In Situ Processing of Silicon Carbide Layer Structures

A novel route to low-cost processing of silicon carbide (SiC) layer structures is desribed. The processing involves pressureless liquid-phase cosintering of compacted power layers of SiC, containing alumina (Al₂O₃) and yttria (Y₂O₃ sintering additives to yield and yttrium aluminum garnet (YAG) second phase. By adjusting the β:α SiC phase ratios in the individual starting powders, alternate layers with distinctively different microstructures are produced: (i) "homogeneous" microstructures, with fine equiaxed SiC grains, designed for high strength; and (ii) "heterogeneous: microstructures with coarse and elongate SiC grains, designed for high toughness. By virtue of the common SiC and YAG phases, the interlayer interfaces are chemically compatible and strongly bonded. Exploratory Hertzian indetation tests across a bilayer interface confirm the capacity of the tough heterogeneous layer to inhibit potentially dangerous cracks propagating through the homogeneous layer. The potential for application of this novel processing approach to other layer architectures and other ceramic systems is considered.     

Maximum dry density test to quantify pumice content in natural soils

Crushable volcanic soils are well-known for their distinctive texture, vesicular nature and grain fragility. These features of volcanic soils lead to difficulty in interpreting the results of laboratory and field testing because of the occurrence of particle crushing. Sands containing pumice particles are commonly found in the Hamilton Basin in the North Island of New Zealand. The pumice particles originated from a series of volcanic eruptions centered in the Taupo and Rotorua regions. As a result of flooding and erosion along the Waikato River, the pumice particles have become mixed with other materials and have been distributed over the Hamilton Basin; these mixtures are referred to herein as natural pumiceous (NP) sands. This paper initially investigates an appropriate technique for measuring the maximum dry density (MDD) of NP sands; then a modified MDD test is proposed for estimating the pumice contents of these sands. In order to examine the applicability of different standard methods for determining MDD, New Zealand and Japanese standards are employed. The results using the Japanese standard show consistent MDD values when repeating the tests due to negligible particle crushing. On the other hand, the results of MDD tests according to the New Zealand standard indicate that a significant amount of particle crushing occurs after each repeated test and, consequently, it is not possible to get the same result when the test is repeated. NP sands reach their ultimate potential breakage during the modified MDD tests (at least, for the level of loading applied) and they experience different levels of particle crushing which may be a function of their pumice content. As a way forward, the relative breakages of the materials tested are used to estimate the pumice contents of the NP sands.     

The incidental nonhyperfunctioning adrenal mass: an imaging algorithm for characterization

Nonhyperfunctioning adrenal lesions such as cysts, myelolipomas, adrenal haemorrhage, adenoma and metastases are described. Definitive imaging features that help characterize adrenal cysts, myelolipomas and adrenal haemorrhage are illustrated and the differentiation of benign from malignant adrenal lesions using an algorithmic approach based on lipid sensitive imaging is provided.     

Problem-Based Learning Approach to Construction Management Teaching

This paper describes construction management teaching for the Master of Engineering in civil engineering course at the University of Glasgow in the United Kingdom. This course is a 5-yr undergraduate degree accredited by the Institution of Civil Engineers for membership in the Institution subject to graduates satisfying the appropriate postgraduate training objectives. Construction management teaching takes place in the third, fourth, and fifth years of the degree and is structured to make effective use of both traditional and problem-based learning teaching methods. Examples are given of two problem-based learning courses used in the fourth and fifth year of the degree course. Both are based on complex construction projects and provide students with the opportunity to apply and synthesis knowledge gained on the traditionally taught third year course. Formal feedback from students and informal feedback from local industry suggests that the courses are meeting their overall objective of producing graduates with relevant knowledge and skills in construction management.     

Flow Resistance and Momentum Flux in Compound Open Channels

New formulations are presented for flow resistance and momentum flux in compound open channels. As implemented in the St. Venant equations, these formulations facilitate a physically enhanced approach to evaluating conveyance, roughness, stage-discharge relationship, and unsteady flood routing in compound open channels. An analysis using steady flow data from the well-controlled experiments at the large-scale Flood Channel Facility, HR Wallingford, demonstrates the ability of the present approach to properly resolve the discontinuity of overall roughness across the main-channel bankfull level. Also, the proposed formulations are shown to be conducive to obviating the long-standing computational difficulty in unsteady flood routing due to small flow depths over flat and wide floodplains. The present work should find general applications in one-dimensional computation of river flows.     

Physicochemical and microbiological quality of water from a pilot domestic rainwater harvesting facility in Ireland

Dublin Institute of Technology personnel were commissioned in 2005 by the Department of Environment, Heritage and Local Government in Ireland to assess the feasibility of utilizing harvested rainwater to replace treated mains water, for nonpotable uses. A pilot project was set up. The project involved the design, installation, commissioning and monitoring of rainwater harvesting facilities in a rural housing development. A monitoring programme was carried out to examine the physicochemical and microbiological quality of the harvested rainwater. Harvested rainwater was sampled monthly and tested. Analysis of the harvested rainwater quality showed a consistently high quality of raw water in general compliance with the requirements of the European Communities (Quality of Bathing Water) Regulations for 100% of samples and the European Communities (Drinking Water) Regulations, 2007 for 37% of sampling dates.     

Explicit Formulation of the Shields Diagram for Incipient Motion of Sediment

The Shields diagram remains the most widely used criterion for incipient motion of sediment. However its implicit nature makes applications rather inconvenient. By deploying Guo’s logarithmic matching method twice, this technical note develops an explicit formulation of the Shields diagram, enabling the critical Shields parameter to be determined directly from fluid and sediment characteristics without resorting to any trial and error procedure or iteration. An extended application of the logarithmic matching method is demonstrated.     

Application of the PPP-mo method to the prediction of colour in di- and tri-arylmethane dyes

The electronic absorption spectra of several examples of the di- and tri-arylmethane dyes have been computed by the PPP molecular orbital in order to test the value of the method for predicting colour properties of cationic dyes. Parameter modification was kept to the absolute minimum, using mainly values derived for unrelated dye classes, but, nevertheless, agreement between calculated and experimental spectral data was satisfactory in most cases. Discrepancies could generally be attributed to severe steric effects in the relevant molecules.     

Investigation on the Impact of Seasonally Frozen Soil on Seismic Response of Bridge Columns

This paper presents the development of numerical models that investigated the seismic response of a simple two span prototype bridge system during warm and frozen temperatures. Models from both temperature conditions were subjected to a range of seismic intensities to examine the effect of seasonal freezing on the response of the system. Stiffness characteristics were defined using cyclic models of a bridge pier that were previously developed and validated using results from an experimental program on identical full-scale column-foundation units, which were tested during the summer and winter months. Dynamic characteristics of the seismic models were defined using approaches found in the literature. Frozen conditions increased the maximum bending moment and shear force demands for all seismic intensities, with nonlinearity in the column/foundation reducing the difference between the peak responses at higher intensities. At the depth of maximum foundation shear for the frozen model, demand was three times higher than the unfrozen for the 500-year return period and twice during the 2,500-year event. This is significant as one will assume shear is not critical at this location if the effects of frozen conditions are ignored. Apart from the smallest intensity event, increased peak lateral displacements were developed by the warm model down the length of the column and foundation. However, the displacement demand to capacity ratio was higher at the column top for the frozen model, exceeding the capacity during the 2,500-year return period event.