cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Interaction of the magnetorotational instability with hydrodynamic turbulence in accretion disks
Creators: name: Workman, Jared C.
name: Armitage, Philip J.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Accretion disks in which angular momentum transport is dominated by the magnetorotational instability (MRI) can also possess additional, purely hydrodynamic, drivers of turbulence. Even when the hydrodynamic processes, on their own, generate negligible levels of transport, they may still affect the evolution of the disk via their influence on the MRI. Here, we study the interaction between the MRI and hydrodynamic turbulence using local MRI simulations that include hydrodynamic forcing. As expected, we find that hydrodynamic forcing is generally negligible if it yields a saturated kinetic energy density that is small compared to the value generated by the MRI. For stronger hydrodynamic forcing levels, we find that hydrodynamic turbulence modifies transport, with the effect varying depending upon the spatial scale of hydrodynamic driving. Large scale forcing boosts transport by an amount that is approximately linear in the forcing strength, and leaves the character of the MRI (for example the ratio between Maxwell and Reynolds stresses) unchanged, up to the point at which the forced turbulence is an order of magnitude stronger than that generated by the MRI. Low amplitude small scale forcing may modestly suppress the MRI. We conclude that the impact of hydrodynamic turbulence on the MRI is generically ignorable in cases, such as convection, where the additional turbulence arises due to the accretion energy liberated by the MRI itself. Hydrodynamic turbulence may affect (and either enhance or suppress) the MRI if it is both strong, and driven by independent mechanisms such as self-gravity, supernovae, or solid-gas interactions in multiphase protoplanetary disks.
description: ApJ, in press
Energy Management in a 100% Renewable Grid
Creators: T. Nguyen
B. Kroposki
R. Tonskoski
Publisher: name: IEEE
Year: 2019

2019 PES ISGT NA Panel Session
As renewable generation, especially wind and solar generation in the grid increase and become more distributed, grid energy management systems (EMS) are becoming increasingly important and complex. In this panel session, we will discuss the research opportunities and challenges related to EMS design and implementation with particular focus on the development of a unified framework for an EMS that can accommodate the additional capabilities that will be required in the 100% renewable energy future.  Specifically, we aim to answer the following questions: What are needed to connect and manage all of these individual systems and components effectively? What software and hardware platforms should be used? Can a standard architecture be developed and used for the majority of applications? What needs to be designed differently for a power system with an increasing number of distributed resources?
Subnanosecond single electron source in the time-domain
Creators: name: Mahé, Adrien
name: Parmentier, François
name: Fève, Gwendal
name: Berroir, Jean-Marc
name: Kontos, Takis
name: Cavanna, A.
name: Etienne, Bernard
name: Jin, Yong
name: Glattli, Christian
name: Plaçais, Bernard
Publisher: name: arXiv
Year: 2008
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We describe here the realization of a single electron source similar to single photon sources in optics. On-demand single electron injection is obtained using a quantum dot connected to the conductor via a tunnel barrier of variable transmission (quantum point contact). Electron emission is triggered by a sudden change of the dot potential which brings a single energy level above the Fermi energy in the conductor. A single charge is emitted on an average time ranging from 100 ps to 10 ns ultimately determined by the barrier transparency and the dot charging energy. The average single electron emission process is recorded with a 0.5 ns time resolution using a real-time fast acquisition card. Single electron signals are compared tosimulation based on scattering theory approach adapted for finite excitation energies.
Polymer drag reduction in surfactant-contaminated turbulent bubbly channel flows
Creators: name: Izbassarov, Daulet
name: Ahmed, Zaheer
name: Costa, Pedro
name: Vuorinen, Ville
name: Tammisola, Outi
name: Muradoglu, Metin
Publisher: name: arXiv
Year: 2021
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: Polymer additives are commonly utilized to manipulate bubbly flows in various applications. Here, we investigate the effects of clean and contaminated bubbles driven upwards (upflow) in Newtonian and viscoelastic turbulent channel flows. Interface-resolved direct numerical simulations are performed to examine sole and combined effects of soluble surfactant and viscoelasticity using an efficient 3D finite-difference/front-tracking method. The incompressible flow equations are solved fully coupled with the FENE-P viscoelastic model and the equations governing interfacial and bulk surfactant concentrations. The latter coupling is accomplished by a non-linear equation of state that relates the surface tension to the surfactant concentration. For Newtonian turbulent bubbly flows, the effects of Triton X-100 and 1-Pentanol surfactant are examined. It is observed that the sorption kinetics highly affect the dynamics of bubbly flow. A minute amount of Triton X-100 is found to be sufficient to prevent the formation of bubble clusters restoring the single-phase behavior while even two orders of magnitude more 1-Pentanol surfactant is not adequate to prevent the formation of layers. For viscoelastic turbulent flows, it is found that the viscoelasticity promotes formation of the bubble-wall layers and thus the polymer drag reduction is completely lost for the surfactant-free bubbly flows, while the addition of small amount of surfactant (Triton X-100) in this system restores the polymer drag reduction resulting in $25\%$ drag reduction for the $Wi=4$ case.
Entanglement entropy of two dimensional systems and holography
Creators: name: Michalogiorgakis, Georgios
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: In this note a new method for computing the entanglement entropy of a CFT holographically is explored. It consists of finding a bulk background with a boundary metric that has the conical singularities needed to compute the entanglement entropy in the usual QFT definition. An explicit calculation is presented for d=2.
description: 20 pages, 1 figure: v2 typos fixed, references and comments added
New distance and depth estimates from observations of eclipsing binaries in the SMC
Creators: name: North, Pierre L.
name: Gauderon, Romain
name: Royer, Frederic
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: A sample of 33 eclipsing binaries observed in a field of the SMC with FLAMES@VLT is presented. The radial velocity curves obtained, together with existing OGLE light curves, allowed the determination of all stellar and orbital parameters of these binary systems. The mean distance modulus of the observed part of the SMC is 19.05, based on the 26 most reliable systems. Assuming an average error of 0.1 mag on the distance modulus to an individual system, and a gaussian distribution of the distance moduli, we obtain a 2-sigma depth of 0.36 mag or 10.6 kpc. Some results on the kinematics of the binary stars and of the H II gas are also given.
description: 6 pages, 4 figures, Proc. IAU Symp. No 256, The Magellanic System: Stars, Gas and Galaxies, eds. Jacco Th. van Loon & Joana M. Oliveira
Evolution of the First Stars with Dark Matter Burning
Creators: name: Yoon, Sung-Chul
name: Iocco, Fabio
name: Akiyama, Shizuka
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Recent theoretical studies have revealed the possibly important role of the capture and annihilation process of weakly interacting massive particles (WIMPs) for the first stars. Using new evolutionary models of metal-free massive stars, we investigate the impact of such ``dark matter burning'' for the first stars in different environments of dark matter (DM) halos, in terms of the ambient WIMP density (rho_chi). We find that, in agreement with existing literature, stellar life times can be significantly prolonged for a certain range of rho_χ(i.e., 10^{10} ~ < ρ_χGeV/cm3 ~ < 10^{11} with the current upper limit for the spin-dependent elastic scattering cross section sigma = 5*10^{-39} cm2}). This greatly enhances the role of rotationally induced chemical mixing in rotating stars, in favor of abundant production of primary nitrogen, massive helium stars and long gamma-ray bursts, from the first stars. We also find that stars with rho_chi > 2*10^{11} GeV/cm3 may not undergo nuclear burning stages, confirming the previous work, and that ionizing photon fluxes from such DM supported stars are very weak. Delayed metal enrichment and slow reionization in the early universe would have resulted if most of the first stars had been born in DM halos with such high rho_χ, unless it had been lowered significantly below the threshold for efficient DM burning on a short time scale.
description: 5 pages, 3 figures, 1 table, ApJ Letter, in press
Emergency Monitoring and Control through New Technologies and Analytics
Creators: M. Vallem
A. Guzman
L. Roald
Y. Maximov
Publisher: name: IEEE
Year: 2019

