A Mixed Convex/Nonconvex Distributed Localization Approach for the Deployment of Indoor Positioning Services

In this paper the indoor wireless localization problem is addressed both from the theoretical and application standpoints. The main result of the paper is on the theoretical side: the topological definition of regular and irregular nodes is introduced, and formal results are presented to support regularity as a desirable network property for the attainment of precise node localization. In force of this definition, a mixed convex/non—convex optimization approach has been derived for the solution of the positioning problem. The two procedures, suitably combined, allow the achievement of better convergence towards the best positioning of a multitude of blind wireless nodes. A completely decentralized, partially asynchronous algorithm is presented, which proceeds locally on each node based on the sole knowledge of the distances measured from, and of the estimated positions of the connected nodes only. Its repeated asynchronous application on each nodes guarantees the convergence of the algorithm to the positioning of the whole network, even in presence of a limited number of peripheral reference points. Indeed, no global information is required for the proper functioning of the algorithm. Simulations of relevant case studies have been performed to qualify the proposed scheme in realistic conditions, and the results are presented.     

Resource allocation in satellite networks: certainty equivalent approaches versus sensitivity estimation algorithms

In this paper, we consider a resource allocation problem for a satellite network, where variations of fading conditions are added to those of traffic load. Since the capacity of the system is finite and divided in finite discrete portions, the resource allocation problem reveals to be a discrete stochastic programming one, which is typically NP‐hard. We propose a new approach based on the minimization over a discrete constraint set using an estimation of the gradient, obtained through a ‘relaxed continuous extension’ of the performance measure. The computation of the gradient estimation is based on the infinitesimal perturbation analysis technique, applied on a stochastic fluid model of the network. No closed‐forms of the performance measure, nor additional feedback concerning the state of the system, and very mild assumptions on the probabilistic properties about the statistical processes involved in the problem are requested. Such optimization approach is compared with a dynamic programming algorithm that maintains a perfect knowledge about the state of the satellite network (traffic load statistics and fading levels). The comparison shows that the sensitivity estimation capability of the proposed algorithm allows to maintain the optimal resource allocation in dynamic conditions and it is able to provide even better performance than the one reached by employing the dynamic programming approach. Copyright © 2004 John Wiley & Sons, Ltd.     

A Layered Alumina Composite Tested at High Temperature in Air

An oxidation-resistant interphase for layered alumina composites was prepared by aerosol spray deposition of submicrometer alumina powder. A model composite specimen was made by placing the interphase between thin layers of monolithic alumina. The composite sandwich was hot-pressed to control the interphase fracture resistance for successful crack deflection. Specimens were tested under four-point bending in air at two crosshead speeds at ambient temperature, 1000°C, and 1200°C. The fracture behavior was temperature dependent, with a higher work of fracture at higher temperatures. Interphase delamination and composite toughening behavior were very pronounced at all temperatures. At the highest temperature, the transition to multiple widely distributed cracks and increased crack deflection may be related to inelastic deformation in the alumina.     

Mortality from tuberculosis in Spain from 1970 to 1993: changes in epidemiological trends during the acquired immune-deficiency syndrome epidemic

SETTING: Spain has the highest rates in Europe of the acquired immune-deficiency syndrome (AIDS), and probably a high rate of dual human immunodeficiency virus (HIV)/tuberculosis infection. OBJECTIVE: To determine the trends of tuberculosis mortality in Spain from 1970 to 1993, and to draw conclusions about the effects of the AIDS epidemic on these trends. DESIGN: Official population figures and data on deaths from tuberculosis were used to calculate specific tuberculosis mortality rates by age and sex (per 100000 population). Causes of death from tuberculosis were grouped according to the International Classification of Diseases. RESULTS: The crude death rate decreased from 10.28 to 1.84, with an annual mean decrease of 8.1% (95% confidence interval 7.5% to 8.7%). No changes in mortality from tuberculosis of the central nervous system (CNS) have been recorded since 1982, and none in mortality from other tuberculosis and in the age group 20-49 years since 1986. Mortality was higher among males and in the older age groups. The peak observed in the 1970s, due to the excess of deaths from CNS tuberculosis in children under the age of 5 years, has disappeared. CONCLUSION: Between 1970 and 1993, tuberculosis mortality in Spain decreased, although an excess of deaths occurred in young adults and from extra-pulmonary tuberculosis, coinciding with the AIDS epidemic.     

