• Journal of Ocean Engineering and Technology
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• v.35 no.3
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• pp.229-237
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• 2021

A numerical hydrodynamic performance analysis of the pitch-type multibody wave energy converter (WEC) is carried out based on both linear potential flow theory and computational fluid dynamics (CFD) in the unidirectional wave condition. In the present study, Salter's duck (rotor) is chosen for the analysis. The basic concept of the WEC rotor, which nods when the pressure-induced motions are in phase, is that it converts the kinetic and potential energies of the wave into rotational mechanical energy with the proper power-take-off system. This energy is converted to useful electric energy. The analysis is carried out using three WEC rotors. A multibody analysis using linear potential flow theory is performed using WAMIT (three-dimensional diffraction/radiation potential analysis program), and a CFD analysis is performed by placing three WEC rotors in a numerical wave tank. In particular, the spacing between the three rotors is set to 0.8, 1, and 1.2 times the rotor width, and the hydrodynamic interaction between adjacent rotors is checked. Finally, it is confirmed that the dynamic performance of the rotors slightly changes, but the difference due to the spacing is not noticeable. In addition, the CFD analysis shows a lateral flow phenomenon that cannot be confirmed by linear potential theory, and it is confirmed that the CFD analysis is necessary for the motion analysis of the rotor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1518-1526
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• 2001

In this paper, the mechanism of unsteady potential interaction and wake interaction in one stage axial turbine is numerically investigated at design point in two-dimensional viewpoint. The numerical technique used is the upwind scheme of Van-Leer's Flux Vector Splitting (FVS) and Cubic spline interpolation is applied on zonal interface between stator and rotor. The inviscid analysis is used to embody the influence of potential interaction only and viscous analysis is used to embody the influences of both potential interaction and wake interaction at the same time. The potential-flow disturbance from the stator into a rotor passage and the periodic blockage effect of rotor produce the unsteady pressure on the blade surface in inviscid analysis. After the wake is cut by rotor, two counterrotating votical patterns flanking the wake centerline in the passage are generated. So, these phenomena magnify the unsteady pressure in viscous analysis than that in inviscid analysis. The resulting unsteady forces on the rotor, generated by the combined interaction of the two effects by potential and wake interaction, are discussed.

• Korean Journal of Breeding Science
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• v.40 no.1
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• pp.8-14
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• 2008

A complete diallel cross was performed to determine the inheritance of allelopathic potential and combining ability of six rice germplasm that showed different level of allelopathic potential against barnyardgrass. Parents and F1 of 30 crosses were assessed for allelophatic potential in field condition. Barnyardgrass (Echinochloa crus-galli (L.) Beauv. var. frumentaceae) was used for rice allelopathic potential indicator which was observed in height and shoot dry weight, then suppression percentage were calculated by comparing to barnyardgrass grown in control plot (no rice). It was found that general combining ability showed no significant effect, whereas specific combining ability and reciprocal effect were significant. Variance analysis confirmed that genetic control of allelopathic potential in rice against barnyardgrass was mostly directed by dominance gene effect. The dominant genes were associated with high allelopathic potential and recessive genes were associated with low allelopathic potential. Heritability in broad sense for barnyardgrass dry weight suppression was around 41%; whereas for barnyardgrass height suppression was 51%. However, heritability in narrow sense was very low. The finding suggests that accumulation of genes associated with allelopathic potential would be a strategy to develop promising varieties in reference with the specific combining ability of cross combinations.

• Journal of Korean Society of Rural Planning
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• v.23 no.3
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• pp.21-36
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• 2017

Climate change is intensifying storms and floods around the world. Where nature has been destroyed by development, communities are at risk from these intensified climate patterns. This study was to suggest a methodology for estimating flood vulnerability using Potential Flood Damage(PFD) concept and classify city/county about Potential Flood Damage(PFD) using various typology techniques. To evaluate the PFD at a spatial resolutions of city/county units, the 20 representative evaluation indexing factors were carefully selected for the three categories such as damage target(FDT), damage potential(FDP) and prevention ability(FPA). The three flood vulnerability indices of FDT, FDP and FPA were applied for the 167 cities and counties in Korea for the pattern classification of potential flood damage. Potential Flood Damage(PFD) was classified by using grouping analysis, decision tree analysis, and cluster analysis, and characteristics of each type were analyzed. It is expected that the suggested PFD can be utilized as the useful flood vulnerability index for more rational and practical risk management plans against flood damage.

