共查询到20条相似文献,搜索用时 15 毫秒
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John D. Norton Bryan W. Roberts 《Centaurus; international magazine of the history of science and medicine》2012,54(2):148-164
Galileo's refutation of the speed‐distance law of fall in his Two New Sciences is routinely dismissed as a moment of confused argumentation. We urge that Galileo's argument correctly identified why the speed‐distance law is untenable, failing only in its very last step. Using an ingenious combination of scaling and self‐similarity arguments, Galileo found correctly that bodies, falling from rest according to this law, fall all distances in equal times. What he failed to recognize in the last step is that this time is infinite, the result of an exponential dependence of distance on time. Instead, Galileo conflated it with the other motion that satisfies this ‘equal time’ property, instantaneous motion. 相似文献
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Marcin Krasnodbski 《Centaurus; international magazine of the history of science and medicine》2018,60(1-2):3-24
Photonic technologies are often advertised as capable of revolutionizing our lives in the near future. However, the exact meaning of the word “photonics” as well as the scope of the field remain unclear. The term was born in the 1970s in both France and the Netherlands where various scholarly communities began research into the phenomenon. Some resulting technologies started circulating in industry and academia and the concept of photonics became very successful in the late 1980s when photons were supposed to replace electrons in every‐day technologies. The failure of optical computing damaged the reputation of photonics in the 1990s but the term lived on as it merged with sister terms such as electro‐optics and optoelectronics. The key problem with photonics is the breadth of its scope. Some argue it is the science of light, others consider it an economic category. Generally, photonics covers lasers, optical fibers as well as solar energy and LEDs. It seems that the only conceptual tool capable of addressing this complexity is that of technological paradigms, which Ernest Sternberg applied to photonics in 1992. Sternberg's approach can help to clarify the epistemological boundaries of the name “photonics,” even when addressing this complex area from a 21st century stand point. 相似文献
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Martin Clutton‐Brock David Topper 《Centaurus; international magazine of the history of science and medicine》2011,53(3):221-235
In Galileo's opinion, his most important argument for the Earth's motion was based on his theory of the tides that combined the Earth's rotation with its orbital motion so that it alternately accelerates and decelerates the sea. His theory deliberately ignored the Moon's influence, which at that time was generally regarded as occult. Galileo's confidence in his theory was strongly reinforced by its providing a mechanical model. That a theory that ignored the Moon's influence could seem plausible is confirmed by comparison with the theories of Bacon and Wallis. That Galileo's theory could seem plausible despite encountering difficulties is confirmed by comparison with Newton's theory, which is deeply flawed by its inclusion of a vertical response to the total tidal force. That many people now regard Galileo's theory as wrong is due to our having absorbed as natural Newton's idea of lunar attraction. 相似文献
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Maria Rentetzi 《Centaurus; international magazine of the history of science and medicine》2009,51(1):63-87
Abstract. In the 1950s a small group of scientists and politicians in Greece became determined to build a center for nuclear reactor research. With the exception of a handful of students trained in nuclear physics, no real expertise existed in the country. There were also no experienced administrators or managers ready to take the lead, and the existing national bureaucracy was labyrinthine. Thus a new scientific network had to be constituted largely from scratch in the Greek postwar sociopolitical order, a network that had to be extended to the international scientific community if it was to be efficient at all. Surprisingly, behind the construction of this scientific nuclear research project in Greece one can discern the female touch of a powerful and determined woman, Queen Frederika of Greece. I argue that she was the one who, by taking advantage of the United States' discourse on atomic energy for peace, was able to exploit the knots and nodes of her own political network, build new alliances and transform scattered resources into a grid that could underlay nuclear research in Greece and her own legitimacy in the country. 相似文献
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C-S-H seeding is a promising approach to accelerate cement hydration in a very effective way. Until now little is known about the way the C-S-H seeds work and how they affect the properties of the hydrated cement paste. To be able to analyse this in detail it is necessary to have a preparation method for the C-S-H seeds, which is reproducible and able to prepare seeds with defined properties. The present work describes two methods for the synthesis of C-S-H seeds, a mechanochemical approach and a sol-gel synthesis. A factorial design of experiments setup was used to find those parameters, which affect the efficiency of the C-S-H seeds to accelerate cement hydration and to adjust these parameters in order to achieve the optimized seeds, which are very effective accelerators. Heat flow calorimetry shows that the dormant period of cement hydration can be eliminated by the use of the optimized C-S-H seeds and compressive strength tests show a multiplication of early compressive strength even at very low concentrations of seeds, indicating that an optimization of the synthesis by factorial design of experiments is a promising way for further studies on the mode of action of C-S-H seeds. 相似文献
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Erica Charters Richard A. McKay 《Centaurus; international magazine of the history of science and medicine》2020,62(2):223-233
