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Robust Results (robust + result)
Selected AbstractsMeasuring finite-frequency body-wave amplitudes and traveltimesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2006Karin Sigloch SUMMARY We have developed a method to measure finite-frequency amplitude and traveltime anomalies of teleseismic P waves. We use a matched filtering approach that models the first 25 s of a seismogram after the P arrival, which includes the depth phases pP and sP. Given a set of broad-band seismograms from a teleseismic event, we compute synthetic Green's functions using published moment tensor solutions. We jointly deconvolve global or regional sets of seismograms with their Green's functions to obtain the broad-band source time function. The matched filter of a seismogram is the convolution of the Green's function with the source time function. Traveltimes are computed by cross-correlating each seismogram with its matched filter. Amplitude anomalies are defined as the multiplicative factors that minimize the RMS misfit between matched filters and data. The procedure is implemented in an iterative fashion, which allows for joint inversion for the source time function, amplitudes, and a correction to the moment tensor. Cluster analysis is used to identify azimuthally distinct groups of seismograms when source effects with azimuthal dependence are prominent. We then invert for one source time function per group. We implement this inversion for a range of source depths to determine the most likely depth, as indicated by the overall RMS misfit, and by the non-negativity and compactness of the source time function. Finite-frequency measurements are obtained by filtering broad-band data and matched filters through a bank of passband filters. The method is validated on a set of 15 events of magnitude 5.8 to 6.9. Our focus is on the densely instrumented Western US. Quasi-duplet events (,quplets') are used to estimate measurement uncertainty on real data. Robust results are achieved for wave periods between 24 and 2 s. Traveltime dispersion is on the order of 0.5 s. Amplitude anomalies are on the order of 1 db in the lowest bands and 3 db in the highest bands, corresponding to amplification factors of 1.2 and 2.0, respectively. Measurement uncertainties for amplitudes and traveltimes depend mostly on station coverage, accuracy of the moment tensor estimate, and frequency band. We investigate the influence of those parameters in tests on synthetic data. Along the RISTRA array in the Western US, we observe amplitude and traveltime patterns that are coherent on scales of hundreds of kilometres. Below two sections of the array, we observe a combination of frequency-dependent amplitude and traveltime patterns that strongly suggest wavefront healing effects. [source] Sex,related self,concepts, cognitive styles and cultural values of traditionality,modernity as predictors of general and domain,specific sexismASIAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 1 2003Jolynn C. X. Pek Previous studies have determined that masculinity, femininity, need for closure and authoritarianism are significant predictors of sexism. The present study attempted to integrate these variables in order to better understand the nature of general ambivalent sexism and workplace,specific sexism in Singapore. Chinese traditionality and Chinese modernity were specifically examined as potential predictors of sexism. Robust results from hierarchical regressions indicated that these indigenous cultural variables were highly important in predicting general and workplace,specific sexism. Although masculinity and need for closure were unrelated to sexism, participant sex, femininity and authoritarianism significantly predicted sexist attitudes towards women. Most important, Chinese values were found to add significant incremental validity in predicting sexist attitudes beyond what was accounted by the aforementioned predictors. Chinese traditionality significantly predicted sexist attitudes towards women, but Chinese modernity was unrelated to sexism. Implications of these findings were discussed. [source] Viability of Auction-Based Revenue Management in Sequential MarketsDECISION SCIENCES, Issue 2 2005Tim Baker ABSTRACT The Internet is providing an opportunity to revenue management practitioners to exploit the potential of auctions as a new price distribution channel. We develop a stochastic model for a high-level abstraction of a revenue management system (RMS) that allows us to understand the potential of incorporating auctions in revenue management in the presence of forecast errors associated with key parameters. Our abstraction is for an environment where two market segments book in sequence and revenue management approaches consider auctions in none, one, or both segments. Key insights from our robust results are (i) limited auctions are best employed closest to the final sale date, (ii) counterbalancing forecast errors associated with overall traffic intensity and the proportion of customer arrivals in a segment is more important if an auction is adopted in that segment, and (iii) it is critically important not to err on the side of overestimating market willingness to pay. [source] Shoreline tracking and implicit source terms for a well balanced inundation modelINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2010Giovanni FranchelloArticle first published online: 31 JUL 200 Abstract The HyFlux2 model has been developed to simulate severe inundation scenario due to dam break, flash flood and tsunami-wave run-up. The model solves the conservative form of the two-dimensional shallow water equations using the finite volume method. The interface flux is computed by a Flux Vector Splitting method for shallow water equations based on a Godunov-type approach. A second-order scheme is applied to the water surface level and velocity, providing results with high accuracy and assuring the balance between fluxes and sources also for complex bathymetry and topography. Physical models are included to deal with bottom steps and shorelines. The second-order scheme together with the