Fast response static var generator for improving the power system performance of an electric arc furnace (EAF)

Cascaded multilevel inverters-based Static Var Generators (SVGs) are FACTS equipment introduced for active and reactive power flow control. They eliminate the need for zigzag transformers and give a fast response. However, with regard to their application for flicker reduction in using Electric Arc Furnace (EAF), the existing multilevel inverter-based SVGs suffer from the following disadvantages. (1) To control the reactive power, an off-line calculation of Modulation Index (MI) is required to adjust the SVG output voltage. This slows down the transient response to the changes of reactive power; and (2) Random active power exchange may cause unbalance to the voltage of the d.c. link (HBI) capacitor when the reactive power control is done by adjusting the power angle d alone. To resolve these problems, a mathematical model of 11-level cascaded SVG, was developed. A new control strategy involving both MI (modulation index) and power angle (d) is proposed. A selected harmonics elimination method (SHEM) is taken for switching pattern calculations. To shorten the response time and simplify the controls system, feed forward neural networks are used for on-line computation of the switching patterns instead of using look-up tables. The proposed controller updates the MI and switching patterns once each line-cycle according to the sampled reactive power Qs. Meanwhile, the remainder reactive power (compensated by the MI) and the reactive power variations during the line-cycle will be continuously compensated by adjusting the power angles, d. The scheme senses both variables MI and d, and takes action through the inverter switching angle, qi. As a result, the proposed SVG is expected to give a faster and more accurate response than present designs allow. In support of the proposal there is a mathematical model for reactive powered distribution and a sensitivity matrix for voltage regulation assessment, MATLAB simulation results are provided to validate the proposed schemes. The performance with non-linear time varying loads is analysed and refers to a general review of flicker, of methods for measuring flickers due to arc furnace and means for mitigation.

Direct power control with common mode voltage elimination for open-winding brushless doubly-fed wind power generators

In this paper, a new open-winding control strategy is proposed for a brushless doubly-fed reluctance generator (BDFRG) applicable for wind turbines. The BDFRG control winding is fed via a dual two-level three-phase converter using a single dc bus. Direct power control based on maximum power point tracking with common mode voltage elimination is designed, which not only the active and reactive power is decoupled, but the reliability and redundancy are all improved greatly by increasing the switching modes of operation, while DC-link voltage and rating of power devices decreased by 50% comparing to the traditional three-level converter systems. Consequently its effectiveness is evaluated by simulation tests based on a 42-kW prototype generator.

The steady state performance of converter type reactive power compensators

As a source or sink of reactive power, compensators can be made from a voltage sourced inverter circuit with the a.c. terminals of the inverter connected to the system through an inductive link and with a capacitor connected across the d.c. terminals. Theoretical calculations on linearised models of the compensators have shown that the parameters characterising the performance are the reduced firing angle and the resonance ratio. The resonance ratio is the ratio of the natural frequency of oscillation of the energy storage components in the circuit to the system frequency. The reduced firing angle of the inverter divided by the damping coefficient, β, where β is half the R to X ratio of the link between the inverter and the system. The theoretical results have been verified by computer simulation and experiment. There is a narrow range of values for the resonance ratio below which there is no appreciable improvement in performance, despite an increase in the cost of the energy storage components, and above which the performance of the equipment is poor with the current being dominated by harmonics. The harmonic performance of the equipment is improved by using multiple inverters and phase shifting transformers to increase the pulse number. The optimum value of the resonance ratio increases pulse number, indicating a reduction in the energy storage components needed at high pulse numbers. The reactive power output from the compensator varies linearly with the reduced firing angle while the losses vary as the square of it.

