• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.6
• /
• pp.347-355
• /
• 2016

This study presents a Lattice Boltzmann Method (LBM) coupled with a momentum-exchange approach/fictitious domain (MEA/FD) method for the simulation of particle suspensions. The method combines the advantages of the LB and the FD methods by using two unrelated meshes, namely, a Eulerian mesh for the flow domain and a Lagrangian mesh for the solid domain. The rigid body conditions are enforced by the momentum-exchange scheme in which the desired value of velocity is imposed directly in the particle inner domain by introducing a pseudo body force to satisfy the constraint of rigid body motion, which is the key idea of a fictitious domain (FD) method. The LB-MEA/FD method has been validated by simulating two different cases, and the results have been compared with those through other methods. The numerical evidence illustrated the capability and robustness of the present method for simulating particle suspensions.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.6
• /
• pp.18-28
• /
• 2006

Numerical analysis of high Mach number flow over a blunt-body poses many difficulties and various numerical schemes have been suggested to overcome the problems. However, the new schemes were used in the limited fields of applications because of the lack of field experience compared to more than 20 years old numerical schemes and the intricacies of modifying the existing code for the special application. In this study, some tips to overcome the numerical difficulties in solving the 3D high-Mach number flows by using Roe's scheme, the most widely used for the past 25 years and adopted in many commercial codes, were examined without a correction of the algorithm or a modification of the CFD code. The well-known carbuncle phenomena of Riemann solvers could be remedied even for an extremely high Mach number by applying the entropy fixing function and a unphysical solution could be overcome by applying a simply modified initial condition regardless of the entropy fixing and grid configuration.

• Journal of the Society of Naval Architects of Korea
• /
• v.49 no.6
• /
• pp.461-468
• /
• 2012

In this study, a Cartesian-grid method based on finite volume approach is applied to simulate the ship motions in large amplitude waves. Fractional step method is applied for pressure-velocity coupling and TVD limiter is used to interpolate the cell face value for the discretization of convective term. Water, air, and solid phases are identified by using the concept of volume-fraction function for each phase. In order to capture the interface between air and water, the tangent of hyperbola for interface capturing (THINC) scheme is used with weighed line interface calculation (WLIC) method which considers multidimensional information. The volume fraction of solid body embedded in the Cartesian grid system is calculated using a level-set based algorithm, and the body boundary condition is imposed by a volume weighted formula. Numerical simulations for the two-dimensional barge type model and Wigley hull in linear waves have been carried out to validate the newly developed code. To demonstrate the applicability for highly nonlinear wave-body interactions such as green water on the deck, numerical analysis on the large-amplitude motion of S175 containership is conducted and all computational results are compared with experimental data.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.7
• /
• pp.1619-1627
• /
• 2014

Wearable computer systems can use the wireless universal serial bus (WUSB) that refers to USB technology that is merged with WiMedia PHY/MAC technical specifications. In this paper, we focus on an integrated system of the wireless USB over the IEEE 802.15.6 wireless body area networks (WBAN) for wireless wearable computer systems supporting U-health services. And a communication structure that performs the time-synchronization is proposed for WUSB over IEEE 802.15.6 hierarchical protocol. Proposed time-synchronization mechanisms adopt the WBAN Polling Access and combine it with a time-synchronization middleware using time stamps. In our performance evaluations, time-synchronization performances with only WBAN Polling Access scheme are analyzed first. After that, performances combined with the time-synchronization middleware are analyzed to evaluate the effectiveness of proposed time-synchronization structure in WUSB over IEEE 802.15.6.

• Journal of Haehwa Medicine
• /
• v.8 no.1
• /
• pp.711-726
• /
• 1999

Aging in the life form occurs due to a gradual progression of the body growth and degeneration. Morphological and functional changes in the body decreases the adaptation and prevention capacity leading into the decline of a life force. Various studies have been released to examine the anti-aging effects of herbal prescriptions. This experiment has chosen Boganhwan which is used for the deficiency of the liver function and studied the anti-aging factors by examining the biotransformation enzymes. The following results were obtained in this study: 1. Hepatic lipid peroxide activity was significantly suppressed in the experimental group treated with Boganhwan for 2 weeks at the dosage of 350mg/kg, while other dosage groups did not present much changes. 2. Insignificant changes were shown for the cytochrome P-450 level, aminopyrine demethylase, and aniline hydroxylase (AH) activities. Cytochrome P-450 do not appears to be a part of the detoxification scheme. 3. Boganhwan decoction treated group showed most significant increase of superoxide dismutase (SOD), catalase, superoxide, and glutathione activities at the concentration of 350mg/kg and 500mg/kg. 4. Glutathione S-transferase and glutathione made most significant increase at the decoction concentration of 350mg/kg and 500mg/kg compared to the control group. 5. Hepatic glutathione concentration, protein bound-SH, and nonprotein bound-SH made most significant increase at the decoction concentration of 350mg/kg and 500mg/kg compared to the control group. From the above results, Boganhwan decoction played an important role in eliminating foreign substances in the body excluding cytochrome P-450 enzyme system. Thus, Boganhwan decoction can provide substantial aid in preventing and treating senile related illnesses.

