Multi-criteria design optimization study of solvent extraction in mixer–settler units

Solvent extraction is considered as a multi-criteria optimization problem, since several chemical species with similar extraction kinetic properties are frequently present in the aqueous phase and the selective extraction is not practicable. This optimization, applied to mixer–settler units, considers the best parameters and operating conditions, as well as the best structure or process flow-sheet. Global process optimization is performed for a specific flow-sheet and a comparison of Pareto curves for different flow-sheets is made. The positive weight sum approach linked to the sequential quadratic programming method is used to obtain the Pareto set.In all investigated structures, recovery increases with hold-up, residence time and agitation speed, while the purity has an opposite behaviour. For the same treatment capacity, counter-current arrangements are shown to promote recovery without significant impairment in purity. Recycling the aqueous phase is shown to be irrelevant, but organic recycling with as many stages as economically feasible clearly improves the design criteria and reduces the most efficient organic flow-rate.     

Experimental behaviour of the reverse channel joint component at elevated and ambient temperatures

The reverse channel connection appears to have the best combination of desirable features under fire loading: moderate construction cost, ability to develop catenary action and extremely high ductility through deformation of the web channel (Ding and Wang, 2007). This paper presents the results of an experimental investigation of a reverse channel component conducted at the University of Coimbra as part of the European RFCS COMPFIRE Project, the main focus of which is to characterise the behaviour of steel joints that connect steel beams to concrete-filled tubular columns under natural fire loading. A series of tensile and compressive tests at ambient and elevated temperatures was conducted. The purposes of the experimental tests were to characterise the strength, stiffness and ductility of this joint component and to establish a relationship between force, displacement and temperature.     

Mycoflora of hazelnut (Corylus avellana L.) and aflatoxin content in hazelnut kernels artificially infected with Aspergillus parasiticus

In this research, 30 hazelnut samples were used to determine their internal mould populations and their aflatoxin contents. The results showed that Aspergillus was the most common genus in the experimental samples (96.6% of all samples). Thirty-one% of isolates were classified as Aspergillus flavus and none of the samples contained aflatoxins. In the second part of the experiment, the kernels were inoculated with conidia of Aspergillus parasiticus and incubated at three different humidified conditions and two different temperatures for 45 days. Aflatoxin contents of the samples kept in 98% relative humidity and at 28 degrees C were higher (904.6 micrograms/kg) than that of the other samples. On the other hand, no aflatoxin was detected in the control samples that were not inoculated but kept at the same conditions.     

What is the source of ochratoxin A in wine?

During a microvinification trial using natural mouldy grapes from a research experimental vineyard, ochratoxin A (OTA) contaminated white wine was obtained. Potential OTA-producing mycobiota of grape samples used in this microvinification process was assessed. Only Aspergillus carbonarius isolates were detected as producers of OTA. Our report is a strong evidence of the contribution of A. carbonarius in the OTA contamination in wine.     

Evanescent wave coupling in light scattering of an off-axis normally incident Gaussian beam by two parallel nonabsorbing cylinders

A theoretical and numerical investigation is devised for resonant light scattering of an off-axis normally incident Gaussian beam by two parallel nonabsorbing cylinders based on the related beam theory developed in J. Opt. Soc. Am. A 14, 640 (1997). By varying the half-beam width, we show that the multireflection process between the two scatterers can be minimized. Moreover, the study is an attempt to understand the underlying physics present in the process of resonance excitation by evanescent wave coupling.     

Practical crack control during the construction of precast segmental box girder bridges

Cracks that occurred in the bottom slab of a precast segmental bridge were investigated through a construction sequence analysis, which revealed that the cracks were caused by excessive deformation during temporary post-tensioning while joining the segments. In addition, a parametric study was performed to evaluate the effects of the prestressing sequence, bottom slab thickness, and position of the prestressing anchors. The structural behavior of the girder sections was greatly affected by the thickness of the bottom slab and the position of prestressing anchors, but not by the prestressing sequence. Based on the results, a construction method that prevents the cracks is proposed.     

Continuous-Time Negotiation Mechanism for Software Agents

While there are several existing mechanisms and systems addressing the crucial and difficult issues of automated one-to-many negotiation, this paper develops a flexible one-to-many negotiation mechanism for software agents. Unlike the existing general one-to-many negotiation mechanism, in which an agent should wait until it has received proposals from all its trading partners before generating counterproposals, in the flexible one-to-many negotiation mechanism, an agent can make a proposal in a flexible way during negotiation, i.e., negotiation is conducted in continuous time. To decide when to make a proposal, two strategies based on fixed waiting time and a fixed waiting ratio is proposed. Results from a series of experiments suggest that, guided by the two strategies for deciding when to make a proposal, the flexible negotiation mechanism achieved more favorable trading outcomes as compared with the general one-to-many negotiation mechanism. To determine the amount of concession, negotiation agents are guided by four mathematical functions based on factors such as time, trading partners' strategies, negotiation situations of other threads, and competition. Experimental results show that agents guided by the four functions react to changing market situations by making prudent and appropriate rates of concession and achieve generally favorable negotiation outcomes     

Integrated position estimation using aerial image sequences

Presents an integrated system for navigation parameter estimation using sequential aerial images, where the navigation parameters represent the positional and velocity information of an aircraft for autonomous navigation. The proposed integrated system is composed of two parts: relative position estimation and absolute position estimation. Relative position estimation recursively computes the current position of an aircraft by accumulating relative displacement estimates extracted from two successive aerial images. Simple accumulation of parameter values reduces the reliability of the extracted parameter estimates as an aircraft goes on navigating, resulting in a large positional error. Therefore, absolute position estimation is required to compensate for the positional error generated by the relative position estimation. Absolute position estimation algorithms using image matching and digital elevation model (DEM) matching are presented. In the image matching, a robust-oriented Hausdorff measure (ROHM) is employed, whereas in the DEM matching, an algorithm using multiple image pairs is used. Experiments with four real aerial image sequences show the effectiveness of the proposed integrated position estimation algorithm     

Influence of Avicel PH-301 on the compressibility of alpha-methyldopa and phenobarbitone in direct compression

The aim of this work was to investigate the compressibility behavior of alpha-methyldopa and phenobarbitone using a Korsch EK0 instrumented eccentric tablet machine, with force-time and force-displacement curves constructed and applied to calculate different compressional values to study the compressional behavior. The results of this work revealed a difference in compressibility behavior between the two drugs during the compressional process. alpha-Methyldopa gave an abnormal compressional curve with high friction in the pre- and postcompressional phases. A residual force could be seen on the lower punch. Furthermore, capping and sticking were observed visually during tablet pressing, indicating poor compressibility behavior. In the case of phenobarbitone, no friction was observed in the precompressional phase, but there was higher friction in the postcompressional phase, especially in the ejection phase. The compressibility of the drugs was improved by the addition of Avicel PH-301 and magnesium stearate.