• 전력전자학회논문지
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• 제6권1호
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• pp.98-106
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• 2001

본 논문에서는 영구자석 동기 전동기의 정밀 속도 제어의 방법으로 외란 관측기를 이용한 외란 보상방법과 파라미터 추정에 의해 보상기의 이득을 조절하도록 함으로서, 외란이 없는 등가 지표시스템의 응답 특성을 추정하도록 제안하였다. 외란 관측기에 의한 보상방법은 잘 알려진 데드비트 외란 관측기를 이용하였으며 잡음에 약한 데드비트 관측기의 단점을 보완하기 위하여 후단필터로서 MA처리를 통하여 잡음에 대한 영향을 줄이도록 하였다. 또한 관측기의 단점을 보완하기 위하여 후단필터로서 MA처리를 통하여 잡음에 대한 영향을 줄이도록 하였다. 또한 관측기의 파라미터와 실제 시스템의 파라미터의 차이로 발생하는 외란 추정 오차를 줄이고자 실제 시스템과 파라미터 보상기로 구성된 등가 시스템이 지표 시스템이 되도록 구성하였다. 시스템에 사용된 RLS파라미터 추정기는 외란에 의하여 편향된 추정 특성을 가진다. 이러한 파라미터 추정문제에 대하여 파라미터 추정기가 높은 성능을 갖는 데드비트 외란 관측기를 포함하도록 함으로서 외란에 의한 문제를 해결하였다. 이와 같이 제안된 제어기는 외란 및 파라미터 변화를 갖는 시스템에서 강인한 고정밀 제어를 할 수 있으며, 이의 안정성과 효용성을 컴퓨터를 이용한 모의 실험과 TMS320C31이 내장된 DS1102 DSP 보드를 이용하여 실험으로써 보였다.

• 대한기계학회논문집A
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• 제38권11호
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• pp.1239-1243
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• 2014

탄소섬유 강화플라스틱은 비강도, 비강성이 크고, 높은 감쇠 특성과 중량감소 측면에서 우수한 특성을 나타낸다. 그러나 탄소섬유 강화플라스틱은 재료의 적층각 또는 적층 순서에 따라 기계적 특성 차이가 크다. 또한 인장과 굽힘과 같은 하중을 받을 때 금속과 달리 파괴 예측이 어렵다. 본 연구에서는 최근 실생활에 밀접한 휴대용 스마트기기에 CFRP 적용을 위한 외부 충격에 정형화, 최적화 설계방식을 제시하고자 한다. CFRP 를 적층각도별 기계적 특성을 얻고자 인장실험을 하였고, 각 적층각도별 체결 특성을 얻고자 판에 탭 가공 후 토크 측정기를 이용하여 풀림 토크와 체결토크를 측정하였다. 위 두 실험에 비교 분석하여 최적의 조건을 찾고자 한다. 인장실험에서 적층각이 Woven 시편에서 강도와 강성 값이 가장 우수하였다. 또한 복합재료에서는 기지와 적층배열 때문에 풀림방지 코팅나사의 효과를 보기 힘들다. [$0_8/+45_2/-45_2/90_8$]s 에서 체결력이 가장 우수했으나, 인장응력이 상대적으로 낮았다. 핸드폰에 적용을 위해 인장 특성과 체결력을 모두 충족하는 최적의 시편은 Woven 이다.

• The Journal of Korean Physical Therapy
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• 제13권2호
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• pp.325-333
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• 2001

The purpose of this study was to find out the effects of hallux valgus on the ankle plantarflexor and dorsiflexor peak torque, on the total work, on the average power, and on the Peak torque of plantarflexor to dorsiflexor ratio values. Isokinetic ankle plantarflexor and dorsiflexor strength was evaluated in 30 women(control: 15, hallux valgus: 15) by Cybex NORM System. Test data was gathered in the right ankle at a speed of 60/sec, 90/sec, 120/sec in the control group and the hallux valgus group. Statistical analysis was performed using SPSS 10.0 for windows software. Mean and standard deviations were measured and calculated for the General characterristic of subjects. A paired t-test was used to examine the differnces in the means for the ankle plantarflexor and dorsiflexor between two groups. Pearson coefficient correlation was used to examine the correlation of the hallux valgus and the peak torque. Analysis of variance indicated that isokinetic values of the control group were greater than the hallux valgus group(p<.05, p<.01).

