cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
M/String Theory, S-branes and Accelerating Universe
Creators: name: Gutperle, Michael
name: Kallosh, Renata
name: Linde, Andrei
Publisher: name: arXiv
Year: 2003
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Astrophysics (astro-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: Recently it was observed that the hyperbolic compactification of M/string theory related to S-branes may lead to a transient period of acceleration of the universe. We study time evolution of the corresponding effective 4d cosmological model supplemented by cold dark matter and show that it is marginally possible to describe observational data for the late-time cosmic acceleration in this model. However, investigation of the compactification 11d -> 4d suggests that the Compton wavelengths of the KK modes in this model are of the same order as the size of the observable part of the universe. Assuming that this problem, as well as several other problems of this scenario, can be resolved, we propose a possible solution of the cosmological coincidence problem due to relation between the dark energy density and the effective dimensionality of the universe.
description: 8 pages, 5 figs, significant modifications are made
Dynamic Cognition Applied to Value Learning in Artificial Intelligence
Creators: name: de Oliveira, Nythamar
name: Corrêa, Nicholas Kluge
Publisher: name: arXiv
Year: 2020
Subjects: subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: Experts in Artificial Intelligence (AI) development predict that advances in the development of intelligent systems and agents will reshape vital areas in our society. Nevertheless, if such an advance isn't done with prudence, it can result in negative outcomes for humanity. For this reason, several researchers in the area are trying to develop a robust, beneficial, and safe concept of artificial intelligence. Currently, several of the open problems in the field of AI research arise from the difficulty of avoiding unwanted behaviors of intelligent agents, and at the same time specifying what we want such systems to do. It is of utmost importance that artificial intelligent agents have their values aligned with human values, given the fact that we cannot expect an AI to develop our moral preferences simply because of its intelligence, as discussed in the Orthogonality Thesis. Perhaps this difficulty comes from the way we are addressing the problem of expressing objectives, values, and ends, using representational cognitive methods. A solution to this problem would be the dynamic cognitive approach proposed by Dreyfus, whose phenomenological philosophy defends that the human experience of being-in-the-world cannot be represented by the symbolic or connectionist cognitive methods. A possible approach to this problem would be to use theoretical models such as SED (situated embodied dynamics) to address the values learning problem in AI.
Grassmann time-evolving matrix product operators: An efficient numerical approach for fermionic path integral simulations
Creators: name: Xu, Xiansong
name: Guo, Chu
name: Chen, Ruofan
Publisher: name: arXiv
Year: 2024
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Developing numerical exact solvers for open quantum systems is a challenging task due to the non-perturbative and non-Markovian nature when coupling to structured environments. The Feynman-Vernon influence functional approach is a powerful analytical tool to study the dynamics of open quantum systems. Numerical treatments of the influence functional including the quasi-adiabatic propagator technique and the tensor-network-based time-evolving matrix product operator method, have proven to be efficient in studying open quantum systems with bosonic environments. However, the numerical implementation of the fermionic path integral suffers from the Grassmann algebra involved. In this work, we present a detailed introduction of the Grassmann time-evolving matrix product operator method for fermionic open quantum systems. In particular, we introduce the concepts of Grassmann tensor, signed matrix product operator, and Grassmann matrix product state to handle the Grassmann path integral. Using the single-orbital Anderson impurity model as an example, we review the numerical benchmarks for structured fermionic environments for real-time nonequilibrium dynamics, real-time and imaginary-time equilibration dynamics, and its application as an impurity solver. These benchmarks show that our method is a robust and promising numerical approach to study strong coupling physics and non-Markovian dynamics. It can also serve as an alternative impurity solver to study strongly-correlated quantum matter with dynamical mean-field theory.
description: 17 pages, 10 figures
Additional file 1 of Development, implementation and user experience of the Veterans Health Administration (VHA) dialysis dashboard
Creators: name: Fischer, Michael J.
name: Kourany, Wissam M.
name: Sovern, Karen
name: Forrester, Kurt
name: Griffin, Cassandra
name: Lightner, Nancy
name: Loftus, Shawn
name: Murphy, Katherine
name: Roth, Greg
name: Palevsky, Paul M.
name: Crowley, Susan T.
Publisher: name: figshare
Year: 2020
Subjects: subject: Space Science
subject: Medicine
subject: Pharmacology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Marine Biology
subject: Cancer
subject: Science Policy

description: Additional file 1: Supplementary Table 1. Initial Clinical Performance Measures Identified by the VHA Dialysis Dashboard Committee.
Petrocephalus frieli Lavoue 2012
Creators: name: Kramer, Bernd
name: Bills, Roger
name: Skelton, Paul
name: Wink, Michael
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Osteoglossiformes
Mormyridae
Petrocephalus
Petrocephalus frieli

