• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.67-79
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• 2003

The purpose of this study is to investigate the effective skill motion through the kinematic analysis of the Yurchenko Streched motion in new horse vaulting. The subjects in this study were 3 male gymnasts who were ranked as national athletes. After the 3D motion analysis, kinematic variables were analyzed to comparison with the difference between this study and the previous study(Yang, D. Y and Lee, C. S, 1999). As a result, the following conclusions was drawn; 1. In the board contact phase, this study showed a shorten contact time to maintain in condition highly extension of hip and hee angle than the previous study. 2. In the pre-flight phase, this study appeared more shortly flight duration time and horizontal flight displacement than the previous study. 3. In the horse contact phase, the contact duration time and horizontal displacement of COG shortened than the previous study, but appeared to the fast horizontal and vertical velocity and highly extension of shoulder an. 4. In the post-flight phase, a stable horse contact appeared to the increase of the flight duration time and the apex height during the post-flight. And it showed that these results have a stable and good landing.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.15-26
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• 2004

The purpose of this study was to investigate the kinematic variables of peters motion in parallel bars. The subjects were 3 male national gymnasts. For this study, kinematic data were collected using video camera. Coordinate data were low-pass filtered using a fourth-order Butterworth with cutoff frequency of 6Hz. Each valuables analyzed was used to compare kinematic features between the subjects. The conclusions were as follows; 1. For a stable regrasp motion, the subjects appeared to increase horizontal and vertical displacement during the DS phase because it induce a vertical elastic of body and reaction of bar for the US phase. 2. For a stable hand standing motion of the regrasp, the subjects appeared to maintain the fast vertical and horizontal velocity during the DS phase, but in contrary during the US and Air phase the vertical and horizontal velocity appeared to do decrease. 3. When the arm lean angle and the trunk lean angle maintain a big angle during the DS phase, the subjects appeared to do a stable performance to release in a high position.

• The korean journal of orthodontics
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• v.13 no.1
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• pp.73-82
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• 1983

The author studied on the dental arch widths and lengths and height of palates at 3 groups of dentition: mixed dentition, early permanent dentition, young adult, having normal occlusion and dentition. The models of the 336 maxillary and mandibular case, made from alginate-base hydrocolloid impressions were measured and analyzed statistically. The result as follows; 1. The upper intercanine width increased between the mixed dentition group and early permanent dentition group but there was no change in the young adult group in both sexes. The lower intercanine width increased between the mixed dentition group and early permanent dention group in the male. 2. The upper and lower 1st bimolar width increased slightly with age in the male but there was no change in the female. 3, The sex difference found in this study was one of absolute size, the female being slightly smaller than the male in the early permanent dentition group and young adult. 4. The arch length had no notable sexual differences and decreased between the mixed dentition group and early permanent dentition group. There was no change in the arch length in the young adult. 5. The height of palate increased gradually with age.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.944-947
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• 2000

Sculptured surface machining plays a vital role in the process of bring new products to the market place. A great variety of products rely on this technology for the production of the dies and moulds used in manufacturing. And, the use of CNC machines and CAD/CAM system has become a vital parts of product development process. The propose of this study is to investigate the effect of cutting parameters on the machinability such as surface roughness and cusp generated in the machining of sculptured surface on a three-axis CNC machining center using the CAD/CAM system. Experimental result showed that: In step down cutting, as the inclined angle of surface became smaller, the cusp height appeared higher. On the other hand, in step over cutting, as the inclined angle of surface became larger, the cusp height appeared higher. In the point of precision machining, step over cutting was more effective. For the minimization of cusp height, step down cutting was effective in larger inclined surface, but step over cutting in smaller inclined surface.