2019 PES ISGT NA Panel Session
As evidenced by recent occurrences such as Superstorm Sandy, Hurricane Katrina, the 2003 Northeast blackout, extreme events pose an enormous threat to the nation's electric grid and the socio-economic systems that depend on reliable delivery of power. Despite the economic costs and social hardships of such events, utilities are unable to adequately plan and prepare for them. Power systems are vulnerable to extreme contingencies (like an outage of a major generating substation or transmission line) that can cause significant generation and load loss and can lead to further cascading outages of other transmission facilities and generators in the system. These could put the power system into 'Alert' state which the operators restore into normal state with corrective controls. Generally, there is sufficient time to implement these actions. However, the possibility of further contingencies as well as collapse conditions can push the system into an emergency state. The operators need to take less common and faster control actions (like customer power disruptions) to protect the system from further collapse. Prevention of possible power system collapse scenarios needs both long-term planning and operational intelligence that can identify optimal emergency controls to ensure that the system can be operated both reliably and economically. This panel will cover implementation of emergency controls using Dynamic Contingency Analysis Tool (DCAT): DCAT provides a hybrid dynamic/steady-state approach to analyzing cascading outages resulting from extreme contingencies; modal analysis for inter-area oscillation detection in real time; and detecting and mitigating imminent voltage collapse using steady-state optimization.
Influence of Population III stars on cosmic chemical evolution
Creators: name: Rollinde, E.
name: Vangioni, E.
name: Maurin, D.
name: Olive, K. A.
name: Daigne, F.
name: Silk, J.
name: Vincent, F.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: New observations from the Hubble ultra deep field suggest that the star formation rate at z>7 drops off faster than previously thought. Using a newly determined star formation rate for the normal mode of Population II/I stars (PopII/I), including this new constraint, we compute the Thomson scattering optical depth and find a result that is marginally consistent with WMAP5 results. We also reconsider the role of Population III stars (PopIII) in light of cosmological and stellar evolution constraints. While this input may be needed for reionization, we show that it is essential in order to account for cosmic chemical evolution in the early Universe. We investigate the consequences of PopIII stars on the local metallicity distribution function of the Galactic halo (from the recent Hamburg/ESO survey of metal-poor stars) and on the evolution of abundances with metallicity (based on the ESO large program on very metal-poor stars), with special emphasis on carbon-enhanced metal-poor stars. Our most important results show that the nucleosynthetic yields of PopIII stars lead to abundance patterns in agreement with those observed in extremely metal-poor stars. In this chemical approach to cosmic evolution, PopIII stars prove to be a compulsory ingredient, and extremely metal-poor stars are inevitably born at high redshift. (Abridged)
description: 11 pages, 7 figures, MNRAS in press
p(x)-Harmonic functions with unbounded exponent in a subdomain
Creators: name: Manfredi, Juan J.
name: Rossi, Julio D.
name: Urbano, José Miguel
Publisher: name: arXiv
Year: 2008
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 35J20; 35J60; 35J70

