Development of a New Conductivity Model for Shaly Sand Interpretation.

In this dissertation, a new theoretical conductivity model for shaly sands is developed. The model is based on dual water concepts. In addition, the equivalent counterion conductivity changes as the diffuse electrical double layer expands and is then a function of temperature, shaliness, and of the conductivity of the far water. The formation resistivity factor used in the model is independent of shaliness. A method to calculate the equivalent counterion conductivity is proposed. This method is based on treating the double layer region as a hypothetical electrolyte, the properties of which are derived from basic electrochemistry theory. The new model was used to calculate conductivities of specific shaly sand samples 25(DEGREES)C. The calculated values display an excellent agreement with published experimental data. The new model is shown to be superior in predicting core conductivities to the two models currently accepted by the industry. The developed model has been extended to represent hydrocarbon bearing formations as well as to predict membrane potentials in shaly sands. Calculated water saturation and membrane potential values from the new model also show excellent agreement with accurate experimental data obtained at laboratory conditions. The effect of temperature on the conductive behavior of shaly sands has been revised under the basis of the new model. The representativity of conductivities predicted by the new model for temperatures up to 200(DEGREES)C warrants its application under actual field conditions. Several new concepts useful in the analysis of shaly sands are introduced in this work. In addition, the new model is used to enhance the interpretation of the SP log in shaly environments. Finally, a new interpretation technique for shaly sands is proposed. This interpretation tool is based on the new conductivity model and makes use of log derived data. It allows the proper evaluation of the potential of a reservoir formation

Towards higher sense of presence: a 3D virtual environment adaptable to confusion and engagement

Virtual Reality scenarios where emitters convey information to receptors can be used as a tool for distance learning and to enable virtual visits to company physical headquarters. However, immersive Virtual Reality setups usually require visualization interfaces such as Head-mounted Displays, Powerwalls or CAVE systems, supported by interaction devices (Microsoft Kinect, Wii Motion, among others), that foster natural interaction but are often inaccessible to users. We propose a virtual presentation scenario, supported by a framework, that provides emotion-driven interaction through ubiquitous devices. An experiment with 3 conditions was designed involving: a control condition; a less confusing text script based on its lexical, syntactical, and bigram features; and a third condition where an adaptive lighting system dynamically acted based on the user’s engagement. Results show that users exposed to the less confusing script reported higher sense of presence, albeit without statistical significance. Users from the last condition reported lower sense of presence, which rejects our hypothesis without statistical significance. We theorize that, as the presentation was given orally and the adaptive lighting system impacts the visual channel, this conflict may have overloaded the users’ cognitive capacity and thus reduced available resources to address the presentation content.info:eu-repo/semantics/publishedVersio

On the global uniqueness for the Einstein-Maxwell-scalar field system with a cosmological constant. Part 3: Mass inflation and extendibility of the solutions

This paper is the third part of a trilogy dedicated to the following problem: given spherically symmetric characteristic initial data for the Einstein-Maxwell-scalar field system with a cosmological constant $\Lambda$, with the data on the outgoing initial null hypersurface given by a subextremal Reissner-Nordstrom black hole event horizon, study the future extendibility of the corresponding maximal globally hyperbolic development as a "suitably regular" Lorentzian manifold. In the first part of this series we established the well posedness of the characteristic problem, whereas in the second part we studied the stability of the radius function at the Cauchy horizon. In this third and final paper we show that, depending on the decay rate of the initial data, mass inflation may or may not occur. When the mass is controlled, it is possible to obtain continuous extensions of the metric across the Cauchy horizon with square integrable Christoffel symbols. Under slightly stronger conditions, we can bound the gradient of the scalar field. This allows the construction of (non-isometric) extensions of the maximal development which are classical solutions of the Einstein equations. Our results provide evidence against the validity of the strong cosmic censorship conjecture when $\Lambda>0$.Comment: 48 pages, 5 figures; v2: some presentation changes, mostly in the Introduction; v3: substantial changes in Section 5; v4: expanded Introduction; some presentation changes; matches final published versio

On the global uniqueness for the Einstein-Maxwell-scalar field system with a cosmological constant. Part 2: Structure of the solutions and stability of the Cauchy horizon

This paper is the second part of a trilogy dedicated to the following problem: given spherically symmetric characteristic initial data for the Einstein-Maxwell-scalar field system with a cosmological constant $\Lambda$, with the data on the outgoing initial null hypersurface given by a subextremal Reissner-Nordstrom black hole event horizon, study the future extendibility of the corresponding maximal globally hyperbolic development as a "suitably regular" Lorentzian manifold. In the first paper of this sequence, we established well posedness of the characteristic problem with general initial data. In this second paper, we generalize the results of Dafermos on the stability of the radius function at the Cauchy horizon by including a cosmological constant. This requires a considerable deviation from the strategy followed by Dafermos, focusing on the level sets of the radius function instead of the red-shift and blue-shift regions. We also present new results on the global structure of the solution when the free data is not identically zero in a neighborhood of the origin. In the third and final paper, we will consider the issue of mass inflation and extendibility of solutions beyond the Cauchy horizon.Comment: 44 pages, 13 figures; v2: a few small changes; v3: a paragraph was added in the Introduction, minor clarifications were made thoughout, the list of references was expanded, matches final published versio

