Effect of the trapped mass and its composition on the heat transfer in the compression cycle of a reciprocating engine

The use of the polytropic coefficient calculation during the compression process in the thermodynamic cycle of a reciprocating internal combustion engine is an interesting tool to minimize errors in the synchronization of pressure and volume signals, and to determine heat flux transferred to the cylinder walls. The accuracy of this calculation depends on the instantaneous values for pressure, volume, trapped mass and its composition, as well as on their variations. In this work the effect of the errors in blow-by, trapped mass and its composition have been studied in detail, specially the effect of errors in the composition estimation, owing to the use of exhaust gas recirculation in typical diesel engines.     

Chemical and physicochemical properties of dried wet masa and dry masa flour

Commercial ‘masas’ and dry ‘masa’ flours (DMFs) were evaluated for chemical composition, water retention capacity (WRC), gelatinization, retrogradation and X‐ray diffraction. Both masas and DMF had similar chemical compositions. The masas had higher soluble carbohydrate contents and lower WRCs than DMF. In the same way, DMFs had lower gelatinization temperatures and enthalpies of gelatinization than masas. These results were confirmed by X‐ray diffraction analysis showing a lower degree of crystallinity in DMFs than in masas. The melting temperature in retrogradated samples of both masas and DMFs had a tendency to increase as storage time increased. This increment was more apparent with the enthalpy of melting. These results were probably associated with crystal perfection during starch retrogradation, ie recrystallization of gelatinized starch occurred as a time‐dependent process. Copyright © 2003 Society of Chemical Industry     

Social relationships impact adoption of agricultural technologies: the case of food crop varieties in Timor-Leste

Factors related to adoption of new agricultural technologies have been given increasing attention, especially in developing countries where such technologies offer opportunities to increase food production. One of the most immediate ways to improve food production significantly is through the adoption of high yielding varieties of food crops, but rates of adoption are often low, especially among the rural poor. In Timor-Leste, improved varieties of food crops with yield advantages across all agro-ecological zones have been introduced. However, despite yield advantages, suitability and high levels of food insecurity, discontinuance occurs and adoption rates are low. To identify factors related to adoption of the improved varieties across agro-ecological zones, binary logistic regression was performed on data collected from 1511 rural households. The results identified several factors related to adoption and showed that their impact varied across agro-ecological zones. The factor most strongly related to adoption was having a relationship to a grower of an improved variety of food crop and the closeness of this relationship. Furthermore, the following factors were related to adoption with variation across agro-ecological zones: age; education; size of farming plots; travel time between household and farming plot; involvement with the programme developing the improved varieties of food crops and participation in groups and training programmes. Overall, the findings of this study emphasize that dissemination strategies should embrace social relationships and be sensitive to agro-ecological zones.     

Study of the optimal layout of cooling fins in forced convection cooling

In this work the influence of the cooling fin shape on the pressure drop caused by flow resistance of a heat sink is studied. A new manner to optimise heat sinks is developed, bringing the emphasis not only on maximum heat transfer flux, but also on minimum flow resistance. The study is done numerically using the computational fluid dynamic software FLUENT. The results show the advantages of using aerodynamic shaped fins if the Reynolds number, based on the spacing between the cooling fins, is greater or equal than about 800. Some preliminary profile shapes are suggested. The authors consider this research as a quite unique approach as compared to other research where the flow resistance has not been taken into account.     

A Mobile Agents Approach to Virtual Laboratories and Remote Supervision

This paper presents the use of adaptive mobile agents for remote operation, enabling real-time response in spite of the limitations of the communication channels in terms of time-delays, availability, and reliability. Autonomy of the mobile agents is achieved through high levels of intelligence including execution monitoring and error recovery. Potential applications range from traditional telerobotics to virtual laboratories where mobile agents act as representatives of users in scientific experiments. Practical results are presented in a scenario where a SCARA-type robot is remotely commanded through the Internet.     

Functional Disambiguation Based on Syntactic Structures

This article presents a disambiguation method which diminishesthe functional combinations of the words of a sentence takinginto account the context in which they appear. This processis built in two phases: the first phase is based on the localsyntactic structures of the Spanish language and reaches anaverage yield of 87%. The second one is supported by syntactictree representation and pushes the results up to an approximatehigh end of 96%. This process constitutes the starting pointtowards an automated syntactic analysis.     

Acid-Catalyzed Homogeneous Esterification Reaction for Biodiesel Production from Palm Fatty Acids

This work deals with esterification of palm fatty acids to produce biodiesel in a batch reactor, using homogeneous acid catalysts, evaluating the effect of the alcohol used, presence of water, type and concentration of catalysts. Methanesulfonic and sulfuric acid were the best catalysts. Reaction with methanol showed greater yields. It was showed very clearly that the presence of water in the reaction medium showed a negative effect in the reaction velocity. Kinetic parameters were estimated and molecular modeling was performed. Protonation of the carboxylic moiety of the fatty acid were defined as rate determinant step for the reaction.     

Transesterification of Jatropha curcas oil glycerides: Theoretical and experimental studies of biodiesel reaction

Vegetal oil, also known as triglycerides, is a mixture of fatty acid triesters of glycerol. In the triglycerides alkyl chains of Jatropha curcas oil, predominate the palmitic, oleic and linoleic fatty acids. The process usually used to convert these triglycerides to biodiesel is called transesterification. The overall process is a sequence of three equivalent, consecutive and reversible reactions, in which di- and monoglycerides are formed as intermediates. Semi-empirical AM1 molecular orbital calculations were used to investigate the reaction pathways of base-catalyzed transesterification of glycerides of palmitic, oleic and linoleic acid. The most probable pathway and the rate determining-step of the reactions were estimated from the molecular orbital calculations. Our results suggest the formation of only one tetrahedral intermediate, which in a subsequent step rearranges to form the products. The rate determining-step is the break of this tetrahedral intermediate.     

Chymotrypsin isolation from jumbo squid (<Emphasis Type="Italic">Dosidicus gigas</Emphasis>) hepatopancreas: Partial characterization and effect on muscle collagen

Chymotrypsin was purified from jumbo squid hepatopancreas (HP) with 2.4-fold and yield 1.9%, and characterized with a molecular weight of 31 kDa, as estimated by sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE). Chymotrypsin effect over collagen extracted from the mantle, fins and arms of the jumbo squid was evaluated. The enzyme exhibited the maximum activity at pH 7 and 65°C using Suc-Ala-Ala-Pro-Phe-p-nitroanilide (SAAPNA) as a substrate and it was identified using the specific inhibitors N-tosyl-L-phenylalaninechloromethyl ketone (TPCK) and phenyl methyl sulfonyl fluoride (PMSF), showing residual activities of 6% and 0%, respectively. Furthermore, high activity was observed in the pH range of 4.0 to 8.0. Purified enzyme showed a moderate in vitro activity using muscle collagen as a substrate. Although further research is needed, the results suggest that the enzyme has a potential application where acidic or slightly alkaline conditions are needed.