Flaw Testing Research Articles

Automated ultrasonic testing for near-surface flaws in CFRP

ABSTRACT In ultrasonic testing of Carbon Fiber Reinforced Polymers (CFRP), signals of near-surface flaws are often submerged in interface signals, resulting in blind spots for defect detection. To address this issue, this paper presents an autocorrelation imaging algorithm that combines Multipoint Optimal Minimum Entropy Deconvolution Adjusted (MOMEDA) with l 0 -norm sparse representation. Firstly, the ultrasonic signal can be modelled as a convolution process. By using MOMEDA, the sequence of reflected pulses in the ultrasonic signal is obtained. Then, the l 0 -norm sparse representation is utilised to enhance the temporal resolution of the sequence, successfully separating near-surface defect signals from interface signals. Finally, the processed data is input into the autocorrelation algorithm, achieving automated imaging of near-surface flaws. Simulation results demonstrate the efficacy of the algorithm in separating overlapping signals. Finally, experimental validation was conducted on flaws at three different depths. The algorithm presented in this paper is capable of identifying all near-surface flaws, with a defect size error rate consistently below 5%.

EFFECT OF ITEM WRITING FLAWS IN MULTIPLE CHOICE QUESTIONS ON STUDENTS’ ACHIEVEMENT GROUPS AND RELIABILITIES OF TESTS IN AZAD JAMMU KASHMIR MEDICAL COLLEGE

BACKGROUND: MCQs can test different levels of cognitive knowledge from recall to analysis. This study was to determine the item writing flaws in multiple choice questions and their effects on students’ academic achievements and test reliabilities. Methods: This study was conducted at the Azad Jammu Kashmir (AJK) Medical College Muzaffarabad from December 2017 to June 2019. Ten end-of-block exams were used in this study. The item review committee went over every MCQ. Two tests from each class of MBBS were taken. The initial tests without being reviewed were deemed to be flawed tests. The outcomes of each test were assessed, and the students were ranked into three achievement levels high, moderate, and low based on their scores of >79.9, between 50 and 79.9, and <50%, respectively. After removal of flawed items from the exams, the scores of each test (the standard test) were calculated, compared to the flawed tests, and its impacts were evaluated among three achievement groups. The post-exam analysis of test items was done on optical mark reading (OMR) classic-4 programme and data analysis on SPSS-25. Results: In one test i.e. test no 6 the null hypothesis was rejected with p<0.05. However, in all other tests null hypothesis could not be rejected on statistical basis. Moderate achievers and low achievers had statistically significant correlation (p<0.05). The flawed tests had better reliabilities with statistically significant (p<0.05). Conclusion: Flawed MCQs had negative impact on high and moderate achievers. Reliabilities of flawed test were greater than standard tests.

TYPES OF ITEM WRITING FLAWS IN MULTIPLE CHOICE QUESTIONS IN MEDICAL EDUCATION AND THEIR EFFECT ON PASSING RATE OF STUDENTS

Background: The most popular written exam in health professions education is the multiple-choice style question (MCQ). This study sought to understand the effects of multiple-choice writing errors on students' academic performance in medical education. Methods: This descriptive study was done from December 2017 to June 2019 in Azad Jammu Kashmir (AJK) Medical College, Muzaffarabad. Ten block examinations were included. The item review committee reviewed all MCQs for flaws. Two tests from each class of MBBS were taken. The original tests containing all items were labeled as flawed tests and the result of each flawed test was evaluated. The students were graded into high, moderate and low achievement groups with scores of more than 79.9, between 50–79.9 and less than 50 percent respectively. Flawed items were then removed from the tests by the review committee and the scores of each test (standard test) were determined and compared with flawed tests and its effects were assessed in three achieving groups of students. Optical mark reading (OMR) classic-4 software was used for post-exam analysis and data were analyzed by using SPSS-25. Results: The passing rate ranged from 68.18% to 90.82% in flawed and 75.54% to 93.69% in standard tests. Most standard tests (7) had higher passing rates than flawed tests. Conclusion: Tests containing in-house developed MCQs have frequent item writing flaws and their inclusion in assessment did affect the passing rates of students but were not statistically significant. Pak J Physiol 2023;19(4):49–52

Freedom of Religion Under the Australian Constitution: Is Proportionality the Answer?

