• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.467-475
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• 1997

In this study, breakwater model which has several outlet pipes to discharge heated water is settled in the experimental open channel and velocity distribution of wall jet is measured. Numerical simulation of velocity structure of wall jet using 3-dimensional computer model. Fluent model, is also carried out. The calculated results are verified with the experimental results and the flow characteristics of wall jet are investigated. The length of zone of flow establishment of wall jet is shorter than that of free jet, and the diminution rate of jet centerline longitudinal velocity is larger than that of free jet. Characteristics of buoyant jet and non-buoyant simple jet simulated by Fluent model are compared. Near the outlet pipe, in the region where x/lQ is over 15, this is reversed. Comparison of vertical distribution of longitudinal velocity shows that positive velocity of non-buoyant jet is bigger than that of buoyant jet in the bottom layer and in the upper layer, negative velocity of non-buoyant jet is bigger too. Flow separation in free surface of the buoyant jet occurs in smaller distances from the outlet than the non-buoyant jet. Buoyant jet expands faster than the non-buoyant jet in vertical direction.

• Journal of The Geomorphological Association of Korea
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• v.20 no.1
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• pp.1-9
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• 2013

This study aims to provide fundamental data for further shape-factor research on karst by measuring and classifying the shape of surface topography in Hogye, Mungyeong. First, in the research area, there are 35 dolines and uvalas. Second, large uvalas are found in three places, including Gulnomjae in Bugokri, and Teotgol and Denjimigol in Urori. Third, there are 13 round dolines and 22 oval dolines. Next examining the cross section of dolines, there are 27 bowl shaped dolines, 2 plate shaped dolines, and 6 funnel shaped dolines. Fourth, most dolines lay over 200m elevation, which is ridge and top of mountain. Fifth, development direction of dolines resembles the strike direction of limestone in Hogye, suggesting that the development direction of limestone affects doline corrosion. From this situation, we can guess sinkholes of the doline would be linked with limestone caves by the underground water pipe. Three limestone caves, karren and dry valley etc. appear in the research area.

• Journal of the Korea Society of Computer and Information
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• v.14 no.1
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• pp.65-72
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• 2009

This study presents a structural design optimizing sizes of high-rise steel plane truss members by maximizing stiffness subjected to given volume constraints. The sizing optimum design is evaluated by using a well-known optimality criteria (OC) of gradient-based optimization methods. In typical size optimization methods, truss structures are optimized with respect to minimum weight with constraints on the value of some displacement and on the member stresses. The proposed method is an inversed size optimization process in comparisons with the typical size optimization methods since it maximizes stiffness associated with stresses or displacements subjected to volume constraints related to weight. The inversed approach is another alternative to classical size optimization methods in order to optimize members' sizes in truss structures. Numerical applications of a round shape steel pipe truss structure are studied to verify that the proposed maximum stiffness-based size optimization design is suitable for optimally developing truss members's sizes.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.4
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• pp.59-68
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• 1992

A Study was made to improve soil and water temperature and mechanized farming for a wetted paddy under the influence of artesian groundwater located at Samcheon-Dong, Chuncheon City, Kangweon Province. Half perforated PVC drainage pipes were installed in the test paddy to observe temperature change of water and soil. The temperature of the water in the paddy and soil itself raised significantly after the installation of the half perforated PVC pipes. A subsequent improvement of growth and yield of rice on the paddy was achieved. Harvesting operation was also improved with firm ground condition so that cutting and threshing could be done simultaneously within the paddy plot. Following results were obtained from the study. 1.Temperature of the water in a paddy under the influence of artesian groundwater was not changed notably although air temperature was fluctuated during the crop period. Soil temperature was mostly affected by the artesian groundwater. However, the half perforated PVC pipe drainage system made it possible to raise temperature of water and soil remarkably up to the level of optimum farming. 2.Total precipitation was 534.Omm during the crop period of the paddy for 118 days from May 26 to September 20 in 1992. Due to heavy rainfalls of 105.6mm and 109.8mm occurred on August 7 and August 27.1992, respectively, the rate of the artesian groundwater increased to 35 litter per minute with two to three days of time lag. 3.Average rate of the artesian groundwater was 28 litter per minute from the one year of observation. The rate varied by 0.7 to 1.3 times of average during the observation period. Peak rate of the artesian groundwater decreased to 14.5 litter per minute when daily precipitation maintained at the amount of 20 to 30mm for a long time period. Contrarily, it showed a tendency to increase to 35 to 40 litter per minute when heavier precipitation of 50 to l00mm occurred in a short period of three to five days. 4.Growth and yield of Yemyung variety of rice planted on the paddy that was facilitated with a drainage system with half perforated PVC pipes were confirmed at a normal level, while paddy without this perporated drainage system showed abnormal growth with low yield.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.2
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• pp.92-103
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• 1993

