• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.1
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• pp.68-73
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• 1986

In order to identify the physiological maturity and to determine the proper time of harvesting as fresh seed for cooking with rice and germination ability according to the harvesting time in cowpea (Vigna unguiculata (L.) Walp), this experiment was conducted. The results obtained are as follows; 1. The length and width of pods became maximum size on 10 days after flowering(DAF) and thickness of them increased to 14 DAF and then decreased to 18 DAF. 2. The weight of pod wall reached the maximum on 14 DAF, the thickness of them increased to 8 DAF and decreased to 18 DAF and it was stabilized. 3. The length and thickness of the seeds became larger to 10 DAF, were not changed from 10 DAF to 16 DAF and then decreased after 16 DAF. 4. The seeds coloured 2 days earlier than the pod wall on 8 DAF and the grade increased by degrees to 16 DAF. 5. The moisture content of seeds and pod wall started to decrease on 8 DAF and the moisture content of pod wall was higher than that of seeds in the middle stage but the condition changed after 18 DAF. 6. When the weight of seeds reached the maximum on 16 DAF, the moisture content of them was 54.5%. 7. The content of total nitrogen, phosphate and oil decreased but the carbohydrate increased by degrees along the passing of DAF. The silicic acid did not exist and K$_2$O, CaO, MgO, protein etc. existed but did not show regular tendency. 8. The physiological maturity was 16 DAF and the proper time of harvesting as fresh seed for cooking with rice was 12 DAF to 16 DAF. 9. Germination was possible after 10 DAF but we could get the normal roots from the seeds harvested after 14 DAF.

• Korean Journal of Plant Resources
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• v.24 no.2
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• pp.243-252
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• 2011

Fermented compost made from medicinal herb wastes (MHWC) as an environment-friendly manure resource was applied to determine physiological activities of Rubus coreanus Miquel (Bokbunja). MHWC, poultry manure compost (PMC), and MHWC+PMC (1:1, w/w) were applied to 2 year-old Bokbunja plant at levels of 0, 20, 40 Mg/ha, respectively. Physiological activities of Bokbunja were investigated at 15, 20 and 25 days after flowering (DAF). Content of total phenolics in fruit was high in order of 25 > 20 > 15 DAF, showing highest value in fruit treated with MHWC at 40 Mg/ha. The flavonoid level showed same pattern to total phenolics. Electron donation abilities at fruits at 15 and 20 DAF were higher than at 25 DAF. Nitrite scavenging ability (NSA) was increased on in order of pH 1.2 > 4.2 > 6.0. NSA in fruit at 15 and 20 DAF was higher than at 25 DAF. Tyrosinase inhibition ability at fruits treated with MHWC showed the highest value among all composts. Xanthine oxidase inhibition ability in fruit treated with MHWC at 25 DAF was the highest. In conclusion, physiological activities of Rubus coreanus Miquel (Bokbunja) were improved in MHWC group.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.242-246
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• 2004

Dissolved air flotation (DAF) is an effective solid/liquid separation process for low density particles, such as algal flocs, humus materials and clay particles produced from low turbidity water. The fraction of humic substances for natural organic matters (NOMs) are considered problematic in water because it can readily react with chlorine to form harmful by-products (trihalomethanes) and can be exposed to undesirable color, tastes and odors in drinking water. A broad class of NOMs includes fulvic acid, humic acid and humin. This paper will discuss the results from a study that performed with a DAF pump process using synthetic wastewater contained humic substance. Batch jar tests were performed to evaluate coagulant dose and recycle ratio on flotation efficiency.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.191-200
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• 2004

DAF process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when the freshwater blooms occut or raw water turbidity become high. Pre-sedimentation iS prepared in case when raw water turbidity is very high by rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while it is difficult to remove in sedimentation. One of the main concerns in adoption of DAF (Dissolved Air-Flotation) process is a high raw water turbidity problem. That is, DAF is not adequate for raw water, which is more turbid than 100NTU. In order to avoid this problem, pre-sedimentation basins are prepared in DAF plant to decrease the turbidity of DAF influent. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, DAF process coupled with sedimentation is suggested that pre-sedimentation with optimum coagulation prior to DAF would be appropriate.

• Journal of Korean Library and Information Science Society
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• v.51 no.2
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• pp.103-131
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• 2020

This study was started with the aim of grasping the current status of research data management of forestry engineering researchers. In order to achieve the research purpose, the survey was conducted using a tool called DAF (Data Asset Framework). DAF is an investigative tool that provides a means to identify, position, describe and evaluate how the agency manages research data. Using this DAF, the research data management status was analyzed for researchers in the field of forestry engineering at the National Institute of Forest Science. As a result of analysis, the current status and problems of the five categories such as the method and type of research data creation, sharing, storage, preservation, and reuse were identified, and solutions were presented in relation to the problems. This study is a basic investigation using a systematic tool such as DAF, and can be used as a reference for analyzing the current status and problems of research data when designing RDM system in a specific field.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.659-666
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• 2011

