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Tighter underestimator for bivariate global optimization 二元全局优化的更紧低估器
IF 0.9
Afrika Matematika Pub Date : 2025-01-13 DOI: 10.1007/s13370-024-01235-z
Mohand Ouanes
{"title":"Tighter underestimator for bivariate global optimization","authors":"Mohand Ouanes","doi":"10.1007/s13370-024-01235-z","DOIUrl":"10.1007/s13370-024-01235-z","url":null,"abstract":"<div><p>We propose in this paper a tighter underestimator for <span>(C^{2})</span>-nonconvex bivariate functions. We show that it is tighter than the classical <span>(alpha -)</span>BB underestimator. A branch and bound algorithm with this tighter underestimator is developed to solve bivariate global optimzation problems. The triangulation is used as an exhaustive subdivision, and a convex/concave test is added to accelerate the convergence of our branch and bound algorithm.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142963060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A model for the dynamics of COVID-19 infection transmission in human with latent delay 具有潜伏延迟的COVID-19人感染传播动力学模型
IF 0.9
Afrika Matematika Pub Date : 2025-01-11 DOI: 10.1007/s13370-024-01226-0
Amar N. Chatterjee, Teklebirhan Abraha, Fahad Al Basir, Delfim F. M. Torres
{"title":"A model for the dynamics of COVID-19 infection transmission in human with latent delay","authors":"Amar N. Chatterjee,&nbsp;Teklebirhan Abraha,&nbsp;Fahad Al Basir,&nbsp;Delfim F. M. Torres","doi":"10.1007/s13370-024-01226-0","DOIUrl":"10.1007/s13370-024-01226-0","url":null,"abstract":"<div><p>In this research, we have derived a mathematical model for within human dynamics of COVID-19 infection using delay differential equations. The new model considers a ’latent period’ and ’the time for immune response’ as delay parameters, allowing us to study the effects of time delays in human COVID-19 infection. We have determined the equilibrium points and analyzed their stability. The disease-free equilibrium is stable when the basic reproduction number, <span>(R_0)</span>, is below unity. Stability switch of the endemic equilibrium occurs through Hopf-bifurcation. This study shows that the effect of latent delay is stabilizing whereas immune response delay has a destabilizing nature.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Periodicity and positivity of solutions for first-order nonlinear neutral differential equations with iterative terms and impulsive effects 具有迭代项和脉冲效应的一阶非线性中立型微分方程解的周期性和正性
IF 0.9
Afrika Matematika Pub Date : 2025-01-11 DOI: 10.1007/s13370-025-01237-5
Mimia Benhadri, Tomás Caraballo
{"title":"Periodicity and positivity of solutions for first-order nonlinear neutral differential equations with iterative terms and impulsive effects","authors":"Mimia Benhadri,&nbsp;Tomás Caraballo","doi":"10.1007/s13370-025-01237-5","DOIUrl":"10.1007/s13370-025-01237-5","url":null,"abstract":"<div><p>In the present paper, sufficient conditions for the existence of bounded positive periodic solutions are established for a class of nonlinear neutral differential equations with iterative source term and nonlinear impulses. The form including an impulsive term of the equations in this paper is rather general and incorporates as special cases various problems which have been studied extensively in the literature. Transforming the considered equation to an equivalent integral equation, we prove the existence of positive periodic solutions using a Krasnoselskii fixed point theorem for the sum of a contraction and a compact mapping. Finally, we present an example to illustrate the effectiveness of our results.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142962989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
An efficient estimation of finite population mean through difference estimator in systematic sampling 用系统抽样差分估计器估计有限总体均值的一种有效方法
IF 0.9
Afrika Matematika Pub Date : 2025-01-10 DOI: 10.1007/s13370-024-01234-0
Surya K. Pal, Sagir A. Mahmud, Housila P. Singh
