scholarly journals Rapid and Non-Destructive Repair of Fused Silica with Cluster Damage by Magnetorheological Removing Method

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 274
Author(s):  
Mingjie Deng ◽  
Ci Song ◽  
Feng Shi ◽  
Yaofei Zhang ◽  
Ye Tian ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Large Scale ◽  
Fused Silica ◽  
Small Scale ◽  
Damage Repair ◽  
Laser Systems ◽  
Computer Controlled Optical Surfacing ◽  
Computer Controlled ◽  
Non Destructive ◽  
Small Scale Damage

The damage repair of fused silica based on the CO2 laser repair technique has been successfully applied in high-power laser systems in the controllable nuclear fusion field. However, this kind of repairing technique mainly focuses on large-scale laser damage with sizes larger than 200 μm, but ignores the influence of cluster small-scale damage with sizes smaller than 50 μm. In order to inhibit the growth of small-scale damage and further improve the effect of fused silica damage repair, this paper carried out a study on the repair of fused silica damage using the magnetorheological (MR) removing method. The feasibility of fused silica damage repairing was verified, and the evolution law of the number, morphology, and the surface roughness of small-scale damage were all analyzed. The results showed that the MR removing method was non-destructive compared to traditional repairing technologies. It not only effectively improved the whole damage repairing rate to more than 90%, but it also restored the optical properties and surface roughness of the damaged components in the repairing process. Based on the study of the MR removing repair law, a combined repairing process of 4 μm MR removal and 700 nm computer controlled optical surfacing (CCOS) removal is proposed. A typical fused silica element was experimentally repaired to verify the process parameters. The repairing rate of small-scale damage was up to 90.4%, and the surface roughness was restored to the level before repairing. The experimental results validate the effectiveness and feasibility of the combined repairing process. This work provides an effective method for the small-scale damage repairing of fused silica components.

on Large-scale dwell time algorithm for computer controlled optical surfacing

2011 ◽  
Vol 23 (12) ◽  
pp. 3207-3212
Author(s):  
罗丽丽 Luo Lili ◽  
何建国 He Jianguo ◽  
王亚军 Wang Yajun ◽  
张云飞 Zhang Yunfei ◽  
黄文 Huang Wen ◽  
...  
Keyword(s):  
Dwell Time ◽  
Large Scale ◽  
Time Algorithm ◽  
Computer Controlled Optical Surfacing ◽  
Computer Controlled

scholarly journals A MODIFIED TWO-SCALE MICROWAVE SCATTERING MODEL FOR A GAUSSIAN-DISTRIBUTED CONDUCTING ROUGH SURFACE

2018 ◽  
Vol XLII-3 ◽  
pp. 2141-2146
Author(s):  
F. Yu ◽  
H. Wang ◽  
Z. Y. Chen
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Large Scale ◽  
Incident Angle ◽  
Wavelet Packet ◽  
Small Scale ◽  
Backscattering Coefficient ◽  
Microwave Scattering ◽  
Scattering Model ◽  
Scale Roughness

A modified two-scale microwave scattering model (MTSM) was presented to describe the scattering coefficient of natural rough surface in this paper. In the model, the surface roughness was assumed to be Gaussian so that the surface height <i>z(x, y)</i> can be split into large-scale and small-scale components relative to the electromagnetic wavelength by the wavelet packet transform. Then, the Kirchhoff Model (KM) and Small Perturbation Method (SPM) were used to estimate the backscattering coefficient of the large-scale and small-scale roughness respectively. Moreover, the ‘tilting effect’ caused by the slope of large-scale roughness should be corrected when we calculated the backscattering contribution of the small-scale roughness. Backscattering coefficient of the MTSM was the sum of backscattering contribution of both scale roughness surface. The MTSM was tested and validated by the advanced integral equation model (AIEM) for dielectric randomly rough surface, the results indicated that, the MTSM accuracy were in good agreement with AIEM when incident angle was less than 30&amp;deg; (<i>&amp;theta;<sub>i</sub></i>&amp;thinsp;&amp;lt;30&amp;deg;) and the surface roughness was small (<i>ks</i>&amp;thinsp;=&amp;thinsp;0.354).

scholarly journals Modeling surface-roughness/solar-ablation feedback: application to small-scale surface channels and crevasses of the Greenland ice sheet

2011 ◽  
Vol 52 (59) ◽  
pp. 99-108 ◽  
Author(s):  
L. Maclagan Cathles ◽  
Dorian S. Abbot ◽  
Jeremy N. Bassis ◽  
Douglas R. MacAyeal
Keyword(s):  
Surface Roughness ◽  
Solar Radiation ◽  
Solar Energy ◽  
Large Scale ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ablation Rate ◽  
Small Scale ◽  
Universal Curve ◽  
Roughness Effects

