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Squares Procedure (square + procedure)
Kinds of Squares Procedure Selected AbstractsSimple modifications for stabilization of the finite point methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2005B. Boroomand Abstract A stabilized version of the finite point method (FPM) is presented. A source of instability due to the evaluation of the base function using a least square procedure is discussed. A suitable mapping is proposed and employed to eliminate the ill-conditioning effect due to directional arrangement of the points. A step by step algorithm is given for finding the local rotated axes and the dimensions of the cloud using local average spacing and inertia moments of the points distribution. It is shown that the conventional version of FPM may lead to wrong results when the proposed mapping algorithm is not used. It is shown that another source for instability and non-monotonic convergence rate in collocation methods lies in the treatment of Neumann boundary conditions. Unlike the conventional FPM, in this work the Neumann boundary conditions and the equilibrium equations appear simultaneously in a weight equation similar to that of weighted residual methods. The stabilization procedure may be considered as an interpretation of the finite calculus (FIC) method. The main difference between the two stabilization procedures lies in choosing the characteristic length in FIC and the weight of the boundary residual in the proposed method. The new approach also provides a unique definition for the sign of the stabilization terms. The reasons for using stabilization terms only at the boundaries is discussed and the two methods are compared. Several numerical examples are presented to demonstrate the performance and convergence of the proposed methods. Copyright © 2005 John Wiley & Sons, Ltd. [source] A confusing world: what to call histology of three-dimensional tumour margins?JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 5 2007M Moehrle Abstract Complete three-dimensional histology of excised skin tumour margins has a long tradition and, unfortunately, a multitude of names as well. Mohs, who introduced it, called it ,microscopically controlled surgery'. Others have described it as ,micrographic surgery', ,Mohs' micrographic surgery', or simply ,Mohs' surgery'. Semantic confusion became truly rampant when variant forms, each useful in its own way for detecting subclinical outgrowths of malignant skin tumours, were later introduced under such names as histographic surgery, systematic histologic control of the tumour bed, histological control of excised tissue margins, the square procedure, the perimeter technique, etc. All of these methods are basically identical in concept. All involve complete, three-dimensional histological visualization and evaluation of excision margins. Their common goal is to detect unseen tumour outgrowths. For greater clarity, the authors of this paper recommend general adoption of ,3D histology' as a collective designation for all the above methods. As an added advantage, 3D histology can also be used in other medical disciplines to confirm true R0 resection of, for example, breast cancer or intestinal cancer. [source] A pilot study of the immediate effects of mirror feedback on sitting postural control in normal healthy adultsPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2008Martin Watson Background and Purpose.,The remediation of postural control problems is a common feature of many physiotherapy interventions. Provision of augmented visual feedback through use of mirror-reflected body image is one means by which therapists can purportedly facilitate patients' postural correction abilities. Despite the historic place of this treatment modality within the physiotherapist's armamentarium, the strategy has however received very limited investigation. The aim of this study was to evaluate the extent to which availability of reflected body image influences the normal subjects' postural control abilities when in a sitting position.,Method.,A pilot investigation was undertaken, utilizing a sample of convenience comprising 18 healthy female subjects (mean age 20.8 years). All subjects underwent testing of their sitting postural control abilities in two separate conditions: with and without mirror feedback. A full length therapy mirror, as typically found in many rehabilitation departments, was used where appropriate to provide the reflected body image. Testing was carried out three times for each condition (six tests in total), obtaining average performance across three tests for each condition. Test order for each subject for the six tests was varied using a Latin square procedure to control for learning effect. Measurement of the subjects' postural control abilities was achieved by Balance Performance Monitor using a seat plate monitor and evaluating body sway path (mm). Postural control was challenged during testing by asking the subjects to maintain a standardized complex sitting position.,Results.,Group mean sway path with mirror feedback was lower than without: means 165.72,mm (standard deviation [SD] = 40.52,mm) versus 244.74,mm (SD = 68.48,mm). This suggested improved postural control ability when the subjects were able to view their reflected body image during testing. A related t test (t = 4.873, n = 18) showed differences between the two conditions to be statistically significant (p < 0.001), 95% confidence interval = 44.80,mm,113.23,mm.,Conclusion.,This relatively unsophisticated evaluation of mirror feedback nonetheless suggested a potential intervention effect. The precise mechanism(s) by which this strategy might effect changes in postural control ability, as well as the likely carryover of the effect and its replication in individuals with movement control problems, are all issues requiring further investigation. Nonetheless, these results provide provisional support for the notion that mirror feedback is a potentially useful strategy in the training of postural control. Copyright © 2008 John Wiley & Sons, Ltd. [source] Structural acclimation and radiation regime of silver fir (Abies alba Mill.) shoots along a light gradientPLANT CELL & ENVIRONMENT, Issue 3 2003A. CESCATTI ABSTRACT Shoot architecture has been investigated using the ratio of mean shoot silhouette area to total needle area ( ) as a structural index of needle clumping in shoot space, and as the effective extinction coefficient of needle area. Although can be used effectively for the prediction of canopy gap fraction, it does not provide information about the within-shoot radiative regime. For this purpose, the estimation of three architectural properties of the shoots is required: needle area density, angular distribution and spatial aggregation. To estimate these features, we developed a method based on the inversion of a Markov three-dimensional interception model. This approach is based on the turbid medium approximation for needle area in the shoot volume, and assumes an ellipsoidal angular distribution of the normals to the needle area. Observed shoot dimensions and silhouette areas for different vertical and azimuth angles (AS) are used as model inputs. The shape coefficient of the ellipsoidal distribution (c) and the Markov