A novel synchronizer for a 17.9ps Nutt Time-to-Digital Converter implemented on FPGA

The evolution of Field-Programmable Gate Array (FPGA) technology triggered the appearance of FPGAs with higher operating frequencies and large number of resources. Simultaneously, the evolution of the FPGAs design tools has simplified the development process, reducing the time to market. These factors made FPGA platforms attractive for several applications, including time-of-flight applications that require the implementation of Time-to-Digital Converters (TDC). This work presents a Nutt TDC, based on a coarse counter and a Tapped Delay Line, with 17.9 picoseconds resolution and 5.4 LSB differential nonlinearity (DNL), implemented in a Xilinx Zynq-7000 FPGA, to be used on LiDAR applications and pull-in time measuring in MEMS accelerometers systems.This work was supported by a Portuguese Scholarship from FCT - Fundação para a Ciência e Tecnologia and Bosch Car Multimedia, under the Advanced Engineering Systems for Industry (AESI) doctoral program. (Scholarship ID: PDE/BDE/114562/2016) and COMPETE and FCT: POCI- 01-0145-FEDER-007043 within the Project Scope: UID/CEC/00319/201

Experimental study on RSS based indoor positioning algorithms

This work compares the performance of indoor positioning systems suitable for low power wireless sensor networks. The research goal is to study positioning techniques that are compatible with real-time positioning in wireless sensor networks, having low-power and low complexity as requirements. Map matching, approximate positioning (weighted centroid) and exact positioning algorithms (least squares) were tested and compared in a small predefined indoor environment. We found that, for our test scenario, weighted centroid algorithms provide better results than map matching. Least squares proved to be completely unreliable when using distances obtained by the one-slope propagation model. Major improvements in the positioning error were found when body influence was removed from the test scenario. The results show that the positioning error can be improved if the body effect in received signal strength is accounted for in the algorithms.Helder D. Silva is supported by the Portuguese Foundation for Science and Technology under the grant SFRBD/78018/2011.info:eu-repo/semantics/publishedVersio

Body attenuation and path loss exponent estimation for RSS-based positioning in WSN

The influence of the human body in antenna systems has significant impact in the received signal strength (RSS) of wireless transmissions. Accounting for body effect is generally considered as being able to improve position estimation based on RSS measurements. In this work we perform several experiments with a wireless sensor network, using a sensor node equipped with an inertial measurement unit (IMU), in order to obtain the relative orientation between the sensor node and multiple anchor nodes. A model of the RSS attenuation induced by the body was created using experimental measurements in a controlled environment and applied to a real-time positioning system. A path loss exponent (PLE) estimation method using RSS information from neighbor anchors was also implemented and evaluated. Weighted centroid localization (WCL) algorithm was the positioning method used in this work. When the sensor node was placed on the user’s body, accounting for body effect produced negligible improvements (6%) in the best-case scenario and consistently degraded accuracy under real conditions, whether the node was placed on the user’s body (in the order of 3%), 10 cm away (from 14% to 35%) or 20 cm away from the body (from 42% to 105%) for results in the 70th percentile. The PLE estimation method showed improvements (in the order of 11%) when the sensor node is further away from the body. Results demonstrate that the distance between sensor node and the body has an extremely important influence on the accuracy of the position estimate.This work has been supported by FCT (Fundação para a Ciência e Tecnologia) in the scope of the project UID/EEA/04436/2013. Helder D. Silva is supported by FCT under the grant SFRH/BD/78018/2011info:eu-repo/semantics/publishedVersio

Strain sensors based on knocked down carbon nanotubes and bucky papers thin films

Recently, carbon nanotubes (CNTs) thin films have been widely applied in sensing applications due to their piezoresistive response. Furthermore, CNT anisotropic electric properties, due to its alignment, can provide useful information regarding strain direction. We present a comparative study between knocked down vertically aligned CNT based sensor, reported in our previous work [1], and CNT bucky papers (BP) based sensors. For this purpose, commercial multi-wall carbon nanotubes (MWCNTs) were dispersed in two different solvents, dimethylformamide (DMF) and ethanol, vacuum filtrated and dried. From these freestanding BP thin films, 10x10 mm squares were cut off and transferred to polyimide (PI) films. The relative electric resistance response and sensitivity of the strained samples was measured and compared with the knocked down CNT/PI based sensor. Moreover, the morphology of the samples was characterized by scanning electron microscopy (SEM). The results showed a high sensitivity to strain, however knocked down CNT/PI based sensor presented better mechanical performance and an anisotropic behaviour that can be used to infer strain direction.FCT, Programa MIT Portugal, projeto "IAMAT (Introduction of Advanced Materials Technologies into New Product Development for the Mobility Industries

