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Cerebral aneurysm is an abnormal dilatation of the blood vessel which affects a high percentage of the worldwide population. One way to investigate this pathology is using in vivo techniques, but these types of experiments have a high cost and low reproducibility. Thus, to understand the local hemodynamics of brain aneurysms, it is imperative to manufacture in vitro models that simulate real brain aneurysms. These biomodels are suitable for experimental testing, as well as for evaluating and validating computational models. In this work, was manufactured a biomodel of a cerebral aneurysm made by polydimethylsiloxane (PDMS), combining rapid prototyping technology with a PDMS gravity casting process. Experimental flow visualizations were performed at different flow rates. The flow visualizations results have shown that there is a transition from laminar to turbulent flow for a flow rate near 6 ml/min. The proposed PDMS biomodels have shown the ability to perform flow visualizations and have the potential to help the development and validation of computational models. The authors acknowledge the financial support provided by Fundação para a Ciência e a Tecnologia (FCT), through the projects EXPL/EME-EME/0732/2021, PTDC/EEI- EEE/2846/2021, funded by NORTE 2020, PORTUGAL2020, and FEDER. This work was also supported by Fundação para a Ciência e a Tecnologia (FCT) under the strategic grants UIDB/04077/2020, UIDB/00690/2020, UIDB/04436/2020 and UIDB/00532/2020. Andrews Souza acknowledges the PhD scholarship 2021.07961.BD attributed by FCT. Partial support from the Junta de Extremadura through Grants No. GR21091 and IB20105 (partially financed by FEDER funds) is gratefully acknowledged. info:eu-repo/semantics/publishedVersion

In this paper we address the problem of ad hoc teamwork and contribute a novel approach, PPAS, that is able to handle non-stationary teammates. Current approaches to ad hoc teamwork assume that the (potentially unknown) teammates behave in a stationary way, which is a significant limitation in real world conditions, since humans and other intelligent systems do not necessarily follow strict policies. In our work we highlight the current limitations of state-of-the-art approaches to ad hoc teamwork problem in the presence of non-stationary teammate, and propose a novel solution that alleviates the stationarity assumption by combining ad hoc teamwork with adversarial online prediction. The proposed architecture is called PLASTIC Policy with Adversarial Selection, or PPAS. We showcase the effectiveness of our approach through an empirical evaluation in the half-field offense environment. Our results show that it is possible to cooperate in an ad hoc manner with non-stationary teammates in complex environments.

Falls, especially in the elderly, are one of the main factors of hospitalization. Time-consuming intervention can be fatal or cause irreversible damages to the victims. On the other hand, there is currently a significant amount of smart clothing equipped with various sensors, particularly gyroscopes and accelerometers, which can be used to detect accidents. The creation of a tool that automatically detects eventual falls allows helping the victims as soon as possible. This works focuses in the automatic fall detection from sensors signals using long short-term memory networks. To train and test this approach, the Sisfall dataset is used, which considers the simulation of 23 adults and 15 older people. These simulations are based on everyday activities and the falls that may result from their execution. The results indicate that the procedure provides an accuracy score of 97.1% on the test set.

In this paper it is presented an educational experiment, that consists of a mechatronic system applied to demonstrate concepts such as prototyping and control. The described mechatronic system is based on a conveyor belt, that was integrated with a manipulator, being physical devices commonly used in the industry. The conveyor Belt was prototyped from scratch, using 3d print technology. Its movement is based on the closed loop control of a DC Motor, based on a PID. The Conveyor Belt was integrated with a Braccio Manipulator from Arduino, using the ZMQ communication library, which is a high-performance asynchronous messaging library. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020). info:eu-repo/semantics/publishedVersion

