86 research outputs found
On the equilibrium problem and infinitesimal mechanisms of class theta tensegrity systems
No full textThis work presents a study on the equilibrium problem and the infinitesimal mechanisms of class θ= 1 tensegrity prisms. Local solutions of the self-equilibrium problem are numerically obtained through Newton-Raphson iterations. The presented results suggest that the analyzed structures can be usefully employed as building blocks of novel tensegrity metamaterials, due to their rich kinematic response and the considerably large number of infinitesimal mechanisms. © 2019 Author(s)
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“Voice of Power, Voice of Terror:” Lyric, Violence, and the Greek Revolution
No full textThis dissertation explores the representation of revolutionary violence in the lyric poetry of the Greek Revolution (1821-1829). By scrutinizing diverse material (political pamphlets, aesthetic treatises, accounts on the origin of language, constitutional texts, and various lyric kinds) I argue that lyric poetry emerges as a site where (1) the Greek subjects of the Ottoman Empire are presented as a sovereign community and (2) the emancipatory role of revolutionary violence in political modernity is tested and contested. Furthermore, I account for lyric’s central role by demonstrating that voice, often conceptualized as rational and deliberative discourse, is a shared category between literary and political discourses on political beginnings.
The study is divided in three chapters. Chapter 1 studies works by Konstantinos Oikonomos and Iakovos Polylas that discuss the role of voice in the formation of specifically modern political communities, that is, communities which are based on popular sovereignty. Taking Adamantios Korais’ ᾎσμα Πολεμιστήριον (1800) as the basis for a broader consideration of exhortative war poems and songs, the chapter then offers a typology of politicizing vocal effects and concludes by explaining the imagery of sacrificial violence as a recuperation or establishment of popular sovereignty during a state of exception.
Chapter 2 turns to the representation of revolutionary violence in philhellenic discourse through an examination of Percy Bysshe Shelley’s Hellas (1821). By reading this “lyrical drama” in the context of Shelley’s engagement with classical and modern Greece and by examining the subversive deployment of the “westering” theme, I demonstrate that Shelley criticizes the appropriation of Hellenism by imperial discourses of the period. This critical outlook is premised on the trope of “willful exception:” far from precluding political action, Shelley’s philhellenism strives to render the exceptional or the revolutionary moment continuously accessible.
Lastly, Chapter 3 peruses the relation between voice and revolution in Dionysios Solomos’ early work. I first propose a new reading of Solomos’ project of renovating the poetic vernacular by showing how his early epiphanic poems stage the emergence of the lyric speaker’s reflective and thinking speech as the proper medium for the representation of revolutionary claims. I then read the interplay between the figurations of voice and the presentation of violence in specific passages of Ὕμνος εἰς τὴν Ἐλευθερίαν (1824) as a challenge to the above understanding of “vocal modernity.” Solomos’ treatment of voice indicates that revolutionary violence remains emancipatory and just only when it is articulated in a transcendent realm and therefore eludes its instrumental appropriation by the revolutionary subject.Comparative Literatur
Goodness-of-fit tests in conditional duration models
No full textWe propose specification tests for the innovation distribution in conditional duration models. The new tests are based either on the cumulative distribution function, or on exponential transforms such as the Laplace transform and the characteristic function, or on characterizations of the innovation-distribution under test. We study the finite-sample performance of the proposed procedures in comparison with alternative tests which employ nonparametric density estimates as well as with tests based on entropy. A bootstrap version of the tests is utilized in order to study the small sample behavior of the procedures. A real-data example illustrates the applicability of our method and confirms conclusions drawn by earlier author
Full 3D CAD procedure for the speedy evaluation of the seismic vulnerability of masonry towers
No full textA very straightforward 3D CAD approach for the speedy evaluation of the seismic vulnerability of existing masonry towers is presented. The procedure requires only the detailed 3D geometric model of the structure and automatically calculates the collapse acceleration on a user defined failure mechanism. In this paper, few pre-assigned mechanisms are tested, as for instance vertical splitting, simple overturning at the base, rocking with inclined yield lines and combined rocking and vertical splitting. The restriction of the possible tower failure within such a few mechanisms grounds on previous numerical research in the field and post-earthquake surveys experience. In any case, any user can define his own mechanisms according to the specificity of the case-study under consideration, directly shaping distinct volumes inside the CAD software. The procedure is automatized and the direct application of the principle of virtual works-assuming that masonry behaves as a no-tension material-allows the immediate evaluation of the horizontal acceleration at collapse. The mechanism associated to the minimum acceleration, in agreement with the kinematic theorem of limit analysis, is that most probably would occur in reality during a seismic event. The approach allows a straightforward evaluation of the seismic vulnerability of a tower and can be used even by practitioners not familiar with advanced FE computations and limit analysis concepts, so adapting well to the heterogeneous community involved in cultural heritage preservation. The automatized procedure is applied in this paper to a historical tower located in central Italy, to show the capabilities of the approach. © 2019 Author(s)
Quantum dot arrays in silicon and germanium
