• Korean Journal of Applied Biomechanics
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• v.18 no.3
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• pp.61-69
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• 2008

The purpose of this study is to examine the success or failure on the balance beam in element group requirements posture which is bending salto side-ward tucked through kinetic analysis. The national team players were participated. The goal was to present training methods to coaches and athletes so as to provide scientifically useful information. The results from this study were summarized as below. When the performance was successful, the features of the body's center of gravity during the side somersault motion showed to spread from the center of the balance beam and the center of the gravity moved to the direction of the body's rotation. In the spring sections - event2 and 3, when the performance was successful, up/down fluctuation became more wider and increased air time. It supported the result that the projecting variable was higher than in failure trial. In addition, the right side hip joint angles and speed, and angular velocity as jumping up for a leap were larger than in failure trial. Those variables showed the optimal conditions for a leap. By increasing the speed of the upper limb from the shoulder and the speed of the shoulder joint angular velocity, the momentum was increased. Especially the right side shoulder joint angular velocity increased dramatically because the right leg was held. As to the side somersault motion, the angular momentum of successful trial with respect to x-axis was bigger than failed trial. It indicated that the increasing angular momentum with respect to x-axis was an important factor in flying motion. Besides, as to side somersault, the appropriate proportion of angular momentum with respect to y-axis and z-axis was a key to successful trails.

• Mineral and Industry
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• v.26
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• pp.13-21
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• 2013

This study is carried out experiments on various factors for improving the grade of low grade scheelite by Knelson concentrator prior to the main beneficiation process. Even though there are several gravity separators such as Jig, Spirals and etc. for rougher concentrate, the KC3 Knelson Concentrator was adopted to get better separation efficiency and beneficiating effects for pre-concentration of the low grade scheelite ore. The feed samples was prepared to minus 1mm in size by crushing and grinding. The important factors in the KC3 Knelson Concentrator test were examined in terms of the variations such as number of treatment, feed rate, rotation speed of bowl(G force), water flow rate, pre-removal of magnetic minerals, feed size and feed grade. According to the result of experiment, it shows that the important technical variations are limited in terms of number of treatment, feed rate, feed size and feed grade. The final result shows that the KC3 Knelson Concentrator obtains the scheelite pre-concentrate of about $3%WO_3$ grade and 90% recovery, respectively, from the feed containing about $0.8-1.0%WO_3$ grade.

• Journal of Korea Soil Environment Society
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• v.3 no.3
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• pp.55-62
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• 1998

Soils contaminated with hydrocarbons and residual metals can be effectively treated by soil washing. In developing the soil washing process several major effects for separating contaminants from coarse soils progressively improved upon combinations of mining and chemical processing approaches. The pilot-scale soils washing process consists of the four major parts : 1) abrasive scouring, 2) scrubbing action using a washwater that is sometimes augmented by surfactants or other agents, 3) rinsing, and 4) regenerating the contaminated washwater. The plant was designed based upon the treatment capacity > 5 ton/hr on site. The lumpy contaminated soil fractions first experience deagglomeration and desliming passing through a rolling mill pipe. In the second unit the attrition scrubbing module equipped with paddles uses high-energy to remove contaminants from the soils. And a final rinsing system is assembled to separate the washwater containing the contaminants and very fine soils from the washed coarse soils. For recycling the contaminated washwater passes through a washwater clarifier specifically designed for flocculation, sedimentation and gravity separation of fine as well as flotation and separation of oils from the washwater. In order to more rapidly assess the applicability of soil washing at a potential site while minimizing the expense of mobilization and operation, a mobile-type soil washing process which is self-contained upon a trailer will be further developed.

• The Korean Journal of Nuclear Medicine
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• v.34 no.1
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• pp.10-21
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• 2000

Purpose: Episodic memory is described as an 'autobiographical' memory responsible for storing a record of the events in our lives. We performed functional brain activation study using ${H_2}^{15}O$ PET to reveal the neural basis of the encoding and the retrieval of episodic memory in human normal volunteers. Materials and Methods: Four repeated ${H_2}^{15}O$ PET scans with two reference and two activation tasks were performed on 6 normal volunteers to activate brain areas engaged in encoding and retrieval with verbal materials. Images from the same subject were spatially registered and normalized using linear and nonlinear transformation. Using the means and variances for every condition which were adjusted with analysis of covariance, t-statistic analysis were performed voxel-wise. Results: Encoding of episodic memory activated the opercular and triangular parts of left inferior frontal gyrus, right prefrontal cortex, medial frontal area, cingulate gyrus, posterior middle and inferior temporal gyri, and cerebellum, and both primary visual and visual association areas. Retrieval of episodic memory activated the triangular part of left inferior frontal gyrus and inferior temporal gyrus, right prefrontal cortex and medial temporal area, and both cerebellum and primary visual and visual association areas. The activations in the opercular part of left inferior frontal gyrus and the right prefrontal cortex meant the essential role of these areas in the encoding and retrieval of episodic memory. Conclusion: We could localize the neural basis of the encoding and retrieval of episodic memory using ${H_2}^{15}O$ PET, which was partly consistent with the hypothesis of hemispheric encoding/retrieval asymmetry.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.314-322
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• 1997

