On evaluating temperature as observable for CMOS technology variability

The temperature at surface of a silicon die depends on the activity of the circuits placed on it. In this paper, it is analyzed how Process, Voltage and Temperature (PVT) variations affect simultaneously some figures of merit (FoM) of some digital and analog circuits and the power dissipated by such circuits. It is shown that in some cases, a strong correlation exists between the variation of the circuit FoM and the variation of the dissipated power. Since local temperature increase at the silicon surface close to the circuit linearly depends on dissipated power, the results show that temperature can be considered as an observable magnitude for CMOS technology variability monitoring.Postprint (published version

A wearable biofeedback device to improve motor symptoms in Parkinson’s disease

Dissertação de mestrado em Engenharia BiomédicaThis dissertation presents the work done during the fifth year of the course Integrated Master’s in Biomedical Engineering, in Medical Electronics. This work was carried out in the Biomedical & Bioinspired Robotic Devices Lab (BiRD Lab) at the MicroElectroMechanics Center (CMEMS) established at the University of Minho. For validation purposes and data acquisition, it was developed a collaboration with the Clinical Academic Center (2CA), located at Braga Hospital. The knowledge acquired in the development of this master thesis is linked to the motor rehabilitation and assistance of abnormal gait caused by a neurological disease. Indeed, this dissertation has two main goals: (1) validate a wearable biofeedback system (WBS) used for Parkinson's disease patients (PD); and (2) develop a digital biomarker of PD based on kinematic-driven data acquired with the WBS. The first goal aims to study the effects of vibrotactile biofeedback to play an augmentative role to help PD patients mitigate gait-associated impairments, while the second goal seeks to bring a step advance in the use of front-end algorithms to develop a biomarker of PD based on inertial data acquired with wearable devices. Indeed, a WBS is intended to provide motor rehabilitation & assistance, but also to be used as a clinical decision support tool for the classification of the motor disability level. This system provides vibrotactile feedback to PD patients, so that they can integrate it into their normal physiological gait system, allowing them to overcome their gait difficulties related to the level/degree of the disease. The system is based on a user- centered design, considering the end-user driven, multitasking and less cognitive effort concepts. This manuscript presents all steps taken along this dissertation regarding: the literature review and respective critical analysis; implemented tech-based procedures; validation outcomes complemented with results discussion; and main conclusions and future challenges.Esta dissertação apresenta o trabalho realizado durante o quinto ano do curso Mestrado Integrado em Engenharia Biomédica, em Eletrónica Médica. Este trabalho foi realizado no Biomedical & Bioinspired Robotic Devices Lab (BiRD Lab) no MicroElectroMechanics Center (CMEMS) estabelecido na Universidade do Minho. Para efeitos de validação e aquisição de dados, foi desenvolvida uma colaboração com Clinical Academic Center (2CA), localizado no Hospital de Braga. Os conhecimentos adquiridos no desenvolvimento desta tese de mestrado estão ligados à reabilitação motora e assistência de marcha anormal causada por uma doença neurológica. De facto, esta dissertação tem dois objetivos principais: (1) validar um sistema de biofeedback vestível (WBS) utilizado por doentes com doença de Parkinson (DP); e (2) desenvolver um biomarcador digital de PD baseado em dados cinemáticos adquiridos com o WBS. O primeiro objetivo visa o estudo dos efeitos do biofeedback vibrotáctil para desempenhar um papel de reforço para ajudar os pacientes com PD a mitigar as deficiências associadas à marcha, enquanto o segundo objetivo procura trazer um avanço na utilização de algoritmos front-end para biomarcar PD baseado em dados inerciais adquiridos com o dispositivos vestível. De facto, a partir de um WBS pretende-se fornecer reabilitação motora e assistência, mas também utilizá-lo como ferramenta de apoio à decisão clínica para a classificação do nível de deficiência motora. Este sistema fornece feedback vibrotáctil aos pacientes com PD, para que possam integrá-lo no seu sistema de marcha fisiológica normal, permitindo-lhes ultrapassar as suas dificuldades de marcha relacionadas com o nível/grau da doença. O sistema baseia-se numa conceção centrada no utilizador, considerando o utilizador final, multitarefas e conceitos de esforço menos cognitivo. Portanto, este manuscrito apresenta todos os passos dados ao longo desta dissertação relativamente a: revisão da literatura e respetiva análise crítica; procedimentos de base tecnológica implementados; resultados de validação complementados com discussão de resultados; e principais conclusões e desafios futuros

