Some Investigations into the Dynamic Mass Transfer at the Slag–Metal Interface Using Sulfur: Concept of Interfacial Velocity

In the current work, dynamic studies of mass transfer of sulfur from the gas phase to the metal phase of pure iron through CaO-SiO₂-Al₂O₃-FeO quaternary slag were carried out. X-ray videos were taken that were later processed to identify the oscillation of the metal drop occurring during the mass transfer. It was observed that the metal drop had hybrid oscillations. Each of these oscillations could be identified as composed of a symmetric and an asymmetric element, which was attributed to the changes in the shape of the droplet. The latter (asymmetric part) could be identified by the deviation of the left and right contact angles from the stable configuration. The symmetric oscillations were traced to the surface movement of sulfur at the interface, which created an instantaneous area change at the slag–metal interface. This area change was due to the combined effect of Marangoni flow and interface dilatation. The velocity of sulfur at the interface was calculated from the area change and had a maximum order of magnitude as 10⁻⁴ m/s. It was also observed that the interfacial velocity increased with increase in temperature.     

Recovery of Manganese Ferrite in Nanoform from the Metallurgical Slags

The present work investigates the formation of manganese ferrite of nanosize by oxidation of MnO- and FeO-containing slag. A horizontal resistance furnace was used as an experimental setup. The experiment was conducted in the temperature range of 1573 K to 1673 K (1300 °C to 1400 °C) in an oxidizing atmosphere. The samples were quenched to the cold end of the furnace and were analyzed by X-ray diffraction (XRD). The XRD patterns of the products showed the presence of two phases??manganese ferrite and calcium silicate. The particle size of the manganese ferrite was estimated by the Scherrer formula to be in the range of nanometers.     

Risk intermediation in supply chains

This paper demonstrates that an important role of intermediaries in supply chains is to reduce the financial risk faced by retailers. It is well known that risk averse retailers when faced by the classical single-period inventory (newsvendor) problem will order less than the expected value maximizing (newsboy) quantity. We show that in such situations a risk neutral distributor can offer a menu of mutually beneficial contracts to the retailers. We show that a menu can be designed to simultaneously: (i) induce every risk averse retailer to select a unique contract from it; (ii) maximize the distributor's expected profit; and (iii) raise the order quantity of the retailers to the expected value maximizing quantity. Thus inefficiency created due to risk aversion on part of the retailers can be avoided. We also investigate the influence of product/market characteristics on the offered menu of contracts.     

Deposition characteristics of coal ash slurries at higher concentrations

High concentration slurry disposal system (HCSD) for transportation of coal ash to ash ponds from coal fired thermal power plants using pipelines has emerged as an economical and environmental friendly method. Coal Ash in slurry form is deposited in the ash pond and hence the deposition characteristics at higher concentrations (C_w >60% by weight) are very important. The settled solid profile in the ash pond at high concentrations is of great interest to the ash pond designers. The present study is an attempt to establish the relationship between the settled solid profile and the physical/rheological properties of coal ash slurry at high concentrations. The settled solid profile is experimentally measured in terms of cone angle for slurries of fly ash as well as mixture of fly ash (FA) and bottom ash (BA) in the ratio of 4:1 at high concentrations. The values of cone angle if the slurries are poured on either a pervious or impervious bed have also been measured. The results obtained from the experiments show that the cone angle depends on rheological properties like yield stress and Bingham plastic viscosity which in turn depend on various properties like solid concentration, particle size distribution etc. Also, cone angle for fly ash slurry is higher than that for the mixture of FA and BA slurry at any given concentration. Further, it was also observed from the experiments that cone angle is higher for pervious bed as compared to impervious bed for both types of slurries.     

