15,444 research outputs found
Measurement of deformation gradients in hot rolling of AA3004
In this paper we describe an experimental technique developed to measure the deformation gradients and temperature in a single hot rolling pass of an AA3004 sample that was fitted with an insert. The insert had been previously hand engraved with a 1 × 1 mm grid pitch, and the analysis of the data digitally captured from the image of the deformed grid enabled the calculation of the components of the deformation gradient tensor. Four steel pins prevented relative motion between the insert and the rest of the sample. No detachment was observed between insert and sample after rolling. The temperature was measured during rolling using two embedded thermocouples, one close to the surface and the other in the centerline. The commercial finite element code ABAQUS was used to create a three-dimensional model of the rolling process. The recorded temperature was compared to the numerical values evaluated after tuning the heat transfer coefficient. The shape of the grid after rolling was checked against the deformed mesh using different friction coefficients in order to obtain the optimum match. The unusually large length of the insert enabled the rolling process to be stopped halfway so that a picture of the roll-gap area could be obtained. This provided a partially deformed grid that represented the transient state during rolling. The experimentally determined deformation gradient in this area as well as in the steady-state area agreed well with the finite element predictions. © 2005 Society for Experimental Mechanics
Evaluation of auto regressive integrated moving average (arima) and artificial neural networks (ann) in the prediction of effluent quality of a wastewater treatment system
The main objective of wastewater treatment is to purify the water by degradation of organic matter in the water to anenvironmentally friendly status. To achieve this objective, some effluent (waste water) quality parameters such asChemical oxygen demand (COD) and Biochemical oxygen demand (BOD5) should be measured continuously in orderto meet up with the said objective and regulatory demands. However, through the prediction on water qualityparameters, effective guidance can be provided to comply with such demand without necessarily engaging in rigorouslaboratory analysis. Box-Jenkin’s Auto Regressive Integrated Moving Average (ARIMA) technique is one of the mostrefined extrapolation techniques for prediction while Artificial Neural Network (ANN) is a modern non-linear methodalso used for prediction. The Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Root MeanSquare Error (RMSE) and Correlation coefficient (r) are used to evaluate the accuracy of the above-mentionedmodels. This paper examined the efficiency of ARIMA and ANN models in prediction of two major water qualityparameters (COD and BOD5) in a wastewater treatment plant. With the aid of R software, it was concluded that in allthe error estimates, ANNs models performed better than the ARIMA model, hence it can be used in the operation ofthe treatment system
Mean proton and alpha-particle reduced widths of the Porter-Thomas distribution and astrophysical applications
The Porter-Thomas distribution is a key prediction of the Gaussian orthogonal ensemble in random matrix theory. It is routinely used to provide a measure for the number of levels that are missing in a given resonance analysis. The Porter-Thomas distribution is also of crucial importance for estimates of thermonuclear reaction
rates where the contributions of certain unobserved resonances to the total reaction rate need to be taken into account. In order to estimate such contributions by randomly sampling over the Porter-Thomas distribution,
the mean value of the reduced width must be known. We present mean reduced width values for protons and α particles of compound nuclei in the A = 28–67 mass range. The values are extracted from charged-particle
elastic scattering and reaction data that weremeasured at the riangle Universities Nuclear Laboratory over several decades. Our new values differ significantly from those previously reported that were based on a preliminary analysis of a smaller data set. As an example for the application of our results, we present new thermonuclear rates for the 40Ca(α,γ)44Ti reaction, which is important for 44Ti production in core-collapse supernovae, and compare with previously reported results.Peer ReviewedPostprint (published version
Effect of Cyclophosphoramide, 6-Mercaptopurine, Actinomycin D and Vincaleukoblastine on the Acquisition of Delayed Hypersensitivity (DNCB Contact Dermatitis) in the Guinea-Pig11From the Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia 4, Pennsylvania.This study was supported in part by U.S.P.H.S. Training Grant 2 G-62.This investigation was carried out during the tenure of a postdoctoral fellowship, held by Dr. Maibach, from the Division of General Medical Sciences, United States Public Health Service.Cyclophosphoramide (Cytoxan®) was supplied by Paul A. Walter, M.D., Mead Johnson Laboratories, Evansville 21, Indiana; 6-mercaptopurine by Donald S. Searle, M.D., Burroughs Wellcome & Co., Tuckahoe, N.Y.; vincaleukoblastine by J. A. Armstrong, M.D., Eli Lilly and Co., Indianapolis 6, Indiana; and Actinomycin D by Elmer Alpert, M.D., Merck Sharp and Dohme, West Point, Pa.Presented at the Twenty-second Annual Meeting of The Society for Investigative Dermatology, Inc., New York, N.Y., June 28, 1961.
