An inflatable circular membrane mirror for space telescopes

Abstract Radial tires for automobiles were subjected to high speed rolling under load on a testing wheel to determine the critical speeds at which standing waves started to form. Tires of different makes had significantly different critical speeds. The damping coefficient and mass per unit length of the tire wall were measured and a correlation between these properties and the observed critical speed of standing wave formation was sought through use of a circular membrane model. As expected from the model, desirably high critical speed calls for a high damping coefficient and a low mass per unit length of the tire wall. The damping coefficient is particularly important. Surprisingly, those tire walls that were reinforced with steel cord had higher damping coefficients than did those reinforced with polymeric cord. Although the individual steel filaments are elastic, the interfilament friction is higher in the steel cords than in the polymeric cords. A steel-reinforced tire wall also has a higher density per unit length. The damping coefficient is directly related to the mechanical loss in cyclic deformation and, hence, to the rolling resistance of a tire. The study shows that, in principle, it is more difficult to design a tire that is both fuel-efficient and free from standing waves when steel cord is used than when polymeric cords are used.

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Differential transformation method for circular membrane vibrations

SERIES III - MATEMATICS, INFORMATICS, PHYSICS ◽

10.31926/but.mif.2019.61.12.2.12 ◽

2020 ◽

Vol 61(12) (2) ◽

pp. 333-350

Author(s):

Jaipong Kasemsuwan ◽

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Sorin Vasile Sabau ◽

Uraiwan Somboon ◽

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...

Keyword(s):

Transformation Method ◽

Differential Transformation Method ◽

Circular Membrane ◽

Differential Transformation ◽

Membrane Vibrations

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Stray light characterization with ultrafast time-of-flight imaging

Scientific Reports ◽

10.1038/s41598-021-89324-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

L. Clermont ◽

W. Uhring ◽

M. Georges

Keyword(s):

Path Length ◽

Imaging System ◽

Time Of Flight ◽

Optical Path Length ◽

Optical Path ◽

Stray Light ◽

Laser Source ◽

Space Telescopes ◽

Characterization Methods ◽

Instance Space

AbstractUnderstanding stray light (SL) is a crucial aspect in the development of high-end optical instruments, for instance space telescopes. As it drives image quality, SL must be controlled by design and characterized experimentally. However, conventional SL characterization methods are limited as they do not provide information on its origins. The problem is complex due to the diversity of light interaction processes with surfaces, creating various SL contributors. Therefore, when SL level is higher than expected, it can be difficult to determine how to improve the system. We demonstrate a new approach, ultrafast time-of-flight SL characterization, where a pulsed laser source and a streak camera are used to record individually SL contributors which travel with a specific optical path length. Furthermore, the optical path length offers a means of identification to determine its origin. We demonstrate this method in an imaging system, measuring and identifying individual ghosts and scattering components. We then show how it can be used to reverse-engineer the instrument SL origins.

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Extinction-free Census of AGNs in the AKARI/IRC North Ecliptic Pole Field from 23-band infrared photometry from Space Telescopes

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2988 ◽

2020 ◽

Vol 499 (3) ◽

pp. 4068-4081 ◽

Cited By ~ 1

Author(s):

Ting-Wen Wang ◽

Tomotsugu Goto ◽

Seong Jin Kim ◽

Tetsuya Hashimoto ◽

Denis Burgarella ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Cosmic Time ◽

Spectral Energy ◽

Wide Field ◽

Space Telescopes ◽

Distribution Modelling ◽

Star Forming ◽

The North ◽

Band Filter ◽

Infrared Survey

ABSTRACT In order to understand the interaction between the central black hole and the whole galaxy or their co-evolution history along with cosmic time, a complete census of active galactic nucleus (AGN) is crucial. However, AGNs are often missed in optical, UV, and soft X-ray observations since they could be obscured by gas and dust. A mid-infrared (MIR) survey supported by multiwavelength data is one of the best ways to find obscured AGN activities because it suffers less from extinction. Previous large IR photometric surveys, e.g. Wide field Infrared Survey Explorer and Spitzer, have gaps between the MIR filters. Therefore, star-forming galaxy-AGN diagnostics in the MIR were limited. The AKARI satellite has a unique continuous nine-band filter coverage in the near to MIR wavelengths. In this work, we take advantage of the state-of-the-art spectral energy distribution modelling software, cigale, to find AGNs in MIR. We found 126 AGNs in the North Ecliptic Pole-Wide field with this method. We also investigate the energy released from the AGN as a fraction of the total IR luminosity of a galaxy. We found that the AGN contribution is larger at higher redshifts for a given IR luminosity. With the upcoming deep IR surveys, e.g. JWST, we expect to find more AGNs with our method.

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Partial aperture imaging system based on sparse point spread holograms and nonlinear cross-correlations

Scientific Reports ◽

10.1038/s41598-020-77912-3 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Angika Bulbul ◽

Joseph Rosen

Keyword(s):

Structural Changes ◽

Imaging System ◽

Current System ◽

Three Dimensional ◽

Phase Mask ◽

Coded Aperture ◽

Space Telescopes ◽

Reconstruction Process ◽

Cross Correlations ◽

Equivalent Systems

AbstractPartial aperture imaging system (PAIS) is a recently developed concept in which the traditional disc-shaped aperture is replaced by an aperture with a much smaller area and yet its imaging capabilities are comparable to the full aperture systems. Recently PAIS was demonstrated as an indirect incoherent digital three-dimensional imaging technique. Later it was successfully implemented in the study of the synthetic marginal aperture with revolving telescopes (SMART) to provide superresolution with subaperture area that was less than one percent of the area of the full synthetic disc-shaped aperture. In the study of SMART, the concept of PAIS was tested by placing eight coded phase reflectors along the boundary of the full synthetic aperture. In the current study, various improvements of PAIS are tested and its performance is compared with the other equivalent systems. Among the structural changes, we test ring-shaped eight coded phase subapertures with the same area as of the previous circular subapertures, distributed along the boundary of the full disc-shaped aperture. Another change in the current system is the use of coded phase mask with a point response of a sparse dot pattern. The third change is in the reconstruction process in which a nonlinear correlation with optimal parameters is implemented. With the improved image quality, the modified-PAIS can save weight and cost of imaging devices in general and of space telescopes in particular. Experimental results with reflective objects show that the concept of coded aperture extends the limits of classical imaging.

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