Fluence and polarisation dependence of GaAs based Lateral Photo-Dember terahertz emitters

We characterise THz output of lateral photo-Dember (LPD) emitters based on semi-insulating (SI), unannealed and annealed low temperature grown (LTG) GaAs. Saturation of THz pulse power with optical fluence is observed, with unannealed LTG GaAs showing highest saturation fluence at 1.1 ± 0.1 mJ cm-2. SI-GaAs LPD emitters show a flip in signal polarity with optical fluence that is attributed to THz emission from the metal-semiconductor contact. Variation in optical polarisation affects THz pulse power that is attributed to a local optical excitation near the metal contact

Level spacing statistics of classically integrable systems -Investigation along the line of the Berry-Robnik approach-

By extending the approach of Berry and Robnik, the limiting level spacing distribution of a system consisting of infinitely many independent components is investigated. The limiting level spacing distribution is characterized by a single monotonically increasing function $\bar{\mu}(S)$ of the level spacing $S$. Three cases are distinguished: (i) Poissonian if $\bar{\mu}(+\infty)=0$, (ii) Poissonian for large $S$, but possibly not for small $S$ if $0<\bar{\mu}(+\infty)< 1$, and (iii) sub-Poissonian if $\bar{\mu}(+\infty)=1$. This implies that, even when energy-level distributions of individual components are statistically independent, non-Poissonian level spacing distributions are possible.Comment: 19 pages, 4 figures. Accepted for publication in Phys. Rev.

Transport Reactor Facility

The Morgantown Energy Technology Center (METC) is currently evaluating hot gas desulfurization (HGD)in its on-site transport reactor facility (TRF). This facility was originally constructed in the early 1980s to explore advanced gasification processes with an entrained reactor, and has recently been modified to incorporate a transport riser reactor. The TRF supports Integrated Gasification Combined Cycle (IGCC) power systems, one of METC`s advanced power generation systems. The HGD subsystem is a key developmental item in reducing the cost and increasing the efficiency of the IGCC concept. The TRF is a unique facility with high-temperature, high-pressure, and multiple reactant gas composition capability. The TRF can be configured for reacting a single flow pass of gas and solids using a variety of gases. The gas input system allows six different gas inputs to be mixed and heated before entering the reaction zones. Current configurations allow the use of air, carbon dioxide, carbon monoxide, hydrogen, hydrogen sulfide, methane, nitrogen, oxygen, steam, or any mixture of these gases. Construction plans include the addition of a coal gas input line. This line will bring hot coal gas from the existing Fluidized-Bed Gasifier (FBG) via the Modular Gas Cleanup Rig (MGCR) after filtering out particulates with ceramic candle filters. Solids can be fed either by a rotary pocket feeder or a screw feeder. Particle sizes may range from 70 to 150 micrometers. Both feeders have a hopper that can hold enough solid for fairly lengthy tests at the higher feed rates, thus eliminating the need for lockhopper transfers during operation

Breakage characteristics of granulated food products for prediction of attrition during lean-phase pneumatic conveying

Pneumatic conveying is utilised in a variety of industries to convey food products exhibiting diverse handling characteristics. Attrition of particles caused by this conveying process can result in a number of undesirable outcomes such as loss in product quality or issues in subsequent handling processes. The ability to predict the breakage behaviour of particulate materials is desirable in both new system design and resolving issues in existing plants. This work considers two different particulate materials (Salt and Golden Breadcrumbs) across a range of particle sizes, and quantifies their breakage behaviour under varying impact conditions. Narrow size fractions of each material was degraded; material retained on 250 µm and 355 µm sieves for salt, and 500µm, 710µm and 1000 µm sieves for Golden Breadcrumbs. Velocity was found to be the most influential factor with respect to particle attrition. The results from the narrow size fraction tests were superimposed to form a simulated full size distribution breakage behaviour, which was then compared to the experimentally determined behaviour. A good agreement was found, however the proportion of material predicted for size fractions smaller than 355 µm for Golden Breadcrumbs and 180 µm for Salt was under-predicted. Recommendations for increasing accuracy of the prediction method are given

