@incollection{KrauseUlke2024, author = {Krause, Thomas and Ulke, Bernd}, title = {Bauabrechnung und Mengenermittlung}, series = {Zahlentafeln f{\"u}r den Baubetrieb}, booktitle = {Zahlentafeln f{\"u}r den Baubetrieb}, editor = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41329-3 (Print)}, doi = {10.1007/978-3-658-41330-9_7}, pages = {333 -- 397}, year = {2024}, abstract = {n diesem Kapitel werden die Abrechnungsvorschriften wichtiger ATV kurz, aber umfassend zusammengestellt. Einigen Abrechnungsbestimmungen f{\"u}r Einzelleistungen, die keine Nebenleistungen sind ((siehe DIN 18299 und Abschnitt 4 der jeweiligen ATV), sind mit aufgenommen worden; die ATV enthalten jedoch weitergehende Festlegungen {\"u}ber Nebenleistungen und Besondere Leistungen. Im Anschluss folgen Hinweise zu den Toleranzen im Hochbau sowie im Straßenbau.}, language = {de} } @incollection{Ferger2024, author = {Ferger, Martin}, title = {Arbeitsvorbereitung und Ablaufplanung}, series = {Zahlentafeln f{\"u}r den Baubetrieb}, booktitle = {Zahlentafeln f{\"u}r den Baubetrieb}, editor = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41329-3 (Print)}, doi = {10.1007/978-3-658-41330-9_6}, pages = {299 -- 332}, year = {2024}, abstract = {Die Arbeitsvorbereitung, als ein wesentliches Aufgabengebiet des Baubetriebswesens, ist von enormer Bedeutung f{\"u}r den Erfolg eines Bauprojektes. Die Arbeitsvorbereitung l{\"a}sst sich zeitlich sowohl in der Angebotsphase (kalkulationsbegleitende Arbeitsvorbereitung), in der Vorbereitungsphase der Baustelle (von Auftragsvergabe bis Baubeginn) als auch baubegleitend einordnen.}, language = {de} } @incollection{Ulke2024, author = {Ulke, Bernd}, title = {{\"O}ffentliches Baurecht, Ausschreibung und Vergabe}, series = {Zahlentafeln f{\"u}r den Baubetrieb}, booktitle = {Zahlentafeln f{\"u}r den Baubetrieb}, editor = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41329-3 (Print)}, doi = {10.1007/978-3-658-41330-9_5}, pages = {263 -- 297}, year = {2024}, abstract = {Durch das {\"o}ffentliche Baurecht werden die Zul{\"a}ssigkeit, die Grenzen, die Ordnung und die F{\"o}rderung der baulichen Nutzung des Bodens geregelt. Die Ausschreibung und die Vergabe sind von essenzieller Bedeutung f{\"u}r ein Bauvorhaben und werden deshalb in der HOAI mit zwei Leistungsphasen abgebildet: n{\"a}mlich mit der Leistungsphase 6 Vorbereitung der Vergabe sowie der Leistungsphase 7 Mitwirkung bei der Vergabe. Im Zuge der Ausschreibung und der Vergabe werden die f{\"u}r den AG anfallenden Kosten festgelegt und bilden somit die letzte gr{\"o}ßere Stellschraube f{\"u}r Preiseinsparungen.}, language = {de} } @incollection{Ulke2024, author = {Ulke, Bernd}, title = {Bauwirtschaft}, series = {Zahlentafeln f{\"u}r den Baubetrieb}, booktitle = {Zahlentafeln f{\"u}r den Baubetrieb}, editor = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41329-3 (Print)}, doi = {10.1007/978-3-658-41330-9_4}, pages = {17 -- 261}, year = {2024}, abstract = {Die Leistungen der Bauwirtschaft und deren wirtschaftliche Bedeutung in Deutschland werden anhand einer Vielzahl statistischer Daten verdeutlicht. Die im Vergleich zu anderen Wirtschaftsbereichen auftretenden branchenspezifischen Besonderheiten der Bauwirtschaft werden anhand von verschiedenen Kriterien herausgearbeitet. Das Zusammenspiel der einzelnen Akteure des Sektors und die dabei sich ergebenden bzw. zu beachtenden Rechts- und Vertragsgrundlagen werden dargestellt. Aufgrund der meist erheblichen H{\"o}he des eingesetzten Kapitals werden auch notwendige Formen der Risikoabsicherungen und der in der Branche {\"u}blichen und teilweise vorgeschriebenen Versicherungsm{\"o}glichkeiten angesprochen.}, language = {de} } @incollection{RickerUlke2024, author = {Ricker, Marcus and Ulke, Bernd}, title = {Baustoffe}, series = {Zahlentafeln f{\"u}r den Baubetrieb}, booktitle = {Zahlentafeln f{\"u}r den Baubetrieb}, editor = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41329-3 (Print)}, doi = {10.1007/978-3-658-41330-9_2}, pages = {61 -- 148}, year = {2024}, abstract = {In diesem Kapitel werden die Eigenschaften der Baustoffe Bitumen, Beton und Mauerwerk insbesondere unter dem Aspekt der Anwendung im Baustellenbetrieb dargestellt.