• Clinical and Experimental Reproductive Medicine
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• v.46 no.1
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• pp.8-13
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• 2019

Objective: Density gradient centrifugation (DGC) is frequently used to isolate high-motility fractions of spermatozoa. We compared the efficacy of four DGC media in terms of the percentage of morphologically normal spermatozoa, DNA fragmentation level, and hyaluronic acid (HA) binding ability. Methods: Thirty men with a total motile spermatozoa count > 80 million participated. Semen samples were divided into four aliquots, which were processed using PureSperm, PureCeption, Sidney, and SpermGrad media, respectively. The DNA fragmentation level was measured using the Halosperm assay kit and HA binding ability was measured using the HBA assay kit. Results: The mean percentage of morphologically normal spermatozoa was significantly enhanced after DGC using all four media (10.3%, 9.9%, 9.8%, and 10.7%, respectively; p< 0.05 for each when compared with 6.9% in raw semen). The DNA fragmentation level was significantly reduced after DGC using PureSperm, PureCeption, and SpermGrad media (6.0%, 6.5%, and 4.9%, respectively; p< 0.05 for each when compared with 11.2% in raw semen), but not after DGC using Sidney media (8.5%, p> 0.05). HA binding ability did not change after DGC using any of the four media. Conclusion: The four media were equally effective for obtaining a sperm fraction with highly motile, morphologically normal sperm. PureSperm, PureCeption, and SpermGrad media were equally effective for acquiring a sperm fraction with less DNA fragmentation.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.687-697
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• 2010

This study was designed to carry out studies on critical seepage velocity and critical hydraulic gradient using a piping test targeting SM and ML which are widely distributed ahead of and behind the depth of E.L(-)10m in Saemangeum area in order to examine stability of embankment built on the ground vulnerable to piping. The effects of relative densities on critical hydraulic gradient and critical velocity were also compared and analyzed using empirical formula and theoretical formula, and relative densities were set up as respectively 9%, 25%, 50%, and 75% for this experiment. As a result, for critical hydraulic gradient, most of specimens detected piping at lower values than the empirical formula of Terzaghi(1922). It is, therefore, considered that the empirical formula devised by Kalin(1977) or Hayashi(1978) is more reasonable to be conservative. It was also found that critical velocity decreased as relative density increased, and critical velocity predicted was mostly lower than the theoretical formula.

• Journal of the Korean Ceramic Society
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• v.31 no.3
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• pp.321-329
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• 1994

Functionally gradient materials(FGM), which have the continuous or stepwise variation in a composition and microstructure, are being noticed as the material that solves problems caused by heterogeneous interface of coating or joining. And these materials also expect new functions occured by gradient composition itself. Therefore, to examine possibility of thermal barrier materials, TZP/Mo·FGM and TZP/Ni·FGM were fabricated by sintering method. As to the sintered specimens, sintering shrinkage, relative density and Vicker's hardness in each composition were examined. The phenomena due to the difference of sintering shrinkage velocity during sintering process and the thermal stress induced through differences of thermal expansion coefficient in FGM were discussed. And the structure changes at interface and microsturcture of FGM were investigated. As a results, the difference of shrinkage between ceramic and metal was about 14% in TZP/Mo and 7% in TZP/Ni. The relative density and hardness were considerably influenced by metal content changes. Owing to unbalance of sintering shrinkage velocity between ceramic and metal, various sintering defects were occured. To control these sintering defects and thermal stress, gradient composition of FGM should be narrow. The microstructure changes of FGM depended on the ceramic or metal volume percents and were analogous to the theoretical design.

• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.627-641
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• 2014

Functionally graded steels (FGSs) are a family of functionally graded materials (FGMs) consisting of ferrite (${\alpha}$), austenite (${\gamma}$), bainite (${\beta}$) and martensite (M) phases placed on each other in different configurations and produced via electroslag remelting (ESR). In this research, the flow stress of dual layer austenitic-martensitic functionally graded steels under hot deformation loading has been modeled considering the constitutive equations which describe the continuous effect of temperature and strain rate on the flow stress. The mechanism-based strain gradient plasticity theory is used here to determine the position of each layer considering the relationship between the hardness of the layer and the composite dislocation density profile. Then, the released energy of each layer under a specified loading condition (temperature and strain rate) is related to the dislocation density utilizing the mechanism-based strain gradient plasticity theory. The flow stress of the considered FGS is obtained by using the appropriate coefficients in the constitutive equations of each layer. Finally, the theoretical model is compared with the experimental results measured in the temperature range $1000-1200^{\circ}C$ and strain rate 0.01-1 s-1 and a sound agreement is found.

