Good Relative Agreement Research Articles

Flexural behavior of assembled FRP-steel Pre-Tightened Teeth Connection (PTTC): Experimental study and failure mechanism

This study focused on understanding the flexural failure behavior of a newly-developed assembled FRP-Steel Pre-Tightened Teeth Connection (PTTC) used for rapid connection of pultruded Fiber Reinforced Polymer (FRP) tubular beams. Four-point bending loading tests were conducted on a specific type of assembled joint that incorporated the FRP-Steel PTTC and threaded connections. The results indicated that each component demonstrated a typical flexural behavior with a desired load-bearing capacity. The assembled FRP-steel PTTC exhibited a gradual occurrence of various failure modes, which significantly differed from those observed under uniaxial compressive or tensile loadings that typically exhibit a more singular failure mode. The initial failure is identified as the local transverse shear failure occurring at the upper junction interface of the composites between the FRP segments and the external steel sleeves. It is thus crucial to carefully assess the stress concentration effects during the design process of FRP-steel PTTC and its assembled joints. Corresponding numerical analysis was performed and compared to experimental results, which demonstrated good agreement in relation to deformation, initial failure modes, and bearing capacity. The comparison results indicated that the developed numerical model is capable of predicting the flexural behavior prior to the initiation of the failure process of the assembled composite joints.

Zeolitization of a devitrified high-silica rhyolitic tuff producing dachiardite: A comparison of hydrothermal experiments with the corresponding reaction progress modeling

We have investigated the hydrothermal alteration of polished wafers of tuff reacted with dilute groundwater at 90 °C, 150 °C and 250 °C for time periods ranging from 2 months to nearly 1 year. The polished rock wafer provided a convenient surface upon which to grow secondary minerals. Reaction product minerals were identified and analyzed at the end of each experiment and, along with the evolving fluid chemistry, were compared to computational results from corresponding reaction progress models.At 250 °C after a few months the run products in the experiment were dominantly the mordenite group zeolite minerals: dachiardite (a Ca-rich variety) and mordenite, itself. At 150 °C after a few months of reaction only minor amounts of clay were produced, but after 1 year of reaction at this temperature both mordenite group zeolites were again present. At this lower temperature the total amount of run products was much smaller. At 90 °C no run products could be seen at all, even after 1 year of reaction. The reaction progress modeling results for reaction products were in good relative agreement with the experimental results.The higher the temperature, and the greater the extent of reaction, the better the fluid phase modeling results agreed with the actual experimental results. At 250 °C the agreement was good for nearly all elements. At 150 °C agreement for pH, SiO2, Na and K were good, but less good for Al, Mg and Ca, especially after short reaction times. At 90 °C agreement for pH, SiO2 and Na was reasonable, but not as good for the other elements, and all modeling results for short reaction times did not match experimental results as well as the longer time results.This study demonstrates that reaction progress modeling provides a powerful tool for predicting hydrothermal rock-water interactions, with results expected to improve, as more and better quality thermodynamic and kinetic data become available and as process-oriented simulators incorporate better and more comprehensive sub-models for mineral dissolution and growth.

Validation and Recalibration of the Asbestos Removal Exposure Assessment Tool (AREAT).

