FE - DI | Documentos por Auto-Depósito
Permanent URI for this collection
Browse
Browsing FE - DI | Documentos por Auto-Depósito by Issue Date
Now showing 1 - 10 of 148
Results Per Page
Sort Options
- Polygonization of Multi-Component Non-Manifold Implicit Surfaces through A Symbolic-Numerical Continuation AlgorithmPublication . Raposo, Adriano; Gomes, Abel J.P.In computer graphics, most algorithms for sampling implicit surfaces use a 2-points numerical method. If the surface-describing function evaluates positive at the first point and negative at the second one, we can say that the surface is located somewhere between them. Surfaces detected this way are called sign-variant implicit surfaces. However, 2-points numerical methods may fail to detect and sample the surface because the functions of many implicit surfaces evaluate either positive or negative everywhere around them. These surfaces are here called sign-invariant implicit surfaces. In this paper, instead of using a 2-points numerical method, we use a 1-point numerical method to guarantee that our algorithm detects and samples both sign-variant and sign-invariant surface components or branches correctly. This algorithm follows a continuation approach to tessellate implicit surfaces, so that it applies symbolic factorization to decompose the function expression into symbolic components, sampling then each symbolic function component separately. This ensures that our algorithm detects, samples, and triangulates most components of implicit surfaces.
- Using Data Mining with Time Series Data in Short-Term Stocks Prediction: A Literature ReviewPublication . Azevedo, José Manuel; Almeida, Rui M.P.; Almeida, Pedro DeData Mining (DM) methods are being increasingly used in prediction with time series data, in addition to traditional statistical approaches. This paper presents a literature review of the use of DM with time series data, focusing on short- time stocks prediction. This is an area that has been attracting a great deal of attention from researchers in the field. The main contribution of this paper is to provide an outline of the use of DM with time series data, using mainly examples related with short-term stocks prediction. This is important to a better understanding of the field. Some of the main trends and open issues will also be introduced.
- Application of texture analysis to muscle MRI: 1-What kind of information should be expected from texture analysis?Publication . Certaines, Jacques De; Larcher, Thibaut; Duda, Dorota; Azzabou, Noura; Eliat, Pierre-Antoine; Escudero, Luis M.; Pinheiro, Antonio M. G.; Yang, Guanyu; Coatrieux, Jean-Louis; Snezkho, Eduard; Shukelovich, Alexey; Pereira, Manuela; Lerski, RichardSeveral previous clinical or preclinical studies using computerized texture analysis of MR Images have demonstrated much more clinical discrimination than visual image analysis by the radiologist. In muscular dystrophy, a discriminating power has been already demonstrated with various methods of texture analysis of magnetic resonance images (MRI-TA). Unfortunately, a scale gap exists between the spatial resolutions of histological and MR images making a direct correlation impossible. Furthermore, the effect of the various histological modifications on the gray level of each pixel is complex and cannot be easily analyzed. Consequently, clinicians will not accept the use of MRI-TA in routine practice if TA remains a “black box” without clinical correspondence at a tissue level. A goal therefore of the multicenter European COST action MYO-MRI is to optimize MRI-TA methods in muscular dystrophy and to elucidate the histological meaning of MRI textures.
- Carbon Fiber Epoxy Composites for Both Strengthening and Health Monitoring of StructuresPublication . Salvado, Rita; Lopes, Catarina; Szojda, Leszek; Araújo, Pedro; Górski, Marcin; Velez, Fernando J.; Castro-Gomes, João; Krzywon, RafalThis paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the “wet process”, which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring.
- A gyro-enhanced smart-phone framework to develop motion-based user interfaces for animation and virtual environmentsPublication . Pereira, Tiago; Pereira, Orlando; Fazendeiro, Paulo; Gomes, AbelIn this paper, the mobile phone is presented as an alternative device to interact with animation systems and virtual environments, including video games. Basically, we show how the gyroscope of a mobile device can work as a sensor to control the pose and motion of a mobile device controlled object or character in a 3D virtual world. More specifically, we introduce a framework that enables the development and rapid prototyping of motion-based user interfaces for animation systems and virtual environments. This framework provides tools to capture and control the motion of mobile devices-binded objects in a 3D virtual scene over a wireless communication channel via a simple, fast and efficient protocol named Open Sound Control (OSC).
