900 resultados para technical error of measurement


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This article deals with complex material flow systems and series connections of conveyor and op-erating elements. These can be characterised by a specific availability. The thus resultant overall availabil-ity of necessary “technical throughput” of the individual elements for the achievement of a specified throughput. When the conveyor and operating elements are subjected to a stochastic distribution, the interposition of buffers is necessary but these can also lead to a reduction of the necessary throughput due faults. The system behaviour of complex installations can only be investigated by simulation. The parame-ter changes required in order to achieve specific target values can also be determined by simulation runs in iteration loops.

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RATIONALE In biomedical journals authors sometimes use the standard error of the mean (SEM) for data description, which has been called inappropriate or incorrect. OBJECTIVE To assess the frequency of incorrect use of SEM in articles in three selected cardiovascular journals. METHODS AND RESULTS All original journal articles published in 2012 in Cardiovascular Research, Circulation: Heart Failure and Circulation Research were assessed by two assessors for inappropriate use of SEM when providing descriptive information of empirical data. We also assessed whether the authors state in the methods section that the SEM will be used for data description. Of 441 articles included in this survey, 64% (282 articles) contained at least one instance of incorrect use of the SEM, with two journals having a prevalence above 70% and "Circulation: Heart Failure" having the lowest value (27%). In 81% of articles with incorrect use of SEM, the authors had explicitly stated that they use the SEM for data description and in 89% SEM bars were also used instead of 95% confidence intervals. Basic science studies had a 7.4-fold higher level of inappropriate SEM use (74%) than clinical studies (10%). LIMITATIONS The selection of the three cardiovascular journals was based on a subjective initial impression of observing inappropriate SEM use. The observed results are not representative for all cardiovascular journals. CONCLUSION In three selected cardiovascular journals we found a high level of inappropriate SEM use and explicit methods statements to use it for data description, especially in basic science studies. To improve on this situation, these and other journals should provide clear instructions to authors on how to report descriptive information of empirical data.

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Several intervals have been proposed to quantify the agreement of two methods intended to measure the same quantity in the situation where only one measurement per method and subject is available. The limits of agreement are probably the most well-known among these intervals, which are all based on the differences between the two measurement methods. The different meanings of the intervals are not always properly recognized in applications. However, at least for small-to-moderate sample sizes, the differences will be substantial. This is illustrated both using the width of the intervals and on probabilistic scales related to the definitions of the intervals. In particular, for small-to-moderate sample sizes, it is shown that limits of agreement and prediction intervals should not be used to make statements about the distribution of the differences between the two measurement methods or about a plausible range for all future differences. Care should therefore be taken to ensure the correct choice of the interval for the intended interpretation.

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This paper uses Data Envelopment Analysis to examine changes in levels of technical efficiency over time in China's state-owned enterprises (SOEs) during 1980-1989. Our paper adds to the growing body of literature in this area by obtaining measures of technical efficiency of individual SOEs over years and by identifying how different aspects of the reforms have affected efficiency. We estimate a Tobit regression model, using the technical efficiency score as the dependent variable and a set of reform variables and firm attributes as regressors. We find that specific aspects of the reforms were very effective in improving technical efficiency.

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This archive consists of the hydrographic data collected on Cruise 82-002 of C.S.S. Hudson, April 11 to May 2, 1982. 78 stations were occupied on a line running near 48°N from the mouth of the English Channel to the Grand Banks of Newfoundland. Pressure, temperature and salinity were measured by a Guildline digital CTP system. Salinity, dissolved oxygen, silicate, nitrate and phosphate were measured from water samples collected on the CTP upcasts. CTP and discrete bottle data and associated derived parameters are tabulated at standard levels. This is the digital version of the printed report (of 1989, see further details), published in 2006 with the information system Pangaea.

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This article describes a research project involving students from nine different engineering degrees at the Technical university of Madrid. The purpose of the project was to analyze the use of peer and self assessment and the students? attitudes toward alternative assessment procedures.

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The apparition of new mobile phones operating systems often leads to a flood of mobile applications rushing into the market without taking into account needs of the most vulnerable users groups: the people with disabilities. The need of accessible applications for mobile is very important especially when it comes to access basic mobile functions such as making calls through a contact manager. This paper presents the technical validation process and results of an Accessible Contact Manager for mobile phones as a part of the evaluation of accessible applications for mobile phones for people with disabilities.

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The competence evaluation promoted by the European High Education Area entails a very important methodological change that requires guiding support to help teachers carry out this new and complex task. In this regard, the Technical University of Madrid (UPM, by its Spanish acronym) has financed a series of coordinated projects with a two-fold objective: a) To develop a model for teaching and evaluating core competences that is useful and easily applicable to its different degrees, and b) to provide support to teachers by creating an area within the Website for Educational Innovation where they can search for information on the model corresponding to each core competence approved by UPM. Information available on each competence includes its definition, the formulation of indicators providing evidence on the level of acquisition, the recommended teaching and evaluation methodology, examples of evaluation rules for the different levels of competence acquisition, and descriptions of best practices. These best practices correspond to pilot tests applied to several of the academic subjects conducted at UPM in order to validate the model. This work describes the general procedure that was used and presents the model developed specifically for the problem-solving competence. Some of the pilot experiences are also summarised and their results analysed

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The verification of compliance with a design specification in manufacturing requires the use of metrological instruments to check if the magnitude associated with the design specification is or not according with tolerance range. Such instrumentation and their use during the measurement process, has associated an uncertainty of measurement whose value must be related to the value of tolerance tested. Most papers dealing jointly tolerance and measurement uncertainties are mainly focused on the establishment of a relationship uncertainty-tolerance without paying much attention to the impact from the standpoint of process cost. This paper analyzes the cost-measurement uncertainty, considering uncertainty as a productive factor in the process outcome. This is done starting from a cost-tolerance model associated with the process. By means of this model the existence of a measurement uncertainty is calculated in quantitative terms of cost and its impact on the process is analyzed.

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Se analiza el absentismo, el fallo y el abandono de los estudiantes en los primeros semestres del grado sobre la base de su formación en la educación secundaria.

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During the first decade of the new millennium, fueled by the economic development in Spain, urban bus services were extended. Since the years 2008 and 2009, the root of the economic crisis, the improvement of these services is at risk due to economic problems. In this paper, the technical efficiency of the main urban bus companies in Spain during the 2004–2009 period are studied using SBM (slack-based measures) models and by establishing the slacks in the services' production inputs. The influence of a series of exogenous variables on the operation of the different services is also analyzed. It is concluded that only the 24% of the case studies are efficient, and some urban form variables can explain part of the inefficiency. The methodology used allows studying the inefficiency in a disaggregated way that other DEA (data envelopment analysis) models do not.

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We present and analyze the results of surveys conducted in recent years with students from two related subjects, but taught in different centers of the University of Madrid. These surveys are part of the objectives of various projects of educational innovation, and applied through the platform Moodle.