• 대한안전경영과학회지
• /
• 제2권1호
• /
• pp.161-170
• /
• 2000

When designing the parameter on the multiple quality characteristics, there has been a study for optimization of problems, but there has been few former study on the possible conflicting phenomena in consideration of the correlations among the characteristics. To solve the issue on the optimal design for multiple quality characteristics, this study modelled the expected loss function with cross-product terms among the characteristics and derived range of the coefficients of the terms. The model will be used to determine the global optimal design parameters where there exists the conflict among the characteristics, which shows difference in optimal design parameters for the individual characteristics.

• 대한산업공학회지
• /
• 제17권1호
• /
• pp.95-108
• /
• 1991

For the case where the lifetime at a constant stress level has exponential distribution, optimal accelerated life test plans are developed under the assumptions of intermittent inspection and Type I censoring. In a optimal plan, the low and high stress levels, the proportion of test units allocated and the inspection times at each stress are determined such that the asymptotic variance of the maximum likelihood estimator of logarithmic transformed mean at the use condition is minimized. In addition to the optimal plan in which numerical technique to solve the set of nonlinear equations must be employed to determine inspection times at each stress level, we also propose another plans which employ equally-spaced or equal probability inspection schemes at two overstress levels of corresponding optimal one. For both optimal and proposed plans, computational results indicate that the asymptotic variance of the estimated mean at the use stress is insensitive to number of inspections at overstress levels for the range of parameter values considered.

• 한국자동차공학회논문집
• /
• 제6권4호
• /
• pp.1-8
• /
• 1998

In order to solve the conflict problem between the ride comfort and the road holding, the optimal design of shock absorber that minimizes the r.m.s. of sprung mass vertical acceleration and pitch rate with the understeer characteristics constraints in the high speed stability is proposed. The design of experiments and the nonlinear optimization algorithm are used together to obtain the optimal design of shock absorber. The second order regression models of the input variables(front and rear damping coefficients) and the output variables (ride comfort index and road holding one) are obtained by the central composite design in the design of experiments. Then the optimal design of shock absorber can be systematically adjusted with applying the nonlinear optimization algorithm to the obtained second order regression model. The frequency response analysis of sprung mass acceleration and pitch rate shows the effectiveness of the proposed optimal design of shock absorber in the sprung mass resonance range with the understeer characteristics constraints.

• 전력전자학회논문지
• /
• 제26권4호
• /
• pp.285-293
• /
• 2021

An optimal operation method based on weighted efficiency for a two-stage boost converter is proposed in this study. Detailed loss analysis of the converter is performed to derive the optimal operation method according to the load and input voltage fluctuations, and the optimal DC-bus voltage is derived by applying the weighted efficiency method. The proposed method can satisfy optimal efficiency in the main operation region without a complicated control method. Using 1kW typical two-stage boost converter and is verified three types of weighted efficiency formulas and loss analysis are utilized to derive high-efficiency optimal DC-bus voltage from each load range.

• 한국정밀공학회지
• /
• 제14권7호
• /
• pp.49-58
• /
• 1997

In process planning for pocket machining, the selection of tool size, tool path, overlap distance, and the calculation of machining time are very important factors to obtain the optimal process planning result. Among those factors, the tool size is the most important one because the others depend on tool size. And also, it is not easy to determine the optimal tool size even though the shape of pocket is simple. Therefore, the optimal selection of tool size is the most essential task in process planning for machining a pocket. This paper presents a method for selecting optimal toos in pocket machining. The branch and bound method is applied to select the optimal tools which minimize the machining time by using the range of feasible tools and the breadth-first search.

• 한국정보과학회논문지:소프트웨어및응용
• /
• 제27권2호
• /
• pp.193-200
• /
• 2000

자연스러운 사용자 작업 환경인 헤드 제스처 인터페이스를 구현하기 위해서는 얼굴 영역 추출에 관한 연구가 선행되어야 하는데, 최근에는 동영상에서 얼굴 영역을 추출하기 위해 색상 정보를 이용하는 연구가 많이 진행되고 있다. 본 논문에서는 대표적으로 사용되는 HSI 컬러 모델과 YIQ 컬러 모델의 각 색상 성분인 H(hue)와 I(in-phase)를 이용하여 얼굴 영역의 추출 성능을 비교한다. 먼저 각 색상 성분에 대해 임계 구간 변화에 따른 최적의 얼굴색 구간을 설정하여 얼굴 영역 추출의 정확도를 비교한다. 다음으로 설정된 최적의 얼굴색 정보와 움직임 정보를 결합한 영상에 대해 얼굴 박스를 추출함으로써 최종적인 얼굴 영역 추출의 정확도를 비교 평가한다. 실험 결과, 최적의 얼굴색 정보를 표현하는 구간은 HSI의 H 성분의 경우 $0^{\circ}{\sim}14^{\circ}$, YIQ의 I 성분은 $-22^{\circ}{\sim}-2^{\circ}$인 것으로 나타났다. 이 최적 구간에 의한 각 색상 성분의 얼굴 영역 추출의 정확도에서는 I 성분이 H 성분에 비해 약 10% 정도 높은 추출율을 나타냈으며, 최적의 얼굴색 정보와 움직임 정보를 결합한 영상의 경우에서도 I 성분이 약 3% 정도의 보다 나은 얼굴 영역 추출 결과를 얻었다.

• 한국전문물리치료학회지
• /
• 제20권1호
• /
• pp.55-63
• /
• 2013

This study investigated the effects of axillary crutch length on trunk muscle activity and lumbo-pelvic-hip complex movements during crutch gait. Eleven healthy men participated in this study. The participants performed a three-point gait with optimal, shorter, and longer crutch lengths. Weight-bearing (WB) side was determined as the dominant leg side. The electromyography (EMG) activity of the bilateral rectus abdominis (RA) and erector spinae (ES) muscles and lumbo-pelvic-hip complex movements were monitored using a three-dimensional motion system with wireless surface EMG. Differences in the EMG activity of RA and ES muscles and range of motion (ROM) of lumbar spine, pelvis, and hip among conditions were analyzed using one-way repeated-measures analysis of variance, and a Bonferroni correction was conducted. There was less RA muscle activity on the WB side under the optimal crutch length condition compared with shorter and longer crutch length conditions (p<.05). The EMG activity of the RA muscle on the non-WB side and ES muscle on the WB side were significantly decreased under the optimal crutch length condition compared with shorter crutch length condition (p<.05). No significant differences in the EMG activity of the ES muscle on the non-WB side and ROM of lumbo-pelvic-hip complex were found among conditions (p>.05). These findings indicate that the optimal crutch length improves the trunk muscle efficiency during crutch gait.

• Journal of Power Electronics
• /
• 제10권5호
• /
• pp.477-484
• /
• 2010

A pulse width modulation-voltage source inverter (PWM-VSI) is used for variable speed permanent magnet synchronous motor (PMSM) drives. The PWM-VSI fed PMSM has two major disadvantages. Firstly, the PWM-VSI DC-link voltage limits the magnitude of the PMSM terminal voltage. As a result, the motor speed is restricted. Secondly, in a low speed range, the PWM-VSI modulation index declines. This is caused by a high DC-link voltage and a low terminal voltage ratio. As a result, the distortion of the voltage command and the stator current are increased. This paper proposes an optimal pulse amplitude modulation (PAM) control which can adjust the inverter DC-link voltage by using a buck-boost DC-DC converter. At a low speed range, the proposed system can reduce the distortion of the voltage command, which improves the stator current waveform. Also, the allowable speed range is extended. In order to verify the proposed method, experimental results are provided to confirm the simulation results.

• 치과방사선
• /
• 제28권1호
• /
• pp.7-16
• /
• 1998

The Scanora/sup (R)/ X-ray unit uses the principles of narrow beam radiography and spiral tomography. Starting with a panoramic overview as a scout image. multiple tomographic projections could be selected. This study evaluated the accuracy of spiral tomography in comparison to routine panoramic radiography for dental implant treatment planning. An experimental study was performed on a cadaver mandible to assess the accuracy of panoramic radiography and spiral tomography film images for measurement of metallic spheres. After radiographic images of the metallic spheres on the surgical stent were measured and corrected for a fixed magnification of radiographic images. following results were obtained. 1. In the optimal position of the mandible. the minimal horizontal and vertical distortion was evident in the panoramic radiography images. The mean horizontal and vertical magnification error in anterior sites was 5.25％ and 0.75％. respectively. The mean horizontal and vertical magnification error in posterior sites was 0.50％ and 1.50％. respectively. 2. In the displaced forward or in an eccentric position of the mandible. the magnification error of the panoramic radiography images increased significantly over the optimal position. Overall, the mean horizontal magnification error of the anterior site in the different positions changed dramatically within a range of -17.25％ to 39.00％, compared to the posterior range of -5.25％ to 8.50％. However, the mean vertical magnification error stayed with the range of 0.5％ to 3.75％ for all the mandibular positions. 3. The magnification effects in the tomographic scans were nearly identical for the anterior and posterior with a range of 2.00％ to 5.75％ in the horizontal and 4.50％ to 5.50％ in the vertical dimension, respectively. 4. A statistically significant difference between the anterior and posterior measurements was found in the horizontal measurements of the panoramic radiography images of the displaced forward and backward position of the mandible(P<0.05). Also a significant difference between the optimal panoramic and tomographic projections was found only in the vertical measurement(P<0.05).

• 한국수산과학회지
• /
• 제54권3호
• /
• pp.293-297
• /
• 2021

Herein, two experiments were performed to determine the appropriate pH range and immersion time for organic acid-activating treatment (OAT) in a Pyropia farm. The effects of pH (0.50, 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00) on the cell mortality of Pyropia yezoensis and Ulva linza thalli were tested after 20 sec of immersion under OAT. In addition, the cell mortality of the two species was estimated under various combinations of immersion time (30, 60, and 120 sec) and pH (1.00, 1.50, and 2.00). Upon 20 sec of immersion under OAT conditions, the cell mortality of P. yezoensis did not differ at any pH but that of U. linza exceeded 90% at a pH range of 0.50-1.00. P. yezoensis showed little cell mortality upon 30 sec of immersion, but its mortality exceeded 55% upon 120 sec of immersion at a pH range of 1.00-1.50. U. linza showed 67.9-100% mortality at a pH of 1.50 and 100% mortality at a pH of 1.00, regardless of the immersion time (30-120 sec). These results indicate that for the effective removal of U. linza, the optimal pH range is 1.00-1.50 and the optimal immersion time is 20-30 sec.