Home About us Contact
|
Home About us Contact | ||
|
|
||
Scaling Methods (scaling + methods)
Selected AbstractsPachepsky, Y., Radcliff, D.E. & Selim, H.M. (eds) Scaling Methods in Soil Physics.EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 20042003. xviii + 434 pp., Boca Raton, CRC Press No abstract is available for this article. [source] Effects of terrain smoothing on topographic shielding correction factors for cosmogenic nuclide-derived estimates of basin-averaged denudation ratesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2009Kevin P. Norton Abstract Estimation of spatially averaged denudation rates from cosmogenic nuclide concentrations in sediments depends on the surface production rates, the scaling methods of cosmic ray intensities, and the correction algorithms for skyline, snow and vegetation shielding used to calculate terrestrial cosmogenic nuclide production. While the calculation of surface nuclide production and application of latitude, altitude and palaeointensity scaling algorithms are subjects of active research, the importance of additional correction for shielding by topographic obstructions, snow and vegetation is the subject of ongoing debate. The derivation of an additional correction factor for skyline shielding for large areas is still problematic. One important issue that has yet to be addressed is the effect of the accuracy and resolution of terrain representation by a digital elevation model (DEM) on topographic shielding correction factors. Topographic metrics scale with the resolution of the elevation data, and terrain smoothing has a potentially large effect on the correction of terrestrial cosmogenic nuclide production rates for skyline shielding. For rough, high-relief landscapes, the effect of terrain smoothing can easily exceed analytical errors, and should be taken into account. Here we demonstrate the effect of terrain smoothing on topographic shielding correction factors for various topographic settings, and introduce an empirical model for the estimation of topographic shielding factors based on landscape metrics. Copyright © 2008 John Wiley and Sons, Ltd. [source] Standard-Setting Methods as Measurement ProcessesEDUCATIONAL MEASUREMENT: ISSUES AND PRACTICE, Issue 1 2010Paul Nichols Some writers in the measurement literature have been skeptical of the meaningfulness of achievement standards and described the standard-setting process as blatantly arbitrary. We argue that standard setting is more appropriately conceived of as a measurement process similar to student assessment. The construct being measured is the panelists' representation of student performance at the threshold of an achievement level. In the first section of this paper, we argue that standard setting is an example of stimulus-centered measurement. In the second section, we elaborate on this idea by comparing some popular standard-setting methods to the stimulus-centered scaling methods known as psychophysical scaling. In the third section, we use the lens of standard setting as a measurement process to take a fresh look at the two criticisms of standard setting: the role of judgment and the variability of results. In the fourth section, we offer a vision of standard-setting research and practice as grounded in the theory and practice of educational measurement. [source] Promoting development and use of systematic reviews in a developing countryJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 6 2009Reza Yousefi-Nooraie MD Abstract Introduction, One major barrier to develop health systems is the limited capacity for conducting research and implementation of research findings. We assessed the views of researchers, decision makers and research policy makers on how the development and usage of evidence from systematic reviews can be promoted in a country with limited resources. Methods, We surveyed 131 participants in six systematic review workshops for their views on important items influencing the production and usage of systematic reviews in a developing country. They were also asked to propose interventions to deal with potential barriers. We analysed the quantitative data using multidimensional scaling methods, and the qualitative data using content analysis approach. Results, We identified seven clusters of items that contribute to the promotion of conducting and using systematic reviews. For each cluster a set of interventions are proposed that health care decision makers and research policy makers may use for promoting conduct and use of systematic reviews. The clusters are ,importance for policy makers', ,access to international research', ,priority and support for systematic reviews', ,competency and willingness of researchers to conduct reviews', ,importance for end-users', ,quality of local primary research' and ,visibility and access to local research'. Discussion, The proposed interventions focus on national level initiatives for making the systematic reviews ,wanted' and improving the capacity to conduct research. Our findings emphasize the essential role of policy makers for promoting systematic reviews. They demonstrate that many barriers stem from the lower quality of and lack of access to primary research originating from developing countries. [source] A COMPARISON OF THE EFFECTIVENESS OF HEDONIC SCALES AND END-ANCHOR COMPRESSION EFFECTSJOURNAL OF SENSORY STUDIES, Issue 2010HARRY T. LAWLESS ABSTRACT Three experiments were conducted to compare the relative performance of hedonic scaling methods, including the labeled affective magnitude (LAM) scale. In the