2,386 research outputs found
Superconducting transition of a two-dimensional Josephson junction array in weak magnetic fields
The superconducting transition of a two-dimensional (2D) Josephson junction
array exposed to weak magnetic fields has been studied experimentally.
Resistance measurements reveal a superconducting-resistive phase boundary in
serious disagreement with the theoretical and numerical expectations. Critical
scaling analyses of the characteristics indicate contrary to the
expectations that the superconducting-to-resistive transition in weak magnetic
fields is associated with a melting transition of magnetic-field-induced
vortices directly from a pinned-solid phase to a liquid phase. The expected
depinning transition of vortices from a pinned-solid phase to an intermediate
floating-solid phase was not observed. We discuss effects of the
disorder-induced random pinning potential on phase transitions of vortices in a
2D Josephson junction array.Comment: 9 pages, 7 figures (EPS+JPG format), RevTeX
The Populations of Carina. I. Decoding the Color-Magnitude Diagram
© 2017. The American Astronomical Society. All rights reserved.. We investigate the color-magnitude diagram (CMD) of the Carina dwarf spheroidal galaxy using data of Stetson et al. and synthetic CMDs based on isochrones of Dotter et al., in terms of the parameters [Fe/H], age, and [α/Fe] , for the cases when (i) [α/Fe] is held constant and (ii) [α/Fe] is varied. The data are well described by four basic epochs of star formation, having [Fe/H] = -1.85, -1.5, -1.2, and ∼-1.15 and ages ∼13, 7, ∼3.5, and ∼1.5 Gyr, respectively (for [α/Fe] = 0.1, constant [α/Fe], and [α/Fe] = 0.2, 0.1, -0.2, -0.2, variable [α/Fe]), with small spreads in [Fe/H] and age of order 0.1 dex and 1-3 Gyr. Within an elliptical radius 13.′1, the mass fractions of the populations, at their times of formation, were (in decreasing age order) 0.34, 0.39, 0.23, and 0.04. This formalism reproduces five observed CMD features (two distinct subgiant branches of old and intermediate-age populations, two younger, main-sequence components, and the small color dispersion on the red giant branch (RGB). The parameters of the youngest population are less certain than those of the others, and given it is less centrally concentrated, it may not be directly related to them. High-resolution spectroscopically analyzed RGB samples appear statistically incomplete compared with those selected using radial velocity, which contain bluer stars comprising ∼5%-10% of the samples. We conjecture these objects may, at least in part, be members of the youngest population. We use the CMD simulations to obtain insight into the population structure of Carina's upper RGB
Wireless sEMG System with a Microneedle-Based High-Density Electrode Array on a Flexible Substrate
Surface electromyography (sEMG) signals reflect muscle contraction and hence, can provide information regarding a user's movement intention. High-density sEMG systems have been proposed to measure muscle activity in small areas and to estimate complex motion using spatial patterns. However, conventional systems based on wet electrodes have several limitations. For example, the electrolyte enclosed in wet electrodes restricts spatial resolution, and these conventional bulky systems limit natural movements. In this paper, a microneedle-based high-density electrode array on a circuit integrated flexible substrate for sEMG is proposed. Microneedles allow for high spatial resolution without requiring conductive substances, and flexible substrates guarantee stable skin-electrode contact. Moreover, a compact signal processing system is integrated with the electrode array. Therefore, sEMG measurements are comfortable to the user and do not interfere with the movement. The system performance was demonstrated by testing its operation and estimating motion using a Gaussian mixture model-based, simplified 2D spatial pattern.111Ysciescopu
P3-194: The palliative effect of endobronchial brachytherapy for previously irradiated patients
Superconducting phase transitions in frustrated Josephson-junction arrays on a dice lattice
Transport measurements are carried out on dice Josephson-junction arrays with
the frustration index and 1/2 which possess, within the limit of the
model, an accidental degeneracy of the ground states as a consequence of
the formation of zero-energy domain walls. The measurements demonstrate that
both the systems undergo a phase transition to a superconducting vortex-ordered
state at considerably high temperatures. The experimental findings are in
apparent contradiction with the theoretical expectation that frustration
effects in the system are particularly strong enough to suppress a
vortex-ordering transition down to near zero temperature. The data for
are more consistent with theoretical evaluations. The agreement between the
experiments and the Monte Carlo simulations of a model for
suggests that the order-from-disorder mechanism for the removal of an
accidental degeneracy may still be effective in the system. The
transport data also reveal that the dice arrays with zero-energy domain walls
experience a much slower critical relaxation than other frustrated arrays only
with finite-energy walls.Comment: 4 pages, 4 figure
Effects of production parameters on microstructure and densification of iron/glass syntactic foam by conventional powder metallurgy
Iron and steel matrix syntactic foams have received a lot of attention owing to their high strength, temperature capability, and corrosion resistance. However, high melting point of the iron and steels complicates applications of some conventional production processes. Since few casting methods were proposed to fabricate iron and steel syntactic foams embedded with the ceramic and metal hollow spheres having macro diameters, most of the foams having micro ceramic and glass hollow spheres were fabricated through powder metallurgy (PM) process, which allows reduction of temperature levels by about 30~40% compared to the casting. Metal injection molding (MIM) was mostly used toward the iron and steel matrix foams because of requiring only limited adaptations for switching from making solid parts to syntactic foams and its capabilities for producing various geometries and sizes. However, if the shape allows the production of the part by conventional PM (pressing and sintering), MIM would in most cases be too expensive. To date, detailed fundamental researches on conventional PM process to fabricate the iron or steel syntactic foams have not been reported. Difficulties of the conventional PM process to fabricate the iron and steel syntactic foams are working pressures and temperatures. For compacting powders to make green bodies, high working pressures can assist the densification of the matrix during sintering while this can deform or fracture the hollow spheres embedded. In case of the foams with the glass hollow spheres, softening of the glass occurs at high temperature thus original shape of the hollow spheres cannot be preserved. Therefore, to overcome the difficulties and to produce sound sintered bodies, the investigation on the production parameters of the conventional PM to fabricate the iron and steel syntactic foams is necessary.
In this study, the iron/glass hollow spheres syntactic foams were fabricated via the conventional PM process. Fabrications were conducted with considering different production parameters, which included the compaction pressures and sintering temperatures in conjunction with various volume fractions and particle sizes of the hollow spheres. The microstructures and densification behaviors of the fabricated syntactic foams were characterized by X-ray diffraction, optical microscope, scanning electron microscope and energy dispersion spectroscope
- …