The dark side of humanity scale: A reconstruction of the Dark Tetrad constructs
There has been an absence of consideration regarding measurement invariance across males and females in the widely available Dark Tetrad (DT) scales which measure psychopathy, Machiavellianism, narcissism and everyday sadism. This has resulted in criticisms of the measures, suggesting that the assessed constructs are not wholly relatable between the groups. This article documents the construction and validation of the Dark Side of Humanity Scale (DSHS), which measures dark personalities from an alternative viewpoint, determined by the constructs as they emerged from the male and female data, whilst aligning with theory and attaining invariance between sex. Across four samples (n = 2409), using a diverse range of statistical methods, including exploratory graph analysis, item response theory and confirmatory factor analysis, a divergence from the widely available DT measures emerged, whereby primary psychopathy and Machiavellianism were unified. This corroborated past research which had discussed the two constructs as being parallel. It further supported the DSHS with a shift away from the traditional DT conceptualisation. The resulting scale encompasses four factors which are sex invariant across samples and time. The first factor represents the successful psychopath, factor two addresses the grandiose form of entitlement, factor three taps into everyday sadism whilst the fourth factor pertains to narcissistic entitlement rage. Construct and external validity of the DSHS across two samples (n = 1338), as well as test-retest reliability (n = 413), was achieved. The DSHS provides an alternative approach to investigating the dark side of human nature, whilst also being sex invariant, thus making it highly suitable for use with mixed sex samples
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Correlated modal mineralogy, aqueous alteration and oxygen isotope composition of CM Chondrites
In this study we move beyond defining alteration sequences in CM chondrites towards understanding the relationship between modal mineralogy, the extent of aqueous alteration and O-isotope compositions
Hydrodynamic induced deformation and orientation of a microscopic elastic filament
We describe simulations of a microscopic elastic filament immersed in a fluid
and subject to a uniform external force. Our method accounts for the
hydrodynamic coupling between the flow generated by the filament and the
friction force it experiences. While models that neglect this coupling predict
a drift in a straight configuration, our findings are very different. Notably,
a force with a component perpendicular to the filament axis induces bending and
perpendicular alignment. Moreover, with increasing force we observe four shape
regimes, ranging from slight distortion to a state of tumbling motion that
lacks a steady state. We also identify the appearance of marginally stable
structures. Both the instability of these shapes and the observed alignment can
be explained by the combined action of induced bending and non-local
hydrodynamic interactions. Most of these effects should be experimentally
relevant for stiff micro-filaments, such as microtubules.Comment: three figures. To appear in Phys Rev Let
Persistence in the Voter model: continuum reaction-diffusion approach
We investigate the persistence probability in the Voter model for dimensions
d\geq 2. This is achieved by mapping the Voter model onto a continuum
reaction-diffusion system. Using path integral methods, we compute the
persistence probability r(q,t), where q is the number of ``opinions'' in the
original Voter model. We find r(q,t)\sim exp[-f_2(q)(ln t)^2] in d=2;
r(q,t)\sim exp[-f_d(q)t^{(d-2)/2}] for 2<d<4; r(q,t)\sim exp[-f_4(q)t/ln t] in
d=4; and r(q,t)\sim exp[-f_d(q)t] for d>4. The results of our analysis are
checked by Monte Carlo simulations.Comment: 10 pages, 3 figures, Latex, submitted to J. Phys. A (letters
Entanglement of indistinguishable particles in condensed matter physics
The concept of entanglement in systems where the particles are
indistinguishable has been the subject of much recent interest and controversy.
In this paper we study the notion of entanglement of particles introduced by
Wiseman and Vaccaro [Phys. Rev. Lett. 91, 097902 (2003)] in several specific
physical systems, including some that occur in condensed matter physics. The
entanglement of particles is relevant when the identical particles are
itinerant and so not distinguished by their position as in spin models. We show
that entanglement of particles can behave differently to other approaches that
have been used previously, such as entanglement of modes (occupation-number
entanglement) and the entanglement in the two-spin reduced density matrix. We
argue that the entanglement of particles is what could actually be measured in
most experimental scenarios and thus its physical significance is clear. This
suggests entanglement of particles may be useful in connecting theoretical and
experimental studies of entanglement in condensed matter systems.Comment: 13 pages, 6 figures, comments welcome, published version (minor
changes, added references
Acute biological effects of chemically dispersed oil spillage : final report to the American Petroleum Institute
Primary productivity, heterotrophic potential, chlorophyll i! and phaeophytin, ATP, and direct bacterial counts were measured in the sea surface layer under controlled spills of La Rosa and Murban crude oils following immediate dispersal with the EXXON dispersant, Corexit 9527. Tests were conducted off New York on November 9, 1978.
The response of productivity to dispersed oil appeared as an initial increase in rates, a reduction to minimal rates 1-2 hours after dispersion, and a return to pre-spill rates after 3 hours. Comparison of productivity measurements from the two tests suggested a more efficient and rapid dispersion of the somewhat lighter La Rosa crude. Heterotrophic uptake at one meter below the La Rosa spill mirrored productivity results; missing samples at the Murban spill prohibited interpretation.
While oil and dispersant appeared to have little effect on chlorophyll-~ and direct bacterial counts, ATP concentrations decreased· to below detectable limits shortly after the application of the dispersant. Phaeophytin, expressed as a percentage of chlorophyll, varied inversely with ATP in both tests
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