November 3rd, 2020

лошадь, диаграмма, Фейнман

О периодических таблицах элементов

включая ядерную по магическим числам протонов.

Three related topics on the periodic tables of elements: https://arxiv.org/abs/2011.00060
Yoshiteru Maeno, Kouichi Hagino, Takehiko Ishiguro
A large variety of periodic tables of the chemical elements have been proposed. It was Mendeleev who proposed a periodic table based on the extensive periodic law and predicted a number of unknown elements at that time. The periodic table currently used worldwide is of a long form pioneered by Werner in 1905. As the first topic, we describe the work of Pfeiffer (1920), who refined Werner's work and rearranged the rare-earth elements in a separate table below the main table for convenience. Today's widely used periodic table essentially inherits Pfeiffer's arrangements. Although long-form tables more precisely represent electron orbitals around a nucleus, they lose some of the features of Mendeleev's short-form table to express similarities of chemical properties of elements when forming compounds. As the second topic, we compare various three-dimensional helical periodic tables that resolve some of the shortcomings of the long-form periodic tables in this respect. In particular, we explain how the 3D periodic table "Elementouch" (Maeno 2001), which combines the s- and p-blocks into one tube, can recover features of Mendeleev's periodic law. Finally we introduce a topic on the recently proposed nuclear periodic table based on the proton magic numbers (Hagino and Maeno 2020). Here, the nuclear shell structure leads to a new arrangement of the elements with the proton magic-number nuclei treated like noble-gas atoms. We show that the resulting alignments of the elements in both the atomic and nuclear periodic tables are common over about two thirds of the tables because of a fortuitous coincidence in their magic numbers.
Comments: 14 pages. To appear in Foundations of Chemistry
лошадь, диаграмма, Фейнман

Учебное и обзорное по алгоритмам выборки

Sampling Algorithms, from Survey Sampling to Monte Carlo Methods: Tutorial and Literature Review: https://arxiv.org/abs/2011.00901

Benyamin Ghojogh, Hadi Nekoei, Aydin Ghojogh, Fakhri Karray, Mark Crowley
This paper is a tutorial and literature review on sampling algorithms. We have two main types of sampling in statistics. The first type is survey sampling which draws samples from a set or population. The second type is sampling from probability distribution where we have a probability density or mass function. In this paper, we cover both types of sampling. First, we review some required background on mean squared error, variance, bias, maximum likelihood estimation, Bernoulli, Binomial, and Hypergeometric distributions, the Horvitz-Thompson estimator, and the Markov property. Then, we explain the theory of simple random sampling, bootstrapping, stratified sampling, and cluster sampling. We also briefly introduce multistage sampling, network sampling, and snowball sampling. Afterwards, we switch to sampling from distribution. We explain sampling from cumulative distribution function, Monte Carlo approximation, simple Monte Carlo methods, and Markov Chain Monte Carlo (MCMC) methods. For simple Monte Carlo methods, whose iterations are independent, we cover importance sampling and rejection sampling. For MCMC methods, we cover Metropolis algorithm, Metropolis-Hastings algorithm, Gibbs sampling, and slice sampling. Then, we explain the random walk behaviour of Monte Carlo methods and more efficient Monte Carlo methods, including Hamiltonian (or hybrid) Monte Carlo, Adler's overrelaxation, and ordered overrelaxation. Finally, we summarize the characteristics, pros, and cons of sampling methods compared to each other. This paper can be useful for different fields of statistics, machine learning, reinforcement learning, and computational physics.
лошадь, диаграмма, Фейнман

Хорошее по формуле Бете-Блоха (почему Блоха стали выкидывать?) и основаниям протонной терапии

On The Relationship Between The Energy, Energy Spread And Distal Slope for Proton Therapy Observed in GEANT4: https://arxiv.org/abs/2011.00285

Tim Fulcher, Richard A Amos, Hywel Owen, Rob Edgecock
In proton therapy both the energy, which determines the range, and the distal slope, which reflects the rate at which the protons decelerate, are of import if we are to ensure accurate dose deposition and maximum tissue sparing. This publication describes a Geant4 model and presents a two-dimensional polynomial relationship between energy, the energy spread and the distal slope for beams with Gaussian energy spectra for proton therapy. This simple polynomial relationship will be useful for non-invasive or minimally invasive near real-time monitoring of the energy and energy spread of a proton therapy beam.
Comments: 16 pages, 13 figures
песец

О человеческих башнях в Каталонии

Когда-то, давным -давно, когда мне предстояло сдавать на работе квалификационный экзамен по английскому, уважаемый ahiin здорово мне помог, подогнав набор тестов для тренировки. И там был один текст - рассказ мужика, который оказался вовлеченным в эту деятельность по формированию пирамид - оказывается, это такое народное развлечение в Каталонии практикуют. И вот, пожалуйста - научный отчет на эту тему, с весьма себе научно-механическим анализом:))

Human towers or castells modelling. 158th European Study Groups with Industry (long report): https://arxiv.org/abs/2010.14248

J. Antunes, F. Brosa Planella, A. Dòria-Cerezo, A. March San José, M. Pellicer, A. Rodríguez-Ferran, J. Saludes
Human towers or castells are human structures played in festivals mainly in Catalonia. These unique cultural and traditional displays have become very popular in the last years, but they date from the XVIII century. On 2010 they became part of the Unesco Representative List of the Intangible Cultural Heritage of Humanity.
Safety is very important in the performance of castells. To this end, it is crucial to understand the mechanisms that allow a castell to be built and, more importantly, the factors that may cause its collapse. This work is focused on the mechanical aspects that make a pilar (the simplest structure in the castells) to stand. We suggest three different but complementary approaches for the running stage of a pilar (stage where it has been built and has not yet collapsed): the N-link pendulum as a first dynamical model, the response of the castellers as a control problem, and a static analysis to capture the feasibility of a given configuration. We include some preliminary simulations to better understand the previous approaches, which seem to match with qualitative perceptions that castellers have of a castell. Possible future developments are also discussed. To our knowledge, this work represents the first one to study the castells from a mechanical point of view.
лошадь, диаграмма, Фейнман

И снова что-то популярно-космологическое на португальском:))

An introduction to the time evolution of model universes: https://arxiv.org/abs/2010.16240
Vinicius S. Aderaldo, Victor P. Goncalves
In this paper we describe the evolution of the Universe in terms of the Friedmann equation, which takes into account of the composition and geometry of the Universe. The dependence of the solution on the geometry and composition for different combinations of the basic constituents are discussed. The distinct behaviors for the temporal evolution of the Universe are determined and the scenario predicted by the Standard Cosmology is presented.
Comments: 23 pages, 8 figures. Text in Portuguese. Published in Revista Brasileira de Ensino de Fisica