The risk of trivial solutions in bipartite top ranking

Machine Learning - Given a sample of instances with binary labels, the bipartite top ranking problem is to produce a ranked list of instances whose head is dominated by positives. One popular...     

Modeling of baking of thin layer of cake using the lumped reaction engineering approach (L-REA)

Baking is a simultaneous heat and mass transfer process commonly applied in the food industry. It is desirable to have a simple, accurate and robust model in order to assist efficient process design and evaluation of product quality. The reaction engineering approach which was proven to be accurate to model several challenging drying cases, was implemented in this study to model the baking of thin layer of cake. The equilibrium activation energy (ΔE_v,b) was evaluated according to the baking oven temperature and corresponding humidity. It was then combined with the relative activation energy (ΔE_v/ΔE_v,b) to produce a unique relationship. Results of the modeling indicate that the L-REA can describe the profiles of moisture content and temperature very well. While the results are accurate, the model itself remains simple. Another significant application of the REA for modeling the processing of food products has been made by this research.     

Effect of particle size distribution of metakaolin on hydration kinetics of tricalcium silicate

The focus of this study is to elucidate the role of particle size distribution (PSD) of metakaolin (MK) on hydration kinetics of tricalcium silicate (C₃S–T₁) pastes. Investigations were carried out utilizing both physical experiments and phase boundary nucleation and growth (pBNG) simulations. [C₃S + MK] pastes, prepared using 8%_mass or 30%_mass MK, were investigated. Three different PSDs of MK were used: fine MK, with particulate sizes <20 µm; intermediate MK, with particulate sizes between 20 and 32 µm; and coarse MK, with particulate sizes >32 µm. Results show that the correlation between specific surface area (SSA) of MK's particulates and the consequent alteration in hydration behavior of C₃S in first 72 hours is nonlinear and nonmonotonic. At low replacement of C₃S (ie, at 8% _mass), fine MK, and, to some extent, coarse MK act as fillers, and facilitate additional nucleation and growth of calcium silicate hydrate (C–S–H). When C₃S replacement increases to 30% _mass, the filler effects of both fine and coarse MK are reversed, leading to suppression of C–S–H nucleation and growth. Such reversal of filler effect is also observed in the case of intermediate MK; but unlike the other PSDs, the intermediate MK shows reversal at both low and high replacement levels. This is due to the ability of intermediate MK to dissolve rapidly—with faster kinetics compared to both coarse and fine MK—which results in faster release of aluminate [Al(OH)₄⁻] ions in the solution. The aluminate ions adsorb onto C₃S and MK particulates and suppress C₃S hydration by blocking C₃S dissolution sites and C–S–H nucleation sites on the substrates’ surfaces and suppressing the post-nucleation growth of C–S–H. Overall, the results suggest that grinding-based enhancement in SSA of MK particulates does not necessarily enhance early-age hydration of C₃S.     

The Filler Effect: The Influence of Filler Content and Surface Area on Cementitious Reaction Rates

Finely ground mineral powders are known to accelerate cement hydration rates. This “filler effect” has been attributed to the effects of dilution (w/c increase) when the cement content is reduced or to the provision of additional surface area by fine powders. The latter contribution (i.e., surface area increase) is speculated to provide additional sites for the nucleation of the hydration products, which accelerates reactions. Through extensive experimentation and simulation this study describes the influence of surface area and mineral type (e.g., quartz or limestone) on cement reaction rates. Simulations using a boundary nucleation and growth (BNG) model and a multiphase reaction ensemble (MRE) indicate that the extent of the acceleration is linked to the: (1) magnitude of surface area increase and (2a) capacity of the filler's surface to offer favorable nucleation sites for hydration products. Other simulations using a kinetic cellular automaton model (HydratiCA) suggest that accelerations are linked to: (2b) the interfacial properties of the filler that alters (increases or decreases) its tendency to serve as a nucleant, and (3) the chemical composition of the filler and the tendency for its dissociated ions to participate in exchange reactions with the calcium silicate hydrate product. The simulations are correlated with accelerations observed using isothermal calorimetry when fillers partially replace cement. The research correlates and unifies the fundamental parameters that drive the filler effect and provides a mechanistic understanding of the influence of filler agents on cementitious reaction rates.     

