• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.68-74
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• 2012

Investigation of the effective soil thermal conductivity($k$) is the first step in designing the ground loop heat exchanger(borehole) of a geothermal heat pump system. Another important factor is the borehole thermal resistance($R_b$). Thermal response tests offer a good method to determine the ground thermal properties for the total heat transport in the ground. The first step is measured for initial soil temperature. This is done by supplying a only pump power into a borehole heat exchanger. They need to supply into water unload heat power more than 30 minutes. In this study, the initial soil temperature was found to analysis $14.1{\sim}16.0^{\circ}C$,the ratio was 68.7% represented. In this case of $k$, was 2.1~3.0 $W/m{\cdot}k$, $R_b$ was 0.11~0.20 $m{\cdot}K/W$. In this work, it is also shown that the distribution of a soil thermal conductivity and borehole thermal resistance were on the influence of initial soil temperature. And soil thermal conductivity was related with factors of equation by linear least square method, borehole thermal resistance was on the influence of composite factors.

• Water for future
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• v.15 no.2
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• pp.11-22
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• 1982

This study is to find out the reasonable drainage system of sewerage in connection with the geographical conditions, the form of city, and the problem of sewerage in and around Seoul. (1) In supplying the sewerage sewer, the separating system is desirable in connection with the problem of sewerage disposal in future. However, in the existing urban district, the conjunction system is used because of the large amount invested according to the diversion of the sewer of the separation system and the influence of the traffic communication. The sewer of the separating system should be used in the case of the fundamental reconstruction of structure as the redevelopment of the urban district or the subway and new-development of area. Therefore, the separating system should be used completely until the goal year. (2) Drainage area was divided for the natural flowing, considering that the 38 streams and topography paly a role of the main stream of drainage. There are the branches, Guyui, Dug-island, Jayang, Hannam, Banpo, Amsa whose divisions are impossible. In these branches, the drain planning was suggested a forced control method by using the exiting pond age and the pumping station. (3) The best available method which improbes the water quality in Han river is as follows. The sewerage is catched and carried to the sewerage disposal plant by establishing the intercept sewer in both or one side of stream. At the same time, the groudwater volume which springs in each stream is drained separatively.

• Journal of Bio-Environment Control
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• v.30 no.4
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• pp.367-376
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• 2021

Strawberry cultivation in Korea is grown in greenhouse, but most farms manage their water supply using a timer control method based on the experience of growers. The timer control has problems in that it is difficult to consider the weather condition, the growth stage of crops, and the moisture content of the substrate, so that the crops cannot be managed at an optimal level, and the accuracy of cultivation management are lacking. The watering methods using integrated solar irradiance and substrate moisture contents are control systems that provide eco-friendly and precise water supply considering the growth conditions of crops. The purpose of this study was to compare the combined water supply control with integrated solar irradiance and substrate moisture contents and timer control method in hydroponic cultivation of strawberries using coir, and to set the optimal integrated solar irradiance level for complex water supply control. The irrigation system was automatically watered when it reached 100, 150, 250 J·cm^-2 based on the external solar irradiance, and forced irrigation was performed at a substrate moisture content of less than 60% in all treatments. The amount of irrigation at once was 50 mL. The timer treatment was applied as a control. The smaller the level of integrated radiation to start watering, the greater the daily amount of irrigation. Both the fresh weight and dry weight per plant were higher in the complex irrigation control method than the timer control, and the 100 and 150 J·cm^-2 treatment had the highest fresh weight, and the 100 J·cm^-2 treatment showed a significantly higher dry weight. The yield was also significantly higher in the complex control method than in the timer, and the early yield increased as the level of integrated solar irradiance was smaller. The fresh weight of fruit was the lowest in the timer-controlled irrigation. As a result of this study, the possibility of combined control irrigation method using integrated solar irradiance and substrate moisture content was confirmed for precise water supply management of strawberries in hydroponics.

• The Plant Pathology Journal
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• v.24 no.4
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• pp.453-460
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• 2008

In the course of in vitro and in vivo screening for bioherbicidal agents, a hyphomycete fungus, Myrothecium sp. F0252 was selected as a candidate for the biocontrol of weeds. The isolate was identified as Myrothecium roridum Tode ex. Fries based on the morphological characteristics and 18S ribosomal DNA sequence analysis and registered as Myrothecium roridum F0252. In order to evaluate the in vitro effect of M. roridum F0252 on germination of ladino clover and white clover (Trifolium repens L.) seeds, spore solution of the fungus was employed in two concentrations, $6.5{\times}10^6$ and $2.5{\times}10^7$ spores per mL and then inoculated to the seeds. The fungal spores inhibited the seed germination, infected the seedlings, and caused an abnormal withering and inhibition of seedling growth. In addition, when the herbicidal activity of crude ethyl acetate extract from the liquid culture was assessed on a mini-plant, duck-weed (Lemna paucicostata (L.) Hegelm.), the extract showed high inhibitory effect at the level of $12.5{\mu}g$ per mL. On the other hand, in vivo herbicidal activity of M. roridum F0252 was evaluated by a whole plant spray method. M. roridum F0252 exhibited strong and broad-spectrum herbicidal activity. The herbicidal values ranged from 95-100% against 7 weeds, including Abutilon avicennae and Xanthium strumarium, and 70-80% against Digitaria sanguinalis and Sagittaria pygmaea. When the nutritional utilization (95 carbon sources) pattern of M. roridum F0252 was investigated, it varied with water activity ($a_w$) and temperature conditions, supplying good, basic information in regard to nutritional utilization for proper cultivation and formulation. Our results showed that M. roridum F0252 might be used as a potential biocontrol agent against weedy plants.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.2
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• pp.52-61
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• 2004

