• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.37-43
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• 2009

In the present study, the flow characteristics of a peristaltic micropump were numerically analyzed. A channel wall motion of the micropump was simulated using a moving mesh technique. A sine wave pattern was assumed to simulate the peristaltic motion of wall. The present numerical method was verified by comparing the result with the available numerical data. The effects of the operating conditions which include the maximum displacement and frequency of the channel wall and the phase difference between top and bottom walls on the flow characteristics were investigated. From these numerical results, the pressure-flowrate characteristic curve was obtained for various maximum displacement and frequencies.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.45-50
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• 2014

In the previous paper, we have reported on the development of foaming sponge seat with the auxiliary spring member and suggested new possibility of the special seat with the auxiliary plastic member for movie theater chair. In this study, we have examined the major design parameters needed in the development of a foaming sponge seat in which the mesh type plastic member are inserted to improve the vibration transfer effect of a chair seat. Through analyzing several prototypes by applying experimentation as well as the experimental modal analysis method, it was confirmed that the effect of vibration transfer can be improved through the use of a mesh type plastic member and applied to the design of practical chair seat.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.207-214
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• 2019

A large-capacity wireless power system is a technology that transmits electric power of kW or more in a noncontact type. Electric cars, electric buses, and electric railways. In order to increase the power transmission efficiency, a resonance method using a frequency of kHz is applied and the efficiency is 80 ~ 90%. In this case, the loss is 10 ~ 20% other than efficiency, and corresponds to several hundreds of W to several kW in kW class wireless power transmission. 35 kW wireless feed system environment, and induced current in the nearby conductive part was measured. As a result of analysis, it was confirmed that induction phenomenon is higher as the loop configuration of the conductive part per area is dense. The increase of the induced current in the mesh loop is characterized by the density of the nearby conductive part having a permeability per unit area. The concentration of the magnetic field by the permeability is increased and the induction phenomenon causing the induction current is increased. It was confirmed that induction phenomenon increases by about 2.7 times when 9 times dense structure is formed.

• Journal of IKEEE
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• v.23 no.3
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• pp.793-799
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• 2019

In this study, the diffusion process and the thermal energy distribution gradient of the sensor were confirmed by using the finite element analysis program (COMSOL) of the mesh method to analyze the thermal diffusion in the wearable fabric (Nylon) + MWCNT gas sensor. To analyze the diffusion process of thermal energy, the structure of the gas sensor was modeled in a two dimension plane. The proposed modeling was presented with the characteristic value for the component of the sensor, and the gas sensor designed using the mesh finite element method (FEM) was proposed and analyzed by suggesting the one-way partial differential equation in the governing equation to know the degree of thermal energy diffusion and the thermal energy gradient. In addition, the temperature gradient 10[K/mm] of the anode-cathode electrode layer and the gas detection unit was investigated by suggesting the heat velocity transfer equation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2004-2010
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• 2009

The characteristic of the backbond for distribution service in WMNs(Wireless Mesh Networks) is that WMNs has multiple links connected to mesh points and dynamic routing protocol such as AODV to establish routing paths. When the terminal is communicating with the service through new AP, mobile nodes can resume communication by setting only the link between new AP and mobile node in the case of existing WLANs, but WMNs needs path establishment process in multihop networks. Our goal in this paper is to support the seamless communication service by eliminating path establishment delay in WMNs. We present the method that eliminates the handover latency by predicting the location of handover using GPS information and making the paths to their destination in advance. We implement mesh nodes using embedded board that contains proposed handover method and evaluate performance of handover latency. Our experiment shows that handover delay time is decreased from 2.47 to 0.05 seconds and data loss rate is decreased from 20~35% in the existing method to 0~10% level.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.11 s.242
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• pp.1455-1462
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• 2005

In this paper, we intend to introduce a nonlinear finite element method based on the fully nonlinear potential flow theory in order to simulate the large amplitude sloshing flow in two-dimensional baffled tank subject to horizontally forced excitation. The free surface is tracked by a direct time differentiation scheme with the four-step predictor-corrector time integration method. The flow velocity is accurately recovered from the velocity potential by second-order least square method. In order to maintain the finite element mesh regularity and total mass, the semi-Lagrangian surface tracking method with area conservation is applied. According to the numerical formulae, we perform the parametric experiments by varying the installation height and the opening width of baffles, in order to examine the effects of baffle on the nonlinear liquid sloshing. From the numerical results, the hydrodynamic characteristics of the large amplitude sloshing are investigated.