Landmark-Based Geometric Morphometric of Apis dorsata and A. d. binghami Wing Venation in Indonesian Archipelagos

The giant honey bee Apis dorsata has a vast distribution in Asia, including in the Indonesian archipelagos, whereas A. d. binghami is endemic to Sulawesi Island. This research aimed to analyze the variations of landmarks in wing venation of A. dorsata from Sumatra, Belitung, Java, Sumbawa, Moluccas islands, and A. d. binghami in Sulawesi, based on geometric morphometric analysis. Nineteen landmarks from 200 wing venations were analyzed using Thin Plate Spline software. Our study found landmarks 16 and 17, known as Cubital Index in traditional morphometrics, contributed to the wing shape of A. dorsata and A. d. binghami Among all samples, these two landmarks show high displacement in the wing shape of A. d. binghami in Sulawesi and A. dorsata in the Moluccas. On the contrary, we found that the Sumatra, Belitung, and Java Apis dorsata revealed low displacement in the deformation grid; resulting in their shapes being more similar to the reference landmark. The variations of wing shape separate A. d. binghami from Sulawesi and Sumbawa in the Principle Component Analysis and agreement with the Neighbor-joining tree. Therefore, the geometric morphometric based on landmarks of wing venation is a powerful tool to discriminate the subspecies level of A. dorsata

Approximate Reachability for Dead Code Elimination in Esterel*

Esterel is an imperative synchronous programming language for the design of reactive systems. Esterel* extends Esterel with a non-instantaneous jump instruction (compatible with concurrency, preemption, etc.) so as to enable powerful source-to-source program transformations, amenable to formal verification. In this work, we propose an approximate reachability algorithm for Esterel* and use its output to remove dead code. We prove the correctness of our techniques

Ultrafast geometric manipulation of electron spin and detection of the geometric phase via Faraday rotation spectroscopy

Time-resolved Faraday rotation spectroscopy is currently exploited as a powerful technique to probe spin dynamics in semiconductors. We propose here an all-optical approach to geometrically manipulate electron spin and to detect the geometric phase by this type of extremely sensitive experiment. The global nature of the geometric phase can make the quantum manipulation more stable, which may find interesting application in quantum devices.Comment: 4 pages, 3 figures, to appear in Phys. Rev.

Conditions for Adiabatic Spin Transport in Disordered Systems

We address the controversy concerning the necessary conditions for the observation of Berry phases in disordered mesoscopic conductors. For this purpose we calculate the spin-dependent conductance of disordered two-dimensional structures in the presence of inhomogeneous magnetic fields. Our numerical results show that for both, the overall conductance and quantum corrections, the relevant parameter defining adiabatic spin transport scales with the square root of the number of scattering events, in generalization of Stern's original proposal [Phys. Rev. Lett. 68, 1022 (1992)]. This could hinder a clear-cut experimental observation of Berry phase effects in diffusive metallic rings.Comment: 5 pages, 4 figures. To appear in Phys. Rev. B (Rapid Communications

Concurrency and Communication: Lessons from the SHIM Project

Describing parallel hardware and software is difficult, especially in an embedded setting. Five years ago, we started the shim project to address this challenge by developing a programming language for hardware/software systems. The resulting language describes asynchronously running processes that has the useful property of scheduling-independence: the i/o of a shim program is not affected by any scheduling choices. This paper presents a history of the shim project with a focus on the key things we have learned along the way

Measurement of the 6s - 7p transition probabilities in atomic cesium and a revised value for the weak charge Q_W

We have measured the 6s - 7p_{1/2,3/2} transition probabilities in atomic cesium using a direct absorption technique. We use our result plus other previously measured transition rates to derive an accurate value of the vector transition polarizability \beta and, consequently, re-evaluate the weak charge Q_W. Our derived value Q_W=-72.65(49) agrees with the prediction of the standard model to within one standard deviation.Comment: 4 pages, 2 figure