Statistics of turbulence-induced laser irradiance fluctuations: impact of receiver aperture size

2021 ◽  
Author(s):  
Valeriy Kolosov ◽  
Victor A. Kulikov ◽  
Ernst Polnau
Keyword(s):  
Laser Irradiance ◽  
Aperture Size ◽  
Statistics Of Turbulence

Resolution Attainable With the Present Day STEM

1973 ◽  
Vol 31 ◽  
pp. 230-231 ◽  
Author(s):  
J. S. Wall ◽  
J. P. Langmore ◽  
H. Isaacson ◽  
A. V. Crewe
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Aperture Size ◽  
Magnetic Lens ◽  
Peak Intensity ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Half Angle

The scanning transmission electron microscope (STEM) constructed by the authors employs a field emission gun and a 1.15 mm focal length magnetic lens to produce a probe on the specimen. The aperture size is chosen to allow one wavelength of spherical aberration at the edge of the objective aperture. Under these conditions the profile of the focused spot is expected to be similar to an Airy intensity distribution with the first zero at the same point but with a peak intensity 80 per cent of that which would be obtained If the lens had no aberration. This condition is attained when the half angle that the incident beam subtends at the specimen, 𝛂 = (4𝛌/Cs)¼

Outcome and Safety of Different Cumulative Doses and Protocols of Intravenous Methylprednisolone in Moderate to Severe and Active Graves’ Ophthalmopathy

2019 ◽  
Vol 43 (1) ◽  
pp. 15
Author(s):  
Amelya Permata Sari ◽  
M Sidik ◽  
Syntia Nusanti
Keyword(s):  
Clinical Outcome ◽  
Literature Search ◽  
Oral Route ◽  
Eye Disease ◽  
Aperture Size ◽  
Journal Articles ◽  
Inclusion Criteria ◽  
Intravenous Methylprednisolone ◽  
Graves Ophthalmopathy ◽  
Graves Orbitopathy

Background: Graves’ ophthalmopathy (GO), also known as Graves’ orbitopathy or thyroid eye disease, has a potential sight-threatening complications. The activity and severity are important determinants in GO and are implications for treatment. Intravenous Glucocorticoid (GC) was associated with significantly greater efficacy and was better tolerated than oral route in the treatment of patients with moderate to severe and active GO. Intravenous GC has a variation cumulative dose and protocols; meanwhile the optimal treatment is still undefined. The aim of this literature review was to analyze the outcome and safety of different cumulative doses and protocols of intravenous methylprednisolone of patients with moderate to severe and active GO. Methods: The literature search was conducted from Google Scholar and Pubmed for journal articles that were published and related to the use of IVGC in moderate to severe and active GO Results: From the keywords mentioned, titles were screened for eligibility and seventeen articles were found. After being checked for the duplication, the articles were screened based on the abstracts and/or full texts. As many as eight articles met the inclusion criteria, others were excluded. Conclusion: Intravenous GC therapy in moderate to severe and active GO provide effect in reducing CAS, decreasing lid aperture size, decreasing proptosis size, and disappearing diplopia. A protocol uses a low cumulative doses (<5 g) of methylprednisolone weekly for 6 weeks and then halved dose weekly for another 6 weeks are preferred due to higher response in clinical outcome and safety profile.

Spatial spikes of laser irradiance propagating over large distances in a turbulent medium

1976 ◽  
Vol 15 (5) ◽  
pp. 1172 ◽  
Author(s):  
V. P. Aksenov ◽  
K. S. Gochelashvily ◽  
V. I. Shishov
Keyword(s):  
Turbulent Medium ◽  
Laser Irradiance

scholarly journals Radiation effects on shock propagation in Al target relevant to equation of state measurements

2007 ◽  
Vol 25 (1) ◽  
pp. 23-30 ◽  
Author(s):  
T. DESAI ◽  
R. DEZULIAN ◽  
D. BATANI
Keyword(s):  
Equation Of State ◽  
Reference Material ◽  
Radiation Effects ◽  
Laser Energy ◽  
Strong Shock ◽  
Shock Propagation ◽  
Laser Irradiance ◽  
X Rays ◽  
High Laser ◽  
High Intensity Laser

We present one-dimensional simulations performed using the multi group radiation hydro code MULTI with the goal of analyzing the target preheating effect under conditions similar to those of recent experiments aimed at studying the Equation of State (EOS) of various materials. In such experiments, aluminum is often used as reference material; therefore its behavior under strong shock compression and high-intensity laser irradiation (1013–1014 W/cm2) should be studied in detail. Our results reveal that at high laser irradiance, the laser energy available to induce shock pressure is reduced due to high X-rays generation. Simultaneously X-rays preheat the bulk of the reference material causing significant heating prior to shock propagation. Such effects induce deviations in shock propagation with respect to cold aluminum.

