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91.
Prudenzano F Mescia L Palmisano T Surico M De Sario M Righini GC 《Applied optics》2012,51(9):1420-1430
Different strategies for designing optical couplers, optimized to enhance the pump absorption in the rare-earth-doped core of microstructured fiber lasers, are illustrated. Three kinds/configurations of optical couplers have been designed and compared as examples of the different design strategies which can be followed. Their effectiveness to enhance the performance of an ytterbium-doped, double cladding, microstructured optical fiber laser has been accurately simulated. They consist of a suitable cascade of multiple long-period gratings (MLPGs) inscribed in the fiber core region. The characteristics of the MLPG couplers have been simulated via a homemade computer code based on both rate equations and an extended coupled mode theory. The proposed MLPG couplers seem particularly useful in the case of low rare-earth concentration but, even for a middle-high ytterbium concentration, as N(Yb)=5×10(25) ions/m(3), the slope efficiency S can be increased up to 20%, depending on the fiber length. 相似文献
92.
Tommaso Gomes Debora Delcuratolo Vito Michele Paradiso 《European Food Research and Technology》2008,226(6):1409-1414
The aim of the research was to evaluate the pro-oxidant action of oxidized triglyceride oliogopolymers, a class of oxidation
compounds present in refined vegetable oils. Silica gel column chromatography was used to obtain the polar compounds from
a thermally oxidized oil and preparative gel permeation chromatography to separate and collect the oxidized triglyceride oligopolymers.
A purified oil that was practically free of oxidation and hydrolytic degradation products, pigments and anti-oxidants was
prepared in the laboratory to evaluate pro-oxidant activity without interferences. Addition of percent amounts of oxidized
triglyceride oligopolymers of 0.25 to 1.0% to both the purified and unpurified oils clearly evidenced the pro-oxidant activity
of this class of compounds. 相似文献
93.
Vito M. Paradiso Tommaso Gomes Raffaella Nasti Francesco Caponio Carmine Summo 《Food research international (Ottawa, Ont.)》2010,43(5):1389-1394
Several studies have investigated the interaction of free fatty acids with the oxidative phenomena involving oils during processing and storage. Nevertheless, the available information is insufficient and, in some cases, contradictory.The aim of this work was to throw light upon this matter, by evaluating – by means of different analytical approaches – the effect of adding increasing amounts of free fatty acids (0.25%, 0.5%, 1%, 3%) on the oxidative processes occurring in purified olive oil during oxidation at 60 °C.The results obtained showed that oxidized forms of triglycerides and polar oligopolymers of triglycerides increased during oxidation. Low amounts of added FFA caused a further increase of the levels of oxidized triglycerides and triglyceride oligopolymers – pointing out a pro-oxidant activity – while higher doses of added free fatty acids lead to lower amounts of oxidized forms of triglycerides respect to the purified oil. This could be due to an increase in peroxide decomposition exerted by free fatty acids when present in higher amounts. 相似文献
94.
Microforming from sheet metals is a technology with high potential and increasing interest in modern factories. The combination of bulk forming technologies in micro-scale together with the easier handling of metal strips allows the high rate production of products with small dimension and is suited for commercial fields like electronics and micromechanics. The need of an efficient FEM aided process design must face the problem of material behavior in microforming, affected by size-effects and not obeying continuum mechanics. A reliable FE model allows the production of a database allowing, additional to process optimization, the design of online process control and the reduction of manufacturing defects, strongly affecting micro-productions because of the high deviations in such processes. In this work, a method for the design of a FEM model of a microforging process is proposed, developed in the commercial software MSC Marc including the modelling of local size effects in the form of variable friction. An increased friction factor is assumed, where typical microforming size effects are expected to take place. Stainless steel and copper-beryllium alloys are studied with the thickness of 300 µm. The microforged geometry consists in 6 parallel protrusions with a width of 200 µm. The experimental study is then performed, by varying punch forces, firstly in a simplified configuration with two protrusions and finally with the complete geometry in a multi-stage microforming process, respectively validating and verifying the developed simulation model. 相似文献
95.
