• Journal of Korea Water Resources Association
• /
• v.30 no.6
• /
• pp.761-768
• /
• 1997

A numerical model is developed to analyze the incompressible unsteady flow induced by the pump trip-out in the cooling water discharge culvert of thermal power plants. The numerical models has various features to deal concureently with the overall behavior of complicated unsteady flow due to the presence of cooling water internal system, seal well, air chamber, culvert, manholes, open channel and sea water. A leap-frog finite difference scheme is employed to solve governing equations, and the model is tested for a simple case of two tanks connected with a pipe. A fixed free surface boundary condition used earlier at the downstream end of culvert for large water body is investigated.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.28 no.6
• /
• pp.96-105
• /
• 2001

The purpose of this study is to establish landscape planning, and to find out to administrative system and improvement way on landscape plan in Korea. We have sought for research trend and the concept of landscape planning related to the landscape planning through the investigation of books and documents, and have analyzed the characteristics on the law for landscape plan in United State of America, United Kingdom,, France, Germany, Japan and Korea. As the results of this study are as follows; 1) A state developing local self-governing body as United State of America, United Kingdom and Germany carried out individually landscape plan. Especially, it raises clarity of administration to fix residents participation(Nonprofit Organization : NPO) and secures responsibility. 2) A state of centralized authoritarian rule as France and Japan applies common law to the nationwide but commission's concrete management or conference. 3) And so in Korea and applicable landscape plan was made on the basis of town-planning law and managed with ordinances for landscape. In here the important thing is division of role of central and local government and residents. This study proposes the system of planning and analyzed the related laws for the landscape formation and management. The future research on the character of the local areas, providing many chances with people in the community through publicity activities, and rearing the expert group on this matter should be made in the future.

• BMB Reports
• /
• v.49 no.3
• /
• pp.137-138
• /
• 2016

Satiety cues a feeding animal to cease further ingestion of food, thus protecting it from excessive energy gain. Impaired control of satiety is often associated with feeding-related disorders such as obesity. In our recent study, we reported the identification of a neural pathway that expresses the myoinhibitory peptide (MIP), critical for satiety responses in Drosophila. Targeted silencing of MIP neuron activity strikingly increased the body weight (BW) through elevated food intake. Similarly, genetic disruption of the gene encoding MIP also elevated feeding and BW. Suppressing the MIP pathway behaviorally transformed the satiated flies to feed similar to the starved ones, with augmented sensitivity to food. Conversely, temporal activation of MIP neuron markedly reduced the food intake and BW, and blunted the sensitivity of the starved flies to food as if they have been satiated. Shortly after termination of MIP neuron activation, the reduced BW reverted to the normal level along with a strong feeding rebound. Together our results reveal the switch-like role of the MIP pathway in feeding regulation by controlling satiety.

• Journal of computational fluids engineering
• /
• v.3 no.1
• /
• pp.11-21
• /
• 1998

A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savart integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity now: (ⅰ) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ⅱ) driven only by uniform shear (of the classical type).

• Structural Engineering and Mechanics
• /
• v.63 no.1
• /
• pp.37-46
• /
• 2017

This paper is concerned with the numerical study on the resonance response of a rigid spar-type floating platform in coupled heave and pitch motion. Spar-type floating platforms, widely used for supporting the offshore structures, offer an economic advantage but those exhibit the dynamically high sensitivity to external excitations due to their shape at the same time. Hence, the investigation of their dynamic responses, particularly at resonance, is prerequisite for the design of spar-type floating platforms which secure the dynamic stability. Spar-type floating platform in 2-D surface wave is assumed to be a rigid body having 2-DOFs, and its coupled dynamic equations are analytically derived using the geometric and kinematic relations. The motion-variance of the metacentric height and the moment of inertia of floating platform are taken into consideration, and the hydrodynamic interaction between the wave and platform motions is reflected into the hydrodynamic force and moment and the frequency-dependent added masses. The coupled nonlinear equations governing the heave and pitch motions are solved by the RK4 method, and the frequency responses are obtained by the digital Fourier transform. Through the numerical experiments to the wave frequency, the resonance responses and the coupling in resonance between heave and pitch motions are investigated in time and frequency domains.

• Geomechanics and Engineering
• /
• v.15 no.6
• /
• pp.1161-1171
• /
• 2018

The interaction between particles and fluid was investigated by IB-SEM numerical method which is a combination of combing the spectral/hp element method and the rigid immersed boundary method. The accuracy of this numerical method was verified based on the computed results with the traditional body-fitted mesh in numerical simulation of the flow through the cylinder. Then the governing equations of particles motion and contact in fluid are constructed. The movement of the particles and the interaction between the fluid and the particles are investigated. This method avoided the problem of low computational efficiency and error caused by the re-division of the grid when the solids moved. Finally, the movement simulation of multi particles in the fluid was carried out, which can provide a completely new numerical simulation method.