The Asbestos Removal Exposure Assessment Tool (AREAT) was previously developed to estimate exposure to respirable asbestos fibres during abatement processes. The current study describes the validation and recalibration of the AREAT model with external data. During model validation, the AREAT model was expanded to be able to estimate asbestos exposure from an additional source category: 'unspecified asbestos remnants'. The validation dataset (n = 281) was derived from exposure measurement studies where for each exposure measurement the AREAT model parameters were coded and estimates were calculated. Pearson correlation coefficients (r) and intra class correlation coefficients (icc) were calculated as an indication of the agreement between the AREAT estimates and measured concentrations. In addition, the bias and the proportion of measurements with higher concentrations than model estimates were calculated. To expand and investigate model performance on exposure from 'unspecified asbestos remnants', a separate dataset was created with measurements collected during working with unspecified asbestos remnants, and similar validation comparisons were performed. Lastly, linear regression techniques were used to investigate possible improvements in model parameters. The model was recalibrated on a combined dataset consisting of the validation dataset and the original calibration dataset to increase model robustness. The validation comparisons showed good relative agreement (r) between AREAT estimates and measurements (r = 0.73) and a moderate absolute agreement (icc = 0.53). The overall relative bias was 108%, indicating an overall overestimation of exposure, and 4% of the estimated concentrations were higher than the actual measured concentrations. For the data subset concerning unspecified asbestos remnants, a moderate correlation between model estimates and measurement outcomes was found (r = 0.63). However, based on the low number of data in this subset, and moderate r, it was decided that cleaning of unspecified asbestos remnants is out of scope until more data are available. The results of this validation study suggested that two input parameters (product type friable material, efficacy of control measure foam) underestimated exposure. The effects of these parameters were updated to improve model performance. Compared to the original model, the recalibrated model resulted in slightly higher explained variance (62% compared to 56%) and lower uncertainty (15 compared to 17.3). The original AREAT model provided reliable asbestos exposure estimates with a sufficient level of conservatism taking into account the 90-percentile estimates. The model was further improved via the addition of a new feature and recalibration to predict asbestos exposure during the clean-up of unspecified asbestos remnants.

First measurements of p11B fusion in a magnetically confined plasma

Proton-boron (p11B) fusion is an attractive potential energy source but technically challenging to implement. Developing techniques to realize its potential requires first developing the experimental capability to produce p11B fusion in the magnetically-confined, thermonuclear plasma environment. Here we report clear experimental measurements supported by simulation of p11B fusion with high-energy neutral beams and boron powder injection in a high-temperature fusion plasma (the Large Helical Device) that have resulted in diagnostically significant levels of alpha particle emission. The injection of boron powder into the plasma edge results in boron accumulation in the core. Three 2 MW, 160 kV hydrogen neutral beam injectors create a large population of well-confined, high -energy protons to react with the boron plasma. The fusion products, MeV alpha particles, are measured with a custom designed particle detector which gives a fusion rate in very good relative agreement with calculations of the global rate. This is the first such realization of p11B fusion in a magnetically confined plasma.

Multi-echo MR thermometry in the upper leg at 7T using near-harmonic 2D reconstruction for initialization.

The aim of this work is the development of a thermometry method to measure temperature increases in vivo, with a precision and accuracy sufficient for validation against thermal simulations. Such an MR thermometry model would be a valuable tool to get an indication on one of the major safety concerns in MR imaging: the tissue heating occurring due to radiofrequency (RF) exposure. To prevent excessive temperature rise, RF power deposition, expressed as specific absorption rate, cannot exceed predefined thresholds. Using these thresholds, MRI has demonstrated an extensive history of safe usage. Nevertheless, MR thermometry would be a valuable tool to address some of the unmet needs in the area of RF safety assessment, such as validation of specific absorption rate and thermal simulations, investigation of local peak temperatures during scanning, or temperature-based safety guidelines. The harmonic initialized model-based multi-echo approach is proposed. The method combines a previously published model-based multi-echo water/fat separated approach with an also previously published near-harmonic 2D reconstruction method. The method is tested on the human thigh with a multi-transmit array at 7T, in three volunteers, and for several RF shims. Precision and accuracy are improved considerably compared to a previous fat-referenced method (precision: 0.09 vs. 0.19°C). Comparison of measured temperature rise distributions to subject-specific simulated counterparts show good relative agreement for multiple RF shim settings. The high precision shows promising potential for validation purposes and other RF safety applications.

Experimental and numerical study of frost formation with natural convection in a triangular arrangement of slender vertical tubes

Frost formation is an undesirable phenomenon in heat exchangers, where a thin layer of frost forms, negatively influencing the performance and operation of the equipment. The frost layer increases the thermal resistance between the air flow and the cold surfaces in evaporators, which reduces the heat transfer rate and decreases the thermal efficiency. In the present study, the phenomenon of frost growth on a triangular array of slender vertical tubes was investigated experimentally in a wind tunnel. Fast CCD cameras were used for frost thickness measurement. A numerical investigation was conducted to simulate the frost thickness growth on the cold tube surface. Volumetric mean approach for frost formation modelling was applied and a modified formulation for calculation of the local Nusselt number in the vertical slender tube case was proposed. The numerical predictions showed a reasonably good agreement in relation to the mean values of the frost thickness measured in experimental tests up to the range of 5,000 to 6,000 s of simulation. Afterwards, in model predictions, the frost growth is bigger than the experimental results in the range of 14% to 33% higher in relation to mean values.

