Empirical Relation (empirical + relation)

Distribution by Scientific Domains


Selected Abstracts


A design database for moulded pulp packaging structure

PACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2004
X. Ma
Abstract In this study, a structural factor approach is developed to allow a modular design method be used for the packaging design of thin-walled structures. Numerical simulations of the structural units are carried out to evaluate the influence of the structural factors under static loading, by using the commercial finite element code ABAQUS/Explicit. Empirical relations between the load-bearing capacity of structural units and structural factors are established based on numerical simulations. A database is then constructed that has the ability to provide valuable information for the loading performances of different structural units. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Empirical prediction of debris-flow mobility and deposition on fans

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2010
Christian Scheidl
Abstract A new method to predict the runout of debris flows is presented. A data base of documented sediment-transporting events in torrent catchments of Austria, Switzerland and northern Italy has been compiled, using common classification techniques. With this data we test an empirical approach between planimetric deposition area and event volume, and compare it with results from other studies. We introduce a new empirical relation to determine the mobility coefficient as a function of geomorphologic catchment parameters. The mobility coefficient is thought to reflect some of the flow properties during the depositional part of the debris-flow event. The empirical equations are implemented in a geographical information system (GIS) based simulation program and combined with a simple flow routing algorithm, to determine the potential runout area covered by debris-flow deposits. For a given volume and starting point of the deposits, a Monte-Carlo technique is used to produce flow paths that simulate the spreading effect of a debris flow. The runout zone is delineated by confining the simulated potential spreading area in the down slope direction with the empirically determined planimetric deposition area. The debris-flow volume is then distributed over the predicted area according to the calculated outflow probability of each cell. The simulation uses the ARC-Objects environment of ESRI© and is adapted to run with high resolution (2·5,m × 2·5,m) digital elevation models, generated for example from LiDAR data. The simulation program called TopRunDF is tested with debris-flow events of 1987 and 2005 in Switzerland. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Predicting the probability of detecting organochlorine pesticides and polychlorinated biphenyls in stream systems on the basis of land use in the Pacific Northwest, USA,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000
Robert W. Black
Abstract We analyzed streambed sediment and fish tissue (Cottus sp.) at 30 sites in the Puget Sound and Willamette basins in Washington and Oregon, USA, respectively, for organochlorine pesticides and polychlorinated biphenyls (PCBs). The study was designed to determine the concentrations of organochlorine pesticides and PCBs in fish tissue and sediment by land use within these basins and to develop an empirical relation between land use and the probability of detecting these compounds in fish tissue or sediment. We identified 14 organochlorines in fish tissue and sediment; three compounds were unique to either fish tissue or sediment samples. The highest number of organochlorines detected in both fish tissue and streambed sediment was at those sites located in watersheds dominated by urban land uses. Using logistic regression, we found a significant relation between percentage agriculture and urban land use and organochlorines in fish tissue. The results of this study indicate that organochlorine pesticides and PCBs are still found in fish tissues and bed sediments in these two basins. In addition, we produced statistically significant models capable of predicting the probability of detecting specific organochlorines in fish on the basis of land use. Although the presented models are specific to the two study basins, the modeling approach could be applied to other basins as well. [source]


Raman microscopy of the mixite mineral BiCu6(AsO4)3(OH)6·3H2O from the Czech Republic

JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2010
Ray L. Frost
Abstract Raman microscopy of the mixite mineral BiCu6(AsO4)3(OH)6·3H2O from Jáchymov and from Smrkovec (both Czech Republic) has been used to study their molecular structure. The presence of (AsO4)3,, (AsO3OH)2,, (PO4)3, and (PO3OH)2, units, as well as molecular water and hydroxyl ions, was inferred. OH···O hydrogen bond lengths were calculated from the Raman and infrared spectra using Libowitzky's empirical relation. Small differences in the Raman spectra between both samples were observed and attributed to compositional and hydrogen-bonding network differences. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Raman spectroscopic study of the uranyl selenite mineral marthozite Cu[(UO2)3(SeO3)2O2]·8H2O

JOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2008
Ray L. Frost
Abstract The mineral marthozite, a uranyl selenite, has been characterised by Raman spectroscopy at 298 K. The bands at 812 and 797 cm,1 were assigned to the symmetric stretching modes of the (UO2)2+ and (SeO3)2, units, respectively. These values gave the calculated UO bond lengths in uranyl of 1.799 and/or 1.814 Å. Average UO bond length in uranyl is 1.795 Å, inferred from the X-ray single crystal structure analysis of marthozite by Cooper and Hawthorne. The broad band at 869 cm,1 was assigned to the ,3 antisymmetric stretching mode of the (UO2)2+ (calculated UO bond length 1.808 Å). The band at 739 cm,1 was attributed to the ,3 antisymmetric stretching vibration of the (SeO3)2, units. The ,4 and the ,2 vibrational modes of the (SeO3)2, units were observed at 424 and 473 cm,1. Bands observed at 257, and 199 and 139 cm,1 were assigned to OUO bending vibrations and lattice vibrations, respectively. OH···O hydrogen bond lengths were inferred using Libowiztky's empirical relation. The infrared spectrum of marthozite was studied for complementation. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Spacer layer thickness effects on the photoluminescence properties of InAs/GaAs quantum dot superlattices

