Daouas N.,University of Monastir
Applied Energy | Year: 2011
In Tunisian climate, both heating in winter and cooling in summer are required to reach comfort levels. Due to the significant increase in building energy consumption, insulation of external walls is recently applied with a thickness typically ranging between 4cm and 5cm regardless of structure and orientation of walls and of economic parameters. In the present study, optimum insulation thickness, energy saving and payback period are calculated for a typical wall structure based on both cooling and heating loads. Yearly transmission loads are rigorously estimated using an analytical method based on Complex Finite Fourier Transform (CFFT). Considering different wall orientations, the west and east facing walls are the least favourite in the cooling season, whereas the north-facing wall is the least favourite in the heating season. A life-cycle cost analysis over a building lifetime of 30years shows that the south orientation is the most economical with an optimum insulation thickness of 10.1cm, 71.33% of energy savings and a payback period of 3.29years. It is noted that wall orientation has a small effect on optimum insulation thickness, but a more significant effect on energy savings which reach a maximum value of 23.78TND/m2 in the case of east facing wall. A sensitivity analysis shows that economic parameters, such as insulation cost, energy cost, inflation and discount rates and building lifetime, have a noticeable effect on optimum insulation and energy savings. Comparison of the present study with the degree-days model is also performed. © 2010 Elsevier Ltd.
Bahloul R.,University of Monastir
Materials and Design | Year: 2011
The objective of this work is modelling and optimisation of sheet bending process by means of numerical simulation. One of the problems to be solved in the sheet metal forming processes of thin sheets is the taking into account of the effects of technological process parameters so that the part takes the desired mechanical characteristics. Accordingly, it has been a crucial research subject for designing bending tools guaranteeing an optimal performance of products in terms of mechanical properties and good rigidity. In this paper, we propose a numerical procedure allowing the definition of the optimal values of process parameters in flanging operation, which minimises the residual stresses and the material damage at the end of the bending phase. The concept of continuum damage mechanics fully coupled with elasto-plasticity has been retained to describe the progressive damage accumulation into the sheet metal. According to parametric investigation on the maximum stress and calculated damage values, it has been found that the punch-die clearance and the die radius have significant effects on mechanical behaviour of parts. An application of design of experiments was developed as a preliminary step for the optimisation of the process parameters by using response surface methodology. This model allows the identification of the influential parameters of an optimisation problem and the reduction of the number of evaluations of the objective function. © 2010 Elsevier Ltd.
Omri A.,University of Monastir
Renewable and Sustainable Energy Reviews | Year: 2014
In this paper, an extensive review of the rapidly growing in the literature on the nexus between economic growth and four types of energy consumption: total energy consumption, electricity consumption, nuclear consumption, and renewable consumption. The various hypotheses associated with the causal interaction between these variables along with a survey of the empirical literature are also discussed. The survey focuses on country coverage, periods, modeling techniques, and empirical conclusions. A general observation from these studies that results are found to be sensitive to methodology and type of energy considered. The empirical results for the specific countries surveyed show that (i) for energy consumption-growth nexus: 29% supported the growth hypothesis, 27% the feedback hypothesis, 23% the conservation hypothesis, and 21% the neutrality hypothesis; (ii) for the electricity consumption-growth nexus: 40% supported the growth hypothesis, 33% the feedback hypothesis, and 27% conservation hypothesis; (iii) for the nuclear consumption-growth nexus: 60% supported the neutrality hypothesis, and 40% the growth hypothesis; and (iv) for the renewable consumption-growth nexus: 40% supported the neutrality hypothesis, 40% the conservation hypothesis, and 20% the growth hypothesis. These mixed results may be attributed to the different used data, selected variables, and econometric approaches undertaken. © 2014 Elsevier Ltd.
La Scola B.,University of Monastir
Expert Review of Molecular Diagnostics | Year: 2011
MALDI-TOF mass spectrometry (MS) on intact cells is at the forefront of a new revolution in the routine identification of microorganisms in clinical microbiology laboratories. In addition to its high accuracy for identification, it provides results in just a few minutes. As correct and timely diagnoses are pivotal for the management of bloodstream infections, MALDI-TOF MS has the potential to replace or at least complement other methods for microorganism identification in bloodstream infections. With the improvement of databases and software, this method has an accurate identification rate of nearly 100% on nearly all agar-grown microorganisms and more than 80% on positive blood culture broth tests. Even if it is highly efficient now, after a decade of developments, the technique is currently still under improvement. It lacks standardization and exhaustive databases or more efficient softwares that are currently under development. Even now, both the technology itself and the reagents are improving significantly. Thus, it is likely that identifications will become more accurate in the future, especially on more complex fluids, such as blood culture broth. © 2011 Expert Reviews Ltd.
Chatti S.,University of Monastir
Computers and Structures | Year: 2010
Commonly finite element analysis uses hypoelastoplastic (HEP) formulation to simulate forming processes and springback. In this study an elastoplastic (EP) formulation in finite strains is used. In the case of large elastic domain it has been found that the HEP law leads to oscillatory responses in shear test. Furthermore we show that the use of this law in springback simulation needs many increments to obtain an accurate solution. Alternatively, the use of an EP law gives a non-oscillatory solution in shear test and it needs a few numbers of increments in springback simulations to obtain accurate results. © 2010 Elsevier Ltd. All rights reserved.