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81.
For the accurate prediction of the performances of saturated synchronous machines, the saturation characteristics in both the direct and quadrature axes are needed. The d-axis saturation characteristic of a synchronous machine can be measured easily by the open-circuit test with the machine excited from its field winding. On the other hand, the q-axis saturation characteristic of a synchronous machine cannot be measured applying a similar easy, simple method and, as a result, these characteristics are usually not experimentally measured and are not available. In this paper, three possible experimental methods for determining the q-axis saturation characteristics of both cylindrical-rotor and salient-pole synchronous machines are presented. The merits and demerits of these experimental methods are discussed from the point of view of their complexity and their accuracy. Comparisons between the measured q-axis saturation characteristics obtained by these experimental methods are made for a cylindrical-rotor machine and two salient-pole machines. Moreover, the various sources of errors, which may affect the accuracy of determining the q-axis saturation characteristics by these methods, are investigated. 相似文献
82.
A mathematical analysis describing the densification of ceramic coating processed with a moving TEM00, mode laser beam has been presented in this paper. Calculations of the depth of the heat affected zone in ZrO2, A12O3 and TiO2 ceramic substances is performed by adopting a three-dimensional quasi-steady state heat conduction model based on the mechanism of viscous solid-phase densification. Also, a working range for these ceramics coating densification is predicted by varying the laser beam power, spot size and scanning velocity. The heat-affected layer in ZrO2 compact is found to be confined within a depth of 50 μm from the surface and it is fully densified for grains of initial radius 5 μm. A simple expression for temperature distribution is presented, which is found to provide sufficiently accurate estimates within a limited region around the laser spot. 相似文献
83.
Asheesh Kumar Raghunandan Sharma Chhatrasal Gayner Siddanathi Nageswara Rao Devendra P. Singh Malay K. Das Kamal K. Kar 《International Journal of Applied Glass Science》2017,8(1):97-104
The (AgBr)x(LiPO3)(1−x) (x=0.4 and 0.5) and [(AgI)x(AgBr)0.4−x](LiPO3)0.6 (x=0.1, 0.2, and 0.3) superionic electrolytes have been prepared by conventional melt quenching using a twin roller. These electrolytes are characterized by X-ray diffraction, SEM, and energy dispersive X-ray analysis (EDAX) for structural investigation. Electrical characterizations have been carried out by the AC impedance analysis. The conductivity of LiPO3 glassy system at room temperature is improved by doping with the silver bromide (AgBr)x(LiPO3)(1−x) and the mixture of silver iodide, silver bromide (AgI-AgBr-LiPO3 system) up to 10−5 and 10−3 Ω−1 cm−1, respectively (improvements by four or five orders of magnitude). The frequency response of ionic conductivity has been analyzed by universal dynamic response model (Jonscher's law) and AC conductivity data are fitted using the Jonscher's power law. The conductivity values obtained by the power law and impedance plots are comparable. The frequency exponent (n) has a value between 0 and 1. The AgI-AgBr-LiPO3 system shows the mixed alkali effect. Summerfield scaling master curve is temperature dependent, which may be due to the contribution of the both lithium and silver ions to ionic conduction. 相似文献
84.
Bishnu Prasad De R. Kar D. Mandal S. P. Ghoshal 《International Journal of Numerical Modelling》2016,29(5):873-896
This paper presents an efficient approach for the optimal designs of two analog circuits, namely complementary metal oxide semiconductor) two‐stage comparator with p‐channel metal oxide semiconductor input driver and n‐channel input and folded‐cascode operational amplifier using a recently proposed meta‐heuristic‐based optimization algorithm named as colliding bodies optimization (CBO). It is a multi‐agent algorithm that does not depend upon any internal control parameter, making the algorithm extremely simple. The main objective of this paper is to optimize the metal oxide semiconductor (MOS) transistors' sizes using CBO in order to reduce the areas occupied by the circuits and to get better performance parameters of the circuits. Simulation Program with Integrated Circuit Emphasis simulation has been carried out by using the optimal values of MOS transistors' sizes and other design parameters to validate that CBO‐based design is satisfying the desired specifications. Simulation results demonstrate that the design specifications are closely met and the required functionalities are achieved. The simulation results also confirm that the CBO‐based approach is superior to the other algorithms in terms of MOS area and performance parameters like gain, power dissipation, etc., for the examples considered. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
85.
