FCT: DCM - Documentos de conferências internacionais
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- Electrosurface properties of nanopowder system based on zirconiaPublication . Shylo, Artem; Gorban, Oksana; Danilenko, Igor; Doroshkevich, Aleksandr; Lyubchyk, Andriy; Gorban, Anton; Konstantinova, Tetyana; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; UNINOVA-Instituto de Desenvolvimento de Novas TecnologiasFor investigation of the influence of temperature of nanopowder calcination on adsorption properties of zirconiananoparticles, the pH-metry method was used. As a result, structure and parameters of double electric layer surrounding zirconia nanoparticles under wetting were calculated. According presented data, titration curves of suspensions based on zirconia nanoparticles at different electrolyte concentrations intersect at values other than σ0 = 0, which indicates the occurrence of specific sorption on the surface of zirconia nanoparticles.
- A High Speed Programmable Ring Oscillator Using InGaZnO Thin-Film TransistorsPublication . Tiwari, Bhawna; Martins, Jorge; Kalla, Shivam; Kaushik, Shashwat; Santa, Ana; Bahubalindruni, Pydi Ganga; Tavares, Vitor Grade; Barquinha, Pedro; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos MateriaisThis paper presents a high speed digitally programmable Ring Oscillator (RO) using Indium-gallium-zinc oxide thin-film transistors (IGZO TFTs). Proposed circuit ensures high speed compared to the conventional ROs using negative skewed scheme, in which each inverter delay is reduced by pre-maturely switching on/off the transistors. In addition, by controlling the load capacitance of each inverter through digital control bits, a programmable frequency of oscillation was attained. Proposed RO performance is compared with two conventional designs under same conditions. From simulation, it has been observed that the proposed circuit has shown a higher frequency of oscillations (283 KHz) compared to the conventional designs (76.52 KHz and 144.9 KHz) under same conditions. Due to the programmable feature, the circuit is able to generate 8 different linearly spaced frequencies ranging from 241.2 KHz to 283 KHz depending upon three digital control bits with almost rail-to-rail voltage swing. The circuit is a potential on-chip clock generator in many real-world flexible systems, such as, smart packaging, wearable devices, RFIDs and displays that need multi frequencies.
- A Comparitive Study of On-Chip Clock Generators Using a-IGZO TFTs for Flexible Electronic SystemsPublication . Wadhwa, Nishtha; Martins, Jorge; Bahubalindruni, Pydi; Deb, Sujay; Barquinha, Pedro; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos MateriaisThis paper presents a comparitive study of ring oscillators (RO) using amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs) to implement on-chip clock generator for flexible electronic systems. A five-stage RO has been implemented with different inverter topologies using IGZO TFTs, which includes Diode connected load, Capacitive bootstrapping (BS), Pseudo-CMOS and Pseudo-CMOS bootstrapping architectures. These topologies have been simulated using in-house IGZO TFT models under similar conditions using different power supplies (10 V, 15 V and 20 V) in cadence environment. Among all architechtures Capacitive bootstrapping RO has ensured highest frequency of operation in the order of MHz and an output swing of 82% of V DD . Whereas, Pseudo-CMOS based RO provides the lowest power consumption in the order of μW with an output swing of 57% of V DD . On the other hand, the combination of Pseudo CMOS and bootstrapping has ensured highest voltage swing of 95% of V DD . In terms of power delay product (PDP) BS RO is superior with respect to other topologies. This work provides a clear insight to the designer to choose a particular topology for given application, mainly for on-chip clock generation for flexible electronic systems based on the requirements.
- A Low-Power Rail-to-Rail Row/Column Selector Operating at 2V Using a-IGZO TFTs for Flexible DisplaysPublication . Santos, Ângelo; Tiwari, Bhawna; Martins, Jorge; Santa, Ana; Chapagai, Kamal; Bahubalindruni, Pydi; Barquinha, Pedro; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos MateriaisThis paper presents design and implementation of 8-bit shift register with low-voltage amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs) for row/column selection of pixel matrix in flexible displays. This circuit is capable of ensuring complete rail-to-rail operation by employing novel NAND gates that were developed based on capacitive bootstrapping load. As a first step, a positive edge triggered D-flip flop (D-FF) is designed using these logic gates, then a complete 8-bit shift register is designed and simulated using in-house low-voltage IGZO TFT models in Cadence Virtuoso. During these circuit simulations a power supply voltage of 2V and a channel length of 2 μm were used. Simulation outcome of 8-bit shift register has shown a power consumption of 72.15 μW with output voltage swing of 95% of V dd at 20 kHz operating frequency, going well beyond the state of the art for oxide TFT technology at very low supply voltage. The proposed circuit can be used as a row/column selector in flexible displays that can operate at low supply voltage and allows small active-area.
- A comparative study of austenitic structure in NiTi and Fe based shape memory alloys after severe plastic deformationPublication . Gurau, C.; Gurau, G.; Bujoreanu, L. G.; Fernandes, F. M. B.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N)The effect of high speed high pressure torsion (HS-HPT) was studied in NiTi and FeMnSiCr SMAs, by comparison. Severe plastic deformation was performed in austenite state for both types of alloys. The alloys subjected to HS-HPT, reduced their grain size due to microstructure fragmentation by compression and torsion. The active elements were achieved being able to support variable ranges of processing parameters like force, pressure, rotation speed and time of torsion. The evolution of microstructural refinement in the samples subjected to different deformation by HS-HPT, were studied by optical and scanning electron microscopy observation and the thermal effect was reveled using differential scanning calorimetry (DSC). (C) 2015 The Authors. Published by Elsevier Ltd.
- Comparative study of NiTi orthodontic wiresPublication . Braz Fernandes, F. M.; Cruz, J. M.; Magalhaes, R. C. A.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N)In this study, two superelastic NiTi orthodontic wires (0.46 x 0.64 mm(2)) were analyzed. The determination of phase transformation temperatures along with the identification of the predominant phase at room and intraoral temperatures were accomplished by DSC analysis. Superelastic behavior was analyzed through tensile tests. 3-point bending tests were performed on a model design which included brackets to compare wires' behavior: lower forces corresponding to Ormco wires' reverse phase transformation plateau when compared to Dentaurum were exhibited. Wire slippage inside the brackets and friction caused by wire-bracket-ligature combinations on bending and pulling tests, respectively, are also discussed. (C) 2014 The Authors. Published by Elsevier Ltd.
- Tungsten-bearing molybdenite from BorralhaPublication . Veiga, João Pedro Botelho; Pereira, Teresa; Figueiredo, Maria-Ondina; Oliveira, Daniel; Noronha, Fernando; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N)