• Journal of Powder Materials
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• v.24 no.3
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• pp.223-228
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• 2017

Nanopowders provide better details for micro features and surface finish in powder injection molding processes. However, the small size of such powders induces processing challenges, such as low solid loading, high feedstock viscosity, difficulty in debinding, and distinctive sintering behavior. Therefore, the optimization of process conditions for nanopowder injection molding is essential, and it should be carefully performed. In this study, the powder injection molding process for Fe nanopowder has been optimized. The feedstock has been formulated using commercially available Fe nanopowder and a wax-based binder system. The optimal solid loading has been determined from the critical solid loading, measured by a torque rheometer. The homogeneously mixed feedstock is injected as a cylindrical green body, and solvent and thermal debinding conditions are determined by observing the weight change of the sample. The influence of the sintering temperature and holding time on the density has also been investigated. Thereafter, the Vickers hardness and grain size of the sintered samples have been measured to optimize the sintering conditions.

• Journal of the East Asian Society of Dietary Life
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• v.4 no.3
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• pp.21-30
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• 1994

The relationship between bone mineral density and the environmental factors were investigated from the view point of preventing osteoporosis in Korean pubescent girls. The effects of calcium, nutrient intake, physical activity on total bone mineral density, lumbar spine and femoral bone mineral density and total bone mineral content were evaluated 33 healthy pubescent girls aged 14∼16y. A convenient method was used to assess nutritional and energy intake and calcium index was used together. Calcium intake in childhood was estimated by asking whether subjects usually drank milk as children. Eating habits data and history of menstruation were obtained by questionnaire and interview. Average energy expenditure was calculated. Bone mineral density and content were measured by dual energy x-ray absorptiometry using a Lunar DPX＋Scanner (Lunar, Madison, WI). The lumbar spine(L2∼L4) and three sites in the proximal femur (femoral neck, trochanteric region, and Ward's triangle)were measured. Height and weight were measured, and the body mass index(BMI) was derived from the formula : BMI=kg/㎡ Statistical analysis was performed by simple correlation using the SAS package. The mean calcium intake (736mg) was below the RDA of 800mg/d. Twelve percent of the total subjects did not drink milk at all because they did not like the taste. Skipping meals, low calcium intake and low energy intake were significantly correlated with the low BMD. Also the data indicate that girls who reported drinking milk with every meal during childhood had significantly higher bone densities than girls who reported drinking milk less frequently. The results suggest that milk consumption in childhood appears to be needed not only for growth and development, but possibly also to assure an optimal peak of bone mass and thus greater latitude for the maintenance or skeletal integrity in the face of bone losses. There was a highly significant correlation between the total BMD and overall level of physical activity. Body weight was a better predictor of total BMD than was and other factor. Simple mechanical loading may explain why body weight, but total BMC was positively relatd to height. Conclusively, increasing calcium intake and physical activity in the pubescent girls could influence BMD.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.67-73
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• 1999

This paper presents resizing design optimization method by utilizing genetic algorithm(GA), which consists of three basic operators : reproduction, crossover and mutation. The fitness and penalty function for resizing optimization problem are defined, and the flowchart of the developed computer program along with the descriptions of each modules is presented. Also, modelling for flexible-body dynamic analysis is presented. The model is composed of bodies, joints, and force elements such as translational spring-damper-actuator. The design objects si to determine the wall thickness for minimum weight under dynamic displacement constraint.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.143-150
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• 1998

The evaluation of joint fatigue strength of light weight materials for electrical vehicle body has been performed through single lap joint tests with the design parameters such as joint style, adherend, bonding overlap length and bonding thickness. Fatigue strength was evaluated through 5-Hz, tension-tension, load controlled test with the stress ratio zero value. It is experimentally observed that fatigue strength of joint increases for the increase of overlap length. The combinations of Al-Al and Al-FRP adherends show that fatigue strength of joint is hardly changed for the increase of bonding thickness, but FRP-FRP adherend specimen shows that fatigue strength of joint increases after decreases for the increase of bonding thickness. Al-Al adherend specimen has much higher fatigue length than Al-FRP and FRP-FRP adherend specimens. Riveting at adgesive bonded joint gives little effect on fatigue strength.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.95-99
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• 2005

