275003 research outputs found
Sort by
Downgrading DNSSEC: How to Exploit Crypto Agility for Hijacking Signed Zones
No full text74297444Cryptographic algorithm agility is an important property for DNSSEC: it allows easy deployment of new algorithms if the existing ones are no longer secure. Significant operational and research efforts are dedicated to pushing the deployment of new algorithms in DNSSEC forward. Recent research shows that DNSSEC is gradually achieving algorithm agility: most DNSSEC supporting resolvers can validate a number of different algorithms and domains are increasingly signed with cryptographically strong ciphers. In this work we show for the first time that the cryptographic agility in DNSSEC, although critical for making DNS secure with strong cryptography, also introduces a severe vulnerability. We find that under certain conditions, when new, unsupported algorithms are listed in signed DNS responses, the resolvers do not validate DNSSEC. As a result, domains that deploy new ciphers, risk exposing the validating resolvers to cache poisoning attacks. We use this to develop DNSSEC-downgrade attacks and experimentally and ethically evaluate our attacks against popular DNS resolver implementations, public DNS providers, and DNS resolvers used by web clients. We validate the success of DNSSEC-downgrade attacks by poisoning the resolvers: we inject fake records, in signed domains, into the caches of validating resolvers. Our evaluations showed that during 2021 major DNS providers, such as Google Public DNS and Cloudflare, as well as 35% of DNS resolvers used by the web clients were vulnerable to our attacks. After coordinated disclosure with the affected operators, that number reduced to 5.03% in 2022. We trace the factors that led to this situation and provide recommendations
The effect of site-specific wind conditions and individual pitch control on wear of blade bearings
No full text14951510The characteristics of a pitch controller determine how the wind turbine reacts to different wind conditions. Control strategies like individual pitch control are known for their ability to reduce the amplitudes of load cycles of the structures of the wind turbine while influencing the operation conditions of the blade bearings in a challenging way. However, the control strategy is not the only influencing factor with respect to failure modes of blade bearings like wear and raceway fatigue. The site-specific and stochastic wind conditions can cause wear-critical operating conditions, which are usually not reflected in the rather short time frames of aeroelastic simulations. This work analyses exemplary wind and operating conditions of one specific site regarding their influence on wear in blade bearings. It is based on measured wind conditions and the modeled behavior of the individual pitch-controlled IWT-7.5-164 reference wind turbine with respect to its pitch activity. The simulation data are used to determine the longest period of uninterrupted wear-critical operation and create a test program based on it for scaled and real-size blade bearings. Experimental results based on this test program show that wear-critical operation conditions can occur during normal operation of a wind turbine and cause mild wear damage to the bearing raceways.81
Time Variant Directional Multi-Link Channel Sounding and Estimation for V2X
No full textWe present our new scalable multi-channel and multi-node sounder, the ILMSoundG3. It is configurable in terms of the number of switched Tx and parallel Rx nodes. The basic structures of the Tx and Rx nodes are given with consideration of the measurement system requirements.The ILMSoundG3 is validated via a proof of concept measurement at 2.53 GHz in an urban environment. The system was configured as a sounder with two Tx nodes and one Rx node, which records two MIMO links simultaneously. Each node uses an antenna array. The transmitters were moved by cars whereas the receiver was elevated 20 m above the ground by a lifting platform acting as a base station. The used system configuration results in a snapshot rate of approx. 0.5 kHz, which covers the expected time variance of the chosen environment.The measurement results were analyzed using HRPE, providing a parametric description of the specular propagation paths of the radio channel per measurement link. Each estimated path is described by its directions of departure and arrival, delay, Doppler shift, and fully polarimetric complex path weights
Handover Management in 5G Non-Terrestrial Networks: Simulations and Testbeds
No full text214220To ensure ubiquitous coverage for different scenarios of broadband and narrowband connectivity, deployment and integration of Non-Terrestrial Networks in a seamless way is quintessential. This requires optimization of handover management in dual mobility scenarios with hybrid terrestrial and non-terrestrial infrastructure. Many solutions that have been researched and investigated so far make some assumptions about the presence of intra-RAN and inter-RAN interfaces. The paper here presents an overview of the available solutions in both 3GPP and O-RAN specifications with selected case studies involving both terrestrial and non-terrestrial networks. Some of the evaluations involving AI-assisted handover are also illustrated for selected scenarios
Air-cleaners for virus removal in classrooms: test chamber vs. real-world room
No full textThe pandemic conditions seriously affect everyday life in schools. Wearing mask, distancing, and permanently open windows are useful measures, but not always an option during the colder season. Therefore, electric air cleaners are discussed to enable safe classes by providing air that is free of infectious aerosols. The clean air delivery rate (CADR) is often used as a measure to select an appropriate air cleaner for a specific room size and situation. In our study we determined the viable virus removal by a commercial air cleaner in a 30 m3 environmental test chamber. The same air cleaner was then operated in a test room with typical classroom furnishing. Here, the concentration of viable viruses was measured under different scenarios (air cleaner positions, window open/closed). The results show that the very effective removal of viruses seen in the test chamber cannot always be observed in the test room
