Improved Test Method Research Articles

Geochemical lessons from Carsington Dam failure of 1984 and reconstruction

The failure in 1984 of Carsington Dam near the end of its construction led to major advances in several areas of geotechnical engineering. It also led to major advances in understanding the nature and extent of geochemical and mineralogical reactions that can occur in earthworks and how these can be allowed for in design and construction. These aspects had not been considered in the original investigations and design. This resulted in much greater degradation of the fill materials than expected during construction, pollution of surface waters and the tragic deaths of four site personnel. The lessons learned in understanding the impact of geochemistry at Carsington were fundamental in further work by the authors in developing improved test methods for sulphur compounds and protocols for assessing their impact. The relevance of these lessons for civil engineering works remains as great as ever. Seven general principles for dealing with geochemical issues are presented.

Improved Test Method for Tribological Evaluation of High Performance Plastics

Improved Test Method for Tribological Evaluation of High Performance Plastics

494. Use of a Clinical Prediction Tool to Predict Clostridium difficile Infection

Background Clostridium difficile is a pathogen that may be a component of normal microbiota. In 2011, there were an estimated 453,000 cases of CDI in the United States and 29,300 deaths. Diagnosis of CDI is of often accomplished through nucleic acid amplification testing (NAAT) for C. difficile toxin genes, which carries a risk of false-positive results. In 1996, Katz et al. created a screen for CDI that was positive if the patient had significant diarrhea and either abdominal pain or prior antibiotic usage. Today, we believe that this tool is worth revisiting with increased incidence of CDI and improved testing methods. Our aim is to determine the current usefulness of the Katz et al. 1996 clinical decision tool for CDI.MethodsWe conducted a retrospective cross-sectional chart review at a Midwestern teaching hospital. All patients tested for CDI between June 1, 2016 and May 31, 2017 were initially eligible. Participants were excluded from data collection on the basis of missing information, a previous positive CDI test in the last 8 weeks or age <18 years. Charts were reviewed for age, sex, diarrhea, abdominal pain, antibiotic use, prior positive testing for CDI, and length of hospitalization. Data were analyzed using SAS Software.ResultsOf the initial 432 charts analyzed, 202 (46.8%) had no documented amount of diarrhea and 16 more were missing other data points, leaving 214 of 432 (49.5%) charts that included all data to be used for analysis. Of these 18 of 214 (8.4%) were positive results. The Katz screen was positive in 85 of 214 (40.2%) cases. The sensitivity, specificity, positive predictive value, and negative predictive value, respectively, were 61, 62, 13, and 95.ConclusionKatz et al. found a sensitivity, specificity, positive predictive value and negative predictive value of 80, 45, 18 and 94, respectively. The differences between these values and our own may be due to changes in the testing methodology and prevalence of CDI compared with a 1992 study population. The negative predictive value remains a strength. If this screening tool had been applied to our population, there may have been 128 (59.8%) fewer tests, but seven (38.9%) missed positive results.Disclosures All authors: No reported disclosures.

Improved particle swarm optimization of designing resonance fatigue tests for large-scale wind turbine blades

As the sizes of wind turbine blades increase, it is becoming more difficult for designing fatigue tests to meet the requirements of blades' certification. In order to design accurate fatigue tests for large-scale wind turbine blades, this paper proposes an improved optimization based on particle swarm optimization. The advantages of this optimization algorithm are its accuracy in predicting test moments and its ability in matching distributions of test moments. The shell model, which can model some special details of large-scale blades, is used to predict test moments instead of the beam model in the optimization algorithm. Besides, removing the blade tip is introduced in to enrich test methods, which enlarges the dimensions of variables in the optimization algorithm. Furthermore, moment errors are measured in both the absolute type and the relative type. Based on the study of these two types of moment errors, the objective function and constraints are designed to guide the decrease and distribution of moment errors. At last, edge-tests of a 38-m blade (shell and beam model), a 60-m blade (beam model), and a 38.75-m blade (beam model) are designed by this improved optimization, and the optimal test moments and distributions of moment errors prove the abilities of this improved optimization. Differences of the moment errors and test durations between the results designed by the standard testing method and those designed by the improved testing method demonstrate the advantages of improved optimization.

A new method for pull out test of reinforcing bars in plain and fibre reinforced concrete

The bond of reinforcing bars in concrete is crucial in anchorage of reinforcing bars and crack control of reinforced concrete. It is generally measured by pull out test of a reinforcing bar embedded in a concrete block. However, the different test methods yield different test results. In this research, finite element analysis was carried out to reveal the variations in stress distribution inside the concrete block due to uneven contact pressure and friction at the concrete block-steel platen interface of the test setup. To minimize the test errors due to such uneven contact pressure and friction, the test setup was redesigned by inserting a rubber pad and a PTFE film at the interface. Using the redesigned setup, pull out tests of reinforcing bars in plain and fibre reinforced concrete were conducted and the results compared to those obtained without rubber pad or PTFE film installed. It was found that the new test would yield lower and less variable bond strength and stiffness results. This improved test method would provide more accurate bond properties for structural analysis and design.

