Tunguska explosion and the Earth's magnetic field

For at least a century, the geophysicists have been wondering about the future of the Earth's magnetic field and whether it is going to flip, while the astrophysicists have been wondering what kind of celestial body exploded on June 30, 1908 by the river of Podkamennaya Tunguska. Using the data recently made available by NOAA, we demonstrate an intimate relationship between the two, previously thought completely unrelated, phenomena

Біологічно активні сполуки кореневищ Iris hungarica

Species of Iris genus (Iridaceae) have a long history of traditional medicinal use in different countries as alternative aperient, tonic, cathartic, diuretic, gall bladder diseases, liver complaints, dropsy, purification of blood, venereal infections, fever, bilious infections and for a variety of heart diseases. The rhizomes of Iris are the rich source of the secondary metabolites, in which flavonoids predominate. The clinical studies of substances from irises gave positive results in the treatment of cancer, bacterial and viral infections. Continuing the search of new biologically active compounds from the plants of Iridaceae family for the first time three isoflavones that are new for this species – irigenin, iristectorigenin B and its glucoside iristectorin B have been isolated from the ethanolic extract of the rhizomes of Iris hungarica Waldst. et Kit., which is widespread in Ukraine. The structure of the compounds is described as 5,7,3’-trihydroxy-6,4’,5’-trimethoxyisoflavone, 5,7,4’-trihydroxy-6,3’-dimethoxyisoflavone and iristectorigenin B-7-O-β-D-glucoside, respectively. The compounds were obtained from the ethyl acetate fraction of the iris rhizomes by column chromatography on silica gel with sequential elution of the chloroform – ethanol solvent with different concentrations. The structure of the compounds has been determined by chemical and spectral methods and in comparison with the literature data.Растения рода Iris (Iridaceae) имеют давнюю историю применения в традиционной медицине различных стран как альтернативное слабительное, тонизирующее, отхаркивающее, мочегонное средство, для лечения заболеваний желчного пузыря, печени, водянки, для очищения крови, лечения венерических инфекций, лихорадки, желчных инфекций и заболеваний сердца. Корневища ирисов являются богатым источником вторичных метаболитов, среди которых преобладают флавоноиды. Клинические исследования веществ из ирисов дали положительные результаты при лечении рака, бактериальных и вирусных инфекций. Продолжая поиск новых биологически активных соединений из растений семейства ирисовые – Iridaceae из этанольного экстракта корневищ ириса венгерского – Iris hungarica Waldst. Et Kit., который широко распространен на территории Украины, впервые выделены три новых для данного вида изофлавоноида: иригенин, иристекторигенин В и его глюкозид иристекторин В. Структура веществ охарактеризована как 5,7,3’-тригидрокси-6,4’,5’-триметоксиизофлавон, 5,7,4’-тригидрокси- 6,3’-диметоксиизофлавон и иристекторигенин В-7-O-β-D-глюкопиранозид, соответственно. Вещества были получены методом колоночной хроматографии на силикагеле из этилацетатной фракции корневищ ириса при последовательном элюировании растворителем хлороформ – этанол различной концентрации. Структура веществ установлена химическими и спектральными методами и в сравнении с литературными данными.Рослини роду Iris (Iridaceae) мають давню історію застосування у традиційній медицині різних країн як альтернативний проносний, тонізуючий, відхаркувальний, сечогінний засіб, для лікування захворювань жовчного міхура, печінки, водянки, для очищення крові, венеричних інфекцій, лихоманки, жовчних інфекцій і для лікування захворювань серця. Кореневища ірисів є багатим джерелом вторинних метаболітів, серед яких переважають флавоноїди. Клінічні дослідження речовин із ірисів дали позитивні результати при лікуванні раку, бактеріальних і вірусних інфекцій. Продовжуючи пошук нових біологічно активних сполук з рослин родини ірисові – Iridaceae з етанольного екстракту кореневищ ірису угорського – Iris hungarica Waldst. et Kit., поширеного на території України, вперше виділено три нові для даного виду ізофлавоноїди: іригенін, іристекторигенін В і його глюкозид іристекторин В. Структура речовин охарактеризована як 5,7,3’-тригідрокси-6,4’,5’-триметоксіізофлавон, 5,7,4’-тригідрокси-6,3’- диметоксіізофлавон та іристекторигенін В-7-O-β-D-глюкопіранозид, відповідно. Речовини були отримані методом колонкової хроматографії на силікагелі з етилацетатної фракції кореневищ ірису при послідовному елююванні розчинником хлороформ – етанол різної концентрації. Структура речовин встановлена хімічними і спектральними методами та у порівнянні з літературними даними

