On the symplectic structures for geometrical theories

We present a new approach for constructing covariant symplectic structures for geometrical theories, based on the concept of adjoint operators. Such geometric structures emerge by direct exterior derivation of underlying symplectic potentials. Differences and similarities with other approaches and future applications are discussed.Comment: LaTeX, 12 page

Simulation of surface effects in energy dissipation of ultrahighfrequency (UHF) nanocantilevers

Devices composed of nanoelectromechanical systems (NEMS) possess distinguished properties which make them quite suitable for a variety of applications including ultra-high-frequency (UHF) resonators. However, most GHz resonators have low quality factor even though it has been well above 10 3∼ 10 5 for very-high-frequency (VHF) microresonators. The motivation for our investigation of single crystal silicon nanoresonator arises from both its technological importance and its extraordinary surface effects. Our simulation results show that the quality factor decreased in a nearly linear manner as the surface area to volume ratio (SVR) was increased, which suggests that surface losses play a significant role in determining the quality factor of nanoresonators.published_or_final_versio

On Improving Capacity and Delay in Multi Tx/Rx Wireless Mesh Networks with Weighted Links

This paper considers the problem of deriving a link schedule for Time Division Multiple Access (TDMA)-based concurrent transmit/receive Wireless Mesh Networks (WMNs) that results in low end-to-end delays as well as high network capacity. We first propose a MAX-CUT heuristic approach, called Algo-2, that maximizes link activations in each slot of a super-frame. Algo-2 is shown to produce better network capacity as compared to existing heuristic approaches and significantly improves the super-frame length of an existing MAX-CUT approach that enforces 2-phase transmit receive restriction – a node that transmits (receives) in slot i ≥ 1 is to become a receiver (transmitter) in slot i + 1. Then, we propose a heuristic solution, called BDA, as a complement to existing schedulers to reduce transmission delays. Since BDA only reorders slots in the super-frame, it maintains each original schedule's super-frame length, and hence capacity, while reducing delays by up to 70% in 6-node random topology networks

Self-gravitating spheres of anisotropic fluid in geodesic flow

The fluid models mentioned in the title are classified. All characteristics of the fluid are expressed through a master potential, satisfying an ordinary second order differential equation. Different constraints are imposed on this core of relations, finding new solutions and deriving the classical results for perfect fluids and dust as particular cases. Many uncharged and charged anisotropic solutions, all conformally flat and some uniform density solutions are found. A number of solutions with linear equation among the two pressures are derived, including the case of vanishing tangential pressure.Comment: 21 page

A comprehensive study of Bluetooth signal parameters for localization

We provide an elaborate discussion on Bluetooth signal parameters with respect to localization, whereby we collectively designate all types of Bluetooth specification parameters that are related to signal strength - such as RSSI, Link Quality, Received and Transmit Power Level - as Bluetooth signal, parameters. According to our analysis and experimental results, "RSSI" and "Transmit Power Level" turn out to be poor candidates for localization, while "Link Quality" has its limitations. On the other hand, "Received Power Level" correlates nicely with distance, which makes it the most desirable Bluetooth signal parameter to be used in location systems. We contend that it is vital to choose the appropriate signal parameter in Bluetooth location systems, and we expect our work to provide useful pointers in any future design of such systems. Existing systems can also benefit by adopting the appropriate Bluetooth signal parameter in their systems, and thereby, improve their location accuracy

Efficient heuristics for energy-aware routing in networks with bundled links

Current networks are typically over-provisioned to ensure low delays, redundancy and reliability. These Quality of Service (QoS) guarantees are typically achieved using high end, high power network equipments. Their use, however, has led to concerns regarding green house gas emissions, which garnered a lot of attention recently and have resulted in a number of global initiatives aim at reducing the carbon footprint of Internet Service Providers (ISPs). These initiatives have motivated ISPs and researchers to design novel network algorithms and hardware that scale the usage or active time of a network according to traffic load. To this end, this paper considers the problem of shutting down a subset of bundled links during off-peak periods in order to minimize energy expenditure. Unfortunately, identifying the cables that minimize this objective is an NP-complete problem. Henceforth, we propose several practical heuristics based on Dijkstra’s algorithm and Yen’s k-shortest paths algorithm. We evaluated our heuristics on the Abilene network – with both real and synthetic traffic matrices and several larger random topologies with various loads. Our results show that the proposed heuristics to be effective and efficient. Moreover, our approaches could potentially reduce the energy usage of cables used in the Abilene network by up to 56.7%, assuming the traffic demands recorded on September 5, 2004