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931.
João António Teixeira de Freitas Carlos Tiago 《International journal for numerical methods in engineering》2020,121(9):1946-1976
The hybrid-Trefftz stress element is used to emulate conventional finite elements for analysis of Kirchhoff and Mindlin-Reissner plate bending problems. The element is hybrid because it is based on the independent approximation of the stress-resultant and boundary displacement fields. The Trefftz variant is consequent on the use of the formal solutions of the governing Lagrange equation to approximate the stress-resultant field. In order to emulate conventional elements, nodal functions are used to approximate the displacements on the boundary of the element. Duality is used to set up the element solving system. The associated variational statements and conditions for existence and uniqueness of solutions are recovered. Triangular and quadrilateral elements are tested and characterized in terms of convergence, sensitivity to shear-locking, and shape distortion. Their relative performance is assessed using assumed strain Mixed Interpolation of Tensorial Components (MITC) elements and recently proposed Trefftz-based elements. This relative assessment is extended to a hypersingular problem to illustrate the effect of enriching the domain and boundary approximation bases. 相似文献
932.
Simon Scarle Sylvester Arnab Ian Dunwell Panagiotis Petridis Aristidis Protopsaltis Sara de Freitas 《Electronic Commerce Research》2012,12(3):379-407
E-commerce is a fundamental method of doing business, such that for a firm to say it is trading at all in the modern market-place it must have some element of on-line presence. Coupled with this is the explosion of the “population” of Massively Multiplayer On-line Role Playing Games and other shared virtual environments. Many suggest this will lead to a further dimension of commerce: virtual commerce. We discuss here the issues, current roadblocks and present state of an e-commerce transaction carried out completely within a virtual environment; a virtual transaction. Although technically such transactions are in a sense trivial, they raise many other issues in complex ways thus making V-transactions a highly interesting cross-disciplinary issue. We also discuss the social, ethical and regulatory implications for the virtual communities in these environments of such v-transactions, how their implementation affects the nature and management of a virtual environment, and how they represent a fundamental merging of the real and virtual worlds for the purpose of commerce. We highlight the minimal set of features a v-transaction capable virtual environment requires and suggest a model of how in the medium term they could be carried out via a methodology we call click-through, and that the developers of such environments will need to take on the multi-modal behavior of their users, as well as elements of the economic and political sciences in order to fully realize the commercial potential of the v-transaction. 相似文献
933.
Vasconcelos MJ Ventura SM Freitas DR Tavares JM 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2012,226(3):185-196
The morphological and dynamic characterisation of the vocal tract during speech production has been gaining greater attention due to the motivation of the latest improvements in magnetic resonance (MR) imaging; namely, with the use of higher magnetic fields, such as 3.0 Tesla. In this work, the automatic study of the vocal tract from 3.0 Tesla MR images was assessed through the application of statistical deformable models. Therefore, the primary goal focused on the analysis of the shape of the vocal tract during the articulation of European Portuguese sounds, followed by the evaluation of the results concerning the automatic segmentation, i.e. identification of the vocal tract in new MR images. In what concerns speech production, this is the first attempt to automatically characterise and reconstruct the vocal tract shape of 3.0 Tesla MR images by using deformable models; particularly, by using active and appearance shape models. The achieved results clearly evidence the adequacy and advantage of the automatic analysis of the 3.0 Tesla MR images of these deformable models in order to extract the vocal tract shape and assess the involved articulatory movements. These achievements are mostly required, for example, for a better knowledge of speech production, mainly of patients suffering from articulatory disorders, and to build enhanced speech synthesizer models. 相似文献
934.
Khalid M. Salama Ashraf M. Abdelbar Fernando E.B. Otero Alex A. Freitas 《Applied Soft Computing》2013,13(1):667-675
The cAnt-Miner algorithm is an Ant Colony Optimization (ACO) based technique for classification rule discovery in problem domains which include continuous attributes. In this paper, we propose several extensions to cAnt-Miner. The main extension is based on the use of multiple pheromone types, one for each class value to be predicted. In the proposed μcAnt-Miner algorithm, an ant first selects a class value to be the consequent of a rule and the terms in the antecedent are selected based on the pheromone levels of the selected class value; pheromone update occurs on the corresponding pheromone type of the class value. The pre-selection of a class value also allows the use of more precise measures for the heuristic function and the dynamic discretization of continuous attributes, and further allows for the use of a rule quality measure that directly takes into account the confidence of the rule. Experimental results on 20 benchmark datasets show that our proposed extension improves classification accuracy to a statistically significant extent compared to cAnt-Miner, and has classification accuracy similar to the well-known Ripper and PART rule induction algorithms. 相似文献
935.
936.
