• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.355-356
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• 2015

This paper proposes a control strategy of total output power ripple cancellation for both of Machine-Side Converter (MSC) and Grid-Side Converter (GSC) in a DFIG under unbalanced grid conditions. The proposed control strategy for the MSC is the zero torque ripple control algorithm with an enhanced LVRT capability. The control algorithm for the MSC exhibits reduced torque pulsation in steady-state unbalanced grid conditions. In addition, this control algorithm also minimizes a peak value of rotor current in transient unbalanced grid conditions. The total output power ripple cancellation control algorithm is adopted in the GSC. The total output power ripple cancellation is achieved by nullifying the oscillating component of the total output active and reactive power at the summing point of stator and rotor of DFIG. The proposed control strategy for the GSC reduces the output power oscillation leading to the improved quality of wind farms output.

• The Journal of Korean Physical Therapy
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• 제10권1호
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• pp.81-98
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• 1998

Isokinetic evaluation of trunk flexors and trunk extensors was performed at $60^{\circ}/sec\;and\;120^{\circ}/sec$ of angular velocity by using cybex 6000TEF Unit on 31 healthy male white workers and 15 post-operative HILD patients with no significant difference in mean age and mean body weight between two groups, and compared each other. The purpose of this study is to obtain the isokinetic normative strength values and endurance latins for Dunk extensors and trunk flexors, and is to provide a guideline for rehabilitation program of post-operative HILD patients. The collected data were analyzed by ANOVA, Duncan's Nyktuoke Range Test, and Pearson correlation coefficiency in PC-SAS program, The results obtained were as follow ; 1. Post-operative subjects has lower isokinetic values than normal subjects in peak torque, peak torque $\%$ by body weight, total work, total work $\%$ by body weight, average power, average power $\%$ by body weight, TAAE of trunk flexors and trunk extensors, and there are significant differences with statistic value in trunk extensors at $60^{\circ}/sec$ and in trunk flexors and trunk extensors at $120^{\circ}/sec$ between two groups(p<0.05). 2. Pest-ooperative subjects has lower values for angle of peak torque than normal subjects in trunk extensors, and there are significant differences with statistic value at $60^{\circ}/sec$ and $120^{\circ}/sec$ between two groups. 3. Post-operative subjects has higher values for endurance ratios than normal subjects in trunk extensors and flexors, but there are no significant differences with statistic value between two groups. 4. Post-operative subjects has higher values than normal subjects in peak torque ratios, total work ratios, average power ratios of trunk flexors to trunk extensors, and there are significant differences with statistic value between two groups(p<0.01). 5. There is significant positive-correlation with statistic valve between peak torque and height and body weight in normal subjects(p<0.05), but Thjere is significant negative-correlation between peak torque of trunk extensor at $120^{\circ}/sec$ and age (p<0.05). 6. There is significant positive-correlation with statistic value between peak torque of trunk flexors and body weight in post-operative subjects (p<0.05), but There is significant negative-correlation between peak torque of trunk extensor add age (p<0.05). In conclusion, post-operative subjects have greater weakness in trunk musculature than normal subjects, especially there is more significant weakness in trunk extensors than in trunk flexors

• 한국유체기계학회 논문집
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• 제6권3호
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• pp.44-50
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• 2003

An experiment is conducted for measuring the performance of an air tool, which is operated at 100,000 RPM in an unloaded state with very low torque. A 551 kPa in gauge pressure is supply to the inlet of an air tool. An experimental apparatus is developed as a friction type dynamometer. Inlet total pressure, air flow rate, rotational speed and operating force are measured simultaneously. Torque, output power and specific output power are obtained with different rotational speeds. Those are compared with the experimental results which were obtained by a commercial dynamometer. However, no commercial dynamometers are available for measuring the torque above 30,000 RPM. In order to reduce the rotational speed, a reduction gear is applied between the air tool and the commercial dynamometer. Torque and power obtained by the commercial dynamometer show $55\%$ lower than those obtained by the developed friction type dynamometer, because the mass is added to the rotor of air tool for the braking system of the commercial dynamometer and power loss is generated by the reduction gear. From the compared results, the friction type dynamometer should be applied for measuring the performance of the air tool operating at low torque and high RPM.