first study, three versions of the LAM were used to evaluate 20 phrases that described diverse sensory experiences. One scale was anchored to "greatest imaginable like/dislike for any experience" and another used the "greatest imaginable like" phrase of the LAM but with the interior phrases repositioned relative to "any experience." The scale anchored to "any experience" showed a smaller range of scale usage and lower statistical differentiation, relative to the LAM scale, with the repositioned scale intermediate. Two further experiments compared the LAM to the nine-point hedonic scale, an 11-point category scale using the LAM phrases, and to a three-label line scale, a simplified version of the LAM with only the end phrases and the neutral center-point phrase. All scales showed similar differentiation of juices in the second study and sensory experience phrases in the third. A modest advantage for the LAM scale in the second experiment did not extend to the third study. Researchers should be careful in the choice of high end anchors for hedonic scales, as a compressed range of scale usage may result in lower product differentiation. PRACTICAL APPLICATIONS Hedonic scales for food acceptability are widely used in new product development for consumer testing and in food preference surveys. A desired goal of efficient sensory evaluation testing is the ability of tests to differentiate samples on the basis of scale data, in this case scales commonly used for food acceptability and preference testing. Scales which are able to differentiate products more effectively are less likely to lead to Type II error in experimentation, in which true differences between products are not detected. Such errors can lead to lost opportunities for product improvements or to enhanced chances for taking undetected risks in the case of false parity conclusions. [source] Grafted Polymer Chains Interacting with Substrates: Computer Simulations and ScalingMACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2008Radu Descas Abstract We review scaling methods and computer simulations used in the study of the static and dynamic properties of polymer chains tethered to adsorbing surfaces under good solvent conditions. By varying both the grafting density and the monomer/surface interactions a variety of phases can form. In particular, for attractive interactions between the chains and the surface the classical mushroom-brush transition known for repulsive substrates splits up into an overlap transition and a saturation transition which enclose a region of semidilute surface states. At high grafting densities oversaturation effects and a transition to a brush state can occur. We emphasize the role of the critical adsorption parameters for a correct description and understanding of such polymer adsorption phenomena. [source] Social distance in Bosnia-Herzegovina and the North Caucasus region of Russia: Inter and intra-ethnic attitudes and identities,NATIONS AND NATIONALISM, Issue 2 2009KRISTIN M. BAKKE ABSTRACT. This article examines attitudinal differences and similarities among ethnic groups in conflict-affected societies. Conventional wisdom tells us that societies that have experienced violent struggles in which individuals of different ethnic groups have (been) mobilized against each other are likely to become polarized along ethnic lines. Indeed, both policy-makers and scholars often assume that such divisions are some of the main challenges that must be overcome to restore peace after war. We comparatively examine this conventional wisdom by mapping dimensions of social distance among 4,000 survey respondents in Bosnia-Herzegovina and the North Caucasus region of Russia. The surveys were carried out in December 2005. Using multidimensional scaling methods, we do not find patterns of clear attitudinal cleavages among members of different ethnic groups in Bosnia-Herzegovina. Nor do we find patterns of clear ethnic division in the North Caucasus, although our social distance matrices reveal a difference between Russians and ethnic minority groups. [source] Computing projections via Householder transformations and Gram,Schmidt orthogonalizationsNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 7 2004Achiya Dax Abstract Let x* denote the solution of a linear least-squares problem of the form where A is a full rank m × n matrix, m > n. Let r*=b - Ax* denote the corresponding residual vector. In most problems one is satisfied with accurate computation of x*. Yet in some applications, such as affine scaling methods, one is also interested in accurate computation of the unit residual vector r*/,r*,2. The difficulties arise when ,r*,2 is much smaller than ,b,2. Let x, and r, denote the computed values of x* and r*, respectively. Let ,denote the machine precision in our computations, and assume that r, is computed from the equality r, =b - Ax,. Then, no matter how accurate x, is, the unit residual vector û =r,/,r,,2 contains an error vector whose size is likely to exceed ,,b,2/,r*,2. That is, the smaller ,r*,2 the larger the error. Thus although the computed unit residual should satisfy ATû=0, in practice the size of ,ATû,2 is about ,,A,2,b,2/,r*,2. The methods discussed in this paper compute a residual vector, r,, for which ,ATr,,2 is not much larger than ,,A,2,r,,2. Numerical experiments illustrate the difficulties in computing small residuals and the usefulness of the proposed safeguards. Copyright © 2004 John Wiley & Sons, Ltd. [source] Comparison of best,worst and hedonic scaling for the measurement of consumer wine preferencesAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 3 2009S. MUELLER Abstract Background and Aims:, Best,worst scaling (BWS) is compared to standard hedonic scaling for measuring consumer wine preferences. BWS is a relatively new method for producing ratio-level scales and has gained recent attention for application in sensory research, but has not been applied to wine. Methods and Results:, Regular wine consumers (112) evaluated eight designed wines with both scaling methods in an intra-subject design over two test periods. The methods did not result in comparable product liking results. The eight wines could almost be differentiated on an aggregated level with hedonic ratings (P = 0.076); there was no significant difference with BWS. Latent class analysis was used to identify two clusters, which differed on the preferences for the designed sensory components. The BWS design had to be split into several blocks, so no complete individual measures were available, which prevented analysing heterogeneity for this method. Conclusions:, BWS needs more wines to be assessed per person in order to discriminate between red wines and to allow modelling of consumer preference heterogeneity. Respondents would have to accomplish complete individual BWS designs, which requires repeated exposure to the same set of wines over several tasting sessions. Significance of the Study:, This study demonstrates that BWS is not as suitable for sensory consumer preference measurement of red wine as hedonic rating. While BWS has shown a higher discriminative ability for different products and in non-sensory research, the factors of alcohol, tannin and memory fatigue make it less practical for red wine sensory measurement compared to hedonic rating. [source] Dosimetric analysis of the carousel setup for the exposure of rats at 1.62 GHzBIOELECTROMAGNETICS, Issue 1 2004Frank Schönborn Abstract The so-called carousel setup has been widely utilized for testing the hypotheses of adverse health effects on the central nervous system (CNS) due to mobile phone exposures in the frequency bands 800,900 MHz. The objectives of this article were to analyze the suitability of the setup for the upper mobile frequency range, i.e., 1.4,2 GHz, and to conduct a detailed experimental and numerical dosimetry for the setup at the IRIDIUM frequency band of 1.62 GHz. The setup consists of a plastic base on which ten rats, restrained in radially positioned tubes, are exposed to the electromagnetic field emanating from a sleeved dipole antenna at the center. Latest generation miniaturized dosimetric E field and temperature probes were used to measure the specific absorption rate (SAR) inside the brain of three rat cadavers of the Lewis strain and two rat cadavers of the Fisher 344 strain. A numerical analysis was conducted on the basis of three numerical rat phantoms with voxel sizes between 1.5 and 0.125 mm3 that are based on high resolution MRI scans of a 300 g male Wistar rat and a 370 g male Sprague,Dawley rat. The average of the assessed SAR values in the brain was 2.8 mW/g per W antenna input power for adult rats with masses between 220 and 350 g and 5.3 mW/g per W antenna input power for a juvenile rat with a mass of 95 g. The strong increase of the SAR in the brain with decreasing animal size was verified by simulations of the absorption in numerical phantoms scaled to sizes between 100 and 500 g with three different scaling methods. The study also demonstrated that current rat phantom models do not provide sufficient spatial resolution to perform absolute SAR assessment for the brain tissue. The variation of the SARbrainav due to changes in position was assessed to be in the range from +15% to ,30%. A study on the dependence of the performance of the carousel setup on the frequency revealed that efficiency, defined as SARbrainav per W antenna input power, and the ratio between SARbrainav and SARbodyav are optimal in the mobile communications frequency range, i.e., 0.8,3 GHz. Bioelectromagnetics 25:16,26, 2004. © 2003 Wiley-Liss, Inc. [source] Pharmacokinetics and allometric scaling of levormeloxifene, a selective oestrogen receptor modulatorBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2003O. Østerberg Abstract The pharmacokinetics of a new selective oestrogen receptor modulator levormeloxifene was investigated in mice, rats, cynomolgus monkeys and humans by compartmental pharmacokinetics. Levormeloxifene was administered as an oral solution in all studies. Allometric scaling was used to predict human pharmacokinetic parameters and the performance of the approach was evaluated. Mean values of clearance confounded by F(CL/F) were 0.073, 0.29, 3.18 and 2.4 l/h in mice, rats, monkeys and humans, respectively. Values of distribution volume at steady state confounded by F(Vss/F) were 0.073 and 7.5 l in mice and rats. In monkeys, values of the central volume F(Vc/F) and volume at steady state F(Vss/F) were 28.9 and 57.9 l, respectively. In humans, values of Vc/F and Vss/F were 106 and 587 l, respectively. Predicted CL/F and Vss/F showed a linear relationship when plotted vs BW on a log,log scale; for CL/F, r was 0.95,0.98 and for Vss/F, r was 0.99. Using allometric scaling the predicted human Vss/F deviated 3-fold from the experimentally determined values. Observed values of CL/F deviated 21,25 fold from the predicted, the latter depending on the scaling method. Confidence intervals for the predicted parameters showed major lack of precision for all the allometric scaling methods. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||||||||