Problems Involved in Using Improper Calibration CRMs in Geochemical Analyses: A Case Study on Mafic Rocks of Boggulakonda Pluton, East of Cuddapah Basin, India

The performance and response of two commonly used certified reference materials (CRMs) for mafic rocks MRG-1 (CANMET, Canada) and JGb-1 (Geological Survey of Japan), both gabbroic in composition, are evaluated for a set of mafic plutonic rocks (gabbros) from Boggulakonda (BK) occurring to the east of Proterozoic Cuddapah Basin, South India. In this study, quadrupole-inductively coupled plasma mass spectrometry was used to generate trace and rare earth element (REE) data using MRG-1 and JGb-1 as calibration standards separately for a comparative study. It is found that the two CRMs show highly variable major, minor and trace element compositions except ΣREE. When used for BK gabbros, JGb-1 has yielded better results than MRG-1 with respect to trace elements (HFS elements Nb and Ta in specific), whereas a good agreement was observed between both CRMs for REE concentrations when compared with certified data. The Nb–Ta element distribution patterns for BK gabbros in the spidergrams plotted using JGb-1 as CRM show relatively prominent and pronounced negatively spiking anomalies with reference to Th, whereas using MRG-1 as calibration CRM yielded unresolved and unclear Nb–Ta anomalies in the present study. The geochemistry (major, minor and trace) of MRG-1 is different when compared to that of JGb-1. Probably this is reason for the disparity in the results obtained by inductively coupled plasma mass spectrometry on mafic plutonic rocks. The study conducted on the BK gabbros, reveals better and reliable results using JGb-1 as CRM. This study also reveals the importance of using proper CRM for calibration having closely matching trace and REE concentrations in addition to major and minor elements, for obtaining reliable data in geological samples.     

Screening efficiency of the Hardy–Rand–Rittler (HRR) colour test (4th edn)

This study evaluates the screening efficiency of the Hardy–Rand–Rittler (HRR) 4th edition colour test. This test was also compared with results from the Ishihara test. Thirty-nine subjects with congenital red–green deficiency and 120 colour normal subjects participated in the study. The subjects were shown the Ishihara (concise version, 2001) and the HRR (4th edn) pseudoisochromatic plates. Each plate was viewed for 3?s. A Macbeth Easel lamp was used for illumination (70?foot-candle). The HRR test had 100% sensitivity and the specificity was 63%. The overall efficiency of the HRR test was less than that of the Ishihara. The results also indicated that plate seven of HRR (4th edn) has poor screening efficiency. Thus the HRR is good for identifying colour deficient subjects but a caveat is that it fails too many normals.     

Dissolution of MgO in CaO–"FeO"–CaF2–SiO2 Slags under Static Conditions

The dissolution of MgO in CaO–"FeO"–CaF₂–SiO₂ slags has been studied in the temperature range 1573°–1673° K under static conditions. The concentration profiles of Mg in the product Mg_1-xFe_xO solid-solution layer as well as slag were determined by EDS analysis. From this, the diffusivities of MgO in the slag and the. interdiffusivities in solid solution were estimated. The dissolution of MgO in CaO–"FeO"–CaF₂–SiO₂ slags increased with CaF₂ content.     

The powder metallurgy processing of refractory metals and alloys

Molybdenum and tungsten are refractory metals in the elemental form with the largest production volume in the world. The fabrication of these refractory metals, as well as their alloys and intermetallics, using high-temperature powder metallurgy (PM) is reviewed in this article. The primary focus is on the role of traditional high-temperature PM in producing alloys with tailor-made properties. An insight into the bulk production of molybdenum and tungsten alloys with nano-grains is highlighted. For more information, contact R.E. Aune, Royal Institute of Technology, Department of Materials Science and Engineering, SE-100 44 Stockholm, Sweden;+46-8-790-8363;fax+46-8-790-0939;e-mail aune@mse.kth.se.     

EVALUATION OF TWO MEDIAN-BASED METHODS FOR ESTIMATING ARRHENIUS PARAMETERS

The performance of two median-based methods, namely, median method (MM) and least median of squares (LMS), for parameter estimation in Arrhenius equation is investigated and compared with least sum of squares, through extensive Monte Carlo tests involving simulated data. Reweighted methods associated with LMS are also included in the study. Different types of experimental noise are considered for simulating variable standard deviation (SD) of noise and the occurrence of outliers. The results indicate the relative precision and accuracy of various methods for each noise type, and hence are useful in selecting the most appropriate method for a specific application provided noise type is known. Often little or no information is available on variation of SD and occurrence of outliers, and in such situations the most appropriate method seems to be MM which is observed to be the best for many noise types.