• Korean Journal of Materials Research
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• v.8 no.4
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• pp.328-336
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• 1998

In metal-carbon system with no mutual solubility between matrix and alloying elements as solid or liquid phases, Cu-C-X nanocomposite metal powders were prepared by high energy ball milling for solid-lubricating bronze bearings. Elemental powder mixtures of Cu-lOwt.%C- 5wt. %Fe and Cu- lOwt. %C- 5wt. %Al were mechanically alloyed with an attritor in an argon atmosphere, and then microstructural evolution of the Cu-C-X nanocomposite metal powders was examined. It has been found that after 10 hours of MA, the approximately 10$\mu\textrm{m}$ sized Cu-C- X nanocomposite metal powders can be produced in both compositions. Morphological characteristics and microstructural evolution of the Cu-C-X powders have shown a similar MA procedure compared to those of metal-metal system. As a result of X - ray diffraction analysis, diffraction peaks of Cu and C were broaden and peak intensities were decreased as a function of MA time. Especially, the gradual disappearance of C peaks in the X- ray spectra is proved to be due to the lower atomic scattering factor of C. The calculated Cu crystallite sizes in Cu- C- X nanocomposite metal powders by Williamson- Hall equation were about lOnm size, on the other hand, the observed ones by TEM were in the range of 10 to 30nm.

• Journal of Food Hygiene and Safety
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• v.22 no.4
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• pp.268-272
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• 2007

A study on the evolution of acid value, peroxide value and biogenic amines in silkworm pupa during 7 days at different temperature of storage (-18, 25 and $35^{\circ}C$) was performed. Seven biogenic amines (putrescine, cadaverine, histamine, tyramine, spermidine, spermine and 2-phenylethylamine) were determined. Acid value in Silkworm pupa increased both during normal temperature $(25^{\circ}C)$ and room temperature $(35^{\circ}C)$ and thebiogenic amine (histamine, tyramine) content generally increased in $25^{\circ}C\;and\;35^{\circ}C$ with storage time. Significant differences were found (P<0.05) in the levels of tyramine and histamine among Silkworm pupa. The relationship of storage time and acid value of Silkworm pupa were resolved a simple linear equation, and histamine and tyramine could be predicted using this equation. Quality indices related to the contents of the major biogenic amines were calculated and they correlated well with physicochemical characteristics qualities such as acid value.

• The Journal of the Korea Contents Association
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• v.14 no.7
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• pp.395-406
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• 2014

This research observes how an adolescent's usage of social network services is related with media use time, and also tries to verify how a parent's participation in acting to limit usage time serves as a mediating effect. For this analysis, data from The Korean Information Society Development Institute [Korea Media Panel Research] was used, being a survey conducted on 1,572 students from primary to secondary and high schools nationwide. The subjects' gender in the final analysis was 818 male students and 754 female students. In addition, primary school students consisted of 672 individuals, 416 were from secondary and 484 from high schools. To verify the appropriateness of the model proposed in this research, analyzed through the structural equation, using social network services(SNS) was not shown to have an effect on media usage time. However, there was an indirect effect from the use of alternative activities. In addition, the parent's limitation of usage showed no effect on media use time. This research attempts to identify the reasons why parents' limiting the usage time, along with alternative activities, do not have any significant effect in reducing media usage time in this era of smart media evolution. Further, this research hopes to suggest meaningful and political implications for the nation and society to understand and resolve media addiction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1652-1662
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• 2013

As smart devices like smartphones and smart pads are prevalent recently, dramatic changes so called 'smart evolution' deployed in many socioeconomic areas. These changes lead the TV industry to develop a smart TV differentiated from a conventional TV by enabling internet connectivity and applications execution. In this study the factors affecting the acceptance of a smart TV are extracted by reviewing the previous works and the structural relationships among these factors are analyzed. Adding 'Social Influence' to consider an environmental factor and 'Innovativeness' for personal characteristics, we build an extended Technology Acceptance Model and analyzed the structural relationships among the factors in the model using Structural Equation Model. In the results we can find that the environmental factors affect the perceived characteristics. The moderating effects of gender and level of experience in smart devices have also been investigated. No difference is found between gender groups. In much-experienced group, Innovativeness affects Perceived Usefulness and acceptance of a smart TV. In less-experienced group, however, Innovativeness affects Perceived Ease of Use, Expected Enjoyment and finally acceptance of a smart TV.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.106-121
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• 2020

