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Gait tests as part of home monitoring study protocols for patients with movement disorders may provide valuable standardized anchor-points for real-world gait analysis using inertial measurement units (IMUs). However, analyzing unsupervised gait tests relies on reliable test annotations by the patients requiring a potentially error-prone interaction with the recording system. To overcome this limitation, this work presents a novel algorithmic pipeline for the automated detection of unsupervised standardized gait tests from continuous real-world IMU data. In a study with twelve Parkinson’s disease patients, we recorded real-world gait data over two weeks using foot-worn IMUs. During continuous daily recordings, the participants performed series of three consecutive ${4}\times {10}$ -Meters-Walking-Tests (${4}\times {10}$ MWTs) at different walking speeds, besides their usual daily-living activities. The algorithm first detected these gait test series using a gait sequence detection algorithm, a peak enhancement pipeline, and subsequence Dynamic Time Warping and then decomposed them into single ${4}\times {10}$ MWTs based on the walking speed. In the evaluation with 419 available gait test series, the detection reached an F1-score of 88.9% and the decomposition an F1-score of 94.0%. A concurrent validity evaluation revealed very good agreement between spatio-temporal gait parameters derived from manually labelled and automatically detected ${4}\times {10}$ MWTs. Our algorithm allows to remove the burden of system interaction from the patients and reduces the time for manual data annotation for researchers. The study contributes to an improved automated processing of real-world IMU gait data and enables a simple integration of standardized tests into continuous long-term recordings. This will help to bridge the gap between supervised and unsupervised gait assessment. [ABSTRACT FROM AUTHOR]

In modern positron emission tomography (PET) readout architectures, the position and energy estimation of scintillation events (singles) and the detection of coincident events (coincidences) are typically carried out on highly integrated, programmable printed circuit boards. The implementation of advanced singles and coincidence processing (SCP) algorithms for these architectures is often limited by the strict constraints of hardware-based data processing. In this paper, we present a software-based data acquisition and processing architecture (DAPA) that offers a high degree of flexibility for advanced SCP algorithms through relaxed real-time constraints and an easily extendible data processing framework. The DAPA is designed to acquire detector raw data from independent (but synchronized) detector modules and process the data for singles and coincidences in real-time using a center-of-gravity (COG)-based, a least-squares (LS)-based, or a maximum-likelihood (ML)-based crystal position and energy estimation approach (CPEEA). To test the DAPA, we adapted it to a preclinical PET detector that outputs detector raw data from 60 independent digital silicon photomultiplier (dSiPM)-based detector stacks and evaluated it with a [^18F]-fluorodeoxyglucose-filled hot-rod phantom. The DAPA is highly reliable with less than 0.1% of all detector raw data lost or corrupted. For high validation thresholds (37.1 $\pm$ 12.8 photons per pixel) of the dSiPM detector tiles, the DAPA is real time capable up to 55 MBq for the COG-based CPEEA, up to 31 MBq for the LS-based CPEEA, and up to 28 MBq for the ML-based CPEEA. Compared to the COG-based CPEEA, the rods in the image reconstruction of the hot-rod phantom are only slightly better separable and less blurred for the LS- and ML-based CPEEA. While the coincidence time resolution ($\sim$ 550 ps) and energy resolution ($\sim$12.3%) are comparable for all three CPEEA, the system sensitivity is up to 2.5$\times$ higher for the LS- and ML-based CPEEA. [ABSTRACT FROM AUTHOR]

Motor drives utilizing power semiconductors play an important role in modern day electric motor control. Although the reliability of power semiconductors is widely studied, the product level reliability of motor drives has been studied markedly less even though their more complex control and measuring electronics often make them more vulnerable to environmental stresses. In order to advance product level accelerated reliability testing, customized test methods with multiple simultaneous or sequential stresses can be used. However, the knowledge of combined effects of different stresses is still largely unknown. In this research the reliability of a commercial motor drive was studied. Environmental conditions used included an 85 °C constant temperature test and an 85 °C test with 85% relative humidity. Additionally, input power interruptions were included to study the effect of sudden shortages of electricity. The results of the study showed that the mean time to failure for the devices tested with the input power interruptions was notably shorter than that for the test series without them. An especially clear effect of the input power interruptions was seen on the power MOSFETs of the motor drives. Moreover, the humidity was found to play an important role in the reliability of the motor drives. [ABSTRACT FROM AUTHOR]

