• Carbon letters
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• v.14 no.3
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• pp.190-192
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• 2013

It has been demonstrated in a previous study that carbon nanotube (CNT)/epoxy/basalt composites produce better flexural properties than epoxy/basalt composites. In this study, mode I fracture tests were conducted using CNT/epoxy/basalt composites with and without seawater absorption in order to investigate the effect of the seawater absorption on the mode I fracture toughness ($G_{Ic}$) of the CNT/epoxy/basalt composites. The results demonstrated that the compliance of the seawater-absorbed specimen was larger than that of the dry specimen at the same crack length, while the opposite result was obtained for the fracture load. The $G_{Ic}$ value of the seawater-absorbed CNT/epoxy/basalt composites was approximately 20% lower than that of the dry CNT/epoxy/basalt composites.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.93-101
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• 2006

This research makes a new attempt to apply the activated seawater by electrolysis in the development of two-stage wet scrubber system to control the exhaust gas of large marine diesel engines. First, with using only seawater that is naturally alkaline (pH typically around 8.1). the $SO_2\;and\;SO_3$ are absorbed by relatively high solubility compared to other components of exhaust pollutants, and PM (Particulate Matter) is removed through direct contact with sprayed seawater droplets. Besides, the electrolyzed alkaline seawater by electrolysis, which contains mainly NaOH together with alkali metal ions $(i.e.\;Na^+,\;Mg^{2+},\;Ca^{2+})$, is used as the absorption medium of NOx and $CO_2$. Especially, to increase NOx absorption rate into the alkaline seawater. nitric oxide (NO) is adequately oxidized to nitrogen dioxide $(NO_2)$ in the acidic seawater, which means both volume fractions are adjusted to identical proportion. The results found that the strong acidic seawater was a valid oxidizer from NO to $NO_2$ and the strong alkaline seawater was effective in $CO_2$ absorption In the scrubber test, the SOx reduction of nearly $100\%$ could be achieved and also led to a sufficientPM reduction. Hence, the author believes that applying seawater and its electrolyte would bring the marine air pollution control system to an economical measure. Additionally it is well known that NOx and SOx concentration has a considerable influence on the $N_2O$ emission of green house gas. Although the $N_2O$ concentration exhausted from diesel engines is not as high, the green house gas effect is around 300 times greater than an equivalent volume of $CO_2$. Therefore, we investigated the $N_2O$ removal efficiency with using the electrolyzed seawater too. Finally this research would also plan to treat the effluent by applying electro-dialysis and electro-flotation technique s in the future.

• Corrosion Science and Technology
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• v.3 no.2
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• pp.47-53
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• 2004

The conditions to simulate the atmospheric corrosion behavior in the laboratory were investigated to clarify atmospheric corrosion mechanism of steel material in coastal area, For airborne sea salt and artificial seawater droplet, the various behaviors were observed by optical microscope, The particle size of the dried airborne sea salt was about $20{\mu}m$, and was about 1/10 compared with the artificial seawater droplet. Though the airborne sea salt represented the same behavior as the thermodynamic water absorption, the behavior of the artificial seawater droplet deviated from the results of the thermodynamic calculation, It is concluded that the water absorption behavior is influenced by the particle size of the dried sea salt. The corrosion behaviors of carbon steels were observed under the deposited condition of airborne sea salt and artificial seawater droplet. The corrosion behaviors showed a different trend, indicating that the corrosion behavior depended on the particle size of the dried sea salt. The corrosion in the actual environrnent progressed greater than that in the chamber. Furthermore, the summer showed the greater corrosion than the spring. It is found that the corrosion behaviors are attributed to the influence of the environmental factors.

