Repeatability Error Research Articles

Three-dimensional measurement of a stationary plasma plume with a Faraday probe array

Recently, an increasing number of small satellites have chosen electric propulsion (EP) as the propulsion system for motion control in space flights. Research on the ejected high energy plasma plumes from EP thrusters has attracted significant interest due to their interactions with the components of satellites. This work demonstrates a probe array diagnostic platform (with 67 Faraday probes on the array) that enables the acquisition of the full three-dimensional morphology of the plume current density from the near-field to the far-field of EP stationary thrusters. The plume parameters of an ion thruster including the 3-D plume morphology, divergence angle, and thrust vector angle are measured using this diagnostic platform. From 250 to 700 mm from the thruster exit, the plume field exhibits a stable divergence angle of 43.6°. By fitting circles to the contours of each cut plane, the average thrust vector angle is calculated to be 1.3°, and the repeatability error for the circle center fitting is approximately 2.2%. The current density profiles on exit cut planes demonstrate an “elliptical distortion” phenomenon in the plume shape. Using the ellipse fitting method, it is found that an elliptical shape was formed in the near-field of the plume. As the plume propagates to the far-field, the distortion of the ellipse becomes more apparent (the aspect ratio is 1:1.14). Some possible causes may be the geo-magnetic field, background vacuum environment distribution, or thruster manufacturing error. The thrust vector data can provide a basis for the control strategy of the satellites. In addition, the 3-D plume current density data can give us a comprehensive understanding of the plume plasma physics. These results may also provide an accurate and rich database for parameters for future plume simulations.

Automatic Correction System Design for English Pronunciation Errors Assisted by High‐Sensitivity Acoustic Wave Sensors

For correction system of English pronunciation errors, the level of correction performance and the reliability, practicability, and adaptability of information feedback are the main basis for evaluating its excellent comprehensive performance. In view of the disadvantages of traditional English pronunciation correction systems, such as failure to timely feedback and correct learners’ pronunciation errors, slow improvement of learners’ English proficiency, and even misleading learners, it is imperative to design a scientific and efficient automatic correction system for English pronunciation errors. High‐sensitivity acoustic wave sensors can identify English pronunciation error signal and convert the dimension of collected pronunciation signal according to channel configuration information; acoustic wave sensors can then assist the automatic correction system of English pronunciation errors to filter out interference components in output signal, analyze real‐time spectrum, and evaluate the sensitivity of the acoustic wave sensor. Therefore, on the basis of summarizing and analyzing previous research works, this paper expounds the current research status and significance of the design of automatic correction system for English pronunciation errors, elaborates the development background, current status and future challenges of high‐sensitivity acoustic wave sensor technology, introduces the methods and principles of time‐domain signal amplitude measurement and pronunciation signal preprocessing, carries out the optimization design of pronunciation recognition sensors, performs the improvement design of pronunciation recognition processors, proposes the hardware design of automatic correction system for English pronunciation errors based on the assistance of high‐sensitivity acoustic wave sensors, analyzes the acquisition program design for English pronunciation errors, implements the parameter extraction of English pronunciation error signal, discusses the software design of automatic correction system for English pronunciation errors based on the assistance of high‐sensitivity sound wave sensor, and finally, conducts system test and its result analysis. The study results show that the automatic correction system of English pronunciation errors assisted by the high‐sensitivity acoustic wave sensors can realize the automatic correction of the amplitude linearity, sensitivity, repeatability error, and return error of English pronunciation errors, which has the robust functions of automatic real‐time data collection, processing, saving, query, and retesting. The system can also minimize external interference and improve the accuracy of acoustic wave sensors’ sensitivity calibration, and it provides functions such as reading and saving English pronunciation error signals and visual operation, which effectively improves the ease of use and completeness of the correction system. The study results in this paper provide a reference for the further researches on the automatic correction system design for English pronunciation errors assisted by high‐sensitivity acoustic wave sensors.

Transgingival probing: a clinical gold standard for assessing gingival thickness.

