• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.22-31
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• 1996

An efficient calculation method of pressure acting on a bluff body is developed. The method is applied to assess the containment capability of an oil fence, considering skirt deformation in current. The pressure on the frontal side of the oil fence is determined by analyzing the potential flow, substituting the wake region as a rigid body which has its boundary at the closed separation streamlines. The pressure at the downstream side of the fence, the so called base pressure, is obtained from the existing experimental results. To verify the calculation method, pressure drag of some bluff bodies in an infinite-fluid medium is calculated, which shows good agreement with the experimental results. The deformed shape of the oil fence is obtained by solving, iteratively, the coupled equations governing the flow field and the deformation of the oil fence, respectively. The deformed shape and the decrease of draft of oil fences with different ballast mass in various current conditions are investigated.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.60-68
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• 1991

The updated Lagrangian Finite Element Method is introduced to analyse rigid body-fluid impact problem which is characterized by incompressible Navier-Stokes equations and impact-contact conditions between free surface and rigid body. For the convenience of numerical computation, velocity fields are splinted into vicous and pressure parts, and then the governing equations and boundary conditions are decomposed in accordance with the decomposition. However, Viscous stresses acting an the solid boundaries are neglected on the assumption that very small velocity gradients may occur during extremely small time interval of the impact. Four coded quadrilateral elements are used to discretize the space domain and the fully explicit time-marching algorithm is employed with a reasonably small time step. At the beginning of each time step, contact velocity of the rigid body is computed from the momentum balance between the body and the fluid. The velocity field is then computed to satisfy the discretized equations of motions and incompressibility and contact constraints as well as an exact free surface boundary condition. At the end of each time step, the fluid domain is updated from the velocity field. In the present time stepping numerical analysis, behaviour of the free surface near the body can be observed without any difficulty which is very important in the water impact problem. The applicability of the algorithm is illustrated by a wedge type falling body problem. The numerical solutions for time-varying pressure distributions and impact loadings acting ion the surface are obtained.

• Journal of Sasang Constitutional Medicine
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• v.15 no.2
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• pp.38-57
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• 2003

Objective: The purpose of this study is to discourse upon that the construction of Sasang Constitutional Medicine has a significant property of Oriental Medicine by explaining the disparity of the viscera and bowels of four constitutions through the special quality of ying-qi and wei-qi circulating in human body on the basis of the channel-qi theory of ${\ulcorner}Huangdi$ $Neijing{\lrcorner}$ Conclusion: 1. Primordial-qi is the congenital essence inherited from the parents and pectoral-qi, ying-qi and wei-qi is the acquired essence derived from the food and air that human eat and breathe. 2. Ying-qi and wei-qi circulates in the meridian system by the strength and pushing of pectoral-qi under the influence of primordial-qi 3. Ying-qi, by the pushing function of pectoral-qi, determines large lung-small liver and small lung-large liver according to the innate quantity of qi and blood. 4. Wei-qi, by the pushing function of pectoral-qi, determines large spleen-small kidney and small spleen-large kidney according to the innate quantity of qi and blood. 5. The heart in the theory of the meridian system's fetus-nourishing and Sasang Constitutional Medicine is involved in the formation of viscera and bowels as governing human body and seven emotions. 6. It is considered that Taiyang person and Taiyin person have the constitution influenced by ying-qi. 7. It is considered that Shaoyang person and Shaoyin person have the constitution influenced by wei-qi. The inquiry into several literatures on the basis of the channel-qi theory of ${\ulcorner}Huangdi$ $Neijing{\lrcorner}$ leads us to the idea that the construction of Sasang Constitotional Medicine is another well-implied representation of the property of the meridian doctrine in the existing Oriental Medicine. And it is considered that the more continual studies of literatures and Sasang Constitutional Medicine Acupuncture are necessary henceforth.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.253-258
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• 2012

The Cartesian grid system has generally been used in casting simulations, even though it does not represent sloped and curved surfaces very well. These distorted boundaries cause several problems, and special treatment is necessary to resolve them. A cut cell method on a Cartesian grid has been developed for the simulation of threedimensional mold filling. Cut cells at a cast/mold interface are generated on Cartesian grids, and the governing equations are computed using the volume and areas of the cast at the cut cells. In this paper, we propose a new method based on the partial cell treatment (PCT) that can consider the cutting cells which are cut by the cast and the mold. This method provides a better representation of the surface geometry, and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian gird system. Various test examples for several casting process are computed and validated.

• Earthquakes and Structures
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• v.14 no.4
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• pp.313-322
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• 2018

The present study is dedicated to investigate the SH body-as well as Love-waves propagation effects in porous media with uncertain porosity and permeability. A unified formulation of the governing equations for one-dimensional (1-D) wave propagation in anisotropic porous layered media is presented deterministically. The uncertainties around the above two cited parameters are taken into account by random fields with the help of Monte Carlo Simulations (MCS). Random samples of the porosity and the permeability are generated according to the normal and lognormal distribution functions, respectively, with a mean value and a coefficient of variation for each one of the two parameters. After performing several thousands of samples, the mathematical expectation (mean) of the solution of the wave propagation equations in terms of amplification functions for SH waves and in terms of dispersion equation for Love-waves are obtained. The limits of the Love wave velocity in a porous soil layer overlaying a homogeneous half-space are obtained where it is found that random variations of porosity change the zeros of the wave equation. Also, the increase of uncertainties in the porosity (high coefficient of variation) decreases the mean amplification function amplitudes and shifts the fundamental frequencies. However, no effects are observed on both Love wave dispersion and amplification function for random variations of permeability. Lastly, the present approach is applied to a case study in the Adapazari town basin so that to estimate ground motion accelerations lacked in the fast-growing during the main shock of the damaging 1999 Kocaeli earthquake.

