Prediction of crushing stress in composite materials

A simple mathematical model for predicting the crushing stress of composite materials was derived and presented in this paper. The present knowledge of fracture mechanics and strength of materials are used as the basis for the model. The fracture mechanics part of the analysis was based on energy release rate approach; the energy release rate, G, of the proposed model was determined by this approach. This energy release rate was based on the Mode I (opening or tensile mode) failure. As for the strength of materials part analysis, buckling theory was used to determine the critical load of the fibre beams. These two engineering concepts were combined to form the equation for the proposed model. The derived equation is a function of the materials properties, geometric and physical parameters of the composite materials. The calculated stresses from the derived equation were compared with experimental data from technical and research papers. Good agreements shown in the results are encouraging and recommendations for future analysis with different modes of failure were also presented. This paper enables engineering designers to predict crushing stress in composite materials with confidence and makes their work more efficient and reliable

Dark Matter in Gauge Mediation from Emergent Supersymmetry

We investigated the viability of neutralino dark matter in the gauge mediation from emergent supersymmetry proposal. In this proposal, supersymmetry is broken at Planck scale and consequently, the gravitino is superheavy and completely decouples from the low energy theory. Squarks and sleptons obtain their soft masses dominantly through gauge mediation with other mechanisms highly suppressed. The lightest supersymmetric partner, in contrast to traditional gauge mediation, is a neutralino which is also a dark matter candidate. By explicit calculation of the low energy spectra, the parameter space was constrained using the WMAP observed relic density of dark matter, LEP2 Higgs mass bounds, collider bounds on supersymmetric partners and exotic B-meson decays. We found that the model has intriguing hybrid features such as a nearly gauge-mediated spectrum (the exception being the superheavy gravitino) but with a dominant mSUGRA-like bino-stau coannihilation channel and at large $\tan \beta$, A-resonance-like annihilation.Comment: 14 pages, 4 figure

Establishing links between organizational climate, employee well-being and historical patient outcomes

This research undertaken in collaboration with Queensland Health analysed the links between dimensions of workplace climate/employee well-being contained in a number of Queensland Health databases, including the Patient Satisfaction Survey, the Clinical Incident database, the compliments and complaints database, the Variable Life Adjusted Display (VLAD) Database and the Better Workplaces Staff Opinion Survey database. Queensland Health sought to identify in what ways workplace climate is related to patient outcomes using existing datasets collected within the Queensland Health Centre for Healthcare Improvement. The process of establishing links involved matching aggregated data for specific facilities (where possible), or failing that, larger facilities (e.g. Hospital), or the Health Service District. Once the datasets had been matched on location or facility, correlations were calculated between the aggregated scores. The results demonstrated links between the data sets. These links showed that a better workplace climate is associated with greater reported numbers of clinical incidents, especially “no harm” clinical incidents. There was also a link between workplace climate and patient compliments/complaints which show that unsolicited compliments received from patients and their families are clearly related to a number of positive aspects of workplace climate (workplace morale, role clarity, and appraisal and recognition) and individual morale. The results linking workplace climate and patient satisfaction showed that there is a strong positive relationship between overall patient satisfaction and role clarity, and a negative relationship between overall patient satisfaction and both workplace distress and excessive work demands. While these results relate to historical data and therefore should not be construed to reflect the current state of operation within Queensland Health, they are still indicative of some very important relationships. This is the first study to demonstrate that more positive clinical management practices, better perceptions of the workplace climate and better employee well-being are a reflection of a better incident reporting and learning culture in a health care organization, ultimately resulting in improved patient outcomes

Internet data packet transport: from global topology to local queueing dynamics

We study structural feature and evolution of the Internet at the autonomous systems level. Extracting relevant parameters for the growth dynamics of the Internet topology, we construct a toy model for the Internet evolution, which includes the ingredients of multiplicative stochastic evolution of nodes and edges and adaptive rewiring of edges. The model reproduces successfully structural features of the Internet at a fundamental level. We also introduce a quantity called the load as the capacity of node needed for handling the communication traffic and study its time-dependent behavior at the hubs across years. The load at hub increases with network size $N$ as $\sim N^{1.8}$. Finally, we study data packet traffic in the microscopic scale. The average delay time of data packets in a queueing system is calculated, in particular, when the number of arrival channels is scale-free. We show that when the number of arriving data packets follows a power law distribution, $\sim n^{-\lambda}$, the queue length distribution decays as $n^{1-\lambda}$ and the average delay time at the hub diverges as $\sim N^{(3-\lambda)/(\gamma-1)}$ in the $N \to \infty$ limit when $2 < \lambda < 3$, $\gamma$ being the network degree exponent.Comment: 5 pages, 4 figures, submitted to International Journal of Bifurcation and Chao

Leadership in Action: The Effects of Leader-Member Exchange on Outcomes within Virtual Organizations

Player-founded organizations, or guilds, within massively multiplayer online games (MMOG) are complex social entities with organizational forms that mirror real-world companies. These guilds require leaders who possess a diverse array of skills. Examples of the skills required read like the introductory course of a business management degree – mediating conflict, planning, controlling, motivating. These skills are important - just as with real-world companies, failures on the part of leaders may explain the high degree of guild failures witnessed. The purpose of this purpose of this dissertation is to explore how relationships between leaders and members within this completely computer-mediated and synchronous environment affect member outcomes within guilds. I discuss how an exploratory study informs the choice of leader-member exchange theory to underpin this dissertation, develop a testable model which seeks to explain how relationship quality between leaders and members affects member outcomes as mediated by relational capital and the allocation of resources, and explain how this model will be operationalized and tested

Classification of scale-free networks

While the emergence of a power law degree distribution in complex networks is intriguing, the degree exponent is not universal. Here we show that the betweenness centrality displays a power-law distribution with an exponent \eta which is robust and use it to classify the scale-free networks. We have observed two universality classes with \eta \approx 2.2(1) and 2.0, respectively. Real world networks for the former are the protein interaction networks, the metabolic networks for eukaryotes and bacteria, and the co-authorship network, and those for the latter one are the Internet, the world-wide web, and the metabolic networks for archaea. Distinct features of the mass-distance relation, generic topology of geodesics and resilience under attack of the two classes are identified. Various model networks also belong to either of the two classes while their degree exponents are tunable.Comment: 6 Pages, 6 Figures, 1 tabl