Calibration Conditions Research Articles

65 - Influence of the calibration conditions of Gafchromic film on the measurement of skin dose in interventional radiology

65 - Influence of the calibration conditions of Gafchromic film on the measurement of skin dose in interventional radiology

Analysis of Water Quality Impact for Water Intake in Jinyang Reservoir Using CE-QUAL-W2

Hydraulic and water quality models with high reliability are necessary for the efficient management of water quality in the reservoir. The model capacity can be demonstrated by the application for the various hydrological conditions. CE-QUAL-W2 model is laterally averaged two-dimensional hydraulic and water quality model. The W2 model, which is suitable for the narrow reservoir like the Jinyang reservoir as compared with the depth and length of waterbody, has been frequently used by many researchers. Namgang watershed is expected to increase the water demand. In this study, the W2 model is validated under two different hydrological conditions; wet year (2011) and normal year (2009). Using hydrological and water quality condition for calibration, 2011, the effect of water intake increase was simulated. The simulation results showed that the increase of water intake led to increase the concentrations in total nitrogen, total phosphorus and Chlorophyll- concentration. Especially the concentration increase was appeared during the dry season in each of up to 62.53% (Total nitrogen), 39.07% (Total phosphorus) and 232.19% (Chlorophyll-). The changes of chlorophyll- is similar to those of total phosphorus concentration.

Uncertainty assessment of enthalpy of fusion measurements performed by using an improved Calvet calorimeter

The French National Metrology Institute LNE-LCM has developed a new in situ electrical calibration system which is integrated into a heat flux Calvet calorimeter in order to perform accurate and reliable measurements of enthalpy of fusion from 23 °C to 1000 °C. The measurement procedure consists in putting a sample inside the calibration system and in performing the heat calibration of the calorimeter by electrical substitution (Joule effect) before and after the enthalpy of fusion measurement during the same heating run. This procedure directly takes into account the temperature dependence of the calibration factor (sensitivity) and keeps the calibration and measurement experimental conditions strictly the same. Uncertainties of the enthalpy of fusion measurements, performed by using this facility and procedure, have been assessed according to the ‘guide to the expression of uncertainty in measurement’. The detailed uncertainty budgets are presented here in the case of three pure metallic materials (indium, tin and silver). The relative expanded uncertainty (k = 2) of the enthalpy of fusion measurement is estimated to be less than 0.4% for the high purity indium and tin, and less than 1% in the case of silver.

The mean photon energy ĒF at the point of measurement determines the detector-specific radiation quality correction factor kQ,M in 192Ir brachytherapy dosimetry

The application of various radiation detectors for brachytherapy dosimetry has motivated this study of the energy dependence of radiation quality correction factor kQ,M, the quotient of the detector responses under calibration conditions at a 60Co unit and under the given non-reference conditions at the point of measurement, M, occurring in photon brachytherapy. The investigated detectors comprise TLD, radiochromic film, ESR, Si diode, plastic scintillator and diamond crystal detectors as well as ionization chambers of various sizes, whose measured response-energy relationships, taken from the literature, served as input data. Brachytherapy photon fields were Monte-Carlo simulated for an ideal isotropic 192Ir point source, a model spherical 192Ir source with steel encapsulation and a commercial HDR GammaMed Plus source. The radial source distance was varied within cylindrical water phantoms with outer radii ranging from 10 to 30cm and heights from 20 to 60cm. By application of this semiempirical method - originally developed for teletherapy dosimetry - it has been shown that factor kQ,M is closely correlated with a single variable, the fluence-weighted mean photon energy ĒF at the point of measurement. The radial profiles of ĒF obtained with either the commercial 192Ir source or the two simplified source variants show little variation. The observed correlations between parameters kQ,M and ĒF are represented by fitting formulae for all investigated detectors, and further variation of the detector type is foreseen. The herewith established close correlation of radiation quality correction factor kQ,M with local mean photon energy ĒF can be regarded as a simple regularity, facilitating the practical application of correction factor kQ,M for in-phantom dosimetry around 192Ir brachytherapy sources. ĒF values can be assessed by Monte Carlo simulation or measurement. A technique describing the local measurement of ĒF will be published separately.

Pyrolysis Model Development for a Multilayer Floor Covering.

Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design of the built environment, and may be used in forensic investigations of fire events. A major limitation to widespread use of comprehensive pyrolysis models is the large number of parameters required to fully define a material and the lack of effective methodologies for measurement of these parameters, especially for complex materials. The work presented here details a methodology used to characterize the pyrolysis of a low-pile carpet tile, an engineered composite material that is common in commercial and institutional occupancies. The studied material includes three distinct layers of varying composition and physical structure. The methodology utilized a comprehensive pyrolysis model (ThermaKin) to conduct inverse analyses on data collected through several experimental techniques. Each layer of the composite was individually parameterized to identify its contribution to the overall response of the composite. The set of properties measured to define the carpet composite were validated against mass loss rate curves collected at conditions outside the range of calibration conditions to demonstrate the predictive capabilities of the model. The mean error between the predicted curve and the mean experimental mass loss rate curve was calculated as approximately 20% on average for heat fluxes ranging from 30 to 70 kW·m−2, which is within the mean experimental uncertainty.

Uncertainty restrictions of transfer click-torque wrenches

For different types of click-torque wrenches, measurement uncertainty contributions of typical calibration conditions were investigated. Procedures which differ from those given in ISO 6789 were suggested for transfer measurements at calibration facilities for click-torque wrenches in order to improve their reproducibility. Examinations were carried out for influences like lever length, rise time, temperature and humidity.

Performance of the COSERO precipitation–runoff model under non-stationary conditions in basins with different climates

This study is a contribution to a model intercomparison experiment initiated during a workshop at the 2013 IAHS conference in Göteborg, Sweden. We present discharge simulations with the conceptual precipitation–runoff model COSERO in 11 basins located under different climates in Europe, Africa and Australia. All of the basins exhibit some form of non-stationary conditions, due, for example, to warming, droughts or land-cover change. The evaluation of the daily discharge simulations focuses on the overall model performance and its decomposition into three components measuring temporal dynamics, mean flow volume and distribution of flows. Calibration performance is similarly high as in previous COSERO applications. However, when looking at evaluation periods independent of the calibration, the model performance drops considerably, mainly due to severely biased discharge simulations in semi-arid basins with strong non-stationarity in rainfall. Simulations are more robust in European basins with humid climates. This highlights the fact that hydrological models frequently fail when simulations are required outside of calibration conditions in basins with non-stationary conditions. As a consequence, calibration periods should be sufficiently long to include both wet and dry periods, which should yield more robust predictions.

Uncertainty evaluation for the dynamic calibration of pressure transducer

The uncertainty of dynamic calibration for pressure transducer is a key indicator of its dynamic measurement precision. A novel grey method( GM) was proposed to evaluate the dynamic calibration uncertainty of pressure transducer. Firstly,a sine pressure generator was used to produce required sine pressure signal to drive the calibrated pressure transducer and obtain output of transducer. Secondly,using the grey relational analysis to deal with the measurement sequences outputted,a weighted value sequence was obtained.Thirdly,a grey model was established to calculate the calibration uncertainty of appointed frequency. Finally,a weighted least-square fitting method was applied to do fitting with the calibration uncertainty of appointed frequency,and then a dynamic calibration uncertainty model was established. An experimental verification under the calibration condition of changing amplitude and unchanging amplitude was set up. Grey method and Huang method( HM) were used to process the output of pressure transducer separately. The results show that the curve models of dynamic calibration uncertainty are consistent with each other in the setting condition. What is more,under changing amplitude,the relative error of calibration uncertainty obtained by the two methods is superior to 6% at appointed frequency points and is also less-than 10% at testing frequency points. Under unchanging amplitude,the relative error is less than 5% at most of frequency points and is superior to 0. 018%at some testing frequency points. Based on the above analysis,it can be approved that the grey method can evaluate the dynamic calibration uncertainty of pressure transducer reliably.

SU‐E‐T‐206: Comparison of EBT and EBT3 RadioChromic Films in Radiation Field of Parotid Cancer Radiotherapy

Purpose:The aim of the current study is to compare EBT and EBT3 RadioChromic films in dosimetry of radiotherapy fields for treatment of parotid cancer.Methods:The calibrations of EBT and EBT3 films were performed with the same setups for doses ranging from 0.2 Gy to 5 Gy using 6 MV photon beam of a Siemens Primus linac. These films were scanned in color mode (RGB) by a Microtek (1000XL) scanner and the red color channel data was extracted. Treatment planning for parotid cancer radiation therapy was performed on a RANDO phantom. Skin dose was measured at different points in the right anterior oblique (RAO) and right posterior oblique (RPO) fields by EBT and EBT3 films.Results:Dosimetry was performed with the same conditions for the two film types for calibration and in‐phantom in parotid cancer radiotherapy. The measured net optical density (NOD) in EBT film was in some extent higher than that from EBT3 film. The minimum difference between these two films under calibration conditions was about 2.9% (for 0.2 Gy). However, the maximum difference was 35.5% (for 0.5 Gy). In the therapeutic fields of parotid cancer radiotherapy at different points, the measured dose from EBT film was higher than the EBT3 film. In these fields the minimum and maximum measured dose differences were 16.0% and 25.5%, respectively.Conclusion:With the same irradiation and reading conditions, EBT film demonstrates higher NOD than the EBT3 film. This effect may be related to the higher sensitivity of EBT film over EBT3 film. However, the obtained dose differences between these two films in low dose range can be due to the differences in fitting functions applied following the calibration process.

