• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.644-653
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• 2018

Landslides occur frequently due to the effects of heavy rainfall and typhoons caused by climate change. Erosion control measures are needed to effectively prevent landslide damage. In order to improve their efficiency, it is necessary to quantitatively measure the sediment discharge from the mountain stream. In this study, a load cell sensor was installed in a mountain stream and the measured values were compared according to the applicability and load test type in the mountain stream. The result of the load test showed that the effect of the loading type (load test 1, 2) was low at average (loadings) of 0.4kgf and 0.6kgf at sites 1 and 2, respectively. The load factor was also derived by regression analysis to increase the accuracy of the measured values. According to the results of the load factor (normalized) to the load-cell measurement value, the output value increased by 14.8% and 24.6% in sites 1 and 2, respectively, and was calculated to be similar to the reference value. The load cell sensor enabled us to quantitatively estimate the amount of sediment discharge in the mountain stream through time series analysis with the water level and rainfall information. If the monitoring is carried out for a long time, it can be used to find the sediment discharge mechanism for the mountain stream. In addition, applying sensors such as load-cells to a mountain stream is expected to contribute to the development of related industries, such as the manufacturing of measurement sensors.

• Geotechnical Engineering
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• v.1 no.1
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• pp.59-72
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• 1985

This paper deals with the numerical analysis by the (mite element method introducing Biot's theory of consolidation and the modified Cambridge model proposed by Roscoe school of Cambridge University as constitutive equation and using Christian-Boehner's technique. Especially, time interval and division of elements are investigated in vies of stability and economics. In order to check the validity of author's program, the program was tested with one-dimensional consolidation case followed by Terzaghi's exact solution and with the results of the Magnan's analysis for existing banking carried out for study at Cubzac-les-ports in France. The main conclusions obtained are summarized as follows: 1. In the case of one-dimensional consolidation, the more divided the elements are near the surface of the foundation, the higher the accuracy of the numerical analysis is. 2. For the time interval, it is stable to divide 20 times per 1-lg cycle. 3. At the element which has long drain distance, the Mandel-fryer effect appears due to time lag. 4. Lateral displacement at an initial loading stage predicted by author's program, in which the load was assumed as not concentrative. but rather in grid form, is well consistent with the value of observation. 5. The pore water pressure predicted by author's program has a better accordance with the value of observation compared with Magnan's results. 6. Optimum construction control by Matsuo-Kawamura's method is possible with the predicted lateral displacement and settlement by the program.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.267-276
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• 2001

The downstream reach of the Han River adjoining Seoul in Korea was the upper boundary of an estuary where tidal effect on the flow rate could be exerted. According to the comprehensive river regulation project, the river was channelize dand impounded by two overflow dams, which provided favorable condition for algal growth in this sewage polluted eutrophic reach. In this study primary productivity of phytoplankton was measured in the down reach and the autochthonous and allochthonous organic carbon loadings were estimated. Primary production of phytoplankton measured by C-14 uptake and P-I model method ranged from 140 to $4,890\;mgC\;m^{-2}\;d^{-1}$ (median value $1,865\;mgC\;m^{-2}\;d^{-1}$) showing the level of eutrophic lakes. Phytoplankton density that varied according to water flow rate was highest in spring. Allochthonous organic carbon loading was dominated by sewage input through tributaries in most of days except flood flow period. The average proportion of autochthonous carbon generation by phytoplankton was 40.9%, which is very high proportion for a lotic habitat.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.611-633
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• 1995

