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This article presents a comparative experimental study of the electrical, structural and chemical properties of large‐format, 180 Ah prismatic lithium iron phosphate (LFP)/graphite lithium‐ion battery cells from two different manufacturers. These cells are particularly used in the field of stationary energy storage such as home‐storage systems. The investigations include (1) cell‐to‐cell performance assessment, for which a total of 28 cells was tested from each manufacturer, (2) electrical charge/discharge characteristics at different currents and ambient temperatures, (3) internal cell geometries, components, and weight analysis after cell opening, (4) microstructural analysis of the electrodes via light microscopy and scanning electron microscopy, (5) chemical analysis of the electrode materials using energy‐dispersive X‐ray spectroscopy, and (6) mathematical analysis of the electrode balances. The combined results give a detailed and comparative insight into the cell characteristics, providing essential information needed for system integration. The study also provides complete and self‐consistent parameter sets for the use in cells models needed for performance prediction or state diagnosis.
eLetter zum Artikel "Plague Through History" von Nils Chr. Stenseth, veröffentlicht in Science, Vol. 321, Issue 5890, Seite 773-774 (doi.org/10.1126/science.1161496)
Modern society is more than ever striving for digital connectivity -- everywhere and at any time, giving rise to megatrends such as the Internet of Things (IoT). Already today, 'things' communicate and interact autonomously with each other and are managed in networks. In the future, people, data, and things will be interlinked, which is also referred to as the Internet of Everything (IoE). Billions of devices will be ubiquitously present in our everyday environment and are being connected over the Internet.
As an emerging technology, printed electronics (PE) is a key enabler for the IoE offering novel device types with free form factors, new materials, and a wide range of substrates that can be flexible, transparent, as well as biodegradable. Furthermore, PE enables new degrees of freedom in circuit customizability, cost-efficiency as well as large-area fabrication at the point of use.
These unique features of PE complement conventional silicon-based technologies. Additive manufacturing processes enable the realization of many envisioned applications such as smart objects, flexible displays, wearables in health care, green electronics, to name but a few.
From the perspective of the IoE, interconnecting billions of heterogeneous devices and systems is one of the major challenges to be solved. Complex high-performance devices interact with highly specialized lightweight electronic devices, such as e.g. smartphones and smart sensors. Data is often measured, stored, and shared continuously with neighboring devices or in the cloud. Thereby, the abundance of data being collected and processed raises privacy and security concerns.
Conventional cryptographic operations are typically based on deterministic algorithms requiring high circuit and system complexity, which makes them unsuitable for lightweight devices.
Many applications do exist, where strong cryptographic operations are not required, such as e.g. in device identification and authentication. Thereby, the security level mainly depends on the quality of the entropy source and the trustworthiness of the derived keys. Statistical properties such as the uniqueness of the keys are of great importance to precisely distinguish between single entities.
In the past decades, hardware-intrinsic security, particularly physically unclonable functions (PUFs), gained a lot of attraction to provide security features for IoT devices. PUFs use their inherent variations to derive device-specific unique identifiers, comparable to fingerprints in biometry.
The potentials of this technology include the use of a true source of randomness, on demand key derivation, as well as inherent key storage.
Combining these potentials with the unique features of PE technology opens up new opportunities to bring security to lightweight electronic devices and systems. Although PE is still far from being matured and from being as reliable as silicon technology, in this thesis we show that PE-based PUFs are promising candidates to provide key derivation suitable for device identification in the IoE.
Thereby, this thesis is primarily concerned with the development, investigation, and assessment of PE-based PUFs to provide security functionalities to resource constrained printed devices and systems.
As a first contribution of this thesis, we introduce the scalable PE-based Differential Circuit PUF (DiffC-PUF) design to provide secure keys to be used in security applications for resource constrained printed devices. The DiffC-PUF is designed as a hybrid system architecture incorporating silicon-based and inkjet-printed components. We develop an embedded PUF platform to enable large-scale characterization of silicon and printed PUF cores.
In the second contribution of this thesis, we fabricate silicon PUF cores based on discrete components and perform statistical tests under realistic operating conditions. A comprehensive experimental analysis on the PUF security metrics is carried out. The results show that the silicon-based DiffC-PUF exhibits nearly ideal values for the uniqueness and reliability metrics. Furthermore, the identification capabilities of the DiffC-PUF are investigated and it is shown that additional post-processing can further improve the quality of the identification system.
In the third contribution of this thesis, we firstly introduce an evaluation workflow to simulate PE-based DiffC-PUFs, also called hybrid PUFs. Hereof, we introduce a Python-based simulation environment to investigate the characteristics and variations of printed PUF cores based on Monte Carlo (MC) simulations. The simulation results show, that the security metrics to be expected from the fabricated devices are close to ideal at the best operating point.
Secondly, we employ fabricated printed PUF cores for statistical tests under varying operating conditions including variations in ambient temperature, relative humidity, and supply voltage. The evaluations of the uniqueness, bit aliasing, and uniformity metrics are in good agreement with the simulation results. The experimentally determined mean reliability value is relatively low, which can be explained by the missing passivation and encapsulation of the printed transistors. The investigation of the identification capabilities based on the raw PUF responses shows that the pure hybrid PUF is not suitable for cryptographic applications, but qualifies for device identification tasks.
The final contribution is to switch to the perspective of an attacker. To judge on the security capabilities of the hybrid PUF, a comprehensive security analysis in the manner of a cryptanalysis is performed. The analysis of the entropy of the hybrid PUF shows that its vulnerability against model-based attacks mainly depends on the selected challenge building method. Furthermore, an attack methodology is introduced to assess the performances of different mathematical cloning attacks on the basis of eavesdropped challenge-response pairs (CRPs). To clone the hybrid PUF, a sorting algorithm is introduced and compared with commonly used supervised machine learning (ML) classifiers including logistic regression (LR), random forest (RF), as well as multi-layer perceptron (MLP).
