• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.5
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• pp.170-180
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• 2000

The surface-drainage system, which consists of bio-swale and detention-infiltration Basins and carries out the function of temporary detention-infiltration of runoff, is defined as the "natural drainage system". It is an environmentally sound and economically beneficial practice to reduce run-off by retaining it in swales as much as possible and letting run-off infiltrate into the ground. In order to estimate appropriate capacity of swales, it is necessary to know how long will it take for certain depths of water to infiltrate. The ponding times, or infiltration times, of various depths and of various soil textures, could be estimated with the Green-Ampt Infiltration Model. Included soil textures are loamy sand, sandy loam, loam, silty loam, sandy clay loam and clay loam. Ponding depths are from 10cm to 100cm intervals. Newton-Raphson method is used for the solution of the Green-Ampt equation by a computer program. The computer program was written with the FORTRAN Developer 4.0 v.. Selected ponding depth is acceptable when the sum of the ponding time and the breeding time of mosquitoes is less than the tolerance period of innundation of grasses and trees.and trees.

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05a
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• pp.170-175
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• 2001

No Abstract (See Full-text)

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.729-736
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• 1989

This study aims to reinforce concrete structure by impregnation of molten sulfur. The improved properties of sulfur impregnated concerete were confirmed by compressive strength test and water proof effect. Following variables were adopted to evaluate impregnation parameters ; 1) the effect of water content in concrete structure (0-8%) 2) impregnation time of molten sulfur(0-22hr) 3) impregnation temprature of molten sulfur(13$0^{\circ}C$, 14$0^{\circ}C$). In partial ponding experiments, the concrete specimen of sulfur impregnated by 2wt% yields 1.5 times higher value of compressive strength than that of control one(non-impregnated concerte). In complete ponding experiments, the mortar specimen of slufur impregnated by 12-14wt% yields 2-3 times higher value of compressive strength than that of control one (non-impregnated mortar). From the examination of X-ray diffractions, $\alpha$-sulfur was found in concrete pores. Homogeneous impregation of molten sulfur into concrete pores was also identified with poresize analysis and micrographs of SEM.

• 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.

• 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.

• 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).

• Corrosion Science and Technology
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• v.3 no.6
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• pp.245-250
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• 2004

A series of classical G109 type concrete specimens was exposed to cyclic wet and dry ponding with 15 w/o NaCl solution for approximately five years. Mix design variables included 1) three cement alkalinities (EqA of 0.97, 0.52, and 0.36) and 2) three water-cement ratios (0.50, 0.41, and 0.37). To determine the corrosion initiation time, corrosion potential and macro-cell current between top and bottom bars were monitored. Subsequent to corrosion initiation, specimens were autopsied and visually inspected. Concrete powder samples were collected from top rebar trace and chloride concentration was measured. Also, time-to-corrosion, $T_i$, for specimens of the individual mix designs was represented using Weibull analysis. Time-to-corrosion was a distributed parameter; and because of this, corrosion initiation of four identical specimens for each mix varied, often over a relatively wide range. Specimens fabricated using the lowest water cement ratio and the highest alkalinity cement exhibited the longest time-to-corrosion initiation and the highest chloride threshold levels. Time-to-corrosion did not increase monotonically with cement alkalinity, however, presumably as a consequence of relatively high $Cl^-$ binding in the lower pore water pH range. The chloride threshold level, $Cl_{th}$, increased with increasing $T_i$ and, consequently, was greatest for the highest cement alkalinity specimens.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.8
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• pp.1270-1281
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• 1989

This paper presents two new storage schemes of 3-D objects to accelerate the finding of the first intersecting object and the shadow computation steps in ray tracing. The 3-D objects which are potentially intersected with the first reflection (refraction)ray are enrolled within a so called reflection (refraction) frustum' for a polygon object. Only those objects registered in the corres ponding frustum are immediately checked for intersection with the secondary rays emanating from the same polygon. The other is called a shadow pyramid' which contains the candidate objects possibly blocking the path from the relevant light source to any point on the relevant polgon. The shadow testing of a point is performed only against the objects contained in the associated shadow pyramid. Despite the cost needed for registration of objects within frusta or shadow pyramids, the total rendering time of ray tracing using the proposed approaches was reduced by approximately 50% (10% in color rendering time and 70% in shadoe testing time) from the conventional cell 50% (10% in color rendering time and 70% in shadow testing time) from the conventional cell traversal scheme under the 3-D uniform subdivision environment due to the fast finding of candidate objects for intersection and the reduced number of intersection calculations.