• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.649-656
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• 2008

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchic void element based on the integrals of Legendre polynomials is used to characterize the fracture behaviour of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of zero stiffness element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem. It is noted that the proposed hierarchical void element can be one of alternatives to analyze the patched crack problems.

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.91-97
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• 2014

A high resolution numerical method aimed at solving cavitating flow was proposed and applied to gas-liquid two-phase shock tube problem with arbitrary void fraction. The present method with compressibility effects employs a finite-difference 4th-order Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL TVD scheme. The Jacobian matrix from the inviscid flux of constitute equation is diagonalized analytically and the speed of sound for the two-phase media is derived by eigenvalues. So that the present method is appropriate for the extension of high order upwind schemes based on the characteristic theory. By this method, a Riemann problem for Euler equations of one dimensional shock tube was computed. Numerical results of high speed flow phenomena such as detailed observations of shock and expansion wave propagations through the gas-liquid two-phase media and some data related to computational efficiency are made. Comparisons of predicted results and solutions at isothermal condition are provided and discussed.

• Korean Institute of Interior Design Journal
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• v.27 no.3
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• pp.100-107
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• 2018

In order to overcome social exclusion and to integrate social housing, it is necessary to plan a communal space in urban collective housing so that residents can have belonging sense and community consciousness. In this study, it is necessary to consider the linkage between social integration and residential space, and to derive the characteristics of planning the collective housing for social integration. We analyzed the planning characteristics of MVRDV's communal spaces of collective housing and suggested a method of planning communal spaces of urban collective housing for social integration. Urban density is an important tool and background for MVRDV's design methodology. For this reason, MVRDV's collective housing is selected as a case study in this study. As a result of case analysis, openness and connection characteristics should be considered by using various devices such as glass exterior, balcony, and void in planning the communal space in urban collective housing for social integration. However, since it has appeared in many cases, it can be criticized that the application of this is merely a logic. In other words, it is possible to suggest that we should actively introduce less accessible access. This problem should be solved through more case studies.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.13
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• pp.5325-5329
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• 2015

Farnesiferol C is a natural compound with various anti-cancer properties that belongs to the class of sesquiterpene coumarins. However, the low bioavailability of farnesiferol C limits its therapeutic potential. Here, we overcame this problem utilizing dendrosome nano-particles and evaluated the anti-cancer effect of dendrosomal farnesiferol C (DFC) on the AGS gastric cancer cell line. The 3-(4,5-dimethyl-thiazol-2yl)-2,5- diphenyl tetrazolium bromide (MTT) assay and reverse transcriptase-polymerase chain reaction (RT-PCR) were respectively used to detect the anti-proliferative properties of DFC and expression ratio of Bax/Bcl-2 as a hallmark of apoptosis. Compared to the void farnesiferol C (FC), our data showed that DFC significantly suppresses the proliferation of AGS cells in a time- and dose-dependent manner (P<0.01). Also, DFC meaningfully increased the expression ratio of Bax/Bcl-2 in AGS cells (P<0.01). The findings demonstrate that our nano-based formulation of farnesiferol C could be considered as a potential therapeutic agent in cancer targeting.

• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.254-263
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• 2017

The cavitation erosion remains an industrial issue for many applications. This paper deals with the cavitation intensity, which can be described as the fluid mechanical loading leading to cavitation damage. The estimation of this quantity is a challenging problem both in terms of modeling the cavitating flow and predicting the erosion due to cavitation. For this purpose, a numerical methodology was proposed to estimate cavitation intensity from 3D unsteady cavitating flow simulations. CFD calculations were carried out using Code_Saturne, which enables U-RANS equations resolution for a homogeneous fluid mixture using the Merkle's model, coupled to a $k-{\varepsilon}$ turbulence model with the Reboud's correction. A post-process cavitation intensity prediction model was developed based on pressure and void fraction derivatives. This model is applied on a flow around a hydrofoil using different physical (inlet velocities) and numerical (meshes and time steps) parameters. The article presents the cavitation intensity model as well as the comparison of this model with experimental results. The numerical predictions of cavitation damage are in good agreement with experimental results obtained by pitting test.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.6
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• pp.641-646
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• 2004

Statement of Problem. Temporary soft relining materials are used in a diverse clinical situations such as tissue conditioner, relining material, functional impression by varying its viscoelasticity. However, reproduction of consistent viscoelasticity has been not possible. Materials and methods. Considering setting mechanism of this material, this study has measured the effect of varying amount of void in dynamic viscoelasticity of soft relining material, with three different mixing methods. In each methods 10 specimens were made and subjected to dynamic viscoelastic test which were measured at specific times over period of 72 hours. Results. The analysis of the result shown that there was no statistically significant differences between different mixing methods. Conclusion. Different mixing methods had no effect over control of viscoelasticity of soft lining material. Further research is recommended for under similar oral environmental condition.

