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Origin of Sexy Prime Numbers, Origin of Cousin Prime Numbers, Equations from Supposedly Prime Numbers, Origin of the Mersenne Number, Origin of the Fermat Number
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作者 Mady Ndiaye 《Advances in Pure Mathematics》 2024年第5期321-332,共12页
We have found through calculations that the differences between the closest supposed prime numbers other than 2 and 3 defined in the articles are: 2;4: and 6. For those whose difference is equal to 6, we showed their ... We have found through calculations that the differences between the closest supposed prime numbers other than 2 and 3 defined in the articles are: 2;4: and 6. For those whose difference is equal to 6, we showed their origin then we classified them into two categories according to their classes, we showed in which context two prime numbers which differ from 6 are called sexy and in what context they are said real sexy prime. For those whose difference is equal to 4, we showed their origin then we showed that two prime numbers which differ from 4, that is to say two cousin prime numbers, are successive. We made an observation on the supposed prime numbers then we established two pairs of equations from this observation and deduced the origin of the Mersenne number and that of the Fermat number. 展开更多
关键词 Cousin Prime numbers Sexy Prime numbers Real Sexy Prime numbers Equations from Supposed Prime numbers Mersenne number Fermat number Supposed Prime numbers Prime numbers
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广义Z-numbers证据下考虑专家影响力和评价值一致性的应急决策方法
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作者 张磊 韩可可 叶鑫 《中国管理科学》 北大核心 2025年第6期160-170,共11页
复杂不确定情景下突发事件应急决策呈现多属性群决策的特征,且在决策信息不确定的情形下,信息的可靠度会影响决策结果。本文提出一种广义Z-numbers证据下考虑专家影响力和评价值一致性的应急决策方法。首先,基于广义Z-numbers对应急决... 复杂不确定情景下突发事件应急决策呈现多属性群决策的特征,且在决策信息不确定的情形下,信息的可靠度会影响决策结果。本文提出一种广义Z-numbers证据下考虑专家影响力和评价值一致性的应急决策方法。首先,基于广义Z-numbers对应急决策问题建模,并构建信任网络分析专家影响力,提出融合专家影响力和评价可靠度的评价值权重分析方法;其次,根据犹豫模糊评价值的交集分析专家的评价值一致性情形,提出不同一致性情形下的证据生成方法,进而利用D-S证据理论融合多证据信息进行备选应对方案的优选决策;最后,以传染性疾病医疗废物处置装置的决策为例,分析验证了所提方法的有效性和决策结果的可信性。 展开更多
关键词 应急决策 广义Z-numbers D-S证据理论 专家影响力 一致性
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A New Fuzzy Number Similarity Measure Based on Quadratic-Mean Operator for Handling Fuzzy Recommendation Problems
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作者 Shijay Chen 《Journal of Computer and Communications》 2025年第1期108-124,共17页
This study presents a new approach that advances the algorithm of similarity measures between generalized fuzzy numbers. Following a brief introduction to some properties of the proposed method, a comparative analysis... This study presents a new approach that advances the algorithm of similarity measures between generalized fuzzy numbers. Following a brief introduction to some properties of the proposed method, a comparative analysis based on 36 sets of generalized fuzzy numbers was performed, in which the degree of similarity of the fuzzy numbers was calculated with the proposed method and seven methods established by previous studies in the literature. The results of the analytical comparison show that the proposed similarity outperforms the existing methods by overcoming their drawbacks and yielding accurate outcomes in all calculations of similarity measures under consideration. Finally, in a numerical example that involves recommending cars to customers based on a nine-member linguistic term set, the proposed similarity measure proves to be competent in addressing fuzzy number recommendation problems. 展开更多
关键词 Quadratic-Mean Operator Generalized Fuzzy numbers Similarity Measures Fuzzy number Recommendation
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Genome-Wide Association Study of Brown Rice Weight Identifies an RNA-Binding Protein Antagonistically Regulating Grain Weight and Panicle Number
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作者 ZHOU Lin JIANG Hong +11 位作者 HUANG Long LI Ziang YAO Zhonghao LI Linhan JI Kangwei LI Yijie TANG Haijuan CHENG Jinping BAO Yongmei HUANG Ji ZHANG Hongsheng CHEN Sunlu 《Rice science》 2025年第4期525-536,I0050-I0065,共28页
