1,720,960 research outputs found
Multifunctional sensor nodes in stretchable network for structural health monitoring
No full textA highly expandable and conductive polymer-based substrate for sensor network applications was recently proposed. The concept of the substrate design was to reduce the amount of material that is ultimately integrated in structures, processing time and integration costs. The key of the flexible substrate expandability was to build a high density array of nodes, at the nano/microscale, interconnected by extendible wires. The nodes in the network house the sensors and the electronics while the wires carry the electrical signals. To facilitate the concept development an investigation is performed to add functionalities to the expandable substrate. The main focus is initially devoted to the implementation of sensors such as resistance temperature detectors (RTDs) in the nodes of an expandable substrate and then turns to the investigation of the concept and implementation of a multifunctional expandable sensor network. Conceptually the multifunctional sensor network is an array of functional and expandable cells each controlled by a microcontroller directly built-into the network. The nodes in each cell can host a wide variety of sensors to monitor different parameters (such as temperature, pressure, strain, etc.). In this paper the circuit design, implementation and testing of functional and multifunctional cells is investigated at the node and at the network level. The functional cell includes an array of RTD sensors, while the circuit of the multifunctional cell was designed to include RTDs, strain gages, digital sensors as well as PZTs. These results represent the first step toward the integration of multiple functionalities on an expandable substrate. The capability to build a multifunctional network consisting of numerous nodes on a highly expandable substrate, capable of covering large areas has the potential to be the foundation of the next generation of SHM systems
Microfabricated expandable sensor networks for intelligent sensing materials
No full textStructural health monitoring (SHM) is a technology
striving to enable automated evaluation of the health condition of
structures. The SHM has recently attracted significant attention
in the aerospace and civil infrastructure industries because of its
potential to improve operational efficiency, reduce maintenance
costs, and enhance the structural reliability in a real-time
operation basis. The SHM is developing to include multiple
types of sensors and even onboard processing for diagnostics
and decision making. Advanced multidisciplinary engineering
and manufacturing technologies are being developed enabling
integration of sensors, network hardware, and semiconductors
into structures with minimal parasitic effects. This is precisely the
foundation for developing intelligent structures. This paper highlights
recent developments in microfabricated expandable sensor
networks for the SHM and intelligent structures at Stanford
University. Fabrication and testing of microfabricated ultrasonic
and temperature sensing systems in expandable networks are
discussed. These advances applied to the SHM and intelligent
structures support a paradigm change in design, manufacturing,
and maintenance of structures. Successful implementation of the
SHM will require a close collaborative effort among academia,
government, and industry
Design of planar electrodes for multifunctional piezoelectric sensors
No full textAcoustic ultrasound methods are at the core of many modern structural health monitoring methods and piezoelectric transducers are favored for this purpose due to their simplicity and functionality as both actuators and sensors. However, ongoing efforts to reduce impact on host structures while increasing resolution requires increasing the number of sensors and decreasing their size and weight. This compels us to re-evaluate the design of the transducers, to reduce their size and facilitate their integration into more complex functional systems like those typically used in the semiconductor industry. Numerous electrode designs have been developed over the years; however none are satisfactory for the task at hand. The piezoelectric transducers most commonly used in SHM simply have electrodes that fully cover the top and bottom surfaces; this requires wiring of two electrodes in two different planes which significantly complicates the fabrication process, design and realization, especially when using nanofabrication techniques. Other designs introduce significant signal directionality that may not be desirable in large networks or require excessive wiring which adds complexity and weight to the system. Creating new electrode patterns for the piezoelectric transducers that are planar, omni-directional, and scalable has become necessary. A feasibility study was conducted to develop a new nanofabrication compatible, multifunctional piezoelectric transducer design based on radially alternating, planar electrodes. Efficient integration of temperature sensors is complementary to the system and enables compensation of temperature effects in ultrasonic signals without additional sensors. Planar, radially alternating electrodes provide major advantages of: 1) significantly simplifying fabrication by reducing the number of layers; 2) eliminating out of plane features which eases manufacture using nanofabrication techniques and eliminates failure points; 3) allowing the overall networking and wiring to be thinner and thus less intrusive in a host structure; 4) reduced directionality compared to other designs; and 5) functional similarity to current designs allows for implementation with current SHM hardware and algorithms with minimal modification
