Segregation in beds of large particles at high velocities

In some industrial fluidized bed processes, notably coal combustion, the bed contains a very wide size range (50 – 5000 μm) of equal density particles. In others the particles change their density as the reaction proceeds, giving a bed of particles having similar sizes but densities varying by a factor of up to 2.

Experiments have been done in a bed 0.29 m diam. at velocities up to 5 m/s, using coarse particles up to 6 mm. They show that segregation by density difference can be reduced to negligible proportions by using high velocities, but that segregation by size appears to be an intrinsic feature of coarse particle systems at all velocities when a very wide size range is present. A tentative form of equation is proposed for segregation by size; the equations of Rowe are useful predictors for segregation by density difference.     

Theoretical assessment of the catalytic (Pt/TiO2) oxidation of formaldehyde at ambient temperature

A recent article [C. Zhang, H. He, K. Tanaka, Catal. Commun. 6 (2005) 211] investigates the use of a Pt/TiO₂ catalyst for the oxidation of formaldehyde. The findings demonstrate nearly complete oxidation at ambient temperature (25 °C) for values of the surface velocity in the range 5–10 × 10⁴ h⁻¹ and a 45% destruction when using a surface velocity of 20 × 10⁴ h⁻¹.In the present communication, this oxidation was assessed by theoretical considerations of the reaction kinetics. The destruction efficiency was predicted using a first-order reaction rate expression, combined with different theoretical or semi-empirical equations for the intrinsic reaction rate constant. Predicted and experimental data are in fair agreement, thus validating the theoretical approach and confirming the experimental results.     

Concreteness training reduces dysphoria: Proof-of-principle for repeated cognitive bias modification in depression.

A tendency toward abstract and overgeneral processing is a cognitive bias hypothesized to causally contribute to symptoms of depression. This hypothesis predicts that training dysphoric individuals to become more concrete and specific in their thinking would reduce depressive symptoms. To test this prediction, 60 participants with dysphoria were randomly allocated either to (a) concreteness training; (b) bogus concreteness training, matched with concreteness training for treatment rationale, experimenter contact, and treatment duration but without active engagement in concrete thinking; (c) a waiting-list, no training control. Concreteness training resulted in significantly greater decreases in depressive symptoms and significantly greater increases in concrete thinking than the waiting-list and the bogus training control, and significantly greater decreases in rumination than the waiting-list control. These findings suggest that concreteness training has potential as a guided self-help intervention for mild-to-moderate depressive symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compact InP-based HBT VCOs with a wide tuning range at W- andD-band

Compact monolithic integrated differential voltage-controlled oscillators (VCOs) operating in W-band were realized using InP-based heterojunction bipolar transistors (HBTs). The oscillators, with a total chip size of 0.6 by 0.35 mm², are based on a balanced Colpitts-type topology with a coplanar transmission-line resonator. By varying the voltage across the base-collector junction of the HBT in the current mirror and by changing the current in the VCO, the oscillation frequency can be tuned between 84 and 106 GHz. At 100 GHz, a differential voltage swing of 400 mV is obtained, which should be sufficient to drive 100 Gb/s digital logic. By combining the balanced outputs of a similar differential VCO in a push-push configuration, a compact source with close to -10 dBm output power and a tuning range between 138 and 150 GHz is obtained     

A Low-Power Linear SiGe BiCMOS Low-Noise Amplifier for Millimeter-Wave Active Imaging

This letter presents a low-power linear and wideband two-stage millimeter-wave low-noise amplifier (LNA) fabricated in a low-cost 0.18 $mu{rm m}$ SiGe BiCMOS technology. Design techniques utilized to optimize the gain and NF and to achieve high linearity and wideband at W-band are addressed. The LNA achieves a peak power gain of 14.5 dB at 77 GHz with a 3 dB bandwidth of 14.5 GHz from 69 to 83.5 GHz. The measured NF is 6.9 dB at 77 GHz and is lower than 8 dB from 64 to 81 GHz. Both input and output return losses are better than 11 dB and 17 dB at 77 GHz, respectively. The measured input 1 dB compression point is $-$11.4 dBm at 77 GHz with low power consumption of only 37 mW.      

Evaluative conditioning in humans: A meta-analysis.