AbstractSurface roughness enhances the net ablation rate associated with direct solar radiation relative to smooth surfaces, because roughness allows solar energy reflected from one part of the surface to be absorbed by another part. In this study we examine the feedback between solar-radiation-driven ablation and growth of surface roughness on the Greenland ice sheet, using a numerical model of radiative transfer. Our experiments extend previous work by examining: (1) the effects of diurnal and seasonal variation of solar zenith angle and azimuth relative to incipient roughness features, (2) the evolution of roughness geometry in response to radiatively driven ablation and (3) the relative solar energy collection efficiencies of various roughness geometries and geographic locations and orientations. A notable result of this examination is that the time evolution of the aspect ratio of surface features under solar-driven ablation collapses onto a roughly universal curve that depends only on latitude, not the detailed shape of the feature. The total enhancement of surface melt relative to a smooth surface over a full ablation season varies with this ratio, and this dependence suggests a way to parameterize roughness effects in large-scale models that cannot treat individual roughness features. Overall, our model results suggest that surface roughness at the latitudes spanned by the Greenland ice sheet tends to dissipate as the ablation season progresses.

scholarly journals Size effect characteristics of structural surfaces by improved projective covering method

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. J. Chen ◽  
J. P. Chang ◽  
X. G. Liu ◽  
Z. H. Li
Keyword(s):  
Surface Roughness ◽  
Fractal Dimension ◽  
Size Effect ◽  
Large Scale ◽  
Stochastic Approach ◽  
Systematic Investigation ◽  
Small Scale ◽  
Structural Surface ◽  
Sampling Windows ◽  
Covering Method

AbstractAccurate characteristic of structural surfaces roughness at the relevant scale is very important to understand mechanical properties of rock mass discontinuities. So, a systematic investigation has been carried out to understand the effect of scale on the structural surface roughness by fractal dimension method. Firstly, considering the shortcoming of the projective covering method (PCM), we improved this method based on stochastic approach. Secondly, to investigate the size effect of the structural surface roughness, we selected six sampling windows, respectively, from the central and four corners part of structural planes (2 m × 2 m). The sampling windows range from 62.5 mm × 62.5 mm to 2000 mm × 2000 mm. And then, we calculated fractal parameters of the different size surfaces using improved projective covering method (IPCM) at the same resolution. Thirdly, we discussed a new method of determining reasonable size of structural surfaces by the parameter $$\Delta D_{\max }^{SD}$$ Δ D max SD . This parameter is difference of the maximum fractal dimension of the same size structural surface in different regions. The results show that: (1) The size effect of structure surfaces is different with different morphological surface. Generally, as the size increases, the roughness of structure surfaces increases and then decreases. There is positive size effect in small scale and negative size effect in large scale. (2) For a given structural surface, when the same size surfaces are selected from different locations of the structural planes, and the size effect characteristics are also different. (3) As the size of structure surfaces increases, the parameter $$\Delta D_{\max }^{SD}$$ Δ D max SD gradually decreases and tends to almost constant. The result of this study is a useful supplement to the comprehensive understanding of the size effect of structural surfaces roughness.

Large Scale Leach Testing of Dwpf Canister Sections

1986 ◽  
Vol 84 ◽  
Author(s):  
Dennis F. Bickford ◽  
Daniel J. Pellarin
Keyword(s):  
Surface Roughness ◽  
Large Scale ◽  
Scale Up ◽  
Test Method ◽  
Waste Form ◽  
Test Facility ◽  
Small Scale ◽  
Glass Product ◽  
Leach Test ◽  
Sampling Statistics

AbstractA Large-Scale Leach Test Facility (LSLTF) has been constructed at the U.S. Department of Energy's Savannah River Laboratory (SRL) to perform static leach tests on 24-inch (610 mm)-diameter canister sections cut from simulated (nonradioactive) waste forms cast under reference conditions. The equipment and test procedures are designed to closely correspond to MCC-l leach test criteria.Less than a factor of 3 increase in leachability results from combined scale-up, glass-cracking, leached surface area estimation, and surface roughness effects. This factor is dominated by surface roughness of saw cut surfaces. The factor is negligible when compared to the 200,000/1 ratio of glass sample masses.The MCC-l, and other small-scale leach tests have been valuable in determining the relative merits of alternative waste form compositions. However, the actual waste glass to be stored in repositories is subject to fracture, devitrification, and container/glass interactions, which are difficult to simulate on a laboratory scale. Large-scale leach tests integrate these and other possible waste form characteristics that are not represented in typical small samples.The facility, equipment, test method and results of one year leach test- ing are discussed. These results substantiate the applicability of small scale test data which precede this work, and the use of small scale tests to simulate leaching of the Defense Waste Processing Facility's borosilicate glass product. Exceptionally good sampling statistics make the large scale data particularly well suited for verification of models of leachability rates.

scholarly journals Layer-by-Layer Repair of Small-Scale Damage of Fused Silica Based on the Magnetorheological Method

