In-field Testing Research Articles

Array Calibration and Digital Predistortion Training Using Embedded Near-Field Feedback Probes and Orthogonal Coding for Enhancing the Performance of Millimeter-Wave Beamforming Arrays

This letter proposes an active array calibration and digital predistortion (DPD) training method that relies on a series of measurement data captured using near-field (NF) probes embedded within the array to enhance the performance of millimeter-wave (mm-wave) radio frequency (RF) beamforming arrays. These measurements are obtained using phase settings that are based on orthogonal coding to enable the characterization of the linear and nonlinear errors in the array’s RF chains. The use of embedded NF probes in the proposed method makes it suitable for infield testing. Specifically, the proposed theory is formulated to allow for beamforming-phase-dependent error calibration as well as array linearization without resorting to element-wise measurement or far-field (FF)-based feedback. Furthermore, the proposed theory does not impose a flat coupling requirement between the NF probes and the array antenna elements. Experimental results are conducted on a custom-built 16-element RF beamforming array with four embedded NF probes and operated at 37.5 GHz. The measurements revealed that applying the proposed calibration method reduced the imbalance in the radiation pattern side lobes by up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2$</tex-math> </inline-formula> dB and achieved comparable performance to element-wise FF-based calibration. Furthermore, the proposed DPD training method enabled increasing the effective isotropic radiated power (EIRP) from 32 to 34.2 dBm while maintaining an error vector magnitude (EVM) below 3.5%.

Development of Recombinase Aided Amplification (RAA)-Exo-Probe Assay for the Rapid Detection of Shiga Toxin-Producing Escherichia coli.

Shiga toxin-producing Escherichia coli (STEC) is a significant cause of foodborne illness causing various gastrointestinal diseases including hemolytic uremic syndrome (HUS), the most severe form, which can lead to kidney failure or even death. Here, we report the development of recombinase aided amplification (RAA)-exo-probe assays targeting the stx1 and stx2 genes for the rapid detection of STEC in food samples. Primers and exo-probes were designed and optimized for the detection of stx1 and stx2 using RAA technology. The optimal STEC RAA-exo-probe assays were then tested for specificity and sensitivity, and validated in both spiked and real food samples. These assays were found to be 100% specific to STEC strains and were also highly sensitive with a detection limit of 1.6 × 103 CFU/mL or 32 copies/reaction. Importantly, the assays were able to successfully detect STEC in spiked and real food samples (beef, mutton, and pork), with a detection limit as low as 0.35 CFU/25g in beef samples after an overnight enrichment step. Overall, the RAA assay reactions completed within ∼20 min and were less dependent on expensive equipment, suggesting they can be easily adopted for in-field testing requiring only a fluorescent reader. As such, we have developed two rapid, sensitive, and specific assays that can be used for the routine monitoring of STEC contamination in food samples, particularly in the field or in poorly equipped labs.

Assessing challenges due to HVAC design constraints and their effects on VAV terminal unit noise - lessons learned from recent projects

For most projects requiring HVAC noise analysis, designers can reliably account for projected noise contributions from VAV terminal units. However, the authors' recent experiences on projects with challenging constraints (e.g., renovations to existing HVAC systems, prohibition of duct liner and/or flex duct, and restriction to packless/no-media silencers), show that manufacturers' published data are not always sufficient. In the provided project examples, published noise levels for terminal units have required greater consideration because of complexities of the HVAC systems and building conditions. A variety of contributing factors are discussed, as well as the challenges of in-field testing, diagnostics, and troubleshooting. Key takeaways include the need for coordinating with mechanical engineers about the accuracy of system set points; improving assumptions made about system pressure drops and manufacturers' data; and identifying project types that require greater consideration when using manufacturers' data.