This article presents a meta-analysis of research on evaluative conditioning (EC), defined as a change in the liking of a stimulus (conditioned stimulus; CS) that results from pairing that stimulus with other positive or negative stimuli (unconditioned stimulus; US). Across a total of 214 studies included in the main sample, the mean EC effect was d = .52, with a 95% confidence interval of .466–.582. As estimated from a random-effects model, about 70% of the variance in effect sizes were attributable to true systematic variation rather than sampling error. Moderator analyses were conducted to partially explain this variation, both as a function of concrete aspects of the procedural implementation and as a function of the abstract aspects of the relation between CS and US. Among a range of other findings, EC effects were stronger for high than for low contingency awareness, for supraliminal than for subliminal US presentation, for postacquisition than for postextinction effects, and for self-report than for implicit measures. These findings are discussed with regard to the procedural boundary conditions of EC and theoretical accounts about the mental processes underlying EC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pilot-scale peroxidation (H2O2) of sewage sludge

Municipal and industrial wastewater treatment plants produce large amounts of sludge. This excess sludge is an inevitable drawback inherent to the waste activated sludge process. Both the reduction of the amount of sludge produced and improving its dewaterability are of paramount importance. Novel pre-treatment processes have been developed in order to improve sludge dewatering, handling and disposal. This paper discusses the oxidation process utilising the catalytic activation of H(2)O(2) by iron salts, referred to as Fenton's reagent. In previous work, the authors described the experimental laboratory results of H(2)O(2)-oxidation of thickened sludge. Based upon the optimum conditions obtained in these laboratory tests, pilot-scale experiments are conducted. Peroxidation under its optimum conditions, i.e. (i) through addition of 25 g H(2)O(2) kg(-1) DS (dry solids content), (ii) in the presence of 1.67 g Fe(2+)-ions kg(-1) DS, (iii) at pH 3, and (iv) at ambient temperature and pressure, significantly reduces the amounts of sludge and improves the product quality: the amount DS per equivalent inhabitant per day (DS/IE.d) was reduced from 60 to 33.1 g DS/IE.d and the percentage DS of the sludge cake was 47%, which is high compared with the 20-25% achieved in a traditional sludge dewatering facility. An economic assessment for a wastewater treatment plant of 300,000 IE confirms the benefits. Considering the fixed and variable costs and the savings obtained when the sludge is incinerated after dewatering, a net saving of approx. 950,000 Euro per year or 140 Euro per ton DS can be expected.     

An InGaAs-InP HBT differential transimpedance amplifier with 47-GHz bandwidth

Return-to-zero differential phase-shift keying applications require a differential amplifier with high bandwidth, high gain, low noise, and good input impedance match. In this paper, we describe an InGaAs-InP heterostructure bipolar transistor differential transimpedance amplifier with high bandwidth of 47 GHz and high gain of 56 dB-/spl Omega/. The input-referred current noise is less than 35 pA//spl radic/Hz over the measurement range up to 40 GHz.     

Particle motion in L-valve as observed by positron emission particle tracking

L-valves are widely used in circulating fluidized beds (CFB) to control the solid circulation rate. Positron emission particle tracking (PEPT) is used to view and study the real-time particle motion in the L-valve. The paper presents experimental results of the solid motion and solid flux in the L-valve, G_s, as a function of the superficial injection air velocity, U. Results are compared with earlier work. The size of the L-valve is 4.5 cm I.D. Two different experimental configurations (L-valve discharge in a CFB riser and free discharge) were used. The L-valve flow regime is stable until approximately 6 U / U_mf, with proportionality between solid flux and U / U_mf. At a higher U / U_mf, unsteady fluctuations in the solid flow gradually increase due to cavity formation around the L-valve elbow. Increasing the air flow even further, a maximum flow is reached, corresponding to the maximum discharge rate through the cyclone or hopper apex. PEPT has also confirmed the existence of a dune flow. For the first time, it gives quantitative data of the velocity profile of the dune flow which is governed by two important factors. The first factor is the distance of solids from the base of the L-valve, with solid velocity increasing away from the base. The second factor is the location of solids with respect to the dune, i.e. solid velocity is minimum at the base of the dunes and maximum at the top of the dunes. The average voidage in the L-valve is approximately constant and independent of U.     

High resolution profiles of thallium, manganese and iron assessed by DET and DGT techniques in riverine sediment pore waters

High resolution profiles of Mn, Tl and Fe concentrations have been assessed in the pore waters of river Leie sediments at Warneton and Menen (at the border of Belgium and France) by DET (Diffusive Equilibrium in Thin Films) and DGT (Diffusive Gradients in Thin Films) techniques. The oxidized, solid Mn (IV), Tl (III) and Fe (III) compounds were reduced in the suboxic (+255 to -20 mV versus Standard Hydrogen Electrode (SHE)) riverine sediments and since these reduced species are much more soluble also they are released into the pore waters. The highest DET (total dissolved) concentrations of Fe (76 mg l(-1)), Mn (2 mg l(-1)) were observed at the station of Menen, while Tl maxima differed only slightly between the 3 surveys (21 to 27 microg l(-1)). The average ratios of Fe/Mn/Tl in the pore waters at the 3 sampling stations are fairly constant for both the DET and DGT samplings. However, the results indicate that compared to Fe and Tl a greater proportion of the Mn measured by DET is accumulated by DGT, reflecting the ready supply of Mn from solid phase to solution.