• Proceedings of the KSRS Conference
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• v.1
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• pp.224-227
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• 2006

For estimation of three inherent optical properties (IOPs), the absorption coefficients for phytoplankton ($a_{ph}$) and suspended solid particle ($a_{ss}$) and dissolved organic matter ($a_{dom}$), from ocean reflectance, we used inversion of remote sensing reflectance model (Ahn et al., 2001) at this study. The IOP inversion model assumes that (1) the relationship between remote sensing reflectance ($R_{rs}$) and absorption (a) and backscattering ($b_{b}$) is well known, (2) the optical coefficients for pure water ($a_{w}$, $b_{bw}$) are known, (3) the spectral shapes of the specific absorption coefficients for phytoplankton ($a^*_{ph}$) and suspended solid particle ($a^*_{ss}$) and the specific backscattering coefficients for phytoplankton ($b_b^*_{ph}$) and suspended solid particle ($b_b^*_{ss}$) are known. The input data of IOP inversion model is used in-situ ocean optical data at the seawater around the Korea Peninsula for 5 years (2001-2005). We compared the output data of the IOP inversion model and the in-situ observation for seawater around the Korea Peninsula.

• Journal of Environmental Health Sciences
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• v.33 no.4
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• pp.325-337
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• 2007

The effect of seawater and air pollutants on the three-story stone pagodas on Gameunsa Temple Site have been studied in order to establish conservation basic plan. Also, an experimental study has been conducted to evaluate the effect of seawater salt and air pollutants on the weathering of granite. The results could be summarized as follows. Because the three-story stone pagodas on Gameunsa Temple Site are located outdoors, the external appearance has been largely deteriorated due to natural and artificial factors such as typhoon, wind, microorganisms, moisture, extreme change in temperature, air pollutants, and seawater, etc. When G.J fresh granite was dipped into the seawater, dissolution rate of three minerals (Mg, Ca, and K) are increased linearly until about 40 days and then increased abruptly. After seawater dipping experiments, the mineral compositions of the granite surface were lower then that of the G.J fresh granite but Poisson's ratio and absorption ratio were slightly increased. Therefore, from these results we can say that stone cultural properties could be weathered by seawater and air pollutants and it's considered being a meaningful experiment to study the conservation method of stone cultural properties from seawater.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.81-87
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• 2006

In marine air pollution control, SCR (Selective Catalytic Reduction) is reconized as the most effect method to control NOx, but on the other hand. seawater scrubber applying the basic characteristic that is naturally alkaline (pH typically around 8.1) is viewed as an economical SOx removal system at present. Especially, seawater scrubber would not be necessary to follow any of the various land based flue gas desulfurization methods. i.e. wet, dry or alkali scrubbing. However, these methods are not readily adaptable to marine conditions due to the quantifies of consumables required i.e. lime or limestone, the means of operation and the commercial availability. This research is undertaken to develop a new method as the main target of eliminating all exhaust emissions, particularly vessel, because of easy access to seawater and apt to apply a wet scrubber system. First, using the acidic seawater by seawater electrolysis, nitric monoxide(NO) is adequately oxidized to nitric dioxide $(NO_2)$by ClOx-in the acidic seawater, the electrolyzed alkaline seawater by electrolysis which contains mainly NaOH together with alkali metal ions $(i.e\;Na^{+}\;K^{+},\;Mg_{2}\;^{+},\;Ca_{2}\;^{+})$, is used as the absorption medium of NOx, the SOx are absorbed by relatively high solubility compared to other components of exhaust pollutants. The results found that the NOx and SOx removals could be achieved nearly Perfect.

• ETRI Journal
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• v.42 no.4
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• pp.575-584
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• 2020

Electromagnetic (EM) waves used to send signals under seawater are normally restricted to low frequencies (f) because of sudden exponential increases of attenuation (𝛼) at higher f. The mathematics of EM wave propagation in seawater demonstrate dependence on relative permeability (𝜇_r), relative permittivity (𝜀_r), conductivity (𝜎), and f of transmission. Estimation of 𝜀_r and 𝜎 based on the W. Ellison interpolation model was performed for averaged real-time data of temperature (T) and salinity (S) from 1955 to 2012 for all oceans with 41 088 latitude/longitude points and 101 depth points up to 5500 m. Estimation of parameters such as real and imaginary parts of 𝜀_r, 𝜀_r', 𝜀_r", 𝜎, loss tangent (tan 𝛿), propagation velocity (V_p), phase constant (𝛽), and α contributes to absorption loss (L_a) for seawater channels carried out by using normal distribution fit in the 3 GHz-40 GHz f range. We also estimated total path loss (L_PL) in seawater for given transmission power P_t and antenna (dipole) gain. MATLAB is the simulation tool used for analysis.