SU‐E‐T‐595: Output Factor Calculation for a Uniform Scanning Proton Therapy System

Purpose:To develop an analytical model that predicts dose output factors for patient treatment fields in a uniform scanning proton therapy system.Methods:A model to predict output factors for patient specific treatment fields was produced based on the methods developed by Kooy et al. (2003). The Kooy model predicts the output factor based on the ratio of the entrance dose under calibration conditions to that for a given range and modulation corrected for the inverse square effect. Field specific output factors were plotted as a function of a single parameter r, where r = (Range‐Modulation)/Modulation. The model targeted user range 1 sub‐span 3 through user range 2 sup‐span 2 of the IBA uniform scanning proton therapy system. The data set included points measured using the 10 cm and 18 cm snout sizes to eliminate stem effects on the monitor unit chambers. The data was fit using equation 15 from Kooy et al. (2003), and the resulting model was tested against measurements that were not included in the original data set.Results:For the range and sub span investigated, 120 data points were tested against the model prediction. The model predicted the output factor within 2% for 96% of the points tested and within 2.5% for 99% of the points tested. All points were within 3% of the predicted values.Conclusion:Monitor units for patient treatment fields with proton ranges that fall within the tested interval can be predicted using a model based on the methods developed at MGH. With further evaluation, it will be possible to model all user ranges and sub‐spans of the IBA system. Further testing is also needed to predict output factors using a 25 cm snout which introduces variable scanning pattern sizes and stem effects on the monitor unit chambers.

Simulations with an Accurately Calibrated Electrochemical Model of Li-Ion Battery to Determine Additional Aging Mechanisms

The growing number of electrified vehicles remains particularly constrained by the performance of the energy storage system, which is a complex and expensive component in the vehicle. Li-ion batteries seem to be the best candidates due to their suitable performances for plug in or full electric vehicle application. However, the aging phenomena in those batteries will have a direct impact on the autonomy, power and maintenance costs of the vehicle and are not yet clearly understood. For automotive industry, this kind of information is critical in determining the performance and durability of the battery in traction applications. For that reason, there is an urgent need of validated predictive models for the long term behavior of those electrochemical components, ensuring an optimal battery sizing on one hand, and a proper energy management onboard on the other hand. The aging of a Li-ion battery is mainly due to a modification of its electrochemical properties which will lead to a loss of capacity (decrease of the autonomy) and an increase of its internal impedance (loss of power). A simplified electrochemical model has already been developed at IFP Energies Nouvelles[1] taking into account the loss of cyclable lithium due to the growth of the Solid electrolyte Interphase (SEI) and the modification of the porosity of the graphite electrode as aging mechanisms. This model allows us to estimate the evolution of the performance (power and autonomy) of a Graphite/LiFePO4-based battery as if it was used on a typical hybrid or electric vehicle. In order to ensure the reliability of this model, a sensitivity analysis based on Zhang et al. work[2] has been performed to find out the impact of the variation of each parameters on the model output (Voltage, Temperature) and determine the optimal testing conditions for this model calibration. Moreover, the discrepancies observed during the validation of our properly calibrated model with experimental data highlighted an additional capacity loss due to another aging mechanism than SEI growth. According to our previous research and to the literature, we decided to add a mechanical stress based mechanism involving cracking into the electrode that leads to a loss of active materials or enhances the loss of lithium inventory. Therefore, specific experiments inducing stress during intercalation of lithium ions in the negative electrode have been carried out to gather data to identify parameters of the new mechanism added to our model. Afterwards, the behavior of this new aging model will be validated on dynamic PHEV duty profiles to ensure its good reliability.

