• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.964-972
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• 2007

Wind turbine experiment was carried out for the horizontal axis wind turbine with the aerodynamically optimized blade. From the comparison of aerodynamic performance between upwind and downwind type wind turbine rotor, the measured torque fluctuation of the latter is larger than that of the former. This phenomenon is owing to the interaction of wake generated from support column and blades. The wind turbine model satisfies the design condition in that the measured result of the power coefficient at zero pitch angle shows maximum peak at the designed tip speed ratio, λ = 6. It also shows that the decrease in aerodynamic power due to negative pitch change is more sensitive than that of the same positive pitch change.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.4
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• pp.234-244
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• 2014

Recently it has been focused that the automobile engine has developed in a strong upward tendency for the use of the high viscosity and poorer quality fuels in achieving the high performance, fuel economy, and emission reduction. Therefore it is not easy to solve the problems between low specific fuel consumption and exhaust emission control at motor cars. In this study, it is designed and used the engine test bed which is installed with turbocharger and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters, and they were engine speeds(rpm), injection timing(bTDC), and engine load(%). From the result of an experimental analysis, peak cylinder pressure and the rate of pressure rise were increased, and the location of it was closer toward top dead center according to the increasing of engine speed and load, and with advancing injection timing. The combustion characteristics are effected by fuel injection timing due to be enhanced the mass burned fraction. Using the engine dynamometer for analyzing the engine performance, the engine torque and power have been enhanced according to advancing the fuel injection timing. In analyzing of exhaust emission, there has been a trade-off between PM and NOx with increasing of engine speed and load, and with advanced injection timing. The experimental data are shown that the formation of NOx has increased and PM, vice versa.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.21 no.1
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• pp.1-4
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• 2015

Background: This study was conducted in order to see if muscle strength is different according to fall experience in female elders by comparing their muscle strength of waist and knee, which is one of factors inducing fall. Method: For this study, 22 female elders aged over 65 sampled from senior centers in D City were surveyed on their fall experiences using a questionnaire asking clinical history. Then, 8 elders with fall experience (FE) and another 8 without (NFE) were selected and participated in the research. Isokinetic muscle strength was measured with isokinetic equipment BIODEX SYSTEM 3 PRO, and the peak torque was obtained from the highest of 9 measurements at angular velocity $60^{\circ}/sec$ according to the method recommended in the manual. Measured items were waist flexion and extension, and knee flexion and extension. Results: The FE group showed higher extensor and flexor muscle strength of the waist, but the difference was not significant (p<.05). In addition, no difference was observed in extensor muscle strength of the knee (p<.05). In flexor muscle strength, however, the FE group was significantly higher than the NFE group (p<.05). Conclusion: The application of regular exercise programs for improving muscle strength, endurance, etc. to those with fall experience will be effective in preventing falls among them.

• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.153-158
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• 2019

The purpose of this study was to compare the isokinetic muscular strength of the knee joint between female volleyball and table tennis players. A total of 27 elite volleyball players and 27 table tennis players participated in the study. This study measured both knee extensor and flexor strengths of volleyball and table tennis players using the isokinetic dynamic test. Peak torque was measured by performing maximal voluntary flexion and extension three times at $60^{\circ}/s$. Volleyball players had higher knee extensor and flexor strengths than table tennis players. No significant difference in both knee strengths was noted in table tennis players. However, volleyball players showed significant differences in both knee strengths. Height and weight showed a positive correlation with knee strength. This study found that volleyball players had greater knee strength than that of table tennis players. We also found that volleyball players have asymmetrical knee strength. Comparison with other sport players is warranted to better understand isokinetic muscular strength of the knee joint.

• Physical Therapy Korea
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• v.26 no.2
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• pp.49-60
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• 2019

Background: After stroke, in order to improve gait function, it is necessary to increase the muscle strength and to enhance the propriocetive function of the lower extremity. Objects: This study aimed to compare the effects of open kinetic chain (OKC) versus closed kinetic chain (CKC) isokinetic exercise of the hemiparetic knee using the isokinetic equipment on lower extremity sensorimotor function and gait ability in patients with chronic stroke. Methods: Thirty participants with chronic hemiplegia (> 6 months post-stroke) were randomly divided into 2 equal groups: CKC group and OKC group. Patients from both groups attended conventional physiotherapy sessions 3 times a week for 6 weeks. Additionally, subjects from the CKC group performed isokinetic exercise using the CKC attachment, while those from the OKC group performed isokinetic exercise using the OKC attachment. The isokinetic knee and ankle muscles strength, position sense of the knee joint, and spatiotemporal gait parameters were measured before and after interventions. Results: The knee muscles peak torque/body weight (PT/BW) and hamstring/quadriceps (H/Q) ratio significantly increased in both groups (p<.01). In particular, ankle plantarflexors PT/BW, position sense of the knee, gait velocity, and spatial gait symmetry significantly improved in the CKC group (p<.01, p<.05, p<.01, and p<.01, respectively). Conclusion: CKC isokinetic exercise can be an effective therapeutic intervention for the improvement of sensorimotor function of the lower extremity and gait functions, such as gait velocity and symmetry. CKC position in isokinetic strength training is effective to improve functional ability in patients with chronic stroke.