Low-cost and rapid sensors for wastewater surveillance at low-resource settings

Wastewater surveillance enables tracking infectious disease dynamics and community prevalence quantification for public health. However, the testing requirement of centralized laboratories and well-trained staff challenges underserved areas and low-resource settings. The development of new rapid and low-cost sensors enables in-field testing of wastewater from the community to the individual building levels for early warning of pandemics.

Anti-Ballistic Performance of PPTA/UHMWPE Laminates.

Poly(p-phenylene terephthalamide) (PPTA) and ultra-high-molecular-weight polyethylene (UHMWPE) are high-performance polymer materials largely used for body armor applications. Although composite structures from a combination of PPTA and UHMWPE have been created and described in the literature, the manufacture of layered composites from PPTA fabrics and UHMWPE films with UHMWPE film as an adhesive layer has not been reported. Such a new design can provide the obvious advantage of simple manufacturing technology. In this study, for the first time, we prepared PPTA fabrics/UHMWPE films laminate panels using plasma treatment and hot-pressing and examined their ballistic performance. Ballistic testing results indicated that samples with moderate interlayer adhesion between PPTA and UHMWPE layers exhibited enhanced performance. A further increase in interlayer adhesion showed a reverse effect. This finding implies that optimization of interface adhesion is essential to achieve maximum impact energy absorption through the delamination process. In addition, it was found that the stacking sequence of the PPTA and UHMWPE layers affected ballistic performance. Samples with PPTA as the outermost layer performed better than those with UHMWPE as the outermost layer. Furthermore, microscopy of the tested laminate samples showed that PPTA fibers exhibited shear cutting failure on the entrance side and tensile failure on the exit side of the panel. UHMWPE films exhibited brittle failure and thermal damage at high compression strain rate on the entrance side and tensile fracture on the exit side. For the first time, findings from this study reported in-field bullet testing results of PPTA/UHMWPE composite panels, which can provide important insights for designing, fabricating, and failure analysis of such composite structures for body armors.

Mind the Gap! A Study on the Transferability of Virtual Versus Physical-World Testing of Autonomous Driving Systems

Safe deployment of self-driving cars (SDC) necessitates thorough simulated and in-field testing. Most testing techniques consider virtualized SDCs within a simulation environment, whereas less effort has been directed towards assessing whether such techniques transfer to and are effective with a physical real-world vehicle. In this paper, we shed light on the problem of generalizing testing results obtained in a driving simulator to a physical platform and provide a characterization and quantification of the sim2real gap affecting SDC testing. In our empirical study, we compare SDC testing when deployed on a physical small-scale vehicle vs its digital twin. Due to the unavailability of driving quality indicators from the physical platform, we use neural rendering to estimate them through visual odometry, hence allowing full comparability with the digital twin. Then, we investigate the transferability of behavior and failure exposure between virtual and real-world environments, targeting both unintended abnormal test data and intended adversarial examples. Our study shows that, despite the usage of a faithful digital twin, there are still critical shortcomings that contribute to the reality gap between the virtual and physical world, threatening existing testing solutions that only consider virtual SDCs. On the positive side, our results present the test configurations for which physical testing can be avoided, either because their outcome does transfer between virtual and physical environments, or because the uncertainty profiles in the simulator can help predict their outcome in the real world.

Using STLs for Effective In-Field Test of GPUs

GPUs have seen an increased adoption in autonomous systems. This article assesses the fault coverage that can be attained through software self-test strategies for in-field test of GPUs.—Nicola Nicolici, McMaster University

