InP D-HBT ICs for 40-Gb/s and higher bitrate lightwave transceivers

The combination of device speed (f/sub T/, f/sub max/ > 150 GHz) and breakdown voltage (V/sub bceo/ > 8 V) makes the double heterojunction bipolar InP-based transistor (D-HBT) an attractive technology to implement the most demanding analog functions of 40-Gb/s transceivers. This is illustrated by the performance of a number of analog circuits realized in an InP D-HBT technology with an 1.2- or 1.6-/spl mu/m-wide emitter finger: a low phase noise push-push voltage-controlled oscillator with -7-dBm output power at 146 GHz, a 40-GHz bandwidth and low-jitter 40-Gb/s limiting amplifier, a lumped 40-Gb/s limiting driver amplifier with 4.5-V/sub pp/ differential output swing, a distributed 40-Gb/s driver amplifier with 6-V/sub pp/ differential output swing, and a number of distributed preamplifiers with up to 1.3-THz gain-bandwidth product.     

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.     

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)     

Advanced sludge treatment affects extracellular polymeric substances to improve activated sludge dewatering

The management of wastewater sludge, now often referred to as biosolids, accounts for a major portion of the cost of the wastewater treatment process and represents significant technical challenges. In many wastewater treatment facilities, the bottleneck of the sludge handling system is the dewatering operation. Advanced sludge treatment (AST) processes have been developed in order to improve sludge dewatering and to facilitate handling and ultimate disposal. The authors have extensively reported lab-scale, semi-pilot and pilot investigations on either thermal and thermochemical processes, or chemical oxidation using hydrogen peroxide. To understand the action of these advanced sludge technologies, the essential role played by extracellular polymeric substances (EPS) needs to be understood. EPS form a highly hydrated biofilm matrix, in which the micro-organisms are embedded. Hence they are of considerable importance in the removal of pollutants from wastewater, in bioflocculation, in settling and in dewatering of activated sludge. The present paper reviews the characteristics of EPS and the influence of thermochemical and oxidation mechanisms on degradation and flocculation of EPS. Experimental investigations on waste activated sludge are conducted by the authors to evaluate the various literature findings. From the experiments, it is concluded that AST methods enhance cake dewaterability in two ways: (i) they degrade EPS proteins and polysaccharides reducing the EPS water retention properties; and (ii) they promote flocculation which reduces the amount of fine flocs.     

Hot acid hydrolysis as a potential treatment of thickened sewage sludge

Municipal and industrial wastewater treatment plants produce large amounts of sludge, containing organic and mineral components and being mechanically dewatered to e.g. 20-25% DS in centrifuges. Both the reduction of the amount of sludge produced and improving its dewaterability are hence of paramount importance. Hot acid hydrolysis can meet these objectives. The current paper describes the results of detailed investigations with respect to acid hydrolysis of thickened sludge (5-6% DS content). A comparison with traditional thermal hydrolysis is also included. As a result of the experimental investigations, it can be concluded that hot acid hydrolysis is efficient in both reducing the residual sludge amounts and improving the dewaterability. Under the proposed optimum conditions it is found that (i) the amount of hydrolysed DS is approximately 70% lower than the initial untreated amount, (ii) the DS-solid content of the dewatered cake is increased from 22.5% (initial untreated) to at least twice this value, (iii) the rate of mechanical dewatering is not significantly affected. The preferential release of ODS into the water phase, and the increased BOD/COD-ratio through hydrolysis, turn this recycle water phase into a possible carbon-source for nitrification/denitrification. Heavy metals and phosphates are also released in the water phase, and can be subsequently precipitated.     