A national plan and global recommendations for the prevention of falls in the elderly Un plan national et des recommandations mondiales au service de la prévention des chutes chez les personnes âgées
No full text28428521
Improving the Resilience of Fast Failover Routing: TREE (Tree Routing to Extend Edge disjoint paths)
No full text17Today's communication networks have stringent availability requirements and hence need to rapidly restore connectivity after failures. Modern networks thus implement various forms of fast reroute mechanisms in the data plane, to bridge the gap to slow global control plane convergence. State-of-the-art fast reroute commonly relies on disjoint route structures, to offer multiple independent paths to the destination. We propose to leverage the network's path diversity to extend edge disjoint path mechanisms to tree routing, in order to improve the performance of fast rerouting. We present two such tree-mechanisms in detail and show that they boost resilience by up to 12% and 25% respectively on real-world, synthetic, and data center topologies. Whereas the first method retains the stretch of edge disjoint path mechanisms, our second method increases it depending on the use case, just below 8% for networks from Topology Zoo on average, but by up to 56% for random graphs in the Erdős-Rényi model
The Brainstem Cavernoma Case Series: A Formula for Surgery and Surgical Technique
No full textBackground and Objectives: Cavernous malformations (CM) are vascular malformations with low blood flow. The removal of brainstem CMs (BS) is associated with high surgical morbidity, and there is no general consensus on when to treat deep-seated BS CMs. The aim of this study is to compare the surgical outcomes of a series of deep-seated BS CMs with the surgical outcomes of a series of superficially located BS CMs operated on at the Department of Neurosurgery, College of Tuebingen, Germany. Materials and Methods: A retrospective evaluation was performed using patient charts, surgical video recordings, and outpatient examinations. Factors were identified in which surgical intervention was performed in cases of BS CMs. Preoperative radiological examinations included MRI and diffusion tensor imaging (DTI). For deep-seated BS CMs, a voxel-based 3D neuronavigation system and electrophysiological mapping of the brainstem surface were used. Results: A total of 34 consecutive patients with primary superficial (n = 20/58.8%) and deep-seated (n = 14/41.2%) brainstem cavernomas (BS CM) were enrolled in this comparative study. Complete removal was achieved in 31 patients (91.2%). Deep-seated BS CMs: The mean diameter was 14.7 mm (range: 8.3 to 27.7 mm). All but one of these lesions were completely removed. The median follow-up time was 5.8 years. Two patients (5.9%) developed new neurologic deficits after surgery. Superficial BS CMs: The median diameter was 14.9 mm (range: 7.2 to 27.3 mm). All but two of the superficial BS CMs could be completely removed. New permanent neurologic deficits were observed in two patients (5.9%) after surgery. The median follow-up time in this group was 3.6 years. Conclusions: The treatment of BS CMs remains complex. However, the results of this study demonstrate that with less invasive posterior fossa approaches, brainstem mapping, and neuronavigation combined with the use of a blunt “spinal cord” dissection technique, deep-seated BS CMs can be completely removed in selected cases, with good functional outcomes comparable to those of superficial BS CM.59
Association between cognition and gait in multiple sclerosis: A smartphone-based longitudinal analysis
No full textBackground: Gait and cognition impairments are common problems among People with Multiple Sclerosis (PwMS). Previous studies have investigated cross-sectional associations between gait and cognition. However, there is a lack of evidence regarding the longitudinal association between these factors in PwMS. Therefore, the objective of this study was to explore this longitudinal relationship using smartphone-based data from the Floodlight study. Methods: Using the publicly available Floodlight dataset, which contains smartphone-based longitudinal data, we used a linear mixed model to investigate the longitudinal relationship between cognition, measured by the Symbol Digit Modalities Test (SDMT), and gait, measured by the 2 Minute Walking test (2 MW) step count and Five-U-Turn Test (FUTT) turning speed. Four mixed models were fitted to explore the association between: 1) SDMT and mean step count; 2) SDMT and variability of step count; 3) SDMT and mean FUTT turning speed; and 4) SDMT and variability of FUTT turningt speed. Results: After controlling for age, sex, weight, and height, there were significant correlations between SDMT and the variability of 2 MW step count, the mean of FUTT turning speed. No significant correlation was observed between SDMT and the 2 MW mean step count. Significance: Our findings support the evidence that gait and cognition are associated in PwMS. This may support clinicians to adjust treatment and intervention programs that address both gait and cognitive impairments.17
Real-time capable simulation of soil interaction for construction machinery: Recurrent neural networks and the discrete element method for force prediction, using the example of an interactive excavator simulator Rekurrente Neuronale Netze und die Diskrete Elemente Methode zur Kraftprädiktion am Beispiel eines interaktiven Baggersimulators: Echtzeitfähige Simulation der Bodenwechselwirkung für Baumaschinen
No full text619628240