Identification and estimation of nonlinear models using two samples with nonclassical measurement errors

KAUST Repository

Carroll, Raymond J.

2010-05-01

This paper considers identification and estimation of a general nonlinear Errors-in-Variables (EIV) model using two samples. Both samples consist of a dependent variable, some error-free covariates, and an error-prone covariate, for which the measurement error has unknown distribution and could be arbitrarily correlated with the latent true values; and neither sample contains an accurate measurement of the corresponding true variable. We assume that the regression model of interest - the conditional distribution of the dependent variable given the latent true covariate and the error-free covariates - is the same in both samples, but the distributions of the latent true covariates vary with observed error-free discrete covariates. We first show that the general latent nonlinear model is nonparametrically identified using the two samples when both could have nonclassical errors, without either instrumental variables or independence between the two samples. When the two samples are independent and the nonlinear regression model is parameterized, we propose sieve Quasi Maximum Likelihood Estimation (Q-MLE) for the parameter of interest, and establish its root-n consistency and asymptotic normality under possible misspecification, and its semiparametric efficiency under correct specification, with easily estimated standard errors. A Monte Carlo simulation and a data application are presented to show the power of the approach.

Evaluation and mitigation of potential errors in radiochromic film dosimetry due to film curvature at scanning.

Science.gov (United States)

Palmer, Antony L; Bradley, David A; Nisbet, Andrew

2015-03-08

This work considers a previously overlooked uncertainty present in film dosimetry which results from moderate curvature of films during the scanning process. Small film samples are particularly susceptible to film curling which may be undetected or deemed insignificant. In this study, we consider test cases with controlled induced curvature of film and with film raised horizontally above the scanner plate. We also evaluate the difference in scans of a film irradiated with a typical brachytherapy dose distribution with the film naturally curved and with the film held flat on the scanner. Typical naturally occurring curvature of film at scanning, giving rise to a maximum height 1 to 2 mm above the scan plane, may introduce dose errors of 1% to 4%, and considerably reduce gamma evaluation passing rates when comparing film-measured doses with treatment planning system-calculated dose distributions, a common application of film dosimetry in radiotherapy. The use of a triple-channel dosimetry algorithm appeared to mitigate the error due to film curvature compared to conventional single-channel film dosimetry. The change in pixel value and calibrated reported dose with film curling or height above the scanner plate may be due to variations in illumination characteristics, optical disturbances, or a Callier-type effect. There is a clear requirement for physically flat films at scanning to avoid the introduction of a substantial error source in film dosimetry. Particularly for small film samples, a compression glass plate above the film is recommended to ensure flat-film scanning. This effect has been overlooked to date in the literature.

Optimization of sample absorbance for quantitative analysis in the presence of pathlength error in the IR and NIR regions

International Nuclear Information System (INIS)

Hirschfeld, T.; Honigs, D.; Hieftje, G.

1985-01-01

Optical absorbance levels for quantiative analysis in the presence of photometric error have been described in the past. In newer instrumentation, such as FT-IR and NIRA spectrometers, the photometric error is no longer limiting. In these instruments, pathlength error due to cell or sampling irreproducibility is often a major concern. One can derive optimal absorbance by taking both pathlength and photometric errors into account. This paper analyzes the cases of pathlength error >> photometric error (trivial) and various cases in which the pathlength errors and the photometric error are of the same order: adjustable concentration (trivial until dilution errors are considered), constant relative pathlength error (trivial), and constant absolute pathlength error. The latter, in particular, is analyzed in detail to give the behavior of the error, the behavior of the optimal absorbance in its presence, and the total error levels attainable

Correction of Sample-Time Error for Time-Interleaved Sampling System Using Cubic Spline Interpolation

Directory of Open Access Journals (Sweden)

Qin Guo-jie

2014-08-01

Full Text Available Sample-time errors can greatly degrade the dynamic range of a time-interleaved sampling system. In this paper, a novel correction technique employing a cubic spline interpolation is proposed for inter-channel sample-time error compensation. The cubic spline interpolation compensation filter is developed in the form of a finite-impulse response (FIR filter structure. The correction method of the interpolation compensation filter coefficients is deduced. A 4GS/s two-channel, time-interleaved ADC prototype system has been implemented to evaluate the performance of the technique. The experimental results showed that the correction technique is effective to attenuate the spurious spurs and improve the dynamic performance of the system.

A method for analysing incidents due to human errors on nuclear installations

International Nuclear Information System (INIS)

Griffon, M.

1980-01-01

This paper deals with the development of a methodology adapted to a detailed analysis of incidents considered to be due to human errors. An identification of human errors and a search for their eventual multiple causes is then needed. They are categorized in eight classes: education and training of personnel, installation design, work organization, time and work duration, physical environment, social environment, history of the plant and performance of the operator. The method is illustrated by the analysis of a handling incident generated by multiple human errors. (author)

Mitigating Observation Perturbation Sampling Errors in the Stochastic EnKF

KAUST Repository

Hoteit, Ibrahim

2015-03-17

The stochastic ensemble Kalman filter (EnKF) updates its ensemble members with observations perturbed with noise sampled from the distribution of the observational errors. This was shown to introduce noise into the system and may become pronounced when the ensemble size is smaller than the rank of the observational error covariance, which is often the case in real oceanic and atmospheric data assimilation applications. This work introduces an efficient serial scheme to mitigate the impact of observations’ perturbations sampling in the analysis step of the EnKF, which should provide more accurate ensemble estimates of the analysis error covariance matrices. The new scheme is simple to implement within the serial EnKF algorithm, requiring only the approximation of the EnKF sample forecast error covariance matrix by a matrix with one rank less. The new EnKF scheme is implemented and tested with the Lorenz-96 model. Results from numerical experiments are conducted to compare its performance with the EnKF and two standard deterministic EnKFs. This study shows that the new scheme enhances the behavior of the EnKF and may lead to better performance than the deterministic EnKFs even when implemented with relatively small ensembles.

Mitigating Observation Perturbation Sampling Errors in the Stochastic EnKF

KAUST Repository

Hoteit, Ibrahim; Pham, D.-T.; El Gharamti, Mohamad; Luo, X.

2015-01-01

The stochastic ensemble Kalman filter (EnKF) updates its ensemble members with observations perturbed with noise sampled from the distribution of the observational errors. This was shown to introduce noise into the system and may become pronounced when the ensemble size is smaller than the rank of the observational error covariance, which is often the case in real oceanic and atmospheric data assimilation applications. This work introduces an efficient serial scheme to mitigate the impact of observations’ perturbations sampling in the analysis step of the EnKF, which should provide more accurate ensemble estimates of the analysis error covariance matrices. The new scheme is simple to implement within the serial EnKF algorithm, requiring only the approximation of the EnKF sample forecast error covariance matrix by a matrix with one rank less. The new EnKF scheme is implemented and tested with the Lorenz-96 model. Results from numerical experiments are conducted to compare its performance with the EnKF and two standard deterministic EnKFs. This study shows that the new scheme enhances the behavior of the EnKF and may lead to better performance than the deterministic EnKFs even when implemented with relatively small ensembles.

Assessing human error during collecting a hydrocarbon sample of ...

African Journals Online (AJOL)

This paper reports the assessment method of the hydrocarbon sample collection standard operation procedure (SOP) using THERP. The Performance Shaping Factors (PSF) from THERP analyzed and assessed the human errors during collecting a hydrocarbon sample of a petrochemical refinery plant. Twenty-two ...

RAMs: the problem of transient errors due to alpha radiation

International Nuclear Information System (INIS)

Goujon, Pierre.

1980-01-01

Errors that remained unexplained for a long time have occurred with dynamic random access memories. It has been known since 1978 that they are due to stray alpha radiation. A good understanding of this phenomenon enables its effects to be neutralized and the reliability of the products to be guarantied [fr

Theory of errors in Coriolis flowmeter readings due to compressibility of the fluid being metered

OpenAIRE

Kutin, Jože; Hemp, John

2015-01-01

The compressibility of fluids in a Coriolis mass flowmeter can cause errors in the meter's measurements of density and mass flow rate. These errors may be better described as errors due to the finite speed of sound in the fluid being metered, or due to the finite wavelength of sound at the operating frequency of the meter. In this paper, they are investigated theoretically and calculated to a first approximation (small degree of compressibility). The investigation is limited to straight beam-...

Consistent errors in first strand cDNA due to random hexamer mispriming.

Directory of Open Access Journals (Sweden)

Thomas P van Gurp

Full Text Available Priming of random hexamers in cDNA synthesis is known to show sequence bias, but in addition it has been suggested recently that mismatches in random hexamer priming could be a cause of mismatches between the original RNA fragment and observed sequence reads. To explore random hexamer mispriming as a potential source of these errors, we analyzed two independently generated RNA-seq datasets of synthetic ERCC spikes for which the reference is known. First strand cDNA synthesized by random hexamer priming on RNA showed consistent position and nucleotide-specific mismatch errors in the first seven nucleotides. The mismatch errors found in both datasets are consistent in distribution and thermodynamically stable mismatches are more common. This strongly indicates that RNA-DNA mispriming of specific random hexamers causes these errors. Due to their consistency and specificity, mispriming errors can have profound implications for downstream applications if not dealt with properly.

Dosage uniformity problems which occur due to technological errors in extemporaneously prepared suppositories in hospitals and pharmacies

Science.gov (United States)

Kalmár, Éva; Lasher, Jason Richard; Tarry, Thomas Dean; Myers, Andrea; Szakonyi, Gerda; Dombi, György; Baki, Gabriella; Alexander, Kenneth S.

2013-01-01

The availability of suppositories in Hungary, especially in clinical pharmacy practice, is usually provided by extemporaneous preparations. Due to the known advantages of rectal drug administration, its benefits are frequently utilized in pediatrics. However, errors during the extemporaneous manufacturing process can lead to non-homogenous drug distribution within the dosage units. To determine the root cause of these errors and provide corrective actions, we studied suppository samples prepared with exactly known errors using both cerimetric titration and HPLC technique. Our results show that the most frequent technological error occurs when the pharmacist fails to use the correct displacement factor in the calculations which could lead to a 4.6% increase/decrease in the assay in individual dosage units. The second most important source of error can occur when the molding excess is calculated solely for the suppository base. This can further dilute the final suppository drug concentration causing the assay to be as low as 80%. As a conclusion we emphasize that the application of predetermined displacement factors in calculations for the formulation of suppositories is highly important, which enables the pharmacist to produce a final product containing exactly the determined dose of an active substance despite the different densities of the components. PMID:25161378

Errors of Inference Due to Errors of Measurement.

Science.gov (United States)

Linn, Robert L.; Werts, Charles E.

Failure to consider errors of measurement when using partial correlation or analysis of covariance techniques can result in erroneous conclusions. Certain aspects of this problem are discussed and particular attention is given to issues raised in a recent article by Brewar, Campbell, and Crano. (Author)

Error due to unresolved scales in estimation problems for atmospheric data assimilation

Science.gov (United States)

Janjic, Tijana

The error arising due to unresolved scales in data assimilation procedures is examined. The problem of estimating the projection of the state of a passive scalar undergoing advection at a sequence of times is considered. The projection belongs to a finite- dimensional function space and is defined on the continuum. Using the continuum projection of the state of a passive scalar, a mathematical definition is obtained for the error arising due to the presence, in the continuum system, of scales unresolved by the discrete dynamical model. This error affects the estimation procedure through point observations that include the unresolved scales. In this work, two approximate methods for taking into account the error due to unresolved scales and the resulting correlations are developed and employed in the estimation procedure. The resulting formulas resemble the Schmidt-Kalman filter and the usual discrete Kalman filter, respectively. For this reason, the newly developed filters are called the Schmidt-Kalman filter and the traditional filter. In order to test the assimilation methods, a two- dimensional advection model with nonstationary spectrum was developed for passive scalar transport in the atmosphere. An analytical solution on the sphere was found depicting the model dynamics evolution. Using this analytical solution the model error is avoided, and the error due to unresolved scales is the only error left in the estimation problem. It is demonstrated that the traditional and the Schmidt- Kalman filter work well provided the exact covariance function of the unresolved scales is known. However, this requirement is not satisfied in practice, and the covariance function must be modeled. The Schmidt-Kalman filter cannot be computed in practice without further approximations. Therefore, the traditional filter is better suited for practical use. Also, the traditional filter does not require modeling of the full covariance function of the unresolved scales, but only

Accounting for Sampling Error in Genetic Eigenvalues Using Random Matrix Theory.

Science.gov (United States)

Sztepanacz, Jacqueline L; Blows, Mark W

2017-07-01

The distribution of genetic variance in multivariate phenotypes is characterized by the empirical spectral distribution of the eigenvalues of the genetic covariance matrix. Empirical estimates of genetic eigenvalues from random effects linear models are known to be overdispersed by sampling error, where large eigenvalues are biased upward, and small eigenvalues are biased downward. The overdispersion of the leading eigenvalues of sample covariance matrices have been demonstrated to conform to the Tracy-Widom (TW) distribution. Here we show that genetic eigenvalues estimated using restricted maximum likelihood (REML) in a multivariate random effects model with an unconstrained genetic covariance structure will also conform to the TW distribution after empirical scaling and centering. However, where estimation procedures using either REML or MCMC impose boundary constraints, the resulting genetic eigenvalues tend not be TW distributed. We show how using confidence intervals from sampling distributions of genetic eigenvalues without reference to the TW distribution is insufficient protection against mistaking sampling error as genetic variance, particularly when eigenvalues are small. By scaling such sampling distributions to the appropriate TW distribution, the critical value of the TW statistic can be used to determine if the magnitude of a genetic eigenvalue exceeds the sampling error for each eigenvalue in the spectral distribution of a given genetic covariance matrix. Copyright © 2017 by the Genetics Society of America.

Sampling of systematic errors to estimate likelihood weights in nuclear data uncertainty propagation

International Nuclear Information System (INIS)

Helgesson, P.; Sjöstrand, H.; Koning, A.J.; Rydén, J.; Rochman, D.; Alhassan, E.; Pomp, S.

2016-01-01

In methodologies for nuclear data (ND) uncertainty assessment and propagation based on random sampling, likelihood weights can be used to infer experimental information into the distributions for the ND. As the included number of correlated experimental points grows large, the computational time for the matrix inversion involved in obtaining the likelihood can become a practical problem. There are also other problems related to the conventional computation of the likelihood, e.g., the assumption that all experimental uncertainties are Gaussian. In this study, a way to estimate the likelihood which avoids matrix inversion is investigated; instead, the experimental correlations are included by sampling of systematic errors. It is shown that the model underlying the sampling methodology (using univariate normal distributions for random and systematic errors) implies a multivariate Gaussian for the experimental points (i.e., the conventional model). It is also shown that the likelihood estimates obtained through sampling of systematic errors approach the likelihood obtained with matrix inversion as the sample size for the systematic errors grows large. In studied practical cases, it is seen that the estimates for the likelihood weights converge impractically slowly with the sample size, compared to matrix inversion. The computational time is estimated to be greater than for matrix inversion in cases with more experimental points, too. Hence, the sampling of systematic errors has little potential to compete with matrix inversion in cases where the latter is applicable. Nevertheless, the underlying model and the likelihood estimates can be easier to intuitively interpret than the conventional model and the likelihood function involving the inverted covariance matrix. Therefore, this work can both have pedagogical value and be used to help motivating the conventional assumption of a multivariate Gaussian for experimental data. The sampling of systematic errors could also

Estimation of sampling error uncertainties in observed surface air temperature change in China

Science.gov (United States)

Hua, Wei; Shen, Samuel S. P.; Weithmann, Alexander; Wang, Huijun

2017-08-01

This study examines the sampling error uncertainties in the monthly surface air temperature (SAT) change in China over recent decades, focusing on the uncertainties of gridded data, national averages, and linear trends. Results indicate that large sampling error variances appear at the station-sparse area of northern and western China with the maximum value exceeding 2.0 K2 while small sampling error variances are found at the station-dense area of southern and eastern China with most grid values being less than 0.05 K2. In general, the negative temperature existed in each month prior to the 1980s, and a warming in temperature began thereafter, which accelerated in the early and mid-1990s. The increasing trend in the SAT series was observed for each month of the year with the largest temperature increase and highest uncertainty of 0.51 ± 0.29 K (10 year)-1 occurring in February and the weakest trend and smallest uncertainty of 0.13 ± 0.07 K (10 year)-1 in August. The sampling error uncertainties in the national average annual mean SAT series are not sufficiently large to alter the conclusion of the persistent warming in China. In addition, the sampling error uncertainties in the SAT series show a clear variation compared with other uncertainty estimation methods, which is a plausible reason for the inconsistent variations between our estimate and other studies during this period.

The Impact of Soil Sampling Errors on Variable Rate Fertilization

Energy Technology Data Exchange (ETDEWEB)

R. L. Hoskinson; R C. Rope; L G. Blackwood; R D. Lee; R K. Fink

2004-07-01

Variable rate fertilization of an agricultural field is done taking into account spatial variability in the soil’s characteristics. Most often, spatial variability in the soil’s fertility is the primary characteristic used to determine the differences in fertilizers applied from one point to the next. For several years the Idaho National Engineering and Environmental Laboratory (INEEL) has been developing a Decision Support System for Agriculture (DSS4Ag) to determine the economically optimum recipe of various fertilizers to apply at each site in a field, based on existing soil fertility at the site, predicted yield of the crop that would result (and a predicted harvest-time market price), and the current costs and compositions of the fertilizers to be applied. Typically, soil is sampled at selected points within a field, the soil samples are analyzed in a lab, and the lab-measured soil fertility of the point samples is used for spatial interpolation, in some statistical manner, to determine the soil fertility at all other points in the field. Then a decision tool determines the fertilizers to apply at each point. Our research was conducted to measure the impact on the variable rate fertilization recipe caused by variability in the measurement of the soil’s fertility at the sampling points. The variability could be laboratory analytical errors or errors from variation in the sample collection method. The results show that for many of the fertility parameters, laboratory measurement error variance exceeds the estimated variability of the fertility measure across grid locations. These errors resulted in DSS4Ag fertilizer recipe recommended application rates that differed by up to 138 pounds of urea per acre, with half the field differing by more than 57 pounds of urea per acre. For potash the difference in application rate was up to 895 pounds per acre and over half the field differed by more than 242 pounds of potash per acre. Urea and potash differences

On the Spatial and Temporal Sampling Errors of Remotely Sensed Precipitation Products

Directory of Open Access Journals (Sweden)

Ali Behrangi

2017-11-01

Full Text Available Observation with coarse spatial and temporal sampling can cause large errors in quantification of the amount, intensity, and duration of precipitation events. In this study, the errors resulting from temporal and spatial sampling of precipitation events were quantified and examined using the latest version (V4 of the Global Precipitation Measurement (GPM mission integrated multi-satellite retrievals for GPM (IMERG, which is available since spring of 2014. Relative mean square error was calculated at 0.1° × 0.1° every 0.5 h between the degraded (temporally and spatially and original IMERG products. The temporal and spatial degradation was performed by producing three-hour (T3, six-hour (T6, 0.5° × 0.5° (S5, and 1.0° × 1.0° (S10 maps. The results show generally larger errors over land than ocean, especially over mountainous regions. The relative error of T6 is almost 20% larger than T3 over tropical land, but is smaller in higher latitudes. Over land relative error of T6 is larger than S5 across all latitudes, while T6 has larger relative error than S10 poleward of 20°S–20°N. Similarly, the relative error of T3 exceeds S5 poleward of 20°S–20°N, but does not exceed S10, except in very high latitudes. Similar results are also seen over ocean, but the error ratios are generally less sensitive to seasonal changes. The results also show that the spatial and temporal relative errors are not highly correlated. Overall, lower correlations between the spatial and temporal relative errors are observed over ocean than over land. Quantification of such spatiotemporal effects provides additional insights into evaluation studies, especially when different products are cross-compared at a range of spatiotemporal scales.

Identification of proteomic biomarkers predicting prostate cancer aggressiveness and lethality despite biopsy-sampling error.

Science.gov (United States)

Shipitsin, M; Small, C; Choudhury, S; Giladi, E; Friedlander, S; Nardone, J; Hussain, S; Hurley, A D; Ernst, C; Huang, Y E; Chang, H; Nifong, T P; Rimm, D L; Dunyak, J; Loda, M; Berman, D M; Blume-Jensen, P

2014-09-09

Key challenges of biopsy-based determination of prostate cancer aggressiveness include tumour heterogeneity, biopsy-sampling error, and variations in biopsy interpretation. The resulting uncertainty in risk assessment leads to significant overtreatment, with associated costs and morbidity. We developed a performance-based strategy to identify protein biomarkers predictive of prostate cancer aggressiveness and lethality regardless of biopsy-sampling variation. Prostatectomy samples from a large patient cohort with long follow-up were blindly assessed by expert pathologists who identified the tissue regions with the highest and lowest Gleason grade from each patient. To simulate biopsy-sampling error, a core from a high- and a low-Gleason area from each patient sample was used to generate a 'high' and a 'low' tumour microarray, respectively. Using a quantitative proteomics approach, we identified from 160 candidates 12 biomarkers that predicted prostate cancer aggressiveness (surgical Gleason and TNM stage) and lethal outcome robustly in both high- and low-Gleason areas. Conversely, a previously reported lethal outcome-predictive marker signature for prostatectomy tissue was unable to perform under circumstances of maximal sampling error. Our results have important implications for cancer biomarker discovery in general and development of a sampling error-resistant clinical biopsy test for prediction of prostate cancer aggressiveness.

Propagation of errors from a null balance terahertz reflectometer to a sample's relative water content

International Nuclear Information System (INIS)

Hadjiloucas, S; Walker, G C; Bowen, J W; Zafiropoulos, A

2009-01-01

The THz water content index of a sample is defined and advantages in using such metric in estimating a sample's relative water content are discussed. The errors from reflectance measurements performed at two different THz frequencies using a quasi-optical null-balance reflectometer are propagated to the errors in estimating the sample water content index.

Statistical errors in Monte Carlo estimates of systematic errors

Energy Technology Data Exchange (ETDEWEB)

Roe, Byron P. [Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States)]. E-mail: byronroe@umich.edu

2007-01-01

For estimating the effects of a number of systematic errors on a data sample, one can generate Monte Carlo (MC) runs with systematic parameters varied and examine the change in the desired observed result. Two methods are often used. In the unisim method, the systematic parameters are varied one at a time by one standard deviation, each parameter corresponding to a MC run. In the multisim method (see ), each MC run has all of the parameters varied; the amount of variation is chosen from the expected distribution of each systematic parameter, usually assumed to be a normal distribution. The variance of the overall systematic error determination is derived for each of the two methods and comparisons are made between them. If one focuses not on the error in the prediction of an individual systematic error, but on the overall error due to all systematic errors in the error matrix element in data bin m, the number of events needed is strongly reduced because of the averaging effect over all of the errors. For simple models presented here the multisim model was far better if the statistical error in the MC samples was larger than an individual systematic error, while for the reverse case, the unisim model was better. Exact formulas and formulas for the simple toy models are presented so that realistic calculations can be made. The calculations in the present note are valid if the errors are in a linear region. If that region extends sufficiently far, one can have the unisims or multisims correspond to k standard deviations instead of one. This reduces the number of events required by a factor of k{sup 2}.

Statistical errors in Monte Carlo estimates of systematic errors

International Nuclear Information System (INIS)

Roe, Byron P.

2007-01-01

For estimating the effects of a number of systematic errors on a data sample, one can generate Monte Carlo (MC) runs with systematic parameters varied and examine the change in the desired observed result. Two methods are often used. In the unisim method, the systematic parameters are varied one at a time by one standard deviation, each parameter corresponding to a MC run. In the multisim method (see ), each MC run has all of the parameters varied; the amount of variation is chosen from the expected distribution of each systematic parameter, usually assumed to be a normal distribution. The variance of the overall systematic error determination is derived for each of the two methods and comparisons are made between them. If one focuses not on the error in the prediction of an individual systematic error, but on the overall error due to all systematic errors in the error matrix element in data bin m, the number of events needed is strongly reduced because of the averaging effect over all of the errors. For simple models presented here the multisim model was far better if the statistical error in the MC samples was larger than an individual systematic error, while for the reverse case, the unisim model was better. Exact formulas and formulas for the simple toy models are presented so that realistic calculations can be made. The calculations in the present note are valid if the errors are in a linear region. If that region extends sufficiently far, one can have the unisims or multisims correspond to k standard deviations instead of one. This reduces the number of events required by a factor of k 2

Analysis of influence on back-EMF based sensorless control of PMSM due to parameter variations and measurement errors

DEFF Research Database (Denmark)

Wang, Z.; Lu, K.; Ye, Y.

2011-01-01

To achieve better performance of sensorless control of PMSM, a precise and stable estimation of rotor position and speed is required. Several parameter uncertainties and variable measurement errors may lead to estimation error, such as resistance and inductance variations due to temperature...... and flux saturation, current and voltage errors due to measurement uncertainties, and signal delay caused by hardwares. This paper reveals some inherent principles for the performance of the back-EMF based sensorless algorithm embedded in a surface mounted PMSM system adapting vector control strategy...

The predicted CLARREO sampling error of the inter-annual SW variability

Science.gov (United States)

Doelling, D. R.; Keyes, D. F.; Nguyen, C.; Macdonnell, D.; Young, D. F.

2009-12-01

The NRC Decadal Survey has called for SI traceability of long-term hyper-spectral flux measurements in order to monitor climate variability. This mission is called the Climate Absolute Radiance and Refractivity Observatory (CLARREO) and is currently defining its mission requirements. The requirements are focused on the ability to measure decadal change of key climate variables at very high accuracy. The accuracy goals are set using anticipated climate change magnitudes, but the accuracy achieved for any given climate variable must take into account the temporal and spatial sampling errors based on satellite orbits and calibration accuracy. The time period to detect a significant trend in the CLARREO record depends on the magnitude of the sampling calibration errors relative to the current inter-annual variability. The largest uncertainty in climate feedbacks remains the effect of changing clouds on planetary energy balance. Some regions on earth have strong diurnal cycles, such as maritime stratus and afternoon land convection; other regions have strong seasonal cycles, such as the monsoon. However, when monitoring inter-annual variability these cycles are only important if the strength of these cycles vary on decadal time scales. This study will attempt to determine the best satellite constellations to reduce sampling error and to compare the error with the current inter-annual variability signal to ensure the viability of the mission. The study will incorporate Clouds and the Earth's Radiant Energy System (CERES) (Monthly TOA/Surface Averages) SRBAVG product TOA LW and SW climate quality fluxes. The fluxes are derived by combining Terra (10:30 local equator crossing time) CERES fluxes with 3-hourly 5-geostationary satellite estimated broadband fluxes, which are normalized using the CERES fluxes, to complete the diurnal cycle. These fluxes were saved hourly during processing and considered the truth dataset. 90°, 83° and 74° inclination precessionary orbits as

GY SAMPLING THEORY IN ENVIRONMENTAL STUDIES 2: SUBSAMPLING ERROR MEASUREMENTS

Science.gov (United States)

Sampling can be a significant source of error in the measurement process. The characterization and cleanup of hazardous waste sites require data that meet site-specific levels of acceptable quality if scientifically supportable decisions are to be made. In support of this effort,...

[Errors in Peruvian medical journals references].

Science.gov (United States)

Huamaní, Charles; Pacheco-Romero, José

2009-01-01

References are fundamental in our studies; an adequate selection is asimportant as an adequate description. To determine the number of errors in a sample of references found in Peruvian medical journals. We reviewed 515 scientific papers references selected by systematic randomized sampling and corroborated reference information with the original document or its citation in Pubmed, LILACS or SciELO-Peru. We found errors in 47,6% (245) of the references, identifying 372 types of errors; the most frequent were errors in presentation style (120), authorship (100) and title (100), mainly due to spelling mistakes (91). References error percentage was high, varied and multiple. We suggest systematic revision of references in the editorial process as well as to extend the discussion on this theme. references, periodicals, research, bibliometrics.

Spanish exit polls. Sampling error or nonresponse bias?

Directory of Open Access Journals (Sweden)

Pavía, Jose M.

2016-09-01

Full Text Available Countless examples of misleading forecasts on behalf of both pre-election and exit polls can be found all over the world. Non-representative samples due to differential nonresponse have been claimed as being the main reason for inaccurate exit-poll projections. In real inference problems, it is seldom possible to compare estimates and true values. Electoral forecasts are an exception. Comparisons between estimates and final outcomes can be carried out once votes have been tallied. In this paper, we examine the raw data collected in seven exit polls conducted in Spain and test the likelihood that the data collected in each sampled voting location can be considered as a random sample of actual results. Knowing the answer to this is relevant for both electoral analysts and forecasters as, if the hypothesis is rejected, the shortcomings of the collected data would need amending. Analysts could improve the quality of their computations by implementing local correction strategies. We find strong evidence of nonsampling error in Spanish exit polls and evidence that the political context matters. Nonresponse bias is larger in polarized elections and in a climate of fearExiste un gran número de ejemplos de predicciones inexactas obtenidas a partir tanto de encuestas pre-electorales como de encuestas a pie de urna a lo largo del mundo. La presencia de tasas de no-respuesta diferencial entre distintos tipos de electores ha sido la principal razón esgrimida para justificar las proyecciones erróneas en las encuestas a pie de urna. En problemas de inferencia rara vez es posible comparar estimaciones y valores reales. Las predicciones electorales son una excepción. La comparación entre estimaciones y resultados finales puede realizarse una vez los votos han sido contabilizados. En este trabajo, examinamos los datos brutos recogidos en siete encuestas a pie de urna realizadas en España y testamos la hipótesis de que los datos recolectados en cada punto

Method for evaluation of risk due to seismic related design and construction errors based on past reactor experience

International Nuclear Information System (INIS)

Gonzalez Cuesta, M.; Okrent, D.

1985-01-01

This paper proposes a methodology for quantification of risk due to seismic related design and construction errors in nuclear power plants, based on information available on errors discovered in the past. For the purposes of this paper, an error is defined as any event that causes the seismic safety margins of a nuclear power plant to be smaller than implied by current regulatory requirements and industry common practice. Also, the actual reduction in the safety margins caused by the error will be called a deficiency. The method is based on a theoretical model of errors, called a deficiency logic diagram. First, an ultimate cause is present. This ultimate cause is consumated as a specific instance, called originating error. As originating errors may occur in actions to be applied a number of times, a deficiency generation system may be involved. Quality assurance activities will hopefully identify most of these deficiencies, requesting their disposition. However, the quality assurance program is not perfect and some operating plant deficiencies may persist, causing different levels of impact to the plant logic. The paper provides a way of extrapolating information about errors discovered in plants under construction in order to assess the risk due to errors that have not been discovered

Bias Errors due to Leakage Effects When Estimating Frequency Response Functions

Directory of Open Access Journals (Sweden)

Andreas Josefsson

2012-01-01

Full Text Available Frequency response functions are often utilized to characterize a system's dynamic response. For a wide range of engineering applications, it is desirable to determine frequency response functions for a system under stochastic excitation. In practice, the measurement data is contaminated by noise and some form of averaging is needed in order to obtain a consistent estimator. With Welch's method, the discrete Fourier transform is used and the data is segmented into smaller blocks so that averaging can be performed when estimating the spectrum. However, this segmentation introduces leakage effects. As a result, the estimated frequency response function suffers from both systematic (bias and random errors due to leakage. In this paper the bias error in the H1 and H2-estimate is studied and a new method is proposed to derive an approximate expression for the relative bias error at the resonance frequency with different window functions. The method is based on using a sum of real exponentials to describe the window's deterministic autocorrelation function. Simple expressions are derived for a rectangular window and a Hanning window. The theoretical expressions are verified with numerical simulations and a very good agreement is found between the results from the proposed bias expressions and the empirical results.

Systematic bias in genomic classification due to contaminating non-neoplastic tissue in breast tumor samples.

Science.gov (United States)

Elloumi, Fathi; Hu, Zhiyuan; Li, Yan; Parker, Joel S; Gulley, Margaret L; Amos, Keith D; Troester, Melissa A

2011-06-30

Genomic tests are available to predict breast cancer recurrence and to guide clinical decision making. These predictors provide recurrence risk scores along with a measure of uncertainty, usually a confidence interval. The confidence interval conveys random error and not systematic bias. Standard tumor sampling methods make this problematic, as it is common to have a substantial proportion (typically 30-50%) of a tumor sample comprised of histologically benign tissue. This "normal" tissue could represent a source of non-random error or systematic bias in genomic classification. To assess the performance characteristics of genomic classification to systematic error from normal contamination, we collected 55 tumor samples and paired tumor-adjacent normal tissue. Using genomic signatures from the tumor and paired normal, we evaluated how increasing normal contamination altered recurrence risk scores for various genomic predictors. Simulations of normal tissue contamination caused misclassification of tumors in all predictors evaluated, but different breast cancer predictors showed different types of vulnerability to normal tissue bias. While two predictors had unpredictable direction of bias (either higher or lower risk of relapse resulted from normal contamination), one signature showed predictable direction of normal tissue effects. Due to this predictable direction of effect, this signature (the PAM50) was adjusted for normal tissue contamination and these corrections improved sensitivity and negative predictive value. For all three assays quality control standards and/or appropriate bias adjustment strategies can be used to improve assay reliability. Normal tissue sampled concurrently with tumor is an important source of bias in breast genomic predictors. All genomic predictors show some sensitivity to normal tissue contamination and ideal strategies for mitigating this bias vary depending upon the particular genes and computational methods used in the predictor.

Active Mycobacterium Infection Due to Intramuscular BCG Administration Following Multi-Steps Medication Errors

Directory of Open Access Journals (Sweden)

MohammadReza Rafati

2015-10-01

Full Text Available Bacillus Calmette-Guérin (BCG is indicated for treatment of primary or relapsing flat urothelial cell carcinoma in situ (CIS of the urinary bladder. Disseminated infectious complications occasionally occur due to BCG as a vaccine and intravesical therapy.  Intramuscular (IM or Intravenous (IV administrations of BCG are rare medication errors which are more probable to produce systemic infections. This report presents 13 years old case that several steps medication errors occurred consequently from physician handwriting, pharmacy dispensing, nursing administration and patient family. The physician wrote βHCG instead of HCG in the prescription. βHCG was read as BCG by the pharmacy staff and 6 vials of intravesical BCG were administered IM twice a week for 3 consecutive weeks. The patient experienced fever and chills after each injection, but he was admitted 2 months after first IM administration of BCG with fever and pancytopenia. Unfortunately four month after using drug, during second admission duo to cellulitis at the sites of BCG injection the physicians diagnosed the medication error. Using handwritten prescription and inappropriate abbreviations, spending inadequate time for taking a brief medical history in pharmacy, lack of verifying name, dose and wrote before medication administration and lack of considering medication error as an important differential diagnosis had roles to occur this multi-steps medication error.

[Responsibility due to medication errors in France: a study based on SHAM insurance data].

Science.gov (United States)

Theissen, A; Orban, J-C; Fuz, F; Guerin, J-P; Flavin, P; Albertini, S; Maricic, S; Saquet, D; Niccolai, P

2015-03-01

The safe medication practices at the hospital constitute a major public health problem. Drug supply chain is a complex process, potentially source of errors and damages for the patient. SHAM insurances are the biggest French provider of medical liability insurances and a relevant source of data on the health care complications. The main objective of the study was to analyze the type and cause of medication errors declared to SHAM and having led to a conviction by a court. We did a retrospective study on insurance claims provided by SHAM insurances with a medication error and leading to a condemnation over a 6-year period (between 2005 and 2010). Thirty-one cases were analysed, 21 for scheduled activity and 10 for emergency activity. Consequences of claims were mostly serious (12 deaths, 14 serious complications, 5 simple complications). The types of medication errors were a drug monitoring error (11 cases), an administration error (5 cases), an overdose (6 cases), an allergy (4 cases), a contraindication (3 cases) and an omission (2 cases). Intravenous route of administration was involved in 19 of 31 cases (61%). The causes identified by the court expert were an error related to service organization (11), an error related to medical practice (11) or nursing practice (13). Only one claim was due to the hospital pharmacy. The claim related to drug supply chain is infrequent but potentially serious. These data should help strengthen quality approach in risk management. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Sample size re-assessment leading to a raised sample size does not inflate type I error rate under mild conditions.

Science.gov (United States)

Broberg, Per

2013-07-19

One major concern with adaptive designs, such as the sample size adjustable designs, has been the fear of inflating the type I error rate. In (Stat Med 23:1023-1038, 2004) it is however proven that when observations follow a normal distribution and the interim result show promise, meaning that the conditional power exceeds 50%, type I error rate is protected. This bound and the distributional assumptions may seem to impose undesirable restrictions on the use of these designs. In (Stat Med 30:3267-3284, 2011) the possibility of going below 50% is explored and a region that permits an increased sample size without inflation is defined in terms of the conditional power at the interim. A criterion which is implicit in (Stat Med 30:3267-3284, 2011) is derived by elementary methods and expressed in terms of the test statistic at the interim to simplify practical use. Mathematical and computational details concerning this criterion are exhibited. Under very general conditions the type I error rate is preserved under sample size adjustable schemes that permit a raise. The main result states that for normally distributed observations raising the sample size when the result looks promising, where the definition of promising depends on the amount of knowledge gathered so far, guarantees the protection of the type I error rate. Also, in the many situations where the test statistic approximately follows a normal law, the deviation from the main result remains negligible. This article provides details regarding the Weibull and binomial distributions and indicates how one may approach these distributions within the current setting. There is thus reason to consider such designs more often, since they offer a means of adjusting an important design feature at little or no cost in terms of error rate.

Statistical errors in Monte Carlo estimates of systematic errors

Science.gov (United States)

Roe, Byron P.

2007-01-01

For estimating the effects of a number of systematic errors on a data sample, one can generate Monte Carlo (MC) runs with systematic parameters varied and examine the change in the desired observed result. Two methods are often used. In the unisim method, the systematic parameters are varied one at a time by one standard deviation, each parameter corresponding to a MC run. In the multisim method (see ), each MC run has all of the parameters varied; the amount of variation is chosen from the expected distribution of each systematic parameter, usually assumed to be a normal distribution. The variance of the overall systematic error determination is derived for each of the two methods and comparisons are made between them. If one focuses not on the error in the prediction of an individual systematic error, but on the overall error due to all systematic errors in the error matrix element in data bin m, the number of events needed is strongly reduced because of the averaging effect over all of the errors. For simple models presented here the multisim model was far better if the statistical error in the MC samples was larger than an individual systematic error, while for the reverse case, the unisim model was better. Exact formulas and formulas for the simple toy models are presented so that realistic calculations can be made. The calculations in the present note are valid if the errors are in a linear region. If that region extends sufficiently far, one can have the unisims or multisims correspond to k standard deviations instead of one. This reduces the number of events required by a factor of k2. The specific terms unisim and multisim were coined by Peter Meyers and Steve Brice, respectively, for the MiniBooNE experiment. However, the concepts have been developed over time and have been in general use for some time.

Sample positioning effects in x-ray spectrometry

International Nuclear Information System (INIS)

Carpenter, D.

Instrument error due to variation in sample position in a crystal x-ray spectrometer can easily exceed the total instrumental error. Lack of reproducibility in sample position in the x-ray optics is the single largest source of system error. The factors that account for sample positioning error are described, and many of the details of flat crystal x-ray optics are discussed

Quantification of errors in ordinal outcome scales using shannon entropy: effect on sample size calculations.

Science.gov (United States)

Mandava, Pitchaiah; Krumpelman, Chase S; Shah, Jharna N; White, Donna L; Kent, Thomas A

2013-01-01

Clinical trial outcomes often involve an ordinal scale of subjective functional assessments but the optimal way to quantify results is not clear. In stroke, the most commonly used scale, the modified Rankin Score (mRS), a range of scores ("Shift") is proposed as superior to dichotomization because of greater information transfer. The influence of known uncertainties in mRS assessment has not been quantified. We hypothesized that errors caused by uncertainties could be quantified by applying information theory. Using Shannon's model, we quantified errors of the "Shift" compared to dichotomized outcomes using published distributions of mRS uncertainties and applied this model to clinical trials. We identified 35 randomized stroke trials that met inclusion criteria. Each trial's mRS distribution was multiplied with the noise distribution from published mRS inter-rater variability to generate an error percentage for "shift" and dichotomized cut-points. For the SAINT I neuroprotectant trial, considered positive by "shift" mRS while the larger follow-up SAINT II trial was negative, we recalculated sample size required if classification uncertainty was taken into account. Considering the full mRS range, error rate was 26.1%±5.31 (Mean±SD). Error rates were lower for all dichotomizations tested using cut-points (e.g. mRS 1; 6.8%±2.89; overall pdecrease in reliability. The resultant errors need to be considered since sample size may otherwise be underestimated. In principle, we have outlined an approach to error estimation for any condition in which there are uncertainties in outcome assessment. We provide the user with programs to calculate and incorporate errors into sample size estimation.

Type-II generalized family-wise error rate formulas with application to sample size determination.

Science.gov (United States)

Delorme, Phillipe; de Micheaux, Pierre Lafaye; Liquet, Benoit; Riou, Jérémie

2016-07-20

Multiple endpoints are increasingly used in clinical trials. The significance of some of these clinical trials is established if at least r null hypotheses are rejected among m that are simultaneously tested. The usual approach in multiple hypothesis testing is to control the family-wise error rate, which is defined as the probability that at least one type-I error is made. More recently, the q-generalized family-wise error rate has been introduced to control the probability of making at least q false rejections. For procedures controlling this global type-I error rate, we define a type-II r-generalized family-wise error rate, which is directly related to the r-power defined as the probability of rejecting at least r false null hypotheses. We obtain very general power formulas that can be used to compute the sample size for single-step and step-wise procedures. These are implemented in our R package rPowerSampleSize available on the CRAN, making them directly available to end users. Complexities of the formulas are presented to gain insight into computation time issues. Comparison with Monte Carlo strategy is also presented. We compute sample sizes for two clinical trials involving multiple endpoints: one designed to investigate the effectiveness of a drug against acute heart failure and the other for the immunogenicity of a vaccine strategy against pneumococcus. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Quantification of errors in ordinal outcome scales using shannon entropy: effect on sample size calculations.

Directory of Open Access Journals (Sweden)

Pitchaiah Mandava

Full Text Available OBJECTIVE: Clinical trial outcomes often involve an ordinal scale of subjective functional assessments but the optimal way to quantify results is not clear. In stroke, the most commonly used scale, the modified Rankin Score (mRS, a range of scores ("Shift" is proposed as superior to dichotomization because of greater information transfer. The influence of known uncertainties in mRS assessment has not been quantified. We hypothesized that errors caused by uncertainties could be quantified by applying information theory. Using Shannon's model, we quantified errors of the "Shift" compared to dichotomized outcomes using published distributions of mRS uncertainties and applied this model to clinical trials. METHODS: We identified 35 randomized stroke trials that met inclusion criteria. Each trial's mRS distribution was multiplied with the noise distribution from published mRS inter-rater variability to generate an error percentage for "shift" and dichotomized cut-points. For the SAINT I neuroprotectant trial, considered positive by "shift" mRS while the larger follow-up SAINT II trial was negative, we recalculated sample size required if classification uncertainty was taken into account. RESULTS: Considering the full mRS range, error rate was 26.1%±5.31 (Mean±SD. Error rates were lower for all dichotomizations tested using cut-points (e.g. mRS 1; 6.8%±2.89; overall p<0.001. Taking errors into account, SAINT I would have required 24% more subjects than were randomized. CONCLUSION: We show when uncertainty in assessments is considered, the lowest error rates are with dichotomization. While using the full range of mRS is conceptually appealing, a gain of information is counter-balanced by a decrease in reliability. The resultant errors need to be considered since sample size may otherwise be underestimated. In principle, we have outlined an approach to error estimation for any condition in which there are uncertainties in outcome assessment. We

Maximum type 1 error rate inflation in multiarmed clinical trials with adaptive interim sample size modifications.

Science.gov (United States)

Graf, Alexandra C; Bauer, Peter; Glimm, Ekkehard; Koenig, Franz

2014-07-01

Sample size modifications in the interim analyses of an adaptive design can inflate the type 1 error rate, if test statistics and critical boundaries are used in the final analysis as if no modification had been made. While this is already true for designs with an overall change of the sample size in a balanced treatment-control comparison, the inflation can be much larger if in addition a modification of allocation ratios is allowed as well. In this paper, we investigate adaptive designs with several treatment arms compared to a single common control group. Regarding modifications, we consider treatment arm selection as well as modifications of overall sample size and allocation ratios. The inflation is quantified for two approaches: a naive procedure that ignores not only all modifications, but also the multiplicity issue arising from the many-to-one comparison, and a Dunnett procedure that ignores modifications, but adjusts for the initially started multiple treatments. The maximum inflation of the type 1 error rate for such types of design can be calculated by searching for the "worst case" scenarios, that are sample size adaptation rules in the interim analysis that lead to the largest conditional type 1 error rate in any point of the sample space. To show the most extreme inflation, we initially assume unconstrained second stage sample size modifications leading to a large inflation of the type 1 error rate. Furthermore, we investigate the inflation when putting constraints on the second stage sample sizes. It turns out that, for example fixing the sample size of the control group, leads to designs controlling the type 1 error rate. © 2014 The Author. Biometrical Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rail-guided robotic end-effector position error due to rail compliance and ship motion

NARCIS (Netherlands)

Borgerink, Dian; Stegenga, J.; Brouwer, Dannis Michel; Woertche, H.J.; Stramigioli, Stefano

2014-01-01

A rail-guided robotic system is currently being designed for the inspection of ballast water tanks in ships. This robotic system will manipulate sensors toward the interior walls of the tank. In this paper, the influence of rail compliance on the end-effector position error due to ship movement is

Principal Stratification in sample selection problems with non normal error terms

DEFF Research Database (Denmark)

Rocci, Roberto; Mellace, Giovanni

The aim of the paper is to relax distributional assumptions on the error terms, often imposed in parametric sample selection models to estimate causal effects, when plausible exclusion restrictions are not available. Within the principal stratification framework, we approximate the true distribut...... an application to the Job Corps training program....

Irregular analytical errors in diagnostic testing - a novel concept.

Science.gov (United States)

Vogeser, Michael; Seger, Christoph

2018-02-23

-isotope-dilution mass spectrometry methods are increasingly used for pre-market validation of routine diagnostic assays (these tests also involve substantial sets of clinical validation samples). Based on this definition/terminology, we list recognized causes of irregular analytical error as a risk catalog for clinical chemistry in this article. These issues include reproducible individual analytical errors (e.g. caused by anti-reagent antibodies) and non-reproducible, sporadic errors (e.g. errors due to incorrect pipetting volume due to air bubbles in a sample), which can both lead to inaccurate results and risks for patients.

Statistical theory for estimating sampling errors of regional radiation averages based on satellite measurements

Science.gov (United States)

Smith, G. L.; Bess, T. D.; Minnis, P.

1983-01-01

The processes which determine the weather and climate are driven by the radiation received by the earth and the radiation subsequently emitted. A knowledge of the absorbed and emitted components of radiation is thus fundamental for the study of these processes. In connection with the desire to improve the quality of long-range forecasting, NASA is developing the Earth Radiation Budget Experiment (ERBE), consisting of a three-channel scanning radiometer and a package of nonscanning radiometers. A set of these instruments is to be flown on both the NOAA-F and NOAA-G spacecraft, in sun-synchronous orbits, and on an Earth Radiation Budget Satellite. The purpose of the scanning radiometer is to obtain measurements from which the average reflected solar radiant exitance and the average earth-emitted radiant exitance at a reference level can be established. The estimate of regional average exitance obtained will not exactly equal the true value of the regional average exitance, but will differ due to spatial sampling. A method is presented for evaluating this spatial sampling error.

Estimation of errors due to inhomogeneous distribution of radionuclides in lungs

International Nuclear Information System (INIS)

Pelled, O.; German, U.; Pollak, G.; Alfassi, Z.B.

2006-01-01

The uncertainty in the activity determination of uranium contamination due to real inhomogeneous distribution and assumption of homogenous distribution can reach more than one order of magnitude when using one detector in a set of 4 detectors covering most of the whole lungs. Using the information from several detectors may improve the accuracy, as obtained by summing the responses from the 3 or 4 detectors. However, even with this improvement, the errors are still very large, up to almost a factor of 10 when the analysis is based on the 92 keV energy peak and up to 7 for the 185 keV peak

The analytical evolution of NLS solitons due to the numerical discretization error

Science.gov (United States)

Hoseini, S. M.; Marchant, T. R.

2011-12-01

Soliton perturbation theory is used to obtain analytical solutions describing solitary wave tails or shelves, due to numerical discretization error, for soliton solutions of the nonlinear Schrödinger equation. Two important implicit numerical schemes for the nonlinear Schrödinger equation, with second-order temporal and spatial discretization errors, are considered. These are the Crank-Nicolson scheme and a scheme, due to Taha [1], based on the inverse scattering transform. The first-order correction for the solitary wave tail, or shelf, is in integral form and an explicit expression is found for large time. The shelf decays slowly, at a rate of t^{-{1\\over 2}}, which is characteristic of the nonlinear Schrödinger equation. Singularity theory, usually used for combustion problems, is applied to the explicit large-time expression for the solitary wave tail. Analytical results are then obtained, such as the parameter regions in which qualitatively different types of solitary wave tails occur, the location of zeros and the location and amplitude of peaks. It is found that three different types of tail occur for the Crank-Nicolson and Taha schemes and that the Taha scheme exhibits some unusual symmetry properties, as the tails for left and right moving solitary waves are different. Optimal choices of the discretization parameters for the numerical schemes are also found, which minimize the amplitude of the solitary wave tail. The analytical solutions are compared with numerical simulations, and an excellent comparison is found.

The analytical evolution of NLS solitons due to the numerical discretization error

International Nuclear Information System (INIS)

Hoseini, S M; Marchant, T R

2011-01-01

Soliton perturbation theory is used to obtain analytical solutions describing solitary wave tails or shelves, due to numerical discretization error, for soliton solutions of the nonlinear Schrödinger equation. Two important implicit numerical schemes for the nonlinear Schrödinger equation, with second-order temporal and spatial discretization errors, are considered. These are the Crank–Nicolson scheme and a scheme, due to Taha, based on the inverse scattering transform. The first-order correction for the solitary wave tail, or shelf, is in integral form and an explicit expression is found for large time. The shelf decays slowly, at a rate of t -1/2 , which is characteristic of the nonlinear Schrödinger equation. Singularity theory, usually used for combustion problems, is applied to the explicit large-time expression for the solitary wave tail. Analytical results are then obtained, such as the parameter regions in which qualitatively different types of solitary wave tails occur, the location of zeros and the location and amplitude of peaks. It is found that three different types of tail occur for the Crank–Nicolson and Taha schemes and that the Taha scheme exhibits some unusual symmetry properties, as the tails for left and right moving solitary waves are different. Optimal choices of the discretization parameters for the numerical schemes are also found, which minimize the amplitude of the solitary wave tail. The analytical solutions are compared with numerical simulations, and an excellent comparison is found. (paper)

Estimation of Total Error in DWPF Reported Radionuclide Inventories

International Nuclear Information System (INIS)

Edwards, T.B.

1995-01-01

This report investigates the impact of random errors due to measurement and sampling on the reported concentrations of radionuclides in DWPF's filled canister inventory resulting from each macro-batch. The objective of this investigation is to estimate the variance of the total error in reporting these radionuclide concentrations

Distribution of the Determinant of the Sample Correlation Matrix: Monte Carlo Type One Error Rates.

Science.gov (United States)

Reddon, John R.; And Others

1985-01-01

Computer sampling from a multivariate normal spherical population was used to evaluate the type one error rates for a test of sphericity based on the distribution of the determinant of the sample correlation matrix. (Author/LMO)

Errors in causal inference: an organizational schema for systematic error and random error.

