Journal articles: 'Density gradient technique'

1

Gölander, C. G., Karin Caldwell, and Y. S. Lin. "A new technique to prepare gradient surfaces using density gradient solutions." Colloids and Surfaces 42, no. 1 (January 1989): 165–72. http://dx.doi.org/10.1016/0166-6622(89)80084-8.

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Kenner, T., M. Moser, and W. Mohl. "Arteriovenous Difference of the Blood Density in the Coronary Circulation." Journal of Biomechanical Engineering 107, no. 1 (February 1, 1985): 34–40. http://dx.doi.org/10.1115/1.3138517.

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The mechanical oscillator technique permits determining blood density continuously with high accuracy. Using this technique arteriovenous density gradients were recorded in the coronary vascular bed of anesthetized dogs. It was found that the coronary sinus blood has a higher density than arterial blood due to the loss of filtered fluid in the microcirculation. The amount of fluid loss corresponds to the lymph flow in the myocardium. Increase of venous pressure leads to an increase of the density gradient. Intermittent coronary sinus occlusion (ICSO) surprisingly leads to a reduction of the density gradient. Injection of osmotically hypertensive fluids influences the arteriovenous gradient by shifting extravascular fluid into the blood. The method permits the determination of filtration coefficients and to estimate the tissue volume available for fluid exchange.

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Gay, Nicolas, Takoua Lamouchi, Franck Agostini, Catherine A. Davy, and Frédéric Skoczylas. "Hydrogen diffusion through polymer membranes." MATEC Web of Conferences 322 (2020): 01044. http://dx.doi.org/10.1051/matecconf/202032201044.

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This experimental study determines H2 transfer properties of High Density PolyEthylene (HDPE) or epoxy membranes. Two different techniques are compared. The pressure gradient technique is analyzed for permeability or diffusion. Results show that the main phenomenon involved is diffusion. The second technique involves a gas concentration gradient. Although implying significantly slower kinetics, this classical technique is consistent with results obtained with the faster pressure gradient technique.

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Cabanis, ALICE, BERNARD Gressier, SOPHIE Lebegue, CLAUDE Brunet, THIERRY Dine, MICHEL Luyckx, MICHELINE Cazin, and JEAN CLAUDE Cazin. "A rapid density gradient technique for separating polymorphonuclear granulocytes." APMIS 102, no. 1-6 (January 1994): 119–21. http://dx.doi.org/10.1111/j.1699-0463.1994.tb04855.x.

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Khare, Saurabh, and Praveen Kaushik. "Gradient nuclear norm minimization-based image filter." Modern Physics Letters B 33, no. 19 (July 8, 2019): 1950214. http://dx.doi.org/10.1142/s0217984919502142.

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Designing an efficient filtering technique is an ill-posed problem especially for image affected from high density of noise. The majority of existing techniques suffer from edge degradation and texture distortion issues. Therefore, in this paper, an efficient weighted nuclear norm minimization (NNM)-based filtering technique to preserve the edges and texture information of filtered images is proposed. The proposed technique significantly improves the quantitative improvements on the low rank approximation of nonlocal self-similarity matrices to deal with the overshrink problem. Extensive experiments reveal that the proposed technique preserves edges and texture details of filtered image with lesser number of visual artifacts on visual quality. The proposed technique outperforms the existing techniques over the competitive filtering techniques in terms of structural similarity index metric (SSIM), peak signal-to-noise ratio (PSNR) and edge preservation index (EPI).

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Wang, Ru-Yue, Jian-Fu Zhang, Alex Lazarian, Hua-Ping Xiao, and Fu-Yuan Xiang. "Gradient measurement of synchrotron polarization diagnostic: Application to spatially separated emission and Faraday rotation regions." Monthly Notices of the Royal Astronomical Society 505, no. 4 (June 17, 2021): 6206–16. http://dx.doi.org/10.1093/mnras/stab1708.

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ABSTRACT Considering the spatially separated polarization radiation and Faraday rotation regions to simulate complex interstellar media, we study synchrotron polarization gradient techniques’ measurement capabilities. We explore how to trace the direction of projected magnetic field of emitting-source region at the multifrequency bands, using the gradient technique compared with the traditional polarization vector method. Furthermore, we study how Faraday rotation density in the foreground region, i.e. a product of electron number density and parallel component of magnetic fields along the line of sight, affects the measurement of projected magnetic field. Numerical results show that synchrotron polarization gradient technique could successfully trace projected magnetic field within emitting-source region independent of radio frequency. Accordingly, the gradient technique can measure the magnetic field properties for a complex astrophysical environment.

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Petraco, Nicholas, and Thomas Kubic. "A Density Gradient Technique for Use in Forensic Soil Analysis." Journal of Forensic Sciences 45, no. 4 (July 1, 2000): 14786J. http://dx.doi.org/10.1520/jfs14786j.

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Nicotra, P., H. Uriondo, E. Barrios, S. Papier, G. Fiszbajn, F. Nodar, and C. Alvarez Sedo. "Multilayer density gradient as a useful technique for sperm sex sorting." Fertility and Sterility 102, no. 3 (September 2014): e100. http://dx.doi.org/10.1016/j.fertnstert.2014.07.341.

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Highland, HyacinthN, ASharma Rishika, SShaikh Almira, and PBansal Kanthi. "Ficoll-400 density gradient method as an effective sperm preparation technique for assisted reproductive techniques." Journal of Human Reproductive Sciences 9, no. 3 (2016): 194. http://dx.doi.org/10.4103/0974-1208.192070.

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10

Sieber, W., and M. Fischer. "Annealing effects in epoxy resins examined by a refined density-gradient technique." Journal of Materials Science 28, no. 6 (January 1, 1993): 1639–44. http://dx.doi.org/10.1007/bf00363360.

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11

Vega, J., M. Rodriguez, D. Dipaz-Berrocal, J. Rivas, C. Huayhua, and E. Mellisho. "61 Swim-up and microfluidic techniques improve the kinetic parameters of selected bovine spermatozoa for invitro fertilization: Preliminary results." Reproduction, Fertility and Development 33, no. 2 (2021): 137. http://dx.doi.org/10.1071/rdv33n2ab61.