• Wind and Structures
• /
• v.20 no.3
• /
• pp.423-448
• /
• 2015

In this paper the unsteady fluid-structure interaction (FSI) problems with large structural displacement are solved by partitioned solution approaches in the arbitrary Lagrangian-Eulerian finite element framework. The incompressible Navier-Stokes equations are solved by the characteristic-based split (CBS) scheme. Both a rigid body and a geometrically nonlinear solid are considered as the structural models. The latter is solved by Newton-Raphson procedure. The equation governing the structural motion is advanced by Newmark-${\beta}$ method in time. The dynamic mesh is updated by using moving submesh approach that cooperates with the ortho-semi-torsional spring analogy method. A mass source term (MST) is introduced into the CBS scheme to satisfy geometric conservation law. Three partitioned coupling strategies are developed to take FSI into account, involving the explicit, implicit and semi-implicit schemes. The semi-implicit scheme is a mixture of the explicit and implicit coupling schemes due to the fluid projection splitting. In this scheme MST is renewed for interfacial elements. Fixed-point algorithm with Aitken's ${\Delta}^2$ method is carried out to couple different solvers within the implicit and semi-implicit schemes. Flow-induced vibrations of a bridge deck and a flexible cantilever behind an obstacle are analyzed to test the performance of the proposed methods. The overall numerical results agree well with the existing data, demonstrating the validity and applicability of the present approaches.

• Wind and Structures
• /
• v.12 no.1
• /
• pp.1-19
• /
• 2009

In this paper, the airflow around an ideal thin plate (hereafter referred to as ITP) with various ratios of central slot is simulated by using the finite-difference-method (FDM)-based Arbitrary-Lagrangian-Eulerian descriptions for the rigid oscillating body. The numerical procedure employs the second-order projection scheme to decouple the governing equations, and the multigrid algorithm with three levels to improve the computational efficiency in evaluating of the pressure equation. The present CFD method is validated through comparing the computed flutter derivatives of the ITP without slot to Theodorsen analytical solutions. Then, the unsteady aerodynamics of the ITP with and without central slot is investigated. It is found that even a smaller ratio of central slot of the ITP has notable effects on pressure distributions of the downstream section, and the pressure distributions on the downstream section will further be significantly affected by the slot ratio and the reduced wind speeds. Continuous increase of $A_2^*$ with the increase of central slot may be the key feature of the slotted ITP. Finally, flutter analyses based on the flutter derivatives of the slotted ITP are performed, and moreover, flutter instabilities of a scaled sectional model of a twin-deck bridge with various ratios of deck slot are investigated. The results confirm that the central slot is effective to improve bridge flutter stabilities, and that the flutter critical wind speeds increase with the increase of slot ratio.

• Geomechanics and Engineering
• /
• v.20 no.4
• /
• pp.359-370
• /
• 2020

Prestressed ground anchors are important structural elements in geotechnical engineering. Despite their widespread usage, the design process is often significantly simplified. One of the major drawbacks of commonly used design methods is the assumption that skin friction is mobilized uniformly along an anchor's fixed length, one consequence of which is that a progressive failure phenomenon is neglected. The following paper introduces an alternative design approach - a computer algorithm employing the load-transfer method. The method is modified for the analysis of anchors and combined with a procedure for the derivation of load-transfer functions based on commonly available laboratory tests. The load-transfer function is divided into a pre-failure (hardening) and a post-failure (softening) segment. In this way, an aspect of non-linear stress-strain soil behavior is incorporated into the algorithm. The influence of post-grouting in terms of radial stress update, diameter enlargement, and grout consolidation is included. The axial stiffness of the anchor body is not held constant. Instead, it gradually decreases as a direct consequence of tensile cracks spreading in the grout material. An analysis of the program's operation is performed via a series of parametric studies in which the influence of governing parameters is investigated. Finally, two case studies concerning three investigation anchor load tests are presented.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.26 no.2
• /
• pp.133-142
• /
• 1998

This paper reviews the difference between the selected village groves and seaside groves in Chonbuk-Do province. In Chonbuk-Do province, village groves were principally found in the east mountainous region and seaside groves were found only in the south seaside. The village groves were located in the roadside and village entrance, but seaside groves were located in the front of crop land for the purpose of windbreak. The planting motive of village groves was historical and cultural background, but that of seaside groves was protection of cropland and village from strong wind. The form of village groves was various, but that of seaside groves was linear and rectangular. Both were small scale in comparison with other province. Both were formed on the slopeless land. In ownership, the rate of seaside groes owned by the slf governing body is higher than village groves. Billage groves were almostly owned by village. In vegetatioin structure, both were one class forest composed of only tall tree of upper class. Principal dominent species of seaside groves in upper tree was Pinus thunbergii, but those of village groves were Pinus densiflora, Carpinus tschonoskii, Zelkova serrata etc. Seaside groves were not growing normally in aspect of height and breast diameter of tree in comparison with village groves. The planting density of seaside groves was 3.7 times higher than village groves in Chonbuk-Do province.