}, language = {de} } @book{KrauseUlkeFerger2024, author = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, title = {Zahlentafeln f{\"u}r den Baubetrieb}, editor = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, edition = {10. Auflage}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41329-3 (Print)}, doi = {10.1007/978-3-658-41330-9}, pages = {XII, 1087 Seiten}, year = {2024}, language = {de} } @article{PogorelovaRogachevAkimbekovetal.2024, author = {Pogorelova, Natalia and Rogachev, Evgeniy and Akimbekov, Nuraly and Digel, Ilya}, title = {Effect of dehydration method on the micro- and nanomorphological properties of bacterial cellulose produced by Medusomyces gisevii on different substrates}, series = {Journal of materials science}, volume = {2024}, journal = {Journal of materials science}, publisher = {Springer Science + Business Media}, address = {Dordrecht}, issn = {1573-4803 (Online)}, doi = {10.1007/s10853-024-09596-3}, pages = {13 Seiten}, year = {2024}, abstract = {Many important properties of bacterial cellulose (BC), such as moisture absorption capacity, elasticity and tensile strength, largely depend on its structure. This paper presents a study on the effect of the drying method on BC films produced by Medusomyces gisevii using two different procedures: room temperature drying (RT, (24 ± 2 °C, humidity 65 ± 1\%, dried until a constant weight was reached) and freeze-drying (FD, treated at - 75 °C for 48 h). BC was synthesized using one of two different carbon sources—either glucose or sucrose. Structural differences in the obtained BC films were evaluated using atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction. Macroscopically, the RT samples appeared semi-transparent and smooth, whereas the FD group exhibited an opaque white color and sponge-like structure. SEM examination showed denser packing of fibrils in FD samples while RT-samples displayed smaller average fiber diameter, lower surface roughness and less porosity. AFM confirmed the SEM observations and showed that the FD material exhibited a more branched structure and a higher surface roughness. The samples cultivated in a glucose-containing nutrient medium, generally displayed a straight and ordered shape of fibrils compared to the sucrose-derived BC, characterized by a rougher and wavier structure. The BC films dried under different conditions showed distinctly different crystallinity degrees, whereas the carbon source in the culture medium was found to have a relatively small effect on the BC crystallinity.}, language = {en} } @article{BertzSchoeningMolinnusetal.2024, author = {Bertz, Morten and Sch{\"o}ning, Michael Josef and Molinnus, Denise and Homma, Takayuki}, title = {Influence of temperature, light, and H₂O₂ concentration on microbial spore inactivation: in-situ Raman spectroscopy combined with optical trapping}, series = {Physica status solidi (a) applications and materials science}, journal = {Physica status solidi (a) applications and materials science}, number = {Early View}, publisher = {Wiley-VCH}, address = {Berlin}, issn = {1862-6319 (Online)}, doi = {10.1002/pssa.202300866}, pages = {8 Seiten}, year = {2024}, abstract = {To gain insight on chemical sterilization processes, the influence of temperature (up to 70 °C), intense green light, and hydrogen peroxide (H₂O₂) concentration (up to 30\% in aqueous solution) on microbial spore inactivation is evaluated by in-situ Raman spectroscopy with an optical trap. Bacillus atrophaeus is utilized as a model organism. Individual spores are isolated and their chemical makeup is monitored under dynamically changing conditions (temperature, light, and H₂O₂ concentration) to mimic industrially relevant process parameters for sterilization in the field of aseptic food processing. While isolated spores in water are highly stable, even at elevated temperatures of 70 °C, exposure to H₂O₂ leads to a loss of spore integrity characterized by the release of the key spore biomarker dipicolinic acid (DPA) in a concentration-dependent manner, which indicates damage to the inner membrane of the spore. Intensive light or heat, both of which accelerate the decomposition of H₂O₂ into reactive oxygen species (ROS), drastically shorten the spore lifetime, suggesting the formation of ROS as a rate-limiting step during sterilization. It is concluded that Raman spectroscopy can deliver mechanistic insight into the mode of action of H₂O₂-based sterilization and reveal the individual contributions of different sterilization methods acting in tandem.