1,721,019 research outputs found
Limited automata and context-free languages
Full text linkLimited automata are one-tape Turing machines which are allowed to rewrite each tape cell only in the first d visits, for a given constant d. For each d ≥ 2, these devices characterize the class of context-free languages. We investigate the equivalence between 2-limited automata and pushdown automata, comparing the relative sizes of their descriptions. We prove exponential upper and lower bounds for the sizes of pushdown automata simulating 2-limited automata. In the case of the conversion of deterministic 2-limited automata into deterministic pushdown automata the upper bound is double exponential and we conjecture that it cannot be reduced. On the other hand, from pushdown automata we can obtain equivalent 2-limited automata of polynomial size, also preserving determinism. From our results, it follows that the class of languages accepted by deterministic 2-limited automata coincides with the class of deterministic context-free languages
Removal torque of osseointegrated mini-implants: an in vivo evaluation
No full textThe possibility of using osseointegrated implants for orthodontic anchorage is well known. When absolute orthodontic anchorage is needed, mini-implants can be inserted in the non-alveolar bone area (e.g. palatal process or retromolar areas of the mandible). However, what happens to these implants at the end of treatment can be a problem as neither trephine explantation nor simply leaving the subgingival part of the implant in the bone permanently are acceptable solutions. In this investigation, 16 Exacta small screw titanium implants (Exacta MS series conical profi le, with a diameter of 3.3 mm and a length of 7.0 mm) were used as indirect orthodontic anchorage in 16 adult patients. The site of implant placement was established based on radiological investigations. There were eight palatal and eight retromolar implants inserted in seven males and nine females (mean age 30.3 years). On completion of treatment, the implants were unscrewed to the maximum limits of their removal torque values (RTVs) and the obtained data were analysed using a t -test. An in vitro study before the clinical trial was also undertaken to determine the maximum mechanical resistance of the unscrewing system. The clinical procedure and average RTV (67.91 ± 12.47 N/cm) were considered compatible with safe, non-invasive removal of the implant followed by rapid anatomical reconstruction of the area involved
Fundraising strategies for early internationalizing startups. The dual model approach
No full textEmploying qualitative case study methods, this chapter investigates the influence of financing strategies on the international approach of a specific subset of early internationalizing European new ventures. Results show how the limited access to financial resources in the home country could be a triggering factor for startups to adopt an early internationalization approach. Investigated startups typically move their headquarters to countries that have a more developed financial market with the goal of having access to capital, while maintaining a strong operational presence in the country of origin (dual model approach). Despite some limitations, the study sheds new light on the issues that European startups, aiming at internationalizing their business since inception, confront regarding scaling-up in their home countries due to the lack of adequate domestic funding. It also identifies a novel international development path that European startups follow to address the obstacles preventing them from growing rapidly in their home country
Investigation on energy transmission constitutive relationships by laser measurements
No full textThe problem of the energy transmission in vibrating structures is of paramount importance under practical and theoretical points of view. In this field the Statistical Energy Analysis is nowadays the most useful theory, even if the effects of its basic assumptions are difficult to evaluate. Based on the thermal behavior of mechanical energy among coupled vibratory systems, S.E.A. provides information on the stored and dissipated energy and on the transmitted power between them. Starting from the S.E.A. thermal assumptions, some energy models have been developed for the dynamic analysis of mechanical systems vibrating in the high frequency range. The basic principle of thermal propagation of mechanical energy has been examined under the theoretical point of view. The results seem to suggest that the analogy between thermal and mechanical energy propagation should be an acceptable approximation only for 1D systems but it is no longer valid for complex 2D and 3D structures. The present paper describes some experiments designed with the aim of validating the theoretical predictions developed. The experimental tests have been performed on one beam and one plate, excited in a relatively high frequency range. Consequently short characteristic wavelengths are generated and a very fine measurement grid is required. The laser measurement technique is in this case the most effective way to investigate the phenomena related to the wave mechanical energy propagation. The results of the comparison between theory and experiments confirm the dependence of the energy transmission law on the spatial scale range and the general failure of the vibrational conductivity principle
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Startups and the hurdles of scaling-up
No full textThe start-up world is obsessed by the concept of scalability and exponential
growth. That’s why scholars and practitioners started making a distinction between
early-stage initiatives (start-ups) and real companies able to produce revenue and employment (the so-called scale-ups). A recently published article by Shepherd et al.
(2021) points out how “too often the start-up and the scaling stages are merged (and
the difference ignored), [this] has obstructed knowledge creation”. Moreover, in this
field of research “wisdom of practice” is often more advanced than theory. Therefore,
in an attempt of providing a clear-cut picture of the topic under investigation, we
adopt the double-side perspective of practitioners and academics, who have been focusing their research efforts on this field for decades. In the end, the chapter also provides an overview of the main hurdles characterizing the scale-up proces
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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