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71.
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 相似文献
72.
G. C. Weatherly A. Perovic D. D. Perovic N. K. Mukhopadhyay D. J. Lloyd 《Metallurgical and Materials Transactions A》2001,32(2):213-218
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. 相似文献
73.
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. 相似文献
74.
Anoop K. Mukhopadhyay Keshaw D. Joshi Arjun Dey Riya Chakraborty Amit Rav Sampad K. Biswas Satish C. Gupta 《Journal of Materials Science》2010,45(13):3635-3651
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. 相似文献
75.
C. Mukhopadhyay P.D. Dragic 《Photonics Technology Letters, IEEE》2005,17(6):1166-1168
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. 相似文献
76.
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. 相似文献
77.
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. 相似文献
78.
A. K. Chaubey B. K. Mishra N. K. Mukhopadhyay P. S. Mukherjee 《Journal of Materials Science》2010,45(6):1507-1513
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. 相似文献
79.
Microfibres 总被引:1,自引:0,他引:1
Microfibres denote synthetic fibres that are finer than any fibre in nature. Microfibres are usually made of polyester, polyamide, acrylic, modal, lyocell and viscose in the range of 0.5-1.2 dtex. The progress starts with direct spinning and post-spinning developments for manufacturing microfibres. Researches on conjugate spinning techniques are reported along with the development in bicomponent spinning. Interesting developments in manufacturing techniques like the change of cross section without altering the spinneret, radial quenching system, etc., have been discussed. Recent developments like electrospinning have also been taken up. The mechanical processing section commences with the properties of microfibres affecting the downstream process and then discusses the processing of microfibres in blow room, carding, draw frame, speed frame and ring frame. Alternative spinning technologies like open-end, air-jet and compact spinning are dealt with. In the fabric forming systems, weaving and knitting with microfibres are discussed in depth highlighting research on such fabrics. High-speed weaving of microfibres is discussed with reference to three major technologies of projectile, rapier and air-jet weaving. The reactions of microfibres to different hydrolysis environments like alkaline, acidic and enzymatic are taken up. Dyeing of microfibres and the specific problems in dyeing of microfibres are discussed. The study of fibre structure by critical dissolution time is addressed. Different uses of microfibres in terms of industrial, medical, apparel and miscellaneous applications are presented. The economics of production along with the limitations and precautions of the fibre are subsequently discussed followed by suggestions for future work. 相似文献
80.
For preparation of solid oxide fuel cell functional anode (Ni-YSZ) by electroless deposition technique, surface adsorption of metallic palladium (Pd0) on zirconia is the most important step during the sensitization process. For the sensitization process, the initial reaction kinetics are based on external mass transfer followed by intra-particle mass transfer phenomena. A kinetic model for the reversible sorption of Pd0 on zirconia is developed that incorporates an effectiveness factor (η) which estimates the extent of intra-particle mass transfer. Based on the proposed model, an expression for Pd0 uptake at equilibrium (p), an important property of YSZ, is developed. The theoretical kinetic model proposed is verified with experimental parameters like electrical properties of these functional anodes prepared under various sensitization conditions, e.g., agitation frequencies, equilibration time etc. Due to intra-particle mass transfer, the concentration gradient of Pd0 from the surface of YSZ to bulk is minimized which favours uniform deposition of Ni on YSZ. Consequently, during subsequent electroless deposition of metallic Ni, the concentration gradient of the same is reduced from the bulk to the YSZ surface and results in enhanced functionality in the cermet anode. The validation is correlated with the electrical properties and surface morphologies of these functional cermets. 相似文献