}, language = {en} } @masterthesis{Albrecht2024, type = {Bachelor Thesis}, author = {Albrecht, Dustin}, title = {„ARRK Journeys" Filmformat-Konzept}, publisher = {FH Aachen}, address = {Aachen}, pages = {26 Seiten}, year = {2024}, abstract = {Das Projekt "ARRK Journeys" entwickelt ein neues Dokumentarfilm-Format, das darauf abzielt, potenzielle Mitarbeiter f{\"u}r die ARRK Engineering GmbH zu gewinnen Das Ziel des Projekts ist es, die Vielfalt an Karrierem{\"o}glichkeiten bei der ARRK Engineering GmbH aufzuzeigen und die Attraktivit{\"a}t des Unternehmens als Arbeitgeber zu betonen. Durch individuelle Mitarbeitergeschichten werden die Fragen beantwortet, warum eine berufliche Laufbahn bei ARRK erstrebenswert ist, ob jeder die M{\"o}glichkeit hat, bei ARRK zu arbeiten, und welche Entwicklungsm{\"o}glichkeiten das Unternehmen bietet. "ARRK Journeys" betont das Wohlbefinden der Mitarbeiter und ihre pers{\"o}nliche Bindung zum Unternehmen, um eine positive Arbeitgebermarke zu schaffen. "ARRK Journeys" pr{\"a}sentiert die ARRK Engineering GmbH als attraktiven Arbeitgeber und inspiriert potenzielle Mitarbeiter dazu, ihren eigenen Weg zu finden.}, language = {de} } @masterthesis{Erkens2024, type = {Bachelor Thesis}, author = {Erkens, Cedric}, title = {En(Joy)Chroma : Entwicklung einer medien{\"u}bergreifenden Werbekampagne f{\"u}r den Brillenhersteller EnChroma}, publisher = {FH Aachen}, address = {Aachen}, school = {Fachhochschule Aachen}, pages = {133 Seiten}, year = {2024}, abstract = {Weltweit sind 350 Millionen Menschen von Farbenfehlsichtigkeit betroffen, doch nur wenige wissen, dass es eine L{\"o}sung f{\"u}r genau dieses Problem gibt. Die ausgearbeitete Werbekampagne und neue Markenkommunikation f{\"u}r EnChroma soll genau diese Menschen ermutigen, sich mit ihrer Krankheit auseinanderzusetzen und das breite Konzept der L{\"o}sung zu verstehen. Die speziellen Brillen erm{\"o}glichen es den Menschen, Farben im Alltag und Berufsleben in echt wahrzunehmen und diese besser differenzieren zu k{\"o}nnen. Unsere Welt ist farbcodiert und deshalb ist es besonders wichtig, dass diese Menschen auf das Produkt aufmerksam gemacht werden.}, language = {de} } @masterthesis{Fleischer2024, type = {Bachelor Thesis}, author = {Fleischer, Rebekka}, title = {Bringing brand experience to marketplaces : ein Online-Marktplatz, der Konsument und Marke verbindet}, publisher = {FH Aachen}, address = {Aachen}, school = {Fachhochschule Aachen}, pages = {101 Seiten}, year = {2024}, abstract = {«Keno» zeigt ein Konzept f{\"u}r einen Online-Marktplatz im Fashion-Segment, mit Fokus auf individueller Beratung, digitaler Anprobe und visueller sowie informativer Pr{\"a}sentation der Marken. Marktpl{\"a}tze werden aufgrund von großer Auswahl und Vertrauensw{\"u}rdigkeit von Konsument:innen bevorzugt aufgesucht. Durch die immersive Darstellung an einem maßgetreuen Avatar und die Einbindung der Marke in das Einkaufserlebnis soll hier die Zahl der Retouren verringert und die Kund:innenzufriedenheit gesteigert werden. Mittels nutzerorientierter Strategien und der Gestaltung eines Designsystems bekam «Keno» seinen Look. Dabei fanden modernste Techniken wie k{\"u}nstliche Intelligenzen und Design Token Systeme Verwendung. Das Projekt zeigt letztendlich M{\"o}glichkeiten auf, wie ein Marktplatz durch Brand Experience, Onlineshopping-Wege verk{\"u}rzen und zu mehr Nachhaltigkeit im E-Commerce beitragen kann.