Sean F. Johnston

WAMDII: wide-angle Michelson Doppler imaging interferometer for Spacelab

A wide-angle Michelson Doppler imaging interferometer (WAMDII) is described that is intended to measure upper atmospheric winds and temperatures from naturally occurring visible region emissions, using Spacelab as a platform. It is an achromatic field-widened instrument, with good thermal stability, that employs four quarterwave phase-stepped images to generate full images of velocity, temperature, and emission rate. For an apparent emission rate of 5 kR and binning into 85 × 105 pixels, the required exposure time is 1 sec. The concept and underlying principles are described, along with some fabrication details for the prototype instrument. The results of laboratory tests and field measurements using auroral emissions are described and discussed.

Ionic conductivity and viscosity correlations in liquid electrolytes for incorporation into PVDF gel electrolytes

The correlation between ionic conductivity and viscosity in liquid electrolytes formed by the dissolution of lithium triflate in N,N-dimethyl formamide and tetraethylene glycol dimethyl ether has been investigated. These liquid electrolytes may be incorporated in polymer gel electrolytes based on poly(vinylidene fluoride). The use of the Walden product to investigate ionic interactions is discussed.

Gas monitors employing infrared LEDs

Infrared light emitting diodes (LEDS) can replace the thermal source, bandpass filters and rotating chopper wheel of conventional infrared gas monitors. Their long-term stability, high modulation rate and compact size also provide design advantages. The performance of a family of mid-infrared monitors for measuring carbon dioxide and hydrocarbons is described. Various schemes are outlined for compensating temperature drift, output/gain fluctuations, changes in cell transparency and mismatch between components.

Optimization of a field-widened Michelson interferometer

This paper considers the optical design of a wide-angle fixed-path Michelson interferometer consisting of two arm glasses and an air gap. It is shown that this configuration can be optimized to give (a) extra large fringes (over 50 degrees in diameter) over a range of wavelength, (b) a path difference nearly independent of wavelength, or (c) a path difference specified differently at two different wavelengths for observing a pair of doublets. Specific examples refer to the airglow wavelengths of 557.7, 630.0, 732.0 nm and others, and to a path difference of 4.5 cm. The properties of different glass combinations are discussed.

A History of Light and Colour Measurement

A history of light and colour measurement , A history of light and colour measurement , کتابخانه دیجیتال جندی شاپور اهواز

In Search of Space: Fourier Spectroscopy 1950–1970

In the large grey area between science and technology, specialisms emerge with associated specialists. But some specialisms remain ‘peripheral sciences,’ never attaining the status of ‘disciplines’ ensconced in universities, and their specialists do not become recognized ‘professionals.’1 A major social component of such side-lined sciences — one important grouping of technoscientific workers — is the ‘research-technology community’ (e.g. Shinn 1997).2 An important question concerning research-technology is to explain how the grouping survives without specialized disciplinary and professional affiliations. The case to be discussed below illustrates the dynamics of one such community.

Patently Contestable: Electrical Technologies and Inventor Identities on Trial in Britain. by Stathis Arapostathis and Graeme Gooday (review)

Johnston reviews Patently Costestable: Electrical Technologies and Inventor Identities on Trial in Britain by Stathis Arapostathis and Graeme Gooday

Telling tales: George Stroke and the historiography of holography

The history of holography, the technology of three‐dimensional imaging that grew rapidly during the 1960s, has been written primarily by its historical actors and, like many new inventions, its concepts and activities became surrounded by myths and myth‐making. The first historical account was disseminated by the central character of this paper, George W. Stroke, while a professor of Electrical Engineering at the University of Michigan. His claims embroiled several workers active in the field of holography and information processing during the 1960s, but transcended personality conflicts: they influenced the early historiography of holography and the awarding of the Nobel Prize for Physics to Dennis Gabor in 1971. An extended discussion of these episodes, based on archival research, publications analysis and interviews with participants, reveals the importance and extraordinary allure of intellectual priority for practicing scientists, and how its history and explanations are woven from multiple accounts and contemporary interpretations.

Reconstructing the history of holography

This paper discusses large-scale but gradual changes in the subject of holography that have only recently become readily observable. Presenting an analysis of publications in holography over the past half century, the paper illustrates and discusses the evolving shape of the subject. Over 40,000 international information sources have been recorded, including some 20,000 papers, 10,000 books, nearly as many of these and at least 500 exhibitions. This statistical and sociological approach is combined with the identification of specific factors - notably the role of individuals, conferences, proof-of-concept demonstrations and exhibitions - to suggest that the development of holography has been unusually contingent on a variety of intellectual and social influences. The paper situates these observations about holography and holographers in the context of a wider discussion about the styles, purposes and difficulties of historical writing on technological subjects. It further suggests that this ongoing process of both recording and reconstructing technological history can be aided by identification of sources sometimes overlooked or undervalued by practitioners: unpublished archival materials such as private file collections; business records; or undervalued by practitioners: unpublished archival material such as private file collections; business records; accounts of unsuccessful activities; and, by no means least, anecdotal accounts inter-linked between participants.

Making light work: practices and practitioners of photometry

Light measurement, a hybrid subject straddling science and technology, was shaped by, and in turn shaped, its cultural environment and disparate communities of investigators. This orphan subject, while not the success story commonly singled out for historical analysis, had developmental features that may be common to other twentieth-century subjects.