• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.127-134
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• 2001

Nano adhesion and friction between a Sj$_3$N$_4$ AFM tip and thin silver films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM(atomic force microscope) and LFM(lateral force microscope) modes in various ranges of normal load. Thin silver films deposited by IBAD (ion beam assisted deposition) on Si-wafer (100) and Si-wafer of different surface roughness were used. Results showed that nano adhesion and friction decreased as the surface roughness increased. When the Si surfaces were coated by pure silver, the adhesion and friction decreased. But the adhesion and friction were not affected by the thickness of IBAD silver coating. As the normal force increased, the adhesion forces of bare Si-wafer and IBAD silver coating film remained constant, but the friction forces increased linearly. Test results suggested that the friction was mainly governed by the adhesion as long as the normal load was low.

• 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 Magnetics
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• v.12 no.1
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• pp.17-20
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• 2007

We performed magnetic force microscopy (MFM) observation on array of Co dots in order to understand magnetic state and magnetization behavior of submicron sized Co dots patterned on GaMnAs bridge. MFM observations showed the magnetization reversal and processes of local magnetization of individual ferromagnetic Co nanodots. Magnetic state of Co dots either single domain or vortex is dependent on geometrical size and thickness. Transition from single domain to vortex state can be realized with MFM tip assisted local field. Magnetization reversal process takes place through sequential reversal of individual dots. Localized inhomogeneous magnetic field can be manipulated by controlling magnetic state of individual Co dot in the array structure.

• International Journal of Control, Automation, and Systems
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• v.4 no.6
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• pp.748-755
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• 2006

In this paper, a trade-off design and fabrication of IPMC(Ionic Polymer Metal Composites) as an actuator for a flapping device have been described. Experiments for the internal solvent loss of IPMCs have been conducted for various combinations of cation and solvent in order to find out the best combination of cation and solvent for minimal solvent loss and higher actuation force. From the experiments, it was found that IPMCs with heavy water as their solvent could operate longer. Relations between length/thickness and tip force of IPMCs were also quantitatively identified for the actuator design from the tip force measurement of 200, 400, 640, and $800{\mu}m$ thick IPMCs. All IPMCs thicker than $200{\mu}m$ were processed by casting $Nafion^{TM}$ solution. The shorter and thicker IPMCs tended to generate higher actuation force but lower actuation displacement. To improve surface conductivity and to minimize solvent evaporation due to electrically heated electrodes, gold was sputtered on both surfaces of the cast IPMCs by the Physical Vapor Deposition(PVD) process. For amplification of a short IPMC's small actuation displacement to a large flapping motion, a rack-and-pinion type hinge was used in the flapping device. An insect wing was attached to the IPMC flapping mechanism for its flapping test. In this test, the wing flapping device using the $800{\mu}m$ thick IPMC. could create around $10^{\circ}{\sim}85^{\circ}$ flapping angles and $0.5{\sim}15Hz$ flapping frequencies by applying $3{\sim|}4V$.

• Korean Journal of Agricultural Science
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• v.39 no.1
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• pp.29-34
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• 2012

This study was carried out to identify the characteristics of 37 corn hybrids, which composed with 18 yellow colored kernel, 9 purple colored kernel, 8 white colored kernel. Days to silking of three colored waxy corn hybrids ranged from 61 to 73 days after sowing as midium-late ecotype. Ear length of hybrids ranged from 10.3 to 22.7 cm, and among them a total 22 waxy corn hybrids including CNU038 showed over 20 cm in ear length. The fresh weight per ear ranged from 58 to 289 g as the 32.9% of large coefficient of variance. In there results, we found yellow colored waxy corn hybrids showed relatively longer in ear length and heavier in fresh weight per ear compare to other colored waxy corn hybrids. In correlation relationships, plant height, ear height, stem diameter, ear length and ear weight showed positive correlation between themselves, while tip filling ratio did negative correlation with silking stage, plant height, ear length, ear weight and kernel thickness. Also, 100 kernel weight did positive correlation between traits related to ear and kernel.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.57-66
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• 2013