• Smart Structures and Systems
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• v.8 no.5
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• pp.433-447
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• 2011

The present paper addresses the nonlinear response of a FG square plate with two smart layers as a sensor and actuator under pressure. Geometric nonlinearity was considered in the strain-displacement relation based on the Von-Karman assumption. All the mechanical and electrical properties except Poisson's ratio can vary continuously along the thickness of the plate based on a power function. Electric potential was assumed as a quadratic function along the thickness direction and trigonometric function along the planar coordinate. By evaluating the mechanical and electrical energy, the total energy equation can be minimized with respect to amplitude of displacements and electrical potential. The effect of non homogenous index was investigated on the responses of the system. Obtained results indicate that with increasing the non homogenous index, the displacements and electric potential tend to an asymptotic value. Displacements and electric potential can be presented in terms of planar coordinate system. A linear analysis was employed and then the achieved results are compared with those results that are obtained using the nonlinear analysis. The effect of the geometric nonlinearity is investigated by using the comparison between the linear and nonlinear results. Displacement-load and potential-load curves verified the necessity of a nonlinear analysis rather than a linear analysis. Improvement of the previous results (by the linear analysis) through employing a nonlinear analysis can be presented as novelty of this study.

• 중국학논총
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• no.72
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• pp.25-45
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• 2021

This study aims to select eight books to see if "potential complement" is sufficiently acquired and properly used in Chinese conversation textbooks, explore the reasons and problems of learners' errors through analysis, and briefly suggest textbook compilation and teaching. Twelve criteria were established and analyzed, including the concept and format of "potential complement", layout order, location of objects, three types of forms, distinction from auxiliary verb "能" and distinction between "能+V+結果補語". Some of the results of the study are simply as follows. All eight textbooks focus only on "possibility," missing an important part of "the impact of objective conditions" that the term "potential complement" does not contain. This is certainly enough to cause confusion for learners. A poor understanding of the concept of "potential complement" results in identifying it with the possible auxiliary verb "能", and incorrect mixing because it does not know exactly what the difference is. Most of the textbooks compiled in China place a high importance on "potential complement". This means that Chinese people often use "potential complement" in real life. on the other hand relatively Korean textbooks do not deal with "potential complement" relatively importantly.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.775-784
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• 1997

A unified theory is presented for the shape analysis of curved surface with a single layer structure composed by frame, membrane or shell. The shapes produced by the theory have no shear stress in elements, and the stress states in the whole shape are as uniform as possible under an ordinary load. The theory starts from defining an element potential function expressed by the measurement of the element length or the element area. Therefore, the shape analysis can produce various forms according to the definition of the potential function, and each of those form or the cable net form with the potential function of the second power of element length is simply gotten by the linear analysis. The form in tensile stress is mechanically equal to an isotropic tension form.

• Journal of Korean Society of Rural Planning
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• v.14 no.4
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• pp.109-119
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• 2008

The objectives of this study are to develop a green tourism potential evaluation method with rural amenity and demand of citizen. The new index which was named GPD(green tourism potential degree) is designed to propose the green tourism potential of rural areas using spatial analysis of geographic information system and spatial interaction of gravity model. And in order to evaluate the green tourism potential with supply side and demand side, two indices were defined; One is green tourism demand degree(GDD) which is developed to quantify a demand side potential by the analysis of urban population and urbanization index, and the other is green tourism attraction degree(GAD) which is developed to quantify a supply side potential by the analysis of rural amenity values using AHP algorithm, based on opinion of related experts. The developed method was applied to a part of Kyounggi province, Seoul and Incheon. All the study area's GAD, GDD and GPD were assessed and the proposed green tourism potential evaluation method could be used in developing rural development plans and green tourism policies considering spatial interaction with citizen and green tourism resources.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.2 no.2
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• pp.53-62
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• 1979

A widely accepted indicator of a project's economic potential is the internal rate of return (IRR). The primary objective of feasibility analysis for any project is to measure the economic potential for the project, normally defined as the expected return on capital investment. The analysis should be designed to determine whether a project is technically and economically sound, and under what conditions. Therefore, there are factors other than economic potential that must be taken into account in the reasonable composition of an investment program. These kinds of factors can be given proper consideration in project selection after the economic feasibility of alternative projects has been determined. The primary reason for having to choose among different projects is that capital resources are scare : the investment budget is limited. The case project, casting facilities investment project, treated in this paper were selected for their value in illustrating the methods of feasibility analysis. This case project an actual potential project and is analyzed on the basis of the best available data for the specific conditions for that project.

• Journal of Ocean Engineering and Technology
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• v.21 no.3 s.76
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• pp.16-25
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• 2007

A comparative study on the turbulent flaw simulation and the potential flaw analysis has been performed. A law Mach number preconditioned Navier-Stokes solver, using the multi-block grid method and a panel method based on the velocity potential, have been developed and validated by comparison to the experimental data. The present numerical analysis methods are applied to the ground effect problem around the NACA 4412 airfoil. It has been confirmed that the potential flaw analysis on the ground effect, using the image method, is consistent, to some degree, with the viscous calculations for high Reynolds number flows.