563 research outputs found

    Proceedings of SIRM 2023 - The 15th European Conference on Rotordynamics

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    It was our great honor and pleasure to host the SIRM Conference after 2003 and 2011 for the third time in Darmstadt. Rotordynamics covers a huge variety of different applications and challenges which are all in the scope of this conference. The conference was opened with a keynote lecture given by Rainer Nordmann, one of the three founders of SIRM “Schwingungen in rotierenden Maschinen”. In total 53 papers passed our strict review process and were presented. This impressively shows that rotordynamics is relevant as ever. These contributions cover a very wide spectrum of session topics: fluid bearings and seals; air foil bearings; magnetic bearings; rotor blade interaction; rotor fluid interactions; unbalance and balancing; vibrations in turbomachines; vibration control; instability; electrical machines; monitoring, identification and diagnosis; advanced numerical tools and nonlinearities as well as general rotordynamics. The international character of the conference has been significantly enhanced by the Scientific Board since the 14th SIRM resulting on one hand in an expanded Scientific Committee which meanwhile consists of 31 members from 13 different European countries and on the other hand in the new name “European Conference on Rotordynamics”. This new international profile has also been emphasized by participants of the 15th SIRM coming from 17 different countries out of three continents. We experienced a vital discussion and dialogue between industry and academia at the conference where roughly one third of the papers were presented by industry and two thirds by academia being an excellent basis to follow a bidirectional transfer what we call xchange at Technical University of Darmstadt. At this point we also want to give our special thanks to the eleven industry sponsors for their great support of the conference. On behalf of the Darmstadt Local Committee I welcome you to read the papers of the 15th SIRM giving you further insight into the topics and presentations

    Study of the tracking performance of a liquid Argon detector based on a novel optical imaging concept

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    The Deep Underground Neutrino Experiment (DUNE) is a long-baseline accelerator experiment designed to make a significant contribution to the study of neutrino oscillations with unprecedented sensitivity. The main goal of DUNE is the determination of the neutrino mass ordering and the leptonic CP violation phase, key parameters of the three-neutrino flavor mixing that have yet to be determined. An important component of the DUNE Near Detector complex is the System for on-Axis Neutrino Detection (SAND) apparatus, which will include GRAIN (GRanular Argon for Interactions of Neutrinos), a novel liquid Argon detector aimed at imaging neutrino interactions using only scintillation light. For this purpose, an innovative optical readout system based on Coded Aperture Masks is investigated. This dissertation aims to demonstrate the feasibility of reconstructing particle tracks and the topology of CCQE (Charged Current Quasi Elastic) neutrino events in GRAIN with such a technique. To this end, the development and implementation of a reconstruction algorithm based on Maximum Likelihood Expectation Maximization was carried out to directly obtain a three-dimensional distribution proportional to the energy deposited by charged particles crossing the LAr volume. This study includes the evaluation of the design of several camera configurations and the simulation of a multi-camera optical system in GRAIN

    Mechanismy a časová měřítka vzniku lineárních mikrokontinentů

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    Koncept lineárních mikrokontinentů (v angličtině "ribbon continents") se v literatuře objevil v 80. letech minulého století, většina výzkumů se však soustředila na jejich akreci a kolizi s kontinentálními okraji. Naopak iniciální fáze jejich vývoje a podmínky jejich vzniku jsou do značné míry stále neobjasněny. Tato disertační práce se zaměřuje na vznik lineárních mikrokontinentů na příkladu teránů, které se odtrhly od původního avalonsko-kadomského orogenního pásma na severním okraji Gondwany během mladšího neoproterozoika až spodního ordoviku. Data získaná v této disertační práci pochází ze tří různých částí Českého masivu, které reprezentují různá stádia iniciální extenze a vzniku mikrodesek a rovněž reprezentují různé krustální úrovně: (1) kdyňský pluton v jihozápadní části tepelsko-barrandienské jednotky, (2) příbramsko-jinecká pánev v její centrální části a (3) metagranity a ortoruly v moldanubické jednotce. tyto různé jednotky byly zkoumány pomocí různých terénních a analytických metod, jež zahrnovaly strukturní mapování, stratigrafickou a sedimentologickou analýzu a zejména anizotropii magnetické susceptibility (AMS) doplněnou termomagnetickými analýzami. Metagranity a ortoruly byly datovány pomocí metody U-Pb na zirkonech metodou ICP-MS. Hlavní závěry disertační práce jsou následující. (1)...Investigation into the ribbon continents has started since the 1980s; however, most studies focued on oceanic closure phase, involving the subduction, accretion, and collision. The formation of ribbon continents has received little attention, perhaps because it has less recent examples. This thesis is designed to address several possible scenarios for the formation of ribbon continent by investigating the tectonics, magmatism, and sedimentation of the former Avalonian-Cadomian belt during the break-up of the peri-Gondwana terranes and transition from the active- to passive-margin settings. The data originated from three different locations within the Bohemian Massif, the Czech Republic, which can also be viewed as a Cambro- Ordovician crustal evolution from the lower crust to the surface level: (1) intermediate to felsic of the Kdyně pluton in the Plzeň region, (2) the continental Příbram-Jince basin in the Central Bohemian region, and (3) metagranites and granitic orthogneisses of the Moldanubian zone in Pardubice and Vysočina regions. The methods used involve the integration of structural mapping, microstructural analysis, stratigraphic and sedimentological analysis, and in particular the anisotropy of magnetic susceptibility (AMS) accompanied by an examination of magnetic mineralogy using...Ústav geologie a paleontologieInstitute of Geology and PaleontologyPřírodovědecká fakultaFaculty of Scienc