description: We study the Dirichlet problem $-÷(|\nabla u|^{p(x)-2} \nabla u) =0 $ in $Ω$, with $u=f$ on $\partial Ω$ and $p(x) = \infty$ in $D$, a subdomain of the reference domain $Ω$. The main issue is to give a proper sense to what a solution is. To this end, we consider the limit as $n \to \infty$ of the solutions $u_n$ to the corresponding problem when $p_n(x) =p(x) \wedge n$, in particular, with $p_n = n$ in $D$. Under suitable assumptions on the data, we find that such a limit exists and that it can be characterized as the unique solution of a variational minimization problem which is, in addition, $\infty$-harmonic within $D$. Moreover, we examine this limit in the viscosity sense and find the boundary value problem it satisfies in the whole of $Ω$.
description: Corrected typos; updated references; section 4. is new. This is the final version, accepted for publication in Ann. Inst. H. Poincar\'e Anal. Non Lin\'eaire
Magnetohydrodynamics of turbulent accretion discs around black holes
Creators: name: Pudritz, Ralph Egon
Publisher: name: University of British Columbia
Year: 2010

description: The Cyg X-1 X-ray source is believed to be comprised of an accretion disc around a central black hole. We apply the methods of Mean Field Electrodynamics to the study of magnetic processes in such an accretion disc. By decomposing the magnetic field in the disc into mean and fluctuating components, the observed X-ray properties of this system may be accounted for. It is found that intense, short lived magnetic fluctuations may occur which give rise to solar-like flares on the surfaces of the accretion disc. The energy releases and time scales of such flares is found to provide a physical basis for the observed shot-noise like character of the X-ray emission from the system. It is demonstrated that a rather strong, large scale magnetic field can be generated by turbulent dynamo action in the accretion disc. This result is the reason why magnetic fields may play a vital role in these systems. The long time averaged structure of the accretion disc is determined by the Maxwell-stress due to the mean field, and is in agreement with the "standard" cool accretion disc models. We prove that on intermediate time and length scales, the Maxwell stresses due to the magnetic fluctuations remove the known instability of "standard" accretion disc models to ring- like "clumping" and subsequent heating of the gas. This result shows that the hard X-ray emission of the Cyg X-1 source must arise from either a hot corona, or intense solar-type flares above the disc surfaces. If the hard X-ray emission arises from non-thermal electron populations accelerated in the flares, it is found that this emission must occur in a rapid "flash-phase" on submillisecond time scales. These flares occur well away from the inner disc boundaries so that we believe that submillisecond variations of the Cyg X-1 source need not be a test of the rotation of the central black hole.
Thermodynamic Properties near the onset of Loop-Current Order in high-$T_c$ superconducting cuprates
Creators: name: Gronsleth, M. S.
name: Nilssen, T. B.
name: Dahl, E. K.
name: Stiansen, E. B.
name: Varma, C. M.
name: Sudbo, A.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We have performed large-scale Monte Carlo simulations on a two-dimensional generalized Ashkin-Teller model to calculate the thermodynamic properties in the critical region near its transitions. The Ashkin-Teller model has a pair of Ising spins at each site which interact with neighboring spins through pair-wise and 4-spin interactions. The model represents the interactions between orbital current loops in $Cu O_2$-plaquettes of high-$T_c$ cuprates, which order with a staggered magnetization $\Mso$ inside each unit-cell in the underdoped region of the phase diagram below a temperature $T^*(x)$ which depends on doping. The pair of Ising spins per unit-cell represent the directions of the currents in the links of the current loops. The generalizations are the inclusion of anisotropy in the pair-wise nearest neighbor current-current couplings consistent with the symmetries of a square lattice and the next nearest neighbor pair-wise couplings. We use the Binder cumulant to estimate the correlation length exponent $ν$ and the order parameter exponent $β$. Our principal results are that in a range of parameters, the Ashkin-Teller model as well as its generalization has an order parameter susceptibility which diverges as $T \to T^*$ and an order parameter below $T^*$. Importantly, however, there is no divergence in the specific heat. This puts the properties of the model in accord with the experimental results in the underdoped cuprates. We also calculate the magnitude of the "bump" in the specific heat in the critical region to put limits on its observability. Finally, we show that the staggered magnetization couples to the uniform magnetization $M_0$ such that the latter has a weak singularity at $T^*$ and also displays a wide critical region, also in accord with recent experiments.
description: 14 pages, 19 figures, to appear in Physical Review B
Spin fluctuations in the magnetically ordered phase of frustrated pyrochlore systems
Creators: name: Bonville, P.
name: Mirebeau, I.
name: Sanchez, J. P.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Two geometrically frustrated pyrochlore stannates, undergoing long range magnetic order below 1K, were investigated at very low temperature. Anomalies in the behaviour of hyperfine quantities are found, by 155Gd Mossbauer spectroscopy in Gd2Sn2O7 and by low temperature specific heat measurements in Tb2Sn2O7. They are interpreted in terms of fluctuations of the correlated Gd or Tb spins, using a model two-level system (the nuclear spins) submitted to a randomly fluctuating (hyperfine) field.
description: 6 pages, 4 figures
Effectiveness of Artificial Intelligence in Stock Market Prediction based on Machine Learning
Creators: name: Mokhtari, Sohrab
name: Yen, Kang K.
name: Liu, Jin
Publisher: name: arXiv
Year: 2021
Subjects: subject: Statistical Finance (q-fin.ST)
subject: FOS: Economics and business

