Fracture stability and residual strength assessment of reinforced concrete beams

In conventional analysis and design procedures of reinforced concrete structures, the ability of concrete to resist tension is neglected. Under cyclic loading, the tension-softening behavior of concrete influences its residual strength and subsequent crack propagation. The stability and the residual strength of a cracked reinforced concrete member under fatigue loading, depends on a number of factors such as, reinforcement ratio, specimen size, grade of concrete, fracture properties, and on the tension-softening behavior of concrete. In this work, a method is proposed to assess the residual strength of reinforced concrete beams subjected to cyclic loading. The crack extension resistance based approach is used for determining the condition for unstable crack propagation. The effect of reinforcement is modeled as a closing force counteracting the effect of crack opening produced by the external moment. The effect of percentage reinforcement and specimen size on the failure of reinforced beams is studied. Finally, the residual strength of the beams are computed by including the softening behavior of concrete.     

Modeling the environmental fate of manganese from methylcyclopentadienyl manganese tricarbonyl in urban landscapes

The environmental impacts of gasoline additives such as lead (Pb) and Methyl Tertiary Butyl Ether (MTBE) are well documented, leading to the phasing out of these additives. In contrast, little is known about the health and environmental impacts of potential replacement chemicals such as Methylcyclopentadienyl Manganese Tricarbonyl (MMT). The combustion of MMT in gasoline leads to the formation of MnPO4 and MnSO4 and MMT is considered a recent source of inorganic Mn in urban landscapes particularly in high traffic areas. The main objective of this study is to estimate the automotive deposition of Mn from MMT relative to the traffic volume at sites near a major highway in the Greater Toronto Area of Canada, where MMT is currently being used. Manganese emission levels were estimated for two sites that varied according to Annual Average Daily Traffic (AADT) density, fuel consumption, distance traveled by automobiles, and Mn concentration (mg l(-1)) in gasoline. Multiple regression analysis was used to predict the AADT volume from year 2002-2010. Comparison of the mass balance between the ANOVA means of 15% Mn emitted from the automobile tailpipes at 10, and 18 mg of Mn l(-1) in gasoline was conducted for both study sites. The percentage difference between the Mn input at the selected concentrations of Mn in gasoline and output into surface soil were found to be 99% significant for both sites. Thus the predicted 15% tailpipe emission levels for 10 mg of Mn l(-1) of gasoline used in automobiles, which represented 1290.03 g/year for site 1 and 555.94 g/year for site 2, will add 5.73 and 2.47 mg/kg of Mn annually, respectively. These input levels are considered negligible when compared to the natural abundance of Mn in soil. Based on these data, it could take more than 95-256 years of continuous MMT usage in the region to double the content of Mn in surface soils at the respective sites.     

An approach to optimization of shape memory alloy hybrid composite plates subjected to low-velocity impact

The paper presents an approach to the problem of optimum design of composite plates subjected to low velocity impact. The deflections and stresses are reduced by employing prestrained shape memory alloy (SMA) fibers which are in the martensitic phase when embedded within the plate. At an elevated temperature, the SMA fibers transform into the austenitic phase and tend to contract. However, due to a constraint, the contraction is either completely prevented or reduced resulting in significant tensile recovery stresses. This tension reduces deformations and stresses in the plate subjected to low-velocity impact.The solution in the paper addresses an impact of cross-ply plates with SMA fibers embedded within the layers oriented in both directions. An approach to optimization considered in the paper involves variations of the volume fractions of SMA fibers in each direction subject to a constraint on the total volume of the shape memory alloy. It is shown that an application of SMA fibers can significantly reduce deflections and stresses. A further benefit can be achieved by an optimization of a distribution of volume fractions of SMA fibers between the layers.     

On the control applications of a determinant equality related to eigenvalue computation

A determinant equality known in linear algebra is shown to be an effective tool for control engineers in reducing complexity of eigenvalue computation and increasing insight into system behavior. Included are its applications to matrix products and singular matrices, to the study of systems with poles at the origin, and to the problem of finding the characteristic equation of an optimal regulator problem.     

