Effect of particle hydrophobicity on particle and water transport across a flotation froth

Froth recovery measurements have been conducted in both the presence (three-phase froth) and absence (two-phase froth) of particles of different contact angles in a specially modified laboratory flotation column. Increasing the particle hydrophobicity increased the flow rate of particles entering the froth, while the recovery of particles across the froth phase itself also increased for particle contact angles to 63 and at all vertical heights of the froth column. However, a further increase in the contact angle to 69 resulted in lower particle recovery across the froth phase. The reduced froth recovery for particles of 69 contact angle was linked to significant bubble coalescence within the froth phase. The reduced froth recovery occurred uniformly across the entire particle size range, and was, presumably, a result of particle detachment from coalescing bubbles. Water flow rates across the froth phase also varied with particle contact angle. The general trend was a decrease in the concentrate flow rate of water with increasing particle contact angle. An inverse relationship between water flow rate and bubble radius was also observed, possibly allowing prediction of water flow rate from bubble size measurements in the froth. Comparison of the froth structure, defined by bubble size, gas hold-up and bubble layer thickness, for two- and three-phase froths, at the same frother concentration, showed there was a relationship between water flow rate and froth structure. (c) 2005 Elsevier B.V. All rights reserved.

Multiple directorships and corporate performance in Australian listed companies

How many directorships are too many? Globally, normative advice emphasises the importance of limiting the number of directorships any individual should hold due to the workloads they entail. However, there is little empirical evidence to support this view. Rather, there is a strong tradition of supporting multiple directorships as a mechanism for the firm to co-opt external resources. To explore the issue of director workloads and multiple directorships, we first consider the issues related to multiple directorships and outline the conclusions of extant international and Australian studies into multiple directorships. We then detail our objectives in undertaking this research and our approach to data collection. Our findings indicate that the incidence of multiple directorships in Australian listed companies is low. We also find that many of the apparent examples of multiple directorships are due to related entities, which share common directors and, due to the nature of these entities, have much lower workload requirements. Further, there does not appear to be any relationship between holding multiple directorships and firm financial performance. Finally, we discuss the implications for boards and those interested in governance, particularly the need to ensure governance recommendations and guidelines reflect empirical findings. We offer one solution to address the concerns of boards, investors, other stakeholders and the community regarding multiple directorships: board and individual director evaluations.

Hydrodynamics and mass transfer coefficient in activated sludge aerated stirred column reactor: Experimental analysis and modeling

The aerated stirred reactor (ASR) has been widely used in biochemical and wastewater treatment processes. The information describing how the activated sludge properties and operation conditions affect the hydrodynamics and mass transfer coefficient is missing in the literature. The aim of this study was to investigate the influence of flow regime, superficial gas velocity (U-G), power consumption unit (P/V-L), sludge loading, and apparent viscosity (pap) of activated sludge fluid on the mixing time (t(m)), gas hold-up (epsilon), and volumetric mass transfer coefficient (kLa) in an activated sludge aerated stirred column reactor (ASCR). The activated sludge fluid performed a non-Newtonian rheological behavior. The sludge loading significantly affected the fluid hydrodynamics and mass transfer. With an increase in the UG and P/V-L, the epsilon and k(L)a increased, and the t(m), decreased. The E, kLa, and tm,were influenced dramatically as the flow regime changed from homogeneous to heterogeneous patterns. The proposed mathematical models predicted the experimental results well under experimental conditions, indicating that the U-G, P/V-L, and mu(ap) had significant impact on the t(m) epsilon, and k(L)a. These models were able to give the tm, F, and kLa values with an error around +/- 8%, and always less than +/- 10%. (c) 2005 Wiley Periodicals, Inc.

Hydrogen production and utilisation opportunities for Australia

Worldwide, research and policy momentum is increasing in the move towards a hydrogen economy. Australia is one of the highest per capita users of energy, but relies heavily on fossil fuels to fulfil its energy requirements-thus making it one of the highest per capita polluters. It is also a country rich in natural resources, giving it the full range of options for a hydrogen economy. With the first Australian Hydrogen Study being completed by the end of 2003, there has as yet been little analysis of the options available to this country specifically. This paper reviews the resources, production and utilisation technology available for a hydrogen economy in Australia, and discusses some of the advantages and disadvantages of the different options. It points out that coal, natural gas, biomass and water are the most promising hydrogen sources at this stage, while solid oxide and molten carbonate fuel cells may hold the advantage in terms of current expertise for utilising hydrogen rich gases for stationary power in Australia. (c) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Hydrodynamics and mass transfer coefficient in three-phase air-lift reactors containing activated sludge

This study was to investigate the impacts of operating conditions and liquid properties on the hydrodynamics and volumetric mass transfer coefficient in activated sludge air-lift reactors. Experiments were conducted in internal and external air-lift reactors. The activated sludge liquid displayed a non-Newtonian rheological behavior. With an increase in the superficial gas velocity, the liquid circulation velocity, gas holdup and mass transfer coefficient increased, and the gas residence time decreased. The liquid circulation velocity, gas holdup and the mass transfer coefficient decreased as the sludge loading increased. The flow regime in the activated sludge air-lift reactors had significant effect on the liquid circulation velocity and the gas holdup, but appeared to have little impact on the mass transfer coefficient. The experimental results in this study were best described by the empirical models, in which the reactor geometry, superficial gas velocity and/or power consumption unit, and solid and fluid properties were employed. (c) 2006 Elsevier B.V. All rights reserved.

