• Journal of the Korean Society of Visualization
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• v.16 no.1
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• pp.30-36
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• 2018

In the present study, we investigate the flow characteristics of a quadrotor UAV in a hovering mode by measuring multiple two-dimensional velocity fields in the wake. The experiment is conducted at Re = 24,000 in a chamber large enough to neglect the ground effect, where Re is the Reynolds number based on the rotor chord length and the rotor tip speed. The rotational speed of the rotor is determined by an optical tachometer so that the lift force can be balanced with the weight of the UAV. The velocity field measured on the center plane of the rotor shows that the vortices are shedding from the tip of the rotor, inducing large fluctuations in the streamwise velocity along the wake shear layer. The strength of the rotor-tip vortex shedding is asymmetric with respect to the rotor axis due to the interaction between the rotor and the wake centerline of each rotor is inclined to the center of the UAV due to the pressure difference caused by the induced velocity. The wake from each rotor moves closer to each other while traveling in the streamwise direction, and then is merged together inducing large fluctuations in the transverse velocity. Due to the wake merging, on the center plane of the UAV, the velocity increases in the streamwise direction showing two-peak structure in the streamwise velocity contours.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.996-1001
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• 2006

Automatic washing machines have been improved and popularized steadily since the first electric washing machine was produced in the early 1900's. Appliance industry has tried to obtain the performance of washing machine with large capacity, high energy efficiency, low vibration and low noise levels. As the installation peace of a washer becomes closer to the living space, vibration and noise problems become more important challenges. In general, a washing machine has four legs to support its body. Four legs of the washing machine should be attached on a floor. If not so, it may cause severe vibration or walking in the spin-drying process. Unfortunately, the floor of an ordinary house is bumpy in general, and the consumers will not accept bolting washing machines to a foundation; moreover, sometimes they move the location of their washing machines to utility rooms or bath rooms or kitchens and don't care for leveling the legs exactly. In this study, we devise an auto-leg system that prevents the occurrence of abnormal vibration and walking of washing machines. It is simply composed of a spring and a friction damper. Some experiments are implemented to show the dynamic characteristics of the three-dimensional auto-legged washing machine model that is located on the even or uneven ground. A spring parameter is optimized to adjust the length of the auto-leg system automatically up to 10 mm irregularity, and the friction damper is designed to decrease a resonance induced by the spring of the auto-leg system. Some numerical results show that placing the proposed auto-leg system in a washing machine makes good performance with low vibration, as well as low noise, regardless of the unevenness of the floor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5180-5188
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• 2015

The purpose of this study was to investigate the effects of a 12-weeks aquarobics on metabolic syndrome risk factors and health fitness in 25 abdominally obese elderly women. As the results, while waist circumference(87.40/82.76cm, p<.01) decreased, HDL-C(41.13/45.42mg/dl, p<.05) increased after the exercise program. Blood pressure and TG, however, decreased with no significance. And while muscle strength increased(17.06/19.08kg, p<.05), the increase in flexibility, muscle endurance, and cardiopulmonary endurance and the decrease in body fat showed some positive effects of the exercise program. In conclusion, we found that the aquarobics improves the aging-induced deterioration in the muscular skeletal function by lowering abdominal obesity and improving metabolic syndrome and physical fitness for health. In addition, the aquarobics can be an effective alternative to an aerobics or a resistance exercise on the ground.

• Korean Journal of Environmental Agriculture
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• v.28 no.2
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• pp.146-157
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• 2009

The influence of Pb-citrate complex formation on Pb uptake and the effect of Pb on organic acid exudation were investigated using four plant species, viz., sunflower (Helianthus annuus L), Indian mustard (Brassica juncea), canola (Brassica napus) and vetiver grass (Vetiveria zizanioides) under hydroponic conditions. Seedlings were exposed to different levels of Pb and Pb-citrate for 24 hrs and subsequently Pb distributions in plant shoot, root and hydroponic solution were measured. The dissolved organic carbon (DOC) concentration generally decreased as the concentration of Pb in the hydroponic solution increased. In contrast to DOC, the total organic acid concentrations exuded from Indian mustard roots significantly increased (424 to 6656 mg $kg^{-1}$) with increased Pb treatment, implying that exuding organic acids were involved in Pb accumulation in Indian mustard. The complexation of Pb with citrate enhanced Pb accumulation in the above ground portions. Lead concentration in Indian mustard increased from 2.05 mg $kg^{-1}$ to 6.42 mg $kg^{-1}$ when the concentration of citrate in solution increased from 0 to 50 mg $L^{-1}$. This result showed enhanced translocation of Pb from root to shoot with observation of transfer coefficient ($K_t$) increase from 2.03E-3 to 5.72E-3.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.13 no.2
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• pp.1-4
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• 1977

