• Journal of Bio-Environment Control
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• v.30 no.3
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• pp.244-249
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• 2021

The hydroponic culture for growing 'Duke' blueberry was evaluated in a protective greenhouse provided with similar environmental conditions to the conventional blueberry cultivations. One year old 'Duke' blueberry bushes planted in 180 L containers filled with 130 L peat moss and 40 L pearlite (v/v) were selected for the experiment. A nutrient solution consisted with NO₃-N 4.6, NH₄-N 3.4, PO₄-P 3.3, K 3, Ca 4.6, and Mg 2.2 mmol^-1 was supplied to the plants, comparing non-hydroponic treatment (provided with only underground water). Hydroponic culture increased number of shoot per bush by 18% and total shoot length by 24% compared with non-hydroponic culture. Total dry weight of a bush increased in the hydroponic with vigorous root growth 1.4-fold more than the non-hydroponic. Higher concentrations of inorganic elements and organic compounds were found in the hydroponic, indicating active nutrient absorption of the bush. The hydroponic produced high yield similar to adult bush from 4 years old age, maintaining the yield until 8 years old age. The findings of this study indicated that hydroponic cultivation systems will be useful for growing blueberry crop.

• Journal of Practical Agriculture & Fisheries Research
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• v.23 no.2
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• pp.51-61
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• 2021

As a result of examining the germination rate between ginseng varieties, Jagyongjong varieties had the highest germination rate, and Yeonpung. had the lowest germination rate. In the ginseng seed germination rate experiment, the highest germination rate and growth condition were shown in artificial soil conditions of the ratio of Peatmoss 6.5: Pearlite 2: Masato 1.5. Good soil conditions require adequate soil moisture forces during the incubation period. The cultivation of ginseng medicinal crops requires optimal soil breathability, soil pH, and soil stabilization, which are important for root breathing. Microbial activity in the soil has a great influence on the growth of ginseng. The optimum pH of the soil for ginseng cultivation is 5.0-5.5 As a result of the experiment, the soil remained in an appropriate range after a month. In general, when the EC concentration value of the soil for ginseng cultivation is 0.2 mS/cm or more, growth deteriorates, and when the EC concentration value is 0.5 mS/cm or more, concentration obstacles such as root decay occur. As a result of the analysis, the higher the concentration value of EC, the more likely it is to interfere with ginseng growth.

• Journal of Conservation Science
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• v.38 no.4
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• pp.289-300
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• 2022

In the 6^th and 7^th centuries, 5 iron artifacts excavated form the Baekje Stone Tomb in Guryong-ri site, Ungcheon, Boryeong, were studied. The sample were metal microscopic observation, SEM-EDS analysis and Raman micro-spectroscopy analysis were conducted to understand the metallurgical characteristics. The microstructure observation showed the presence of ferrite and pearlite throughout, and differences in carbon content existed depending on the direction. Non-metallic inclusions were in the form of long lines, and most of them were wüstite, fayalite. It is indicated that the artifacts were forge welded using hypoeutectoid steel, with signs of carburizing and decarburizing processes. Some crystals with high P₂O₅, TiO₂, CaO content were identified as sarcopside, ulvöspinel, and perovskite, respectively, through Raman spectroscopy. A comparison of the results with previous studies on the sites of Bujang-ri site in Seosan and Bongseon-ri site in Seocheon, which are adjacent sites in the coastal area, revealed that, while heat treatment technology was available, the artifacts were not heat-treated considering the purpose for use for these artifacts. The chemical composition of the non-metallic inclusions P₂O₅, TiO₂, CaO were plotted in proportions to SiO₂ and compared with adjacent sites. Considering that the P₂O₅/SiO₂ ratio was widely distributed, the refining technology was not uniform. In addition, the TiO₂/SiO₂ ratio was found to be higher than that of other sites, meaning that a titanium-containing ore was used to manufacture the artifacts, unlike in surrounding sites, but it is not detected in all artifacts, so it may have been affected by various factors such as furnace walls in addition to raw materials. Although slag formers were used, considering the CaO/SiO₂ ratio and the (Al₂O₃/SiO₂)/(CaO/SiO₂) ratio, which appear to be similar to the surrounding sites, but it is possible that CaO containing raw ore was used because it is also affected by the components of raw ore. As a result of the study, it is highly likely that ore different from that of the surrounding sites was used for production, but a more comprehensive comparative study with the surrounding sites is needed in the future.

