• Journal of Bio-Environment Control
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• v.2 no.2
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• pp.119-125
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• 1993

The effect of NO$_3$-N and NH$_4$-N ratio on the growth of Perilla frutescens in deep flow culture was studied in winter season. NO$_3$-N and NH$_4$-N were treated in the ratios of 12 : 0, 9 : 3, 6 : 6(me/ $\ell$ ). The pH of the nutrient solution was increased an NO$_3$-N:NH$_4$-N=12 : 0 treatment, and decreased in the treatments containing NH$_4$-N, greatly in NO$_3$-N : NH$_4$-N = 6 : 6 treatment. The EC was increased regardless of treatments, but more increased in the treatments containing NH$_4$-N. The stem-base circumference, plant height, root weight, shoot weight, and yields of leaves were by far the highest in NO$_3$-N:NH$_4$-N=6 : 6 treatment and the lowest in NO$_3$-N:NH$_4$-N= 12 : 0 treatment. Among the mineral contents of leaves, N, K, Fe and P were higher in the treatments containing NH$_4$-N. Ca, Mg and Mn were higher in NO$_3$-N :NH$_4$-N= 12 : 0 treatment.

• Microbiology and Biotechnology Letters
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• v.10 no.1
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• pp.15-26
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• 1982

A potential fungal lipid producer from starch, which was identified as Muror plumbeus, was isolated from natural sources and its optimum cultivation condition for lipid production was investigated. The Mucor plumbeus FRI 0007 showed the highest felt weight and lipid content which were 2.09 $\pm$ 0.24g per 50$m\ell$ of medium and 37.43% on dry weight basis respectively after 20 days incubation on the medium containing 21% of starch as a carbon source. The urea was the best nitrogen source as compared with sodium nitrate, potassium nitrate, magnesium nitrate, ammonium nitrate and ammonium acetate and its optimum concentration was 2.14g/$\ell$, showing 2.39 $\pm$ 0.07 g felt/50$m\ell$ of medium and 50.73% lipid content on dry weight basis after 25 days incubation. Besides the starch as a carbon source and urea as a nitrogen source, the Mucor plumbeus FRI 0007 utilized ZnSO$_4$, MgSO$_4$, NaH$_2$PO$_4$, $K_2$SO$_4$and FeCl$_3$as mineral sources. However, it did not require ail the above 5 minerals in group in-dispensably for its growth and lipid accumulation. The lipid and economic coefficient of Mucor plumbeus FRI 0007 grown on the medium containing 0.44g $K_2$SO$_4$or 5.00g MgSO$_4$/$\ell$solely were 14.96 and 15.37 and 31.12 and 26.10 which was higher than those on the medium containing the above 5 minerals.

• Journal of the Korean Wood Science and Technology
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• v.14 no.4
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• pp.21-28
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• 1986

Plywood used for construction as a decorative inner material is inflammable and can fire accident, causing destruction of human life and property. In this study, 3.5mm Kapur plywoods were soaked in the 23% monoammonium phosphate solutions by cold soaking method 3, 6, 9hrs and hot-cold bath method for 3/3hrs, and redrying was carried out by press-drying at the platen temperature of 110, 130, 160, 180$^{\circ}C$, and then fire test was carried out to investigate burning point, flame exhausted length, frame spread length, back side carbonized area and weight loss. The results are as follows; 1. In cold soaking method for 3, 6, 9hrs. retentions of monoammonium phosphate were 0.377, 0.448, 0.498kg/(30cm)$^3$ respectively, and in hot-cold bath method for 3/3hrs, the retention was 1.331kg(30cm)$^3$ that exceeded the minimum retention 1.124kg/(30cm)$^3$. 2. Correlation coefficients among the variable were shown in table 2. From the table, it could be recognized that there were close negative correlations between the treatment and burning point, flame spread length, back side carbonized area, flame exhausted time and weight loss, and there was negative correlation between treating time and back side carbonized area, but there was positive correlation between platen temperature and burning point. 3. From table 3, it can be observed that there were highly significant differences for burning point, flame spread length, flame exhausted time, back side carhonized area, weight loss between treatments. And in 2-way interactions, there were also highly significant for burning point, flame spread length, flame exhausted time, weight loss between time x treatment. 4. It was observed that burning point, flame exhausted time, flame spread length, back side carbonized area, and weight loss in fire-retardant treated plywood were the best effects in fire-retardant treated plywood, water treated plywood and nontreated plywood. In conclusion, I can estimate that absorbed chemical contents by hot-cold bath method for 3/3hrs, have a lot of effects on fire-retardant factors such as burning point, flame spread length, flame exhausted time, backside carbonized area and weight loss, but platen temperatures have a little effects on the fire factors.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.1
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• pp.29-39
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• 2020

