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Durch die dezentrale Energiegewinnung, welche aus dem Fokus auf regenerative Stromerzeugung resultiert, ist ein Ausbau des Übertragungsnetzes alternativlos – auch mit Hinblick auf den steigenden Strombedarf in den kommenden Jahrzehnten. Der Ausbau ist bereits beschlossene Sache, schreitet aber schleppend voran. Die Gründe hierfür sind jedoch nicht etwa Verzögerungen in der Bauausführung, sondern vor allem die Ablehnung innerhalb der Bevölkerung gegenüber dem Neubau von Stromtrassen. Jahrelange Planungs- und Genehmigungsphasen sowie regelmäßige Änderungen der Trassenverläufe sind die Folge. Die Bürgerbewegungen gegen den Netzausbau sind meist mit auf dem Einfluss auf das Landschaftsbild, der Strahlungsbelastung oder Lärmbelästigung begründet. Eine Erdverlegung würde hinsichtlich dieser Probleme (trotz kurzfristiger Mehrbelastung während der Bauphase) eine Alternative darstellen, weist jedoch baubedingte Problematiken wie den Abtransport der Verlustwärme auf. Bei einer klassischen Sandbettung hängt die Wärmeleitfähigkeit maßgeblich vom Wassergehalt des Sandes ab, welcher je nach Witterungslage und geologischen Gegebenheiten sehr stark schwankt. Als Folge muss die Trasse für den ungünstigsten Fall und damit unwirtschaftlich bemessen werden.
Im Rahmen des Forschungsprojekts „DC-CTL DBI“ wurde eine gasisolierte HGÜ-Leitung (GIL) erdverlegt und einem Langzeitversuch unterzogen. Anstelle einer Sandbettung wurde jedoch ein zeitweise fließfähiger, selbstverdichtender Verfüllbaustoff (ZFSV) verwendet. Für den Einsatz als thermische Bettung bietet ein ZFSV mehrere Eigenschaften, welche eine klassische Sandbettung nicht bietet. So ist mit Hinblick auf die verschweißte Aluminium-Hülle der GIL kein Verdichtungsaufwand nötig, welcher bei aktueller Bauform zweifelsfrei in Schäden resultieren würde. Darüber hinaus weisen Flüssigböden durch den Bentonit-Gehalt eine höhere adsorbierende Oberfläche auf, wodurch der Anteil des Haftwassers im Boden zunimmt und die Wärmeleitfähigkeit der Bettung in ihrer Konstanz positiv beeinflusst wird.
Im Zuge dieser Arbeit wurden die thermischen und hydraulischen Transportprozesse um die GIL mittels FEM in Plaxis2D untersucht und transient über den gesamten Messzeitraum (18 Monate) berechnet. Hierfür wurden die Materialparameter durch labortechnische Versuche ermittelt und die Messergebnisse einer verbauten Wetterstation als Randbedingungen (Niederschlag, Temperatur, Evapotranspiration) aufgebracht. Die Ergebnisse aus Plaxis2D wurden abschließend mit der im Feldversuch verbauten Sensorik verglichen. Es zeigte sich, dass sowohl die Boden- als auch die Leitertemperaturen nur um wenige Grad von den Messwerten der Sensorik abweichen. Anders als bei den etablierten analytischen Bemessungsrechnungen, welche stets auf Vereinfachungen basieren, können auch Effekte wie konvektiver Wärmetransport oder Austrocknung bei gleichzeitig höherer Genauigkeit der Ergebnisse untersucht werden.
Um den Rechenaufwand gering zu halten, wurden lediglich die thermischen und hydraulischen Entwicklungen und Einflüsse des Bodens berücksichtigt. Es ist aber durchaus möglich, Verformungen und Kräfte in die Berechnung zu integrieren und so ein ganzheitliches Berechnungsmodell zu erstellen.
Non-road sectors, such as agriculture and construction machinery, require high energy densities and flexibility in use, which is why diesel engines are mainly used. The use of climate-neutral fuels, produced from renewable energies, such as Oxymethylene Ether (OME) as a diesel substitute, can significantly reduce CO2 and pollutant emissions in these sectors. In addition to CO2 neutrality, OME also offers improved combustion characteristics compared to diesel fuel, eliminating the soot–NOx trade-off and thus enabling new opportunities in engine design and calibration. In this paper, the combustion of pure OME on a close-to-production, single-cylinder non-road diesel engine with a pump–line–nozzle injection system is analyzed. A variation of the center of combustion at constant power output was performed for diesel and OME at different operating points. Two injectors were investigated with OME. A study on ignition delay and a detailed thermodynamic analysis was carried out. In addition, the exhaust emissions CO, NOx, VOC, as well as particulate-matter, -number and -size distributions were measured. With OME, a significantly shorter ignition delay as well as a shortened combustion duration could be observed, despite a longer injection duration. In addition, the maximum injection pressure increases. VOC and CO emissions are reduced. Particulate matter was reduced by more than 99% and particle number (>10 nm) was reduced by multiple orders of magnitude. The median of the particle size distribution shifts from 60 to 85 nm (diesel) into a diameter range of sub 23 nm (OME). A significant reduction of NOx emissions with OME enables new degrees of freedom in engine calibration and an efficiency advantage without hardware adaption.
We have a platform, but nobody builds on it – what influences Platform-as-a-Service post-adoption?