• 대한치과교정학회지
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• 제44권4호
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• pp.177-183
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• 2014

Objective: To determine the unique contribution of geometrical design characteristics of orthodontic mini-implants on maximum insertion torque while controlling for the influence of cortical bone thickness. Methods: Total number of 100 cylindrical orthodontic mini-implants was used. Geometrical design characteristics of ten specimens of ten types of cylindrical self-drilling orthodontic mini-implants (Ortho Easy$^{(R)}$, Aarhus, and Dual Top$^{TM}$) with diameters ranging from 1.4 to 2.0 mm and lengths of 6 and 8 mm were measured. Maximum insertion torque was recorded during manual insertion of mini-implants into bone samples. Cortical bone thickness was measured. Retrieved data were analyzed in a multiple regression model. Results: Significant predictors for higher maximum insertion torque included larger outer diameter of implant, higher lead angle of thread, and thicker cortical bone, and their unique contribution to maximum insertion torque was 12.3%, 10.7%, and 24.7%, respectively. Conclusions: The maximum insertion torque values are best controlled by choosing an implant diameter and lead angle according to the assessed thickness of cortical bone.

• 구강회복응용과학지
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• 제31권4호
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• pp.310-315
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• 2015

목적: 본 연구는 토크 게이지를 이용하여, 치과 기공사들이 임플란트 기공을 진행할 때 가하는 토크의 양을 측정해 분석하고, 이러한 결과가 보철물에 어떠한 결과를 미치는 알아보기 위함이다. 연구 재료 및 방법: 치과 기공사들이 임플란트 기공시 임플란트 나사에 가하는 토크를 디지털 토크 게이지를 이용하여 측정한다. 이후 기성지대주와 analog를 이용하여, 제조사의 권장 토크로 조였을 때의 길이를 통계학적으로 비교 분석하였다. 결과: 치과 기공사들의 임플란트 기공시 평균 토크는 $1.563{\pm}0.332Ncm$로 나타났으며, 제조사의 권장토크 값으로 조였을 때와 비교하면, 외부연결형의 침하량 차이는 없으나, 내부연결형의 침하량의 차이는 통계적으로 유의한 차이를 보였다(P < 0.05). 결론: 치과기공실에서도 제조사의 권장토크를 이용하여 보철물 기공작업을 시행하고, 정확한 토크 게이지의 사용법을 익히면, 기공오차에 따른 임플란트의 부적합을 어느 정도 해소할 수 있을 것이라 사료된다.

• 한국운동역학회지
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• 제31권2호
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• pp.140-147
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• 2021

Objective: The purpose of this study is to identify the mechanism of changes in maximum voluntary torque with the magnitude and duration of pre-activation torque during voluntary isometric knee extension. Method: 11 male subjects (age: 25.91±2.43 yrs., height: 173.12±3.51 cm, weight: 76.45±7.74 kg) participated in this study. The subjects were required to produce maximal voluntary isometric torque with a particular pre-activation torque condition. The properties of pre-activation torque consisted of the combinations of 1) three levels of magnitude, e.g., 32 Nm, 64 Nm, 96 Nm, and 2) two levels of duration, e.g., 1 sec, and 3 sec; thus, a total of six conditions were given to the subjects. The force and EMG data were measured using the force transducers and wireless EMG sensor, respectively. Results: The results showed that the maximum voluntary torque increased the most with relatively large and fast (96 Nm, 1 sec) pre-activation condition. Similarly, with relatively large and fast (96 Nm, 1 sec) preactivation, it was found that the integrated EMG (iEMG) of the agonist muscles increased, while no significant changes in the co-contraction of the antagonist muscles for the knee extension. Also, the effect of pre-activation conditions on the rate of torque development was not statistically significant. Conclusion: The current findings suggest that relatively larger in magnitude and shorter in duration as the properties of pre-activation lead to a larger magnitude of maximal voluntary torque, possibly due to the increased activity of the agonist muscles during knee extension.

• Journal of Magnetics
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• 제22권2호
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• pp.257-265
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• 2017

This paper presents a 2-D analytical method to calculate the back EMF of the axial flux permanent magnet synchronous generator (AFPMSG) with coreless stator and dual rotor having magnets mounted on both sides of rotor yoke. Furthermore, in order to reduce the no load voltage total harmonics distortion (VTHD), the initial model of the coreless AFPMSG is optimized by using a developed analytical method. Optimization using the 2-D analytical method reduces the optimization time to less than a minute. The back EMF obtained by using the 2-D analytical method is verified by a time stepped 3-D finite element analysis (FEA) for both the initial and optimized model. Finally, the VTHD, output torque and torque ripples of both the initial and optimized models are compared with 3D-FEA. The result shows that the optimized model reduces the VTHD and torque ripples as compared to the initial model. Furthermore, the result also shows that output torque increases as the result of the optimization.