This study has been carried out to classify forest vegetation in south and north slopes of Donghaksa valley for supplying basic data for conservation and restoration of the valley. With the phytosociological method, the forest of the south and north slopes of Donghaksa valley was classified as four groups; Quercus variabilis community, Quercus mongolica community, Pinus densiflora community and Carpinus laxiflora community. The dominant species were found in the order of Pinus densiflora, Quercus variabilis, Carpinus laxiflora, and Quercus mongolica. Comparing the north and south slopes, Quercus variabilis were the highest dominant species in the south and Carpinus laxiflora in the north. Pinus densiflora were the next dominant species in both south and north slopes. According to the DBH analysis result, Pinus densiflora and Quercus variabilis had density of normal distribution style among the entire community. Therefore, their dominance are expected to continue for now. But, Quercus mongolica and Carpinus laxiflora are expected to extend their influence in the future in terms of competition with Pinus densiflora. The correlation between each community and the environment according to DCCA ordination was examined in this study. The result told us that Quercus variabilis is distributed mainly on the south slope in a mid-steep and mid-altitude area. Quercus mongolica community appeared on the north slope in the steep high-altitude area that has high percentage in total nitrogen and CEC. Pinus densiflora community is distributed on both south and north slopes in a gentle slope and low-altitude area. Carpinus laxiflora is distributed on the north slope in a mid-steep and mid-altitude area.

• Clean Technology
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• v.27 no.1
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• pp.39-46
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• 2021

A road structure washing vehicle equipped with a 4 HP, 80 LPM ultrafine bubble generator was used to clean a tunnel wall and the surface of the surrounding structure, consisting of concrete and tiles, in a heavy traffic area around an apartment complex in the city. Ultrafine bubbles were generated by supplying air at 2 to 3 LPM and using a specially designed nozzle, whereas fine bubbles made by an impeller in a gas-liquid mixing self-priming pump were produced with an average diameter of 165.4 nm and 6.81 × 107 particles mL-1. Using a high pressure washer gun that can perform high-pressure cleaning at 150 bar and 30 LPM, ultrafine bubbles were used to wash dust adsorbed on the surface of the road structures. The experimental analysis was divided into before and after washing. The samples were analyzed by applying ISO 8502-3 to measure surface contamination of dust adsorbed on the surface. Using the transparent tape attached to the surface, the removal rate was calculated by measuring the weight of the dust, and the number of particles was calculated using the gravimetric method and the software, ImageJ. The results of the experiment showed that the number of dust particles adsorbed on the tile wall surface before and after washing were 3,063 ± 218 particles mL-1 and 20 ± 5 particles mL-1, respectively, with weights of 580 ± 82 mg and 13 ± 4 mg. Particles on the surface of the concrete structure before and after washing were 8,105 ± 1,738 particles mL-1 and 39 ± 6 particles mL-1, respectively, with weights of 1,448 ± 190 mg and 118 ± 32 mg.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.409-415
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• 2022

Plant growth and development are also affected by root-zone environment. Therefore, it is important to consider the variables of the root-zone environment when establishing an irrigation strategy. The purpose of this study is to analyze the relationship between the volumetric moisture content (VWC), Bulk EC (ECb), and Pore EC (ECp) used by plant roots using FDR sensors in two types of rockwool media with different water transmission characteristics, using the method above this was used to establish a method for collecting and correcting available root-zone environmental data. For the experiment, two types of rockwool medium (RW1, RW2) with different physical characteristics were used. The moisture content (MC) and ECb were measured using an FDR sensor, ECp was measured after extracting the residual nutrient solution from the medium using a disposable syringe in the center of the medium at a volumetric moisture content (VWC) of 10-100%. Then, ECb and ECp are measured by supplying nutrient solution having different concentration (distilled water, 0.5-5.0) to two types of media (RW1, RW2) in each volume water content range (0 to 100%). The relationship between ECb and ECp in RW1 and RW2 media is best suited for cubic polynomial. The relationship between ECb and ECp according to volume moisture content (VWC) range showed a large error rate in the low volume moisture content (VWC) range of 10-60%. The correlation between the sensor measured value (ECb) and the ECp used by plant roots according to the volumetric water content (VWC) range was the most suitable for the Paraboloid equation in both media (RW1, RW2). The coefficient of determination the calibration equation for RW1 and RW2 media were 0.936, 0.947, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.1
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• pp.57-65
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• 2017

