170,773 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)
Passive energy dissipation enhancement of linear frame structures by the damped cable system
No full textThe Damped Cable System (DCS) is an innovative seismic protection technology of frame structures that incorporates pre-stressed steel cables linked to fluid viscous spring-dampers fixed to the foundation, at their lower ends, and to the top floor, or one of the upper floors, at their upper ends. The cables have sliding contacts with the floor slabs, to which they are joined by steel deviators. This determines a high-dissipative dynamic coupling between DCS and structure, capable of remarkably enhancing the seismic performance of the latter. An extensive research activity has been developed by the authors on the system, which included laboratory and field testing campaigns, structural modelling and assessment, and the formulation of design procedures. In this paper attention is focused on the finite element model of the DCS, conceived to be easily generated by commercial structural analysis programs, and validated by comparison with the results of the experimental surveys carried out. The model was ultimately updated, and its computational performance is examined by application to a demonstrative case study, constituted by a steel school built in the late 1960s. © 2013 AIP Publishing LLC
Using the SimOS Machine Simulator to Study Complex Computer Systems
No full textThis paper identifies two challenges that machine simulators such as SimOS must overcome in order to effectively analyze large complex workloads: handling long workload execution times and collecting data effectively. To study long-running workloads, SimOS includes multiple interchangeable simulation models for each hardware component. By selecting the appropriate combination of simulation models, the user can explicitly control the tradeoff between simulation speed and simulation detail. To handle the large amount of low-level data generated by the hardware simulation models, SimOS contains flexible annotation and event classification mechanisms that map the data back to concepts meaningful to the user. SimOS has been extensively used to study new computer hardware designs, to analyze application performance, and to study operating systems. We include two case studies that demonstrate how a low-level machine simulator such as SimOS can be used to study large and complex workloads. Categories and Subject Descriptors: C.4 [Computer Systems Organization]: Performance of Systems; B.3.3 [Hardware]: Memory Structures---performance analysis, and design aid
Symplecticity properties of Euler-Maclaurin methods
No full textIn this note we consider the use of Euler-Maclaurin methods for the solution of canonical Hamiltonian problems. As a subclass of multi-derivative Runge-Kutta methods, these integrators cannot be symplectic, however they turn out to be conjugate symplectic. The numerical solutions provided by a conjugate symplectic integrator essentially share the same qualitative long time behavior as those yielded by a symplectic integrator. This aspect, along with an efficient evaluation of the derivatives, suggests that Euler-Maclaurin methods could play an interesting role in the context of geometric integration
An Approach to Modeling of 3D Masonry Structures For Dynamic Analyses, Refurbishment And Control Of Vibrations
No full textThe paper focuses on the problem of analysis of masonry structures with spatial geometries, even under the perspective of performing adequate forecasts for design and planning of protection strategies and provisions. In this case an approach is outlined for handling the modelling of the structure without renouncing to the proper nonlinear material assumption, which means overpassing the drastic simplifications and gross schematizations that are usually introduced when dealing with 3D structures made of masonry
Numerical Analysis of Passively Mode-Locked Quantum-Dot Lasers With Absorber Section at the Low-Reflectivity Output Facet
No full textIn this paper, we present a theoretical study on the optimization of passively mode-locked quantum dot lasers based on an alternative cavity design. In particular, we investigate a geometry in which the saturable absorber is located near the low reflection facet of the chip (output facet). The investigation is carried out by means of a time-domain traveling wave numerical model for quantum-dot active medium for both the gain and absorbing sections. The analysis shows superior performance in terms of pulsewidth and peak power of devices based on the new geometry compared to devices based on the conventional geometry, where the saturable absorber is placed near the high reflectivity facet. The optimization relies on the enhanced bleaching of the saturable absorber when the latter is located near the output facet, which prevents the generation of colliding or self-colliding pulse effect
An approach to dynamic control design for 3D masonry structures
No full textIn the paper one proposes the formulation of an approach aimed at effectively designing dynamic control systems for spatial masonry structures. Managing 3D masonry structures for protection purposes with regards to dynamic events is usually handled through drastic simplifications of the original structure or of the nonlinear material behaviour. The proposed approach is aimed at controlling the dynamic vibrations of the spatial structure on the basis of its proper modelling, in such a way to embed in the design process its nonlinearity. The presented algorithm, which is outlined together with some numerical results, is shown to be able to produce significant beneficial effects in terms of response mitigation
Broadband parametric amplification for multiplexed SiMOS quantum dot signals
No full textInternational audienceSpins in semiconductor quantum dots hold great promise as building blocks of quantum processors. Trapping them in SiMOS transistor-like devices eases future industrial scale fabrication. Among the potentially scalable readout solutions, gate-based dispersive radiofrequency reflectometry only requires the already existing transistor gates to readout a quantum dot state, relieving the need for additional elements. In this effort towards scalability, traveling-wave superconducting parametric amplifiers significantly enhance the readout signal-to-noise ratio (SNR) by reducing the noise below typical cryogenic low-noise amplifiers, while offering a broad amplification band, essential to multiplex the readout of multiple resonators. In this work, we demonstrate a 3GHz gate-based reflectometry readout of electron charge states trapped in quantum dots formed in SiMOS multi-gate devices, with SNR enhanced thanks to a Josephson traveling-wave parametric amplifier (JTWPA). The broad, tunable 2GHz amplification bandwidth combined with more than 10dB ON/OFF SNR improvement of the JTWPA enables frequency and time division multiplexed readout of interdot transitions, and noise performance near the quantum limit. In addition, owing to a design without superconducting loops and with a metallic ground plane, the JTWPA is flux insensitive and shows stable performances up to a magnetic field of 1.2T at the quantum dot device, compatible with standard SiMOS spin qubit experiments
Broadband parametric amplification for multiplexed SiMOS quantum dot signals
No full textSpins in semiconductor quantum dots hold great promise as building blocks of
quantum processors. Trapping them in SiMOS transistor-like devices eases future
industrial scale fabrication. Among the potentially scalable readout solutions,
gate-based dispersive radiofrequency reflectometry only requires the already
existing transistor gates to readout a quantum dot state, relieving the need
for additional elements. In this effort towards scalability, traveling-wave
superconducting parametric amplifiers significantly enhance the readout
signal-to-noise ratio (SNR) by reducing the noise below typical cryogenic
low-noise amplifiers, while offering a broad amplification band, essential to
multiplex the readout of multiple resonators. In this work, we demonstrate a
3GHz gate-based reflectometry readout of electron charge states trapped in
quantum dots formed in SiMOS multi-gate devices, with SNR enhanced thanks to a
Josephson traveling-wave parametric amplifier (JTWPA). The broad, tunable 2GHz
amplification bandwidth combined with more than 10dB ON/OFF SNR improvement of
the JTWPA enables frequency and time division multiplexed readout of interdot
transitions, and noise performance near the quantum limit. In addition, owing
to a design without superconducting loops and with a metallic ground plane, the
JTWPA is flux insensitive and shows stable performances up to a magnetic field
of 1.2T at the quantum dot device, compatible with standard SiMOS spin qubit
experiments
Principles of Stochastic Geometric Numerical Integrations: Dissipative Problems and Stochastic Oscillators
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