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581.
Allan J.C. Silva Marcos André Gonçalves Alberto H.F. Laender Marco A.B. Modesto Marco Cristo Nivio Ziviani 《Information processing & management》2009
This article proposes a process to retrieve the URL of a document for which metadata records exist in a digital library catalog but a pointer to the full text of the document is not available. The process uses results from queries submitted to Web search engines for finding the URL of the corresponding full text or any related material. We present a comprehensive study of this process in different situations by investigating different query strategies applied to three general purpose search engines (Google, Yahoo!, MSN) and two specialized ones (Scholar and CiteSeer), considering five user scenarios. Specifically, we have conducted experiments with metadata records taken from the Brazilian Digital Library of Computing (BDBComp) and The DBLP Computer Science Bibliography (DBLP). We found that Scholar was the most effective search engine for this task in all considered scenarios and that simple strategies for combining and re-ranking results from Scholar and Google significantly improve the retrieval quality. Moreover, we study the influence of the number of query results on the effectiveness of finding missing information as well as the coverage of the proposed scenarios. 相似文献
582.
The technology acceptance model (TAM) has been widely used to study user acceptance of new computer technologies. However, it does not incorporate social structure and influence as a significant factor. In this study, we ask the following questions: (i) What are the limitations of the existing TAM for studying virtual community? (ii) What is effect of social networks on user acceptance of technology for virtual community? and (iii) How can the influence of different types of social ties serve as a basis for exploring the user acceptance of technology in a virtual community? Here, we explore the possibility for extending TAM to incorporate the influence of the different types of social ties as a new theoretical construct. Preliminary analysis of data from a virtual community results show that weak and strong ties influence technology acceptance. The findings enable HCI researchers to account for influence of social ties in future investigations using TAM. 相似文献
583.
Rodrigo P. Lemos Jonas A. Kunzler Diego F. Burgos B. Mário J. de Souza Hugo V.L. e Silva Yroá R. Ferreira Edna L. Flôres Oliver Sander 《Journal of The Franklin Institute》2019,356(9):4949-4969
SEAD method estimates the direction-of-arrival angles on an uniform linear array based on the difference between the two largest singular values, what is called differential spectrum. Although it presented an outstanding performance, the ability to indicate the source positions was not elucidated yet. Inspired by the differential spectrum formulation we derived a total differential spectrum and found out that the matrix norm induced by the vector 2-norm of a modified spatial covariance matrix can be used to estimate the direction-of-arrival of multiple plane waves. Indeed we show that matrix norms are estimators and we propose their use instead of the singular value decomposition in SEAD-based methods. We present a general mathematical expression in order to explicit the operating principles of the proposed methods. Consequently, we were able to explain how the relation between the arriving and the search angles produces the larger peaks on the differential spectrum. To evaluate the important role played by matrix norms, a thousand experiments were carried out. They showed that the proposed approach proved to be as accurate as the previous SEAD-based methods, while providing a significant reduction on runtime. It also outperformed well-established methods like MODEX regarding the estimation error. 相似文献
584.
Bowen Li Jonathan R Silva Xiancui Lu Lei Luo Yunfei Wang Lizhen Xu Aerziguli Aierken Zhanserik Shynykul Peter Muiruri Kamau Anna Luo Jian Yang Deyuan Su Fan Yang Jianmin Cui Shilong Yang Ren Lai 《国家科学评论(英文版)》2019,6(6):1191
Animal toxins that are used to subdue prey and deter predators act as the key drivers in natural food chains and ecosystems. However, the predators of venomous animals may exploit feeding adaptation strategies to overcome toxins their prey produce. Much remains unknown about the genetic and molecular game process in the toxin-dominant food chain model. Here, we show an evolutionary strategy in different trophic levels of scorpion-eating amphibians, scorpions and insects, representing each predation relationship in habitats dominated by the paralytic toxins of scorpions. For scorpions preying on insects, we found that the scorpion α-toxins irreversibly activate the skeletal muscle sodium channel of their prey (insect, BgNaV1) through a membrane delivery mechanism and an efficient binding with the Asp/Lys-Tyr motif of BgNaV1. However, in the predatory game between frogs and scorpions, with a single point mutation (Lys to Glu) in this motif of the frog''s skeletal muscle sodium channel (fNaV1.4), fNaV1.4 breaks this interaction and diminishes muscular toxicity to the frog; thus, frogs can regularly prey on scorpions without showing paralysis. Interestingly, this molecular strategy also has been employed by some other scorpion-eating amphibians, especially anurans. In contrast to these amphibians, the Asp/Lys-Tyr motifs are structurally and functionally conserved in other animals that do not prey on scorpions. Together, our findings elucidate the protein-protein interacting mechanism of a toxin-dominant predator-prey system, implying the evolutionary game theory at a molecular level. 相似文献
585.
586.
