cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Non-Hermitian Hamiltonian Deformations in Quantum Mechanics
Creators: name: Matsoukas-Roubeas, Apollonas S.
name: Roccati, Federico
name: Cornelius, Julien
name: Xu, Zhenyu
name: Chenu, Aurelia
name: del Campo, Adolfo
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Mathematical Physics (math-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The construction of exactly-solvable models has recently been advanced by considering integrable $T\bar{T}$ deformations and related Hamiltonian deformations in quantum mechanics. We introduce a broader class of non-Hermitian Hamiltonian deformations in a nonrelativistic setting, to account for the description of a large class of open quantum systems, which includes, e.g., arbitrary Markovian evolutions conditioned to the absence of quantum jumps. We relate the time evolution operator and the time-evolving density matrix in the undeformed and deformed theories in terms of integral transforms with a specific kernel. Non-Hermitian Hamiltonian deformations naturally arise in the description of energy diffusion that emerges in quantum systems from time-keeping errors in a real clock used to track time evolution. We show that the latter can be related to an inverse $T\bar{T}$ deformation with a purely imaginary deformation parameter. In this case, the integral transforms take a particularly simple form when the initial state is a coherent Gibbs state or a thermofield double state, as we illustrate by characterizing the purity, Rényi entropies, logarithmic negativity, and the spectral form factor. As the dissipative evolution of a quantum system can be conveniently described in Liouville space, we further discuss the spectral properties of the Liouvillians, i.e., the dynamical generators associated with the deformed theories. As an application, we discuss the interplay between decoherence and quantum chaos in non-Hermitian deformations of random matrix Hamiltonians and the Sachdev-Ye-Kitaev model.
description: 28 pages, 6 figures
Convexity for twisted conjugation
Creators: name: Meinrenken, Eckhard
Publisher: name: arXiv
Year: 2015
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics

description: Let $G$ be a compact, simply connected Lie group. If $\mathcal{C}_1,\mathcal{C}_2$ are two $G$-conjugacy classes, then the set of elements in $G$ that can be written as products $g=g_1g_2$ of elements $g_i\in \mathcal{C}_i$ is invariant under conjugation, and its image under the quotient map $G\to G/\operatorname{Ad}(G)$ is a convex polytope inside the Weyl alcove. In this note, we will prove an analogous statement for twisted conjugations relative to group automorphisms. The result will be obtained as a special case of a convexity theorem for group-valued moment maps which are equivariant with respect to the twisted conjugation action.
description: To appear in Mathematical Research Letters
Characterization of Defects in PV-Modules by Their Temperature Development Using IR-Thermography
Creators: name: Buerhop-Lutz, C.
name: Scheuerpflug, H.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1789-1792
description: Infrared thermography is a valuable method for inspecting installed photovoltaics. Easily IR-inspections can be
repeated without influencing the operational state. However, the ambient conditions may differ between the
measurements. This fact makes the comparability of the results difficult. – Therefore, we studied the influence of
differing ambient conditions on the characteristics and the temperature profile on areal and point-shaped defect
sites in PV-modules. An especially developed measurement unit recorded simultaneously IR-images, weather
data and electric module data. – The evaluated data show that areal cell defects behave linearly with the solar
irradiance, while point-shaped defects (e. g. solder joints) exhibit a non-linear dependence.
Tunable transmission of quantum Hall edge channels with full degeneracy lifting in split-gated graphene devices
Creators: name: Zimmermann, Katrin
name: Jordan, Anna
name: Gay, Frédéric
name: Watanabe, Kenji
name: Taniguchi, Takashi
name: Han, Zheng
name: Bouchiat, Vincent
name: Sellier, Hermann
name: Sacépé, Benjamin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Charge carriers in the quantum Hall regime propagate via one-dimensional conducting channels that form along the edges of a two-dimensional electron gas. Controlling their transmission through a gate-tunable constriction, also called quantum point contact (QPC), is fundamental for many coherent transport experiments. However, in graphene, tailoring a QPC with electrostatic gates remains challenging due to the formation of p-n junctions below gate electrodes along which electron and hole edge channels co-propagate and mix, short-circuiting the constriction. Here we show that this electron-hole mixing is drastically reduced in high mobility boron-nitride/graphene/boron-nitride van-der-Waals heterostructures thanks to the full degeneracy lifting of the Landau levels, enabling QPC operation with full channel pinch-off. We demonstrate gate-tunable selective transmission of quantum Hall edge channels through the QPC, both in the integer and the fractional quantum Hall regimes. This gate-control of edge channel propagation in graphene van-der-Waals heterostructures opens the door to quantum Hall interferometry and electron quantum optics experiments in the integer and fractional quantum Hall regimes of graphene.
