1,720,973 research outputs found
Emerging carbon-based nanosensor devices: structures, functions and applications
No full textBionanosensors and nanosensors have been devised in recent years with the use of various materials including carbon-based nanomaterials, for applications in diagnostics, environmental science and microelectronics. Carbon-based materials are critical for sensing applications, as they have physical and electronic properties which facilitate the detection of substances in solutions, gaseous compounds and pollutants through their conductive properties and resonance-frequency transmission capacities. In this review, a series of recent studies of carbon nanotubes (CNTs) based nanosensors and optical systems are reported, with emphasis on biochemical, chemical and environmental detection. This study also encompasses a background and description of the various properties of the nanomaterials, and the operation mechanism of the manufactured nanosensors. The use of computational chemistry is applied in describing the electronic properties and molecular events of the included nanomaterials during operation. This review shows that resonance-based sensing technologies reach detection limits for gases, such as ammonia down to 10(-24) level. The study also shows that the properties of the carbon nanomaterials give them unique features that are critical for designing new sensors based on electrocatalysis and other reactive detection mechanisms. Several research fields can benefit from the described emerging technologies, such as areas of research in environmental monitoring, rapid-on site diagnostics, in situ analyses, and blood and urine sampling in medical and sport industry. Carbon nanomaterials are critical for the operational sensitivity of nanosensors. Considering the low cost of fabrication, carbon nanomaterials can represent an essential step in the manufacturing of tomorrow's commercial sensors
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Integration of Antenna Array and Self-Switching Graphene Diode for Detection at 28 GHz
Full text linkMicrowave Detection Using 2-Atom-Thick Heterojunction Diodes
No full textIn this paper, a two-dimensional material-based diode for microwave detection at 2.49 GHz with photo detector capabilities is presented. The diode consists of a molybdenum disulphide monolayer/graphene monolayer heterojunction transferred onto a silicon/silicon dioxide substrate, and patterned by means of nanolithography techniques to obtain a geometrical self-switching diode. The interaction between the two monolayers gives rise to a double-stage device, which behaves as a back-to-back diode in the [-3, +3] V range, and as a tunnel diode when exceeding +10 V. The heterojunction can be reproduced on large scale due to its CMOS compatibility; it does not need any particular doping process thanks to its geometrical nature and can be used efficiently as microwave detector up to 10 GHz, with the best performance around the ISM 2.45 GHz band. Last, a rigorous equivalent circuit model based on the Foster's method is provided, which relies on the measured scattering parameters at high frequencies. This way, the device can be exploited in circuit-based numerical tools for the desian of complex microwave front-ends
Compact membrane-supported band-pass filter for millimetre-wave applications
No full textThe design and testing of a new configuration of micromachined bandpass filter for millimetre-wave applications is presented. The design is based on image parameter representation of identical symmetrical cells connected in cascade. The measurements demonstrate transmission losses lower than 1 dB and very good agreement with the electromagnetic simulations
Graphene diodes for 5G energy harvesting: Design, simulations and experiments
No full textIn this paper, we propose a rectenna based on a graphene self-switching diode for Ka band applications in view of the upcoming 5G and internet-of-things telecommunication systems. A 4-element patch antenna array has been designed, simulated, and fabricated using a high-resistivity silicon/silicon dioxide/graphene multi-layer and tested on-wafer. By using analytical formulas to optimize the number of parallel channels for the diode, we have achieved highly improved DC current values (average value of ±2mA at ±3V). The diode has been integrated with the array in coplanar waveguide technology using a matching open stub, in order to maximize the array-to-diode power transfer. The rectenna has then been measured by using a 28GHz RF source: at 0V DC bias, a maximum DC voltage VDC of 2.4mV has been obtained, with a maximum DC current IDC of 1.2μA and a maximum DC power PDC of 2.9nW; when applying a small DC bias (1.2V), VDC reaches 71mV, IDC=35.5μA and PDC=2.5μW
27-GHz Silicon-Integrated Rectenna Based on Novel Multilayer Substrate
No full textThis paper presents the design, fabrication, and characterization of a multi-layer 27-GHz rectenna integrated entirely on silicon, aimed at achieving full CMOS compatibility for energy harvesting applications. The device is fabricated on a high-resistivity silicon (HRSi) substrate, which is selectively etched to create a low-permittivity region for the antenna while maintaining a high-permittivity full substrate for the rectifier circuit. The rectenna, operating in the millimeter-wave (mmWave) band, features a compact single-cell design with dimensions of 13 x 13 mm2 only, making it suitable for integrating IoT devices to support energy autonomy. The rectenna utilizes a GaAs diode rectifier and achieves a measured maximum RF-to-DC power conversion efficiency (PCE) of about 49% at an input power of 12 dBm. This work demonstrates the potential of HRSi-based, silicon-integrated rectennas for efficient energy harvesting in IoT applications. The proposed multilayer fabrication technology allows the realization of high-radiation-efficiency directive antennas and RF circuits directly onto the CMOS substrate, without increasing the overall size of the circuit and maintaining the structural integrity of the device
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