Bioerosion Research Before and After 1996 - A Discussion of What Has Changed Since the First International Bioerosion Workshop

The First International Bioerosion Workshop held in 1996 provided a forum for an increasing interest in bioerosion research and helped foster convivial relations among researchers in this specialization. The current trend in bioerosion publishing is positive and will be aided with consolidated efforts to attract both new recruits and grant awards. Contributors of the Fourth IBW in Prague decided to hold the next meeting in Erlangen, Germany.

Auditor's engagement risk and audit fees:the role of the audit firm alumni

This study explores the effect of the association of audit firm alumni with their alma mater on audit prices. The tests indicate that there is a moderate reduction of up to 21% in the level of audit fee when alumni (i.e., former employees) of the incumbent audit firm sit on the client board of directors which is consistent with the engagement risk theory. This suggests that there is an 'alumni effect' in the market for audit services. The findings hold only in the large company segment of the market. The results are robust to different model specifications and alternative samples. The sample comprises all executive and non-executive directors who run the UK quoted companies and are simultaneously ICAEW qualified chartered accountants. The study's implications for the accounting profession and the regulators are also discussed. © 2007 The Author Journal compilation © 2007 Blackwell Publishing Ltd.

Group diversity and group identification:the moderating role of diversity beliefs

Research on diversity in teams and organizations has revealed ambiguous results regarding the effects of group composition on workgroup performance. The categorization—elaboration model (van Knippenberg et al., 2004) accounts for this variety and proposes two different underlying processes. On the one hand diversity may bring about intergroup bias which leads to less group identification, which in turn is followed by more conflict and decreased workgroup performance. On the other hand, the information processing approach proposes positive effects of diversity because of a more elaborate processing of information brought about by a wider pool and variety of perspectives in more diverse groups. We propose that the former process is contingent on individual team members' beliefs that diversity is good or bad for achieving the team's aims. We predict that the relationship between subjective diversity and identification is more positive in ethnically diverse project teams when group members hold beliefs that are pro-diversity. Results of two longitudinal studies involving postgraduate students working in project teams confirm this hypothesis. Analyses further reveal that group identification is positively related to students' desire to stay in their groups and to their information elaboration. Finally, we found evidence for the expected moderated mediation model with indirect effects of subjective diversity on elaboration and the desire to stay, mediated through group identification, moderated by diversity beliefs.

A genetic algorithm approach to optimising component placement and retrieval sequence for chip shooter machines

A chip shooter machine in printed circuit board (PCB) assembly has three movable mechanisms: an X-Y table carrying a PCB, a feeder carrier with several feeders holding components and a rotary turret with multiple assembly heads to pick up and place components. In order to get the minimal placement or assembly time for a PCB on the machine, all the components on the board should be placed in a perfect sequence, and the components should be set up on a right feeder, or feeders since two feeders can hold the same type of components, and additionally, the assembly head should retrieve or pick up a component from a right feeder. The entire problem is very complicated, and this paper presents a genetic algorithm approach to tackle it.

Corporate boards and incentives: empirical evidence from the UK in 1935

We investigate boardroom governance using UK historical data for 1935. We demonstrate that there is a negative relationship between risk and incentives in this year. Prior research has produced anomalous results (Prendergast, 2002). Second, we show that average (median) board ownership of ordinary shares is about 7.95% (2.88%). Heuristically this figure is less than previously reported estimates for the US also using 1935 data. Finally, we show the phenomenon of multiple board membership. UK directors in 1935 hold many directorships – sometimes exceeding 10 concurrent memberships.

Range of self-tests available to buy in the United Kingdom: an Internet survey

We aimed to describe the availability in the United Kingdom of self-tests that are used to diagnose or screen for conditions without involving a health professional. A systematic Internet search identified 104 unique self-tests related to 24 named conditions including cancers, chronic conditions and infections. These self-tests require various samples including blood obtained using a lancet. The samples are processed at home with results available in minutes or sent to a laboratory for processing with results returned to the individual by e-mail or post. Prices per self-test and condition range from <1 pound to 76 pound. Self-tests are readily available, and further work is needed to assess their impact.

Enforceability of leasehold covenants and the landlord and tenant (Covenants) Act 1995

Describes the impact of the English Landlord and Tenant (Covenants) Act 1995, reforming liability in the context of new leases, extending the 'touching and concerning' requirement so all covenants 'run with the land' (with some exceptions), and abolishing the enduring liability of the original tenants and landlords. Explains that landlords will have more freedom to prescribe in advance the circumstances in which they consent to an assignment, referring also to changes in default notices requiring an 'early warning' to defaulters, and overriding leases, with a remedy for former tenants. Expects future leases to be shorter as landlords realize they cannot hold original tenants liable any more.

Ethnic diversity as a multilevel construct:the combined effects of dissimilarity, group diversity, and societal status on learning performance in work groups

The authors present a model of the multilevel effects of diversity on individual learning performance in work groups. For ethnically diverse work groups, the model predicts that group diversity elicits either positive or negative effects on individual learning performance, depending on whether a focal individual’s ethnic dissimilarity from other group members is high or low. By further considering the societal status of an individual’s ethnic origin within society (Anglo versus non-Anglo for our U.K. context), the authors hypothesize that the model’s predictions hold more strongly for non-Anglo group members than for Anglo group members. We test this model with data from 412 individuals working on a 24-week business simulation in 87 four- to seven-person groups with varying degrees of ethnic diversity. Two of the three hypotheses derived from the model received full support and one hypothesis received partial support. Implications for theory development, methods, and practice in applied group diversity research are discussed.