}, language = {de} } @article{HafidiElHatkaSchmitzetal.2024, author = {Hafidi, Youssef and El Hatka, Hicham and Schmitz, Dominik and Krauss, Manuel and Pettrak, J{\"u}rgen and Biel, Markus and Ittobane, Najim}, title = {Sustainable soil additives for water and micronutrient supply: swelling and chelating properties of polyaspartic acid hydrogels utilizing newly developed crosslinkers}, series = {Gels}, volume = {10}, journal = {Gels}, number = {3}, publisher = {MDPI}, address = {Basel}, issn = {2310-2861}, doi = {10.3390/gels10030170}, pages = {Artikel 170}, year = {2024}, abstract = {Drought and water shortage are serious problems in many arid and semi-arid regions. This problem is getting worse and even continues in temperate climatic regions due to climate change. To address this problem, the use of biodegradable hydrogels is increasingly important for the application as water-retaining additives in soil. Furthermore, efficient (micro-)nutrient supply can be provided by the use of tailored hydrogels. Biodegradable polyaspartic acid (PASP) hydrogels with different available (1,6-hexamethylene diamine (HMD) and L-lysine (LYS)) and newly developed crosslinkers based on diesters of glycine (GLY) and (di-)ethylene glycol (DEG and EG, respectively) were synthesized and characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) and regarding their swelling properties (kinetic, absorbency under load (AUL)) as well as biodegradability of PASP hydrogel. Copper (II) and zinc (II), respectively, were loaded as micronutrients in two different approaches: in situ with crosslinking and subsequent loading of prepared hydrogels. The results showed successful syntheses of di-glycine-ester-based crosslinkers. Hydrogels with good water-absorbing properties were formed. Moreover, the developed crosslinking agents in combination with the specific reaction conditions resulted in higher water absorbency with increased crosslinker content used in synthesis (10\% vs. 20\%). The prepared hydrogels are candidates for water-storing soil additives due to the biodegradability of PASP, which is shown in an exemple. The incorporation of Cu(II) and Zn(II) ions can provide these micronutrients for plant growth.}, language = {en} } @techreport{Drescher2024, type = {Working Paper}, author = {Drescher, Hans Paul}, title = {Critical review of the 1. Stokes' problem and consequences for mixed turbulent/laminar flow}, pages = {27 Seiten}, year = {2024}, abstract = {The "1. Stokes' problem", the "suddenly accelerated flat wall", is the oldest application of the Navier-Stokes equations. Stokes' solution of the "problem" does not comply with the mathematical theorem of Cauchy and Kowalewskaya on the "Uniqueness and Existence" of solutions of partial differential equations and violates the physical theorem of minimum entropy production/dissipation of the Thermodynamics of Irreversible Processes. The result includes very high local shear stresses and dissipation rates. That is of special interest for the theory of turbulent and mixed turbulent/laminar flow. A textbook solution of the "1. Stokes Problem" is the Couette flow, which has a constant sheer stress along a linear profile. A consequence is that the Navier-Stokes equations do not describe any S-shaped part of a turbulent profile found in any turbulent Couette experiment. The paper surveys arguments referring to that statement, concerning the history of >150 years. Contrary to this there is always a Navier-Stokes solution near the wall, observed by a linear part of the Couette profile. There a turbulent description (e.g. by the logarithmic law-of-the-wall) fails completely. That is explained by the minimum dissipation requirement together with the Couette feature τ = const. The local co-existence of a turbulent zone and a laminar zone near the wall is stable and observed also at high Reynolds-Numbers.}, language = {en} } @misc{Huening2024, author = {H{\"u}ning, Felix}, title = {Positionssensorvorrichtung}, year = {2024}, abstract = {Die Erfindung betrifft eine Positionssensorvorrichtung zur Bestimmung einer Absolutposition eines beweglichen ersten Teils relativ zu einem ortsfesten zweiten Teil mit einem mit dem beweglichen ersten Teil gekoppelter Codek{\"o}rper, der dazu eingerichtet ist, eine Codespur mit einer Mehrzahl von in Spurrichtung aufeinanderfolgenden Codeelementen zu enthalten zur Bildung eines Codewortes, mit einer magnetischen Detektionseinrichtung zur Detektion der Codespur, wobei die Detektionseinrichtung zum einen an dem Codek{\"o}rper befestigte und entlang der Spurrichtung in einem solchen Abstand gegenpolig zueinander angeordnete Permanentmagneten aufweist, dass der Abstand mit einer vorgegebenen L{\"a}nge der jeweiligen Codeelemente {\"u}bereinstimmt, und zum anderen eine Anzahl von ortsfest und quer zu dem Codek{\"o}rper versetzt angeordnete Wiegandsensoren aufweist, wobei der Abstand des Wiegandsensors zu einer Erstreckungsebene der Permanentmagneten derart gew{\"a}hlt ist, dass bei {\"U}berdeckung des Wiegandsensors durch den Permanentmagneten ein Wiegandpuls in dem Wiegandsensor induziert wird.