• Toxicological Research
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• v.28 no.3
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• pp.143-149
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• 2012

To prepare measures for practical policy utilization and the control of heavy metals, hazard control related institutions by country, present states of control by country, and present states of control by heavy metals were examined. Hazard control cases by heavy metals in various countries were compared and analyzed. In certain countries (e.g., the U.S., the U.K., and Japan), hazardous substances found in foods (e.g., arsenic, lead, cadmium, and mercury) are controlled. In addition, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) recommends calculating the provisional tolerable weekly intake (PTWI) of individual heavy metals instead of the acceptable daily intake (ADI) to compare their pollution levels considering their toxicity accumulated in the human body. In Korea, exposure assessments have been conducted, and in other countries, hazardous substances are controlled by various governing bodies. As such, in Korea and other countries, diverse food heavy metal monitoring and human body exposure assessments are conducted, and reducing measures are prepared accordingly. To reduce the danger of hazardous substances, many countries provide leaflets and guidelines, develop hazardous heavy metal intake recommendations, and take necessary actions. Hazard control case analyses can assist in securing consumer safety by establishing systematic and reliable hazard control methods.

• The KIPS Transactions:PartA
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• v.16A no.4
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• pp.255-262
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• 2009

We present an autonomous entertainment dolphin robot system based on ubiquitous sensor networks(USN). Generally, It is impossible to apply to USN and GPS in underwater bio-mimetic robots. But An Entertainment dolphin robot which presented in this paper operates on the water not underwater. Navigation of the underwater robot in a given area is based on GPS data and the acquired position information from deployed USN motes with emphasis on user interaction. Body structures, sensors and actuators, governing microcontroller boards, and swimming and interaction features are described for a typical entertainment dolphin robot. Actions of mouth-opening, tail splash or water blow through a spout hole are typical responses of interaction when touch sensors on the body detect users' demand. Dolphin robots should turn towards people who demand to interact with them, while swimming autonomously. The functions that are relevant to human-robot interaction as well as robot movement such as path control, obstacle detection and avoidance are managed by microcontrollers on the robot for autonomy. Distance errors are calibrated periodically by the known position data of the deployed USN motes.

• Structural Engineering and Mechanics
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• v.80 no.6
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• pp.749-765
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• 2021

Suspension bridges bear large eccentric live loads in rush hours when most vehicles travel in one direction on the left or right side of the bridge. With the increasing number and weight of vehicles and the girder widening, the eccentric live load effect on the bridge behavior, including bending and distortion of the main girder, gets more pronounced, even jeopardizing bridge safety. This study proposes an analytical algorithm based on multi-catenary theory for predicting the suspension bridge responses to eccentric live load via the nonlinear generalized reduced gradient method. A set of governing equations is derived to solve the following unknown values: the girder rigid-body displacement in the longitudinal direction; the horizontal projection lengths of main cable's segments; the parameters of catenary equations and horizontal forces of the side span cable segments and the leftmost segments of middle span cables; the suspender tensions and the bearing reactions. Then girder's responses, including rigid-body displacement in the longitudinal direction, deflections, and torsion angles; suspenders' responses, including the suspender tensions and the hanging point displacements; main cables' responses, including the horizontal forces of each segment; and the longitudinal displacement of the pylons' tower top under eccentric load can be calculated. The response of an exemplar suspension bridge with three spans of 168, 548, and 168 m is calculated by the proposed analytical method and the finite element method in two eccentric live load cases, and their results prove the former's feasibility. The nonuniform distribution of the live load in the lateral direction is shown to impose a greater threat to suspension bridge safety than that in the longitudinal direction, while some other specific features revealed by the proposed method are discussed in detail.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.237-245
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• 2008

We developed a computational method on coupled dynamics of tracked vehicle on seafloor and long flexible pipe. The tracked vehicle is modeled as rigid-body vehicle, and the linked flexible pipe is discretized according to a lumped-parameter model. The equations of motion of the rigid-body vehicle on the soft seafloor are combined with the governing equations of flexible pipe dynamics. Four Euler parameters method is used to express the orientations of the vehicle and the flexible pipe. In order to solve the nonlinear coupled dynamics of vehicle and flexible pipe an incremental-iterative formulation is implemented. For the time-domain integration $Newmark-\beta$ method is adopted. The total Jacobean matrix has been derived based on the incremental-iterative formulation. The interactions between the dynamics of flexible pipe and the mobility of the tracked vehicle on soft seafloor are investigated through numerical simulations in time domain.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.222-228
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• 2004

The effects of rotation on the unsteady laminar flow past a circular cylinder is numerically investigated in the present study. We obtained the numerical solutions for unsteady two-dimensional governing equation for the flow using two different numerical schemes. One is an accurate spectral method and another is finite volume method. Above all, the flow around a stationary circular cylinder is investigated to understand the basic phenomenon of flow separation, bluff body wake. Also, the validation of our own codes, expecially based on FVM, is carried out by the comparison of results obtained from our simulations using two different schemes and previous numerical and experimental studies. By the effect of rotation, the mean lift increases and drag deceases, which well represent the previous study.