shoreline-tracking method and the implicit source term treatment makes the model well balanced in respect to mass and momentum conservation laws, providing reliable and robust results. The developed model is validated in this paper with a 2D numerical test case and with the Okushiri tsunami run up problem. It is shown that the HyFlux2 model is able to model inundation problems, with a satisfactory prediction of the major flow characteristics such as water depth, water velocity, flood extent, and flood-wave arrival time. The results provided by the model are of great importance for the risk assessment and management. Copyright © 2009 John Wiley & Sons, Ltd. [source] Repeatability of Dietary Patterns Derived Using ,-Priori and ,-Posterior MethodsJOURNAL OF APPLIED BIOBEHAVIORAL RESEARCH, Issue 1 2010Vassiliki Bountziouka We aimed to examine the repeatability of dietary patterns derived using ,-priori and ,-posterior techniques. During 2008, 500 participants were enrolled and asked to fill-in a food frequency questionnaire twice. The Mediterranean dietary pattern was ,-priori assessed by the MedDietScore, while principal components analysis (PCA) and cluster analysis (CA) were used as the ,-posterior techniques. Results revealed that the overall MedDietScore was similar between the two recordings (M = 28, SD = 3.7 vs. M = 28, SD = 3.8). Although PCA revealed 13 patterns in each record (60% of explained variability), the food items characterizing each pattern were varying through the two recordings. According to CA, three clusters were revealed from both records. The ,-posterior methods should be used with caution, while the ,-priori approach leads to more robust results. [source] Are commodity prices chaotic?AGRICULTURAL ECONOMICS, Issue 2 2002Arjun Chatrath Abstract We conduct tests for the presence of low-dimensional chaotic structure in the futures prices of four important agricultural commodities. Though there is strong evidence of non-linear dependence, the evidence suggests that there is no long-lasting chaotic structure. The dimension estimates for the commodity futures series are generally much higher than would be for low dimension chaotic series. Our test results indicate that autoregressive conditional heteroskedasticity (ARCH)-type processes, with controls for seasonality and contract-maturity effects, explain much of the non-linearity in the data. We make a case that employing seasonally adjusted price series is important in obtaining robust results via some of the existing tests for chaotic structure. Finally, maximum likelihood methodologies, that are robust to the non-linear dynamics, lend strong support to the Samuelson hypothesis of maturity effects in futures price changes. [source] Measuring Knowledge Stocks: A Process of Creative DestructionKYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 3 2005Jürgen Bitzer Summary This paper proposes a new method for constructing R&D capital stocks developed to avoid the common assumption of a constant rate of knowledge depreciation, which implies wear and tear of knowledge. The method models the development of R&D capital stocks as a process of creative destruction linking the depreciation of knowledge to the emergence of new knowledge. A first empirical assessment of the new method , measuring the influence of R&D capital stocks on production in the manufacturing sectors of 12 OECD countries , produces plausible and robust results. [source] Rethinking Historical Reproductive Change: Insights from Longitudinal Data for a Spanish TownPOPULATION AND DEVELOPMENT REVIEW, Issue 4 2007David Sven Reher A set of linked reproductive histories taken from the Spanish town of Aranjuez between 1871 and 1950 is used to address key issues regarding reproductive change during the demographic transition. These include the role of child survival as a stimulus for reproductive change, the use of stopping and/or spacing strategies to achieve reproductive goals, and the timing of change. Straightforward demographic measures are used and robust results are achieved. Initial strategies of fertility limitation are shown to exist but are inefficient, are mostly visible during the latter part of the reproductive period, are designed mostly to protect families from the effects of increases in child survival, and are based almost entirely on stopping behavior. As mortality decline accelerates, strategies become much more efficient, are visible at the outset of married life, include spacing behavior, and eventually lead to important declines in completed family size. The results of this study have implications for our understanding of the demographic transition both in historical Europe and in other regions of the world. [source] Interventions to improve recall of medical information in cancer patients: a systematic review of the literaturePSYCHO-ONCOLOGY, Issue 9 2008Nienke van der Meulen Abstract This systematic review investigates which interventions are effective to improve recall of medical information in cancer patients. A literature research was done in PubMed, PsychINFO, CINAHL and Cochrane Library, following the guidelines of the Cochrane Collaboration. The methodological quality of selected studies was assessed independently by two reviewers. The results were synthesized with a Best Evidence Synthesis. Of initially 5173 found publications, 10 met all selection criteria. The results indicate that an audiotape of the patients' own consultation has added value upon oral information only. However, providing patients with a general audiotape does not improve recall of information and might even inhibit patients' recall. Furthermore, there is scientific evidence, although limited, that the use of a question prompt sheet (QPS) has a positive effect on recall of information, provided that the physician actively endorses this sheet. No evidence was found for an effect of providing patients with a summary letter of the consultation on recall, although research on this subject is scarce. In conclusion, the review suggests that interventions that are tailored to the individual cancer patient, such as an audiotape of the consultation or a QPS, are most