Pulse width modulation (PWM) method for power components estimation in power meters

The scope of this paper is to present the Pulse Width Modulation (PWM) based method for Active Power (AP) and Reactive Power (RP) measurements as can be applied in Power Meters. Necessarily, the main aim of the material presented is a twofold, first to present a realization methodology of the proposed algorithm, and second to verify the algorithm’s robustness and validity. The method takes advantage of the fact that frequencies present in a power line are of a specific fundamental frequency range (a range centred on the 50 Hz or 60 Hz) and that in case of the presence of harmonics the frequencies of those dominating in the power line spectrum can be specified on the basis of the fundamental. In contrast to a number of existing methods a time delay or shifting of the input signal is not required by the method presented and the time delay by n/2 of the Current signal with respect to the Voltage signal required by many of the existing measurement techniques, does not apply in the case of the PWM method as well.

Orthodoxy and the Cold War:religion and political power in Romania, 1947-65

This book examines the unique dynamics between Orthodoxy and politics in Romania. It provides an accessible narrative on church-state relations in the early Cold War period within a wider timeframe, from the establishment of the state in 1859 to the rise of Nicolae Ceausescu in 1965. In the 1950s Romania began to distance itself from Moscow's influence, developing its own form of communism. Based on new archival resources, the book argues that Romanian national communism, outside Moscow's influence, had an ally in a strong Church. It addresses the following questions: How did the Church, which openly opposed communism in the interwar period, survive the atheist regime? How did the regime use religion to its political advantage? What was the Church's influence on Romanian politics? The book analyses the political interests of the Romanian Orthodox Church and its religious diplomacy with actors in the West, in particular with the Church of England.

From apartheid to unity: white capital and black power in the racial integration of South African football, 1976-1992

This article analyses the complex process that deracialised and democratised South African football between the early 1970s and 1990s. Based mainly on archival documents, it argues that growing isolation from world sport, exemplified by South Africa's expulsion from the Olympic movement in 1970 and FIFA in 1976, and the reinvigoration of the liberation struggle with the Soweto youth uprising triggered a process of gradual desegregation in the South African professional game. While Pretoria viewed such changes as a potential bulwark against rising black militancy, white football and big business had their own reasons for eventually supporting racial integration, as seen in the founding of the National Soccer League. As negotiations for a new democratic South Africa began in earnest between the African National Congress (ANC) and the National Party (NP) in the latter half of the 1980s, transformations in football and politics paralleled and informed each other. Previously antagonistic football associations began a series of 'unity talks' between 1985 and 1986 that eventually culminated in the formation of a single, non-racial South African Football Association in December 1991, just a few days before the Convention for a Democratic South Africa (CODESA) opened the process of writing a new post-apartheid constitution. Finally, three decades of isolation came to an end as FIFA welcomed South Africa back into world football in 1992 - a powerful example of the seemingly boundless potential of a liberated and united South Africa ahead of the first democratic elections in 1994.

Mild cognitive decline. A position statement of the Cognitive Decline Group of the European Innovation Partnership for Active and Healthy Ageing (EIPAHA)

Introduction Mild cognitive impairment (MCI) is a term used to describe a level of decline in cognition which is seen as an intermediate stage between normal ageing and dementia, and which many consider to be a prodromal stage of neurodegeneration that may become dementia. That is, it is perceived as a high risk level of cognitive change. The increasing burden of dementia in our society, but also our increasing understanding of its risk factors and potential interventions, require diligent management of MCI in order to find strategies that produce effective prevention of dementia. Aim To update knowledge regarding mild cognitive impairment, and to bring together and appraise evidence about the main features of clinical interest: definitions, prevalence and stability, risk factors, screening, and management and intervention. Methods Literature review and consensus of expert opinion. Results and conclusion MCI describes a level of impairment in which deteriorating cognitive functions still allow for reasonable independent living, including some compensatory strategies. While there is evidence for some early risk factors, there is still a need to more precisely delineate and distinguish early manifestations of frank dementia from cognitive impairment that is less likely to progress to dementia, and furthermore to develop improved prospective evidence for positive response to intervention. An important limitation derives from the scarcity of studies that take MCI as an endpoint. Strategies for effective management suffer from the same limitation, since most studies have focused on dementia. Behavioural changes may represent the most cost-effective approach.