• Progress in Superconductivity
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• v.5 no.2
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• pp.114-117
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• 2004

We fabricated large single grain YBa$_2$Cu$_3$O$_{x}$ (Y-123) superconductors. The single grain Y-123 was grown by top seeded melt growth (TSMG) method. In a conventional box furnace with uniform temperature distribution, it was very difficult to grow large single grain Y-123 superconductors due to the size limitation in growth. To overcome the size limitation, we applied a radial thermal gradient (lower temperature at sample center and higher temperature on the sample edge) to the TSMG process. In this case, large single grain Y-123 could be easily grown. This is attributed that the liquid of the sample edge was maintained at the high temperature compared to the growth front. Using this method, we successfully fabricated a large single grain Y-123 of 6.4 cm X6.4 cm

• Progress in Superconductivity
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• v.5 no.2
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• pp.132-135
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• 2004

We fabricated YBCO thick films by using a screen printing method with $Y_2$BaCuO$_{5}$(Y211) and BaCO$_3$ powders on Cu-substrate in $N_2$ atmosphere. Cu-sheathed YBCO thick film process is more simple and economic than YBCO coated conductor methods. The heat treatment is performed in the range of 860 - 875 $^{\circ}C$ for 5 min in the tube furnace of $N_2$ atmosphere. The flow rate of $N_2$ gas is fixed 60 $m\ell$/min. Microstructure and phases of thick films were investigated by optical microscope, X-ray diffraction(XRD) and SEM. At heat-treatment temperature, the thick films were partially melted by liquid reaction between CuO of oxidized copper substrate and the powders screen-printed on Cu-sheath. During the heat-treatment procedure, YBCO superconducting grains nucleate.e.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.1-15
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• 2004

The purpose of this study was to investigate the kinematic variables of the upper part of the body for 8 elderly men during walking. For this study, kinematic data were collected using a six-camera (240Hz) Qualisys ProReflex system. The room coordinate system was right-handed and fixed in space, with righted orthogonal segment coordinate systems defined for the head, trunk, and pelvis. Based on a rigid body model, reflective marker triads were attached on the 3 segments. Three-dimensional Cartesian coordinates for each marker were determined at the time of recording using a nonlinear transformation(NLT) technique with ProReflex software (Qualisys, Inc.). Coordinate data were low-pass filtered using a fourth-order Butterworth with cutoff frequency of 6Hz. Three-dimensional angles of the head, trunk, and pelvis segment were determined using a Cardan method. On the basis of each segment angle, angle-angle plot used to estimated the movement coordinations between segments. The conclusions were as follows; (1) During the support phase of walking, the elderly people generally kept their, head the flexional and abductional posture. Particularly, the elderly displayed little internal/external rotation. (2) The elderly people showed extensional and external rotation postures in the trunk movement. Particularly, It showed the change from adduction into abduction at the heel contact event of the stance phase. (3) The elderly people showed almost same pelvis movement from the flexion into extension, from the abduction into adduction, and from internal rotation into external rotation at the mid stance and toe off of the stance phase.

• Physical Therapy Korea
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• v.6 no.1
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• pp.23-34
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• 1999

The purposes of this study were to investigate biomechanical variables of the lumbar spine for women who enjoy recreational exercises regularly, and to determine the factors that influence these variables. These variables were determined by the X-ray pictures of the lumbar area of 80 housewives who visited the department of rehabilitation at the Y Hospital from October 1997 to March 1998. The sacral inclination angle, the sacrohorizontal angle, the lumbosacral joint angle, and the lumbar lordotic angle were analysed. The t-test, correlation analysis, and multiple regression analysis were used to determine the significant differences and relationships among variables. The result were as follows: 1) There was a significant difference in the sacral inclination angle (p<0.01), the sacrohorizontal angle (p<0.05) and the lumbar lordotic angle (p<0.05) between the bilateral and the unilateral exercise group. 2) With the sacral inclination angle, the sacrohorizontal angle, the lumbosacral joint angle and the lumbar lordotic angle, correlation was found between the sacral inclination angle and the sacrohorizontal angle (p<0.01), the sacral inclination angle and the lumbosacral joint angle (p<0.05), the sacral inclination angle and the lumbar lordotic angle (p<0.05), and the sacrohorizontal angle and the lumbosacral joint angle (p<0.01). 3) In the bilateral exercise group, the sacral inclination angle correlated with age (p<0.01). The sacrohorizontal angle correlated with age (p<0.01) and exercise time (p<0.01). The lumbar lordotic angle correlated with age (p<0.05) and exercise duration (p<0.05). In the unilateral exercise group, the sacral inclination angle correlated with age (p<0.01), while the sacrohorizontal angle correlated with age (p<0.01) and exercise duration (p<0.05). The lumbar lordotic angle correlated with age (p<0.05).

