• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1779-1786
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• 2002

When the topology optimization is applied to the design of compliant mechanism, unexpected displacements of input and output port are generated since the displacement control is not included in the formulation. To devise a more precise mechanism, displacement constraint is formulated using the mutual potential energy concept and added to multi-objective function defined with flexibility and stiffness of a structure. The optimization problem is resolved by using Finite Element Method(FEM) and Sequential Linear Programming(SLP). Design examples of compliant mechanism with displacement constraint are presented to validate the proposed design method.

• Biotechnology and Bioprocess Engineering:BBE
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• v.4 no.1
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• pp.78-81
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• 1999

Light penetration depth in high-density Chlorella cultures can be successfully estimated by Beer-Lambert's law. The efficiency of light energy absorption algal cultures was so high that algal cells near the illuminating surface shade the cells deep in the culture. To exploit the potential of high-density algal cultures, this mutual shading should be eliminated or minimized. However, providing more light energy will not ease the situation and it will simply drop the overall light utilization efficiency.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.155-156
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• 2012

In the modern age, as man's demand of energy is continuously grew, tidal becomes one of the sustainable energy sources that have been investigating thoroughly recently. Tidal turbine has proved high potential as a future power-generating device. To effectively capture tidal energy on site, a group of tidal turbines should be used and positioned in some formation with proper size and space so that energy can be absorbed from multiple point. Thus, the turbines together with the flow filed becomes a huge domain, a tidal farm. So, it becomes more convenient if a whole turbine farm is simulated by means of actuator discs since the time and cost for analysis can be reduced. This paper aims to evaluate the operating performance (power efficiency and energy restoration rate), mutual influence (for different longitudinal and lateral spaces), the influence of velocity profiles, turbulence intensity and the far wake characteristic of tidal turbines operating in farm formation. The results of this study help contributing to the present development of tidal turbine as the future potential energy conversion machinery.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.153-156
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• 1992

Transient stability analysis of Korea Electric power Corporation(KEPCO) system is conducted by time simulation method, and the method is robust and reliable. But, time simulation consumes enormous computing resources and engineering time, and it does not provide a measure of the degree of stability of the system. Therefore, this method does not apply to every changed condition appropriately and quickly in planning and operating. And Transient Energy Function (TEF) method whis can assess quickly and quantatively the degree of stability of the system and which judges the stability and the instability to analyse transient dynamic charater of the system by mutual changing kinetic energy and potential energy, is developed. TEF method analyses the first Swing transient stability of the system by using the thought that if after disturbance happening, the increase of all the rotator kinetic energy changes into the potential energy after diturbance clearing, the system is stable, otherwise the system is unstable. This paper represents the availabiIity of the TEF method by comparing with time simulation method on the two cases.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.3
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• pp.266-273
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• 2013

With the worldwide trend of controlling the utilization of fossil fuels inducing global climate change, many efforts will have to be made on securing a sustainable energy supply. Tidal current is a concentrated form of gravitational energy, its resource is significant, but limited locations. To effectively capture tidal current energy from the sea, a group of tidal turbines should be formed and positioned with optimal size and spacing for absorbing from multiple points. Thus, the flow field including turbines becomes a huge domain, a so-called tidal farm. It can be very convenient technically and economically if a whole turbine farm is simulated by means of actuator disc thoery. So, the analysis method using actuator discs coupled with a solution of Reynolds Averaged Navier-Stokes (RANS) equations is adopted for actual tidal turbines. Actuator discs have regions where similar forces imposed by actual turbines are applied to a flow. As working in group formation, turbines naturally have interaction effects on one another. Therefore, the present paper investigate the evaluation on the operating performance of tidal farm in terms of the mutual influence among turbine units with various lateral and longitudinal spacing. Authors expect that results of the present study contribute to the development of tidal farm for the future potential energy.

• Smart Structures and Systems
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• v.20 no.6
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• pp.769-780
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• 2017

Cable force monitoring is an essential and critical part of the safety evaluation of cable-supported bridges. A reasonable cable force monitoring scheme, particularly, sensor placement related to accurate safety assessment and budget cost-saving becomes a major concern of bridge administrative authorities. This paper presents optimal sensor placement for cable force monitoring by selecting representative sensor positions, which consider the spatial correlativeness existing in the cable group. The limited sensors would be utilized for maximizing useful information from the monitored bridges. The maximum information coefficient (MIC), mutual information (MI) based kernel density estimation, as well as Pearson coefficients, were all employed to detect potential spatial correlation in the cable group. Compared with the Pearson coefficient and MIC, the mutual information is more suitable for identifying the association existing in cable group and thus, is selected to describe the spatial relevance in this study. Then, the bond energy algorithm, which collects clusters based on the relationship of surrounding elements, is used for the optimal placement of cable sensors. Several optimal placement strategies are discussed with different correlation thresholds for the cable group of Nanjing No.3 Yangtze River Bridge, verifying the effectiveness of the proposed method.

