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Ice melting probes
(2023)
The exploration of icy environments in the solar system, such as the poles of Mars and the icy moons (a.k.a. ocean worlds), is a key aspect for understanding their astrobiological potential as well as for extraterrestrial resource inspection. On these worlds, ice melting probes are considered to be well suited for the robotic clean execution of such missions. In this chapter, we describe ice melting probes and their applications, the physics of ice melting and how the melting behavior can be modeled and simulated numerically, the challenges for ice melting, and the required key technologies to deal with those challenges. We also give an overview of existing ice melting probes and report some results and lessons learned from laboratory and field tests.
This paper describes the potential for developing a digital twin of society- a dynamic model that can be used to observe, analyze, and predict the evolution of various societal aspects. Such a digital twin can help governmental agencies and policy makers in interpreting trends, understanding challenges, and making decisions regarding investments or policies necessary to support societal development and ensure future prosperity. The paper reviews related work regarding the digital twin paradigm and its applications. The paper presents a motivating case study- an analysis of opportunities and challenges faced by the German federal employment agency, Bundesagentur f¨ur Arbeit (BA), proposes solutions using digital twins, and describes initial proofs of concept for such solutions.
Deammonification for nitrogen removal in municipal wastewater in temperate and cold climate zones is currently limited to the side stream of municipal wastewater treatment plants (MWWTP). This study developed a conceptual model of a mainstream deammonification plant, designed for 30,000 P.E., considering possible solutions corresponding to the challenging mainstream conditions in Germany. In addition, the energy-saving potential, nitrogen elimination performance and construction-related costs of mainstream deammonification were compared to a conventional plant model, having a single-stage activated sludge process with upstream denitrification. The results revealed that an additional treatment step by combining chemical precipitation and ultra-fine screening is advantageous prior the mainstream deammonification. Hereby chemical oxygen demand (COD) can be reduced by 80% so that the COD:N ratio can be reduced from 12 to 2.5. Laboratory experiments testing mainstream conditions of temperature (8–20°C), pH (6–9) and COD:N ratio (1–6) showed an achievable volumetric nitrogen removal rate (VNRR) of at least 50 gN/(m3∙d) for various deammonifying sludges from side stream deammonification systems in the state of North Rhine-Westphalia, Germany, where m3 denotes reactor volume. Assuming a retained Norganic content of 0.0035 kgNorg./(P.E.∙d) from the daily loads of N at carbon removal stage and a VNRR of 50 gN/(m3∙d) under mainstream conditions, a resident-specific reactor volume of 0.115 m3/(P.E.) is required for mainstream deammonification. This is in the same order of magnitude as the conventional activated sludge process, i.e., 0.173 m3/(P.E.) for an MWWTP of size class of 4. The conventional plant model yielded a total specific electricity demand of 35 kWh/(P.E.∙a) for the operation of the whole MWWTP and an energy recovery potential of 15.8 kWh/(P.E.∙a) through anaerobic digestion. In contrast, the developed mainstream deammonification model plant would require only a 21.5 kWh/(P.E.∙a) energy demand and result in 24 kWh/(P.E.∙a) energy recovery potential, enabling the mainstream deammonification model plant to be self-sufficient. The retrofitting costs for the implementation of mainstream deammonification in existing conventional MWWTPs are nearly negligible as the existing units like activated sludge reactors, aerators and monitoring technology are reusable. However, the mainstream deammonification must meet the performance requirement of VNRR of about 50 gN/(m3∙d) in this case.
Messenger apps like WhatsApp and Telegram are frequently used for everyday communication, but they can also be utilized as a platform for illegal activity. Telegram allows public groups with up to 200.000 participants. Criminals use these public groups for trading illegal commodities and services, which becomes a concern for law enforcement agencies, who manually monitor suspicious activity in these chat rooms. This research demonstrates how natural language processing (NLP) can assist in analyzing these chat rooms, providing an explorative overview of the domain and facilitating purposeful analyses of user behavior. We provide a publicly available corpus of annotated text messages with entities and relations from four self-proclaimed black market chat rooms. Our pipeline approach aggregates the extracted product attributes from user messages to profiles and uses these with their sold products as features for clustering. The extracted structured information is the foundation for further data exploration, such as identifying the top vendors or fine-granular price analyses. Our evaluation shows that pretrained word vectors perform better for unsupervised clustering than state-of-the-art transformer models, while the latter is still superior for sequence labeling.
Next-generation aircraft designs often incorporate multiple large propellers attached along the wingspan. These highly flexible dynamic systems can exhibit uncommon aeroelastic instabilities, which should be carefully investigated to ensure safe operation. The interaction between the propeller and the wing is of particular importance. It is known that whirl flutter is stabilized by wing motion and wing aerodynamics. This paper investigates the effect of a propeller onto wing flutter as a function of span position and mounting stiffness between the propeller and wing. The analysis of a comparison between a tractor and pusher configuration has shown that the coupled system is more stable than the standalone wing for propeller positions near the wing tip for both configurations. The wing fluttermechanism is mostly affected by the mass of the propeller and the resulting change in eigenfrequencies of the wing. For very weak mounting stiffnesses, whirl flutter occurs, which was shown to be stabilized compared to a standalone propeller due to wing motion. On the other hand, the pusher configuration is, as to be expected, the more critical configuration due to the attached mass behind the elastic axis.
