Calibration Function Research Articles

Calibration of an Arduino-based low-cost capacitive soil moisture sensor for smart agriculture

Abstract Agriculture faces several challenges to use the available resources in a more environmentally sustainable manner. One of the most significant is to develop sustainable water management. The modern Internet of Things (IoT) techniques with real-time data collection and visualisation can play an important role in monitoring the readily available moisture in the soil. An automated Arduino-based low-cost capacitive soil moisture sensor has been calibrated and developed for data acquisition. A sensor- and soil-specific calibration was performed for the soil moisture sensors (SKU:SEN0193 - DFROBOT, Shanghai, China). A Repeatability and Reproducibility study was conducted by range of mean methods on clay loam, sandy loam and silt loam soil textures. The calibration process was based on the data provided by the capacitive sensors and the continuously and parallelly measured soil moisture content by the thermogravimetric method. It can be stated that the response of the sensors to changes in soil moisture differs from each other, which was also greatly influenced by different soil textures. Therefore, the calibration according to soil texture was required to ensure adequate measurement accuracy. After the calibration, it was found that a polynomial calibration function (R2 ≥ 0.89) was the most appropriate way for modelling the behaviour of the sensors at different soil textures.

Quantification of THC, metabolites, and related compounds in whole blood using LC-MS/MS

The objective of this study was to develop and validate a method for cannabinoids in whole blood. Cannabis is a frequently used recreational drug in Sweden. Even though smoking is the preferred route of administration an increase in the use of edible products have increased during recent years. Edibles can be products mainly containing cannabidiol (CBD) and only minor amounts of tetrahydrocannabinol (THC) but also products with THC as the main active compound. Studies have shown that the metabolism of THC is different when consumed by the oral route compared to smoking. To enable better interpretation, we aimed to develop an automated supported liquid extraction routine method including the analytes THC, carboxy-THC, 11-hydroxy-THC, CBD, tetrahydrocannabinolic acid A (THCA-A), and cannabidiolic acid (CBDA). Sample preparation was performed on a Hamilton Star and a Biotage Extrahera robot. A 0.2 g whole blood aliquot was transferred to a 96-well plate and diluted with 0.1% formic acid and internal standard (1:1) before extraction with 3 × 600 μL of tertbutylmethylether. After evaporation samples were reconstituted in 100 μL 0.2% formic acid in water/methanol 30/70. All analytes were detected using Waters Xevo TQ-XS triple quadrupole MS with a UniSpray ionization source operated in both positive and negative ion mode. Chromatographic separation was achieved using a 10 μL injection and an 8.0 min gradient elution on a Waters Acquity Premier HSS T3 column with a Waters Acquity I-Class UHPLC system. Mobile phase A was 0.2% formic acid in water and mobile phase B was methanol. Method validation included selectivity, qualitative matrix effects, extraction recovery, calibration function, limit of quantitation, precision and accuracy, carry over, dilution integrity, stability in matrix as well as in extracted samples. The method was applied to authentic cases as a proof of concept. All analytes were baseline separated. No interferences were seen at the retention times of the analytes. Qualitative matrix effects were less than 10% except carboxy-THC (27%) and 11-hydroxy-THC (66%). Extraction recoveries were 29% for THC, 68% for carboxy-THC, 49% for 11-hydroxy-THC, 29% for CBD, 63% for THCA-A and 67% for CBDA. All analytes were best described by quadratic calibration curves using 1/X weighting with observed mean deviations from the nominal value of -8% to 8%. Calibration ranges were established from 0.0002–0.03 μg/g for all analytes except carboxy-THC (0.002–0.3 μg/g). Within-day precision was less than 5% for all analytes with accuracies between 93 and 101%. Between-day precision was less than 10% for THC, carboxy-THC, 11-hydroxy-THC, and CBD but 14% and 25% for THCA-A and CBDA, respectively. All accuracies within 95–108%. A maximum carry over of 0.8% was seen but did not result in false positive samples. Up to 4 times dilution gave results within 20% of the true value. All analytes except THCA-A were stable during two days at room temperature, three weeks at 4 °C as well as in extracts stored at 10 C. THCA-A showed significant degradation over time at room temperature as well as in extracts. Results from 254 samples run during the first weeks of routine showed that 99.9% of concentrations were within the calibration ranges. The mean concentrations (μg/g) were 0.0053, 0.0023, 0.042, 0.00073, and 0.00094 for THC, 11-hydroxy-THC, carboxy-THC, CBD, and THCA-A, respectively. 97.7% of 11-hydroxy-THC/THC ratios were below 1.0 pointing towards smoking as the route of administration but showed detectable THCA-A in 23.1% suggesting that combustion was not complete. Only one case had a CBD concentration higher than THC suggesting intake of CBD products. We conclude that the method showed acceptable validation results and was suitable for routine analyses of cannabinoids in whole blood samples.

