• The Journal of Engineering Geology
• /
• v.28 no.4
• /
• pp.565-582
• /
• 2018

We investigated the hydrochemical properties of ChusanYongchulso Spring located in Buk-myeon, Ulleung Island, focusing on the formation and characteristics of aquifers in and around the Nari caldera. Abundant pumice with high permeability and numerous fractures (including faults and joints) that formed as a result of caldera subsidence are widely distributed in the subsurface, favoring the formation of aquifers. Because of the presence of porous pyroclastic rocks with a high internal surface area, the water type of the springs is characterized by $NaHCO_3$, with upper stream waters and the upper spring being characterized by $NaHCO_3$ and NaCl, respectively. Components with a high coefficient of determination with EC are $HCO_3$, Na, F, Ca, Mg, Cl, $SiO_2$, and $SO_4$. The high concentrations of Na and Cl might be attributable to the main lithologies in the area, given that alkaline volcanic rocks are distributed extensively across Ulleung Island. Eh and pH, which are considered to be important indicators of water-rock interaction, are unrelated to most components. According to the results obtained from factor analysis, the variance explained by factor 1 is 54% and by factor 2 is 25.8%. Components with a high loading on factor 1 are F, Na, EC, Cl, $HCO_3$, $SO_4$, $SiO_2$, Ca, $NO_3$, and Mg, whereas components with a high loading on factor 2 are Mg and Ca, along with K, $NO_3$, and DO with negative loadings. It is suggested that the high concentrations of Na, Cl, F, and $SO_4$ are closely related to the presence of fine-grained alkaline pyroclastic rocks with high permeability and porosity, which favorintensewater-rock interaction. However, a wide-ranging investigation that encompasses methods such as geophysical prospecting and geochemical analysis (including isotope, trace-element, and tracer techniques) will be necessary to gain a better understanding of the groundwater chemistry, aquifer distribution, and water cycling of Ulleung Island.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.3 no.2
• /
• pp.79-89
• /
• 1995

Changes of microbial activity and physicochemical environment during composting of papermill sludge(PMS) in the pilot plant equipped with an agitated bed reactor were monitored for establishing the efficient composting system. Microbial activity determined as the evolution of $CO_2$ increased for the first 10 days after introduction of PMS to the reactor and decreased thereafter. Population changes of microorganisms in the reactor-PMS were not typical as in windrow system. The ratio of thermophilic bacteria to mesophilic bacteria, however, increased slowly even 23 days after introduction. Temperature of PMS increased rapidly from the first day and reached $62^{\circ}C$ at 7 days after introduction and decreased slowly thereafter. The acidity of PMS was pH 6.8 initially, increased to pH 8.0 after 7 days and decreased to pH 7.4 after 23 days. Redox potential(Eh) of PMS was -320mV at the beginning of composting, but it was increased with time to reach -15mV after 23 days composting. However, Eh of PMS pre-sterilized before measurement was average 50mV, regardless of composting periods indicating the major role of microorganisms during composting process. Water content of PMS was 67% initially and decreased to about 50% after 23 days composting in the reactor. Less than 13 days-old compost inhibited growth of radish in the container mixture with bed soil. Based on statistical analysis of microbial and physicochemical parameters of PMS during composting, an equation was developed for determining compost maturity. A number of experiments using various organic wastes are required before application of the formular to the practical use.

• Korean Journal of Mineralogy and Petrology
• /
• v.35 no.2
• /
• pp.111-123
• /
• 2022

Carbonate green rust (CGR) and sulfate green rust (SGR) commonly occur in nature. In this study, CGR and SGR were synthesized through co-precipitation, and their formation mechanisms and physicochemical properties were investigated. X-ray diffraction (XRD) and Rietveld refinement showed both CGR and SGR with layered double hydroxide structure were successfully synthesized without any secondary phases under each synthetic condition. Refined structural parameters (unit cell) for two green rusts were a (=b) = 3.17 Å and c = 22.52 Å for CGR and a (=b) = 5.50 Å and c = 10.97 Å for SGR with the crystallite size 57.8 nm in diameter from (003) reflection and 40.1 nm from (001) reflections, respectively. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) results showed that both CGR and SGR had typical hexagonal plate-like crystal morphologies but their chemical composition is different in the content of C and S. In addition, Fourier transform infrared (FT-IR) spectroscopy analysis revealed that carbonate (CO₃^2-) and sulfate (SO₄^2-) molecules were occupied as interlayer anions of CGR and SGR, respectively. These SEM/EDS and FT-IR results were in good agreement with XRD results. Changes in the solution chemistry (i.e., pH, Eh and residual iron concentrations (Fe(II):Fe(III)) of the mixed solution) were observed as a function of the injection time of hydroxyl ion (OH^-) into the iron solution. Three different stages were observed in the formation of both CGR and SGR; precursor, intermediator, and green rust in the formation of both CGR and SGR. This study provides co-precipitation methods for CGR and SGR in a way of the stable synthesis. In addition, our findings for the formation mechanisms of the two green rusts and their physicochemical properties will provide crucial information with researches and industrials in utilizing green rust.