This spotlight issue encourages reflection on the current COVID-19 pandemic, not simply through comparisons with previous epidemics, but also by illustrating that epidemics deserve study within their broader cultural, political, scientific, and geographic contexts. Epidemics are not solely a function of pathogens; they are also a function of how society is structured, how political power is wielded in the name of public health, how quantitative data is collected, how diseases are categorised and modelled, and how histories of disease are narrated. Each of these activities has its own history. As historians of science and medicine have long pointed out, even the most basic methodologies that underpin scientific research—observation, trust in numbers, the use of models, even the experimental method itself—have a history. They should not be taken as a given, but understood as processes, or even strategies, that were negotiated, argued for and against, and developed within particular historical contexts and explanatory schemes. Knowing the history of something—whether of numbers, narratives, or disease—enables us to see a broader range of trajectories available to us. These varied histories also remind us that we are currently in the midst of a chaotic drama of uncertainty, within our own unstable and unfolding narrative. 相似文献
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本文先从经典力学出发,论述了加速度极小原理,接着论述了变形体中的加速度极小原理的理论及应用,最后根据加速度极小原理的变分方程,推演了大挠度梁的动力方程以说明该原理的普遍性和优越性。文中还谈及塑性动力响应研究现状及今后发展的方向。 相似文献
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Massimiliano Badino 《Centaurus; international magazine of the history of science and medicine》2016,58(4):327-346
Once one of the main protagonists of history of science, the historiography on quantum theory has recently gone through a process of reconfiguration of methods, research questions and epistemological framework. In this paper, I review the recent developments and propose some reflections on its future evolution. 相似文献
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Olivier Darrigol 《Centaurus; international magazine of the history of science and medicine》2010,52(3):206-257
Analogies between hearing and seeing already existed in ancient Greek theories of perception. The present paper follows the evolution of such analogies until the rise of 17th century optics, with due regard to the diversity of their origins and nature but with particular emphasis on their bearing on the physical concepts of light and sound. Whereas the old Greek analogies were only side effects of the unifying concepts of perception, the analogies of the 17th century played an important role in constructing optical theories by imitation of acoustic theories, or vice versa. This transition depended on several factors including the changing relations between optics, music, mathematics, and physics, the diversity of early modern concepts of sound, and the rise of a new physics based on experimentation and mechanical explanation. 相似文献
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Olivier Darrigol 《Centaurus; international magazine of the history of science and medicine》2010,52(2):117-155
Analogies between hearing and seeing already existed in ancient Greek theories of perception. The present paper follows the evolution of such analogies until the rise of 17th century optics, with due regard to the diversity of their origins and nature but with particular emphasis on their bearing on the physical concepts of light and sound. Whereas the old Greek analogies were only side effects of the unifying concepts of perception, the analogies of the 17th century played an important role in constructing optical theories by imitation of acoustic theories, or vice versa. This transition depended on several factors including the changing relations between optics, music, mathematics, and physics, the diversity of early modern concepts of sound, and the rise of a new physics based on experimentation and mechanical explanation. 相似文献
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D. Fragoulis A. Skembris C. Papaodysseus P. Rousopoulos Th. Panagopoulos M. Panagopoulos C. Triantafyllou A. Vlachopoulos C. Doumas 《Centaurus; international magazine of the history of science and medicine》2005,47(4):316-340
Abstract. The present paper offers strong evidence that there was a particularly advanced, for the era, sense and application of geometry in the prehistoric civilization of the island of Thera (Santorini), Greece, ca. 1650 BC. First, by applying an original method, it is demonstrated that specific shapes, depicted on so far unpublished wall paintings initially decorating the third floor of Xeste 3, correspond to advanced geometric configurations with remarkable accuracy. Thus, it is shown that there are configurations corresponding to linear spiral prototypes, others matching elliptical prototypes and sets of points lying on isogonal lines that are radii of regular polygons with 48, 32, and 24 angles. Subsequently, it is shown that the use of geometric archetypes for drawing played a prominent role in the Late Bronze Age Thera civilization. In fact, it is demonstrated that celebrated wall paintings have border lines that impressively match a limited number of linear (Archimedes') spirals, hyperbolas, and ellipses in a piecewise manner. This practically excludes the probability that these wall paintings were drawn by freehand, while, on the contrary, it strongly suggests that they were mainly drawn by means of geometric stencils. 相似文献
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随着测试技术的不断数字化、智能化和计算机化,振动传感器成为振动测试中的关键因素,一般可选择加速度来测量振动。本文以某一型号的测振仪为被测对象,选用比较法中频振动标准装置,在一定的环境条件下,对参考频率和参考加速度下的示值进行测量,并对振动传感器加速度的示值误差测量结果的不确定度进行分析和评定。 相似文献
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分析了目前最新的卫星导航定位系统——伽利略系统所采用的若干关键技术.从卫星轨道布置方式、信号与频率设计方法、伪卫星技术及信号服务等几个方面与GPS进行了对比研究.研究结果表明,Galileo系统具有定位精度高、兼容性好、功能全等优点,在新一代导航系统中具有重要地位. 相似文献
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S. Gratch 《International Journal of Thermophysics》1985,6(6):541-544
Historical developments regarding the realization of the importance of reliable thermophysical properties data in engineering applications are presented. The events leading to the establishment of the Symposium on Thermophysical Properties in 1959 and the accomplishments of the symposia series since then are discussed. Contributions of the National Bureau of Standards to the thermophysical properties field are described.Welcoming address presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献
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弹塑性结构在变值荷载作用下具有交变塑性和增量破坏两种可能的破坏型式,安定性分析就是要确定荷载变动的最大范围。确定安定荷载上限的机动型安定性定理之关键在于构造运动许可的塑性应变增量场,而在实际问题求解中这一数值实施过程往往是很困难的。为此,König放松了经典机动安定定理的某些条件,分别得到了在不发生交变塑性变形意义上的安定准则和在不发生累积塑性变形意义上的安定准则。本文以此为基础分别构造了相应的上限数值求解格式。并将其应用到土工安定性分析中,对海洋平台地基的安定性问题进行了数值分析。 相似文献
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目的厘清设计史叙述的多元性成因,其中包括学者们对现代设计史开端的不同理解与写法。方法以西方设计史著作对现代设计史开端的描写进行论述与分析,得出现代设计史开端每种写法的影响与成因。结论由于设计史的叙述方式受到了历史学、社会学、艺术学和技术等的影响,设计史学家们对不同方面的侧重,结合不同的著作目的进行设计史写作,形成了现代设计史开端的多种叙述,最后对中国现代设计史的构建进行了展望。 相似文献