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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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A Theoretical and Numerical Study of Nanoscale Heat Transfer
Get PDFIn order to continue the progress of nanotechnology in producing effective and efficient mechanical, electrical, and optical nanostructure devices, the physics of the devices in micro and nanoscale need to be understood and accurately modeled. For instance, the demand for high areal density data storage devices such as hard disk drives (HDDs) has led to heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) technologies. These technologies require layered nanostructures with thicknesses of a few nanometers and a high temperature difference across the layers. These technologies introduce thermo-mechanical design challenges since the nanoscale heat transfer mechanics do not follow the classical heat transfer theories. In this work, the mechanisms of heat transfer in the nanoscale are studied.A typical nanostructure is composed of several conductive and thin insulating layers (a few microns to a few nanometers) with a temperature difference between the layers where some insulating layers maintain the temperature gradient in such small spacings. In these structures, the dominant heat transfer mechanisms are radiation due to high temperature gradient and phonon conduction due to thin conductive layers. First, we review the fundamentals of electromagnetism and lattice vibrations and derive the classical heat transfer theories, and discuss the assumptions that lead to them. We show that the classical theories do not consider the wave nature of the heat transfer mechanisms (heat carriers) and are derived based on equilibrium thermodynamics. These assumptions make the obtained results inapplicable to our problems. Next, we study the recent theories and methods used to solve steady-state nanoscale heat transfer problems, and we further develop more accurate models of calculations.In this work, we study the mechanisms of heat transfer in nanostructures and present simulations for the thermal analysis of various multilayered structures. We show how the radiative and phonon conduction heat fluxes across a nanoscale vacuum gap vary as a function of the gap spacing, and focus on the problems with large heat flux across nanostructures. Next, we consider the effect of the interference of the heat carriers, due to their wave nature, on radiation and phonon conduction. The heat transfer coefficient (HTC) for various structures used in the current HDD technology is characterized by different temperature differences and conditions. The presented results are also used in collaboration with other researchers in simulations of HDI of HAMR HDDs.Next, the presented algorithms are used to simulate radiation in multilayered structures with absorbing materials, where the speed of propagation for absorbing materials is based on a recent model in literature that predicts the depth-dependent speed of electromagnet waves inside materials. We also present a novel way to describe the distribution of the thermal emission inside a multilayered structure using one distribution function instead of using multiple distributions for layers with different temperatures, which we call the unified field. This model is more accurate than the models in the preceding chapters at predicting the HTC for the phonon conduction in materials under some conditions
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Thermal Transport, Thermal Protrusion, and Thermally-Induced Material Transfer in the Head-Disk Interface of Heat-Assisted Magnetic Recording
Get PDFAs data generated worldwide are growing explosively, it is crucial to increase the areal density of traditional storage devices to satisfy the requirements. Conventional hard disk drive (HDD) technology, perpendicular magnetic recording (PMR), has reached the superparamagnetic limit of ~ 1 Tb/in2. To realize the areal density over 1 Tb/in2, the size of the media bits must be further decreased to tens of nanometers, which requires high coercivity magnetic media. The high coercivity can avoid superparamagnetism and thus store data safely at the small bit size under room temperature, but it makes data writing challenging. To assist the writing process, energy is input to the media to lower its coercivity temporarily. Current technologies such as heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) utilize two different methods to lower the coercivity. HAMR integrates a laser to locally heat the media to its Curie temperature (400–500 °C), while MAMR uses a spin torque oscillator to induce ferromagnetic resonance in the media grains. In the HAMR head-disk interface (HDI), a recording head flies over a rotating disk with a relative velocity of 5–40 m/s and an initial spacing of 10–15 nm controlled by an air bearing. Then, the spacing is reduced by energizing a joule heater inside the head. The heater generates a protrusion on the head surface to lower the initial spacing to 1–2 nm so that data reading/writing can be performed using the read/write transducers in the head. The head is also integrated with a laser diode, a waveguide (WG) and a near-field transducer (NFT) for laser delivery. The laser beam is launched from the recording head and is focused on the recording disk to locally heat the disk (400–500 °C), which is even hotter than the head temperature (150–250 °C). Therefore, the head-disk interface of HAMR is a system that combines nanoscale spacing (< 15 nm), high temperatures (head ∼ 150–250 °C, disk ∼ 400–500 °C), steep thermal gradient (∼ 10 K/nm), and a high-speed sliding condition (5–40 m/s). Furthermore, the introduction of the laser affects thermal transport and thermal protrusion, and causes thermally-induced material transfer in the interface, which needs to be investigated both for fundamental understanding and for practical applications such as HAMR and other microelectronics devices.To study the thermal transport across a closing gap between the head and the disk, we conducted static touchdown experiments using a custom-made setup where the disk is not rotating to exclude the air cooling effect. The head temperature rise was measured as a function of the heater power under various conditions such as different substrate materials, relative humidity and laser on/off. An enhanced thermal transport due to phonon heat conduction is observed for the gap < ∼ 2 nm. The thermal transport across the gap becomes stronger when a better thermal conductor is used as the substrate or when the humidity is higher than 75%. With the presence of the laser, the head undergoes a joule heat dissipation inside the head and a back-heating from the hot spot on the substrate. In the HAMR operations, the laser delivery involves energy loss, which leads to a localized angstrom-level laser-induced protrusion (LIP) and a fly height change (FHC). They need to be considered and compensated in the spacing control. Flying touchdown experiments were performed to evaluate their overall effect on the spacing change, then they were separated using their different time constants in microseconds and milliseconds. In addition, HAMR operations may utilize two heaters in the head. It is demonstrated that the head protrusion shape can be modulated by use of the dual heaters, and that the touchdown area can be controlled precisely. During the laser exposure under HAMR operations, material transfer also happens due to the high level of thermal transport. The temperature of the hot spot on the disk is much higher than the lubricant evaporation temperature, so the lubricant is evaporated from the disk and then condenses on the head surface. The material accumulation on the head surface, also known as smear, is a challenging reliability issue for HAMR. We experimentally investigate the smear formation mechanism and propose two smear mitigation strategies. The results show that the smear forms when the lubricant evaporation occurs for a certain time, and that the smear can be mitigated by a mechanical burnishing approach or a thermal approach. Next, we report a thermal mapping technique using a phase change material Ge2Sb2Te5. Ge2Sb2Te5 undergoes a crystalline transition at 149 °C with changes in its density and optical reflectivity. By use of these changes, we can map surface temperatures from nanoscale to microscale with minimal calibration, which is demonstrated using a recording head. Finally, we propose a near-field thermal transport based scheme for lubricant thickness measurement. The thermal effect of the lubricant is investigated when the head approaches the disk in the flying touchdown experiments, which is then used to determine the lubricant thickness. Most previous lubricant measurements require an ex-situ tool such as optical surface analyzer (OSA), but the proposed scheme is an in-situ method with a sub-angstrom resolution and a faster response time. Using the scheme, we performed in-situ measurements of the lubricant depletion and reflow dynamics under HAMR operations
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