• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.1
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• pp.10-17
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• 2000

In boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants, conventional measurement techniques(replica method, electric resistance method, and hardness test method) for measuring creep damage have such disadvantages as complex preparation and measurement procedures, too many control parameters. And also, these techniques have low practicality and applied only to component surfaces with good accessibility. It needs to apply a reliable and quantitative ultrasonic nondestructive evaluation method that can be replaced for these equipment. In this study, both artificial creep degradation test using life prediction formula and frequency analysis by ultrasonic tests for crept specimens were carried out for the purpose of nondestructive evaluation for creep damage. As a result of ultrasonic tests for crept specimens, we conformed that the high frequency side spectra decrease and central frequency components shift to low frequency band, and also their bandwidth decreases as increasing creep damage in backwall echos.

• Journal of Nutrition and Health
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• v.16 no.4
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• pp.296-302
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• 1983

The estimation of the nutritional requirements at the national or population level has a great difficulty in calculating the cumulative effects of the several variables, i. e. age, sex, weight activity, etc., in order to adapt nutrient requirements to the condition of a country or to a population group. The Joint FAO/WHO Expert Group on nutrient requirements had proposed a simpler model, an average daily per capita nutritional requirements that will enable the different parameters to incorporated in a single calculation table. The average daily per caita nutritional requirements for Korean-1982 calculated by this proposed method are as follows : energy, 2,200 kcal ; protein, 70g : calcium, 0.72g ; iron, 14mg; vitamin A, 1,900 IU ; ascorbic acid, 50mg ; thiamin, 0.9mg ; riboflavin, 1.2mg ; niacin equivalent, 15mg. The average daily per capita nutritional requirements would be used to assess the adequacy of the national dietary intakes and provide basic information for the establishment of national food production and consumption policies and the planning of programmes aiming at an adequate and equitable distribution of food supplies. On a different levels, they would be used widely in the planning of diets for a specific population group, and also provide important reference information for the epidemiology study of nutritional deficiencies.

• Journal of the Korean Society of Physical Medicine
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• v.13 no.3
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• pp.1-9
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• 2018

PURPOSE: The purpose of this study was to determine the effect of exercise therapy on low back pain (LBP), the function of paraspinal and abdominis muscles, and the sacrohorizontal angle as seen on the radiographs of the lumbar spine in a young female golf player with LBP. METHODS: This case report describes an 11-year-old female golfer who presented with LBP. The exercise therapy program comprised lumbar joint mobilization, lumbar spine flexion distraction, abdominal bridge, plank, side plank, and single-leg extensions from a 4-point kneeling position for 40 min/day; this was done twice a week for 8-weeks. LBP [visual analog scale (VAS) and Oswestry disability index (ODI)] and function of paraspinal and abdominis muscles [Ito test, curl-up test, $90^{\circ}$ stop test, squat test, opened eye one leg stance test (OEOL), and closed eye one leg stance test (CEOL)] were measured before and after 4 and 8 weeks of exercise therapy. The radiographs were analyzed for the lumbar Cobb's angle and sacrohorizontal angle before and after 8 weeks of exercise therapy. RESULTS: After 4 and/or 8 weeks of exercise therapy, VAS and ODI scores decreased; results for the Ito test, curl-up test, $90^{\circ}$ stop test, squat test, and OEOL and CEOL of muscle function improved; and the lumbar Cobb's angle and sacrohorizontal angle improved. CONCLUSION: These results suggest that exercise therapy improves LBP, muscle function, and radiographic parameters associated with LBP in young golf players. These findings have clinical implications for exercise therapy in young female golf players who have LBP.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.81-87
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• 2017

This paper describes the dynamic behavior and enhancement of Korean high-speed trains. The tail vibration reduction method of the yaw damper installation method change, which was derived from previous research, was applied to the running test of high-speed train. In addition, the vibration reduction method for the entire vehicle was derived by a numerical method and its effect was confirmed by a running test. The improved design was applied to the double-deck high-speed train coaches and the commissioning proceeded without problems in dynamic behavior. Sensitivity analysis of the suspension parameters affecting the critical speed of Korean next-generation high-speed trains was performed and four design variables that greatly affected the critical speed were derived. These were in the order of the primary elastic joint x-directional stiffness, the secondary yaw damper series stiffness, the secondary lateral damper damping coefficient, and the carbody damper damping coefficient. By optimizing the design variables, the suspension parameter that improves the critical speed by 23.3% can be used in the commercial designs of Korean next-generation high-speed trains.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.280-286
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• 2019

This study verified the difference in biomechanical variation and the pattern of the lower limb between using or not using functional insoles on the gait of elderly people. Ten females subjects were selected (age: 73.2 years, height: 152.1 cm, body mass: 59.4 kg) for testing their gait with using functional insoles and without using functional insoles. The gait motions were captured with the Qualisys system and the gait parameters were calculated with Visual-3D. As a result, the subjects' stride length and swing time were significantly increased (p<.05). Also, the lower limb's extension moment was significantly increased (p<.05) when using the insole. These differences suggest the functional insole used in the experiment increases the subjects' gait stability. However, to generalize the results of this study, it is necessary to accumulate more quantitative data with more subjects. Further studies to examine gait variables and changes of walking patterns need to be conducted by gathering and utilizing the results of those subjects who have used insoles for a long period of time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.66-74
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• 2016

The objective of this study is the investigation of the influence of carbonation on the penetration of chloride ions in reinforced concrete sections for different mix proportions and environmental conditions. A comprehensive numerical model based on the change of the pore structure and the chemical equilibrium was used for this combined action of carbonation and chloride ingress. The empirical formulae of some parameters in this model are estimated according to numerous experimental data. And, a set of data analysis is carried out to simplify the estimation of model variables to reduce the computational cost. A coupled simulation of the transports of carbon dioxide, chloride ions, heat and moisture is carried out. Then, the parametric analysis is given and the numerical results show that the effect of carbonation of the free chloride ingress is significant and depends on the binder types and concrete mix proportion.

