• Convergence Security Journal
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• v.13 no.1
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• pp.71-78
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• 2013

In this study, software products developed in the course of testing, software managers in the process of testing software test and test tools for effective learning effects perspective has been studied using the NHPP software. The doubly bounded power law distribution model makeup Weibull distribution applied to distribution was based on finite failure NHPP. Software error detection techniques known in advance, but influencing factors for considering the errors found automatically and learning factors, by prior experience, to find precisely the error factor setting up the testing manager are presented comparing the problem. As a result, the learning factor is greater than automatic error that is generally efficient model could be confirmed. This paper, a numerical example of applying using time between failures and parameter estimation using maximum likelihood estimation method, after the efficiency of the data through trend analysis model selection were efficient using the mean square error and $R^2$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.95-104
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• 2003

This paper deals with the analytic and FEM analyses of sloshing frequency response of incompressible, invicid and irrotational flow in two dimensional rectangular tank. We use Laplace equation based on potential theory as governing equation. For small amplitude sloshing motion, the linearized free surface condition was applied and the analytic solution as obtained by the separation of variables. To simulate the effect of the energy dissipation due to viscous damping, artificial viscous coefficient is introduced and the divergence of response at resonance frequencies may be avoided by this coefficient. This problem was solved by FEM using 9-node elements in order to predict the maximum amplitude of sloshing response. Numerical results of free surface height, fluid pressure and fluid force show good agreement with those by analytic solution. After verifying the test FEM program, we analyze the frequency response characteristics of sloshing to the fluid height.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.389-398
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• 2002

The mixed mode problem (I and II) of a peny-shaped interface cracks in remote tension loading on a bi-material cylinder is studied using finite element method. The energy release rates for the tip of the crack in the interface were calibrated for several different moduli combinations and crack ratios using the modified crack closure integral technique and J-integral method, with numerical results obtained from a commercial finite element program. Numerical results show that non-dimensional value of$\sqrt{G_{II}E^*}/\sqrt[p]{\pi a}$ increases as the crack size or moduli ratio increases. Meanwhile, non-dimensional value of$\sqrt{G_{I}E^*}/\sqrt[p]{\pi a}$ decreases as the moduli ratio increases, but above the moduli ratio of 3 its value decreases then increases again as the crack size increases. Reliability of the numerical analysis in this study was acquired with comparison to an analytical solution for the peny-shaped interface crack in an infinite medium.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.219-226
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• 2005

In this study, the problem formulation and solution technique using genetic algorithms for design optimization of laminate composite cylindrical beam section are presented. The hollow cylindrical beams we usually used in the wheel chair. If the weight of wheel chair is reduced, it will lead to huge improvement in passenger's mobility and comfort. In this context, the replacement of steel by high performance and light weight composite material along with optimal design will be a good contribution in the process of weight reduction of a wheel chair. An artificial genetics approach for the design optimization of hollow cylindrical composite beam is presented. On applying the genetic algorithm, the optimal dimensions of hollow cylindrical composite beams which have equivalent rigidities to those of corresponding hollow cylindrical steel beams are obtained. Also structural analysis is conducted on the entire wheel chair structure incorporating Tsai-Wu failure criteria. The maximum Tsai-Wu failure criteria index is $0.192\times10^{-3}$ which is moth less than value of 1.00 indicating no failure is observed under excessive loading condition. It is found that the substitution of steel by composite material could reduce the weight of wheel chair up to 45%.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.239-245
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• 2008

A level set based topological shape optimization using extended B-spline basis functions is developed for steady-state heat conduction problems. The only inside of complicated domain identified by the level set functions is taken into account in computation, so we can remove the effects of domain outside parts in heat conduction problem. The solution of Hamilton-Jacobi equation leads to an optimal shape according to the normal velocity field determined from the sensitivity analysis, minimizing a thermal compliance while satisfying a volume constraint. To obtain exact shape sensitivity, the precise normal and curvature of geometry need to be determined using the level set and B-spline basis functions. Using topological derivative concept, the nucleation of holes for topological changes can be made whenever and wherever necessary during the optimization.

