• The Journal of Engineering Geology
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• v.15 no.2 s.42
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• pp.145-154
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• 2005

This study conducted to develop an assessment method of runout distance of debris flow that is a major type of landslides in Korea. In order to accomplish the objectives, this study performed detailed field survey of runout distance and laboratory soil tests using 24 landslides over three pilot sites. Based on the data of the field survey and the laboratory tests, an assessment method of runout distance was suggested using the artificial neural network. The input data for the analysis of artificial neural network are change rate of slope angle, Permeability coefficient of in-situ soil, dry density, void ratio, volume of debris and the measured runout distance. The analyzed results using the artificial neural network show low error rate of inference distributing lower than $10\%$. Some cases have $5\%$ and $2\%$ of error rates of inferences. The results can be thought as excellent teaming rates. However, it is difficult to be accepted as excellent results if it is considered with the results derived using only 24 landslide data. Therefore, more landslide data should be surveyed and analyzed to increase the confidence in the assessment results.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.61-72
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• 2013

The consolidation tests are conducted to investigate the soil particle crushing stress for understanding the secondary compression characteristics of carbonate sandy sabkha soil caused by particle crushing under a high confining stress. The rate of secondary crushing compression ($C_{{\alpha}{\epsilon}}{^*}$) is introduced instead of the rate of secondary compression to define the characteristic of the particle crushing compression settlement ($S_s{^*}$). Void ratio ($e_p{^*}$) and settlement ($H_p{^*}$) in particle crushing are used as a reference point of secondary behavior, and the ratio of primary compression index ($C_c$) to secondary crushing compression ($C_{{\alpha}{\epsilon}}{^*}$), $C_{{\alpha}{\epsilon}}{^*}/C_c$ value was changed from 0.0105 to 0.0187. When comparing with quartz sands, secondary compression settlement of sabkha is very large due to particle crushing which is not usually observed in quartz sand. It is observed that as the depth of sabkha layer becomes deep, the $S_s{^*}$ and $C_{{\alpha}{\epsilon}}{^*}$ increase under the same stress level.

• Childhood Kidney Diseases
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• v.5 no.1
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• pp.51-58
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• 2001

Purpose : Treatment of primary nocturnal enuresis (PNE) includs folk remedies and various treatments based on pathogenesis. We assessed the therapeutic effect of nocturnal water restrict ion as the primary treatment of PNE. Materials and methods : From October 1998 to June 1999, 41 children with PNE (>3 wet nights per week) who visited Ewha Womans University Mokdong hospital and who had good compliances to nocturnal water restriction for 2 months were included. Before and during nocturnal water restriction, daily fluid intake and urine volume were recorded for 2 days every 2 weeks. Responses to nocturnal water restriction were classified according to the decrease of wet nights as complete (>90$\%$), partial (50-90$\%$) and no (<50$\%$) response. Predictors such as age, sex, daytime voiding dysfunction, fluid intake, urine volume, maximum urine volume per void and fasting urine osmolality were evaluated. Results . The response rate to nocturnal water restriction fir 2 month was 82.9$\%$(34/41) [complete response 39.0$\%$(16/41), partial response : 43.9$\%$(18/41)]. The response rate to nocturnal water restriction was significantly higher in monosymptomatic PNE than polysymptomatic PNE and more effective in PNE with or nocturnal fluid intake, nocturnal urine volume, and maximum urine volume than lower nocturnal fluid intake, nocturnal urine volume and maximum urine volume per void (P<0.05). Nocturnal urine volume, maximum urine volume per void and luting urine osmolality after nocturnal water restriction has significantly increased higher in complete response and partial response group than in no response group (P<0.05). Conclusion : The nocturnal water restriction was effective in monosymptomatic PNE with nocturnal polydypsia, nocturnal polyuria and high bladder capacity. (J, Korean Soc Pediatr Nephrol 5 : 51- 8, 2001)

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.57-64
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• 2007

One of the cause of insulation failure in power cable is well known by electrical treeing discharge. This is occurred for imposed continuous stress at cable. And this event is related to safety, reliability and maintenance. In this paper, throughout analysis of partial discharge(PD) distribution when occurring the electrical tree, is studied for the purpose of knowing of electrical treeing discharge characteristics according to defects. Own characteristic of tree will be differently processed in each defect and this reason is the first purpose of this paper. To acquire PD data, three defective tree models were made. And their own data is shown by the phase-resolved partial discharge method (PRPD). As a result of PRPD, tree discharge sources have their own characteristics. And if other defects (void, metal particle) exist internal power cable then their characteristics are shown very different. This result Is related to the time of breakdown and this is importance of cable diagnosis. And classification method of PD sources was studied in this paper. It needs select the most useful method to apply PD data classification one of the proposed method. To meet the requirement, we select methods of different type. That is, neural network(NN-BP), adaptive neuro-fuzzy inference system and PCA-LDA were applied to result. As a result of, ANFIS shows the highest rate which value is 98 %. Generally, PCA-LDA and ANFIS are better than BP. Finally, we performed classification of tree progress using ANFIS and that result is 92 %.