• Physical Therapy Korea
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• v.21 no.4
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• pp.1-8
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• 2014

Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers low-intensity direct current to cortical areas, thereby facilitating or inhibiting spontaneous neuronal activity. This study was designed to investigate changes in various sensory functions after tDCS. We conducted a single-center, single-blinded, randomized trial to determine the effect of a single session of tDCS with the current perception threshold (CPT) in 50 healthy volunteers. Nerve conduction studies were performed in relation to the median sensory and motor nerves on the dominant hand to discriminate peripheral nerve lesions. The subjects received anodal tDCS with 1 mA for 15 minutes under two different conditions, with 25 subjects in each groups: the conditions were as follows tDCS on the primary motor cortex (M1) and sham tDCS on M1. We recorded the parameters of the CPT a with Neurometer$^{(R)}$ at frequencies of 2000, 250, and 5 Hz in the dominant index finger to assess the tactile sense, fast pain and slow pain, respectively. In the test to measure CPT values of the M1 in the tDCS group, the values of the distal part of the distal interphalangeal joint of the second finger statistically increased in all of 2000 Hz (p=.000), 250 Hz (p=.002), and 5 Hz (p=.008). However, the values of the sham tDCS group decreased in all of 2000 Hz (p=.285), 250 Hz (p=.552), and 5 Hz (p=.062), and were not statistically significant. These results show that M1 anodal tDCS can modulate sensory perception and pain thresholds in healthy adult volunteers. The study suggests that tDCS may be a useful strategy for treating central neurogenic pain in rehabilitation medicine.

• Steel and Composite Structures
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• v.27 no.6
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• pp.717-725
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• 2018

One of the most important design criteria in military tunnels and armoured doors is to resist the blast loads with minimum structural weight. This can be achieved by using steel sandwich panels. In this paper, the nonlinear behaviour of steel sandwich panels, with different core materials: (1) Hollow (no core material); (2) Rigid Polyurethane Foam (RPF); and (3) Vulcanized Rubber (VR) under free air blast loads, was investigated using detailed 3D nonlinear finite element models in Ansys Autodyn. The accuracy of the finite element model proposed was verified using available experimental test data of a similar steel sandwich panel tested. The results show the developed finite element model can be reliably used to simulate the nonlinear behaviour of the steel sandwich panels under free air blast loads. The verified finite element model was used to examine the different parameters of the steel sandwich panel with different core materials. The result shows that the sandwich panel with RPF core material is more efficient than the VR sandwich panel followed by the Hollow sandwich panels. The average maximum displacement of RPF sandwich panel under different ranges of TNT charge (1 kg to 10 kg at a standoff distance of 1 m) is 49% and 53% less than the VR and Hollow sandwich panels, respectively. Detailed empirical design equations were provided to quantify the maximum deformation of the steel sandwich panels with different core materials and core thickness under a different range of blast loads. The developed equations can be used as a guide for engineer to design steel sandwich panels with RPF and VR core material under a different range of free air blast loads.

• 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 Rehabilitation Science
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• v.5 no.4
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• pp.210-214
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• 2016

Objective: The aim of this study was to measure the muscle architectural parameters of abdominal muscles in healthy individuals by rehabilitative ultrasound imaging (RUSI) and to investigate their changes after bridging exercise in various environments. Design: Cross-sectional study. Methods: The study included 40 healthy participants (19 men, 21 women). Subjects were randomly allocated to a stable surface group (SG, n=20) or an unstable surface group (UG, n=20). The participants assumed three positions in rest, bridging exercise with knee flexion $60^{\circ}$, and bridging exercise with knee flexion $90^{\circ}$ for the measurement of abdominal muscle thickness by RUSI. For the resting position, the participants held the head neutral in a hook-lying position and the dominant side was measured. For contraction, the participants performed the bridging exercise with the knee joint in $60^{\circ}$ and $90^{\circ}$ of flexion for 10 seconds each. Results: For transversus abdominis, external oblique muscle thickness, within the stable surface group and the unstable surface group, no significant contraction difference was observed in both the $60^{\circ}$ and $90^{\circ}$ bridge exercise conditions. Contraction difference of internal oblique muscle was significantly larger at $90^{\circ}$ than at $60^{\circ}$ within the SG (p<0.05). But within the UG, no significant contraction difference was shown. There was no significant contraction difference between the surface group and the unstable SG at $60^{\circ}$ condition and at $90^{\circ}$ condition in all measured muscles. Conclusions: The contraction difference is different for each muscle during bridge exercise with knee flexion $60^{\circ}$ and bridging exercise with knee flexion $90^{\circ}$. Muscle contraction difference is generally large when exercised on an unstable surface than a stable surface, but these are not statistically significant when bridging exercise is performed using dynamic air cushion for unstable surface.