• Journal of computational fluids engineering
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• v.20 no.3
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• pp.79-86
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• 2015

A blood pump is an important part of a cardiac assist device. Since the shear rate in blood is known to be a primary factor on hemolysis generation, it has been very important to evaluate hemolysis inside blood pumps for understanding performance and reliability of cardiac assist devices. In this study, hemolysis generation inside blood pumps is analyzed using CFD with power-law based models for the blood damage index(BDI), in order to overcome difficulties in measuring hemolysis by experiment. The BDI values in blood pumps can be evaluated using Lagrangian or Eulerian approaches. In this study, several Lagrangian and Eulerian approaches are compared to estimate the efficiency of the numerical methods in a practice sense. It is found that the Eulerian approaches are advantageous in terms of the efficiency and robustness. Two different Eulerian approaches are used to evaluate the BDI values of a few commercial blood pumps. For the conditions of extracorporeal membrane oxygenator(ECMO) and ventricular assist device(VAD), local generation of hemolysis is analyzed using divided regions of blood pumps, in order to investigate the effects of the pump geometry.

• Journal of Computational Design and Engineering
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• v.3 no.1
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• pp.53-62
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• 2016

The current trends of product customization and repair of high value parts with individual defects demand automation and a high degree of flexibility of the involved manufacturing process chains. To determine the corresponding requirements this paper gives an overview of manufacturing process chains by distinguishing between horizontal and vertical process chains. The established way of modeling and programming processes with CAx systems and existing approaches is shown. Furthermore, the different types of possible adaptions of a manufacturing process chain are shown and considered as a cascaded control loop. Following this it is discussed which key requirements of repair process chains are unresolved by existing approaches. To overcome the deficits this paper introduces repair features which comprise the idea of geometric features and defines analytical auxiliary geometries based on the measurement input data. This meets challenges normally caused by working directly on reconstructed geometries in the form of triangulated surfaces which are prone to artifacts. Embedded into function blocks, this allows the use of traditional approaches for manufacturing process chains to be applied to adaptive repair process chains.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2627-2631
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• 2003

With the development of RAIM techniques for single failure, there has been increasing interest in the multiple failure problem. There have been many approaches to tackle the problem from various points of view. This paper approaches to two failure problem with total least squares (TLS) technique, which has rarely been addressed because TLS requires a great number of computations. In this paper, the special form of the observation matrix H, that is, one column is exactly known, is exploited so as to develop an algorithm in a sequential form, which reduces computational burden. The algorithm makes us enjoy the advantages of TLS without much computational burden. The proposed algorithm is verified through a numerical simulation.

• Journal of the Korea Society of Computer and Information
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• v.22 no.9
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• pp.17-24
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• 2017

Core citation recognition is to identify influential ones among the prior articles that a scholarly article cite. Previous approaches have employed citing-text occurrence information, textual similarities between citing and cited article, etc. This study proposes a term-based approach to core citation recognition, which exploits the importance of individual terms appearing in in-text citation to calculate influence-strength for each cited article. Term importance is computed using various frequency information such as term frequency(tf) in in-text citation, tf in the citing article, inverse sentence frequency in the citing article, inverse document frequency in a collection of articles. Experiments using a previous test set consisting of computational linguistics articles show that the term-based approach performs comparably with the previous approaches. The proposed technique could be easily extended by employing other term units such as n-grams and phrases, or by using new term-importance formulae.

• Journal of computational fluids engineering
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• v.11 no.4 s.35
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• pp.81-89
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• 2006

Two dimensional turbulent flow simulations on the low Mach number - high Reynolds number flow about the NACA 4412 airfoil are carried out as the airfoil approaches a ground. It has turned out that angle of attack between 2 and 8 degrees is recommended for the airfoil to utilize the benefit of ground effect. For the large angle of attack, the increment of lift due to the ground effect is faded away and negative aerodynamic effect such as destabilizing aspect in static longitudinal stability occurs and the separation point moves to forward as the airfoil approaches a ground.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.510-513
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• 2008

