scholarly journals Métricas de resiliência: uma reflexão conceptual no contexto da gestão do risco

2021 ◽  
pp. 5-12
Author(s):  
António Betâmio de Almeida
Keyword(s):  
Lord Kelvin

A aplicação do conceito de resiliência no domínio da gestão de crises e do risco é relativamente recente mas tem tido um desenvolvimento muito relevante. O termo resiliência tem sido aplicado ao longo do tempo a diferentes áreas e a palavra resiliência pode ser considerada como parcialmente polissémica. Desde a mecânica dos materiais, a psicologia e a ecologia, a resiliência veio no século XXI acompanhar o termo sustentabilidade e caracterizar uma característica de gestão e da capacidade de reabilitação de instalações e sistemas naturais. A gestão da resiliência constitui um processo complementar e interligado ao da gestão do risco e que envolve diversas dimensões sociais e técnicas.Com a evolução da técnica e em particular com a aplicação de novas tecnologias de análise e de apoio à decisão, as frases atribuídas a Lord Kelvin (1824-1907) “o que não se pode medir não é possível melhorar” ou “o que é real pode sempre ser mensurável” poderão ser uma justificação filosófica, entre outras razões práticas, do interesse na caracterização e nas análises quantitativas. Com efeito, os conceitos de risco e de resiliência podem ser abordados por diferentes metodologias mas verifica-se um grande interesse prático na quantificação desses conceitos. Surge assim o tema da conceptualização e da métrica da resiliência. Na bibliografia podem-se encontrar diferentes modos para definir e quantificar a resiliência em engenharia, envolvendo as suas múltiplas dimensõesO texto é baseado numa análise bibliográfica da matéria e numa subsequente reflexão pessoal com a finalidade de apresentar métodos simplificados de métrica da resiliência bem como numa análise crítica das vantagens na quantificação da resiliência e também das suas limitações.

Amontons y la construcción de la idea de la existencia de un cero absoluto

2018 ◽  
Vol 14 (3) ◽  
pp. 174
Author(s):  
Alexandre Madeiros ◽  
Carlos Antonio López Ruíz
Keyword(s):  
Siglo Xix ◽  
Lord Kelvin

<div>La idea de la existencia de un cero absoluto en la naturaleza aparece frecuentemente en los libros de ciencia casi siempre asociada, exclusivamente, al nombre de Lord Kelvin. Algunos textos hacen, igualmente, breves referencias a otros importantes personajes del siglo XIX, como, por ejemplo, Rankine, Gay-Lussac y, con mucho menor frecuencia, a Henry-Victor Regnault. Rarísimos son los casos que, sin embargo, mencionan la intuición pionera, aun en el siglo XVII, de Guillaume Amontons. Este artículo es una tentativa de rescatar un poco de la historia y de las ideas de este ilustre mas desconocido personaje, así como de mostrar cómo sus intuiciones pueden ser, aún hoy, de una gran utilidad en las aulas de química y de física.</div><div> </div>

scholarly journals Obituary notices of fellows deceased

1908 ◽  
Vol 81 (543) ◽  
Keyword(s):  
Physical Science ◽  
Physical Knowledge ◽  
General Impression ◽  
The World ◽  
Two Generations ◽  
Practical Engineering ◽  
Creative Force ◽  
The Many ◽  
Effective Development ◽  
Lord Kelvin

It would be impossible in an obituary of ordinary length to convey any idea of the many-sided activity by which Lord Kelvin was continually transforming physical knowledge, through more than two generations, more especially in the earlier period before practical engineering engrossed much of his attention in importunate problems which only he could solve. It is not until one tries to arrange his scattered work into the different years and periods, that the intensity of his creative force is fully realised, and some otion is acquired of what a happy strenuous career his must have been in early days, with new discoveries and new aspects of knowledge crowding in upon him faster than be could express them to the world. The general impression left on one's mind by a connected survey of his work is overwhelming. The instinct of his own country and of the civilised world, in assigning to him a unique place among the intellectual forces of the ast century, was not mistaken. Other men have been as great in some special department of physical science: no one since Newton—hardly even Faraday, whose limitation was in a sense his strength—has exerted such a masterful influence over its whole domain. He might have been a more learned mathematician or an expert chemist; but he would then probably have been less activity, the immediate grasp of connecting principles and relations; each subject that he tackled was transformed by direct hints and analogies brought to bear from profound contemplation of the related domains of knowledge. In the first half of his life, fundamental results arrived in such volume as often to leave behind all chance of effective development. In the nidst of such accumulations he became a bad expositor; it is only by tracing his activity up and down through its fragmentary published records, and thus obtaining a consecutive view of his occupation, that a just idea of the vistas continually opening upon him may be reached. Nowhere is the supremacy of intellect more impressively illustrated. One is at times almost tempted o wish that the electric cabling of the Atlantic, his popularly best known achievement, as it was one of the most strenuous, had never been undertaken by him; nor even, perhaps, the practical settlement of electric units and instruments and methods to which it led on, thus leaving the ground largely prepared for the modern refined electric transformation of general engineering. In the absence of such pressing and absorbing distractions, what might the world not have received during the years of his prime in new discoveries and explorations among the inner processes of nature.