CFRP bioinspirados para melhoria da resistência ao impacto e autossensorização

Os compósitos reforçados com fibras de carbono (CFRP) são cada vez mais usados em aplicações de elevado desempenho devido às excelentes propriedades mecânicas e baixo peso que apresentam. A resistência interlaminar continua, no entanto, a ser uma das maiores limitações do seu desempenho mecânico [1-3]. Recentemente, tem-se vindo a tentar superar o problema aplicando nos CFRP mecanismos semelhantes aos que garantem um elevado desempenho ao impacto em organismos vivos, p.e., o exosqueleto dos artrópodes que apresenta uma estrutura fibrosa laminada helicoidal (Bouligand) à escala micrométrica [4-6]. Sistemas sensoriais estudados em seres vivos também têm inspirado o desenvolvimento de compósitos multifuncionais [7], sendo ainda um desafio a criação de tecnologias de fabrico capazes de replicar estas estruturas/sistemas. Neste trabalho fabricaram-se CFRPs com desempenho mecânico melhorado, usando laminados bioinspirados com fibras orientadas helicoidalmente (tipo Bouligand) e nanotubos de carbono (CNT) como sensores capazes de lhes conferiram multifuncionalidade (monitorização de dano). Produziram-se por infusão por vácuo, usando uma resina epóxída reforçada com fibras contínuas de carbono, placas CFRP (550x180x4 mm) com empilhamentos helicoidal e standard que, para comparação de propriedades, foram sujeitas a ensaios de impacto e de compressão após-impacto. Para garantir a multifuncionalidade, transferiram-se florestas de CNT verticalmente alinhados (VA-CNT) obtidas por deposição química a vapor (CVD) para o laminado. Usaram-se ainda técnicas não-destrutivas (NDT) de ultrassons (C-Scan) na análise da microestrutura e avaliação dos danos produzidos após impacto. Os resultados evidenciam as dificuldades encontradas em fabricar as placas e as melhorias que a integração de estruturas bioinspiradas conferem às características e multifuncionalidade dos compósitosProjeto IAMATinfo:eu-repo/semantics/publishedVersio

Frequency modulated magnetometer using a double-ended tuning fork resonator

A Lorentz force MEMS magnetometer based on a double-ended tuning fork (DETF) for out-of-plane sensing is presented here. A novel configuration using a hexagonal-shaped Lorentz force transducer is used, which simplifies the sensor configuration and improves its sensitivity. Frequency modulated devices were fabricated in an in-house process on silicon on insulator wafers (SOI) and then tested in vacuum. The final devices have a differential configuration and experimental characterization shows a sensitivity of 4.59 Hz/mT for a total input current (on the Lorentz bar) of 1.5 mA.The first author is supported by FCT—Fundação para a Ciência e Tecnologia through the grant PDE/BDE/114564/2016. This work is supported by FCT with the reference project UID/EEA/04436/2013, COMPETE 2020 with the code POCI-01-0145-FEDER-006941.info:eu-repo/semantics/publishedVersio

Costo económico del tratamiento de las úlceras por presión : una aproximación teórica

O presente artigo consiste numa abordagem teórica sobre a problemática dos custos económicos das úlceras por pressão. Parte-se do conhecimento do problema, numa perspetiva conceptual, para, de seguida, apresentar resultados de estudos de prevalência, a partir dos quais foram delineados estudos de impacto económico. O objectivo deste artigo é o de reflectir sobre os custos económicos associados às úlceras por pressão, quer numa perspetiva global, considerando a repercussão financeira, quer numa vertente personalista, atendendo aos custos intangíveis. Relativamente ao impacto económico das úlceras por pressão, foi efectuada uma estimativa ao nível da Região Autónoma dos Açores do custo total do tratamento por ambiente de cuidados. Nos cuidados domiciliários o custo com o tratamento de todas as categorias é calculado em 7.086.415 euros; nos cuidados hospitalares, em 1.723.509 euros, e nos cuidados prestados em lares de idosos, em 1.002.562 euros. Nos Açores, a estimativa do custo total do tratamento das úlceras por pressão, considerando todas as suas categorias, ronda os 9.812.486 euros. Quanto ao impacto emocional associado, este tem elevados custos para pessoa e para os familiares, nomeadamente pelo sofrimento gerado. De facto, as úlceras por pressão acarretam elevados custos económicos associados ao tratamento, bem como custos intangíveis pelo sofrimento vivenciado por pessoas e cuidadores.RESUMEN: El presente artículo consiste en una reflexión teórica sobre el problema de los costos económicos de las úlceras por presión. Se empieza por el conocimiento del problema, desde una perspectiva conceptual, y, a continuación, se presentan los resultados de estudios de prevalencia, a partir de los cuales se diseñaron estudios de impacto económico. El objetivo del artículo es reflexionar sobre los costos económicos asociados a las úlceras por presión tanto en una perspectiva global, considerando la repercusión financiera, como en una vertiente personalista, de acuerdo a los costos intangibles. En cuanto al impacto económico de las úlceras por presión, se realizó una estimación de la Región Autónoma de Açores del costo total del tratamiento por ámbito de atención. En la atención domiciliaria el costo con el tratamiento de todas las categorías se estima en € 7.086.415, en la atención hospitalaria, se estima € 1.723.509 y en la atención en los asilos se estima en €1.002.562. En Açores, el costo total estimado del tratamiento de las úlceras por presión en todas las categorías, es de alrededor de € 9.812.486. En cuanto al impacto emocional asociado, éste tiene elevados costos para la persona y para los familiares, principalmente, por el sufrimiento causado. De hecho, las úlceras por presión implican altos costos económicos asociados con el tratamiento, así como, costos intangibles generados por el sufrimiento experimentado por los individuos y los cuidadores.ABSTRACT: The present study consisted of a theoretical approach to the problem posed by the economic costs associated with pressure ulcers (PUs). The initial aim was to assess the target problem from a conceptual perspective and then to report the results of prevalence studies that formed the basis for investigations of the disease’s economic impact. The purpose of the present article is to discuss the economic costs associated with PUs from both the global point of view (appraising their financial repercussion) and the individual point of view (addressing the intangible costs). Regarding the economic impact of the costs associated with PUs, the total cost of treatment per healthcare setting was estimated relative to the Autonomous Community of Azores. The total cost of all the PU categories was EUR 7,086,415 in the homecare setting, EUR 1,723,509 in the hospital setting, and EUR 1,002,562 in older people’s homes. Therefore, the estimated total treatment cost of all the PU categories was approximately EUR 9,812,486 in Azores. However, the emotional impact of this disease imposes high costs on patients and their relatives as a function of the resultant suffering. Indeed, PUs impose high costs not only related to the treatment but also related to the intangible costs of the suffering caused to patients and their caregivers.Project ICE 2 – Investigação Científica em Enfermagem – Estudo do “Custo Económico das Úlceras por Pressão na Macaronésia” (MAC/1/A029) de Iniciativa Comunitária – Programa de Cooperação Transnacional Madeira-Açores-Canárias 2007-2013info:eu-repo/semantics/publishedVersio

