Reducing the lightpath establishing time of FWM-aware dynamic RWA for wavelength-routed optical networks

A dynamic routing and wavelength allocation technique with an interplay between physical and network layer parameters encompassing Four-wave mixing (FWM) awareness and teletraffic performance of wavelength-routed optical networks has previously been proposed for a distributed approach. In this article, we present a fast computational algorithm for our routing and wavelength assignment (RWA) encompassing FWM-induced crosstalk. The objective is to minimize the time of establishing a dynamic lightpath. For this purpose, a precomputed matrix of FWM crosstalk products is used in an adapted version of the FWM-aware dynamic RWA algorithm. The approach is validated through simulations showing improvement up to 30–50% on the provisioning time of lightpaths for different network topologies compared to an online full computational scheme.

The visualization of hepatic vasculature by X-ray micro-computed tomography

In this study, X-ray micro-computed tomography (CT) was used to reconstruct the fine structure macro- and microvasculature in three dimensions in contrast-enhanced rat liver samples. The subsequent application in the experimental CC531s colorectal cancer model was concurrent with results obtained from confocal microscopy in earlier studies. The en bloc stains osmium tetroxide in combination with uranyl acetate provided an excellent contrasting result for hepatic tissue after a trial of several contrasting agents. X-ray micro-CT allowed us to image the large blood vessels together with the branching sinusoids of hepatic tissue in three dimensions. Furthermore, interruption of the microvasculature was noted when rats were injected with CC531s colorectal cancer cells indicating the presence of hepatic metastases.     

Bodily concerns and the WISC Object Assembly subtest.

Previous examinations of the hypothesis that bodily concerns are reflected in impaired WISC Object Assembly performance have produced contradictory results, but have also used different criteria for assignment of Ss to 2 S groups. To investigate whether these differences account for the discrepant results, 73 white, latency and early adolescent boys were assigned to 3 groups differing in intensity of bodily concerns. 1-way analyses of variance with covariance adjustments of relevant variables failed to yield any support for the hypothesis. Theoretical limitations of the hypothesis are discussed and a more appropriate approach suggested and supported by prima facie evidence gleaned from analysis of the finding that intensely bodily concerned boys performed significantly better (p     

Dynamics and generation of stress waves in cracked graphite moderator bricks

In the present study, static and dynamic analyses have been performed for graphite moderator bricks with and without key grooves under the different initial loading conditions of pure bending and slot rotation by using the finite element method. The possibilities of the occurrence of multiple cracking due to internal stresses have been investigated in terms of the (1) initial loading condition; (2) vibration mode shapes; and (3) damping of the bricks. Firstly, modal dynamic analysis has been carried out, and the effect of the initial loading conditions, such as pure bending and slot rotation, on the dynamic stress responses was investigated. It was found that stress enhancement was more significant under the condition of pure bending than that of slot rotation. For pure bending, the key groove which was opposite to the primary cracking site had the maximum dynamic circumferential stress. This implied that secondary cracking might occur at this position under pure bending. Secondly, in order to investigate the dominant mode shape for the stress enhancement, natural frequency analysis has been conducted. Fast Fourier Transformation (FFT) has also been performed to convert time–domain stress responses into frequency–domain stress responses. The initial loading conditions determined which mode shape was dominant for the stress enhancement. It was also suggested that a fundamental mode shape principally contributed to the occurrence of the multiple cracking. Thirdly, modal damping analysis has been performed, and the effect of damping on the stress enhancement was studied. It was found that damping had little effect on the initial peak of the dynamic stress response. This suggested that secondary cracking might still occur at the key groove opposite the primary cracking site, even if damping was present. The results of the analysis give a fundamental insight into the mechanism that may lead to multiple cracking in graphite components subject to internal stresses. However, the effects of 3-D, crack propagation speed and external restraint have not been taken into consideration in the present study. These effects may mitigate the possibility of secondary cracking, and are parts of further investigation.     

Optimal Aeroacoustic Shape Design Using the Surrogate Management Framework

Shape optimization is applied to time-dependent trailing-edge flow in order to minimize aerodynamic noise. Optimization is performed using the surrogate management framework (SMF), a non-gradient based pattern search method chosen for its efficiency and rigorous convergence properties. Using SMF, design space exploration is performed not with the expensive actual function but with an inexpensive surrogate function. The use of a polling step in the SMF guarantees that the algorithm generates a convergent subsequence of mesh points in the parameter space. Each term of this subsequence is a weak local minimizer of the cost function on the mesh in a sense to be made precise later. We will discuss necessary optimality conditions for the design problem that are satisfied by the limit of this subsequence. Results are presented for an unsteady laminar flow past an acoustically compact airfoil. Constraints on lift and drag are handled within SMF by applying the filter pattern search method of Audet and Dennis, within which a penalty function is used to form and optimize a surrogate function. Optimal shapes that minimize noise have been identified for the trailing-edge problem in constrained and unconstrained cases. Results show a significant reduction (as much as 80%) in acoustic power with reasonable computational cost using several shape parameters. Physical mechanisms for noise reduction are discussed.     

Numerical simulation of strength test on graphite moderator bricks using a continuum damage mechanics model

Experimental tests on graphite moderator bricks with keyways have been simulated using a failure model recently developed by the authors based on continuum damage mechanics. Failure of the specimens, induced by the application of pure bending moment, is characterised by unstable crack propagation, with very small cracks and damage zones formed at the keyway corners immediately before final rupture. Sensitivity of the predictions to the keyway corner radius, variations in material properties and the presence of methane holes have also been investigated. Good agreement has been achieved between the predicted failure strengths and the available experimental data.     

A standard Pascal event simulation package

A package implemented using standard Pascal is described. It provides the user with basic tools for discrete event-orientated simulation, and includes facilities for scheduling and causing pending events, handling of LIFO and FIFO queues, control of periodical dumping of statistics and comprehensive initialization and error routines. Two versions of the package have been implemented, using tree and linked list structures for scheduled events. Their relative performances are compared. The tree structure proves to be more efficient except in the minority of cases where the set of scheduled events has to be searched frequently; it also provides a much more efficient scheduling algorithm than does a linked list structure. This package is primarily intended as a communication network design tool, and a simple example of this type of usage is included. It could also be used in undergraduate teaching. Coding examples are given for the main procedures, in the two implementations.     

Theoretically predicted rate constants for mercury oxidation by hydrogen chloride in coal combustion flue gases

In this work, theoretical rate constants are estimated for mercury oxidation reactions by hydrogen chloride that may occur in the flue gases of coal combustion. Rate constants are calculated using transition state theory at the quadratic configuration interaction (QCI) level of theory with single and double excitations, and are compared to results obtained from density functional theory, both including high level pseudopotentials for mercury. Thermodynamic and kinetic data from the literature are used to assess the accuracy of the theoretical calculations when possible. Validation of the chosen methods and basis sets is based upon previous and current research on mercury reactions involving chlorine. The present research shows that the QCISD method with the 1992 Stevens et al. basis set leads to the most accurate kinetic and thermodynamic results for the oxidation of mercury via chlorine containing molecules. Also, a comparison of the heats of reaction data for a series of mercury oxidation reactions reveals that the density functional method, B3LYP, with the 1997 Stuttgart basis set provides reasonably accurate results for these large systems.