Logics with Multiteam Semantics

Team semantics is the mathematical basis of modern logics of dependence and independence. In contrast to classical Tarski semantics, a formula is evaluated not for a single assignment of values to the free variables, but on a set of such assignments, called a team. Team semantics is appropriate for a purely logical understanding of dependency notions, where only the presence or absence of data matters, but being based on sets, it does not take into account multiple occurrences of data values. It is therefore insufficient in scenarios where such multiplicities matter, in particular for reasoning about probabilities and statistical independencies. Therefore, an extension from teams to multiteams (i.e. multisets of assignments) has been proposed by several authors. In this paper we aim at a systematic development of logics of dependence and independence based on multiteam semantics. We study atomic dependency properties of finite multiteams and discuss the appropriate meaning of logical operators to extend the atomic dependencies to full-fledged logics for reasoning about dependence properties in a multiteam setting. We explore properties and expressive power of a wide spectrum of different multiteam logics and compare them to second-order logic and to logics with team semantics. In many cases the results resemble what is known in team semantics, but there are also interesting differences. While in team semantics, the combination of inclusion and exclusion dependencies leads to a logic with the full power of both independence logic and existential second-order logic, independence properties of multiteams are not definable by any combination of properties that are downwards closed or union closed and thus are strictly more powerful than inclusion-exclusion logic. We also study the relationship of logics with multiteam semantics with existential second-order logic for a specific class of metafinite structures. It turns out that inclusion-exclusion logic can be characterised in a precise sense by the Presburger fragment of this logic, but for capturing independence, we need to go beyond it and add some form of multiplication. Finally, we also consider multiteams with weights in the reals and study the expressive power of formulae by means of topological properties.

Hyporheic hydraulic geometry: Conceptualizing relationships among hyporheic exchange, storage, and water age

Hyporheic exchange is now widely acknowledged as a key driver of ecosystem processes in many streams. Yet stream ecologists have been slow to adopt nuanced hydrologic frameworks developed and applied by engineers and hydrologists to describe the relationship between water storage, water age, and water balance in finite hydrosystems such as hyporheic zones. Here, in the context of hyporheic hydrology, we summarize a well-established mathematical framework useful for describing hyporheic hydrology, while also applying the framework heuristically to visualize the relationships between water age, rates of hyporheic exchange, and water volume within hyporheic zones. Building on this heuristic application, we discuss how improved accuracy in the conceptualization of hyporheic exchange can yield a deeper understanding of the role of the hyporheic zone in stream ecosystems. Although the equations presented here have been well-described for decades, our aim is to make the mathematical basis as accessible as possible and to encourage broader understanding among aquatic ecologists of the implications of tailed age distributions commonly observed in water discharged from and stored within hyporheic zones. Our quantitative description of “hyporheic hydraulic geometry,” associated visualizations, and discussion offer a nuanced and realistic understanding of hyporheic hydrology to aid in considering hyporheic exchange in the context of river and stream ecosystem science and management.

Comparative analysis of models for adjustment procedure in assets value independent evaluation performed by comparative approach

This paper addresses the field of economic measurements of the value of assets, carried out by the methods of independent expert evaluation. The mathematical principles of application, within a comparative methodical approach, of additive and multiplicative models for correcting the cost of single indicator of compared objects have been considered. The differences of mathematical basis of the compared models were analyzed. It has been shown that the ambiguity in the methodology of correction procedure requires studying the advantages and disadvantages of known models, as well as the justification and elaboration of recommendations for their application. Possible forms of correction representation using several alternative units of measurement have been defined; formulas for their interconnection have been built. Analytic expressions have been derived that mathematically describe the algorithms for performing the evaluation correction procedure using various forms of correction representation. The influence of the correction execution model on the characteristics of uncertainty in the independent evaluation result has been analyzed. The scope of two possible types of correction introduction models has been determined. A specific numerical example was used to demonstrate the methodological advantages of using a multiplicative model when summarizing percentage corrections. The independence of the correction result on the sequence of correction introduction has been confirmed. It is proposed to use the selected measure of partial corrections as a criterion for the adequacy of the correction introduction model. It is proved that the result of the independent expert evaluation depends on the chosen model and does not depend on the sequence of correction introduction. The reported study results are important in terms of theory and practice since they make it possible to improve the accuracy and reliability of the result of independent expert evaluation.

