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On categories with semidirect products
Publication . Martins-Ferreira, Nelson; Sobral, Manuela
Necessary and sufficient conditions for a pointed category to admit semidirect products, in the sense of Bourn and Janelidze (1998) [3], are provided and interpreted in terms of
protomodularity and exactness of appropriate split chains.
What happens when I write? Pupils’ writing about writing
Publication . Barbeiro, Luís
This article presents pupils’ awareness of writing as elicited through a metawriting task, in other words a task in which pupils from the third, fourth and sixth forms (grades) were required to write about writing. The analysis of the texts revealed the pupils’ increasing ability to write texts focusing on writing and on the subject’s relationship to writing. There are significant differences concerning the number of processes mobilised by the pupils to describe the writing process and the operations that take place within it. The increase in awareness is particularly salient in the case of planning during pre-writing. The pupils from the sixth form also mobilise a significantly higher number of processes concerned with the components of textualising (translating) and revising. The results for awareness of text and of reader do not present significant differences or any gradual increase. On the textual dimension, attention is given predominantly to the formal aspects of the texts, especially in the lower forms, while the emergence of other factors, such as genre, is still limited. As for the reader, this aspect of awareness receives the lowest number of associated processes when pupils write about their writing. The results revealed the dimensions and factors to which pupils in different school forms have conscious access when reflecting on their writing. The outcomes support the strategy of using metawriting as consciousness raising tool to increase pupils’ writing skills.
Clock Repeater Characterization for Jitter-Aware Clock Tree Synthesis
Publication . Figueiredo, Monica; Aguiar, Rui L.
This paper presents a simple jitter model for clock repeaters. The model is scalable and technology independent, which makes it suitable for integration in current clock tree synthesis algorithms. It is based on the timing characterization of a reference inverter, which can be performed for different process corners to account for process variability. Simulation results show that the model is accurate to within 10% for the most common inverter and NAND based repeaters.
Amplified ribosomal DNA restriction analysis as a routine tool to assess toxicant driven changes in hindgut bacterial populations of Porcellio dilatatus (Crustacea: Isopoda)
Publication . Santos, Miguel J. G.; Sousa, José Paulo; Tiago, Igor; Veríssimo, António; Lemos, Marco
Changes in saprophytic organism's gut microbial communities may present a threat to organic matter breakdown which can ultimately lead to soil function impairment. In this study, Amplified Ribosomal DNA Restriction Analysis (ARDRA) was evaluated as a potential simple molecular tool to assess shifts in bacterial community structure in hindgut populations of Porcellio dilatatus exposed to contaminated food. This prospective tool can also be used for a variety of purposes and samples prior to the use of more specific and sophisticated methods.
Performance study about biodiesel impact on buses engines using dynamometer tests and fleet consumption data
Publication . Serrano, Luis M.V.; Câmara, Rui M.O.; Carreira, Vasco J.R.; Gameiro da Silva, M.C.
The problem of reducing harmful emissions, mainly particulate matter (PM) and nitrogen oxides (NOxs) originated in compression ignition combustion engines, and also the mandatory intention of lowering the CO2 impacts of road transportation define the need to improve our knowledge on biodiesel use in engines.
A 6 in line cylinders Volvo engine was submitted to a 100 min cycle with 27 stabilized steps for seven different fuel blends from pure fossil diesel (B0) to pure biodiesel (B100), considering also B10, B15, B20, B30, B50 fuel blends. The cycle imposed tries to simulate a normal use of a bus in an urban and extraurban circuit, considering different engine rotation and loads applied.
An analysis on consumption data obtained of a fleet was made. The fleet had near 200 buses, used different fuel blends, and operated in the north of Portugal.
Results reveal that the cycle imposed reflects very well the tendency of consumption, allowing to confirm the methodology and also to check influences on consumption, mainly associated with possibilities to decrease CO2 emissions by using some biodiesel blends on buses. This allows increasing the quality of data in vehicle real use and tightening the uncertainties on the actual effects of using biodiesel.