description: New data in the fractional quantum Hall regime added
Monitoring Inhomogeneities Through Initial Operation of Thin-Film Photovoltaic Modules
Creators: name: Bokalic, M.
name: Kimovec, R.
name: Kirn, B.
name: Brecl, K.
name: Topic, M.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
PV Modules

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1744-1747
description: We expose five pairs of thin-film photovoltaic modules including amorphous silicon, tandem
micromorph silicon, two types of CIGS, and CdTe to outdoor conditions for one year. During outdoor exposure they
are operated in individual maximum power points with periodic real-time performance measurements and frequent
outdoor performance characterization and electroluminescence (EL) inspection. We observe module type specific
metastability of performance and EL intensity and the correlation between the two. EL inspection reveals several
inhomogeneities, many of which show dynamic character, such as general inhomogeneity redistribution, shunt
formation and mitigation, scribing failure mitigation and bright spot formation. Some inhomogeneities are module
type specific, while some are not. Despite the presence of dynamic inhomogeneities we predict that they are not
responsible for all the observed performance changes and that performance changes arise from the more
homogeneous changes on micro-level across the whole module.
Discrete Lossy Gray-Wyner Revisited: Second-Order Asymptotics, Large and Moderate Deviations
Creators: name: Zhou, Lin
name: Tan, Vincent Y. F.
name: Motani, Mehul
Publisher: name: arXiv
Year: 2015
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: In this paper, we revisit the discrete lossy Gray-Wyner problem. In particular, we derive its optimal second-order coding rate region, its error exponent (reliability function) and its moderate deviations constant under mild conditions on the source. To obtain the second-order asymptotics, we extend some ideas from Watanabe's work (2015). In particular, we leverage the properties of an appropriate generalization of the conditional distortion-tilted information density, which was first introduced by Kostina and Verdú (2012). The converse part uses a perturbation argument by Gu and Effros (2009) in their strong converse proof of the discrete Gray-Wyner problem. The achievability part uses two novel elements: (i) a generalization of various type covering lemmas; and (ii) the uniform continuity of the conditional rate-distortion function in both the source (joint) distribution and the distortion level. To obtain the error exponent, for the achievability part, we use the same generalized type covering lemma and for the converse, we use the strong converse together with a change-of-measure technique. Finally, to obtain the moderate deviations constant, we apply the moderate deviations theorem to probabilities defined in terms of information spectrum quantities.
description: 33 pages, accepted to IEEE Transactions on Information Theory; Short version v_1 presented at IEEE ISIT 2016, Barcelona, Spain
Non-Markovian Dynamics in Ultracold Rydberg Aggregates
Creators: name: Genkin, M.
name: Schönleber, D. W.
name: Wüster, S.
name: Eisfeld, A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We propose a setup of an open quantum system in which the environment can be tuned such that either Markovian or non-Markovian system dynamics can be achieved. The implementation uses ultracold Rydberg atoms, relying on their strong long-range interactions. Our suggestion extends the features available for quantum simulators of molecular systems employing Rydberg aggregates and presents a new test bench for fundamental studies of the classification of system-environment interactions and the resulting system dynamics in open quantum systems.
description: 13 pages, 4 figures
Correlation between the Monitoring Data of a Photovoltaic Power Plant and Module Defects Detected by Drone-Mounted Thermography
Creators: name: Dalsass, M.
name: Scheuerpflug, H.
name: Maier, M.
name: Brabec, C.J.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1793-1798
description: Recently, drone-based aerial thermography has become a convenient quality assessment tool for the
precise localization of defective modules and cells in a large photovoltaic power plant. However, thermographic
recordings cannot be utilized for a quantitative estimation of the overall power generation of a solar park yet. In this
context, a solar generator with a nominal power of approximately 2.36 MWp and 10,500 modules was examined
using drone-based aerial thermography. The subsequent analysis of both the recorded radiometric data as well as the
monitoring data of the inverters indicates a strong correlation between defective modules and the current generated in
the associated string. Moreover, a cost-benefit calculation reveals that the cumulative effect of all found defective
modules can result in a noticeable deficiency of receipts for both operators and investors. The results of this work will
advance future automatic monitoring and early detection systems.