The pupose of this study was to compare the fracture strength of five kinds of all-ceramic crowns(Vintage, Dicor Empress-staining, Empress-layering, In-Ceram) luted with glass ionomer cerment and composite resin cement and to evaluate the effect of cements on the fracture stregth of all ceramic crowns. Five groups of twelve uniform sized all-ceramic crown specimens were fabricated. Six specimens of each group were cemented with glass ionomer cement(Fuji G.I. Cement) and the remaining six specimens of each group were etched, silane-treated, and cemented with composite resin cement(Bistite resin cement). The crowns were stored in water$(37^{\circ}C)$ for 1 day prior to loading in an Instron, using a steel ball(diameter 4mm) at a crosshead speed of 0.5mm/min. The crowns were angled $30^{\circ}$, so the steel ball contacted with the crowns 2mm lingual from the mid-incisal edge. The results obtained were summarized as follows ; 1. With G.I. cement, mean fracture load(Kg) Were : Intage : $18.33{\pm}1.47$ ; Empress-staining : $23.92{\pm}6.67$ ; Dicor : $24.0{\pm}5.81$ ; Empress-layering : $26.92{\pm}2.80$ ; In-Ceram : $51.58{\pm}6.87$ ; ANOVA revealed a significant difference existed(p<0.05) between the group A(Vintage, Dicor, Empress-staining, Empress-layering) and group B(In-Ceram). 2. With Resin cement, mean fracture load(Kg) were : Intage : $22.75{\pm}4.97$ ; Dicor : $42.75{\pm}7.07$ ; Empress-staining : $44.08{\pm}7.99$ ; Empresslayering : $50.42{\pm}5.43$ ; In-Ceram : $52.58{\pm}6.51$ ; ANOVA revealed a significatnt difference existed(p<0.05) between the group A(Vintage) and B(Dicor, Empress-staining Empress-alyering, In-Ceram). 3. Resin cement significantly increased the fracture strength of the all-ceramic crowns for Dicor(156%), Empress-staining(185%), Empress-alyering(187%)(p<0.05); but did not increase the fracture strength of Vintage(128%) and In-Ceram(101%)(p>0.05). 4. Majority of the all-ceramic crowns show a wedge fracture extending through proximal surfaces to an apex, usually apical third(with G.I. cement) or middle third(with Resin cement) of the facial surface.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.581-586
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• 2017

In this study, in order to find the feasibility of thermophilic biological pre-treatment for the co-digestion of food wastewater and sewage sludge, digestion efficiency of the combined thermophilic aerobic and mesophilic anaerobic process and its effect on methane production were investigated. Also, a lab-scale co-digestion process was operated to observe parameter changes according to the increase of organic loading rates using different dilution ratios of distilled water and food wastewater (1/3 [Run I], 2/3 [Run II] in addition to using the raw food wastewater [Run III]). The results indicated that co-digestion process maintained quite stable and constant pH during entire experiments. With regard to VS removal, the higher removal was observed in the combined process and the removal efficiency was 52.24% (Run I), 66.59% (Run II) and 72.53 (Run III), respectively. In addition, the combined process showed about an 1.6-fold improved methane production rate and significantly higher methane yield than that of using single anaerobic digestion process.

• Polymer(Korea)
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• v.31 no.3
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• pp.189-193
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• 2007

We developed the doxorubicin-loaded PLGA double-layered microspheres using relatively simple oil-in-water (O/W) solvent evaporation method for sustained release of doxorubicin and investigated the release behavior according to PLGA molecular weight and initial drug loading. The double-layered microsphere was characterized on the surface, the cross-section morphology, the behavior of doxorubicin release for 5 weeks by SEM and fluorescence spectrophotometer. Double-layered microspheres showed smooth surfaces and clear difference between core and outer-shell. As the PLGA molecular weight increased, the release rate of doxorubicin-loaded, double-layered microspheres decreased. These results showed that the release behaviors can be controlled by the variation of molecular weight of PLGA.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.97-106
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• 2009

self-loading, various problems related to construction can be solved as well as the save of construction cost. Thus, this study has an aim of applying foam concrete to structural purpose by adding bottom ash as a reinforcing material like fine aggregate, in contrast to conventional non-structural usage such as soundproofing or insulating materials. In addition, it was evaluated in terms of unit volume weight, flow value, air void, water absorption and dosage of foam agent wether replacement of cement by granulated blast furnace slag or fly-ash has an effect on the material characteristics of foam concrete. As results of experiments, it can be found that the increase of fine aggregate ratio, that is to say, the increase of bottom ash results in the increase of unit volume weight, while decreasing air void and flow value. But, appropriate addition of bottom ash to foam concrete makes it easy to control a homogeneous and uniform quality in foam concrete due to less sensitive to bubbles. As the replacement ratio of mineral admixtures such as granulated blast furnace slag and fly-ash increases, as unit volume weight tends to decrease. In the meanwhile, serious effects were shown on fluidity of foam concrete when more than limit of replacement ratio was applied.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.49-56
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• 2014

