Long-term water quality monitoring of the Sejnane reservoir in northeast Tunisia

The Sejnane reservoir in northeast Tunisia provides drinking and irrigation water. Long-term water quality monitoring data including precipitation, evaporation, temperature, pH, conductivity, dissolved oxygen, turbidity, total suspended solids, major anions and cations, fluoride, BOD₅, NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, P _tot, fecal coliform bacteria, boron and heavy metals (Fe, Zn, Cu, Ni, Pb, Cr and Cd) are reported. The appropriateness for irrigation was estimated by the SAR and Na percentage and the water quality assessed using the Canadian Water Quality Index as good to excellent, which confirmed its suitability for drinking, aquatic life and irrigation purposes.      

The Role of Nuclear Power in Reducing Risk of the Fossil Fuel Prices and Diversity of Electricity Generation in Tunisia: A Portfolio Approach

This paper applies real options and mean–variance portfolio theories to analyze the electricity generation planning into presence of nuclear power plant for the Tunisian case. First, we analyze the choice between fossil fuel and nuclear production. A dynamic model is presented to illustrate the impact of fossil fuel cost uncertainty on the optimal timing to switch from gas to nuclear. Next, we use the portfolio theory to manage risk of the electricity generation portfolio and to determine the optimal fuel mix with the nuclear alternative. Based on portfolio theory, the results show that there is other optimal mix than the mix fixed for the Tunisian mix for the horizon 2010–2020, with lower cost for the same risk degree. In the presence of nuclear technology, we found that the optimal generating portfolio must include 13% of nuclear power technology share.     

The effects of crude oil shocks on stock market shifts behaviour: A regime switching approach

In this paper we develop a two regime Markov-switching EGARCH model introduced by Henry [Henry, O., 2009. Regime switching in the relationship between equity returns and short-term interest rates. Journal of Banking and Finance 33, 405–414.] to examine the relationship between crude oil shocks and stock markets. An application to stock markets of UK, France and Japan over the sample period January 1989 to December 2007 illustrates plausible results. We detect two episodes of series behaviour one relative to low mean/high variance regime and the other to high mean/low variance regime. Furthermore, there is evidence that common recessions coincide with the low mean/high variance regime. In addition, we allow both real stock returns and probability of transitions from one regime to another to depend on the net oil price increase variable. The findings show that rises in oil price has a significant role in determining both the volatility of stock returns and the probability of transition across regimes.     

Experimental investigations of a gamma Stirling engine

The present work deals with the measurement and performance of a gamma Stirling engine of 500 W of mechanical shaft power and 600 rpm of maximal revolutions per minute. Series of measurements concerning the pressure distribution, temperature evolution, and brake power were performed. The study of the different functioning parameters such as initial charge pressure, engine velocity, cooling water flowrate, and temperature gradient (between the sources of heat) has been analyzed. The engine brake power increases with the initial charge pressure, with the cooling water flow, and with the engine revolutions per minute. The working fluid temperature measurements have been recorded in different locations symmetrically along both regenerator sides. The recorded temperature in regenerator side one is about 252 °C and about 174 °C in the opposite side (side two). It shows an asymmetric temperature distribution in the Stirling engine regenerator; consequently, heat transfer inside this porous medium is deteriorated. Copyright © 2011 John Wiley & Sons, Ltd.     

Liquid hydrocarbon fuels from fish oil industrial residues by catalytic cracking

In the present work, catalytic cracking of fish oil industrial residue was investigated to study the effect of temperature, type of catalyst and the heating rate on the yield of organic liquid fraction (OLF) and its acid value. The highest bio‐oil yield of 72% (wt.) was obtained at temperature range of 300–500 °C and heating rate of 10 °C/min with the mixture of Al₂O₃ and Na₂CO₃ as a catalyst. It was found that the mixture of Na₂CO₃ and MgSO₄ as a catalyst gives lowest acid value of 8.75 mg_KOH/g_oil and 68.1% of OLF yield. Furthermore, the acid value is reduced to 0.36 mg_KOH/g_oil using Na₂CO₃ as an absorbent. The results show that the catalytic cracking process represents a sustainable method to produce bio‐oil from fish oil industrial residues with physicochemical characteristics similar to the diesel fuel. Copyright © 2012 John Wiley & Sons, Ltd.     

