• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.196-202
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• 1998

Because the journal and bearing surface are fully separated by the oil film during the normal operation, fluid film bearings operating in the hydrodynamic lubrication region are expected to have an infinite life. However, there are many parameters that lead to interfere with the normal operation of the bearing and lead to its failure. In this paper, both the causes and countermeasures of the bearing failure are described. Also, the characteristics of wiped bearing surface are investigated through mechanical and chemical test.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.31.3-32
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• 2020

The surface brightness fluctuation (SBF) is one of the most crucial distance indicators for unresolved stellar systems at large distances. Here, we present an evolutionary population synthesis model of the surface brightness fluctuation (SBF) for normal and He-enriched simple stellar populations (SSPs). Our SBF model for the normal-He population agrees well with other existing models, but the He-rich populations bring about a substantial change in the SBF of SSPs. Our normal-He SBF model well reproduces the observed SBFs of the Milky Way globular clusters, but the SBFs of early-type galaxies in the Virgo Cluster are placed between the normal-He and He-rich SBF models. We show that the SBF-based distance estimation would be affected by up to a 10-20% level in I- and near-IR bands at given colors. Finally, we propose that when combined with independent metallicity and age indicators such as Mg2 and H��, the UV and optical SBFs can readily detect underlying He-rich populations in unresolved stellar systems. Given the degree of the SBF variation resulting from the population difference, we suggest that the distance measurement before the proper in-depth analysis of stellar populations should be done with great caution.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1449-1454
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• 2014

The co-sensitization of N719 with a cyclic thiourea functionalized organic dye, coded AZ5, for dye-sensitized solar cells (DSSCs) was demonstrated. Due to its intensive absorption in ultraviolet region, AZ5 could compensate the loss of light harvest induced by triiodide, thereby the short-circuit photocurrent density ($J_{sc}$) was increased for co-sensitized (N719+AZ5) DSSC. Moreover, the electron recombination and dye aggregation were retarded upon N719 cocktail co-sensitized with AZ5, thus the open-circuit voltage ($V_{oc}$) of co-sensitized device was enhanced as well. The increased $J_{sc}$ (17.9 $mA{\cdot}cm^{-2}$) combined with the enhanced $V_{oc}$ (698 mV) ultimately resulted in an improved power conversion efficiency (PCE) of 7.91% for co-sensitized DSSC, which was raised by 8.6% in comparison with that of N719 (PCE = 7.28%) sensitized alone. In addition, co-sensitized DSSC exhibited a better stability than that of N719 sensitized device probably due to the depression of dye desorption.

• Wind and Structures
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• v.12 no.3
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• pp.179-204
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• 2009

A physical and numerical steady flow impinging jet has been used to simulate the bulk characteristics of a downburst-like wind field. The influence of downdraft tilt and surface roughness on the ensuing wall jet flow has been investigated. It was found that a simulated downdraft impinging the surface at a non-normal angle has the potential for causing larger structural loads than the normal impingement case. It was also found that for the current impinging jet simulations, surface roughness played a minor role in determining the storm maximum wind structure, but this influence increased as the wall jet diverged. However, through comparison with previous research it was found that the influence of surface roughness is Reynolds number dependent and therefore may differ from that reported herein for full-scale downburst cases. Using the current experimental results an empirical model has been developed for laboratory-scale impinging jet velocity structure that includes the influence of both jet tilt and surface roughness.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.2
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• pp.71-75
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• 2002

GaAs polycrystalline thin films with good performance were prepared on conducting glass by hot wall epitaxy (HWE), which were used for solar cell. Electron probe micro-analyzer (EPMA) was applied for the composition, morphology of surface and cross-section of grown films, and X-ray diffraction (XRD) for their phase structure; Raman scattering spectum (RSS) and photoluminescence (PL) were used for evaluating their optical characteristics. The results show that, there is textured structure on the surface of grown GaAs polycrystalline films, which is greatly promised to be suitable for the candidate of solar cell with low cost and high efficiency. It is concluded that the source and substrate at temperature of 900 ~ 930 $\^{C}$ and 500 $\^{C}$ respectively would be beneficial for such films.

