Selective caching : a persistent memory approach for multi-dimensional index structures. - In: Distributed and parallel databases, ISSN 1573-7578, Bd. 40 (2022), 1, S. 47-66
Special Issue on Self-Managing and Hardware-Optimized Database Systems 2020
https://doi.org/10.1007/s10619-021-07327-0
Stereoscopic 3D dashboards : an investigation of performance, workload, and gaze behavior during take-overs in semi-autonomous driving. - In: Personal and ubiquitous computing, ISSN 1617-4917, Bd. 26 (2022), 3, S. 697-719
When operating a conditionally automated vehicle, humans occasionally have to take over control. If the driver is out of the loop, a certain amount of time is necessary to gain situation awareness. This work evaluates the potential of stereoscopic 3D (S3D) dashboards for presenting smart S3D take-over-requests (TORs) to support situation assessment. In a driving simulator study with a 4 × 2 between-within design, we presented 3 smart TORs showing the current traffic situation and a baseline TOR in 2D and S3D to 52 participants doing the n-back task. We further investigate if non-standard locations affect the results. Take-over performance indicates that participants looked at and processed the TORs' visual information and by that, could perform more safe take-overs. S3D warnings in general, as well as warnings appearing at the participants’ focus of attention and warnings at the instrument cluster, performed best. We conclude that visual warnings, presented on an S3D dashboard, can be a valid option to support take-over while not increasing workload. We further discuss participants’ gaze behavior in the context of visual warnings for automotive user interfaces.
https://doi.org/10.1007/s00779-020-01438-8
Soft touch between a highly flexible bio-inspired tactile sensor and 3D objects. - In: Proceedings in applied mathematics and mechanics, ISSN 1617-7061, Bd. 21 (2021), 1, e202100003, S. 1-3
Scanning and reconstructing the environment using tactile sensors alongside optical sensors is a promising approach in mobile robotics. Within the present paper, we take advantage of a recently presented vibrissa-inspired tactile sensor concept for 3D object scanning and reconstruction, broadening our previous studies. The sensor consists of a slender, cylindrical, highly flexible probe, one-sided clamped to some force-torque measuring device. The probe is shifted relatively to an object of interest by displacing its clamping position quasi-statically. Consequently, the probe gets bent, sweeps over the object and transmits mechanical signals (observables) to its support. The focus of the present investigation is on how the probe sweeps over a new type of object (paraboloid), verifying a necessary condition for optional contact points. Finally, this condition allows to find multiple equilibrium states for a single clamping position.
https://doi.org/10.1002/pamm.202100003
Influence of initial temperature and convective heat loss on the self-propagating reaction in Al/Ni multilayer foils. - In: Materials, ISSN 1996-1944, Bd. 14 (2021), 24, 7815, insges. 15 S.
A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, these Al/Ni multilayer foils were fabricated by the magnetron sputtering technique with a 1:1 atomic ratio. Heat of reaction of the fabricated foils was determined employing Differential Scanning Calorimetry (DSC). Self-propagating reaction was initiated by an electrical spark on the surface of the foils. The movement of the reaction front was recorded with a high-speed camera. Activation energy is fitted with these velocity data from the high-speed camera to adjust the numerical model. Calculated reaction front temperature of the self-propagating reaction was compared with the temperature obtained by time-resolved pyrometer measurements. X-ray diffraction results confirmed that all reactants reacted and formed a B2 NiAl phase. Finally, it is predicted that (1) increasing thermal conductivity of the final product increases the reaction front velocity; (2) effect of heat convection losses on reaction characteristics is insignificant, e.g., the foils can maintain their characteristics in water; and (3) with increasing initial temperature of the foils, the reaction front velocity and the reaction temperature increased.
https://doi.org/10.3390/ma14247815
Chemoheteroepitaxy of 3C-SiC(111) on Si(111): influence of predeposited Ge on structure and composition. - In: Physica status solidi, ISSN 1862-6319, Bd. 218 (2021), 24, 2100399, S. 1-10
Secondary ion mass spectroscopy, Fourier transformed infrared spectroscopy, ellipsometry, reflection high energy diffraction and transmission electron microscopy are used to gain inside into the effect of Ge on the formation of ultrathin 3C-SiC layers on Si(111) substrates. Accompanying the experimental investigations with simulations it is found that the ultrathin single crystalline 3C-SiC layer is formed on top of a gradient Si1-x-yGexCy buffer layer due to a complex alloying and alloy decomposition processes promoted by carbon and germanium interdiffusion and SiC nucleation. This approach allows tuning residual stress at very early growth stages as well as the interface properties of the 3C-SiC/Si heterostructure. Useful yields of secondary ions of Ge in Si matrix and Si dimer are estimated.
