19,858 research outputs found
An Analysis Tool for Push-Sum Based Distributed Optimization
The push-sum algorithm is probably the most important distributed averaging
approach over directed graphs, which has been applied to various problems
including distributed optimization. This paper establishes the explicit
absolute probability sequence for the push-sum algorithm, and based on which,
constructs quadratic Lyapunov functions for push-sum based distributed
optimization algorithms. As illustrative examples, the proposed novel analysis
tool can improve the convergence rates of the subgradient-push and stochastic
gradient-push, two important algorithms for distributed convex optimization
over unbalanced directed graphs. Specifically, the paper proves that the
subgradient-push algorithm converges at a rate of for general
convex functions and stochastic gradient-push algorithm converges at a rate of
for strongly convex functions, over time-varying unbalanced directed
graphs. Both rates are respectively the same as the state-of-the-art rates of
their single-agent counterparts and thus optimal, which closes the theoretical
gap between the centralized and push-sum based (sub)gradient methods. The paper
further proposes a heterogeneous push-sum based subgradient algorithm in which
each agent can arbitrarily switch between subgradient-push and
push-subgradient. The heterogeneous algorithm thus subsumes both
subgradient-push and push-subgradient as special cases, and still converges to
an optimal point at an optimal rate. The proposed tool can also be extended to
analyze distributed weighted averaging.Comment: arXiv admin note: substantial text overlap with arXiv:2203.16623,
arXiv:2303.1706
Quantum Mechanics Lecture Notes. Selected Chapters
These are extended lecture notes of the quantum mechanics course which I am
teaching in the Weizmann Institute of Science graduate physics program. They
cover the topics listed below. The first four chapter are posted here. Their
content is detailed on the next page. The other chapters are planned to be
added in the coming months.
1. Motion in External Electromagnetic Field. Gauge Fields in Quantum
Mechanics.
2. Quantum Mechanics of Electromagnetic Field
3. Photon-Matter Interactions
4. Quantization of the Schr\"odinger Field (The Second Quantization)
5. Open Systems. Density Matrix
6. Adiabatic Theory. The Berry Phase. The Born-Oppenheimer Approximation
7. Mean Field Approaches for Many Body Systems -- Fermions and Boson
Bayesian networks for disease diagnosis: What are they, who has used them and how?
A Bayesian network (BN) is a probabilistic graph based on Bayes' theorem,
used to show dependencies or cause-and-effect relationships between variables.
They are widely applied in diagnostic processes since they allow the
incorporation of medical knowledge to the model while expressing uncertainty in
terms of probability. This systematic review presents the state of the art in
the applications of BNs in medicine in general and in the diagnosis and
prognosis of diseases in particular. Indexed articles from the last 40 years
were included. The studies generally used the typical measures of diagnostic
and prognostic accuracy: sensitivity, specificity, accuracy, precision, and the
area under the ROC curve. Overall, we found that disease diagnosis and
prognosis based on BNs can be successfully used to model complex medical
problems that require reasoning under conditions of uncertainty.Comment: 22 pages, 5 figures, 1 table, Student PhD first pape
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Performance analysis of RIS-assisted full-duplex communications with infinite and finite blocklength codes
With the advancement of wireless communication technologies, reconfigurable intelligent surfaces (RISs) have recently paved the way to augmenting the performance of wireless networks with the aid of multiple reflecting surfaces by efficiently attuning the signal reflection through a large number of low-cost passive elements. In this paper, we consider an RIS-aided full-duplex (FD) communication network consisting of a FD access point (AP) that communicates with an uplink and a downlink user simultaneously with the aid of an RIS as well as through the direct link between the AP and users. To evaluate the system performance under infinite blocklength (IBL) and finite blocklength (FBL) codes, we derive the analytical expressions for the outage probability and throughput in case of IBL, and for block-error rate (BLER) and goodput in the case of FBL, for both uplink and downlink transmission. Furthermore, the expressions for the maximum achievable rate under FBL and IBL transmission are derived. Next, we also extend the analysis of the single-user framework to a more practical scenario with multiple users utilizing non-orthogonal multiple access (NOMA) and derive analytical expressions for the outage probability and BLER at each downlink user and at the AP. The accuracy of the derived expressions is validated via simulation results, and insights are provided regarding the impact of the number of reflecting elements and imperfect channel state information (CSI) on the performance of the considered system. Finally, from the comparative analysis, it is shown that the RIS-aided system outperforms the system without RIS in both IBL and FBL scenarios, providing remarkable improvement in the outage probability and BLER
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The Epidemiology and Genetic Architecture of Vitamin D Deficiency in African Children
Vitamin D deficiency is a common public health problem worldwide. However, little is known about the epidemiology of vitamin D deficiency in Africa. In this thesis, I aimed to determine: 1) the prevalence of and risk factors associated with vitamin D deficiency in studies conducted in Africa; 2) the prevalence and predictors of vitamin D deficiency in African children; 3) the association between vitamin D and iron deficiency in African children; and 4) genetic variants that influence vitamin D status in Africans.
