Institute of Mathematics AS CR, v. v. i.
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    JU\sqrt {J}U rings

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    summary:We intend to unviel a new class of rings, called JU\sqrt {J}U rings, if the units of a ring RR equal the sum of 1 and an element from J(R)\sqrt {J(R)}. Recall that J(R)\sqrt {J(R)} is a subset of RR, not necessarily a subring, which equals {zR ⁣:znR\{ z\in R \colon z^n \in R for some n1}n \geq 1 \}. Both UUUU and JUJU rings are JU\sqrt {J}U rings credited to the fact that nilpotents and J(R)J(R) are subsets of J(R)\sqrt {J(R)}. The properties exhibited by JU\sqrt {J}U rings are explored in a thorough manner following which its relations with other rings are observed. For instance, UNJUNJ rings are JU\sqrt {J}U and no matrix ring, when n>1n > 1 is JU\sqrt {J}U. We have focused on extensions of JU\sqrt {J}U rings like T(R,M)T(R,M), H(p,q)(R)H_{(p,q)}(R), L(p,q)(R)L_{(p,q)}(R), Morita context and group rings

    Semiclean and quasi-clean elements in rings

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    summary:We prove uniquely semiclean rings are reduced and hence Abelian. The semiclean elements of RR, R[x]R[x], and Mn(R)M_n(R) are compared. In particular, we show that the indeterminate xx is never semiclean. The 2-primality of a ring RR is characterized via the semiclean elements of R[x]R[x]. We also consider the quasi-clean elements of a ring RR and compare them with the semiclean elements of RR

    Editorial

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    summary:Úvodní slovo vedoucí redaktorky čtenářům časopisu

    Some Didactic Approaches to Euler's Number e in Secondary-School Mathematics Teaching

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    summary:Článek shrnuje některé didaktické přístupy k výuce Eulerova čísla e na středních školách. Kromě transmisivního a formálně algebraického přístupu k výuce tohoto obtížného abstraktního matematického pojmu ukazujeme také konstruktivisticko-heuristický přístup, který se může opírat o reálnou situaci, vizualizace či experimenty a simulace. Do výuky je možné doporučit takovou didaktickou transformaci učiva o čísle e, která bude odpovídat učebním schopnostem studentů.summary:The article summarizes some didactic approaches to teaching Euler's number e in secondary schools. In addition to the transmissive and formally algebraic approach to teaching this difficult abstract mathematical concept, we also show a constructivist-heuristic approach, which can be based on a real situation, visualizations or experiments and simulations. It is possible to recommend such a didactic transformation of the subject matter about the number e that will correspond to the learning abilities of students

    Exponential and Logarithmic Functions

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    summary:Článek zkoumá exponenciální a logaritmické funkce, jejich matematický význam a různé aplikace. Diskutuje jejich historický vývoj, význam v matematice a přírodních vědách, řešení rovnic a grafické znázornění. Mezi praktické aplikace patří růst populace, radioaktivní rozpad, stupnice pH a Richterova stupnice. Článek také propojuje tyto funkce s moderními technologiemi, jako jsou algoritmy, šifrování a vizualizace dat. V neposlední řadě vyzdvihuje jejich přínos k vědeckému pochopení přírodních jevů.summary:The article explores exponential and logarithmic functions, their mathematical significance, and various applications. It discusses their historical development, importance in mathematics and natural sciences, equation solving, and graphical representation. Practical applications include population growth, radioactive decay, the pH scale, and the Richter scale. The article also connects these functions to modern technologies, such as algorithms, encryption, and data visualization. Finally, it highlights their contribution to scientific understanding of natural phenomena

    ET-DMGing: Event-triggered distributed momentum-gradient tracking optimization algorithm for multi-agent systems

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    summary:This paper proposes an event-triggered distributed momentum-gradient tracking optimization algorithm (ET-DMGing) for the collaborative optimization problem of minimizing the sum of all agents' local objective functions in multi-agent systems. Firstly, gradient tracking is employed to precisely track the average momentum gradient for updating agent states, which effectively reduces their dwell time in flat and oscillatory regions. The proposed ET-DMGing exhibits enhanced directional consistency and dynamic stability during optimization by leveraging momentum accumulation effects, achieving a linear convergence rate. Secondly, a new event-triggered condition is proposed, which considers the dual metrics of state error and momentum gradient error. This allows for a more comprehensive assessment of the agents' triggering needs, avoiding instability caused by single-dimensional triggering, and improving the triggering threshold. This event-triggered condition reduces the communication frequency among agents. Thirdly, we rigorously proved that the proposed ET-DMGing converges to the global optimum at a linear convergence rate by employing the small-gain theorem. Furthermore, explicit convergence conditions have been derived for parameter selection, including step size parameters and event-triggered weighting coefficients. Finally, numerical simulations are performed to verify the effectiveness and accuracy of the theoretical results

    New methods to construct uninorms by extending uninorms with closure operators and t-superconorms

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    summary:In this paper, we provide new methods to construct uninorms by extending given uninorms on a subinterval of a bounded lattice with closure operators (resp. interior operators) and t-superconorms (resp. t-subnorms). Meanwhile, these methods for uninorms generalize some known methods for uninorms in the literature. An example is also provided to show our method

    Energie větru

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    Sakaguchi type functions defined by balancing polynomials

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    summary:The class of Sakaguchi type functions defined by balancing polynomials has been introduced as a novel subclass of bi-univalent functions. The bounds for the Fekete-Szegö inequality and the initial coefficients a2\vert a_{2}\vert and a3\vert a_{3}\vert have also been estimated

    Dynamic behavior of vector solutions of a class of 2-D neutral differential systems

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    summary:This work deals with the analysis pertaining some dynamic behavior of vector solutions of first order two-dimensional neutral delay differential systems of the form ddt[u(t)+pu(tτ)v(t)+pv(tτ)]=[abcd][u(tα)v(tβ)]. \frac {{\rm d}}{{\rm d}t} \begin {bmatrix} u(t)+pu(t-\tau )\\ v(t)+pv(t-\tau )\\ \end {bmatrix} = \begin {bmatrix} a & b \\ c & d \\ \end {bmatrix} \begin {bmatrix} u(t-\alpha )\\ v(t-\beta )\\ \end {bmatrix}. The effort has been made to study ddt[x(t)p(t)h1(x(tτ))y(t)p(t)h2(y(tτ))]+[a(t)b(t)c(t)d(t)][f1(x(tα))f2(y(tβ))]=0, \frac {{\rm d}}{{\rm d}t} \begin {bmatrix} x(t)-p(t)h_{1}(x(t-\tau ))\\ y(t)-p(t)h_{2}(y(t-\tau )) \end {bmatrix} + \begin {bmatrix} a(t) & b(t)\\ c(t) & d(t) \end {bmatrix} \begin {bmatrix} f_{1}(x(t-\alpha ))\\ f_{2}(y(t-\beta )) \end {bmatrix} =0, where p,a,b,c,d,h1,h2,f1,f2C(R,R)p,a,b,c,d,h_1,h_2,f_1,f_2 \in C(\mathbb {R},\mathbb {R}); α,β,τR+\alpha ,\beta ,\tau \in \mathbb {R}^+. We verify our results with the examples

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