• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.483-491
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• 2009

In this study, a jetty construction is taken into account for the reduction of sediment diffusive concentration incoming from the upstream river due to the urbanization and industrial development and to minimize the effects on the coastal ecosystems. The field observation and numerical calculation are conducted to analyze the diffusion zone of sediment concentration in the small estuary and coastal area. The specification of the installed jetty which is able to control the sediment concentration was decided based on the prediction of the dispersion area changes in space and time. The selected size and layout for the jetty design were examined for the dispersion zone by numerical calculation and field observation. As a result, the jetties constructed in the estuary retarded the dispersion rate of sediment concentration, so that the effect area of sediment dispersion was obviously decreased. In addition, the measured field data indicated that the sediment deposition in the inside of dikes could be controlled and the right side area of jetties could be preserved without influx sediment diffusion.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.11
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• pp.613-625
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• 2017

For two agricultural reservoirs that are rented for fishing spots, benthic nutrient fluxes experiment were performed two times with two sediments from fishing-effective zone and one sediment from fishing-ineffective zone using laboratory core incubation in oxic and anoxic conditions. During benthic nutrient fluxes experiment, the changes in DO, EC, pH, and ORP in the supernatant were not significantly different between fishing-effective zone and fishing-ineffective zone, and were similar to the sediment-hypolimnetic diffused boundary layer in agricultural reservoir. Except for $NO_3{^-}-N$, more benthic nutrient fluxes of $NH_4{^+}-N$, T-P, and $PO{_4}^{3-}-P$ from sediment to hypolimnetic was measured in anoxic than in oxic conditions (p<0.05). As the DO concentration in hypolimnetic decreases, the microorganism-mediated ammonification is promoted, the nitrification is suppressed, and finally the $NH_4{^+}-N$ diffuses out from sediment to hypolimnetic. Also, the diffusion of T-P and $PO{_4}^{3-}-P$ from sediments to hypolimnetic is accelerated through the dissociation of the phosphorus bound to both organic matters and metal hydroxides. The difference in the benthic nutrient diffusive fluxes between fishing-effective zone and fishing-ineffective zone was not statistically significant (p>0.05). Therefore, it was found that fishing activities did not increase the benthic nutrient diffusive fluxes to a statistically significant level. Due to the short fishing activities of 10 years and the rate-limited diffusion of the laboratory core incubation, the contribution of fishing activities on sediment pollution is estimated to be low. No significant correlation was found between the total amount of nutrients in sediment and the benthic nutrient diffusive fluxes in both aerobic and anaerobic conditions. Therefore, nutrients input from various nonpoint sources of watersheds are considered to be a more dominant factor rather than fishing activities in water quality deterioration, and both aeration and water circulation in hypolimnetic were required to suppress the anoxic environment in agricultural reservoirs.

• Computers and Concrete
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• v.22 no.3
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• pp.319-326
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• 2018

RC (Reinforced Concrete) members are always subjected to loading conditions and have construction joints when constructed on a big scale. Service life for RC structure exposed to chloride attack is usually estimated through chloride diffusion test in sound concrete, however the test is performed without consideration of effect of loading and joint. In the present work, chloride diffusion coefficient is measured in concrete cured for 1 year. In order to evaluate the effect of applied load, cold joint, and mineral admixtures, OPC (Ordinary Portland Cement) and 40%-replaced GGBFS (Ground Granulated Blast Furnace Slag) concrete are prepared. The diffusion test is performed under loading conditions for concrete containing cold joint. Investigating the previous test results for 91 days-cured condition and the present work, changing diffusion coefficients with applied stress are normalized considering material type and cold joint. For evaluation of service life in RC continuous beam with 2 spans, non-linear analytical model is adopted, and service life in each location is evaluated considering the effects of applied stress, cold joint, and GGBFS. From the work, varying service life is simulated under various loading conditions, and the reduced results due to cold joint and tensile zone are quantitatively evaluated. The effect of various conditions on diffusion can provide more quantitative evaluation of chloride behavior and the related service life.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.114-116
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• 2005

