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Efficient practical Byzantine consensus using random linear network coding
Get PDFUsing random linear network coding (RLNC) in asynchronous networks with one-to-many information flow has already been proven to be a valid approach to maximize the channel capacities. Message-based consensus protocols such as practical Byzantine fault tolerance (pBFT) adhere partially to said scenario. Protocol phases with many-to-many communication, however, still suffer from quadratic growth in the number of required transmissions to reach consensus. We show that an enhancement in the data transmission behavior in the quadratic phases is possible through combining RLNC with pBFT as one hybrid protocol. We present several experiments conducted on random network topologies. We conclude that using RLNC-based data transmission offers a significantly better performance under specific circumstances, which depend on the number of participating network nodes and the chosen coding parameters. Applying the same approach to other combinations of message-based consensus and network coding protocols promises not only a gain in performance, but may also improve robustness and security and open up new application scenarios for RLNC, e.g., running it on the application layer
Stress-rate dependency of uniaxial compressive strength of hard rock with regard to test procedure standards
Get PDFThe uniaxial compressive strength test of hard rock is one of the most worldwide applied tests for characterization of hard rock in rock engineering and engineering geology. The uniaxial compressive strength as the results of this test is a basic parameter, used, for example, for the design of rock engineering structures. In the commonly applied standards, stress-controlled test procedures using constant stress rates are recommended by a wide range of stress rates varying between 2 and 60 MPa/min and/or a specific minimum test time. Though the effect of stress-rate dependency of hard rock is generally known, most investigation is focused on dynamic action behavior using high stress rates and/or fast actions. Strain-controlled test procedures are often used as well. For stress-controlled test procedures within the recommended range of stress-rates, the data base is rather poor, the effects to the results are reported by only very few researchers. The research described in this paper aims to close this gap and focuses on the stress-rate dependency of uniaxial compressive strength of hard rock. Seven different stress rates varying between 1 and 100 MPa/min on five different types of hard rock (quartzite, granodiorite, gabbro, sandstone, basalt) using five to fifteen single tests per stress rate have been executed. A significant increase of uniaxial compressive strength by increasing stress rates has been stated; the increase may not be ignored in assessing rock strength in rock engineering projects. The effect has to be considered especially when different parties are involved in the site investigation programs
Beharrlichkeit – Messung und erste Validierung
Get PDFIn der Untersuchung wurde ein Verfahren erprobt und überprüft, mit dem dispositionelle Beharrlichkeit reliabel und valide gemessen werden kann. Untersuchungsteilnehmer*innen waren 213 Studierende, die einen „forced-choice“-skalierten Beharrlichkeitsfragebogen sowie rating-skalierte Fragebögen zur Resilienzneigung, Selbstführungskompetenz, Studienzufriedenheit und unternehmerischen Präferenz beantworteten. Eine konfirmatorische Faktorenanalyse ergab eine zufriedenstellende Modellanpassung für sieben Items des Beharrlichkeitsfragebogens. Korrelationen mit Kriteriumsvariablen weisen auf Übereinstimmungsvalidität und differentielle Validität sowie in eingeschränktem Umfang auf die prognostische Validität der Skalenwerte hin. Implikationen, praktische Anwendungen und Gültigkeitsgrenzen der Untersuchungsbefunde werden diskutiert.The study was conducted to examine and validate a scale by which dispositional perseverance may be measured and individual differences of perseverance may be assessed. Subjects were 213 students, who had to answer forced-choice-items of a new perseverance questionnaire as well as rating scale items of resilience, self-leadership, satisfaction with studies, and entrepreneurial preference. Confirmatory factor analysis revealed good fit indices for a seven-item-questionnaire of perseverance. Correlations with criterion measures gave preliminary indications of the questionnaire’s concurrent and differential validity, and, to a minor degree, predictive validity. Implications, applications, and limitations of the obtained findings are discussed
A comparison of AutoML solutions ATM and AWS Sagemaker Autopilot
Get PDFWe compare the open-source library ATM with the fully managed
Amazon Web Services solution Sagemaker Autopilot. Depending of prior
knowledge and experience there are found individual advantages. Two Datasets
are tested representing a classification and a regression task. During classification,
Autopilot achieves an F1 score of 0.971 whereas the average F1 score of
ATM is 0.916. Due to the limited available budget settings in Autopilot, this
comparison has marginal value. The results of the regression dataset cannot be
compared due to the missing functionality of ATM to calculate regression problems.
