• Korean Journal of Applied Biomechanics
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• v.23 no.3
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• pp.209-218
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• 2013

This study was to perform the kinetic analysis of forward $1\frac{1}{2}$ somersault on the platform diving. Six men's diving players of the Korea national reserve athletes participated in this study. The variables were analyzed response time, velocity, center of mass (COM), angle, center of pressure (COP) and ground reaction force (GRF) of motion. For measure and analysis of this study, used to synchronized to 4 camcorder and 1 force plate, used to the Kwon3D XP (Ver. 4.0, Visol, Korea) and Kwon GRF (Ver. 2.0, Visol, Korea) for analyzed of variables. The results were as follows; Time factor were observed in maximum knee flexion depending on the extent of use at phase 1 of take-off to execute the somersault. This enabled the subject to secure the highest possible body position in space at the moment of jumping to execute the somersault and prepare for the entry into the water with more ease. Regarding the displacement of COM, all subjects showed rightward movement in the lateral displacement during technical execution. Changes in forward and downward movements were observed in the horizontal and vertical displacements, respectively. In terms of angular shift, the shoulder joint angle tended to decrease on average, and the elbow joints showed gradually increasing angles. This finding can be explained by the shift of the coordinate points of body segments around the rotational axis in order to execute the half-bending movement that can be implemented by pulling the lower limb segments toward the trunk using the upper limb segments. The hip joint angles gradually decreased; this accelerated the rotational movement by narrowing the distance to the trunk. Movement-specific shifts in the COP occurred in the front of and vertical directions. Regarding the changes in GRF, which is influenced by the strong compressive load exerted by the supporting feet, efficient aerial movements were executed through a vertical jump, with no energy lost to the lateral GRF.

• Journal of Soil and Groundwater Environment
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• v.9 no.3
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• pp.1-11
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• 2004

To evaluate the applicability of dielectric constant measurement method on the geoenvironmental investigation of subsurface contaminated by landfill leachate, the analysis on dielectric characteristics of sand containing contaminated pore water by landfill leachate was performed. The separate real and imaginary parts of dielectric constant were investigated in the frequency range of 75kHz to 12MHz. The real part of dielectric constant increased at the lower frequency wherea the real part of dielectric constant decreased at the higher frequency as the concentration of leachate increased. These results can be explained by the frequency dependence of space charge polarization and orientation polarization. The imaginary part of dielectric constant on the contaminated sand with leachate increased with their concentration for whole frequency range. These results are caused by the increase of energy loss due to the enhancement of conduction in soil with leachate concentration. The results in this study indicate that the dielectric constant measurement method has potential in evaluating the contaminated soil and pore water by landfill leachate.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.181-191
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• 2016

In geological storage of $CO_2$, the behavior of $CO_2$ is influenced by pore network of rock. In this study, the drilling cores from Pohang Basin were analyzed quantitatively using three-dimensional images acquired by X-ray micro computed tomography. The porosities of sandstone specimens around 740 m-depth (T1), 780 m-depth (T2) and 810 m-depth (T3) which were target strata were 25.22%, 23.97%, 6.28%, respectively. Equivalent diameter, volume, area, local thickness of pores inside the sandstone specimens were analyzed. As a result, the microstructural properties of T1 and T2 specimens were more suitable for geological storage of $CO_2$ than those of T3 specimens. The result of the study can be used as input data of the site for decision of injection condition, flow simulation and so on.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.143-153
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• 2016

This study analyzed the features and various applications of Bluetooth beacon technology for utilization in the mining and construction industries. Through a literature survey, the concept and version-specific features of Bluetooth were reviewed, and representative types of the Bluetooth beacon-based service and its real-world applications in other fields were analyzed. Although a few previous studies that used the Bluetooth Classic (the old version of Bluetooth technology) in the mining industry have been reported, no mine site could be found where the Bluetooth beacon technology was utilized. In the construction industry, this study could find a site where the Bluetooth beacon technology was used to improve the haulage works of construction raw materials. Since the Bluetooth beacon technology has low power consumption and is easy to integrate with smartphones, it will be effectively utilized to improve the productivity and safety in the mining and construction industries.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.60-60
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• 2000

The adhesion interface formation between copper and poly(ethylene terephthalate)(PET), poly(methyl methacrylate)(PMMA) and Polyimide films was treated using Ion assisted reaction system to sequential sputter deposition by High-Frequency ion source. The ion beam modification system used a new type of low power HF ion thruster for space application as new low thruster electric propulsion system. Low power HF ion thruster with diameter 100mm gives the opportunity to obtain beams of Ar+ with currents 20~150 mA (current density 0.5~3.5 mA/cm2) and energy 200~2500eV at HF power level 10~150 W. Using Ar as a working gas it is possible to obtain thrust within 3~8 mN. Contact angles for untreated films were over 95$^{\circ}$ and 80 for Pet, 10o for PMMA and 12o for PI samples as a condition of ion assisted reaction at the ion dose of 10$\times$1016 ions/cm2, the ion beam potential of 1.2 keV and 4 ml/min for environmental gas flow rate. 900o peel tests yielded values of 15 to 35 for PET, 18 to 40 and 12 to 36 g/min. respectively. High resolution X-ray photoelectron spectrocopy is the Cls region for Cu metal on these polymer substrates showed increases in C=O-O groups for polymide, whereas PET and PMMA treated samples showed only C=O groups with increase the ion dose. Finally, unstable polymer surface can be changed from hydrophobic to hydrophilic formation such as C-O and C=O that were confirmed by the XPS analysis, conclusionally, the ion assisted reaction is very effective tools to attach reactive ion species to form functional groups on C-C bond chains of PET, PMMA and PI.