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For invitro embryo production, spermatozoa with fertilizing capacity must possess optimal kinetic, morphometric, vitality, and DNA integrity characteristics. The objective of this study was to evaluate the effect of 3 sperm selection methods on sperm quality and invitro embryonic development in bovine. Frozen commercial semen (0.5 mL/straws) from one bull with known fertility was thawed at 37°C for 20s and was divided for 3 sperm selection techniques: density gradient, swim-up, and microfluidic sperm sorting. The sperm kinetic parameters (VCL=curvilinear velocity, VSL=straight line velocity, VAP=average path velocity, ALH=lateral displacement of sperm head, BCF=beat frequency cross, STR=path straightness) were assessed using computer-assisted sperm analysis (CASA). Sperm morphometric parameters were evaluated using Diff-Quick staining followed by automated analysis. To assess vitality, the sperm were stained with propidium iodide and acridine orange, then analysed under a fluorescence microscope. In addition, DNA fragmentation was assessed using sperm chromatin dispersion method. Last, the fertilizing capacity of the selected sperm was tested by fertilizing cumulus–oocyte complexes (2×106 sperm mL−1) obtained from slaughterhouse ovaries and matured invitro for 24h. A standardized invitro embryo production protocol was used with commercial medium from Vitrogen. The cleavage rate and blastocyst yield were measured on Day 2 and 7, respectively (fertilization=Day 0). The results were calculated with analysis of variance and Tukey’s test (P<0.05). The values of sperm kinetic parameters obtained with swim-up (VCL 132.5µm/s; VSL 73.5µm/s) and microfluidic technique (VCL 129.5µm/s; VSL 64.4µm/s) were significantly higher (P<0.05) than those obtained by density gradient (VCL 98.3µm/s; VSL 45.01µm/s). However, the total and progressive motility by density gradient method was slightly higher (89% and 57%) compared with that assessed by swim-up (64% and 43%) or microfluidic technique (74% and 54%) respectively. Microfluidic sorting (11.3%) showed lower (P<0.05) DNA fragmentation levels compared with density gradient method (16.6%), whereas the swim-up technique (12.5%) was similar between both groups. No significant difference was detected between the 3 groups for sperm morphometric and vitality parameters. Moreover, cleavage rates were similar (P>0.05) between the 3 sperm selection techniques: density gradient (84.0%), swim-up (75.2%), and microfluidic sorting (67.3%). However, blastocyst yield was significantly higher (P<0.05) using sperm selected by density gradient (28.1%) and swim-up (21.9%) compared with microfluidic sorting (15.3%). In conclusion, sperm selection using microfluidic and swim-up techniques improved kinetic parameters with lower levels of DNA fragmentation, without affecting sperm morphometry. However, both the density gradient and swim-up techniques are efficient systems for producing invitro bovine embryo.

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Vega, J., M. Rodriguez, D. Dipaz-Berrocal, J. Rivas, C. Huayhua, and E. Mellisho. "61 Swim-up and microfluidic techniques improve the kinetic parameters of selected bovine spermatozoa for invitro fertilization: Preliminary results." Reproduction, Fertility and Development 33, no. 2 (2021): 137. http://dx.doi.org/10.1071/rdv33n2ab61.

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For invitro embryo production, spermatozoa with fertilizing capacity must possess optimal kinetic, morphometric, vitality, and DNA integrity characteristics. The objective of this study was to evaluate the effect of 3 sperm selection methods on sperm quality and invitro embryonic development in bovine. Frozen commercial semen (0.5 mL/straws) from one bull with known fertility was thawed at 37°C for 20s and was divided for 3 sperm selection techniques: density gradient, swim-up, and microfluidic sperm sorting. The sperm kinetic parameters (VCL=curvilinear velocity, VSL=straight line velocity, VAP=average path velocity, ALH=lateral displacement of sperm head, BCF=beat frequency cross, STR=path straightness) were assessed using computer-assisted sperm analysis (CASA). Sperm morphometric parameters were evaluated using Diff-Quick staining followed by automated analysis. To assess vitality, the sperm were stained with propidium iodide and acridine orange, then analysed under a fluorescence microscope. In addition, DNA fragmentation was assessed using sperm chromatin dispersion method. Last, the fertilizing capacity of the selected sperm was tested by fertilizing cumulus–oocyte complexes (2×106 sperm mL−1) obtained from slaughterhouse ovaries and matured invitro for 24h. A standardized invitro embryo production protocol was used with commercial medium from Vitrogen. The cleavage rate and blastocyst yield were measured on Day 2 and 7, respectively (fertilization=Day 0). The results were calculated with analysis of variance and Tukey’s test (P<0.05). The values of sperm kinetic parameters obtained with swim-up (VCL 132.5µm/s; VSL 73.5µm/s) and microfluidic technique (VCL 129.5µm/s; VSL 64.4µm/s) were significantly higher (P<0.05) than those obtained by density gradient (VCL 98.3µm/s; VSL 45.01µm/s). However, the total and progressive motility by density gradient method was slightly higher (89% and 57%) compared with that assessed by swim-up (64% and 43%) or microfluidic technique (74% and 54%) respectively. Microfluidic sorting (11.3%) showed lower (P<0.05) DNA fragmentation levels compared with density gradient method (16.6%), whereas the swim-up technique (12.5%) was similar between both groups. No significant difference was detected between the 3 groups for sperm morphometric and vitality parameters. Moreover, cleavage rates were similar (P>0.05) between the 3 sperm selection techniques: density gradient (84.0%), swim-up (75.2%), and microfluidic sorting (67.3%). However, blastocyst yield was significantly higher (P<0.05) using sperm selected by density gradient (28.1%) and swim-up (21.9%) compared with microfluidic sorting (15.3%). In conclusion, sperm selection using microfluidic and swim-up techniques improved kinetic parameters with lower levels of DNA fragmentation, without affecting sperm morphometry. However, both the density gradient and swim-up techniques are efficient systems for producing invitro bovine embryo.