description: This paper tries to address the problem of stock market prediction leveraging artificial intelligence (AI) strategies. The stock market prediction can be modeled based on two principal analyses called technical and fundamental. In the technical analysis approach, the regression machine learning (ML) algorithms are employed to predict the stock price trend at the end of a business day based on the historical price data. In contrast, in the fundamental analysis, the classification ML algorithms are applied to classify the public sentiment based on news and social media. In the technical analysis, the historical price data is exploited from Yahoo Finance, and in fundamental analysis, public tweets on Twitter associated with the stock market are investigated to assess the impact of sentiments on the stock market's forecast. The results show a median performance, implying that with the current technology of AI, it is too soon to claim AI can beat the stock markets.
EVALUATE A CHANGE IN PRACTICE FOR PREDIABETES IN A RURAL AMBULATORY CARE SETTING
Creators: name: Yepez-Michel, Lupe
Publisher: name: Zenodo
Year: 2018

description: Prediabetes is the precursor to diabetes mellitus. It is an important health condition that is largely undiagnosed or simply overlooked. Prediabetes affects more than 84 million adults in America and is growing at 4.5% annually. Without lifestyle modifications such as physical activity and diet, individuals with prediabetes are at high risk to develop diabetes mellitus type II with consequent complications. The prediabetes health crisis is significant for several reasons: large numbers of people diagnosed annually, large numbers of people undiagnosed, rapid growth rate, and rate of progression from prediabetes to diabetes. The American Diabetes Association reported in 2015 that prediabetes impacts 1 out of 3 adults in the United States. The method used for this project was the implementation of a prediabetes algorithm in a rural ambulatory care setting in southern California. The four algorithm steps were: (1) identify and screen at-risk individuals; (2) obtain a hemoglobin A1c (HgbA1c) laboratory value for each at-risk individual; (3) confirm prediabetes diagnosis and, for those who tested positive, provide consultation on illness, need for lifestyle modifications (e.g., increase physical activity and healthy eating), enrollment into prediabetes/nutrition class; and (4) remain in contact with identified individuals and recheck HgbA1c laboratory values at 3-month intervals until the HgbA1c was below 5.6%. A paired samples t test was used to compare HgbA1c laboratory values between baseline and 3-month values. iv Out of 264 patients, 162 returned at the 3-month interval to have their HgbA1c laboratory test repeated. Of these, 83% were Hispanic and 79% were female. Individuals completing initial and 3-month HgbA1c laboratory testing demonstrated a mean decrease of -0.314, from 5.964 to 5.650 (p < .0001). This would mean a decreased progression into diabetes mellitus type II. Additionally, a one-way analysis of variance (ANOVA) test indicated there was a statistically significant decrease in HgbA1c laboratory value at the 3-month follow-up in those who engaged in physical activity (p = .013). This would mean a decreased progression into diabetes mellitus type II. In contrast to physical activity, which did provide statistical significance in lowering HgbA1c laboratory values, prediabetes class attendance did not yield statistically significant results. However, only 37 participants attended the prediabetes class. Preliminary data showed a positive impact on the predominately Hispanic and female prediabetic patients’ HgbA1c laboratory value at the 3-month follow-up for those who were identified and received counseling on prediabetes. Further investigation is needed to identify behavior patterns, including changes to diet, types and amount of exercise, as well as changes in weight following initial counseling to determine the greatest impact on HgbA1c laboratory value reduction.
Origin of X-ray Emission from Transient Black Hole Candidates in Quiescence
Creators: name: Pszota, Gabor
name: Zhang, Hui
name: Yuan, Feng
name: Cui, Wei
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We report results from a systematic study of X-ray emission from black hole transients in quiescence. In this state mass accretion is thought to follow the geometry of an outer optically thick, geometrically thin disc and an inner optically thin, geometrically thick radiatively inefficient accretion flow (RIAF). The inner flow is likely also coupled to the jets near the black hole that are often seen in such systems. The goal of the study is to see whether the X-ray emission in the quiescent state is mainly powered by the accretion flow or the jets. Using data from deep XMM-Newton observations of selected black hole transients, we have found that the quiescent X-ray spectra are, to a high precision, of power-law shape in the cases of GRO J1655-40 and V404 Cyg. Such spectra deviate significantly from the expected X-ray spectrum of the RIAF at very low accretion rates. On the other hand, they can naturally be explained by emission from the jets, if the emitting electrons follow a power-law spectral distribution (as is often assumed). The situation remains ambiguous in the case of XTE J1550-564, due to the relatively poorer quality of the data. We discuss the implication of the results.
description: 6 pages, 2 figures and 3 tables. Accepted to MNRAS on 2008 June 16
2019 IEEE General Meeting Panel Presentation: PSDP Handling Uncertainties and Use of Equivalents in DSA
Creators: T. Van Cutsem
I. Dobson
Publisher: name: IEEE
Year: 2019

