• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.5-11
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• 2015

The development of Controlled Low Strength Material (CLSM), which is a highly flowable material, has been performed for the application of backfill. The objective of this study is to compare the compressive strength and compressive wave velocity of CLSM according to the curing time. To investigate the characteristics of the CLSM consisting of sand, silt, water, flyash, and CSA cement, uniaxial compression test and flow test were carried out. For the measurement of compressional waves, a cell and a couple of transducers were used. The test results show that the compressive strength increases with the curing time, while the increment of compressive strength decreases with the curing time. In addition, the compressive wave velocity increases with the curing time, and the correlation between the compressive wave velocity and compressive strength is similar to exponential function. This study suggests that the correlation between the compressive wave velocity and compressive strength may be effectively used for the estimation of compressive strength of the CLSM at early curing time.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.103-114
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• 2011

Usage of bicycle has been supported the universal reduction of energy consumption and $CO_2$. For the same purpose, new constructions for long length bike roads are planned in Korea. Recently, laboratory tests of physical properties and resistance against environmental loading about optimum mix design of roller compacted concrete, that have advantages of high structural performance by cement hydration and aggregate interlocking, simple construction procedure and low construction cost, are performed for the effective construction of new bike roads. However, properties of roller compacted concrete had different results between laboratory and field tests since it had different compaction method. Also, construction method of roller compacted concrete are not defined for the application of bike roads since it had different demand performance such as thin pavement thickness, low strength and etc with road pavements. Thus, in this experimental research was launched to evaluate the core properties, visual inspection, compaction ratio, water content, thickness reduction rate of roller compaction, skid resistance and roughness by experimental construction about variable mix proportion and compaction method based on laboratory test results. And construction method of roller compacted concrete pavement were suggested for the application of bike roads.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.4019-4023
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• 2014

This study examined the effectiveness of ultrasound on enhancing the dewaterability and volume reduction of bio solids from a waste treatment plant. The test specimen was obtained from a storage tank immediately before the dewatering process at a local treatment plant. The test conditions included the energy levels of ultrasonic waves and treatment time. The tests were undertaken using three types of different treatment processors (7 liter, 1 ton, 7 ton container). The capillary suction time (CST) and the viscosity of sludge, which is one of the influencing factors for dewaterbility, were obtained under various test conditions. The results showed that ultrasound increases the CST of the raw specimens, whereas a significant reduction (20 % of the maximum value) of CST occurred in the sample with ultrasound and flocculent. The decrease in viscosity reached 40 % of the maximum value. A centrifugal test was performed to examine the characteristics of the sludge settlement. The settling rate and time required to reach the final values were both enhanced by the ultrasonic energy. An ultrasonic treatment is potentially useful tool for reducing the amount of released sludge. To examine the possible use of field application, the real scale sonic processor was designed and operated. The results were similar (50 % of the maximum value) to those of laboratory experiments.

• Journal of Life Science
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• v.27 no.2
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• pp.211-216
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• 2017

This study aims to reduce the production cost of mushrooms and therefore boost the income of mushroom producers. The addition of a 10% concentration of herb medicine refuse was adequate for promoting mycelium growth in Flammulina velutipes. A moisture content of 60% in the culture medium was adequate for promoting hyphal growth. The optimum temperature and humidity were $16^{\circ}C$ and 70%-85%, respectively. The average yield of Flammulina velutipes fruting body per 1,100 ml bottle was 275-282 g, which is similar to that of the control. The outbreak of diseases such as mildew and bacterial blotch in mushroom was never observed in the bottle treated with herb medicine refuse. Fewer deformed and second-class quality mushrooms were observed than in the control group. Deviation reduced, and mushroom growth was observed to be significantly uniform. The winter mushroom had a white fruiting body with a hemispherical shape. The diameter of the mushroom cap was 9.2-9.3 mm, stipe length was 12.7-12.8 cm, and thickness was 3.3-3.4 mm; these were almost the same as those in the control group. The partial hardness of winter mushrooms in both the experimental and the control groups showed that the stipe ($54.6-57.3g/cm^2$) is a little harder than the mushroom cap ($46.8-47.6g/cm^2$). The calories and nutrients per 100 g of mushrooms in the control and samples were similar to each other.