The results show that the hybrid PUF is vulnerable against model-based attacks. The sorting algorithm benefits from shorter training times compared to the ML algorithms. If the eavesdropped CRPs are erroneous, the ML algorithms outperform the sorting algorithm.
eLetter zum Artikel "The Hannes hand prosthesis replicates the key biological properties of the human hand" von Matteo Laffranchi et al., veröffentlicht in Science Robotics, Vol. 5, Issue 46, eabb0467 (doi.org/10.1126/scirobotics.abb0467)
Photonics meet digital art
(2014)
The paper focuses on the work of an interdisciplinary project between photonics and digital art. The result is a poster collection dedicated to the International Year of Light 2015. In addition, an internet platform was created that presents the project. It can be accessed at http://www.magic-of-light.org/iyl2015/index.htm. From the idea to the final realization, milestones with tasks and steps will be presented in the paper. As an interdisciplinary project, students from technological degree programs were involved as well as art program students. The 2015 Anniversaries: Alhazen (1015), De Caus (1615), Fresnel (1815), Maxwell (1865), Einstein (1905), Penzias Wilson, Kao (1965) and their milestone contributions in optics and photonics will be highlighted.
PHOTOPUR hat die Entwicklung eines photokatalytischen Prozesses zur Beseitigung von Pflanzenschutzmitteln (PSM) aus dem Reinigungswasser von Spritzgeräten zum Ziel. Am INES wurde eine Energieversorgung für die photokatalytische Reinigung in zwei Bachelorarbeiten entwickelt und als Demosystem aufgebaut. Das Gesamtsystem ist nun als mobile Einheit verfügbar und wurde zuletzt um das Reaktormodul für den photokatalytischen Prozeß erweitert und den Partnern für intensive Tests übergeben.
In this work, we evaluate two different image clustering objectives, k-means clustering and correlation clustering, in the context of Triplet Loss induced feature space embeddings. Specifically, we train a convolutional neural network to learn discriminative features by optimizing two popular versions of the Triplet Loss in order to study their clustering properties under the assumption of noisy labels. Additionally, we propose a new, simple Triplet Loss formulation, which shows desirable properties with respect to formal clustering objectives and outperforms the existing methods. We evaluate all three Triplet loss formulations for K-means and correlation clustering on the CIFAR-10 image classification dataset.
Die angestrebten Klimaschutzziele erfordern, dass Erneuerbare Energien längerfristig zur Hauptenergiequelle der Energieversorgung werden. Um dieses ehrgeizige Ziel zu erreichen, ist es angebracht konventionelle und erneuerbare Energie oder noch besser nachhaltige Einzelprozesse intelligent miteinander zu verknüpfen.
Das Projekt EBIPREP wird von einer interdisziplinären Forschergruppe bestehend aus Chemikern, Prozessingenieuren und Bioprozessingenieuren sowie Physikern, die auf Sensoren und Prozesssteuerung spezialisiert sind durchgeführt. Das Ziel ist es, neue Lösungen für die Nutzungswege von Holzhackschnitzeln und den bei der mechanischen Trocknung anfallenden Holzpresssaft zu entwickeln. Neben der Hackschnitzelvergasung und der katalytischen Reinigung des Holzgases steht die Nutzung des Holzpresssafts in Biogasanlagen und bei der biotechnologischen Wertstofferzeugung, z.B. bei der Enzymherstellung, im Vordergrund.
Was wir tun?
Das EBIPREP-Projekt wird von einer interdisziplinären Forschungsgruppe durchgeführt, die sich aus Chemikern, Prozessingenieuren, Bioprozessingenieuren und Physikern zusammensetzt. Ziel ist es, neue Lösungen für den Einsatz von Hackschnitzeln und Holzpresssaft zu entwickeln, die durch ein innovatives mechanisches Trocknungsverfahren gewonnen werden. Neben der Holzvergasung und katalytischen Reinigung des Holzgases ist der Einsatz von Holzpresssaft in Biogasanlagen und in biotechnologischen Produktionsprozessen von Wertstoffen vorgesehen. Holzhackschnitzel werden thermisch vergast. Es werden Online-Sensoren entwickelt, um die relevanten Parameter der stabilisierten und optimierten Einzelprozesse auszuwerten. Die Verknüpfung von thermischen und biotechnologischer Konversionsprozessen könnte dazu beitragen, die Dimension von Biogasreaktoren erheblich zu reduzieren. Diese Tatsache wird folglich zu einer spürbaren Kostensenkung führen.
Ziele des EBIPREP-Projekts
• die Vorteile der thermischen und biologischen Umwandlung von Biomasse zu kombinieren;
• Entwicklung eines Verfahrens zur Reduzierung von Schadstoffemissionen mit innovativen Sensoren und katalytische Behandlung von Synthesegasen;
• nachhaltige Produktion biotechnologischer wertvoller Produkte
• wirtschaftliche und ökologische Analyse des Gesamtprozesses im Vergleich zu den Einzelprozessen
• Einsatz von Prozessabwässern zur Erzeugung regenerativer Energie oder biotechnologischer Wertstoffe
• Erwerb neuer Kenntnisse auf dem Gebiet der Rückgewinnungstechnik von Rückständen
• und Energieerzeugung;
• Erweiterung neuer Anwendungsfelder für innovative Sensoren und Keramik
• Schäume für Katalysatoren;
• Senkung der Kosten für die Biogasproduktion
Im geplanten Übersichtsvortrag werden die vernetzten Strukturen des Projekts EBIPREP und deren zentralen Ergebnisse vorgestellt.