The thin film processing and the applicability as a IMD material of SiO2 aerogels providing ultralow dielec-tric properties were studied. The SiO2 aerogel films with 0.5g/㎤ density (78% porosity) and 4000~21000$\AA$ thickness could be prepared at 25$0^{\circ}C$ and 1160 psig by supercritical drying of wet-gel films, which were spin-coated at the spin rate of 1000~7000 rpm on p-Si(111) wafer under the isopropanol atmosphere. The optimum viscosity of polymeric SiO2 sols for spin coating was in the range of 10~14 cP. The main fac-tors being able to control the film thickness and microstructures were found to be sol concentration, spin rpm, and aging time of wet-gel films. The dielectric constant of the SiO2 aerogel thin film was around 2.0 low enough to be applied to the next generation semiconductor device beyond the giga level.

• The KSFM Journal of Fluid Machinery
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• v.19 no.6
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• pp.50-54
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• 2016

The performance of a scroll expander is the most important factor for the efficiency of small scale Organic Rankine cycle waste heat power generation systems. In this research, a scroll compressor was purchased and operated in reverse to function as a scroll expander. With air as a working fluid, a series of performance test were conducted on this expander by varying the inlet and outlet pressure. Secondly, We have tested through 2000 to 3500 rpm rotational speed to find the maximum power and efficiency of the expander. And last, It was observed in the initial experiments that the design of the expander's orbiting scroll wrap partially blocked the fluid intake which may have caused unnecessary flow resistance. To verify this theory, a small part of the scroll wrap was removed and the performance test was redone. It was observed that the lower back pressure assure the higher efficiency and power of expander and the rotational speed that shows maximum adiabetic efficiency of scroll expander is 69% at 2500 rpm. And by modified wrap of the scroll, we could get volume flow rate for 13% to 19% and power for 5% to 18% increased. But the maximum efficiency of the modified scroll was decreased 8%.

• Explosives and Blasting
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• v.36 no.1
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• pp.20-33
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• 2018

A locally damaged structure is a structure that cannot be reused due to having parts that have lost their structural function as a result of abnormal load across the interior or exterior of the structure. The causes of the abnormal load occurrences can be classified into natural disaster and artificial disaster. Locally damaged structures caused by this abnormal load have risk factors that may lead to the possibility of additional secondary collapses, so such structures require immediate and complete dismantling. The case presented in this study involves the application of explosive demolition to a steel truss structured bridge in the Philippines that was damaged due to construction failures and the hurricane. Although shaped charges were needed in explosive demolitions, difficulties in locally obtaining such material. So, we made a charge container to charging of emulsion explosive during the explosive demolition. The explosive demolition resulted in the vertical free fall of the mid-section of the bridge and the free fall rotating of the both end section of the bridge. The neighboring posts and bridge piers did not show signs of damages, while post-demolition fragmentation of removed parts was found to be satisfactory.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.3
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• pp.177-184
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• 1987

The quantitative mechanics on the sideways walking of the crabs may provide a basic solution for entanglements of the walking legs in gillnets. The gaiting behaviour of the crabs on the flat board and the nettings 10, 16 and 23 mm in mesh size were experimented concerning about stepping positions and times in the laboratory using video set on July, 1984, It was found that the irregular movements of walking crabs in stepping positions and patterns were appeared on the nettings due to the absence of mechanical contact in spite of neural control of compensating, while on the flat surface evolved systematic leg movements. The mean stride length and walking velocity, which were increased with the carapace width on the flat board, as well as the step period and forward by backward stroke time were greater than those values on the netting, not associated with the carapace or the mesh size. Also, the step period and the Phase difference on the nettings revealed larger fluctuation than on the flat board. The joint angles of the walking legs, on the nettings in meropodite-carporodite and thorax-meropodite, which joint was varied especially up to below horizon because of the falling legs through the netting twine, were virtually wider than those on the flat substrate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.401-407
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• 2011

The conventional method of magnetic abrasive polishing is not suitable for non-magnetic materials because such polishing is basically possible when magnetic force exists and the magnetic force in non-magnetic materials is very low. The installation of an electromagnet under the working area of a non-magnetic material, which is called second-generation magnetic abrasive polishing in this study, can enhance the magnetic force. Experimental evaluation and optimization of process parameters for polishing magnesium alloy steel was performed by adopting the design of experiments and the response surface method. The results indicated that the intensity of the magnetic force and spindle speed are significant parameters that affect the improvement of surface roughness. A prediction model for the surface roughness of the magnesium alloy steel is developed using the second-order response surface method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.8
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• pp.783-790
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• 2010

In this paper, we propose a turbine mass flow rate model for a variable geometry turbocharger (VGT) using an artificial neural network (ANN). The model predicts the turbine mass flow rate using the VGT vane position, engine rotational speed, exhaust manifold pressure, exhaust manifold temperature, and turbine outlet pressure. The ANN is used for the estimation of the effective flow area. In order to validate the results estimated by the proposed model, we have compared estimation results with engine experimental results. The results, in addition, represent improved estimation accuracy when compared with the performance using the turbine map.