• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.105-112
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• 2019

Objective: The main purpose of this study was to investigate the effects of wearing an ankle weight belt while performing gait in water by focusing on the effect of using ankle weights have on the gait kinematics and the muscle activities for developing optimum training strategies. Method: A total of 10 healthy male university students were recruited for the study. Each participant was instructed to perform 3 gait conditions; normal walking over ground, walking in water chest height, and walking in water chest height while using ankle weights. All walking conditions were set at control speed of $4km/h{\pm}0.05km/h$. The depth of the swimming pool was at 1.3 m, approximately chest height. The motion capture data was recorded using 6 digital cameras and the EMG was recorded using waterproof Mini Wave. From the motion capture data, the following variables were calculated for analysis; double and single support phase (s), swing phase (s), step length (%height), step rate (m/s), ankle, knee, and hip joint angles ($^{\circ}$). From the electromyography the %RVC of the lower limb muscles medial gastrocnemius, rectus femoris, erector spinae, semitendinosus, tibialis anterior, vastus lateralis oblique was calculated. Results: The results show significant differences between the gait time, and step length between the right and left leg. Additionally, the joint angular velocities and gait velocity were significantly affected by the water resistance. As expected, the use of the ankle weights increased all of the lower leg maximum muscle activities except for the lower back muscle. Conclusion: In conclusion, the ankle weights can be shown to stimulate more muscle activity during walking in chest height water and therefore, may be useful for rehabilitation purposes.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.815-827
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• 2020

The epidermal growth factor (EGF) transgenic soybean was developed and biosynthesis of human epidermal growth factor (hEGF) in soybean seeds was confirmed. Also, EGF transgenic soybean were found to contain a herbicide resistance selectable marker by introduction of phosphinothricin acetyltransferase (PAT) gene from the Streptomyces hygroscopicus. For biosafety assessment, the EGF transgenic soybean expressing the EGF biosynthesis gene EGF and herbicide resistant gene PAT was tested to determine effects on survival of Cyprinus carpio, commonly used as a model organism in ecotoxicological studies. C. carpio was fed 100% ground soybean suspension, EGF soybean or non-genetically modified (GM) counterpart soybean (Gwangan). Gene expression of EGF soybean was confirmed by PCR and ELISA to have EGF/PAT. Feeding test showed that no significant differences in cumulative immobility or abnormal response between C. carpio samples fed on EGF soybean and non-GM counterpart soybean. The 48 h-EC50 values of the EGF and non-GM soybean were 1,688 mg·L-1 (95% confidence limits: 1,585 - 1,798 mg·L-1) and 1,575 mg·L-1 (95% confidence limits: 1,433 - 1,731 mg·L-1), respectively. The soybean NOEC (no observed effect concentration) value for C. carpio was suggested to be 625 mg·L-1. We concluded that there was no significant difference in toxicity for non-target organisms (C. carpio) between the EGF soybean and non-GM counterparts.

• Journal of the Korean GEO-environmental Society
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• v.12 no.8
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• pp.39-50
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• 2011

Nowadays, H-piles are usually used as temporary retaining walls, and sometimes buried in the ground after construction. The purpose of this study is the development of flowable fill materials that are easy to fill holes of retaining wall structure and minimize friction during pulling out H-pile. The first test was performed to decide mix proportion that is reasonable for purpose, in the second test, direct shear test was performed to get pullout resistance between flowable fills material and H-pile, and one dimensional consolidation test was performed to analyze the compressibility. In the test result, it showed that flowable fill material mix proportion is 350-450% of water, 70-100% of cement and 70-100% of sand based on the bentonite weight.

• Journal of the Korean Society of Safety
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• v.36 no.2
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• pp.10-17
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• 2021

This paper presents the robust design of each component used in the development of an induction bolt heating system for dismantling the high-temperature high-pressure casing heating bolts of turbines in power plants. The induction bolt heating system comprises seven assemblies, namely AC breaker, AC filter, inverter, transformer, work coil, cable, and CT/PT. For each of these assemblies, the various failure modes are identified by the failure mode and effects analysis (FMEA) method, and the causes and effects of these failure modes are presented. In addition, the risk priority numbers are deduced for the individual parts. To ensure robust design, the insulated-gate bipolar transistor (IGBT), switched-mode power supply (SMPS), C/T (adjusting current), capacitor, and coupling are selected. The IGBT is changed to a field-effect transistor (FET) to enhance the voltage applied to the induction heating system, and a dual-safety device is added to the SMPS. For C/T (adjusting current), the turns ratio is adjusted to ensure an appropriate amount of induced current. The capacitor is replaced by a product with heat resistance and durability; further, coupling with a water-resistant structure is improved such that the connecting parts are not easily destroyed. The ground connection is chosen for management priority.

