344 research outputs found
An Analytical Model of the Route Acquisition Process in AODV Protocol
No full textThe paper presents an analysis of the route acquisition process in the ad hoc on demand distance vector (AODV) routing protocol. We develop an analytical model describing the probability of realizing the route request process in a certain number of hops, taking into account some possible errors and link breaks during the path toward destination. Comparisons between simulations performed with a simple simulator developed in C and model results confirm the effectiveness of the proposed model. Other interesting numerical results about the influence of some scenario parameters over the route request process performances are described
Videonet: Cloud Videomanagement Service for the Public Administrations
No full textThis paper describes a cloud videomanagement ser-
vice, result of an upgrade of a previous test-bed version, designed
and realized in order to give sustainable videosurveillance service
to the smallest Public Administrations of Emilia-Romagna Italian
region. We focus on some implementative solutions adopted in
order to optimize the performances in terms of usability and
cloud resource management
CHIMICA ANALITICA QUANTITATIVA di D.C. Harris. Seconda edizione italiana condotta sulla sesta edizione americana
No full textUno degli scopi fondamentali di questo libro, giunto ormai alle sesta edizione americana e tradotto in più lingue, è quello di presentare gli argomenti avvalendosi di esempi concreti, interessanti e di attualità. Finora era stata tradotta in italiano solo la seconda edizione americana (traduttrice L. Cioppettini, revisore M. Taddia, editore Zanichelli, 1991). La precedente edizione italiana è stata adottata in diverse Università. Il libro contiene ventinove capitoli, un glossario, una raccolta di note e bibliografia, nonchè una ricca appendice. Risulta ampiamente rinnovato ed aggiornato rispetto all'edizione tradotta in precedenza. Tratta sia i metodi classici di analisi e relativi fondamenti che i principali metodi strumentali. Questa edizione contiene un capitolo sulla preparazione del campione e uno sull'assicurazione di qualità, assenti in precedenza, ma assai utili nella moderna didattica della chimica analitica. Invoglia altresì all'uso del calcolatore, in quanto mostra come utilizzare i fogli di calcolo per la risoluzione di numerosi problemi. La bibliografia è aggiornata ai primi del duemila. Per rendere ancor più fruibile il testo dagli studenti italiani, sono state aggiunte numerose note espilcative
Horn of Africa 20th Century. Politics and History
No full textIn the last decades, the Horn of Africa has been stigmatized as one of the
most unstable regions in the world with no place for peace-building,
institution building, or democratic processes.This volume deals with Eritrea
in the context of recent political developments in the Horn of Africa and
neighboring countries. The author analyzes the emergence of nationalism
and the political struggle in Eritrea while trying to identify the main
dynamics of state formation and the role of colonialism according to
different scholarly perspectives. Twenty years later, Eritrea has received a
great deal of attention and an international debate is still ongoing. This
gives a new contribution to the dynamics of sub-Saharan Africa
On the Application Wide-Trail Strategy to Improve an Extended Feistel Cryptosystem
No full textIn this paper, we discuss a wide-trail-strategy-based method able to enhance the security offered by an encryption scheme developed in the University of Ferrara and based on an extended Feistel structure. By adding a new diffusion layer to the basic round transformation of the original system, we are able to increase the amount of active transformations, improving both the strength of the scheme against linear and differential attacks and the whole cipher performance by considerably reducing the system decoding tim
Gas. Fritz Haber, inventore dello Zyclon B di Tiziano Colombi
