Journal articles: 'Local void'

1

Lindner, U., K. J. Fricke, J. Einasto, and M. Einasto. "Void Hierarchy in the Northern Local Void." Symposium - International Astronomical Union 183 (1999): 185–90. http://dx.doi.org/10.1017/s0074180900132516.

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Empirical studies of the Large–Scale Structure in the nearby Universe come in two complementary modes, namely the investigation of either the distribution of luminous matter or voids: (i) The description of the galaxy and cluster distribution employs correlation functions, clustering analysis, topological methods, et cetera. (ii) The investigation of the empty regions between systems of galaxies uses void probability functions, mean diameters of voids, the compilation of void catalogues, and so forth.

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Tully, R. Brent. "The Local Void is Really Empty." Proceedings of the International Astronomical Union 3, S244 (2007): 146–51. http://dx.doi.org/10.1017/s1743921307013932.

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AbstractAre voids in the distribution of galaxies only places with reduced matter density and low star formation efficiency or are they empty of matter? There is now compelling evidence of expansion away from the Local Void at very high velocities. The motion is most reasonably interpreted as an evacuation of the void, which requires that the void be very large and very empty.

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Rizzi, Luca, R. Brent Tully, Edward J. Shaya, Ehsan Kourkchi, and Igor D. Karachentsev. "DRAINING THE LOCAL VOID." Astrophysical Journal 835, no. 1 (2017): 78. http://dx.doi.org/10.3847/1538-4357/835/1/78.

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Pustilnik, Simon A., Dmitri I. Makarov, and Arina L. Tepliakova. "Nearby void dwarf galaxies: recent results, the ongoing project and prospects." Proceedings of the International Astronomical Union 14, S344 (2018): 396–99. http://dx.doi.org/10.1017/s1743921318006713.

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AbstractProperties of dwarf galaxies formed and evolved in the lowest density environment remain largely unexplored and poorly understood. Especially this concerns the low-mass end (Mbar < 109M⊙). We overview the results of systematic study of a hundred void dwarfs from the nearby Lynx-Cancer void. We describe the ongoing project aiming to form Nearby Void galaxy sample (R < 25 Mpc) over the whole sky. 1354 objects with distances less than 25 Mpc fall within 25 voids delineated by 460 luminous galaxies/groups. The void major sizes range from 13 to 37 Mpc. 1088 of 1354 void galaxies reside deeply in voids, having distances to the nearest luminous neighbour of 2–11 Mpc. 195 nearest void galaxies reside in the Local Volume. We summarize the main statistical properties of the new sample and outline the prospects of study of both, the void dwarf properties and the fine structure of voids.

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Seehaus, Thorsten, Veniamin I. Morgenshtern, Fabian Hübner, Eberhard Bänsch, and Matthias H. Braun. "Novel Techniques for Void Filling in Glacier Elevation Change Data Sets." Remote Sensing 12, no. 23 (2020): 3917. http://dx.doi.org/10.3390/rs12233917.

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The increasing availability of digital elevation models (DEMs) facilitates the monitoring of glacier mass balances on local and regional scales. Geodetic glacier mass balances are obtained by differentiating DEMs. However, these computations are usually affected by voids in the derived elevation change data sets. Different approaches, using spatial statistics or interpolation techniques, were developed to account for these voids in glacier mass balance estimations. In this study, we apply novel void filling techniques, which are typically used for the reconstruction and retouche of images and photos, for the first time on elevation change maps. We selected 6210 km2 of glacier area in southeast Alaska, USA, covered by two void-free DEMs as the study site to test different inpainting methods. Different artificially voided setups were generated using manually defined voids and a correlation mask based on stereoscopic processing of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) acquisition. Three “novel” (Telea, Navier–Stokes and shearlet) as well as three “classical” (bilinear interpolation, local and global hypsometric methods) void filling approaches for glacier elevation data sets were implemented and evaluated. The hypsometric approaches showed, in general, the worst performance, leading to high average and local offsets. Telea and Navier–Stokes void filling showed an overall stable and reasonable quality. The best results are obtained for shearlet and bilinear void filling, if certain criteria are met. Considering also computational costs and feasibility, we recommend using the bilinear void filling method in glacier volume change analyses. Moreover, we propose and validate a formula to estimate the uncertainties caused by void filling in glacier volume change computations. The formula is transferable to other study sites, where no ground truth data on the void areas exist, and leads to higher accuracy of the error estimates on void-filled areas. In the spirit of reproducible research, we publish a software repository with the implementation of the novel void filling algorithms and the code reproducing the statistical analysis of the data, along with the data sets themselves.

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Bland-Hawthorn, J., and S. Sharma. "Void asymmetries in the cosmic web: a mechanism for bulk flows." Proceedings of the International Astronomical Union 11, S308 (2014): 561–70. http://dx.doi.org/10.1017/s1743921316010589.

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AbstractBulk flows of galaxies moving with respect to the cosmic microwave background are well established observationally and seen in the most recent ΛCDM simulations. With the aid of an idealised Gadget-2 simulation, we show that void asymmetries in the cosmic web can exacerbate local bulk flows of galaxies. The {\it Cosmicflows-2} survey, which has mapped in detail the 3D structure of the Local Universe, reveals that the Local Group resides in a “local sheet” of galaxies that borders a “local void” with a diameter of about 40 Mpc. The void is emptying out at a rate of 16 km s-1Mpc-1. In a co-moving frame, the Local Sheet is found to be moving away from the Local Void at ∼ 260 km s-1. Our model shows how asymmetric collapse due to unbalanced voids on either side of a developing sheet or wall can lead to a systematic movement of the sheet. We conjectured that asymmetries could lead to a large-scale separation of dark matter and baryons, thereby driving a dependence of galaxy properties with environment, but we do {\it not} find any evidence for this effect.

