• Korean Journal of Environmental Agriculture
• /
• v.18 no.4
• /
• pp.355-360
• /
• 1999

In order to identify the effect of cadmium uptake by soil ameliorators in rice plants, compost, lime, silicate, and phosphate were treated. Plants were grown with irrigation water containing $0.01mg\;l^{-1}$ cadmium and treated with two irrigation systems, intermittent irrigation and continuous submersion. Soil pH was higher at the panicle formation stage compared to other growing stages. However, Eh value was decreased as growing stage was proceeded. Eh values measured at the continuous submersion plots were lower than those at the intermittent irrigation plots. Cadmium contents in the both leaves and roots of rice plants grown at the continuous submersion plots were lower than intermittent irrigation plots in the middle of growing season. Among the continuous submersion plots, cadmium uptake was highly reduced at the both silicate and lime treated plot compared to other treatments. In the harvest season, cadmium contents in the both leaves and brown rice were higher at the intermittent irrigation plots than the continuous submersion plots. Cadmium uptake was highly reduced at the compost and lime mixture plot compared to other treatments among the continuous submersion plots. Soil pH was negatively correlated with the cadmium contents of the both shoot and brown rice while Eh was positively correlated with those. The cadmium content of shoot was positively correlated with that of brown rice in the harvest season.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.18 no.4
• /
• pp.69-76
• /
• 2010

After feeding mixed samples, VS ranged from 60 to 80% of total costs in 15 days. EC ranged from1.21 to 2.45, 1.25 to 2.1 and 1.2 to 1.88mS/cm when worms were fed with a mixture of by-products of tidal current and sewage sludge, a mixture of by-products of algae producy, and food wastes and a mixture of by-products of algae producy, sewage sludge and food wastes. That means the kinds of mixture don't have any negative impacts on worms survival. With the feed with a mixture of by-products of algae producy and food wastes and a mixture of by-products of algae producy, sewage sludge and food wastes, pH shows stable 5.4 to 6.7, and 6.2 to 7.4 where is suitable for worms. But a mixture of by-products of algae producy and sewage sludge is out of proper scope for raising worms, in other words, extra care will be necessary. In case of Eh, a mixture of by-products of algae producy and sewage sludge make eh negative (-) in early stage so also when feeding worms, also extra care will be needed. NaCl ranged from 0.32 to 0.82% or form 0.23 to 0.61% when a mixture of by-products of algae producy and food wastes and a mixture of by-products of algae producy, sewage sludge and food wastes were fed. So taking care of salts will be essential whenever feeding.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.68 no.1
• /
• pp.98-101
• /
• 2019

In this paper, we propose the power-based pipelined-forwarding MAC protocol which can select relay nodes according to the residual power and energy harvesting rate in EH-WSN (energy-harvesting wireless sensor networks). The proposed MAC follows a pipelined-forwarding scheme in which nodes repeatedly sleep and wake up in an EH-WSN environment and data is continuously transmitted from a high-level node to a low-level node. The sleep interval is adaptively controlled so that nodes with low energy harvesting rate can be charged sufficiently, thereby minimizing the transmission delay and increasing the network lifetime. Simulation shows that the proposed MAC protocol improves the balance of residual power and network lifetime.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.45 no.5
• /
• pp.472-479
• /
• 2012

The formation of volatile fatty acids(VFAs) and changes in pH, oxidation and reduction potential(Eh) and acid volatile sulfide(AVS) with the addition of yellow clay were investigated using microcosm systems to examine the effects of yellow clay dispersion on the anaerobic decomposition of Cochlodinium polykrikoides in marine sediments. The acetate concentration reached a maximum by day 4 and was 1.2-1.8 fold less in the sample treated with yellow clay compared to the untreated sample (224-270 vs. 333 uM). The formate concentration reached a maximum by day 1 and was 1.3-2.8 fold less in the sample treated with yellow clay compared to the untreated sample (202-439 vs. 563 uM). The propionate concentration reached a maximum by day 2 and was 1.5-1.8 fold less in the sample treated with yellow clay compared to the untreated sample (32.6 vs. 57.2 uM). After the amounts of acetate, formate and propionate peaked the levels dropped dramatically due to the utilization by sulfate reducing bacteria. The Eh of the samples treated with yellow clay was similar to the untreated sample on day 0 but was higher in the sample treated with yellow clay(140-206 mV) from days 4 to 17. AVS started to form on day 3 and this was sustained until day 6, and 1.2-2.2 fold less was produced in the sample treated with yellow clay compared to the untreated sample (40.2-69.3 vs. 83.2-93.8 mg/L). Accordingly, during the anaerobic decomposition of C. polykrikoides in marine sediments, yellow clay dispersal seems to suppress the reduction state of Eh and the formation of volatile fatty acids(acetate, formate and propionate) used as an energy source by sulfate reducing bacteria, indicating that this process controls the production of hydrogen sulfide that negatively affects marine organisms and the marine sediment environment.