Science.gov (United States)

Suzuki, Etsuji; Tsuda, Toshihide; Mitsuhashi, Toshiharu; Mansournia, Mohammad Ali; Yamamoto, Eiji

2016-11-01

To provide an organizational schema for systematic error and random error in estimating causal measures, aimed at clarifying the concept of errors from the perspective of causal inference. We propose to divide systematic error into structural error and analytic error. With regard to random error, our schema shows its four major sources: nondeterministic counterfactuals, sampling variability, a mechanism that generates exposure events and measurement variability. Structural error is defined from the perspective of counterfactual reasoning and divided into nonexchangeability bias (which comprises confounding bias and selection bias) and measurement bias. Directed acyclic graphs are useful to illustrate this kind of error. Nonexchangeability bias implies a lack of "exchangeability" between the selected exposed and unexposed groups. A lack of exchangeability is not a primary concern of measurement bias, justifying its separation from confounding bias and selection bias. Many forms of analytic errors result from the small-sample properties of the estimator used and vanish asymptotically. Analytic error also results from wrong (misspecified) statistical models and inappropriate statistical methods. Our organizational schema is helpful for understanding the relationship between systematic error and random error from a previously less investigated aspect, enabling us to better understand the relationship between accuracy, validity, and precision. Copyright © 2016 Elsevier Inc. All rights reserved.

Dipole estimation errors due to not incorporating anisotropic conductivities in realistic head models for EEG source analysis

Science.gov (United States)

Hallez, Hans; Staelens, Steven; Lemahieu, Ignace

2009-10-01

EEG source analysis is a valuable tool for brain functionality research and for diagnosing neurological disorders, such as epilepsy. It requires a geometrical representation of the human head or a head model, which is often modeled as an isotropic conductor. However, it is known that some brain tissues, such as the skull or white matter, have an anisotropic conductivity. Many studies reported that the anisotropic conductivities have an influence on the calculated electrode potentials. However, few studies have assessed the influence of anisotropic conductivities on the dipole estimations. In this study, we want to determine the dipole estimation errors due to not taking into account the anisotropic conductivities of the skull and/or brain tissues. Therefore, head models are constructed with the same geometry, but with an anisotropically conducting skull and/or brain tissue compartment. These head models are used in simulation studies where the dipole location and orientation error is calculated due to neglecting anisotropic conductivities of the skull and brain tissue. Results show that not taking into account the anisotropic conductivities of the skull yields a dipole location error between 2 and 25 mm, with an average of 10 mm. When the anisotropic conductivities of the brain tissues are neglected, the dipole location error ranges between 0 and 5 mm. In this case, the average dipole location error was 2.3 mm. In all simulations, the dipole orientation error was smaller than 10°. We can conclude that the anisotropic conductivities of the skull have to be incorporated to improve the accuracy of EEG source analysis. The results of the simulation, as presented here, also suggest that incorporation of the anisotropic conductivities of brain tissues is not necessary. However, more studies are needed to confirm these suggestions.

Dipole estimation errors due to not incorporating anisotropic conductivities in realistic head models for EEG source analysis

International Nuclear Information System (INIS)

Hallez, Hans; Staelens, Steven; Lemahieu, Ignace

2009-01-01

EEG source analysis is a valuable tool for brain functionality research and for diagnosing neurological disorders, such as epilepsy. It requires a geometrical representation of the human head or a head model, which is often modeled as an isotropic conductor. However, it is known that some brain tissues, such as the skull or white matter, have an anisotropic conductivity. Many studies reported that the anisotropic conductivities have an influence on the calculated electrode potentials. However, few studies have assessed the influence of anisotropic conductivities on the dipole estimations. In this study, we want to determine the dipole estimation errors due to not taking into account the anisotropic conductivities of the skull and/or brain tissues. Therefore, head models are constructed with the same geometry, but with an anisotropically conducting skull and/or brain tissue compartment. These head models are used in simulation studies where the dipole location and orientation error is calculated due to neglecting anisotropic conductivities of the skull and brain tissue. Results show that not taking into account the anisotropic conductivities of the skull yields a dipole location error between 2 and 25 mm, with an average of 10 mm. When the anisotropic conductivities of the brain tissues are neglected, the dipole location error ranges between 0 and 5 mm. In this case, the average dipole location error was 2.3 mm. In all simulations, the dipole orientation error was smaller than 10 deg. We can conclude that the anisotropic conductivities of the skull have to be incorporated to improve the accuracy of EEG source analysis. The results of the simulation, as presented here, also suggest that incorporation of the anisotropic conductivities of brain tissues is not necessary. However, more studies are needed to confirm these suggestions.

Climatologies from satellite measurements: the impact of orbital sampling on the standard error of the mean

Directory of Open Access Journals (Sweden)

M. Toohey

2013-04-01

Full Text Available Climatologies of atmospheric observations are often produced by binning measurements according to latitude and calculating zonal means. The uncertainty in these climatological means is characterised by the standard error of the mean (SEM. However, the usual estimator of the SEM, i.e., the sample standard deviation divided by the square root of the sample size, holds only for uncorrelated randomly sampled measurements. Measurements of the atmospheric state along a satellite orbit cannot always be considered as independent because (a the time-space interval between two nearest observations is often smaller than the typical scale of variations in the atmospheric state, and (b the regular time-space sampling pattern of a satellite instrument strongly deviates from random sampling. We have developed a numerical experiment where global chemical fields from a chemistry climate model are sampled according to real sampling patterns of satellite-borne instruments. As case studies, the model fields are sampled using sampling patterns of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS and Atmospheric Chemistry Experiment Fourier-Transform Spectrometer (ACE-FTS satellite instruments. Through an iterative subsampling technique, and by incorporating information on the random errors of the MIPAS and ACE-FTS measurements, we produce empirical estimates of the standard error of monthly mean zonal mean model O3 in 5° latitude bins. We find that generally the classic SEM estimator is a conservative estimate of the SEM, i.e., the empirical SEM is often less than or approximately equal to the classic estimate. Exceptions occur only when natural variability is larger than the random measurement error, and specifically in instances where the zonal sampling distribution shows non-uniformity with a similar zonal structure as variations in the sampled field, leading to maximum sensitivity to arbitrary phase shifts between the sample distribution and

A basic framework for the analysis of the human error potential due to the computerization in nuclear power plants

International Nuclear Information System (INIS)

Lee, Y. H.

1999-01-01

Computerization and its vivid benefits expected in the nuclear power plant design cannot be realized without verifying the inherent safety problems. Human error aspect is also included in the verification issues. The verification spans from the perception of the changes in operation functions such as automation to the unfamiliar experience of operators due to the interface change. Therefore, a new framework for human error analysis might capture both the positive and the negative effect of the computerization. This paper suggest a basic framework for error identification through the review of the existing human error studies and the experience of computerizations in nuclear power plants

Accurate recapture identification for genetic mark–recapture studies with error-tolerant likelihood-based match calling and sample clustering

Science.gov (United States)

Sethi, Suresh; Linden, Daniel; Wenburg, John; Lewis, Cara; Lemons, Patrick R.; Fuller, Angela K.; Hare, Matthew P.

2016-01-01

Error-tolerant likelihood-based match calling presents a promising technique to accurately identify recapture events in genetic mark–recapture studies by combining probabilities of latent genotypes and probabilities of observed genotypes, which may contain genotyping errors. Combined with clustering algorithms to group samples into sets of recaptures based upon pairwise match calls, these tools can be used to reconstruct accurate capture histories for mark–recapture modelling. Here, we assess the performance of a recently introduced error-tolerant likelihood-based match-calling model and sample clustering algorithm for genetic mark–recapture studies. We assessed both biallelic (i.e. single nucleotide polymorphisms; SNP) and multiallelic (i.e. microsatellite; MSAT) markers using a combination of simulation analyses and case study data on Pacific walrus (Odobenus rosmarus divergens) and fishers (Pekania pennanti). A novel two-stage clustering approach is demonstrated for genetic mark–recapture applications. First, repeat captures within a sampling occasion are identified. Subsequently, recaptures across sampling occasions are identified. The likelihood-based matching protocol performed well in simulation trials, demonstrating utility for use in a wide range of genetic mark–recapture studies. Moderately sized SNP (64+) and MSAT (10–15) panels produced accurate match calls for recaptures and accurate non-match calls for samples from closely related individuals in the face of low to moderate genotyping error. Furthermore, matching performance remained stable or increased as the number of genetic markers increased, genotyping error notwithstanding.

Sampling Error in Relation to Cyst Nematode Population Density Estimation in Small Field Plots.

Science.gov (United States)

Župunski, Vesna; Jevtić, Radivoje; Jokić, Vesna Spasić; Župunski, Ljubica; Lalošević, Mirjana; Ćirić, Mihajlo; Ćurčić, Živko

2017-06-01

Cyst nematodes are serious plant-parasitic pests which could cause severe yield losses and extensive damage. Since there is still very little information about error of population density estimation in small field plots, this study contributes to the broad issue of population density assessment. It was shown that there was no significant difference between cyst counts of five or seven bulk samples taken per each 1-m 2 plot, if average cyst count per examined plot exceeds 75 cysts per 100 g of soil. Goodness of fit of data to probability distribution tested with χ 2 test confirmed a negative binomial distribution of cyst counts for 21 out of 23 plots. The recommended measure of sampling precision of 17% expressed through coefficient of variation ( cv ) was achieved if the plots of 1 m 2 contaminated with more than 90 cysts per 100 g of soil were sampled with 10-core bulk samples taken in five repetitions. If plots were contaminated with less than 75 cysts per 100 g of soil, 10-core bulk samples taken in seven repetitions gave cv higher than 23%. This study indicates that more attention should be paid on estimation of sampling error in experimental field plots to ensure more reliable estimation of population density of cyst nematodes.

Optical Waveform Sampling and Error-Free Demultiplexing of 1.28 Tb/s Serial Data in a Nanoengineered Silicon Waveguide

DEFF Research Database (Denmark)

Ji, Hua; Pu, Minhao; Hu, Hao

2011-01-01

This paper presents the experimental demonstrations of using a pure nanoengineered silicon waveguide for 1.28 Tb/s serial data optical waveform sampling and 1.28 Tb/s–10 Gb/s error free demultiplexing. The 330-fs pulses are resolved in each 780-fs time slot in waveform sampling. Error...

Identification of proteomic biomarkers predicting prostate cancer aggressiveness and lethality despite biopsy-sampling error

OpenAIRE

Shipitsin, M; Small, C; Choudhury, S; Giladi, E; Friedlander, S; Nardone, J; Hussain, S; Hurley, A D; Ernst, C; Huang, Y E; Chang, H; Nifong, T P; Rimm, D L; Dunyak, J; Loda, M

2014-01-01

Background: Key challenges of biopsy-based determination of prostate cancer aggressiveness include tumour heterogeneity, biopsy-sampling error, and variations in biopsy interpretation. The resulting uncertainty in risk assessment leads to significant overtreatment, with associated costs and morbidity. We developed a performance-based strategy to identify protein biomarkers predictive of prostate cancer aggressiveness and lethality regardless of biopsy-sampling variation. Methods: Prostatectom...

Simulating systematic errors in X-ray absorption spectroscopy experiments: Sample and beam effects

Energy Technology Data Exchange (ETDEWEB)

Curis, Emmanuel [Laboratoire de Biomathematiques, Faculte de Pharmacie, Universite Rene, Descartes (Paris V)-4, Avenue de l' Observatoire, 75006 Paris (France)]. E-mail: emmanuel.curis@univ-paris5.fr; Osan, Janos [KFKI Atomic Energy Research Institute (AEKI)-P.O. Box 49, H-1525 Budapest (Hungary); Falkenberg, Gerald [Hamburger Synchrotronstrahlungslabor (HASYLAB), Deutsches Elektronen-Synchrotron (DESY)-Notkestrasse 85, 22607 Hamburg (Germany); Benazeth, Simone [Laboratoire de Biomathematiques, Faculte de Pharmacie, Universite Rene, Descartes (Paris V)-4, Avenue de l' Observatoire, 75006 Paris (France); Laboratoire d' Utilisation du Rayonnement Electromagnetique (LURE)-Ba-hat timent 209D, Campus d' Orsay, 91406 Orsay (France); Toeroek, Szabina [KFKI Atomic Energy Research Institute (AEKI)-P.O. Box 49, H-1525 Budapest (Hungary)

2005-07-15

The article presents an analytical model to simulate experimental imperfections in the realization of an X-ray absorption spectroscopy experiment, performed in transmission or fluorescence mode. Distinction is made between sources of systematic errors on a time-scale basis, to select the more appropriate model for their handling. For short time-scale, statistical models are the most suited. For large time-scale, the model is developed for sample and beam imperfections: mainly sample inhomogeneity, sample self-absorption, beam achromaticity. The ability of this model to reproduce the effects of these imperfections is exemplified, and the model is validated on real samples. Various potential application fields of the model are then presented.

Simulating systematic errors in X-ray absorption spectroscopy experiments: Sample and beam effects

International Nuclear Information System (INIS)

Curis, Emmanuel; Osan, Janos; Falkenberg, Gerald; Benazeth, Simone; Toeroek, Szabina

2005-01-01

The article presents an analytical model to simulate experimental imperfections in the realization of an X-ray absorption spectroscopy experiment, performed in transmission or fluorescence mode. Distinction is made between sources of systematic errors on a time-scale basis, to select the more appropriate model for their handling. For short time-scale, statistical models are the most suited. For large time-scale, the model is developed for sample and beam imperfections: mainly sample inhomogeneity, sample self-absorption, beam achromaticity. The ability of this model to reproduce the effects of these imperfections is exemplified, and the model is validated on real samples. Various potential application fields of the model are then presented

Bit Error Rate Due to Misalignment of Earth Station Antenna Pointing to Satellite

Directory of Open Access Journals (Sweden)

Wahyu Pamungkas

2010-04-01

Full Text Available One problem causing reduction of energy in satellite communications system is the misalignment of earth station antenna pointing to satellite. Error in pointing would affect the quality of information signal to energy bit in earth station. In this research, error in pointing angle occurred only at receiver (Rx antenna, while the transmitter (Tx antennas precisely point to satellite. The research was conducted towards two satellites, namely TELKOM-1 and TELKOM-2. At first, measurement was made by directing Tx antenna precisely to satellite, resulting in an antenna pattern shown by spectrum analyzer. The output from spectrum analyzers is drawn with the right scale to describe swift of azimuth and elevation pointing angle towards satellite. Due to drifting from the precise pointing, it influenced the received link budget indicated by pattern antenna. This antenna pattern shows reduction of power level received as a result of pointing misalignment. As a conclusion, the increasing misalignment of pointing to satellite would affect in the reduction of received signal parameters link budget of down-link traffic.

Refractive Error in a Sample of Black High School Children in South Africa.

Science.gov (United States)

Wajuihian, Samuel Otabor; Hansraj, Rekha

2017-12-01

This study focused on a cohort that has not been studied and who currently have limited access to eye care services. The findings, while improving the understanding of the distribution of refractive errors, also enabled identification of children requiring intervention and provided a guide for future resource allocation. The aim of conducting the study was to determine the prevalence and distribution of refractive error and its association with gender, age, and school grade level. Using a multistage random cluster sampling, 1586 children, 632 males (40%) and 954 females (60%), were selected. Their ages ranged between 13 and 18 years with a mean of 15.81 ± 1.56 years. The visual functions evaluated included visual acuity using the logarithm of minimum angle of resolution chart and refractive error measured using the autorefractor and then refined subjectively. Axis astigmatism was presented in the vector method where positive values of J0 indicated with-the-rule astigmatism, negative values indicated against-the-rule astigmatism, whereas J45 represented oblique astigmatism. Overall, patients were myopic with a mean spherical power for right eye of -0.02 ± 0.47; mean astigmatic cylinder power was -0.09 ± 0.27 with mainly with-the-rule astigmatism (J0 = 0.01 ± 0.11). The prevalence estimates were as follows: myopia (at least -0.50) 7% (95% confidence interval [CI], 6 to 9%), hyperopia (at least 0.5) 5% (95% CI, 4 to 6%), astigmatism (at least -0.75 cylinder) 3% (95% CI, 2 to 4%), and anisometropia 3% (95% CI, 2 to 4%). There was no significant association between refractive error and any of the categories (gender, age, and grade levels). The prevalence of refractive error in the sample of high school children was relatively low. Myopia was the most prevalent, and findings on its association with age suggest that the prevalence of myopia may be stabilizing at late teenage years.

Maximum type I error rate inflation from sample size reassessment when investigators are blind to treatment labels.

Science.gov (United States)

Żebrowska, Magdalena; Posch, Martin; Magirr, Dominic

2016-05-30

Consider a parallel group trial for the comparison of an experimental treatment to a control, where the second-stage sample size may depend on the blinded primary endpoint data as well as on additional blinded data from a secondary endpoint. For the setting of normally distributed endpoints, we demonstrate that this may lead to an inflation of the type I error rate if the null hypothesis holds for the primary but not the secondary endpoint. We derive upper bounds for the inflation of the type I error rate, both for trials that employ random allocation and for those that use block randomization. We illustrate the worst-case sample size reassessment rule in a case study. For both randomization strategies, the maximum type I error rate increases with the effect size in the secondary endpoint and the correlation between endpoints. The maximum inflation increases with smaller block sizes if information on the block size is used in the reassessment rule. Based on our findings, we do not question the well-established use of blinded sample size reassessment methods with nuisance parameter estimates computed from the blinded interim data of the primary endpoint. However, we demonstrate that the type I error rate control of these methods relies on the application of specific, binding, pre-planned and fully algorithmic sample size reassessment rules and does not extend to general or unplanned sample size adjustments based on blinded data. © 2015 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. © 2015 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

Evidence Report: Risk of Performance Errors Due to Training Deficiencies

Science.gov (United States)

Barshi, Immanuel; Dempsey, Donna L.

2016-01-01

Substantial evidence supports the claim that inadequate training leads to performance errors. Barshi and Loukopoulos (2012) demonstrate that even a task as carefully developed and refined over many years as operating an aircraft can be significantly improved by a systematic analysis, followed by improved procedures and improved training (see also Loukopoulos, Dismukes, & Barshi, 2009a). Unfortunately, such a systematic analysis of training needs rarely occurs during the preliminary design phase, when modifications are most feasible. Training is often seen as a way to compensate for deficiencies in task and system design, which in turn increases the training load. As a result, task performance often suffers, and with it, the operators suffer and so does the mission. On the other hand, effective training can indeed compensate for such design deficiencies, and can even go beyond to compensate for failures of our imagination to anticipate all that might be needed when we send our crew members to go where no one else has gone before. Much of the research literature on training is motivated by current training practices aimed at current training needs. Although there is some experience with operations in extreme environments on Earth, there is no experience with long-duration space missions where crews must practice semi-autonomous operations, where ground support must accommodate significant communication delays, and where so little is known about the environment. Thus, we must develop robust methodologies and tools to prepare our crews for the unknown. The research necessary to support such an endeavor does not currently exist, but existing research does reveal general challenges that are relevant to long-duration, high-autonomy missions. The evidence presented here describes issues related to the risk of performance errors due to training deficiencies. Contributing factors regarding training deficiencies may pertain to organizational process and training programs for

Quantum tomography via compressed sensing: error bounds, sample complexity and efficient estimators

International Nuclear Information System (INIS)

Flammia, Steven T; Gross, David; Liu, Yi-Kai; Eisert, Jens

2012-01-01

Intuitively, if a density operator has small rank, then it should be easier to estimate from experimental data, since in this case only a few eigenvectors need to be learned. We prove two complementary results that confirm this intuition. Firstly, we show that a low-rank density matrix can be estimated using fewer copies of the state, i.e. the sample complexity of tomography decreases with the rank. Secondly, we show that unknown low-rank states can be reconstructed from an incomplete set of measurements, using techniques from compressed sensing and matrix completion. These techniques use simple Pauli measurements, and their output can be certified without making any assumptions about the unknown state. In this paper, we present a new theoretical analysis of compressed tomography, based on the restricted isometry property for low-rank matrices. Using these tools, we obtain near-optimal error bounds for the realistic situation where the data contain noise due to finite statistics, and the density matrix is full-rank with decaying eigenvalues. We also obtain upper bounds on the sample complexity of compressed tomography, and almost-matching lower bounds on the sample complexity of any procedure using adaptive sequences of Pauli measurements. Using numerical simulations, we compare the performance of two compressed sensing estimators—the matrix Dantzig selector and the matrix Lasso—with standard maximum-likelihood estimation (MLE). We find that, given comparable experimental resources, the compressed sensing estimators consistently produce higher fidelity state reconstructions than MLE. In addition, the use of an incomplete set of measurements leads to faster classical processing with no loss of accuracy. Finally, we show how to certify the accuracy of a low-rank estimate using direct fidelity estimation, and describe a method for compressed quantum process tomography that works for processes with small Kraus rank and requires only Pauli eigenstate preparations

Systematic errors in digital volume correlation due to the self-heating effect of a laboratory x-ray CT scanner

International Nuclear Information System (INIS)

Wang, B; Pan, B; Tao, R; Lubineau, G

2017-01-01

The use of digital volume correlation (DVC) in combination with a laboratory x-ray computed tomography (CT) for full-field internal 3D deformation measurement of opaque materials has flourished in recent years. During x-ray tomographic imaging, the heat generated by the x-ray tube changes the imaging geometry of x-ray scanner, and further introduces noticeable errors in DVC measurements. In this work, to provide practical guidance high-accuracy DVC measurement, the errors in displacements and strains measured by DVC due to the self-heating for effect of a commercially available x-ray scanner were experimentally investigated. The errors were characterized by performing simple rescan tests with different scan durations. The results indicate that the maximum strain errors associated with the self-heating of the x-ray scanner exceed 400 µε . Possible approaches for minimizing or correcting these displacement and strain errors are discussed. Finally, a series of translation and uniaxial compression tests were performed, in which strain errors were detected and then removed using pre-established artificial dilatational strain-time curve. Experimental results demonstrate the efficacy and accuracy of the proposed strain error correction approach. (paper)

Systematic errors in digital volume correlation due to the self-heating effect of a laboratory x-ray CT scanner

KAUST Repository

Wang, B

2017-02-15

The use of digital volume correlation (DVC) in combination with a laboratory x-ray computed tomography (CT) for full-field internal 3D deformation measurement of opaque materials has flourished in recent years. During x-ray tomographic imaging, the heat generated by the x-ray tube changes the imaging geometry of x-ray scanner, and further introduces noticeable errors in DVC measurements. In this work, to provide practical guidance high-accuracy DVC measurement, the errors in displacements and strains measured by DVC due to the self-heating for effect of a commercially available x-ray scanner were experimentally investigated. The errors were characterized by performing simple rescan tests with different scan durations. The results indicate that the maximum strain errors associated with the self-heating of the x-ray scanner exceed 400 µε. Possible approaches for minimizing or correcting these displacement and strain errors are discussed. Finally, a series of translation and uniaxial compression tests were performed, in which strain errors were detected and then removed using pre-established artificial dilatational strain-time curve. Experimental results demonstrate the efficacy and accuracy of the proposed strain error correction approach.

The nature of articulation errors in Egyptian Arabic-speaking children with velopharyngeal insufficiency due to cleft palate.

Science.gov (United States)

Abou-Elsaad, Tamer; Baz, Hemmat; Afsah, Omayma; Mansy, Alzahraa

2015-09-01

Even with early surgical repair, the majority of cleft palate children demonstrate articulation errors and have typical cleft palate speech. Was to determine the nature of articulation errors of Arabic consonants in Egyptian Arabic-speaking children with velopharyngeal insufficiency (VPI). Thirty Egyptian Arabic-speaking children with VPI due to cleft palate (whether primary repaired or secondary repaired) were studied. Auditory perceptual assessment (APA) of children speech was conducted. Nasopharyngoscopy was done to assess the velopharyngeal port (VPP) movements while the child was repeating speech tasks. Mansoura Arabic Articulation test (MAAT) was performed to analyze the consonants articulation of these children. The most frequent type of articulatory errors observed was substitution, more specifically, backing. Pharyngealization of anterior fricatives was the most frequent substitution, especially for the /s/ sound. The most frequent substituting sounds for other sounds were /ʔ/ followed by /k/ and /n/ sounds. Significant correlations were found between the degrees of the open nasality and VPP closure and the articulation errors. On the other hand, the sounds (/ʔ/,/ħ/,/ʕ/,/n/,/w/,/j/) were normally articulated in all studied group. The determination of articulation errors in VPI children could guide the therapists for designing appropriate speech therapy programs for these cases. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Errors due to random noise in velocity measurement using incoherent-scatter radar

Directory of Open Access Journals (Sweden)

P. J. S. Williams

1996-12-01

Full Text Available The random-noise errors involved in measuring the Doppler shift of an 'incoherent-scatter' spectrum are predicted theoretically for all values of Te/Ti from 1.0 to 3.0. After correction has been made for the effects of convolution during transmission and reception and the additional errors introduced by subtracting the average of the background gates, the rms errors can be expressed by a simple semi-empirical formula. The observed errors are determined from a comparison of simultaneous EISCAT measurements using an identical pulse code on several adjacent frequencies. The plot of observed versus predicted error has a slope of 0.991 and a correlation coefficient of 99.3%. The prediction also agrees well with the mean of the error distribution reported by the standard EISCAT analysis programme.

Power and sample size calculations in the presence of phenotype errors for case/control genetic association studies

Directory of Open Access Journals (Sweden)

Finch Stephen J

2005-04-01

Full Text Available Abstract Background Phenotype error causes reduction in power to detect genetic association. We present a quantification of phenotype error, also known as diagnostic error, on power and sample size calculations for case-control genetic association studies between a marker locus and a disease phenotype. We consider the classic Pearson chi-square test for independence as our test of genetic association. To determine asymptotic power analytically, we compute the distribution's non-centrality parameter, which is a function of the case and control sample sizes, genotype frequencies, disease prevalence, and phenotype misclassification probabilities. We derive the non-centrality parameter in the presence of phenotype errors and equivalent formulas for misclassification cost (the percentage increase in minimum sample size needed to maintain constant asymptotic power at a fixed significance level for each percentage increase in a given misclassification parameter. We use a linear Taylor Series approximation for the cost of phenotype misclassification to determine lower bounds for the relative costs of misclassifying a true affected (respectively, unaffected as a control (respectively, case. Power is verified by computer simulation. Results Our major findings are that: (i the median absolute difference between analytic power with our method and simulation power was 0.001 and the absolute difference was no larger than 0.011; (ii as the disease prevalence approaches 0, the cost of misclassifying a unaffected as a case becomes infinitely large while the cost of misclassifying an affected as a control approaches 0. Conclusion Our work enables researchers to specifically quantify power loss and minimum sample size requirements in the presence of phenotype errors, thereby allowing for more realistic study design. For most diseases of current interest, verifying that cases are correctly classified is of paramount importance.

Sampling for quality assurance of grading decisions in diabetic retinopathy screening: designing the system to detect errors.

Science.gov (United States)

Slattery, Jim

2005-01-01

To evaluate various designs for a quality assurance system to detect and control human errors in a national screening programme for diabetic retinopathy. A computer simulation was performed of some possible ways of sampling the referral decisions made during grading and of different criteria for initiating more intensive QA investigations. The effectiveness of QA systems was assessed by the ability to detect a grader making occasional errors in referral. Substantial QA sample sizes are needed to ensure against inappropriate failure to refer. Detection of a grader who failed to refer one in ten cases can be achieved with a probability of 0.58 using an annual sample size of 300 and 0.77 using a sample size of 500. An unmasked verification of a sample of non-referrals by a specialist is the most effective method of internal QA for the diabetic retinopathy screening programme. Preferential sampling of those with some degree of disease may improve the efficiency of the system.

Errors in clinical laboratories or errors in laboratory medicine?

Science.gov (United States)

Plebani, Mario

2006-01-01

Laboratory testing is a highly complex process and, although laboratory services are relatively safe, they are not as safe as they could or should be. Clinical laboratories have long focused their attention on quality control methods and quality assessment programs dealing with analytical aspects of testing. However, a growing body of evidence accumulated in recent decades demonstrates that quality in clinical laboratories cannot be assured by merely focusing on purely analytical aspects. The more recent surveys on errors in laboratory medicine conclude that in the delivery of laboratory testing, mistakes occur more frequently before (pre-analytical) and after (post-analytical) the test has been performed. Most errors are due to pre-analytical factors (46-68.2% of total errors), while a high error rate (18.5-47% of total errors) has also been found in the post-analytical phase. Errors due to analytical problems have been significantly reduced over time, but there is evidence that, particularly for immunoassays, interference may have a serious impact on patients. A description of the most frequent and risky pre-, intra- and post-analytical errors and advice on practical steps for measuring and reducing the risk of errors is therefore given in the present paper. Many mistakes in the Total Testing Process are called "laboratory errors", although these may be due to poor communication, action taken by others involved in the testing process (e.g., physicians, nurses and phlebotomists), or poorly designed processes, all of which are beyond the laboratory's control. Likewise, there is evidence that laboratory information is only partially utilized. A recent document from the International Organization for Standardization (ISO) recommends a new, broader definition of the term "laboratory error" and a classification of errors according to different criteria. In a modern approach to total quality, centered on patients' needs and satisfaction, the risk of errors and mistakes

On the errors on Omega(0): Monte Carlo simulations of the EMSS cluster sample

DEFF Research Database (Denmark)

Oukbir, J.; Arnaud, M.

2001-01-01

We perform Monte Carlo simulations of synthetic EMSS cluster samples, to quantify the systematic errors and the statistical uncertainties on the estimate of Omega (0) derived from fits to the cluster number density evolution and to the X-ray temperature distribution up to z=0.83. We identify...... the scatter around the relation between cluster X-ray luminosity and temperature to be a source of systematic error, of the order of Delta (syst)Omega (0) = 0.09, if not properly taken into account in the modelling. After correcting for this bias, our best Omega (0) is 0.66. The uncertainties on the shape...

Sample Size Bounding and Context Ranking as Approaches to the Human Error Quantification Problem

Energy Technology Data Exchange (ETDEWEB)

Reer, B

2004-03-01

The paper describes a technique denoted as Sub-Sample-Size Bounding (SSSB), which is useable for the statistical derivation of context-specific probabilities from data available in existing reports on operating experience. Applications to human reliability analysis (HRA) are emphasised in the presentation of this technique. Exemplified by a sample of 180 abnormal event sequences, the manner in which SSSB can provide viable input for the quantification of errors of commission (EOCs) are outlined. (author)

Sample Size Bounding and Context Ranking as Approaches to the Human Error Quantification Problem

International Nuclear Information System (INIS)

Reer, B.

2004-01-01

The paper describes a technique denoted as Sub-Sample-Size Bounding (SSSB), which is useable for the statistical derivation of context-specific probabilities from data available in existing reports on operating experience. Applications to human reliability analysis (HRA) are emphasised in the presentation of this technique. Exemplified by a sample of 180 abnormal event sequences, the manner in which SSSB can provide viable input for the quantification of errors of commission (EOCs) are outlined. (author)

Micro-organism distribution sampling for bioassays

Science.gov (United States)

Nelson, B. A.

1975-01-01

Purpose of sampling distribution is to characterize sample-to-sample variation so statistical tests may be applied, to estimate error due to sampling (confidence limits) and to evaluate observed differences between samples. Distribution could be used for bioassays taken in hospitals, breweries, food-processing plants, and pharmaceutical plants.

Accounting for sampling error when inferring population synchrony from time-series data: a Bayesian state-space modelling approach with applications.

Directory of Open Access Journals (Sweden)

Hugues Santin-Janin

Full Text Available BACKGROUND: Data collected to inform time variations in natural population size are tainted by sampling error. Ignoring sampling error in population dynamics models induces bias in parameter estimators, e.g., density-dependence. In particular, when sampling errors are independent among populations, the classical estimator of the synchrony strength (zero-lag correlation is biased downward. However, this bias is rarely taken into account in synchrony studies although it may lead to overemphasizing the role of intrinsic factors (e.g., dispersal with respect to extrinsic factors (the Moran effect in generating population synchrony as well as to underestimating the extinction risk of a metapopulation. METHODOLOGY/PRINCIPAL FINDINGS: The aim of this paper was first to illustrate the extent of the bias that can be encountered in empirical studies when sampling error is neglected. Second, we presented a space-state modelling approach that explicitly accounts for sampling error when quantifying population synchrony. Third, we exemplify our approach with datasets for which sampling variance (i has been previously estimated, and (ii has to be jointly estimated with population synchrony. Finally, we compared our results to those of a standard approach neglecting sampling variance. We showed that ignoring sampling variance can mask a synchrony pattern whatever its true value and that the common practice of averaging few replicates of population size estimates poorly performed at decreasing the bias of the classical estimator of the synchrony strength. CONCLUSION/SIGNIFICANCE: The state-space model used in this study provides a flexible way of accurately quantifying the strength of synchrony patterns from most population size data encountered in field studies, including over-dispersed count data. We provided a user-friendly R-program and a tutorial example to encourage further studies aiming at quantifying the strength of population synchrony to account for

Evaluation of alignment error due to a speed artifact in stereotactic ultrasound image guidance

International Nuclear Information System (INIS)

Salter, Bill J; Wang, Brian; Szegedi, Martin W; Rassiah-Szegedi, Prema; Shrieve, Dennis C; Cheng, Roger; Fuss, Martin

2008-01-01

Ultrasound (US) image guidance systems used in radiotherapy are typically calibrated for soft tissue applications, thus introducing errors in depth-from-transducer representation when used in media with a different speed of sound propagation (e.g. fat). This error is commonly referred to as the speed artifact. In this study we utilized a standard US phantom to demonstrate the existence of the speed artifact when using a commercial US image guidance system to image through layers of simulated body fat, and we compared the results with calculated/predicted values. A general purpose US phantom (speed of sound (SOS) = 1540 m s -1 ) was imaged on a multi-slice CT scanner at a 0.625 mm slice thickness and 0.5 mm x 0.5 mm axial pixel size. Target-simulating wires inside the phantom were contoured and later transferred to the US guidance system. Layers of various thickness (1-8 cm) of commercially manufactured fat-simulating material (SOS = 1435 m s -1 ) were placed on top of the phantom to study the depth-related alignment error. In order to demonstrate that the speed artifact is not caused by adding additional layers on top of the phantom, we repeated these measurements in an identical setup using commercially manufactured tissue-simulating material (SOS = 1540 m s -1 ) for the top layers. For the fat-simulating material used in this study, we observed the magnitude of the depth-related alignment errors resulting from the speed artifact to be 0.7 mm cm -1 of fat imaged through. The measured alignment errors caused by the speed artifact agreed with the calculated values within one standard deviation for all of the different thicknesses of fat-simulating material studied here. We demonstrated the depth-related alignment error due to the speed artifact when using US image guidance for radiation treatment alignment and note that the presence of fat causes the target to be aliased to a depth greater than it actually is. For typical US guidance systems in use today, this will

Evaluation of alignment error due to a speed artifact in stereotactic ultrasound image guidance.

Science.gov (United States)

Salter, Bill J; Wang, Brian; Szegedi, Martin W; Rassiah-Szegedi, Prema; Shrieve, Dennis C; Cheng, Roger; Fuss, Martin

2008-12-07

Ultrasound (US) image guidance systems used in radiotherapy are typically calibrated for soft tissue applications, thus introducing errors in depth-from-transducer representation when used in media with a different speed of sound propagation (e.g. fat). This error is commonly referred to as the speed artifact. In this study we utilized a standard US phantom to demonstrate the existence of the speed artifact when using a commercial US image guidance system to image through layers of simulated body fat, and we compared the results with calculated/predicted values. A general purpose US phantom (speed of sound (SOS) = 1540 m s(-1)) was imaged on a multi-slice CT scanner at a 0.625 mm slice thickness and 0.5 mm x 0.5 mm axial pixel size. Target-simulating wires inside the phantom were contoured and later transferred to the US guidance system. Layers of various thickness (1-8 cm) of commercially manufactured fat-simulating material (SOS = 1435 m s(-1)) were placed on top of the phantom to study the depth-related alignment error. In order to demonstrate that the speed artifact is not caused by adding additional layers on top of the phantom, we repeated these measurements in an identical setup using commercially manufactured tissue-simulating material (SOS = 1540 m s(-1)) for the top layers. For the fat-simulating material used in this study, we observed the magnitude of the depth-related alignment errors resulting from the speed artifact to be 0.7 mm cm(-1) of fat imaged through. The measured alignment errors caused by the speed artifact agreed with the calculated values within one standard deviation for all of the different thicknesses of fat-simulating material studied here. We demonstrated the depth-related alignment error due to the speed artifact when using US image guidance for radiation treatment alignment and note that the presence of fat causes the target to be aliased to a depth greater than it actually is. For typical US guidance systems in use today, this will

Sporadic error probability due to alpha particles in dynamic memories of various technologies

International Nuclear Information System (INIS)

Edwards, D.G.

1980-01-01

The sensitivity of MOS memory components to errors induced by alpha particles is expected to increase with integration level. The soft error rate of a 65-kbit VMOS memory has been compared experimentally with that of three field-proven 16-kbit designs. The technological and design advantages of the VMOS RAM ensure an error rate which is lower than those of the 16-kbit memories. Calculation of the error probability for the 65-kbit RAM and comparison with the measurements show that for large duty cycles single particle hits lead to sensing errors and for small duty cycles cell errors caused by multiple hits predominate. (Auth.)

Testing and Inference in Nonlinear Cointegrating Vector Error Correction Models

DEFF Research Database (Denmark)

Kristensen, Dennis; Rahbæk, Anders

In this paper, we consider a general class of vector error correction models which allow for asymmetric and non-linear error correction. We provide asymptotic results for (quasi-)maximum likelihood (QML) based estimators and tests. General hypothesis testing is considered, where testing...... of non-stationary non-linear time series models. Thus the paper provides a full asymptotic theory for estimators as well as standard and non-standard test statistics. The derived asymptotic results prove to be new compared to results found elsewhere in the literature due to the impact of the estimated...... symmetric non-linear error correction considered. A simulation study shows that the fi…nite sample properties of the bootstrapped tests are satisfactory with good size and power properties for reasonable sample sizes....

Testing and Inference in Nonlinear Cointegrating Vector Error Correction Models

DEFF Research Database (Denmark)

Kristensen, Dennis; Rahbek, Anders

In this paper, we consider a general class of vector error correction models which allow for asymmetric and non-linear error correction. We provide asymptotic results for (quasi-)maximum likelihood (QML) based estimators and tests. General hypothesis testing is considered, where testing...... of non-stationary non-linear time series models. Thus the paper provides a full asymptotic theory for estimators as well as standard and non-standard test statistics. The derived asymptotic results prove to be new compared to results found elsewhere in the literature due to the impact of the estimated...... symmetric non-linear error correction are considered. A simulation study shows that the finite sample properties of the bootstrapped tests are satisfactory with good size and power properties for reasonable sample sizes....

Quantification and handling of sampling errors in instrumental measurements: a case study

DEFF Research Database (Denmark)

Andersen, Charlotte Møller; Bro, R.

2004-01-01

in certain situations, the effect of systematic errors is also considerable. The relevant errors contributing to the prediction error are: error in instrumental measurements (x-error), error in reference measurements (y-error), error in the estimated calibration model (regression coefficient error) and model...

Optical waveform sampling and error-free demultiplexing of 1.28 Tbit/s serial data in a silicon nanowire

DEFF Research Database (Denmark)

Ji, Hua; Hu, Hao; Galili, Michael

2010-01-01

We experimentally demonstrate 640 Gbit/s and 1.28 Tbit/s serial data optical waveform sampling and 640-to-10 Gbit/s and 1.28 Tbit/s-to-10 Gbit/s error-free demultiplexing using four-wave mixing in a 300nm$$450nm$$5mm silicon nanowire.......We experimentally demonstrate 640 Gbit/s and 1.28 Tbit/s serial data optical waveform sampling and 640-to-10 Gbit/s and 1.28 Tbit/s-to-10 Gbit/s error-free demultiplexing using four-wave mixing in a 300nm$$450nm$$5mm silicon nanowire....

SYSTEMATIC ERROR REDUCTION: NON-TILTED REFERENCE BEAM METHOD FOR LONG TRACE PROFILER

International Nuclear Information System (INIS)

QIAN, S.; QIAN, K.; HONG, Y.; SENG, L.; HO, T.; TAKACS, P.

2007-01-01

Systematic error in the Long Trace Profiler (LTP) has become the major error source as measurement accuracy enters the nanoradian and nanometer regime. Great efforts have been made to reduce the systematic error at a number of synchrotron radiation laboratories around the world. Generally, the LTP reference beam has to be tilted away from the optical axis in order to avoid fringe overlap between the sample and reference beams. However, a tilted reference beam will result in considerable systematic error due to optical system imperfections, which is difficult to correct. Six methods of implementing a non-tilted reference beam in the LTP are introduced: (1) application of an external precision angle device to measure and remove slide pitch error without a reference beam, (2) independent slide pitch test by use of not tilted reference beam, (3) non-tilted reference test combined with tilted sample, (4) penta-prism scanning mode without a reference beam correction, (5) non-tilted reference using a second optical head, and (6) alternate switching of data acquisition between the sample and reference beams. With a non-tilted reference method, the measurement accuracy can be improved significantly. Some measurement results are presented. Systematic error in the sample beam arm is not addressed in this paper and should be treated separately

Apparently conclusive meta-analyses may be inconclusive--Trial sequential analysis adjustment of random error risk due to repetitive testing of accumulating data in apparently conclusive neonatal meta-analyses

DEFF Research Database (Denmark)

Brok, Jesper; Thorlund, Kristian; Wetterslev, Jørn

2008-01-01

BACKGROUND: Random error may cause misleading evidence in meta-analyses. The required number of participants in a meta-analysis (i.e. information size) should be at least as large as an adequately powered single trial. Trial sequential analysis (TSA) may reduce risk of random errors due to repeti......BACKGROUND: Random error may cause misleading evidence in meta-analyses. The required number of participants in a meta-analysis (i.e. information size) should be at least as large as an adequately powered single trial. Trial sequential analysis (TSA) may reduce risk of random errors due...

Determining the sample size for co-dominant molecular marker-assisted linkage detection for a monogenic qualitative trait by controlling the type-I and type-II errors in a segregating F2 population.

Science.gov (United States)

Hühn, M; Piepho, H P

2003-03-01

Tests for linkage are usually performed using the lod score method. A critical question in linkage analyses is the choice of sample size. The appropriate sample size depends on the desired type-I error and power of the test. This paper investigates the exact type-I error and power of the lod score method in a segregating F(2) population with co-dominant markers and a qualitative monogenic dominant-recessive trait. For illustration, a disease-resistance trait is considered, where the susceptible allele is recessive. A procedure is suggested for finding the appropriate sample size. It is shown that recessive plants have about twice the information content of dominant plants, so the former should be preferred for linkage detection. In some cases the exact alpha-values for a given nominal alpha may be rather small due to the discrete nature of the sampling distribution in small samples. We show that a gain in power is possible by using exact methods.

In-Situ Systematic Error Correction for Digital Volume Correlation Using a Reference Sample

KAUST Repository

Wang, B.

2017-11-27

The self-heating effect of a laboratory X-ray computed tomography (CT) scanner causes slight change in its imaging geometry, which induces translation and dilatation (i.e., artificial displacement and strain) in reconstructed volume images recorded at different times. To realize high-accuracy internal full-field deformation measurements using digital volume correlation (DVC), these artificial displacements and strains associated with unstable CT imaging must be eliminated. In this work, an effective and easily implemented reference sample compensation (RSC) method is proposed for in-situ systematic error correction in DVC. The proposed method utilizes a stationary reference sample, which is placed beside the test sample to record the artificial displacement fields caused by the self-heating effect of CT scanners. The detected displacement fields are then fitted by a parametric polynomial model, which is used to remove the unwanted artificial deformations in the test sample. Rescan tests of a stationary sample and real uniaxial compression tests performed on copper foam specimens demonstrate the accuracy, efficacy, and practicality of the presented RSC method.

In-Situ Systematic Error Correction for Digital Volume Correlation Using a Reference Sample

KAUST Repository

Wang, B.; Pan, B.; Lubineau, Gilles

2017-01-01

The self-heating effect of a laboratory X-ray computed tomography (CT) scanner causes slight change in its imaging geometry, which induces translation and dilatation (i.e., artificial displacement and strain) in reconstructed volume images recorded at different times. To realize high-accuracy internal full-field deformation measurements using digital volume correlation (DVC), these artificial displacements and strains associated with unstable CT imaging must be eliminated. In this work, an effective and easily implemented reference sample compensation (RSC) method is proposed for in-situ systematic error correction in DVC. The proposed method utilizes a stationary reference sample, which is placed beside the test sample to record the artificial displacement fields caused by the self-heating effect of CT scanners. The detected displacement fields are then fitted by a parametric polynomial model, which is used to remove the unwanted artificial deformations in the test sample. Rescan tests of a stationary sample and real uniaxial compression tests performed on copper foam specimens demonstrate the accuracy, efficacy, and practicality of the presented RSC method.

Prediction of DVH parameter changes due to setup errors for breast cancer treatment based on 2D portal dosimetry

International Nuclear Information System (INIS)

Nijsten, S. M. J. J. G.; Elmpt, W. J. C. van; Mijnheer, B. J.; Minken, A. W. H.; Persoon, L. C. G. G.; Lambin, P.; Dekker, A. L. A. J.

2009-01-01

Electronic portal imaging devices (EPIDs) are increasingly used for portal dosimetry applications. In our department, EPIDs are clinically used for two-dimensional (2D) transit dosimetry. Predicted and measured portal dose images are compared to detect dose delivery errors caused for instance by setup errors or organ motion. The aim of this work is to develop a model to predict dose-volume histogram (DVH) changes due to setup errors during breast cancer treatment using 2D transit dosimetry. First, correlations between DVH parameter changes and 2D gamma parameters are investigated for different simulated setup errors, which are described by a binomial logistic regression model. The model calculates the probability that a DVH parameter changes more than a specific tolerance level and uses several gamma evaluation parameters for the planning target volume (PTV) projection in the EPID plane as input. Second, the predictive model is applied to clinically measured portal images. Predicted DVH parameter changes are compared to calculated DVH parameter changes using the measured setup error resulting from a dosimetric registration procedure. Statistical accuracy is investigated by using receiver operating characteristic (ROC) curves and values for the area under the curve (AUC), sensitivity, specificity, positive and negative predictive values. Changes in the mean PTV dose larger than 5%, and changes in V 90 and V 95 larger than 10% are accurately predicted based on a set of 2D gamma parameters. Most pronounced changes in the three DVH parameters are found for setup errors in the lateral-medial direction. AUC, sensitivity, specificity, and negative predictive values were between 85% and 100% while the positive predictive values were lower but still higher than 54%. Clinical predictive value is decreased due to the occurrence of patient rotations or breast deformations during treatment, but the overall reliability of the predictive model remains high. Based on our

Errors in dual x-ray beam differential absorptiometry

International Nuclear Information System (INIS)

Bolin, F.; Preuss, L.; Gilbert, K.; Bugenis, C.

1977-01-01

Errors pertinent to the dual beam absorptiometry system have been studied and five areas are given in detail: (1) scattering, in which a computer analysis of multiple scattering shows little error due to this effect; (2) geometrical configuration effects, in which the slope of the sample is shown to influence the accuracy of the measurement; (3) Poisson variations, wherein it is shown that a simultaneous reduction can be obtained in both dosage and statistical error; (4) absorption coefficients, in which the effect of variation in absorption coefficient compilations is shown to have a critical effect on the interpretations of experimental data; and (5) filtering, wherein is shown the need for filters on dual beam systems using a characteristic x-ray output. A zero filter system is outlined

Thermal error analysis and compensation for digital image/volume correlation

Science.gov (United States)

Pan, Bing

2018-02-01

Digital image/volume correlation (DIC/DVC) rely on the digital images acquired by digital cameras and x-ray CT scanners to extract the motion and deformation of test samples. Regrettably, these imaging devices are unstable optical systems, whose imaging geometry may undergo unavoidable slight and continual changes due to self-heating effect or ambient temperature variations. Changes in imaging geometry lead to both shift and expansion in the recorded 2D or 3D images, and finally manifest as systematic displacement and strain errors in DIC/DVC measurements. Since measurement accuracy is always the most important requirement in various experimental mechanics applications, these thermal-induced errors (referred to as thermal errors) should be given serious consideration in order to achieve high accuracy, reproducible DIC/DVC measurements. In this work, theoretical analyses are first given to understand the origin of thermal errors. Then real experiments are conducted to quantify thermal errors. Three solutions are suggested to mitigate or correct thermal errors. Among these solutions, a reference sample compensation approach is highly recommended because of its easy implementation, high accuracy and in-situ error correction capability. Most of the work has appeared in our previously published papers, thus its originality is not claimed. Instead, this paper aims to give a comprehensive overview and more insights of our work on thermal error analysis and compensation for DIC/DVC measurements.

Overview about bias in Customer Satisfaction Surveys and focus on self-selection error

OpenAIRE

Giovanna Nicolini; Luciana Dalla Valle

2009-01-01

The present paper provides an overview of the main types of surveys carried out for customer satisfaction analyses. In order to carry out these surveys it is possible to plan a census or select a sample. The higher the accuracy of the survey, the more reliable the results of the analysis. For this very reason, researchers pay special attention to surveys with bias due to non sampling errors, in particular to self-selection errors. These phenomena are very frequent especially in web surveys. S...

Maximum inflation of the type 1 error rate when sample size and allocation rate are adapted in a pre-planned interim look.

Science.gov (United States)

Graf, Alexandra C; Bauer, Peter

2011-06-30

We calculate the maximum type 1 error rate of the pre-planned conventional fixed sample size test for comparing the means of independent normal distributions (with common known variance) which can be yielded when sample size and allocation rate to the treatment arms can be modified in an interim analysis. Thereby it is assumed that the experimenter fully exploits knowledge of the unblinded interim estimates of the treatment effects in order to maximize the conditional type 1 error rate. The 'worst-case' strategies require knowledge of the unknown common treatment effect under the null hypothesis. Although this is a rather hypothetical scenario it may be approached in practice when using a standard control treatment for which precise estimates are available from historical data. The maximum inflation of the type 1 error rate is substantially larger than derived by Proschan and Hunsberger (Biometrics 1995; 51:1315-1324) for design modifications applying balanced samples before and after the interim analysis. Corresponding upper limits for the maximum type 1 error rate are calculated for a number of situations arising from practical considerations (e.g. restricting the maximum sample size, not allowing sample size to decrease, allowing only increase in the sample size in the experimental treatment). The application is discussed for a motivating example. Copyright © 2011 John Wiley & Sons, Ltd.

Evaluation of linear registration algorithms for brain SPECT and the errors due to hypoperfusion lesions

International Nuclear Information System (INIS)

Radau, Perry E.; Slomka, Piotr J.; Julin, Per; Svensson, Leif; Wahlund, Lars-Olof

2001-01-01

The semiquantitative analysis of perfusion single-photon emission computed tomography (SPECT) images requires a reproducible, objective method. Automated spatial standardization (registration) of images is a prerequisite to this goal. A source of registration error is the presence of hypoperfusion defects, which was evaluated in this study with simulated lesions. The brain perfusion images measured by 99m Tc-HMPAO SPECT from 21 patients with probable Alzheimer's disease and 35 control subjects were retrospectively analyzed. An automatic segmentation method was developed to remove external activity. Three registration methods, robust least squares, normalized mutual information (NMI), and count difference were implemented and the effects of simulated defects were compared. The tested registration methods required segmentation of the cerebrum from external activity, and the automatic and manual methods differed by a three-dimensional displacement of 1.4±1.1 mm. NMI registration proved to be least adversely effected by simulated defects with 3 mm average displacement caused by severe defects. The error in quantifying the patient-template parietal ratio due to misregistration was 2.0% for large defects (70% hypoperfusion) and 0.5% for smaller defects (85% hypoperfusion)

Density dependence and climate effects in Rocky Mountain elk: an application of regression with instrumental variables for population time series with sampling error.

Science.gov (United States)

Creel, Scott; Creel, Michael

2009-11-01

1. Sampling error in annual estimates of population size creates two widely recognized problems for the analysis of population growth. First, if sampling error is mistakenly treated as process error, one obtains inflated estimates of the variation in true population trajectories (Staples, Taper & Dennis 2004). Second, treating sampling error as process error is thought to overestimate the importance of density dependence in population growth (Viljugrein et al. 2005; Dennis et al. 2006). 2. In ecology, state-space models are used to account for sampling error when estimating the effects of density and other variables on population growth (Staples et al. 2004; Dennis et al. 2006). In econometrics, regression with instrumental variables is a well-established method that addresses the problem of correlation between regressors and the error term, but requires fewer assumptions than state-space models (Davidson & MacKinnon 1993; Cameron & Trivedi 2005). 3. We used instrumental variables to account for sampling error and fit a generalized linear model to 472 annual observations of population size for 35 Elk Management Units in Montana, from 1928 to 2004. We compared this model with state-space models fit with the likelihood function of Dennis et al. (2006). We discuss the general advantages and disadvantages of each method. Briefly, regression with instrumental variables is valid with fewer distributional assumptions, but state-space models are more efficient when their distributional assumptions are met. 4. Both methods found that population growth was negatively related to population density and winter snow accumulation. Summer rainfall and wolf (Canis lupus) presence had much weaker effects on elk (Cervus elaphus) dynamics [though limitation by wolves is strong in some elk populations with well-established wolf populations (Creel et al. 2007; Creel & Christianson 2008)]. 5. Coupled with predictions for Montana from global and regional climate models, our results

Estimation of total error in DWPF reported radionuclide inventories. Revision 1

International Nuclear Information System (INIS)

Edwards, T.B.

1995-01-01

The Defense Waste Processing Facility (DWPF) at the Savannah River Site is required to determine and report the radionuclide inventory of its glass product. For each macro-batch, the DWPF will report both the total amount (in curies) of each reportable radionuclide and the average concentration (in curies/gram of glass) of each reportable radionuclide. The DWPF is to provide the estimated error of these reported values of its radionuclide inventory as well. The objective of this document is to provide a framework for determining the estimated error in DWPF's reporting of these radionuclide inventories. This report investigates the impact of random errors due to measurement and sampling on the total amount of each reportable radionuclide in a given macro-batch. In addition, the impact of these measurement and sampling errors and process variation are evaluated to determine the uncertainty in the reported average concentrations of radionuclides in DWPF's filled canister inventory resulting from each macro-batch

On the evaluation of the sensitivity of SRAM-Based FPGA to errors due to natural radiation environment

International Nuclear Information System (INIS)

Bocquillon, Alexandre

2009-01-01

This work aims at designing a test methodology to analyze the effect of natural radiation on FPGA SRAM-based chip-sets. Study of likely errors due to single or multiple events occurring in the configuration memory will be based on fault-injection experiments performed with laser devices. It relies on both a description of scientific background and a description of complex architecture of FPGA SRAM-Based and usual testing apparatus. Fault injection experiments with laser are conducted on several classes of components in order to perform static tests of the configuration memory and identify the links with the application. It shows the organization and sensitivity of SRAM configuration cells. Criticality criteria for configuration bits have been specified following dynamic tests in protons accelerator, in regard to their impact on the application. From this classification was developed a predicting tool for critical error rate estimation. (author) [fr

Impact of shrinking measurement error budgets on qualification metrology sampling and cost

Science.gov (United States)

Sendelbach, Matthew; Sarig, Niv; Wakamoto, Koichi; Kim, Hyang Kyun (Helen); Isbester, Paul; Asano, Masafumi; Matsuki, Kazuto; Vaid, Alok; Osorio, Carmen; Archie, Chas

2014-04-01

When designing an experiment to assess the accuracy of a tool as compared to a reference tool, semiconductor metrologists are often confronted with the situation that they must decide on the sampling strategy before the measurements begin. This decision is usually based largely on the previous experience of the metrologist and the available resources, and not on the statistics that are needed to achieve acceptable confidence limits on the final result. This paper shows a solution to this problem, called inverse TMU analysis, by presenting statistically-based equations that allow the user to estimate the needed sampling after providing appropriate inputs, allowing him to make important "risk vs. reward" sampling, cost, and equipment decisions. Application examples using experimental data from scatterometry and critical dimension scanning electron microscope (CD-SEM) tools are used first to demonstrate how the inverse TMU analysis methodology can be used to make intelligent sampling decisions before the start of the experiment, and then to reveal why low sampling can lead to unstable and misleading results. A model is developed that can help an experimenter minimize the costs associated both with increased sampling and with making wrong decisions caused by insufficient sampling. A second cost model is described that reveals the inadequacy of current TEM (Transmission Electron Microscopy) sampling practices and the enormous costs associated with TEM sampling that is needed to provide reasonable levels of certainty in the result. These high costs reach into the tens of millions of dollars for TEM reference metrology as the measurement error budgets reach angstrom levels. The paper concludes with strategies on how to manage and mitigate these costs.

Medication errors: prescribing faults and prescription errors.

Science.gov (United States)

Velo, Giampaolo P; Minuz, Pietro

2009-06-01

1. Medication errors are common in general practice and in hospitals. Both errors in the act of writing (prescription errors) and prescribing faults due to erroneous medical decisions can result in harm to patients. 2. Any step in the prescribing process can generate errors. Slips, lapses, or mistakes are sources of errors, as in unintended omissions in the transcription of drugs. Faults in dose selection, omitted transcription, and poor handwriting are common. 3. Inadequate knowledge or competence and incomplete information about clinical characteristics and previous treatment of individual patients can result in prescribing faults, including the use of potentially inappropriate medications. 4. An unsafe working environment, complex or undefined procedures, and inadequate communication among health-care personnel, particularly between doctors and nurses, have been identified as important underlying factors that contribute to prescription errors and prescribing faults. 5. Active interventions aimed at reducing prescription errors and prescribing faults are strongly recommended. These should be focused on the education and training of prescribers and the use of on-line aids. The complexity of the prescribing procedure should be reduced by introducing automated systems or uniform prescribing charts, in order to avoid transcription and omission errors. Feedback control systems and immediate review of prescriptions, which can be performed with the assistance of a hospital pharmacist, are also helpful. Audits should be performed periodically.

Correction for Measurement Error from Genotyping-by-Sequencing in Genomic Variance and Genomic Prediction Models

DEFF Research Database (Denmark)

Ashraf, Bilal; Janss, Luc; Jensen, Just

sample). The GBSeq data can be used directly in genomic models in the form of individual SNP allele-frequency estimates (e.g., reference reads/total reads per polymorphic site per individual), but is subject to measurement error due to the low sequencing depth per individual. Due to technical reasons....... In the current work we show how the correction for measurement error in GBSeq can also be applied in whole genome genomic variance and genomic prediction models. Bayesian whole-genome random regression models are proposed to allow implementation of large-scale SNP-based models with a per-SNP correction...... for measurement error. We show correct retrieval of genomic explained variance, and improved genomic prediction when accounting for the measurement error in GBSeq data...

Strategies to reduce the systematic error due to tumor and rectum motion in radiotherapy of prostate cancer

International Nuclear Information System (INIS)

Hoogeman, Mischa S.; Herk, Marcel van; Bois, Josien de; Lebesque, Joos V.

2005-01-01

Background and purpose: The goal of this work is to develop and evaluate strategies to reduce the uncertainty in the prostate position and rectum shape that arises in the preparation stage of the radiation treatment of prostate cancer. Patients and methods: Nineteen prostate cancer patients, who were treated with 3-dimensional conformal radiotherapy, received each a planning CT scan and 8-13 repeat CT scans during the treatment period. We quantified prostate motion relative to the pelvic bone by first matching the repeat CT scans on the planning CT scan using the bony anatomy. Subsequently, each contoured prostate, including seminal vesicles, was matched on the prostate in the planning CT scan to obtain the translations and rotations. The variation in prostate position was determined in terms of the systematic, random and group mean error. We tested the performance of two correction strategies to reduce the systematic error due to prostate motion. The first strategy, the pre-treatment strategy, used only the initial rectum volume in the planning CT scan to adjust the angle of the prostate with respect to the left-right (LR) axis and the shape and position of the rectum. The second strategy, the adaptive strategy, used the data of repeat CT scans to improve the estimate of the prostate position and rectum shape during the treatment. Results: The largest component of prostate motion was a rotation around the LR axis. The systematic error (1 SD) was 5.1 deg and the random error was 3.6 deg (1 SD). The average LR-axis rotation between the planning and the repeat CT scans correlated significantly with the rectum volume in the planning CT scan (r=0.86, P<0.0001). Correction of the rotational position on the basis of the planning rectum volume alone reduced the systematic error by 28%. A correction, based on the data of the planning CT scan and 4 repeat CT scans reduced the systematic error over the complete treatment period by a factor of 2. When the correction was

Edge profile analysis of Joint European Torus (JET) Thomson scattering data: Quantifying the systematic error due to edge localised mode synchronisation.

Science.gov (United States)

Leyland, M J; Beurskens, M N A; Flanagan, J C; Frassinetti, L; Gibson, K J; Kempenaars, M; Maslov, M; Scannell, R

2016-01-01

The Joint European Torus (JET) high resolution Thomson scattering (HRTS) system measures radial electron temperature and density profiles. One of the key capabilities of this diagnostic is measuring the steep pressure gradient, termed the pedestal, at the edge of JET plasmas. The pedestal is susceptible to limiting instabilities, such as Edge Localised Modes (ELMs), characterised by a periodic collapse of the steep gradient region. A common method to extract the pedestal width, gradient, and height, used on numerous machines, is by performing a modified hyperbolic tangent (mtanh) fit to overlaid profiles selected from the same region of the ELM cycle. This process of overlaying profiles, termed ELM synchronisation, maximises the number of data points defining the pedestal region for a given phase of the ELM cycle. When fitting to HRTS profiles, it is necessary to incorporate the diagnostic radial instrument function, particularly important when considering the pedestal width. A deconvolved fit is determined by a forward convolution method requiring knowledge of only the instrument function and profiles. The systematic error due to the deconvolution technique incorporated into the JET pedestal fitting tool has been documented by Frassinetti et al. [Rev. Sci. Instrum. 83, 013506 (2012)]. This paper seeks to understand and quantify the systematic error introduced to the pedestal width due to ELM synchronisation. Synthetic profiles, generated with error bars and point-to-point variation characteristic of real HRTS profiles, are used to evaluate the deviation from the underlying pedestal width. We find on JET that the ELM synchronisation systematic error is negligible in comparison to the statistical error when assuming ten overlaid profiles (typical for a pre-ELM fit to HRTS profiles). This confirms that fitting a mtanh to ELM synchronised profiles is a robust and practical technique for extracting the pedestal structure.

Evapotranspiration estimates and consequences due to errors in the determination of the net radiation and advective effects

International Nuclear Information System (INIS)

Oliveira, G.M. de; Leitao, M. de M.V.B.R.

2000-01-01

The objective of this study was to analyze the consequences in the evapotranspiration estimates (ET) during the growing cycle of a peanut crop due to the errors committed in the determination of the radiation balance (Rn), as well as those caused by the advective effects. This research was conducted at the Experimental Station of CODEVASF in an irrigated perimeter located in the city of Rodelas, BA, during the period of September to December of 1996. The results showed that errors of the order of 2.2 MJ m -2 d -1 in the calculation of Rn, and consequently in the estimate of ET, can occur depending on the time considered for the daily total of Rn. It was verified that the surrounding areas of the experimental field, as well as the areas of exposed soil within the field, contributed significantly to the generation of local advection of sensible heat, which resulted in the increase of the evapotranspiration [pt

Non-uniform sampling and wide range angular spectrum method

International Nuclear Information System (INIS)

Kim, Yong-Hae; Byun, Chun-Won; Oh, Himchan; Lee, JaeWon; Pi, Jae-Eun; Heon Kim, Gi; Lee, Myung-Lae; Ryu, Hojun; Chu, Hye-Yong; Hwang, Chi-Sun

2014-01-01

A novel method is proposed for simulating free space field propagation from a source plane to a destination plane that is applicable for both small and large propagation distances. The angular spectrum method (ASM) was widely used for simulating near field propagation, but it caused a numerical error when the propagation distance was large because of aliasing due to under sampling. Band limited ASM satisfied the Nyquist condition on sampling by limiting a bandwidth of a propagation field to avoid an aliasing error so that it could extend the applicable propagation distance of the ASM. However, the band limited ASM also made an error due to the decrease of an effective sampling number in a Fourier space when the propagation distance was large. In the proposed wide range ASM, we use a non-uniform sampling in a Fourier space to keep a constant effective sampling number even though the propagation distance is large. As a result, the wide range ASM can produce simulation results with high accuracy for both far and near field propagation. For non-paraxial wave propagation, we applied the wide range ASM to a shifted destination plane as well. (paper)

Repeated speech errors: evidence for learning.

Science.gov (United States)

Humphreys, Karin R; Menzies, Heather; Lake, Johanna K

2010-11-01

Three experiments elicited phonological speech errors using the SLIP procedure to investigate whether there is a tendency for speech errors on specific words to reoccur, and whether this effect can be attributed to implicit learning of an incorrect mapping from lemma to phonology for that word. In Experiment 1, when speakers made a phonological speech error in the study phase of the experiment (e.g. saying "beg pet" in place of "peg bet") they were over four times as likely to make an error on that same item several minutes later at test. A pseudo-error condition demonstrated that the effect is not simply due to a propensity for speakers to repeat phonological forms, regardless of whether or not they have been made in error. That is, saying "beg pet" correctly at study did not induce speakers to say "beg pet" in error instead of "peg bet" at test. Instead, the effect appeared to be due to learning of the error pathway. Experiment 2 replicated this finding, but also showed that after 48 h, errors made at study were no longer more likely to reoccur. As well as providing constraints on the longevity of the effect, this provides strong evidence that the error reoccurrences observed are not due to item-specific difficulty that leads individual speakers to make habitual mistakes on certain items. Experiment 3 showed that the diminishment of the effect 48 h later is not due to specific extra practice at the task. We discuss how these results fit in with a larger view of language as a dynamic system that is constantly adapting in response to experience. Copyright © 2010 Elsevier B.V. All rights reserved.

Incorporating measurement error in n = 1 psychological autoregressive modeling

Science.gov (United States)

Schuurman, Noémi K.; Houtveen, Jan H.; Hamaker, Ellen L.

2015-01-01

Measurement error is omnipresent in psychological data. However, the vast majority of applications of autoregressive time series analyses in psychology do not take measurement error into account. Disregarding measurement error when it is present in the data results in a bias of the autoregressive parameters. We discuss two models that take measurement error into account: An autoregressive model with a white noise term (AR+WN), and an autoregressive moving average (ARMA) model. In a simulation study we compare the parameter recovery performance of these models, and compare this performance for both a Bayesian and frequentist approach. We find that overall, the AR+WN model performs better. Furthermore, we find that for realistic (i.e., small) sample sizes, psychological research would benefit from a Bayesian approach in fitting these models. Finally, we illustrate the effect of disregarding measurement error in an AR(1) model by means of an empirical application on mood data in women. We find that, depending on the person, approximately 30–50% of the total variance was due to measurement error, and that disregarding this measurement error results in a substantial underestimation of the autoregressive parameters. PMID:26283988

Droplet Size-Aware and Error-Correcting Sample Preparation Using Micro-Electrode-Dot-Array Digital Microfluidic Biochips.

Science.gov (United States)

Li, Zipeng; Lai, Kelvin Yi-Tse; Chakrabarty, Krishnendu; Ho, Tsung-Yi; Lee, Chen-Yi

2017-12-01

Sample preparation in digital microfluidics refers to the generation of droplets with target concentrations for on-chip biochemical applications. In recent years, digital microfluidic biochips (DMFBs) have been adopted as a platform for sample preparation. However, there remain two major problems associated with sample preparation on a conventional DMFB. First, only a (1:1) mixing/splitting model can be used, leading to an increase in the number of fluidic operations required for sample preparation. Second, only a limited number of sensors can be integrated on a conventional DMFB; as a result, the latency for error detection during sample preparation is significant. To overcome these drawbacks, we adopt a next generation DMFB platform, referred to as micro-electrode-dot-array (MEDA), for sample preparation. We propose the first sample-preparation method that exploits the MEDA-specific advantages of fine-grained control of droplet sizes and real-time droplet sensing. Experimental demonstration using a fabricated MEDA biochip and simulation results highlight the effectiveness of the proposed sample-preparation method.

Error Parsing: An alternative method of implementing social judgment theory

OpenAIRE

Crystal C. Hall; Daniel M. Oppenheimer

2015-01-01

We present a novel method of judgment analysis called Error Parsing, based upon an alternative method of implementing Social Judgment Theory (SJT). SJT and Error Parsing both posit the same three components of error in human judgment: error due to noise, error due to cue weighting, and error due to inconsistency. In that sense, the broad theory and framework are the same. However, SJT and Error Parsing were developed to answer different questions, and thus use different m...

Sample size and classification error for Bayesian change-point models with unlabelled sub-groups and incomplete follow-up.

Science.gov (United States)

White, Simon R; Muniz-Terrera, Graciela; Matthews, Fiona E

2018-05-01

Many medical (and ecological) processes involve the change of shape, whereby one trajectory changes into another trajectory at a specific time point. There has been little investigation into the study design needed to investigate these models. We consider the class of fixed effect change-point models with an underlying shape comprised two joined linear segments, also known as broken-stick models. We extend this model to include two sub-groups with different trajectories at the change-point, a change and no change class, and also include a missingness model to account for individuals with incomplete follow-up. Through a simulation study, we consider the relationship of sample size to the estimates of the underlying shape, the existence of a change-point, and the classification-error of sub-group labels. We use a Bayesian framework to account for the missing labels, and the analysis of each simulation is performed using standard Markov chain Monte Carlo techniques. Our simulation study is inspired by cognitive decline as measured by the Mini-Mental State Examination, where our extended model is appropriate due to the commonly observed mixture of individuals within studies who do or do not exhibit accelerated decline. We find that even for studies of modest size ( n = 500, with 50 individuals observed past the change-point) in the fixed effect setting, a change-point can be detected and reliably estimated across a range of observation-errors.

Counting OCR errors in typeset text

Science.gov (United States)

Sandberg, Jonathan S.

1995-03-01

Frequently object recognition accuracy is a key component in the performance analysis of pattern matching systems. In the past three years, the results of numerous excellent and rigorous studies of OCR system typeset-character accuracy (henceforth OCR accuracy) have been published, encouraging performance comparisons between a variety of OCR products and technologies. These published figures are important; OCR vendor advertisements in the popular trade magazines lead readers to believe that published OCR accuracy figures effect market share in the lucrative OCR market. Curiously, a detailed review of many of these OCR error occurrence counting results reveals that they are not reproducible as published and they are not strictly comparable due to larger variances in the counts than would be expected by the sampling variance. Naturally, since OCR accuracy is based on a ratio of the number of OCR errors over the size of the text searched for errors, imprecise OCR error accounting leads to similar imprecision in OCR accuracy. Some published papers use informal, non-automatic, or intuitively correct OCR error accounting. Still other published results present OCR error accounting methods based on string matching algorithms such as dynamic programming using Levenshtein (edit) distance but omit critical implementation details (such as the existence of suspect markers in the OCR generated output or the weights used in the dynamic programming minimization procedure). The problem with not specifically revealing the accounting method is that the number of errors found by different methods are significantly different. This paper identifies the basic accounting methods used to measure OCR errors in typeset text and offers an evaluation and comparison of the various accounting methods.

A novel knot selection method for the error-bounded B-spline curve fitting of sampling points in the measuring process

International Nuclear Information System (INIS)

Liang, Fusheng; Zhao, Ji; Ji, Shijun; Zhang, Bing; Fan, Cheng

2017-01-01

The B-spline curve has been widely used in the reconstruction of measurement data. The error-bounded sampling points reconstruction can be achieved by the knot addition method (KAM) based B-spline curve fitting. In KAM, the selection pattern of initial knot vector has been associated with the ultimate necessary number of knots. This paper provides a novel initial knots selection method to condense the knot vector required for the error-bounded B-spline curve fitting. The initial knots are determined by the distribution of features which include the chord length (arc length) and bending degree (curvature) contained in the discrete sampling points. Firstly, the sampling points are fitted into an approximate B-spline curve Gs with intensively uniform knot vector to substitute the description of the feature of the sampling points. The feature integral of Gs is built as a monotone increasing function in an analytic form. Then, the initial knots are selected according to the constant increment of the feature integral. After that, an iterative knot insertion (IKI) process starting from the initial knots is introduced to improve the fitting precision, and the ultimate knot vector for the error-bounded B-spline curve fitting is achieved. Lastly, two simulations and the measurement experiment are provided, and the results indicate that the proposed knot selection method can reduce the number of ultimate knots available. (paper)

How to Avoid Errors in Error Propagation: Prediction Intervals and Confidence Intervals in Forest Biomass

Science.gov (United States)

Lilly, P.; Yanai, R. D.; Buckley, H. L.; Case, B. S.; Woollons, R. C.; Holdaway, R. J.; Johnson, J.

2016-12-01

Calculations of forest biomass and elemental content require many measurements and models, each contributing uncertainty to the final estimates. While sampling error is commonly reported, based on replicate plots, error due to uncertainty in the regression used to estimate biomass from tree diameter is usually not quantified. Some published estimates of uncertainty due to the regression models have used the uncertainty in the prediction of individuals, ignoring uncertainty in the mean, while others have propagated uncertainty in the mean while ignoring individual variation. Using the simple case of the calcium concentration of sugar maple leaves, we compare the variation among individuals (the standard deviation) to the uncertainty in the mean (the standard error) and illustrate the declining importance in the prediction of individual concentrations as the number of individuals increases. For allometric models, the analogous statistics are the prediction interval (or the residual variation in the model fit) and the confidence interval (describing the uncertainty in the best fit model). The effect of propagating these two sources of error is illustrated using the mass of sugar maple foliage. The uncertainty in individual tree predictions was large for plots with few trees; for plots with 30 trees or more, the uncertainty in individuals was less important than the uncertainty in the mean. Authors of previously published analyses have reanalyzed their data to show the magnitude of these two sources of uncertainty in scales ranging from experimental plots to entire countries. The most correct analysis will take both sources of uncertainty into account, but for practical purposes, country-level reports of uncertainty in carbon stocks, as required by the IPCC, can ignore the uncertainty in individuals. Ignoring the uncertainty in the mean will lead to exaggerated estimates of confidence in estimates of forest biomass and carbon and nutrient contents.

A Research on the Responsibility of Accounting Professionals to Determine and Prevent Accounting Errors and Frauds: Edirne Sample

Directory of Open Access Journals (Sweden)

Semanur Adalı

2017-09-01

Full Text Available In this study, the ethical dimensions of accounting professionals related to accounting errors and frauds were examined. Firstly, general and technical information about accounting were provided. Then, some terminology on error, fraud and ethics in accounting were discussed. Study also included recent statistics about accounting errors and fraud as well as presenting a literature review. As the methodology of research, a questionnaire was distributed to 36 accounting professionals residing in Edirne city of Turkey. The collected data were then entered to the SPSS package program for analysis. The study revealed very important results. Accounting professionals think that, accounting chambers do not organize enough seminars/conferences on errors and fraud. They also believe that supervision and disciplinary boards of professional accounting chambers fulfill their responsibilities partially. Attitude of professional accounting chambers in terms of errors, fraud and ethics is considered neither strict nor lenient. But, most accounting professionals are aware of colleagues who had disciplinary penalties. Most important and effective tool to prevent errors and fraud is indicated as external audit, but internal audit and internal control are valued as well. According to accounting professionals, most errors occur due to incorrect data received from clients and as a result of recording. Fraud is generally made in order to get credit from banks and for providing benefits to the organization by not showing the real situation of the firm. Finally, accounting professionals state that being honest, trustworthy and impartial is the basis of accounting profession and accountants must adhere to ethical rules.

Determination of corrosion rate of reinforcement with a modulated guard ring electrode; analysis of errors due to lateral current distribution

International Nuclear Information System (INIS)

Wojtas, H.

2004-01-01

The main source of errors in measuring the corrosion rate of rebars on site is a non-uniform current distribution between the small counter electrode (CE) on the concrete surface and the large rebar network. Guard ring electrodes (GEs) are used in an attempt to confine the excitation current within a defined area. In order to better understand the functioning of modulated guard ring electrode and to assess its effectiveness in eliminating errors due to lateral spread of current signal from the small CE, measurements of the polarisation resistance performed on a concrete beam have been numerically simulated. Effect of parameters such as rebar corrosion activity, concrete resistivity, concrete cover depth and size of the corroding area on errors in the estimation of polarisation resistance of a single rebar has been examined. The results indicate that modulated GE arrangement fails to confine the lateral spread of the CE current within a constant area. Using the constant diameter of confinement for the calculation of corrosion rate may lead to serious errors when test conditions change. When high corrosion activity of rebar and/or local corrosion occur, the use of the modulated GE confinement may lead to significant underestimation of the corrosion rate

Measurement error in mobile source air pollution exposure estimates due to residential mobility during pregnancy.

Science.gov (United States)

Pennington, Audrey Flak; Strickland, Matthew J; Klein, Mitchel; Zhai, Xinxin; Russell, Armistead G; Hansen, Craig; Darrow, Lyndsey A

2017-09-01

Prenatal air pollution exposure is frequently estimated using maternal residential location at the time of delivery as a proxy for residence during pregnancy. We describe residential mobility during pregnancy among 19,951 children from the Kaiser Air Pollution and Pediatric Asthma Study, quantify measurement error in spatially resolved estimates of prenatal exposure to mobile source fine particulate matter (PM 2.5 ) due to ignoring this mobility, and simulate the impact of this error on estimates of epidemiologic associations. Two exposure estimates were compared, one calculated using complete residential histories during pregnancy (weighted average based on time spent at each address) and the second calculated using only residence at birth. Estimates were computed using annual averages of primary PM 2.5 from traffic emissions modeled using a Research LINE-source dispersion model for near-surface releases (RLINE) at 250 m resolution. In this cohort, 18.6% of children were born to mothers who moved at least once during pregnancy. Mobile source PM 2.5 exposure estimates calculated using complete residential histories during pregnancy and only residence at birth were highly correlated (r S >0.9). Simulations indicated that ignoring residential mobility resulted in modest bias of epidemiologic associations toward the null, but varied by maternal characteristics and prenatal exposure windows of interest (ranging from -2% to -10% bias).

Generalized Gaussian Error Calculus

CERN Document Server

Grabe, Michael

2010-01-01

For the first time in 200 years Generalized Gaussian Error Calculus addresses a rigorous, complete and self-consistent revision of the Gaussian error calculus. Since experimentalists realized that measurements in general are burdened by unknown systematic errors, the classical, widespread used evaluation procedures scrutinizing the consequences of random errors alone turned out to be obsolete. As a matter of course, the error calculus to-be, treating random and unknown systematic errors side by side, should ensure the consistency and traceability of physical units, physical constants and physical quantities at large. The generalized Gaussian error calculus considers unknown systematic errors to spawn biased estimators. Beyond, random errors are asked to conform to the idea of what the author calls well-defined measuring conditions. The approach features the properties of a building kit: any overall uncertainty turns out to be the sum of a contribution due to random errors, to be taken from a confidence inter...

Video Error Correction Using Steganography

Science.gov (United States)

Robie, David L.; Mersereau, Russell M.

2002-12-01

The transmission of any data is always subject to corruption due to errors, but video transmission, because of its real time nature must deal with these errors without retransmission of the corrupted data. The error can be handled using forward error correction in the encoder or error concealment techniques in the decoder. This MPEG-2 compliant codec uses data hiding to transmit error correction information and several error concealment techniques in the decoder. The decoder resynchronizes more quickly with fewer errors than traditional resynchronization techniques. It also allows for perfect recovery of differentially encoded DCT-DC components and motion vectors. This provides for a much higher quality picture in an error-prone environment while creating an almost imperceptible degradation of the picture in an error-free environment.

An in-process form error measurement system for precision machining

International Nuclear Information System (INIS)

Gao, Y; Huang, X; Zhang, Y

2010-01-01

In-process form error measurement for precision machining is studied. Due to two key problems, opaque barrier and vibration, the study of in-process form error optical measurement for precision machining has been a hard topic and so far very few existing research works can be found. In this project, an in-process form error measurement device is proposed to deal with the two key problems. Based on our existing studies, a prototype system has been developed. It is the first one of the kind that overcomes the two key problems. The prototype is based on a single laser sensor design of 50 nm resolution together with two techniques, a damping technique and a moving average technique, proposed for use with the device. The proposed damping technique is able to improve vibration attenuation by up to 21 times compared to the case of natural attenuation. The proposed moving average technique is able to reduce errors by seven to ten times without distortion to the form profile results. The two proposed techniques are simple but they are especially useful for the proposed device. For a workpiece sample, the measurement result under coolant condition is only 2.5% larger compared with the one under no coolant condition. For a certified Wyko test sample, the overall system measurement error can be as low as 0.3 µm. The measurement repeatability error can be as low as 2.2%. The experimental results give confidence in using the proposed in-process form error measurement device. For better results, further improvement in design and tests are necessary

Measurement-based analysis of error latency. [in computer operating system

Science.gov (United States)

Chillarege, Ram; Iyer, Ravishankar K.

1987-01-01

This paper demonstrates a practical methodology for the study of error latency under a real workload. The method is illustrated with sampled data on the physical memory activity, gathered by hardware instrumentation on a VAX 11/780 during the normal workload cycle of the installation. These data are used to simulate fault occurrence and to reconstruct the error discovery process in the system. The technique provides a means to study the system under different workloads and for multiple days. An approach to determine the percentage of undiscovered errors is also developed and a verification of the entire methodology is performed. This study finds that the mean error latency, in the memory containing the operating system, varies by a factor of 10 to 1 (in hours) between the low and high workloads. It is found that of all errors occurring within a day, 70 percent are detected in the same day, 82 percent within the following day, and 91 percent within the third day. The increase in failure rate due to latency is not so much a function of remaining errors but is dependent on whether or not there is a latent error.

Analyzing the errors of DFT approximations for compressed water systems

International Nuclear Information System (INIS)

Alfè, D.; Bartók, A. P.; Csányi, G.; Gillan, M. J.

2014-01-01

We report an extensive study of the errors of density functional theory (DFT) approximations for compressed water systems. The approximations studied are based on the widely used PBE and BLYP exchange-correlation functionals, and we characterize their errors before and after correction for 1- and 2-body errors, the corrections being performed using the methods of Gaussian approximation potentials. The errors of the uncorrected and corrected approximations are investigated for two related types of water system: first, the compressed liquid at temperature 420 K and density 1.245 g/cm 3 where the experimental pressure is 15 kilobars; second, thermal samples of compressed water clusters from the trimer to the 27-mer. For the liquid, we report four first-principles molecular dynamics simulations, two generated with the uncorrected PBE and BLYP approximations and a further two with their 1- and 2-body corrected counterparts. The errors of the simulations are characterized by comparing with experimental data for the pressure, with neutron-diffraction data for the three radial distribution functions, and with quantum Monte Carlo (QMC) benchmarks for the energies of sets of configurations of the liquid in periodic boundary conditions. The DFT errors of the configuration samples of compressed water clusters are computed using QMC benchmarks. We find that the 2-body and beyond-2-body errors in the liquid are closely related to similar errors exhibited by the clusters. For both the liquid and the clusters, beyond-2-body errors of DFT make a substantial contribution to the overall errors, so that correction for 1- and 2-body errors does not suffice to give a satisfactory description. For BLYP, a recent representation of 3-body energies due to Medders, Babin, and Paesani [J. Chem. Theory Comput. 9, 1103 (2013)] gives a reasonably good way of correcting for beyond-2-body errors, after which the remaining errors are typically 0.5 mE h ≃ 15 meV/monomer for the liquid and the

Medication errors in anesthesia: unacceptable or unavoidable?

Directory of Open Access Journals (Sweden)

Ira Dhawan

Full Text Available Abstract Medication errors are the common causes of patient morbidity and mortality. It adds financial burden to the institution as well. Though the impact varies from no harm to serious adverse effects including death, it needs attention on priority basis since medication errors' are preventable. In today's world where people are aware and medical claims are on the hike, it is of utmost priority that we curb this issue. Individual effort to decrease medication error alone might not be successful until a change in the existing protocols and system is incorporated. Often drug errors that occur cannot be reversed. The best way to ‘treat' drug errors is to prevent them. Wrong medication (due to syringe swap, overdose (due to misunderstanding or preconception of the dose, pump misuse and dilution error, incorrect administration route, under dosing and omission are common causes of medication error that occur perioperatively. Drug omission and calculation mistakes occur commonly in ICU. Medication errors can occur perioperatively either during preparation, administration or record keeping. Numerous human and system errors can be blamed for occurrence of medication errors. The need of the hour is to stop the blame - game, accept mistakes and develop a safe and ‘just' culture in order to prevent medication errors. The newly devised systems like VEINROM, a fluid delivery system is a novel approach in preventing drug errors due to most commonly used medications in anesthesia. Similar developments along with vigilant doctors, safe workplace culture and organizational support all together can help prevent these errors.

Video Error Correction Using Steganography

Directory of Open Access Journals (Sweden)

Robie David L

2002-01-01

Full Text Available The transmission of any data is always subject to corruption due to errors, but video transmission, because of its real time nature must deal with these errors without retransmission of the corrupted data. The error can be handled using forward error correction in the encoder or error concealment techniques in the decoder. This MPEG-2 compliant codec uses data hiding to transmit error correction information and several error concealment techniques in the decoder. The decoder resynchronizes more quickly with fewer errors than traditional resynchronization techniques. It also allows for perfect recovery of differentially encoded DCT-DC components and motion vectors. This provides for a much higher quality picture in an error-prone environment while creating an almost imperceptible degradation of the picture in an error-free environment.

Outlier removal, sum scores, and the inflation of the Type I error rate in independent samples t tests: the power of alternatives and recommendations.

Science.gov (United States)

Bakker, Marjan; Wicherts, Jelte M

2014-09-01

In psychology, outliers are often excluded before running an independent samples t test, and data are often nonnormal because of the use of sum scores based on tests and questionnaires. This article concerns the handling of outliers in the context of independent samples t tests applied to nonnormal sum scores. After reviewing common practice, we present results of simulations of artificial and actual psychological data, which show that the removal of outliers based on commonly used Z value thresholds severely increases the Type I error rate. We found Type I error rates of above 20% after removing outliers with a threshold value of Z = 2 in a short and difficult test. Inflations of Type I error rates are particularly severe when researchers are given the freedom to alter threshold values of Z after having seen the effects thereof on outcomes. We recommend the use of nonparametric Mann-Whitney-Wilcoxon tests or robust Yuen-Welch tests without removing outliers. These alternatives to independent samples t tests are found to have nominal Type I error rates with a minimal loss of power when no outliers are present in the data and to have nominal Type I error rates and good power when outliers are present. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Global tropospheric ozone modeling: Quantifying errors due to grid resolution

Science.gov (United States)

Wild, Oliver; Prather, Michael J.

2006-06-01

Ozone production in global chemical models is dependent on model resolution because ozone chemistry is inherently nonlinear, the timescales for chemical production are short, and precursors are artificially distributed over the spatial scale of the model grid. In this study we examine the sensitivity of ozone, its precursors, and its production to resolution by running a global chemical transport model at four different resolutions between T21 (5.6° × 5.6°) and T106 (1.1° × 1.1°) and by quantifying the errors in regional and global budgets. The sensitivity to vertical mixing through the parameterization of boundary layer turbulence is also examined. We find less ozone production in the boundary layer at higher resolution, consistent with slower chemical production in polluted emission regions and greater export of precursors. Agreement with ozonesonde and aircraft measurements made during the NASA TRACE-P campaign over the western Pacific in spring 2001 is consistently better at higher resolution. We demonstrate that the numerical errors in transport processes on a given resolution converge geometrically for a tracer at successively higher resolutions. The convergence in ozone production on progressing from T21 to T42, T63, and T106 resolution is likewise monotonic but indicates that there are still large errors at 120 km scales, suggesting that T106 resolution is too coarse to resolve regional ozone production. Diagnosing the ozone production and precursor transport that follow a short pulse of emissions over east Asia in springtime allows us to quantify the impacts of resolution on both regional and global ozone. Production close to continental emission regions is overestimated by 27% at T21 resolution, by 13% at T42 resolution, and by 5% at T106 resolution. However, subsequent ozone production in the free troposphere is not greatly affected. We find that the export of short-lived precursors such as NOx by convection is overestimated at coarse resolution.

[Patient identification errors and biological samples in the analytical process: Is it possible to improve patient safety?].

Science.gov (United States)

Cuadrado-Cenzual, M A; García Briñón, M; de Gracia Hills, Y; González Estecha, M; Collado Yurrita, L; de Pedro Moro, J A; Fernández Pérez, C; Arroyo Fernández, M

2015-01-01

Patient identification errors and biological samples are one of the problems with the highest risk factor in causing an adverse event in the patient. To detect and analyse the causes of patient identification errors in analytical requests (PIEAR) from emergency departments, and to develop improvement strategies. A process and protocol was designed, to be followed by all professionals involved in the requesting and performing of laboratory tests. Evaluation and monitoring indicators of PIEAR were determined, before and after the implementation of these improvement measures (years 2010-2014). A total of 316 PIEAR were detected in a total of 483,254 emergency service requests during the study period, representing a mean of 6.80/10,000 requests. Patient identification failure was the most frequent in all the 6-monthly periods assessed, with a significant difference (Perrors. However, we must continue working with this strategy, promoting a culture of safety for all the professionals involved, and trying to achieve the goal that 100% of the analytical and samples are properly identified. Copyright © 2015 SECA. Published by Elsevier Espana. All rights reserved.

Medication Error, What Is the Reason?

Directory of Open Access Journals (Sweden)

Ali Banaozar Mohammadi

2015-09-01

Full Text Available Background: Medication errors due to different reasons may alter the outcome of all patients, especially patients with drug poisoning. We introduce one of the most common type of medication error in the present article. Case:A 48 year old woman with suspected organophosphate poisoning was died due to lethal medication error. Unfortunately these types of errors are not rare and had some preventable reasons included lack of suitable and enough training and practicing of medical students and some failures in medical students’ educational curriculum. Conclusion:Hereby some important reasons are discussed because sometimes they are tre-mendous. We found that most of them are easily preventable. If someone be aware about the method of use, complications, dosage and contraindication of drugs, we can minimize most of these fatal errors.

Errors in Computing the Normalized Protein Catabolic Rate due to Use of Single-pool Urea Kinetic Modeling or to Omission of the Residual Kidney Urea Clearance.

Science.gov (United States)

Daugirdas, John T

2017-07-01

The protein catabolic rate normalized to body size (PCRn) often is computed in dialysis units to obtain information about protein ingestion. However, errors can manifest when inappropriate modeling methods are used. We used a variable volume 2-pool urea kinetic model to examine the percent errors in PCRn due to use of a 1-pool urea kinetic model or after omission of residual urea clearance (Kru). When a single-pool model was used, 2 sources of errors were identified. The first, dependent on the ratio of dialyzer urea clearance to urea distribution volume (K/V), resulted in a 7% inflation of the PCRn when K/V was in the range of 6 mL/min per L. A second, larger error appeared when Kt/V values were below 1.0 and was related to underestimation of urea distribution volume (due to overestimation of effective clearance) by the single-pool model. A previously reported prediction equation for PCRn was valid, but data suggest that it should be modified using 2-pool eKt/V and V coefficients instead of single-pool values. A third source of error, this one unrelated to use of a single-pool model, namely omission of Kru, was shown to result in an underestimation of PCRn, such that each ml/minute Kru per 35 L of V caused a 5.6% underestimate in PCRn. Marked overestimation of PCRn can result due to inappropriate use of a single-pool urea kinetic model, particularly when Kt/V <1.0 (as in short daily dialysis), or after omission of residual native kidney clearance. Copyright © 2017 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Competition increases binding errors in visual working memory.

Science.gov (United States)

Emrich, Stephen M; Ferber, Susanne

2012-04-20

When faced with maintaining multiple objects in visual working memory, item information must be bound to the correct object in order to be correctly recalled. Sometimes, however, binding errors occur, and participants report the feature (e.g., color) of an unprobed, non-target item. In the present study, we examine whether the configuration of sample stimuli affects the proportion of these binding errors. The results demonstrate that participants mistakenly report the identity of the unprobed item (i.e., they make a non-target response) when sample items are presented close together in space, suggesting that binding errors can increase independent of increases in memory load. Moreover, the proportion of these non-target responses is linearly related to the distance between sample items, suggesting that these errors are spatially specific. Finally, presenting sample items sequentially decreases non-target responses, suggesting that reducing competition between sample stimuli reduces the number of binding errors. Importantly, these effects all occurred without increases in the amount of error in the memory representation. These results suggest that competition during encoding can account for some of the binding errors made during VWM recall.

Error-related potentials during continuous feedback: using EEG to detect errors of different type and severity

Science.gov (United States)

Spüler, Martin; Niethammer, Christian

2015-01-01

When a person recognizes an error during a task, an error-related potential (ErrP) can be measured as response. It has been shown that ErrPs can be automatically detected in tasks with time-discrete feedback, which is widely applied in the field of Brain-Computer Interfaces (BCIs) for error correction or adaptation. However, there are only a few studies that concentrate on ErrPs during continuous feedback. With this study, we wanted to answer three different questions: (i) Can ErrPs be measured in electroencephalography (EEG) recordings during a task with continuous cursor control? (ii) Can ErrPs be classified using machine learning methods and is it possible to discriminate errors of different origins? (iii) Can we use EEG to detect the severity of an error? To answer these questions, we recorded EEG data from 10 subjects during a video game task and investigated two different types of error (execution error, due to inaccurate feedback; outcome error, due to not achieving the goal of an action). We analyzed the recorded data to show that during the same task, different kinds of error produce different ErrP waveforms and have a different spectral response. This allows us to detect and discriminate errors of different origin in an event-locked manner. By utilizing the error-related spectral response, we show that also a continuous, asynchronous detection of errors is possible. Although the detection of error severity based on EEG was one goal of this study, we did not find any significant influence of the severity on the EEG. PMID:25859204

Error-related potentials during continuous feedback: using EEG to detect errors of different type and severity

Directory of Open Access Journals (Sweden)

Martin eSpüler

2015-03-01

Full Text Available When a person recognizes an error during a task, an error-related potential (ErrP can be measured as response. It has been shown that ErrPs can be automatically detected in tasks with time-discrete feedback, which is widely applied in the field of Brain-Computer Interfaces (BCIs for error correction or adaptation. However, there are only a few studies that concentrate on ErrPs during continuous feedback.With this study, we wanted to answer three different questions: (i Can ErrPs be measured in electroencephalography (EEG recordings during a task with continuous cursor control? (ii Can ErrPs be classified using machine learning methods and is it possible to discriminate errors of different origins? (iii Can we use EEG to detect the severity of an error? To answer these questions, we recorded EEG data from 10 subjects during a video game task and investigated two different types of error (execution error, due to inaccurate feedback; outcome error, due to not achieving the goal of an action. We analyzed the recorded data to show that during the same task, different kinds of error produce different ErrP waveforms and have a different spectral response. This allows us to detect and discriminate errors of different origin in an event-locked manner. By utilizing the error-related spectral response, we show that also a continuous, asynchronous detection of errors is possible.Although the detection of error severity based on EEG was one goal of this study, we did not find any significant influence of the severity on the EEG.

Validation of Metrics as Error Predictors

Science.gov (United States)

Mendling, Jan

In this chapter, we test the validity of metrics that were defined in the previous chapter for predicting errors in EPC business process models. In Section 5.1, we provide an overview of how the analysis data is generated. Section 5.2 describes the sample of EPCs from practice that we use for the analysis. Here we discuss a disaggregation by the EPC model group and by error as well as a correlation analysis between metrics and error. Based on this sample, we calculate a logistic regression model for predicting error probability with the metrics as input variables in Section 5.3. In Section 5.4, we then test the regression function for an independent sample of EPC models from textbooks as a cross-validation. Section 5.5 summarizes the findings.

Sensitivity of Multicarrier Two-Dimensional Spreading Schemes to Synchronization Errors

Directory of Open Access Journals (Sweden)

Geneviève Jourdain

2008-06-01

Full Text Available This paper presents the impact of synchronization errors on the performance of a downlink multicarrier two-dimensional spreading OFDM-CDMA system. This impact is measured by the degradation of the signal to interference and noise ratio (SINR obtained after despreading and equalization. The contribution of this paper is twofold. First, we use some properties of random matrix and free probability theories to derive a new expression of the SINR. This expression is then independent of the actual value of the spreading codes while still accounting for the orthogonality between codes. This model is validated by means of Monte Carlo simulations. Secondly, the model is exploited to derive the SINR degradation of OFDM-CDMA systems due to synchronization errors which include a timing error, a carrier frequency offset, and a sampling frequency offset. It is also exploited to compare the sensitivities of MC-CDMA and MC-DS-CDMA systems to these errors in a frequency selective channel. This work is carried out for zero-forcing and minimum mean square error equalizers.

New PAT tools for assessing content uniformity, sampling error, and degree of crystallinity in pharmaceutical tablets

DEFF Research Database (Denmark)

Warnecke, Solveig

of the pharmaceutical drug, both during development and throughout the production. The usage of PAT tools is encouraged by the regulatory authorities, and therefore the interest in new and improved PAT tools is increasing. The main purpose of introducing Quality by Design (QbD) and PAT in pharmaceutical production...... practice in traditional pharmaceutical industry. In this thesis, three spectroscopic PAT tools are investigated, near-infrared-, terahertz-, and fluorescence-spectroscopy. These techniques have been evaluated with chemometrics and theory of sampling. The first study focused on the critical but rather...... overlooked sampling uncertainty that exist in all analytical measurements. The sampling error was studied using an example involving near infrared transmission (NIT) spectroscopy to study content of uniformity of five batches of escitalopram tablets, produced at different active pharmaceutical ingredients...

Over-Sampling Codebook-Based Hybrid Minimum Sum-Mean-Square-Error Precoding for Millimeter-Wave 3D-MIMO

KAUST Repository

Mao, Jiening

2018-05-23

Abstract: Hybrid precoding design is challenging for millimeter-wave (mmWave) massive MIMO. Most prior hybrid precoding schemes are designed to maximize the sum spectral efficiency (SSE), while seldom investigate the bit-error-rate (BER). Therefore, this letter designs an over-sampling codebook (OSC)-based hybrid minimum sum-mean-square-error (min-SMSE) precoding to optimize the BER. Specifically, given the effective baseband channel consisting of the real channel and analog precoding, we first design the digital precoder/combiner based on min-SMSE criterion to optimize the BER. To further reduce the SMSE between the transmit and receive signals, we propose an OSC-based joint analog precoder/combiner (JAPC) design. Simulation results show that the proposed scheme can achieve the better performance than its conventional counterparts.

Over-Sampling Codebook-Based Hybrid Minimum Sum-Mean-Square-Error Precoding for Millimeter-Wave 3D-MIMO

KAUST Repository

Mao, Jiening; Gao, Zhen; Wu, Yongpeng; Alouini, Mohamed-Slim

2018-01-01

Hybrid precoding design is challenging for millimeter-wave (mmWave) massive MIMO. Most prior hybrid precoding schemes are designed to maximize the sum spectral efficiency (SSE), while seldom investigate the bit-error-rate (BER). Therefore, this letter designs an over-sampling codebook (OSC)-based hybrid minimum sum-mean-square-error (min-SMSE) precoding to optimize the BER. Specifically, given the effective baseband channel consisting of the real channel and analog precoding, we first design the digital precoder/combiner based on min-SMSE criterion to optimize the BER. To further reduce the SMSE between the transmit and receive signals, we propose an OSC-based joint analog precoder/combiner (JAPC) design. Simulation results show that the proposed scheme can achieve the better performance than its conventional counterparts.

Modelling vertical error in LiDAR-derived digital elevation models

Science.gov (United States)

Aguilar, Fernando J.; Mills, Jon P.; Delgado, Jorge; Aguilar, Manuel A.; Negreiros, J. G.; Pérez, José L.

2010-01-01

A hybrid theoretical-empirical model has been developed for modelling the error in LiDAR-derived digital elevation models (DEMs) of non-open terrain. The theoretical component seeks to model the propagation of the sample data error (SDE), i.e. the error from light detection and ranging (LiDAR) data capture of ground sampled points in open terrain, towards interpolated points. The interpolation methods used for infilling gaps may produce a non-negligible error that is referred to as gridding error. In this case, interpolation is performed using an inverse distance weighting (IDW) method with the local support of the five closest neighbours, although it would be possible to utilize other interpolation methods. The empirical component refers to what is known as "information loss". This is the error purely due to modelling the continuous terrain surface from only a discrete number of points plus the error arising from the interpolation process. The SDE must be previously calculated from a suitable number of check points located in open terrain and assumes that the LiDAR point density was sufficiently high to neglect the gridding error. For model calibration, data for 29 study sites, 200×200 m in size, belonging to different areas around Almeria province, south-east Spain, were acquired by means of stereo photogrammetric methods. The developed methodology was validated against two different LiDAR datasets. The first dataset used was an Ordnance Survey (OS) LiDAR survey carried out over a region of Bristol in the UK. The second dataset was an area located at Gador mountain range, south of Almería province, Spain. Both terrain slope and sampling density were incorporated in the empirical component through the calibration phase, resulting in a very good agreement between predicted and observed data (R2 = 0.9856 ; p reasonably good fit to the predicted errors. Even better results were achieved in the more rugged morphology of the Gador mountain range dataset. The findings

Calculation of stochastic broadening due to noise and field errors in the simple map in action-angle coordinates

Science.gov (United States)

Hinton, Courtney; Punjabi, Alkesh; Ali, Halima

2008-11-01

The simple map is the simplest map that has topology of divertor tokamaks [1]. Recently, the action-angle coordinates for simple map are analytically calculated, and simple map is constructed in action-angle coordinates [2]. Action-angle coordinates for simple map can not be inverted to real space coordinates (R,Z). Because there is logarithmic singularity on the ideal separatrix, trajectories can not cross separatrix [2]. Simple map in action-angle coordinates is applied to calculate stochastic broadening due to magnetic noise and field errors. Mode numbers for noise + field errors from the DIII-D tokamak are used. Mode numbers are (m,n)=(3,1), (4,1), (6,2), (7,2), (8,2), (9,3), (10,3), (11,3), (12,3) [3]. The common amplitude δ is varied from 0.8X10-5 to 2.0X10-5. For this noise and field errors, the width of stochastic layer in simple map is calculated. This work is supported by US Department of Energy grants DE-FG02-07ER54937, DE-FG02-01ER54624 and DE-FG02-04ER54793 1. A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Let. A 364, 140--145 (2007). 2. O. Kerwin, A. Punjabi, and H. Ali, to appear in Physics of Plasmas. 3. A. Punjabi and H. Ali, P1.012, 35^th EPS Conference on Plasma Physics, June 9-13, 2008, Hersonissos, Crete, Greece.

Potential errors in optical density measurements due to scanning side in EBT and EBT2 Gafchromic film dosimetry.

Science.gov (United States)

Desroches, Joannie; Bouchard, Hugo; Lacroix, Frédéric

2010-04-01

The purpose of this study is to determine the effect on the measured optical density of scanning on either side of a Gafchromic EBT and EBT2 film using an Epson (Epson Canada Ltd., Toronto, Ontario) 10000XL flat bed scanner. Calibration curves were constructed using EBT2 film scanned in landscape orientation in both reflection and transmission mode on an Epson 10000XL scanner. Calibration curves were also constructed using EBT film. Potential errors due to an optical density difference from scanning the film on either side ("face up" or "face down") were simulated. Scanning the film face up or face down on the scanner bed while keeping the film angular orientation constant affects the measured optical density when scanning in reflection mode. In contrast, no statistically significant effect was seen when scanning in transmission mode. This effect can significantly affect relative and absolute dose measurements. As an application example, the authors demonstrate potential errors of 17.8% by inverting the film scanning side on the gamma index for 3%-3 mm criteria on a head and neck intensity modulated radiotherapy plan, and errors in absolute dose measurements ranging from 10% to 35% between 2 and 5 Gy. Process consistency is the key to obtaining accurate and precise results in Gafchromic film dosimetry. When scanning in reflection mode, care must be taken to place the film consistently on the same side on the scanner bed.

Global Vision Impairment and Blindness Due to Uncorrected Refractive Error, 1990-2010.

Science.gov (United States)

Naidoo, Kovin S; Leasher, Janet; Bourne, Rupert R; Flaxman, Seth R; Jonas, Jost B; Keeffe, Jill; Limburg, Hans; Pesudovs, Konrad; Price, Holly; White, Richard A; Wong, Tien Y; Taylor, Hugh R; Resnikoff, Serge

2016-03-01

The purpose of this systematic review was to estimate worldwide the number of people with moderate and severe visual impairment (MSVI; presenting visual acuity blindness (presenting visual acuity blind (7.9% increase from 1990) and 101.2 million (95% CI: 87.88-125.5 million) vision impaired due to URE (15% increase since 1990), while the global population increased by 30% (1990-2010). The all-age age-standardized prevalence of URE blindness decreased 33% from 0.2% (95% CI: 0.1-0.2%) in 1990 to 0.1% (95% CI: 0.1-0.1%) in 2010, whereas the prevalence of URE MSVI decreased 25% from 2.1% (95% CI: 1.6-2.4%) in 1990 to 1.5% (95% CI: 1.3-1.9%) in 2010. In 2010, URE contributed 20.9% (95% CI: 15.2-25.9%) of all blindness and 52.9% (95% CI: 47.2-57.3%) of all MSVI worldwide. The contribution of URE to all MSVI ranged from 44.2 to 48.1% in all regions except in South Asia which was at 65.4% (95% CI: 62-72%). : We conclude that in 2010, uncorrected refractive error continues as the leading cause of vision impairment and the second leading cause of blindness worldwide, affecting a total of 108 million people or 1 in 90 persons.

Reducing Bias and Error in the Correlation Coefficient Due to Nonnormality

Science.gov (United States)

Bishara, Anthony J.; Hittner, James B.

2015-01-01

It is more common for educational and psychological data to be nonnormal than to be approximately normal. This tendency may lead to bias and error in point estimates of the Pearson correlation coefficient. In a series of Monte Carlo simulations, the Pearson correlation was examined under conditions of normal and nonnormal data, and it was compared…

Uncorrected refractive errors.

Science.gov (United States)

Naidoo, Kovin S; Jaggernath, Jyoti

2012-01-01

Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship.

Uncorrected refractive errors

Directory of Open Access Journals (Sweden)

Kovin S Naidoo

2012-01-01

Full Text Available Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC, were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR Development, Service Development and Social Entrepreneurship.

Frecuencia de errores de los pacientes con su medicación Frequency of medication errors by patients

Directory of Open Access Journals (Sweden)

José Joaquín Mira

2012-02-01

Full Text Available OBJETIVO: Analizar la frecuencia de errores de medicación que son cometidos e informados por los pacientes. MÉTODOS: Estudio descriptivo basado en encuestas telefónicas a una muestra aleatoria de pacientes adultos del nivel primario de salud del sistema público español. Respondieron un total de 1 247 pacientes (tasa de respuesta, 75%. El 63% eran mujeres y 29% eran mayores de 70 años. RESULTADOS: Mientras 37 pacientes (3%, IC 95%: 2-4 sufrieron complicaciones asociadas a la medicación en el curso del tratamiento, 241 (19,4%, IC 95%: 17-21 informaron haber cometido algún error con la medicación. Un menor tiempo de consulta (P OBJECTIVE: Analyze the frequency of medication errors committed and reported by patients. METHODS: Descriptive study based on a telephone survey of a random sample of adult patients from the primary care level of the Spanish public health care system. A total of 1 247 patients responded (75% response rate; 63% were women and 29% were older than 70 years. RESULTS: While 37 patients (3%, 95% CI: 2-4 experienced complications associated with medication in the course of treatment, 241 (19.4%, 95% CI: 17-21 reported having made some mistake with their medication. A shorter consultation time (P < 0.01 and a worse assessment of the information provided by the physician (P < 0.01 were associated with the fact that during pharmacy dispensing the patient was told that the prescribed treatment was not appropriate. CONCLUSIONS: In addition to the known risks of an adverse event due to a health intervention resulting from a system or practitioner error, there are risks associated with patient errors in the self-administration of medication. Patients who were unsatisfied with the information provided by the physician reported a greater number of errors.

Outlier Removal and the Relation with Reporting Errors and Quality of Psychological Research

Science.gov (United States)

Bakker, Marjan; Wicherts, Jelte M.

2014-01-01

Background The removal of outliers to acquire a significant result is a questionable research practice that appears to be commonly used in psychology. In this study, we investigated whether the removal of outliers in psychology papers is related to weaker evidence (against the null hypothesis of no effect), a higher prevalence of reporting errors, and smaller sample sizes in these papers compared to papers in the same journals that did not report the exclusion of outliers from the analyses. Methods and Findings We retrieved a total of 2667 statistical results of null hypothesis significance tests from 153 articles in main psychology journals, and compared results from articles in which outliers were removed (N = 92) with results from articles that reported no exclusion of outliers (N = 61). We preregistered our hypotheses and methods and analyzed the data at the level of articles. Results show no significant difference between the two types of articles in median p value, sample sizes, or prevalence of all reporting errors, large reporting errors, and reporting errors that concerned the statistical significance. However, we did find a discrepancy between the reported degrees of freedom of t tests and the reported sample size in 41% of articles that did not report removal of any data values. This suggests common failure to report data exclusions (or missingness) in psychological articles. Conclusions We failed to find that the removal of outliers from the analysis in psychological articles was related to weaker evidence (against the null hypothesis of no effect), sample size, or the prevalence of errors. However, our control sample might be contaminated due to nondisclosure of excluded values in articles that did not report exclusion of outliers. Results therefore highlight the importance of more transparent reporting of statistical analyses. PMID:25072606

Defining And Characterizing Sample Representativeness For DWPF Melter Feed Samples

Energy Technology Data Exchange (ETDEWEB)

Shine, E. P.; Poirier, M. R.

2013-10-29

Representative sampling is important throughout the Defense Waste Processing Facility (DWPF) process, and the demonstrated success of the DWPF process to achieve glass product quality over the past two decades is a direct result of the quality of information obtained from the process. The objective of this report was to present sampling methods that the Savannah River Site (SRS) used to qualify waste being dispositioned at the DWPF. The goal was to emphasize the methodology, not a list of outcomes from those studies. This methodology includes proven methods for taking representative samples, the use of controlled analytical methods, and data interpretation and reporting that considers the uncertainty of all error sources. Numerous sampling studies were conducted during the development of the DWPF process and still continue to be performed in order to evaluate options for process improvement. Study designs were based on use of statistical tools applicable to the determination of uncertainties associated with the data needs. Successful designs are apt to be repeated, so this report chose only to include prototypic case studies that typify the characteristics of frequently used designs. Case studies have been presented for studying in-tank homogeneity, evaluating the suitability of sampler systems, determining factors that affect mixing and sampling, comparing the final waste glass product chemical composition and durability to that of the glass pour stream sample and other samples from process vessels, and assessing the uniformity of the chemical composition in the waste glass product. Many of these studies efficiently addressed more than one of these areas of concern associated with demonstrating sample representativeness and provide examples of statistical tools in use for DWPF. The time when many of these designs were implemented was in an age when the sampling ideas of Pierre Gy were not as widespread as they are today. Nonetheless, the engineers and

Defining And Characterizing Sample Representativeness For DWPF Melter Feed Samples

International Nuclear Information System (INIS)

Shine, E. P.; Poirier, M. R.

2013-01-01

Representative sampling is important throughout the Defense Waste Processing Facility (DWPF) process, and the demonstrated success of the DWPF process to achieve glass product quality over the past two decades is a direct result of the quality of information obtained from the process. The objective of this report was to present sampling methods that the Savannah River Site (SRS) used to qualify waste being dispositioned at the DWPF. The goal was to emphasize the methodology, not a list of outcomes from those studies. This methodology includes proven methods for taking representative samples, the use of controlled analytical methods, and data interpretation and reporting that considers the uncertainty of all error sources. Numerous sampling studies were conducted during the development of the DWPF process and still continue to be performed in order to evaluate options for process improvement. Study designs were based on use of statistical tools applicable to the determination of uncertainties associated with the data needs. Successful designs are apt to be repeated, so this report chose only to include prototypic case studies that typify the characteristics of frequently used designs. Case studies have been presented for studying in-tank homogeneity, evaluating the suitability of sampler systems, determining factors that affect mixing and sampling, comparing the final waste glass product chemical composition and durability to that of the glass pour stream sample and other samples from process vessels, and assessing the uniformity of the chemical composition in the waste glass product. Many of these studies efficiently addressed more than one of these areas of concern associated with demonstrating sample representativeness and provide examples of statistical tools in use for DWPF. The time when many of these designs were implemented was in an age when the sampling ideas of Pierre Gy were not as widespread as they are today. Nonetheless, the engineers and

Perceptual learning eases crowding by reducing recognition errors but not position errors.

Science.gov (United States)

Xiong, Ying-Zi; Yu, Cong; Zhang, Jun-Yun

2015-08-01

When an observer reports a letter flanked by additional letters in the visual periphery, the response errors (the crowding effect) may result from failure to recognize the target letter (recognition errors), from mislocating a correctly recognized target letter at a flanker location (target misplacement errors), or from reporting a flanker as the target letter (flanker substitution errors). Crowding can be reduced through perceptual learning. However, it is not known how perceptual learning operates to reduce crowding. In this study we trained observers with a partial-report task (Experiment 1), in which they reported the central target letter of a three-letter string presented in the visual periphery, or a whole-report task (Experiment 2), in which they reported all three letters in order. We then assessed the impact of training on recognition of both unflanked and flanked targets, with particular attention to how perceptual learning affected the types of errors. Our results show that training improved target recognition but not single-letter recognition, indicating that training indeed affected crowding. However, training did not reduce target misplacement errors or flanker substitution errors. This dissociation between target recognition and flanker substitution errors supports the view that flanker substitution may be more likely a by-product (due to response bias), rather than a cause, of crowding. Moreover, the dissociation is not consistent with hypothesized mechanisms of crowding that would predict reduced positional errors.

Achieving Accuracy Requirements for Forest Biomass Mapping: A Data Fusion Method for Estimating Forest Biomass and LiDAR Sampling Error with Spaceborne Data

Science.gov (United States)

Montesano, P. M.; Cook, B. D.; Sun, G.; Simard, M.; Zhang, Z.; Nelson, R. F.; Ranson, K. J.; Lutchke, S.; Blair, J. B.

2012-01-01

The synergistic use of active and passive remote sensing (i.e., data fusion) demonstrates the ability of spaceborne light detection and ranging (LiDAR), synthetic aperture radar (SAR) and multispectral imagery for achieving the accuracy requirements of a global forest biomass mapping mission. This data fusion approach also provides a means to extend 3D information from discrete spaceborne LiDAR measurements of forest structure across scales much larger than that of the LiDAR footprint. For estimating biomass, these measurements mix a number of errors including those associated with LiDAR footprint sampling over regional - global extents. A general framework for mapping above ground live forest biomass (AGB) with a data fusion approach is presented and verified using data from NASA field campaigns near Howland, ME, USA, to assess AGB and LiDAR sampling errors across a regionally representative landscape. We combined SAR and Landsat-derived optical (passive optical) image data to identify forest patches, and used image and simulated spaceborne LiDAR data to compute AGB and estimate LiDAR sampling error for forest patches and 100m, 250m, 500m, and 1km grid cells. Forest patches were delineated with Landsat-derived data and airborne SAR imagery, and simulated spaceborne LiDAR (SSL) data were derived from orbit and cloud cover simulations and airborne data from NASA's Laser Vegetation Imaging Sensor (L VIS). At both the patch and grid scales, we evaluated differences in AGB estimation and sampling error from the combined use of LiDAR with both SAR and passive optical and with either SAR or passive optical alone. This data fusion approach demonstrates that incorporating forest patches into the AGB mapping framework can provide sub-grid forest information for coarser grid-level AGB reporting, and that combining simulated spaceborne LiDAR with SAR and passive optical data are most useful for estimating AGB when measurements from LiDAR are limited because they minimized

Bayesian networks modeling for thermal error of numerical control machine tools

Institute of Scientific and Technical Information of China (English)

Xin-hua YAO; Jian-zhong FU; Zi-chen CHEN

2008-01-01

The interaction between the heat source location,its intensity,thermal expansion coefficient,the machine system configuration and the running environment creates complex thermal behavior of a machine tool,and also makes thermal error prediction difficult.To address this issue,a novel prediction method for machine tool thermal error based on Bayesian networks (BNs) was presented.The method described causal relationships of factors inducing thermal deformation by graph theory and estimated the thermal error by Bayesian statistical techniques.Due to the effective combination of domain knowledge and sampled data,the BN method could adapt to the change of running state of machine,and obtain satisfactory prediction accuracy.Ex-periments on spindle thermal deformation were conducted to evaluate the modeling performance.Experimental results indicate that the BN method performs far better than the least squares(LS)analysis in terms of modeling estimation accuracy.

Error-related anterior cingulate cortex activity and the prediction of conscious error awareness

Directory of Open Access Journals (Sweden)

Catherine eOrr

2012-06-01

Full Text Available Research examining the neural mechanisms associated with error awareness has consistently identified dorsal anterior cingulate activity (ACC as necessary but not predictive of conscious error detection. Two recent studies (Steinhauser and Yeung, 2010; Wessel et al. 2011 have found a contrary pattern of greater dorsal ACC activity (in the form of the error-related negativity during detected errors, but suggested that the greater activity may instead reflect task influences (e.g., response conflict, error probability and or individual variability (e.g., statistical power. We re-analyzed fMRI BOLD data from 56 healthy participants who had previously been administered the Error Awareness Task, a motor Go/No-go response inhibition task in which subjects make errors of commission of which they are aware (Aware errors, or unaware (Unaware errors. Consistent with previous data, the activity in a number of cortical regions was predictive of error awareness, including bilateral inferior parietal and insula cortices, however in contrast to previous studies, including our own smaller sample studies using the same task, error-related dorsal ACC activity was significantly greater during aware errors when compared to unaware errors. While the significantly faster RT for aware errors (compared to unaware was consistent with the hypothesis of higher response conflict increasing ACC activity, we could find no relationship between dorsal ACC activity and the error RT difference. The data suggests that individual variability in error awareness is associated with error-related dorsal ACC activity, and therefore this region may be important to conscious error detection, but it remains unclear what task and individual factors influence error awareness.

Responsibility for reporting patient death due to hospital error in Japan when an error occurred at a referring institution.

Science.gov (United States)

Maeda, Shoichi; Starkey, Jay; Kamishiraki, Etsuko; Ikeda, Noriaki

2013-12-01

In Japan, physicians are required to report unexpected health care-associated patient deaths to the police. Patients needing to be transferred to another institution often have complex medical problems. If a medical error occurs, it may be either at the final or the referring institution. Some fear that liability will fall on the final institution regardless of where the error occurred or that the referring facility may oppose such reporting, leading to a failure to report to police or to recommend an autopsy. Little is known about the actual opinions of physicians and risk managers in this regard. The authors sent standardised, self-administered questionnaires to all hospitals in Japan that participate in the national general residency program. Most physicians and risk managers in Japan indicated that they would report a patient's death to the police where the patient has been transferred. Of those who indicated they would not report to the police, the majority still indicated they would recommend an autopsy

[Errors in laboratory daily practice].

Science.gov (United States)

Larrose, C; Le Carrer, D

2007-01-01

Legislation set by GBEA (Guide de bonne exécution des analyses) requires that, before performing analysis, the laboratory directors have to check both the nature of the samples and the patients identity. The data processing of requisition forms, which identifies key errors, was established in 2000 and in 2002 by the specialized biochemistry laboratory, also with the contribution of the reception centre for biological samples. The laboratories follow a strict criteria of defining acceptability as a starting point for the reception to then check requisition forms and biological samples. All errors are logged into the laboratory database and analysis report are sent to the care unit specifying the problems and the consequences they have on the analysis. The data is then assessed by the laboratory directors to produce monthly or annual statistical reports. This indicates the number of errors, which are then indexed to patient files to reveal the specific problem areas, therefore allowing the laboratory directors to teach the nurses and enable corrective action.

[Statistical Process Control (SPC) can help prevent treatment errors without increasing costs in radiotherapy].

Science.gov (United States)

Govindarajan, R; Llueguera, E; Melero, A; Molero, J; Soler, N; Rueda, C; Paradinas, C

2010-01-01

Statistical Process Control (SPC) was applied to monitor patient set-up in radiotherapy and, when the measured set-up error values indicated a loss of process stability, its root cause was identified and eliminated to prevent set-up errors. Set up errors were measured for medial-lateral (ml), cranial-caudal (cc) and anterior-posterior (ap) dimensions and then the upper control limits were calculated. Once the control limits were known and the range variability was acceptable, treatment set-up errors were monitored using sub-groups of 3 patients, three times each shift. These values were plotted on a control chart in real time. Control limit values showed that the existing variation was acceptable. Set-up errors, measured and plotted on a X chart, helped monitor the set-up process stability and, if and when the stability was lost, treatment was interrupted, the particular cause responsible for the non-random pattern was identified and corrective action was taken before proceeding with the treatment. SPC protocol focuses on controlling the variability due to assignable cause instead of focusing on patient-to-patient variability which normally does not exist. Compared to weekly sampling of set-up error in each and every patient, which may only ensure that just those sampled sessions were set-up correctly, the SPC method enables set-up error prevention in all treatment sessions for all patients and, at the same time, reduces the control costs. Copyright © 2009 SECA. Published by Elsevier Espana. All rights reserved.

A heteroskedastic error covariance matrix estimator using a first-order conditional autoregressive Markov simulation for deriving asympotical efficient estimates from ecological sampled Anopheles arabiensis aquatic habitat covariates

Directory of Open Access Journals (Sweden)

Githure John I

2009-09-01

Full Text Available Abstract Background Autoregressive regression coefficients for Anopheles arabiensis aquatic habitat models are usually assessed using global error techniques and are reported as error covariance matrices. A global statistic, however, will summarize error estimates from multiple habitat locations. This makes it difficult to identify where there are clusters of An. arabiensis aquatic habitats of acceptable prediction. It is therefore useful to conduct some form of spatial error analysis to detect clusters of An. arabiensis aquatic habitats based on uncertainty residuals from individual sampled habitats. In this research, a method of error estimation for spatial simulation models was demonstrated using autocorrelation indices and eigenfunction spatial filters to distinguish among the effects of parameter uncertainty on a stochastic simulation of ecological sampled Anopheles aquatic habitat covariates. A test for diagnostic checking error residuals in an An. arabiensis aquatic habitat model may enable intervention efforts targeting productive habitats clusters, based on larval/pupal productivity, by using the asymptotic distribution of parameter estimates from a residual autocovariance matrix. The models considered in this research extends a normal regression analysis previously considered in the literature. Methods Field and remote-sampled data were collected during July 2006 to December 2007 in Karima rice-village complex in Mwea, Kenya. SAS 9.1.4® was used to explore univariate statistics, correlations, distributions, and to generate global autocorrelation statistics from the ecological sampled datasets. A local autocorrelation index was also generated using spatial covariance parameters (i.e., Moran's Indices in a SAS/GIS® database. The Moran's statistic was decomposed into orthogonal and uncorrelated synthetic map pattern components using a Poisson model with a gamma-distributed mean (i.e. negative binomial regression. The eigenfunction

Impact of exposure measurement error in air pollution epidemiology: effect of error type in time-series studies.

Science.gov (United States)

Goldman, Gretchen T; Mulholland, James A; Russell, Armistead G; Strickland, Matthew J; Klein, Mitchel; Waller, Lance A; Tolbert, Paige E

2011-06-22

Two distinctly different types of measurement error are Berkson and classical. Impacts of measurement error in epidemiologic studies of ambient air pollution are expected to depend on error type. We characterize measurement error due to instrument imprecision and spatial variability as multiplicative (i.e. additive on the log scale) and model it over a range of error types to assess impacts on risk ratio estimates both on a per measurement unit basis and on a per interquartile range (IQR) basis in a time-series study in Atlanta. Daily measures of twelve ambient air pollutants were analyzed: NO2, NOx, O3, SO2, CO, PM10 mass, PM2.5 mass, and PM2.5 components sulfate, nitrate, ammonium, elemental carbon and organic carbon. Semivariogram analysis was applied to assess spatial variability. Error due to this spatial variability was added to a reference pollutant time-series on the log scale using Monte Carlo simulations. Each of these time-series was exponentiated and introduced to a Poisson generalized linear model of cardiovascular disease emergency department visits. Measurement error resulted in reduced statistical significance for the risk ratio estimates for all amounts (corresponding to different pollutants) and types of error. When modelled as classical-type error, risk ratios were attenuated, particularly for primary air pollutants, with average attenuation in risk ratios on a per unit of measurement basis ranging from 18% to 92% and on an IQR basis ranging from 18% to 86%. When modelled as Berkson-type error, risk ratios per unit of measurement were biased away from the null hypothesis by 2% to 31%, whereas risk ratios per IQR were attenuated (i.e. biased toward the null) by 5% to 34%. For CO modelled error amount, a range of error types were simulated and effects on risk ratio bias and significance were observed. For multiplicative error, both the amount and type of measurement error impact health effect estimates in air pollution epidemiology. By modelling

Error Modeling and Design Optimization of Parallel Manipulators

DEFF Research Database (Denmark)

Wu, Guanglei

/backlash, manufacturing and assembly errors and joint clearances. From the error prediction model, the distributions of the pose errors due to joint clearances are mapped within its constant-orientation workspace and the correctness of the developed model is validated experimentally. ix Additionally, using the screw......, dynamic modeling etc. Next, the rst-order dierential equation of the kinematic closure equation of planar parallel manipulator is obtained to develop its error model both in Polar and Cartesian coordinate systems. The established error model contains the error sources of actuation error...

Pollutant forecasting error based on persistence of wind direction

International Nuclear Information System (INIS)

Cooper, R.E.

1978-01-01

The purpose of this report is to provide a means of estimating the reliability of forecasts of downwind pollutant concentrations from atmospheric puff releases. These forecasts are based on assuming the persistence of wind direction as determined at the time of release. This initial forecast will be used to deploy survey teams, to predict population centers that may be affected, and to estimate the amount of time available for emergency response. Reliability of forecasting is evaluated by developing a cumulative probability distribution of error as a function of lapsed time following an assumed release. The cumulative error is determined by comparing the forecast pollutant concentration with the concentration measured by sampling along the real-time meteorological trajectory. It may be concluded that the assumption of meteorological persistence for emergency response is not very good for periods longer than 3 hours. Even within this period, the possibiity for large error exists due to wind direction shifts. These shifts could affect population areas totally different from those areas first indicated

Density meter algorithm and system for estimating sampling/mixing uncertainty

International Nuclear Information System (INIS)

Shine, E.P.

1986-01-01

The Laboratories Department at the Savannah River Plant (SRP) has installed a six-place density meter with an automatic sampling device. This paper describes the statistical software developed to analyze the density of uranyl nitrate solutions using this automated system. The purpose of this software is twofold: to estimate the sampling/mixing and measurement uncertainties in the process and to provide a measurement control program for the density meter. Non-uniformities in density are analyzed both analytically and graphically. The mean density and its limit of error are estimated. Quality control standards are analyzed concurrently with process samples and used to control the density meter measurement error. The analyses are corrected for concentration due to evaporation of samples waiting to be analyzed. The results of this program have been successful in identifying sampling/mixing problems and controlling the quality of analyses

Density meter algorithm and system for estimating sampling/mixing uncertainty

International Nuclear Information System (INIS)

Shine, E.P.

1986-01-01

The Laboratories Department at the Savannah River Plant (SRP) has installed a six-place density meter with an automatic sampling device. This paper describes the statisical software developed to analyze the density of uranyl nitrate solutions using this automated system. The purpose of this software is twofold: to estimate the sampling/mixing and measurement uncertainties in the process and to provide a measurement control program for the density meter. Non-uniformities in density are analyzed both analytically and graphically. The mean density and its limit of error are estimated. Quality control standards are analyzed concurrently with process samples and used to control the density meter measurement error. The analyses are corrected for concentration due to evaporation of samples waiting to be analyzed. The results of this program have been successful in identifying sampling/mixing problems and controlling the quality of analyses

Dual-energy X-ray absorptiometry: analysis of pediatric fat estimate errors due to tissue hydration effects.

Science.gov (United States)

Testolin, C G; Gore, R; Rivkin, T; Horlick, M; Arbo, J; Wang, Z; Chiumello, G; Heymsfield, S B

2000-12-01

Dual-energy X-ray absorptiometry (DXA) percent (%) fat estimates may be inaccurate in young children, who typically have high tissue hydration levels. This study was designed to provide a comprehensive analysis of pediatric tissue hydration effects on DXA %fat estimates. Phase 1 was experimental and included three in vitro studies to establish the physical basis of DXA %fat-estimation models. Phase 2 extended phase 1 models and consisted of theoretical calculations to estimate the %fat errors emanating from previously reported pediatric hydration effects. Phase 1 experiments supported the two-compartment DXA soft tissue model and established that pixel ratio of low to high energy (R values) are a predictable function of tissue elemental content. In phase 2, modeling of reference body composition values from birth to age 120 mo revealed that %fat errors will arise if a "constant" adult lean soft tissue R value is applied to the pediatric population; the maximum %fat error, approximately 0.8%, would be present at birth. High tissue hydration, as observed in infants and young children, leads to errors in DXA %fat estimates. The magnitude of these errors based on theoretical calculations is small and may not be of clinical or research significance.

Ozone Production in Global Tropospheric Models: Quantifying Errors due to Grid Resolution

Science.gov (United States)

Wild, O.; Prather, M. J.

2005-12-01

Ozone production in global chemical models is dependent on model resolution because ozone chemistry is inherently nonlinear, the timescales for chemical production are short, and precursors are artificially distributed over the spatial scale of the model grid. In this study we examine the sensitivity of ozone, its precursors, and its production to resolution by running a global chemical transport model at four different resolutions between T21 (5.6° × 5.6°) and T106 (1.1° × 1.1°) and by quantifying the errors in regional and global budgets. The sensitivity to vertical mixing through the parameterization of boundary layer turbulence is also examined. We find less ozone production in the boundary layer at higher resolution, consistent with slower chemical production in polluted emission regions and greater export of precursors. Agreement with ozonesonde and aircraft measurements made during the NASA TRACE-P campaign over the Western Pacific in spring 2001 is consistently better at higher resolution. We demonstrate that the numerical errors in transport processes at a given resolution converge geometrically for a tracer at successively higher resolutions. The convergence in ozone production on progressing from T21 to T42, T63 and T106 resolution is likewise monotonic but still indicates large errors at 120~km scales, suggesting that T106 resolution is still too coarse to resolve regional ozone production. Diagnosing the ozone production and precursor transport that follow a short pulse of emissions over East Asia in springtime allows us to quantify the impacts of resolution on both regional and global ozone. Production close to continental emission regions is overestimated by 27% at T21 resolution, by 13% at T42 resolution, and by 5% at T106 resolution, but subsequent ozone production in the free troposphere is less significantly affected.

A 2 × 2 taxonomy of multilevel latent contextual models: accuracy-bias trade-offs in full and partial error correction models.

Science.gov (United States)

Lüdtke, Oliver; Marsh, Herbert W; Robitzsch, Alexander; Trautwein, Ulrich

2011-12-01

In multilevel modeling, group-level variables (L2) for assessing contextual effects are frequently generated by aggregating variables from a lower level (L1). A major problem of contextual analyses in the social sciences is that there is no error-free measurement of constructs. In the present article, 2 types of error occurring in multilevel data when estimating contextual effects are distinguished: unreliability that is due to measurement error and unreliability that is due to sampling error. The fact that studies may or may not correct for these 2 types of error can be translated into a 2 × 2 taxonomy of multilevel latent contextual models comprising 4 approaches: an uncorrected approach, partial correction approaches correcting for either measurement or sampling error (but not both), and a full correction approach that adjusts for both sources of error. It is shown mathematically and with simulated data that the uncorrected and partial correction approaches can result in substantially biased estimates of contextual effects, depending on the number of L1 individuals per group, the number of groups, the intraclass correlation, the number of indicators, and the size of the factor loadings. However, the simulation study also shows that partial correction approaches can outperform full correction approaches when the data provide only limited information in terms of the L2 construct (i.e., small number of groups, low intraclass correlation). A real-data application from educational psychology is used to illustrate the different approaches.

Analysis of methods commonly used in biomedicine for treatment versus control comparison of very small samples.

Science.gov (United States)

Ristić-Djurović, Jasna L; Ćirković, Saša; Mladenović, Pavle; Romčević, Nebojša; Trbovich, Alexander M

2018-04-01

A rough estimate indicated that use of samples of size not larger than ten is not uncommon in biomedical research and that many of such studies are limited to strong effects due to sample sizes smaller than six. For data collected from biomedical experiments it is also often unknown if mathematical requirements incorporated in the sample comparison methods are satisfied. Computer simulated experiments were used to examine performance of methods for qualitative sample comparison and its dependence on the effectiveness of exposure, effect intensity, distribution of studied parameter values in the population, and sample size. The Type I and Type II errors, their average, as well as the maximal errors were considered. The sample size 9 and the t-test method with p = 5% ensured error smaller than 5% even for weak effects. For sample sizes 6-8 the same method enabled detection of weak effects with errors smaller than 20%. If the sample sizes were 3-5, weak effects could not be detected with an acceptable error; however, the smallest maximal error in the most general case that includes weak effects is granted by the standard error of the mean method. The increase of sample size from 5 to 9 led to seven times more accurate detection of weak effects. Strong effects were detected regardless of the sample size and method used. The minimal recommended sample size for biomedical experiments is 9. Use of smaller sizes and the method of their comparison should be justified by the objective of the experiment. Copyright © 2018 Elsevier B.V. All rights reserved.

High energy hadron-induced errors in memory chips

Energy Technology Data Exchange (ETDEWEB)

Peterson, R.J. [University of Colorado, Boulder, CO (United States)

2001-09-01

We have measured probabilities for proton, neutron and pion beams from accelerators to induce temporary or soft errors in a wide range of modern 16 Mb and 64 Mb dRAM memory chips, typical of those used in aircraft electronics. Relations among the cross sections for these particles are deduced, and failure rates for aircraft avionics due to cosmic rays are evaluated. Measurement of alpha pha particle yields from pions on aluminum, as a surrogate for silicon, indicate that these reaction products are the proximate cause of the charge deposition resulting in errors. Heavy ions can cause damage to solar panels and other components in satellites above the atmosphere, by the heavy ionization trails they leave. However, at the earth's surface or at aircraft altitude it is known that cosmic rays, other than heavy ions, can cause soft errors in memory circuit components. Soft errors are those confusions between ones and zeroes that cause wrong contents to be stored in the memory, but without causing permanent damage to the circuit. As modern aircraft rely increasingly upon computerized and automated systems, these soft errors are important threats to safety. Protons, neutrons and pions resulting from high energy cosmic ray bombardment of the atmosphere pervade our environment. These particles do not induce damage directly by their ionization loss, but rather by reactions in the materials of the microcircuits. We have measured many cross sections for soft error upsets (SEU) in a broad range of commercial 16 Mb and 64 Mb dRAMs with accelerator beams. Here we define {sigma} SEU = induced errors/number of sample bits x particles/cm{sup 2}. We compare {sigma} SEU to find relations among results for these beams, and relations to reaction cross sections in order to systematize effects. We have modelled cosmic ray effects upon the components we have studied. (Author)

High energy hadron-induced errors in memory chips

International Nuclear Information System (INIS)

Peterson, R.J.

2001-01-01

We have measured probabilities for proton, neutron and pion beams from accelerators to induce temporary or soft errors in a wide range of modern 16 Mb and 64 Mb dRAM memory chips, typical of those used in aircraft electronics. Relations among the cross sections for these particles are deduced, and failure rates for aircraft avionics due to cosmic rays are evaluated. Measurement of alpha pha particle yields from pions on aluminum, as a surrogate for silicon, indicate that these reaction products are the proximate cause of the charge deposition resulting in errors. Heavy ions can cause damage to solar panels and other components in satellites above the atmosphere, by the heavy ionization trails they leave. However, at the earth's surface or at aircraft altitude it is known that cosmic rays, other than heavy ions, can cause soft errors in memory circuit components. Soft errors are those confusions between ones and zeroes that cause wrong contents to be stored in the memory, but without causing permanent damage to the circuit. As modern aircraft rely increasingly upon computerized and automated systems, these soft errors are important threats to safety. Protons, neutrons and pions resulting from high energy cosmic ray bombardment of the atmosphere pervade our environment. These particles do not induce damage directly by their ionization loss, but rather by reactions in the materials of the microcircuits. We have measured many cross sections for soft error upsets (SEU) in a broad range of commercial 16 Mb and 64 Mb dRAMs with accelerator beams. Here we define σ SEU = induced errors/number of sample bits x particles/cm 2 . We compare σ SEU to find relations among results for these beams, and relations to reaction cross sections in order to systematize effects. We have modelled cosmic ray effects upon the components we have studied. (Author)

Controlling errors in unidosis carts

Directory of Open Access Journals (Sweden)

Inmaculada Díaz Fernández

2010-01-01

Full Text Available Objective: To identify errors in the unidosis system carts. Method: For two months, the Pharmacy Service controlled medication either returned or missing from the unidosis carts both in the pharmacy and in the wards. Results: Uncorrected unidosis carts show a 0.9% of medication errors (264 versus 0.6% (154 which appeared in unidosis carts previously revised. In carts not revised, the error is 70.83% and mainly caused when setting up unidosis carts. The rest are due to a lack of stock or unavailability (21.6%, errors in the transcription of medical orders (6.81% or that the boxes had not been emptied previously (0.76%. The errors found in the units correspond to errors in the transcription of the treatment (3.46%, non-receipt of the unidosis copy (23.14%, the patient did not take the medication (14.36%or was discharged without medication (12.77%, was not provided by nurses (14.09%, was withdrawn from the stocks of the unit (14.62%, and errors of the pharmacy service (17.56% . Conclusions: It is concluded the need to redress unidosis carts and a computerized prescription system to avoid errors in transcription.Discussion: A high percentage of medication errors is caused by human error. If unidosis carts are overlooked before sent to hospitalization units, the error diminishes to 0.3%.

Technical Note: Potential errors in optical density measurements due to scanning side in EBT and EBT2 Gafchromic film dosimetry

International Nuclear Information System (INIS)

Desroches, Joannie; Bouchard, Hugo; Lacroix, Frederic

2010-01-01

Purpose: The purpose of this study is to determine the effect on the measured optical density of scanning on either side of a Gafchromic EBT and EBT2 film using an Epson (Epson Canada Ltd., Toronto, Ontario) 10000XL flat bed scanner. Methods: Calibration curves were constructed using EBT2 film scanned in landscape orientation in both reflection and transmission mode on an Epson 10000XL scanner. Calibration curves were also constructed using EBT film. Potential errors due to an optical density difference from scanning the film on either side (''face up'' or ''face down'') were simulated. Results: Scanning the film face up or face down on the scanner bed while keeping the film angular orientation constant affects the measured optical density when scanning in reflection mode. In contrast, no statistically significant effect was seen when scanning in transmission mode. This effect can significantly affect relative and absolute dose measurements. As an application example, the authors demonstrate potential errors of 17.8% by inverting the film scanning side on the gamma index for 3%--3 mm criteria on a head and neck intensity modulated radiotherapy plan, and errors in absolute dose measurements ranging from 10% to 35% between 2 and 5 Gy. Conclusions: Process consistency is the key to obtaining accurate and precise results in Gafchromic film dosimetry. When scanning in reflection mode, care must be taken to place the film consistently on the same side on the scanner bed.

Systematic errors due to linear congruential random-number generators with the Swendsen-Wang algorithm: a warning.

Science.gov (United States)

Ossola, Giovanni; Sokal, Alan D

2004-08-01

We show that linear congruential pseudo-random-number generators can cause systematic errors in Monte Carlo simulations using the Swendsen-Wang algorithm, if the lattice size is a multiple of a very large power of 2 and one random number is used per bond. These systematic errors arise from correlations within a single bond-update half-sweep. The errors can be eliminated (or at least radically reduced) by updating the bonds in a random order or in an aperiodic manner. It also helps to use a generator of large modulus (e.g., 60 or more bits).

Stochastic and sensitivity analysis of shape error of inflatable antenna reflectors

Science.gov (United States)

San, Bingbing; Yang, Qingshan; Yin, Liwei

2017-03-01

Inflatable antennas are promising candidates to realize future satellite communications and space observations since they are lightweight, low-cost and small-packaged-volume. However, due to their high flexibility, inflatable reflectors are difficult to manufacture accurately, which may result in undesirable shape errors, and thus affect their performance negatively. In this paper, the stochastic characteristics of shape errors induced during manufacturing process are investigated using Latin hypercube sampling coupled with manufacture simulations. Four main random error sources are involved, including errors in membrane thickness, errors in elastic modulus of membrane, boundary deviations and pressure variations. Using regression and correlation analysis, a global sensitivity study is conducted to rank the importance of these error sources. This global sensitivity analysis is novel in that it can take into account the random variation and the interaction between error sources. Analyses are parametrically carried out with various focal-length-to-diameter ratios (F/D) and aperture sizes (D) of reflectors to investigate their effects on significance ranking of error sources. The research reveals that RMS (Root Mean Square) of shape error is a random quantity with an exponent probability distribution and features great dispersion; with the increase of F/D and D, both mean value and standard deviation of shape errors are increased; in the proposed range, the significance ranking of error sources is independent of F/D and D; boundary deviation imposes the greatest effect with a much higher weight than the others; pressure variation ranks the second; error in thickness and elastic modulus of membrane ranks the last with very close sensitivities to pressure variation. Finally, suggestions are given for the control of the shape accuracy of reflectors and allowable values of error sources are proposed from the perspective of reliability.

Magnetic Nanoparticle Thermometer: An Investigation of Minimum Error Transmission Path and AC Bias Error

Directory of Open Access Journals (Sweden)

Zhongzhou Du

2015-04-01

Full Text Available The signal transmission module of a magnetic nanoparticle thermometer (MNPT was established in this study to analyze the error sources introduced during the signal flow in the hardware system. The underlying error sources that significantly affected the precision of the MNPT were determined through mathematical modeling and simulation. A transfer module path with the minimum error in the hardware system was then proposed through the analysis of the variations of the system error caused by the significant error sources when the signal flew through the signal transmission module. In addition, a system parameter, named the signal-to-AC bias ratio (i.e., the ratio between the signal and AC bias, was identified as a direct determinant of the precision of the measured temperature. The temperature error was below 0.1 K when the signal-to-AC bias ratio was higher than 80 dB, and other system errors were not considered. The temperature error was below 0.1 K in the experiments with a commercial magnetic fluid (Sample SOR-10, Ocean Nanotechnology, Springdale, AR, USA when the hardware system of the MNPT was designed with the aforementioned method.

The uncorrected refractive error challenge

Directory of Open Access Journals (Sweden)

Kovin Naidoo

2016-11-01

Full Text Available Refractive error affects people of all ages, socio-economic status and ethnic groups. The most recent statistics estimate that, worldwide, 32.4 million people are blind and 191 million people have vision impairment. Vision impairment has been defined based on distance visual acuity only, and uncorrected distance refractive error (mainly myopia is the single biggest cause of worldwide vision impairment. However, when we also consider near visual impairment, it is clear that even more people are affected. From research it was estimated that the number of people with vision impairment due to uncorrected distance refractive error was 107.8 million,1 and the number of people affected by uncorrected near refractive error was 517 million, giving a total of 624.8 million people.

[Monitoring medication errors in personalised dispensing using the Sentinel Surveillance System method].

Science.gov (United States)

Pérez-Cebrián, M; Font-Noguera, I; Doménech-Moral, L; Bosó-Ribelles, V; Romero-Boyero, P; Poveda-Andrés, J L

2011-01-01

To assess the efficacy of a new quality control strategy based on daily randomised sampling and monitoring a Sentinel Surveillance System (SSS) medication cart, in order to identify medication errors and their origin at different levels of the process. Prospective quality control study with one year follow-up. A SSS medication cart was randomly selected once a week and double-checked before dispensing medication. Medication errors were recorded before it was taken to the relevant hospital ward. Information concerning complaints after receiving medication and 24-hour monitoring were also noted. Type and origin error data were assessed by a Unit Dose Quality Control Group, which proposed relevant improvement measures. Thirty-four SSS carts were assessed, including 5130 medication lines and 9952 dispensed doses, corresponding to 753 patients. Ninety erroneous lines (1.8%) and 142 mistaken doses (1.4%) were identified at the Pharmacy Department. The most frequent error was dose duplication (38%) and its main cause inappropriate management and forgetfulness (69%). Fifty medication complaints (6.6% of patients) were mainly due to new treatment at admission (52%), and 41 (0.8% of all medication lines), did not completely match the prescription (0.6% lines) as recorded by the Pharmacy Department. Thirty-seven (4.9% of patients) medication complaints due to changes at admission and 32 matching errors (0.6% medication lines) were recorded. The main cause also was inappropriate management and forgetfulness (24%). The simultaneous recording of incidences due to complaints and new medication coincided in 33.3%. In addition, 433 (4.3%) of dispensed doses were returned to the Pharmacy Department. After the Unit Dose Quality Control Group conducted their feedback analysis, 64 improvement measures for Pharmacy Department nurses, 37 for pharmacists, and 24 for the hospital ward were introduced. The SSS programme has proven to be useful as a quality control strategy to identify Unit

Trans-dimensional matched-field geoacoustic inversion with hierarchical error models and interacting Markov chains.

Science.gov (United States)

Dettmer, Jan; Dosso, Stan E

2012-10-01

This paper develops a trans-dimensional approach to matched-field geoacoustic inversion, including interacting Markov chains to improve efficiency and an autoregressive model to account for correlated errors. The trans-dimensional approach and hierarchical seabed model allows inversion without assuming any particular parametrization by relaxing model specification to a range of plausible seabed models (e.g., in this case, the number of sediment layers is an unknown parameter). Data errors are addressed by sampling statistical error-distribution parameters, including correlated errors (covariance), by applying a hierarchical autoregressive error model. The well-known difficulty of low acceptance rates for trans-dimensional jumps is addressed with interacting Markov chains, resulting in a substantial increase in efficiency. The trans-dimensional seabed model and the hierarchical error model relax the degree of prior assumptions required in the inversion, resulting in substantially improved (more realistic) uncertainty estimates and a more automated algorithm. In particular, the approach gives seabed parameter uncertainty estimates that account for uncertainty due to prior model choice (layering and data error statistics). The approach is applied to data measured on a vertical array in the Mediterranean Sea.

Learning from errors in super-resolution.

Science.gov (United States)

Tang, Yi; Yuan, Yuan

2014-11-01

A novel framework of learning-based super-resolution is proposed by employing the process of learning from the estimation errors. The estimation errors generated by different learning-based super-resolution algorithms are statistically shown to be sparse and uncertain. The sparsity of the estimation errors means most of estimation errors are small enough. The uncertainty of the estimation errors means the location of the pixel with larger estimation error is random. Noticing the prior information about the estimation errors, a nonlinear boosting process of learning from these estimation errors is introduced into the general framework of the learning-based super-resolution. Within the novel framework of super-resolution, a low-rank decomposition technique is used to share the information of different super-resolution estimations and to remove the sparse estimation errors from different learning algorithms or training samples. The experimental results show the effectiveness and the efficiency of the proposed framework in enhancing the performance of different learning-based algorithms.

Introduction to precision machine design and error assessment

CERN Document Server

Mekid, Samir

2008-01-01

While ultra-precision machines are now achieving sub-nanometer accuracy, unique challenges continue to arise due to their tight specifications. Written to meet the growing needs of mechanical engineers and other professionals to understand these specialized design process issues, Introduction to Precision Machine Design and Error Assessment places a particular focus on the errors associated with precision design, machine diagnostics, error modeling, and error compensation. Error Assessment and ControlThe book begins with a brief overview of precision engineering and applications before introdu

Radiologic errors, past, present and future.

Science.gov (United States)

Berlin, Leonard

2014-01-01

During the 10-year period beginning in 1949 with publication of five articles in two radiology journals and UKs The Lancet, a California radiologist named L.H. Garland almost single-handedly shocked the entire medical and especially the radiologic community. He focused their attention on the fact now known and accepted by all, but at that time not previously recognized and acknowledged only with great reluctance, that a substantial degree of observer error was prevalent in radiologic interpretation. In the more than half-century that followed, Garland's pioneering work has been affirmed and reaffirmed by numerous researchers. Retrospective studies disclosed then and still disclose today that diagnostic errors in radiologic interpretations of plain radiographic (as well as CT, MR, ultrasound, and radionuclide) images hover in the 30% range, not too dissimilar to the error rates in clinical medicine. Seventy percent of these errors are perceptual in nature, i.e., the radiologist does not "see" the abnormality on the imaging exam, perhaps due to poor conspicuity, satisfaction of search, or simply the "inexplicable psycho-visual phenomena of human perception." The remainder are cognitive errors: the radiologist sees an abnormality but fails to render a correct diagnoses by attaching the wrong significance to what is seen, perhaps due to inadequate knowledge, or an alliterative or judgmental error. Computer-assisted detection (CAD), a technology that for the past two decades has been utilized primarily in mammographic interpretation, increases sensitivity but at the same time decreases specificity; whether it reduces errors is debatable. Efforts to reduce diagnostic radiological errors continue, but the degree to which they will be successful remains to be determined.

VOLUMETRIC ERROR COMPENSATION IN FIVE-AXIS CNC MACHINING CENTER THROUGH KINEMATICS MODELING OF GEOMETRIC ERROR

Directory of Open Access Journals (Sweden)

Pooyan Vahidi Pashsaki

2016-06-01

Full Text Available Accuracy of a five-axis CNC machine tool is affected by a vast number of error sources. This paper investigates volumetric error modeling and its compensation to the basis for creation of new tool path for improvement of work pieces accuracy. The volumetric error model of a five-axis machine tool with the configuration RTTTR (tilting head B-axis and rotary table in work piece side A΄ was set up taking into consideration rigid body kinematics and homogeneous transformation matrix, in which 43 error components are included. Volumetric error comprises 43 error components that can separately reduce geometrical and dimensional accuracy of work pieces. The machining accuracy of work piece is guaranteed due to the position of the cutting tool center point (TCP relative to the work piece. The cutting tool is deviated from its ideal position relative to the work piece and machining error is experienced. For compensation process detection of the present tool path and analysis of the RTTTR five-axis CNC machine tools geometrical error, translating current position of component to compensated positions using the Kinematics error model, converting newly created component to new tool paths using the compensation algorithms and finally editing old G-codes using G-code generator algorithm have been employed.

A Third Moment Adjusted Test Statistic for Small Sample Factor Analysis.

Science.gov (United States)

Lin, Johnny; Bentler, Peter M

2012-01-01

Goodness of fit testing in factor analysis is based on the assumption that the test statistic is asymptotically chi-square; but this property may not hold in small samples even when the factors and errors are normally distributed in the population. Robust methods such as Browne's asymptotically distribution-free method and Satorra Bentler's mean scaling statistic were developed under the presumption of non-normality in the factors and errors. This paper finds new application to the case where factors and errors are normally distributed in the population but the skewness of the obtained test statistic is still high due to sampling error in the observed indicators. An extension of Satorra Bentler's statistic is proposed that not only scales the mean but also adjusts the degrees of freedom based on the skewness of the obtained test statistic in order to improve its robustness under small samples. A simple simulation study shows that this third moment adjusted statistic asymptotically performs on par with previously proposed methods, and at a very small sample size offers superior Type I error rates under a properly specified model. Data from Mardia, Kent and Bibby's study of students tested for their ability in five content areas that were either open or closed book were used to illustrate the real-world performance of this statistic.

Systematic error in the precision measurement of the mean wavelength of a nearly monochromatic neutron beam due to geometric errors

Energy Technology Data Exchange (ETDEWEB)

Coakley, K.J., E-mail: kevin.coakley@nist.go [National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305 (United States); Dewey, M.S. [National Institute of Standards and Technology, Gaithersburg, MD (United States); Yue, A.T. [University of Tennessee, Knoxville, TN (United States); Laptev, A.B. [Tulane University, New Orleans, LA (United States)

2009-12-11

Many experiments at neutron scattering facilities require nearly monochromatic neutron beams. In such experiments, one must accurately measure the mean wavelength of the beam. We seek to reduce the systematic uncertainty of this measurement to approximately 0.1%. This work is motivated mainly by an effort to improve the measurement of the neutron lifetime determined from data collected in a 2003 in-beam experiment performed at NIST. More specifically, we seek to reduce systematic uncertainty by calibrating the neutron detector used in this lifetime experiment. This calibration requires simultaneous measurement of the responses of both the neutron detector used in the lifetime experiment and an absolute black neutron detector to a highly collimated nearly monochromatic beam of cold neutrons, as well as a separate measurement of the mean wavelength of the neutron beam. The calibration uncertainty will depend on the uncertainty of the measured efficiency of the black neutron detector and the uncertainty of the measured mean wavelength. The mean wavelength of the beam is measured by Bragg diffracting the beam from a nearly perfect silicon analyzer crystal. Given the rocking curve data and knowledge of the directions of the rocking axis and the normal to the scattering planes in the silicon crystal, one determines the mean wavelength of the beam. In practice, the direction of the rocking axis and the normal to the silicon scattering planes are not known exactly. Based on Monte Carlo simulation studies, we quantify systematic uncertainties in the mean wavelength measurement due to these geometric errors. Both theoretical and empirical results are presented and compared.

A method to correct sampling ghosts in historic near-infrared Fourier transform spectrometer (FTS) measurements

Science.gov (United States)

Dohe, S.; Sherlock, V.; Hase, F.; Gisi, M.; Robinson, J.; Sepúlveda, E.; Schneider, M.; Blumenstock, T.

2013-08-01

The Total Carbon Column Observing Network (TCCON) has been established to provide ground-based remote sensing measurements of the column-averaged dry air mole fractions (DMF) of key greenhouse gases. To ensure network-wide consistency, biases between Fourier transform spectrometers at different sites have to be well controlled. Errors in interferogram sampling can introduce significant biases in retrievals. In this study we investigate a two-step scheme to correct these errors. In the first step the laser sampling error (LSE) is estimated by determining the sampling shift which minimises the magnitude of the signal intensity in selected, fully absorbed regions of the solar spectrum. The LSE is estimated for every day with measurements which meet certain selection criteria to derive the site-specific time series of the LSEs. In the second step, this sequence of LSEs is used to resample all the interferograms acquired at the site, and hence correct the sampling errors. Measurements acquired at the Izaña and Lauder TCCON sites are used to demonstrate the method. At both sites the sampling error histories show changes in LSE due to instrument interventions (e.g. realignment). Estimated LSEs are in good agreement with sampling errors inferred from the ratio of primary and ghost spectral signatures in optically bandpass-limited tungsten lamp spectra acquired at Lauder. The original time series of Xair and XCO2 (XY: column-averaged DMF of the target gas Y) at both sites show discrepancies of 0.2-0.5% due to changes in the LSE associated with instrument interventions or changes in the measurement sample rate. After resampling, discrepancies are reduced to 0.1% or less at Lauder and 0.2% at Izaña. In the latter case, coincident changes in interferometer alignment may also have contributed to the residual difference. In the future the proposed method will be used to correct historical spectra at all TCCON sites.

A method to correct sampling ghosts in historic near-infrared Fourier transform spectrometer (FTS measurements

Directory of Open Access Journals (Sweden)

S. Dohe

2013-08-01

Full Text Available The Total Carbon Column Observing Network (TCCON has been established to provide ground-based remote sensing measurements of the column-averaged dry air mole fractions (DMF of key greenhouse gases. To ensure network-wide consistency, biases between Fourier transform spectrometers at different sites have to be well controlled. Errors in interferogram sampling can introduce significant biases in retrievals. In this study we investigate a two-step scheme to correct these errors. In the first step the laser sampling error (LSE is estimated by determining the sampling shift which minimises the magnitude of the signal intensity in selected, fully absorbed regions of the solar spectrum. The LSE is estimated for every day with measurements which meet certain selection criteria to derive the site-specific time series of the LSEs. In the second step, this sequence of LSEs is used to resample all the interferograms acquired at the site, and hence correct the sampling errors. Measurements acquired at the Izaña and Lauder TCCON sites are used to demonstrate the method. At both sites the sampling error histories show changes in LSE due to instrument interventions (e.g. realignment. Estimated LSEs are in good agreement with sampling errors inferred from the ratio of primary and ghost spectral signatures in optically bandpass-limited tungsten lamp spectra acquired at Lauder. The original time series of Xair and XCO2 (XY: column-averaged DMF of the target gas Y at both sites show discrepancies of 0.2–0.5% due to changes in the LSE associated with instrument interventions or changes in the measurement sample rate. After resampling, discrepancies are reduced to 0.1% or less at Lauder and 0.2% at Izaña. In the latter case, coincident changes in interferometer alignment may also have contributed to the residual difference. In the future the proposed method will be used to correct historical spectra at all TCCON sites.

Error of image saturation in the structured-light method.

Science.gov (United States)

Qi, Zhaoshuai; Wang, Zhao; Huang, Junhui; Xing, Chao; Gao, Jianmin

2018-01-01

In the phase-measuring structured-light method, image saturation will induce large phase errors. Usually, by selecting proper system parameters (such as the phase-shift number, exposure time, projection intensity, etc.), the phase error can be reduced. However, due to lack of a complete theory of phase error, there is no rational principle or basis for the selection of the optimal system parameters. For this reason, the phase error due to image saturation is analyzed completely, and the effects of the two main factors, including the phase-shift number and saturation degree, on the phase error are studied in depth. In addition, the selection of optimal system parameters is discussed, including the proper range and the selection principle of the system parameters. The error analysis and the conclusion are verified by simulation and experiment results, and the conclusion can be used for optimal parameter selection in practice.

Does semantic impairment explain surface dyslexia? VLSM evidence for a double dissociation between regularization errors in reading and semantic errors in picture naming

Directory of Open Access Journals (Sweden)

Sara Pillay

2014-04-01

Full Text Available The correlation between semantic deficits and exception word regularization errors ("surface dyslexia" in semantic dementia has been taken as strong evidence for involvement of semantic codes in exception word pronunciation. Rare cases with semantic deficits but no exception word reading deficit have been explained as due to individual differences in reading strategy, but this account is hotly debated. Semantic dementia is a diffuse process that always includes semantic impairment, making lesion localization difficult and independent assessment of semantic deficits and reading errors impossible. We addressed this problem using voxel-based lesion symptom mapping in 38 patients with left hemisphere stroke. Patients were all right-handed, native English speakers and at least 6 months from stroke onset. Patients performed an oral reading task that included 80 exception words (words with inconsistent orthographic-phonologic correspondence, e.g., pint, plaid, glove. Regularization errors were defined as plausible but incorrect pronunciations based on application of spelling-sound correspondence rules (e.g., 'plaid' pronounced as "played". Two additional tests examined explicit semantic knowledge and retrieval. The first measured semantic substitution errors during naming of 80 standard line drawings of objects. This error type is generally presumed to arise at the level of concept selection. The second test (semantic matching required patients to match a printed sample word (e.g., bus with one of two alternative choice words (e.g., car, taxi on the basis of greater similarity of meaning. Lesions were labeled on high-resolution T1 MRI volumes using a semi-automated segmentation method, followed by diffeomorphic registration to a template. VLSM used an ANCOVA approach to remove variance due to age, education, and total lesion volume. Regularization errors during reading were correlated with damage in the posterior half of the middle temporal gyrus and

Fusing metabolomics data sets with heterogeneous measurement errors

Science.gov (United States)

Waaijenborg, Sandra; Korobko, Oksana; Willems van Dijk, Ko; Lips, Mirjam; Hankemeier, Thomas; Wilderjans, Tom F.; Smilde, Age K.

2018-01-01

Combining different metabolomics platforms can contribute significantly to the discovery of complementary processes expressed under different conditions. However, analysing the fused data might be hampered by the difference in their quality. In metabolomics data, one often observes that measurement errors increase with increasing measurement level and that different platforms have different measurement error variance. In this paper we compare three different approaches to correct for the measurement error heterogeneity, by transformation of the raw data, by weighted filtering before modelling and by a modelling approach using a weighted sum of residuals. For an illustration of these different approaches we analyse data from healthy obese and diabetic obese individuals, obtained from two metabolomics platforms. Concluding, the filtering and modelling approaches that both estimate a model of the measurement error did not outperform the data transformation approaches for this application. This is probably due to the limited difference in measurement error and the fact that estimation of measurement error models is unstable due to the small number of repeats available. A transformation of the data improves the classification of the two groups. PMID:29698490

Modeling the Error of the Medtronic Paradigm Veo Enlite Glucose Sensor.

Science.gov (United States)

Biagi, Lyvia; Ramkissoon, Charrise M; Facchinetti, Andrea; Leal, Yenny; Vehi, Josep

2017-06-12

Continuous glucose monitors (CGMs) are prone to inaccuracy due to time lags, sensor drift, calibration errors, and measurement noise. The aim of this study is to derive the model of the error of the second generation Medtronic Paradigm Veo Enlite (ENL) sensor and compare it with the Dexcom SEVEN PLUS (7P), G4 PLATINUM (G4P), and advanced G4 for Artificial Pancreas studies (G4AP) systems. An enhanced methodology to a previously employed technique was utilized to dissect the sensor error into several components. The dataset used included 37 inpatient sessions in 10 subjects with type 1 diabetes (T1D), in which CGMs were worn in parallel and blood glucose (BG) samples were analyzed every 15 ± 5 min Calibration error and sensor drift of the ENL sensor was best described by a linear relationship related to the gain and offset. The mean time lag estimated by the model is 9.4 ± 6.5 min. The overall average mean absolute relative difference (MARD) of the ENL sensor was 11.68 ± 5.07% Calibration error had the highest contribution to total error in the ENL sensor. This was also reported in the 7P, G4P, and G4AP. The model of the ENL sensor error will be useful to test the in silico performance of CGM-based applications, i.e., the artificial pancreas, employing this kind of sensor.

Error evaluation method for material accountancy measurement. Evaluation of random and systematic errors based on material accountancy data

International Nuclear Information System (INIS)

Nidaira, Kazuo

2008-01-01

International Target Values (ITV) shows random and systematic measurement uncertainty components as a reference for routinely achievable measurement quality in the accountancy measurement. The measurement uncertainty, called error henceforth, needs to be periodically evaluated and checked against ITV for consistency as the error varies according to measurement methods, instruments, operators, certified reference samples, frequency of calibration, and so on. In the paper an error evaluation method was developed with focuses on (1) Specifying clearly error calculation model, (2) Getting always positive random and systematic error variances, (3) Obtaining probability density distribution of an error variance and (4) Confirming the evaluation method by simulation. In addition the method was demonstrated by applying real data. (author)

A platform-independent method for detecting errors in metagenomic sequencing data: DRISEE.

Directory of Open Access Journals (Sweden)

Kevin P Keegan

Full Text Available We provide a novel method, DRISEE (duplicate read inferred sequencing error estimation, to assess sequencing quality (alternatively referred to as "noise" or "error" within and/or between sequencing samples. DRISEE provides positional error estimates that can be used to inform read trimming within a sample. It also provides global (whole sample error estimates that can be used to identify samples with high or varying levels of sequencing error that may confound downstream analyses, particularly in the case of studies that utilize data from multiple sequencing samples. For shotgun metagenomic data, we believe that DRISEE provides estimates of sequencing error that are more accurate and less constrained by technical limitations than existing methods that rely on reference genomes or the use of scores (e.g. Phred. Here, DRISEE is applied to (non amplicon data sets from both the 454 and Illumina platforms. The DRISEE error estimate is obtained by analyzing sets of artifactual duplicate reads (ADRs, a known by-product of both sequencing platforms. We present DRISEE as an open-source, platform-independent method to assess sequencing error in shotgun metagenomic data, and utilize it to discover previously uncharacterized error in de novo sequence data from the 454 and Illumina sequencing platforms.

Remote tritium-in-air sampling in reactor building at NAPS

International Nuclear Information System (INIS)

Mitra, S.R.; Lal Chand

2000-01-01

Tritium-in-air activity is an important parameter in PHW reactors from the point of view of internal exposure and heavy water escape from the system. The sampling technique in vogue in PHWRs, for measurement of tritium-in-air activity, requires collection of on the spot sample from different areas using a portable sampler. This sampler uses the bubbler method of sampling. As the areas of sampling are numerous, this technique is time consuming, laborious and can lead to significant internal exposure in areas where tritium-in-air activity is high. This technique is also error prone due to the heavy workload involved. A new scheme, in which the sampling of all the areas of reactor building is done through a sampling station, has been introduced for the first time in NAPS. This sampling station facilitates collection of samples from all the areas of reactor building, remotely and simultaneously at one place thereby reducing time, labour, exposure and error. This paper gives the details of the sampling system installed at NAPS. (author)

Efficient sampling techniques for uncertainty quantification in history matching using nonlinear error models and ensemble level upscaling techniques

KAUST Repository

Efendiev, Y.

2009-11-01

The Markov chain Monte Carlo (MCMC) is a rigorous sampling method to quantify uncertainty in subsurface characterization. However, the MCMC usually requires many flow and transport simulations in evaluating the posterior distribution and can be computationally expensive for fine-scale geological models. We propose a methodology that combines coarse- and fine-scale information to improve the efficiency of MCMC methods. The proposed method employs off-line computations for modeling the relation between coarse- and fine-scale error responses. This relation is modeled using nonlinear functions with prescribed error precisions which are used in efficient sampling within the MCMC framework. We propose a two-stage MCMC where inexpensive coarse-scale simulations are performed to determine whether or not to run the fine-scale (resolved) simulations. The latter is determined on the basis of a statistical model developed off line. The proposed method is an extension of the approaches considered earlier where linear relations are used for modeling the response between coarse-scale and fine-scale models. The approach considered here does not rely on the proximity of approximate and resolved models and can employ much coarser and more inexpensive models to guide the fine-scale simulations. Numerical results for three-phase flow and transport demonstrate the advantages, efficiency, and utility of the method for uncertainty assessment in the history matching. Copyright 2009 by the American Geophysical Union.

Quantile Regression With Measurement Error

KAUST Repository

Wei, Ying

2009-08-27

Regression quantiles can be substantially biased when the covariates are measured with error. In this paper we propose a new method that produces consistent linear quantile estimation in the presence of covariate measurement error. The method corrects the measurement error induced bias by constructing joint estimating equations that simultaneously hold for all the quantile levels. An iterative EM-type estimation algorithm to obtain the solutions to such joint estimation equations is provided. The finite sample performance of the proposed method is investigated in a simulation study, and compared to the standard regression calibration approach. Finally, we apply our methodology to part of the National Collaborative Perinatal Project growth data, a longitudinal study with an unusual measurement error structure. © 2009 American Statistical Association.

Compact disk error measurements

Science.gov (United States)

Howe, D.; Harriman, K.; Tehranchi, B.

1993-01-01

The objectives of this project are as follows: provide hardware and software that will perform simple, real-time, high resolution (single-byte) measurement of the error burst and good data gap statistics seen by a photoCD player read channel when recorded CD write-once discs of variable quality (i.e., condition) are being read; extend the above system to enable measurement of the hard decision (i.e., 1-bit error flags) and soft decision (i.e., 2-bit error flags) decoding information that is produced/used by the Cross Interleaved - Reed - Solomon - Code (CIRC) block decoder employed in the photoCD player read channel; construct a model that uses data obtained via the systems described above to produce meaningful estimates of output error rates (due to both uncorrected ECC words and misdecoded ECC words) when a CD disc having specific (measured) error statistics is read (completion date to be determined); and check the hypothesis that current adaptive CIRC block decoders are optimized for pressed (DAD/ROM) CD discs. If warranted, do a conceptual design of an adaptive CIRC decoder that is optimized for write-once CD discs.

IMPROVED SPECTROPHOTOMETRIC CALIBRATION OF THE SDSS-III BOSS QUASAR SAMPLE

Energy Technology Data Exchange (ETDEWEB)

Margala, Daniel; Kirkby, David [Frederick Reines Hall, Department of Physics and Astronomy, University of California, Irvine, CA (United States); Dawson, Kyle [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Bailey, Stephen [Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720 (United States); Blanton, Michael [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Schneider, Donald P., E-mail: dmargala@uci.edu [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

2016-11-10

We present a model for spectrophotometric calibration errors in observations of quasars from the third generation of the Sloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey (BOSS) and describe the correction procedure we have developed and applied to this sample. Calibration errors are primarily due to atmospheric differential refraction and guiding offsets during each exposure. The corrections potentially reduce the systematics for any studies of BOSS quasars, including the measurement of baryon acoustic oscillations using the Ly α forest. Our model suggests that, on average, the observed quasar flux in BOSS is overestimated by ∼19% at 3600 Å and underestimated by ∼24% at 10,000 Å. Our corrections for the entire BOSS quasar sample are publicly available.

Negligence, genuine error, and litigation

OpenAIRE

Sohn DH

2013-01-01

David H SohnDepartment of Orthopedic Surgery, University of Toledo Medical Center, Toledo, OH, USAAbstract: Not all medical injuries are the result of negligence. In fact, most medical injuries are the result either of the inherent risk in the practice of medicine, or due to system errors, which cannot be prevented simply through fear of disciplinary action. This paper will discuss the differences between adverse events, negligence, and system errors; the current medical malpractice tort syst...

The error analysis of coke moisture measured by neutron moisture gauge

International Nuclear Information System (INIS)

Tian Huixing

1995-01-01

The error of coke moisture measured by neutron method in the iron and steel industry is analyzed. The errors are caused by inaccurate sampling location in the calibration procedure on site. By comparison, the instrument error and the statistical fluctuation error are smaller. So the sampling proportion should be increased as large as possible in the calibration procedure on site, and a satisfied calibration effect can be obtained on a suitable size hopper

Angular truncation errors in integrating nephelometry

International Nuclear Information System (INIS)

Moosmueller, Hans; Arnott, W. Patrick

2003-01-01

Ideal integrating nephelometers integrate light scattered by particles over all directions. However, real nephelometers truncate light scattered in near-forward and near-backward directions below a certain truncation angle (typically 7 deg. ). This results in truncation errors, with the forward truncation error becoming important for large particles. Truncation errors are commonly calculated using Mie theory, which offers little physical insight and no generalization to nonspherical particles. We show that large particle forward truncation errors can be calculated and understood using geometric optics and diffraction theory. For small truncation angles (i.e., <10 deg. ) as typical for modern nephelometers, diffraction theory by itself is sufficient. Forward truncation errors are, by nearly a factor of 2, larger for absorbing particles than for nonabsorbing particles because for large absorbing particles most of the scattered light is due to diffraction as transmission is suppressed. Nephelometers calibration procedures are also discussed as they influence the effective truncation error

Sensitivity of APSIM/ORYZA model due to estimation errors in solar radiation

OpenAIRE

Alexandre Bryan Heinemann; Pepijn A.J. van Oort; Diogo Simões Fernandes; Aline de Holanda Nunes Maia

2012-01-01

Crop models are ideally suited to quantify existing climatic risks. However, they require historic climate data as input. While daily temperature and rainfall data are often available, the lack of observed solar radiation (Rs) data severely limits site-specific crop modelling. The objective of this study was to estimate Rs based on air temperature solar radiation models and to quantify the propagation of errors in simulated radiation on several APSIM/ORYZA crop model seasonal outputs, yield, ...

The Causes of Medical Error from the Perspective of Nurses

Directory of Open Access Journals (Sweden)

Oguz Isik

2012-08-01

Full Text Available This study was conducted as a descriptive study in order to determine the medical errors in hospital services and preventive measures that could be taken to reduce these errors, from the perspective of nurses. The population of the study is composed of nurses working in 2 public hospitals in center of the province of Sakarya. We haven’t selected sample and it was aimed to reach as many nurses as possible in the study. A total of 441 questionnaires were send and 324 were returned. A questionnaire as a means of data collection was prepared and used by the authors. Structural Equation Modeling, confirmatory factor analysis, descriptive statistical methods, the significance control test between compared means and ANOVA test were used in statistical analysis. Physicians, nurses, work environment and lack of communication are stated as possible causes of medical error. According to nurses, the major causes of medical errors, in order of their frequency, were inadequate number of health personnel, excessive work stress, high number of patients per nurse, the weariness due to the behavior and attitudes of superiors and the pressure to care so many patients in a very short period of time, and long time of study. Compensation of medical error is very difficult in health care. A great amount of health care is provided in hospitals and medical errors in hospital services must be prevented. In order to prevent these errors which directly affect human life, it is thought that adequate number of staff should be employed in hospitals and the attitude of superiors towards the employees should be motivating. [TAF Prev Med Bull 2012; 11(4.000: 421-430

Locked modes and magnetic field errors in MST

International Nuclear Information System (INIS)

Almagri, A.F.; Assadi, S.; Prager, S.C.; Sarff, J.S.; Kerst, D.W.

1992-06-01

In the MST reversed field pinch magnetic oscillations become stationary (locked) in the lab frame as a result of a process involving interactions between the modes, sawteeth, and field errors. Several helical modes become phase locked to each other to form a rotating localized disturbance, the disturbance locks to an impulsive field error generated at a sawtooth crash, the error fields grow monotonically after locking (perhaps due to an unstable interaction between the modes and field error), and over the tens of milliseconds of growth confinement degrades and the discharge eventually terminates. Field error control has been partially successful in eliminating locking

Error-related brain activity and error awareness in an error classification paradigm.

Science.gov (United States)

Di Gregorio, Francesco; Steinhauser, Marco; Maier, Martin E

2016-10-01

Error-related brain activity has been linked to error detection enabling adaptive behavioral adjustments. However, it is still unclear which role error awareness plays in this process. Here, we show that the error-related negativity (Ne/ERN), an event-related potential reflecting early error monitoring, is dissociable from the degree of error awareness. Participants responded to a target while ignoring two different incongruent distractors. After responding, they indicated whether they had committed an error, and if so, whether they had responded to one or to the other distractor. This error classification paradigm allowed distinguishing partially aware errors, (i.e., errors that were noticed but misclassified) and fully aware errors (i.e., errors that were correctly classified). The Ne/ERN was larger for partially aware errors than for fully aware errors. Whereas this speaks against the idea that the Ne/ERN foreshadows the degree of error awareness, it confirms the prediction of a computational model, which relates the Ne/ERN to post-response conflict. This model predicts that stronger distractor processing - a prerequisite of error classification in our paradigm - leads to lower post-response conflict and thus a smaller Ne/ERN. This implies that the relationship between Ne/ERN and error awareness depends on how error awareness is related to response conflict in a specific task. Our results further indicate that the Ne/ERN but not the degree of error awareness determines adaptive performance adjustments. Taken together, we conclude that the Ne/ERN is dissociable from error awareness and foreshadows adaptive performance adjustments. Our results suggest that the relationship between the Ne/ERN and error awareness is correlative and mediated by response conflict. Copyright © 2016 Elsevier Inc. All rights reserved.

Prediction Errors of Molecular Machine Learning Models Lower than Hybrid DFT Error.

Science.gov (United States)

Faber, Felix A; Hutchison, Luke; Huang, Bing; Gilmer, Justin; Schoenholz, Samuel S; Dahl, George E; Vinyals, Oriol; Kearnes, Steven; Riley, Patrick F; von Lilienfeld, O Anatole

2017-11-14

We investigate the impact of choosing regressors and molecular representations for the construction of fast machine learning (ML) models of 13 electronic ground-state properties of organic molecules. The performance of each regressor/representation/property combination is assessed using learning curves which report out-of-sample errors as a function of training set size with up to ∼118k distinct molecules. Molecular structures and properties at the hybrid density functional theory (DFT) level of theory come from the QM9 database [ Ramakrishnan et al. Sci. Data 2014 , 1 , 140022 ] and include enthalpies and free energies of atomization, HOMO/LUMO energies and gap, dipole moment, polarizability, zero point vibrational energy, heat capacity, and the highest fundamental vibrational frequency. Various molecular representations have been studied (Coulomb matrix, bag of bonds, BAML and ECFP4, molecular graphs (MG)), as well as newly developed distribution based variants including histograms of distances (HD), angles (HDA/MARAD), and dihedrals (HDAD). Regressors include linear models (Bayesian ridge regression (BR) and linear regression with elastic net regularization (EN)), random forest (RF), kernel ridge regression (KRR), and two types of neural networks, graph convolutions (GC) and gated graph networks (GG). Out-of sample errors are strongly dependent on the choice of representation and regressor and molecular property. Electronic properties are typically best accounted for by MG and GC, while energetic properties are better described by HDAD and KRR. The specific combinations with the lowest out-of-sample errors in the ∼118k training set size limit are (free) energies and enthalpies of atomization (HDAD/KRR), HOMO/LUMO eigenvalue and gap (MG/GC), dipole moment (MG/GC), static polarizability (MG/GG), zero point vibrational energy (HDAD/KRR), heat capacity at room temperature (HDAD/KRR), and highest fundamental vibrational frequency (BAML/RF). We present numerical

Medication errors in anaesthetic practice: a report of two cases and ...

African Journals Online (AJOL)

EB

2013-09-03

Sep 3, 2013 ... Key words: Medication errors, anaesthetic practice, vigilance, safety .... reports in the Australian Incident Monitoring Study. (AIMS). ... contribute to systems failure and prescription errors were most ... being due to equipment error.17 Previous studies have ... errors reported occurred during day shifts and they.

Covariate measurement error correction methods in mediation analysis with failure time data.

Science.gov (United States)

Zhao, Shanshan; Prentice, Ross L

2014-12-01

Mediation analysis is important for understanding the mechanisms whereby one variable causes changes in another. Measurement error could obscure the ability of the potential mediator to explain such changes. This article focuses on developing correction methods for measurement error in the mediator with failure time outcomes. We consider a broad definition of measurement error, including technical error, and error associated with temporal variation. The underlying model with the "true" mediator is assumed to be of the Cox proportional hazards model form. The induced hazard ratio for the observed mediator no longer has a simple form independent of the baseline hazard function, due to the conditioning event. We propose a mean-variance regression calibration approach and a follow-up time regression calibration approach, to approximate the partial likelihood for the induced hazard function. Both methods demonstrate value in assessing mediation effects in simulation studies. These methods are generalized to multiple biomarkers and to both case-cohort and nested case-control sampling designs. We apply these correction methods to the Women's Health Initiative hormone therapy trials to understand the mediation effect of several serum sex hormone measures on the relationship between postmenopausal hormone therapy and breast cancer risk. © 2014, The International Biometric Society.

Lightweight link dimensioning using sFlow sampling

DEFF Research Database (Denmark)

de Oliviera Schmidt, Ricardo; Sadre, Ramin; Sperotto, Anna

2013-01-01

not be trivial in high-speed links. Aiming scalability, operators often deploy packet sampling on monitoring, but little is known how it affects link dimensioning. In this paper we assess the feasibility of lightweight link dimensioning using sFlow, which is a widely-deployed traffic monitoring tool. We...... implement sFlow sampling algorithm and use a previously proposed and validated dimensioning formula that needs traffic variance. We validate our approach using packet captures from real networks. Results show that the proposed procedure is successful for a range of sampling rates and that, due to randomness...... of sampling algorithm, the error introduced by scaling the traffic variance yields more conservative results that cope with short-term traffic fluctuations....

A study of total measurement error in tomographic gamma scanning to assay nuclear material with emphasis on a bias issue for low-activity samples

International Nuclear Information System (INIS)

Burr, T.L.; Mercer, D.J.; Prettyman, T.H.

1998-01-01

Field experience with the tomographic gamma scanner to assay nuclear material suggests that the analysis techniques can significantly impact the assay uncertainty. For example, currently implemented image reconstruction methods exhibit a positive bias for low-activity samples. Preliminary studies indicate that bias reduction could be achieved at the expense of increased random error variance. In this paper, the authors examine three possible bias sources: (1) measurement error in the estimated transmission matrix, (2) the positivity constraint on the estimated mass of nuclear material, and (3) improper treatment of the measurement error structure. The authors present results from many small-scale simulation studies to examine this bias/variance tradeoff for a few image reconstruction methods in the presence of the three possible bias sources

Group representations, error bases and quantum codes

Energy Technology Data Exchange (ETDEWEB)

Knill, E

1996-01-01

This report continues the discussion of unitary error bases and quantum codes. Nice error bases are characterized in terms of the existence of certain characters in a group. A general construction for error bases which are non-abelian over the center is given. The method for obtaining codes due to Calderbank et al. is generalized and expressed purely in representation theoretic terms. The significance of the inertia subgroup both for constructing codes and obtaining the set of transversally implementable operations is demonstrated.

Prevalence of Refractive errors among Primary School Pupils in ...

African Journals Online (AJOL)

Administrator

Effective management of blindness due to refractive errors is readily available in developed countries. 1 ... Key words: Refractive errors, Children, Prevalence, Kenya. 165 .... financial support towards the funding of this study. REFERENCES. 1.

45 CFR 98.100 - Error Rate Report.

Science.gov (United States)

2010-10-01

... Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL ADMINISTRATION CHILD CARE AND DEVELOPMENT FUND... the total dollar amount of payments made in the sample); the average amount of improper payment; and... not received. (e) Costs of Preparing the Error Rate Report—Provided the error rate calculations and...

High cortisol awakening response is associated with impaired error monitoring and decreased post-error adjustment.

Science.gov (United States)

Zhang, Liang; Duan, Hongxia; Qin, Shaozheng; Yuan, Yiran; Buchanan, Tony W; Zhang, Kan; Wu, Jianhui

2015-01-01

The cortisol awakening response (CAR), a rapid increase in cortisol levels following morning awakening, is an important aspect of hypothalamic-pituitary-adrenocortical axis activity. Alterations in the CAR have been linked to a variety of mental disorders and cognitive function. However, little is known regarding the relationship between the CAR and error processing, a phenomenon that is vital for cognitive control and behavioral adaptation. Using high-temporal resolution measures of event-related potentials (ERPs) combined with behavioral assessment of error processing, we investigated whether and how the CAR is associated with two key components of error processing: error detection and subsequent behavioral adjustment. Sixty university students performed a Go/No-go task while their ERPs were recorded. Saliva samples were collected at 0, 15, 30 and 60 min after awakening on the two consecutive days following ERP data collection. The results showed that a higher CAR was associated with slowed latency of the error-related negativity (ERN) and a higher post-error miss rate. The CAR was not associated with other behavioral measures such as the false alarm rate and the post-correct miss rate. These findings suggest that high CAR is a biological factor linked to impairments of multiple steps of error processing in healthy populations, specifically, the automatic detection of error and post-error behavioral adjustment. A common underlying neural mechanism of physiological and cognitive control may be crucial for engaging in both CAR and error processing.

Errors due to the cylindrical cell approximation in lattice calculations

Energy Technology Data Exchange (ETDEWEB)

Newmarch, D A [Reactor Development Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

1960-06-15

It is shown that serious errors in fine structure calculations may arise through the use of the cylindrical cell approximation together with transport theory methods. The effect of this approximation is to overestimate the ratio of the flux in the moderator to the flux in the fuel. It is demonstrated that the use of the cylindrical cell approximation gives a flux in the moderator which is considerably higher than in the fuel, even when the cell dimensions in units of mean free path tend to zero; whereas, for the case of real cells (e.g. square or hexagonal), the flux ratio must tend to unity. It is also shown that, for cylindrical cells of any size, the ratio of the flux in the moderator to flux in the fuel tends to infinity as the total neutron cross section in the moderator tends to zero; whereas the ratio remains finite for real cells. (author)

Uncertainty of the 20th century sea-level rise due to vertical land motion errors

Science.gov (United States)

Santamaría-Gómez, Alvaro; Gravelle, Médéric; Dangendorf, Sönke; Marcos, Marta; Spada, Giorgio; Wöppelmann, Guy

2017-09-01

Assessing the vertical land motion (VLM) at tide gauges (TG) is crucial to understanding global and regional mean sea-level changes (SLC) over the last century. However, estimating VLM with accuracy better than a few tenths of a millimeter per year is not a trivial undertaking and many factors, including the reference frame uncertainty, must be considered. Using a novel reconstruction approach and updated geodetic VLM corrections, we found the terrestrial reference frame and the estimated VLM uncertainty may contribute to the global SLC rate error by ± 0.2 mmyr-1. In addition, a spurious global SLC acceleration may be introduced up to ± 4.8 ×10-3 mmyr-2. Regional SLC rate and acceleration errors may be inflated by a factor 3 compared to the global. The difference of VLM from two independent Glacio-Isostatic Adjustment models introduces global SLC rate and acceleration biases at the level of ± 0.1 mmyr-1 and 2.8 ×10-3 mmyr-2, increasing up to 0.5 mm yr-1 and 9 ×10-3 mmyr-2 for the regional SLC. Errors in VLM corrections need to be budgeted when considering past and future SLC scenarios.

Errors and untimely radiodiagnosis of occupational diseases

International Nuclear Information System (INIS)

Sokolik, L.I.; Shkondin, A.N.; Sergienko, N.S.; Doroshenko, A.N.; Shumakov, A.V.

1987-01-01

Most errors in the diagnosis of occupational diseases occur due to hyperdiagnosis (37%), because data of dynamic clinico-roentgenological examination were not considered (23%). Defects in the organization of prophylactic fluorography results in untimely diagnosis of dust-induced occupational diseases. Errors also occurred because working conditions were not always considered atypical development and course were not always analyzed

Population size estimation in Yellowstone wolves with error-prone noninvasive microsatellite genotypes.

Science.gov (United States)

Creel, Scott; Spong, Goran; Sands, Jennifer L; Rotella, Jay; Zeigle, Janet; Joe, Lawrence; Murphy, Kerry M; Smith, Douglas

2003-07-01

Determining population sizes can be difficult, but is essential for conservation. By counting distinct microsatellite genotypes, DNA from noninvasive samples (hair, faeces) allows estimation of population size. Problems arise because genotypes from noninvasive samples are error-prone, but genotyping errors can be reduced by multiple polymerase chain reaction (PCR). For faecal genotypes from wolves in Yellowstone National Park, error rates varied substantially among samples, often above the 'worst-case threshold' suggested by simulation. Consequently, a substantial proportion of multilocus genotypes held one or more errors, despite multiple PCR. These genotyping errors created several genotypes per individual and caused overestimation (up to 5.5-fold) of population size. We propose a 'matching approach' to eliminate this overestimation bias.

On systematic and statistic errors in radionuclide mass activity estimation procedure

International Nuclear Information System (INIS)

Smelcerovic, M.; Djuric, G.; Popovic, D.

1989-01-01

One of the most important requirements during nuclear accidents is the fast estimation of the mass activity of the radionuclides that suddenly and without control reach the environment. The paper points to systematic errors in the procedures of sampling, sample preparation and measurement itself, that in high degree contribute to total mass activity evaluation error. Statistic errors in gamma spectrometry as well as in total mass alpha and beta activity evaluation are also discussed. Beside, some of the possible sources of errors in the partial mass activity evaluation for some of the radionuclides are presented. The contribution of the errors in the total mass activity evaluation error is estimated and procedures that could possibly reduce it are discussed (author)

Internal Error Propagation in Explicit Runge--Kutta Methods

KAUST Repository

Ketcheson, David I.

2014-09-11

In practical computation with Runge--Kutta methods, the stage equations are not satisfied exactly, due to roundoff errors, algebraic solver errors, and so forth. We show by example that propagation of such errors within a single step can have catastrophic effects for otherwise practical and well-known methods. We perform a general analysis of internal error propagation, emphasizing that it depends significantly on how the method is implemented. We show that for a fixed method, essentially any set of internal stability polynomials can be obtained by modifying the implementation details. We provide bounds on the internal error amplification constants for some classes of methods with many stages, including strong stability preserving methods and extrapolation methods. These results are used to prove error bounds in the presence of roundoff or other internal errors.

Development of graph self-generating program of radiation sampling for geophysical prospecting with AutoLISP

International Nuclear Information System (INIS)

Zhou Hongsheng

2009-01-01

A program of self-generating graph of radiation sampling for geophysical prospecting is developed with AutoLISP, which is developed wholly by the author and can self-generate and explain sampling graphs. The program has largely increased drawing efficiency and can avoid the graph errors due to manual drawing. (authors)

Accurate and fast methods to estimate the population mutation rate from error prone sequences

Directory of Open Access Journals (Sweden)

Miyamoto Michael M

2009-08-01

Full Text Available Abstract Background The population mutation rate (θ remains one of the most fundamental parameters in genetics, ecology, and evolutionary biology. However, its accurate estimation can be seriously compromised when working with error prone data such as expressed sequence tags, low coverage draft sequences, and other such unfinished products. This study is premised on the simple idea that a random sequence error due to a chance accident during data collection or recording will be distributed within a population dataset as a singleton (i.e., as a polymorphic site where one sampled sequence exhibits a unique base relative to the common nucleotide of the others. Thus, one can avoid these random errors by ignoring the singletons within a dataset. Results This strategy is implemented under an infinite sites model that focuses on only the internal branches of the sample genealogy where a shared polymorphism can arise (i.e., a variable site where each alternative base is represented by at least two sequences. This approach is first used to derive independently the same new Watterson and Tajima estimators of θ, as recently reported by Achaz 1 for error prone sequences. It is then used to modify the recent, full, maximum-likelihood model of Knudsen and Miyamoto 2, which incorporates various factors for experimental error and design with those for coalescence and mutation. These new methods are all accurate and fast according to evolutionary simulations and analyses of a real complex population dataset for the California seahare. Conclusion In light of these results, we recommend the use of these three new methods for the determination of θ from error prone sequences. In particular, we advocate the new maximum likelihood model as a starting point for the further development of more complex coalescent/mutation models that also account for experimental error and design.

Forecast Combination under Heavy-Tailed Errors

Directory of Open Access Journals (Sweden)

Gang Cheng

2015-11-01

Full Text Available Forecast combination has been proven to be a very important technique to obtain accurate predictions for various applications in economics, finance, marketing and many other areas. In many applications, forecast errors exhibit heavy-tailed behaviors for various reasons. Unfortunately, to our knowledge, little has been done to obtain reliable forecast combinations for such situations. The familiar forecast combination methods, such as simple average, least squares regression or those based on the variance-covariance of the forecasts, may perform very poorly due to the fact that outliers tend to occur, and they make these methods have unstable weights, leading to un-robust forecasts. To address this problem, in this paper, we propose two nonparametric forecast combination methods. One is specially proposed for the situations in which the forecast errors are strongly believed to have heavy tails that can be modeled by a scaled Student’s t-distribution; the other is designed for relatively more general situations when there is a lack of strong or consistent evidence on the tail behaviors of the forecast errors due to a shortage of data and/or an evolving data-generating process. Adaptive risk bounds of both methods are developed. They show that the resulting combined forecasts yield near optimal mean forecast errors relative to the candidate forecasts. Simulations and a real example demonstrate their superior performance in that they indeed tend to have significantly smaller prediction errors than the previous combination methods in the presence of forecast outliers.

SU-F-J-131: Reproducibility of Positioning Error Due to Temporarily Indwelled Urethral Catheter for Urethra-Sparing Prostate IMRT

International Nuclear Information System (INIS)

Hirose, K; Takai, Y; Sato, M; Hatayama, Y; Kawaguchi, H; Aoki, M; Akimoto, H; Komai, F; Souma, M; Obara, H; Suzuki, M

2016-01-01

Purpose: The purpose of this study was to prospectively assess the reproducibility of positioning errors due to temporarily indwelled catheter in urethra-sparing image-guided (IG) IMRT. Methods: Ten patients received urethra-sparing prostate IG-IMRT with implanted fiducials. After the first CT scan was performed in supine position, 6-Fr catheter was indwelled into urethra, and the second CT images were taken for planning. While the PTV received 80 Gy, 5% dose reduction was applied for the urethral PRV along the catheter. Additional CT scans were also performed at 5th and 30th fraction. Positions of interests (POIs) were set on posterior edge of prostate at beam isocenter level (POI1) and cranial and caudal edge of prostatic urethra on the post-indwelled CT images. POIs were copied into the pre-indwelled, 5th and 30th fraction’s CT images after fiducial matching on these CT images. The deviation of each POI between pre- and post-indwelled CT and the reproducibility of prostate displacement due to catheter were evaluated. Results: The deviation of POI1 caused by the indwelled catheter to the directions of RL/AP/SI (mm) was 0.20±0.27/−0.64±2.43/1.02±2.31, respectively, and the absolute distances (mm) were 3.15±1.41. The deviation tends to be larger if closer to the caudal edge of prostate. Compared with the pre-indwelled CT scan, a median displacement of all POIs (mm) were 0.3±0.2/2.2±1.1/2.0±2.6 in the post-indwelled, 0.4±0.4/3.4±2.1/2.3±2.6 in 5th, and 0.5±0.5/1.7±2.2/1.9±3.1 in 30th fraction’s CT scan with a similar data distribution. There were 6 patients with 5-mm-over displacement in AP and/or CC directions. Conclusion: Reproducibility of positioning errors due to temporarily indwelling catheter was observed. Especially in case of patients with unusually large shifts by indwelling catheter at the planning process, treatment planning should be performed by using the pre-indwelled CT images with transferred contour of the urethra identified by

SU-F-J-131: Reproducibility of Positioning Error Due to Temporarily Indwelled Urethral Catheter for Urethra-Sparing Prostate IMRT

Energy Technology Data Exchange (ETDEWEB)

Hirose, K; Takai, Y [Hirosaki University, Hirosaki (Japan); Southern Tohoku BNCT Research Center, Koriyama (Japan); Sato, M; Hatayama, Y; Kawaguchi, H; Aoki, M; Akimoto, H [Hirosaki University, Hirosaki (Japan); Komai, F; Souma, M; Obara, H; Suzuki, M [Hirosaki University Hospital, Hirosaki (Japan)

2016-06-15

Purpose: The purpose of this study was to prospectively assess the reproducibility of positioning errors due to temporarily indwelled catheter in urethra-sparing image-guided (IG) IMRT. Methods: Ten patients received urethra-sparing prostate IG-IMRT with implanted fiducials. After the first CT scan was performed in supine position, 6-Fr catheter was indwelled into urethra, and the second CT images were taken for planning. While the PTV received 80 Gy, 5% dose reduction was applied for the urethral PRV along the catheter. Additional CT scans were also performed at 5th and 30th fraction. Positions of interests (POIs) were set on posterior edge of prostate at beam isocenter level (POI1) and cranial and caudal edge of prostatic urethra on the post-indwelled CT images. POIs were copied into the pre-indwelled, 5th and 30th fraction’s CT images after fiducial matching on these CT images. The deviation of each POI between pre- and post-indwelled CT and the reproducibility of prostate displacement due to catheter were evaluated. Results: The deviation of POI1 caused by the indwelled catheter to the directions of RL/AP/SI (mm) was 0.20±0.27/−0.64±2.43/1.02±2.31, respectively, and the absolute distances (mm) were 3.15±1.41. The deviation tends to be larger if closer to the caudal edge of prostate. Compared with the pre-indwelled CT scan, a median displacement of all POIs (mm) were 0.3±0.2/2.2±1.1/2.0±2.6 in the post-indwelled, 0.4±0.4/3.4±2.1/2.3±2.6 in 5th, and 0.5±0.5/1.7±2.2/1.9±3.1 in 30th fraction’s CT scan with a similar data distribution. There were 6 patients with 5-mm-over displacement in AP and/or CC directions. Conclusion: Reproducibility of positioning errors due to temporarily indwelling catheter was observed. Especially in case of patients with unusually large shifts by indwelling catheter at the planning process, treatment planning should be performed by using the pre-indwelled CT images with transferred contour of the urethra identified by

Alignment error of mirror modules of advanced telescope for high-energy astrophysics due to wavefront aberrations

Science.gov (United States)

Zocchi, Fabio E.

2017-10-01

One of the approaches that is being tested for the integration of the mirror modules of the advanced telescope for high-energy astrophysics x-ray mission of the European Space Agency consists in aligning each module on an optical bench operated at an ultraviolet wavelength. The mirror module is illuminated by a plane wave and, in order to overcome diffraction effects, the centroid of the image produced by the module is used as a reference to assess the accuracy of the optical alignment of the mirror module itself. Among other sources of uncertainty, the wave-front error of the plane wave also introduces an error in the position of the centroid, thus affecting the quality of the mirror module alignment. The power spectral density of the position of the point spread function centroid is here derived from the power spectral density of the wave-front error of the plane wave in the framework of the scalar theory of Fourier diffraction. This allows the defining of a specification on the collimator quality used for generating the plane wave starting from the contribution to the error budget allocated for the uncertainty of the centroid position. The theory generally applies whenever Fourier diffraction is a valid approximation, in which case the obtained result is identical to that derived by geometrical optics considerations.

Reducing systematic errors in measurements made by a SQUID magnetometer

International Nuclear Information System (INIS)

Kiss, L.F.; Kaptás, D.; Balogh, J.

2014-01-01

A simple method is described which reduces those systematic errors of a superconducting quantum interference device (SQUID) magnetometer that arise from possible radial displacements of the sample in the second-order gradiometer superconducting pickup coil. By rotating the sample rod (and hence the sample) around its axis into a position where the best fit is obtained to the output voltage of the SQUID as the sample is moved through the pickup coil, the accuracy of measuring magnetic moments can be increased significantly. In the cases of an examined Co 1.9 Fe 1.1 Si Heusler alloy, pure iron and nickel samples, the accuracy could be increased over the value given in the specification of the device. The suggested method is only meaningful if the measurement uncertainty is dominated by systematic errors – radial displacement in particular – and not by instrumental or environmental noise. - Highlights: • A simple method is described which reduces systematic errors of a SQUID. • The errors arise from a radial displacement of the sample in the gradiometer coil. • The procedure is to rotate the sample rod (with the sample) around its axis. • The best fit to the SQUID voltage has to be attained moving the sample through the coil. • The accuracy of measuring magnetic moment can be increased significantly

Risk Management and the Concept of Human Error

DEFF Research Database (Denmark)

Rasmussen, Jens

1995-01-01

by a stochastic coincidence of faults and human errors, but by a systemic erosion of the defenses due to decision making under competitive pressure in a dynamic environment. The presentation will discuss the nature of human error and the risk management problems found in a dynamic, competitive society facing...

(How) do we learn from errors? A prospective study of the link between the ward's learning practices and medication administration errors.

Science.gov (United States)

Drach-Zahavy, A; Somech, A; Admi, H; Peterfreund, I; Peker, H; Priente, O

2014-03-01

Attention in the ward should shift from preventing medication administration errors to managing them. Nevertheless, little is known in regard with the practices nursing wards apply to learn from medication administration errors as a means of limiting them. To test the effectiveness of four types of learning practices, namely, non-integrated, integrated, supervisory and patchy learning practices in limiting medication administration errors. Data were collected from a convenient sample of 4 hospitals in Israel by multiple methods (observations and self-report questionnaires) at two time points. The sample included 76 wards (360 nurses). Medication administration error was defined as any deviation from prescribed medication processes and measured by a validated structured observation sheet. Wards' use of medication administration technologies, location of the medication station, and workload were observed; learning practices and demographics were measured by validated questionnaires. Results of the mixed linear model analysis indicated that the use of technology and quiet location of the medication cabinet were significantly associated with reduced medication administration errors (estimate=.03, perrors (estimate=.04, plearning practices, supervisory learning was the only practice significantly linked to reduced medication administration errors (estimate=-.04, plearning were significantly linked to higher levels of medication administration errors (estimate=-.03, plearning was not associated with it (p>.05). How wards manage errors might have implications for medication administration errors beyond the effects of typical individual, organizational and technology risk factors. Head nurse can facilitate learning from errors by "management by walking around" and monitoring nurses' medication administration behaviors. Copyright © 2013 Elsevier Ltd. All rights reserved.

Total elimination of sampling errors in polarization imagery obtained with integrated microgrid polarimeters.

Science.gov (United States)

Tyo, J Scott; LaCasse, Charles F; Ratliff, Bradley M

2009-10-15

Microgrid polarimeters operate by integrating a focal plane array with an array of micropolarizers. The Stokes parameters are estimated by comparing polarization measurements from pixels in a neighborhood around the point of interest. The main drawback is that the measurements used to estimate the Stokes vector are made at different locations, leading to a false polarization signature owing to instantaneous field-of-view (IFOV) errors. We demonstrate for the first time, to our knowledge, that spatially band limited polarization images can be ideally reconstructed with no IFOV error by using a linear system framework.

Random and systematic sampling error when hooking fish to monitor skin fluke (Benedenia seriolae) and gill fluke (Zeuxapta seriolae) burden in Australian farmed yellowtail kingfish (Seriola lalandi).

Science.gov (United States)

Fensham, J R; Bubner, E; D'Antignana, T; Landos, M; Caraguel, C G B

2018-05-01

The Australian farmed yellowtail kingfish (Seriola lalandi, YTK) industry monitor skin fluke (Benedenia seriolae) and gill fluke (Zeuxapta seriolae) burden by pooling the fluke count of 10 hooked YTK. The random and systematic error of this sampling strategy was evaluated to assess potential impact on treatment decisions. Fluke abundance (fluke count per fish) in a study cage (estimated 30,502 fish) was assessed five times using the current sampling protocol and its repeatability was estimated the repeatability coefficient (CR) and the coefficient of variation (CV). Individual body weight, fork length, fluke abundance, prevalence, intensity (fluke count per infested fish) and density (fluke count per Kg of fish) were compared between 100 hooked and 100 seined YTK (assumed representative of the entire population) to estimate potential selection bias. Depending on the fluke species and age category, CR (expected difference in parasite count between 2 sampling iterations) ranged from 0.78 to 114 flukes per fish. Capturing YTK by hooking increased the selection of fish of a weight and length in the lowest 5th percentile of the cage (RR = 5.75, 95% CI: 2.06-16.03, P-value = 0.0001). These lower end YTK had on average an extra 31 juveniles and 6 adults Z. seriolae per Kg of fish and an extra 3 juvenile and 0.4 adult B. seriolae per Kg of fish, compared to the rest of the cage population (P-value sampling towards the smallest and most heavily infested fish in the population, resulting in poor repeatability (more variability amongst sampled fish) and an overestimation of parasite burden in the population. In this particular commercial situation these finding supported that health management program, where the finding of an underestimation of parasite burden could provide a production impact on the study population. In instances where fish populations and parasite burdens are more homogenous, sampling error may be less severe. Sampling error when capturing fish

Accounting for measurement error: a critical but often overlooked process.

Science.gov (United States)

Harris, Edward F; Smith, Richard N

2009-12-01

Due to instrument imprecision and human inconsistencies, measurements are not free of error. Technical error of measurement (TEM) is the variability encountered between dimensions when the same specimens are measured at multiple sessions. A goal of a data collection regimen is to minimise TEM. The few studies that actually quantify TEM, regardless of discipline, report that it is substantial and can affect results and inferences. This paper reviews some statistical approaches for identifying and controlling TEM. Statistically, TEM is part of the residual ('unexplained') variance in a statistical test, so accounting for TEM, which requires repeated measurements, enhances the chances of finding a statistically significant difference if one exists. The aim of this paper was to review and discuss common statistical designs relating to types of error and statistical approaches to error accountability. This paper addresses issues of landmark location, validity, technical and systematic error, analysis of variance, scaled measures and correlation coefficients in order to guide the reader towards correct identification of true experimental differences. Researchers commonly infer characteristics about populations from comparatively restricted study samples. Most inferences are statistical and, aside from concerns about adequate accounting for known sources of variation with the research design, an important source of variability is measurement error. Variability in locating landmarks that define variables is obvious in odontometrics, cephalometrics and anthropometry, but the same concerns about measurement accuracy and precision extend to all disciplines. With increasing accessibility to computer-assisted methods of data collection, the ease of incorporating repeated measures into statistical designs has improved. Accounting for this technical source of variation increases the chance of finding biologically true differences when they exist.

CORRECTING ERRORS: THE RELATIVE EFFICACY OF DIFFERENT FORMS OF ERROR FEEDBACK IN SECOND LANGUAGE WRITING

Directory of Open Access Journals (Sweden)

Chitra Jayathilake

2013-01-01

Full Text Available Error correction in ESL (English as a Second Language classes has been a focal phenomenon in SLA (Second Language Acquisition research due to some controversial research results and diverse feedback practices. This paper presents a study which explored the relative efficacy of three forms of error correction employed in ESL writing classes: focusing on the acquisition of one grammar element both for immediate and delayed language contexts, and collecting data from university undergraduates, this study employed an experimental research design with a pretest-treatment-posttests structure. The research revealed that the degree of success in acquiring L2 (Second Language grammar through error correction differs according to the form of the correction and to learning contexts. While the findings are discussed in relation to the previous literature, this paper concludes creating a cline of error correction forms to be promoted in Sri Lankan L2 writing contexts, particularly in ESL contexts in Universities.

Approximation errors during variance propagation

International Nuclear Information System (INIS)

Dinsmore, Stephen

1986-01-01

Risk and reliability analyses are often performed by constructing and quantifying large fault trees. The inputs to these models are component failure events whose probability of occuring are best represented as random variables. This paper examines the errors inherent in two approximation techniques used to calculate the top event's variance from the inputs' variance. Two sample fault trees are evaluated and several three dimensional plots illustrating the magnitude of the error over a wide range of input means and variances are given

Estimating misclassification error: a closer look at cross-validation based methods

Directory of Open Access Journals (Sweden)

Ounpraseuth Songthip

2012-11-01

Full Text Available Abstract Background To estimate a classifier’s error in predicting future observations, bootstrap methods have been proposed as reduced-variation alternatives to traditional cross-validation (CV methods based on sampling without replacement. Monte Carlo (MC simulation studies aimed at estimating the true misclassification error conditional on the training set are commonly used to compare CV methods. We conducted an MC simulation study to compare a new method of bootstrap CV (BCV to k-fold CV for estimating clasification error. Findings For the low-dimensional conditions simulated, the modest positive bias of k-fold CV contrasted sharply with the substantial negative bias of the new BCV method. This behavior was corroborated using a real-world dataset of prognostic gene-expression profiles in breast cancer patients. Our simulation results demonstrate some extreme characteristics of variance and bias that can occur due to a fault in the design of CV exercises aimed at estimating the true conditional error of a classifier, and that appear not to have been fully appreciated in previous studies. Although CV is a sound practice for estimating a classifier’s generalization error, using CV to estimate the fixed misclassification error of a trained classifier conditional on the training set is problematic. While MC simulation of this estimation exercise can correctly represent the average bias of a classifier, it will overstate the between-run variance of the bias. Conclusions We recommend k-fold CV over the new BCV method for estimating a classifier’s generalization error. The extreme negative bias of BCV is too high a price to pay for its reduced variance.

Learning from errors: analysis of medication order voiding in CPOE systems.

Science.gov (United States)

Kannampallil, Thomas G; Abraham, Joanna; Solotskaya, Anna; Philip, Sneha G; Lambert, Bruce L; Schiff, Gordon D; Wright, Adam; Galanter, William L

2017-07-01

Medication order voiding allows clinicians to indicate that an existing order was placed in error. We explored whether the order voiding function could be used to record and study medication ordering errors. We examined medication orders from an academic medical center for a 6-year period (2006-2011; n  = 5 804 150). We categorized orders based on status (void, not void) and clinician-provided reasons for voiding. We used multivariable logistic regression to investigate the association between order voiding and clinician, patient, and order characteristics. We conducted chart reviews on a random sample of voided orders ( n  = 198) to investigate the rate of medication ordering errors among voided orders, and the accuracy of clinician-provided reasons for voiding. We found that 0.49% of all orders were voided. Order voiding was associated with clinician type (physician, pharmacist, nurse, student, other) and order type (inpatient, prescription, home medications by history). An estimated 70 ± 10% of voided orders were due to medication ordering errors. Clinician-provided reasons for voiding were reasonably predictive of the actual cause of error for duplicate orders (72%), but not for other reasons. Medication safety initiatives require availability of error data to create repositories for learning and training. The voiding function is available in several electronic health record systems, so order voiding could provide a low-effort mechanism for self-reporting of medication ordering errors. Additional clinician training could help increase the quality of such reporting. © The Author 2017. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com

How Much Confidence Can We Have in EU-SILC? Complex Sample Designs and the Standard Error of the Europe 2020 Poverty Indicators

Science.gov (United States)

Goedeme, Tim

2013-01-01

If estimates are based on samples, they should be accompanied by appropriate standard errors and confidence intervals. This is true for scientific research in general, and is even more important if estimates are used to inform and evaluate policy measures such as those aimed at attaining the Europe 2020 poverty reduction target. In this article I…

Errors in practical measurement in surveying, engineering, and technology

International Nuclear Information System (INIS)

Barry, B.A.; Morris, M.D.

1991-01-01

This book discusses statistical measurement, error theory, and statistical error analysis. The topics of the book include an introduction to measurement, measurement errors, the reliability of measurements, probability theory of errors, measures of reliability, reliability of repeated measurements, propagation of errors in computing, errors and weights, practical application of the theory of errors in measurement, two-dimensional errors and includes a bibliography. Appendices are included which address significant figures in measurement, basic concepts of probability and the normal probability curve, writing a sample specification for a procedure, classification, standards of accuracy, and general specifications of geodetic control surveys, the geoid, the frequency distribution curve and the computer and calculator solution of problems

Errors in self-reports of health services use: impact on alzheimer disease clinical trial designs.

Science.gov (United States)

Callahan, Christopher M; Tu, Wanzhu; Stump, Timothy E; Clark, Daniel O; Unroe, Kathleen T; Hendrie, Hugh C

2015-01-01

Most Alzheimer disease clinical trials that compare the use of health services rely on reports of caregivers. The goal of this study was to assess the accuracy of self-reports among older adults with Alzheimer disease and their caregiver proxy respondents. This issue is particularly relevant to Alzheimer disease clinical trials because inaccuracy can lead both to loss of power and increased bias in study outcomes. We compared respondent accuracy in reporting any use and in reporting the frequency of use with actual utilization data as documented in a comprehensive database. We next simulated the impact of underreporting and overreporting on sample size estimates and treatment effect bias for clinical trials comparing utilization between experimental groups. Respondents self-reports have a poor level of accuracy with κ-values often below 0.5. Respondents tend to underreport use even for rare events such as hospitalizations and nursing home stays. In analyses simulating underreporting and overreporting of varying magnitude, we found that errors in self-reports can increase the required sample size by 15% to 30%. In addition, bias in the reported treatment effect ranged from 3% to 18% due to both underreporting and overreporting errors. Use of self-report data in clinical trials of Alzheimer disease treatments may inflate sample size needs. Even when adequate power is achieved by increasing sample size, reporting errors can result in a biased estimate of the true effect size of the intervention.

Meniscal tear. Diagnostic errors in MR imaging

International Nuclear Information System (INIS)

Barrera, M. C.; Recondo, J. A.; Gervas, C.; Fernandez, E.; Villanua, J. A.M.; Salvador, E.

2003-01-01

To analyze diagnostic discrepancies found between magnetic resonance (MR) and arthroscopy, and the determine the reasons that they occur. Two-hundred and forty-eight MR knee explorations were retrospectively checked. Forty of these showed diagnostic discrepancies between MR and arthroscopy. Two radiologists independently re-analyzed the images from 29 of the 40 studies without knowing which diagnosis had resulted from which of the two techniques. Their interpretations were correlated with the initial MR diagnosis, MR images and arthroscopic results. Initial errors in MR imaging were classified as either unavoidable, interpretive, or secondary to equivocal findings. Eleven MR examinations could not be checked since their corresponding imaging results could not be located. Of 34 errors found in the original diagnoses, 12 (35.5%)were classified as unavoidable, 14 (41.2%) as interpretative and 8 (23.5%) as secondary to equivocal findings. 41.2% of the errors were avoided in the retrospective study probably due to our department having greater experience in interpreting MR images, 25.5% were unavailable even in the retrospective study. A small percentage of diagnostic errors were due to the presence of subtle equivocal findings. (Author) 15 refs

Action errors, error management, and learning in organizations.

Science.gov (United States)

Frese, Michael; Keith, Nina

2015-01-03

Every organization is confronted with errors. Most errors are corrected easily, but some may lead to negative consequences. Organizations often focus on error prevention as a single strategy for dealing with errors. Our review suggests that error prevention needs to be supplemented by error management--an approach directed at effectively dealing with errors after they have occurred, with the goal of minimizing negative and maximizing positive error consequences (examples of the latter are learning and innovations). After defining errors and related concepts, we review research on error-related processes affected by error management (error detection, damage control). Empirical evidence on positive effects of error management in individuals and organizations is then discussed, along with emotional, motivational, cognitive, and behavioral pathways of these effects. Learning from errors is central, but like other positive consequences, learning occurs under certain circumstances--one being the development of a mind-set of acceptance of human error.

Automated bar coding of air samples at Hanford (ABCASH)

International Nuclear Information System (INIS)

Troyer, G.L.; Brayton, D.D.; McNeece, S.G.

1992-10-01

This article describes the basis, main features and benefits of an automated system for tracking and reporting radioactive air particulate samples. The system was developed due to recognized need for improving the quality and integrity of air sample data related to personnel and environmental protection. The data capture, storage, and retrieval of air sample data are described. The automation aspect of the associated and data input eliminates a large potential for human error. The system utilizes personal computers, handheld computers, a commercial personal computer database package, commercial programming languages, and complete documentation to satisfy the system's automation objective

Modeling coherent errors in quantum error correction

Science.gov (United States)

Greenbaum, Daniel; Dutton, Zachary

2018-01-01

Analysis of quantum error correcting codes is typically done using a stochastic, Pauli channel error model for describing the noise on physical qubits. However, it was recently found that coherent errors (systematic rotations) on physical data qubits result in both physical and logical error rates that differ significantly from those predicted by a Pauli model. Here we examine the accuracy of the Pauli approximation for noise containing coherent errors (characterized by a rotation angle ɛ) under the repetition code. We derive an analytic expression for the logical error channel as a function of arbitrary code distance d and concatenation level n, in the small error limit. We find that coherent physical errors result in logical errors that are partially coherent and therefore non-Pauli. However, the coherent part of the logical error is negligible at fewer than {ε }-({dn-1)} error correction cycles when the decoder is optimized for independent Pauli errors, thus providing a regime of validity for the Pauli approximation. Above this number of correction cycles, the persistent coherent logical error will cause logical failure more quickly than the Pauli model would predict, and this may need to be combated with coherent suppression methods at the physical level or larger codes.

Big Data, Small Sample.

Science.gov (United States)

Gerlovina, Inna; van der Laan, Mark J; Hubbard, Alan

2017-05-20

Multiple comparisons and small sample size, common characteristics of many types of "Big Data" including those that are produced by genomic studies, present specific challenges that affect reliability of inference. Use of multiple testing procedures necessitates calculation of very small tail probabilities of a test statistic distribution. Results based on large deviation theory provide a formal condition that is necessary to guarantee error rate control given practical sample sizes, linking the number of tests and the sample size; this condition, however, is rarely satisfied. Using methods that are based on Edgeworth expansions (relying especially on the work of Peter Hall), we explore the impact of departures of sampling distributions from typical assumptions on actual error rates. Our investigation illustrates how far the actual error rates can be from the declared nominal levels, suggesting potentially wide-spread problems with error rate control, specifically excessive false positives. This is an important factor that contributes to "reproducibility crisis". We also review some other commonly used methods (such as permutation and methods based on finite sampling inequalities) in their application to multiple testing/small sample data. We point out that Edgeworth expansions, providing higher order approximations to the sampling distribution, offer a promising direction for data analysis that could improve reliability of studies relying on large numbers of comparisons with modest sample sizes.

Errors due to non-uniform distribution of fat in dual X-ray absorptiometry of the lumbar spine

International Nuclear Information System (INIS)

Tothill, P.; Pye, D.W.

1992-01-01

Errors in spinal dual X-ray absorptiometry (DXA) were studied by analysing X-ray CT scans taken for diagnostic purposes on 20 patients representing a wide range of fat content. The mean difference between the fat thickness over the vertebral bodies and that over a background area in antero-posterior (AP) scanning was 6.7 ± 8.1 mm for men and 13.4 ± 4.7 mm for women. For AP scanning a non-uniform fat distribution leads to a mean overestimate of 0.029 g/cm 2 for men and 0.057 g/cm 2 for women. The error exceeded 0.1 g/cm 2 in 10% of slices. For lateral scanning the error exceeded 0.1 g/cm 2 (about 15% of normal) in a quarter of slices. (author)

Dose error analysis for a scanned proton beam delivery system

International Nuclear Information System (INIS)

Coutrakon, G; Wang, N; Miller, D W; Yang, Y

2010-01-01

All particle beam scanning systems are subject to dose delivery errors due to errors in position, energy and intensity of the delivered beam. In addition, finite scan speeds, beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in delivery. In this paper, we present dose errors for an 8 x 10 x 8 cm 3 target of uniform water equivalent density with 8 cm spread out Bragg peak and a prescribed dose of 2 Gy. Lower doses are also analyzed and presented later in the paper. Beam energy errors and errors due to limitations of scanning system hardware have been included in the analysis. By using Gaussian shaped pencil beams derived from measurements in the research room of the James M Slater Proton Treatment and Research Center at Loma Linda, CA and executing treatment simulations multiple times, statistical dose errors have been calculated in each 2.5 mm cubic voxel in the target. These errors were calculated by delivering multiple treatments to the same volume and calculating the rms variation in delivered dose at each voxel in the target. The variations in dose were the result of random beam delivery errors such as proton energy, spot position and intensity fluctuations. The results show that with reasonable assumptions of random beam delivery errors, the spot scanning technique yielded an rms dose error in each voxel less than 2% or 3% of the 2 Gy prescribed dose. These calculated errors are within acceptable clinical limits for radiation therapy.

[Medication reconciliation: an innovative experience in an internal medicine unit to decrease errors due to inacurrate medication histories].

Science.gov (United States)

Pérennes, Maud; Carde, Axel; Nicolas, Xavier; Dolz, Manuel; Bihannic, René; Grimont, Pauline; Chapot, Thierry; Granier, Hervé

2012-03-01

An inaccurate medication history may prevent the discovery of a pre-admission iatrogenic event or lead to interrupted drug therapy during hospitalization. Medication reconciliation is a process that ensures the transfer of medication information at admission to the hospital. The aims of this prospective study were to evaluate the interest in clinical practice of this concept and the resources needed for its implementation. We chose to include patients aged 65 years or over admitted in the internal medicine unit between June and October 2010. We obtained an accurate list of each patient's home medications. This list was then compared with medication orders. All medication variances were classified as intended or unintended. An internist and a pharmacist classified the clinical importance of each unintended variance. Sixty-one patients (mean age: 78 ± 7.4 years) were included in our study. We identified 38 unintended discrepancies. The average number of unintended discrepancies was 0.62 per patient. Twenty-five patients (41%) had one or more unintended discrepancies at admission. The contact with the community pharmacist permitted us to identify 21 (55%) unintended discrepancies. The most common errors were the omission of a regularly used medication (76%) and an incorrect dosage (16%). Our intervention resulted in order changes by the physician for 30 (79%) unintended discrepancies. Fifty percent of the unintended variances were judged by the internist and 76% by the pharmacist to be clinically significant. The admission to the hospital is a critical transition point for the continuity of care in medication management. Medication reconciliation can identify and resolve errors due to inaccurate medication histories. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

The decline and fall of Type II error rates

Science.gov (United States)

Steve Verrill; Mark Durst

2005-01-01

For general linear models with normally distributed random errors, the probability of a Type II error decreases exponentially as a function of sample size. This potentially rapid decline reemphasizes the importance of performing power calculations.

Inference on rare errors using asymptotic expansions and bootstrap calibration

NARCIS (Netherlands)

R. Helmers (Roelof)

1998-01-01

textabstractThe number of items in error in an audit population is usually quite small, whereas the error distribution is typically highly skewed to the right. For applications in statistical auditing, where line item sampling is appropriate, a new upper confidence limit for the total error amount

Putting a face on medical errors: a patient perspective.

Science.gov (United States)

Kooienga, Sarah; Stewart, Valerie T

2011-01-01

Knowledge of the patient's perspective on medical error is limited. Research efforts have centered on how best to disclose error and how patients desire to have medical error disclosed. On the basis of a qualitative descriptive component of a mixed method study, a purposive sample of 30 community members told their stories of medical error. Their experiences focused on lack of communication, missed communication, or provider's poor interpersonal style of communication, greatly contrasting with the formal definition of error as failure to follow a set standard of care. For these participants, being a patient was more important than error or how an error is disclosed. The patient's understanding of error must be a key aspect of any quality improvement strategy. © 2010 National Association for Healthcare Quality.

The results of experimental studies of VLF–ULF electromagnetic emission by rock samples due to mechanical action

OpenAIRE

A. A. Panfilov

2013-01-01

The paper presents the results of laboratory experiments on electromagnetic emission excitation (electric component of electromagnetic field) by rock samples due to different forms of mechanical stress applications. It was shown that samples generate electric impulses with different spectra when the impact action, gradual loading or dynamic friction is applied. It was ascertained that level and spectral compositions of signals, generated by rock samples, cha...

Teacher knowledge of error analysis in differential calculus

Directory of Open Access Journals (Sweden)

Eunice K. Moru

2014-12-01

Full Text Available The study investigated teacher knowledge of error analysis in differential calculus. Two teachers were the sample of the study: one a subject specialist and the other a mathematics education specialist. Questionnaires and interviews were used for data collection. The findings of the study reflect that the teachers’ knowledge of error analysis was characterised by the following assertions, which are backed up with some evidence: (1 teachers identified the errors correctly, (2 the generalised error identification resulted in opaque analysis, (3 some of the identified errors were not interpreted from multiple perspectives, (4 teachers’ evaluation of errors was either local or global and (5 in remedying errors accuracy and efficiency were emphasised more than conceptual understanding. The implications of the findings of the study for teaching include engaging in error analysis continuously as this is one way of improving knowledge for teaching.

Selection bias in population-based cancer case-control studies due to incomplete sampling frame coverage.

Science.gov (United States)

Walsh, Matthew C; Trentham-Dietz, Amy; Gangnon, Ronald E; Nieto, F Javier; Newcomb, Polly A; Palta, Mari

2012-06-01

Increasing numbers of individuals are choosing to opt out of population-based sampling frames due to privacy concerns. This is especially a problem in the selection of controls for case-control studies, as the cases often arise from relatively complete population-based registries, whereas control selection requires a sampling frame. If opt out is also related to risk factors, bias can arise. We linked breast cancer cases who reported having a valid driver's license from the 2004-2008 Wisconsin women's health study (N = 2,988) with a master list of licensed drivers from the Wisconsin Department of Transportation (WDOT). This master list excludes Wisconsin drivers that requested their information not be sold by the state. Multivariate-adjusted selection probability ratios (SPR) were calculated to estimate potential bias when using this driver's license sampling frame to select controls. A total of 962 cases (32%) had opted out of the WDOT sampling frame. Cases age <40 (SPR = 0.90), income either unreported (SPR = 0.89) or greater than $50,000 (SPR = 0.94), lower parity (SPR = 0.96 per one-child decrease), and hormone use (SPR = 0.93) were significantly less likely to be covered by the WDOT sampling frame (α = 0.05 level). Our results indicate the potential for selection bias due to differential opt out between various demographic and behavioral subgroups of controls. As selection bias may differ by exposure and study base, the assessment of potential bias needs to be ongoing. SPRs can be used to predict the direction of bias when cases and controls stem from different sampling frames in population-based case-control studies.

AN ERROR ANALYSIS OF ENGLISH SIMPLE PRESENT TENSE OF THE SECOND YEAR STUDENTS OF SMP N 1 SUSUKAN REGENCY OF SEMARANG IN THE ACADEMIC YEAR 2003/2004

Directory of Open Access Journals (Sweden)

Agus Safudin

2016-07-01

Full Text Available The aim of this research is to find out how far the errors of simple present tense produced bythe second year students of SMP N 1 Susukan. The research was conducted at State Junior High School (SMP N 1 Susukan, Regency of Semarang, Central Java, Indonesia. The objects of this research were the eighth graders. This is quantitative research. The writer uses random sampling by lottery. There are about 75 students and the writer took 50% as the sample.The errors made by the students were divided into eight aspects. (1 Error in using auxiliary is 36.75%. (2 Error in using plural noun is 22.90%. (3 Error in using to be is (am, is, are, is 7.69%.(4 Error in adverb of manneris 4.27%. (5 Error in using verb in simple present tense is 4.78%. (6 Error in using possessive sentence 5.24%. (7 Error in using imperative sentence is 0.34%. (8 Error due to ignorant is 11.28%. Relating to those errors there should be the preventing efforts by the teachers such as providing lots of examples of English and Indonesian sentences so that the students have greater understanding about the difference of those languages.

Impact of error fields on equilibrium configurations in ITER

Energy Technology Data Exchange (ETDEWEB)

Barbato, Lucio [DIEI, Università di Cassino and Lazio Meridionale, Cassino (Italy); Formisano, Alessandro, E-mail: alessandro.formisano@unina2.it [Department of Industrial and Information Engineering, Seconda Univ. di Napoli, Aversa (Italy); Martone, Raffaele [Department of Industrial and Information Engineering, Seconda Univ. di Napoli, Aversa (Italy); Villone, Fabio [DIEI, Università di Cassino and Lazio Meridionale, Cassino (Italy)

2015-10-15

Highlights: • Error fields (EF) are discrepancies from nominal magnetic field, and may alter plasma behaviour. • They are due to, e.g., coils manufacturing and assembly errors. • EF impact in ITER equilibria is analyzed using numerical simulations. • A high accuracy 3D field computation module and a Grad-Shafranov solver are used. • Deformations size allow using a linearized model, and performing a sensitivity analysis. - Abstract: Discrepancies between design and actual magnetic field maps in tokamaks are unavoidable, and are associated to a number of causes, e.g. manufacturing and assembly tolerances on magnets, presence of feeders and joints, non-symmetric iron parts. Such error fields may drive plasma to loss of stability, and must be carefully controlled using suitable correction coils. Anyway, even when kept below safety threshold, error fields may alter the behavior of plasma. The present paper, using as example the error fields induced by tolerances in toroidal field coils, quantifies their effect on the plasma boundary shape in equilibrium configurations. In particular, a procedure able to compute the shape perturbations due to given deformations of the coils has been set up and used to carry out a thorough statistical analysis of the error field-shape perturbations relationship.

Intraoperative visualization and assessment of electromagnetic tracking error

Science.gov (United States)

Harish, Vinyas; Ungi, Tamas; Lasso, Andras; MacDonald, Andrew; Nanji, Sulaiman; Fichtinger, Gabor

2015-03-01

Electromagnetic tracking allows for increased flexibility in designing image-guided interventions, however it is well understood that electromagnetic tracking is prone to error. Visualization and assessment of the tracking error should take place in the operating room with minimal interference with the clinical procedure. The goal was to achieve this ideal in an open-source software implementation in a plug and play manner, without requiring programming from the user. We use optical tracking as a ground truth. An electromagnetic sensor and optical markers are mounted onto a stylus device, pivot calibrated for both trackers. Electromagnetic tracking error is defined as difference of tool tip position between electromagnetic and optical readings. Multiple measurements are interpolated into the thin-plate B-spline transform visualized in real time using 3D Slicer. All tracked devices are used in a plug and play manner through the open-source SlicerIGT and PLUS extensions of the 3D Slicer platform. Tracking error was measured multiple times to assess reproducibility of the method, both with and without placing ferromagnetic objects in the workspace. Results from exhaustive grid sampling and freehand sampling were similar, indicating that a quick freehand sampling is sufficient to detect unexpected or excessive field distortion in the operating room. The software is available as a plug-in for the 3D Slicer platforms. Results demonstrate potential for visualizing electromagnetic tracking error in real time for intraoperative environments in feasibility clinical trials in image-guided interventions.

(AJST) RELATIVE EFFICIENCY OF NON-PARAMETRIC ERROR ...

African Journals Online (AJOL)

NORBERT OPIYO AKECH

on 100 bootstrap samples, a sample of size n being taken with replacement in each initial sample of size n. .... the overlap (or optimal error rate) of the populations. However, the expression (2.3) for the computation of ..... Analysis and Machine Intelligence, 9, 628-633. Lachenbruch P. A. (1967). An almost unbiased method ...

Assessment of the uncertainty associated with systematic errors in digital instruments: an experimental study on offset errors

International Nuclear Information System (INIS)

Attivissimo, F; Giaquinto, N; Savino, M; Cataldo, A

2012-01-01

This paper deals with the assessment of the uncertainty due to systematic errors, particularly in A/D conversion-based instruments. The problem of defining and assessing systematic errors is briefly discussed, and the conceptual scheme of gauge repeatability and reproducibility is adopted. A practical example regarding the evaluation of the uncertainty caused by the systematic offset error is presented. The experimental results, obtained under various ambient conditions, show that modelling the variability of systematic errors is more problematic than suggested by the ISO 5725 norm. Additionally, the paper demonstrates the substantial difference between the type B uncertainty evaluation, obtained via the maximum entropy principle applied to manufacturer's specifications, and the type A (experimental) uncertainty evaluation, which reflects actually observable reality. Although it is reasonable to assume a uniform distribution of the offset error, experiments demonstrate that the distribution is not centred and that a correction must be applied. In such a context, this work motivates a more pragmatic and experimental approach to uncertainty, with respect to the directions of supplement 1 of GUM. (paper)

Prevalence of technical errors and periapical lesions in a sample of endodontically treated teeth: a CBCT analysis.

Science.gov (United States)

Nascimento, Eduarda Helena Leandro; Gaêta-Araujo, Hugo; Andrade, Maria Fernanda Silva; Freitas, Deborah Queiroz

2018-01-21

The aims of this study are to identify the most frequent technical errors in endodontically treated teeth and to determine which root canals were most often associated with those errors, as well as to relate endodontic technical errors and the presence of coronal restorations with periapical status by means of cone-beam computed tomography images. Six hundred eighteen endodontically treated teeth (1146 root canals) were evaluated for the quality of their endodontic treatment and for the presence of coronal restorations and periapical lesions. Each root canal was classified according to dental groups, and the endodontic technical errors were recorded. Chi-square's test and descriptive analyses were performed. Six hundred eighty root canals (59.3%) had periapical lesions. Maxillary molars and anterior teeth showed higher prevalence of periapical lesions (p technical error in all root canals, except for the second mesiobuccal root canal of maxillary molars and the distobuccal root canal of mandibular molars, which were non-filled in 78.4 and 30% of the cases, respectively. There is a high prevalence of apical radiolucencies, which increased in the presence of poor coronal restorations, endodontic technical errors, and when both conditions were concomitant. Underfilling was the most frequent technical error, followed by non-homogeneous and non-filled canals. Evaluation of endodontic treatment quality that considers every single root canal aims on warning dental practitioners of the prevalence of technical errors that could be avoided with careful treatment planning and execution.

Estimation methods with ordered exposure subject to measurement error and missingness in semi-ecological design

Directory of Open Access Journals (Sweden)

Kim Hyang-Mi

2012-09-01

Full Text Available Abstract Background In epidemiological studies, it is often not possible to measure accurately exposures of participants even if their response variable can be measured without error. When there are several groups of subjects, occupational epidemiologists employ group-based strategy (GBS for exposure assessment to reduce bias due to measurement errors: individuals of a group/job within study sample are assigned commonly to the sample mean of exposure measurements from their group in evaluating the effect of exposure on the response. Therefore, exposure is estimated on an ecological level while health outcomes are ascertained for each subject. Such study design leads to negligible bias in risk estimates when group means are estimated from ‘large’ samples. However, in many cases, only a small number of observations are available to estimate the group means, and this causes bias in the observed exposure-disease association. Also, the analysis in a semi-ecological design may involve exposure data with the majority missing and the rest observed with measurement errors and complete response data collected with ascertainment. Methods In workplaces groups/jobs are naturally ordered and this could be incorporated in estimation procedure by constrained estimation methods together with the expectation and maximization (EM algorithms for regression models having measurement error and missing values. Four methods were compared by a simulation study: naive complete-case analysis, GBS, the constrained GBS (CGBS, and the constrained expectation and maximization (CEM. We illustrated the methods in the analysis of decline in lung function due to exposures to carbon black. Results Naive and GBS approaches were shown to be inadequate when the number of exposure measurements is too small to accurately estimate group means. The CEM method appears to be best among them when within each exposure group at least a ’moderate’ number of individuals have their

Fast Outage Probability Simulation for FSO Links with a Generalized Pointing Error Model

KAUST Repository

Ben Issaid, Chaouki

2017-02-07

Over the past few years, free-space optical (FSO) communication has gained significant attention. In fact, FSO can provide cost-effective and unlicensed links, with high-bandwidth capacity and low error rate, making it an exciting alternative to traditional wireless radio-frequency communication systems. However, the system performance is affected not only by the presence of atmospheric turbulences, which occur due to random fluctuations in the air refractive index but also by the existence of pointing errors. Metrics, such as the outage probability which quantifies the probability that the instantaneous signal-to-noise ratio is smaller than a given threshold, can be used to analyze the performance of this system. In this work, we consider weak and strong turbulence regimes, and we study the outage probability of an FSO communication system under a generalized pointing error model with both a nonzero boresight component and different horizontal and vertical jitter effects. More specifically, we use an importance sampling approach which is based on the exponential twisting technique to offer fast and accurate results.

Error begat error: design error analysis and prevention in social infrastructure projects.

Science.gov (United States)

Love, Peter E D; Lopez, Robert; Edwards, David J; Goh, Yang M

2012-09-01

Design errors contribute significantly to cost and schedule growth in social infrastructure projects and to engineering failures, which can result in accidents and loss of life. Despite considerable research that has addressed their error causation in construction projects they still remain prevalent. This paper identifies the underlying conditions that contribute to design errors in social infrastructure projects (e.g. hospitals, education, law and order type buildings). A systemic model of error causation is propagated and subsequently used to develop a learning framework for design error prevention. The research suggests that a multitude of strategies should be adopted in congruence to prevent design errors from occurring and so ensure that safety and project performance are ameliorated. Copyright © 2011. Published by Elsevier Ltd.

Medication errors with the use of allopurinol and colchicine: a retrospective study of a national, anonymous Internet-accessible error reporting system.

Science.gov (United States)

Mikuls, Ted R; Curtis, Jeffrey R; Allison, Jeroan J; Hicks, Rodney W; Saag, Kenneth G

2006-03-01

To more closely assess medication errors in gout care, we examined data from a national, Internet-accessible error reporting program over a 5-year reporting period. We examined data from the MEDMARX database, covering the period from January 1, 1999 through December 31, 2003. For allopurinol and colchicine, we examined error severity, source, type, contributing factors, and healthcare personnel involved in errors, and we detailed errors resulting in patient harm. Causes of error and the frequency of other error characteristics were compared for gout medications versus other musculoskeletal treatments using the chi-square statistic. Gout medication errors occurred in 39% (n = 273) of facilities participating in the MEDMARX program. Reported errors were predominantly from the inpatient hospital setting and related to the use of allopurinol (n = 524), followed by colchicine (n = 315), probenecid (n = 50), and sulfinpyrazone (n = 2). Compared to errors involving other musculoskeletal treatments, allopurinol and colchicine errors were more often ascribed to problems with physician prescribing (7% for other therapies versus 23-39% for allopurinol and colchicine, p < 0.0001) and less often due to problems with drug administration or nursing error (50% vs 23-27%, p < 0.0001). Our results suggest that inappropriate prescribing practices are characteristic of errors occurring with the use of allopurinol and colchicine. Physician prescribing practices are a potential target for quality improvement interventions in gout care.

Effect of Pharmacist Participation During Physician Rounds and Prescription Error in the Intensive Care Unit

Directory of Open Access Journals (Sweden)

Marlina A. Turnodihardjo

2016-09-01

Full Text Available Patient’s safety is now a prominent issue in pharmaceutical care because of adverse drug events that is common in hospitalized patients. Majority of error are likely occured during prescribing, which is the first stage of pharmacy process. Prescription errors mostly occured in an Intensive Care Unit (ICU, which is due to the severity of the illness of its patients as well as the large number of medications prescribed. Pharmacist participation actually could reduce prescribing error made by doctors. The main objective of this study was to determine the effect of pharmacist participation during physician rounds on prescription errors in the ICU. This study was a quasi-experimental design with one group pre-post test. A prospective study was conducted from April to May 2015 by screening 110 samples of orders. Screening was done to identify type of prescription errors. Prescription error was defined as error in the prescription writing process – incomplete information and not according to agreement. Mann-Whitney test was used to analyze the differences in prescribing errors. The results showed that there was the differences between prescription errors before and during the pharmacist participation (p<0.05. There was also a significant negative correlation between the frequency of pharmacist recommendation on drug ordering and prescription errors (r= –0.638; p<0.05. It means the pharmacist participation was one of the strategies that can be adopted to prevent in prescribing errors and implementation of collaboration between both doctors and pharmacists. In other words, the supporting hospital management system which would encourage interpersonal communication among health care proffesionals is needed.

Potential loss of revenue due to errors in clinical coding during the implementation of the Malaysia diagnosis related group (MY-DRG®) Casemix system in a teaching hospital in Malaysia.

Science.gov (United States)

Zafirah, S A; Nur, Amrizal Muhammad; Puteh, Sharifa Ezat Wan; Aljunid, Syed Mohamed

2018-01-25

The accuracy of clinical coding is crucial in the assignment of Diagnosis Related Groups (DRGs) codes, especially if the hospital is using Casemix System as a tool for resource allocations and efficiency monitoring. The aim of this study was to estimate the potential loss of income due to an error in clinical coding during the implementation of the Malaysia Diagnosis Related Group (MY-DRG ® ) Casemix System in a teaching hospital in Malaysia. Four hundred and sixty-four (464) coded medical records were selected, re-examined and re-coded by an independent senior coder (ISC). This ISC re-examined and re-coded the error code that was originally entered by the hospital coders. The pre- and post-coding results were compared, and if there was any disagreement, the codes by the ISC were considered the accurate codes. The cases were then re-grouped using a MY-DRG ® grouper to assess and compare the changes in the DRG assignment and the hospital tariff assignment. The outcomes were then verified by a casemix expert. Coding errors were found in 89.4% (415/424) of the selected patient medical records. Coding errors in secondary diagnoses were the highest, at 81.3% (377/464), followed by secondary procedures at 58.2% (270/464), principal procedures of 50.9% (236/464) and primary diagnoses at 49.8% (231/464), respectively. The coding errors resulted in the assignment of different MY-DRG ® codes in 74.0% (307/415) of the cases. From this result, 52.1% (160/307) of the cases had a lower assigned hospital tariff. In total, the potential loss of income due to changes in the assignment of the MY-DRG ® code was RM654,303.91. The quality of coding is a crucial aspect in implementing casemix systems. Intensive re-training and the close monitoring of coder performance in the hospital should be performed to prevent the potential loss of hospital income.

Bifurcated states of the error-field-induced magnetic islands

International Nuclear Information System (INIS)

Zheng, L.-J.; Li, B.; Hazeltine, R.D.

2008-01-01

We find that the formation of the magnetic islands due to error fields shows bifurcation when neoclassical effects are included. The bifurcation, which follows from including bootstrap current terms in a description of island growth in the presence of error fields, provides a path to avoid the island-width pole in the classical description. The theory offers possible theoretical explanations for the recent DIII-D and JT-60 experimental observations concerning confinement deterioration with increasing error field

Prevalence of Pre-Analytical Errors in Clinical Chemistry Diagnostic Labs in Sulaimani City of Iraqi Kurdistan.

Science.gov (United States)

Najat, Dereen

2017-01-01

Laboratory testing is roughly divided into three phases: a pre-analytical phase, an analytical phase and a post-analytical phase. Most analytical errors have been attributed to the analytical phase. However, recent studies have shown that up to 70% of analytical errors reflect the pre-analytical phase. The pre-analytical phase comprises all processes from the time a laboratory request is made by a physician until the specimen is analyzed at the lab. Generally, the pre-analytical phase includes patient preparation, specimen transportation, specimen collection and storage. In the present study, we report the first comprehensive assessment of the frequency and types of pre-analytical errors at the Sulaimani diagnostic labs in Iraqi Kurdistan. Over 2 months, 5500 venous blood samples were observed in 10 public diagnostic labs of Sulaimani City. The percentages of rejected samples and types of sample inappropriateness were evaluated. The percentage of each of the following pre-analytical errors were recorded: delay in sample transportation, clotted samples, expired reagents, hemolyzed samples, samples not on ice, incorrect sample identification, insufficient sample, tube broken in centrifuge, request procedure errors, sample mix-ups, communication conflicts, misinterpreted orders, lipemic samples, contaminated samples and missed physician's request orders. The difference between the relative frequencies of errors observed in the hospitals considered was tested using a proportional Z test. In particular, the survey aimed to discover whether analytical errors were recorded and examine the types of platforms used in the selected diagnostic labs. The analysis showed a high prevalence of improper sample handling during the pre-analytical phase. In appropriate samples, the percentage error was as high as 39%. The major reasons for rejection were hemolyzed samples (9%), incorrect sample identification (8%) and clotted samples (6%). Most quality control schemes at Sulaimani

Prevalence of Pre-Analytical Errors in Clinical Chemistry Diagnostic Labs in Sulaimani City of Iraqi Kurdistan.

Directory of Open Access Journals (Sweden)

Dereen Najat

Full Text Available Laboratory testing is roughly divided into three phases: a pre-analytical phase, an analytical phase and a post-analytical phase. Most analytical errors have been attributed to the analytical phase. However, recent studies have shown that up to 70% of analytical errors reflect the pre-analytical phase. The pre-analytical phase comprises all processes from the time a laboratory request is made by a physician until the specimen is analyzed at the lab. Generally, the pre-analytical phase includes patient preparation, specimen transportation, specimen collection and storage. In the present study, we report the first comprehensive assessment of the frequency and types of pre-analytical errors at the Sulaimani diagnostic labs in Iraqi Kurdistan.Over 2 months, 5500 venous blood samples were observed in 10 public diagnostic labs of Sulaimani City. The percentages of rejected samples and types of sample inappropriateness were evaluated. The percentage of each of the following pre-analytical errors were recorded: delay in sample transportation, clotted samples, expired reagents, hemolyzed samples, samples not on ice, incorrect sample identification, insufficient sample, tube broken in centrifuge, request procedure errors, sample mix-ups, communication conflicts, misinterpreted orders, lipemic samples, contaminated samples and missed physician's request orders. The difference between the relative frequencies of errors observed in the hospitals considered was tested using a proportional Z test. In particular, the survey aimed to discover whether analytical errors were recorded and examine the types of platforms used in the selected diagnostic labs.The analysis showed a high prevalence of improper sample handling during the pre-analytical phase. In appropriate samples, the percentage error was as high as 39%. The major reasons for rejection were hemolyzed samples (9%, incorrect sample identification (8% and clotted samples (6%. Most quality control schemes

Detecting genotyping errors and describing black bear movement in northern Idaho

Science.gov (United States)

Michael K. Schwartz; Samuel A. Cushman; Kevin S. McKelvey; Jim Hayden; Cory Engkjer

2006-01-01

Non-invasive genetic sampling has become a favored tool to enumerate wildlife. Genetic errors, caused by poor quality samples, can lead to substantial biases in numerical estimates of individuals. We demonstrate how the computer program DROPOUT can detect amplification errors (false alleles and allelic dropout) in a black bear (Ursus americanus) dataset collected in...

Analytical sensitivity analysis of geometric errors in a three axis machine tool

International Nuclear Information System (INIS)

Park, Sung Ryung; Yang, Seung Han

2012-01-01

In this paper, an analytical method is used to perform a sensitivity analysis of geometric errors in a three axis machine tool. First, an error synthesis model is constructed for evaluating the position volumetric error due to the geometric errors, and then an output variable is defined, such as the magnitude of the position volumetric error. Next, the global sensitivity analysis is executed using an analytical method. Finally, the sensitivity indices are calculated using the quantitative values of the geometric errors

FRamework Assessing Notorious Contributing Influences for Error (FRANCIE): Perspective on Taxonomy Development to Support Error Reporting and Analysis

Energy Technology Data Exchange (ETDEWEB)

Lon N. Haney; David I. Gertman

2003-04-01

Beginning in the 1980s a primary focus of human reliability analysis was estimation of human error probabilities. However, detailed qualitative modeling with comprehensive representation of contextual variables often was lacking. This was likely due to the lack of comprehensive error and performance shaping factor taxonomies, and the limited data available on observed error rates and their relationship to specific contextual variables. In the mid 90s Boeing, America West Airlines, NASA Ames Research Center and INEEL partnered in a NASA sponsored Advanced Concepts grant to: assess the state of the art in human error analysis, identify future needs for human error analysis, and develop an approach addressing these needs. Identified needs included the need for a method to identify and prioritize task and contextual characteristics affecting human reliability. Other needs identified included developing comprehensive taxonomies to support detailed qualitative modeling and to structure meaningful data collection efforts across domains. A result was the development of the FRamework Assessing Notorious Contributing Influences for Error (FRANCIE) with a taxonomy for airline maintenance tasks. The assignment of performance shaping factors to generic errors by experts proved to be valuable to qualitative modeling. Performance shaping factors and error types from such detailed approaches can be used to structure error reporting schemes. In a recent NASA Advanced Human Support Technology grant FRANCIE was refined, and two new taxonomies for use on space missions were developed. The development, sharing, and use of error taxonomies, and the refinement of approaches for increased fidelity of qualitative modeling is offered as a means to help direct useful data collection strategies.

Technical Note: Interference errors in infrared remote sounding of the atmosphere

Directory of Open Access Journals (Sweden)

R. Sussmann

2007-07-01

Full Text Available Classical error analysis in remote sounding distinguishes between four classes: "smoothing errors," "model parameter errors," "forward model errors," and "retrieval noise errors". For infrared sounding "interference errors", which, in general, cannot be described by these four terms, can be significant. Interference errors originate from spectral residuals due to "interfering species" whose spectral features overlap with the signatures of the target species. A general method for quantification of interference errors is presented, which covers all possible algorithmic implementations, i.e., fine-grid retrievals of the interfering species or coarse-grid retrievals, and cases where the interfering species are not retrieved. In classical retrieval setups interference errors can exceed smoothing errors and can vary by orders of magnitude due to state dependency. An optimum strategy is suggested which practically eliminates interference errors by systematically minimizing the regularization strength applied to joint profile retrieval of the interfering species. This leads to an interfering-species selective deweighting of the retrieval. Details of microwindow selection are no longer critical for this optimum retrieval and widened microwindows even lead to reduced overall (smoothing and interference errors. Since computational power will increase, more and more operational algorithms will be able to utilize this optimum strategy in the future. The findings of this paper can be applied to soundings of all infrared-active atmospheric species, which include more than two dozen different gases relevant to climate and ozone. This holds for all kinds of infrared remote sounding systems, i.e., retrievals from ground-based, balloon-borne, airborne, or satellite spectroradiometers.

Large errors and severe conditions

CERN Document Server

Smith, D L; Van Wormer, L A

2002-01-01

Physical parameters that can assume real-number values over a continuous range are generally represented by inherently positive random variables. However, if the uncertainties in these parameters are significant (large errors), conventional means of representing and manipulating the associated variables can lead to erroneous results. Instead, all analyses involving them must be conducted in a probabilistic framework. Several issues must be considered: First, non-linear functional relations between primary and derived variables may lead to significant 'error amplification' (severe conditions). Second, the commonly used normal (Gaussian) probability distribution must be replaced by a more appropriate function that avoids the occurrence of negative sampling results. Third, both primary random variables and those derived through well-defined functions must be dealt with entirely in terms of their probability distributions. Parameter 'values' and 'errors' should be interpreted as specific moments of these probabil...

Terrestrial neutron-induced soft errors in advanced memory devices

CERN Document Server

Nakamura, Takashi; Ibe, Eishi; Yahagi, Yasuo; Kameyama, Hideaki

2008-01-01

Terrestrial neutron-induced soft errors in semiconductor memory devices are currently a major concern in reliability issues. Understanding the mechanism and quantifying soft-error rates are primarily crucial for the design and quality assurance of semiconductor memory devices. This book covers the relevant up-to-date topics in terrestrial neutron-induced soft errors, and aims to provide succinct knowledge on neutron-induced soft errors to the readers by presenting several valuable and unique features. Sample Chapter(s). Chapter 1: Introduction (238 KB). Table A.30 mentioned in Appendix A.6 on

M/T method based incremental encoder velocity measurement error analysis and self-adaptive error elimination algorithm

DEFF Research Database (Denmark)

Chen, Yangyang; Yang, Ming; Long, Jiang

2017-01-01

For motor control applications, the speed loop performance is largely depended on the accuracy of speed feedback signal. M/T method, due to its high theoretical accuracy, is the most widely used in incremental encoder adopted speed measurement. However, the inherent encoder optical grating error...

Logical error rate scaling of the toric code

International Nuclear Information System (INIS)

Watson, Fern H E; Barrett, Sean D

2014-01-01

To date, a great deal of attention has focused on characterizing the performance of quantum error correcting codes via their thresholds, the maximum correctable physical error rate for a given noise model and decoding strategy. Practical quantum computers will necessarily operate below these thresholds meaning that other performance indicators become important. In this work we consider the scaling of the logical error rate of the toric code and demonstrate how, in turn, this may be used to calculate a key performance indicator. We use a perfect matching decoding algorithm to find the scaling of the logical error rate and find two distinct operating regimes. The first regime admits a universal scaling analysis due to a mapping to a statistical physics model. The second regime characterizes the behaviour in the limit of small physical error rate and can be understood by counting the error configurations leading to the failure of the decoder. We present a conjecture for the ranges of validity of these two regimes and use them to quantify the overhead—the total number of physical qubits required to perform error correction. (paper)

Counteracting structural errors in ensemble forecast of influenza outbreaks.

Science.gov (United States)

Pei, Sen; Shaman, Jeffrey

2017-10-13

For influenza forecasts generated using dynamical models, forecast inaccuracy is partly attributable to the nonlinear growth of error. As a consequence, quantification of the nonlinear error structure in current forecast models is needed so that this growth can be corrected and forecast skill improved. Here, we inspect the error growth of a compartmental influenza model and find that a robust error structure arises naturally from the nonlinear model dynamics. By counteracting these structural errors, diagnosed using error breeding, we develop a new forecast approach that combines dynamical error correction and statistical filtering techniques. In retrospective forecasts of historical influenza outbreaks for 95 US cities from 2003 to 2014, overall forecast accuracy for outbreak peak timing, peak intensity and attack rate, are substantially improved for predicted lead times up to 10 weeks. This error growth correction method can be generalized to improve the forecast accuracy of other infectious disease dynamical models.Inaccuracy of influenza forecasts based on dynamical models is partly due to nonlinear error growth. Here the authors address the error structure of a compartmental influenza model, and develop a new improved forecast approach combining dynamical error correction and statistical filtering techniques.

How Sample Size Affects a Sampling Distribution

Science.gov (United States)

Mulekar, Madhuri S.; Siegel, Murray H.

2009-01-01

If students are to understand inferential statistics successfully, they must have a profound understanding of the nature of the sampling distribution. Specifically, they must comprehend the determination of the expected value and standard error of a sampling distribution as well as the meaning of the central limit theorem. Many students in a high…

Accounting for optical errors in microtensiometry.

Science.gov (United States)

Hinton, Zachary R; Alvarez, Nicolas J

2018-09-15

Drop shape analysis (DSA) techniques measure interfacial tension subject to error in image analysis and the optical system. While considerable efforts have been made to minimize image analysis errors, very little work has treated optical errors. There are two main sources of error when considering the optical system: the angle of misalignment and the choice of focal plane. Due to the convoluted nature of these sources, small angles of misalignment can lead to large errors in measured curvature. We demonstrate using microtensiometry the contributions of these sources to measured errors in radius, and, more importantly, deconvolute the effects of misalignment and focal plane. Our findings are expected to have broad implications on all optical techniques measuring interfacial curvature. A geometric model is developed to analytically determine the contributions of misalignment angle and choice of focal plane on measurement error for spherical cap interfaces. This work utilizes a microtensiometer to validate the geometric model and to quantify the effect of both sources of error. For the case of a microtensiometer, an empirical calibration is demonstrated that corrects for optical errors and drastically simplifies implementation. The combination of geometric modeling and experimental results reveal a convoluted relationship between the true and measured interfacial radius as a function of the misalignment angle and choice of focal plane. The validated geometric model produces a full operating window that is strongly dependent on the capillary radius and spherical cap height. In all cases, the contribution of optical errors is minimized when the height of the spherical cap is equivalent to the capillary radius, i.e. a hemispherical interface. The understanding of these errors allow for correct measure of interfacial curvature and interfacial tension regardless of experimental setup. For the case of microtensiometry, this greatly decreases the time for experimental setup

The results of experimental studies of VLF-ULF electromagnetic emission by rock samples due to mechanical action

Science.gov (United States)

Panfilov, A. A.

2014-06-01

The paper presents the results of laboratory experiments on electromagnetic emissions excitation (the electric component of electromagnetic fields) by rock samples due to different forms of mechanical stress applications. It was shown that samples generate electric impulses with different spectra when the impact action, gradual loading or dynamic friction is applied. It was ascertained that level and spectral compositions of signals, generated by rock samples, change with an increasing number of hits. It was found that strong electromagnetic signals, generated while rock samples were fracturing, were accompanied by repetitive weak but perceptible variations in the electric field intensity in short frequency ranges.

Errors, error detection, error correction and hippocampal-region damage: data and theories.

Science.gov (United States)

MacKay, Donald G; Johnson, Laura W

2013-11-01

This review and perspective article outlines 15 observational constraints on theories of errors, error detection, and error correction, and their relation to hippocampal-region (HR) damage. The core observations come from 10 studies with H.M., an amnesic with cerebellar and HR damage but virtually no neocortical damage. Three studies examined the detection of errors planted in visual scenes (e.g., a bird flying in a fish bowl in a school classroom) and sentences (e.g., I helped themselves to the birthday cake). In all three experiments, H.M. detected reliably fewer errors than carefully matched memory-normal controls. Other studies examined the detection and correction of self-produced errors, with controls for comprehension of the instructions, impaired visual acuity, temporal factors, motoric slowing, forgetting, excessive memory load, lack of motivation, and deficits in visual scanning or attention. In these studies, H.M. corrected reliably fewer errors than memory-normal and cerebellar controls, and his uncorrected errors in speech, object naming, and reading aloud exhibited two consistent features: omission and anomaly. For example, in sentence production tasks, H.M. omitted one or more words in uncorrected encoding errors that rendered his sentences anomalous (incoherent, incomplete, or ungrammatical) reliably more often than controls. Besides explaining these core findings, the theoretical principles discussed here explain H.M.'s retrograde amnesia for once familiar episodic and semantic information; his anterograde amnesia for novel information; his deficits in visual cognition, sentence comprehension, sentence production, sentence reading, and object naming; and effects of aging on his ability to read isolated low frequency words aloud. These theoretical principles also explain a wide range of other data on error detection and correction and generate new predictions for future test. Copyright © 2013 Elsevier Ltd. All rights reserved.

Negligence, genuine error, and litigation

Directory of Open Access Journals (Sweden)

Sohn DH

2013-02-01

Full Text Available David H SohnDepartment of Orthopedic Surgery, University of Toledo Medical Center, Toledo, OH, USAAbstract: Not all medical injuries are the result of negligence. In fact, most medical injuries are the result either of the inherent risk in the practice of medicine, or due to system errors, which cannot be prevented simply through fear of disciplinary action. This paper will discuss the differences between adverse events, negligence, and system errors; the current medical malpractice tort system in the United States; and review current and future solutions, including medical malpractice reform, alternative dispute resolution, health courts, and no-fault compensation systems. The current political environment favors investigation of non-cap tort reform remedies; investment into more rational oversight systems, such as health courts or no-fault systems may reap both quantitative and qualitative benefits for a less costly and safer health system.Keywords: medical malpractice, tort reform, no fault compensation, alternative dispute resolution, system errors

Spelling Errors of Iranian School-Level EFL Learners: Potential Sources

Directory of Open Access Journals (Sweden)

Mahnaz Saeidi

2010-05-01

Full Text Available With the purpose of examining the sources of spelling errors of Iranian school level EFL learners, the present researchers analyzed the dictation samples of 51 Iranian senior and junior high school male and female students majoring at an Iranian school in Baku, Azerbaijan. The content analysis of the data revealed three main sources (intralingual, interlingual, and unique with seven patterns of errors. The frequency of intralingual errors far outnumbers that of interlingual errors. Unique errors were even less. Therefore, in-service training programs may include some instruction on raising the teachers’ awareness of the different sources of errors to focus on during the teaching program.

Structural evaluation for the core sampling trucks, RMCS operations, 200 Area

International Nuclear Information System (INIS)

Islam, M.A.

1996-01-01

This report evaluates the structural adequacy and the integrity of the existing core sampling trucks to withstand impact should the trucks drop off the ramp, either onto the soft ground or onto a non-yielding surface due to operational error, wind, or earthquake. The report also addresses if the allowable tank dome load will be exceeded by the addition of the impact load

Internal consistency, test-retest reliability and measurement error of the self-report version of the social skills rating system in a sample of Australian adolescents.

