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121.
The effect of the shear modulus, size and dispersion of second phase particles on rate of growth of fatigue cracks in two-phase materials is determined using the kinetic theory approach. The results obtained explain the experimental observations in pearlitic steels.
Résumé L'étude du module de sélectivité de la dimension et de la disposition des particules de face secondaire sur la croissance de fissure de fatigue dans des matériaux comportant 2 faces a été déterminée en utilisant une théorie cynétique. Les résultats obtenus rendent compte des observations expérimentales effectuées dans les aciers perlitiques.相似文献
122.
Aud Traetteberg V. S. Ramachandran 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1974,24(3):157-170
A sequential examination of strength development in terms of microhardness was studied during paste hydration of C3S in the presence of 2 and 5% CaCl2 and at w/s ratios of 0.3 or 0.5. An attempt has been made to relate strength with microstructural features studied by means of Scanning Electron Microscopy. Generally, at earlier periods it was found that the 2% addition of CaCl2 gave the strongest material; the effect was most pronounced in the 6-month sample of the series with 0.3 w/s. The high strength for the sample prepared at a w/s ratio of 0.3 may be related to a high CaO/SiO2 C-S-H-phase, low porosity, and possibly a hydrated calcium hydroxy chloride complex. The pore size distribution was also measured. In general, the higher the porosity the lower the strengths but the relationship was not perfectly linear even on the semi-logarithmic plot. 相似文献
123.
P. A. Ramachandran B. D. Kulkarni Ajit Sadana 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1981,31(1):546-552
A general theory for the identification of criteria within which an enzymic reaction can exhibit multiplicity (i.e. multiple steady states) is reviewed. Application of the theory to four types of kinetic models encountered in biochemical reactions is illustrated and figures are presented to delineate the region of multiplicity. The stability of the steady states is analysed for small perturbation about the steady state. 相似文献
124.
The addition reaction between the compacted powders of phthalic anhydride and p-nitroaniline was studied. Both the reactants of equal particle size, were mixed in 1-to-1 molar ratio and compacted. Three particle sizes — 0.0065 cm, 0.0178 cm and 0.0376 cm and three compaction pressures — 302.0 kgf/cm2, 785.0 kgf/cm2 and 1208.0 kgf/cm2 were used for the study. Conversions were measured at 80°, 90°, 100°, 110° and 120°C for 1/2, 1, 2, 4, 8, 12, 16, 20 and 24 hours. The reaction rate changed to a constant value, after an initial phase boundary process. The mole percentage conversions increased with decrease in particle size, increase in compaction pressure corresponding to a decrease in the initial porosity of the compact. It was also observed that the final porosity of the compact increased with increase in reaction temperature. Combination of Jander's model and parabolic rate law was used to calculate the values of the reaction rate constant equivalent. The activation energy was calculated to be 14 to 34 kilocalories per gram mole. 相似文献
125.
The electron spin resonance spectrum of the nitroxide label 2,2,6,6 – TetraMethyl – 4 – Piperidone – Oxide (TEMPO) has been investigated in aqueous solutions of a purified and commercially available impure samples of sodium lauryl sulphate (NaLS) for a wide range of concentrations. The spectra were recorded at 24°C as a function of surfactant concentration. The reorientational correlation times Tθ of the TEMPO label in aqueous solutions were calculated using the Kivelson's theory. Using the Tθ data qualitative analysis has been carried out in an attempt to understand the microscopic effects produced by the hydrophobic part of the surfactant on the water structure and the hydrophobic-hydrophobic interactions in water. Four major discontinuities in the τθ results have been identified with the purified NaLS system. They are found to occur at NaLS concentrations of 0.008 wt.%, 0.015 wt.%, 0.23 and 1.73 wt.%. The latter two concentrations represent the first and the second critical micelle concentration (CMC) of the surfactant while the first two concentrations reveal the existence of premicellar association and dissociation processes, respectively. These discontinuities have been also confirmed by the pH data and by surface tension results from the du Noüy ring method. The effect of addition of lauryl alcohol and sodium chloride on τθ values was also studied. The additive action has been found to produce an additional discontinuity, corresponding to the mixture CMC, in the τθ versus concentration plot. Analysis of other effects such as solution aging and hydrolysis of NaLS are also included. The applicability of the spin labelling technique for the study of aqueous solution behavior of NaLS is discussed by comparing data reported in the literature. 相似文献
126.
127.