• Journal of Biosystems Engineering
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• 제16권2호
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• pp.124-132
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• 1991

This study was carried out to obtain the information needed in the development of forward speed control system and the improvement of combine performance. The effects of variety, grain moisture content and forward speed on the combine load characteristics were investigated through experiments. The results of this study are summarized as follows. 1. A data acquisition system was developed to measure the engine speed and the torques and speeds of the threshing cylinder, dean-grain auger and tailings-return auger. The system consisted of transducers, signal conditioner, interface board and microcomputer. The system accuracy is better than ${\pm}2.3%$ full scale. 2. Linear regression equations were obtained for the torque, speed and power requirement of threshing cylinder for different paddy varieties, grain moisture contents and feed rates. 3. The maximum value of relative frequency for threshing cylinder torque decreased as the increase in feed rate and moisture content. The range of torque fluctuation was 1.2~3.7 and 1.2~1.9 times the average and maximum torque, respectively. The maximum value of power spectrum density (PSD) appeared to be about 11 Hz regardless of paddy variety, grain moisture content and feed rate. 4. The speed of tailings return thrower decreased rapidly at below 900rpm, and it fell to near zero about 3 seconds after that time. When the travelling of combine harvester was stopped immediately after sensing the overload, it took about 7 seconds for a full recovery of the no-load speed of tailings return thrower.

• Journal of Biosystems Engineering
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• 제20권3호
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• pp.245-249
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• 1995

In this study power requirements to saw shoots with circular saw were determined by measuring and analyzing the required maximum torque to provide the information for the mechanization of Korean pine cone harvest. Two levels of feed rate of shoots, 10.4mm/s and 20.8mm/s, three levels of sawing speed 5.8㎧, 11.6㎧, and 17.4㎧, and 14 levels of shoot diameter from 7.7 to 18.1mm were used as variables. 1) The maximum torques were significantly affected by all three variables. The average maximum torque, 18.2 N-cm for feed rate of 20.Bmm/s was greater as much as 80% of 10.1 N-cm for feed rate of 10.4mm/s. 2) As the sawing speed was increased from 5.8㎧ to 11.6㎧ and 17.4㎧, the maximum torques were decreased to 14.8N-cm, 8.5N-cm, and 7.IN-cm, respectively when the feed rate was 10.4mm/s. The maximum torque ranged from 4.5 to 19.3N-cm as shoot diameter increased from 7.7 to 18.1mm. The minimum power requirements to saw shoots of 18.1mm with circular saw was 30W for the feed rate of 10.4mm/s. 3) The maximum torques were 28.6N-cm, 14.6N-cm, and 11.4N-cm when sawing speeds were 5.8㎧, 11.6㎧, and 17.4㎧, respectively when the feed rate was 20.8mm/s and these torques were increased as much as 93%, 36%, and 61% of those for the feed rate of 10.4mm/s. The maximum torque increased from 9.7N-cm to 30.7N-cm as shoot diameter increased from 7.7 to 18.1mm. The minimum power requirements to saw shoots of 18.1mm was 54W which was 1.8 times of 30W for the feed rate of 10.4mm/s.

