• Journal of the Korean GEO-environmental Society
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• v.25 no.5
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• pp.29-37
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• 2024

This study aimed to investigate the changes in chemical components that occur when weak clay is mixed with steel slag modified with calcium oxide, and to understand the expression characteristics of compressive strength according to hydrophilicity and curing time. XRF testing, SEM imaging, vane shear strength and uniaxial compressive strength testing were conducted. Calcium (Ca) released from the steel slag increases the Ca content in clay by increasing the number of crystal particles and forming a coating layer known as calcium silicate hydrate (CaO-SiO₂-H₂O) through chemical reactions with SiO₂ and Al₂O₃ components. The weak clay stabilized with steel slag is classified into an initial inactive zone where strength relatively does not increase and an activation zone where strength increases over curing time. The vane shear strength of the initial inactive area was found to be 4.4 to 18.4 kN/m² in the state of the weight mixing ratio Rss 30% (steel slag 30% + clay 70%). In the case of the active area, the maximum uniaxial compressive strength increased to 431.8 kN/m² after 480 hours of curing time, which increased due to the apparent adhesion strength of clay through pozzolanic reaction. Therefore, considering the strength expression characteristics of stabilized mixed clay based on the mixing ratio (Rss) during the recycling of steel slag can enhance its practicality in civil engineering sites.

• Computers and Concrete
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• v.33 no.5
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• pp.605-619
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• 2024

The increase of reclaimed asphalt pavement (RAP) content in recycled asphalt concrete (RAC) is accompanied by the degradation of low-temperature cracking resistance, which has become an obstacle to the development of RAC. This paper aims to reveal the meso-scale mechanisms of the low-temperature fracture behavior of RAC and provide a theoretical basis for the economical recycling of RAP. For this purpose, micromechanical heterogeneous peridynamic model of RAC was established and validated by comparing three-point bending (TPB) test results against corresponding numerical simulation results of RAC with 50% RAP content. Furthermore, the models with different aggregate shapes (i.e., average aggregates circularity (${\bar{C_r}}=1.00$, 0.75, and 0.50) and RAP content (i.e., 0%, 15%, 30%, 50%, 75%, and 100%) were constructed to investigate the effect of aggregate shape and RAP content on the low-temperature cracking resistance. The results show that peridynamic models can accurately simulate the low-temperature fracture behavior of RAC, with only 2.9% and 13.9% differences from the TPB test in flexural strength and failure strain, respectively. On the meso-scale, the damage in the RAC is mainly controlled by horizontal tensile stress and the stress concentration appears in the interface transition zone (ITZ). Aggregate shape has a significant effect on the low-temperature fracture resistance, i.e., higher aggregate circularity leads to better low-temperature performance. The large number of microcracks generated during the damage evolution process for the peridynamic model with circular aggregates contributes to slowing down the fracture, whereas the severe stress concentration at the corners leads to the fracture of the aggregates with low circularity under lower stress levels. The effect of RAP content below 30% or above 50% is not significant, but a substantial reduction (16.9% in flexural strength and 16.4% in failure strain) is observed between the RAP content of 30% and 50%. This reduction is mainly attributed to the fact that the damage in the ITZ region transfers significantly to the aggregates, especially the RAP aggregates, when the RAP content ranges from 30% to 50%.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.30 no.1
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• pp.1-14
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• 2024

As awareness of environmental issues continues to grow, there is an escalating demand for recycling and repurposing byproducts of agricultural and food production processes and their conversion to high-value products. Coffee is the most widely consumed beverage globally; during coffee beverage processing and consumption, byproducts such as coffee silverskin (CS), spent coffee grounds (SCGs), and oil are generated. Despite containing beneficial materials such as cellulose, hemicellulose, lignin, lipids, and bioactive substances, these byproducts are typically discarded in landfills or incinerated. The utilization of CS, SCGs, and oil in the development of packaging materials holds significant potentials toward the realization of a sustainable society. To this end, considerable research efforts have been dedicated to the development of high-value materials derived from coffee byproducts, including functional fillers, polymer composites, and biodegradable polymers. Notably, CS and SCGs have been employed as functional fillers in polymer composites. Additionally, lipids extracted from SCGs have been used as plasticizers for polymers and cultured with microorganisms to produce biodegradable polymers. This review focuses on the research and development of polymer/CS and polymer/SCG composites as well as cellulose extraction and utilization from CS and SCGs and its applications, oil extraction from SCGs, and cultivation with microorganisms using extracted oil for polyhydroxyalkanoates(PHA) production.

