A survey and taxonomy on virtual data center embedding

The Journal of Supercomputing - Data center network virtualization is being considered as a promising technology to provide a performance guarantee for cloud computing applications. One important...     

Adaptive fuzzy regulation of the DC-bus capacitor voltage in a wind energy conversion system (WECS)

This paper proposes a new voltage regulator of the DC-bus capacitor of a variable speed wind power generation system based on adaptive fuzzy system. The change in the fuzzy rule base is done using a variable-structure direct adaptive control algorithm to achieve the pre-defined control objectives. This algorithm has two merits. First, it has a good performance in the training phase as it makes use of the initial rule base defined for the fuzzy logic controller. Second, it has a robust estimator since it depends on variable structure technique. The adaptive nature of the new controller significantly reduces the rule base size and improves its performance.     

Global characterization of soft magnetic materials under rotating flux density conditions

Although several authors have proposed different devices to measure the iron loss in magnetic sheets used in the building of electrical machines, few of them take into account the real electromagnetic working context. This paper deals with the possibility of determining the iron loss and the apparent magnetic permeability from the measurement of the flux density in the air gap with the use of the Maxwell's tensor and an analog computer. We propose new methods to obtain the power loss and the magnetic permeability of magnetic samples.     

Achievement in hydrogen storage on adsorbents with high surface-to-bulk ratio – Prospects for Si-containing matrices

In hydrogen storage, the concept of the reversible capture still remains a major issue to be addressed. The advances in chemical storage provide useful data that demonstrate that purely physical adsorption offer promising prospects, even though the hydrogen uptakes barely attain 11 wt%. The emerging nanotubes, fullerenes, metal-organic frameworks are sophisticated structures that display weak affinity toward hydrogen, and require complex synthesis procedures. Adsorption rather consists of a gas condensation at low temperatures and/or high pressures. That is why the present review is devoted to the most recent achievements in developing novel microporous materials with emphasis on silicon-based structures, aluminosilicates and related materials. Their large availability and low production costs open promising prospects. On aluminosilicates, low Si:Al ratio, high porosity and specific surface area, along with alkali or alkaline-earth exchangeable cations are essential requirements for effective hydrogen adsorption even at room temperature.     

Enhancing the performance of household refrigerators with latent heat storage: An experimental investigation

This paper presents the results of experimental tests carried out to investigate the performance of a household refrigerator using a phase change material (PCM). The PCM is located on the back side of the evaporator in order to improve its efficiency and to provide a storage capacity allowing several hours of refrigeration without power supply. The system has been tested with water and with a eutectic mixture (freezing point ?3 °C) and for a range of operating conditions (PCM thickness, ambient temperature, thermal load). The analysis of the results shows a significant improvement of the performance compared to a conventional system.     

Colza oil bleaching through optimized acid activation of bentonite. A comparative study

The acid activation of an Algerian bentonite was investigated using a factorial 3³ experiment design in order to improve the bleaching capacity in the colza oil processing. Optimized acid treatment of this bentonite gave rise to an effective bleaching earth in colza oil treatment. The 80 °C temperature value was regarded as being convenient in this study. For this purpose, the effects at 80 °C of three key parameters were investigated, namely the effects of the acid concentration in aqueous solution, the contact time and the clay to acid (S/L) ratio upon the clay effectiveness, regarded as the response function to be prone to modeling, simulation and optimization. The results showed that the acid concentration displays a stronger individual effect, as compared to the other parameters. In optimal activation conditions (acid concentration 31%, contact time 10 h and solid to liquid ratio 320 g/L), the highest bleaching capacity was found to be 99%. Comparison of the bleaching capacity from our bentonite shows that similar performances require less acid activated bentonite than any other bentonite. The acid acid-activated bentonite displayed also even higher color and chlorophyll removal than both the Tonsil and Maghnia standards, for similar bleaching earth amounts. The recommended features for the colza oil were obtained using only 1 wt.% of acid-activated bentonite, as compared to the Tonsil and Maghnia standard (1.2–1.4 and 2 wt.%, respectively). The model adequacy was also verified through additional bleaching experiment within the fixed parameters ranges, and was discussed.     

