• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.396.2-396
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• 2002

Dynamic stability and behavior are analyzed fur Pendulum Automatic Dynamic Balancer which is a device to reduce an unbalanced mass of rotors. The nonlinear equations of motion for a system including a Pendulum Balancer are derived with respect to polar coordinate by Lagrange's equations. The perturbation method is applied to find the equilibrium positions and to obtain the linear variation equations. Based on linearized equations, the dynamic stability of the system around the equilibrium positions is investigated by the eigenvalue problem. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.579-585
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• 2003

This paper investigates the whirling, tilting and flying motion of a HDD spindle system supported by FDB experimentally. Experimental setup is built to measure the flying, whirling and tilting motion of the HDD spindle system, and three capacitance probes fixed on the xyz-micrometers measure the displacement of a HDD spindle system in the xyz-directions. This research shows that the tilting and whirling motion is mostly dependent on the centrifugal force and the gyroscopic moment due to the unbalanced mass of a HDD spindle. It also shows that the rotating HDD spindle starts to float to the equilibrium position in the z-direction until the weight of the rotating spindle is equal to the supporting pressure generated in the upper and lower thrust bearing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.529-536
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• 2006

In high-speed optical disk drive, the excitation caused by rotation of a mass-unbalanced disk is a major source of vibration. The vibration can be a disturbance to the servo system, which is sufficient to cause severe failures in the reading and writing process. The vibration also causes users to feel unpleasantness. The vibration reduction is therefore essential for the reliable operation of optical disk drive. One of the approaches to reduce the vibration is a dynamic vibration absorber(DVA). In this paper, we analyze the dynamic behavior of $DVD{\pm}RW$ combo drive system with DVA through 12-dof rigid multi-body dynamic model. The effective location and the optimal frequency ratio for the DVA are obtained from the analysis. The DVA are fabricated based on the analysis and its usefulness is confirmed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.103-109
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• 2007

With the increase of track density, high rotational speed and the compatibility for various media in optical disk drives, the effective design to vibration reduction is very important for robust operation. Especially when a slim optical disk drive for a notebook PC is excited by a mass-unbalanced disk, internal vibration and its transmission to external case bring about severer problem than that of conventional one. In this paper a design process of a rubber mount in a slim optical disk drive for vibration reduction is presented. The characteristics of rubbery materials - hyper-elastic and visco-elastic - are measured with standard specimens. The static stiffness of a rubber mount was calculated by FEM and the dynamic stiffness is predicted with the static stiffness and the impedance test data of the standard specimen. The transmissibility tests are performed for the purpose of verification of the design process.

• Transactions of the Society of Information Storage Systems
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• v.6 no.2
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• pp.57-62
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• 2010

This paper measured and analyzed the source of total power loss of an ODD of a notebook computer. It shows that the biggest power loss is the windage loss due to the friction between rotating disk and surrounding air. It measured the power loss by the tilting motion of a rotating disc which is originated from the unbalanced mass of the rotating disc or the squareness between case-rotor and shaft. The power loss of rotating disc due to tilting motion was also calculated by using FLUENT, and it was correlated with the measured one. This paper shows that the one of the effective methods to reduce the power loss of an ODD is to reduce the tilting motion of a rotating disc.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.459-466
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• 2000

A new control method for precision robust speed control of a PMSM(Permanent Magnet Synchronous Motor) using load torque observer is presented. Using this system, we can more precisely evacuate of vestibular function. Until now a rotating chair system, so called 2D-stimulator, which has vertical rotate axis is used to make dizziness. However, an inclined rotating chair system witch is called 3D-stimulator is needed to obtain the precise dizziness data. This 3D-stimulator include unbalanced load caused by unbalanced center of mass. In this case, new compensation method is considered to obtain robust speed control using load torque observer. To reduce the effect of this disturbance, we can use dead-beat observer that has high gain. The application of the load to torque observer is published in for position control. However, there is a problem of using speed information such as amplifying effect of noise. Therefore, we can reduce a noise effect by moving average process. The experimental results are depicted in this paper to show the effect of this proposed algorithm.

• Journal of Nutrition and Health
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• v.54 no.5
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• pp.474-488
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• 2021

Purpose: Malnutrition in children with cerebral palsy (CP) is a significant factor affecting their adequate growth and development. This study aimed at conducting surveys and evaluating the dietary intake of children with CP according to their BMI classification and to thereby highlight the dietary factors affecting the nutritional status of these children. Methods: A total of 16 children were enrolled between the age of four and twelve. These subjects were further classified into three groups, namely underweight, normal and obese, with 6, 8, and 2 children in each group, respectively. The general characteristics, motor disturbances, body composition, feeding problems, eating habits, nutritional intake, dietary variety, and food frequency for children with CP were evaluated. Results: It was observed that motor disturbances tended to increase in underweight children with CP. A significant decrease (p < 0.05) in disturbances related to oral feeding was observed with an increase in obesity. The pattern of eating habits revealed that subjects in the underweight group consumed unbalanced meals, while those in the obese group tended to consume larger meals at a faster pace. The feeding disturbance data revealed that those in the underweight group could not prepare their meals while the obese group had the problem of overeating and consuming an unbalanced diet (p < 0.05). Conclusion: It is necessary for both children with CP, who have a high degree of disability, and their caregivers to take lessons on adequate nutrient intake to prevent malnutrition. Moreover, it is necessary for the caregivers and children with CP having a low degree of disability to take lessons on providing and consuming a balanced diet and to focus on the intake of sufficient calcium in order to prevent obesity.

• Journal of Korean Academy of Nursing
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• v.33 no.3
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• pp.312-320
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• 2003

Purpose: To investigate body compositons and bone mineral density(BMD) in college women and to find the relationship between them. Method: From January to March of 2001, BMD at four parts(forearm, lumbar, femur and whole body), body mass index(BMI), body fat mass(BFM), lean body mass(LBM) and body fat percentage(%Fat) were measured with the Dual Energy X-ray Absorptiometry. Other physical characteristics were measured with a scale, a height measurer, and questionnaires. Result: Grouping by the BMI, 43.2% showed low weight, and 5% over weight. When applying the percent Fat, 43.8 % was diagnosed as obesity group. The fact indicate that a majority of college women have unbalanced body composition with high percent Fat, compared to their body weight. Assessing the BMD with the WHO standards, 91.4～95.7% of the BMD of forearm and whole body was normal. But, 40.3% and 33.1～43.9% showed osteopenia at lumbar and femur, and 104 %, 0.7～7.2% showed osteoporosis. The BMD at all parts showed significant correlation each other(r=.29～.89, p=.001～.000). Body weight and BMI showed correlations to with BMDs at all parts of the body(r=.19～46, p=.025～.000; r=18～.45, p=.039～.000). But the percent Fat had a correlation with only femur neck BMD(r=.19, p=.024). Conclusion: This study showed a majority of healthy college women were exposed to the risk for osteoporosis. Additional study is required to develop nursing interventions to remove the risk factors of osteoporosis. In particular, the acquisition of balanced body composition is necessary, increasing body weight and BMI through the increase of LBM, not through the quantitative increase of BFM.

• Korean Journal of Community Nutrition
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• v.14 no.5
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• pp.483-494
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• 2009

In order to give basic data to teenager's healthcare, we investigated the food habits according to BMI (Body Mass Index), life style, dietary related self-efficacy and food intake through conducting a research surveying 732 middle school students of the Kwang-ju and Chonnam areas. The results of this study were compared groups in under weight (UW), normal weight (NW), and overweight (OW) groups according to BMI levels. In the male students, height was significantly differently in the UW group as $158.2\pm0.7$ cm compared to other NW and OW groups respectively as $163.7\pm0.6$ cm and $162.6\pm0.7$ cm but in the female students there was no significantly difference within groups. Weight was significantly different between the groups in the male students, whereas there were minor differences in the female students. The average of BMI was $20.7\pm0.1$ on the male students and $20.6\pm0.1$ on the female students which were all within the average, and their obesity was increased as the school grade was higher. Under less than 30,000 won of pocket money was dominating, and most of the students were in a nuclear family. In all male and female students, the inactive hours like watching TV and using computers had no differences between groups. The difference between groups was minor on breakfast time and most of the students thought their problems on unbalanced diet. There was significant difference in the OW group in female students as they thought their problems on unbalanced diets. The frequency of snack was significantly low in the OW group of male students but there were no differences in snack and eating-out food. All students chose fruits as snack food and Korean-style food as eating out food. The OW group in male students were significantly low in the dietary related self-efficacy when they were with their families and feeling depressed but there were no differences in female students between groups. When all students were getting higher BMI, they evaluated themselves badly in their self-dietary habits. Also the more male students had non-physical activity time, the less they had the dietary related self-efficacy and the more female students had physical activity time, the higher they had the dietary related self-efficacy. In conclusion, the OW group had good habits in physical activities for weekends, meal times, frequency of snack consumption but it showed undesirable when they were low in dietary related self-efficacy. Therefore we will provide the systematic nutrition education to them through this study.

• Korean Journal of Community Nutrition
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• v.15 no.3
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• pp.342-350
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• 2010

This study investigates differences in middle school male students' anthropometric variables and dietary habits using BMI (Body Mass Index) classifications. $\chi^2$ -test for frequency and ANOVA test for mean value and duncan value were used to analyze results. Averaged results of three groups of middle school male students' anthropometry including height (normal group 164.4 cm, overweight group 165.0 cm, obese group 167.0 cm), weight (normal group 56.0 kg, overweight group 70.0 kg, obese group 83.2 kg) and waist circumference (normal group 20.7 cm, overweight group 79.8 cm, overweight group 89.6 cm) were resulted. Classification of obese group was based upon 2007 growth charts using BMI criteria. This study indicates the normal weight group boys have over-eating related dietary habits and the obese groups have less calorie dietary habits. They answered oppositely to normal recognition. The obese group reflected dietary problems, such as preferences for sweet fruit rather than normal group males. Dinnertime of the groups were significantly different and obese group's earlier dinnertime can influence on their late night snack eating. Forty precent of obese male group like fruits as late night eating food. Three meal amount of three groups were significantly different, as obese group answered they ate same amount at every meal. It can mean obese group ate more amount of food in every meal. Overweight and obese male students have dietary problem of fast eating and answers of unbalanced eating were higher in normal group. These could mean obese group eats well in every food and fast eating habit could lead a lot of food eating habit. Obese group chooses out-going food of less calorie and frequency of fast food eating was lower than normal group. In result, obese group answered that they have less calorie related dietary habits, it could mean their answers were false or fixed dietary habit. Therefore, more researches should be followed.