• Journal of Digital Contents Society
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• v.13 no.2
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• pp.197-203
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• 2012

Although the increase in number of the programs provides rich entertainment to viewers, it also has caused a negative of making it hard for viewers to find out their favorite programs. To address the problem, several researches have been performed mainly focusing on the technologies to analyze a viewer's TV watching-patterns and to recommend a program (or a channel) based on the analysis when a viewer changes channels. The researches, however, have the trouble of frequently failing to choose proper programs because, in the real-world broadcasting circumstance, the programs are re-broadcast over a number of the channels and a set of programs of a genre are usually playing in the overlapped times. To avoid the trouble, the data service, proposed in the paper, allows a viewer to book "explicitly" his/her favorite programs and provides a set of functions of listing up the booked program's broadcasting schedules and reserving viewing or recording the booked programs.

• Journal of Digital Contents Society
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• v.14 no.1
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• pp.25-33
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• 2013

P2P(Peer-to-Peer) architecture can reduce the network bandwidth and resource on the server since peers exchange data chunks with each other, while server-client architecture causes a lot of traffic on the server. Peers receive a data more reliably when the number of participating peer increases. Currently, P2P traffic has accounted for about 65% of the world's Internet traffic and diverse P2P streaming services have launched combining to video streaming technology. However, the requirements and data chunk delivery algorithms for mobile P2P streaming service should be investigated, since the existing P2P technologies have been developed and designed for the wired network. In particular, the bandwidth fluctuation caused by user mobility, wireless packet collisions, and packet losses brings about different problems on the mobile P2P streaming service compared to existing P2P streaming service. In this paper, we analyzed the problem of mobile P2P streaming services in the 802.11n wireless LAN environment through experiments.

• Journal of the Korean Dietetic Association
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• v.24 no.2
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• pp.169-180
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• 2018

Depression is a major health problem that can lead to mortality. This study was conducted to assess the risk factors associated with depression in a group aged over 65 years by analyzing nationally representative Korean survey data. A total of 1,209 subjects were analyzed among the participants of the 2014 Korean National Health and Nutrition Examination Survey. Statistical methods for a complex sample were applied by using SPSS program(windows ver. 24.0). Depression assessments were carried out by using the 9-item depression module of the Patient Health Questionnaire-9 (PHQ-9). Depression ($PHQ-9{\geq}5$) was more frequently found in females (33.2%) compared to males (16.1%). However, there was no evidence suggesting that characteristics such as residence area, income level and age, except for educational level, were related with depression. The results of the logistic regression analysis showed that i) health habits such as smoking (OR: 2.26) and lack of aerobic physical activity (OR: 1.62), ii) mental health status such as bad self-rating of health status (OR: 4.30), more stress (OR: 8.31), and bad health-related quality of life (by EQ_5D, OR: 3.41), iii) chronic diseases such as obesity (OR: 0.66), hypercholesterolemia (OR: 1.57), anemia (OR: 1.91), and iv) low intake of energy (OR: 1.84) and calcium (OR: 1.71) were significantly associated with depression. This study suggests that certain characteristics of health habits, mental health status, chronic diseases and nutrient intake may be associated with depression. Prospective research on long-term control is needed to establish causal connections among those factors with depression.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.795-801
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• 2013

As the life which existed only offline has changed into a life part of which is led online, it is an important problem to identify whether an online user is legitimate one or not. Biometric authentication technology was developed to identify the user more correctly either online or in offline daily life. Biometric authentication is a technology where a person is identified by his or her unique characteristics, and is highlighted as a next-generation authentication technology replacing password. There are various kinds of traits unique to each individual, and biometric authentication technologies drawing on such traits use various devices and algorithms. Firstly, this paper classified such various biometric authentication technologies, and analyzed the effects of them when they are applied on smartphone, smartwatch and M2M of the different devices platforms. Secondly, it suggested the effectiveness-based AIB(Authentication for Integrated Biometrics) authentication technique, a comprehensive authentication technique, which can be used in different devices platforms. We have successfully included the establishment scheme of the effectiveness authentication using biometrics.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.305-312
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• 2013

This research suggests the security countermeasures for solving technology outflow of small-medium companies in New IT Environment through level comparison of security cognition and security management between small-medium companies and major big companies. According to analysis results, it is poor for small-medium companies' level of security cognition and security management compared with major big companies. Small-medium companies need to manage technology outflow to major big companies' level in New IT Environment. Small-medium companies has started to build New IT Environment recently and it must build the appropriate security system for small-medium companies at the same time. Small-medium company has more problem with budget and proffessionals to maintain the security of technology outflow. Therefore government has to support systematic management for the security of technology outflow to Small-medium companies