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61.
Stéphane Bressan Alfredo Cuzzocrea Panagiotis Karras Xuesong Lu Sadegh Heyrani Nobari 《Journal of Parallel and Distributed Computing》2013
The widespread usage of random graphs has been highlighted in the context of database applications for several years. This because such data structures turn out to be very useful in a large family of database applications ranging from simulation to sampling, from analysis of complex networks to study of randomized algorithms, and so forth. Amongst others, Erd?s–Rényi Γv,p is the most popular model to obtain and manipulate random graphs. Unfortunately, it has been demonstrated that classical algorithms for generating Erd?s–Rényi based random graphs do not scale well in large instances and, in addition to this, fail to make use of the parallel processing capabilities of modern hardware. Inspired by this main motivation, in this paper we propose and experimentally assess a novel parallel algorithm for generating random graphs under the Erd?s–Rényi model that is designed and implemented in a Graphics Processing Unit (GPU), called PPreZER. We demonstrate the nice amenities due to our solution via a succession of several intermediary algorithms, both sequential and parallel, which show the limitations of classical approaches and the benefits due to the PPreZER algorithm. Finally, our comprehensive experimental assessment and analysis brings to light a relevant average speedup gain of PPreZER over baseline algorithms. 相似文献
62.
Marios Belk Efi Papatheocharous Panagiotis Germanakos George Samaras 《Journal of Systems and Software》2013
This paper focuses on modeling users’ cognitive styles based on a set of Web usage mining techniques on user navigation patterns and clickstream data. Main aim is to investigate whether specific clustering techniques can group users of particular cognitive style using measures obtained from psychometric tests and content navigation behavior. Three navigation metrics are proposed and utilized to find identifiable groups of users that have similar navigation patterns in relation to their cognitive style. The proposed work has been evaluated with two user studies which entail a psychometric-based survey for extracting the users’ cognitive styles, combined with a real usage scenario of users navigating in a controlled Web 2.0 environment. A total of 106 participants of age between 17 and 25 participated in the study providing interesting insights with respect to cognitive styles and navigation behavior of users. Studies like the reported one can be useful for modeling users and assist adaptive Web 2.0 environments to organize and present information and functionalities in an adaptive format to diverse user groups. 相似文献
63.
This work provides one of the first attempts to derive computationally tractable criteria for analysing the stability of linear parameter varying (LPV) time-delayed systems. We present both delay-independent and delay-dependent stability conditions, which are derived using appropriately selected Lyapunov-Krasovskii functionals. According to the system parameter dependence, these functionals can be selected to obtain increasingly non-conservative results. Gridding techniques may be used to cast these tests as linear matrix inequalities (LMIs). In cases when the system matrices depend affinely or quadratically on the parameter, gridding may be avoided. These LMIs can be solved efficiently using available software. A numerical example of a time-delayed system motivated by a metal removal process is used to demonstrate the theoretical results. 相似文献
64.
Network synchronization plays a significant role
in transmitting multimedia objects over computer networks.
Even packets from a single channel must be synchronized due to
the problems in a packet switching environment, such as
network jitter, frequency, and time offsets. We present an
algorithm that determines the set of packets generated
periodically by various participants arriving at a node. The basic
advantage of the proposed algorithm is that the receiver
estimates the reference times (expected arrival times of the
packets) and achieves synchronization, without knowledge of the
packet delays.
The
accuracy is improved and the complexity is reduced by
predicting the time/frequency offsets between the clocks at the
source and the mixer. The error is calculated by the Chernoff
bound, demonstrated by simulation, and shown to be acceptable
in practical applications. 相似文献
65.
Kostas Tsagkaris Gerard Nguengang Aristi Galani Imen Grida Ben Yahia Majid Ghader Alexandros Kaloxylos Markus Gruber Apostolis Kousaridas Mathieu Bouet Stylianos Georgoulas Aimilia Bantouna Nancy Alonistioti Panagiotis Demestichas 《International Journal of Network Management》2013,23(6):402-423
Academic and industrial research initiatives have sought to make fully autonomic networks a reality. Some of these initiatives pursued a holistic approach, while others focused on setting up functionalities for specific networking domains. These efforts did not succeed in being extensively deployed, because the goals of network operators were not satisfactorily met. These goals include unification of management operations, enablement of end‐to‐end management and enhancement of the overall system performance in a trusted way, while reducing management cost. In this paper, we analyse a set of existing autonomic management architectures and frameworks with respect to a selected set of criteria. We then identify missing parts and challenges and propose a framework to unify the most promising attributes towards a novel approach of realization of autonomic networking management. We call this proposal Unified Management Framework (UMF). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
66.