• Advances in concrete construction
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• v.14 no.3
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• pp.205-214
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• 2022

Due to seawater's physical and chemical deterioration effects on concrete structures, it is crucial to investigate the durability of these structures in marine environments. In some conditions, concrete structures are exposed to seawater from the first days of construction or because of the lack of potable water, part of the concrete curing stage is done with seawater. In this research, the effects of exposure to seawater after 7 days of curing in standard conditions were evaluated. To improve the durability of concrete, fly ash has been used as a substitute for a part of the cement in the mixing design. For this purpose, 5, 15, and 30% of the mixing design cement were replaced with type F fly ash, and the samples were examined after curing in seawater. The resistance of concrete against chloride ion penetration based on the rapid chloride penetration test (RCPT), water permeability based on the depth of water penetration under pressure, and water absorption test was done. The changes in the compressive strength of concrete in different curing conditions were also investigated. The results show that the curing in seawater has slightly reduced concrete resistance to chloride ion permeation. In the long-term, samples containing FA cured in seawater had up to 10% less resistance to chloride ion penetration. The amount of reduction in chloride ion penetration resistance was more for samples without FA. Whiles, for both curing conditions in the long-term up to 15%, FA improved the chloride ion penetration resistance up to 40%. Curing in seawater slightly increased the penetration depth of water under pressure in samples containing FA, while this increase was up to 12% for samples without FA. In the long-term the compressive strength of samples cured in seawater is not much different from the compressive strength of samples cured in plain water, while at the age of 28 days, due to seawater salts' accelerating effects the difference is more noticeable.

• Proceedings of the KSRS Conference
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• v.1
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• pp.479-482
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• 2006

The absorption coefficient and backscattering properties of phytoplankton were calculated from the Mie theory. Given a simple case that phytoplankton and mineral particles are the only constitutions in seawater, the reflectance $b_b({\lambda})/[a({\lambda})+b_b({\lambda})]$was analyzed. Then the chlorophyll concentrations were estimated from remote sensing OC2 algorithm. The results show that reflectance in short wavelength region is more sensitive to the Chl variation; High mineral concentrations in seawater have significant influence on the reflectance spectrum; the existence of high mineral concentration may result in the mistake in chlorophyll estimation from OC2 algorithm.

• Current Optics and Photonics
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• v.7 no.2
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• pp.136-146
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• 2023

Based on calculations using the macroscopic Maxwell's equations with mesoscopic boundary conditions, light absorption by a layered metal-insulator-metal (MIM) metamaterial system embedded in three different environments is investigated. Increasing the top metal thickness shifts the broad absorption band to lower dielectric-constant regions and longer wavelengths, for either TM or TE waves. Boosting the dielectric-layer thickness redshifts the broadband absorption to regions of larger dielectric constant. In air, for the dielectric-constant range of 0.86-3.40, the absorption of the system exceeds 98% across 680-1,033 nm. In seawater with optimized dielectric constant, ≥94% light absorption over 400-1,200 nm can be achieved; particularly in the wavelength range of 480-960 nm and dielectric-constant range of 0.82-3.50, the absorption is greater than 98%. In an environment with even higher refractive index (1.74), ≥98% light absorption over 400-1,200 nm can be achieved, giving better performance. The influence of angle of incidence on light absorption of the MIM system is also analyzed, and the angle tolerance for ≥90% broadband absorption of a TM wave is up to 40° in an environment with large refractive index. While the incident-angle dependence of the absorption of a TE wave is nearly the same for different circumstances, the situation is different for a TM wave.