Geochemical modelling of arsenic and selenium leaching in alkaline water treatment sludge from the production of non-ferrous metals

Geochemical modelling of leaching of oxyanion forming elements such as arsenic (As) and selenium (Se) is frequently not successful. A consistent thermodynamic dataset of As and Se was therefore composed, not only including precipitation, but also adsorption and solid solution, and was applied to the pH-dependent leaching behaviour of As and Se in an alkaline residue with a pH 11.1 from the lime treatment of sulphuric acid wastewaters from the production of non-ferrous metals. The As and Se content ranged up to 6.7 wt% and 0.29 wt%, respectively and speciation analysis showed that 96.3% of As occured as arsenate whereas Se speciation comprised 79% selenate and 21.0% selenite. XRD and SEM/EDX analysis showed that arsenate occurred as rauenthalite (Ca(3)(AsO(4))(2).10H(2)O), associated with gypsum, the most important mineral. Arsenate and arsenite concentrations were only slightly below equilibrium with rauenthalite and calciumarsenite (CaHAsO(3)), respectively and consideration of adsorption and solid solution only marginally improved model predictions. Selenate (Se(VI)) and selenite (Se(IV)), on the other hand, were far from equilibrium with their corresponding calcium metalate. The application of solid solutions and adsorption of Se(VI) and Se(IV) oxyanions with gypsum, calcite and ettringite significantly improved model predictions but missing thermodynamic data and especially the lack of a comprehensive model for solid solution and surface exchange with calcite and ettringite still hampered efficient modelling.     

Field effects of pollutants at the community level--experimental challenges and significance of community shifts for ecosystem functioning

In the Stimulation Program System-oriented Ecotoxicological Research (SSEO) three sites in The Netherlands were investigated for field effects of the grey veil of pollutants. At each site several studies were performed in order to arrive at an adequate weight of evidence and to improve causal inference of pollutant effects. This paper contains a synthesis of results of the studies, performed at one of the sites, the Demmerikse polder. This site is characterized by an anthropogenic layer of soil (in old Dutch: ‘toemaakdek’) on top of the natural peat. Lead, copper and zinc concentrations were elevated, with lead concentrations above a Netherlands environmental quality criterion (Intervention Value) in 66% of the samples. Issues discussed in the paper are: the sampling strategy, selection of maximum gradient and suitable community end-points, both in space and in time. Specific emphasis was given to causal inference of ecological effects of pollutants, related to direct versus indirect effects, functioning of ecosystems, normal operation range and risk assessment. The plausibility of metal effects could be demonstrated on a number of occasions. In the Demmerikse polder changes in the bacterial and nematode communities could be related significantly to metal concentrations and separated from other environmental variables, such as organic matter content and pH.     

A Fully Integrated Class 1 Bluetooth 0.25 μm CMOS PA

A fully integrated 0.25 m CMOS bluetooth class 1 power amplifier is presented. On this chip all inductors and decoupling capacitors are situated on the silicon die. Due to the high level of integration, a cheap flip chip assembly method has been used. The chip delivers 138 mW (21.4 dBm) of output power with a power added efficiency of 25.8%. When the amplifier is tuned to its optimum frequency of 2.1 GHz, the output power increases to 184 mW and the power added efficiency increases to 29.5%. To compare the performance of this realisation with other recently published PA, a figure of merit for saturated (switched) power amplifiers is introduced.Koen Mertens was born in Antwerpen, Belgium in 1971. He received the M.Sc. degree in Electrical Engineering from the Katholieke Universiteit Leuven, Belgium in 1998. The subject of his M.Sc. thesis was the design of a 2.14 GHz BICMOS oscillator. The thesis was in cooperation with IMEC. Since 1998. He has been a research assistant at the ESAT-MICAS laboratories, where he is currently working towards a Ph.D. degree in CMOS RF Power Amplifiers. His research promotor is Prof. Michiel Steyaert.Michiel Steyaert Michel S.J. Steyaert was born in Aalst, Belgium, in 1959. He received the masters degree in electrical-mechanical engineering and the Ph.D. degree in electronics from the Katholieke Universiteit Leuven (K.U. Leuven), Heverlee, Belgium in 1983 and 1987, respectively.From 1983 to 1986 he obtained an IWNOL fellowship (Belgian National Fundation for Industrial Research) which allowed him to work as a Research Assistant at the Laboratory ESAT at K.U. Leuven. In 1987 he was responsible for several industrial projects in the field of analog micropower circuits at the Laboratory ESAT as an IWONL Project Researcher. In 1988 he was a Visiting Assistant Professor at the University of California, Los Angeles. In 1989 he was appointed by the National Fund of Scientific Research (Belgium) as Research Associate, in 1992 as a Senior Research Associate and in 1996 as a Research Director at the Laboratory ESAT, K.U. Leuven. Between 1989 and 1996 he was also a part-time Associate Professor. He is now a Full Professor at the K.U. Leuven. His current research interests are in high-performance and high-frequency analog integrated circuits for telecommunication systems and analog signal processing.Prof. Steyaert received the 1990 European Solid-State Circuits Conference Best Paper Award, the 1995 and 1997 ISSCC Evening Session Award, the 1999 IEEE Circuit and Systems Society Guillemin-Cauer Award and the 1991 NFWO Alcatel-Bell-Telephone award for innovative work in integrated circuits for telecommunications.     