(2022)
When higher-level management of a company has strategically decided to adopt Platform-as-a-Service (PaaS) as a Cloud Computing (CC) delivery model, decision-makers at lower hierarchy levels still need to decide whether they want to post-adopt PaaS for building or running an information system (IS) – a decision that numerous companies are currently facing. This research analyzes the influential factors of this managerial post-adoption decision on the IS-level. A survey of 168 business and Information Technology (IT) professionals investigated the influential factors of this PaaS post-adoption decision. The results show that decision-makers’ perceptions of risks inhibit post-adoption. Vendor trust and trialability reduce these perceived risks. While competitive pressure increases perceived benefits, it does not significantly influence PaaS post-adoption. Controversially, security and privacy, cost savings, and top management support do not influence post-adoption, as opposed to findings on company-level adoption. Subsamples constructed by the form of post-adoptive use (migration of IS, enhancement of IS, new IS development) exhibit better goodness-of-fit measures than the full sample. Future research should explore this interrelation of the form of post-adoptive use and the post-adoption influence factors.
Most large-scale organizations adopted Cloud Computing (CC) on a company level in recent years. Managers now face the challenge to appropriately implement CC "operationally", i.e., for information systems (ISs). We refer to this as post-adoption, addressing the extent of technology usage after adoption. Specifically, managers need to choose among the CC delivery models Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS), and Software-asa-Service (SaaS). We differentiate the determinants of this post-adoption decision for IaaS, PaaS, and SaaS. Based on this analysis, we derive criteria that guide managers' delivery model selection: Adopt 1) IaaS for ISs requiring flexibility and reduced time to market, 2) PaaS to access specialized resources, and 3) SaaS to focus on core competencies. Moreover, we analyze the impact on the CC strategy and postulate them as recommendations: I) acknowledge the interplay between governance and time-to-market, II) realize cost savings on company level, and III) consider strategically important ISs for CC.
It is state of technology in district heating systems to use sand as backfill material for district heating pipes (DHP). In conventional pipeline construction, Temporarily Flowable Backfill Materials (TFB) have been already used for backfilling the pipe zone. TFB consists of the excavated material, cement, water and optionally bentonite. Environmental and economic advantages are that the excavated material can be reused and that TFB requires no compaction. In order to embed district heating pipes in TFB, soil mechanical parameters of the TFB are required. Above all the resistance to temperature-induced axial displacement should be well-known in order to estimate the displacements of the DHP, as well as the stress distribution along the DHP. Compared to sand as a non-cohesive backfill TFB have remarkable adhesive contact stresses which result in considerable resistance forces.In this article, the contact behavior between TFB and DHP is described as well as the effect on the DHP statics. Therefore, the results of various laboratory tests are summarized and presented to understand the interface-resistance-characteristics (IRC) of the DHP/ TFB interface. Then, the deduced IRC was implemented in a computer program for some comparative calculations with sand and TFB. Finally, the results of cyclic loading are presented and discussed.
Identifying different functional regions during a brain surgery is a challenging task usually performed by highly specialized neurophysiologists. Progress in this field may be used to improve in situ brain navigation and will serve as an important building block to minimize the number of animals in preclinical brain research required by properly positioning implants intraoperatively. The study at hand aims to correlate recorded extracellular signals with the volume of origin by deep learning methods. Our work establishes connections between the position in the brain and recorded high-density neural signals. This was achieved by evaluating the performance of BLSTM, BGRU, QRNN and CNN neural network architectures on multisite electrophysiological data sets. All networks were able to successfully distinguish cortical and thalamic brain regions according to their respective neural signals. The BGRU provides the best results with an accuracy of 88.6 % and demonstrates that this classification task might be solved in higher detail while minimizing complex preprocessing steps.
Experimental investigations are conducted to quantify the influence of specimen thickness and orientation on the mechanical properties of selective laser melted stainless steel 316 L. The results indicate that the mechanical strength and ductility increase with increasing specimen thickness until a saturation value is reached from a specimen thickness of about 2 mm. Specimen orientation dependency is pronounced for thin specimens (<1.5 mm), whereas only small deviations in strength are observed for thicker specimens with orientations of 30°, 45° and 90° to build direction. The mechanical properties of the specimen orientation of 0° to build direction shows great deviation to the other orientations and the smallest overall strength. A reliable design of selective laser melted components should account for specimen thickness and orientation, e. g. by a correction factor. Furthermore, it is recommended to avoid loads vertical (90°) and parallel (0°) to build direction to guarantee higher ductility and strength.
Das Bauwesen erfährt zurzeit eine zunehmende Digitalisierung von Planungs- und Bauprozessen. Ein Begriff, der dabei zwingend fallen muss, ist Building Information Modeling (BIM). Es handelt sich dabei um eine kooperative Arbeitsmethode mit dem Ziel einer höheren Planungs-, Kosten- und Terminsicherheit. Wesentlicher Bestandteil von BIM ist das digitale Modell des Bauwerks, das über dessen gesamten Lebenszyklus von der Planung über die Ausführung bis zum Unterhalt und Rückbau mit Informationen ergänzt wird. Der gewünschte Effekt ist dabei eine größere Informationsdichte, auf welche die Projektbeteiligten über die Projektphasen hinweg zugreifen und somit einem Informationsverlust
vorbeugen können.
A basic task in the design of an industrial robot application
is the relative placement of robot and workpiece. Process points are defined in Cartesian coordinates relative to the workpiece coordinate system, and the workpiece has to be located such that the robot can reach all points. Finding such a location is still an iterative procedure based on the developers' intuition. One difficulty is the choice of one of the several solutions of the backward transform of a typical 6R robot.
We present a novel algorithm that simultaneously optimizes the workpiece location and the robot configuration at all process points using higher order optimization algorithms. A key ingredient is the extension of the robot with a virtual prismatic axis. The practical feasibility of the approach is shown with an example using a commercial industrial robot.