1,330 research outputs found

    Numerical evaluation of three non-coaxial kinematic models using the distinct element method for elliptical granular materials

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    This is the accepted version of the following article: [Jiang, M. J., Liu, J. D., and Arroyo, M. (2016) Numerical evaluation of three non-coaxial kinematic models using the distinct element method for elliptical granular materials. Int. J. Numer. Anal. Meth. Geomech., 40: 2468–2488. doi: 10.1002/nag.2540.], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/nag.2540/fullThis paper presents a numerical evaluation of three non-coaxial kinematic models by performing Distinct Element Method (DEM) simple shear tests on specimens composed of elliptical particles with different aspect ratios of 1.4 and 1.7. The models evaluated are the double-shearing model, the double-sliding free-rotating model and the double slip and rotation rate model (DSR2 model). Two modes of monotonic and cyclic simple shear tests were simulated to evaluate the role played by the inherent anisotropy of the specimens. The main findings are supported by all the DEM simple shear tests, irrespective of particle shape, specimen density or shear mode. The evaluation demonstrates that the assumption in the double-shearing model is inconsistent with the DEM results and that the energy dissipation requirements in the double-sliding free-rotating model appear to be too restrictive to describe the kinematic flow of elliptical particle systems. In contrast, the predictions made by the DSR2 model agree reasonably well with the DEM data, which demonstrates that the DSR2 model can effectively predict the non-coaxial kinematic behavior of elliptical particle systems.Peer ReviewedPostprint (author's final draft

    TransverseDiff gravity is to scalar-tensor as unimodular gravity is to General Relativity

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    Transverse Diffeomorphism (TDiff) theories are well-motivated theories of gravity from the quantum perspective, which are based upon a gauge symmetry principle. The main contribution of this work is to firmly establish a correspondence between TransverseDiff and the better-known scalar-tensor gravity --- in its more general form ---, a relation which is completely analogous to that between unimodular gravity and General Relativity. We then comment on observational aspects of TDiff. In connection with this proof, we derive a very general rule that determines under what conditions the procedure of fixing a gauge symmetry can be equivalently applied before the variational principle leading to the equations of motion, as opposed to the standard procedure, which takes place afterwards; this rule applies to gauge-fixing terms without derivatives.Comment: 10 pages; amsart style; v3: version as appeared in JCAP, redaction improve

    The Human Factor in Transmission Network Expansion Planning: The Grid That a Sustainable Energy System Needs

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    The decarbonization of the energy sector puts additional pressure on the transmission network. The main cause for this is that renewable sources are often more abundant in geographical areas far away from the main demand centers, so new transmission lines are required to connect the new renewable energy capacity. In addition, by connecting different geographical zones, the transmission network could smooth the intermittency and the variability of renewable energy production. Thus, the changing energy landscape leads to a need to reinforce the transmission network through the Network Transmission Expansion Planning. Ideally, all the idiosyncrasies of the electricity system are considered in the operation and expansion planning process. However, several critical dimensions of the planning process are routinely ignored since they may introduce parameters that are difficult to quantify and complexity that state-of-the-art planning methods cannot handle. This paper identifies the most relevant elements related to the human factor, which have been grouped around the main topics: the human behind the technical, the human at the institutional level, and the human at the individual level. This paper also provides an additional formulation that can be used to upgrade existing models to include the human element and discusses the implications of these upgrades. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research has been carried out thanks to the Spanish Ministry of Economy and Competitiveness MINECO through BC3 María de Maeztu excellence accreditation MDM-2017-0714 Maria de Maeztu Grant, and through the funding of openENTRANCE project (Open ENergy TRansition ANalyses for a low-carbon Economy) that belongs to LC-SC3-CC-2-2018—Modelling in support to the transition to a Low-Carbon Energy System in Europe