Criterion Validity of an Automated Method of Detecting Live Play Periods in Basketball.

This study aimed to develop an automated method to detect live play periods from accelerometry-derived relative exercise intensity in basketball, and to assess the criterion validity of this method. Relative exercise intensity (% oxygen uptake reserve) was quantified for two men's semi-professional basketball matches. Live play period durations were automatically determined using a moving average sample window and relative exercise intensity threshold, and manually determined using annotation of video footage. The sample window duration and intensity threshold were optimised to determine the input parameters for the automated method that would result in the most similarity to the manual method. These input parameters were used to compare the automated and manual active play period durations in another men's semi-professional match and a women's professional match to assess the criterion validity of the automated method. The optimal input parameters were a 9-s sample window and relative exercise intensity threshold of 31% oxygen uptake reserve. The automated method showed good relative (ρ = 0.95–0.96 and ICC = 0.96–0.98, p < 0.01) and absolute (median bias = 0 s) agreement with the manual method. These findings support the use of an automated method using accelerometry-derived relative exercise intensity and a moving average sample window to detect live play periods in basketball.

Analysis of strain and disordering kinetics based on combined RBS-channeling and X-ray diffraction atomic-scale modelling

Ion beams delivered by particle accelerators are routinely used to emulate harsh, radiative environments and they also constitute the foundations of the modern microelectronics industry. To characterize irradiated materials, numerous experimental and computational techniques can be implemented, but it is extremely difficult to effectively intertwine them, and to compare the associated data. In the present work, we present an integrated, experimental and computational approach that uses a same set of molecular dynamics simulations to generate signals of Rutherford backscattering spectrometry in channelling condition and X-ray diffraction, with UO2 as a test-case material. From these signals, parameters to monitor the damage level are computed, compared and confronted with experimental data. Although the evolution of the strain and disordering kinetics obtained by simulations differ on an absolute scale from those obtained experimentally (a discrepancy inherent to the method used to generate the atomic-scale data), a very good relative agreement is obtained, which demonstrates the validity of the approach, hence providing a new tool for the fine study of irradiation effects in materials.

Remarks on energy harvesting of nonlinear charge and voltage piezoelectric models in a two-degrees-of-freedom nonlinear portal frame model

In this paper, a piezoelectric energy harvesting application on a portal frame of two-degrees-of-freedom considering a quadratic coupling between the coordinates with two-to-one internal resonance is considered. The piezoelectric material is considered as a linear device using a voltage and a charge mathematical model. The equations of motion of the system were obtained by applying the energy method of Lagrange, and the method of multiple scales is applied to find an analytical approximated solution of the equations of motion. Numerical results showed that the voltage model and a charge model have good agreement in relation to the behavior and amplitudes of displacement of the system.

Automated FTIR mapping of boron distribution in diamond

Type IIb diamonds are those that contain more boron than nitrogen. The presence of this uncompensated boron gives rise to absorption in the infrared part of the electromagnetic spectrum, extending into the visible region and often resulting in blue colouration. Here we report on the expansion of the DiaMap freeware (for the automated spectral deconvolution of Type I [nitrogen containing] diamonds) to work on Type IIb diamonds, returning concentrations from three boron-related absorption bands, and determining which band provides the most reliable value. The program uses the calibration coefficients of Collins (2010), which show good relative agreement between the three bands, but might require some further study to confirm their absolute accuracy to the uncompensated boron concentration. The methodology of DiaMap_IIb is applicable to all Type IIb diamonds, both natural and synthetic. Analysis of high-resolution Fourier-transform infrared (FTIR) maps of two high-pressure high-temperature (HPHT) synthetic diamonds using DiaMap_IIb, confirm the growth sector dependence of the boron incorporation. Partitioning of boron strongly favours the octahedral {111} sectors.