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1233
Author(s):  
Mingjie Deng ◽  
Ci Song ◽  
Feng Shi ◽  
Wanli Zhang ◽  
Ye Tian ◽  
...  
Keyword(s):  
Repair Process ◽  
Dark Field ◽  
Fused Silica ◽  
Small Scale ◽  
Layer By Layer ◽  
Mr Fluid ◽  
Repair Method ◽  
Area Distribution ◽  
Laser Induced Damage ◽  
Small Scale Damage

The magnetorheological (MR) repair method can effectively repair the small-scale damage of fused silica optics and further improve the laser-induced damage threshold of fused silica optics. However, at present, the rules of MR repair of small-scale damage of fused silica are not clear and cannot provide further guidance for the repair process. In this paper, the fused silica damage samples were repaired layer by layer by the MR method. The number and size changes of all the surface damage, the morphology, the fluorescence area distribution, and photothermal-absorption value of a single typical small-scale damage were measured. Through dark field scattering imaging, it is found that when the repair depth is 5 μm, the repair completion rate of damage with a transverse size less than 50 μm can reach 44%, and the repair efficiency decreases gradually with the repair process. Focusing on the whole repair process of a single typical, small-scale damage—due to the flexible shear removal mechanism of the MR method—the repair process of damage can be divided into three stages, which as a whole is a top-down, from outside to inside process. The first stage is the process of removing the surface of the damage layer by layer. In this process, MR fluid will introduce pollution to the inside of the damage. In the second stage, MR fluid begins to repair the inside of the damage. In the third stage, the MR ribbon completely covers the inside of the damage, and the repair effect is the most obvious. The measurement results of photothermal absorption and fluorescence area distribution of damage confirm this process. The photothermal absorption value and fluorescence area distribution of damage do not simply decrease with the repair process. On the contrary, they gradually increase first, and then decrease significantly when the damage depth reaches less than 1 μm. As the thickness of the MR ribbon is 1 μm, the reduction in the photothermal absorption value and fluorescence area of the damage is due to the process of repairing the inside of the damage. The results show that the absorbent impurities inside the small-scale damage of fused silica are the main factor affecting the performance. The key to repairing the small-scale damage of fused silica by the MR method is that the damaged interior must be repaired effectively. This paper outlines the MR repair method of small-scale damage of fused silica, which is of great significance to optimize the MR repair process.

Small-Scale Science to Large-Scale Profession

2000 ◽  
Vol 45 (4) ◽  
pp. 396-398
Author(s):  
Roger Smith
Keyword(s):  
Large Scale ◽  
Small Scale

Development of Physics Learning Module Based on Guided Inquiry with Light Wave Material in Class XI of Senior High School

2020 ◽  
Vol 1 (1) ◽  
pp. 1-10
Author(s):  
Evi Rahmawati ◽  
Irnin Agustina Dwi Astuti ◽  
N Nurhayati
Keyword(s):  
Large Scale ◽  
Learning Strategy ◽  
Student Response ◽  
Average Score ◽  
Small Scale ◽  
Design Development ◽  
Teacher Response ◽  
Student Responses ◽  
Analysis Design ◽  
Scientific Skills

IPA Integrated is a place for students to study themselves and the surrounding environment applied in daily life. Integrated IPA Learning provides a direct experience to students through the use and development of scientific skills and attitudes. The importance of integrated IPA requires to pack learning well, integrated IPA integration with the preparation of modules combined with learning strategy can maximize the learning process in school. In SMP 209 Jakarta, the value of the integrated IPA is obtained from 34 students there are 10 students completed and 24 students are not complete because they get the value below the KKM of 68. This research is a development study with the development model of ADDIE (Analysis, Design, Development, Implementation, and Evaluation). The use of KPS-based integrated IPA modules (Science Process sSkills) on the theme of rainbow phenomenon obtained by media expert validation results with an average score of 84.38%, average material expert 82.18%, average linguist 75.37%. So the average of all aspects obtained by 80.55% is worth using and tested to students. The results of the teacher response obtained 88.69% value with excellent criteria. Student responses on a small scale acquired an average score of 85.19% with highly agreed criteria and on the large-scale student response gained a yield of 86.44% with very agreed criteria. So the module can be concluded receiving a good response by the teacher and students.

Planetary gentrification and urban (re)development

2019 ◽  
Vol 61 (1) ◽  
pp. 5-13 ◽  
Author(s):  
Loretta Lees
Keyword(s):  
Low Income ◽  
Policy Making ◽  
Large Scale ◽  
Urban Redevelopment ◽  
Urban Transformation ◽  
Small Scale ◽  
Income Groups ◽  
Low Income Groups

Abstract Gentrification is no-longer, if it ever was, a small scale process of urban transformation. Gentrification globally is more often practised as large scale urban redevelopment. It is state-led or state-induced. The results are clear – the displacement and disenfranchisement of low income groups in favour of wealthier in-movers. So, why has gentrification come to dominate policy making worldwide and what can be done about it?

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