• Journal of Magnetics
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• v.17 no.3
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• pp.190-195
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• 2012

This paper presents an analytical approach to the magnetic field and the inductances of slotless permanent magnet machines with two types of winding. On the basis of a magnetic vector potential and a two-dimensional polar system, analytical solutions for flux density due to a permanent magnet and current are obtained. In addition, self and mutual inductances are obtained using the energy relationship. The analytical results are extensively validated by the nonlinear finite element method and by experimental results.

• Environmental and Resource Economics Review
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• v.9 no.2
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• pp.421-449
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• 2000

The objective of this paper is to examine whether it is feasible to introduce an crude oil futures contract on domestic commodity exchange in order to minimize the price risks of imported crude oil. In addition. this study suggests the policy issues to promote futures trading and the alternatives to use foreign energy compares the five criteria to evaluate the feasibility of crude oil futures trading on the domestic exchange. Related to the possibility of successful futures trading of imported crude oil on the domestic exchange, they are evaluated as follows: it is highly possible to succeed for the aspects of price volatility, potential market size or liquidity, and commodity homogeneity; but it is inappropriate for the aspects of deliverable amounts and market power or market structure. Therefore, it is concluded that trading a new futures contract for the underlying imported crude oil on the domestic exchange is inappropriate. For the policy issues and the hedging alternatives, first, it is urgent to establish an atmosphere for futures trading by promoting spot trading. Second, for the case of futures trading on the domestic exchange it is important to consider the simultaneous hedging of crude oil price and foreign exchange risks and mutual offsetting mechanism with major foreign exchanges. Third, for the case of futures trading on foreign exchanges it is reasonable to regard cooperation among concerned companies, government support for futures trading and direct participation into futures trading by the government.

• Economic and Environmental Geology
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• v.24 no.4
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• pp.335-346
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• 1991

It is observed that calcareous nodules of the Hwajeol Formation are locally skarnized in the Sangdong district, in which the skarn mineralization extends 5 Km westward from the Sangdong mine area to the Hwajeolchi area. After a hidden granite beneath the Sangdong mine was discovered by exploration drillings, the exploration teams of the Sangdong mine and the Korean Mining Promotion Corporation have assumed that the skarn nodule of the Hwajeol Formation was derived from emplacement of a granite in deep place and the occurrence of hidden ore bodies below the skarn, and they have discovered high grades of tungsten orebody in the same horizon of the Sangdong ore body. Mutual genetic relatioships between epidote and garnet may be explained by following chemical reactions $Ca_2FeA_{12}$ $Si_3O_{12}(OH)+CaCO_3=Ca_3(Fe,\;Al)_2$ $SiO_{12}+1/2CO_2+1/2H^+Ca_3FeSi_3O_{12}+SiO_2+CO_2=2CaFeSi_{12}O_6+CaCO_3+1/2O_3$. It is concluded that epidote and garnet are useful as target minerals indicating a potential occurrence of deep seated hidden ore body. Since the epidote may inform the emplacement of the granite, while the garnet in the skarn nodule of the Hwajeol Formation may reflect a strong hydrothermal mineralization taking place from the depth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.688-695
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• 2017

This paper deals with characteristics analysis of a permanent magnet (PM) linear generator using analytical methods for wave energy harvesting. The wave energy is carried out from the movement of a yo-yo system. A linear generator using permanent magnets to generate a magnetic force itself does not require a separate power supply and has the advantage of simple maintenance. In addition to the use of a rare earth, a permanent magnet having a high-energy density can be miniaturized and lightweight, and can obtain high energy-conversion efficiency. We derived magnetic field solutions produced by the permanent magnet and armature reaction based on 2D polar coordinates and magnetic vector potential. Induced voltage is obtained via arbitrary sinusoidal input. In addition, electrical parameters are obtained, such as back-EMF constant, resistance, and self- and mutual-winding inductances. The space harmonic method used in this paper is confirmed by comparing it with finite element method (FEM) results. These facilitate the characterization of the PM-type linear generator and provide a basis for comparative studies, design optimization, and machine dynamic modeling.