Fast and sensitive method for the determination of 17 designer benzodiazepines in hair by liquid chromatography tandem mass spectrometry

Our aim was to develop and validate a fast, sensitive, and specific method determining 17 designer benzodiazepines (adinazolam, clobazam, clonazolam, delorazepam, deschloroetizolam, diclazepam, etizolam, flualprazolam, flubromazepam, flubromazolam, flunitrazolam, N-desmethylclobazam, nifoxipam, nitrazolam, meclonazepam, pyrazolam and zolazepam) in hair by liquid chromatography tandem mass spectrometry (LC-MS/MS). In recent years, identification and analysis of designer benzodiazepines have become a challenge in forensic toxicology. These substances are analogues of the classic benzodiazepines, but their pharmacology is not well known, and many of them have been associated with overdoses and deaths. As a result, there has been a surge in efforts to develop analytical methods to determine these compounds in different biological samples. Most publications have been focused on blood and urine; however, publications concerning alternative matrices, such as hair, are scarce. Hair samples were decontaminated, pulverized, and a 20 mg aliquot was incubated in methanol in an ultrasonic bath (1 h, 25 °C). The supernatant was evaporated and reconstituted in 200 μL of mobile phase composed of 0.1% formic acid and acetonitrile (95:5). The extracts were filtered before injection into the LC-MS/MS. Chromatographic separation was performed in reversed phase using a C18 column in gradient mode. All analytes eluted from the chromatographic column in 8 min. Two multiple-reaction monitoring transitions in positive mode were used to identify each compound. The method was validated based on the AAFS Standards Board (ASB) Standard Practices for Method Validation in Forensic Toxicology and applied to authentic cases as proof of concept. The best calibration model for all analytes was a linear model with 1/x weighting. The limits of quantification were 5 or 25 pg/mg, depending on the analyte, and calibration functions were linear up to 200 pg/mg. Imprecision was < 20% ( n = 15) and bias was from −13 to 18% ( n = 15). All the analytes yielded high extraction efficiencies > 70% but displayed ion suppression between −63% and −24% ( n = 10). No carryover was observed. All samples showed good stability after 48 h at 10 °C in the autosampler, except for nifoxipam, etizolam, flubromazepam and diclazepam, which showed significant loss in signal. The method was applied to 19 authentic cases. Five 3-cm segments from three different cases were positive for flualprazolam (< LOQ – > 200 pg/mg) and/or etizolam (47.4–88.5 pg/mg). Few publications have focused on the analysis of a limited number of designer benzodiazepines in hair. As a result, limited information is available regarding hair concentrations of these type of substances. The present method is the most comprehensive method to date including 17 analytes. In the analysis of authentic cases, etizolam concentrations were within the range of previous reports; however, no hair concentrations for flualprazolam have been previously described in the literature. The present validated method has proven to be fast, sensitive, specific, and capable of determining 17 designer benzodiazepines in hair using LC-MS/MS.

