Planning tool requirements for flexible manufacturing: an analytical approach

The problem of tool and fixture resources dimensioning is considered and examined for a productive environment with flexible features. With reference to previous studies, different tool management strategies are pointed out and commented upon; a further control policy based on workpiece batching is suggested and tested. In the second section of the paper, an analytical interpretation of the question in hand is presented and discussed; the effectiveness of the procedure itself is tested by comparing analytical data with results derived from the detailed simulation of a real tool management area. Results are shown in the last section     

DESIGNING COMPLEX SYSTEMS WITHIN DISTRIBUTED ARCHITECTURES: AN INTELLIGENT TUTORING SYSTEMS PERSPECTIVE

The goal of this work is to introduce the basic concepts of distributed artificial intelligence as new methodologies to conceive and realize complex intelligent systems. We focused our attention on the design of intelligent tutoring systems, and using a distributed framework, we reached a fine control on the communicability process, one of the key issues in the realization of intelligent tutoring systems. A prototype is presented as an open information system in which classical modules, such as the domain expertise module and the tutor, are seen as populations of intelligent actors that share their fragmentary knowledge and organize their tasks in a concurrent universe in order to accomplish a common goal, the teaching session. The system has been written in a concurrent object-oriented language, realized on top of the Common Lisp Object System.     

EFFECT OF OPERATING CONDITIONS ON GAS HOLDUP IN SLURRY BUBBLE COLUMNS WITH A FOAMING LIQUID

This work presents experimental data on gas holdup in slurry bubble columns with a foaming liquid. The effects of solids concentration, solid particle size, superficial phase velocities and column dimensions on the gas holdup are analyzed. At low superficial gas velocities (less than 4cm/s), for which the liquid does not foam, the presence of solids with small particle size does not affect the gas holdup whereas solids with large particle size induce foam formation and thus their presence increases the gas holdup. In the foaming regime, an increase of solids concentration decreases the gas holdup. The operating mode has a strong effect on the gas holdup: the semi-batch operating mode (stagnant liquid-solid suspension) increases the ability of the liquid to foam with respect to the continuous mode. Regarding the effect of column dimensions, the results presented show that the height of the bubble column does not affect at an appreciable extent the gas holdup in the range 6 < LID < 12. At high gas velocities (greater than 6 cm/s) the gas holdups obtained in a 30 cm-internal diameter column are the same as those measured in a 10 cm-internal diameter column.     

THREE PHASE COUNTERCURRENT EXTRACTION

Partitioning of bovine serum albumin (BSA) in an aqueous double countercurrent distribution (DCCD) using a three-phase system was studied and compared with countercurrent distribution using a two-phase system. The two-phase system was composed of Dextran and Polyethylene glycol (PEG) solulions, and the three-phase system consisted of Dextran, Ficoll, and PEG solutions. In the double countercurrent distribution experiment, BSA was partitioned from the stationary bottom phase into the moving middle and top phases. Two peaks resulted from these transfers. A mathematical model that predicts peak positions and shapes based on the partitioning behavior of the solute is provided. Based on model predictions, the DCCD method has potential extraction selectivity and recovery advantages over the traditional CCD method.     

An Engineering Model for Three-Dimensional Elastic-Plastic Rolling Contact Analyses

Fatigue life of heavily loaded rolling bearings is strongly dependent on elastic-plastic material properties. For bearing steels these elastic-plastic properties can be accurately obtained by performing monotonic or half-compressive tests. A three-dimensional strain deformation analysis based on the incremental theory of plasticity and the use of Prandtl-Reuss relations in conjunction with the von Mises yield criterion was developed in order to evaluate the permanent deformation in dry contacts loaded above the elastic limit in case of normal loading. The Ramberg-Osgood stress-strain relation for two martensitically hardened variants of SAE 52100 bearing steel considered the nonlinear kinematic and/or isotropic material behavior. Parameters describing the influence of retained austenite are modeled by using a nonlinear isotropic law. Pressure distribution and contact surface displacements during incremental loading are evaluated by using a conjugate gradient method and the internal stress field is derived by using the superposition principle. Further, a fast analysis of smooth surfaces in elastic-plastic static and rolling contact is developed based on analytical relations for the internal stress field. Cyclic evaluation of plastic strains and residual stresses is carried out until shakedown. In order to verify the theoretical model, rolling contact tests under high normal load were performed. Residual stresses and residual profiles measurements show excellent agreement between numerical and measured cyclic values.     

A REVIEW of FUNDAMENTAL PROCESS ASPECTS FOR the PRODUCTION of MUSHROOM MYCELIUM

A review of fundamental process aspects to produce mushroom mycelium in submerged culture is presented. With peat hydrolysate as the main nutrient source, the operations of substrate preparation, cultivation and product recovery are explained. Based on the growth of Agaricus spp. mushroom mycelium, the conditions for the production of the desired mycelial pellets are analyzed.     

SIMULATION OF THIN-FILM DEODORIZERS IN PALM OIL REFINING

As the need for healthier fats and oils (natural vitamin and trans fat contents) and interest in biofuels are growing, many changes in the world's vegetable oil market are driving the oil industry to developing new technologies and recycling traditional ones. Computational simulation is widely used in the chemical and petrochemical industries as a tool for optimization and design of (new) processes, but that is not the case for the edible oil industry. Thin-film deodorizers are novel equipment developed for steam deacidification of vegetable oils, and no work on the simulation of this type of equipment could be found in the open literature. This paper tries to fill this gap by presenting results from the study of the effect of processing variables, such as temperature, pressure and percentage of stripping steam, in the final quality of product (deacidified palm oil) in terms of final oil acidity, the tocopherol content and neutral oil loss. The simulation results have been evaluated by using the response surface methodology. The model generated by the statistical analysis for tocopherol retention has been validated by matching its results with industrial data published in the open literature.

PRACTICAL APPLICATIONS

This work is a continuation of our previous works ( Ceriani and Meirelles 2004a, 2006 ; Ceriani et al. 2008 ), dealing with the simulation of continuous deodorization and/or steam deacidification for a variety of vegetable oils using stage-wised columns, and analyzing both the countercurrent and the cross-flow patterns. In this work, we have studied thin-film deodorizers, which are novel equipment developed for steam deacidification of vegetable oils. Here, we highlight issues related to final oil product quality and the corresponding process variables.