}, language = {de} } @inproceedings{NeumannAdamBackesetal.2021, author = {Neumann, Hannah and Adam, Mario and Backes, Klaus and B{\"o}rner, Martin and Clees, Tanja and Doetsch, Christian and Glaeser, Susanne and Herrmann, Ulf and May, Johanna and Rosenthal, Florian and Sauer, Dirk Uwe and Stadler, Ingo}, title = {Development of open educational resources for renewable energy and the energy transition process}, series = {ISES SWC 2021}, booktitle = {ISES SWC 2021}, publisher = {International Solar Energy Society}, address = {Freiburg}, doi = {10.18086/swc.2021.47.03}, pages = {6 Seiten}, year = {2021}, abstract = {The dissemination of knowledge about renewable energies is understood as a social task with the highest topicality. The transfer of teaching content on renewable energies into digital open educational resources offers the opportunity to significantly accelerate the implementation of the energy transition. Thus, in the here presented project six German universities create open educational resources for the energy transition. These materials are available to the public on the internet under a free license. So far there has been no publicly accessible, editable media that cover entire learning units about renewable energies extensively and in high technical quality. Thus, in this project, the content that remains up-to-date for a longer period is appropriately prepared in terms of media didactics. The materials enable lecturers to provide students with in-depth training about technologies for the energy transition. In a particular way, the created material is also suitable for making the general public knowledgeable about the energy transition with scientifically based material.}, language = {en} } @inproceedings{NiederwestbergSchneiderTeixeiraBouraetal.2022, author = {Niederwestberg, Stefan and Schneider, Falko and Teixeira Boura, Cristiano Jos{\´e} and Herrmann, Ulf}, title = {Introduction to a direct irradiated transparent tube particle receiver}, series = {SOLARPACES 2020}, booktitle = {SOLARPACES 2020}, number = {2445 / 1}, publisher = {AIP conference proceedings / American Institute of Physics}, address = {Melville, NY}, isbn = {978-0-7354-4195-8}, issn = {1551-7616 (online)}, doi = {10.1063/5.0086735}, pages = {9 Seiten}, year = {2022}, abstract = {New materials often lead to innovations and advantages in technical applications. This also applies to the particle receiver proposed in this work that deploys high-temperature and scratch resistant transparent ceramics. With this receiver design, particles are heated through direct-contact concentrated solar irradiance while flowing downwards through tubular transparent ceramics from top to bottom. In this paper, the developed particle receiver as well as advantages and disadvantages are described. Investigations on the particle heat-up characteristics from solar irradiance were carried out with DEM simulations which indicate that particle temperatures can reach up to 1200 K. Additionally, a simulation model was set up for investigating the dynamic behavior. A test receiver at laboratory scale has been designed and is currently being built. In upcoming tests, the receiver test rig will be used to validate the simulation results. The design and the measurement equipment is described in this work.