Evangelos Koustas Eleni-Myrto Trifylli Panagiotis Sarantis Nikolaos Papadopoulos Eleni Karapedi Georgios Aloizos Christos Damaskos Nikolaos Garmpis Anna Garmpi Kostas A. Papavassiliou Michalis V. Karamouzis Athanasios G. Papavassiliou 《International journal of molecular sciences》2022,23(12)
Gastrointestinal (GI) cancer constitutes a highly lethal entity among malignancies in the last decades and is still a major challenge for cancer therapeutic options. Despite the current combinational treatment strategies, including chemotherapy, surgery, radiotherapy, and targeted therapies, the survival rates remain notably low for patients with advanced disease. A better knowledge of the molecular mechanisms that influence tumor progression and the development of optimal therapeutic strategies for GI malignancies are urgently needed. Currently, the development and the assessment of the efficacy of immunotherapeutic agents in GI cancer are in the spotlight of several clinical trials. Thus, several new modalities and combinational treatments with other anti-neoplastic agents have been identified and evaluated for their efficiency in cancer management, including immune checkpoint inhibitors, adoptive cell transfer, chimeric antigen receptor (CAR)-T cell therapy, cancer vaccines, and/or combinations thereof. Understanding the interrelation among the tumor microenvironment, cancer progression, and immune resistance is pivotal for the optimal therapeutic management of all gastrointestinal solid tumors. This review will shed light on the recent advances and future directions of immunotherapy for malignant tumors of the GI system. 相似文献
67.
68.
Panagiotis I. Dallas Dr. Fotini-Niovi Pavlidou 《International Journal of Wireless Information Networks》1996,3(3):163-172
DS/CDMA noncoherentM-ary orthogonal signaling is presented in a hexagonal cell with three and six corner-based antennas. Multipath Rayleigh channel
with lognormal shadowing and perfect power control are assumed. The asynchronous case (uplink) is studied. Bit error rate
analysis is carried out to investigate the benefits of combining theM-ary orthogonal signaling and macrodiversity techniques either with uncorrelated or correlated base stations. Comparative
analysis between the one central antenna arrangement and the proposed one is presented. The results show that the combination
ofM-ary signaling with multiple corner-based antennas improves system performance especially in terms of accommodating more users
and supporting new services. The results also show that shadowing does not degrade system performance significantly. 相似文献
69.
Panagiotis Papastamoulis 《Computational statistics & data analysis》2009,53(4):900-911
The Bayesian estimation of a special case of mixtures of normal distributions with an unknown number of components is considered. More specifically, the case where some components may have identical means is studied. The standard Reversible Jump MCMC algorithm for the estimation of a normal mixture model consisting of components with distinct parameters naturally fails to give precise results in the case where (at least) two of the mixture components have equal means. In particular, this algorithm either tends to combine such components resulting in a posterior distribution for their number having mode at a model with fewer components than those of the true one, or overestimates the number of components. This problem is overcome by defining-for every number of components-models with different number of parameters and introducing a new move type that bridges these competing models. The proposed method is applied in conjunction with suitable modifications of the standard split-combine and birth-death moves for updating the number of components. The method is illustrated by using two simulated datasets and the well-known galaxy dataset. 相似文献
70.
Panagiotis Michaleris Daniel A. Tortorelli Creto A. Vidal 《International journal for numerical methods in engineering》1995,38(8):1259-1285
A systematic approach for the design of weakly coupled thermoelastoplastic systems is presented. The Newton–Raphson iteration method is used in the solution process so that analytic design sensitivity formulations may be efficiently derived via the direct differentiation technique. The derived formulations are suitable for finite element implementations. Analysis and sensitivity analysis capabilities are combined with numerical optimization to form an optimum design algorithm. To demonstrate the algorithm, we optimally design a weldment with respect to manufacturing and service life aspects. 相似文献