• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.95-104
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• 2005

To know the proper setup posture for the various clubs, changes of setup variables according to the change of golf club length was investigated. Swing motions of three male low handicappers including a professional were taken using two high-speed videocameras. Four clubs iron 7, iron 5, iron 3 and driver (wood 1) were selected for this experiment. Three dimensional motion analysis techniques were used to get the kinematical variables. Mathcad and Kwon3D motion analysis program were used to analyze the position, distance and angle data in three dimensions. The variables divided into three categories 1) position and width of anterior-posterior direction 2) position and width of lateral direction 3) angles and evaluated based on the theories of many good golf teachers. Major findings of this study were as follows. 1.The stance (distance between ankle joints) was increased as the length of the club increased but the increasing width was not large. It ranges from 5cm to 10cm and professional player showed small changes. 2. Forward lean angle of trunk was decreased (more erected) as the length of the club increased. It ranges from 30 degrees for iron7 to 25 degrees for driver. 3. Angle between horizontal and right shoulder were increased as the length of the club increased. It ranges from 10 degrees to 20 degrees and professional player showed small changes. 4. Anterior-posterior position of the shoulders were located in front of the foot for all clubs and the difference between the shoulder and knee position was decreased as the length of the club increased. 5. Anterior-posterior position of grip (hand) was located almost beneath the shoulders (2.5cm front) for iron7, but it increased to 10cm for the driver. This grip adjustment makes the height of the posture increased only 5cm from iron7 to driver. 6. Lateral position of grip located at 5cm left for the face of iron7, but it located at the right side (behind) for the face of driver. 7. Lateral position of the ball located at the 40%(15cm) of stance from left ankle for iron7 and located at the 10% (5cm) of stance for driver. 8. Head always located at the right side of the stance and the midpoint of the eyes located at the 37% of stance from the right ankle for all clubs. This means that the axis of swing always maintained consistently for all clubs. 9. Left foot opened to the target for all subject and clubs. The maximum open angle was 25 degrees. Overall result shows that the changes of the setup variables vary only small ranges from iron7 to driver. Paradoxically it could be concluded that the failure of swing result from the excessive changes of setup not from the incorrect changes. These findings will be useful for evaluating the setup motion of golf swing and helpful to most golfers.

• Korean Journal of Applied Biomechanics
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• v.26 no.4
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• pp.343-351
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• 2016

Objective: The purpose of this study was to help improve game performance and provide preliminary data to enhance the efficiency of the kick and stability of the support foot by comparing the kinematic characteristics of the repeated side kick (geodeupyeopchagi) in poomsaeKoryo between expert and non-expert groups. Method: The subjects were divided into 2 groups according to proficiency in Taekwondo, an expert group and a non-expert group (n = 7 in each group), to observe the repeated side-kick technique. Four video cameras were set at a speed of 60 frames/sec and exposure time of 1/500 sec to measure the kinematic factors of the 2 groups. The Kwon3D XPprogramas used to collect and analyze three-dimensional spatial coordinates. Ground reaction force data were obtained through a force plate with a 1.200-Hz frequency. An independent samplesttest was performed, and statistical significance was defined as .05. The SPSS 18.0 software was used to calculate the mean and standard deviation of the kinematic factors and to identify the difference between the experts and non-experts. Results: The angular displacement of the hip joint in both the expert and non-expert groups showed statistical significance on E1 and E4 of the left support foot and E5 of the right foot (p<.05). The angle displacement of the knee joint in both groups showed statistical significance on E4 of the left support foot, and E1 and E2 of the right foot (p<.05). The angular velocity of the lower leg in both groups showed no statistical significance on the left support foot but showed statistical significance on E2 and E6 of the right foot (p<.05). The angular velocity of the foot in both groups showed no statistical significance on the left support foot but showed statistical significance on E2 of the right foot (p<.05). The vertical ground reaction force in both groups showed statistical significance on E2 (p<.05). The center of pressure in all directions in both groups showed statistical significance (p<.5). Conclusion: While performing the repeated side kick (geodeupyeopchagi), the experts maintainedconsistency and stability of the angle of the support leg while the kick foot moved high and fast. On the other hand, the angle of the support foot of non-experts appeared inconsistent, and the kick foot was raised, relying on the support leg, resulting in unstable and inaccurate movement.

