A strain hardening failure assessment diagram derived from carbon-manganese steel compact tension specimens

A failure assessment diagram is derived from carbon-manganese steel compact tension specimens. The diagram has been determined from an elastic-plastic finite element analysis of a compact tension specimen geometry. The diagram has been validated by using experimental fracture toughness data obtained on the same steel and specimen geometry modelled in the finite element analysis. The plastic collapse load has been determined empirically for this geometry.It is shown that a non-work-hardening failure assessment diagram is not a good representation of the experimental data and that the computed failure assessment diagram is more appropriate for describing the behaviour of the carbon-manganese steel specimens.     

Fourth International Conference on Durability of Building Materials and Components

RILEM Bulletin

Fourth International Conference on Durability of Building Materials and Components     

Incorporation of surface-modified UHMWPE powders and fibers in tough polyurethane composites

Ultrahigh molecular weight polyethylene (UHMWPE) powder (60 micron diameter) and chopped fiber (6.5 mm length) were surface treated with a blend of reactive gases (fluorine and oxygen.) These powders and fibers were then compounded into a thermoset polyurethane matrix. Surface-treated and control reinforcements are compared at a 10 vol.% loading level. Tensile testing indicates improved stress transfer with surface treatment. Stress transfer is also improved with fibers versus powders. Fracture toughness is characterized by measuring the essential work of fracture, w_e. Surface-treated fiber composites exhibit work of fracture values almost three times the unfilled polyurethane values. Abrasion resistance was also measured. Surface treatment was found to significantly lower wear rates of powder composites. Fiber composites had lower wear rates than powder composites, although surface treatment had little effect. An approximate inverse relationship was found between wear rate and essential work of fracture.     

Characterization of Ceramics by X-Ray and Neutron Small-Angle Scattering

This paper reviews some recent advances in small-angle X-ray and neutron scattering methods and their application to address complex issues in ceramic systems of technological importance. It is shown how small-angle scattering (SAS) can be applied to ceramic systems in order to extract statistically representative microstructure information (e.g., void volume fraction size distributions, internal surface areas, pore morphologies) that complements the information obtained from diffraction methods, X-ray microtomography, or electron microscopy. It is demonstrated how SAS studies provide insights, not obtainable by other means, on the processing–microstructure–property relationships that frequently govern technological performance.     

Automatic and Efficient Human Pose Estimation for Sign Language Videos

We present a fully automatic arm and hand tracker that detects joint positions over continuous sign language video sequences of more than an hour in length. To achieve this, we make contributions in four areas: (i) we show that the overlaid signer can be separated from the background TV broadcast using co-segmentation over all frames with a layered model; (ii) we show that joint positions (shoulders, elbows, wrists) can be predicted per-frame using a random forest regressor given only this segmentation and a colour model; (iii) we show that the random forest can be trained from an existing semi-automatic, but computationally expensive, tracker; and, (iv) introduce an evaluator to assess whether the predicted joint positions are correct for each frame. The method is applied to 20 signing footage videos with changing background, challenging imaging conditions, and for different signers. Our framework outperforms the state-of-the-art long term tracker by Buehler et al. (International Journal of Computer Vision 95:180–197, 2011), does not require the manual annotation of that work, and, after automatic initialisation, performs tracking in real-time. We also achieve superior joint localisation results to those obtained using the pose estimation method of Yang and Ramanan  (Proceedings of the IEEE conference on computer vision and pattern recognition, 2011).     

Increased α-linolenic acid intake increases tissue α-linolenic acid content and apparent oxidation with little effect on tissue docosahexaenoic acid in the guinea pig

The essential fatty acids do not have identical roles in nutrition. Linoleic acid (LA) accumulates throughout the body of most mammals, whereas α-linolenic acid (ALA) is rarely found in tissue lipids to the same extent as LA. It has been argued that this is the result of metabolism of ALA to docosahexaenoic acid (DHA) or that ALA is rapidly β-oxidized to acetyl CoA and CO₂. In this study, we consider the effect of high and low ALA levels on the tissue distribution of ALA and other n-3 polyunsaturated fatty acids (PUFA) in all tissues. Guinea pigs were fed one of two defined diets for 3 wk from wearning with both diets containing 1.8% (by weight) of LA and either 1.7% ALA or 0.03% ALA. The high ALA diet was associated with significantly increased ALA levels in all tissues except the brain and significantly increased levels of long-chain n-3 PUFA in all tissues except intestines, brain, carcass, and skin. The long-chain n-3 PUFA content of the whole body was less than 5% of that of the ALA content in both diet groups, and the major long-chain n-3 PUFA (>66% of total) in the body was 22∶5n−3. The brain was the only tissue where the DHA content exceeded that of 22∶5n−3. On the low ALA diet, there appeared to be conservation of ALA based on a comparison of the ratio of LA to ALA in the tissues compared with that in the diet. On the high ALA diet there was a loss of ALA relative to LA in the tissues compared with the diet. These studies suggest that the low levels of tissue ALA in the guinea pig are likely the result of β-oxidation or excretion via the skin and fur rather than metabolism to DHA.     

In situ observation of methoxide hydrogenation on the Ni(111) surface

The surface chemistry of methoxide (CH₃O-) on the Ni(111) surface has been studied in the presence of hydrogen pressures up to 2 Torr. During heating in vacuum methoxide decomposes to H₂ and CO, which desorb at 380 and 445 K, respectively. The CH₃O-decomposition process is rate limited by CH bond breaking and exhibits a strong deuterium kinetic isotope effect in CD₃O-. In the presence of ambient hydrogen pressures of 0.02–2.0 Torr both CH₃O- and CD₃O-are hydrogenated directly to methanol at 310 K. Methoxide is hydrogenated by adsorbed hydrogen, which nearly saturates the surface at these pressures and temperatures.     

Feeding pure docosahexaenoate or arachidonate decreases plasma triacylglycerol secretion in rats

Essential fatty acid (EFA)-deficient rats were fed highly purified methyl esters of docosahexaenoate (22∶6n−3), arachidonate (20∶4n−6), alpha-linolenate (18∶3n−3) or oleate (18∶1n−9) (100 mg/day, tube fed for 3–10 days), and their plasma triacylglycerol (TG) secretion rates were measured. Secretion rates of TG into plasma were reduced by tube-feeding 22∶6n−3, 20∶4n−6, 18∶3n−3, but not 18∶1n−9, to EFA-deficient rats. A significant reduction occurred after feeding 22∶6n−3 for only three days. Feeding 22∶6n−3 or 18∶3n−3 to EFA-deficient rats for three days also reduced the activities of liver lipogenic enzymes and sharply increased the proportions of 22∶6n−3 and 20∶5n−3 in liver phospholipid fractions. Mechanisms by which these EFA may reduce lipogenesis are discussed.