Examples and Counterexamples最新文献

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Quadrature based innovative techniques concerning nonlinear equations having unknown multiplicity 基于正交的有关未知倍数非线性方程的创新技术
Examples and Counterexamples Pub Date : 2024-12-01 Epub Date: 2024-07-09 DOI: 10.1016/j.exco.2024.100150
Farooq Ahmed Shah , Muhammad Waseem
{"title":"Quadrature based innovative techniques concerning nonlinear equations having unknown multiplicity","authors":"Farooq Ahmed Shah ,&nbsp;Muhammad Waseem","doi":"10.1016/j.exco.2024.100150","DOIUrl":"https://doi.org/10.1016/j.exco.2024.100150","url":null,"abstract":"<div><p>Solution of nonlinear equations is one of the most frequently encountered issue in engineering and applied sciences. Most of the intricateed engineering problems are modeled in the frame work of nonlinear equation <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>x</mi><mo>)</mo></mrow><mo>=</mo><mn>0</mn><mo>.</mo></mrow></math></span> The significance of iterative algorithms executed by computers in resolving such functions is of paramount importance and undeniable in contemporary times. If we study the simple roots and the roots having multiplicity greater of any nonlinear equations we come to the point that finding the roots of nonlinear equations having multiplicity greater than one is not trivialvia classical iterative methods. Instability or slow convergence rate is faced by these methods, and also sometimes these methods diverge. In this article, we give some innovative and robust iterative techniques for obtaining the approximate solution of nonlinear equations having multiplicity <span><math><mrow><mi>m</mi><mo>&gt;</mo><mn>1</mn></mrow></math></span>. Quadrature formulas are implemented to obtain iterative techniques for finding roots of nonlinear equations having unknown multiplicity. The derived methods are the variants of modified Newton method with high order of convergence and better accuracy. The convergence criteria of the new techniques are studied by using Taylor series method. Some examples are tested for the sack of implementations of these techniques. Numerical and graphical comparison shows the performance and efficiency of these new techniques.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"6 ","pages":"Article 100150"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X24000168/pdfft?md5=1401656be5f763d7bc65918548e7c152&pid=1-s2.0-S2666657X24000168-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141594856","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
On the elastic instability of a simple truss structure subjected to a tensile dead load 关于简单桁架结构在拉伸自重作用下的弹性失稳问题
Examples and Counterexamples Pub Date : 2024-12-01 Epub Date: 2024-10-23 DOI: 10.1016/j.exco.2024.100165
Alfredo Canelas, Ana I. Abreu
{"title":"On the elastic instability of a simple truss structure subjected to a tensile dead load","authors":"Alfredo Canelas,&nbsp;Ana I. Abreu","doi":"10.1016/j.exco.2024.100165","DOIUrl":"10.1016/j.exco.2024.100165","url":null,"abstract":"<div><div>There are a significant number of examples of structures that fail due to elastic instability of elements subjected to compressive forces. There are also examples of elastic instability caused by tensile forces, but they are less well known. This paper presents an interesting example of the latter type, whose main feature is its counterintuitive post-critical behavior. In fact, the applied dead load does negative work in the movement from the critical to the post-critical equilibrium configuration. The example admits a complete analytical solution, which makes it ideal for teaching use and as a benchmark problem for testing computational codes.</div></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"6 ","pages":"Article 100165"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528944","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
Whether the singularities are removable in some metrics 奇点在某些度量中是否可移动
Examples and Counterexamples Pub Date : 2024-12-01 Epub Date: 2024-10-15 DOI: 10.1016/j.exco.2024.100164
Ting-Han Pei
