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71.
Optical properties of nano-silicon 总被引:2,自引:0,他引:2
We investigated the optical properties of silicon clusters and Si nanocrystallites using photolumine-scence (PL) and Raman
scattering technique. Broad luminescence band in the red region was observed from Si-doped SiO2 thin films deposited by co-sputtering of Si and SiO2 onp-type Si (100) substrates, annealed in Ar and O2 atmosphere. Nanocrystalline Si particles fabricated by pulsed plasma processing technique showed infrared luminescence from
as grown film at room temperature. Raman spectra from these films consisted of broad band superimposed on a sharp line near
516 cm−1 whose intensity, frequency, and width depend on the particle sizes arising from the phonon confinement in the nanocrystalline
silicon. We also performed PL, Raman and resonantly excited PL measurements on porous silicon film to compare the optical
properties of Si nanostructures grown by different techniques. An extensive computer simulation using empirical pseudo-potential
method was carried out for 5–18 atoms Si clusters and the calculated gap energies were close to our PL data.
Paper presented at the 5th IUMRS ICA98, October 1998, Bangalore. 相似文献
72.
An indirect method of estimation of size distribution of nanoparticles in a nanocomposite is proposed in this paper. The present approach exploits DC electrical current–voltage characteristics (CVC) of ZnO nanocomposite specimen in bio-polymer background. The nature of DC CVC is found to be oscillatory with respect to applied voltage. The nature of CVC is a consequence of Coulomb blockade (CB) phenomena of electrical conduction through a tiny nanoparticle. Considering the ZnO nanocomposites to be spherical, Coulomb-blockade model of quantum dot is applied here. The size distribution of particle is estimated from that model and compared with the results obtained from AFM and XRD analyses. The results from CVC are found to be consistent with these conventional microscopic results. 相似文献
73.
74.
75.
The scattering of elastic waves in polycrystalline materials is relevant for ultrasonic materials characterization and nondestructive evaluation (NDE). Diffuse ultrasonic backscatter measurements are used widely to extract the microstructural parameters such as grain size and also to detect flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Line transducers are often used for ultrasonic experiments such that an appropriate model for these two-dimensional problems is needed. Here, a theoretical expression for the temporal diffuse backscatter is derived for such domains under a single-scattering assumption. The result is given in terms of transducer and microstructural parameters. In addition, the problem is examined in terms of numerical simulations using Voronoi polycrystals that are discretized using finite elements in a plane-strain formulation. The material properties of the individual Voronoi cells are chosen according to appropriate material distributions. Such numerical models also allow scattering theories, including the one discussed here, to be examined for well-controlled microstructures. Example numerical results for materials with varying degrees of scattering that are of common interest are presented. The numerical results are compared with the theory developed with good agreement. These results are anticipated to impact ultrasonic NDE of polycrystalline media. 相似文献
76.
Debasis Mitra Sarmishtha Ghoshal Hafizur Rahaman Krishnendu Chakrabarty Bhargab B. Bhattacharya 《Journal of Electronic Testing》2011,27(5):657-671
Digital microfluidic technology is now being extensively used for implementing a lab-on-a-chip. Microfluidic biochips are
often used for safety-critical applications, clinical diagnosis, and for genome analysis. Thus, devising effective and faster
testing methodologies to warrant correct operations of these devices after manufacture and during bioassay operations, is
very much needed. In this paper, we propose an Euler tour based technique to obtain the route plan of a test droplet for the
purpose of structural testing of biochips. The method is applicable to various digital microfluidic biochip architectures,
e.g., fully reconfigurable arrays, application specific biochips, pin-constrained irregular geometry biochips, and to defect-tolerant
biochips. We show that in general, the optimal Eulerization and subsequent determination of an Euler tour in the graph model
of a biochip can be abstracted in terms of the classical Chinese postman problem. The Euler tour can be identified by running
the classical Hierholzer’s algorithm, which relies on a simple cycle decomposition and splicing method. This improved Eulerization
technique leads to an efficient test plan for the chip. This can also be used in phase-based test planning that yields savings
in testing time. The method provides a unified approach towards structural testing and can be easily adopted to design a droplet
routing procedure for functional testing of digital microfluidic biochips. 相似文献
77.
Increasing levels of wind generation have resulted in an urgent need for the assessment of their impact on frequency control of power systems. The displacement of conventional generation with wind generation will result in erosion of system frequency. The paper analyzed the dynamic participation of doubly fed induction generator (DFIG) to system frequency responses of two-area interconnected power system having variety of conventional generating units. Frequency control support function responding proportionally to frequency deviation is proposed to take out the kinetic energy of turbine blades in order to improve the frequency response of the system. Impacts of different wind penetrations in the system and varying active power support from wind farm on frequency control have been investigated. Integral gains of AGC loop are optimized through craziness-based particle swarm optimization (CRPSO) in order to have optimal transient responses of area frequencies, tie-line power deviation and DFIG parameters. 相似文献
78.
79.
Silicon - This paper exemplifies an exhaustive, figurative and subjective study on the RF performance and DC characteristics analysis of an Underlapped Double-Gate (U-DG) AlGaN/GaN... 相似文献
80.
Aditi Bhadra Arnab Bandyopadhyay Rajendra Singh Narendra S. Raghuwanshi 《Water Resources Management》2010,24(13):3679-3700
Alternative delivery scheduling approaches were tried to overcome the problem of low efficiency in eastern Indian irrigation
projects. The features of the existing delivery schedules in the Left Bank Feeder Canal (LBFC) system of Kangsabati irrigation
project, located in the state of West Bengal, India, have been studied. Four simulation scenarios were considered in the study.
These are (1) actual canal scheduling with original transplanting date (S1), (2) Integrated Reservoir-based Canal Irrigation
Model (IRCIM) scheduling for usual transplanting date (S2), (3) IRCIM scheduling for 5 days advanced transplanting date (S3),
and (4) IRCIM scheduling for 5 days lagged transplanting date (S4). An attempt was made to develop a year-independent alternative
delivery schedule based on the analysis of 11 years simulation results with all the above scenarios. For maximum number of
simulation years, model performance was better for paddy transplanted on July 24, three irrigations from the reservoir between
transplanting and harvesting, and restricting the release to minimum rule curve (MRC), i.e., maintaining the stage on any
day above the minimum stage actually found in 16 years period. Hence, it was proposed as the year-independent alternative
delivery schedule. This alternative delivery schedule saved 18.36% irrigation water over actual schedules, but increased the
crop evapotranspiration by 0.61%. The proposed alternative delivery schedule also considered both the expected dry spells
as well as critical growth periods of the crop during the simulation period. Thus, it was recommended to adopt the alternative
delivery schedule instead of existing delivery schedule in the future years for the LBFC system of Kangsabati irrigation project. 相似文献