Alkali Capacity and Physical Properties of Blast Furnace Type Slags

Alkali compounds, mainly those of Na and K, generally play a negative role in ironmaking blast furnaces. As easily circulating substances they consume energy, disturb furnace operation in the shaft and represent undesired impurities in the discharged slag and dust. An important task is to concentrate the alkalis in the slag as the best possible way. Control and optimisation of BF slag composition with respect to the alkalis requires reliable knowledge of basic data on the thermochemical and physical properties of the various slag compositions in the relevant iron‐slag system and in a wider range of temperatures according to the different reaction zones in the blast furnace. In the present paper, data are critically reviewed on free energies of reaction, the solubilities, bacicities and capacities of alkali oxides as well as on physical properties of alkali‐containing slags such as density, viscosity and surface tension. Furthermore alkali behaviour in primary and secondary BF slags and alkali circulation in the blast furnace are outlined. In a subsequent paper, new data on the chemical activities of alkali oxides in BF type slags and the kinetics and rates of alkali evaporation from these slags will be presented.     

Fiber-optic transmission of microwave 64-QAM signals

Experimental results on fiber-optic transmission of microwave 64-level quadrature amplitude modulated (QAM) signals at a 1.3 μm wavelength at a 90 Mb/s transmission rate are presented. Two important methods of improving the system performance are discussed and demonstrated: laser intensity noise minimization and error-correction coding using a self-orthogonal convolutional code. The applicability of this transmission technique to the distribution of digital TV services is assessed     

Comparison of different order GTD solutions of double-edgediffraction problem

A second order diffraction coefficient for the uniform geometrical theory of diffraction (GTD) is obtained explicitly for two knife edges in terms of the usual complex transition function (a modified Fresnel integral). The results from conventional GTD (zero order), slope diffraction GTD (first order), and second order GTD are compared with those obtained from physical optics (PO), which uses the complex Fresnel double integral. The results from second order GTD are close to those from PO in most of the cases studied     

An experimental comparison between LPG and engine exhaust gas as energy source for an absorption refrigeration system

This paper presents an experimental analysis of an absorption refrigeration system, comparing two different energy sources. The exhaust gas from an internal combustion engine was evaluated against the original energy source, liquefied petroleum gas (LPG). The experiments were performed in a domestic refrigerator, monitoring the air temperature and humidity inside the equipment. A production engine was tested with 25% and wide‐open throttle valve (WOT), mounted on a bench dynamometer. The energy demand, cooling capacity and coefficient of performance (COP) were determined for both energy sources. The results showed that engine exhaust gas is a potential source for absorption refrigeration systems. When the engine exhaust gas was used as energy source, the energy available for the refrigerator was higher with 25% throttle valve opening. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of the boundary layer development on the ozone concentration over an urban area

Results obtained during two campaigns (summer 2004 and autumn 2005) of observation of the planetary boundary layer dynamics over the Sofia city urban area are presented. An EARLINET scanning aerosol lidar, an ozone analyser and a ground meteorological station were used during the observations. The stable boundary layer height varied from 200 m to 600 m during the different seasons. The residual layer was found to be at 700–1200 m, being destroyed between 10:30 and 12:30 LST. The mixing layer developed up to heights of about 800–1300 m. The ground level ozone concentration was measured to be from 10 µg/m³ to 90 µg/m³. The convective boundary layer formation in three case studies (a clear sunny day, a partial solar eclipse, and in the presence of internal atmospheric gravity waves) are presented. In particular, the mixing layer development and the residual layer destruction are studied and considered, along with the relevant ground level ozone concentration variation.     

Urinary excretion and bactericidal activities of a single oral dose of 400 milligrams of fleroxacin versus a single oral dose of 800 milligrams of pefloxacin in healthy volunteers

Twelve healthy volunteers participated in this randomized crossover study to compare the concentrations and recovery levels of fleroxacin and pefloxacin in urine and to assess their bactericidal activities against 12 strains of urinary pathogens with different susceptibilities over a wide range of MICs. The volunteers received a single oral dose of 400 mg of fleroxacin or 800 mg of pefloxacin. The mean cumulative renal excretion of unchanged fleroxacin, N-demethyl-fleroxacin, and N-oxide-fleroxacin accounted for 67, 7, and 6% of the total dose, respectively. The total urinary recovery of pefloxacin and the active metabolite norfloxacin was 34%. In the time-kill and the urinary bactericidal titer (UBT) studies, only the subjects' urine not supplemented with broth was used. With most tested organisms and both quinolones it took more than 8 h to achieve a reduction in CFU of 99.9% (3 log units). Overall, there was a good correlation between UBTs and MICs for the strains. Against Escherichia coli ATCC 25922 the median UBTs were similar for both antibiotics and at least 1:8 for 96 h; against the E. coli strain for which the MIC was 0.5 microgram/ml the UBT was at least 1:4 for 48 h. The UBTs of both drugs against Klebsiella pneumoniae were at least 1:16 for 72 h. The UBTs for Staphylococcus aureus (the MIC for which was 16 micrograms/ml) of both antibiotics were low, and in some of the samples, no bactericidal titers were observed. UBTs for Proteus mirabilis of pefloxacin are significantly higher than those of fleroxacin. For Pseudomonas aeruginosa the median UBTs were present for the 24-to-48-h interval. The same is true for Enterococcus faecalis. Against Staphylococcus saprophyticus, UBTs were present for at least 48 h with both quinolones. Overall, a single oral dose of 400 mg of fleroxacin exhibits UBTs comparable to those of 800 mg of pefloxacin. Therefore, it may be expected that half of the dose of fleroxacin gives comparable results in the treatment of urinary tract infections; this should be substantiated in comparative clinical trials.     

A comment on the radiation resistance

For original paper see ibid., vol. 44, no. 5, p. 98-101 (2002). States that the second expression for the radiation resistance, developed with the help of Mahony's comments [2003], has some advantages, being more concise analytically and having more stable and rapidly convergent behavior numerically.     

A STUDY ON THE BEHAVIOUR OF GALLIUM IN THE IRONMAKING PROCESS

Gallium is a valuable rare metal which is mainly being used in the production of GaAs. The demand for gallium is increasing but production is limited since gallium is extracted only as a by-product of bauxite processing. On the other hand coal, ironmaking coke and iron ore gangue contain traces of gallium. However little is known about the behaviour of gallium in ironmaking. The aim of the study is to clarify the distribution of gallium between hot metal, slag and top gas by means of laboratory experiments. It was found that Ga2O3 is not stable in blast furnace slags and that gallium is retained in hot metal. Vacuum distillation experiments with hot metal showed that gallium is not transferred to the gas phase. Data on the input and output of gallium at two industrial blast furnaces, as well as chemical analyses of the gallium content of several cokes are presented, too.     

On a method for determining limit cycles in nonlinear circuits

A theory for determining the existence, number and position of limit cycles in perturbed Hamiltonian systems, that depends on a small parameter, is presented. The limit cycle emerges from the periodic trajectories surrounding a centre of the unperturbed system. By means of this theory a sinusoidal oscillator with a nonlinear element has been analysed. It is shown that only the terms with odd degrees in the approximation polynomial of the nonlinear element's characteristic exert an influence on the initiation of limit cycles.