Recently the investigation of periodic motion of the delayed functional differential equations (DDEs) and the associated variation systems become the focus of many studies. One of the most important motivations is the milling process analysis. Different techniques are used to obtain approximate solutions for the delayed functional differential equations (DDE). All these models used the stability lobe diagrams in order to choose the maximum axial depth of cut, for a given spindle speed associated with the chatter free machining. In this work, a semi discretization method is briefly explained and has been applied for 1-DOF (degree of freedom) and 2-DOF milling system in order to build the stability lobe diagrams.

In this paper, an adaptive tracking controller for a piezo-actuated stage is designed considering the LUGRE model. The adaptation algorithm of the parameterized hysteretic function is used to achieve a displacement-tracking objective under the mechanical parameters uncertainties. The Lyapunov theory is used to derive an adaptive law for the system stability. The effectiveness of the proposed controller is validated considering real-time simulation. The validation results of the proposed controller presents good performances and robustness under an external load-disturbance and parameter uncertainties.

focuses on the Cenomano-Turonian sediments observed in Thénièt El Manchar, the Bellezma-Batna Mountains, their evolution and the recognition of the main dating markers. The analysis (qualitative and quantitative) of the planktonic and benthic foraminifera and that of the ostracodes makes it possible to reconstitute the evolution of the paleo-environment and to estimate the variations of the relative paleo-depths. During the lower middle Cenomanian (Units IA, IB, IC and the lower part of ID), the microfaunistic associations are dominated by agglutinated benthic foraminifera testifying to a cold environment corresponding to the circalittoral deposits, in association with whole shells of ostracods indicating a weak hydrodynamism. In these deposits, the associations show a low to medium specific diversity and a more or less high faunistic richness, indicating trophic conditions and oxygenation considered normal. As for Unit ID (upper Cenomanian), it contains benthic foraminiferal biocenoses characteristic of warm and agitated seas. The return to deeper conditions, in the final terms of the Cenomanian and the beginning of the Turonian (Unit IIA), during a transgressive phase, is justified by the classical success of the events selected in North Africa, namely: The abundance of planktonic foraminifera, filaments and the drastic reduction of ostracofauna. These different elements open a reflection on the recorded paleo-environmental perturbations, the gradual disappearance of environmental stress and the return to relative normal conditions. These paleo-environmental interpretations agree with the data of the regional palaeogeographic context and highlight Tethysian features. Key words: sedimentology, geochemistry, paleo-environment, Cenomanian, Turonian, Batna, Algeria.

Selenium (Se), an essential micronutrient of several major metabolic pathways, including thyroid hormone metabolism, antioxidant defense systems, and immune function becomes toxic to animal when it is elevated above a threshold concentration. The aim of the present study was to determine the effect of selenium in rats Wistar albino on plasma levels of cholesterol, triglycerides, urea, uric acid, albumin and calcium. The experimental groups received subcutaneously graded doses of Selenium (0.3 and 0.5 mg/kg, BW) for a period of 21 days and plasma biochemical parameters were evaluated after 3, 6 and 21 days. The results indicated that the graded doses of Selenium significantly decreased both the calcium and plasma cholesterol level during short-term and long-term respectively. On the other hand, Se elevated significantly the levels of plasma urea by 104% after the first three days, uric acid by 126%, on day 6 and triglycerides by 120% on day 21. Whereas, the higher dose increased the level of plasma urea only on day 21 by 67%. Furthermore, 0.5 mg s.c provoked an immediate and a significant increase in plasma cholesterol level by 47% and in uric acid by 60% during the first three days after treatment. Doses of Se augmented significantly on day 6, the level of plasma albumin by 85% and 52 % respectively. The results of the current study suggested that selenium alters the plasma biochemical parameters in rats. Keywords: Albumin, calcium, cholesterol, selenium, triglyceride, urea. uric acid