86.
A new AFM (atomic force microscopy) nanotribology method using a T-shape cantilever with an off-axis tip (Nat Nanotechnol
2:507–514, 2007) has been developed for measuring friction coefficient at nanometer scale. In this method, signals due to both bending and
twisting of the T-shape AFM cantilever are detected simultaneously. For a T-shape AFM cantilever, the bending is caused by
the normal load and the twisting is caused by both the normal and the lateral loads. The twisting generated by the normal
load is calibrated in advance. Consequently, the twisting only due to the lateral load can be decoupled from the total lateral
voltage signal. And the friction coefficient can be finally determined based on a conversion relationship between the normal
and lateral voltage signals of the AFM photodetector. A practical procedure for minimizing Abbé error in friction coefficient
measurement has also been introduced. The proposed new method is simple and accurate, and requires the least operation for
friction coefficient measurement at nanometer scale. 相似文献
87.
We report a study of the role of mid-gap defect levels due to surface states in SnO(2) nanowires on carrier trapping. Ultrafast pump-probe spectroscopy provides carrier relaxation time constants that reveal the nature and positions of various defect levels due to the surface states which in turn provide details on how the carriers relax after their injection. The effect of oxygen annealing on carrier concentration is also studied through XPS valence band photoemission spectroscopy, a sensitive non-contact surface characterization technique. These measurements show that charge transfer associated with chemisorption of oxygen in different forms produces an upward band bending and leads to an increase in the depletion layer width by approximately 70 nm, thereby decreasing surface conductivity and forming the basis for the molecular sensing capability of the nanowires. 相似文献
88.
An uncooled mid-wave infrared (MWIR) detector is developed by doping an n-type 4H-SiC with Ga using a laser doping technique. 4H-SiC is one of the polytypes of crystalline silicon carbide and a wide bandgap semiconductor. The dopant creates an energy level of 0.30 eV, which was confirmed by optical spectroscopy of the doped sample. This energy level corresponds to the MWIR wavelength of 4.21 μm. The detection mechanism is based on the photoexcitation of electrons by the photons of this wavelength absorbed in the semiconductor. This process modifies the electron density, which changes the refractive index, and, therefore, the reflectance of the semiconductor is also changed. The change in the reflectance, which is the optical response of the detector, can be measured remotely with a laser beam, such as a He-Ne laser. This capability of measuring the detector response remotely makes it a wireless detector. The variation of refractive index was calculated as a function of absorbed irradiance based on the reflectance data for the as-received and doped samples. A distinct change was observed for the refractive index of the doped sample, indicating that the detector is suitable for applications at the 4.21 μm wavelength. 相似文献
89.
The effects of betel leaf extract (0.10, 0.40, 0.80 and 2.0 g kg-1 day-1 for 15 days) on the alterations in thyroid hormone concentrations. lipid peroxidation (LPO) and on the activities of superoxide dismutase (SOD) and catalase (CAT) were investigated in male Swiss mice. Administration of betel leaf extract exhibited a dual role, depending on the different doses. While the lowest dose decreased thyroxine (T4) and increased serum triiodothyronine (T3) concentrations, reverse effects were observed at two higher doses. Higher doses also increased LPO with a concomitant decrease in SOD and CAT activities. However, with the lowest dose most of these effects were reversed. These findings suggest that betel leaf can be both stimulatory and inhibitory to thyroid function, particularly for T3 generation and lipid peroxidation in male mice, depending on the amount consumed. 相似文献
90.
For the accurate analysis of salient-pole synchronous machines using the two-axis frame models, the direct- (d-) and quadrature-axis (q-axis) saturation characteristics are needed. Usually, the d-axis saturation characteristics can be obtained easily by the conventional open-circuit test with the machines excited from their field winding. On the other hand, the q-axis saturation characteristics of synchronous machines cannot be measured applying simple, conventional methods, and thus, they are usually not available. In this paper, four different methods for calculating the q-axis saturation characteristics of salient-pole synchronous machines from the measured d-axis saturation characteristics are explored. In these methods, the q-axis saturation characteristics can be calculated from the readily available test data, namely the d-axis saturation characteristics and the d- and q-axis unsaturated magnetizing reactances. Finally, a comparison between these methods is made. 相似文献