Maximum Relative Uncertainty Research Articles

Accurately Measuring the Infrared Spectral Emissivity of Inconel 601, Inconel 625, and Inconel 718 Alloys during the Oxidation Process.

Accurate measurement of the infrared spectral emissivity of nickel-based alloys is significant for applications in aerospace. The low thermal conductivity of these alloys limits the accuracy of direct emissivity measurement, especially during the oxidation process. To improve measurement accuracy, a surface temperature correction method based on two thermocouples was proposed to eliminate the effect of thermal conductivity changes on emissivity measurement. By using this method, the infrared spectral emissivity of Inconel 601, Inconel 625, and Inconel 718 alloys was accurately measured during the oxidation process, with a temperature range of 673-873 K, a wavelength range of 3-20 μm, and a zenith angle range of 0-80°. The results show that the emissivity of the three alloys is similar in value and variation law; the emissivity of Inconel 718 is slightly less than that of Inconel 601 and Inconel 625; and the spectral emissivity of the three alloys strongly increases in the first hour, whereafter it grows gradually with the increase in oxidation time. Finally, Inconel 601 has a lower emissivity growth rate, which illustrates that it possesses stronger oxidation resistance and thermal stability. The maximum relative uncertainty of the emissivity measurement of the three alloys does not exceed 2.6%, except for the atmospheric absorption wavebands.

A method for the reproducible and accurate determination of electrical resistances based on multi-layer joints in lithium-ion batteries

The transition from fossil fuels to renewable energy sources is significantly influenced by the development of energy storage systems such as batteries. One of the crucial steps in the production of lithium-ion batteries is the electrical connection of the individual electrodes by weld seams. Various joining processes, such as laser beam welding or ultrasonic metal welding, are used for this purpose. An important quality feature of the connections is a low electrical joint resistance, which is essential for reducing cell-internal energy losses and avoiding thermal inhomogeneities in the cells.The aim of this work was to determine the electrical resistance of the joint between a stack of foils and an arrester tab. For this purpose, a measuring method was developed and applied to different sample configurations. The influence of different probe tips on the measurement results was compared using single current collector foils and arrester tabs. The measurement of the electrical resistance was possible in the considered range with a maximum relative uncertainty of 2.38%. Using the presented approach made it possible to evaluate the influence of the seam trajectory on the electrical resistance for cell-internal contacting. In addition, the measuring method is suitable for comparing different welding strategies and, thus, for designing the cell-internal joining processes regarding the resulting electrical joint resistances.

A novel insulation design for high-temperature pipe penetrating the walls of molten salt reactor cavity

The design of molten salt reactor has high-temperature pipes penetrating the walls of reactor cavity, the working temperature of which is about 530 K higher than the ordinary concrete wall. The insulation of high-temperature pipes is important to prevent local overheating of the walls of molten salt reactor cavity. A heat insulation scheme with multilayer different materials for the high-temperature pipe is analyzed. In order to verify the correctness and rationality of the design, one experimental set-up was built. The maximum relative deviation between the numerical results and experimental ones is 2.74% and the maximum relative uncertainty of the experimental results is 0.62%. The design scheme is used in a molten salt reactor and the maximum temperature of the ordinary concrete wall of the molten salt reactor cavity is 338.58 K, which is within the safety limit value of 343.15 K. The design of heat insulation for high-temperature pipe can also be used in other molten salt reactors.

Design of ultrasonic flowmeter for wet gas measurement

When an ultrasonic flowmeter (UFM) is applied in the measurement of wet gas, the ultrasonic signal attenuates and fluctuates strongly because of the liquid film and droplets in gas. It is hard to obtain the accurate time of flight (TOF) of ultrasound. Besides, the gas velocity distribution on a pipe cross section changes with different flow patterns, making it difficult to determine the measurement model. In order to solve these problems, a dual-channel UFM is specially designed and a measurement system is built. Then, a dynamic threshold method based on statistical average signal amplitude is proposed to obtain the TOF of ultrasound in wet gas. Combined with the classical void fraction model, the wet gas velocity measurement model for the dual-channel UFM is established based on a neural network. Finally, experiments are carried out on a DN50 wet gas device, where pressure is 0.1 MPa, gas superficial velocity is 5–20 m s−1 and liquid volume fraction is 0.2%–5%. The results show that the average relative error of gas velocity is 0.52% and the maximum relative uncertainty is 0.491%.

