• Computers and Concrete
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• v.19 no.1
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• pp.99-110
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• 2017

In this paper, the effect of normal load on the failure mechanism of echelon joint has been studied using PFC2D. In the first step, calibration of PFC was undertaken with respect to the data obtained from experimental laboratory tests. Then, six different models consisting various echelon joint were prepared and tested under two low and high normal loads. Furthermore, validation of the simulated models were cross checked with the results of direct shear tests performed on non-persistent jointed physical models. The simulations demonstrated that failure patterns were mostly influenced by normal loading, while the shear strength was linked to failure mechanism. When ligament angle is less than $90^{\circ}$, the stable crack growth length is increased by increasing the normal loading. In this condition, fish eyes failure pattern occur in rock bridge. With higher ligament angles, the rock bridge was broken under high normal loading. Applying higher normal loading increases the number of fracture sets while dilation angle and mean orientations of fracture sets with respect to ligament direction will be decreased.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.237-242
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• 2012

Cyber attacks have rapidly increased by exploiting the underlying vulnerabilities in the target software. However, identifying and correcting these vulnerabilities are extremely difficult and time consuming tasks. To address these problems efficiently, we propose a systematic methodology for security vulnerability assessment process on binary code in the paper. Specifically, we first classified the existing vulnerabilities based on whether the target software run in a Web environment and features of the software. Based on the classification, we determined the list and scope of the vulnerabilities. As our future research direction, we need to further refine and validate our methodology.

• Journal of computational fluids engineering
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• v.17 no.3
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• pp.99-107
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• 2012

In this paper, the shock waves in compressible solids and liquids are simulated using a six-equation diffuse interface multiphase flow model that is extended to the Cochran and Chan equation of state. A pressure relaxation method based on a volume fraction function and a pressure-correction equation are newly implemented to the six-equation model. The developed code has been validated by a shock tube problem with liquid nitromethane and an impact problem of a copper plate on a solid explosive. In addition, a new problem, an impact of a copper plate on liquid nitromethane, has been solved. The present code well shows the wave structures in compressible solids and liquids without any numerical oscillations and overshoots. After the impact of a solid copper plate on liquid, two shock waves (one propagates into liquid and the other into solid) are generated and a material interface moves to the impacting direction. The computational results show that the shock velocity inside the liquid linearly increases with the impact velocity.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.4
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• pp.318-330
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• 2011

This paper investigates the convergence characteristics of the modified artificial compressibility method proposed by Turkel. In particular, a focus is mode on the convergence characteristics due to variation of the preconditioning factor (${\alpha}_u$) and the artificial compressibility (${\beta}$) in conjunction with an upwind method. For the investigations, a code using the modified artificial compressibility is developed. The code solves the axisymmetric incompressible Reynolds averaged Navier-Stokes equations. The cell-centered finite volume method is used in conjunction with Roe's approximate Riemann solver for the inviscid flux, and the central difference discretization is used for the viscous flux. Time marching is accomplished by the approximated factorization-alternate direction implicit method. In addition, Menter's k-${\omega}$ shear stress transport turbulence model is adopted for analysis of turbulent flows. Inviscid, laminar, and turbulent flows are solved to investigate the accuracy of solutions and convergence behavior in the modified artificial compressibility method. The possible reason for loss of robustness of the modified artificial compressibility method with ${\alpha}_u$ >1.0 is given.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.4
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• pp.51-62
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• 2019

Recently, as the number of Smart Phone users increase, the simple payment system has been able to make payments using only card information such as a registered password without extra authorized certificate authentication or input of card information. In this paper, it will examine and analyze simple payment system provided by IT companies and financial institutions and the simple payment system that operates global online payment system by case view of operational direction. Then with this examination, it will study ways to improve the problems with terms of convenience and stability in terms of users. In this paper, it will analyze the inconvenient problem in using the QR code system that recently introduced and will propose solutions. Also, it will propose suggestions to solve inconvenience that caused by system that supports NFC simple payment terminal in Korea is not universalize by analyze case study on the overseas simple payment system. It will also propose opinions on the matters that customer having responsible for event of a small financial accident related to loss or theft when using the simple payment system. Then it will suggest expected requirements to prepare new security technical countermeasures and solve the conditions of meeting expectation satisfaction of users.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.75.1-75.1
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• 2014

