• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.10a
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• pp.153-160
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• 1995

Mixed finite element formulations for incompressible materials show pressure oscillations or pressure modes in four-node quadrilateral elements. The criterion for the stability in the pressure solution is the so-called Babufka-Brezzi stability condition, and the four-node elements based on mixed variational principles do not appear to satisfy this condition. In this study, a pressure continuity residual based on the pressure discontinuity at element edges is used to study the stabilization of pressure solutions in bilinear displacement-constant pressure four-node quadrilateral elements. It is shown that the pressure solutions, although stable, exhibit sensitivity to the stabilization parameters.

• Structural Engineering and Mechanics
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• v.6 no.6
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• pp.711-725
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• 1998

Mixed finite element formulations for incompressible materials show pressure oscillations or pressure modes in four-node quadrilateral elements. The criterion for the stability in the pressure solution is the so-called Babu$\check{s}$ka-Brezzi stability condition, and the four-node elements based on mixed variational principles do not appear to satisfy this condition. In this study, a pressure continuity residual based on the pressure discontinuity at element edges proposed by Hughes and Franca is used to study the stabilization of pressure solutions in bilinear displacement-constant pressure four-node quadrilateral elements. Also, a solid mechanics problem is presented by which the stability of mixed elements can be studied. It is shown that the pressure solutions, although stable, are shown to exhibit sensitivity to the stabilization parameters.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.197-206
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• 2006

The leakage in the water distribution system means both the loss of money and water resource. To minimize the leakage, we introduced the pressure control method using the pressure reducing valve and pump schedule. For the pressure control, the total leakage is needed to divide into each node. In this study, EPANET 2.0 was used to simulate the water networks in two selected blocks after the total leakage was distributed with each node by four ways. The leakage was allocated into each node as water measured by meter, water pressure, water faucets and Lpcd and simulated by EPANET 2.0. Regardless of the leakage distribution ways, there was no significant difference between the measured water and the estimated water pressure. Thus, the leakage distribution way using water pressures estimated by simulation could be recommended. The scenarios controlling the pressure reducing valve and pump were made in two blocks(A and B). $86,713m^3/year$ leakage in the A block and $11,442m^3/year$ in the B block could be reduced as controlling the pressure reducing valve and pump schedule. It was shown that the fifty million won a year can be saved in the A block and 6.8 million won in the B block.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.195-202
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• 1999

In this Paper, a so-called volume-control method for nonlinear failure analysis of reinforced concrete cylindrical structures is proposed. The pressure node which defines uniform change of pressure on finite element is added into layered shell element utilizing in-plane constitutive models of reinforced concrete and layered formulation. With the pressure node formulation, one can control the change in volume enclosed by the cylindrical structures and determine the required change in pressure. An algorith of volume-control method is employed and failure analyses for RC cylindrical structures are carried out using proposed method.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.11
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• pp.1031-1040
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• 2014

In this paper, a new condition diagnosis algorithm for the lens injection molding process using various features extracted from cavity pressure, nozzle pressure and screw position signals is developed with the aid of probability neural network (PNN) method. A new feature extraction method is developed for identifying five (5), seven (7) and two (2) critical features from cavity pressure, nozzle pressure and screw position signals, respectively. The node energies extracted from cavity and nozzle pressure signals are also considered based on wavelet packet decomposition (WPD). The PNN method is introduced to build the condition diagnosis model by considering the extracted features and node energies. A series of the lens injection molding experiments are conducted to validate the model, and it is demonstrated that the proposed condition diagnosis model is useful with high diagnosis accuracy.

• Computational Structural Engineering
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• v.8 no.4
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• pp.189-198
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• 1995

The conventional finite element formulations for incompressible materials show pressure oscillations or pressure modes in four-node quadrilateral elements of commonly used displacement and pressure interpolations. The criterion for the stability in the pressure solution is the so-called Babugka-Brezzi stability condition, and the above elements do not satisfy this condition. In this study, a pressure continuity residual based on the pressure discontinuity at element interfaces is used to study the stabilization of pressure solutions in bilinear displacement-constant pressure four-node quadrilateral elements. This pressure residual is implemented in Q1P0 element derived from the conventional incompressible elasticity. The pressure solutions can be stable with the pressure residual though they exhibit sensitivity to the stabilization parameters. Parametric study for the solution stabilization is also discussed.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2951-2954
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• 2007

Tumor hemodynamics in vascular state is numerically simulated using pressure node solution. The tumor angiogenesis pattern in our previous study is used for the geometry of vessel networks. For tumor angiogenesis, the equation that governed angiogenesis comprises a tumor angiogenesis factor (TAF) conservation equation in time and space, which is solved numerically using the Galerkin finite element method. A stochastic process model is used to simulate vessel formation and vessel. In this study, we use a two-dimensional model with planar vessel structure. Hemodynamics in vessel is assumed as incompressible steady flow with Newtonian fluid properties. In parent vessel, arterial pressure is assigned as a boundary condition whereas a constant terminal pressure is specified in tumor inside. Kirchhoff's law is applied to each pressure node to simulate the pressure distribution in vessel networks. Transient pressure distribution along with angiogenesis pattern is presented to investigate the effect of tumor growth in tumor hemodynamics.

• Journal of the Korea Society of Computer and Information
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• v.11 no.6 s.44
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• pp.143-150
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• 2006

In this paper, we have implemented a ubiquitous healthcare system that can measure and check the blood pressure of human in anytime and anywhere. The implemented prototype are composed of blood pressure measurement terminal, data gathering base node, and medial information server. The implemented node constructs a sensor network using the Zigbee protocol and is ported the TinyOS. The data gathering base node is linux-based node that can transfer a sensed medial data through wireless LAN. And, the medical information server stores the processed medical data and can promptly notify the urgent status to the connected medical team. Through experiment, we confirmed the possibility of ubiquitous healthcare system based on sensor network using the Zigbee.

• Journal of IKEEE
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• v.22 no.3
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• pp.570-577
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• 2018

With the increasing number of network nodes, traditional client/server node selection mechanisms are under tremendous pressure. In order to select efficient cooperative nodes in a highly dynamic P2P network topology, this article uses greedy algorithm to translate the overall optimization into multiple local optimal problems, and to quickly select service nodes. Therefore, the service node with the largest comprehensive capacity is selected to reduce the transmission delay and improve the throughput of the service node. The final simulation results show that the node selection strategy based on greedy algorithm can effectively improve the overall performance of P2P streaming media system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.359-362
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• 2009

Damping characteristics of pressure oscillation induced by an orifice in fluid feeding line for are investigated numerically and experimentally. Assuming small pressure oscillation, acoustic damping effect of orifice is confirmed experimentally, and with the mean flow, damping characteristics of an orifice are investigated numerically. When an orifice is installed at the node of pressure oscillation corresponding to the anti-node of velocity oscillation, suppression of pressure oscillation is maximized and with the mean flow, the resonant frequency is decreased. And, it is found that the optimal position of an orifice for damping shouled be changed.