta we use only two momentum eigen states (p1 and p2) that are perpendicular to the Lorentz boost direction. Consequently, in 2D momentum subspace we show that the entanglement of spin-momentum in the moving frame depends on the angle between them. Therefore, when spin and momentum are perpendicular the measure of entanglement is not observer-dependent quantity in inertial frame. Likewise, we have calculated the measure of entanglement (by using the concurrence) and has shown that entanglement decreases with respect to the increasing of observer velocity. Finally, we argue that, Wigner rotation is induced by Lorentz transformations can be realized as controlling operator.
description: 17 pages
Coulomb-coupled concentric quantum rings
Creators: name: Mühle, A.
name: Wegscheider, Werner
name: Haug, Rolf J.
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: Quantum rings; Aharonov–Bohm effect
subject: 530 Physik
subject: 73.21.La; 73.23.-b; 73.63.-b

description: We present measurements done on a novel device consisting of two concentric quantum rings realized by local anodic oxidation in a GaAs/AlGaAs heterostructure. The outer ring is connected to external leads while the inner ring is only Coulomb-coupled to the rest of the system. We studied the electronic transport through the outer ring in dependence of an external magnetic field and found a superposition of oscillations with two distinct Aharonov–Bohm periods in the signal. These matched the diameters of the outer and inner ring respectively, demonstrating an influence of the inner ring on the conductance of the outer one. We attribute this influence to charge redistributions in the inner ring induced by the magnetic field.
Evolution of Coordination in Social Networks: A Numerical Study
Creators: name: Tomassini, Marco
name: Pestelacci, Enea
Publisher: name: arXiv
Year: 2010
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Social and Information Networks (cs.SI)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Coordination games are important to explain efficient and desirable social behavior. Here we study these games by extensive numerical simulation on networked social structures using an evolutionary approach. We show that local network effects may promote selection of efficient equilibria in both pure and general coordination games and may explain social polarization. These results are put into perspective with respect to known theoretical results. The main insight we obtain is that clustering, and especially community structure in social networks has a positive role in promoting socially efficient outcomes.
description: preprint submitted to IJMPC
Social Enterprise in Ethiopia: Examining Major Regulatory Issues
Creators: name: Enyew, Tajebe Getaneh
Publisher: name: Bahir Dar University Journal of Law
Year: 2024

