• Ocean and Polar Research
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• v.28 no.3
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• pp.317-329
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• 2006

To assess the contamination status of organochlorine pesticides in the marine environment of Saemangeum, surface seawater and sediments were collected and analyzed. Organochlorine pesticides were widely distributed in the Saemangeum environment, with DDT, HCH and endosulfan II contamination being particularly prevalent. The overall concentrations of DDTs, HCHs, and endosulfan II in surface seawater were in the rage of 0.03-0.65ng/l (mean value: 0.36ng/l), 1.31-4.54ng/l (2.63 ng/l), and not detected (ND)-0.96ng/l (0.49ng/l), respectively. Among the target organochlorine pesticides, endosulfan II showed the hi띤est level at the river mouth flowing into the Saemangeum. Additionally, its negative gradient from the rivers to the outside and a good correlation with $NO_3^-$ indicate that endosulfan ll inflows to the Saemangeum through the river; this conclusion is also supported by the elevated levels of endosulfan II in sediments at the river mouth. In sediment, the concentration of DDTs, HCHs, CHLs, and endosulfan II were in the range of 0.05-1.96 ng/g, 0.03-0.31ng/g, 0.01-0.13ng/g, and ND-0.62ng/g, respectively. Levels of contamination in Saemangeum are relatively lower than the median concentrations previously observed at the Korean coastal regions and sediment quality guidelines suggested by NOAA (Long et at. 1995).

• The Journal of Information Systems
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• v.14 no.1
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• pp.171-195
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• 2005

The current study investigates major factors which influence the consumer's selection of internet shopping malls. Based on the technology acceptance model(TAM)(Davis, 1989) and trust theory(McKnight & Chervany, 2001), consumer selection factors from marketing research(Burke, 1997;Dodds et al, 2001), perceived usefulness, perceived ease of use, trust, service quality, and product price were hypothesized as to affect the consumer's decision to choose one's specific internet shopping malls. The study developed a research model to explain the shopping mall selection and collected the survey responses from 312 internet shopping mall users. The results of the current research indicate that all the research variables employed in the study, perceived usefulness, perceived ease of use, trust, service quality, and product price, are found to significantly influence the consumer's shopping mall selection decision. Among the influencing factors, price, service quality, and trust showed a greater effect on the shopping mall selection than usefulness and ease of use. This result implies that purchase-related variables such as price and service quality may be more critical to attracting customers and thereby raising the sales volume of the shopping mall, than the web site's usefulness and ease of use.

• Advances in concrete construction
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• v.7 no.1
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• pp.11-22
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• 2019

A comprehensive assessing approach for durability of reinforced concrete structures dealing with the corrosion process of rebar subjected to the attack of aggressive agent from environment was proposed in this paper. Corrosion of rebar was suggested in the form of combination of global corrosion and pitting. Firstly, for the purposed of considering the influence of rebar's radius, a type of Plane Corrosion Model (PCM) based on uniform corrosion of rebar was introduced. By means of FE simulation approach, global corrosion process of rebar regarding PCM and LCM (Linear Corrosion Model) was regressed and compared according to the data from Laboratoire $Mat{\acute{e}}riaux$ et $Durabilit{\acute{e}}$ des Constructions (LMDC). Secondly, pitting factor model of rebar in general descend law with corrosion degree was introduced in terms of existing experimental data. Finally, with the comprehensive numerical simulation, the durability of an existing arch bridge was studied in depth in deterministic way, including diffusion process and sectional strength of typical cross section of arch, crossbeam and deck slab. Evolution of structural capacity considering life-cycle rehabilitation strategy indicated the degradation law of durability of reinforced arch bridges.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.400-401
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• 2003

Atmospheric fine aerosol particles play an important role in controlling a number of atmospheric processes, such as the deposition of different compounds, the optical properties etc. (Molnar et al., 1999). In this report, water-soluble species of PM$_{2.5}$ obtained from simultaneous measurements at four Asia sites (Beijng (39.56$^{\circ}$N, 116.17$^{\circ}$E), China; Gwangju (35.10$^{\circ}$N, 126.53$^{\circ}$E), South Korea; Kyoto (35.01$^{\circ}$N, 135.44$^{\circ}$E), Japan; and Ulan-Bator (47.55$^{\circ}$N, 106.52$^{\circ}$E), Mongolia) during the periods of 14-22 August, 30 October-06 November 2000, 14-21 January 2001, 23 July-02 August and 05-16 November 2002, within the framework of an APN (The Asia-Pacific Network for Global Change Research) project are reported. Ion components in 23 July-02 August 2002 were not obtained because of the technical problem of equipments.s.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.350-362
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• 2017

The Eulerian nearshore current model is more advantageous than the Lagrangian model in the way that numerical results from the Eulerian model can be directly compared with the measurements by the stationary equipment. It is because the wave mass flux is not included in the computed mass flux of Euleran nearshore current model. In addition, the Eulerian model can simulate the longshore currents with depth varying parabolic profile. However, the numerical models proposed by different researcher have different forms of the wave stress terms. For example, wave stresses in Newberger and Allen's (2007) model is constant over the depth, while those of Chun (2012) are vertically distributed. In the present study, these wave stress terms were compared against Hamilton et al.'s (2001) laboratory experiments to see the effects of different wave stress terms performed on the computation of nearshore currents.

