• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.2
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• pp.121-132
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• 2018

Along with climate change, it is reported that the extreme climate events such as severe drought could cause difficulties of agricultural water supply. To minimize such damages, it is necessary to secure the agricultural water resources by using or saving the amount of irrigation water efficiently. The objectives of this study were to develop paddy water management scenarios and to evaluate their effectiveness on water saving. Three water management scenarios (a) deep irrigation with ponding depth of 20~80 mm (control, CT), (b) no/intermittent irrigation until paddy cracks (water management A, WM-A), and (c) intermittent irrigation with ponding depth under 20 mm (water management B, WM-B) were developed. Water saving effects were analyzed using monitored data from experimental paddy fields, and agricultural water supply was analyzed on a reservoir-scale using MASA model. The observed irrigation amounts were reduced by 21 % and 17 % for WM-A and WM-B compared to CT, respectively, and mainly occurred by the increase of effective rainfall. The simulation results showed that water management scenarios could reduce irrigation by 21~51 % and total inflow by 10~24 % compared to CT. The long-term simulated water level change of agricultural reservoir resulted in the decrease of dead level occurrence for WM-A and WM-B. The study results showed that WT-A and WT-B have more benefit than CT in the aspect of agricultural reservoir water supply.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.117-125
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• 2017

The role of fly ash in concrete become impotent with finding the characteristics of fly ash in which it is used as cement replacement material. In this paper, corrosion test results obtained by two test methods such as the long-term exposure corrosion test and the accelerated corrosion test method, were compared to investigated the corrosion resistance between fly ash concrete and normal concrete. Corrosion initiation time was measured in two types of concrete, i.e., one mixed with fly ash(FA) and the other without admixture(OPC). The accelerated corrosion test was carried out by four case, i.e., two samples is a cyclic drying-wetting method combined without carbonation(case 1) and combined with carbonation(case 2), and the other two samples is a artificial seawater ponding test method combined without carbonation(case 3) and combined with carbonation(case 4). Whether corrosion occurs, it was measures using half-cell potential method. The ponding test combined without carbonation was most effective in accelerating corrosion time of steel bars. The results indicated that the corrosion of rebar embedded in concrete occurred according to the order of OPC, FA. The delay relative ratio of corrosion obtained by corrosion initiation time between FA and OPC is 1.04 to 1.27. Consequently, fly ash concrete as the age increases its corrosion resistance was improved compared with OPC concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.136-143
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• 2016

There are various method for evaluating the durability life of concrete structures due to salt damage. The best way is to perform a corrosion test for a rebar embedded in concrete specimen was exposure to marine environment. However, this method has the disadvantage that it takes a long period of time. Also, accelerated corrosion test which was complemented complements the time-consuming weakness is limited to apply because it could not reveal a correlation between long-term exposure test. Accordingly, the purpose of this study is to derive a correlation coefficient between cycle drying-wetting accelerated corrosion test and long-term exposure test. Corrosion initiation time was measured in four types of concrete samples, i.e., two samples mixed with fly ash(FA) and blast furnace slag(BS), and the other two samples having two water/cement ratio(W/C = 0.6, 0.35) without admixture(OPC 60 and OPC 35). The accelerated corrosion test was carried out by two case, i.e., one is a cyclic drying-wetting method(case 1), and the other is a artificial seawater ponding test method(case 2). Whether corrosion occurs, it was measures using half-cell potential method. The results indicated that case 1 is to accelerated the corrosion of rebar about 24~36% as compared with case 2, then the corrosion of rebar embedded in concrete occurred according to the order of OPC60, FA, BS, OPC35. Correlation coefficient between accelerated corrosion test and long-term exposure test, case 1 is 4.23 to 5.42, and case 2 is 6.54 to 7.82.

