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Small Error (small + error)
Selected AbstractsConsistency of dynamic site response at Port IslandEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2001Laurie G. Baise Abstract System identification (SI) methods are used to determine empirical Green's functions (EGF) for soil intervals at the Port Island Site in Kobe, Japan and in shake table model tests performed by the Port and Harbor Research Institute (PHRI) to emulate the site during the 17 January 1995 Hyogo-ken Nanbu earthquake. The model form for the EGFs is a parametric auto-regressive moving average (ARMA) model mapping the ground motions recorded at the base of a soil interval to the top of that interval, hence capturing the effect of the soil on the through-passing wave. The consistency of site response at Port Island before, during, and after the mainshock is examined by application of small motion foreshock EGFs to incoming ground motions over these time intervals. The prediction errors (or misfits) for the foreshocks, the mainshock, and the aftershocks, are assessed to determine the extent of altered soil response as a result of liquefaction of the ground during the mainshock. In addition, the consistency of soil response between field and model test is verified by application of EGFs calculated from the shake table test to the 17 January input data. The prediction error is then used to assess the consistency of behaviour between the two cases. By using EGFs developed for small-amplitude foreshock ground motions, ground motions were predicted for all intervals of the vertical array except those that liquefied with small error. Analysis of the post-liquefied ground conditions implies that the site response gradually returns to a pre-earthquake state. Site behaviour is found to be consistent between foreshocks and the mainshock for the native ground (below 16 m in the field) with a normalized mean square error (NMSE) of 0.080 and a peak ground acceleration (PGA) of 0.5g. When the soil actually liquefies (change of state), recursive models are needed to track the variable soil behaviour for the remainder of the shaking. The recursive models are shown to demonstrate consistency between the shake table tests and the field with a NMSE of 0.102 for the 16 m to surface interval that liquefied. The aftershock ground response was not modelled well with the foreshock EGF immediately after the mainshock (NMSE ranging from 0.37 to 0.92). One month after the mainshock, the prediction error from the foreshock modeled was back to the foreshock error level. Copyright © 2001 John Wiley Sons, Ltd. [source] Assessment of the increase in variability when combining volumetric data from different scannersHUMAN BRAIN MAPPING, Issue 2 2009Santiago Reig Abstract In multicenter MRI studies, pooling of volumetric data requires a prior evaluation of compatibility between the different machines used. We tested the compatibility of five different scanners (2 General Electric Signa, 2 Siemens Symphony, and a Philips Gyroscan) at five different sites by repeating the scans of five volunteers at each of the sites. Using a semiautomatic method based on the Talairach atlas, and SPM algorithms for tissue segmentation (multimodal T1 and T2, or T1-only), we obtained volume measurements of the main brain lobes (frontal, parietal, occipital, temporal) and for each tissue type. Our results suggest that pooling of multisite data adds small error for whole brain measurements, intersite coefficient of variation (CV) ranging from 1.8 to 5.2%, respectively, for GM and CSF. However, in the occipital lobe, intersite CV can be as high as 11.7% for WM and 17.3% for CSF. Compared with the intersite, intrasite CV values were always much lower. Whenever possible, T1 and T2 tissue segmentation methods should be used because they yield more consistent volume measurements between sites than T1-only, especially when some of the scans were obtained with different sequence parameters and pixel size from those of the other sites. Our study shows that highest compatibility among scanners would be obtained using equipments of the same manufacturer and also image acquisition parameters as similar as possible. After validation, data from a specific ROI or scanner showing values markedly different from the other sites might be excluded from the analysis. Hum Brain Mapp, 2009. © 2007 Wiley-Liss, Inc. [source] Solutions of pore pressure build up due to progressive wavesINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2001L. Cheng Abstract The analytical solution of soil pore pressure accumulations due to a progressive wave is examined in detail. First of all, the errors contained in a published analytical solution for wave-induced pore pressure accumulation are addressed, and the correct solution is presented in a more general form. The behaviour of the solution