12,948 research outputs found

    System-Level Modelling and Simulation of MEMS-Based Sensors

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    Transistor-Level Synthesis of Pipeline Analog-to-Digital Converters Using a Design-Space Reduction Algorithm

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    A novel transistor-level synthesis procedure for pipeline ADCs is presented. This procedure is able to directly map high-level converter specifications onto transistor sizes and biasing conditions. It is based on the combination of behavioral models for performance evaluation, optimization routines to minimize the power and area consumption of the circuit solution, and an algorithm to efficiently constraint the converter design space. This algorithm precludes the cost of lengthy bottom-up verifications and speeds up the synthesis task. The approach is herein demonstrated via the design of a 0.13 μm CMOS 10 bits@60 MS/s pipeline ADC with energy consumption per conversion of only 0.54 pJ@1 MHz, making it one of the most energy-efficient 10-bit video-rate pipeline ADCs reported to date. The computational cost of this design is of only 25 min of CPU time, and includes the evaluation of 13 different pipeline architectures potentially feasible for the targeted specifications. The optimum design derived from the synthesis procedure has been fine tuned to support PVT variations, laid out together with other auxiliary blocks, and fabricated. The experimental results show a power consumption of 23 [email protected] V and an effective resolution of 9.47-bit@1 MHz. Bearing in mind that no specific power reduction strategy has been applied; the mentioned results confirm the reliability of the proposed approach.Ministerio de Ciencia e Innovación TEC2009-08447Junta de Andalucía TIC-0281

    Framing quality improvement tools and techniques in healthcare: the case of Improvement Leaders' Guides

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    The paper presents a study of how quality improvement tools are framed within healthcare settings.\ud \ud The paper employs an interpretive approach to understand how quality improvement tools and techniques are mobilised and legitimated using a case study of the NHS Modernisation Agency Improvement Leaders’ Guides.\ud \ud Improvement Leaders’ Guides were framed within a service improvement approach encouraging the use of quality improvement tools and techniques within healthcare settings. Their use formed part of enacting tools and techniques across different contexts. Whilst this enactment was believed to support the mobililsation of tools and techniques, the experience also illustrated the challenges in distributing such approaches.\ud \ud The paper provides a contribution to our understanding of framing the 'social act' of quality improvement. Given the ongoing emphasis on quality improvement and the persistent challenges involved, it also provides information for healthcare leaders globally in seeking to develop, implement or modify similar tools and distribute leadership within health and social care settings.\ud \ud \u

    Nanoenergetic Materials for MEMS: A Review

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    New energetic materials (EMs) are the key to great advances in microscale energy-demanding systems as actuation part, igniter, propulsion unit, and power. Nanoscale EMs (nEMs)particularly offer the promise of much higher energy densities, faster rate of energy release, greater stability, and more security sensitivity to unwanted initiation). nEMs could therefore give response to microenergetics challenges. This paper provides a comprehensive review of current research activities in nEMs for microenergetics application. While thermodynamic calculations of flame temperature and reaction enthalpies are tools to choose desirable EMs, they are not sufficient for the choice of good material for microscale application where thermal losses are very penalizing. A strategy to select nEM is therefore proposed based on an analysis of the material diffusivity and heat of reaction. Finally, after a description of the different nEMs synthesis approaches, some guidelines for future investigations are provided

    Distributed Integrated Circuits: An Alternative Approach to High-Frequency Design

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    Distributed integrated circuits are presented as a methodology to design high-frequency communication building blocks. Distributed circuits operate based on multiple parallel signal paths working in synchronization that can be used to enhance the frequency of operation, combine power, and enhance the robustness of the design. These multiple signal paths usually result in strong couplings inside the circuit that necessitate a treatment spanning architecture, circuits, devices, and electromagnetic levels of abstraction

    Temperature compensated tactile sensing using MOSFET with P(VDF-TrFE)/BaTiO3 capacitor as extended gate

