Search results for "Continuous"
showing 10 items of 899 documents
Parametric frequency conversion of optical simulton pulses
2007
We present an analytical description of the parametric frequency conversion of short solitary wave optical pulses in quadratic nonlinear crystals controlled by means of a continuous wave background.
Extreme Statistics in Raman Fiber Amplifiers: From Analytical Description to Experiments
2011
International audience; In this work, we investigate the emergence of rare and intense events during the Raman fiber amplification of a continuous wave. We highlight how dispersive properties and pump depletion can strongly influence the statistical properties of the amplified signal and its optical spectrum. Under certain conditions, the probability density functions of the amplified signal are calculated analytically and compared with the results of the numerical simulations. The conclusions are qualitatively validated by experiments carried out at telecommunication wavelengths.
Ultraviolet generation in periodically poled Lithium Tantalate waveguides
2008
We demonstrate ultraviolet generation in lithium tantalate channel waveguides for frequency doubling via quasi-phase-matching. The samples, proton exchanged and nanostructured by electric-field assisted surface periodic poling with domains as deep as 40 μm, yield continuous wave light at 365.4 nm with conversion efficiencies larger than 7.5% W-1 cm-2.
Analysis and design of elastic plastic structures subjected to dynamic loads
In the last decades, the concept of “optimization” has reached considerable value in many different fields of scientific research and, in particular, it has assumed great importance in the field of structural mechanics. The present study describes and shows the scientific path followed in the three years of doctoral studies. The state of the art concerning the optimization of elastic plastic structures subjected to quasi-static loads was already well established at the beginning of the Ph.D. course. Actually, it was already faced the study of structures subjected to quasi-static cyclic loads able to ensure different structural behaviors in relation to different intensity levels of the appli…
A design algorithm for the optimization of laminated composite structures
1999
This paper is devoted to the optimal design of laminated composite structures. The goal of the study is to assess the quality and the performance of an algorithm based on the directional derivative method. Particular attention is paid to the one‐dimensional search, a critical step of the process, performed by cubic splines approximation. The optimization problem is formulated as weight minimization, under constraints on the mechanical behavior of the structure. The assumed design variables are the ply thicknesses, treated as continuous design variables, constrained by technological requirements. The structural analysis is performed making use of quadrilateral four‐node composite elements, b…
Minimum volume design of structures with constraints on ductility and stability
2014
Abstract A minimum volume design problem of elastic perfectly plastic frame structures subjected to different combinations of fixed and seismic loads is presented, in which the design variables are considered as appertaining alternatively to a continuous assigned range as well as to appropriate discrete sets. The structure is designed so as to behave elastically for the applied fixed loads, to shakedown in presence of serviceability seismic conditions and to prevent the instantaneous collapse for suitably chosen combinations of fixed and high seismic loadings. In order to avoid further undesired collapse modes, the P-Delta effects are considered and the structure is also constrained to prev…
Structural contagion and vulnerability to unexpected liquidity shortfalls
2012
This paper assumes that financial fluctuations are the result of the dynamic interaction between liquidity and solvency conditions of individual economic units. The framework is an extention of Sordi and Vercelli (2012) designed as an heterogeneous agent model which proceeds through discrete time steps within a finite time horizon. The interaction at the micro-level between economic units monitors the spread of contagion and systemic risk, producing interesting complex dynamics. The model is analysed by means of numerical simulations and systemic risk modelling, where local interaction of units is captured and analysed by the bilateral provision of liquidity among units. The behaviour and e…
How to create international business competences and their impact on firm performance
2014
[EN] This work aims to analyse the effect of the holistic view, continuous learning and information technology infrastructure on the creation of international business competences. The study also investigates whether the creation of this type of competence significantly affects firm performance using the structural equation modelling method of hypothesis testing. A survey of 257 companies from the biotechnology and telecommunications industries verifies the mediating role of international business competences. These findings suggest that managers should emphasise the creation of a holistic view, promote continuous learning and improve the information technology infrastructure in order to de…
Microstructure alterations of rotary files after multiple simulated operative procedures.
2009
Aim: To assess morphological alterations of ProTaper rotary NiTi files before and after continuous use by scanning electron microscopy (SEM). Study Design: 30 root canals were chosen with an angle between 15 and 30º. Before starting to prepare the canals the files were observed microscopically using a scanning electronic microscope. The ProTaper sequence recommended by the manufacturer was used, with NaOCl as irrigant. The instruments were sterilised after every three canals were shaped. The instruments were observed with the same microscope after shaping each canal, until 30 root canals were shaped. The criteria used for checking the instruments were: blunt cutting edges, disruption of cut…
Influence of the Geometrical Cross-Section Design on the Dynamic Cyclic Fatigue Resistance of NiTi Endodontic Rotary Files—An In Vitro Study
2021
The aim of this study was to analyze and compare the influence of the geometrical cross-section design on the dynamic cyclic fatigue resistance of NiTi endodontic rotary files. Materials and Methods: Forty sterile endodontic rotary files were selected and distributed into the following study groups: A: 25.06 double S-shaped cross-section NiTi alloy endodontic rotary files (Mtwo) (n = 10)