Journal articles: 'Angular homogeneity'

1

Avila, F., C. P. Novaes, A. Bernui, E. de Carvalho, and J. P. Nogueira-Cavalcante. "The angular scale of homogeneity in the local Universe with the SDSS blue galaxies." Monthly Notices of the Royal Astronomical Society 488, no. 1 (2019): 1481–87. http://dx.doi.org/10.1093/mnras/stz1765.

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ABSTRACT We probe the angular scale of homogeneity in the local Universe using blue galaxies from the SDSS survey as a cosmological tracer. Through the scaled counts in spherical caps, $\mathcal {N}(\lt \theta)$, and the fractal correlation dimension, $\mathcal {D}_{2}(\theta)$, we find an angular scale of transition to homogeneity for this sample of θH = 22.19° ± 1.02°. A comparison of this measurement with another obtained using a different cosmic tracer at a similar redshift range (z < 0.06), namely, the H i extragalactic sources from the ALFALFA catalogue, confirms that both results are in excellent agreement (taking into account the corresponding bias correction). We also perform tests to assess the robustness of our results. For instance, we test if the size of the surveyed area is large enough to identify the transition scale we search for, and also we investigate a reduced sample of blue galaxies, obtaining in both cases a similar angular scale for the transition to homogeneity. Our results, besides confirming the existence of an angular scale of transition to homogeneity in different cosmic tracers present in the local Universe, show that the observed angular scale θH agrees well with what is expected in the ΛCDM scenario. Although we cannot prove spatial homogeneity within the approach followed, our results provide one more evidence of it, strengthening the validity of the Cosmological Principle.

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Cherukuri, B., and R. Srinivasan. "Optimization of the Equal Channel Angular Pressing (ECAP) Process for Strain Homogeneity." Materials Science Forum 539-543 (March 2007): 3655–60. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.3655.

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Two-Dimensional finite element analysis was carried out to optimize the equal channel angular pressing process (ECAP) for strain homogeneity under frictionless and frictional conditions. The effect of outside corner angle (Ψ), inner radius (r) and shear friction (m) on the strain homogeneity was investigated. The strain homogeneity can be increased by correcting the outside corner to eliminate the corner gap between the sample and the die at the expense of average strain. Small inside radius and outside corner radius would provide large deformations without much loss in the strain homogeneity under frictionless conditions. The work piece deformation is by bending if the inner radius exceeds a critical value. No improvement in strain homogeneity was observed under frictional conditions.

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Pantic, Igor, Senka Pantic, and Gordana Basta-Jovanovic. "Gray Level Co-Occurrence Matrix Texture Analysis of Germinal Center Light Zone Lymphocyte Nuclei: Physiology Viewpoint with Focus on Apoptosis." Microscopy and Microanalysis 18, no. 3 (2012): 470–75. http://dx.doi.org/10.1017/s1431927612000098.

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AbstractIn our study we investigated the relationship between conventional morphometric indicators of nuclear size and shape (area and circularity) and the parameters of gray level co-occurrence matrix texture analysis (entropy, homogeneity, and angular second moment) in cells committed to apoptosis. A total of 432 lymphocyte nuclei images from the spleen germinal center light zones (cells in early stages of apoptosis) were obtained from eight healthy male guinea pigs previously immunized with sheep red blood cells (antigen). For each nucleus, area, circularity, entropy, homogeneity, and angular second moment were determined. All measured parameters of gray level co-occurrence matrix (GLCM) were significantly correlated with morphometric indicators of nuclear size and shape. The strongest correlation was observed between GLCM homogeneity and nuclear area (p < 0.0001, rs = 0.61). Angular second moment values were also highly significantly correlated with nuclear area (rs = 0.39, p < 0.0001). These results indicate that the GLCM method may be a powerful tool in evaluation of ultrastructural nuclear changes during early stages of the apoptotic process.

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NAGASEKHAR, A. V., TICK-HON YIP, and S. LI. "FINITE ELEMENT STUDY OF MULTIPASS EQUAL CHANNEL ANGULAR EXTRUSION/PRESSING." International Journal of Nanoscience 04, no. 04 (2005): 745–51. http://dx.doi.org/10.1142/s0219581x05003346.

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Equal channel angular extrusion/pressing multipass simulations were carried for two routes, Route A and Route C, by using finite element code Abaqus/Explicit. Realistic parameters like strain hardening behavior of material, friction between the sample and die were considered for simulations. The strain homogeneity and deformation behavior of samples during multipass ECAE with different routes were studied. The deformation behavior of the sample processed through Route A is smooth. Accordingly strain homogeneity of the samples was more of a possibility with Route A than with Route C.

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Si, Jia Yong, Ze Hao Hu та Li Ping Zhong. "Finite Element Analysis of β-Titanium during Equal Channel Angular Extrusion". Advanced Materials Research 399-401 (листопад 2011): 1702–7. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.1702.

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The finite element analysis was applied to evaluate the respective influences of die geometry and process conditions on plastic strain distribution for β-titanium (Ti-13V11Cr3Al) during the equal channel angular extrusion. It was found that optimum ECAE die geometry is strongly material dependent. Optimal strain homogeneity in the Ti-13V11Cr3Al alloy may be achieved at r (inner radius) =5mm, R (outer radius) =3mm. The equivalent plastic strain increases with increasing friction coefficient. And the better homogeneity of the equivalent plastic strain distribution can be achieved when m=0.1. The faster is the ram speed, the lower is the homogeneity of the equivalent plastic strain distribution. The back-pressure can increase the strain level across the workpiece and prevent the problem of surface cracking induced by tensile stresses. The distribution of the plastic strain is not temperature sensitive between 400°C and 600°C.

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Attarilar, Shokouh, Mohammad-Taghi Salehi, and Faramarz Djavanroodi. "Microhardness evolution of pure titanium deformed by equal channel angular extrusion." Metallurgical Research & Technology 116, no. 4 (2019): 408. http://dx.doi.org/10.1051/metal/2018135.

