Behaviour of composite slab-beam systems at elevated temperatures: Experimental and numerical investigation

This paper presents the experimental observations and results of three one-quarter scale composite slab-beam systems, 3.15 m by 3.15 m in plan, and tested in fire conditions. The tests aimed to examine the effects of unprotected interior secondary beams and edge rotational restraint on the behaviour of floor assemblies. The test results show that continuity of reinforcement in the slab over the supporting beams, and the presence of interior beams, can reduce the slab deflection and enhance its load-bearing capacity. Interior beams can be left unprotected without leading to a structural failure. The interior beams play a major role in helping the slab to move from biaxial bending stage to membrane behaviour, enabling the slab to mobilize higher tensile membrane forces. Rotational restraint along the protected edge beams induces intense stress concentration above these beams, resulting in more severe concrete crushing at the four corners and wide cracks over the edge beams. In addition to the experimental study, a numerical model using ABAQUS has been developed to simulate the tests. The numerical predictions agree well with the experimental results, showing that the proposed model is reliable. A shortcoming of the study is that the fire resistance performance of the specimens cannot be compared with those in practical design because a real furnace fire and small-scale fire tests were used due to limits of the furnace. However, the experimental results do provide basic information on the membrane behaviour in fire and also allow analytical methods and numerical models to be validated

The Richit-Richards family of distributions and its use in forestry

Johnson's SB and the logit-logistic are four-parameter distribution models that may be obtained from the standard normal and logistic distributions by a four-parameter transformation. For relatively small data sets, such as diameter at breast height measurements obtained from typical sample plots, distribution models with four or less parameters have been found to be empirically adequate. However, in situations in which the distributions are complex, for example in mixed stands or when the stand has been thinned or when working with aggregated data, then distribution models with more shape parameters may prove to be necessary. By replacing the symmetric standard logistic distribution of the logit-logistic with a one-parameter “standard Richards” distribution and transforming by a five-parameter Richards function, we obtain a new six-parameter distribution model, the “Richit-Richards”. The Richit-Richards includes the “logit-Richards”, the “Richit-logistic”, and the logit-logistic as submodels. Maximum likelihood estimation is used to fit the model, and some problems in the maximum likelihood estimation of bounding parameters are discussed. An empirical case study of the Richit-Richards and its submodels is conducted on pooled diameter at breast height data from 107 sample plots of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.). It is found that the new models provide significantly better fits than the four-parameter logit-logistic for large data sets

Study of the three-dimensional geometry of the central conducting airways in man using computed tomographic (CT) images

Clinical research on the deposition of inhaled substances (e.g. inhaled medications, airborne contaminants, fumes) in the lungs necessitates anatomical models of the airways. Current conducting airway models lack three-dimensional (3D) reality as little information is available in the literature on the distribution of the airways in space. This is a limitation to the assessment or predictions of the particle deposition in relation to the subject's anatomy. Detailed information on the full topology and morphology of the airways is thus required to model the airway tree realistically. This paper presents the length, diameter, gravity, coronal and sagittal angles that together describe completely the airways in 3D space. The angle at which the airways branch out from their parent (branching angle) and the rotation angle between successive bifurcation planes are also included. These data are from the study of two sets of airways computed tomography (CT) images. One CT scan was performed on a human tracheobronchial tree cast and the other on a healthy male volunteer. The airways in the first nine generations of the cast and in the first six conducting generations of the volunteer were measured using a computer-based algorithm. The data contribute to the knowledge of the lung anatomy. In particular, the spatial structure of the airways is shown to be strongly defined by the central airways with clear angular lobar patterns. Such patterns tend to disappear with a mean gravity, coronal and sagittal angles of 90° in each generation higher than 13–15. The mean branching angle per generation appears independent of the lobe to which the airways belong. Non-planar geometry at bifurcation is observed with the mean (± SD) bifurcation plane rotation angle of 79 ± 41° (n = 229). This angle appears constant over the generations studied. The data are useful for improving the 3D realism of the conducting airway structure modelling as well as for studying aerosol deposition, flow and biological significance of non-planar airway trees using analytical and computational flow dynamics modelling

A novel method for detection of viable Giardia cysts in water samples

Assessment of Giardia viability is a major requirement for public health purveyors and the water industry. Several indicators of viability such as stains, excystation and animal infectivity have been used to enumerate cysts with varying degrees of success. A combined detection-viability method for use in water samples would be useful for detecting and determining the viability of cysts in raw and drinking waters and the efficacy of disinfection at treatment plants. Distilled water samples were seeded with purified Giardia cysts and incubated with fluorescein diacetate (FDA) initially to stain viable cysts followed by tetramethyl red labelled anti- Giardia monoclonal antibodies (TMR) for confirmation of identity. As a result of FDA staining, green fluorescence of intact viable cysts was observed microscopically using a 450-490 nm exciter filter while nonviable cysts were not stained. Giardia cysts reacted positively with TMR and glowed red using a triple band microscope filter with excitations of 400/450/570 nm. At this wavelength a combination of FDA and TMR stained viable cysts green internally with a red wall while nonviable cysts only stained red. This simple, reliable and quick method allowed differentiation of Giardia cysts in water samples while simultaneously determining their viability