Antonietta Baiano Tommaso Gomes & Francesco Caponio 《International Journal of Food Science & Technology》2005,40(8):829-834
The hydrolytic and oxidative degradation of olive oil and extra‐virgin olive oil, used as covering liquids in canned dried tomatoes, was studied during storage by means of conventional (acidity, peroxide value, p‐anisidine value) and non conventional (polar compounds) analyses. The effects of the addition of spices were also considered. The hydrolysis and oxidation of olive oil increased faster and was higher than that of extra‐virgin olive oil in terms of absolute values but some other indices, such as percentage of oligopolymers and percentage of oxidized triglycerides, increased faster in extra‐virgin olive oil than in olive oil. The antioxidant effect given by a higher concentration of polyphenols in the extra‐virgin olive oil was shown by a reduced amount of secondary oxidation. However, olive oil and extra‐virgin olive oils showed similar behaviour in terms of peroxide formation. 相似文献
96.
De Paolis Lucio Tommaso Gatto Carola Corchia Laura De Luca Valerio 《Virtual Reality》2023,27(2):1117-1143
Virtual Reality - Augmented Reality (AR) has become an increasingly used technology to support and enhance the enjoyment of cultural heritage. Particularly relevant is its importance for... 相似文献
97.
In this paper, an exception-based programming paradigm is envisioned to deal with timing constraints violations occurring in soft real-time and multimedia applications written in the C language. In order to prove viability of the approach, a mechanism allowing to use such paradigm has been designed and implemented as an open-source library of C macros making use of the standard POSIX API (a few Linux-specific optimizations are also briefly discussed).The proposed approach has been validated by modifying mplayer, one of the most widely used multimedia player for Linux, so as to use the introduced library. An extensive experimental evaluation has been made, both when running the player alone and when mixing it with a workload of other synthetic real-time applications. In the latter case, different scheduling policies have been used, including both standard priority-based ones as available on the mainline Linux, and an experimental deadline-based one available as a separate patch.The shown results demonstrate how the exception-based paradigm is effective in improving the audio/video delay exhibited by the player achieving a superior performance and a dramatically better quality of experience as compared to the original heuristic frame-dropping mechanism of the player. 相似文献
98.
Adaptive reservation is a real-time scheduling technique in which each application is associated a fraction of the computational resource (a reservation) that can be dynamically adapted to the varying requirements of the application by using appropriate feedback control algorithms. An adaptive reservation is typically implemented by using an aperiodic server (e.g. sporadic server) algorithm with fixed period and variable budget. When the feedback law demands an increase of the reservation budget, the system must run a schedulability test to check if there is enough spare bandwidth to accommodate such increase. The schedulability test must be very fast, as it may be performed at each budget update, i.e. potentially at each instance of a task; yet, it must be as efficient as possible, to maximize resource usage. In this paper, we tackle the problem of performing an efficient on-line schedulability test for adaptive resource reservations in fixed priority schedulers. In the literature, a number of algorithms have been proposed for on-line admission control in fixed priority systems. We describe four of these tests, with increasing complexity and performance. In addition, we propose a novel on-line test, called Spare-Pot algorithm, which has been specifically designed for the problem at hand, and which shows a good cost/performance ratio compared to the other tests. 相似文献
99.
The connections between symmetries and conserved quantities of a dynamical system brought to light by Noether??s theorem depend in an essential way on the symplectic nature of the underlying kinematics. In the discrete dynamics realm, a rather suggestive analogy for this structure is offered by second-order cellular automata. We ask to what extent the latter systems may enjoy properties analogous to those conferred, for continuous systems, by Noether??s theorem. For definiteness, as a second-order cellular automaton we use the Ising spin model with both ferromagnetic and antiferromagnetic bonds. We show that??and why??energy not only acts as a generator of the dynamics for this family of systems, but is also conserved when the dynamics is time-invariant. We then begin to explore the issue of whether, in these systems, it may hold as well that translation invariance entails momentum conservation. 相似文献