{"title":"Whether the singularities are removable in some metrics","authors":"Ting-Han Pei","doi":"10.1016/j.exco.2024.100164","DOIUrl":"10.1016/j.exco.2024.100164","url":null,"abstract":"<div><div>For a long time, the singularities in certain metrics have been problematic and must be removed to avoid unreasonable results in spacetime. Therefore, some new metrics were proposed to eliminate these singularities through coordinate transformations, but they seem not to be workable. In this paper, we re-examine the mathematical structures of the Schwarzschild metric, Reissner-Nordström metric, and Kerr metric. We find that after some transformations, the timelike Eddington-Finkelstein coordinate and the Kruskal-Szekeres coordinates do not delete the singularity problem in the original Schwarzschild metric. It is also true for the tortoise coordinates that it does not solve the singularities at two event horizons in the Kerr metric. After some discussions on those coordinate transformations, a counterexample is given where the singularities are not eliminated.</div></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"6 ","pages":"Article 100164"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142540290","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
A dispersive dynamical system that is chain transitive 具有链传递性的分散动力系统
Examples and Counterexamples Pub Date : 2024-12-01 Epub Date: 2024-07-16 DOI: 10.1016/j.exco.2024.100153
Eduardo C. Viscovini, Josiney A. Souza
{"title":"A dispersive dynamical system that is chain transitive","authors":"Eduardo C. Viscovini,&nbsp;Josiney A. Souza","doi":"10.1016/j.exco.2024.100153","DOIUrl":"10.1016/j.exco.2024.100153","url":null,"abstract":"<div><p>This paper compares the notions of Auslander generalized recurrence and chain recurrence of dynamical systems. Generalized recurrent points are chain recurrent, however, chain recurrent points may not be generalized recurrent of any order. Because of the absence of recursiveness, the dispersive systems have no generalized recurrent point. Examples of systems with generalized recurrent points and systems with no generalized recurrent points are presented. The main example shows a dispersive system that is chain transitive.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"6 ","pages":"Article 100153"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X24000193/pdfft?md5=b5a91c98f35a5ef489f7935a208858b4&pid=1-s2.0-S2666657X24000193-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141622845","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
Degree-based topological indices of the idempotent graph of the ring Zn 环 Zn 的幂等图的基于度的拓扑指数
Examples and Counterexamples Pub Date : 2024-12-01 Epub Date: 2024-10-05 DOI: 10.1016/j.exco.2024.100161
Osman Gani Mondal, Sk. Md. Abu Nayeem
{"title":"Degree-based topological indices of the idempotent graph of the ring Zn","authors":"Osman Gani Mondal,&nbsp;Sk. Md. Abu Nayeem","doi":"10.1016/j.exco.2024.100161","DOIUrl":"10.1016/j.exco.2024.100161","url":null,"abstract":"<div><div>Let <span><math><mi>R</mi></math></span> be a finite commutative ring with a non-zero identity, and <span><math><mrow><mi>I</mi><mi>d</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow></mrow></math></span> be the set of idempotent elements of <span><math><mi>R</mi></math></span>. The idempotent graph of <span><math><mi>R</mi></math></span>, denoted by <span><math><mrow><msub><mrow><mi>G</mi></mrow><mrow><mi>I</mi><mi>d</mi></mrow></msub><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow></mrow></math></span>, is a simple undirected graph with all elements of <span><math><mi>R</mi></math></span> as vertices, and two distinct vertices <span><math><mi>u</mi></math></span>, <span><math><mi>v</mi></math></span> are adjacent if and only if <span><math><mrow><mi>u</mi><mo>+</mo><mi>v</mi><mo>∈</mo><mi>I</mi><mi>d</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow></mrow></math></span>. In this paper, we consider the idempotent graph of the ring <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> and investigate some degree-based topological indices, such as the general sum-connectivity index, the general Randić index, the general Zagreb index, and the Sombor index of that graph by considering the <span><math><mi>M</mi></math></span>-polynomial of the graph.</div></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"6 ","pages":"Article 100161"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438424","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
