Reducing Calibration Time in PET Systems Based on Monolithic Crystals

In the past years, the gamma-ray detector designs based on the monolithic crystals have demonstrated to be excellent candidates for the design of high-performance PET systems. The monolithic crystals allow to achieve the intrinsic detector resolutions well below state-of-the-art; to increase packing fraction thus, increasing the system sensitivity; and to improve lesion detectability at the edges of the scanner field of view (FOV) because of their intrinsic depth of interaction (DOI) capabilities. The bottleneck to translate to the clinical PET systems based on a large number of monolithic detectors is eventually the requirement of mechanically complex and time-consuming calibration processes. To mitigate this drawback, several methods have been already proposed, such as using non-physically collimated radioactive sources or implementing the neuronal networks (NN) algorithms trained with simulated data. In this work, we aimed to simplify and fasten a calibration process of the monolithic based systems. The Normal procedure consists of individually acquiring a 11 × 11 22Na source array for all the detectors composing the PET system and obtaining the calibration map for each module using a method based on the Voronoi diagrams. Two reducing time methodologies are presented: (i) TEST1, where the calibration map of one detector is estimated and shared among all others, and (ii) TEST2, where the calibration map is slightly modified for each module as a function of their detector uniformity map. The experimental data from a dedicated prostate PET system was used to compare the standard calibration procedure with both the proposed methods. A greater similarity was exhibited between the TEST2 methodology and the Normal procedure; obtaining spatial resolution variances within 0.1 mm error bars and count rate deviations as small as 0.2%. Moreover, the negligible reconstructed image differences (13% deviation at most in the contrast-to-noise ratio) and almost identical contrast values were reported. Therefore, this proposed method allows us to calibrate the PET systems based on the monolithic crystals reducing the calibration time by approximately 80% compared with the Normal procedure.

A Comparison of Fresh Pork Colour Measurements by Using Four Commercial Handheld Devices

The objective of this study was to evaluate the performance of different low-cost instruments to measure pork colour in comparison to Minolta spectrophotometers and industry subjective standards. Canadian pork colour standards and commercial meat (252 loin chops and 46 tenderloins) were measured using two Minolta (CM 700D) spectrophotometers, four Nix sensors (two Nix Pro II and two Nix QC), and four Spectro devices (two Spectro 1 and two Spectro 1 Pro). Using Bland-Altman plots, all hand-held devices revealed similar performance on colour coordinates, except for the Nix Pro II, which had more variability on a* value, and Spectro 1 Pro on b* value, when compared to Minolta measurements. Low RSD values (< 5%) were obtained from repeated measurements on Canadian colour standards. The trend of colour coordinates on colour scores (0–6) were similar for all four commercial instruments, except for a* from Nix Pro and b* from Spectro 1. The correlation coefficients between subjective standards and colour coordinates from the Nix and Spectro devices were slightly higher than the Minolta spectrophotometers. Even though Nix and Spectro 1 series instruments generated different absolute colour coordinate values on meat samples, these pocket-size instruments presented great reliability to measure pork surface colour. However, operational limitations of the instruments, such as the internal calibration time between samples for the Spectro 1 series, should also be considered.

On-Site Calibration Method for Line-Structured Light Sensor-Based Railway Wheel Size Measurement System

Line-structured light has been widely used in the field of railway measurement, owing to its high capability of anti-interference, fast scanning speed and high accuracy. Traditional calibration methods of line-structured light sensors have the disadvantages of long calibration time and complicated calibration process, which is not suitable for railway field application. In this paper, a fast calibration method based on a self-developed calibration device was proposed. Compared with traditional methods, the calibration process is simplified and the calibration time is greatly shortened. This method does not need to extract light strips; thus, the influence of ambient light on the measurement is reduced. In addition, the calibration error resulting from the misalignment was corrected by epipolar constraint, and the calibration accuracy was improved. Calibration experiments in laboratory and field tests were conducted to verify the effectiveness of this method, and the results showed that the proposed method can achieve a better calibration accuracy compared to a traditional calibration method based on Zhang’s method.

Calibration and Optimization of an Insertion Electromagnetic Flowmeter with the Aid of Numerical Analysis

Accurate measurement of the volumetric flow rate of working liquids is essential for process control, as well as energy consumption evaluation. Electromagnetic flowmeters have gained popularity in applications where low-pressure drop and low maintenance are required. Dwyer Instruments, Inc. recently developed an adjustable insertion electromagnetic flowmeter (IEF) featuring accurate and reliable measurement. However, unexpected and non-repeatable behavior in the K-factor was observed during the calibration process. The K-factor is the coefficient used to convert the measured electric potential to the flow velocity in pipes, and the non-repeatable behavior imposes challenges for precise measurement. A one-way coupled magnetohydrodynamics model was developed to reduce the effort and time of on-site troubleshooting and optimization. By modeling the measurement process, the transition of flow regimes and the regeneration of the boundary layer on the electrode surface were identified as the causes of the non-repeatable issue. Then, a series of parametric studies were performed to provide reliable solutions. A new design with further embedded electrodes to allow the smooth transition between boundary layers was recommended. The field test showed excellent repeatability by using the new design, and the non-repeatable issue was entirely resolved. The improvement in the IEF design was implemented in production in less than one week, and it reduced the calibration time by 50%.