• Korean Journal of Environmental Agriculture
• /
• v.26 no.3
• /
• pp.197-203
• /
• 2007

Zerovalent iron (ZVI) has been widely used in the removal of environmental contaminants from water. The objective of this research was to assess the efficiency of ZVI for immobilization of As (V) in the contaminated water under various chemical conditions. Batch-type experiments showed that the immobilization process followed a first-order kinetic model. Rate constant (k) of the reaction increased consistently and proportionally as increasing ZVI concentrations from 1% (0.158 $hr^{-1}$) to 3% (0.342 $hr^{-1}$), and temperatures from $15^{\circ}C$ (0.117 $hr^{-1}$) to $35^{\circ}C$ (0.246 $hr^{-1}$), respectively. Whereas the rate constant decreased as increasing As (V) concentrations from 1 mg $\Gamma^{-1}$ (0.284 $hr^{-1}$) to 3 mg $\Gamma^{-1}$ (0.153 $hr^{-1}$), and the initial pH from 3 (0.393 $hr^{-1}$) to 9 (0.067 $hr^{-1}$), respectively. Results demonstrated that As (V) in an aqueous solution was rapidly immobilized by ZVI treatments. Zerovalent iron was fast method for remediation of As (V) contaminated water.

• Korean Chemical Engineering Research
• /
• v.56 no.4
• /
• pp.496-523
• /
• 2018

The objective of this study is to evaluate the economic feasibility of two fast pyrolysis and biooil upgrading (FPBU) plants including feed drying, fast pyrolysis by fluidized-bed, biooil recovery, hydro-processing for biooil upgrading, electricity generation, and wastewater treatment. The two FPBU plants are Case 1 of an FPBU plant with steam methane reforming (SMR) for $H_2$ generation (FPBU-HG, 20% yield), and Case 2 of an FPBU with external $H_2$ supply (FPBUEH, 25% yield). The process flow diagrams (PFDs) for the two plants were constructed, and the mass and energy balances were calculated, using a commercial process simulator (ASPEN Plus). A four-level economic potential approach (4-level EP) was used for techno-economic analysis (TEA) under the assumption of sawdust 100 t//d containing 40% water, 30% equity, capital expenditure equal to the equity, $H_2$ price of $1050/ton, and hydrocarbon yield from dried sawdust equal to 20 and 25 % for Case 1 and 2, respectively. TCI (total capital investment), TPC (total production cost), ASR (annual sales revenue), and MFSP (minimum fuel selling price) of Case 1 were $22.2 million, $3.98 million/yr, $4.64 million/yr, and $1.56/l, respectively. Those of Case 2 were $16.1 million, $5.20 million/yr, $5.55 million/yr, and $1.18/l, respectively. Both ROI (return on investment) and PBP (payback period) of Case 1(FPBU-HG) and Case 2(FPBU-EH) were the almost same. If the plant capacity increases into 1,500 t/d for Case 1 and Case 2, ROI would be improved into 15%/yr.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.3
• /
• pp.73-84
• /
• 2011

