ESTG - Comunicações em conferências e congressos internacionais
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- Two-dimensional transmitarray beamsteering using stacked tunable metamaterialsPublication . Reis, João; Al-Daher, Zaid; Copner, Nigel; Hammoudeh, Akram; Caldeirinha, Rafael; Fernandes, TelmoA new 2D-beamsteering antenna technique using an electronically controlled transmitarray is presented in this paper. When coupled to a conventional horn or an array patch antenna, the proposed transmitarray has the ability to steer the main lobe of the original antenna radiation pattern in both elevation and azimuth planes, with ranges up to 30° and 30°, respectively. The transmitarray is implemented using varactor-diode controlled unit-cells with bandpass filtering characteristics around 5.35GHz. Electromagnetic simulations are presented to prove the concept.
- On the Evaluation of Software Maintainability Using Automatic Test Case GenerationPublication . Nogueira, Ana Filipa; Ribeiro, José C. B.; Zenha-Rela, Mário A.The measurement of external software attributes and the analysis of how those attributes have evolved through the software's releases are challenging activities. This is particularly evident when we discuss the maintainability of Object-Oriented (OO) systems which, due to their specific characteristics, hide information that cannot be gathered through static analysis. As maintainability can be defined as the "speed and ease with which a program can be corrected or changed", we believe that test data are reflective of the changes performed during maintenance. Moreover, empirical observations allow to speculate about the relationships between maintainability and the behaviour of the software when executed by test cases (e.g., coverage values) and the test cases' characteristics (e.g., generation time). Our aim is to complement the state-of-the art by proposing a new approach for understanding and characterizing the maintainability of OO systems, which makes use of test data and of the information gathered from the tests' execution.
- The Impact of the Employer's Brand Image on Knowledge SharingPublication . Espírito Santo, Pedro Manuel do; Ferreira, Vítor Hugo Santos; Marques, Alzira Maria AscensãoKnowledge Sharing is a key driver of firm performance, but it relies on firm’s ability of retaining its most capable human resources and creating workercentered environments to encourage the open sharing and use of all forms of knowledge. Attracting the right people through brand image and creating the conditions for employees to live the company in a passionate way, with high trust and commitment (with high team cohesion), will lead to a more long-term orientation thus allowing for increased Knowledge sharing (tacit and explicit). Through a case-study based approach, using data from a Portuguese company with 302 employees, we analyzed the impact of the employer's brand image on knowledge sharing mediated by team cohesion and long-term employee orientation. The results of the model tested through PLS-SEM showed that brand image produces effects on knowledge sharing. These effects are mediated through the decisive role of team cohesion.
- A method for early-splitting of HEVC inter blocks based on decision treesPublication . Correa, Guilherme; Assuncao, Pedro; Agostini, Luciano; Cruz, Luis A. da SilvaThe High Efficiency Video Coding (HEVC) standard provides a large improvement in terms of compression efficiency in comparison to its predecessors, mainly due to the introduction of new coding tools and more flexible data structures. However, since much more options are tested in a Rate-Distortion (R-D) optimization scheme, such improvement is accompanied by a significant increase in the encoding computational complexity. We propose in this paper a novel method for efficient early-splitting decision of inter-predicted Coding Blocks (CB). The method employs a set of decision trees which are trained using information from unconstrained HEVC encoding runs. The resulting early-splitting decision process has an accuracy of 86% with a negligible computational overhead and an average computational complexity decrease of 42% at the cost of a very small Bjontegaard Delta (BD)-rate increase (0.3%).
- Dynamic Motion Vector Refreshing For Enhanced Error Resilience In HevcPublication . Carreira, J.; Silva, V. de; Ekmekcioglu, E.; Kondoz, A.; Assuncao, P.; Faria, S.The high level of compression efficiency achieved by HEVC coding techniques decreases the error resilience performance under error prone conditions. This paper addresses the error resiliency of the HEVC standard, focusing on the new motion estimation tools. It is shown that the temporal dependency of motion information is comparatively higher than that in the H.264/AVC standard, causing an increase in the error propagation. Based on this evidence, this paper proposes a method to make intelligent use of temporal motion vector (MV) candidates during the motion estimation process, in order to decrease the temporal dependency, and improve the error resiliency without penalising the rate-distortion performance. The simulation results show that the proposed method improves the error resilience under tested conditions by increasing the video quality by up to 1.7 dB in average, compared to the reference method that always enables temporal MV candidates.
- Experimental assessment of strengthening Strategies against the out-of-plane collapse of Masonry infills in existing RC structuresPublication . De Risi, Maria Teresa; Furtado, André; Rodrigues, Hugo; Melo, José; Verderame, Gerardo Mario; Arêde, António; Varum, Humberto; Manfredi, GaetanoPast and more recent seismic events worldwide clearly showed that a crucial issue for life-safety and loss reduction due to earthquakes for existing reinforced concrete (RC) buildings is related to the out-of-plane (OOP) collapse of infill masonry walls. In literature, few studies addressed this paramount topic, above all about the proposal of strengthening strategies to prevent the infills’ collapse. This paper presents an experimental work about the assessment of possible strengthening solutions designed to mitigate or prevent the out-of-plane collapse of masonry infills in existing RC buildings. Three nominally identical full-scale one-bay-one-story RC frames were built and infilled with a thin masonry wall made up of horizontal hollow clay bricks. The first specimen was representative of the enclosure of a typical existing RC building in the Mediterranean region in its “as-built” condition. The remaining two specimens were strengthened against the out-of-plane collapse by means of two different strengthening techniques based on the application of innovative systems made up of high-ductility mortar plaster and fibre-reinforced polymer nets. All the tests consisted in the application of a semi-cyclic (loading-unloading-reloading) history of imposed displacements in the OOP direction by means of small pneumatic jacks through a uniform distributed load. Experimental results are shown in terms of OOP force-displacement responses, deformed shapes and damage evolution. In the end, the results of the tests are compared to assess the effectiveness of the selected strengthening techniques and to provide a support towards the choice of the best strategies for future further investigations and applications.