Transgingival probing is often used in the clinic to assess gingival thickness. However, what is not completely known is how well this method represents the true value of soft tissue thickness. The aim of this study was to assess differences and variation in gingival thickness when measured with transgingival probing or scanned with an intraoral device. This ex vivo study evaluated gingival thickness on 20 porcine cadavers. Gingival thickness was assessed at both central and lateral mandibular incisors through transgingival probing with a standard metal periodontal probe and also using intraoral scanning, which was considered as the method providing the 'true value' of soft tissue thickness. Intra-examiner repeatability and method error were evaluated. No evidence of systematic difference for any of the mandibular central or lateral incisors (mandibular right incisors: mean difference -0.17 to -0.01 mm, and mandibular left incisors: mean difference -0.11 to 0.04 mm) was observed between the periodontal probe and intraoral scanning methods. The absolute differences between the repeated measurements with intraoral scanning for each tooth type (n = 30) were calculated: the overall median was 0.089 mm and the interquartile range was 0.080 mm. Transgingival probing with a standard metal periodontal probe for assessing gingival thickness is a reliable method, with values very close to the true gingival thickness, and it can thus be considered as the clinical gold standard.

Research on Nonlinearity in In situ Calibration of Permanent Magnet Sodium Flowmeter Without Bluff Body

The permanent magnet sodium flowmeter (PMSF) without the bluff body installed on the large-diameter pipe in the fast reactors to measure the sodium coolant flow rate has to be calibrated in situ owing to the degradation of the magnetic field. Since the length of the magnetic field of the PMSF is limited in practical engineering applications, the characteristic between the cross correlation flow rate (CCFR) and the standard flow rate is nonlinear in in situ calibration based on the cross correlation method. Moreover, the nonlinear characteristic has a large repeatability error, which is difficult to apply to in situ calibration. In order to realize the in situ calibration, an “M-type” mean velocity profile in the pipe is obtained by analyzing the influence of the magnetic field on the fluid field. The distribution of the CCFR of the signal at each frequency is analyzed by using the phase-frequency characteristic of the cross-power spectral density (CPSD) of the two signals, and a physical model of the turbulence distribution in the pipe cross section is obtained combining with the “M-type” mean velocity profile. A nonlinearity correction method based on signal frequency band selection is proposed according to the physical model. The in situ calibration experiments of DN150 PMSF without the bluff body are carried out at the sodium temperatures of 400 °C. The signals within 11–20 and 18–35 Hz are used to calculate the CCFR for correcting the nonlinear characteristic, and sodium flow rate measurement accuracy is ±3.0%.

A Differential Split-Type Pressure Sensor for High-Temperature Applications

This study proposes a split-type pressure sensor based on differential capacitance that can be applied to in-situ accurate pressure testing in high-temperature environments. The sensor is mainly composed of a high-temperature resistant chip and a high-temperature resistant encapsulation structure. The chip is made of a ceramic substrate and presents a differential capacitance structure that can withstand high temperatures and effectively restrain the temperature drift. The encapsulation presents a split-type structure, in which the chip and the test circuit board are placed at the front and back ends of the sensor, respectively. Therefore, the front end of the sensor can work in the high-temperature area for in-situ testing, while the back-end temperature remains below 60°C all the time, which ensures normal operation of the circuit board. Finally, the test results show that the pressure sensor's temperature drift coefficient is only 6.6% within the temperature range of 25°C-400°C. The sensor's sensitivity can reach 9.27 mV/kPa and the maximum repeatability error is less than 2.2% at 400°C, which shows that the proposed sensor has a higher working temperature and higher precision than the existing pressure sensors.

THE INFLUENCE OF NEGATIVE TRANSFER ON STUDENTS' ABILITY TO USE GOOD ENGLISH

Native speakers of Arabic face a number of problems in their attempt to acquire the English language. One of these problems is found in their attempt to use determiners, such as articles, quantifiers, adjectival possessive pronouns, and so forth. The most common reason of mistake, error and failure in appropriately learning and communicating in English as a second/foreign language is due to what is known as mother-tongue interference and negative transfer from one's native language, especially by L1 Arabic learners. The Arabic language has a structural system which, in many features, is different from that in English. Therefore, mistakes and errors occur when students refer back to their native language (Arabic) when communicating in the second/foreign language (English). The aim of this paper is to pinpoint the influence of Arabic mother-tongue interference and negative transfer from the students' first language on proper command of English, especially regarding the above mentioned structural features. This is done by illustrating how the differences between the Arabic and English languages in concern to the certain grammatical and structural features cause L1 Arabic learners of English as a second/foreign language to make repeatable mistakes and errors in English. Given the fact that determiners, articles, as well as prepositions, and other below mentioned structural features are one of the most frequent words used in the English language, this paper has, therefore, aimed to discuss such an important matter.

