Behaviour of ±45° glass/epoxy filament wound composite tubes under quasi-static equal biaxial tension–compression loading: experimental results

The primary aim of this paper is to present results describing in detail the behaviour of ±45° E-glass/MY750 (GRP) tubes, of various wall thicknesses, subjected to equal biaxial tension–compression loading, generated under combined internal pressure and axial compression. The role played by the non-linear lamina shear has also been assessed by comparing various shear stress–strain curves for embedded laminae (extracted from tests on ±45° tubes subjected to circumferential: axial stress ratios SR=1:0, 1:−1 and 2.3:−1) with that of an ‘isolated’ lamina (measured from torsion of 90° tubes). Extracted shear failure strains, for embedded laminae, were more than four fold larger than those measured at ultimate failure for an ‘isolated’ lamina. Soft characteristics were observed in the embedded lamina and these were believed to be due to interaction between early matrix damage initiation (and propagation) and shear. Factors affecting the behaviour of the tubes, such as bulging, scissoring, thermal stresses and stress variation through the thickness are discussed.     

Switching to photonics

The use of hardware that exploits the interplay of photons and electrons to switch voice, data, and video is discussed. The two directions being taken by current research-guided-wave and free-space photonics-are examined. Photonic time-slot interchanges are described. Multidivisional fabrics, based on a combination of space-division and time-division multiplexing, are considered, as is the wavelength-division-based photonic packet switch, another kind of multidimensional fabric. The use of self-electrooptic effect devices, (SEEDs) is discussed     

Preservation of myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest with 2, 3-butanedione monoxime

One proposed contributory mechanism for depressed ventricular performance after hypothermic, hyperkalemic cardioplegic arrest is a reduction in myocyte contractile function caused by alterations in intracellular calcium homeostasis. Because 2,3-butanedione monoxime decreases intracellular calcium transients, this study tested the hypothesis that 2,3-butanedione monoxime supplementation of the hyperkalemic cardioplegic solution could preserve isolated myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest. Myocytes were isolated from the left ventricles of six pigs. Magnitude and velocity of myocyte shortening were measured after 2 hours of incubation under normothermic conditions (37 degrees C, standard medium), hypothermic, hyperkalemic cardioplegic arrest (4 degrees C in Ringer's solution with 20 mEq potassium chloride and 20 mmol/L 2,3-butanedione monoxime). Because beta-adrenergic agonists are commonly employed after cardioplegic arrest, myocyte contractile function was examined in the presence of the beta-agonist isoproterenol (25 nmol/L). Hypothermic, hyperkalemic cardioplegic arrest and rewarming reduced the velocity (32%) and percentage of myocyte shortening (27%, p < 0.05). Supplementation with 2,3 butanedione monoxime normalized myocyte contractile function after hypothermic, hyperkalemic cardioplegic arrest. Although beta-adrenergic stimulation significantly increased myocyte contractile function under normothermic conditions and after hypothermic, hyperkalemic cardioplegic arrest, contractile function of myocytes exposed to beta-agonist after hypothermic, hyperkalemic cardioplegic arrest remained significantly reduced relative to the normothermic control group. Supplementation with 2,3-butanedione monoxime restored beta-adrenergic responsiveness of myocytes after hypothermic, hyperkalemic cardioplegic arrest. Thus, supplementation of a hyperkalemic cardioplegic solution with 2,3-butanedione monoxime had direct and beneficial effects on myocyte contractile function and beta-adrenergic responsiveness after cardioplegic arrest. A potential mechanism for the effects of 2,3-butanedione monoxime includes modulation of intracellular calcium transients or alterations in sensitivity to calcium. Supplementation with 2,3-butanedione monoxime may have clinical utility in improving myocardial contractile function after hypothermic, hyperkalemic cardioplegic arrest.     

Laser turn-on delay and chirp noise effects in Gb/sintensity-modulated direct-detection systems

This paper describes a new IM/DD optical transmission system simulation which incorporates the impact of laser diode stochastic turn-on effects on system performance. Using this simulation, experimentally observed error rate floors, due to inappropriate laser diode biasing, can be theoretically modelled and predicted, for the first time     

FE-shape sensitivity of elastoplastic response

A new approach for performing FE-shape design sensitivity analyses (DSA) of structural models with both linear elastic and elastoplastic material behaviour is presented. In the formulation of the method the derivation of the FE equilibrium equations is performed analytically leading to various terms. The differentiation of some parts of these terms is determined numerically, therefore the method is semianalytical. The formulation is particularized for isoparametric finite elements for which exact numerical differentiation can be obtained (exact up to round-off error). Examples of some plane stress problems testify that the results of the new method are not dependent either on the size of perturbation of the design variables or on the FE mesh refinement among other factors.     

