Energy advantages of microprocessor platforms with on-chip configurable logic

System chips that incorporate configurable logic can reduce the energy consumed in executing software. The key is to use the configurable logic to execute performance-critical loops, producing average energy savings of 25% to 71% for embedded-system benchmarks.     

Improved cloud detection in AVHRR daytime and night-time scenes over the ocean

Accurate cloud detection is a requirement of many geophysical applications that use visible and infrared satellite data (e.g. cloud climatologies, multichannel sea surface temperature (MCSST)). Unfortunately, a significant source of residual error in such satellite-based products is undetected cloud. Here, a new, computationally efficient cloud detection procedure for both daytime and night-time Advanced Very High Resolution Radiometer (AVHRR) data is developed. It differs substantially from our prior related work. First, a new clustering procedure is used, which produces more homogeneous and distinct clusters than those produced by either our previous work or the ISODATA algorithm of Ball and Hall. Second, the input information vector is reduced in size, incorporates both radiance and spatial components and each component is normalized. These changes improve the clustering/subsequent classification, tend to decrease execution time, and simplify post-processing of the classified (cloud, clear ocean) data to remove any residual outliers. Third, the enhanced performance makes possible the use of a multipass procedure which is very effective in identifying the complex multilayer cloud structures common in satellite data. Validation with independent lidar observations confirms the accuracy of the new procedure. Marine low stratiform clouds (LSCs-fog, stratus and stratocumulus) are also detected effectively. This advance is important because LSCs are a major source of residual cloud contamination in contemporary sea surface temperature (SST) products. Finally, the method is sufficiently general that it can be adapted to other sensors (e.g. the Along-Track Scanning Radiometer (ATSR), the Moderate Resolution Imaging Spectroradiometer (MODIS)).     

A survey of total hydrocyanic acid content in ready-to-eat cassava-based chips obtained in the Australian market in 2008

Cassava (Manihot esculenta Crantz) is a widely consumed food in the tropics that naturally contains cyanogenic glycosides (cyanogens, mainly composed of linamarin, acetone cyanohydrin, and hydrocyanic acid). If cassava is not adequately processed to reduce the level of cyanogens prior to consumption, these compounds can lead to the formation of hydrocyanic acid in the gut. Exposure to hydrocyanic acid can cause symptoms ranging from vomiting and abdominal pain to coma and death. In 2008, a survey of ready-to-eat (RTE) cassava-based snack foods was undertaken to determine levels of cyanogens measured as total hydrocyanic acid. This survey was undertaken in response to the New South Wales Food Authority being alerted to the detection of elevated levels of cyanogens in an RTE cassava-based snack food. This survey took 374 samples of RTE cassava chips available in the Australian marketplace. Significant variation in the levels of total hydrocyanic acid were observed in the 317 samples testing positive for cyanogens, with levels ranging from 13 to 165 mg of HCN equivalents per kg (mean value, 64.2 mg of HCN eq/kg for positive samples). The results from this survey serve as a timely warning for manufacturers of RTE cassava chips and other cassava-based snack foods to ensure there is tight control over the levels of cyanogens in the cassava ingredient. Evidence from this survey contributed to an amendment to the Australia New Zealand Food Standards Code, which now prescribes a maximum level for hydrocyanic acid in RTE cassava chips of 10 mg of HCN eq/kg, which aligns with the Codex Alimentarius Commission international standard for edible cassava flour.     

Endothelin expression in ocular tissues of diabetic and insulin-treated rats

PURPOSE: The endothelins are potent vasoactive peptides that are widely distributed in ocular tissues. There is evidence linking the endothelins to vascular dysfunction in diabetic microangiopathy. Thus, the synthesis and distribution of endothelin-1 (ET-1) and endothelin-3 (ET-3) were studied in the retinas of diabetic and nondiabetic animals. METHODS: Levels of ET-1 and ET-3 were determined by radioimmunoassay in ocular tissues of normal rats, and in rats with streptozotocin-induced diabetes of 6 and 12 weeks' duration, insulin-treated and untreated. In a separate cohort of similarly treated animals, retinal vascular trypsin digest preparations were immunostained, using antibodies raised against ET-1 and ET-3. RESULTS: Ocular ET-1 levels were elevated twofold in diabetic animals that received insulin treatment for 7 days when compared with levels in normal rats. Insulin treatment for 10 days before death caused a fourfold elevation of ET-1 in ocular tissues. Endothelin-1 was also increased in 12-week-old diabetic animals and in those maintained on insulin throughout their period of diabetes. Immunofluorescence to anti-ET-1 within the capillary bed and veins of the retina in diabetic insulin-treated animals was elevated when compared with digests from normal litter-matched control animals. Ocular tissue ET-3 levels were unaffected by diabetes. CONCLUSIONS: Overall ocular and retinal tissue levels of ET-1 were selectively elevated by diabetes and insulin treatment, suggesting that the endothelins may be involved in the pathogenesis of diabetic retinal microangiopathy.     