The traditional computational fluid or structure dynamics analysis approaches have contributed to solve many delicate engineering problems. But for the most of recent engineering problems which are influenced by fluid-structure interaction effect strongly, traditional individual approaches have limited analysis abilities for the exact simulation. Owing to above-mentioned reason, nowadays fluid-structure interaction analysis has become a matter of concern and interest. FSI analysis require several unprecedented techniques for the combining individual analysis tool into integrated analysis tool. The Arbitrary Lagrangian-Eulerian(ALE, in short) method is the new description of continum motion,which combines the advantages of the classical kinematical descriptions, i.e. Lagrangian and Eulerian description, while minimizing their respective drawbacks. In this paper, the ALE description is adapted to simulate fluid-structure interaction problems. An automatic re-mesh algorithm and a fluid-structure coupling process are included to analyze the interaction and moving motion during the 2-D axisymmetric solid rocket interior FSI phenomena simulation.

• Bioinformatics and Biosystems
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• v.2 no.1
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• pp.12-16
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• 2007

DNA repair means a collection of processes that a cell identifies and corrects damage to genome sequence. The DNA repair processes are important because a genome would not be able to maintain its essential cellular functions without the processes. In this research, we make some gene regulatory networks of DNA repair in S. cerevisiae to know how each gene interacts with others. Two approaches are adapted to make the networks; Bayesian Network and ARACNE. After construction of gene regulatory networks based on the two approaches, the two networks are compared to each other to predict which genes have important roles in the DNA repair processes by finding conserved interactions and looking for hubs. In addition, each interaction between genes in the networks is validated with interaction information in S. cerevisiae genome database to support the meaning of predicted interactions in the networks.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.101-108
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• 2000

An optimum design algorithm using efficient reanalysis is proposed for reliability-based optimization problems formulated as the minimization of initial cost and expected failure cost with reliability constraints. The reliability-based optimization is high cost to evaluate objective function and constraints needed reliability analysis. Therefore the sensitivity analysis of reliability index for approximated reanalysis is necessary. In this paper, three solution approaches are suggested and tested. The approaches include : (1) sensitivity analysis using finite difference; (2) sensitivity analysis using automatic differentiation (AD); and (3) sensitivity analysis with respect to intermediate variables using AD. Numerical example is optimized to show the reliability and effectiveness of the new algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.36.5-36
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• 2001

Localization is one of the key problems in the navigation of autonomous mobile robots. The probabilistic Markov localization approaches offer a good mathematical framework to deal with the uncertainty of environment and sensor readings but their use for realtime applications is limited by their computational complexity. This paper aims to reduce the high computational cost associated with the probabilistic Markov localization algorithm. We propose a hybrid landmark-based localization method combining triangulation and probabilistic approaches, which can efficiently update position probability grid, while the probabilistic framework allows to make use of any available sensor data to refine robot´s belief about its current location. The simulation results show the effectiveness and robustness of the method.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.68-73
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• 2007

Computational Fluid Dynamics (CFD) approach is now playing an important role in the engineering process in these days. Generating proper grid system in time for the region of interest is prerequisite for the efficient numerical calculation of flow physics using CFD approach. Grid generation is, however, usually considered as a major obstacle for a routine and successful application of numerical approaches in the engineering process. CFD approach based on the unstructured grid system is gaining popularity due to its simplicity and efficiency for generating grid system compared to the structured grid approaches, especially for complex geometries. In this paper an automated triangular surface grid generation using CAD(Computer Aided Design) surface data is proposed. According to the present method, the CAD surface data imported in the STL(Stereo-lithography) format is processed to identify feature edges defining the topology and geometry of the surface shape first. When the feature edges are identified, node points along the edges are distributed. The initial fronts which connect those feature edge nodes are constructed and then they are advanced along the CAD surface data inward until the surface is fully covered by triangular surface grid cells using Advancing Front Method. It is found that this approach can be implemented in an automated way successfully saving man-hours and reducing human-errors in generating triangular surface grid system.