No full textElectrons and holes confined in quantum dots define excellent building blocks for quantum emergence, simulation, and computation. Silicon and germanium are compatible with standard semiconductor manufacturing and contain stable isotopes with zero nuclear spin, thereby serving as excellent hosts for spins with long quantum coherence. Here, we demonstrate quantum dot arrays in a silicon metal-oxide-semiconductor (SiMOS), strained silicon (Si/SiGe), and strained germanium (Ge/SiGe). We fabricate using a multi-layer technique to achieve tightly confined quantum dots and compare integration processes. While SiMOS can benefit from a larger temperature budget and Ge/SiGe can make an Ohmic contact to metals, the overlapping gate structure to define the quantum dots can be based on a nearly identical integration. We realize charge sensing in each platform, for the first time in Ge/SiGe, and demonstrate fully functional linear and two-dimensional arrays where all quantum dots can be depleted to the last charge state. In Si/SiGe, we tune a quintuple quantum dot using the N + 1 method to simultaneously reach the few electron regime for each quantum dot. We compare capacitive crosstalk and find it to be the smallest in SiMOS, relevant for the tuning of quantum dot arrays. We put these results into perspective for quantum technology and identify industrial qubits, hybrid technology, automated tuning, and two-dimensional qubit arrays as four key trajectories that, when combined, enable fault-tolerant quantum computation.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.QCD/Veldhorst LabQCD/Vandersypen LabQCD/Scappucci LabBUS/Quantum DelftQN/Vandersypen La
Hot qubits in silicon for quantum computation
No full textThe understanding of quantum mechanics enabled the development of technology such as transistors and has been the foundation of today’s information age. Actively using quantum mechanics to build quantum technology may cause a second revolution in handling information. However, to execute meaningful algorithms, largescale quantum computers have to be built. Such systems are constructed from many qubits, the quantum version of the classical bit. While exciting progress is being made across a range of different qubit platforms, achieving the radical scalability that is necessary to build a largescale processor could be a roadblock. Huge challenges are put on reproducibility, inand output connectivity and material quality. Qubits based on the spins of electrons and holes confined in semiconductor quantum dots may have an important advantage in constructing quantum processors. This platform can profit from the advanced semiconductor industry that was responsible for the first computing revolution. Group IV semiconductors such as silicon and germanium have a high compatibility with industrial semiconductor manufacturing and contain stable isotopes with zero nuclear spin. The materials can be isotopically purified and serve as excellent hosts for spins with long quantum coherence. In Chapter 3 we present quantum dot arrays in silicon metaloxidesemiconductor (SiMOS), strained silicon (Si/SiGe) and strained germanium (Ge/SiGe). A nearly identical integration scheme based on an overlapping gate structure can be used to define quantum dots in each platform. Each platform has its own opportunities, which are carefully assessed. By employing charge sensing we confirm that all quantum dots can be depleted to the singleelectron regime. We compare capacitive crosstalk and find it to be the smallest in SiMOS, relevant for the tuning of quantum dot arrays. Using this crossplatform integration, we can study qubits in each platform with minimal overhead. Long coherence times, excellent singlequbit gate fidelities and twoqubit logic have been demonstrated with SiMOS spin qubits, making it one of the leading platforms for quantum information processing. However, due to the high disorder at the Si/SiO2 interface compared to Ge/SiGe and Si/SiGe interface, quantum dots defined in SiMOS are small and achieving sufficient control over single electrons has been a long standing challenge. In Chapter 5 we show experiments on a double quantum dot that can be isolated from its reservoir. We demonstrate a tunable tunnel coupling between single electrons up to 13 GHz and tunable tunnel rates down to below 1 Hz. These results mark an important step towards the required degree of control over the location of and coupling between quantum dots, necessary for the operation of a large array.QCD/Veldhorst La
Transfer matrix method for fundamental LP<sub>01</sub> core mode coupling in a tilted FBG sensor
No full textFibre Bragg gratings (FBGs) are obtained through a permanent and periodic refractive index modulation in the core of the single-mode optical fibre. For many years, they have been employed in telecommunication industry as a passive device for wavelength division multiplexing and dispersion compensation components, or in laser apparatus for laser fibre stabilization, Erbium amplifier gain flattening device and amplifier pump reflectors. In aerospace structures, FBGs are used as sensors for structural health monitoring of composite materials as they are able to perform measurements of several parameters inside the material in an elegant and low intrusiveness way. Based on the Bragg and optical fibre structure many kind of customizations can be applied on FBG sensors during the manufacturing process. Each of them gives to the FBG sensor different proprieties and sensing abilities. In this work, we address the numerical simulation of the reflected spectrum by a special FBG sensor called a tilted FBG (TFBG), in which the core refractive index modulation is performed in way to obtain a tilted Bragg super-structure. By considering the classic Coupled-Mode theory for weakly-guided waveguides, we solved the mode propagation equations with the Transfer Matrix method (TMM) obtaining the TFBG reflectivity for different tilt angles.Structural Integrity & CompositesFlight Performance and Propulsio
A family of three stages embedded explicit six–step methods with eliminated phase-lag and its derivatives for the numerical solution of second order problems
No full textModeling and simulation of diffusion-convection-reaction in heterogeneous nanochannels using OpenFOAM
No full textWe present a finite volume implementation of a phase field method in OpenFOAM as a tool to simulate reactive multiphase flows on heterogeneous surfaces. Using this tool, we simulate the formation and growth of a droplet due to a chemical reaction on a hydrophilic catalytic patch surrounded by a hydrophobic wall. We compare the growth dynamics with a quasi-static growth model from literature and show that they qualitatively agree.ChemE/Transport PhenomenaChemE/Product and Process EngineeringChemE/Chemical Engineerin
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