Fundamental Optical Absorption Edge of Sputter-Deposited Zirconia and Yttria

Zirconia and yttria films were sputter deposited onto unheated fused silica substrates using a metal target and rare gas-oxygen discharges. Double-beam spectrophotometry was used to measure the transmission and reflection as a function of incident photon energy, E , from which the absorption coefficient, α( E ), was calculated. An indirect interband transition at E _i= 4.70 eV and two direct interband transitions at E _g1= 5.17 eV and E _g2= 5.93 eV occur in monoclinic zirconia. Two direct interband transitions at E _g1= 5.07 eV and E _g2= 5.73 eV occur in cubic yttria. The absorption edge structure is modified when unusual phases, such as tetragonal zirconia, and zirconia and yttria with no longrange crystallographic order, are present.     

Tensile deformation mechanisms of polypropylene/elastomer blends reinforced with short glass fiber

Polypropylene hybrid composites reinforced with short glass fiber (SGF) and toughened with styrene–ethylene butylenes–styrene (SEBS) elastomer were prepared using extrusion and injection‐molding techniques. Moreover, hybrids compatibilized with SEBS‐grafted maleic anhydride (SEBS‐g‐MA) and hybrid compatibilized with PP grafted with maleic anhydride (PP‐g‐MA) were also fabricated. The matrix of the latter hybrid was designated as mPP and consisted of 95% PP and 5% PP‐g‐MA. Tensile dilatometry was carried out to characterize the fracture mechanisms of hybrid composites. Dilatometric responses showed that the elastic deformation was the dominant deformation mechanism for the SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrids. However, cavitation deformation prevailed over shearing deformation for both hybrids at the higher strain regime. The cavitation strain resulted from the debonding of glass fibers and from the crazing of the matrix in the SGF/SEBS/PP hybrid. In contrast, the cavitation was caused by the debonding of SEBS particles from the matrix of the SGF/SEBS‐g‐MA/PP hybrid. The use of PP‐g‐MA resulting in elastic deformation was the main mode of deformation in the low‐strain region for the SGF/SEBS/mPP and SEBS/SEBS‐g‐MA/mPP hybrids; thereafter, shearing appeared to dominate at the higher strain regime. This was attributed to the MA functional group improving the bonding between the SGF and PP. The correlation between fracture morphology and dilatometric responses also is presented in the article. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 441–451, 2003     

A perturbation-incremental scheme for studying Hopf bifurcation in delayed differential systems

A new method, called perturbation-incremental scheme (PIS), is presented to investigate the periodic solution derived from Hopf bifurcation due to time delay in a system of first-order delayed differential equations. The method is summarized as three steps, namely linear analysis at critical value, perturba- tion and increment for continuation. The PIS can bypass and avoid the tedious calculation of the center manifold reduction (CMR) and normal form. Meanwhile, the PIS not only inherits the advantages of t...     

Aggregate‐induced emission in light‐emitting liquid crystal display technology

Nowadays, liquid crystal displays (LCDs) with light‐emission are considered as energy‐efficient devices and are promising alternatives to conventional LCDs. To realize such possibility, strong fluorescent materials with a dichroic properties are required. Aggregate‐induced emission (AIE) is an unusual photophysical phenomenon shown by some luminogenic materials that will be highly emissive in their aggregate state. In this work, we studied the AIE effect of a luminescent liquid crystalline molecule TPE‐PPE in our LC system as a luminophore dopant. The result showed the excellent AIE effect that higher concentration of luminogen in the nematic LC host induced stronger luminescent intensity. Through exposure of a photoisomeriable alignment material sulfonic‐dye‐1, the photopatterning of a light‐emitting LC device was achieved with the use of the TPE‐PPE/nematic LC mixture.     

Ferroelectric liquid crystals: Excellent tool for modern displays and photonics

The ferroelectric liquid crystals, because of their fast electro‐optical response, are one of the most important classes of liquid crystals. Here, in this review, we have summarized the different electro‐optical modes for ferroelectric liquid crystals. Clark–Lagerwall effect (surface stabilized ferroelectric liquid crystal), deformed helix ferroelectric (DHF) effect, electrically suppressed helix (ESH) mode, DHF orientational Kerr effect, and ESH diffraction modes have been discussed. All of the crucial features, that is, optics, electro‐optics, dynamics, and their dependence on material parameters, operational regime, and applications, have been reviewed.     