Although DAF(Dissolved Air Flotation) has been successfully accepted for water and wastewater treatment, the fundamental characteristics of the process have not been fully investigated. Water is saturated with compressed air to dissolve the air into the water at high pressure in saturation tank. Then the water containing dissolved air is released into a floatation tank at a lower pressure, generating micro-bubbles that rise gently through the water and carry the suspended matter to the surface. This study investigated the removal of sewage using automatic mixture type DAF pump and non-powered flotation tank. Characteristics of two devices were compared and analyzed with samples. The results showed that the PAC exhibited higher performance than other coagulants. When air dosage was 2.5ml/l/min, treatment was stable in operation. In the DAF pump with a pressure of 4 atm., the average size of bubbles was 36.2${\mu}m$. Removal efficiency of SS was 80%. At this time removal efficiency of COD was about 80%, of T-N was 30% and T-P was 70% in stable operation. It was concluded that DAF pump system with micro bubble performed higher efficiencies compared to general DAF system for treating wastewater.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.4
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• pp.1-9
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• 1980

To determine the optimum harvest time of recent rice varieties from Indica/Japonica remote crosses, leading varieties Suweon 264 and Milyang 23 were tested for the changes in dry matter weight and moisture content of grain, shattering, shelling ratio, milling ratio, and apparant physical quality during grain development at 5 day-intervals from 20 days to 55 days after heading. The results are summarized as follows: 1. Grain weight (dry matter) reached its maximum (physiological maturity) at 30 days after flowering (DAF) in Suweon 264, and at 35 days in Milyang 23, and thereafter it did not change significantly until 55 DAF. 2. Time course of decrease in grain moisture content (Y, %) during maturation (X, DAF) consisted of two linear phases, i.e. a fast and a slow period: Y=68.245-1.33X until 34DAF, and Y=23.025-0.470X until 55DAF after 34DAF in Suweon 264; Y=73.62-1.634X until 24.5DAF, and Y=33.59-0.570X until 55DAF after 24.5DAF in Milyang 23. Two varieties showed the same grain moisture content of 28% (wet basis) at physiological maturity in spite of the distinct differences in the heading date, time of physiological maturity and thereby ripening climate. 3. Force to shatter a grain ranged about 90 to 100g in Milyang 23, and about 200 to 250g in Suweon 264 and in a Japonica variety, Jinheung. The force, however, did not change significantly with harvest time from 35DAF to 50DAF. 4. The changes in the ratios of shelling, milling, broken rice and tinted rice with harvest time were insignificant during a period from 35DAF to 55DAF. However, ratios of green rice and white belly rice decreased significantly with delay in harvest time during 10 days after physiological maturity. 5. The best time of harvest for maximum yield and good quality is thought to be 10 days after physiological maturity, and grain moisture content at this time was about 20% on wet basis.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.837-842
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• 2007

This study was conducted to test the effect of residual Al on plankton community after dissolved air flotation (DAF) application. Growth rate of phytoplankton after DAF application ($0.37day^{-1}$) was about 2 times lower than that before DAF application ($0.70day^{-1}$). Under the condition of addition of nitrogen and phosphorus without light, growth rate phytoplankton in treatment without residual Al increased in difference with showing the negative growth rate in treatment with residual Al. Under the condition of light without addition of nutrient, growth rate of phytoplankton was no noticeable difference between the before and after DAF application. The relatively high settling rate (0.47 m/day) was observed in treatment after DAF application. Although the abundance of rotifer decreased, the abundance of copepod and cladoceran such as Daphnia galeata, Diaphanosoma sp. and Bosmina longirostris with relative higher grazing was no noticeable difference between the before and after DAF application. In the treatments before and after DAF application with zooplankton, growth rate of phytoplankton was $0.41{\pm}0.08day^{-1}$, $0.20{\pm}0.03day^{-1}$, respectively. This difference was in treatment after DAF application similar with those in treatments before and after DAF application without zooplankton. Those indicate that the filter-feeding effect of zooplankton on phytoplankton community may be not changed by residual Al after the DAF application. These results suggest that residual Al after DAF application be to improve water quality by inhibition of growth rate as well as increasing settling rate of phytoplankton.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.293-303
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• 2011

An efficient diagonalized approximate factorization algorithm (DAF) is developed for the solution of three-dimensional incompressible viscous flows. The pressure-based, artificial compressibility (AC) method is used for calculating steady incompressible Navier-Stokes equations. The AC form of the governing equations is discretized in space using a second-order-accurate finite volume method. The present DAF method is applied to derive a second-order accurate splitting of the discrete system of equations. The primary objective of this study is to investigate the computational efficiency of the present DAF method. The solutions of the DAF method are evaluated relative to those of well-known four-stage Runge-Kutta (RK4) method for fully developed and developing laminar flows in curved square ducts and a laminar flow in a cavity. While converged solutions obtained by DAF and RK4 methods on the same computational meshes are essentially identical because of employing the same discrete schemes in space, both algorithms shows significant discrepancy in the computing efficiency. The results reveal that the DAF method requires substantially at least two times less computational time than RK4 to solve all applied flow fields. The increase in computational efficiency of the DAF methods is achieved with no increase in computational resources and coding complexity.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.2
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• pp.80-87
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• 1996

Treatment efficiencies of water quality parameters such as $KMnO_4$ Demand, $UV_{254}$, Turbidity, and LAS(Linear Alkyl Sulfonate) were compared between DAF(Dissolved Air Flotation) and CGS(Conventional Gravitational Sedimentation). The experimental results showed that DAF is much more efficient in treatment of water quality parameters than CGS. The optimum pH was about 7, and optimum alum($Al_2(SO_4)_3$) dose was about 30 ppm for DAF treatment. Economic aspects were also analyzed for bath systems. Even though production cost per ton of drinking water is slightly higher in DAF than in CGS, it turned out that construction cost and land value of CGS far surpass the production cost. DAF system is superior in removal efficiency of impurities and in production cost as a whole to CGS system.