Bond-slip law and short tie behavior without main cracks

The aim of this paper is to study the reinforced concrete short tie-rods behavior using the adhesion-slip curve shape between steel and concrete adopted by the European Concrete Committee. We are interested here in short tie-rods without main cracks for which we calculate and measure the maximum mobilization state of steel-concrete adhesion, and beyond the decrease mode of this bond. For this, tests of short tie-rods, with different high adhesion rebar diameters have been carried out. To characterize the first phase of the adhesion-slip behavior law (τ?g), pull out tests have been carried out with the same concrete, the same reinforcement and the same cross-section such as the tie-rod tests, with a proposed method to estimate the adhesion peak and the corresponding slip. For this adhesion peak value, slightly underestimated by the conventional curve of the European Concrete Committee, a new expression is suggested. A numerical model with theoretical relations of the behavior of such tie-rods is proposed. The comparison of this model with the obtained test curves of the short tie-rods shows a suitable approach. Also, we deduce that the steel (coated with concrete) fictitious module slope is even higher than the percentage of reinforcement is low. These results may help to understand the tie-rods behavior generally, in the phase of cracks stabilization, during which the tie-rod is composed of short tie-rods without main cracks.     

Morphological,electrical and electromagnetic interference shielding characterization of vapor grown carbon nanofiber/polystyrene nanocomposites

The influence of melt mixing conditions on the level of dispersion and the aspect ratio of vapor grown carbon nanofibers (VGCNFs) in a polystyrene (PS) matrix was studied. Final electrical and electromagnetic shielding capabilities in the 0.05–1.5 GHz frequency range are reported and discussed in the light of the composites' microstructure. The morphological study was based on analyzing scanning electron microscopy and optical microscopy micrographs and measuring the VGCNF length as a function of shear mixing conditions. The influence of mixing conditions on the microstructure was also indirectly studied by analyzing the dynamic mechanical behavior of the composites via rheology. Degradation of the VGCNF aspect ratio was found to be a function of the mixing energy. VGCNFs lost one‐third of their aspect ratio under gentle (low shear stress and mixing energy) mixing conditions. After VGCNFs had lost 40% of their aspect ratio, they had more resistance to breakage with increase in mixing energy. The dispersion of the VGCNFs was remarkably enhanced with increase in mixing energy. The percentage of area taken up by big agglomerates in the micrographs decreased from 14.1% to 5.5% when the mixing energy was increased from 100 J mL^?1 to 453 J mL^?1. The electrical and electromagnetic shielding properties of the 7.5 vol% VGCNF/PS composites were not affected by changing the processing energy because the enhancement of VGCNF dispersion with increasing mixing energy was accompanied by a loss in nanofiber aspect ratio. © 2012 Society of Chemical Industry     

PlanMine: Predicting Plan Failures Using Sequence Mining

This paper presents the PlanMine sequence mining algorithm to extract patterns of events that predict failures in databases of plan executions. New techniques were needed because previous data miningalgorithms were overwhelmed by the staggering number of very frequent,but entirely unpredictive patterns that exist in the plan database.This paper combines several techniques for pruning out unpredictiveand redundant patterns which reduce the size of the returned rule setby more than three orders of magnitude. PlanMine has also beenfully integrated into two real-world planning systems. We experimentally evaluate the rules discovered by PlanMine, and show that theyare extremely useful for understanding and improving plans, as wellas for building monitors that raise alarms before failures happen.     

