Kinetics of the Photoreduction of \u3cem\u3ep\u3c/em\u3e-nitrobenzoic Acid on Ag and AgxAu1-x Nanoparticle Films

A recent strategy to increase the efficiency of photovoltaic and photoemissive devices has been to include metal nanolayers in contact with an organic layer inside these devices. Metal nanoparticles (especially Ag and Au) are known to catalyze photoreactions of organic molecules on their surfaces. The reactivity of organics at nanometal surfaces has implications for device lifetimes; therefore, it is important to understand how nanoparticle size and composition influence reaction rates. The photoreduction of p-nitrobenzoate (PNBA) to p,p’-azodibenzoate (PPADBA) on Ag nanoparticles is an excellent model system for studying such reactions. We have measured the reaction rate of PNBA to PPADBA on Ag and Au based nanoparticle surfaces using surface-enhanced Raman spectroscopy (SERS). SERS is a highly sensitive spectroscopic tool, which provides molecular fingerprints that can be used to identify molecular species present on metal nanoparticle surfaces. These surfaces are made from layers from Ag and AgxAu1-x alloy nanoparticles with diameters ranging from 50-80 nm

A process algebra for synchronous concurrent constraint programming

Concurrent constraint programming is classically based on asynchronous communication via a shared store. This paper presents new version of the ask and tell primitives which features synchronicity. Our approach is based on the idea of telling new information just in the case that a concurrently running process is asking for it. An operational and an algebraic semantics are defined. The algebraic semantics is proved to be sound and complete with respect to a compositional operational semantics which is also presented in the paper

Reduction of alternator apparent-power requirements and harmonic distortion caused by phase-controlled parasitic loads

Reduction of alternator apparent power requirements and harmonic distortion caused by phase-controlled parasitic load

Non-Volatile Magnonic Logic Circuits Engineering

We propose a concept of magnetic logic circuits engineering, which takes an advantage of magnetization as a computational state variable and exploits spin waves for information transmission. The circuits consist of magneto-electric cells connected via spin wave buses. We present the result of numerical modeling showing the magneto-electric cell switching as a function of the amplitude as well as the phase of the spin wave. The phase-dependent switching makes it possible to engineer logic gates by exploiting spin wave buses as passive logic elements providing a certain phase-shift to the propagating spin waves. We present a library of logic gates consisting of magneto-electric cells and spin wave buses providing 0 or p phase shifts. The utilization of phases in addition to amplitudes is a powerful tool which let us construct logic circuits with a fewer number of elements than required for CMOS technology. As an example, we present the design of the magnonic Full Adder Circuit comprising only 5 magneto-electric cells. The proposed concept may provide a route to more functional wave-based logic circuitry with capabilities far beyond the limits of the traditional transistor-based approach

Chaos in cylindrical stadium billiards via a generic nonlinear mechanism

We describe conditions under which higher-dimensional billiard models in bounded, convex regions are fully chaotic, generalizing the Bunimovich stadium to dimensions above two. An example is a three-dimensional stadium bounded by a cylinder and several planes; the combination of these elements may give rise to defocusing, allowing large chaotic regions in phase space. By studying families of marginally-stable periodic orbits that populate the residual part of phase space, we identify conditions under which a nonlinear instability mechanism arises in their vicinity. For particular geometries, this mechanism rather induces stable nonlinear oscillations, including in the form of whispering-gallery modes.Comment: 4 pages, 4 figure

Hysteresis loops of magnetic thin films with perpendicular anisotropy

We model the magnetization of quasi two-dimensional systems with easy perpendicular (z-)axis anisotropy upon change of external magnetic field along z. The model is derived from the Landau-Lifshitz-Gilbert equation for magnetization evolution, written in closed form in terms of the z component of the magnetization only. The model includes--in addition to the external field--magnetic exchange, dipolar interactions and structural disorder. The phase diagram in the disorder/interaction strength plane is presented, and the different qualitative regimes are analyzed. The results compare very well with observed experimental hysteresis loops and spatial magnetization patterns, as for instance for the case of Co-Pt multilayers.Comment: 8 pages, 8 figure

Detection of spin reversal and nutations through current measurements

The dynamics of a single spin embedded in a the tunnel junction between ferromagnetic contacts is strongly affected by the exchange coupling to the tunneling electrons. Moment reversal of the local spin induced by the bias voltage across the junction is shown to have a measurable effect on the tunneling current. Furthermore, the frequency of a harmonic bias voltage is picked up by the local spin dynamics and transferred back to the current generating a double frequency component.Comment: 5 pages, 5 figures; published version (with minor corrections

Low-speed stability and control wind-tunnel investigations of effects of spanwise blowing on fighter flight characteristics at high angles of attack

The effects of spanwise blowing on two configurations representative of current fighter airplanes were investigated. The two configurations differed only in wing planform, with one incorporating a trapezoidal wing and the other a 60 delta wing. Emphasis was on determining the lateral-directional characteristics, particularly in the stall/departure angle-of-attack range; however, the effects of spanwise blowing on the longitudinal aerodynamics were also determined. The-tunnel tests included measurement of static force and forced-oscillation aerodynamic data, visualization of the airflow changes created by the spanwise blowing, and free-flight model tests. The effects of blowing rate, chordwise location of the blowing ports, asymmetric blowing, and blowing on the conventional aerodynamic control characteristics were investigated. In the angle-of-attack regions in which the spanwise blowing substantially improved the wing upper-surface flow field (i.e., provided reattachment of the flow aft of the leading-edge vortex), improvements in both static and dynamic lateral-directional stability were observed. Blowing effects on stability could be proverse or adverse depending on blowing rate, blowing port loaction, and wing planform. Free-flight model tests of the trapezoidal wing confirmed the beneficial effects of spanwise blowing measured in the static and dynamic force tests

Motor starting techniques for the 2 to 15 kW Brayton space power system

Motor starting techniques for 2-15 kW Brayton space power syste