On the extension of quadrant dependence 关于象限依存性的扩展
Examples and Counterexamples Pub Date : 2024-06-01 Epub Date: 2024-06-04 DOI: 10.1016/j.exco.2024.100146
João Lita da Silva
{"title":"On the extension of quadrant dependence","authors":"João Lita da Silva","doi":"10.1016/j.exco.2024.100146","DOIUrl":"https://doi.org/10.1016/j.exco.2024.100146","url":null,"abstract":"<div><p>In this short note, it is propounded an extension for quadrant dependence, and shown that some of the original proprieties of this popular concept remain valid, while others are necessarily generalized. A second Borel–Cantelli lemma due to Petrov (Statist. Probab. Lett. 58: 283–286, 2002) is revisited for events enjoying this new dependence notion and demonstrated by means of simpler arguments.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"5 ","pages":"Article 100146"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X24000120/pdfft?md5=7ab76f0ec02449bb41d1ed97e3dbd4c2&pid=1-s2.0-S2666657X24000120-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141242913","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
A note on non-supercyclic vectors of Hilbert space operators 关于希尔伯特空间算子的非超循环向量的说明
Examples and Counterexamples Pub Date : 2024-06-01 Epub Date: 2024-01-12 DOI: 10.1016/j.exco.2023.100131
Masoumeh Faghih-Ahmadi, Karim Hedayatian
{"title":"A note on non-supercyclic vectors of Hilbert space operators","authors":"Masoumeh Faghih-Ahmadi,&nbsp;Karim Hedayatian","doi":"10.1016/j.exco.2023.100131","DOIUrl":"https://doi.org/10.1016/j.exco.2023.100131","url":null,"abstract":"<div><p>In this note it is shown that there is a bounded linear operator <span><math><mi>T</mi></math></span> on the Hardy Hilbert space <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> and a vector <span><math><mi>f</mi></math></span> in <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> such that the closure of the set <span><math><mrow><mo>{</mo><mi>α</mi><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup><mi>f</mi><mo>:</mo><mi>α</mi><mo>∈</mo><mi>ℂ</mi><mo>,</mo><mspace></mspace><mi>n</mi><mo>≥</mo><mn>0</mn><mo>}</mo></mrow></math></span> is not <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>, but for every subsequence <span><math><msubsup><mrow><mrow><mo>(</mo><msub><mrow><mi>n</mi></mrow><mrow><mi>k</mi></mrow></msub><mo>)</mo></mrow></mrow><mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>∞</mi></mrow></msubsup></math></span> the closed linear span of <span><math><mrow><mo>{</mo><msup><mrow><mi>T</mi></mrow><mrow><msub><mrow><mi>n</mi></mrow><mrow><mi>k</mi></mrow></msub></mrow></msup><mi>f</mi><mo>:</mo><mi>k</mi><mo>≥</mo><mn>1</mn><mo>}</mo></mrow></math></span> is the whole space <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>. Furthermore, the closure of <span><math><mrow><mo>{</mo><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup><mi>g</mi><mo>:</mo><mi>n</mi><mo>≥</mo><mn>0</mn><mo>}</mo></mrow></math></span> is <span><math><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> for some <span><math><mrow><mi>g</mi><mo>∈</mo><msup><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"5 ","pages":"Article 100131"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X23000332/pdfft?md5=d5b92bb3f23309e6fdacec6aceef1367&pid=1-s2.0-S2666657X23000332-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139433408","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
On a convex combination of Lotka–Volterra operators 关于洛特卡-伏特拉算子的凸组合
Examples and Counterexamples Pub Date : 2024-06-01 Epub Date: 2023-12-29 DOI: 10.1016/j.exco.2023.100133
Farrukh Mukhamedov , Chin Hee Pah , Azizi Rosli
{"title":"On a convex combination of Lotka–Volterra operators","authors":"Farrukh Mukhamedov ,&nbsp;Chin Hee Pah ,&nbsp;Azizi Rosli","doi":"10.1016/j.exco.2023.100133","DOIUrl":"https://doi.org/10.1016/j.exco.2023.100133","url":null,"abstract":"<div><p>We consider a convex combination of two classes of Lotka–Volterra operators defined on 2-dimensional simplex. Earlier, the dynamics of a particular case of the considered operators has been investigated. However, its bijective property was not studied. In this paper, we are able to establish that such maps are homeomorphism of the simplex.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"5 ","pages":"Article 100133"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X23000356/pdfft?md5=07391a1148694cb6898e73ab372d547e&pid=1-s2.0-S2666657X23000356-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139100859","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