Elastoplastic stability analysis of mine haulage drift in the vicinity of mined stopes

This paper is focused on the interaction between the haulage drift and nearby mining activity related to sublevel stoping method with delayed backfill, one of the most popular mining methods in Canadian underground metal mines. The stability of the haulage drift is examined through a detailed parametric study of a nonlinear, elastoplastic, two-dimensional finite element model representing typical mining layout most commonly adopted in Canadian underground metal mines. The model parametric study examines the influence of critical factors such as the stope mining sequence, mining depth and the distance between the stope and the haulage drift. Stability indicators are defined in terms of displacement, stress and the extent of yield zones, which serve as a basis for assessing the effect of different parameters on the stability of the haulage drift. The model parametric study demonstrates that stope mining causes a footwall lateral shift of the entire drift. The severity of such shift is increased with shorter distance between the stope and haulage drift. Of all mining excavations examined, same-level mining appears to be the most critical. It is also found that more stress relaxation zones and yield zones develop around the haulage drift as the mining depth increases and as distance between haulage drift and the stope decreases.     

MC‐MIPOG: A Parallel t‐Way Test Generation Strategy for Multicore Systems

Combinatorial testing has been an active research area in recent years. One challenge in this area is dealing with the combinatorial explosion problem, which typically requires a very expensive computational process to find a good test set that covers all the combinations for a given interaction strength (t). Parallelization can be an effective approach to manage this computational cost, that is, by taking advantage of the recent advancement of multicore architectures. In line with such alluring prospects, this paper presents a new deterministic strategy, called multicore modified input parameter order (MC‐MIPOG) based on an earlier strategy, input parameter order generalized (IPOG). Unlike its predecessor strategy, MC‐MIPOG adopts a novel approach by removing control and data dependency to permit the harnessing of multicore systems. Experiments are undertaken to demonstrate speedup gain and to compare the proposed strategy with other strategies, including IPOG. The overall results demonstrate that MC‐MIPOG outperforms most existing strategies (IPOG, IPOF, IPOF2, IPOG‐D, ITCH, TConfig, Jenny, and TVG) in terms of test size within acceptable execution time. Unlike most strategies, MC‐MIPOG is also capable of supporting high interaction strengths of t > 6.     

Study effect of different parameters on the sulphate sorption onto nano alumina

The aim of this research work is to investigate sorption characteristic of modified nano alumina (n-Al) for the removal of SO₄^2? from aqueous solutions and wastewater. The sorption of SO₄^2? by batch method is carried out. The optimum conditions of sorption were found to be: a sorbent dose of 0.3 g in 100 ml of SO₄^2?, contact time of 35 min, pH = 5. In optimum condition, removal efficiency was 85.6% for the SO₄^2?. Three equations, i.e. Morris–Weber, Lagergren and pseudo second order have been tested to track the kinetics of removal process. The Langmuir, Freundlich and D–R are subjected to sorption data to estimate sorption capacity. It can be concluded that n-Al has potential to remove SO₄^2? ions from aqueous solutions at different concentrations. It was found that the temperature has positive effect on the process and negative ΔG values indicated thermodynamically feasible and spontaneous nature of the sorption. Positive value of ΔS reveals the increased randomness at the solid–solution interface during the fixation of the ion on the active sites of the sorbent. The effect of other anions was studied and it was found the existence of them in the solution has considerable effect on the sulphate removal.     

Experimental Study of Boiling Heat Transfer on Multiple and Single Nucleation Sites Using a Boiling-Meter

The general objective of this study is to contribute to a better understanding of heat transfer in a nucleate boiling regime. The aim is to determine the heat transfer characteristics under controlled operating conditions (thermodynamics of the fluid, noncondensable gas, surface state). Experimental investigations have been carried out in natural convection and nucleate boiling regimes. An experimental device was realized to perform boiling experiments using a boiling-meter, allowing investigations for different orientations of the wall. The boiling-meter is designed to investigate boiling for single and multiple nucleation sites. The purpose of this paper is to detail the experimental setup as well as the boiling-meter. This device allows the determination of the temporal heat transfer characteristics evolutions. In particular, this new device allows bringing to light the phenomenon of nucleation, growth, and detachment of generated vapor bubbles on a single artificial nucleate site, as well as for multiple natural nucleation sites. First results of the influence of the orientation of the heating wall for multiple and single nucleation sites on heat transfer are presented and analyzed.