A PIV study of hydrodynamics in gas-liquid high throughput experimentation (HTE) reactors with eccentric impeller configurations

High-throughput experimentation (HTE) is used for the screening of novel catalyst formulations via miniature agitated gas-liquid reactors with vessel volumes of an order of magnitude below the laboratory scale. An investigation of the macroscopic hydrodynamic performance of a miniaturised unbaffled stirred vessel of diameter 45 mm for an air-water system has been carried out at gassing rates of 0.25 and 0.5 vvm (dispersed flow regime) using particle image velocimetry (PIV). Measurements of bubble size and gas hold-up were also made. Eccentric agitation was employed as a means of breaking solid body rotation within the vessel, using a 6-blade, up-pumping pitched blade turbine. The gas phase was introduced via sintered glass panel spargers mounted in the vessel base. Two different configurations were used: firstly where the sparger located directly below the impeller, and secondly where the sparger was located opposite the impeller on the other side of the vessel. Measured distributions of turbulent kinetic energy (TKE) for both gassed configurations were similar and showed significant differences to the ungassed case. Estimates of the gas-liquid interfacial area were at least 2-3 times higher than those found in conventional, lab-scale baffled vessels; this was attributed to the creation of very small bubbles at the sparger ().     

Measuring gas hold-up in gas–liquid/gas–solid–liquid stirred tanks with an electrical resistance tomography linear probe

An electrical resistance tomography (ERT) linear probe was used to measure gas hold-up in a two-phase (gas–liquid) and three phase (gas–solid–liquid) stirred-tank system equipped with a Rushton turbine. The ERT linear probe was chosen rather than the more commonly used ring cage geometry to achieve higher resolution in the axial direction as well as its potential for use on manufacturing plant. Gas-phase distribution was measured as a function of flow regime by varying both impeller speed and gas flow rate. Global and local gas hold-up values were calculated using ERT data by applying Maxwell's equation for conduction through heterogeneous media. The results were compared with correlations, hard-field tomography data, and computational fluid dynamic simulations available in the literature, showing good agreement. This study thus demonstrates the capability of ERT using a linear probe to offer, besides qualitative tomographic images, reliable quantitative data regarding phase distribution in gas–liquid systems.     

Bubble sizes in agitated air-alcohol systems with and without particles: Turbulent and transitional flow

In heterogeneous catalytic processes, the relationship between bubble size and various process parameters is important in determining interfacial area, hence mass transfer rate. This paper presents the results of an experimental study of bubble sizes in air-alcohol dispersions with and without the presence of catalyst particles in a batch stirred reactor at different agitation speeds and mean specific energy dissipation rates. Factors investigated include catalyst type, particle size and concentration. It has been found that:

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Since there are large differences in the viscosity of the various alcohols used, by dividing them into two groups based on the flow type (turbulent or transitional), a consistent correlation has been found for mean bubble size as a function of Weber number, We, for each region, though neither correlation agrees with the precise relationship suggested by Kolmogoroff's theory of locally, homogeneous, isotropic turbulence.

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At the same We number, the size is bigger in transitional flow than in turbulent. The functionality of the correlation of d₃₂/D versus We is similar whether particles are present or not.

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In fully developed turbulent flow, the bubble size is slightly reduced when catalyst particles are present, independent of catalyst size or type.

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In transitional flow, the effect of catalyst particles on bubble size is much stronger, the size being reduced by approximately 30%.

     

Systematic mesh development for 3D CFD simulation of fixed beds: Single sphere study

To develop and validate meshes for computational fluid dynamics (CFD) simulations of transport in fixed beds, a single particle is often used as a test case. We present results for drag coefficient (C_D) and heat transfer Nusselt number (Nu) for flow past a sphere, focusing on high flow rates typical of industrial steam reformers (400 < Re < 20,000). Over this range, good predictions of C_D were obtained using large eddy simulation (LES) to capture vortex shedding and wake dynamics, with a mesh refined downstream from the sphere. The small time-steps and high cell count required make this too expensive for fixed beds. Nu can be accurately calculated using a Reynolds-averaged Navier-Stokes (RANS) method with shear-stress transport (SST) k-ω closure provided the mesh at the particle surface is fine enough and covers most of the boundary layer. Single sphere simulations of heat transfer are more useful for fixed bed mesh development than drag coefficient calculations.