A series of struvite (MgNH₄PO₄·6H₂O) was synthesized and dried at various temperatures (15-60℃). Crystallization of struvite and its structural properties were significantly influenced by synthetic and drying temperature. Struvite was favorably formed at synthetic temperatures ≤30℃ with an inverse relationship between the crystallinity and synthetic temperature. The crystallinity of struvite was also significantly reduced by an increase in drying temperature from 45℃ to 60℃ due to the loss of structural water molecules and ammonium ions by the facilitated thermal decomposition. However, struvite formed at lower synthetic temperature showed higher crystallinity, and its amorphization by thermal decomposition was inhibited. These results demonstrate that struvite formed at low temperature with an stable condition thermodynamically through favorable crystallization shows high crystallinity and stability with respect to the structural and thermal resistance.

• Journal of the Korean Wood Science and Technology
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• v.23 no.4
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• pp.39-45
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• 1995

The plywoods commonly used as decorative interior materials for the construction are inflammable and so it is a causative factor for making fire accidents, resulting in the destruction of human life and personal properties. Indeed, it is, therefore, required to produce fire-retardant plywoods. In this study, a special grade of defect-free, Kapur plywood was used. Specimens were cut into 3- by 20cm dimensions from 120- by 240- by 0.33-cm panels(thin panel) or 120- by 240- by 0.5-cm panels(thick panel). Some specimens were treated with diammonium phosphate(DAP), but some were not treated with diammonium phosphate to use as control panels. Chemical absorption, drying curves, drying rates and dynamic Young's modulus were investigated. The results were summaries as follows; 1. The specimens were soaked into 19% diammonium phosphate solution by a full cell pressure process and the diammonium phosphate retained in the thin and thick plywoods was 1.409kg/$(30cm)^3$, 1.487kg/$(30cm)^3$, respectively. 2. Diammonium phosphate-treated plywoods were redried with press-drying process at one of either condition dried on the platen($115^{\circ}C$) for a period of time or dried on the platen($50^{\circ}C$) for 3 hrs plus in a dry-oven($30^{\circ}C$) for 24 hrs. or dried on the platen($60^{\circ}C$) for 2 hrs plus in a dry-oven($30^{\circ}C$) for 24 hrs. The drying rate of treated thin specimens dried at $60^{\circ}C$ plus $30^{\circ}C$ and $115^{\circ}C$ only was found to be 0.04 %/min. and 8.53 %/min. Similarly, the drying rate of treated thick specimens were 0.03 %/min. and 6.77 %/min. respectively. 3. It was evident that highly-significantly different drying rate of treated plywoods was observed between plywood thicknesses and platen temperatures and the rate was increased by elevating the platen temperature up to $115^{\circ}C$. Based on the two-way variance analysis, highly significant drying rate was observed from the interaction between plywood thicknesses and platen temperatures. 4. After redrying, the specimens were weighed and reconditioned to a constant weight in a facility maintained temperature ($20^{\circ}C$) and relative humidity(65%) prior to test dynamic Young's modulus. The test revealed that the thin specimens dried at the platen temperature of $50^{\circ}C$, $60^{\circ}C$, $115^{\circ}C$ and untreated specimens showed 1.070E+09 dyne/$cm^2$, 1.156E+09 dyne/$cm^2$, 1.243E+09 dyne/$cm^2$, and 1.052E+09 dyne/$cm^2$, respectively. Likewise, the thick specimens revealed 5.647E+09 dyne/$cm^2$ 5.670E+09 dyne/$cm^2$, 6.395E+09 dyne/$cm^2$ and 5.415E+09 dyne/$cm^2$, respectively. 5. It was evident that significantly different dynamic Young's modulus was observed between the plywood thickness and the platen temperature, but not in the two-way interaction between the plywood thickness${\times}$the platen temperature.

