261 research outputs found
Microstructures and mechanical properties of as cast Mg‐Zr‐Ca alloys for biomedical applications
The microstructures and mechanical properties of as cast Mg-Zr-Ca alloys were investigated for potential use in biomedical applications. The Mg-Zr-Ca alloys were fabricated by commercial pure Mg (99.9 mass-%), Ca (99.9 mass-%) and master Mg-33 mass-%Zr alloy. The microstructures of the alloys were examined by X-ray diffraction analysis and optical microscopy, and the mechanical properties were determined from tensile tests. The experimental results indicate that the Mg-Zr-Ca alloys with 1 mass-%Ca are composed of one single a phase; these alloys with 2 mass-%Ca consist of both Mg 2Ca and α phase, and all the alloys exhibit typical coarse microstructures. An increase in Zr increases the strength of Mg-Zr-Ca alloys with 1 mass-%Ca, and the formation of Mg2Ca decreases the strength of the alloys. Mg-1Zr-1Ca alloy (mass-%) has the highest strength and best ductility among all the studied alloys
Ground state of a polydisperse electrorheological solid: Beyond the dipole approximation
The ground state of an electrorheological (ER) fluid has been studied based
on our recently proposed dipole-induced dipole (DID) model. We obtained an
analytic expression of the interaction between chains of particles which are of
the same or different dielectric constants. The effects of dielectric constants
on the structure formation in monodisperse and polydisperse electrorheological
fluids are studied in a wide range of dielectric contrasts between the
particles and the base fluid. Our results showed that the established
body-centered tetragonal ground state in monodisperse ER fluids may become
unstable due to a polydispersity in the particle dielectric constants. While
our results agree with that of the fully multipole theory, the DID model is
much simpler, which offers a basis for computer simulations in polydisperse ER
fluids.Comment: Accepted for publications by Phys. Rev.
Added Value of Computed Tomography Virtual Intravascular Endoscopy in the Evaluation of Coronary Arteries with Stents or Plaques
Coronary computed tomography angiography (CCTA) is a widely used imaging modality for diagnosing coronary artery disease (CAD) but is limited by a high false positive rate when evaluating coronary arteries with stents and heavy calcifications. Virtual intravascular endoscopy (VIE) images generated from CCTA can be used to qualitatively assess the vascular lumen and might be helpful for overcoming this challenge. In this study, one hundred subjects with coronary stents underwent both CCTA and invasive coronary angiography (ICA). A total of 902 vessel segments were analyzed using CCTA and VIE. The vessel segments were first analyzed on CCTA alone. Then, using VIE, the segments were classified qualitatively as either negative or positive for in-stent restenosis (ISR) or CAD. These results were compared, using ICA as the reference, to determine the added diagnostic value of VIE. Of the 902 analyzed vessel segments, CCTA/VIE had sensitivity, specificity, accuracy, positive predictive value, and negative predictive value (shown in %) of 93.9/90.2, 96.2/98.2, 96.0/97.7, 70.0/83.1, and 99.4/99.0, respectively, in diagnosing ISR or CAD, with significantly improved specificity (p = 0.025), accuracy (p = 0.046), and positive predictive value (p = 0.047). VIE can be a helpful addition to CCTA when evaluating coronary arterie
Medium-evolved fragmentation functions
Medium-induced gluon radiation is usually identified as the dominant
dynamical mechanism underling the {\it jet quenching} phenomenon observed in
heavy-ion collisions. In its actual implementation, multiple medium-induced
gluon emissions are assumed to be independent, leading, in the eikonal
approximation, to a Poisson distribution. Here, we introduce a medium term in
the splitting probabilities so that both medium and vacuum contributions are
included on the same footing in a DGLAP approach. The improvements include
energy-momentum conservation at each individual splitting, medium-modified
virtuality evolution and a coherent implementation of vacuum and medium
splitting probabilities. Noticeably, the usual formalism is recovered when the
virtuality and the energy of the parton are very large. This leads to a similar
description of the suppression observed in heavy-ion collisions with values of
the transport coefficient of the same order as those obtained using the {\it
quenching weights}.Comment: LaTeX, 18 pages, 13 figures included using epsfig, uses JHEP3; v2:
enlarged discussions, one figure replaced, some references added, final
versio
Anti-plane interfacial crack with functionally graded coating: static and dynamic
