NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTAZ SpiegelauZeitschriftenartikel
J.-M. Batke, S. Wittman, Günther Ruhl, I. Costina, M. Lemme, T. Preis, M. König, A. Gahoi
Accurate Graphene-Metal Junction Characterization
IEEE Journal of the Electron Devices Society (J-EDS), vol. 7, pp. 219-226
2019
DOI: 10.1109/JEDS.2019.2891516
Abstract anzeigen
A reliable method is proposed for measuring specific contact resistivity (p C ) for graphenemetal contacts, which is based on a contact end resistance measurement. We investigate the proposed method with simulations and confirm that the sheet resistance under the metal contact (R SK ) plays an important role, as it influences the potential barrier at the graphene-metal junction. Two different complementary metal-oxide-semiconductor-compatible aluminum-based contacts are investigated to demonstrate the importance of the sheet resistance under the metal contact: the difference in R SK arises from the formation of insulating aluminum oxide (Al 2 O 3 ) and aluminum carbide (Al 4 C 3 ) interfacial layers, which depends on the graphene pretreatment and process conditions. Auger electron spectroscopy and X-ray photoelectron spectroscopy support electrical data. The method allows direct measurements of contact parameters with one contact pair and enables small test structures. It is further more reliable than the conventional transfer length method when the sheet resistance of the material under the contact is large. The proposed method is thus ideal for geometrically small contacts where it minimizes measurement errors and it can be applied in particular to study emerging devices and materials.
DigitalMobilElektrotechnik und MedientechnikInstitut ProtectITBeitrag (Sammelband oder Tagungsband)
Martin Schramm, D. Fiala, Michael Heigl
A Lightweight Quantum-Safe Security Concept for Wireless Sensor Network Communication
Proceedings of the IEEE Annual International Conference on Pervasive Computing and Communications Workshops (March 11-15, 2019; Kyoto, Japan)
2019
ISBN: 978-1-5386-9150-2
DOI: 10.1109/PERCOMW.2019.8730749
Abstract anzeigen
The ubiquitous internetworking of devices in all areas of life is boosted by various trends for instance the Internet of Things. Promising technologies that can be used for such future environments come from Wireless Sensor Networks. It ensures connectivity between distributed, tiny and simple sensor nodes as well as sensor nodes and base stations in order to monitor physical or environmental conditions such as vibrations, temperature or motion. Security plays an increasingly important role in the coming decades in which attacking strategies are becoming more and more sophisticated. Contemporary cryptographic mechanisms face a great threat from quantum computers in the near future and together with Intrusion Detection Systems are hardly applicable on sensors due to strict resource constraints. Thus, in this work a future-proof lightweight and resource-aware security concept for sensor networks with a processing stage permeated filtering mechanism is proposed. A special focus in the concepts evaluation lies on the novel Magic Number filter to mitigate a special kind of Denial-of-Service attack performed on CC1350 LaunchPad ARM Cortex-M3 microcontroller boards.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenZeitschriftenartikel
Hongyu Zhang, Jizhong Sun, Ali Hamid, Thomas Stirner, Arvind Jadon
Molecular dynamics simulations of helium clustering and bubble growth under tungsten surfaces
Computational Materials Science, vol. 163, no. June, pp. 141-147
2019
DOI: 10.1016/j.commatsci.2019.03.008
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We study the surface response of W to helium bombardment using molecular dynamics simulations. Simulations have been performed for incident helium of energy 80 eV and surface temperature 2100 K. The saturation of He retention has been observed to be high, a result of the bubbles trapping helium atoms and preventing them from diffusing to the surface and further back into the plasma. On the other hand, we have observe near-surface “cluster rupture” leading to the expulsion of helium atoms towards the vacuum. We have found that bubbles typically grow in a relatively narrow band of He/V ratios (1–3). Besides, it was observed that tungsten atoms migrated from the top surface into the bulk. The coalescence of helium bubbles has also been observed.
NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenZeitschriftenartikel
Thomas Stirner, David Scholz
Convergence of surface energy calculations for various methods: (0 0 1) hematite as benchmark
Journal of Physics: Condensed Matter, vol. 31, no. 19
2019
DOI: 10.1088/1361-648X/ab069d
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Different methods for calculating the surface energy from ab initio simulations are applied to the relaxed (0 0 1) surface of the metal oxide hematite ([Formula: see text]-Fe2O3). The simulations are carried out with a rather moderate k-point grid with shrinking factors of (6 6 6) for all bulk and (6 6) for all slab simulations. Very good convergence is obtained if a linear fit of the slab energies with respect to the number of layers in the slab is performed. In comparison to the other methods employed, this procedure is ultimately the most accurate and reliable method for extracting convergent surface energies from (0 0 1) hematite slabs. Additionally, we propose a way to determine the least possible starting point for calculating the surface energy by the linear-fit method. Furthermore, we find the Boettger method to perform nearly equally well, if the bulk energy is extracted from the energy difference per layer between the slabs with 12 and 18 layers thickness. Both methods give a surface energy of 2.43 J m-2 with a deviation of less than [Formula: see text]0.005 J m-2. The standard approach, which uses a separate bulk simulation, instead shows a significant linear divergence with increasing number of layers in the slab. We also carried out bulk simulations with a surface-oriented bulk unit cell, but found it in our case not to improve the convergence of the standard approach.
MobilElektrotechnik und MedientechnikTC FreyungZeitschriftenartikel
Raphaela Pagany, Anna Marquardt, Roland Zink
Electric Charging Demand Location Model—A User- and Destination-Based Locating Approach for Electric Vehicle Charging Stations
Sustainability, vol. 11, no. 8
2019
DOI: 10.3390/su11082301
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In recent years, with the increased focus on climate protection, electric vehicles (EVs) have become a relevant alternative to conventional motorized vehicles. Even though the market share of EVs is still comparatively low, there are ongoing considerations for integrating EVs in transportation systems. Along with pushing EV sales numbers, the installation of charging infrastructure is necessary. This paper presents a user- and destination-based approach for locating charging stations (CSs) for EVs—the electric charging demand location (ECDL) model. With regard to the daily activities of potential EV users, potential positions for CSs are derived on a micro-location level in public and semipublic spaces using geographic information systems (GIS). Depending on the vehicle users’ dwell times and visiting frequencies at potential points of interest (POIs), the charging demand at such locations is calculated. The model is mainly based on a survey analyzing the average time spent per daily activity, regional data about driver and vehicle ownership numbers, and the georeferenced localization of regularly visited POIs. Optimal sites for parking and charging EVs within the POIs neighborhood are selected based on walking distance calculations, including spatial neighborhood effects, such as the density of POIs. In a case study in southeastern Germany, the model identifies concrete places with the highest overall demand for CSs, resulting in an extensive coverage of the electric energy demand while considering as many destinations within the acceptable walking distance threshold as possible.
DigitalMobilElektrotechnik und MedientechnikInstitut ProtectITZeitschriftenartikel
Nicolas Tiefnig, Martin Schramm, D. Fiala, Laurin Dörr, Michael Heigl
A Resource-Preserving Self-Regulating Uncoupled MAC Algorithm to be Applied in Incident Detection
Computers & Security, vol. 85, no. August, pp. 270-285
2019
DOI: 10.1016/j.cose.2019.05.010
Abstract anzeigen
The connectivity of embedded systems is increasing accompanied with thriving technology such as Internet of Things/Everything (IoT/E), Connected Cars, Smart Cities, Industry 4.0, 5G or Software-Defined Everything. Apart from the benefits of these trends, the continuous networking offers hackers a broad spectrum of attack vectors. The identification of attacks or unknown behavior through Intrusion Detection Systems (IDS) has established itself as a conducive and mandatory mechanism apart from the protection by cryptographic schemes in a holistic security eco-system. In systems where resources are valuable goods and stand in contrast to the ever increasing amount of network traffic, sampling has become a useful utility in order to detect malicious activities on a manageable amount of data. In this work an algorithm – Uncoupled MAC – is presented which secures network communication through a cryptographic scheme by uncoupled Message Authentication Codes (MAC) but as a side effect also provides IDS functionality producing alarms based on the violation of Uncoupled MAC values. Through a novel self-regulation extension, the algorithm adapts it’s sampling parameters based on the detection of malicious actions. The evaluation in a virtualized environment clearly shows that the detection rate increases over runtime for different attack scenarios. Those even cover scenarios in which intelligent attackers try to exploit the downsides of sampling.
