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"measurement system"
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The seven measures of the world
\"From the beginning of history, measurement has been interwoven into the human experience, shaping our understanding of nature, personal relationships, and the supernatural. We measure the world to know our past, comprehend the present, and plan the future. Renowned physicist Piero Martin explores how scientific knowledge is built around seven key pillars of measurement: the meter for length; the second for time; the kilogram for mass; the kelvin for temperature; the ampere for electricity; the mole for quantity of substance; and the candela for luminous intensity. Martin examines the history and function of these units and illustrates their applications in rich vignettes on a range of topics--from quarks to black holes, from a glass of wine to space exploration. He delves into not only the all-important numbers but also anecdotes that underline each unit's special quality. At the same time, he explains how each unit contributes to important aspects of science, from classical physics to quantum mechanics, from relativity to chemistry, from cosmology to elementary particle physics, and from medicine to modern technology. Martin eloquently shows how the entire universe can be measured and understood using just seven units.\"--Dust jacket.
Book
Design and Metrological Analysis of a Backlit Vision System for Surface Roughness Measurements of Turned Parts
The focus of this study is to design a backlit vision instrument capable of measuring surface roughness and to discuss its metrological performance compared to traditional measurement instruments. The instrument is a non-contact high-magnification imaging system characterized by short inspection time which opens the perspective of in-line implementation. We combined the use of the modulation transfer function to evaluate the imaging conditions of an electrically tunable lens to obtain an optimally focused image. We prepared a set of turned steel samples with different roughness in the range Ra 2.4 µm to 15.1 µm. The layout of the instrument is presented, including a discussion on how optimal imaging conditions were obtained. The paper describes the comparison performed on measurements collected with the vision system designed in this work and state-of-the-art instruments. A comparison of the results of the backlit system depends on the values of surface roughness considered; while at larger values of roughness the offset increases, the results are compatible with the ones of the stylus at lower values of roughness. In fact, the error bands are superimposed by at least 58% based on the cases analyzed.
Journal Article
On the same track : how schools can join the twenty-first-century struggle against resegregation
\"A public school principal's account of the courageous leaders who have dismantled the tracking systems in their schools in order to desegregate classrooms and provide better learning experiences for all students. Since the beginning of the last century, the sorting of students into different \"tracks\" has resulted in segregated classrooms and unequal learning opportunities for students. This book traces the origins of tracking, from its beginnings in the early 20th century to today. As Burris takes readers through this history, she argues that tracking perpetuates de facto segregation within districts that were ordered by the courts to desegregate. Drawing on the latest research, Burris shows how tracking results in achievement gaps and racial and class stratification. Burris then chronicles the struggles of courageous school leaders, teachers and parents as they sought to overcome race, class and intellectual prejudice and dismantle the student sorting systems in their schools. Finally, she provides timely caution regarding how some of the present day reforms may result in further racial and socioeconomic segregation, undermining some of the progress that schools have made in creating more equitable learning experiences for children\"-- Provided by publisher.
Book
Standardized pivot shift test improves measurement accuracy
Purpose
The variability of the pivot shift test techniques greatly interferes with achieving a quantitative and generally comparable measurement. The purpose of this study was to compare the variation of the quantitative pivot shift measurements with different surgeons’ preferred techniques to a standardized technique. The hypothesis was that standardizing the pivot shift test would improve consistency in the quantitative evaluation when compared with surgeon-specific techniques.
Methods
A whole lower body cadaveric specimen was prepared to have a low-grade pivot shift on one side and high-grade pivot shift on the other side. Twelve expert surgeons performed the pivot shift test using (1) their preferred technique and (2) a standardized technique. Electromagnetic tracking was utilized to measure anterior tibial translation and acceleration of the reduction during the pivot shift test. The variation of the measurement was compared between the surgeons’ preferred technique and the standardized technique.
Results
The anterior tibial translation during pivot shift test was similar between using surgeons’ preferred technique (left 24.0 ± 4.3 mm; right 15.5 ± 3.8 mm) and using standardized technique (left 25.1 ± 3.2 mm; right 15.6 ± 4.0 mm; n.s.). However, the variation in acceleration was significantly smaller with the standardized technique (left 3.0 ± 1.3 mm/s
2
; right 2.5 ± 0.7 mm/s
2
) compared with the surgeons’ preferred technique (left 4.3 ± 3.3 mm/s
2
; right 3.4 ± 2.3 mm/s
2
; both
P
< 0.01).
Conclusion
Standardizing the pivot shift test maneuver provides a more consistent quantitative evaluation and may be helpful in designing future multicenter clinical outcome trials.
Level of evidence
Diagnostic study, Level I.
Journal Article
The Influence of Camera and Optical System Parameters on the Uncertainty of Object Location Measurement in Vision Systems
The article presents the influence of the camera and its optical system on the uncertainty of object position measurement in vision systems. The aim of the article is to present the methodology for estimating the combined standard uncertainty of measuring the object position with a vision camera treated as a measuring device. The identification of factors affecting the location measurement uncertainty and the determination of their share in the combined standard uncertainty will allow determining the parameters of the camera operation, so that the expanded uncertainty is as small as possible in the given measurement conditions. The analysis of the uncertainty estimation presented in the article was performed with the assumption that there is no influence of any external factors (e.g., temperature, humidity, or vibrations).
