• 한국산학기술학회논문지
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• 제19권5호
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• pp.72-81
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• 2018

본 논문에서는 영구자석형 동기전동기를 구동하는 인버터에서 사용할 수 있는 정현파 전류 운전 방식과 120도 운전 방식 및 150도 운전 방식에 대하여 각각 시뮬레이션을 수행하고 이것들의 운전 특성을 비교 분석한다. 이 운전 방식들은 통전각과 전동기의 상전류에 형태로 구분이 된다. 종래에는 인버터의 효율 향상을 위하여 정현파 전류 운전 방식과 120도 운전 방식 간의 전환 방법에 중점을 둔 연구가 많았으나, 본 논문에서는 이들 각각의 운전 방식에 대한 운전 특성을 비교 분석하여 그것들의 장점을 다양한 전환 방법으로 응용할 수 있도록 하는데 중점을 둔다. 이를 위하여 각각의 운전 방식에 대하여 전동기의 발생 토크, 속도 응답 특성, 상전류 THD에 대하여 시뮬레이션을 수행하였다. 그 결과로 정현파 전류 운전 방식이 3가지 운전 방식들 중에서 전체적으로 가장 좋은 성능을 보였고, 120도 운전 방식은 150도 운전 방식에 비하여 속도 응답 특성이 다소 우수하였으며, 150도 운전 방식은 120도 운전 방식에 비하여 상전류 THD가 낮은 것을 확인하였다.

• 전기전자학회논문지
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• 제23권1호
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• pp.9-13
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• 2019

본 논문에서는 원가 절감을 위한 개선된 $165^{\circ}$ 12 스텝 제어를 고려한 브러시리스 DC 전동기의 최적화 설계에 대하여 논한다. 개선된 12 스텝 제어는 기존 제어의 도통각 $150^{\circ}$을 확장시켜 전동기의 출력을 향상 시킬 수 있다. 향상된 전동기 출력을 고려한 반응 표면법을 이용한 최적화 설계를 통해서 회전자, 고정자 및 영구자석의 부피를 감소시켜 원가절감이 가능한 설계를 제시한다. 제안된 설계는 기존 전동기의 요구 사양 및 효율 향상을 만족하고 기존 전동기 중량의 약 3.5%를 저감하였다. 유한요소법을 이용한 전자계 해석을 통해 최적화 설계의 타당성을 입증하였다.

• 전기학회논문지
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• 제66권9호
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• pp.1325-1333
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• 2017

The sensorless control of blushless DC motor(BLDCM) is based on the $120^{\circ}$ control in which the back electromotive force(Back EMF) for estimating the position of the rotor can be detected. However, the $120^{\circ}$ control has a disadvantage that the torque constant is small as compared with $180^{\circ}$ control which can not detect the back EMF. The $150^{\circ}$ control which complements these problems makes it possible to detect the back EMF and improve the torque constant by 12.5% compared to the $120^{\circ}$ control. Therefore, this paper compares the output characteristics of BLDCM through finite element method analysis (FEA) by the conventional and proposed control methods of BLDCM for water circulation system and proposes design for downsizing and weight reduction of BLDCM according to secured torque constant. The validity of the proposed control and design proposal is proved through simulation and experimental results by comparing the output characteristics of $120^{\circ}$ control and $150^{\circ}$ control.

• Physical Therapy Rehabilitation Science
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• 제11권4호
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• pp.384-390
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• 2022

Objective: The purpose of this study was to investigate the effect of the side-step tasks based circular training program (STCT) on balance and gait characteristics in stroke patients. Design: A randomized controlled trial Methods: Twenty-four stroke patients were randomly divided into two groups of twelve patients each. One group was applied with the STCT whereas the other group was treated with conservative physiotherapy (CP). The ability of gait was measured in 10m walking test and stride length on both side using BTS G-WALK (BTS Bioengineering S.p.A, Italy) and the ability of balance was measured in Berg Balance Scale (BBS) and Timed Up and Go Test (TUG). Results: The STCT group was significant differences in the balance parameters of BBS and TUG (p<0.05) and showed significant differences in gait variables in 10m walking speed, stride length of affected and non-affected side after the experiment before and after the experiment (p<0.05). In addition, the STCT group showed a significant difference in BBS compared to the control group (p<0.05). Conclusions: The results of this study confirmed that the side-step tasks based circular training program (STCT) improves balance and walking ability in stroke patients. STCT is expected to be used as a useful intervention method for stroke rehabilitation.

