2,588 research outputs found
A Modified Arnoldi Iteration for Transition Probability Matrices of Reversible Markov Chains.
M.S. Thesis. University of Hawaiʻi at Mānoa 2018
Role of structural relaxations and vibrational excitations in the high-frequency dynamics of liquids and glasses
We present theoretical investigation on the high-frequency collective
dynamics in liquids and glasses at microscopic length scales and terahertz
frequency region based on the mode-coupling theory for ideal liquid-glass
transition. We focus on recently investigated issues from
inelastic-X-ray-scattering and computer-simulation studies for dynamic
structure factors and longitudinal and transversal current spectra: the
anomalous dispersion of the high-frequency sound velocity and the nature of the
low-frequency excitation called the boson peak. It will be discussed how the
sound mode interferes with other low-lying modes present in the system.
Thereby, we provide a systematic explanation of the anomalous sound-velocity
dispersion in systems -- ranging from high temperature liquid down to deep
inside the glass state -- in terms of the contributions from the
structural-relaxation processes and from vibrational excitations called the
anomalous-oscillation peak (AOP). A possibility of observing negative
dispersion -- the {\em decrease} of the sound velocity upon increase of the
wave number -- is argued when the sound-velocity dispersion is dominated by the
contribution from the vibrational dynamics. We also show that the low-frequency
excitation, observable in both of the glass-state longitudinal and transversal
current spectra at the same resonance frequency, is the manifestation of the
AOP. As a consequence of the presence of the AOP in the transversal current
spectra, it is predicted that the transversal sound velocity also exhibits the
anomalous dispersion. These results of the theory are demonstrated for a model
of the Lennard-Jones system.Comment: 25 pages, 22 figure
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Air quality evaluation of London Paddington train station
Enclosed railway stations hosting diesel trains are at risk of reduced air quality as a result of exhaust emissions that may endanger passengers and workers. Air quality measurements were conducted inside London Paddington Station, a semi-enclosed railway station where 70% of trains are powered by diesel engines. Particulate matter (PM2.5) mass was measured at five station locations. PM size, PM number, oxides of nitrogen (NOx), and sulfur dioxide (SO2) were measured at two station locations. Paddington Station’s hourly mean PM2.5 mass concentrations averaged 16 μg/m3 [min 2, max 68]. Paddington Station’s hourly mean NO2 concentrations averaged 73 ppb [49, 120] and SO2 concentrations averaged 25 ppb [15, 37]. While UK train stations are not required to comply with air quality standards, there were five instances where the hourly mean NO2 concentrations exceeded the EU hourly mean limits (106 ppb) for outdoor air quality. PM2.5, SO2, and NO2 concentrations were compared against Marylebone, a busy London roadside 1.5 km from the station. The comparisons indicated that train station air quality was more polluted than the nearby roadside. PM2.5 for at least one measurement location within Paddington Station was shown to be statistically higher (P-value < 0.05) than Marylebone on 3 out of 4 days. Measured NO2 within Paddington Station was statistically higher than Marylebone on 4 out of 5 days. Measured SO2 within Paddington Station was statistically higher than Marylebone on all 3 days.We thank the Engineering and Physical Sciences Research Council (EP/F034350/1) for funding the Energy Efficient Cities Initiative and the Schiff Foundation for doctoral studentship funding.This is the final version of the article. It first appeared from IOP via http://dx.doi.org/10.1088/1748-9326/10/9/09401
Computationally Modeling Narratives of Social Group Membership with the Chimeria System
Narratives are often used to form, convey, and reinforce memberships in social groups. Our system, called Chimeria, implements a model of social group membership. Here, we report upon the Chimeria Social Narrative Interface (Chimeria-SN), a component of the Chimeria system, that conveys this model to users through narrative. This component is grounded in a sociolinguistics model of conversational narrative, with some adaptations and extensions in order for it to be applied to an interactive social networking domain. One eventual goal of this work is to be able to extrapolate social group membership by analyzing narratives in social networks; this paper deals with the inverse of that problem, namely, synthesizing narratives from a model of social group membership dynamics
Análise do art. 170º do Código Penal Português e do art. 164º A do Código Penal de Macau : o que a incriminação de importunação sexual realmente serve?
