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Development and Testing of the A1 Volumetric Air Sampler, an Automatic Pollen Trap Suitable for Long-Term Monitoring of eDNA Pollen Diversity
(2022-08-29)
Airborne pollen surveys provide information on various aspects of biodiversity and human health monitoring. Such surveys are typically conducted using the Burkard Multi-Vial Cyclone Sampler, but have to be technically optimized for eDNA barcoding. We here developed and tested a new airborne pollen trap, especially suitable for autonomous eDNA-metabarcoding analyses, called the A1 volumetric air sampler. The trap can sample pollen in 24 different tubes with flexible intervals, allowing it to operate independently in ...
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Receding-Horizon Control of Constrained Switched Systems with Neural Networks as Parametric Function Approximators
(2022-11-21)
This work studies receding-horizon control of discrete-time switched linear systems subject to polytopic constraints for the continuous states and inputs. The objective is to approximate the optimal receding-horizon control strategy for cases in which the online computation is intractable due to the necessity of solving mixed-integer quadratic programs in each discrete time instant. The proposed approach builds upon an approximated optimal finite-horizon control law in closed-loop form with guaranteed constraint ...
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Shearographic Detection of Internal Defects in Austenitic Stainless Steels
(2022-12-28)
Despite the formation of a passive layer, corrosion also occurs in austenitic stainless steels. One of the most common and most dangerous types is pitting corrosion, in which the material beneath the surface is completely dissolved. Since this type of corrosion only produces small holes on the surface, it is difficult to detect without nondestructive testing. This paper presents induction-excited shearography as an optical, nondestructive testing method for quick inspection of inner defects and corrosion. The ...
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Grain growth and precipitation behaviour of AISI 430 ferritic stainless steel subjected to pulsed laser beam welding using free-form pulse shaping
(2022-10-26)
Ferritic stainless steels are prone to grain coarsening and precipitation of chromium-rich grain boundary phases during fusion welding, which increase intergranular corrosion susceptibility. State-of-the-art techniques to overcome these challenges mainly feature heterogeneous nucleating agents with regard to grain coarsening or alternating alloy concepts as well as post-weld heat treatments as for restoration of intergranular corrosion resistance. The present investigation seeks to depart from these traditional ...
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Dissimilar micro beam welding of titanium to Nitinol and stainless steel using biocompatible filler materials for medical applications
(2022-11-16)
In the present investigation, thin sheet geometries of commercially pure titanium (cp, grade 4) are butt-welded to AISI 316L stainless steel as well as Nitinol by means of micro electron beam welding using filler materials. In order to avoid mixing of the base materials, the refractory metals tantalum, niobium and hafnium are applied as intermediate layers. Owing to the biocompatibility of these filler materials, the final products are suitable for medical technology applications. In combination with low energy inputs ...
Aufsatz
Influence of Fiber Volume in Hybrid Short Glass/Cellulose Reinforced Thermoplastic Compounds
(2022-09-22)
Glass fibers (GF) and regenerated cellulose fibers (RCF) are possible partners in the hybrid reinforcement of thermoplastics because of their different properties. Due to the weak bonding properties of polypropylene, coupling agents are used and the fiber volume content is set high to achieve high reinforcing effects. A lower fiber content of GF can raise the toughness properties of a reinforced polypropylene which is investigated in this study with different ratios of GF and RCF.
The composites are tested in tensile ...
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Metastable CrMnNi steels processed by laser powder bed fusion: experimental assessment of elementary mechanisms contributing to microstructure, properties and residual stress
(2022-12-18)
The complex thermal history imposed by the laser-based powder bed fusion of metals (PBF-LB/M) process is known to promote the evolution of unique microstructures. In the present study, metastable CrMnNi steels with different nickel contents and, thus, different phase stabilities are manufactured by PBF-LB/M. Results clearly reveal that an adequate choice of materials will allow to tailor mechanical properties as well as residual stress states in the as-built material to eventually redundantize any thermal post-treatment. ...
Aufsatz
Three‑dimensional close‑to‑substrate trajectories of magnetic microparticles in dynamically changing magnetic field landscapes
(2022-12-03)
The transport of magnetic particles (MPs) by dynamic magnetic field landscapes (MFLs) using magnetically patterned substrates is promising for the development of Lab‑on‑a‑chip (LOC) systems. The inherent close‑to‑substrate MP motion is sensitive to changing particle–substrate interactions. Thus, the detection of a modified particle–substrate separation distance caused by surface binding of an analyte is expected to be a promising probe in analytics and diagnostics. Here, we present an essential prerequisite for such ...
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The role of design patterns in the development and legal assessment of lawful technologies
(2022-10-22)
Novel technologies such as smart personal assistants integrate digital services into everyday life. These services use personal data to offer personalized services. While they are subject to special data protection regulations at the time of development, there are few guidelines describing the transition from legal requirements to implementation. To reduce risks, services depend on external legal assessments. With developers and legal experts often missing either legal or technical knowledge, the challenge lies in ...
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Cooling rate as a process parameter in advanced roll forming to tailor microstructure,mechanical and corrosion properties of EN AW 7075 tubes
(2022-12-14)
The effects of solution heat treatment parameters and quench media as a processing tool for tailoring microstructure, mechanical and corrosion properties in roll forming of EN AW 7075 alloy were studied. The highest yield stress and ultimate tensile strength were obtained for the specimens quenched in water, while the air-cooled specimens exhibited inferior mechanical properties. Microstructural analysis of specimens showed that except water-quenched specimens, the parts cooled/quenched in oil, in direct contact with ...