American Board of Orthodontics: Time for change.

The American Board of Orthodontics (ABO) works to certify orthodontists in a fair, reliable, and valid manner. The process must examine an orthodontist's knowledge, abilities, and critical thinking skills to ensure that each certified orthodontist has the expertise to provide the highest level of patient care. Many medical specialty boards and 4 American Dental Association specialty boards use scenario-based testing for board certification. Changing to a scenario-based clinical examination will allow the ABO to test more orthodontists. The new process will not result in an easier examination; standards will not be lowered. It will offer an improved testing method that will be fair, valid, and reliable for the specialty of orthodontics while increasing accessibility and complementing residency curricula. The ABO's written examination will remain as it is.

An improved test method for refrigerant flammability limits in a 12 L vessel

The current study presents an improved test method for refrigerant flammability limit measurements. Such measurements are essential for determining refrigerant safety classifications. Predicated on expert interviews and experiments, several changes to ASTM E681 and related standards are recommended, as follows. The 12 L glass vessel should be replaced with transparent polycarbonate. The orientation of the electrode supports and the temperature probe should be changed from vertical to horizontal. All penetrations should be removed from the rubber stopper, it should be weighted for a total mass of 2.5 kg, and the initial pressure should be 90 kPa absolute. The flame angle should be plotted versus refrigerant concentration to obtain flammability limits. Finally, the vessel pressure should be measured during each test. These changes are relatively easy to implement and they will improve the test precision and reproducibility without significantly changing previously established flammability limits.

The improved design method of shear strength of reinforced concrete beams without transverse reinforcement

Abstract In this article, results of experimental testing of reinforced concrete beams without transverse shear reinforcement are given. Three prototypes for improved testing methods were tested. The testing variable parameter was the shear span to the effective depth ratio. In the result of the tests we noticed that bearing capacity of RC beams is increased with the decreasing shear span to the effective depth ratio. The design method according to current codes was applied to test samples and it showed a significant discrepancy results. Than we proposed the improved design method using the adjusted value of shear strength of concrete CRd,c. The results obtained by the improved design method showed satisfactory reproducibility.

Experimental Evaluation on Fatigue Strength of Adhesive-Bonded Sandwich Panels with CFRP Faces and Honeycomb Cores

There is no existed standard testing method suitable to evaluate the fatigue strength of thick adhesive bonded structures like honeycomb sandwich panels. Fatigue strengths of adhesive-bonded sandwich panels constructed with aluminum honeycomb cores and CFRP (Carbon Fiber Reinforced Plastics) laminate faces were interested in this study. Fatigue experiments on sample cantilever beams of such honeycomb sandwich panels were carried out to validate the experimental method by improving the configurations of specimens, testing fixtures and instruments etc. Based on the improved testing method, influences of design parameters, such as specimen length and height, foil thickness and cell size of honeycomb cores, on the fatigue strength of adhesive bonded sandwich panels will be investigated in future experimental study.

Radon barrier: Method of testing airtightness - 2. Edition

The test method NBI 167/02 Radon membrane: Test of airtightness can be used for determining the airtightness of a radon barrier as a system solution. The test determines the air infiltration through the radon barrier for a number of levels of air pressure differences. The airflow through versus the difference in air pressure over the barrier is measured. The air pressure difference is kept constant, at a number of manually controlled levels. At each pressure level, the difference is measured in a single point close to the point where the suction for lowering the air pressure is located. Improvements to the test method were suggested. A digital stirring and control system, and a method for determining the mean air pressure difference, as well as a method for testing barriers with a very low air infiltration, were provided. The digital stirring and control system ensured automatic control and measuring of coherent values of the airflow and the difference in air pressure. The method determining the mean air pressure difference was based on measurements from 5 units placed at specific locations. The method for testing barriers with a very low air infiltration introduced the need to provide air to the side of the barrier with the low air pressure, through a well-defined opening, as a modification of the test method in general. Results, obtained using the improved test method, are shown for a number of radon barriers tested.