• Journal of Practical Agriculture & Fisheries Research
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• v.6 no.1
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• pp.63-72
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• 2004

This study was conducted to determine the growth and properties of green soybean sprouts(Vigna umbellata Thunb.) in soil culture. Patkong which is a small grain variety was sawn on electric heated hot bed in the greenhouse. Temperature of the culture bed were respectively 17, 20, 25, and 30℃ and water temperature were respectively 14, 17, 20 and 25℃. The kinds of soil used for this study were upland soil, sand, peatmoss and Pearlite, loess, loess and activated carbon. BA was treated in the concentrations of 240 times, 80 times, 40 times besides control. High temperature of 25 and 30℃ increased sprout yield compared to lower temperature but caused to decay from 7 days after sawing. Thus, the most optimum temperature for soil culture was 20℃. The best soil was sand of which increased fresh weight of 850g during same period. Addition of BA was most effective to promote sprout growth in the concentration of 80 times. Compared to general soybean sprouts, green soybean sprouts were 50% higher in fiber but 72% lower in glucide. Vitamin B was 200% higher in green soybean sprouts but vitamin C was higher in general soybean sprouts.

• Journal of Korea Foundry Society
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• v.43 no.6
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• pp.279-285
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• 2023

In order to predict the mechanical properties of ductile cast iron heat treated in an intercritical temperature range, samples machined from cast iron with a tensile strength of 450 MPa were heat-treated at various intercritical temperatures and air-cooled, after which a microstructural analysis and Brinell hardness test were conducted. As the heat treatment temperature was increased in the intercritical temperature range, the ferrite fraction in the ductile cast iron decreased and the pearlite fraction increased, whereas the nodularity and nodule count did not change considerably from the corresponding values in the as-cast condition. The Brinell hardness values of the heat-treated ductile cast iron increased gradually as the heat treatment temperature was increased. Based on the measured alloy composition, the fraction of each stable phase and the hardness model from the literature, the hardness of the ductile cast iron heat treated in the intercritical temperature range was calculated, showing values very similar to the measured hardness data. In order to check whether it is possible to predict the hardness of heat-treated ductile cast iron by using the phase fraction obtained from thermodynamic calculations, the volumes of graphite, ferrite, and austenite in the alloy were calculated for each temperature condition. Those volume fractions were then converted into areas of each phase for hardness prediction of the heat-treated ductile cast iron. The hardness values of the cast iron samples based on thermodynamic calculations and on the hardness prediction model were similar within an error range up to 27 compared to the measured hardness data.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.1
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• pp.49-59
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• 1984

Optimizing investigation of characteristics of underwater welding by a gravity type arc welding process was experimentally carried out by using six types of domestic coated welding electrodes for welding of domestic marine structural steel plates (KR Grade A-1, SWS41A, SWS41B,) in order to develop the underwater welding techniques in practical use. Main results obtained are summarized as follows: 1. The absorption speed of the coating of domestic coated lime titania type welding-electrode became constant at about 60 minutes in water and it was about 0.18%/min during initial 8 minutes of absorption time. 2. Thus, the immediate welding electrode could be used in underwater welding for such a short time in comparison with the joint strength of in-atmosphere-and on-water-welding by dry-, wet-or immediate-welding-electrode. 3. By bead appearance and X-ray inspection, ilmenite, limetitania and high titanium oxide types of electrodes were found better for underwater-welding of 10 mm KR Grade A-1 steel plates, while proper welding angle, current and electrode diameter were 6$0^{\circ}C$, above 160A and 4mm respectively under 28cm/min of welding speed. 4. The weld metal tensile strength or proof stress of underwater-welded-joints has a quadratic relationship with the heat input, and the optimal heat input zone is about 13 to 15KJ/cm for 10mm SWS41A steel plates, resulting from consideration upon both joint efficiency of above-100% and recovery of impact strength and strain. Meanwhile, the optimal heat input zone resulting from tension-tension fatigue limit above the base metal's of SWS41A plates is 16 to 19KJ/cm. Reliability of all the empirical equations reveals 95% confidence level. 6. The microstructure of the underwater welds of SES41A welded in such a zone has no weld defects such as hydrogen brittleness with supreme high hardness, since the HAZ-bond boundary area adjacent to both surface and base metal has only Hv400 max with the microstructure of fine martensite, bainite, pearlite and small amount of ferrite.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.319-325
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• 2018

