Proposal for optical switch using nonlinear refraction

We propose that using the phenomenon of refraction of two coaxially copropagating beams at the interface of two nonlinear media, a passive all-optical switch could be constructed for future integrated photonic circuits.     

Minimum-energy state estimation for systems with perspective outputs

This paper addresses the state estimation of systems with perspective outputs. We derive a minimum-energy estimator which produces an estimate of the state that is "most compatible" with the dynamics, in the sense that it requires the least amount of noise energy to explain the measured outputs. Under suitable observability assumptions, the estimate converges globally asymptotically to the true value of the state in the absence of noise and disturbance. In the presence of noise, the estimate converges to a neighborhood of the true value of the state. These results are also extended to solve the estimation problem when the measured outputs are transmitted through a network. In that case, we assume that the measurements arrive at discrete-time instants, are time-delayed, noisy, and may not be complete. We show that the redesigned minimum-energy estimator preserves the same convergence properties. We apply these results to the estimation of position and orientation for a mobile robot that uses a monocular charged-coupled device (CCD) camera mounted on-board to observe the apparent motion of stationary points. In the context of our application, the estimator can deal directly with the usual problems associated with vision systems such as noise, latency and intermittency of observations. Experimental results are presented and discussed.     

Securing safe operation of VVÉR reactor systems in nuclear power plants

The safe operation of VVéR reactors has been discussed throughout the entire design process, taking account of the normative documentation, including the international requirements (IAEA, EUR). After the first domestic normative document “Basic principles for securing the safety of nuclear power plants” was approved in 1973, work began on the reconstruction of the first-generation VVéR-440 power-generating units. The measures taken to increase safety concerned all types of reactors VVéR-440 and-1000. Information on implementing these measures is presented. __________ Translated from Atomnaya énergiya, Vol. 101, No. 2, pp. 87–93, August, 2006.     

Development and adoption of measures for increasing the safety of power-generating units of nuclear power plants with RBMK reactors in 1986–2005

The basic stages and directions of upgrading and reconstruction of the power-generating units of nuclear power plants with RBMK reactors over a period of 20 yr since the Chernobyl accident are reflected in this paper. The greatest amount of work was done in 1986–1990 on all units with RBMK-1000 and-1500 reactors which were operating at that time in the USSR. The purpose of the upgrade was to improve the neutron-physical characteristics of the reactor cores, increase the response speed of the safety and control system and decrease the positive effect of water outflow from the cooling loop of this system, increase the flow capacity of the systems performing emergency discharge of the steam-gas mixture from the reactor, and improve the basic operating documentation. The subsequent stages of the upgrading and reconstruction concerned mainly the first-generation power-generating units (Nos. 1 and 2 units of the Leningrad and Kursk nuclear power plants). These works were performed to make the power-generating units conform to the requirements of the modern normative documents on safety and allow for the possibility of these units to remain in operation after the nominal 30-yr service life has been exhausted. __________ Translated from Atomnaya énergiya, Vol. 100, No. 4, pp. 312–320, April, 2006.     

Screen‐printed biosensor for allergens

Allergen levels in indoor environments, leading to many diseases, eg asthma, rhinitis and conjunctivitis, affect a large and increasing fraction of the population. A quite effective and inexpensive method of a rough but very rapid overall assessment of total allergen level in the environment has been developed. The method involved estimation of protein in allergen extracts by screen‐printed electrodes using two different techniques. The biosensor comprised a rhodinised carbon working electrode, a silver/silver chloride reference electrode and a carbon counter electrode. In the first method the enzyme protease reacted with allergen protein to release amino acid, which produced hydrogen peroxide in the presence of amino acid oxidase. This was detected amperometrically. The second method used potassium bromide as electrolyte and the electrode was subjected to dual potential. Bromine, released due to electrolysis at higher potential, was consumed by the allergen protein at lower potential. In the first method, a unique technique was used to microencapsulate the enzyme protease and immobilise it on the surface of the electrode by in‐situ polymerisation to avoid contact with the amino acid oxidase. A total of seven allergens were tested and the results gave a good correlation with the standard protein measurement method. Environmental specimens from indoors, schools and workplaces can be evaluated for the aeroallergens produced by dust mites, animal hairs, cockroach debris, pollens, etc as a means of determining the exposure risk. Copyright © 2005 Society of Chemical Industry     

Nitrification parameter measurement for plant design: experience and experimental issues with new methods.

