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排序方式: 共有523条查询结果,搜索用时 8 毫秒
51.
V. Sridharan D. Ravi Chandran S. Srinivasan S. Sivasankaran L. Giridharan K. Suresh T. Nagarajan A. Raman 《Journal of Materials Science》1992,27(16):4483-4488
The synthesis conditions and oxygen stoichiometry were determined using a thermogravimetric analyser. The kinetics of oxygenation at different temperatures and at different atmospheres were studied. The oxygenation kinetics were found to be sensitive to porosity of the material. The appropriate oxygenation temperature was found to be 400 °C. For oxygenation temperatures below 400 °C, the oxygenation occurs by a nucleation and growth process, whereas for higher temperatures it is diffusion limited. 相似文献
52.
C V Tomy R Nagarajan S K Malik Ram Prasad N C Soni Kalyan Adhikary 《Bulletin of Materials Science》1991,14(3):691-695
151Eu Mössbauer studies have been performed on the compounds EuBa2(Cu1?x Zn x )3O7?y withx=0·0, 0·025, 0·05, 0·075 and 0·1. The parent compound, EuBa2Cu3O7?y is superconducting with a transition temperature (T c ) of 88 K.T c is depressed as Zn is substituted for Cu in this system and the compounds withx>0·05 do not show superconductivity down to 12 K.151Eu Mössbauer studies at 295 K show a single Mössbauer line in all the compounds (whether superconducting or not) with isomer shift value typical of Eu3 + ion. Further, the isomer shift values are nearly independent ofx and the temperatures down to 10 K. These observations imply that the Cu-O network responsible for superconductivity is very weakly coupled to the Eu sublattice. 相似文献
53.
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55.
R. Nagarajan 《Journal of Low Temperature Physics》1997,107(5-6):517-526
Quaternary borocarbide superconductors have attracted attention and are of current interest due to a variety of reasons. Some
of them exhibit high Tc's for intermetallics, including the material which shows highest known Tc for intermetallics. Though the structure of RNi2B2C (R=Sc, Y, rare earth, Th, U) is effectively a layered structure like that of high Tc cuprates, rare earth ions influence the superconducting properties of these materials. Coexistence of superconductivity and
magnetism has been found in these materials with magnetic ordering temperatures much higher than those of earlier known magnetic
superconductors which implies stronger coupling of rare earth moment to conduction electrons. These features make quaternary
borocarbides an altogether different class of materials. Being quaternary, and with the possibility of having more than one
rare earth-carbon layer in the structure, this family offers the possibility of finding many new materials with wide ranging
properties. Highlights of recent developments in this new subject of quaternary borocarbides are reviewed here. 相似文献
56.
We present a ten-channel parallel fiber optic link consisting of a transmitter based on an edge emitting laser diode array operating nominally at 1 μm wavelength and a complementary receiver based on an InGaAs pin photodetector array. We demonstrate fiber optic link performance up to data rates of 1 Gb/s per channel with low skew at measurement time limited bit error rates lower than 10-11 over 100 m of multimode fiber ribbon cable. The transmitter is operational, with very clear eye opening, up to baseplate temperatures of 105°C 相似文献
57.
Using the steady-state solution to the carrier transport rate equation model for the quantum-well laser that they had previously proposed, the authors derive analytic expressions for the laser internal efficiency, carrier injection efficiency, and wavelength chirping under current modulation and show that the various carrier transport times can have a significant effect on these quantities. They present experimental data and theoretical calculations that clearly demonstrate that, as in the case of device optimization for high-speed operation, one has to minimize the transport time across the optical and current confinement regions and maximize the escape time out of the quantum-well active region in order to maximize the internal and the injection efficiencies and minimize the wavelength chirping 相似文献
58.
The letter presents an identification scheme incorporating a set of relays, which lessens the online computations, for discrete-time model reference adaptive systems (MRAS). 相似文献
59.
We present the theoretical analysis and the experimental implementation of a narrowband millimeter wave optical fiber communication system using an external cavity semiconductor laser. We derive analytic expressions and present experimental data for the modulation response, relative intensity noise, carrier-to-noise ratio, and harmonic distortion for a semiconductor laser in an external cavity operating as a transmitter in the millimeter wave frequency range. We present a system implementation of this capable of transmitting 40-Mbt/s digital data at a 35-GHz subcarrier frequency with bit-error rates below 10-9 over a 6.3-km-long optical fiber link 相似文献
60.