description: Traditionally, private entities were divided into for-profit and non-profit organizations, with the goal of maximizing profit and social impact, respectively. Recently, however, both social and financial maximization have begun to be carried out in a single institution. Investors start a firm with the primary purpose of fixing the community's social, environmental, economic, and cultural (SEEC) concerns while earning a modest profit. These types of businesses are called social enterprises. Social enterprises combine profit and social mission into a single company. Though their income is primarily derived from their business, they also get donor-funded grants and government subsidies. Though these types of businesses are flourishing in Ethiopia, there is no special regulatory framework in Ethiopia designed for social enterprise so far. They are treated and regulated as ordinary for-profit businesses under Ethiopia's existing Commercial Code. The goal of this article is to investigate the regulatory concerns of social enterprises and the viability of regulating them within Ethiopia's existing commercial laws. To achieve this goal, the author applies doctrinal research methods. Finally, the author discusses important regulatory challenges for social companies in Ethiopia. The major issues of social enterprise regulation identified by this study include business legal form, evaluation of the social mission, profit allocation, asset transfer, business sale and merger, disclosure of enterprise performance, the duty and liability of directors and managers to stakeholders, and supervision. The author concluded that the existing rules of the Commercial Code are not suitable to regulate these major concerns of social enterprises. Thus, the author recommends that the government promulgate a specific law that regulates these issues of social enterprises.
description: Bahir Dar University Journal of Law, Vol 14 No 2 (2024)
BTZ-like black holes in even dimensional Lovelock theories
Creators: name: Canfora, Fabrizio
name: Giacomini, Alex
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In the present paper, a new class of black hole solutions is constructed in even dimensional Lovelock Born-Infeld theory. These solutions are interesting since, in some respects, they are closer to black hole solutions of an odd dimensional Lovelock Chern-Simons theory than to the more usual black hole solutions in even dimensions. This hybrid behavior arises when non-Einstein base manifolds are considered. The entropies of these solutions have been analyzed using Wald formalism. These metrics exhibit a quite non-trivial behavior. Their entropies can change sign and can even be identically zero depending on the geometry of the corresponding base manifolds. Therefore, the request of thermodynamical stability constrains the geometry of the non-Einstein base manifolds. It will be shown that some of these solutions can support non-vanishing torsion. Eventually, the possibility to define a sort of topological charge associated with torsion will be discussed.
description: LaTeX, 22 pages, references added, typos corrected, minor changes in the text. No figures
Ferromagnetic GaMnAs grown on (110) faced GaAs
Creators: name: Wurstbauer, Ursula
name: Sperl, Matthias
name: Soda, Marcello
name: Neumaier, Daniel
name: Schuh, Dieter
name: Bayreuther, Günther
name: Zweck, Josef
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: annealing, Curie temperature, ferromagnetic materials, gallium arsenide, galvanomagnetic effects, III-V semiconductors, magnetic anisotropy, magnetic epitaxial layers, manganese compounds, molecular beam epitaxial growth, semiconductor epitaxial layers, semiconductor growth, semimagnetic semiconductors
subject: 530 Physik
subject: 81.05.Ea; 81.15.Hi; 68.55.ag; 75.50.Pp; 75.50.Dd; 73.61.Ey

description: Thin Ga0.94Mn0.06As layers have been grown by low temperature molecular beam epitaxy on (110) GaAs substrates and on [110] and [−110] oriented GaAs cleaved edges. The Curie temperatures TC for the as-grown samples ranges from 46 to 80 K. After annealing at low temperatures TC increases up to 115 K. In addition, magnetic anisotropies determined by superconducting quantum interference device magnetometry and magnetotransport measurements are reported.
Measurement of 37Ar to support technology for On-site Inspection under the Comprehensive Nuclear-Test-Ban Treaty
Creators: name: Aalseth, C. E.
name: Day, A. R.
name: Haas, D. A.
name: Hoppe, E. W.
name: Hyronimus, B. J.
name: Keillor, M. E.
name: Mace, E. K.
name: Orrell, J. L.
name: Seifert, A.
name: Woods, V. T.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: On-Site Inspection (OSI) is a key component of the verification regime for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Measurements of radionuclide isotopes created by an underground nuclear explosion are a valuable signature of a Treaty violation. Argon-37 is produced from neutron interaction with calcium in soil, 40Ca(n,α)37Ar. For OSI, the 35-day half-life of 37Ar provides both high specific activity and sufficient time for completion of an inspection before decay limits sensitivity. This paper presents a low-background internal-source gas proportional counter with an 37Ar measurement sensitivity level equivalent to 45.1 mBq/SCM in whole air.
description: Submitted to Nucl. Instru. Meth. A for peer review a part of the proceedings of the 2010 Symposium on Radiation Measurements and Applications (SORMA XII), May 24-28, 2010 at the University of Michigan, Ann Arbor, Michigan, USA. Document details: 5 pages, 4 figures
Fano effect in a quantum-ring–quantum-dot system with tunable coupling
Creators: name: Fuhrer, A.
name: Brusheim, P.
name: Ihn, T.
name: Sigrist, Martin
name: Ensslin, Klaus
name: Wegscheider, Werner
name: Bichler, Max
Publisher: name: Universität Regensburg
Year: 2006
Subjects: subject: 530 Physik
subject: 73.23.−b, 73.21.La, 73.21.Hb