Gerfeson Mendonça Alex Antonio Florindo Cassiano Ricardo Rech Delma Katiana Silva de Freitas José Cazuza de Farias Júnior 《Journal of sports sciences》2018,36(9):1068-1075
Little is known about the association between environmental characteristics and types of physical activity in adolescents in a Latin American context. The aim of this study was to examine the association between perceived neighborhood environmental characteristics and different types of physical activity in 2,874 adolescents from Joao Pessoa, Paraiba State, Northeastern Brazil. The types of activity measured by questionnaire (≥10 min/day) included sports, physical exercises, active commuting and recreational activities. Neighborhood characteristics were measured by a 15-item scale. Multilevel analyses showed that adolescents who reported “having places they liked to go to” (OR = 1.41; 95%CI: 1.10–1.79) and “places with opportunities to practice” (OR = 1.29; 95%CI: 1.01–1.65) were more likely to play sports. “Seeing interesting things while walking” (OR = 1.24; 95%CI: 1.01–1.53) and “Seeing other adolescents engaged in physical activity” (OR = 1.47; 95%CI: 1,05–2,06) were associated with exercises. “Seeing other adolescents engaged in physical activity” (OR = 1.47; 95%CI: 1.18–1.82), “the neighborhood is not violent” (OR = 1.29; 95%CI: 1.04–1.60) and “having places they like to go to” (OR = 1.59; 95%CI: 1.13–2.25) were positively associated and “places with opportunities to practice” (OR = 0.79; 95%CI: 0.63–0.98) inversely related to active commuting. “Seeing other adolescents engaged in physical activities” (OR = 1.31; 95%CI: 1.05–1.63) and “seeing interesting things while walking” (OR = 1.26; 95%CI: 1.02–1.56) were associated with recreational activities. Neighborhood environmental characteristics associated with the physical activity vary with the type of practices adopted by adolescents. 相似文献
587.
Ricardo Berton Manoel E. Lixandrão Claudio M. Pinto e Silva 《Journal of sports sciences》2018,36(18):2038-2044
Jump performance is considered an important factor in many sports. Thus, strategies such as weightlifting (WL) exercises, traditional resistance training (TRT) and plyometric training (PT) are effective at improving jump performance. However, it is not entirely clear which of these strategies can enable greater improvements on jump height. Thus, the purpose of the meta-analysis was to compare the improvements on countermovement jump (CMJ) performance between training methods which focus on WL exercises, TRT, and PT. Seven studies were included, of which one study performed both comparison. Therefore, four studies comparing WL exercises vs. TRT (total n = 78) and four studies comparing WL exercises vs. PT (total n = 76). The results showed greater improvements on CMJ performance for WL exercises compared to TRT (ESdiff: 0.72 ± 0.23; 95%CI: 0.26, 1.19; P = 0.002; Δ % = 7.5 and 2.1, respectively). The comparison between WL exercises vs. PT revealed no significant difference between protocols (ESdiff: 0.15 ± 0.23; 95%CI: ?0.30, 0.60; P = 0.518; Δ % = 8.8 and 8.1, respectively). In conclusion, WL exercises are superior to promote positive changes on CMJ performance compared to TRT; however, WL exercises and PT are equally effective at improving CMJ performance. 相似文献
588.
João Martins Adilson Marques António Rodrigues Hugo Sarmento Marcos Onofre Francisco Carreiro da Costa 《Sport, Education and Society》2018,23(5):505-519
Based on a socio-ecological framework for physical education (PE), this study explored and analysed the perspectives of physically active and inactive adolescent boys and girls with different socioeconomic status (SES), regarding the meanings that PE had on their physical activity (PA) lifestyles throughout childhood and adolescence. An interpretative and qualitative design was adopted and operationalised through an individual two-hours in-depth interview. Thematic analysis identified five main themes that distinguish active from inactive adolescents: ‘Early experiences of PE at primary school’; ‘PE experiences in middle and secondary school’; ‘Friendly, professional and pedagogue. That’s what I want from my PE teacher’; ‘Friends in PE and PA’; ‘Active lifestyles? Are schools and PE ready for making a difference?…’. Regardless of the lifestyle, girls revealed more PE negative experiences, related to uninteresting and competitive activities, groups’ constitution and logistic factors. SES played a major role on their PA and PE experiences, with low SES adolescents having limited opportunities inclusively within the primary school PE context. This study provides evidence for the importance of promoting positive PE and PA experiences in early years. Based on adolescents’ voices, several recommendations are discussed that can be considered for improving PE professionals’ effectiveness in promoting active lifestyles. 相似文献
589.
AbstractWe explored the outcomes of running a sport camp for children and youth with visual impairment on faculty members’ roles. Seven adapted physical activity faculty members were interviewed. Questionnaires and documents were also analyzed and a variety of strategies were employed to ensure the study’s trustworthiness. Regarding the teaching role, disability knowledge and real life examples gave faculty more credibility in conducting their class. As for the research role, the outcomes were not shared by the majority of participants and seemed to rely on aspects such as camp maturity, directors’ aptitudes, and partnerships. In turn, running the camp was a means for faculty members to perform their external service roles. These potential outcomes may become a significant part of the process by which people enact their institutional roles and may serve as a framework for future studies with a more hypothesis-driven approach. 相似文献
590.
The fiddle of using the Paralympic Games as a vehicle for expanding [dis]ability sport participation
AbstractIn this paper, we highlight the need to explore the excessive significance given to the Paralympic Games as a vehicle for the encouragement of participation of people with a disability within sport. The media spectacle around the games that the International Paralympic Committee (IPC) has worked tirelessly to develop has become, for policy-makers and the public alike, a sufficient outlet for disability sport provision. The honourable goals of the IPC articulated through the ethos of Paralympism have been assumed to be valid for all people with a disability, yet in terms of widening participation, their utility is limited. This paper first illuminates the relationship between the International Olympic Committee and the IPC before we turn our attention to the ethos of Paralympism. Highlighting the necessity for ‘sport for all’, we use a human rights lens, aided by a capabilities approach to facilitate better ways to educate the public about the need for equality of access to sporting participation opportunities. 相似文献