Dispersion and collapse of wave maps

We study numerically the Cauchy problem for equivariant wave maps from 3+1 Minkowski spacetime into the 3-sphere. On the basis of numerical evidence combined with stability analysis of self-similar solutions we formulate two conjectures. The first conjecture states that singularities which are produced in the evolution of sufficiently large initial data are approached in a universal manner given by the profile of a stable self-similar solution. The second conjecture states that the codimension-one stable manifold of a self-similar solution with exactly one instability determines the threshold of singularity formation for a large class of initial data. Our results can be considered as a toy-model for some aspects of the critical behavior in formation of black holes.Comment: 14 pages, Latex, 9 eps figures included, typos correcte

Global existence for coupled systems of nonlinear wave and Klein-Gordon equations in three space dimensions

We consider the Cauchy problem for coupled systems of wave and Klein-Gordon equations with quadratic nonlinearity in three space dimensions. We show global existence of small amplitude solutions under certain condition including the null condition on self-interactions between wave equations. Our condition is much weaker than the strong null condition introduced by Georgiev for this kind of coupled system. Consequently our result is applicable to certain physical systems, such as the Dirac-Klein-Gordon equations, the Dirac-Proca equations, and the Klein-Gordon-Zakharov equations.Comment: 31 pages. The final versio

The comparison of solar-powered hydrogen closed-cycle system capacities for selected locations

The exhaustion of fossil fuels causes decarbonized industries to be powered by renewable energy sources and, owing to their intermittent nature, it is important to devise an efficient energy storage method. To make them more sustainable, a storage system is required. Modern electricity storage systems are based on different types of chemical batteries, electromechanical devices, and hydrogen power plants. However, the parameters of power plant components vary from one geographical location to another. The idea of the present research is to compare the composition of a solar-powered hydrogen processing closed-cycle power plant among the selected geographical locations (Russia, India, and Australia), assuming the same power consumption conditions, but different insolation conditions, and thus the hydrogen equipment capacity accordingly. The number of solar modules in an array is different, thus the required hydrogen tank capacity is also different. The comparison of equipment requires building an uninterrupted power supply for the selected geographical locations, which shows that the capacity of the equipment components would be significantly different. These numbers may serve as the base for further economic calculations of energy cost

Интеллектуализация контроля вагонов в железнодорожном сортировочном парке

The railway marshalling station occupies a central place in the technological chain of freight transportation processes, since the speed of processing trains at marshalling yards determines the volume and cost of transportation. Therefore, development of automation and computerization of sorting processes results in growing efficiency of freight transportation in general. The objective of the study is to formalize the problem of cars’ monitoring within the railway marshalling yard and to develop a method for solving it with the use of algorithms of recognizing and positioning of dynamic objects through the intelligent data analysis of streaming video. The article presents a new approach to solution of the problem of monitoring moving units in the hump (sorting) yard of marshalling stations. The article suggests core criteria for identifying speed and positioning of the railway wagons when they are running after been separated at the hump. The article specifies that monitoring of moving units at hump yard is less automated in comparison with the monitoring at the hump itself, and that confirms the relevance of the research. To get the problem of the automation monitoring of moving units in the hump yard solved, the authors have suggested an algorithm that is based on the image data intelligent analysis, that is on computer vision, and have described the model of its implementation at a station. The methods used are based on the theory of computer vision and are aimed at recognizing key dynamic objects in streaming video and at their subsequent positioning. The study has resulted in substantiation of acceptability of the use of computer vision in the process of separation and formation of trains. It is planned to proceed with further improvement of the presented approach to develop a software product allowing to objectify information about hump yard in order to increase the efficiency of targeted braking at the hump.Железнодорожная сортировочная станция занимает центральное место в технологической цепочке грузовых перевозочных процессов, поскольку скорость переработки железнодорожных составов на ней определяет объём и стоимость перевозок. Поэтому развитие средств автоматизации и информатизации сортировочных процессов ведёт к повышению эффективности грузовых перевозок в целом. Целью работы является формализация задачи контроля вагонов в железнодорожном сортировочном парке иразработка метода её решения, основанного на использовании алгоритмов распознавания и позиционирования динамических объектов путём интеллектуального анализа данных потокового видео. В работе представлен новый подход к решению задачи контроля подвижных единиц в подгорочном (сортировочном) парке железнодорожных сортировочных станций. Приводятся основные критерии определения скорости движения и позиционирования групп вагонов при их движении после расформирования на сортировочной горке. Определено, что контроль подвижных единиц в сортировочном парке является менее автоматизированным процессом по сравнению с контролем на сортировочной горке. Для решения поставленной задачи автоматизации контроля подвижных единиц в сортировочном парке предложен алгоритм на базе методов интеллектуального анализа видеоданных – компьютерного зрения – и представлена его модель реализации на конкретном объекте. Методы работы основаны на теории компьютерного зрения и направлены на распознавание ключевых динамических объектов на потоковом видео с их последующим позиционированием. Результатом проведённой работы является обоснование актуальности использования компьютерного зрения в процессе расформирования-формирования железнодорожных составов. В дальнейшем планируется совершенствование представленных разработок для подготовки готового программного продукта, позволяющего объективизировать информацию о сортировочном парке для повышения эффективности прицельного торможения на сортировочной горке