}, language = {en} } @inproceedings{CaminosSchmitzAttietal.2022, author = {Caminos, Ricardo Alexander Chico and Schmitz, Pascal and Atti, Vikrama and Mahdi, Zahra and Teixeira Boura, Cristiano Jos{\´e} and Sattler, Johannes Christoph and Herrmann, Ulf and Hilger, Patrick and Dieckmann, Simon}, title = {Development of a micro heliostat and optical qualification assessment with a 3D laser scanning method}, series = {SOLARPACES 2020}, booktitle = {SOLARPACES 2020}, number = {2445 / 1}, publisher = {AIP conference proceedings / American Institute of Physics}, address = {Melville, NY}, isbn = {978-0-7354-4195-8}, issn = {1551-7616 (online)}, doi = {10.1063/5.0086262}, pages = {8 Seiten}, year = {2022}, abstract = {The Solar-Institut J{\"u}lich (SIJ) and the companies Hilger GmbH and Heliokon GmbH from Germany have developed a small-scale cost-effective heliostat, called "micro heliostat". Micro heliostats can be deployed in small-scale concentrated solar power (CSP) plants to concentrate the sun's radiation for electricity generation, space or domestic water heating or industrial process heat. In contrast to conventional heliostats, the special feature of a micro heliostat is that it consists of dozens of parallel-moving, interconnected, rotatable mirror facets. The mirror facets array is fixed inside a box-shaped module and is protected from weathering and wind forces by a transparent glass cover. The choice of the building materials for the box, tracking mechanism and mirrors is largely dependent on the selected production process and the intended application of the micro heliostat. Special attention was paid to the material of the tracking mechanism as this has a direct influence on the accuracy of the micro heliostat. The choice of materials for the mirror support structure and the tracking mechanism is made in favor of plastic molded parts. A qualification assessment method has been developed by the SIJ in which a 3D laser scanner is used in combination with a coordinate measuring machine (CMM). For the validation of this assessment method, a single mirror facet was scanned and the slope deviation was computed.}, language = {en} } @inproceedings{ZahraPhaniSrujanCaminosetal.2022, author = {Zahra, Mahdi and Phani Srujan, Merige and Caminos, Ricardo Alexander Chico and Schmitz, Pascal and Herrmann, Ulf and Teixeira Boura, Cristiano Jos{\´e} and Schmitz, Mark and Gielen, Hans and Gedle, Yibekal and Dersch, J{\"u}rgen}, title = {Modeling the thermal behavior of solar salt in electrical resistance heaters for the application in PV-CSP hybrid power plants}, series = {SOLARPACES 2020}, booktitle = {SOLARPACES 2020}, number = {2445 / 1}, publisher = {AIP conference proceedings / American Institute of Physics}, address = {Melville, NY}, isbn = {978-0-7354-4195-8}, issn = {1551-7616 (online)}, doi = {10.1063/5.0086268}, pages = {9 Seiten}, year = {2022}, abstract = {Concentrated Solar Power (CSP) systems are able to store energy cost-effectively in their integrated thermal energy storage (TES). By intelligently combining Photovoltaics (PV) systems with CSP, a further cost reduction of solar power plants is expected, as well as an increase in dispatchability and flexibility of power generation. PV-powered Resistance Heaters (RH) can be deployed to raise the temperature of the molten salt hot storage from 385 °C up to 565 °C in a Parabolic Trough Collector (PTC) plant. To avoid freezing and decomposition of molten salt, the temperature distribution in the electrical resistance heater is investigated in the present study. For this purpose, a RH has been modeled and CFD simulations have been performed. The simulation results show that the hottest regions occur on the electric rod surface behind the last baffle. A technical optimization was performed by adjusting three parameters: Shell-baffle clearance, electric rod-baffle clearance and number of baffles. After the technical optimization was carried out, the temperature difference between the maximum temperature and the average outlet temperature of the salt is within the acceptable limits, thus critical salt decomposition has been avoided. Additionally, the CFD simulations results were analyzed and compared with results obtained with a one-dimensional model in Modelica.