Parallel rendezvous multi-channel MAC mechanisms are regarded as an efficient method for media access control in cognitive radio networks since they do not need a control channel and use only one transceiver. However, existing parallel rendezvous MAC mechanisms assume that all channels have the same maximum capacity and channel availability for secondary users. In this paper, we propose a dynam...

This paper presents and discusses the ongoing developments towards definition of a multi-knowledge level seismic assessment procedure for large-scale risk applications. The involves analytical-mechanical SLaMA (Simple Lateral Mechanism Analysis) method allows an adaptive updatable performance buildings accounting different data acquisition (knowledge) levels. By coupling this approach with vuln...

Using the enhanced data rates for GSM evolution (EDGE) system with cyclic frequency hopping as an example, we apply a Kalman-filter power control method based on interference tracking to packet voice service in wireless networks. Our results show that the power-control method significantly improves the spectral efficiency by enabling the 1/3 frequency reuse while maintaining a stringent require...

| In this paper we study the system capacity of cellular systems with time-division multiple access and slow time-frequency hopping (F-TDMA). System capacity is deened as the number of users/cell bit/s/Hz, for a given maximum outage probability. Outage is deened as the event that the mutual information of the interference channel falls below the actual code rate. We develop a general framework ...

The optimization between the average received power and the theoretically achievable average channel capacity per user (in the Shannon sense) of a hybrid direct-sequence/fast frequency hopping codedivision multiple-access (DS/FFH-CDMA) cellular system, when operating in a Rayleigh fading environment, is presented. The analysis leads to a novel-closed form expression for the optimal average rece...

Smart antenna is considered as one of the most effective means for enhancing wireless system capacity. When fractional loading is accompanied with slow-frequency hopping (SFH), soft capacity can be realized in time-division multiple access (TDMA) wireless networks. Then, the interference reduction due to smart antennas, power control, and discontinuous transmission can be directly translated in...

Early, pre-code, reinforced concrete structures present undetermined resistance to earthquakes. This situation is particularly unacceptable in the case of essential facilities, such as healthcare structures. Amongst these, the Santa Maria Hospital – finished in 1953 with a total area of 120,000 m – in Lisbon, was designed without explicit consideration for earthquake loading. Given the crucial ...

In recent numerical simulations of spherically symmetric gravitational collapse a new type of critical behaviour, dominated by a sphaleron solution, has been found. In contrast to the previously studied models, in this case there is a finite gap in the spectrum of black-hole masses which is reminiscent of a first order phase transition. We briefly summarize the essential features of this phase ...

in this paper, we have used density functional perturbation theory (dfpt) and pseudo-potential method to calculate the phonon spectrum, phonon density of states (dos), specific heat capacity and mechanical properties of (5,5) armchair and (9,0) zigzag single wall carbon nanotubes (swcnts). our calculations show that young’s modulusfor (5,5) and (9,0) nanotubesare higher than 1tpa. we have also ...