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    This work presents Poly(vinylidene fluoride – trifluoroethylene))/Barium Titanate (P(VDF-TrFE)-BT) nanocomposite based touch sensors tightly coupled with MOSFET devices in extended gate configuration. The P(VDF-TrFE)-BT nanocomposite exploits the distinct piezo and pyroelectric properties of P(VDF-TrFE) polymer matrix and BT fillers to suppress the temperature response when force and temperature are varied simultaneously. The reasons for this unique feature have been established through structural and electrical characterization of nanocomposite. The proposed touch sensor was tested over a wide range of force/pressure (0-4N)/(0-364 Pa) and temperature (26-70°C) with almost linear response. The sensitivity towards force/pressure and temperature sensor are 670 mV/N/7.36 mV/Pa and 15.34 mV/°C respectively. With this modified touch sensing capability, the proposed sensors will open new direction for tactile sensing in robotic applications

    Geometric Effects on the Wear of Microfabricated Silicon Journal Bearings

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    This dissertation presents an investigation of geometric effects on the wear of large aspect ratio silicon journal microbearings. The consideration of geometric conformality of rotor and hub as a critical design parameter manifests from the inherent properties of deep reactive ion etching as part of the current MEMS fabrication process employed in this dissertation. The investigation is conducted in two phases, each characterized by novel microbearing designs, fabrication processes, experimental test methodologies, and characterization techniques. The intent of Phase 1 is to focus on the effects of conformality of wear, while the intent of Phase 2 is to focus on the effects of clearance on wear. Manual assembly of rotors and hubs allows a broader range of custom bearing clearances than would otherwise be available from lithographic, pattern transfer, and etching capabilities of current in situ MEMS fabrication technologies. Novel wear indicators, intended to facilitate the rapid quantitative and qualitative determination of wear, are incorporated in the Phase 2 rotor designs. Two particular enabling features of the novel fabrication processes, namely the sprue and float etching methods, are developed in this dissertation. The sprues, patterned using the DRIE mask, hold the rotors in place during the KOH etching process. The float etching technique entails floating the device wafer on top of the KOH etchant bath. The results obtained from using the first apparatus indicate that microbearing performance, as measured by rotor rotational speed and rotor cumulative wear, is strongly dependent on conformality. The results obtained using the second apparatus indicate that microbearing rotor rotational velocity is strongly dependent on radial clearance parameter C0. A dynamic impact model of the bearing system based on classical impulse-momentum relations is formulated in order to assess the effect of clearance on rotor rotational speed. A coefficient of restitution is obtained for silicon-on-silicon surfaces over the range of kinematically allowable radial clearance specifications

    Mega-modeling of complex, distributed, heterogeneous CPS systems

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    Model-Driven Design (MDD) has proven to be a powerful technology to address the development of increasingly complex embedded systems. Beyond complexity itself, challenges come from the need to deal with parallelism and heterogeneity. System design must target different execution platforms with different OSs and HW resources, even bare-metal, support local and distributed systems, and integrate on top of these heterogeneous platforms multiple functional component coming from different sources (developed from scratch, legacy code and third-party code), with different behaviors operating under different models of computation and communication. Additionally, system optimization to improve performance, power consumption, cost, etc. requires analyzing huge lists of possible design solutions. Addressing these challenges require flexible design technologies able to support from a single-source model its architectural mapping to different computing resources, of different kind and in different platforms. Traditional MDD methods and tools typically rely on fixed elements, which makes difficult their integration under this variability. For example, it is unlikely to integrate in the same system legacy code with a third-party component. Usually some re-coding is required to enable such interconnection. This paper proposes a UML/MARTE system modeling methodology able to address the challenges mentioned above by improving flexibility and scalability. This approach is illustrated and demonstrated on a flight management system. The model is flexible enough to be adapted to different architectural solutions with a minimal effort by changing its underlying Model of Computation and Communication (MoCC). Being completely platform independent, from the same model it is possible to explore various solutions on different execution platforms.This work has been partially funded by the EU and the Spanish MICINN through the ECSEL MegaMart and Comp4Drones projects and the TEC2017-86722-C4-3-R PLATINO project
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