description: Petrocephalus frieli Lavoué, 2012
 SAIAB 76825 (3), 6.1–7.4 cm SL, Zambia Province: Luapula System: Lake Bangweulu shoreline at rocky point near Samfya Ferry dock, 11 ◦ 21 ′ 19.44 ′′ S, 29 ◦ 33 ′ 47.52 ′′ E, coll: R. Bills, A. Chilala, J. Friel, 25. September 2005, field no. JPF-05-014,
 SAIAB 76859 (1), 5.6 cm SL, Zambia Province: Luapula System: Lake Bangweulu shoreline at rocky point near Samfya Zambian Fisheries building, 11 ◦ 22 ′ 20.64 ′′ S, 29 ◦ 33 ′ 53.64 ′′ E, coll: R. Bills, A. Chilala, J. Friel, 25 September 2005, field no. JPF-05-015,
description: Published as part of Kramer, Bernd, Bills, Roger, Skelton, Paul & Wink, Michael, 2012, A critical revision of the churchill snoutfish, genus Petrocephalus Marcusen, 1854 (Actinopterygii: Teleostei: Mormyridae), from southern and eastern Africa, with the recognition of Petrocephalus tanensis, and the description of five new species, pp. 2179-2258 in Journal of Natural History 46 (35 - 36) on page 2190, DOI: 10.1080/00222933.2012.708452, http://zenodo.org/record/4590828
Ensembles of Deep Neural Networks for Action Recognition in Still Images
Creators: name: Mohammadi, Sina
name: Majelan, Sina Ghofrani
name: Shokouhi, Shahriar B.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Despite the fact that notable improvements have been made recently in the field of feature extraction and classification, human action recognition is still challenging, especially in images, in which, unlike videos, there is no motion. Thus, the methods proposed for recognizing human actions in videos cannot be applied to still images. A big challenge in action recognition in still images is the lack of large enough datasets, which is problematic for training deep Convolutional Neural Networks (CNNs) due to the overfitting issue. In this paper, by taking advantage of pre-trained CNNs, we employ the transfer learning technique to tackle the lack of massive labeled action recognition datasets. Furthermore, since the last layer of the CNN has class-specific information, we apply an attention mechanism on the output feature maps of the CNN to extract more discriminative and powerful features for classification of human actions. Moreover, we use eight different pre-trained CNNs in our framework and investigate their performance on Stanford 40 dataset. Finally, we propose using the Ensemble Learning technique to enhance the overall accuracy of action classification by combining the predictions of multiple models. The best setting of our method is able to achieve 93.17$\%$ accuracy on the Stanford 40 dataset.
description: 5 pages, 2 figures, 3 tables, Accepted by ICCKE 2019
Symmetry of stochastic equations
Creators: name: Gaeta, Giuseppe
Publisher: name: arXiv
Year: 2004
Subjects: subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: Symmetry methods are by now recognized as one of the main tools to attack deterministic differential equations (both ODEs and PDEs); the situation is quite different for what concerns stochastic differential equations: here, symmetry considerations are of course quite widely used by theoretical physicists, but a rigorous and general theory comparable to the one developed for deterministic equation is still lacking. In the following I will report on some work I have done on symmetries of stochastic (Ito) equations, and how these compare with the symmetries of the associated diffusion (Fokker-Planck) equations.
description: Work prepared for the Kyev SNMP2003 conference proceedings
The block structure spaces of real projective spaces and orthogonal calculus of functors
Creators: name: Macko, Tibor
Publisher: name: arXiv
Year: 2004
Subjects: subject: Algebraic Topology (math.AT)
subject: FOS: Mathematics
subject: Primary: 57N99, 57P99; Secondary: 57R67