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13

Li, Jing De, Hong Yuan Zhou, and Guo Wei Ma. "Numerical Simulation of Blast Mitigation Cladding with Gradient Metallic Foam Core." Applied Mechanics and Materials 82 (July 2011): 461–66. http://dx.doi.org/10.4028/www.scientific.net/amm.82.461.

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In the present study, numerical simulation is performed by using the commercial software ANSYS/LS-DYNA to investigate the various effects on crushing stress and energy absorption capacity of the blast mitigation cladding with gradient density aluminium foam in irregular manners, a 2D Voronoi technique is employed to generate the stochastic gradient metallic foam core. Results show that a properly designed energy absorption foam cladding with graded density is able to absorb high blast energy while with a lower force transferred to the substrate or the protected structure. Parametric study with respect to impact velocity and density gradient indicates that the density gradient foam cladding is effective in increasing energy absorption capacity especially under high velocity blast load.

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14

Ricci, Giuseppe, Sandra Perticarari, Rita Boscolo, Marcella Montico, Secondo Guaschino, and Gianni Presani. "Semen preparation methods and sperm apoptosis: swim-up versus gradient-density centrifugation technique." Fertility and Sterility 91, no. 2 (February 2009): 632–38. http://dx.doi.org/10.1016/j.fertnstert.2007.11.068.

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15

Hilal, Sadek K., Donn G. Mosser, Merle K. Loken, and Robert W. Johnson. "A NEW TECHNIQUE FOR HIGH-RESOLUTION DENSITY GRADIENT-SEPARATION OF BONE-MARROW CELLS*." Annals of the New York Academy of Sciences 114, no. 1 (December 16, 2006): 661–76. http://dx.doi.org/10.1111/j.1749-6632.1964.tb53619.x.

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16

Kulikov, Igor, Anthony J. Mannucci, Xiaoqing Pi, Carol Raymond, and George A. Hajj. "Electron density retrieval from occulting GNSS signals using a gradient-aided inversion technique." Advances in Space Research 47, no. 2 (January 2011): 289–95. http://dx.doi.org/10.1016/j.asr.2010.07.002.

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17

Borisenko, N. G., W. Nazarov, C. S. A. Musgrave, Yu A. Merkuliev, A. S. Orekhov, and L. A. Borisenko. "Characterization of divinyl benzene aerogels with density gradient using X-ray tomography technique." Journal of Radioanalytical and Nuclear Chemistry 299, no. 2 (July 23, 2013): 961–64. http://dx.doi.org/10.1007/s10967-013-2628-2.

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18

Martina, A. Della, and J. G. Hilborn. "Gradient porosity poly(dicyclopentadiene)." Journal of Materials Research 16, no. 7 (July 2001): 2045–52. http://dx.doi.org/10.1557/jmr.2001.0280.

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This article describes the preparation of gradient porosity thermoset polymers. The technique used is based on polymerizing a solution of cross-linkable dicyclopentadiene and 2-propanol. The forming polymer being insoluble in 2-propanol, phase separation occurs. Subsequent drying of the 2-propanol gives porosities up to 80%. An apparatus was built to produce a gradient in 2-propanol concentration in a flask, resulting in polymerized gradient porosity rods. The resulting materials have been characterized by scanning electron microscopy (SEM) and density measurements. A mathematical model which allows prediction of the gradient produced is also presented.

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Astarto, Nanang Winarto, Dian Tjahyadi, and Sintya Jatnikasari. "Comparison between Two-Layer Density Gradient and Three-Layer Density Gradient Technique for Sperm Preparation at Aster Fertility Clinic, Dr. Hasan Sadikin General Hospital." International Journal of Integrated Health Sciences 2, no. 1 (2014): 40–44. http://dx.doi.org/10.15850/ijihs.v2n1.286.

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20

Dettenhofer, Markus, and Xiao-Fang Yu. "Highly Purified Human Immunodeficiency Virus Type 1 Reveals a Virtual Absence of Vif in Virions." Journal of Virology 73, no. 2 (February 1, 1999): 1460–67. http://dx.doi.org/10.1128/jvi.73.2.1460-1467.1999.

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ABSTRACT The vif gene of human immunodeficiency virus type 1 (HIV-1) is essential for the productive infection of primary blood-derived lymphocytes, macrophages, and certain human T-cell lines. It has been shown that Vif is associated with HIV-1 virions purified by sucrose density-equilibrium gradient analysis. However, the specificity of Vif incorporation into virions has not been determined. Moreover, recent studies have demonstrated that standard HIV-1 particle preparations created with sucrose density-equilibrium gradients are contaminated with cell-derived microvesicles. Here we demonstrate, as previously reported, that Vif cosediments with HIV-1 particles in sucrose density-equilibrium gradient analysis. However, we also found that, when Vif was expressed in the absence of all other HIV-1-encoded gene products and then isolated by sucrose density-equilibrium gradient centrifugation from extracellular supernatants, its sedimentation pattern was largely unaltered, suggesting that Vif can be secreted from cells. Using a newly developed OptiPrep velocity gradient method, we were able to physically separate most of the extracellular Vif from the HIV-1 virions without disrupting the infectivity of the virus. By titrating serial dilutions of purified Vif and Gag against the viral peak fraction in the OptiPrep gradient, we demonstrate that <1.0 Vif molecule per virion was present. This study shows that Vif is not significantly present in HIV-1 virions, a finding which is consistent with the idea that Vif functions predominantly in the virus-producing cells during virus assembly. The OptiPrep velocity gradient technique described here could be an easy and rapid way to purify HIV and other enveloped viruses from microvesicles and/or cell debris.

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Zhang, Lian Meng, Ming Gao, Guo Qiang Luo, Zhuo Chen, and Qiang Shen. "Preparation of Tungsten-Epoxy Composites and FGMs with Density Gradient." Materials Science Forum 631-632 (October 2009): 461–64. http://dx.doi.org/10.4028/www.scientific.net/msf.631-632.461.