Analysis of a microchannel interconnect based on the clustering of smart-pixel-device windows

A design analysis of a telecentric microchannel relay system developed for use with a smart-pixel-based photonic backplane is presented. The interconnect uses a clustered-window geometry in which optoelectronic device windows are grouped together about the axis of each microchannel. A Gaussian-beam propagation model is used to analyze the trade-off between window size, window density, transistor count per smart pixel, and lenslet ?-number for three cases of window clustering. The results of this analysis show that, with this approach, a window density of 4000 windows/cm(2) is obtained for a window size of 30 μm and a device plane separation of 25 mm. In addition, an optical power model is developed to determine the nominal power requirements of a 32 × 32 smart-pixel array as a function of window size. The power requirements are obtained assuming a complementary metal-oxide semiconductor inverter-amplifier and dual-rail multiple-quantum-well self-electro-optic-effect devices as the receiver stage of the smart pixel.     

An efficient learning procedure for deep Boltzmann machines

We present a new learning algorithm for Boltzmann machines that contain many layers of hidden variables. Data-dependent statistics are estimated using a variational approximation that tends to focus on a single mode, and data-independent statistics are estimated using persistent Markov chains. The use of two quite different techniques for estimating the two types of statistic that enter into the gradient of the log likelihood makes it practical to learn Boltzmann machines with multiple hidden layers and millions of parameters. The learning can be made more efficient by using a layer-by-layer pretraining phase that initializes the weights sensibly. The pretraining also allows the variational inference to be initialized sensibly with a single bottom-up pass. We present results on the MNIST and NORB data sets showing that deep Boltzmann machines learn very good generative models of handwritten digits and 3D objects. We also show that the features discovered by deep Boltzmann machines are a very effective way to initialize the hidden layers of feedforward neural nets, which are then discriminatively fine-tuned.     

A psychobiocultural model of orthostatic panic among Cambodian refugees: Flashbacks, catastrophic cognitions, and reduced orthostatic blood-pressure response.

This paper investigates cognitive and physiological precursors of orthostatic panic (OP), that is, panic upon standing, which is a key complaint among traumatized Cambodian refugees. Prior research links OP to hypotension (lower blood pressure) and catastrophic cognitions. A clinical sample of 102 Cambodian refugees were assessed for posttraumatic stress disorder (PTSD), recent OP attacks, and anticipatory anxiety before engaging in an orthostatic challenge (OC) task during which they were monitored for blood pressure. After the task, they were assessed for OC-induced culture-related catastrophic cognitions, flashbacks, and panic attacks. We found that participants with recent OP (n = 60) had more PTSD, greater anticipatory anxiety before the OC, a larger drop in systolic blood pressure during the OC, more OC-induced catastrophic cognitions and flashbacks, and more severe OC-induced panic attack symptoms. Regression models showed that the severity of OC-induced panic symptoms was predicted by the magnitude of SBP drop and mediated by more severe catastrophic cognitions and flashbacks. Implications of the findings for cross-cultural psychopathology research and the treatment of both panic and PTSD in Cambodian refugees are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Field-programmable smart-pixel arrays: design, VLSI implementation, and applications

A smart-pixel array is a two-dimensional array of optoelectronic devices that combine optical inputs and outputs with electronic processing circuitry. A field-programmable smart-pixel array (FP-SPA) is a smart-pixel array capable of having its electronic functionality dynamically programmed in the field. Such devices could be used in a diverse range of applications, including optical switching, optical digital signal processing, and optical image processing. We describe the design, VLSI implementation, and applications of a first-generation FP-SPA implemented with the 0.8-microm complementary metal-oxide semiconductor-self-electro-optic effect device technology made available through the Lucent Technologies-Advanced Research Projects Agency Cooperative (Lucent/ARPA/COOP) program. We report spice simulations and experimental results of two sample applications: In the first application, we configure this FP-SPA as an array of free-space optical binary switches that can be used in optical multistage networks. In the second, we configure the device as an optoelectronic transceiver for a dynamically reconfigurable free-space intelligent optical backplane called the hyperplane. We also describe the testing setup and the electrical and the optical tests that demonstrate the correct functionality of the fabricated device. Such devices have the potential to reduce significantly the need for custom design and fabrication of application-specific optoelectronic devices in the same manner that field-programmable gate arrays have largely eliminated the need for custom design and fabrication of application-specific gate arrays, except in the most demanding applications.