Spelling suggestions: "subject:"ascendente""
41 |
Towards Systematic Improvement of Density Functional ApproximationsLi, Chen January 2016 (has links)
<p>Density functional theory is a formally exact theory to describe ground state properties due to the existence of the exact functional. In practice, the usefulness of density functional theory relies on the accuracy of density functional approximations. After decades of effort of functional developments, the present-day state-of-the-art density functional approximations have achieved reasonably good accuracy for small systems. However, the error grows with system size. One of the dominant errors intrinsic in the mainstream density functional approximations is the delocalization error, which arises because of the violation of Perdew-Parr-Levy-Balduz (PPLB) linearity condition. The PPLB condition governs the formulation of the density functional theory for fractional-charge systems, for which the ground state energy for the exact functional, as a function of the fractional electron number, should yield a series of line-segments across the integer points. In this dissertation, by imposing the PPLB condition in a local, size-consistent way, we develop the local scaling correction (LSC) and its updated version, the localized orbital scaling correction (LOSC), which largely improve upon the mainstream density functional approximations across system sizes. With the LOSC, we open a door towards a systematic elimination of delocalization error. Besides the ground state functional development, we also develop a gentlest ascent dynamics approach for accessing the excited states via time-independent ground state density functionals. This is also useful for exploring Kohn-Sham energy landscapes of approximate density functionals. I will also review the PPLB formulation of density functional theory for fractionally charged systems, and show that it is equivalent to the formulation normally used for fractional system calculations under certain assumptions. Furthermore, I will examine the behavior of the fractional system energy as a function of the fractional number of electrons for different mainstream functionals, and relate it to their errors for integer systems.</p> / Dissertation
|
42 |
Sobolev Gradient Flows and Image ProcessingCalder, Jeffrey 25 August 2010 (has links)
In this thesis we study Sobolev gradient flows for Perona-Malik style energy functionals and generalizations thereof. We begin with first order isotropic flows which are shown to be regularizations of the heat equation. We show that these flows are well-posed in the forward and reverse directions which yields an effective linear sharpening algorithm. We furthermore establish a number of maximum principles for the forward flow and show that edges are preserved for a finite period of time. We then go on to study isotropic Sobolev gradient flows with respect to higher order Sobolev metrics. As the Sobolev order is increased, we observe an increasing reluctance to destroy fine details and texture. We then consider Sobolev gradient flows for non-linear anisotropic diffusion functionals of arbitrary order. We establish existence, uniqueness and continuous dependence on initial data for a broad class of such equations. The well-posedness of these new anisotropic gradient flows opens the door to a wide variety of sharpening and diffusion techniques which were previously impossible under L2 gradient descent. We show how one can easily use this framework to design an anisotropic sharpening algorithm which can sharpen image features while suppressing noise. We compare our sharpening algorithm to the well-known shock filter and show that Sobolev sharpening produces natural looking images without the "staircasing" artifacts that plague the shock filter. / Thesis (Master, Mathematics & Statistics) -- Queen's University, 2010-08-25 10:44:12.23
|
43 |
Data sampling strategies in stochastic algorithms for empirical risk minimizationCsiba, Dominik January 2018 (has links)
Gradient descent methods and especially their stochastic variants have become highly popular in the last decade due to their efficiency on big data optimization problems. In this thesis we present the development of data sampling strategies for these methods. In the first four chapters we focus on four views on the sampling for convex problems, developing and analyzing new state-of-the-art methods using non-standard data sampling strategies. Finally, in the last chapter we present a more flexible framework, which generalizes to more problems as well as more sampling rules. In the first chapter we propose an adaptive variant of stochastic dual coordinate ascent (SDCA) for solving the regularized empirical risk minimization (ERM) problem. Our modification consists in allowing the method to adaptively change the probability distribution over the dual variables throughout the iterative process. AdaSDCA achieves a provably better complexity bound than SDCA with the best fixed probability distribution, known as importance sampling. However, it is of a theoretical