Due to the impact of arcing on high-purity surfaces and bound residual gases, current interruption operations may influence the internal pressure in vacuum interrupters (VIs). In this paper, we investigate the temporal development of internal pressure in VIs immediately after a current interruption operation, both intrusively using a vacuum gauge and nonintrusively using the magnetron method. By means of an experimental test setup that consists of a vacuum test system to vary the internal pressure in punctured, nonvented VIs with active getter elements, we performed experimental test series under variation of internal pressure and arcing time. The experimental results indicate that arcing during the interruption operation predominantly causes a significant decrease in the internal pressure of up to several orders of magnitude, depending on the arcing time and the initial pressure before the current interruption operation. Based on a test series with passivated getter elements, we found that active getter elements have only a minor influence on the observed pressure decrease. With regard to a condition assessment of vacuum circuit breakers, we discuss the impact of the observed pressure reduction effect on the possibility of predicting the remaining service life of installed VIs. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to investigate an impact of the inrush current on the prestrike and restrike characteristics of vacuum interrupters (VIs) during capacitive current switching duty. Eleven 7.2 kV VIs are used. Their contact parameters are contact gap 4 mm and contact material CuCr25 (25%weight of Cr). A series of 80 CO operations are executed for each test VI. The amplitude of inrush current Iinrush (3800 Hz) is set to 0 kA, 2 kA, 5 kA and 10 kA, respectively. The switching current is less than 1 A rms. The (1-cosωt) shape of the recovery voltage with a peak of 15 kV is applied to the test VI. The experimental results show that the prestrike and restrike phenomena are significantly influenced by the contact surface conditions damaged by the inrush current. The cumulative probability of the prestrike gap dpre follows a 3- parameter Weibull distribution. When Iinrush increases from 2 kA to 5 kA, the prestrike gap increases accordingly. The 10% dpre increases from 0.5 mm to 0.7 mm. The 50% dpre increases from 0.7 mm to 1.0 mm. The 90% dpre increases from 1.0 mm to 1.5 mm. The scale in the Weibull distribution, which can describe the scattering of dpre, is 0.2 mm and 0.6 mm in the case of Iinrush = 2 kA and Iinrush = 5 kA, respectively. It is found that the occurrence frequency of the inrush current interruption increases from 37.9% to 68.3% with the increase of Iinrush from 2 kA to 5 kA. Moreover, the inrush current also has an impact on the restrike types, which are classified into three types according to the waveform features. The average restrike probability increases from 4.6% to 17.9% and further to 30.4% with the increase of the inrush current from 0 kA to 2 kA and 5 kA, respectively. In addition, the higher the inrush current, the restrike tends to occur earlier during the recovery voltage period. [ABSTRACT FROM AUTHOR]

An E2 class(also known as extended electrical endurance) circuit breaker is designed such that it does not require maintenance of the interrupting parts during its expected operating life. Normally, life expectancy of the design is higher than the expected operating life. Although, it is not a mandatory type test as per internationalstandards, the customer may demand this test duty in addition to the required type test series. An E2 test duty is a highly time consuming and an extremely expensive test. In view of this, an innovative calculation procedure has been developed utilizing the outcome of the cleared type/development test. This will not only save time significantly but will also serve as sufficient proof for performance. Simulations are done only for SF6 circuit breakers and results are presented for both puffer and self-blast type circuit breaker. In order to prove the robustness of the calculation method, simulations have been performed for different frequencies (50 Hz and 60 Hz), rated voltages and short circuit current. The simulation results have been validated by means of testing and are found to be in good agreement with the test results. Further, the calculation procedure can be extended to circuit breakers having different gases/gas mixtures. [ABSTRACT FROM AUTHOR]

Radio frequency identification (RFID) tags with anisotropically conductive joints (ACAs) are used in different applications where the environmental conditions may impair their reliability. Thus the effects of different environmental stresses on reliability need to be investigated. The effects of high temperature and humidity may change the performance of the tags. Moreover, the effects of constantly varying temperature and humidity conditions may be even more harmful. In this study, the effects of changing humidity conditions on the performance of a passive ultra high frequency (UHF) RFID tag with ACA joints were studied. The tags were tested in a humidity cycling test where humidity varied from 85%RH to 10%RH, and temperature from 85 ^\circC to 25 ^\circC. Tags with four different sets of bonding parameters were tested. Significant differences in the reliability between the tags with different bonding parameters were observed. The results were also compared with results from a corresponding constant humidity test where the humidity was 85%RH, and the temperature 85 ^\circC. The tags had different failure times, modes, and mechanisms in these two tests. Furthermore, the effects of bonding parameters on the reliability were different in these tests. According to this study, it is important to investigate the effects of changing humidity, when the reliability in different environments is investigated, but the constant humidity test cannot be replaced with the faster humidity cycling test. [ABSTRACT FROM PUBLISHER]

At the French-German Research Institute (ISL), several railgun setups are used to investigate different military scenarios. One compelling scenario for a railgun application is the long-range artillery. For this, it is required to be able to handle multimegaampere currents to accelerate heavy launch packages of velocities above 2 km/s and to do so as efficient as possible. The NGL-60 is a 6-m-long open-barrel breech-fed railgun with a square caliber of 60 mm. With this railgun, it will be possible to fully utilize the currently available 10-MJ capacitor-based power supply unit (PSU). To validate the concept of the NGL-60 design, a 2-m-long prototype was installed. Subsequent tests showed that the railgun design is able to handle currents above 2 MA without structural damages or electrical failures. After the successful test series with the prototype, the construction of the full NGL-60 started and is finished by now. In this report, results from the prototype tests are reported, and the first experiments with the 6-m-long NGL-60 are presented. [ABSTRACT FROM AUTHOR]