People, technology, processes and risk knowledge sharing

The present global economic crisis creates doubts about the good use of accumulated experience and knowledge in managing risk in financial services. Typically, risk management practice does not use knowledge management (KM) to improve and to develop new answers to the threats. A key reason is that it is not clear how to break down the “organizational silos” view of risk management (RM) that is commonly taken. As a result, there has been relatively little work on finding the relationships between RM and KM. We have been doing research for the last couple of years on the identification of relationships between these two disciplines. At ECKM 2007 we presented a general review of the literature(s) and some hypotheses for starting research on KM and its relationship to the perceived value of enterprise risk management. This article presents findings based on our preliminary analyses, concentrating on those factors affecting the perceived quality of risk knowledge sharing. These come from a questionnaire survey of RM employees in organisations in the financial services sector, which yielded 121 responses. We have included five explanatory variables for the perceived quality of risk knowledge sharing. These comprised two variables relating to people (organizational capacity for work coordination and perceived quality of communication among groups), one relating to process (perceived quality of risk control) and two related to technology (web channel functionality and RM information system functionality). Our findings so far are that four of these five variables have a significant positive association with the perceived quality of risk knowledge sharing: contrary to expectations, web channel functionality did not have a significant association. Indeed, in some of our exploratory regression studies its coefficient (although not significant) was negative. In stepwise regression, the variable organizational capacity for work coordination accounted for by far the largest part of the variation in the dependent variable perceived quality of risk knowledge sharing. The “people” variables thus appear to have the greatest influence on the perceived quality of risk knowledge sharing, even in a sector that relies heavily on technology and on quantitative approaches to decision making. We have also found similar results with the dependent variable perceived value of Enterprise Risk Management (ERM) implementation.

Sample size estimation and statistical power analyses

The concept of sample size and statistical power estimation is now something that Optometrists that want to perform research, whether it be in practice or in an academic institution, cannot simply hide away from. Ethics committees, journal editors and grant awarding bodies are now increasingly requesting that all research be backed up with sample size and statistical power estimation in order to justify any study and its findings. This article presents a step-by-step guide of the process for determining sample sizeand statistical power. It builds on statistical concepts presented in earlier articles in Optometry Today by Richard Armstrong and Frank Eperjesi.

Social capital and tacit knowledge sharing in organisational projects in Malaysian ICT companies

An increasing number of organisational researchers have turned to social capital theory in an attempt to better understand the impetus for knowledge sharing at the individual and organisational level. This thesis extends that research by investigating the impact of social capital on knowledge sharing at the group-level in the organisational project context. The objective of the thesis is to investigate the importance of social capital in fostering tacit knowledge sharing among the team members of a project. The analytical focus is on the Nahapiet and Ghoshal framework of social capital but also includes elements of other scholars' work. In brief, social capital is defined as an asset that is embedded in the network of relationships possessed by an individual or social unit. It is argued that the main dimensions of social capital that are of relevance to knowledge sharing are structural, cognitive, and relational because these, among other things, foster the exchange and combination of knowledge and resources among the team members. Empirically, the study is based on the grounded theory method. Data were collected from five projects in large, medium, and small ICT companies in Malaysia. Underpinned by the constant comparative method, data were derived from 55 interviews, and observations. The data were analysed using open, axial, and selective coding. The analysis also involved counting frequency occurrence from the coding generated by grounded theory to find the important items and categories under social capital dimensions and knowledge sharing, and for further explaining sub-groups within the data. The analysis shows that the most important dimension for tacit knowledge sharing is structural capital. Most importantly, the findings also suggest that structural capital is a prerequisite of cognitive capital and relational capital at the group-level in an organisational project. It also found that in a project context, relational capital is hard to realise because it requires time and frequent interactions among the team members. The findings from quantitative analysis show that frequent meetings and interactions, relationship, positions, shared visions, shared objectives, and collaboration are among the factors that foster the sharing of tacit knowledge among the team members. In conclusion, the present study adds to the existing literature on social capital in two main ways. Firstly, it distinguishes the dimensions of social capital and identifies that structural capital is the most important dimension in social capital and it is a prerequisite of cognitive and relational capital in a project context. Secondly, it identifies the causal sequence in the dimension of social capital suggesting avenues for further theoretical and empirical work in this emerging area of inquiry.