Rice grain yield is primarily determined by three key agronomic traits:panicle number,grain number per panicle,and grain weight(GW).However,the inherent tradeoffs among these yield components remain a persistent chall... Rice grain yield is primarily determined by three key agronomic traits:panicle number,grain number per panicle,and grain weight(GW).However,the inherent tradeoffs among these yield components remain a persistent challenge in rice breeding programs.Notably,compared with GW,brown rice weight(BRW)provides a more direct metric associated with actual grain yield potential.In this study,we conducted a two-year replicated genome-wide association study to elucidate the genetic architecture of BRW and identify new loci regulating GW.Among seven consistently detected loci across experimental replicates,four were not co-localized with previously reported genes associated with BRW or GW traits.BRW1.1,one of the four newly identified loci,was found to encode a novel RNA-binding protein.Functional characterization revealed that BRW1.1 acts as a negative regulator of BRW,potentially through modulating mRNA translation processes.Intriguingly,through integrated analysis of mutant phenotypes and haplotype variations,we demonstrated that BRW1.1 mediates the physiological tradeoff between GW and panicle number.This study not only delineates the genetic determinants of BRW but also identifies BRW1.1 as a promising molecular target for breaking the yield component tradeoff in precision rice breeding. 展开更多
关键词 genome-wide association study brown rice weight RNA-binding protein TRADEOFF grain weight panicle number grain number rice yield
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Changes in source contribution to particle number concentrations during the 2022 COVID-19Lockdown on southern edge of North China Plain
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作者 Zeyu Gao Nan Zhang +6 位作者 Guotao Zhang Dawei Niu Wen Yang Xinhua Wang Shengli Wang Bin Han Zhipeng Bai 《Journal of Environmental Sciences》 2025年第12期447-460,共14页
The COVID-19 lockdown was a typical example of extreme emission reduction,providing an opportunity to study the impact of lockdown measures on air pollution.Particle number concentrations(PNC)originate from direct emi... The COVID-19 lockdown was a typical example of extreme emission reduction,providing an opportunity to study the impact of lockdown measures on air pollution.Particle number concentrations(PNC)originate from direct emissions or through new particle formation events.However,their variations during the lockdown period are under investigation.This study focuses on Luohe,a city on the southern edge of the North China Plain,analyzing the changes in PNC and its sources before,during,and after the COVID-19 lockdown.From March 25^(th)to May 31^(st),2022,real-time PNC measurements were conducted using a Scanning Mobility Particle Sizer for particle size.Results showed an 11.2%decrease in PNC during the lockdown compared to pre-lockdown and a 3.6%decrease compared to post-lockdown,indicating reduced local emissions and weakened regional transportation during the lockdown.Positive Matrix Factorization analysis identified six sources contributing to the total PNC,including photochemical nucleation,aged photochemical nucleation,gasoline vehicle emissions,diesel vehicle emissions,coal and biomass combustion,and secondary aerosols.The significant changes in source emissions indicate a substantially reduced traffic volume after the implementation of lockdown measures(2644.8#/cm^(3),2202.2#/cm^(3),2792.7#/cm^(3)).Concurrently,photochemical nucleation(310.1#/cm^(3),306.3#/cm^(3),393.1#/cm^(3))and photochemical nucleation aging(592.8#/cm^(3),744.1#/cm^(3),810.7#/cm^(3))exhibited increasing trends,while coal/biomass combustion(1656.6#/cm^(3),1586.2#/cm^(3),980.0#/cm^(3))and secondary sources(999.4#/cm^(3),791.1#/cm^(3),804.1#/cm^(3))showed decreasing trends.In summary,the contributions of traffic emissions to PNC highlight the potential for targeted traffic management strategies to improve urban air quality. 展开更多
关键词 Particle number concentration Particle number size distribution Source apportionment Epidemic lockdown
