Iterative finite element model updating in the time domain

An iterative time domain formulation for finite element model updating in structural dynamics is presented. The approach is supported on a derivation showing that the discrepancy between observations and model predictions can be expressed as a convolution between the state of the system and a sequence of pseudo-Markov parameters which are linear in the change of the free parameters. The approach is illustrated by updating all the stiffness and damping parameters of a twenty degree of freedom shear beam using four noise contaminated measurements.     

Recycling heterogeneous americium targets in a boiling water reactor

One of the limiting contributors to the heat load constraint for a long term spent fuel repository is the decay of americium-241. A possible option to reduce the heat load produced by Am-241 is to eliminate it via transmutation in a light water reactor thermal neutron environment, in particular, by taking advantage of the large thermal fission cross section of Am-242 and Am-242m. In this study we employ lattice loading optimization techniques to define the loadings and arrangements of fuel pins with blended americium and uranium oxide in boiling water reactor bundles, specifically, by defining the incineration of pre-loaded americium as an objective function to maximize americium transmutation. Subsequently, the viability of these optimized lattices is tested by assembling them into bundles with Am-spiked fuel pins and by loading these bundles into realistic three-dimensional BWR core-wide simulations that model multiple reload cycles and observe standard operational constraints. These simulations are possible via our collaboration with the Westinghouse Electric Co. which facilitates the use of industrial-caliber design tools such as the PHOENIX-4/POLCA-7 sequence and the Core Master 2^© GUI work environment for fuel management.     

Nanoindentation and microstructure analysis of resistance spot welded dual phase steel

A nanoindentation hardness study has been conducted on the tempered region and the base metal in a dual phase steel subjected to rapid thermal cycles of resistance spot welding. Nanohardness results revealed “softening” at nano-scale for tempered martensite when compared to martensite in the base metal. At the tempered region, the ferritic matrix presented a slight reduction in hardness while the tempered martensite seemed to have a major contribution to the measured softening at micro-scale.     

Improving the performance of natural gas pipeline networks fuel consumption minimization problems

As the gas industry has developed, gas pipeline networks have evolved over decades into very complex systems. A typical network today might consist of thousands of pipes, dozens of stations, and many other devices, such as valves and regulators. Inside each station, there can be several groups of compressor units of various vintages that were installed as the capacity of the system expanded. The compressor stations typically consume about 3–5% of the transported gas. It is estimated that the global optimization of operations can save considerably the fuel consumed by the stations. Hence, the problem of minimizing fuel cost is of great importance. Consequently, the objective is to operate a given compressor station or a set of compressor stations so that the total fuel consumption is reduced while maintaining the desired throughput in the line. Two case studies illustrate the proposed methodology. Case 1 was chosen for its simple and small‐size design, developed for the sake of illustration. The implementation of the methodology is thoroughly presented and typical results are analyzed. Case 2 was submitted by the French Company Gaz de France. It is a more complex network containing several loops, supply nodes, and delivery points, referred as a multisupply multidelivery transmission network. The key points of implementation of an optimization framework are presented. The treatment of both case studies provides some guidelines for optimization of the operating performances of pipeline networks, according to the complexity of the involved problems. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Managing emergency response operations for electric utility maintenance

One of the most important criteria used to measure the quality of service in the electric utility industry is the uninterrupted service supplied to the customers. So, preventive maintenance is very relevant to avoid failures in the electric utility network. However, when failure is inevitable, it is very important that emergency repair operations are accomplished as soon as possible so the operators can avoid high-risk situations. Service unavailability can be decreased, reducing the frequency of power interruptions, number of customers affected per interruption, and duration of the interruption. A MAS for managing maintenance and emergency response operations in the electric utility industry was presented. The proposed system has the capability to support maintenance operations and make planning decisions.     

Poly(pyridinium salt)s with organic counterions derived from an aromatic diamine containing tetraoxyethylene units exhibiting amphotropic liquid‐crystalline and photoluminescence properties

