TU Wien
  • Vienna, Vienna, Austria
Recent publications
This paper presents a method for determining the performance of shuttle-based storage and retrieval systems (SBS/RS) with tier-captive, single-aisle shuttles serving tiers of multiple-deep storage and using a class-based storage policy. This approach is used in the design process of SBS/RS and in the upgrading process of existing SBS/RS. With this approach, it is possible to evaluate the improvement in the performance of multiple-deep storage system by applying a class-based storage policy. The basis of this calculation method is a continuous-time, open-queueing system with limited capacity. The cycle times of lifts and shuttles, as determined by a spatial value approach, combined with a probability-based approach to mention the storage policy. To take the multiple-deep storage into account, another probability-based approach is applied. A European material handling provider had given the data used in this publication. Through an example, the influences of the storage policy and the storage depth are depicted.
Magnetoelectric phenomena are intimately linked to relativistic effects and also require the material to break spatial inversion symmetry and time-reversal invariance. Magnetoelectric coupling can substantially affect light–matter interaction and lead to non-reciprocal light propagation. Here, we confirm on a fully experimental basis, without invoking either symmetry-based or material-specific assumptions, that the optical magnetoelectric effect in materials with non-parallel magnetization ( M ) and electric polarization ( P ) generates a trilinear term in the refractive index, δ n ∝ k ⋅ ( P × M ), where k is the propagation vector of light. Its sharp magnetoelectric resonances in the terahertz regime, which are simultaneously electric and magnetic dipole active excitations, make Co 2 Mo 3 O 8 an ideal compound to demonstrate this fundamental relation via independent variation of M , P , and k . Remarkably, the material shows almost perfect one-way transparency in moderate magnetic fields for one of these magnetoelectric resonances.
Objective To assess the biomechanical effects of different prosthetic/implant configurations and load directions on 3-unit fixed prostheses supported by short dental implants in the posterior mandible using validated 3-D finite element (FE) models. Methods Models represented an atrophic mandible, missing the 2nd premolar, 1st and 2nd molars, and rehabilitated with either two short implants (implant length-IL = 8 mm and 4 mm) supporting a 3-unit dental bridge or three short implants (IL = 8 mm, 6 mm and 4 mm) supporting zirconia prosthesis in splinted or single crowns design. Load simulations were performed in ABAQUS (Dassault Systèmes, France) under axial and oblique (30°) force of 100 N to assess the global stiffness and forces within the implant prosthesis. Local stresses within implant/prosthesis system and strain energy density (SED) within surrounding bone were determined and compared between configurations. Results The global stiffness was around 1.5 times higher in splinted configurations vs. single crowns, whereby off-axis loading lead to a decrease of 39%. Splinted prostheses exhibited a better stress distribution than single crowns. Local stresses were larger and distributed over a larger area under oblique loads compared to axial load direction. The forces on each implant in the 2-implant-splinted configurations increased by 25% compared to splinted crowns on 3 implants. Loading of un-splinted configurations resulted in increased local SED magnitude. Conclusion Splinting of adjacent short implants in posterior mandible by the prosthetic restoration has a profound effect on the magnitude and distribution of the local stress peaks in peri-implant regions. Replacing each missing tooth with an implant is recommended, whenever bone supply and costs permit.
Aim There is a growing literature analyzing money laundering and the policies to fight it, but the overall effectiveness of anti-money laundering policies is still unclear. This paper investigates whether anti-money laundering policies affect the behavior of money launderers and their networks. Method With an algorithm to match clusters over time, we build a unique dataset of multi-mode, undirected, binary, dynamic networks of natural and legal persons. The data includes ownership and employment relations and associated financial ties and is enriched with criminal records and police-related activities. The networks of money launderers, other criminals, and non-criminal individuals are analyzed and compared with temporal social network analysis techniques and panel data regressions on centrality measures, transitivity and assortativity indicators, and levels of constraint. Findings We find that after the announcement of the fourth EU anti-money laundering directive in 2015, money laundering networks show a significant increase in the use of foreigners and corporate structures. At the individual level, money launderers become more dominant in criminal clusters (increased closeness centrality). This paper shows that (the announcement of) anti-money laundering policies can affect criminal networks and how such effects can be tested.
Polaron defects are ubiquitous in materials and play an important role in many processes involving carrier mobility, charge transfer and surface reactivity. Determining small polarons’ spatial distributions is essential to understand materials properties and functionalities. However, the required exploration of the configurational space is computationally demanding when using first principles methods. Here, we propose a machine-learning (ML) accelerated search that determines the ground state polaronic configuration. The ML model is trained on databases of polaron configurations generated by density functional theory (DFT) via molecular dynamics or random sampling. To establish a mapping between configurations and their stability, we designed descriptors modelling the interactions among polarons and charged point defects. We used the DFT+ML protocol to explore the polaron configurational space for two surface-systems, reduced rutile TiO 2 (110) and Nb-doped SrTiO 3 (001). The ML-aided search proposes additional polaronic configurations and can be utilized to determine optimal polaron distributions at any charge concentration.
