Numerical study of the RBF-FD level set based method for partial differential equations on evolving-in-time surfaces

In this article we present a Radial Basis Function (RBF)-Finite Difference (FD) level set based method for numerical solution of partial differential equations (PDEs) of the reaction-diffusion-convection type on an evolving-in-time hypersurface Γ (t). In a series of numerical experiments we study the accuracy and robustness of the proposed scheme and demonstrate that the method is applicable to practical models

A flux-corrected RBF-FD method for convection dominated problems in domains and on manifolds

In this article we introduce a FCT stabilized Radial Basis Function (RBF)-Finite Difference (FD) method for the numerical solution of convection dominated problems. The proposed algorithm is designed to maintain mass conservation and to guarantee positivity of the solution for an almost random placement of scattered data nodes. The method can be applicable both for problems defined in a domain or if equipped with level set techniques, on a stationary manifold. We demonstrate the numerical behavior of the method by performing numerical tests for the solid-body rotation benchmark in a unit square and for a transport problem along a curve implicitly prescribed by a level set function. Extension of the proposed method to higher dimensions is straightforward and easily realizable

ПОРІВНЯННЯ СУЧАСНИХ ТЕХНІЧНИХ ЗАСОБІВ АЕРОРОЗВІДКИ ДЛЯ ЗАБЕЗПЕЧЕННЯ БЕЗПЕКИ КОНТРОЛЬОВАНОЇ ЗОНИ

This article highlights the current practical capabilities of visual and thermal imaging UAV cameras, which allows to effectively and safely identify potentially dangerous objects that may threaten the object of information activities or the safety of citizens or critical infrastructure of Ukraine. Based on many years of flight experience and training specialists for private and public institutions, it was decided to compare the quality characteristics and capabilities of detecting, recognizing, and identifying objects using modern uncrewed vehicles. To ensure public safety and control of the territory, there are models with multiple optical zooms, which from a distance of 500 m allow recognizing the license plate of the car, or versions with a thermal imager, which in the middle of the night can help see the car, the temperature difference against other cars, and the fact that a person comes out of it. Test flights were performed at altitudes from 10 to 100 m, in the open, without bushes, trees, or obstacles. Depending on the camera model and weather conditions, the figures obtained may differ significantly. The main advantages and differences in the quality of visual and thermal imaging cameras for UAVs are described. The quality of the obtained image is demonstrated on real examples and under the same conditions. Detailed visual cameras have been analyzed. According to Johnson’s criteria, several requirements have been developed for quadcopter imaging of objects such as a car and a person from different heights. A work plan has been formed for further research to prepare and provide practical recommendations for pilots who use this technique in protecting the territory of information activities and during service in the air reconnaissance units of the security forces of UkraineДана стаття присвячена висвітленню реальних практичних можливостей візуальних та тепловізійних камер БПЛА, що дають змогу ефективно і з максимально безпечної висоти визначати потенційно небезпечні об’єкти, що можуть нанести загрозу об’єкту інформаційної діяльності, або безпеці громадян чи об’єктам критичної інфраструктури України. Спираючись на багаторічних досвід польотів та навчання фахівців для приватних та державних установ, прийнято рішення провести порівняння якісних характеристик та можливостей виявлення, розпізнавання та ідентифікації об’єктів з використанням сучасної безпілотної техніки. Для напряму забезпечення громадської безпеки та контролю територій існують моделі з багатократним оптичним збільшенням, які з відстані у 500 м дають змогу розпізнати номерний знак автомобіля, або версії з тепловізором, які серед ночі, можуть допомогти побачити автомобіль, різницю температур на фоні інших авто, та факт того, що людина виходить з нього. Тестові польоти виконувались на висотах від 10 до 100 м, на відкритій місцевості, без наявності кущів, дерев чи перешкод. Залежно від моделі камери та погодних умов, отримані показники можуть значно відрізнятись. Охарактеризовано основні переваги та відмінності в якості роботи візуальниї та тепловізійних камер для БПЛА. Продемонстровано якість отриманого зображення на реальних прикладах та при однакових умовах. Проаналізовано деталізацію візуальних камер та розроблено ряд вимог до зйомки тепловізором з квадрокоптера таких об’єктів, як автомобіль та людина, з різних висот, відповідно до критеріїв Джонсона. Сформовано план робіт для подальших досліджень, з метою підготовки та надання ефективних рекомендацій для пілотів, що використовують дану техніку при охороні території об’єктів інформаційної діяльності та під час виконання служби в підрозділах аеророзвідки силових структур України

Population Balances Coupled with the CFD-Code FeatFlow

The simulation of drop size distributions in stirred liquid-liquid systems is studied. The simulation is realized via the coupling of the CFD code FeatFlow with the population balance solver Parsival. It is shown how such a coupling may be constructed and the properties of the coupled solver are critically analyzed

Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7

We report complex metamagnetic transitions in single crystals of the new low carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization, and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K. Neutron diffraction measurements show that the magnetic ground state of YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab plane. With such an ordered state, no metamagnetic transitions are expected when a magnetic field is applied along the c axis. It is therefore surprising that high field magnetization, torque, and resistivity measurements with H||c reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When the field is tilted away from the c axis, towards the ab plane, both metamagnetic transitions are shifted to higher fields. The first metamagnetic transition leads to an abrupt increase in the electrical resistivity, while the second transition is accompanied by a dramatic reduction in the electrical resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7 are strongly coupled. We discuss the origin of the anomalous metamagnetism and conclude that it is related to competition between crystal electric field anisotropy and anisotropic exchange interactions.Comment: 23 pages and 4 figures in the main text. 7 pages and 5 figures in the supplementary materia

Non-Standard Errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

Analysis and numerical realisation of discrete . . .

The first splitting schemes for solving the system of incompressible Navier-Stokes equations have been proposed already in the second half of the last century. Among them are continuous and discrete projection methods, ILUbased factorisation schemes, etc. The main purpose of splitting schemes is to divide the velocity-pressure coupled problem into smaller subproblems to be solved in an iterative way. Very often this leads to a drastic reduction of computational work and resources. The most popular splitting schemes are projection methods proposed by A. Chorin and R. Temam in the late 1960’s. Since then, the projection methods were thoroughly analysed and constantly improved, particularly for new CFD configurations and applications. In a broad class of industrial applications one has to deal with incompressible rotating flows. Very often it is helpful to perform coordinate transformation to a nonintertial frame of reference. On one hand, this technique facilitates the prescription of boundaries, since complex rotating objects become stationary, their mesh is constructed once and for all during the preprocessing phase. On the other hand, one has to consider the Navier-Stokes equations with rotational forces, which consist of Coriolis and centrifugal forces. In order to obtain an efficient and robust solver, it is important to come up with a proper handling of these extra terms. For coupled methods implementation of rotational forces is pretty much straightforward. For projection methods, however, some modifications in ever

Every Cloud Has a Silver Lining: Fast Trading, Microwave Connectivity, and Trading Costs

Modern markets are characterized by speed differentials, with some traders being fractions of a second faster than others. Theoretical models suggest that such differentials may have both positive and negative effects on liquidity and gains from trade. We examine these effects by studying a series of exogenous weather episodes that temporarily remove the speed advantages of the fastest traders by disrupting their microwave networks. The disruptions are associated with lower adverse selection and lower trading costs. In additional analysis, we show that the long-term removal of speed differentials results in similar effects and also increases gains from trade