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1. Memristor-Symposium 2023
(2023)
The 1.Memristor-Symposium was held from 27-28.02.2023 in Bamberg. Young scientists and PhD students presented their research and covered several topics regarding ongoing memristive research in Germany. Several talks on the topic of memristive devices, their testing, modeling and usage were presented and discussed, covering the whole vertical integration from material and divice up to application level.
Recent challenges and novel approaches of wireless communication networks are characterized by high performance requirements on the radio channel and by concepts of self-organization, in-network processing, or resource optimization which ultimately lead to distributed network applications, communication architectures, and radio transceivers.
Associated evaluation is driven by a multitude of ever-increasing requirements that call for multidisciplinary expertise. Depending on the discipline, simulation is one of the most widely used technologies, whereby often abstract assumptions and models do not allow for sufficiently accurate, comparable results.
In contrast, real-world measurements and field-tests can only be performed on actual systems, commonly under non-reproducible conditions.
This thesis establishes with the Split-Protocol-Stack a new type of evaluation method that intends to help closing the gap between purely simulative analyzes and real-world tests.
With the inclusion of real radio hardware and radio channels in the event-based simulation, this central hybrid approach in connection with the Radio-in-the-Loop methodology creates synergies in interdisciplinary fields.
The approach contains analytical discussions, methodological strategies, and practical contributions that are summarized as key elements in the subsequent central considerations and challenges.
With Real-Time-Shift, a pseudo-real-time synchronization approach for parallel simulation and radio channel emulation of communication flows is introduced.
Based on the underlying time compensation scheme, the discrete event simulation is decoupled from real-time constraints when exchanging event messages with real-world wireless hardware.
A physical layer emulation methodology and radio channel interface concept, called Radio-in-the-Loop, is introduced along with two practical realization approaches.
Furthermore, strategic details on radio network planning with an approach to automatic hardware resource allocation are presented for radio channel emulation-capable network testbeds.
The contributions of this work are evaluated using real-world reference measurements, practical application scenarios, and experiments that provide proof of concepts.
By means of an exemplary selected cross-layer optimization scenario, the benefits are practically demonstrated and discussed.
Finally, based on IEEE 802.15.4 as the reference protocol standard for low-power wireless networks, this thesis provides feasibility studies and analysis results using the representative prototype SEmulate for the Split-Protocol-Stack approach.
Eines der am intensivsten untersuchten Probleme aus dem Bereich der Optimierung stellt das sogenannte Traveling Salesman Problem (TSP, in deutsch: Handlungsreisendenproblem) dar. Die Aufgabe hinter dem Handlungsreisendenproblem besteht darin, für eine gegebene Anzahl an Orten eine Route zu entwickeln, sodass die Gesamtlänge der Route minimal ist. Zudem darf kein Ort, bis auf den ersten, mehrmals besucht werden. Ziel der vorliegenden Bachelorarbeit ist es, statistische Untersuchungen bezüglich der Tourlänge des TSP in Abhängig der Anzahl der besuchten Städte vorzunehmen, wobei der Fokus auf einer kleinen Anzahl von Städten liegt. Dazu wurde das Problem einerseits numerisch gelöst und die Verteilung der Lösungen analysiert. Für Teilaspekte wurden analytische Lösungen berechnet.
Human life depends on water of good quality. Freshwater ecosystems are being degraded as a result of anthropogenic activities. Managing freshwater resources require a good understanding of the dynamics of the processes affecting water quality and the interrelationship existing between them. Signal analysis methods are used to extract information from water quality time series. The information obtained from such analysis is required for developing dynamic models as an aid in investigating the outcome of different management scenarios. They are equally useful in determining the appropriate sampling frequency required for monitoring ecological indicators. Modern methods developed in other field such as mathematical statistics need to be investigated in the fields of water quality management so as to enhance the knowledge of the functioning and the structure of water bodies. Classical methods consisting of time domain and frequency domain methods in combination with a modern method, wavelet analysis, were used to extract information from water quality indicators from the River Havel in the State of Brandenburg in Germany. The indicators were dissolved oxygen, chlorophyll-a and water temperature which are respectively chemical, biological and physical indicators. The time domain methods revealed the behavior of the signal across time as well as the relationship between them. The frequency domain methods proved quite inadequate because the signals from water quality are non-stationary with changing variance across time. The wavelet methods were quite good in unraveling the behavior of these signals at different time-scales. This analysis revealed that the high frequency changes have no significant effect on the long term dynamics of water quality signals. Given that only the low frequency components influence the long term behavior of these signals, it was found that it makes more sense to sample most of the signals at a weekly or two weekly intervals so as to avoid noisy or redundant information. In addition, the time-scale decomposition allows for noisy or redundant information that blurs the long term dynamics thereby negatively affecting the quality of models to be detected and kicked out. Moreover, it was also found that the use of a time delay in a dynamic model should be based on the delay from the time-scale that influence the long term dynamics the most in the freshwater body by the help of the wavelet cross-correlation rather than the classical cross-correlation. Finally, the same indicator from different water bodies of the same watershed portrayed different time and frequency dependent behavior implying that each freshwater body needs to be uniquely investigated. Applying the same management techniques to different water bodies without prior investigation will not be sound. Freshwater ecosystems are more and more threatened by phenomena such as global warming, pharmaceuticals in water bodies, invasive species requiring more investigation on the applicability of tools developed in other fields of science in the field of water resource management. Enhanced knowledge will improve the existing knowledge on the structure and functioning of freshwater bodies, the quality of models developed as management decision aid and the quality of the data used for decision making.