Practice-oriented tasks as a means of teaching mathematics to cadets of fire-technical specialties

The article is devoted to the problem of mathematical training of future fire safety engineers. In the process of training, cadets should have developed mathematical thinking, focused on the problems of civil protection. The basis for the formation of such thinking is the implementation of practice-oriented teaching of mathematics. Practice-oriented mathematical problems are an effective teaching tool. In the process of training specialists in fire-technical specialties, such tasks ensure the assimilation of mathematical concepts in the context of their interpretation in the professional field of activity of rescue engineers; creation of the mathematical basis necessary for studying the disciplines of the professional training cycle; development of the skill of constructing mathematical models of processes and phenomena in the field of protection of the population and territories. In this work, the author's definition of a practice-oriented mathematical problem is given, reflecting the real conditions of the service activities of specialists of the Ministry of Emergency Situations. Requirements for the content of such tasks for cadets of fire-technical specialties are formulated. A classification of practice-oriented tasks is proposed, taking into account the specifics of the future service activities of fire and technosphere safety engineers. Mathematical skills and abilities are indicated, the formation of which presents each type of problem, the corresponding practice-oriented mathematical skills necessary in the practical activities of civil protection specialists. Examples of tasks of all considered types are given.

A Modified Multi-Winding DC–DC Flyback Converter for Photovoltaic Applications

DC–DC power converters have generated much interest, as they can be used in a wide range of applications. In micro-inverter applications, flyback topologies are a relevant research topic due to their efficiency and simplicity. On the other hand, solar photovoltaic (PV) systems are one of the fastest growing and most promising renewable energy sources in the world. A power electronic converter (either DC/DC or DC/AC) is needed to interface the PV array with the load/grid. In this paper, a modified interleaved-type step-up DC–DC flyback converter is presented for a PV application. The topology is based on a multi-winding flyback converter with N parallel connected inputs and a single output. Each input is supplied by an independent PV module, and a maximum power point tracking algorithm is implemented in each module to maximize solar energy harvesting. A single flyback transformer is used, and it manages only 1/N of the converter rated power, reducing the size of the magnetic core compared to other similar topologies. The design of the magnetic core is also presented in this work. Moreover, the proposed converter includes active snubber networks to increase the efficiency, consisting of a capacitor connected in series with a power switch, to protect the main switches from damaging dv/dt when returning part of the commutation energy back to the source. In this work, the operating principle of the topology is fully described on a mathematical basis, and an efficiency analysis is also included. The converter is simulated and experimentally validated with a 1 kW prototype considering three PV panels. The experimental results are in agreement with the simulations, verifying the feasibility of the proposal.

A new method for determining stoichiometric coefficients using minors of a matrix

The motivation of this study was the investigation into the metallothermic reduction of chromite ores. Spinel materials have complex structures and as a result, balancing of the reduction reactions by traditional methods become very time consuming. A method to calculate the stoichiometric coefficients for chemical reactions using first a modified matrix-inverse method and then a new optimised method is proposed. The mathematical basis of both methods is explored using matrix algebra and then demonstrated using a typical chromite reduction reaction.

MATHEMATICAL BASIS FOR ANALYSING SIGNALS REMOVED FROM FROM THE HUMAN CEREBRAL CORTEX USING DOBESHI AND HAAR METHODS

The article presents the results of the study of signals taken from the human cerebral cortex, and presents the mathematical foundations of analysis using the methods of Daubechy and Haar. A comparative analysis of the method of the Daubechy and Haar wavelet transform implemented in MATLAB and developed using the C++ programming language in the course of the study on the example of a recorded audio signal with natural interference is given.

Elements of number theory as a mathematical basis for solving problems for processing integer numbers information

The article describes the methodology for preparing schoolchildren to solve problems for processing integer numbers information, where the use of a brute force algorithm is not rational. The statements of number theory necessary to solve the problems of fnding numbers with a given number of divisors of a certain form are formulated; their evidence is given. A set of exercises is presented that promotes the independent "discovery" of the listed statements by schoolchildren and the formation of a skill to identify the structure of a number with given properties. At the end of the article, algorithms and programs are presented to solve problem No. 25, presented in the training control and measuring materials of the Unifed State Exam in informatics in the 2020/2021 academic year. The exercise sets described in the article can be useful to both informatics teachers and schoolchildren preparing for the Unifed State Exam in informatics.