The feasibility of a scheme in which the concentration of COsub.2 in gas-liquid solution is directly measured based on PZT piezoelectric-photoacoustic spectroscopy was evaluated. The existing device ...used for the measurement of gas concentration in gas-liquid solution has several limitations, including prolonged duration, loss of gas, and high cost due to the degassing component. In this study, we developed a measuring device in order to solve the problems mentioned above. Using this device, how the intensity of the photoacoustic signal changes with the concentration of COsub.2 was demonstrated through experiment. The impact that variation of the laser modulation frequency has on the photoacoustic signal was also studied. Furthermore, the experimental data generated from measuring the concentration of COsub.2 in gas-liquid solution was verified for a wide range of concentrations. It was found that, not only can the error rate of the device be less than 7%, but the time of measurement can be within 60 s. To sum up, the scheme is highly feasible according to the experimental results, which makes measurement of the concentration of a gas in gas-liquid solution in the future more straightforward.
This paper gives an elaboration on the source of uncertainty, general class and its difference with error, followed by detailed analysis and verification of a real case of measurement uncertainty. ...Taking a multi-function three-phase electrical measuring instrument calibration device as an example, the paper describes how to evaluate the uncertainty in measurement result of indication errors in mathematical model.
Background: Ensuring the validity of assessments requires a thorough examination of the test content. Subject matter experts (SMEs) are commonly employed to evaluate the relevance, ...representativeness, and appropriateness of the items. This article proposes incorporating item response theory (IRT) into model assessments conducted by SMEs. Using IRT allows for the estimation of discrimination and threshold parameters for each SME, providing evidence of their performance in differentiating relevant from irrelevant items, thus facilitating the detection of suboptimal SME performance while improving item relevance scores. Method: Use of IRT was compared to traditional validity indices (content validity index and Aiken's V) in the evaluation of conscientiousness items. The aim was to assess the SMEs' accuracy in identifying whether items were designed to measure conscientiousness or not, and predicting their factor loadings. Results: The IRT-based scores effectively identified conscientiousness items (R.sup.2 = 0.57) and accurately predicted their factor loadings (R.sup.2 = 0.45). These scores demonstrated incremental validity, explaining 11% more variance than Aiken's V and up to 17% more than the content validity index. Conclusions: Modeling SME assessments with IRT improves item alignment and provides better predictions of factor loadings, enabling improvement of the content validity of measurement instruments. Keywords: Content validity Subject matter experts Item response theory Validity Test development Antecedentes: Garantizar la validez de evaluaciones requiere un examen exhaustivo del contenido de una prueba. Es comun emplear expertos en la materia (EM) para evaluar la relevancia, representatividad y adecuacion de los items. Este articulo propone integrar la teoria de respuesta al item (TRI) en las evaluaciones hechas por EM. La TRI ofrece parametros de discriminacion y umbral de los EM, evidenciando su desempeno al diferenciar items relevantes/irrelevantes, detectando desempenos suboptimos, mejorando tambien la estimacion de la relevancia de los items. Metodo: Se comparo el uso de la TRI frente a indices tradicionales (indice de validez de contenido y V de Aiken) en items de responsabilidad. Se evaluo la precision de los EM al discriminar si los items median responsabilidad o no, y si sus evaluaciones permitian predecir los pesos factoriales de los items. Resultados: Las puntuaciones de TRI identificaron bien los items de responsabilidad (R.sup.2 = 0,57) y predijeron sus cargas factoriales (R.sup.2 = 0,45). Ademas, mostraron validez incremental, explicando entre 11% y 17% mas de varianza que los indices tradicionales. Conclusiones: La TRI en las evaluaciones de los EM mejora la alineacion de items y predice mejor los pesos factoriales, mejorando validez del contenido de los instrumentos. Palabras clave: Validez de contenido Expertos en la materia Teoria de respuesta al item Validez Desarrollo de tests
Open-path measurements of atmospheric composition provide spatial averages of trace gases that are less sensitive to small-scale variations and the effects of meteorology. In this study we introduce ...improvements to open-path near-infrared (OP-NIR) Fourier transform spectrometer measurements of CO.sub.2 and CH.sub.4 . In an extended field trial, the OP-NIR achieved measurement repeatability 6 times better for CO.sub.2 (0.28 ppm) and 10 times better for CH.sub.4 (2.1 ppb) over a 1.55 km one-way path than its predecessor. The measurement repeatability was independent of path length up to 1.55 km, the longest distance tested. Comparisons to co-located in situ measurements under well-mixed conditions characterise biases of 1.41 % for CO.sub.2 and 1.61 % for CH.sub.4 relative to in situ measurements calibrated to World Meteorological Organisation - Global Atmosphere Watch (WMO-GAW) scales. The OP-NIR measurements can detect signals due to local photosynthesis and respiration, and local point sources of CH.sub.4 . The OP-NIR is well-suited for deployment in urban or rural settings to quantify atmospheric composition on kilometre scales.