description: Given a compact manifold X, the set of simple manifold structures on X x Δ^k relative to the boundary can be viewed as the k-th homotopy group of a space §^s (X). This space is called the block structure space of X. We study the block structure spaces of real projective spaces. Generalizing Wall's join construction we show that there is a functor from the category of finite dimensional real vector spaces with inner product to the category of pointed spaces which sends the vector space V to the block structure space of the projective space of V. We study this functor from the point of view of orthogonal calculus of functors; we show that it is polynomial of degree <= 1 in the sense of orthogonal calculus. This result suggests an attractive description of the block structure space of the infinite dimensional real projective space via the Taylor tower of orthogonal calculus. This space is defined as a colimit of block structure spaces of projective spaces of finite-dimensional real vector spaces and is closely related to some automorphisms spaces of real projective spaces.
description: corrected version, 32 pages, published in Transactions of the AMS at http://www.ams.org/tran/2007-359-01/S0002-9947-06-04180-8/
Detecting nonclassical correlations in levitated cavity optomechanics
Creators: name: Rakhubovsky, Andrey A.
name: Moore, Darren W.
name: Delić, Uroš
name: Kiesel, Nikolai
name: Aspelmeyer, Markus
name: Filip, Radim
Publisher: name: arXiv
Year: 2020
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Nonclassical optomechanical correlations enable optical control of mechanical motion beyond the limitations of classical driving. Here we investigate the feasibility of using pulsed cavity-optomechanics to create and verify nonclassical phase-sensitive correlations between light and the motion of a levitated nanoparticle in a realistic scenario. We show that optomechanical two-mode squeezing can persist even at the elevated temperatures of state-of-the-art experimental setups. We introduce a detection scheme based on optical homodyning that allows revealing nonclassical correlations without full optomechanical state tomography. We provide an analytical treatment using the rotating wave approximation (RWA) in the resolved-sideband regime and prove its validity with a full numerical solution of the Lyapunov equation beyond the RWA. We build on parameters of current experiments for our analysis and conclude that the observation of nonclassical correlations is possible today.
description: 5 + 5 pages, 3 figures, 1 table. Comments welcome!
Fermi-surface topology and the effects of intrinsic disorder in a class of charge-transfer salts containing magnetic ions, β''-(BEDT-TTF)_4[(H_3O)M(C_2O_4)_3]Y
Creators: name: Coldea, A. I.
name: Bangura, A. F.
name: Singleton, J.
name: Ardavan, A.
name: Akutsu-Sato, A.
name: Akutsu, H.
name: Turner, S. S.
name: Day, P.
Publisher: name: arXiv
Year: 2003
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We report high-field magnetotransport measurements on β''-(BEDT-TTF)_4[(H_3O)M(C_2O_4)_3]Y, where M=Ga, Cr and Fe and Y=C_5H_5N. We observe similar Shubnikov-de Haas oscillations in all compounds, attributable to four quasi-two-dimensional Fermi-surface pockets, the largest of which corresponds to a cross-sectional area ~8.5\% of the Brillouin zone. The cross-sectional areas of the pockets are in agreement with the expectations for a compensated semimetal, and the corresponding effective masses are ~m_e, rather small compared to those of other BEDT-TTF salts. Apart from the case of the smallest Fermi-surface pocket, varying the $M$ ion seems to have little effect on the overall Fermi-surface topology or on the effective masses. Despite the fact that all samples show quantum oscillations at low temperatures, indicative of Fermi liquid behavior, the sample- and temperature-dependence of the interlayer resistivity suggest that these systems are intrinsically inhomogeneous. It is thought that intrinsic tendency to disorder in the anions and/or the ethylene groups of the BEDT-TTF molecules leads to the coexistence of insulating and metallic states at low temperatures; comparison with other charge-transfer salts suggests that this might be a rather general phenomenon. A notional phase diagram is given for the general family of β''-(BEDT-TTF)_4[(H_3O)M(C_2O_4)_3]Y salts, which exhibits several marked similarities with that of the κ-(BEDT-TTF)_2X superconductors.
description: 12 pages, 7 figures, 2 tables
Technical Inefficiency of Chili Farms in Thailand
Creators: name: Krasachat, Wirat
name: Krasachat, Wirat
Publisher: name: Unknown
Year: 2017
Subjects: subject: Agricultural and Food Policy
subject: Crop Production/Industries
subject: Productivity Analysis
subject: technical inefficiency
subject: stochastic frontier production function
subject: chili farms
subject: Thailand
subject: Good Agricultural Practice

description: The primary purpose of this study is to measure and investigate factors affecting technical inefficiency of chili farms in Thailand. This study applies a stochastic frontier production function approach to measure farm-specific technical inefficiency using the 2013 farm-level cross-sectional survey data of Thai chili farms in a single estimation technique applying the maximum likelihood estimation method. The non-negative technical inefficiency effects are modeled as a function of farm-specific management and socio-economic factors. The empirical results suggest two important findings. First, there is confirmation that the difference in variety used has influenced the technical inefficiency of chili farms. Second, good agricultural practice (GAP) also has different impacts on technical inefficiency in Thai chili production in different farms.
Petrocephalus longianalis Kramer & Bills & Skelton & Wink 2012, sp. nov.
Creators: name: Kramer, Bernd
name: Bills, Roger
name: Skelton, Paul
name: Wink, Michael
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Osteoglossiformes
Mormyridae
Petrocephalus
Petrocephalus longianalis

description: Petrocephalus longianalis sp. nov.
 SAIAB 76758, holotype, specimen R9, 8.2 cm SL, Zambia Province: Luapula System: Luongo River: Lufubu River, Lufubu River Falls below bridge at Chipili on Mensa- Mununga road, 10 ◦ 43 ′ 46.92 ′′ S, 29 ◦ 05 ′ 36.96 ′′ E, coll: R. Bills, A. Chilala, J. Friel, 2 October 2005, field no. JPF-05-025,
 SAIAB 186060 (48), paratypes, 3.8–8.2 cm SL, Zambia Province: Luapula System: Luongo River: Lufubu River, Lufubu River Falls below bridge at Chipili on Mensa- Mununga road, 10 ◦ 43 ′ 46.92 ′′ S, 29 ◦ 05 ′ 36.96 ′′ E, coll: R. Bills, A. Chilala, J. Friel, 2 October 2005, field no. JPF-05-025,
 Non-types: SAIAB 76582 (5), 7.0– 7.3 cm SL, Zambia Province: Central System: Luapula River: Luapula, Luapula River Bridge, 12 ◦ 06 ′ 56.16 ′′ S, 29 ◦ 50 ′ 49.92 ′′ E, coll: R. Bills, A. Chilala, J. Friel, 22 September 2005, field no. JPF-05-006,
 SAIAB 76733 (2), 10.1–11.9 cm SL, Zambia Province: Luapula System: Luongo River at bridge on Kashiba-Mwenda road, 10 ◦ 28 ′ 12.72 ′′ S, 29 ◦ 01 ′ 28.2 ′′ E, coll: R. Bills, A. Chilala, J. Friel, 1 October 2005, field no. JPF-05-023.
description: Published as part of Kramer, Bernd, Bills, Roger, Skelton, Paul & Wink, Michael, 2012, A critical revision of the churchill snoutfish, genus Petrocephalus Marcusen, 1854 (Actinopterygii: Teleostei: Mormyridae), from southern and eastern Africa, with the recognition of Petrocephalus tanensis, and the description of five new species, pp. 2179-2258 in Journal of Natural History 46 (35 - 36) on page 2190, DOI: 10.1080/00222933.2012.708452, http://zenodo.org/record/4590828
INSTITUTIONAL LIMITS TO LAND GOVERNANCE REFORM: FEDERAL-STATE DYNAMICS IN NIGERIA
Creators: name: Resnik, Danielle
name: Okumo, Austen
name: Resnik, Danielle
name: Okumo, Austen
Publisher: name: Unknown
Year: 2017
Subjects: subject: Agricultural and Food Policy
subject: Food Security and Poverty
subject: International Development
subject: Land Economics/Use
subject: Political Economy
subject: Nigeria
subject: land governance reform

