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Constant Parameters (constant + parameter)
Selected AbstractsA fractal comminution approach to evaluate the drilling energy dissipationINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2002Alberto Carpinteri The drilling comminution is theoretically and experimentally analysed by a fractal approach. An extension of the Third Comminution Theory is developed to evaluate the energy dissipation in the process: it occurs in a fractal domain intermediate between a surface and a volume. The theoretical assumption of a material ,quantum' is experimentally observed. The experimental fragment analysis evidences the characteristic size of separation between primary cutting and secondary milling. A global power balance for the drilling process is also presented and permits the prediction of drilling velocity. It shows also how the dissipation energy density (drilling strength) is not a constant parameter, but decreases considerably with the size scale. Copyright © 2002 John Wiley & Sons, Ltd. [source] The influence of species and growing conditions on the 18-O enrichment of leaf water and its impact on ,effective path length'NEW PHYTOLOGIST, Issue 3 2009Ansgar Kahmen Summary ,,The stable oxygen isotope ratio (,18O) of plant material has been shown to contain essential information on water and carbon fluxes at the plant and ecosystem scales. However, the effective path length (Lm), a parameter introduced to leaf-water models still requires a comprehensive biological characterization to allow interpretation of ,18O values in plant material with confidence. ,,Here, we tested the variability of Lm across and within three species that developed leaves in environments with different relative humidity. We also tested whether the Lm of fully developed leaves is affected by short-term fluctuations in relative humidity. ,,We determined that significant differences in Lm exist among Phaseolus vulgaris, Rizinus communis and Helianthus annuus. Within a given species, however, Lm values did not differ significantly among individuals. ,,These findings indicate that Lm is species specific and a relatively constant parameter and that Lm will not obscure the interpretation of ,18O values in plant material of a given species. We urge caution, however, because values for Lm are derived from fitting leaf-water models to measured values of ,18O, so care must be taken in assigning a ,cause' to values of Lm as they likely capture a combination of different biological leaf properties [source] Yet another look at the reaction CH3 + H + M = CH4 + MINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2008David M. GoldenArticle first published online: 10 APR 200 Rate and equilibrium constant parameters for the title system have been evaluated. In general the format used by Baulch et al. (J Phys Chem Ref Data 2005, 34, 757) is compatible with the results. For Ar as the bath gas, the following parameters are suggested: k0 (cm6 molec,2 s,1) = 1.53 × 10,23T,2.17 with Fc = 0.876 exp(,T/1801) + 0.124 exp(,T/33.1). k, = 3.5 × 10,10 cm3 molec,1 s,1 as suggested in Baulch et al. (2005). However, since master equation calculations based on a hindered-Gorin transition state along with an exponential-down energy transfer model (Golden et al., J Phys Chem 2003, 107, 11057,11057) have been carried out herein and compared with data, the results can be stored in lookup tables, avoiding errors introduced by universal expressions, or values can be computed on the fly using the parameters for the master equation calculation given in the paper. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 310,319, 2008 [source] Optical and electronic conduction behavior in germanium ferrite additive with transition metalPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2007S. A. Fayek Abstract The effects of adding transition metals (Ni and Co) on the optical and electrical properties of four thin films Ni1.25Fe1.5Ge0.25O4, Ni1.5Fe1Ge0.5O4, Co1Fe1Ge0.5O4 and Co1.25Fe1.5Ge0.25O4 are reported. X-ray diffraction was used to ascertain the amorphization nature of the deposited films. The optical absorption behavior of these films was studied from the transmission and reflection in the range 200,1100 nm. It was found that the optical band gap increases on increasing GeO2 and arises from direct forbidden transitions. The opposite trend was found with the band tail width of the localized state. Optical constant parameters such as refractive index and absorption index were obtained for the films. The results for the alternating-current (ac) conductivity and the dielectric constant of the four films are presented over the temperature range 277,357 K and the frequency range 0.1 to 1000 kHz. The ac conductivity increases with temperature and frequency and decreases with the increase in Ni2+ or Co2+ content. The effect of composition and temperature on the dielectric constant was also studied. The frequency variation of the dielectric constant does not have a peak, unlike many semiconductor glasses. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Progress from forecast failure,the Norwegian consumption functionTHE ECONOMETRICS JOURNAL, Issue 1 2002Řyvind Eitrheim After a forecast failure, a respecification is usually necessary to account for the data ex post, in which case there is a gain in knowledge as a result of the forecast failure. Using Norwegian consumption as an example, we show that the financial deregulation in the mid-1980s led to forecast failure both for consumption functions (CFs) and Euler equations (EEs). We argue in the paper that such forecast failures would appear to be at odds with an underlying DGP belonging to the class of EEs, a result that also explains why progress took the form of a respecified CF where wealth plays a central role. That model is updated and is shown to have constant parameters despite huge changes in the income to wealth ratio over nine years of new data. [source] Experimental validation of a high-gain observer for composition estimation in an ethanol,water distillation columnASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009A. C. Téllez-Anguiano Abstract In this paper a high-gain observer used to estimate the product compositions in a distillation column for a non-ideal mixture (ethanol,water) through the tray temperature measurements is presented. The design of this observer is based on a simplified mathematical model. One of the main advantages of this observer is its constant gain, therefore its tuning depends only on choosing a few constant parameters satisfying some simple algebraic inequalities. The effectiveness of the proposed method is demonstrated through on-line experiments in a distillation pilot plant. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||