An enhanced scalable probe-based multicast admission control scheme

To guarantee QoS for multicast transmission, admission control for multicast sessions is expected. Probe-based multicast admission control (PBMAC) scheme is a scalable and simple approach. However, PBMAC suffers from the subsequent request problem which can significantly reduce the maximum number of multicast sessions that a network can admit. In this letter, we describe the subsequent request problem and propose an enhanced PBMAC scheme to solve this problem. The enhanced scheme makes use of complementary probing and remarking which require only minor modification to the original scheme. By using a fluid-based analytical model, we are able to prove that the enhanced scheme can always admit a higher number of multicast sessions. Furthermore, we present validation of the analytical model using packet based simulation. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.

Összegződnek-e az egyéni törekvések? A cselekvés és az eredmény közötti szakadék problémája (Can individual efforts be aggregated? The problem of the action-impact gap)

A szerző arra a kérdésre keresi a választ, hogyan alakulhat ki látványos szakadék az egyéni cselekvések iránya és azok együttes hatása között. A szándékok és tettek hatását felülírhatja a társadalmi gazdasági tényezőkből adódó tehetetlenség: a kritikus tömeg hiánya, szervezeti-infrastrukturális tényezők, kompenzációs hatások, egymás hatását kioltó cselekvések. A szerző a környezettudatosság és az ökológiai lábnyom példáján - ezerfős reprezentatív felmérésre alapozva - mutatja be, hogy az önkéntességre alapozó megközelítés sokszor túlbecsüli a fogyasztó - társadalmi-gazdasági tényezők által korlátozott - lehetőségeit és szuverenitását. _____ Behaviour impact gaps are demonstrably present in everyday life. It is increasingly found that environmental awareness in individuals fails to lead to reductions in the ecological footprint. Intensive agricultural practice reduces biodiversity in the EU even in areas where massive agri-environmental grant schemes are available and applied. Labour market training programmes do not necessarily facilitate job-finding for underprivileged segments of the society. So individual efforts may not add up or induce the expected effect. This outcome appears even for programmes that are successful in attaining the required behavioural change in a target group. The impact of attitudes and individual acts may be wiped out by structural and economic lock-ins such as trade-offs made for the gains, lack of a critical mass of actions, infrastructural deficiencies, or interfering acts of economic actors. The discrepancy between environmental awareness and ecological footprint is used to point out how awareness-raising programmes may miss their targets by overestimating the sovereignty and capabilities of consumers. Consumers are unwillingly locked into unsustainable practices and cannot be moved from that position unless economic and structural premises are also changed.

Deployment of a Hybrid Multicast Switch in Energy-Aware Data Center Network: A Case of Fat-Tree Topology

Recently, energy efficiency or green IT has become a hot issue for many IT infrastructures as they attempt to utilize energy-efficient strategies in their enterprise IT systems in order to minimize operational costs. Networking devices are shared resources connecting important IT infrastructures, especially in a data center network they are always operated 24/7 which consume a huge amount of energy, and it has been obviously shown that this energy consumption is largely independent of the traffic through the devices. As a result, power consumption in networking devices is becoming more and more a critical problem, which is of interest for both research community and general public. Multicast benefits group communications in saving link bandwidth and improving application throughput, both of which are important for green data center. In this paper, we study the deployment strategy of multicast switches in hybrid mode in energy-aware data center network: a case of famous fat-tree topology. The objective is to find the best location to deploy multicast switch not only to achieve optimal bandwidth utilization but also to minimize power consumption. We show that it is possible to easily achieve nearly 50% of energy consumption after applying our proposed algorithm.

D3M: multicast listener mobility support mechanisms over distributed mobility anchoring architectures

The explosion in mobile data traffic is a driver for future network operator technologies, given its large potential to affect both network performance and generated revenue. The concept of distributed mobility management (DMM) has emerged in order to overcome efficiency-wise limitations in centralized mobility approaches, proposing not only the distribution of anchoring functions but also dynamic mobility activation sensitive to the applications needs. Nevertheless, there is not an acceptable solution for IP multicast in DMM environments, as the first proposals based on MLD Proxy are prone to tunnel replication problem or service disruption. We propose the application of PIM-SM in mobility entities as an alternative solution for multicast support in DMM, and introduce an architecture enabling mobile multicast listeners support over distributed anchoring frameworks in a network-efficient way. The architecture aims at providing operators with flexible options to provide multicast mobility, supporting three modes: the first one introduces basic IP multicast support in DMM; the second improves subscription time through extensions to the mobility protocol, obliterating the dependence on MLD protocol; and the third enables fast listener mobility by avoiding potentially slow multicast tree convergence latency in larger infrastructures, by benefiting from mobility tunnels. The different modes were evaluated by mathematical analysis regarding disruption time and packet loss during handoff against several parameters, total and tunneling packet delivery cost, and regarding packet and signaling overhead.

