Miles Away Dir. Nick Cope: Video/DVD 6’19”, 2009, soundtrack: Phil Thornton.

Short Documentary exploring the Tibetan Shoton Festival, Drepung Monastery, Lhasa

Real-time terahertz imaging with a single-pixel detector

Terahertz (THz) radiation is poised to have an essential role in many imaging applications, from industrial inspections to medical diagnosis. However, commercialization is prevented by impractical and expensive THz instrumentation. Single-pixel cameras have emerged as alternatives to multi-pixel cameras due to reduced costs and superior durability. Here, by optimizing the modulation geometry and post-processing algorithms, we demonstrate the acquisition of a THz-video (32 × 32 pixels at 6 frames-per-second), shown in real-time, using a single-pixel fiber-coupled photoconductive THz detector. A laser diode with a digital micromirror device shining visible light onto silicon acts as the spatial THz modulator. We mathematically account for the temporal response of the system, reduce noise with a lock-in free carrier-wave modulation and realize quick, noise-robust image undersampling. Since our modifications do not impose intricate manufacturing, require long post-processing, nor sacrifice the time-resolving capabilities of THz-spectrometers, their greatest asset, this work has the potential to serve as a foundation for all future single-pixel THz imaging systems

Sampling Moments and Reconstructing Signals of Finite Rate of Innovation: Shannon Meets Strang-Fix

Consider the problem of sampling signals which are not bandlimited, but still have a finite number of degrees of freedom per unit of time, such as, for example, nonuniform splines or piecewise polynomials, and call the number of degrees of freedom per unit of time the rate of innovation. Classical sampling theory does not enable a perfect reconstruction of such signals since they are not bandlimited. Recently, it was shown that, by using an adequate sampling kernel and a sampling rate greater or equal to the rate of innovation, it is possible to reconstruct such signals uniquely . These sampling schemes, however, use kernels with infinite support, and this leads to complex and potentially unstable reconstruction algorithms. In this paper, we show that many signals with a finite rate of innovation can be sampled and perfectly reconstructed using physically realizable kernels of compact support and a local reconstruction algorithm. The class of kernels that we can use is very rich and includes functions satisfying Strang–Fix conditions, exponential splines and functions with rational Fourier transform. This last class of kernels is quite general and includes, for instance, any linear electric circuit. We, thus, show with an example how to estimate a signal of finite rate of innovation at the output of an RC circuit. The case of noisy measurements is also analyzed, and we present a novel algorithm that reduces the effect of noise by oversampling

Generalized Sampling: A Variational Approach. Part I: Theory

We consider the problem of reconstructing a multidimensional vector function fin: Rm→Rn from a finite set of linear measures. These can be irregularly sampled responses of several linear filters. Traditional approaches reconstruct in an a priori given space, e.g., the space of bandlimited functions. Instead, we have chosen to specify a reconstruction that is optimal in the sense of a quadratic plausibility criterion J. First, we present the solution of the generalized interpolation problem. Later, we also consider the approximation problem, and we show that both lead to the same class of solutions. Imposing generally desirable properties on the reconstruction largely limits the choice of the criterion J. Linearity leads to a quadratic criterion based on bilinear forms. Specifically, we show that the requirements of translation, rotation, and scale-invariance restrict the form of the criterion to essentially a one-parameter family. We show that the solution can be obtained as a linear combination of generating functions. We provide analytical techniques to find these functions and the solution itself. Practical implementation issues and examples of applications are treated in a companion paper

Using iterated rational filter banks within the ARSIS method for producing 10 m Landsat multispectral images

International audienceThe ARSIS concept makes use of wavelet transforms and multiresolution analysis to improve the spatial resolutions of images from a set made of a low resolution image in the same spectral band and a high resolution image in an other spectral band. The paper deals with the use of rational filter banks in ARSIS. Indeed, first this concept was operationally applied with dyadic wavelet transforms that limit the merging of images with a ratio between spatial resolutions equals to a power of two. Provided some conditions, rational filter banks can be seen as a good approximation of rational wavelet transforms and, thus, enable a more general merging of images with ARSIS. The advantages of those rational filter banks compared to other methods are discussed and illustrated by an example of fusion of a 10 m SPOT Panchromatic image and a 30 m Landsat Thematic Mapper (TM) multispectral image into a synthetic 10 m multispectral image called hereafter TM-HR

Sparse sampling of signal innovations

Sparse sampling of continuous-time sparse signals is addressed. In particular, it is shown that sampling at the rate of innovation is possible, in some sense applying Occam's razor to the sampling of sparse signals. The noisy case is analyzed and solved, proposing methods reaching the optimal performance given by the Cramer-Rao bounds. Finally, a number of applications have been discussed where sparsity can be taken advantage of. The comprehensive coverage given in this article should lead to further research in sparse sampling, as well as new applications. One main application to use the theory presented in this article is ultra-wide band (UWB) communications

Using iterated rational filter banks within the ARSIS concept for producing 10 m Landsat multispectral images

International audienceThe ARSIS concept is meant to increase the spatial resolution of an image without modification of its spectral contents by merging structures extracted from a higher resolution image of the same scene but in a different spectral band. It makes use of wavelet transforms and multiresolution analysis. It is currently applied in an operational way with dyadic wavelet transforms that limit the merging of images whose ratio of their resolution is a power of two. Nevertheless, provided some conditions, rational discrete wavelet transforms can be numerically approximated by rational filter banks which would enable a more general merging: indeed, in theory, the ratio of the resolution of the images to merge is a power of a certain family of rational numbers. The aim of this article is to examine whether the use of those approximations of rational wavelet transforms are efficient within the ARSIS concept. This work relies on a particular case: the merging of a 10 m SPOT Panchromatic image and a 30 m Landsat Thematic Mapper multispectral image to synthesize 10 m multispectral image called TM-HR

The unusually large population of Blazhko variables in the globular cluster NGC 5024 (M53)

We report the discovery of amplitude and phase modulations typical of the Blazhko effect in 22 RRc and 9 RRab type RR Lyrae stars in NGC 5024 (M53). This brings the confirmed Blazhko variables in this cluster to 23 RRc and 11 RRab, that represent 66% and 37% of the total population of RRc and RRab stars in the cluster respectively, making NGC 5024 the globular cluster with the largest presently known population of Blazhko RRc stars. We place a lower limit on the overall incidence rate of the Blazhko effect among the RR Lyrae population in this cluster of 52%. New data have allowed us to refine the pulsation periods. The limitations imposed by the time span and sampling of our data prevents reliable estimations of the modulation periods. The amplitudes of the modulations range between 0.02 and 0.39 mag. The RRab and RRc are neatly separated in the CMD, and the RRc Blazhko variables are on averge redder than their stable couterparts; these two facts may support the hypothesis that the HB evolution in this cluster is towards the red and that the Blazhko modulations in the RRc stars are connected with the pulsation mode switch.Comment: ACCEPTED IN MNRAS 14 pages, 9 figures and 6 table

Women in Traditional Judaism: Rights, Roles, and Obligations

Author of On Women and Judaism: A View from Tradition, and How to Run a Traditional Jewish Household.https://digitalcommons.fairfield.edu/bennettcenter-posters/1240/thumbnail.jp