58 research outputs found

    A Note On The Cross-Sperner Families

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    Let (F,G)(\mathcal{F},\mathcal{G}) be a pair of families of [n][n], where [n]={1,2,...,n}[n]=\{1,2,...,n\}. If A⊄BA\not\subset B and B⊄AB\not\subset A hold for all AFA\in\mathcal{F} and BGB\in\mathcal{G}, then (F,G)(\mathcal{F},\mathcal{G}) is called a Cross-Sperner pair. P. Frankl and Jian Wang introduced the extremal problem that m(n)=max{I(F,G):F,G2[n] are crossm(n)={\rm{max}}\{|\mathcal{I}(\mathcal{F},\mathcal{G})|:\mathcal{F},\mathcal{G}\subset2^{[n]}~{\rm{are~cross}}-sperner}{\rm{sperner}}\}, where I(F,G)={AB:AF,BG}\mathcal{I}(\mathcal{F},\mathcal{G})=\{A\cap B:A\in\mathcal{F},B\in\mathcal{G}\}. In this note, we prove that m(n)=2n2n22n2+1m(n)=2^n-2^{\lfloor\frac{n}{2}\rfloor}-2^{\lceil\frac{n}{2}\rceil}+1 for all n>1n>1. This solves an open problem proposed by P. Frankl and Jian Wang.Comment: We solve an open problem proposed by P. Frankl and Jian Wan

    On a conjecture about pattern avoidance of cycle permutations

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    Let ππ be a cycle permutation that can be expressed as one-line π=π1π2πnπ= π_1π_2 \cdot\cdot\cdot π_n and a cycle form π=(c1,c2,...,cn)π= (c_1,c_2, ..., c_n). Archer et al. introduced the notion of pattern avoidance of one-line and all cycle forms for a cycle permutation ππ, defined as π1π2πnπ_1π_2 \cdot\cdot\cdot π_n and its arbitrary cycle form cici+1cnc1c2ci1c_ic_{i+1}\cdot\cdot\cdot c_nc_1c_2\cdot\cdot\cdot c_{i-1} avoid a given pattern. Let An(σ;τ)\mathcal{A}^\circ_n(σ; τ) denote the set of cyclic permutations in the symmetric group SnS_n that avoid σσ in their one-line form and avoid ττ in their all cycle forms. In this note, we prove that An(2431;1324)|\mathcal{A}^\circ_n(2431; 1324)| is the (n1)st(n-1)^{\rm{st}} Pell number for any positive integer nn. Thereby, we give a positive answer to a conjecture of Archer et al

    The full automorphism groups of general position graphs

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    Let SS be a non-empty finite set. A flag of SS is a set ff of non-empty proper subsets of SS such that XYX\subseteq Y or YXY\subseteq X for all X,YfX,Y\in f. The set {X:Xf}\{|X|:X\in f\} is called the type of ff. Two flags ff and ff' are in general position with respect to SS if XY=X\cap Y=\emptyset or XY=SX\cup Y=S for all XfX\in f and YfY\in f'. For a fixed type TT, Klaus Metsch defined the general position graph Γ(S,T)\Gamma(S,T) whose vertices are the flags of SS of type TT with two vertices being adjacent when the corresponding flags are in general position. In this paper, we characterize the full automorphism groups of Γ(S,T)\Gamma(S,T) in the case that T=2|T|=2. In particular, we solve an open problem proposed by Klaus Metsch.Comment: we solve an open problem proposed by Klaus Metsc