• Economic and Environmental Geology
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• v.37 no.1
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• pp.107-111
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• 2004

This study was undertaken to summarize of the efficiencies of the passive treatment system and suggest future studies for the solution of mine drainage problem. Flow rates of mine drainage from the abandoned coal mines are about 80,000 ton/day. Contaminated mine drainages over about 50 ton/day of flow rate were treated by passive treatment facilities such as Successive Alkalinity Producing Systems(SAPS), oxidation pond and oxic wetland. Chemical analysis for 13 passive coal mine treatment facilities showed that SAPS was the core of treatment facilities because the variation of Fe removal rates was relatively smaller than any other processes and re-leaching of Fe was not measured. The performance and life of SAPS depended on decrease in permeability and retention time due to accumulation of sludge. It is inferred that upgrade of design of the passive treatment system and in-situ treatment using underground void will be necessary for the amelioration of the mine drainage with high metal loading rates.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1D
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• pp.33-39
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• 2012

More and more pavements are suffering from damage these days due to the below-zero winter temperatures and frequent snowfalls. From this research, the freeze-thawing mechanisms of pavements will be observed, and the freeze-thawing resistance of porous asphalt concrete mixture is to be evaluated according to various assessment methods. The investigation was conducted through applying rigid and flexible pavements to freeze-thawing resistance experiments, which include various experiments such as deformation rate measurements, Lottman tests, repeated cyclic freeze-thawing experiments, stripping resistance tests and so on. Test results revealed that the porous asphalt concrete had less deformations according to temperatures compared to dense-graded asphalt concrete due to the 20% void gap. In addition, according to the freeze-thawing repetition experiments which are effected by moisture, the porous asphalt concrete mixture showed superior resistance to repeated cyclic freeze-thawing compared to other asphalt concrete mixtures due to the drainage and the voids within the specimen.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.9-18
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• 1994

In this study, we conducted experimental tests to evaluate fracture behaviors of fresh-butt welded metal by Acoustic Emission technique. We selected similar welding and dissimilar welding process, the one welded for SM45C, SS41 and SUS304 of each material, the other for SM45C and SS41, SM45C and SUS304 and SS41 and SUS304. The fracturing processes of weld metal were estimatied through the fracture toughness test with compact tension specimens and fractography analysis. In ASTM test method E-399, type I curves for materials of this study were obtained by load-cod diagram of fracture toughness test. and 5% offset load( $P_{5}$) was estimated as the estimated crack initial load( $P_{Q}$), The estimated crack initial load( $P_{Q}$) of similar welding materials generally lower than base matal, and then SM45C appeared greatly in decreasing rate of PB, SS41 and SUS304 appeared in order. $P_{Q}$ of dissimilar welding materials were lower than the similar welding materials. $P_{Q}$ of welding of SM45C and SS41 appeared in small, SUS304 and SS41 appeared greatly in dissimilar welding materials. In fracture toughness test, AE counts increased before the inflection point of the slope, decreased after that. It was found that increasing of AE counts were due to the microcrack formation at the crack tip near the $P_{5}$ point through AE data. For welding materials in this study, both low and high AE amplitude appeared simulataneously. It was confirmed that the low AE amplotude was due to formation of micro void, micro crack or micro dimple, the high AE amplitude was caused by microvoid coalescence and quasi-cleavage fracture through analyses of fractograpy.apy.apy.apy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.139-146
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• 2014

Sodium borohydride ($NaBH_4$) is considered as a secure metal hydride for hydrogen storage and supply. In this study, the interfacial friction of two-phase flow in the dehydrogenation of aqueous $NaBH_4$ solution in a microchannel with a hydraulic diameter of $461{\mu}m$ is investigated for designing a dehydrogenation chemical reactor flow passage. Because hydrogen gas is generated by the hydrolysis of $NaBH_4$ in the presence of a ruthenium catalyst, two different flow phases (aqueous $NaBH_4$ solution and hydrogen gas) exist in the channel. For experimental studies, a microchannel was fabricated on a silicon wafer substrate, and 100-nm ruthenium catalyst was deposited on three sides of the channel surface. A bubbly flow pattern was observed. The experimental results indicate that the two-phase multiplier increases linearly with the void fraction, which depends on the initial concentration, reaction rate, and flow residence time.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.302-317
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• 1995

After initial structure of AISI 9260 steel is changed into pearlite and martensite, one is isothermally annealed at $700^{\circ}C$ below of $A_1$ transformation point and the other is isothermally annealed at the same condition after 3 cycles of heating and cooling between $680^{\circ}C$ and $780^{\circ}C$ of $A_1$ transformation point. Analyzing the changes of microstructure, mechanical properties and fractography of tension test, we obtained result as follows. The fastest spheroidization rate by changes of initial structure and heat treatment cycles is appeared at the heat treatment cycle which is isothermally annealed after 3 cycles of heating and cooling at below and above $A_1$ transformation point for martensite. At the above condition, the perfect spheroidization structure is appeared after 60hrs and after then, globular carbide is being coarsened. The mean diameter of globular carbide is $2.4{\times}10^{-3}mm$ after 90hrs. The changes of tension strength during spheroidization heat treatment follows Orwan function, ${\sigma}_o={\sigma}_i+Gb/l$, where l is interspacing of carbide particles and at the above condition, ${\sigma}_o=70.48+2.5{\times}10^{-3}/l(kg/mm^2)$. Fractography of fracture of spheroidization structure in tension test is appeared as dimple which is ductile rupture type by nucleation and growth of void, size of dimple is larger and deeper with increasing of heat treatment time.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.573-580
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• 2005

This study was to investigate the removal characteristics of toluene in a gas stream by using a biotrickling filter packed with zeolite-contained polyethylene media. The specific surface area and the void fraction of the media were $500\;m^2/m^3$ and 82%. The surface roughness of the media was higher than that of pure polyethylene media. The toluene removal efficiency decreased with increasing the inlet toluene concentration and gas flow rate. The maximum elimination capacity of toluene in the biotrickling filter was $64\;g/m^3{\cdot}hr$. During 200 days operation, toluene removal efficiency was maintained from 90% to 98% until 167 days, hereafter, it was rapidly reduced with a rise in pressure drop due to an excess proliferation of biomass on the media. Pressure drop and removal capability of the biotrickling filter was fully recovered after backwashing.