Magnetic tweezers with magnetic flux density feedback control.

In this work, we present a single-pole magnetic tweezers (MT) device designed for integration with substrate deformation tracking microscopy and/or traction force microscopy experiments intended to explore extracellular matrix rheology and human epidermal keratinocyte mechanobiology. Assembled from commercially available off-the-shelf electronics hardware and software, the MT device is amenable to replication in the basic biology laboratory. In contrast to conventional solenoid current-controlled MT devices, operation of this instrument is based on real-time feedback control of the magnetic flux density emanating from the blunt end of the needle core using a cascade control scheme and a digital proportional-integral-derivative (PID) controller. Algorithms that compensate for a spatially non-uniform remnant magnetization of the needle core that develops during actuation are implemented into the feedback control scheme. Through optimization of PID gain scheduling, the MT device exhibits magnetization and demagnetization response times of less than 100ms without overshoot over a wide range of magnetic flux density setpoints. Compared to current-based control, magnetic flux density-based control allows for more accurate and precise magnetic actuation forces by compensating for temperature increases within the needle core due to heat generated by the applied solenoid currents. Near field calibrations validate the ability of the MT device to actuate 4.5 μm-diameter superparamagnetic beads with forces up to 25 nN with maximum relative uncertainties of ±30% for beads positioned between 2.5 and 40 µm from the needle tip.

UNCERTAINTY ANALYSIS TO C5G7-TD BENCHMARK BASED ON THE COST METHOD

A method of Covariance-Oriented Sample Transformation (COST) has been proposed in our previous work to provide the converged uncertainty analysis results with a minimal sample size. The transient calculation of nuclear reactor is a key part of the reactor-physics simulation, so the accuracy and confidence of the neutron kinetics results have attracted much attention. In this paper, the Uncertainty Quantification (UQ) function of the high fidelity neutronics code NECP-X has been developed based on our home-developed uncertainty analysis code UNICORN, building a platform for the UQ of the transient calculation. Furthermore, the well-known space-time heterogeneous neutron kinetics benchmark C5G7 and its uncertainty propagation from the nuclear data to the interested key parameters of the core have been investigated. To address the problem of “the curse of dimensionality” caused by the large number of input parameters, the COST method has been applied to generate multivariate normal-distribution samples in uncertainty analysis. As a result, the law of the assembly/pin normalized power and their uncertainty with respect to time after introducing an instantaneous perturbation has been obtained. From the numerical results, it can be observed that the maximum relative uncertainties for the assembly normalized power can up to be about 1.65% and the value for the pin-wise power distributions can be about 2.71%.

Noise reduction and quantification of fiber orientations in greyscale images.

Quantification of the angular orientation distribution of fibrous tissue structures in scientific images benefits from the Fourier image analysis to obtain quantitative information. Measurement uncertainties represent a major challenge and need to be considered by propagating them in order to determine an adaptive anisotropic Fourier filter. Our adaptive filter method (AF) is based on the maximum relative uncertainty δcut of the power spectrum as well as a weighted radial sum with weighting factor α. We use a Monte-Carlo simulation to obtain realistic greyscale images that include defined variations in fiber thickness, length, and angular dispersion as well as variations in noise. From this simulation the best agreement between predefined and derived angular orientation distribution is found for evaluation parameters δcut = 2.1% and α = 1.5. The resulting cumulative orientation distribution was modeled by a sigmoid function to obtain the mean angle and the fiber dispersion. A comparison to a state-of-the-art band-pass method revealed that the AF method is more suitable for the application on greyscale fiber images, since the error of the fiber dispersion significantly decreased from (33.9 ± 26.5)% to (13.2 ± 12.7)%. Both methods were found to accurately quantify the mean fiber orientation with an error of (1.9 ± 1.5)° and (2.3 ± 2.1)° in case of the AF and the band-pass method, respectively. We demonstrate that the AF method is able to accurately quantify the fiber orientation distribution in in vivo second-harmonic generation images of dermal collagen with a mean fiber orientation error of (6.0 ± 4.0)° and a dispersion error of (9.3 ± 12.1)%.