DigitalElektrotechnik und MedientechnikBeitrag (Sammelband oder Tagungsband)
A. Paler, Andreas Fischer
On the analogy between quantum circuit design automation and virtual network embedding
Proceedings of 34th ACM/SIGAPP Symposium on Applied Computing (SAC'19) [April 8-12, 2019; Limassol, Cyprus], New York, NY, USA
2019
DOI: 10.1145/3297280.3297419
Abstract anzeigen
Quantum computing and network virtualisation share more similarities than it would seem on first thought: both reach their potential by using the underlying hardware as efficiently as possible - a classical computer science problem. Quantum computing research has already been focusing on key problems related to the scarcity of the quantum hardware, hoping that once scalable quantum computers will be available, quantum circuit design automation methods (QCDA) are mature. Consequently, a significant methodological apparatus exists for a technology envisioned to scale in the future. Likewise, the optimisation of resource assignment for virtual networks has received much attention in the literature. As such, any scalability improvement of virtual network embedding (VNE) would be of high practical importance in the present. There is an interesting and promising relationship between VNE and QCDA. This work introduces the possibility to use QCDA methodology for VNE, and vice versa. VNE problem instances can be modeled using the quantum circuit formalism, and we offer some basic examples. To the best of our knowledge, this is the first work that highlights this analogy.
DigitalElektrotechnik und MedientechnikBeitrag (Sammelband oder Tagungsband)
D. Bhamare, A. Kassler, Andreas Fischer
On the Construction of Optimal Embedding Problems for Delay-Sensitive Sercice Function Chains
[Accepted for publication]
Proceedings of the 28th International Conference on Computer Communications and Networks (ICCCN 2019) [July 29-August 1, 2019; Valencia, Spain]
2019
DigitalMobilEuropan Campus Rottal-InnBeitrag (Sammelband oder Tagungsband)
L. Patane, T. Hoinville, H. Cruse, M. Schilling, A. Drimus, P. Arena, Ch.J. Dallmann, T. Krause, R. Strauss, A. Schneider, V. Dürr, J. Paskarbeit, A. Vitanza, Stefan Mátéfi-Tempfli, J. Schmitz
Integrative Biomimetics of Autonomous Hexapedal Locomotion
[Review paper under publication]
Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) [November 3-8, 2019; Macau, China]
2019
NachhaltigElektrotechnik und MedientechnikMaschinenbau und MechatronikZeitschriftenartikel
L. Larcher, F. Puglisi, L. Jiang, Jonas Weber, Günther Benstetter, P. Pavan, M. Lanza, Werner Frammelsberger
Understanding Current Instabilities in Conductive Atomic Force Microscopy
Materials, vol. 12, no. 3
2019
DOI: 10.3390/ma12030459
Abstract anzeigen
Conductive atomic force microscopy (CAFM) is one of the most powerful techniques in studying the electrical properties of various materials at the nanoscale. However, understanding current fluctuations within one study (due to degradation of the probe tips) and from one study to another (due to the use of probe tips with different characteristics), are still two major problems that may drive CAFM researchers to extract wrong conclusions. In this manuscript, these two issues are statistically analyzed by collecting experimental CAFM data and processing them using two different computational models. Our study indicates that: (i) before their complete degradation, CAFM tips show a stable state with degraded conductance, which is difficult to detect and it requires CAFM tip conductivity characterization before and after the CAFM experiments; and (ii) CAFM tips with low spring constants may unavoidably lead to the presence of a ~1.2 nm thick water film at the tip/sample junction, even if the maximum contact force allowed by the setup is applied. These two phenomena can easily drive CAFM users to overestimate the properties of the samples under test (e.g., oxide thickness). Our study can help researchers to better understand the current shifts that were observed during their CAFM experiments, as well as which probe tip to use and how it degrades. Ultimately, this work may contribute to enhancing the reliability of CAFM investigations.
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