The deviation of Universal Time from atomic time, expressed as UT1-UTC, reflects the irregularities of the Earth rotation speed and is key to precise geodetic applications which depend on the transformation between celestial and terrestrial reference frames. A rapidly varying quantity such as UT1-UTC demands observation scenarios enabling fast delivery of good results. These criteria are currently met only by the Very Long Baseline Interferometry (VLBI) Intensive sessions. Due to stringent requirements of a fast UT1-UTC turnaround, the observations are limited to a few baselines and a duration of one hour. Hence, the estimation of UT1-UTC from Intensives is liable to constraints and prone to errors introduced by inaccurate a priori information. One aspect in this context is that the regularly operated Intensive VLBI sessions organised by the International VLBI Service for Geodesy and Astrometry solely use stations in the northern hemisphere. Any potential systematic errors due to this northern hemisphere dominated geometry are so far unknown. Besides the general need for stimulating global geodetic measurements with southern observatories, this served as a powerful motivation to launch the SI (Southern Intensive) program in 2020. The SI sessions are observed using three VLBI antennas in the southern hemisphere: Ht (South Africa), Hb (Tasmania) and Yg (Western Australia). On the basis of UT1-UTC results from 53 sessions observed throughout 2020 and 2021, we demonstrate the competitiveness of the SI with routinely operated Intensive sessions in terms of operations and UT1-UTC accuracy. The UT1-UTC values of the SI reach an average agreement of 32 µs in terms of weighted standard deviation when compared with the conventional Intensives results of five independent analysis centers and of 27 µs compared with the 14C04 series. The mean scatter of all solutions of the considered northern hemisphere Intensives with respect to C04 is at a comparable level of 29 µs. The quality of the results is only slightly degraded if just the baseline HtHb is evaluated. In combination with the e-transfer capabilities from Ht to Hb, this facilitates continuation of the SI by ensuring rapid service UT1-UTC provision. Graphical abstract:
This paper investigates how the European electricity and heating system is impacted when medium-scale energy communities (ECs) are developed widely across Europe. We study the response on the capacity expansion of the cross-border transmission and national generation and storage within the European electricity and heating system with and without ECs in selected European countries. The representation of ECs has a special focus on flexibility, and we analyze the difference between flexibility responses by ECs towards local versus global cost minimization. Results show that EC development decreases total electricity and heating system costs on the transition towards a decarbonized European system in line with the 1.5 °C target, and less generation and storage capacity expansion is needed on a national scale to achieve climate targets. We also identify a conflict of interest between optimizing EC flexibility towards local cost minimization versus European cost minimization.
A complete family of functional Steiner formulas is established. As applications, an explicit representation of functional intrinsic volumes using special mixed Monge–Ampère measures and a new version of the Hadwiger theorem on convex functions are obtained.
As for the construction of a metro line, excavated stations usually serve as departure and receiving shafts of the shield tunneling machines, used for drilling of station-to-station tunnels. However, the shield tunneling machines may reach the stations before their excavation. In order to avoid stopping of tunneling to wait for the completion of the station, a Shield Twice Tunneling Method (STTM) is developed and applied to a real engineering example. It permits the station-to-station tunneling machines to pass through the stations first. Subsequently, larger-diameter shield tunneling machines are driven from one end of the station to the other one. The resulting tunnels serve as side-platform stations. A model test, simulating the tunneling process of the larger-diameter shield tunneling machines, was carried out. It was designed according to the concept of equivalent specific energy. The experimental results corroborate the rationality of the selected tunneling machine and of its equipment with cutters. In addition, suitable tunneling parameters are provided. The average values of the thrust forces and the torsional moments are predicted, based on the results of the model test. They agree with the monitored results on site. This demonstrates the usefulness of the model test. Application of the STTM to a real engineering project shows that the entire construction period was reduced by 45%.
The construction sector consumes high amounts of resources and energy while generating significant amounts of waste. This development is contrary to Circular Economy principles, which require buildings that are resource and energy efficient and enable material recycling to the greatest possible extent. To effectively tackle this problem, the EU places a strong focus on sustainable building design. However, to assess this development, indicators that measure the potential recyclability of buildings already at the design stage are necessary. In this study, the “Relative product-inherent recyclability” (RPR) assessment method is applied to evaluate the recyclability of buildings. The RPR method considers buildings’ material composition and structure (assembly) to measure recyclability, thereby describing recycling-relevant factors. The method is based on the statistical entropy approach, which aims to describe material distributions. The RPR increases the more building parts can be disassembled, allowing recovery of concentrated materials. A case study on a timber and concrete building is used to demonstrate the applicability of the RPR metric. The results show that the RPR metric is a suitable indicator for expressing buildings’ inherent recyclability, thus identifying significant differences between building variants. Relevant design optimizations can be deduced from the RPR results. In our case, the timber building achieves higher recyclability than the concrete building. Applying the RPR indicator on the EU level can be recommended and offers significant insights into the design and recyclability of buildings. Architects and constructors could use the metric as a planning and evaluation tool, thereby promoting circular building design concepts.