    User-Centered Modelling and Design of Assistive Exoskeletons

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    Advanced experimental techniques for SiPM characterization at cryogenic temperatures

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    The main topic of this thesis is the characterization of silicon photomultipliers (SiPM) detectors for the DUNE experiment, in particular for the ProtoDUNE-HD and DUNE-FD1 modules, and the development of novel experimental setups and techniques to perform this task. The initial overview of DUNE outlines the main features of the experiment (underlying physics, scientific program and current design for single components), giving particular attention to the first of the four DUNE far detector modules (DUNE-FD1). This includes the general working principles of a LArTPC, the current plan for the DUNE-FD1 design and lastly the role of SiPMs in this design (i.e. fundamental units of the photon detection system PDS). A brief description of the ProtoDUNE2-HD detector is also reported, since it shares the same PDS design with the DUNE-FD1 detector. A detailed description of the SiPM fundamental properties and working principles is also reported, discussing the most important parameters involved in their characterization (in the context of the DUNE experiment). The presented work falls in the context of the SiPM test campaign engaged by the DUNE PDS consortium to down-select and test SiPMs for both the ProtoDUNE-HD and DUNE-FD1 detectors. The Ferrara group took active participation on both the first test phase, that consisted in the full characterization of single sensors to down-select two SiPM models as most promising devices, and the second phase, which is a quality assurance test campaign for a large number of SiPMs of the selected models. The Ferrara group, together with the Bologna group, developed a custom apparatus (CACTUS) to perform fast and automatized characterizations in order to leverage the time involved in the aforementioned massive SiPM test campaign. This apparatus was used for test the ProtoDUNE2-HD SiPM production (6000 units), which resulted in all the sensors being within the DUNE specifications (failure rate around 0.05%), and it is currently operating for the DUNEFD1-HD SiPM characterization campaign (288000 units). The CACTUS system permits to characterize automatically up to 120 SiPMs in parallel, both at room temperature and at LN2 temperature, in a single measurement session, and it is planned to be installed in other 3 sites to join the DUNEFD1-HD SiPM characterization campaign in 2023.Il tema principale di questo trattato è lo sviluppo di apparati di misura e procedure sperimentali per la caratterizzazione delle proprietà optoelettroniche di fotomoltiplicatori al Silicio (SiPMs) nel contesto dell’esperimento DUNE (Deep Underground Neutrino Experiment), al fine di predisporre il loro utilizzo nei rivelatori ProtoDUNE-HD e DUNE-FD1. Inizialmente viene fornita una visione generale dell’esperimento DUNE, in cui vengono descritti i punti salienti del programma scientifico, la teoria fisica sottostante, e il design attualmente previsto per le singole componenti. La descrizione diventa più dettagliata per quanto riguarda il primo modulo del far detector (DUNE-FD1), dato che i SiPM in questione verranno utilizzati come unità fondamentale del sistema di foto-rivelazione (PDS) della camera a proiezione temporale ad argon liquido (LArTPC). Per completare la contestualizzazione del tema principale, il trattato contiene anche una descrizione dettagliata delle proprietà elettriche e optoelettroniche dei SiPM, dei modelli teorici adottati per descrivere il loro funzionamento e delle procedure comunemente adottate per caratterizzarli. La caratterizzazione dei SiPM per ProtoDUNE-HD e DUNE-FD1 svolta dalla divisione di Ferrara del Consorzio DUNE-PDS è l’argomento centrale di questo trattato. Questo contributo è consistito nella caratterizzazione di singoli sensori SiPM, a temperatura ambiente e alla temperatura di azoto liquido, che ha permesso la selezione dei modelli più promettenti per applicazioni nel contesto dell’esperimento DUNE, assieme alla definizione delle migliori condizioni di lavoro per massimizzare le loro performance. Il gruppo DUNE-PDS Ferrara sta contribuendo anche alla seconda fase della campagna di test, che prevede lo svolgimento di test di garanzia per un grande numero di SiPM. In particolare, il gruppo DUNE-PDS Ferrara, in collaborazione con il gruppo DUNE-PDS Bologna, hanno sviluppato un setup sperimentale per velocizzare questa procedura. Il sistema, denominato CACTUS, permette la caratterizzazione automatizzata di 120 sensori in parallelo a livello di caratteristica IV e conteggi di buio (DCR), sia a temperatura ambiente che in azoto liquido, in una singola sessione di misura. L’apparato CACTUS è stato già utilizzato per testare la produzione di SiPM per ProtoDUNE-HD, un prototipo in scala ridotta di DUNE-FD1 che condivide con esso lo stesso design a livello di singole componenti. Le 6000 unit`a testate con CACTUS per ProtoDUNE-HD non hanno riportato anomalie (failure rate circa 0.05%). Il sistema CACTUS verrà replicato anche nelle università di Milano Bicocca, Granada e Praga, queste si aggiungeranno ai siti di Ferrara e Bologna nella campagna di caratterizzazione di SiPM per la produzione DUNEFD1-HD, che conta 288000 sensor

