A branch and bound enhanced genetic algorithm for scheduling a flowline manufacturing cell with sequence dependent family setup times

This paper addresses the permutation flowline manufacturing cell with sequence dependent family setup times problem with the objective to minimize the makespan criterion. We develop a cooperative approach including a genetic algorithm and a branch and bound procedure. The latter is probabilistically integrated in the genetic algorithm in order to enhance the current solution. Moreover, the application of the branch and bound algorithm is based upon the decomposition of the problem into subproblems. The performance of the proposed method is tested by numerical experiments on a large number of representative problems.     

Nanoarchitectonics of Niobium-Doped,Lead-Free BLT (Ba0.97La0.02Ti0.98Nb0.016O3) for Electrical Properties with Unusual d.c Bias Voltage Independence

Polycrystalline sample of Ba_0.97La_0.02Ti_0.98Nb_0.016O₃ (distinguished as BLTi_0.98Nb_0.016) has been prepared through Molten-Salt-Flux reaction route. The XRD, surface morphology, absorption spectra, impedance, and dielectric behaviors were employed to typify the prepared polycrystalline ceramic. The XRD analysis reflects that obtained perovskite having the pure-tetragonal structure with space group P4/mmm. As of the absorption spectra, the optical band gap (Eg), Urbach energy (Eu), and refractive index values have designed. The electrical properties of synthesized compound have been inspected via complex impedance spectroscopy vs. frequency (f) (10² Hz–10⁶ Hz) within the d.c-bias voltage range [0.5 V–5 V]. The fitting of the Nyquist plot exposes that both intra- and intra grains contribute to relaxation and the grain limits are more resistive and capacitive than the grains. Modulus analysis confirms that relaxation in our sample is of non-Debye nature and d.c-bias voltages dependent. Depending on the frequency, the change of ε′ can be discussed founded on the principle of interfacial polarization of the Maxwell–Wagner category. BLTi_0.98Nb_0.016 shows notable frequency independent relative studied properties, it is a potential candidate for devices.

     

Widgets Dedicated to User Interface Evaluation

In this article, evaluation-based widgets are proposed as a contribution to assist evaluators for early evaluation of user interfaces. This contribution imbricates the ergonomic quality evaluation process into widgets used for user-interface graphical composition. In other words, these widgets evaluate themselves according to a defined set of ergonomic guidelines. The proposed widgets indicate the possible interface design ergonomic inconsistencies as a notification to the designer. The guidelines set can be modified through an interface dedicated to guidelines definition into XML files. The proposed widgets are intended for the evaluation of different kind of user interfaces: WIMP, web, and mobile. An experimental evaluation, involving these evaluation-based widgets, is proposed to illustrate and to validate the approach.     

Investigation of the liquid crystal alignment layer: effect on electrical properties

We investigate the electrical behavior of a symmetric liquid crystal (LC) cell: elecrode-silane-LC-silane-electrode. The silane (chlorodimethyloctadecyl-silane) layer induces a homeotropic orientation of the nematic liquid crystal (NLC) molecules. The wettability technique is used to detect the change of the surface energy of the electrode upon cleaning and silane layer deposition. We report on the dynamic impedance measurements of the nematic liquid crystal cell. It is found that the silane alignment layer has a blocking effect on the liquid crystal (LC) cell. We also study the relaxation behavior of the cell which is later assimilated as an electrical equivalent circuit.     

A fault tolerant tracking control for a quadrotor UAV subject to simultaneous actuator faults and exogenous disturbances

ABSTRACT

An observer-based robust adaptive Fault Tolerant Control approach is proposed in this paper to tackle the problem of trajectory tracking for a quadrotor unmanned aerial vehicle (UAV) suffering simultaneous actuator faults, exogenous disturbances and actuator saturation limits. An adaptive fuzzy state observer is proposed to estimate the immeasurable states by using fuzzy logic systems to approximate the unknown nonlinear functions of the uncertain system model. Based on the estimates of the fuzzy observer, an Integral Terminal Sliding Mode Controller that guarantees finite time convergence of the states to a small neighbourhood of zero, even under impaired conditions, is developed. Stability analysis was carried over using the Lyapunov method. The proposed approach was implemented to a quadrotor UAV and its performance was assessed under nominal conditions, and by subjecting the quadrotor to disturbances, simultaneously occurring actuator faults and input saturation limits. Excellent tracking performance and robustness even under worst-case scenarios are among the positive features of the proposed approach.     

Hierarchical production planning with flexibility in agroalimentary environment: a case study

In this paper we address to the planning problem in the agroalimentary domain. In such industry, several specific constraints should be taken into account for planning task such as the constraints of interdependencies between the products and variable production modes. Furthermore, we present the relationship between two large fields as the production hierarchical planning and the flexibility. Especially, we show that the flexibility planning should be made a priori and then integrated in the hierarchical planning process. Indeed, we have established a mathematical model according to different production levels. While taking into account real capacities of the shop and the interdependencies between the products, the results of our formulation are satisfactory in terms of quality of solution and time requirements. It??s shown that our model is able to reach all optimal solutions for all treated models and for all system levels.     

Purification and Biochemical Characterization of Lipase from Tunisian Euphorbia peplus Latex

Lipases from vegetable sources have been the focus of intense and growing research. The use of enzymes from plants has the advantage of employing industrial waste products. The lipase activity of Euphorbia peplus L. (Euphorbiaceae) was investigated for the first time. The Euphorbia peplus latex lipase (EpLL) was purified after ammonium sulfate fractionation and anion exchange chromatography on a DEAE-Cellulose column leading to 12.57-fold purification. The EpLL displayed a probable molecular weight of about 40 kDa. The lipase activity was optimum at a temperature of 40 °C and pH 8, the specific activities of EpLL were found to be 249 ± 12.45 and 161.4 ± 8.07 U/mg when tributyrin (TC₄) and olive oil were used as substrate respectively. The enzyme retained 80 % of its activity when incubated for 1 h at 50 °C. The EpLL was strongly destabilised by divalent metal ions (Fe²⁺, Mg²⁺, Zn²⁺ and Cu²⁺). Lipase was slightly stimulated by Triton X-100 and Tween-80, while strongly inhibited by sodium dodecyl sulfate. A good stability of the enzyme in the presence of organic solvents was reveled suggesting its industrial utility.     

Characterization of nanocrystalline Al-based alloy produced by mechanical milling followed by cold-pressing consolidation

In the present study high energy mechanical milling followed by high-pressing consolidation has been used to obtain bulk nanocrystalline aluminum based alloy. Fully dense disks with homogenous microstructure were obtained. X-ray analysis indicates that high strain imposed by mechanical milling and severe plastic deformation (SPD) processing causes microstructure showing a mixture of a significant lower value of the crystallite size (around 60 nm) and the creation of a large number of linear defects which induces microstrains (around 0.7%). In addition, the elevated value of hardness which was obtained for the consolidated disks and the favorable comparison with the value measured for the same as-received alloy confirm the potential of the SPD technique when it is collected with high energy mechanical milling for producing higher performance materials. On the basis of calorimetric measurements, as a function of consolidation stresses, we can say that the thermal behaviour was characterized by a significant heat release and grain growth during the heating cycle. Moreover, the noticed broad endothermic peak can be attributed to some precipitants containing magnesium.