The anti-plane displacement discontinuity method is applied to establish the Fredholm integral equation of the first kind for the orthotropic Functionally Graded Material (FGM) coatings subjected to static/dynamic shears. The shear modulus and mass density are assumed to vary exponentially through the thickness. The static and dynamic fundamental solutions with anti-plane displacement discontinuity are derived for orthotropic FGM coating by using Fourier transform method and Laplace transform method. It has been shown that the transformed fundamental solution with orthotropic coatings has the same order of hyper-singularity as in the static case, i.e. O(1/r2), and the Chebyshev polynomials of the second kind are used to solve the integral equations numerically. The time dependent stress intensity factors are obtained directly from the coefficients of the Chebyshev polynomials with the aid of Durbin’s Laplace transform inversion method. A comparative study of FGM versus homogeneous coating is conducted, and the dependence of the stress intensity factors in the coating/substrate system on the material property (orthotropic) and thickness of coating is examined. Two examples including the static/dynamic loads are given as benchmarks for the numerical methods and application in composite engineering
Novel D-hordein-like HMW glutenin sequences isolated from Psathyrostachys juncea by thermal asymmetric interlaced PCR
New high-molecular-weight glutenin (HMW glutenin) sequences isolated from six Psathyrostachys juncea accessions by thermal asymmetric interlaced PCR differ from previous sequences from this species. They showed novel modifications in all of the structural domains, with unique C-terminal residues, and their N-terminal lengths were the longest among the HMW glutenins reported to date. In their repetitive domains, there were three repeatable motif units: 13-residue [GYWH(/I/Y)YT(/Q)S(/T)VTSPQQ], hexapeptide (PGQGQQ), and tetrapeptide (ITVS). The 13-residue repeats were restricted to the current sequences, while the tetrapeptides were only shared by D-hordein and the current sequences. However, these sequences were not expressed as normal HMW glutenin proteins because an in-frame stop codon located in the C-termini interrupted the intact open reading frames. A phylogenetic analysis supported different origins of the P. juncea HMW glutenin sequences than that revealed by a previous study. The current sequences showed a close relationship with D-hordein but appeared to be more primitive
Science Development
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68479/2/10.1177_107554708500600404.pd
Tightly Coupled Array Antennas for Ultra-Wideband Wireless Systems
Tightly coupled array (TCA) antenna has become a hot topic of research recently, due to its
potential of enabling one single antenna array to operate over an extremely wide frequency range. Such an
array antenna is promising for applications in numerous wideband/multi-band and multi-function wireless
systems such as wideband high-resolution radars, 5G mobile communications, satellite communications,
global navigation satellite systems, sensors, wireless power transmission, internet of things and so on. Many
papers on this topic have been published by researchers internationally. This paper provides a detailed
review of the recent development on TCA that utilizes the capacitive coupling. The basic principles and the
historical evolution of the TCAs are introduced firstly. Then, recent development in the analysis and design
of TCAs, such as equivalent circuit analysis, bandwidth limitation analysis, array elements, feed structures,
substrates/superstrates loading, etc., are explained and discussed. The performances of the state-of-the-art
TCAs are presented and a comparison amongst some TCAs reported recently is summarized and discussed.
To illustrate the practical designs of TCA, one case study is provided, and the detailed design procedures of
the TCA are explained so as to demonstrate the TCA design methodology. Simulated results including the
VSWR at different angles of scanning, patterns and antenna gain are shown and discussed. A conclusion
and future work are given in the end
Lyapunov spectrum of asymptotically sub-additive potentials
For general asymptotically sub-additive potentials (resp. asymptotically
additive potentials) on general topological dynamical systems, we establish
some variational relations between the topological entropy of the level sets of
Lyapunov exponents, measure-theoretic entropies and topological pressures in
this general situation. Most of our results are obtained without the assumption
of the existence of unique equilibrium measures or the differentiability of
pressure functions. Some examples are constructed to illustrate the
irregularity and the complexity of multifractal behaviors in the sub-additive
case and in the case that the entropy map that is not upper-semi continuous.Comment: 44 page
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