description: Transport measurements are presented on a quantum ring that is tunnel-coupled to a quantum dot. When the dot is in the Coulomb blockade regime, but strongly coupled to the open ring, Fano line shapes are observed in the current through the ring, when the electron number in the dot changes by 1. The symmetry of the Fano resonances is found to depend on the magnetic flux penetrating the area of the ring and on the strength of the ring–dot coupling. At temperatures above T=0.65 K the Fano effect disappears, while the Aharonov-Bohm interference in the ring persists up to T=4.2 K. Good agreement is found between these experimental observations and a single-channel scattering matrix model including decoherence in the dot.
Shock waves in suspended low-dimensional electron gases
Creators: name: Beil, Florian W.
name: Shaji, Nakul
name: Schoeffer, Felix
name: Wixforth, Achim
name: Wegscheider, Werner
name: Schuh, Dieter
name: Bichler, Max
name: Blick, Robert H.
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: Suspended low-dimensional electron gas; Electron–phonon interaction
subject: 530 Physik
subject: 68.60.Bs

description: We study the formation of shock waves in a suspended two-dimensional electron gas using surface acoustic waves. The mechanical displacement of the nano-resonator is read out via the induced acoustoelectric current. Applying acoustical standing waves, we are able to determine the anomalous acoustocurrent. This current is only obtained in the regime of shock wave formation. We find very good agreement with model calculations.
Daridrata Kuchakra Aur ArthvyavasthaDaridra Vyaktiyon Kee Samasyayen
Creators: name: Tomar, Neetusingh
Publisher: name: figshare
Year: 2019
Subjects: subject: Sociology
subject: FOS: Sociology

description: Daridrata Kuchakra Aur Arthvyavastha
Optically induced charge transport through submicron channels
Creators: name: Hof, Klaus-Dieter
name: Rossler, Clemens
name: Wegscheider, Werner
name: Ludwig, Stefan
name: Holleitner, Alexander W.
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: Optical properties; Quantum wires; Photodetector
subject: 530 Physik
subject: 78.67.Lt; 73.21.Hb; 85.60.Bt

description: We report on optically induced charge transport measurements through conducting submicron channels in AlGaAs/GaAs heterostructures. The channels are defined within a two-dimensional electron gas in a quantum well by chemical etching. By applying a voltage to a top gate, the channels can be depleted electrostatically. We present two different heterostructure designs and two processing techniques to build nanostructured optoelectronic detectors. We demonstrate the suitability of our devices for optically induced charge transport measurements in the mesoscopic regime.
Governing Using Criminal Law: Historicising the Instrumentality of Criminal Law in Ethiopian Political Power
Creators: name: Assefa, Simeneh Kiros
name: Wotere, Cherinet Hordofa
Publisher: name: Bahir Dar University Journal of Law
Year: 2024

description: While a constitution vests (limited) power on a government, criminal law may be used to effectively deny power to any contending party (group). This article argues that besides achieving its legitimate ends of prevention of crime, the criminal law is used to govern the country by denying power to contending parties. This is done based on the analysis of the adoption of the respective constitutions, the adoption of the criminal laws and the attending socio-political circumstances of the adoption of the criminal law.Emperor Haile Selassie adopted the 1930 Penal Code on the day of his coronation which is later sanctioned by the 1931 Constitution which makes his power perpetual „divine right‟. When the Provisional Military Government had come to power, it adopted a Special Penal Code to be applied by a Special Courts-Martial, and the PDRE Constitution came only 13 years later. Likewise, as soon as EPRDF came to power, it detained the previous regime officials, both civilian and military, in the first few days. It is only after such action that the Transitional Period Charter was drawn up.
description: Bahir Dar University Journal of Law, Vol 14 No 2 (2024)
Hole-density dependence of the cyclotron mass of 2D holes in a GaAs(001) quantum well
Creators: name: Khannanov, M. N.
name: Kukushkin, I. V.
name: Gubarev, S. I.
name: Smet, J. H.
name: Klitzing, Klaus von
name: Wegscheider, Werner
name: Gerl, Christian
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: 530 Physik
subject: 71.35.Cc, 78.66.Fd