effective. Further research needs to be done to establish robust results. Copyright © 2007 John Wiley & Sons, Ltd. [source] HUMAN CAPITAL INEQUALITY AND ECONOMIC GROWTH: SOME NEW EVIDENCETHE ECONOMIC JOURNAL, Issue 478 2002Amparo Castelló This paper provides new measures of human capital inequality for a broad panel of countries. Taking attainment levels from Barro and Lee (2001), we compute Gini coefficients and the distribution of education by quintiles for 108 countries over five-year intervals from 1960 to 2000. Using this new cross-country data on human capital inequality two main conclusions are obtained. First, most countries in the world have tended to reduce the inequality in human capital distribution. Second, human capital inequality measures provide more robust results than income inequality measures in the estimation of standard growth and investment equations. [source] I,Varieties of Support and Confirmation of Climate ModelsARISTOTELIAN SOCIETY SUPPLEMENTARY VOLUME, Issue 1 2009Elisabeth A. Lloyd Today's climate models are supported in a couple of ways that receive little attention from philosophers or climate scientists. In addition to standard ,model fit', wherein a model's simulation is compared to observational data, there is an additional type of confirmation available through the variety of instances of model fit. When a model performs well at fitting first one variable and then another, the probability of the model under some standard confirmation function, say, likelihood, goes up more than under each individual case of fit alone. Thus, two instances of fit of distinct variables of a global climate model using distinct data sets considered collectively will provide stronger evidence for a model than either one of the instances considered individually. This has consequences for model robustness. Sets of models that produce robust results will, if their assumptions vary enough and they each are observationally sound, provide reasons to endorse common structures found in those models. Finally, independent empirical support for aspects and assumptions of the model provides an additional confirmational virtue for climate models, contrary to what is implied by some current philosophical writing on this topic. [source] Sampling termites in forest habitats: A reply to Roisin and LeponceAUSTRAL ECOLOGY, Issue 4 2006DAVID T. JONES Abstract To characterize the structure and species density of termite assemblages in tropical forests, we developed a sampling protocol based on a single large quadrat (belt transect) that standardises sampling effort and area. Emphasizing the estimation of species richness, Roisin and Leponce (2004, Austral Ecology, 29: 637,46) recommend sampling numerous small quadrats, and varying the number of quadrats depending on local species density. However, their method would result in the loss of standardisation and speed, taking up to four times longer to collect and process the samples. We show that even for a subtropical forest with low species density, our protocol produces robust results. [source] Determination of Sample Sizes for Demonstrating Efficacy of Radiation CountermeasuresBIOMETRICS, Issue 1 2010Ralph L. Kodell Summary In response to the ever increasing threat of radiological and nuclear terrorism, active development of nontoxic new drugs and other countermeasures to protect against and/or mitigate adverse health effects of radiation is ongoing. Although the classical LD50 study used for many decades as a first step in preclinical toxicity testing of new drugs has been largely replaced by experiments that use fewer animals, the need to evaluate the radioprotective efficacy of new drugs necessitates the conduct of traditional LD50 comparative studies (FDA, 2002,,Federal Register,67, 37988,37998). There is, however, no readily available method to determine the number of animals needed for establishing efficacy in these comparative potency studies. This article presents a sample-size formula based on Student's,t,for comparative potency testing. It is motivated by the U.S. Food and Drug Administration's (FDA's) requirements for robust efficacy data in the testing of response modifiers in total body irradiation experiments where human studies are not ethical or feasible. Monte Carlo simulation demonstrated the formula's performance for Student's,t, Wald, and likelihood ratio tests in both logistic and probit models. Importantly, the results showed clear potential for justifying the use of substantially fewer animals than are customarily used in these studies. The present article may thus initiate a dialogue among researchers who use animals for radioprotection survival studies, institutional animal care and use committees, and drug regulatory bodies to reach a consensus on the number of animals needed to achieve statistically robust results for demonstrating efficacy of radioprotective drugs. [source] Cross- and self-fertilization of plants , Darwin's experiments and what we know nowBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009SIMON J. OWENS The scientific work recorded by Darwin in his book on the cross- and self-fertilization of plants is an exemplar of interesting choices, careful technique, decades of work and methodical analyses that provided a plethora of robust results. The conclusions Darwin drew from his studies are, for the most part, valid and still relevant today. They focus primarily on providing data to support Darwin's hypothesis about the nature and importance of the benefits derived from cross-fertilization, although he conceded that a few plants seem to be invariably self-fertilized. The work is also a significant forerunner for the concepts of hybrid vigour and inbreeding depression. A wealth of information relating to flowers, flowering time, pollen efficacy, the results of cross- and self-pollination, the behaviour and impact of insects, seed and seed germination and plant breeding systems is scattered throughout the book. Darwin also related this book to several others he wrote in which some of these topics are included. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 357,395. [source] | |||||||||||||||||||