• KCID journal
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• v.11 no.2
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• pp.64-71
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• 2004

This study was carried out to obtain the desalinization effect of saline-sodic soils as water pending condition. Three soils with different salinity were collected and packed at 115000a pot. With artificial 1,000 mg/L water made of sea salt, three cases w

• Proceedings of the ESK Conference
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• 1996.10a
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• pp.91-96
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• 1996

A keyboard is deveoped which can be used for Korean stenograph. Korean characters are of combinaton type : a Korean character is composed of upper or lower consonants and a vowel. This keyboard can process more than one character at a time by pressing corres- ponding buttons together. The space-bar is divided into 6 buttons for lower consonants. If some reserved words for special stings are entered, the corresponding strings are auto- matically sent to the computers. The keyboard can also be served as a normal one.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.901-910
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• 2003

The hydrologic behavior of paddy field depends largely on the irrigation and levee height management by farmers. The storage and drainage amount of paddy for storm events certainly influences the stream discharge. To understand the paddy storage effect during storm periods, a daily paddy water balance model embedding farmer's water management was developed by using 4 years (1996, 1997, 2001, 2002) field experimental data at 2 locations (Suwon and Yeoju) From the modeling, it was possible to simulate the daily ponding depth of paddy by treating paddy levee height and threshold pending depth indicating irrigation time as 10 days average parameters of the model. The storage amount(306.9 mm to 343.6 mm) showed little deviation to rainfall amount(425.1 mm to 850.8 mm).

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.15-22
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• 2010

Chloride-induced corrosion of steel bars in concrete exposed to marine environments has become one of the major causes of deterioration in many important facilities made of reinforced concrete. A study on chloride penetration in concrete has developed through long period exposure test along seawater, assesment of chloride ion diffusion by electrochemical techniques and so on. However, reasonable and exclusive chloride penetration model considering concrete material properties with mixture, degree of hydration, binding capacity has not been established. Therefore, in this paper, chloride penetration analysis of non-steady state is accomplished with material properties of concrete. Comparing with the results of analysis and chloride ponding test, we could accept the effect of binding capacity on chloride penetration in concrete and these results could be applied to a service life prediction of R.C. structures submerged in seawater. Therefore, there are 20~40% differences of service life to SHRP prediction.

• Journal of Korea Water Resources Association
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• v.35 no.3
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• pp.285-294
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• 2002

Infiltration is one of the important processes of the hydrologic cycle determining the distribution of water and has been studied extensively. Various theories and models proposed for this process are usually applicable only when the rainfall intensity is higher than the infiltration capacity. The study by Diskin and Nazimov (1995, 1996) suggested a conceptual infiltration model that comprises two elements. The model can make an reasonable approach to the infiltration process, instead of representing the infiltration as a function of time. The study presented herein improved the existing conceptual infiltration model by an additional consideration of the initial moisture contents. The analysis results for the variation of the infiltration capacity curries for various initial moisture contents demonstrate that the model is more reasonable for the approach to the infiltration process. In addition, the results for the relationship of stormwater events-ponding time are compared with the literature values of that for a number of soil types. The agreement is rather good, leading to the conclusion that the improved model is vapid for describing the infiltration process.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.4
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• pp.13-21
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• 2004

The purpose of this study was to investigate tile effects of pending depth treatment on water balance in paddy fields. Field experiment was performed in an experimental farm in Taegu, southern part of Korea during the rice growing season In 2001, 2002 and 2003. Experimental plots were three 8m ${\times}$ 80m rectangular plots. Three pending depth treatments, very shallow, shallow, and deep were used. Daily values of water balance components were measured in the field. The irrigation amounts measured at the experimental plots showed that the very shallow and the shallow ponded plots required smaller amount than the deep ponded plot. The shallow ponded plot saved irrigation water about 17.7% compared with the traditional deep ponded plot in 2001 The very shallow ponded plot saved irrigation water about 25.7% compared with the traditional deep ponded Plot in 2002, The shallow ponded plot saved irrigation water about 18% compared with the deep ponded plot in 2003.

• Computers and Concrete
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• v.9 no.6
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• pp.457-467
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• 2012

This study evaluates the permeability of cement-based composites, which are a mix of polyolefin fibers and silica fume. Test results indicate that permeability increases as the water/cementitious ratio increases. Silica fume in cement-based composites produced hydrated calcium silicate and filled the pores. However, permeability decreased as the addition of silica fume increased. Specimens containing polyolefin fibers also provided higher permeability resistance. The polyolefin fiber length did not have a significant effect on permeability. The decrease in the permeability is mainly due to the addition of silica fume and lower water/cementitious ratio. Addition of fibers marginally decreases the permeability. Incorporating polyolefin fiber and silica fume in composites achieved more significant decreases in permeability. The correlated test results reveal the interrelationship between them.