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Cu supported on modified ceria as catalysts for reverse water gas shift as first step in CO2 utilization pathways
No full textSalt hydrate heat pipe: Proof of concept for a breakthrough heat transfer technology
No full textThis article introduces a novel type of thermosyphon heat pipe (THP) utilizing salt hydrates (SH) as an additive to
the working medium. The study evaluates the performance of the proposed SH heat pipe concept (SH-HP) both
experimentally and numerically employing MgSO₄⋅7H₂O as a sample SH additive. The MgSO₄⋅7H₂O SH-HP (in
powdered and aqueous forms) was investigated and compared with a conventional HP of the same physical
features and operation conditions but pure water as the medium. Effects of various concentrations and filling
ratios on the performance of the SH-HP were evaluated throughout the experimental, CFD, and parametric
analyses. The system performance with powdered MgSO₄⋅7H₂O showed a decrease in heat transfer efficiency due
to the presence of salt crystals in the heat transfer path. Investigations on the aqueous material indicated that
physical properties and crystal formation play a crucial role in the final performance of the system. The SH-HP
containing aqueous MgSO₄ at a concentration of 9.8 wt% demonstrated about 33 % reduction in thermal
resistance. Overall, the study with its primary results proves the effectiveness of a highly efficient passive HP
concept using magnesium sulfate heptahydrate as a sample additive, which could serve as a competitive
candidate for various heat transfer and even heat storage applications. The results and effectiveness of the system
for practical applications are expected to be more impressive upon rigorous optimization of the operating
conditions, HP geometry, and additive characteristics
Unsupervised linear discrimination using skewness
No full textIt is well-known that, in Gaussian two-group separation, the optimally discriminating projection direction can be estimated without any knowledge on the group labels. In this work, we gather several such unsupervised estimators based on skewness and derive their limiting distributions. As one of our main results, we show that all affine equivariant estimators of the optimal direction have proportional asymptotic covariance matrices, making their comparison straightforward. Two of our four estimators are novel and two have been proposed already earlier. We use simulations to verify our results and to inspect the finite-sample behaviors of the estimators
HD Maps for Autonomous Vehicles: Implications for Cartographic Theory and Practice
No full textHigh-Definition (HD) Maps have become a cornerstone of autonomous vehicle (AV) technology, enabling precise localization, perception, and decision-making. Despite their increasing prominence in the automotive and geospatial industries, HD Maps remain underexplored in the field of cartography. There are many studies and publications on HD Maps, but only a few of them directly address their links with cartography. Therefore, the research presented in this article focuses on this issue, filling an existing research gap. This paper examines the origins, technical characteristics, and conceptual frameworks of HD Maps, drawing on both the established literature and conceptual reflections. The results highlight that an extension of traditional cartographic definitions needs to be considered in order to encompass the concept of HD Maps as dynamic, machine-oriented infrastructures. By placing HD Maps as an important element in the development of cartography, the authors note both the prospect of a broader application of cartographic theory and the potential contribution of cartographers to the further development of HD Maps, as well as a potential paradigm shift toward the era of “maps for machines”
Dot-Cathode APD Receiver OEICs Achieving Sensitivity Gaps to the Quantum Limit Down to 10 dB
No full textPlayful First Steps: Virtual Reality and Gamification to Ease Employee Onboarding
No full textEffective onboarding of new employees ensures efficient integration, productivity, and retention. The user study presented in this paper explores the potential of Virtual Reality (VR) to support learning and skill development in onboarding processes, addressing a gap where traditional approaches might lack VR’s immersive and engaging attributes, potentially limiting knowledge retention and transfer. While VR's benefits in educational and training scenarios are known, direct comparisons between VR and conventional onboarding methods in industrial settings remain sparse. In response, we compared a VR-based onboarding prototype to a traditional tutor-led approach to ascertain its effectiveness. In this study, 46 new employees were divided into two groups. The experimental group underwent VR onboarding, while the control group experienced the traditional method. The results show that the control group achieved a higher overall learning success than the experimental group. On the other hand, VR onboarding was rated as more entertaining, and participants said they would be more likely to recommend it to others. Our findings suggest that incorporating VR, especially with preliminary hardware training, can lead to enhanced onboarding processes and more openness to XR technology integration within companies. Considering these findings, harnessing VR for engaging and impactful onboarding experiences could signify a transformative shift in how companies train and integrate their workforce, indicating a future where immersive technologies play a central role in education and professional development
Elemental Mapping of Historical Daguerreotypes Using Monochromatic Micro-XRF: Imaging, Degradation, and Conservation Potential
