Microoptical phased arrays for spatial and spectral switching

This article describes two optical devices based on linear arrays of micromirrors. The first is a phased array of micromirrors that can be rotated as well as translated vertically to maintain coherence across the array. We demonstrate experimentally that such micromirrors are capable of high-diffraction-efficiency phased-array scanning of laser beams. The second device is a Gires-Tournois (1969) interferometer with a micromirror array that provides tunable phase modulation for the multitude of partially reflected beams within the interferometer. We demonstrate experimentally that the MEMS-GT interferometer can operate as a tunable deinterleaver for dense wavelength-division multiplexed fiber optic communication.     

Reactive ion etching and characterization of p-silk ultra low-k film

Reactive ion etch (RIE) of p-SiLK, a spin-on polymer based ultra low-k (ULK) material with a k value of /spl sim/2.2 was characterized and its influence on electrical yield and dielectric breakdown is presented here. Material characterization was done using blanket films after curing and the effect of exposure to different conventional plasma etch gas mixtures was studied for surface composition, roughness and dielectric constant. Trench etch process was developed for 130-nm technology node for single damascene process integration. Dual hard mask approach was taken and two etch schemes viz., etching under hardmask and etching under photoresist were evaluated. In both schemes, trench etch profiles were near vertical and critical dimension (CD) control was within 10%. RIE lag and the carbon depletion at the sidewalls were found to be insignificant confirming acceptable etch process performance. Etching under photoresist scheme was found advantageous in terms of trench profile for isolated structures, reduced cycle time making the process cost effective and reduced post-CMP defects. However, from the comparison of electrical test results, etch under hardmask scheme showed higher electrical yield and better performance than etch under PR scheme. Although trench sidewalls were exposed to plasma during both schemes, sidewall damage did not contribute to overall leakage. The RIE process developed and the characterization results have confirmed the compatibility of material and RIE process for successful process integration.     

Tamarind Fruit Fiber and Glass Fiber Reinforced Polyester Composites

Polyester-based hybrid composites were developed by combining the tamarind fruit (Tf) and glass fibers into a polyester matrix. Hardness, impact strength, frictional coefficient, and chemical resistance of hybrid composites with and without alkali treatments were studied. Variation of the aforementioned mechanical properties and chemical resistance was studied with different fiber lengths, such as 1, 2, and 3 cm. A 9 vol% of the tamarind and glass fibers was reinforced into the polyester matrix. The aforementioned mechanical properties were optimally improved at 2-cm fiber length when compared with 1- and 3-cm fiber lengths. Chemical resistance was also significantly improved for all chemicals except toluene. A 3°C rise in decomposition temperature while a 2°C rise in glass transition temperature was observed from TGA and DSC micrograms, respectively.     

Enhancement in Strain Hardening on Boron Addition in As-Cast Ti–6Al–4V Alloy

It has been previously reported that the addition of boron to Ti–6Al–4V results in significant refinement of the as-cast microstructure and enhancement in the strain hardening. However, the mechanism for the latter effect has not been adequately studied. The aim of this study was to understand the reasons for the enhancement in room temperature strain hardening on addition of boron to as cast Ti–6Al–4V alloy. A study was conducted on slip transmission using SEM, TEM, optical profilometry and four point probe resistivity measurements on un-deformed and deformed samples of Ti–6Al–4V–xB with five levels of boron. Optical profilometry was used to quantify the magnitude of offsets on slip traces which in turn provided information about the extent of planar or multiple slip. Studies on deformed samples reveal that while lath boundaries appear to easily permit dislocation slip transmission, colony boundaries are potent barriers to slip. From TEM studies it was also observed that while alloys containing lower boron underwent planar slip, deformation was more homogeneous in higher boron alloys due to multiple slip resulting from large number of colony boundaries. Multiple slip is also proposed to be the prime cause of the enhanced strain hardening.     

