• 제어로봇시스템학회논문지
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• 제3권3호
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• pp.280-288
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• 1997

In this paper, we will show that the torque ripple in closed-loop drives of permanent magnet stepping motors is reduced as properly selected lead angle control method. We propose an instantaneous torque equation, which is the function of lead angle, to estimate the influence on torque ripple. We design a closed-loop lead angle control system based on the proposed instantaneous torque equation and measure the instantaneous torque in various excitation modes. It is shown that torque ripple is greatly reduced, as seen from the experimental results as well as from the computer simulation results. For example, torque ripple reduced from 78.25% to 46.82% in the case of 50 PPS single-phase excitation mode operation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.230-233
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• 2003

Simulation model of induction type fixed speed wind power generator is developed. It is shown that the peak value of inrush current during start up changes according to the firing angle control strategy of soft starter. New proposed firing angle control scheme showed $25\%$ of reduction of peak current which results in smaller drop of gird voltage at the point of common coupling during start up.

• 한국기계가공학회지
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• 제19권12호
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• pp.8-13
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• 2020

Seamless pipes are fabricated by drilling a hole in a cylindrical material and drawing the material to the desired diameter. These pipes are used in environments where high reliability is required. In this study, the pipe drawing process was simulated using DEFORM, a commercial finite element method (FEM) analysis program. The outer diameter of the steel cylinder used herein before drawing was 70 mm, and the target outer diameter was 58 mm. The drawing process consisted of two stages. In this study, the effect of cross-sectional reduction rate on the pipe was investigated by varying the cross-sectional reduction rate in each step to achieve the target outer diameter. The results of this study showed that the first section reduction rate of 26% and the second section reduction rate of 13.9% caused the lowest damage to the material. Moreover, the FEM simulation results confirmed the influence of the drawing die angle on the pipe drawing process. The drawing die angles of 15° in the first step and 9° in the second step caused the least damage to the material.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제43권4호
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• pp.239-246
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• 2017

Objectives: This paper proposes Han's ratio as an objective and quantitative comparative result obtained from pre and postoperative data in patients with a mandibular angle reduction. Materials and Methods: Thirty patients, 12 men and 18 women, who visited the Department of Oral and Maxillofacial Surgery with the chief complaints of skeletal mandibular prognathism and prominent mandibular angle were selected. The subjects were classified into 3 groups according to the types of surgical procedures involved. Group A consisted of patients who underwent mandibular angle resection and mandibular setback. Group B was comprised of patients with mandibular angle resection, mandibular setback and genioplasty. Group C consisted of patients with mandibular angle resection, mandibular setback, Le Fort I osteotomy, and genioplasty. The landmarks placed in pre and postoperative frontal photographs were used to obtain the Han's ratio in each group. The Han's ratios were compared pre- and postoperation and according to the surgical techniques applied. Results: Of the 3 groups who had undergone a mandibular angle resection, all showed a statistically significant increase in Han's ratio. On the other hand, there was no statistically significant difference based on the surgical techniques used. Conclusion: The ratio of the lateral lower face proposed in this study is a potential indicator of postoperative esthetic enhancement in mandibular angle reduction surgery.

• 융합신호처리학회논문지
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• 제22권4호
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• pp.171-178
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• 2021

카라반은 외부의 물리적 요인에 쉽게 영향을 받아 탑승자에게 위험한 상황을 초래하는 경우가 많다. 따라서 탑승자의 안정성을 확보하기 위해 스웨이 현상을 사전에 예방할 수 있는 스웨이 저감 장치를 개발할 필요성이 있다. 본 논문에서는 견인차량과 카라반 사이의 Hitch angle을 최소화하는 것을 목표로 한다. 구체적으로는 견인차량과 카라반 각각에 장착된 IMU 센서를 통해 카라반의 초기 불안정성을 감지하고, PID 제어기를 이용하여 Hitch angle, Hitch yaw rate가 Desired hitch angle, Desired hitch yaw rate에 수렴할 수 있도록 제어 값을 산출한다. 산출된 제어 값에 따라 카라반 좌우 브레이크에 다른 제동토크를 생성하여 분배하고 제어한다. 주행 실험을 통해 스웨이 저감 장치의 성능을 검증한 결과, 제어하지 않은 경우보다 Hitch angle이 감소한 것을 확인할 수 있었고, 횡 방향 안정성 향상률은 제어 전에 비해 78.9% 향상된 것을 확인하였다.