The author determined the relationship between the hauling veloicty and the hydrodynamic resistance of the sablefish pot shaped conic frustum like, and induced the formulae to determine the diameter of the main line and the net horse power of the pot hauler. The results are summarized as follows: 1. The maximum hydrodynamic resistance (with its weight in water) of the pot T(kg), when the bottom webbing is covered by a cloth to imitate the catches are scattered on the bottom, is eatimated as $$ T=120v^{1.1} (0.3{\leqq}v{\leqq}0.8) $$ where v denotes the hauling velocity of the pot in m/sec. 2. When P. P. 3 strand rope is used as main line, the diameter d(mm)is recommended to satisfy the formula $$ d=72 \frac{D}{H} V^{1.1} where H denotes the depth of the fishing ground and D the intervals of the pots linked to the main in m respectively. 3. The pot hauler must displace the net horse power p(ps) of $$ P= \frac{75}{120} \frac{D}{H} v^{2.1}$$

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.97-108
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• 2018

It is definitely important to measure thrust during ground test when developing air-breathing engine, and in case of air-breathing engine, gross thrust should be calculated considering not only the measured thrust but also the force induced by the air flow of engine intake. Also, side thrust like yaw and pitch should be measured and analyzed using multi-component thrust measurement system. Engine performance was accurately evaluated by calculating the gross thrust of air breathing engine precisely which is analyzed from below serial procedure: labyrinth seal isolation, 1-axis gross thrust calculation, develop multi-component thrust measurement system, and side thrust analysis.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.248-256
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• 2017

Groundwater drawdown was pointed out as one of the causes of induced settlement on high speed railways, especially concrete track. In this study, the effect of groundwater variation on settlement was evaluated through a comparison of field measurements with numerical analysis results. A trial and error method, i.e., repeated numerical analyses by changing material properties, was used to calibrate the model. The model was applied to investigate the effect of groundwater drawdown, thickness of soft layer, and embankment height on residual settlement after concrete track completion. A soft layer thicker than 4m would result in more than 30mm of settlement; a detailed analysis of groundwater behavior thus should be conducted from the design stage to construction.

• Korean Journal of Plant Resources
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• v.26 no.4
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• pp.516-518
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• 2013

A new leaf variegated cultvar 'White Edge' was developed by ethyle methane sulfonate(EMS) treatment on seed of Hosta minor. Among induced leaf variegated plant, some with white color on the edge of the leaves was selected. They were cultivated via vegetative propagation. 'White Edge' was finally selected through the test of characteristics from 2003 to 2005. Assessment of botanical characteristics was conducted for three years. The major characteristic of these cultivar is that they maintain uniformly all year round. 'White Edge'(Grant No.1880) was registered to the Korea Seed and Variety Service(KSVS) for commercialization in 2007. These cultivar are useful as materials for pot or as ground cover plants.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.67-74
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• 2015

In this study, effects of micropores on the freezing-thawing resistance of high volume slag concrete are reviewed. Concrete was made with slag which contains the ground granulated blast furnace slag(GGBS) and the pig iron preliminary treatment slag(PS) by replacing 0, 40, 70 %, then compressive strength, freezing-thawing resistance, micropores were reviewed. Also, specified design strength, target air contents were set. Deterioration was induced by using 14-day-age specimen which has low compressive strength for evaluating deterioration by freeze-thawing action. As results of the experiment, despite of specified design strength which has been set similarly and ensured target air contents, the pore size distribution of the concrete showed different results. Micropores in GGBS70 specimen have small amount of water which is likely to freeze because there is small amount of pore volume of 10~100 nm size at 0 cycle which has not been influenced by freezing-thawing. For these reasons, it was confirmed that the freezing-thawing resistance performance of GGBS70 is significantly superior than other specimens because relatively small expansion pressure is generated compared to the other specimens.

• Journal of Acupuncture Research
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• v.32 no.2
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• pp.131-145
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• 2015

Objectives : The purpose of this study was to demonstrate the effectiveness and availability of salt pharmacopuncture of Korean sun-dried salt and processing salt on the basis of bibliographical review. Methods : This study was done through a narrative review of related bibliography including medical books, journals, general bibliography, and web sites. Results : 1. Korean sun-dried salt is produced in the ground with soil, tiles, and pottery. Sun-dried, traditional, granulated, bamboo, and grilled salts are all appropriate for medical use. They are composed of a lower level of NaCl and unnecessary substances, and have a higher water and mineral content. 2. The 9~30 g of NaCl included in the physiological saline matches the ratio of a normal human body. However, if the saline is used for water supply, it should be improved because the recommended amount is much lower. 3. Medicine that includes NaCl is applied for lessening the congestion of the nasal cavity, alleviating cornea swelling, or for a lack of water. NaCl can also be used for washing contact lenses as well as cleaning the mucous membrane of the eyes and nose. 4. Salt relieves anger, detoxifies, induces vomiting, builds strong muscles and bones, gives energy, slows aging, and ultimately improves health. 5. Salt treats many diseases including: cardiovascular, hematosis, respirometer, obstetric, musculoskeletal, mineral supplement, eye, teeth and skin issues, etc.. However, salt is not used for treating asthma, cough, or other ailments mainly affecting the vascular system. 6. While NaCl in salt absorbs water and the vascular constriction results in higher blood pressure, the pressure induced from salt is actually a physiologically temporary rise. Rather, salt helps remove oil from the body and its potassium lowers blood pressure. Conclusions : It was suggested that salt pharmacopuncture of Korean sun-dried salt and processing salt should be made available for adjusting the physiological salt concentration and control of the Na side effects, therefore it would be useful in the treatment of diseases.