Natural attenuation has been actively studied and often selected as final clean-up process in remediation of contaminated ground-water and soil for the last decade. Accordingly, understanding of natural processes affecting the fate and transport of contaminants in the subsurface becomes important for a success of implementation of the natural remediation strategy, Contaminant advection and diffusion processes in the unsaturated zone are naturally related to environmental changes in the atmosphere. The atmospheric pressure changes affecting the transport of contaminants in the subsurface are investigated in this study. Moisture content, trichloroethylene (TCE) concentration, temperature, and pressure variations in the subsurface were measured for the July, August, November, and December 2001 at Picatinny Arsenal, New Jersey. These data were used for a one-phase flow and one-component transport model in simulating the soil-gas flow and accordingly the TCE transport in the subsurface in accordance with the atmosphere pressure variations at the surface. The soil-gas velocities during the sampling periods varied with a magnitude of $10^{-6}\;to\;10^{-7}\;m\;s^{-1}$ at land surface. The TCE advection fluxes at land surface were several orders of magnitude smaller than the TCE diffusion fluxes. A sensitivy analysis indicated that advection fluxes were more sensitive to changes in geo-environmental conditions compared to diffusion fluxes. Of all the parameters investigated in this study, moisture content has the most significant effect on TCE advection and diffusion fluxes.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.419-426
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• 1999

It is essential for port planning, coastal zone management and environmental impact study to analyze the variation of current and water quality due to the development of water area and discharged water from estuary barrage and basin etc. Mokpo sea area downstreams from a long river and two large basins, the Yongsan river and Yongam-Kumho basins discharging much of water through water gates for the purpose of flood control and prohibition of salt intrusion to the inland fresh water area. In this study, the numerical calculations were carried out for the analysis of diffusion characteristics due to discharging operation, adapting the results of tidal current simulation ADI methord is applied to the governing equation for the movement of sea water and diffusion and 6-point method to the advection terms of diffusion equation. As the results of this study, it is known that the discharging operation causes increasing and/or decreasing of current velocity and enlarging and/or depressing of pollutant diffusion limits depending on the distance from the discharging gates and the mode of discharging operation. To utilize these result, the linked gate operation and the method increasing exchange of sea water must be considered.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.253-261
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• 1999

It is essential for port planning, coastal zone management and environmental impact study to analyze the variation of current and water quality due to the development of water area and discharged water from the estuary barrage and basin, etc. Mokpo sea area has downstream from a long river and two large basins, the Yongsan river and Yongam-Kumho basins, discharging much of water through water gates for the purpose of flood and prohibition of salt intrusion to the inland fresh water area. In this study, the numerical calculation were carried out for the analysis of diffusion characteristics due to discharging operation, adopting the results of tidal current simulation. ADI method is applied to the governing equation for the movement of sea water and diffusion and 6-point method to the advection terms of diffusion equation. As the results of this study, it is known that the discharging operation causes increasing and/or decreasing of current velocity and enlarging and/or depressing of pollutant diffusion limits depending on the distance from the discharging gates and the modes of discharging operation. To utilize these result, the linked gate operation and the method increasing exchange of sea water must be considered.

• Journal of the Korean GEO-environmental Society
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• v.12 no.6
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• pp.25-34
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• 2011

Dredged and reclaimed ground in progress at the West Coast has a high content of coarse particles. There will be different behaviors depending on the location of outlet and engineering properties of soil when its ground is dredged by a pump. Therefore, the experiments were conducted that were manufactured about the chamber equipment of length 2,650mm, width 770mm, height 735mm, experimented step filling method and water content about 300%, 500% and 700% respectively with SM and ML samples in order to realize segregating sediment characteristics of dredged ground with changing much fine. With results of analysis, ML sample by higher initial water content was reached to the period of complete sedimentation and coefficient of sedimentation consolidation increased with increases of diffusion distance. SM samples showed behavior of coarse soil with diffusion distance 120cm, diffusion distance of more than 120cm showed a similar tendency with ML sample under the influence of fines. In ML sample, it could be also found that lower depth and the more increasing diffusion distance increase in percentage of sieve #200 but water content decreases. In SM sample, it could be also found that coarse soil was piled at near the diffusion distance zone but fine soil was piled at the far diffusion distance zone and prominent difference showed between percentage of sieve #200 and water content(%) by boundary point 120cm~160cm of both samples. Also, shear strength was expressed ML-maximum 2.97kPa, SM-maximum 10.2kPa with diffusion distance.