Under the current approach set out in the 1997 ‘Stolen Generations’ case of Kruger v Commonwealth, the free exercise clause of s 116 of the Australian Constitution is only violated if a law has the purpose of prohibiting the free exercise of religion. In the light of the introduction of structured proportionality testing in some areas of Australian constitutional law, scholars have recently considered whether the current test under the free exercise clause might be replaced with proportionality, given its current momentum. However, proportionality is a controversial test whose introduction to Australian law has been contested. This article seeks to contribute to the debate over proportionality in Australian law by outlining a case for why proportionality should not be adopted in respect of the free exercise clause under s 116. After first considering the current interpretation given to the free exercise clause, the article assesses proportionality as a possible test. It contends that proportionality is a flawed test because its final balancing stage involves a weighing of incommensurable values that confers excessive discretion on the judiciary. Rather than proportionality, the High Court should return to earlier dicta and develop a means-end test of reasonable necessity for assessing interference with the free exercise of religion.

Strength activity index and bulk resistivity index modifications that differentiate inert and reactive materials

The ASTM C311 strength activity index test is a potentially flawed test because inert materials are known to be able to pass the test. The early age of testing, low fly ash replacement levels, variable water-to-cementitious materials ratio, and low strength limits all contribute to the inability of the test to successfully distinguish inert and reactive materials. Test modifications utilizing higher replacement levels (50% by mass) and higher temperatures (50 °C) are evaluated in this study for three fly ashes and two inert materials. Bulk resistivity is also measured in addition to strength. Using higher replacement levels and higher temperatures provides improved differentiation of inert and reactive materials when using strength, however, the magnitude of differences is somewhat small, when considering variability in strength measurements. On the other hand, higher replacements and especially higher temperatures result in a very substantial increase in bulk resistivity for the fly ashes but not for inert materials. Therefore, a bulk resistivity index test carried out at higher temperatures provides for clear differentiation of inert and reactive materials and should considered for standardization/specification. The calcium hydroxide contents and heat release measured in corresponding cement pastes show that increased temperature enhances fly ash reaction but does not affect inert materials. At higher replacement levels, greater effects of fly ash reaction are manifested, resulting in better differentiation from inert materials than at lower replacement levels.

Intelligence Systems for Quality Assessment of Threaded Surfaces and Flaw Monitoring Based on Digital Light Field Recording

The topical issues of constructing an intelligence system for assessing the quality of processing threaded surfaces and testing for flaws when manufacturing critical products based on light field (LF) recording have been considered. Algorithms and methods have been developed for monitoring the main geometric parameters of the shape and of the surface defects in images obtained from a light field recorder by digitizing the images and morphologically analyzing image layers. An implementation is proposed for the developed algorithms on the platform of the National Instruments software using intelligence algorithms based on the principle of programmable logic. It has been shown that the accuracy of the results of determining the geometric characteristics with the proposed solutions allows one to diagnose technological equipment in the process of material machining.

Advancing Pervious Pavements through Nomenclature, Standards, and Holistic Green Design

Researchers developing pervious pavements over the past few decades have commendably demonstrated long-term run-off reduction using a diverse collection of materials. Today, pervious pavements are widely recognized as a low impact development technique and a type of green infrastructure, and installations are proliferating throughout the United States and worldwide. The entire field of pervious pavements though, is being profoundly stunted by three persistent problems: conflicting nomenclature, flawed testing standards, and the absence of a holistic green design framework. This study examines each problem and proposes novel solutions. On nomenclature, a multi-channeled study of the terms “pervious”, “permeable”, and “porous” considers each word’s etymology and usage in the academic literature, in ASTM International standards, and by (U.S.-based) governmental entities. Support is found for using pervious pavements (i.e., “through” the “road”) as the over-arching category of all water passable pavements, branching down into porous pavements (i.e., “full of pores”, including porous asphalt and porous concrete) and permeable pavements (i.e., “containing passages”, often between paver units). ASTM International standards are shown to insufficiently account for the impact of paver unit size on infiltration rate, warranting the development of a more reliable testing method featuring variable infiltration ring size, shape, and placement. Finally, a ten-part holistic green design framework is elucidated for use in assessing candidate pavements and engineering new pavements, contextualizing the latest pervious pavement research and illuminating a brighter path forward.