character as it is expensive to implement. We also propose AdaSDCA+: a practical variant which in our experiments outperforms existing non-adaptive methods. In the second chapter we extend the dual-free analysis of SDCA, to arbitrary mini-batching schemes. Our method is able to better utilize the information in the data defining the ERM problem. For convex loss functions, our complexity results match those of QUARTZ, which is a primal-dual method also allowing for arbitrary mini-batching schemes. The advantage of a dual-free analysis comes from the fact that it guarantees convergence even for non-convex loss functions, as long as the average loss is convex. We illustrate through experiments the utility of being able to design arbitrary mini-batching schemes. In the third chapter we study importance sampling of minibatches. Minibatching is a well studied and highly popular technique in supervised learning, used by practitioners due to its ability to accelerate training through better utilization of parallel processing power and reduction of stochastic variance. Another popular technique is importance sampling { a strategy for preferential sampling of more important examples also capable of accelerating the training process. However, despite considerable effort by the community in these areas, and due to the inherent technical difficulty of the problem, there is no existing work combining the power of importance sampling with the strength of minibatching. In this chapter we propose the first importance sampling for minibatches and give simple and rigorous complexity analysis of its performance. We illustrate on synthetic problems that for training data of certain properties, our sampling can lead to several orders of magnitude improvement in training time. We then test the new sampling on several popular datasets, and show that the improvement can reach an order of magnitude. In the fourth chapter we ask whether randomized coordinate descent (RCD) methods should be applied to the ERM problem or rather to its dual. When the number of examples (n) is much larger than the number of features (d), a common strategy is to apply RCD to the dual problem. On the other hand, when the number of features is much larger than the number of examples, it makes sense to apply RCD directly to the primal problem. In this paper we provide the first joint study of these two approaches when applied to L2-regularized ERM. First, we show through a rigorous analysis that for dense data, the above intuition is precisely correct. However, we find that for sparse and structured data, primal RCD can significantly outperform dual RCD even if d ≪ n, and vice versa, dual RCD can be much faster than primal RCD even if n ≫ d. Moreover, we show that, surprisingly, a single sampling strategy minimizes both the (bound on the) number of iterations and the overall expected complexity of RCD. Note that the latter complexity measure also takes into account the average cost of the iterations, which depends on the structure and sparsity of the data, and on the sampling strategy employed. We confirm our theoretical predictions using extensive experiments with both synthetic and real data sets. In the last chapter we introduce two novel generalizations of the theory for gradient descent type methods in the proximal setting. Firstly, we introduce the proportion function, which we further use to analyze all the known block-selection rules for coordinate descent methods under a single framework. This framework includes randomized methods with uniform, non-uniform or even adaptive sampling strategies, as well as deterministic methods with batch, greedy or cyclic selection rules. We additionally introduce a novel block selection technique called greedy minibatches, for which we provide competitive convergence guarantees. Secondly, the whole theory of strongly-convex optimization was recently generalized to a specific class of non-convex functions satisfying the so-called Polyak- Lojasiewicz condition. To mirror this generalization in the weakly convex case, we introduce the Weak Polyak- Lojasiewicz condition, using which we give global convergence guarantees for a class of non-convex functions previously not considered in theory. Additionally, we give local convergence guarantees for an even larger class of non-convex functions satisfying only a certain smoothness assumption. By combining the two above mentioned generalizations we recover the state-of-the-art convergence guarantees for a large class of previously known methods and setups as special cases of our framework. Also, we provide new guarantees for many previously not considered combinations of methods and setups, as well as a huge class of novel non-convex objectives. The flexibility of our approach offers a lot of potential for future research, as any new block selection procedure will have a convergence guarantee for all objectives considered in our framework, while any new objective analyzed under our approach will have a whole fleet of block selection rules with convergence guarantees readily available.
