Hugo Silva

Optimization of a flow injection analysis system for tartaric acid determination in wines.

The objective of this work is the development and optimization of a method for tartaric acid analysis in wines that does not require any sample pre-treatment and with adequate accuracy. A flow injection analysis manifold with three channels, using a dialysis unit to eliminate sample matrix interferences and to accomplish on-line dilution, is proposed for the spectrophotometrical determination of tartaric acid in wines making use of its reaction with vanadate. The proposed method is fast, accurate, simple, economic and does not require any sample pre-treatment. Preliminary studies using factorial designs were performed to determine which operational parameters should be included in the optimization stage. The optimization was performed using a modified simplex algorithm with a response function that included sensitivity, deviation from linearity at low concentrations and residence time, used as an inverse measure of sampling rate. The most relevant analytical parameters of the method are presented, including a comparison between the results provided by the proposed method and by an alternative procedure in the analysis of a set of wine samples from Portugal, with tartaric acid values in the range 0.5-4 gl(-1).

Zirconium Oxide Modified Sulfonated Poly (Ether Ether Ketone) Membranes for Direct Methanol Fuel Cell Applications

In order to perform a critical analysis of the zirconium oxide effects in sulfonated poly(ether ether ketone) (SPEEK) membranes with two sulfonation degrees (SD), 71 and 87%, the characterization of composite membranes prepared with a systematic variation of the inorganic content is proposed. The method involves preparation of inorganic composite membranes with a wide range of properties which concern water swelling, chemical and thermal stability, methanol and water permeations and, finally, proton conductivity. A good balance between high proton conductivity, good chemical stability and low methanol permeability is reached for the SPEEK polymer with a 7.5% (w/w) ZrO2 content and SD=87%. Compared to NAFION ® 112, this membrane is 3-times more selective towards water/methanol permeation and has a similar proton conductivity (81 compared to 88 mS/cm).

Simple hydrothermal synthesis method for tailoring the physicochemical properties of ZnO: morphology, surface area and polarity

A simple urea-assisted hydrothermal synthesis method was used to tailor the physicochemical properties of ZnO materials. The role of Pluronic P123 block copolymer in the crystal growth, morphology and specific surface area of the as-prepared ZnO was studied. When Pluronic P123 is used, well-dispersed hierarchical microspheres, with a flower-like morphology, are obtained, but in its absence large spherical agglomerated clusters are formed. The polarity of the ZnO, measured as the ratio between plane (002) and plane (100), is also significantly higher for the Pluronic P123 sample. The influence of zinc salt precursors was also analysed. The use of zinc nitrate led to the formation of urchin-like ZnO structures, instead of the microflowers that result from zinc acetate salt. Despite having similar surface areas, the polarity of the zinc nitrate sample was much smaller. The decomposition of methylene blue corroborated the higher photocatalytic activity of the ZnO materials with a higher proportion of polar planes (higher polarity). The formation mechanism of the crystals is also suggested based on the observed gradual growth and assembly of the hydrozincite during the initial steps of the synthesis for the samples with and without Pluronic P123.

Pre‐treatment Effect on the Sulfonated Poly(ether ether ketone) Membrane Transport Properties and Direct Methanol Fuel Cell Performance

Abstract In this paper a critical study is presented on how the direct methanol fuel cell (DMFC) membrane properties are affected by a pre‐treatment. Membranes based on sulfonated poly(ether ether ketone) (sPEEK) with sulfonation degree (SD) of 42% were used, plain and modified inorganically with 1 wt.% of zirconium oxide. Nafion® 1135 was used as reference. The results obtained show that the sPEEK polymer (SD=42%) enables the preparation of proton exchange membranes with improved properties compared to Nafion® and to the ZrO2‐modified sPEEK membrane, mainly due to its improved relation between proton conductivity and methanol permeation. After the pre‐treatment, the plain sPEEK membrane had a performance 6.4 times higher in terms of maximum power output when used in the DMFC.

Towards Location-based Augmented Reality games☆

Abstract Location-based games have become more popular thanks to the growth of mobile devices technology. This paper presents a framework for the development of location-based augmented reality games and wARms, an augmented-reality location- based mobile game prototype based on said framework that uses the players real position and orientation in order to play against others. The game shows how modern mobile devices sensors can be used for providing new and unusual gaming experiences.

User Redirection and Direct Haptics in Virtual Environments

This paper proposes a haptic interaction system for Virtual Reality (VR) based on a combination of tracking devices for hands and objects and a real-to-virtual mapping system for user redirection. In our solution the user receives haptic stimuli by manipulating real objects mapped to virtual ob- jects. This solution departs from systems that rely on haptic devices (e.g., haptic gloves) as interfaces for the user to inter- act with objects in the Virtual Environment (VE). As such, the proposed solution makes use of direct haptics (touching) and redirection techniques to guide the user through the vir- tual environment. Using the mapping framework, when the user touches a virtual object in the VE, he will simultane- ously be physically touching the equivalent real object. A relevant feature of the framework is the possibility to de- fine a warped mapping between the real and virtual worlds, such that the relation between the user and the virtual space can be different from the one between the user and the real space. This is particularly useful when the application re- quires the emulation of large virtual spaces but the physical space available is more confined. To achieve this, both the users hands and the objects are tracked. In the presented prototype we use a head-mounted depth sensor (i.e., Leap Motion) and a depth-sensing camera (i.e., Kinect). To assess the feasibility of this solution, a functional prototype and a room setup with core functionality were implemented. The test sessions with users evaluated the mapping accuracy, the user execution time and the awareness of the user regarding the warped space when performing tasks with redirection. The results gathered indicate that the solution can be used to provide direct haptic feedback in VR applications and for warping space perception within certain limits.