Optical turbulence can cause substantial distortions in imaging over long horizontal paths. For Lambertian objects, these distortions are only seen where there is a gradient in the object's radiance. It is possible to establish a relationship between the intensity variance of a turbulent image and the average image's gradient squared. We test the validity of a linear relationship between these quantities using turbulent imaging data. We find that it performs reasonably well for weak and intermediate optical turbulence regimes, but that some discrepancies remain to be explained.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1364/JOSAA.516238 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Improving MRI turbulence quantification by addressing the measurement errors caused by the derivatives of the turbulent velocity field - Sequence development and in-vitro validation.
Magn Reson Imaging
January 2025
Institute of Fluid Mechanics, University of Rostock, Rostock, Germany.
Purpose: To improve the current method for MRI turbulence quantification which is the intravoxel phase dispersion (IVPD) method. Turbulence is commonly characterized by the Reynolds stress tensor (RST) which describes the velocity covariance matrix. A major source for systematic errors in MRI is the sequence's sensitivity to the variance of the derivatives of velocity, such as the acceleration variance, which can lead to a substantial measurement bias.
View Article and Find Full Text PDFWavefront Correction for Extended Sources Imaging Based on a 97-Element MEMS Deformable Mirror.
Micromachines (Basel)
December 2024
Engineering School of Networks & Telecommunications, Jinling Institute of Technology, Nanjing 211169, China.
Adaptive optics (AO) systems are capable of correcting wavefront aberrations caused by transmission media or defects in optical systems. The deformable mirror (DM) plays a crucial role as a component of the adaptive optics system. In this study, our focus is on analyzing the ability of a 97-element MEMS (Micro-Electro-Mechanical System) DM to correct blurred images of extended sources affected by atmospheric turbulence.
View Article and Find Full Text PDFSimulation of Flow Around a Finite Rectangular Prism: Influence of Mesh, Model, and Subgrid Length Scale.
Entropy (Basel)
January 2025
Department of Mechanical and Aerospace Engineering, The University of Manchester, Manchester M1 3PL, UK.
This study investigates the flow field around a finite rectangular prism using both experimental and computational methods, with a particular focus on the influence of the turbulence approach adopted, the mesh resolution employed, and different subgrid length scales. Ten turbulence modelling and simulation approaches, including both 'scale-modelling' Reynolds-Averaged Navier-Stokes (RANS) models and 'scale-resolving' Delayed Detached Eddy Simulation (DDES), were tested across six different mesh resolutions. A case with sharp corners allows the location of the flow separation to be fixed, which facilitates a focus on the separated flow region and, in this instance, the three-dimensional interaction of three such regions.
View Article and Find Full Text PDFPlatelet Function Assay Using Dielectric Blood Coagulometry.
Anal Chem
January 2025
Department of Anesthesiology, Tokyo Medical and Dental University, Graduate School of Medical and Dental Sciences, 1-5-45 Yushima, Bunkyo-ku 113-8510, Tokyo, Japan.
The hemostatic function of platelets is complementary to blood coagulation. However, traditional platelet function tests have primarily focused on measuring platelet aggregation, reducing their clinical effectiveness for antiplatelet drug monitoring. To address this limitation, we propose a new test principle that evaluates platelet function and the effects of antiplatelet drugs through blood coagulation reactions.
View Article and Find Full Text PDFAn in silico analysis of heart rate impact on wall shear stress hemodynamic parameters in aortic coarctation.
Sci Rep
January 2025
School of Engineering, The University of Manchester, Manchester, UK.
This study examines how heart rate (HR) affects hemodynamics in a South African infant with Coarctation of the Aorta. Computed tomography angiography segments aortic coarctation anatomy; Doppler echocardiography derives inlet flow waveforms. Simulations occur at 100, 120, and 160 beats per minute, representing reduced, resting, and elevated HR levels.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!