• 대한통합의학회지
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• 제7권3호
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• pp.149-157
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• 2019

Purpose : This study aims to check the relationship between the size of curvature in scoliosis patients and the reduction rate of curvature after wearing a brace and the relationships of the size of curvature and correction angle with Body Mass Index (BMI). Methods : With 30 adolescent girls who had never worn a brace, their Cobb angle and BMI were measured before manufacturing braces, and their corrected Cobb angle was measured after wearing the manufactured scoliosis braces. Results : The size of the major curvature before wearing the brace and the reduction rate of the curvature after putting it on had a negative correlation in both the major curvature (r=-.465, p<.01) and the minor curvature (r=-.516, p<.01). The size of the minor curvature and the reduction rate of the minor curvature before and after putting it on also had a negative correlation (r=-.429, p<.05). As for the relationship between the size of curvature and BMI, they had a negative correlation in both the major curvature (r=-.141) and the minor curvature (r=-.123), and as for the relationship between the reduction rate of curvature and BMI after wearing the brace, they had a positive correlation in both the major curvature (r=.251) and the minor curvature (r=.136); however, it was not statistically significant (p>.05). Conclusion : In conclusion, the larger the size of curvature, the lower the reduction rate of curvature after wearing the brace became. The larger the size of curvature, the lower the BMI became. The higher the BMI, the higher the correction ratio of the brace became. Therefore, it is judged that it is necessary to provide early treatment and manage body composition before scoliosis progresses.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권5호
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• pp.473-479
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• 2008

Asians tend to have prominent mandibular angle. The causes of wide lower third of the facial contour are obtuse mandibular angle and hypertrophy of masseter muscles. In cases of hypertrophy of masseter muscles, conventional treatment intends to the contraction of masseter muscle. Recently, volumetric reduction of masseter muscles using botulinum toxin type A injection and radiofrequency (RF) reduction have been introduced. The use of RF energy for masseter muscle reduction is known as a safe, simple, and effective method for aesthetic lower facial contouring. The purpose of this study is to present the effects of RF reduction applied to hypertrophy of masseter muscles, to review and to encourage RF practices in oral and maxillofacial region.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제27권3호
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• pp.258-265
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• 2001

A prognathic mandible and prominent gonial angle are considered to be unattractive in the Orient because it gives the face a square and muscular appearance. Requests for contouring of the mandibular angle are rare in the other race but are much more common in Korea and, through out the Orient. So, we often encounter a patient with a prognathic mandible and squarish or broad face who wishes to have his or her facial size reduced minimally or to acquire a round or slender appearance. But, mandibular angle is located in the deepest part of the operative field and the strong tension of the lateral soft tissue makes retraction difficult. It is extremely difficult to reduce the gonial angle with sagittal split ramus osteotomy by intraoral approach at the same time. We apply the method of gonial angle reduction during SSRO and had satisfactory results. We will present our results and hope to give some useful information for management of mandibular deformity.

• 한국정밀공학회지
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• 제17권6호
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• pp.143-152
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• 2000

The comer filling in shaped drawing process is an important characteristic, unlike the round drawing. It has also influence on the dimensional accuracy of the product. In this study, therefore, the shaped drawing process has been simulated by the three dimensional rigid-plastic finite element method in order to investigate the effect of process variables such as reduction in area and semi-die angle to the corner filling. The artificial neural network has also been introduced to reduce the number of simulations. To verify the results of simulations, experiments have been performed on the real industrial products. According to the results, the main process variable on the corner filling is the combination of semi-die angle in the irregular shaped drawing processes, but in the case of regular shaped drawing processes, reduction in area has great influence on the corner filling.

• 동력기계공학회지
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• 제18권1호
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• pp.22-31
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• 2014

This paper introduced the new calibration algorithm of a straight-type five-hole pressure probe necessary for calculating three-dimensional flow velocity components. The new velocity data reduction method using both a commercial two-dimensional curve-fitting program and the zone partition method of a calibration map was firstly introduced in this study. This new calibration method can be applied up to the wide flow angle of ${\pm}80^{\circ}$ despite of using a five-hole pressure probe because this data reduction method showed a comparatively good performance in calculating yaw and pitch angles from the calibration map.