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Jones, M. K., M. F. Horstemeyer, and A. D. Belvin. "A Multiscale Analysis of Void Coalescence in Nickel." Journal of Engineering Materials and Technology 129, no. 1 (2006): 94–104. http://dx.doi.org/10.1115/1.2400265.

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An internal state variable void coalescence equation developed by Horstemeyer, Lathrop, Gokhale, and Dighe (2000, Theor. Appl. Fract. Mech., 33(1), pp. 31–47) that comprises void impingement and void sheet mechanisms is updated based on three-dimensional micromechanical simulations and novel experiments. This macroscale coalescence equation, developed originally from two-dimensional finite element simulations, was formulated to enhance void growth. In this study, three-dimensional micromechanical finite element simulations were employed using cylindrical and spherical void geometries in nickel that were validated by experiments. The number of voids, void orientation, and void spacing were all varied and tested and simulated under uniaxial loading conditions. The micromechanical results showed excellent agreement with experiments in terms of void volume fractions versus strain and local void geometry images. Perhaps more importantly, the macroscale internal state variable void coalescence equation did not require a functional form change but just a coefficient value modification.

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Tikhonov, Anton V., and Anatoly A. Klypin. "Voids in the Local Volume: a Limit on Appearance of a Galaxy in a Dark Matter Halo." Proceedings of the International Astronomical Union 3, S244 (2007): 152–56. http://dx.doi.org/10.1017/s1743921307013944.

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AbstractCurrent explanation of the overabundance of dark matter subhalos in the Local Group (LG) indicates that there maybe a limit on mass of a halo, which can host a galaxy. This idea can be tested using voids in the distribution of galaxies: at some level small voids should not contain any (even dwarf) galaxies. We use observational samples complete to MB = −12 with distances less than 8 Mpc to construct the void function (VF): the distribution of sizes of voids empty of any galaxies. There are ~ 30 voids with sizes ranging from 1 to 5 Mpc. We then study the distribution of dark matter halos in very high resolution simulations of the LCDM model. The theoretical VF matches the observations remarkably well only if we use halos with circular velocities larger than 45 ± 10 km/s. This agrees with the Local Group predictions. There are smaller halos in the voids, but they should not produce any luminous matter. Small voids look quite similar to their giant cousins: the density has a minimum at the center of a void and it increases as we get closer to the border. Small nonluminous halos inside the void form a web of tiny filaments. Thus, both the Local Group data and the nearby voids indicate that isolated halos below 45 ± 10 km/s must not host galaxies and that small (few Mpc) voids are truly dark.

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Nasonova, O. G., and I. D. Karachentsev. "Kinematics of the Local cosmic void." Astrophysics 54, no. 1 (2011): 1–14. http://dx.doi.org/10.1007/s10511-011-9153-1.

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10

Moffat, J. W., and D. C. Tatarski. "Cosmological Observations in a Local Void." Astrophysical Journal 453 (November 1995): 17. http://dx.doi.org/10.1086/176365.

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Villata, M. "“Dark energy” in the Local Void." Astrophysics and Space Science 339, no. 1 (2012): 7–12. http://dx.doi.org/10.1007/s10509-012-0994-9.

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Lindner, Ulrich, Klaus J. Fricke, Jaan Einasto, and Maret Einasto. "The Distribution of BCDGs in Voids." Highlights of Astronomy 11, no. 1 (1998): 111–12. http://dx.doi.org/10.1017/s1539299600020128.

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Generally the density of the environment is important for the formation and evolution of galaxies: bright elliptical galaxies reside in the centers of galaxy clusters, whereas late type galaxies preferentially populate small groups, filaments or the outskirts of rich clusters of galaxies. Furthermore, fainter galaxies define smaller voids than bright galaxies. Our investigation of void catalogues in the Northern Local Void region shows that large voids are interlaced by systems of faint galaxies dividing them into smaller subvoids (Lindner et al., 1995). This void hierarchy is an important property of the Large Scale Structure in the nearby Universe and can help to solve problems concerning the distribution of dwarf galaxies and BCDGs.

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Lee, Kyo-Moon, Soo-Jeong Park, Tianyu Yu, Seong-Jae Park, and Yun-Hae Kim. "Experimental prediction of internal defects according to defect area on NDI via water absorption behavior." International Journal of Modern Physics B 35, no. 14n16 (2021): 2140021. http://dx.doi.org/10.1142/s021797922140021x.

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This study analyzed the relationship between the defect area identified through a C-scan and the void volume in CF-PEKK composite materials through the water absorption behavior to predict the void volume. The water absorption content varies with the defect area; however, the defect area identified through a C-scan and the water absorption content did not show a proportional relationship. This is because voids are distributed in the through-thickness. The results indicated that the absorption behavior could be used to predict the void volume. Irreversible absorption was found to be independent of the void volume. Further, no matrix degradation was seen with water immersion at [Formula: see text]C; however, some local swelling was seen.

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Lindner, U., K. J. Fricke, J. Einasto, and M. Einasto. "Faint Structures in Low Density Regions of the Nearby Universe." Symposium - International Astronomical Union 183 (1999): 256. http://dx.doi.org/10.1017/s0074180900132735.

