Contribution of small and medium enterprises to economic development of Algeria during period (2001-2017)

     تهدف الورقة البحثية إلى التعرف على واقع المؤسسات الصغيرة والمتوسطة في الجزائر، بالإضافة إلى إبراز مدى مساهمتها في تحقيق التنمية الاقتصادية، وباستخدام  المنهج الوصفي والمنهج التحليلي في عرض المعلومات تبين لنا، أن المؤسسات الصغيرة والمتوسطة تساهم بشكل كبير في الاقتصاد الوطني من خلال توفير مناصب الشغل، زيادة في الناتج الداخلي الخام، زيادة في القيمة المضافة وتنمية الصادرات وبالتالي تحقيق فائض في الميزان التجاري.     The purpose of this paper is to identify the reality of small and medium enterprises in Algeria, in addition to highlighting their contribution to economic development, and using the descriptive and analytical approaches in the presentation of information, we found that SMEs contribute significantly to the national economy by providing jobs, Increase in GDP, increase in value added and export development, thus achieving a trade surplus

Investigation of residual stresses on the fire resistance of unrestrained cellular beams

It is being a common engineering practice to use steel beams with web openings in buildings requiring long spans, besides giving an important additional advantage of allowing services through instead of underneath the beams. The presence of these openings is penalizing the carrying capacity at ambient temperature and in the case of fire due to large cells and double nonlinearity geometric and material a complex behaviour take place. In this study, numerical models for beams having closely spaced large openings are simulated with ISO834 fire loading including both nonlinearities cited above in the primal investigation. Followed as a second investigation, is the effect of residual imperfections added to the numerical model mentioned above and simulated for different diagrams as presented within updated literature. All simulations were done using the finite element software ANSYS, to analyse the results captured for lateral torsional buckling (LTB) behaviour in terms of vertical and lateral displacement, von Mises stresses for different sections at ambient and fire conditions. For this parametric study, the change in cross-section geometries, opening spacing, beam length on the LTB of cellular beams is analysed.info:eu-repo/semantics/publishedVersio

Behaviour of cellular steel beams at ambient and high-temperature conditions

New developments in building construction have been observed to attain sustainable design criteria and the efficient use of raw materials, as steel is an example. This led to an increase in recent research on the optimization of geometric configurations of web-opening steel sections to meet cost-effectiveness in structural design. Improvement of the design method for perforated unrestrained steel beams to assess their behaviour under lateral torsional buckling (LTB) is still an ongoing issue for scientists and designers alike. In this article, cellular beams bound to instability were studied analytically by Eurocode and numerically by the finite element method to investigate their behaviour at ambient and elevated temperatures due to fire. The analysis encompasses the effect of the coupling and the endplates' thickness on the cellular beams' collapse strength considering the initial geometric imperfections and material nonlinearities. A parametric study including changing temperature, crosssection geometry, and web aperture configurations was done for beams subjected to uniform bending and distributed load. The analyses depicted the following failure modes: LTB and LTB+ plastification of the two Tsection (P-2 T) for end moment load and yielding of top tee section's flange (B-1 T), P-2 T, web post-buckling (WPB), Vierendeel mechanism (VM) and LTB for a distributed load. Combined failure modes such as LTB + WPB, LTB + VM and LTB + VM + WPB have also been observed. Buckling curves for cellular beams were assessed by comparing FE reduction factors with those of the buckling curve recommended by Eurocode 3 for equivalent solid steel beams. A new proposed formula for the plateau length of the LTB curves was obtained, based on the mean squared error method (MSE) between the numerical results and Eurocode formulae. The comparison between the numerical and the simplified design method predicted results shows that the proposed formulae have reduced the discrepancy and improved the LTB curve to better assess the cellular beams behaviour.The Ministry of Higher Education and Scientific Research, MESRS, of Algeria, is gratefully acknowledged for the PhD grant funding support: ref. 714/PNE/Doctorant/Portugal/2019-2020.info:eu-repo/semantics/publishedVersio