The energy-dependent position of the IBEX ribbon due to the solar wind structure
Creators: name: Swaczyna, Paweł
name: Bzowski, Maciej
name: Sokół, Justyna M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Observations of energetic neutral atoms (ENAs) allow for remote studies of the plasma condition in the heliosphere and the neighboring local interstellar medium. The first IBEX results revealed an arc-like enhancement of the ENA intensity in the sky, known as the ribbon. The ribbon was not expected from the heliospheric models prior to the IBEX launch. One of the proposed explanations of the ribbon is the mechanism of the secondary ENA emission. The ribbon reveals energy-dependent structure in the relative intensity along its circumference and in the position. Namely, the ribbon geometric center varies systematically by about 10$^\circ$ in the energy range 0.7-4.3 keV. Here, we show by analytic modeling that this effect is a consequence of the helio-latitudinal structure of the solar wind reflected in the secondary ENAs. Along with a recently measured distance to the ribbon source just beyond the heliopause, our findings support the connection of the ribbon with the local interstellar magnetic field by the mechanism of the secondary ENA emission. However, the magnitude of the center shift in the highest IBEX energy channel is much larger in the observations than expected from the modeling. This may be due to another, not currently recognized, process of ENA generation.
description: 14 pages, 8 figures, 1 table, v3: corrected caption to Figure 3
Measuring the scatter of the mass-richness relation in galaxy clusters in photometric imaging surveys by means of their correlation function
Creators: name: Campa, Julia
name: Flaugher, Brenna
name: Estrada, Juan
Publisher: name: arXiv
Year: 2015
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Knowledge of the scatter in the mass-observable relation is a key ingredient for a cosmological analysis based on galaxy clusters in a photometric survey. In this paper we aim to quantify the capability of the correlation function of galaxy cluster to constrain the intrinsic scatter $σ_{\ln M}$. We demonstrate how the linear bias measured in the correlation function of clusters can be used to determine the value of this parameter. The new method is tested in simulations of a $5, 000 deg^2$ optical survey up to $z \sim 1$, similar to the ongoing Dark Energy Survey (DES). Our results show that our method works better at lower scatter values. We can measured the intrinsic scatter $σ_{ln M} = 0.1$ with a standard deviation of $σ(σ_{ln M}) \sim 0.03$ using this technique. However, the expected intrinsic scatter of the DES RedMaPPer cluster catalog $σ_{ln M} \sim 0.2$ cannot be recovered with this method at suitable accuracy and precision because the area coverage is insufficient. For future photometric surveys with a larger area such as LSST and Euclid, the statistical errors will be reduced. Therefore, we forecast higher precision to measure the intrinsic scatter including the value mention before. We conclude that this method can be used as an internal consistency check method on their simplifying assumptions and complementary to cross-calibration techniques in multi-wavelength cluster observations
description: Accepted for publication on ApJ
Supplementary document for The speckled output of a multi-mode optical fibre and sensitivity to fibre perturbations - 7116527.pdf
Creators: name: Hu, Hao-Wei
name: Mekhail, Simon
name: Archibald, Robert
name: Wolley, Osian
name: Padgett, Miles
Publisher: name: Optica Publishing Group
Year: 2024
Subjects: Uncategorized

description: Supplement 1
Influence of rhombohedral stacking order in the electrical resistance of bulk and mesoscopic graphite
Creators: name: Zoraghi, M.
name: Barzola-Quiquia, J.
name: Stiller, M.
name: Setzer, A.
name: Esquinazi, P.
name: Kloess, G. H.
name: Muenster, T.
name: Lühmann, T.
name: Estrela-Lopis, I.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The electrical, in-plane resistance as a function of temperature $R(T)$ of bulk and mesoscopic thin graphite flakes obtained from the same batch was investigated. Samples thicker than $\sim 30$ nm show metalliclike contribution in a temperature range that increases with the sample thickness, whereas a semiconductinglike behavior was observed for thinner samples. The temperature dependence of the in-plane resistance of all measured samples and several others from literature can be very well explained between 2 K and 1100 K assuming three contributions in parallel: a metalliclike conducting path at the interfaces between crystalline regions, composed of two semiconducting phases, i.e. Bernal and rhombohedral stacking. From the fits of $R(T)$ we obtain a semiconducting energy gap of $110 \pm 20$meV for the rhombohedral and $38\pm 8 $meV for the Bernal phase. The presence of these crystalline phases was confirmed by x-ray diffraction measurements. We review similar experimental data from literature of the last 33 years and two more theoretical models used to fit $R(T)$.