clumping index (,0) are estimated by a least square procedure, in order to minimize the differences between model prediction and measurements of AS. This methodology was applied to silver fir (Abies alba Mill.) shoots collected in a mixed fir,beech,spruce forest in the Italian Alps. The model worked effectively over the entire range of shoot morphologies: c ranged from 1 to 8 and ,0 from 0·3 to 1 moving from the top to the base of the canopy. Finally, the shoot model was applied to reconstruct the within-shoot light regime, and the potential of this technique in upscaling photosynthesis to the canopy level is discussed. [source] A fully robust PARAFAC method for analyzing fluorescence dataJOURNAL OF CHEMOMETRICS, Issue 3 2009Sanne Engelen Abstract Parallel factor analysis (PARAFAC) is a widespread method for modeling fluorescence data by means of an alternating least squares procedure. Consequently, the PARAFAC estimates are highly influenced by outlying excitation,emission landscapes (EEM) and element-wise outliers, like for example Raman and Rayleigh scatter. Recently, a robust PARAFAC method that circumvents the harmful effects of outlying samples has been developed. For removing the scatter effects on the final PARAFAC model, different techniques exist. Newly, an automated scatter identification tool has been constructed. However, there still exists no robust method for handling fluorescence data encountering both outlying EEM landscapes and scatter. In this paper, we present an iterative algorithm where the robust PARAFAC method and the scatter identification tool are alternately performed. A fully automated robust PARAFAC method is obtained in that way. The method is assessed by means of simulations and a laboratory-made data set. Copyright © 2009 John Wiley & Sons, Ltd. [source] Kinematic Calibration and Pose Measurement of a Medical Parallel Manipulator by Optical Position SensorsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 4 2003Shaoping Bai In the applications of parallel manipulators, kinematic calibration is required to eliminate the errors resulting from the manufacturing and assembly of both base and tools. In this paper, a calibration method of base and tool transformation is developed by virtue of optical position sensors. An error model for calibration is constructed using differential geometry method. The pose error is obtained based on pose measurement results of OPTOTRAK 3020, a commercial 3D position measurement system. An iterative least squares procedure is used to identify the error parameters in the base and tool transformations. Simulation and experiment results are presented to demonstrate the effectiveness of the method for transformation matrices calibration. © 2003 Wiley Periodicals, Inc. [source] The impact of multiple volatilities on import demand for U.S. commodities: the case of soybeansAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2010Qiang Zhang The focus of this study is the effects of exchange rate, commodity price, and ocean freight cost risks on import demand with forward-futures markets. The case of U.S. and Brazilian soybeans is analyzed empirically using monthly data. A two-way error component two-stage least squares procedure for panel data is used for the analysis. Risk for these three effects is measured by the moving average of the standard deviation. Major soybean importers are sensitive to exchange rate risk. Importing countries in general are not sensitive to soybean price and ocean shipping cost risks for Brazilian or U.S. soybeans. © 2010 Wiley Periodicals, Inc. [source] Fish condition analysis by a weighted least squares procedure: testing geographical differences of an endangered Iberian cyprinodontidJOURNAL OF FISH BIOLOGY, Issue 6 2001A. Vila-Gispert A weighted procedure for analysing fish condition, when conventional ANCOVA assumptions cannot be assumed because the coefficients of regression and residual variances were not equal among groups, proved adequate for most data sets. Data for an Iberian cyprinodontid fish were used to demonstrate the proposed method. [source] Efficiency measure, modelling and estimation in combined array designsAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 4 2003Tak Mak Abstract In off-line quality control, the settings that minimize the variance of a quality characteristic are unknown and must be determined based on an estimated dual response model of mean and variance. The present paper proposes a direct measure of the efficiency of any given design-estimation procedure for variance minimization. This not only facilitates the comparison of different design-estimation procedures, but may also provide a guideline for choosing a better solution when the estimated dual response model suggests multiple solutions. Motivated by the analysis of an industrial experiment on spray painting, the present paper also applies a class of link functions to model process variances in off-line quality control. For model fitting, a parametric distribution is employed in updating the variance estimates used in an iteratively weighted least squares procedure for mean estimation. In analysing combined array experiments, Engel and Huele (Technometrics, 1996; 39:365) used log-link to model process variances and considered an iteratively weighted least squares leading to the pseudo-likelihood estimates of variances as discussed in Carroll and Ruppert (Transformation and Weighting in Regression, Chapman & Hall: New York). Their method is a special case of the approach considered in this paper. It is seen for the spray paint data that the log-link may not be satisfactory and the class of link functions considered here improves substantially the fit to process variances. This conclusion is reached with a suggested method of comparing ,empirical variances' with the ,theoretical variances' based on the assumed model. Copyright © 2003 John Wiley & Sons, Ltd. [source] Application of equality constraints on variables during alternating least squares proceduresJOURNAL OF CHEMOMETRICS, Issue 12 2002Mark H. Van Benthem Abstract We describe several methods of applying equality constraints while performing procedures that employ alternating least squares. Among these are mathematically rigorous methods of applying equality constraints, as well as approximate methods, commonly used in chemometrics, that are not mathematically rigorous. The rigorous methods are extensions of the methods described in detail in Lawson and Hanson's landmark text on solving least squares problems, which exhibit well-behaved least squares performance. The approximate methods tend to be easy to use and code, but they exhibit poor least squares behaviors and have properties that are not well understood. This paper explains the application of rigorous equality-constrained least squares and demonstrates the dangers of employing non-rigorous methods. We found that in some cases, upon initiating multivariate curve resolution with the exact basis vectors underlying synthetic data overlaid with noise, the approximate method actually results in an increase in the magnitude of residuals. This phenomenon indicates that the solutions for the approximate methods may actually diverge from the least squares solution. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||