description: The dependence of the heavy-hole cyclotron mass in GaAs(001) quantum wells on the 2D-hole density has been measured by the optical detection method for resonance microwave by-absorption. A significant increase (almost doubling) has been observed in the cyclotron mass of heavy holes with an increase in the charge carrier density from 1.2 × 1010 cm−2 to 1.3 × 1011 cm−2.
Numerically efficient modelling and simulation of integrated ac-dc power systems using dynamic phasor type solutions
Creators: name: Huang, Yingwei
Publisher: name: University of British Columbia
Year: 2018

description: Modern power systems, from continent-spanning networks down to isolated microgrids, are experiencing unprecedented technological changes with broader use of direct current (dc) in addition to traditional alternating current (ac). Such integrated ac-dc power systems present notable challenges in all aspects of design, analysis, control, and operation, where extensive computer simulations play the essential and enabling role. Due to the use of diverse types of signal representation and component formulation, state-of-the-art power system simulation tools are limited to their distinct time scales of transient phenomena. This thesis considers the dynamic phasor (DP) type modelling approaches, where two types of DP theories, namely the shifted-frequency analysis (SFA) and the generalized averaging method (GAM), are considered. In DP-type simulations, power systems are modelled using analogous low-pass time-phasor signals, thereby offering flexible selection of time-step sizes and superior combination of numerical accuracy and efficiency. The ultimate goal of this research is to increase the numerical efficiency of DP-type simulations for the integrated ac-dc power systems. This is achieved by proposing several new DP component models with desirable features and improved numerical properties. First, the constant-parameter SFA model of synchronous machines is proposed to avoid numerically-costly recalculations of the time-varying stator-network matrices. This model is then extended to induction machines for modelling in state-variable based (SV-based) simulation tools. Next, we propose a new, highly efficient model of line-commutated rectifiers using a parametric DP formulation, which is demonstrated as valid for various system operating conditions. Moreover, the effect of ac side harmonics is incorporated to improve modelling fidelity. Finally, the interface between SFA- and GAM-type DPs is achieved to interconnect the proposed DP models. Rigorous case studies demonstrate the superior numerical efficiency of the proposed models, and their advantageous accuracy in capturing the desired phenomena of ac-dc power systems. It is envisioned that the proposed models will become highly useful to many researchers and engineers worldwide, and facilitate the development of next-generation power system simulation tools.
Microscopic origins of the mechanical response of nanostructured elastomeric materials
Creators: name: Parker, Amanda J.
Publisher: name: University of British Columbia
Year: 2018

description: We use a molecular dynamics (MD) framework to study the mechanical properties of triblock copolymer materials which form thermoplastic elastomers (TPEs). These materials form physical, rather than chemical, cross-links as a result of their phaseseparated nano-structure. It is difficult, or impossible, to measure the details of network chains and monomers experimentally. However, it is these microscopic features that give rise to the material’s elastomeric properties. We use a coarsegrained bead-spring model which retains the vital details of the chain network and the nano-structured regions while removing unnecessary atomistic detail. We first present a simulation strategy for the equilibration of nano-structured copolymer melt morphologies. MD simulations with a soft pair potential that allows for chain crossing result in efficient modelling of phase segregation. We successfully reintroduce excluded volume pair interactions with only a short re-equilibration of the local structure, allowing configurations generated (with this method) to be used for studies of structural and mechanical properties. We then study the plastic deformation of triblock TPEs, probing the microscopic mechanisms operative during deformation and how they connect to the macroscopic stress response. We compare two deformation modes, uniaxial stress and strain, which emulate experimental tests and conditions around material failure. We find that triblocks’ stress response exhibits a significant increase in strain hardening compared to homopolymeric chains. We analyse several microscopic properties, including: the chain deformation, monomer displacement, deformation and division of glassy domains, and void formation. We introduce an entropic network model for the stress response utilising microscopic information about chain configurations and their topological constrains. The model assumes additive contributions from chain stretch and the stretch between chain entanglement points and results in quantitative prediction of the stress response. Only one parameter fit is required to describe both triblock and homopolymers systems. We compare our model to recent entropic models developed for vulcanised rubbers and probe its limitations and more general applicability. Extensions to more complicated architectures are possible (e.g. stars).
Coupling in concentric double quantum rings
Creators: name: Mühle, A.
name: Wegscheider, Werner
name: Haug, R. J.
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: Aharonov-Bohm effect, aluminium compounds, electrical conductivity, gallium arsenide, III-V semiconductors, semiconductor quantum dots
subject: 530 Physik
subject: 73.21.La; 72.80.Ey; 73.23.Ad