Plasma characterization of dry ��-EDM

An attempt was made to characterize the dry microelectric discharge machining (??-EDM) plasma systematically by using optical emission spectroscopy. In order to characterize the plasma and its parameters such as plasma temperature, electron density, Debye length, and gamma parameter, the optical spectra were recorded for different energies and with different diameters of tool electrode. From the recorded spectra, using line pair method and modified Saha equation, plasma temperature and electron density, respectively were calculated. From these two, Debye length and plasma parameter were also calculated. These studies indicate that the plasma produced in dry ??-EDM is ideal. In addition to this, we found that the dry ??-EDM region is below the conventional EDM region in log electron density and log temperature plot. Morphological analysis was carried out on crater produced by different energies on the workpiece using a scanning electron microscope. The crater shape may dependent on the geometry of the tool tip, number of discharges, and energy of discharge.     

Performance Analysis of Layer Pruning on Sphere Decoding in MIMO Systems

Sphere decoding (SD) for multiple‐input and multiple‐output systems is a well‐recognized approach for achieving near‐maximum likelihood performance with reduced complexity. SD is a tree search process, whereby a large number of nodes can be searched in an effort to find an estimation of a transmitted symbol vector. In this paper, a simple and generalized approach called layer pruning is proposed to achieve complexity reduction in SD. Pruning a layer from a search process reduces the total number of nodes in a sphere search. The symbols corresponding to the pruned layer are obtained by adopting a QRM‐MLD receiver. Simulation results show that the proposed method reduces the number of nodes to be searched for decoding the transmitted symbols by maintaining negligible performance loss. The proposed technique reduces the complexity by 35% to 42% in the low and medium signal‐to‐noise ratio regime. To demonstrate the potential of our method, we compare the results with another well‐known method — namely, probabilistic tree pruning SD.     

N-tuple features for OCR revisited

N-tuple features for optical character recognition have received only scattered attention since the 1960s. Our main purpose is to show that advances in computer technology and computer science compel renewed interest. N-tuple features are useful for printed character classification because they indicate the presence or absence of a given rigid configuration of n black and white pixels in a pattern. Desirable n-tuples fit each pattern of a specified (positive) training set of characters in at least p different shift positions, and fail to fit each pattern of a specified (negative) training set by at least n-q pixels in each shift position. We prove that the problem of finding a distinguishing n-tuple is NP-complete, by examining a natural subproblem with binary strings called the missing configuration problem. The NP-completeness result notwithstanding, distinguishing n-tuples are found automatically in a few seconds on contemporary workstations. We exhibit a practical search algorithm for generating, from a small training set, a collection of n-tuples with low class-conditional correlation and with specified design parameters n, p, and q. The generator, which is available on the Internet, is empirically shown to be effective through a comparison with a benchmark generator. We show experimentally that the design parameters provide a useful tradeoff between distinguishing power and generation time, and also between the conditional probabilities for the positive and negative classes. We explore the feature probabilities obtainable for various dichotomies, and show that the design parameters control the feature probabilities     

Probing the dynamics of planar supported membranes by Nile red fluorescence lifetime distribution

The structure and dynamics of planar supported membranes were studied by using the fluorescence probe Nile red. The width of fluorescence lifetime distribution of Nile red was used to infer the heterogeneity of membranes. The width of fluorescence lifetime was larger and the lifetime was shorter in supported membranes when compared to vesicle membranes. This was interpreted as due to the presence of water-filled membrane discontinuity leading to a heterogeneous surface in supported membranes. Microdomain causing agents such as cholesterol, sphingomyelin, etc. caused a larger level of heterogeneity in supported membranes when compared to vesicle membranes.     

Optimization of Machining Characteristics for Al／SiCp Composites using ANN／GA

The present work is focused on optimization of machining characteristics of Al/SiCp composites.The machining characteristics such as specific energy,tool wear and surface roughness were studied.The parameters such as volume fraction of SiC,cutting speed and feed rate were considered.Artificial neural networks(NN) was used to train and simulate the experimental data.Genetic algorithms(GA) was interfaced with ANN to optimize the machining conditions for the desired machining characteristics .Validation of optimized results was also performed by confirmation experiments.