1,721,005 research outputs found
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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Design and Characterization of Circuits for Next-Generation Wireless Communications Systems
Get PDFDemand for wireless data transfer has been increasing rapidly with the rise of smart devices and mobile video streaming. With dozens of wireless applications currently in use and only a finite bandwidth to work with, engineers are challenged to both expand the upward frequency limit of high-performance, high-efficiency wireless systems and to increase the spectral efficiency of the frequency bands already in use. The development of deep sub-um silicon-on-insulator transistor technology and powerful computer-aided circuit designing tools have allowed us to create more affordable silicon-based phased array ICs at frequencies previously achievable by only military applications. The 5th generation of mobile systems (5G) is now expected to use this type of IC to offer increased wireless data capacity in densely-populated areas using mm-wave frequencies. Demand for wireless data is only expected to continue rising, particularly as new IoT applications such as autonomous vehicles become commercially viable.The work presented in this dissertation addresses both the need for expanding the usable frequency spectrum and the need to increase spectral efficiency in available bands. It includes a design for an analog beamforming matrix for a spatially multiplexed phased array receiver in silicon SOI technology, low-power high-linearity w-band amplifiers in InP HBT technology, and ultra-wideband mm-wave power amplifiers in InP HBT technology. Spatially multiplexed phased array transceivers have the potential to greatly increase the spectral efficiency of mm-wave frequency bands by re-using frequency spectrum for many data channels. This type of system can be used to create short-range high-capacity line-of-sight wireless backhaul for crowded city squares or event venues. Mm-wave power amplifiers and high-linearity amplifiers in new 130 nm InP HBT technology represent an IC performance boost which pushes the frequency limits of feasible power-efficient wireless systems. The measured power amplifier ICs produce output power of larger than 16.5 dBm at the 3-dB gain compression condition from 50 GHz to 100 GHz, and a small signal gain of 15 dB over a 90 GHz 3-dB bandwidth. The peak power-added efficiency (PAE) is larger than 8% over that same frequency range. At 90 GHz, the ICs produce 22 dBm of saturated output power and 14.7% PAE. The measured high-linearity amplifier ICs demonstrate an output-referred 3rd order intercept (OIP3) of 22 dBm, a gain of 6.4 dB, and a noise figure below 7 dB at 100 GHz. New designs for an analog MIMO beamforming matrix IC, a 100-165 GHz power amplifier, and an improved w-band high-linearity amplifier are also outlined in this dissertation
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A 238 GHz, 0.5 W, 2.3 mm2 InP HBT Power Amplifier with Cascade Topology and 4:1 Series Power Combining Technique
Get PDFThis work demonstrates the design of a MMIC solid state class-A power amplifier in 250nm InP HBT technology achieving 0.5W saturated output power at 238 GHz at compressed gain of 14dB and power added efficiency of 10%. The 3dB bandwidth is 230 GHz to 242GHz. The power amplifier uses 4:1 travelling wave combiner to combine the output power of 8 power cells. Each power cell is a 3-stage cascaded amplifier with 2 common-base gain stage and 1 common emitter power stage
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III-V Ultra-Thin-Body InGaAs/InAs MOSFETs for Low Standby Power Logic Applications
Get PDFAs device scaling continues to sub-10-nm regime, III-V InGaAs/InAs metal-oxide-semiconductor field-effect transistors (MOSFETs) are promising candidatesfor replacing Si-based MOSFETs for future very-large-scale integration (VLSI)logic applications. III-V InGaAs materials have low electron effective mass andhigh electron velocity, allowing higher on-state current at lower VDD and reducingthe switching power consumption. However, III-V InGaAs materials have a nar-rower band gap and higher permittivity, leading to large band-to-band tunneling(BTBT) leakage or gate-induced drain leakage (GIDL) at the drain end of thechannel, and large subthreshold leakage due to worse electrostatic integrity. Toutilize III-V MOSFETs in future logic circuits, III-V MOSFETs must have highon-state performance over Si MOSFETs as well as very low leakage current andlow standby power consumption. In this dissertation, we will report InGaAs/InAsultra-thin-body MOSFETs. Three techniques for reducing the leakage currents inInGaAs/InAs MOSFETs are reported as described below.1) Wide band-gap barriers: We developed AlAs0.44Sb0.56 barriers lattice-matchto InP by molecular beam epitaxy (MBE), and studied the electron transportin In0.53Ga0.47As/AlAs0.44Sb0.56 