In a systematic review and meta-analyses of previous vitamin D studies in Africa, the average prevalence of low vitamin D status was 18.5%, 34.2% and 59.5% using cut-offs of 25-hydroxyvitamin D (25(OH)D) levels of <30 nmol/L, <50 nmol/L and <75 nmol/L, respectively. Populations at risk of vitamin D deficiency included newborns, women, and people living in high latitudes or urban areas.
In an epidemiological study of young children living in Africa, the prevalence of low vitamin D status was 0.6%, 7.8% and 44.5% using cut-offs of 25(OH)D levels of GC2 variant of the group-specific component (GC) gene, which encodes vitamin D binding protein.
Vitamin D deficiency was also associated with 80% higher odds of iron deficiency in these children. Adjusted regression models revealed that vitamin D deficiency was associated with higher ferritin and hepcidin levels suggesting lower iron status, and reduced sTfR and transferrin levels and increased TSAT and serum iron levels suggesting improved iron status.
Genome-wide association study (GWAS) in Africans revealed genetic variants that influence vitamin D status in vitamin D metabolism genes: DHCR7/NADSYN1, CYP2R1 and GC. However, the majority of SNPs from previous European GWASs did not replicate in the current GWAS.
Findings from this thesis indicate that vitamin D deficiency is prevalent in many African populations and should be considered in public health strategies in Africa
Strategies for Early Learners
Welcome to learning about how to effectively plan curriculum for young children. This textbook will address: • Developing curriculum through the planning cycle • Theories that inform what we know about how children learn and the best ways for teachers to support learning • The three components of developmentally appropriate practice • Importance and value of play and intentional teaching • Different models of curriculum • Process of lesson planning (documenting planned experiences for children) • Physical, temporal, and social environments that set the stage for children’s learning • Appropriate guidance techniques to support children’s behaviors as the self-regulation abilities mature. • Planning for preschool-aged children in specific domains including o Physical development o Language and literacy o Math o Science o Creative (the visual and performing arts) o Diversity (social science and history) o Health and safety • Making children’s learning visible through documentation and assessmenthttps://scholar.utc.edu/open-textbooks/1001/thumbnail.jp
Variables controlling the resurgence of previously reinforced behaviour in hens
Resurgence is defined as the occurrence of previously reinforced behaviours when reinforcer delivery ceases for a recently reinforced behaviour. In five experiments, variables suggested to control the degree of occurrence of a first-trained behaviour during the extinction of a second-trained behaviour (resurgence) were investigated. All experiments used hens and behaviours were selected from door push, key peck, and head bob. In Experiment 1, using 6 naive hens, Behaviour 1 was reinforced on a random-interval (RI) 60-s schedule followed by two sessions of extinction. Each occurrence of Behaviour 2 was then reinforced followed by another period of extinction. The degree of occurrence of Behaviour 1 during the final extinction was less than that which occurred during the period of Behaviour 1 extinction, suggesting that the extinction of Behaviour 2 did not increase the occurrence of Behaviour 1. This result failed to support the idea that resurgence is induced by the extinction of Behaviour 2. In Experiment 2, using the same hens and an additional hen, Experiment 1 was repeated five times and then there were either 0 or 9 sessions of Behaviour 1 extinction in a further five conditions. The degree of resurgence was generally less when there were 9 sessions than when there were no sessions but not consistently different from either when there were 2 sessions. Experiment 3 used six naive hens. Two first-trained behaviours were initially reinforced on RI 45-s schedules under a multiple schedule. One first behaviour then received a period of extinction and then each occurrence of two second behaviours was reinforced under the multiple schedule followed by extinction. The sequence from training of the first behaviours to the extinction of the second behaviours was repeated 10 times with the number of occurrences of the component for which extinction was in effect for the first behaviour varying across conditions from 12 to 0. The degree of resurgence was an inverse function of the amount of Behaviour 1 extinction. Experiment 4 used six naive hens. In a multiple schedule two first behaviours were reinforced on RI 20-s schedules and then two second behaviours were reinforced followed by extinction. This was repeated 8 times with the RI schedule in effect for one of the second behaviours varying from 80 s to 10 s across conditions while the other remained at 40 s. The degree of occurrence of Behaviour 1 when Behaviour 2 was reinforced was a direct function of the varied RI schedule of Behaviour 2. The degree of resurgence of Behaviour 1 in extinction was an inverse function of the varied RI schedule of Behaviour 2. The degree of resurgence was also inversely related to the degree of occurrence of this Behaviour 1 when Behaviour 2 was reinforced. Experiment 5 used five naive hens and one hen from Experiment 3 in a multiple-schedule design where the length of training of the second behaviours varied from 124 to O occurrences of a component over three conditions. No effect of this was found on the degree of resurgence. The results are consistent with the hypothesis that resurgence is the result of the prevention of extinction of Behaviour 1 by the reinforcement of Behaviour 2, but they are not definitive proof that this hypothesis is correct. Models derived from the Generalised Matching Law and Behavioural Momentum are also proposed as descriptions of resurgence