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Microhardness homogeneity was assessed on commercial pure titanium processed by equal channel angular extrusion (ECAE). The operation was performed with die channel angle of 90° and processing temperature of 450 °C by route BC up to six passes. The Vickers microhardness measurements were investigated on both cross-sectional and longitudinal planes of the annealed, one-, two-, four-, and six-pass ECAEed titanium. It was found that the application of the process and the addition of pass numbers lead to the improvement of hardness magnitude. It was shown that there are some areas of microhardness heterogeneity in surrounding and bottom regions of the one-pass and two-pass specimens at the cross-sectional plane which is slightly disappeared by adding the pass numbers. Furthermore, there is a suitable amount of hardness homogeneity in the longitudinal plane, irrespective of the specimen condition. It can be concluded that a desirable homogeneity of hardness can be attained after imposing six passes of ECAE process on both cross-sectional and longitudinal planes of titanium.

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My, Hanh Nguyen Thi1, and Ton That Phung. "The analysis of MF resin and CaCO3 diffuser-loaded encapsulations to enhance the homogeneity of correlated color temperature for phosphor-converted LEDs." TELKOMNIKA Telecommunication, Computing, Electronics and Control 19, no. 2 (2021): pp. 608~615. https://doi.org/10.12928/TELKOMNIKA.v19i2.16519.

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The most popular method used in the production of phosphor-converted LEDs (pc-LEDs) is dispensing phosphor freely. However, this method is inferior in generating good angular correlated color temperature (CCT) homogeneity. Thus, in this article, a diffuser-loaded encapsulation is proposed as a potential solution for better CCT uniformity. The paper provides a detailed investigation on how melamine formaldehyde (MF) resin and CaCO3 loaded encapsulations impact the uniformity of CCT, as well as the lumen efficacy of pc-LEDs. The results demonstrate that between MF resin and CaCO3 loaded encapsulations, the MF resin yields a higher light diffusion efficiency while the CaCO3 maintains greater lumen efficacy. The photon scattering development is the key force behind the enhancement of the angular CCT uniformity in pc-LEDs’ output when using the loaded encapsulations of MF resin and CaCO3 particles. Since this package utilized mineral, it has reasonable cost and is quite easy to control while still being effective in enhancing the angular CCT homogeneity of pc-LEDs. Diffusers with 1% concentration of MF resin or 10% concentration of CaCO3 are determined as an optimal solution for reducing the variance of angular CCT and increasing the lumen output.

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Mak, Jonathon, Richard Wuhrer, Norman Booth, Paul Fanos, Greg Heness, and Wing Yiu Yeung. "Equal Channel Angular Extrusion of Zinc-Aluminium Metal Matrix Composites." Key Engineering Materials 345-346 (August 2007): 113–16. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.113.

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Equal channel angular extrusion (ECAE) was employed in an attempt to develop nanostructural metal matrix composites with homogenized distribution of reinforcing particles. Zn- Al metal matrix composites reinforced with 5 μm SiC particulates were produced by casting method. A non-uniform distribution of the reinforcing particles was evident in the metal matrix. With repetitive shear deformation imposed via the ECAE process, substantial structural improvement was achieved and the reinforcing particulates were de-clustered into a finely dispersed distribution throughout the metal matrix. The homogeneity of the particle distribution was studied by the Quadrat method and the skew factors were determined. It was found that the skew factors were substantially reduced after 8 extrusion passes, showing the homogeneity of the particle distribution was greatly improved in the composites.

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Saxl, Ivan, L. Ilucová, Milan Svoboda, et al. "Structural Non-Homogeneity and Thermal Instability of ECAP Aluminium." Materials Science Forum 567-568 (December 2007): 193–96. http://dx.doi.org/10.4028/www.scientific.net/msf.567-568.193.

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The grain structure of pure aluminium processed by equal channel angular pressing (ECAP) was examined electron backscattered diffraction (EBSD) in the as pressed state and after heating preceding the creep deformation using various stereological methods. Area intensities of grain and subgrain boundaries, length intensities of triple grain and subgrain junctions, structural homogeneity and its thermal stability are strictly dependent on the number of passes.

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Alonso, D., A. Bueno Belloso, F. J. Sánchez, J. García-Bellido, and E. Sánchez. "Measuring the transition to homogeneity with photometric redshift surveys." Monthly Notices of the Royal Astronomical Society 440, no. 1 (2014): 10–23. http://dx.doi.org/10.1093/mnras/stu255.

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Abstract We study the possibility of detecting the transition to homogeneity using photometric redshift catalogues. Our method is based on measuring the fractality of the projected galaxy distribution, using angular distances, and relies only on observable quantities. It thus provides a way to test the cosmological principle in a model-independent unbiased way. We have tested our method on different synthetic inhomogeneous catalogues and shown that it is capable of discriminating some fractal models with relatively large fractal dimensions, in spite of the loss of information due to the radial projection. We have also studied the influence of the redshift bin width, photometric redshift errors, bias, non-linear clustering, and surveyed area on the angular homogeneity index H2(θ) in a Λ cold dark matter cosmology. The level to which an upcoming galaxy survey will be able to constrain the transition to homogeneity will depend mainly on the total surveyed area and the compactness of the surveyed region. In particular, a Dark Energy Survey (DES)-like survey should be able to easily discriminate certain fractal models with fractal dimensions as large as D2 = 2.95. We believe that this method will have relevant applications for upcoming large photometric redshift surveys, such as DES or the Large Synoptic Survey Telescope.

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Rao, Radhakrishna, and Pranab Sen. "Permutation scores tests for homogeneity of angular and compositional gaussian distributions." Journal of Nonparametric Statistics 14, no. 4 (2002): 421–33. http://dx.doi.org/10.1080/10485250213110.

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Nagasekhar, A. V., Yip Tick-Hon, and H. P. Seow. "Deformation behavior and strain homogeneity in equal channel angular extrusion/pressing." Journal of Materials Processing Technology 192-193 (October 2007): 449–52. http://dx.doi.org/10.1016/j.jmatprotec.2007.04.093.

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13

Shabong, R. A., A. J. Sonowal, A. Pukhrambam, et al. "An experimental study on the effect of particle size and non-homogeneity on the shear strength of soil." IOP Conference Series: Materials Science and Engineering 1282, no. 1 (2023): 012021. http://dx.doi.org/10.1088/1757-899x/1282/1/012021.