description: Over the last decade, land governance has become a major priority for the development community1. A particular focus has been on sub-Saharan Africa due to the recognized paradox of high levels of land availability and low productivity in the region (see Deininger et al. 2012). While poor land governance systems have long been identified as a key reason for this disjuncture, the relatively recent large-scale impetus to improve land governance emerged from the inclusion of land management in 2009 as one of the four pillars under the African Union’s Comprehensive Africa Agriculture Development Program (CAADP). Subsequently, in the wake of the G-8’s launch of the New Alliance for Food Security and Nutrition in 2012, many international initiatives have emerged to promote better land governance. These include the African Union’s Land Policy Initiative (AULPI) and the World Bank’s Land Governance Assessment Framework (LGAF). At the national level in Africa, land registration and land titling are the most common approaches to reform (Sikor and Müller 2009), with governments selecting among a broad spectrum of modalities to pilot. These include rural land use plans in some francophone countries (e.g., Benin, Burkina Faso, and Côte d’Ivoire), systematic land tenure regularization (Ethiopia, Madagascar, Rwanda), and communal land demarcation and registration (e.g., Ghana, Mozambique, Tanzania) (see Byamugisha 2013).
Transient effects in fission evidenced from new experimental signatures
Creators: name: Jurado, B.
name: Schmitt, C.
name: Schmidt, K. -H.
name: Benlliure, J.
name: Enqvist, T.
name: Junghans, A. R.
name: Kelic, A.
name: Rejmund, F.
Publisher: name: arXiv
Year: 2004
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: A new experimental approach is introduced to investigate the relaxation of the nuclear deformation degrees of freedom. Highly excited fissioning systems with compact shapes and low angular momenta are produced in peripheral relativistic heavy-ion collisions. Both fission fragments are identified in atomic number. Fission cross sections and fission-fragment element distributions are determined as a function of the fissioning element. From the comparison of these new observables with a nuclear-reaction code a value for the transient time is deduced.
description: 6 pages, 2 figures, background information at http://www-w2k.gsi.de/kschmidt/
Pembuatan Sistem dan Pendampingan Siaga Bencana Gunung Agung di SMPN 3 Bebandem dan SMPN 5 Kubu, Karangasem, Bali
Creators: name: Saepuloh, A.
name: Sucipta, IGBE
name: Darajat, F.I.
name: Nugraha, Y.A.
Publisher: name: Zenodo
Year: 2018
Subjects: disaster preparedness
siaga bencana
gunung agung
bali

description: Pembuatan Sistem dan Pendampingan Siaga Bencana Gunung Agung di SMPN 3 Bebandem dan SMPN 5 Kubu, Karangasem, Bali (in English) The making of system and coaching for Mount Agung disaster preparedness for junior high students in SMPN 3 Bebandem and SMPN 5 Kubu, Karangasem, Bali.
On the $p$-divisibility of class numbers of an infinite family of imaginary quadratic fields $\mathbb{Q} (\sqrt{d})$ and $\mathbb{Q} (\sqrt{d+1}).$
Creators: name: Kumar, Pasupulati Sunil
name: Krishnamoorthy, Srilakshmi
Publisher: name: arXiv
Year: 2020
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: Primary: 11R29, Secondary : 11R11

description: For any odd prime $p,$ we construct an infinite family of pairs of imaginary quadratic fields $\mathbb{Q}(\sqrt{d}),\mathbb{Q}(\sqrt{d+1})$ whose class numbers are both divisible by $p.$ One of our theorems settles Iizuka's conjecture for the case $n=1$ and $p >2.$
description: 6 pages
Additional file 1 of Treatment-related changes in neuroendocrine tumors as assessed by textural features derived from 68Ga-DOTATOC PET/MRI with simultaneous acquisition of apparent diffusion coefficient
Creators: name: Weber, Manuel
name: Kessler, Lukas
name: Schaarschmidt, Benedikt
name: Fendler, Wolfgang Peter
name: Lahner, Harald
name: Antoch, Gerald
name: Umutlu, Lale
name: Herrmann, Ken
name: Rischpler, Christoph
Publisher: name: figshare
Year: 2020
Subjects: subject: Medicine
subject: Cell Biology
subject: Molecular Biology
subject: Neuroscience
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Ecology
subject: FOS: Biological sciences
subject: Cancer
subject: 111714 Mental Health
subject: FOS: Health sciences