• Geomechanics and Engineering
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• v.10 no.2
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• pp.125-135
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• 2016

Adhesion in geotechnical engineering is the interaction between cohesive soil and a solid surface which can cause clogging in mechanized tunnelling through clayey formations. Normal piston pull out and modified direct shear tests were performed on clayey soil samples to determine which type of adhesion stress, normal or tangential, could be most effectively measured. Measured values for normal adhesion ranged from 0.9 to 18 kPa. The range of tangential adhesion was 2.4 to 10 kPa. The results indicate normal adhesion results were more accurate than those for the modified direct shear test that measure tangential adhesion. Direct shear test on identical samples did not show any correlation between measured cohesion and normal adhesion values. Normal adhesion values have shown significantly meaningful variation with consistency index and so are compatible with the base of field clogging assessment criteria. But tangential adhesion and cohesion were not compatible with these assessment criteria.

• Journal of Ginseng Research
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• v.25 no.2
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• pp.82-88
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• 2001

This study was carried out to investigate a point of difference between normal and inferior Korean red ginseng (Naeback red ginseng = red ginseng with white part of clear boundary in phloem and/or xylem of ginseng body, saengnaeback red ginseng red ginseng with white part of indistinct boundary). White part with clear or indistinct boundary in center of ginseng body was observed in inferior red ginseng (naeback and saengnaeback red ginseng), and the differences in the internal color intensity was also found with naked eye. In hunter color values of normal and inferior parts of red ginseng in accordance with particle size, L value was increased with a diminishment in particle size, while a and b value were decreased. Absorbance at visible spectrum did not differ from water and 70% ethanol extract from normal and inferior parts of red ginseng, but absorbance in UV spectrum of extract from naeback part showed higher than those of normal and saengnaeback part. In comparison of intrastructure by electron microscope, the horizontal and vertical section of cortex and pith layer from normal part showed the very dense state, but small holes were found in naeback part of red ginseng by naked eye and electron microscope. The specific surface area of normal, naeback and saengnaeback part appeared 3.02, 3.33 and 6.55 ㎡/g, respectively. From above results, we consider saengnaeback red ginseng is red ginseng in the intermediate process which normal red ginseng changes to naeback red ginseng.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.824-828
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• 2003

This paper explains problems of force-reflecting teleoperation grinding work and proposes some methods to solve those. For stable contact between robot tool(grindstone) and contact surface the mechanical impedance force control is used. The sliding phenomenon of grindstone has been appeared at the contact surface during the grinding work. The sliding problems caused by friction and rotation of grindstone are eliminated by using tangential direction sliding compensation control. The rotation force of grindstone makes the tool move to tangential direction along the surface suddenly even though an operator pushes the tool only in normal direction to the surface. Normal direction force control is applied for grinder not to roll and fracture on the grinding surface. Vibration problem of grindstone is decreased by second order low-pass filter. Therefore we can precise grinding work at the grinding surface and feel the reality

• Tribology and Lubricants
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• v.20 no.3
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• pp.125-131
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• 2004

Nano-wear behavior of amorphous carbon films was studied by Atomic Force Microscopy. The a-C films are deposited on Si(100) substrate by DC magnetron sputtering method. The influences of different surface roughness on the nano-wear are investigated. Nano-wear tests were carried out using a very sharp diamond coated tip. Its spring constant was 1.6 N/m and radius of curvature was 110 nm. Normal force used in the wear tests ranged 0 to 400 nN. It was found that surface depression occurred during scratching because of plastic deformation and abrasive wear (cutting St ploughing). Wear depth increased linearly with normal force. Changing the surface roughness variables according to the bias pulse control, the less surface roughness decreased the wear depth. The thickness did not affect the wear resistance.

• Journal of Chest Surgery
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• v.7 no.1
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• pp.1-8
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• 1974

Acute pulmonary edema was induced by intravenous injection of epinephrine, intravenous infusion of dextran and intratracheal instillation of acid solution index was determined from pressure volume curves in excised lungs. Surface activity was also investigated with measurements of maximum and minimum surface tension and stability index on saline extracts of same lungs. The results were as follows. 1. The expansion index of excised lung in which pulmonary edema was induced by intravenous injection of epinephrine, intravenous infusion of dextran and intratracheal instillation of acid solution was ignificantly decreased as compared with the normal control of $0.86{\pm}0.017$ to $0.74{\pm}0.03$, $0.71{\pm}0.081$and $0.76{\pm}0.02$, respectively. 2. The deflation curves of excised lungs in which pulmonary edema was induced were significantly decreased as compared with the normal controls. 3. The minimum surface tension of excised lung in which pulmonary edema was induced was significantly increased in each groups and stability index was significantly decreased as compared with the normal controls 0.78 to $0.35{\pm}0.039$, $0.29{\pm}0.02 $ and $0.31{\pm}0.083$, respectively. 4. The decrease of pulmonary surface activity in acute pulmonary edema was in proportion to the degree of pulmonary edema regardless of their etiology.