Purpose:
Methods for quantification of breast density on MRI using semiautomatic approaches are commonly used. In this study, the authors report on a fully automatic chest template-based method.
...Methods:
Nonfat-suppressed breast MR images from 31 healthy women were analyzed. Among them, one case was randomly selected and used as the template, and the remaining 30 cases were used for testing. Unlike most model-based breast segmentation methods that use the breast region as the template, the chest body region on a middle slice was used as the template. Within the chest template, three body landmarks (thoracic spine and bilateral boundary of the pectoral muscle) were identified for performing the initial V-shape cut to determine the posterior lateral boundary of the breast. The chest template was mapped to each subject's image space to obtain a subject-specific chest model for exclusion. On the remaining image, the chest wall muscle was identified and excluded to obtain clean breast segmentation. The chest and muscle boundaries determined on the middle slice were used as the reference for the segmentation of adjacent slices, and the process continued superiorly and inferiorly until all 3D slices were segmented. The segmentation results were evaluated by an experienced radiologist to mark voxels that were wrongly included or excluded for error analysis.
Results:
The breast volumes measured by the proposed algorithm were very close to the radiologist's corrected volumes, showing a % difference ranging from 0.01% to 3.04% in 30 tested subjects with a mean of 0.86% ± 0.72%. The total error was calculated by adding the inclusion and the exclusion errors (so they did not cancel each other out), which ranged from 0.05% to 6.75% with a mean of 3.05% ± 1.93%. The fibroglandular tissue segmented within the breast region determined by the algorithm and the radiologist were also very close, showing a % difference ranging from 0.02% to 2.52% with a mean of 1.03% ± 1.03%. The total error by adding the inclusion and exclusion errors ranged from 0.16% to 11.8%, with a mean of 2.89% ± 2.55%.
Conclusions:
The automatic chest template-based breast MRI segmentation method worked well for cases with different body and breast shapes and different density patterns. Compared to the radiologist-established truth, the mean difference in segmented breast volume was approximately 1%, and the total error by considering the additive inclusion and exclusion errors was approximately 3%. This method may provide a reliable tool for MRI-based segmentation of breast density.
Purpose:
Kilovoltage intrafraction monitoring (KIM) is a real‐time image guidance method that uses widely available radiotherapy technology, i.e., a gantry‐mounted x‐ray imager. The authors report on ...the geometric and dosimetric results of the first patient treatment using KIM which occurred on September 16, 2014.
Methods:
KIM uses current and prior 2D x‐ray images to estimate the 3D target position during cancer radiotherapy treatment delivery. KIM software was written to process kilovoltage (kV) images streamed from a standard C‐arm linear accelerator with a gantry‐mounted kV x‐ray imaging system. A 120° pretreatment kV imaging arc was acquired to build the patient‐specific 2D to 3D motion correlation. The kV imager was activated during the megavoltage (MV) treatment, a dual arc VMAT prostate treatment, to estimate the 3D prostate position in real‐time. All necessary ethics, legal, and regulatory requirements were met for this clinical study. The quality assurance processes were completed and peer reviewed.
