Disc filtration for separation of flocs from a moving bed bio-film reactor.

A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis.     

Static and pulsed pressures measured using electrically conducting rubbers

A method of measuring static and pulsed pressures using electrically conducting rubber sensors is proposed. The method is based on a change in the volume resistivity of a filled rubber under the action of external pressure. The pressure-induced change in resistance of the rubber sensor is proportional to the applied pressure and can be measured by a bridge circuit. Using this method, it is possible to evaluate the degree of homogeneity of the pressure distribution over a solid surface. This is achieved by distributing rubber sensors over the given surface.     

Performance analysis of information dissemination by flooding

Performance properties are established for the dissemination by flooding of a database that is initially distributed among the nodes of a communications network. An example of this general process is the dissemination of network status information as a component of the adaptive routing mechanism in a network like Arpanet. Bounds are given on the progress of the dissemination process at a sequence of times before the completion of the process, whereas earlier results only bounded the time until completion. The present bounds further extended earlier analysis by treating the diameter explicitly as a parameter. Specialized versions of the bounds are given for k-connected networks. The bounds yield a recognition property whereby a node can recognize that it has received the entire database without having a priori knowledge of the size of the database. An earlier assumption about a fixed time for correct message transmission over any edge is relaxed to assume only an upper bound on these transmission times     

Three-Phase Induction Generator for Single-Phase Line

Hydroelectric generators of less than 20 kilowatts can be in remote areas served only by a single-phase line. For high efficiency and low cost, a three-phase induction generator should be used. This three-phase generator can operate with balanced voltages and currents when the ``phase-splitting' circuit uses two capacitors connetted to two different single-phase voltage sources.     

Force criteria of the state of limiting equilibrium of a cracked plate under biaxial loading

We deduce the theoretical formula taking into account the influence of biaxial loading of a plate weakened by a crack on the stress intensity factor K _I. This enables us to compute the characteristic of crack resistance K _c according to the known boundary forces. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 6, pp. 14–16, November–December, 2007.     

Development of Free-Electron x-Ray Lasers on the TESLA Test Accelerator (DESY, Germany)

The program for developing free-electron x-ray lasers at TESLA started in 1994. The plan is to use the TESLA test accelerator to develop an x-ray laser with minimum wavelength 0.1–6 nm. The first phase of the project was successfully completed in 2001. At saturation, the laser produces ultrashort 30–100 fsec, gigawatt, radiation pulses. The wavelength can be tuned smoothly over the range 80–120 nm.     

Inference of message sequence charts

Software designers draw message sequence charts for early modeling of the individual behaviors they expect from the concurrent system under design. Can they be sure that precisely the behaviors they have described are realizable by some implementation of the components of the concurrent system? If so, can we automatically synthesize concurrent state machines realizing the given MSCs? If, on the other hand, other unspecified and possibly unwanted scenarios are "implied" by their MSCs, can the software designer be automatically warned and provided the implied MSCs? In this paper, we provide a framework in which all these questions are answered positively. We first describe the formal framework within which one can derive implied MSCs and then provide polynomial-time algorithms for implication, realizability, and synthesis.     

Emission of trace toxic metals during pulverized fuel combustion of Czech coals

A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd.