Search results for "ERROR"

Investigations into under-registration of costumers meters in Palermo (Italy) and the effect of introducing unmetered flow reducers

2009

A posteriori error estimates for Webster's equation in wave propagation

2015

We consider a generalised Webster’s equation for describing wave propagation in curved tubular structures such as variable diameter acoustic wave guides. Webster’s equation in generalised form has been rigorously derived in a previous article starting from the wave equation, and it approximates cross-sectional averages of the propagating wave. Here, the approximation error is estimated by an a posteriori technique. peerReviewed

Comparison of higher order aberrations measured by NIDEK OPD-Scan dynamic skiascopy and Zeiss WASCA Hartmann-Shack aberrometers.

2008

<h4>PURPOSE</h4><p>To compare the measurement of wavefront aberrations in non-cyclopleged human eyes with Hartmann-Shack and dynamic skiascopy wavefront analyzers.</p> <h4>METHODS</h4><p>Eighty eyes of 40 healthy young adults (19 men, 21 women; mean age 20.8±2.5 years) with refractive errors ranging from +1.50 to –9.75 diopters (D) sphere and up to 1.75 D cylinder (mean spherical equivalent refraction –2.12±2.69 D) were examined with the Zeiss/Meditec WASCA and NIDEK OPD-Scan wavefront analyzers and with the Nippon SRW5000 binocular, open-field autorefractor without the instillation of antimuscarinic agents. Three measurements were taken with each s…

A pilot study on the differences in wavefront aberrations between two ethnic groups of young generally myopic subjects

2008

A comparative population-based cross-sectional study design was used to examine the prevalence of wavefront patterns in two different ethnic groups, and the relationship of these patterns with ocular biometrics and gender. The Shin–Nippon SRW5000 open field autorefractor, the Wavefront Analysis Supported Customized Ablation (WASCA) wavefront analyser and the IOLMaster were used to determine wavefront aberrations, mean spherical equivalent (SE) refractive error and axial length (AL). Seventy-four eyes from 74 young healthy subjects (44 British Asians, 30 Caucasians; 36 men, 38 women; mean age 22.51 ± 3.89 years) with mean SE averaging )1.90 ± 2.76 D (range )10.88 to +2.19 D) were examined. R…

Neural Adaptation to Optical Quality Defects

2010

From an optical perspective the eye is far from perfect. This is a fact that is extensively supported by literature; for instance, Prof. Navarro recently provided us with a fantastic critical review on the various theories behind the different eye models and their flaws.1 The human eye has considerable amounts of higher-order aberrations even when it is emmetropic,2 with great inter-individual variability. Besides, higher-order aberrations are still postulated to have a role in the development of the refractive error, although it is not clear the extent to which this may be (see Charman WN for a review).3 The known optical limitations of the normal human eye raised the question as to what t…

Accessibility of the Italian institutional web pages: a survey on the compliance of the Italian public administration web pages to the Stanca Act and…

2014

Accessibility of the Italian public administration web pages is ruled by the Stanca Act and in particular the Decree of the Minister issued on July 8, 2005. In this paper, an objective test is performed on the official web pages of the Italian province and region chief towns to check their compliance to the 22 technical requirements defined by the Stanca Act. A sample of 976 web pages belonging to the websites of the Italian chief towns have been downloaded in the period October---December 2012. Such a data collection has been submitted to Achecker, the worldwide recognized syntax and accessibility validation service. Several accessibility and syntax errors have been found following the aut…

Constructing Knowledge through a Role-Play in a Web-Based Learning Environment

2003

This study aimed to find out how and on what level the students of two separate secondary schools shared and constructed knowledge on imperialism by interacting through historical role characters in a Web-based environment. Furthermore, the study aimed to find out how social and contextual features affected the nature of knowledge sharing and construction. The data about the history project were gathered by various means in order to validate the findings of the case study. The results demonstrated that the level of the Web-based messages remained quite low. Also the use of the Web-based environment in terms of shared knowledge construction was rather weak. In comparison, different instruct…

Detection of bias errors in ETAASDetermination of copper in beer and wine samples

2005

A method that evidences changes in the shape of the absorbance profiles obtained by graphite furnace atomic absorption spectrometry (ETAAS) is proposed. The method is based upon the apparent content curves model previously described for molecular spectroscopy and it permits the detection of possible sources of bias errors. Moreover, a procedure that allows to detect the existence of constant and/or proportional errors is also described. Both models has been applied to the determination of copper in wine and beer samples with and without pre-treatment of the samples. Results obtained evidence the usefulness of the proposed models.

Overdispersion tests in count-data analysis.

2008

Count data are commonly assumed to have a Poisson distribution, especially when there is no diagnostic procedure for checking this assumption. However, count data rarely fit the restrictive assumptions of the Poisson distribution. The violation of much of such assumptions commonly results in overdispersion, which invalidates the Poisson distribution. Undetected overdispersion may entail important misleading inferences, so its detection is essential. In this study, different overdispersion diagnostic tests are evaluated through two simulation studies. In Exp. 1, the nominal error rate is compared under different sample sizes and Λ conditions. Analysis shows a remarkable performance of the χ…

SisHiTra : A Hybrid Machine Translation System from Spanish to Catalan

2004

In the current European scenario, characterized by the coexistence of communities writing and speaking a great variety of languages, machine translation has become a technology of capital importance. In areas of Spain and of other countries, coofficiality of several languages implies producing several versions of public information. Machine translation between all the languages of the Iberian Peninsula and from them into English will allow for a better integration of Iberian linguistic communities among them and inside Europe. The purpose of this paper is to show a machine translation system from Spanish to Catalan that deals with text input. In our approach, both deductive (linguistic) and…