Calibration and characterisation of four chlorophyll meters and transmittance spectroscopy for non-destructive estimation of forest leaf chlorophyll concentration

Chlorophyll meters enable efficient and non-destructive estimation of leaf chlorophyll concentration (LCC), but require calibration against destructively-determined values to provide an absolute quantity that is comparable between different studies and species. Well-established instruments can provide accurate LCC estimates, but the performance of recent low-cost devices is less clear. Questions also remain over the choice of generic or species-specific calibration functions. Additionally, little attention has been paid to transmittance spectroscopy, which offers substantially increased spectral sampling, as a potential alternative. We investigated the well-established Konica Minolta SPAD-502+ and Opti-Sciences CCM-200 instruments and the low-cost atLEAF CHL PLUS and PhotosynQ MultispeQ V1.0 devices for non-destructive estimation of forest LCC. We calibrated each chlorophyll meter against destructively-determined LCC values for eight temperate deciduous broadleaf forest species, and characterised relationships between the different instruments. We also assessed whether transmittance spectroscopy could provide improved accuracy. All investigated chlorophyll meters demonstrated similarly strong relationships with destructively-determined LCC, indicating that once calibrated, even the low-cost devices represent a suitable choice for non-destructive forest LCC estimation. With the exception of oak, chlorophyll meter – LCC relationships were consistent between species, indicating that for these species, a generic calibration function may be suitable depending on required accuracy. Specifically, LCC values provided by the generic calibration functions fell within the prediction uncertainties of species-specific calibration functions for most considered species. The generic calibration functions explained between 2% and 16% less variation in LCC than the species-specific calibration functions, resulting in a mean increase in RMSE (NRMSE) of just 0.01 g m−2 to 0.02 g m−2 (2% to 5%). Transmittance spectroscopy was able to provide improved performance over the chlorophyll meters, indicating that they may miss some relevant spectral information at blue and green wavelengths. However, this improved performance comes at the expense of reduced practicality in the field.

Theoretical Model of a RI THz Sensor Realized by Coherent Perfect Absorption With Optical Phase Modulation

In this work, a theoretical model for the refractive index (RI) detection that employs phase modulation for absorption compensation based on the mechanism of coherent perfect absorption (CPA) is presented. Different from most sensors using frequency modulation, the proposed sensor measures RI with phase modulation in a narrow frequency range. Due to the fragility of CPA, the narrow absorption peak is highly sensitive to changes in RI values of the dielectric layers inserted in the structure. Benefiting from this, the proposed sensing method is a feasible scheme of high-precision and high-sensitivity detection. By filling the structure with the substance to be detected, the measurement and analysis of substances with RI of 3.510-3.565 and 1.45-1.52 can be accurately achieved, respectively. For the measurement of RI from 3.51 to 3.565, the maximum sensitivity (S) is up to 3749.79 °/RIU, and the limit of detection (LoD) is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> RIU on average. If this sensor is used to measure RI of 1.45-1.52, the maximum S is 2775.1 °/RIU, and the average LoD is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.8\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> RIU. The structure consists of ferrites and other conventional materials. The magnetic field applied to the ferrite layers is proved to provide a sensor calibration function. The effects of the thicknesses of the dielectric layers and the incident angle on the sensing performance are also discussed. The suggested theoretical model has a better performance compared with the conventional sensors. This theoretical study introduces a novel idea for RI sensing and expands on the use of CPA in sensors.