In a column experiment with low rank coal, rice straw was additionally supplied to induce methane gas generation by microorganisms in the state of supplying microorganisms and nutrients, and long-term biogas production characteristics were observed. When the weight ratio of the rice straw to coal was 0.04 or less, there was no significant gas generation. At 0.08, the biogas was generated for about 90 days. However, the methane gas generation was only 5% compared with the vial test result at optimum condition. Therefore, in order to produce biogas in the coal deposit in situ, a reactor that operates at COD concentration of 2000 mg/L or more at a ratio of 1:3 or more of rice straw to coal should be installed on the ground or under the ground. Liquid from the column filled with coal and rice straw and a liquid from vial containing rice straw were analyzed by microbial community analysis using pyrosequencing method, and compared the dominant microbial species among the two samples. In terms of the uniformity and diversity of the bacteria, the coal-filled column showed various species distribution, which has shown to be a disadvantageous microbial distribution to methane production.

• Korean Journal of Soil Science and Fertilizer
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• v.10 no.3
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• pp.153-170
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• 1977

Considering the ways for the possible improvement of soil test for upland crops, various methods for the evaluation of K supplying power and testing of available soil K were reviewed in terms of theoretical principles and practical usefulness of the each method. The review was also made on the characteristics of upland crops in K requirement and on the chemical properties of major korean upland and lowland rice soils in terms of K availability. Following is the few remarks drawn from the review. 1. Quite large number of methods have been known for the evaluation of K supplying power and testing for available soil K. In nature, they can be divided into two categories; capacity-based methods and intensity-based methcds. The capacity-based methods usually measure the exchangeable and some portion of nonexchangeable K, while the intensity-based methods suggest to consider the ractivity ratios of major cations in soil solution and the energy requirement for the replacement of exchangeable soil K into soil solution. 2. As methodology for extraction of interested part of soil K, chemical extraction, electrodialysis and ion exchange methods have been known. Among these, chemical extract ion is favorable because of its simplicity. However, recently suggested Electro-Ultra-Filtration method seems to merit further study for wider use for not only K but also other nutrient availability of soils. 3. The intensity-based methods, although they are more theoretical, because of their complexity, in methods may not be adapted for practical soil tests. 4. The exchangeable K which is rather simple to measure and which well reflects the status of K reserve as nonexchangeable and is immediate pool of water soluble K may be good, if not best, criterion of soil K availability to plant in common soil testing. 5. Because there are evidences that the abundance of available K alone may not be good inclication for availability of K to plant, it is recommendable to interprete the exchangeable K data as percent saturation of exchangeable K to total C. E. C. of soil for the recommend ation of K fertilizer based on soil tests. 6. Some pot and field trial results showed the trends that percent potassium saturation to total C. E. C. better serve as the parameter for K fertilizer recommendation.

• Journal of Practical Agriculture & Fisheries Research
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• v.20 no.2
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• pp.105-114
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• 2018

The aim of this study was to evaluate the change of phenolic compounds after phosphite treatment on Cheorwon onion. Onion is a perennial plant belonging to the lily family. It is native to Persia of Southwest Asia. It is widely cultivated in the temperate regions of the world. Onion is a good name for the 'Okchong' to drop blood cholesterol and cardiovascular blood flow to increase the prevention of adult diseases. Cheorwon area is inland, but it has high continental climate due to its high altitude. Therefore it is said that the onion cultivated in this region has higher sugar content and higher taste than onion grown in the southern region. Phosphorus components are particularly important ingredients for promoting muscle development. However, if the phosphoric acid content of the soil part is maintained to a large extent until the harvest, the competition of the nutrients tends to cause decay of the root part. Therefore, it is important to improve the quality and shelf life of onion by inducing nutrient balance by applying foliar fertilization method on the reducing phosphorus at harvest time. In this study, acidity was controlled by diluting phosphorous acid(H₃PO₃) and potassium hydroxide(KOH), followed by leaf surface treatment with phosphite on onion. In this study, the concentration of phosphite was diluted to 500, 1,000, 1,500ppm and sprayed three times over the onion leaves in May 2018 using an atomizer and harvested at the end of June, and the phenolic compounds were analyzed by HPLC. As a result, the content of quercetin, one of the important substances in onion, was phosphite 500ppm(179.70㎍/g), 1,000(150.27), 1,500(105.95). The contents of caffeic acid, p-coumaric acid, ferulic acid, rutin, kaempferol, and sugar content were higher in the treatments than in the control. Therefore, the phosphite does not have a great influence on the growth, but it may play a role as a method of achieving balance with nitrogen in the rainy season by supplying the role of the material catalyst and the water soluble phosphoric acid and the potassium in the influence of the material change.