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Preliminary Identification of a Prime Number Other Than 2 and 3, the Origin of Twin Prime Numbers, the Structure of the Chain of Prime Numbers and the Set of Prime Numbers Less Than a Given Integer
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作者 Mady Ndiaye 《Advances in Pure Mathematics》 2024年第1期30-48,共19页
The application of the Euclidean division theorem for the positive integers allowed us to establish a set which contains all the prime numbers and this set we called it set of supposedly prime numbers and we noted it ... The application of the Euclidean division theorem for the positive integers allowed us to establish a set which contains all the prime numbers and this set we called it set of supposedly prime numbers and we noted it E<sub>sp</sub>. We subsequently established from the previous set the set of non-prime numbers (the set of numbers belonging to this set and which are not prime) denoted E<sub>np</sub>. We then extracted from the set of supposedly prime numbers the numbers which are not prime and the set of remaining number constitutes the set of prime numbers denoted E<sub>p</sub>. We have deduced from the previous set, the set of prime numbers between two natural numbers. We have explained during our demonstrations the origin of the twin prime numbers and the structure of the chain of prime numbers. 展开更多
关键词 Supposedly Prime numbers Non-Prime numbers Prime numbers Prime numbers Less Than a Given Integer Prime numbers between Two Given Integers
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Single-nucleotide polymorphisms and copy number variations drive adaptive evolution to freezing stress in a subtropical evergreen broadleaved tree:Hexaploid wild Camellia oleifera 被引量:1
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作者 Haoxing Xie Kaifeng Xing +3 位作者 Jun Zhou Yao Zhao Jian Zhang Jun Rong 《Plant Diversity》 2025年第2期214-228,共15页
Subtropical evergreen broad-leaved trees are usually vulnerable to freezing stress,while hexaploid wild Camellia oleifera shows strong freezing tolerance.As a valuable genetic resource of woody oil crop C.oleifera,wil... Subtropical evergreen broad-leaved trees are usually vulnerable to freezing stress,while hexaploid wild Camellia oleifera shows strong freezing tolerance.As a valuable genetic resource of woody oil crop C.oleifera,wild C.oleifera can serve as a case for studying the molecular bases of adaptive evolution to freezing stress.Here,47 wild C.oleifera from 11 natural distribution sites in China and 4 relative species of C.oleifera were selected for genome sequencing.“Min Temperature of Coldest Month”(BIO6)had the highest comprehensive contribution to wild C.oleifera distribution.The population genetic structure of wild C.oleifera could be divided into two groups:in cold winter(BIO6≤0℃)and warm winter(BIO6>0℃)areas.Wild C.oleifera in cold winter areas might have experienced stronger selection pressures and population bottlenecks with lower N_(e) than those in warm winter areas.155 singlenucleotide polymorphisms(SNPs)were significantly correlated with the key bioclimatic variables(106 SNPs significantly correlated with BIO6).Twenty key SNPs and 15 key copy number variation regions(CNVRs)were found with genotype differentiation>50%between the two groups of wild C.oleifera.Key SNPs in cis-regulatory elements might affect the expression of key genes associated with freezing tolerance,and they were also found within a CNVR suggesting interactions between them.Some key CNVRs in the exon regions were closely related to the differentially expressed genes under freezing stress.The findings suggest that rich SNPs and CNVRs in polyploid trees may contribute to the adaptive evolution to freezing stress. 展开更多
关键词 Adaptive evolution Camellia oleifera Copy number variations Freezing stress POLYPLOID Single-nucleotide polymorphisms
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A low Mach number asymptotic analysis of dissipation-reducing methods for curing shock instability 被引量:1
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作者 Hongping GUO Xun WANG Zhijun SHEN 《Applied Mathematics and Mechanics(English Edition)》 2025年第4期723-744,共22页