• Journal of the Korean Geotechnical Society
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• v.21 no.7
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• pp.55-62
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• 2005

The use of the bearing capacity equation is subjected to several uncertainties. In this study, estimation of the bearing capacity of footings based on the cone resistance q$_{c}$ is investigated. Non-linear finite element analyses based on a state-dependent stress-strain model were performed to obtain the load-settlement responses of axially loaded circular footings. Various soil and footing conditions, including different relative densities, depths of embedment, and footing diameters were considered in the analyses. Based on the finite element results, load-settlement curves were obtained and used to determine the unit limit bearing capacity in terms of the cone resistance q$_{c}$ for footings subjected to surcharge. Values of the unit bearing capacity for different embedment depths were in a narrow range, while considerable variation was observed with relative density D$_{R}$. It was observed that the unit limit bearing capacity normalized with respect to q$_{c}$ decreases as D$_{R}$ increases for a given surcharge.

• Resources Recycling
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• v.26 no.6
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• pp.73-83
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• 2017

Used small household appliances have a wide variety of product types and component materials, and contain high percentage of black plastics. However, they are not being recycled efficiently as conventional sensors such as near-infrared ray (NIR), etc. are not able to detect black plastic by types. In the present study, an automatic sorting system was developed based on laser-induced breakdown spectroscopy (LIBS) to promote the recycling of waste plastics. The system we developed mainly consists of sample feeder, automatic position recognition system, LIBS device, separator and control unit. By applying laser pulse on the target sample, characteristic spectral data can be obtained and analyzed by using CCD detectors. The obtained data was then treated by using a classifier, which was developed based on artificial intelligent algorithm. The separation tests on waste plastics also were carried out by using a lab-scale automatic sorting system and the test results will be discussed. The classification rate of the radial basis neural network (RBFNNs) classifier developed in this study was about > 97%. The recognition rate of the black plastic by types with the automatic sorting system was more than 94.0% and the sorting efficiency was more than 80.0%. Automatic sorting system based on LIBS technology is in its infant stage and it has a high potential for utilization in and outside Korea due to its excellent economic efficiency.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.149-159
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• 2006

This research is a development of useful S/W program for real industry about optimal product scheduling in real plant for manufacturing polymer products. For this, we used a fine model with total amount of losses in weight(ton) as an objective for optimal scheduling and a genetic algorithm for optimization in this factory they manufacture three different products. Major products are A and B but the product which can be process in the period of products change over. They also sells them as a chap product in market. The major products have several types of packing process-bulk, pack for domestic market, pack for export. The demands of product with each packing type are increased, and frequently they failed keep the deadline for sail. Based on realistic production situation, we composed a fine modeling for optimal scheduling. And we also develop a S/W program for optimal scheduling which can be used by non-specialist in scheduling problem. We used a modified genetic algorithm and it gave us a better solution in process. We can have a result of reducing the total amount of losses in weight by half compared with the losses when existing production schedule.

• Resources Recycling
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• v.26 no.2
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• pp.66-70
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• 2017

The purpose of this research was to estimate density changes of sea sand by washing. To examine water content test, field density test, particle density test and measuring of dump regarding extracted sea sand and selling one. Measured result of mean particle density of barge and dump were $2.666g/cm^3$, $2.651g/cm^3$, respectively. Also, measured result of field density for each sea sand was $1.716g/cm^3$, $1.331g/cm^3$ on average. Converted to the volume of 1ton of each sea sand, $0.583m^3$, $0.751m^3$, respectively. Occurring to volume change approximately 28.8% on average. The mean field densities of measuring of sea sand that dump and barge were $1.398g/cm^3$ and $1.716g/cm^3$ respectively. This values indicated $0.715m^3$ and $0.583m^3$ each, when converted to the volume of sea sand 1ton. It was found that the average of 22.6% volume change occurred between the amount of sea sand and the sales volume.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.8
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• pp.554-563
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• 2013

