1,894 research outputs found
Evolution of structural and magnetic properties in Ta/Ni_81Fe_(19) multilayer thin films
The interdiffusion kinetics in short period (12.8 nm) Ta/Ni81Fe19 polycrystalline multilayer films has been investigated and related to the evolution of soft magnetic properties upon thermal annealing in the temperature range 300-600-degrees-C. Small angle x-ray diffraction and transmission electron microscopy were used to estimate the multilayer period. Interdiffusion in the multilayers was directly computed from the decay of the satellites near (000) in a small angle x-ray diffraction spectrum. A kinetic analysis of interdiffusion suggests that grain growth is concurrent with grain boundary diffusion of Ta in Ni81Fe19. The evolution of soft magnetic properties of Ni81Fe19, i.e., lowering of 4piM(s) and increase in coercivity H(c), also lend support to the above analysis
Nonstoichiometric doping and Bi antisite defect in single crystal Bi2Se3
We studied the defects of Bi2Se3 generated from Bridgman growth of
stoichiometric and nonstoichiometric self-fluxes. Growth habit, lattice size,
and transport properties are strongly affected by the types of defect
generated. Major defect types of Bi_Se antisite and partial Bi_2-layer
intercalation are identified through combined studies of direct atomic-scale
imaging with scanning transmission electron microscopy (STEM) in conjunction
with energy-dispersive X-ray spectroscopy (STEM-EDX), X-ray diffraction, and
Hall effect measurements. We propose a consistent explanation to the origin of
defect type, growth morphology, and transport property.Comment: 5 pages, 5 figure
Electrical characteristics of amorphous molybdenum-nickel contacts to silicon
The electrical characteristics of sputtered, amorphous Mo-Ni contacts have been measured on both p- and n-type Si, as functions of composition (30, 54, and 58 at. % Mo). The contact resistivity on both p+ and n+ Si is in the 10^−6 Ω cm^2 range. The barrier height for as-deposited samples varies between φbp=0.47–0.42 V on p-type Si and between φbn=0.63–0.68 V on n-type Si, as the composition of the amorphous layer goes from Ni-rich to Mo-rich. The sum φbp+φbn always equals 1.12 V, within experimental error. After thermal treatment at 500 °C for 1/2 h, the contact resistivity changes by a factor of two or less, while the barrier height changes by at most ~0.05 V. In light of these results, the amorphous Mo-Ni film makes good ohmic contacts to silicon
The Muscular Function for Human Knee Movement Revealed from Electromyography: A Preliminary Study
Abstract: The electromyography (EMG) of a male teenager performing isokinetic exercise is conducted to realize the characteristics of femoral muscles in human knee movement. The raw EMG data of rectus femoris muscle and biceps femoris muscle are full-wave rectified to demonstrate the electromechanical delay that ranges from 50 to 100 ms. The mean of biceps femoris EMG in isokinetics knee flexion is approximately 3-4 times as much as that of rectus femoris EMG in isokinetics knee extension. The rectified EMG signals are smoothed by using moving average method to receive a linear envelope that outlines the mean trend of EMG signals. It gives a clear perspective to observe the relation between the micro-scale EMG signal and the macro-scale kinetic data. This paper presents an important basis to establish a mechanical model of muscle for human knee movement
Dependence of the flux creep activation energy on current density and magnetic field for MgB2 superconductor
Systematic ac susceptibility measurements have been performed on a MgB
bulk sample. We demonstrate that the flux creep activation energy is a
nonlinear function of the current density , indicating a
nonlogarithmic relaxation of the current density in this material. The
dependence of the activation energy on the magnetic field is determined to be a
power law , showing a steep decline in the activation
energy with the magnetic field, which accounts for the steep drop in the
critical current density with magnetic field that is observed in MgB. The
irreversibility field is also found to be rather low, therefore, the pinning
properties of this new material will need to be enhanced for practical
applications.Comment: 11 pages, 6 figures, Revtex forma
Extracting inter-dot tunnel couplings between few donor quantum dots in silicon
The long term scaling prospects for solid-state quantum computing architectures relies heavily on the
ability to simply and reliably measure and control the coherent electron interaction strength, known
as the tunnel coupling, tc. Here, we describe a method to extract the tc between two quantum dots
(QDs) utilising their different tunnel rates to a reservoir. We demonstrate the technique on a few
donor triple QD tunnel coupled to a nearby single-electron transistor(SET)in silicon. The device was
patterned using scanning tunneling microscopy-hydrogen lithography allowing for a direct
measurement of the tunnel coupling for a given inter-dot distance. We extract tc = ± 5.5 1.8 GHz
and tc = ± 2.2 1.3 GHz between each of the nearest-neighbour QDs which are separated by 14.5 nm
and 14.0 nm, respectively. The technique allows for an accurate measurement of tc for nanoscale
devices even when it is smaller than the electron temperature and is an ideal characterisation tool for
multi-dot systems with a charge senso
Networking - A Statistical Physics Perspective
Efficient networking has a substantial economic and societal impact in a
broad range of areas including transportation systems, wired and wireless
communications and a range of Internet applications. As transportation and
communication networks become increasingly more complex, the ever increasing
demand for congestion control, higher traffic capacity, quality of service,
robustness and reduced energy consumption require new tools and methods to meet
these conflicting requirements. The new methodology should serve for gaining
better understanding of the properties of networking systems at the macroscopic
level, as well as for the development of new principled optimization and
management algorithms at the microscopic level. Methods of statistical physics
seem best placed to provide new approaches as they have been developed
specifically to deal with non-linear large scale systems. This paper aims at
presenting an overview of tools and methods that have been developed within the
statistical physics community and that can be readily applied to address the
emerging problems in networking. These include diffusion processes, methods
from disordered systems and polymer physics, probabilistic inference, which
have direct relevance to network routing, file and frequency distribution, the
exploration of network structures and vulnerability, and various other
practical networking applications.Comment: (Review article) 71 pages, 14 figure
Isotropic singularity in inhomogeneous brane cosmological models
We discuss the asymptotic dynamical evolution of spatially inhomogeneous
brane-world cosmological models close to the initial singularity. By
introducing suitable scale-invariant dependent variables and a suitable gauge,
we write the evolution equations of the spatially inhomogeneous brane
cosmological models with one spatial degree of freedom as a system of
autonomous first-order partial differential equations. We study the system
numerically, and we find that there always exists an initial singularity, which
is characterized by the fact that spatial derivatives are dynamically
negligible. More importantly, from the numerical analysis we conclude that
there is an initial isotropic singularity in all of these spatially
inhomogeneous brane cosmologies for a range of parameter values which include
the physically important cases of radiation and a scalar field source. The
numerical results are supported by a qualitative dynamical analysis and a
calculation of the past asymptotic decay rates. Although the analysis is local
in nature, the numerics indicates that the singularity is isotropic for all
relevant initial conditions. Therefore this analysis, and a preliminary
investigation of general inhomogeneous () models, indicates that it is
plausible that the initial singularity is isotropic in spatially inhomogeneous
brane-world cosmological models and consequently that brane cosmology naturally
gives rise to a set of initial data that provide the conditions for inflation
to subsequently take place.Comment: 32 pages with 8 pictures. submitted to Class. Quant. Gra
- …