The motivation and need for Automated Machine Learning is discussed
and benefits are given, explained with the two practical examples. We expect a
great demand of Automated Machine Learning solutions with growing machine
learning problems and a limited number of experts in the field. The available
models and algorithms within the solutions presented here are discussed and a
missing ongoing development and support for ATM is found whereas Autopilot
is provided with regular updates. The experiments are limited to the local usage
of ATM and focused on the GUI approach with Autopilot. There is an additional
option to deploy ATM in a distributed and scalable manner and to use Autopilot
only with Jupyter Notebooks or as Python SDK. These options are to be evaluated
in further research
Semantically Valid Integration of Development Processes and Toolchains
Get PDFAs an indispensable component of today’s world economy and an increasing success factor in production and other processes, as well as products, software needs to handle a growing number of specific requirements and influencing factors that are driven by globalization. Two common success factors in the domain of Software Systems Engineering are standardized software development processes and process-supported toolchains. Development processes should be formally integrated with toolchains. The sequence and the results of toolchains must also be validated with the specifications of the development process on several levels. The outcome of a conceptual deductive analysis is that there is neither a formal general mapping nor a generally accepted validation mechanism for the challenges that such an integrated concept faces. To close this research gap, this paper focuses on the core issue of the integration of development processes and toolchains in order to create benefits for modeling and automatization in the domain of systems engineering. Therefore, it describes a self-developed integration approach related to the recently introduced prototypical technical implementation TOPWATER. A unified metamodel specifies how processes and toolchains are linked by a general mapping mechanism that considers test options for the structural, content, and semantic levels
Time Synchronization in Converged Wired and Wireless Communication Networks for Industrial Real-Time Application
Get PDFFactory automation becomes a subject of the transformation through Industry 4.0 and Industrial Internet of Things, and this introduces a new set of requirements due to novel industrial use cases. Future industrial communication is based on a unified network infrastructure that serves diverse communication services ranging from time-critical to best-effort data. Driven by the industrial domain, Time-Sensitive Networking (TSN) is the communication technology for enabling full connectivity in the smart factory. In conjunction to the Ethernet-based TSN, wireless technologies become a key enabler for future automation scenarios in order to support mobility and modularity aspects that are being demanded by flexible manufacturing and advanced automation. The latest cellular networking standard 5G develops the Ultra Reliable Low Latency Communication profile which supports the novel requirements through an advanced Quality of Service framework
and an enhanced 5G New Radio physical layer. The convergence of TSN and 5G is a promising solution for future industrial networks. Time synchronization is a key aspect of industrial communication networks. It establishes a common sense of time between all network nodes. This is one enabler for the alignment of time-critical processes across
distributed systems such as time-triggered data transmission to achieve ultra reliable bounded low latency, i.e. deterministic communication.
This work researches the time synchronization in converged TSN/5G networks. A comprehensive use case analysis identifies potential applications and their corresponding requirements for the integration of converged TSN/5G networks. Particular use cases are highlighted due to their stringent requirements regarding synchronization. According
network topologies are derived which are later used to review practical aspects of the synchronization. In order to research the synchronization in converged TSN/5G networks, the involved heterogeneous procedures are modeled. Consequently, the individual
models are merged to establish a novel model which describes the joint synchronization in converged TSN/5G networks and thus allows to investigate how the heterogeneous mechanism engage. Departing from this joint synchronization model, potential improvements are derived. The discussed improvements are manifold and address the distribution
of timing information, the reference clock selection, and the correction of timing information. As evaluation, the joint synchronization model is applied to generic networks under worst-case parameterization, that is derived from related specification and standardization works. This allows to study the general behavior of the synchronization in converged TSN/5G networks. Supplementary, the joint synchronization model is also applied to use case specific networks. This permits to obtain a practical perspective of the
synchronization in converged TSN/5G networks. These analyses yield the determination of synchronization boundaries which indicate the worst to be expected synchronization quality in the given networks. Consequent simulative experiments validate the previous evaluation of the synchronization in converged TSN/5G networks. It draws a more natural picture of the synchronization as probabilistic parameterization and random effects are considered.
