Carbide Precipitation in 2.25 Cr-1 Mo Bainitic Steel: Effect of Heating and Isothermal Tempering Conditions

The effect of the tempering heat treatment, including heating prior to the isothermal step, on carbide precipitation has been determined in a 2.25 Cr-1 Mo bainitic steel for thick-walled applications. The carbides were identified using their amount of metallic elements, morphology, nucleation sites, and diffraction patterns. The evolution of carbide phase fraction, morphology, and composition was investigated using transmission electron microscopy, X-ray diffraction, as well as thermodynamic calculations. Upon heating, retained austenite into the as-quenched material decomposes into ferrite and cementite. M₇C₃ carbides then nucleate at the interface between the cementite and the matrix, triggering the dissolution of cementite. M₂C carbides precipitate separately within the bainitic laths during slow heating. M₂₃C₆ carbides precipitate at the interfaces (lath boundaries or prior austenite grain boundaries) and grow by attracting nearby chromium atoms, which results in the dissolution of M₇C₃ and, depending on the temperature, coarsening, or dissolution of M₂C carbides, respectively.     

Optimization of fluid bed formulations of metoprolol granules and tablets using an experimental design

Background: The granulation process of a metoprolol tartrate (very difficult to process active pharmaceutical ingredient) formulation in laboratory scale fluid bed equipment was studied. Aim: To study the influence of two formulation factors and three process parameters on the characteristics of the granules and subsequently of the tablets, in the case of fluid bed granulating of a powder mix containing metoprolol tartrate. Method: In order to study the influence of formulation factors (binder solution concentration and the silicon dioxide ratio) and process factors (atomizing pressure, the length of the final drying phase, and the inlet air temperature) on the technological and pharmaceutical properties of granules and tablets, a fractional factorial experimental design resolution V+ with five factors and two levels was used. Results: A high atomizing pressure allows us to obtain fine granules with large poly-dispersion index and granules with high tapped and untapped density, tablets with short disintegration time, short mean dissolution time, and a high percentage metoprolol tartrate release in the first 15 minutes. A lower concentration of binder solution allows us to obtain granules with very good flow properties, tablets which have no tendency to stick on the set punch of tabletting machine and no capping. The final drying time of granules has an influence only on the granule's relative humidity and tapped and untapped density, without any influence on the granules flow properties. Conclusions: The practical experimental results from the formulation processed in optimal working conditions were close to the predicted ones by Modde 6.0 software.     

Prediction of Damage Factor in end Milling of Glass Fibre Reinforced Plastic Composites Using Artificial Neural Network

Glass fibre reinforced plastic (GFRP) composites are an economic alternative to engineering materials because of their superior properties. Some damages on the surface occur due to their complex cutting mechanics in cutting process. Minimisation of the damages is fairly important in terms of product quality. In this study, a GFRP composite material was milled to experimentally minimise the damages on the machined surfaces, using two, three and four flute end mills at different combinations of cutting parameters. Experimental results showed that the damage factor increased with increasing cutting speed and feed rate, on the other hand, it was found that the damage factor decreased with increasing depth of cut and number of the flutes. In addition, analysis of variance (ANOVA) results clearly revealed that the feed rate was the most influential parameter affecting the damage factor in end milling of GFRP composites. Also, in present study, Artificial Neural Network (ANN) models with five learning algorithms were used in predicting the damage factor to reduce number of expensive and time-consuming experiments. The highest performance was obtained by 4-10-1 network structure with LM learning algorithm. ANN was notably successful in predicting the damage factor due to higher R² and lower RMSE and MEP.     

Effects of annealing and deposition temperature on the structural and optical properties of AZO thin films

Al-doped ZnO (AZO) thin films were deposited on p- type Si(100) substrate by r.f magnetron sputtering at 200, 300 and 400 °C substrate temperatures. The deposited films were annealed in air atmosphere for 1 h at temperatures of 700, 800 and 900 °C. The deposition temperature and post-deposition annealing effects on structural and optical properties of the AZO samples were analyzed using X-ray diffraction, atomic force microscope and photoluminescence (PL). After annealing, the value of full width half maximum of the diffraction peaks was decreased as well as, the intensity of visible and strong UV PL emission peaks were increased with temperature. However, the deep-level emission related with zinc point defects was removed by annealing of the samples. Results revealed that all of the as-deposited and annealed AZO films have hexagonal structure along (002) direction and their crystallinity were improved with the increased deposition and post-growth annealing temperatures. In addition, the surface roughness and the particle size of the films were increased with increased deposition and annealing temperatures.     