• Journal of Yeungnam Medical Science
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• 제36권1호
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• pp.43-49
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• 2019

Background: In the osseointegration of dental implants, the implant surface properties have been reported to be some of the most important critical factors. The effect of implant's surfaces created by resorbable blast media (RBM) followed by laser ablation on bone tissue reactions was examined using the removal torque test and histomorphometric analysis. Methods: Two types of dental implants, RBM-laser implants (experimental group) and RBM implants (control group) (CSM implant system, Daegu, Korea; L=6 mm, diameter=3.75 mm) were placed into the right and left distal femoral metaphysis of 17 adult rabbits. Six weeks after placement, removal torque was measured and histomorphometric analysis was performed. Results: The mean removal torque was $24.0{\pm}10.2Ncm$ and $46.6{\pm}16.4Ncm$ for the control and test specimens, respectively. The experimental RBM-laser implants had significantly higher removal torque values than the control RBM implants (p=0.013). The mean values of total and cortical bone to implant contact (BIC) were respectively $46.3{\pm}10.8%$ and $65.3{\pm}12.5%$ for the experimental group, and $41.9{\pm}18.5%$ and $57.6{\pm}10.6%$ for the control group. The experimental RBM-laser implants showed a higher degree of total and cortical BIC compared with RBM implants, but there was no statistical significance (p=0.482, 0.225). Conclusion: The removal torque and BIC of the test group were higher than those of the control group. In this study, the surface treatment created by RBM treatment followed by laser ablation appears to have a potential in improving bone tissue reactions of dental implants.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.75-78
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• 2004

Various jet engines (Turbine engine family and RAM Jet engine) have been developed for high speed aircrafts. but their application to hypersonic flight is restricted by principle problems such as increase of total pressure loss and thermal stress. Therefore, the development of next generation propulsion system for hypersonic aircraft is a very important subject in the aerospace engineering field, SCRAM Jet engine based on a key technology, Supersonic Combustion. is supposed as the best choice for the hypersonic flight. Since Supersonic Combustion requires both rapid ignition and stable flame holding within supersonic air stream, much attention have to be given on the mixing state between air stream and fuel flow. However. the wider diffusion of fuel is expected with less total pressure loss in the supersonic air stream. So. in this study the direction of fuel injection is inclined 30 degree to downstream and the total pressure of jet is controlled for lower penetration height than thickness of boundary layer. Under these flow configuration both streams, fuel and supersonic air stream, would not mix enough. To spread fuel wider into supersonic air an aerodynamic force, baroclinic torque, is adopted. Baroclinic torque is generated by a spatial misalignment between pressure gradient (shock wave plane) and density gradient (mixing layer). A wedge is installed in downstream of injector orifice to induce an oblique shock. The schlieren optical visualization from side transparent wall and the total pressure measurement at exit cross section of combustor estimate how mixing is enhanced by the incidence of shock wave into supersonic boundary layer composed by fuel and air. In this study non-combustionable helium gas is injected with total pressure 0.66㎫ instead of flammable fuel to clarify mixing process. Mach number 1.8. total pressure O.5㎫, total temperature 288K are set up for supersonic air stream.

• 대한물리치료과학회지
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• 제3권3호
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• pp.51-56
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• 1996

Isokinetic test of muscle strength was performed on 20 patients operated laminectomy & discectomy. Peak torque of ankle dorsi flexors & plantar flexors at the angular velocity of $30^{\circ}$/sec and average power and total work of ankle dorsi flexors & plantar flexors at the angular velocity $90^{\circ}$/sec were measured and analyzed. The result were as follows: 1. Peak torque of non - dominant dorsi flexors at $30^{\circ}$/sec showed no significant difference statistically, but dominant dorsi flexors at $30^{\circ}$/sec showed significant difference statistically(p<0.05). 2. Peak torque of dominant & non - dominant plantar flexors at $30^{\circ}$/sec showed significant difference statistically(p<0.05). 3. Average power of dominant & non - dominant dorsi flexors at $90^{\circ}$/sec showed no significant difference statistically. 4. Average power of dominant & non - dominant plantar flexors at $90^{\circ}$/sec showed significant difference statistically (p<0.05). 5. Total work of dominant & non - dominant dorsi flexors at $90^{\circ}$/sec showed no significant difference statistically. 6. Total work of dominant & non - dominant plantar flexors at $90^{\circ}$/sec showed significant difference statistically(p<0.05).