4,457 research outputs found
Influence of temperature and sliding speed on the subsurface microstructure evolution of EN AW-6060 under sticking friction conditions
Get PDFThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in AIP Conference Proceedings 1896, 140012 (2017) and may be found at https://doi.org/10.1063/1.5008168.The microstructure evolution of the friction boundary layer of the aluminum alloy EN AW-6060 was investigated. Sticking friction tests at different temperatures and sliding speeds were carried out. A severe deformation below the friction surface was observed by means of LOM and EBSD mapping. Thus, the thickness variation and the grain structure of the high deformation zone could be described. Fibrous structure was observed at 300 °C and 400 °C, while equiaxed grains with high misorientation angle (>15°) were generated at higher temperatures. Additionally, abnormal grain growth and coarse grains were detected at high sliding speeds (10 mm/s, 42 mm/s) at 450°C and 500 °C respectively
AW -Convergence and Well-Posedness of Non Convex Functions
No full textLet us consider the set of lower semicontinuous functions defined on a Banach space, equipped with the AW-convergence. A function is called Tikhonov well-posed provided it has a unique minimizer to which every minimizing sequence converges. We show that well-posedness of f guarantees strong convergence of approximate minimizers of τaw -approximating functions (under conditions of equiboundedness of sublevel sets), to the minimizer of f. Moreover we show that a lower semicontinuous function f which satisfies growth conditions at ∞ is well-posed iff its lower semicontinuous convex regularization is. Finally we investigate the link between AW-convergence of non convex integrands and that of the associated integral functionals
Author-Suggested, Weighted Citation Index: A Novel Approach for Determining the Contribution of Individual Researchers
No full textA novel scientometric index, named ‘author-suggested, weighted citation index’ (Aw-index) is proposed to indicate the scientific contribution of any individual researcher. For calculation of the Aw-index, it is suggested that during the submission of a scholarly article, the corresponding author would provide a statement, agreed upon by all the authors, containing weightage factors against each author of the article. The author who contributed more to the article would secure a higher weightage factor. The summation of the weightage factors of all the authors of an article should be unity. The citation points a researcher receives from a scholarly publication is the product of his/her weightage factor for that article and the total number of citations of the article. The Aw-index of any individual researcher is the summation of the citation points he/she receives for all his/her publications as an author. The Aw-index provides the opportunity to the group of authors of a multi-authored article to determine the quantum of partial citations to be attributed to each of them. Through an illustrative example, a comparison of the proposed index with the major scientometric indexes is presented to highlight the advantages of the Aw-index
Ecology of A.carbonarius and ochratoxin A production in vine fruits and control in the production chain
Get PDFThis study examined black aspergilli, especially A. carbonarius and A. niger and
ochratoxin A (OTA) contamination of grapes, during drying and industrial processing
of dried vine fruits. This was complemented by studies on potential control using
preservatives and physical factors such as modified atmospheres. Fungal population
kinetics were determined in relation to grapes at harvest, and during drying at three
different altitudes (sea level: 0-200 m; medium level: 250-500 m; high level: >500 m)
in two seasons. At pre-harvest, A. niger aggregate species were the predominant
fungal species while A. carbonarius was occasionally isolated, in both years studied.
Both altitude and bunch position affected black aspergilli population dynamics.
Overall, they were increased during drying. However, both black aspergilli groups
were mostly isolated, at low and medium altitudes (<500 m). OTA contamination
was influenced by bunch position, although altitude did not significantly influenced
amounts. The fungal biodiversity was decreased during sun-drying of sultanas. The
widest diversity of species occurred at the sea level. However, A. niger aggregate,
were dominant during drying. Time of drying and altitude significantly influenced
fungal loads of black aspergilli. In contrast, OTA production (ca 0.001 - 0.0025 μg g
-
1
) was not significantly influenced by altitude and drying time. Shannon Index of
Biodiversity (H), for pre-harvest and pos-harvest studies, was determined for the first
time.
A. niger aggregate (ca 5.0 Log10 CFUs g
-1
) was predominant during industrial
processing, while A. carbonarius was only isolated at low levels (1.5-2.0 Log10 CFUs
g
-1
). Heat treatment (up to 90
o
C) appeared to be the key-procedure for the
elimination of fungal populations. In the contrary, SO2 treatment did not statistically
alter fungal population dynamics. OTA contamination was not significantly affected
by industrial processing.
In vitro studies conducted on both White Grape Juice Medium (WGJM) and in
sultanas with strains of A. carbonarius originated from Cretan sultanas and compared with a strain isolated from Italian wine grapes. They examined the impact of sodium
metabisulphite (NaMBS), elevated CO2 (up to 50%) concentrations and aw levels, on
black aspergilli spore germination, growth and OTA production. Moreover, fungal
interactions in vitro and in situ were also investigated.