Analysis of Position Estimation Techniques in a Surgical EM Tracking System

Electromagnetic tracking systems (EMTSs) are widely used in surgical navigation, allowing to improve the outcome of diagnosis and surgical interventions in terms of shorter hospitalization times, reduction of wound pain and increased accuracy, by providing the surgeon with real-time position of surgical instruments during medical procedures. Particular effort must be made on the development of an efficient and robust algorithm to obtain an accurate estimation of the instrument position, for distances from the magnetic field generator beyond 500 mm, which represents the maximum measurement range of current commercial systems, which strongly affects the freedom of movement of the medical team. In this paper we describe two position estimation techniques, based on a model of the magnetic field, then we analyze the robustness to errors and distortions in a set of simulations for different conditions, discussing their pros and cons in a large measurement volume, and we propose a solution by combining the two techniques. The performance of the new technique is tested on experimental data from a novel EMTS prototype, developed to increase the measurement range of current EMTSs, at a mean distance of 600 mm, and a calibration procedure is performed to reduce systematic errors. A mean position and orientation accuracy of 2.2 mm and 0.5° is achieved, along with mean repeatability errors of 1.5 mm and 0.25°, within the specifications required in many surgical applications.

Study on the characteristics of thermo-electrodes of various deposition parameters for the flexible temperature sensor.

In the paper, the flexible temperature sensor based on polyimide is designed and fabricated by magnetron sputtering technology. The impact of vacuum degree, sputtering power, and argon flow rate on the roughness and deposition rate of two thermo-electrodes [indium tin oxide (ITO)/indium oxide (In2O3)] is investigated with orthogonal experiment. The thermoelectric properties of the sensor are greatly improved by low temperature heat treatment. The sensitivity of the ITO film and In2O3 film increases by 2.61 times and 2.89 times, respectively, after 1 h low-temperature heat treatment. According to the comprehensive evaluation, an innovative step annealing process is proposed to optimize the heat treatment of the prepared thermo-electrodes. The fabricated flexible thin film thermocouples exhibit great operating characteristics in the low temperature measurement range. When the hot end's temperature reaches 181.5 °C, the thermoelectric force can reach 7.84 mV and the average Seebeck coefficient can reach 50.55 µV/°C. The repeatability and hysteresis error of the sensor is ±0.88% and 1.90%, respectively. The sensor in this work shows great application potential for in situ real-time temperature measurement in robotic dexterous hands, electronic skin, and foldable devices.

Study on the Gradation of Crushed Sand by Using a Novel Digital Image Processing Methodology

It is a trend to replace the increasing shortage of natural sand with crushed sand for the development of building materials. To meet the construction requirements, it is necessary to measure the shape and gradation of crushed sand that is difficult to control. To solve this problem, a novel digital image processing methodology is proposed in this paper. Through the setting of camera resolution, lens and light source selection, the hardware platform of the measurement system was developed. The shape and gradation characterization method of dynamic falling crushed sand was studied, and the measurement software system was developed. Comparative experimental study of equivalent particle size, study of gradations repeatability experiment, comparative experimental study of dynamic digital image methodology and vibration sieving method of gradations and comparative experimental study before and after correction were conducted, respectively. The experimental results show that the equivalent elliptic Feret short diameter is suitable as the equivalent particle size. The maximum repeatability error appears in the size interval of 1.18–2.36 mm, which is 0.9%. The maximum gradation error is reduced from 6.93% before correction to 2.77% after correction. The maximum error of fineness modulus is reduced from − 0.13 to − 0.01. The accuracy of the developed measurement system can meet the actual engineering requirements, and it can realize the quality monitoring of crushed sand.