description: 11 pages, 10 figures
Tilting refractive x-ray lenses for fine-tuning their focal length
Creators: name: Celestre, Rafael
name: Roth, Thomas
name: Detlefs, Carsten
name: Qi, Peng
name: Cammarata, Marco
name: del Rio, Manuel Sanchez
name: Barrett, Raymond
Publisher: name: arXiv
Year: 2022
Subjects: subject: Optics (physics.optics)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: In this work, we measure and model tilted x-ray refractive lenses to investigate their effects on an x-ray beam. The modelling is benchmarked against at-wavelength metrology obtained with x-ray speckle vector tracking experiments (XSVT) at the BM05 beamline at the ESRF-EBS light source, showing very good agreement. This validation permits us to explore possible applications of tilted x-ray lenses in optical design: we demonstrate that tilting 1D lenses around their focusing direction can be used for fine-tuning their focal length with possible applications in beamline optical design.
description: 15 pages, 13 figures, 38 references to be submitted to Optics Express
Indoor and Outdoor Evaluation of Global Irradiance Sensors
Creators: name: Driesse, A.
name: Zaaiman, W.
name: Riley, D.S.
name: Taylor, N.
name: Stein, J.S.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1704-1709
description: Global irradiance sensors supply essential information in the business of planning and operating PV Systems.
Errors and uncertainty in irradiance measurements propagate to uncertainty about performance and profitability.
PV Performance Labs initiated the PVSENSOR project in 2014 to more fully characterize commercial irradiance
sensors, with the objective of reducing such uncertainties.
In the first phase of indoor testing we tested 21 pairs of instruments using multiple solar simulators (both pulsed
& continuous, large area & small), environmental chambers, spectrally selective and neutral density filters, and
corresponding reference instruments. The second phase has all sensors mounted outdoors on a two-axis tracker
that is programmed to follow different trajectories while all sensor outputs are recorded. This paper provides
selected results from both tests sets, highlighting differences between sensor categories.
Characterization and Efficiency Test of a Li-ion Energy Storage System for PV Systems
Creators: name: Makibar, A.
name: Narvarte, L.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Balance of System Components

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1652-1658
description: Li-ion batteries are modern electrical energy storage systems which are undergoing an intense
development in their technological features. Their high specific energy, efficiency and durability, together with the
lowering of their production costs, are placing them as one of the most promising actors in the field of electrical
energy storage technology used as tool for integrating renewable energy sources. But due to the fact that they are in
an early stage of development, their reliability must be trusted. This paper describes a method and the results for
testing round trip efficiencies of a modern Li-ion battery based energy storage system integrated in a PV system.
According to the related standards, the efficiency of a battery and an inverter/charger has been characterised, under
technical restrictions and specific operation conditions for its use with PV systems.
Costs of Residential Solar PV Plants in Distribution Grid Networks
Creators: name: Kjær, S.B.
name: Yang, G.
name: Ipsen, H.H.
name: Frederiksen, K.H.B.
name: Østergaard, J.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1739-1743
description: In this article we investigate the impact of residential solar PV plants on energy losses in distribution
networks and their impact on distribution transformers lifetime. Current guidelines in Denmark states that distribution
transformers should not be loaded with more than 67% solar PV power to avoid accelerated loss of life. If a solar PV
plant causes this limit to be exceeded, the particular owner has to pay for upgrading the transformer. Distribution
Network Operators also charge an annual tariff from the solar PV plants to cover the expenses to keep the grid
capacity available, the so called “Availability Tariff”. According to the Danish Energy Regulatory Authority, the
Availability Tariff must cover the exact expenses, with energy savings etc. from the solar PV plants taken into
consideration. Our conclusion is that a distribution network, which represents a typical residential network, can
handle up to 110-120% of the transformer nominal ratings before the value of solar PV plants in the distribution
network becomes negative. The results suggest that from a technical perspective the aforementioned limit can be
increased from 67 to 100%
Classical limits of quantum toroidal and affine Yangian algebras
Creators: name: Tsymbaliuk, Alexander
Publisher: name: arXiv
Year: 2016
Subjects: subject: Representation Theory (math.RT)
subject: FOS: Mathematics

description: In this short note, we compute the classical limits of the quantum toroidal and the affine Yangian algebras of sl(n) by generalizing our arguments for gl(1) from arXiv:1404.5240. These results were mentioned as motivation in the recent study of toroidal algebras by [Feigin-Jimbo-Miwa-Mukhin], while they played a crucial role in the recent paper arXiv:1512.09109 of the author and Bershtein. An alternative proof of our key isomorphisms for n>2 was first established by [Varagnolo-Vasserot]. We also discuss some consequences of these results.
description: v1: 10 pages; v2: 12 pages, minor corrections, some details added
Tools for the High Penetration of PV Systems in the EU Electrical Networks: Results of PVCROPS Project
Creators: name: Narvarte, L.
name: Marroyo, L.
name: Collares-Pereira, M.
name: Tyutyundzhiev, N.
name: Conlon, M.F.
name: Bouzzan, N.E.
name: Guelbenzu Michelena, E.
name: González, R.
name: Desportes, A.
name: Simmonds, G.
name: Wilkin, B.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1663-1666
description: The Solar Energy Industrial Initiative established the objective of integrating PV into the grid to
provide up to 12% of the EU electricity demand. The FP7 project PVCROPS has developed solutions to allow the
high penetration of PV systems in EU electrical networks and to reduce its Levelized Cost (LCoE) increasing PV
system performance. The solutions consist of documents like technical specifications and toolboxes for design,
prediction, integration of batteries and automatic detection of performance failures. Six of them are on-line free tools
and thirteen are marketable products. These tools allow reducing the LCoE up to 30%, increasing the Performance
Ratio up to 9% and PV penetration of 30%. The tools developed by PVCROPS are detailed in www.pvcrops.eu
A Multigrid-like Algorithm for Probabilistic Domain Decomposition
Creators: name: Bernal, Francisco
name: Acebrón, Juan A.
Publisher: name: arXiv
Year: 2015
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics

description: We present an iterative scheme, reminiscent of the Multigrid method, to solve large boundary value problems with Probabilistic Domain Decomposition (PDD). In it, increasingly accurate approximations to the solution are used as control variates in order to reduce the Monte Carlo error of the following iterates--resulting in an overall acceleration of PDD for a given error tolerance. The key ingredient of the proposed algorithm is the ability to approximately predict the speedup with little computational overhead and in parallel. Besides, the theoretical framework allows to explore other aspects of PDD, such as stability. One numerical example is worked out, yielding an improvement of between one and two orders of magnitude over the previous version of PDD.
description: Original research paper
Top-Down Synthesis for Library Learning
Creators: name: Bowers, Matthew
name: Olausson, Theo X.
name: Wong, Lionel
name: Grand, Gabriel
name: Tenenbaum, Joshua B.
name: Ellis, Kevin
name: Solar-Lezama, Armando
Publisher: name: arXiv
Year: 2022
Subjects: subject: Programming Languages (cs.PL)
subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: This paper introduces corpus-guided top-down synthesis as a mechanism for synthesizing library functions that capture common functionality from a corpus of programs in a domain specific language (DSL). The algorithm builds abstractions directly from initial DSL primitives, using syntactic pattern matching of intermediate abstractions to intelligently prune the search space and guide the algorithm towards abstractions that maximally capture shared structures in the corpus. We present an implementation of the approach in a tool called Stitch and evaluate it against the state-of-the-art deductive library learning algorithm from DreamCoder. Our evaluation shows that Stitch is 3-4 orders of magnitude faster and uses 2 orders of magnitude less memory while maintaining comparable or better library quality (as measured by compressivity). We also demonstrate Stitch's scalability on corpora containing hundreds of complex programs that are intractable with prior deductive approaches and show empirically that it is robust to terminating the search procedure early -- further allowing it to scale to challenging datasets by means of early stopping.
description: Published at POPL 2023
Vorlesungsskript "Grundlagen der Elektrischen Energieversorgung"
Creators: name: Oswald, Bernd Rüdiger
Publisher: name: Hannover : Leibniz Universität Hannover, Institut für Energieversorgung und Hochspannungstechnik
Year: 2005
Subjects: subject: Elektrische Energieversorgung
subject: Kraftwerke
subject: Schaltanlagen
subject: Generator
subject: Hochspannungs-Gleichstrom-Übertragung
subject: Elektrizitätswerk
subject: Elektrizitätsversorgung
subject: Dewey Decimal Classification::600 | Technik

description: Vorlesungsskript zu "Grundlagen der Elektrischen Energieversorgung" von Prof. B. R. Oswald.
Experiences with a Performance Package for Multi-MW PV Plants Based on Computations on Top of Monitoring
Creators: name: Mütter, G.
name: Krametz, T.
name: Steirer, P.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1675-1678
description: This paper is a report out of practical life with a huge theoretical background and the experience of a 4 years operating
and monitoring of more than 700 MWp, located in Eastern Europe, grid connection 2010-2014 and O&M supervision
done by the team of Alternative Energy Solution GmbH. Methodologies for the specific tools were scientifically
analysed by AIT. The parks had and an overall performance already beyond the predicted energy yields.
