Microprocessor-based on-line monitoring and characterization ofpower factor of a synchronous motor

An attempt is made to develop a microprocessor-based system for online monitoring of the power factor of a synchronous motor. The method is based purely on software design with the use of two resistors (of small ohmic values and high current carrying capacity) connected in series with the field circuit and load circuit, which generate the reference signals for the microprocessor. However, for mechanical loading, the resistance in the load circuit may be replaced by a torque transducer. The interesting feature of the system is its capability to characterize the status (i.e. leading, lagging, or unity) of the power factor. The system is helpful in providing necessary information for power factor corrections leading to the best utilization of the synchronous motor     

The precipitation of the Q phase in an AA6111 Alloy

The precipitation behavior of the quaternary Q phase in an Al 6111 alloy has been studied by analytical electron microscopy. The transformation strain associated with the Q phase has been determined from high resolution electron microscopy and electron diffraction. The habit plane of the Q laths is shown to be fully coherent with the Al matrix. The transformation strain is used to explain the pattern of heterogeneous precipitation of the Q phase at dislocations and grain boundaries. The crystal structure and composition of the Q phase, whether it forms in the matrix or at grain boundaries, appears similar to that formed directly from the melt in a quaternary Al-Cu-Mg-Si alloy.     

Determination of Physical Parameters of Stiffened Plates using Genetic Algorithm

An investigation on stiffened isotropic and composite plates has been conducted to determine the geometric and material parameters for the plate, as well as the stiffener from experimental modal data and finite element predictions using a genetic algorithm (GA). The problem is formulated as a global minimization of the error function defined by the difference in undamped eigenvalues and eigenvectors, as predicted from the finite-element modeling to that obtained experimentally. The parameter estimation problem is solved using a GA implementing selection, crossover, and mutation operators to obtain the global minimum solution. Because stiffeners contribute substantially to the overall rigidity of the plate assembly, their position, physical properties, and orientation create considerable variation of the modal properties, as compared to the bare plate with similar construction. This makes each of the stiffened plate identification problems rather unique. GAs have been the subject of considerable interest in providing a robust search procedure for a global optimum solution for such difficult minimization problems. The method is demonstrated on a few simulated examples on stiffened plates to investigate the uniqueness and convergence of results. The methodology, although slow in execution, is found to be very robust, even in the presence of noise, for isolating interesting zones of the search space. Unlike many traditional optimization techniques, it does not get stuck at a particular local minimum due to its parallelism.     

Shock deformation of coarse grain alumina above Hugoniot elastic limit

Symmetric shock experiments were conducted on a 10 μm grain size coarse alumina ceramic with a gas gun to identify its Hugoniot elastic limit (HEL). To understand the damage initiation and their subsequent growth mechanisms in coarse grain alumina subjected to shock impact at levels much above the HEL, additional asymmetric shock recovery experiments with the same gas gun were then deliberately conducted on the same alumina at shock pressure levels more than three times as high as the HEL and the fragments collected by a dedicated catcher system. Detailed characterization of the shock recovered alumina fragments by X-ray diffraction, nanoindentation, scanning electron microscopy, field emission scanning electron microscopy and transmission electron microscopy were utilized to understand the nature and process of failure initiation, incubational growth, coalescence and propagation leading to fragmentation. Based on these data a new qualitative damage model was developed to explain the deformation mechanism.     

Broad-band injection seeding of an erbium-doped fiber ring laser

We present a broad-band (40 MHz) injection-seeded erbium-doped fiber ring laser with a low finesse cavity. Broad-band operation is achieved by seeding an arbitrary number of longitudinal modes in this cavity. This fiber laser is advantageous because it has the potential to substantially suppress stimulated Brillouin scattering for lidar applications.     

Evaluation of the nutritional quality of four unexplored aquatic weeds from northeast India for the formulation of cost-effective fish feeds

A study was conducted to evaluate the nutritional potential of four commonly available, unexplored aquatic weeds namely, Salvinia cuculata, Trapa natans, Lemna minor and Ipomoea reptans from northeast India for ascertaining their suitability for utilization as supplementary fish feed with the aim to reduce the cost of commercial feeds. Results of proximate analysis showed that the crude protein content of the aquatic weeds ranged between 11.0% and 32.2% (w/w), whereas crude fibre and ash contents varied between 4.2% and 20% (w/w), and 13.3% and 31.2% (w/w), respectively. Protein to energy ratio (P/E) of these weeds ranged between 30.7 mg/kcal and 95.3 mg/kcal and the highest value was displayed by I. reptans. All these aquatic weeds contained high amounts of vitamins E and C and mineral elements required for the normal growth and development of fish.     

Optimization in a multivariate generalized linear model situation

The purpose of this article is to find the settings of the factors which simultaneously optimize several mean responses in a multivariate generalized linear model (GLM) environment. The generalized distance approach, initially developed for the simultaneous optimization of several linear response surface models, is adapted to this multivariate GLM situation. An application of the proposed methodology is presented in the special case of a bivariate binary distribution resulting from a drug testing experiment concerning two responses, namely, the efficacy and toxicity of a particular drug combination. One of the objectives of this application is to find the dose levels of two drugs that simultaneously maximize their therapeutic effect and minimize any possible toxic effects. A second application is presented in the case of a multivariate gamma distribution.     

Effect of compact density and preheating temperature of the Al–Ti–C preform on the fabrication of in situ Mg–TiC composites

Magnesium reinforced in situ TiC particulates was successfully synthesized by utilizing the self-propagating high temperature synthesis (SHS) process. The result showed that preform temperature and compact density have effects on the SHS reaction. It is observed that when the compact density was below 68% of the theoretical density, no SHS reaction occurred. However, with an increase in density from 68 to 72%, the successful thermal explosion reaction was observed in the Mg melt. Besides this, the effect of preheat temperature on the fabrication of Mg/TiC composite was extensively studied and found that the preheat temperature below 300 °C failed to give rise to SHS reaction. However, the preheat temperature of 450, 500, and 550 °C favors the reaction inside the liquid melt, but the temperature of 600 °C leads to the ignition reaction in the preheating furnace itself. SEM and EDX study confirms fine distribution of TiC in the matrix.