|
44 |
The 'divine' confused and abused : cultural memories of royal ritual netherworld descent and heavenly ascent in the Hebrew BibleBeadle, David Nathaniel January 2016 (has links)
This thesis proposes that integrated rituals of netherworld descent and heavenly ascent are represented in the Hebrew Bible as having been performed by Davidic royals – royal women, as well as male monarchs. In some instances (e.g. Psalms 2; 18; 24; 89:2-38; and 110) these rituals are represented idealistically, with Yahweh confirming the king’s ritual status and potency, through re-presented speech acts. In other instances, however, while an idealistic picture of monarchy continues to be upheld, it is subverted from within in varying ways (e.g. 2 Kgs 9:30-37; 11; Ps. 89:39-52; Isa. 14.4b-20; Jer. 13:18-20; Ezekiel 19). The differing portrayals of monarchy reflect the differing ways with which biblical texts are negotiating and interacting with ambiguous discourses embodying memories of monarchy. On the one hand, after the fall of monarchic Judah, ‘foreign’ monarchy (and especially trading monarchies, such as those of Phoenicia) were fetishised within biblical authors’ discourses of political and economic imperialism, and so Davidic monarchy became a signifier of an enchanting and mystifying ‘indigenous’ past. On the other hand, discourses concerning the past frequently referenced exile, and the collapse of monarchy. Some biblical representations of ritual netherworld descent and heavenly ascent acknowledge this latter, uncomfortable kind of remembering – even as they reify and reinforce these enchanting memories which they subvert. The remembered, cosmically liminal first temple and the remembered royal body become loci for these paradoxical, contradictory, and competing memories. This much is evident in mystifying royal cosmic liminality and heavenly ascent, access to divine knowledge, and mimesis of Yahweh; in cathartic myths of the subjugation of the forces of chaos and disorder, both cosmic and military; and in the subversion of the enchanting remembered Davidic cultic praxis of descent and ascent, through these motifs’ re-presentations in montages alongside rituals which connote displacement, destruction, profanation, desecration, subjugation and being forgotten. In these instances, the vulnerabilities inherent in cultural idealising of the Davidic monarchy’s potent cosmic liminality are brought into sharp relief.
|
45 |
A ASCENSÃO CELESTIAL DE PAULO DE TARSO: ANÁLISE DE 2 CORÍNTIOS 12,1-10 A PARTIR DA HISTÓRIA DA RELIGIÃO E DA NEUROTEOLOGIA / THE HEAVENLY ASCENT OF PAUL OF TARSUS: AN ANALYSIS OF 2 CORINTHIANS 12, 1-10 FROM HISTORY OF RELIGION AND NEUROTHEOLOGYNogueira, Sebastiana Maria Silva 11 September 2012 (has links)
Made available in DSpace on 2016-08-03T12:19:14Z (GMT). No. of bitstreams: 1
Sebastiana maria Silva.pdf: 1536000 bytes, checksum: 2487c2d3e1207d1baf47cde8279add8a (MD5)
Previous issue date: 2012-09-11 / Fundação de Amparo a Pesquisa do Estado de São Paulo / The subject celestial journey , well familiar to the old mediterranean world, is based on the
belief that the visionary can cross the boundary between humanity and divinity, a constant
characteristic in apocalyptic literature. Old Jewish mysticism was seen as an important
dimension of this tradition, that is the reason why the mystics used the term apocalypse to
describe the revelation of their experiences. Paul s ascension to heaven, recounted in 2 Cor
12,1-10, is the only first hand account and the best evidence of ecstatic practice of celestial
journey in first century Judaism. This text, one of great interest in the studies of New
Testament, has been examined in thematic forms that extend from the recognition of the
apostle as enjoyable to divinity - what granted him such a heroic achievement - to a
punishment experience by the guardians of the celestial gates for finding in him no merit to
approach the place of the presence of God. For long time, the studies that prevailed in the
academy were those of the theological aspects of the passage, such as the spine in the flesh ,
the apostolic mission , Paul s opponents , among others. The language of the passage
reveals important topics that were not considered together for a coherent interpretation of the
text. The use of expressions from the Jewish mystical apocalyptic circle like "caught up",
"Third Heaven", "hear unutterable words" and "a thorn for the flesh" by the apostle needs to
be investigated for the comprehension of what Paul had in mind while using those terms.