- On the Evaluation of Energy-Efficient Deep Learning Using Stacked Autoencoders on Mobile GPUsPublication . Falcao, Gabriel; Alexandre, Luís; Marques, J.; Frazão, Xavier; Maria, J.Over the last years, deep learning architectures have gained attention by winning important international detection and classification challenges. However, due to high levels of energy consumption, the need to use low-power devices at acceptable throughput performance is higher than ever. This paper tries to solve this problem by introducing energy efficient deep learning based on local training and using low-power mobile GPU parallel architectures, all conveniently supported by the same high-level description of the deep network. Also, it proposes to discover the maximum dimensions that a particular type of deep learning architecture—the stacked autoencoder—can support by finding the hardware limitations of a representative group of mobile GPUs and platforms.
- Multi-GPU-Based Detection of Protein Cavities using Critical PointsPublication . Dias, Sérgio; Nguyen, Quoc; Jorge, Joaquim A; Gomes, AbelProtein cavities are specific regions on the protein surface where ligands (small molecules) may bind. Such cavities are putative binding sites of proteins for ligands. Usually, cavities correspond to voids, pockets, and depressions of molecular surfaces. The location of such cavities is important to better understand protein functions, as needed in, for example, structure-based drug design. This article introduces a geometric method to detecting cavities on the molecular surface based on the theory of critical points. The method, called CriticalFinder, differs from other surface-based methods found in the literature because it directly uses the curvature of the scalar field (or function) that represents the molecular surface, instead of evaluating the curvature of the Connolly function over the molecular surface. To evaluate the accuracy of CriticalFinder, we compare it to other seven geometric methods (i.e., LIGSITE-CS, GHECOM, ConCavity, POCASA, SURFNET, PASS, and Fpocket). The benchmark results show that CriticalFinder outperforms those methods in terms of accuracy. In addition, the performance analysis of the GPU implementation of CriticalFinder in terms of time consumption and memory space occupancy was carried out.
- Applications of Trusted Computing in Cloud ContextPublication . Memarian, Mohammad Reza; Fernandes, Diogo A. B.; Inácio, Pedro R. M.; Leppänen, Ville; Conti, MauroTrusted computing is a technology that enables computer systems to behave in a given expected way. Achieving that goal happens by arming an isolated piece of hardware with embedded processing, cryptographic ca- pabilities such as encryption key that is kept safe from software layer attacks. The mentioned module is accessible to the rest of the computer system via a well de ned and tested application programming interface. Trusted com- puting protects the system against external attackers and even against the owner of the system. Cloud computing enables users to have access to vast amounts of computational resources remotely, in a seamless and ubiquitous manner. However, in some cloud deployment models, such as public cloud computing, users do not have much control over how their data is remotely handled and are not able to assure that their data is securely processed and stored. Cloud administrators and other parties can be considered threats in such cases. Given the ground that cloud has been gaining and the rate at which data is generated, transmitted, processed and stored remotely, it is vital to protect it using means that address the ubiquitous nature of the cloud, including trusted computing. This chapter investigates applications of trusted computing in cloud computing areas where security threats exist, namely in live virtual machine migration.
- A User Trust System for Online Games: Part IPublication . Cardoso, Rui Costa; Freire, Mario; Gomes, AbelIn virtual worlds (including computer games), users develop trust relationships from their in-world interactions with others. However, these trust relationships end up not being represented in the data structures (or databases) of such virtual worlds, though they sometimes appear associated with reputation and recommendation systems. In addition, as far as we know, the user is not provided with a personal trust tool to sustain his/her decision-making while he/she interacts with other users in the virtual or game world. In order to come up with a computational formal representation of these personal trust relationships, we need to succeed in converting in-world interactions into reliable sources of trust-related data. In this paper, we develop the required formalisms to gather and represent in-world interactions-which are based on the activity theory-as well as a method to convert in-world interactions into trust networks. In the companion paper, we use these trust networks to produce a computational trust decision based on subjective logic. This solution aims at supporting in-world user (or avatar) decisions about others in the game world.
- Applications of artificial immune systems to computer security: A surveyPublication . Fernandes, Diogo A. B.; Freire, Mario; Fazendeiro, Paulo; Inácio, Pedro R. M.For the last two decades, artificial immune systems have been studied in various fields of knowledge. They were shown to be particularly effective tools at detecting anomalous behavior in the security domain of computer systems. This article introduces the principles of artificial immune systems and surveys several works applying such systems to computer security problems. The works herein discussed are summarized and open issues are pointed out afterwards, elaborating on a novel applicability of these systems to cloud computing environments.