description: We designed a device consisting of two concentric quantum rings in a GaAs/AlGaAs heterostructure. The outer ring is connected to leads while the inner ring is only capacitively coupled to the rest of the system. Measuring electronic transport in a regime with strong coupling to the leads we found that the conductivity not only shows an Aharonov-Bohm effect with a periodicity fitting to the diameter of the outer ring but also another component matching the inner ring. This can be explained by magnetic-field dependent charge redistributions in the inner ring which affect the outer ring via Coulomb interaction.
Counterflow of Electrons in Two Isolated Quantum Point Contacts
Creators: name: Khrapai, V. S.
name: Ludwig, S.
name: Kotthaus, Jörg P.
name: Tranitz, Hans-Peter
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: 530 Physik
subject: 73.23.Ad, 73.50.Lw, 73.63.Rt

description: We study the interaction between two adjacent but electrically isolated quantum point contacts (QPCs). At high enough source-drain bias on one QPC, the drive QPC, we detect a finite electric current in the second, unbiased, detector QPC. The current generated at the detector QPC always flows in the opposite direction than the current of the drive QPC. The generated current is maximal, if the detector QPC is tuned to a transition region between its quantized conductance plateaus and the drive QPC is almost pinched-off. We interpret this counterflow phenomenon in terms of an asymmetric phonon-induced excitation of electrons in the leads of the detector QPC.
Daridrata Aur KuposanDaridra Vyaktiyon Kee SamasyayenDr. NEETU SINGH TOMAR, Post Doctoral Fellow, University Grant Commission New Delhi
Creators: name: Tomar, Neetusingh
Publisher: name: figshare
Year: 2021
Subjects: subject: Sociology
subject: FOS: Sociology

description: Daridrata Aur Kuposan
Transport properties in n-type AlGaN/AlN/GaN-superlattices
Creators: name: Hertkorn, J.
name: Brückner, P.
name: Gao, C.
name: Scholz, Ferdinand
name: Chuvilin, A.
name: Kaiser, U.
name: Wurstbauer, Ursula
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2008
Subjects: subject: 530 Physik
subject: 73.21.Cd, 73.40.Kp, 73.61.Ey, 81.05.Ea, 81.15.Kk

description: In order to improve the lateral conductivity in optoelectronic devices, we have investigated Si-doped AlGaN/AlN/GaN-superlattices. As a first step we performed calculations of the band structure of Al-GaN/AlN/GaN modulation doped multi heterostructures. Based on these results we worked on optimizing the growth of low Al content (xAl 20%) superlattices by MOVPE. Several tens of abrupt and graded AlGaN/AlN/GaN-layer pairs could be grown crack-free on 2 m thick n-GaN layers deposited on sapphire substrates with AlN nucleation. By Van-der-Pauw Hall measurements, we determined that the lateral conductivity of a 1.5 m thick superlattice structure is a factor of four higher than in highly n-doped bulk material with comparable thickness without compromising too much the vertical conductivity as confirmed by two step TLM-measurements. At 4K we could demonstrate an extremely high effective mobility of 18760 cm2/Vs at n=2×1014 cm-2 (R=1.6/®), a clear verification of our excellent crystal quality.
Magneto-gyrotropic photogalvanic effects due to inter-subband absorption in quantum wells
Creators: name: Diehl, Helgi
name: Shalygin, Vadim
name: Danilov, Sergey
name: Tarasenko, Sergey
name: Belkov, Vassilij
name: Schuh, Dieter
name: Wegscheider, Werner
name: Prettl, Wilhelm
name: Ganichev, Sergey
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: 530 Physik

