An economic method for the solution of the scalar wave equation for arbitrarily shaped optical waveguides

The discrete sine method, in which the basis functions consist of sine functions defined on a set of parallel discretization lines, is discussed. The method is a combination of a scalar version of the finite difference method and sine method. The choice of the basis set leads for the eigenvalue equation to be solved, to a sparse matrix with a small bandwidth. As a consequence, the propagation constant of guided modes in optical waveguides may be calculated with short computation times and low storage needs. Results obtained with the method for three different wave guiding structures are compared with those of other method

Dynamic Energy Budget (DEB) parameters for ensis directus

In this report a Dynamic Energy Budget (DEB) model for razor clams (Ensis directus) is presented. A DEB model is a generic model describing growth and development of individual organisms as a function of environmental conditions. The DEB model for Ensis directus is based on the standard DEB model. The species specific primary DEB parameters are estimated with the Add_my_pet procedure, using literature data and the results of laboratory experiments with Ensis directus. The performance of the model is demonstrated by theoretical model experiments with varying environmental conditions. In following projects, the model will be used to predict and quantify the effects of sand mining on the shellfish community in the Dutch coastal zone. For this purpose the functional response of the model should be adapted so that the combined effect of changing phytoplankton and suspended sediment concentration on the uptake rate can be simulated

Factors Influencing Reinforcement of NR and EPDM Rubbers with Short Aramid Fibers

Among short fiber reinforced composites, those with rubbery matrices have gained great importance due to the advantages they have in processing and low cost, coupled with high strength. These composites combine the elastic behavior of rubbers with strength and stiffness of fibers. Reinforcement with short fibers offers additional features such as design flexibility, high modulus, tear strength, etc. The degree of reinforcement depends on parameters such as: the nature of the rubber matrix, the type of fibers, the concentration and orientation of fibers, fiber to rubber adhesion (generation of a strong interface), fiber length and aspect ratio of the fibers. In this research aramid fibers have been chosen because of their significantly higher modulus and strength, compared to other commercial fibers. Compounds based on NR and EPDM are prepared. Short aramid fibers with different kinds of surface treatments, standard finish and RFL-coating result in different rubber-fiber interfaces. The reinforcing effect of these short aramid fibers is characterized by mechanical and viscoelastic experiments, and by studying the fracture surfaces with microscopic techniques

Tire Tread Reinforcement with Short Aramid Fibers

Tensile testing on short fiber reinforced composites is helping to identify the advantages and disadvantages of different rubber compound

Manipulation of expressions in a relational algebra

This paper describes a syntax for expressions based on the relational algebra. A tree representation is generated when an expression is analyzed. Transformations on the tree representations of expressions are applied in order to obtain improvements with respect to the speed of evaluation in a data base environment

Friction and wear behaviour of 18 polymers in contact with steel in environments of air and water

18 polymers were characterized with respect to their friction and wear behaviour in contact with steel in environments of air and water. These were six unfilled materials, i.e. polyamide 66 (PA 66), polyoxymethylene (POM), polyethyleneterephthalate (PETP), polyetheretherketone (PEEK), polyphenylenesulphide (PPS) and polyetherimide; also, the same base materials filled with polytetrafluoroethylene (PTFE) or PTFE plus glass fibre were used.\ud \ud Two types of experiments were performed, i.e. measurement of the coefficient of friction f as a function of the contact temperature Tc (¿f;¿Tc diagrams¿), and measurements of friction and wear in 20 h tests. The f¿Tc diagrams were obtained in air; the 20 h tests were performed in air and in water at a temperature of 20 °C. In air the polymers ran against rings of ball-bearing steel (AISI 52100); in water the rings were made of stainless steel (AISI 316).\ud \ud It turned out that in air addition of PTFE was generally beneficial; PA 66, POM, PETP and PEEK, all filled with PTFE, performed exceptionally well (specific wear rates k appreciably lower than 1×10¿15 m3 N¿1 m¿1). In water, however, PTFE did not function at all. Now PA (with or without PTFE), unfilled POM and PETP filled with PTFE and glass fibre met the k<1× 10¿15 m3 N¿1 m¿1 criterion. With a few exceptions, addition of glass fibre produced unfavourable effects, in air as well as in water.\ud \ud The observed phenomena are explained tentatively in terms of polymer structures and transfer and wear mechanisms, whereby special attention is paid to the ratio of friction over strength

Experimental Investigation of Percieved Risk in Random Walk Processes

The hypothesis that, on average, people accurately estimate probabilities in random walk processes is experimentally investigated.Individuals are confronted with a process that starts with $X, and in every stage either goes up or down by$1, with probabilities p and 1 - p respectively.For different values of p, individuals were asked to estimate what is the chance that after 10 stages the system will be at a point higher than or equal to $X.Systematic mistakes in estimations were observed.In particular, estimations were centered around the stage-by-stage probability (p) rather then around the actual probability. Implication of this result to random walk processes in finance is considered.random walks;risk

Enhancing the Performance of Integrated Optical Sensor by Slow-light: Theoretical Study on Ring-Resonator Based Structures

In this work, the performance of three kinds of integrated optical ring-resonator based slow-light structures for sensing applications is theoretically studied using the transfer matrix method and the complex transmission coefficient approach. Enhancement of sensing performance due to the slowlight phenomenon is quantitatively formulated. The modeling results show that using realistic structure parameters, a refractive index detection limit of one order better than the state of the art Mach-Zehnder interferometer sensing structure is possible by the inclusion of such a slow-light structure. The role of ring(s) attenuation constant in limiting the usable light slowness and the achievable sensor resolution is also discussed. For a sufficiently small ring attenuation constant, the optimal sensing performance of a single resonator circuit can be better than that of multiple resonator circuits, while offering less fabrication complexities, cleaner spectra, shorter device length, and higher figure of merit

Freshwater immersion as a method to remove Urosalpinx cinerea and Ocinebrellus inornatus from mussel seed

A simple experiment to test whether immersion in freshwater for ≤24 hours would kill two oyster drills, Urosalpinx cinerea and Ocinebrellus inornatus was conducted to test the proposal of using freshwater to rid mussel seed of the drills before translocation from the Oosterschelde to the Wadden Sea. Freshwater failed to kill any individuals of either species, but did cause them to detach from the substratum for the entire time of immersion. Immersion in freshwater is therefore not recommended as a method to control the drills. Rinsing in freshwater may be an option to remove the drills without killing them, but has no guarantee of 100 % success. Further investigation may result in the development of other treatment options

Basic elements for photodeposited high Tc thin film devices

Flat films, high quality insulating layers and adequately superconducting via contacts are basic elements for high Tc device fabrication. We studied the influence of the process parameters of laser deposition on the occurrence of droplets and outgrowths in YBaCuO films. The droplet density is minimal when a laser fluence below about 1.0 J cm-2 is used. The outgrowth density decreases with increasing laser pulse rate or decreasing deposition temperature. High quality flat films were obtained with a rate of 10 Hz and at a temperature of 720 °C. Wet chemical etching and etching with an Argon ion source were used for structuring multilayers with SrTiO3 as an insulating layer. Smooth edges were obtained with an argon gun. Bromine and EDTA etching are not adequate techniques for fabricating controllable well-defined edges. Cross-overs, via contacts and coils were prepared