2019 IEEE General Meeting Panel Presentation: PSDP Handling Uncertainties and Use of Equivalents in DSA
With the emerging new mix of generation and consumption of electricity, power systems are exhibiting more and stronger dynamic and stochastic behaviors. Wind and solar introduced uncertainties from the source, and the decreasing inertia makes systems more dynamic. Loads are becoming more responsive and introduce additional uncertainties and new dynamics. It becomes essential to consider these new behaviors in the function of Dynamic Security Assessment (DSA) in several aspects: DSA needs to consider scenarios of uncertainty samples beyond the traditional topology contingency, esp. in look-ahead and cascading situations; DSA needs to handle the challenge of making equivalent models of responsive loads, active distribution networks, and external systems; and DSA needs to have a better method for initializing the simulation process with a dynamic starting point different than traditional steady-state initialization. This panel will discuss all these challenges and solutions with experts in the relevant areas. The objective is to understand how DSA would adapt and what needs to be done to make DSA effective and efficient in the new era of power systems.
FORWARD Visual identity and promotional material
Creators: name: Cruz, Alma
name: Dobarro, Lucia
name: Perez, Iru
Publisher: name: Zenodo
Year: 2020
Subjects: ORs
Outermost regions
Research
Innovation
Visual identity
Research excellence

description: Project deliverable describing the FORWARD visual identity and promotional material: logo, project brochure, roll-up and diverse templates produced to ensure a well-defined visual identity.
Spin-Statistics Violations in Superstring Theory
Creators: name: Jackson, Mark G.
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: I describe how superstring theory may violate spin-statistics in an experimentally observable manner. Reviewing the basics of superstring interactions and how to utilize these to produce a statistical phase, I then apply these ideas to two specific examples. The first is the case of heterotic worldsheet linkings, whereby one small closed string momentarily enlarges sufficiently to pass over another, producing such a statistical phase. The second is the braneworld model with noncommutative geometry, whereby matter composed of open strings may couple to a background in which spacetime coordinates do not commute, modifying the field (anti)commutator algebra. I conclude with ways to sharpen and experimentally test these exciting avenues to possibly verify superstring theory.
description: 18 pages, 3 figures; v2: references added and typos corrected
Simulation of the flow of an explosive atmosphere exposed to a hot surface
Creators: name: Velagala, Subrahmanyeswara
name: Chowhan, Priyank Raval Sai Charan Singh
name: Esmaeelzade, Ghazaleh
name: Beyer, Michael
name: Grosshans, Holger
Publisher: name: arXiv
Year: 2021
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: The accidental ignition of combustible atmospheres by hot surfaces is of great concern for chemical and process plant safety. In this paper, we present our research regarding the evolution of thermal plumes originating from hot hemispheres and discs. In particular, we focus on the effect of the orientation of the surface on the ignition process. The auto-ignition temperatures and ignition locations were studied experimentally. To get further insight, we conducted detailed numerical simulations and validated them with measurements. Three-dimensional simulations were performed on hot hemispheres and hot discs for different orientations ranging from 0° to 180°. The solver employs a transient, implicit scheme which is based on the coupled heat transfer and flow equations. The mesh in the vicinity of the hot surfaces is refined to resolve the steep temperature gradients and to capture the boundary layer separation. The influence of the orientation on critical hot spots in the gas mixture is analysed by examining the flow structures and the temperature evolution of the buoyancy-driven flow. Using the obtained results, we discuss the change of the onset and location of the ignition.
Research Needs for Transforming the Grid Edge
Creators: L. Slezak
A. Hahn
K. Rajashekara
E. Mallada
Publisher: name: IEEE
Year: 2019