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Abstract Soil deposits available in nature are often present as homogeneous mixtures of particles of different sizes and base minerals or as a combination of soils in different layers forming a non-homogeneous configuration. This variability in soil has great influence on the shear strength behaviour. In this study, different naturally occurring soil particle sizes and shapes (angular and flaky) have been utilized as reinforcements in the form of layers to determine their influence on the soil shear strength. Therefore, triaxial tests have been conducted on homogeneous sand (where particles are mixed proportionately), and on non-homogeneous sand (different layer combinations of different particle sizes as well as the inclusion of angular and flaky particles). It has been observed that there was a substantial increase in the shear strength for non-homogeneous arrangement compared to homogeneous sand sample. Furthermore, the addition of flaky particles from 10% to 30% by weight of fine grained sand increased the angle of internal friction (ϕ) and cohesion (c) values thereby increasing the shear strength. However, for angular-fine sand layer combination, the addition of 10-20% of angular particles by weight shows a significant increase in shear strength in comparison to 30-100% of angular particles.

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14

Andrade, Uendert, Rodrigo S. Gonçalves, Gabriela C. Carvalho, Carlos A. P. Bengaly, Joel C. Carvalho, and Jailson Alcaniz. "The angular scale of homogeneity with SDSS-IV DR16 luminous red galaxies." Journal of Cosmology and Astroparticle Physics 2022, no. 10 (2022): 088. http://dx.doi.org/10.1088/1475-7516/2022/10/088.

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Abstract We report measurements of the angular scale of cosmic homogeneity (θH ) using the recently released luminous red galaxy sample of the sixteenth data release of the Sloan Digital Sky Survey (SDSS-IV LRG DR16). It consists of a model-independent method, as we only use the celestial coordinates of these objects to carry out such an analysis. The observational data is divided into thin redshift bins, namely 0.67 < z < 0.68, 0.70 < z < 0.71, and 0.73 < z < 0.74, in order to avoid projection biases, and we estimate our uncertainties through a bootstrap method and a suite of mock catalogues. We find that the LRGs exhibit an angular scale of homogeneity consistent with the predictions of the standard cosmology within the redshift interval studied. Considering the bootstrap method, in which the measurements are obtained in a model-independent way, we found at 1σ level that θH boot(0.675) = 7.57 ± 2.91 deg, θH boot (0.705) = 7.49 ± 2.63 deg and θH boot (0.735) = 8.88 ± 2.81 deg. Such results are in good agreement with the ones obtained using mock catalogues built under the assumption of the standard cosmological model.

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Wang, Hongfei, Chunyan Ban, Nannan Zhao, Lei Li, Qingfeng Zhu, and Jianzhong Cui. "Cryogenic temperature equal channel angular pressing of pure titanium: microstructure and homogeneity." Journal of Materials Research and Technology 14 (September 2021): 1167–79. http://dx.doi.org/10.1016/j.jmrt.2021.07.019.

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Osman, Mohamed, Dian Tao Zhang, Yun Xiang Tong, Yu Feng Zheng, and Li Li. "Graded Transitions Homogeneity for Ti-50.8%Ni Processed by ECAP." Advanced Materials Research 1082 (December 2014): 90–94. http://dx.doi.org/10.4028/www.scientific.net/amr.1082.90.

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Ti-50.8%Ni shape memory alloy was subjected to four passes equal channel angular pressing (ECAP) with angle 120◦ via route Bc at 450°C. The deformation homogeneity was analyzed on planes across the thickness of the deformed sample by Deform-3D software. Two methods were used from the simulation model to quantify deformation homogeneity , including strain standard deviation (SSD) and inhomogeneity index (Ci). In addition, The deformation heterogeneity of ECAP was analyzed experimentally from microhardness inhomogeneity index ( HII) based on Vickers microhardness test results.In the present work, Ci and SSD had been testified to detect which one could give better results experimentally. It was demonstrated that the simulation results of SSD measurements were in good agreement with experimental results .

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dos Santos, Reinan T. F., Thamyres M. Lima, and Wilton W. Batista. "Analysis of Hardness Homogeneity in Pure Niobium Subjected to Equal Channel Angular Pressing." MATERIALS TRANSACTIONS 63, no. 2 (2022): 261–64. http://dx.doi.org/10.2320/matertrans.mt-m2021163.

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Moon, B. S., H. S. Kim, and S. I. Hong. "Plastic flow and deformation homogeneity of 6061 Al during equal channel angular pressing." Scripta Materialia 46, no. 2 (2002): 131–36. http://dx.doi.org/10.1016/s1359-6462(01)01209-x.

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Tham, Y. W., M. W. Fu, H. H. Hng, M. S. Yong, and K. B. Lim. "Study of deformation homogeneity in the multi-pass equal channel angular extrusion process." Journal of Materials Processing Technology 192-193 (October 2007): 121–27. http://dx.doi.org/10.1016/j.jmatprotec.2007.04.030.

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Shamsborhan, Mahmoud, Ali Shokuhfar, Omid Nejadseyfi, Jamal Kakemam, and Mahmoud Moradi. "Experimental and numerical comparison of equal channel angular extrusion (ECAE) with planar twist channel angular extrusion (PTCAE)." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 16 (2014): 3059–67. http://dx.doi.org/10.1177/0954406214566035.

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Planar twist channel angular extrusion (PTCAE) is a new severe plastic deformation (SPD) method to impose large strain and to increase the efficiency of SPD methods. This novel process was conducted on commercially pure aluminum and was investigated by finite element analysis and experimental tests. The results revealed that performing PTCAE made it possible to impose large strain values per pass while maintaining a homogenous hardness distribution on the cross-section of sample. The objective of this paper is comparison of hardness after one pass of PTCAE and equal channel angular pressing (ECAP) processed samples. The results revealed that an increase in the hardness from 29 Hv to ∼49 Hv and ∼41 Hv could be achieved after one pass of PTCAE and ECAP, respectively. PTCAE process has two important advantages of inducing higher plastic strain and excellent strain and hardness homogeneity. Therefore, PTCAE is a promising SPD technique for specific applications to produce ultrafine-grained or nanostructured materials.

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Jiang, Fei, Yin-Quan Ye, Jin-Min Zuo, Xin Huang, Chen Yu, and Xian-Jun Zeng. "Frequency-specific oscillations synchronization in primary angle-closure glaucoma." Acta Radiologica 61, no. 4 (2019): 537–48. http://dx.doi.org/10.1177/0284185119870975.

