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31.
32.
This paper presents an artificial neural network-based multiscale method for coupling continuum and molecular simulations. Molecular dynamics modelling is employed as a local “high resolution” refinement of computational data required by the continuum computational fluid dynamics solver. The coupling between atomistic and continuum simulations is obtained by an artificial neural network (ANN) methodology. The ANN aims to optimise the transfer of information through minimisation of (1) the computational cost by avoiding repetitive atomistic simulations of nearly identical states, and (2) the fluctuation strength of the atomistic outputs that are fed back to the continuum solver. Results are presented for prototype flows such as the isothermal Couette flow with slip boundary conditions and the slip Couette flow with heat transfer. 相似文献
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34.
Stamatis Zampetakis Yannis Tzitzikas Asterios Leonidis Dimitris Kotzinos 《Journal of Visual Languages and Computing》2012,23(3):137-153
The visualization of ontologies is a challenging task especially if they are large. In this paper we propose a visualization approach which is based on star-like graphs of variable radius which enables users to gradually explore and navigate through the entire ontology without overloading them. The star-like graphs are visualized using a Force Directed Placement algorithm (FDP) specially suited for RDF schemas whose configuration parameters can be adjusted interactively by the end-user via an intuitive on-screen tool bar. In addition, and since each star-like graph exhibits different graph features, we propose a novel automatic configuration method for the FDP algorithm parameters that is based on a number of quality metrics (area density and verticality of subclass hierarchies) and corresponding corrective actions. The experimental evaluation showed the quality of the yielded layout is significantly improved and the proposed approach is acceptably fast for real-time exploration. The user study showed that users prefer these views and perform various very common tasks faster. 相似文献
35.
Our interest lies in solving sum of squares (SOS) relaxations of large-scale unconstrained polynomial optimization problems. Because interior-point methods for solving these problems are severely limited by the large-scale, we are motivated to explore efficient implementations of an accelerated first-order method to solve this class of problems. By exploiting special structural properties of this problem class, we greatly reduce the computational cost of the first-order method at each iteration. We report promising computational results as well as a curious observation about the behaviour of the first-order method for the SOS relaxations of the unconstrained polynomial optimization problem. 相似文献
36.
The Mahalanobis-Taguchi (MT) strategy combines mathematical and statistical concepts like Mahalanobis distance, Gram-Schmidt
orthogonalization and experimental designs to support diagnosis and decision-making based on multivariate data. The primary
purpose is to develop a scale to measure the degree of abnormality of cases, compared to “normal” or “healthy” cases, i.e.
a continuous scale from a set of binary classified cases. An optimal subset of variables for measuring abnormality is then
selected and rules for future diagnosis are defined based on them and the measurement scale. This maps well to problems in
software defect prediction based on a multivariate set of software metrics and attributes. In this paper, the MT strategy
combined with a cluster analysis technique for determining the most appropriate training set, is described and applied to
well-known datasets in order to evaluate the fault-proneness of software modules. The measurement scale resulting from the
MT strategy is evaluated using ROC curves and shows that it is a promising technique for software defect diagnosis. It compares
favorably to previously evaluated methods on a number of publically available data sets. The special characteristic of the
MT strategy that it quantifies the level of abnormality can also stimulate and inform discussions with engineers and managers
in different defect prediction situations. 相似文献
37.
Stavros Papadopoulos Yin Yang Dimitris Papadias 《The VLDB Journal The International Journal on Very Large Data Bases》2010,19(2):161-180
According to the database outsourcing model, a data owner delegates database functionality to a third-party service provider, which answers queries received from clients.
Authenticated query processing enables the clients to verify the correctness of query results. Despite the abundance of methods for authenticated processing
in conventional databases, there is limited work on outsourced data streams. Stream environments pose new challenges such
as the need for fast structure updating, support for continuous query processing and authentication, and provision for temporal completeness. Specifically, in addition to the correctness of individual results, the client must be able to verify that there are no
missing results in between data updates. This paper presents a comprehensive set of methods covering relational streams. We
first describe REF, a technique that achieves correctness and temporal completeness but incurs false transmissions, i.e.,
the provider has to inform the clients whenever there is a data update, even if their results are not affected. Then, we propose
CADS, which minimizes the processing and transmission overhead through an elaborate indexing scheme and a virtual caching
mechanism. In addition, we present an analytical study to determine the optimal indexing granularity, and extend CADS for
the case that the data distribution changes over time. Finally, we evaluate the effectiveness of our techniques through extensive
experiments. 相似文献
38.
Athena Tsetsekou Fotini Petrakli M. G. Tsoutsouva Dimitris Sioulas 《Journal of the American Ceramic Society》2015,98(8):2366-2372
The processing of nanosized powders to produce dense components is a difficult task, mainly due to the strong agglomeration of nanoparticles. In this work, deagglomeration studies were carried out on sol–gel‐derived γ‐alumina suspensions through the addition of dispersant or dispersant in combination with ethylene glycol as binder and the proper wet ball‐milling. For this purpose, zeta‐potential, viscosity, and sedimentation studies were carried out, whereas dilatometric studies accompanied by XRD analyses were performed on the powders derived from the most stable suspensions. Sintering studies followed and the as received ceramics were evaluated by SEM. The optimum stabilization was achieved through the synergistic addition of 2.75 mg/g ammonium polymethacrylate with 1 wt% ethylene glycol. The respective powder, although it indicates a shift of the sintering start to higher temperature, leads to the densest ceramic with the finest (500 nm mean grain size) and the most homogeneous microstructure. 相似文献
39.
40.
Marios Sagris Emmanouil P. Vardas Panagiotis Theofilis Alexios S. Antonopoulos Evangelos Oikonomou Dimitris Tousoulis 《International journal of molecular sciences》2022,23(1)
Atrial fibrillation (AF) is the most frequent arrhythmia managed in clinical practice, and it is linked to an increased risk of death, stroke, and peripheral embolism. The Global Burden of Disease shows that the estimated prevalence of AF is up to 33.5 million patients. So far, successful therapeutic techniques have been implemented, with a high health-care cost burden. As a result, identifying modifiable risk factors for AF and suitable preventive measures may play a significant role in enhancing community health and lowering health-care system expenditures. Several mechanisms, including electrical and structural remodeling of atrial tissue, have been proposed to contribute to the development of AF. This review article discusses the predisposing factors in AF including the different pathogenic mechanisms, sedentary lifestyle, and dietary habits, as well as the potential genetic burden. 相似文献