Compact and automated eDNA sampler for in situ monitoring of marine environments

Using environmental DNA (eDNA) to monitor biodiversity in aquatic environments is becoming an efficient and cost-effective alternative to other methods such as visual and acoustic identification. Until recently, eDNA sampling was accomplished primarily through manual sampling methods; however, with technological advances, automated samplers are being developed to make sampling easier and more accessible. This paper describes a new eDNA sampler capable of self-cleaning and multi-sample capture and preservation, all within a single unit capable of being deployed by a single person. The first in-field test of this sampler took place in the Bedford Basin, Nova Scotia, Canada alongside parallel samples taken using the typical Niskin bottle collection and post-collection filtration method. Both methods were able to capture the same aquatic microbial community and counts of representative DNA sequences were well correlated between methods with R^{2} values ranging from 0.71–0.93. The two collection methods returned the same top 10 families in near identical relative abundance, demonstrating that the sampler was able to capture the same community composition of common microbes as the Niskin. The presented eDNA sampler provides a robust alternative to manual sampling methods, is amenable to autonomous vehicle payload constraints, and will facilitate persistent monitoring of remote and inaccessible sites.

The Anti-Snow Behaviour of Icephobic Coatings: Laboratory and In-Field Testing

Overhead power line conductors and ground wires are affected by ice and snow accretion which can easily adhere to their surface, causing the breakage of cables and the collapse of pylons due to excessive weight. In Italy, the main concern is about wet snow: this phenomenon occurs close to zero degrees Celsius with snow density reaching up to 350 Kg/m3. Anti-icing and anti-snow coatings represent a possible strategy to mitigate ice accretion on overhead power line structures. Many works are oriented to achieve anti-icing properties, starting from superhydrophobic coatings or slippery coatings; however, there is a lack of knowledge about the anti-snow behaviour of these surfaces. In this work, aluminium alloy conductor and ground-wire samples were prepared with different coatings, which include hydrophobic, superhydrophobic and slippery surfaces prepared in the laboratory. Characterisations of sample wettability at room and low temperatures and ice adhesion strength were carried out in the laboratory. Anti-snow behaviour was studied in outdoor test facilities in the Italian Alps during several snowfall events. Furthermore, the environmental parameters were also recorded. Two figures of merit were developed to quantify anti-snow behaviour of the samples: one describing the fraction of surfaces covered by snow during the snowfall event and the other representing the maximum accretion load reached on the samples. Results of laboratory and field testing are compared and discussed. Field testing evidenced a promising snowphobic behaviour for all the samples, despite the different anti-icing and wettability properties measured in the laboratory. The mitigation of the phenomenon was found to occur mainly with two different mechanisms: the delay in snow accretion on the surface and/or the early shedding of the snow-sleeve.

Review of Mn-Doped Semiconductor Nanocrystals for Time-Resolved Luminescence Biosensing/Imaging.

Colloidal semiconductor nanocrystals (NCs) have been developed for decades and are widely applied in biosensing/imaging. However, their biosensing/imaging applications are mainly based on luminescence-intensity measurement, which suffers from autofluorescence in complex biological samples and thus limits the biosensing/imaging sensitivities. It is expected for these NCs to be further developed to gain luminescence features that can overcome sample autofluorescence. On the other hand, time-resolved luminescence measurement utilizing long-lived-luminescence probes is an efficient technique to eliminate short-lived autofluorescence of samples while recording time-resolved luminescence of the probes for signal measurement after pulsed excitation from a light source. Despite time-resolved measurement being very sensitive, the optical limitations of many of the current long-lived-luminescence probes cause time-resolved measurement to be generally performed in laboratories with bulky and costly instruments. In order to apply highly sensitive time-resolved measurement for in-field or point-of-care (POC) testing, it is essential to develop probes possessing high brightness, low-energy (visible-light) excitation, and long lifetimes of up to milliseconds. Such desired optical features can significantly simplify the design criteria of time-resolved measurement instruments and facilitate the development of low-cost, compact, sensitive instruments for in-field or POC testing. Mn-doped NCs have recently been in rapid development and provide a strategy to solve the challenges faced by both colloidal semiconductor NCs and time-resolved luminescence measurement. In this review, we outline the major achievements in the development of Mn-doped binary and multinary NCs, with emphasis on their synthesis approaches and luminescence mechanisms. Specifically, we demonstrate how researchers approached these obstacles to achieve the aforementioned desired optical properties on the basis of the progressive understanding of Mn emission mechanisms. Afterward, we review representative applications of Mn-doped NCs in time-resolved luminescence biosensing/imaging and present the potential of Mn-doped NCs in advancing time-resolved luminescence biosensing/imaging for in-field or POC testing.

