An Efficient Local Block Sobolev Gradient and Laplacian Approach for Elimination of Atmospheric Turbulence

2021 ◽  
pp. 2150043
Author(s):  
Krina Patel ◽  
Dippal Israni ◽  
Dweepna Garg
Keyword(s):  
Performance Measures ◽  
Moving Objects ◽  
Atmospheric Conditions ◽  
Real Motion ◽  
Air Turbulence ◽  
Sobolev Gradient ◽  
Turbulence Effect ◽  
Atmospheric Distortion ◽  
Local Block ◽  
Observing Systems

A long range observing systems can be sturdily affected by scintillations. These scintillations are caused by changes in atmospheric conditions. In recent years, various turbulence mitigation approaches for turbulence mitigation have been exhibiting a promising nature. In this paper, we propose an effectual method to alleviate the effects of atmospheric distortion on observed images and video sequences. These sequences are mainly affected through floating air turbulence which can severely degrade the image quality. The existing algorithms primarily focus on the removal of turbulence and provides a solution only for static scenes, where there is no moving entity (real motion). As in the traditional SGL algorithm, the updated frame is iteratively used to correct the turbulence. This approach reduces the turbulence effect. However, it imposes some artifacts on the real motion that blurs the object. The proposed method is an alteration of the existing Sobolev Gradient and Laplacian (SGL) algorithm to eliminate turbulence. It eliminates the ghost artifact formed on moving object in the existing approach. The proposed method alleviates turbulence without harming the moving objects in the scene. The method is demonstrated on significantly distorted sequences provided by OTIS and compared with the SGL technique. The information conveyed in the scene becomes clearly visible through the method on exclusion of turbulence. The proposed approach is evaluated using standard performance measures such as MSE, PSNR and SSIM. The evaluation results depict that the proposed method outperforms the existing state-of-the-art approaches for all three standard performance measures.

scholarly journals Derivation of Clear-Air Turbulence Parameters from High-Resolution Radiosonde Data

2017 ◽  
Vol 34 (2) ◽  
pp. 277-293 ◽  
Author(s):  
E. Martini ◽  
A. Freni ◽  
F. Cuccoli ◽  
L. Facheris
Keyword(s):  
Refractive Index ◽  
High Resolution ◽  
Potential Temperature ◽  
Structure Constant ◽  
Thin Layers ◽  
Index Structure ◽  
Radiosonde Data ◽  
Atmospheric Conditions ◽  
Air Turbulence ◽  
The Impact

AbstractThe knowledge of atmospheric refractive index structure constant () profiles is fundamental to determine the intensity of turbulence, and hence the impact of the scintillation impairment on the signals propagating in the troposphere. However, their relation with atmospheric variables is not straightforward, and profiles based on statistical considerations are normally employed. This can be a shortcoming when performing simulations for which scintillation disturbances need to be consistent with the assumed atmospheric conditions. To overcome this limitation, this work describes a procedure to obtain an estimate of the refractive index structure constant profile of clear-air turbulence under given atmospheric conditions. The procedure is based on the application of the vertical gradient approach to high-resolution radiosonde data. Since turbulence is known to be confined to vertically thin layers, a preliminary identification of turbulent layers is required. This is accomplished by analyzing the profiles of the Richardson number. The value of the outer scale length is estimated using the Thorpe length calculated from the potential temperature profile. The procedure is applied to high-resolution radiosonde data that have been acquired from the Stratosphere–Troposphere Processes and their Role in Climate (SPARC) Data Center, and the obtained results are consistent with measured profiles previously published in the literature.

scholarly journals Pupillary response to real, illusory, and implied motion

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254105
Author(s):  
Serena Castellotti ◽  
Carlo Francisci ◽  
Maria Michela Del Viva
Keyword(s):  
Moving Objects ◽  
Dynamic Environment ◽  
Structural Features ◽  
Motion Processing ◽  
Illusory Motion ◽  
Critical Function ◽  
Real Motion ◽  
Cortical Areas ◽  
Implied Motion ◽  
Pupillary Responses