Performance Evaluation of Capacitive Based Force Sensor for Electroencephalography Head Caps

Accurate electrode signal measurement using EEG head caps can only be achieved through sufficient contact or force. A flexible force sensor is required to obtain accurate force measurement underneath EEG head caps. In this study, we evaluate the performance of a capacitive based sensor including its accuracy, repeatability, hysteresis, and stability. The result shows that accuracy error and repeatability error were 3.03±2.8 % and 3.84±2.92 %, respectively. The stability errors were 2.37±0.15 %(10 gram), 2.54±0.00 % (50 gram), 2.37±0.15 % (100 gram), 5.07±1.16 % (150 gram), 7.27±0.39 % (200 gram). The hysteresis error of the sensor was 4.48±0.47 %. Based on the results, the capacitive based force sensor provides sufficiently low errors in accuracy, repeatability, stability, and hysteresis and is thus suitable for measuring adduction force in EEG cap applications

Photonic Microwave Distance Interferometry Using a Mode-Locked Laser with Systematic Error Correction

We report an absolute interferometer configured with a 1 GHz microwave source photonically synthesized from a fiber mode-locked laser of a 100 MHz pulse repetition rate. Special attention is paid to the identification of the repeatable systematic error with its subsequent suppression by means of passive compensation as well as active correction. Experimental results show that passive compensation permits the measurement error to be less than 7.8 μm (1 σ) over a 2 m range, which further reduces to 3.5 μm (1 σ) by active correction as it is limited ultimately by the phase-resolving power of the phasemeter employed in this study. With precise absolute distance ranging capability, the proposed scheme of the photonic microwave interferometer is expected to replace conventional incremental-type interferometers in diverse long-distance measurement applications, particularly for large machine axis control, precision geodetic surveying and inter-satellite ranging in space.

Corner detection using the point‐to‐centroid distance technique

Corners, highly important local features of images and corner finding, play a crucial role in computer vision and image processing, such as object tracking and vehicle detection. Proposing effective and efficient corner detectors is the aim of corner detection. In this study, the authors first present a new measure of corner sharpness termed as the point-to-centroid distance (PCD) and then examine its behaviours, which display beneficial characteristics that help distinguish corners from non-corners. Based on PCD behaviours, the authors propose a novel corner detector. Extensive experimental results demonstrate that the PCD technique is effective and simultaneously efficient for corner detection compared with six other contour-based corner detectors in terms of two commonly used evaluation metrics – average repeatability and localisation error.

MgO Single Crystals MEMS-Based Fiber-Optic Fabry–Perot Pressure Sensor for Harsh Monitoring

A single crystalline magnesium oxide (MgO) MEMS-based fiber-optic Fabry-Perot (FP) pressure sensor was designed, fabricated and tested for 800 °C high-temperature environmental applications. In this article, MgO was selected as the sensitive materials of the optical sensor owing to its high melting point, and excellent mechanical and optical properties at elevated temperatures. The sensor head was constructed by combining wet chemical etching with direct bonding. This MEMS process technique realized all-MgO sensor head structure, which is beneficial to reduce the temperature gradient within the sensor structure, and avoid sensor failures. In addition, a non-scanning cross-correlated interrogation method is used to realize the demodulation of FP pressure cavity length having multiple reflectors. The experimental tests demonstrate that the proposed sensor can stably operate at an ambient environment of 22-800 °C and 0-0.6 MPa with a pressure sensitivity of 5.21 μm/MPa (room temperature), a repeatability error of 1.67% and a zero drift of 0.00353 μm/°C. In addition, the high-temperature testing proves that the adhesive-free well-sealed pressure cavity is conducive to improve the operating temperature and the performance of the sensor. To our best knowledge, this is the first research to realize fabrication of high-temperature pressure sensor by developing MgO micromachining technology. Our work is of fundamental importance in realization of pressure detecting in harsh environments.