Perspectives on meeting the COVID‐19 testing challenge: A dental school collaborative

Perspectives on meeting the COVID‐19 testing challenge: A dental school collaborative

LSTM-RNN-based defect classification in honeycomb structures using infrared thermography

Honeycomb-structured materials are widely used in commercial and military aircraft. Manufacturing defects and damage during operation have become primary safety threats. This has increased the demand for non-destructive testing (NDT) for damage and flaws during aircraft operation and maintenance. Characterizing, or classifying defects, in addition to detecting them, is important. Classifying the liquids trapped in aircraft honeycomb cells is an example. A small amount of ingressed water is often tolerable, whereas a small amount of hydraulic oil may be an early warning of hydraulic system malfunction. This paper proposes an infrared thermography-based NDT technique and a long short term memory recurrent neural network (LSTM-RNN) model which automatically classifies common defects occurring in honeycomb materials. These including debonding, adhesive pooling, and liquid ingress. This LSTM-based algorithm has a greater than 90% sensitivity in classifying water, and hydraulic oil ingress. It has a greater than 70% sensitivity in classifying debonding and adhesive pooling.

Fracture evolution in artificial bedded rocks containing a structural flaw under uniaxial compression

The Observation and prediction of crack propagation are important in understanding rock behavior in engineering practice. Previous studies have focused on homogeneous and isotropic rocks, but the influence of bedding planes on rock fracture is sparingly documented. In this study, we investigate the fracturing response in uniaxial compression of artificial bedded rocks containing variable-inclination bedding planes and single structural flaws. The recorded stress-strain data and captured cracking patterns are examined together. Nine separate crack types are identified in which bedding-plane sliding and splitting are potentially new. The presence of bedding planes plays a decisive role in crack propagation. With a steepening of the bedding plane, tensile cracks initiating from the structural flaw are better able to propagate along bedding planes, and the accumulative length of bedding fractures accordingly increases. Failure transforms from a purely tensile mode to a bedding sliding mode and subsequently to a bedding splitting mode as the bedding inclination increases. Compared to pro-dip flaw tests, the fracturing of bedding planes is triggered by both the tensile and shear stress with more far-field tensile cracks initiating from bedding planes in the specimens containing anti-dip flaws. Finally, the results are applied to predict the failure mode and fracture evolution in bedded rock slopes.

Issues in evaluating the user performance of new home medical devices: a field test of two devices produced by a leading provider

Purpose: this paper reports a case study, which investigates the approach to testing user performance of home medical devices (HMDs) produced by a leading provider in the sector. Method: we field-tested two HMDs with 41 users, and deployed both the provider's approach and our own to compare the results. Results: the results revealed three issues concerning the provider's approach: usability features had little to do with the positive user feedback; lack of understanding of the characteristics of the target audience; and conflicting results related to user performance and preference. The causes were related to the purpose of the user testing, to the expertise of the staff undertaking it, and to the tacit and unarticulated nature of users' experience and expectations. Conclusions: the user performance of some existing HMDs may not reflect critical user needs and expectations since the positive user feedback might be produced by flawed testing approaches adopted by the provider.

