• Asian-Australasian Journal of Animal Sciences
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• v.12 no.4
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• pp.629-632
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• 1999

Constructed wetlands are being used for the removal of nutrients from livestock wastewater. However, natural vegetation typically used in constructed wetlands does not have marketable value. As an alternative, agronomic plants grown under flooded or saturated soil conditions that promote denitrification can be used. Studies on constructed wetlands for swine wastewater were conducted in wetland cells that contained either natural wetland plants or a combination of soybeans and rice for two years with the objective of maximum nitrogen reduction to minimize the amount of land required for terminal treatment. Three systems, of two 3.6 by 33.5 m wetland cells connected in series were used; two systems each contained a different combination of emergent wetland vegetation: rush/bulrush (system 1) and bur-reed/cattail (system 2). The third system contained soybean (Glycine max) in saturated-soil-culture (SSC) in the first cell, and flooded rice (Oryza sativa) in the second cell. Nitrogen (N) loading rates of 3 and $10kg\;ha^{-1}\;day^{-1}$ were used in the first and second years, respectively. These loading rates were obtained by mixing swine lagoon liquid with fresh water before it was applied to the wetland. The nutrient removal efficiency was similar in the rush/bulrush, bur-reed/cattails and agronomic plant systems. Mean mass removal of N was 94 % at the loading rate of $3kg\;N\;ha^{-1}\;day^{-1}$ and decreased to 71% at the higher rate of $10kg\;N\;ha^{-1}\;day^{-1}$. The two years means for above-ground dry matter production for rush/bulrushes and bur-reed/cattails was l2 and $33Mg\;ha^{-1}$, respectively. Flooded rice yield was $4.5Mg\;ha^{-1}$ and soybean grown in saturation culture yielded $2.8Mg\;ha^{-1}$. Additionally, the performance of seven soybean cultivars using SSC in constructed wetlands with swine wastewater as the water source was evaluated for two years, The cultivar Young had the highest yield with 4.0 and $2.8Mg\;ha^{-1}$ in each year, This indicated that production of acceptable soybean yields in constructed wetlands seems feasible with SSC using swine lagoon liquid. Two microcosms studies were established to further investigate the management of constructed wetlands. In the first microcosm experiment, the effects of swine lagoon liquid on the growth of wetland plants at half (about 175 mg/l ammonia) and full strength (about 350 mg/l ammonia) was investigated. It was concluded that wetland plants can grow well in at least half strength lagoon liquid. In the second microcosm experiment, sequencing nitrification-wetland treatments was studied. When nitrified lagoon liquid was added in batch applications ($48kg\;N\;ha^{-1}\;day^{-1}$) to wetland microcosms the nitrogen removal rate was four to five times higher than when non-nitrified lagoon liquid was added. Wetland microcosms with plants were more effective than those with bare soil. These results suggest that vegetated wetlands with nitrification pretreatment are viable treatment systems for removal of large quantities of nitrogen from swine lagoon liquid.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.75-81
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• 2012

In case of crushing rock to produce materials for lean concrete subbase layer in concrete pavement, natural sand is used for the gradation adjustment of aggregates, and the percentage of natural sand used is 30%~40% of the weight ratio of aggregate mix. The supply of natural sand that is used in lean concrete as a fine aggregate is getting harder due to the current of exhaustion of source, and the cost for the purchase of natural sand is included in the cost of roadway construction. This study, therefore, was conducted in order to resolve the exhaustion of materials and economize in construction expenditure by the application of screenings, which is by-product of crushing rock in quarry, as an alternative to natural sand. As a result of a comparative analysis on the application of screenings and natural sand with typical types of rock that is produced in domestic, which was conducted in the first year, It is found out that the use of screenings as a fine aggregate showed better unconfined compression strength. Verification of actual application of screenings was conducted in the second year, after test construction and follow-up investigation. The compressive strength, compaction density, settlement of screenings applied case was higher than that of natural sand. Thus, it is expected that application of screenings to construction in field will contribute to the cost saving, material recycling and the protection of environment.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.63-70
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• 2009

This study is part of an ongoing research project on the development of a sound-absorbing lightweight foamed concrete manufactured by a hydro-thermal reaction between silica and calcium. As the silica source, pulverized bottom ash was used, and as several cementitious powders of ordinary portland cement, alumina cement and calcium hydroxide were used. Manufacture of foamed concrete was accomplished using the pre-foaming method to make a continuous pore system, which is the method of making the foam by using a foaming agent, then making the slurry by mixing the foam, water, and powders. The experiment factors are W/B, foam agent dilution ratio, and foam ratio, and test items are compressive strength, dry density, void ratio, and absorption rate, as evaluated by NRC. The experiment results showed that the sound absorption of lightweight foamed concrete satisfied NRC requirements for the absorbing materials in most of the experiments. It is thus concluded that foam ratio was the most dominant factor, and significantly affected all properties of lightweight foamed concrete in this study. W/B rarely affected total void ratio and continuous void ratio as well as compressive strength, and dry density and foam agent dilution ratio also had little effect onalmost all properties. The analysis of the correlation between NRC, absorption time, continuous void ratio, and absorption time showed that the interrelationship of the continuous void ratio was high.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.767-776
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• 2004