The perception of moving objects (real motion) is a critical function for interacting with a dynamic environment. Motion perception can be also induced by particular structural features of static images (illusory motion) or by photographic images of subjects in motion (implied motion, IM). Many cortical areas are involved in motion processing, particularly the medial temporal cortical area (MT), dedicated to the processing of real, illusory, and implied motion. Recently, there has been a growing interest in the influence of high-level visual processes on pupillary responses. However, just a few studies have measured the effect of motion processing on the pupil, and not always with consistent results. Here we systematically investigate the effects of real, illusory, and implied motion on the pupil diameter for the first time, by showing different types of stimuli (movies, illusions, and photos) with the same average luminance to the same observers. We find different pupillary responses depending on the nature of motion. Real motion elicits a larger pupillary dilation than IM, which in turn induces more dilation than control photos representing static subjects (No-IM). The pupil response is sensitive even to the strength of IM, as photos with enhanced IM (blur, motion streaks, speed lines) induce larger dilation than simple freezed IM (subjects captured in the instant they are moving). Also, the subject represented in the stimulus matters: human figures are interpreted as more dynamic and induce larger dilation than objects/animals. Interestingly, illusory motion induces much less dilation than all the other motion categories, despite being seen as moving. Overall, pupil responses depend on the individual perception of dynamicity, confirming that the pupil is modulated by the subjective interpretation of complex stimuli. We argue that the different pupillary responses to real, illusory, and implied motion reflect the top-down modulations of different cortical areas involved in their processing.

scholarly journals Detection of Small Moving Objects in Long Range Infrared Videos from a Change Detection Perspective

Photonics ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 394
Author(s):  
Chiman Kwan ◽  
Jude Larkin
Keyword(s):  
Change Detection ◽  
Long Range ◽  
Target Detection ◽  
Moving Objects ◽  
Small Target ◽  
Air Turbulence ◽  
Comparable Performance ◽  
Background Clutter ◽  
Local Intensity ◽  
Better Than

Detection of small moving objects in long range infrared (IR) videos is challenging due to background clutter, air turbulence, and small target size. In this paper, we present two unsupervised, modular, and flexible frameworks to detect small moving targets. The key idea was inspired by change detection (CD) algorithms where frame differences can help detect motions. Our frameworks consist of change detection, small target detection, and some post-processing algorithms such as image denoising and dilation. Extensive experiments using actual long range mid-wave infrared (MWIR) videos with target distances beyond 3500 m from the camera demonstrated that one approach, using Local Intensity Gradient (LIG) only once in the workflow, performed better than the other, which used LIG in two places, in a 3500 m video, but slightly worse in 4000 m and 5000 m videos. Moreover, we also investigated the use of synthetic bands for target detection and observed promising results for 4000 m and 5000 m videos. Finally, a comparative study with two conventional methods demonstrated that our proposed scheme has comparable performance.

scholarly journals Enhancing Small Moving Target Detection Performance in Low-Quality and Long-Range Infrared Videos Using Optical Flow Techniques

2020 ◽  
Vol 12 (24) ◽  
pp. 4024
Author(s):  
Chiman Kwan ◽  
Bence Budavari
Keyword(s):  
Optical Flow ◽  
Long Range ◽  
Target Detection ◽  
Moving Objects ◽  
Performance Enhancement ◽  
Detection Performance ◽  
Small Target ◽  
Air Turbulence ◽  
Analysis Center ◽  
Background Clutter

The detection of small moving objects in long-range infrared videos is challenging due to background clutter, air turbulence, and small target size. In this paper, we summarize the investigation of efficient ways to enhance the performance of small target detection in long-range and low-quality infrared videos containing moving objects. In particular, we focus on unsupervised, modular, flexible, and efficient methods for target detection performance enhancement using motion information extracted from optical flow methods. Three well-known optical flow methods were studied. It was found that optical flow methods need to be combined with contrast enhancement, connected component analysis, and target association in order to be effective for target detection. Extensive experiments using long-range mid-wave infrared (MWIR) videos from the Defense Systems Information Analysis Center (DSIAC) dataset clearly demonstrated the efficacy of our proposed approach.