Ceramide and reactive oxygen species (ROS) as signal transduction molecules in inflammation

Reactive oxygen species (ROS) and the sphingolipid ceramide are each partly responsible for the intracellular signal transduction of a variety of physiological, pharmacological or environmental agents. Furthermore, the enhanced production of many of these agents, that utilise ROS and ceramide as signalling intermediates, is associated with the aetiologies of several vascular diseases (e.g. atherosclerosis) or disorders of inflammatory origin (e.g. rheumatoid arthritis; RA). Excessive monocyte recruitment and uncontrolled T cell activation are both strongly implicated in the chronic inflammatory responses that are associated with these pathologies. Therefore the aims of this thesis are (1) to further elucidate the cellular responses to modulations in intracellular ceramide/ROS levels in monocytes and T cells, in order to help resolve the mechanisms of progression of these diseases and (2) to examine both existing agents (methotrexate) and novel targets for possible therapeutic manipulation. Utilising synthetic, short chain ceramide to mimic the cellular responses to fluctuations in natural endogenous ceramide or, stimulation of CD95 to induce ceramide formation, it is described here that ceramide targets and manipulates two discrete sites responsible for ROS generation, preceding the cellular responses of growth arrest in U937 monocytes and apoptosis in Jurkat T-cells. In both cell types, transient elevations in mitochondrial ROS generation were observed. However, the prominent redox altering effects appear to be the ceramide-mediated reduction in cytosolic peroxide, the magnitude of which dictates in part the cellular response in U937 monocytes, Jurkat T-cells and primary human peripheral blood resting or PHA-activated T-cells in vitro. The application of synthetic ceramides to U937 monocytes for short (2 hours) or long (16 hours) treatment periods reduced the membrane expression of proteins associated with cell-cell interaction. Furthermore, ceramide treated U937 monocytes demonstrated reduced adhesion to 5 or 24 hour LPS activated human umbilical vein endothelial cells (HUVEC) but not resting HUVEC. Consequently it is hypothesised that the targeted treatment of monocytes from patients with cardiovascular diseases with short chain synthetic ceramide may reduce disease progression. Herein, the anti-inflammatory and immunosuppressant drug, methotrexate, is described to require ROS production for the induction of cytostasis or cytotoxicity in U937 monocytes and Jurkat T-cells respectively. Further, ROS are critical for methotrexate to abrogate monocyte interaction with activated HUVEC in vitro. The histological feature of RA of enhanced infiltration, survivability and hyporesponsiveness of T-cells within the diseased synovium has been suggested to arise from aberrant signalling. No difference in the concentrations of endogenous T-cell ceramide, the related lipid diacylglycerol (DAG) and cytosolic peroxide ex vivo was observed. TCR activation following PHA exposure in vitro for 72 hours did not induced maintained perturbations in DAG or ceramide in T-cells from RA patients or healthy individuals. However, T-cells from RA patients failed to upregulate cytosolic peroxide in response to PHA, unlike those from normals, despite expressing identical levels of the activation marker CD25. This inability to upregulate cytosolic peroxide may contribute to the T-cell pathology associated with RA by affecting the signalling capacity of redox sensitive biomolecules. These data highlight the importance of two distinctive cellular pools of ROS in mediating complex biological events associated with inflammatory disease and suggest that modulation of cellular ceramides represents a novel therapeutic strategy to minimise monocyte recruitment.

The Rover Task Force:a case study in proactive and reactive policy intervention?

