Use of context-awareness in mobile peer-to-peer networks

Mobile ad-hoc network are an emerging research field due to the potential range of applications that they support and for the problems they present due to their dynamic nature. Peer-to-peer is an example of a class of applications that have recently been deployed on top of ad-hoc networks. In this paper we propose an approach based on context-awareness to allow peer-to-peer applications to exploit information on the underlying network context to achieve better performance and better group organization. Information such as availability of resources, battery power, services in reach and relative distances can be used to improve the routing structures of the peer-to-peer network, thus reducing the routing overhead

Competing magnetic interactions in CeNi9-xCoxGe4

CeNi9Ge4 exhibits outstanding heavy fermion features with remarkable non-Fermi- liquid behavior which is mainly driven by single-ion effects. The substitution of Ni by Cu causes a reduction of both, the RKKY coupling and Kondo interaction, coming along with a dramatic change of the crystal field (CF) splitting. Thereby a quasi-quartet ground state observed in CeNi9Ge4 reduces to a two-fold degenerate one in CeNi8CuGe4. This leads to a modiffcation of the effective spin degeneracy of the Kondo lattice ground state and to the appearance of antiferromagnetic (AFM) order. To obtain a better understanding of consequences resulting from a reduction of the effective spin degeneracy, we stepwise replaced Ni by Co. Thereby an increase of the Kondo and RKKY interactions through the reduction of the effective d-electron count is expected. Accordingly, a paramagnetic Fermi liquid ground state should arise. Our experimental studies, however, reveal AFM order already for small Co concentrations, which becomes even more pronounced with increasing Co content x. Thereby the modiffcation of the effective spin degeneracy seems to play a crucial role in this system

Incentives in peer-to-peer and grid networking

Today, most peer-to-peer networks are based on the assumptionthat the participating nodes are cooperative. Thisworks if the nodes are indifferent or ignorant about the resourcesthey offer, but limits the usability of peer-to-peernetworks to very few scenarios. It specifically excludes theirusage in any non-cooperative peer-to-peer environment, beit Grid networks or mobile ad-hoc networks. By introducingsoft incentives to offer resources to other nodes, we seean overall performance gain in traditional file-sharing networks.We also see soft incentives promoting the convergenceof peer-to-peer and Grid networks, as they increasethe predictability of the participating nodes, and thereforethe reliability of the services provided by the system as awhole. Reliability is what is required by Grid networks, butmissing in peer-to-peer networks

The design and use of macroeconomics simulation using maple software: A pilot study

The mathematical models used in intermediate macroeconomics have become increasingly more sophisticated and challenging for students to learn. This paper demonstrates how mathematics software, such as Maple, can be used to design a simulation as a pedagogical aid. The paper proceeds by developing a system of equations to model the economy, simulating the system with Maple, and illustrating the impacts of fiscal and monetary policy changes. A pilot test of the simulation was performed to see if higher levels of mathematical rigor could be introduced in a principles course. The results indicate that symbolic mathematics software can be an effective teaching and student learning tool.Economics instruction; macroeconomic simulation; Maple software

On the Disalignment of Interstellar Grains

Several mechanisms have been proposed to explain the alignment of grains with the interstellar magnetic field, including paramagnetic dissipation, radiative torques, and supersonic gas-grain streaming. These must compete with disaligning processes, including randomly directed torques arising from collisions with gas atoms. I describe a novel disalignment mechanism for grains that have a time-varying electric dipole moment and that drift across the magnetic field. Depending on the drift speed, this mechanism may yield a much shorter disalignment timescale than that associated with random gas atom impacts. For suprathermally rotating grains, the new disaligning process may be more potent for carbonaceous dust than for silicate dust. This could result in efficient alignment for silicate grains but poor alignment for carbonaceous grains.Comment: 19 pages, 3 figures, submitted to Ap

Chemical species and chemical reactions of importance in nonequilibrium performance calculations

Computer programs to determine inviscid one dimensional and axisymmetric nonequilibrium nozzle flow field

Droplet size and morphology characterization for diesel sprays under atmospheric operating conditions

The shape of microscopic fuel droplets may differ from the perfect sphere, affecting their external surface area and thus the heat transfer with the surrounding gas. Hence there is a need for the characterization of droplet shapes, and the estimation of external surface area, in order to enable the development of physically accurate mathematical models for the heating and evaporation of diesel fuel sprays. We present ongoing work to automat-ically identify and reconstruct the morphology of fuel droplets, primarily focusing in this study on irregularly-shaped, partially-deformed and oscillating droplets under atmospheric conditions. We used direct imaging tech-niques based on long-working distance microscopy and ultra-high-speed video to conduct a detailed temporal investigation of droplet morphology. We applied purpose-built algorithms to extract droplet size, velocity, vol-ume and external surface area from the microscopic ultra-high-speed video frames. High resolution images of oscillating droplets and a formation of a droplet form ligament, sphericity factors, volume as well as external surface area are presented for 500 bar injection pressure in the near nozzle region (up to 0.7 mm from nozzle exit) under atmospheric conditions. We observed a range of different liquid structures, including perfectly spher-ical, non-spherical droplets and stretched ligaments. We found that large droplets and ligaments exceeding the size of the nozzle hole could be found at the end of injection. In order to estimate droplet volume and external surface area from two-dimensional droplet information, a discrete revolution of the droplet silhouette about its major centroidal axis was used. Special attention was paid to the estimation of actual errors in the prediction of volume and surface characteristics from a droplet silhouette. In addition to the estimation of droplet volume and external surface area, the actual shape reconstruction in 3D coordinates from a droplet silhouette was performed in order to enable future numerical modelling studies of real droplets