Design of a Class E Power Amplifier with LDMOS in Standard CMOS

This paper describes the development of a high-voltage transistor in a standard 0.35 μm CMOS technology and its application on a class E power amplifier for mobile communications. The use of a higher voltage already available in the battery has the benefit of reducing the electromigration constrains and having lower voltage drops in the interconnects due to the use of a lower current.Measured results on the active device and simulation show that is possible to achieve a higher power added efficiency using a lateral double diffused MOS, while reducing the current draining the battery.João Ramos (S’02) was born in Angola, in 1974. He received the Licenciatura degree in Electrical Engineering and Computer Science from Instituto Superior Técnico, Lisbon, Portugal.Currently, he is a research assistant at the ESAT-MICAS group of the Katholieke Universiteit Leuven. He is working towards a Ph.D. degree on RF CMOS Power Amplifiers. For this work, he obtained a scholarship from the FCT, Portugal.Michiel S.J. Steyaert (S’85–A’89–SM’92–F’03) was born in Aalst, Belgium, in 1959. He received the M.Sc. degree in electrical-mechanical engineering and the Ph.D. degree in electronics from the Katholieke Universiteit Leuven (KU Leuven), Heverlee, Belgium, in 1983 and 1987, respectively.From 1983 to 1986, he was a Research Assistant with the Laboratory ESAT at KU Leuven, funded by an IWNOL fellowship (Belgian National Foundation for Industrial Research). In 1987, as an IWONL Project Researcher, he was responsible for several industrial projects in the field of analog micropower circuits with the Laboratory ESAT. In 1988, he was a Visiting Assistant Professor at the University of California, Los Angeles. In 1989, he was a Research Associate appointed by the National Fund of Scientific Research (Belgium); in 1992, he was promoted to a Senior Research Associate, and in 1996, he became Research Director at the Laboratory ESAT, KU Leuven. Between 1989 and 1996, he was also a part-time Associate Professor. He is currently a Full Professor at the KU Leuven. His current research interests include high-performance and high-frequency analog integrated circuits for telecommunication systems and analog signal processing.Prof. Steyaert received the European Solid-State Circuits Conference Best Paper Award in 1990 and 2001. He received the 1991 and the 2000 NFWO Alcatel-Bell-Telephone Award for innovative work in integrated circuits for telecommunications. In 1995 and 1997, he received the IEEE-ISSCC Evening Session Award, and the 1999 IEEE Circuit and Systems Society Guillemin-Cauer Award.     

Extremely slowly desorbing polycyclic aromatic hydrocarbons from soot and soot-like materials: evidence by supercritical fluid extraction

Combustion-derived PAHs are strongly sorbed to their particulate carrier (i.e., soot, charcoal), and therefore, very slow desorption kinetics of the chemicals might be anticipated. Measurements are however lacking, because conventional methods (Tenax, XAD, gas-purging) fail to accurately determine desorption kinetics due to practical problems. In this study, we used a mild supercritical fluid extraction (SFE) method, which mimics desorption into water and circumvents these problems, to quantify desorption kinetics of 13 native PAHs from pure charcoal, coal, and four types of soot. The results show that generally only very small PAH fractions are released. Desorption behavior was, however, not related to common sorbent/sorbate characteristics. Two-site model-derived "fast desorbing fractions" were <0.01 in the majority of cases, and for the dominant "slow sites", the calculated rate constants for desorption into water measured from 10(-7) to 10(-5) h(-1). These data suggest that desorption of coal and combustion-derived PAHs can be even slower than the "very slow" desorption observed in sediments. Estimated time scales required for removal of pyrogenic PAHs from these extremely slow sites into water amount to several millennia. Our results imply reduced chemical risks for soot and soot-like materials, casting doubts on current risk assessment procedures and environmental quality standards of pyrogenic PAHs.     