When a car starts moving, it performs mechanical work that is used to move along a specific road. At that moment, the energy injected into the car, coming from the transformation of chemical energy into mechanical energy via fuel oxidation into the engine, changes rapidly. The human body is an amazing machine whose motion can be compared to a car driven on the road. Whenever we got up from a chair, run to catch the bus, or even participate in any athletic event, the energy demands of our muscles change rapidly. In fact, our energy transfer activity’ systems become higher in order to fulfill the energy requirement, whether to perform a simple task or whether to perform a more complex and energy-demanding one. The predominance of the three energy-supplying processes (ATP-PCr, glycolytic, and oxidative systems) depends on the duration and intensity of the activity to be performed. Therefore, identifying the energy required for this activity, as well as producing a measure that relates to a specific aerobic physiological state (maximal oxygen uptake and anaerobic threshold), implies an athlete, or team of athletes, to be tested, in field or laboratory conditions. The energetic profile determination of an athlete has become one of the important things for an effective exercise training prescription, monitoring training adaptations, and subsequently enhancing performance.

In last years, some studies have been proved that there is an association between the wall shear stress with intracranial aneurysm rupture, however, is very difficult to understand the mechanical tissue behaviour when subjected to shear stresses. In this work, it is implemented numerical simulations to characterise the polydimethylsiloxane (PDMS) material when it is subjected to a shear solicitation. For this, it was initially necessary to perform some experimental tests to characterize the mechanical behaviour of the material. Based on these results, several numerical simulations were performed with the most common constitutive models in the simulation of hyperelastic materials by varying numerical factors and parameters of the numerical models. info:eu-repo/semantics/publishedVersion

Information-theoretic secret-key agreement between two parties Alice and Bob is a well-studied problem that is provably impossible in a plain model with public (authenticated) communication, but is known to be possible in a model where the parties also have access to some correlated randomness. One particular type of such correlated randomness is the so-called satellite setting, where uniform random bits (e.g., sent by a satellite) are received by the parties and the adversary Eve over inherently noisy channels. The antenna size determines the error probability, and the antenna is the adversary’s limiting resource much as computing power is the limiting resource in traditional complexity-based security. The natural assumption about the adversary is that her antenna is at most Q times larger than both Alice’s and Bob’s antenna, where, to be realistic, Q can be very large.

The aneurysm is a fragile region on the wall of a blood vessel that causes it to form a bulge. In limiting situations, this weakening can lead to vessel disruption. The main goal of this work was to understand how the deformation of the aneurysm occurs when subjected to an internal pressure similar to blood pressure. The strain state of the aneurysm will allow to define which regions are subject to higher stresses and which can give an indication of potential rupture. To carry out this study we have employed a numerical approach using a commercial software (Ansys®). With this software the pressure caused by the fluid was calculated using known parameters through the experimental measurement of the pressure drop. It was possible to define a velocity profile for the fluid and to characterize its flow through the channel. The aneurysm was subjected to a pressure previously determined for the fluid, simulating the pressure to which the channel is subjected by the bloodstream. Note that the current study have always taken into consideration that the blood vessels have a hyperelastic behaviour, defined through experimental stress/strain curves. Analysing the obtained results, it was verified that the expansion of the aneurysm is predominant in its lateral regions where the greater strain values were obtained. In these regions is where a greater risk of vessel rupture can occur. info:eu-repo/semantics/publishedVersion

Nowadays, increasing pollution is causing climate change, and therefore the need to reduce carbon footprints has brought the growing use of autochthonous natural materials. On the other hand, there is new demand from the world population that requires the increased use of recyclable materials, and natural fibres are excellent candidates for this role. However, only in the last few years has this subject been studied for technical applications [1]. Natural fibre is a very interesting material, and in association with a matrix it forms a composite material. Natural fibre composites (NFCs) have some advantages compared with synthetic ones, with the most relevant being their lower density and higher specific strength and stiffness. Furthermore, they are a renewable resource whose production requires little energy and involves CO2 absorption. Nevertheless, NFCs also have disadvantages, such as lower durability when compared to synthetic fibre composites, although this can be improved significantly with specific treatments; a greater variability of properties; and the fact that they suffer from higher moisture absorption, which results in swelling [2]. info:eu-repo/semantics/publishedVersion