Elastic and anelastic properties of Marval 18 steel

Marval 18 is a precipitation hardened steel with particularly high hardness and low creep, presently used for constructing parts of the interferometers for the detection of gravitational waves in the experiments VIRGO and LIGO. The elastic moduli have been measured in samples subjected to the same treatments as the parts of the interferometer VIRGO. In addition, the anelastic spectra of samples subjected to different thermal treatments have been measured between 50 and 350 K. It is found that, in the absence of plastic deformation, the elastic energy loss coefficient under flexural vibrations around 1 kHz can vary by more than one order of magnitude depending on the thermal treatments, and is dominated by the thermoelastic effect. The main reason for such strong variations is supposed to be the dependence of the thermal conductivity on the average sizes and distances between the precipitate particles.     

Ozone Reaction with C70 and C60 Fullerenes: The Effect of Temperature on the Reaction Kinetics

It has been confirmed that the effect of temperature on the rate constants (k) of ozone reaction with C₇₀ and C₆₀ fullerenes follows the Arrhenius law. The experimental values of activation energy (E_a) and pre-exponential factor (A), like as those of other simple alkenes, are in the order of 2.4-2.6 kcal mol^-1 and (1.2-1.8) × 10⁷ L mol^-1 sec^-1, respectively. They are practically equal for the both fullerenes. It has also been found that the value of the rate constant k of C₇₀ fullerene ozonolysis is higher in comparison to the respective k-value of C₆₀.     

Effect of four-wave mixing on WDM optical systems: a statistical analysis

The dense wavelength-division-multiplexed system design requires an accurate knowledge of the four-wave mixing (FWM), which gives rise to intermodulation effects, especially when using very low-dispersion fibers. In this letter, a statistical analysis is presented that takes into account both the effect on the FWM intermodulation products due to dispersive propagation, and the statistics of such intermodulation terms, which must be considered as random processes. In particular, the autocorrelation function of the FWM process is calculated for the independent wavelength-division-multiplexing optical channel.     

Su una estensione di un particolare modello (non lineare) per trasporti interni industriali

Recently, by using the method of dynamic programming, M. Volpato determined a policy of minimized costs to supply many destinations from a single source, the transport costs being functions (linear or not linear) which satisfy only the condition of inferior semi-continuity. Among the feasible policies he admitted also the indireact shipping from source to destination (i.e. a policy, where a larger quantity than required is sent to certain destination, and the surplus is delivered to a destination which follows it in a given order). In this paper the problem is studied for the case in which there is more than one source, and the availability of every source is limited. In this case it is possible to consider the problem as a multi-stage process, and to solve again it by the method of dynamic programming.

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Lavoro eseguito nell'ambito del Gruppo di ricerca matematica n. 38 (Ca' Foscari, Venezia) del C.N.R. per l'anno accademico 1964–65.     

Evidences of Rubber Grafting on Activated Carbon Surfaces Containing Fullerene-like Structures

It is shown that graphite is converted into an high disordered carbon black by prolonged ball milling. The kinetics of this transformation has been followed by powder x-ray diffraction, measurements of the crystallinity and of the surface area. Ball milling is able to introduce an high concentration of defective sites in the pristine graphite including the fullerene-like structures. By mixing with natural rubber both the pristine and the ball-milled graphite, it is shown by bound rubber measurements that the amount of rubber grafted (chemically linked) on the pristine graphite surface is negligible but reaches a very high level in the ball-milled graphite. Similarly, ball-milling of N660 carbon black causes a deep activation of its surface activity which can be measured by a significant increase in the bound rubber level and in the amount of grafted rubber in comparison to the pristine N660 sample. The bound rubber measurement has been performed also on a natural rubber masterbatch with extracted fullerene carbon black (EFCB). Also in this case extremely high levels of rubber grafting have been achieved in comparison to graphite. It is discussed and demonstrated that the fullerene-like nanostructures in carbon blacks play a key role in the formation of bound rubber phenomenon and in grafting natural rubber on carbon black surface.     

Influence of temperature,pH and ionic strength on the production of isoflavone-rich soy protein isolates

Soy protein isolates (SPI) may present different isoflavone profiles and contents, depending on processing conditions. In the present work, seven different SPI, resulting from changes in the processing steps, were obtained. The best parameters for obtaining isoflavone-richer SPI were: extraction at pH 9 and temperature of 55 °C, acid precipitation performed at pH 4.5, acid-washing of the precipitate and mild centrifugation conditions for the separation of acid-precipitated proteins. Isoflavones were soluble in aqueous solution in the pH range 2–10 (73–93% of the amount solubilized in 80% methanol). The profile of isoflavones was dependent on the temperature used for the aqueous extraction. Temperatures below 50 °C caused hydrolysis of β-glucosides with increase of aglucones, by endogenous β-glucosidase activity.