Saturation of anisoplanatic error in Kolmogorov and non-Kolmogorov turbulence.

This work explores the conditions resulting in the saturation of angular anisoplanatic error. When turbulence is modeled with a von Kármán outer scale or when the piston and aperture tilt are compensated the anisoplanatic error can saturate to less than one squared radian. In Kolmogorov turbulence anisoplanatic error is limited to values smaller than one when the ratio of the Fried parameter to the outer scale is 0.349. To understand the effect of compensation on saturation both a first-order asymptotic approach and numerical integration are considered for both plane and spherical wave sources and in non-Kolmogorov turbulence. Asymptotic expressions are found to agree with the numerical results as long as the ratio of the outer scale to aperture size is less than five. For a plane wave propagating in Kolmogorov turbulence, the compensated anisoplanatic error is found to saturate when D/r 0=3.9, and the outer scale is equal to the aperture size. When a spherical wave source is considered D/r 0 increases to 5.8; as expected these values are related by a factor of 1.8. This work also formulates the anisoplanatic error in terms of an integrated strength parameter and the mean turbulence height allowing extension to arbitrary path geometries and power law exponents. Using this approach I find smaller power law exponents increase the mean turbulence height, thereby decreasing the isoplanatic angle; the opposite applies as the power law exponent is increased relative to Kolmogorov turbulence.

Propagation through and characterization of atmospheric and oceanic phenomena: introduction to the joint feature issue in Applied Optics and Journal of the Optical Society of America A.

This joint feature issue in Applied Optics and JOSA A collects articles focused on the topic of propagation through and characterization of atmospheric oceanic phenomena. The papers cover a broad range of topics, many of which were addressed at the 2023 Propagation Through and Characterization of Atmospheric Oceanic Phenomena (pcAOP) Topical Meeting at the Optica Imaging Congress in Boston, Massachusetts, 14-17 August 2023. These papers are supplemented by numerous examples of the current state of research in the field. This is the first pcAOP feature issue, with the intention to produce an issue on this topic every two years.

Propagation through and characterization of atmospheric and oceanic phenomena: introduction to the joint feature issue in Applied Optics and Journal of the Optical Society of America A.

This joint feature issue in Applied Optics and JOSA A collects articles focused on the topic of propagation through and characterization of atmospheric oceanic phenomena. The papers cover a broad range of topics, many of which were addressed at the 2023 Propagation Through and Characterization of Atmospheric Oceanic Phenomena (pcAOP) Topical Meeting at the Optica Imaging Congress in Boston, Massachusetts, 14-17 August 2023. These papers are supplemented by numerous examples of the current state of research in the field. This is the first pcAOP feature issue, with the intention to produce an issue on this topic every two years.

Cable deployment system for unmanned ground vehicle (UGV) mobile microgrids.

An ad hoc autonomous mobile microgrid system requires electrical connections to be formed between physically separated resources. This work proposes the use of unmanned ground vehicles (UGVs) as the means to deploy the electrical cable that creates these connections. This operation requires careful control of the cabling at variable speeds to avoid entanglement with the deploying UGV or obstacles in complex outdoor environments. Searching for a product that could supply the needed control and flexibility revealed a lack of compact and low-cost options. Existing options are very heavy ( > 100  lbs) and do not supply precision in their deployment. There is no commercial off-the-shelf option available for small-scale cable deployment operations with size and weight constraints. To fulfill the application requirements and to combat this deficiency, a custom design and build of an "Adjustable Cable Management Mechanism" (ACMM) was required. This ACMM provides a low cost, compact platform for powered and controlled deployment and retraction of different-sized cable under moderate loads, utilizing Commercial Off-The-Shelf components (COTS). Employing this design has enabled a variety of tasks that require distribution of electrical or data cables to be accomplished for small-scale projects. The goal of this paper is to give detailed design specifications of the ACMM and instructions on how to recreate it and calibrate it to be useful for tethering robots in various applications such as steep terrain, internet connection through tight spaces, or electrical connection between nodes for complex microgrids.

Angular anisoplanatism in non-Kolmogorov turbulence over horizontal paths.

