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71.
James R. Currie Ashok K. Batra Mohammad A. Alim Manmohan D. Aggarwal Ravindra B. Lal 《Journal of Materials Science: Materials in Electronics》2007,18(4):433-439
Polycrystalline SnO2 samples prepared in the laboratory were irradiated with 2 MeV He ions having doses of 3.62 × 1015 ion/cm2. The ac small-signal electrical data acquired for the polycrystalline SnO2 in the frequency (f) range 100 Hz ≤ f ≤ 1 MHz and temperature (T) range 26°C ≤ T ≤ 100°C revealed one semicircular relaxation in the impedance plane for the He implanted sample. However, two semicircular
relaxations were obtained in the same plane for the samples without He implantation. The He implantation indicated enhancement
in the donor density in the polycrystalline SnO2 as depicted via terminal conductance (or resistance).
An erratum to this article can be found at 相似文献
72.
Tso Yee Fan Ripin D.J. Aggarwal R.L. Ochoa J.R. Bien Chann Tilleman M. Spitzberg J. 《IEEE journal of selected topics in quantum electronics》2007,13(3):448-459
Cryogenically cooled solid-state lasers promise a revolution in power scalability while maintaining a good beam quality because of significant improvements in efficiency and thermo-optic properties. This is particularly true for Yb lasers because of their relatively low quantum defect and relatively broadband absorption even at cryogenic temperatures. Thermo-optic properties of host materials, including thermal conductivity, thermal expansion, and refractive index at low temperature, are reviewed and data presented for YAG (ceramic and single crystal), GGG, GdVO4, and Y2O3. Spectroscopic properties of Yb:YAG and Yb:LiYF4 (YLF) including absorption cross sections, emission cross sections, and fluorescence lifetimes at cryogenic temperatures are characterized. Recent experiments have pushed the power from an end-pumped cryogenically cooled Yb:YAG laser to 455-W continuous-wave output power from 640-W incident pump power at an of M2 1.4. 相似文献
73.
74.
Hevea brasiliensis ) esterified with acetic anhydride, maleic anhydride and phthalic anhydride was studied for moisture adsorption behaviour.
FTIR spectroscopic technique was used to analyse the chemical changes in the wood through the correspondent reactions. Spectra
indicated increasing intensity of the C=O and C-O stretching bands, and reduction in O-H stretching vibrations that reflects
formation of less hygroscopic ester bonds with hydroxyl groups of cell wall polymers. Moisture adsorption isotherms show low
equilibrium moisture content in esterified wood at all relative humidity values as compared to a control. The adsorption data
was analysed by applying Hailwood-Horrobin theory which separated the adsorbed water into hydrated water and dissolved water
corresponding to mono-layer and multi-layer adsorption. Curve for Mh and Ms were similar in pattern for esterified wood and control with different magnitude. Low Mh and Ms in esterified wood indicate reduction in moisture adsorption sites. Inaccessible fraction of wood for water vapour was increased
by 43%, 32% and 26% in acetic, maleic and phthalic anhydride treated wood, respectively, compared to the control. Acetic anhydride
treatment was found most effective in reducing hygroscopicity of wood.
Hevea brasiliensis ) wurde verestert mit Anhydriden der Maleins?ure, Essigs?ure und Phtals?ure. Das Adsorptionsverhalten bei verschiedenen Feuchten wurde mit FTIR-Methoden untersucht, um die entsprechenden chemischen Abl?ufe zu erfassen. Intensivere C=O, und -C-O- Streckschwingungen sowie reduzierte OH-Schwingungen reflektieren die neu gebildeten, weniger hygroskopischen Esterbindungen. Bei allen modifizierten Proben ergaben sich niedrigere Gleichgewichtsfeuchten. Die Adsorptions-Isothermen wurden mit Hilfe der Hailwood-Horrobin Theorie analysiert, um adsorbiertes (Mh) und gel?stes (Ms) Wasser zu unterscheiden. Der Kurvenverlauf für Mh und Ms für modifiziertes und unbehandeltes Holz war qualitativ ?hnlich, und unterschied sich nur quantitativ. Geringe Werte für Mh und Ms zeigen eine Verringerung der m?glichen Adsorptionsstellen an. Der nicht zug?ngliche Anteil des Holzes, bezogen auf Kontrollproben, verringerte sich auf 43% (Acetanhydrid), 32% (Maleins?ureanhydrid) und 26% (Phthals?ureanhydrid). Acetanhydrid erwies sich als das effektivste Mittel, um die Hygroskopizit?t zu erniedrigen.相似文献
75.
76.
Zirconia-mullite composites were prepared byin situ reaction between zircon and alumina. Stabilizers like yttria and magnesium carbonate were used. Almost vitrified bodies were
obtained by sintering at 1465–1535°C. Flexural strength increased on annealing at 1040°C. 相似文献
77.
78.
Redefining clustering for high-dimensional applications 总被引:1,自引:0,他引:1
Clustering problems are well-known in the database literature for their use in numerous applications, such as customer segmentation, classification, and trend analysis. High-dimensional data has always been a challenge for clustering algorithms because of the inherent sparsity of the points. Recent research results indicate that, in high-dimensional data, even the concept of proximity or clustering may not be meaningful. We introduce a very general concept of projected clustering which is able to construct clusters in arbitrarily aligned subspaces of lower dimensionality. The subspaces are specific to the clusters themselves. This definition is substantially more general and realistic than the currently available techniques which limit the method to only projections from the original set of attributes. The generalized projected clustering technique may also be viewed as a way of trying to redefine clustering for high-dimensional applications by searching for hidden subspaces with clusters which are created by interattribute correlations. We provide a new concept of using extended cluster feature vectors in order to make the algorithm scalable for very large databases. The running time and space requirements of the algorithm are adjustable and are likely to trade-off with better accuracy 相似文献
79.
K. K. Aggarwal 《Sadhana》1987,11(1-2):155-165
The complexity of computer communication networks has taken a dramatic upswing, following significant developments in electronic
technology such as medium and large scale integrated circuits and microprocessors. Although components of a computer communication
network are broadly classified into software, hardware and communications, the most important problem is that of ensuring
the reliable flow of information from source to destination.
An important parameter in the analysis of these networks is to find the probability of obtaining a situation in which each
node in the network communicates with all other remaining communication centres (nodes). This probability, termed as overall
reliability, can be determined using the concept of spanning trees.
As the exact reliability evaluation becomes unmanageable even for a reasonable sized system, we present an approximate technique
using clustering methods. It has been shown that when component reliability ⩾ 0.9, the suggested technique gives results quite
close to those obtained by exact methods with an enormous saving in computation time and memory usage.
For still quicker reliability analysis while designing the topological configuration of real-time computer systems, an empirical
form of the reliability index is proposed which serves as a fairly good indicator of overall reliability and can be easily
incorporated in a design procedure, such as local search, to design maximally reliable computer communication network. 相似文献
80.