Quantification in bioimaging by LA-ICPMS - Evaluation of isotope dilution and standard addition enabled by micro-droplets

This study explores quantitative bioimaging as enabled by laser ablation-inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOFMS), designing standardization methods based on robotic micro-droplet dispensing. The potential of producing controlled and highly precise pL-volume droplets was exploited to establish on-tissue isotope dilution and standard addition. Both strategies eliminate matrix effects and offer high metrological order traceable to SI units. The absolute quantity was obtained for μm-sized regions of interest in tissue samples, as defined by the extension of the deposited pL-volume droplet. While the gold standard isotope dilution (ID) was restricted to the accurate quantification of a single element, i.d. platinum in different tissue samples (mouse liver, spleen and tumor tissue), multiplexed matrix-matched calibration was obtained by on-tissue standard addition by depositing a dilution series of certified multi-element standards. Here, the working range was determined by the heterogeneity of the tissue samples and the background levels of elements intrinsically present and/or artificially introduced during sample preparation. Both methods, ID and standard addition served as reference methods for validation of external calibration using gelatin-based micro-droplet standards. Given full ablation, these external standards revealed a high dynamic range together with an excellent repeatability. Where applicable, the cross-validation revealed consistent quantitative results for the three quantification approaches. The comparable sensitivity obtained for standard addition and external standardization, respectively expressed as slope of the calibration function, provided proof that gelatin-based micro-droplets could serve as matrix-matched calibrations. Therefore, gelatin micro-droplets offer a valid tool for multiplexed matrix-mimicking standardization at high-throughput.

Accelerating and improving radiochromic film calibration by utilizing the dose ratio in photon and proton beams.

PurposeRadiochromic films are versatile 2D dosimeters with high‐resolution and near tissue equivalence. To assure high precision and accuracy, a time‐consuming calibration process is required. To improve the time efficiency, a novel calibration method utilizing the ratio of the same dose profile measured at different monitor units (MUs) is introduced and tested in a proton and photon beam.MethodsThe calibration procedure employs the dose ratio of film measurements of the same relative profile for different absolute dose values. Hence, the ratio of the dose is constant at any point of the profile, but the ratio of the net optical densities is not constant. The key idea of the method is to optimize the calibration function until the ratio of the calculated doses is constant. The proposed method was tested in the dose range between 0.25–12 and 1–6 Gy in a proton and photon beam, respectively. A radial symmetric profile and a rectangular profile were created, both having a central plateau region of about 3 cm diameter and a dose falloff of about 1.5 cm at larger distances. The dose falloff region was used as input for the optimization method and the central plateau region served as dose reference points. Only the plateau region of the highest dose entered the optimization as an additional objective. The measured data were randomly split into differently sized training and test sets. The optimization was repeated 1000 times with random start value initialization using the same start values for the standard and the gradient method. Finally, a proton plan with four dose levels was created, which were separated spatially, to test the possibility of a full calibration within a single measurement.ResultsParameter estimation was possible with as low as one dose ratio used for optimization in both the photon and the proton case, yet exhibiting a high sensitivity on the dose level. The root mean squared deviation (RMSD) of the dose was less than 1% when the dose ratio was in the order of 20, whereas the median RMSD of all optimizations was 1.7%. Using four dose levels for optimization resulted in a median RMSD of 1% when randomly selecting the dose levels. Having at least one dose ratio of about 20 included in the optimization considerably improved the RMSD of the calibration function. Using six or eight dose levels reduced the sensitivity on the dose level selection and the median RMSD was 0.8%. A full calibration was possible in a single measurement having four dose levels in one plan but spatially separated.ConclusionsThe number of measurements required to obtain an EBT3 film calibration function could be reduced using the proposed dose ratio method while maintaining the same accuracy as with the standard method.

Digital Quantification Method for Sensitive Point-of-Care Detection of Salivary Uric Acid Using Smartphone-Assisted μPADs.

Uric acid (UA) is an important biomarker for many diseases. A sensitive point-of-care (POC) testing platform is designed for the digital quantification of salivary UA based on a colorimetric reaction on an easy-to-build smartphone-assisted microfluidic paper-based analytical device (SμPAD). UA levels are quantified according to the color intensity of Prussian blue on the SμPAD with the aid of a MATLAB code or a smartphone APP. A color correction method is specifically applied to exclude the light effect. Together with the engineering design of SμPADs, the background calibration function with the APP increases the UA sensitivity by 100-fold to reach 0.1 ppm with a linear range of 0.1-200 ppm. The assay time is less than 10 min. SμPADs demonstrate a correlation of 0.97 with a commercial UA kit for the detection of salivary UA in clinical samples. SμPADs provide a sensitive, fast, affordable, and reliable tool for the noninvasive POC quantification of salivary UA for early diagnosis of abnormal UA level-associated health conditions.

