Lightweight Security for Network Coding

Under the emerging network coding paradigm, intermediate nodes in the network are allowed not only to store and forward packets but also to process and mix different data flows. We propose a low-complexity cryptographic scheme that exploits the inherent security provided by random linear network coding and offers the advantage of reduced overhead in comparison to traditional end-to-end encryption of the entire data. Confidentiality is achieved by protecting (or "locking") the source coefficients required to decode the encoded data, without preventing intermediate nodes from running their standard network coding operations. Our scheme can be easily combined with existing techniques that counter active attacks.Comment: Proc. of the IEEE International Conference on Communications (ICC 2008), Beijing, China, May 200

Storm surge dynamics over wide continental shelves: numerical experiments using the Finite-Volume Coastal Ocean Model

Storm surge is an abnormal rise of the sea surface caused by atmospheric forcing, including the wind stress and atmospheric pressure associated with extra-tropical and tropical cyclones. Hurricanes and typhoons have a great impact on coastal regions, and can cause severe loss of lives and great damages. A systematic investigation of storm surge impact to the coasts of Louisiana and Texas, where the continental shelf reaches up to 200 km in width, is conducted here using the hydrodynamics Finite-Volume Coastal Ocean Model, FVCOM (Chen et al., 2003). The model is applied to the northern Gulf of Mexico to simulate the storm surges caused by Hurricanes Rita (September 2005) and Ike (September 2008), and allows the resolution of the flooding along the Louisiana and Texas coasts. Observations of inland flooding from USGS are used to validate the model with satisfactory results. Various idealized scenarios are also simulated using FVCOM, to gain insight into specific surge mechanisms. This study focuses on the following topics: 1) The roles of shelf geometry and tides in a hurricane surge are explored in a set of experiments where the nonlinear interaction between tide and surge is investigated and found to be important, relative to the tidal amplitude; 2) The receding flow of Hurricane Rita’s surge waters back to the Gulf of Mexico and the different dynamics that produce the remarkably different flooding (~0.5 days) and return (\u3e7 days) periods are explained; 3) The effect of the often overlooked forward speed of a hurricane, which was found to have an unexpected and significant impact on coastal surges, in that faster storms produce higher coastal peak surges but smaller overall inland flooding (vice-versa for slower storms); and 4) The importance of Galveston Bay’s barrier islands on the propagation of Hurricane Ike’s surge, where results suggested that under a realistic erosion scenario for Bolivar Peninsula’s, the bay is exposed to dangerously high water levels almost as much as if the Peninsula was leveled to about Mean Sea Level, underlining the non-linear nature of this bay-barrier system

Physical Connectivity Between the NE Atlantic Seamounts

Within the Portuguese Exclusive Economic Zone, the Great Meteor and Madeira-Tore complexes are highly productive areas, which are likely to be classified as marine protected areas (MPAs) due to their ecological vulnerability. This was the main focus of the BIOMETORE project and, framed on it, the aim of the present study was to investigate the physical connectivity between both seamount complexes. Using the HYbrid Coordinate Ocean Model coupled with the Connectivity Modeling System (CMS) (a Lagrangian tool), a series of experiments was conducted in order to determine the influence of the main oceanographic phenomena governing the area in: (i) the origin of the particles that reach each complex, (ii) their capacity to capture and retain incoming particles, and (iii) the physical connectivity between them as well as the intra-connectivity within each seamount system. Due to the geographical location of both groups of seamounts, the Azores Current (AzC) and its associated eddies were identified as the main transport pathways, its influence being stronger at intermediate waters and decreasing with depth. Notwithstanding, the Great Meteor and the MadeiraTore were mainly affected by the AzC southward and eastward branches, respectively, resulting in a non-significant connectivity between the two groups. Meanwhile, the inter-connectivity between seamounts slightly varied with depth at the Great Meteor complex while increasing at Madeira-Tore. In addition, the Plateau, Irving, and Cruiser (PIC) seamounts from the Great Meteor complex and Gorringe and Coral from the Madeira-Tore complex proved to incorporate the regional connectivity routes. Although containing the three smallest seamounts, Madeira-Tore showed the higher capturing capacity per square kilometer, highlighting the influence of the "sticky water effect." In the Great Meteor complex, the "seamount effect" seems to be the main phenomenon responsible for the greater retention and self-recruitment abilities of these seamounts. The presented results provide valuable information for the design of a MPA to preserve these vulnerable habitat

Politics and Aesthetics: Partitions and Partioning in Contemporary Art

Jacques Rancière defined the “distribution of the sensible” as the effect of a type of aesthetico-political decision-making that creates a partitioning of the realm of the perceivable in relation to both art and society. The artworld itself constructs its own particular types of curatorial partitioning: between “art” and “non-art,” between “dominant, residual, and emergent,” and between “mainstream” and “periphery.” This essay examines certain “boundary effects” that develop as a result of the act of the partitioning itself and closely examines what arguably are two new categories in contemporary art: “crossover” and “interventionist.” Both categories have a certain relationship to a culturally constructed boundary or partition. In the former, we see a type of artwork emerge that is the result of the overdetermination of the partition itself. In the latter, artworks appear that are antinomically situated at both sides of a partition simultaneously

Team-Based Learning in Chemistry Courses with Laboratory Sessions

[EN] The implementation of Team-Based Learning (TBL, http://www.teambasedlearning.org) in one-semester undergraduate courses of chemistry offered to first year students is reported. TBL is an active learning instructional strategy heavily relying on small group interaction. Teaching lab classes in a TBL context presented a specific challenge, as decisions were required about their role in the global framework and the possibility of incorporating lab activities as “teamwork”. The design of lab sessions as TBL team application activities is here also illustrated, both for a course of General Chemistry and a course of Organic Chemistry. TBL dramatically improved students class attendance and participation. Its implementation has provided a unique opportunity for the pedagogical development of teaching staff. A moderate number of students reported discomfort with TBL: the requirement of individual preparation before classes and the impact of team participation in the final grade is indeed a new ground for most students, often perceived as a troubling deviation from the common social paradigm of the learning process. The role of the instructor as a facilitator of individual and team work, and the clear explanation of the method are thus of utmost relevance.The authors thank Faculdade de Ciências e Tecnologia (Universidade Nova de Lisboa) for financial supportAires-De-Sousa, J.; Cardoso, MM.; Ferreira, L.; Lima, J.; Noronha, J.; Nunes, A.; Ponte, M. (2017). Team-Based Learning in Chemistry Courses with Laboratory Sessions. En Proceedings of the 3rd International Conference on Higher Education Advances. Editorial Universitat Politècnica de València. 1213-1218. https://doi.org/10.4995/HEAD17.2017.5559OCS1213121