2019 PES ISGT NA Panel Session
Transformational changes in the future energy systems are driving changes in multiple sectors including the electric power grid, transportation, and buildings. The intersection of the electric power grid with these other sectors is often called the �Grid Edge.� The common themes of change in the Grid Edge are electrification, decentralization, and digitalization. The way in which emerging technologies will affect the Grid Edge, how these sectors will interact in the future, and the associated challenges and opportunities are the topics of this panel session. Specifically, we aim to answer the questions: What currently emerging technologies will be prevalent in the next ten years? What changes need to take place in the Grid Edge to accommodate and effectively utilize these new technologies? What are the research questions that need to be answered before these changes can take place? Of particular interest will be the future developments, and interactions between, the following topics: 1) Electrification of the transportation sector 2) Behind-the-meter technologies with bi-directional communication (smart meters, smart loads, rooftop solar, EVs, battery storage) 3) Distributed control, sensing, data, computation challenges and opportunities 4) Foundational changes required for off-grid and micro-grid scenarios
From optimal martingales to randomized dual optimal stopping
Creators: name: Belomestny, Denis
name: Schoenmakers, John G. M.
Publisher: name: Weierstrass Institute
Year: 2021
Subjects: subject: Optimal stopping problem
subject: Doob-martingale
subject: randomization
subject: 60G40
subject: 65C05
subject: 91G60

description: In this article we study and classify optimal martingales in the dual formulation of optimal stopping problems. In this respect we distinguish between weakly optimal and surely optimal martingales. It is shown that the family of weakly optimal and surely optimal martingales may be quite large. On the other hand it is shown that the Doob-martingale, that is, the martingale part of the Snell envelope, is in a certain sense the most robust surely optimal martingale under random perturbations. This new insight leads to a novel randomized dual martingale minimization algorithm that does`nt require nested simulation. As a main feature, in a possibly large family of optimal martingales the algorithm efficiently selects a martingale that is as close as possible to the Doob martingale. As a result, one obtains the dual upper bound for the optimal stopping problem with low variance.
Exclusive decay study of the 16.62\,MeV (2$^-$, T=1) resonance in $^{12}$C
Creators: name: Kuhlwein, Morten
name: Lytje, Kristian
name: Fynbo, Hans Otto Uldall
name: Gad, Andreas
name: Jensen, Erik
name: Kirsebom, Oliver Sølund
name: Munch, Michael
name: Refsgaard, Jonas
name: Riisager, Karsten
Publisher: name: arXiv
Year: 2021
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: The 3$α$ decay of the 16.62\,MeV (2$^-$, T=1) resonance in $^{12}$C has been studied for nearly a century starting with one of the first nuclear reaction studies at the Cavendish Laboratory in the 1930s. In the hitherto latest study published a decade ago a model based on earlier work from the 1960s was found to give a good account of a set of inclusive data. This model describes the decay as an l=3 $α$-particle populating the 2$^+$ state of $^8$Be. Here we provide new exclusive data on the 3$α$ decay of the 16.62\,MeV resonance, and demonstrate that the decay is best described by a model with predominantly l=1 emission with an admixture of l=3.
description: 5 pages, 3 figures
String GUT Scenarios with Stabilised Moduli
Creators: name: Blumenhagen, Ralph
name: Moster, Sebastian
name: Plauschinn, Erik
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: Taking into account the recently proposed poly-instanton corrections to the superpotential and combining the race-track with a KKLT respectively LARGE Volume Scenario in an intricate manner, we show that we gain exponential control over the parameters in an effective superpotential. This allows us to dynamically stabilise moduli such that a conventional MSSM scenario with the string scale lowered to the GUT scale is realised. Depending on the cycles wrapped by the MSSM branes, two different scenarios for the hierarchy of soft masses arise. The first one is a supergravity mediated model with M_3/2=1TeV while the second one features mixed anomaly-supergravity mediation with M_3/2=10^10GeV and split supersymmetry. We also comment on dynamically lowering the scales such that the tree-level cosmological constant is of the order Λ=(10^-3eV)^4.
description: 22 pages, 13 figures; v2: refs. and explanation added
Political trust and democracy: the critical citizens thesis re-examined
Creators: name: Dawson, Andrew
name: Krakoff, Isabel L.
Publisher: name: Taylor & Francis
Year: 2023
Subjects: subject: Neuroscience
subject: Biotechnology
subject: Sociology
subject: FOS: Sociology
subject: Science Policy
subject: Mental Health

description: This article empirically assesses competing perspectives of the relationship between democracy and political trust. We conduct multilevel analyses on a cross-national panel dataset of 82 countries for the period 1990–2020. The findings suggest that there is a strong, negative relationship between democracy and political trust that cannot easily be dismissed as an artifact of model misspecification or response bias. Moreover, we re-examine the critical citizens thesis by disaggregating political trust into trust in partisan and “non-partisan” institutions to test the claim that well-functioning democracies contain and channel distrust into the more partisan political institutions to keep distrust from generalizing to the entire political system. The results fail to find a statistically significant difference of the effect of democracy on trust between partisan and non-partisan institutions, suggesting that low political trust within democracies may be a more acute problem than much of the literature suggests.
Experimental investigation of the Rayleigh-Taylor instability
Creators: name: Popil, Roman
Publisher: name: University of British Columbia
Year: 2010

