A new public-domain simulator for power electronic circuits

A new public-domain simulator (SEQUEL) for power electronic circuits is described. The organization of the simulator is briefly discussed. The most important feature of the simulator is that the user can define new elements in a flexible manner. The differences between the new simulator and other simulators are enumerated. Some simulation examples are discussed to demonstrate the applications of the simulator. It is pointed out that the new simulator is particularly attractive for engineering institutes in developing countries where access to expensive commercial packages with similar capabilities may be difficult     

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.     

Fourier transform infrared-probed O(3P) microreactor: demonstration with ethylene reactions in argon matrix

To demonstrate the development of an oxygen atom microreactor in the form of liquid-helium-cooled solid argon matrix deposited on an infrared (IR) window, the oxidation of ethylene by mobile O atoms has been investigated. O atom diffusion through the argon matrix is confirmed and used to examine ethylene-oxygen atom reactions. In a bench-scale matrix isolation system probed with a Fourier transform infrared (FT-IR) spectrometer, matrices of solid Ar at 8-10 K doped with NO2 and ethylene have been prepared on a ZnSe window within an evacuated cryostat. The matrices have been photolyzed using 350-450 nm photons, and the reaction products resulting from the reaction of O(3P), one of the photolysis products of NO2, with ethylene have been identified using FT-IR and a Gaussian 98W simulation program. These products include oxirane, acetaldehyde, ethyl nitrite radical, and ketene. The temperature effect in the range of 10-30 K on the products formed has also been investigated. The reaction mechanisms are discussed and the viability of the solid Ar matrix being a low temperature microreactor to examine reaction mechanisms of mobile oxygen atoms is elaborated.     

Water-related matrix isolation phenomena during NO2 photolysis in argon matrix

Photolysis (350-450 nm) of NO(2) molecules trapped in argon matrices at 10 K has been studied using Fourier transform infrared (FTIR) spectroscopy to examine the mobility of the photolysis products, O((3)P) and NO, and their subsequent reactions. The formation of N(2)O(5) and N(2)O(3) from reactions of these mobile species with immobilized NO(2) and N(2)O(4) is confirmed. Water molecules from the background gases in the vacuum have been found to be isolated in the argon matrix during deposition of diluted NO(2) in Ar. The entrapped water molecules along with some of their NO(2) adducts have been characterized. Exposure of the matrix to photons to photolyze NO() resulted in not only internal matrix reactions, but also an enhanced deposition of ice over the surface of the argon matrix. This is caused by photodesorption of water molecules from the walls of the matrix isolation chamber and their subsequent condensation on the matrix surface. This ice overlayer has been found to give a very significant dangling OH band and a substantial librational band in the FT-IR spectra, indicating substantial surface area and internal porosity, respectively. The potential of using photodesorbed water to establish high surface area ice interfaces with dangling OH groups for heterogeneous photoreaction studies is discussed.     

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.     

Optimal Design of a Stable Trapezoidal Channel Section Using Hybrid Optimization Techniques

A cost effective channel section for a specified flow rate, roughness coefficients, longitudinal slope, and various cost parameters can be determined using an optimization technique. However, the derived optimal channel section may not be feasible for construction because of in situ conditions. The local soil conditions may not support the optimal side slope of the channel and if constructed, the slope may fail. It is therefore necessary to also incorporate the criteria for side slope stability in designing an optimal open channel section. In this paper, a new methodology has been developed to design a stable and optimal channel section using hybrid optimization techniques. A genetic algorithm based optimization model is developed initially to determine the factor of safety of a channel slope for given soil parameters. This optimization model is then externally linked with a separate sequential quadratic programming based optimization model to evaluate the parameters of the stable and optimal channel section. Solution for various example problems incorporating different soil parameters are illustrated to demonstrate the applicability of the developed methodology.