This paper presents the optimum design of cylindrical shell under external pressure loading. Two kinds of material, Al7075-T6, Ti-6Al-4V, are considered. For each material, the design variable is a thickness of the unstiffened parallel middle body shell, and the state variable, constraint, is hoop stress and the object .function is total weight of the cylindrical shell. Optimization is performed by conventional FE Program, ANSYS. In addition, buckling analysis is performed for the middle body of the cylindrical shell. Finally, we calculates the payload of the cylindrical shell to keep neutral buoyancy with optimized thickness in deep-sea applications.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.3
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• pp.73-79
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• 2015

PURPOSE: This study aims to examine the impact of the location of a walker-aid pocket that is attached to the walker while walking. METHODS: The research subjects included 10 male adults and 10 elderly people. The subjects used a two-wheeled walker for the walking analysis, and a firm velcro-type pocket that can be attached to the walker aid was used for weight loading. The size of the external loads was set at 2kg, which corresponds to approximately 2.5% of the mean body weight of the subjects. The pocket was attached to the left, center, and right sides of the walker aid. Stride length, stride, step width, and time were investigated according to the location change. RESULTS: No statistical differences were observed in all the walking factors among the adults and elderly people regardless of the changes in the location of the walker pocket. In cases of no weight and the 2kg walker pocket, stride length and strides were longer for the adults, while the step width was greater and walking time was longer for the elderly people. CONCLUSION: The weight of the walker pocket turn out to retard walking speed, although the location of the walker pocket is not affect walking with the walker-aid.

• Journal of Nutrition and Health
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• v.24 no.1
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• pp.1-11
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• 1991

In this study. the importance of body fat distribution as an indicator of metabolic aberrations in diabetics was'evaluated. Skinfold thicknesses at eight sites and circumferences at five sites and total body fat content were measured on 105 diabetics. 1) The waist/thigh girth ratio(WTR) was positively correlated(r=0.38-0.54) to plasma glucose levels during oral glucose loading in diabetic men alone. 2) There was no significant difference in serum total cholesterol of diabetics and nondiabetics. However, HDL-cholesterol was significantly lower(p : 0.000. in male and female) in diabetics(male : 36.31$\pm$ 16.98mg/dl, female: 37.89$\pm$14.67mg/dl) than nodiabetics(male 61.75$\pm$14.08mg/dl, female : 62.29$\pm$12.65mg/dl) and serum triglyceride was significantly higher(p=0.0212) in diabetic women(171.90$\pm$ 76.61mg/dl) than nondiabetic women(111.10$\pm$42.84mg/dl) . 3) In both sexes. anthropometric measurements that significantly correlated to serum triglyceride concentration were percentage of ideal body weight. body mass index(BMI) and waist circumference. Positive and significant correlations were found between serum cholestrol, and BMI(R: 0.31, 0.34) and waist circumference(r=0.29) in diabetic men. Moreover, skinfolds of trunk area(r=0.29~0.32) especially abdomen, were closely associated with serum lipids than other fat deposits. Increasing percentage of total body fat content was accompanied by progressively increasing serum triglyceride concentration(r=0.41) in dieabetic men. This study shows that knowledge of body fat localization may help identify risks of carbohydrate intolerance and hyperlipidemia in diabetics.