Thermal decomposition kinetics of guarana seed residue through thermogravimetric analysis under inert and oxidizing atmospheres

This work aims to analyze the thermal decomposition kinetics of guarana seed residue applying inert and oxidizing atmospheres. Thermal decomposition experiments were carried out in a thermogravimetric analyser using heating rates of 5, 10 and 15 °C/min. Three thermal decomposition stages were identified: dehydration; pyrolysis/oxidative pyrolysis, and carbonization/combustion, respectively. In order to obtain the estimation of the activation energies, the isoconversional method proposed by Vyazovkin (1997) was applied. Besides that, three and six independent parallel reactions schemes were applied for respective atmospheres. The ranges of activation energy were of 52–140 kJ/mol and 71–171 kJ/mol for inert and oxidizing atmosphere, respectively. The modeling of conversion rates presented a good agreement in relation to the experimental data (AD < 4%).

Plus Disease in Retinopathy of Prematurity: Improving Diagnosis by Ranking Disease Severity and Using Quantitative Image Analysis

To determine expert agreement on relative retinopathy of prematurity (ROP) disease severity and whether computer-based image analysis can model relative disease severity, and to propose consideration of a more continuous severity score for ROP. We developed 2 databases of clinical images of varying disease severity (100 images and 34 images) as part of the Imaging and Informatics in ROP (i-ROP) cohort study and recruited expert physician, nonexpert physician, and nonphysician graders to classify and perform pairwise comparisons on both databases. Six participating expert ROP clinician-scientists, each with a minimum of 10 years of clinical ROP experience and 5 ROP publications, and 5 image graders (3 physicians and 2 nonphysician graders) who analyzed images that were obtained during routine ROP screening in neonatal intensive care units. Images in both databases were ranked by average disease classification (classification ranking), by pairwise comparison using the Elo rating method (comparison ranking), and by correlation with the i-ROP computer-based image analysis system. Interexpert agreement (weighted κ statistic) compared with the correlation coefficient (CC) between experts on pairwise comparisons and correlation between expert rankings and computer-based image analysis modeling. There was variable interexpert agreement on diagnostic classification of disease (plus, preplus, or normal) among the 6 experts (mean weighted κ, 0.27; range, 0.06-0.63), but good correlation between experts on comparison ranking of disease severity (mean CC, 0.84; range, 0.74-0.93) on the set of 34 images. Comparison ranking provided a severity ranking that was in good agreement with ranking obtained by classification ranking (CC, 0.92). Comparison ranking on the larger dataset by both expert and nonexpert graders demonstrated good correlation (mean CC, 0.97; range, 0.95-0.98). The i-ROP system was able to model this continuous severity with good correlation (CC, 0.86). Experts diagnose plus disease on a continuum, with poor absolute agreement on classification but good relative agreement on disease severity. These results suggest that the use of pairwise rankings and a continuous severity score, such as that provided by the i-ROP system, may improve agreement on disease severity in the future.

Going the distance: validation of Acuros and AAA at an extended SSD of 400 cm

Accurate dose calculation and treatment delivery is essential for total body irradiation (TBI). In an effort to verify the accuracy of TBI dose calculation at our institution, we evaluated both the Varian Eclipse AAA and Acuros algorithms to predict dose distributions at an extended source‐to‐surface distance (SSD) of 400 cm. Measurements were compared to calculated values for a 6 MV beam in physical and virtual phantoms at 400 cm SSD using open beams for both 5×5 and 40×40 cm2 field sizes. Inline and crossline profiles were acquired at equivalent depths of 5 cm, 10 cm, and 20 cm. Depth‐dose curves were acquired using EBT2 film and an ion chamber for both field sizes. Finally, a RANDO phantom was used to simulate an actual TBI treatment. At this extended SSD, care must be taken using the planning system as there is good relative agreement between measured and calculated profiles for both algorithms, but there are deviations in terms of the absolute dose. Acuros has better agreement than AAA in the penumbra region.PACS number(s): 87.55.kd

Accuracy and re-test reliability of mobile eye-tracking in Parkinson's disease and older adults