The aim of the present study was to determine the influence of different fertilizer combinations on the growth, yield, and fruit quality of 'Duke' blueberry cultivar and the water quality of growth medium. The experiment was carried out with three year old 'Duke' blueberry bushes which were cultivated in containers ($60{\times}80{\times}40cm$) filled with 130 L peat moss and 40 L pearlite (v/v). Sawdust was used as the mulch in growth containers. Three different fertilizer combinations (FC) i.e., FC-1 consisted with standard solution, FC-2 consisted with nitrogen reduced by 10% from FC-1, and FC-3 consisted with nitrogen reduced by 20% from FC-1 were tested while, the ground water used as the control. The effects of different fertilizer combinations on shoot diameter, shoot length, number of shoots, leaf length, SPAD value (the relative content of chlorophyll), berry weight, soluble solids content, titratable acidity, and yield per bush in 'Duke' blueberry were examined. Also, the effects of different fertilizer combinations on pH, EC, $NH_4$ and $NO_3$ in 'Duke' blueberry growth medium were monitored. The highest pH and lowest EC, $NH_4$ and $NO_3$ in growth medium was recorded with control treatment during the experiment period. The maximum shoot diameter (3.7 mm) and shoot length (35.7 cm) was recorded for the FC-1. Highest number of shoots (47%) were recorded from 'Duke' blueberry bushes supplemented with FC-1 compared to other treatments. The fertilizer combinations supplemented with nitrogen showed significant influence on leaf length and SPAD value compared to control 'Duke' blueberry bushes. However, the fruit quality attributes, i.e., berry weight, soluble solids content, and titratable acidity were not significant different among fertilizer treatments. The significantly highest yields per bush were recorded for FC-1, FC-2, and FC-3, as 2.2, 2.9, and 2.7 kg, respectively compared to control (0.2 kg). Although, the FC-1 was supplemented with highest nitrogen content it resulted low yield per bush while having high number of shoots and vigorous growth.

• Journal of Environmental Impact Assessment
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• v.28 no.6
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• pp.604-615
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• 2019

In this study, we produce a new type of the algae soil conditioner(ASC) using discarded algae biomass through a composting process and evaluate its nutritional characteristics. As the main ingredient, the ASCs used algae biomass collected through the coagulation-floating method and made by adding a variety of additional supporting materials (sawdust, pearlite, oilcake etc.). ASCs were divided into 0% in blank, 11.7% in ASC1, 21.6% in ASC2, 37.6% in ASC3, 59.5% in ASC4, and composted during 127 days. ASCs showed a sharp increase in temperature by aerobic microbial reaction, and 6~7 high and low temperature peaks were observed. As a result of physicochemical analysis, mineralization proceeded according to decomposing the organic matter and there was a marked increase not only in macronutrients (TN, P₂O₅, K₂O), but also in secondary macronutrients (CaO, MgO). The microbial community change was found in stage 1 (bacteria, filamentous fungi) → stage 2 (actinomycetes, bacteria) → stage 3 (Bacillus sp.), depending on the maturation process. It was estimated that microbial transition was closely related to temperature change and nutritional behavior. The quality of soil conditioner can be determined according to the maturity of compost process, and it was determined that effective microbial activity could be induced by controlling algae biomass below 59.5% in this study. In conclusion, we found out the possibility of manufacturing and utilizing soil conditioner recycled algae biomass and if further technological development is made on the basis it can be used as an effective soil conditioner.

