Directional earth fault relay operation in mutually coupled multiple circuit distribution lines

Many of the power utilities around the world experienced spurious tripping of directional earth fault relays in their mesh distribution networks due to induced circulating currents. This circulating current is zero sequence and induced in the healthy circuit due to the zero sequence current flow resulting from a ground fault of a parallel circuit. This paper quantitatively discusses the effects of mutual coupling on earth fault protection of distribution systems. An actual spurious tripping event is analyzed to support the theory and to present options for improved resilience to spurious tripping.

Identification of factors contributing to recurrence of venous leg ulcers

Background and Significance Venous leg ulcers are a significant cause of chronic ill-health for 1–3% of those aged over 60 years, increasing in incidence with age. The condition is difficult and costly to heal, consuming 1–2.5% of total health budgets in developed countries and up to 50% of community nursing time. Unfortunately after healing, there is a recurrence rate of 60 to 70%, frequently within the first 12 months after heaing. Although some risk factors associated with higher recurrence rates have been identified (e.g. prolonged ulcer duration, deep vein thrombosis), in general there is limited evidence on treatments to effectively prevent recurrence. Patients are generally advised to undertake activities which aim to improve the impaired venous return (e.g. compression therapy, leg elevation, exercise). However, only compression therapy has some evidence to support its effectiveness in prevention and problems with adherence to this strategy are well documented. Aim The aim of this research was to identify factors associated with recurrence by determining relationships between recurrence and demographic factors, health, physical activity, psychosocial factors and self-care activities to prevent recurrence. Methods Two studies were undertaken: a retrospective study of participants diagnosed with a venous leg ulcer which healed 12 to 36 months prior to the study (n=122); and a prospective longitudinal study of participants recruited as their ulcer healed and data collected for 12 months following healing (n=80). Data were collected from medical records on demographics, medical history and ulcer history and treatments; and from self-report questionnaires on physical activity, nutrition, psychosocial measures, ulcer history, compression and other self-care activities. Follow-up data for the prospective study were collected every three months for 12 months after healing. For the retrospective study, a logistic regression model determined the independent influences of variables on recurrence. For the prospective study, median time to recurrence was calculated using the Kaplan-Meier method and a Cox proportional-hazards regression model was used to adjust for potential confounders and determine effects of preventive strategies and psychosocial factors on recurrence. Results In total, 68% of participants in the retrospective study and 44% of participants in the prospective study suffered a recurrence. After mutual adjustment for all variables in multivariable regression models, leg elevation, compression therapy, self efficacy and physical activity were found to be consistently related to recurrence in both studies. In the retrospective study, leg elevation, wearing Class 2 or 3 compression hosiery, the level of physical activity, cardiac disease and self efficacy scores remained significantly associated (p<0.05) with recurrence. The model was significant (p <0.001); with a R2 equivalent of 0.62. Examination of relationships between psychosocial factors and adherence to wearing compression hosiery found wearing compression hosiery was significantly positively associated with participants’ knowledge of the cause of their condition (p=0.002), higher self-efficacy scores (p=0.026) and lower depression scores (p=0.009). Analysis of data from the prospective study found there were 35 recurrences (44%) in the 12 months following healing and median time to recurrence was 27 weeks. After adjustment for potential confounders, a Cox proportional hazards regression model found that at least an hour/day of leg elevation, six or more days/week in Class 2 (20–25mmHg) or 3 (30–40mmHg) compression hosiery, higher social support scale scores and higher General Self-Efficacy scores remained significantly associated (p<0.05) with a lower risk of recurrence, while male gender and a history of DVT remained significant risk factors for recurrence. Overall the model was significant (p <0.001); with an R2 equivalent 0.72. Conclusions The high rates of recurrence found in the studies highlight the urgent need for further information in this area to support development of effective strategies for prevention. Overall, results indicate leg elevation, physical activity, compression hosiery and strategies to improve self-efficacy are likely to prevent recurrence. In addition, optimal management of depression and strategies to improve patient knowledge and self-efficacy may positively influence adherence to compression therapy. This research provides important information for development of strategies to prevent recurrence of venous leg ulcers, with the potential to improve health and decrease health care costs in this population.