• Korean Journal of Pharmacognosy
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• v.37 no.4 s.147
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• pp.246-252
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• 2006

Processing of traditional herbal medicine is one of the pharmaceutical technique in oriental medicine. Most frequently used processing method in oriental medicine are roasting and steaming. In this studies, to elucidate the pharmacological transformation of traditional herbal medicine by means of processing them, Ginseng Radix (root of Panax ginseng, Araliaceae) was used as a sample. Processed ginseng radix (SGR, Sun Ginseng) was prepared by steaming of roots of white ginseng (GR) for 3 hours at $120^{\circ}C$. The biological activities of methanol extract of GR and SGR were investigated. According to DPPH radical scavenging effects, and inhibitory effects of xanthine oxidase and AAPH induced hemolysis, PGR exhibited more effective than those of GR in vitro. And, the antifatigue effect of GR and SGR were investigated using a weight-loading forced swimming test by monitoring swimming times and prolonged intensity exercise model rats by measuring blood biochemical parameters. GR and SGR were significantly prolonged swimming times in 8% body weight ratio loaded mice. Also, they had the inhibitory effects on the decrease of blood glucose levels, the elevation of serum creatinine, lactic acid and free fatty acid, and lactic dehydrogenase activities in forces swimming rats with 1% of the body weight attached to the neck for 3 hours. SGR was more excellent than GR on these effect. Also, these effects were transformed to the n-butanol fraction of methanol extract of SGR. From these results, it can be considered that SGR has antifatigue effect.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.101-108
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• 2006

The purpose of this study was to compare GRF characteristics during walking wearing jogging and roller shoes. Twelve male middle school students (age: $15.0{\pm}0.0\;yrs$, height: $173.6{\pm}5.0\;cm$, weight: $587.6{\pm}89.3\;N$) who have no known musculoskeletal disorders were recruited as the subjects. Kinematic data from six S-VHS camcorders(Panasonic AG456, 60 fields/s) and GRF data from two force platform; (AMII OR6-5) were collected while subjects walked wearing roller and jogging shoes in random order at a speed of 1.1 m/s. An event sync unit with a bright LED light was used to synchronize the video and GRF recordings. GRF data were filtered using a 20 Hz low pass Butterworth. digital filter and further normalized to the subject's body weight. For each trial being analyzed, five critical instants and four phases were identified from the recording. Temporal parameters, GRFs, displacement of center of pressure (DCP), and loading and decay rates were determined for each trial. For each dependent variable, paired t-test was performed to test if significant difference existed between shoe conditions (p <.05). Vertical GRFs at heel contact increased and braking forces at the end of initial double limb stance reduced significantly when going from jogging shoe to roller shoe condition. Robbins and Waked (1997) reported that balance and vertical GRF are closely related It seems that the ankle and knee joints are locked in an awkward fashion at the heel contact to compensate for the imbalance. The DCP in the antero-posterior direction for the roller shoe condition was significantly less than the corresponding value for the jogging shoe condition. Because the subjects tried to keep their upper body weight in front of the hip to prevent falling backward, the DCP for the roller shoe condition was restricted The results indicate that walking with roller shoes had little effect on temporal parameters, and loading and decay rates. It seems that there are differences in GRF characteristics between roller shoe and jogging shoe conditions. The differences in GRF pattern may be caused primarily by the altered position of ankle, knee, and center of mass throughout the walking cycle. Future studies should examine muscle activation patterns and joint kinematics during walking with roller shoes.

• Physical Therapy Korea
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• v.9 no.3
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• pp.39-46
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• 2002

In this study, vertical acceleration of center of mass was observed along normal gait phases in 9 healthy male volunteers (aged $25.7{\pm}2.18$). The developed wireless accelerometric device was attached on the intervertebral space between L3 and L4 using a semi-elastic waist belt. A three-dimensional motion analysis system, synchronized with the accelerometry, was used for detecting gait phases. There was no significant correlation between the body weight and the acceleration. The first peak curve covered loading response phase. The second downward peak point was matched accurately with the opposite toe-off. In mid-stance and terminal stance, the acceleration curve highly resembled the vertical ground reaction force curve. There was no significant difference in timing between the final upward peak point and the initial contact. Therefore, the developed accelerometry system would be helpful in determining determine temporal gait pattems in patients with gait disorders.