Single Test Run Research Articles

High-throughput experimental method for measuring fatigue crack growth rate curve of soft materials

The fatigue properties of soft materials, including fatigue crack initiation and propagation, fatigue life and threshold, have been a significant concern in the past few decades. Measuring the fatigue crack growth rate (FCGR) curve is a standard method to characterize fatigue fracture and has been extensively studied in the literature. Conventional methods employing a pure shear configuration measure only one data point on the FCGR curve per test run. Thus, obtaining the whole FCGR curve with numerous data points becomes excessively time-consuming. This work proposes a high-throughput experimental method for measuring the FCGR curve of soft materials. We prepare ten thermoplastic polyurethane (TPU) specimens in single edge notch tensile configuration with different precut crack lengths, use a mechanical mechanism to apply the same cyclic loads to the ten specimens simultaneously, and identify the crack growth of each specimen by image processing. The proposed high-throughput experimental method enables the measurement of over 90 data points on the FCGR curve in a single test run, facilitating the acquisition of the entire curve with just two runs. The obtained FCGR curve exhibits a linear relationship within its middle region on double logarithmic coordinates. The proposed method is further applied to study the effect of temperature on the FCGR curve of TPU specimens. The current experimental setup can be further optimized to accommodate a wider range of soft materials with diverse mechanical properties and specific loading conditions.

Fast Power Coefficient vs. Tip–Speed Ratio Curves for Small Wind Turbines with Single-Variable Measurements following a Single Test Run

Small wind turbines (SWTs) face tremendous challenges in being developed into a more reliable and widespread energy solution, with a number of efficiency, reliability, and cost issues that are yet to be resolved. As part of the development stages of an SWT, testing the resulting efficiency and determining appropriate working ranges are of high importance. In this paper, a methodology is presented for testing SWTs to obtain characteristic performance curves such as Cp (power coefficient) vs. TSR (tip–speed ratio), and torque vs. ω, in a simpler and faster yet accurate manner as an alternative energy solution when a wind tunnel is not available. The performance curves are obtained with the SWT mounted on a platform moving along a runway, requiring only a few minutes of data acquisition. Furthermore, it is only required to measure a single variable, i.e., the generator output voltage. A suitable physics-based mathematical model for the system allows for deriving the desired performance curves from this set of minimal data. The methodology was demonstrated by testing a prototype SWT developed by the authors. The tested prototype had a permanent magnet synchronous generator, but the methodology can be applied to any type of generator with a suitable mathematical model. Given its level of simplicity, accuracy, low cost, and ease of implementation, the proposed testing method has advantages that are helpful in the development process of SWTs, especially if access to a proper wind tunnel is prevented for any reason. To validate the methodology, Cp vs. TSR curves were obtained for an SWT prototype tested under different test conditions, arriving always at the same curve as would be expected. In this case, the test prototype reached a maximum power coefficient (Cp) of 0.35 for wind velocities from 20 to 50 km/h for a TSR of 5.5.

Evolutionary algorithms for solving single- and multiple-objective political redistricting problems: The case study of Poland

We propose novel evolutionary algorithms for solving single- and multi-objective political redistricting problems. The objectives include population equality, compactness of districts, deviation from the current districting, and an expected number of mandates attainable by some parties. The former two ensure the constructed solutions are reasonable, while the latter pair is meaningful for the post-analysis on how the alternation of existing districts may affect election outcomes. We operate on data concerning geography, demography, and politics in Poland. The experiments reveal that our algorithms efficiently handle the four-objective variant of the problem. In a single test run, we evaluate around one million solutions in nearly two hours on an average class computer, which is satisfactory given the problem’s complexity. The methods construct high-quality non-dominated solutions, outperforming the current districting and revealing the trade-offs between the objectives. The post-analysis allows us to observe connections between the expected number of mandates and the remaining three objectives. Specifically, attaining a greater number of mandates requires more significant changes in delineating the districts and potential violations of constraints. We also exhibit that the space for possible political manipulations increases when more districts can be determined.