(Invited) SiC MOSFET Reliability and Implications for Qualification Testing

There are a number of potential reliability issues associated with SiC power MOSFETs, including threshold-voltage stability, gate-oxide reliability, body-diode robustness, short-circuit current robustness, and radiation effects. This talk is primarily focused on threshold-voltage stability and the need for an improved test method to unambiguously separate out good devices from bad ones. Threshold-voltage stability is affected primarily by active charge traps in the near-interfacial region of the insulating gate oxide. Their close proximity to the semiconductor interface leads to a strong time dependence in the direct-tunneling mechanism in response to changes in gate bias. This time dependence is not properly accounted for in the existing test methods for assessing high-temperature gate-bias (HTGB) effects, which allow temporary removal of bias during cool down and significant un-biased delay (up to 96 hours) before the post-stress measurements are performed. However, this delay, introduced to accommodate the practical constraints of industrial testing, renders this test practically meaningless due to the significant recovery that occurs in the charge states of the near-interfacial oxide traps. This difficulty can be overcome by reapplying the gate bias for a brief period of time before measuring. Details of the nature of the near-interfacial oxide traps will be discussed, including their activation energy. All this work will be presented within the context of standards development within JEDEC, and a new SiC power-devices qualification working group.

An improved test method for characterising touch properties of porous polymeric materials

A new test method and instrument was developed to provide overall evaluation and characterisation of touch properties of porous polymeric materials. The test method and instrument can simulate the dynamic contact process between human skin and porous polymeric materials and obtain the mechanical and physical performance during contact. In the improved test method, a new measurement principle was proposed, and the mechanical device was redesigned, including surface friction measurement components. Most indices were redefined and the grading and classification methods were studied to give a direct overall evaluation of the touch properties for industrial applications. The objective test results and analysis, subjective evaluation method and prediction model of touch properties are also presented. The improved test method provides an objective measurement of thermal-mechanical properties using a single measuring instrument for new product development and quality control of porous polymeric materials.

The Problem of Experimental Evaluation for Corona Resistance of VFD Cables

This article describes an approach for evaluating experimental cable insulation resistance electro-thermal aging, typical for the drive frequency being adjusted. It estimates the average time until the insulation breakdown when exposed to a sample of high electrical loads. The possibility for an adequate choice of insulating materials, which are used in the insulation of VFD cable and shown ways to improve testing methods.

Experimental Full-Scale Test Cell Optimizing for Research of Novel Concepts towards Climatically Active Solar Façade Design

The passive solar test facilities have recently been created in many research centers all over the world to analyse dynamic outdoor phenomena on buildings and their components. The main objective of these research activities is primarily to evolve a methodology, improve test methods, validate numerical models and measure real thermodynamic properties of building components under outdoor climate conditions. An integration of advanced material solutions into buildings need to be investigated within specific conditions related specifically to outdoor test methods. A research project on Contemporary concepts of climatically active solar facades at the Brno University of Technology does have an ambition to create an experimental full-scale test cell for research of thermal aspects in progressive advances of future solar façade concepts exposed to the real climate conditions. This paper describes the design optimization phase preceding the test cell assembly. This phase includes the analysis of energy and thermal properties based on parametric study features. Computer simulations based on finite element and volume methods are involved in the optimization process. The proposed optimized test cell design is confronted with parametrization of typical thermal aspects to present final test cell demonstration.

Improved testing method for the compressive strength of single fiber

In this study, an improved method is developed to test the compressive strength of single fibers. Two improvements were carried out compared with the previous work, and they were composed of: (1) a skillful device for preparing the compression sample with the advantage of greatly saving time and highly efficiency; (2) an improved system for directly testing the single fiber’s compressive strength with high accuracy and repeatability. More than fifteen qualified samples were successfully prepared within two hour compared with even only one sample in a day for the poor manipulation accuracy of previous work. Compressive strength of single fiber was tested based on four kinds of PAN-based carbon fibers. Experimental results from the new method show great agreement with the data published, which prove the designed method and improved device is more applicable for testing the compressive strength of single fiber in the optimization of cost and efficiency.

Threshold-Voltage Instability in SiC MOSFETs Due to Near-Interfacial Oxide Traps

There are two basic mechanisms that affect the threshold-voltage (VT) stability: oxide-trap activation and oxide-trap charging. Once additional oxide traps are activated, then they are free to participate in the charge-trapping processes that can, especially for older vintage devices, result in large VT shifts and potential device failure. More recent commercially-available devices show much smaller effects, and minimal trap activation. Given the dramatic improvements, it is now imperative that improved test methods be employed to properly separate out bad devices from good devices.