No full textC’è un brevetto al cui nome è legato uno dei momenti più tragici del secolo scorso, anzi dell’intera storia umana, quello del disinfestante a base di acido cianidrico denonimato ZyKlon B, registrato il 20 giugno 1922 e pubblicato il 27 dicembre 1926 con il numero DE438818 C. L’inventore ufficiale del nuovo metodo per il controllo dei parassiti (Verfahren zur Schaedlingsbekaempfung) risulta dalla scheda il Dr. Walter Heerdt (1888-1957) della Deutsche Gesellschaft für Schädlingsbekämpfung MBH (Degesch). In realtà gli inventori furono tre e a quello di Heerdt vanno aggiunti i nomi di Bruno Tesch and Gerhard Peters. Tutti lavoravano per Fritz Haber che all’epoca dirigeva la Degesch. Il nome di quest'ultimo, premio Nobel per la Chimica 1918, si collega quindi soltanto indirettamente al famigerato gas impiegato dai nazisti per sterminare gli ebrei, tanto più che sotto la guida di Haber la forma brevettata fu sviluppata per tutt’altro scopo. Il libro di Colombi, ben scritto e conciso, si sforza di scavare, per quanto possibile, negli oscuri recessi di un personaggio discusso e odiato al tempo stesso per il suo attivismo nella guerra chimica. Non è un saggio storico ma una biografia romanzata per “quadri” e come tale va inteso e valutato
Analysis of Performance of Multicast Routing Protocols over 802.11b
No full textAbstract—In this paper we present a simulation study of the
performance of AMRIS and ODMRP multicast routing protocols,
in the presence of the rate adaptation mechanism of IEEE
802.11b MAC protocol. We have chosen these two protocols
because they are representative of the different multicast routing
strategies proposed in the literature, the tree-based approach and
the mesh-based approach. To evaluate the performance of these
protocols we have considered figures of merit like packet delivery
fraction and energy spent by the network
(Edition and translation from the Amharic of the “Letter to Menilek by Blatta Gäbrä Egzi’abeḥēr”) Ethiopian Source Material and Colonial Rule in the Nineteenth Century: The Letter to Menilek (1899) By Blatta Gäbrä Egzi'abehēr
No full textDespite his important political and literary activities, Blatta Gäbrä Egzi'abeḥēr is almost unknown to scholars of Menilek’s Ethiopia. This historical period is not particularly well researched, and the author stands out as one of the few Ethiopian intellectuals to have written such an important number of literary works focused on nationalistic and anti-Italian feelings. The Amharic/Geʿez text under discussion, his letter to Menilek written in 1899, is a remarkable document from this point of view because it reveals a strong opposition to colonialism and the Italian occupation of Eritrea. This document is one of the first Ethiopian sources to testify to the growing nationalism and the growth of concepts of unity and independence. It allows us to consider more carefully the beginning of an Ethiopian secular ideology of the modern state. And such an ideology must be placed in the colonial context. The letter to Menilek raises some important questions regarding the new source material in the late nineteenth century available to historians of modern Ethiopia. A translation of the text is given as well as a comment on its historical significance
Energy efficient unicast routing protocols over 802.11b
No full textThe paper compares the performance of the AODV, DSR, OESR classic routing protocols for ad hoc networks, when an IEEE 802.11b MAC protocol is used. The investigation, performed by means of simulations, evaluates the energy efficiency of these protocols and the effect of the 802.11b rate adaptation capability on the performance. The paper evaluates the effectiveness of a distributed power control (DPC) scheme (P. Bergamo et al., 2002) applied to the classic AODV, DSR and OESR routing algorithms. The DPC scheme, acting both at MAC and network layers, has the aim to reduce the overall power consumption of the network. In particular, DPC evaluates, hop-by-hop, the suitable transmit power level and then selects, end-to-end, for any destination, the path which minimizes the total transmit power required. A final comparison between classic and DPC routing protocols is also reported
Multi-radio resource allocation strategies for heterogeneous wireless networks
No full textAbstract: In this paper we present algorithms for dynamic
channel allocation with QoS support. In particular,
we focus on the integration of networks with different Radio
Access Technologies (RATs), as is currently subject of investigation
within the novel concept of Ambient Networks.
On this matter, we investigate the introduction of collaborative
channel assignment, which exploits service elasticity
and the tunability offered by QoS management. To this end,
the comparison between non cooperative and cooperative
resource allocation is briefly discussed and simulations are
performed to demonstrate how collaborative strategies are
able to improve system performance
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