- Locally Linear Embedding-Based Prediction For 3D Holoscopic Image Coding Using HevcPublication . Lucas, Luís F. R.; Conti, Caroline; Nunes, Paulo; Soares, Luís Ducla; Rodrigues, Nuno M. M.; Pagliari, Carla L.; Silva, Eduardo A. B. da; Faria, Sérgio M. M. deHoloscopic imaging is a prospective acquisition and display solution for providing true 3D content and fatigue-free 3D visualization. However, efficient coding schemes for this particular type of content are needed to enable proper storage and delivery of the large amount of data involved in these systems. Therefore, this paper proposes an alternative HEVC-based coding scheme for efficient representation of holoscopic images. In this scheme, some directional intra prediction modes of the HEVC are replaced by a more efficient prediction framework based on locally linear embedding techniques. Experimental results show the advantage of the proposed prediction for 3D holoscopic image coding, compared to the reference HEVC standard as well as previously presented approaches in this field.
- Image coding using Variable-Size Transforms and a full binary tree recursive optimizationPublication . Oliveira, Anderson V. C. de; Rodrigues, Nuno M. M.; Faria, Sérgio M. M. de; Silva, Eduardo A. B. da; Pagliari, Carla L.In this work, we present the first results of a new algorithm for image compression, called Variable Size Transform Coder (VSTC). This algorithm uses spatial transforms and recursive optimization functions combined with a highly adaptive segmentation scheme, similar to the one proposed by the MMP algorithm (Multi-dimensional Multiscale Parser), that uses pattern matching. We replaced the pattern matching by spatial multiscale transforms, which include symmetric and asymmetric blocks, and we investigated and implemented some of the required tools for encoding these new blocks. The proposed method uses a much more dynamic adaptive-size transforms than the H.264/AVC standard and compares favorably with this encoder. It also consistently outperforms the pattern matching scheme of the MMP algorithm. Moreover, we have considerably reduced the computational complexity when compared to the MMP algorithm.
- Fused Deposition of WC+Co powderPublication . Cerejo, F.; Raimundo, A. M.; Vieira, M. T.; Barreiros, FatimaAdditive manufacturing (AM) of WC-Co is a great challenge. Up to now, powder bed fusion reveals enormous problems for WC-Co. New techniques are necessary to enlarge AM to hard materials. Based on feedstock developed for injection of metallic and ceramic powders (MIM/CIM) it was possible to extrude WC-Co filaments with success. This study is focused on development filaments based on WC-Co (d50=8 µm) to be applied in fused deposition modelling additive process, but assuming the acronym of FDC, to highlight that powder is a ceramic (C). Thus, it was evaluated the critical powder volume concentration (CPVC) of WC-Co in feedstock specially developed to fulfil the filament characteristics need. Different binder system (master + backbone+ additive) were tested. Parts were printed through a filament with 48.5 (vol.%) of WC-10Co. A suitable selection of thermal parameters for debinding and sintering has led to guarantee geometry and mechanical properties required for the part. © European Powder Metallurgy Association (EPMA)
- Healthcare information systems promotion: From an Improved Management of Telemedicine Processes to Home Healthcare ProcessesPublication . Latifa Ilahi; Sonia Ayachi Ghannouchi; Martinho, RicardoCrucial advancements in science education and information technology provide promising resources that require many academic disciplines to work together. Innovations of Information Systems (IS) and Technology (IT) offer major potential to improve quality and efficiency of care delivery, enable new forms of healthcare organizations, enhance interactions between patients and healthcare providers, and transform care delivery. Closely linked to the integration into a global world, our work is focusing on electronic health (e-Health). Worldwide, there have been some pilot projects on Telemedicine and e-Health and researchers are working to advance and support e-Health services. Unfortunately, this still suffers from problems of understanding, lack of techniques and legal texts, huge costs, and it is still rarely used especially in Tunisia. Accordingly, fully exploiting the power of IS/IT within the healthcare sector requires overcoming significant challenges. To tackle these issues and following some previous works, our research aims at identifying the main challenges behind home healthcare processes, and to find better ways of improving them through the use of BPM-related technologies. We briefly describe our experience in this kind of processes by presenting our experience with telemedicine processes and the use of Business Process Modeling Notation 2.0 process models. We have tested our telemedicine processes through the Activiti BPMS, which proved its usefulness to enhance the design and therefore the implementation of telemedicine processes. From this experience, we derive the main challenges of using a BPM approach to implement home healthcare processes, and propose also the research questions that can enhance this implementation.