It is important to keep stable effluent water quality and minimize operation cost in biological wastewater treatment plant. However, the optimal operation is difficult because of the change of influent flow rate and concentrations, the nonlinear dynamics of microbiology growth rate and other environmental factors. Therefore, many wastewater treatment plants are operated for much more redundant oxygen or chemical dosing than the necessary. In this study, the optimal control scheme for dissolved oxygen (DO) is suggested to prevent over-aeration and the reduction of the electric cost in plant operation while maintaining the dissolved oxygen (DO) concentration for the metabolism of microorganisms in oxic reactor. For optimal control, The oxygen uptake rate (OUR) is realtime measured for the identification of influent characterization and the identification of microorganisms' oxygen requirement in oxic reactor. Optimal DO seT-Point needed for the microorganism is suggested based on real time measurement of oxygen uptake of microorganism and the control of air blower. Therefore, both stable effluent quality and minimization of electric cost are satisfied with a suggested optimal setpoint decision system by providing the necessary oxygen supply requirement to the microorganisms coping with the variations of influent loading.

• International Journal of Highway Engineering
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• v.4 no.4 s.14
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• pp.13-21
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• 2002

This study examines the importance of conditioning temperature and period before measuring fundamental properties of asphalt mixture. Marshall specimens were made and cured in the air for one day and conditioned by submerging at $60^{\circ}C$ water for 30 min before loading. It was observed that if the specimen was cured in a lower (or higher) than normal lab temperature ($25^{\circ}C$) before submerging, the measured values were not consistent. Indirect tensile strength (ITS) was also measured on the specimens cured at different temperatures. Although there is no regulation specifying how long the specimen should be conditioned before testing, it is recommended that the conditioning time be for the specimen to be at $25^{\circ}C$. Test must be conducted for the specimen cured well before conditioning for desired test. If curing temperature was lower or higher than normal, and mixture was not properly cured, then test results would not be reliable. This study showed how long the specimen should be submerged at $60^{\circ}C$ for Marshall test and conditioned at $25^{\circ}C$ for ITS test for the specimens cured in different temperature.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.4
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• pp.682-688
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• 1997

This study was performed to investigate whether ascorbic acid can modulate the induction of CYP2E1 and prevent the lipid peroxidation which may cause diabetic chronic complication. Diabetes was induced by intraperitoneal injection of streptozotocin to 5-week-old male Sprague-Dawley rats(150~170g). Normal and diabetic group was randomly divided into three groups each; Control(CON, no supplementation), SUP1 (50mg/d ascorbate supplementation) and SUP2(250mg/d ascorbate supplementation). Ascobic acid was prepared daily by dissolving in drinking water and supplied for 4 weeks. There was no difference in hepatic microsomal and mitochondrial P450 contents between normal and diabetes. Hepatic microsomal N-nitrosodimethylamine(NDMA) demethylase activity, which repre-sents contents of CYP2E1, was elevated in diabetes, but not significantly. The NDMA demethylase activity of diabetic SUP2 group was significantly lower activity than that of the diabetic CON group. However, no difference in hepatic mitochondrial NDMA demethylase activity was observed between the diabetes and the normal group. The result suggests that the induction of CYP2E1 in diabetes can be alleviated by ascorbic acid supplementation at the dose of 50mg1d. In addition, ascorbic acid supplementation showed dose-dependent reduction of hepatic microsomal TBARS contents in diabetic rats.