Effects of diagenesis (cement precipitation) during fracture opening on fracture aperture-size scaling in carbonate rocks

2012 ◽  
Vol 370 (1) ◽  
pp. 187-206 ◽  
Author(s):  
J. N. Hooker ◽  
L. A. Gomez ◽  
S. E. Laubach ◽  
J. F. W. Gale ◽  
R. Marrett
Keyword(s):  
Carbonate Rocks ◽  
Fracture Aperture ◽  
Aperture Size ◽  
Size Scaling ◽  
Fracture Opening

Structure and dynamics of homogeneous turbulence: models and simulations

1991 ◽  
Vol 434 (1890) ◽  
pp. 101-124 ◽  
Keyword(s):  
Turbulence Models ◽  
Background Field ◽  
Quantitative Model ◽  
Homogeneous Turbulence ◽  
Strongly Correlated ◽  
Structure And Dynamics ◽  
Localized Structures ◽  
Kolmogorov Theory ◽  
Statistics Of Turbulence ◽  
Random Background

This paper presents a review of recent results on homogeneous turbulence. We discuss results obtained by direct numerical simulation as well as phenomenological models for the interpretation and understanding of these flows. In particular, we show that homogeneous turbulence can be well described in terms of a weakly correlated, random background field that is generally consistent with the classical Kolmogorov theory of turbulence, and strongly correlated, highly localized structures, that are largely responsible for intermittency effects and deviations from Kolmogorov scaling. These results give a unified dynamical picture of turbulence that describes both the energetics and intermittency of homogeneous turbulence, and allows us to develop a quantitative model for the description of the statistics of turbulence at small scales.

Fiber laser processing of GFRP composites and multi-objective optimization of the process using response surface methodology

2018 ◽  
Vol 53 (11) ◽  
pp. 1459-1473 ◽  
Author(s):  
Shiva Dayal Rao B ◽  
Abhijeet Sethi ◽  
Alok Kumar Das
Keyword(s):  
Response Surface Methodology ◽  
Fiber Laser ◽  
Response Surface ◽  
Process Parameters ◽  
Heat Affected Zone ◽  
Cutting Speed ◽  
Kerf Width ◽  
Laser Irradiance ◽  
Input Process ◽  
Cut Surface

In the present investigation, a continuous wave fiber laser with maximum power of 400 W was used to cut a glass fiber reinforced plastic sheet of 4.56 mm thickness using Nitrogen as assisting gas. The influence processing parameters such as laser irradiance, gas pressure, and cutting speed on the cut surface quality were investigated by using response surface methodology. The different responses of laser cut surface such as upper kerf width, taper percentage along the cut depth, and heat-affected zone on the top surface were measured to analyze the influence of input process parameters on the responses. A statistical analysis on the obtained results was conducted and found that the optimum values of different input process parameters were laser irradiance: 8.28 × 105 watt/cm2, cutting speed: 600 mm/min and assisting gas pressure: 7.84 bar. The corresponding values of responses were upper kerf width: 177.4 µm, taper 0.73%, and heat-affected zone on top surface: 109.23 µm. The confirmation experiments were conducted with the obtained optimum parameter setting and observed that the predicted values and experimental values for upper kerf width, taper percentage and top surface heat-affected zone were within the error limits of 2.52%, 1.84%, and 0.45%, respectively. Furthermore, damages like loose fibers, interlayer fractures, evaporation of matrix material and fiber breakages were observed.

High-resolution stratigraphic characterization of natural fracture attributes in the Woodford Shale, Arbuckle Wilderness and US-77D Outcrops, Murray County, Oklahoma

2018 ◽  
Vol 6 (1) ◽  
pp. SC29-SC41 ◽  
Author(s):  
Sayantan Ghosh ◽  
John N. Hooker ◽  
Caleb P. Bontempi ◽  
Roger M. Slatt
Keyword(s):  
Natural Fracture ◽  
Fracture Aperture ◽  
Aperture Size ◽  
Fracture Density ◽  
Area Formula ◽  
Woodford Shale ◽  
Fracture Spacing ◽  
Spacing Ratio ◽  
Fracture Intensity ◽  
Bed Thickness

Natural fracture aperture-size, spacing, and stratigraphic variation in fracture density are factors determining the fluid-flow capacity of low-permeability formations. In this study, several facies were identified in a Woodford Shale complete section. The section was divided into four broad stratigraphic zones based on interbedding of similar facies. Average thicknesses and percentages of brittle and ductile beds in each stratigraphic foot were recorded. Also, five fracture sets were identified. These sets were split into two groups based on their trace exposures. Fracture linear intensity (number of fractures normalized to the scanline length [[Formula: see text]]) values were quantified for brittle and ductile beds. Individual fracture intensity-bed thickness linear equations were derived. These equations, along with the average bed thickness and percentage of brittle and ductile lithologies in each stratigraphic foot, were used to construct a fracture areal density (number of fracture traces normalized to the trace exposure area [[Formula: see text]]) profile. Finally, the fracture opening-displacement size variations, clustering tendencies, and fracture saturation were quantified. Fracture intensity-bed thickness equations predict approximately 1.5–3 times more fractures in the brittle beds compared with ductile beds at any given bed thickness. Parts of zone 2 and almost entire zone 3, located in the upper and middle Woodford, respectively, have high fracture densities and are situated within relatively organic-rich (high-GR) intervals. These intervals may be suitable horizontal well landing targets. All observed fracture cement exhibit a lack of crack-seal texture. Characteristic aperture-size distributions exist, with most apertures in the 0.05–1 mm (0.00016–0.0032 ft) range. In the chert beds, fracture cement is primarily bitumen or silica or both. Fractures in dolomite beds primarily have calcite cement. The average fracture spacing indices (i.e., bed thickness-fracture spacing ratio) in brittle and ductile beds were determined to be 2 and 1.2, respectively. Uniform fracture spacing was observed along all scanlines in the studied beds.

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