FSHD / OPMD / MYOTONIC DYSTROPHY: P.235 Development and evaluation of a whole-body MRI imaging protocol and analysis algorithms to measure changes in skeletal muscle in FSHD

Establish a whole-body MRI imaging protocol and analysis algorithms to measure replacement of skeletal muscle tissue by fat in FSHD. FSHD is caused by aberrant expression of the DUX4 transcriptional program resulting in skeletal muscle loss and replacement by fat causing slowly progressive descending weakness and disability. Clinical severity, ambulation, and muscle strength are strongly correlated with muscle fat fraction (MFF) as measured by musculoskeletal fat-water separated MRI (MSK-MRI). There is little established consensus on standards for repeatability, reproducibility, and measurement error in whole-body MSK-MRI targeting individual muscles (WB-MSK-MRI) for multicenter clinical trials.

Diagnosis of left ventricular hypertrophy using convolutional neural network

BackgroundClinically, doctors obtain the left ventricular posterior wall thickness (LVPWT) mainly by observing ultrasonic echocardiographic video stream to capture a single frame of images with diagnostic significance, and then mark two key points on both sides of the posterior wall of the left ventricle with their own experience for computer measurement. In the actual measurement, the doctor’s selection point is subjective, and difficult to accurately locate the edge, which will bring errors to the measurement results.MethodsIn this paper, a convolutional neural network model of left ventricular posterior wall positioning was built under the TensorFlow framework, and the target region images were obtained after the positioning results were processed by non-local mean filtering and opening operation. Then the edge detection algorithm based on threshold segmentation is used. After the contour was extracted by adjusting the segmentation threshold through prior analysis and the OTSU algorithm, the design algorithm completed the computer selection point measurement of the thickness of the posterior wall of the left ventricle.ResultsThe proposed method can effectively extract the left ventricular posterior wall contour and measure its thickness. The experimental results show that the relative error between the measurement result and the hospital measurement value is less than 15%, which is less than 20% of the acceptable repeatability error in clinical practice.ConclusionsTherefore, the measurement method proposed in this paper has the advantages of less manual intervention, and the processing method is reasonable and has practical value.

Numerical modeling of two microwave sensors for biomedical applications

AbstractThe purpose of this invited paper is to give readers a critical and comprehensive overview on how to extract dielectric properties of a bioliquid within a broad frequency range. Two sensors are used in the paper to characterize saline solutions by measuring the broadband complex permittivity. The two sensors are based on transmission line and interdigital electrodes designed for low‐ and high‐ frequency measurements, respectively, on the basis of the coplanar waveguide structure due to its convenience of fabrication and integration with microfluidic structures for liquid measurements. Different from traditional work where the finite element simulation method is used, the characterization theories of the two sensors are built based on a numerical modeling procedure, which can dramatically increase the device design efficiency, taking just a few seconds. Differently from the finite element method, the proposed numerical analysis utilizes a conformal mapping technique for both sensors. The characterization theories of the two sensors are validated by measuring de‐ionized water. The platform is finally used to measure 0.1 and 0.5 mol/L saline solutions within a broadband frequency range going from 10 up to 50 GHz, with the repeatability error within 5%.

High-repeatability macro-porous sponge piezoresistive pressure sensor with polydopamine/polypyrrole composite coating based on in situ polymerization method

High-stability piezoresistive sensors are an important part of smart wearable systems. In this study, an in situ polymerization method was used to polymerize a layer of polydopamine (PDA) and poly-pyrrole (PPy) on the surface of the macro-porous sponge (MPS). The deposition of PDA was done using para toluene sulfonic acid (p-TSA), the pH of the solution being used to control the thickness of the PDA, that followed by PPy coating. The thin layer of PDA effects to give better adherent in-between MPS surface and PPy coating. The morphology, chemical composition, and pressure-sensing properties of the fabricated PDA/PPy pressure sensors have been widely investigated. The experimental results show that the PDA/PPy-MPS pressure sensor with the concentration of p-TSA is 0.05 M with PDA coating shows better performance in the pressure range of 1–10 kPa. The pressure sensor performance of PDA (0.05 M p-TSA)/PPy-MPS near 1000 pressure cycles related to average sensitivity, hysteresis, and non-linear errors are 7.20 ± 2.46 kPa−1, 13.51 ± 0.03%, and 3.30 ± 0.59%, respectively. The repeatability error of up and down near conductive signals are reported as 2.70 ± 0.93% and 2.25 ± 0.63%. Its minimum resistance is reported as 9.94 Ω when the pressure increased up to 119 kPa. The developed applications of PDA/PPy-MPS show promising ability to use as a pressure sensor and switching element in smart wearable devices.

