The Machine Scenario: A Computational Perspective on Alternative Representations of Indeterminism

In philosophical logic and metaphysics there is a long-standing debate around the most appropriate structures to represent indeterministic scenarios concerning the future. We reconstruct here such a debate in a computational setting, focusing on the fundamental difference between moment-based and history-based structures. Our presentation is centered around two versions of an indeterministic scenario in which a programmer wants a machine to perform a given task at some point after a specified time. One of the two versions includes an assumption about the future behaviour of the machine that cannot be encoded in any programming instruction; such version has models over history-based structures but no model over a moment-based structure. Therefore, our work adds a new stance to the debate: moment-based structures can be said to rule out certain indeterministic scenarios that are computationally unfeasible.

     

Calibrations scheduling with arbitrary lengths and activation length

Bender et al. (SPAA 2013) proposed a theoretical framework for testing in contexts where safety mistakes must be avoided. Testing in such a context is made by machines that need to be calibrated on a regular basis. Since calibrations have a non-negligible cost, it is important to study policies minimizing the total calibration cost while performing all the necessary tests. We focus on the single-machine setting, and we study the complexity status of different variants of the problem. First, we extend the model by considering that the jobs have arbitrary processing times, and we propose an optimal polynomial-time algorithm when the preemption of jobs is allowed. Then, we study the case where there are many types of calibrations with their corresponding lengths and costs. We prove that the problem becomes NP-hard for arbitrary processing times even when the preemption of the jobs is allowed. Finally, we focus on the case of unit processing time jobs, and we show that a more general problem, where the recalibration of the machine is not instantaneous, can be solved in polynomial time via dynamic programming.

     

Duration modelling and evaluation for Arabic statistical parametric speech synthesis

Multimedia Tools and Applications - Sound duration is responsible for rhythm and speech rate. Furthermore, in some languages phoneme length is an important phonetic and prosodic factor. For...     

Localized corrosion of lean duplex stainless steels in H2S-containing wet atmosphere from urban wastewater treatment units

With lower alloying costs and higher mechanical properties, lean duplex stainless steels can be a good alternative to the more commonly used austenitic stainless steels. A study was initiated to define the limits of the use of lean duplex stainless steels for urban wastewater treatment (WWT) units. This paper gives and discusses the corrosion results in an aerated wet atmosphere containing H₂S at different levels. Exposures were performed both at laboratory scale and in the field WWT plant for 1 year. A specific probe was also designed to study the corrosion process below water condensate film contaminated with H₂S. Under such conditions, the properties of stainless steel were strongly modified with an enhanced risk of localized corrosion. The results obtained on lean duplex materials (UNS S32101, S32202, and S32304) are compared with austenitic UNS S30403 and UNS S31603 and with the more standard duplexes UNS S82441 and UNS S32205. The results show that lean duplexes can be used in aerated wet atmospheres in case of moderate contamination of H₂S (<10 ppm) and chloride (<200 ppm). For higher contaminations (e.g., H₂S around 100 ppm/chloride around 1000 ppm) the duplex S32205 should be preferred.     

An Artificial Cofactor Catalyzing the Baylis-Hillman Reaction with Designed Streptavidin as Protein Host**

An artificial cofactor based on an organocatalyst embedded in a protein has been used to conduct the Baylis-Hillman reaction in a buffered system. As protein host, we chose streptavidin, as it can be easily crystallized and thereby supports the design process. The protein host around the cofactor was rationally designed on the basis of high-resolution crystal structures obtained after each variation of the amino acid sequence. Additionally, DFT-calculated intermediates and transition states were used to rationalize the observed activity. Finally, repeated cycles of structure determination and redesign led to a system with an up to one order of magnitude increase in activity over the bare cofactor and to the most active proteinogenic catalyst for the Baylis-Hillman reaction known today.     

Modelling heterogeneous photocatalytic oxidation using suspended TiO2 in a photoreactor working in continuous mode: Application to dynamic irradiation conditions simulating typical days in July and February

Compared to more conventional techniques, advanced oxidation processes (AOP) hold significant promise in terms of elimination of organic (especially persistent) compounds and microorganisms (disinfection) in wastewater. If the objective is to power these processes using solar energy, we need to be able to manage the intermittency in the solar resource. This is an essential step for design and to ensure efficient operation of the treatment processes. As solar radiation is inherently variable due to day/night cycles, seasonal cycles, and weather meteorological conditions, solar AOP performances are difficult to establish using conventional measures. To address this gap, we carry out experimental campaigns under controlled conditions and develop modelling tools capable of describing dynamic‐mode photocatalytic degradation. Here we develop a way to capture the responses of a photoreactor subjected to various stresses, including irradiation conditions, via an LED panel. Using a model that considers the influence of UV flux density and pollutant concentration made, it was possible to represent photoreactor responses under different irradiation conditions and feeds (concentration or flow at the input). The ultimate objective is to study the photocatalytic capacity of the photoreactor under irradiation conditions simulating a real day of sunshine.     

Permeability spectra of planar M-type barium hexaferrites with high Snoek’s product by two-step sintering

High-frequency ferrite ceramics exhibiting high permeability and low magnetic loss have been recently attracting more and more attention owing to the rapid development of modern communication technologies. It is known that the magnetic performance of ferrites is strongly associated with the morphology of their polycrystalline structure. In this work, we focus on the control of grain growth and densification process for planar Co-Ti doped M-type barium hexaferrites, BaCo_xTi_xFe_12-xO₁₉, by one-step sintering (OSS) and two-step sintering (TSS) techniques. Experimental results indicate that a uniform and fine-grained microstructure is achieved by the TSS method. More importantly, the ferrites prepared by TSS demonstrate high permeability (µ' = 18-20), low magnetic loss (tan δ_m = 0.1-0.3), and high Snoek's product (>25 GHz) in the frequency range of 100-400 MHz. By fitting experimental data, we have determined that low magnetic loss is derived from the small damping coefficient of spin rotation in terms of Kittel's theory. Therefore, the TSS technique provides an effective and efficient approach to prepare planar BaM hexaferrite materials for ultra-high frequency (UHF) communication devices requiring low loss and high Snoek's product.