• Economic and Environmental Geology
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• v.26 no.3
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• pp.421-429
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• 1993

Dissolution reactions of chemical grade zinc sulfide and natural sphalerite were studied in ferric chloride solution as an oxidant. To enhance the leaching reaction, ultrasonic technique was employed in this investigation. For the reaction with pure zinc sulfide, chemical reaction was the rate limiting step in the range of low conversion irrespective of applying ultrasonic wave. And the diffusion through liquid film instead of diffusion through product layer of free sulfur was the rate determining step because ultrasonic vibration removes the product from reaction zone. In the case of sphalerite with the ultrasonic vibrator, it was found that inert mineral layer diffusion was the rate determining step, in which the elemental sulfurs formed were removed by the ultrasonic action. Experimental results showed that the ultrasonic technique proved to be the methods which can significants improve the leaching performance.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.320-325
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• 2003

Acoustic-Pressure Response of diluted hydrogen-air diffusion flames is investigated numerically by adopting a fully unsteady analysis of flame structures. In the low-pressure regime, the amplification index remains low and constant at low frequencies. As acoustic frequency increases, finite-rate chemistry is enhanced through a nonlinear accumulation of heat release rate, leading to a high amplification index. Finally, the flame responses decrease at high frequency due to the response lag of the transport zone. For a medium-pressure operation and low-frequency excitation, the amplification index is low and constant. It then decreases at moderate frequencies. As frequency increases further, the amplification index increases appreciably due to an intense accumulation effect.

• Economic and Environmental Geology
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• v.18 no.2
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• pp.139-150
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• 1985

Skarn at the Dielette formed largely in calc-silicate hornfels at the contact with the Flamanville granite. The skarn consists mainly of garnet and pyroxene, and less frequently vesuvianite. Traversing toward calc-silicate hornfels wall rock from a central zone of the skarn, the general sequence of formation of mineral assemblages is: (1) dark brown garnet (2) pale brown garnet-vesuvianite-pyroxene, and (3) pyroxene-prehnite-scapolite-wollastonite envelopes (designated as transition zone) developed between skarn and calc-silicate hornfels. The central zone of the skarn consists mainly of dark brown garnets (garnet I) that contain little or no pyroxene. The pale brown garnet (garnet II) is associated with pyroxene and vesuvianite. The sequence of these garnets results from the zonal growth outward. There is an abrupt discontinuity in composition between garnet I formed in early stage and garnet II in late stage, while each garnet shows relatively uniform composition. At the zone in contact with the granite, the iron contents of garnets decrease toward the marginal zone of the skarn, from an average value of 36 mole % andradite in garnet I to 18 mole % andradite in garnet II. At the zone distant from the granite, the andradite component decreases from 28 mole % in garnet 1 to 19 mole % in garnet II. The variation of the iron contents of pyroxenes is also similar to that of garnets. The sharp discontinuity in composition of garnets and pyroxenes suggests that the skarn of study area was formed by infiltration metasomatic process. The results of the analyses of mineral assemblages of the transition zone by chemical potential diagrams suggest that the transition zone was made by the diffusion of the elements Ca, K and Fe from the skarn to the calc-silicate hornfels contact zone. The estimated temperatures and $Xco_2$ for the formation of the transition zone show $300^{\circ}C$$440^{\circ}C$ and $0.07{\pm}0.05<Xco_2<0.02{\pm}0.01$ at 1 Kb respectively.