620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
Refine
Year of publication
Document Type
- Article (31)
- Book (8)
- Working Paper (5)
- Doctoral Thesis (4)
- Contribution to a Periodical (2)
Has Fulltext
- yes (50)
Is part of the Bibliography
- no (50)
Keywords
- radiation-induced nanostructures (4)
- Energy system design (2)
- Large-scale integration of renewable power generation (2)
- AM-PM noise conversion (1)
- Adoption (1)
- Agile work (1)
- Assistive technology (1)
- Background work (1)
- Bericht (1)
- COGNIMUSE (1)
Institute
This study presents an ultra-wideband, elliptical slot, planar monopole antenna for early breast cancer microwave imaging. The on-body antenna's operation is optimised by direct contact with the patient's skin. With a compact size of 9 × 7 mm, the antenna covers a wide bandwidth from 16 to 24 GHz for reflection coefficients lower than –10 dB. Besides, it also features an electrode for electrical impedance tomography applications. Verification on a volunteer's breast gives an excellent agreement with the simulation for the defined bandwidth. Furthermore, as the first stage of the system's characterisation, pork fat is also used to demonstrate the possibility to enhance the transmission between the antennas within the high loss environment. Those results propose the feasibility of implementing a high-frequency radar system for breast cancer detection.
Consequences of minimal length discretization on line element, metric tensor, and geodesic equation
(2021)
When minimal length uncertainty emerging from a generalized uncertainty principle (GUP) is thoughtfully implemented, it is of great interest to consider its impacts on gravitational Einstein field equations (gEFEs) and to try to assess consequential modifications in metric manifesting properties of quantum geometry due to quantum gravity. GUP takes into account the gravitational impacts on the noncommutation relations of length (distance) and momentum operators or time and energy operators and so on. On the other hand, gEFE relates classical geometry or general relativity gravity to the energy–momentum tensors, that is, proposing quantum equations of state. Despite the technical difficulties, we intend to insert GUP into the metric tensor so that the line element and the geodesic equation in flat and curved space are accordingly modified. The latter apparently encompasses acceleration, jerk, and snap (jounce) of a particle in the quasi-quantized gravitational field. Finite higher orders of acceleration apparently manifest phenomena such as accelerating expansion and transitions between different radii of curvature and so on.
Objectives: The four-dimensional ultrasound (4D-US) enables imaging of the aortic segment and simultaneous determination of the wall expansion. The method shows a high spatial and temporal resolution, but its in vivo reliability is so far unknown for low-measure values. The present study determines the intraobserver repeatability and interobserver reproducibility of 4D-US in the atherosclerotic and non-atherosclerotic infrarenal aorta. Methods: In all, 22 patients with non-aneurysmal aorta were examined by an experienced examiner and a medical student. After registration of 4D images, both the examiners marked the aortic wall manually before the commercially implemented speckle tracking algorithm was applied. The cyclic changes of the aortic diameter and circumferential strain were determined with the help of custom-made software. The reliability of 4D-US was tested by the intraclass correlation coefficient (ICC). Results: The 4D-US measurements showed very good reliability for the maximum aortic diameter and the circumferential strain for all patients and for the non-atherosclerotic aortae (ICC >0.7), but low reliability for circumferential strain in calcified aortae (ICC = 0.29). The observer- and masking-related variances for both maximum diameter and circumferential strain were close to zero. Conclusions: Despite the low-measured values, the high spatial and temporal resolution of the 4D-US enables a reliable evaluation of cyclic diameter changes and circumferential strain in non-aneurysmal aortae independent from the observer experience but with some limitations for calcified aortae. The 4D-US opens up a new perspective with regard to noninvasive, in vivo assessment of kinematic properties of the vessel wall in the abdominal aorta.
This paper explores the many interesting implications for oscillator design, with optimized phase-noise performance, deriving from a newly proposed model based on the concept of oscillator conjugacy. For the case of 2-D (planar) oscillators, the model prominently predicts that only circuits producing a perfectly symmetric steady-state can have zero amplitude-to-phase (AM-PM) noise conversion, a so-called zero-state. Simulations on standard industry oscillator circuits verify all model predictions and, however, also show that these circuit classes cannot attain zero-states except in special limit-cases which are not practically relevant. Guided by the newly acquired design rules, we describe the synthesis of a novel 2-D reduced-order LC oscillator circuit which achieves several zero-states while operating at realistic output power levels. The potential future application of this developed theoretical framework for implementation of numerical algorithms aimed at optimizing oscillator phase-noise performance is briefly discussed.
Nano-granular metals are materials that fall into the general class of granular electronic systems in which the interplay of electronic correlations, disorder and finite size effects can be studied. The charge transport in nano-granular metals is dominated by thermally-assisted, sequential and correlated tunneling over a temperature-dependent number of metallic grains. Here we study the frequency-dependent conductivity (AC conductivity) of nano-granular Platinum with Pt nano-grains embedded into amorphous carbon (C). We focus on the transport regime on the insulating side of the insulator metal transition reflected by a set of samples covering a range of tunnel-coupling strengths. In this transport regime polarization contributions to the AC conductivity are small and correlation effects in the transport of free charges are expected to be particularly pronounced. We find a universal behavior in the frequency dependence that can be traced back to the temperature-dependent zero-frequency conductivity (DC conductivity) of Pt/C within a simple lumped-circuit analysis. Our results are in contradistinction to previous work on nano-granular Pd/ZrO2ZrO2 in the very weak coupling regime where polarization contributions to the AC conductivity dominated. We describe possible future applications of nano-granular metals in proximity impedance spectroscopy of dielectric materials.
In this roadmap article, we have focused on the most recent advances in terahertz (THz) imaging with particular attention paid to the optimization and miniaturization of the THz imaging systems. Such systems entail enhanced functionality, reduced power consumption, and increased convenience, thus being geared toward the implementation of THz imaging systems in real operational conditions. The article will touch upon the advanced solid-state-based THz imaging systems, including room temperature THz sensors and arrays, as well as their on-chip integration with diffractive THz optical components. We will cover the current-state of compact room temperature THz emission sources, both optolectronic and electrically driven; particular emphasis is attributed to the beam-forming role in THz imaging, THz holography and spatial filtering, THz nano-imaging, and computational imaging. A number of advanced THz techniques, such as light-field THz imaging, homodyne spectroscopy, and phase sensitive spectrometry, THz modulated continuous wave imaging, room temperature THz frequency combs, and passive THz imaging, as well as the use of artificial intelligence in THz data processing and optics development, will be reviewed. This roadmap presents a structured snapshot of current advances in THz imaging as of 2021 and provides an opinion on contemporary scientific and technological challenges in this field, as well as extrapolations of possible further evolution in THz imaging.
Organ-on-a-chip technology has the potential to accelerate pharmaceutical drug development, improve the clinical translation of basic research, and provide personalized intervention strategies. In the last decade, big pharma has engaged in many academic research cooperations to develop organ-on-a-chip systems for future drug discoveries. Although most organ-on-a-chip systems present proof-of-concept studies, miniaturized organ systems still need to demonstrate translational relevance and predictive power in clinical and pharmaceutical settings. This review explores whether microfluidic technology succeeded in paving the way for developing physiologically relevant human in vitro models for pharmacology and toxicology in biomedical research within the last decade. Individual organ-on-a-chip systems are discussed, focusing on relevant applications and highlighting their ability to tackle current challenges in pharmacological research.
Collaboration is an important 21st Century skill. Co-located (or face-to-face) collaboration (CC) analytics gained momentum with the advent of sensor technology. Most of these works have used the audio modality to detect the quality of CC. The CC quality can be detected from simple indicators of collaboration such as total speaking time or complex indicators like synchrony in the rise and fall of the average pitch. Most studies in the past focused on “how group members talk” (i.e., spectral, temporal features of audio like pitch) and not “what they talk”. The “what” of the conversations is more overt contrary to the “how” of the conversations. Very few studies studied “what” group members talk about, and these studies were lab based showing a representative overview of specific words as topic clusters instead of analysing the richness of the content of the conversations by understanding the linkage between these words. To overcome this, we made a starting step in this technical paper based on field trials to prototype a tool to move towards automatic collaboration analytics. We designed a technical setup to collect, process and visualize audio data automatically. The data collection took place while a board game was played among the university staff with pre-assigned roles to create awareness of the connection between learning analytics and learning design. We not only did a word-level analysis of the conversations, but also analysed the richness of these conversations by visualizing the strength of the linkage between these words and phrases interactively. In this visualization, we used a network graph to visualize turn taking exchange between different roles along with the word-level and phrase-level analysis. We also used centrality measures to understand the network graph further based on how much words have hold over the network of words and how influential are certain words. Finally, we found that this approach had certain limitations in terms of automation in speaker diarization (i.e., who spoke when) and text data pre-processing. Therefore, we concluded that even though the technical setup was partially automated, it is a way forward to understand the richness of the conversations between different roles and makes a significant step towards automatic collaboration analytics.
