• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.560-564
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• 2004

The optimal design and combustion analysis of the gas generator for Liquid Rocket Engine (LRE) were performed. A fuel-rich gas generator in open cycle turbopump system was designed for 10ton$_{f}$ in thrust with RP-1/Lox propellant. The optimal design was done for maximizing specific impulse of main combustion chamber with constraints of combustion temperature and power matching required by turbopump system. Design variables were selected as total mass flow rate to gas generator, O/F ratio in gas generator, turbine injection angle, partial admission ratio, and turbine rotational speed. Results of optimal design show the dimension of length, diameter, and contraction ratio of gas generator. Also, the combustion test was conducted to evaluate the performance of injector and combustion chamber. And the effect of the turbulence ring was investigated on the mixing enhancement in the chamber.r.

• Physical Therapy Korea
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• v.7 no.2
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• pp.88-95
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• 2000

Thirty normal adults were tested to measure the electrical activity of the anterior (AD), middle (MD), and posterior portion (PD) of the deltoid muscle and sternal portion of the pectoralis major muscle (PM) during the performance of four upper extremity PNF diagonal patterns with elbow flexion angle in $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$. The PNF patterns in which these muscles function optimally have been theoretically advanced by Kabat and further described by Knott and Voss. They theorize that the MD should be most active with shoulder flexion, abduction, and external rotation (D2F); the PD with shoulder extension, abduction, and internal rotation (D1E); the AD with shoulder flexion, adduction, and external rotation (D1F); and the PM with shoulder extension, adduction and internal rotation (D2E). The patterns were performed through range of motion, with an isometric contraction performed in the shortened range. When the EMG activity of AD, MD, PD and PM in its optimal patterns was measured, it does not have significant difference among fixed elbow flexion angle $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ (p>.05). In addition, suggestions were made for study of patients who exhibit imbalance of muscle strength and have muscle weakness.

• Journal of Korean Physical Therapy Science
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• v.24 no.1
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• pp.14-21
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• 2017

Background; This study was to investigate effects of distance of muscle activity of 4 sections of rectus abdominis(RS-RA, LS-RA, RI-RA, LI-RA) by the shoulder width(x0.5, x1.0, x1.5) and the angle of the elbow joint($0^{\circ}$, $45^{\circ}$, $90^{\circ}$) Method : This study was conducted on 20 healthy male and 20 female adult. respectively, elbow joints were maintained at $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ flex postures on The shoulder width is 0.5, 1.0, and 1.5 times. at the same time 4 sections of rectus abdominis were measured using EMG with maintaining isometric contraction of the rectus abdominis for 5 seconds. Results; The results were as follows: First, muscle activity of 4 sections of rectus abdominis(RS-RA, LS-RA, RI-RA, LI-RA) by angle of the elbow joint($0^{\circ}$, $45^{\circ}$, $90^{\circ}$) was a statistically significant(p<0.05), Second, muscle activity of 4 sections of rectus abdominis(RS-RA, LS-RA, RI-RA, LI-RA) by the shoulder width(x0.5, x1.0, x1.5) was a statistically non-significant Conclusion; It was found to be most effective to perform arm posture with rectus abdominis muscle strength exercise.

• The Journal of Korean Physical Therapy
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• v.23 no.1
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• pp.13-19
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• 2011

Purpose:This study was designed to investigate difference in isokinetic muscle strength in the knee extensor muscle and characteristic differences in muscle strength between males and females through the ankle joint angles. Methods: Seventy-four subjects participated in this study. There were two groups: 36 males and 38 females. The mean age of the men was 24.58 years and women was 23.74 years. Subjects were seated on a CON-TREX LP (leg press) lean to back of chair, and there bodies were fixed by straps with the hip joint at an angle of $130^{\circ}$. After randomly fixing the ankle joint at $0^{\circ}$, $20^{\circ}$, and $40^{\circ}$ of plantar flexion (PF) in range of full extension of knee joint. We studied force max average, force max average/kg, power average, and total work through the angle of the ankle joint when the knee joint was extended from $90^{\circ}$ to $180^{\circ}$. Results: In the male group, all maximum measured value showed at the ankle joint $0^{\circ}$, all minimum measured value showed at $40^{\circ}$ PF (p<0.01). In the female group, all maximum measured value showed at the ankle joint $20^{\circ}$ PF, especially the power average increased significantly. All minimum measured value showed $40^{\circ}$ PF (p<0.01). Conclusion: There are differences between males and females in isokinetic muscle strength of the knee extensor through ankle joint angles in healthy adults. Males and Females have different characteristics of muscle strength through the ankle joint angles.