Wearable strain sensors enabled by integrating one-dimensional polydopamine-enhanced graphene/polyurethane sensing fibers into textile structures

A new yarn sensor-weaving integration approach was developed for fabricating textile sensor through integrating the strain-sensing yarn element into fabric structure, not only attaining the sensing function but also maintaining the exceptional property and appearance of the fabric. The effects of fabric structure and parameters were investigated; on that basis, a sateen and modified sateen structure with the optimized structural parameters were identified for fabricating sensing textiles with desired sensing performance. Based on the rational design of materials and fabric structure, the resultant textile strain sensor exhibits good sensitivity, excellent linearity, low hysteresis and outstanding repeatability (repeatability error) of 14.1, 0.976, 10.6% and 3.25% as well as 22.3, 0.961, 11.4% and 3.11% for sateen and modified sateen sensors, respectively. Especially, the sensors show superior durability under 20000 stretch-release cycles. Moreover, the sensing mechanism of such textile sensor was revealed through the examination and analysis of deformation of the strain-sensing yarn within fabric structure with the extension of fabric.

Metrological framework for selecting morphological characters to identify species and estimate developmental maturity of forensically significant insect specimens

Accurate age estimates of immature necrophagous insects associated with a human or animal body can provide evidence of how long the body has been dead. These estimates are based on species-specific details of the insects’ aging processes, and therefore require accurate species identification and developmental stage estimation. Many professionals who produce or use identified organisms as forensic evidence have little training in taxonomy or metrology, and appreciate the availability of formalized principles and standards for biological identification. Taxonomic identifications are usually most readily and economically made using categorical and qualitative morphological characters, but it may be necessary to use less convenient and potentially more ambiguous characters that are continuous and quantitative if two candidate species are closely related, or if identifying developmental stages within a species. Characters should be selected by criteria such as taxonomic specificity and metrological repeatability and relative error. We propose such a hierarchical framework, critique various measurements of immature insects, and suggest some standard approaches to determine the reliability of organismal identifications and measurements in estimating postmortem intervals. Relevant criteria for good characters include high repeatability (including low scope for ambiguity or parallax effects), pronounced discreteness, and small relative error in measurements. These same principles apply to individuation of unique objects in general. Key points Metrological rigour can increase in forensic entomology by selecting measurements based on their metrological qualities. Selection of high-quality features for morphological identification of organisms should consider these criteria: (1) pronounced discreteness of features (minimising group overlap or maximizing interval); (2) high repeatability of assessment (such as symmetrical width rather than asymmetrical length); (3) small relative error in measurement (selecting the physically largest continuous rigid feature for measurement). These metrological principles also apply to individuation of unique objects in general.

CALIBRATION OF A WEIGHING LYSIMETER FOR MEASURING COCOA EVAPOTRANSPIRATION

ABSTRACT Well-operated and calibrated weighing lysimeters reliably determine the water demand of agricultural crops, and the quality of the data is evaluated through the error analyses attributed to the instrument. The objective of this study was to determine performance parameters of a weighing lysimeter and to evaluate its adequacy for the direct determination of cocoa crop evapotranspiration. The lysimeter with 1.44 m2 surface, supported on four load cells installed in the experimental area of the Graduate Program in Agricultural Engineering of the Universidade Federal do Recôncavo da Bahia, was calibrated at 3:00 a.m., using known masses at intervals of 02 minutes in five cycles of addition and removal. Data were collected using a datalogger coupled to four load cells with an individual capacity of 1000 kg, programmed to perform readings every 01 second, storing the averages of 15 minutes. The lysimeter showed excellent accuracy, with r2greater than 0.99 in the correlation between the standard masses and the signal of the load cells and standard error of linear regression estimate of 0.03 mm. The combination of repeatability and hysteresis errors with an uncertainty of 0.19% showed that the load cells have accuracy of ±0.07 mm, with resolution of 0.00033 mV, and sensitivity to detect mass changes below 0.1 mm, the system is adequate for direct measurement of cocoa ETc at time intervals of less than one hour.