11,423 research outputs found
Literature review and experimental investigation of heat pipes
Tests on heat pipes determine operational limits, external boundary conditions, noncondensable gas effects, startup behavior, and geometric configurations. Experiment consists of design, construction, and testing of an apparatus for measuring wick properties, conventional heat pipes and coplanar heat pipes
Phonon spectral function for an interacting electron-phonon system
Using exact diagonalzation techniques, we study a model of interacting
electrons and phonons. The spectral width of the phonons is found to be reduced
as the Coulomb interaction U is increased. For a system with two modes per
site, we find a transfer of coupling strength from the upper to the lower mode.
This transfer is reduced as U is increased. These results give a qualitative
explanation of differences between Raman and photoemission estimates of the
electron-phonon coupling constants for A3C60 (A= K, Rb).Comment: 4 pages, RevTeX, 2 eps figur
Compilation and review manual, volume 1
https://egrove.olemiss.edu/aicpa_guides/1392/thumbnail.jp
Compilation and review manual, volume 2
https://egrove.olemiss.edu/aicpa_guides/1393/thumbnail.jp
Open Source Dataset and Machine Learning Techniques for Automatic Recognition of Historical Graffiti
Machine learning techniques are presented for automatic recognition of the
historical letters (XI-XVIII centuries) carved on the stoned walls of St.Sophia
cathedral in Kyiv (Ukraine). A new image dataset of these carved Glagolitic and
Cyrillic letters (CGCL) was assembled and pre-processed for recognition and
prediction by machine learning methods. The dataset consists of more than 4000
images for 34 types of letters. The explanatory data analysis of CGCL and
notMNIST datasets shown that the carved letters can hardly be differentiated by
dimensionality reduction methods, for example, by t-distributed stochastic
neighbor embedding (tSNE) due to the worse letter representation by stone
carving in comparison to hand writing. The multinomial logistic regression
(MLR) and a 2D convolutional neural network (CNN) models were applied. The MLR
model demonstrated the area under curve (AUC) values for receiver operating
characteristic (ROC) are not lower than 0.92 and 0.60 for notMNIST and CGCL,
respectively. The CNN model gave AUC values close to 0.99 for both notMNIST and
CGCL (despite the much smaller size and quality of CGCL in comparison to
notMNIST) under condition of the high lossy data augmentation. CGCL dataset was
published to be available for the data science community as an open source
resource.Comment: 11 pages, 9 figures, accepted for 25th International Conference on
Neural Information Processing (ICONIP 2018), 14-16 December, 2018 (Siem Reap,
Cambodia
Decolonisation of curricula in undergraduate dental education: an exploratory study.
Aims To explore experiences and perceptions of students and staff regarding decolonisation of the curriculum in a dental undergraduate programme.Methods Participants were invited to respond to an online survey on decolonisation of the dental curriculum. The target population included current students on the Bachelor of Dental Surgery and Bachelor of Dental Therapy and Hygiene programmes, as well as dental staff at a university in the South West region of England. The common items for student and staff versions of the survey were focused on six themes: representation; content; peer engagement; assessment; language and communication; and culture. All responses were anonymous. Data on programme, year of study, age, sex and ethnicity were captured on a voluntary basis.Results In total, 34 staff members and 120 students from two different programmes participated in the survey, yielding a response rate of 87.17% for staff and 45.28% for students. A comparison showed that average student responses were lower compared with average staff responses. Of the 24 survey items, 17 showed significantly lower scores reported by minority ethnic (ME) students. ME students were, when compared with white counterparts, less likely to report that their programme included opportunities for group discussions about ethnicity and privilege. Similar comparisons of staff responses did not show significant differences between white and ME staff. Nevertheless, responses by staff and students across the board highlighted the need for further steps to improve the representation of ME groups in the curriculum.Conclusions This study provides useful insights into the perceptions and experiences of students and staff regarding the decolonisation of the dental curriculum in an undergraduate dental programme. Responses by the participants across the board identified several areas which could benefit from better representation of ME groups. Significant differences were noted between staff and student scores and also between white and ME students, indicating the latter group demonstrated more awareness regarding issues of representation. The findings underscore the need to take further steps to decolonise dental curricula
Unstable Disk Galaxies. II. the Origin of Growing and Stationary Modes
I decompose the unstable growing modes of stellar disks to their Fourier
components and present the physical mechanism of instabilities in the context
of resonances. When the equilibrium distribution function is a non-uniform
function of the orbital angular momentum, the capture of stars into the
corotation resonance imbalances the disk angular momentum and triggers growing
bar and spiral modes. The stellar disk can then recover its angular momentum
balance through the response of non-resonant stars. I carry out a complete
analysis of orbital structure corresponding to each Fourier component in the
radial angle, and present a mathematical condition for the occurrence of van
Kampen modes, which constitute a continuous family. I discuss on the
discreteness and allowable pattern speeds of unstable modes and argue that the
mode growth is saturated due to the resonance overlapping mechanism. An
individually growing mode can also be suppressed if the corotation and inner
Lindblad resonances coexist and compete to capture a group of stars. Based on
this mechanism, I show that self-consistent scale-free disks with a sufficient
distribution of non-circular orbits should be stable under perturbations of
angular wavenumber . I also derive a criterion for the stability of
stellar disks against non-axisymmetric excitations.Comment: 15 Pages (emulateapj), 7 Figures, Accepted for Publication in The
Astrophysical Journa
Rokhlin Dimension for Flows
This research was supported by GIF Grant 1137/2011, SFB 878 Groups, Geometry and Actions and ERC Grant No. 267079. Part of the research was conducted at the Fields institute during the 2014 thematic program on abstract harmonic analysis, Banach and operator algebras, and at the MittagâLeffler institute during the 2016 program on Classification of Operator Algebras: Complexity, Rigidity, and Dynamics.Peer reviewedPostprin
Retrieval methods of effective cloud cover from the GOME instrument: an intercomparison
The radiative scattering by clouds leads to errors in the retrieval of column densities and concentration profiles of atmospheric trace gas species from satellites. Moreover, the presence of clouds changes the UV actinic flux and the photo-dissociation rates of various species significantly. The Global Ozone Monitoring Experiment (GOME) instrument on the ERS-2 satellite, principally designed to retrieve trace gases in the atmosphere, is also capable of detecting clouds. Four cloud fraction retrieval methods for GOME data that have been developed are discussed in this paper (the Initial Cloud Fitting Algorithm, the PMD Cloud Recognition Algorithm, the Optical Cloud Recognition Algorithm (an in-house version and the official implementation) and the Fast Retrieval Scheme for Clouds from the Oxygen A-band). Their results of cloud fraction retrieval are compared to each-other and also to synoptic surface observations. It is shown that all studied retrieval methods calculate an effective cloud fraction that is related to a cloud with a high optical thickness. Generally, we found ICFA to produce the lowest cloud fractions, followed by our in-house OCRA implementation, FRESCO, PC2K and finally the official OCRA implementation along four processed tracks (+2%, +10%, +15% and +25% compared to ICFA respectively). Synoptical surface observations gave the highest absolute cloud fraction when compared with individual PMD sub-pixels of roughly the same size
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