A Lower Bound Technique for Communication in BSP

Communication is a major factor determining the performance of algorithms on current computing systems; it is therefore valuable to provide tight lower bounds on the communication complexity of computations. This paper presents a lower bound technique for the communication complexity in the bulk-synchronous parallel (BSP) model of a given class of DAG computations. The derived bound is expressed in terms of the switching potential of a DAG, that is, the number of permutations that the DAG can realize when viewed as a switching network. The proposed technique yields tight lower bounds for the fast Fourier transform (FFT), and for any sorting and permutation network. A stronger bound is also derived for the periodic balanced sorting network, by applying this technique to suitable subnetworks. Finally, we demonstrate that the switching potential captures communication requirements even in computational models different from BSP, such as the I/O model and the LPRAM

Studio, sviluppo e validazione di un sistema di visione stereoscopica per chirurgia robotica

Il lavoro di tesi ha previsto lo sviluppo di un sistema di visione stereoscopica per laparoscopia a singolo accesso, comprendente due videocamere CMOS commerciali, un sistema di illuminazione con LED ad alta efficienza e uno schermo autostereoscopico per la visualizzazione. Tale sistema è stato realizzato e testato su di un pool di medici. I risultati ottenuti sono stati sfruttati per lo sviluppo e la realizzazione di un PCB multistrato con videocamere BGA ad alta risoluzione

Communication Lower Bounds for Distributed-Memory Computations

In this paper we propose a new approach to the study of the communication requirements of distributed computations, which advocates for the removal of the restrictive assumptions under which earlier results were derived. We illustrate our approach by giving tight lower bounds on the communication complexity required to solve several computational problems in a distributed-memory parallel machine, namely standard matrix multiplication, stencil computations, comparison sorting, and the Fast Fourier Transform. Our bounds rely only on a mild assumption on work distribution, and significantly strengthen previous results which require either the computation to be balanced among the processors, or specific initial distributions of the input data, or an upper bound on the size of processors\u27 local memories

Damping reduction factors for adjacent buildings connected by fluid-viscous dampers

This work investigates the dynamic behaviour of a multi-storey frame building, assumed as the structure to be controlled, connected with an adjacent support structure by means of horizontal fluid viscous dampers. The dampers connection system has two main effects: (i) energy dissipation provided by the viscous dissipative forces, (ii) energy transfer between modes leading to modes coupling effects between the two buildings without a significant dissipation of energy. The relative contribution of the two effects is highly dependent on the main properties of the coupled system. To investigate this complex behaviour, first the minimal coupled dynamic system composed by two Single-Degree-Of-Freedom systems connected by a viscous damper is analysed. The theory of complex damping is used to determine complex frequencies and damping ratios, while analytical expressions of steady state response under harmonic excitation are determined to investigate the influence of the system parameters on the maximum dynamic amplifications. The seismic response is also investigated through a wide parametric study with the aim of evaluating the trends of the damping reduction factors with respect to the main dynamic parameters of the coupled system. Minimum values of the damping reduction factors and corresponding optimal damping coefficients are determined. Then, the analyses are extended to uniform multistorey structures for which minimum damping reduction factors are provided for a wide range of the key system parameters. Comparisons between one-storey and uniform multi-storey systems are provided. The results can be useful for a preliminary design of the dampers connection system and for the evaluation of its effectiveness based on the fundamental dynamic properties of the connected buildings

The "direct-five step procedure for existing buildings": development and first application

This paper provides design indications for the seismic retrofitting of existing frame buildings by means of fluid viscous dampers. They are based on a simplified procedure developed in the last years for new buildings and called "direct five-step procedure". This design procedure, which must be then followed by appropriate verification of the seismic behaviour through non-linear dynamic analyses, consists of 5 steps and is based on a prefixed seismic performance, such as a target damping ratio. The procedure aims at the full definition of the mechanical characteristics of the commercial non-linear viscous dampers, and at the estimation of the maximum forces both in the devices and in the structural elements (columns). In the case of new buildings, the objective of sizing the viscous dampers in such a way as to keep the structural elements within the linear elastic range even for "rare" earthquakes of high intensity is easily achievable. In the case of existing buildings designed for vertical loads only, the introduction of a damper system is not generally sufficient to keep the structural elements in the elastic range. Thus, it might be necessary to accept local plastic excursion of the structural elements, by taking into account the ductility capacity (albeit probably limited) of the existing building (hysteretic dissipations associated with damage in beams and columns). This paper reports the extension of the so-called "direct five-step procedure" to the case of existing buildings and its first application to a 6-storey frame structure case study, which is representative of reinforced concrete buildings designed for vertical loads only, before the enforcement of seismic codes

On the Fundamental Periods of Vibration of Flat-Bottom Ground-Supported Circular Silos containing Gran-like Material

Despite the significant amount of research effort devoted to understanding the structural behavior of grain-silos, each year a large number of silos still fails due to bad design, poor construction, with a frequency much larger than other civil structures. In particular, silos frequently fails during large earthquakes, as occurred during the 1999 Chi-Chi, Taiwan earthquake when almost all the silos located in Taichung Port, 70 km far from the epicenter, collapsed. The EQE report stated that "the seismic design of practice that is used for the design and construction of such facilities clearly requires a major revision". The fact indicates that actual design procedures have limits and therefore significant advancements in the knowledge of the structural behavior of silo structures are still necessary. The present work presents an analytical formulation for the assessment of the natural periods of grain silos. The predictions of the novel formulation are compared with experimental findings and numerical simulations

An analysis of Universal Differential Equations for data-driven discovery of Ordinary Differential Equations

In the last decade, the scientific community has devolved its attention to the deployment of data-driven approaches in scientific research to provide accurate and reliable analysis of a plethora of phenomena. Most notably, Physics-informed Neural Networks and, more recently, Universal Differential Equations (UDEs) proved to be effective both in system integration and identification. However, there is a lack of an in-depth analysis of the proposed techniques. In this work, we make a contribution by testing the UDE framework in the context of Ordinary Differential Equations (ODEs) discovery. In our analysis, performed on two case studies, we highlight some of the issues arising when combining data-driven approaches and numerical solvers, and we investigate the importance of the data collection process. We believe that our analysis represents a significant contribution in investigating the capabilities and limitations of Physics-informed Machine Learning frameworks

Goods Relocation Management in City Fashion Retailers with an Incentive System

n/

Studying the universality of field induced tunnel ionization times via high-order harmonic spectroscopy

High-harmonics generation spectroscopy is a promising tool for resolving electron dynamics and structure in atomic and molecular systems. This scheme, commonly described by the strong field approximation, requires a deep insight into the basic mechanism that leads to the harmonics generation. Recently, we have demonstrated the ability to resolve the first stage of the process -- field induced tunnel ionization -- by adding a weak perturbation to the strong fundamental field. Here we generalize this approach and show that the assumptions behind the strong field approximation are valid over a wide range of tunnel ionization conditions. Performing a systematic study -- modifying the fundamental wavelength, intensity and atomic system -- we observed a good agreement with quantum path analysis over a range of Keldysh parameters. The generality of this scheme opens new perspectives in high harmonics spectroscopy, holding the potential of probing large, complex molecular systems.Comment: 11 pages, 5 figure