Developments in iron and steel making

A survey is presented of the direct reduction processes which are presently in commercial operation for the production of iron and steel as an alternative to the classical blast furnace route. The relative advantages and disadvantages of each technology are presented and their relative energy efficiencies discussed.     

Gas-based direct reduction processes for iron and steel production

Gas-based processes for the direct reduction of iron are discussed and compared in terms of their costs and energy effectiveness. Possible future lines of development are presented.     

Adaptive epidemic dissemination as a finite-horizon optimal stopping problem

Wireless Networks - Wireless ad hoc networks are characterized by their limited capabilities and their routine deployment in unfavorable environments. This creates the strong requirement to...     

In vivo fluoride profiles at different sites of buccal and lingual enamel surfaces obtained by enamel biopsy of human maxillary first permanent molars in young adults

Twenty male volunteers, average age 24 years, participated in this study. Specimens were obtained by enamel biopsy using 5 microliters of 0.5 M HClO4 for 30 s. Using a regression curve, comparisons of fluoride concentrations were made at different depths. The fluoride concentrations (mean +/- SE) at a depth of 5 microns were highest in the distobuccal (1698 +/- 136), high in the mesiobuccal (1343 +/- 122), low in the distolingual (1119 +/- 107), and lowest in the mesiolingual sites (819 +/- 78). Of the interior enamels (> or = 10 microns in depth), the distobuccal site (1330 +/- 88 parts/10(6) F at 10 microns) had a higher-concentration than all other sites. The fluoride profiles were steepest to shallowest in the order: distobuccal, mesiobuccal, distolingual and mesiolingual. There were no correlations between the enamel fluoride concentrations and the fluoride concentration in parotid saliva. It was concluded that in vivo fluoride profiles of maxillary first molars reflect the wear of the tooth surface with age and the condition of dental plaque deposition, and, to some extent, the site-specific distribution of saliva between buccal and lingual surfaces.     

Interlaboratory Test of Exhaust PM Using ELPI

Abstract

The Particulate Measurement Programme (PMP) works on the development of an improved method for the exhaust particulate matter (PM) measurement, which can include, if feasible and necessary, the measurement of particle number. The French PMP subgroup, composed of IFP, PSA Peugeot-Citroën, Renault, and UTAC, has defined a measurement protocol based on electrical low-pressure impactor (ELPI) and conducted an interlaboratory test to evaluate its performances. The technical program was based on tests carried out on three Euro3 passenger cars (one gasoline operating under stoichiometric conditions, one Diesel, and one Diesel equipped with a diesel particulate filter (DPF)) that were tested on the New European Driving Cycle (NEDC). The regulated pollutants are also measured, as indicators of test repeatability and good working conditions. The interlaboratory reproducibility value of the tunnel background tests is quite high (337%) due to low particle numbers. The repeatability values increase at low particle numbers independently of the vehicle used. On the NEDC, the reproducibility of total particle number is 59, 47, and 131% for the gasoline, Diesel, and DPF-equipped Diesel vehicles, respectively (compare to 67, 29, and 164% for PM collected on filters). These results show that the protocol used in this study allows a reliable measurement of exhaust particle number in the case of vehicles emitting at least two orders of magnitude more than the tunnel background. In the other cases, the measurement variability is too high, especially for regulatory purposes, without taking into account other metrological aspects, such as calibration.     

Emissions of regulated pollutants from a spark ignition engine. Influence of fuel and air/fuel equivalence ratio

A spark ignition engine is used to determine the influence of fuel composition and air/fuel equivalence ratio on the exhaust emissions of regulated pollutants. Two specific fuel matrices are used: the first contains eight hydrocarbons and the second contains four oxygenated compounds. A specific experimental design is used for these tests. Fuel aromatics increase the exhaust CO, HC, and NOx at stoichiometry, lean and rich conditions. Lambda is more important than fuel composition in the case of CO and HC. At stoichiometry, the addition of oxygenated compounds can decrease exhaust CO, HC, and NOx up to 30%, 50%, and 60%, respectively. Under these conditions, the addition of 5% of 2-propanol is the most effective for the reduction of CO, the addition of 20% of ethanol forthe reduction of HC, and this of 5% of methyl tributyl ester (MTBE) for the NOx. The addition of oxygenated compounds can decrease CO by 30% at lean conditions, while no decrease is observed at rich ones; HC and NOx can decrease up to 30% and 80%, respectively, under lean conditions and 50% under rich ones. At all lambda tested, exhaust NOx increases with the addition of 20% of 2-propanol.     

Design considerations in optical add/drop multiplexers based ongrating-assisted null couplers

The performance of a fully optimized optical add/drop multiplexer (OADM), based on null couplers and tilted Bragg gratings, is studied in detail. It is shown that maximization of the device performance involves three main optimization steps. First, the waveguide asymmetry (V₂ /V₁ ratio) should be optimized in order to minimize the extinction ratio of the unwanted mode at the null coupler waist. Second, the coupler taper shape should he optimized in order to further minimize the aforementioned extinction ratio. Third, the grating tilt angle and relative width can be also optimized to give negligible backreflections at the input port and minimize radiation losses. The results show that the proposed high-performance OADM configuration can meet stringent telecom specifications