Polymer concrete shows excellent mechanical properties and chemical resistance compared with conventional normal cement concrete. The polymer concrete is drawing a strong interest as high-performance materials in the construction industry. Resins using recycled PET offer the possibility of a lower source cost of materials for making useful polymer concrete products. Also the recycling of PET in polymer concrete would help solve some of the solid waste problems posed by plastics and save energy. The purposed of this paper is to propose the model for the stress-strain relation of recycled-PET polymer concrete at monotonic uniaxial compression and is to investigate for the stress-strain behavior characteristics of recycled-PET polymer concrete with different variables(strength, resin contents, curing conditions, addition of silane and ages). The maximum stress and strain of recycled-PET polymer concrete was found to increase with an increase in resin content, however, it decreased beyond a particular level of resin content. A ascending and descending branch of stress-strain curve represented more sharply at high temperature curing more than normal temperature curing. Addition of silane increases compressive strength and postpeak ductility. In addition, results show that the proposed model accurately predicts the stress-strain relation of recycled-PET polymer concrete

• Proceedings of the Korea Society of Poultry Science Conference
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• 2002.11a
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• pp.133-135
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• 2002

This study was designed to investigate the effects of dietary isoflavones(IF) on bone ash content in young chicks. Daidzein(DE) and genistein(GE), aglycone forms of IF, were added to purified-type basal diet containing calcium at 50% of NRC requirement. The two IF at two different levels(1.0 and 2.0 mM) were added to the diets prepared to be very low in IF using soy protein concentrate(SPC) as the only source of protein. The diets Including control with no IF-added were fed for three weeks. One hundred, Hy-Line Brown, day-old male chicks were divided into five dietary groups with four replicates and five chicks per replication. General performances of the chicks were not affected by the dietary treatments. Serum alkaline phosphatase(ALP) activities, an indicator for bone formation, of the birds fed DE diet were lowered compared to those fed GE and control diets. However, the levels of IF did not show any differences in the responses. Bone ash o/o of birds fed the IF diets were significantly increased compared to that of control group (p〈0.05), and, however, not affected by levels of IF in diets. Bone breaking strength measured with an Instron appeared to be equivalent among the birds of all treatments. The observations that equivalences in bone ash o/o and bone breaking strength even with lowered activity of ALP by DE ingestion compared to GE suggest a necessity of further investigation.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.47-51
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• 2001

There are two strategies to cope with the troubles in landfill site after closure. The first method is active in a way that the wastes are dug up and the recyclable materials are reutilized, meanwhile the materials not recyclable are incinerated in order to minimize the volume of residues to be disposed of. The second method is rather passive and defensive in a way that the source of contamination, that is, buried wastes are not treated. Instead, the transport of leaking leachate and gases generated from the wastes are intercepted and controlled. In this study, as a passive way of the efficient leachate blocking process, applicabilities of geocrete and soluble sodium silicate as a substitute to control leachate leaking from landfill sidewall were investigated. In case of compression test, the strength of mixture I (Geocrete:Sodium silicate=1:3.9 v/v) and mixture II (Geocrete:Sodium silicate=1:2.5 v/v), even after 7 days' curing was higher than the minimum allowance to tolerate the loading(5 kg/$\textrm{cm}^2$). Soaking in the acid fur 4 days and 7 days respectively, the compressive strength of the specimens reduced seriously. The toxicity of geocrete is not detected through the bioassay test, once it was mixed with sodium silicate and the complex was formed. The hydraulic conductivity of the mixtures even after 7 days' curing was lower than the threshold limit $(1.0\times10_{-7}cm/s)$.

• Korean Journal of Plant Resources
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• v.22 no.4
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• pp.337-342
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• 2009

Present studies were conducted to evaluate the effects of medium strength(MS and Hyponex), carbon sources and their concentrations, agar concentrations, and inoculation amounts on prothallus propagation of Pterdium aquilinum var. latiusculum(Desv.) Underw. ex Hell in vitro. The optimum MS medium strength for prothallus propagation was 2MS concentration. Phosphate source was most effective for prothallus growth of P. aquilinum var. latisculum. The addition of 1% sucrose or glucose to MS medium promoted prothallus multiplication. Growth of prothallus was not affected by agar concentration. Propagation of homogenized prothallus was vigorous even in liquid medium. Chopped gametophytes(100 and 200 mg) were inoculated on 250 ml ${\Delta}$flask with 100 mL of 2MS concentration medium and suspension culture was done at 100 rpm for 22 days. After 20 days, prothallus multiplication slowed down, so 100 mg of chopped prothalli is recommended for initial inoculation, since initial amount of inoculum did not affect subsequent prothallus multiplication. Consequently after 20 days of suspension culture, prothallus should be subcultured or transplanted outside of growing vessels.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.295-302
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• 2011