New stress and velocity fields for highly frictional granular materials

The idealised theory for the quasi-static flow of granular materials which satisfy the Coulomb-Mohr hypothesis is considered. This theory arises in the limit that the angle of internal friction approaches $\pi/2$, and accordingly these materials may be referred to as being `highly frictional'. In this limit, the stress field for both two-dimensional and axially symmetric flows may be formulated in terms of a single nonlinear second order partial differential equation for the stress angle. To obtain an accompanying velocity field, a flow rule must be employed. Assuming the non-dilatant double-shearing flow rule, a further partial differential equation may be derived in each case, this time for the streamfunction. Using Lie symmetry methods, a complete set of group-invariant solutions is derived for both systems, and through this process new exact solutions are constructed. Only a limited number of exact solutions for gravity driven granular flows are known, so these results are potentially important in many practical applications. The problem of mass flow through a two-dimensional wedge hopper is examined as an illustration.

Lie group symmetry analysis for granular media stress equations

The Airy stress function, although frequently employed in classical linear elasticity, does not receive similar usage for granular media problems. For plane strain quasi-static deformations of a cohesionless Coulomb–Mohr granular solid, a single nonlinear partial differential equation is formulated for the Airy stress function by combining the equilibrium equations with the yield condition. This has certain advantages from the usual approach, in which two stress invariants and a stress angle are introduced, and a system of two partial differential equations is needed to describe the flow. In the present study, the symmetry analysis of differential equations is utilised for our single partial differential equation, and by computing an optimal system of one-dimensional Lie algebras, a complete set of group-invariant solutions is derived. By this it is meant that any group-invariant solution of the governing partial differential equation (provided it can be derived via the classical symmetries method) may be obtained as a member of this set by a suitable group transformation. For general values of the parameters (angle of internal friction and gravity g) it is found there are three distinct classes of solutions which correspond to granular flows considered previously in the literature. For the two limiting cases of high angle of internal friction and zero gravity, the governing partial differential equation admit larger families of Lie point symmetries, and from these symmetries, further solutions are derived, many of which are new. Furthermore, the majority of these solutions are exact, which is rare for granular flow, especially in the case of gravity driven flows.

Free surface problems for static Coulomb-Mohr granular solids

This paper is concerned with some plane strain and axially symmetric free surface problems which arise in the study of static granular solids that satisfy the Coulomb-Mohr yield condition. Such problems are inherently nonlinear, and hence difficult to attack analytically. Given a Coulomb friction condition holds on a solid boundary, it is shown that the angle a free surface is allowed to attach to the boundary is dependent only on the angle of wall friction, assuming the stresses are all continuous at the attachment point, and assuming also that the coefficient of cohesion is nonzero. As a model problem, the formation of stable cohesive arches in hoppers is considered. This undesirable phenomena is an obstacle to flow, and occurs when the hopper outlet is too small. Typically, engineers are concerned with predicting the critical outlet size for a given hopper and granular solid, so that for hoppers with outlets larger than this critical value, arching cannot occur. This is a topic of considerable practical interest, with most accepted engineering methods being conservative in nature. Here, the governing equations in two limiting cases (small cohesion and high angle of internal friction) are considered directly. No information on the critical outlet size is found; however solutions for the shape of the free boundary (the arch) are presented, for both plane and axially symmetric geometries.

Perturbation solutions for flow through symmetrical hoppers with inserts and asymmetrical wedge hoppers

Under certain circumstances, an industrial hopper which operates under the "funnel-flow" regime can be converted to the "mass-flow" regime with the addition of a flow-corrective insert. This paper is concerned with calculating granular flow patterns near the outlet of hoppers that incorporate a particular type of insert, the cone-in-cone insert. The flow is considered to be quasi-static, and governed by the Coulomb-Mohr yield condition together with the non-dilatant double-shearing theory. In two dimensions, the hoppers are wedge-shaped, and as such the formulation for the wedge-in-wedge hopper also includes the case of asymmetrical hoppers. A perturbation approach, valid for high angles of internal friction, is used for both two-dimensional and axially symmetric flows, with analytic results possible for both leading order and correction terms. This perturbation scheme is compared with numerical solutions to the governing equations, and is shown to work very well for angles of internal friction in excess of 45 degree.

Book review : Kellett, M (2010) Rethinking children and research : attitudes in contemporary society

Rethinking Children and Research characterizes Mary Kellett’s vision as campaigner and sociologist actively working for and with children for many years. The book itself is not only visionary; it is informative, thought provoking and pragmatic. From a contemporary standpoint, the manuscript presents a detailed synopsis of the shifts in thinking about research with children and provides an appraisal of the theoretical movements that have driven a participatory research agenda. A strong theoretical approach of the combined lenses of sociologies of childhood and rights discourse is introduced early in the book. From the outset, the reader receives loud and clear, the key message of the book: that children in research should and can be included as competent members who lead research in the study of their everyday lives. The argument for a more mutual research approach is shaped throughout the book using research examples and practical suggestions on how this might be achieved. Overall, the reader is left feeling compelled to adopt such an approach.