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Background Previous neuroimaging studies demonstrated that patients with primary angle-closure glaucoma were accompanied by abnormal neuronal activity. Purpose To investigate frequency-dependent local oscillations synchronization in primary angle-closure glaucoma using the regional homogeneity method. Material and Methods In total, 37 individuals with primary angle-closure glaucoma (20 men, 17 women) and 37 normal-sighted controls (20 men, 17 women) closely matched in age, sex, and education underwent resting-state MRI scans. We compared the different regional homogeneity values in full band (0.01–0.08 Hz) and two different frequency bands (slow-4: 0.027–0.073 Hz and slow-5: 0.010–0.027 Hz) between two groups. Results Compared to the normal-sighted group, the primary angle-closure glaucoma group showed decreased regional homogeneity values in the left calcarine and left postcentral in full band. The primary angle-closure glaucoma group showed increased regional homogeneity values in the bilateral superior medial frontal lobe in the slow-4 band. The primary angle-closure glaucoma group exhibited decreased regional homogeneity values in the right calcarine in the slow-5 band. Specifically, we found that the regional homogeneity values in the right superior frontal lobe were greater in the slow-4 than in the slow-5 band, whereas regional homogeneity in the left calcarine, right pallidum, left inferior occipital gyrus, left superior occipital gyrus, left postcentral/angular gyrus, left paracentral lobule, left superior parietal gyrus, and right precuneus gyrus were greater in the slow-5 than in the slow-4 band. Conclusion Primary angle-closure glaucoma groups showed abnormal regional homogeneity in visual network (calcarine) and default mode network (superior medial frontal lobe) at two frequency bands. Moreover, the regional homogeneity signals in slow-5 band showed closely related to the severity of individuals with primary angle-closure glaucoma.

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Kim, Hyoung Seop. "On the effect of acute angles on deformation homogeneity in equal channel angular pressing." Materials Science and Engineering: A 430, no. 1-2 (2006): 346–49. http://dx.doi.org/10.1016/j.msea.2006.05.146.

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Zhang, Xiaohua, and Yuansheng Cheng. "Influence of inner fillet radius on effective strain homogeneity in equal channel angular pressing." International Journal of Advanced Manufacturing Technology 92, no. 9-12 (2017): 4001–8. http://dx.doi.org/10.1007/s00170-017-0468-x.

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Nagasekhar, A. V., W. Wei, Y. Tick-Hon, and G. Chen. "Equal Channel Angular Pressing Die Outer Corner Angle Influence on Flow and Strain Homogeneity." Advanced Engineering Materials 9, no. 7 (2007): 572–76. http://dx.doi.org/10.1002/adem.200700004.

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Wongsa-Ngam, Jittraporn, Nitikorn Noraphaiphipaksa, Chaosuan Kanchanomai, and Terence G. Langdon. "Numerical Investigation of Plastic Strain Homogeneity during Equal-Channel Angular Pressing of a Cu-Zr Alloy." Crystals 11, no. 12 (2021): 1505. http://dx.doi.org/10.3390/cryst11121505.

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A three-dimensional finite element method (3D FEM) simulation was carried out using ABAQUS/Explicit software to simulate multi-pass processing by equal-channel angular pressing (ECAP) of a circular cross-sectional workpiece of a Cu-Zr alloy. The effective plastic strain distribution, the strain homogeneity and the occurrence of a steady-state zone in the workpiece were investigated during ECAP processing for up to eight passes. The simulation results show that a strain inhomogeneity was developed in ECAP after one pass due to the formation of a corner gap in the outer corner of the die. The calculations show that the average effective plastic strain and the degree of homogeneity both increase with the number of ECAP passes. Based on the coefficient of variance, a steady-state zone was identified in the middle section of the ECAP workpiece, and this was numerically evaluated as extending over a length of approximately 40 mm along the longitudinal axis for the Cu-Zr alloy.

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Awang Sh'ri, D. N., M. A. H. Abu Hassan, Z. S. Zahari, and W. S. Wan Harun. "Finite Element Simulation of Equal Channel Angular Pressing: Effect of Die Angle and Number of Passes." International Journal of Automotive and Mechanical Engineering 16, no. 1 (2019): 6402–14. http://dx.doi.org/10.15282/ijame.16.1.2019.22.0484.

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Equal channel angular pressing (ECAP) is one of the popular severe plastic deformation processes used to produce bulk nanostructured materials. The degree of homogeneity of nanostructured is affected by various die parameters. In this paper, the effect of internal die angle (ϕ) and number of passes (N) on the strain behaviour of Aluminium Alloy 6061 (AA6061) during ECAP was investigated by using three-dimensional finite element analysis. The effect of number of passes and die angle on the homogeneity within the workpiece was analysed in terms of contours, radial view contour and inhomogeneity index. The analysis is done by comparing workpiece extruded up to 8 passes at die angle of 120° and 126°. It is observed that the resulting strain is higher at 120° die. However, the inhomogeneity index is decreasing in a similar pattern in both dies. The simulation results shed some lights on the optimum design of ECAP die for homogeneous microstructure.

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Kästner, Philipp, Basma Elsaka, Mustaqim Siddi Que Iskhandar, et al. "Homogeneity of Electro-Mechanical and Optical Characteristics in Ring-Shaped MEMS Shutter Arrays with Subfield Addressing for Interference Microscopy." Micromachines 16, no. 2 (2025): 168. https://doi.org/10.3390/mi16020168.

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We present a MEMS array-based approach for micro-irises called “ring shutter”, utilizing subfield addressing for applications in advanced micro-optics, such as interference microscopy. This experimental study is focused on investigating the homogeneity of electro-mechanical and optical characteristics within and between subfields of a lab demonstrator device. The characterization aims to ensure crosstalk-free and swift optical performance, as demonstrated in a previous study. For this purpose, the transmission in the initial state, actuation voltages, and response dynamics are measured for each electrode and the entire device, and the results are thoroughly compared. The measurements are conducted by expanding an existing optical actuation setup via tailored 3D-printed apertures, to isolate selected rings and zones. Evaluation of measurement data confirms the stable and crosstalk-free operation of the ring shutter. Both angular and radial homogeneity are robust and follow the expectations in the experiment. While transmission, actuation voltage and closing time slightly rise (up to 25%) with increased radial position represented by five discrete ring sections, the characteristics for different angular zones remain nearly constant. Response times are measured below 40 µs, actuation voltages do not exceed 60 V, and the overall transmission of the ring shutter yields 53.6%.