The setting time which is the important element for the determination of slip-up speed of Slip-Form system is the hardening time of early-age concrete when the in place concrete has minimum compressive strength before the concrete appears out of Slip-Form system. But it is very difficult to predict the setting time because it depends on not only the composition ratio of concrete but also various conditions of construction fields. Thus, the technique to estimate accurately and continuously the hardening time of early-age in place concrete during operating Slip-Form system is necessary to guarantee the safety of Slip-Form system and the maintenance of the shape of concrete. Ultrasonic wave-based nondestructive testing methods have the advantages which are accurate and continuous in estimating concrete compressive strength. Of such methods, the method using surface wave which propagates along the surface of material is effective for thick member such as a pylon. Thus, in this paper a study on the determination of slip-up speed for Slip-Form system using surface wave velocity is performed. The relation between the slip-up speed of Slip-Form system and the setting time is formulated, and the surface wave velocity is estimated from continuous wavelet transform of the numerical results for surface wave propagation. Finally, the accuracy of this method according to the distance between the wave source and receivers and the relation between the estimated surface wave velocity and the elastic modulus are investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.339-345
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• 2018

We investigated the curing properties of cured coatings for a multi-focal UV-LED. The coatings are for LEDs that operate at multiple UV wavelengths, unlike conventional single-wavelength UV-LEDs. Using UV-LED light sources with wavelengths of 365, 395, 420, and 450 nm, we analyzed the optical characteristics such as the direction of light flux and light source. We also analyzed the curing characteristics at each UV-LED wavelength to optimize the LED for composite wavelengths. The curing performance state was predicted through computer simulation for when the multiple wavelengths of UV light sources are superimposed, and then actual LEDs were designed and fabricated. To improve the internal high-speed curing, a multi-spot module was fabricated, in which each LED is condensed, and multiple wavelengths are synthesized and condensed at the same position. The adhesive strength, surface hardness, and internal hardness of the curing agent were tested by varying the wavelength combination conditions. The surface hardening and internal hardening were compared and analyzed using a hardness tester and FT-IR analyzer. As a result, the characteristics of the surface and internal hardness were improved by a multi-spot method in which four wavelengths were overlapped in a UV-LED rather than a single wavelength.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.6
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• pp.818-829
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• 2013

The collection of rainwater samples was made at Jeju area during 2009~2010, and the major ionic species were analyzed. In the comparison of ion balance, conductivity, and acid fraction for the validation of analytical data, the correlation coefficients showed a good linear relationship within the range of 0.966~0.990. The volume-weighted mean pH and electric conductivity were 4.9 and $17.8{\mu}S/cm$, respectively, at the Jeju area. The volume-weighted mean concentrations of ionic species in rainwater were in the order of $Cl^-$ > $Na^+$ > $nss-SO_4{^{2-}}$ > $NH_4{^+}$ > $NO_3{^-}$ > $Mg^{2+}$ > $H^+$ > $nss-Ca^{2+}$ > $HCOO^-$ > $K^+$ > $PO_4{^{3-}}$ > $CH_3COO^-$ > $NO_2{^-}$ > $F^-$ > $HCO_3{^-}$ > $CH_3SO_3{^-}$. The ionic strength of rainwater was $0.26{\pm}0.21$ mM during the study period. The composition ratios of ionic species were such as 50.1% for the marine sources ($Na^+$, $Mg^{2+}$, $Cl^-$), 30.9% for the anthropogenic sources ($NH_4{^+}$, $nss-SO_4{^{2-}}$, $NO_3{^-}$), and 4.7% for the soil source ($nss-Ca^{2+}$), and 3.1% for organic acids ($HCOO^-$, $CH_3COO^-$). From the seasonal comparison, the concentrations of $NO_3{^-}$, $nss-Ca^{2+}$, and $nss-SO_4{^{2-}}$ increased in winter and spring seasons, indicating a reasonable possibility of long range transport from Asia continent. Especially, the acidifying contributions by major inorganic acids ($nss-SO_4{^{2-}}$ and $NO_3{^-}$) and organic acids ($HCOO^-$ and $CH_3COO^-$) were 87.6% and 12.4%, respectively. In comparison by sectional inflow pathway of air mass during the rainy sampling days, the concentrations of $nss-SO_4{^{2-}}$ and $NO_3{^-}$ were relatively high when the air mass was moved from the China continent into Jeju area.