Nuclear-data uncertainty propagation in transient simulation for the C5G7-TD benchmark problem

In this study, uncertainty analysis has been performed to the time-dependent transient simulation of the C5G7-TD benchmark problem, propagating the nuclear-data uncertainties to the key parameters of interest. The detailed material compositions and geometries of C5G7-TD have been applied for the time-dependent transient simulation. For uncertainty analysis of the transient simulation, multigroup cross-section covariance library has been generated based on ENDF/B-VII.1 using the NJOY code. Our home-developed uncertainty-analysis code named UNICORN has been utilized for the uncertainty analysis, using the statistical sampling method. For the steady-state and transient simulations, our home-developed high-fidelity neutronics code NECP-X has been utilized. The relative uncertainties of the fuel-assembly normalized power and pin-wise power have been quantified as function of time. The numerical results show that the maximum relative uncertainties for the assembly normalized power can up to be about 2.14% and the value for the pin-wise power distributions can be about 3.54%.

Experimental determination of flame speed and flame stretch using an optically accessible, spark-ignition engine

The current research experimentally studied flame speed and stretch under engine in-cylinder conditions. A direct-injection, spark-ignition, and optically accessible engine was utilized to image the flame propagation, and E10 was selected as the fuel. Also, three fuel–air mixtures (stoichiometric, lean, and rich) were examined. The flame front was located by processing high-speed images. This study introduces a novel approach for calculation of equivalent spherical flame radius for analysis of flame speed and stretch. Flame front propagation analysis showed that during the flame propagation period, the stretch decreased until the flame front touched the piston surface. This was a common trend for stoichiometric, lean, and rich mixtures, which occurred because the flame radius was the dominant factor in the stretch calculation. In addition, the rich fuel–air mixture showed a lower flame stretch compared to stoichiometric or lean mixture. This was the result of a lower Markstein number for the rich fuel–air mixture. To study the sensitivity of different fuel–air mixtures to the flame stretch, the trajectory of the flame centroid was tracked until the flame front touched the piston surface. The results showed that the end centroid for the lean mixture deviated from the start point more than those of the rich and stoichiometric mixtures because the lean mixture had a higher flame stretch and lower flame speed. Furthermore, comparing the flame stretch at three different engine speeds revealed that increasing the engine speed increased the flame stretch, especially during the early flame development period. According to previous studies which discussed flame stretch as a flame extinguishment mechanism, the probability of flame extinction is higher when the engine speed is higher. Also, uncertainty analysis was conducted to determine the effect of camera setting on the flame stretch. Results showed that a maximum relative uncertainty of 4.5% occurred during the early flame development.

Uncertainty quantification for the first-cycle modeling and simulations of the BEAVRS benchmark problem

In this paper, the uncertainty quantification has been implemented to the first-cycle modeling and simulations for the BEAVRS benchmark problem, propagating the nuclear-data uncertainties to the key core parameters. NJOY has been applied to generate the nuclear-data covariance library based on ENDF/B-VII.1 in the research. The statistical sampling method has been utilized for the uncertainty quantification, based on the conventional “two-step” scheme. First, the nuclear-data uncertainties are propagated to the few-group constants through the lattice modeling and simulations; and then the uncertainties of the key core parameters are quantified through the reactor modeling and simulations. As interests, the uncertainties have been quantified to the critical boron concentrations, axial-power offset and radial assembly-power distributions through the whole life of first cycle. From the numerical results, it can be observed that for the critical boron concentration, the nuclear-data introduced uncertainties can up to be 51 ppm as maximum; for the axial-power offset, the relative uncertainties vary within 1.3% and for the radial assembly-power distributions, the maximum relative uncertainties is about 3.8% at BOL and 0.8% at EOL.

