Numerical simulation and investigation of induction through-heaters in dynamic operation mode

Purpose - Because of their widespread use in industry, induction through-heaters of various metal products must be of high effectiveness not only in "quasi" steady-state operation but in different transient modes as well. Nowadays, they are usually designed to provide the required characteristics in "quasi" steady-state operation mode mainly. The purpose of this paper is to examine numerical simulation of transient processes in induction through-heating lines generally and investigate dynamic temperature fields during the first start of the heaters particularly. Design/methodology/ approach - The research methodology is based on coupled numerical electromagnetic and thermal analyses using FEM approach. ANSYS simulations are supported with the developed tools for imitation of mass transfer effects in continuous induction heating lines. Findings - The results show that transient temperature fields in the heated strip or slab significantly differ from their "quasi" steady-state descriptions. Local temperature variations acquired in longitudinal as well as transverse flux induction heaters during the first start have been predicted. Practical implications - The received results can be used for design of induction through-heaters and improvement of their characteristics in dynamic operation modes. Originality/value - Investigation of dynamic characteristics of the heaters in dynamic modes can be only done by numerical modelling based on special algorithms providing a time loop additional to coupling between electromagnetic and thermal analyses. Such algorithms have been developed and used for investigation of two types of induction installations: through-heaters of cylindrical billets for forging and heating lines of strip or thin slab for rolling mills. © 2011 Emerald Group Publishing Limited. All rights reserved

Design of a medium voltage generator with dc-cascade for high power wind energy conversion systems

This paper shows a new concept to generate medium voltage (MV) in wind power application to avoid an additional transformer. Therefore, the generator must be redesigned with additional constraints and a new topology for the power rectifier system by using multiple low voltage (LV) power rectifiers connected in series and parallel to increase the DC output voltage. The combination of parallel and series connection of rectifiers is further introduced as DC-cascade. With the resulting DC-cascade, medium output voltage is achieved with low voltage rectifiers and without a bulky transformer. This approach to form a DC-cascade reduces the effort required to achieve medium DC voltage with a simple rectifier system. In this context, a suitable DC-cascade control was presented and verified with a laboratory test setup. A gearless synchronous generator, which is highly segmented so that each segment can be connected to its own power rectifier, is investigated. Due to the mixed AC and DC voltage given by the DC-cascade structure, it becomes more demanding to the design of the generator insulation, which influences the copper fill factor and the design of the cooling system. A design strategy for the overall generator design is carried out considering the new boundary conditions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Towards a new therapy concept for acute microbial karatides, including Acanthamoebae

Purpose The purpose of this study was to develop novel therapeutic approaches for the management and treatment of microbial keratitides, especially pathologies resulting from Acantamoeba castellanii inoculations. Methods Growth inhibitory effects of plasma-induced reactive species on cultures of Staphylococcus aureus, Pseudomonas aeruginosa, Acantamoeba castellanii, and MRSA were assayed for in in an in-vitro setting. Human donor corneas were inoculated and cultured with cultures of above pathogens, followed by staining of cells and microscopic analysis. Results Our results show a substantial inhibitory effect of plasma-induced reactive species on the growth and migration of the pathogens tested. Conclusions The effects observed provide foundation for the development of new avenues for the management and therapy of microbial keratitides

Plasma Activation as a Powerful Tool for Selective Modification of Cellulose Fibers towards Biomedical Applications

Cellulosic substrates are known for their biocompatibility, non-cytotoxicity, hypoallergenicity and sterilizability. It is therefore desirable to have a bundle of methods to equip them with tailored properties such as affinity profiles for various applications. In the case of highly swelling materials such as cellulose sponges, “dry” functionalization using plasma activation is the method of choice. The purpose of the study was to adapt low-pressure plasma technology for targeted cellulose modification. Using plasma (pre-) treatment combined with gaseous reactants like O2, ethylene oxide or silane, three different cellulose modifications were obtained and characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Swelling measurements and bacterial adhesion tests revealed distinctive material properties compared to educt. The development of these non-aqueous methods demonstrated an effective procedural route towards modified cellulosic materials for usage in wound dressing, micro patterned assays or bacterial filtration

«Magnetic Micro-Actuators (MAGMAS)

International audienc

Design of a Medium Voltage Generator with DC-Cascade for High Power Wind Energy Conversion Systems

This paper shows a new concept to generate medium voltage (MV) in wind power application to avoid an additional transformer. Therefore, the generator must be redesigned with additional constraints and a new topology for the power rectifier system by using multiple low voltage (LV) power rectifiers connected in series and parallel to increase the DC output voltage. The combination of parallel and series connection of rectifiers is further introduced as DC-cascade. With the resulting DC-cascade, medium output voltage is achieved with low voltage rectifiers and without a bulky transformer. This approach to form a DC-cascade reduces the effort required to achieve medium DC voltage with a simple rectifier system. In this context, a suitable DC-cascade control was presented and verified with a laboratory test setup. A gearless synchronous generator, which is highly segmented so that each segment can be connected to its own power rectifier, is investigated. Due to the mixed AC and DC voltage given by the DC-cascade structure, it becomes more demanding to the design of the generator insulation, which influences the copper fill factor and the design of the cooling system. A design strategy for the overall generator design is carried out considering the new boundary conditions

Functional Glyco-Nanogels for Multivalent Interaction with Lectins

Interactions between glycans and proteins have tremendous impact in biomolecular interactions. They are important for cell–cell interactions, proliferation and much more. Here, we emphasize the glycan-mediated interactions between pathogens and host cells. Pseudomonas aeruginosa, responsible for a huge number of nosocomial infections, is especially the focus when it comes to glycan-derivatives as pathoblockers. We present a microwave assisted protecting group free synthesis of glycomonomers based on lactose, melibiose and fucose. The monomers were polymerized in a precipitation polymerization in the presence of NiPAm to form crosslinked glyco-nanogels. The influence of reaction parameters like crosslinker type or stabilizer amount was investigated. The gels were characterized in lectin binding studies using model lectins and showed size and composition-dependent inhibition of lectin binding. Due to multivalent presentation of glycans in the gel, the inhibition was clearly stronger than with unmodified saccharides, which was compared after determination of the glycan loading. First studies with Pseudomonas aeruginosa revealed a surprising influence on the secretion of virulence factors. Functional glycogels may be in the future potent alternatives or adjuvants for antibiotic treatment of infections based on glycan interactions between host and pathogen