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Mitsak, A., B. Aour, and F. Khelil. "Numerical Investigation of Plastic Deformation in Two-turn Equal Channel Angular Extrusion." Engineering, Technology & Applied Science Research 4, no. 6 (2014): 728–33. http://dx.doi.org/10.48084/etasr.517.

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There has been a number of investigations in recent years reporting on the structure and properties of materials deformed to super plastic deformation (SPD). During SPD new textures can be formed and abnormal characteristics are displayed, attracting a growing research interest.¶ Equal channel angular extrusion (ECAE) is a method often used to obtain large plastic strains. However, according to experimental results, there is a large tensile stress in the sample during deformation, which may lead in some cases, to cracking in metallic alloys and large curvature in polymeric materials. In order to overcome these drawbacks, the ECAE process can be conducted at high temperatures. But this contributes significantly to a decreased level of plastic deformation induced in the sample. Hence, a tool with multi-pass seems to be a very appropriate solution. In this paper, a new geometry die composed of two elbows has been simulated by finite element method aiming to provide an insight into the mechanisms of deformation and to determine the optimum geometry of the tool. The numerical results show that the length and the section of the second channel play a significant role on the homogeneity of the plastic strain distribution. It has been found that good homogeneity was obtained when the second channel has the same section as that of the entrance and the exit channels and with a length equal to three times of its width.

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Mitsak, A., B. Aour, and F. Khelil. "Numerical Investigation of Plastic Deformation in Two-turn Equal Channel Angular Extrusion." Engineering, Technology & Applied Science Research 4, no. 6 (2014): 728–33. https://doi.org/10.5281/zenodo.14694.

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There has been a number of investigations in recent years reporting on the structure and properties of materials deformed to super plastic deformation (SPD). During SPD new textures can be formed and abnormal characteristics are displayed, attracting a growing research interest.¶ Equal channel angular extrusion (ECAE) is a method often used to obtain large plastic strains. However, according to experimental results, there is a large tensile stress in the sample during deformation, which may lead in some cases, to cracking in metallic alloys and large curvature in polymeric materials. In order to overcome these drawbacks, the ECAE process can be conducted at high temperatures.  But this contributes significantly to a decreased level of plastic deformation induced in the sample. Hence, a tool with multi-pass seems to be a very appropriate solution. In this paper, a new geometry die composed of two elbows has been simulated by finite element method aiming to provide an insight into the mechanisms of deformation and to determine the optimum geometry of the tool. The numerical results show that the length and the section of the second channel play a significant role on the homogeneity of the plastic strain distribution. It has been found that good homogeneity was obtained when the second channel has the same section as that of the entrance and the exit channels and with a length equal to three times of its width.

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Kasradze, David, and Ričardas Kubilius. "The Influence of Guiding Concept on the Accuracy of Static Computer-Assisted Implant Surgery in Partially Edentulous Cases: An In Vitro Study." Medicina 61, no. 4 (2025): 617. https://doi.org/10.3390/medicina61040617.

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Background and Objectives: Static Computer-Assisted Implant Surgery (sCAIS) can be performed with different drill guiding systems. This study aimed to compare the accuracy of two guiding concepts of sCAIS in partially edentulous cases. Materials and Methods: Forty polyamide models of partially edentulous maxillae with seven implantation sites were fabricated. In total, 140 replica implants were placed with keyless (KL) and drill-key (DK) guiding systems using static, full-arch, tooth-supported surgical guides. Three-dimensional crestal and apical, angular and vertical deviations from the planned implant positions were compared using Mann–Whitney U and Kruskal–Wallis H tests. Intergroup homogeneity of variance homogeneity was examined using Levene’s test to assess the precision. Results: Overall median 3D crestal and apical deviations of implants placed in the KL group were significantly higher compared to the DK group (0.86 mm [0.63–0.98] vs. 0.72 mm [0.52–0.89], p = 0.006 and 1.26 [0.98–1.52] vs. 1.13 [0.70–1.45], p = 0.012). In the subgroup analysis, implants placed with a KL system showed higher 3D crestal (p = 0.029), 3D apical (p < 0.001) and angular (p < 0.001) deviations in the extended anterior area, higher 3D crestal (p < 0.001) deviations in the proximal posterior single-tooth gap and higher vertical (p < 0.001) deviations in the distal site of free-end situation. Contrarily, the KL group showed lower 3D crestal (p = 0.007), 3D apical (p < 0.001), angular (p < 0.001) and vertical (p = 0.003) deviations in the distal posterior single-tooth gap, lower 3D apical (p = 0.007) and angular (p = 0.007) deviations in the distal site of free-end situation and lower vertical (p = 0.019) deviations in the proximal site of free-end situation. Conclusions: The deviations of both guiding concepts did not exceed the recommended safety margins. Statistically significant differences in deviations were found between two guiding concepts. Guiding concepts with superior accuracy varied across different sites of implantation.

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He, Shaoming, Wei Wang, and Jiang Wang. "Robust finite-time line-of-sight angular rate estimation in missile guidance." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 8 (2016): 1550–59. http://dx.doi.org/10.1177/0954410016654178.

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This paper documents a robust finite-time line-of-sight angular rate estimation in missile guidance. Through geometric homogeneity and Lyapunov theories, it is shown that the observer estimation errors can converge into a bounded nonzero residual set in finite time and the upper bound can be lowered by parameter tunings. For estimation performance improvement, the sliding mode gains are also determined theoretically. With the help of these gains, it is proved that the observer estimation errors can converge to zero in finite time. Detailed simulation results with some comparisons are performed to validate the proposed formulation.

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32

Journal, Baghdad Science. "Clouds Height Classification Using Texture Analysis of Meteosat Images." Baghdad Science Journal 11, no. 2 (2014): 652–59. http://dx.doi.org/10.21123/bsj.11.2.652-659.