• Korean Journal of Organic Agriculture
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• v.25 no.2
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• pp.373-386
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• 2017

The study was conducted to investigate seasonal nutrient dynamics in rice-cultivated soils collected from farmhouses of three large-scale environment-friendly agricultural districts (LEAD), Jangheung, Suncheon, and Okcheon in which environmental-friendly agriculture has been exemplarily practiced in Korea. Among three districts, Crop- livestock cycling organic farming system had been introduced only in Jangheung. pH and EC of farmhouse soils of three LEADs were ranged between 5.5 - 6.7 and $0.4-1.0dS\;m^{-1}$ from March to September, respectively. T-N was observed to be high on the farmhouse soil in Suncheon and K was observed to be lowest on farmhouse soil in Okcheon. Concentration of $NH_4-N$ in soil was observed to be highest on June, in particular on the farmhouse in Jangheung, but rapidly decreased due to the loss of fertilizer applied in Spring. Yield and harvest index were the highest on the farmhouse in Okcheon in which total annual gross production $ha^{-1}$ was nearly three time higher than those of other two farmhouses. Farmhouse soil of Okcheon was maintained the highest seasonal nutrient balance due to the high input of fertilizer. It was estimated that K balance in the farmhouse soil in Suncheon dropped to $-60kg\;ha^{-1}$ on September, and it might have some effect on the less rice productivity due to K deficiency. Farmhouse soil in Jangheung was maintained low seasonal balance of T-N and P but showed the highest N use efficiency in the rice grain. Based on above-mentioned results, we think Jangheung farmhouse can be recommended as a model farmhouse of LEADs.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.3
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• pp.104-110
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• 2001

In this study, the effect of physico-chemical variables on sludge conditioning was determined to enhance dewaterability of effluent produced from the thermophilic anaerobic digestion of food waste. The gas production rate and methane content during the anaerobic digestion of food waste were $1.1m^3/kg$ VS and 63%, respectively, and the biodegradability of volatile solids was 87.5%. The concentrations of CODcr, TKN and TP of effluent from digestor were 18,500mg/L, 2,800mg/L, and 582mg/L, respectively. At the jar test to screen the flocculant for the dewatering of effluent from digestor, $FeCl_3$ and strong cationic polymer were effective on making flocs in the effluent. The condition of flocculation of effluent were 500mg/L of $FeCl_3$ and 50-100 mg/L of strong cationic polymer, respectively. As the result of measuring of dewaterability potential of effluent to determine the mixing ratio between $FeCl_3$ and polymer by capillary suction time(SCT), optimum condition was 500mg/L of $FeCl_3$ and 80mg/L of strong cationic polymer.