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FGMs with density gradient are of great interest in field of dynamic high-pressure physics. In this paper, tungsten particles reinforced epoxy resin composites, and FGMs with density gradient were prepared by calendering technique. Microstructures of tungsten-epoxy composites with various tungsten contents were analyzed, and the density distribution of the FGMs was characterized. The results show that the distribution of tungsten particles in tungsten-epoxy composites is homogeneous, and the combination of tungsten particles with epoxy matrix is good. The density of tungsten-epoxy composites varies from 1.26gcm-3 to 4.0gcm-3, and the thickness of each layer is about 200μm. Tungsten-epoxy FGMs with density gradient were obtained by laminating thin layers of tungsten-epoxy composites with different tungsten contents. The highly enough bonding strength between these transition layers and good parallelism were achieved. The density distribution of the tungsten-epoxy FGMs can meet the demand of the power function equation of density and thickness.

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Adiga, Murali. "Cost Effective Technique of Removal of Platelets for HLA Crossmatching by Density Gradient Centrifugation." Acta Scientific Gastrointestinal Disorders 3, no. 10 (September 30, 2020): 17–19. http://dx.doi.org/10.31080/asgis.2020.03.0179.

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Ko *, H. S., and K. D. Kihm. "An extended algebraic reconstruction technique (ART) for density-gradient projections: laser speckle photographic tomography." Experiments in Fluids 27, no. 6 (November 4, 1999): 542–50. http://dx.doi.org/10.1007/s003480050378.

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Woo, Dong-Jin, Jeong Min Mun, Suck-Hyun Lee, and Moon Ho Suh. "Dielectrophoretic technique for the preparation of density gradient polymers doped with a dipolar modifier." Macromolecular Research 11, no. 6 (December 2003): 467–70. http://dx.doi.org/10.1007/bf03218977.

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Kandhal, Prithvi S., and Rajib B. Mallick. "Study of Longitudinal-Joint Construction Techniques in Hot-Mix Asphalt Pavements." Transportation Research Record: Journal of the Transportation Research Board 1543, no. 1 (January 1996): 106–12. http://dx.doi.org/10.1177/0361198196154300113.

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There is a need to identify suitable longitudinal-joint construction techniques for multilane, hot-mix asphalt pavements that can minimize or eliminate cracking at the joint and raveling adjacent to the joint. It is believed that the longitudinal cracks result primarily from the density gradient that is usually encountered across the joint. This density gradient can be attributed to low density at the unconfined edge when the first lane is paved and relatively high density at the confined edge when the adjacent lane is paved. Seven different longitudinal-joint construction techniques were used on I-25 in Colorado in 1994, including various rolling procedures to compact the joint, provision of a vertical face with a cutting wheel, and use of rubberized asphalt tack coat on the face of the unconfined edge. Two longitudinal-joint construction techniques were used on I-79 in Pennsylvania in 1994: the conventional technique (control) and the New Jersey–type wedge joint. The latter technique uses a 3:1 taper at the unconfined edge of the first lane. The face of the taper is heated with an infrared heater before the adjacent lane is placed. Pavement cores were taken on the joint and 305 mm (1 ft) away from the joint for density measurements in all experimental test sections. Different techniques for joint construction have been ranked on the basis of statistical analysis of all density data. Various joints were also evaluated visually by teams of at least four engineers in June 1995. The performance, or ranking, of the joints in both Colorado and Pennsylvania projects after one winter seems to have been influenced by the overall density at the joint. The joints with high densities indicate better performance than those with relatively low densities. These rankings may change in the future on the basis of the long-term performance as measured by cracking and raveling.

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Yudiwati, Rina, MPBD Pramesti, Agustinus Agustinus, E. Pradana, and Bambang Purwanto. "IMPACT OF PREPARATION USING CONVENTIONAL AND MODIFIED DENSITY GRADIENT CENTRIFUGATION METHODS ON SPERM CONCENTRATION, MOTILITY AND NUMBER OF NORMAL MOTILE SPERM RECOVERY (NMSR)." Folia Medica Indonesiana 53, no. 3 (November 4, 2017): 196. http://dx.doi.org/10.20473/fmi.v53i3.6447.

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Some preparation techniques, either conventional or advanced, have been provided. Advanced technique may overcome the limitations of conventional techniques. Recently, not all fertility clinics in Indonesia are able to provide advanced preparation techniques. Some techniques require expensive equipments and can only be used for intracytoplasmic sperm injection (ICSI). Some fertility clinics use a modified procedure, namely the combination of density gradient centrifugation with a swim-up method for the preparation of the sperm to be used in ART. This study aimed to determine whether the modified density gradient centrifugation, which is density gradient centrifugation followed by a swim-up, is able to yield better results than conventional density gradient centrifugation. This study was a laboratory experimental pre and pos-test control group design. Population was all adult men aged 21-40 years old and the sampling unit was the man donor’s semen which fulfilled inclusion criterias, collected during the periode of the study. Sample size was eight. Sperm analysis were done before and after preparation in conventional and modified group. Descriptive comparation analysis have been used. This study obtained NMSR 7.9+5.5 million/ejaculate and recovery rate (RR) 27.66+11.8 %. RR was lower compared to RR obtained conventional DGC method. RR might be lower because in modified DGC samples undergo two steps selection while conventional DGC only one step selection. But conventional DGC samples should be centrifuged twice, therefore sperms might experience more trauma. Lower RR sperm does not exclude the possibility to be used for ART, because still within the required number for all TRBs. In conclusion, modified DGC preparation method obtained lower NMSR and RR, nevertheless harvested sperms can still be used in all kind of ART.

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Xia, Chang Qi, Qi Bin Liu, and Mo He. "Effect of Sintering Temperature on Electrical Properties of ZnO Varistor Ceramics." Advanced Materials Research 442 (January 2012): 31–34. http://dx.doi.org/10.4028/www.scientific.net/amr.442.31.

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To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, the effect of different sintering temperature (1135～1155 °C) on electrical properties of ZnO varistors were investigated. The experimental results show that with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. When the sintering temperature is at 1135 °C, the voltage gradient of varistor is up to 329V/mm, the leakage current is 8μA and the density is 96.4%. When the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%. Compared the results at 1135 °C with 1140 °C , it is found that the comprehensive electrical properties of ZnO varistors reach maximum at 1140 °C.