A Two-Camera Depth From Defocus Imaging System And Sensitivity Analysis

A single lens, two-camera imaging system using backlight photography has been previously proposed based on Depth from Defocus (DFD) for the measurement of size and three-dimensional position of particles or drops. It makes use of two images with different degrees of defocus blur captured simultaneously at different imaging planes. In the present study, the influence of system and particle parameters on the calibration functions and measurement uncertainties of such a system have been comprehensively investigated and experimentally verified. The parameters varied include the distance between the imaging planes, the image bit resolution, pixel resolution and the random image noise. Furthermore, the intensity and position of the backlighting and the type of particle and its relative refractive index have been varied. Experimental verification was conducted using calibration dot targets, polystyrene latex spheres, and pulverized coal powders. A sensitivity analysis was performed using relative errors or differences for the three quantities - calibration function, particle size and particle position. The study concludes with explicit recommendations on which quantities are most influential in determining measurement accuracy and therefore, must be carefully controlled. Using this imaging system, measurements were conducted for a mono-sized standard latex sphere clouds suspended in a water container, and the results of particle size distribution were compared with that obtained using a common single lens, one-camera imaging system with thresholding image processing. Subsequently, the system is used for measurement of a sparse spray. Comparison measurements using the laser diffraction technique and the analysis of focused images are provided,with relatively good quantitative agreement. The measurement depth range based on the DFD method exhibits a simple proportional relationship with particle size, which can be used for bias correction of the particle size distribution and number density. This leads to a highly resolved measurement volume depth; hence, an accurate estimation of the overall measurement volume, allowing very accurate volume number density distributions to be estimated. This constitutes a decisive advantage over existing optical techniques for particle size measurements.

EMG-Informed Neuromusculoskeletal Models Accurately Predict Knee Loading Measured Using Instrumented Implants.

Using a musculoskeletal modelling framework, we aimed to (1) estimate knee joint loading using static optimization (SO); (2) explore different calibration functions in electromyogram (EMG)-informed models used in estimating knee load; and (3) determine, when using an EMG-informed stochastic method, if the measured joint loadings are solutions to the muscle redundancy problem when investigating only the uncertainty in muscle forces. Musculoskeletal models for three individuals with instrumented knee replacements were generated. Muscle forces were calculated using SO, EMG-informed, and EMG-informed stochastic methods. Measured knee joint loads from the prostheses were compared to the SO and EMG-informed solutions. Root mean square error (RMSE) in joint load estimation was calculated, and the muscle force ranges were compared. The RMSE ranged between 192-674 N, 152-487 N, and 7-108 N for the SO, the calibrated EMG-informed solution, and the best fit stochastic result, respectively. The stochastic method produced solution spaces encompassing the measured joint loading up to 98% of stance. Uncertainty in muscle forces can account for total knee loading and it is recommended that, where possible, EMG measurements should be included to estimate knee joint loading. This work shows that the inclusion of EMG-informed modelling allows for better estimation of knee joint loading when compared to SO.