Barley haplotyping using biplex deoxyribozyme nanomachine

Direct sequencing is the gold standard for genome haplotyping, while PCR is used for detection of limited number of genetic variations. However, these methods are not suitable for fast low-cost in-field testing of plant specimens. Here, we developed a two-color florescent nanosensor system (named here biplex deoxyribozyme nanomachine or bixDNM) that can haplotype dsDNA amplicons. The sensor is based on fluorescent binary deoxyribozyme embedded in a nanostructure containing together four DNA binding arms. Two allele specific sensors were tailored for producing signals at two different wavelengths (525 and 662 nM) only in the presence of fully matched analytes. Accurate haplotyping of seven barley samples was achieved. This is the first technique showing detected of both short (146 bp) and long (1348 bp) dsDNA amplicons with single nucleotide specificity. The study demonstrated bixDNM can become a foundation for future development of a plant haplotyping technology that can be used in field or at the low resource agricultural settings.

Erroneous Vehicle Velocity Estimation Correction Using Anisotropic Magnetoresistive (AMR) Sensors.

Magnetic field sensors installed in the road infrastructure can be used for autonomous traffic flow parametrization. Although the main goal of such a measuring system is the recognition of the class of vehicle and classification, velocity is the essential parameter for further calculation and it must be estimated with high reliability. In-field test campaigns, during actual traffic conditions, showed that commonly accepted velocity estimation methods occasionally produce highly erroneous results. For anomaly detection, we propose a criterion and two different correction algorithms. Non-linear signal rescaling and time-based segmentation algorithms are presented and compared for faulty result mitigation. The first one consists of suppressing the highly distorted signal peaks and looking for the best match with cross-correlation. The second approach relies on signals segmentation according to the feature points and multiple cross-correlation comparisons. The proposed two algorithms are evaluated with a dataset of over 300 magnetic signatures of a vehicle from unconstraint traffic conditions. Results show that the proposed criteria highlight all greatly faulty results and that the correction algorithms reduce the maximum error by twofold, but due to the increased mean error, mitigation technics shall be used explicitly with distorted signals.

A pipette-adapted biosensor for Salmonella detection

In-field screening of pathogenic bacteria is important for preventing food poisoning. Here, a portable pipette-adapted biosensor using magnetic grid separation and nanocatalyst signal amplification was elaboratively developed for rapid detection of Salmonella typhimurium. A common pipette was innovatively adapted with multiple functions to complete the whole bacterial detection procedure, including mixing, separation, catalysis, washing, detection, analysis and display. The target bacteria were effectively captured by the immune magnetic nanobeads and labeled with immune gold@platinum nanocatalysts through pipette-blowing mixing to form the nanobeads-bacteria-nanocatalyst complexes, which were separated against the magnetic grid separation tip under the magnetic field. The pressure change resulting from oxygen production due to mimicking catalysis of hydrogen peroxide by these nanocatalysts on the complexes was quantified through measuring the moving duration of the conductive liquid in the pipette for bacteria determination. Under optimal conditions, this biosensor could detect target bacteria in 90 min with low detection limit of 180 CFU/mL. This pipette-adapted biosensor is affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end-users (ASSURED), and has the potential for in-field testing of foodborne pathogens to ensure food safety, especially in resource-constrained areas.

A Low-Cost, Low-Power Water Velocity Sensor Utilizing Acoustic Doppler Measurement.