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In the present work, pattern recognition is carried out by the contrast and relative variance of clouds. The K-mean clustering process is then applied to classify the cloud type; also, texture analysis being adopted to extract the textural features and using them in cloud classification process. The test image used in the classification process is the Meteosat-7 image for the D3 region.The K-mean method is adopted as an unsupervised classification. This method depends on the initial chosen seeds of cluster. Since, the initial seeds are chosen randomly, the user supply a set of means, or cluster centers in the n-dimensional space.The K-mean cluster has been applied on two bands (IR2 band) and (water vapour band).The textural analysis is used where six parameters are calculated from the Co-occurrence matrix. These parameter were inserted in the K-mean. The best classifier feature is the angular second moment. When we use the angular second moment is used with any textural feature a good result were obtained for cloud classification, since the angular second moment gives indications on cloud homogeneity.

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George, Loay A., Laith A. Al Ani, and Alyaa H. Ali. "Clouds Height Classification Using Texture Analysis of Meteosat Images." Baghdad Science Journal 11, no. 2 (2014): 652–59. http://dx.doi.org/10.21123/bsj.2014.11.2.652-659.

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In the present work, pattern recognition is carried out by the contrast and relative variance of clouds. The K-mean clustering process is then applied to classify the cloud type; also, texture analysis being adopted to extract the textural features and using them in cloud classification process. The test image used in the classification process is the Meteosat-7 image for the D3 region.The K-mean method is adopted as an unsupervised classification. This method depends on the initial chosen seeds of cluster. Since, the initial seeds are chosen randomly, the user supply a set of means, or cluster centers in the n-dimensional space.The K-mean cluster has been applied on two bands (IR2 band) and (water vapour band).The textural analysis is used where six parameters are calculated from the Co-occurrence matrix. These parameter were inserted in the K-mean. The best classifier feature is the angular second moment. When we use the angular second moment is used with any textural feature a good result were obtained for cloud classification, since the angular second moment gives indications on cloud homogeneity.

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34

Elkaseer, AM, SS Dimov, DT Pham, KP Popov, L. Olejnik, and A. Rosochowski. "Material microstructure effects in micro-endmilling of Cu99.9E." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, no. 7 (2016): 1143–55. http://dx.doi.org/10.1177/0954405416666898.

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This article presents an investigation of the machining response of metallurgically and mechanically modified materials at the micro-scale. Tests were conducted that involved micro-milling slots in coarse-grained Cu99.9E with an average grain size of 30 µm and ultrafine-grained Cu99.9E with an average grain size of 200 nm, produced by equal channel angular pressing. A new method based on atomic force microscope measurements is proposed for assessing the effects of material homogeneity changes on the minimum chip thickness required for a robust micro-cutting process with a minimum surface roughness. The investigation has shown that by refining the material microstructure the minimum chip thickness can be reduced and a high surface finish can be obtained. Also, it was concluded that material homogeneity improvements lead to a reduction in surface roughness and surface defects in micro-cutting.

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35

Jung, Jaimyun, Seung Chae Yoon, Hyun-Joon Jun, and Hyoung Seop Kim. "Finite Element Analysis of Deformation Homogeneity During Continuous and Batch Type Equal Channel Angular Pressing." Journal of Materials Engineering and Performance 22, no. 11 (2013): 3222–27. http://dx.doi.org/10.1007/s11665-013-0632-x.

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Ma, Muzhi, Zhou Li, Wenting Qiu, et al. "Development of homogeneity in a Cu-Mg-Ca alloy processed by equal channel angular pressing." Journal of Alloys and Compounds 820 (April 2020): 153112. http://dx.doi.org/10.1016/j.jallcom.2019.153112.

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37

McLean, B. J., H. Böhringer, R. Burg, R. Giacconi, J. P. Huchra, and W. Voges. "Optical Identification of Rosat All-Sky Survey Galaxy Cluster Candidates." Symposium - International Astronomical Union 161 (1994): 653–57. http://dx.doi.org/10.1017/s0074180900048294.

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Clusters of galaxies are used to study large scale structure and evolution in the universe. The luminosity functions of clusters can be used to investigate their evolutionary effects while their spatial and angular correlation functions are a measure of large-scale clustering. There are, however, many problems with the traditional cluster catalogues that were derived by visual inspection of plate material. The widely used Abell catalogue (Abell 1958) has been shown to have significant problems in homogeneity and completeness (Postman et al. 1986).

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38

Hu, Hong Jun, Ding Fei Zhang, and Fu Sheng Pan. "Computer Simulation and Optimization of Equal Channel Angular Extrusion of AZ31 Magnesium Alloy." Materials Science Forum 610-613 (January 2009): 780–82. http://dx.doi.org/10.4028/www.scientific.net/msf.610-613.780.

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In order to study the influence of die structures and process parameters on ECAE for wrought magnesium alloy AZ31 and obtain optimized process parameters, the three-dimension(3D) new geometric models with different corner angles (90o,120o,135o) and with or without inner round fillets in the bottom die were designed. The simulation results showed that the loads of top dies declined mainly with the corner angles increasing and inner round fillets of the bottom dies manufactured, the bottom die with inner round corner and the corner angle of 90o was propitious to improve the plasticity and deformation homogeneity of the billets.

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39

Alhajeri, Saleh N., Nong Gao, and Terence G. Langdon. "The Evolution of Homogeneity during Processing of Commercial Purity Aluminium by ECAP." Materials Science Forum 584-586 (June 2008): 446–51. http://dx.doi.org/10.4028/www.scientific.net/msf.584-586.446.

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Billets of a commercial purity aluminium Al-1050 alloy were processed by equal-channel angular pressing (ECAP) for up to a maximum of 6 passes. Following processing, the billets were sectioned and hardness measurements were recorded on both longitudinal and transverse sections. These measurements showed the hardness increases significantly in the first pass and continues to increase by small amounts in subsequent passes. Initially, there are regions of lower hardness running in bands near the top and bottom surface of each billet. The region of lower hardness near the upper surface disappears with increasing numbers of passes but near the bottom surface the lower hardness remains even after 6 passes. The results show that, neglecting the small region near the bottom of the billet, there is an excellent potential for achieving microstructural homogeneity within the Al-1050 alloy after pressing through a sufficient number of passes in ECAP.

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Alateyah, A. I., Mohamed M. Z. Ahmed, Yasser Zedan, H. Abd El-Hafez, Majed O. Alawad, and W. H. El-Garaihy. "Experimental and Numerical Investigation of the ECAP Processed Copper: Microstructural Evolution, Crystallographic Texture and Hardness Homogeneity." Metals 11, no. 4 (2021): 607. http://dx.doi.org/10.3390/met11040607.