Formulation of Wavelet Based Multi‐Scale Multi‐Objective Performance Evaluation (WMMPE) Metric for Improved Calibration of Hydrological Models

AbstractEstimation of the hydrological model parameters, known as model calibration, is an important step in application of these models for various water resources problems. In the auto‐calibration approach, the match between the simulated and observed variables is assessed using the statistical performance measures, which are used as objective functions. Earlier studies show that the use of traditional single‐objective functions alone cannot capture all the features of the hydrographs, motivating the utilization of multi‐objective calibration. Further, wavelet‐based approaches can capture features that occur at different time scales. In this study, Wavelet Transforms are employed to formulate a Wavelet based Multi‐Scale Multi‐Objective Performance Evaluation (WMMPE) metric that combines multiple standard metrics at multiple time scales. The performance of WMMPE along with other objective functions such as Nash Sutcliffe Efficiency (NSE), Kling Gupta Efficiency (KGE)), Euclidean distance based Multi Objective Calibration Function and wavelet based Multi‐Scale NSE in calibrating two conceptual hydrologic models were tested on 53 watersheds. The performance of the five calibrated models were evaluated for their efficacy in simulating different characteristics of hydrograph such as, low and high flows, water balance components, frequency domain characteristics and average error magnitude. The results show that WMMPE calibrated models are performing well in matching all the flow segments of hydrograph in &gt;22 basins for the two conceptual models. Further, results of the analysis suggested that the presence of outliers have minimum impact on the simulation of WMMPE calibrated models in the validation period.

Fast and Sensitive Method for the Determination of 17 Designer Benzodiazepines in Hair by Liquid Chromatography-Tandem Mass Spectrometry.

In recent years, identification and analysis of designer benzodiazepines have become a challenge in forensic toxicology. These substances are analogs of the classic benzodiazepines, but their pharmacology is not well known, and many of them have been associated with overdoses and deaths. As a result, there has been a surge in efforts to develop analytical methods to determine these compounds in different biological samples. Our aim was to develop and validate a fast, sensitive and specific method for determining 17 designer benzodiazepines (adinazolam, clobazam, clonazolam, delorazepam, deschloroetizolam, diclazepam, etizolam, flualprazolam, flubromazepam, flubromazolam, flunitrazolam, N-desmethylclobazam, nifoxipam, nitrazolam, meclonazepam, pyrazolam and zolazepam) in hair by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Hair samples were decontaminated and pulverized, and a 20 mg aliquot was incubated in methanol in an ultrasound bath (1 h, 25°C). The supernatant was evaporated and reconstituted in 200 µL of mobile phase, and the extracts were filtered (nano-filter vials) before injection into LC-MS-MS. All analytes were eluted from the chromatographic column in 8 min, and two multiple-reaction monitoring (MRM) transitions were used to identify each compound. The limits of quantification were 5 or 25 pg/mg depending on the analyte, and the calibration functions were linear to 200 pg/mg. Imprecision was <19.2% (n = 15), and bias was from -13.7 to 18.3% (n = 15). All the analytes yielded high extraction efficiencies >70% and displayed ion suppression between -62.8% and -23.9% (n = 10). The method was applied to 19 authentic cases. Five samples were positive for flualprazolam (<LOQ-> 200 pg/mg) and/or etizolam (47.4-88.5 pg/mg). In conclusion, the present validated method has proven to be fast, sensitive, specific and capable of determining 17 designer benzodiazepines in hair using LC-MS-MS.

Experimental and Simulated Spectral Gamma-Ray Response of a NaI(Tl) Scintillation Detector used in Airborne Gamma-Ray Spectrometry

Abstract. The objective of this work is to simulate the spectral gamma-ray response of NaI(Tl) scintillation detectors for airborne gamma-ray spectrometry (AGRS) using the state-of-the-art multi-purpose Monte Carlo code FLUKA. The study is based on a commercial airborne gamma-ray spectrometry detector system with four individual NaI(Tl) scintillation crystals and a total volume of 16.8 L. To validate the developed model, radiation measurements were conducted using 57Co, 60Co, 88Y, 109Cd, 133Ba, 137Cs and 152Eu calibration point sources with known activities and source-detector geometries under laboratory conditions. In addition, empirical calibration and resolution functions were derived from these measurements combined with additional radiation measurements adopting natural uranium, thorium and potassium volume sources. The simulation results show superior accuracy and precision compared to previous AGRS simulation models with a median relative spectral error &lt; 10 % for most of the radiation sources. Moreover, the implementation of a lower level discriminator model and detailed modelling of the laboratory result in a significant improvement in model accuracy for spectral energies &lt; 100 keV compared to previous studies. Yet thorough statistical analysis incorporating statistical and systematic uncertainty estimates revealed statistically significant deviations between the simulated and measured spectra in the spectral region around the Compton edge, which could be attributed to the scintillator non-proportionality. These findings imply that the linear energy deposition model applied in this and previously developed AGRS simulation models should be revised and considered to be replaced by more accurate non-proportional models.