Quadrature demodulation based circuit implementation of pulse stream for ultrasonic signal FRI sparse sampling

Converting ultrasonic signal to ultrasonic pulse stream is the key step of finite rate of innovation (FRI) sparse sampling. At present, ultrasonic pulse-stream-forming techniques are mainly based on digital algorithms. No hardware circuit that can achieve it has been reported. This paper proposes a new quadrature demodulation (QD) based circuit implementation method for forming an ultrasonic pulse stream. Elaborating on FRI sparse sampling theory, the process of ultrasonic signal is explained, followed by a discussion and analysis of ultrasonic pulse-stream-forming methods. In contrast to ultrasonic signal envelope extracting techniques, a quadrature demodulation method (QDM) is proposed. Simulation experiments were performed to determine its performance at various signal-to-noise ratios (SNRs). The circuit was then designed, with mixing module, oscillator, low pass filter (LPF), and root of square sum module. Finally, application experiments were carried out on pipeline sample ultrasonic flaw testing. The experimental results indicate that the QDM can accurately convert ultrasonic signal to ultrasonic pulse stream, and reverse the original signal information, such as pulse width, amplitude, and time of arrival. This technique lays the foundation for ultrasonic signal FRI sparse sampling directly with hardware circuitry.

Will the Supreme Court Clean Up Takings Law in Murr v. Wisconsin?

This article examines Murr v. Wisconsin, which will be the Supreme Court’s latest addition to its takings jurisprudence for the 2016–17 term. The precise question in the case asks how the “parcel-as-a-whole” test of Penn Central Transportation Co. v. City of New York applies to two contiguous parcels that ended up under common ownership by different routes.The first part of the article argues that under the flawed Penn Central test, the two parcels should be treated as separate because their merger under common ownership did not increase any negative externalities on the protected St. Croix River. A simple mistake in conveyancing, easily avoided, should not wipe out development rights that any other owner could possess over the undeveloped parcel.The second part of this article attacks the dominant Penn Central test that makes the availability of any compensation turn on the ratio of the value taken to the full value of the parcel. The same political considerations that justify a per se compensation rule (subject to a police power exception) in physical cases apply equally in the regulatory context, given that both circumstances present opportunities for majoritarian abuses. The article then examines many of the cases cited in Penn Central, and some decided after it, to support the conclusion that in dealing with partial interests in land, be they air rights, mineral rights, liens, or covenants, the simple rule that sets compensation equal to the fair market value of the property lost outperforms on administrative and welfare grounds the Penn Central test, under which huge private losses are routinely ignored because they do not count as a sufficient diminution in value by a standard that is nowhere either articulated or defended. Penn Central should be overruled or cut down in size.

Nondestructive testing for flaws in the insulation of winding wires

Peculiarities of discharge that is initiated by a flawed section of wire insulation that passes through a primary gas-discharge flaw transducer have been studied. Analysis of the structure of signals has been carried out, and possible mechanism and type of discharge in the sensor have been considered. Informative zones have also been singled out in the signal structure. A technique is described for testing enamel-insulated wires for flaws. The technique makes it possible to determine the number and extent of flawed sections in an enameled wire that is fed through the system at any variable speed. Ways and means are considered for reducing the errors in evaluating the number and extent of flaws. Flow chart of a faultiness-measurement device is suggested, and the principle of its operation is described.

Domestic Political Problems and the Uneven Contenders Paradox

Extant research has not produced consistent findings on the relationship between domestic political problems and the use of force abroad. We argue that this ambiguity results from incomplete theorizing and flawed empirical tests. We advance the understanding of diversionary uses of force by highlighting the political bias that domestic problems create for a leader and how this political bias interacts with the power relationship between diverters and potential targets. This conceptual discussion clarifies the political incentives each actor has to engage in military conflict and leads to a novel hypothesis. For example, domestic problems increase the probability that a weak state will attack a strong state, but domestic problems will have little effect on changing the probability of conflict between strong and weak. Empirical tests of the hypotheses for the period 1946–2000 are consistent with the argument.

Flawed multiple-choice questions put on the scale: What is their impact on students′ achievement in a final undergraduate surgical examination?

