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"Light Speed Measurement History."
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The Computer from Pascal to von Neumann
In 1942, Lt. Herman H. Goldstine, a former mathematics professor, was stationed at the Moore School of Electrical Engineering at the University of Pennsylvania. It was there that he assisted in the creation of the ENIAC, the first electronic digital computer. The ENIAC was operational in 1945, but plans for a new computer were already underway. The principal source of ideas for the new computer was John von Neumann, who became Goldstine's chief collaborator. Together they developed EDVAC, successor to ENIAC. After World War II, at the Institute for Advanced Study, they built what was to become the prototype of the present-day computer. Herman Goldstine writes as both historian and scientist in this first examination of the development of computing machinery, from the seventeenth century through the early 1950s. His personal involvement lends a special authenticity to his narrative, as he sprinkles anecdotes and stories liberally through his text.
eBook
On the speed of light in a vacuum in the presence of a magnetic field
The nature of light, the existence of magnetism, and the physical meaning of a vacuum are the problems so deeply related to philosophy that they have been discussed for thousands of years. In this paper, we concentrate ourselves on a question that concerns the three of them: does light speed in a vacuum change when a magnetic field is present? The experimental answer to this fundamental question has not yet been given even if it has been stated in modern terms for more than a century. To fully understand the importance of such a question in physics, we review the main facts and concepts from the historical point of view.
Journal Article
Generation Mechanism and Development Characteristics of Rail Corrugation of Cologne Egg Fastener Track in Metro
By establishing vehicle-track space coupled model and rail corrugation evaluation model, the generation mechanism of rail corrugation was analyzed in frequency domain and time domain, and development characteristics of corrugation were studied by using corrugation growth rate. Analysis based on frequency domain: through modal analysis and frequency response analysis on the finite element model of track structure, it is found that there are natural frequencies of track structure close to measured corrugation passing frequencies. It shows that the vibration modes corresponding to these frequencies can be more easily excited, which can cause the resonance phenomenon of track structure and form the rail corrugation at corresponding frequencies. Analysis based on time domain: the time-history curves of rail vertical vibration acceleration and rail vertical displacement are calculated by using vehicle-track coupled model and the frequency domain transformation of the time-history data is carried out. It is found that there are characteristic frequencies close to the measured corrugation passing frequencies, which indicates that the vibration of track structure at corresponding frequencies is an important reason to promote the formation of corrugation. The change of vehicle speed has no effect on characteristic frequencies of corrugation growth rate curves, which reflects the fixed frequency characteristic of corrugation. With the increase of train operation times, the corrugation corresponding to characteristic frequencies will gradually form and develop, and the increase of vehicle speed will increase the wavelength range and development speed of rail corrugation.
Journal Article
Photogenic Venus
During the late nineteenth century, scientists around the world disagreed as to the types of instruments and methods that should be used for determining the most important constant of celestial mechanics: the solar parallax. Venus’s 1874 transit across the sun was seen as the best opportunity for ending decades of debate. However, a mysterious “black drop” that appeared between Venus and the sun and individual differences in observations of the phenomenon brought traditional methods into disrepute. To combat these difficulties, the astronomer Jules Janssen devised a controversial new instrument, the “photographic revolver,” that photographed Venus at regular intervals. Another solution came from physicists, who rivaled the astronomers’ dominance in precision measurements by deducing the solar parallax from physical measurements of the speed of light. Yet other astronomers relied on drawings and well‐trained observers. The new space emerging from this debate was characterized by a decline in faith in (nonstandardized, nonreproducible) photography and in (pure) geometry and by the growing realization of the importance of alternative elements needed for establishing scientific truths: power and authority, skill and discipline, standardization, mechanical reproducibility, and theatricality. By examining the “cinematographic turn” in science and its alternatives, this essay brings to light unexplored multidisciplinary connections that contribute to the histories of psychology, philosophy, physics, and film studies.
Journal Article
MoneyWatch Report
Meanwhile, stocks closed mixed yesterday led by gains in tech and industrial companies. The Dow did decline twenty-six points. The NASDAQ closed up eighteen, hitting a new record. The S&P 500 gained three points.
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