Analysis of combustion phenomena and knock mitigation techniques for high efficient spark ignition engines through experimental and simulation investigations

Different technologies are being utilized nowadays aiming to boost the fuel efficiency of Spark-Ignition (SI) engines. Two promising technologies which are used to improve the part load efficiency of SI engines are the utilization of downsizing in combination with turbocharging and cylinder deactivation. Both technologies allow a shift of load points towards higher loads and therefore towards more efficient zones of the engine map, while performance is being preserved or even enhanced despite the smaller displacement thanks to high boost levels. However, utilization of both technologies will increase the risk of knock dramatically. Therefore, the abovementioned systems can be coupled with other technologies such as gasoline direct injection, Miller cycle and water injection to mitigate knock at higher load operating conditions. Therefore, the aim of the current work is to investigate, through experimental and numerical analysis, the potential benefits of different knock mitigation techniques and to develop reliable and predictive simulation models aiming to detect root cause of cyclic variations and knock phenomena in downsized turbocharged SI engines. After a brief introduction in Chapter 1, three different typical European downsized turbocharged SI engines have been introduced in Chapter 2, which were used for both experimental and simulation investigations, named as Engine A, which is downsized and turbocharged, Port Fuel Injection (PFI) with fixed valve lift and represents the baseline; Engine B, represents an upgraded version of Engine A, featuring Variable Valve Actuation (VVA), and Engine C which is a direct injection and further downsized engine. Engine B, equipped with MultiAir VVA system, was utilized to evaluate the possible benefits of cylinder deactivation in terms of fuel economy at part load condition, which is discussed in Chapter 3. Since the MultiAir VVA system does not allow exhaust valve deactivation, an innovative strategy was developed, exploiting internal Exhaust Gas Recirculation (iEGR) in the inactive cylinders in order to minimize their pumping losses. However, at higher load operating condition, risk of knock occurrence limits the performance of the engine. Therefore, the possible benefits of different knock mitigation techniques such as Miller Cycle and water injection in terms of fuel consumption were discussed in Chapter 4. Potential benefits of Miller cycle in terms of knock mitigation are evaluated experimentally using Engine B, as shown in Chapter 4.2. After a preliminary investigation, the superior knock mitigation effect of Late Intake Valve Closure (LIVC) with respect to Early Intake Valve Closure (EIVC) strategy was confirmed; therefore, the study was mainly focused on the latter system. It was found out that utilization of LIVC leads up to 20% improvement in the engine indicated fuel conversion efficiency. Afterwards, Engine C, a gasoline direct injection engine, has been utilized in order to understand the potential benefits of water injection for knock mitigation technology coupled with the Miller Cycle, which is discussed in Chapter 4.3. Thanks to water injection potential for knock mitigation, the compression ratio could be increased from 10 to 13, which leads to an impressive efficiency improvement of 4.5%. However, utilization of various advanced knock mitigation techniques in the development of SI engines make the system more complex, which invokes the necessity to develop reliable models to predict knock and to find the optimized configuration of modern high-performance, downsized and turbocharged SI engines. Considering that knock is strictly related to Cycle-to-Cycle Variations (CCV) of in-cylinder pressure, CCV prediction is an important step to predict the risk of abnormal combustion on a cycle by cycle basis. Consequently, in Chapter 5, a procedure has been introduced aiming to predict the mean in-cylinder pressure and to mimic CCV at different operating conditions. First, a 0D turbulent combustion model has been calibrated based on the experimental data including various technologies used for knock mitigation which can impact significantly on the combustion process, such as Long Route EGR and water injection. Afterwards, suitable perturbations are adapted to the mean cycle aiming to mimic CCV. Finally, the model has been coupled with a 0D knock model aiming to predict knock limited spark advance at different operating conditions. Finally, in order to provide a further contribution towards the prediction of CCV, 3D-CFD Large Eddy Simulation (LES) has been carried out in order to better understand the root cause of CCV, presented in Chapter 6. Such analysis could be used to extract the physical perturbation from the 3D-CFD and to use it as an input for the 0D combustion model to predict CCV. The operating condition studied in this work is at 2500 rpm, 16 bar brake mean effective pressure (bmep) and stoichiometric condition. Based on the analysis conducted using LES, it was found out that the variability in combustion can be mainly attributed to both the direction of the velocity flow-field and its magnitude in the region around the spark plug. Furthermore, the effect of velocity field and equivalence ratio on the combustion has been decoupled, confirming that the former has the dominant effect while the latter has minor impact on combustion variability. In conclusion, simulation models using 0D and 3D-CFD tools when calibrated properly based on experimental measurements can be used to support the design and the development of innovative downsized turbocharged SI engines considering the effects of CCV and knock on engine performance parameters