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.47-65
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• 2003

The purpose of this study was to investigate the differences of the kinematical and the kinetical factors that calculated from preflight to postflight of salto forward straight 3/2 turn motion between skitters and less-skitters. four S-VHS video cameras operating at 60Hz were used to record the performances. five elite male gymnasts were participated in this study as subjects. three-dimensional coordinates of 20 body landmarks during each trial were collected using a Direct Linear Transformation method. The digitized body landmarks were smoothed using a Butterworth second order with low pass digital filter and a cutoff frequency of 10Hz. 1. A skitter, got a high score for performance, showed shorter time and faster horizontal velocity than a less-skitter at the board contact. also, a skitter extended quickly his knee and hip joint after contacting board for preflight phase. 2. A skitter revealed faster time and horizontal velocity the vault from taking off board than a less-skiller. A skitter took a long time and high distance to get the vertical peak compared with a less-skiller. 3. For the second phase, a skitter, who executes the most optimal motions among the subjects, displayed a long flight time, a high height, and a far flight distance as well as maintaining consistent horizontal speed even at the peak of post flight. On the other side, a less-scorer displayed a slow vertical velocity, distance and a short time at the point of take-off from vault as well as low height at the peak of post flight.

• Journal of the Korean Vacuum Society
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• v.1 no.3
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• pp.360-370
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• 1992

HWE(Hot-Wall Epitaxy) 방법에 의하여 pyrex 유리기판 위에 CdS 다결정 박막을 성장하였다. X-선 회절실험 결과 CdS 박막은 육방정이었는데 (0002)면보다 91013)면이 강 하게 성장됨을 알 수 있었다. 전자현미경으로 표면을 분석한 결과 입자의 크기는 기판의 온 도가 48$0^{\circ}C$, 증발원의 온도가 $610^{\circ}C$일 때 1~1.5$mu extrm{m}$로서 가장 컸다. 박막의 표면저항은 4-point probe로서 측정한 결과 10-8$\Omega$/\ulcorner이상이었다. 성장된 CdS 다결정 박막의 photoluminesence을 20K에서 측정하였는데 bound exciton, donor acceptor pair에 의한 발광이 관측되었다. Spectral response의 peak는 505nm이었다. CdS 다결정 박막의 표면 저항을 줄이기 위하여 여러 가지 온도에서 Indium을 확산시켰다. 그 결과 표면저항은 ~ $\times$ 101에서 ~ $\times$ 103$\Omega$/\ulcorner 정도 감소되었다. 50$0^{\circ}C$에 In을 1시간 확산시켰을 때 표면저항은 1300$\Omega$/\ulcorner이었다. 이 때 CdS : In의 운반자 농도는 1.2 $\times$ 1018cm-3, 이동도는 1.8cm-2/V-sec, 비저항은 1.3 $\times$ 10-2$\Omega$-cm이었다. CdS : In의 photoluminescence는 20K 에서 Gaussian curve를 보여 주었으며 peak의 위치는 510nm이었다. CdS : In 박막의 spectral response의 peak는 상온에서 500nm이다. CdS : In 광전도 cell의 sensitivity ${\gamma}$ =0.77이고, 최대 허용소비전력은 p=120mW, 100lux에서 rise time은 8 msec, decay time 은 6 msec이다.