1,662 research outputs found
Minimal Generators in Optimal Time
No full textA walk of length n on a string S of length m is a function f : {1, … , n} → {1, … , m} such that ∀ i ∈ {2, … , n} : |f(i) - f(i - 1)| ≤ 1. The walk generates the string T of length n defined by {∀ i ∈ {1, … , n} : T[i] = S[f(i)]}. Intuitively, this can be seen as walking n steps in S and outputting the encountered symbols, where in each step we either remain at the same position, or move one position to the left or to the right. The minimal generator of a string T is the shortest string S such that a walk on S generates T. Recently, it was shown that each string admits exactly one (up to reversal) minimal generator (Pratt-Hartmann, CPM 2024). However, no efficient algorithm for computing the minimal generator was known. We provide an optimal algorithm for this task, taking {O}(n) time for a string of length n over general unordered alphabet, i.e., accessing the string only by equality comparisons of symbols. The main challenge is to detect substrings of the form axbx̃axb and replace them with axb, where a,b are symbols and x is a string with reversal x̃. We solve this problem with a non-trivial adaptation of Manacher’s classic algorithm for computing maximal palindromic substrings (Manacher, J. ACM 1975). To obtain the final algorithm, we solve small subinstances of the problem in optimal time by adapting the "Four Russians" technique to strings over general unordered alphabet, which may be of independent interest
Many is beautiful : commoditization as a source of disruptive innovation
No full textThesis (S.M.M.O.T.)--Massachusetts Institute of Technology, Sloan School of Management, Management of Technology Program, 2003.Includes bibliographical references (leaves 44-45).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.The expression "disruptive technology" is now firmly embedded in the modern business lexicon. The mental model summarized by this concise phrase has great explanatory power for ex-post analysis of many revolutionary changes in business. Unfortunately, this paradigm can rarely be applied prescriptively. The classic formulation of a "disruptive technology" sheds little light on potential sources of innovation. This thesis seeks to extend this analysis by suggesting that many important disruptive technologies arise from commodities. The sudden availability of a high performance factor input at a low price often enables innovation in adjacent market segments. The thesis suggests main five reasons that commodities spur innovation: ** The emergence of a commodity collapses competition to the single dimension of price. Sudden changes in factor prices create new opportunities for supply driven innovation. Low prices enable innovators to substitute quantity for quality. ** The price / performance curve of a commodity creates an attractor that promotes demand aggregation. ** Commodities emerge after the establishment of a dominant design. Commodities have defined and stable interfaces. Well developed tool sets and experienced developer communities are available to work with commodities, decreasing the price of experimentation. ** Distributed architectures based on large number of simple, redundant components offer more predictable performance. Systems based on a small number of high performance components will have a higher standard deviation for uptime than high granularity systems based on large numbers of low power components. ** Distributed architectures are much more flexible than low granularity systems. Large integrated facilities often provide cost advantages when operating at the Minimum Efficient Scale of production. However, distributed architectures that can efficiently change production levels over time may be a superior solution based on the ability to adapt to changing market demand patterns. The evolution of third generation bus architectures in personal computers provides a comprehensive example of commodity based disruption, incorporating all five forces.by Richard Ellert Willey.S.M.M.O.T
EUV and fast ion emission from cryogenic liquid jet target laser-generated plasma
No full textA liquid jet of either nitrogen or argon of 20 mum diameter was exposed to intense laser fields with pulse durations between 70 fs and 250 ps, leading to intensities of 10(16) W cm(-2) and 10(13) W cm(-2), respectively. The emission of extreme UV light and soft X-rays shows the characteristic lines of hydrogen-like nitrogen and carbon-like argon. For nitrogen the emitted photon flux at 250 ps was about two orders of magnitude higher than for 70 fs pulses. A weak dependence on the laser polarization with respect to the liquid jet axis was found. The kinetic energy of the emitted ions easily exceeded 100 keV for nitrogen and 200 keV for argon for a pulse duration close to 2 ps