In this study, pullout tests were carried out to evaluate pullout characteristics of waste fishing net (WFN), which added into bottom ash for recycling both bottom ash and WFN. Three different mesh size of WFN (WFN20:$20mm{\times}20mm$, WFN30:$30mm{\times}30mm$, WFN40:$40mm{\times}40mm$) and geogrid were added as a reinforcement. Pullout characteristics of waste fishing net were compared with those of the geogrid. Pullout test results showed that pullout strength and stiffness of WFN20 are a little less than those of geogrid. However, the pullout friction angle of WFN20 is similar to that of geogrid due to bearing resistance induced from transverse rib because thickness of WFN20 is greater than geogrid. Pullout test results also indicated that distribution of residual strain along reinforcement after test depends on overburden stress. Residual strain at the tip of reinforcement increased with an increase in overburden stress due to concentration of pullout force on the tip of reinforcement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.723-726
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• 2005

The two major obstacles in the application of IPMC to flapping actuators operated in the air are solvent loss and actuation force. In this paper, solvent loss of various IPMCs made of Nafion$^{TM}$117(183$\mu$m thickness) has been experimentally investigated to find out the best combination of cation and solvent for minimal solvent loss in IPMCs and higher actuation force. For this purpose. experiments for the internal solvent loss measurement of IMPCs have been conducted for various combinations of cation and solvent. From the experiments, it was found that heavy water showed improvement in the operating time up to more than two minutes. in the tip force measurement of IPMCs, it was found that smaller and thicker IPMCs produced larger tip forces. However, the shorter IPMCs generated reduced actuation displacements and created flapping motion with decreased natural frequency. For the design of flapping device actuated by 5mm wide, 10mm long, 0.2mm thick IPMCs were used in the stacked form. Since the actuation force is a few gram-force, we stacked five IPMCs to improve actuation force. To amply the actuation force, rack-and-pin ion type hinge was used for the flapping device and insect (Cicadidae) wing was attached to the stacked IPMC actuator. In the flapping test, the device could generate flapping angle of 15$^{\circ}$ at 6Hz excitation by 2.5 voltage square wave input.

• The korean journal of orthodontics
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• v.12 no.2
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• pp.79-93
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• 1982

The purpose of orthodontic treatment is to achieve normal occlusion and good facial esthetics for individual patients. To produce harmonized facial balance, treatment planning for patient who require orthodontic treatment should include both a hard tissue and soft tissue cephalometric analysis. Author studied to derive the normal standards of soft tissue profile in Koreans by roentgenocephalometric analysis. For this study 12 soft tissue profile landmarks were plotted and 23 linear length, 9 soft tissue thickness, 8 vertical height length, 12 angles of soft tissue profile, and 3 vertical proportion were measured. The subjects consisted of 166 males and 209 females from 7 to 19 years with normal occlusion and acceptable profiles, and were divided into five groups according to age. The obtained results were as follows; 1. From the basis of N-Pog (Nasion-Pogonion) plane, the growth of facial soft tissue in the middle region especially nose area was greater than others facial region. 2. From the basis of G-Pog' (Glabella-soft tissue Pogonion) plane, the values of linear measurement of soft tissue Nasion and Inferior labial sulcus decreased and nose tip grew forward as growing older. 3. The growth of the facial soft tissue thickness was greatest in superior labial sulcus and the thickness of soft tissue nasion gradually became thinner as growing old. 4. The thickness of upper and lower lip was 14.47mm, 14.57mm in adulr male, 12.76mm, 13.78mm in adult female. 5. The soft tissue thickness of the lower lip was thicker than that of upper lip in all age groups and both sexes, 6. The vertical length of the upper and lower lips were 25.04mm, 49.97mm in adult male and 23.50mm, 48.39mm in adult female. 7. By the significant test, there were significant difference between male and female in fifth adult group on all vertical length measurements of lower face. 8. In fifth adult group, the perpendicular distance from LS, LI to Steiner's line and Ricketts' esthetic line were as follow; Steiner line to LS, LI were 7.98mm, 5.84mm in male. Steiner line to LS, LI were 6.71mm, 5.08mm in female. Ricketts' esthetic line to LS, LI were -0.40mm, 1.72mm in male. Ricketts' esthetic line to Ls, LI were -1.38mm 0.65mm in female. 9. In fifth adult group, the facial convexity angle and lower facial component angle were $171.17^{\circ}142.94^{\circ}$ in male and $172.5^{\circ}$, $144.41^{\circ}$ in female.