• Proceedings of the Korea Multimedia Society Conference
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• 2000.11a
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• pp.250-255
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• 2000

This paper is concerning off-line signature verification using a density function which is obtained by convolving the signature image with twelve-directional 5$\times$5 gradient masks and the weighted fuzzy mean classifier. The twelve-directional density function based on Nevatia-Babu template gradient is related to the overall shape of a signature image and thus, utilized as a feature set. The weighted fuzzy mean classifier with the reference feature vectors extracted from only genuine signature samples is evaluated for the verification of freehand forgeries. The experimental results show that the proposed system can classify a signature whether genuine or forged with more than 98% overall accuracy even without any knowledge of vaned freehand forgeries.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.164-176
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• 2003

During summer, the DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphate) observed in the Jindong Bay in the southern sea of Korea show much higher values in the inner area of the bay. In general, they have high values in the upper (0-1 m) and lower layers (8 m-bottom), but are relatively lower in the middle layer (1-8 m). These features in their distribution are examined using an ecosystem model with considering the wind, tidal current, horizontal gradient of water density and residual flow. The experiments were focused on how to influence nutrients associated with these conditions. In the experiment with tide-induced residual flow, the values of nutrients appeared lower than the observation, and were well corresponded to it when the effects of wind, tide-induced residual current and horizontal gradient of water density were additionally imposed. A statistical analysis identifies these results. This paper suggests that variation of nutrient in the Jindong Bay during summer should be seriously a(footed wind-driven current by the wind and density-driven current is induced by the horizontal gradient of water density as well as tidal current.

• Journal of Astronomy and Space Sciences
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• v.16 no.2
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• pp.91-104
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• 1999

We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of ~0.39 $\pm$ 0.07 mag/$arcsec^2$ in (B - V). In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V) color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

• Journal of radiological science and technology
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• v.13 no.2
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• pp.21-25
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• 1990

This report is study about difference of H-D curve in regular film and ortho type film, and obtained results as follows : 1. In the blue-color emission intensifying screen, ortho type films and in the green-color emission intensifying screens, regular type are decreased in their gradient. 2. When joint use of regular type film and ortho type film, the gradient difference not seen in blue color screen. 3. The gradient difference seen clearly in G4, KM screens(green color emission intensifying). Especially, in part of high film density, the gradient difference are great. So we have to right use of screen and film because not matched used of theare the sensitivity and gradient are decrease.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.57.1-57.1
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• 2011

It has been suggested that merging plays an important role in the formation and the evolution of early-type galaxies (ETGs). Optical-NIR color gradients of ETGs in high density environments are found to be less steep than those of ETGs in low density environments, hinting frequent merger activities in ETGs in high density environments. In order to examine if the flat color gradients are the result of dry mergers, we studied the relations between merging features, color gradient, and environments of 281 low redshift ETGs selected from Sloan Digital Sky Survey (SDSS) Stripe82. The sample contains 222 relaxed ETGs, 38 ETGs with tidal features, 10 galaxies with dust features and 11 galaxies with tidal and dust features, and Near Infrared (NIR) images are taken from UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). We find that r-K color gradients of field sample galaxies are steeper than those of sample ETGs within cluster environments. For the field sample galaxies, a relatively large number of galaxies with peculiar features contribute to the steeper color gradients, while the absence of these peculiar early-type galaxies make color gradients of the cluster sample galaxies intact. In high density environment, ETGs are already evolved and relaxed, resulting flat color gradients. However, in low density environments, a majority of ETGs undergone merging recently which makes the color gradients steep.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.99-99
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• 2009

Two different micro-flows during the evaporation of ink droplets were achieved by engineering both surface tension gradient and compositional gradient across the ink droplet: (1) Coffee-ring generating flow resulting from the outward flow inside the ink droplet & (2) Marangoni flow leading to the circulation flow inside the ink droplet. The surface tension gradient and the compositional gradient in the ink droplets were tailored by mixing two different solvents with difference surface tension and boiling point. In order to create the coffee-ring generating flow (outward flow), a single-solvent system using N,N-dimethylformamide with nano-sized spherical alumina particles was formulated, Marangoni flow (circulation flow) was created in the ink droplets by combining N,N-dimethylformamide and fotmamide with the spherical alumina powders as a co-solvent ink system. We have investigated the effect of these two different flows on the formation of ceramic films by inkjet printing method, The packing density of the ceramic films printed with two different ink systems (single- and co-solvent systems) and their surface roughness were characterized. The dielectric properties of these inkjet-printed ceramic films such as dielectric constant and dissipation factor were also studied in order to evaluate the feasibility of their application to the electronic ceramic package substrate.