Dependence of network capacity requirements on the allowable flowconvergence overloads in ATM backup VP restoration

Work on capacity design for VP restoration in ATM has to date either been heuristic in nature or has treated the capacity design problem in a 1 for 1 VP replacement manner that is essentially the same as for STM path restorable networks. However, the inherently statistical nature of the traffic in ATM should allow formulation of a backup VP restoration capacity design that permits a controlled maximum of convergent flow overloads on spans during restoration. Results show that significant capacity savings can be obtained relative to STM if ATM restoration is allowed even modest restoration overload factors. We give an integer program formulation permitting controlled exploitation of this intrinsic difference between ATM and STM transport and present results showing the significant capacity benefits motivating this approach     

Forward-error-control (FEC)-assisted adaptive equalization fordigital cellular mobile radio

An adaptive equalization technique using forward error control coding is described and evaluated. Computer simulation is used to compare the FEC-assisted adaptive equalization to conventional adaptive equalization. The system model employed is based on the proposed digital cellular communication standard for North America. The FEC-assisted adaptive equalization technique performs better than the conventional equalization method at low and moderate Doppler frequencies with the same level of redundancy in the transmitted data. For systems employing both FEC coding and adaptive equalization, the FEC-assisted adaptive equalization method successfully combines these two functions while using the redundancy required for only one of them. In other words, training required for adaptive equalization can be provided at no extra cost in terms of data redundancy in a system using FEC coding and vice versa     

A free-electron laser with enhanced energy spread acceptance

It is shown that by cascadingNwiggler sections through compensating sections a gain of N²times the gain of a single wiggler section may be attained, whereas the energy acceptance of theNsections is the same as that of a single section. The relative phase shift of electrons with different energies in the compensating section is opposite that in the wiggler. A realization of a compensating section is presented. Finally, an application of this idea is considered to a free-electron laser in a storage ring. It is shown that at 0.15μm wavelength, using a 250 MeV storage ring, a gain 100 times higher may be obtained as compared to the uniform wiggler free-electron laser, for the same energy acceptance of 2.5 percent in the two cases.     

Forward error correction in dispersion-limited lightwave systems

A rate 0.964 forward error correcting (FEC) code is integrated into the low-speed tributaries of a 565-Mb/s lightwave system as an exploratory system design approach toward relaxing requirements on laser sources in dispersion-limited operation. By virtually removing error rate floors, regardless of their cause, FEC is shown to provide an increasing advantage in conditions of greater degradation and to be effective against mode partition noise (MPN), mode jumping, and reflection impairments.The experimental FEC code is implemented in a standard gate array. The FEC code is described and its performance is analyzed. A new system design strategy is suggested for low-cost gigabit lightwave systems using FEC     

Chemosensory conditioning of Hermissenda crassicornis..

Bite–strike responses of Hermissenda crassicornis, elicited by chemosensory stimulation of the lips, were found to be modified when food extracts were paired with rotation-produced stimulation of the statocysts. Animals that received repeated pairings of an extract of 1 food (conditioned stimulus, CS) with rotation exhibited suppressed bite–strike responses to that food for up to 48 hr after training. This suppression was usually specific to the trained food and was pairing-specific as well. Discriminative conditioning was also demonstrated. Animals trained with 1 CS paired with rotation and a second CS that was unpaired (CS–) showed suppressed bite–strike responses to the first CS. The results demonstrate that Hermissenda can learn to avoid foods that reliably signal an aversive event and may allow an analysis of higher order conditioning phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

COMMUNICATIONS' PLACE IN THE ORGANIZATION

Communications channels—from mobile phones to value-added networks to corporate-owned communications lines—are vital to business. Organizations must redesign their corporate structures to readily and effectively handle internal information flows and link with external customers and suppliers. A survey reveals how leading US corporations define responsibilities and specializations in this area and examines some management approaches to adopting communications technologies.     

Calcium oxalate crystallization in urine of healthy men and women: a comparative study

This study aimed to compare calcium oxalate (CaOx) crystallization in undiluted urine from healthy men and women with the object of clarifying the difference in stone incidence between the two sexes. Twenty-four hour urine specimens were collected from 37 men and 28 women. Urinary pH, and concentrations of Ca, oxalate and urate were measured, and indices of crystallization determined by Coulter Counter particle analysis following induction of CaOx crystallization by addition of oxalate. The amount of oxalate required to induce crystallization was significantly (p < 0.01) higher in females than in males, as was the overall particle volume deposited after 90 minutes incubation (p < 0.006). Scanning electron microscopy revealed larger individual crystals in female urine, and a greater degree of crystal aggregation in male urine, although the average overall size of the precipitated crystal particles did not differ between the two sexes. There were no significant differences between men and women with regard to median pH, or Ca and oxalate concentrations, but the median urate concentrations were slightly, but significantly, higher (p < 0.05) in the women's urines than in the men's. It was concluded that the greater risk of CaOx stones in men is related to an increased propensity to nucleate CaOx crystals per se, rather than to a tendency to form larger crystalline particles.     

Finding an appropriate radio propagation model for rate aware congestion control mechanism in wireless sensor networks

Wireless Networks - Congestion control techniques are considered to be one of the most imperative ways to overcome various challenges in wireless sensor networks (WSNs). Undeniably, congestion has...