400 research outputs found
Mechanical Properties of Friction Stir-Welded Joints of Aluminum Alloys
Mechanical properties, intergranular corrosion, and a chemical composition of the welded joint, produced with friction stir welding of a 6061T651 aluminum alloy were investigated. The results show that the welded seam is uniform, with a smooth surface. There are no deformation and defects, such as cracks or gas-filled porosity. The average tensile strength of welded joints is 73% of that of the base material, while the average yield strength and elongation are only 54% and 43% of those of the base material. After intergranular corrosion, microhardness changes evidently and corrosion resistance is lower in the root of the weld nugget zone. The change in microhardness is not pronounced in the weld nugget zone and welded surface, but the change in microhardness is well-pronounced and corrosion resistance is lower in the thermomechanically- and heat-affected zones.Исследованы механические свойства, межкристаллитная коррозия и химический состав сварного шва, полученного ротационной сваркой трением, алюминиевого сплава 6061Т651. Результаты показывают, что сварной шов равномерен, имеет гладкую поверхность. Отсутствуют деформация и такие дефекты, как трещины или газонасыщенная пористость. Средний предел прочности при растяжении для сварных соединений составляет 73% такового для основного материала, тогда как предел текучести и удлинение лишь 54 и 43% соответственно для основного материала. После межкристаллитной коррозии микротвердость явно изменяется, и коррозионная стойкость ниже у основания зоны ядра сварной точки. В зоне ядра сварной точки и на поверхности не наблюдается изменения микротвердости, хотя изменение микротвердости явно выражено, а коррозионная стойкость ниже в зонах термомеханического и термического влияния
A hybrid algorithm to improve the accuracy of support vector machines on skewed data-sets
Over the past few years, has been shown that generalization power of Support Vector Machines (SVM) falls dramatically on imbalanced data-sets. In this paper, we propose a new method to improve accuracy of SVM on imbalanced data-sets. To get this outcome, firstly, we used undersampling and SVM to obtain the initial SVs and a sketch of the hyperplane. These support vectors help to generate new artificial instances, which will take part as the initial population of a genetic algorithm. The genetic algorithm improves the population in artificial instances from one generation to another and eliminates instances that produce noise in the hyperplane. Finally, the generated and evolved data were included in the original data-set for minimizing the imbalance and improving the generalization ability of the SVM on skewed data-sets
Sign reversal of the Hall resistance in the mixed-state of La CeCuO and LaCe(CuCo)O thin films
The transport properties of LaCeCuO(LCCO) and
LaCe(CuCo)O (LCCO:Co) superconducting
thin films are investigated. When the external field is applied along
the crystallographic c-axis, a double sign reversal of the Hall voltage in the
mixed state of LCCO:Co thin films is observed whereas a single sign reversal is
detected in LCCO. A double sign reversal of the Hall signal in LCCO can be
recovered if the magnetic field is tilted away from the plane of the film. We
find that the transition from one to two of the Hall sign reversal coincides
with the change in the pinning from strong to weak. This temperature/field
induced transition is caused either by the magnetic impurities in LCCO:Co or by
the coupling between the pancake vortices and the in-plane Josephson vortices
in LCCO. These results are in agreement with early theoretical and numerical
predictions.Comment: 6 pages, 4 figures, the proceedings of VORTEX VII in Physica
A study of charged kappa in
Based on events collected by BESII, the decay
is studied. In the invariant mass
spectrum recoiling against the charged , the charged
particle is found as a low mass enhancement. If a Breit-Wigner function of
constant width is used to parameterize the kappa, its pole locates at MeV/. Also in this channel,
the decay is observed for the first time.
Its branching ratio is .Comment: 14 pages, 4 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
The pole in
Using a sample of 58 million events recorded in the BESII detector,
the decay is studied. There are conspicuous
and signals. At low mass, a large
broad peak due to the is observed, and its pole position is determined
to be - MeV from the mean of six analyses.
The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
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