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2003
B. Ilahi
Abstract InAs/GaAs vertically stacked self-assembled quantum dot (QD) structures with different GaAs spacer layer thicknesses are grown by solid source molecular beam epitaxy (SSMBE) and investigated by transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. An increase in the polarization anisotropy is observed when the spacer layer thickness decreases. For a 10 monolayer (ML) thick inter-dots GaAs spacer, the TEM image shows an increase in the QD size when moving to the upper layer accompanied by the generation of dislocations. Consequently, the corresponding temperature-dependant PL properties are found to exhibit an unusual behaviour. The main PL peak is quenched at a temperature around 190 K giving rise to a broad background correlated with the formation of a miniband in the growth direction due to the strong interlayer coupling. For a thicker GaAs spacer layer (30 ML), multilayer QDs align vertically in stacks with no apparent structural defects. Over the whole temperature range, the excitonic band energies are governed by the Varshni empirical relation using InAs bulk parameters and the PL line width shows a slight monotonic increase. For a thinner GaAs interlayer, the thermal activation energies of the carrier emission out of the quantum dots are found to be considerably small (about 25 meV) due to the existence of defects. By combining these structural and optical results, we can conclude that a thinner GaAs spacer has a poorer quality. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Prediction of new displacive ferroelectrics through systematic pseudosymmetry search.

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2002
Pmc21 symmetry, Results for materials with Pba
Polar structures with pseudosymmetry related to a hypothetical non-polar configuration are considered as good candidates for ferroelectrics. Recently, a procedure has been developed for a systematic pseudosymmetry search among structures with a given space-group symmetry. The aim of this paper is the extension of the pseudosymmetry procedure to the case of structures with polar symmetry and its application in the search for new ferroelectrics. The results obtained by the generalized pseudosymmetry search among the compounds with symmetries and listed in the Inorganic Crystal Structure Database are discussed. The calculations have been performed by the program PSEUDO, which forms part of the Bilbao Crystallographic Server (http://www.cryst.ehu.es). In addition, an empirical relation between the atomic displacements necessary to reach the non-polar structure and the transition temperature is proposed and compared with the Abrahams,Kurtz,Jamieson relation. [source]


Magnetic activity on 12 Cam and 29 Dra from long-term photometry

ASTRONOMISCHE NACHRICHTEN, Issue 4 2009
M. Zboril
Abstract We present newly discovered magnetic cycles of two late-type and long-period SB1 systems: 12 Cam and 29 Dra. The long-term photometry study revealed the presence of magnetic multiperiodic cycles on both stars, namely 14.8 and 8.5 yr for 12 Cam and 20.3, 11.1, and 7.6 yr for 29 Dra. Furthermore, the modelling of the V -band light curves revealed the existence of two active longitudes on 12 Cam and probably on 29 Dra as well. Both stars show changes of rotational period. The 12 Cam is the slowest rotating star whose activity cycle has been determined. The activity cycles determined by us allow us to extend to the slower rotation regime and to improve the significance of the empirical relation between rotation period and magnetic cycle length (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


The Interest Rate Risk Exposure of Financial Intermediaries: A Review of the Theory and Empirical Evidence

FINANCIAL MARKETS, INSTITUTIONS & INSTRUMENTS, Issue 4 2003
By Sotiris K. Staikouras
The paper surveys current and previous research on financial institutions' interest rate risk exposure. The implications of such exposure are discussed and motivating insights are emphasized. Various theoretical frameworks and models are presented. For each one an overview of the studies and any relationship to each other is provided. In a cross-industry analysis, other idiosyncratic risk factors are considered and their importance is delineated. A number of empirical relations are established. More specifically, there is an inverse relationship between interest rate changes and common stock returns of financial institutions. The intermediaries' apparent yield sensitivity is mainly attributed to the duration gap inherent in their balance sheet structure. Furthermore, the aforesaid equity sensitivity due to other possible dynamics such as dividend yield, unanticipated inflation and regulatory lags is also considered. Changes in economic regimes have altered volatility in market yields with a subsequent effect, positive or negative, on financial intermediaries' equity returns. The issue of the risk-return compensation is further analyzed, and findings suggest that the interest rate risk is priced by capital markets. Finally, a few other issues are identified as avenues for future research. [source]


Accurate fundamental parameters for lower main-sequence stars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006
Luca Casagrande
ABSTRACT We derive an empirical effective temperature and bolometric luminosity calibration for G and K dwarfs, by applying our own implementation of the Infrared Flux Method to multiband photometry. Our study is based on 104 stars for which we have excellent BV(RI)CJHKS photometry, excellent parallaxes and good metallicities. Colours computed from the most recent synthetic libraries (ATLAS9 and MARCS) are found to be in good agreement with the empirical colours in the optical bands, but some discrepancies still remain in the infrared. Synthetic and empirical bolometric corrections also show fair agreement. A careful comparison to temperatures, luminosities and angular diameters obtained with other methods in the literature shows that systematic effects still exist in the calibrations at the level of a few per cent. Our Infrared Flux Method temperature scale is 100-K hotter than recent analogous determinations in the literature, but is in agreement with spectroscopically calibrated temperature scales and fits well the colours of the Sun. Our angular diameters are typically 3 per cent smaller when compared to other (indirect) determinations of angular diameter for such stars, but are consistent with the limb-darkening corrected predictions of the latest 3D model atmospheres and also with the results of asteroseismology. Very tight empirical relations are derived for bolometric luminosity, effective temperature and angular diameter from photometric indices. We find that much of the discrepancy with other temperature scales and the uncertainties in the infrared synthetic colours arise from the uncertainties in the use of Vega as the flux calibrator. Angular diameter measurements for a well-chosen set of G and K dwarfs would go a long way to addressing this problem. [source]