• 전력전자학회논문지
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• 제12권4호
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• pp.318-323
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• 2007

본 논문에서는 영구자석형 5상 전동기(Five-phase permanent magnet motor)의 약계자 제어에 대한 연구를 수행한다. 제안된 전동기는 집중권 방식의 권선분포를 가지고 있고 사다리꼴 형태의 역기전력을 나타내고 있으며, 사다리꼴 형태의 전류를 인가하기 위하여 사인파의 기본파 성분에 3고조파 성분을 첨가하였다. 따라서 BLDC 전동기(Brushless dc motor)와 등가적으로 같은 평균토크를 발생시키면서 BLDC 전동기의 단점을 극복할 수 있었다. 전동기 전류의 토크성분과 자속성분은 다중 레퍼런스 프래임을 이용하여 분리할 수 있었으며, 결과적으로 쉽게 벡터제어가 이루어질 수 있었다. 사용된 전동기는 고속영역에서부터 저속영역까지 BLDC 전동기와 같이 높은 토크 밀도를 가지며, 약계자 영역이나 고속영역에서 영구자석형 전동기와 같이 제어의 용이함을 가진다는 장점을 가지고 있으며 실험결과를 통하여 제안된 전동기와 알고리즘을 검증하였다.

• The Journal of Korean Physical Therapy
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• 제12권2호
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• pp.145-152
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• 2000

슬관절 자세에 따라 족관절 저측굴곡관의 근력을 비교 분석하기 위하여 건강한 남녀 20명을 대상으로 Cybex 6000을 사용하여 측정한 결과는 다음과 같다. 1. 최대 토오크 값은 양쪽 모두 슬관절 신전상태서 $90^{\circ}$ 굴곡에서보다 높았다. 슬관절 신전상태에 대한 $90^{\circ}$ 굴곡에서의 토오크 값의 비는 운동속도 $30{\circ}/sec$ 와 $90{\circ}/sec$에서 각각 $75.7\%\;85.2\%$였다. 2. 최대 토오크는 $30{\circ}/sec\;90^{\circ}/sec$에서 모두 슬관절 신전상태에서 $90^{\circ}$ 굴곡상태에서보다 운동의 초기에서 나타났으나 유의란 차이는 업었다. 3. 저측룰곡근의 총일량은 굴곡보다 신전상태서 높았다. 슬관절 신전상태 대한 $90^{\circ}$ 굴곡에서의 총일량의 비는 운동속도 $30{\circ}/sec$와$90{\circ}/sec$에서 각각$81\%,\;89\%$였다. 4 저측굴곡근의 근지구력은 슬관절 신전상태와 $90^{\circ}$ 굴곡상태애서 $78.35\%,\;92.70\%$로 굴곡상태에서 높았다. 5. 일률은 $30{\circ}/sec$에서 슬관절 신전에서 높았다. 위 연구 결과는 족관절 손상환자의 물리치료 시에 배 측굴곡근과 저측굴곡근의 근력 비와 더불어 근재교육에 유용한 자료로 사용될 수 있을 것으로 사료된다. 또한 근력증가를 위한 목적으로 운동치료 시 슬관절 신전상태에서의 저측굴곡운동이 더 효율적인 방법이라 생각된다.

• 한국융합학회논문지
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• 제9권4호
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• pp.1-7
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• 2018

전기자동차용 전동기는 운전모드에 따라 효율특성이 차이가 나기 때문에 저속 및 고속의 운전모드에서 고효율특성을 평가하기 위한 연구는 매우 중요하다. 따라서 전기자동차 구동용 전동기의 고토크 및 고출력 밀도, 고효율특성을 변경할 수 있는 설계 방안이 필요하다. 본 논문에서는 매입형 영구자석 동기전동기의 고정자와 회전자의 직경비를 각각 0.62, 0.65, 0.68로 변경 설계하여 전 운전구간의 효율특성과 시내 및 고속도로 운전모드에서의 평균효율특성을 분석하였다. 전 운전구간의 효율특성을 분석한 결과, 직경비가 증가할수록 고효율 구간이 저속 저토크 구간으로 이동하고, 직경비가 감소할수록 고효율 구간이 고속 저토크 부근으로 이동함을 확인하였다. 시내 및 고속도로 운전모드에서의 평균효율특성을 분석한 결과, 직경비 0.68 모델이 직경비 0.63 및 0.65 모델보다 평균효율이 높게 분석되었으며 시내 및 고속도로 주행모드에 적합함을 확인하였다.