• 대한정형도수물리치료학회지
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• 제25권1호
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• pp.63-70
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• 2019

Background: The purpose of this study was to determine the effects of a pelvic compression belt on gait abilities and balance in subacute stroke patients. Methods: Twenty two patients with subacute were recruited and randomly assigned into two group: Two group offered conventional physical therapy and occupational therapy for five day. The group was composed of twelve patients. Participants in the experimental group were given the pelvic compression belt and conventional physical therapy, conventional occupational therapy, although conventional physical therapy and occupational therapy provided in the subjects in the control group. To assess the gait ability, the GAITRITE system was used and the Balance system SD was used to test balance. All measurements were performed before and after intervention. Results: The experimental group shows a significant improvement the cadence, velocity, step length and stride length in gait (p<.05) and show significant increase in the dynamic standing balance (p<.05). However, control group shows a significant improvement the cadence, velocity, step length and stride length in gait (p<.05), but shows no significant differences in dynamic standing balance. Furthermore, there were significant differences gait velocity, dynamic standing balance between two groups (p<.05). Conclusions: The results demonstrated that the elastic pelvic belt application is effective to improve gait velocity, dynamic balance in the subacute stroke patients. Thus, the elastic pelvic belt is seemed to be one of the potential methods to facilitate the active rehabilitation program for hemiplegia patients.

• 한국안전학회지
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• 제23권6호
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• pp.158-163
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• 2008

Although prior researches have been investigated the impact of insured cost(direct cost) on employers and employees, little work has attempted to categorize the items of unsecured cost(indirect cost) by accidents. On this basis, the goal of this study was to achieve a better understanding of the nature of accident cost of unsecured cost. Specifically, this study aimed to categorize the unsecured cost items according to the domestic industry circumstances and use these results for a basis of other accident cost related studies. The results of this study are as follows: (1) accident development steps were categorized as twelve items for improved management according to each step of accident development (2) the points of occurrence and termination of the unsecured cost were identified for the improved management according to each step of accident development and (3) characteristics of each item in unsecured cost were studied and identified for a better control of accident costs. These results provide a basis for further researches on the unsecured cost.

• 약학회지
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• 제36권4호
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• pp.370-378
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• 1992

A simple and sensitive high performance liquid chromatographic method to quantitate ${\alpha}-keto$ acids in serum and urine was investigated. ${\alpha}-Keto$ acids react with 1,2-diamino-4,5-methylenedioxybenzene (DMB) in the presence of 2-mercapto-ethanol and sodium hydrogen sulfite to form highly fluorescent derivatives, substituted 6,7-methylenedioxyquinoxalinol. The derivatization procedure was performed in water bath at $100^{\circ}C$, and completed within 50 min. By the use of a reversed-phase column and multi-step gradient with two solvents, a mixture containing twelve of these derivatives were efficiently resolved within 35 minutes. The optimal wavelengh of the fluorescence detector are ${\lambda}_{ex}=364\;nm$ and ${\lambda}_{em}=445\;nm$. The quantitation of the individual ${\alpha}-Keto$ acids was reproducible with relative standard deviation of $3.0{\sim}7.9%$ and had a detection limits of $10{\sim}60$ fmol, except for p-hydroxyphenylpyruvic acid (960 fmol).