• Journal of Environmental Health Sciences
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• v.30 no.4
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• pp.329-343
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• 2004

We conducted to investigate citizen's attitude to the treatment of food waste in Yongin city. The respondent of $41.81\%$ throws the food waste eliminate from home and store less than 1l in Yongin. When they dump the food waste, they speak out the inconvenience of damaged envelope by animals in case of home and store. This caused troubles for reason of sanitary. So a local autonomous entity must carefully consider of expand use specially designed container as like apartment house. They give an answer that the collecting time of food waste is suitable form dawn till morning. This answer shows the satisfaction of the period time to collect the food waste. They prefer to be appointed the exclusive place to collect food waste. The service interval of collect is suitable 1 time a day. They want to increase the number of washing of the collecting container. This is good method for sanitary condition, but the care of the period time to collect the food waste is more efficient than the care of the number of washing the collecting container. The care of the period time minimizes to incur the enmity of the people and to pollute in environment. The major of respondent handled the food waste after keeping the basket or a kit. This fact shows to us almost citizen doesn't feel the seriousness to remove the moisture of the food waste. Recently, many solutions which can be disposal efficiently are getting magnified and improved owing to increase utilities channel to loss in quantities and dry the food waste. We expect the reduction of food waste is solved getting easily step by step. The results of the awareness about the facility of food waste show citizen prefer recycling facility to the other facilities. If recycle facility and incineration facility are constructed, they were worried about bed smell. When some facility of the food waste is constructed, they have to maintain and to handle not to incur the enmity of the people. The spread rate of specially designed container already increased, the citizen set a high value on the use of specially designed container more than amount-rate vinyl envelope that people have used for several years. In the cost treatment about food waste, the major respondent answered the use cost of specially designed container is suitable price. So we can know the use charge is proper level. The majority of citizen more prefer autonomous plan which voluntary atmosphere creation and public information by mass media than levy system and rising treatment cost which forced plan. The citizens have pretty positive thinking of incineration, so the government needs more efforts for a public notice, which includes the incineration is no more than abandoned thing. Each of local self government has to sort the food waste and make kind of resource system related to collecting and carrying, constructing a suitable facility, proper disposal of the food waste and producing harmless in our surrounding in order to solve the invisible problems. To do above mentioned things, we have to analyze referred several problems till now. Also, to minimize the side effect, the government will have to improve through enforce the system.

• 한국해양학회지
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• v.23 no.4
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• pp.194-206
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• 1989

Seasonal variations of nutrients (ammonium, nitrite, nitrate, phosphate and silicate), primary productivity and ammonium regeneration rate of macrozooplankton were investigate to understand the relationship between nitrogen recycling and nitrogen requirement by phytoplankton from Feburuary 1986 to November 1987 in the Kyunggi Bay, shallow estuarine water of Yellow Sea. In general, nutrients increased during the winter and depleted during the spring and the early summer except temporally sharp increase after flood in September. Ammonium was prevalently generally found in high concentration throughout the study area and it occasionally raised N/P ratio in the range of 30 to 70 as in the freshwater environment. Daily net primary productivity ranged from 30.3 to 3580.0 mgC/$m^2$/d with an average of 883.9 mgC/$m^2$/d. Annual primary productivity was determined to be 320.0 gC/$m^2$/yr. Carbon assimilation number ranged from 2.9 to 19.4 mgC/mg chl-a/h which increased in the summer and decreased in the winter. Nitrogen requirement by phytoplankton ranged from 0.4 to 45.0 mg at-N/$m^2$/d and turnover time of inorganic nitrogen ranged from 2.4 in the late summer to 122.7 days in the winter. Nitrogen regeneration rate of mixed macrozooplankton determined by bottle incubation method ranged from 0.02 to 1.34 mg at-N $m^2$/d and it could contribute from 2.8 to 38.7% with an annual average of 14.9% of total nitrogen requirement by phytoplankton in this shallow estuarine environment.