    Explore a new book discovery experience in the public library

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    Nowadays, a public library is no longer a place just for the collection of books. It has offered multiple functions to take the responsibility of being a public cultural institution for all citizens. However, in the Netherlands, libraries are losing their members, especially young adults. With the development of technology, a public library is no longer the only choice for books. Libraries are encountering a challenge to attract young people back. They need to strive for providing new kinds of public services to attract this potential new audience.Westfriese Bibliotheken is one of these libraries which has 10 decentralized community libraries in 6 places in the north of the Netherlands. Westfriese Bibliotheken is facing a challenge to reach a bigger group of the generation of youngsters who think a public library is a dull place to go. To narrow down the scope, the book discovery experience for young adults between 18-25 years old was focused. Augmented reality as the technology this project worked with has been proved to benefit the library context.Hence, the objective of this thesis is to explore a new book discovery experience for young adults in the public library in Stede Broec.From the theoretical study (chapter 2) about the book discovery behavior, the behavior pattern was investigated and worked as the design requirements. User research (chapter 3) was conducted to understand the current book discovery experience in the context through contextmapping. It discovered users' concerns and expectations about the book discovery experience. Moreover, the opportunity of this project: designing a new book discovery experience to facilitate serendipity was concluded based on user research findings. Under the framework of the serendipity theory (chapter 4), design opportunities for facilitating serendipity in the current library were gathered. The study on augmented reality (chapter 5) helped to define design qualities and technologies that this project can make use of.With the research insights, a design goal with three design qualities (fascinating, playful, and inviting) and relevant design requirements were formulated (chapter 6). They contributed as a guideline to the design solution.Ideas were gathered through a creative session and based on these ideas three initial concepts were generated. Concepts were evaluated and iterated with users, clients, and fellow students. The final design outcome is a phone-based AR application with two main parts: exploring and browsing parts. It offers both basic and additional information about books to stimulate users to experience serendipity in the public library. Finally, an evaluation test was conducted to validate if the final design can fulfill the design goal. The final design achieves a good usability and desirability performance evaluated by 6 participants in the library. The evaluation test demonstrated that the additional information about books and interaction between the physical and digital world can let users feel fascinated, invited, and playful during the book discovery experience.Design for Interactio

    Sign-Balanced Pattern-Avoiding Permutation Classes

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    A set of permutations is called sign-balanced if the set contains the same number of even permutations as odd permutations. Let Sn(σ1,σ2,,σr)S_n(\sigma_1, \sigma_2, \ldots, \sigma_r) be the set of permutations in the symmetric group SnS_n which avoids patterns σ1,σ2,,σr\sigma_1, \sigma_2, \ldots, \sigma_r. The aim of this paper is to investigate when, for certain patterns σ1,σ2,,σr\sigma_1, \sigma_2, \ldots, \sigma_r, Sn(σ1,σ2,,σr)S_n(\sigma_1, \sigma_2, \ldots, \sigma_r) is sign-balanced for every integer n>1n>1. We prove that for any {σ1,σ2,,σr}S3\{\sigma_1, \sigma_2, \ldots, \sigma_r\}\subseteq S_3, if {σ1,σ2,,σr}\{\sigma_1, \sigma_2, \ldots, \sigma_r\} is sign-balanced except {132,213,231,312}\{132, 213, 231, 312\}, then Sn(σ1,σ2,,σr)S_n(\sigma_1, \sigma_2, \ldots, \sigma_r) is sign-balanced for every integer n>1n>1. In addition, we give some results in the case of avoiding some patterns of length 44

    On the permutations that strongly avoid the pattern 312 or 231

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    In 2019, B\'ona and Smith introduced the notion of \emph{strong pattern avoidance}, that is, a permutation and its square both avoid a given pattern. In this paper, we enumerate the set of permutations π\pi which not only strongly avoid the pattern 312312 or 231231 but also avoid the pattern τ\tau, for τS3\tau\in S_3 and some τS4\tau\in S_4. One of them is to give a positive answer to a conjecture of Archer and Geary

    Investigation into the Promotion and Instruction of Chinese Traditional Music in Liaocheng Peiwen School of Peking University

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    This research investigates the promotion and instruction of Chinese Traditional music in Liaocheng Peiwen School of Peking University. The first author, an alum with a decade of pedagogical experience, examined the challenges faced by private schools in providing tailored regulatory frameworks for Chinese Traditional music education. We share practical experience, drawing on the successful establishment of the school-based course "Chinese Folk Music and Geography." As the course is offered each year during the geography exam for students in their second year of junior high school, singing folk songs while learning geography enables students to explore China's beautiful landscapes while broadening their horizons. Students can understand the connection between folk music and geography, assisting their preparation for the exam

    Simulation Based Value-at-Risk for High-dimensional Nonlinear Portfolios

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    Chen, Junyao.Thesis M.Phil. Chinese University of Hong Kong 2016.Includes bibliographical references (leaves ).Abstracts also in Chinese.Title from PDF title page (viewed on …)
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