under different soil conditions is then investigated. It is found that the solution for deep soil conditions is sensitive to the soil shear stress in the top thin layer of the soil. However the solution is significantly influenced by the shear stress in the thin layer of soil near the impermeable base, for shallow and finite depth soil conditions. It is also found that a small error in the soil shear stress can lead to a large error in the accumulated pore pressure. An error analysis reveals the relationships between the accuracy of the pore pressure accumulation and the accuracy of the soil shear stress. A numerical solution to the simplified Biot consolidation equation is also developed. It is shown that the error analysis is of significant value for the numerical modelling of pore pressure buildup in marine soils. Both analytical and numerical examples are given to validate the error estimation method proposed in the present paper. Copyright © 2001 John Wiley & Sons, Ltd. [source] On the efficient evaluation of Fourier patterns for nanoparticles and clustersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2006Antonio Cervellino Abstract Samples made of an isotropically oriented ensemble of atomic clusters or structures that are not large crystals (i.e. extended less than 10 periods in each direction) are at the frontier of today's material science and chemistry. Examples are nanoparticles, nanotubes, amorphous matter, polymers, and macromolecules in suspension. For such systems the computation of powder diffraction patterns (which may provide an efficient characterization) is to be performed the hard way, by summing contributions from each atom pair. This work deals with performing such computation in the most practical and efficient way. Three main points are developed: how to encode the enormous array of interatomic distances (which increase as the square or higher powers of the cluster diameter) to a much smaller array of equispaced values on a coarse grid (whose size increases linearly with the diameter); how to perform a fast computation of the diffraction pattern from this equispaced grid; how to optimize the grid step to obtain an arbitrarily small error on the computed diffraction pattern. Theory and examples are jointly developed and presented. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 995,1008, 2006 [source] Embedded dual fiber Bragg grating sensor for simultaneous measurement of temperature and load (strain) with enhanced sensitivityMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2009Samir K. Mondal Abstract An embedded dual fiber Bragg gratings sensor for simultaneous measurement of temperature and load (strain) is proposed and experimentally demonstrated. Two nearly identical gratings are mounted on opposite side of an arch-shaped steel strip. The grating in concave and convex position experiences equal blue and red shift, respectively, due to bending of the strip which is exploited in temperature and load (strain) discrimination. The temperature and load (strain) sensitivity of the sensor improves to 28.5 pm/°C and 2.8 pm/g (2.6 pm/,,). The sensor can measure temperature and load (strain) accurately with small error of ±1°C and ±1 g, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1621,1624, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24439 [source] Correcting wind-induced bias in solid precipitation measurements in case of limited and uncertain dataHYDROLOGICAL PROCESSES, Issue 17 2008Vincent Fortin Abstract Automatic precipitation gauges tend to underestimate solid precipitation in the presence of wind. Loss as a function of wind speed is typically evaluated by comparing the gauge with a more accurate measurement made using a double-fence intercomparison reference gauge (DFIR). For small precipitation events, small errors in the observations can induce large errors in the ,catch' ratio, i.e. the ratio of the automatic gauge measurement to the DFIR observation. For this reason, precipitation events of less than 3 mm are typically discarded before performing the regression analysis. This can mean discarding more than 90% of the observations. This paper shows how the method of weighted least squares can be used to perform a regression analysis that can take into account the whole sample to provide a more accurate estimation of the relationship between the catch ratio and the wind speed. This methodology is then used to obtain an adjustment curve for a shielded Geonor T-200B precipitation gauge in Northern Québec. Copyright © 2008 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada. [source] Impact of Terminal Digit Preference by Family Physicians and Sphygmomanometer Calibration Errors on Blood Pressure Value: Implication for Hypertension ScreeningJOURNAL OF CLINICAL HYPERTENSION, Issue 5 2008Theophile Niyonsenga PhD The accuracy of blood pressure (BP) measurement is important; systematic small errors can mislabel BP status in many persons. The objective of this study was to assess the impact of 2 types of measurement errors on the evaluation of BP in family medicine: errors associated with terminal digit preference and those associated with calibration errors of sphygmomanometers. Secondary data analyses from 2 different projects were used to derive empiric distributions of terminal digit and BP device errors. Taking into account both types of errors, the proportion of false positives (falsely high BP) and false negatives (falsely normal BP) varied between 0. 