• The KSFM Journal of Fluid Machinery
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• v.10 no.1 s.40
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• pp.34-40
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• 2007

In this study, the characteristic of a vane pump of automotive power steering system is numerically analyzed. The vane pump changes the energy level of operation fluid by converting mechanical input power to hydraulic output. To simulate this mechanism, moving mesh technique is adopted. As a result, the flow rate and pressure are obtained by numerical analysis. The flow rate agrees well with the experimental data. Moreover, the variation and oscillation of the pressure around the rotating vane are observed. As a result of flow characteristics, The difference of pressure between both side of vane tip causes the back flow into the rotor. As the rotational velocity increases, the flow rate at the outlet and the pressure in the vane tip rises with higher amplitude of oscillation. In order to reducing the oscillation, the design of devices for decreasing the cross-area of the outlet part and returning the flow from the outlet to the inlet is required.

• Journal of Power System Engineering
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• v.17 no.6
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• pp.40-46
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• 2013

This paper describes the suggestion of the special seat with the auxiliary plastic member for movie theater chair. In the previous paper, we have reported on the development of foaming sponge seat with the auxiliary spring member. And we have confirmed that it was more effective on vibration transfer than the chair seat of foaming sponge only. In this study, we have examined the major design parameters needed in the development of a foaming sponge seat in which the mesh type plastic member are inserted to improve the vibration transfer effect of a chair seat. By applying experimentation to the prototype as well as the experimental modal analysis method, we made sure that the effect of the vibration transfer could be improved through the use of a mesh type plastic member as similar as the auxiliary spring member.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.10
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• pp.4042-4059
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• 2020

The development of new multimedia techniques such as 3D printing is increasingly attracting the public's attention towards 3D objects. An optimized robust and imperceptible watermarking method based on Ant Colony Optimization (ACO) and Weber Law is proposed for 3D polygonal models. The proposed approach partitions the host model into smaller sub meshes and generates a secret watermark from the sub meshes using Weber Law. ACO based optimized strength factor is identified for embedding the watermark. The secret watermark is embedded and extracted on the wavelet domain. The proposed scheme is robust against geometric and photometric attacks that overcomes the synchronization problem and authenticates the secret watermark from the distorted models. The primary characteristic of the proposed system is the flexibility achieved in data embedding capacity due to the optimized strength factor. Extensive simulation results shows enhanced performance of the recommended framework and robustness towards the most common attacks like geometric transformations, noise, cropping, mesh smoothening, and the combination of such attacks.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.895-906
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• 2014

A fundamental study of the dynamically penetrating anchor (DPA - colloquially known as torpedo anchor) embedded into deep seabed was conducted using measurement data and numerical approaches. Numerical simulation of such a structure penetration was often suffered by severe mesh distortion arising from very large soil deformation, complex contact condition and nonlinear soil behavior. In recent years, a Coupled Eulerian-Lagrangian method (CEL) has been used to solve geomechanical boundary value problems involving large deformations. In this study, 3D finite element analyses using the CEL formulation are carried out to simulate the construction process of dynamic anchors. Through comparisons with results of field measurements, the CEL method in the present study is in good agreement with the general trend observed by in-situ measurements and thus, predicts a realistic large deformation movement for the dynamic anchors by free-fall dropping, which the conventional FE method cannot. Additionally, the appropriate parametric studies needed for verifying the characteristic of dynamic anchor are also discussed.