Building and evaluation of a dynamic model for assessing impact of smallholder endowments on food security in agricultural systems in highland areas of central America (SASHACA)

Smallholder agricultural systems have an important role in world food production. Agricultural smallholders in highland areas of the Mesoamerican dry-corridor are central to improve farming systems. The key issue is that the subsistence smallholders are joint producer-consumers, with insufficient food production due to extreme environmental and weather conditions or incomes to supplement their own production from market sources. Modelling offers an approach for testing and improving knowledge about complex systems. The aim of this paper is to describe and assess a biophysical and socio-economic model of the smallholder agricultural systems based on maize-bean intercropping in highland areas of Central America. A Vensim® DSS system dynamics model was developed for assessing the impact of Smallholder endowments on food security and to identify critical points to achieve sustainable food security and poverty alleviation in Agricultural Systems in Highland Areas of Central America (SASHACA). The SASHACA model integrates scientific and practical knowledge of crop management, labour, soil water content, soil nitrogen, food consumption and economic components of the system. Model evaluation was conducted through a wide set of tests for assessment of dynamic models and statistical comparison of simulated versus observed data derived from surveys. The model simulates realistic outputs and presents logical behavioural representation. The maximum relative uncertainty of output variables ranged from 30% to 53% for univariate and multivariate sensitivity analyses respectively. The model proved to be adequate for assessing food security under scenarios in low data availability areas. The SASHACA model could be adapted to simulate a wide range of smallholder agricultural systems in highland areas of Central America, and potentially in other locations.

Intercomparison and Uncertainty Assessment of Nine Evapotranspiration Estimates Over South America

AbstractThis study examines the uncertainties and the representations of anomalies of a set of evapotranspiration products over climatologically distinct regions of South America. The products, coming from land surface models, reanalysis, and remote sensing, are chosen from sources that are readily available to the community of users. The results show that the spatial patterns of maximum uncertainty differ among metrics, with dry regions showing maximum relative uncertainties of annual mean evapotranspiration, while energy‐limited regions present maximum uncertainties in the representation of the annual cycle and monsoon regions in the representation of anomalous conditions. Furthermore, it is found that land surface models driven by observed atmospheric fields detect meteorological and agricultural droughts in dry regions unequivocally. The remote sensing products employed do not distinguish all agricultural droughts and this could be attributed to the forcing net radiation. The study also highlights important characteristics of individual data sets and recommends users to include assessments of sensitivity to evapotranspiration data sets in their studies, depending on region and nature of study to be conducted.

Experimental ultrasonic characterization of polyester-based materials for cultural heritage applications

For several years, the Réunion des musées nationaux – Grand-Palais has produced polyester resin reproductions in order to replace marble sculptures that have weakened by outdoor exposure. These objects are made of a complex multilayered polyester composite material including reinforcements to ensure the mechanical strength of the final structure and mineral fillers that allow to imitate the original aesthetics. However, the final structure also weakens because of constant outdoor exposure and ageing. This observation leads today to conduct research related to the structural health monitoring of reproductions for preventive conservation of cultural heritage. This paper presents a nondestructive technique to study the properties of the composite material used to produce reproductions of marble sculptures. Firstly, classical ultrasonic contact measurements were performed to estimate bulk properties and Rayleigh wave velocity. Secondly, experimental Rayleigh wave was measured using contact and laser vibrometry methods. The results show the potential of using ultrasonic surface wave propagation and laser vibrometry method to develop a minimum contact technique to study these polyester-based materials. The maximum relative uncertainty with respect to the expected theoretical Rayleigh wave velocity was close to 12%.

Acceleration of calculation of nuclear heating distributions in ITER toroidal field coils using hybrid Monte Carlo/deterministic techniques

Because the superconductivity of the ITER toroidal field coils (TFC) must be protected against local overheating, detailed spatial distribution of the TFC nuclear heating is needed to assess the acceptability of the designs of the blanket, vacuum vessel (VV), and VV thermal shield. Accurate Monte Carlo calculations of the distributions of the TFC nuclear heating are challenged by the small volumes of the tally segmentations and by the thick layers of shielding provided by the blanket and VV. To speed up the MCNP calculation of the nuclear heating distribution in different segments of the coil casing, ground insulation, and winding packs of the ITER TFC, the ITER Organization (IO) used the MCNP weight window generator (WWG). The maximum relative uncertainty of the tallies in this calculation was 82.7%. In this work, this MCNP calculation was repeated using variance reduction parameters generated by the Oak Ridge National Laboratory AutomateD VAriaNce reducTion Generator (ADVANTG) code and both MCNP calculations were compared in terms of computational efficiency and reliability. Even though the ADVANTG MCNP calculation used less than one-sixth of the computational resources of the IO calculation, the relative uncertainties of all the tallies in the ADVANTG MCNP calculation were less than 6.1%. The nuclear heating results of the two calculations were significantly different by factors between 1.5 and 2.3 in some of the segments of the furthest winding pack turn from the plasma neutron source. Even though the nuclear heating in this turn may not affect the ITER design because it is much smaller than the nuclear heating in the turns that are closer to the plasma source, it is our recommendation to adopt the utilization of ADVANTG in similar calculations to increase the reliability of MCNP calculations of detailed distributions of nuclear responses.