Current commercial sensors to monitor water flow velocities are expensive, bulky, and require significant effort to install. Low-cost sensors open the possibility of monitoring storm and waste water systems at a much greater spatial and temporal resolution without prohibitive costs and resource investment. To aid in this, this work developed a low-cost, low-power velocity sensor based on acoustic Doppler velocimetry. The sensor, costing less than 50 USD is open-source, open-hardware, compact, and easily interfaceable to a wide range of data-logging systems. A freely available sensor design at this price point does not currently exist, and its novelty is in enabling high-resolution real-time monitoring schemes. The design is capable of measuring water velocities up to 1200 mm/s. The sensor is characterised and then verified in an in-field long-term test. Finally, the data from this test are then used to evaluate the performance of the sensor in a real-world scenario. The analysis concludes that the sensor is capable of effectively measuring water velocity.

In-field test solution for enhancing safety in automotive applications

Automotive market is evolving rapidly, while boosting and growing semiconductor industry significantly. According to the experts, we are only in the beginning of this exciting new chapter in the evolution – Autonomous Driving. Functional safety and quality requirements for Automotive are taking clearer shape while the industry is progressing for maturity. Therefore, System-on-Chip (SoC) and Intellectual Property (IP) providers must come up with a tailored and adaptive solution, to overcome various challenges. This process is enriching for all parties – SoC providers in incorporating various IPs that addresses different aspects, as well as providing the IP vendors with comprehensive guidelines to enhance their products to adhere these requirements. As a direct consequence to this process, Test and Repair IPs are influenced heavily. This paper presents a full-scale in-field test and repair solution concept for Automotive SoCs which conforms to all safety and quality requirements.

A Systematic Method to Generate Effective STLs for the In-Field Test of CAN Bus Controllers

In order to match the strict reliability requirements mandated by regulations and standards adopted in the automotive sector, as well as other domains where safety is a major concern, the in-field testing of the most critical devices, including microcontrollers and systems on chip, is a crucial task. Since the controller area network (CAN) bus is widely used in the automotive domain, the corresponding controller ubiquitously appears in all these devices. This paper presents a generic and systematic methodology to develop an effective in-field test procedure for CAN controllers based on a functional approach (i.e., on the adoption of self-test libraries). The method can be customized to match the requirements coming from different scenarios, and allows the test engineer to maximize the achieved fault coverage in terms of structural faults in the different cases. The experimental results we gathered on a representative CAN controller model show that, given two typical testing scenarios, we are able to detect 84.28% and 87.62% of stuck-at faults, respectively, hence demonstrating the effectiveness of the proposed approach.

Highly Efficient Test Architecture for Low-Power AI Accelerators

Low-power artificial intelligence (AI) accelerators are being developed to support the battery-operated edge devices at a minimum expense of classification error. However, the testing of such large AI accelerators with traditional techniques is inefficient in achieving the required certifications for Autonomous Driving Assistant Systems (ISO 26262). ISO 26262 sets very stringent requirements on the testing time and fault coverage during the diagnosability of faults leading to system-level failures during in-field testing. This article proposes a test architecture for low-power AI accelerators by reusing the existing data paths for large AI accelerator arrays. As compared to the full scan-DFT, the proposed test architecture reduces the test time and peak test power, which enhances the reliability of the test responses. The proposed technique reduces 1) the switching power by 87%; 2) testing times by 72% on average for cases up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$32\times 32$ </tex-math></inline-formula> ; and 3) the peak power by 59%. Further, there is an average reduction in the area by 10% for the accelerator.

Validity and Reliability of a Commercial Force Sensor for the Measurement of Upper Body Strength in Sport Climbing.