Several poly(pyridinium salt)s containing various organic counterions and tetraoxyethylene units in their backbones were synthesized by either ring‐transmutation polymerization reaction of 4,4'‐(1,4‐phenylene)bis(2,6‐diphenylpyrylium tosylate) with bis(2‐(2‐(4‐aminophenoxy)ethoxy)ethyl) ether on heating in dimethyl sulfoxide or metathesis reaction of the tosylate polymer with the corresponding lithium or sodium salts in acetonitrile. Their chemical structures were determined by ¹H‐NMR and ¹³C‐NMR spectroscopy, and elemental analyses. Their number‐average molecular weights and polydispersity indices were in the range of 34,000–52,000 and 1.14–1.38, respectively, as determined by gel permeation chromatography. They were characterized both for their thermotropic and lyotropic liquid‐crystalline properties by using differential scanning calorimetry and polarizing optical microscopy. As these polymers exhibited liquid‐crystalline phase both in the melt and in solutions, they are classified as an amphotropic class of ionic polymers. Their light‐emitting properties in a large number of organic solvents that ranged from nonpolar to polar solvents and in films cast from methanol and acetonitrile were also studied by using spectrofluorometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Potassium ion transport by gramicidin and valinomycin across a Ag(1 1 1)-supported tethered bilayer lipid membrane

A tethered bilayer lipid membrane (tBLM) was prepared by anchoring a thiolipid monolayer to a Ag(1 1 1) single crystal from a thiolipid solution in ethanol; a diphytanoylphosphatidylcholine monolayer was then self-assembled on top of the thiolipid monolayer from a lipid solution in hexane or ethanol. The thickness of the mixed thiolipid|lipid bilayer was estimated at 7.5 ± 0.5 nm by scratching holes in the tBLM with an AFM tip and determining their height profile and the frequency distribution of height. The effect of the incorporation of gramicidin A and valinomycin upon K⁺ ion transport across the tBLM was investigated by electrochemical impedance spectroscopy. The position of the inflection point of the sigmoidal curve of the in-phase component of the electrode admittance against potential allowed the determination of an approximate scale of the absolute potential difference across the whole Ag(1 1 1)|(aqueous solution) interface, on the basis of a model of the electrified interface.     

Modulation of biotransformation and elimination systems by BM-21, an aqueous ethanolic extract from Thalassia testudinum,and thalassiolin B on human hepatocytes

BM-21 is an extract obtained from Thalassia testudinum marine plant with pharmacological properties. The effects of BM-21 and thalassiolin B (TB), its main component, on enzyme and transport proteins involved in drug metabolism and excretion in human cultured hepatocytes were evaluated. Cells were exposed for 48 h to sub-cytotoxic concentrations of BM-21 or TB. Effects on P450 isoforms revealed significant reductions of CYP1A2, 3A4 and 2D6 activities (up to 56%, 66% and 44% inhibition, respectively) after exposition to BM-21, no changes on CYP2A6 and 2C9 activities. TB produced a concentration-dependent reduction of all P450 activities. In addition, a decrease in total UGT and UGT2B7 activities was found at 250 μg/mL BM-21, while UGT1A1 and 1A9 were significantly reduced (50 μg/mL). TB only inhibited significantly UGT1A9 activity. Both products were able to reduce P-gp activity in treated hepatocytes. Quantification of specific mRNAs revealed a reduction in CYP3A4 and 3A5 mRNAs content and an increase in CYP1A1 and 1A2 mRNAs. No appreciable effects in the levels of CYP2A6, 2B6, 2C9, 2C19, 2D6, 2E1, UGT1A1, UGT1A9 and ABCB1 (P-gp) were found. BM-21 inhibited P450, UGTs and P-gp activities in human hepatocytes; therefore, it should be examined for potential pharmacokinetic drug interactions in vivo.     

Impact of paint and wall-paper on mould growth on plasterboards and aluminum

Biocide-free and biocide-treated plasterboards as well as aluminum plate as a reference material normally considered as being insensitive to mould growth have been used as substrate to check the influence of different common wall coverings, i.e. paints and wall papers, on fungal growth. The results described in this paper show that any non-biodegradable material (such as aluminum) can become a substrate to fungal infestation once painted or wall paper applied, depending on the type of paint or wall paper used. Moreover, a biodegradable material treated with a biocide (biocide-treated plasterboard) offers partial resistance to fungal growth at a biodegradable surface covering.     

Nanoporous Films with Low Refractive Index for Large‐Surface Broad‐Band Anti‐Reflection Coatings

Nowadays, nanoporous films are widely employed in biochemical applications or in opto‐photonic devices such as displays, solar cells, or light‐guiding systems. In particular, the technological feasibility of nanoporous layers with low refractive indices has recently enabled the development of high‐efficiency anti‐reflection coatings. In this paper, we report on hybrid polymer nanoporous films that can be fabricated in a single coating step with an industrial aqueous‐based method on very large surfaces. Both high transparency and low refractive index are simultaneously achieved over the entire visible spectrum. We eventually demonstrate the potential of such films for broadband AR applications by combining them in a graded‐index multilayer that reduces the surface reflectivity of a polymer substrate from 10% to few ‰.