40,646 research outputs found
Generalized theory and application of Stokes parameter measurements made with a single photoelastic modulator
We report in this paper a generalized theory that describes the interaction between a monochromatic light beam and an optical system that includes one photoelastic modulator, one analyzer, and one photodetector. Based on the theory, a detailed four-step procedure is presented, which allows a precise measurement of the four Stokes parameters. An analysis of the systematic and random errors arising from the four-step measurements is also given as well as a calibration procedure that involves the use of a general retardation plate. As a practical application the procedure is used to analyze the magneto-optical properties of magnetic thin films grown on GaAs(001) substrates
A probabilistic model checking approach to analysing reliability, availability, and maintainability of a single satellite system
Satellites now form a core component for space
based systems such as GPS and GLONAS which provide
location and timing information for a variety of uses. Such
satellites are designed to operate in-orbit and have lifetimes of
10 years or more. Reliability, availability and maintainability
(RAM) analysis of these systems has been indispensable in
the design phase of satellites in order to achieve minimum
failures or to increase mean time between failures (MTBF)
and thus to plan maintainability strategies, optimise reliability
and maximise availability. In this paper, we present formal
modelling of a single satellite and logical specification of
its reliability, availability and maintainability properties. The
probabilistic model checker PRISM has been used to perform
automated quantitative analyses of these properties
Co-rich cobalt platinum nanowire arrays: effects of annealing
The effects of annealing on the crystal structure and magnetic properties of Co-rich cobalt platinum nanowire arrays embedded in anodic aluminium oxide membranes have been investigated. For this purpose, a rapid thermal annealing to temperatures of 300 °C to 800 °C has been used. Transmission electron microscopy and scanning electron microscopy show that the nanowires have a mean diameter of 14 nm and an estimated wire density of 7.8Ă1010 cm-2. From x-ray diffraction patterns, we find that the nanowires are hcp and possess a preferred texture in which the c axis of the grains tends to lie along the major axis of the wire. Vibrating sample magnetometry measurements indicate that the easy axis is along the nanowire axis direction. Hysteresis loops, saturation magnetization, squareness ratio (Mr/Ms), and coercivity (perpendicular and parallel to the nanowire axis) have all been investigated as a function of the annealing temperature (TA). Coercivity parallel to the wire axis first increases with TA, attains a maximum at 600 °C (which is 150% of the as-deposited sample), and then decreases. By contrast there is relatively little change in the coercivity measured perpendicular to the wires. The saturation magnetization for the as-deposited sample is 1360 emu/cc and remains almost constant for annealing temperatures up to 500 °C: for TA>500 °C it decreases significantly. The maximum (Mr/Ms) ratio attained in this study is 0.99, the highest value reported thus far for cobalt platinum alloy nanowires. The data suggest that these materials are potential candidates for high-density magnetic recording media
Angular Momentum of a Brane-world Model
In this paper we discuss the properties of the general covariant angular
momentum of a five-dimensional brane-world model. Through calculating the total
angular momentum of this model, we are able to analyze the properties of the
total angular momentum in the inflationary RS model. We show that the
space-like components of the total angular momentum of are all zero while the
others are non-zero, which agrees with the results from ordinary RS model.Comment: 8 pages; accepted by Chinese Physics
The Ramsey Number for 3-Uniform Tight Hypergraph Cycles
Let C(3)n denote the 3-uniform tight cycle, that is, the hypergraph with vertices v1, .â.â., vn and edges v1v2v3, v2v3v4, .â.â., vnâ1vnv1, vnv1v2. We prove that the smallest integer N = N(n) for which every redâblue colouring of the edges of the complete 3-uniform hypergraph with N vertices contains a monochromatic copy of C(3)n is asymptotically equal to 4n/3 if n is divisible by 3, and 2n otherwise. The proof uses the regularity lemma for hypergraphs of Frankl and RĂśdl
Magneto-optical characteristics of magnetic nanowire arrays in anodic aluminium oxide templates
Nanocomposite films consisting of regularly ordered iron nanowires embedded in anodic aluminum oxide templates have been fabricated and their magneto-optical properties studied by determining the four Stokes parameters of the transmitted laser beam (Îť=670 nm), originally linearly polarized and at normal incidence to the film surfaces. The results of the nanowire arrays are found to be considerably different from that of bulk iron. While an increase in diameter of the nanowire leads to a substantial increase in the values of the Faraday rotation angles per unit length at a fixed value of the magnetic fields, they are substantially less than that of bulk iron, indicating that the effective media theory may not be directly applicable
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A low-bandgap dimeric porphyrin molecule for 10% efficiency solar cells with small photon energy loss
Dimeric porphyrin molecules have great potential as donor materials for high performance bulk heterojunction organic solar cells (OSCs). Recently reported dimeric porphyrins bridged by ethynylenes showed power conversion efficiencies (PCEs) of more than 8%. In this study, we design and synthesize a new conjugated dimeric D-A porphyrin ZnP2BT-RH, in which the two porphyrin units are linked by an electron accepting benzothiadiazole (BT) unit. The introduction of the BT unit enhances the electron delocalization, resulting in a lower highest occupied molecular orbital (HOMO) energy level and an increased molar extinction coefficient in the near-infrared (NIR) region. The bulk heterojunction solar cells with ZnP2BT-RH as the donor material exhibit a high PCE of up to 10% with a low energy loss (Eloss) of only 0.56 eV. The 10% PCE is the highest for porphyrin-based OSCs with a conventional structure, and this Eloss is also the smallest among those reported for small molecule-based OSCs with a PCE higher than 10% to date
On the existence and uniqueness of solutions to stochastic differential equations driven by G-Brownian motion with integral-Lipschitz coefficients
In this paper, we study the existence and uniqueness of solutions to
stochastic differential equations driven by G-Brownian motion (GSDEs) with
integral-Lipschitz conditions on their coefficients
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