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We present an investigation of the galaxy distribution in the huge underdense region between the Hercules, Coma and Local Superclusters, the so-called Northern Local Void (NLV), using void statistics (for details refer to Lindner et al. this Volume). Reshift data for galaxies and poor clusters of galaxies are available in low and high density regions as well. Samples of galaxies with different morphological type and various luminosity limits have been studied separately and void catalogues have been compiled from three different luminosity limited galaxy samples for the first time. Voids have been found using the empty sphere method which has the potential to detect and describe subtle structures in the galaxy distribution. Our approach is complementary to most other methods usually used in Large–Scale Structure studies.

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Tully, R. Brent, Daniel Pomarède, Romain Graziani, Hélène M. Courtois, Yehuda Hoffman, and Edward J. Shaya. "Cosmicflows-3: Cosmography of the Local Void." Astrophysical Journal 880, no. 1 (2019): 24. http://dx.doi.org/10.3847/1538-4357/ab2597.

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Tomita, K. "A local void and the accelerating Universe." Monthly Notices of the Royal Astronomical Society 326, no. 1 (2001): 287–92. http://dx.doi.org/10.1046/j.1365-8711.2001.04597.x.

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Xie, L., L. Gao, and Q. Guo. "The Local Void: for or against CDM?" Monthly Notices of the Royal Astronomical Society 441, no. 2 (2014): 933–38. http://dx.doi.org/10.1093/mnras/stu513.

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Banabic, Dorel, and Abdolvahed Kami. "Applications of the Gurson’s model in sheet metal forming." MATEC Web of Conferences 190 (2018): 01002. http://dx.doi.org/10.1051/matecconf/201819001002.

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Recent advances in the modelling of metals encompass modelling of metals structural inhomogeneity, damage, porosity, twinning/untwining and non-local and second order effects. This presentation is focused on modelling the void growth in ductile fractures. The growth and coalescence of microscopic voids are the main mechanisms in ductile fracture of bulk metallic parts. In sheet metals, ductile fracture is preceded by necking during which existing voids do not have significant growth. However, necking is highly sensitive to plastic flow direction which in turn is sensitive to the presence of voids. Also, under biaxial strain loading, the final fracture in the necking region is still controlled by void growth; hence an accurate fracture prediction is crucial for crash simulations. Finally, in super-plastic sheet forming, void growth and coalescence may precede or accompany necking. Therefore, there is as increasing interest in modelling of voids in the sheet metals. As an application, we show how the predictions of some forming limit curves (FLCs) can be affected by accurate simulation of voids growth.

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Xiong, Rui, Wenyu Jiang, Fa Yang, Kehong Li, Bowen Guan, and Hua Zhao. "Investigation of Voids Characteristics in an Asphalt Mixture Exposed to Salt Erosion Based on CT Images." Materials 12, no. 22 (2019): 3774. http://dx.doi.org/10.3390/ma12223774.

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The performance of an asphalt mixture will deteriorate under the condition of salt erosion, but there are different opinions on the mechanism of deterioration. Few studies have focused on the relation between the change of void characteristics and performance deterioration of an asphalt mixture exposed to salt erosion. To explore the relation between the air voids characteristics of an asphalt mixture and mechanical damage under salt erosion, the mechanical damage in an asphalt mixture was measured by splitting strength. The asphalt mixture specimens, immersion solutions, asphalt mortar, and aggregate were scanned with CT technology. To segment the voids, the Otsu method was used over asphalt mortar and solution range of CT values. A three-dimensional reconstruction of the CT image was performed with Mimics 20 software to calculate the asphalt mixture’s void characteristics. On this basis, the relationships between the change in void characteristics and splitting strength were analyzed. The results showed that the ideal calculated void fraction can be obtained by threshold segmentation of the image void/asphalt mortar interface with the local CT value Otsu method. Under the salt corrosion environment, the increase of open voids of an asphalt mixture is linearly correlated with the decrease of splitting strength, while salts’ crystallization in the open voids produces crystallization pressure, accelerating the volume growth of open voids. The early damage of an asphalt mixture suffered from the salt may be mainly physical damage. These results can provide a useful reference for the performance of damage research on asphalt mixtures in salt enrichment areas.

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Lian, H. Y., G. Noghrehkar, A. M. C. Chan, and M. Kawaji. "Effect of Void Fraction on Vibrational Behavior of Tubes in Tube Bundle Under Two-Phase Cross Flow." Journal of Vibration and Acoustics 119, no. 3 (1997): 457–63. http://dx.doi.org/10.1115/1.2889745.

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The effects of local two-phase flow parameters on the vibrational behavior of tubes have been studied in an in-line 5 × 20 tube bundle subjected to air-water cross-flow. One of the tubes was flexibly mounted and instrumented for vibration measurement and the others were rigid. Parameters obtained include local void fraction fluctuations, RMS amplitude of void fraction fluctuations, void fraction distributions across the tube bundle, flow regimes based on probability density function of void fraction signals, damping ratio, and tube vibration response as a function of mass flux, void fraction and dynamic pressure. Damping and tube vibration amplitude in two-phase flow have been found to be closely related to the RMS amplitudes of the local void fraction fluctuations and dynamic pressure fluctuations, respectively.

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ANH, HO LE TUAN, and SHAO CHIN CINDY NG. "COSMOLOGICAL CONSTRAINTS ON THE LOCAL VOID WITH THE UNION SUPERNOVA COMPILATION." International Journal of Modern Physics A 24, no. 18n19 (2009): 3531–37. http://dx.doi.org/10.1142/s0217751x09047156.

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A simple inhomogeneous cosmological model with a local void is constrained with the latest Union supernova compilation. To fit the supernova data, a large local void on the scales of 1 Gpc is found, contrary to the small scales of 200 Mpc in the previous finding. A more realistic inhomogeneous cosmological model may be required to fit the supernova data. Alternatively, a clumpy universe with α < 1 can fit the supernova data with reduced local void scales.