Surface plasmon polaritons on (silver) nanowires are promising components for future photonic technologies. Here, we study near-field patterns on silver nanowires with a scattering-type scanning near-field optical microscope that enables the direct mapping of surface waves. We analyze the spatial pattern of the plasmon signatures for different excitation geometries and polarization and observe a plasmon wave pattern that is canted relative to the nanowire axis, which we show is due to a superposition of two different plasmon modes, as supported by electromagnetic simulations including the influence of the substrate. These findings yield new insights into the excitation and propagation of plasmon polaritons for applications in nanoplasmonic devices.
In power systems, flow allocation (FA) methods enable to allocate the usage and costs of the transmission grid to each single market participant. Based on predefined assumptions, the power flow is split into isolated generator-specific or producer-specific sub-flows. Two prominent FA methods, Marginal Participation (MP) and Equivalent Bilateral Exchanges (EBEs), build upon the linearized power flow and thus on the Power Transfer Distribution Factors (PTDFs). Despite their intuitive and computationally efficient concepts, they are restricted to networks with passive transmission elements only. As soon as a significant number of controllable transmission elements, such as high-voltage direct current (HVDC) lines, operate in the system, they lose their applicability. This work reformulates the two methods in terms of Virtual Injection Patterns (VIPs), which allows one to efficiently introduce a shift parameter q to tune contributions of net sources and net sinks in the network. In this work, major properties and differences in the methods are pointed out, and it is shown how the MP and EBE algorithms can be applied to generic meshed AC-DC electricity grids: by introducing a pseudo-impedance ω¯ , which reflects the operational state of controllable elements and allows one to extend the PTDF matrix under the assumption of knowing the current flow in the system. Basic properties from graph theory are used to solve for the pseudo-impedance in dependence of the position within the network. This directly enables, e.g., HVDC lines to be considered in the MP and EBE algorithms. The extended methods are applied to a low-carbon European network model (PyPSA-EUR) with a spatial resolution of 181 nodes and an 18% transmission expansion compared to today’s total transmission capacity volume. The allocations of MP and EBE show that countries with high wind potentials profit most from the transmission grid expansion. Based on the average usage of transmission system expansion, a method of distributing operational and capital expenditures is proposed. In addition, it is shown how injections from renewable resources strongly drive country-to-country allocations and thus cross-border electricity flows.
Python for Power System Analysis (PyPSA) is a free software toolbox for simulating and optimising modern electrical power systems over multiple periods. PyPSA includes models for conventional generators with unit commitment, variable renewable generation, storage units, coupling to other energy sectors, and mixed alternating and direct current networks. It is designed to be easily extensible and to scale well with large networks and long time series. In this paper the basic functionality of PyPSA is described, including the formulation of the full power flow equations and the multi-period optimisation of operation and investment with linear power flow equations. PyPSA is positioned in the existing free software landscape as a bridge between traditional power flow analysis tools for steady-state analysis and full multi-period energy system models. The functionality is demonstrated on two open datasets of the transmission system in Germany (based on SciGRID) and Europe (based on GridKit).
Variable renewable energy sources (VRES), such as solarphotovoltaic (PV) and wind turbines (WT), are starting to play a significant role in several energy systems around the globe. To overcome the problem of their non-dispatchable and stochastic nature, several approaches have been proposed so far. This paper describes a novel mathematical model for scheduling the operation of a wind-powered pumped-storage hydroelectricity (PSH) hybrid for 25 to 48 h ahead. The model is based on mathematical programming and wind speed forecasts for the next 1 to 24 h, along with predicted upper reservoir occupancy for the 24th hour ahead. The results indicate that by coupling a 2-MW conventional wind turbine with a PSH of energy storing capacity equal to 54 MWh it is possible to significantly reduce the intraday energy generation coefficient of variation from 31% for pure wind turbine to 1.15% for a wind-powered PSH The scheduling errors calculated based on mean absolute percentage error (MAPE) are significantly smaller for such a coupling than those seen for wind generation forecasts, at 2.39% and 27%, respectively. This is even stronger emphasized by the fact that, those for wind generation were calculated for forecasts made for the next 1 to 24 h, while those for scheduled generation were calculated for forecasts made for the next 25 to 48 h. The results clearly show that the proposed scheduling approach ensures the high reliability of the WT–PSH energy source
The use of decentralised, sustainable urban drainage systems (SUDS) for the treatment of stormwater runoff is becoming increasingly prevalent in Germany. Decentralised SUDS can offer a viable and attractive alternative to end of pipe treatment systems for stormwater runoff from urban areas. However, there is still some uncertainty regarding the long-term performance of SUDS, and the general legislative requirements for SUDS approval and testing. Whilst the allowable pollution levels in stormwater runoff that infiltrate into ground and/or water table are regulated across Germany by the Federal Soil Protection Law, there is presently no federal law addressing the discharge requirements for surface water runoff. The lack of clear guidance can make it difficult for planners and designers to implement these innovative and sustainable stormwater treatment systems. This study clarifies the current understanding of urban stormwater treatment requirements and new technical approval guidelines for decentralised SUDS devices in Germany. The study findings should assist researchers, designers and asset managers to better anticipate and understand the performance, effective life-spans, and the planning and maintenance requirements for decentralised SUDS systems. This should help promote even greater use of these systems in the future.