description: The Rayleigh-Taylor instability of a water-air interface was investigated using electrical and photographic methods. An apparatus is described which accelerates a rectangular tank of water downwards and produces reproducible instabilities from a pure sinusoidal standing surface water wave of known phase and amplitude. The electrical measurements revealed that in addition to the bulk motion, films of water are produced on the walls of the water tank. The existence of these and other features of the instability are substantiated by photographs of the various instabilities that were produced. The electrical measurements led to a new scaling law for the phenomenon of climbing fluid films at accelerations greater than gravity. Several linear devices were also developed for measuring the amplitudes of surface water waves.
Design and implementation of an islanded hybrid microgrid system for a large resort center for Penang Island with the proper application of excess energy
Creators: name: Shezan, SK. A.
name: Rawdah, S.
name: Ali, Shafin
name: Rahman, Ziaur
Publisher: name: arXiv
Year: 2021
Subjects: subject: Systems and Control (eess.SY)
subject: Machine Learning (cs.LG)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Computer and information sciences
subject: J.7

description: The energy demand is growing daily at an accelerated pace due to the internationalization and development of civilization. Yet proper economic utilization of additional energy generated by the Islanded Hybrid Microgrid System (IHMS) that was not consumed by the load is a major global challenge. To resolve the above-stated summons, this research focuses on a multi-optimal combination of IHMS for the Penang Hill Resort located on Penang Island, Malaysia, with effective use of redundant energy. To avail this excess energy efficiently, an electrical heater along with a storage tank has been designed concerning diversion load having proper energy management. Furthermore, the system design has adopted the HOMER Pro software for profitable and practical analysis. Alongside, MATLAB Simulink had stabilized the whole system by representing the values of 2068 and 19,072 kW that have been determined as the approximated peak and average load per day for the resort. Moreover, the optimized IHMS is comprehended of Photovoltaic (PV) cells, Diesel Generator, Wind Turbine, Battery, and Converter. Adjacent to this, the optimized system ensued in having a Net Present Cost (NPC) of $21.66 million, Renewable Fraction (RF) of 27.8%, Cost of Energy (COE) of $0.165/kWh, CO2 of 1,735,836 kg/year, and excess energy of 517.29MWh per annum. Since the diesel generator lead system was included in the scheme, a COE of $0.217/kWh, CO2 of 5,124,879 kg/year, and NPC of $23.25 million were attained. The amount of excess energy is effectively utilized with an electrical heater as a diversion load.
description: 15 Pages, 14 Figures, 6 Tables
Planning and Operating a Flexible and Resilient Grid: Insights of Recent ITS TF Technical Reports
Creators: D. Houseman
E. Bernabeu
G. Kobet
B. Chiu
Publisher: name: IEEE
Year: 2019

2019 PES ISGT NA Panel Session
The electric power industry has been working extensively on innovative technologies that can help ensure the resilience of the grid and policies that support resilient system operation. To address the need to provide a strategic vision and coordinate multiple efforts directed toward improving resilience, reliability, security, and stability of the transmission and distribution grids, the IEEE PES formed the Industry Technical Support Task Force (ITS TF). The Task Force works closely with the IEEE Standards Association, IEEE-USA, DOE, FERC, NERC, and other industry, government and regulatory agencies on complex issues impacting the energy sector. In respond to stakeholder's requests, ITSTF has published a series of technical reports, whitepapers, and testimonies in 2018. At this panel session, the leaders of these publications will provide their insights in these works and share their vision on the out most challenges and opportunities.
2019 IEEE General Meeting 8/7 Panel Presentation: Microgrid Tools - Design, Optimization, Business Case and Resiliency
Creators: J. Eddy
M. Heleno
D. Black
A. Annaswamy
Publisher: name: IEEE
Year: 2019

2019 IEEE General Meeting 8/7 Panel Presentation: Microgrid Tools - Design, Optimization, Business Case and Resiliency
This panel session will offer an overview of tools available to aid microgrid design, assessment, business case, resiliency and performance. Microgrids offer a path to energy resiliency for many applications and energy users. However, the process of designing, constructing, commissioning, and assessing a microgrid is not always straightforward. The panelists will describe tools that aid microgrid resource selection, design, construction, cyber security, resiliency and performance assessment. The panel will also review methodologies for assessing economic contributions that generate business cases for microgrid implementation.
Model Predictive Control with Models of Different Granularity and a Non-uniformly Spaced Prediction Horizon
Creators: name: Brüdigam, Tim
name: Prader, Daniel
name: Wollherr, Dirk
name: Leibold, Marion
Publisher: name: arXiv
Year: 2021
Subjects: subject: Systems and Control (eess.SY)
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Horizon length and model accuracy are defining factors when designing a Model Predictive Controller. While long horizons and detailed models have a positive effect on control performance, computational complexity increases. As predictions become less precise over the horizon length, it is worth investigating a combination of different models and varying time step size. Here, we propose a Model Predictive Control scheme that splits the prediction horizon into two segments. A detailed model is used for the short-term prediction horizon and a simplified model with an increased sampling time is employed for the long-term horizon. This approach combines the advantage of a long prediction horizon with a reduction of computational effort due to a simplified model and less decision variables. The presented Model Predictive Control is recursively feasible. A simulation study demonstrates the effectiveness of the proposed method: employing a long prediction horizon with advantages regarding computational complexity.
description: This work has been accepted to the 2021 American Control Conference. The published version is available at https://doi.org/10.23919/ACC50511.2021.9482617
SponGES Policy Brief: The ecological value of deep-sea sponges
Creators: name: FAO
Publisher: name: Zenodo
Year: 2021
Subjects: Sponges
Features
Use value
European Union (EU)
Horizon 2020
Grant Agreement No 679849
Deep-sea Sponge Grounds Ecosystems of the North Atlantic: an integrated approach towards their preservation and sustainable exploitation
SponGES