O esporte paraolímpico no Brasil : abordagem da sociologia do esporte de Pierre Bourdieu

Universidade Estadual de Campinas . Faculdade de Educação Física

Um modelo estocástico combinado de previsão sazonal para a precipitação no Brasil

Este artigo discute um modelo de previsão combinada para a realização de prognósticos climáticos na escala sazonal. Nele, previsões pontuais de modelos estocásticos são agregadas para obter as melhores projeções no tempo. Utilizam-se modelos estocásticos autoregressivos integrados a médias móveis, de suavização exponencial e previsões por análise de correlações canônicas. O controle de qualidade das previsões é feito através da análise dos resíduos e da avaliação do percentual de redução da variância não-explicada da modelagem combinada em relação às previsões dos modelos individuais. Exemplos da aplicação desses conceitos em modelos desenvolvidos no Instituto Nacional de Meteorologia (INMET) mostram bons resultados e ilustram que as previsões do modelo combinado, superam na maior parte dos casos a de cada modelo componente, quando comparadas aos dados observados.

Quasiharmonic elastic constants corrected for deviatoric thermal stresses

The quasiharmonic approximation (QHA), in its simplest form also called the statically constrained (SC) QHA, has been shown to be a straightforward method to compute thermoelastic properties of crystals. Recently we showed that for noncubic solids SC-QHA calculations develop deviatoric thermal stresses at high temperatures. Relaxation of these stresses leads to a series of corrections to the free energy that may be taken to any desired order, up to self-consistency. Here we show how to correct the elastic constants obtained using the SC-QHA. We exemplify the procedure by correcting to first order the elastic constants of MgSiO(3) perovskite and MgSiO(3) postperovskite, the major phases of the Earth's lower mantle. We show that this first-order correction is quite satisfactory for obtaining the aggregated elastic averages of these minerals and their velocities in the lower mantle. This type of correction is also shown to be applicable to experimental measurements of elastic constants in situations where deviatoric stresses can develop, such as in diamond-anvil cells.

Developmental Potential of Bovine Hand-Made Clone Embryos Reconstructed by Aggregation or Fusion with Distinct Cytoplasmic Volumes

Animal cloning has been associated with developmental abnormalities, with the level of heteroplasmy caused by the procedure being one of its potential limiting factors. The aim of this study was to determine the effect of the fusion of hemicytoplasts or aggregation of hemiembryos, varying the final cytoplasmic volume, on development and cell density of embryos produced by hand-made cloning (HMC), parthenogenesis or by in vitro fertilization (IVF). One or two enucleated hemicytoplasts were paired and fused with one skin somatic cell. Activated clone and zona-free parthenote embryos and hemiembryos were in vitro cultured in the well-of-the-well (WOW) system, being allocated to one of six experimental groups, on a per WOW basis: single clone or parthenote hemiembryos (1 x 50%); aggregation of two (2 x 50%), three (3 x 50%), or four (4 x 50%) clone or parthenote hemiembryos; single clone or parthenote embryos (1 x 100%); or aggregation of two clone or parthenote embryos (2 x 100%). Control zona-intact parthenote or IVF embryos were in vitro cultured in four-well dishes. Results indicated that the increase in the number of aggregated structures within each WOW was followed by a linear increase in cleavage, blastocyst rate, and cell density. The increase in cytoplasmic volume, either by fusion or by aggregation, had a positive effect on embryo development, supporting the establishment of pregnancies and the birth of a viable clone calf after transfer to recipients. However, embryo aggregation did not improve development on a hemicytoplast basis, except for the aggregation of two clone embryos.