• The Journal of Korean Physical Therapy
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• 제36권1호
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• pp.27-32
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• 2024

Purpose: This study was conducted to verify the effect of applying a pressure biofeedback unit on walking ability and knee joint function while performing knee joint extensor strengthening exercises using resistance exercise equipment in total knee replacement (TKR) patients. Methods: This study was conducted on twelve patients receiving rehabilitation treatment after being admitted to a rehabilitation hospital post-TKR. Of these, six were allocated to a feedback group with a pressure biofeedback unit, and the other 6 were allocated to a control group without a pressure biofeedback unit. The subjects performed an exercise program for 45 minutes per session, five times a week, for two weeks. Walking ability and knee joint function were evaluated and analyzed before and after exercise. Results: The feedback group showed significantly better improvements in walking speed, gait cycle, step length on the non-operation side, time on the foot on the operation side, K-WOMAC stiffness, and K-WOMAC function than the control group (p<0.05). Conclusion: When strengthening the knee joint extensor muscles using resistance exercise equipment in TKR patients, the provision of a pressure biofeedback unit was found to improve walking ability and knee joint function by inducing concentric-eccentric contraction of the knee joint extensor muscles. Therefore, the study shows that exercise based on the provision of a pressure biofeedback unit should be considered when strengthening knee joint extensor muscles to improve the walking ability and knee joint function of TKR patients in clinical practice.

• 한국전문물리치료학회지
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• 제28권4호
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• pp.266-272
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• 2021

Background: Considering the kinetic chain of the lower extremity, a pronated foot position (PFP) can affect malalignment of the lower extremity, such as a dynamic knee valgus (DKV). Although the DKV during several single-leg movement tests has been investigated, no studies have compared the differences in DKV during a single-leg step down (SLSD) between subjects with and without PFP. Objects: The purpose of this study was to compare the DKV during SLSD between subjects with and without PFP. Methods: Twelve subjects with PFP (9 men, 3 women) and 15 subjects without PFP (12 men, 3 women) participated in this study. To calculate the DKV, frontal plane projection angle (FPPA), knee-in distance (KID), and hip-out distance (HOD) during SLSD were analyzed by two-dimensional video analysis software (Kinovea). Results: The FPPA was significantly lower in PFP group, compared with control group (166.4° ± 7.5° and 174.5° ± 5.5°, p < 0.05). Also, the KID was significantly greater in PFP group, compared with control group (12.7 ± 3.9 cm and 7.3 ± 2.4 cm, p < 0.05). However, the HOD not significantly differed between two groups (12.7 ± 1.7 cm and 11.4 ± 2.5 cm, p > 0.05). Conclusion: The PFP is associated with lower FPPA and greater KID. When assess the DKV during SLSD, the PFP should be considered as a crucial factor for occurrence of DKV.

• 한국농공학회지
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• 제16권2호
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• pp.3410-3419
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• 1974

The purpose of this study is to find out the correlation between pumping rates and influential factors in the tube wells for irrigation through the analysis of various statistical data of the existing tube wells for irrigation and pumping tests. Statistical data of the existing tube wells for irrigation were collected from the authorities concerned, and pumping tests were carried out for twelve tube wells. The results of this study are summarized as follows: 1. The drilled tube wells are the most useful among various tube wells in securing pumping rates. 2. The enlargement of well diameter or the improvement of pumping equipments is necessary in drilled tube wells with pumping rates more than 806 ㎥/day, and the adjustment of foot valves or the special control of pumping equipments is necessary in tube wells with pumping rates less than 300 ㎥/day. 3. The choking of aquifer and slits can be prevented by removing earth and sand piled in tube wells. 4. The increase of well loss and the destruction of aquifer can be prevented by determining the optimum pumping rates through the step draw down tests. 5. The thickness of gravel packing is rather thin in drilled tube tube wells. 6. High pamping rates can be gained by deepening the depth of tube wells in the place the ground water storage is abundant, the thickness of aquifer is thick. and the depth of tube wells is deep. 7. Higher pumping rates can be obtained by constructing tube wells in the place where the drawdown is little and the coefficient of transmissibility is large.