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Saravana Kumar, M. N., and R. Murugan. "Analysis of Inductance Gradient and Current Density Distribution Over Different Cross-section of Rails." International Journal of Electrical and Computer Engineering (IJECE) 8, no. 2 (April 1, 2018): 723. http://dx.doi.org/10.11591/ijece.v8i2.pp723-729.

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In a rail gun system the armature accelerated due to the Lorentz force caused by the current which is diffused in to the rails. The entire system depends on the inductance gradient of the rail which is directly connected to the accelerating performance and efficiency of railgun. Hence, the exact analysis of inductance gradient is extremely significant for the railgun design. Since short duration of current pulse is applied to the rails determination of inductance gradient is very difficult. The inductance gradient varies with the geometric dimensions of the rails and armature. And it can be calculated with analytical method and numerical methods. In this paper inductance gradient of the rail has been computed and compared with the different rail cross-sectional models using Ansoft Maxwell Eddy current solver uses finite element technique to calculate the field distribution in a space. The current density, magnetic flux density, repulsive force acting on the rails also computed to analyze the performance of rail gun.

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Salpeter, M. M., M. Marchaterre, and R. Harris. "Distribution of extrajunctional acetylcholine receptors on a vertebrate muscle: evaluated by using a scanning electron microscope autoradiographic procedure." Journal of Cell Biology 106, no. 6 (June 1, 1988): 2087–93. http://dx.doi.org/10.1083/jcb.106.6.2087.

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A scanning electron microscope (SEM) autoradiographic technique was calibrated and used to determine the site density of acetylcholine receptors within 250 micron of the neuromuscular junction in innervated as well as 3- and 10-d denervated sternomastoid muscle of the mouse. In all these groups sharp gradients of receptor site density are seen around the endplates in the first 2-7 micron, continuing less sharply to between 25 and 50 micron. Beyond 50 micron (to 250 micron) a spatial density gradient is present 3 d after denervation, but none exist by 10 d. These results suggest that the postdenervation steady-state extrajunctional receptor site density is reached sooner near the junction than away from the junction. The usefulness of SEM autoradiography to study the expression and distribution of membrane molecules at high resolution is demonstrated.

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Sas-Boca, Monica. "Experimental Study Regarding Compressing Process with Assisted Friction Force." Advanced Materials Research 23 (October 2007): 177–80. http://dx.doi.org/10.4028/www.scientific.net/amr.23.177.

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Friction between powder and tools plays a major role during cold compaction of PM components with results on the inhomogeneous densification. The present work deals with a new method of compaction for PM components by using the friction force between die and compacts as an active pressing force in order to reduce the density gradient. The proposal technique consists in moving the container of the die, during pressing stage to the punch direction with a well determined speed. As a result, the friction force acts in the same sense as the pressing load with better distribution of powder flow during compaction. The experimental results of compaction parameters versus density have proved the decreasing of the density gradient by increasing die/punch speed rate. A sharp density gradient on the specimen height moving container contrarily to the punch.

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31

Barnes, Gary, and John Lumley. "Processing gravity gradient data." GEOPHYSICS 76, no. 2 (March 2011): I33—I47. http://dx.doi.org/10.1190/1.3548548.

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As the demand for high-resolution gravity gradient data increases and surveys are undertaken over larger areas, new challenges for data processing have emerged. In the case of full-tensor gradiometry, the processor is faced with multiple derivative measurements of the gravity field with useful signal content down to a few hundred meters’ wavelength. Ideally, all measurement data should be processed together in a joint scheme to exploit the fact that all components derive from a common source. We have investigated two methods used in commercial practice to process airborne full-tensor gravity gradient data; the methods result in enhanced, noise-reduced estimates of the tensor. The first is based around Fourier operators that perform integration and differentiation in the spatial frequency domain. By transforming the tensor measurements to a common component, the data can be combined in a way that reduces noise. The second method is based on the equivalent-source technique, where all measurements are inverted into a single density distribution. This technique incorporates a model that accommodates low-order drift in the measurements, thereby making the inversion less susceptible to correlated time-domain noise. A leveling stage is therefore not required in processing. In our work, using data generated from a geologic model along with noise and survey patterns taken from a real survey, we have analyzed the difference between the processed data and the known signal to show that, when considering the Gzz component, the modified equivalent-source processing method can reduce the noise level by a factor of 2.4. The technique has proven useful for processing data from airborne gradiometer surveys over mountainous terrain where the flight lines tend to be flown at vastly differing heights.

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Kathuria, Y. P. "Net shaping via aluminium foaming." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 217, no. 2 (February 1, 2003): 193–99. http://dx.doi.org/10.1243/095440503321148830.

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The marriage between net shaping and aluminium alloy foaming has given a new dimension to the rapid prototyping technique for manufacturing of the lightweight structure in the automotive and aerospace industries. The present paper is focused on laser-assisted aluminium foaming from a foamable precursor material and its possible applications in net shaping of three-dimensional structures. Preliminary results suggest that a pore size gradient and a density gradient exist in the structure as the processing condition changes. The foam has large pores and lower density for slow processing speed, in contrast with the fast processing speed with small pore size but higher density. For pilot-scale production of the foamed plates, sandwiches panel and localized foamed structure, specially intended for heat exchanger in the electronic industries, the laser foaming technique may be the most appropriate.

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Georgiadis, H. G. "The Mode III Crack Problem in Microstructured Solids Governed by Dipolar Gradient Elasticity: Static and Dynamic Analysis." Journal of Applied Mechanics 70, no. 4 (July 1, 2003): 517–30. http://dx.doi.org/10.1115/1.1574061.