Another problem is the omission of the experimental approach described in the passage. The
apostle reveals that he lived the experience recounted in 2 Cor 12,1-10. While he was telling
the unknown status of his body during the rising, he highlights signs of the altered state of
consciousness, an aspect that was not considered in the traditional analysis of the text. These
problems are analyzed in this thesis take as instruments of the Religion History and the
Neurotheology analysis. Models were built trying to demonstrate a correlation between brain
activity and mystical experience. In this respect, we have to point out that the emergence of
neurotheology, or spiritual neurology brings a progress to the area of religious experience.
Some points of difficult interpretation in pauline text have been clarified under this
perspective. The proposal of this study was to build a contextual frame to analyse the ecstatic
experience of Paul. The study made it possible to infer that the interdisciplinary approach
allows a more appropriate scenario to the understanding and interpretation of the text. / O tema viagem celestial , bem familiar ao mundo mediterrâneo antigo fundamenta-se na
crença de que o visionário pode cruzar a fronteira entre a humanidade e a divindade, uma
característica constante na literatura apocalíptica. O misticismo judaico antigo era visto como
uma importante dimensão dessa tradição, razão pela qual os místicos usaram o termo
apocalipse para descrever a revelação de suas experiências. A ascensão de Paulo ao céu,
recontada em 2 Cor 12,1-10, é o único relato de primeira mão e a melhor evidência para a
prática extática de viagem celestial no judaísmo do primeiro século. De grande interesse nos
estudos do Novo Testamento o texto tem sido abordado em forma temática que se estende
desde o reconhecimento do apóstolo como agradável à divindade o que lhe rendeu tal feito
heróico a uma experiência de punição pelos guardiões dos portões celestiais por não ter sido
encontrado nele mérito para aproximar-se do lugar da presença de Deus. Por muito tempo os
estudos que predominavam na academia eram os de aspectos teológicos da passagem, tais
como o espinho na carne , a missão apostólica , os oponentes de Paulo , entre outros. A
linguagem da passagem revela pontos importantes não considerados de forma conjunta para
uma interpretação coerente do texto. O uso por parte do apóstolo de expressões do círculo
místico-apocalíptico judaico, tais como foi arrebatado , Terceiro Céu , ouviu palavras
inefáveis e um espinho na carne precisa ser investigado para a compreensão do que Paulo
tinha em mente ao utilizar tais terminologias. Outro problema é a omissão do enfoque
experimental descrito na passagem. O apóstolo revela que vivenciou tal experiência recontada
em 2 Cor 12,1-10. Ao relatar o desconhecimento do status do seu corpo durante a ascensão
ele evidencia sinais do estado alterado de consciência, aspecto não considerado nas análises
tradicionais do texto. Esses problemas que são abordados nesta tese tomam como
instrumentos da análise a História da Religião e o da Neuroteologia. Modelos foram
construídos tentando demonstrar uma correlação entre a atividade cerebral e a experiência
mística. Há que se destacar, nesse sentido, que o surgimento da neuroteologia ou neurologia
espiritual constitui-se em um avanço na área da experiência religiosa. Pontos de difícil
interpretação no texto paulino foram elucidados dentro dessa perspectiva. A proposta deste
trabalho, portanto, foi construir um quadro contextual em que a experiência extática de Paulo
pudesse ser analisada. O estudo possibilitou inferir que a abordagem interdisciplinar permite
alcançar um cenário mais apropriado para a compreensão e interpretação do referido texto.
|
46 |
The Three Lives of James: From Jewish-Christian Traditions to a Valentinian Revelation, Preserved in Two Late Antique AttestationsEdwards, Robert Michael January 2015 (has links)
Though discovered in 1945, the First Apocalypse of James from Nag Hammadi Codex V, 3 has received very little attention from the scholarly community. This is primarily due to the fragmentary condition of the text. Previous scholarly engagements with the text have led to the conclusion that the purpose of such a revelatory dialogue was to impart instructions for the ascent of the soul to one about to be martyred. The recent discovery of a second copy of the text simply titled “James” as part of the Tchacos Codex has led to not only a greater amount of scholarly interest, but also to different possible interpretations. From NHC V, 3 it was possible to ascertain a pre- and post- martyrdom revelation of Jesus to James, however, the text from Al Minya clearly shows a third revelatory section wherein the martyrdom of James is used as a means of revelation to Addai, the legendary founder of Eastern Syrian Christianity. Chapters one and two answer the question of why James was chosen as the protagonist of the narrative. In chapter one I look in detail at the literary construction of the martyrdom of James and problematize the development of the traditions. Chapter two then turns to a discussion of the figure of James as an authority in the developing Christian community. Chapters three and four are concerned with the literary classification of the text. Chapter three situates the First Apocalypse of James within the overarching genre of apocalyptic literature, and the specific sub-genre of gnostic apocalypses. Chapter four discusses how the text might be understood as a commission narrative while interrogating the lineage of descent beginning with the transmission of the revelation from James to Addai. Following this in chapter five I explore the cosmology of the text with particular attention to the ascent of the soul.
