Spin waves: theory and applications

Magnetic materials can support propagating waves of magnetization; since these are oscillations in the magneto static properties of the material, they are called magneto static waves (sometimes 'magnons' or 'magnetic polarons'). This book discusses magnetic properties of materials, and magnetic moments of atoms and ionsIntroduces magnetism and discusses magnetic properties of materials, magnetic moments of atoms and ions, and the elements important to magnetismCovers magnetic susceptibilities and electromagnetic waves in anisotropic dispersive media among other topicsContains problems at the end of each chapter, many of which serve to expand or explain the material in the textIncludes bibliographies for each chapter that give an entry to the research literature

Design and prototype of an all digital system for baseband FM multiplex signal demodulation

textThe continuing increase in transistor densities and operation frequencies of digital circuits is leading to the replacement of many analog circuits by their digital circuit counterparts. This trend can be attributed to the flexibility and robustness provided by digital circuits over analog circuits. One application in which digital circuits are replacing analog circuits is in the modulation and demodulation of baseband frequency modulated (FM) radio signals. In this project, an all digital system for demodulating baseband FM Multiplex (MPX) signals is simulated, designed, and prototyped on a Xilinx Spartan-3AN FPGA. The design architecture is simulated using Scilab numerical computation software; implemented in Verilog Hardware Description Language; and tested using the digital to analog converters (DACs) on the Xilinx Spartan-3AN Starter Kit. The oscilloscope images at the end of this report show that the implemented system can successfully demodulate the 19kHz pilot tone, left channel signal, and right channel signal of a digitized FM MPX modulated signal sampled at 192kHz.Electrical and Computer Engineerin

Visible-Light-Driven Photocatalytic Activity of SnO2-ZnO Quantum Dots Anchored on g-C3N4 Nanosheets for Photocatalytic Pollutant Degradation and H-2 Production

A zero-dimensional/two-dimensional heterostructure consists of binary SnO2-ZnO quantum dots (QDs) deposited on the surface of graphitic carbon nitride (g-C3N4) nanosheets. The so-called SnO2-ZnO QDs/g-C3N4 hybrid was successfully synthesized via an in situ co-pyrolysis approach to achieve efficient photoactivity for the degradation of pollutants and production of hydrogen (H-2) under visible-light irradiation. High-resolution transmission electron microscopy images show the close contacts between SnO2-ZnO QDs with the g-C3N4 in the ternary SnO2-ZnO QDs/g-C3N4 hybrid. The optimized hybrid shows excellent photocatalytic efficiency, achieving 99% rhodamine B dye degradation in 60 min under visible-light irradiation. The enriched charge-carrier separation and transportation in the SnO2-ZnO QDs/g-C3N4 hybrid was determined based on electrochemical impedance and photocurrent analyses. This remarkable photoactivity is ascribed to the "smart" heterostructure, which yields numerous benefits, such as visible-light-driven fast electron and hole transfer, due to the strong interaction between the SnO2-ZnO QDs with the g-C3N4 matrix. In addition, the SnO2-ZnO QDs/g-C3N4 hybrid demonstrated a high rate of hydrogen production (13 673.61 mu mol g(-1)), which is 1.06 and 2.27 times higher than that of the binary ZnO/g-C3N4 hybrid (12 785.54 mu mol g(-1)) and pristine g-C3N4 photocatalyst (6017.72 mu mol g(-1)). The synergistic effect of increased visible absorption and diminished recombination results in enhanced performance of the as-synthesized tin oxide-and zinc oxide-modified g-C3N4. We conclude that the present ternary SnO2-ZnO QDs/g-C3N4 hybrid is a promising electrode material for H-2 production and photoelectrochemical cells

Equivalence of space and time-bins in DPS-QKD

We set up differential phase shift quantum key distribution (DPS-QKD), over 105 km of single-mode optical fiber, with a quantum bit error rate of less than 15% at a secure key rate of 2 kbps. The testbed was first used to investigate the effect of excess bias voltage and hold-off time on the temporal distribution of photons within a gate window of an InGaAs single-photon detector (SPD) and quantified the effects of afterpulsing. The key generation efficiency, and security, in DPS-QKDimprove with an increase in the number of path delays or time-bin superpositions. We finally demonstrate the implementation of superposition states using a time-bin approach, and establish equivalence with the path-based superposition approach, thus yielding a simpler approach to implementing superposition states for use in DPS-QKD.Comment: 7 pages, 14 figure

Tiny MoO3 nanocrystals self-assembled on folded molybdenum disulfide nanosheets via a hydrothermal method for supercapacitor

Coupling of two active semiconductors can easily lead to a deterioration of their intrinsic properties. In this work, tiny MoO3 nanocrystals were deposited on 3D MoS2 frameworks via a hydrothermal reaction, with heterostructures forming by oxygen-bonding interactions at their interface. When tested as a supercapacitor electrode, the MoS2/MoO3 heterostructure exhibited a high specific capacitance of 287.7 F g(-1) at a current density of 1 A g(-1), and a remarkable cycling stability after 1000 cycles at 1 A g(-1) in an aqueous solution compared to pristine MoS2. The results thus reveal the superior properties of the MoS2/MoO3 heterostructure for supercapacitor electrode

Review of Maximum Power Point Tracking for Photovoltaic Systems

The demand of electrical energy is increasing with industrial development and the rate ofgeneration is unable to keep pace with increasing demand. The conventional energy sourcesare limited so the obvious choice of clean, free source of energy which provides safety for thedevelopment is solar energy. But PV system has certain disadvantages like: low conversionefficiency, high cost of installation hence we preferred MPPT for extracting the maximumpower output from Photovoltaic system. The output characteristic of photovoltaic array isnon-linear