This is the fifth in a series of companion papers dealing with the dynamic hardening properties of various marine structural steels at intermediate strain rates. Five steps of strain rate levels (0.001, 1, 10, 100, 200/s) and three steps of temperature levels (LT ($-40^{\circ}C$), RT, and HT ($200^{\circ}C$)) were taken into account for the dynamic tensile tests of three types of marine structural steels: API 2W50 and Classifications EH36 and DH36. The total number of specimens was 180 pieces. It was seen that the effects of dynamic hardening became clearer at LT than at RT. Dynamic strain aging accompanying serrated flow stress curves was also observed from high temperature tests for all kinds of steels. The dynamic hardening factors (DHFs) at the two temperature levels of LT and RT were derived at the three plastic strain levels of 0.05, 0.10, 0.15 from dynamic tensile tests. Meanwhile, no DHFs were found for the high temperature tests because a slight negative strain rate dependency due to dynamic strain aging had occurred. A new formulation to determine material constant D in a Cowper-Symonds constitutive equation is provided as a function of the plastic strain rate, as well as the plastic strain level. The proposed formula is verified by comparing with test flow stress curves, not only at intermediate strain rate ranges but also at high strain rate ranges.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.6
• /
• pp.925-927
• /
• 2012

On-site diagnosis applied to soil having a symptom of yellowing and whitening in cucumber leaf and stem. Soil pH determined 4.2 by methods of on-site analysis and 4.5 by soil test analysis. High aluminum in soil solution extracted with water saturation was detected. Leaf and stem tissue were abundant in Al content but not in Ca. Also, N content of leaf and stem was low compared to normal N ranges. This symptom of cucumber assumed to be from the Al and nitrous acid gas toxicity by low soil pH and Eh. Conclusionally, symptom in leaf and stem of cucumber was alleviated and cucumber normally recovered during cultivation period by applying calcium hydroxide solution to correct soil pH up to 6.5. These results showed that low soil pH resulted in aluminum toxicity and N deficiency to plant growth in on-site farming.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.1
• /
• pp.152-167
• /
• 2016

This paper investigates the simultaneous wireless information and power transfer (SWIPT) for two-hop orthogonal frequency division multiplexing (OFDM) decode-and-forward (DF) relay network, where a relay harvests energy from radio frequency signals transmitted by a source and then uses the harvested energy to assist information transmission from the source to its destination. The power splitting receiver is considered at the relay. To explore the performance limit of such a SWIPT-enabled system, a resource allocation (RA) optimization problem is formulated to maximize the achievable information rate of the system, where the power allocation, the subcarrier pairing and the power splitting factor are jointly optimized. As the problem is non-convex and there is no known solution method, we first decompose it into two separate subproblems and then design an efficient RA algorithm. Simulation results demonstrate that our proposed algorithm can achieve the maximum achievable rate of the system and also show that to achieve a better system performance, the relay node should be deployed near the source in the SWIPT-enabled two-hop OFDM DF relay system, which is very different from that in conventional non-SWIPT system where the relay should be deployed at the midpoint of the line between the source and the destination.

• Magazine of the Korea Concrete Institute
• /
• v.8 no.4
• /
• pp.171-179
• /
• 1996

A proposal of the basic fbrm on the design of joint parts that can increase the shear strength by the useful joint shapes of each member is intended. The vertical joint parameters are the number of' shear key and a variety of' reinfbrcement details and the horizontal joint paramctcrs arc t,hc number of shear key and the direction of' shear f'orcc. 10 PC panel vortical joint arid 12 PC panel horizontal joint specimens were tested to investigate the effects of these parameters. Test results show that : 1. The ductility of the test specimen that has the horizontal reinforcing steels is larger than that does not have. 2. The maximum resisting force of round bar specimen is similar to that of strand wire specimen under the condition of fixed horizontal displacement.

• Journal of the Korean Chemical Society
• /
• v.17 no.3
• /
• pp.154-162
• /
• 1973

The rates and activation parameters for the halide $(Cl^{-}, Br^{-}, I^{-})$TeX> exchange reactions of substituted benzenesulfonyl-chloride, $XC_6H_4SO_2Cl$(X:p-MeO, H, p-Cl, p-Br, p-NO$_2l$) in dry acetone at two temperatures have been determined. It was found that the ion-pair of metal halide,$M^{+}X^{-}$, have negligible reactivity compared to free halide ions. It was also found that the nucleophilic order is $Cl^{-}>Br^{-}>I^{-}$for electron-donating substituent, and $Cl^{-}>I^{-}>Br^{-}$ for electron-withdrawing substituents. These results and convex nature of the Hammett plot are interpreted in the light of simple $S_N2$mechanism with the bond breaking becoming important for compounds with the electron withdra-wing substituents.