UEG915016 Supplemental Material - Supplemental material for Antimicrobial therapy of 3 days or less is sufficient after successful ERCP for acute cholangitis
No full textSupplemental material, UEG915016 Supplemental Material for Antimicrobial therapy of 3 days or less is sufficient after successful ERCP for acute cholangitis by Sylke Haal, Britt ten Böhmer, Sebastiaan Balkema, Annekatrien CTM Depla, Paul Fockens, Jeroen M Jansen, Sjoerd D Kuiken, Boris I Liberov, Ellert van Soest, Jeanin E van Hooft, Elske Sieswerda and Rogier P Voermans in United European Gastroenterology Journal</p
Identifying with fun and family in the time of changes and downsize
No full textTitle: Identifying with fun and family in the time of changes and downsize. Seminar date: June 1st, 2009 Course: Masters thesis in Business Administration Programme for Managing People, Knowledge and Change, 15 University Credit Points (15 ECTS). Author: Ellert Örn Erlingsson and Elvar Ólafsson Advisor: Sara Louise Muhr Key words: Cultural family metaphor, Resistance, Cynicism, Organizational identity, Purpose: To explore identification within a small office where employees emphasize family ideology and whether they use cynicism to cope with other organizational changes made in the financial crises. Methodology: We have studies our empirical material by using reflective pragmatic approaches such as hermeneutics and critical theory. Theoretical perspectives: This study main structure derives from the use of three main topics; the cultural family metaphor, organizational identity and the use of cynicism in resistance. Empirical foundation: Empirical data was gathered through qualitative open-ended interviews of employees from a small freight office in Sweden. The employees was interviewed one at a time by the two researchers, who followed list of topics that where to be covered in the interviews. Conclusions: Employees at Shipper use the family metaphor to tighten them together in several ways in this hard times and they all identify them self as proud employees due to the good family environment within the office. But due to the fluid and unstable concept of the organizational identity it may be necessary to try to focus the identity construction of the employees to reflect on what they do. We have identified examples where the employees use cynicism to protect and/or justify themselves in situations where they are powerless
Prioridades para a conservação de Butia (Arecaceae)
No full textButia (Arecaceae) é um gênero de palmeiras que reúne 21 espécies nativas na América do Sul. Os fatores que determinam a distribuição e conservação das espécies do gênero ainda são pouco compreendidos. O trabalho tem como objetivos mapear os espécimes com ocorrência natural na América do Sul e avaliar o estado de conservação e critérios de ameaça das espécies. Áreas com espécies prioritárias para conservação in situ e espécies prioritárias para a conservação ex situ são propostas. Onze espécies foram avaliadas como vulneráveis (VU), cinco espécies como criticamente em perigo (CR), três espécies como em perigo (EN), uma espécie como quase ameaçada de extinção (NT) e uma espécie não foi possível avaliar o estado de conservação (dados insuficientes - DD). Foram reconhecidas oito prioridades de áreas para a conservação in situ e oito espécies foram consideradas prioritárias para conservação ex situ e coleta de germoplasma. Os resultados irão subsidiar a proposição de áreas para conservação in situ e manejo sustentável, e estratégias para a conservação ex situ e coleta de germoplasma.Butia (Arecaceae) is a palm genus of 21 South American species. The factors that determine the geographical distribution and conservation status of Butia species are still poorly understood. We mapped the specimens with a natural occurrence in South America and evaluated the state of conservation of the species and their respective threat criteria. These results allowed the proposition of priorities for in situ and ex situ conservation. Eleven species were evaluated as Vulnerable (VU), five species as Critically Endangered (CR), three species as Endangered (EN), one species was assessed as Near Threatened (NT) and one species could not be assessed due to Deficient Data (DD). Eight priorities for in situ conservation are recognized and seven species are considered as priorities for ex situ conservation and germplasm collection. The results support the choice of priority areas for in situ conservation and sustainable management, and strategies for ex situ conservation of the species and germplasm collection
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