Dynamic analysis and drilling degrees of freedom

Finite element methods for dynamic analysis employing elements with drilling degrees of freedom are presented. The formulation is based on a variational principle in which displacements and rotations are interpolated independently. The issue of zero masses corresponding to rotational degrees of freedom is addressed and techniques for defining consistent and lumped rotational mass matrices are presented.     

Design and fabrication of a p-i-n photodiode with high responsivity and large alignment tolerances for 40-gb/s applications

This letter demonstrates an evanescently coupled p-i-n photodiode combined with a multimode diluted waveguide using a simple all 2-in InP processing that includes on-wafer mirrors etching and antireflection coating. A high responsivity of 0.81 A/W at 1.55 /spl mu/m with less than 0.4-dB polarization dependence and a large -1-dB vertical alignment tolerance of 2.70 /spl mu/m were achieved simultaneously with a bandwidth of 47 GHz. Stable operation for over 1000 h was obtained under bias stress and temperature at 200/spl deg/C.     

Design and Analysis of Experiments on Nonconvex Regions

Modeling a response over a nonconvex design region is a common problem in diverse areas such as engineering and geophysics. The tools available to model and design for such responses are limited and have received little attention. We propose a new method for selecting design points over nonconvex regions that is based on the application of multidimensional scaling to the geodesic distance. Optimal designs for prediction are described, with special emphasis on Gaussian process models, followed by a simulation study and an application in glaciology. Supplementary materials for this article are available online.     

Combined continuum damage‐embedded discontinuity model for explicit dynamic fracture analyses of quasi‐brittle materials

In this paper, a novel constitutive model combining continuum damage with embedded discontinuity is developed for explicit dynamic analyses of quasi‐brittle failure phenomena. The model is capable of describing the rate‐dependent behavior in dynamics and the three phases in failure of quasi‐brittle materials. The first phase is always linear elastic, followed by the second phase corresponding to fracture‐process zone creation, represented with rate‐dependent continuum damage with isotropic hardening formulated by utilizing consistency approach. The third and final phase, involving nonlinear softening, is formulated by using an embedded displacement discontinuity model with constant displacement jumps both in normal and tangential directions. The proposed model is capable of describing the rate‐dependent ductile to brittle transition typical of cohesive materials (e.g., rocks and ice). The model is implemented in the finite element setting by using the CST elements. The displacement jump vector is solved for implicitly at the local (finite element) level along with a viscoplastic return mapping algorithm, whereas the global equations of motion are solved with explicit time‐stepping scheme. The model performance is illustrated by several numerical simulations, including both material point and structural tests. The final validation example concerns the dynamic Brazilian disc test on rock material under plane stress assumption. Copyright © 2014 John Wiley & Sons, Ltd.     

An efficient finite element method for embedded interface problems

A stabilized finite element method based on the Nitsche technique for enforcing constraints leads to an efficient computational procedure for embedded interface problems. We consider cases in which the jump of a field across the interface is given, as well as cases in which the primary field on the interface is given. The finite element mesh need not be aligned with the interface geometry. We present closed‐form analytical expressions for interfacial stabilization terms and simple procedures for accurate flux evaluations. Representative numerical examples demonstrate the effectiveness of the proposed methodology. Copyright © 2008 John Wiley & Sons, Ltd.     

Interface Modifications of InAs Quantum‐Dots Solids and their Effects on FET Performance

InAs nanocrystals field‐effect transistors with an ON/OFF ratio of 10⁵ are reported. By tailoring the interface regions in the active layer step‐by‐step, the evolution of the ON/OFF ratio can be followed from approximately 5 all the way to around 10⁵. The formation of a semiconducting solid from colloidal nanocrystals is achieved through targeted design of the nanocrystal–nanocrystal interaction. The manipulation characteristics of the nanocrystal interfaces include the matrix surrounding the inorganic core, the interparticle distance, and the order of nanocrystals in the 3D array. Through careful analysis of device characteristics following each treatment, the effect of each on the physical properties of the films are able to be verified. The enhanced performance is related to interparticle spacing, reduction in sub‐gap states, and better electronic order (lower σ parameter). Films with enhanced charge transport qualities retain their quantum‐confined characteristics throughout the procedure, thus making them useful for optoelectronic applications.     

Design, optimization, and fabrication of side-illuminated p-i-nphotodetectors with high responsivity and high alignment tolerance for1.3and 1.55-μm wavelength use

We describe the design, optimization and fabrication of side-illuminated p-i-n photodetectors, grown on InP substrate, suitable for surface hybrid integration in low-cost modules. The targeted functionalities of these photodetectors were a very high responsivity at 1.3- and 1.55-μm wavelengths and quasi-independent on the optical polarization, and had a high alignment tolerance. Moreover, in order to avoid any reliability problem, the principle of evanescent coupling was adopted. Two photodetectors were optimized, fabricated, and tested; the first was for classical cleaved fiber, and the second was for lensed fiber. Because the considered epitaxial structures were complicated to optimize, the method of the genetic algorithm was used, associated with a beam propagation method (BPM). The photodetectors are based on multimode diluted waveguides, which are promising structures in the field of optoelectronics and integrated optics. Starting from the presented comparisons between experimental and theoretical results, the interest of the design method is discussed and the complete performances of newly fabricated devices are presented. The aspect of the cutoff frequency is also considered     

Clinical evaluation of the osteoarthritic patient

It is well-established that in heart, both the L-type Ca2+ channel and the cystic fibrosis transmembrane conductance regulator Cl- channel are regulated by cAMP-dependent phosphorylation. However, it is not clear whether both of these channels are regulated in concert by protein kinase A (PKA) or whether there are mechanisms that independently control the phosphorylation of these two PKA targets. The purpose of this study was to compare the effects of various protein phosphatase and protein kinase inhibitors on these two ionic currents (ICa and ICl) in guinea pig ventricular myocytes to gain insight into these questions. We found that both the stimulation and washout of the effects of isoproterenol on ICl are about twice as fast as the effects on ICa, probably because the dephosphorylation reaction for ICl is faster than that for ICa. In contrast, inhibition of protein phosphatases with 10 microM microcystin stimulated both ICa and ICl, but the stimulation of ICl was much slower and smaller than the stimulation of ICa. The effect of microcystin was inhibited by staurosporine (Ki = 171.5 and 161 nM for ICa and ICl, respectively), suggesting that the stimulation was due to a kinase. The kinase was not protein kinase C (PKC) because it was not inhibited by the specific pseudosubstrate inhibitor of PKC, PKC(19-31), and it was not PKA because it was not inhibited by adenosine 3',5'-cyclic phosphorothioate. These results suggest that although both the Ca2+ and Cl- channels are regulated by cAMP-dependent phosphorylation, another protein kinase may also regulate these channels, and the kinetics of the response of the channels to phosphorylation can be modulated independently by protein phosphatases.     

Système de protection contre les erreurs pour la liaison ionosphérique

This paper presents an error correcting system designed for a 1 200 bit/s self adaptative modem operating on the HF channel. An analysis of error statistics has been made simulating a specific link whose characteristics had been measured beforehand by a HF backscattering probe. The coding system which has been chosen consists of a cascade of two cyclic codes. One corrects long bursts of errors (Kasami code), the other corrects single errors and small bursts (Reed Solomon code). Both codes are interleaved. The overall rate is 50 %. An error correction simulation has shown that in most of the cases studied, with a ber of 10^?4 a coding gain of at least 10^?2 has been achieved.