Nitrification kinetics are important for process design, optimization, and capacity rating of activated sludge wastewater treatment plants. A Water Environment Research Foundation (WERF) project on Methods for Wastewater Characterization in Activated Sludge Modeling (WERF, 2003) focused significantly on the development of procedures for measuring the nitrifier maximum specific growth rate, micro(AUT). In addition, the importance of (and lack of data for) the nitrifier decay rate, b(AUT), was identified. This paper describes three bench-scale methods for measuring micro(AUT): the Low F/M SBR, Washout and High F/M methods. During the WERF project, the importance of pH and temperature control was investigated briefly; this paper summarizes further experimental work performed to address these issues. A summary of micro(AUT) measurements in a number of locations and using the different measurement techniques is provided.     

Degradation of wine industry wastewaters by photocatalytic advanced oxidation.

Wine industry wastewaters contain a high concentration of organic biodegradable compounds as well as a great amount of suspended solids. These waters are difficult to treat by conventional biological processes because they are seasonal and a great flow variation exists. Photocatalytic advanced oxidation is a promising technology for waters containing high amounts of organic matter. In this study we firstly investigated the application of H2O2 as oxidant combined with light (artificial or natural) in order to reduce the organic matter in samples from wine industry effluents. Secondly, we studied its combination with heterogeneous catalysts: titanium dioxide and clays containing iron minerals. The addition of photocatalysts to the system reduces the required H2O2 concentration. Although the H2O2/TiO2 system produces higher efficiencies, the H2O2/clays system requires a H2O2 dosage between three and six times lower.     

Removal of E. coli and helminth eggs in UASB: Polishing pond systems in Brazil.

Ponds following anaerobic reactors, such as Upflow Anaerobic Sludge Blanket (UASB) reactors, have been termed polishing ponds in the literature. The present paper analyses the removal of E. coli and helminth eggs in five UASB-polishing pond systems in Brazil. Since there were ponds in series, the total number of ponds was 10. The ponds had average retention times varying from 2 to 21 days, and depths ranging from 0.40 to 2.00 m. The shallow ponds in series, even with low retention times, were able to produce effluents complying with the coliform WHO guidelines for unrestricted irrigation (< or = 1000 MPN/100 ml). An equation for the coliform decay coefficient was proposed: Kb (dispersed flow) = 0.710H(-0955) (20 degrees C). The equation highlights the inverse relationship between the pond depth and the decay coefficient. All polishing pond systems were able to produce effluents with helminth eggs concentrations predominantly equal to zero, and satisfying the WHO guidelines for unrestricted and restricted irrigation (< or = 1 egg/L, arithmetic mean). The approximate range of helminth eggs removal efficiency was predicted satisfactorily.     

An Investigation of Milk Powders Produced by a Laboratory-Scale Spray Dryer

A mini spray dryer has been used to investigate morphological changes that occur to milk particles during the spray drying process. We have found that the mini spray dryer is ideal for such investigations, because phenomena such as skin and vacuole formation in particles can be analyzed without the added complication of particle agglomeration, which only occurs in much larger spray dryers where particle number concentrations are higher. We have confirmed observations made by various researchers that the bulk density of spray-dried milk powder is greatly affected by the drying temperature, due to the strong influence of the latter on the porosity of the particles. In addition, we have attempted to explain observations made by various workers that fat accumulates preferentially at the surface of a particle during drying by postulating that fluid fat is transported towards the surface, via a network of cracks and pores, by the development of a vacuole overpressure which is also responsible for the inflation of the particle. Finally, we have shown that milk powders can be spray dried a second time, by reconstitution with water, with no change to the thermodynamic characteristics of the resultant powder. Thus, milk concentrates for spray drying research can be prepared from already-spray-dried milk powders rather than using the more arduous evaporation method to concentrate unprocessed milk.