Investigation on combustion characteristics and emissions of biogas/hydrogen blends in gas turbine combustors

In the present work, numerical investigations are performed to study the combustion characteristics of biogas fuel blended with hydrogen at various compositions for a non-premixed swirling flame in a can-type gas turbine combustor. The amount of hydrogen enrichment varies from 0 to 50% by volume. A numerical approach using the non-premixed flamelet model, turbulent standard (k–ε) model, and P-1 radiation model was adopted for simulating the can-type combustor power at a fixed operating power of 60 kW. The steady laminar flamelet model was used to analyze the effect of hydrogen enrichment, global equivalence ratio with different swirl numbers on a stable flame operation, temperature distribution and contours, velocity streamline contours, NO emissions, and species concentrations. The results indicate that hydrogen enrichment and the variation of the equivalence ratio and the swirl numbers significantly impacted the flame macrostructure. Hydrogen enrichment in the fuel intensifi combustion, leading to higher flame temperature and wider flammability than bure biogas. Maximum NO emissions in the outlet chamber have been dropped by 43 and 78 (ppm @15 % by volume of O 2) for the biogas and biogas-50% H 2, respectively, due to the reduced flame temperature leading to reduction in thermal NOx formation with reduction equivalence ratio from 0.5 to 0.2. The flame temperature and NO emissions at ϕ=0.2 with a high rate of hydrogen (50% H 2) are close to the results of pure biogas (0% H 2) at the same equivalence ratio. The results show that CO and CO 2 emissions decrease with increasing hydrogen addition and decreasing the equivalence ratio; due to a decrease in the amount of carbon, the cooling effect, and an increase in the OH concentration

Urethral duplication in male children’s: report of four cases

To evaluate the medium-term outcomes of the management of children with urethral duplication. We report a retrospective study of four children carrying urethral duplication followed in our department over a period of 5 years from 2010 to 2015; Preoperative exploration was based on ultrasound, urethra cystography retrograde and the fistulography. Results: In our study, three of our patients, who has a rare form of epispadias urethral duplication (complete type II of Effmann and Leibowitz) and one case of Y duplication (type II A2). We proceeded in all cases, to the resection of a super urethra excision. The follow up was from 6 months to 2 years for our patients, there was no infectious complication. In one patient with Y urethral duplication, a stenosis of the path of the dorsal urethra was preserved within complete urination. Conclusion: Urethral duplication on a boy is a rare anomaly of the urinary tract. The diagnosis and the determination of its type are based on the retrograde cystography. Its varied clinical expression depends on its anatomical type. If the diagnosis is established in a symptomatic context, the surgical indication is posed with good performances in most cases

A new praseodymium-based coordination polymers with 1,10-phenantroline and glutarate ligands: Synthesis, crystal structure and luminescent properties

International audienceA praseodymium-based coordination polymer with chemical formula [Pr(Hglu)(glu)phen·2H2O]∞ (phen = 1,10-phenanthroline, glu = glutarate) has been hydrothermally synthesized as single crystal, structurally characterized by X-ray diffraction, IR spectroscopy and ATG measurements. This compound crystallizes in the triclinic system, space group , with the following cell parameters: a = 9.8254(9) Å, b = 11.0617(9) Å, c = 12.8552(12) Å, α = 97.588(3)°, β = 108.427(3)°, γ = 112.643(3)°, V = 1170.87(19) Å3 and Z = 2. The praseodymium cation is nine-fold coordinated by one chelating phenanthroline ligand, two mono-protonated glutarate ligands, and three fully de-protonated glutarate ligands. The crystal structure is 1D and can be described on the basis of double molecular chains that bridge di-nuclear units. Inside a di-nuclear unit, Pr(III)-Pr(III) distance is 4.0475(3) Å. Room temperature solid-state emission spectrum has been recorded under 295 nm excitation wavelength. It shows the characteristic peaks of Pr3+ ion between 480 and 750 nm

Highly Luminescent Europium-Based Heteroleptic Coordination Polymers with Phenantroline and Glutarate Ligands