Comparative study on passive and active projector nonlinear gamma calibration

This paper compares the active and passive projector nonlinear gamma compensation methods for phase error reduction. The active method modifies fringe patterns before their projection to ensure sinusoidality; the passive method, in contrast, compensates for the phase error after capturing those distorted sinusoidal fringe patterns. Our study finds that the active method tends to provide more consistent high-quality fringe patterns regardless of the amount of projectors defocusing; yet the effectiveness of the passive method is diminished if the measurement condition deviates from the calibration condition. Experimental results will be presented to demonstrate the differences between these two nonlinear gamma compensation methods.

Estimating Population Proportions by Means of Calibration Estimators

This paper considers the problem of estimating the population proportion of a categorical variable using the calibration framework. Different situations are explored according to the level of auxiliary information available and the theoretical properties are investigated. A new class of estimator based upon the proposed calibration estimators is also defined, and the optimal estimator in the class, in the sense of minimal variance, is derived. Finally, an estimator of the population proportion, under new calibration conditions, is defined. Simulation studies are considered to evaluate the performance of the proposed calibration estimators via the empirical relative bias and the empirical relative efficiency, and favourable results are achieved.

Modeling the Northern Coastline of Yucatan, Mexico, with GENESIS

The sandy coast of the State of Yucatan is subject to natural and anthropogenic disturbances. Coastal erosion is a clear example of these disturbances. Many actions have been proposed and implemented to combat this problem; however, they have been counterproductive. In the present work the evolution of the northern coastline of Yucatan, Mexico was studied. The GENESIS model was applied to assess the effect of groins, breakwaters parallel to the coast and sand nourishment. The model was calibrated with available oceanographic information; a thorough treatment of this information made the calibration consistent. It was found that: a) the obliquity of the incidence wave is the main cause of longitudinal sediment transport; b) the sediment transport produced as a result of the wave height gradient along the coast is negligible; and c) the incident waves on the coast present very low energy and are governed mainly by local wind action. The flexibility provided by the calibration coefficients in GENESIS allowed it to be used on the beaches of Yucatan; the values obtained during this research reproduced in an acceptable manner both the morphological changes observed and the volumetric variability of sediments. For these values and the calibration conditions, the model can be applied to analyze the evolution of the beaches in the Yucatan. Furthermore, it reinforces the hypothesis that the groins have accelerated erosion, breakwaters off the coast are a viable alternative to coastal erosion in the study area, and the placement of artificial sand is just a temporary solution.

Investigation into calibration performance of small volume prover for hydrocarbon flow

Several kinds of commercial flowmeters, namely, Coriolis flowmeters, turbine meters, ultrasonic flowmeters, and positive displacement flowmeters, have been calibrated using the primary standard for hydrocarbon flow measurement in Japan (which is based on static and gravimetric methods with a flying start and finish) and a small volume prover (SVP) at the same calibration condition in order to investigate the performance of the SVP. The differences in calibration results for the mechanical flowmeters between the primary standard and the SVP apparently depend on the flow rate, although the results show agreement within 0.04%. The computer-based flowmeters, which have a time delay in the output pulse signal, indicated larger differences due to the effect of the sudden flow rate change caused by the proving action of the SVP at larger flow damping times.

A novel simple phantom for verifying the dose of radiation therapy.

A standard protocol of dosimetric measurements is used by the organizations responsible for verifying that the doses delivered in radiation-therapy institutions are within authorized limits. This study evaluated a self-designed simple auditing phantom for use in verifying the dose of radiation therapy; the phantom design, dose audit system, and clinical tests are described. Thermoluminescent dosimeters (TLDs) were used as postal dosimeters, and mailable phantoms were produced for use in postal audits. Correction factors are important for converting TLD readout values from phantoms into the absorbed dose in water. The phantom scatter correction factor was used to quantify the difference in the scattered dose between a solid water phantom and homemade phantoms; its value ranged from 1.084 to 1.031. The energy-dependence correction factor was used to compare the TLD readout of the unit dose irradiated by audit beam energies with 60Co in the solid water phantom; its value was 0.99 to 1.01. The setup-condition factor was used to correct for differences in dose-output calibration conditions. Clinical tests of the device calibrating the dose output revealed that the dose deviation was within 3%. Therefore, our homemade phantoms and dosimetric system can be applied for accurately verifying the doses applied in radiation-therapy institutions.