Etude de l'influence du mode d'anodisation sur la cinétique de croissance des films d'alumine en milieu acide sulfurique

The kinetics of growth of Al₂O₃ oxide films made by anode oxidation of ALuminium 1050A with two anodization techniques has been investigatedan compared. The first technique is the classical method based on continuous tension during the complete electrlysis duration, and the second one is the modern method ofpulsed tensions, whcih consists of periodically imposing to the material two anodc tensions E₁ and E₂ (E₁ > E₂) during time T₁ and T₂ until the end on anodization. We have shown that the second technique allows the fabrication of films more rapidly for the same electrolysis duraton. Energy and electrolysis time are saved, making it attractive from an economical viewpoint. This advantage arises from the positive effect of excess heat disiption gathered during the imposition of tension, E₁, when E₂ is imposed thereafter (recovery effect). The logging of in situ transient responses in the case of pulsed anodization is a significant asset to explain the growth film kinetics obtained with this method.     

Extra Virgin Olive Oil Components and Oxidative Stability from Olives Grown in Tunisia

The effects of the contents of lipids, pigments, α-tocopherol and phenols were studied in relation to the antioxidant capacity of five virgin olive oils obtained from five olive cultivars planted in Tunisia (Arbequina, Koroneiki, Leccino, Oueslati and Chemchali). The antioxidant capacities were evaluated by two different radical scavenging activities: radical scavenging activity by the DPPH assay (RSA-DPPH) and total antioxidant status by the ABTS test (TAA-ABTS). The highest contents of antioxidant compounds (75.96, 10.34, 6.32, 15.39 and 241.52 mg kg⁻¹ for oleic acid, O/L ratio, carotenes, chlorophylls and total phenols, respectively) were found for the Koroneiki cultivar except for α-tocopherol and o-diphenols, which had the highest contents (369 and 160.7 mg kg⁻¹, respectively) in the Leccino and Chemchali cultivars (cvs). Furthermore, the highest antioxidant capacity in virgin olive oil was observed in the Koroneiki cultivar (0.24 mmol TE kg⁻¹) followed by the Chemchali and Leccino cvs (0.22 and 0.13 mmol TE kg⁻¹) for the TAA-ABTS test. However, the RSA-DPPH activity was higher for the Chemchali cultivar (19.9%) than for the Koroneiki and Leccino cvs (18.4 and 13.5%, respectively). Correlation between these capacities and the oil composition revealed that they were mainly influenced by the carotene content, followed by chlorophyll and phenolic contents where the ABTS test was more pronounced. Then, the antioxidant capacity of the virgin olive oils was correlated with polar components and the lipid profile which are important for its shelf life.     

Intrinsic growth rate: a new approach to evaluate the effects of temperature, photoperiod and phosphorus-nitrogen concentrations on duckweed growth under controlled eutrophication

A comprehensive model based on a new approach was developed to simulate the duckweed growth under controlled conditions. Contrary to other approaches which use the specific growth rate, this approach uses the intrinsic growth rate which permits to differentiate the effect of duckweed mat density from that of temperature, photoperiod and phosphorus-nitrogen concentrations. The model was calibrated using data from laboratory experiments carried out during the present study and validated using other data from two literature sources. In both cases, the results demonstrated that the model was capable of predicting duckweed growth with a reliability of 95%.     

Algorithms for automatic modulation recognition of communicationsignals

This paper introduces two algorithms for analog and digital modulations recognition. The first algorithm utilizes the decision-theoretic approach in which a set of decision criteria for identifying different types of modulations is developed. In the second algorithm the artificial neural network (ANN) is used as a new approach for the modulation recognition process. Computer simulations of different types of band-limited analog and digitally modulated signals corrupted by band-limited Gaussian noise sequences have been carried out to measure the performance of the developed algorithms. In the decision-theoretic algorithm it is found that the overall success rate is over 94% at the signal-to-noise ratio (SNR) of 15 dB, while in the ANN algorithm the overall success rate is over 96% at the SNR of 15 dB