Aufbauend auf einer Literaturanalyse wird der derzeitige technische Entwicklungsstand im Bereich der Wiedergewinnung von Phosphat und Stickstoffverbindungen aus dem häuslichen Abwasser skizziert: Neben der (chemischen) Wiedergewinnung aus dem Abwasser und der Verwendung von Anaerobverfahren sowie die Wiedergewinnung aus Klärschlamm ist auch die Bewässerung mit Abwasser, die Kompostierung sowie die Fraktionierung von Abwasser („Gelbwasser“) eine Möglichkeit zur besseren Ausnutzung der Nährstoffgehalte des Abwassers. Der erzielte Überblick über den derzeitigen Stand der Nährstoffrückgewinnung diente dazu, mögliche Entwicklungsaufgaben zu identifizieren, die einerseits vordringlich (insbesondere zur Lösung globaler Probleme, z.B. zur Beendigung des Ressourcenmangels) erscheinen und deren Lösung andererseits besonders innovative Leistungen erfordern. Die Entwicklungsaufgaben wurden thesenhaft zugespitzt, um so anschließend in einer Delphi-Befragung überprüft werden zu können.
Aufbauend auf einer Literaturanalyse wird der derzeitige technische Entwicklungsstand im Bereich des Grauwasserrecyclings skizziert. Neben mechanisch-biologische Anlagen treten vereinzelt Membranfilteranlagen, aber auch „Low-Tech“-Anlagen. Der Überblick half, mögliche Entwicklungsaufgaben zu identifizieren, die einerseits vordringlich (insbesondere zur Lösung künftiger Wassermengenprobleme) erscheinen und deren Lösung andererseits besonders innovative Leistungen erfordern. Die Entwicklungsaufgaben wurden thesenhaft zugespitzt, um so anschließend in einer Delphi-Befragung überprüft werden zu können.
Aufbauend auf einer Literaturanalyse wird der derzeitige technische Entwicklungsstand im Bereich der Energierückgewinnung aus dem Siedlungsabwasser skizziert. Neben der Wärmerückgewinnung, die sowohl im Kanalnetz als auch dezentral in Gebäuden möglich ist, wurde die Biogasgewinnung sowohl auf Aerobkläranlagen als auch in Anaerobanlagen und die anschließende Aufbereitung der Klärgase in Erdgasqualität ebenso diskutiert wie die Nutzung von Schlämmen als Brennmaterial. Die Darstellung des derzeitigen Entwicklungsstandes half dabei, mögliche Entwicklungsaufgaben zu identifizieren, die einerseits vordringlich erlauben könnten, Abwasser künftig als Energieressource zu betrachten, und deren Lösung andererseits besonders innovative Leistungen erfordern. Die Entwicklungsaufgaben wurden thesenhaft zugespitzt, um so anschließend in einer Delphi-Befragung überprüft zu werden.
Vorarbeiten zu einer sozial-ökologischen RisDie Nanotechnologie gilt als eine der Schlüsseltechnologien der Zukunft: Die Verringerung der Teilchengröße in den nanoskaligen Bereich führt zu neuartigen physikalischen und chemischen Stoffeigenschaften, welche Innovationspotenzial in vielfältigen Anwendungsfeldern versprechen. Besonders in den letzten zwei Jahrzehnten hat die Nanotechnologie wirtschaftlich an Bedeutung gewonnen, da immer mehr nanotechnologische Entwicklungen kommerziell umgesetzt werden. Aufgrund des breiten Anwendungsspektrums und der Vielzahl unterschiedlicher Materialien ist bisher weder eine transparente Darstellung der tatsächlichen wirtschaftlichen Bedeutung noch eine adäquate Bewertung potenzieller Gesundheits- und Umweltrisiken, die aus den neuartigen nanospezifischen Eigenschaften hervorgehen könnten, möglich.
Das Papier gibt einen aktuellen Überblick über den Stand des Wissens zum Thema Nanotechnologie, wobei besonderer Fokus auf den Bereich Risiko, Toxikologie und Ökotoxikologie sowie Risikowahrnehmung und -kommunikation gelegt wird. Die Ergebnisse der Literaturstudie sollen künftig dazu dienen, zu prüfen, welchen Beitrag ein sozial-ökologischer Forschungsansatz zur nachhaltigen Entwicklung und Nutzung der Nanotechnologie leisten kann.