Batch Scheduling of Deteriorating Products

In this paper we consider the problem of scheduling N jobs on a single machine, where the jobs are processed in batches and the processing time of each job is a simple linear increasing function depending on job’s waiting time, which is the time between the start of the processing of the batch to which the job belongs and the start of the processing of the job. Each batch starts from the setup time S. Jobs which are assigned to the batch are being prepared for the processing during time S0 < S. After this preparation they are ready to be processed one by one. The non-negative number bi is associated with job i. The processing time of the i-th job is equal to bi(si − (sib + S0)), where sib and si are the starting time of the b-th batch to which the i-th job belongs and the starting time of this job, respectively. The objective is to minimize the completion time of the last job. We show that the problem is NP-hard. After that we present an O(N) time algorithm solving the problem optimally for the case bi = b. We further present an O(N2) time approximation algorithm with a performance guarantee 2

Dynamic pricing with demand disaggregation for hotel revenue management

In this paper we present a novel approach to the dynamic pricing problem for hotel businesses. It includes disaggregation of the demand into several categories, forecasting, elastic demand simulation, and a mathematical programming model with concave quadratic objective function and linear constraints for dynamic price optimization. The approach is computationally efficient and easy to implement. In computer experiments with a hotel data set, the hotel revenue is increased by about 6% on average in comparison with the actual revenue gained in a past period, where the fixed price policy was employed, subject to an assumption that the demand can deviate from the suggested elastic model. The approach and the developed software can be a useful tool for small hotels recovering from the economic consequences of the COVID-19 pandemic

Spinors, Inflation, and Non-Singular Cyclic Cosmologies

We consider toy cosmological models in which a classical, homogeneous, spinor field provides a dominant or sub-dominant contribution to the energy-momentum tensor of a flat Friedmann-Robertson-Walker universe. We find that, if such a field were to exist, appropriate choices of the spinor self-interaction would generate a rich variety of behaviors, quite different from their widely studied scalar field counterparts. We first discuss solutions that incorporate a stage of cosmic inflation and estimate the primordial spectrum of density perturbations seeded during such a stage. Inflation driven by a spinor field turns out to be unappealing as it leads to a blue spectrum of perturbations and requires considerable fine-tuning of parameters. We next find that, for simple, quartic spinor self-interactions, non-singular cyclic cosmologies exist with reasonable parameter choices. These solutions might eventually be incorporated into a successful past- and future-eternal cosmological model free of singularities. In an Appendix, we discuss the classical treatment of spinors and argue that certain quantum systems might be approximated in terms of such fields.Comment: 12 two-column pages, 3 figures; uses RevTeX

Experimentation with a dynamic pricing approach for hotel industry

A dynamic pricing approach for hotel revenue management is suggested. It aims at increasing revenue over the baseline