114 research outputs found
Optimization of Moulding Composition for Quality Improvement of Sand Casting
Sand casting is a versatile and commonly used manufacturing process in the metal casting industry. This method can be used in almost all types of metal and the sand is recyclable. However, the defects in casting production such as blowholes, pinholes, shrinkage, and porosity cause imperfection in green sand moulding. The aim of this project is to optimise the composition of silica sand, bentonite, water, and coal dust in green sand to reduce the defects in the casting products using the 24-factorial experiment design method, which can produce a total of 16 runs for experiment to investigate the ratio of the four parameters. Then the experiment results of compression strength are collected and the composition effect of green sand was investigated. The results shows value of the adjusted R-square indicated that 86.92% of the total variability was explained by the model and the model predicted and actual fitted well with the experiment data. An analysis using the Design Expert software identified that bentonite and water are the main interaction effects in all of the experiments. The optimal settings for green sand composition are 95g silica sand, 24g bentonite, 8g water, and 8g coal dust. This composition has an effect of compression strength 35kN/m2
Anomalous dimensions and phase transitions in superconductors
The anomalous scaling in the Ginzburg-Landau model for the superconducting
phase transition is studied. It is argued that the negative sign of the
exponent is a consequence of a special singular behavior in momentum space. The
negative sign of comes from the divergence of the critical correlation
function at finite distances. This behavior implies the existence of a Lifshitz
point in the phase diagram. The anomalous scaling of the vector potential is
also discussed. It is shown that the anomalous dimension of the vector
potential has important consequences for the critical dynamics in
superconductors. The frequency-dependent conductivity is shown to obey the
scaling . The prediction is
obtained from existing Monte Carlo data.Comment: RevTex, 20 pages, no figures; small changes; version accepted in PR
Resonant and nonresonant D+ -> K- pi+ l+ nu(l) semileptonic decays
We analyse the semileptonic decay D+ -> K- pi+ l+ nu(l) using an effective
Lagrangian developed previously to describe the decays D -> P l nu(l) and D ->
V l nu(l). Light vector mesons are included in the model which combines the
heavy quark effective Lagrangian and chiral perturbation theory approach. The
nonresonant and resonant contributions are compared. With no new parameters the
model correctly reproduces the measured ratio Gamma(nres)/Gamma(nres + res). We
also present useful nonresonant decay distributions. Finally, a similar model,
but with a modified current which satisfies the soft pion theorems at the
expense of introducing another parameter, is analyzed and the results of the
models are compared.Comment: 17 pages, 3 Postscript figures, standard Latex, extended revision,
title, abstract and text (especially Sec. IV) changed, results unchange
Nonleptonic Weak Decays of Bottom Baryons
Cabibbo-allowed two-body hadronic weak decays of bottom baryons are analyzed.
Contrary to the charmed baryon sector, many channels of bottom baryon decays
proceed only through the external or internal W-emission diagrams. Moreover,
W-exchange is likely to be suppressed in the bottom baryon sector.
Consequently, the factorization approach suffices to describe most of the
Cabibbo-allowed bottom baryon decays. We use the nonrelativistic quark model to
evaluate heavy-to-heavy and heavy-to-light baryon form factors at zero recoil.
When applied to the heavy quark limit, the quark model results do satisfy all
the constraints imposed by heavy quark symmetry. The decay rates and up-down
asymmetries for bottom baryons decaying into and
are calculated. It is found that the up-down asymmetry is negative except for
decay and for decay modes with in the final
state. The prediction for
is consistent with the recent CDF measurement. We also present
estimates for decays and compare with various model
calculations.Comment: 24 pages, to appear in Phys. Rev. Uncertainties with form factor q^2
dependence are discusse
Pharmacognostic and Acute Toxicity Study of Burkea Africana Root
Burkea africana is a plant that belongs to then family Fabaceae; it is widely spread in tropical Africa including Nigeria. It is of valuable in ethnomedicine especially in the treatment of antidote for venomous stings and bites, cutaneous and sub cutaneous parasitic infection, convulsion and pulmonary troubles. Despite the fact that roots of Burkea africana have several medicinal properties, no standardization parameter has been assessed. Due to lack of standard parameters, proper identification and ascertaining quality and purity in the events of adulteration has been thwarted. The objective of the study was to establish some important pharmacognostic profile and safety margin of Burkea africana root with the hope of assisting in its standardization for quality, purity and safety. Elemental analysis was carried out using acid digestion method and phytochemical composition of the plants was evaluated using standard method. Acute toxicity was achieved using Lorke method to determine the LD50. Chemomicroscopical evaluation revealed the presence of cellulose, tannins, starch, lignin, calcium oxalate, suberin, aleurone grain and mucilage with the exception of calcium carbonate. The average moisture contents, total ash, acid insoluble, water soluble ash, alcohol extractive value and water extractive values in the powdered plant material were 3.8%, 7.5%, 4.43%, 8.07%, 25.0% and 20.33% respectively. In addition, Fe, Mn, Ni, Pb, Cd and Cu were found to be within the safety limit. Phytochemicals which include alkaloids, flavonoids, saponins, tannins, carbohydrates and triterpenes were detected in both aqueous and methanolic extracts. The LD50 of Burkea africana was found to be greater than 5000 mg /kg and could be considered safe for consumption.
Keywords: Elemental analysis, Burkea africana, Pharmacognostic, Phytochemica
Effective Lagrangian Approach to the Theory of Eta Photoproduction in the Region
We investigate eta photoproduction in the resonance region
within the effective Lagrangian approach (ELA), wherein leading contributions
to the amplitude at the tree level are taken into account. These include the
nucleon Born terms and the leading -channel vector meson exchanges as the
non-resonant pieces. In addition, we consider five resonance contributions in
the - and - channel; besides the dominant , these are:
and . The amplitudes for the
and the photoproduction near threshold have significant
differences, even as they share common contributions, such as those of the
nucleon Born terms. Among these differences, the contribution to the
photoproduction of the -channel excitation of the is the most
significant. We find the off-shell properties of the spin-3/2 resonances to be
important in determining the background contributions. Fitting our effective
amplitude to the available data base allows us to extract the quantity
, characteristic of the
photoexcitation of the resonance and its decay into the
-nucleon channel, of interest to precise tests of hadron models. At the
photon point, we determine it to be from
the old data base, and from a
combination of old data base and new Bates data. We obtain the helicity
amplitude for to be from the old data base, and from the combination of the old data base and new Bates
data, compared with the results of the analysis of pion photoproduction
yielding , in the same units.Comment: 43 pages, RevTeX, 9 figures available upon request, to appear in
Phys. Rev.
Measurement of the branching ratio Î(Îbâ° â Ď(2S)Î0)/Î(Îbâ° â J/ĎÎ0) with the ATLAS detector
An observation of the decay and
a comparison of its branching fraction with that of the decay has been made with the ATLAS detector in
proton--proton collisions at TeV at the LHC using an integrated
luminosity of fb. The and mesons are
reconstructed in their decays to a muon pair, while the decay is exploited for the baryon reconstruction. The
baryons are reconstructed with transverse momentum GeV and pseudorapidity . The measured branching ratio of
the and decays is , lower than the expectation from the
covariant quark model.Comment: 12 pages plus author list (28 pages total), 5 figures, 1 table,
published on Physics Letters B 751 (2015) 63-80. All figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2013-08
Track D Social Science, Human Rights and Political Science
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd
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