Directory of Open Access Journals (Sweden)

Sharmila Vaz

Full Text Available The social skills rating system (SSRS is used to assess social skills and competence in children and adolescents. While its characteristics based on United States samples (US are published, corresponding Australian figures are unavailable. Using a 4-week retest design, we examined the internal consistency, retest reliability and measurement error (ME of the SSRS secondary student form (SSF in a sample of Year 7 students (N = 187, from five randomly selected public schools in Perth, western Australia. Internal consistency (IC of the total scale and most subscale scores (except empathy on the frequency rating scale was adequate to permit independent use. On the importance rating scale, most IC estimates for girls fell below the benchmark. Test-retest estimates of the total scale and subscales were insufficient to permit reliable use. ME of the total scale score (frequency rating for boys was equivalent to the US estimate, while that for girls was lower than the US error. ME of the total scale score (importance rating was larger than the error using the frequency rating scale. The study finding supports the idea of using multiple informants (e.g. teacher and parent reports, not just student as recommended in the manual. Future research needs to substantiate the clinical meaningfulness of the MEs calculated in this study by corroborating them against the respective Minimum Clinically Important Difference (MCID.

Internal consistency, test-retest reliability and measurement error of the self-report version of the social skills rating system in a sample of Australian adolescents.

Science.gov (United States)

Vaz, Sharmila; Parsons, Richard; Passmore, Anne Elizabeth; Andreou, Pantelis; Falkmer, Torbjörn

2013-01-01

The social skills rating system (SSRS) is used to assess social skills and competence in children and adolescents. While its characteristics based on United States samples (US) are published, corresponding Australian figures are unavailable. Using a 4-week retest design, we examined the internal consistency, retest reliability and measurement error (ME) of the SSRS secondary student form (SSF) in a sample of Year 7 students (N = 187), from five randomly selected public schools in Perth, western Australia. Internal consistency (IC) of the total scale and most subscale scores (except empathy) on the frequency rating scale was adequate to permit independent use. On the importance rating scale, most IC estimates for girls fell below the benchmark. Test-retest estimates of the total scale and subscales were insufficient to permit reliable use. ME of the total scale score (frequency rating) for boys was equivalent to the US estimate, while that for girls was lower than the US error. ME of the total scale score (importance rating) was larger than the error using the frequency rating scale. The study finding supports the idea of using multiple informants (e.g. teacher and parent reports), not just student as recommended in the manual. Future research needs to substantiate the clinical meaningfulness of the MEs calculated in this study by corroborating them against the respective Minimum Clinically Important Difference (MCID).

Error monitoring issues for common channel signaling

Science.gov (United States)

Hou, Victor T.; Kant, Krishna; Ramaswami, V.; Wang, Jonathan L.

1994-04-01

Motivated by field data which showed a large number of link changeovers and incidences of link oscillations between in-service and out-of-service states in common channel signaling (CCS) networks, a number of analyses of the link error monitoring procedures in the SS7 protocol were performed by the authors. This paper summarizes the results obtained thus far and include the following: (1) results of an exact analysis of the performance of the error monitoring procedures under both random and bursty errors; (2) a demonstration that there exists a range of error rates within which the error monitoring procedures of SS7 may induce frequent changeovers and changebacks; (3) an analysis of the performance ofthe SS7 level-2 transmission protocol to determine the tolerable error rates within which the delay requirements can be met; (4) a demonstration that the tolerable error rate depends strongly on various link and traffic characteristics, thereby implying that a single set of error monitor parameters will not work well in all situations; (5) some recommendations on a customizable/adaptable scheme of error monitoring with a discussion on their implementability. These issues may be particularly relevant in the presence of anticipated increases in SS7 traffic due to widespread deployment of Advanced Intelligent Network (AIN) and Personal Communications Service (PCS) as well as for developing procedures for high-speed SS7 links currently under consideration by standards bodies.

Intra- and interobserver error of the Greulich-Pyle method as used on a Danish forensic sample

DEFF Research Database (Denmark)

Lynnerup, N; Belard, E; Buch-Olsen, K

2008-01-01

that atlas-based techniques are obsolete and ought to be replaced by other methods. Specifically, the GPA test sample consisted of American "white" children "above average in economic and educational status", leading to the question as to how comparable subjects being scored by the GPA method today...... and intraoral dental radiographs. Different methods are used depending on the maturity of the individual examined; and (3) a carpal X-ray examination, using the Greulich and Pyle Atlas (GPA) method. We present the results of intra- and interobserver tests of carpal X-rays in blind trials, and a comparison...... of the age estimations by carpal X-rays and odontological age estimation. We retrieved 159 cases from the years 2000-2002 (inclusive). The intra- and interobserver errors are overall small. We found full agreement in 126/159 cases, and this was between experienced users and novices. Overall, the mean...

Re-Normalization Method of Doppler Lidar Signal for Error Reduction

Energy Technology Data Exchange (ETDEWEB)

Park, Nakgyu; Baik, Sunghoon; Park, Seungkyu; Kim, Donglyul [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Dukhyeon [Hanbat National Univ., Daejeon (Korea, Republic of)

2014-05-15

In this paper, we presented a re-normalization method for the fluctuations of Doppler signals from the various noises mainly due to the frequency locking error for a Doppler lidar system. For the Doppler lidar system, we used an injection-seeded pulsed Nd:YAG laser as the transmitter and an iodine filter as the Doppler frequency discriminator. For the Doppler frequency shift measurement, the transmission ratio using the injection-seeded laser is locked to stabilize the frequency. If the frequency locking system is not perfect, the Doppler signal has some error due to the frequency locking error. The re-normalization process of the Doppler signals was performed to reduce this error using an additional laser beam to an Iodine cell. We confirmed that the renormalized Doppler signal shows the stable experimental data much more than that of the averaged Doppler signal using our calibration method, the reduced standard deviation was 4.838 Χ 10{sup -3}.

Organizational safety culture and medical error reporting by Israeli nurses.

Science.gov (United States)

Kagan, Ilya; Barnoy, Sivia

2013-09-01

To investigate the association between patient safety culture (PSC) and the incidence and reporting rate of medical errors by Israeli nurses. Self-administered structured questionnaires were distributed to a convenience sample of 247 registered nurses enrolled in training programs at Tel Aviv University (response rate = 91%). The questionnaire's three sections examined the incidence of medication mistakes in clinical practice, the reporting rate for these errors, and the participants' views and perceptions of the safety culture in their workplace at three levels (organizational, departmental, and individual performance). Pearson correlation coefficients, t tests, and multiple regression analysis were used to analyze the data. Most nurses encountered medical errors from a daily to a weekly basis. Six percent of the sample never reported their own errors, while half reported their own errors "rarely or sometimes." The level of PSC was positively and significantly correlated with the error reporting rate. PSC, place of birth, error incidence, and not having an academic nursing degree were significant predictors of error reporting, together explaining 28% of variance. This study confirms the influence of an organizational safety climate on readiness to report errors. Senior healthcare executives and managers can make a major impact on safety culture development by creating and promoting a vision and strategy for quality and safety and fostering their employees' motivation to implement improvement programs at the departmental and individual level. A positive, carefully designed organizational safety culture can encourage error reporting by staff and so improve patient safety. © 2013 Sigma Theta Tau International.

Medication errors as malpractice-a qualitative content analysis of 585 medication errors by nurses in Sweden.

Science.gov (United States)

Björkstén, Karin Sparring; Bergqvist, Monica; Andersén-Karlsson, Eva; Benson, Lina; Ulfvarson, Johanna

2016-08-24

Many studies address the prevalence of medication errors but few address medication errors serious enough to be regarded as malpractice. Other studies have analyzed the individual and system contributory factor leading to a medication error. Nurses have a key role in medication administration, and there are contradictory reports on the nurses' work experience in relation to the risk and type for medication errors. All medication errors where a nurse was held responsible for malpractice (n = 585) during 11 years in Sweden were included. A qualitative content analysis and classification according to the type and the individual and system contributory factors was made. In order to test for possible differences between nurses' work experience and associations within and between the errors and contributory factors, Fisher's exact test was used, and Cohen's kappa (k) was performed to estimate the magnitude and direction of the associations. There were a total of 613 medication errors in the 585 cases, the most common being "Wrong dose" (41 %), "Wrong patient" (13 %) and "Omission of drug" (12 %). In 95 % of the cases, an average of 1.4 individual contributory factors was found; the most common being "Negligence, forgetfulness or lack of attentiveness" (68 %), "Proper protocol not followed" (25 %), "Lack of knowledge" (13 %) and "Practice beyond scope" (12 %). In 78 % of the cases, an average of 1.7 system contributory factors was found; the most common being "Role overload" (36 %), "Unclear communication or orders" (30 %) and "Lack of adequate access to guidelines or unclear organisational routines" (30 %). The errors "Wrong patient due to mix-up of patients" and "Wrong route" and the contributory factors "Lack of knowledge" and "Negligence, forgetfulness or lack of attentiveness" were more common in less experienced nurses. The experienced nurses were more prone to "Practice beyond scope of practice" and to make errors in spite of "Lack of adequate

Review of a fluid resuscitation protocol: "fluid creep" is not due to nursing error.

Science.gov (United States)

Faraklas, Iris; Cochran, Amalia; Saffle, Jeffrey

2012-01-01

Recent reviews of burn resuscitation have included the suggestion that "fluid creep" may be influenced by practitioner error. Our center uses a nursing-driven resuscitation protocol that permits titration of fluid based on hourly urine output, including the addition of colloid when patients fail to respond appropriately. The purpose of this study was to examine protocol compliance. We reviewed 140 patients (26 children) with burns of ≥20% TBSA who received protocol-directed resuscitation from 2005 to 2010. We compared each patient's actual hourly fluid infusion with that predicted by the protocol. Sixty-seven patients (48%) completed resuscitation using crystalloid alone, whereas 73 patients required colloid supplementation. Groups did not differ in age, gender, weight, or time from injury to admission. Patients requiring colloid had larger median total burns (33.0 vs 23.5% TBSA) and full-thickness burns (15.5 vs 4.5% TBSA) and more inhalation injuries (60.3 vs 28.4%; P patients had median predicted requirements of 5.4 ml/kg/%TBSA. Crystalloid-only patients required fluid volumes close to Parkland predictions (4.7 ml/kg/%TBSA), whereas patients who received colloid required more fluid than the predicted volume (7.5 ml/kg/%TBSA). However, the hourly difference between the predicted and received fluids was a median of only 1.0% (interquartile range: -6.1 to 11.1%) and did not differ between groups. Pediatric patients had greater calculated differences than adults. Crystalloid patients exhibited higher urine outputs than colloid patients until colloid was started, suggesting that early over-resuscitation did not contribute to fluid creep. Adherence to our protocol for burn shock resuscitation was excellent overall. Fluid creep exhibited by more seriously injured patients was not due to nurses' failure to follow the protocol. This review has illuminated some opportunities for practice improvement, possibly using a computerized decision support system.

Estimating and comparing microbial diversity in the presence of sequencing errors

Science.gov (United States)

Chiu, Chun-Huo

2016-01-01

Estimating and comparing microbial diversity are statistically challenging due to limited sampling and possible sequencing errors for low-frequency counts, producing spurious singletons. The inflated singleton count seriously affects statistical analysis and inferences about microbial diversity. Previous statistical approaches to tackle the sequencing errors generally require different parametric assumptions about the sampling model or about the functional form of frequency counts. Different parametric assumptions may lead to drastically different diversity estimates. We focus on nonparametric methods which are universally valid for all parametric assumptions and can be used to compare diversity across communities. We develop here a nonparametric estimator of the true singleton count to replace the spurious singleton count in all methods/approaches. Our estimator of the true singleton count is in terms of the frequency counts of doubletons, tripletons and quadrupletons, provided these three frequency counts are reliable. To quantify microbial alpha diversity for an individual community, we adopt the measure of Hill numbers (effective number of taxa) under a nonparametric framework. Hill numbers, parameterized by an order q that determines the measures’ emphasis on rare or common species, include taxa richness (q = 0), Shannon diversity (q = 1, the exponential of Shannon entropy), and Simpson diversity (q = 2, the inverse of Simpson index). A diversity profile which depicts the Hill number as a function of order q conveys all information contained in a taxa abundance distribution. Based on the estimated singleton count and the original non-singleton frequency counts, two statistical approaches (non-asymptotic and asymptotic) are developed to compare microbial diversity for multiple communities. (1) A non-asymptotic approach refers to the comparison of estimated diversities of standardized samples with a common finite sample size or sample completeness. This

Systematic errors in VLF direction-finding of whistler ducts

International Nuclear Information System (INIS)

Strangeways, H.J.; Rycroft, M.J.

1980-01-01

In the previous paper it was shown that the systematic error in the azimuthal bearing due to multipath propagation and incident wave polarisation (when this also constitutes an error) was given by only three different forms for all VLF direction-finders currently used to investigate the position of whistler ducts. In this paper the magnitude of this error is investigated for different ionospheric and ground parameters for these three different systematic error types. By incorporating an ionosphere for which the refractive index is given by the full Appleton-Hartree formula, the variation of the systematic error with ionospheric electron density and latitude and direction of propagation is investigated in addition to the variation with wave frequency, ground conductivity and dielectric constant and distance of propagation. The systematic bearing error is also investigated for the three methods when the azimuthal bearing is averaged over a 2 kHz bandwidth. This is found to lead to a significantly smaller bearing error which, for the crossed-loops goniometer, approximates the bearing error calculated when phase-dependent terms in the receiver response are ignored. (author)

Joint adaptive modulation and diversity combining with feedback error compensation

KAUST Repository

Choi, Seyeong; Hong-Chuan, Yang; Alouini, Mohamed-Slim; Qaraqe, Khalid A.

2009-01-01

This letter investigates the effect of feedback error on the performance of the joint adaptive modulation and diversity combining (AMDC) scheme which was previously studied with an assumption of error-free feedback channels. We also propose to utilize adaptive diversity to compensate for the performance degradation due to feedback error. We accurately quantify the performance of the joint AMDC scheme in the presence of feedback error, in terms of the average number of combined paths, the average spectral efficiency, and the average bit error rate. Selected numerical examples are presented and discussed to illustrate the effectiveness of the proposed feedback error compensation strategy with adaptive combining. It is observed that the proposed compensation strategy can offer considerable error performance improvement with little loss in processing power and spectral efficiency in comparison with the no compensation case. Copyright © 2009 IEEE.

Joint adaptive modulation and diversity combining with feedback error compensation

KAUST Repository

Choi, Seyeong

2009-11-01

This letter investigates the effect of feedback error on the performance of the joint adaptive modulation and diversity combining (AMDC) scheme which was previously studied with an assumption of error-free feedback channels. We also propose to utilize adaptive diversity to compensate for the performance degradation due to feedback error. We accurately quantify the performance of the joint AMDC scheme in the presence of feedback error, in terms of the average number of combined paths, the average spectral efficiency, and the average bit error rate. Selected numerical examples are presented and discussed to illustrate the effectiveness of the proposed feedback error compensation strategy with adaptive combining. It is observed that the proposed compensation strategy can offer considerable error performance improvement with little loss in processing power and spectral efficiency in comparison with the no compensation case. Copyright © 2009 IEEE.

Characterizing Air Pollution Exposure Misclassification Errors Using Detailed Cell Phone Location Data

Science.gov (United States)

Yu, H.; Russell, A. G.; Mulholland, J. A.

2017-12-01

In air pollution epidemiologic studies with spatially resolved air pollution data, exposures are often estimated using the home locations of individual subjects. Due primarily to lack of data or logistic difficulties, the spatiotemporal mobility of subjects are mostly neglected, which are expected to result in exposure misclassification errors. In this study, we applied detailed cell phone location data to characterize potential exposure misclassification errors associated with home-based exposure estimation of air pollution. The cell phone data sample consists of 9,886 unique simcard IDs collected on one mid-week day in October, 2013 from Shenzhen, China. The Community Multi-scale Air Quality model was used to simulate hourly ambient concentrations of six chosen pollutants at 3 km spatial resolution, which were then fused with observational data to correct for potential modeling biases and errors. Air pollution exposure for each simcard ID was estimated by matching hourly pollutant concentrations with detailed location data for corresponding IDs. Finally, the results were compared with exposure estimates obtained using the home location method to assess potential exposure misclassification errors. Our results show that the home-based method is likely to have substantial exposure misclassification errors, over-estimating exposures for subjects with higher exposure levels and under-estimating exposures for those with lower exposure levels. This has the potential to lead to a bias-to-the-null in the health effect estimates. Our findings suggest that the use of cell phone data has the potential for improving the characterization of exposure and exposure misclassification in air pollution epidemiology studies.

Learning time-dependent noise to reduce logical errors: real time error rate estimation in quantum error correction

Science.gov (United States)

Huo, Ming-Xia; Li, Ying

2017-12-01

Quantum error correction is important to quantum information processing, which allows us to reliably process information encoded in quantum error correction codes. Efficient quantum error correction benefits from the knowledge of error rates. We propose a protocol for monitoring error rates in real time without interrupting the quantum error correction. Any adaptation of the quantum error correction code or its implementation circuit is not required. The protocol can be directly applied to the most advanced quantum error correction techniques, e.g. surface code. A Gaussian processes algorithm is used to estimate and predict error rates based on error correction data in the past. We find that using these estimated error rates, the probability of error correction failures can be significantly reduced by a factor increasing with the code distance.

External exposure due to natural radiation (KINKI)

International Nuclear Information System (INIS)

1978-01-01

A field survey of exposure rates due to natural radiation has been conducted throughout the Kinki district of Japan during both September and October 1973. In each location, measurements of exposures at one to fifteen sites, one of where contained 5 stations at least, were made. A total of 143 sites were measured. Observations were made using a spherical ionization chamber and several scintillation surveymeters. The spherical plastic ionization chamber of which inner diameter and wall thickness are 200 mm and 3 mm (acrylate) respectively has adequate sensitivity for field survey. The chamber was used as a standard of apparatus, but it is difficult to use the apparatus in all locations only by the apparatus, so that a surveymeter with a NaI(Tl) 1''phi x 1'' scintillator was used for regular measurements. Two types of surveymeters, the one with a 2''phi x 2'' NaI(Tl) scintillator and the other with a 3''phi x 3'' NaI(Tl) scintillator, were used as auxiliary devices. Both the chamber and the surveymeter were used in 20 sites and their readings were compared for drawing a relationship between them. Practically the direct reading of the surveymeter were reduced into the corresponding value of the plastic chamber through the relationship of linear proportion. Systematic error at calibration ( 60 Co) and reading error (rodoh) of the plastic chamber were within +-6% (maximum over all error) and within +-3.5% (standard error for 6μ R/hr) respectively. Reading error of the surveymeter is about +-3% (standard error for 6μ R/hr). Measurements in open bare field were made at one meter above the ground and outdoor gamma-rays exposure rates (μ R/hr) were due to cosmic rays as well as terrestrial radiation, as it may be considered that the contribution of fallout due to artificial origin was very small. (J.P.N.)

Digital Particle Image Velocimetry: Partial Image Error (PIE)

International Nuclear Information System (INIS)

Anandarajah, K; Hargrave, G K; Halliwell, N A

2006-01-01

This paper quantifies the errors due to partial imaging of seeding particles which occur at the edges of interrogation regions in Digital Particle Image Velocimetry (DPIV). Hitherto, in the scientific literature the effect of these partial images has been assumed to be negligible. The results show that the error is significant even at a commonly used interrogation region size of 32 x 32 pixels. If correlation of interrogation region sizes of 16 x 16 pixels and smaller is attempted, the error which occurs can preclude meaningful results being obtained. In order to reduce the error normalisation of the correlation peak values is necessary. The paper introduces Normalisation by Signal Strength (NSS) as the preferred means of normalisation for optimum accuracy. In addition, it is shown that NSS increases the dynamic range of DPIV

Refractive error and visual impairment in private school children in Ghana.

Science.gov (United States)

Kumah, Ben D; Ebri, Anne; Abdul-Kabir, Mohammed; Ahmed, Abdul-Sadik; Koomson, Nana Ya; Aikins, Samual; Aikins, Amos; Amedo, Angela; Lartey, Seth; Naidoo, Kovin

2013-12-01

To assess the prevalence of refractive error and visual impairment in private school children in Ghana. A random selection of geographically defined classes in clusters was used to identify a sample of school children aged 12 to 15 years in the Ashanti Region. Children in 60 clusters were enumerated and examined in classrooms. The examination included visual acuity, retinoscopy, autorefraction under cycloplegia, and examination of anterior segment, media, and fundus. For quality assurance, a random sample of children with reduced and normal vision were selected and re-examined independently. A total of 2454 children attending 53 private schools were enumerated, and of these, 2435 (99.2%) were examined. Prevalence of uncorrected, presenting, and best visual acuity of 20/40 or worse in the better eye was 3.7, 3.5, and 0.4%, respectively. Refractive error was the cause of reduced vision in 71.7% of 152 eyes, amblyopia in 9.9%, retinal disorders in 5.9%, and corneal opacity in 4.6%. Exterior and anterior segment abnormalities occurred in 43 (1.8%) children. Myopia (at least -0.50 D) in one or both eyes was present in 3.2% of children when measured with retinoscopy and in 3.4% measured with autorefraction. Myopia was not significantly associated with gender (P = 0.82). Hyperopia (+2.00 D or more) in at least one eye was present in 0.3% of children with retinoscopy and autorefraction. The prevalence of reduced vision in Ghanaian private school children due to uncorrected refractive error was low. However, the prevalence of amblyopia, retinal disorders, and corneal opacities indicate the need for early interventions.

Alpha-particle-induced soft errors in high speed bipolar RAM

International Nuclear Information System (INIS)

Mitsusada, Kazumichi; Kato, Yukio; Yamaguchi, Kunihiko; Inadachi, Masaaki

1980-01-01

As bipolar RAM (Random Access Memory) has been improved to a fast acting and highly integrated device, the problems negligible in the past have become the ones that can not be ignored. The problem of a-particles emitted from the radioactive substances in semiconductor package materials should be specifically noticed, which cause soft errors. The authors have produced experimentally the special 1 kbit bipolar RAM to investigate its soft errors. The package used was the standard 16 pin dual in-line type, with which the practical system mounting test and a-particle irradiation test have been performed. The results showed the occurrence of soft errors at the average rate of about 1 bit/700 device hour. It is concluded that the cause was due to the a-particles emitted from the package materials, and at the same time, it was found that the rate of soft error occurrence was able to be greatly reduced by shielding a-particles. The error rate significantly increased with the decrease of the stand-by current of memory cells and with the accumulated charge determined by time constant. The mechanism of soft error was also investigated, for which an approximate model to estimate the error rate by means of the effective noise charge due to a-particles and of the amount of reversible charges of memory cells is shown to compare it with the experimental results. (Wakatsuki, Y.)

Margin of Valuation Error Among Nigerian Valuers: Postulating an ...

African Journals Online (AJOL)

Study on margin of error aims at capturing the response of Nigerian valuers and their clients from the financial sector to their permissable margin of error with a view to establishing the bracket outside which the valuer is considered incompetent. The opinion of 300 Estate Surveyors and Valuers were sampled using simple ...

Students' errors in solving linear equation word problems: Case ...

African Journals Online (AJOL)

The study examined errors students make in solving linear equation word problems with a view to expose the nature of these errors and to make suggestions for classroom teaching. A diagnostic test comprising 10 linear equation word problems, was administered to a sample (n=130) of senior high school first year Home ...

Evaluation of errors and limits of the 63-μm house-dust-fraction method, a surrogate to predict hidden moisture damage

Directory of Open Access Journals (Sweden)

Assadian Ojan

2009-10-01

Full Text Available Abstract Background The aim of this study is to analyze possible random and systematic measurement errors and to detect methodological limits of the previously established method. Findings To examine the distribution of random errors (repeatability standard deviation of the detection procedure, collective samples were taken from two uncontaminated rooms using a sampling vacuum cleaner, and 10 sub-samples each were examined with 3 parallel cultivation plates (DG18. In this two collective samples of new dust, the total counts of Aspergillus spp. varied moderately by 25 and 29% (both 9 cfu per plate. At an average of 28 cfu/plate, the total number varied only by 13%. For the evaluation of the influence of old dust, old and fresh dust samples were examined. In both cases with old dust, the old dust influenced the results indicating false positive results, where hidden moist was indicated but was not present. To quantify the influence of sand and sieving, 13 sites were sampled in parallel using the 63-μm- and total dust collection approaches. Sieving to 63-μm resulted in a more then 10-fold enrichment, due to the different quantity of inert sand in each total dust sample. Conclusion The major errors during the quantitative evaluation from house dust samples for mould fungi as reference values for assessment resulted from missing filtration, contamination with old dust and the massive influence of soil. If the assessment is guided by indicator genera, the percentage standard deviation lies in a moderate range.

Cluster-sample surveys and lot quality assurance sampling to evaluate yellow fever immunisation coverage following a national campaign, Bolivia, 2007.

Science.gov (United States)

Pezzoli, Lorenzo; Pineda, Silvia; Halkyer, Percy; Crespo, Gladys; Andrews, Nick; Ronveaux, Olivier

2009-03-01

To estimate the yellow fever (YF) vaccine coverage for the endemic and non-endemic areas of Bolivia and to determine whether selected districts had acceptable levels of coverage (>70%). We conducted two surveys of 600 individuals (25 x 12 clusters) to estimate coverage in the endemic and non-endemic areas. We assessed 11 districts using lot quality assurance sampling (LQAS). The lot (district) sample was 35 individuals with six as decision value (alpha error 6% if true coverage 70%; beta error 6% if true coverage 90%). To increase feasibility, we divided the lots into five clusters of seven individuals; to investigate the effect of clustering, we calculated alpha and beta by conducting simulations where each cluster's true coverage was sampled from a normal distribution with a mean of 70% or 90% and standard deviations of 5% or 10%. Estimated coverage was 84.3% (95% CI: 78.9-89.7) in endemic areas, 86.8% (82.5-91.0) in non-endemic and 86.0% (82.8-89.1) nationally. LQAS showed that four lots had unacceptable coverage levels. In six lots, results were inconsistent with the estimated administrative coverage. The simulations suggested that the effect of clustering the lots is unlikely to have significantly increased the risk of making incorrect accept/reject decisions. Estimated YF coverage was high. Discrepancies between administrative coverage and LQAS results may be due to incorrect population data. Even allowing for clustering in LQAS, the statistical errors would remain low. Catch-up campaigns are recommended in districts with unacceptable coverage.

[Modal failure analysis and effects in the detection of errors in the transport of samples to the clinical laboratory].

Science.gov (United States)

Parés-Pollán, L; Gonzalez-Quintana, A; Docampo-Cordeiro, J; Vargas-Gallego, C; García-Álvarez, G; Ramos-Rodríguez, V; Diaz Rubio-García, M P

2014-01-01

Owing to the decrease in values of biochemical glucose parameter in some samples from external extraction centres, and the risk this implies to patient safety; it was decided to apply an adaptation of the «Health Services Failure Mode and Effects Analysis» (HFMEA) to manage risk during the pre-analytical phase of sample transportation from external centres to clinical laboratories. A retrospective study of glucose parameter was conducted during two consecutive months. The analysis was performed in its different phases: to define the HFMEA topic, assemble the team, graphically describe the process, conduct a hazard analysis, design the intervention and indicators, and identify a person to be responsible for ensuring completion of each action. The results of glucose parameter in one of the transport routes, were significantly lower (P=.006). The errors and potential causes of this problem were analysed, and criteria of criticality and detectability were applied (score≥8) in the decision tree. It was decided to: develop a document management system; reorganise extractions and transport routes in some centres; quality control of the sample container ice-packs, and the time and temperature during transportation. This work proposes quality indicators for controlling time and temperature of transported samples in the pre-analytical phase. Periodic review of certain laboratory parameters can help to detect problems in transporting samples. The HFMEA technique is useful for the clinical laboratory. Copyright © 2013 SECA. Published by Elsevier Espana. All rights reserved.

Rational learning and information sampling: on the "naivety" assumption in sampling explanations of judgment biases.

Science.gov (United States)

Le Mens, Gaël; Denrell, Jerker

2011-04-01

Recent research has argued that several well-known judgment biases may be due to biases in the available information sample rather than to biased information processing. Most of these sample-based explanations assume that decision makers are "naive": They are not aware of the biases in the available information sample and do not correct for them. Here, we show that this "naivety" assumption is not necessary. Systematically biased judgments can emerge even when decision makers process available information perfectly and are also aware of how the information sample has been generated. Specifically, we develop a rational analysis of Denrell's (2005) experience sampling model, and we prove that when information search is interested rather than disinterested, even rational information sampling and processing can give rise to systematic patterns of errors in judgments. Our results illustrate that a tendency to favor alternatives for which outcome information is more accessible can be consistent with rational behavior. The model offers a rational explanation for behaviors that had previously been attributed to cognitive and motivational biases, such as the in-group bias or the tendency to prefer popular alternatives. 2011 APA, all rights reserved

Theoretical-and experimental analysis of the errors involved in the wood moisture determination by gamma-ray attenuation

International Nuclear Information System (INIS)

Aguiar, O.

1983-01-01

The sources of errors in wood moisture determination by gamma-ray attenuation were sought. Equations were proposed for determining errors and for ideal sample thickness. A series of measurements of moisture content in wood samples of Pinus oocarpa was made and the experimental errors were compared with the theoretical errors. (Author) [pt

Intrinsic errors in transporting a single-spin qubit through a double quantum dot

Science.gov (United States)

Li, Xiao; Barnes, Edwin; Kestner, J. P.; Das Sarma, S.

2017-07-01

Coherent spatial transport or shuttling of a single electron spin through semiconductor nanostructures is an important ingredient in many spintronic and quantum computing applications. In this work we analyze the possible errors in solid-state quantum computation due to leakage in transporting a single-spin qubit through a semiconductor double quantum dot. In particular, we consider three possible sources of leakage errors associated with such transport: finite ramping times, spin-dependent tunneling rates between quantum dots induced by finite spin-orbit couplings, and the presence of multiple valley states. In each case we present quantitative estimates of the leakage errors, and discuss how they can be minimized. The emphasis of this work is on how to deal with the errors intrinsic to the ideal semiconductor structure, such as leakage due to spin-orbit couplings, rather than on errors due to defects or noise sources. In particular, we show that in order to minimize leakage errors induced by spin-dependent tunnelings, it is necessary to apply pulses to perform certain carefully designed spin rotations. We further develop a formalism that allows one to systematically derive constraints on the pulse shapes and present a few examples to highlight the advantage of such an approach.

Sensitivity of APSIM/ORYZA model due to estimation errors in solar radiation

Directory of Open Access Journals (Sweden)

Alexandre Bryan Heinemann

2012-01-01

Full Text Available Crop models are ideally suited to quantify existing climatic risks. However, they require historic climate data as input. While daily temperature and rainfall data are often available, the lack of observed solar radiation (Rs data severely limits site-specific crop modelling. The objective of this study was to estimate Rs based on air temperature solar radiation models and to quantify the propagation of errors in simulated radiation on several APSIM/ORYZA crop model seasonal outputs, yield, biomass, leaf area (LAI and total accumulated solar radiation (SRA during the crop cycle. The accuracy of the 5 models for estimated daily solar radiation was similar, and it was not substantially different among sites. For water limited environments (no irrigation, crop model outputs yield, biomass and LAI was not sensitive for the uncertainties in radiation models studied here.

Sampling or gambling

Energy Technology Data Exchange (ETDEWEB)

Gy, P.M.

1981-12-01

Sampling can be compared to no other technique. A mechanical sampler must above all be selected according to its aptitude for supressing or reducing all components of the sampling error. Sampling is said to be correct when it gives all elements making up the batch of matter submitted to sampling an uniform probability of being selected. A sampler must be correctly designed, built, installed, operated and maintained. When the conditions of sampling correctness are not strictly respected, the sampling error can no longer be controlled and can, unknown to the user, be unacceptably large: the sample is no longer representative. The implementation of an incorrect sampler is a form of gambling and this paper intends to show that at this game the user is nearly always the loser in the long run. The users' and the manufacturers' interests may diverge and the standards which should safeguard the users' interests very often fail to do so by tolerating or even recommending incorrect techniques such as the implementation of too narrow cutters traveling too fast through the stream to be sampled.

Radon measurements-discussion of error estimates for selected methods

International Nuclear Information System (INIS)

Zhukovsky, Michael; Onischenko, Alexandra; Bastrikov, Vladislav

2010-01-01

The main sources of uncertainties for grab sampling, short-term (charcoal canisters) and long term (track detectors) measurements are: systematic bias of reference equipment; random Poisson and non-Poisson errors during calibration; random Poisson and non-Poisson errors during measurements. The origins of non-Poisson random errors during calibration are different for different kinds of instrumental measurements. The main sources of uncertainties for retrospective measurements conducted by surface traps techniques can be divided in two groups: errors of surface 210 Pb ( 210 Po) activity measurements and uncertainties of transfer from 210 Pb surface activity in glass objects to average radon concentration during this object exposure. It's shown that total measurement error of surface trap retrospective technique can be decreased to 35%.

Investigating Medication Errors in Educational Health Centers of Kermanshah

Directory of Open Access Journals (Sweden)

Mohsen Mohammadi

2015-08-01

Full Text Available Background and objectives : Medication errors can be a threat to the safety of patients. Preventing medication errors requires reporting and investigating such errors. The present study was conducted with the purpose of investigating medication errors in educational health centers of Kermanshah. Material and Methods: The present research is an applied, descriptive-analytical study and is done as a survey. Error Report of Ministry of Health and Medical Education was used for data collection. The population of the study included all the personnel (nurses, doctors, paramedics of educational health centers of Kermanshah. Among them, those who reported the committed errors were selected as the sample of the study. The data analysis was done using descriptive statistics and Chi 2 Test using SPSS version 18. Results: The findings of the study showed that most errors were related to not using medication properly, the least number of errors were related to improper dose, and the majority of errors occurred in the morning. The most frequent reason for errors was staff negligence and the least frequent was the lack of knowledge. Conclusion: The health care system should create an environment for detecting and reporting errors by the personnel, recognizing related factors causing errors, training the personnel and create a good working environment and standard workload.

Kalman filter application to mitigate the errors in the trajectory simulations due to the lunar gravitational model uncertainty

International Nuclear Information System (INIS)

Gonçalves, L D; Rocco, E M; De Moraes, R V; Kuga, H K

2015-01-01

This paper aims to simulate part of the orbital trajectory of Lunar Prospector mission to analyze the relevance of using a Kalman filter to estimate the trajectory. For this study it is considered the disturbance due to the lunar gravitational potential using one of the most recent models, the LP100K model, which is based on spherical harmonics, and considers the maximum degree and order up to the value 100. In order to simplify the expression of the gravitational potential and, consequently, to reduce the computational effort required in the simulation, in some cases, lower values for degree and order are used. Following this aim, it is made an analysis of the inserted error in the simulations when using such values of degree and order to propagate the spacecraft trajectory and control. This analysis was done using the standard deviation that characterizes the uncertainty for each one of the values of the degree and order used in LP100K model for the satellite orbit. With knowledge of the uncertainty of the gravity model adopted, lunar orbital trajectory simulations may be accomplished considering these values of uncertainty. Furthermore, it was also used a Kalman filter, where is considered the sensor's uncertainty that defines the satellite position at each step of the simulation and the uncertainty of the model, by means of the characteristic variance of the truncated gravity model. Thus, this procedure represents an effort to approximate the results obtained using lower values for the degree and order of the spherical harmonics, to the results that would be attained if the maximum accuracy of the model LP100K were adopted. Also a comparison is made between the error in the satellite position in the situation in which the Kalman filter is used and the situation in which the filter is not used. The data for the comparison were obtained from the standard deviation in the velocity increment of the space vehicle. (paper)

Refractive Errors in State Junior High School Students in Bandung

Directory of Open Access Journals (Sweden)

Sabila Tasyakur Nikmah

2016-12-01

Full Text Available Background: Uncorrected refractive error is one of the avoidable causes of vision impairment in children and adults. Vision problem in children has been shown to affect their psychological and academic performance. This study aims at identifying and gaining more insights on the characteristic of the refractive errors in state junior high school students in Bandung to avoid uncorrected refractive errors. Methods: A cross-sectional study was conducted in September–November 2015 in state junior high schools in Bandung, West Java, Indonesia. Sample was selected using multistage random sampling technique. Children were examined using tumbling E examination; then students with visual acuity worse than 6/12 underwent Snellen Chart test, refractometry without pupil dilatation, correction with trial lens, then was followed by direct ophthalmoscopy. Results: From a total of 435 children who completed all the examination, 80 children (18.39% had refractive errors; consisted of 151 eyes (94.38% with myopia and 9 eyes (5.62% with astigmatism. Refractive errors were found to be more common in female children (73.7% than male children (26.3%. Among those with refractive errors, 45 children (56.3% did not use any corrective glasses before the examination. Conclusions: Routine refractive error test in vision screening examination is needed for students. It is equally important to raise more awareness toward eye disease in community.

Neutron-induced soft errors in CMOS circuits

International Nuclear Information System (INIS)

Hazucha, P.

1999-01-01

The subject of this thesis is a systematic study of soft errors occurring in CMOS integrated circuits when being exposed to radiation. The vast majority of commercial circuits operate in the natural environment ranging from the sea level to aircraft flight altitudes (less than 20 km), where the errors are caused mainly by interaction of atmospheric neutrons with silicon. Initially, the soft error rate (SER) of a static memory was measured for supply voltages from 2V to 5V when irradiated by 14 MeV and 100 MeV neutrons. Increased error rate due to the decreased supply voltage has been identified as a potential hazard for operation of future low-voltage circuits. A novel methodology was proposed for accurate SER characterization of a manufacturing process and it was validated by measurements on a 0.6 μm process and 100 MeV neutrons. The methodology can be applied to the prediction of SER in the natural environment

Selection of anchor values for human error probability estimation

International Nuclear Information System (INIS)

Buffardi, L.C.; Fleishman, E.A.; Allen, J.A.

1989-01-01

There is a need for more dependable information to assist in the prediction of human errors in nuclear power environments. The major objective of the current project is to establish guidelines for using error probabilities from other task settings to estimate errors in the nuclear environment. This involves: (1) identifying critical nuclear tasks, (2) discovering similar tasks in non-nuclear environments, (3) finding error data for non-nuclear tasks, and (4) establishing error-rate values for the nuclear tasks based on the non-nuclear data. A key feature is the application of a classification system to nuclear and non-nuclear tasks to evaluate their similarities and differences in order to provide a basis for generalizing human error estimates across tasks. During the first eight months of the project, several classification systems have been applied to a sample of nuclear tasks. They are discussed in terms of their potential for establishing task equivalence and transferability of human error rates across situations

Design of an error-free nondestructive plutonium assay facility

International Nuclear Information System (INIS)

Moore, C.B.; Steward, W.E.

1987-01-01

An automated, at-line nondestructive assay (NDA) laboratory is installed in facilities recently constructed at the Savannah River Plant. The laboratory will enhance nuclear materials accounting in new plutonium scrap and waste recovery facilities. The advantages of at-line NDA operations will not be realized if results are clouded by errors in analytical procedures, sample identification, record keeping, or techniques for extracting samples from process streams. Minimization of such errors has been a primary design objective for the new facility. Concepts for achieving that objective include mechanizing the administrative tasks of scheduling activities in the laboratory, identifying samples, recording and storing assay data, and transmitting results information to process control and materials accounting functions. These concepts have been implemented in an analytical computer system that is programmed to avoid the obvious sources of error encountered in laboratory operations. The laboratory computer exchanges information with process control and materials accounting computers, transmitting results information and obtaining process data and accounting information as required to guide process operations and maintain current records of materials flow through the new facility

Errors as a Means of Reducing Impulsive Food Choice.

Science.gov (United States)

Sellitto, Manuela; di Pellegrino, Giuseppe

2016-06-05

Nowadays, the increasing incidence of eating disorders due to poor self-control has given rise to increased obesity and other chronic weight problems, and ultimately, to reduced life expectancy. The capacity to refrain from automatic responses is usually high in situations in which making errors is highly likely. The protocol described here aims at reducing imprudent preference in women during hypothetical intertemporal choices about appetitive food by associating it with errors. First, participants undergo an error task where two different edible stimuli are associated with two different error likelihoods (high and low). Second, they make intertemporal choices about the two edible stimuli, separately. As a result, this method decreases the discount rate for future amounts of the edible reward that cued higher error likelihood, selectively. This effect is under the influence of the self-reported hunger level. The present protocol demonstrates that errors, well known as motivationally salient events, can induce the recruitment of cognitive control, thus being ultimately useful in reducing impatient choices for edible commodities.

Students’ Errors in Geometry Viewed from Spatial Intelligence

Science.gov (United States)

Riastuti, N.; Mardiyana, M.; Pramudya, I.

2017-09-01

Geometry is one of the difficult materials because students must have ability to visualize, describe images, draw shapes, and know the kind of shapes. This study aim is to describe student error based on Newmans’ Error Analysis in solving geometry problems viewed from spatial intelligence. This research uses descriptive qualitative method by using purposive sampling technique. The datas in this research are the result of geometri material test and interview by the 8th graders of Junior High School in Indonesia. The results of this study show that in each category of spatial intelligence has a different type of error in solving the problem on the material geometry. Errors are mostly made by students with low spatial intelligence because they have deficiencies in visual abilities. Analysis of student error viewed from spatial intelligence is expected to help students do reflection in solving the problem of geometry.

Eigen's Error Threshold and Mutational Meltdown in a Quasispecies Model

OpenAIRE

Bagnoli, F.; Bezzi, M.

1998-01-01

We introduce a toy model for interacting populations connected by mutations and limited by a shared resource. We study the presence of Eigen's error threshold and mutational meltdown. The phase diagram of the system shows that the extinction of the whole population due to mutational meltdown can occur well before an eventual error threshold transition.

Reduced error signalling in medication-naive children with ADHD

DEFF Research Database (Denmark)

Plessen, Kerstin J; Allen, Elena A; Eichele, Heike

2016-01-01

reduced in children with ADHD. This adaptation was inversely related to activation of the right-lateralized ventral attention network (VAN) on error trials and to task-driven connectivity between the cingulo-opercular system and the VAN. LIMITATIONS: Our study was limited by the modest sample size......BACKGROUND: We examined the blood-oxygen level-dependent (BOLD) activation in brain regions that signal errors and their association with intraindividual behavioural variability and adaptation to errors in children with attention-deficit/hyperactivity disorder (ADHD). METHODS: We acquired...

Analysis of Employee's Survey for Preventing Human-Errors

International Nuclear Information System (INIS)

Sung, Chanho; Kim, Younggab; Joung, Sanghoun

2013-01-01

Human errors in nuclear power plant can cause large and small events or incidents. These events or incidents are one of main contributors of reactor trip and might threaten the safety of nuclear plants. To prevent human-errors, KHNP(nuclear power plants) introduced 'Human-error prevention techniques' and have applied the techniques to main parts such as plant operation, operation support, and maintenance and engineering. This paper proposes the methods to prevent and reduce human-errors in nuclear power plants through analyzing survey results which includes the utilization of the human-error prevention techniques and the employees' awareness of preventing human-errors. With regard to human-error prevention, this survey analysis presented the status of the human-error prevention techniques and the employees' awareness of preventing human-errors. Employees' understanding and utilization of the techniques was generally high and training level of employee and training effect on actual works were in good condition. Also, employees answered that the root causes of human-error were due to working environment including tight process, manpower shortage, and excessive mission rather than personal negligence or lack of personal knowledge. Consideration of working environment is certainly needed. At the present time, based on analyzing this survey, the best methods of preventing human-error are personal equipment, training/education substantiality, private mental health check before starting work, prohibit of multiple task performing, compliance with procedures, and enhancement of job site review. However, the most important and basic things for preventing human-error are interests of workers and organizational atmosphere such as communication between managers and workers, and communication between employees and bosses

Influence of random setup error on dose distribution

International Nuclear Information System (INIS)

Zhai Zhenyu

2008-01-01

Objective: To investigate the influence of random setup error on dose distribution in radiotherapy and determine the margin from ITV to PTV. Methods: A random sample approach was used to simulate the fields position in target coordinate system. Cumulative effect of random setup error was the sum of dose distributions of all individual treatment fractions. Study of 100 cumulative effects might get shift sizes of 90% dose point position. Margins from ITV to PTV caused by random setup error were chosen by 95% probability. Spearman's correlation was used to analyze the influence of each factor. Results: The average shift sizes of 90% dose point position was 0.62, 1.84, 3.13, 4.78, 6.34 and 8.03 mm if random setup error was 1,2,3,4,5 and 6 mm,respectively. Univariate analysis showed the size of margin was associated only by the size of random setup error. Conclusions: Margin of ITV to PTV is 1.2 times random setup error for head-and-neck cancer and 1.5 times for thoracic and abdominal cancer. Field size, energy and target depth, unlike random setup error, have no relation with the size of the margin. (authors)

Disclosing harmful medical errors to patients: tackling three tough cases.

Science.gov (United States)

Gallagher, Thomas H; Bell, Sigall K; Smith, Kelly M; Mello, Michelle M; McDonald, Timothy B

2009-09-01

A gap exists between recommendations to disclose errors to patients and current practice. This gap may reflect important, yet unanswered questions about implementing disclosure principles. We explore some of these unanswered questions by presenting three real cases that pose challenging disclosure dilemmas. The first case involves a pancreas transplant that failed due to the pancreas graft being discarded, an error that was not disclosed partly because the family did not ask clarifying questions. Relying on patient or family questions to determine the content of disclosure is problematic. We propose a standard of materiality that can help clinicians to decide what information to disclose. The second case involves a fatal diagnostic error that the patient's widower was unaware had happened. The error was not disclosed out of concern that disclosure would cause the widower more harm than good. This case highlights how institutions can overlook patients' and families' needs following errors and emphasizes that benevolent deception has little role in disclosure. Institutions should consider whether involving neutral third parties could make disclosures more patient centered. The third case presents an intraoperative cardiac arrest due to a large air embolism where uncertainty around the clinical event was high and complicated the disclosure. Uncertainty is common to many medical errors but should not deter open conversations with patients and families about what is and is not known about the event. Continued discussion within the medical profession about applying disclosure principles to real-world cases can help to better meet patients' and families' needs following medical errors.

Quantifying error of lidar and sodar Doppler beam swinging measurements of wind turbine wakes using computational fluid dynamics

Science.gov (United States)

Lundquist, J. K.; Churchfield, M. J.; Lee, S.; Clifton, A.

2015-02-01

Wind-profiling lidars are now regularly used in boundary-layer meteorology and in applications such as wind energy and air quality. Lidar wind profilers exploit the Doppler shift of laser light backscattered from particulates carried by the wind to measure a line-of-sight (LOS) velocity. The Doppler beam swinging (DBS) technique, used by many commercial systems, considers measurements of this LOS velocity in multiple radial directions in order to estimate horizontal and vertical winds. The method relies on the assumption of homogeneous flow across the region sampled by the beams. Using such a system in inhomogeneous flow, such as wind turbine wakes or complex terrain, will result in errors. To quantify the errors expected from such violation of the assumption of horizontal homogeneity, we simulate inhomogeneous flow in the atmospheric boundary layer, notably stably stratified flow past a wind turbine, with a mean wind speed of 6.5 m s-1 at the turbine hub-height of 80 m. This slightly stable case results in 15° of wind direction change across the turbine rotor disk. The resulting flow field is sampled in the same fashion that a lidar samples the atmosphere with the DBS approach, including the lidar range weighting function, enabling quantification of the error in the DBS observations. The observations from the instruments located upwind have small errors, which are ameliorated with time averaging. However, the downwind observations, particularly within the first two rotor diameters downwind from the wind turbine, suffer from errors due to the heterogeneity of the wind turbine wake. Errors in the stream-wise component of the flow approach 30% of the hub-height inflow wind speed close to the rotor disk. Errors in the cross-stream and vertical velocity components are also significant: cross-stream component errors are on the order of 15% of the hub-height inflow wind speed (1.0 m s-1) and errors in the vertical velocity measurement exceed the actual vertical velocity

Prevalence of refractive errors in the Slovak population calculated using the Gullstrand schematic eye model.

Science.gov (United States)

Popov, I; Valašková, J; Štefaničková, J; Krásnik, V

2017-01-01

A substantial part of the population suffers from some kind of refractive errors. It is envisaged that their prevalence may change with the development of society. The aim of this study is to determine the prevalence of refractive errors using calculations based on the Gullstrand schematic eye model. We used the Gullstrand schematic eye model to calculate refraction retrospectively. Refraction was presented as the need for glasses correction at a vertex distance of 12 mm. The necessary data was obtained using the optical biometer Lenstar LS900. Data which could not be obtained due to the limitations of the device was substituted by theoretical data from the Gullstrand schematic eye model. Only analyses from the right eyes were presented. The data was interpreted using descriptive statistics, Pearson correlation and t-test. The statistical tests were conducted at a level of significance of 5%. Our sample included 1663 patients (665 male, 998 female) within the age range of 19 to 96 years. Average age was 70.8 ± 9.53 years. Average refraction of the eye was 2.73 ± 2.13D (males 2.49 ± 2.34, females 2.90 ± 2.76). The mean absolute error from emmetropia was 3.01 ± 1.58 (males 2.83 ± 2.95, females 3.25 ± 3.35). 89.06% of the sample was hyperopic, 6.61% was myopic and 4.33% emmetropic. We did not find any correlation between refraction and age. Females were more hyperopic than males. We did not find any statistically significant hypermetopic shift of refraction with age. According to our estimation, the calculations of refractive errors using the Gullstrand schematic eye model showed a significant hypermetropic shift of more than +2D. Our results could be used in future for comparing the prevalence of refractive errors using same methods we used.Key words: refractive errors, refraction, Gullstrand schematic eye model, population, emmetropia.

Error orientation questionnaire (EOQ): reliability, validity, and different language equivalence

NARCIS (Netherlands)

Rybowiak, V.; Garst, H.; Frese, M.; Batinic, B.