Successful treatment of carbamazepine poisoning with hemodialysis: a case report and review of the literature

A 48-year-old man was brought to the emergency room after ingesting an unknown amount of carbamazepine. He was unconscious and not responding to the noxious stimuli. He was intubated and was placed on mechanical ventilation because of respiratory insufficiency. Primary detoxification was performed with a gastric lavage and charcoal instillation. His serum carbamazepine level was 25.6 mcg/mL at the time of admission. His computed tomography of the brain was normal. He was managed conservatively but there was no improvement in his neurological status in the next 24 hours. Serum carbamazepine level was repeated and reported to be 28.3 mcg/mL. As there was no improvement in his sensorium and the serum carbamazepine levels remained persistently high, extracorporeal removal of carbamazepine was attempted. As the facility to carry out hemoperfusion was not available immediately, the decision to initiate hemodialysis was taken. After 3 sessions of hemodialysis, his sensorium improved markedly and the carbamazepine level at this time was within the therapeutic range. He was discharged after psychiatry consultation and counseling. We review the literature regarding extra corporeal techniques for the removal of carbamazepine and discuss them in this article.     

The influence of sulfur on interfacial reaction kinetics in the decarburization of liquid iron by carbon dioxide

The kinetics of decarburization of continuously carbon-saturated liquid iron by CO₂ have been studied between 1280 and 1600?C at sulfur concentrations between 0.01 and 1 wt pct. The results are consistent with a surface blockage mechanism by chemisorbed sulfur which shows an essentially ideal adsorption isotherm. The adsorption coefficient of sulfur, in (wt pct)^-1, is given by the equation logK = 3600/T + 0.57 for carbon-saturated alloys. A small residual rate at apparent surface saturation is observed. This leaves about 1.4 pct of the active surface sites available for reaction, essentially independent of temperature. Studies with varying carbon concentration suggest that to a first approximation, and above about 3 wt pct C, the adsorption equilibrium for sulfur depends only on the thermodynamic activity of sulfur.     

A control-oriented model for cylinder pressure in internalcombustion engines

The cylinder-pressure modeling problem is formulated and a perturbation solution is presented. Control-oriented perturbation models (COPMs) for cylinder pressure in spark-ignited internation combustion engines are novel in that the smallest regions of realistic interest already include nonlinear effects which may be neglected, so linear perturbation is not adequate. Moreover, the crank angle frame of reference leads to a perturbation on the independent variable as well. These features require higher order local representations of vector-valued functions of several vector-valued variables, in a form suitable for computation. A COPM for cylinder pressure in a 1.8-L Opel Family II engine, with inputs of spark advance and air-fuel ratio, demonstrates that increased accuracy and consistency result from the increasing model degree made possible with these models     

A simplified HF field strength prediction procedure for India

Field strength measurements of several HF broadcast transmissions were made at New Delhi during 1987-1990 with a view to evolving a simple procedure for estimation of the skywave field strength in the HF bands (3-30 MHz). An attempt has been made using the measured field strength values to arrive at a single combined loss factor which can account for all the losses in excess of basic free space and ionospheric absorption losses. The present study has shown that a provision of 4 dB for transmission losses other than free space and ionospheric absorption losses can bring the predicted values closer to measured field strength values for single-hop circuits in India for about 50% of the cases, and 10 dB increases it to 90%. Transmission losses in general were found to be much higher during equinoctial months in India, particularly around the peak region of equatorial anomaly     

Optimization of mechanical strength of reinforced composites. 1. Study on the effect of reactive bismaleimide on the mechanical performance of CaCo3-filled polypropylene

The effect of 3-phenylene bismaleimide on the mechanical performance of an inorganic filler-based polypropylene composite was studied. The selection of processing temperature played a significant role in the preparation of such composites. A positive effect of the bismaleimide compound was obtained for a processing temperature above the decomposition temperature of bismaleimide. The chemical composition of the modified composite was correlated to its mechanical strength by experimentation involving a rotatable design. An interaction between polymer and CaCO₃ has been proposed based on ESCA analysis.