An absorptive capacity interpretation of Six Sigma

Purpose – The Six Sigma approach to business improvement has emerged as a phenomenon in both the practitioner and academic literature with potential for achieving increased competitiveness and contributing. However, there is a lack of critical reviews covering both theory and practice. Therefore, the purpose of this paper is to critically review the literature of Six Sigma using a consistent theoretical perspective, namely absorptive capacity.

Design/methodology/approach – The literature from peer-reviewed journals has been critically reviewed using the absorptive capacity framework and dimensions of acquisition, assimilation, transformation, and exploitation.

Findings – There is evidence of emerging theoretical underpinning in relation to Six Sigma borrowing from an eclectic range of organisational theories. However, this theoretical development lags behind practice in the area. The development of Six Sigma in practice is expanding mainly through more rigorous studies and applications in service-based environments (profit and not for profit). The absorptive capacity framework is found to be a useful overarching framework within which to situate existing theoretical and practice studies.

Research limitations/implications – Agendas for further research from the critical review, in relation to both theory and practice, have been established in relation to each dimension of the absorptive capacity framework.

Practical implications – The paper shows that Six Sigma is both a strategic and operational issue and that focussing solely on define, measure, analyse, improve control-based projects can limit the strategic effectiveness of the approach within organisations.

Originality/value – Despite the increasing volume of Six Sigma literature and organisational applications, there is a paucity of critical reviews which cover both theory and practice and which suggest research agendas derived from such reviews.

Phosphorus Adsorption onto an Industrial Acidified Laterite By‒Product: Equilibrium and Thermodynamic Investigation

The present research investigates the uptake of phosphate ions from aqueous solutions using acidified laterite (ALS), a by-product from the production of ferric aluminium sulfate using laterite. Phosphate adsorption experiments were performed in batch systems to determine the amount of phosphate adsorbed as a function of solution pH, adsorbent dosage and thermodynamic parameters per fixed P concentration. Kinetic studies were also carried out to study the effect of adsorbent particle sizes. The maximum removal capacity of ALS observed at pH 5 was 3.68 mg P g^-1. It was found that as the adsorbent dosage increases, the equilibrium pH decreases, so an adsorbent dosage of 1.0 g L^-1 of ALS was selected. Adsorption capacity (q_m) calculated from the Langmuir isotherm was found to be 2.73 mg g^-1. Kinetic experimental data were mathematically well described using the pseudo first-order model over the full range of the adsorbent particle size. The adsorption reactions were endothermic, and the process of adsorption was favoured at high temperature; the ΔG and ΔH values implied that the main adsorption mechanism of P onto ALS is physisorption. The desorption studies indicated the need to consider a NaOH 0.1M solution as an optimal solution for practical regeneration applications.

Production of porous aluminium and iron sulphated oxyhydroxides using industrial grade coagulants for optimised arsenic removal from groundwater

The optimisation of Fe and Al oxyhydroxide materials produced using industrial grade coagulants is presented in this work. The effects of synthesis pH and post-synthesis washing procedure onto the arsenic adsorption capacity of the materials were investigated. It was shown that the materials produced at higher pH were more efficient in removing As(V), especially after cleaning procedure. The materials produced at lower pH were less efficient in removing As(V) but the higher presence of sulphate groups in the materials produced at lower pH enhanced As(III) adsorption. Most performing materials can remove up to 84.7 mg As(V) g^-1 or 77.9 mg As(III) g^-1.

New SR drive with integrated charging capacity for plug-in hybrid electric vehicles (PHEVs)

Plug-in hybrid electric vehicles (PHEVs) provide much promise in reducing greenhouse gas emissions and, thus, are a focal point of research and development. Existing on-board charging capacity is effective but requires the use of several power conversion devices and power converters, which reduce reliability and cost efficiency. This paper presents a novel three-phase switched reluctance (SR) motor drive with integrated charging functions (including internal combustion engine and grid charging). The electrical energy flow within the drivetrain is controlled by a power electronic converter with less power switching devices and magnetic devices. It allows the desired energy conversion between the engine generator, the battery, and the SR motor under different operation modes. Battery-charging techniques are developed to operate under both motor-driving mode and standstill-charging mode. During the magnetization mode, the machine's phase windings are energized by the dc-link voltage. The power converter and the machine phase windings are controlled with a three-phase relay to enable the use of the ac-dc rectifier. The power converter can work as a buck-boost-type or a buck-type dc-dc converter for charging the battery. Simulation results in MATLAB/Simulink and experiments on a 3-kW SR motor validate the effectiveness of the proposed technologies, which may have significant economic implications and improve the PHEVs' market acceptance

Industrial scale microwave processing of tomato juice using a novel continuous microwave system

This study evaluated the effect of an industrial scale continuous flow microwave volumetric heating system in comparison to conventional commercial scale pasteurisation for the processing of tomato juice in terms of physicochemical properties, microbial characteristics and antioxidant capacity. The effect against oxidative stress in Caco-2 cells, after in vitro digestion was also investigated. Physicochemical and colour characteristics of juices were very similar between technologies and during storage. Both conventional and microwave pasteurisation inactivated microorganisms and kept them in low levels throughout storage. ABTS⁺ values, but not ORAC, were higher for the microwave pasteurised juice at day 0 however no significant differences between juices were observed during storage. Juice processed with the microwave system showed an increased cytoprotective effect against H₂O₂ induced oxidation in Caco-2 cells. Organoleptic analysis revealed that the two tomato juices were very similar. The continuous microwave volumetric heating system appears to be a viable alternative to conventional pasteurisation.

National incomes and economic growth in pre-industrial Europe: insights from recent research

Pessimistic Malthusian verdicts on the capacity of pre-industrial European economies to sustain a degree of real economic growth under conditions of population growth are challenged using current reconstructions of urbanisation ratios, the real wage rates of building and agricultural labourers, and GDP per capita estimated by a range of methods. Economic growth is shown to have outpaced population growth and raised GDP per capita to in excess of $1,500 (1990 $ international at PPP) in Italy during its twelfth- and thirteenth-century commercial revolution, Holland during its fifteenth- and sixteenth-century golden age, and England during the seventeenth- and eighteenth-century runup to its industrial revolution. During each of these Smithian growth episodes expanding trade and commerce sustained significant output and employment growth in the manufacturing and service sectors. These positive developments were not necessarily reflected by trends in real wage rates for the latter were powerfully influenced by associated changes in relative factor prices and the per capita supply of labour as workers varied the length of the working year in order to consume either more leisure or more goods. The scale of the divergence between trends in real wage rates and GDP per capita nevertheless varied a great deal between countries for reasons which have yet to be adequately explained.