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The current study presents a detailed investigation for the equal channel angular pressing of pure copper through two regimes. The first was equal channel angular pressing (ECAP) processing at room temperature and the second was ECAP processing at 200 °C for up to 4-passes of route Bc. The grain structure and texture was investigated using electron back scattering diffraction (EBSD) across the whole sample cross-section and also the hardness and the tensile properties. The microstructure obtained after 1-pass at room temperature revealed finer equiaxed grains of about 3.89 µm down to submicrons with a high density of twin compared to the starting material. Additionally, a notable increase in the low angle grain boundaries (LAGBs) density was observed. This microstructure was found to be homogenous through the sample cross section. Further straining up to 2-passes showed a significant reduction of the average grain size to 2.97 µm with observable heterogeneous distribution of grains size. On the other hand, increasing the strain up to 4-passes enhanced the homogeneity of grain size distribution. The texture after 4-passes resembled the simple shear texture with about 7 times random. Conducting the ECAP processing at 200 °C resulted in a severely deformed microstructure with the highest fraction of submicron grains and high density of substructures was also observed. ECAP processing through 4-passes at room temperature experienced a significant increase in both hardness and tensile strength up to 180% and 124%, respectively.

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41

Gentil, Anthony, Jeremy Deverdun, Nicolas Menjot de Champfleur, Jean-Luc Puel, Emmanuelle Le Bars, and Frédéric Venail. "Alterations in Regional Homogeneity in Patients With Unilateral Chronic Tinnitus." Trends in Hearing 23 (January 2019): 233121651983023. http://dx.doi.org/10.1177/2331216519830237.

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Chronic subjective tinnitus is a widespread disorder. This perceptual anomaly is assumed to result from a dysbalance of excitatory and inhibitory mechanisms on different levels of the auditory pathways. However, the brain areas involved are still under discussion. Using resting-state functional magnetic resonance imaging, we investigate differences in cerebral regional homogeneity (ReHo) between patients with unilateral chronic tinnitus and nontinnitus control subjects. To our knowledge, our study is the first to investigate the intraregional connectivity of patients with unilateral tinnitus in relation to hearing loss. Our analyses, based on strict recruitment and characterization of the participants, showed reduced ReHo in the primary auditory cortex contralateral to the side of the perceived tinnitus percept in patients. Reduced ReHo in this same region was also correlated with increased Tinnitus Handicap Inventory and Visual Analogue Scale for loudness scores, reflecting an alteration of synchronization in this region related to the perceived loudness of the tinnitus and the related distress. Furthermore, increased ReHo in the supramarginal and angular gyri ipsilateral to the tinnitus side was correlated with increased tinnitus duration and hearing threshold at the tinnitus pitch. The correlations observed in these brain areas, which are normally related to the nontinnitus ear, could highlight compensatory mechanisms in these secondary auditory regions.

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42

Ananda Babu, Varadala, Gurugubelli Swami Naidu, and B. Sateesh. "Equal Channel Angular Extrusion of AA 5083." Advanced Materials Research 1148 (June 2018): 82–87. http://dx.doi.org/10.4028/www.scientific.net/amr.1148.82.

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Equal Channel Angular Extrusion (ECAE) is used as a top down process to produce bulk nano/ultrafine grain structured materials by inducing high amount of strain with less experimental set up. In the present study AA 5083 alloy with circular and square cross sections are extruded at room temperature using two dies having cannels with circular and square cross sections respectively. Both the dies used in this study are having same channel angle (Φ)1200and outer corner angle (Ψ) 200. The circular and square billets are extruded for four times in route BC. The objective of this work is to study the effect of cross section of the billet, number of passes on grain refinement, mechanical properties and wear behaviour of AA 5083. Significant reduction in grain size is observed in extruded material using Field Emission Scanning Electron Microscope (FE-SEM) in the range of 80nm to 600nm after four passes. The microhardness in extruded materials is improved with no. of passes in both cross sectioned billets and it is more predominant for square billets even after two passes. The effect of dead zone is less in case of square billets and hence they have shown more structural homogeneity. The dry sliding wear tests are conducted to study the wear behaviour of the ECAEd materials. It is observed that the wear rate and coefficient of friction are reduced with number of passes in both the cases and rate of decrease is more in case of square billets.

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43

Zhao, Xiao Lian, Na Chen, and Ning Ning Zhao. "Numerical Simulation of Equal Channel Angular Pressing for Multi-Pass in Different Routes." Applied Mechanics and Materials 268-270 (December 2012): 373–77. http://dx.doi.org/10.4028/www.scientific.net/amm.268-270.373.

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In order to investigate the effect of continued equal channel angular pressing (ECAP) with different routes and passes on the homogeneity of structure, the process of continued ECAP for pure aluminum bar was simulated by DEFORM-3D software. It obtains the load-stroke curves for different passes, distribution of effective stress and effective strain in different routes after the sample is extruded eight passes by ECAP in routes A, BC and C. The results show that the uniformity of the sample is improved with the increase of passes. The microstructure of specimen which is extruded in route BC is the most uniform, but it is the worst in route A.

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44

Anh-Minh, D. Tran, Doan Quoc Anh Nguyen, and Thi Phuong Loan Nguyen. "Enhancing light sources color homogeneity in high-power phosphor-based white LED using ZnO particles." TELKOMNIKA Telecommunication, Computing, Electronics and Control 18, no. 5 (2020): 2628~2634. https://doi.org/10.12928/TELKOMNIKA.v18i5.14198.

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Color uniformity is one of the essentials for the on-going development of WLED. To achieve a high color uniformity index, increasing the scattering events within the phosphor layers was reported to be the most efficient method and in this article, ZnO is the chosen material to apply in this method. After analyzing the scattering properties through the scattering cross-section 𝐶𝑠𝑐𝑎(𝐷,𝜆), scattering coefficient 𝜇𝑠𝑐𝑎(𝜆) and scattering phase function 𝜌(𝜃,𝜆), the which outcomes comfirm that ZnO can enhance the scattered light in the phosphor layers. Moreover, the findings from the study of ZnO concentration from 2% to 26% suggest that color uniformity also depends on the fluctuation of ZnO concentration, therefore, to control color uniformity the focus should be implied on both size and concentration of ZnO. The experimental results from this research show that the luminous flux of WLED is at the peak if the concentration of ZnO is at 6%, and when the concentration of ZnO is at 18% and has 100 nm particles size, the ΔCCT reaches the lowest level. The final choice should be based on the desired characteristic of WLEDs, however, if the WLED need to excel in both luminous flux and ΔCCT then 6% ZnO concentration with particles size from 100 nm-300 nm is the optimal choice.