82% and 5.18% of the population of consulting family physicians. In the United States, false positives and false negatives in patients' BP evaluations might lead to overtreating or undertreating 1.15 million to 7.25 million patients. Results support the need for the development of systematic interventions for quality control of BP measurements and periodic retraining for health professionals. [source] Assessing number-specific error in the recall of onset of last menstrual periodPAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 3 2000D.K. Waller The goal of this investigation was to determine whether women who did not report preferred numbers for their last menstrual period (LMP) may be a group of women who are particularly careful in keeping track of their menstrual cycles and therefore have more accurate LMP dating , based on a comparison with ultrasound examinations. We also sought to estimate the frequency with which preferred numbers are reported in different sources of data and for different subgroups of women. First, we examined the 1987 California birth certificates in which LMP was collected at the time of birth (n = 504 853). We also examined the records of 43 880 women participating in the California Alpha-fetoprotein (AFP) Screening Program between 1986 and 1987, for whom gestational ages based on both early ultrasound examination and LMP were collected before 20 weeks of gestation. In the 1987 California birth certificates, seven numbers,1, 5, 10, 15, 20, 25 and 28,were recorded more frequently than expected. An estimated 12.9% of these records had preferred numbers. The most frequently recorded number was 15, occurring 2.5 times more often than expected (P < 0.01). In the data of the AFP Screening Program, the same seven numbers were preferred, and approximately 7.9% of records were affected by number preference. Comparisons with measurements of gestational age based on ultrasound demonstrated that LMP-based gestational ages in which non-preferred numbers are reported for the LMP are slightly more accurate than those in which preferred numbers are reported (P < 0.01). In most cases, number preference appears to introduce small errors into measurements of gestational age, probably as a result of rounding. Thus, the effect of number preference may be primarily of interest to research studies in which small errors in the measurement of gestational age will have a significant impact on findings. [source] Safety on an inpatient pediatric otolaryngology service: Many small errors, few adverse eventsTHE LARYNGOSCOPE, Issue 5 2009Rahul K. Shah MD Abstract Objectives: Studies of medical error demonstrate that errors and adverse events (AEs) are common in hospitals. There are little data of errors on pediatric surgical services. Methods: We retrospectively reviewed 50 randomly selected inpatient admissions to the otolaryngology service at a tertiary care children's hospital. We used a "zero-defect" paradigm, recording any error or adverse event,from minor errors such as illegible notes to more significant errors such as mismanagement resulting in a bleeding emergency. Results: A total of 553 errors/AEs were identified in 50 admissions. Most (449) were charting or record-keeping deficiencies. Minor AEs (n = 26) and moderate AEs (n = 8) were present in 38% of admissions; there were no major AEs or permanent morbidity. Medication-related errors occurred in 22% of admissions, but only two resulted in minor AEs. There was a positive correlation between minor errors and AEs; however, this was not statistically significant. Conclusions: Multiple errors occurred in every inpatient pediatric otolaryngology admission; however, only 26 minor and eight moderate AEs were identified. The rate of errors per 1,000 hospital days (6,356 per 1,000 days) is higher than previously reported in voluntary reporting studies, possibly due to our methodology of physician review with a "zero-defect" standard. Trends in the data suggest that the presence of small errors may be associated with the risk of adverse events. Although labor-intensive, physician chart review is a valuable tool for identifying areas for improvement. Although small errors were common, there were few harms and no major morbidity. Laryngoscope, 2009 [source] | |||||||||||||