{"title":"An efficient estimation of finite population mean through difference estimator in systematic sampling","authors":"Surya K. Pal,&nbsp;Sagir A. Mahmud,&nbsp;Housila P. Singh","doi":"10.1007/s13370-024-01234-0","DOIUrl":"10.1007/s13370-024-01234-0","url":null,"abstract":"<div><p>This paper addresses the problem of estimating the finite population mean <span>(overline{Y})</span> of the study variable <span>(y)</span> using two auxiliary variables in systematic sampling. We have suggested a difference-type estimator and its improved version, and then their properties have been studied. It has been shown that the proposed class of estimators is more efficient than the recently proposed estimators due to Tailor et al. (Stat Transit 14: 391–398, 2013) and Khan and Singh (J Prob Stat https://doi.org/10.1155/2015/248374, 2015). An empirical study has been undertaken to evaluate the performance of the suggested estimator over other existing estimators.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142938828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
An accelerated Tseng type method for solving zero point problems and certain optimization problems 求解零点问题及若干优化问题的加速Tseng型方法
IF 0.9
Afrika Matematika Pub Date : 2025-01-09 DOI: 10.1007/s13370-024-01217-1
A. A. Mebawondu, H. A. Abass, O. K. Oyewole
{"title":"An accelerated Tseng type method for solving zero point problems and certain optimization problems","authors":"A. A. Mebawondu,&nbsp;H. A. Abass,&nbsp;O. K. Oyewole","doi":"10.1007/s13370-024-01217-1","DOIUrl":"10.1007/s13370-024-01217-1","url":null,"abstract":"<div><p>In this paper, we proposed a modified Tseng’s splitting iterative algorithm for approximating a solution of split feasibility problem for zero and fixed point problems. By incorporating an inertial extrapolation method and Halpern iterative technique, we established a strong convergence result for approximating a solution of split fixed point problem for a nonexpansive and quasinonexpansive mapping which is also a zero point of sum of two monotone operators in the framework of real Hilbert spaces. Furthermore, we present a numerical example to support our main result. The results obtained in this paper improve, extend and unify some related results in the literature.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13370-024-01217-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Optimal classes of estimators for population mean using higher order moments 利用高阶矩对总体均值进行最优估计
IF 0.9
Afrika Matematika Pub Date : 2025-01-08 DOI: 10.1007/s13370-024-01232-2
Shashi Bhushan, Anoop Kumar
{"title":"Optimal classes of estimators for population mean using higher order moments","authors":"Shashi Bhushan,&nbsp;Anoop Kumar","doi":"10.1007/s13370-024-01232-2","DOIUrl":"10.1007/s13370-024-01232-2","url":null,"abstract":"<div><p>This paper considers some optimal classes of difference and ratio type estimators for the estimation of population mean using higher order moments viz variance of auxiliary variable with the aim of improvement over its entrants existing till date. The bias and mean square error of the considered estimators are derived using Taylor series method up to the first order of approximation. The theoretical results have been determined and appraised with a computational study using real and artificially generated data sets. The computational results are turned out to be rather advance providing better improvement over the contemporary estimators.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142938850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
(i–v) Pseudo-symmetric fuzzy ideal in semigroups （i-v）半群中的伪对称模糊理想
IF 0.9
Afrika Matematika Pub Date : 2025-01-07 DOI: 10.1007/s13370-024-01236-y
Paltu Sarkar, Sukhendu Kar
{"title":"(i–v) Pseudo-symmetric fuzzy ideal in semigroups","authors":"Paltu Sarkar,&nbsp;Sukhendu Kar","doi":"10.1007/s13370-024-01236-y","DOIUrl":"10.1007/s13370-024-01236-y","url":null,"abstract":"<div><p>In this paper, we discover Anjaneyulu’s pseudo-symmetricity with the help of interval-valued fuzzy membership function. In semigroups, we propose the concept of (<i>i–v</i>) pseudo-symmetric (semipseudo-symmetric, semiprimary) fuzzy ideals and cultivate their different properties. Moreover, we mention some relationships among three (<i>i–v</i>) fuzzy radicals. Lastly, we verify that the (<i>i–v</i>) fuzzy ideals, namely, (<i>i–v</i>) completely prime, (<i>i–v</i>) completely semiprime, (<i>i–v</i>) pseudo-symmetric and (<i>i–v</i>) primary fuzzy ideals are equivalent in some specific semigroups.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142938945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Different solitons associated with 3-dimensional generalized Sasakian-space-forms 与三维广义sasaki空间形式相关的不同孤子
IF 0.9
Afrika Matematika Pub Date : 2025-01-03 DOI: 10.1007/s13370-024-01233-1
Arpan Sardar, Avijit Sarkar