An Optimal Usage of NOx in a Combined Pt/Ceramic Foam and a Wall-Flow Monolith Filter for an Effective NOx-Assisted Soot Oxidation

An NO₂-assisted soot oxidation based filter candidate consists of Pt-coated ceramic foam in combination with a wall-flow monolith is proposed to acquire for an optimal usage of exhaust NO _x . The configuration is designed to operate as deep bed filtration on Pt/ceramic foam and surface filtration on the wall-flow monolith. The oxidation of soot by NO₂ takes place by multi-cycle reaction in Pt/ceramic foam and by the normal CRT on the wall-flow monolith. The filter performs with a higher oxidation rate and a lower NO₂-slip.     

Supporting subject matter annotation using heterogeneous thesauri: A user study in Web data reuse

We performed a user experiment in which museum professionals used vocabularies from the Web for annotating the subject matter of museum objects. In this paper, we study the requirements on the underlying RDF dataset, search algorithms and user interface design in a real world setting. We identify the advantages of reusing vocabularies from the Web and discuss how and to what extent the disadvantages can be overcome. The study is performed at the Print Room of the Rijksmuseum Amsterdam, where currently a large collection of prints, photographs and drawings is being catalogued. We report on the analysis of the current practice of professional cataloguers, the iterative design of an annotation tool and a qualitative evaluation of this tool with a user experiment in a realistic annotation environment. We discuss our findings in terms of their impact on the RDF data, the semantic search functionality and the user interface.     

Sensor selection for cost-effective virtual torque measurements on a wind turbine gearbox

Forschung im Ingenieurwesen - Measuring the operational torques during the lifetime of a&nbsp;wind turbine gearbox offers a&nbsp;valuable source of information for design, monitoring,...     

The virtual stuntman: dynamic characters with a repertoire of autonomous motor skills

An ambitious goal in the area of physics-based computer animation is the creation of virtual actors that autonomously synthesize realistic human motions and possess a broad repertoire of lifelike motor skills. To this end, the control of dynamic, anthropomorphic figures subject to gravity and contact forces remains a difficult open problem. In this paper, we report on our ongoing development of a virtual stuntman, a dynamic graphical character that possesses a nontrivial repertoire of lifelike motor skills. The repertoire includes basic actions such as balance, protective stepping when balance is disturbed, protective arm reactions when falling, multiple ways of rising upright after a fall, and several more vigorously dynamic motor skills. Our virtual stuntman is the product of a recently proposed framework for integrating motor controllers, which includes among other ingredients an explicit model of pre-conditions; i.e., those regions of a dynamic figure's state space within which a given motor controller is applicable and expected to work properly.     

Left ventricular geometric patterns in end‐stage kidney disease: Determinants and course over time

Introduction : While concentric left ventricular hypertrophy (cLVH) predominates in non–dialysis‐dependent chronic kidney disease (CKD), eccentric left ventricular hypertrophy (eLVH) is most prevalent in dialysis‐dependent CKD stage 5 (CKD5D). In these patients, the risk of sudden death is 5× higher than in individuals with cLVH. Currently, it is unknown which factors determine left ventricular (LV) geometry and how it changes over time in CKD5D. Methods : Data from participants of the CONvective TRAnsport Study who underwent serial transthoracic echocardiography were used. Based on left ventricular mass (LVM) and relative wall thickness (RWT), 4 types of left ventricular geometry were distinguished: normal, concentric remodeling, eLVH, and cLVH. Determinants of eLVH were assessed with logistic regression. Left ventricular geometry of patients who died and survived were compared. Long‐term changes in RWT and LVM were evaluated with a linear mixed model. Findings : Three hundred twenty‐two patients (63.1 ± 13.3 years) were included. At baseline, LVH was present in 71% (cLVH: 27%; eLVH: 44%). Prior cardiovascular disease (CVD) was positively associated with eLVH and ß‐blocker use inversely. None of the putative volume parameters showed any relationship with eLVH. Although eLVH was most prevalent in non‐survivors, the distribution of left ventricular geometry did not vary over time. Discussion : The finding that previous CVD was positively associated with eLVH may result from the permanent high cardiac output and the strong tendency for aortic valve calcification in this group of long‐term hemodialysis patients, who suffer generally also from chronic anemia and various other metabolic derangements. No association was found between eLVH and parameters of fluid balance. The distribution of left ventricular geometry did not alter over time. The assumption that LV geometry worsens over time in susceptible individuals, who then suffer from a high risk of dying, may explain these findings.