Effects of inter-fibre spacing and matrix cracks on stress amplification factors in carbon-fibre/epoxy matrix composites. Part I: planar array of fibres

When the loading on a composite is sufficient to cause fracture of an individual fibre, the resulting stress amplification in the adjacent intact fibres may be large enough to cause failure of these fibres. In this work, 3D elasto-plastic finite element analysis was used to investigate the effect of inter-fibre spacing on the stress amplification factor in a composite comprising a planar array of fibres. A Progressional Approach was used in the FE analysis to simulate the constituent non-linear processes associated with the generation of thermal residual stresses from fabrication, the fibre fracture event and the subsequent initiation and propagation of conical matrix cracks induced with incremental tensile loading. As the inter-fibre spacing increases, the effect of fibre fracture on the stress distribution in the neighbouring intact fibres is reduced, whereas the effect on the matrix material is increased, thereby inducing localised yielding. The presence of a conical-shaped matrix crack was found to increase both the stress amplification factor and the positively affected length in neighbouring fibres. For a large inter-fibre spacing, a longer matrix crack is required to obtain good agreement with LRS measurements of fibre stress.     

Species-specific identification of microsporidia in stool and intestinal biopsy specimens by the polymerase chain reaction

Horton temporal arteritis, or gigantocellular arteritis, is a panarteritis involving the mid-size and large arteries, in particular the temporal surface artery. This pathology is normally found in the elderly, particularly females. It can be manifest with some typical symptoms (i.e. cephalea, fever, visual disorders even leading to blindness mandibular claudication, high ESR, moderate anemia), there may be aspecific, atypical signs (i.e. only cephalea and fever, or widespread myalgia and artralgia) or it may arise following a cerebro-vascular accident. Treatment of this form of arteritis is based on the use of high doses of corticosteroids over a long period of time (at least 1-2 years). The present work describes a surgical technique for biopsying the temporal artery. The technique consists of withdrawal of a segment of the artery from the main branch and the frontal branch of the temporal surface artery. Since this form of arteritis often presents segmentary lesions, it is advisable to take a 4-5 cm sample so as to prevent false negatives. This simple surgical procedure can be performed under local anesthesia and is practically complication-free. The authors then discuss the indications for temporal artery biopsy and report 3 clinical cases (case no. 1 is an example of the classical manifestation while cases no. 2 and 3 are atypical, aspecific forms). Since both the classical and atypical forms of gigantocellular arteritis require high doses of corticosteriods over a long period of time, the temporal artery biopsy procedure is highly useful in formulating an accurate diagnosis. The well known side effects to long-term cortisone use make it necessary to use all the available instruments in making the correct diagnosis. Bilateral biopsy can be performed in those cases where the first biopsy proved negative but gigantocellular arteritis is still suspected.     

A New Kinetic Model for Ultraviolet Disinfection of Greywater

Ultraviolet (UV) disinfection of greywater has a number of advantages for small scale applications, but the UV disinfection efficiency can be impeded by high levels of particulates and chemicals in the greywater, micro-organism aggregation, and the geometry between the UV lamp and surrounding sleeve leading to suboptimal flow paths through the lamp assembly. Most process models for UV systems are empirical in nature and do not adequately represent the distribution of UV dose that is actually delivered to micro-organisms in a continuous flow system. This paper presents a model which incorporates: (1) variations in micro-organism sensitivity to UV radiation, (2) the variation of dose received in the UV reactor chamber, and (3) the shielding effect of part of the micro-organism population by the presence of particulates. The model is capable of predicting the asymptotic decay observed in bacterial survival curves when organisms are exposed to a UV dose in a greywater matrix and has been calibrated using experimental data on a series of synthetic greywaters of differing composition and validated against a series of real greywater samples. The model compares favorably to other UV disinfection models and allows the influence of water quality parameters such as turbidity, suspended solids, and UV absorbance to be examined. This allows water quality limits to be defined beyond which the UV disinfection of greywater becomes ineffective. Acceptable performance criteria are established for low power UV systems for the treatment of greywater, which have implications for the selection of suitable annular UV reactors.     

Hot air drying of yacon (Smallanthus sonchifolius) and its effect on sugar concentrations

This work aimed to experimentally study the drying behaviour of yacon tubers with and without steam blanching. Drying was carried out for 5 h and 30 min in a forced air dryer at 50 °C, 60 °C and 70 °C. The results indicated that the shortest drying time was obtained at 70 °C for blanched samples, and that the equilibrium water activity values were significantly lower for the blanched samples at all temperatures. The yacon dried without prior blanching showed lowest concentrations of reducing sugars when dried at 70 °C, significantly lower than those dried at 50 °C and 60 °C. This indicates hydrolysis of the fructo-oligosaccharides at 70 °C, a fact verified by the significant increase in reducing sugars content from 36.65 ± 0.54–44.10 ± 0.96% and reduction in the non-reducing sugars from 31.62 ± 0.55–26.18 ± 0.29%.     

A new device design methodology for manufacturability

As future technology generations for integrated circuits continue to “shrink”, TCAD tools must be made more central to manufacturing issues; thus, yield optimization and design for manufacturing (DFM) should be addressed integrally with performance and reliability when using TCAD during the initial product design. This paper defines the goals for DFM in TCAD simulations and outlines a formal procedure for achieving an optimized result (ODFM). New design of experiments (DOE), weighted least squares modeling and multiple-objective mean-variance optimization methods are developed as significant parts of the new ODFM procedure. Examples of designing a 0.18-μm MOSFET device are given to show the impact of device design procedures on device performance distributions and sensitivity variance profiles     

A general boundary element method approach to the solution of three-dimensional frictionless contact problems

A direct boundary element method is presented for three-dimensional stress analysis of frictionless contact problems. The isoparametric formulation of the boundary element method is implemented for the general case of contact in the absence of friction, which is limited to linear elastic homogeneous and isotropic materials. An iterative procedure is employed to determine the correct size of the contact zone by finding a boundary solution compatible with the contact condition. The applicability of the procedure is tested by application to three problems of advancing and conforming contact. The computed results are compared with numerical and analytical solutions where possible.