AWJ cutting of copper processed by ECAP

Copper samples, processed by equal channel angular pressing (ECAP), were cut using abrasive water jet (AWJ) and the cut walls were investigated. The aim was to prove a relation between AWJ declination angle and selected material properties, especially hardness, strength, and grain size. Three groups of samples were cut: the first one just after pressing (fresh samples), the second one after 1 month past ECAP application, and the third one after 6 months after ECAP processing. The comparison shows the following results. Just after the ECAP process, the declination angle increases with increasing number of passes through the ECAP die, i.e., the characteristic material properties (strength and hardness) increase throughout the tested angle range. The character of relations between number of passes and investigated parameters, such as declination angle, hardness, or strength, is parabolic for 1-month-old samples, with maximum around eight ECAP passes. The last group of samples, cut after 6 months after their preparation, does not indicate simple relations between number of ECAP passes and either the declination angle or material parameters, namely hardness. The mutual comparison of a theoretical model based on values of material properties from measurements and literature and experiment shows maximum relative uncertainty 5.9 %. This result proves that declination angle measurement on striations present on cut walls of AWJ can be used for evaluation of hardness, strength, and grain size.

Analytical model for photon peripheral dose estimation in radiotherapy treatments

This work aims to generate a simple analytical model that allows estimation of peripheral photon equivalent dose to organs of individual patients, valid for any isocentric technique. Photon radiation scattered in the LINAC head has been simulated as a virtual source of radiation emitting isotropically so that, before reaching a point inside the patient, it decreases with the square law and with attenuation due to air and tissue. Leakage has been simulated as a constant background dose along the patient. Firstly, a dose-to-points basic model was proposed and parameterized by fitting it to absorbed doses measured with TLD-700 in a humanoid phantom. Secondly, this model was generalized to any other situation involving intensity-modulated beams of any size and shape. Validation of this general model, usable beyond 10 cm from the field edge, was carried out by comparing estimation with TLD-100 doses for VMAT and IMRT treatments as well as with experimental data and models existing in the bibliography. Finally, an equivalent dose-to-organs model has been proposed by rescaling individual anatomical dimensions onto a mathematical phantom in order to make an estimation of organ length for dose calculation. The parameterized extended model, accounting for intensity-modulated beams of any shape, predicts measurements with a maximum relative uncertainty of ±25%. This general model, easy to apply in a clinical routine thanks to the ready availability of input parameters, has been proposed and validated for estimation of photon equivalent doses to peripheral organs. Finally, as a first step, it has been implemented into a piece of software termed PERIPHOCAL (PERIpheral PHOton CALculation), which is easily transferred to a commercial treatment planning system (TPS).

FORCE CALIBRATION OF NANO UNIVERSAL TESTING MACHINE USING MILLIGRAM WEIGHTS

This paper presents an approach for calibrating the force transducer on the nano universal testing machine using milligram weights. Previous research on force calibration of such a system focused on the range from 10 mN to 200 mN, ignoring forces below 10 mN. The main purpose of this study is to analyze and calculate the uncertainty of force measurements within the range from 0.2 mN to 10 mN. The ABA calibration method in accordance with OIML R111-1 is adopted to determine the uncertainty in force measurement. The results indicate that the maximum relative uncertainty of force measurement is 7.0 × 10−3 with a 95% confidence level. The investigation can be used as the basis for evaluating measurement uncertainty of the system in small force range.