In order to make harbor outskirt facilities robust using the reliability-based design, probabilistic models of wave heights at varying stage of shoaling process optimized for Korean sea waves are prerequisite. In this rationale, we numerically simulate the nonlinear shoaling process of random waves over the beach with a sandbar at its foreshore. In doing so, comprehensive numerical models made of spatially filtered Navier-Stokes Eq., LES [Large Eddy Simulation], dynamic Smagorinsky turbulence closure were used. Considering the characteristics of swells observed at the east coast of Korean Peninsula, random waves were simulated using JONSWAP wave spectrum of various peak enhancement coefficients and random phase method. The coefficients of probabilistic models proposed in this study are estimated from the results of frequency analysis of wave crests and its associated trough detected by Wave by Wave Analysis of the time series of numerically simulated free surface displacements based on the threshold crossing method. Numerical results show that Modified Glukhovskiy wave height distribution, the most referred probabilistic models at finite water depth in the literature, over-predicts the occurring probability of relatively large and small wave heights, and under predicts the occurrence rate of waves of moderate heights. On the other hand, probabilistic models developed in this study show vary encouraging agreements. In addition, the discrepancy of the Modified Glukhovskiy distribution from the measured one are most visible over the surf zone, and as a result, the Modified Glukhovskiy distribution should be applied with caution for the reliability-based design of harbor outskirt facilities deployed near the surf-zone.

• Journal of Information Technology Applications and Management
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• v.20 no.3_spc
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• pp.259-278
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• 2013

At the center of the repeating evolution of IT industry, there is mobile computing in the ubiquitous environment, and the increasing usage of smart phones contribute more to its growth. P corporation co-developed with Google and implemented smart work system called SWP for the purpose of 'communication and collaboration with co-workers' beyond the general goal of increasing productivity and comfort of employees. The primary objective of this study is to objectively analyze the influence of the effect factor from end user's perspective and user satisfaction on SWP usage, intention for continuous usage and individual performance. To accomplish this research purpose, this study established research models and hypothesis by collective review about information system success models, and tested the research hypotheses using the structural equation modeling technique by data collected from 320 SWP system users of P corporation. Variations for system satisfaction evaluation standard are 1)SW system usage 2) intention for continuous usage 3) individual performance, effect variations are 1) social factors 2) technical factors 3) combination of social and technical factors. Therefore, this study is about influence factors on success of SWP system and how the factors impact the outcome. The test results of this research model is summarized as follows. Firstly, system user's satisfaction had positive impact on all three; SWP system usage, intention for continuous usage and individual performance. Secondly, social factor 'SWP control system' and technical factor 'information quality' and 'system quality' had positive impact on SWP system user satisfaction, while social factor 'shared value' and technical factor 'service quality' did not have significant effect on user satisfaction. Shared value however, had interactive effect with 'information quality' and 'service quality'. This study is expected to contribute to spread of academic research on smart work system by suggesting a model that can show important factors for corporation while explaining the successful implementation of SWP and its continuous usage.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.135-135
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• 2017

Greenhouse have been developed to provide the plants with good environmental conditions for cultivation crop, two major factors of which are the inside air temperature and humidity. The inside temperature are influenced by the heating systems, ventilators and for systems among others, which in turn are geverned by some type of controller. Likewise, humidity environment is the result of complex mass exchanges between the inside air and the several elements of the greenhouse and the outside boundaries. Most of the existing models are based on the energy balance method and heat balance equation for modelling the heat and mass fluxes and generating dynamic elements. However, greenhouse are classified as complex system, and need to make a sophisticated modeling. Furthermore, there is a difficulty in using classical control methods for complex process system due to the process are non linear and multi-output(MIMO) systems. In order to predict the time evolution of conditions in certain greenhouse as a function, we present here to use of recurrent neural networks(RNN) which has been used to implement the direct dynamics of the inside temperature and inside humidity of greenhouse. For the training, we used algorithm of a backpropagation Through Time (BPTT). Because the environmental parameters are shared by all time steps in the network, the gradient at each output depends not only on the calculations of the current time step, but also the previous time steps. The training data was emulated to 13 input variables during March 1 to 7, and the model was tested with database file of March 8. The RMSE of results of the temperature modeling was $0.976^{\circ}C$, and the RMSE of humidity simulation was 4.11%, which will be given to prove the performance of RNN in prediction of the greenhouse environment.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.367-381
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• 2019