We are intrigued by the issues of shock instability,with a particular emphasis on numerical schemes that address the carbuncle phenomenon by reducing dissipation rather than increasing it.For a specific class of plana... We are intrigued by the issues of shock instability,with a particular emphasis on numerical schemes that address the carbuncle phenomenon by reducing dissipation rather than increasing it.For a specific class of planar flow fields where the transverse direction exhibits vanishing but non-zero velocity components,such as a disturbed onedimensional(1D)steady shock wave,we conduct a formal asymptotic analysis for the Euler system and associated numerical methods.This analysis aims to illustrate the discrepancies among various low-dissipative numerical algorithms.Furthermore,a numerical stability analysis of steady shock is undertaken to identify the key factors underlying shock-stable algorithms.To verify the stability mechanism,a consistent,low-dissipation,and shock-stable HLLC-type Riemann solver is presented. 展开更多
关键词 Riemann solver numerical shock instability low Mach number HLLC
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基于T-球形模糊Z-number的扩展TODIM方法及应用
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作者 程玮玲 毛军军 张胜 《武汉理工大学学报(信息与管理工程版)》 2025年第1期65-72,共8页
Z-number作为一种表达不确定信息的方法,其核心在于处理信息的模糊性和概率不确定性。然而,当前关于Z-number的研究相对有限,许多研究未能充分揭示其性质。T-球形模糊Z-number为表示数据的随机性和模糊性提供了新的视角。首先,引入了T-... Z-number作为一种表达不确定信息的方法,其核心在于处理信息的模糊性和概率不确定性。然而,当前关于Z-number的研究相对有限,许多研究未能充分揭示其性质。T-球形模糊Z-number为表示数据的随机性和模糊性提供了新的视角。首先,引入了T-球形模糊Z-number,利用T-球形模糊数和相应可靠性度量的组合表示数据信息,可以很好地体现决策数据的模糊性和适用性。其次,提出了T-球形模糊Z-number的运算法则和聚合算子,并基于所提出的聚合算子和TODIM方法,提出了两种算法来处理T-球形模糊Z-number形式的不确定信息。最后,以安徽省4个城市数字经济的评估问题为实例进行对比分析,论证了所提出算法的实用性和有效性。 展开更多
关键词 T-球形模糊 Z-number TODIM 多属性决策 数字经济评估
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Star-quadrilateral Ramsey Number and Beyond
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作者 CHEN Yaojun ZHANG Xuemei ZHANG Yanbo 《数学进展》 北大核心 2025年第2期292-314,共23页
For k given graphs H_(1),...,H_(k) with k≥2,the k-color Ramsey number R(H_(1),...,H_(k)) represents the minimum integer N with the following property:if the edges of the complete graph K_(N) are colored with k colors... For k given graphs H_(1),...,H_(k) with k≥2,the k-color Ramsey number R(H_(1),...,H_(k)) represents the minimum integer N with the following property:if the edges of the complete graph K_(N) are colored with k colors,then there exists some i with 1≤i≤k such that K_(N) has a subgraph in color i isomorphic to H_(i).Let C_(m) be a cycle of length m and K_(1,n) a star of order n+1.In this paper,we systematically introduce the latest research progress on star-quadrilateral Ramsey numbers and provide an overview of Ramsey numbers concerning quadrilaterals,including multicolor cases. 展开更多
关键词 multicolor Ramsey number polarity graph QUADRILATERAL STAR WHEEL BOOK
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Health Phys.Abstracts,Volume 128,Number 1
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《辐射防护》 北大核心 2025年第2期191-196,共6页
TENORM Regulation in the United States of America post-West Virginia vs.EPA Spenser Lynn,Charles Wilson,Emily Caffrey1(1.University of Alabama at Birmingham,School of Health Professions,Clinical and Diagnostic Science... TENORM Regulation in the United States of America post-West Virginia vs.EPA Spenser Lynn,Charles Wilson,Emily Caffrey1(1.University of Alabama at Birmingham,School of Health Professions,Clinical and Diagnostic Sciences,Health Physics Program,1720 University Blvd,Birmingham,AL 35294)Abstract:The regulation of technologically enhanced naturally occurring radioactive materials(TENORM)in the United States of America consists of fragmentary rules split between the federal and state governments. 展开更多
关键词 ABSTRACTS number naturally
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Asymptotic Probability of Record Numbers in Random Walks
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作者 PENG Wenjie LI Yuqiang 《应用概率统计》 北大核心 2025年第1期17-27,共11页