The identification of Malaysian contractor satisfaction dimensions : a strategy for continuous improvement

The unique characteristics of the construction industry - such as the fragmentation of its processes, varied scope of works and diversity of its participants - are contributory factors to poor project performance. Several issues are unresolved due to the lack of a comprehensive technique to measure project outcomes including: inefficient decision making, insufficient communication, uncertain site conditions, a continuously changing environment, inharmonious working relationships, mismatched objectives within the project team and a blame culture. One approach to overcoming these problems appears to be to measure performance by gauging contractor satisfaction (Co-S) levels, but this has not been widely investigated as yet. Additionally, the key Co-S dimensions at the project level are still not fully identified. ----- ----- This paper concerns a study of satisfaction dimensions, primarily by a postal questionnaire survey of construction contractors registered by the Malaysian Construction Industry Development Board (CIDB). Eight satisfaction dimensions are identified that are significantly and substantially relate to these contractors - comprising: project cost performance, schedule performance, product performance, design satisfaction, site safety, project profitability, business performance and relationships between participants. -Each of these dimensions is accorded different priority levels of satisfaction by different contractors. ----- ----- The output of this study will be useful in raising the awareness and understanding of project teams regarding contractors’ needs, mutual objectives and open communication to help to deliver a successful project.

A probability-based approach for assessing the relationship between crash accidents and pavement properties

Skid resistance is a condition parameter characterising the contribution that a road makes to the friction between a road surface and a vehicle tyre. Studies of traffic crash histories around the world have consistently found that a disproportionate number of crashes occur where the road surface has a low level of surface friction and/or surface texture, particularly when the road surface is wet. Various research results have been published over many years and have tried to quantify the influence of skid resistance on accident occurrence and to characterise a correlation between skid resistance and accident frequency. Most of the research studies used simple statistical correlation methods in analysing skid resistance and crash data.----- ------ Preliminary findings of a systematic and extensive literature search conclude that there is rarely a single causation factor in a crash. Findings from research projects do affirm various levels of correlation between skid resistance and accident occurrence. Studies indicate that the level of skid resistance at critical places such as intersections, curves, roundabouts, ramps and approaches to pedestrian crossings needs to be well maintained.----- ----- Management of risk is an integral aspect of the Queensland Department of Main Roads (QDMR) strategy for managing its infrastructure assets. The risk-based approach has been used in many areas of infrastructure engineering. However, very limited information is reported on using risk-based approach to mitigate crash rates related to road surface. Low skid resistance and surface texture may increase the risk of traffic crashes.----- ----- The objectives of this paper are to explore current issues of skid resistance in relation to crashes, to provide a framework of probability-based approach to be adopted by QDMR in assessing the relationship between crash accidents and pavement properties, and to explain why the probability-based approach is a suitable tool for QDMR in order to reduce accident rates due to skid resistance.

Using data mining to predict road crash count with a focus on skid resistance values

Road crashes cost world and Australian society a significant proportion of GDP, affecting productivity and causing significant suffering for communities and individuals. This paper presents a case study that generates data mining models that contribute to understanding of road crashes by allowing examination of the role of skid resistance (F60) and other road attributes in road crashes. Predictive data mining algorithms, primarily regression trees, were used to produce road segment crash count models from the road and traffic attributes of crash scenarios. The rules derived from the regression trees provide evidence of the significance of road attributes in contributing to crash, with a focus on the evaluation of skid resistance.

Tailoring secretion of proteoglycan 4 (PRG4) in tissue-engineered cartilage

Articular cartilage provides a low-friction surface for joint articulation, with boundary lubrication facilitated by proteoglycan 4 (PRG4), which is secreted by chondrocytes of the superficial zone. Chondrocytes from different zones are phenotypically distinct, and their phenotypes in vitro are influenced by the system in which they are cultured. We hypothesized that culturing cells from the superficial (S) zone in two-dimensional monolayer or three-dimensional alginate would affect their synthesis of PRG4, and that subsequently seeding them atop alginate-recovered cells from the middle/ deep (M) zone in various proportions would result in tissue-engineered constructs with varying levels of PRG4 secretion and matrix accumulation. During monolayer culture, S cells retained their PRG4-secreting phenotype, whereas in alginate culture the percentage of cells secreting PRG4 decreased with time. Constructs formed with increasing percentages of S cells decreased in thickness and matrix accumulation, depending on both the culture conditions before construct formation and the S-cell density. PRG4-secreting cells were localized to the S-cell seeded construct surface, with secretion rates of 0.1–4 pg/cell/day or 0.1–1 pg/cell/day for constructs formed with monolayer-recovered or alginate-recovered S cells, respectively. Tailoring secretion of PRG4 in cartilage constructs may be useful for enhancing low-friction properties at the articular surface, while maintaining other surfaces free of PRG4 for enhancing integration with surrounding tissues.