A fast and effective routine method based on HS-SPME–GC–MS/MS for the analysis of organotin compounds in biota samples

This work validated an automated, fast, and low solvent- consuming methodology suited for routine analysis of tributyltin (TBT) and degradation products (dibutyltin, DBT; monobutyltin, MBT) in biota samples. The method was based on the headspace solid-phase microextraction methodology (HS-SPME), coupled with gas chromatographic separation and tandem mass-spectrometry (GC–MS/MS). The effectiveness of the matrix-matched signal ratio external calibration was tested for quantification purposes. The exclusion of matrix influences in the calibration curves proved the suitability of this versatile quantification method. The method detection limits obtained were of 3ngSng−1dw for all the analytes. The analysis of references materials showed satisfying accuracy under optimum calibration conditions (% recovery between 87–111%; |Z-scores|<2). The repeatability RSD% and intra-laboratory reproducibility RSD% were lower than 9.6% and 12.6%, respectively. The work proved the remarkable analytical performances of the method and its high potential for routine application in monitoring organotin compounds (OTC).

Calibration of a Ti-in-muscovite geothermometer for ilmenite- and Al2SiO5-bearing metapelites

Abstract The Ti-in-muscovite geothermometer was empirically calibrated as ln[T(oC)] = 7.258 + 0.289 ln(Ti) + 0.158[Mg/(Fe + Mg)] + 0.031 ln[P(kbar)] using ilmenite- and Al2SiO5-bearing assemblages in metapelites under P–T conditions of 450–800 °C and 0.1–1.4 GPa. The calibration was conducted for muscovites containing Ti = 0.01–0.07, Fe = 0.03–0.16, Mg = 0.01–0.32 and Mg/(Fe + Mg) = 0.05–0.73, respectively, on the basis of 11 oxygen per formula unit. Such compositional range covers more than 90% natural muscovites, and the random error of this thermometer is estimated to be of ± 65 °C. The geothermometer was validated against a set of independently determined temperature conditions between different degrees in samples from different prograde, inverted and contact metamorphic terranes. Application of this thermometer beyond the calibration conditions is not encouraged.

Artificial neural network prediction of multilinear gradient retention in reversed-phase HPLC: comprehensive QSRR-based models combining categorical or structural solute descriptors and gradient profile parameters.

A multilayer artificial neural network (ANN) is used to model the reversed-phase liquid chromatography retention times of 16 selected compounds, including purines, pyrimidines and nucleosides. The analysed data, taken from literature, were collected in acetonitrile-water eluents under the application of 16 different multilinear gradients. The parameters describing the gradient profile together with solute descriptors are considered as the independent variables of an ANN-based model providing the retention time as response. Categorical variables or, alternatively, a selected set of molecular descriptors of computational origin are adopted to represent the solutes. Network training, validation and testing are performed preliminarily using data of 12, 2 and 4 gradients, respectively and successively, to investigate model performance under more severe calibration conditions, with data of 9, 2 and 7 gradients. The proposed approach allows a quite accurate prediction of retention times of the target analytes in external multilinear gradients. Categorical variables can successfully represent the target solutes when the model is called to transfer retention data from calibration to external gradients. In particular, using a five-dimensional bit string to represent the analytes, mean errors on retention times are 2 and 3% under the most and less favourable calibration conditions, respectively. A comparable performance is observed if the categorical variables are replaced by five molecular descriptors, selected by a genetic algorithm within a large set of structural variables of computational origin.

NOTA TÉCNICA: INSPEÇÃO DE PULVERIZADORES HIDROPNEUMÁTICOS NA REGIÃO DO ALTO PARANAÍBA-MG - DOI: 10.13083/1414-3984.v22n05a08

O objetivo desse trabalho foi inspecionar pulverizadores hidropneumáticos na Região do Alto Paranaíba-MG, a fim de se verificar o estado de conservação dos mesmos e validar procedimentos de avaliação condizentes com a região. Para isso, avaliou-se 30 pulverizadores que foram selecionados ao acaso. O processo de avaliação constitui-se da aplicação de um questionário dividido em duas partes, com as seguintes pontuações máximas: condições do equipamento (300) e calibração (150). Dessa forma, o pulverizador em condições perfeitas de operação atingiria nota final igual a 450. Quando o pulverizador possuía os itens em conformidade, recebia a pontuação, caso o contrário, não recebia, e, assim, a nota máxima alcançada do pulverizador era reduzida. Utilizou-se a análise discriminante, o teste de qui-quadrado e Correlação de Pearson. O fator que mais contribuiu para a nota final do pulverizador foi a calibração. No fator equipamento, o item que mais influenciou foi marcador de nível de tanque, seguido por partes móveis protegidas e vazamentos em mangueiras. No fator calibração, o item que mais interferiu foi a rotação nominal do motor, seguido pelo monitoramento das condições climáticas e desvio da vazão das pontas. O método de avaliação se mostrou adequado, exceto para a avaliação de perdas de calda.