In this paper,large deviations principle(LDP)and moderate deviations principle(MDP)of record numbers in random walks are studied under certain conditions.The results show that the rate functions of LDP and MDP are dif... In this paper,large deviations principle(LDP)and moderate deviations principle(MDP)of record numbers in random walks are studied under certain conditions.The results show that the rate functions of LDP and MDP are different from those of weak record numbers,which are interesting complements of the conclusions by Li and Yao[1]. 展开更多
关键词 random walk record number large deviation moderate deviation
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The Crossing Number of Two Classes of Join Graphs
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作者 LU Shengxiang WANG Shu WANG Jing 《数学进展》 北大核心 2025年第5期983-991,共9页
Determining the crossing number of a given graph is NP-complete. The cycle of length m is denoted by Cm = v1v2…vmv1. G^((1))_(m) (m ≥ 5) is the graph obtained from Cm by adding two edges v1v3 and vlvl+2 (3 ≤ l ≤ m... Determining the crossing number of a given graph is NP-complete. The cycle of length m is denoted by Cm = v1v2…vmv1. G^((1))_(m) (m ≥ 5) is the graph obtained from Cm by adding two edges v1v3 and vlvl+2 (3 ≤ l ≤ m−2), G^((2))m (m ≥ 4) is the graph obtained from Cm by adding two edges v1v3 and v2v4. The famous Zarankiewicz’s conjecture on the crossing number of the complete bipartite graph Km,n states that cr(Km,n)=Z(m,n)=[m/2][m-1/2][n/2[n-1/2].Based on Zarankiewicz’s conjecture, a natural problem is to study the change in the crossingnumber of the graphs obtained from the complete bipartite graph by adding certain edge sets.If Zarankiewicz’s conjecture is true, this paper proves that cr(G^((1))_(m)+Kn)=Z(m,n)+2[n/2] and cr(G^((2))_(m)+Kn)=Z(m,n)+n. 展开更多
关键词 crossing number DRAWING join graph
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On the Turán Number of k_(1)P_(ι)∪k_(2)S_(ι-1)
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作者 FANG Tao YUAN Xiying 《数学进展》 北大核心 2025年第4期687-695,共9页
The Turan number of a graph H,denoted by ex(n,H),is the maximum number of edges in any graph on n vertices containing no H as a subgraph.Let P_(ι)denote the path onιvertices,S_(ι-1)denote the star onιvertices and ... The Turan number of a graph H,denoted by ex(n,H),is the maximum number of edges in any graph on n vertices containing no H as a subgraph.Let P_(ι)denote the path onιvertices,S_(ι-1)denote the star onιvertices and k_(1)P_(ι)∪k_(2)S_(ι-1)denote the path-star forest with disjoint union of k_(1)copies of P_(ι)and k_(2)copies of S_(ι-1).In 2022,[Graphs Combin.,2022,38(3):Paper No.84,16 pp.] raised a conjecture about the Turan number of k_(1)P_(2ι)∪k_(2)S_(2ι-1).In this paper,we determine the Turan numbers of P_(ι)∪kS_(ι-1)and k_(1)P_(2ι)∪k_(2)S_(2ι-1)for n appropriately large,which implies the above conjecture.The corresponding extremal graphs are also completely characterized. 展开更多
关键词 Turan number path-star forest extremal graph
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Ramsey numbers of edge-critical graphs versus large generalized fans
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作者 Taiping Jiang Xinmin Hou 《中国科学技术大学学报》 北大核心 2025年第5期62-66,61,I0002,共7页
Given two graphs G and H,the Ramsey number R(G,H)is the smallest positive integer N such that every 2-coloring of the edges of K_(N)contains either a red G or a blue H.Let K_(N-1)■K_(1,k)be the graph obtained from K_... Given two graphs G and H,the Ramsey number R(G,H)is the smallest positive integer N such that every 2-coloring of the edges of K_(N)contains either a red G or a blue H.Let K_(N-1)■K_(1,k)be the graph obtained from K_(N-1)by adding anew vertexνconnecting k vertices of K_(N-1).A graph G withχ(G)=k+1 is called edge-critical if G contains an edge e such thatχ(G-e)=k.A considerable amount of research has been conducted by previous scholars on Ramsey numbers ofgraphs.In this study,we show that for an edge-critical graph G with x(G)=k+1,when k≥2,1≥2,and n is sufficiently large,R(G,K_(1)+nK_(t))=knt+1 and r,(G,K_(1)+nK_(t))=(k-1)nt+1. 展开更多
关键词 Ramsey number color critical graph generalized fan
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The A_(α)-spectral Radius of Block Graphs with Given Dissociation Number
