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Related Methods (relate + methods)
Selected AbstractsHow to deal with multiple endpoints in clinical trialsFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 6 2006Markus Neuhäuser Abstract Multiple endpoints are common in clinical trials. This article discusses statistical methods that can be applied to control the rate of false positive conclusions at an acceptable level. The considered methods include the Bonferroni adjustment and related methods, the intersection-union test, ordered hypotheses and gatekeeper procedures, composite endpoints and global assessment measures, closed testing procedures, and combinations of different approaches. [source] Empirical orthogonal functions and related techniques in atmospheric science: A reviewINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2007A. Hannachi Abstract Climate and weather constitute a typical example where high dimensional and complex phenomena meet. The atmospheric system is the result of highly complex interactions between many degrees of freedom or modes. In order to gain insight in understanding the dynamical/physical behaviour involved it is useful to attempt to understand their interactions in terms of a much smaller number of prominent modes of variability. This has led to the development by atmospheric researchers of methods that give a space display and a time display of large space-time atmospheric data. Empirical orthogonal functions (EOFs) were first used in meteorology in the late 1940s. The method, which decomposes a space-time field into spatial patterns and associated time indices, contributed much in advancing our knowledge of the atmosphere. However, since the atmosphere contains all sorts of features, e.g. stationary and propagating, EOFs are unable to provide a full picture. For example, EOFs tend, in general, to be difficult to interpret because of their geometric properties, such as their global feature, and their orthogonality in space and time. To obtain more localised features, modifications, e.g. rotated EOFs (REOFs), have been introduced. At the same time, because these methods cannot deal with propagating features, since they only use spatial correlation of the field, it was necessary to use both spatial and time information in order to identify such features. Extended and complex EOFs were introduced to serve that purpose. Because of the importance of EOFs and closely related methods in atmospheric science, and because the existing reviews of the subject are slightly out of date, there seems to be a need to update our knowledge by including new developments that could not be presented in previous reviews. This review proposes to achieve precisely this goal. The basic theory of the main types of EOFs is reviewed, and a wide range of applications using various data sets are also provided. Copyright © 2007 Royal Meteorological Society [source] Pattern hunting in climate: a new method for finding trends in gridded climate dataINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2007A. Hannachi Abstract Trends are very important in climate research and are ubiquitous in the climate system. Trends are usually estimated using simple linear regression. Given the complexity of the system, trends are expected to have various features such as global and local characters. It is therefore important to develop methods that permit a systematic decomposition of climate data into different trend patterns and remaining no-trend patterns. Empirical orthogonal functions and closely related methods, widely used in atmospheric science, are unable in general to capture trends because they are not devised for that purpose. The present paper presents a novel method capable of systematically capturing trend patterns from gridded data. The method is based on an eigenanalysis of the covariance/correlation matrix obtained using correlations between time positions of the sorted data, and trends are associated with the leading nondegenerate eigenvalues. Application to simple low-dimensional time series models and reanalyses data are presented and discussed. Copyright © 2006 Royal Meteorological Society. [source] Application of possibility theory in the life-cycle inventory assessment of biofuelsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2002Raymond R. Tan Abstract Data uncertainty issues have constrained the widespread acceptance of life-cycle analysis (LCA) and related methods. This is particularly important in the LCA of fuels due to the wide range of available feedstocks and processing options. Despite recent attempts at standardization, there remain persistent doubts about the general validity of LCA results, often due to uncertainties about data quality. This paper demonstrates the application of possibility theory as a tool for handling life-cycle inventory data imprecision for the case of the net energy balance of coconut methyl ester (CME) as a biodiesel transport fuel. Results derived using a possibililistic computation are contrasted with those arrived at by probabilistic (Monte Carlo) simulation. The two approaches yield comparable results but possibilistic modelling offers significant advantages with respect to computational efficiency. The net energy balance of CME is estimated to be approximately 36 MJ kg,1, significantly higher than the 28 MJ kg,1 net energy typical of rapeseed oil methyl ester (RME) relevant to the U.K. Copyright © 2002 John Wiley & Sons, Ltd. [source] Friction and wear effects on a micro/nano-scaleLUBRICATION SCIENCE, Issue 1 2001E. Santner Abstract In this paper are described tribological effects which can be found in micro-tribological systems, and in those macro-systems which can be analysed by micro-methods, e.g., by atomic force microscopy (AFM) or related methods. Micro-tribology systems have friction contacts with loads in the micro/nano-newton range and/or dimensions in the micro/nanometre range. Experiments on the micro/nano-scale should be easier to explain by theoretical modelling due to their simpler system structure. An example is discussed of adhesion and friction measurements between AFM tips and clean, flat, solid surfaces in ultra-high vacuum, which shows some of the special aspects of micro/nano-tribology. Surprising friction characteristics on surfaces with an artificial micro-structure can be explained by skilled and careful topographical analysis of the friction path with an AFM. In micro-sensor contacts, ,single wear events' can be detected using AFM analysis of the contact region. For ceramic compounds, different friction levels for the components of the material can be found. The problems, difficulties, and dangers of misinterpretation are also discussed. [source] Improving k - t SENSE by adaptive regularizationMAGNETIC RESONANCE IN MEDICINE, Issue 5 2007Dan Xu Abstract The recently proposed method known as k - t sensitivity encoding (SENSE) has emerged as an effective means of improving imaging speed for several dynamic imaging applications. However, k - t SENSE uses temporally averaged data as a regularization term for image reconstruction. This may not only compromise temporal resolution, it may also make some of the temporal frequency components irrecoverable. To address that issue, we present a new method called spatiotemporal domain-based unaliasing employing sensitivity encoding and adaptive regularization (SPEAR). Specifically, SPEAR provides an improvement over k - t SENSE by generating adaptive regularization images. It also uses a variable-density (VD), sequentially interleaved k - t space sampling pattern with reference frames for data acquisition. Simulations based on experimental data were performed to compare SPEAR, k - t SENSE, and several other related methods, and the results showed that SPEAR can provide higher temporal resolution with significantly reduced image artifacts. Ungated 3D cardiac imaging experiments were also carried out to test the effectiveness of SPEAR, and real-time 3D short-axis images of the human heart were produced at 5.5 frames/s temporal resolution and 2.4 × 1.2 × 8 mm3 spatial resolution with eight slices. Magn Reson Med 57:918,930, 2007. © 2007 Wiley-Liss, Inc. [source] Strong population structure despite evidence of recent migration in a selfing hermaphroditic vertebrate, the mangrove killifish (Kryptolebias marmoratus)MOLECULAR ECOLOGY, Issue 13 2007ANDREY TATARENKOV Abstract We employ a battery of 33 polymorphic microsatellite loci to describe geographical population structure of the mangrove killifish (Kryptolebias marmoratus), the only vertebrate species known to have a mixed-mating system of selfing and outcrossing. Significant population genetic structure was detected at spatial scales ranging from tens to hundreds of kilometres in Florida, Belize, and the Bahamas. The wealth of genotypic information, coupled with the highly inbred nature of most killifish lineages due to predominant selfing, also permitted treatments of individual fish as units of analysis. Genetic clustering algorithms, neighbour-joining trees, factorial correspondence, and related methods all earmarked particular killifish specimens as products of recent outcross events that could often be provisionally linked to specific migration events. Although mutation is the ultimate source of genetic diversity in K. marmoratus, our data indicate that interlocality dispersal and outcross-mediated genetic recombination (and probably genetic drift also) play key proximate roles in the local ,clonal' dynamics of this species. [source] DETECTING INFLUENTIAL OBSERVATIONS IN SLICED INVERSE REGRESSION ANALYSISAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2006Luke A. Prendergast Summary The detection of influential observations on the estimation of the dimension reduction subspace returned by Sliced Inverse Regression (SIR) is considered. Although there are many measures to detect influential observations in related methods such as multiple linear regression, there has been little development in this area with respect to dimension reduction. One particular influence measure for a version of SIR is examined and it is shown, via simulation and example, how this may be used to detect influential observations in practice. [source] State of the Art Pump Technology for Reverse Osmosis SystemsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2003R. Schmitz The industrial significance of diaphragm processes in mass separation is ever increasing; this is particularly true for the use of reverse osmosis (RO) and related methods. Decisive factors for the economy of RO processes, and thus for the future of this technology, are the reliability and energy consumption of the high-pressure pumps involved. Current pump developments reflect clear progress in this field. [source] | |||||||||||||