Gamification in E-Learning: game factors to strengthen specific English pronunciation features in undergraduate students at UPTC Sogamoso
Appendix A Characterization survey (104), Appendix B. EFL Students’ questionnaire (109), Appendix C. Characterization survey: data treatment question (113), Appendix D. Informed consent letter, English version (114), Appendix E. Carta de consentimiento informado, versión en español (117), Appendix F. Time Schedule (120), Appendix G. Sample Challenges at Moodle (126), Appendix H. Participants’ questionnaire results (128).La gamificación es un término que suele denotar el uso de componentes del juego en situaciones no relacionadas con el juego en sí para crear experiencias de aprendizaje agradables, divertidas y motivadoras para los estudiantes (Werbach y Hunter, 2012). Por lo tanto, el análisis de los factores básicos de los juegos se convierte en algo esencial a la hora de definir y utilizar la gamificación como estrategia de mediación del inglés como lengua extranjera para fortalecer rasgos específicos de pronunciación en los estudiantes de pregrado de la UPTC Sogamoso.
El procedimiento de estudio se basa en la investigación acción mediante la implementación de la estrategia de gamificación para la mediación en la pronunciación del inglés, orientada a treinta estudiantes de diferentes programas de ingeniería, administración y tecnología con niveles heterogéneos de dominio del inglés. Las actividades se centran principalmente en la producción de sonidos, el ritmo, el acento y la entonación, los rasgos de pronunciación segmental y suprasegmental.
Los resultados arrojaron una evidente mejora en las características segméntales y suprasegmentales de la percepción en la pronunciación de los participantes así como la contribución del objetivo de los juegos a la instrucción fonética y fonológica, la sensación en el juego a la motivación para mejorar la pronunciación, el reto establecido en los juegos a la actitud positiva de los participantes, y la sociabilidad a la exposición practica de la pronunciación inglesa.Gamification is a relatively new term that often denotes the use of game components in situations unrelated to the game itself to create enjoyable, fun, and motivating learning experiences for students (Werbach and Hunter, 2012). Therefore, analyzing the games' basic factors becomes essential when defining and using gamification as a strategy for English as Foreign Language mediation to strengthen specific pronunciation features in UPTC Sogamoso undergraduate students.
The study procedure is based on action research by implementing the gamification strategy for mediation in English pronunciation, oriented to thirty students from different engineering, management, and technology programs at heterogeneous levels of English proficiency. The activities mainly focus on sound production, rhythm, stress, and intonation, segmental and suprasegmental pronunciation features.
The results showed an evident improvement in the segmental and suprasegmental features of the participants' pronunciation perception as well as the contribution of game goals to phonetics and phonological instruction, the game sensation to the motivation for pronunciation improvement, the game challenge to the participants' positive attitude, and the sociality to the English pronunciation exposure practice
Exploring the Structure of Scattering Amplitudes in Quantum Field Theory: Scattering Equations, On-Shell Diagrams and Ambitwistor String Models in Gauge Theory and Gravity
In this thesis I analyse the structure of scattering amplitudes in super-symmetric gauge and gravitational theories in four dimensional spacetime, starting with a detailed review of background material accessible to a non-expert. I then analyse the 4D scattering equations, developing the theory of how they can be used to express scattering amplitudes at tree level. I go on to explain how the equations can be solved numerically using a Monte Carlo algorithm, and introduce my Mathematica package treeamps4dJAF which performs these calculations. Next I analyse the relation between the 4D scattering equations and on-shell diagrams in N = 4 super Yang-Mills, which provides a new perspective on the tree level amplitudes of the theory. I apply a similar analysis to N = 8 supergravity, developing the theory of on-shell diagrams to derive new Grassmannian integral formulae for the amplitudes of the theory. In both theories I derive a new worldsheet expression for the 4 point one loop amplitude supported on 4D scattering equations. Finally I use 4D ambitwistor string theory to analyse scattering amplitudes in N = 4 conformal supergravity, deriving new worldsheet formulae for both plane wave and non-plane wave amplitudes supported on 4D scattering equations. I introduce a new prescription to calculate the derivatives of on-shell variables with respect to momenta, and I use this to show that certain non-plane wave amplitudes can be calculated as momentum derivatives of amplitudes with plane wave states
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