The goal was the improvement of a special quality program tailored to particular needs with scientific analysis including
complex simulation and 3D modelling, evaluation of huge datasets from monitoring and new data handling
methodologies as well as usage of this tools to set up and select the right corrective and preventive actions to increase
the performance of already well operating multi-MW PV plants.
Actual needs during operation of the parks led to a structure with set up of specific software tools in short time with
huge amount of data to localize and quantify real impact of faults and upcoming production losses. The structure of the
toolset will be presented as well the examples of the usage of some of these tools with the specific results and projection
to similar situations.
In addition to the results of the usage of some specific tools in comparison the breakdown of parks are shown where
the O&M services were not possible for a time of 6 month.
The Kontsevich matrix integral: convergence to the Painlevé hierarchy and Stokes' phenomenon
Creators: name: Bertola, Marco
name: Cafasso, Mattia
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mathematical Physics (math-ph)
subject: Exactly Solvable and Integrable Systems (nlin.SI)
subject: FOS: Physical sciences
subject: 34M40, 34M55, 34M56, 35Q15

description: We show that the Kontsevich integral on $n\times n$ matrices ($n< \infty$) is the isomonodromic tau function associated to a $2\times 2$ Riemann--Hilbert problem. The approach allows us to gain control of the analysis of the convergence as $n\to\infty$. By an appropriate choice of the external source matrix in Kontsevich's integral, we show that the limit produces the isomonodromic tau function of a special tronquée solution of the first Painlevé hierarchy, and we identify the solution in terms of the Stokes' data of the associated linear problem. We also show that there are several tau functions that are analytic in appropriate sectors of the space of parameters and that the formal Witten-Kontsevich tau function is the asymptotic expansion of each of them in their respective sectors, thus providing an analytic tool to analyze its nonlinear Stokes' phenomenon.
description: 33 pages, 9 figures; ver2 improved introduction
Defect Analysis of Installed PV-Modules - IR-Thermography and in-String Power Measurement
Creators: name: Buerhop-Lutz, C.
name: Scheuerpflug, H.
name: Pickel, T.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1692-1697
description: Inspecting installed PV-modules with IR-thermography is a frequently used method nowadays. Modules with defects, that
heat up under operating conditions, can easily be identified. The electric and thermal performance of these defect modules
will be studied under operating conditions. Here, the module temperature and its temperature distribution as well as the series
connection and the resulting string operating point are of importance. In order to measure the electric current and voltage of
every module within a string a special measurement unit linked with an IR-camera was developed. The temperature
distribution and the module powers were monitored simultaneously. The data evaluation showed that the module power
differs from that measured under STC –conditions. The temperature at the defect site increases with string length and the
power decreases respectively. Both, temperature and power approach a certain limiting value.
Characterization and Classification of Daily Sky Conditions in Cyprus and France Based on Ground Measurements of Solar Irradiance
Creators: name: Koumparou, I.
name: Makrides, G.
name: Hadjipanayi, M.
name: Efthymiou, V.
name: Georghiou, G.E.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1698-1703
description: The quality and quantity of the electrical power produced from solar systems is directly related to the
available solar irradiance and therefore any irradiance fluctuations affect the power produced from such systems. In
this paper, four years of solar irradiance data from Cyprus and France are analysed using the K-POP method. This
method characterises and classifies each day based on the quantity and quality of the available solar irradiance. The
quantity of solar irradiance is defined as the ration of the daily integration of the solar irradiance at the earth to the
extraterrestrial solar irradiance. The quality of solar irradiance is found using a probabilistic approach that detects the
difference between successive instantaneous clearance indices and calculates the probability that the differences are
equal to zero. Finally, a statistical analysis of the solar irradiance ramp rates present in both countries enhances the
findings of the K-POP method and reveals the magnitude of the most common irradiance fluctuations. The analysis
showed that Cyprus experiences high or medium quantity solar irradiance with rare and infrequent solar fluctuations
for 88 % of the time. On the other hand, France experiences the same situation only 61.3 % of the time.
Toward a Catalog of Software Engineering Practices to Handle Machine Learning Fairness - Online Appendix
Creators: name: Ferrara, Carmine
name: Sellitto, Giulia
name: Ferrucci, Filomena
name: Palomba, Fabio
name: De Lucia, Andrea
Publisher: name: figshare
Year: 2023
Subjects: Empirical software engineering
Fairness, accountability, transparency, trust and ethics of computer systems
Machine learning not elsewhere classified

description: Machine learning is now, more than ever, pervasive in the daily life of billion of people and companies, which often make decisions on the basis of the information provided by machine learning-enabled systems. Despite such an increasing spread, the reliability, accountability, and credibility of machine learning solutions may be threatened by risks connected to low software fairness, i.e., the inappropriate treatment of sensitive features that may lead the machine learner to act unfairly with respect to minorities. In the recent past, the software engineering research community has been giving machine learning fairness an engineering connotation, proposing empirical studies, novel metrics, and ad-hoc fairness-aware approaches. In spite of these research advances, we still highlight a lack of knowledge and categorization of the practices that may be used to engineer software fairness within the lifecycle of machine learning solutions.