description: Additional file 1: Figure S1. Axial ADC maps (a + c) and PET (b + d) of 21 years-old patient with G3 NET of the pancreas and disease progression under chemotherapy. Interval between baseline (a + b) and follow-up (c + d) is 5 months.
LAND ADMINISTRATION SERVICE DELIVERY AND ITS CHALLENGES IN NIGERIA: A CASE STUDY OF EIGHT STATES
Creators: name: Ghebru, Hosaena
name: Okumo, Austen
name: Ghebru, Hosaena
name: Okumo, Austen
Publisher: name: Unknown
Year: 2017
Subjects: subject: Agricultural and Food Policy
subject: Food Security and Poverty
subject: International Development
subject: Land Economics/Use
subject: Political Economy
subject: Nigeria
subject: land administration

description: This paper assesses the nature of land administration service delivery in Nigeria using data collected from three sets of participants in land administration processes: 76 service providers, 253 beneficiaries, and 172 professionals. The data were collected from eight states selected from the six geopolitical zones of the country—Cross River, Benue, Bauchi, Ekiti, Enugu, Kaduna, and Lagos states, plus the Federal Capital Territory (Abuja). These were chosen because they are considered to have advanced land administration systems.
ASSESSING THE STATE OF THE RICE MILLING SECTOR IN NIGERIA: THE ROLE OF POLICY FOR GROWTH AND MODERNIZATION
Creators: name: Johnson, Michael
name: Masias, Ian
name: Johnson, Michael
name: Masias, Ian
Publisher: name: Unknown
Year: 2017
Subjects: subject: Agricultural and Food Policy
subject: Food Security and Poverty
subject: International Development
subject: Political Economy
subject: Productivity Analysis
subject: rice
subject: Nigeria

description: We use an industry profit maximization model to conduct an ex-post impact assessment on the extent the rice milling sector in Nigeria has grown and improved its performance in producing high quality premium rice following major public sector interventions made under the Agricultural Transformation Agenda. Given challenges with the availability and quality of data, this assessment looks at the changes between two periods, 2009 and 2013, and simulates the performance of the sector under different technology capacities and policy scenarios. We find that the government has been successful in expanding quality paddy production and milling capacity in the country along with an increase in capacity utilization in the medium and large-scale milling sub-sectors. As a result, the production of premium quality rice has increased by approximately 0.5 million metric tons between the two periods. Despite these gains, the industry did not see any overall increase in employment in the medium and large-scale sub-sectors. Further focus by the government on expanding the supply of high quality rice paddy, while maintaining high tariffs to keep the medium and large scale milling sector viable, may provide the best opportunity for Nigeria to reach its goal of self-sufficiency in rice production.
title: Estimating Systematic Risk Under Extremely Adverse Market Conditions
Creators: name: van Oordt, Maarten
name: Zhou, Chen
Publisher: name: Bank of Canada
Year: 2016

description: This paper considers the problem of estimating a linear model between two heavy-tailed variables if the explanatory variable has an extremely low (or high) value. We propose an estimator for the model coefficient by exploiting the tail dependence between the two variables and prove its asymptotic properties. Simulations show that our estimation method yields a lower mean squared error than regressions conditional on tail observations. In an empirical application we illustrate the better performance of our approach relative to the conditional regression approach in projecting the losses of industry-specific stock portfolios in the event of a market crash.
description: Dans cet article, nous examinons l’estimation d’un modèle de régression linéaire entre deux variables qui suivent des lois de probabilité à queue épaisse lorsque la variable explicative a des valeurs extrêmement faibles (ou élevées). En exploitant la relation de dépendance entre les extrema des deux variables, nous proposons un estimateur du coefficient de régression. Nous établissons les propriétés asymptotiques de cet estimateur. Les simulations montrent que notre méthode d’estimation génère une plus faible erreur quadratique moyenne que l’outil de référence, c’est-à-dire l’estimateur des moindres carrés ordinaires obtenu à partir des observations extrêmes. Nous illustrons également la supériorité de notre approche par rapport à l’outil de référence dans la prévision des pertes qu’enregistreraient des portefeuilles d’actions propres à un secteur particulier en cas de crash boursier.
A short proof of the conjecture of Erdös--Straus for every $n\equiv 13 \textrm{ mod }24$
Creators: name: Gionfriddo, Mario
name: Guardo, Elena
Publisher: name: arXiv
Year: 2020
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11D72, 11D45, 11P81

