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Engineering qubit dynamics in open systems with photonic synthetic lattices
No full textThe evolution of a quantum system interacting with an environment can be described as a unitary process acting on both the system and the environment. In this framework, the system's evolution can be predicted by tracing out the environmental degrees of freedom. Here, we establish a precise mapping between the global unitary dynamics and the quantum operation involving the system, wherein the system is a single qubit, and the environment is modeled as a discrete lattice space. This approach enables the implementation of arbitrary noise operations on single-polarization qubits using a minimal set of three liquid-crystal metasurfaces, whose transverse distribution of the optic axes can be patterned to reproduce the target process. We experimentally validate this method by simulating common noise processes, such as phase errors and depolarization. Besides providing a practical solution for quantum state purification, this work demonstrates a versatile approach for the simulation of open qubit dynamics, with potential implications for quantum error correction and environment-induced quantum phase transitions
Segregated supply of sustainable aviation fuel to reduce contrail energy forcing – demonstration and potentials
No full textAviation contributes about 4 % to net anthropogenic climate forcing, with contrails being the largest individual contributor to radiative forcing from aviation. One option to mitigate contrail-related climate impacts is using kerosene containing fewer or no aromatic components and thus showing a higher hydrogen content compared to conventional kerosene (i.e., fossil fuel-based). Such “low contrail” kerosene can be provided as a blend of conventional (crude oil-based) and synthetic kerosene or from hydroprocessing conventional kerosene. Low contrail kerosene reduces contrail lifetime and optical thickness and thus the magnitude of contrail climate forcing. However, market shares of such kerosene are presently very low. Simultaneously, a small fraction ( 80 %) of global warming contrail climate forcing. Hence, the targeted use of low contrail kerosene on those flights appears promising. But, such an approach would require additional operational efforts, such as a duplication of supply lines and storage tanks. This study evaluates the feasibility and operational efforts of a segregated supply of a 35 m-% SAF-blend (14.34 m-% hydrogen content) to 84 winter time demonstration flights to reduce contrail climate forcing. Between 17th January 2023 and 2nd February 2023, low contrail kerosene was supplied to commercial A320 type aircraft flights on the route between Stockholm and Copenhagen in northern Europe. The operational feasibility and related efforts to target flights with the highest contrail energy forcing as well as a large-scale application are described. The evolution of contrails is tracked using data from the Meteosat Second Generation (MSG) satellite. The contrail energy forcing is calculated for the corresponding flight trajectories assuming another, well-validated engine model (CFM56–5B4 for the simulations instead of LEAP1A-26 for the demonstration flights) using the Contrail Cirrus Prediction (CoCiP) model with meteorological input fields from European Reanalysis data (ERA5). For the first time, the experiment demonstrates the operational feasibility for a segregated supply of low contrail kerosene to medium range aircraft at Stockholm airport. The segregated supply of low contrail kerosene can be realized for short to medium range flights, which can be fueled by a refueller truck. Targeting individual flights via single line hydrant fueling systems seems impractical as of now. Operational efforts to target single flights with highest contrail energy forcing are almost identical to the efforts in this demonstration experiment. Simulations estimate that the segregated supply of the medium blend kerosene (14.34 m-% hydrogen content) can reduce contrail energy forcing by about 11 % assuming the use of a “Rich-Quench-Lean” (RQL) engine (CFM56–5B4). The contrail climate benefit increases to >20 % for a 50 % blend ratio (14.7 m-% hydrogen content). Also, the location and evolution of the demonstration flights’ 28 contrails calculated with CoCiP was tracked with satellite data. The uncertainty of absolute contrail climate forcing estimates is mainly limited due to meteorological data input and also by lacking information on fuel composition in terms of cycloalkane, mono- and polycyclic aromatics content. Contrarily, the uncertainty of relative changes in contrail climate forcing is subject to low uncertainty, since it compares the use of different fuels for an identical fleet and identical weather conditions
A review of composite materials for marine purposes: Historical perspective and current state
No full textThis study offers a concise review of the application of composite materials in marine environments, encompassing both historical perspectives and current conditions. Composite materials, which are both lightweight and robust, have been widely used in maritime structures, such as ships and offshore platforms, to enhance resistance to structural failure. The main focus of this study encompasses three aspects: the historical development of composites, failure theories of composite materials with an emphasis on damage caused by external loads, and recent advances in failure criteria for durability optimization. In this study, several failure theories, including the maximum stress-strain, Hashin, Tsai-Hill, Tsai-Wu, and Puck theories, are presented and reviewed, along with recent research results presented in tabular form. The expected results of this study can provide essential guidance for future research directions aimed at enhancing the reliability of composite materials in the maritime sector
