Load Bearing Capacity of Reinforced Concrete Beams Subjected to Dynamic Cyclic Loads

A kinematic method is developed to determine the shakedown limits of elastic-perfectly plastic steel-reinforced concrete beams under quasi-static and dynamic cyclic loads. This procedure, like the respective kinematic approach of plastic limit analysis, is visual and easy to use in engineering applications. The load parameters (amplitudes, frequency) versus yield moment diagrams, constructed from possible collapse modes, should assist in choosing the reinforcement scheme and amounts of reinforcement to meet the load bearing requirements for the structures.     

Effect of the addition of t-ZrO2 on the material properties of β-TCP/PCL composites

Using poly-methyl methacrylate as a pore-forming agent, porous β-tricalcium phosphate (β-TCP)/t-ZrO₂ composites were fabricated depending on the volume percentages (vol.%) of t-ZrO₂ powder. In the porous sintered bodies, hybrid pores, about 20 and 200 μm in diameter, were homogenously dispersed in the β-TCP/t-ZrO₂ matrix and showed good interconnection. On the other hand, β-TCP-(t-ZrO₂)/polycaprolactone (PCL) composites were fabricated by the melt infiltration process using porous β-TCP/t-ZrO₂ bodies. The relative density of the β-TCP-(t-ZrO₂)/PCL composites increased as the vol.% of t-ZrO₂ increased and its maximum value was about 98.6%. However, the hardness, bending strength and elastic modulus of β-TCP-(t-ZrO₂)/PCL composites decreased due to the low densification of porous β-TCP/t-ZrO₂ bodies as the volume percentages of t-ZrO₂ content increased. The values (using 20 vol.% of t-ZrO₂) were 11.4 Hv, 25.5 MPa and 17.2 GPa, respectively.     

Comments on `A Bayes sensitivity analysis when using the betadistribution as a prior'

The commenter makes several critical comments concerning the above-named work of B.S. Duran and J.M. Booker (see ibid., vol.37, p.239-47, June 1988). Duran and Booker present a detailed reply, pointing out, among other things, that the commenter is assuming a much more well-defined problem than theirs     

Adjusting software failure rates that are estimated from test data

Software test environments are often different from field environments. Using test data exclusively to estimate a field failure rate will not usually give a very accurate estimate. In this paper, we extend an empirical calibration methodology for adjusting the failure rate estimate obtained from analysing test data. In addition to scaling the estimated failure rate of a fault, we propose scaling the estimated number of residual faults as well. We also derive likelihood ratio tests to formally determine (from previous releases of the software) if test, and field environments are significantly different. We illustrate our new results with two telecommunications case studies. The combination of the likelihood ratio test, and the calibration methodology offers a practical way to extend the application of software reliability growth models to less formal test environments.     

Corrosion protection of molybdate doped polypyrrole film prepared in succinic acid solution

ABSTRACT

Polypyrrole (PPy) was prepared on the mild steel substrate by electrochemical polymerisation in the solution containing pyrrole monomer and succinic acid. The mild steel surface could be passivated before and during electropolymerisation by molybdate. The morphology and structure of the PPy film were studied with SEM. The typical cauliflower structure of PPy was observed. Raman and IR spectroscopy showed that the obtained PPy was in an oxidised state. The thermal stability of PPy was investigated by the thermal gravimetric analysis, showing that PPy was stable at higher than 480°C. The electrochemical property of the PPy film was performed by open circuit potential, polarisation curves (I/E), and electrochemical impedance spectroscopy. The corrosion behaviour of mild steel (CT3) with PPy film in solution NaCl 3% was studied.

This paper is part of a supplementary issue from the 17th Asia-Pacific Corrosion Control Conference (APCCC-17).     

A Review on Metal‐Free Doped Carbon Materials Used as Oxygen Reduction Catalysts in Solid Electrolyte Proton Exchange Fuel Cells

Within the last decade, metal‐free heteroatom doped carbon nanomaterials have gained attention as effective electrocatalysts for the oxygen reduction reaction (ORR) in many electrochemical systems. Since then, reports have stated that the ORR catalytic activity, onset potential, and H₂O production selectivity of these materials is similar to that of platinum‐based catalysts. These statements rely on cyclic voltammetry (CV) and rotating disc electrode (RDE) measurements in liquid alkaline electrolyte. However, fuel cell researchers aim to replace the costly platinum catalysts in the more prominent acidic solid electrolyte proton exchange fuel cell (PEFC). In this respect, there are only a few reports of unpromising activity, stability, and H₂O production selectivity. In addition, only few reports have been presented on the implementation of such materials in cathode catalyst layers of actual PEFC devices. This mini‐review aims to summarize and evaluate results of these reports. Material synthesis, cell power, open circuit voltage, stability properties, and proposed active sites are reviewed. To date, the highest reported PEFC power densities with guaranteed metal‐free heteroatom doped carbon cathode catalysts have reached up to 321 mW cm⁻²; which although a promising value is substantially short of values obtained for platinum based catalysts.     

Electro ultrasonic remediation of polycyclic aromatic hydrocarbons from contaminated soil

The polycyclic aromatic hydrocarbons (PAHs) with high molecular mass are renown for their high persistence in the soil, hydrophobic and toxicity. Remediation of these pollutants is still an unsolved task and needs more researches to be performed. The coupling of electrokinetics (EK) with ultrasonic energy (US) has advantages on desorbing and migrating PAHs from contaminated soil. US and EK work together to destroy PAHs. The objective of this study was to treat PAHs contaminated soil by using EK and ultrasonication. The contaminated oil contained about 100 mg kg⁻¹ chrysene. Experiments with US, EK and combined EK and ultrasound were conducted in reactors and pans with and without iron anodes. Results indicated that the removal was more effective with lower concentrations of chrysene. The average removal was better in experiment with combined EK and ultrasound using iron anode. This might be due to increase in electroconductivity by iron ions.     

Determination of the heat transfer coefficient from short‐shots studies and precise simulation of microinjection molding

The filling process of a micro‐cavity was analyzed by modeling the compressible filling stage by using pressure‐dependent viscosity and adjusted heat transfer coefficients. Experimental filling studies were carried out at the same time on an accurately controlled microinjection molding machine. On the basis of the relationship between the injection pressure and the filling degree, essential factors for the quality of the simulation can be identified. It can be shown that the flow behavior of the melt in a micro‐cavity with a high aspect ratio is extremely dependent on the melt compressibility in the injection cylinder. This phenomenon needs to be considered in the simulation to predict an accurate flow rate. The heat transfer coefficient between the melt and the mold wall that was determined by the reverse engineering varies significantly even during the filling stage. With increasing injection speed and increasing cavity thickness, the heat transfer coefficient decreases. It is believed that the level of the cavity pressure is responsible for the resulting heat transfer between the polymer and the mold. A pressure‐dependent model for the heat transfer coefficient would be able to significantly improve the quality of the process simulation. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers