• 소음진동
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• 제11권1호
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• pp.147-155
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• 2001

This paper is concerned with the real-time automatic tuning of the multi-input multi-output positive position feedback controllers for smart structures by the genetic algorithms. The genetic algorithms have proven its effectiveness in searching optimal design parameters without falling into local minimums thus rendering globally optimal solutions. The previous real-time algorithm that tunes a single control parameter is extended to tune more parameters of the MIMO PPF controller. We employ the MIMO PPF controller since it can enhance the damping value of a target mode without affecting other modes if tuned properly. Hence, the traditional positive position feedback controller can be used in adaptive fashion in real time. The final form of the MIMO PPF controller results in the centralized control, thus it involves many parameters. The bounds of the control Parameters are estimated from the theoretical model to guarantee the stability. As in the previous research, the digital MIMO PPF control law is downloaded to the DSP chip and a main program, which runs genetic algorithms in real time, updates the parameters of the controller in real time. The experimental frequency response results show that the MIMO PPF controller tuned by GA gives better performance than the theoretically designed PPF. The time response also shows that the GA tuned MIMO PPF controller can suppress vibrations very well.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.527-535
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• 2012

This paper reports the active vibration control of plates using positive position feedback controller (PPF). The equations of motion of the plate under force and moment pairs were derived and the equations of PPF controllers were formulated. The effect of the parameters - gain and damping ratio - of the PPF controllers on the open loop transfer function was investigated mainly in terms of the system stability. Increasing the gain of the PPF controller tuned at a mode, the magnitude of the open loop transfer function is increased at all frequencies without changing the phase behavior. The increase of the damping ratio of the PPF controller leads to decrease the magnitude of the open loop transfer function and to modify its phase characteristics to be more stable. Two PPF controllers connected in parallel, Each PPF controller is tuned at the $1^{st}$ and $2^{nd}$ modes, respectively. Their parameters were determined to remain the system to be stable based on the results of the parametric study. A significant reduction in vibration at the 2 modes can be obtained.

• 대한영양사협회학술지
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• 제2권1호
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• pp.49-61
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• 1996

For the purpose of disclosing the relationship between job characteristics and satisfaction and organizational commitment for foodservice employees, questionnaire survey was carried out on 427 subjects of 14 general hospitals in Seoul, Korea. Questionnaire items consisted of general characteristics, organizational commitment, job satisfaction and characteristics. Data were analyzed by ANOVA, Duncan's multiple range test and Pearson correlation using SPSS PC package. The results were as follows 1. Mean score of value commitment and commitment to stay were 3.57 and 3.67. 2. There were significant differences between value commitment and age, marital status department, period and management, and between commitment to stay and experience and management. 3. Mean score of job satisfaction was the highest in co-workers(3.37) and work itself (3.37) and followed by in supervision(3.25), wage(2.43) and promotion(2.01). There were significant differences between job satisfaction for work itself and age, educational status and job department and management, between job satisfaction for wage and position, department, period and management, between job satisfaction for supervision and age, educational status and department, between job satisfaction for promotion and age, marital status, position, period, and management, between job satisfaction for co-workers and sex and educational status. 4. Mean score of job characteristics was the highest in dealing with others(4.13) and followed by in feedback(3.51), autonomy(3.29), task identify(3.07), variety(2.71) and friendship(2.47). 5. Job satisfaction for work itself, supervision and co-workers were significantly increased with increasing value commitment. Job satisfaction for work itself, supervision were significantly increased with increasing commitment to stay. Job satisfaction for promotion had negative correlation with organizational commitment in all job position. 6. Value commitment had significantly positive correlations with variety, autonomy, identity, feedback and dealing with others, and significantly negative correlation with friendship. Commitment to stay had significantly positive correlations with dealing with others, and significantly negative correlations with friendship. In all job position organizational commitment had significantly negative correlations with friendship.

• 전기학회논문지
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• 제58권1호
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• pp.203-209
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• 2009

The purpose of this study is to develop a minimally constraint joint angle measurement system for the feedback control of FES (functional electrical stimulation) locomotion. Feedback control is desirable for the efficient FES locomotion, however, the simple on-off control schemes are mainly used in clinic because the currently available angle measurement systems are heavily constraint or cosmetically poor. We designed a new angle measurement system consisting of a magnet and magnetic sensors located below and above the ankle joint, respectively, in the rear side of ipsilateral leg. Two magnetic sensors are arranged so that the sensing axes are perpendicular each other. Multiple positions of sensors attachment on the shank part of the ankle joint model and also human ankle joint were selected and the accuracy of the measured angle at each position was investigated. The reference ankle joint angle was measured by potentiometer and motion capture system. The ankle joint angle was determined from the fitting curve of the reference angle and magnetic flux density relationship. The errors of the measured angle were calculated at each sensor position for the ankle range of motion (ROM) $-20{\sim}15$ degrees (dorsiflexion as positive) which covers the ankle ROM of both stroke patients and normal subjects during locomotion. The error was the smallest with the sensor at the position 1 which was the nearest position to the ankle joint. In case of human experiment, the RMS (root mean square) errors were $0.51{\pm}1.78(0.31{\sim}0.64)$ degrees and the maximum errors were $1.19{\pm}0.46(0.68{\sim}1.58)$ degrees. The proposed system is less constraint and cosmetically better than the existing angle measurement system because the wires are not needed.

• 한국항공우주학회지
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• 제35권3호
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• pp.218-224
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• 2007

PZT와 같은 압전 재료는 능동 진동 억제 분야에서 널리 사용되고 있지만 단일 PZT의 경우 장착 과정에서의 손상, 전기 누전, 낮은 피로 성능과 같은 문제가 지적되고 있다. 이러한 문제를 해결하기 위하여 개발된 LIPCA 작동기는 여러 층의 복합재료와 PZT 층으로 구성되어 있다. 본 연구에서는 LIPCA 작동기를 끝단 질량이 부착된 알루미늄 외팔보의 진동을 억제하는데 적용하였다. 양변위 되먹임 제어 알고리듬을 사용하였으며, 필터 주파수를 대상 모드의 첫 번째 고유진동수에 맞추었다. 실험적으로 구한 알루미늄 보의 고유 진동수는 유한요소 해석의 결과와 잘 일치하였다. LIPCA 작동기를 능동 진동제어에 적용할 때 효율성을 시간과 주파수 영역에서 확인하고자 하였는데, 실험 결과 PPF제어를 사용한 LIPCA 작동기가 자유 진동의 안정화 시간과 강제 진동의 진폭을 효과적으로 제어할 수 있었다. 사례 연구로 다른 두께를 가지는 보의 강제 진동 제어를 수행하였다.

• 농촌의학ㆍ지역보건
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• 제23권1호
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• pp.91-108
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• 1998

This study was conducted to use the feedback of health personnel to improve the Visiting Health Service. The data was collected from 471 Home Health Workers serving 24 local health organizations in the Kyung-Pook province. 62.5% of the respondents were men under thirty-nine years of age. 92.8% of the respondents are married. 47.1% had degrees from junior colleges. It was ascertained 52.7% of the workers visited their patients six to twelve times within a six month period. And one to three patients were visited per day by one worker. Workers of older age, higher job position, and more experience were more positive in their feedback about the program. In addition, local health center employees, including nurses, were more positive about the program. Younger workers with a higher level of education, less experience, and lower job position had more insight into the problems of the program. Deeper insight into these problems led to a more negative conception of the program. Older workers with higher ranking jobs were found to be most competent. in their jobs. Workers at the main health center were assessed higher than the workers at the health sub-center or the primary health post. In addison nurses at all centers were found to be slightly more competent than the nurses' aide. The primary health post established the highest degree of patient satisfaction. It was discovered that the more positive the workers felt about the program, the higher their patient satisfaction feedback. There was a positive correlation between management assessment and patient satisfaction. This means that better program management was found to produce higher patient satisfaction. Workers feel being more educated about patient management would lead to better service. However, they take no action to produce these results. Where the problems of the system are most commented upon, the need for further education is greatest. Through multiple regression analyses it is apparent that the assessment of patient management is the greatest variable affecting patient satisfaction of patients is dependent on the management by the visiting health worker. Therefore, the development of the visiting health program is highly dependant on the feedback of those workers with a negative conception of the program. So the development of programs, motivation, education and training must be established. These works would lead to active participation by visiting health workers in the improvement of the Visiting health program.

• The Journal of Korean Physical Therapy
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• 제29권4호
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• pp.153-157
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• 2017

Purpose: The purpose of this study was to investigate the effect of self-postural control on foot pressure in subjects with forward head posture. Methods: Forty-two healthy adults were recruited in this study. Participants were divided into two groups: The forward-head postural (FHP) group (craniovertebral angle<$53^{\circ}$, n=22) and the control group (craniovertebral angle${\geq}53^{\circ}$, n=20). In the FHP group, foot pressure was measured using three different standing postures: Comfortable standing posture (CSP), subjective neutral standing posture (SNSP), and neutral standing posture with visual feedback (NSP-VP). Each position was performed in random order. In the control group, foot pressure was measured only using the comfortable standing posture. Results: With respect to CSP and SNSP, there was a significant difference on heel pressure between the two groups (p<0.05). Regarding NSP-VP, however, there was no significant differences on heel pressure between the two groups (p>0.05). Conclusion: We suggest that cervical posture control using visual feedback has a positive effect on the distribution of foot pressure in subjects with forward head posture.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.309.1-309
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• 2002

This paper is concerned with the dynamic modeling of a rectangular plate with piezoelectric actuators and sensors. The experimental frequency response plots can be used to verify the theoretical modeling. The active vibration control was achived by using positive position feedback controller. Theoretical analysis will follow.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.471-475
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• 2001

This paper is concerned with the experiments on the dynamic characteristics and active vibration control of plate with piezoceramic sensors and actuators. The experimental frequency response plots can be used to verify the theoretical modeling. The active vibration control was achived by using a single-input single-output positive position feedback controller. Theoretical analysis will follow.

• 한국정밀공학회지
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• 제24권3호
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• pp.67-75
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• 2007

This paper deals with a problem of vibration suppression of a piezoelectric beam using a self-sensing algorithm. Two methods, which are PPF(positive position feedback) and SRF(strain rate feedback), are considered to suppress a residual vibration of a piezoelectric beam developed during the step positioning of a beam end point. A self-sensing algorithm treated here is basically a strain rate estimator of a beam movement and is to be used for the closed loop control. The efficacy of the proposed idea is evaluated through experiments.