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Linear Extrapolation (linear + extrapolation)
Selected AbstractsEffect of Ti addition on magnetic properties of TbCu7 -type Sm-Fe-Co-Mn system nitridesELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 7 2008Hiroshi Yamamoto Abstract To support the development of high-performance isotropic bonded magnets, experiments were carried out to investigate the effect of Ti addition on the magnetic properties of Sm-Fe-Co-Mn system nitride compounds with TbCu7 -type structure. Sm10(Fe0.9Co0.1)89.5,xMn0.5Tix (x=0 to 1.0) alloy ribbons were prepared by the single-roller rapid-quenching method. The effects of alloy composition and of heat treatment and nitriding conditions on the magnetic properties were examined. The optimum preparation conditions of the compounds were as follows. Composition: {Sm10(F0.9Co0.1)89Mn0.5Ti0.5}86.8N13.2; roller speed: 50 m/s; heat treatment: 700°C×60 min in high-purity Ar gas; nitriding conditions: 420°C×15 h in high-purity N2 gas. Typical magnetic properties of the obtained compound powders were Jr = 0.97 T, HcJ = 730.8 kA/m,(BH)max = 140.0 kJ/m3 (17.6 MGOe), Tc=500°C. XRD, TEM photographs, and recoil loops of the hysteresis curve demonstrated that this sample had the characteristics of an exchange spring magnet. The value of (BH)max for the isotropic compression molding bonded magnet prepared from the {Sm10(F0.9Co0.1)89Mn0.5Ti0.5}86.8N13.2 powder was 94.8 kJ/m3 (11.9 MGOe) at a bonded magnet density of 6.07 Mg/m3. The reversible temperature coefficient of Jr was ,(Jr)=,0.04%/°C and the temperature coefficient of HcJ in the range from 25°C to 125°C obtained by linear extrapolation was ,(HcJ)=,0.40%/°C. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(7): 25,31, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10124 [source] An empirical method for inferring species richness from samplesENVIRONMETRICS, Issue 2 2006Paul A. Murtaugh Abstract We introduce an empirical method of estimating the number of species in a community based on a random sample. The numbers of sampled individuals of different species are modeled as a multinomial random vector, with cell probabilities estimated by the relative abundances of species in the sample and, for hypothetical species missing from the sample, by linear extrapolation from the abundance of the rarest observed species. Inference is then based on likelihoods derived from the multinomial distribution, conditioning on a range of possible values of the true richness in the community. The method is shown to work well in simulations based on a variety of real data sets. Copyright © 2005 John Wiley & Sons, Ltd. [source] Spatiotemporal characterization of interswarm period seismicity in the focal area Nový Kostel (West Bohemia/Vogtland) by a short-term microseismic studyGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2009Martin Häge SUMMARY The West Bohemia/Vogtland region is one of the seismically most interesting areas in Europe because of its swarm-like occurrence of seismicity. The installation of the local West Bohemian seismological network (WEBNET) has made the recording of small magnitude seismicity (detection threshold ML,,0.5) possible. We investigated if microseismicity exists below the detection threshold of WEBNET. A microseismic field campaign was carried out in the focal area Nový Kostel. The measurement was performed with three small arrays lasting for 6 d in a seismically quiet, interswarm period. We were able to detect and locate 13 microearthquakes in the magnitude range ,1.5 ,ML,,0.1 and achieved a detection threshold about one magnitude lower than the local network. A relative location suggests that the recorded seismicity is rather related to a specific fault segment than randomly distributed. The determined fault zone is aligned NW,SW and confirms the viability of mapping active faults with short-term measurements. The results demonstrate that a linear extrapolation of the b -value, determined by the network bulletin, down to ML=,0.5 fits well with the amount of our recorded events. [source] Uncertainties in interpretation of isotope signals for estimation of fine root longevity: theoretical considerationsGLOBAL CHANGE BIOLOGY, Issue 7 2003YIQI LUOArticle first published online: 25 JUN 200 Abstract This paper examines uncertainties in the interpretation of isotope signals when estimating fine root longevity, particularly in forests. The isotope signals are depleted ,13C values from elevated CO2 experiments and enriched ,14C values from bomb 14C in atmospheric CO2. For the CO2 experiments, I explored the effects of six root mortality patterns (on,off, proportional, constant, normal, left skew, and right skew distributions), five levels of nonstructural carbohydrate (NSC) reserves, and increased root growth on root ,13C values after CO2 fumigation. My analysis indicates that fitting a linear equation to ,13C data provides unbiased estimates of longevity only if root mortality follows an on,off model, without dilution of isotope signals by pretreatment NSC reserves, and under a steady state between growth and death. If root mortality follows the other patterns, the linear extrapolation considerably overestimates root longevity. In contrast, fitting an exponential equation to ,13C data underestimates longevity with all the mortality patterns except the proportional one. With either linear or exponential extrapolation, dilution of isotope signals by pretreatment NSC reserves could result in overestimation of root longevity by several-fold. Root longevity is underestimated if elevated CO2 stimulates fine root growth. For the bomb 14C approach, I examined the effects of four mortality patterns (on,off, proportional, constant, and normal distribution) on root ,14C values. For a given ,14C value, the proportional pattern usually provides a shorter estimate of root longevity than the other patterns. Overall, we have to improve our understanding of root growth and mortality patterns and to measure NSC reserves in order to reduce uncertainties in estimated fine root longevity from isotope data. [source] Inter-relations between experimental and computational aspects of slope stability analysisINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2003R. Baker Abstract Most conventional slope stability calculations are based on the linear Mohr,Coulomb failure criterion. However, a substantial amount of experimental evidence suggests that failure