A Lagrangian Identification of the Main Sources of Moisture Affecting Northeastern Brazil during Its Pre-Rainy and Rainy Seasons

This work examines the sources of moisture affecting the semi-arid Brazilian Northeast (NEB) during its pre-rainy and rainy season (JFMAM) through a Lagrangian diagnosis method. The FLEXPART model identifies the humidity contributions to the moisture budget over a region through the continuous computation of changes in the specific humidity along back or forward trajectories up to 10 days period. The numerical experiments were done for the period that spans between 2000 and 2004 and results were aggregated on a monthly basis. Results show that besides a minor local recycling component, the vast majority of moisture reaching NEB area is originated in the south Atlantic basin and that the nearby wet Amazon basin bears almost no impact. Moreover, although the maximum precipitation in the ""Poligono das Secas'' region (PS) occurs in March and the maximum precipitation associated with air parcels emanating from the South Atlantic towards PS is observed along January to March, the highest moisture contribution from this oceanic region occurs slightly later (April). A dynamical analysis suggests that the maximum precipitation observed in the PS sector does not coincide with the maximum moisture supply probably due to the combined effect of the Walker and Hadley cells in inhibiting the rising motions over the region in the months following April.

Spatial patterns in the brood combs of Nannotrigona testaceicornis (Hymenoptera: Meliponinae): male clusters

Genetic models of sex and caste determination in eusocial stingless bees suggest specific patterns of male, worker and gyne cell distribution in the brood comb. Conflict between queen and laying workers over male parentage and center-periphery gradients of conditions, such as food and temperature, could also contribute to non-random spatial configuration. We converted the positions of the hexagonal cells in a brood comb to Cartesian coordinates, labeled by sex or caste of the individuals inside. To detect and locate clustered patterns, the mapped brood combs were evaluated by indexes of dispersion (MMC, mean distance of cells of a given category from their centroid) and eccentricity (DMB, distance between this centroid and the overall brood comb centroid) that we developed. After randomizing the labels and recalculating the indexes, we calculated probabilities that the original values had been generated by chance. We created sets of binary brood combs in which males were aggregated, regularly or randomly distributed among females. These stylized maps were used to describe the power of MMC and DMB, and they were applied to evaluate the male distribution in the sampled Nannotrigona testaceicornis brood combs. MMC was very sensitive to slight deviations from a perfectly rounded clump; DMB detected any asymmetry in the location of these compact to fuzzy clusters. Six of the 82 brood combs of N. testaceicornis that we analyzed had more than nine males, distributed according to variations in spatial patterns, as indicated by the two indexes.

A preliminary study of the incorparation of NPK fertilizer into chitosan nanoparticles

The use of slow release fertilizer has become a new trend to save fertilizer consumption and to minimize environmental pollution. Due to its polymeric cationic, biodegradable, bioabsorbable, and bactericidal characteristics, chitosan (CS) nanoparticle is an interesting material for use in controlled release systems. However, there are no attempts to explore the potential of chitosan nanoparticles as controlled release for NPK fertilizers. In this work chitosan nanoparticles were obtained by polymerizing methacrylic acid for the incorporation of NPK fertilizers. The interaction and stability of chitosan nanoparticle suspensions containing nitrogen (N), phosphorus (P) and potassium (K) were evaluated by FTIR spectroscopy, particle size analysis and zeta-potential. The FTIR results indicated the existence of electrostatic interactions between chitosan nanoparticles and the elements N, P and K. The stability of the CS-PMAA colloidal suspension was higher with the addition of nitrogen and potassium than with the addition of phosphorus, due to the higher anion charge from the calcium phosphate than the anion charges from the potassium chloride and urea. The mean diameter increase of the CS-PMAA nanoparticles in suspension with the addition of different compounds indicated that the elements are being aggregated on the surface of the chitosan nanoparticles.

Using of the residues and wood composites for production of an electric guitar

The residues generation is a quite serious problem in several industrial areas and also in the lumbering area. The search for the elimination or reduction of the volume of generated residues is endless, however limited, resulting in the search for a proper destination or better use, instead of simply burning it. A lot of uses and services are commonly proposed, but with low aggregated value to the residue. This work shows the usage viability of different discarded residues and wood composites in the production of an electric guitar. Cupiuba, ipe and jatoba residues have been used besides wood composites of pinus. The residues and wood composites have shown appropriate resistance, surfacing quality and design terms, and could be used to substitute the traditionally wood used in the production of the instrument as well as in other products of similar characteristics and with larger aggregated value.