The behaviour of a single catalyst pellet for the selective hydrogenation of ethyne in ethene

The steady-state and dynamic behaviour of a single Pd---Al2O3 catalyst particle is studied for the selective hydrogenation of ethyne in the presence of ethene, without addition of carbon monoxide. The particle-to-gas heat transfer in the reactor is characterized. During selective hydrogenation, not only the ignition and the extinction phenomena but also oscillatory behaviour is observed. The nature of the single and multipeak oscillations is discussed. With a dynamic model, based on relatively simple kinetic equations and an additional slow mechanism, e.g. the formation of ethylidyne on the catalyst surface, the qualitative features of this system can be described

Monitoring 2009 Forest Disturbance Across the Conterminous United States, Based on Near-Real Time and Historical MODIS 250 Meter NDVI Products

This case study shows the promise of computing current season forest disturbance detection products at regional to CONUS scales. Use of the eMODIS expedited product enabled a NRT CONUS forest disturbance detection product, a requirement for an eventual, operational forest threat EWS. The 2009 classification product from this study can be used to quantify the areal extent of forest disturbance across CONUS, although a quantitative accuracy assessment still needs to be completed. However, the results would not include disturbances that occurred after July 27, such as the Station Fire. While not shown here, the project also produced maximum NDVI products for the June 10-July 27 period of each year of the 2000-2009 time frame. These products could be applied to compute forest change products on an annual basis. GIS could then be used to assess disturbance persistence. Such follow-on work could lead to attribution of year in which a disturbance occurred. These products (e.g., Figures 6 and 7) may also be useful for assessing forest change associated with climate change, such as carbon losses from bark beetle-induced forest mortality in the Western United States. Other MODIS phenological products are being assessed for aiding forest monitoring needs of the EWS, including cumulative NDVI products (Figure 10)

An exactly solvable phase transition model: generalized statistics and generalized Bose-Einstein condensation

In this paper, we present an exactly solvable phase transition model in which the phase transition is purely statistically derived. The phase transition in this model is a generalized Bose-Einstein condensation. The exact expression of the thermodynamic quantity which can simultaneously describe both gas phase and condensed phase is solved with the help of the homogeneous Riemann-Hilbert problem, so one can judge whether there exists a phase transition and determine the phase transition point mathematically rigorously. A generalized statistics in which the maximum occupation numbers of different quantum states can take on different values is introduced, as a generalization of Bose-Einstein and Fermi-Dirac statistics.Comment: 17 pages, 2 figure

LASER WELDING FOR TURBOMACHINERY ROTOR RESTORATION

TutorialsLaser cladding is gaining acceptance for restoration of turbine and compressor shafts, which has resulted in increased customer demand for laser cladding options. This has increased the number of laser welding suppliers, who are offering a variety of solutions. Therefore, it is important to understand the basic capabilities, limitations, and potential pitfalls of the laser cladding process. For example, it is still unclear how the process should be qualified to ensure that laser weld repairs meet the requirements for the given application. As with any welding process, the desired outcome is a metallurgically sound deposit that meets or exceeds the minimum design criteria for the application. Filler material alloy selection, form, and delivery methods can have a significant impact on the quality and suitability of the weld deposit. For example, all fusion welding processes generate a heat affected zone, and the properties in that region are unlikely to meet base metal requirements without a post weld heat treatment when the base metal is quenched and tempered steel, which is commonly used for turbomachinery shafts. However, it is commonly claimed that a post weld heat treatment is not required with laser welding due to the low heat input of the process, which greatly reduces the size of the heat affected zone. While this may be true in some cases, it is important to recognize that the heat affected zone will still be present and testing must be completed to ensure that the repaired component will be suitable for the application. This paper discusses the most commonly repaired shaft areas, the risks associated with laser welding in these locations, and the types of tests that should be required to qualify a procedure. Additionally, examples of successful repairs are shared including experimental results from the qualification process

Alcohol and breast cancer risk: the alcoholism paradox

A population-based cohort study of 36 856 women diagnosed with alcoholism in Sweden between 1965 and 1995 found that alcoholic women had only a small 15% increase in breast-cancer incidence compared to the general female population. It is therefore apparent, contrary to expectation, that alcoholism does not increase breast-cancer risk in proportion to presumed ethanol intake. © 2000 Cancer Research Campaig

Small, Highly Accurate Quantum Processor for Intermediate-Depth Quantum Simulations

Analog quantum simulation is widely considered a step on the path to fault tolerant quantum computation. If based on current noisy hardware, the accuracy of an analog simulator will degrade after just a few time steps, especially when simulating complex systems that are likely to exhibit quantum chaos. Here we describe a small, highly accurate quantum simulator and its use to run high fidelity simulations of three different model Hamiltonians for $>100$ time steps. While not scalable to exponentially large Hilbert spaces, this platform provides the accuracy and programmability required for systematic exploration of the interplay between dynamics, imperfections, and accuracy in quantum simulation.Comment: Published version. 10 pages, 5 figures, including Supplemental Materia