    Novel glassy behavior in a ferromagnetic p-spin model

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    Recent work has suggested the existence of glassy behavior in a ferromagnetic model with a four-spin interaction. Motivated by these findings, we have studied the dynamics of this model using Monte Carlo simulations with particular attention being paid to two-time quantities. We find that the system shares many features in common with glass forming liquids. In particular, the model exhibits: (i) a very long-lived metastable state, (ii) autocorrelation functions that show stretched exponential relaxation, (iii) a non-equilibrium timescale that appears to diverge at a well defined temperature, and (iv) low temperature aging behaviour characteristic of glasses.Comment: 6 pages, 5 figure

    Extended Supersymmetries and the Dirac Operator

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    We consider supersymmetric quantum mechanical systems in arbitrary dimensions on curved spaces with nontrivial gauge fields. The square of the Dirac operator serves as Hamiltonian. We derive a relation between the number of supercharges that exist and restrictions on the geometry of the underlying spaces as well as the admissible gauge field configurations. From the superalgebra with two or more real supercharges we infer the existence of integrability conditions and obtain a corresponding superpotential. This potential can be used to deform the supercharges and to determine zero modes of the Dirac operator. The general results are applied to the Kahler spaces CP^n.Comment: 22 pages, no figure

    Cystic Fibrosis At A Brazilian Center Of Excellence: Clinical And Laboratory Characteristics Of 104 Patients And Their Association With Genotype And Disease Severity

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    Objective: To identify the clinical, laboratory and radiographic characteristics of the cystic fibrosis patients under care at Universidade Estadual de Campinas (UNICAMP) in the last decade of the twentieth century, and to investigate the association of these characteristics with genotype and severity of the disease as measured by the Shwachman score. Methods: Descriptive, retrospective and cross-sectional study of the patients assisted at UNICAMP hospital's Cystic Fibrosis Clinic from July 1990 to July 2000. Results: One hundred and four patients were studied; 53.8% male; 93.3% Caucasian; 89.4% presented with respiratory symptoms; 59.6% presented with digestive symptoms; 5.8% had meconium ileus; 4.8% had diabetes. The mean age at onset of symptoms was 3 months, and the mean age at diagnosis was 2 years and 4 months. At diagnosis, 69.9 and 56.6% of the patients had weight and height below 10th percentile, respectively; in 10.6%, sweat chloride was < 60 mEq/l. Staphylococcus aureus was found in 80.2%, Pseudomonas aeruginosa in 76.0%, and Burkholderia cepacia in 5.2%. ΔF508 homozygosis was observed in 18.75%, whereas 62.50% of the patients were ΔF508 heterozygous. A moderate/severe Shwachman score was found in 15.7%. Eighteen patients died in that period (17.3%). The mean age at death was 7 years and 8 months; median survival after diagnosis was 18 years and 4 months. Patients who have at least one ΔF508 mutation have more frequent alterations in fecal fat levels when compared to patients who do not have this mutation (p < 0.05). There were no differences in any parameter between ΔF508 homozygous and heterozygous patients. Conclusions: The clinical and laboratory characteristics of the 104 patients studied were similar to the characteristics described for patients in other countries. Exceptions are the higher age at diagnosis and lower survival. Our results support the recommendation for early diagnosis and the need for more treatment opportunities in the population of cystic fibrosis patients. 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    A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La

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    An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1/10th scale test of the design for the forthcoming n+p->d+gamma experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current mode readout, measurements were made of asymmetries in gamma-ray emission following neutron capture on 35Cl, 113Cd, and 139La targets. Upper limits on the parity-allowed asymmetry sn⋅(kγ×kn)s_n \cdot (k_{\gamma} \times k_n) were set at the level of 7 x 10^-6 for all three targets. Parity-violating asymmetries sn⋅kγs_n \cdot k_{\gamma} were observed in 35Cl, A_gamma = (-29.1 +- 6.7) x 10^-6, and 139La, A_gamma = (-15.5 +- 7.1) x 10^-6, values consistent with previous measurements.Comment: 19 pages, 4 figures, submitted to Nucl. Instr. and Meth.
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