The purpose of this study is to evaluate the possibility of nutrient release at up and downstream of Kangchun weir, upstream of Yuju and Ipo weir in Namhan River. For this survey, we measured basic characteristics of the sediments (water content, ignition loss, TOC, TP, SRP, TN, phosphorus fractionation) and conducted nutrients release experiments under both aerobic and anaerobic condition. The overlying water from the sediment-water column was analyzed for nutrients (i.e. TP, $PO_4$-P, TN, $NO_3$-N, $NH_3$-N) everyday for 18days. Result of soil texture experiment showed that sediments are Sand. SRP concentration before the release experiment was different with the value after the release experiment. According to this result, we can find that there were more activated release processes in anaerobic condition. $PO_4$-P increased from 1 to 8 days and remained at the maximum value (7~8 days) afterward. The rapidly increase of $PO_4$-P was observed from 1 to 2~3 days whereas the TP continuously increase from 1 to 18 days. The $PO_4$-P release rate calculated by up to 7~8 days data highly correlated with initial SRP concentration with $R^2$=0.8502. $NO_3$-N release rate appears constantly decreasing trend as -5.7~-3.08 $mg/m^2{\cdot}day$, otherwise the $NH_3$-N release rate, by-product of a organic matter decomposition using nitrate as electron acceptor, was 0.57~2.41 $mg/m^2{\cdot}day$. Substantial portion in TN can be induced by organic nitrogen which originated from the tributary passing through non-point pollutant source. Compared with other similar researches, phosphorus and nitrogen release rates obtained in this study can be considered as relatively low values. Since this study targeted the sediments accumulated by one time of flooding season, there are limitation to generalize theses results. Therefore, it is necessary to consistently monitor and investigate the accumulation of nutrients in the sediment for understanding the effect of weir construction on the overlying water quality.

• Korean Journal of School Psychology
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• v.8 no.2
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• pp.133-152
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• 2011

This is a short-term longitudinal study investigating the relationships between changes in mental health and academic burnout among Korean middle school students. Study sample consisted of 409 middle school students in Seoul provision, with 161 male, 216 female, and 32 unidentified. Both Symptom Check List(SCL-47) and Maslach Burnout Inventory-Student Survey(MBI-SS) were used. In order to examine the pattern of changes in mental health and academic burnout among students, standardized residuals were calculated using regression equations which were then put into canonical correlation analysis. The results of this study are as follows. First, according to Function 1, among sub-factors of mental health, decreases in depression, compulsion, anxiety, and hostility were particularly associated with decreases in exhaustion and cynicism among academic burnout. Put in another way, students who showed increases in depression, compulsion, anxiety, and hostility experienced more academic exhaustion and cynicism. Second, according to Function 2, increases in phobic anxiety, compulsion with decreases in anxiety, depression were associated with decrease in academic exhaustion and increase in cynicism. Considering Russell's dimensional theory of emotion, Function 1 showed that mental health symptoms including both aroused and non-aroused affects were related with increases in exhaustion and cynicism while Function 2 showed that mental health symptoms including only aroused aspects were related with decrease in exhaustion and increase in cynicism. Thus, a conclusive intervention program seems to be required to deal with both aroused and non-aroused affects of students who are experiencing increased exhaustion and cynicism. On the other hand, an intervention program focused on aroused affects seems appropriate to students who are experiencing decreased exhaustion and increased cynicism. This study has its value in that it has enhanced understanding of students in school and counseling settings by revealing the relationships between mental health and academic burnout among adolescents and suggested differentiated intervention strategies based on patterns of students' academic burnout.