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作者 HUANG Peng LI Jianxi 《数学进展》 北大核心 2025年第4期696-708,共13页
For a simple graph G,let A(G)and D(G)be the adjacency matrix and the diagonal degree matrix of G,respectively.[Appl.Anal.Discrete Math.,2017,11(1):81-107]defined the matrix A_(α)(G)of G as A_(α)(G)=αD(G)(1-α)A(G)... For a simple graph G,let A(G)and D(G)be the adjacency matrix and the diagonal degree matrix of G,respectively.[Appl.Anal.Discrete Math.,2017,11(1):81-107]defined the matrix A_(α)(G)of G as A_(α)(G)=αD(G)(1-α)A(G),α∈[0,1].The Aa-spectral radius is the largest eigenvalue of A_(α)(G).Let G_(n,β) be the set graphs with order n and dissociation numberβ.In this paper,we identify the b with maximal A_(α)-spectral radius among all graphs in G_(n,β). 展开更多
关键词 A_(α)-spectral radius block graph SIZE dissociation number
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On the Lebesgue Integral and the Lebesgue Measure: Mathematical Applications in Some Sectors of Chern-Simons Theory and Yang-Mills Gauge Theory and Mathematical Connections with Some Sectors of String Theory and Number Theory
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作者 Michele Nardelli 《Journal of Modern Physics》 2025年第1期93-132,共40页
In this paper, in Section 1, we have described some equations and theorems concerning the Lebesgue integral and the Lebesgue measure. In Section 2, we have described the possible mathematical applications, of Lebesgue... In this paper, in Section 1, we have described some equations and theorems concerning the Lebesgue integral and the Lebesgue measure. In Section 2, we have described the possible mathematical applications, of Lebesgue integration, in some equations concerning various sectors of Chern-Simons theory and Yang-Mills gauge theory, precisely the two dimensional quantum Yang-Mills theory. In conclusion, in Section 3, we have described also the possible mathematical connections with some sectors of String Theory and Number Theory, principally with some equations concerning the Ramanujan’s modular equations that are related to the physical vibrations of the bosonic strings and of the superstrings, some Ramanujan’s identities concerning π and the zeta strings. 展开更多
关键词 Lebesgue Integral Chern-Simons Theory Yang-Mills Gauge Theory String Theory number Theory
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Numbering and Generating Quantum Algorithms
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作者 Mohamed A. El-Dosuky 《Journal of Computer and Communications》 2025年第2期126-141,共16页
Quantum computing offers unprecedented computational power, enabling simultaneous computations beyond traditional computers. Quantum computers differ significantly from classical computers, necessitating a distinct ap... Quantum computing offers unprecedented computational power, enabling simultaneous computations beyond traditional computers. Quantum computers differ significantly from classical computers, necessitating a distinct approach to algorithm design, which involves taming quantum mechanical phenomena. This paper extends the numbering of computable programs to be applied in the quantum computing context. Numbering computable programs is a theoretical computer science concept that assigns unique numbers to individual programs or algorithms. Common methods include Gödel numbering which encodes programs as strings of symbols or characters, often used in formal systems and mathematical logic. Based on the proposed numbering approach, this paper presents a mechanism to explore the set of possible quantum algorithms. The proposed approach is able to construct useful circuits such as Quantum Key Distribution BB84 protocol, which enables sender and receiver to establish a secure cryptographic key via a quantum channel. The proposed approach facilitates the process of exploring and constructing quantum algorithms. 展开更多
关键词 Quantum Algorithms numbering Computable Programs Quantum Key Distribution
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Numerical simulation on the combustion characteristics of scramjet at high Mach number