• Journal of Engineering Education Research
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• v.20 no.1
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• pp.63-68
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• 2017

This research is as a case study of innovative engineering education system through idea factory of korea maritime and ocean university and deals with development of temperature-humidity control device (THCD) for fiber storage on composites in viewpoint of problem solving method. Fiber reinforced plastic (FRP) includes many variables on the composite manufacturing process. Above all, the interfacial adhesion between the fiber and the matrix acts as an important thing that decided mechanical property of the FRP, and also it is profoundly linked to external temperature and relative humidity. High void fraction leads to a result in interlaminar fracture. Therefore, in this research, to establish correlation between fiber reinforcement and fiber storage conditions of temperature and relative humidity we developed a THCD for fiber reinforcement. To evaluate performance of the THCD, glass fiber reinforced plastic (GFRP) is made under the extreme conditions each temperature $34^{\circ}C$, relative humidity 98 % and it can be said that there are the change of mechanical properties according to fiber storage conditions. As a result, the THCD showed sufficient possible application for understanding and applied research of composites field in material engineering. Also, we could check that the necessity of introduction of innovative system such as idea factory existed.

• Korean Management Science Review
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• v.24 no.2
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• pp.157-176
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• 2007

Fuzzy cognitive map(FCM) has long been used as an effective way of constructing the human's decision making process explicitly. By taking advantage of this feature, FCM has been extensively used in providing what-if solutions to a wide variety of business decision making problems. In contrast, the goal-seeking analysis mechanism by using the FCM is rarely observed in literature, which remains a research void in the fields of FCM. In this sense, this study proposes a new type of the FCM-based goal-seeking analysis which is based on utilizing the genetic algorithm. Its main recipe lies in the fact that the what-if analysis as well as goal-seeking analysis are enabled very effectively by incorporating the genetic algorithm into the FCM-driven inference process. To prove the empirical validity of the proposed approach, valid questionnaires were gathered from a number of experts on software sales, and analyzed statistically. Results showed that the proposed approach is robust and significant.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1147-1157
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• 2009

Recently this country has carried out the coast reclamation centering on the west and south coast for effective practical use of a country, considering purchase of materials and environmental problem, and carrying into effort the reclamation method after dredging the ground in the ocean. In this large scale ocean dredging reclaiming work, prediction the ground subsidence after reclaiming is very important for not only expense lose by overestimation or underestimation but also hereafter the best suited project establishment. this study carries out sedimentation and self weight consolidation in each cases and searches the features to analyze effect on kinds of soil of ground before dredging, abandonment height when it abandons momentary, void ratio, difference of abandonment height when it abandons by stages and difference of particle content of spoil.

• Smart Structures and Systems
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• v.17 no.1
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• pp.17-29
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• 2016

Ultrasonic tomography is a powerful tool for identifying defects within an object or structure. But practical application of ultrasonic tomography to solids is often limited by time consuming transducer coupling. Air-coupled ultrasonic measurements may eliminate the coupling problem and allow for more rapid data collection and tomographic image construction. This research aims to integrate recent developments in air-coupled ultrasonic measurements with current tomography reconstruction routines to improve testing capability. The goal is to identify low velocity inclusions (air-filled voids and notches) within solids using constructed velocity images. Finite element analysis is used to simulate the experiment in order to determine efficient data collection schemes. Comparable air-coupled ultrasonic signals are then collected through homogeneous and isotropic solid (PVC polymer) samples. Volumetric (void) and planar (notch) inclusions within the samples are identified in the constructed velocity tomograms for a variety of transducer configurations. Although there is some distortion of the inclusions, the experimentally obtained tomograms accurately indicate their size and location. Reconstruction error values, defined as misidentification of the inclusion size and position, were in the range of 1.5-1.7%. Part 2 of this paper set will describe the application of this imaging technique to concrete that contains inclusions.