• Journal of Periodontal and Implant Science
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• 제34권1호
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• pp.177-193
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• 2004

Several experimental studies showed that the application of small amounts of electric current to bone stimulated osteogenesis at the site of the cathode and suggested that electrical currents promote osseointegration around dental implants. The purpose of this study was to determine the effect of direct microcurrent to endosseous titanium implants placed in bone defects. The right and left 2nd, 3rd and 4th mandibular premolars in ten mongrel dogs (15Kg of weight) were extracted. One monthe later, Ti-machined screw type implants(3.8 mm diameter x 8.5 mm length, $AVANA^{(R)}$, Ostem) were placed in surgically created circumferential defect area(width 5mm, depth 4mm). The implants were divided into three groups according to the treatment modalities: Control group- implants without electrical stimulation; Experimental group I- implants with allogenic demineralized freeze dried bone grafting; and Experimental group II-implants allogenic demineralized freeze dried bone grafting and electric stimulation. The animals were sacrificed in the 4th and 8th week after implant placement and un-decalcified specimens were prepared for histological and histometrical evaluation of bone-implant contact ratio (BIC) and bone formation area ratio (BFA) in defect area. Some specimens at 8 weeks after implantation were used for removal torque testing. Histologically, there was connective tissue infiltration in the coronal part of defect area in control and the experimental group I, whereas direct bone contact was found in the experimental group II without connective tissue invasion. Average BIC ratios at 4 weeks of healing were 60.1% in the experimental group II, 47.4% in the experimental group I and 42.7% in the control. Average BIC ratios at 8 weeks after implantation were 67.6% in the experimental group II, 55.9% in the experimental group I and 54.6% in the control. The average BFA ratio was 84.0% in the experimental group II, 71.8% in the experimental group I and 58.8% in the control at 4 weeks, and the BFA ratios were 89.6% in the experimental group II, 81.4% in the experimental group I and 70.5% in the control at 8 weeks after implantation. The experimental group II showed also significantly greater BIC and BFA ratios compared to the control and the experimental group I (p<0.05). The removal torque values at 8 weeks after implantation were 56 Ncm in the experimental group II, 49 Ncm in the experimental group I and 43 Ncm in the control. There was a statistically significant difference among 3 groups (p<0.05). These results suggest that electrical stimulation improve and accelerate bone healing around endosseous titanium implants in bone defect.

• PNF and Movement
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• 제16권1호
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• pp.43-50
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• 2018

Purpose: This study examined the effects of a shoulder-strengthening exercise on muscle strength of shoulder flexors and extensors of caregivers. Methods: The study consisted of 19 caregivers (2 males and 17 females) employed by Medical Center B. All the participants took part in an 8-week shoulder muscle strengthening exercise, based on previous studies. In the first week, the subjects took part in a stretching exercise enhance the range of motion. In the second week, they participated in an exercise aimed at improving shoulder blade stability. From the third to seventh weeks, a resistance exercise of different intensities was applied in a phased manner. Finally, in the eight week, the subjects took part in plyometric exercise. Peak torque, average power, and total work of shoulder flexors and extensors in both sides were measured before and after the exercise at an angular speed of 120deg/sec using an isokinetic device. Wilcoxon's singed-ranks test was conducted to analyze differences in muscle strength before and after the intervention. Results: After the exercise, there was a significant improvement in peak torque and average power of flexors of the right arm. After the exercise, peak torque, total work, and average power showed a significant improvement in the flexors of the left arm (p<0.05). However, there was no statistically significant difference in extensor muscle strength in either arm after the exercise. Conclusion: Shoulder flexors of caregivers are utilized frequently in the workplace. Implementation of extensor-strengthening exercises, in addition to flexor-strengthening exercises, can contribute to reducing the incidence rate of shoulder injuries among caregivers.