Exploration of novel analytical solutions of boundary layer equation via the modified sumudu transform 通过修正的苏木杜变换探索边界层方程的新型解析解
Examples and Counterexamples Pub Date : 2024-06-01 Epub Date: 2024-02-04 DOI: 10.1016/j.exco.2024.100140
Shailesh A. Bhanotar
{"title":"Exploration of novel analytical solutions of boundary layer equation via the modified sumudu transform","authors":"Shailesh A. Bhanotar","doi":"10.1016/j.exco.2024.100140","DOIUrl":"https://doi.org/10.1016/j.exco.2024.100140","url":null,"abstract":"<div><p>The research introduces the Modified Sumudu Decomposition Method (MSDM) as a novel approach for solving non-linear ordinary differential equations. Stemming from the Sumudu Transformation (ST), proposed by Watugala in the 1990s, MSDM demonstrates its efficacy through the solution of a specific third-order non-homogeneous nonlinear ordinary differential equation. This method is particularly highlighted for its application in fluid mechanics, specifically addressing a boundary layer problem. Furthermore, the study employs Pade´ Approximants to evaluate a crucial parameter, ρ=φ''(0), and compares the results with other established methods, including Modified Laplace Decomposition Method (MLDM), Modified Adomian Decomposition Method (MADM), Modified Variational Iteration Method (MVIM), and the Homotopy Perturbation Method (HPM). The findings not only contribute to the advancement of mathematical techniques for solving complex differential equations but also provide a comparative analysis, elucidating the strengths and limitations of different methodologies. This research is anticipated to have significant implications for researchers and practitioners in the field, offering a valuable toolkit for tackling a wide range of mathematical modeling challenges.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"5 ","pages":"Article 100140"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X24000065/pdfft?md5=1031fe8a65f66ccd5bb3e0c15042941d&pid=1-s2.0-S2666657X24000065-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139714721","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
New examples of self-dual near-extremal ternary codes of length 48 derived from 2-(47,23,11) designs 从 2-(47,23,11) 设计衍生出长度为 48 的自双近极三元码的新实例
Examples and Counterexamples Pub Date : 2024-06-01 Epub Date: 2023-12-15 DOI: 10.1016/j.exco.2023.100130
Sanja Rukavina , Vladimir D. Tonchev
{"title":"New examples of self-dual near-extremal ternary codes of length 48 derived from 2-(47,23,11) designs","authors":"Sanja Rukavina ,&nbsp;Vladimir D. Tonchev","doi":"10.1016/j.exco.2023.100130","DOIUrl":"https://doi.org/10.1016/j.exco.2023.100130","url":null,"abstract":"<div><p>In a recent paper (Araya and Harada, 2023), Araya and Harada gave examples of self-dual near-extremal ternary codes of length 48 for 145 distinct values of the number <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>12</mn></mrow></msub></math></span> of codewords of minimum weight 12, and raised the question about the existence of codes for other values of <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>12</mn></mrow></msub></math></span>. In this note, we use symmetric 2-<span><math><mrow><mo>(</mo><mn>47</mn><mo>,</mo><mn>23</mn><mo>,</mo><mn>11</mn><mo>)</mo></mrow></math></span> designs with an automorphism group of order 6 to construct self-dual near-extremal ternary codes of length 48 for 150 new values of <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>12</mn></mrow></msub></math></span>.</p></div>","PeriodicalId":100517,"journal":{"name":"Examples and Counterexamples","volume":"5 ","pages":"Article 100130"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666657X23000320/pdfft?md5=d212aa3ada7931c19aa8f5ca886b223c&pid=1-s2.0-S2666657X23000320-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138656393","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
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