1,721,205 research outputs found
Reversed bias Pt/nanostructured ZnO Schottky diode with enhanced electric field for hydrogen sensing
No full textIn this paper, the effect of electric field enhancement on Pt/nanostructured ZnO Schottky diode based hydrogen sensors under reverse bias condition has been investigated. Current–voltage characteristics of these diodes have been studied at temperatures from 25 to 620◦C and their free carrier density con- centration was estimated by exposing the sensors to hydrogen gas. The experimental results show a significantly lower breakdown voltage in reversed bias current–voltage characteristics than the conven- tional Schottky diodes and also greater lateral voltage shift in reverse bias operation than the forward bias. This can be ascribed to the increased localized electric fields emanating from the sharp edges and corners of the nanostructured morphologies. At 620◦C, voltage shifts of 114 and 325mV for 0.06% and 1% hydrogen have been recorded from dynamic response under the reverse bias condition
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
Pt/SnO2 nanowires/SiC based hydrogen gas sensors
No full textPt/SnO2 nanowires/SiC based metal-oxidesemiconductor\ud
(MOS) devices were fabricated and tested for their gas sensitivity towards hydrogen. Tin oxide (SnO2)\ud
nanowires were grown on SiC substrates by the vapour liquid\ud
solid growth process. The material properties of the SnO2\ud
nanowires such as its formation and dimensions were analyzed\ud
using scanning electron microscopy (SEM). The currentvoltage\ud
(I-V) characteristics at different hydrogen\ud
concentrations are presented. The effective change in the\ud
barrier height for 0.06 and 1% hydrogen were found to be\ud
20.78 and 131.59 meV, respectively. A voltage shift of 310 mV at 530°C for 1% hydrogen was measured
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Electrical Control, Read-out and Initialization of Single Electron Spins
No full textAn electron, in addition to its electric charge, possesses a small magnetic moment, called spin. The spin of an electron can point parallel (spin-up) or antiparallel (spin-down) to the magnetic field. These two states are analogous to zero and one of the logical bit in current digital electronic devices. However, according to the laws of quantum mechanics, the spin of an electron can be both up and down at the same time. Exploiting the spin degree of freedom has opened up a new era in the field of semiconductor electronics which may revolution current electronic devices. The electron spin could act as a quantum bit (qubit) in a futuristic quantum computer. With recent advances in nanotechnology, it is now feasible to create tiny electrostatic islands called quantum dots to controllably trap single electrons and explore their spin properties. This thesis presents experiments aiming at combining the indispensable ingredients of a quantum computer: read-out, control and initialization of single electron spins. It also seeks a deeper understanding of the properties of single electron spins in GaAs quantum dots. The measurements are performed on a double quantum dot which is defined in a two dimensional electron gas (2DEG) of GaAs/AlGaAs heterostructure. Applying negative voltages to the metallic gates on top of the heterostructure depletes the electron gas beneath them and thereby creates the quantum dots. By applying more and more negative voltages on the gates, we remove the electrons from the quantum dots one by one, reaching the single electron regime. Applying a magnetic field creates an energy difference between the spin states and defines the two states of the qubit. The device used in the experiments is cooled down to about 100\,mK where quantum mechanical behaviour is observed. In the first part of the thesis, we have realized independent single-shot read-out of two electron spins in our double quantum dot. The capability to measure the quantum state of multiple qubits individually and in a single-shot manner is essential for efficient characterization of quantum information protocols. Additionally, in a quantum computer, the result of computation needs to be read-out. The presented read-out method is all-electrical and the cross talk between two measurements is negligible. The read-out fidelities are about 86\% on average. This allows us to directly probe the anticorrelations between two spins prepared in a singlet state, an entangled two-spin state. The independent single-shot read-out of two electron spins also enabled us to fully characterize the operation of the two-qubit exchange gate, an important operation in a spin-based quantum computer, on a complete set of basis states. We observe a deviation of the two qubit gate from the pure exchange which we later account for. In the next step we combine the single-shot read-out with electrical manipulation of single electrons. Manipulation of single electrons can be done using so-called electric dipole spin resonance (EDSR) where the electric field couples to the spin degree of freedom. In quantum dots, EDSR can be mediated in several ways such as spin-orbit interaction, where the spin of an electron is coupled to its momentum, and the hyperfine interaction, where the electron spin is coupled to the nuclear spins of three isotopes of GaAs. We show that at high magnetic fields there is a clearly observable shift in the resonance condition between spin-orbit mediated and hyperfine-mediated EDSR. In these experiments, we introduce adiabatic rapid passage using fast frequency chirps as a robust technique to invert the electron spin in quantum dots. Furthermore, by modeling the EDSR response, we get a deeper understanding of the interplay between spin-orbit and hyperfine mediated driving. These findings could be exploited for enhanced control of dynamic nuclear polarization processes, including selective control of the three nuclear spin species. The focus of the penultimate part of the thesis is to combine single-shot read-out with fast initialization of single electron spins. The capability of fast qubit initialization to a well-known state is crucial for the implementation of the quantum computer for two reasons. First, at the start of the computation qubits need to be initialized. Second, for the error correction schemes, a continuous source of initialized qubits is required where the speed of initialization needs to be faster than the relevant gate operations. In the experiments described in the thesis, we demonstrate electrically controlled fast initialization of a single-spin qubit making use of ``hot spots'' where spin relaxation is enhanced by more than three orders of magnitude. These hot spots occur when the spin splitting matches the quantized orbital level spacing. Voltage pulses applied to the gates defining the double quantum dot allow us to rapidly move to one of the hot spots. There, spin-orbit and hyperfine interactions efficiently mix the spin and orbital excited states and spin-conserving orbital relaxation syphons the entire population to the ground state, thus achieving s-scale initialization. In the last part of the thesis, all-electrical independent addressing of a single-electron spins is presented. In those measurements we perform single electron manipulation using EDSR. Surprisingly, we observe well-separated Zeeman splittings in neighbouring quantum dots. This finding provides a direct route to selective addressing of spins in quantum dot arrays without the need for micro-fabricated magnets. The observed splitting also accounts for the deviation of the two-qubit gate from pure exchange, as observed in the first part of the thesis. All results presented in this thesis contribute to meeting the fundamental requirements for physical implementation of a spin-based quantum computer.Kavli Institute of NanoscienceApplied Science
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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