On scheduling and clustering in hierarchical TH-PPM UWB wireless ad hoc networks

Ultra wideband (UWB) systems are considered as the key wireless infrastructure platforms for efficient short-range communications. In particular, the UWB based mobile computing systems are envisioned to be attractive solutions to various ad hoc networking applications. However, due to UWB’s unique physical characteristics, the traditional resource management schemes for ad hoc networks cannot be applied to UWB based systems directly. In this paper, we consider the bandwidth scheduling problem in a UWB based hierarchical wireless ad hoc network, which is typically used in an enterprise-scale mobile computing environment. Based on the mathematical analysis and the computer simulations, it is demonstrated that our proposed scheduling scheme exhibits close-to-optimal performance governed by the proportional fairness (PF) constraint. Moreover, a novel self-organized clustering method is designed to improve the system throughput while meeting the PF constraint. Simulation results suggest that the proposed clustering method is effective under various system configurations.

Building Sparse Multiple-Kernel SVM Classifiers

The support vector machines (SVMs) have been very successful in many machine learning problems. However, they can be slow during testing because of the possibly large number of support vectors obtained. Recently, Wu (2005) proposed a sparse formulation that restricts the SVM to use a small number of expansion vectors. In this paper, we further extend this idea by integrating with techniques from multiple-kernel learning (MKL). The kernel function in this sparse SVM formulation no longer needs to be fixed but can be automatically learned as a linear combination of kernels. Two formulations of such sparse multiple-kernel classifiers are proposed. The first one is based on a convex combination of the given base kernels, while the second one uses a convex combination of the so-called ldquoequivalentrdquo kernels. Empirically, the second formulation is particularly competitive. Experiments on a large number of toy and real-world data sets show that the resultant classifier is compact and accurate, and can also be easily trained by simply alternating linear program and standard SVM solver.     

MatSeek: An Ontology-Based Federated Search Interface for Materials Scientists

The MatSeek system is an ontology-based federated search interface to key materials science databases and analytical tools. By combining Semantic Web and Web 2.0 technologies, MatSeek provides materials scientists with a single Web interface that enables them to search across disparate databases containing crystal-structure data, ionic-conductivity data, and phase stability data; render 3D crystal-structure images; calculate bond lengths and angles; retrieve relevant scholarly references; and identify potential new materials with the structure and properties required to satisfy specific applications. The MatOnto ontology underlying MatSeek enables integration of data across disparate databases, and Web 2.0 technologies enable iterative searching across the databases. The results retrieved from searching the previous database are used as input to the query on the next database. By providing materials scientists with a single, integrated Web interface to the critical materials science databases and analytical tools, MatSeek represents a significant advance toward a full-fledged materials-informatics workbench.     

Maximum Penalized Likelihood Kernel Regression for Fast Adaptation

This paper proposes a nonlinear generalization of the popular maximum-likelihood linear regression (MLLR) adaptation algorithm using kernel methods. The proposed method, called maximum penalized likelihood kernel regression adaptation (MPLKR), applies kernel regression with appropriate regularization to determine the affine model transform in a kernel-induced high-dimensional feature space. Although this is not the first attempt of applying kernel methods to conventional linear adaptation algorithms, unlike most of other kernelized adaptation methods such as kernel eigenvoice or kernel eigen-MLLR, MPLKR has the advantage that it is a convex optimization and its solution is always guaranteed to be globally optimal. In fact, the adapted Gaussian means can be obtained analytically by simply solving a system of linear equations. From the Bayesian perspective, MPLKR can also be considered as the kernel version of maximum a posteriori linear regression (MAPLR) adaptation. Supervised and unsupervised speaker adaptation using MPLKR were evaluated on the Resource Management and Wall Street Journal 5K tasks, respectively, achieving a word error rate reduction of 23.6% and 15.5% respectively over the speaker-independently model.