In general, spore germination occurred over a wide range of sodium metabisulphite
concentrations, although germ tube extension was significantly controlled. At ≥ 750
mg L
-1
NaMBS, no spore germination was observed while both mycelial growth and
OTA production were completely inhibited. Medium concentrations of NaMBS (≤
250 mg L
-1
) enabled optimum spore germination, growth and OTA production (x
0.965 aw). The efficacy of controlled atmospheres x aw showed that there was very
little inhibitory effect on spore germination. However, both germ tube extension and
fungal growth were inhibited by 50% CO2. After 10 days, growth was not as
effectively controlled. Aw had a bigger effect on OTA production than modified
atmospheres. In situ experiments on sultanas confirmed these results. Competition
and dominance of A. carbonarius over other fungal species showed that aw and
temperature influenced Indices of Dominance and OTA production. In vitro and in
situ, OTA production by A. carbonarius was significantly influenced by the fungal
competitor used
GWAS of non-adjusted AW.
No full text<p>A. Composite Manhattan plot superimposing the four EMMA scans for non-adjusted AW. Association scores (-log<sub>10 </sub><i>p</i>-value; y-axis) are shown for each chromosomal position (x-axis) tested by EMMA. Suggestive and significant thresholds of association are indicated by orange and red lines, respectively. B. QQ-plots reporting the -log<sub>10</sub> of <i>p</i>-values as obtained by EMMA. The null hypothesis (<i>H<sub>0</sub></i>) is indicated by the dotted line. A strong upper deviation from this line in the region of the lowest <i>p</i>-values is indicative of a true association. C, D. Zoom-in on loci 1 and 2. Genes are displayed as indicated in the NCBI37/mm9 assembly of the UCSC genome browser <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041032#pone.0041032-Fujita1" target="_blank">[86]</a>.</p
Influence of Process Parameters on the Quality of Aluminium Alloy EN AW 7075 Using Selective Laser Melting (SLM)
No full textAbstractSelective laser melting (SLM) is an additive manufacturing process, forming the desired geometry by selective layer fusion of powder material. Unlike conventional manufacturing processes, highly complex parts can be manufactured with high accuracy and little post processing. Currently, different steel, aluminium, titanium and nickel-based alloys have been successfully processed; however, high strength aluminium alloy EN AW 7075 has not been processed with satisfying quality. The main focus of the investigation is to develop the SLM process for the wide used aluminium alloy EN AW 7075. Before process development, the gas-atomized powder material was characterized in terms of statistical distribution: size and shape. A wide range of process parameters were selected to optimize the process in terms of optimum volume density. The investigations resulted in a relative density of over 99%. However, all laser-melted parts exhibit hot cracks which typically appear in aluminium alloy EN AW 7075 during the welding process. Furthermore the influence of processing parameters on the chemical composition of the selected alloy was determined
Zhedanov's Algebra AW(3) and the Double Affine Hecke Algebra in the Rank One Case. II. The Spherical Subalgebra
Get PDFThis paper builds on the previous paper by the author, where a relationship between Zhedanov's algebra AW(3) and the double affine Hecke algebra (DAHA) corresponding to the Askey-Wilson polynomials was established. It is shown here that the spherical subalgebra of this DAHA is isomorphic to AW(3) with an additional relation that the Casimir operator equals an explicit constant. A similar result with q-shifted parameters holds for the antispherical subalgebra. Some theorems on centralizers and centers for the algebras under consideration will finally be proved as corollaries of the characterization of the spherical and antispherical subalgebra
Heterogeneity and anisotropy of Earth's inner core
No full textSeismic observations provide strong evidence that Earth's inner core is anisotropic, with larger velocity in the polar than in the equatorial direction. The top 60-80 km of the inner core is isotropic; evidence for an innermost inner core is less compelling. The anisotropy is most likely due to alignment of hcp (hexagonal close-packed) iron crystals, aligned either during solidification or by deformation afterward. The existence of hemispherical variations used to be controversial, but there is now strong evidence from both seismic body wave and normal mode observations, showing stronger anisotropy, less attenuation, and a lower isotropic velocity in the western hemisphere. Two mechanisms have been proposed to explain the hemispherical pattern: either (a) inner core translation, wherein one hemisphere is melting and the other is solidifying, or (b) thermochemical convection in the outer core, leading to different solidification conditions at the inner core boundary. Neither is (yet) able to explain all seismically observed features, and a combination of different mechanisms is probably required
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Extensions and amplifications of a traffic model of Aw and Rascle
Get PDFIn a recent paper [1] Aw and Rascle introduced a new model of traffic on a uni-directional highway. Here the author studies an extension of this model, one which accounts for drivers attempting to travel at their maximum allowable speed. The author looks at a Lagrangian reformulation of this problem; a formulation that leads to an effective computational algorithm for solving the resulting system. He also investigates approximation scheme introduced by Dafermos [5] for scalar conservation laws and demonstrates that this Dafermos scheme works well on this 2 x 2 system
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