description: We report on the observation of the magneto-photogalvanic effect (MPGE) due to inter-subband transitions in (001)-oriented GaAs quantum wells. This effect is related to the gyrotropic properties of the structures. It is shown that inter-subband absorption of linearly polarized radiation may lead to spin-related as well as spin-independent photocurrents if an external magnetic field is applied in the plane of the quantum well. The experimental results are analysed in terms of the phenomenological theory and microscopic models of MPGE based on either asymmetric optical excitation or asymmetric relaxation of carriers in k-space. We observed resonant photocurrents not only at oblique incidence of radiation but also at normal incidence, demonstrating that conventionally applied selection rules for the inter-subband optical transitions are not rigorous.
SEREN - A new SPH code for star and planet formation simulations
Creators: name: Hubber, D. A.
name: Batty, C. P.
name: McLeod, A.
name: Whitworth, A. P.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present SEREN, a new hybrid Smoothed Particle Hydrodynamics and N-body code designed to simulate astrophysical processes such as star and planet formation. It is written in Fortran 95/2003 and has been parallelised using OpenMP. SEREN is designed in a flexible, modular style, thereby allowing a large number of options to be selected or disabled easily and without compromising performance. SEREN uses the conservative `grad-h' formulation of SPH, but can easily be configured to use traditional SPH or Godunov SPH. Thermal physics is treated either with a barotropic equation of state, or by solving the energy equation and modelling the transport of cooling radiation. A Barnes-Hut tree is used to obtain neighbour lists and compute gravitational accelerations efficiently, and an hierarchical time-stepping scheme is used to reduce the number of computations per timestep. Dense gravitationally bound objects are replaced by sink particles, to allow the simulation to be evolved longer, and to facilitate the identification of protostars and the compilation of stellar and binary properties. At the termination of a hydrodynamical simulation, SEREN has the option of switching to a pure N-body simulation, using a 4th-order Hermite integrator, and following the ballistic evolution of the sink particles (e.g. to determine the final binary statistics once a star cluster has relaxed). We describe in detail all the algorithms implemented in SEREN and we present the results of a suite of tests designed to demonstrate the fidelity of SEREN and its performance and scalability. Further information and additional tests of SEREN can be found at the web-page http://www.astro.group.shef.ac.uk/seren.
description: 28 pages, 17 figures, accepted for publication in Astronomy and Astrophysics
Cryogenic amplifier for fast real-time detection of single-electron tunneling
Creators: name: Vink, I. T.
name: Nooitgedagt, T.
name: Schouten, R. N.
name: Vandersypen, L. M. K.
name: Wegscheider, Werner
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: electron mobility, quantum dots, tunnelling
subject: 530 Physik
subject: 73.40.Gk; 73.63.Kv