We use Mellin-transform techniques to derive generalized expressions for the piston-removed and piston-and-tilt-removed anisoplanatic error in non-Kolmogorov turbulence with a finite outer scale. We use these expressions to investigate the behavior of the anisoplanatic error when imaging over long horizontal paths where the angular extent of the scene is often many times the isoplanatic angle. By evaluating these expressions, we first find that in many cases, the anisoplanatic error saturates to a value less than 1rad2. Next, as power law increases, the contributions due to piston and tilt dominate the anisoplanatic error expression. Last, the size of the outer scale contributes primarily to the piston and tilt terms. Together, these behaviors imply that when piston and tilt are removed, anisoplanatism is reduced by as much as 60%.

Differential piston phase variance in non-Kolmogorov atmospheres.

We derive a generalized expression for the differential piston phase variance in non-Kolmogorov turbulence. Specifically, our result applies in the case where index of refraction is described by a power-law medium with an exponent between 0 and 1. Kolmogorov assumptions of homogeneity and isotropy are maintained. After some development, our expression is derived using the Mellin-transform techniques and may be generalized to other forms for the three-dimensional index of refraction turbulence power spectrum. This analytical result has two regions of convergence. The separation between these regions is defined by a characteristic time given as the ratio of the mean wind speed and aperture size. By evaluating this expression, we find the differential piston phase variance exhibits a power-law behavior roughly proportional to that of the medium. In addition, we find that piston phase variance decreases with increase in aperture size. We also find that the differential piston phase variance is independent of aperture size as the power law approaches unity.

Cost of diabetic eye, renal and foot complications: a methodological review.

INTRODUCTION: Diabetic retinopathy (DR), diabetic kidney disease (DKD) and diabetic foot ulcer (DFU) represent a public health and economic concern that may be assessed with cost-of-illness (COI) studies. OBJECTIVES: (1) To review COI studies published between 2000 and 2015, about DR, DKD and DFU; (2) to analyse methods used. METHODS: Disease definition, epidemiological approach, perspective, type of costs, activity data sources, cost valuation, sensitivity analysis, cost discounting and presentation of costs may be described in COI studies. Each reviewed study was assessed with a methodological grid including these nine items. RESULTS: The five following items have been detailed in the reviewed studies: epidemiological approach (59 % of studies described it), perspective (75 %), type of costs (98 %), activity data sources (91 %) and cost valuation (59 %). The disease definition and the presentation of results were detailed in fewer studies (respectively 50 and 46 %). In contrast, sensitivity analysis was only performed in 14 % of studies and cost discounting in 7 %. Considering the studies showing an average cost per patient and per year with a societal perspective, DR cost estimates were US $2297 (range 5-67,486), DKD cost ranged from US $1095 to US $16,384, and DFU cost was US $10,604 (range 1444-85,718). DISCUSSION: This review reinforces the need to adequately describe the method to facilitate literature comparisons and projections. It also recalls that COI studies represent complementary tools to cost-effectiveness studies to help decision makers in the allocation of economic resources for the management of DR, DKD and DFU.

Massive parallel processing of image reconstruction from bispectrum through turbulence.

This paper presents a massively parallel method for the phase reconstruction of an object from its bispectrum phase. Our aim is to recover an enhanced version of a turbulence-corrupted image by developing an efficient and fast parallel image-restoration algorithm. The proposed massively parallel bispectrum algorithm relies on multiple block parallelization. Further, in each block, we employ wavefront processing through strength reduction to parallelize an iterative algorithm. Results are presented and compared with the existing iterative bispectrum method. We report a speed-up factor of 85.94 with respect to sequential implementation of the same algorithm for an image size of 1024×1024.

Anisotropic non-Kolmogorov turbulence phase screens with variable orientation.

We describe a modification to fast Fourier transform (FFT)-based, subharmonic, phase screen generation techniques that accounts for non-Kolmogorov and anisotropic turbulence. Our model also allows for the angle of anisotropy to vary in the plane orthogonal to the direction of propagation. In addition, turbulence strength in our model is specified via a characteristic length equivalent to the Fried parameter in isotropic, Kolmogorov turbulence. Incorporating this feature enables comparison between propagating scenarios with differing anisotropies and power-law exponents to the standard Kolmogorov, isotropic model. We show that the accuracy of this technique is comparable to other FFT-based subharmonic methods up to three-dimensional spectral power-law exponents around 3.9.