description: The Erdös--Straus conjecture states that the equation $\frac{4}{n}=\frac{1}{x}+\frac{1}{y}+\frac{1}{z}$ has positive integer solutions $x,y,z$ for every postive integers $n\geq 2$. In this short note we find explicity the solutions of the famous conjecture for the case $n\equiv13 \textrm{ mod } 24.$
description: 6 pages, J. Interdiscip. Math published on line 23 June 2021, In press
Solvation force for long ranged wall-fluid potentials
Creators: name: Maciolek, A.
name: Drzewinski, A.
name: Bryk, P.
Publisher: name: arXiv
Year: 2003
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: The solvation force of a simple fluid confined between identical planar walls is studied in two model systems with short ranged fluid-fluid interactions and long ranged wall-fluid potentials decaying as $-Az^{-p}, z\to \infty$, for various values of $p$. Results for the Ising spins system are obtained in two dimensions at vanishing bulk magnetic field $h=0$ by means of the density-matrix renormalization-group method; results for the truncated Lennard-Jones (LJ) fluid are obtained within the nonlocal density functional theory. At low temperatures the solvation force $f_{solv}$ for the Ising film is repulsive and decays for large wall separations $L$ in the same fashion as the boundary field $f_{solv}\sim L^{-p}$, whereas for temperatures larger than the bulk critical temperature $f_{solv}$ is attractive and the asymptotic decay is $f_{solv}\sim L^{-(p+1)}$. For the LJ fluid system $f_{solv}$ is always repulsive away from the critical region and decays for large $L$ with the the same power law as the wall-fluid potential. We discuss the influence of the critical Casimir effect and of capillary condensation on the behaviour of the solvation force.
description: 48 pages, 12 figures
Model for Gravitational Interaction between Dark Matter and Baryons
Creators: name: Piazza, Federico
name: Marinoni, Christian
Publisher: name: arXiv
Year: 2003
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Astrophysics (astro-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We propose a phenomenological model where the gravitational interaction between dark matter and baryons is suppressed on small, subgalactic scales. We describe the gravitational force by adding a Yukawa contribution to the standard Newtonian potential and show that this interaction scheme is effectively suggested by the available observations of the inner rotation curves of small mass galaxies. Besides helping in interpreting the cuspy profile of dark matter halos observed in N-body simulations, this potential regulates the quantity of baryons within halos of different masses.
description: 4 pages, 2 figures, final version
Growth of the Brownian forest
Creators: name: Pitman, Jim
name: Winkel, Matthias
Publisher: name: arXiv
Year: 2004
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics
subject: 60J65, 60J80 (Primary)

description: Trees in Brownian excursions have been studied since the late 1980s. Forests in excursions of Brownian motion above its past minimum are a natural extension of this notion. In this paper we study a forest-valued Markov process which describes the growth of the Brownian forest. The key result is a composition rule for binary Galton--Watson forests with i.i.d. exponential branch lengths. We give elementary proofs of this composition rule and explain how it is intimately linked with Williams' decomposition for Brownian motion with drift.
description: Published at http://dx.doi.org/10.1214/009117905000000422 in the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org)
General Aspects of the de Sitter phase
Creators: name: Imponente, Giovanni
name: Montani, Giovanni
Publisher: name: arXiv
Year: 2004
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present a detailed discussion of the inflationary scenario in the context of inhomogeneous cosmologies. After a review of the fundamental features characterizing the inflationary model, as referred to a homogeneous and isotropic Universe, we develop a generalization in view of including small inhomogeneous corrections in the theory. A second step in our discussion is devoted to show that the inflationary scenario provides a valuable dynamical ``bridge'' between a generic Kasner-like regime and a homogeneous and isotropic Universe in the horizon scale. This result is achieved by solving the Hamilton-Jacobi equation for a Bianchi IX model in the presence of a cosmological space-dependent term. In this respect, we construct a quasi-isotropic inflationary solution based on the expansion of the Einstein equations up to first-two orders of approximation, in which the isotropy of the Universe is due to the dominance of the scalar field kinetic term; the first order of approximation corresponds to the inhomogeneous corrections and is driven by the matter evolution. We show how such a quasi-isotropic solution contains a certain freedom in fixing the space functions involved in the problem. The main physical issue of this analysis corresponds to outline the impossibility for the classical origin of density perturbations, due to the exponential decay of the matter term during the de Sitter phase.
description: 30 pages with cimento.cls, no figures, to appear on "Il Nuovo Cimento B"
ANALYSIS OF NEWSPAPER ADVERTISING OF FRESH APPLES IN NORTH CAROLINA
Creators: name: Ghura, Dhaneshwar
name: Schrimper, Ronald A.
name: Ghura, Dhaneshwar
name: Schrimper, Ronald A.
Publisher: name: Unknown
Year: 1991
Subjects: subject: Crop Production/Industries
subject: Marketing
subject: FOS: Economics and business

description: In recer1t years, producers of many agricultural products have become more involved in promoting their products. Morrison (1984) reports that the total costs of generic advertising of agricultural products tripled between 1972 and· 1982. During the same period, expenditures by agricultural prodcers for generic advertising of non-citrus fruits (including apples) increased from $2.2 to $15.2 million. Many other forms of advertising are used to promote sales of agricultural products. These include advertising of various brands of specific agricultural products by retailers via local newspapers; radio and television, and magazines (to a lesser extent). Local newspapers are an important vehicle for ail types of advertising. Between the mid-1970s and the mid-1980s, newspapers have accounted for approximately one-fourth of all advertising expenditures (U.S. Department of Commerce, 1987). Local newspapers account for a significant amount of food· advertisements. In 1985, local newspapers accounted 17 percent of all food marketing advertising (U.S. Department of Agriculture, February 1987). The purpose of this study was to examine the extent and type of advertising for fresh apples included in retail food ads in selected newspapers in North Carolina. Particular interest existed in identifying · specific apple characteristics retailers selected to emphasize in their newspaper promotions. Also of interest was determining whether the type of information used by retailers to promote apples changed over time or differed in two cities in North Carolina. The results of this study are intended to provide background information to producers, retailers and other parties interested in fresh apple promotion in North Carolina
FEA-Net: A Physics-guided Data-driven Model for Efficient Mechanical Response Prediction
Creators: name: Yao, Houpu
name: Gao, Yi
name: Liu, Yongming
Publisher: name: arXiv
Year: 2020
Subjects: subject: Computational Engineering, Finance, and Science (cs.CE)
subject: Machine Learning (cs.LG)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences

description: An innovative physics-guided learning algorithm for predicting the mechanical response of materials and structures is proposed in this paper. The key concept of the proposed study is based on the fact that physics models are governed by Partial Differential Equation (PDE), and its loading/ response mapping can be solved using Finite Element Analysis (FEA). Based on this, a special type of deep convolutional neural network (DCNN) is proposed that takes advantage of our prior knowledge in physics to build data-driven models whose architectures are of physics meaning. This type of network is named as FEA-Net and is used to solve the mechanical response under external loading. Thus, the identification of a mechanical system parameters and the computation of its responses are treated as the learning and inference of FEA-Net, respectively. Case studies on multi-physics (e.g., coupled mechanical-thermal analysis) and multi-phase problems (e.g., composite materials with random micro-structures) are used to demonstrate and verify the theoretical and computational advantages of the proposed method.
Pseudo-Newtonion potential for the relativistic accretion disk around rotating central objects having hard surface
Creators: name: Ghosh, Shubhrangshu
Publisher: name: arXiv
Year: 2003
Subjects: subject: Astrophysics (astro-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Here we furnish a pseudo-Newtonion potential for accretion disk modeling around rotating central objects having hard sueface. That means, the potential may be useful to describe the accretion disk around rotating neutron stars and strange stars. The potential can describe the general relativistic effects in accretion disk properly, essentially studying the relativistic hydrodynamics of disk. As our intention lies in understanding the fluid dynamics of the accretion disk around rotating central objects with hard surface, it is necessary to incorporate the rotation of the central object which affects the inner edge of the disk. We derive our potential, starting from the Hartle Thorne metric. The potential can reproduce all the essential properties of general relativity with 10% error at most, for slowly rotating neutron/strange stars.
description: 8 pages, aa.cls style; Accepted for publication in Astronomy and Astrophysics (A&A)
A Non-Iterative Transformation Method for an Extended Blasius Problem
Creators: name: Fazio, Riccardo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 65L10, 34B15, 65L08

description: In this paper we define a non-iterative transformation method for an Extended Blasius Problem. The original non-iterative transformation method, which is based on scaling invariance properties, was defined for the classical Blasius problem by Töpfer in 1912. This method allows us to solve numerically a boundary value problem by solving a related initial value problem and then rescaling the obtained numerical solution. In recent years, we have seen applications of the non-iterative transformation method to several problems of interest. The obtained numerical results, are improved by both a mesh refinement strategy and the Richardson's extrapolation technique.%, are found to be in good agreement with those available in literature.
description: 12 pages,1 figure, 2 tables. arXiv admin note: substantial text overlap with arXiv:1501.06015
title: Timing of Banks’ Loan Loss Provisioning During the Crisis
Creators: name: de Haan, Leo
name: van Oordt, Maarten
Publisher: name: Bank of Canada
Year: 2016

description: We estimate a panel error correction model for loan loss provisions, using unique supervisory data on flow of funds into and out of the allowance for loan losses of 25 Dutch banks in the post-2008 crisis period. We find that these banks aim for an allowance of 49% of impaired loans. In the short run, however, the adjustment of the allowance is only 29% of the change in impaired loans. The deviation from the target is made up by (a) larger additions to allowances in subsequent quarters and (b) smaller reversals of allowances when loan losses do not materialize. After one quarter, the adjustment toward the target level is 34% and after four quarters is 81%. For individual banks, there are substantial differences in timing of provisioning for bad loan losses. We present two model-based metrics that inform supervisors on the extent to which banks’ short-term provisioning behaviour is out of sync with their target levels.
description: Dans cette étude, nous estimons un modèle à correction d’erreurs sur données de panel permettant d’analyser les provisions pour pertes sur prêts. À cette fin, nous utilisons des données prudentielles uniques sur les flux de fonds (entrées et sorties) dans les provisions pour pertes sur prêts de 25 banques des Pays-Bas après la crise de 2008. Nos recherches indiquent que ces banques visent une couverture de 49 % des prêts douteux. Toutefois, à court terme, l’ajustement des provisions apporté à la suite d’un changement dans le volume des prêts douteux ne représente que 29 % du changement. L’écart par rapport au niveau cible est réduit par deux moyens : a) en accroissant les provisions pour pertes sur prêts aux trimestres suivants, et b) en diminuant les reprises sur provisions lorsque les pertes ne se matérialisent pas. Nous constatons que l’ajustement vers le niveau cible est de 34 % et de 81 % au bout d’un trimestre et de quatre trimestres, respectivement. Nous observons des différences considérables entre les banques en ce qui concerne le moment de constituer des provisions pour les pertes dues aux prêts douteux. Nous présentons deux mesures fondées sur des modèles qui renseignent les autorités de surveillance sur l’étendue du décalage entre le comportement à court terme des banques en matière de provisionnement et leur niveau cible.
Bistability in the Unstable Flow of Polymer Solutions Through Porous Media
Creators: name: Browne, Christopher A.
name: Shih, Audrey
name: Datta, Sujit S.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: Polymer solutions are often injected in porous media for applications such as oil recovery and groundwater remediation. As the fluid navigates the tortuous pore space, elastic stresses build up, causing the flow to become unstable at sufficiently large injection rates. However, it is poorly understood how the spatial and temporal characteristics of this unstable flow depend on pore space geometry. We elucidate this dependence by systematically varying the spacing between pore constrictions in a model porous medium. We find that when the pore spacing is large, unstable eddies form upstream of each pore, similar to observations of an isolated pore. By contrast, when the pore spacing is sufficiently small, the flow exhibits a surprising bistability, stochastically switching between two distinct unstable flow states. We hypothesize that this unusual behavior arises from the interplay between flow-induced polymer elongation and relaxation of polymers as they are advected through the porous medium. Consistent with this idea, we find that the flow state in a given pore persists for long times. Moreover, we find that the flow state is correlated between neighboring pores; however, these correlations do not persist long-range. Our results thus help to elucidate the rich array of flow behaviors that can arise in polymer solution flow through porous media.
description: In press; this version is pre-review. Updated version will be posted in six months
title: Housing and Tax-Deferred Retirement Accounts
Creators: name: Ho, Anson T. Y.
name: Zhou, Jie
Publisher: name: Bank of Canada
Year: 2016

