• Journal of Biomedical Engineering Research
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• v.12 no.3
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• pp.149-156
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• 1991

In this paper, fluttering behavior of mechanical bileaflet heart valve prosthesis was analyzed taking into consideration of the impact between valve plate and stopper Vibration system of the valve was modeled as a rotating system, and equations are induced by moment equilibrium equations. Lift force, drag force, gravity and buoyancy were considered as external forces acting on the valve plate/ The 4th order Runge-Kutta method was used to solve the equations. Valve plate does not come to the static equilibrium position at a stretch, but come to that position after under damping vibration. Damping ratio increases as the cardiac optput increases, and the mean damping ratio is in the range of 0.16~40.25. Fluttering frequency does not have any specific value, but varies as a function of time. It is in the range of 10~40Hz. Valve opening appears to be affected by the orientation of the of the valve relative to gravitational forces.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1309-1313
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• 2010

In this paper, we propose a novel guidance law for controlling an UAV(Unmanned Air-Vehicle) to follow a reference line in vertical plane. A kinematics model representing the relative motion of the UAV to the reference line is derived. And then LQR(Linear Quadratic Regulator) theory is applied to the model to derive the VLFG(Vertical Line Following Guidance) law. The resultant guidance law forms a gain-scheduling controller scheduled by a simple parameter $\sigma$ which is a function of the UAV's velocity, axial acceleration, gravity, and the slope of the reference line. Also derived is a stability condition for the $\sigma$ variation based on Lyapunov theory. Simulation results show that the proposed guidance law can be applied effectively to UAV guidance algorithm design.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.59.1-59.1
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• 2021

The Korean spacecraft for the exploration of Apophis will be equipped with an optical navigation camera with a wide-angle lens. The major purpose of the wide-angle camera is to capture imagery during the rendezvous phase in order to determine the spacecraft's position and the pointing direction relative to the asteroid Apophis. Two potential sciences, however, can be achieved by the wide-angle camera: (1) to measure the high-order gravity terms, and (2) to capture possible ejecting small particles. In this presentation, we will discuss instrument specification and operation scenario required to accomplish the given science objectives.

• Journal of Environmental Health Sciences
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• v.1 no.1
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• pp.9-13
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• 1974

For the purpose of determining the degree of freshness and bacterial contamiation of poultry farm eggs, the author collected 550 specimens from poultry farm, during the period from July 22 through October 3, 1973. Eggs of poultry farm were stored at $4{\pm} 1{\circ}$(Relative humidity 67~86%), $18\pm 1\circ$(70~80%) and $25\pm 1\circ$(73~82%) during 20 days. The results are summarized as follows: 1) Egg weight was decreased $0.97\pm 0.27$ gm at $4\pm 1\circ$, $1.68\pm 0.25$ gm at $18\pm 1\circ$ and $2.76\pm 0.30$ gm at $25\pm 1\circ$ after 20 days. 2) Specific gravity of fresh eggs was found to average 1.0785. 3) Yolk index of fresh eggs was found to average 0.419. 4) The regression equation between Yolk index and days was obtained y=0.417-0.001x (r=-0.481, p<0.05) at $4\pm 1\circ$, y=0.394-0.004 x (r=-0.738, p<0.01) at $18\pm 1\circ$ and y=0.391-0.011 x (r=-0.958, p<0.001) at $25\pm 1\circ$. 5) The regression equation between Yolk index and NaCl concentration (specific gravity) was obtained y=-0.001+0.04 x (r=0.796, p<0.001). 6) pH of albumin was changed from 8.0 to 8.8, 9.2 and 9.3 at $4\pm 1\circ$, $18\pm 1\circ$ and $25\pm 1\circ$ after 20 days. 7) Total Viable Bacteria in air cell was increased slowly according to the stored period at each temperature.

• Resources Recycling
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• v.18 no.2
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• pp.30-38
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• 2009

In this research, we studied the scale-up triboelectrostatic process for separation of PVC from higher gravity fraction of plastic wastes produced from wet gravity separation process. High density polyethylene (HDPE) was found to be the most effective materials for a tribo-charger in the separation of plastic tailings. In a commercial scale triboelelctrostatic separator unit, using the HDPE pipe-line charger, a grade of 99.1% with PET, PS and others and a recovery of 86% was obtained under optimum conditions at over 250 kV/m electric field, a splitter position of -8 cm from the center, and less than 40% relative humidity. The developed unit can process the plastic wastes at a 300 kg/h, and the product can be utilized as RPF or RDF of over grade 2.

• Journal of Industrial Convergence
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• v.21 no.5
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• pp.43-50
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• 2023

The South Korean government announced its plan to pursue membership in the CPTPP in 2022, aiming to establish a stable supply chain within the Asia-Pacific region. The CPTPP, led by Japan, was ratified in 2018 by 11 countries with the goal of eliminating tariffs and establishing new trade rules. According to our analysis, since the implementation of the CPTPP, there has been a trade promotion effect among Japan and member countries, with greater effects observed in countries with higher GDP per capita and closer geographical distance. As long as tariff elimination and reduction proceed as planned, the trade promotion effects are expected to expand gradually. However, the expansion of trade between Japan and CPTPP member countries may also indicate a relative contraction in trade with non-member countries, potentially posing a threat to the stable supply chain in the Korean industry within the Asia-Pacific region. As Japan is Korea's fourth-largest trading partner, it is necessary to carefully consider the impact of CPTPP on Japan's future trade with member countries and engage in discussions regarding Korea's participation and negotiation content based on a thorough examination of the matter.