|
47 |
An Investigation of Preservice Teachers' Understanding of BuoyancyKirby, Benjamin S. 05 1900 (has links)
The purpose of this study was to examine the conceptual understandings of 55 elementary preservice teachers for the concept of buoyancy. This study used Ausubel’s Assimilation Theory (Ausubel, 1963) as a framework for a 15-week intervention that used pre/post concept maps (Cmaps), pre/post face-to-face semi-structured interviews, and drawings as evidences for change of formation of cognitive structures. Using a convergent parallel design and mixed methods approach, preservice teachers’ conceptions were analyzed using these evidences. Results of the study show that preservice teachers held both scientific conceptions and misconceptions about buoyancy as a force before and after an instructional intervention. Of importance were the existence of robust misconceptions about buoyancy that included inaccurate scientific knowledge about the foundational concepts of gravity, weight, mass, and density. The largest gains in scientific knowledge included the concepts of gravity, surface area, opposing forces, and the buoyant force. These concepts were consistently supported with evidence from post-concept maps, post, semi-structured interviews, and drawings. However, high frequencies of misconceptions were associated with these same aforementioned concepts as well as additional misconceptions about buoyancy-related concepts (i.e., weight, density, displacement, and sinking/floating). A paired t test showed a statistically significant difference (t = -3.504, p = .001) in the total number of scientifically correct concepts for the pre-concept maps (M = 0.51, SD = .879) and post-concept maps (M = 1.25, SD = 1.542). The Cohen’s d effect size was small, .47. Even through gains for the pre/post concept maps were noted, a qualitative analysis of the results indicated that not only were there serious gaps in the participant’s scientific understanding of buoyancy, after the instructional intervention an increased number of misconceptions were presented alongside the newly learned concepts. A paired t test examining misconceptions showed that there was a statistically significant difference (t = -3.160, p = .003) in the total number of misconceptions for the pre-concept maps (M = 2.709, SD = 1.449) and post-concept maps (M = 3.363, SD = 2.094) after the intervention. The Cohen’s d effect size was small, .43. Taken together, these results revealed that, in general, the preservice teachers had understandings of buoyancy that align with children in preschool and elementary school (Biddulph and Osborne, 1983; Grimellini-Tomasini et al., 1990; Halford, Brown & Thompson, 1986; Hsin and Wu, 2011; Kohn, 1993; Rappolt-Schlichtmann et al., 2007; Yin et al., 2008). Based on these findings, implications for this study suggest that elementary preservice teacher candidates should be carefully screened to ensure they have mastered foundational scientific knowledge that they are expected to teach to children. As such knowledge is a prerequisite to the development of pedagogical content knowledge, it is unlikely that large numbers of robust misconceptions will be significantly reduced or eliminated during a science methods course that is designed to focus on pedagogical content knowledge.