Radio frequency identification (RFID) tags with anisotropic conductive adhesive (ACA) joints are used in various applications where the environmental conditions may impair their reliability. Therefore, it is essential to investigate the effects of different environmental stresses on reliability and to analyze failure mechanisms. The purpose of this paper was to study the effects of changing humidity conditions on the performance of a passive ultrahigh frequency RFID tag with ACA joints. The tags were tested in a humidity cycling test where the humidity varied from 85%RH to 10%RH and temperature from 85^\circC to 25^\circC. Tags with four different sets of bonding parameters were tested. Significant differences in reliability between tags with different bonding parameters were observed. Different failure times, failure modes, and failure mechanisms were observed. Full-wave electromagnetic antenna simulations were used to support the analysis on the failure mechanisms manifesting themselves through changes in the common tag performance parameters. Changes in impedance matching between the chip and the antenna were found to be the most likely failure mechanism. The impedance matching may have changed due to cracks formed in the antenna during testing or due to chemical and mechanical changes in the ACA joints. It was observed that several failure factors might act simultaneously. [ABSTRACT FROM PUBLISHER]

Die-to-wafer interconnections such as copper pillars play a vital role in order to enable 3-D integration. This interconnection type allows increasing the density of interconnects but the occurrence of defects, especially intermetallic compounds (IMC) and Kirkendall voids, may reduce the lifetime at elevated operating conditions. This paper investigates the physical degradation mechanisms in copper pillars and micro-bumps, caused by IMC and void formation during stress tests such as electromigration (EM) and high temperature storage. The resistance evolution of the tested interconnections motivated the derivation of a novel analytical model to separate the resistance increases caused by IMC growth and void formation. This allows the real time monitoring of changes in the kinetics, which gives a better understanding of the underlying physics and of the failure mechanisms. In order to validate the model, an additional test series on copper pillars under EM stress with varying conditions is conducted and the model is applied on the monitored resistance evolution. The different stress conditions allowed the extraction of the IMC formation activation energy, which is compared against parameter extraction using classical mean time to failure analysis as well as material parameters of IMC growth that are already reported in the literature. [ABSTRACT FROM AUTHOR]

Material ejected from aluminum armatures at the rail–armature interface has been identified as a mechanism that degrades both rails and insulators in a railgun, significantly reducing the bore lifetime. With the goal of controlling the onset of armature ejecta, a series of single-shot tests was conducted in a small railgun with a bore cross section of 22 \times 44 mm. The tests utilized channels of various sizes and geometries machined into the rail contact surface of the armatures to see if ejecta could be controlled. These tests identified several channel patterns as having the potential to delay the onset of armature ejecta. A series of multiple-shot tests was subsequently conducted in a larger railgun having a bore cross section of 38 \times 76 mm. The goal of these experiments was to see if the channel patterns that delayed armature ejecta had a significant impact on rail erosion at start-up. Three test series were conducted. In the first series, three armatures with a nested circular channel pattern were tested. In the second series, three armatures with a large centrally located channel were tested. Both armature designs used equivalent contact areas. These results were then compared to a standard armature contact face with no modifications in a third test series. [ABSTRACT FROM AUTHOR]

According to the relevant IEC standards vacuum circuit-breakers have to meet various needs, e.g. the interruption capability, making operations, and dielectric strength. Besides the interruption of short-circuit currents, switching of capacitive currents causes high stress of the circuit-breaker. Switching of capacitor banks, overhead lines, or cables leads to very small currents in comparison with short circuit currents. After current interruption the circuit-breaker must withstand twice the peak value of the system voltage. Furthermore, restrikes can lead to voltage multiplication. This conjunction of relatively small breaking currents with high voltage stress must be considered in detail. This work introduces a test arrangement for combined tests of making operation, current interruption, and dielectric stress of a vacuum gap under capacitive switching condition. A test vessel permits investigations of various contact materials and designs. It is connected to a synthetic test circuit which provides the appropriate test currents and capacitive voltage. During the test sequence the contacts are stressed by inrush-currents up to 4.5 kA peak, followed by a breaking operation at 500 A peak and a subsequent capacitive voltage up to 50 kV peak. Both the appearance of pre-ignitions at contact closing and the behavior under capacitive voltage stress after breaking are indications of the contact surface conditions. [ABSTRACT FROM AUTHOR]

Diagnostic measurements performed for surge arresters are normally studied by evaluating their suitability to detect aging and degradation of metal oxide material. The suitability of different methods for revealing internal moisture in arresters has not been studied much. This aspect is considered in the paper based on measurement results obtained during a 1.5-yr laboratory test series conducted for six different types of polymer-housed distribution class arresters. AC power losses, third-harmonic content of resistive leakage current, dc leakage current, and partial discharge measurement results over the test period are given and discussed. Details of the measurement procedures suitable for measuring polymeric arresters with internal moisture are also studied. AC power loss and dc leakage current measurements were found to be good methods, whereas the other two can only be used as additional methods when diagnosing internal moisture in polymer-housed arresters. [ABSTRACT FROM AUTHOR]