Characterisation of Flame Development with Hydrous and Anhydrous Ethanol Fuels in a Spark-Ignition Engine with Direct Injection and Port Injection Systems

This paper presents a study of the combustion mechanism of hydrous and anhydrous ethanol in comparison to iso-octane and gasoline fuels in a single-cylinder spark-ignition research engine operated at 1000 rpm with 0.5 bar intake plenum pressure. The engine was equipped with optical access and tests were conducted with both Port Fuel Injection (PFI) and Direct Injection (DI) mixture preparation methods; all tests were conducted at stoichiometric conditions. The results showed that all alcohol fuels, both hydrous and anhydrous, burned faster than iso-octane and gasoline for both PFI and DI operation. The rate of combustion and peak cylinder pressure decreased with water content in ethanol for both modes of mixture preparation. Flame growth data were obtained by high-speed chemiluminescence imaging. These showed similar trends to the mass fraction burned curves obtained by in-cylinder heat release analysis for PFI operation; however, the trend with DI was not as consistent as with PFI. OH planar Laser induced fluorescence images were also acquired for identification of the local flame front structure of all tested fuels

PICES Press, Vol. 8, No. 1, January 2000

The state of PICES science - 1999 The status of the Bering Sea: January - July, 1999 The state of the western North Pacific in the second half of 1998 The state of the eastern North Pacific since February 1999 MEQ/WG 8 Practical Workshop Michael M. Mullin - A biography Highlights of Eighth Annual Meeting Mechanism causing the variability of the Japanese sardine population: Achievements of the Bio-Cosmos Project in Japan Climate change, global warming, and the PICES mandate – The need for improved monitoring The new age of China-GLOBEC study GLOBEC activities in Korean waters Aspects of the Global Ocean Observing System (GOOS

Investigating the Neural Basis of Audiovisual Speech Perception with Intracranial Recordings in Humans

Speech is inherently multisensory, containing auditory information from the voice and visual information from the mouth movements of the talker. Hearing the voice is usually sufficient to understand speech, however in noisy environments or when audition is impaired due to aging or disabilities, seeing mouth movements greatly improves speech perception. Although behavioral studies have well established this perceptual benefit, it is still not clear how the brain processes visual information from mouth movements to improve speech perception. To clarify this issue, I studied the neural activity recorded from the brain surfaces of human subjects using intracranial electrodes, a technique known as electrocorticography (ECoG). First, I studied responses to noisy speech in the auditory cortex, specifically in the superior temporal gyrus (STG). Previous studies identified the anterior parts of the STG as unisensory, responding only to auditory stimulus. On the other hand, posterior parts of the STG are known to be multisensory, responding to both auditory and visual stimuli, which makes it a key region for audiovisual speech perception. I examined how these different parts of the STG respond to clear versus noisy speech. I found that noisy speech decreased the amplitude and increased the across-trial variability of the response in the anterior STG. However, possibly due to its multisensory composition, posterior STG was not as sensitive to auditory noise as the anterior STG and responded similarly to clear and noisy speech. I also found that these two response patterns in the STG were separated by a sharp boundary demarcated by the posterior-most portion of the Heschl’s gyrus. Second, I studied responses to silent speech in the visual cortex. Previous studies demonstrated that visual cortex shows response enhancement when the auditory component of speech is noisy or absent, however it was not clear which regions of the visual cortex specifically show this response enhancement and whether this response enhancement is a result of top-down modulation from a higher region. To test this, I first mapped the receptive fields of different regions in the visual cortex and then measured their responses to visual (silent) and audiovisual speech stimuli. I found that visual regions that have central receptive fields show greater response enhancement to visual speech, possibly because these regions receive more visual information from mouth movements. I found similar response enhancement to visual speech in frontal cortex, specifically in the inferior frontal gyrus, premotor and dorsolateral prefrontal cortices, which have been implicated in speech reading in previous studies. I showed that these frontal regions display strong functional connectivity with visual regions that have central receptive fields during speech perception