Today’s society is undergoing a paradigm shift driven by the megatrend of sustainability. This undeniably affects all areas of Western life. This paper aims to find out how the luxury industry is dealing with this change and what adjustments are made by the companies. For this purpose, interviews were conducted with managers from the luxury industry, in which they were asked about specific measures taken by their companies as well as trends in the industry. In a subsequent evaluation, the trends in the luxury industry were summarized for the areas of ecological, social, and economic sustainability. It was found that the area of environmental sustainability is significantly more focused than the other sub-areas. Furthermore, the need for a customer survey to validate the industry-based measures was identified.
The major advantage of labyrinth weirs over linear weirs is hydraulic efficiency. In hydraulic modeling efforts, this strength contrasts with limited pump capacity as well as limited computational power for CFD simulations. For the latter, reducing the number of investigated cycles can significantly reduce necessary computational time. In this study, a labyrinth weir with different cycle numbers was investigated. The simulations were conducted in FLOW-3D HYDRO as a Large Eddy Simulation. With a mean deviation of 1.75 % between simulated discharge coefficients and literature design equations, a reasonable agreement was found. For downstream conditions, overall consistent results were observed as well. However, the orientation of labyrinth weirs with a single cycle should be chosen carefully under consideration of the individual research purpose.
This thesis aims at the presentation and discussion of well-accepted and new
imaging techniques applied to different types of flow in common hydraulic
engineering environments. All studies are conducted in laboratory conditions and
focus on flow depth and velocity measurements. Investigated flows cover a wide
range of complexity, e.g. propagation of waves, dam-break flows, slightly and fully
aerated spillway flows as well as highly turbulent hydraulic jumps.
Newimagingmethods are compared to different types of sensorswhich are frequently
employed in contemporary laboratory studies. This classical instrumentation as well
as the general concept of hydraulic modeling is introduced to give an overview on
experimental methods.
Flow depths are commonly measured by means of ultrasonic sensors, also known as
acoustic displacement sensors. These sensors may provide accurate data with high
sample rates in case of simple flow conditions, e.g. low-turbulent clear water flows.
However, with increasing turbulence, higher uncertainty must be considered.
Moreover, ultrasonic sensors can provide point data only, while the relatively large
acoustic beam footprint may lead to another source of uncertainty in case of
relatively short, highly turbulent surface fluctuations (ripples) or free-surface
air-water flows. Analysis of turbulent length and time scales of surface fluctuations
from point measurements is also difficult. Imaging techniques with different
dimensionality, however, may close this gap. It is shown in this thesis that edge
detection methods (known from computer vision) may be used for two-dimensional
free-surface extraction (i.e. from images taken through transparant sidewalls in
laboratory flumes). Another opportunity in hydraulic laboratory studies comes with
the application of stereo vision. Low-cost RGB-D sensors can be used to gather
instantaneous, three-dimensional free-surface elevations, even in flows with very
high complexity (e.g. aerated hydraulic jumps). It will be shown that the uncertainty
of these methods is of similar order as for classical instruments.
Particle Image Velocimetry (PIV) is a well-accepted and widespread imaging
technique for velocity determination in laboratory conditions. In combination with
high-speed cameras, PIV can give time-resolved velocity fields in 2D/3D or even as
volumetric flow fields. PIV is based on a cross-correlation technique applied to small
subimages of seeded flows. The minimum size of these subimages defines the
maximum spatial resolution of resulting velocity fields. A derivative of PIV for
aerated flows is also available, i.e. the so-called Bubble Image Velocimetry (BIV). This
thesis emphasizes the capacities and limitations of both methods, using relatively
simple setups with halogen and LED illuminations. It will be demonstrated that
PIV/BIV images may also be processed by means of Optical Flow (OF) techniques.
OF is another method originating from the computer vision discipline, based on the
assumption of image brightness conservation within a sequence of images. The
Horn-Schunck approach, which has been first employed to hydraulic engineering
problems in the studies presented herein, yields dense velocity fields, i.e. pixelwise
velocity data. As discussed hereinafter, the accuracy of OF competes well with PIV
for clear-water flows and even improves results (compared to BIV) for aerated flow
conditions. In order to independently benchmark the OF approach, synthetic images
with defined turbulence intensitiy are used.
Computer vision offers new opportunities that may help to improve the
understanding of fluid mechanics and fluid-structure interactions in laboratory
investigations. In prototype environments, it can be employed for obstacle detection
(e.g. identification of potential fish migration corridors) and recognition (e.g. fish
species for monitoring in a fishway) or surface reconstruction (e.g. inspection of
hydraulic structures). It can thus be expected that applications to hydraulic
engineering problems will develop rapidly in near future. Current methods have not
been developed for fluids in motion. Systematic future developments are needed to
improve the results in such difficult conditions.