136,650 research outputs found
« Petit commerce aléatoire de chiens tibétains » Nouvelle de He Liwei
No full textLiwei He, Naour Françoise. « Petit commerce aléatoire de chiens tibétains » Nouvelle de He Liwei. In: Perspectives chinoises, n°42, 1997. pp. 61-66
Low Rank Approximation of Binary Matrices: Column Subset Selection and Generalizations
No full textLow rank approximation of matrices is an important tool in machine learning. Given a data matrix, low rank approximation helps to find factors, patterns, and provides concise representations for the data. Research on low rank approximation usually focuses on real matrices. However, in many applications data are binary (categorical) rather than continuous. This leads to the problem of low rank approximation of binary matrices. Here we are given a d x n binary matrix A and a small integer k < d. The goal is to find two binary matrices U and V of sizes d x k and k x n respectively, so that the Frobenius norm of A - U V is minimized. There are two models of this problem, depending on the definition of the dot product of binary vectors: The GF(2) model and the Boolean semiring model. Unlike low rank approximation of a real matrix which can be efficiently solved by Singular Value Decomposition, we show that approximation of a binary matrix is NP-hard, even for k=1.
In this paper, our main concern is the problem of Column Subset Selection (CSS), in which the low rank matrix U must be formed by k columns of the data matrix, and we are interested in the approximation ratio achievable by CSS for binary matrices. For the GF(2) model, we show that CSS has approximation ratio bounded by k/2+1+k/(2(2^k-1)) and this is asymptotically tight. For the Boolean model, it turns out that CSS is no longer sufficient to obtain a bound. We then develop a Generalized CSS (GCSS) procedure in which the columns of U are generated from Boolean formulas operating bitwise on selected columns of the data matrix. We show that the approximation ratio achieved by GCSS is bounded by 2^(k-1)+1, and argue that an exponential dependency on k is seems inherent
Polynomial policies in supply chain networks
No full textThesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 63-64).This thesis aims to solve the periodic-reviewed inventory control problem in supply chain networks with uncertain demand so as to minimize the overall cost of the system over a fixed planning time horizon. In such problems, one seeks to optimally determine ordering quantities at different stages in time. We investigate the class of polynomial policies, where the control policy is directly parametrized polynomially in the observed uncertainties of previous stages. We use sum-of-square relaxations to reformulate the problem into a single semidefinite optimization problem for a specific polynomial degree. We consider both robust and stochastic approaches in order to address the uncertainties in demand. In extensive numerical studies, we find that polynomial policies exhibit better performance over basestock policies across a variety of networks and demand distributions under the mean and standard deviation criteria. However, when the uncertainty set turns out to be larger than planned, basestock policies start outperforming polynomial policies. Comparing the policies obtained under the robust and stochastic frameworks, we find that they are comparable in the average performance criterion, but the robust approach leads to better tail behavior and lower standard deviation in general.by Liwei He.S.M
Protecting Animals 36: Author Witi Ihimaera
No full textIn this very special episode of Knowing Animals I am joined by beloved New Zealand author Witi Ihimaera. Witi has written many books featuring nonhuman animals. He offers us a non-colonial lens through which to think about the human/nonhuman relationship
sj-docx-1-ijl-10.1177_15347346231201696 - Supplemental material for Acellular Dermal Matrix for Treatment of Diabetic Foot Ulcer: An Overview of Systematic Reviews
No full textSupplemental material, sj-docx-1-ijl-10.1177_15347346231201696 for Acellular Dermal Matrix for Treatment of Diabetic Foot Ulcer: An Overview of Systematic Reviews by Li Lingyan, Zhao Han, Li Jialu, He Bingyang, Ma Yuanyuan, Qin Peiwei, Ma Peifen and Xu Liwei in The International Journal of Lower Extremity Wounds</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
Complete mitochondrial genome of<i>Tetraophasis szechenyii</i>Madarász, 1885 (Aves: Galliformes: Phasianidae), and its genetic variation as inferred from the mitochondrial DNA Control Region
No full textFigure 2. Median-joining network of all the control region haplotypes found in Tetraophasis szechenyii. Notes: Missing haplotypes in the network are represented by black dots; circle sizes are proportional to the number of individuals sharing the same haplotypes (n); each mutation step is shown as a short line connecting neighbouring haplotypes; numbers of mutations between haplotypes are indicated near branches if greater than 1.Published as part of Meng, Yang, He, Liwei, Wu, Ailin, Fan, Zhenxin, Ran, Jianghong, Yue, Bisong & Li, Jing, 2010, Complete mitochondrial genome of Tetraophasis szechenyii Madarász, 1885 (Aves: Galliformes: Phasianidae), and its genetic variation as inferred from the mitochondrial DNA Control Region, pp. 2955-2964 in Journal of Natural History 44 (47-48) on page 2960, DOI: 10.1080/00222933.2010.502596, http://zenodo.org/record/521226
Leaf stoichiometry is synergistically-driven by climate, site, soil characteristics and phylogeny in karst areas, Southwest China
No full textLeaf stoichiometry and its biogeography play vital roles in nutrient cycling of plant communities. To understand the potential drivers of leaf stoichiometry in karst ecosystems, we measured leaf morphological traits (dry mass content (DM), specific leaf area (SLA)), and biochemical traits (C, N, P, K and Ca stoichiometry) of 53 species of different functional groups, as well as soil properties, across seven karst sites in Southwest China, and explored the relationships between these leaf traits and environmental factors. The results showed that: (1) in karst areas of Southwest China, there were higher leaf C and Ca concentrations as well as higher N/P and K/P ratios compared to other ecosystems, plants were more limited by P rather than by N; (2) mean annual temperature positively influenced leaf N, P, and Ca, while mean annual precipitation exerted more influence on leaf K; (3) a strong phylogeny signal was detected in leaf N (p < 0.05), and significant influence of species composition on the variance of leaf N, K, and Ca was observed (p < 0.05); (4) the influence of soil properties on leaf P and Ca, and the influence of leaf features (SLA and DM) on leaf K were also observed based on a variance partitioning analysis. Abiotic factors such as soil, site, and climate were more important than biotic factors (leaf features and phylogeny) in determining leaf N, P, and Ca. In general, the driving factors exhibited a synergistic effect on leaf stoichiometry across different sites, offering a key mechanism that needs to be integrated into the modeling of biogeochemical nutrients cycling in karst ecosystems.link_to_subscribed_fulltex
Correction to: Leaf stoichiometry is synergistically-driven by climate, site, soil characteristics and phylogeny in karst areas, Southwest China
No full textIn the original version of this article the figure legends of Figs. 3–7 were incorrect. The correct legends are given below. The original article has been updated.</p
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