Mobile eye-tracking is important for understanding the role of vision during real-world tasks in older adults (OA) and people with Parkinson's disease (PD). However, accuracy and reliability of such devices have not been established in these populations. We used a novel protocol to quantify accuracy and reliability of a mobile eye-tracker in OA and PD.A mobile eye-tracker (Dikablis) measured the saccade amplitudes of 20 OA and 14 PD on two occasions. Participants made saccades between targets placed 5°, 10° and 15° apart. Impact of visual correction (glasses) on saccadic amplitude measurement was also investigated in 10 OA.Saccade amplitude accuracy (median bias) was −1.21° but a wide range of bias (−7.73° to 5.81°) was seen in OA and PD, with large vertical saccades (15°) being least accurate. Reliability assessment showed a median difference between sessions of <1° for both groups, with poor to good relative agreement (Spearman rho: 0.14 to 0.85). Greater accuracy and reliability was observed in people without visual correction.Saccade amplitude can be measured with variable accuracy and reliability using a mobile eye-tracker in OA and PD. Human, technological and study-specific protocol factors may introduce error and are discussed along with methodological recommendations.

A Molality-Based BET Equation for Modeling the Activity of Water Sorbed on Clay Minerals

AbstractThe Brunauer-Emmett-Teller (BET) theory models the effective specific surface area and water content of solids as a function of the relative vapor pressure of water. A modified form of the BET equation has been used successfully to model water activity in concentrated electrolyte solutions as a function of electrolyte concentration. This modified form, referred to here as the Stokes-Robinson BET model, is based on the electrolyte molality rather than on the mass of solute sorbed. The present study evaluates the Stokes-Robinson form of the BET equation to model water-sorption data on two smectites with different layer charges. One smectite was saturated with Na+ and another with Na+, Ca2+, or Mg2+. These results are compared to the Stokes-Robinson BET results of aqueous electrolyte solutions. Given published data on cation exchange capacities and water-vapor sorption isotherms for various clays, the molality of the aqueous phase in contact with the clay surface is calculated and related to water activity. The Stokes-Robinson BET model was found to describe accurately the water activity as a function of cation molality below water activities of 0.5 for the smectites. Good relative agreement was obtained between the number of water binding sites predicted by the model and the experimental data reported in the literature for other smectites. Water molecules were found to have a significantly greater affinity for montmorillonite than electrolyte solutions with the same cation molality as the montmorillonite interlayer. This modified BET approach simplifies water-activity modeling in highly saline environments because the same equation can be used for both the liquid- and mineral-surface phases.

Development of an In Vitro Model to Assess Deposition of Aerosol Particles in a Representative Replica of the Rat's Respiratory Tract

Small rodents continue to be the mainstay for the assessment of pharmacological and toxicological data of inhaled therapeutics. For meaningful interpretation of the results information about deposition of aerosol particles in the respiratory tract is warranted, but not trivial to obtain for animals with nose-only aerosol exposure. The purpose of this study was to develop and evaluate a general method to characterize the deposition of inhaled test particles in an in vitro model (IVR) of the rat's respiratory tract. A highly detailed, realistic and representative image using micro-CT scanning technology was obtained and the generated morphological data was used to construct a plastic replica of the average rat respiratory tract. The model was connected to a rodent ventilator, which allowed the breathing frequency (f, min(-1)) and tidal volume (V(T), mL) to be varied as required. Polydisperse fluorescent microsphere particles with an average mass median aerodynamic diameter (MMAD) of 3.1 μm and geometric standard deviation (GSD) of 2.2 μm were used as model compound. Comparison of the experimental data for total and regional deposition levels with predicted outputs using the in silico MPPD model showed reasonably good relative agreement between the two models. The predictions were closest to the experimental values when default respiratory conditions of f=102 breaths/min and V(T) of 2.0 mL were used. Moreover, the IVR model revealed good correlation with published in vivo data. Using the IVR model allows an easy, fast and reasonably precise estimation of the inhaled dose in rodent inhalation studies. The IVR has the potential to be used along with live rats in inhalation exposure studies, and thus provides the unique possibility to run an internal standard for dose deposition in the respiratory tract in each inhalation experiment. This should contribute to enable a greater understanding of drug pharmacokinetics and dynamics in rats and may improve dose extrapolation from animals to humans.