Background : Violation of item-writing guidelines is still frequently encountered in assessments in medical colleges. Flawed multiple-choice (MC) items affect students' performance and distort examinations' results. Aims: The aim was to assess the frequency and impact of flawed MC items on students' achievement in our setting. Settings and Design: This is a quantitative descriptive study conducted at the Faculty of Medicine in the University of Tabuk, Saudi Arabia. Methods: We evaluated a 100 single-correct answer MC questions summative surgical examination administered to 44 6 th year final medical students in November 2014. MC items, which contain one or more violation of item-writing guidelines, were classified as flawed, those with no violation, were classified as standard. The passing rates and median scores of high- and low-achieving students were calculated on both standard and flawed test scales. Item performance parameters (difficulty index, discrimination power and internal consistency reliability (Kuder-Richardson formula 20) were calculated for standard and flawed items. Descriptive and comparative statistics with the relevant tests of significance were performed using the SPSS (IBM SPSS Inc. Chicago, Illinois) computer software version 16. Results: Thirty-nine flawed items were identified (39%) which contain 49 violations of the item-writing guidelines. The passing rate was 93.2% and 91.8% on the total and standard scales, respectively. Flawed items benefited low-achieving students and disadvantaged the high-achieving students. Overall, flawed items were less difficult, less discriminating and less reliable than standard items. Conclusions: The frequency of flawed items in our examination was high and reflects the need for more training and faculty development programmes.

Flaw Testing of Fiber Reinforced Composite Pressure Vessels

The ASME Boiler Pressure Vessel Project Team on Hydrogen Tanks, in conjunction with other ASME Codes and Standards groups, is developing Code Cases and revisions to the Boiler and Pressure Vessel Code, including such to address the design of composite pressure vessels. The Project Team had an interest in further understanding the effect of cuts to the surface of composite tanks, and how the burst pressure would be affected during the lifetime of the pressure vessel. A test program was initiated to provide data on initial burst pressure, and burst pressure after pressure cycling, of composite cylinders with cuts of different depth. This test program was conducted by Lincoln Composites under contract to ASME Standards Technology LLC, and was funded by National Renewable Energy Laboratory (NREL) [1]. These results were considered during the development and approval of the ASME Code Cases and Code Rules. Thirteen pressure vessels with a design pressure of 24.8 MPa (3600 psi), approximately 0.406 m (16.0 in.) in diameter and 1.02 m (40.2 in.) long, were tested to investigate the effects of cuts to the structural laminate of a composite overwrapped pressure vessel with respect to cycling and burst pressure. Two flaws, one longitudinal and one circumferential, were machined into the structural composite. The flaws were 57 mm long by 1 mm wide (2.25 in. × 0.04 in.) and varied in depth from 10% to 40% of the structural composite thickness of 11.4 mm (0.45 in.). These pressure vessels were cycled to design pressure 0, 10,000, and 20,000 times then burst. The resulting burst pressures were evaluated against the performance of a pressure vessel without flaws or cycling. The burst pressures were affected by depth of cut, but the pressure cycling did not have a significant effect on the burst pressure.

Post-colonoscopy Recommendations After Inadequate Bowel Preparation: All in the Timing

Post-colonoscopy Recommendations After Inadequate Bowel Preparation: All in the Timing

Biomarkers in the Clinic: A Cautionary Tale

Biomarker profiling is well established as a powerful research tool. These so-called “omics” tests are based on signatures of molecules, such as nucleic acids, proteins, and metabolites. In recent years, the potential utility of such tests in diagnosis and prognosis has attracted much commercial investment. Consequently, the institutions developing these tests are under increasing pressure to deliver them to the clinic. In some cases, this urgency has led to clinical trials of tests that are unfit for purpose, having been generated from error-ridden data. A notable example of this situation occurred at Duke University, where flawed genomic test profiles were used in cancer trials. The recent article by Kaiser (1), summarized below, discusses the failures that led to the controversy at Duke and reviews the lessons learned to help …

Another Look at Baseball Player Initials and Longevity

Abel and Kruger (2007) reported that Major League Baseball players whose names have positive initials (such as ACE or GOD) live an average of 13 years longer than do players with negative initials (such as ASS or BAD) or players with neutral initials (such as GHR or TSW). However, this conclusion is based on a very small sample, selective initials, and a flawed statistical test. There is no statistically significant relationship between initials and longevity for Major League Baseball players when a correct test is applied to independently selected initials.