This work shows that a synchronization accuracy well below 1 μs can be achieved converged TSN/5G networks. At the same time it is shown that the synchronization strongly depends on the actual network architecture and the quality of the 5G Radio Access Network (RAN) synchronization. The size of the network affects the synchronization accuracy since each intermediate device between the reference clock and the synchronization target introduces additional inaccuracy to the synchronization. The RAN synchronization, on the other hand, is the big challenge in converged TSN/5G networks as it comprises the
radio link which exposes uncertainty and varying transmission characteristics. But just that enables the synchronization of distributed devices
3‐Chloro‐5‐Substituted‐1,2,4‐Thiadiazoles (TDZs) as Selective and Efficient Protein Thiol Modifiers
Get PDFAbstract
The study of cysteine modifications has gained much attention in recent years. This includes detailed investigations in the field of redox biology with focus on numerous redox derivatives like nitrosothiols, sulfenic acids, sulfinic acids and sulfonic acids resulting from increasing oxidation, S‐lipidation, and perthiols. For these studies selective and rapid blocking of free protein thiols is required to prevent disulfide rearrangement. In our attempt to find new inhibitors of human histone deacetylase 8 (HDAC8) we discovered 5‐sulfonyl and 5‐sulfinyl substituted 1,2,4‐thiadiazoles (TDZ), which surprisingly show an outstanding reactivity against thiols in aqueous solution. Encouraged by these observations we investigated the mechanism of action in detail and show that these compounds react more specifically and faster than commonly used N‐ethyl maleimide, making them superior alternatives for efficient blocking of free thiols in proteins. We show that 5‐sulfonyl‐TDZ can be readily applied in commonly used biotin switch assays. Using the example of human HDAC8, we demonstrate that cysteine modification by a 5‐sulfonyl‐TDZ is easily measurable using quantitative HPLC/ESI‐QTOF‐MS/MS, and allows for the simultaneous measurement of the modification kinetics of seven solvent‐accessible cysteines in HDAC8
Data-driven, adaptive control of servo drives for industrial robots
Get PDFDatenbasierte Schätzalgorithmen (z. B. künstliche neuronale Netze oder Support Vector Machines) sind eine robuste Alternative zu konventionellen, physikalischen Modellen für adaptive Regler. Dieser Typ Algorithmus kann anhand von empirischen Daten nichtlineare und zeitvariante dynamische Systeme identifizieren sowie zukünftige Ausgangsgrößen prognostizieren. Tiefere Kenntnisse über die Physik des technischen Systems sind somit nicht mehr notwendig, und es können einfach und schnell Modelle abgeleitet werden. Speziell für Industrieroboter eröffnen datenbasierte Schätzalgorithmen neue Möglichkeiten. So muss die nichtlineare Dynamik des Roboters je nach Pose und Last nicht durch komplexe kinematische Gleichungen berechnet, sondern kann aufgrund von Sensordaten geschätzt werden. Dies spart Berechnungszeit bei gleichbleibend hoher Modellgüte. Des Weiteren kann der Regler deutlich schneller bei geänderten Randbedingungen des Roboters, wie beispielsweise stark unterschiedlichen mechanischen Lasten am Endeffektor, adaptiert werden. In diesem Beitrag wird exemplarisch die Auslegung eines datenbasierten, modellprädiktiven Reglers sowohl für einen sechs- als auch für einen einachsigen Gelenkprüfstand diskutiert. Hierbei erfolgen der Entwurf und die Validierung des Reglers anhand einer Co-Simulation bestehend aus Mehrkörper- und Systemsimulation. Designparameter der Regelung (Größe des Modells, Trainingsdaten, Optimierer etc.) werden diskutiert. Schließlich erfolgt eine experimentelle Validierung an einem einachsigen Gelenkprüfstand.Data-driven estimation algorithms (i.e., artificial neural networks or support vector machines) are a robust alternative to conventional, physical models for adaptive controllers. These algorithms can identify non-linear and time-variant dynamic systems and predict the systems’ future outputs using empirical data. Thus, deep knowledge of the system’s physics is not required anymore, and models can be implemented and derived easily and quickly. Especially for industrial robots, data-driven estimation algorithms offer new possibilities. For example, depending on the pose and load, the non-linear dynamics of the robot do not need to be calculated by means of complex kinematic equations but can be estimated based on sensor data. This saves computational time and provides a constant model accuracy. Furthermore, the controller can adapt to changed boundary conditions, such as varying mechanical loads on the end effector. This paper discusses the design of a data-driven, model predictive controller for a six- and a single-axis joint test rig. Here, the design and validation of the controller are based on a co-simulation consisting of a multibody and system simulation. All design parameters of the control (order of magnitude of the model, training data, optimization, etc.) are discussed. Finally, the control will be validated in an experiment using a single-axis joint test rig