FRF-based non-simultaneous real-time hybrid testing of multiple subsystems with moderate nonlinearities

The existing cyber physical testing methods have been extended in a recent publication by non-simultaneous real-time hybrid testing, see Witteveen et al. [1]. There, an overall system is decomposed into two subsystems, one experimental and one numerical. The subsystems are loaded by certain inputs and simulated or tested separately in loops until compatibility conditions are fulfilled. If not, an input update based on the error of the kinematic compatibility in the frequency domain is computed for the next loop run. Each single test run is independent from the numerical model and therefore both is possible: Slow speed and real-time testing. In this work, the generalization to a systematic approach for an arbitrary number of subsystems is presented. The subsystems can be of numerical or experimental nature. While in the last publication the subsystems had to be tested one after the other within a loop run, they can be processed totally independently from each other in this generalized method. Further, both compatibility conditions (kinematic and cutting force) are considered for the update of the input signals. Finally, approximate models of the tested components can be considered in the numerical subsystems to improve convergence. The update for the inputs is again computed in the frequency domain based on FRFs of the isolated subsystems. The theory section is followed by two examples. The first one is of academic nature, and it is demonstrated that in case of convergence, all subsystems behave as they were part of one assembled overall system. The second one is a full vehicle hybrid testing where two shock absorbers are considered as real hardware while the vehicle is a multibody simulation model on a virtual four-poster test rig.

Note on the Application of Transient Wave Packets for Wave–Ice Interaction Experiments

This paper presents the transient wave packet (TWP) technique as an efficient method for wave–ice interaction experiments. TWPs are deterministic wave groups, where both the amplitude spectrum and the associated phases are tailor-made and manipulated, being well established for efficient wave–structure interaction experiments. One major benefit of TWPs is the possibility to determine the response amplitude operator (RAO) of a structure in a single test run compared to the classical approach by investigating regular waves of different wave lengths. Thus, applying TWPs for wave–ice interaction offers the determination of the RAO of the ice at specific locations. In this context, the determination of RAO means that the ice characteristics in terms of wave damping over a wide frequency range are obtained. Besides this, the wave dispersion of the underlying wave components of the TWP can be additionally investigated between the specific locations with the same single test run. For the purpose of this study, experiments in an ice tank, capable of generating tailored waves, were performed with a solid ice sheet. Besides the generation of one TWP, regular waves of different wave lengths were generated as a reference to validate the TWP results for specific wave periods. It is shown that the TWP technique is not only applicable for wave–ice interaction investigations, but is also an efficient alternative to investigations with regular waves.

Statistical Significance Testing for Natural Language Processing. By Rotem Dror, Lotem Peled-Cohen, Segev Shlomov, and Roi Reichart (Technion Israel Institute of Technology)). Morgan & Claypool (Synthesis Lectures on Human Language Technologies, edited by Graeme Hirst, volume 45), 2020, xx+98 pp; paperback, ISBN 978-1-68173-795-9, $49.95; ebook, ISBN 978-1-68173-796-6, $39.96; hardcover, $69.95; doi:10.2200/S00994ED1V01Y202002HLT045

<i>Statistical Significance Testing for Natural Language Processing</i>. By Rotem Dror, Lotem Peled-Cohen, Segev Shlomov, and Roi Reichart (Technion Israel Institute of Technology)). Morgan &amp; Claypool (Synthesis Lectures on Human Language Technologies, edited by Graeme Hirst, volume 45), 2020, xx+98 pp; paperback, ISBN 978-1-68173-795-9, $49.95; ebook, ISBN 978-1-68173-796-6, $39.96; hardcover, $69.95; doi:10.2200/S00994ED1V01Y202002HLT045

Multiplex PCR Assay for the Simultaneous Detection of the Brucella Genus in Human Whole Blood and Serum