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This study aims at determining the elastic stress and displacement fields around a crack in a microstructured body under a remotely applied loading of the antiplane shear (mode III) type. The material microstructure is modeled through the Mindlin-Green-Rivlin dipolar gradient theory (or strain-gradient theory of grade two). A simple but yet rigorous version of this generalized continuum theory is taken here by considering an isotropic linear expression of the elastic strain-energy density in antiplane shearing that involves only two material constants (the shear modulus and the so-called gradient coefficient). In particular, the strain-energy density function, besides its dependence upon the standard strain terms, depends also on strain gradients. This expression derives from form II of Mindlin’s theory, a form that is appropriate for a gradient formulation with no couple-stress effects (in this case the strain-energy density function does not contain any rotation gradients). Here, both the formulation of the problem and the solution method are exact and lead to results for the near-tip field showing significant departure from the predictions of the classical fracture mechanics. In view of these results, it seems that the conventional fracture mechanics is inadequate to analyze crack problems in microstructured materials. Indeed, the present results suggest that the stress distribution ahead of the tip exhibits a local maximum that is bounded. Therefore, this maximum value may serve as a measure of the critical stress level at which further advancement of the crack may occur. Also, in the vicinity of the crack tip, the crack-face displacement closes more smoothly as compared to the classical results. The latter can be explained physically since materials with microstructure behave in a more rigid way (having increased stiffness) as compared to materials without microstructure (i.e., materials governed by classical continuum mechanics). The new formulation of the crack problem required also new extended definitions for the J-integral and the energy release rate. It is shown that these quantities can be determined through the use of distribution (generalized function) theory. The boundary value problem was attacked by both the asymptotic Williams technique and the exact Wiener-Hopf technique. Both static and time-harmonic dynamic analyses are provided.

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Asaki, T. J., E. M. Bollt, and K. R. Vixie. "Sparse Radiographic Tomography and System Identification Imaging from Single View, Multiple Time Sample Density Plots." Computational Methods in Applied Mathematics 6, no. 4 (2006): 354–66. http://dx.doi.org/10.2478/cmam-2006-0022.

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Abstract Tomography is a classic inverse problem in which multiple density projections of an object are processed to infer some approximation of the original. We consider the highly sparse inverse problem of single angle projection, but seek to reduce the ambiguity through multiple time observations in a dynamic system of known or partially known dynamics. In this work we solve the planar problem by optimization techniques based on a gradient-free multi-directional search algorithm to minimize our nonlinear functional. We demonstrate convincingly successful numerical examples to support our relatively simple technique.

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Kan, Wen Bin, Yong Feng Li, and Hong Liang Pan. "Estimation of Hydrogen Diffusivity in Austenitic Stainless Steels by Microhardness Gradient Technique." Advanced Materials Research 197-198 (February 2011): 696–700. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.696.

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The present study developed a subsurface microhardness gradient technique to estimate hydrogen diffusivity of stainless steels, as per the similarity between concentration distribution and hardness gradient. Cathodic charging were performed on 304 stainless steels for 24 h in a 0.5 mol/L H2SO4 solution using a current density of 100 mA/cm2, with 0.25g/L Na2S as the hydrogen recombination poison. Microhardness in the cross-sectional region had an increase than the uncharged materials due to the hardening mechanism as found by martensite transformation. Hydrogen diffusivity was estimated using the microhardness data and the diffusion equation. The estimated diffusivity of hydrogen at 306 K in 304 stainless steels is 3.28×10-13 m2/s, which has good agreements with the one measured by time-lag electrochemical method in a previous research.

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Bartles, J. R., L. T. Braiterman, and A. L. Hubbard. "Endogenous and exogenous domain markers of the rat hepatocyte plasma membrane." Journal of Cell Biology 100, no. 4 (April 1, 1985): 1126–38. http://dx.doi.org/10.1083/jcb.100.4.1126.

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We have used a combined biochemical and morphological approach to establish the suitability of certain endogenous and exogenous domain markers for monitoring the separation of rat hepatocyte plasma membrane domains in sucrose density gradients. As endogenous domain markers, we employed two of the integral plasma membrane protein antigens, HA 4 and CE 9, localized to the bile canalicular and sinusoidal/lateral domains, respectively, of the hepatocyte plasma membrane in rat liver tissue (Hubbard, A. L., J. R. Bartles, and L. T. Braiterman, 1985, J. Cell Biol., 100:1115-1125). We used immunoelectron microscopy with a colloidal gold probe to demonstrate that HA 4 and CE 9 retained their domain-specific localizations on isolated hepatocyte plasma membrane sheets. When the plasma membrane sheets were vesiculated by sonication and the resulting vesicles were centrifuged to equilibrium in sucrose density gradients, quantitative immunoblotting revealed that the vesicles containing HA 4 and those containing CE 9 exhibited distinct density profiles. The density profile for the bile canalicular vesicles (marked by HA 4) was characterized by a single peak at a density of 1.10 g/cm3. The density profile for the sinusoidal/lateral vesicles (marked by CE 9) was bimodal, with a peak in the body of the gradient at a density of 1.14 g/cm3 and a smaller amount in the pellet (density greater than or equal to 1.17 g/cm3). We used this sucrose gradient fractionation as a diagnostic procedure to assign domain localizations for several other hepatocyte plasma membrane antigens and enzyme activities. In addition, we used the technique to demonstrate that 125I-wheat germ agglutinin, introduced during isolated liver perfusion at 4 degrees C, can serve as an exogenous domain marker for the sinusoidal domain of the rat hepatocyte plasma membrane.

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VARIER, GEETHA K., S. S. HARILAL, C. V. BINDHU, RIJU C. ISSAC, V. P. N. NAMPOORI, and C. P. G. VALLABHAN. "ELECTRON DENSITY DETERMINATION OF LASER INDUCED PLASMA FROM POLYMETHYL METHACRYLATE USING PHASESHIFT DETECTION TECHNIQUE." Modern Physics Letters B 10, no. 06 (March 10, 1996): 235–39. http://dx.doi.org/10.1142/s0217984996000286.