FEA calculation of pressure distortion coefficients of gas-operated pressure balances – EURAMET project 1039

Finite element analysis methods were developed and applied to gas piston–cylinder units (PCUs) of piston- and cylinder-floating configuration (2, 5, 10 and 20)cm2 nominal effective area, operated in gauge and absolute mode at pressures (0.06–7.5)MPa to determine their zero pressure and pressure-dependent effective areas, as well as pressure distortion coefficients (λ) with associated uncertainties. Real dimensional properties of the PCUs were used. λ were found to be independent of gas (ideal, N2, He) within the viscous flow model, but strongly dependent on the gap shape, operation mode and elastic properties. Results demonstrate good agreement for λ, with its uncertainty for different PCUs varying between (0.03 and 0.21)×10−6MPa−1 corresponding to maximum relative uncertainties in pressure of (0.07–0.34)×10−6.

TU-D-BRB-06: A Monte-Carlo Investigation of the Beam Quality Conversion Factor

Purpose: Clinical reference dosimetry based on absorbed dose standards requires the use of a beam quality conversion factor, kQ. This parameter is ionization chamber-specific and varies with beam quality. Current dosimetry protocols provide values of kQ for commonly used chambers (AAPM TG-51 (1999), IAEA TRS-398 (2000)). However, additional chambers are being used clinically for which values are not available. The aim is to obtain values of kQ for various ionization chambers over a range of photon beam quality using Monte Carle (MC) simulations. There is particular interest in obtaining values for those chambers which cannot be calculated using the TG-51 approach because of missing data, specifically for chambers with a relatively small collecting volume. Method and Materials: Direct MC calculations were made of the absorbed dose to water and the absorbed dose to gas in an ionization chamber at the reference depth in a water phantom. The simulations were performed using the EGSnrc user-codes cavity and egs_chamber to model the ionization chambers using the extended geometry package. The source input used a collimated point source from tabulated spectra for Cobalt-60 beams and various clinical linear accelerators. The chamber geometries were modeled using specifications from the various manufacturers' manuals. Values for seven of the eleven chambers that were simulated in this study are available in TG-51. Results: The calculations of values which are available in TG-51 had a maximum difference of 0.4% from the TG-51 values. The maximum relative uncertainty in these calculations was 0.2%. In cases where experimental results were available the calculations were compared with measurements. Values were obtained for the chambers not provided in TG-51. Conclusion: Direct calculations of kQ show agreement with those provided in TG-51. The simulations are being extended to cylindrical chambers in electron beams and to plane-parallel chambers in photon beams.

SU‐FF‐T‐452: Verification of Cell Irradiation Dose Deposition Using Radiochromic Film

Purpose: A standard technique for cell survival curve determination is based on the cell culture technique. Survival curve is reconstructed by plotting the fraction of surviving cells as a function of delivered dose. We describe a technique that irradiates all cells at once by using two wedges (static and dynamic wedge concurrently) on a linear accelerator whereby we irradiate the multi‐compartmental dish to a desired dose range from 1 – 5 Gy. We also employed EBT model GAFCHROMIC™ film to verify the dose delivered in each of the compartments within the dish. Our technique overcomes the problem of possible contamination during the re‐plating after irradiation and all cells are kept under the same conditions.Method and Materials: Cells, plated within a multi‐compartmental (8 × 12) dish were irradiated using a 6 MV photon beam employing a combination of 60° physical (“static”) wedge and 60° Enhanced Dynamic Wedge. A 10 cm by 12.5 cm piece of EBT film was positioned below cells. Spatial dosimetry was performed using the AGFA Arcus II document scanner. The change in optical density of the unexposed film piece was subtracted from the exposed film piece to obtain the final netOD that was converted to dose using previously determined calibration curve for the reference type dosimetry. Results: Technique described delivers a dose gradient ranging from 1 Gy within the first compartment to 5 Gy within the last compartment. Maximum relative uncertainty of 2% was observed at 5 Gy. Conclusions: In this work, we describe a technique using a combination of static and dynamic wedge to obtain doses necessary to reliably perform MTT Assay in a dose range from 1 Gy to 5 Gy within a multi compartmental dish. We have also described a method to verify the dose delivered using the EBT model radiochromic film.