2020, Rowolt, Christian, Milkereit, Benjamin, Springer, Armin, Kreyenschulte, Carsten, Kessler, Olaf

Continuous heating transformation (CHT) diagrams and continuous cooling transformation (CCT) diagrams of precipitation-hardening steels have the drawback that important information on the dissolution and precipitation of Cu-rich phases during continuous heating and cooling are missing. This work uses a comparison of different techniques, namely dilatometry and differential scanning calorimetry for the in situ analysis of the so far neglected dissolution and precipitation of Cu-rich phases during continuous heating and cooling to overcome these drawbacks. Compared to dilatometry, DSC is much more sensitive to phase transformation affecting small volume fractions, like precipitation. Thus, the important solvus temperature for the dissolution of Cu-rich phases was revealed from DSC and integrated into the CHT diagram. Moreover, DSC reveals that during continuous cooling from solution treatment, premature Cu-rich phases may form depending on cooling rate. Those quench-induced precipitates were analysed for a broad range of cooling rates and imaged for microstructural analysis using optical microscopy, scanning electron microscopy and transmission electron microscopy. This information substantially improves the CCT diagram.

2021, Kabin, Ievgen, Dyka, Zoya, Klann, Dan, Aftowicz, Marcin, Langendoerfer, Peter

The Montgomery kP algorithm i.e. the Montgomery ladder is reported in literature as resistant against simple SCA due to the fact that the processing of each key bit value of the scalar k is done using the same sequence of operations. We implemented the Montgomery kP algorithm using Lopez-Dahab projective coordinates for the NIST elliptic curve B-233. We instantiated the same VHDL code for a wide range of clock frequencies for the same target FPGA and using the same compiler options. We measured electromagnetic traces of the kP executions using the same input data, i.e. scalar k and elliptic curve point P, and measurement setup. Additionally, we synthesized the same VHDL code for two IHP CMOS technologies, for a broad spectrum of frequencies. We simulated the power consumption of each synthesized design during an execution of the kP operation, always using the same scalar k and elliptic curve point P as inputs. Our experiments clearly show that the success of simple electromagnetic analysis attacks against FPGA implementations as well as the one of simple power analysis attacks against synthesized ASIC designs depends on the target frequency for which the design was implemented and at which it is executed significantly. In our experiments the scalar k was successfully revealed via simple visual inspection of the electromagnetic traces of the FPGA for frequencies from 40 to 100 MHz when standard compile options were used as well as from 50 MHz up to 240 MHz when performance optimizing compile options were used. We obtained similar results attacking the power traces simulated for the ASIC. Despite the significant differences of the here investigated technologies the designs’ resistance against the attacks performed is similar: only a few points in the traces represent strong leakage sources allowing to reveal the key at very low and very high frequencies. For the “middle” frequencies the number of points which allow to successfully reveal the key increases when increasing the frequency.

2019, Yu, Dan, Hensel, René, Beckelmann, Dirk, Opsölder, Michael, Schäfer, Bruno, Moh, Karsten, de Oliveira, Peter William, Arzt, Eduard

Continuous roll-to-roll fabrication is essential for transferring the idea of bio-inspired, fibrillar dry adhesives into large-scale, synthetic, high-performance adhesive tapes. Toward this aim, we investigated process parameters that allow us to control the morphology and the resulting adhesion of mushroom-shaped micropatterned surfaces. Flexible silicone templates enabled the replication process of the polyurethane acrylate pre-polymer involving UV-light-induced cross-linking. For this paper, we particularly tailored the polyurethane acrylate pre-polymer by adding chemical components to tune UV curing kinetics and to reduce oxygen inhibition of radicals. We found that higher intensities of the UV light and faster reaction kinetics improved the quality of the microstructures, i.e., a larger cap diameter of the mushroom tips was achieved. The polymer blend U6E4 exhibited the fastest curing kinetics, which resulted in a micromorphology similar to that of the Ni-shim master structures. Best adhesion results were obtained for adhesive tapes made from U6E4 with 116 kPa pull-off stress, 1.4 N cm−1 peel strength and 71 kPa shear strength. In addition, repeated attachment–detachment tests over 100,000 cycles demonstrated strong robustness and reusability.