• Physical Therapy Rehabilitation Science
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• v.11 no.1
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• pp.16-23
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• 2022

Objective: This study aimed to investigate the effect of adding hip abductor strengthening to conventional rehabilitation on muscle strength and physical function following total knee replacement (TKR) for knee osteoarthritis. Design: Randomized controlled trial Methods: Thirty-five participants were randomly allocated to exercise groups I (n=18) and II (n=17). Group I underwent hip abductor training and conventional rehabilitation for 30 min per day, 5 days per week for 4 weeks. Group II underwent conventional rehabilitation for 30 min per day, 5 days per week for 4 weeks. The participants in both groups also received continuous passive motion therapy for 15 min per day, 5 days per week for 4 weeks. To investigate the effect of the intervention, the Biodex dynamometer was used to measure the peak torque of both knee extensors and hip abductors. This study used the Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS) to assess physical function, as well as the figure-of-8 walk test (F8W) and the stair climb test (SCT). Results: According to the interventions, exercise groups I and II showed significantly improved muscle strength and KOS-ADLS, F8W, and SCT scores (p<0.001). Compared with that of exercise group II, exercise group I showed significantly improved hip abductor strength (p<0.001) and KOS-ADLS, F8W, and SCT scores (p<0.05). Conclusions: The results of this study indicate that the combination of hip abductor strengthening and conventional rehabilitation is an effective exercise method to increase hip abductor muscle strength and physical function after TKR.

• The Journal of Korean Physical Therapy
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• v.33 no.6
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• pp.278-285
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• 2021

Purpose: This study investigated the effects of open kinetic chain (OKC) exercise for the gastrocnemius (GCM) and tibialis anterior (TA) muscles on static and dynamic balance and muscle strength. Methods: We recruited 21 healthy participants, dividing them into 3 groups (GCM, TA, and non-exercise). Each group contains 7 participants. Two exercise groups (GCM and TA) performed OKC exercise with elastic bands twice per week for 4 weeks, while non-exercise group did nothing. We obtained the data for static and dynamic balance and muscle strength before and after the intervention. We used the Kruskal-Wallis test to compare and analyze the pre-post-intervention differences among the groups. Results: For static balance, the stability index of the TA group was the lowest for the dynamic platform (p<0.05). The dynamic balance of the TA group increased for the anterior and posteromedial directions (p<0.05). The peak torque increased in the TA group for dorsiflexion (D/F) movement and in the GCM group for plantar flexion movement compared with the other groups, except for the left direction during D/F (p<0.05). Conclusion: OKC exercises with elastic bands were effective for selectively increasing muscle strength. It is clinically thought that strength training for TA muscles will be effective among the muscles of the ankle.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.214-220
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• 2023

Because there exist a region in the rotational speed and torque map that the a particular combination of a motor and an ESC (Electronic Speed Control) can maintain its peak efficiency, identifying this region is important for designing an efficient system. Firstly the accuracy of the measurement device is verified using the published propeller measurement data. And then, the combined motor-ESC efficiencies of an individual propeller are measured at a wide range of rotational speeds. With measurements obtained from a large number of different propellers, efficiency contours are obtained. It is shown that there exist a significant difference between the measured combined efficiency and the motor efficiency computed using a simple model. In addition, with the same motor, the combined efficiency can have a meaningful variation depending on the model of the ESC. The efficiency contours derived from this study will be useful for the design and optimization of electric propulsion systems of an aircraft where propulsion efficiency is critical.

• Physical Therapy Rehabilitation Science
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• v.11 no.4
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• pp.414-420
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• 2022

Objective: In this study, the test-retest reliability and validity were presented to evaluate the usability of isokinetic rehabilitation equipment for the knee joint. Design: Cross-sectional design, reliability & validity study. Methods: Thirty healthy adults participated in the study. A CSMI dynamometer was used as a standardized measuring device to present the validity of the equipment. It was measured based on the dominant leg. The average peak torque value was selected as the measurement variable. After the measurement, a questionnaire was conducted on safety, satisfaction, and performance through the usability evaluation questionnaire. Results: The knee joint isokinetic rehabilitation equipment showed high reliability with Intraclass Correlations Coefficients (ICC) =0.883~0.956. In order to check the validity of the equipment, the 95% confidence interval of the mean difference limit was confirmed by the Bland & Altman plot. As a result, all three angular velocities showed a smaller confidence interval in the flexion than in extension. There were less than 10 plots that were not included in 2 Standard Deviation (SD) between all measurements. As a result of the usability evaluation questionnaire, the average of the safety domain(4.9±0.4), satisfaction domain(4.1±0.8), performance domain(4.3±0.8). Conclusions: If the product is improved by supplementing the items identified in the usability evaluation process, it is judged that it can be used as a useful device in various knee joint rehabilitation fields.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.335-341
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• 2009

Statements of problem: Adequate bone quality and quantity were important to achieve initial stability and to prevent early failures. However there were few published data available regarding the actual effect of dimensional change in implant geometry on initial stability. Purpose: The purpose of the current study was to investigate the influence of diameter and length changes on initial stability of implants. Material and methods: Four types of dummy bone (D1, D2, D3 and D4) consisted of cortical and cancellous layers with different thickness were simulated. Implants which had similar surface area to each other ($3.5{\times}13.0-mm$, $4.0{\times}11.5-mm$, $4.5{\times}10.0-mm$, $5.0{\times}8.5-mm$) were inserted in dummy bones. Implant stability as a function of peak insertion torque and resonance frequency values were recorded for each implant. Results: 1. Bone quality was a major influential factor to achieve initial stability (P <.05). 2. In D1, D2 and D3 dummy bones, implant stability quotient values were not significantly different to each other (P >.05), however insertion torques were increased with wider and shorter implants (P <.05). 3. In D4 dummy bone, implant stability quotient values and insertion torques were decreased with wider and shorter implants (P <.05). Conclusion: From a point of view of initial stability, it is suggested that use of wide and short implant may be helpful in avoiding bone augmentation procedures in area of adequate bone quality.