• 한국해양학회지
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• v.25 no.2
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• pp.62-73
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• 1990

An experimental study is performed in order to catch the characteristics of the flow field at arrested salt wedge, using a rectangular open channel. Arrested salt wedge is generally so stable that the observations are easy, but velocities and interfacial waves are measured with the aid of visualization method, by injection of fluorescent dyes. The density interface, which is defined as the zone of maximum density variation with depth, exists in about 0.5 cm below the visual interface, and vertical density profile is quite well satisfied with Homeborn model. Interfacial layer has high turbulent intensity and its thickness decreases as the overall Richardson number increases and has magnitude of roughly 17% of upper layer. Cross-sectional velocity distribution just shows the influence of a side-wall friction and in the upper layer vertical velocity profile also becomes uniformly as Reynolds number increases, but in the lower layer it shows nearly parabolic type. Supposes that we divide salt wedge into three domains, that is, river mouth, intermediate and tip zone, entertainment coefficient is small at the intermediate zone and large at the river mouth and the tip zone. River mouth or intermediate zone has comparatively stable interface and capillary wave therefore s produced and propagated downstream. On the other hand, tip zone is very unstable, cusping ripple or bursting ripple is then produced incessantly. Arrested salt wedge form is nearly linear and has no relation to densimetric Froude number and Reynolds number.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.563-572
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• 2004

Since bacterial plaque is known as the major cause of every oral disease, it is necessary to control plaque to maintain periodontal health. Although tooth brushing has been the typical method of plaque control, additional use of plaque control devices are necessary for cleansing interdental areas. Dental floss has been used for a long time as the additional plaque control device and proved to be effective. The newly developed embossed new dental pick is composed of elastic plastic material in form with its tip longer than other toothpick. In addition, as thickness of the tip gradually increases, it can be adapted easily with minimal trauma to interdental gingiva. The embossed tip can remove dental plaque easily, and the opposite end can approach lingual and palatal areas through triple angulation. Therefore, the authors studied the effect of embossed new dental pick and dental floss on periodontally involved 15 patient. The following results were obtained. 1. For embossed new dental pick, probing depth at baseline, 1 week, 4 weeks were $3.6{\pm}0.6mm$, $3.4{\pm}0.5mm$, $3.2{\pm}0.5mm$, respectively, and $4.2{\pm}0.9mm$, $4.1{\pm}0.9mm$, $4.0{\pm}0.9mm$, respectivly for clinical attachment level. 2. In case of embossed new dental pick, bleeding on probing at baseline, 1 week, 4 weeks were $43.0{\pm}4.4%$, $28.5{\pm}5.1%$, $22.2{\pm}5.6%$, respectively, and, at 1 week and 4 weeks, they were significantly different from that of dental floss. 3. Gingival index of toαhpick at baseline, 1 week, 4 weeks were $1.7{\pm}0.5$, $1.0{\pm}0.3$, $0.9{\pm}0.2$, respectively, and, $1.7{\pm}0.5$, $1.1{\pm}0.4$, $1.0{\pm}0.4$, respectively for plaque index, and $3.0{\pm}0.5$, $1.7{\pm}0.5$, $1.4{\pm}0.4$, respectively for proximal plaque index. proximal plaque index at 4 weeks was significantly different from that of dental floss. 4. The result of questionnaire showed that the two types of device were both satisfactory, however, embossed new dental pick had higher preference as well as satisfaction. As a result, embossed new dental pick is thought to be clinically effective for its simplicity and good accessibility.