Online environmental information systems

In today’s information society, electronic tools, such as computer networks for the rapid transfer of data and composite databases for information storage and management, are critical in ensuring effective environmental management. In particular environmental policies and programs for federal, state, and local governments need a large volume of up-to-date information on the quality of water, air, and soil in order to conserve and protect natural resources and to carry out meteorology. In line with this, the utilization of information and communication technologies (ICTs) is crucial to preserve and improve the quality of life. In handling tasks in the field of environmental protection a range of environmental and technical information is often required for a complex and mutual decision making in a multidisciplinary team environment. In this regard e-government provides a foundation of the transformative ICT initiative which can lead to better environmental governance, better services, and increased public participation in environmental decision- making process.

Interactional competence in a paired speaking test : features salient to raters

Paired speaking tests are now commonly used in both high-stakes testing and classroom assessment contexts. The co-construction of discourse by candidates is regarded as a strength of paired speaking tests, as candidates have the opportunity to display a wider range of interactional competencies, including turn taking, initiating topics and engaging in extended discourse with a partner, rather than an examiner. However, the impact of the interlocutor in such jointly negotiated discourse and the implications for assessing interactional competence are areas of concern. This article reports on the features of interactional competence that were salient to four trained raters of 12 paired speaking tests through the analysis of rater notes, stimulated verbal recalls and rater discussions. Findings enabled the identification of features of the performance noted by raters when awarding scores for interactional competence, and the particular features associated with higher and lower scores. A number of these features were seen by the raters as mutual achievements, which raises the issue of the extent to which it is possible to assess individual contributions to the co-constructed performance. The findings have implications for defining the construct of interactional competence in paired speaking tests and operationalising this in rating scales.

Relationship management implementation in the Australian construction industry from the contractor's perspective

Many studies carried out in relation to construction procurement methods reveal evidence of a need to change of culture and attitude in the construction industry. This culture change would transition from traditional adversarial relationships to cooperative and collaborative relationships. Relational contracting approaches, such as partnering and relationship management, are business strategies whereby client, commercial participants’ and stakeholders’ objectives are aligned for mutual benefit. The efficacy of relationship management in the client and contractor groups is proven and well documented. However, the industry has a slow implementation of relational contracting down the value chain. This paper reports the findings of an empirical study which examined the practices and prerequisites for relationship management implementation success and for supply chain engagement to develop. Questionnaire survey, interviews and case studies were conducted with Australian contracting organisations in this study. The study reveals that the adaption of relational contracting approach in the supply chain is found to be limited and contractors still prefer to keep suppliers and subcontractors at arm’s length. Findings also show that the degree of match and mismatch between organizational structuring and organizational process is found to have an impact on staff’s commitment level and performance effectiveness.

Inter-sector leader transitions and organisation transformation : a research agenda

Faced with the need for strategic change, structural and cultural realignment, innovation and value-adding, many public sector organisations are tapping into a wider senior leadership talent pool and attracting successful leaders from other sectors (Flynn and Thompson, 2009). Leadership renewal has resulted, in some cases, in the external recruitment of whole senior leadership teams (Hockridge, 2008), raising issues about the influence of context on leader success (Pawar and Eastman, 1997) and potential leader transition failure, a costly outcome for leaders and organisations (Howard, 2001). There is little research on inter-sector leader transitions, which is surprising given the significant costs associated with leader acquisition and failure(Conger, 2010; Day and Halpin, 2004). For example, it is not clear what organizations do (or do not do) to ensure the outcomes of their significant investment in inter sector transitions are realised. In addition, it is not clear how the individual leader manages the challenging transition into a new leadership context and how their approach to leadership facilitates or inhibits successful transition (Avolio, 2010). Leader assimilation programs have been developed to assimilate new leaders (Manderscheid, 2008); however, assimilation is not necessarily a desired organisational outcome (Denis and Pineault, 2000). In this paper we critically review the limited literature on inter-sector leader transitions and transformational change outcomes and argue for a mutual accommodation approach. We draw on our own initial empirical work to propose the elements of a program for achieving this outcome from the perspective of the public organisation and the inter-sector appointee.