Abstract

Abstract
The effect of an erbium-doped fiber amplifier (EDFA) placed inside the fiber ring of a cavity ring down (CRD) configuration is studied. The limitations and advantages of this configuration are discussed, and the study of the ring-down time as a function of the current applied and gain to the EDFA is also presented. In this case, the power fluctuations in the output signal are strongly dependent on the cavity ring-down time with the EDFA gain.

Abstract
Fault tolerance is essential for building reliable services; however, it comes at the price of redundancy, mainly the 'replication factor' and 'diversity'. With the increasing reliance on Internet-based services, more machines (mainly servers) are needed to scale out, multiplied with the extra expense of replication. This paper revisits the very fundamentals of fault tolerance and presents 'artificial redundancy': a formal generalization of 'exact copy' redundancy in which new sources of redundancy are exploited to build fault tolerant systems. On this concept, we show how to build 'artificial replication' and design 'artificial fault tolerance' (AFT). We discuss the properties of these new techniques showing that AFT extends current fault tolerant approaches to use other forms of redundancy aiming at reduced cost and high diversity. © 2016 IEEE.

Abstract

Abstract
The effectiveness of UV-A Light emitting diodes (UV-A LEDs) for decolourization of Reactive Black 5 (RB5) solutions in a continuous photoreactor and the effect of different operational parameters on the photocatalytic decolourization of RB5 were investigated in the present work. The operational parameters included catalyst load, initial dye concentration, irradiance and solution flowrate. Photocatalytic experiments were conducted in a self-designed photoreactor with a matrix of 96 UV-A LEDs (375 nm) and Evonik P-25 TiO2 was used as a photocatalyst. The optimum experimental conditions that allowed the highest decolourization of RB5 (89%) were an irradiance of 40 W/m(2), 1.0 g/L of TiO2, 50 mg/L of RB5 and a flowrate of 0.8 mL/min. A continuous stirred tank reactor (CSTR) design equation, subsequently simplified to a pseudo-first order rate equation, was used to analyse the kinetics of the experimental results. From the kinetics it is possible to observe that high TiO2 concentrations (1.0 g/L) and light irradiances (40 W/m(2)) positively affect the reaction rate (r, 2.483 x 10 (7) mol/L min) and the reaction rate constants (k, 7.351 x 10 (3) min (1)). The figure-of-merit electrical energy per order (E-EO) was calculated for the photoreactor, and values of 220 kWh/m(3)/order were reached for an electric power consumption of 0.0129 kW and a solution flowrate of 4.8 x 10 (6)m(3)/h. Results demonstrated that a UV-A LED/TiO2 process can effectively decolourize RB5 dye solutions within the selected optimum conditions.

Abstract
Reconfigurability, understood as the ability of a system to behave differently in different modes of operation and commute between them along its lifetime, is a cross-cutting concern in modern Software Engineering. This paper introduces a specification method for reconfigurable software based on a global transition structure to capture the system's reconfiguration space, and a local specification of each operation mode in whatever logic (equational, first-order, partial, fuzzy, probabilistic, etc.) is found expressive enough for handling its requirements. In the method these two levels are not only made explicit and juxtaposed, but formally interrelated. The key to achieve such a goal is a systematic process of hybridisation of logics through which the relationship between the local and global levels of a specification becomes internalised in the logic itself.