Background:Brucellosis disease is a serious zoonosis worldwide and only 17 countries have been recognized as free of brucellosis. The World Health Organization has reported that the incidence of brucellosis is 500,000 cases in a year. Multiplex polymerase chain reaction (PCR) is an ideal method for the identification of brucellosis. The most common primers for the diagnosis of Brucella include B4/B5 and F4/R2. The advantages of multiplex PCR include targeting multiple sequences at the same time, and multiple results are produced in a single test run which saves time and the reagents simultaneously. The purpose of this investigation was to extend and optimize a multiplex PCR for the identification of genus Brucella from serum and whole blood samples.Methods:In this experimental and sectional study, blood samples of 25 suspected patients in the acute phase of brucellosis with serum titers higher than 1:80 were collected. Two pairs of specific primers of B4 and B5 the specific gene was amplified. PCR and Multiplex PCR were performed on blood and serum samples.Results:Among 25 blood samples, 15 cases (60%) and 9 cases (36%) and among 25 serum samples, 23 cases (92%) and 13 cases (52%) were positive for B4/B5 and F4/R2 in PCR, respectively. In multiplex PCR, among 25 blood samples, 5 cases (20%) showed both bands, 11 cases (44%) showed band 222bp, 4 cases (16%) showed band 905bp and 5 cases (20%) showed no bands. Among 25 serum samples, 6 cases (24%) showed both bands, 15 cases (60%) showed band 222bp, 3 cases (12%) showed band 905bp and 1 case (4%) showed no bands.Conclusion:The results of this study show that this multiplex PCR can be used for the diagnosis of brucellosis with high sensitivity in clinical laboratories routinely and it can serve as an alternative substitution for risky culture method and nonspecific serological methods.

An efficient laboratory method to measure the combined effects of Knudsen diffusion and mechanical deformation on shale permeability

In a shale gas reservoir, the rock matrix has a relatively large porosity and gas in place, but extremely low permeability. Thus, the rock matrix is a bottleneck for shale gas flow from the reservoir to hydraulic fractures and then to the production well. We speculate that the next big thing after hydraulic fracturing for unconventional resources development is to enhance the matrix permeability in an economically feasible way. Consequently, the efficient and accurate characterization of rock matrix permeability in the laboratory is a critical task. The current laboratory techniques for source rock permeability measurement follow a “point-by-point” approach. They need multiple test runs to obtain a permeability-pressure curve, because they can only measure one permeability data point for one test run, and are thus time consuming. The root cause of this “point-by-point” approach is that these laboratory techniques are based on linearized gas flow theory requiring only small pore pressure disturbances to the experiment system. Liu et al. (2019) and this work introduce a new methodology that is based on the nonlinear gas flow theory and allows for direct measurement of the permeability-pressure curve with a single test run. This makes the approach highly time efficient. The feasibility and validity of the methodology are demonstrated in this work based on laboratory measurement results and their consistency with theoretical expectations and other independent measurements. The observed permeability exhibits a complex relationship with pore pressure as a result of the combined effects of Knudsen diffusion and mechanical deformation. For a given confining pressure, the observed permeability initially decreases with pore pressure because of Knudsen diffusion and then increases with pore pressure owing to the mechanical deformation. A rock sample with a lower permeability corresponds to a stronger Knudsen diffusion effect and weaker mechanical diffusion effect. This complex behavior highlights the need to accurately and efficiently measure the combined effects that may have important impacts on shale gas production.

Systematization of Shock Response Control Based on Momentum Exchange and Energy Exchange and Its Application to Lunar/Planetary Spacecraft