• Journal of Forest and Environmental Science
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• v.33 no.3
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• pp.187-196
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• 2017

The use of unmanned aerial vehicles (UAV) for the estimation of tree height is gaining recognition. This study aims to assess the effectiveness of tree height estimation of Pinus densiflora Sieb. et Zucc. and Pinus koraiensis Sieb. et Zucc. using digital surface model (DSM) generated from UAV-acquired imageries. Images were taken with the $Trimble^{(R)}$ UX5 equipped with Sony ${\alpha}5100$. The generated DSM, together with the digital elevation model (DEM) generated from a digital map of the study areas, were used in the estimation of tree height. Field measurements were conducted in order to generate a regression model and carry out accuracy assessment. The obtained coefficients of determination (R2) and root mean square error (RMSE) for P. densiflora (R2=0.71; RMSE=1.00 m) and P. koraiensis (R2=0.64; RMSE=0.85 m) are comparable to the results of similar studies. The results of the paired two-tailed t-test show that the two tree height estimation methods are not significantly different (p-value=0.04 and 0.10, alpha level=0.01), which means that tree height estimation using UAV imagery could be used as an alternative to field measurement.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.309-316
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• 2014

A large particle accelerator requires an ultrahigh vacuum (UHV) system of average pressure under $1{\times}10^{-7}$ Pa for mitigating the impact of beam scattering from the residual gas molecules. The surface inside the beam ducts should be controlled with an extremely low thermal outgassing rate under $1{\times}10^{-9}Pa{\cdot}m^3/(s{\cdot}m^2)$ for the sake of the insufficient pumping speed. To fulfil the requirements, the aluminum alloys were adopted as the materials of the beam ducts for large accelerator that thanks to the good features of higher thermal conductivity, non-radioactivity, non-magnetism, precise machining capability, et al. To put the aluminum into the large accelerator vacuum systems, several key technologies have been developed will be introduced. The concepts contain the precise computer numerical control (CNC) machining process for the large aluminum ducts and parts in pure alcohol and in an oil-free environment, surface cleaning with ozonized water, stringent welding process control manually or automatically to form a large sector of aluminum ducts, ex-situ baking process to reach UHV and sealed for transportation and installation, UHV pumping with the sputtering ion pumps and the non-evaporable getters (NEG), et al. The developed UHV technologies have been applied to the 3 GeV Taiwan Photon Source (TPS) and revealed good results as the expectation. The problems of leakage encountered during the assembling were most associated with the vacuum baking which result in the consequent trouble shootings and more times of baking. Then the installation of the well-sealed UHV systems is recommended.

• Korean Journal of Environmental Agriculture
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• v.27 no.4
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• pp.413-420
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• 2008

The phytosociological study was carried out to investigate the structural characteristics of paddy levee vegetation in South Korea. The vegetation data of total 59 releves were analyzed by the Zurich-Montpellier school's method. 6 syntaxa (3 associations and 3 communities) of paddy levee were recognized : Echinochlo-Digitaretum ciliaris ass. nov. hoc., Artemisia princeps-Erigeron annus community, Imperata cylindrica v. koenigii community, Glycine soja-Humulus scandens community, Miscantheum sinensis f. purpurascens ass. nov. hoc,, Polygonetum thunbergii Lohm. et Miyawaki 1962. Detrended correspondence analysis(DCA) showed that Artemisia princeps-Erigeron annus community and Imperata cylindrica v. koenigii community were positively correlated with soil hardness. Polygonetum thunbergii Lohm. et association and Miscantheum sinensis f. purpurascens ass. nov. hoc. was intimately correlated with high soil total nitrogen.

• Resources Recycling
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• v.28 no.4
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• pp.37-43
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• 2019

Due to environment problems in end of Life Vehicle in the country, the interest in remanufacturing is heightened than ever. In this study, it is important to quantitatively evaluate the economic effect of the introduction of the automotive remanufacturing business and analyzed cost-benefit for the three species of bumpers, doors, fenders, which is relatively lower remanufactured automotive component. The results showed that cost-beneift of each parts were analyzed 54,000 per one part, and if remanufacturing were 50%, benefits were to occur with a profit of 226,060 won. Thus, remanufacturing of bumpers, doors, fender resulted a significant benefit, and then it is possible that remanufacturing company have enough economic value for remanufacturing.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.5
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• pp.492-502
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• 2021

In electronic warfare, source enumeration and direction-of-arrival estimation are important. The source enumeration method based on eigenvalues of covariance matrix from received is one of the most used methods. However, there are some drawbacks such as accuracy less than 100 % at high SNR, poor performance at low SNR and reduction of maximum number of estimating sources. We suggested new method based on eigenvalues gaps, which is named AREG(Accumulated Ratio of Eigenvalues Gaps). Meanwhile, FGML(Fast Gridless Maximum Likelihood) which reconstructs the covariance matrix was suggested by Wu et al., and it improves performance of the existing source enumeration methods without modification of algorithms. In this paper, first, we combine AREG with FGML to improve the performance. Second, we compare the performance of source enumeration and direction-of-arrival estimation methods in Rayleigh fading. Third, we suggest new method named REG(Ratio of Eigenvalues Gaps) to reduce performance degradation in Rayleigh Fading environment of AREG.