Compliments from Lord Kelvin

Nature ◽  
2007 ◽  
Vol 446 (7135) ◽  
pp. 505-506 ◽  
Author(s):  
Laurence D. Barron
Keyword(s):  
Lord Kelvin

Note on Mr Joseph O. Thompson's Results regarding Vibrating Wires

1899 ◽  
Vol 22 ◽  
pp. 598-600
Author(s):  
Dr W. Peddie
Keyword(s):  
Constant Temperature ◽  
Breaking Strength ◽  
Copper Wire ◽  
Physical Review ◽  
Logarithmic Decrement ◽  
Constant Amplitude ◽  
Vibrating Wire ◽  
Constant Quantity ◽  
The Wire ◽  
Lord Kelvin

In 1865 Lord Kelvin published the results of experiments which first made evident “a very remarkable fatigue of elasticity, according to which a wire which has been kept vibrating for several hours or days through a certain range came to rest much quicker when left to itself than when set in vibration after it has been at rest for several days and then immediately left to itself.” On the strength of Lord Kelvin's statement this elastic fatigue of metals has been regarded as a definitely ascertained fact. But, quite recently (Physical Review, March 1899), Mr Joseph O. Thompson has published a paper “On the period and logarithmic decrement of a continuously vibrating wire,” in which he states that it seems probable that “for constant temperature and constant amplitude the logarithmic decrement is constant.” This conclusion is based upon his observation that the logarithmic decrement, in the case of a copper wire, when the amplitude of vibration varied from about 185° to 175°, had the same value after it had been continuously vibrated through the average arc of 180° for fifty consecutive hours as it had at the commencement of that period. Observations upon other metals seemed to support the conclusion.Lord Kelvin also stated that fatigue caused an increase of the period of vibration. Mr Thompson finds that “no matter what metal was used, no matter whether the arc of vibration was as small as 20° or as high as 200°, no matter whether the wire was long or short, thick or thin (provided of course the breaking strength of the wire was at least twice the weight of the disc), the result was uniformly the same, namely, that when temperature and amplitude of vibration remained constant, the period of vibration was a constant quantity.”

scholarly journals Mechanically axially chiral catenanes and noncanonical mechanically axially chiral rotaxanes

2022 ◽  
Author(s):  
Stephen Goldup ◽  
John Maynard ◽  
Peter Gallagher ◽  
David Lozano ◽  
Patrick Butler
Keyword(s):  
Building Blocks ◽  
Biological Properties ◽  
Mirror Image ◽  
Symmetry Properties ◽  
Covalently Bonded ◽  
Axially Chiral ◽  
Mechanical Bond ◽  
A Chain ◽  
Lord Kelvin ◽  
Molecular Rings

Abstract The term chiral was introduced by Lord Kelvin over a century ago to describe objects that are distinct from their own mirror image. Chirality is relevant in many scientific areas, but particularly chemistry because different mirror image forms of a molecule famously have different biological properties. Chirality typically arises in molecules due to a rigidly chiral arrangement of covalently bonded atoms. Less generally appreciated is that molecular chirality can arise when molecules are threaded through one another to create a mechanical bond. For example, when two molecular rings with chemically distinct faces are joined like links in a chain the resulting structure is chiral even when the rings themselves are not. We re-examined the symmetry properties of such mechanically axially chiral catenanes and in doing so identified a straightforward route to these molecules from simple building blocks. This also led to the discovery of a previously overlooked mechanical stereogenic unit that can arise when such a ring encircles a dumbbell-shaped axle to generate a rotaxane. These insights allowed us to produce the first highly enantioenriched axially chiral catenane and the same approach gave access to a molecule containing the newly identified noncanonical axially chiral rotaxane motif. With methods to access these structures in hand, the process of exploring their properties and applications can now begin.

Charles Darwin's Manuscript of Pangenesis

1963 ◽  
Vol 1 (3) ◽  
pp. 251-263 ◽  
Author(s):  
R. C. Olby
Keyword(s):  
Evolutionary Theory ◽  
Theory Of Evolution ◽  
William Thomson ◽  
Lord Kelvin ◽  
Short Time

Darwin only published one account of his provisional hypothesis of pangenesis, and that is to be found in chapter xxvii of his book The Variation of Animals and Plants under Domestication, the first edition of which is dated 1868. The absence of any earlier account in Darwin's works has led some to assume that he had recourse to this hypothesis only a short time before the published date of the book containing it, and on the basis of this assumption they have asserted that he produced it as a part of his defence of the theory of evolution against the criticisms made of it by the physicists Sir William Thomson, afterwards Lord Kelvin, and Fleeming Jenkin. But to make such an assertion is to ignore the fact that Darwin had already sent his manuscript of pangenesis to Huxley in the year 1865, two years before Fleeming Jenkin's article appeared and three years before Lord Kelvin openly attacked the evolutionary theory. The discovery of this manuscript of pangenesis has, therefore, some importance, for it should reveal Darwin's conception of pangenesis in 1865.

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