Towards a dynamic modeling of the predator prey problem

This article addresses a new dynamic optimization problem (DOP) based on the Predator-Prey (PP) relationship in nature. Indeed, a PP system involves two adversary species where the predator’s objective is to hunt the prey while the prey’s objective is to escape from its predator. By analogy to dynamic optimization, a DOP can be seen as a predation between potential solution(s) in the search space, which represents the predator, and the moving optimum, as the prey. Therefore we define the dynamic predator-prey problem (DPP) whose objective is to keep track of the moving prey, so as to minimize the distance to the optimum. To solve this problem, a dynamic approach that continuously adapts to the changing environment is required. Accordingly, we propose a new evolutionary approach based on three main techniques for DOPs, namely: multi-population scheme, random immigrants, and memory of past solutions. This hybridization of methods aims at improving the evolutionary approaches ability to deal with DOPs and to restrain as much as possible their drawbacks. Our computational experiments show that the proposed approach achieves high performance for DPP and and competes with state of the art approaches.     

Traps centers and deep defects contribution in current instabilities for AlGaN/GaN HEMT's on silicon and sapphire substrates

AlGaN/GaN high electron mobility transistors (HEMTs) with Si and Al₂O₃ substrates reveals anomalies on I_ds-V_ds-T and I_gs-V_gs-T characteristics (degradation in drain current, kink effect, barrier height fluctuations, etc.). Stress and random telegraph signal (RTS) measurements prove the presence of trap centers responsible for drain current degradation. An explanation of the trapping mechanism responsible for current instabilities is proposed. Deep defects analysis performed by capacitance transient spectroscopy (C-DLTS), frequency dispersion of the output conductance (G_ds(f)), respectively, on gate/source and drain/source contacts and RTS prove the presence of deep defects localized, respectively, in the gate and in the channel regions. Defects detected by C-DLTS and G_ds(f) are strongly correlated, respectively, to barrier height inhomogeneities and kink anomalies. Gate current analysis confirms the presence of (G-R) centers acting like traps at the interface GaN/AlGaN. Finally, the localization of these traps defects is proposed.     

An Oral Mixed Fat Load Is Followed by a Modest Anti-inflammatory Adipocytokine Response in Overweight Patients with Metabolic Syndrome

We investigated the postprandial changes in plasma levels of adipocytokines in overweight patients with metabolic syndrome after an oral fat load. After an oral fat load and during a prolonged fast, blood was drawn at 0, 2, 3, 4 and 8 h for measurement of adiponectin, adipsin, cathepsin S, chemerin, hepatic growth factor, interferon‐γ‐inducible protein‐10, leptin, macrophage chemoattractant protein‐1, macrophage migration inhibitory factor, nerve growth factor, retinol binding protein‐4, resistin, serum amyloid A1, tissue inhibitor of metalloproteinase‐1 and thrombopoietin using a microbead‐based Luminex assay. Area under the curves (AUC) were calculated and compared. Plasma adiponectin levels were higher after an oral fat load compared to fasting at t = 2 h (950 ± 513 vs. ?1,881 ± 713 ng/ml) while the plasma levels for adipsin (?9 ± 5 vs. 16 ± 5 ng/ml), chemerin (?122 ± 35 vs. 13 ± 21 ng/ml), SAA‐1 (?391 ± 213 vs. 522 ± 173 ng/ml) and TPO (?335 ± 144 vs. 622 ± 216 ng/ml) were lower after an oral fat load compared to fasting. The baseline corrected AUC for IP‐10 was higher after fat load compared to fasting (median ?116 pg h/ml; IQR ?270 to 10 vs. ?21 pg h/ml; IQR ?136 to 418 (p = 0.047). In conclusion, in overweight male subjects with the metabolic syndrome, an oral fat load is accompanied with a modest anti‐inflammatory response of adipose tissue‐derived adipocytokines.     

Experimental comparison of new adaptive PI controllers based on the ultra-local model parameter identification

This paper is devoted to an experimental comparison between two different methods of ultra-local model control. The concept of the first proposed technique is based on the linear system resolution technique to estimate the ultra-local model parameters. The second proposed method is based on the linear adaptive observer which allows the joint estimation of state and unknown system parameters. The closed-loop control is implemented via an adaptive PID controller. In order to show the efficiency of these two control strategies, experimental validations are carried out on a two-tank system. The experimental results show the effectiveness and robustness of the proposed controllers.     

Extraction of Cadmium from Phosphoric Acid Media by Di(2‐ethylhexyl) Dithiophosphoric Acid

Di(2‐ethylhexyl) dithiophosphoric acid (D₂EHDTPA) was examined for cadmium removal from phosphoric acid solutions. High extraction performance was achieved. By means of slope and saturation methods, the stoichiometry of the complex was postulated. Both methods indicated the presence of anhydrous CdR₂ as being the metallic extracted complex, HR denoting the D₂EHDTPA molecule. The stripping of cadmium from the organic phase was ensured by aqueous solutions of HCl; quantitative stripping was achieved with either HCl (4 M) or an HCl‐NaCl mixture.