• Journal of the Society of Naval Architects of Korea
• /
• v.28 no.1
• /
• pp.38-52
• /
• 1991

In this paper, a semi-Lagrangian method is used to solve the nonlinear hydrodynamics of a three-dimensional body beneath the free surface in the time domain. The boundary value problem is solved by using the boundary integral method. The geometries of the body and the free surface are represented by the curved panels. The surfaces are discretized into the small surface elements using a bi-cubic B-spline algorithm. The boundary values of $\phi$ and $\frac{\partial{\phi}}{\partial{n}}$ are assumed to be bilinear on the subdivided surface. The singular part proportional to $\frac{1}{R}$ are subtracted off and are integrated analytically in the calculation of the induced potential by singularities. The far field flow away from the body is represented by a dipole at the origin of the coordinate system. The Runge-Kutta 4-th order algorithm is employed in the time stepping scheme. The three-dimensional form of the integral equation and the boundary conditions for the time derivative of the potential Is derived. By using these formulas, the free surface shape and the equations of motion are calculated simultaneously. The free surface shape and fille forces acting on a body oscillating sinusoidally with large amplitude are calculated and compared with published results. Nonlinear effects on a body near the free surface are investigated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.05a
• /
• pp.229-232
• /
• 2008

A Neural network classification of human activity data is presented. The data acquisition system involves a tri-axial accelerometer in wireless sensor network environment. The wireless ad-hoc system has the advantage of small size, convenience for wearability and cost effectiveness. The system can further improve the range of user mobility with the inclusion of ad-hoc environment. The classification is based on the frequencies of the involved activities. The most significant Fast Fourier coefficients, of the acceleration of the body movement, are used for classification of the daily activities like, Rest walk and Run. A supervised learning approach is used. The work presents classification accuracy with the available fast batch training algorithms i.e. Levenberg-Marquardt and Resilient back propagation scheme is used for training and calculation of accuracy.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.124-127
• /
• 1997

In this paper, we propose a method of cooperative control based on immune system in distributed autonomous robotic system(DARS). Immune system is living body's self-protection and self-maintenance system. Thus these features can be applied to decision making of optimal swarm behavior in dynamically changing environment. For the purpose of applying immune system to DARS, a robot is regarded as a B lymphocyte(B cell), each environmental condition as an antigen, and a behavior strategy as an antibody respectively. The executing process of proposed method is as follows. When the environmental condition changes, a robot selects an appropriate behavior strategy. And its behavior strategy is simulated and suppressed by other robot using communication. Finally much simulated strategy is adopted as a swarm behavior strategy. This control scheme is based on clonal selection and idiotopic network hypothesis. And it is used for decision making of optimal swarm strategy.

• Journal of Ocean Engineering and Technology
• /
• v.31 no.3
• /
• pp.183-188
• /
• 2017

This paper provides numerical results for the estimation of the efficiency of KRISO energy saving devices in the design stage. A finite volume method is used to solve Reynolds averaged Navier-Stokes (RANS) equations, where the SST k-$\omega$ model is selected for turbulence closure. The propeller rotating motion is determined using a rigid body motion (RBM) scheme, which is called a sliding mesh technique. The numerical analysis focuses on predicting the power reduction by the designed KRISO devices (K-DUCT) under a self-propulsion condition. The present numerical results show good agreement with the available experimental data. Finally, it is concluded that CFD can be a useful method, along with model tests, for assessing the performance of energy saving devices for propulsion efficiency improvement.

• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.2
• /
• pp.165-176
• /
• 2015

A numerical analysis was conducted to investigate the inlet buzz and combustion oscillation in an axisymmetric ramjet engine with wedge-type flame holders. The physical model of concern includes the entire engine flow path, extending from the leading edge of the inlet center-body through the exhaust nozzle. The theoretical formulation is based on the Farve-averaged conservation equations of mass, momentum, energy, and species concentration, and accommodates finite-rate chemical kinetics and variable thermo-physical properties. Turbulence closure is achieved using a combined scheme comprising of a low-Reynolds number k-${\varepsilon}$ two-equation model and Sarkar's compressible turbulence model. Detailed flow phenomena such as inlet flow aerodynamics, flame evolution, and acoustic excitation as well as their interactions, are investigated. Mechanisms responsible for driving the inlet buzz are identified and quantified for the engine operating at subcritical conditions.