1,721,149 research outputs found
"Pocula dans genti degenti nunc Agrigenti" : ricerche intorno a una epigrafe di fine Duecento
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Sistemi Operativi. Seconda edizione
No full textIl libro è specificamente concepito come testo per un primo insegnamento sui sistemi operativi che rappresenta una parte essenziale di ogni corso di laurea in Ingegneria Informatica ed Informatica. Rispetto alla prima edizione il libro e' stato arricchito di un nuovo capitolo sulle problematiche di protezione e sicurezza e di due nuove appendici, una relativa al linguaggio dei comandi (shell) di Unix ed una relativa ai sitemi sommersi (embedded). Inoltre sono stati approfonditi alcuni argomenti chiave come ,per esempio, gli algoritmi di scheduling della CPU, le tecniche di gestione delle condizioni di stallo ed i sistemi operativi real-time
Schedulability Analysis of Global Scheduling Algorithms on Multiprocessor Platforms
Full text linkThis paper addresses the schedulability problem of periodic and sporadic real-time task sets with constrained deadlines preemptively scheduled on a multiprocessor platform composed by identical processors. We assume that a global work-conserving scheduler is used and migration from one processor to another is allowed during task lifetime. First, a general method to derive schedulability conditions for multiprocessor real-time systems will be presented. The analysis will be applied to two typical scheduling algorithms: Earliest Deadline First (EDF) and Fixed Priority (FP). Then, the derived schedulability conditions will be tightened, refining the analysis with a simple and effective technique that significantly improves the percentage of accepted task sets. The effectiveness of the proposed test is shown through an extensive set of synthetic experiments
Improved schedulability analysis of EDF on multiprocessor platforms
No full textMultiprocessor hardware platforms are now being considered for embedded systems, due to their high computational power and little additional cost when compared to single processor systems. When scheduling real-time applications on multiprocessor platforms, a possibility is to use global scheduling, where a scheduling algorithm dynamically assign tasks to processors, and tasks can migrate from one processor to another during their execution. In this paper, we tackle the problem of schedulability analysis of sporadic tasks in global scheduling systems, where the scheduler is the earliest deadline first (EDF) algorithm. We provide two main contributions. First, we show that two recently proposed tests perform poorly when the task set contains heavy tasks (i.e. tasks with high utilization). We also show that neither test dominates the other. As a second contribution, we introduce a new schedulability test that improves significantly the percentage of accepted task sets, especially when considering task sets containing heavy tasks. We show the effectiveness of the proposed test through an extensive set of experiments
TREATMENT OF SIX HEPATIC ARTERY ANEURYSMS
No full textHepatic artery aneurysms are rare lesions but of significant clinical importance because rupture
is associated with elevated mortality. Although diagnosis using CT scanning and, more importantly,
angiography has been well defined, the therapeutic choices are less clear. We retrospectively
selected patients from 1985 to 2000 who were treated with either traditional surgical
or percutaneous techniques. In total we treated six patients, four males and two females. This
represents 17.6% of 34 patients treated by us for splanchnic artery aneurysms. The treatment
was surgical in two cases (33.3%) and percutaneous in four cases (66.6%). All lesions were
successfully treated with exclusion/ablation of the aneurysm. Mortality was nil; in one of the
surgical cases we reported a transient hepatic failure and in the endovascular group, one right
pleural effusion, one small splenic infarction, and one pseudoaneurysm of the gastroduodenal
artery. The first therapeutic strategy to be taken into consideration is always the percutaneous
approach. However, surgery still has a role in those cases where the lesion cannot be repaired
percutaneously. Based on our own experience (good results, no mortality, and few complications)
and in accordance with the literature, it is clear that an aggressive approach is warranted
in those patients
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