• Korean Journal of Soil Science and Fertilizer
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• v.49 no.4
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• pp.310-317
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• 2016

This study aimed to evaluate the nutrient load balance from rice paddy fields with different topographies, alluvial plain and local valley. Continuous monitoring from May to September, 2013 was conducted for water quantification and qualification from alluvial plain in Yeoju region (32 ha) and local valley in Jincheon region (24 ha). The discharge rates of T-N from the alluvial plain were 57.2, 5.84, 22.7, and $5.20kg\;ha^{-1}$ for irrigation, precipitation, drainage, and percolation, respectively. In case of local valley, T-N loads were 34.6, 4.73, 21.1, and $4.15kg\;ha^{-1}$ for irrigation, precipitation, drainage, and percolation, respectively. In contrary, the T-P loads from the alluvial plain were 2.23, 2.22, 2.54, and $0.41kg\;ha^{-1}$ for irrigation, precipitation, drainage, and percolation, respectively. In case of local valley, T-P loads were 1.44, 1.57, 1.82, and $0.34kg\;ha^{-1}$ for irrigation, precipitation, drainage, and percolation, respectively. The nutrient contents in drainage water were influenced by the amount of waters, rainfall, and surface drainage water. The Pearson correlation analysis showed that rainfall was significantly correlated with nutrient loads from July to August due to the amount of runoff in local valley paddy field, and irrigation was related with nutrient loads of drainage from July to August. This study showed that paddy rice farming in alluvial plain and local valley might be beneficial to water quality protection.

• Journal of Korea Water Resources Association
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• v.31 no.5
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• pp.515-528
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• 1998

A quasi-two-dimensional model for simulating the flood plain flow is developed. The model consists, in general, of a multiply-connected network which combines the main channel and two-dimensional flood plain cells. The main channel flow is described by the Saint Venant equations for one-dimensional unsteady flow, and the flood plain flow by the cell continuity and river-or weir-type stage-discharge relations between flood plain cells. The implicit algorithm for unsteady flow in looped channel network is extended to incorporate the flood plain flow. To verify the performance of the model, it is applied to three test problems, and sensitivities to various model parameters are analyzed. It turns out that the present model gives more accurate result than that by Cunge (1975) as the shape of cross section becomes more complex and irregular. Not only the inundation of water from the main channel but the return flow from the flood plain is successfully simulated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.8
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• pp.656-663
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• 2002

Flow condensation heat transfer coefficients (HTCs) of R22, R134a, R407C, and R410A were measured on horizontal plain and microfin tubes. The experimental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water/glycol loop. The test section in the refrigerant loop was made of both a plain and a microfin copper tube of 9.52 mm outside diameter and 1.0 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. Tests were performed at a fixed refrigerant saturation temperature of $40^{\circ}C$ with mass fluxes of 100, 200, and 300 kg/$m^2s$. Test results showed that at similar mass flux the flow condensation HTCs of R134a were similar to those of R22 for both plain and microfin tubes. On the other hand, HTCs of R407C were lower than those of R22 by 11~l5% and 23~53% for plain and microfin tubes respectively. And HTCs of R410A were similar to those of R22 for a plain tube but lower than those of R22 by 10~21% for a microfin tube. In general, HTCs of a microfin tube were 2.0~3.0 times higher than those of a plain tube.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.641-646
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• 2001

Generally, when Fly-Ash was used as replacement material of cement in concrete, it might occur retardation of setting and hardening. So, it is unable to use a large amount of Fly-Ash as replacement for cement. However, if it is used as replacement material of fine aggregate in concrete, we can use a large amount of Fly-Ash and settle a problem of natural-aggregate exhaustion. Furthermore, engineering properties of High Volume Fly-Ash Concrete Is better than that of plain concrete But, the larger Fly-Ash is replaced, the more fluidity of High Volume Fly-Ash Concrete decrease, because porous organization of Fly-Ash adsorb water and Superplasticizer. In this study, after appending additional water to High Volume Fly-Ash Concrete in proportion to weight of Fly-Ash, we intend to find proper ratio which doesn't affect strength and satisfy fluidity As a result of this study, it was found that fluidity of mortar with 25~28 percentage of additional water was satisfied with fluidity of plain mortar, and compressive strength of that was similar to plain mortar's

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.2
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• pp.67-75
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• 1982

A study on the effect of water reducing agent on the various characteristics of concrete has been conducted. The experimental results of the study are summarized as follows. 1. Slump test for the concrete added water reducing setretarding agent in proper quantity have been conducted. According to the test results, the decreasing rate of slump value become bigger than plain concrete with increase of the unit weight of cement and elapse of time 2. In case the proper quantity content of maximum compressive strength in Fig. 5 of water reducing set retarding agent is added, unit weight of water is decreased about 15% or so as compared with plain concrete. with the increase of water reducing set accelerating agent content unit weight of water is decreased much more, And other hand, amount of air entraining shows the increasing tendency with the increase of water reducing agent content. 3. The adding rate of water reducing agent which produce maximum strength shows that WR-CH and WR-SA which is water reducing set-starding agent is 0.2% and WR-CO is 0.5% and that WS-PO which is water reducing set accelerating agent is 0.5 4. compressive strength jof the concrete made of sulfate resistant cement shows less than the strength of normal portland cement at initial strength but the strength of both cement shows almost same at curing age of 28 days. 5. when proper quantity of water reducing set retarding agent is used, boned strength is increased about 15% at curing age of 28days. 6. According to the result of durability test, dynamic young's mudulus of elasticity at plain concrete is decreased about 50% as compared with initial step at 300 cycle of freezing and thawing after curing age of days. on the contarary the concrete used water reducing agent is decreased less than 7%.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.56-66
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• 1990