Professor Susumu Hara is based at the Department of Aerospace Engineering, Nagoya University in Japan explains that when the Mars rover Opportunity was set to land on that planet in the first weeks of 2004, onlookers held their breath as it dropped from orbit and hurtled toward the red surface. 'Any failure in the calculations or landing systems would mean a harder than expected impact,' he highlights. 'The impacts sustained by a rover such as Opportunity can derail a mission before it even starts, damaging cargo or vital systems required to complete the mission.' Impacts occur during landing but also as the craft enters the atmosphere, when it makes sudden moves, while it is on surface or when debris strikes it. 'Therefore, a system and materials to protect a craft are vital,' outlines Hara. 'Surprisingly, the solutions to this problem are not sophisticated. In fact, most craft still employ devices resembling automobile bumpers, which absorb the energy from an impact by crumpling under the force of said impact.' Unfortunately, these cannot be reused, even during testing phases a new prototype is required after every single test run. Recent missions also employed techniques like airbags or sky cranes. While successful they too have drawbacks. 'Airbags create huge rebounds which can jostle the craft and the contents inside while sky cranes are extremely costly to develop,' Hara says. For this reason, he is dedicated to designing a new highly reliable and cost-effective shock control mechanism.

High-fidelity PIV measurement of cross flow in 5 × 5 rod bundle with mixing vane grids

In order to achieve high-fidelity PIV measurement for cross flow in rod bundles, the measurement approach with the two-dimensional (2D) PIV has been optimized systematically and the systematic and random errors are analyzed. The optimizations, covering the design of test section, the setting of optical system, the PIV parameter configuration and the PIV correlation algorithm, were established based on massive sensitivity analysis. Utilizing the optimized PIV configuration, cross flow measurements were conducted in a 5 × 5 rod bundle with the rods 9.5 mm in diameter and the rod pitch of 12.6 mm, which is the typical configuration of fuel assembly in pressurized water reactors (PWRs). The FEP tubes filled with deionized water are employed as the matched index of refraction (MIR) rods to realize uniform illumination across the rod bundle. On each investigated cross section the cross flow was measured in the 16 inner subchannels. In order to maximize the magnification factor, four subchannels are measured in a single test run. Several substantial error sources were identified and accounted for in the error and uncertainty analysis. The systematic error consists mainly of the perspective error and displacement variation error, which were quantified and used to correct the measured results. The uncertainty of RMS velocity is the combination of random error and error due to limited sampling number, while the uncertainty of mean velocity equals to the error resulted from limited sampling number assuming that the systematic error is perfectly compensated. In the experiment the relative standard uncertainty of RMS velocity (to the bulk velocity) is within 0.6%, and the relative standard uncertainty of mean velocity (to the bulk velocity) is less than 0.4%. The measurements were carried out with the subchannel Reynolds number (Re) of 39600 at five cross sections, i.e. 3Dh, 5Dh, 10Dh, 15Dh and 20Dh downstream of a spacer grid. The experimental results showed the detailed cross flow features, including the evolution of vortices, in the rod bundle. The measured lateral flow was substantially dominated by the mixing vanes. Drastic turbulence generation by mixing vanes was observed downstream of a spacer grid. The generated turbulence decayed rapidly within 10Dh downstream of the spacer grid and then damped gradually.

An Innovative Laboratory Method To Measure Pore-Pressure-Dependent Gas Permeability of Shale: Theory and Numerical Experiments

Summary This work proposes an innovative laboratory method to measure shale gas permeability as a function of pore pressure, a key parameter for characterizing and modeling gas flow in a shale gas reservoir. The development is based on a solution to 1D gas flow under certain boundary and initial conditions. The details of the theoretical background, including formulations to estimate gas permeability and conceptual design of the test setup, are provided. The advantages of our approach, surpassing the currently available ones, include that it measures gas permeability (as a function of pressure) with a single test run and without any presumption regarding the form of parametric relationship between gas permeability and pore pressure. In addition, our approach allows for estimating both shale permeability and porosity at the same time from the related measurements. Numerical experiments are conducted to verify the feasibility of the proposed methodology.