• Journal of Korean Society of Transportation
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• v.19 no.6
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• pp.195-205
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• 2001

The objective of the paper is to analyze the traffic characteristics for freeway merging area. Freeway merging area is different from basic section due to ramp vehicles. Therefore, to understand the traffic characteristics of (leeway merging area, this study focused on two factors including critical time headway required in merging maneuver and maximum possible merging volume. In this paper, new model that adopts critical time headway instead of critical time gap in calculating the maximum possible merging volume based on probability function was developed In previous studies, for calculating the maximum possible merging volume, it was considered that merging vehicles could merge freely if a given time gap was greater than the critical time gap. Also, the critical time gap was used as the same value in all traffic flow conditions. But, a time gap required in merging maneuver could be changed, even to the same driver, because difference of relative speed varies in different traffic flow conditions. So, in some cases, the critical time gap could be insufficient value in merging maneuver. Therefore, in this study. a calculating procedure for critical time headway in all traffic flow conditions was presented. Also, the maximum possible merging volume and capacity for freeway merging area were calculated by using the previously found critical time headway.

• Journal of The Korean Society of Grassland and Forage Science
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• v.34 no.1
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• pp.60-67
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• 2014

The comparisons between cellulolytic bacteria adhesion on rice straw and fiber digestion in time course during rumen fermentation were studied in situ. The adhesions of cellulolytic bacteria, F. succinogenes. R. albus and R. flavefaciens, were measured by RT-PCR. When the rice straws were incubated at 0. 2, 4, 8, 12 and 24 hours of the in situ rumen, straw was degraded with increasing speed during the incubation and showed the highest disappearance increasing rate (DM g/h) from 8 to 12 hour. The adhesions of F. succinogenes, R. flavefaciens and R. albus were achieved above 80% in 1 hour of in situ rumen fermentation and then keep adhesive population up after the time of fermentation. When the in situ samples were collected at 0, 5, 10, 30 and 60 min to detect the early stages of adhesion on the rice straws ingested into rumen, the numberous adhesive colony of F. succinogenes, R. flavefaciens and R. albus were detected in 5 min. In case of rice straw treated with 0, 2, 4 and 8% NaOH, all of three cellulolytic bacteria showed the increasing trends of adhesion with increasing DM disappearance of rice straw by higher concentration of NaOH at 12 hour of in situ. However, there were showed respectively difference at 24 hour. The present results gave certain evidence that adhesion of cellulolytic bacteria is definitely achieved in early stage of roughage ingestion into rumen, their colony develop the stable communities on roughage in process of rumen fermentation and then fiber degradation is accelerated.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.4
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• pp.286-292
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• 1991

The authors propose to use the vortex generators in order to improve of the efficiency for the cambered otter boards. The equipments and testing method of this model test was the same as the previous report. This study was tested for 6 models such as the single cambered, the V-shaped cambered and the slotted cambered otter board without and with vortex generators. The results obtained are as follows: \circled1 C sub(L) of the single cambered model otter board with vortex generators was increased about 10% in comparison with that of model without vortex generators, C sub(D) decreased 2%, and L/D increased 5~20%. \circled2 L/D of the V-shaped cambered model otter board with vortex generators was increased 10~20% in comparison with that of model without vortex generators. \circled3 C sub(L) of the two slotted cambered model otter board with vortex generators was increased about 20% within an angle of attack 25$^{\circ}$ in comparison with that of without vortex generators, C sub(D) increased 5~20%, and L/D was higher than prototype within an angle of attack 20$^{\circ}$. \circled4 The separation point of the model otter boards with vortex generators was removed back ward a little in comparison with that of the model without vortex generators. \circled5 Flow speed difference of the back side to the front side of model otter boards with vortex generators was increased a little in comparison with that of the models without vortex generators. \circled6 The size of separation zone in case of the model otter boards with vortex generators was decreased about 10% in comparison with that of the models without vortex generators.

• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.45-53
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• 1987

The purpose of this study was to evaluate the tensile bond strength between composite resin and the human enamel. Three composite resin systems, two chemical (Clearfil Posterior, and Clearfil Posterior-3) and one light cure (Photo Clearfil-A), used with and without an intermediate resin (clearfil bonding agent), were evaluated under different amounts of load (10g, 200g and 200g for a moment) for in vitro tensile bond strength to acid-eched human enamel. Clinically intact buccal or lingual surfaces of 144 freshly extracted human permanent molars, embedded in acrylic were flattened with No #600 carborundum discs. Samples were randomly assigned to the different materials and treatments using a table of random numbers. Eight samples were thus prepared for each group(Table 2) these surfaces were etched with an acid etchant (Kurarey Co. Japan) in a mode of etching for 30 seconds, washing for 15 seconds, and drying for 30-seconds. During the polymerization of composite resin on the acid-etched enamel surfaces with and without bonding agent 10-gram, 200 gram and temporary 200 gram of load were applied. The specimens were stored in 50% relation humidity at $37^{\circ}C$ for 24 hours before testing. An universal Testing machine (Intesco model No. 2010, Tokyo, Japan) was used to apply tensile loads in the vertical directed (fig 5), and the force required for separation was recorded with a cross head speed of 0.25 mm/min and 20 kg in full scale. The results were as follow: 1. The tensile bond strength was much greater in applying a bonding agent than in not doing that. 2. The tensile bond strength of chemical cure composite resin was higher than that of light cure composite resin with applying on bonding agent on the acid-etched enamel. 3. In case of not applying a bonding agents on the acid-etching enamel, the highest tensile bond strength under 200 gram of load was measured in light cure composite resin. 4. The tensile bond strength under 200-gram of load has no relation with applying the bonding agent. 5. Under the load of 10-gram, There was significant difference in tensile bond strength as applying the bonding agent.

• Restorative Dentistry and Endodontics
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• v.30 no.1
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• pp.7-15
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• 2005

The purpose of this study was to compare the sealing ability of root canal obturation with or without the use of dentin adhesive system. Forty extracted human teeth with one canal were selected and decoronated. The teeth were divided into two Groups. The obturation procedure of Group 1 was the same as that of Group 2 with the exception of dentin adhesive system. Group 2 were obturated with dentin adhesive system, AH-26, and gutta-percha. After obturation, the teeth were immersed in methylene blue solution for 84 hours. The teeth were sectioned horizontally at 1.5 mm (Level 1), 2.0 mm (Level 2) 2.5 mm (Level 3) from the root apex using a low speed microtome. Distance of dye-penetrated surface and total dentinal surface were measured using SigmaScan Pro 5.0, and the ratio of dye-penetrated distance to the total dentinal distance was analyzed statistically by Mann-Whitney U-test. 1. In both groups, the mean leakage ratio was decreased cervically. 2. At level 1, there was no significant difference between group 1 and group 2 (p > 0.05). 3. At level 2 and 3, group 1 showed significantly higher mean leakage ratio than group 2 (p < 0.05). The results suggest that using dentin adhesive system in root canal obturation procedure reduces the apical microleakage.

• Restorative Dentistry and Endodontics
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• v.30 no.1
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• pp.31-37
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• 2005

The aim of this study was to evaluate the effectiveness of sealer placement in simulated root canal extensions. Forty resin blocks were attained from the Endo-training Bloc. In each block. The simulated root canal was made with $\#20$, 80taper GT file. After each block was longitudinally split into two halves, a standardized groove was prepared on one canal wall of two halves to simulate the canal extensions with various irregularities. The two halves of each block were assembled and all simulated root canals were obturated by single cone method with AH26 sealer. Four different methods of sealer placement were used: group A, $\#20$ K-file; group B, ultrasonic file; group C, lentulo spiral; group D, EZ-Fill bi-directional spiral. All obturated blocks were stored in $100\%$ humidity at $37^{\circ}C$ for 1 week, Using a low speed saw, each block was sectioned horizontally. Images of the sections were taken using a stereomicroscope at $\times$ 30 magnification and a digital camera. The amount of the sealer in the groove was evaluated using a scoring system, a higher score indicated better sealing effectiveness. The data was statistically analysed by Fisher's Exact Test. The sealing score was the lowest, specially at the middle area of canal extensions in group A, and that was statistically significant difference from other groups. In conclusion, the ultrasonic file, lentulo spiral and EZ-Fill bi-directional spiral were effective methods of sealer placement in simulated canal extensions. The K file was the least effective method, specially at the middle area of canal extensions.