• Journal of the Mineralogical Society of Korea
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• v.27 no.1
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• pp.17-30
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• 2014

Waste cement generated from recycling processes of waste concrete is a potential raw material for mineral carbonation. For the $CO_2$ sequestration utilizing waste cement, this study was conducted to obtain basic information on the aqueous carbonation methods and the characteristics of carbonate mineral formation. Cement paste was made with W:C= 6:4 and stored for 28 days in water bath. Leaching tests using two additives (NaCl and $MgCl_2$) and two aqueous carbonation experiments (direct and indirect aqueous carbonation) were conducted. The maximum leaching of $Ca^{2+}$ ion was occurred at 1.0 M NaCl and 0.5 M $MgCl_2$ solution rather than higher tested concentration. The concentration of extracted $Ca^{2+}$ ion in $MgCl_2$ solution was more than 10 times greater than in NaCl solution. Portlandite ($Ca(OH)_2$) was completely changed to carbonate minerals in the fine cement paste (< 0.15 mm) within one hour and the carbonation of CSH (calcium silicate hydrate) was also progressed by direct aqueous carbonation method. The both additives, however, were not highly effective in direct aqueous carbonation method. 100% pure calcite minerals were formed by indirect carbonation method with NaCl and $MgCl_2$ additives. pH control using alkaline solution was important for the carbonation in the leaching solution produced from $MgCl_2$ additive and carbonation rate was slow due to the effect of $Mg^{2+}$ ions in solution. The type and crystallinity of calcium carbonate mineral were affected by aqueous carbonation method and additive type.

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.111-118
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• 2014

The electrochemical properties using the cells assembled with the synthesized $LiCoO_2$(LCO) were evaluated in this study. The LCO was synthesized from high-purity cobalt sulfate($CoSO_4$) which is recovered from the cathode scrap in the wastes lithium ion secondary battery(LIB). The leaching process for dissolving the metallic elements from the LCO scrap was controlled by the quantities of the sulfuric acid and hydrogen peroxide. The metal precipitation to remove the impurities was controlled by the pH value using the caustic soda. And also, D2EHPA and $CYANEX^{(R)}272$ were used in the solvent extraction process in order to remove the impurities again. The high-purity $CoSO_4$ solution was recovered by the processes mentioned above. We made the 6 wt.% $CoSO_4$ solution mixed with distilled water. And the 6 wt.% $CoSO_4$ solution was mixed with oxalic acid by the stirring method and dried in oven. $LiCoO_2$ as a cathode material for LIB was formed by the calcination after the drying and synthesis with the $Li_2CO_3$ powder. We assembled the cells using the $LiCoO_2$ powders and evaluated the electrochemical properties. And then, we confirmed possibility of the recyclability about the cathode materials for LIBs.

• Korean Journal of Environmental Agriculture
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• v.32 no.4
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• pp.348-354
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• 2013

BACKGROUND: Globally, concern about emerging infectious diseases of livestock is growing. For the disposal of the animal carcass, it is necessary to recycle the carcass into an agriculturally usable product. The objective of this study was to investigate the composting conditions of liquid by-product obtained from degradation of animal carcass. METHODS AND RESULTS: Optimum conditions of liquid fertilizer were investigated using different microorganisms, pHs, and volumes of microorganisms (Lactobacillus rhamnosus+Pichia deserticola). Based on the results from the optimum conditions, compost maturity and quality of liquid fertilizer were evaluated for 112 days. The compost maturity of liquid fertilizer were higher in the order of LP(Lactobacillus rhamnosus + Pichia deserticola) > BC(Bacillus cereus) > BS(Bacillus subtilis). The optimum condition under different volumes of LP was injection of 0.5 mL/100 mL. The compost maturity under different pHs were higher in the order of pH 7 > $$5{\geq_-}9{\frac{._-}{.}}11$$. The liquid by-product at 56 days after composting was completely decomposed. The concentrations of T-N, T-P and $K_2O$ in liquid fertilizer at 56 days were 0.94, 0.17 and 3.78%, respectively, and the sum of those concentrations was 4.89%. CONCLUSION(S): Liquid fertilizer of by-product using pig carcass was decomposed with optimum conditions(LP, pH 7, injection of 0.5 mL/100 mL) in 56 days after composting, and was suitable for official standard of commercial fertilizer.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.2
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• pp.149-160
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• 2013