Influence of Rolling Path on Microstructure and Mechanical Properties in EB Refined Tantalum

This work reports the effectiveness of multidirectional forging in breaking up the as-cast microstructure, and also discusses the influence of variation in rolling path on the homogeneity and grain size in heavily deformed tantalum (Ta) plates that are subjected to static recrystallization annealing. Ingots of electron-beam-refined, Ta were multi-directionally forged and subsequently cold rolled to a strain of 250?%. Cold rolling was performed in three distinct modes and the effect of the change in the rolling path on the microstructure and mechanical properties in as-rolled and annealed condition were investigated. The influence of such rolling path was found to be significantly strong. Results show that the kinetics of static recrystallization in differently rolled products are equal. Microstructural evaluation has revealed a high degree of homogeneity and elimination of orientation effects in cross rolled products. Discussion on the hardness and tensile properties in various conditions is also presented.     

In Vivo Molding of Airway Stents

Like ready-to-wear clothing, medical devices come in a fixed set of sizes. While this may accommodate a large fraction of the patient population, others must either experience suboptimal results due to poor sizing or must do without the device. Although techniques have been proposed to fabricate patient-specific devices in advance of a procedure, this process is expensive and time consuming. An alternative solution that provides every patient with a tailored fit is to create devices that can be customized to the patient's anatomy as they are delivered. This paper reports an in vivo molding process in which a soft flexible photocurable stent is delivered into the trachea or bronchi over a ultraviolet (UV)-transparent balloon. The balloon is expanded such that the stent conforms to the varying cross-sectional shape of the airways. UV light is then delivered through the balloon curing the stent into its expanded conformal shape. The potential of this method is demonstrated using phantom, ex vivo, and in vivo experiments. This approach can produce stents providing equivalent airway support to those made from standard materials while providing a customized fit.     

Effect of iron & boron content on the Spark Plasma Sintering of Ti-B-Fe alloys

The effect of a change in iron and boron contents on the Spark Plasma Sintering behaviour in the Ti-B-Fe alloys has been investigated through dilatometric sintering study using various samples having Ti-rich compositions. These samples are adequately chosen to study the sintering behaviour on the addition of boron and iron on the Ti-rich corner. The rate of sintering of Ti-B-Fe alloys was found to increase with an increase in iron content. The sintering enhancement can be attributed to the high diffusivity of iron in α-Ti and β-Ti phases and due to the formation of the intermetallic phase which results in greater overall shrinkage. The shrinkage was found to decrease with increase in boron content due to a greater amount of TiB₂ which doesn’t participate in sintering in the observed range.     

Control of a nonlinear continuous bioreactor with bifurcation by a type-2 fuzzy logic controller

The object of this paper is the application of a type-2 fuzzy logic controller to a nonlinear system that presents bifurcations. A bifurcation can cause instability in the system or can create new working conditions which, although stable, are unacceptable. The only practical solution for an efficient control is the use of high performance controllers that take into account the uncertainties of the process. A type-2 fuzzy logic controller is tested by simulation on a nonlinear bioreactor system that is characterized by a transcritical bifurcation. Simulation results show the validity of the proposed controllers in preventing the system from reaching bifurcation and instable or undesirable stable conditions.     

In vitro evaluation of red and green lettuce (Lactuca sativa) for functional food properties

Lettuce (Lactuca sativa) is an important leafy vegetable consumed fresh or in salad mixes. We have compared the functional food properties of selected commercial red and green lettuce varieties grown under field conditions. Both lettuce cultivars were extracted with water at biological (38 °C) and room temperatures (22 °C) at pH 2. The residues from each extraction were further extracted, sequentially with methanol and ethyl acetate. The extracts were evaluated for their in vitro lipid peroxidation (LPO) and cyclooxygenase enzyme (COX) inhibitory activities. Amongst the extracts tested, all three extracts of red lettuce showed higher LPO and COX-1 and -2 enzyme inhibitory activities than did the green lettuce extracts. Red lettuce contained a single anthocyanin, cyanidin-3-O-(6″-malonyl-β-glucopyranoside) (1), which immediately converted to cyanidin-3-O-(6″-malonyl-β-glucopyranoside methyl ester) (2) and cyanidin-3-O-β-glucopyranoside (3) under laboratory conditions. Anthocyanins 1 and 2 inhibited LPO by 88% and 91.5%, respectively, at 0.25 μM concentration. Also, they inhibited COX-2 enzyme by 78.9% and 84.3% and COX-1 by 64% and 65.8%, respectively, at 5 μM. The chicoric acid (4), amongst other phenolics, such as quercetin glucoside, ferulic and caffeic acids, isolated from both green and red lettuce, showed 85.6%, 45.6% and 94% of LPO, COX-1 and -2 enzyme inhibitions at 50 μM, respectively. This is the first report of the LPO, COX-1 and -2 enzyme inhibitory activities of compounds 1, 2 and 4. The variation of phenolics in the red and green lettuces, and specifically the lack of anthocyanins in green lettuce, might account for the higher biological activity obtained with the red variety in our study.