Sunspot penumbrae show supersonic downflow patches along the periphery. These patches are believed to be the return channels of the Evershed flow. There was previous study to investigate their structure in detail using Hinode SOT/SP observations (M. van Noort et al. 2013) but their data sample was only two sunspots. To make general description it needs to check more sunspot sample. We selected 242 downflow patches of 17 sunspots using Hinode SOT/SP observations from 2006 to 2012. Height-dependent maps of atmospheric parameters of these downflows was produced by using HeLix which was height dependent LTE inversion code of Stokes profiles. The inversion code at high resolution allows for the accurate determination of small scale structures. The recovered atmospheric structure of three layers indicates that regions with very high downflow velocities contain very strong magnetic fields reaching up to 7kG. The higher downflow velocity patches have bigger patch size. Magnetic fields of downflow patches are more vertical while penumbra shows horizontal field and neighbor of downflow patches have opposite polarity. Temperature of downflow patches at highest layer have more strong value than penumbra at deepest layer. The direction of velocity of downflow patches at highest layer have two branches. These result shows that we can expect some heating precess in the middle of layer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.4
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• pp.566-576
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• 1995

A Computational code has been developed in order to design axial fans by the numerical optimization techniques incorporated with flow analysis code solving three-dimensional Navier-Stokes equation. The steepest descent method and the conjugate gradient method are used to look for the search direction in the design space, and the golden section method is used for one-dimensional search. To solve the constrained optimization problem, sequential unconstrained minimization technique, SUMT, is used with imposed quadratic extended interior penalty functions. In the optimization of two-dimensional cascade design, the ratio of drag coefficient to lift coefficient is minimized by the design variables such as maximum thickness, maximum ordinate of camber and chord wise position of maximum ordinate. In the application of this numerical optimization technique to the design of an axial fan, the efficiency is maximized by the design variables related to the sweep angle distributed by quadratic function along the hub to tip of fan.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2202-2209
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• 2009

Joint paths are induced mathematically for many kinds of joint pattern between master- and sub-pipes. By compensating them with root gap of welds and kerf width, real cutting paths are determined. Their NC codes are generated, and the paths generated by NC code are verified by a ghost function. A beveling is implemented through tilting a torch in the A- and B-axis direction for 8 sections in the chuck rotation of C-axis. The effective CAM program was developed specially for 6-axis CNC pipe coasters which cut a master or sub- pipe along the cutting path and simultaneously fulfill a beveling process.

• Journal of the Korea Society of Computer and Information
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• v.24 no.6
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• pp.135-140
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• 2019

The purpose of this study was to find the ethical values of dental hygiene students, to establish the right ethical values of the students, and to provide a fundamental material for the ethical education direction and curriculum of the students. In order to examine the general characteristics and ethical job behavior level among dental hygiene students, a research was conducted from 1st April 2017 to $30^{th}$ June 2017 through selecting freshman, sophomore, junior and senior students currently enrolled in the department of dental hygiene at 5 different colleges as the subjects. Statistical analysis was performed using IBM SPSS 22. The frequency analysis was used to examine their general characteristics. The independent t-test was used to examine their ethical job behavior according to their religion, hospital practice experience and code of ethics as a dental hygienist, and the one-way ANOVA was used to examine their ethical job behavior according to grade-specific characteristics. Lastly, the Scheffe's post hoc test was conducted. The significance level was 0.05. Given the results, ethical job behavior was significantly different between the group of students with religion, the group of students with hospital practice experience, different school year students, and the group of students aware of code of ethics as a dental hygienist.

• Journal of the Korea Society of Computer and Information
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• v.24 no.1
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• pp.25-32
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• 2019

With the rapid development of artificial intelligence technology, the patenting activities related to the fields of AI is increasing worldwide. In particular, a share of patent filed in China has exploded in recent years and overtakes the numbers in the US. In the present study, we focus our attention on the patenting activity of China and the US. We analyzed 6,281 and 13,664 patent applications in the US and China respectively between 2008 and 2018, and belonging to the "G06F(Electric Digital Data Processing)", "G06N(Computer Systems Based on Specific Computational Models)", "H04L(Transmission of Digital Information)" and nine more relevant technological classes, as indicated by the International Patent Classification(IPC). Our analysis contributes to: first, the understanding of patent application trends from foreign countries filed in the US and China, 2) patent application status by applicants category such as companies, universities and individuals, 3) the development direction and forecasting vacant technology of AI according to main IPC code. Through the analysis of this paper, we can suggest some implications for patent research related to artificial intelligence in Korea. Plus, by analyzing the most recent patent data, we can provide important information for future artificial intelligence technology research.