The objective of present study was to simultaneously isolate of isoflavone and soyasaponin compounds from the germ of soybean seeds. Soy germ flours were defatted with hexane for 48h at room temperature, and methanolic extracts were prepared using reflux apparatus at $90^{\circ}C$ for 6h, two times. After extraction, extracts were separated with preparative RP-$C_{18}$ packing column ($125{\AA}$, $55-105{\mu}m$, $40{\times}150mm$), and collected 52 fractions were identified with TLC plate (Kieselgel 60 F-254) and HPLC, respectively. Among the identified isoflavone and soyasaponin fractions, isoflavone fractions were re-separated using a recycling HPLC with gel permeation column (Jaigel-W252, $20{\times}500mm$). Final fractions were air-dried, and the purified compounds of two isoflavones (ISF-1-1, ISF-1-2) and four soyasaponins (SAP-1, SAP-2, SAP-3, SAP-4) were obtained. Two isoflavone compounds (ISF-1-1, ISF-1-2) were acid-hydrolyzed for the identification of their aglycones, and confirmed by comparing with 12 types of isoflavone isomers. While the four kinds of soyasaponins were identified by using a micro Q-TOF mass spectrometer in the ESI positive mode with capillary voltage of 4.5kV, and dry temperature of $200^{\circ}C$. Base on the obtained results, it was conclude that ISF-1-1 is the mixture isomers of daidzin (43.4%), glycitin (47.0%), and genistin (9.6%), but ISF-1-2 is the single compound of genistin (99.8% <). On the other hand, soyasaponin SAP-1 is the mixture compounds of soyasaponin A-group (Aa, Ab, Ac, Ae, Af); SAP-2 is soyasaponin B-group (Ba, Bb, Bc) and E-group (Bd, Be); SAP-3 is soyasaponin B-group (Ba, Bb, Bc), E-group (Bd, Be), and DDMP-group (${\beta}g$); SAP-4 is soyasaponin B-group (Ba, Bb, Bc), E-group (Bd, Be), and DDMP-group (${\beta}g$, ${\beta}a$), respectively.

• Journal of the Korean Institute of Landscape Architecture
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• v.46 no.1
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• pp.72-85
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• 2018

This study focused on cases that led sustainable urban development through the construction and utilization of organic greenery systems linking green spaces of urban peripheries with metropolitan areas. To that end, Berlin - Brandenburg's regional parks in Germany and Milan's Raggi Verdi, a radial green axis project, in Italy were selected for analysis as case studies. As frameworks for this analysis, this study has established existing infrastructure accessibility and linkage, recycling and cooperative management. The results of the case study analysis are as follows: First, the specialized spatial strategy based on the individuality of the green space outside the city rather than a uniform landscape was used as the foundation of the sustainable development plan. Second, physical linkage from the center of the city to the periphery contributed to the sustainable development of the overall metropolis by improving the economic value of the surrounding area as well as ecological and environmental values. Third, the central management system was established to reduce the administrative inconvenience caused by multiple administrative districts in the green space of urban periphery. The implications of applying the above results to Seoul, Korea are as follows. First, it is necessary to establish a differentiation strategy by re-establishing the identity of a green landscape in the urban periphery, because the green spaces of Seoul's periphery are dispersed and mostly have a repetitious mountain landscape. Also, it is necessary to actively link peripheral mountains and urban green areas to create ecological value and economic value, and ultimately to help the sustainable development of the city. Finally, building an integrated management system is required to solve fragmented green space management departments in most of the urban periphery's green spaces. In conclusion, this study shows the significant possibility that the sustainable development of a metropolis can be derived from the utilization, linkage, and management of the green space in the urban peripheries, which is extraordinary compared to normal centralized urban development.