    Design and Validation of a Variable Stiffness Three Degree of Freedom Planar Robot Arm

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    The need exists for robotic manipulators that can interact with an environment having uncertain kinematic constraints. A robot has been designed and built for proof of concept of a passive variable compliance control strategy that can vary joint stiffness to achieve higher performance dexterous manipulation. This novel planar robot incorporating variable stiffness actuators and common industrial controls allows the robot to comply with its environment when needed but also have high stiffness for precise motion control in free space. To perform both functions well, a high stiffness ratio (max/min stiffness) is required. A stiffness ratio up to 492 was achieved. The robot performance was evaluated with the task of turning a crank to lift a weight despite nominal positioning inaccuracy. The novel variable stiffness robot was able to complete the task faster and with lower constraint forces than a traditional force-controlled stiff robot. The time to complete the task using passive variable stiffness control was twenty-nine times faster with constraint forces less than one fifth those achieved using traditional active compliance control

    Energy-based control approaches in human-robot collaborative disassembly

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    Interpreting GPS observations of the megathrust earthquake cycle: insights from numerical models

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    During a megathrust earthquake cycle, the plates accumulate strain in the interseismic stage due to locking of a portion of the megathrust that separates them. This strain is released during the earthquake and following rapid postseismic relaxation. As summarised in Chapter 1, this understanding was built through decades of seismological and geodetic observations and of advances in physics-based models. Models link properties and structures to observable quantities and are crucial to interpreting observed surface deformation in terms of the processes and materials in the inaccessible subsurface. However, different models can approximate the same observations roughly equally well. Furthermore, more sophisticated models do not necessarily reflect better the processes and properties of the subsurface; at the same time, simpler models that can explain some observations do not necessarily reflect the key processes occurring throughout one or multiple earthquake cycles. This thesis uses relatively simple three-dimensional models that still capture the key processes occurring during repeated earthquake cycles, without attempting to reproduce the structure or properties of specific subduction zones, to examine possible explanations of geodetic observations from global navigation satellite systems (GNSSs) at different stages of the cycle. Chapter 2 focuses on the interseismic, horizontal deformation of the overriding plate, which is in apparent contrast with observations of far-reaching coseismic displacement. We estimate the spatial patterns, with uncertainties, of GNSS velocities in South America, Southeast Asia, and northern Japan. Interseismic velocities with respect to the overriding plate generally decrease with distance from the trench with a steep gradient up to a “hurdle”, beyond which the gradient is distinctly lower and velocities are small. The hurdle is located 500-1000 km away from the trench for the trench-perpendicular velocity component, and either at the same distance or closer for the trench-parallel component. The trench-perpendicular hurdle generally follows major tectonic or geological boundaries and seismological contrasts. We formulate and test the hypothesis that both the interseismic hurdle and the coseismic response result from a mechanical contrast in the overriding plate. Our models show that overriding plates with a sufficient contrast respond to locked interseismic convergence similarly to observations. The compliance contrast is probably mainly responsible for the observed hurdle and in turn results from thermal, compositional and thickness contrasts. Chapter 3 is concerned with the increased landward velocities that were recorded onshore after 6 megathrust earthquakes in subduction zone regions adjacent to the ruptured portion. We investigate whether bending can be expected to reproduce this observed enhanced landward motion (ELM). We find that viscous relaxation, but not afterslip, produces ELM when a depth limit is imposed on afterslip. This ELM results primarily from in-plane elastic bending of the overriding plate due to trenchward viscous flow in the mantle wedge near the rupture. Modeled ELM is, however, incompatible with the observations, which are an order of magnitude greater and last longer. This conclusion does not significantly change when varying key model parameters. The observed ELM consequently appears to reflect faster slip deficit accumulation, implying a greater seismic hazard in lateral segments of the subduction zone. In Chapter 4, we study postseismic landward motion observed on the overriding plate in the vicinity of a major megathrust rupture. We argue that relocking of the megathrust, particularly at shallow depths, is needed for postseismic relaxation to produce landward motion on the tip of the overriding plate. We discuss how that this finding is consistent with previous simulations that implicitly relock the megathrust where afterslip is not included. We conclude that the Tohoku megathrust relocked within less than two months of the earthquake. This suggests that the shallow megathrust probably behaves as a true, unstably sliding asperity
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