Small-size MEMS accelerometer encapsulated in vacuum using Sigma-Delta modulation

A vacuum encapsulated MEMS accelerometer using Sigma-Delta modulation is here presented. Three different modulation orders (second, third, and fourth) were implemented in a field-programable gate array (FPGA), enabling flexibility for tuning the loop parameters in real-time. Three devices were measured, and the results are in good agreement with simulations performed in Simulink. A noise figure of 123 μg/√Hz for a bandwidth of 400 Hz and a range of at least ±1 g was experimentally measured. A figure of merit considering device size and bandwidth is proposed, highlighting the relevance of the results for the current state of the art.FCT - Fundação para a Ciência e a Tecnologia (PDE/BDE/114563/2016

Postural stability analysis with inertial measurement units in alzheimer’s disease

BACKGROUND: The cause of frequent falls in patients with Alzheimer's disease (AD) is still not well understood. Nevertheless, balance control and sensory organization are known to be critical for moving safely and adapting to the environment. METHODS: We evaluated postural stability in 20 AD patients (11 fallers and 9 nonfallers) and 16 healthy controls with an inertial measurement unit (triaxial accelerometers and gyroscopes) attached to the center of mass (COM) in different balance conditions (Romberg on flat surface and frontward/backward-inclined surface, with or without visual suppression) in a motor lab. RESULTS: In AD patients, the group of fallers showed a different kinetic pattern of postural stability characterized by higher vulnerability to visual suppression, higher total/maximal displacement and a mediolateral/anteroposterior range of sway, and a consequent need for more corrections of COM pitch and roll angles. CONCLUSION: Further studies are needed to consolidate the normative values of the discriminatory kinetic variables with the potential of inclusion in a multifactorial analysis of the risk of falls. Nevertheless, these results highlight signs of impairment of central postural control in AD, which may require early therapeutic intervention.The Center ALGORITMI was funded by the Neural Engineering Transformative Technologies (NETT) project

Compensatory postural adjustments in na oculus virtual reality environment and the risk of falling in Alzheimer’s disease

Background/Aims Alzheimer's disease (AD) patients have an impaired ability to quickly reweight central sensory dependence in response to unexpected body perturbations. Herein, we aim to study provoked compensatory postural adjustments (CPAs) in a conflicting sensory paradigm with unpredictable visual displacements using virtual reality goggles. Methods We used kinematic time-frequency analyses of two frequency bands: a low-frequency band (LB; 0.3-1.5 Hz; mechanical strategy) and a high-frequency band (HB; 1.5-3.5 Hz; cognitive strategy). We enrolled 19 healthy subjects (controls) and 21 AD patients, divided according to their previous history of falls. Results The AD faller group presented higher-power LB CPAs, reflecting their worse inherent postural stability. The AD patients had a time lag in their HB CPA reaction. Conclusion The slower reaction by CPA in AD may be a reflection of different cognitive resources including body schema self-perception, visual motion, depth perception, or a different state of fear and/or anxiety.The Centro ALGORITMI was funded by the FP7 Marie Curie ITN Neural Engineering Transformative Technologies (NETT) project. The authors have no conflicts of interest to report.info:eu-repo/semantics/publishedVersio