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Divergence Angle (divergence + angle)

Distribution by Scientific Domains
Engineering60%

Selected Abstracts

Modelling of a downdraft biomass gasifier with finite rate kinetics in the reduction zone

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2009
Prokash C. Roy
Abstract A model of a downdraft gasifier has been developed based on chemical equilibrium in the pyro-oxidation zone and finite rate kinetic-controlled chemical reactions in the reduction zone. The char reactivity factor (CRF) in the reduction zone, representing the number of active sites on the char and its degree of burn out, has been optimized by comparing the model predictions against the experimental results from the literature. The model predictions agree well with the temperature distribution and exit gas composition obtained from the experiments at CRF=100. A detailed parametric study has been performed at different equivalence ratios (between 2 and 3.4) and moisture content (in the range of 0,40%) in the fuel to obtain the composition of the producer gas as well as its heating value. It is observed that the heating value of the producer gas increases with the increase in the equivalence ratio and decrease in the biomass moisture content. The effect of divergence angle of the reduction zone geometry (in the range of 30,150°) on the temperature and species concentration distributions in the gasifier has been studied. An optimum divergence angle, giving the best quality of the producer gas, has been identified for a particular height of the reduction zone. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Laser diodes semicircular side-pumped laser rod with a round-sharped output

LASER PHYSICS LETTERS, Issue 7 2006
Y. X. Guo
Abstract In order to keep the symmetric of the pump geometry and obtain a low-level, high quality laser output, the temperature of the side-pumped laser rod is more often be controlled by a water cooling system than a conduction cooling system in the diode-pumped solid-state lasers. But the use of the water cooling system increases the volume and decreases the mobility. To solve the confliction between the beam quality and the mobility of the laser system, a novel, compact and all-solid design of the pump structure is applied to the side-pumped laser system. The Nd:YAG rod is pumped by semicircular mounted LD arrays inthe pump module, and two pump modules are working together to compensate each other. Numerical calculation and experiment are performed, the output laser has a round-sharped beam with a beam waist of 5 mm and a divergence angle less than 7 mrad, and a maxim output pulse energy of 75.8 mJ is obtained under the working frequency of 20Hz, the slope efficiency is 35.8%. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Characteristics of two-segment lensed fiber collimator

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010
Yu-Cheng Lin
Abstract A two-segment lensed fiber collimator using gradient index fiber (GIF) of 140 ,m diameter spliced to a coreless fiber (CLF) of 125 ,m, and a single mode fiber (SMF) is demonstrated. The CLF and GIF are treated as a beam expander and lens, respectively. The complex beam parameter method and ABCD law are applied for theoretical analysis. Both numerical and experimental data are presented for optical characterization of the divergence angle and insertion loss in lateral and axial displacement of the device. The divergence angle of 1.5 degrees is obtained for the wavelength of 1.31 ,m at the GIF length of 180 ± 5 ,m and the CLF length of 350 ,m. The variation of insertion loss due to lateral and axial displacement shows good agreement with theory. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1846,1848, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25353 [source]

Physiological and anatomical changes during the early ontogeny of the heteroblastic bromeliad, Vriesea sanguinolenta, do not concur with the morphological change from atmospheric to tank form

PLANT CELL & ENVIRONMENT, Issue 11 2004
G. ZOTZ
ABSTRACT Two distinct morphological forms characterize the ontogeny of many epiphytic bromeliads. Smaller plants exhibit an atmospheric habit, while larger plants form water-impounding tanks. The study of the functional significance of heteroblasty in epiphytes is severely hampered by considerable size-related variation in morphological, anatomical and physiological parameters. To overcome this problem, plants of varying size of both atmospheric and tank form were included in the present study with Vriesea sanguinolenta. The results show that virtually all morphological, anatomical and physiological characteristics vary during ontogeny, but changes were rarely directly related to the step change in gross morphology. Changes were either: (1) gradual from smallest atmospheric to small tank (e.g. leaf divergence angles, reduction in photosystem II efficiency during drought, speed of recovery after drought); (2) there was no change between atmospheric and small tank, but a gradual or step change within the tank form (stomatal density, relationship of leaf N and specific leaf area); or (3) developmental patterns were more complicated with decreases and increases during ontogeny (photosynthetic capacity, carbon isotope ratios, abscisic acid levels during drought). Although the comparisons between ontogenetic phases were always confounded by size differences, a hypothetical small tank plant is expected to suffer higher water loss than a real atmospheric, whereas a hypothetical, large atmospheric plant would show reduced access to resources, such as nutrients, in comparison with the real tank. The present results are consistent with the notion of heteroblasty as an adaptation of early ontogenetic stages to drought, but highlight that size-related variation greatly modifies any difference directly associated with the step change from atmospheric to tank. [source]