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45

Gaite, José. "Scaling Laws in the Stellar Mass Distribution and the Transition to Homogeneity." Advances in Astronomy 2021 (February 5, 2021): 1–13. http://dx.doi.org/10.1155/2021/6680938.

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We present a new statistical analysis of the large-scale stellar mass distribution in the Sloan Digital Sky Survey (data release 7). A set of volume-limited samples shows that the stellar mass of galaxies is concentrated in a range of galaxy luminosities that is very different from the range selected by the usual analysis of galaxy positions. Nevertheless, the two-point correlation function is a power-law with the usual exponent γ = 1.71 − 1.82 , which varies with luminosity. The mass concentration property allows us to make a meaningful analysis of the angular distribution of the full flux-limited sample. With this analysis, after suppressing the shot noise, we extend further the scaling range and thus obtain γ = 1.83 and a clustering length r 0 = 5.8 − 7.0 h − 1 Mpc . Fractional statistical moments of the coarse-grained stellar mass density exhibit multifractal scaling. Our results support a multifractal model with a transition to homogeneity at about 10 h − 1 Mpc .

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Bouazza, Abdelkader, and Abderrahmane Settaouti. "Understanding the contribution of energy and angular distribution in the morphology of thin films using Monte Carlo simulation." Monte Carlo Methods and Applications 24, no. 3 (2018): 215–24. http://dx.doi.org/10.1515/mcma-2018-0019.

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Abstract The energy and the angular distribution of atoms are considered like two parameters most influent in the optimization of the sputtering and subsequently on the deposit, resulting in films having the desired properties (homogeneity in thickness, composition identical to that of the evaporated material). Moreover, a great influence on the shape and quality of thin films is obtained. In this work, a simulation with a Monte Carlo (MC) method is used to calculate the sputtering yield for different energies and angular distributions of atoms of metals (Cu, Al and Ag) and semiconductors (Ge, Si and Te) bombarded by different gas particles (Ar, Xe and Ne). Our results showed that when arriving at a certain energy value E_{\rm max} , sputtering yield will be in maximum Y1_{\rm max} . Applying this E_{\rm max} and with variation in the angular distribution, we will obtain \theta_{\rm max} corresponding to the maximum of sputtering yield Y2_{\rm max} . These two values ( E_{\rm max} , \theta_{\rm max} ) give the maximum of atoms sputtered and as a result, the films will be uniform. The obtained results are in very high agreement with other works, which validates our calculations.

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47

Quang, Pham, Do Minh Nghiep, and Hyoung Seop Kim. "Simulation of the Effective of Friction on the Deformation in Equal Channel Angular Pressing (ECAP)." Key Engineering Materials 656-657 (July 2015): 526–31. http://dx.doi.org/10.4028/www.scientific.net/kem.656-657.526.

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A influence of friction on the deformation behavior and strain homogeneity during ECAP has been studied by conducting 2D and 3D finite element simulations for a range of friction conditions m = 0 – 0.2. The deformation was more uniform in central steady zone as compared to the ends of the sample. The calculated ram load was higher in 3D simulations than 2D simulations. For a frictionless condition, the ram load was similar in both 2D and 3D simulations. Keywords: ECAP, SPD, FEM, Coulomb friction model, friction condition, ram load.

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Avtokratova, Elena, Oleg Sitdikov, Michael Markushev, and Radik R. Mulyukov. "Extraordinary High Strain Rate Superplasticity of an Al-Mg-Sc-Zr Alloy Subjected to Equal Channel Angular Pressing." Materials Science Forum 735 (December 2012): 295–300. http://dx.doi.org/10.4028/www.scientific.net/msf.735.295.

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Unique superplastic elongations up to 4100% were achieved at 450°C in the strain rate range of 10-2-10-1s-1for Al-Mg-Sc-Zr alloy with a grain size ~1 μm processed by warm-to-hot equal channel angular pressing. Such a behavior is attributed to the synergy of complementary factors resulted in high homogeneity and stability of ultrafine-grained microstructure and superplastic flow, involving large proportion of high-angle grain boundaries, presence of dispersoids of aluminides of transition metals and negligible amount of coarse excess phases.

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Osman, Mohamed, Dian Tao Zhang, Yun Xiang Tong, Yu Feng Zheng, and Li Li. "3D FEM Simulation of Multipass ECAP Ti-50.8%Ni at Various Temperatures." Advanced Materials Research 1004-1005 (August 2014): 1204–10. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.1204.

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Equal channel angular pressing (ECAP) is widely studied for its potential to produce ultra-fine grained (UFG) structure in TiNi shape memory alloys (SMA). In the present work, the effect of multipass ECAP parameters on the deformation behavior and strain distribution was investigated, at various deformation temperatures through different planes in the ECAPed billet. Three-dimensional (3D) geometric model with corner angle 120◦was designed by finite element method (FEM) software for ECAPing Ti-50.8%Ni by route Bcin DEFORM-3D software. Two methods were used to quantify deformation homogeneity through various planes in the processed billet, including strain standard deviation (SSD) and inhomogenity index (Ci). The simulation results demonstrate that by increasing ECAP passes, the cumulative average strain can increase and obtain UFG structure, but heterogeneity still exist across planes. In addition, temperature has a remarkable effect on homogeneity distribution .As well as Ciexhibits good results for multipass ECAP at various deformation temperature compared to SSD value.

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Zhang, Diantao, Mohamed Osman, Li Li, Yufeng Zheng, and Yunxiang Tong. "Simulation and Experimental Investigation for the Homogeneity of Ti49.2Ni50.8 Alloy Processed by Equal Channel Angular Pressing." Metals 6, no. 3 (2016): 45. http://dx.doi.org/10.3390/met6030045.

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Journal articles on the topic 'Angular homogeneity'

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