Modified atmosphere packaging (MAP) comprises a multilayer structure of polymers and adhesives offering excellent protection to food products. While this widely used structure improves shelf life, its recyclability is restricted by polymer incompatibilities and difficulty separating individual layers during sorting, which limits the viability of this prominent waste stream for 2030 European Union (EU) reuse and recycling targets. This study assessed the recycling potential of MAPs by system part and functional layer based on composition, component miscibility and temperature and incompatibility induced changes in physical and mechanical properties. Lids and trays alone exhibited similar compositions, but when combined their PET (polyethylene terephthalate)-PE (polyethylene) ratios varied considerably resulting in embrittlement and reduced toughness indicating limited compatibility and recyclability. Although PET-PE immiscibility resulted in phase separation causing inhomogeneity induced loss in ductility and toughness, barrier structures exhibited better phase adhesion and more homogeneous morphologies. Nonetheless, the PET dictated processing temperature, greatly exceeding that of PE, promoted cross-linking effects. The barrier and carrier layers of current MAPs must be delaminated within waste sorting processes to be recyclable. More economic and ecological recycling of MAPs to meet EU targets will require designs with more compatible polymer components.
Immediate and widespread changes in energy generation and use are critical to safeguard our future on this planet. However, while the necessity of renewable electricity generation is clear, the aviation, transport and mobility, chemical and material sectors are challenging to fully electrify. The age-old Fischer-Tropsch process and natural gas industry could be the bridging solution needed to accelerate the energy revolution in these sectors – temporarily powering obsolete vehicles, acting as renewable energy’s battery, supporting expansion of hydrogen fuel cell technologies and the agricultural and waste sectors as they struggle to keep up with a full switch to biofuels. Natural gas can be converted into hydrogen, synthetic natural gas, or heat during periods of low electricity demand and converted back to electricity again when needed. Moving methane through existing networks and converting it to hydrogen on-site at tanking stations also overcomes hydrogen distribution, storage problems and infrastructure deficiencies. Useful co-products include carbon nanotubes, a valuable engineering material, that offset emissions in the carbon nanotube and black industries. Finally, excess carbon can be converted back into syngas if desired. This flexibility and the compatibility of natural gas with both existing and future technologies provides a unique opportunity to rapidly decarbonise sectors struggling with complex requirements.
Today, different methods are used to measure two-dimensional (2D) and three-dimensional (3D) attributes of trees. One of these methods, which is considered in recent years is using point clouds and a 3D model extracted from terrestrial photogrammetry (TP). This study aims to estimate the 2D and 3D attributes of urban trees at three levels of seedlings, single trees and sample plot using TP. Structure-from-Motion with Multi-View Stereo-photogrammetry (SfM-MVS) method was used to derive the point clouds and the 3D model. Comparing estimated values of diameter at the middle of trunk of seedlings and diameter at breast height (DBH) of trees, using TP with measured values showed that the values of RMSE% were < 2% at three levels of seedlings, single trees and sample plot. Furthermore, validation of the estimated values of total height and crown height attributes of seedlings and trees at three levels showed that the RMSE% did not exceed 4% and 5%, respectively. Considering the overlap of tree crowns with each other in the sample plot, the average diameter of the crown attribute was estimated only in seedlings and single tree levels with RMSE% = 6.51% and 9.34%, respectively. The validation of estimated values of stem volume of seedlings and trees at three levels showed that the lowest errors were returned from trees within a sample plot with RMSE% = 14.37%, whereas the highest rates of errors were achieved for seedlings with RMSE% = 20.99%. As an alternative to approaches such as employing laser scanners, this method is quick, inexpensive, non-destructive, and does not need specialized equipment.
An external-cavity quantum cascade laser (EC-QCL)-based flow-through mid-infrared (IR) spectrometer was placed in line with a preparative size exclusion chromatography system to demonstrate real-time analysis of protein elutions with strongly overlapping chromatographic peaks. Two different case studies involving three and four model proteins were performed under typical lab-scale purification conditions. The large optical path length (25 μm), high signal-to-noise ratios, and wide spectral coverage (1350 to 1750 cm-1) of the QCL-IR spectrometer allow for robust spectra acquisition across both the amide I and II bands. Chemometric analysis by self-modeling mixture analysis and multivariate curve resolution enabled accurate quantitation and structural fingerprinting across the protein elution transient. The acquired concentration profiles were found to be in excellent agreement with the off-line high-performance liquid chromatography reference analytics performed on the collected effluent fractions. These results demonstrate that QCL-IR detectors can be used effectively for in-line, real-time analysis of protein elutions, providing critical quality attribute data that are typically only accessible through time-consuming and resource-intensive off-line methods.
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7,553 members
Paul Panek
  • Institute of Design and Assessment of Technology
Jörg Schmiedmayer
  • Institute of Atomic and Subatomic Physics
Peter Purgathofer
  • Institute of Visual Computing and Human Centered Technology
Jurgen Stampfl
  • Institute of Materials Science and Technology
Karlsplatz 13, A-1040, Vienna, Vienna, Austria
Head of institution
Sabine Seidler