• PNF and Movement
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• v.9 no.1
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• pp.21-29
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• 2011

Purpose : The purpose of this study was to assess the effects of the lower extremity muscle activity on bridging exercise according to the knee joint angle. Methods : Twenty-five healthy adults volunteered to participate in this study. Subjects were required to complete following four bridging exercises; knee joint flexion $120^{\circ}$, $90^{\circ}$, $60^{\circ}$, $45^{\circ}$. Surface electromyography from selected lower extremity muscles was normalized to maximum voluntary isometric contraction. Muscle activity was measured by QEMG-4 system (LXM 3204, Laxtha Korea). A repeated measures of one-way ANOVA was used to determine the influence of bridging exercise on muscle activity for each muscle and descriptive statistics was used to determine muscle ratio. Results : The biceps femoris of all bridging exercises showed significantly(p<.05). The vastus medialis and lateralis of all bridging exercises showed significant excepted $120^{\circ}$(p<.05). The rectus femoris of all bridging exercises showed no significant. Median of vastus medialis/rectus femoris ratio of $120^{\circ}$ was 2.03, $90^{\circ}$ was 2.16, $60^{\circ}$ was 2.67, $45^{\circ}$ was 4.10. Median of vastus lateralis/rectus femoris ratio of $120^{\circ}$ was 1.70, $90^{\circ}$ was 1.70, $60^{\circ}$ was 2.08, $45^{\circ}$ was 2.58. Median of vastus medialis/vastus lateralis ratio of $120^{\circ}$ was 1.26, $90^{\circ}$ was 1.50, $60^{\circ}$ was 1.52, $45^{\circ}$ was 1.47. Conclusion : Angular motion decreasing with knee joint flexion made increase biceps femoris and vastus medialis activation. This result will be use knee joint stabilizing exercises during bridging or unstable surface training and biceps femoris strength training.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.3
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• pp.289-296
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• 2016

This study presents the kinematics of an intrinsic continuum robot actuated by pneumatic artificial muscles. The single section of a developed continuum robot consisted of three muscles in parallel. The contraction of each muscle according to applied air pressure produced spatial motions of a distal plate with respect to a base plate. Based on the bending behaviors of artificial muscles, the orientation and position of the end-effector of a continuum robot were formulated using a transformation matrix. The orientation and position was also determined for a single section of the distal plate. A Jacobian matrix relating the contraction rate or the pressure rate of the muscles to the velocity vector of the end-effector was calculated considering the assembled position of actuators between neighboring sections of the robot. Experimental results showed that the motions of the intrinsic continuum robot were accurately estimated by the proposed kinematics.

• Journal of Power System Engineering
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• v.20 no.5
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• pp.46-51
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• 2016

The TMCP steel has expanded in the marine structure during manufacturing process because of its excellent weld-ability and impact toughness. In the case of merchant ships, coverage of TMCP steel has been used widely on over DH36 Classifications material. The line heating process is applied to the outer surface of the steel plate for the shipbuilding. In this study, We compared between TMCP and normalizing steel for shipbuilding by analyzing some basic data through performing the natural cooling after the line heating. The experimental results show the angular misalignment changes in line heating. Heated surface of normalizing steel material expanded to $-0.3^{\circ}$ and reduced to $+0.2^{\circ}$ after cooling. And during cooling at $194^{\circ}C$ for 1,500 seconds, Angular Misalignment began from - direction to + direction, passed the critical point to the default at 2,200 seconds and did not take place any more at $103^{\circ}C$ after the 2,700 seconds. Angular Misalignment results of TMCP steels and Normalizing steel material show same angular misalignment lasted 1,200 seconds, TMCP steel has given more expansion and contraction angle which is $0.2^{\circ}$ than that of the Normalizing steel. Length difference between expansion and contraction is about 0.3 mm.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.8 no.2
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• pp.31-43
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• 2002

The subjects of this study were 15 woman soccer players and 15 untrained woman students at H-Cheju University. Each subject was measured on the muscle strength and peak torque of knee extensors and knee flexors with isokinetic load ($60^{\circ}$/sec, $180^{\circ}$/sec). The results were as follows: 1. There was no significant difference between right and left leg strength measured isokinetically in each group. 2. The peak torque of knee extensors and flexors was significantly higher in scoccer players than untrainded students (p<0.001). 3. For the angle of knee joint showing the highest peak torque, there was significant difference between soccer players and untrained students in knee extensors(p<0.05) and right flexors (p<0.01). 4. For knee H/Q ratio, there was significant difference between two groups(p<0.05). 5. For the total work and average power at $180^{\circ}$/sec, there was significant difference between two groups in knee extensors(p<0.001) and flexors(p<0.01). 6. In soccer players at $60^{\circ}$/sec, there were significant correlations between peak torque and height and between peak torque and weight.(p<0.001). 7. For the muscular contraction velocity at $60^{\circ}$/sec, there was significant difference between two groups in flexors (p<0.01). 8. For the muscular indurance at $180^{\circ}$/sec in extensors and flexors, there was no significant difference between two groups(p<0.05). In conclusion, there were significantly higher in peak torque, contraction velocity, knee joint's angle with the highest peak torque, H/Q ratio, total work and average power in woman scoccer player than general students. But there was no significant difference in muscular endurance. Soccer performance is based on the various components including muscular endurance that is one of the most important components. So it is necessary that the training method to improve the various components (especially including muscular endurance) should be done.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.91-108
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• 2000