To investigate the status of irrigation water use and the degree of repeated use of irrigation water, observations for water balance analysis were made during the irrigation periods in 1986 and 1987 crop year. The total area of studied site is 1,441 ha. The site is a major portion of Jedaecheon basin which is located in Bubuk-myeon, Miryang-gun, Gyeongnam Province. The studied area was subdivided into six small blocks. The water balance analysis for these subdivided blocks were carried out considering characteristics of each block. Obtained results are as follow: 1.In mountainous sloppy paddy area(less than 7% slope), the surface inflow was 5A mm/day in average that is one third of the surface inflow into plain paddy area ; 16.7 mm/day. 2.The surface inflows at the vegetative stage and the ripening stage were 15.5 mm/day and 10.4 mm/day, respectively. Those figures were larger than the actual consumptive use at respective same stages ; 13.3 mm/day and 9.2 mm/day, respectively. Whereas, the surface inflow at generative stage was 12.5 mm/day which was less than 14.0 mm/day ; the actual consumptive use. 3.The range of the variation of water storage term was 1 mm/day. This means that there were no change in depth of ponded water on paddy fields. The relationship between the variation of water storage(AS) and the variation of ground water table(H) could be expressed as follow: : AS=0.14H+0.26 4.The ground water inflow: into the transition region ; paddy fields which are located continuously from the mountainous area to the plain area, was larger than the out flow from this region, in general. Rowever, in the plain region where the ground water utilization was predominant, the ground water outflow from this region was larger than inflow: to this region. The relationship between the ground water flow(G2- G1) and the consumptive use in large paddy area(D1-D2) could be expressed as follow: (G2-G1) =0.95(D1-D2) -3.79

• Journal of Environmental Science International
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• v.12 no.2
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• pp.185-193
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• 2003

The purpose of this study was attempted to establish concepts of environmental-friendly applications of flood plain and to suggest the application plans. The results of this study can be summarized as follows; 1. Roles of flood plain as biotop (restoration, preservation, and creation of stream corridor ecosystem) should be considered. 2. Application methods considering environmental and scenic values should be reviewed. 3. Application methods reflecting values as regional ecological resources should be planned. 4. Preservation and application should be considered together, and obtaining a means of living for regional residents and creation of economic profits should be considered together. 5. Land application and approach method by usages (integrated management model) should be applied to utilize and manage flood plain efficiently. 6. Flood plain application programs should be designed reflecting opinions of regional residents. 7. With respect to space planning of flood plain, introduction of facilities focused on ecosystem preservation/ecosystem restoration/experiences/observation/learning/culture/ recreation/water purification could be reviewed positively.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.6
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• pp.1872-1879
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• 2015

The present study was conducted on the improvement of the heat transfer performance of double pipe heat exchangers with helical insert device. Double pipe heat exchangers with helical insert device were studied for improvement of the heat transfer performance of double pipe heat exchangers with helical insert device and plain double pipe heat exchangers were also studied to comparatively analyze heat transfer performance. Experimental results were derived on changes in the Reynold's numbers of the cooling water flowing in helical and plain double pipe heat exchangers and changes in the heat flux of the air. Thereafter, to verify the reliability of the experimental results, the theoretical total energy and the experimental total energy were comparatively analyzed and the following results were derived. The thermal energy of the calorie lost by the hot air and that of the calorie obtained by the cooling water were well balanced. The experiments of plain double pipe heat exchangers and double pipe heat exchangers with helical insert device were conducted under normal conditions and the theoretical overall heat transfer coefficient value and the experimental overall heat transfer coefficient value coincided well with each other. In both plain double pipe heat exchangers and double pipe heat exchangers with helical insert device, heat transfer rates increased as the cooling water flow velocity increased. Under the same experimental conditions, the heat transfer performance of double pipe heat exchangers with helical insert device was shown to be higher by approximately 1.5 times than that of plain double pipe heat exchangers.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.505-508
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• 2004

This paper investigated the setting and compressive strength of concrete with the combination of mineral and chemical admixture. According to test results, plain concrete with high early strength development type AE water reducing agent(HEAEWRA) and $10\%$ of CKD respectively had earlier setting time than concrete with AE water reducing agent by $0.5\~1.5$ hours. Setting time of concrete with retarding type AE water reducing agent(RAEWRA) and FA $30\%$, BS $60\%$ respectively retarded by as much as $4\~7.5$ hours compared with plain concrete. Plain concrete with HEA WRA, $10\%$ of CKD and RAEWRA had higher strength than that of AE water reducing agent by as much as 5MPa at 28days. From the result of the paper, it is found that the combination of mineral admixture and setting accelerating or retarding agent can reduce the hydration heat cracks by setting time difference and hydration heat reduction effects.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.67-73
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• 2007

Anhui Province, with a total north-south length of 570km and an east-west width of 450km and a total area of 139.6 thousand km2, accounts for 1.45% of China's total area. The landform and land feature of Anhui Province is diverse, and generally it can be divided into 5 natural regions: (1) Huaibei Plain; (2) Jianghuai Hillocks; (3) Dabie Mountains in the West of Anhui Province; (4) Yanjiang Plain, (5) Mountain Area of southern Anhui Province. Anhui Province is located in the transitional zone of warm and humid zone and subtropical zone, and its mean annual precipitation is 800-1800mm. The province, which has diverse climate, multiple land forms and many rivers and lakes, passes three basins (Huaihe River, Yangtze River and Xin'an River) and has large differences in the time distribution and regional distribution of water resource. Therefore, the development and usage conditions of the water resource in different regions are different.