An ATS-based approach for the operational assessment of takeoff and landing assisting technology
No full textModular micro reaction engineering for carboligation catalyzed by benzoylformate decarboxylase
No full textAbstract The downscale of different unit operations for the biocatalytic carboligation of benzaldehyde and acetaldehyde catalyzed by benzoylformate decarboxylase from Pseudomonas putida was investigated. The reactor volume was reduced to 115 μl thus enabling a substrate and enzyme saving by a factor of 52 in comparison to standard laboratory techniques. Additionally, the successful downscale of membrane based liquid-liquid contactors was shown, which allows, for example, the screening of solvents for extraction as well as the feed of a substrate. Here, comparable volumes as well as residence times were realized, enabling the integration of all three unit operations
Towards event-triggered NMPC for efficient 6G communications: experimental results and open problems
No full textNetworked control systems enable real-time control and coordination of distributed systems, lever-aging the low latency, high reliability, and massive connectivity offered by 5G and future 6G networks. Applications include autonomous vehicles, robotics, industrial automation, and smart grids. Despite networked control algorithms admitting nominal stability guarantees even in the presence of delays and packet dropouts, their practical performance still heavily depends on the specific characteristics and conditions of the underlying network. To achieve the desired performance while efficiently using communication resources, co-design of control and communication is pivotal. Although periodic schemes, where communication instances are fixed, can provide reliable control performance, unnecessary transmissions, when updates are not needed, result in inefficient usage of network resources. In this paper, we investigate the potential for co-design of model predictive control and network communication. To this end, we design and implement an event-triggered nonlinear model predictive controller for stabilizing a Furuta pendulum communicating over a tailored open radio access network 6G research platform. We analyze the control performance as well as network utilization under varying channel conditions and event-triggering criteria. Additionally, we analyze the network-induced delay pattern and its interaction with the event-triggered controller. Our results show that the event-triggered control scheme achieves similar performance to periodic control with reduced communication demand
Connecting topology, mechanical behavior, and hydrogen interaction dynamics in nanoporous Nb and Pd
No full textStudying the mechanical performance of nano- and microscale porous materials enhances our understanding of small-scale solids and improves materials design for functional applications. This study investigates the microstructure and mechanical behavior of millimeter-sized samples with a nanoscale random network structure, integrating metal hydrides to expand their functionality. Notably, metals such as Nb and Pd can form solid solutions with hydrogen across a broad concentration range at relatively low temperatures. Therefore, nanoporous (np) Nb and np Pd, representing body-centered cubic (BCC) and face-centered cubic (FCC) crystal structures respectively, are fabricated and studied, with np Au serving as a benchmark.
In the first part of the thesis, the mechanical behavior of np material is investigated with a focus on the role of its microstructure size and topology. Results from macro-compression tests and X-ray nanotomography of np Nb confirm that coarsening degrades yield strength and that its Young’s modulus deviates from scaling laws developed for np Au, a widely-investigated model system produced via aqueous dealloying. The scaled genus, a measure of the network's connectivity, of np Nb is lower than that reported for np Au, and this reduced connectivity provides an obvious explanation for the low modulus. From these observations, a novel scaling law that explicitly involves the scaled genus is established. Furthermore, the comparison between np Au and np Nb implies that structural dispersion should be acknowledged as an additional structural descriptor to draw an analogy between liquid-metal dealloyed and electrochemically dealloyed materials.
The second part of the thesis focuses on the interaction dynamics between np Pd and hydrogen. Compared to np Nb, np Pd demonstrates significantly higher hydrogen absorption efficiency. The study aims to understand the role of geometry on the hydrogen charging kinetics by tuning the ligament size of np Pd and to understand the limiting subprocess. Hydrogen ad/absorption and desorption kinetics are analyzed using electrochemical impedance spectroscopy and potential jump tests. The results suggest that the interfacial injection of hydrogen is the controlling factor of the sorption rate. This injection process is analyzed from a thermodynamic perspective, with the Pd-H miscibility gap taken into account. The Butler-Volmer equation is adapted to model the injection rate consistent with the equation of state for the composition-dependent chemical potential at equilibrium in an interacting solid solution. The model successfully predicts the characteristic charging time observed in the np Pd-H system.