|
48 |
Mixed convection in vertical rod bundlesSymolon, Paul D. January 1982 (has links)
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1982 / Includes bibliographical references. / by Paul Douglas Symolon. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Mechanical Engineering
|
49 |
Didactique de l'enquête pour une lecture interprétative d'une fable de Jean de la Fontaine, selon une épistémologie de l'élévation de l'abstrait au concret : étude de cas au sein d'une ingénierie coopérative / Didactics of an inquiry-based interpretative reading of a fable by Jean de La Fontaine, by using an epistemology of the ascent from the abstract to the concrete : a case study within a cooperative engineeringLefeuvre, Loïs 12 November 2018 (has links)
Une lecture interprétative de la fable de La Fontaine Le Loup et l’Agneau est une mise à l’épreuve de la relation abstrait-concret entre morale et récit. Cette interprétation peut donner à son lecteur un pouvoir heuristique sur le monde, par analogie entre la fable et son expérience du monde. Nous faisons l'hypothèse que l’enquête de lecture dirigée, pour l'interprétation de cette oeuvre littéraire, s’enseigne à l’école primaire. Dans le cadre de la Théorie de l’Action Conjointe en Didactique, nous analysons les principes de cette enquête à partir de la mise en oeuvre d'une séquence d'enseignement dans une classe de cours moyen. Depuis 2008, cette séquence a été conçue, analysée et transformée par un collectif de professeurs d'école, de formateurs et de chercheurs travaillant en ingénierie coopérative. Dans cette thèse, nous montrons comment la résolution de problèmes de lecture crée le style de pensée du collectif-classe, avec ses certitudes raisonnées. Nous donnons à voir l’institution-aItération des concepts en jeu dans cette résolution, selon une épistémologie de l’élévation de l’abstrait au concret. Nous mettons en évidence que cette institution-altération de concepts dépend d’une recherche d’équilibration entre contrat et milieu didactiques. Nous développons les facteurs influençant cette équilibration : travail épistémique du professeur, pour une connaissance approfondie de la fable ; réticence-expression du professeur vis-à-vis du savoir en jeu ; greffe des significations savantes en lien avec l'institutionnalisation des commentaires ; réécriture de la fable par une paraphrase stricto sensu ; recours aux analogies provoquées. / An interpretative reading of The Wolf and The Lamb by La Fontaine puts to the test the abstract-concrete relationship, through its moral and narrative. The interpretation of this fable can give its readers heuristic power, through an analogy between the fable and their knowledge of the world. We assume that the guided-reading inquiry leading to the interpretation of this literary work is taught in primary school. Following the Joint Action Theory in Didactics, we analyse the principles of this inquiry through the implementation of a teaching sequence in a fifth grade class. Since 2008, this sequence has been designed, analysed and altered by a group composed of primary school teachers, teacher educators and researchers working within the framework of a cooperative engineering.In this thesis, we show how the solving of reading problems leads the « thought collective » formed by the class to develop a thought style with its reasoned certainties. We show how concepts at stake in this resolution are established and altered, following an epistemology of the ascent from the abstract to the concrete. We highlight the way this establishment-alteration of concepts depends on a search for balance between the didactic milieu and contract. We develop the factors which impact this balancing : the teacher’s work to access a comprehensive understanding of the fable; the teacher's reticence-expression towards the knowledge at stake ; the graft of meanings linked to the institutionalization of pupils'comments; the rewriting of the fable by using a stricto sensu paraphrase ; the use of provoked analogies.
|
50 |
Variáveis laboratoriais, desempenho e pacing no ciclismo contra-relógio de 20 minutos realizado em subidaBossi, Arthur Henrique Souza Neto 22 August 2014 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-06-22T14:27:00Z
No. of bitstreams: 1
arthurhenriquesouzanetobossi.pdf: 861040 bytes, checksum: c3c1cec3feee16cacb22f14eb9d27f1c (MD5) / Rejected by Adriana Oliveira (adriana.oliveira@ufjf.edu.br), reason: on 2017-06-22T14:35:05Z (GMT) / Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-06-22T14:39:20Z