International audienceIsostructural lanthanide-based coordination polymers with general chemical formula [Ln(phen)(glu)(NO)] with Ln = La-Tm (except Ce and Pm) have been synthesized by hydrothermal methods (Hglu stands for glutaric acid and phen stands for 1,10-phenantroline). They crystallize in the monoclinic system with the 2/ (no. 14) space group. The crystal structure has been solved on the basis of the La derivative. It can be described as the superimposition of molecular chains of dimeric La(phen)(NO)-La(phen)(NO) units bridged by glutarate ligands. Luminescent properties have been explored and show that the Eu derivative exhibits the highest luminance observed for Eu-based coordination polymers (85 to 105 cd·m). Effects of the dilution of the Eu and Tb luminescent ions by Gd optically inactive ions are unexpected and to the best of our knowledge unprecedented. This could be related to the different intermetallic energy-transfer mechanisms in competition and to the nonisotropic distribution of the lanthanide ions in these molecular alloys. The investigation of molecular alloys with general chemical formula [EuTb(phen)(glu)(NO)] with 0 ≤ ≤ 1 highlights a very sizable and constant Eu luminescence whatever the value, which further confirms the existence of very strong intermetallic energy transfers in this family of compounds. It is also noticeable that some coordination polymers based on weakly emissive lanthanide ions exhibit very well defined emission spectra

Luminescence properties of lanthanide complexes-based molecular alloys

International audienceSix lanthanides complexes with chemical formula [Ln(phen)2(NO3)3] (Ln = Sm(1), Tb (2), Nd (3), Eu (4), Ho (5) and Y (6), phen = 1,10-phenanthroline) were synthesized. 1 and 2 were obtained as single crystals by slow diffusion. Structural characterization was based on single crystal X-ray diffraction and IR and 89Y-NMR spectroscopies. NMR spectroscopic measurements were performed on [Y(phen)2(NO3)3] (6) and [Y0.75Lu0.25(phen)2(NO3)3] (7). Compounds obtained as microcrystalline powders were characterized by powder X-ray diffraction. The complexes crystallize in the monoclinic system, space group P21/n. Each Ln(III) ion is surrounded by four N atoms from two bidentate phenanthroline ligands and six O atoms from three chelating nitrate groups. The phenanthroline ligand provides efficient sensitization of the complexes that exhibit sizeable luminescence under UV irradiation. Thermal properties have been studied. They confirm the absence of water molecules in the crystal structure. The complexes are thermally stable up to 290 °C. Microcrystalline powders of hetero-lanthanide complexes, with global chemical formula [Tb1−xEux(phen)2(NO3)3] (series 8) and [Tb1−xGdx(phen)2(NO3)3] (series 9) were synthesized. Their photo-physical properties have been investigated. They demonstrate that luminescent molecular alloys can be obtained from lanthanides complexes and not only from hetero-nuclear coordination polymers as previously reported

Primary ciliary dyskinesia gene contribution in Tunisia: Identification of a major Mediterranean allele

International audiencePrimary ciliary dyskinesia (PCD) is a genetically heterogeneous disease of motile cilia. Even though PCD is widely studied, North-African patients have been rarely explored. In this study, we aim at confirming the clinical diagnosis and explore the genetic spectrum of PCD in a cohort of Tunisian patients. Forty clinically diagnosed patients with PCD belonging to 34 families were recruited from Tunisian pediatric departments. In each proband, targeted capture PCD panel sequencing of the 40 PCD genes was performed. PCD panel sequencing identified bi-allelic mutations in 82% of the families in eight PCD genes. Remarkably, 23.5% of patients carried the same c.2190del CCDC39 mutation. Single nucleotide polymorphism profiling in six unrelated patients carrying this mutation has revealed a founder effect in North-African patients. This mutation is estimated to date back at least 1,400-1,750 years ago. The identification of this major allele allowed us to suggest a cost-effective genetic diagnostic strategy in North-African patients with PC