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Irradiation of a Polymethyl methacrylate target using a pulsed Nd-YAG laser causes plasma formation in the vicinity of the target. The refractive index gradient due to the presence of the plasma is probed using phase-shift detection technique. The phase-shift technique is a simple but sensitive technique for the determination of laser ablation threshold of solids. The number density of laser generated plasma above the ablation threshold from Polymethyl methacrylate is calculated as a function of laser fluence. The number density varies from 2×1016 cm −3 to 2×1017 cm −3 in the fluence interval 2.8−13 J · cm –2.

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Hsu, Ta-I., Yu-Ting Jhong, and Meng-Hsiu Tsai. "Effect of Gradient Energy Density on the Microstructure and Mechanical Properties of Ti6Al4V Fabricated by Selective Electron Beam Additive Manufacture." Materials 13, no. 7 (March 26, 2020): 1509. http://dx.doi.org/10.3390/ma13071509.

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Selective Electron Beam Additive Manufacturing (SEBAM) is a promising powder bed fusion additive manufacturing technique for titanium alloys that select particular area melting in different energy density for producing complexly shaped biomedical devices. For most commercial Ti6Al4V porous medical devices, the gradient energy density is usually applied to manufacture in one component during the SEBAM process which selects different energy density built on particular zones. This paper presents gradient energy density base characterization study on an SEBAM built rectangular specimen with a size of 3 mm × 20 mm × 60 mm. The specimen was divided into three zones were built in gradient energy density from 16 to 26.5 J/mm3. The microstructure and mechanical properties were investigated by means of scanning electron microscopy, X-ray diffraction, transmission electron microscopy and mechanical test. The α′ martensitic and lack of fusion were observed in the low energy density (LED) built zone. However, no α′ phase and no irregular pores were observed both in overlap energy density (OED) and high energy density (HED) built zones located at the middle and bottom of the specimen respectively. This implies the top location and lower energy density have positive effects on the cooling rate but negative effects on densification. The subsequence mechanical properties result also supports this point. Moreover, the intermetallic Ti3Al found in the bottom may be due to the heat transfer from the following melting layer. Furthermore, the microstructure evolution in gradient energy built zones is discussed based on the findings of the microstructure and thermal history correlation analysis.

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Yan, Yingwei, Zhejiang Wang, Jing Li, Nan Huai, Yujia Zhang, and Fei Han. "A preconditioned technique for SH- and Love-wave full-waveform inversion in time domain and crosstalk analysis." Journal of Geophysics and Engineering 17, no. 1 (November 22, 2019): 160–74. http://dx.doi.org/10.1093/jge/gxz101.

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Abstract For the problem of low horizontal resolution in the method of surface wave dispersion analysis, we apply the SH- and Love-wave full-waveforms to achieve 2D and 3D imaging of the subsurface. The gradient obtained by classical full-waveform inversion (FWI) is not scaled with increasing depth. The limited source frequency band, the non-uniform coverage between shot and geophone positions and double scattering are the main reasons for the phenomenon. The Hessian operator of the misfit function can clearly predict the inherent defocusing phenomenon and the artefacts generated by the double scattering in the gradient vector, and the inverse Hessian operator is used as a deconvolution operator to realise gradient preconditioning. We present an expression of the quasi-Hessian operator in SH- and Love-wave FWI based on inverse scattering theory in prestack depth migration, and apply a new preconditioned technique to the fault and large contrast (LC) model reconstruction test. The inverted results show that the new preconditioned technique can greatly improve the imaging accuracy compared with the gradient-based methods of FWI. From single-parameter tests, we can conclude that the quasi-Hessian operator plays roles in illumination compensation and parameter complement estimation in FWI. From the final reconstructed results of a dual-parameter model, we find that the inverted result of the density is slightly closer to the true model than S-wave velocity under the condition of the same comparative distance between the initial and true model, but parametric crosstalk of density is more serious.

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Liu, Liying, Jian Xing, Qingwei Yang, and Yangjun Luo. "Design of Large-Displacement Compliant Mechanisms by Topology Optimization Incorporating Modified Additive Hyperelasticity Technique." Mathematical Problems in Engineering 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/4679746.

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This paper is focused on the topology design of compliant mechanisms undergoing large displacement (over 20% of the structural dimension). Based on the artificial spring model and the geometrically nonlinear finite element analysis, the optimization problem is formulated so as to maximize the output displacement under a given material volume constraint. A modified additive hyperelasticity technique is proposed to circumvent numerical instabilities that occurred in the low-density or intermediate-density elements during the optimization process. Compared to the previous method, the modified technique is very effective and can provide more accurate response analysis for the large-displacement compliant mechanism. The whole optimization process is carried out by the gradient-based mathematical programming method. Numerical examples of a force-inverting mechanism and a microgripping mechanism are presented. The obtained optimal solutions verify the applicability of the proposed numerical techniques and show the necessity of considering large displacement in the design problem.

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Kobayashi, T., H. Sato, S. Kaneko, R. Aoki, T. Ohno, and S. Nozawa. "Intrauterine insemination with semen of oligozoospermic men: effectiveness of the continuous-step density gradient centrifugation technique." Andrologia 23, no. 3 (April 24, 2009): 251–54. http://dx.doi.org/10.1111/j.1439-0272.1991.tb02551.x.

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Henriksson, A., and P. L. Conway. "Use of a Density Gradient Technique for Studying Adhesion of Lactobacillus Strains to Squamous Epithelial Cells." Microbial Ecology in Health and Disease 4, no. 6 (January 1991): 357–62. http://dx.doi.org/10.3109/08910609109140150.

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Qiang, Shen, Zhang Lian-meng, Tan Hua, and Jing Fu-qian. "Preparation of Mg−Ti system alloy and FGM with density gradient by spark plasma sintering technique." Journal of Wuhan University of Technology-Mater. Sci. Ed. 19, no. 1 (March 2004): 58–60. http://dx.doi.org/10.1007/bf02838365.

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Du, Yi Xian, Jin Run Hu, and Yi Zhang. "An Adaptive Element-Free Galerkin Method Based on the Strain Energy Density." Advanced Materials Research 677 (March 2013): 225–29. http://dx.doi.org/10.4028/www.scientific.net/amr.677.225.