The inhibitory effects of heavy metals and organic compounds on the net maximum specific growth rate of the autotrophic biomass in activated sludge

A respirometry technique can be applied as an effective method to determine the net maximum specific growth rate of autotrophic biomass under both normal conditions and when inhibition occurs. The net maximum specific growth rate of uninhibited autotrophic biomass, expressed as (mu(A)-b(A)), is approximately 0.8 per day [Proceeding of the International Congress on CHISA, Prague, 2002, p. 1]. Several heavy metals and organic compounds have inhibitory effects. Copper (Cu(2+)) has stronger inhibitory effects than zinc (Zn(2+)), and inhibits the nitrification process by 50% at 0.08 mg/l [(mu(A)-b(A)) = 0.4 per day], while the same concentration of Zn(2+) establishes 12% inhibition only [(mu(A)-b(A)) = 0.75 per day]. Inhibition with Cu(2+) starts at concentrations above 0.05 mg/l, while this is above 0.3mg/l for Zn(2+). The inhibition of the nitrification process is complete at 1.2mg/l for both Cu(2+) and Zn(2+). Among the selected organic compounds tested n the experiments, the degree of inhibition decreases as follow: chlorobenzene>trichloroethylene (TCE)>phenol>ethylbenzene. Chlorobenzene already inhibits the autotrophic biomass at 0.25 mg/l. The nitrification process is totally inhibited by adding 0.75 mg/l of chlorobenzene. TCE has a less inhibitory effect on the nitrification process and 50% inhibition is noticed at 0.75 mg/l TCE. The nitrification process is totally inhibited at 1mg/l TCE. Phenol inhibits the nitrification for 50% at 3 mg/l. The inhibitory effect of phenol is almost constant in the range 4-10 mg/l and complete inhibition is reached at 50 mg/l. The inhibitory effect of ethylbenzene is 50% at 8 mg/l and the autotrophic biomass is totally inhibited at 50 mg/l. Experimental findings are compared with literature data, which generally and significantly overestimate the inhibition threshold concentrations.     

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.     

NOx formation and selective non-catalytic reduction (SNCR) in a fluidized bed combustor of biomass

Caledonian Paper (CaPa) is a major paper mill, located in Ayr, Scotland. For its steam supply, it previously relied on the use of a Circulating Fluidized Bed Combustor (CFBC) of 58 MW_th, burning coal, wood bark and wastewater treatment sludge.It currently uses a bubbling fluidized bed combustor (BFBC) of 102 MW_th to generate steam at 99 bar, superheated to 465 °C. The boiler is followed by steam turbines and a 15 kg/s steam circuit into the mill. Whereas previously coal, wood bark and wastewater treatment sludge were used as fuel, currently only plantation wood (mainly spruce), demolition wood, wood bark and sludge are used.Since these biosolids contain nitrogen, fuel NO_x is formed at the combustion temperature of 850–900 °C. NO_x emissions (NO + NO₂) vary on average between 300 and 600 mg/Nm³ (dry gas). The current emission standard is 350 mg/Nm³ but will be reduced in the future to a maximum of 233 mg/Nm³ for stand-alone biomass combustors of capacity between 50 and 300 MW_th according to the EU LCP standards. NO_x abatement is therefore necessary.In the present paper we firstly review the NO_x formation mechanisms, proving that for applications of fluidized bed combustion, fuel NO_x is the main consideration, and the contribution of thermal NO_x to the emissions insignificant.We then assess the deNO_x techniques presented in the literature, with an updated review and special focus upon the techniques that are applicable at CaPa. From these techniques, Selective Non-catalytic Reduction (SNCR) using ammonia or urea emerges as the most appropriate NO_x abatement solution.Although SNCR deNO_x is a selective reduction, the reactions of NO_x reduction by NH₃ in the presence of oxygen, and the oxidation of NH₃ proceed competitively.Both reactions were therefore studied in a lab-scale reactor and the results were transformed into design equations starting from the respective reaction kinetics. An overall deNO_x yield can then be predicted for any operating temperature and NH₃/NO_x ratio.We then present data from large-scale SNCR-experiments at the CFBC of CaPa and compare results with the lab-scale model predictions, leading to recommendations for design and operation. Finally the economic impact is assessed of implementing SNCR-technology when applying an NH₃ SNCR or urea SNCR to the CFBC at CaPa.     

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.