Fullerene functionalized polymers

Summary The recent synthesis and macroscopic isolation of C₆₀ (buckminsterfullerene) has stimulated interest in its properties and chemical reactivity. Fullerenes are known to be attacked by nucleophiles and it has been reported that they react with small amines. There is, however, no report on the reaction of fullerenes with polymeric amines. Fullerenes were found to add to amine containing flexible hydrocarbon polymers such as ethylene propylene terpolymer (EPDM-amine) to obtain novel C₆₀ functionalized polymers. These materials are soluble in common solvents. The reaction of the fullerene and polymer was followed by infra-red spectroscopy and viscosity measurements.     

Servo controller design using neural networks

The dynamics of a physical plant may be difficult to express as concise mathematical equations. In practice there exist uncertainties that cannot be modeled with the system equations. Hence, robustness against system uncertainties is essential in a control system design. In this article, multilayered neural networks (MNNs) are used to compensate for model uncertainties of a dynamical system. Neural network models are used along with a classical linear servo controller derived from the linear state space equations. These models are trained so that system uncertainties are compensated. The design of a servo system indicates the enhanced performance of the neural-network-based servo controller as compared to the classical servo controller.     

Cyclopropenoids and Fatty Acid Composition of Five Varieties of Cotton Seed Oils

Five varieties of cotton seed oils from Jayadhar, Bhagya, Mysore Vijaya, Hampi and 170 CO₂ have been analysed for their fatty acid content and the results (Wt.%) are in the following range: Myristic 0.8–1.1; Palmitic 23.0–23.9; Stearic 2.7–4.2; Arachidic 0.3–0.7; Behenic 0.3–1.4; Oleic 11.9–22.8; Linoleic 47.5–58.1; and Cyclopropenoid acids 0.6–2.1. The oil content and iodine value from 20.2–22.5 percent and 104.3–115.3 respectively. Protein content ranges from 24.8–48.4 percent.     

Thermoluminescence of CaS:Ag:Dy phosphors

CaS phosphors co-activated with varying concentrations of Ag and Dy have been prepared and their thermoluminescence behaviour is studied in the temperature range of 300°K to 443°K. The activation energies corresponding to the glow peaks have been evaluated by four different methods. The effect of addition of activators on general features of glow curves and on distribution of traps is discussed. Conclusions are drawn regarding the nature and origin of traps and about the type of kinetics involved in the thermoluminescence process.     

Classification of melanoma using tree structured wavelet transforms

This paper presents a wavelet transform based tree structure model developed and evaluated for the classification of skin lesion images into melanoma and dysplastic nevus. The tree structure model utilizes a semantic representation of the spatial-frequency information contained in the skin lesion images including textural information. Results show that the presented method is effective in discriminating melanoma from dysplastic nevus. The results are also compared with those obtained using another method of developing tree structures utilizing the maximum channel energy criteria with a fixed energy ratio threshold.     

Theoretical analysis of effect of temperature on threshold parameters and field intensity in GaN material based heterostructure

Temperature dependent analysis to achieve better performance by reducing threshold current requirements and field intensity has been carried out for GaN/AlGaN heterostructure lasers. The mirror loss in the GaN cavity has been obtained as a function of temperature and cavity length. The quantum efficiency has been deduced for different values of cavity length. Dependence of recombination rate on band gap and temperature has been investigated. Threshold current density has been deduced for GaN lasers and effect of temperature on it has been investigated. The near field intensity analysis has been carried out at different temperatures for 10% aluminum mole fraction in GaN/AlGaN heterostructure lasers. Furthermore, the effective index and FWHM of near field has been investigated as a function of temperature. It has been deduced from our analysis that temperature has a dominant effect on the threshold conditions and near field intensity in the wide band gap GaN based lasers.     

Diamond like carbon coatings deposited by microwave plasma CVD: XPS and ellipsometric studies

Diamond-like carbon (DLC) films were deposited by microwave assisted chemical vapour deposition system using d.c. bias voltage ranging from −100 V to −300 V. These films were characterized by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry techniques for estimating sp ³/sp ² ratio. The sp ³/sp ² ratio obtained by XPS is found to have an opposite trend to that obtained by spectroscopic ellipsometry. These results are explained using sub-plantation picture of DLC growth. Our results clearly indicate that the film is composed of two different layers, having entirely different properties in terms of void percentage and sp ³/sp ² ratio. The upper layer is relatively thinner as compared to the bottom layer.     

Polyphase Conditions and Structures for 2-D Quincunx FIR Filter Banks Having Quadrantal or Diagonal Symmetries

In this brief, we derive conditions on the polyphase matrix of 2-D finite-impulse response (FIR) quincunx filter banks, for the filters in the filter bank to have quadrantal or diagonal symmetry. These conditions provide a framework for synthesizing polyphase structures which structurally enforce the symmetry. This is demonstrated by constructing examples of small parameterized matrix structures which satisfy the above conditions, thus giving perfect reconstruction FIR quincunx filter banks with quadrantal or diagonally symmetric short-kernel (i.e., short-support) filters. It is also shown that cascades of the above constructed small structures can be used to construct filters of higher order.     

Ultra-Thin Si<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Dislocation Blocking Layers for Ge/Strained Si CMOS Devices

We demonstrate ultra-thin (<150 nm) Si_1−x Ge _x dislocation blocking layers on Si substrates used for the fabrication of tensile-strained Si N channel metal oxide semiconductor (NMOS) and Ge P channel metal oxide semiconductor (PMOS) devices. These layers were grown using ultra high vacuum chemical vapor deposition (UHVCVD). The Ge mole fraction was varied in rapid, but distinct steps during the epitaxial layer growth. This results in several Si_1−x Ge _x interfaces in the epitaxially grown material with significant strain fields at these interfaces. The strain fields enable a dislocation blocking mechanism at the Si_1−x Ge _x interfaces on which we were able to deposit very smooth, atomically flat, tensile-strained Si and relaxed Ge layers for the fabrication of high mobility N and P channel metal oxide semiconductor (MOS) devices, respectively. Both N and P channel metal oxide semiconductor field effect transister (MOSFETs) were successfully fabricated using high-k dielectric and metal gates on these layers, demonstrating that this technique of using ultra-thin dislocation blocking layers might be ideal for incorporating high mobility channel materials in a conventional CMOS process.     

Comparison of predicted vehicular pollution concentration with air quality standards for different time periods

Air pollution is caused by variety of sources such as industries, vehicles, cremation, bakeries, and open burning. These sources have variation in emission with different time scales. Industry and bakeries have variation in emission with day or week, rest of the sources like vehicles and domestic sector have variation with time in a day. In fact, vehicles have a large variation in emission with time period of the day. The average concentration of 24 h is much less than hourly concentration of peak time when there is heavy vehicular emissions. The hourly concentration of off-peak time or lean time is very low due to low emission for that period. The air quality standards of India are prescribed for 24-h average concentration with which the predicted average concentration from models is compared. However, the peak time concentration may be much higher than the standard. In the peak time, outdoor concentration is more and since a large proportion of the population is out the exposure is also very high and can cause severe health effect. In this paper, vehicular pollution modeling has been carried out using AERMOD with simulated meteorology by Weather Research and Forecasting model. NO_x and PM concentrations were 3.6 and 1.45 times higher in peak time than off-peak and evening peak, respectively. Lean time has higher concentration for both NO_x and PM than off-peak and evening peak. It shows the misleading concept of comparing average predicted concentration of 24 h with standards for vehicles.