High-Precision Regulation of Nano-Grating Linewidth Based on ALD.

A nano-grating standard with accurate linewidth can not only calibrate the magnification of nano-measurement instruments, but can also enable comparison of linewidths. Unfortunately, it is still a challenging task to control the linewidth of nano-grating standards. Accordingly, in this paper, atomic layer deposition (ALD) was used to regulate the linewidth of the one-dimensional grating standards with a pitch of 1000 nm, fabricated by electron beam lithography (EBL). The standards were measured using an atomic force microscope (AFM) before and after ALD, and the linewidth and pitch of the grating were calculated through the gravity center method. The obtained results prove that the width of a single grating line in the standard can be regulated with great uniformity by precisely utilizing ALD. Meanwhile, the proposed method does not affect the pitch of grating, and the measurement uncertainty of standards is less than 0.16% of the pitch, thereby demonstrating a high surface quality and calibration reliability of the standards, and realizing the integration of linewidth and pitch calibration functions. Moreover, the precise and controllable fabrication method of the micro-nano periodic structure based on ALD technology has many potential applications in the fields of optoelectronic devices and biosensors.

Flexible, Equipment-Wearable Piezoelectric Sensor With Piezoelectricity Calibration Enabled by In-Situ Temperature Self-Sensing

Flexible piezoelectric sensors have attracted much attention due to good dynamic response, high sensitivity, and self-powered sensing advantages. However, piezoelectric outputs are usually affected by temperature variation, thus limit their applications on industrial intelligent equipment. Here, a new flexible piezoelectric sensor with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> temperature sensing and piezoelectricity calibration function is developed. The sensor can calibrate the piezoelectric output based on temperature to achieve high-accuracy sensing capability. It consists of a flexible polyimide substrate, S-shaped platinum interdigital electrodes and aligned piezoelectric fibers. The designed S-type electrode with thermosensitive effect measures the temperature <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> , and then the piezoelectric strain output from P(VDF-TrFE) fibers is calibrated according to the temperature. The temperature sensor has a high sensitivity of 19.2 Ω/°C with good linearity, and keeps good accuracy under bending deformation. When the working temperature range is 25 °C–60 °C, the sensor has a good piezoelectricity calibration effect, so that it maintains a stable sensitivity of 244 mV/μϵ without being affected by temperature. Furthermore, this article systematically studied the influence of temperature on piezoelectric output, and established a calibration method to improve the accuracy of piezoelectric output under temperature changes. Finally, the flexible integrated sensor was conformally attached on the bearing surface to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> sensing temperature and micro-strain. The structural design and piezoelectricity calibration method can promote the application of flexible piezoelectric sensors in the industrial field.

Evaluation of Default, Soil-Specific, and Clay Content Correction Calibration Functions for Dielectric Sensors in Soils with Differing Properties

Evaluation of Default, Soil-Specific, and Clay Content Correction Calibration Functions for Dielectric Sensors in Soils with Differing Properties

