A flow environment for studying vortex interactions

The vortex formed at the tip of a propeller interacting with the vortex formed at the tip of a stator vane provides a unique environment for the study of vortex interactions. Changes in the relative vortex strengths and vortex rotational directions were determined to impact the resulting vortex structures and are easily implemented with the experimental apparatus described herein. Study of the development of the vortex interaction was determined to be possible by increasing the initial separation between the two vortices. Vortex interaction phenomenon has been observed using smoke flow visualization.The authors would like to thank the NASA Lewis Research Center for their funding of propeller related research from which this experiment evolved and the National Sciences and Engineering Research Council of Canada for R. Johnston's Post Graduate Scholarships.     

Mesoporous silicabis(ethylsulfanyl)propane palladium catalysts for hydrogenation and one-pot two-step Suzuki cross-coupling followed by hydrogenation

The solid phase catalytic activity of mesoporous silicabis(ethylsulfanyl)propane palladium catalysts for hydrogenation and novel one-pot two-step Suzuki cross-coupling followed by hydrogenation is described. The efficiency of catalytic hydrogenation was measured for substrate nitrobenzene with 5, 7 and 14 nm average pore diameter materials. The 5 nm pore material performed best and was also very effective in the catalytic hydrogenation of alkene, nitrile and imine substrates. Novel one-pot two-step Suzuki cross-coupling and hydrogenation was demonstrated using bromonitro- and bromodinitrobenzene and phenylboronic acid as substrates with conversion to the corresponding coupled amino compounds. As a consequence of the high affinity of the sulfur ligands for palladium, none was detected in leaching tests and the catalyst is easily separated and recycled.     

Total synthesis of norcembrenolide B and scabrolide D

An efficient stereoselective synthesis of norcembrenolide B (8) and scabrolide D (9) is reported. The strategy is inspired by biogenetic relationships of related cembrenoids. Central to this approach is the construction of norbipinnatin J which upon selective C2 deoxygenation and C8 oxygenation produces norrubifolide and norcoralloidolide A. A sequence of site-selective oxidations and skeletal reorganizations then yields, in a divergent manner, compounds 8 and 9. The studies allow revision of the proposed structure of scabrolide D (9), which is identical to norcembrenolide C.     

The effect of heating temperature and nitric acid treatments on the performance of Cu- and Zn-based broad spectrum respirator carbons

Impregnated activated carbons (IACs) that are used in broad spectrum gas mask applications have historically contained copper and/or zinc impregnants. The addition of an oxidizing agent, such as nitric acid (HNO(3)) can be useful in distributing the metallic impregnants uniformly on the activated carbon substrate. In this work, we study IACs prepared from copper nitrate (Cu(NO(3))(2)) and zinc nitrate (Zn(NO(3))(2)) precursors as a function of HNO(3) content present in the impregnating solution and as a function of heating temperature. The gas adsorption capacity of the IACs was determined by dynamic flow testing using sulfur dioxide (SO(2)), ammonia (NH(3)), hydrogen cyanide (HCN) and cyclohexane (C(6)H(12)) challenge gases under dry and humid conditions. The thermal decomposition and distribution of the impregnant on the activated carbon substrate is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal analysis techniques. Relationships between gas adsorption capacity, impregnant distribution and the species of surface impregnants are discussed.     

Raman, infrared and XPS study of bamboo phytoliths after chemical digestion

Many phosphate containing minerals are found in the Jenolan Caves. Such minerals are formed by the reaction of bat guano and clays from the caves. Among these cave minerals is the mineral taranakite (K,NH(4))Al(3)(PO(4))(3)(OH)·9(H(2)O) which has been identified by X-ray diffraction. Jenolan Caves taranakite has been characterised by Raman spectroscopy. Raman and infrared bands are assigned to H(2)PO(4), OH and NH stretching vibrations. By using a combination of XRD and Raman spectroscopy, the existence of taranakite in the caves has been proven.     

An investigation of the changes in the natural frequency of a pile affected by scour

Scour around bridge foundations is one of the leading causes of bridge failure. Up until recently, the monitoring of this phenomenon was primarily based around using underwater instrumentation to monitor the progression of scour holes as they develop around foundation systems. Vibration-based damage detection techniques have been used to detect damage in bridge beams. The application of these vibration based methods to the detection of scour has come to the fore in research in recent years. This paper examines the effect that scour has on the frequency response of a driven pile foundation system, similar to those used to support road and rail bridges. The effect of scour on the vibration characteristics of the pile is examined using laboratory and field testing. It is clear that there is a very clear reduction in the natural frequency of the pile as the severity of scour increases. It is shown that by combining state-of-the-art geotechnical techniques with relatively simple finite element modelling approaches, it is possible to accurately predict the natural frequency of the pile for a given scour depth. Therefore, the paper proposes a method that would allow the estimation of scour depth for a given observed pile frequency.     

A solution-scheme for the convective-diffusion equation

This paper presents a versatile solution-scheme for the convective-diffusion equation. A small-time, asymptotic, solution for an instantaneous point source of scalar contaminant is expressed as a three-dimensional, Hermite polynomial expansion and manipulated, using superposition, to generate the contaminant concentration field that results at larger times and for arbitrary, continuous or instantaneous, source contaminant distribution. This equation is commonly used to model contaminant dispersion in complex environmental flows so that the considerable degree of generality, flexibility and efficiency of this solution-scheme highly commends it to this application. The off-diagonal terms in the diffusivity tensor and the non-zero gradient of this term and the mean-velocity field are shown to make a significant contribution to the evolution of the contaminant concentration field resulting from the instantaneous release of contaminant from a point source.

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Zusammenfassung Die vorliegende Arbeit gibt eine vielseitig brauchbare Lösungsmethode für die konvektive Diffusionsgleichung. Die für kurze Zeiten gültige asymptotische Lösung für eine plötzlich wirkende Punktquelle der diffundierenden Skalargröße wird als dreidimensionale Entwicklung in Hermite'schen Polynomen dargestellt. Dies wird benützt um das Feld für größere Zeiten darzustellen, für beliebige, kontinuierliche oder diskontinuierliche Quellverteilungen. Diese Gleichung wird allgemein benützt als Modell für Dispersion von Schadstoffen in komplizierten Strömungen bei natürlichen Umgebungsverhältnissen; die Allgemeingültigkeit, Anpassungsfähigkeit und Wirksamkeit der Lösung machen die Methode für diese Anwendungen besonders geeignet. Es wird gezeigt, daß die Nichtdiagonalterme des Diffusionstensors sowie die nichtverschwindenden Gradienten dieses Termes und der mittleren Geschwindigkeit wesentliche Beiträge zur Entwicklung des Feldes leisten, die von der Punktquelle erzeugt wurde.