We investigate pore pressure conditions and reservoir compaction associated with oil and gas production using 3 different permeability models, which are all based on one-dimensional radial flow diffusion model, but differ in considering permeability evolution during production. Model 1 assumes the most simplistic constant and invariable permeability regardless of production; Model 2 considers permeability reduction associated with reservoir compaction only due to pore pressure drawdown during production; Model 3 also considers permeability reduction but due to the effects of both pore pressure drawdown and coupled pore pressure-stress process. We first derive a unified stress-permeability relation that can be used for various sandstones. We then apply this equation to calculate pore pressure and permeability changes in the reservoir due to fluid extraction using the three permeability models. All the three models yield pore pressure profiles in the form of pressure funnel with different amounts of drawdown. Model 1, assuming constant permeability, obviously predicts the least amount of drawdown with pore pressure condition highest among the three models investigated. Model 2 estimates the largest amount of drawdown and lowest pore pressure condition. Model 3 shows slightly higher pore pressure condition than Model 2 because stress-pore pressure coupling process reduces the effective stress increase due to pore pressure depletion. We compare field data of production rate with the results of the three models. While models 1 and 2 respectively overestimates and underestimates the production rate, Model 3 estimates the field data fairly well. Our result affirms that coupling process between stress and pore pressure occurs during production, and that it is important to incorporate the coupling process in the permeability modeling, especially for tight reservoir having low permeability.

• Computational Structural Engineering
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• v.9 no.1
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• pp.65-76
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• 1996

The initiation and growth of microcracks or microvoids inside concrete results in the progressive degradation of concrete. This damage processing along processing along with plastic deformation is main cause of nonlinear behavior of concrete. In this study, a continuum damage model of concrete is developed for the analysis of the nonlinear behavior of concrete due to damage and elasto-plastic deformation. Anisotropic damage tensor is used to describe the anisotropy of concrete and hypothesis of equivalent elastic energy is used to define the effective elastic tensor. The damage model including the damage evolution law and constitutive equation is derived with damage variable and damage surface which is defined by damage energy release rate by using the Helmholtz free energy and dissipation potential based on the thermodynamic principles. By adopting a typical plasticity model of concrete, plasticity of concrete is included to this model. Afinite element analysis program implemented with this model was developed and finite element analysis was performed for the analyses of concrete subjected to uniaxial and biaxial loadings. Comparison of the results of analysis with those of experiments and other models shows that the model successfully predicts the nonlinear behavior of concrete.

• East Asian Economic Review
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• v.20 no.3
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• pp.279-309
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• 2016

The proposed Trans-Pacific Partnership (TPP) is a free trade agreement among 12 Pacific Rim countries whose joint gross domestic products (GDPs) account for 36 percent of world GDP and whose mutual trade accounts for approximately 24 percent of world trade. As for most proposed free trade agreements (FTAs), trade economists have provided ex ante computable general equilibrium (CGE) estimates to predict the trade, employment, and real per capita income effects of this agreement, such as ITC (2016). This paper-intended to complement these studies-examines the potential impacts of TPP beyond such traditional CGE estimates, taking a broader economic, governance, and historical perspective. First, we contrast these traditional CGE trade and welfare estimates that treat all firms within an industry as homogeneous with more recent CGE analyses that allow firms' productivities to be heterogeneous. We show that the latter models' trade predictions are much more consistent with ex post empirical evidence of average trade effects of FTAs. Second, empirical evidence now strongly confirms the existence of FTA "contagion." We review this evidence and show that predictive models of the evolution of FTAs indicate that the TPP should be formed. With China now having formed 12 FTAs and negotiating five new ones (including a sixteen member Asia-Pacific FTA), the United States would likely face considerable trade diversion without the TPP. Third, we examine empirical evidence on the likely further economic growth implications of FTAs by reducing firms' uncertainty over trade relations and trade policies. Fourth, we examine empirical evidence on the additional impact of FTAs on consolidating democratic institutions in countries. The TPP would likely help consolidate some of the less mature democracies. Fifth, we examine empirical evidence on the reductions of conflicts (and enhanced peace) between countries owing to the formations of FTAs. We conclude the paper noting that the potential net benefits to member countries of the proposed TPP extend well beyond the real income gains to households based upon traditional CGE models.