No. of bitstreams: 1
arthurhenriquesouzanetobossi.pdf: 861040 bytes, checksum: c3c1cec3feee16cacb22f14eb9d27f1c (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-07T19:21:44Z (GMT) No. of bitstreams: 1
arthurhenriquesouzanetobossi.pdf: 861040 bytes, checksum: c3c1cec3feee16cacb22f14eb9d27f1c (MD5) / Made available in DSpace on 2017-08-07T19:21:44Z (GMT). No. of bitstreams: 1
arthurhenriquesouzanetobossi.pdf: 861040 bytes, checksum: c3c1cec3feee16cacb22f14eb9d27f1c (MD5)
Previous issue date: 2014-08-22 / Para maior empregabilidade do protocolo de teste contra-relógio (CR) de 20 min em campo, é necessária a compreensão (1) de como o desempenho em percurso de subida se relaciona com as medidas laboratoriais típicas e (2) do perfil de pacing adotado. Separados por pelo menos 48 horas, 15 ciclistas moderadamente treinados, incluindo 1 do sexo feminino (30,8±4,8 anos; 176,5±8,0 cm; 78,9±14,5 kg; 56,1±7,7 ml.kg-1.min-1; média ± desvio padrão), realizaram inicialmente um teste anaeróbio Wingate, um teste de esforço incremental até a exaustão e um contrarelógio de campo por 20 min em percurso de subida com 2,7% de inclinação média. Após 5 semanas de treinamento não supervisionado, 10 dos 15 voluntários realizaram um segundo CR para comparação do pacing adotado. As regressões lineares múltiplas stepwise demonstraram que 91% da variação na potência média produzida no CR (W.kg-1) pode ser explicada pelo pico do consumo de oxigênio (ml.kg-1.min-1) e pelo ponto de compensação respiratória (W.kg-1), com coeficientes beta padronizados de 0,64 e 0,39 respectivamente. A realização do CR em aclive pressupõe um ajuste de 94,6% da potência média, de modo a aperfeiçoar a concordância com a potência referente ao ponto de compensação respiratória, em que o diagrama de Bland-Altman demonstrou um viés ± erro aleatório de 0,4±49,7 W ou -0,1±19,7 %. A ANOVA two-way (CR X tempo) para medidas repetidas revelou efeito principal dos intervalos de tempo (p < 0,001) na potência média produzida em cada trecho (122,2±10,0; 97,8±1,2 e 95,1±7,1% para os trechos 0-2, 2-18 e 18-20 min, respectivamente) caracterizando perfil de pacing positivo, tanto no primeiro, quanto no segundo teste (p = 0,116). Em conjunto, estas informações indicam que o protocolo de teste CR de 20 min realizado em subida, aparentemente, seja robusto para monitorar o desempenho de ciclistas de diferentes níveis competitivos. Entretanto, novos estudos mais específicos são importantes para confirmar a reprodutibilidade do desempenho e para verificar a influência do feedback instantâneo da potência produzida. / For a wider applicability of the 20-min time trial (TT) testing protocol in field, it is necessary to understand (1) how performance in an uphill course relates with typical laboratory measures and (2) the pacing profile adopted. Separated by at least 48 hours, 15 moderately trained cyclists, including 1 female (30.8±4.8 years; 176.5±8.0 cm; 78.9±14.5 kg; 56.1±7.7 ml.kg-1.min-1; mean ± standard deviation), initially performed a Wingate anaerobic test, a graded exercise test to exhaustion and a 20-min field time trial in a 2.7% gradient uphill course. After 5 weeks of nonsupervised training, 10 from 15 volunteers performed a second TT for comparison of the pacing adopted. Stepwise multiple linear regressions demonstrated that 91% of TT mean power output variation (W.kg-1) can be explained by peak oxygen consumption (ml.kg-1.min-1) and respiratory compensation point (W.kg-1), with standardized beta coefficients of 0.64 and 0.39 respectively. Performing TT on ascents premises a 94.6% mean power output adjustment in order to improve the agreement with respiratory compensation point power output, which Bland-Altman plot showed a bias ± random error of 0.4±49.7 W or -0.1±19.7 %. Repeated measures two-way ANOVA (TT X time) revealed a main effect of the time intervals (p < 0.001) on the power output of each portion (122.2±10.0; 97.8±1.2 e 95.1±7.1% for the portions 0-2, 2-18 e 18-20 min, respectively) characterizing a positive pacing profile, either in the first and in the second test (p = 0.116). Together, this information indicates that the 20-min TT testing protocol performed on ascent is apparently robust for performance monitoring of different competitive level cyclists. However, more specific new studies are important to confirm performance reproducibility and to verify the influence of power output instant feedback.
|
Page generated in 0.0679 seconds