A sunday system with a horizontal bin-type composter was constructed and operated to evaluate its composting performance for four days for each test in October, 1992. A sundry system is one of popular systems for composting livestock manure, of which main benefit is to utilize unlimited, clean, and free solar radiation. A rectangular concrete bin(composter) with dimension of 300cm(length) X90cm(width) X60cm(height) was bedded alternatively with four lanes of aeration pipes and heating pipes, and was insulated at three walls with 50mm styrofoam. Each aeration pipe of a diameter of 25mm had 4mm perforated holes at every 15cm longitudinally, and supplied air of about 2m$^3$/min to the composter to maintain aerobic condition . A stirrer rotating at 1 rpm made one round trip every 20 minutes on the conveying chain along the the length of the composter. Five tests (Test 1~Test 5) were implemented to evaluate the composting effectiveness of a sundry system with a horizontal bin-type composter. Treatments of two levels of the mixture ratio of swine manure and paper sludge cakes(manure : paper sludge cakes= 1 : 4 and 1 : 2) and two levels of the water content(W/C ; 70% and 50%) were made to test the significance of the physicochemical properties for decomposition of the mixture materials. Temperature, C/N ratio, water content, microbial activity of the composting materials were taken measurements to evaluate its performance with the lapse of composting time for tests. A small-scale sundry system with a bin-type composter did not appear to be an appropriate system for composting livestock manure. Since heat generation by the composting materials could not overcome heat loss due to areation in a small-scale composter, a proper thermal enviroment could not be maintained to propagate massively thermopilic microorganism relatively in a short period of time. Different from the result of Chol et al.(1992) 6), a temperature variation of the composting materials did not show the peak clearly and C/N ratio didn't lower with time as expected. Mesophilic microoragnism seemed to play an important role for decomposition of the mixture materials. A sundry system with a bin-type composter may be good for a large-scale livestock farm household which may produce enough animal manure. Therefore a decision should be made very carefully to choose a system for composting livestock waste.

• Korean Journal of Environmental Agriculture
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• v.13 no.2
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• pp.223-230
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• 1994

A practical study on a drying and fermentation system equipped with a stirring machine operated mechanically, of pig manure was conducted to prove the efficiency of and practicability to an ordinary pig farm. The type of the drying bed was a round-shaped (r=3m) concrete structure and the stirring machine was adopted to stir and transfer dried pig manure to the fermentation tank. The dried pig manure was put into a fermentation tank ($V=18m^3$), which was aerated from pipe lines installed at the bottom. While water content of pig manure passing through a drying bed was remarkably reduced than before drying, the drying efficiency of this system decreased in winter. However, the temperature of pig manure piled up in the fermentation room in winter reached over $60^{\circ}C$ and excess water of pig manure was removed during the fermentation process. The reduction rate of water content of pig manure, to which dried pig manure was added as bulking material on the drying bed, was 52.1%, but when dried without bulking material it was only 19.7%. Although the content of $P_2O_5$ of dried pig manure was slightly higher than that of fresh pig manure, progressive changes in chemical composition between fresh and dried pig manure made no great difference. Among the contents of minerals of fresh and dried pig manure, CaO was the highest and the rest were in the decreasing order of $K_2O$, MgO, and $Na_2O$. Population density of E. coli and Streptococci of dried pig manure was reduced by 142 and 236 times that of fresh pig manure, respectively. The installation cost of this drying and fermentation system was 4,185,630 won (approximately 5,232 US $) and operating cost per year was 190,000 won (237.5US $) on the basis of self-labor condition.