• Journal of Korea Trade
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• v.27 no.2
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• pp.47-60
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• 2023

Purpose - This paper assesses the trade potential and efficiency of Korea and China in the aquatic products trade. Trade efficiency and potential are the main factors that affect the growth of a country's trade. In this study, a time-varying stochastic frontier trade gravity model was constructed to analyze the trade potential and efficiency between Korea and China. By integrating the results of trade theory and empirical analysis, measures and suggestions were proposed to encourage the release of trade potential of fish exports between Korea and China. Design/methodology - In this paper, GDP per capita instead of economic size was chosen as an explanatory variable, and population size and relative distance were selected as explanatory variables to measure trade potential. For trade non-efficiency terms, regional organizations, political factors, and economic factors were mainly considered, and variables such as free trade agreements, political stability, regulatory quality, government efficiency, currency freedom, investment freedom, financial freedom, and trade freedom were selected. Panel data for South Korea and 14 aquatic products trading partners (including China) from 2002 to 2020 were used in the empirical analysis. Findings - In the past 19 years, South Korea's export trade potential of aquatic products to China has never been lower than 70%. It was above 90% from 2006 to 2018, and has been at a high level for a long time. This shows that China's aquatic product market has large potential for development. Originality/value - This study examines the effectiveness and potential of South Korea's exports of aquatic items to China in a methodical and comprehensive empirical manner. The evaluation of the export trade potential of South Korea's aquatic goods to China is more precise when the effects of regional organization, political, and economic variables are taken into account in the trade non-efficiency term of the stochastic frontier gravity model. At the same time, we propose to increase the scale of South Korea's aquatic products trade from the perspective of China's demand. This issue of trade studies is underexplored both empirically and in theory, although the issue has long been important to Korean and world trade.

• Economic and Environmental Geology
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• v.43 no.6
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• pp.625-636
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• 2010

The geophysical characteristics and geological structure of the northeastern part of the Ulleung Basin were investigated from interpretation of geophysical data including gravity, magnetic, bathymetry data, and seismic data. Relative correction was applied to reduce errors between sets of gravity and magnetic data, obtained at different times and by different equipments. The northeastern margin of the Ulleung Basin is characterized by complicated morphology consisting of volcanic islands (Ulleungdo and Dokdo), the Dokdo seamounts, and a deep pathway (Korea Gap) with the maximum depth of -2500 m. Free-air anomalies generally reflect the topography effect. There are high anomalies over the volcanic islands and the Dokdo seamounts. Except local anomalous zones of volcanic edifices, the gradual increasing of the Bouguer anomalies from the Oki Bank toward the Ulleung Basin and the Korea Gap is related to higher mantle level and denser crust in the central of the Ulleung Basin. Complicated magnetic anomalies in the study area occur over volcanic islands and seamounts. The power spectrum analysis of the Bouguer anomalies indicates that the depth to the averaged Moho discontinuity is -16.1 km. The inversion of the Bouguer anomaly shows that the Moho depth under the Korea Gap is about -16~17 km and the Moho depths towards the Oki Bank and the northwestern part of Ulleung Island are gradually deeper. The inversion result suggests that the crust of the Ulleung Basin is thicker than normal oceanic crusts. The result of 20 gravity modeling is in good agreement with the results of the power spectrum analysis and the inversion of the Bouguer anomaly. Except the volcanic edifices, the main pattern of magnetization distribution shows lineation in NE-SW. The inversion results, the 2D gravity modeling, and the magnetization distribution support possible NE-SW spreading of the Ulleung Basin proposed by other papers.

• Journal of the Korean Geosynthetics Society
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• v.15 no.2
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• pp.25-33
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• 2016

This study was a basic research to obtain the knowledge of physical properties of the upper sedimented sandy soil in the Nakdong river delta area. The characteristics of shear strength and permeability with fine content and relative density were also investigated. The upper sedimented sandy soil near paddy and lower soft clay layers showed high percentage of fine content, and the rest parts had about 5% of fine content. The specific gravity regardless of depth and location was almost constant. The upper sedimented sandy soil mostly had particle size about 0.1 ~ 0.4mm regardless of sedimentation environment and has illite, a clay mineral, in the entire soil samples. The results of direct shear tests on remolded specimens of the upper sedimented sandy soil revealed that the friction angle and cohesion increased with relative density, but its effect was not significant. The fine content was significant, that as increasing it, the friction angle decreased and cohesion increased linearly. The permeability decreased with relative density and fine content, and the permeability of soil containing more than 15% of fine content was independent on the relative density.

• Journal of the Korea Society for Simulation
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• v.29 no.1
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• pp.1-9
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• 2020

The ballistic missile threat continues to increase with the proliferation of missile technology. In response to this threat, many kinds of interceptors have been emphasized over the years. For development of interceptor, systematic flight tests are essential. Flight tests provide valuable data that can be used to verify performance and confirm the technological progress of ballistic missile defense system including interceptor. However, during flight tests, civilians near the test region could be risk due to a lot of intercept debris. For this reason, reliable estimate of safety area for the flight tests should be preceded. In this study, prediction of safety area is performed through modeling and simulation. Firstly, behaviors of ballistic missile and interceptor are simulated for those entire phase including interception to obtain the relative intercept velocity and the relative impact angle. By using obtained data of kinetic energy, the fragment ejection velocity is calculated and fragment trajectories are simulated by considering drag, gravity and wind effects. Based on the debris field formation and hazard evaluation of debris, final safety area is calculated.