}, language = {en} } @article{ZhenLiangStaatetal.2024, author = {Zhen, Manghao and Liang, Yunpei and Staat, Manfred and Li, Quanqui and Li, Jianbo}, title = {Discontinuous fracture behaviors and constitutive model of sandstone specimens containing non-parallel prefabricated fissures under uniaxial compression}, series = {Theoretical and Applied Fracture Mechanics}, volume = {131}, journal = {Theoretical and Applied Fracture Mechanics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-8442}, doi = {10.1016/j.tafmec.2024.104373}, pages = {Artikel 104373}, year = {2024}, abstract = {The deformation and damage laws of non-homogeneous irregular structural planes in rocks are the basis for studying the stability of rock engineering. To investigate the damage characteristics of rock containing non-parallel fissures, uniaxial compression tests and numerical simulations were conducted on sandstone specimens containing three non-parallel fissures inclined at 0°, 45° and 90° in this study. The characteristics of crack initiation and crack evolution of fissures with different inclinations were analyzed. A constitutive model for the discontinuous fractures of fissured sandstone was proposed. The results show that the fracture behaviors of fissured sandstone specimens are discontinuous. The stress-strain curves are non-smooth and can be divided into nonlinear crack closure stage, linear elastic stage, plastic stage and brittle failure stage, of which the plastic stage contains discontinuous stress drops. During the uniaxial compression test, the middle or ends of 0° fissures were the first to crack compared to 45° and 90° fissures. The end with small distance between 0° and 45° fissures cracked first, and the end with large distance cracked later. After the final failure, 0° fissures in all specimens were fractured, while 45° and 90° fissures were not necessarily fractured. Numerical simulation results show that the concentration of compressive stress at the tips of 0°, 45° and 90° fissures, as well as the concentration of tensile stress on both sides, decreased with the increase of the inclination angle. A constitutive model for the discontinuous fractures of fissured sandstone specimens was derived by combining the logistic model and damage mechanic theory. This model can well describe the discontinuous drops of stress and agrees well with the whole processes of the stress-strain curves of the fissured sandstone specimens.}, language = {en} } @article{EngelmannSimsekShalabyetal.2024, author = {Engelmann, Ulrich M. and Simsek, Beril and Shalaby, Ahmed and Krause, Hans-Joachim}, title = {Key contributors to signal generation in frequency mixing magnetic detection (FMMD): an in silico study}, series = {Sensors}, volume = {24}, journal = {Sensors}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {1424-8220}, doi = {10.3390/s24061945}, pages = {Artikel 1945}, year = {2024}, abstract = {Frequency mixing magnetic detection (FMMD) is a sensitive and selective technique to detect magnetic nanoparticles (MNPs) serving as probes for binding biological targets. Its principle relies on the nonlinear magnetic relaxation dynamics of a particle ensemble interacting with a dual frequency external magnetic field. In order to increase its sensitivity, lower its limit of detection and overall improve its applicability in biosensing, matching combinations of external field parameters and internal particle properties are being sought to advance FMMD. In this study, we systematically probe the aforementioned interaction with coupled N{\´e}el-Brownian dynamic relaxation simulations to examine how key MNP properties as well as applied field parameters affect the frequency mixing signal generation. It is found that the core size of MNPs dominates their nonlinear magnetic response, with the strongest contributions from the largest particles. The drive field amplitude dominates the shape of the field-dependent response, whereas effective anisotropy and hydrodynamic size of the particles only weakly influence the signal generation in FMMD. For tailoring the MNP properties and parameters of the setup towards optimal FMMD signal generation, our findings suggest choosing large particles of core sizes dc > 25 nm nm with narrow size distributions (σ < 0.1) to minimize the required drive field amplitude. This allows potential improvements of FMMD as a stand-alone application, as well as advances in magnetic particle imaging, hyperthermia and magnetic immunoassays.}, language = {en} }