Impact characterisation of doubly curved composite structure

Under repeated impact composite domes subjected 6 J energy, changes locally with increasing drop height. The action of the dynamic load generates reactions at the support and bending moments at points on the surface of the composite. The peak loads were noted to increase and stabilise about some mean value; and the 150mm diameter shell was more damage tolerant compared to the 200 mm diameter one

An experimental study of damage accumulation in balanced CFRP laminates due to repeated impact

The behaviour of balanced laminates (symmetric, antisymmetric and asymmetric) under repeated low energy hits of a 12.1 mm hemispheric impactor was evaluated. The resistance to the impulsive force was found to be influenced by the stacking sequence and the crack path through the laminate. The symmetric plate with different ply directions proved to have best resistance to impact. The rate of damage progression in the event was characterised by an equation from the energy profile that correlates the propagation energy and time. This was differentiated to give the rate of damage evolution. A comparison of the bending stiffness obtained from the force-displacement plot of the first impact, revealed that the symmetric composite had the highest stiffness. Noted at perforation were fibre breakage and matrix cracking

A study of repeated impact loading on a symmetrical carbon fibre laminate

The behaviour of a symmetric laminate under repeated low energy hits of a 12.1mm hemispheric impactor was evaluated. The laminate was able to endure 20 collisions with the striker before perforation. The rate of damage progression was characterised by an equation from the energy profile that correlates the propagation energy and time. The function was represented by a sixth order polynomial. This was differentiated to give the rate of damage evolution. The contact time related to theimpact events with the same degree of polynomial. At perforation fibre breakage and matrix cracking were observed

The Facilitation of Learning Groups: A Study of a Dairy Discussion Group Facilitator

Farm Management,

False positive dobutamine stress echocardiograms: Characterization of clinical, echocardiographic and angiographic findings

AbstractObjectives. This study was designed to characterize the clinical, echocardiographic and angiographic findings in patients who have regional wall motion abnormalities predictive of coronary artery disease on dobutamine stress echocardiograms, although coronary angiography reveals no critical stenoses.Background. The specificity of dobutamine stress echocardiography has been reported to be lower than its sensitivity; the sources of false positive findings on dobutamine stress echocardiograms have not been previously defined.Methods. Clinical and echocardiographic characteristics were retrospectively reviewed for patients who had both a dobutamine stress echocardiogram indicate of coronary artery disease on the basis of wall motion abnormalities and <50% stenoses reported on coronary angiography performed within 6 weeks of the echocardiogram. A 16-segment model was used to perform wall motion scoring. Angiograms were independently reviewed, and stenosis severity was quantified with the use of digital calipers.Results. Thirty-nine (11.4%) of 342 studies met criteria for false positive test results, which occurred predominantly in women (72%, p < 0.601). Regional wall motion abnormalities were evident more often in the posterior circulation (62%), and 65% of them were limited to the basal segments. Twelve (28%) of 43 wall motion abnormalities were associated with coronary stenoses of at least intermediate grade (lumen diameter 40.3% to 68.1%). Abnormalities confined to basal segments of the posterior circulation were unlikely to have associated coronary lesions (p = 0.03).Conclusions. False positive findings on dobutamine stress echocardiograms tend to involve small wall motion abnormalities that are frequently located in basal segments of the posterior myocardial circulation. Approximately one third of false positive results occurred in patients with intermediate-grade coronary stenoses, and these studies may reflect true inducible ischemia. Additional sources of false positive study results may include poor endocardial visualization and abnormal motion dye to tethering to the fibrous skeleton of the heart. Altered echocardiographic diagnostic criteria may be appropriate for small wall motion abnormalities confined to basal segments of the posterior circulation

Evaluating Conflict between Employees: Exploring the Costs to an Organization

Conflicts between employees result in decreased job satisfaction, negative relationships within the organization, and a loss of employee commitment to both the organization and the specific job performed. Workplace conflicts have high costs to businesses. In aviation, the results of conflict can be deadly. The Strength Deployment Inventory (SDI) is designed to help people learn practical strategies to mitigate conflict. A sample of 228 people from the aviation industry completed a pre-training survey, participated in scenario-based SDI training, and then completed a post-training survey regarding the effectiveness of the SDI to help them manage conflict. Repeated Measures Analysis of Variance was conducted to determine how conflict management training, based on the Strength Deployment Inventory assessment, affected cognitive improvement in handling and successfully managing conflict situations. Results show following training, conflict management skills increased. Additional studies should be conducted to further validate these findings across other industries