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Chen, Feng Yun, and Wei Min Liu. "Research on Measurement of Void Fraction for Vertically Rising Pipes by Optical Fiber Probe." Advanced Materials Research 361-363 (October 2011): 671–75. http://dx.doi.org/10.4028/www.scientific.net/amr.361-363.671.

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A way of measuring the average cross-sectional void fraction for vertically rising oil pipes by using closing valves quickly and optical fiber probe has been researched. Experiments were performed in oil-gas two-phase flow and the range of the average void fraction is 0.1～0.5. The relationship between average cross-sectional void fraction of a oil-gas two-phase flow and pipe’s center void fraction in vertically rising oil pipes, for different pipe diameters and varying oil flow, is obtained. An exponential model of average void fraction is also obtained with reference to Bankoff’s[1] variable density model. It is found that local void fraction reduces from center in radial direction and the local void fraction maximum value appears in the pipe’s center.

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Umminger, Klaus, Simon Schollenberger, Lars Dennhardt, Holger Schmidt, Oliver Herbst, and Ingo Ganzmann. "Development of procedures for local void fraction measurements." Nuclear Engineering and Design 336 (September 2018): 163–70. http://dx.doi.org/10.1016/j.nucengdes.2018.05.014.

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Teyssedou, A., A. Tapucu, and M. Lortie. "Impedance probe to measure local void fraction profiles." Review of Scientific Instruments 59, no. 4 (1988): 631–38. http://dx.doi.org/10.1063/1.1139847.

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Tully, R. Brent, Edward J. Shaya, Igor D. Karachentsev, et al. "Our Peculiar Motion Away from the Local Void." Astrophysical Journal 676, no. 1 (2008): 184–205. http://dx.doi.org/10.1086/527428.

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Kukuryk, Marcin. "Experimental and FEM Analysis of Void Closure in the Hot Cogging Process of Tool Steel." Metals 9, no. 5 (2019): 538. http://dx.doi.org/10.3390/met9050538.

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In the present study, a new complex methodology for the analysis the closure of voids and a new forging system were developed and tested. The efficiency of the forging parameters and the effective geometric shapes of anvils to improve void closure were determined. A new cogging process provided a complete closure of an ingot’s axial defects, as confirmed by experimental tests. The evolution behavior of these defects with different sizes was investigated during the hot cogging process by means of the professional plastic forming software Deform-3D. A comprehensive procedure was developed using the finite-element method (FEM) for the three-dimensional cogging process and laboratory experimentation to predict the degree of void closure. The hot multi-pass cogging process was used to eliminate void defects in the forgings so as to obtain sound products. In the compression process, the effects of the reduction ratio and forging ratio, the void size, and the types of anvil were discussed to obtain the effective elimination of a void. For the purpose of the assessment of the effectiveness of the void closure process, the following indices were introduced: the relative void volume evolution ratio, the relative void diameter ratio, and the internal void closure evaluation index. Moreover, the void closure process was assessed on the basis of stress triaxiality, hydrostatic stress, forging ratio, value of local effective strain around the void, and critical reduction ratio. The results of this research were complemented by experiments predicting the formation of fractures in the regions near the void and in the volume of the forging in the course of the cogging process. The comparison between the predicted and the experimental results showed a good agreement.

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Ladani, Leila Jannesari, and Abhijit Dasgupta. "Effect of Voids on Thermomechanical Durability of Pb-Free BGA Solder Joints: Modeling and Simulation." Journal of Electronic Packaging 129, no. 3 (2006): 273–77. http://dx.doi.org/10.1115/1.2753911.

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The effect of process-induced voids on the durability of Sn–Pb and Pb-free solder interconnects in electronic products is not clearly understood. Experimental studies have provided conflicting ambiguous conclusions, showing that voids may sometimes be detrimental to reliability, but they may sometimes even increase the reliability of joints, depending on the size and location. Because of the higher level of process-induced voids in Pb-free solders, this debate is more intensified in Pb-free joints. This study presents finite element analysis (FEA) of the influence of void size, location, and spacing on the durability of Pb-free solders. A three-dimensional, global-local, viscoplastic FEA is conducted for a CTBAG132 assembly under thermal cycling. The displacement result of the global FEA at the top and bottom of the critical ball is used as the boundary condition in a local model, which focuses on the details of a single ball of the CTBGA package under temperature cycling. Parametric study is conducted to model a solder ball with voids of different sizes and locations. The maximum void area fraction modeled is from 1% to 49% of the ball area. An energy-partitioning model for cyclic creep-fatigue damage is used to estimate the damage and to monitor the trends as the size and location of voids are varied. Potential sites for maximum damage and crack initiation are identified. FEA results show that as void size increases up to about 15% of the area fraction of the ball, durability increases. For voids bigger than that, the durability starts to decrease. This study also confirms that as voids are located closer to the damage initiation site and the propagation path, their lifespan decreases.

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Sysyn, Mykola, Michal Przybylowicz, Olga Nabochenko, and Jianxing Liu. "Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers." Sustainability 13, no. 14 (2021): 7740. http://dx.doi.org/10.3390/su13147740.