Journal Article
NOx Emission of a Correlation between the PEMS and SEMS over Different Test Modes and Real Driving Emission
The aim of this study is to verify the reliability of NOx emissions measured using Smart Emissions Measurement System (SEMS) equipment in comparison with the NOx emissions measured using certified Portable Emissions Measurement System (PEMS) equipment. The SEMS equipment is simple system, and it is less expensive than the PEMS equipment, as it comprises an On-Board Diagnostics (OBD) signal from the test vehicle and a NOx sensor. The SEMS equipment based on low-cost sensors has an advantage of building big data, but there are insufficient previous studies comparing of NOx emissions with certified the PEMS equipment. Therefore, this study is important in verifying the suitability of the SEMS equipment by comparing the NOx emissions measured by the various test modes and RDE using the two types of equipment. To analyze the correlation between the PEMS and SEMS equipment, the advanced diesel vehicle was equipped with the two types of equipment to simultaneously measure NOx emissions. After installing the equipment on the test vehicle, it was conducted under various test modes in the laboratory and the Real Driving Emission (RDE) test to verify the correlation of NOx emissions measured by the SEMS equipment. The correlation analysis for the NOx emissions measured by the PEMS and SEMS equipment under various test conditions and the RDE test indicated that the slope of the NOx emissions was approximately equal to 1, and the coefficient of determination was 0.9 or higher. Based on these test results, it was concluded that NOx emissions measured by the PEMS and SEMS equipment are highly similar.
Journal Article
Data-driven disturbance source identification for power system oscillations using credibility search ensemble learning
Low-frequency oscillations in power system degrade power quality and may trigger blackouts. This study identifies the source location of these oscillations using measurements from phasor measurement unit (PMU), offline credibility estimation and classification models. The performance of these classification models is ranked for each reported feature to use highly ranked models during the online stage. This proposed framework named as credibility search ensemble learning was tested and validated with promising results using western interconnection power system in North America (WECC-179). The reliability and robustness of the proposed framework were checked against measurement errors in PMUs as well as for practical topology change scenarios. Experimental results and performance comparison with average weight-based approach proved that the proposed approach is capable enough to predict the source location of oscillations with good accuracy. An interfacing tool, for MATLAB-WEKA, was developed and employed in this work for validation and testing of the proposed approach.
Journal Article
Optical Measurement System for Monitoring Railway Infrastructure—A Review
Rail infrastructure plays an important role in fulfilling the demand for freight and passenger transportation. Increases in traffic volume, heavier axles and vehicles, higher speeds, and increasing climate extremes all contribute to the constant strain on the infrastructure. Due to their major importance in the transportation of people and freight, they are subject to continuous condition monitoring. This is an essential requirement for the selective planning of maintenance tasks and ultimately for safe and reliable operation. Various measuring systems have been developed for this purpose. These must measure precisely, quickly, and robustly under difficult conditions. Whether installed from mobile or stationary platforms, they have to cope with a wide range of ambient temperatures and lighting conditions, harsh environmental influences, and varying degrees of reflection. Despite these circumstances, railway operators require precise measurement data, high data densities even at high traveling speeds, and a user-friendly presentation of the results. Photogrammetry, laser scanning, and fiber optics are light-based measurement methods that are used in this sector. They are able to record with high precision rail infrastructure such as overhead contact systems, clearance profiles, rail tracks, and much more. This article provides an overview of the established and modern optical sensing methods, as well as the use of artificial intelligence as an evaluation method, and highlights their advantages and disadvantages.
Journal Article
Modernising Receiver Operating Characteristic (ROC) Curves
The justification for making a measurement can be sought in asking what decisions are based on measurement, such as in assessing the compliance of a quality characteristic of an entity in relation to a specification limit, SL. The relative performance of testing devices and classification algorithms used in assessing compliance is often evaluated using the venerable and ever popular receiver operating characteristic (ROC). However, the ROC tool has potentially all the limitations of classic test theory (CTT) such as the non-linearity, effects of ordinality and confounding task difficulty and instrument ability. These limitations, inherent and often unacknowledged when using the ROC tool, are tackled here for the first time with a modernised approach combining measurement system analysis (MSA) and item response theory (IRT), using data from pregnancy testing as an example. The new method of assessing device ability from separate Rasch IRT regressions for each axis of ROC curves is found to perform significantly better, with correlation coefficients with traditional area-under-curve metrics of at least 0.92 which exceeds that of linearised ROC plots, such as Linacre’s, and is recommended to replace other approaches for device assessment. The resulting improved measurement quality of each ROC curve achieved with this original approach should enable more reliable decision-making in conformity assessment in many scenarios, including machine learning, where its use as a metric for assessing classification algorithms has become almost indispensable.
Journal Article
Survey of machine learning methods for detecting false data injection attacks in power systems
Over the last decade, the number of cyber attacks targeting power systems and causing physical and economic damages has increased rapidly. Among them, false data injection attacks (FDIAs) are a class of cyber-attacks against power grid monitoring systems. Adversaries can successfully perform FDIAs to manipulate the power system state estimation (SE) by compromising sensors or modifying system data. SE is an essential process performed by the energy management system towards estimating unknown state variables based on system redundant measurements and network topology. SE routines include bad data detection algorithms to eliminate errors from the acquired measurements, e.g. in case of sensor failures. FDIAs can bypass BDD modules to inject malicious data vectors into a subset of measurements without being detected, and thus manipulate the results of the SE process. To overcome the limitations of traditional residual-based BDD approaches, data-driven solutions based on machine learning algorithms have been widely adopted for detecting malicious manipulation of sensor data due to their fast execution times and accurate results. This study provides a comprehensive review of the most up-to-date machine learning methods for detecting FDIAs against power system SE algorithms.
Journal Article