Recreational and professional climbing is gaining popularity. Thus, valid and reliable infield strength monitoring and testing devices are required. This study aims at assessing the validity as well as within- and between-day reliability of two climbing-specific hanging positions for assessing the maximum force with a new force measurement device. Therefore, 25 experienced male (n = 16) and female (n = 9) climbers (age: 25.5 ± 4.2 years, height: 176.0 ± 9.9 cm, weight: 69.7 ± 14.5 kg, body composition: 11.8 ± 5.7% body fat, climbing level: 17.5 ± 3.9 International Rock Climbing Research Association scale) were randomly tested with climbing-specific hang board strength tests (one-handed rung pulling and one-handed bent arm lock-off at 90°). The Tindeq, a load cell-based sensor for assessing different force-related variables, was employed together with a force plate (Kistler Quattro Jump) during both conditions. Data analysis revealed excellent validity for assessment with Tindeq: The intra-class correlation coefficient (ICC) was 0.99 (both positions), while the standard error of the measurement (SEM), coefficient of variation (CV), and limits of agreement (LoA) showed low values. Within day reliability for the assessment with Tindeq was excellent: rung pulling showed an ICC of 0.90 and arm lock-off an ICC of 0.98; between-day reliability was excellent as well: rung pulling indicated an ICC of 0.95 and arm lock-off an ICC of 0.98. Other reliability indicators such as SEM, CV, and LoA were low. The Tindeq progressor can be applied for the cross-sectional and longitudinal climbing strength assessment as this device can detect training-induced changes reliably.

Ultrathin MnO2-Coated FeOOH Catalyst for Indoor Formaldehyde Oxidation at Ambient Temperature: New Insight into Surface Reactive Oxygen Species and In-Field Testing in an Air Cleaner.

Herein, we tailored a series of ultrathin MnO2 nanolayers coated on the surface of commercial goethite (α-FeOOH) by a facile in situ chemical precipitation method. α-FeOOH inhibited the MnO2 crystal growth via the incorporation of K+ ions between MnO2 and α-FeOOH interfaces during the synthesis process. The hybrid design of MnO2 with an ultrathin nanolayer structure could reduce the electron transfer resistance and bring abundant oxygen vacancies, accelerating the activation of molecular O2 to generate more oxygen-free radical species and favoring the thermodynamic HCHO oxidation. The ROS quenching in gas/aqueous systems and DRIFTS results demonstrated that •O2- was responsible for HCHO oxidization, which assisted the preliminary intermediate dioxymethylene dehydrogenation into formate species. The 25%MnO2@FeOOH(25wt% of MnO2) catalyst was subsequently loaded into the filter substrates of a commercial air cleaner and tested in an indoor room with actual application conditions. As a result, the composite filter could eliminate different initial concentrations of HCHO (150-450 ppb) to the WHO guideline value (≈81 ppb) within 60 min. Furthermore, the 25%MnO2@FeOOH sample was also effective against the representative bacteria and mold in indoor air. This study provides new insight into the role of the chemisorbed ROS for HCHO oxidation at ambient temperature.

The Testing Of High Voltage Silicon Carbide Lightning Arresters

The majority of high voltage gapped silicon carbide lightning arresters on transmission and sub transmission systems have been in service for over 10 years. A testing program is required that can accurately and efficiently determine the condition of these high voltage arresters. The essential theory of silicon carbide arresters was investigated, focusing particularly on arrester construction, performance and the unique characteristics of high voltage arresters. The effectiveness of available testing procedures was then evaluated and a set of tests selected, based on their expected performance, their ability to assess all facets of arrester behavior, the ease with which they could be completed in the available laboratory and their possible application to in-field testing. The testing program implemented consisted of a series of procedures including the lightning impulse sparkover voltage test, power frequency sparkover voltage test, power frequency withstand test, AC and DC leakage current measurements, 5 kV insulation resistance test, and finally a non-standard current impulse test. The tests were performed on a set of 6 arresters rated at 33 and 132 kV and a set of 5 arrester sections. The results of the investigation verified the effectiveness of the selected procedure with a consistent and accurate assessment of arrester condition obtained for all arresters under test. All arresters exhibited satisfactory performance in the selected tests, indicating that high voltage gapped silicon carbide arresters are more durable than those used on distribution systems.