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Unsupported sleepers or void zones in ballasted tracks are one of the most recent and frequent track failures. The void failures have the property of intensive development that, without timely maintenance measures, can cause the appearance of cost-expensive local instabilities such as subgrade damages. The reason for the intensive void development lies in the mechanics of the sleeper and ballast bed interaction. The particularity of the interaction is a dynamic impact that occurs due to void closure. Additionally, void zones cause inhomogeneous ballast pressure distribution between the void zone and fully supported neighbour zones. The present paper is devoted to studying the mechanism of the sleeper–ballast dynamic impact in the void zone. The results of experimental in situ measurements of rail deflections showed the significant impact accelerations in the zone even for lightweight slow vehicles. A simple three-beam numerical model of track and rolling stock interaction has shown dynamic interaction similar to the experimental measurements. Moreover, the model shows that the sleeper accelerations are more than 3 times higher than the corresponding wheel accelerations and the impact point appears before the wheel enters the impact point. The analysis of ballast loadings shows the specific impact behaviour in combination with the quasistatic part that is different for void and neighbour zones, which are characterised by high ballast pre-stressed conditions. The analysis of void size influence demonstrates that the maximal impact loadings and maximal wheel and sleeper accelerations appear at a certain void depth, after which the values decrease. The ballast quasistatic loading analysis indicates an increase of more than 2 times in the ballast loading in neighbour zones for long voids and almost full quasistatic unloading for short-length voids. However, the used imitation model cannot explain the nature of the dynamic impact. The mechanism of the void impact is clearly explained by the analytic solution using a simple clamped beam. A simplified analytical expression of the void impact velocity shows that it is linearly related to the wheel speed and loading. The comparison to the numerically simulated impact velocities shows a good agreement and the existence of the void depth with the maximal impact. An estimation of the long-term influences for the cases of normal sleeper loading, high ballast pre-stress and quasistatic loading in the neighbour zones and high impact inside the void is performed.

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Sauter, Anne I., and W. D. Nix. "A study of stress-driven diffusive growth of voids in encapsulated interconnect lines." Journal of Materials Research 7, no. 5 (1992): 1133–43. http://dx.doi.org/10.1557/jmr.1992.1133.

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Stress-driven diffusive growth of voids in encapsulated interconnect lines is studied. By calculating the rate of growth of a single void in a passivated line subjected to an initial hydrostatic tension stress and by assuming that failure occurs when the void reaches a critical size, a model for failure of encapsulated interconnect lines by stress voiding can be developed. The model for the prediction of void growth and failure is based on two limiting kinds of void growth. In one limit, which applies at short times, radial displacements occur by diffusional flow processes around the growing void and relax the local hydrostatic tension stress. In the long time limit, vacancies flow to the void from distant parts of the line by diffusion along grain boundaries, thereby relaxing the stress in a growing section of the line. A model based on a combination of these behaviors leads to a failure law for aluminum lines of the form tfσ2/d = 1019.2 exp(Q/RT) where tf is the failure time in seconds, σ is the initial hydrostatic tension stress in the line in Pa, d is the grain size in meters, and the activation energy, Q = 80.9 kJ/mol, is close to that for grain boundary diffusion in aluminum. The model predictions appear to be in good agreement with the few experiments on stress voiding that have been conducted.

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Xiao, Xiu, Qingzi Zhu, Shao-Wen Chen, Mamoru Ishii, Yajun Zhang, and Haijun Jia. "Experimental Study on Interfacial Area Transport of Two-Phase Flow under Vibration Conditions." Science and Technology of Nuclear Installations 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/5809541.

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An experimental study on air-water two-phase flow under vibration condition has been conducted using double-sensor conductivity probe. The test section is an annular geometry with hydraulic diameter of 19.1 mm. The vibration frequency ranges from 0.47 Hz to 2.47 Hz. Local measurements of void fraction, interfacial area concentration (IAC), and Sauter mean diameter have been performed along one radius in the vibration direction. The result shows that local parameters fluctuate continuously around the base values in the vibration cycle. Additional bubble force due to inertia is used to explain lateral bubble motions. The fluctuation amplitudes of local void fraction and IAC increase significantly with vibration frequency. The radial distribution of local parameters at the maximum vibration displacement is specifically analyzed. In the void fraction and IAC profiles, the peak near the inner wall is weakened or even disappearing and a strong peak skewed to outer wall is gradually observed with the increase of vibration frequency. The nondimensional peak void fraction can reach a maximum of 49% and the mean relative variation of local void fraction can increase to more than 29% as the vibration frequency increases to 2.47 Hz. But the increase of vibration frequency does not bring significant change to bubble diameter.

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Morris, Denis, Alberto Teyssedou, Jean Lapierre, and Altan Tapucu. "Optical fiber probe to measure local void fraction profiles." Applied Optics 26, no. 21 (1987): 4660. http://dx.doi.org/10.1364/ao.26.004660.

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Nicholls, David C., Helmut Jerjen, Michael A. Dopita, and Hassan Basurah. "NEBULAR METALLICITIES IN TWO ISOLATED LOCAL VOID DWARF GALAXIES." Astrophysical Journal 780, no. 1 (2013): 88. http://dx.doi.org/10.1088/0004-637x/780/1/88.

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Wang, Tie-Jun. "Improved local void growth ratio criterion for ductile fracture." International Journal of Fracture 57, no. 1 (1992): R3—R6. http://dx.doi.org/10.1007/bf00013011.

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Yu, Bo. "Impact of the local void on the cosmological parameters." Journal of Cosmology and Astroparticle Physics 2013, no. 03 (2013): 013. http://dx.doi.org/10.1088/1475-7516/2013/03/013.

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Iwata, I., and P. Chamaraux. "Is the far border of the Local Void expanding?" Astronomy & Astrophysics 531 (June 20, 2011): A87. http://dx.doi.org/10.1051/0004-6361/201116687.