This paper discusses the significance of segmental and prosodic knowledge sources for developing a text-to-speech system for
Indian languages. Acoustic parameters such as linear prediction coefficients, formants, pitch and gain are prestored for the
basic speech sound units corresponding to the orthographic characters of Hindi. The parameters are concatenated based on the
input text. These parameters are modified by stored knowledge sources corresponding to coarticulation, duration and intonation.
The coarticulation rules specify the pattern of joining the basic units. The duration rules modify the inherent duration of
the basic units based on the linguistic context in which the units occur. The intonation rules specify the overall pitch contour
for the utterance (declination or rising contour), fall-rise patterns, resetting phenomena and inherent fundamental frequency
of vowels. Appropriate pauses between syntactic units are specified to enhance intelligibility and naturalness. 相似文献
128.
We generalize earlier results in VLSI layout theory by considering variable aspect ratio embeddings for VLSI graphs. By aspect ratio we mean the ratio of the length of the longer side to the length of the shorter side of the bounding rectangle of the embedding. Our results are based on separators and bifurcators. We obtain embeddings with existentially optimal area and any desired aspect ratio. Additionally, we can obtain either bounded capacitive delay or existentially optimal minimax edge length in the embeddings; both of these features reduce delays in the circuit. A special feature of our results on minimax edge length is that they unify earlier separator- and bifurcator-based results for square embeddings, and also provide a simplified lower bound proof. 相似文献
129.
A Multi-radio 802.11 Mesh Network Architecture 总被引:2,自引:0,他引:2
Krishna Ramachandran Irfan Sheriff Elizabeth M. Belding Kevin Almeroth 《Mobile Networks and Applications》2008,13(1-2):132-146
The focus of this paper is to offer a practical multi-radio mesh network architecture that can realize the benefits of multiple radios. Our architecture provides solutions to challenges in three key areas. The first is the construction of a split wireless router that enables modular wireless mesh routers to be constructed from commodity hardware. The second is the design of a centralized channel assignment algorithm that considers the inter-dependence between channel assignment and routing in order to create high-throughput channel-diversified routes. Third is the design and implementation of several communication protocols that are necessary to make our architecture operational. Our system is comprehensively evaluated on a 20-node multi-radio wireless testbed. Results demonstrate that our architecture makes feasible the deployment of large-scale high-capacity multi-radio mesh networks built entirely with commodity hardware. Our implementation is available to the community for research and development purposes. 相似文献
130.
Gonadotropin-inhibitory hormone (GnIH) receptor gene is expressed in the chicken ovary: potential role of GnIH in follicular maturation 总被引:1,自引:0,他引:1
Maddineni SR Ocón-Grove OM Krzysik-Walker SM Hendricks GL Ramachandran R 《Reproduction (Cambridge, England)》2008,135(2):267-274
Gonadotropin-inhibitory hormone (GnIH), an RFamide peptide, has been found to inhibit pituitary LH secretion in avian and mammalian species. The gene encoding a putative receptor for GnIH (GnIHR) was recently identified in the chicken and Japanese quail brain and pituitary gland. GnIHR appears to be a seven-transmembrane protein belonging to a family of G-protein-coupled receptors. In the present study, we have characterized the expression of GnIHR mRNA in the chicken ovary and demonstrate that GnIHR may exert an inhibitory effect on ovarian follicular development. By RT-PCR, we detected GnIHR mRNA in the chicken testis and in the ovary, specifically both thecal and granulosa cell layers. Real-time quantitative PCR analysis revealed greater GnIHR mRNA quantity in theca cells of prehierarchial follicles compared with that of preovulatory follicles. GnIHR mRNA quantity was significantly decreased in sexually mature chicken ovaries versus ovaries of sexually immature chickens. Estradiol (E(2)) and/or progesterone (P(4)) treatment of sexually immature chickens significantly decreased ovarian GnIHR mRNA abundance. Treatment of prehierarchial follicular granulosa cells in vitro with chicken GnIH peptide significantly decreased basal but not FSH-stimulated cellular viability. Collectively, our results indicate that the ovarian GnIHR is likely to be involved in ovarian follicular development. A decrease in ovarian GnIHR mRNA abundance due to sexual maturation or by E(2) and/or P(4) treatment would implicate an inhibitory role for GnIHR in ovarian follicular development. Furthermore, GnIH may affect follicular maturation by decreasing the viability of prehierarchial follicular granulosa cells through binding to GnIHR. 相似文献