Experimental Wear Modelling of Lifeboat Slipway Launches

It is necessary to use an inclined slipway to launch lifeboats in locations where there is no natural harbour. Slipway stations consist of an initial roller section followed by an inclined keelway, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. Contact is between the lifeboat keel and a lined, greased keelway and this that determines the friction along the slipway. This paper describes a bench test methodology to investigate this contact. The selection of a modified TE57 reciprocating tribometer and design of a modified pin on plate arrangement is discussed. A test schedule for both the original nickel/chromium coated steel lining and the new low-friction jute fibre/phenolic resin composite lining is developed to accurately reflect real world conditions including environmental contamination such as seawater or wind-blown sand. Environmentally conscious lubricants including water and bio-greases are investigated and compared for their effects in reducing slipway panel friction and wear. Experimental data is collected to establish wear mechanisms, wear volumes and friction characteristics for a range of lubricants and environmental contaminants for the two most common lifeboat keelway lining materials. Implications of this research for future lifeboat slipway design are discussed

The intensity of cosmic ray muons deep underground

The vertical intensity, I(_v), and exponent of the angular distribution, n, (where I(_o) = I(_v)cos(^n) 0), of muons underground have been measured using simple telescopes comprising plastic scintillators, geiger counters and neon flash tubes at depths of 816, 1812 and 4110 m.w.e. in the Kolar Gold Fields, India. The observed values of n are 1.92 ± 0.33, 3.26 ± 0.10 and 5.33 ± 0.50 respectively, and those of I(_v) are (2.29 ± 0.09)10(^-6), (1.98 ± 0.05)10(^-7) and (4.47 ± 0.34)10(^-9) cm(^-2)sr(^-1)sec(^-1). These results have been compared with the results of other workers and the intensity-depth relation of Osborne et al (1964). The agreement is quite good at 816 and 4110 m.w.e. but the observed intensity is higher by ~30% at 1812 m.w.e. The integral sea-level muon intensities have been inferred from the range-energy relation, allowing for fluctuations in energy losses. From comparison with ɤ - ray cascade data it is shown the K/π ratio is sensibly constant at ~30% over the range of primary energy 10(^3) – 10(^6_) GeV. No significant non-Poissonian contribution to the distribution of time intervals between the arrival of successive events underground was noted indicating that the phenomenon of bursts of particles at short time intervals reported by Cowan et al (1964) has not been observed in the present experiment. The probability of electromagnetic interactions of muons in rock and lead was found to Increase (with increasing depth) demonstrating the growing Importance of energy losses by bremsstrahlung and direct pair production. Analysis of multiple penetrating particle events shows that they cfm be attributed to the production o muons (via pions) in extensive air showers, and to the nuclear interaction of muons in rock. Several neutrino induced muons and atmospheric muons have been detected in a new experiment, still in operation, at 7600 m.w.e. The vertical intensity of muons has been derived from the latter and compared with that inferred from the South African neutrino experiment at 8500 m.w.e. Finally, a best estimate of the intensity depth relation is given

A sampling strategy to assess banana crops for damage by Radopholus similis and Pratylenchus goodeyi

The economic threshold of burrowing (Radopholus similis) and lesion nematode (Pratylenchus goodeyi) on banana may be used to determine whether it is economic to apply nematicide. However, to use such a threshold, a sampling strategy is essential to determine the severity of root damage caused by the nematode. Ten banana crops in south-eastern Queensland and northern New South Wales and 10 in northern Queensland were sampled several times over several years to determine the disease index (percentage cortical root damage caused by R. similis and P. goodeyi) and nematode populations in roots. The negative binomial distribution and Taylor’s power law analysis were used to determine the relationship between the mean and variance of the disease index and nematode populations. Taylor’s power law gave the better fit, and was therefore used to determine fixed-precision stop lines for sequential sampling for precision at 20–30% for disease index and 20–40% for nematode populations. Twenty samples per crop were sufficient to achieve 25% precision when assessing nematode infestations using disease index but only 40% precision when using nematode populations

Dialogic pedagogy in graduate teacher education research advisement: A narrative account of three teacher educators

Research methods courses often tend to focus on transferring technical information to students rather than offer a more dialogical approach to learning (Barraket, 2005; Kilburn et al., 2014). By drawing on the concept of self-study (Bullough & Pinnegar, 2001), through personal journals and retrospective reflections, this paper explores learning activities introduced in three teacher education graduate research methods courses to support student learning beyond the mastering of research skills or techniques. Narratives of three teacher educators illustrate how teacher candidates can dialogically reflect on research-related topics with peers, bring questions forward for discussion in class and online, apply their emerging technical research skills through collective analysis of a situation, and grow collective knowledge. Teacher candidates recognize the importance of research in their work, although their passion for conducting research is influenced by varied constraints, including research design, programmatic and personal limitations

Facile Pyrolytic Synthesis of Silicon Nanowires

One-dimensional nanostructures such as silicon nanowires (SiNW) are attractive candidates for low power density electronic and optoelectronic devices including sensors. A new simple method for SiNW bulk synthesis[1, 2] is demonstrated in this work, which is inexpensive and uses low toxicity materials, thereby offering a safe, energy efficient and green approach. The method uses low flammability liquid phenylsilanes, offering a safer avenue for SiNW growth compared with using silane gas. A novel, duo-chamber glass vessel is used to create a low-pressure environment where SiNWs are grown through vapor-liquid-solid mechanism using gold nanoparticles as a catalyst. The catalyst decomposes silicon precursor vapors of diphenylsilane and triphenylsilane and precipitates single crystal SiNWs, which appear to grow parallel to the substrate surface. This opens up possibilities for synthesizing nano-junctions amongst wires which is important for the grid architecture of nanoelectronics proposed by Likharev[3]. Even bulk synthesis of SiNW is feasible using sacrificial substrates such as CaCO(3) that can be dissolved post-synthesis. Furthermore, by dissolving appropriate dopants in liquid diphenylsilane, a controlled doping of the nanowires is realized without the use of toxic gases and expensive mass flow controllers. Upon boron doping, we observe a characteristic red shift in photoluminescence spectra. In summary, an inexpensive and versatile method for SiNW is presented that makes these exotic materials available to any lab at low cost

Impact hammer-based analysis of nonlinear effects in bolted lap joint

This work presents an experimental investigation into the dynamic behavior of a bolted joint beam configuration. The impact hammer is chosen as an alternative to classical harmonic excitation methods. The structural responses are explored for a range of the joint tightening toques and various levels of impulse hammer excitations. A symmetric beam assembly made of two nominally identical steel beams is studied. Symmetric modes are found to be sensitive to the test parameters. For given torque, impact-based varying joint loading conditions are used to induce the nonlinear joint effects. A linear data processing strategy is used to observe the nonlinear behavior indirectly. The dynamic joint behavior is described in the form of the modal frequency-damping ratio performance maps represented by the two-parametric approximating quadratic response surface models. This model maps the joint conditions on the corresponding dynamic characteristics of interest and it will serve as a basis for the parametric linear joint model developmen