The Taguchi method is a powerful tool to experiment design optimization and is used in this work to optimize the cutting parameters, which reduce the chatter effect on surface quality. The present study includes feed per tooth, cutting speed, radial and axial depth of cut as control factors. An orthogonal array of L16 was used with the ANOVA analyses in order to identify the significant factors associated to the surface roughness and chatter vibration in three different directions. The optimal cutting combination for the surface finishing was determined through the analysis of surface roughness. This are correlated with the vibrations levels recorded during the experimental tests. The study was carry-out by machining a hardened steel block with tungsten carbide coated tools. The results led to the minimum of arithmetic mean surface roughness of 1.05 µm which corresponded to a minimum of the mean vibration level.

In this work we present a collection of compilers that take secret sharing schemes for an arbitrary access structure as input and produce either leakage-resilient or non-malleable secret sharing schemes for the same access structure. A leakage-resilient secret sharing scheme hides the secret from an adversary, who has access to an unqualified set of shares, even if the adversary additionally obtains some size-bounded leakage from all other secret shares. A non-malleable secret sharing scheme guarantees that a secret that is reconstructed from a set of tampered shares is either equal to the original secret or completely unrelated. To the best of our knowledge we present the first generic compiler for leakage-resilient secret sharing for general access structures. In the case of non-malleable secret sharing, we strengthen previous definitions, provide separations between them, and construct a non-malleable secret sharing scheme for general access structures that fulfills the strongest definition with respect to independent share tampering functions. More precisely, our scheme is secure against concurrent tampering: The adversary is allowed to (non-adaptively) tamper the shares multiple times, and in each tampering attempt can freely choose the qualified set of shares to be used by the reconstruction algorithm to reconstruct the tampered secret. This is a strong analogue of the multiple-tampering setting for split-state non-malleable codes and extractors. We show how to use leakage-resilient and non-malleable secret sharing schemes to construct leakage-resilient and non-malleable threshold signatures. Classical threshold signatures allow to distribute the secret key of a signature scheme among a set of parties, such that certain qualified subsets can sign messages. We construct threshold signature schemes that remain secure even if an adversary leaks from or tampers with all secret shares.

For more than 30 years, cryptographers have been looking for public sources of uniform randomness in order to use them as a set-up to run appealing cryptographic protocols without relying on trusted third parties. Unfortunately, nowadays it is fair to assess that assuming the existence of physical phenomena producing public uniform randomness is far from reality. It is known that uniform randomness cannot be extracted from a single weak source. A well-studied way to overcome this is to consider several independent weak sources. However, this means we must trust the various sampling processes of weak randomness from physical processes. Motivated by the above state of affairs, this work considers a set-up where players can access multiple potential sources of weak randomness, several of which may be jointly corrupted by a computationally unbounded adversary. We introduce SHELA (Somewhere Honest Entropic Look Ahead) sources to model this situation. We show that there is no hope of extracting uniform randomness from a SHELA source. Instead, we focus on the task of Somewhere-Extraction (i.e., outputting several candidate strings, some of which are uniformly distributed – yet we do not know which). We give explicit constructions of Somewhere-Extractors for SHELA sources with good parameters. Then, we present applications of the above somewhere-extractor where the public uniform randomness can be replaced by the output of such extraction from corruptible sources, greatly outperforming trivial solutions. The output of somewhere-extraction is also useful in other settings, such as a suitable source of random coins for many randomized algorithms. In another front, we comprehensively study the problem of Somewhere-Extraction from a weak source, resulting in a series of bounds. Our bounds highlight the fact that, in most regimes of parameters (including those relevant for applications), SHELA sources significantly outperform weak sources of comparable parameters both when it comes to the process of Somewhere-Extraction, and in the task of amplification of success probability in randomized algorithms. Moreover, the low quality of somewhere-extraction from weak sources excludes its use in various efficient applications.