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Experimental Investigation on Silica Dust Lofting in the Vacuum Chamber and Predictions of Lunar Dust Heights due to Charging within Micro-Cavities and Surface Electric Field
No full text1 Introduction||2 Lunar Surface Charging Simulations||3 Electrostatic Lunar Dust Transportation||4 Experimental Investigation on Silica Dust Lofting||5 Discussion||6 Conclusions and RecommendationsThere is a soil-like layer above the bedrock of the Moon that is produced by the small meteoroid impacts on the lunar surface, which is also called as the lunar regolith. The size of the regolith particles ranges from several centimeters to submicron size, and the small-scale particles are also referred as the lunar dust, which can be transported by the electrostatic forces above the lunar surface. Electrostatically lofted and/or levitated dust grains were detected while scattering the sunlight above the lunar terminator region, and this physical phenomenon has been called the lunar horizon glow （LHG）. TV cameras of Surveyor missions first monitored the LHG in 1966 and 1968, and the excessive brightness to coronal and zodiacal light （CZL） indicated that the dust population was considerably denser than the levels that can be produced by micrometeorite ejecta on the lunar surface. In addition, all observations of the LHG were under the solar wind plasma, and the lunar surface directly interacts with the charged particles in the absence of a global magnetic field and a dense atmosphere. Even though the solar wind plasma has a lower temperature and higher density than the magnetospheric plasma, enhanced fluxes of charged particles can be observed in some cases such as solar energetic particle events or coronal mass ejections （CMEs）. In this research, the purpose can be described as （1） predicting the maximum height variation of the dust grains above the lunar terminator under various ambient plasma conditions and （2） experimentally investigating the silica dust lofting in the vacuum chamber under the electron beam. Therefore, the equations that are used in the simulations are compared to the experimental results, and the significance of the surface parameters such as the presence of the horizontal electric field and the increased packing density on the electrostatical dust launching are investigated as well. The LHG observations, the lunar dust exosphere measurements, and the previous studies on the lunar dust simulations and experiments are presented in chapter 1. In addition, the simulation method of the lunar surface charging and the results of the surface potential, the electric field and Debye length are discussed for the plasma parameters of the regular solar wind and three selected geoeffective CME events in chapter 2. In chapter 3, the initial separation of the dust particles and the maximum height calculations are presented in detail. The simulation results show that the surface potential is highly variable on the lunar terminator region, and the dust launching rates are significantly controlled by the secondary electron emission and the dust sizes. Even though the micron-sized dust grains are launched from the surface more frequently than the submicron-sized dust particles, their heights are less influenced by the surface electric field in all cases. The simulations are performed for the dust particles with 0.1, 1 and 5 μm radius, and the uncertainty range of the height predictions are represented as well. In chapter 4, the experiments on the silica dust grains are explained in detail. The experiments are performed under 4×10-3 Pa pressure in a general-purpose vacuum chamber. In addition, an electron beam is produced from a cathode ray tube, and the electron current density is measured as approximately 2.87×10-4 Am-2. Different from the previous dust lofting experiments, the initial launching velocities of the grains are detected by the microscopic telescope and the high-speed camera by focusing on the near-surface area above the dust sample. Three different types of experiments are performed on the silica dust grains. First, the dust grains are loaded on the graphite plate without applying additional pressure or external horizontal electric field during the experiment. Therefore, it is called the simple case, and the measurements are compared with the estimated values. Second, the separate dust samples are compressed after loading on to the graphite plate with approximately 781 and 3780 Pa in order to increase the contact surface areas among the dust grains while decreasing the number of the microcavities. Third, the graphite plate is placed between two parallel aluminum plates that are separated by 5 and 12 cm distance and biased to 240 V in both cases. Therefore, it is expected to increase the number of the rolling particles over the surface while increasing the number of the inter-particle collisions. Finally, all of the results are discussed for the simulations and the experiments in chapter 5. First, the dust grains with 5 μm radius reach significantly similar heights with the LHG observations of Surveyor mission in the simulations. Second, the dust grains 0.1 μm in radius are lofted to the heights similar to the Lunokhod-2 astrophotometer observations under the regular solar wind. Third, the laboratory experiments point out that several factors are determinative to estimate the dust lofting such as the contact surface areas between the dust grains, the packing density, the existence of the microcavities, and the inter-particle collisions in the presence of the horizontal electric field. Most of the particles are launched within the estimated range for the simple case. Furthermore, increased packing density reduces the number of the lofted dust grains; however, their vertical launching velocities are increased due to stronger electrostatic potential energy built-up between the dust grains. In addition, strong horizontal electric field contributes to the dust release from the surface by potentially increasing the inter-particle collisions; and the current results suggest lower launching velocities than the previous cases. Finally, the aggregates are lofted as well as the single particles, and some of them separated during the lofting motion. Therefore, the separation of charged dust grains on the flight can be an additional source for the smaller grains. In chapter 6, the conclusions and the recommendations are explained, and the future tasks are determined as the investigation of the correlation between the micrometeorite impact regions and the electrostatic transportation of the dust grains.九州工業大学博士学位論文 学位記番号：工博甲第460号 学位授与年月日：平成30年9月21日平成30年
Experimental Investigation on Silica Dust Lofting in the Vacuum Chamber and Predictions of Lunar Dust Heights due to Charging within Micro-Cavities and Surface Electric Field
Get PDF九州工業大学九州工業大学博士学位論文（要旨）学位記番号：工博甲第460号 学位授与年月日：平成30年9月21日thesi
Experimental Investigation on Silica Dust Lofting in the Vacuum Chamber and Predictions of Lunar Dust Heights due to Charging within Micro-Cavities and Surface Electric Field
No full text九州工業大学博士学位論文（要旨）学位記番号：工博甲第460号 学位授与年月日：平成30年9月21
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
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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