description: The authors employ a cryogenic high electron mobility transistor (HEMT) amplifier to increase the bandwidth of a charge detection setup with a quantum point contact (QPC) charge sensor. The HEMT is operating at 1 K and the circuit has a bandwidth of 1 MHz. The noise contribution of the HEMT at high frequencies is only a few times higher than that of the QPC shot noise. The authors use this setup to monitor single-electron tunneling to and from an adjacent quantum dot. The authors measure fluctuations in the dot occupation as short as 400 ns, 20 times faster than in previous work.
Effects of large-scale structure on the accuracy of weak lensing mass measurements
Creators: name: Hoekstra, Henk
name: Hartlap, Jan
name: Hilbert, Stefan
name: van Uitert, Edo
Publisher: name: arXiv
Year: 2010
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Weak gravitational lensing has become an important method to determine the masses of galaxy clusters. The intrinsic shapes of the galaxies are a dominant source of uncertainty, but there are other limitations to the precision that can be achieved. In this paper we revisit a typically ignored source of uncertainty: structure along the line-of sight. Using results from the Millennium Simulation we confirm the validity of analytical calculations that have shown that such random projections are particularly important for studies of the cluster density profile. In general the contribution of large-scale structure to the total error budget is comparable to the statistical errors. We find that the precision of the mass measurement can be improved only slightly by modelling the large-scale structure using readily available data.
description: submitted to MNRAS; 10 pages, 8 figures
Aparaadh Nyay Aur Dand Ka Vartman SwaroopDaridra Vyaktiyon Kee SamasyayenDr. NEETU SINGH TOMAR, Post Doctoral Fellow, University Grant Commission New Delhi
Creators: name: Tomar, Neetusingh
Publisher: name: figshare
Year: 2021
Subjects: subject: Sociology
subject: FOS: Sociology

description: Aparaadh Nyay Aur Dand Ka Vartman Swaroop
Effects of Electromagnetic Field on the Dynamics of Bianchi type $VI_0$ Universe with Anisotropic Dark Energy
Creators: name: Sharif, M.
name: Zubair, M.
Publisher: name: arXiv
Year: 2010
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Spatially homogeneous and anisotropic Bianchi type $VI_0$ cosmological models with cosmological constant are investigated in the presence of anisotropic dark energy. We examine the effects of electromagnetic field on the dynamics of the universe and anisotropic behavior of dark energy. The law of variation of the mean Hubble parameter is used to find exact solutions of the Einstein field equations. We find that electromagnetic field promotes anisotropic behavior of dark energy which becomes isotropic for future evolution. It is concluded that the isotropic behavior of the universe model is seen even in the presence of electromagnetic field and anisotropic fluid.
description: 21 pages, 10 figures, accepted for publication in Int. J. Mod. Phys. D
title: Kognitive und kooperative Systeme in der Fahrzeugführung: Selektiver Rückblick über die letzten Dekaden und Spekulation über die Zukunft
Creators: name: Flemisch, Frank
name: Meier, Sonja
name: Neuhöfer, Jan
name: Baltzer, Marcel
name: Altendorf, Eugen
name: Özyurt, Emre
Publisher: name: DuEPublico: Duisburg-Essen Publications Online, University of Duisburg-Essen, Germany
Year: 2013

description: In the last decades science in a variety of domains did an impressive amount of research in the field of cooperative and cognitive technical systems. This paper focuses on the domain of (air and ground) vehicle guidance and control and presents selected milestones in this field: Beginning with autonomous vehicles and cognitive pilot support systems, sketching the H-Metaphor and the H-Mode and synthesising it to a cooperative guidance and control of cognitive systems, technically realised by a cognitive core and future standardized cognitive architectures. The paper ends with speculations about future developments in the field of cognitive and cooperative vehicle guidance and control.
Epuraea (Haptoncus) ocularis Fairmaire, 1849 (Coleoptera: Nitidulidae): the first record in Poland
Creators: name: Andrzej Lasoń
name: Roland Dobosz
name: Czesław Greń
name: Janusz Grzywocz
Publisher: name: Zenodo
Year: 2023
Subjects: Coleoptera, Nitidulidae, Epuraea, invasive species, Poland

description: Epuraea (Haptoncus) ocularis Fairmaire, 1849, an invasive species of sap beetle, was found on rotting apples in several localities in Upper Silesia. The species is native to south-eastern Asia and was first recorded in Europe in 1997.
Spin photocurrents in (110)-grown quantum well structures
Creators: name: Diehl, Helgi
name: Shalygin, Vadim
name: Belkov, Vassilij
name: Hoffmann, Christoph
name: Danilov, Sergey
name: Herrle, Thomas
name: Tarasenko, Sergey
name: Schuh, Dieter
name: Gerl, Christian
name: Wegscheider, Werner
name: Prettl, Wilhelm
name: Ganichev, Sergey
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: 530 Physik