Vehicle-wet snow interaction: Testing, modeling and validation

For a vehicle interacting with snow, whether dry or wet, uncertainties exist in the mechanical properties of snow, and in the interfacial properties between the tires of the vehicle and snow. For dry snow, these uncertainties have been studied recently using methods within a statistical framework employing a simple stochastic tire-snow interaction model and several validation metrics. Wet snow is more complicated and much less studied than dry snow, especially for tire-snow interaction. In this paper, the authors used a physical tire-snow interaction model and a similar statistical framework as was used to analyze dry snow, and presented results of calibration and validation of the interaction model for wet snow in conjunction with new test data based on a single test run with the assumption that it would provide needed sampling points for statistical analysis. Four local and global statistical validation metrics were used to assess the physical and statistical models with good results. Comparison between wet and dry snow, based on a single test run, shows that the former has a lower interfacial coefficient of friction, and a higher drawbar pull than the latter.

FlowPing - The New Tool for Throughput and Stress Testing

This article presents a new tool for network throughput and stress testing. The FlowPing tool is easy to use, and its basic output is very similar to standard Linux ping application. The FlowPing tool is not limited to reach-ability or round trip time testing but is capable of complex UDP based throughput stress testing with rich reporting capabilities on client and server sides. Our new tool implements features, which allow the user to perform tests with variable packet size and traffic rate. All these features can be used in one single test run. This allows the user to use and develop new methodologies for network throughput and stress testing. With the FlowPing tool, it is easy to perform the test with the slowly increasing the amount of network traffic and monitor the behavior of network when the congestion occurs.

Experimental investigation on the interaction of planar shock wave with cylindrical gaseous inhomogeneity

The interaction of a planar shock wave (Mach number of 1.2) with a gas cylinder (helium cylinder or SF6 cylinder) is experimentally studied using the high-speed schlieren photography. Because the soap film has less influence on the interface evolution than the solid diaphragm and the soap film cylinder can effectively suppress the gas exchange at the interface compared with the diaphragm-less cylinder, a circular wire-restriction method of using the soap film technique is introduced to generate the interface separating the experimental gas from the ambient gas. Illuminated by a DC source, the evolution of the gas cylinder accelerated by a shock wave is captured by the high-speed video camera in a single test run and the wave patterns are also observed. It is shown from the results that the SF6 cylinder is firstly compressed and accelerated by the shock, and then a jet is formed at the downstream interface due to the transmitted shock focusing. Subsequently, induced by the vorticity, the cylinder is developed into a mushroom shape and finally the turbulent mixing occurs. After the impact of the shock wave, the helium cylinder is firstly accelerated and the reversal phase occurs at the upstream interface. Afterwards, a jet is generated from the upstream interface and gradually tears through the downstream interface. Eventually, the interface is developed into two independent vortexes. Compared with the previous studies, the results in this work behave more symmetry and fewer disturbances are generated in the flow field due to the absence of the holder. Moreover, the variation of the interface scales with time is measured from which the changes of the interface can be well interpreted. At last, the shock and interface velocities in SF6 case obtained in the experiment are found to have a satisfactory agreement with the theoretical prediction from one-dimensional gas dynamics, which verifies the interface formation method to some extent.

TEFIS: A single access point for conducting multifaceted experiments on heterogeneous test facilities

A few years ago, an experimental facility composed of networking gear and simulation tools was sufficient for testing the main features of a prototype before the final product could be launched to the Internet market. This paradigm has certainly changed, but the lack of platforms enabling the realistic assessment of the different facets of a product, including cross-cutting trials across different testbeds, poses strong limitations for researchers and developers. In light of this, we present an open platform that offers a versatile combination of heterogeneous experimental facilities called “TEstbed for Future Internet Services” (TEFIS). TEFIS provides a single access point for conducting cutting-edge experiments on testbeds that supply different capabilities, including testbeds dedicated to network performance, software performance, grid computing, and living labs. We shall show that TEFIS covers the entire life-cycle of a multifaceted experiment, with the advantage that a single testrun can seamlessly execute across different experimental facilities. In order to demonstrate the potential and versatility of the TEFIS platform, we describe the deployment of four distinct experiments and provide a set of results highlighting the benefits of using TEFIS. The experiments described in this article cover: (i) the experimentation with an open API called OPENER (which is an open and programmable environment for managing experimentation with SDN applications); (ii) an application for skiers and tourists at the Megève ski resort in France; (iii) an application that can dynamically adapt the Quality of Experience (QoE) of multimedia services for mobile users; and (iv) an augmented reality workspace for remote education and learning purposes based on videoconferencing.