Review of the shadow-test approach to adaptive testing

Constrained adaptive testing is reviewed as an instance of discrete maximization with the shadow-test approach delivering its solution. The approach may look counterintuitive in that it assumes sequential assembly of full test forms as its basic operation. But it always produces real-time solutions that are optimal and satisfy the set of specifications in effect for the test. Equally importantly, it can be used to run testing programs with different degrees of adaptation for the same set of specifications and/or as a tool to manage programs with simultaneous processes as adaptive item calibration, time management, and/or item-security monitoring.

A Review on Signal Processing Approaches to Reduce Calibration Time in EEG-Based Brain–Computer Interface

In an electroencephalogram- (EEG-) based brain–computer interface (BCI), a subject can directly communicate with an electronic device using his EEG signals in a safe and convenient way. However, the sensitivity to noise/artifact and the non-stationarity of EEG signals result in high inter-subject/session variability. Therefore, each subject usually spends long and tedious calibration time in building a subject-specific classifier. To solve this problem, we review existing signal processing approaches, including transfer learning (TL), semi-supervised learning (SSL), and a combination of TL and SSL. Cross-subject TL can transfer amounts of labeled samples from different source subjects for the target subject. Moreover, Cross-session/task/device TL can reduce the calibration time of the subject for the target session, task, or device by importing the labeled samples from the source sessions, tasks, or devices. SSL simultaneously utilizes the labeled and unlabeled samples from the target subject. The combination of TL and SSL can take advantage of each other. For each kind of signal processing approaches, we introduce their concepts and representative methods. The experimental results show that TL, SSL, and their combination can obtain good classification performance by effectively utilizing the samples available. In the end, we draw a conclusion and point to research directions in the future.

Real Driving Emissions—Conception of a Data-Driven Calibration Methodology for Hybrid Powertrains Combining Statistical Analysis and Virtual Calibration Platforms

The combination of different propulsion and energy storage systems for hybrid vehicles is changing the focus in the field of powertrain calibration. Shorter time-to-market as well as stricter legal requirements regarding the validation of Real Driving Emissions (RDE) require the adaptation of current procedures and the implementation of new technologies in the powertrain development process. In order to achieve highest efficiencies and lowest pollutant emissions at the same time, the layout and calibration of the control strategies for the powertrain and the exhaust gas aftertreatment system must be precisely matched. An optimal operating strategy must take into account possible trade-offs in fuel consumption and emission levels, both under highly dynamic engine operation and under extended environmental operating conditions. To achieve this with a high degree of statistical certainty, the combination of advanced methods and the use of virtual test benches offers significant potential. An approach for such a combination is presented in this paper. Together with a Hardware-in-the-Loop (HiL) test bench, the novel methodology enables a targeted calibration process, specifically designed to address calibration challenges of hybridized powertrains. Virtual tests executed on a HiL test bench are used to efficiently generate data characterizing the behavior of the system under various conditions with a statistically based evaluation identifying white spots in measurement data, used for calibration and emission validation. In addition, critical sequences are identified in terms of emission intensity, fuel consumption or component conditions. Dedicated test scenarios are generated and applied on the HiL test bench, which take into account the state of the system and are adjusted depending on it. The example of one emission calibration use case is used to illustrate the benefits of using a HiL platform, which achieves approximately 20% reduction in calibration time by only showing differences of less than 2% for fuel consumption and emission levels compared to real vehicle tests.

Difference between calibration and practical force proving instruments

This is an experimental work on seventy load cells which aims to highlight the difference between results out of force, proving instruments calibration according to ISO 376:2011 and its practical use. It spots on the difference between the relative error of repeatability and reproducibility and their contributions on load cells classifications, uncertainty estimation and calibration time. Results show that there is no significant effect for relative error of repeatability on load cell classification, ignoring the relative repeatability error in estimating the relative expanded uncertainty lead to decrease with values between 1 ppm and 270 ppm in the range from 20 % to 50 % of load cell capacity and by values between 1 ppm and 183 ppm in the range from 50 % to 100 % of the load cell capacity. It is concluded that performing measurements to calculate the relative error of repeatability is not effective in the normal calibration process for the examined seventy load cells, further measurements over subsequent years are recommended to ensure results reproducibility aiming to generalize the conclusion and recommend measurements for the relative repeatability error for load cell conformity assessment after manufacturing.