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Search Results: 1 - 10 of 5930 matches for " Fabio Perna "
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Optimization of UMTS Network Planning Using Genetic Algorithms  [PDF]
Fabio Garzia, Cristina Perna, Roberto Cusani
Communications and Network (CN) , 2010, DOI: 10.4236/cn.2010.23028
Abstract: The continuously growing of cellular networks complexity, which followed the introduction of UMTS technology, has reduced the usefulness of traditional design tools, making them quite unworthy. The purpose of this paper is to illustrate a design tool for UMTS optimized net planning based on genetic algorithms. In particular, some utilities for 3G net designers, useful to respect important aspects (such as the environmental one) of the cellular network, are shown.
Ad Hoc Network Hybrid Management Protocol Based on Genetic Classifiers  [PDF]
Fabio Garzia, Cristina Perna, Roberto Cusani
Wireless Engineering and Technology (WET) , 2010, DOI: 10.4236/wet.2010.12011
Abstract: The purpose of this paper is to solve the problem of Ad Hoc network routing protocol using a Genetic Algorithm based approach. In particular, the greater reliability and efficiency, in term of duration of communication paths, due to the introduction of Genetic Classifier is demonstrated.
Feedback Power Control Strategies inWireless Sensor Networks with Joint Channel Decoding
Andrea Abrardo,Gianluigi Ferrari,Marco Martalò,Fabio Perna
Sensors , 2009, DOI: 10.3390/s91108776
Abstract: In this paper, we derive feedback power control strategies for block-faded multiple access schemes with correlated sources and joint channel decoding (JCD). In particular, upon the derivation of the feasible signal-to-noise ratio (SNR) region for the considered multiple access schemes, i.e., the multidimensional SNR region where error-free communications are, in principle, possible, two feedback power control strategies are proposed: (i) a classical feedback power control strategy, which aims at equalizing all link SNRs at the access point (AP), and (ii) an innovative optimized feedback power control strategy, which tries to make the network operational point fall in the feasible SNR region at the lowest overall transmit energy consumption. These strategies will be referred to as “balanced SNR” and “unbalanced SNR,” respectively. While they require, in principle, an unlimited power control range at the sources, we also propose practical versions with a limited power control range. We preliminary consider a scenario with orthogonal links and ideal feedback. Then, we analyze the robustness of the proposed power control strategies to possible non-idealities, in terms of residual multiple access interference and noisy feedback channels. Finally, we successfully apply the proposed feedback power control strategies to a limiting case of the class of considered multiple access schemes, namely a central estimating officer (CEO) scenario, where the sensors observe noisy versions of a common binary information sequence and the AP’s goal is to estimate this sequence by properly fusing the soft-output information output by the JCD algorithm.
Gamma-ray Burst Remnants: How can we find them?
Rosalba Perna
Physics , 2001, DOI: 10.1007/10853853_64
Abstract: By now there is substantial evidence that Gamma-Ray Bursts (GRBs) originate at cosmological distances from very powerful explosions. The interaction between a GRB and its surrounding environment has dramatic consequences on the environment itself. At early times, the strong X-ray UV afterglow flux photoionizes the medium on distance scales on the order of 100 pc or more. Here I discuss the long-term effects resulting from the interaction between a GRB and its environment, and in particular the signatures of the emission spectrum produced while the heated and ionized gas slowly cools and recombines. Besides photoionizing the medium with its afterglow, a GRB explosion drives a blast wave which is expected to have a very long lifetime. I discuss possible candidates for such GRB remnants in our own and in nearby galaxies, and ways to distinguish them from remnants due to other phenomena, such as multiple supernova (SN) explosions.
Heat equation for theta functions and vector-valued modular forms
Sara Perna
Mathematics , 2015,
Abstract: We give a new method for constructing vector-valued modular forms with singular scalar-valued modular forms. As an application we prove that the vector space generated by vector-valued modular forms that can be defined using gradients of odd theta functions coincide with the one generated by vector-valued modular forms arising from second order theta constants with our new construction. This latter result is also a direct consequence of the "heat equation'' for theta functions.
On isomorphisms between Siegel modular threefolds
Sara Perna
Mathematics , 2014, DOI: 10.1007/s12188-015-0116-z
Abstract: The Satake compactification of the moduli space of principally polarized abelian surfaces with a level two structure has a degree 8 endomorphism. The aim of this paper is to show that this result can be extended to other modular threefolds. The main tools are Siegel modular forms and Satake compactifications of arithmetic quotients of the Siegel upper-half space. Indeed, the construction of the degree 8 endomorphism on suitable modular threefolds is done via an isomorphism of graded rings of modular forms. By studying the action of the Fricke involution one gets a further extension of the previous result to other modular threefolds. The possibility of a similar situation in higher dimensions is also discussed.