The paper examines the policy responses in the UK West Midlands to the successive crises at the car maker MG-Rover. Whilst the firm’s eventual collapse in 2005 was a substantial shock to the West Midlands economy, the impact was much less than was anticipated when the firm was first threatened with closure in 2000 at the time of its break-up and sale by the German car firm BMW. Although the firm struggled as an independent producer, the five years of continued production until 2005 and the work of the initial Rover Task Force (RTF1), enabled many suppliers to adjust and diversify away from their hitherto dependence on MG-Rover resulting in as many as 10,000–12,000 jobs being ‘saved’. This first intervention was later followed by a programme to help ex-workers to find new jobs or re-train and assist supply firms to continue trading in the short term. Examination of the effectiveness of these emergency initiatives enables a wider discussion about the nature of industrial policy in the region and the work of the local regional development agency’s cluster-based approach to economic development and business support. Whilst the actions taken were successful in a number of aspects, there were a number of significant ‘failures’ at both national and local level. The MG-Rover case also illustrates a number of critical issues pertaining to regionally based cluster policies and the organization of cluster management groups where the ‘cluster’ in question not only crosses both administrative and ‘sector’ boundaries but is also subject to the imperatives of the global market car market.

The nitric oxide-donating pravastatin derivative, NCX 6550 [(1S-[1α(βS*, δS*), 2α, 6α, 8β-(R*), 8aα]]-1,2,6,7,8,8a-hexahydro-β, δ, 6-trihydroxy-2-methyl-8-(2-methyl-1-oxobutoxy)-1-naphtalene-heptanoic acid 4-(nitrooxy)butyl ester)], reduces splenocyte adhesion and reactive oxygen species generation in normal and atherosclerotic mice

Statins possess anti-inflammatory effects that may contribute to their ability to slow atherogenesis, whereas nitric oxide (NO) also influences inflammatory cell adhesion. This study aimed to determine whether a novel NO-donating pravastatin derivative, NCX 6550 [(1S-[1∝(ßS*,dS*),2∝,6a∝,8ß-(R*),8a∝]]-1,2,6,7,8,8a-hexahydro-ß,δ,6-trihydroxy-2-methyl-8-(2-methyl-1-oxobutoxy)-1-naphthalene-heptanoic acid 4-(nitrooxy)butyl ester)], has greater anti-inflammatory properties compared with pravastatin in normal and atherosclerotic apolipoprotein E receptor knockout (ApoE-/-) mice. C57BL/6 and ApoE-/- mice were administered pravastatin (40 mg/kg), NCX 6550 (48.5 mg/kg), or vehicle orally for 5 days. Ex vivo studies assessed splenocyte adhesion to arterial segments and splenocyte reactive oxygen species (ROS) generation. NCX 6550 significantly reduced splenocyte adhesion to artery segments in both C57BL/6 (8.8 ± 1.9% versus 16.6 ± 6.7% adhesion; P < 0.05) and ApoE-/- mice (9.3 ± 2.9% versus 23.4 ± 4.6% adhesion; P < 0.05) concomitant with an inhibition of endothelial intercellular adhesion molecule-1 expression. NCX 6550 also significantly reduced phorbol 12-myristate 13-acetate-induced ROS production that was enhanced in isolated ApoE-/- splenocytes. Conversely, pravastatin had no significant effects on adhesion in normal or ApoE-/- mice but reduced the enhanced ROS production from ApoE-/- splenocytes. In separate groups of ApoE-/- mice, NCX 6550 significantly enhanced endothelium-dependent relaxation to carbachol in aortic segments precon-tracted with phenylephrine (-logEC50, 6.37 ± 0.37) compared with both vehicle-treated (-logEC50, 5.81 ± 0.15; P < 0.001) and pravastatin-treated (-logEC50, 5.57 ± 0.45; P < 0.05) mice. NCX 6550 also significantly reduced plasma monocyte chemoattractant protein-1 levels (648.8 pg/ml) compared with both vehicle (1191.1 pg/ml; P < 0.001) and pravastatin (847 ± 71.0 pg/ml; P < 0.05) treatment. These data show that NCX 6550 exerts superior anti-inflammatory actions compared with pravastatin, possibly through NO-related mechanisms.

Hybrid gain-flattened and reduced power excursion scheme for distributed Raman amplification

We propose and evaluate through extensive numerical modelling a novel distributed hybrid amplification scheme combining first and second-order Raman pumping which gives reduced signal power excursion over a wide spatial-spectral range of 60 km × 80 nm in C + L-bands. © 2013 Optical Society of America.