{"title":"Different solitons associated with 3-dimensional generalized Sasakian-space-forms","authors":"Arpan Sardar,&nbsp;Avijit Sarkar","doi":"10.1007/s13370-024-01233-1","DOIUrl":"10.1007/s13370-024-01233-1","url":null,"abstract":"<div><p>In the present paper we characterize 3-dimensional generalized Sasakian-space-forms admitting some solitons such as Einstein solitons, <span>(eta )</span>-Einstein solitons,<span>(eta )</span>-Ricci solitons, gradient <span>(eta )</span>-Ricci solitons and <span>(eta )</span>-Yamabe solitons. First we show that an Einstein soliton on a 3-dimensional generalized Sasakian-space-form <span>(M(f_1,f_2,f_3))</span> becomes a Ricci soliton and the soliton is shrinking, steady and expanding according as <span>((f_1 - f_3) &lt; 0, = 0)</span> and <span>(&gt; 0)</span>, respectively, where <span>(f_1)</span>, <span>(f_2)</span> and <span>(f_3)</span> are smooth functions. Also, we establish that if a 3-dimensional generalized Sasakian-space-form <span>(M(f_1,f_2,f_3))</span> admits a gradient <span>(eta )</span>-Ricci soliton with potential function <i>f</i>, then <span>(f = log(frac{f_1-f_3}{k})^2,)</span> where <i>k</i> is a constant. Next, we prove that if a 3-dimensional generalized Sasakian-space-form <span>(M(f_1,f_2,f_3))</span> is an <span>(eta )</span>-Yamabe soliton, then the soliton reduces to a Yamabe soliton and the scalar curvature is constant. Finally, we construct an example which proves the existence of our results.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Inference on overlapping coefficient in two exponential populations based on adaptive type-II progressive hybrid censoring 基于自适应型渐进式混合滤波的两指数种群重叠系数推断
IF 0.9
Afrika Matematika Pub Date : 2024-12-27 DOI: 10.1007/s13370-024-01222-4
Amal Helu
{"title":"Inference on overlapping coefficient in two exponential populations based on adaptive type-II progressive hybrid censoring","authors":"Amal Helu","doi":"10.1007/s13370-024-01222-4","DOIUrl":"10.1007/s13370-024-01222-4","url":null,"abstract":"<div><p>This article considers a life test scheme called the adaptive type-II progressive hybrid censoring scheme introduced by Ng et al. (Naval Res Logist 5(8):687–698, 2009). Based on this type of censoring, we draw inferences about the three well-known measures of overlap, namely Matusita’s measure (<span>( rho )</span>), Morisita’s measure (<span>(lambda )</span>), and Weitzman’s (<span>(Delta )</span>) for two exponential populations with different means. The asymptotic bias and variance of the overlap measure estimators are derived. Monte Carlo evaluations are employed in cases with small sample sizes, where computing the precision or bias of these estimators becomes challenging due to the lack of closed-form expressions for their variances and exact sampling distributions. Confidence intervals for those measures are also constructed via the bootstrap method and Taylor expansion approximation. To emphasize the practical relevance of our proposed estimators, we illustrate their application using a real data set from head and neck cancer research.</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142889479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Generalized Drazin-Riesz invertible elements in a semi-simple Banach algebra 半简单Banach代数中的广义Drazin-Riesz可逆元
IF 0.9
Afrika Matematika Pub Date : 2024-12-27 DOI: 10.1007/s13370-024-01227-z
Othman Abad, Hassane Zguitti
{"title":"Generalized Drazin-Riesz invertible elements in a semi-simple Banach algebra","authors":"Othman Abad,&nbsp;Hassane Zguitti","doi":"10.1007/s13370-024-01227-z","DOIUrl":"10.1007/s13370-024-01227-z","url":null,"abstract":"<div><p>We extend the notion of generalized Drazin-Riesz inverse introduced for bounded linear operators in Živković-Zlatanović and Cvetković (Linear Multilinear Algebra 65(6):1171–1193, 2017) to elements in a complex unital semi-simple Banach algebra. Several characterizations and properties of generalized Drazin-Riesz invertible elements are given. In particular, we extend those of Abad and Zguitti (Ann Funct Anal 12:Article number: 55, 2021), Djordjević and Stanimirovic (Czech Math J 51(3):617–634, 2001) and Živković-Zlatanović and Cvetković (2017).</p></div>","PeriodicalId":46107,"journal":{"name":"Afrika Matematika","volume":"36 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142890443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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