• Korean Journal of Heritage: History & Science
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• v.53 no.2
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• pp.4-23
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• 2020

The purpose of this study was to explore the diversity of Korea's iron casting technology and to examine various casting methods. The study involved a literature review, analysis of artifacts, local investigation of production tools and technology, and scientific analysis of casting and cast materials. Bellows technology, or Bulmi technology, is a form of iron casting technology that uses bellows to melt cast iron before the molten iron is poured into a clay cast. This technology, handed down only in Jeju Island, relies on use of a clay cast instead of the sand cast that is more common in mainland Korea. Casting methods for cast iron pots can be broadly divided into two: sand mold casting and porcelain casting. The former uses a sand cast made from mixing seokbire (clay mixed with soft stones), sand and clay, while the latter uses a clay cast, formed by mixing clay with rice straw and reed. The five steps in the sand mold casting method for iron pot are cast making, filling, melting iron into molten iron, pouring the molten iron into the cast mold, and refining the final product. The six steps in the porcelain clay casting method are cast making, cast firing, spreading jilmeok, melting iron into molten iron, pouring the molten iron, and refining the final product. The two casting methods differ in terms of materials, cast firing, and spreading of jilmeok. This study provided insight into Korea's unique iron casting technology by examining the scientific principles behind the materials and tools used in each stage of iron pot casting: collecting and kneading mud, producing a cast, biscuit firing, hwajeokmosal (building sand on the heated cast) and spreading jilmeok, drying and biyaljil (spreading jilmeok evenly on the cast), hapjang (combining two half-sized casts to make one complete cast), producing a smelting furnace, roasting twice, smelting, pouring molten iron into a cast, and refining the final product. Scientific analysis of the final product and materials involved in porcelain clay casting showed that the main components were mud and sand (SiO₂, Al₂O₃, and Fe₂O₃). The release agent was found to be graphite, containing SiO₂, Al₂O₃, Fe₂O₃, and K₂O. The completed cast iron pot had the structure of white cast iron, comprised of cementite (Fe₃C) and pearlite (a layered structure of ferrite and cementite).

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.447-453
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• 2019

In this study, the effect of supplying volume and frequency of a nutrient solution consisted with $NO_3-N$ 4.6, $NH_4-N$ 3.4, $PO_4-P$ 3, K 3, Ca 4.6 and Mg $2.2mmol{\cdot}L^{-1}$ on growth and fruit quality of 'Duke' blueberry was investigated. Three years old 'Duke' blueberry bushes cultivated in containers ($60{\times}80{\times}40cm$) filled with 130L peat moss and 40L pearlite (v/v) were selected for the experiment. The growth containers were mulched with sawdust. Two different volumes (4L and 8L) of nutrient solution was tested at three different supplying frequencies (one time, two times, and three times) per week and the drainage quality of nutrient solution and fruit quality of 'Duke' blueberry was evaluated. The optimal drainage rate for the vegetable cultivation is known to be 20-30%. The results revealed that the average drainage rates of 27% and 29% for the nutrient solution supplied in 'Duke' blueberry growth medium at 4L, 2 times/7 days and 4L, 3 times/7days, respectively. The highest shoot diameter (4.2mm) and shoot length (31cm) of 'Duke' blueberry was recorded with the 8L of nutrient solution supplied at 3 times per 7 days. According to the analysis of inorganic components in the drainage of nutrient solution, there was a tendency of absorbing nitrogen at the early stage of growth. The supplying volume and frequency of nutrient solution was not significantly affected on 'Duke' blueberry fruit weight, soluble solids content, and titratable acidity. The highest yield per bush (2.7kg) was recorded for the nutrient solution supplied with 4L at three times per 7 days, while the 4L nutrient solution supplied at one time per 7 days resulted the lowest yield of 1.4kg per bush. Consequently, the tested nutrient solution can be applied for the 'Duke' blueberry bushes with the volume of 4L at three times per week for the better crop growth.