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О специфической асимптотической устойчивости решений линейного однородного вольтеррова интегродифференциального уравнения четвертого порядка


Makale | 2021 | Вестник Московского университета. Серия 1: Математика. Механика ( 1 )

Устанавливаются достаточные условия асимптотической устойчивости решений линейного однородного вольтеррова интегродифференциального уравнения четвертого порядка в случае, когда любое ненулевое решение соответствующего линейного однородного дифференциального уравнения четвертого порядка не является асимптотически устойчивым. Приводится иллюстрирующий пример. . . . Daha fazlası Daha az

Superabsorbent hydrogels based on N,N-dimethylacrylamide and maleic acid for applications in agriculture as water purifier and nitrogen carrier


Makale | 2021 | Polymer Bulletin79 ( 10 )

To reduce water pollution caused by fertilizers in agricultural irrigation, highly swelling crosslinked hydrogels (p(DMAAm-co-MA) or DM1) based on N,N-dimethylacrylamide (DMAAm) and maleic acid (MA) were prepared using a chemical initiator with the redox polymerization technique. Negative and positive surface modifications of DM1 were achieved using hydrochloric acid (HCl) (p(DMAAm-co-MA)/HCl or DM2) and sodium hydroxide (NaOH) (p(DMAAm-co-MA)/NaOH or DM3), respectively. The synthesized hydrogels were named DM1, DM2 and DM3, respectively. The swelling properties, urea sorption and urea release kinetics of synthesized hydrogels were . . .analyzed in deionized water at different pHs. The sorption isotherms and sorption parameters were investigated thoroughly for all hydrogels and the Langmuir (L) isotherm showed the best fit. In order to examine the urea release mechanism from all hydrogels, four mathematical models of zero-order kinetic model (Z-O), first-order kinetic model (F-O), Higuchi (H) and the Korsmeyer-Peppas power law (K-P) were studied to fit the experimental data. The hydrogels exhibited swelling and releasing properties that were highly dependent on their functional groups and the ionic forces in the medium. Cumulative urea release values for DM1, DM2 and DM3 were calculated as 100?t pH 10, 100?t pH 8 and 100?t pH 8 within 48, 41 and 18 h, respectively. It was confirmed by experimental studies that the prepared hydrogels and their derivatives can be used as carriers for fertilizers, particularly urea, as well as controlled water release sources. As a result, the use of the synthesized hydrogels to prevent contamination of water resources with agricultural products and to provide a nitrogen source that plants require comprise the innovative and original aspect of the article Daha fazlası Daha az

Of Silica Gel-Glasses on the 4 I 13/2 → 4 I 15/2 Luminescence Bandwidth of Er3 Ions


Makale | 2023 | Journal of Applied Spectroscopy90 ( 5 )

The luminescence of Er3 ions in silica glasses synthesized by the direct sol–gel–glass transition method and by melting of activated gel grit using various precursors of optical centers was studied. The formation of complex centers including erbium, aluminum, and alkali metal ions was found to be one way of essentially increasing the half-width of the 4 I 13/2 → 4 I 15/2 luminescence band of these ions. Keyword: complex optical centers; luminescence; rare earth ions; sol–gel method

On The Recursive Sequence x(n+1)=x(n-20)/[1+x(n-2)x(n-5)x(n-8)x(n-11)x(n-14)x(n-17)]

Burak OĞUL

Makale | 2019 | MANAS Journal of Engineering (MJEN)7 ( 2 )

The behaivour of the solutions of the following system of difference equations is examined, x(n+1)=x(n-20)/[1+x(n-2)x(n-5)x(n-8)x(n-11)x(n-14)x(n-17)] where the initial conditions are positive real numbers. The initial conditions of the equation are arbitrary positive real numbers. Also, we discuss and illustrate the stability of the solutions in the neighborhood of the critical points and the periodicity of the considered equations

Possibilities for Prediction And Evaluation of the Carbon Footprint in Furnace Fuel Oil Combustion in Medium- and Low-Power Boilers


Makale | 2023 | Theoretical Foundations of Chemical Engineering57 ( 5 )

To predict and evaluate the carbon footprint in the gas phase, furnace fuel oil oxidation in excess air (alpha factor 1.3) was studied over a wide temperature (T 298–3000 K, P 0.1 MPa). Equilibrium thermodynamic parameters (entropy, enthalpy, and internal energy) and the concentration distributions of C-, S-, N-, O-, and H-containing components and active particles in the gas phase were determined. Based on the total concentration distribution of C-, S-, N-, O-, and H-containing components and active particles in the gas phase, the weight content of carbon was calculated. Taking into account the chemical matrix of the furnace fuel o . . .il–air system and the weight content of carbon, the man-made load of carbon in the gas phase was found. The results of the work made it possible to evaluate the carbon footprint in the gas phase because of the combustion of fuel, in particular, furnace fuel oil in air. Reduction of the man-made load of carbon oxides (CO, CO2) in the gas phase was achieved by modifying and burning furnace fuel oil in the form of oil-in-water (reverse) emulsions in E-1/9M industrial boilers. Keyword: carbon footprint; concentration distribution; furnace fuel oil–air; gas phase; man-made loa Daha fazlası Daha az

Tuned CuCr layered double hydroxide/carbon-based nanocomposites inducing sonophotocatalytic degradation of dimethyl phthalate