 In this paper, we propose a novel catalog of software engineering practices to handle fairness within each step of an MLOps development pipeline. The catalog is established through two complementary research methods. First, we conduct a systematic mapping study to extract, categorize, and map onto MLOps pipelines a set of 28 practices proposed in the literature. Second, we define a survey study involving three samples of ≈50 practitioners each with experience in machine learning engineering, in which we validate the practices by assessing their frequency, impact, and application effort in practice. We distil from the catalog a set of actionable items and implications for software engineering researchers and practitioners.
Micro-Inverters: Comparison of Costs, Performance and Yield
Creators: name: Krauter, S.
name: Bendfeld, J.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Balance of System Components

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1620-1623
description: To examine efficiency and yield of most micro-inverters available on the world market in 2013-14, an
in- and outdoor test field at the University of Paderborn have been set up. The inverters have been fed by identical &
calibrated crystalline silicon PV modules of 215 W at STC. To monitor accurately AC power output and yield, each
of the micro-inverters has been equipped with a calibrated precision electricity meter. For micro-inverters that require
control units for grid-feeding this has been purchased also. The test field is equipped with pyranometers in the
module plane for global and diffuse irradiance, temperature, wind speed and wind direction measurement. The
comparison includes energy yield over almost one year, efficiency-load characteristics, recovery times after switchoff,
cost comparisons (including control units necessary and wiring), basic safety, reliability, warranty duration
comparisons, and lifetime costs for generated electricity. While the market is quite new, the range of purchase costs
varies considerably between the models in comparison, sometimes inverter costs are higher than module costs,
particularly if an additional grid-connection or interface box is necessary for operation.
Realistic Snowload Testing for Extreme Alpine Conditions
Creators: name: Bohren, A.
name: Friesen, T.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Balance of System Components

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1635-1638
description: Solar installations in alpine regions provide a valuable contribution to the energy demand, especially in
winter times with very high irradiance levels. Considerable snow loads have to be expected frequently in these
regions and the records of the building insurances show an alarming increase of snow loads damages in mountainous
regions. For several reasons, the standard test procedures are not suitable to assess the snow load resistance of solar
installations. We have therefore developed a completely new test rig to test solar devices with extreme snow loads of
up to 20 kPa. By individually controlling the forces perpendicular and parallel to the surface of the test sample,
almost any installation inclination can be simulated. Furthermore, the new test rig allows for testing very large
modules or even fields of modules using the original mounting systems of the manufacturers. Based on this new test
method we introduced an assessment procedure simulating 30 years of lifetime in alpine regions. Together with the
Association of the Swiss Building Insurances, a corresponding snow load certificate is issued to allow for selecting
appropriate products even for installations in regions with a high risk of snow load damages.
Scale invariance in X-ray flares of gamma-ray bursts
Creators: name: Wei, Jun-Jie
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: X-ray flares are generally believed to be produced by the reactivation of the central engine, and may have the same energy dissipation mechanism as the prompt emission of gamma-ray bursts (GRBs). X-ray flares can therefore provide important clues to understanding the nature of the central engines of GRBs. In this work, we study for the first time the physical connection between differential size and return distributions of X-ray flares of GRBs with known redshifts. We find that the differential distributions of duration, energy, and waiting time can be well fitted by a power-law function. In particular, the distributions for the differences of durations, energies, and waiting times at different times (i.e., the return distributions) well follow a $q$-Gaussian form. The $q$ values in the $q$-Gaussian distributions remain nearly steady for different temporal interval scales, implying a scale-invariant structure of GRB X-ray flares. Moreover, we verify that the $q$ parameters are related to the power-law indices $α$ of the differential size distributions, characterized as $q=(α+2)/α$. These statistical features can be well explained within the physical framework of a self-organizing criticality system.
description: 6 pages, 3 figures, 2 tables. Published in Phys. Rev. Research
Model Requirements for Accurate Short Term Energy Yield Predictions during Fast-Varying Weather Conditions
Creators: name: Goverde, H.
name: Anagnostos, D.
name: Herteleer, B.
name: Govaerts, J.
name: Baert, K.
name: Aldalali, B.
name: Catthoor, F.
name: Driesen, J.
name: Poortmans, J.