heterostructures. The InGaAs channel MOS-FETs using AlAs0.44Sb0.56 bottom barriers or p-doped In0.52Al0.48As barriers were demonstrated, showing significant suppression on the back barrier leakage.2) Ultra-thin channels: We investigated the electron transport in InGaAs andInAs ultra-thin quantum wells and ultra-thin body MOSFETs (tch∼2-4 nm).For high performance logic, InAs channels enable higher on-state current, whilefor low power logic, InGaAs channels allow lower BTBT leakage current.3) Source/Drain engineering: We developed raised InGaAs and recessed InPsource/drain spacers. The raised InGaAs source/drain spacers improve electro-statics, reducing subthreshold leakage, and smooth the electric field near drain,reducing BTBT leakage. With further replacement of raised InGaAs spacers byrecessed, doping-graded InP spacers at high field regions, BTBT leakage can bereduced ∼100:1.Using the above-mentioned techniques, record high performance InAs MOS-FETs with a 2.7 nm InAs channel and a ZrO2 gate dielectric were demonstratedwith Ion = 500 µA/µm at Ioff = 100 nA/µm and VDS =0.5 V, showing the higheston-state performance among all the III-V MOSFETs and comparable performanceto 22 nm Si FinFETs. Record low leakage InGaAs MOSFETs with recessed InPsource/drain spacers were also demonstrated with minimum Ioff = 60 pA/µm at30 nm-Lg , and Ion = 150 µA/µm at Ioff = 1 nA/µm and VDS =0.5 V. This re-cessed InP source/drain spacer technique improves device scalability and enablesIII-V MOSFETs for low standby power logic applications. Furthermore, ultra-thin InAs channel MOSFETs were fabricated on Si substrates, exhibiting highyield and high transconductance gm ∼2.0 mS/µm at 20 nm-Lg and VDS =0.5 V.With further scaling of gate lengths, a 12 nm-Lg III-V MOSFET has shown max-imum Ion/Ioff ratio ∼8.3×10 5 , confirming that III-V MOSFETs are scalable tosub-10-nm technology nodes
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ICs, Modules, and Links for 200–300GHz Wireless Communications
Get PDFThere is an increasing demand for high data-rate wireless communications in endpoint and backhaul links. In this research, we develop next-generation wireless communication systems (200–300 GHz), as millimeter frequencies provide vast amounts of available bandwidth, and shorter wavelengths permit many elements in physically compact arrays. This thesis focuses on building the necessary hardware and infrastructure for such systems.First, we investigate two important building blocks: low noise amplifiers (LNAs) and frequency multipliers. We present a comprehensive study on multi-stage LNA design based on low total (cascaded) noise figure, i.e., noise measure (NM). 200 GHz LNAs in common-base (CB) and common-emitter (CE) topologies were presented with record noise figure among HBT technologies: 7.4±0.7 dB over 196–216 GHz (CB) and 7.2±0.4 dB over 196–216 GHz (CE). 280 GHz frequency multipliers (8:1 and 16:1) are presented with record spectral purity. The 8:1 frequency multiplier generates −0.6dBm output power and has a 3-dB bandwidth of 48 GHz. Spurious harmonics are suppressed by more than 28 dBc over the 3-dB bandwidth. The 16:1 frequency multiplier generates −0.6dBm output power and has a 3-dB bandwidth of 44 GHz. Spurious harmonics are suppressed by more than 26 dBc over the 3-dB bandwidth.Next, 200 and 280 GHz broadband transceivers in Teledyne 250nm InP HBT technology are presented. The 280 GHz transmitter IC has a peak conversion gain of 21.6 dB with 36 GHz of 6-dB modulation bandwidth, and dissipates 1535mW. The measured saturated output power is 14.1dBm at 272 GHz. The 280 GHz receiver IC has a peak conversion gain of 22 dB with 34.5 GHz of 6-dB modulation bandwidth, and dissipates 455mW. The measured double sideband (DSB) noise figure is 10.8 dB at 281.5 GHz. These are the record output power and noise figure reported at and around 280 GHz. The 200 GHz transmitter IC has a record output power (15.3–16.5 dBm) and efficiency (2.71–3.57%) over 195–200 GHz. The 200 GHz receiver IC has a record DSB noise figure (7.7–9.3 dB) over 200–212 GHz.Finally, we demonstrate packaged 200 GHz 1-channel transmitter and receiver modules with series-fed microstrip patch antennas on glass. The packaged transmitter module has effective isotropic radiated power (EIRP) of 21.6dBm with 20 GHz 3-dB modulation bandwidth and 62-degree E-plane and H-plane 3-dB beamwidth. The packaged receiver module has a 14 GHz 3-dB modulation bandwidth and 62-degree E-plane and H-plane 3-dB beamwidth. Modules can support a wide range of modulation schemes (i.e., QPSK, 16QAM). The link measurements at 7.15 meters showed 13.4% error vector magnitude (EVM) during 32Gb/s, 16 quadratic-amplitude modulation (QAM) transmission. The integrated transmitter and receiver modules can be used for a broad range of applications, including wireless backhaul, imaging, and radar applications
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