Viscoelasticity as a Biomarker for High-Throughput Flow Cytometry

AbstractThe mechanical properties of living cells are a label-free biophysical marker of cell viability and health; however, their use has been greatly limited by low measurement throughput. Although examining individual cells at high rates is now commonplace with fluorescence activated cell sorters, development of comparable techniques that nondestructively probe cell mechanics remains challenging. A fundamental hurdle is the signal response time. Where light scattering and fluorescence signatures are virtually instantaneous, the cell stress relaxation, typically occurring on the order of seconds, limits the potential speed of elastic property measurement. To overcome this intrinsic barrier to rapid analysis, we show here that cell viscoelastic properties measured at frequencies far higher than those associated with cell relaxation can be used as a means of identifying significant differences in cell phenotype. In these studies, we explore changes in erythrocyte mechanical properties caused by infection with Plasmodium falciparum and find that the elastic response alone fails to detect malaria at high frequencies. At timescales associated with rapid assays, however, we observe that the inelastic response shows significant changes and can be used as a reliable indicator of infection, establishing the dynamic viscoelasticity as a basis for nondestructive mechanical analogs of current high-throughput cell classification methods

Root induction in radiata pine using Agrobacterium rhizogenes

Root induction using Agrobacterium rhizogenes was conducted in hypocotyl explants, intact seedlings, de-rooted seedling cuttings and adventitious shoots of radiata pine (Pinus radiata D. Don). Use of two A. rhizogenes strains (A4T and LB9402), with or without application of IBA, can trigger root formation in different explants. Strain LBA9402 was more effective than A4T in increasing rooting percentage and root number. Addition of 4.4 uMIBA to the medium further enhanced rooting from the cultured hypocotyl segments inoculated with the two A. rhizogenes strains. Strain LBA9402+IBA induced in about 75% of the cultured hypocotyl segments to form roots. In contrast the controls failed to initiate roots on intact seedlings or cultured segments in presence or absence of IBA. Rooting of adventitious shoots from 3 year-old radiata pine was improved following inoculation with LBA9402, suggesting that this rooting treatment has potential to aid clonal propagation of radiata pine

Tensile testing of cellulose based natural fibers for structural composite applications

A series of tensile tests were conducted on a Lloyd LRX tensile testing machine for numerous natural fibers deemed potential candidates for development in composite applications. The tensile tests were conducted on the fibers jute, kenaf, flax, abaca, sisal, hemp, and coir for samples exposed to moisture conditions of (1) room temperature and humidity, (2) 65% moisture content, (3) 90% moisture content, and (4) soaked fiber. These seven fibers were then tested for the four conditions and the mechanical properties of tensile strength, tensile strain to failure, and Young's modulus were calculated for the results. These results were then compared and verified with those from the literature, with some of the fibers showing distinctly promising potential. Additionally, a study on the effect of alkalization using 3% NaOH solution was carried out on flax, kenaf, abaca, and sisal to observe impact that this common fiber pre-treatment process has on fiber mechanical properties. The result of the investigation indicated that over treatment of natural fibers using NaOH could have a negative effect on the base fiber properties. It is consequently apparent that a treatment time of less than 10 min is sufficient to remove hemicelluloses and to give the optimum effect

We haven't got a seat on the bus for you or All the seats are mine: Narratives and career transitions in professional golf

In this article we explore how the stories an athlete tells throughout life in sport affect her career transition experiences. We base our enquiry on a social constructionist conception of narrative theory which holds that storytelling is integral to the creation and maintenance of identity and sense of self. Life stories were gathered through interviews with two professional women golfers (Christiana and Kandy) over a six‐year period. Through a narrative analysis of structure and form we explored each participant’s stories of living in and withdrawing from professional golf. We suggest Christiana told monological performance‐oriented stories which, while aligning with the culture of elite sport, resulted in an exclusive athletic identity and foreclosure of alternative selves and roles. On withdrawal, Christiana experienced narrative wreckage, identity collapse, mental health difficulties and considerable psychological trauma. In contrast, Kandy told dialogical discovery‐oriented stories which, while being in tension with the dominant performance narrative, created and sustained a multidimensional identity and self. Her stories and identity remained intact, authentic and continuous on withdrawal from tournament golf and she experienced few psychological problems