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作者 Jiahang Li Zhaoyang Xia +3 位作者 Mi Yan Hao Zhang Jinfeng Dang Majie Zhao 《Defence Technology(防务技术)》 2025年第8期155-165,共11页
To investigate the problem of ethylene jet mixing and combustion in the scramjet at high Mach number(Ma = 8), numerical simulations were carried out for different equivalent ratios at cold and combustion conditions, i... To investigate the problem of ethylene jet mixing and combustion in the scramjet at high Mach number(Ma = 8), numerical simulations were carried out for different equivalent ratios at cold and combustion conditions, in which three-dimensional steady compressible RANS and k-ω SST turbulence model were adopted. It demonstrates that as the equivalence ratio increases from 0.42 to 1.08, the combustion becomes more intensified, and the higher backpressure pushes flame to propagate upstream. The supersonic combustion region in the combustor decreases from 92% to 85% with the increase of equivalence ratio from 0.42 to 1.08, resulting in the transition of the combustor from scram-mode to dual-mode. Both mixing and combustion efficiencies decrease by 35% and 16% respectively when the equivalence ratio increases from 0.42 to 1.08, indicating that the high equivalence ratio is unfavorable to the mixing and combustion processes. Combustion mode analysis reveals that the flame in the cavity under the high Mach number is dominated by non-premixed flames, i.e., more than 95% behaves as non-premixed mode, and the heat release is also mainly contributed by non-premixed flame. Increasing the equivalence ratio is beneficial to the thrust performance. Although the viscous force hardly changes with equivalence ratio, the percentage of pressure force used to balance the viscous force increases gradually,which limits the engine performance. 展开更多
关键词 SCRAMJET High Mach number Equivalence ratio Combustion mode Flame structure
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Numerical Study of the Vibration Characteristics and Vortex Shedding Modes of Piggyback Pipelines at Low Reynolds Numbers
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作者 ZHAO Li-meng ZANG Zhi-peng +1 位作者 BO Zhao ZHAO Ming 《China Ocean Engineering》 2025年第3期455-469,共15页
A piggyback pipeline is a special configuration of offshore pipelines for offshore oil and gas exploration and is characterized by the coupling of a large-diameter pipe with a small-diameter pipe. This study conducts ... A piggyback pipeline is a special configuration of offshore pipelines for offshore oil and gas exploration and is characterized by the coupling of a large-diameter pipe with a small-diameter pipe. This study conducts a numerical investigation of the transverse VIV characteristics of a piggyback pipeline at low Reynolds numbers, as the vortex shedding modes and vibration characteristics can be accurately represented under laminar flow conditions with minimal computational expense. The effects of influential factors, such as the mass ratio, position angle of the small pipe relative to the main pipe, and Reynolds number, on the VIV amplitude, frequency, vibration center, and mean lift coefficient are specifically examined. The results indicate that the mass ratio has a limited effect on the maximum VIV amplitude. However, as the mass ratio decreases, the lock-in region expands, and the vibration center of the piggyback pipeline deviates further from its original position. The VIV amplitude is minimized, and the lock-in region is the narrowest at a position angle of 45°, whereas the vibration center reaches its maximum displacement at a position angle of 135°. As the Reynolds number increases, the VIV amplitude slightly increases, accompanied by convergence of the vibration center toward its initial position. The mean lift coefficient and wake vortices are also analyzed to establish a connection with the vibration characteristics of the piggyback pipeline. The optimal configuration of the piggyback pipeline is also proposed on the basis of the present numerical results. 展开更多
关键词 piggyback pipelines vortex-induced vibration mass ratio position angle Reynolds number
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