criteria of many soils are not linear particularly in the range of small normal stresses. This departure from linearity is significant for slope stability calculations since for a wide range of practical stability problems, critical slip surfaces are shallow and normal stresses acting on such surfaces are small. There exists a technical difficulty in performing strength measurements in the range of small normal stresses relevant to such slope stability problems. As a result, in many practical situations strength measurements are performed at much larger normal stresses then those relevant for the stability problem under consideration. When this is the case, use of the Mohr,Coulomb criterion amounts to a linear extrapolation of experimental information (obtained at large normal stresses), into the range of small normal stresses, which is relevant to the problem. This extrapolation results with very significant overestimation of calculated safety factors in cases when there is large mismatch between experimental and relevant ranges of normal stresses. The present work delineates the extent of this problem and suggests a practical way to overcome it. Copyright © 2003 John Wiley & Sons, Ltd. [source] Structure-factor extrapolation using the scalar approximation: theory, applications and limitationsACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2007Ulrich K. Genick For many experiments in macromolecular crystallography, the overall structure of the protein/nucleic acid is already known and the aim of the experiment is to determine the effect a chemical or physical perturbation/activation has on the structure of the molecule. In a typical experiment, an experimenter will collect a data set from a crystal in the unperturbed state, perform the perturbation (i.e. soaking a ligand into the crystal or activating the sample with light) and finally collect a data set from the perturbed crystal. In many cases the perturbation fails to activate all molecules, so that the crystal contains a mix of molecules in the activated and native states. In these cases, it has become common practice to calculate a data set corresponding to a hypothetical fully activated crystal by linear extrapolation of structure-factor amplitudes. These extrapolated data sets often aid greatly in the interpretation of electron-density maps. However, the extrapolation of structure-factor amplitudes is based on a mathematical shortcut that treats structure factors as scalars, not vectors. Here, a full derivation is provided of the error introduced by this approximation and it is determined how this error scales with key experimental parameters. The perhaps surprising result of this analysis is that for most structural changes encountered in protein crystals, the error introduced by the scalar approximation is very small. As a result, the extrapolation procedure is largely limited by the propagation of experimental uncertainties of individual structure-factor amplitudes. Ultimately, propagation of these uncertainties leads to a reduction in the effective resolution of the extrapolated data set. The program XTRA, which implements SASFE (scalar approximation to structure-factor extrapolation), performs error-propagation calculations and determines the effective resolution of the extrapolated data set, is further introduced. [source] Oligomer-to-Polymer Transition in Short Ethylene Glycol Chains Connected to Mobile Hydrophobic AnchorsCHEMPHYSCHEM, Issue 1 2005Motomu Tanaka Dr. Abstract We studied the structure of short ethylene glycol (EG) chains with N repeating units (EGN, N=3, 6, 9, 12, and 15) connected to hydrophobic dihexadecyl chains by means of a combination of differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS/WAXS). These synthetic amphiphiles dispersed in water form planar lamellar stacks and hexagonal cylinders confining the EG chains to restricted geometries. Owing to the self-assembly of the anchoring points, the lateral density of EG chains in planar lamella can be quantitatively controlled. Furthermore, the chain-melting phase transition of the anchors enables us to "switch" the intermolecular distance reversibly. SAXS/WAXS results suggest that the shorter EG chains (N=3, 6, and 9) assume a helical conformation in stacks of planar lamella. When the EG chains are further elongated (N=12 and 15), the lamellar periodicities cannot be explained by a linear extrapolation of shorter oligomers, but can be interpreted well as polymer brushes following the scaling theorem. Such rich phase behaviors of EGN molecules can be used as a simple model of oligo/poly-saccharide chains on cell surfaces, which act not only as flexible repellers between neighboring cells but also as stable spacers for functional ligands. [source] The usefulness of sensitivity analysis for predicting the effects of cat predation on the population dynamics of their avian preyIBIS, Issue 2008MAIREAD M. MACLEAN Sensitivity analyses of population projection matrix (PPM) models are often used to identify life-history perturbations that will most influence a population's future dynamics. Sensitivities are linear extrapolations of the relationship between a population's growth rate and perturbations to its demographic parameters. Their effectiveness depends on the validity of the assumption of linearity. Here we assess whether sensitivity analysis is an appropriate tool to investigate the effect of predation by cats on the population growth rates of their avian prey. We assess whether predation by cats leads to non-linear effects on population growth and compare population growth rates predicted by sensitivity analysis with those predicted by a non-linear simulation. For a two-stage, age-classified House Sparrow Passer domesticus PPM slight non-linearity arose when PPM elements were perturbed, but perturbation to the vital rates underlying the matrix elements had a linear impact on population growth rate. We found a similar effect with a slightly larger three-stage, age-classified PPM for a Winter Wren Troglodytes troglodytes population perturbed by cat predation. For some avian species, predation by cats may cause linear or only slightly nonlinear impacts on population growth rates. For these species, sensitivity analysis appears to be a useful conservation tool. However, further work on multiple perturbations to avian prey species with more complicated life histories and higher-dimension PPM models is required. [source] | ||||||||||||||||