Publisher: name: WIP
Year: 2015
Subjects: OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Operation of PV Systems and Plants

description: 31st European Photovoltaic Solar Energy Conference and Exhibition; 1556-1559
description: The effect of fast-varying weather conditions on (simplified-) models on simulated solar cell temperature and energy yield prediction is investigated. The models have first been calibrated with indoor measurement data. We focus especially on short-term behavior (second to minute level). Frequency response analyses show that the solar cell temperature is mainly influenced by high-frequency illumination conditions, while the effect of highly varying wind on the solar cell temperature is more limited. For a period with highly varying weather, energy yield is calculated to illustrate the effect of the parameters in the model on the overall energy yield outcome.
CFHTLenS and RCSLenS: Testing Photometric Redshift Distributions Using Angular Cross-Correlations with Spectroscopic Galaxy Surveys
Creators: name: Choi, Ami
name: Heymans, Catherine
name: Blake, Chris
name: Hildebrandt, Hendrik
name: Duncan, Christopher A. J.
name: Erben, Thomas
name: Nakajima, Reiko
name: Van Waerbeke, Ludovic
name: Viola, Massimo
Publisher: name: arXiv
Year: 2015
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We determine the accuracy of galaxy redshift distributions as estimated from photometric redshift probability distributions $p(z)$. Our method utilises measurements of the angular cross-correlation between photometric galaxies and an overlapping sample of galaxies with spectroscopic redshifts. We describe the redshift leakage from a galaxy photometric redshift bin $j$ into a spectroscopic redshift bin $i$ using the sum of the $p(z)$ for the galaxies residing in bin $j$. We can then predict the angular cross-correlation between photometric and spectroscopic galaxies due to intrinsic galaxy clustering when $i \neq j$ as a function of the measured angular cross-correlation when $i=j$. We also account for enhanced clustering arising from lensing magnification using a halo model. The comparison of this prediction with the measured signal provides a consistency check on the validity of using the summed $p(z)$ to determine galaxy redshift distributions in cosmological analyses, as advocated by the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We present an analysis of the photometric redshifts measured by CFHTLenS, which overlaps the Baryon Oscillation Spectroscopic Survey (BOSS). We also analyse the Red-sequence Cluster Lensing Survey (RCSLenS), which overlaps both BOSS and the WiggleZ Dark Energy Survey. We find that the summed $p(z)$ from both surveys are generally biased with respect to the true underlying distributions. If unaccounted for, this bias would lead to errors in cosmological parameter estimation from CFHTLenS by less than $\sim 4\%$. For photometric redshift bins which spatially overlap in 3-D with our spectroscopic sample, we determine redshift bias corrections which can be used in future cosmological analyses that rely on accurate galaxy redshift distributions.
description: 20 pages, 14 figures, version accepted to MNRAS including minor clarifications
The optical spectral features of 27 Fermi blazars
Creators: name: Zhang, Bing-Kai
name: Tang, Wei-Feng
name: Wang, Chun-Xiao
name: Wu, Qi
name: Jin, Min
name: Dai, Ben-Zhong
name: Zhu, Feng-Rong
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: A spectral variation accompanied with flux variability is a commonly-observed phenomenon for blazars. In order to further investigate the optical spectral feature of blazars, we have collected the long-term optical V and R band data of 27 blazars (14 BL Lacs and 13 FSRQs), and calculated their optical spectral indices. The results show that the spectral indices vary with respect to the brightness for all of these blazars. In general, the optical spectrum progressively becomes flatter (or steeper), when the brightness increases. However the spectrum changes more and more slowly, until it tends to be stable. In other words, the source becomes bluer (or redder) and then gradually stabilizes when it brightens, which are briefly named the bluer-stable-when-brighter (BSWB) and redder-stable-when-brighter (RSWB) behaviors, respectively. Thirteen of the 14 BL Lacs show the BSWB behavior, with an exception of AO 0235+164. On the contrary, most of FSRQs (10 out of 13) exhibit the RSWB trend. It is confirmed that blazars follow the two universal optical spectral behaviors, namely, BSWB and RSWB. The model of two constant-spectral-index components can well explain the optical spectral features qualitatively and quantitatively. The results illustrate that the optical emission are mainly composed of two stable-color components, i.e., less variable thermal emission and high variable synchrotron radiation. And in most cases, the thermal component of BL Lacs is redder than that of synchrotron radiation, whereas FSRQs are the opposite.
description: 9 pages, 14 figures, accepted by MNRAS