Robust Dual Optical Sensor for pH and Dissolved Oxygen

As part of moving our optical pH and dissolved oxygen (DO) optical chemosensors toward industrial applications, we decided to explore a many-sensors-in-one principle. It was tested if physical segregation of the optical sensor components in a single sensor polymer could remove cross-talk and quenching. It was found that a design concept with an oxygen-responsive dye in polymer nanoparticles and a pH-responsive dye in an organically modified siloxane polymer resulted in a robust pH/O2 dual optical sensor. Individually, the O2-sensitive nanoparticles, a known component for optical DO sensing, and the pH sensor are operational. Thus, it was decided to test if nanoparticles enclosed within the pH-sensitive responsive sol-gel (i) could work together if segregated and (ii) could operate with a single intensity signal that is without a reference signal; developments within industrial optical sensor technology indicate that this should be feasible. The prototype optode produced in this work was shown to have a negligible drift over 60 h, bulk diffusion-limited DO response, and independent response to pH and O2. On the individual optode, pH calibration was found to show the expected sigmoidal shape and pKa, while the complexity of the calibration function for the DO signal was significant. While the engineering of the sensor device, optics, and hardware are not robust enough to attempt generic sensor calibration, it was decided to demonstrate the design concept in simple fermentation experiments. We conclude that the dual sensor design with the physical segregation of components is viable.

Calibration of soil moisture sensors, determination of soil water retention properties for precision irrigation based on soil water content measurements

Water is becoming a scarce commodity. Therefore, proper water management in precision irrigation is crucial to increase productivity and reduce the cost of crop production. Precision irrigation is based on measuring the soil water content, which is often measured with dielectric sensors that measure the apparent permittivity of the soil. Although the sensors are already equipped with a factory calibration function that converts the measured permittivity into volumetric water content, the function does not work properly for all soil types. It is therefore recommended to check whether a soil-specific calibration is required for accurate soil water content measurements. Precise irrigation also requires adequate determination of soil water retention properties, which can be determined using various procedures and methods. In this paper, we presented the results of applying different approaches to determine soil-specific calibration functions using two types of dielectric sensors (SM150T, Delta-T Devices and MVZ 100, Eltratec) in different soil samples obtained from locations in Slovenia where precision irrigation is performed. In addition, the results of determining the water retention properties of the soil using different methods were also compared.

A simulation analysis to explore when using a calibration function is preferred over a scalar factor for calibrating safety performance functions

The Highway Safety Manual (HSM) recommends calibrating Safety Performance Functions using a scalar calibration factor. Recently, a few studies explored the merits of estimating a calibration function instead of a calibration factor. Although it seems a promising approach, it is not clear when a calibration function should be preferred over a scalar calibration factor. On the one hand estimating a scalar factor is easier than estimating a calibration function; on the other hand, the calibration results may improve using a calibration function. This study performs a simulation study to compare the two calibration strategies for different ranges of data characteristics (i.e.: sample mean and variance) as well as the sample size. A measure of prediction accuracy is used to compare the two methods. The results show that as the sample size increases, or variation of data decreases, the calibration function performs better than the scalar calibration factor. If the analyst can collect a sample of at least 150 locations, calibration function is recommended over the scalar factor. If the HSM recommendation of 30-50 locations is used and the analyst desires a better accuracy, calibration function is recommended only if the coefficient of variation of data is less than 2. Otherwise, calibration factor yields better results.

Chlorophyll measurements in Alstroemeria sp. using SPAD-502 meterand the color space CIE L*a*b*, and its validation in foliar senescence

Our research aimed to study the correlation between the SPAD-502 readings and the color space CIE L*a*b* values in two cultivars of Alstroemeria sp. during leaf senescence and to evaluate the statistical criteria used in the selection of the best fit calibration functions. We demonstrate the importance of the Akaike information criterion and the parsimonious function besides the coefficient of determination. The reliability of the functions was tested by Student's t-test comparison between the chlorophyll (Chl) estimated from SPAD readings and their chemical concentrations. Polynomial and Hoerl function described well the changes in Chl a and total Chl (a+b) during senescence, but calibration functions are required to perform for each cultivar. We demonstrated that CIE L*a*b* system is reliable to estimate SPAD reading at stages of leaf senescence of Alstroemeria sp. and can be used instead of SPAD-502.