• Korean Journal of Soil Science and Fertilizer
• /
• v.17 no.1
• /
• pp.35-38
• /
• 1984

A laboratory experiment was carried out to investigate the effects of the additions of lime soluble starch on the behavior of silica in submerged soil. 1. Available silica in the submerged soil was increased as pH come up to neutral condition and Eh decreased. 2. Application of soluble starch accelerating the soil reduction nearly doubled the amount of silica sorbed in soil from silica solution. 3. Silica sorption of soil treated with slaked lime was increased to some extent in the low silica solution but was not showed that constancy in high silica solution. 4. The reaction between amount of silica sorbed in soil and silica concentration in solution followed not Lamgmuir but Freundlich adsorption isotherm.

• Journal of Ocean Engineering and Technology
• /
• v.30 no.4
• /
• pp.268-276
• /
• 2016

This paper presents a study on the crashworthiness of the scaled-down stiffened panels used on a Korean icebreaker. In order to validate the crashworthiness of the panels, this paper provides various mechanical properties such as the results of a CVN test, quasi-static tensile test, and high-speed tensile test at arctic temperatures. Two types of steels (EH32 and FH32) were chosen for the material tests. CVN tests revealed that the two steels were equivalent up to −60℃ in terms of their impact energy absorption capacity. However, the toughness of FH32 was significantly superior to that of EH32. EH32 showed slightly higher flow stresses at all temperature levels compared to FH32. The improvement ratios of the yield strengths, tensile strengths, plastic hardening exponents, etc. for FH32, which were obtained from quasi-static tensile tests, showed an apparent ascending tendency with a decrease in temperature. Dynamic tensile test results were obtained for the two temperatures levels of 20℃ and −60℃ with two plastic strain rate levels of 1 s⁻¹ and 100 s⁻¹. A closed form empirical formula proposed by Choung et al. (2011;2013) was shown to be effective at predicting the flow stress increase due to a strain rate increase.

• Journal of Welding and Joining
• /
• v.30 no.1
• /
• pp.64-71
• /
• 2012

The characteristics of high heat input (342kJ/cm) EG (Electro Gas Arc) welded joint of EH36-TM steel has been investigated. The weld metal microstructure consisted of fine acicular ferrite (AF), a little volume of polygonal ferrite (PF) and grain boundary ferrite (GBF). Charpy impact test results of the weld metal and heat affected zone (HAZ) met the requirement of classification rule (Min. 34J at $-20^{\circ}C$). In order to evaluate the relationship between the impact toughness property and the grain size of HAZ, the austenite grain size of HAZ was measured. The prior austenite grain size in Fusion line (F.L+0.1 mm) was about $350{\mu}m$. The grain size in F.L+1.5 mm was measured to be less than $30{\mu}m$ and this region was identified as being included in FGHAZ(Fine Grain HAZ). It is seen that as the austenite grain size decreases, the size of GBF, FSP (Ferrite Side Plate) become smaller and the impact toughness of HAZ increases. Therefore, the CGHAZ was considered to be area up to 1.3mm away from the fusion line. Results of TEM replica analysis for a welded joint implied that very small size ($0.8\sim1.2{\mu}m$) oxygen inclusions played a role of forming fine acicular ferrite in the weld metal. A large amount of (Ti, Mn, Al)xOy oxygen inclusions dispersed, and oxides density was measured to be 4,600-5,300 (ea/mm2). During the welding thermal cycle, the area near a fusion line was reheated to temperature exceeding $1400^{\circ}C$. However, the nitrides and carbides were not completely dissolved near the fusion line because of rapid heating and cooling rate. Instead, they might grow during the cooling process. TiC precipitates of about 50 ~ 100nm size dispersed near the fusion line.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.40 no.10
• /
• pp.1371-1377
• /
• 2011

This study was carried out to compare the antioxidative effects of various Nandina domestica fruits extracts. Organic fractions, including n-hexane, chloroform, ethyl acetate, and butanol fractions, were obtained from the water and ethanol extracts of N. domestica fruits. The phenolic compound content of the EE fraction was 922.22 mg/g. The flavonoid compound content was highest in the EB fraction (282.49 mg/g). The electron-donating ability was highest (93%) in the WA and EH fractions at 0.1 mg/mL. The SOD-like activity was showed the highest in the EA fraction (56.36%), and EH and EC both showed higher than 50% activity. The nitrite-scavenging ability of the EC fraction at 1.0 mg/mL under pH 1.2 conditions was 82.03%. The xanthine oxidase inhibitory activities of all the fractions, except WE, were higher than 90% at 0.5 mg/mL. The effect of tyrosinase inhibition was highest in the WE fraction (46.75%). These results show that the N. domestica fruits fractions contained high levels of polyphenol and flavonoid compounds, along with excellent antioxidative effects. This suggests that N. domestica fruits can be used as a functional material.

• Korean Journal of Environmental Agriculture
• /
• v.24 no.3
• /
• pp.203-209
• /
• 2005

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.

• Computational Structural Engineering
• /
• v.27 no.1
• /
• pp.34-40
• /
• 2014