description: Assets in tax-deferred retirement accounts (TDA) and housing are two major components of household portfolios. In this paper, we develop a life-cycle model to examine the interaction between households’ use of TDA and their housing decisions. The model generates life-cycle patterns of home ownership and the composition of net worth that are broadly consistent with the data from the Survey of Consumer Finances. We find that TDA promotes home ownership, as households take advantage of the preferential tax treatments for both TDA and home ownership. They substitute TDA assets for home equity by accumulating wealth in TDA and making smaller down payments (taking out bigger mortgages); consequently, they become homeowners earlier in their lives. On the other hand, housing-related policies, such as a minimum down payment requirement and mortgage interest deductibility, affect households’ housing decisions more than their use of TDA.
description: Les comptes de retraite à impôt différé et l’immobilier sont deux composantes importantes du portefeuille d’actifs des ménages. Dans notre étude, nous élaborons un modèle de cycle de vie qui permet d’examiner l’interaction entre l’utilisation des comptes de retraite à impôt différé et les décisions en matière de logement. Le modèle génère des profils d’accession à la propriété durant le cycle de vie et une composition de la valeur nette des ménages qui sont conformes, dans l’ensemble, aux données provenant de la Survey of Consumer Finances (enquête sur les finances des consommateurs). Nos résultats indiquent que les comptes de retraite à impôt différé favorisent l’accession à la propriété, car les ménages tirent avantage du traitement fiscal préférentiel que leur procurent à la fois ce type de compte et la possession d’une résidence. À l’avoir propre foncier, les ménages substituent les actifs détenus dans des comptes de retraite à impôt différé. En effet, ils accumulent leur épargne dans ces comptes et réduisent leurs mises de fonds (ils contractent donc des prêts hypothécaires plus élevés); par conséquent, ils deviennent propriétaires plus tôt dans leur vie. Cela dit, les politiques relatives au logement, comme l’exigence de mise de fonds minimale et la déductibilité des intérêts hypothécaires, influencent davantage les décisions des ménages concernant le logement que l’utilisation des comptes de retraite à impôt différé.
Solving Large-Scale Sparse PCA to Certifiable (Near) Optimality
Creators: name: Bertsimas, Dimitris
name: Cory-Wright, Ryan
name: Pauphilet, Jean
Publisher: name: arXiv
Year: 2020
Subjects: subject: Optimization and Control (math.OC)
subject: Machine Learning (cs.LG)
subject: Statistics Theory (math.ST)
subject: Computation (stat.CO)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences

description: Sparse principal component analysis (PCA) is a popular dimensionality reduction technique for obtaining principal components which are linear combinations of a small subset of the original features. Existing approaches cannot supply certifiably optimal principal components with more than $p=100s$ of variables. By reformulating sparse PCA as a convex mixed-integer semidefinite optimization problem, we design a cutting-plane method which solves the problem to certifiable optimality at the scale of selecting k=5 covariates from p=300 variables, and provides small bound gaps at a larger scale. We also propose a convex relaxation and greedy rounding scheme that provides bound gaps of $1-2\%$ in practice within minutes for $p=100$s or hours for $p=1,000$s and is therefore a viable alternative to the exact method at scale. Using real-world financial and medical datasets, we illustrate our approach's ability to derive interpretable principal components tractably at scale.
description: Revision submitted to JMLR
Development of a Laser Double-wire Directed Energy Deposition Process for Functionally Graded Materials and In-situ alloying
Creators: name: Schwarz, Nick
name: Hermsdorf, Jörg
name: Ahlers, Henning
name: Lachmayer, Roland
Publisher: name: Hannover : Institutionelles Repositorium der Leibniz Universität Hannover
Year: 2024
Subjects: subject: Functionally Graded Materials
subject: Laser Double-wire Directed Energy Deposition
subject: Directed Energy Deposition
subject: Laser Metal Deposition
subject: IPDAM
subject: SAM
subject: Dewey Decimal Classification::600 | Technik

description: Development of a Laser Double-wire Directed Energy Deposition process (LD-DED). Utilizing high material efficiency of the laser wire process for multi-material additive manufacturing. Enabling omnidirectional wire based build up of in-situ fabricated alloys and Functionally Graded Materials