• Asian Journal of Turfgrass Science
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• v.20 no.2
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• pp.223-235
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• 2006

Soil testing laboratories unfamiliar with turfgrasses will often overestimate the plant's need for phosphorus and underestimate the need for potassium. This is partly due to differences in rooting between grasses and many garden plants and crops. The grasses are generally more efficient in extracting phosphorus from the soil, reducing their need for phosphorus fertilizer. The fact that crop yield is often the primary objective in field crop production, and is usually of little interest in turfgrass management, may affect soil test interpretation for potassium. Potassium levels above those required for maximum tissue yield of grasses may improve stress tolerance and turfgrasses will usually benefit from higher applications of this element. There are also diffrrences in soil testing philosophies. Some laboratories use the sufficiency level of available nutrients(SLAN) approach, whereas others prefer the basic cation saturation ratio(BCSR) approach. Some will use a combination of the two methods. The use of the BCSR theory easily lends itself to abuse and questionable fertilizer applications and products are sometimes recommended citing imbalances in cation ratios. The usefulness of the BCSR ratio theory of soil testing varies with soil texture and interpretations on tests performed on sand-based media are particularly a problem. Other soil testing problems occur when sand-based media used on sports fields and golf greens contain free calcium carbonate. The ammonium acetate extractant at pH 7.0 dissolves excessive amounts of calcium that can bias cation exchange capacity measurements and measurements of cation ratios. Adjusting the pH of the extractant to 8.1 can improve the accuracy of the testing procedure for calcareous media.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.4
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• pp.333-341
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• 2008

Three embankments are located in the Chunggye Bay, each named as Changpo, Bokkil and Kuil and environmental changes are expected due to freshwater input. To investigate this phenomenon, three sample sites in front of each embankment gate were selected in Nov. 2006(autumn), Feb. 2007(winter), May. 2007(spring) and Aug. 2007(summer). At every point of embankment spot, large cells(micro-size, >$20\;{\mu}m$) of phytoplankton were turned out to be a major cause of algal bloom in Feb. 2007 and nano-size($2-20\;{\mu}m$) phytoplankton became dominant during rainy season. In rainy season, each point of embankment showed low salinity and transparency with higher ammonium and phosphorus concentrations than dry season. However, the number of phytoplankton has decreased and it is expected that freshwater influx has more influence on high turbidity and radical decrease of salinity than nutrient. According to the results of this study, therefore, nutrient could have more influence on growth of phytoplankton in dry season, but high turbidity and radical changes of salinity have more influence in rainy season.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.11
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• pp.613-625
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• 2017

For two agricultural reservoirs that are rented for fishing spots, benthic nutrient fluxes experiment were performed two times with two sediments from fishing-effective zone and one sediment from fishing-ineffective zone using laboratory core incubation in oxic and anoxic conditions. During benthic nutrient fluxes experiment, the changes in DO, EC, pH, and ORP in the supernatant were not significantly different between fishing-effective zone and fishing-ineffective zone, and were similar to the sediment-hypolimnetic diffused boundary layer in agricultural reservoir. Except for $NO_3{^-}-N$, more benthic nutrient fluxes of $NH_4{^+}-N$, T-P, and $PO{_4}^{3-}-P$ from sediment to hypolimnetic was measured in anoxic than in oxic conditions (p<0.05). As the DO concentration in hypolimnetic decreases, the microorganism-mediated ammonification is promoted, the nitrification is suppressed, and finally the $NH_4{^+}-N$ diffuses out from sediment to hypolimnetic. Also, the diffusion of T-P and $PO{_4}^{3-}-P$ from sediments to hypolimnetic is accelerated through the dissociation of the phosphorus bound to both organic matters and metal hydroxides. The difference in the benthic nutrient diffusive fluxes between fishing-effective zone and fishing-ineffective zone was not statistically significant (p>0.05). Therefore, it was found that fishing activities did not increase the benthic nutrient diffusive fluxes to a statistically significant level. Due to the short fishing activities of 10 years and the rate-limited diffusion of the laboratory core incubation, the contribution of fishing activities on sediment pollution is estimated to be low. No significant correlation was found between the total amount of nutrients in sediment and the benthic nutrient diffusive fluxes in both aerobic and anaerobic conditions. Therefore, nutrients input from various nonpoint sources of watersheds are considered to be a more dominant factor rather than fishing activities in water quality deterioration, and both aeration and water circulation in hypolimnetic were required to suppress the anoxic environment in agricultural reservoirs.