Mould susceptibility of Scots pine (Pinus sylvestris L.) sapwood: Impact of drying, thermal modification, and copper-based preservative

The development of mould on wood surfaces depends on several factors. Although mould does not affect the mechanical properties of wood, it greatly reduces the aesthetic value of wood such as the sapwood of Scots pine (Pinus sylvestris L.), which is very prone to mould. In addition, adverse health effects of mould on humans are a great concern. Different types of dried and treated wood were used to observe whether they had enhanced durability against mould following an accelerated laboratory test method in a climate chamber. Samples were green, air-dried, industrially thermally modified, treated with copper-based preservative, and kiln-dried wood, which were tested within a single test run. The test produced the following main results: The thermal modification increased the durability of the wood, and the protective effectiveness of alternative treatments was comparable to that of commercially available copper-based treatment. However, the initial moisture content of the samples during mould exposure had a great influence on the onset of mould growth. The risk of mould susceptibility of industrial kiln-dried lumber can be reduced by drying using the double-layering technique and planing off the nutrient enriched evaporation surfaces.

Virtues of polymerase chain reaction in ophthalmology

Dear Editor, We read the article titled ‘DNA chip-assisted diagnosis of a previously unknown etiology of intermediate uveitis- Toxoplasma gondii’, by Basu et al., with great interest.[1] We appreciate their attempt to draw attention towards the superior efficacy of Polymerase Chain Reaction (PCR) as a diagnostic tool in the etiology of uveitis and take this opportunity to put forth our views. The biggest thorn in the side in a case of uveitis (especially posterior) is the diagnosis of the specific causative agent or factor, thereafter ensuring appropriate treatment for complete resolution of the condition. Being an inflammatory condition, uveitis is most commonly seen as a sequel to a rigmarole of infectious or non-infectious pathologies. Picking out a specific etiological factor or agent is like finding needle in a haystack. The clinical evaluation here gives a direction and the ancillary laboratory investigations help in shaping the diagnosis. But sometimes, especially in cases of non-responders or relapsers we need a bull's eye diagnosis, which is provided by sophisticated modalities like PCR, presenting irrefutable evidence, therefore assisting in pinpoint diagnosis and specific treatment. Multiplex PCR mentioned in the article by Basu et al., is one of the various modifications of PCR used to rapidly detect deletions or duplications in a large gene. By targeting multiple genes at once, it gains additional information from a single test run which otherwise would require several times the reagents and more time to perform.[1,2] To elaborate our point, we analyze the role of PCR in the diagnosis of various conditions leading to uveitis by exemplification. Beginning with viral infections, the viral DNA or RNA can be identified by gene detection using quantitative real-time PCR in the intraocular fluid samples.[3] For parasitic protozoans like Toxoplasma, PCR testing for antibody titers in aqueous or vitreous has been proved to carry a high degree of specificity and sensitivity. PCR is also effective in identifying bacterial infections, e.g., detection of the Mycobacterium tuberculosis complex by IS6II0 primer-based PCR. Not only does it identify the agents but also distinguishes amongst organisms belonging to the same genus.[4] To cite an example of the diagnostic capability of PCR in non-infectious conditions we take the Vogt-Koyanagi-Harada disease, in which the Interleukin-21 messenger RNA expression by peripheral blood mononuclear cells is determined by reverse transcriptase-PCR.[5] These few examples are just the tip of the iceberg of the numerous conditions in which PCR is useful. Despite all these benefits, the major constraints in using this investigation regularly in a country like ours are cost, availability and the enormous patient load, especially in rural areas. Such an advanced investigation is available in precious few centers located in cities making it inaccessible to the masses. Adequate patient education and providing economical services to remote areas may serve as an answer to this problem.