https://doi.org/10.1002/pssa.202100399
Magnetic field compensation coil design for magnetoencephalography. - In: Scientific reports, ISSN 2045-2322, Bd. 11 (2021), 22650, S. 1-12
While optically pumped magnetometers (OPMs) can be attached to the head of a person and allow for highly sensitive recordings of the human magnetoencephalogram (MEG), they are mostly limited to an operational range of approximately 5 nT. Consequently, even inside a magnetically shielded room (MSR), movements in the remnant magnetic field disable the OPMs. Active suppression of the remnant field utilizing compensation coils is therefore essential. We propose 8 compensation coils on 5 sides of a cube with a side length of approximately 2 m which were optimized for operation inside an MSR. Compared to previously built bi-planar compensation coils, the coils proposed in this report are more complex in geometry and achieved smaller errors for simulated compensation fields. The proposed coils will allow for larger head movements or smaller movement artifacts in future MEG experiments compared to existing coils.
https://doi.org/10.1038/s41598-021-01894-z
Contamination-assisted rather than metal catalyst-free bottom-up growth of silicon nanowires. - In: Advanced materials interfaces, ISSN 2196-7350, Bd. 8 (2021), 22, 2101121, insges. 9 S.
Well-established metal-catalyzed vapor-liquid-solid (VLS) growth represents still undoubtedly the key technology for bottom-up synthesis of single-crystalline silicon nanowires (SiNWs). Although various SiNW applications are demonstrated, electrical and optical properties are exposed to the inherent risk of electronic deep trap state formation by metal impurities. Therefore, metal catalyst-free growth strategies are intriguing. The oxid-assisted SiNW synthesis is explored and it is shown that contamination control is absolutely crucial. Slightest metal impurities, such as iron, are sufficient to trigger SiNW growth, calling into question true metal catalyst-free SiNW synthesis. Therefore, the term contamination-assisted is rather introduced and it is shown that contamination-assisted SiNW growth is determined by the chemical surface treatment (e.g., with KOH solution), but also by the crystal orientation of a silicon substrate. SiNWs are grown in this regards in a reproducible manner, but so far with a distinct tapering, using a conventional gas-phase reactor system at temperatures of about 680 ˚C and monosilane (SiH4) as the precursor gas. The synthesized SiNWs show convincing electrical properties compared to Au-catalyzed SiNWs. Nevertheless, contamination-assisted growth of SiNWs appears to be an important step toward bottom-up synthesis of high-quality SiNWs with a lower risk of metal poisoning, such as those needed for CMOS and other technologies.
https://doi.org/10.1002/admi.202101121
What is in the KGQA benchmark datasets? Survey on challenges in datasets for question answering on knowledge graphs. - In: Journal on data semantics, ISSN 1861-2040, Bd. 10 (2021), 3/4, S. 241-265
Question Answering based on Knowledge Graphs (KGQA) still faces difficult challenges when transforming natural language (NL) to SPARQL queries. Simple questions only referring to one triple are answerable by most QA systems, but more complex questions requiring complex queries containing subqueries or several functions are still a tough challenge within this field of research. Evaluation results of QA systems therefore also might depend on the benchmark dataset the system has been tested on. For the purpose to give an overview and reveal specific characteristics, we examined currently available KGQA datasets regarding several challenging aspects. This paper presents a detailed look into the datasets and compares them in terms of challenges a KGQA system is facing.
https://doi.org/10.1007/s13740-021-00128-9
Updated insights into 3D architecture electrodes for micropower sources. - In: Advanced materials, ISSN 1521-4095, Bd. 33 (2021), 45, 2103304, insges. 17 S.
Microbatteries (MBs) and microsupercapacitors (MSCs) are primary on-chip micropower sources that drive autonomous and stand-alone microelectronic devices for implementation of the Internet of Things (IoT). However, the performance of conventional MBs and MSCs is restricted by their 2D thin-film electrode design, and these devices struggle to satisfy the increasing IoT energy demands for high energy density, high power density, and long lifespan. The energy densities of MBs and MSCs can be improved significantly through adoption of a 2D thick-film electrode design; however, their power densities and lifespans deteriorate with increased electrode thickness. In contrast, 3D architecture electrodes offer remarkable opportunities to simultaneously improve MB and MSC energy density, power density, and lifespan. To date, various 3D architecture electrodes have been designed, fabricated, and investigated for MBs and MSCs. This review provides an update on the principal superiorities of 3D architecture electrodes over 2D thick-film electrodes in the context of improved MB and MSC energy density, power density, and lifespan. In addition, the most recent and representative progress in 3D architecture electrode development for MBs and MSCs is highlighted. Finally, present challenges are discussed and key perspectives for future research in this field are outlined.
https://doi.org/10.1002/adma.202103304
Modulation of human intraocular pressure using a pneumatic system. - In: Translational Vision Science & Technology, ISSN 2164-2591, Bd. 10 (2021), 14, 4, S. 1-9
https://doi.org/10.1167/tvst.10.14.4