• Tunnel and Underground Space
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• v.20 no.6
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• pp.446-454
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• 2010

CAES-G/T (Compressed Air Energy Storage - Gas Turbine) power generation is a likely option for the buffer facility stabilizing the fluctuation of the renewable powers, such as wind and solar powers. Considering the geological conditions, the underground CAES facility is most probable if the CAES-G/T generation is planed in Korea. In this kind of facility, a concrete plug is installed to seal the compressed air in the container, so that the selection of the shape and dimension of concrete plug could be a critical design factor. The stability evaluation of two types of plug was carried out by investigating the distribution of the factor of safety in the plugs and the distribution of contact pressure over the contact surface. The analysis result shows that the taper-shaped plug is more structurally stable than the wedge-shaped plug for the given geological condition. Possible separation of the rock-concrete interface around the spring line of the wedge-shaped plug is anticipated, which means the possible leakage of compressed air through the side wall and also means the poor mobilization of frictional resistance on that area.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.203-211
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• 2013

Shear behavior of joint plane has been investigated considering the magnitude of normal stresses and initial surface roughness. Shear strength of joint plane has been measured by performing the multi-stage shear test in which applied normal stress level has been increased stepwise. Multi-stage shear test within the specified normal stress range has been repeated and two types of strength parameter variation have been observed: type 1 - both cohesion and friction angle decrease, type 2 - cohesion decrease and friction angle increase. Trends of strength parameter variation for the three rock types, gneiss, granite and shale, have been investigated and the influence of initial roughness of joint plane on the sequential shear strength change for the repeated multi-stage shear tests also has been analyzed.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1587-1599
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• 2017

This paper proposes a real-time implementation of an optimal operation of a double stage grid connected wind power system incorporating an active power filter (APF). The system is used to supply the nonlinear loads with harmonics and reactive power compensation. On the generator side, a new adaptive neuro fuzzy inference system (ANFIS) based maximum power point tracking (MPPT) control is proposed to track the maximum wind power point regardless of wind speed fluctuations. Whereas on the grid side, a modified predictive current control (PCC) algorithm is used to control the APF, and allow to ensure both compensating harmonic currents and injecting the generated power into the grid. Also a type 2 fuzzy logic controller is used to control the DC-link capacitor in order to improve the dynamic response of the APF, and to ensure a well-smoothed DC-Link capacitor voltage. The gained benefits from these proposed control algorithms are the main contribution in this work. The proposed control scheme is implemented on a small-scale wind energy conversion system (WECS) controlled by a dSPACE 1104 card. Experimental results show that the proposed T2FLC maintains the DC-Link capacitor voltage within the limit for injecting the power into the grid. In addition, the PCC of the APF guarantees a flexible settlement of real power exchanges from the WECS to the grid with a high power factor operation.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.99-107
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• 2018

In this study, the injector transfer function (ITF) of a gas-gas coaxial jet-swirl injector is measured by perturbing jet or swirl flow using a speaker as jet flow increases. As a result of measuring the ITF varying feed system length, a peak occurs at a resonance frequency of space where the perturbed flow passes. With jet excitation, the ITF magnitude decreases, but increases thereafter as increasing the jet flow. Therefore the larger the velocity difference between jet and swirl flow, the larger the ITF. With swirl excitation, ITF decreases as increasing the jet flow because of the energy decrease with respect to the constant downstream flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.4
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• pp.222-228
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• 2009

Various types of refrigerators become popular in the market such as a common refrigerator, kimchi refrigerator and wine cellar. It is required to develop a multi type refrigerator combining these refrigerators to save space and energy consumption. In this study, the performance of a multi type refrigerator, which consists of one machine room and three evaporators, was measured in a bench type multi refrigerator. The multi type refrigerator was tested by varying the number of refrigerator cabinet, refrigerant charge, and temperature conditions. In addition, the multi type refrigerator with a suction line heat exchanger(SLHX) was tested to improve system performance. Based on the experimental data, the multi type refrigerator showed better performance than the conventional refrigerator(single type system). Besides, the COP of the single system increased from 1.0 to 1.37, and those of the dual and triple system increased from 1.29 to 1.39, and 1.22 to 1.51, respectively, by applying the SLHX.