• Restorative Dentistry and Endodontics
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• v.30 no.1
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• pp.16-21
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• 2005

The purpose of present study was to compare the speed of coronal leakage before and after post space preparation using Streptococcus mutans. Forty straight extracted human teeth were selected. The crowns were removed to a uniform remaining root length 14 mm. Canals were enlarged by 06 taper $Profiles^{(R)}$ to a size $\#40$ as a master apical file. And these were filled with gutta percha point and $Tubuliseal^{(R)}$ sealer, using continuous wave technique. Groupings are as follows. Group 1 - These teeth were obturated without sealer. Group 2 - These teeth were obturated and covered the surface of the root completely with sticky wax. Group 3 - These teeth were obturated. Group 4 - These teeth were obturated and prepared for post space remaining 5 mm of gutta percha. The teeth were suspended in plastic tubes. The upper chamber received the bacterial suspension everyday to simulate clinical situation. The lower chamber consisted of BHI added Andrade's indicator. All roots in the positive control group (Group 1) turned yellow within 24 h and those of negative control group (Group 2) remained red throughout the experimental period (70 days) The samples of group 3 were contaminated within an average of 27.2 days. The samples of group 4 were contaminated within an average of 15.7 days, ranging from 9 to 22 days. There was significant difference between group 3 and group 4 statistically (p < 0.05).

• Restorative Dentistry and Endodontics
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• v.25 no.2
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• pp.243-253
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• 2000

The purpose of this in vitro study was to evaluate dentin bonding by two different dentin bonding systems(DBS) using acetone based primer or adhesive [All Bond 2(AB2), One Step(OS)] when they were applied by wet or dry bonding technique. Morphology of resin-dentin interface and hybrid layer thickness(HLT) were investigated using Confocal Laser Scanning Microscope(CLSM) and compared to shear bond strength(SBS). 72 extracted sound human molars were randomly divided into 4 groups of 18 teeth each - Group 1.(AW); AB2 by wet bonding. Group 2(AD); AB2 by dry bonding. Group 3.(OW); OS by wet bonding, Group 4.(OD); OS by dry bonding. In 6 teeth of each group, notch-shaped class V cavities(depth 2mm) were prepared on buccal and lingual surface at the cementoenamel juction(12 cavities per group). To obtain color contrast in CLSM observation, bonding resins of each DBS were mixed with rhodamine B and primer of AB2 was mixed with sodium fluorescein. Prepared teeth of each group were treated with AB2, OS, respectively according to the manufacturer's instructions except for dentin surface moisture treatment after acid etching. In group 1 and 3, after acid etching, excess water was removed with wet tissue(Kimwipes), leaving consistently shiny, visibly hydrated dentin surface. In group 2 and 4, dentin surface was dried for 10 seconds at 1 inch distance. The treated teeth were then packed with composite resin(${\AE}$litefil) and light-cured. 12 microscopic samples($60{\sim}80{\mu}m$ thickness) of each group were obtained after longitudinal section and grinding(Exakt cutting and grinding system). Morphological investigation of resin-dentin interface and HLT measurement using CLSM were done. For measurement of SBS, remaining 12 teeth of each group were flattened occlusally to remove all enamel and grinded to 500 grit SiC(Pedemet Specimen Preparation Equipment). After applying DBS on the exposed dentin surface, composite resin was applied in the shape of cylinder, which has 5mm diameter, 1.5mm thickness, and light cured. SBS was measured using Instron with a crosshead speed of 0.5mm/min. It was concluded as follows, 1. HLT of AW(mean: $2.59{\mu}m$) was thicker than any other group, and followed by AD, OW, OD in descending order(mean; 2.37, 2.28, $1.92{\mu}m$). Only OD had statistically significant differences(p<0.05) to AW and AD. 2. There were intimate contact of resin and dentin at the interface in wet bonding groups, but gaps or irregular interfaces were observed in dry bonding groups. 3. The length, diameter, density of resin tags were various even in the same group without significant differences between groups and lots of adhesive lateral branches were observed. 4. There were no statistically significant difference of SBS between AB2 and OS, but SBS of wet bonding groups were significantly higher(p<0.05) than dry bonding groups. 5. There were no consistent relationships between HLT and SBS.