Ana Clarissa dos Santos PiresAuthor VitaeNilda de Fátima Ferreira SoaresAuthor Vitae Luis Henrique Mendes da SilvaAuthor VitaeMaria do Carmo Hespanhol da SilvaAuthor Vitae Mauro Vieira De AlmeidaAuthor VitaeMireille Le HyaricAuthor Vitae Nélio José de AndradeAuthor VitaeRêmili Freitas SoaresAuthor Vitae Aparecida Barbosa MagesteAuthor VitaeSamira Gama ReisAuthor Vitae 《Sensors and actuators. B, Chemical》2011,153(1):17-23
We have synthesized 10,12-pentacosadyinoic acid (PCDA) + N-[(2-tetradecanamide)-ethyl]-ribonamide (TDER) vesicles to determine the colorimetric response induced by pathogenic bacteria (Staphylococcus aureus and Escherichia coli). The addition of bacterial supernatants caused a colorimetric transition in TDER/PCDA vesicles, even in diluted concentrations, indicating that chemical interactions occur between the vesicles and bacterial compounds. Bacterial substrates released from S. aureus induced a greater color change compared to the color change induced by E. coli. S. aureus metabolites also induced a greater color change when TDER/PCDA vesicles were incorporated into the cellulose strips. We determined the energy involved in the interaction between the bacterial substrates and the TDER/PCDA vesicles to be exothermic (and very high) for both bacterial supernatants. In addition, we analyzed the colorimetric transition in the presence of other molecules, using apple juice as a food matrix. Both apple juice and apple juice inoculated with bacterial substrates induced a TDER/PCDA color change; however, the S. aureus supernatant induced a slightly greater color change in the vesicles both in the suspension and in the cellulose strips. TDER/PCDA vesicles show great potential to be used as a biosensor to detect food pathogens in intelligent food packaging. 相似文献
937.
Nakadate M Amizuka N Li M Freitas PH Oda K Nomura S Uoshima K Maeda T 《Microscopy research and technique》2008,71(2):93-104
This study aimed to evaluate the histological characteristics of the new bone formed at dental implant placement sites concomitantly grafted with a self-setting tricalcium phosphate cement (BIOPEX-R). Standardized defects were created adjacent to the implants in maxillae of 4-week-old male Wistar rats, and were concomitantly filled with BIOPEX-R. Osteogenesis was examined in two sites of extreme clinical relevance: (1) the BIOPEX-R-grafted surface corresponding to the previous alveolar ridge (alveolar ridge area), and (2) the interface between the grafting material and implants (interface area). At the alveolar ridge area, many tartrate-resistant acid phosphatase (TRAPase)-reactive osteoclasts had accumulated on the BIOPEX-R surface and were shown to migrate toward the implant. After that, alkaline phosphatase (ALPase)-positive osteoblasts deposited new bone matrix, demonstrating their coupling with osteoclasts. On the other hand, the interface area showed several osteoclasts initially invading the narrow gap between the implant and graft material. Again, ALPase-positive osteoblasts were shown to couple with osteoclasts, having deposited new bone matrix after bone resorption. Transmission electron microscopic observations revealed direct contact between the implant and the new bone at the interface area, although few thin cells could still be identified. At both the alveolar ridge and the interface areas, newly formed bone resembled compact bone histologically. Also, concentrations of Ca, P, and Mg were much alike with those of the preexistent cortical bone. In summary, when dental implant placement and grafting with BIOPEX-R are done concomitantly, the result is a new bone that resembles compact bone, an ideal achievement in reconstructive procedures for dental implantology. 相似文献
938.
Ana Sofia C. Marçal Bruno Celso C. de Freitas Felipe S. Furtado Soares Maria Elizabeth S. Furtado Teresa M. Maciel Arnaldo D. Belchior 《Innovations in Systems and Software Engineering》2008,4(1):17-29
Software development organizations that have been employing capability maturity models, such as SW-CMM or CMMI for improving their processes are now increasingly interested in the possibility of adopting agile development methods. In the context of project management, what can we say about Scrum’s alignment with CMMI? The aim of our paper is to present the mapping between CMMI and the agile method Scrum, showing major gaps between them and identifying how organizations are adopting complementary practices in their projects to make these two approaches more compliant. This is useful for organizations that have a plan-driven process based on the CMMI model and are planning to improve the agility of processes or to help organizations to define a new project management framework based on both CMMI and Scrum practices. 相似文献
939.
Ren C Liu S Ghoshal K Hsu PH Jacob ST Marcucci G Freitas MA 《Proteomics. Clinical applications》2007,1(1):130-142
Simultaneous metabolic labeling of cells with multiple amino acids combined with acetic acid urea-PAGE and MS was used to characterize histones in Kasumi-1 cells treated with the histone deacetylase inhibitor depsipeptide (DDP). The approach allowed for rapid targeting, identification, and subsequent characterization of peptides containing sites of acetylation or methylation. Multiple methylation sites were determined for histone H3 including: di- and tri-methylation of K9 and K27; mono- and di-methylation of K36 and K79; and mono-methylation of K37. The acetylation patterns for histones H4 and H3 were established. Quantitative analysis of the modification change after treatment with DDP was also performed and the dynamics of H4 acetylation determined. Functional analysis by RT-PCR showed that DDP unregulated p21 expression with a maximum after 18-h exposure. Chromatin immunoprecipitation experiments indicated that DDP treatment caused an accumulation of hyperacetylated histone H4 and H3 isoforms and a decrease in K9 di-methylation of H3 on the p21 promoter. 相似文献
940.
We present results about a general-purpose chain datatype specified in the Z notation and mechanised using the Z/Eves theorem prover. Our particular interest comes from its use in the specification and refinement of operating system kernels for embedded real-time devices as part of a pilot project within the international Grand Challenge in Verified Software, and to contribute to the Verified Software Repository. We show—at afairly high level—the sort of dogged work that is needed to get a body of results together to form a basis for future projects. Our work discusses important hidden and missing properties in the specification of the chain datatype and its relation to kernel design. 相似文献