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Niordson, Christian F. "Void growth to coalescence in a non-local material." European Journal of Mechanics - A/Solids 27, no. 2 (2008): 222–33. http://dx.doi.org/10.1016/j.euromechsol.2007.07.001.

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Großer, Stephan, Martina Werner, and Christian Hagendorf. "Microstructure of Void Formation Stages at Local Rear Contacts." Energy Procedia 77 (August 2015): 701–6. http://dx.doi.org/10.1016/j.egypro.2015.07.100.

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Sysyn, Mykola, Olga Nabochenko, and Vitalii Kovalchuk. "Experimental investigation of the dynamic behavior of railway track with sleeper voids." Railway Engineering Science 28, no. 3 (2020): 290–304. http://dx.doi.org/10.1007/s40534-020-00217-8.

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Abstract The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids. The increased dynamic loading in the voided zone and the ballast contact conditions cause the accelerated growth of the settlements in the voided zones, which results in the appearance of local instabilities like ballast breakdown, white spots, subgrade defects, etc. The recent detection and quantification of the sleeper voids with track-side and onboard monitoring can help to avoid or delay the development of local instabilities. The present paper is devoted to the study of the dynamic behavior of railway track with sleeper voids in the ballast breakdown zone. The result of the experimental track-side measurements of rail acceleration and deflection is presented. The analysis shows the existence of the dynamic impact during wheel entry in the voided zone. However, the measured dynamic impact is subjected to the bias of the track-side measurement method. Both the mechanism of the impact and the measurement aspects are explained by using the one-beam model on viscoelastic foundation. The void features in the dynamic behavior are analyzed for the purpose of track-side and onboard monitoring. A practical method of the void parameter quantification is proposed.

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Fan, Xunli, and Feifei Du. "An Efficient Bypassing Void Routing Algorithm for Wireless Sensor Network." Journal of Sensors 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/686809.

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Since the sensor node’s distribution in a wireless sensor network (WSN) is irregular, geographic routing protocols using the greedy algorithm can cause local minima problem. This problem may fail due to routing voids and lead to failure of data transmission. Based on the virtual coordinate mapping, this paper proposes an efficient bypassing void routing protocol to solve the control packet overhead and transmission delay in routing void of WSN, which is called EBVRPVCM. The basic idea is to transfer the random structure of void edge to a regular one through mapping the coordinates on a virtual circle. In EBVRPVCM, some strategies, executed in different regions, are selected through virtual coordinates to bypass routing void efficiently. The regular edge is established by coordinate mapping that can shorten the average routing path length and decrease the transmission delay. The virtual coordinate mapping is not affected by the real geographic node position, and the control packet overhead can be reduced accordingly. Compared with RGP and GPSR, simulation results demonstrate that EBVRPVCM can successfully find the shortest routing path with higher delivery ratio and less control packet overhead and energy consumption.

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Chang, Ching-Ray, and Jyh-Shinn Yang. "Magnetization Configurations and Magnetization Reversal of Thin Submicron Permalloy Ellipses with Structural Defects." Journal of Nanoscience and Nanotechnology 8, no. 6 (2008): 2901–4. http://dx.doi.org/10.1166/jnn.2008.18316.

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We have studied the magnetic switching behavior of thin elliptical permalloy films with structural defects by micromagnetic simulations. The nonmagnetic void was found to tend to pin the adjacent magnetic moment, which alters the local equilibrium magnetization patterns and modifies the switching behavior of magnetization. In particular, for the case of voids close to the edge, the curling effect of voids is significant, and induces the occurrence of the multiple-stage modes of magnetization reversal, resulting in a high switching field.

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Ishikawa, Takashi, T. Ishiguro, N. Yukawa, H. Yoshida, and N. Fujita. "Experimental Approach for Investigation of Micro Void Behavior on Dual Phase Steel during Plastic Deformation." Key Engineering Materials 535-536 (January 2013): 393–96. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.393.

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In this research, micro void behavior of DPS, which has different phase volume fraction, is investigated experimentally. Prepared specimens have different amount of alloy element and heat treatment condition. Although both these specimens have almost the same strength and total elongation, these showed quite different local elongations, hole expanding ratio and bending ductility. In order to observe micro void behavior specimens, that have different strain levels, are prepared. These sectional areas are observed by laser microscope after cutting and polishing. The change ratio of micro void volume fraction of DPS, which showed high local ductility, is lower than that of the other DPS. Concerning low ductility DPS, small size void (less than 3µm diameter) increases rapidly not only at grain boundary but in the ferrite grain, especially at initial stage of deformation. On the other hand, nucleation of micro void of high ductility DPS is inhibited.

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Lewis, Christine S., Jordan Katz, Maribel I. Baker, Peter R. Supronowicz, Elise Gill, and Ronald R. Cobb. "Local Antibiotic Delivery with Bovine Cancellous Chips." Journal of Biomaterials Applications 26, no. 4 (2010): 491–506. http://dx.doi.org/10.1177/0885328210375729.

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Infected bone defects and osteomyelitis are encountered frequently in trauma cases. Currently, the standard of care for osteomyelitis cases is prolonged systemic antibiotic therapy and implantation of antibiotic carrier beads. However, this method requires a secondary surgery to remove the beads after the infection has cleared. In the present study a common bone void filler was investigated for its ability to be infused with an antibiotic. This study demonstrates that the xenograft material tested can be loaded with gentamicin and release clinically relevant levels of the drug for at least 14 days in vitro allowing for the inhibition of bacterial growth on the graft. This study also demonstrates that the levels of gentamicin released did not have an adverse effect on primary osteoblast cell proliferation or ability to generate alkaline phosphatase. This bone void filler may represent a viable alternative to current methods of local antibiotic delivery in orthopedic applications.