Mehmet KOBYA

Makale | 2023 | Ultrasonics Sonochemistry95

This study is the first to explore the possibility of utilizing CuCr LDH decorated on reduced graphene oxide (rGO) and graphene oxide (GO) as sonophotocatalysts for the degradation of dimethyl phthalate (DMP). CuCr LDH and its nanocomposites were successfully fabricated and characterized. Scanning electron microscopy (SEM) along with high-resolution transmission electron microscope (HRTEM) both evidenced the formation of randomly oriented nanosheet structures of CuCr LDH coupled with thin and folded sheets of GO and rGO. The impact of diverse processes on the degradation efficiency of DMP in the presence of the so-prepared catalysts . . . was compared. Benefiting from the low bandgap and high specific surface area, the as-obtained CuCr LDH/rGO represented outstanding catalytic activity (100 ) toward 15 mg L−1 of DMP within 30 min when subjected to light and ultrasonic irradiations simultaneously. Radical quenching experiments and visual spectrophotometry using an O-phenylenediamine revealed the crucial role of hydroxyl radicals compared to holes and superoxide radicals. Overall, outcomes disclosed that CuCr LDH/rGO is a stable and proper sonophotocatalyst for environmental remediation. Keywords: Layered double hydroxide, Graphene, Advanced oxidation processes, Sonophotocatalysis, Dimethyl phthalat Daha fazlası Daha az

An Electric Arc Furnace Model Based on Resynthesis Using Frequency Spectrum Distributions of EAF Currents


Konferans Bildirisi | 2023 | IEEE Industry Applications Society Annual Meeting

The research work presented in this paper proposes a method for modeling the behavior of the Electric Arc Furnace (EAF) currents for a tap-to-tap time based on the DFT amplitude histograms of the EAF current waves. The method is used to model the EAF current behavior separately for each phase of the EAF operation: boring, melting and refining. The model is verified by comparing the THD histograms and the flicker measurements of the original and modeled EAF current waveforms. The proposed model can be used as an EAF model in the simulation environment for various purposes before the installation of an EAF. The method has low computat . . .ional load compared to various other techniques, since it utilizes only the amplitude distribution parameters of the first 13 frequency components and the one-cycle signal representing the higher order harmonics. The model is novel in the sense that every time the EAF current signal is generated, a unique waveform reflecting the corresponding distributions is generated, which is compatible with the random behavior of the EAF operation. Keyword: EAF current; EAF modeling; electric arc furnace (EAF); power quality; steel makin Daha fazlası Daha az

Well-Posedness and Blow-Up of Solutions for a Variable Exponent Nonlinear Petrovsky Equation


Makale | 2023 | Advances in Mathematical Physics2023

In this article, we investigate a nonlinear Petrovsky equation with variable exponent and damping terms. First, we establish the local existence using the Faedo-Galerkin approximation method under the conditions of positive initial energy and appropriate constraints on the variable exponents p & sdot; and q & sdot;. Finally, we prove a finite-time blow-up result for negative initial energy. Keyword: global existence; wave-equation

Singularly Perturbed Multidimensional Parabolic Equation with Rapidly Oscillating Free Term


Makale | 2022 | Ukrainian Mathematical Journal73 ( 12 )

The regularized asymptotics of the solution of the first boundary-value problem for a two-dimensional differential equation of parabolic type is constructed in the case where the phase derivative vanishes at a single point. It is shown that angular and multidimensional boundary-layer functions appear in problems of this kind parallel with other types of boundary layers.

Социальные сети, цифровые образовательные ресурсы и гаджеты в учебном процессе (на примере Кыргызстана)


Makale | 2018 | Современные наукоемкие технологии ( 6 )

В данной статье представлены результаты проведенного исследования по использованию социальных сетей, облачных технологий, гаджетов и цифровых образовательных ресурсов в образовательных учреждениях Кыргызстана. Исследование проводилось путем интервьюирования, анкетирования преподавателей и студентов университетов Кыргызстана, а также был проведен статистический анализ полученных данных. В опросе принял участие 291 студент из пяти университетов Кыргызстана, из них 90% обучаются по направлению «Информационные технологии», 10% на юридических и медицинских специальностях. Также в опросе приняли участие пятнадцать преподавателей. В ходе а . . .нкетирования была выявлена востребованность, доступность и удовлетворенность всех участников учебного процесса предоставляемым университетами техническим оборудованием, интернетом. Полученные результаты отображают мнение студентов и преподавателей о том, каким образом используются вышеперечисленные технологии в учебном процессе. В стране разрабатываются образовательные ресурсы на национальном языке как для школ, так и для университетов. Проведенное исследование дает картину степени их востребованности среди преподавателей и студентов университетов. Полученные результаты позволят оценить готовность участников учебного процесса к использованию современных информационных технологий в учебном процесс Daha fazlası Daha az

The Consecutive Substitution Method for Boundary Value Problems (BVPs) with Retarded Argument


Makale | 2023 | Journal of Applied Mathematics2023

In this study, we applied an approximate solution method for solving the boundary value problems (BVPs) with retarded argument. The method is the consecutive substitution method. The consecutive substitution method was applied and an approximate solution was obtained. The numerical solution and the analytical solution are compared in the table. The solutions were found to be compatible. Keywords: approximate solution; boundary-value problem; numerical solution; retarded argument; solution methods; substitution method; boundary value problems

Solutions Of The Rational Difference Equations X(n 1)=x(n (2k 1)) /1 X(n-k) = Rasyonel Fark Denkleminin Çözümleri

Dağıstan ŞİMŞEK | Burak OĞUL

Makale | 2017 | MANAS Journal of Engineering (MJEN)5 ( 3 )

In this paper the solutions of the following difference equation is examined, x(n 1)=x(n (2k 1)) /1 x(n-k) (1) where the initial conditions are positive real numbers.

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