description: The circular photogalvanic effect and the circular photon drag effect are observed and investigated in detail in (110)-grown quantum well structures. The experimental data are well described by phenomenological theory and microscopic models of both effects are developed being in agreement with experimental data.
The collective experience of Universal Constructivism
Creators: name: Izquierdo Salvador, Jorge
Publisher: name: University of British Columbia
Year: 2018

description: This dissertation deals with aspects of constructivist art in Uruguay during the nineteen thirties and forties that have been largely relegated and put aside until now. Mainly it involves the collective experience of the artistic movement known as Universal Constructivism, which operated under the guidance and leadership of Joaquin Torres Garcia (1874-1949) and cultivated his figure as the “maestro”, but was far from being homogeneous. The aim of this work is to transfer the focus of studies from the individual, or “maestro”, and his “masterpieces”, towards the collective and its own core set of pieces and/or attitudes that can be put into context in order to enrich an ongoing debate about this movement. The study on the collective functioning of Universal Constructivism, furthermore, can be extended to research and better understand other collective enterprises in Latin American modern art. There is no single way to study a collective. This thesis will make use of different theoretical approximations but mostly it will offer close readings of the collective’s own work which includes visual arts, architecture, literature and sculpture.
Approaching ideal weak link behavior with three dimensional aluminum nanobridges
Creators: name: Vijay, R.
name: Levenson-Falk, E. M.
name: Slichter, D. H.
name: Siddiqi, I.
Publisher: name: arXiv
Year: 2010
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We present transport measurements of unshunted dc superconducting quantum interference devices (SQUIDs) consisting of 30 nm wide aluminum nanobridges of varying length L contacted with two and three dimensional banks. 3D nanobridge SQUIDs with L $\leq$ 150 nm (approximately 3-4 times the superconducting coherence length) exhibit $\approx 70%$ critical current modulation with applied magnetic field, approaching the theoretical limit for an ideal short metallic weak link. In contrast, 2D nanobridge SQUIDs exhibit significantly lower critical current modulation. This enhanced nonlinearity makes 3D nanobridge Josephson junctions well suited to optimize sensitivity in weak link SQUID magnetometers as well as realize ultra low-noise amplifiers and qubits.
description: 3 pages, 4 figures
TAMR effect in (Ga,Mn)As-based tunnel structures
Creators: name: Ciorga, Mariusz
name: Schlapps, Markus
name: Einwanger, Andreas
name: Geißler, Stefan
name: Sadowski, Janusz
name: Wegscheider, Werner
name: Weiss, Dieter
Publisher: name: Universität Regensburg
Year: 2007
Subjects: subject: 530 Physik

description: We discuss the results of our experiments on tunnel devices based on (Ga,Mn)As structures. Those include p+-(Ga, Mn)As/n+-GaAs Esaki diodes and laterally defined narrow nanoconstrictions in (Ga,Mn)As epilayers. We found in those structures strong anisotropic magnetoresistance behaviour with features that could be attributed to the novel tunnelling anisotropic magnetoresistance effect. We argue however, that in case of nanoconstricted (Ga,Mn)As wires, some other physics has to be additionally employed to fully explain the observed effects.
KANPUR PARIKSHETRA KE KSHATRIYON KAA VARTMAN SWAROOPDaridra Vyaktiyon Kee SamasyayenDr. NEETU SINGH TOMAR, Post Doctoral Fellow, University Grant Commission New Delhi
Creators: name: Tomar, Neetusingh
Publisher: name: figshare
Year: 2021
Subjects: subject: Sociology
subject: FOS: Sociology

description: KANPUR PARIKSHETRA KE KSHATRIYON KAA VARTMAN SWAROOP