Eolian sediment transport during dust storms: Slims River Valley, Yukon Territory

1978 ◽  
Vol 15 (7) ◽  
pp. 1069-1084 ◽  
Author(s):  
W. G. Nickling
Keyword(s):  
Sediment Transport ◽  
Shear Velocity ◽  
Yukon Territory ◽  
River Valley ◽  
Dust Storms ◽  
Atmospheric Conditions ◽  
Creep Flow ◽  
Air Turbulence ◽  
Surface Creep ◽  
Individual Grains

The amount of sediment transported by wind in surface creep, saltation, and suspension was measured during 15 dust storms in the Slims River Valley, Yukon Territory. Results of the investigation showed that the quantity of sediment transported in creep and saltation varied approximately with the cube of shear velocity, which supports theoretical and empirical models presented by other investigators. The suspended sediment flow rate, however, seemed to be more directly controlled by the degree of air turbulence than by shear velocity. The total sediment transport rate was also shown to be directly affected by the surface moisture content and the presence of soluble salts at or near the surface. Both these factors tend to stabilize the surface by holding individual grains in place. Although eolian sediment transport is common in the Slims River Valley, high saltation–creep flow rates and major dust storms appear to be associated with a distinct set of atmospheric conditions, which are best developed on warm clear days following periods of heavy or extended rainfall.

Selective Corrosion of brazed joint between BNi-2 filler metal and stainless steel 316

1996 ◽  
Vol 54 ◽  
pp. 218-219
Author(s):  
H. S. Kim ◽  
R. U. Lee
Keyword(s):  
Stainless Steel ◽  
Filler Metal ◽  
Surface Preparation ◽  
Optical Microscope ◽  
Heating Element ◽  
Incomplete Fusion ◽  
Atmospheric Conditions ◽  
Leak Test ◽  
High Temperature Side ◽  
Inconel 600

A heating element/electrical conduit assembly used in the Orbiter Maneuvering System failed a leak test during a routine refurbishment inspection. The conduit, approximately 100 mm in length and 12 mm in diameter, was fabricated from two tubes and braze-joined with a sleeve. The tube on the high temperature side (heating element side) and the sleeve were made of Inconel 600 and the other tube was stainless steel (SS) 316. For the filler metal, a Ni-Cr-B brazing alloy per AWS BNi-2, was used. A Helium leak test spotted the leak located at the joint between the sleeve and SS 316 tubing. This joint was dissected, mounted in a plastic mold, polished, and examined with an optical microscope. Debonding of the brazed surfaces was noticed, more pronounced toward the sleeve end which was exposed to uncontrolled atmospheric conditions intermittently. Initially, lack of wetting was suspected, presumably caused by inadequate surface preparation or incomplete fusion of the filler metal. However, this postulation was later discarded based upon the following observations: (1) The angle of wetting between the fillet and tube was small, an indication of adequate wetting, (2) the fillet did not exhibit a globular microstructure which would be an indication of insufficient melting of the filler metal, and (3) debonding was intermittent toward the midsection of the sleeve.

Recent Progress In High-Resolution Shadowing For Biological Transmission Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 510-511 ◽  
Author(s):  
Heinz Gross ◽  
Katarina Krusche ◽  
Peter Tittmann
Keyword(s):  
Heavy Metal ◽  
High Resolution ◽  
Freeze Drying ◽  
Atmospheric Conditions ◽  
Vacuum Equipment ◽  
Transmission Electron ◽  
Gas Atmosphere ◽  
Gas Molecules ◽  
Residual Gas ◽  
Backing Layer

Freeze-drying followed by heavy metal shadowing is a long established and straight forward approach to routinely study the structure of dehydrated macromolecules. Very thin specimens such as isolated membranes or single macromolecules are directly adsorbed on C-coated grids. After rapid freezing the grids are transferred into a suitable vacuum equipment for freeze-drying and heavy metal shadowing.To improve the resolution power of shadowing films we introduced shadowing at very low specimen temperature (−250°C). To routinely do that without the danger of contamination we developed in collaboration with Balzers an UHV (p≤10-9 mbar) machine (BAF500K, Fig.2). It should be mentioned here that at −250°C the specimen surface acts as effective cryopump for practically all impinging residual gas molecules from the residual gas atmosphere.Common high resolution shadowing films (Pt/C, Ta/W) have to be protected from alterations due to air contact by a relatively thick C-backing layer, when transferred via atmospheric conditions into the TEM. Such an additional C-coat contributes disturbingly to the contrast at high resolution.

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