Admission Control in Multiservice IP Networks: Architectural Issues and Trends

The trend toward the integration of current and emerging applications and services in the Internet has launched new challenges regarding service deployment and management. Within service management, admission control has been recognized as a convenient mechanism to keep services under controlled load and ensure the required QoS levels, bringing consistency to the services offered. In this context, this article discusses the role of AC in multiservice IP networks, and surveys current and representative AC approaches. We address and compare the architectural principles of these AC approaches and their main features, virtues, and limitations that have an impact on the quality control of network services. We identify important design aspects that contribute to the successful deployment of flexible and scalable AC solutions in multiservice networks     

Transient response analysis and modeling of near wall flow conditions in a micro channel: evidence of slip flow

An experimental tool for determination of the near wall transport parameters in a micro channel, supported by flow simulation, is presented. The method is based on the transient flow response due to convective diffusion, in absence of specific adsorption. An approximately step-function type temporal solute concentration variation serves as the input signal. The associated response signal of a surface plasmon resonance sensor, acting as an integral part of a micro channel, has been taken as the output signal. It provides the flow-dependent change of the NaOH solute concentration in the channel within the optical detection and near wall distance interval 0 < d < 0.5 μm. The temporal signal evolution and response time, until an initially plain aqueous solution is replaced by the solute, varies inversely with solute concentration and flow rate. In the asymptotic limits, the near wall forced convective and diffusive channel transit times, along with the associated velocities, can be extracted and separated. A low convective near wall flow speed would account for 100% adsorption efficiency. The validity of the scaling relation for Fickian diffusive transport has been confirmed by experiments. Convective near wall flow reveals a distorted parabolic flow profile. This indicates relaxation of the no-slip condition, and presence of slip flow. Neither boundary layer formation, nor near wall micro turbulences have been observed. Eventually, a compact mathematical transient flow model, outlined in the Laplace domain for the electrical equivalent analogue circuit and applicable to the convective diffusion equation, has been developed for the flow transients.     

Antennas, Nimny, and regulation

NIMBY ("not in my back yard") opposition to antenna siting in suburban areas is already a major issue in the rollout of new wire less services and is likely to worsen in the next few years. This paper examines the nature of this problem, the regulatory response, and possible alternative approaches to defuse the situation.     

Structural evolution of Ti-Al-Si-N nanocomposite coatings

Ti-Si-Al-N films were prepared by rf reactive magnetron sputtering, in static and rotation modes, using a wide range of different deposition conditions, which created conditions to obtain Ti-Al-Si-N coatings with different structural arrangements.Films prepared below a critical nitrogen flow, under conditions out of thermodynamic equilibrium, revealed a preferential growth of an fcc (Ti,Al,Si)N_x compound with a small N deficiency. With nitrogen flow above that critical value, the reduction of the lattice parameter was no longer detected. However, a thermal annealing showed that a complete thermodynamically driven segregation of the TiN and Si₃N₄ phases was not yet obtained. The segregation upon annealing induced a self-hardening and showed a multiphase system, where the crystalline TiN, (Ti,Al)N and (Ti,Al,Si)N_x phases were identified by X-ray diffraction. This behavior is due to the de-mixing of the solid solution associated to a small N deficiency.     

When do scientists “adopt” the Internet? Dimensions of connectivity in developing areas

Summary We examine the diffusion of information and communication technologies (ICTs) in the knowledge production sectors of three developing areas. Using interviews with 918 scientists in one South Asian and two African locations, we address three fundamental questions: (1) To what degree has the research community in the developing world adopted the Internet? (2) How can the disparities in Internet adoption best be characterized? (3) To what extent is Internet use associated with research productivity? Our findings indicate that while the vast majority of scientists describe themselves as current email users, far fewer have ready access to the technology, use it in diverse ways, or have extensive experience. These results are consistent with the notion that Internet adoption should not be characterized as a single act on the part of users. The rapid development of the Internet and the cumulative skills required for its effective use are equally important, particularly its impact on productivity. These findings lead us to qualify crude generalizations about the diffusion of the Internet in developing areas.     

Determinants of electricity demand for newly electrified low-income African households

Access to clean, affordable and appropriate energy is an important enabler of development. Energy allows households to meet their most basic subsistence needs; it is a central feature of all the millennium development goals (MDGs) and, while a lack of access to energy may not be a cause of poverty, addressing the energy needs of the impoverished lets them access services which in turn address the causes of poverty.     

Thermal expansion of the V5Si3 and T2 phases of the V–Si–B system investigated by high-temperature X-ray diffraction

The thermal expansion anisotropy of the V₅Si₃ and T₂-phase of the V–Si–B system were determined by high-temperature X-ray diffraction from 298 to 1273 K. Alloys with nominal compositions V_62.5Si_37.5 (V₅Si₃ phase) and V₆₃Si₁₂B₂₅ (T₂-phase) were prepared from high-purity materials through arc-melting followed by heat-treatment at 1873 K by 24 h, under argon atmosphere. The V₅Si₃ phase exhibits thermal expansion anisotropy equals to 1.3, with thermal expansion coefficients along the a and c-axis equal to 9.3 × 10^?6 K^?1 and 11.7 × 10^?6 K^?1, respectively. Similarly, the thermal expansion anisotropy value of the T₂-phase is 0.9 with thermal expansion coefficients equal to 8.8 × 10^?6 K^?1 and 8.3 × 10^?6 K^?1, along the a and c-axis respectively. Compared to other isostructural silicides of the 5:3 type and the Ti₅Si₃ phase, the V₅Si₃ phase presents lower thermal expansion anisotropy. The T₂-phase present in the V–Si–B system exhibits low thermal expansion anisotropy, as the T₂-phase of the Mo–Si–B, Nb–Si–B and W–Si–B systems.     

Potential of roof-integrated solar collectors for preheating air at drying facilities in Northern Thailand

Longan is one of the most widely cropped fruits in Northern Thailand, where a significant amount of the annual harvest is commercially dried and exported as a commodity. Liquefied petroleum gas is generally used as the energy source for heating the drying air, but concern is growing as fuel prices are expected to increase for the foreseeable future. Meanwhile, with the ample solar radiation in Thailand, the roofs of drying facilities could be adapted to serve as solar collectors to preheat the drying air, thus reducing the energy requirement from fossil fuels. In this study, a simulation program for a flat-plate solar air heater was used to estimate the potential to preheat drying air given the conditions of several longan drying facilities. Results showed that solar collectors can replace up to 19.6% of the thermal energy demand during the drying season. Bigger collectors and smaller air channels result in more useful heat, but attention has to be paid to costs and pressure drop, respectively. Annual monetary savings can reach up to THB 56,000 (≈US$ 1800 at US$ 1 = THB 31).     

Does Brazil need new nuclear power plants?

In October 2008, the Brazilian Government announced plans to invest US$212 billion in the construction of nuclear power plants, totaling a joint capacity of 60,000 MW. Apart from this program, officials had already announced the completion of the construction of the nuclear plant Angra III; the construction of large-scale hydroelectric plans in the Amazon and the implantation of natural gas, biomass and coal thermoelectric plants in other regions throughout the country. Each of these projects has its proponents and its opponents, who bring forth concerns and create heated debates in the specialized forums. In this article, some of these concerns are explained, especially under the perspective of the comparative analysis of costs involved. Under such merit figures, the nuclear option, when compared to hydro plants, combined with conventional thermal and biomass-fueled plants, and even wind, to expand Brazilian power-generation capacity, does not appear as a priority.