Study on growth and characterizations of GaxIn1−xP/GaAs solar cell structure

Ga_xIn_1?xP/GaAs solar cell (SC) structure was grown on p-type (100)-oriented GaAs substrate by using solid-source molecular beam epitaxy technique. The structural, optical and morphological properties of Ga_xIn_1?xP/GaAs SC structure have been evaluated by means of high resolution X-ray diffraction, photoluminescence, spectroscopic ellipsometry and atomic force microscopy measurements at room temperature. In addition, Ga_xIn_1?xP/GaAs SC structure was fabricated for obtaining the cell’s electrical output parameters. For this purpose, the current–voltage characteristics of Ga_xIn_1?xP/GaAs SC structure were performed and analyzed at the room temperature under both dark and illuminations by using air mass global 1.5 (AM1.5) solar simulator. The device parameters such as the open-circuit voltage, the short-circuit current (I _sc ), the fill factor and the energy convertion efficiency (η) of Ga_xIn_1?xP/GaAs SC structure were extracted from the current–voltage characteristics.     

Application of hierarchical matrices to boundary element methods for elastodynamics based on Green's functions for a horizontally layered halfspace

This paper presents the application of hierarchical matrices to boundary element methods for elastodynamics based on Green's functions for a horizontally layered halfspace. These Green's functions are computed by means of the direct stiffness method; their application avoids meshing of the free surface and the layer interfaces. The effectiveness of the methodology is demonstrated through numerical examples, indicating that a significant reduction of memory and CPU time can be achieved with respect to the classical boundary element method. This allows increasing the problem size by one order of magnitude. The proposed methodology therefore offers perspectives to study large scale problems involving three-dimensional elastodynamic wave propagation in a layered halfspace, with possible applications in seismology and dynamic soil–structure interaction.     

Two-sided U-type assembly line balancing problem

U-type and two-sided assembly lines are two types of design having advantages over traditional straight assembly lines. In this paper, a new line design hybrid of U-type and two-sided lines is presented. A bi-objective 0-1 integer programming model is developed to solve the line balancing problem of the proposed design. Zoning constraints are also considered for the proposed design. A number of test problems from the literature with up to 65 tasks are solved. Benefits of two-sided U-type lines are discussed.     

Multi-population genetic algorithm to solve the synchronized and integrated two-level lot sizing and scheduling problem

This paper introduces an evolutionary algorithm as a procedure to solve the Synchronized and Integrated Two-Level Lot Sizing and Scheduling Problem (SITLSP). This problem can be found in some industrial settings, mainly soft drink companies, where the production process involves two interdependent levels with decisions concerning raw material storage and soft drink bottling. The challenge is to simultaneously determine the lot-sizing and scheduling of raw materials in tanks and soft drinks in bottling lines, where setup costs and times depend on the previous items stored and bottled. A multi-population genetic algorithm approach with a novel representation of solutions for individuals and a hierarchical ternary tree structure for populations is proposed. Computational tests include comparisons with an exact approach for small-to-moderate-sized instances and with real-world production plans provided by a manufacturer.     

Providing practitioners with techniques for cognitive work analysis

Contributing to the advancement of cognitive ergonomics, both as a scientific discipline and as a field of professional activity, is a major challenge for the future of ergonomics. It is to advance this objective that I want to make my contribution: while cognitive ergonomics has undoubtedly become established as a scientific discipline, it is still only applied in an approximate fashion by consultant ergonomists in their day-to-day work of analysing and improving socio-technical systems. The cognitive analysis of work is still too close to a research activity rather than a practice. Beyond the protected frontiers of university laboratories and research departments of large corporations, cognitive engineering often draws more on intuition derived from operators' cognitive activities than from the results of rigorous methodological approaches. This hampers the expansion of cognitive ergonomics as a vehicle for transforming socio-technical systems. Developing practical means of applying cognitive ergonomics within the context of operation on the ground is, thus, a challenge to be met, if this scientific discipline is to contribute fully to the improvement of working systems on a daily basis.