Simulating particle agglomeration in the flash smelting reaction shaft

A steady-state, axi-symmetric, numerical model was developed to investigate the agglomeration of molten particles of sulphide ore in the reaction shaft of a flash smelting process used for extracting copper. The turbulent, particle-laden, gas flow was simulated in conjunction with a population balance model to account for agglomeration. The agglomeration was found to depend primarily on the particle to gas mass loading ratio, and the particle size and turbulence intensity at the shaft inlet. Predictions compared well with the limited experimental data in the literature. Increasing the angle at which the flow enters the shaft from the burner was found to increase agglomeration up to a critical angle at which the flow behaviour changes. The results have implications for the control and reduction of dust levels in the waste gas stream.     

Organizational learning: conceptual challenges from a project perspective

Do-it-yourself (DIY) is a staple element of the spare time activities of many households, but little is known about the extent to which basic repair work is carried out through DIY and about the quality of this work. Through secondary analyses of UK government data (English House Condition Survey and Family Expenditure Survey), this paper examines the scale of DIY work by owner-occupiers, how work is organized, the interrelationship of DIY work, the use of unpaid help, and the use of contractors. It considers the types of work carried out, the characteristics of those who tackle DIY or use unpaid help, the dwelling types most likely to experience DIY work, and the motivations of and constraints on those home-owners who do it. The paper concludes with a discussion on the policy implications of these findings for government and the building industry. Although most DIY work is cosmetic and does not deal with basic repair and maintenance, the sheer scale of DIY ensures that it makes a contribution to improving housing conditions. The provision of more advice, information and education by government, local authorities and the private sector could ensure that more DIY work is of better quality and that home owners give priority to essential repairs whether or not they tackle these themselves.     

Adenovirus-mediated gene transfer is augmented in basilar and carotid arteries of heritable hyperlipidemic rabbits

OBJECTIVE: Regional presynaptic dopaminergic function and its regulation by dopamine agonists in different stages of PD can be measured by L-[11C]dopa and PET. In the current investigation, we studied the effects of therapeutic apomorphine on L-[11C]dopa uptake in patients with early and advanced PD. BACKGROUND: With disease progression and chronic dopamine agonist treatment, motor response complications supervene in a majority of PD patients. It is assumed that both presynaptic and postsynaptic changes in the dopaminergic system act to modify dopaminergic efficacy. METHODS: Patients with early and advanced stages of PD were included in the study. All patients were investigated twice with PET and L-[11C]dopa drug free and during a subsequent standardized therapeutic apomorphine infusion. RESULTS: Subregional analysis of the striatum showed differences in the effects of apomorphine infusion on the L-[11C]dopa influx rate in the two patient categories. In patients with early and uncomplicated PD, apomorphine infusion decreased the L-[11C]dopa influx rate. This decrease was most pronounced in the dorsal part of the putamen. In advanced PD patients, apomorphine did not affect the striatal L-[11C]dopa influx rate. CONCLUSIONS: We suggest that in mild and stable PD an upregulated presynaptic inhibitory feedback regulation, particularly in the dorsal putamen, acts to maintain congruity within the dopaminergic system in response to antiparkinsonian medication. However, this inhibitory feedback regulation is diminished with the progression of nigrostriatal degeneration and chronic dopamine agonist treatment.     

Ozone production in electrostatic air cleaners with contaminatedelectrodes

Runaway ozone generation due to contamination of electrode surfaces is a limiting factor in the long-term effectiveness of electrostatic air cleaners. Modification of the form of the corona discharge, accompanied by a significant rise in current, is the cause of increased ozone levels. After one week of operation in filtered air containing Arizona Road Dust, ozone concentration in a laboratory air cleaner increases by 460%. In this case, there is slight contamination on the discharge wires, but the ozone increase is attributed exclusively to back corona on the collection plates. On the other hand, oxidized discharge wires are believed to contribute to an order of magnitude increase in ozone concentration in a commercial air cleaner, operated in room air for 7 weeks. Wire contamination alone can increase ozone generation. An insulating tape adhesive applied to a 0.254 mm diameter stainless steel wire causes a 10-fold increase in ozone concentration     

SPIFI: a direct-detection imaging spectrometer for submillimeter wavelengths

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind-a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI's focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 microm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI's sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument's large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope.     

Preliminary investigation into the application of scratch testing to marine coatings

Controlled scratch testing has been applied to experimental coatings of the kind used on marine structures, based on epoxy-amine resins. Measurements of the scratch hardness and the critical load to failure have been made. Inspection of the scratch tracks by reflected light microscopy and scanning electron microscopy enabled identification of the failure mechanism. Failure could be by though-thickness cracking or adhesion failure. The failure mechanism is sensitive to the coating thickness and detachment from the substrate was obtained only from coatings less than 300 m thick in the as-prepared state for tests conducted with a limiting load of 80 N. The deterioration of properties of samples immersed in hot seawater was very sensitive to composition.     

Oxide films, pores and the fatigue lives of cast aluminum alloys

In the absence of gross defects such as cold shuts, the fatigue properties of castings are largely determined by the sizes of microstructural defects, particularly pores and oxide films. In contrast, the effects of grain size, second-phase particles, and nonmetallic inclusions are insignificant. The authors review the fatigue properties of castings made by gravity die casting, sand casting, lost-foam casting, squeeze casting, and semisolid casting, and compare A356/357 alloys with 319-type alloys. The application of fracture mechanics enables the properties to be rationalized in terms of the defects that are characteristic of each casting process, noting both the sizes and types of defect. The differences in the properties of castings are entirely attributed to their different defect populations. No single process is inherently superior. For defects of the same size (in terms of projected area normal to the loading direction), oxide films are less detrimental to fatigue life than pores. Areas of current controversy are highlighted and suggestions for further work are made. This article is based on a presentation made in the John Campbell Symposium on Shape Casting, held during the TMS Annual Meeting, February 13–17, 2005, in San Francisco, CA.     

Adjusting Nodal Demands in SCADA Constrained Real-Time Water Distribution Network Models

This paper describes the proportional demand method and the target demand method, two techniques for adjusting estimated demands in hydraulic models of water distribution networks to produce solutions that are consistent with available supervisory control and data acquisition (SCADA) data. The two techniques assume that pipe resistances and SCADA data are accurate and that the combination of SCADA data and demand estimates produce overdetermined problems. Nodal demands are regarded as stochastic variables which fluctuate about an estimated mean value. The method of weighted least squares is used to obtain solutions that satisfy all of the constraints imposed by SCADA data with adjusted nodal demands that most closely resemble the estimates. The methods are intended for use in real-time modeling but are limited to quasi-steady state flow. The paper demonstrates the methods on two example problems.     

An empirical examination of a process-oriented IT business success model

The value of information technology (IT) to modern organizations is almost undeniable. However, the determination of that value has been elusive in research and practice. We used a process-oriented research model developed using two streams of IT research to examine the value of IT in business organizations. One stream is characterized by examining how IT and non-IT variables affect other so-called IT success variables. The second stream is commonly referred to as IT business value, defined as the contribution of IT to firm performance. The resulting research model is referred to in our paper as the IT business success model. Data was collected from 225 top IS executives in fairly large organizations to empirically examine several hypotheses derived from theory concerning the causal nature of the IT business success model. A set of measures for the IT business success model was developed through an intense investigation of the IT literature. The measures were tested for validity and reliability using confirmatory factor analysis. The hypotheses that resulted from past research and conceptually illustrated in the research model were assessed using structural equation analysis. The implications of these findings and the limitations of the study are discussed in an effort to contribute to building a process-oriented theory base for IT business success at the organizational level of analysis.