Modeling player self-representation in multiplayer online games using social network data
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 101-105).Game players express values related to self-expression through various means such as avatar customization, gameplay style, and interactions with other players. Multiplayer online games are now often integrated with social networks that provide social contexts in which player-to-player interactions take place, such as conversation and trading of virtual items. Building upon a theoretical framework based in machine learning and cognitive science, I present results from a novel approach to modeling and analyzing player values in terms of both preferences in avatar customization and patterns in social network use. To facilitate this work, I developed the Steam-Player- Preference Analyzer (Steam-PPA) system, which performs advanced data collection on publicly available social networking profile information. The primary contribution of this thesis is the AIR Toolkit Status Performance Classifier (AIR-SPC), which uses machine learning techniques including k-means clustering, natural language processing (NLP), and support vector machines (SVM) to perform inference on the data. As an initial case study, I use Steam-PPA to collect gameplay and avatar customization information from players in the popular, and commercially successful, multi-player first-person-shooter game Team Fortress 2 (TF2). Next, I use AIR-SPC to analyze the information from profiles on the social network Steam. The upshot is that I use social networking information to predict the likelihood of players customizing their profile in several ways associated with the monetary values of their avatars. In this manner I have developed a computational model of aspects of players' digital social identity capable of predicting specific values in terms of preferences exhibited within a virtual game-world.by Chong-U Lim.S.M
General Supersymmetric Solutions of Five-Dimensional Supergravity
The classification of 1/4-supersymmetric solutions of five dimensional gauged
supergravity coupled to arbitrary many abelian vector multiplets, which was
initiated in hep-th/0401129, is completed. The structure of all solutions for
which the Killing vector constructed from the Killing spinor is null is
investigated in both the gauged and the ungauged theories and some new
solutions are constructed.Comment: 24 pages, references added, uses JHEP3.cl
In a free healthcare system, why do men not consult for lower urinary tract symptoms (LUTS)?
<p>Abstract</p> <p>Background</p> <p>The prevalence of lower urinary tract symptoms (LUTS) varies among different populations but the rate of seeking medical advice is consistently low. Little is known about the reasons for this low rate. In the city of Macau, China, primary healthcare is free and easily accessible to all citizens. We aim to study the patients' rate of consulting for LUTS and their reasons for not consulting under a free healthcare system.</p> <p>Method</p> <p>A convenience sample of 549 male patients aged 40-85 years in a government health centre filled in the International Prostate Symptoms Scale (IPSS) questionnaire. They were also asked if they had consulted doctors for LUTS, and if not, why not.</p> <p>Result</p> <p>Of the whole sample, 64 men (11.7%) had ever consulted doctors for LUTS. Of 145 with moderate to severe LUTS, 35 (24.1%) consulted. Of 73 who were dissatisfied with their quality of life, 22 (30.1%) consulted. Regarding the symptoms as normal or not problematic was the main reason for not consulting. Advancing age and duration of symptoms were the significant factors for consulting.</p> <p>Conclusion</p> <p>Primary care doctors could help many of LUTS patients by sensitively initiating the discussion when these patients consult for other problems.</p
Stochastic dynamics of model proteins on a directed graph
A method for reconstructing the energy landscape of simple polypeptidic
chains is described. We show that we can construct an equivalent representation
of the energy landscape by a suitable directed graph. Its topological and
dynamical features are shown to yield an effective estimate of the time scales
associated with the folding and with the equilibration processes. This
conclusion is drawn by comparing molecular dynamics simulations at constant
temperature with the dynamics on the graph, defined by a temperature dependent
Markov process. The main advantage of the graph representation is that its
dynamics can be naturally renormalized by collecting nodes into "hubs", while
redefining their connectivity. We show that both topological and dynamical
properties are preserved by the renormalization procedure. Moreover, we obtain
clear indications that the heteropolymers exhibit common topological
properties, at variance with the homopolymer, whose peculiar graph structure
stems from its spatial homogeneity. In order to obtain a clear distinction
between a "fast folder" and a "slow folder" in the heteropolymers one has to
look at kinetic features of the directed graph. We find that the average time
needed to the fast folder for reaching its native configuration is two orders
of magnitude smaller than its equilibration time, while for the bad folder
these time scales are comparable. Accordingly, we can conclude that the
strategy described in this paper can be successfully applied also to more
realistic models, by studying their renormalized dynamics on the directed
graph, rather than performing lengthy molecular dynamics simulations.Comment: 15 pages, 12 figure
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