Value-at-risk estimations of energy commodities via long-memory,asymmetry and fat-tailed GARCH models

In this paper, we evaluate the value-at-risk (VaR) and the expected shortfalls for some major crude oil and gas commodities for both short and long trading positions. Classical VaR estimations as well as RiskMetrics and other extensions to cases considering for long-range memory, asymmetry and fat-tail in energy markets volatility were conducted. We computed the VaR for three ARCH/GARCH-type models including FIGARCH, FIAPARCH and HYGARCH. These models were estimated in the presence of three alternative innovation’s distributions: normal, Student and skewed Student. Our results show that considering for long-range memory, fat-tails and asymmetry performs better in predicting a one-day-ahead VaR for both short and long trading positions. Moreover, the FIAPARCH model outperforms the other models in the VaR’s prediction. These results present several potential implications for energy markets risk quantifications and hedging strategies.     

Alginate coatings containing grapefruit essential oil or grapefruit seed extract for grapes preservation

Biodegradable coatings based on 1% and 2% sodium alginate (NaAlg) with and without grapefruit seed extract (GSE) or grapefruit essential oil (GEO) were applied to table grapes to preserve their quality. Changes in weight loss, firmness and antioxidant activity were assessed over 15 days of cold storage. The effectiveness of developed coatings to control postharvest decay of inoculated grape berries stored for 5 days at 20 °C was also investigated. Biodegradable coatings based on pure NaAlg and those containing GSE were efficient in reducing weight loss and maintaining firmness during storage. Coatings incorporating either GEO or GSE were able to preserve the antioxidant activity of treated grapes and to reduce decay incidence in inoculated fruits. Coatings formulated with 2% NaAlg‐1% GSE showed the greatest preservation of antioxidant activity and the highest antifungal effect, with an effective control of water and firmness losses. These coatings can be recommended for maintaining table grapes quality.     

Development of a novel composite film based on polyurethane and defatted Chlorella biomass: Physical and functional characterization

Novel composite films made of polyurethane (PU) and defatted Chlorella biomass (DCB) at different mass proportions (10–70 wt%) were prepared using polyethylene glycol (PEG) as a model polyol and hexamethylene diisocyanate (HMDI) as a coupling agent. Increasing DCB content led to a respective increase in tensile strength and elongation at break of the composites in the range of 33.9–116% and 69.6–248%, compared to the neat PU-PEG film. As confirmed by Fourier transform infrared and scanning electron microscopy analysis, such improvement in mechanical properties can be attributed to the establishment of hydrogen bonds and other molecular interactions between isocyanate groups of PEG-HMDI prepolymer and hydroxyl groups of DCB biofiller along with the uniform distribution of the incorporated DCB into the PU-PEG based matrix. DCB incorporation at the highest content of 70% increased both antioxidant activity and bulk hydrophilicity of the composites by more than 69.3 and 85.0%, respectively, compared to the neat PU-PEG.     

Treatment of olive oil mill wastewater by combined process electro-Fenton reaction and anaerobic digestion

In this work, we investigated an integrated technology for the treatment of the recalcitrant contaminants of olive mill wastewaters (OMW), allowing water recovery and reuse for agricultural purposes. The method involves an electrochemical pre-treatment step of the wastewater using the electro-Fenton reaction followed by an anaerobic bio-treatment. The electro-Fenton process removed 65.8% of the total polyphenolic compounds and subsequently decreased the OMW toxicity from 100% to 66.9%, which resulted in improving the performance of the anaerobic digestion. A continuous lab-scale methanogenic reactor was operated at a loading rate of 10 g chemical oxygen demand (COD)l(-1) d(-1) without any apparent toxicity. Furthermore, in the combined process, a high overall reduction in COD, suspended solids, polyphenols and lipid content was achieved by the two successive stages. This result opens promising perspectives since its conception as a fast and cheap pre-treatment prior to conventional anaerobic post-treatment. The use of electro-coagulation as post-treatment technology completely detoxified the anaerobic effluent and removed its toxic compounds.     

On the Net Neutrality Efficiency under Congestion Price Discrimination

Networks and Spatial Economics - In this paper, we study the extent to which net neutrality, defined as price non-discrimination, is welfare improving in comparison to non-net-neutrality. We...