Torrefaction of beechwood: A parametric study including heat of reaction and grindability

Torrefaction describes a thermal treatment of biomass in order to obtain a solid product with more or less coal-like properties. Therefore a mild pyrolysis in an oxygen-free atmosphere is applied. In this work beechwood was used as feedstock because of its consistent quality in commercially available chips. A parametric study was conducted with a continuously working, indirectly heated reactor having a throughput on the order of 1kgproduct/h, wherein each parameter was varied independently. The reactor temperature ranged from 270 to 300 °C, residence time from 20 to 60min, and feed moisture content from 0% to 20%. Ultimate and proximate analysis of the products as well as grindability tests have been performed. Additionally, the integral heat of reaction was determined for each test run by measurement of the heat consumption of the reactor. Mass loss of the dry solid is shown to be a good indicator of the degree of torrefaction and ultimate as well as proximate analysis show good agreement with existing literature data. Grindability in terms of HGI depends on the degree of torrefaction and reaches from difficult to grind to very easy to grind. In terms of beater wheel mills used for combined drying and milling in lignite fired power plants, grindability is poor and in general worse than that of Rhenish lignite. The heat of reaction is found to be close to the border between endo- and exothermic with a trend to more exothermic behaviour for increasing degree of torrefaction. Despite the uncertainty of the heat capacity of wood and torrefied wood above a temperature of 420K, the determined heat of reaction is found to be in the range of −199J/g (exothermic) to 148J/g (endothermic) for all tests with spans of about ±70J/g for each single test run. Besides severe torrefaction, caused by a high reactor temperature, an increased residence time is found to cause a remarkable exothermic heat of reaction.

Cost-Efficient Built-In Redundancy Analysis With Optimal Repair Rate for RAMs

Built-in self-repair (BISR) techniques are widely used for the repair of embedded memories. One of the key components of a BISR circuit is the built-in redundancy-analysis (BIRA) module, which allocates redundancies according to the designed redundancy analysis algorithm. Thus, the BIRA module affects the repair rate of the BISR circuit. Existing BIRA schemes for RAMs can provide the optimal repair rate (the ratio of the number of repaired RAMs to the number of defective RAMs), but they require either high area cost or multiple test runs. This paper proposes a BIRA scheme for RAMs, which can provide the optimal repair rate using very low area cost and single test run. Furthermore, the BIRA is designed as reconfigurable such that it can be shared by multiple RAMs. Experimental results show that the area cost for implementing the proposed BIRA scheme is much lower than that of existing BIRA schemes with optimal repair rate. A test chip is also implemented to demonstrate the proposed BIRA scheme.

The Load-Scanning Test – Evaluation of a Universal Tribological Model Test in View of Sheet Bulk Metal Forming

Combining the loading conditions of two different classes of forming operations, in sheet bulk metal forming processes, contact pressures ranging from a few hundred MPa up to loads exceeding 2,500 MPa are experienced. With the additional need for an enhanced control of the material flow, which is best implemented by locally adapted frictional properties of the contact tool/workpiece, sheet bulk metal forming represents a challenge to tribology. As a consequence, the evaluation of the friction and wear properties of different surface modifications and lubricants within a variety of loading conditions is required. The load-scanning test is a universal tribological model test. Its most distinctive feature is the ability to assess the friction and wear behaviour of a tribological pairing within a whole range of contact loads in a single test run. The simple and quick test method also allows the investigation of plastic contacts. Due to these features, the load-scanning test is of particular interest with regard to the quantitative and qualitative evaluation of the application potentials and limits of use of tribological measures intended for sheet bulk metal forming. Like any model test, the load-scanning test has also specific drawbacks. In some test setups, the stress distribution in the contact area may be non-uniform. Further, the maximum realizable contact pressure may be limited by low yield strengths of the tested materials in combination with the insufficient flow restriction of the contact geometry and/or the moderate machine force. By comparison to other test methods and by giving examples of its application in different scenarios, the present paper discusses the potentials and limitations of the load-scanning test against the background of sheet bulk metal forming.