Periodic long range proton conduction pathways in pseudo-cubic and orthorhombic perovskites

Dynamic programming is used to find periodic proton conduction paths in pseudo-cubic and orthorhombic perovskites. Periodic paths through a large periodic simulation box are compared to periodic paths through a smaller simulation box and pathways stitched from small simulation box periodic and aperiodic paths. For both size systems in the 900–1300K temperature range, overall average limiting barriers over the N-step periodic pathways considered are 0.3, 0.4, and 0.6eV for BaZr0.875Y0.125O3 , SrZr0.875Y0.125O3 and SrZr0.875Al0.125O3, respectively, in good relative agreement with earlier experiments. However, differences in the ensemble weighted fraction of rotation, intraoctahedral transfer, and interoctahedral transfer limiting steps highlights differences in the small and large system periodic path ensembles. In contrast, the averages over the stitched ensemble are in excellent agreement with the large system averages. This suggests that a careful combining of small system pathways can yield pathways representative of a large system.

Comparative study of vibration-based parametric identification techniques for a three-dimensional frame structure

SUMMARY The entire structural identification process, starting from measurement of the experimental response to ambient vibration, and concluding with the assessment of a representative dynamic model, depends upon an informed selection of appropriate data treatment techniques. The paper compares different procedures for identifying both modal and physical models. Four approaches (EFFD, ERA, SSI, and TFIE) for output-only modal identification are discussed. Their performance is evaluated using experimental data extracted from the ambient vibration response of a three-dimensional frame. The discussion of the identification results throws light on the intrinsic characteristics of each procedure, while the particular features of the structure, presenting unexpected local modes, demonstrate the necessity of a hierarchical treatment of the available information, based on a solid engineering knowledge. The calibration of a physical model is approached using an exact inverse procedure, based on a parametric analytical model, or automatic techniques of error minimization, based on finite element multi-models. The achievement of a good relative agreement, measured through performance-based indexes, increases the general confidence on the results independently obtained from each modal identification and model updating method. Copyright © 2011 John Wiley & Sons, Ltd.

Simulation of a tunable metamaterial with nematic liquid crystal layers

Due to their unique electromagnetic properties, left-handed metamaterials (LHMs) have interesting potential application values at microwave frequencies. A tunable LHM employing nematic liquid crystal BL006 at microwave frequencies was analysed. A full-wave analysis technique based on the finite-difference time-domain method (FDTD) was performed using QuickWave software for a electromagnetic design program. Parameters of the structure of the tunable metamaterial such as transmission and effective refractive index show good agreement in relation to literature data. The tunable structure was analysed in the 10 to 14 GHz range.

Comparative analysis of two FFQ

To examine the utility of a shorter FFQ compared with a longer FFQ, both of which are commonly used in Australia. Comparative study. Community setting. One hundred and fifty-nine men (mean 55 (sem 7) years) screened for participation in an intervention study completed both the Commonwealth Scientific and Industrial Research Organisation FFQ and the Cancer Council of Victoria FFQ. Agreement between both questionnaires was assessed according to Bland-Altman plots and limits of agreement (LOA) and ordinary least products regression to test for the presence of fixed and proportional bias. There was good relative agreement between the methods for energy and macronutrients (Pearson's correlation coefficients: energy r = 0.7, protein r = 0.6, fat r = 0.8, carbohydrate r = 0.7, alcohol r = 0.8; P < 0.01). Mean group-level agreement for the majority of nutrients (70 %) fell between 80 % and 110 %. According to the criteria used (maximum LOA was 50-200 % and no significant proportional bias), there was acceptable agreement between the FFQ for energy and total saturated and monounsaturated fat, but not for protein, carbohydrate and fibre. Micronutrients that did not meet the agreement criteria including calcium, iron, thiamin, niacin, riboflavin and folate. When the data were analysed according to quintiles, the majority of subjects were either in exactly the same quintile or within one quintile for most nutrients, and 1-2 % were grossly misclassified by three or four quintiles. We conclude that there is sufficient agreement between the instruments for group-level comparisons in men, but they are not interchangeable for estimation of individual intakes.