Results:
During treatment, a prostate position offset of nearly 3 mm in the posterior direction was observed with KIM. This position offset did not trigger a gating event. After the treatment, the prostate motion was independently measured using kV/MV triangulation, resulting in a mean difference of less than 0.6 mm and standard deviation of less than 0.6 mm in each direction. The accuracy of the marker segmentation was visually assessed during and after treatment and found to be performing well. During treatment, there were no interruptions due to performance of the KIM software.
Conclusions:
For the first time, KIM has been used for real‐time image guidance during cancer radiotherapy. The measured accuracy and precision were both submillimeter for the first treatment fraction. This clinical translational research milestone paves the way for the broad implementation of real‐time image guidance to facilitate the detection and correction of geometric and dosimetric errors, and resultant improved clinical outcomes, in cancer radiotherapy.
The aquatic eddy covariance technique stands out as a powerful method for benthic O.sub.2 flux measurements in shelf environments because it integrates effects of naturally varying drivers of the ...flux such as current flow and light. In conventional eddy covariance instruments, the time shift caused by spatial separation of the measuring locations of flow and O.sub.2 concentration can produce substantial flux errors that are difficult to correct. We here introduce a triple O.sub.2 sensor eddy covariance instrument (3OEC) that by instrument design eliminates these errors. This is achieved by positioning three O.sub.2 sensors around the flow measuring volume, which allows the O.sub.2 concentration to be calculated at the point of the current flow measurements. The new instrument was tested in an energetic coastal environment with highly permeable coral reef sands colonised by microphytobenthos. Parallel deployments of the 3OEC and a conventional eddy covariance system (2OEC) demonstrate that the new instrument produces more consistent fluxes with lower error margin. 3OEC fluxes in general were lower than 2OEC fluxes, and the nighttime fluxes recorded by the two instruments were statistically different. We attribute this to the elimination of uncertainties associated with the time shift correction. The deployments at â¼ 10 m water depth revealed high day- and nighttime O.sub.2 fluxes despite the relatively low organic content of the coarse sediment and overlying water. High light utilisation efficiency of the microphytobenthos and bottom currents increasing pore water exchange facilitated the high benthic production and coupled respiration. 3OEC measurements after sunset documented a gradual transfer of negative flux signals from the small turbulence generated at the sediment-water interface to the larger wave-dominated eddies of the overlying water column that still carried a positive flux signal, suggesting concurrent fluxes in opposite directions depending on eddy size and a memory effect of large eddies. The results demonstrate that the 3OEC can improve the precision of benthic flux measurements, including measurements in environments considered challenging for the eddy covariance technique, and thereby produce novel insights into the mechanisms that control flux. We consider the fluxes produced by this instrument for the permeable reef sands the most realistic achievable with present-day technology.
A still current challenge of paramount importance for manufacturing metrology is the industry and laboratories’ increasing demand for faster inspection and verification measuring procedures to ...determine the conformance of products to dimensional or functional requirements. Within this context, a measuring system group that has gained great importance in the field of high precision dimensional verification are the portable coordinate measuring machines (PCMMs) such as articulated arm coordinate measuring machine (AACMM). Nevertheless, an important drawback of these type of instruments are the time-consuming, tedious, and expensive tasks inherent to their verification and kinematic parameter identification procedures. In this work, a kinematic parameter identification procedure of an AACMM by means of an indexed metrology platform is presented. Moreover, the kinematic modeling of the AACMM is developed, and the optimization of the arm kinematic parameters to minimize the measurement error is carried out in terms of eight objective functions. Finally, a comparison between the optimized parameters and the nominal parameters is discussed, showing the advantages of using the indexed metrology platform (IMP) in the optimization procedure.
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