Vector wave expansion method for leaky modes of microstructured optical fibers

A new method for calculating the confinement loss of leaky modes in arbitrary microstructured optical fibers is presented. The full vector algorithm is based on a polar coordinate Fourier decomposition method with adjustable boundary conditions, capable of accurately determining the outward radiating fields of the waveguide. Example waveguides with circular and elliptical hole shapes and their leaky mode solutions are presented and discussed.     

Influence of the catalyst on the kinetics of a RIM formulation

The influence of three different catalysts [triethylendiamine (TD), stannous octoate (SO), and dibutylindilaurate (DBTDL)] and their blends (TD + SO and TD + DBTDL) on the kinetics of a RIM formulation, based on a high functionality polyether–polyol and a polymeric MDI, has been studied using the adiabatic temperature rise method and Fourier transform infrared spectroscopy. The synergism observed in the DBTDL/TD systems is explained by means of complex formation between the amine-based and metal-based catalysts. Infrared spectroscopy data support this complex formation. The SO/TD systems do not exhibit synergetic behaviour, being the reaction rate controlled by the metal catalyst which complexes the isocyanate group.     

Effect of Construction Loads and Vibrations on New Concrete Bridge Decks

This paper presents an investigation on the effects of construction loads and vibrations on typical newly poured reinforced concrete bridge decks. The main objective of this paper was to perform dynamic finite-element analyses of concrete bridge decks under construction loads and vibrations. Two types of bridges were modeled by effectively simulating the loads encountered during construction. Separate analyses were performed to simulate one truck as well as two side-by-side trucks. Additional analyses were performed to simulate the loads during construction and pouring sequence. The loads imposed by concrete mixer trucks, including the full concrete load and the load imposed by a trailer unit carrying the pump, were taken into consideration during the modeling of the bridges. The results obtained consisted of vibration modes and frequencies for each structure in addition to top and bottom stresses in each principal direction. A separate analysis was performed that took into account the sequence of pour to determine the effect of moving loads from adjacent traffic and construction loads on fresh concrete. The time history and dynamic analysis indicated that the sequence of pour has a significant effect on the deformation of the concrete at early ages. As a result, the first three mode shapes obtained by the finite-element analysis will be used to optimize sensor locations for future dynamic field testing.     

Application of knowledge-based expert systems for rating highway bridges

This paper presents the establishment of a Bridge Rating Expert System (BRES) by using a knowledge-based computer artificial intelligent expert system for analysis and rating of existing short span prestressed concrete highway bridges. The rating methods considered were: Inventory Rating, Operation Rating, Rating Factor Rating and Sufficiency Rating. A strength rating is based on the evaluation of existing prestressed concrete bridges in accordance with the American Association of State Highway Transportation Officials (AASHTO) specifications, and inventory rating for all bridges according to the Federal Highway Administration (FHWA) guide for the Structure Inventory and Appraisal of the Nation's Bridges. The parameters considered were bridge type, dead loads, type of vehicle loading, bridge dimensions and cross-section, material properties, reinforcement details, and existing physical condition of the bridge. The results show that, through its runtime rule controller, user interface and linkage mechanisms, the BRES is a friendly user system for rating highway bridges. In addition, the EXSYSP shell provides an effective tool for other possible applications in civil engineering practice.     

Polymerization of some oxiranes using the diphenylzinc-butanone system in benzene at 60°C

The diphenylzinc-butanone system was used as polymerization catalyst for some oxiranes in benzene solution at 60°C. This system is greatly influenced by the molar ratio of butanone to diphenylzinc, and the maximum catalytic activity for propylene oxide and ethylene oxide was found for a ratio of unity. GPC results strongly suggest the presence of more than one active species for the system. ¹³C NMR analysis indicates that the resulting poly(propylene oxide) has a head-to-tail arrangement. For the polymerization of propylene oxide with butanone/diphenylzinc = 1, after an initial induction period, the reaction was first-order with respect to monomer with k = 2·51 × 10^?5 s^?1. Ethylene oxide polymerizations using butanone/diphenylzinc = 1 and 5 were also first-order with respect to monomer after an initial induction period with k = 7·80 × 10^?6 s^?1 and k = 5·71 × 10^?6 s^?1, respectively. The diphenylzinc-butanone system was not an effective catalyst for styrene oxide polymerization.     

Anodic behaviour of α-PbO2 substrates containing different percentages of lower lead oxides

A study has been made of the anodic behavior of lead oxide deposits containing 92, 80 and 60%α-PbO₂. The non-porous deposits were prepared by electrodeposition from a plumbite bath containing different proportions of 30% formaldehyde solution, acting as a reductant in the cases of 80 and 60%α-PbO₂. Measurements of the steady-state oxygen evolution reaction under constant surface conditions of the electrodes, were carried out galvanostatically within the current-density range 30–190μAcm^?2. The oxygen overpotential values were found to increase with increasing the amount of superficially formedβ-PbO₂ during anodization in sulphuric acid solution. In the proposed mechanism for the o.e.r, the rate determining step is an electron-transfer reaction. Tafel slopes having values of 220±10 mV dec^?1 were obtained. Possible interpretation of these higher slopes is given which is based on the dual barrier model. Potential-time decay curves reveal a retarded oxygen diffusion process.     

Copolymerization of dimethylaminoethylacrylate-methyl chloride and acrylamide in inverse emulsion

The inverse emulsion copolymerization of acrylamide (AM) with dimethylaminoethylacrylate methyl chloride (Q9) using redox initiation with low surfactant concentration in an isoparaffinic solvent has been studied. The kinetics of conversions of inverse-emulsion polymerizations were investigated by HPLC method. It was an interesting way to know rapidly the conversion of each monomer with high reproducibility. In all experiments the monomer concentration was 25% respect the total weight or higher and the experiments were carried out at 50^∘C. The effects of initiator concentration, composition of the monomer mixture and monomer concentration on the polymerization conversion and viscosity of copolymers solutions have been examined. For copolymer characterization, the results of viscosity were compared with commercial copolymer viscosities. The formulations with 3,000 ppm of initiator were the most interesting of all copolymer compositions since they presented very high conversions and their viscosities were higher than those of commercial copolymer solutions. The analysis of monomer concentration was carried out with 3,000 ppm and the conversion and viscosity were higher when the monomer concentration was increased.     

Acceleration of electrocatalytic reactions by pulsation of potential: Oxidation of formic acid on Pt and Pt/Pbads electrodes

Pulsating potential electrolysis has been applied to one typical electrocatalytic reaction ie, the oxidation of formic acid on platinum and platinum partially covered by lead adatoms electrodes. It has been found that much higher average cds can be obtained with such regimes than in constant potential electrolysis. The effect can be of considerable interest for the application in electrochemical power sources. An analysis of the mechanism of effects of pulsating potentials has been given. A calculated frequency dependence of the average current density is in agreement with experimental one for both electrodes.     

Multiple congenital defects associated with trisomy for long arm of No. 4

The most prevalent microorganisms isolated from urine specimens of dogs (385) and cats (132) with clinical signs of urinary tract infections were Escherichia coli, Proteus spp., and Staphylococcus aureus. The results of quantitative urine-culturing methods showed 48.6% of the canine and 12.1% of the feline specimens had more than 10(5) organisms per ml of urine. The bacteria isolated appear to have a greater resistance to antibacterial agents than previously reported.