86,949 research outputs found
Considerazioni su alcune statuine rinvenute sul Piazzale dei Sacelli di Hagia Triada
No full textLo scavo del Piazzale dei Sacelli a sud della Villa Reale di Haghia Triada, condotto da F. Halbherr (1902) e da R. Paribeni (1903-1904) ha messo in luce una stipe votiva composta da quasi 500 terrecotte e oltre 100 bronzetti. L’interesse della ricerca si concentra su due piccoli busti in terracotta, conservati al Museo di Iraklion. Le due statuine, mai studiate singolarmente ma sempre in relazione all’intero contesto, presentano diversi problemi di interpretazione. La proposta è quella di considerarli una coppia di devoti (uomo e donna) facenti parte di una composizione fittile, mentre la datazione è da porre tra l’VIII e il VII secolo a.C
Sorting and searching in faulty memories
No full textIn this paper we investigate the design and analysis of algorithms resilient to memory faults. We focus on algorithms that, despite the corruption of some memory values during their execution, are nevertheless able to produce a correct output at least on the set of uncorrupted values. In this framework, we consider two fundamental problems: sorting and searching. In particular, we prove that any O(nlog∈n) comparison-based sorting algorithm can tolerate the corruption of at most O((nlog∈n) 1/2) keys. Furthermore, we present one comparison-based sorting algorithm with optimal space and running time that is resilient to O((nlog∈n) 1/3) memory faults. We also prove polylogarithmic lower and upper bounds on resilient searching. © 2007 Springer Science+Business Media, LLC
Resilient dictionaries
No full textWe address the problem of designing data structures in the presence of faults that may arbitrarily corrupt memory locations. More precisely, we assume that an adaptive adversary can arbitrarily overwrite the content of up to Δ memory locations, that corrupted locations cannot be detected, and that only O(1) memory locations are safe. In this framework, we call a data structure resilient if it is able to operate correctly (at least) on the set of uncorrupted values. We present a resilient dictionary, implementing search, insert, and delete operations. Our dictionary has O(log n + Δ) expected amortized time per operation, and O(n) space complexity, where n denotes the current number of keys in the dictionary. We also describe a deterministic resilient dictionary, with the same amortized cost per operation over a sequence of at least Δepsi; operations, where ε > 0 is an arbitrary constant. Finally, we show that any resilient comparison-based dictionary must take ω(log n + Δ) expected time per search. Our results are achieved by means of simple, new techniques which might be of independent interest for the design of other resilient algorithms. © 2009 ACM
Electron density profiles at charged metal surfaces in the weighted density approximation
No full textWe present a selfconsistent calculation of the electron distribution at metal surfaces in thepresence of a static electric field in the semi-infinite jellium model. The calculation is based on theHohenberg-Kohn-Sham theory with a nonlocal approximation for the exchange-correlationenergy and potential. For different metallic density r s = 2, 3, 4 we present numerical results for themean position and the spread of the induced charge density. The results for the centroid of thecharge induced by a small field are discussed and compared with the image plane position valuesobtained from the exchange-correlation potential
Ground state properties and excitation energies of cubic MgO and SrO
No full textElectronic ground-state properties and quasiparticle energies of the charge-transfer insulating oxides SrO and MgO have been computed. Structural properties calculations have been performed within DFT-LDA, while for the electronic excitations an efficient DFT-GW scheme, founded on the use of a model dielectric function, has been used. The comparison of our results with available theoretical and experimental data turns out to be satisfactory either for the ground state or for the excitation spectrum
“l’adornò fuori di terretta con istorie di sua mano molto belle”. Sulla decorazione esterna di villa Chigi alla Lungara
No full textSulla base di nuovi accertamenti sul progetto e l’esecuzione della villa Chigi alla Lungara, una serie di disegni del primo Cinquecento finora ritenuti copia delle fronti esterne dell’edificio, si rivelano essere disegni di progetto che allineano l’aspetto esterno della villa alla monumentalità all’antica dei grandi progetti raffaelleschi nella Roma di Leone X Medici
Optimal resilient sorting and searching in the presence of memory faults
No full textWe investigate the problem of reliable computation in the presence of faults that may arbitrarily corrupt memory locations. In this framework, we consider the problems of sorting and searching in optimal time while tolerating the largest possible number of memory faults. In particular, we design an O(n log n) time sorting algorithm that can optimally tolerate up to O(sqrt(n log n)) memory faults. In the special case of integer sorting, we present an algorithm with linear expected running time that can tolerate O(sqrt(n))faults. We also present a randomized searching algorithm that can optimally tolerate up to O(log n) memory faults in O(log n) expected time, and an almost optimal deterministic searching algorithm that can tolerate O((log n)^(1?eps)) faults, for any small positive constant eps, in O(log n) worst-case time. All these results improve over previous bounds
Designing reliable algorithms in unreliable memories
No full textSome of the present day applications run on computer platforms with large and inexpensive memories, which are also error-prone. Unfortunately, the appearance of even very few memory faults may jeopardize the correctness of the computational results. We say that an algorithm is resilient to memory faults if, despite the corruption of some memory values before or during its execution, it is nevertheless able to get a correct output at least on the set of uncorrupted values (i.e., the algorithm works correctly on uncorrupted data). In this paper we will survey some recent works on resilient algorithms and try to give some insight into the main algorithmic techniques used. © 2007
Sorting and searching in the presence of memory faults (without redundancy)
No full textWe investigate the design of algorithms resilient to memory faults, i.e., algorithms that, despite the corruption of some memory values during their execution, are able to produce a correct output on the set of uncorrupted values. In this framework, we consider two fundamental problems: sorting and searching. In particular, we prove that any O(n log n) comparison-based sorting algorithm can tolerate at most O((n log n)1/2) memory faults. Furthermore, we present one comparison-based sorting algorithm with optimal space and running time that is resilient to O((n log n)1/3) faults. We also prove polylogarithmic lower and upper bounds on fault-tolerant searching
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