8,837 research outputs found
Microstructure and mechanical properties of ductile aluminium alloy manufactured by recycled materials
The present paper introduces the microstructure and mechanical properties of the Al-Mg- Si-Mn alloy made by recycled materials, in which the impurity levels of iron are mainly concerned. It is found that the increased Fe content reduces the ductility and yield strength but slightly increases the UTS of the diecast alloy. The tolerable Fe content is 0.45wt.%, at which the recycled alloys are still able to produce castings with the mechanical properties of yield strength over 140MPa, UTS over 280MPa and elongation over 15%.The Fe content is steadily accumulated in the alloy with the increase of recycle times. However, after 13 cycles, the recycled alloys are still able to produce ductile alloys with satisfied mechanical properties.The TSB (UK
A New Approach to Large-Scale Nuclear Structure Calculations
A new approach to large-scale nuclear structure calculations, based on the
Density Matrix Renormalization Group (DMRG), is described. The method is tested
in the context of a problem involving many identical nucleons constrained to
move in a single large-j shell and interacting via a pairing plus quadrupole
interaction. In cases in which exact diagonalization of the hamiltonian is
possible, the method is able to reproduce the exact results for the ground
state energy and the energies of low-lying excited states with extreme
precision. Results are also presented for a model problem in which exact
solution is not feasible.Comment: 6 pages + 1 eps figur
Student-Centered Pedagogy: Using Moses’ Five-Step Approach as a Scaffolding Framework to Teach Diverse Learners
In this article, two teacher educators and three preservice teachers reflect on the critical role Moses’ Five-Step Approach (Moses & Cobb, 2001) played as a scaffolding pedagogical framework in preservice teacher and faculty learning. Using Moses’ approach to frame their presentations, preservice teachers work in their groups to teach abstract Educational Psychology concepts to actively engage classmates from diverse backgrounds. During this process, the presenters co-construct knowledge with their peers and instructor, applying the framework by putting common activities and everyday language first before teaching abstract concepts and academic language. The authors, including a preservice teacher who also teaches a university biology course, explicate the process of their experience, beginning with conceptualizing a theme, generating engaging activities that represent the concepts and tap into multimodalities of learning, and breaking down key vocabulary to connect to students’ prior knowledge in a socially constructed environment. The authors reflect on the power of this student-centered framework as well as its challenges. Ultimately, Moses’ approach serves as a liberating framework, allowing diverse learners a common entry point to experience and comprehend complex concepts and vocabulary. This pedagogical framework fosters a rich student-centered environment where students become active agents of their own learning
Implications of X-Ray Line Variations for 4U1822-371
4U 1822-371 is one of the proto-type accretion disk coronal sources with an
orbital period of about 5.6 hours. The binary is viewed almost edge-on at a
high inclination angle of 83 degrees, which makes it a unique candidate to
study binary orbital and accretion disk dynamics in high powered X-ray sources.
We observed the X-ray source in 4U 1822-371 with the Chandra High Energy
Transmission Grating Spectrometer (HETGS) for almost nine binary orbits. X-ray
eclipse times provide an update of the orbital ephemeris. We find that our
result follows the quadratic function implied by previous observations;
however, it suggests a flatter trend. Detailed line dynamics also confirm a
previous suggestion that the observed photo-ionized line emission originates
from a confined region in the outer edge of the accretion disk near the hot
spot. Line properties allow us to impose limits on the size of accretion disk,
the central corona, and the emission region. The photo-ionized plasma is
consistent with ionization parameters of log(xi) > 2, and when combined with
disk size and reasonable assumptions for the plasma density, this suggests
illuminating disk luminosities which are over an order of magnitude higher than
what is actually observed. That is, we do not directly observe the central
emitting X-ray source. The spectral continua are best fit by a flat power law
with a high energy cut-off and partial covering absorption (N_H ranging from
5.4-6.3x10^{22} cm^{-2}) with a covering fraction of about 50%. We discuss some
implications of our findings with respect to the photo-ionized line emission
for the basic properties of the X-ray source.Comment: Submitted to the Astrophysical Journa
Twist-three observables in deeply virtual Compton scattering on the nucleon
We study twist-three effects in deeply virtual Compton scattering on an
unpolarized spin-1/2 target. A careful definition of observables as Fourier
moments w.r.t. the azimuthal angle allows for a clear separation of twist-two
and -three effects. Although the latter are power suppressed, they give leading
contributions to the twist-three asymmetries and do not affect the twist-two
observables.Comment: 10 pages, LaTe
The Impact of QCD and Light-Cone Quantum Mechanics on Nuclear Physics
We discuss a number of novel applications of Quantum Chromodynamics to
nuclear structure and dynamics, such as the reduced amplitude formalism for
exclusive nuclear amplitudes. We particularly emphasize the importance of
light-cone Hamiltonian and Fock State methods as a tool for describing the
wavefunctions of composite relativistic many-body systems and their
interactions. We also show that the use of covariant kinematics leads to
nontrivial corrections to the standard formulae for the axial, magnetic, and
quadrupole moments of nucleons and nuclei.Comment: 25 pages, uuencoded postscript file---To obtain a hard copy of this
paper, send e-mail to [email protected] and ask fo
Thermal and structural properties of unusual starches from developmental corn lines
Starches from exotic corn lines were screened by using differential scanning calorimetry (DSC) to find thermal properties that were significantly different from those exhibited by starches from normal Corn Belt lines. Two independent gelatinization transitions, one corresponding to the melting of a peak at ∼66 °C and the other to a peak melting at ∼69 °C, were found in some starches. The melting characteristics were traced to two separate types of granules within the endosperm. Strong correlations were found between DSC properties and proportion of large granules with equivalent diameter ≥17 μm. Starches with a lower peak onset gelatinization temperature (ToG), had a lower normalized concentration of chains with a degree of polymerization (dp) of 15–24 and/or a greater normalized concentration of chains with a dp of 6–12. These studies will aid in understanding structure–thermal property relationships of starches, and in identifying corn lines of interest for commercial breeding
Prediction of prostate cancer Gleason score upgrading from biopsy to radical prostatectomy using pre-biopsy multiparametric MRI PIRADS scoring system
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