Bio-inspired intelligent sensing materials for fly-by-feel autonomous vehicles
No full textStructural health monitoring (SHM) is a technology that provides automated inspection for assessing and evaluating the health condition of structures. Recently SHM has attracted significant attention in the aerospace and civil infrastructure industries because of its potential to improve operational efficiency, reduce maintenance costs, and enhance the structural reliability in a real-time operation basis. SHM is developing to include multiple types of sensors and even onboard processing for diagnostic and decision making. Advanced manufacturing technologies are utilized enabling integration of sensors, network hardware, and processors into structures with minimal parasitic effects. This is precisely the foundation for developing 'intelligent structures'. This presentation will highlight recent progress of SHM technologies toward creating intelligent structures at Stanford University and also focus on technical challenges in three areas: quantification, validation, and implementation. SHM is involved with not only multidisciplinary engineering fields, but also a paradigm change in design, manufacturing, and maintenance of structures. Successful implementation of SHM will require a close collaborative effort among academia, government and industry
Bio-inspired smart skin based on expandable network
No full textMethods for creating an electronic skin with integrated temperature sensors based on highly expandable polyimide substrate have been developed. Stresses and strains due to electronic skin expansion are minimized through unique designs developed using finite element analysis. Through the use of a uniquely patterned polyimide substrate an expansion ratio of 1,000% is achieved and the electrical resistance of wire components is maintained from pre-expansion to full expansion. Platinum resistance temperature detectors and electrodes are integrated directly in the polyimide-based electronic skin through a non-standard micro fabrication process. Real-time distributed temperature measurement has been achieved through this highly expandable electronic skin
Micro-fabricated, expandable temperature sensor network for macro-scale deployment in composite structures
No full textWe have developed methods for creating a highly expandable temperature sensor network for distributed temperature measurement. Stresses and strains due to network expansion are minimized through finite element analysis. Through the use of a uniquely patterned polyimide substrate and wire pattern an expansion ratio of 1,000% is achieved and the electrical resistance of components is maintained from pre-expansion to full expansion. Platinum resistance temperature detectors and electrodes are integrated directly in the polyimide-based network through a non-standard micro fabrication process. Calibration and interpolation algorithms have been developed for temperature measurement. Real-time distributed temperature measurement has been achieved through this sensor network, and it has shown great potential to be integrated into composites
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Screen Printed Piezoceramic Actuators/Sensors Microfabricated on Organic Films and Stretchable Networks
No full textIntegration, deployment, and installation of SHM network hardware remains a
significant challenge inhibiting fielding of SHM systems. SHM systems typically
consist of sparse arrays of numerous transducers and large scale wiring in order to
span target structures. These systems are currently assembled, one piece at a time, and
installed by hand leading to significant labor costs. Because of the size and weight of
the components they adversely affect and are parasitic to the host structure. This is
particularly detrimental to high performance aerospace structures.
Microfabricated stretchable sensor networks have received a lot of interest recently
and have the potential to overcome these issues. These systems leverage nonstandard
C-MOS processing techniques to mass fabricate micro and nano-scale device in a
single integrated system. The complete system of devices with interconnecting wires
is then expanded to span an area orders of magnitude greater than the original
fabrication area. The result is a complete integrated network of numerous of small
scale devices that will have minimal parasitic effects on a host structure and can be
installed monolithically over large areas. However, fabrication limitations previously
restricted the types of systems that could be created on these networks to passive,
resistive devices like resistive temperature sensors and wiring.
This paper presents an overview of recent research that has enabled the mass
fabrication and deployment of screen printed piezoceramic transducers on organic
stretchable network substrates including fabrication, deployment, and testing.
Ultrasonic signals typical to SHM were actuated and detected as were strain waves
from impacts. Results indicate that the screen printed piezoceramic transducers
released and deployed on an organic substrate produce similar signal amplitudes as a
baseline sample as printed on a silicon substrate.
This work enables the mass fabrication and deployment of large arrays of
microfabricated sensors, applicable to ultrasonic damage detection systems, on
stretchable networks. This has the potential to revolutionize structural health
monitoring by simplifying fabrication, installation and reducing the parasitic effects on
host structures like added weight or volume
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