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Sysyn, Mykola, Michal Przybylowicz, Olga Nabochenko, and Lei Kou. "Identification of Sleeper Support Conditions Using Mechanical Model Supported Data-Driven Approach." Sensors 21, no. 11 (2021): 3609. http://dx.doi.org/10.3390/s21113609.

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The ballasted track superstructure is characterized by a relative quick deterioration of track geometry due to ballast settlements and the accumulation of sleeper voids. The track zones with the sleeper voids differ from the geometrical irregularities with increased dynamic loading, high vibration, and unfavorable ballast-bed and sleeper contact conditions. This causes the accelerated growth of the inhomogeneous settlements, resulting in maintenance-expensive local instabilities that influence transportation reliability and availability. The recent identification and evaluation of the sleeper support conditions using track-side and on-board monitoring methods can help planning prevention activities to avoid or delay the development of local instabilities such as ballast breakdown, white spots, subgrade defects, etc. The paper presents theoretical and experimental studies that are directed at the development of the methods for sleeper support identification. The distinctive features of the dynamic behavior in the void zone compared to the equivalent geometrical irregularity are identified by numeric simulation using a three-beam dynamic model, taking into account superstructure and rolling stock dynamic interaction. The spectral features in time domain in scalograms and scattergrams are analyzed. Additionally, the theoretical research enabled to determine the similarities and differences of the dynamic interaction from the viewpoint of track-side and on-board measurements. The method of experimental investigation is presented by multipoint track-side measurements of rail-dynamic displacements using high-speed video records and digital imaging correlation (DIC) methods. The method is used to collect the statistical information from different-extent voided zones and the corresponding reference zones without voids. The applied machine learning methods enable the exact recent void identification using the wavelet scattering feature extraction from track-side measurements. A case study of the method application for an on-board measurement shows the moderate results of the recent void identification as well as the potential ways of its improvement.

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Mo̸rch, Knud A. "Cavitation Nuclei and Bubble Formation—A Dynamic Liquid-Solid Interface Problem." Journal of Fluids Engineering 122, no. 3 (2000): 494–98. http://dx.doi.org/10.1115/1.1287506.

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A model of the formation of cavitation nuclei is developed assuming local detachment of the liquid at locations of concave solid surface topography. The detachment is attributed to diffusion of gas molecules into the interfacial liquid, where the liquid-solid bonds are strained due to interfacial tension in the liquid. Calculations indicate that attached interfacial voids may grow into stabilized cavitation nuclei as a consequence of broad-band resonance, excited by external sources of noise or vibration in the whole range of frequencies up to the MHz regime. The gas content in the liquid and the amplitude and frequency of the sound field determine a balance between rectified diffusion of gas into the void and diffusion out of it due to the excess pressure in the void. In strong acoustic fields and in supersaturated liquids the voids may grow into bubbles that detach and form free gas bubbles. [S0098-2202(00)01503-0]

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Kreckel, Kathryn, Jacqueline H. van Gorkom, Burcu Beygu, et al. "The Void Galaxy Survey: Galaxy Evolution and Gas Accretion in Voids." Proceedings of the International Astronomical Union 11, S308 (2014): 591–99. http://dx.doi.org/10.1017/s1743921316010644.

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AbstractVoids represent a unique environment for the study of galaxy evolution, as the lower density environment is expected to result in shorter merger histories and slower evolution of galaxies. This provides an ideal opportunity to test theories of galaxy formation and evolution. Imaging of the neutral hydrogen, central in both driving and regulating star formation, directly traces the gas reservoir and can reveal interactions and signs of cold gas accretion. For a new Void Galaxy Survey (VGS), we have carefully selected a sample of 59 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS at distances of ∼100 Mpc, and pursued deep UV, optical, Hα, IR, and HI imaging to study in detail the morphology and kinematics of both the stellar and gaseous components. This sample allows us to not only examine the global statistical properties of void galaxies, but also to explore the details of the dynamical properties. We present an overview of the VGS, and highlight key results on the HI content and individually interesting systems. In general, we find that the void galaxies are gas rich, low luminosity, blue disk galaxies, with optical and HI properties that are not unusual for their luminosity and morphology. We see evidence of both ongoing assembly, through the gas dynamics between interacting systems, and significant gas accretion, seen in extended gas disks and kinematic misalignments. The VGS establishes a local reference sample to be used in future HI surveys (CHILES, DINGO, LADUMA) that will directly observe the HI evolution of void galaxies over cosmic time.

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Mebold, Ulrich, Jürgen Kerp, and Peter M. W. Kalberla. "Radio, Millimeter and Infrared Observations of the Local Hot Bubble and Its Environment." International Astronomical Union Colloquium 166 (1997): 199–210. http://dx.doi.org/10.1017/s0252921100070986.

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AbstractWe present a definition of the local void of neutral gas from observations in the radio frequency window. We question the concept of the Local Bubble in sense of a more or less spherical volume which is surrounded by a shell of denser gas. The concept of the Local Bubble is challenged by the discovery of numerous neutral, dense clouds inside the local void. The search for a “shell” around the suspected Bubble has resulted only in inconclusive findings so far. The sample of high latitude molecular clouds illustrates the situation particularly well. The statistical properties of their spatial distribution, e.g. the mean distance, seem to fit very nicely to the spatial extent of the Local Bubble. But a more detailed investigation shows that the concept of a bubble – in particular an expanding bubble – is not supported. We suggest that the local void is nothing more than a typical place in an interarm region of our Galaxy.Finally, a discussion of the high latitude boundary of the local void does not give strong evidence for the concept of a bubble, that has once been in rapid expansion and is still showing signs of interaction with its environment. However, indications for interactions of IVCs or HVCs with their surroundings are found. These hint at the presence of a gaseous disk which is much more vertically extended than previously believed, or at a Galactic wind which may be blowing from the Galactic neighbourhood of the Sun.