No full textThe daguerreotype, introduced by Louis-Jacques-Mandé Daguerre in 1839, marked the beginning of photography. This early photographic process, based on halide-sensitized silver-coated copper plates developed with mercury vapor, produces highly reflective, image-bearing surfaces that are both visually unique and chemically complex. As part of the interdisciplinary Heritage Science project PHELETYPIA, this study investigates the surface morphology and elemental composition of two historical daguerreotypes from the Varaždin City Museum (Croatia) using monochromatic micro-x-ray fluorescence (μXRF), scanning electron microscopy with energy-dispersive x-ray spectrometry (SEM/EDS), and optical microscopy. By comparing elemental distribution maps based on Hg-L and Au-L lines, we assess the relationship between image particle composition, visual contrast, and degradation patterns. Our results suggest that differences in image formation and preservation are linked to original manufacturing processes, including uneven thermal development and subsequent environmental exposure. High-resolution elemental imaging reveals how visual information is distributed across tonal zones and how it may be affected by previous conservation interventions. These findings highlight the potential of non-invasive analytical imaging to enhance our understanding of daguerreotype image structure, support condition assessment, and inform long-term digital preservation strategies
An Ising machine formulation for design updates in topology optimization of flow channels
No full textTopology optimization is an essential tool in computational engineering, for example, to improve the design and efficiency of flow channels. At the same time, Ising machines, including digital or quantum annealers, have been used as efficient solvers for combinatorial optimization problems. Beyond combinatorial optimization, recent works have demonstrated applicability to other engineering tasks by tailoring corresponding problem formulations. In this study, we present a novel Ising machine formulation for computing design updates during topology optimization with the goal of minimizing dissipation energy in flow channels. We explore the potential of this approach to improve the efficiency and performance of the optimization process. To this end, we conduct experiments to study the impact of various factors within the novel formulation. Additionally, we compare it to a classical method from the literature using the number of optimization steps and the final values of the objective function as indicators of the time intensity of the optimization and the performance of the resulting designs, respectively. Our findings show that the proposed update strategy can accelerate the topology optimization process while producing comparable designs. However, it tends to be less exploratory, which may lead to lower performance of the designs. These results highlight the potential of incorporating Ising formulations for optimization tasks but also show their limitations when used to compute design updates in an iterative optimization process. In conclusion, this work provides an efficient alternative for design updates in topology optimization and enhances the understanding of integrating Ising machine formulations in engineering optimization
Exhausted culture media reuse in autotrophic microalgae production: Optimization and modelling of Pseudococcomyxa simplex cultures
Get PDFThis study investigated strategies to reduce the water footprint in autotrophic microalgae cultivation by recycling exhausted culture medium under semi-continuous operation. Pseudococcomyxa simplex, a polyextremotolerant strain, was evaluated for medium reuse suitability. Experimental results demonstrated stable biomass productivity (∼0.2 g·L⁻¹·day⁻¹) over 30 days at a purge ratio of 30 % and dilution rate of 0.19 day⁻¹, reducing water consumption from 1000 to 320 kg·kg⁻¹ biomass and lowering medium costs to 0.05 €·g⁻¹. Full medium recycling, even with nitrogen supplementation, caused growth inhibition due to impaired photosystem II efficiency and chlorophyll synthesis. Partial recycling maintained the biochemical profiles, with stable proteins and lipids and a slight increase in carbohydrates at higher purge ratios. ASPEN PLUS® simulations provided mass and energy balances, CO₂ absorption dynamics, and water loss estimates, confirming experimental trends and identifying optimal operating conditions for maximizing biomass and metabolite yields while minimizing environmental impact. Limitations in modeling nitrogen uptake suggest the need for advanced kinetic–stoichiometric models to improve scalability. This integrated experimental-modeling approach demonstrates that controlled medium recycling significantly enhances process sustainability without compromising productivity, providing critical insights into sustainable bioprocess optimization
All-Inorganic TiO₂ Nanoparticle-Based Metalenses Manufactured by Direct Nanoimprint Lithography for High Energy Applications: Femtosecond Laser-Induced Damage Threshold Testing
No full textFemtosecond laser-induced damage threshold (LIDT) testing is carried out at 515 nm on 4-mm-sized metalens arrays that are manufactured by direct nanoimprinting of a TiO₂ nanoparticle (NP)-based ink containing either polymeric or inorganic binders. The all-inorganic TiO₂ metalenses exhibit ≈80% absolute focusing efficiency and demonstrate an LIDT of ≈90 mJ cm⁻² based on a single-shot determination using Liu's method, while the metalenses with the polymeric binder achieve ≈137 mJ cm⁻² and an efficiency of ≈76%. Despite the higher LIDT of the TiO₂-polymer composite metalenses in the single-shot experiment, these lenses exhibit significant damage at fluences as low as ≈8 mJ cm⁻² when subjected to ≈6 × 10⁸ pulses at 60 kHz. On the other hand, the all-inorganic metalenses remain intact under identical conditions at ≈64 mJ cm⁻². That is, the inorganic binder provides superior long-term stability relative to the polymeric binder and is a more viable solution for high-energy applications. Structural damages observed in nanostructures result in a reduced deflection efficiency and increase light scattering at the focal plane of the metalens. The LIDT testing is also performed in the nanosecond regime at 532 and 1064 nm with the all-inorganic metalenses, yielding thresholds of ≈0.5 and ≈5 J cm⁻², respectively