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The utilization of geothermal energy is crucial for achieving sustainable heating solutions during the transition to renewable energy sources.Geothermal probes, also known as borehole heat exchangers, are used to extract heat from the ground.These probes can operate individually or be combined into probe fields to meet larger heating demands.The design of these fields must account for potential undercooling or overheating over extended periods.G-functions are typically employed to calculate the thermal behavior of the ground with interconnected borehole heat exchangers.However, calculating numerical solutions for these functions can be very time-consuming.This study involves training artificial neural networks (\gls{ANN}) using pre-calculated g-functions.The accuracies and calculation times of the trained \gls{ANN} were then compared.The study created a dataset with over \num{\sizeOfData} g-functions for a rectangular probe field.Two different ANNs were trained using 80 \% of the dataset.The study then determined the accuracy of the g-functions generated by the ANN and the calculation speed.The results indicate that the mean absolute percentage error was below 2.3 \%.On average, the calculation time was less than 0.1 \% of the original time.Large probe fields performed better than average in terms of calculation time.The reduced calculation time enables the computation of complex tasks within a reasonable timeframe, including depth sizing and borefield design optimizations.
Combining buildings into districts aggregates the diverse peak loads from individual buildings to improve the sizing of new energy supply systems.The non-simultaneity of peak loads (both electric and thermal) is evaluated using simultaneity factors.The simultaneity factor is the maximum of the district load profile divided by the maximum of the individual load profile.As the simulation of individual buildings works very well, this publication aims to present algorithms that calculate the combined load profile of district buildings from individual building load profiles using the simultaneity factor.Four different methods are presented for this purpose: (Mean) linear scaling of the load profile to a constant mean value, (Ref. P.) scaling to a reference load profile, (N. D.) normal distribution of the load profile to the neighboring time steps and (N. D. Ref.) normal distribution of the difference between the individual building load profiles and a reference profile to the neighboring time steps.All methods take a predetermined simultaneity factor into account to smooth the maximum load peak until this simultaneity factor is met.All methods are applied to measured electrical and thermal load profiles, and the calculation accuracy is compared.The results show that linear scaling to a reference profile model has the lowest errors.The normal distribution models lead to the lowest fluctuations.
Ökobilanzen, die alle Phasen im Lebenszyklus eines Gebäudes berücksichtigen, gewinnen zunehmend an Bedeutung.Aufgrund ihrer langen Lebensdauer kommt bei Gebäuden mit strombasierten Wärmeversorgungssystemen, wie Wärmepumpen, der Interaktion mit dem Stromnetz eine herausragende Bedeutung zu, insbesondere im Zusammenhang mit der Dekarbonisierung der Stromerzeugung.Der Einfluss der Dekarbonisierung über die kommenden Jahrzehnte sowie die kurzfristige Variabilität der Emissionsfaktoren auf der Basis von stundenbasierten Werten für den Strommix auf die Ökobilanz von vier verschiedenen Gebäudetypen soll hier aufgezeigt werden.Die betrachteten Gebäudetypen umfassen ein Einfamilienhaus, ein Bürogebäude, ein Bildungsgebäude und eine Industriehalle.Ziel ist es den Einfluss der Dekarbonisierung und der Stundenauflösung auf die Auswahl der optimalen Dämmstärke für ein Wärmepumpen-basiertes System aufzuzeigen.Hierzu werden thermische und elektrische Lastprofile für die verschiedenen Gebäudetypen erzeugt.Dabei werden verschiedene Nutzungsprofile, Standorte, Dämmstärken, Fensteranteile, Ausrichtungen, Fensterverglasungen, Lüftungsvarianten und Sonnenschutzvarianten betrachtet.Für all diese Varianten werden verschiedene Szenarien in Bezug auf die Gebäudetechnik untersucht und hinsichtlich ihrer Dämmstärke sowie der Größe der gebäudetechnischen Komponenten mit GWP-Auswirkungen optimiert.Die Ergebnisse zeigen, dass die Berücksichtigung der Dekarbonisierung der Stromerzeugung die ökobilanziell optimale Dämmstärke im Vergleich zum statischen Ansatz mit heutigen Werten halbieren kann.Auch die Berücksichtigung stundenbasierter Stromemissionswerte führt zu einer Reduzierung der optimalen Dämmstärke um nahezu
In common with most infrastructure systems, sewers are often inspected visually. Currently, the results from these inspections inform decisions for significant investments regarding sewer rehabilitation or replacement. In practice, the quality of the data and its analysis are not questioned although psychological research indicates that, as a consequence of the use of subjective analysis of the collected images, errors are inevitable. This article assesses the quality of the analysis of visual sewer inspection data by analysing data reproducibility; three types of capabilities to subjectively assess data are distinguished: the recognition of defects, the description of defects according to a prescribed coding system and the interpretation of sewer inspection reports. The introduced uncertainty is studied using three types of data: inspector examination results of sewer inspection courses, data gathered in day-to-day practice, and the results of repetitive interpretation of the inspection results. After a thorough analysis of the data it can be concluded that for all cases visual sewer inspection data proved poorly reproducible. For the recognition of defects, it was found that the probability of a false positive is in the order of a few percent, the probability of a false negative is in the order of 25%.
Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existing research gaps while giving an outlook on future developments and research areas.
Air–water flows
(2024)
High Froude-number open-channel flows can entrain significant volumes of air, a phenomenon that occurs continuously in spillways, in free-falling jets and in hydraulic jumps, or as localized events, notably at the toe of hydraulic jumps or in plunging jets. Within these flows, turbulence generates millions of bubbles and droplets as well as highly distorted wavy air–water interfaces. This phenomenon is crucial from a design perspective, as it influences the behaviour of high-velocity flows, potentially impairing the safety of dam operations. This review examines recent scientific and engineering progress, highlighting foundational studies and emerging developments. Notable advances have been achieved in the past decades through improved sampling of flows and the development of physics-based models. Current challenges are also identified for instrumentation, numerical modelling and (up)scaling that hinder the formulation of fundamental theories, which are instrumental for improving predictive models, able to offer robust support for the design of large hydraulic structures at prototype scale.
Effective government services rely on accurate population numbers to allocate resources. In Colombia and globally, census enumeration is challenging in remote regions and where armed conflict is occurring. During census preparations, the Colombian National Administrative Department of Statistics conducted social cartography workshops, where community representatives estimated numbers of dwellings and people throughout their regions. We repurposed this information, combining it with remotely sensed buildings data and other geospatial data. To estimate building counts and population sizes, we developed hierarchical Bayesian models, trained using nearby full-coverage census enumerations and assessed using 10-fold cross-validation. We compared models to assess the relative contributions of community knowledge, remotely sensed buildings, and their combination to model fit. The Community model was unbiased but imprecise; the Satellite model was more precise but biased; and the Combination model was best for overall accuracy. Results reaffirmed the power of remotely sensed buildings data for population estimation and highlighted the value of incorporating local knowledge.
Purpose: A precise determination of the corneal diameter is essential for the diagnosis of various ocular diseases, cataract and refractive surgery as well as for the selection and fitting of contact lenses. The aim of this study was to investigate the agreement between two automatic and one manual method for corneal diameter determination and to evaluate possible diurnal variations in corneal diameter.
Patients and Methods: Horizontal white-to-white corneal diameter of 20 volunteers was measured at three different fixed times of a day with three methods: Scheimpflug method (Pentacam HR, Oculus), placido based topography (Keratograph 5M, Oculus) and manual method using an image analysis software at a slitlamp (BQ900, Haag-Streit).
Results: The two-factorial analysis of variance could not show a significant effect of the different instruments (p = 0.117), the different time points (p = 0.506) and the interaction between instrument and time point (p = 0.182). Very good repeatability (intraclass correlation coefficient ICC, quartile coefficient of dispersion QCD) was found for all three devices. However, manual slitlamp measurements showed a higher QCD than the automatic measurements with the Keratograph 5M and the Pentacam HR at all measurement times.
Conclusion: The manual and automated methods used in the study to determine corneal diameter showed good agreement and repeatability. No significant diurnal variations of corneal diameter were observed during the period of time studied.
Elastic transmission eigenvalues and their computation via the method of fundamental solutions
(2020)
A stabilized version of the fundamental solution method to catch ill-conditioning effects is investigated with focus on the computation of complex-valued elastic interior transmission eigenvalues in two dimensions for homogeneous and isotropic media. Its algorithm can be implemented very shortly and adopts to many similar partial differential equation-based eigenproblems as long as the underlying fundamental solution function can be easily generated. We develop a corroborative approximation analysis which also implicates new basic results for transmission eigenfunctions and present some numerical examples which together prove successful feasibility of our eigenvalue recovery approach.
Analysis and computation of the transmission eigenvalues with a conductive boundary condition
(2022)
We provide a new analytical and computational study of the transmission eigenvalues with a conductive boundary condition. These eigenvalues are derived from the scalar inverse scattering problem for an inhomogeneous material with a conductive boundary condition. The goal is to study how these eigenvalues depend on the material parameters in order to estimate the refractive index. The analytical questions we study are: deriving Faber–Krahn type lower bounds, the discreteness and limiting behavior of the transmission eigenvalues as the conductivity tends to infinity for a sign changing contrast. We also provide a numerical study of a new boundary integral equation for computing the eigenvalues. Lastly, using the limiting behavior we will numerically estimate the refractive index from the eigenvalues provided the conductivity is sufficiently large but unknown.