description: This SponGES policy brief provides a list of ecosystem features of deep-sea sponges covering five different domains: distribution, biodiversity, genetic diversity, nutrient and element fluxes, and response to threats and impacts. It also presents the results of a questionnaire that was administered to sponge experts within the SponGES project, to gain further knowledge and understanding on the overall ecological value of deep-sea sponges and possible consequences of their damage/destruction.
Boundary Lax pairs for the $A_{n}^{(1)}$ Toda field theories
Creators: name: Avan, Jean
name: Doikou, Anastasia
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: Exactly Solvable and Integrable Systems (nlin.SI)
subject: FOS: Physical sciences

description: Based on the recent formulation of a general scheme to construct boundary Lax pairs,we develop this systematic construction for the $A_n^{(1)}$ affine Toda field theories (ATFT). We work out explicitly the first two models of the hierarchy, i.e. the sine-Gordon ($A_1^{(1)}$) and the $A_2^{(1)}$ models. The $A_2^{(1)}$ Toda theory is the first non-trivial example of the hierarchy that exhibits two distinct types of boundary conditions. We provide here novel expressions of boundary Lax pairs associated to both types of boundary conditions.
description: 30 pages, Latex. Typos corrected, clarifications added. Version to appear in NBP
2019 IEEE General Meeting 8/7 Panel Presentation: PSDP Microgrid Stability Definitions, Analysis, and Modeling
Creators: N. Hatziargyriou
P. Mendoza-Araya
E. Nasr
R. Wies
F. Milano
Publisher: name: IEEE
Year: 2019

2019 IEEE General Meeting 8/7 Panel Presentation: PSDP Microgrid Stability Definitions, Analysis, and Modeling
The panel will focus of reviewing in detail the �Microgrid Stability Definitions, Analysis, and Modeling� TF report. Thus, the proposed microgrid stability definitions and classification will be first presented. The various models of the different microgrid components such as diesel generators, converters, RES, and associated controls, feeders, load models, and energy storage, will also be discussed, as well as the analysis techniques and tools used for stability studies. Finally, various examples of stability problems, controls, and modeling will be presented.
SponGES Policy Brief – Databases and models: new tools for management
Creators: name: FAO
Publisher: name: Zenodo
Year: 2020
Subjects: Fishery management
Marine Ecosystems
Sponge fisheries
Databases
European Union (EU)
Horizon 2020
Grant Agreement No 679849
Deep-sea Sponge Grounds Ecosystems of the North Atlantic: an integrated approach towards their preservation and sustainable exploitation
SponGES

description: This policy brief highlights SponGES project findings that are relevant to policymakers and fisheries managers. It provides an overview of the tools that are increasingly being used to build knowledge on where deep-sea sponges occur, their quantity and quality, and the role they play in the larger ocean ecosystem in order to enhance their protection, management, and conservation against anthropogenic pressures.
2019 IEEE General Meeting 8/7 Panel Presentation: Energy Internet and Energy System Integration - Applications and Experiences
Creators: Dr. X. Shen
Y. Liu
J. Hongjie
L. Ochoa
A. Conejo
Publisher: name: IEEE
Year: 2019

2019 IEEE General Meeting 8/7 Panel Presentation: Energy Internet and Energy System Integration - Applications and Experiences
Energy Internet (EI), a deep combination of energy system and the Internet, with Energy System Integration (ESI) as its interpretation in physical layer, is an emerging concept to shape the next-generation energy system. After years of research and development, there are already some demonstration project and successful applications with EI and ESI in different scenes, which can provide us a better understanding and clearer future trend of EI and ESI�s development. The panelists will give talks about the details of EI and ESI by summarizing some testbed, tools and real examples for advanced technology related with EI and ESI, based on the topic they�ve been working on these years, e.g. smart cities, industrial park, smart buildings, etc. Some observed benefits in terms of planning and operation, including energy efficiency improvement, reduced energy cost, etc. will be introduced with suggestions and pathway on how to realize those benefits.