Ontogenetic foraging activity and feeding selectivity of the Brazilian endemic parrotfishScarus zelindae

Parrotfish are fundamental species in controlling algal phase-shifts and ensuring the resilience of coral reefs. Nevertheless, little is known on their ecological role in the south-western Atlantic Ocean. The present study analysed the ontogenetic foraging activity and feeding selectivity of the Brazilian endemic parrotfish Scarus zelindae using behavioural observation and benthic composition analyses. We found a significant negative relationship between fish size and feeding rates for S. zelindae individuals. Thus, terminal phase individuals forage with lower feeding rates compared to juveniles and initial phase individuals. The highest relative foraging frequency of S. zelindae was on epilithic algae matrix (EAM) with similar values for juveniles (86.6%), initial phase (88.1%) and terminal phase (88.6%) individuals. The second preferred benthos for juveniles was sponge (11.6%) compared with initial (4.5%) and terminal life phases (1.3%). Different life phases of S. zelindae foraged on different benthos according to their availability. Based on Ivlev's electivity index, juveniles selected EAM and sponge, while initial phase and terminal phase individuals only selected EAM. Our findings demonstrate that the foraging frequency of the endemic parrotfish S. zelindae is reduced according to body size and that there is a slight ontogenetic change in feeding selectivity. Therefore, ecological knowledge of ontogenetic variations on resource use is critical for the remaining parrotfish populations which have been dramatically reduced in the Southwestern Atlantic Ocean

Sensitivity analysis of a crawl gait multi-objective optimization system

This paper describes the analysis of a crawl gait multi-objective optimization system that combines bio-inspired Central Patterns Generators (CPGs) and a multi-objective evolutionary algorithm. In order to optimize the crawl gait, a multiobjective problem, an optimization system based on NSGAII allows to find a set of non-dominated solutions that correspond to different motor solutions The experimental results highlight the effectiveness of this multi-objective approach.(undefined

Calcific uraemic arteriolopathy - A mini-review

Calcific Uraemic Arteriolopathy (CUA) or calciphylaxis, is a thrombotic disorder of skin and subcutaneous tissue which typically presents with painful purpuric nodules that may progress to necrotic ulcers, and is a severe, life-threatening condition. CUA is an uncommon clinical entity that affects mostly haemodialysis (HD) patients. Although the process of vascular calcification was initially thought to be the result of a passive deposition of calcium-phosphate crystals, current knowledge suggests a distinct mechanism, including cellular activity with differentiation of vascular smooth muscle cells (VSMCs) into chondrocyte as well as osteoblast-like cellular phenotypes and deficiencies in calcification inhibitors. Although multiple studies suggest a potential relationship between warfarin and CUA, larger prospective studies are needed in order to better evaluate this association, and randomised controlled trials are needed to assess the benefit of distinct interventions in this setting. In this article the topic of CUA is reviewed based on a clinical case of a 65-year-old man undergoing haemodialysis, who underwent an aortic valve replacement one year earlier, receiving a mechanical heart valve, and who has been under warfarin therapy since the

Predicting the confusion level of text excerpts with syntactic, lexical and n-gram features

Distance learning, offline presentations (presentations that are not being carried in a live fashion but were instead pre-recorded) and such activities whose main goal is to convey information are getting increasingly relevant with digital media such as Virtual Reality (VR) and Massive Online Open Courses (MOOCs). While MOOCs are a well-established reality in the learning environment, VR is also being used to promote learning in virtual rooms, be it in the academia or in the industry. Oftentimes these methods are based on written scripts that take the learner through the content, making them critical components to these tools. With such an important role, it is important to ensure the efficiency of these scripts. Confusion is a non-basic emotion associated with learning. This process often leads to a cognitive disequilibrium either caused by the content itself or due to the way it is conveyed when it comes to its syntactic and lexical features. We hereby propose a supervised model that can predict the likelihood of confusion an input text excerpt can cause on the learner. To achieve this, we performed syntactic and lexical analyses over 300 text excerpts and collected 5 confusion level classifications (0 – 6) per excerpt from 51 annotators to use their respective means as labels. These examples that compose the dataset were collected from random presentations transcripts across various fields of knowledge. The learning model was trained with this data with the results being included in the body of the paper. This model allows the design of clearer scripts of offline presentations and similar approaches and we expect that it improves the efficiency of these speeches. While this model is applied to this specific case, we hope to pave the way to generalize this approach to other contexts where clearness of text is critical, such as the scripts of MOOCs or academic abstracts.info:eu-repo/semantics/acceptedVersio

Homogenization on multi-materials' elements: application to printed circuit boards and warpage analysis

Multi-material domains are often found in industrial applications. Modelling them can be computationally very expensive due to meshing requirements. The finite element properties comprising different materials are hardly accurate. In this work, a new homogenization method that simplifies the computation of the homogenized Young modulus, Poisson ratio and thermal expansion coefficient is proposed, and applied to composite-like material on a printed circuit board. The results show a good properties correspondence between the homogenized domain and the real geometry simulation.This research is sponsored: - by the Portugal Incentive System for Research and Technological Development. Project in co - promotion nº 36265/2013 (Project HMIExcel - 2013 - 2015), and - by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI - 01 - 0145 - FEDER - 006941info:eu-repo/semantics/publishedVersio