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In practical study, an adaptive procedure based on the gradient of the strain energy density is developed for element-free Galerkin method using moving least-squares (MLS) approximation and global Galerkin formulation require a background mesh for domain integration. It comprises nodal strain energy density and a local domain refinement technique. The numerical experiments in this paper show that this adaptive element-free Galerkin method is simple, effective and efficient.

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Xia, Chang Qi, Qi Bin Liu, and Mo He. "Study on Microstructure and Electrical Properties of ZnO Varistor Ceramics." Advanced Materials Research 415-417 (December 2011): 2008–11. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.2008.

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To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, which were sintered from 1135 to 1155 °C, the microstructure and properties of varistors were characterized by SEM, X-rays diffraction and DC parameter instrument for varistors. The experimental results show that the spinel phase Zn7Sb2O12 generated during sintering process, very thin amorphous Bi rich films are formed between the ZnO/ZnO grain boundaries, with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. The optimized parameters are that when the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%, the comprehensive electrical properties of ZnO varistors reach maximum.

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Chen, C. D., Y. C. Chen, and C. C. Chen. "The Electro-Elastic Fields in a Functionally Gradient Piezoelectric Strip with an Internal Electrode." Journal of Mechanics 31, no. 6 (July 15, 2015): 665–70. http://dx.doi.org/10.1017/jmech.2015.43.

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ABSTRACTIn this paper, the electro-elastic fields in a functionally gradient piezoelectric strip with an internal semi-infinite electrode are analyzed by using Fourier transform and Wiener-Hopf technique. The exact forms of asymptotic solutions and intensity factor and energy are obtained. The energy density criterion is proposed to study the fracture behavior near the electrode tip. The fracture initiation angle depends on the fracture resistance of the piezoelectric ceramic, bonding strength between piezoelectric and electrode, and the direction of least energy density factor S inside the piezoceramic.

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Qu, Jia Hui, Tao Huang, Ming Gao, and Fu Wang. "Effects of Annealing Technique on Texture Attenuation of Hot-Rolling AZ31 Magnesium Alloy Sheets." Advanced Materials Research 311-313 (August 2011): 609–14. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.609.

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A strong basal plane texture of AZ31 magnesium alloy was obtained by severe hot-rolling with three passes falling temperature. The effects of annealing time and annealing temperature on the evolution of texture at different layers were studied by means of X-ray texture analysis. The results showed that the orientation density of basal plane texture component was reduced greatly tending to dispersion with increasing annealing time and temperature. The hard orientation can be greatly weakened by softening annealing, the best basal plane orientation was obtained when the annealing time is 60min and the annealing temperature is 150~300°C. A texture gradient along thickness direction with annealing has been found in the sheet. The texture gradient was the lowest when the annealing time is 60min and the annealing temperature is 300°C.

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Pánisová, Jaroslava, and Roman Pašteka. "The use of microgravity technique in archaeology: A case study from the St. Nicolas Church in Pukanec, Slovakia." Contributions to Geophysics and Geodesy 39, no. 3 (January 1, 2009): 237–54. http://dx.doi.org/10.2478/v10126-009-0009-1.

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The use of microgravity technique in archaeology: A case study from the St. Nicolas Church in Pukanec, SlovakiaThe detection of subsurface cavities, such as crypts, cellars and tunnels, in churches and castles belongs to successful applications of the employment of surface gravity measurement techniques in archaeo-prospecting. The old historic building exploration requires using of non-invasive methods, and hence the microgravity technique is a proper candidate for this task. On a case study from the Roman-Catholic Church of St. Nicolas in the town Pukanec the results of using microgravity for detection and delineation of local density variations caused by a near-surface void are shown. The acquired negative anomaly in the residual Bouguer anomalies field suggested the presence of a possible void feature. Euler deconvolution and 3D modelling were used to estimate the depth and shape of the anomalous source. Additionally, measurements of the vertical gravity gradient on several stations were performed. We tested how the use of a downward continuation of gravity, utilizing the real vertical gravity gradient, influences the shape and amplitude of the final Bouguer anomaly map.

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Ullrich, CA, and EKU Gross. "Density Functional Theory of Normal and Superconducting Electron Liquids: Explicit Functionals via the Gradient Expansion." Australian Journal of Physics 49, no. 1 (1996): 103. http://dx.doi.org/10.1071/ph960103.

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The basic idea of density functional theory is to map an interacting many-particle system on an effective non-interacting system in such a way that the ground-state densities of the two systems are identical. The non-interacting particles move in an effective local potential which is a functional of the density. The central task of density functional theory is to find good approximations for the density dependence of this local single-particle potential. An overview of recent advances in the construction of this potential (beyond the local-density approximation) will be given along with successful applications in quantum chemistry and solid state theory. We then turn to the extension of density functional theory to superconductors and first discuss the Hohenberg-Kohn-Sham-type existence theorems. In the superconducting analogue of the the normal-state Kohn-Sham formalism, a local single-particle potential is needed which now depends on two densities, the ordinary density n(r) and the anomalous density △(r,r/). As a first step towards the construction of such a potential, a gradient expansion technique for superconductors is presented and applied to calculate an approximation of the non-interacting kinetic energy functional Ts[n, △]. We also obtain a Thomas-Fermi-type variational equation for superconductors.

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Usarek, Zbigniew, Marek Chmielewski, and Leszek Piotrowski. "Magnetic field gradient as the most useful signal for detection of flaws using MFL technique." Journal of Electrical Engineering 69, no. 6 (December 1, 2018): 422–25. http://dx.doi.org/10.2478/jee-2018-0065.

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Abstract The magnetic flux leakage (MFL) technique is extensively used for detection of flaws as well as for evaluation of their dimensions in ferromagnetic materials. However, proper analysis of the MFL signal is hindered by the MFL sensor velocity causing distortions of this signal. Traditionally measured components of the MFL signal are particularly sensitive to the scanning velocity. In this paper, an another signal – the gradient of the normal component of magnetic flux density – was proposed as it is less sensitive to the scanning velocity. Results obtained for scans of the steel plate with artificially manufactured flaws confirm this statement.

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Journal articles on the topic 'Density gradient technique'

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