1999-01-01

An Error Orientation Questionnaire (EOQ) was developed, consisting of eight scales on attitudes to and on coping with errors at work. In Study I (representative sample of a German city, N=478) six scales were developed with the help of a confirmatory factor analysis using LISREL techniques. They

Failures without errors: quantification of context in HRA

International Nuclear Information System (INIS)

Fujita, Yushi; Hollnagel, Erik

2004-01-01

PSA-cum-human reliability analysis (HRA) has traditionally used individual human actions, hence individual 'human errors', as a meaningful unit of analysis. This is inconsistent with the current understanding of accidents, which points out that the notion of 'human error' is ill defined and that adverse events more often are the due to the working conditions than to people. Several HRA approaches, such as ATHEANA and CREAM have recognised this conflict and proposed ways to deal with it. This paper describes an improvement of the basic screening method in CREAM, whereby a rating of the performance conditions can be used to calculate a Mean Failure Rate directly without invoking the notion of human error

Sensitivity analysis of periodic errors in heterodyne interferometry

International Nuclear Information System (INIS)

Ganguly, Vasishta; Kim, Nam Ho; Kim, Hyo Soo; Schmitz, Tony

2011-01-01

Periodic errors in heterodyne displacement measuring interferometry occur due to frequency mixing in the interferometer. These nonlinearities are typically characterized as first- and second-order periodic errors which cause a cyclical (non-cumulative) variation in the reported displacement about the true value. This study implements an existing analytical periodic error model in order to identify sensitivities of the first- and second-order periodic errors to the input parameters, including rotational misalignments of the polarizing beam splitter and mixing polarizer, non-orthogonality of the two laser frequencies, ellipticity in the polarizations of the two laser beams, and different transmission coefficients in the polarizing beam splitter. A local sensitivity analysis is first conducted to examine the sensitivities of the periodic errors with respect to each input parameter about the nominal input values. Next, a variance-based approach is used to study the global sensitivities of the periodic errors by calculating the Sobol' sensitivity indices using Monte Carlo simulation. The effect of variation in the input uncertainty on the computed sensitivity indices is examined. It is seen that the first-order periodic error is highly sensitive to non-orthogonality of the two linearly polarized laser frequencies, while the second-order error is most sensitive to the rotational misalignment between the laser beams and the polarizing beam splitter. A particle swarm optimization technique is finally used to predict the possible setup imperfections based on experimentally generated values for periodic errors

Sensitivity analysis of periodic errors in heterodyne interferometry

Science.gov (United States)

Ganguly, Vasishta; Kim, Nam Ho; Kim, Hyo Soo; Schmitz, Tony

2011-03-01

Periodic errors in heterodyne displacement measuring interferometry occur due to frequency mixing in the interferometer. These nonlinearities are typically characterized as first- and second-order periodic errors which cause a cyclical (non-cumulative) variation in the reported displacement about the true value. This study implements an existing analytical periodic error model in order to identify sensitivities of the first- and second-order periodic errors to the input parameters, including rotational misalignments of the polarizing beam splitter and mixing polarizer, non-orthogonality of the two laser frequencies, ellipticity in the polarizations of the two laser beams, and different transmission coefficients in the polarizing beam splitter. A local sensitivity analysis is first conducted to examine the sensitivities of the periodic errors with respect to each input parameter about the nominal input values. Next, a variance-based approach is used to study the global sensitivities of the periodic errors by calculating the Sobol' sensitivity indices using Monte Carlo simulation. The effect of variation in the input uncertainty on the computed sensitivity indices is examined. It is seen that the first-order periodic error is highly sensitive to non-orthogonality of the two linearly polarized laser frequencies, while the second-order error is most sensitive to the rotational misalignment between the laser beams and the polarizing beam splitter. A particle swarm optimization technique is finally used to predict the possible setup imperfections based on experimentally generated values for periodic errors.

Sample presentation, sources of error and future perspectives on the application of vibrational spectroscopy in the wine industry.

Science.gov (United States)

Cozzolino, Daniel

2015-03-30

Vibrational spectroscopy encompasses a number of techniques and methods including ultra-violet, visible, Fourier transform infrared or mid infrared, near infrared and Raman spectroscopy. The use and application of spectroscopy generates spectra containing hundreds of variables (absorbances at each wavenumbers or wavelengths), resulting in the production of large data sets representing the chemical and biochemical wine fingerprint. Multivariate data analysis techniques are then required to handle the large amount of data generated in order to interpret the spectra in a meaningful way in order to develop a specific application. This paper focuses on the developments of sample presentation and main sources of error when vibrational spectroscopy methods are applied in wine analysis. Recent and novel applications will be discussed as examples of these developments. © 2014 Society of Chemical Industry.

Bayesian ensemble approach to error estimation of interatomic potentials

DEFF Research Database (Denmark)

Frederiksen, Søren Lund; Jacobsen, Karsten Wedel; Brown, K.S.

2004-01-01

Using a Bayesian approach a general method is developed to assess error bars on predictions made by models fitted to data. The error bars are estimated from fluctuations in ensembles of models sampling the model-parameter space with a probability density set by the minimum cost. The method...... is applied to the development of interatomic potentials for molybdenum using various potential forms and databases based on atomic forces. The calculated error bars on elastic constants, gamma-surface energies, structural energies, and dislocation properties are shown to provide realistic estimates...

Errors in short circuit measurements due to spectral mismatch between sunlight and solar simulators

Science.gov (United States)

Curtis, H. B.

1976-01-01

Errors in short circuit current measurement were calculated for a variety of spectral mismatch conditions. The differences in spectral irradiance between terrestrial sunlight and three types of solar simulator were studied, as well as the differences in spectral response between three types of reference solar cells and various test cells. The simulators considered were a short arc xenon lamp AMO sunlight simulator, an ordinary quartz halogen lamp, and an ELH-type quartz halogen lamp. Three types of solar cells studied were a silicon cell, a cadmium sulfide cell and a gallium arsenide cell.

Challenge and Error: Critical Events and Attention-Related Errors

Science.gov (United States)

Cheyne, James Allan; Carriere, Jonathan S. A.; Solman, Grayden J. F.; Smilek, Daniel

2011-01-01

Attention lapses resulting from reactivity to task challenges and their consequences constitute a pervasive factor affecting everyday performance errors and accidents. A bidirectional model of attention lapses (error [image omitted] attention-lapse: Cheyne, Solman, Carriere, & Smilek, 2009) argues that errors beget errors by generating attention…

Modifying Spearman's Attenuation Equation to Yield Partial Corrections for Measurement Error--With Application to Sample Size Calculations

Science.gov (United States)

Nicewander, W. Alan

2018-01-01

Spearman's correction for attenuation (measurement error) corrects a correlation coefficient for measurement errors in either-or-both of two variables, and follows from the assumptions of classical test theory. Spearman's equation removes all measurement error from a correlation coefficient which translates into "increasing the reliability of…

Error forecasting schemes of error correction at receiver

International Nuclear Information System (INIS)

Bhunia, C.T.

2007-08-01

To combat error in computer communication networks, ARQ (Automatic Repeat Request) techniques are used. Recently Chakraborty has proposed a simple technique called the packet combining scheme in which error is corrected at the receiver from the erroneous copies. Packet Combining (PC) scheme fails: (i) when bit error locations in erroneous copies are the same and (ii) when multiple bit errors occur. Both these have been addressed recently by two schemes known as Packet Reversed Packet Combining (PRPC) Scheme, and Modified Packet Combining (MPC) Scheme respectively. In the letter, two error forecasting correction schemes are reported, which in combination with PRPC offer higher throughput. (author)

The Pupillary Orienting Response Predicts Adaptive Behavioral Adjustment after Errors.

Directory of Open Access Journals (Sweden)

Peter R Murphy

Full Text Available Reaction time (RT is commonly observed to slow down after an error. This post-error slowing (PES has been thought to arise from the strategic adoption of a more cautious response mode following deployment of cognitive control. Recently, an alternative account has suggested that PES results from interference due to an error-evoked orienting response. We investigated whether error-related orienting may in fact be a pre-cursor to adaptive post-error behavioral adjustment when the orienting response resolves before subsequent trial onset. We measured pupil dilation, a prototypical measure of autonomic orienting, during performance of a choice RT task with long inter-stimulus intervals, and found that the trial-by-trial magnitude of the error-evoked pupil response positively predicted both PES magnitude and the likelihood that the following response would be correct. These combined findings suggest that the magnitude of the error-related orienting response predicts an adaptive change of response strategy following errors, and thereby promote a reconciliation of the orienting and adaptive control accounts of PES.

A preliminary taxonomy of medical errors in family practice.

Science.gov (United States)

Dovey, S M; Meyers, D S; Phillips, R L; Green, L A; Fryer, G E; Galliher, J M; Kappus, J; Grob, P

2002-09-01

To develop a preliminary taxonomy of primary care medical errors. Qualitative analysis to identify categories of error reported during a randomized controlled trial of computer and paper reporting methods. The National Network for Family Practice and Primary Care Research. Family physicians. Medical error category, context, and consequence. Forty two physicians made 344 reports: 284 (82.6%) arose from healthcare systems dysfunction; 46 (13.4%) were errors due to gaps in knowledge or skills; and 14 (4.1%) were reports of adverse events, not errors. The main subcategories were: administrative failure (102; 30.9% of errors), investigation failures (82; 24.8%), treatment delivery lapses (76; 23.0%), miscommunication (19; 5.8%), payment systems problems (4; 1.2%), error in the execution of a clinical task (19; 5.8%), wrong treatment decision (14; 4.2%), and wrong diagnosis (13; 3.9%). Most reports were of errors that were recognized and occurred in reporters' practices. Affected patients ranged in age from 8 months to 100 years, were of both sexes, and represented all major US ethnic groups. Almost half the reports were of events which had adverse consequences. Ten errors resulted in patients being admitted to hospital and one patient died. This medical error taxonomy, developed from self-reports of errors observed by family physicians during their routine clinical practice, emphasizes problems in healthcare processes and acknowledges medical errors arising from shortfalls in clinical knowledge and skills. Patient safety strategies with most effect in primary care settings need to be broader than the current focus on medication errors.

Prevalence of refractive errors among junior high school students in ...

African Journals Online (AJOL)

Among school children, uncorrected refractive errors have a considerable impact on their participation and learning in class. The aim of this study was to assess the prevalence of refractive error among students in the Ejisu-Juabeng Municipality of Ghana. A survey with multi-stage sampling was undertaken. We interviewed ...

An Empirical State Error Covariance Matrix for Batch State Estimation

Science.gov (United States)

Frisbee, Joseph H., Jr.

2011-01-01

State estimation techniques serve effectively to provide mean state estimates. However, the state error covariance matrices provided as part of these techniques suffer from some degree of lack of confidence in their ability to adequately describe the uncertainty in the estimated states. A specific problem with the traditional form of state error covariance matrices is that they represent only a mapping of the assumed observation error characteristics into the state space. Any errors that arise from other sources (environment modeling, precision, etc.) are not directly represented in a traditional, theoretical state error covariance matrix. Consider that an actual observation contains only measurement error and that an estimated observation contains all other errors, known and unknown. It then follows that a measurement residual (the difference between expected and observed measurements) contains all errors for that measurement. Therefore, a direct and appropriate inclusion of the actual measurement residuals in the state error covariance matrix will result in an empirical state error covariance matrix. This empirical state error covariance matrix will fully account for the error in the state estimate. By way of a literal reinterpretation of the equations involved in the weighted least squares estimation algorithm, it is possible to arrive at an appropriate, and formally correct, empirical state error covariance matrix. The first specific step of the method is to use the average form of the weighted measurement residual variance performance index rather than its usual total weighted residual form. Next it is helpful to interpret the solution to the normal equations as the average of a collection of sample vectors drawn from a hypothetical parent population. From here, using a standard statistical analysis approach, it directly follows as to how to determine the standard empirical state error covariance matrix. This matrix will contain the total uncertainty in the

Negligence, genuine error, and litigation

Science.gov (United States)

Sohn, David H

2013-01-01

Not all medical injuries are the result of negligence. In fact, most medical injuries are the result either of the inherent risk in the practice of medicine, or due to system errors, which cannot be prevented simply through fear of disciplinary action. This paper will discuss the differences between adverse events, negligence, and system errors; the current medical malpractice tort system in the United States; and review current and future solutions, including medical malpractice reform, alternative dispute resolution, health courts, and no-fault compensation systems. The current political environment favors investigation of non-cap tort reform remedies; investment into more rational oversight systems, such as health courts or no-fault systems may reap both quantitative and qualitative benefits for a less costly and safer health system. PMID:23426783

Investigation of experimental pole-figure errors by simulation of individual spectra

International Nuclear Information System (INIS)

Lychagina, T. A.; Nikolaev, D. I.

2007-01-01

The errors in measuring the crystallographic texture described by pole figures are studied. A set of diffraction spectra for a sample of the MA2-1 alloy (Mg + 4.5% Al + 1% Zn) are measured, simulation of individual spectra on the basis of which the pole figures were obtained is performed, and their errors are determined. The conclusion about the possibility of determining the effect of errors of the diffraction peak half-width on the pole figure errors that was drawn in our previous studies is confirmed

'Intelligent' approach to radioimmunoassay sample counting employing a microprocessor controlled sample counter

International Nuclear Information System (INIS)

Ekins, R.P.; Sufi, S.; Malan, P.G.

1977-01-01

The enormous impact on medical science in the last two decades of microanalytical techniques employing radioisotopic labels has, in turn, generated a large demand for automatic radioisotopic sample counters. Such instruments frequently comprise the most important item of capital equipment required in the use of radioimmunoassay and related techniques and often form a principle bottleneck in the flow of samples through a busy laboratory. It is therefore particularly imperitive that such instruments should be used 'intelligently' and in an optimal fashion to avoid both the very large capital expenditure involved in the unnecessary proliferation of instruments and the time delays arising from their sub-optimal use. The majority of the current generation of radioactive sample counters nevertheless rely on primitive control mechanisms based on a simplistic statistical theory of radioactive sample counting which preclude their efficient and rational use. The fundamental principle upon which this approach is based is that it is useless to continue counting a radioactive sample for a time longer than that required to yield a significant increase in precision of the measurement. Thus, since substantial experimental errors occur during sample preparation, these errors should be assessed and must be releted to the counting errors for that sample. It is the objective of this presentation to demonstrate that the combination of a realistic statistical assessment of radioactive sample measurement, together with the more sophisticated control mechanisms that modern microprocessor technology make possible, may often enable savings in counter usage of the order of 5-10 fold to be made. (orig.) [de

Tracking errors in a prototype real-time tumour tracking system

International Nuclear Information System (INIS)

Sharp, Gregory C; Jiang, Steve B; Shimizu, Shinichi; Shirato, Hiroki

2004-01-01

In motion-compensated radiation therapy, radio-opaque markers can be implanted in or near a tumour and tracked in real-time using fluoroscopic imaging. Tracking these implanted markers gives highly accurate position information, except when tracking fails due to poor or ambiguous imaging conditions. This study investigates methods for automatic detection of tracking errors, and assesses the frequency and impact of tracking errors on treatments using the prototype real-time tumour tracking system. We investigated four indicators for automatic detection of tracking errors, and found that the distance between corresponding rays was most effective. We also found that tracking errors cause a loss of gating efficiency of between 7.6 and 10.2%. The incidence of treatment beam delivery during tracking errors was estimated at between 0.8% and 1.25%

Transfer Error and Correction Approach in Mobile Network

Science.gov (United States)

Xiao-kai, Wu; Yong-jin, Shi; Da-jin, Chen; Bing-he, Ma; Qi-li, Zhou

With the development of information technology and social progress, human demand for information has become increasingly diverse, wherever and whenever people want to be able to easily, quickly and flexibly via voice, data, images and video and other means to communicate. Visual information to the people direct and vivid image, image / video transmission also been widespread attention. Although the third generation mobile communication systems and the emergence and rapid development of IP networks, making video communications is becoming the main business of the wireless communications, however, the actual wireless and IP channel will lead to error generation, such as: wireless channel multi- fading channels generated error and blocking IP packet loss and so on. Due to channel bandwidth limitations, the video communication compression coding of data is often beyond the data, and compress data after the error is very sensitive to error conditions caused a serious decline in image quality.

Operator errors

International Nuclear Information System (INIS)

Knuefer; Lindauer

1980-01-01

Besides that at spectacular events a combination of component failure and human error is often found. Especially the Rasmussen-Report and the German Risk Assessment Study show for pressurised water reactors that human error must not be underestimated. Although operator errors as a form of human error can never be eliminated entirely, they can be minimized and their effects kept within acceptable limits if a thorough training of personnel is combined with an adequate design of the plant against accidents. Contrary to the investigation of engineering errors, the investigation of human errors has so far been carried out with relatively small budgets. Intensified investigations in this field appear to be a worthwhile effort. (orig.)

Visual disability, visual function, and myopia among rural chinese secondary school children: the Xichang Pediatric Refractive Error Study (X-PRES)--report 1.

Science.gov (United States)

Congdon, Nathan; Wang, Yunfei; Song, Yue; Choi, Kai; Zhang, Mingzhi; Zhou, Zhongxia; Xie, Zhenling; Li, Liping; Liu, Xueyu; Sharma, Abhishek; Wu, Bin; Lam, Dennis S C

2008-07-01

To evaluate visual acuity, visual function, and prevalence of refractive error among Chinese secondary-school children in a cross-sectional school-based study. Uncorrected, presenting, and best corrected visual acuity, cycloplegic autorefraction with refinement, and self-reported visual function were assessed in a random, cluster sample of rural secondary school students in Xichang, China. Among the 1892 subjects (97.3% of the consenting children, 84.7% of the total sample), mean age was 14.7 +/- 0.8 years, 51.2% were female, and 26.4% were wearing glasses. The proportion of children with uncorrected, presenting, and corrected visual disability (visual disability when tested without correction, 98.7% was due to refractive error, while only 53.8% (414/770) of these children had appropriate correction. The girls had significantly (P visual disability and myopia visual function (ANOVA trend test, P Visual disability in this population was common, highly correctable, and frequently uncorrected. The impact of refractive error on self-reported visual function was significant. Strategies and studies to understand and remove barriers to spectacle wear are needed.

A Posteriori Error Estimation for Finite Element Methods and Iterative Linear Solvers

Energy Technology Data Exchange (ETDEWEB)

Melboe, Hallgeir

2001-10-01

This thesis addresses a posteriori error estimation for finite element methods and iterative linear solvers. Adaptive finite element methods have gained a lot of popularity over the last decades due to their ability to produce accurate results with limited computer power. In these methods a posteriori error estimates play an essential role. Not only do they give information about how large the total error is, they also indicate which parts of the computational domain should be given a more sophisticated treatment in order to reduce the error. A posteriori error estimates are traditionally aimed at estimating the global error, but more recently so called goal oriented error estimators have been shown a lot of interest. The name reflects the fact that they estimate the error in user-defined local quantities. In this thesis the main focus is on global error estimators for highly stretched grids and goal oriented error estimators for flow problems on regular grids. Numerical methods for partial differential equations, such as finite element methods and other similar techniques, typically result in a linear system of equations that needs to be solved. Usually such systems are solved using some iterative procedure which due to a finite number of iterations introduces an additional error. Most such algorithms apply the residual in the stopping criterion, whereas the control of the actual error may be rather poor. A secondary focus in this thesis is on estimating the errors that are introduced during this last part of the solution procedure. The thesis contains new theoretical results regarding the behaviour of some well known, and a few new, a posteriori error estimators for finite element methods on anisotropic grids. Further, a goal oriented strategy for the computation of forces in flow problems is devised and investigated. Finally, an approach for estimating the actual errors associated with the iterative solution of linear systems of equations is suggested. (author)

How Do Simulated Error Experiences Impact Attitudes Related to Error Prevention?

Science.gov (United States)

Breitkreuz, Karen R; Dougal, Renae L; Wright, Melanie C

2016-10-01

The objective of this project was to determine whether simulated exposure to error situations changes attitudes in a way that may have a positive impact on error prevention behaviors. Using a stratified quasi-randomized experiment design, we compared risk perception attitudes of a control group of nursing students who received standard error education (reviewed medication error content and watched movies about error experiences) to an experimental group of students who reviewed medication error content and participated in simulated error experiences. Dependent measures included perceived memorability of the educational experience, perceived frequency of errors, and perceived caution with respect to preventing errors. Experienced nursing students perceived the simulated error experiences to be more memorable than movies. Less experienced students perceived both simulated error experiences and movies to be highly memorable. After the intervention, compared with movie participants, simulation participants believed errors occurred more frequently. Both types of education increased the participants' intentions to be more cautious and reported caution remained higher than baseline for medication errors 6 months after the intervention. This study provides limited evidence of an advantage of simulation over watching movies describing actual errors with respect to manipulating attitudes related to error prevention. Both interventions resulted in long-term impacts on perceived caution in medication administration. Simulated error experiences made participants more aware of how easily errors can occur, and the movie education made participants more aware of the devastating consequences of errors.

Role of memory errors in quantum repeaters

International Nuclear Information System (INIS)

Hartmann, L.; Kraus, B.; Briegel, H.-J.; Duer, W.

2007-01-01

We investigate the influence of memory errors in the quantum repeater scheme for long-range quantum communication. We show that the communication distance is limited in standard operation mode due to memory errors resulting from unavoidable waiting times for classical signals. We show how to overcome these limitations by (i) improving local memory and (ii) introducing two operational modes of the quantum repeater. In both operational modes, the repeater is run blindly, i.e., without waiting for classical signals to arrive. In the first scheme, entanglement purification protocols based on one-way classical communication are used allowing to communicate over arbitrary distances. However, the error thresholds for noise in local control operations are very stringent. The second scheme makes use of entanglement purification protocols with two-way classical communication and inherits the favorable error thresholds of the repeater run in standard mode. One can increase the possible communication distance by an order of magnitude with reasonable overhead in physical resources. We outline the architecture of a quantum repeater that can possibly ensure intercontinental quantum communication

Coping with medical error: a systematic review of papers to assess the effects of involvement in medical errors on healthcare professionals' psychological well-being.

Science.gov (United States)

Sirriyeh, Reema; Lawton, Rebecca; Gardner, Peter; Armitage, Gerry

2010-12-01

Previous research has established health professionals as secondary victims of medical error, with the identification of a range of emotional and psychological repercussions that may occur as a result of involvement in error.2 3 Due to the vast range of emotional and psychological outcomes, research to date has been inconsistent in the variables measured and tools used. Therefore, differing conclusions have been drawn as to the nature of the impact of error on professionals and the subsequent repercussions for their team, patients and healthcare institution. A systematic review was conducted. Data sources were identified using database searches, with additional reference and hand searching. Eligibility criteria were applied to all studies identified, resulting in a total of 24 included studies. Quality assessment was conducted with the included studies using a tool that was developed as part of this research, but due to the limited number and diverse nature of studies, no exclusions were made on this basis. Review findings suggest that there is consistent evidence for the widespread impact of medical error on health professionals. Psychological repercussions may include negative states such as shame, self-doubt, anxiety and guilt. Despite much attention devoted to the assessment of negative outcomes, the potential for positive outcomes resulting from error also became apparent, with increased assertiveness, confidence and improved colleague relationships reported. It is evident that involvement in a medical error can elicit a significant psychological response from the health professional involved. However, a lack of literature around coping and support, coupled with inconsistencies and weaknesses in methodology, may need be addressed in future work.

Rovno Amber Ant Assamblage: Bias toward Arboreal Strata or Sampling Effect?

Directory of Open Access Journals (Sweden)

Perkovsky E. E.

2016-06-01

Full Text Available In 2015 B. Guenard with co-authors indicated that the Rovno amber ant assemblage, as described by G. Dlussky and A. Rasnitsyn (2009, showed modest support for a bias towards arboreal origin comparing the Baltic and Bitterfeld assemblages, although it is not clear whether this reflects a sampling error or a signal of real deviation. Since 2009, the Rovno ant collection has now grown more than twice in volume which makes possible to check if the above inference about the essentially arboreal character of the assemblage is real or due to a sampling error. The comparison provided suggests in favour of the latter reason for the bias revealed by B. Guenard and co-authors. The new and larger data on the Rovno assemblage show that the share of non-arboreal ants is now well comparable with those concerning the Baltic and Bitterfeld assemblages. This holds true for the both total assemblages and subassemblages of worker ants only.

Evaluation of positioning errors of the patient using cone beam CT megavoltage; Evaluacion de errores de posicionamiento del paciente mediante Cone Beam CT de megavoltaje

Energy Technology Data Exchange (ETDEWEB)

Garcia Ruiz-Zorrilla, J.; Fernandez Leton, J. P.; Zucca Aparicio, D.; Perez Moreno, J. M.; Minambres Moro, A.

2013-07-01

Image-guided radiation therapy allows you to assess and fix the positioning of the patient in the treatment unit, thus reducing the uncertainties due to the positioning of the patient. This work assesses errors systematic and errors of randomness from the corrections made to a series of patients of different diseases through a protocol off line of cone beam CT (CBCT) megavoltage. (Author)

Due Diligence Processes for Public Acquisition of Mining-Impacted Landscapes

Science.gov (United States)

Martin, E.; Monohan, C.; Keeble-Toll, A. K.

2016-12-01

The acquisition of public land is critical for achieving conservation and habitat goals in rural regions projected to experience continuously high rates of population growth. To ensure that public funds are utilized responsibly in the purchase of conservation easements appropriate due diligence processes must be established that limit landowner liability post-acquisition. Traditional methods of characterizing contamination in regions where legacy mining activities were prevalent may not utilize current scientific knowledge and understanding of contaminant fate, transport and bioavailability, and therefore are likely to have type two error. Agency prescribed assessment methods utilized under CERLA in many cases fail to detect contamination that presents liability issues by failing to require water quality sampling that would reveal offsite transport potential of contaminants posing human health risks, including mercury. Historical analysis can be used to inform judgmental sampling to identify hotspots and contaminants of concern. Land acquisition projects at two historic mine sites in Nevada County, California, the Champion Mine Complex and the Black Swan Preserve have established the necessity of re-thinking due diligence processes for mining-impacted landscapes. These pilot projects demonstrate that pre-acquisition assessment in the Gold Country must include judgmental sampling and evaluation of contaminant transport. Best practices using the current scientific knowledge must be codified by agencies, consultants, and NGOs in order to ensure responsible use of public funds and to safeguard public health.

Advancing the research agenda for diagnostic error reduction.

Science.gov (United States)

Zwaan, Laura; Schiff, Gordon D; Singh, Hardeep

2013-10-01

Diagnostic errors remain an underemphasised and understudied area of patient safety research. We briefly summarise the methods that have been used to conduct research on epidemiology, contributing factors and interventions related to diagnostic error and outline directions for future research. Research methods that have studied epidemiology of diagnostic error provide some estimate on diagnostic error rates. However, there appears to be a large variability in the reported rates due to the heterogeneity of definitions and study methods used. Thus, future methods should focus on obtaining more precise estimates in different settings of care. This would lay the foundation for measuring error rates over time to evaluate improvements. Research methods have studied contributing factors for diagnostic error in both naturalistic and experimental settings. Both approaches have revealed important and complementary information. Newer conceptual models from outside healthcare are needed to advance the depth and rigour of analysis of systems and cognitive insights of causes of error. While the literature has suggested many potentially fruitful interventions for reducing diagnostic errors, most have not been systematically evaluated and/or widely implemented in practice. Research is needed to study promising intervention areas such as enhanced patient involvement in diagnosis, improving diagnosis through the use of electronic tools and identification and reduction of specific diagnostic process 'pitfalls' (eg, failure to conduct appropriate diagnostic evaluation of a breast lump after a 'normal' mammogram). The last decade of research on diagnostic error has made promising steps and laid a foundation for more rigorous methods to advance the field.

Examination of the program to avoid round-off error

International Nuclear Information System (INIS)

Shiota, Y.; Kusunoki, T.; Tabushi, K.; Shimomura, K.; Kitou, S.

2005-01-01

The MACRO programs which express a simple shape such as PLANE, SPHERE, CYLINDER and CONE, are used to the formation of the geometry in EGS4. Each MACRO calculates the important value for the main code to recognize the configured geometry. This calculation process may generate the calculation error due to the effect of a round-off error. SPHERE, CYLINDER and CONE MACRO include the function to avoid the effect, but PLANE MACRO dose not include. The effect of the round-off error is small usually in case of PLANE MACRO, however a slant plane may cause the expansion of the effect. Therefore, we have configured the DELPLANE program with the function to avoid the effect of the round-off error. In this study, we examine the DELPLANE program using the simply geometry with slant plane. As a result, the normal PLANE MACRO generates the round-off error, however DELPLANE program dose not generates one. (author)

Burnout, engagement and resident physicians' self-reported errors.

Science.gov (United States)

Prins, J T; van der Heijden, F M M A; Hoekstra-Weebers, J E H M; Bakker, A B; van de Wiel, H B M; Jacobs, B; Gazendam-Donofrio, S M

2009-12-01

Burnout is a work-related syndrome that may negatively affect more than just the resident physician. On the other hand, engagement has been shown to protect employees; it may also positively affect the patient care that the residents provide. Little is known about the relationship between residents' self-reported errors and burnout and engagement. In our national study that included all residents and physicians in The Netherlands, 2115 questionnaires were returned (response rate 41.1%). The residents reported on burnout (Maslach Burnout Inventory-Health and Social Services), engagement (Utrecht Work Engagement Scale) and self-assessed patient care practices (six items, two factors: errors in action/judgment, errors due to lack of time). Ninety-four percent of the residents reported making one or more mistake without negative consequences for the patient during their training. Seventy-one percent reported performing procedures for which they did not feel properly trained. More than half (56%) of the residents stated they had made a mistake with a negative consequence. Seventy-six percent felt they had fallen short in the quality of care they provided on at least one occasion. Men reported more errors in action/judgment than women. Significant effects of specialty and clinical setting were found on both types of errors. Residents with burnout reported significantly more errors (p engaged residents reported fewer errors (p burnout and to keep residents engaged in their work.

Bayesian approach to errors-in-variables in regression models

Science.gov (United States)

Rozliman, Nur Aainaa; Ibrahim, Adriana Irawati Nur; Yunus, Rossita Mohammad

2017-05-01

In many applications and experiments, data sets are often contaminated with error or mismeasured covariates. When at least one of the covariates in a model is measured with error, Errors-in-Variables (EIV) model can be used. Measurement error, when not corrected, would cause misleading statistical inferences and analysis. Therefore, our goal is to examine the relationship of the outcome variable and the unobserved exposure variable given the observed mismeasured surrogate by applying the Bayesian formulation to the EIV model. We shall extend the flexible parametric method proposed by Hossain and Gustafson (2009) to another nonlinear regression model which is the Poisson regression model. We shall then illustrate the application of this approach via a simulation study using Markov chain Monte Carlo sampling methods.

The role of comprehensive check at the blood bank reception on blood requisitions in detecting potential transfusion errors.

Science.gov (United States)

Jain, Ashish; Kumari, Sonam; Marwaha, Neelam; Sharma, Ratti Ram

2015-06-01

Pre-transfusion testing includes proper requisitions, compatibility testing and pre-release checks. Proper labelling of samples and blood units and accurate patient details check helps to minimize the risk of errors in transfusion. This study was aimed to identify requisition errors before compatibility testing. The study was conducted in the blood bank of a tertiary care hospital in north India over a period of 3 months. The requisitions were screened at the reception counter and inside the pre-transfusion testing laboratory for errors. This included checking the Central Registration number (C.R. No.) and name of patient on the requisition form and the sample label; appropriateness of sample container and sample label; incomplete requisitions; blood group discrepancy. Out of the 17,148 blood requisitions, 474 (2.76 %) requisition errors were detected before the compatibility testing. There were 192 (1.11 %) requisitions where the C.R. No. on the form and the sample were not tallying and in 70 (0.40 %) requisitions patient's name on the requisition form and the sample were different. Highest number of requisitions errors were observed in those received from the Emergency and Trauma services (27.38 %) followed by Medical wards (15.82 %) and the lowest number (3.16 %) of requisition errors were observed from Hematology and Oncology wards. C.R. No. error was the most common error observed in our study. Thus a careful check of the blood requisitions at the blood bank reception counter helps in identifying the potential transfusion errors.

A new stochastic model considering satellite clock interpolation errors in precise point positioning

Science.gov (United States)

Wang, Shengli; Yang, Fanlin; Gao, Wang; Yan, Lizi; Ge, Yulong

2018-03-01

Precise clock products are typically interpolated based on the sampling interval of the observational data when they are used for in precise point positioning. However, due to the occurrence of white noise in atomic clocks, a residual component of such noise will inevitable reside within the observations when clock errors are interpolated, and such noise will affect the resolution of the positioning results. In this paper, which is based on a twenty-one-week analysis of the atomic clock noise characteristics of numerous satellites, a new stochastic observation model that considers satellite clock interpolation errors is proposed. First, the systematic error of each satellite in the IGR clock product was extracted using a wavelet de-noising method to obtain the empirical characteristics of atomic clock noise within each clock product. Then, based on those empirical characteristics, a stochastic observation model was structured that considered the satellite clock interpolation errors. Subsequently, the IGR and IGS clock products at different time intervals were used for experimental validation. A verification using 179 stations worldwide from the IGS showed that, compared with the conventional model, the convergence times using the stochastic model proposed in this study were respectively shortened by 4.8% and 4.0% when the IGR and IGS 300-s-interval clock products were used and by 19.1% and 19.4% when the 900-s-interval clock products were used. Furthermore, the disturbances during the initial phase of the calculation were also effectively improved.

Approaches to relativistic positioning around Earth and error estimations

Science.gov (United States)

Puchades, Neus; Sáez, Diego

2016-01-01

In the context of relativistic positioning, the coordinates of a given user may be calculated by using suitable information broadcast by a 4-tuple of satellites. Our 4-tuples belong to the Galileo constellation. Recently, we estimated the positioning errors due to uncertainties in the satellite world lines (U-errors). A distribution of U-errors was obtained, at various times, in a set of points covering a large region surrounding Earth. Here, the positioning errors associated to the simplifying assumption that photons move in Minkowski space-time (S-errors) are estimated and compared with the U-errors. Both errors have been calculated for the same points and times to make comparisons possible. For a certain realistic modeling of the world line uncertainties, the estimated S-errors have proved to be smaller than the U-errors, which shows that the approach based on the assumption that the Earth's gravitational field produces negligible effects on photons may be used in a large region surrounding Earth. The applicability of this approach - which simplifies numerical calculations - to positioning problems, and the usefulness of our S-error maps, are pointed out. A better approach, based on the assumption that photons move in the Schwarzschild space-time governed by an idealized Earth, is also analyzed. More accurate descriptions of photon propagation involving non symmetric space-time structures are not necessary for ordinary positioning and spacecraft navigation around Earth.

Missing citations due to exact reference matching: Analysis of a random sample from WoS. Are publications from peripheral countries disadvantaged?

Energy Technology Data Exchange (ETDEWEB)

Donner, P.

2016-07-01

Citation counts of scientific research contributions are one fundamental data in scientometrics. Accuracy and completeness of citation links are therefore crucial data quality issues (Moed, 2005, Ch. 13). However, despite the known flaws of reference matching algorithms, usually no attempts are made to incorporate uncertainty about citation counts into indicators. This study is a step towards that goal. Particular attention is paid to the question whether publications from countries not using basic Latin script are differently affected by missed citations. The proprietary reference matching procedure of Web of Science (WoS) is based on (near) exact agreement of cited reference data (normalized during processing) to the target papers bibliographical data. Consequently, the procedure has near-optimal precision but incomplete recall - it is known to miss some slightly inaccurate reference links (Olensky, 2015). However, there has been no attempt so far to estimate the rate of missed citations by a principled method for a random sample. For this study a simple random sample of WoS source papers was drawn and it was attempted to find all reference strings of WoS indexed documents that refer to them, in particular inexact matches. The objective is to give a statistical estimate of the proportion of missed citations and to describe the relationship of the number of found citations to the number of missed citations, i.e. the conditional error distribution. The empirical error distribution is statistically analyzed and modelled. (Author)

Quantum superposition of the state discrete spectrum of mathematical correlation molecule for small samples of biometric data

Directory of Open Access Journals (Sweden)

Vladimir I. Volchikhin

2017-06-01

Full Text Available Introduction: The study promotes to decrease a number of errors of calculating the correlation coefficient in small test samples. Materials and Methods: We used simulation tool for the distribution functions of the density values of the correlation coefficient in small samples. A method for quantization of the data, allows obtaining a discrete spectrum states of one of the varieties of correlation functional. This allows us to consider the proposed structure as a mathematical correlation molecule, described by some analogue continuous-quantum Schrödinger equation. Results: The chi-squared Pearson’s molecule on small samples allows enhancing power of classical chi-squared test to 20 times. A mathematical correlation molecule described in the article has similar properties. It allows in the future reducing calculation errors of the classical correlation coefficients in small samples. Discussion and Conclusions: The authors suggest that there are infinitely many mathematical molecules are similar in their properties to the actual physical molecules. Schrödinger equations are not unique, their analogues can be constructed for each mathematical molecule. You can expect a mathematical synthesis of molecules for a large number of known statistical tests and statistical moments. All this should make it possible to reduce calculation errors due to quantum effects that occur in small test samples.

Equating error in observed-score equating

NARCIS (Netherlands)

van der Linden, Willem J.

2006-01-01

Traditionally, error in equating observed scores on two versions of a test is defined as the difference between the transformations that equate the quantiles of their distributions in the sample and population of test takers. But it is argued that if the goal of equating is to adjust the scores of

Slope Error Measurement Tool for Solar Parabolic Trough Collectors: Preprint

Energy Technology Data Exchange (ETDEWEB)

Stynes, J. K.; Ihas, B.

2012-04-01

The National Renewable Energy Laboratory (NREL) has developed an optical measurement tool for parabolic solar collectors that measures the combined errors due to absorber misalignment and reflector slope error. The combined absorber alignment and reflector slope errors are measured using a digital camera to photograph the reflected image of the absorber in the collector. Previous work using the image of the reflection of the absorber finds the reflector slope errors from the reflection of the absorber and an independent measurement of the absorber location. The accuracy of the reflector slope error measurement is thus dependent on the accuracy of the absorber location measurement. By measuring the combined reflector-absorber errors, the uncertainty in the absorber location measurement is eliminated. The related performance merit, the intercept factor, depends on the combined effects of the absorber alignment and reflector slope errors. Measuring the combined effect provides a simpler measurement and a more accurate input to the intercept factor estimate. The minimal equipment and setup required for this measurement technique make it ideal for field measurements.

Field error lottery

Energy Technology Data Exchange (ETDEWEB)

Elliott, C.J.; McVey, B. (Los Alamos National Lab., NM (USA)); Quimby, D.C. (Spectra Technology, Inc., Bellevue, WA (USA))

1990-01-01

The level of field errors in an FEL is an important determinant of its performance. We have computed 3D performance of a large laser subsystem subjected to field errors of various types. These calculations have been guided by simple models such as SWOOP. The technique of choice is utilization of the FELEX free electron laser code that now possesses extensive engineering capabilities. Modeling includes the ability to establish tolerances of various types: fast and slow scale field bowing, field error level, beam position monitor error level, gap errors, defocusing errors, energy slew, displacement and pointing errors. Many effects of these errors on relative gain and relative power extraction are displayed and are the essential elements of determining an error budget. The random errors also depend on the particular random number seed used in the calculation. The simultaneous display of the performance versus error level of cases with multiple seeds illustrates the variations attributable to stochasticity of this model. All these errors are evaluated numerically for comprehensive engineering of the system. In particular, gap errors are found to place requirements beyond mechanical tolerances of {plus minus}25{mu}m, and amelioration of these may occur by a procedure utilizing direct measurement of the magnetic fields at assembly time. 4 refs., 12 figs.

Propagation of resist heating mask error to wafer level

Science.gov (United States)

Babin, S. V.; Karklin, Linard

2006-10-01

As technology is approaching 45 nm and below the IC industry is experiencing a severe product yield hit due to rapidly shrinking process windows and unavoidable manufacturing process variations. Current EDA tools are unable by their nature to deliver optimized and process-centered designs that call for 'post design' localized layout optimization DFM tools. To evaluate the impact of different manufacturing process variations on final product it is important to trace and evaluate all errors through design to manufacturing flow. Photo mask is one of the critical parts of this flow, and special attention should be paid to photo mask manufacturing process and especially to mask tight CD control. Electron beam lithography (EBL) is a major technique which is used for fabrication of high-end photo masks. During the writing process, resist heating is one of the sources for mask CD variations. Electron energy is released in the mask body mainly as heat, leading to significant temperature fluctuations in local areas. The temperature fluctuations cause changes in resist sensitivity, which in turn leads to CD variations. These CD variations depend on mask writing speed, order of exposure, pattern density and its distribution. Recent measurements revealed up to 45 nm CD variation on the mask when using ZEP resist. The resist heating problem with CAR resists is significantly smaller compared to other types of resists. This is partially due to higher resist sensitivity and the lower exposure dose required. However, there is no data yet showing CD errors on the wafer induced by CAR resist heating on the mask. This effect can be amplified by high MEEF values and should be carefully evaluated at 45nm and below technology nodes where tight CD control is required. In this paper, we simulated CD variation on the mask due to resist heating; then a mask pattern with the heating error was transferred onto the wafer. So, a CD error on the wafer was evaluated subject to only one term of the

Wind speed errors for LIDARs and SODARs in complex terrain

International Nuclear Information System (INIS)

Bradley, S

2008-01-01

All commercial LIDARs and SODARs are monostatic and hence sample distributed volumes to construct wind vector components. We use an analytic potential flow model to estimate errors arising for a range of LIDAR and SODAR configurations on hills and escarpments. Wind speed errors peak at a height relevant to wind turbines and can be typically 20%

Wind speed errors for LIDARs and SODARs in complex terrain

Energy Technology Data Exchange (ETDEWEB)

Bradley, S [Physics Department, The University of Auckland, Private Bag 92019, Auckland (New Zealand) and School of Computing, Science and Engineering, University of Salford, M5 4WT (United Kingdom)], E-mail: s.bradley@auckland.ac.nz

2008-05-01

All commercial LIDARs and SODARs are monostatic and hence sample distributed volumes to construct wind vector components. We use an analytic potential flow model to estimate errors arising for a range of LIDAR and SODAR configurations on hills and escarpments. Wind speed errors peak at a height relevant to wind turbines and can be typically 20%.

Dependence of fluence errors in dynamic IMRT on leaf-positional errors varying with time and leaf number

International Nuclear Information System (INIS)

Zygmanski, Piotr; Kung, Jong H.; Jiang, Steve B.; Chin, Lee

2003-01-01

In d-MLC based IMRT, leaves move along a trajectory that lies within a user-defined tolerance (TOL) about the ideal trajectory specified in a d-MLC sequence file. The MLC controller measures leaf positions multiple times per second and corrects them if they deviate from ideal positions by a value greater than TOL. The magnitude of leaf-positional errors resulting from finite mechanical precision depends on the performance of the MLC motors executing leaf motions and is generally larger if leaves are forced to move at higher speeds. The maximum value of leaf-positional errors can be limited by decreasing TOL. However, due to the inherent time delay in the MLC controller, this may not happen at all times. Furthermore, decreasing the leaf tolerance results in a larger number of beam hold-offs, which, in turn leads, to a longer delivery time and, paradoxically, to higher chances of leaf-positional errors (≤TOL). On the other end, the magnitude of leaf-positional errors depends on the complexity of the fluence map to be delivered. Recently, it has been shown that it is possible to determine the actual distribution of leaf-positional errors either by the imaging of moving MLC apertures with a digital imager or by analysis of a MLC log file saved by a MLC controller. This leads next to an important question: What is the relation between the distribution of leaf-positional errors and fluence errors. In this work, we introduce an analytical method to determine this relation in dynamic IMRT delivery. We model MLC errors as Random-Leaf Positional (RLP) errors described by a truncated normal distribution defined by two characteristic parameters: a standard deviation σ and a cut-off value Δx 0 (Δx 0 ∼TOL). We quantify fluence errors for two cases: (i) Δx 0 >>σ (unrestricted normal distribution) and (ii) Δx 0 0 --limited normal distribution). We show that an average fluence error of an IMRT field is proportional to (i) σ/ALPO and (ii) Δx 0 /ALPO, respectively, where

Medication errors of nurses and factors in refusal to report medication errors among nurses in a teaching medical center of iran in 2012.

Science.gov (United States)

Mostafaei, Davoud; Barati Marnani, Ahmad; Mosavi Esfahani, Haleh; Estebsari, Fatemeh; Shahzaidi, Shiva; Jamshidi, Ensiyeh; Aghamiri, Seyed Samad

2014-10-01

About one third of unwanted reported medication consequences are due to medication errors, resulting in one-fifth of hospital injuries. The aim of this study was determined formal and informal medication errors of nurses and the level of importance of factors in refusal to report medication errors among nurses. The cross-sectional study was done on the nursing staff of Shohada Tajrish Hospital, Tehran, Iran in 2012. The data was gathered through a questionnaire, made by the researchers. The questionnaires' face and content validity was confirmed by experts and for measuring its reliability test-retest was used. The data was analyzed by descriptive statistics. We used SPSS for related statistical analyses. The most important factors in refusal to report medication errors respectively were: lack of medication error recording and reporting system in the hospital (3.3%), non-significant error reporting to hospital authorities and lack of appropriate feedback (3.1%), and lack of a clear definition for a medication error (3%). There were both formal and informal reporting of medication errors in this study. Factors pertaining to management in hospitals as well as the fear of the consequences of reporting are two broad fields among the factors that make nurses not report their medication errors. In this regard, providing enough education to nurses, boosting the job security for nurses, management support and revising related processes and definitions are some factors that can help decreasing medication errors and increasing their report in case of occurrence.

[Medication errors in Spanish intensive care units].

Science.gov (United States)

Merino, P; Martín, M C; Alonso, A; Gutiérrez, I; Alvarez, J; Becerril, F

2013-01-01

To estimate the incidence of medication errors in Spanish intensive care units. Post hoc study of the SYREC trial. A longitudinal observational study carried out during 24 hours in patients admitted to the ICU. Spanish intensive care units. Patients admitted to the intensive care unit participating in the SYREC during the period of study. Risk, individual risk, and rate of medication errors. The final study sample consisted of 1017 patients from 79 intensive care units; 591 (58%) were affected by one or more incidents. Of these, 253 (43%) had at least one medication-related incident. The total number of incidents reported was 1424, of which 350 (25%) were medication errors. The risk of suffering at least one incident was 22% (IQR: 8-50%) while the individual risk was 21% (IQR: 8-42%). The medication error rate was 1.13 medication errors per 100 patient-days of stay. Most incidents occurred in the prescription (34%) and administration (28%) phases, 16% resulted in patient harm, and 82% were considered "totally avoidable". Medication errors are among the most frequent types of incidents in critically ill patients, and are more common in the prescription and administration stages. Although most such incidents have no clinical consequences, a significant percentage prove harmful for the patient, and a large proportion are avoidable. Copyright © 2012 Elsevier España, S.L. and SEMICYUC. All rights reserved.

Pharyngitis – fatal infectious disease or medical error?

Directory of Open Access Journals (Sweden)

Marta Rorat

2015-08-01

Full Text Available Reporting on adverse events is essential to create a culture of safety, which focuses on protecting doctors and patients from medical errors. We present a fatal case of Streptococcus C pharyngitis in a 56-year-old man. The clinical course and the results of additional diagnostics and autopsy showed that sepsis followed by multiple organ failure was the ultimate cause of death. The clinical course appeared fatal due to a chain of adverse events, including errors made by the physicians caring for the patient for 10 days.

The use of gamma ray computed tomography to investigate soil compaction due to core sampling devices

International Nuclear Information System (INIS)

Pires, Luiz F.; Arthur, Robson C.J.; Correchel, Vladia; Bacchi, Osny O.S.; Reichardt, Klaus; Brasil, Rene P. Camponez do

2004-01-01

Compaction processes can influence soil physical properties such as soil density, porosity, pore size distribution, and processes like soil water and nutrient movements, root system distribution, and others. Soil porosity modification has important consequences like alterations in results of soil water retention curves. These alterations may cause differences in soil water storage calculations and matrix potential values, which are utilized in irrigation management systems. Because of this, soil-sampling techniques should avoid alterations of sample structure. In this work soil sample compaction caused by core sampling devices was investigated using the gamma ray computed tomography technique. A first generation tomograph with fixed source-detector arrangement and translation/rotational movements of the sample was utilized to obtain the images. The radioactive source is 241 Am, with an activity of 3.7 GBq, and the detector consists of a 3 in. x 3 in. NaI(Tl) scintillation crystal coupled to a photomultiplier tube. Soil samples were taken from an experimental field utilizing cylinders 4.0 cm high and 2.6 cm in diameter. Based on image analyses it was possible to detect compacted regions in all samples next to the cylinder wall due to the sampling system. Tomographic unit profiles of the sample permitted to identify higher values of soil density for deeper regions of the sample, and it was possible to determine the average densities and thickness of these layers. Tomographic analyses showed to be a very useful tool for soil compaction characterization and presented many advantages in relation to traditional methods. (author)

An 'intelligent' approach to radioimmunoassay sample counting employing a microprocessor-controlled sample counter

International Nuclear Information System (INIS)

Ekins, R.P.; Sufi, S.; Malan, P.G.

1978-01-01

The enormous impact on medical science in the last two decades of microanalytical techniques employing radioisotopic labels has, in turn, generated a large demand for automatic radioisotopic sample counters. Such instruments frequently comprise the most important item of capital equipment required in the use of radioimmunoassay and related techniques and often form a principle bottleneck in the flow of samples through a busy laboratory. It is therefore imperative that such instruments should be used 'intelligently' and in an optimal fashion to avoid both the very large capital expenditure involved in the unnecessary proliferation of instruments and the time delays arising from their sub-optimal use. Most of the current generation of radioactive sample counters nevertheless rely on primitive control mechanisms based on a simplistic statistical theory of radioactive sample counting which preclude their efficient and rational use. The fundamental principle upon which this approach is based is that it is useless to continue counting a radioactive sample for a time longer than that required to yield a significant increase in precision of the measurement. Thus, since substantial experimental errors occur during sample preparation, these errors should be assessed and must be related to the counting errors for that sample. The objective of the paper is to demonstrate that the combination of a realistic statistical assessment of radioactive sample measurement, together with the more sophisticated control mechanisms that modern microprocessor technology make possible, may often enable savings in counter usage of the order of 5- to 10-fold to be made. (author)

Analytical expression for the bit error rate of cascaded all-optical regenerators

DEFF Research Database (Denmark)

Mørk, Jesper; Öhman, Filip; Bischoff, S.

2003-01-01

We derive an approximate analytical expression for the bit error rate of cascaded fiber links containing all-optical 2R-regenerators. A general analysis of the interplay between noise due to amplification and the degree of reshaping (nonlinearity) of the regenerator is performed.......We derive an approximate analytical expression for the bit error rate of cascaded fiber links containing all-optical 2R-regenerators. A general analysis of the interplay between noise due to amplification and the degree of reshaping (nonlinearity) of the regenerator is performed....

Medication administration errors in Eastern Saudi Arabia

International Nuclear Information System (INIS)

Mir Sadat-Ali

2010-01-01

To assess the prevalence and characteristics of medication errors (ME) in patients admitted to King Fahd University Hospital, Alkhobar, Kingdom of Saudi Arabia. Medication errors are documented by the nurses and physicians standard reporting forms (Hospital Based Incident Report). The study was carried out in King Fahd University Hospital, Alkhobar, Kingdom of Saudi Arabia and all the incident reports were collected during the period from January 2008 to December 2009. The incident reports were analyzed for age, gender, nationality, nursing unit, and time where ME was reported. The data were analyzed and the statistical significance differences between groups were determined by Student's t-test, and p-values of <0.05 using confidence interval of 95% were considered significant. There were 38 ME reported for the study period. The youngest patient was 5 days and the oldest 70 years. There were 31 Saudis, and 7 non-Saudi patients involved. The most common error was missed medication, which was seen in 15 (39.5%) patients. Over 15 (39.5%) of errors occurred in 2 units (pediatric medicine, and obstetrics and gynecology). Nineteen (50%) of the errors occurred during the 3-11 pm shift. Our study shows that the prevalence of ME in our institution is low, in comparison with the world literature. This could be due to under reporting of the errors, and we believe that ME reporting should be made less punitive so that ME can be studied and preventive measures implemented (Author).

Effects of Target Positioning Error on Motion Compensation for Airborne Interferometric SAR

Directory of Open Access Journals (Sweden)

Li Yin-wei

2013-12-01

Full Text Available The measurement inaccuracies of Inertial Measurement Unit/Global Positioning System (IMU/GPS as well as the positioning error of the target may contribute to the residual uncompensated motion errors in the MOtion COmpensation (MOCO approach based on the measurement of IMU/GPS. Aiming at the effects of target positioning error on MOCO for airborne interferometric SAR, the paper firstly deduces a mathematical model of residual motion error bring out by target positioning error under the condition of squint. And the paper analyzes the effects on the residual motion error caused by system sampling delay error, the Doppler center frequency error and reference DEM error which result in target positioning error based on the model. Then, the paper discusses the effects of the reference DEM error on the interferometric SAR image quality, the interferometric phase and the coherent coefficient. The research provides theoretical bases for the MOCO precision in signal processing of airborne high precision SAR and airborne repeat-pass interferometric SAR.