Conducting interfaces between band insulating oxides: the LaGaO3/SrTiO3
Paolo Perna,Davide Maccariello,Milan Radovic,Umberto Scotti di Uccio,Ilaria Pallecchi,Marta Codda,Daniele Marré,Claudia Cantoni,Jaume Gazquez,Maria Varela,Steve Pennycook,Fabio Miletto Granozio
Physics , 2010, DOI: 10.1063/1.3496440
Abstract: We show that the growth of the heterostructure LaGaO3/SrTiO3 yields the formation of a highly conductive interface. Our samples were carefully analyzed by high resolution electron microscopy, in order to assess their crystal perfection and to evaluate the abruptness of the interface. Their carrier density and sheet resistance are compared to the case of LaAlO3/SrTiO3 and a superconducting transition is found. The results open the route to widening the field of polar-non polar interfaces, pose some phenomenological constrains to their underlying physics and highlight the chance of tailoring their properties for future applications by adopting suitable polar materials.
Utilidad de los marcadores serológicos en el diagnóstico y estratificación de riesgo de la insuficiencia cardíaca
Perna,Eduardo R;
Insuficiencia card?-aca , 2007,
Abstract: the evaluation of patients with suspicion of heart failure (hf) has two main objectives: early diagnosis and concurrently, identification of low- and high-risk subjects. despite hf is a highly prevalent condition, limitations in diagnosis, monitoring and risk stratification may be present. in this paper, the usefulness of natriuretic peptides (np) and cardiac troponin (tn) in chronic and decompensated hf is revisited. np (bnp and nt-probnp) contribute with the differential diagnosis, provide prognostic information and may guide the treatment. tn elevation identifies patients with stable hf or admitted for worsening hf, with higher incidence of events. the hypothesis to be demonstrated is that the measurement of np and tn during admisión and before discharge in decompensated hf might simultaneously help to identifying patients with high-risk during hospitalization, to monitoring the response to treatment, to detecting deleterious effect of drugs, to evaluating pre-discharge status, and to stratifying long-term prognosis. during the ambulatory phase of chronic hf, the periodic determination of both biomarkers may be useful to early identification of subjects at risk of decompensation, or to select candidates to advanced therapeutic options.
THE ALUMINA-SILICATES IN STABILIZATION PROCESSES IN FLUIDIZED-BED ASH
TOMAS HANZLICEK,IVANA PERNA
Ceramics-Silikáty , 2011,
Abstract: Presented study of coal fluidized-bed ash solidification was accompanied with specific studies of alumino-silicates residues in ashes. The specific technology of fluid coal burning and its relatively low temperature combustion combines coal burning and decomposition of calcium carbonate added to the fluid layer in the main endeavor to capture all sulfur oxides. The burning temperature seems be decisive to the behavior of clayed residues and calcium carbonate decomposition in connection for the future solidification of fluidized bed ash. The calcareous substances in combination with alumino-silicate residues form solid bodies where silicates play decisive role of long-term stability and insolubility of obtained solids. The position of aluminum ions in clayed residues of burned coal were studied by MAS-NMR with attention on aluminum ion coordination to oxygen and formation of roentgen amorphous phase of poly-condensed calcium alumina-silicate.
Microlensing of Quasars By Stars In Their Damped Lyman alpha Absorbers
Rosalba Perna,Abraham Loeb
Physics , 1997, DOI: 10.1086/304806
Abstract: The damped Lyman alpha absorbers (DLAs) in quasar spectra are believed to be the progenitors of present-day disk galaxies. We examine the probability for microlensing of background quasars by stars in their DLAs. Microlensing by an individual star should magnify the continuum but not the broad emission lines of the quasars. Consequently, the equivalent width distribution of microlensed quasars would be distorted. We model a representative spiral galaxy as a closed system composed of a bulge, a disk, and a halo, and evolve the mass fraction of stars in the disk based on the observed metallicity of DLAs at high redshifts. The microlensing signatures are stronger if the halo of the galaxy is made of Massive Compact Halo Objects (MACHOs). In this case, the distortion imprinted by microlensing on the equivalent width distribution of quasar emission lines can be detected with high significance in a sample of about 10 DLAs with HI column densities N>10^21 cm^-2 and absorption redshifts z_abs<1. About a tenth of all quasars with DLAs (N>10^20 cm^-2) might show excess variability on timescales shorter than five years. A search for these signals would complement microlensing searches in local galaxies and calibrate the MACHO mass fraction in galactic halos at high redshifts.
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