Flexural Behavior of Ski Boots Under Realistic Loads – The Concept of an Improved Test Method

The design of ski and ski touring boots should consider three key elements: performance, safety and comfort. For all three aspects, the boot's (shaft) flexural behavior is one of the crucial characteristics. Knowing the importance of this design parameter it is surprising that up to now no generally accepted standardized method exists to test and quantify the stiffness of the boot. First test methods, developed in the late eighties, used a leg prosthesis loaded with a horizontal force at the top of the shank in order to apply a bending moment to the boot hinge. Since then the basic principle has not been changed and it is widely used to quantify the dorsal and plantar flexion under slope conditions as well as the effect of buckle closure, temperature and fit of the boot. This common approach however neglects some of the important boundary conditions such as the realistic plantar pressure distribution underneath the artificial foot or the correct location and shift of the point of force application during the flexion movement. The aim of this study was to design a new test bench which overcomes some of the previous limitations thus being able to improve validity of the load simulation. The major addition to the current state is that the new test bench simulates ground reaction forces by using a pneumatic driven active leg-prosthesis generating an internal extension moment in knee and ankle. Further a linear bearing allows simultaneous displacement of the foot in the sagittal plane, simulating forward or backward shift of the center of pressure, which is typical for skiing maneuvers. The presentation will illustrate the theory behind this new concept and describe the details of its design.

Conventional and improved cytotoxicity test methods of newly developed biodegradable magnesium alloys

Unique biodegradable property of magnesium has spawned countless studies to develop ideal biodegradable orthopedic implant materials in the last decade. However, due to the rapid pH change and extensive amount of hydrogen gas generated during biocorrosion, it is extremely difficult to determine the accurate cytotoxicity of newly developed magnesium alloys using the existing methods. Herein, we report a new method to accurately determine the cytotoxicity of magnesium alloys with varying corrosion rate while taking in-vivo condition into the consideration. For conventional method, extract quantities of each metal ion were determined using ICP-MS and the result showed that the cytotoxicity due to pH change caused by corrosion affected the cell viability rather than the intrinsic cytotoxicity of magnesium alloy. In physiological environment, pH is regulated and adjusted within normal pH (∼7.4) range by homeostasis. Two new methods using pH buffered extracts were proposed and performed to show that environmental buffering effect of pH, dilution of the extract, and the regulation of eluate surface area must be taken into consideration for accurate cytotoxicity measurement of biodegradable magnesium alloys.

Distinguishing between anti–platelet factor 4/heparin antibodies that can and cannot cause heparin‐induced thrombocytopenia

Many patients exposed to heparin develop antibodies against platelet factor 4 (PF4) and heparin, yet only those antibodies that activate platelets cause heparin-induced thrombocytopenia (HIT). Patients who produce anti-PF4/heparin antibodies without developing HIT either have antibodies that do not cause platelet activation or produce pathogenic antibodies at levels that are insufficient to cause HIT. Understanding the differences between anti-PF4/heparin antibodies with and without HIT will improve test methods and reduce overdiagnosis. To investigate the presence of low levels of platelet-activating antibodies in patients investigated for HIT who had anti-PF4/heparin antibodies but failed to cause platelet activation in the (14) C-serotonin release assay (SRA). We developed a platelet activation assay similar to the SRA using exogenous PF4 without added heparin (PF4-SRA). This assay was able to detect low levels of platelet-activating antibodies. We used this PF4-SRA to test for platelet-activating antibodies in patients investigated for HIT. The PF4-SRA detected platelet-activating antibodies in seven (100%) of seven SRA-positive sera even after the samples were diluted until they were no longer positive in the standard SRA. Platelet-activating antibodies were detected in 14 (36%) of 39 patients who had anti-PF4/heparin antibodies but tested negative in the SRA and did not have clinical HIT. The clinical diagnosis of HIT was confirmed by chart review and concordant with the SRA results. A subset of heparin-treated patients produce subthreshold levels of platelet-activating anti-PF4/heparin antibodies that do not cause HIT. An increase in the titer of these pathogenic antibodies, along with permissive clinical conditions, could lead to HIT.

Improved testing method of dynamic cone penetrometer in laboratory for evaluating compaction properties of soil subgrade

Based on the wide application of dynamic cone penetrometer (DCP) in detecting engineering for subgrade, this paper analyses the influence of moisture content on penetration ratios (PRs) when DCP penetrates the compaction specimens of soil and proposes a laboratory testing method of DCP. Through contrasting experiments in the laboratory, degree of compaction, initial moisture content and PRs are regressed with multivariate linear correlation equations of which the correlation coefficients are all greater than 0.9. The corresponding tests including the DCP test, portable falling weight deflectometer test, CBR test and sand cone test are also carried out in the field, the field test results were regressed according to the corresponding regression equations proposed in the laboratory. Parameters of the regression equations for laboratory and field test results are compared and deviations are analysed, the results show that the relative deviations are less than 0.1, which indicates that there are good consistencies between laboratory and field regression equations. Therefore, as long as the moisture content and PR of the soil are measured, compaction qualities and mechanical indexes of subgrade in the field can be accurately predicted according to multivariate regression proposed in the laboratory.