Overall, this thesis establishes a coupled relationship between mechanics, microstructure, and hydrogen absorption kinetics, providing insights into the optimization of structural design in np materials, thereby paving the way for their applications as integrated material systems.Diese Studie untersucht das Zusammenspiel von Mechanik, mikrostruktureller Geometrie und Wasserstoffwechselwirkung in nanoporösen (np) Materialien, mit Fokus auf np Nb und np Pd sowie np Au als Referenz. Ein Skalierungsgesetz für den elastischen Modul, das die topologische Konnektivität einbezieht, wird entwickelt. Weitergehende experimentelle Untersuchungen an np Nb zeigen, dass strukturelle Dispersion beim Vergleich verschiedener Entlegierungsmethoden berücksichtigt werden muss. Im zweiten Teil wird die Wasserstoff-Sorptionskinetik von np Pd analysiert. Im Ergebnis dominiert die Grenzflächeninjektion die Sorptionskinetik, was zur Formulierung eines neuen Gesetzes für die Reaktionsgeschwindigkeit führt.Deutsche Forschungsgemeinschaft (DFG
A microservice based control architecture for mobile robots in safety-critical applications
No full textMobile robots have become more and more common in public space. This increases the importance of meeting safety requirements of autonomous robots. Simple mechanisms, such as emergency braking, alone do not suffice in these highly dynamic situations. Moreover, actual robotic control approaches in literature and practice do not take safety particularly into account. A more sophisticated situational approach for assessment and planning is needed as part of the high-level process control. This paper presents the concept of a safety-critical Robot Control Architecture for mobile robots based on microservices and a Hierarchical Finite State Machine. It expands already existing architectures by drastically reducing the amount of centralized logic and thus increasing the overall system’s level of concurrency, interruptibility and fail-safety. Furthermore, it introduces new potential for code reuse that allows for straightforward implementation of safety mechanisms such as internal diagnostics systems. In doing so, this concept presents the template of a new type of state machine implementation. It is demonstrated with the application of a delivery robot, which was implemented and operated in real public during a broader research project
Smaller stencil preconditioners for linear systems in RBF-FD discretizations
No full textRadial basis function finite difference (RBF-FD) discretization has recently emerged as an alternative to classical finite difference or finite element discretization of (systems) of partial differential equations. In this paper, we focus on the construction of preconditioners for the iterative solution of the resulting linear systems of equations. In RBF-FD, a higher discretization accuracy may be obtained by increasing the stencil size. This, however, leads to a less sparse and often also worse conditioned stiffness matrix which are both challenges for subsequent iterative solvers. We propose to construct preconditioners based on stiffness matrices resulting from RBF-FD discretization with smaller stencil sizes compared to the one for the actual system to be solved. In our numerical results, we focus on RBF-FD discretizations based on polyharmonic splines (PHS) with polynomial augmentation. We illustrate the performance of smaller stencil preconditioners in the solution of the three-dimensional convection-diffusion equation
Investigation of the uniformity of gel shrinkage by imaging tracer particles using X-Ray microtomography
No full textMass transfer and structural changes in the polymer matrix need to be understood for a rational optimization of the biopolymer-based aerogels production. Herein, the uniformity of changes that occur in the gel structure during the aerogel production by a newly developed method which is based on the imaging of metal tracer particles using X-ray microtomography (X-ray micro-CT) alongside the application of point pattern techniques such as the K-nearest-neighbor (KNN) distances is studied. Agar is initially used as a system of validation for the developed method, after which other polysaccharide and protein-based gels such as alginate, whey protein isolate (WPI), and gelatine are studied. The KNN distance is seen to reduce from hydrogel to aerogel. Furthermore, by means of the KNN distances, the biopolymers are observed to experience a nonuniform distribution of tracer particles correlating to nonuniform shrinkage. Densification at specific sites of the gel represented by lower KNN distance values could be distinguished for each biopolymer. Finally, the spatially resolved polymer network density profile is estimated from the KNN distance by correlating it to experimentally determined polymer network density