Most of cervical abrasion and erosion lesions show gingival margin where the cavosurface angle is on cementum or dentin. Composite resin restoration of cervical lesion shrink toward enamel margin due to polymerization contraction. This shrinkage has clinical problem such as microleakage and secondary caries. Several methods to diminish contraction stress of composite resin restoration, such as modifying cavity form and building up restorations in several increments have been attempted. The purpose of this study was to compare polymerization contraction stress of composite resin in Class V cavity subjected to cavity forms and placement methods. In this study, finite element model of 5 types of Class V cavity was developed on computer tomogram of maxillary central incisor. The types are : 1) Box cavity 2) Box cavity with incisal bevel 3) V shape cavity 4) V shape cavity with incisal bevel 5) Saucer shape cavity. The placement methods are 1) Incisal first oblique incremental curing 2) Bulk curing. An FEM based program for light activated polymerization is not available. For simulation of curing dynamics, time dependent transient thermal conduction analysis was conducted on each cavity and each placement method. For simulation of polymerization shrinkage, thermal stress analysis was performed with each cavity and each placement method. The time-temperature dependent volume shrinkage rate, elastic modulus, and Poisson's ratio were determined in thermal conduction data. The results were as follows : 1. With all five Class V cavifies, the highest Von Mises stress at the composite-tooth interface occurred at gingival margin. 2. With box cavity, V shape cavity and saucer cavity, Von Mises stress at gingival margin of V shape cavity was lower than the others. And that of box cavity was lower than that of saucer cavity. 3. Preparing bevel at incisal cavosurface margin decreased the rate of stress development in early polymerization stage. 4. Preparing bevel at incisal cavosurface margin of V shape cavity increased the Von Mises stress at gingival margin, but decreased at incisal margin. 5. At incisal margin, stress development by bulk curing method was rapid at early stage. Stress development by first increment of incremental curing method was also rapid but lower than that by bulk curing method, however after second increment curing final stress was the same for two placement methods. 6. At gingival margin, stress development by incremental curing method was suddenly rapid at early stage of second increment curing, but final stress was the same for two placement methods.

• Journal of Oral Medicine and Pain
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• v.30 no.4
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• pp.411-426
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• 2005

The purpose of this study was to investigate the effects of occlusal condition and clenching level on the mandibular torque rotational movement. For this study, healthy 14 men without any symptoms and signs of temporomandibular disorders were selected. Mandibular torque rotational movement was observed in each circumstance of combination of three occlusal conditions such as natural dentition, with wafer of 3.6 mm thickness, and wafer with resin stop of 14 mm thickness total during hard biting of bite stick at maximum voluntary contraction(MVC) and 50% of MVC level of surface EMG activity of masseter muscle. Electromyographic activity and mandibular torque rotational movement were observed using BioEMG and BioEGN in $BioPak^{(R)}$ system. Each biting movement in each circumstance was composed of clenching one time and hard biting of wooden stick two times. The observed items were opening distance, velocity and amount of torque rotational movement in mandibular movement, and the data were statistically processed with $SPSS^{(R)}$ windows (ver.10.0). The results of this study were as follows: 1. There were no differences in the mandibular movement distance between those value in both biting sides, and between those in both clenching forces, but the mandibular velocity showed a different results by clenching force. For the amount of torque rotational movement, there were no difference in the value of the frontal plane but some significant difference was in the value of the horizontal plane by biting side. 2. The mandibular movement distance and the mandibular velocity in both planes were higher by maximum voluntary contraction than those by half maximum voluntary contraction, and amount of torque rotational movement in the horizontal plane was also increased by maximum voluntary contraction. 3. The opening distance in both planes were decreased with the increase of vertical dimension of occlusion, namely, by the occlusal appliances, and this pattern was also showed in the mandibular velocity in case of hard biting by maximum voluntary contraction. However, the amount of torque rotational movement were not different by the increase of vertical dimension of occlusion. 4. The value of angle and distance of the torque rotational movement in the hard biting of wooden stick were generally higher than those in the clenching without wooden stick in both planes without regard to occlusal conditions and/or clenching forces.