• Steel and Composite Structures
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• v.39 no.1
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• pp.65-80
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• 2021

Irregularities of a building in plan and elevation, which results in the change in stiffness on different floors highly affect the seismic performance and resistance of a structure. This study motivated to investigate the seismic responses of high-rise steel-frame buildings of twelve stories with various stiffness irregularities. The building has five spans of 3200 mm distance in both X- and Z-directions in the plan. The design package SAP2000 was adopted for the design of beams and columns and resulted in the profile IPE500 for the beams of all floors and box sections for columns. The column cross-section dimensions vary concerning the number of the story; one to three: 0.50×0.50×0.05m, four to seven: 0.45×0.45×0.05 m, and eight to twelve: 0.40×0.40×0.05 m. Real recorded ground accelerations obtained from the Vrancea earthquake in Romania together with dead and live loads corresponding to each story were considered for the applied load. The model was validated by comparing the results of the current method and literature considering a three-bay steel moment-resisting frame of eight-story height subject to seismic load. To investigate the seismic performance of the buildings, the time-history analysis was performed using ABAQUS. Deformed shapes corresponding to negative and positive peaks were provided followed by the story drifts and fragility curves which were used to examine the probability of collapse of the building. From the results, it was concluded that regular buildings provided a seismic performance much better than irregular buildings. Furthermore, it was observed that building with torsional irregularity was more vulnerable to seismic failure.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.78-87
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• 2021

Understanding the liquid propellant transport phenomena in low gravity is essential for developing Korea Space Launch Vehicle (KSLV) upper-stage for the diversity of space missions. A low-gravity environment can be simulated via the free-fall method on the ground; however, the air drag is inevitable. To reduce air resistance during free fall, air-drag shield is usually adopted. In this study, the free-fall method was performed with an air-drag shield from a 7-m height tower. The acceleration of a falling object was measured and analyzed. Low gravity below 0.01 g was achieved during 1.2-s free fall with the air-drag shield. The minimum gravitational acceleration value at 1.2-s after free fall was ±0.005 g, which is comparable to the value obtained from Bremen drop tower experiments, ±0.002 g. A prolonged free-fall duration may enhance the low-gravity quality during the drop tower experiments.

• Journal of Aerospace System Engineering
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• v.15 no.3
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• pp.79-86
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• 2021

For a preliminary study on a thrust-throttleable Variable Flow Ducted Rocket, a gas generator and flow control valve were developed, and ground combustion tests were performed. The gas generator and flow control valve operated at the required performance level for parameters, such as heat-resistance, combustion-time, pressure, and temperature. The combustion characteristics of a fuel-rich solid propellant mixed with Boron/MgAl/AP, etc., were also analyzed. A Plunger-type flow control valve was designed to control the discharge flow area, and it was confirmed that the flow control valve was able to control the combustion gas flow rate and pressure. However, due to the reduction of the discharge flow area caused by adhesion of combustion products, the combustion pressure continuously increased. The analysis of the pressure increase is covered in Part 2 of this paper.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.151-167
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• 2023

This study compares the revised method in loose saturated sandy ground where the LNG storage tank will be installed with an evaluation method by one-dimensional effective stress analysis using the UBC3D-PLM model. Various laboratory and field tests were conducted to establish the parameters necessary for evaluation. The revised liquefaction evaluation method using the seismic response analysis result and N value from standard penetration testing evaluated the possibility of liquefaction as high, but assessment using effective stress analysis, which can consider various liquefaction resistance factors, found the site to be somewhat stable against liquefaction. One-dimensional finite element analysis using UBC3D-PLM modeling facilitated easier assessment of stability against liquefaction than the other methods and minimized the area required for reinforcement against liquefaction. In addition, it is expected that two-and three-dimensional numerical analysis considering the foundation of the LNG storage tank can identify the seismic design and behavior when liquefaction occurs.

• Journal of the Korean GEO-environmental Society
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• v.24 no.10
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• pp.15-23
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• 2023

In this study, the infiltration behavior of slopes composed of mixed soils with clay contents of 0%, 5%, and 10% in weathered Gneiss soil, which is a representative weathered soil in Korea, was investigated, and the stability of unsaturated slopes due to rainfall infiltration was examined. For this, in this study, the soil water characteristic curve was obtained through the water retention test, and the strength constant was obtained through the triaxial compression test. Based on the obtained results, the influence of clay content and antecedent rainfall effect (i.e., initial suction) on the formation of saturated zone (i.e., wetting band) and slope stability due to rainfall infiltration was examined through infiltration and stability analyses. As a result, it was found that the hig her the initial suction, the slower the formation of the saturated zone on the slope. In addition, it was found that as the clay content increases, the shear strength of the ground increases and the resistance to rainfall infiltration increases, and eventually the slope stability is greatly improved.

• Journal of the Korean Geotechnical Society
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• v.26 no.2
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• pp.15-22
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• 2010

A series of field pull-out tests were carried out to investigate the behaviour of multi-pressurized soil nails. Ten soil nails were constructed in weathered soil and then, subjected to pull-out loads. The test results showed that the ultimate pull-out resistances of soil nails constructed with high pressure were about 42~142% larger than those obtained from conventional soil nails. The deduced interface shear strength at the ground-grout interface was 71 kPa for conventional soil nails, while higher shear strength of 95~166 kPa was obtained for pressurized nails. The diameter of grouted borehole increased by about 12~27% compared to ordinary soil nails under low pressure. Also, the predicted value by the cavity expansion theory is in good agreement with the measured expanded radius of grout under injection pressure by field pull-out tests.