The current state of the art in large CCD mosaic cameras, and a new strategy for wide field, high resolution optical imaging

Author(s):  
Gerard A. Luppino ◽  
John Tonry ◽  
Nick Kaiser
2000 ◽  
Vol 112 (772) ◽  
pp. 768-800 ◽  
Author(s):  
N. Kaiser ◽  
J. L. Tonry ◽  
G. A. Luppino

2020 ◽  
Vol 34 (04) ◽  
pp. 4844-4851
Author(s):  
Fanghui Liu ◽  
Xiaolin Huang ◽  
Yudong Chen ◽  
Jie Yang ◽  
Johan Suykens

In this paper, we propose a fast surrogate leverage weighted sampling strategy to generate refined random Fourier features for kernel approximation. Compared to the current state-of-the-art method that uses the leverage weighted scheme (Li et al. 2019), our new strategy is simpler and more effective. It uses kernel alignment to guide the sampling process and it can avoid the matrix inversion operator when we compute the leverage function. Given n observations and s random features, our strategy can reduce the time complexity for sampling from O(ns2+s3) to O(ns2), while achieving comparable (or even slightly better) prediction performance when applied to kernel ridge regression (KRR). In addition, we provide theoretical guarantees on the generalization performance of our approach, and in particular characterize the number of random features required to achieve statistical guarantees in KRR. Experiments on several benchmark datasets demonstrate that our algorithm achieves comparable prediction performance and takes less time cost when compared to (Li et al. 2019).


2019 ◽  
Vol 11 (9) ◽  
pp. 1128 ◽  
Author(s):  
Maryam Rahnemoonfar ◽  
Dugan Dobbs ◽  
Masoud Yari ◽  
Michael J. Starek

Recent deep-learning counting techniques revolve around two distinct features of data—sparse data, which favors detection networks, or dense data where density map networks are used. Both techniques fail to address a third scenario, where dense objects are sparsely located. Raw aerial images represent sparse distributions of data in most situations. To address this issue, we propose a novel and exceedingly portable end-to-end model, DisCountNet, and an example dataset to test it on. DisCountNet is a two-stage network that uses theories from both detection and heat-map networks to provide a simple yet powerful design. The first stage, DiscNet, operates on the theory of coarse detection, but does so by converting a rich and high-resolution image into a sparse representation where only important information is encoded. Following this, CountNet operates on the dense regions of the sparse matrix to generate a density map, which provides fine locations and count predictions on densities of objects. Comparing the proposed network to current state-of-the-art networks, we find that we can maintain competitive performance while using a fraction of the computational complexity, resulting in a real-time solution.


2010 ◽  
Author(s):  
Mark C. Pierce ◽  
Richard A. Schwarz ◽  
Kelsey Rosbach ◽  
Darren Roblyer ◽  
Tim Muldoon ◽  
...  

NeuroImage ◽  
2012 ◽  
Vol 59 (3) ◽  
pp. 2569-2588 ◽  
Author(s):  
Thomas Deneux ◽  
Sylvain Takerkart ◽  
Amiram Grinvald ◽  
Guillaume S. Masson ◽  
Ivo Vanzetta

2010 ◽  
Vol 2 (S1) ◽  
Author(s):  
Mark Pierce ◽  
Kelsey Rosbach ◽  
Darren Roblyer ◽  
Tim Muldoon ◽  
Michelle Williams ◽  
...  

2019 ◽  
Vol 218 ◽  
pp. 72-100 ◽  
Author(s):  
Gino Groeneveld ◽  
Bob W. J. Pirok ◽  
Peter J. Schoenmakers

A practical example, the characterization of polysorbates by high-resolution comprehensive two-dimensional liquid chromatography in combination with high-resolution mass spectrometry, is described as a culmination of recent developments in 2D-LC and as an illustration of the current state of the art.


2019 ◽  
Vol 625 ◽  
pp. A40 ◽  
Author(s):  
C. Abia ◽  
S. Cristallo ◽  
K. Cunha ◽  
P. de Laverny ◽  
V. V. Smith

We present new fluorine abundance measurements for a sample of carbon-rich asymptotic giant branch (AGB) stars and two other metal-poor evolved stars of Ba/CH types. The abundances are derived from IR, K-band, high-resolution spectra obtained using GEMINI-S/Phoenix and TNG/Giano-b. Our sample includes an extragalactic AGB carbon star belonging to the Sagittarius dSph galaxy. The metallicity of our stars ranges from [Fe/H] = 0.0 down to − 1.4 dex. The new measurements, together with those previously derived in similar stars, show that normal (N-type) and SC-type AGB carbon stars of near solar metallicity present similar F enhancements, discarding previous hints that suggested that SC-type stars have larger enhancements. These mild F enhancements are compatible with current chemical-evolution models pointing out that AGB stars, although relevant, are not the main sources of this element in the solar neighbourhood. Larger [F/Fe] ratios are found for lower-metallicity stars. This is confirmed by theory. We highlight a tight relation between the [F/⟨s⟩] ratio and the average s-element enhancement [⟨s⟩/Fe] for stars with [Fe/H] > −0.5, which can be explained by the current state-of-the-art low-mass AGB models assuming an extended 13C pocket. For stars with [Fe/H] < −0.5, discrepancies between observations and model predictions still exist. We conclude that the mechanism of F production in AGB stars needs further scrutiny and that simultaneous F and s-element measurements in a larger number of metal-poor AGB stars are needed to better constrain the models.


2019 ◽  
Vol 491 (3) ◽  
pp. 3515-3522 ◽  
Author(s):  
B Wehbe ◽  
A Cabral ◽  
J H C Martins ◽  
P Figueira ◽  
N C Santos ◽  
...  

ABSTRACT Differential atmospheric dispersion is a wavelength-dependent effect introduced by the atmosphere. It is one of the instrumental errors that can affect the position of the target as perceived on the sky and its flux distribution. This effect will affect the results of astronomical observations if not corrected by an atmospheric dispersion corrector (ADC). In high-resolution spectrographs, in order to reach a radial velocity (RV) precision of 10 cm s−1, an ADC is expected to return residuals at only a few tens of milliarcseconds (mas). In fact, current state-of-the-art spectrograph conservatively require this level of residuals, although no work has been done to quantify the impact of atmospheric dispersion. In this work, we test the effect of atmospheric dispersion on astronomical observations in general, and in particular on RV precision degradation and flux losses. Our scientific objective was to quantify the amount of residuals needed to fulfil the requirements set on an ADC during the design phase. We found that up to a dispersion of 100 mas, the effect on the RV is negligible. However, on the flux losses, such a dispersion can create a loss of ∼2 per cent at 380 nm, a significant value when efficiency is critical. The requirements set on ADC residuals should take into consideration the atmospheric conditions where the ADC will function, and also all the aspects related with not only the RV precision requirements but also the guiding camera used, the tolerances on the flux loss, and the different melt data of the chosen glasses.


1979 ◽  
Vol 50 ◽  
pp. 34-1-34-14
Author(s):  
P Nisenson ◽  
R. V. Stachnik

AbstractThe success of speckle interferometry in recovering high resolution information from atmospheric turbulence degraded images has renewed interest in the restoration of images recorded through a turbulent medium. There are a number of different approaches to image restoration which have been proposed. The effectiveness of each of these techniques is strongly dependent on the brightness and the angular extent of the object being observed. This paper will attempt to summarize the areas of application of such techniques, the current state-of-the-art in this field, and the expected performance range of the various techniques.


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