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Haslbauer, Moritz, Indranil Banik та Pavel Kroupa. "The KBC void and Hubble tension contradict ΛCDM on a Gpc scale − Milgromian dynamics as a possible solution". Monthly Notices of the Royal Astronomical Society 499, № 2 (2020): 2845–83. http://dx.doi.org/10.1093/mnras/staa2348.

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ABSTRACT The KBC void is a local underdensity with the observed relative density contrast δ ≡ 1 − ρ/ρ0 = 0.46 ± 0.06 between 40 and 300 Mpc around the Local Group. If mass is conserved in the Universe, such a void could explain the 5.3σ Hubble tension. However, the MXXL simulation shows that the KBC void causes 6.04σ tension with standard cosmology (ΛCDM). Combined with the Hubble tension, ΛCDM is ruled out at 7.09σ confidence. Consequently, the density and velocity distribution on Gpc scales suggest a long-range modification to gravity. In this context, we consider a cosmological MOND model supplemented with $11 \, \rm {eV}/c^{2}$ sterile neutrinos. We explain why this νHDM model has a nearly standard expansion history, primordial abundances of light elements, and cosmic microwave background (CMB) anisotropies. In MOND, structure growth is self-regulated by external fields from surrounding structures. We constrain our model parameters with the KBC void density profile, the local Hubble and deceleration parameters derived jointly from supernovae at redshifts 0.023−0.15, time delays in strong lensing systems, and the Local Group velocity relative to the CMB. Our best-fitting model simultaneously explains these observables at the $1.14{{\ \rm per\ cent}}$ confidence level (2.53σ tension) if the void is embedded in a time-independent external field of ${0.055 \, a_{_0}}$. Thus, we show for the first time that the KBC void can naturally resolve the Hubble tension in Milgromian dynamics. Given the many successful a priori MOND predictions on galaxy scales that are difficult to reconcile with ΛCDM, Milgromian dynamics supplemented by $11 \, \rm {eV}/c^{2}$ sterile neutrinos may provide a more holistic explanation for astronomical observations across all scales.

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Gao, Qun. "Performance of Transient Temperature in Hot Spot Ignition." Applied Mechanics and Materials 575 (June 2014): 425–30. http://dx.doi.org/10.4028/www.scientific.net/amm.575.425.

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This work presents a method to estimate probability initiating combustion and detonation by temperature load in void in energetic material. When a void is compressed its volume decreases and the temperature in the void increases. The local thermal source due to the void deformation in energetic material forms a temperature load which may initiate combustion and detonation. The temperature-time history in the void was called temperature load in this work. Its peak value and holding time are the necessary and sufficient condition initiating combustion or detonation of energetic material surrounding the void. Comparing with the energy acted on the unit area of hot spot, the performance of transient temperature which can better serve to reflect the physical essence in ignition. The main object of this work is to study transmitting process of temperature load from void to energetic material and probability initiating combustion and detonation by temperature load in void.

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Liu, Weiling, Chao Tan, and Feng Dong. "Local characteristic of horizontal air–water two-phase flow by wire-mesh sensor." Transactions of the Institute of Measurement and Control 40, no. 3 (2016): 746–61. http://dx.doi.org/10.1177/0142331216665689.

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Two-phase flow widely exists in many industries. Understanding local characteristics of two-phase flow under different flow conditions in piping systems is important to design and optimize the industrial process for higher productivity and lower cost. Air–water two-phase flow experiments were conducted with a 16×16 conductivity wire-mesh sensor (WMS) in a horizontal pipe of a multiphase flow facility. The cross-sectional void fraction time series was analysed by the probability density function (PDF), which described the void fraction fluctuation at different flow conditions. The changes and causes of PDFs during a flow regime transition were analysed. The local structure and flow behaviour were characterized by the local flow spectrum energy analysis and the local void fraction distribution (horizontal, vertical and radial direction) analysis. Finally, three-dimensional transient flow fluctuation energy evolution and characteristic scale distribution based on wavelet analysis of air–water two-phase flow were presented, which revealed the structural features of each phase in two-phase flow.

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Felleman, Fred, and Sally Ann Lentz. "Filling the Void: Local Control of Oil Spill Prevention Efforts." International Oil Spill Conference Proceedings 1999, no. 1 (1999): 383–88. http://dx.doi.org/10.7901/2169-3358-1999-1-383.

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ABSTRACT This paper examines the implementation of OPA 90 in the context of its mandates to determine if the roles undertaken by federal, state and local entities have been effective in furthering marine environmental protection on the local level and makes recommendations for increasing pollution prevention. The analysis reveals that the federal government—through the work of the Coast Guard—has not been successful in implementing the pollution prevention provisions of OPA. This has resulted in some states exercising their authority under OPA to address issues of local concern as regards shipping and potential oil spills. Where States have stepped in to fill the void; they are often faced with industry and federal government opposition or recalcitrance. OPA's PWS RCAC provides a model for cooperative relationships between government, industry and the public to address local concerns. We conclude that the RCAC model should be extended to other regions of high volume shipping activity and that the GAO should undertake an investigation of the Coast Guard's Marine Environmental Protection and Compliance Programs for the purpose of identifying the obstacles to timely and effective implementation of OPA, and for developing a strategy for overcoming those obstacles.

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Journal articles on the topic 'Local void'

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