• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.2
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• pp.61-72
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• 2007

The relationship between North Pacific chum salmon (Oncorhynchus keta) population and climate variability was investigated in the North Pacific ecosystem. Time-series for the Aleutian Low Pressure, Southern Oscillation, Arctic Oscillation, and Pacific Decadal Oscillation (PDO) indices dating back to 1950 are compared with the chum salmon catch using a cross-correlation function (CCF) and cumulative sum (CuSum) of anomalies. The results of CCF and CuSum analyses indicated that there was a major change in climate during the mid 1970s, and that the chum salmon population responded to this climate event with a time-lag. The PDO and chum salmon returns showed a highly significant correlation with a time-lag of 3 years, while the AOI with a time-lag of $6{\sim}7$ years. The favorable environments for fry chum salmon might cause better growth in the coastal areas, but higher growth rate during the early stage does not seem to be related to the improved return rate of spawning adults. Rather, growth in the Okhotsk Sea or the Bering Sea during immature stages has a significant correlation with return rate, which implies the size-related mortality process. The development of a local climate index is necessary to elucidate the effect of climate variability on the marine ecosystem around the Korean Peninsula.

• Korean Journal of Ecology and Environment
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• v.57 no.2
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• pp.61-74
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• 2024

Daemadeung, located in the estuary of the Nakdong River, is formed by sand dunes and possesses well-developed intertidal flats. This study aimed to investigate the habitat of benthic microalgae, photosynthetic pigments, and photosynthetic efficiency in the intertidal flats of Daemadeung from January to December 2011. The inorganic nitrogen content in the sediment pore water was primarily composed of ammonium, while nitrate + nitrite was dominant in the upper layer water. The concentration of chlorophyll a and fucoxanthin in the sediment surface was significantly higher than the mean of all the sediment layer. The average Fv/Fm of benthic microalgae during the entire survey period was 0.52±0.03, with the highest value (0.61±0.08) observed in February. The rETR_max showed a seasonal trend, being high from spring to early autumn (April to October) and low from winter to early spring (January to March, November, December), with the highest value (153.05±2.30 µmol electrons m^-2 s^-1) in July and the lowest (38.49±5.17 µmol electrons m^-2 s^-1) in January. The average Fv/Fm of diurnal microalgae was 0.48±0.03, with the highest value (0.61±0.08) observed at noon. The rETR_max showed a highest peak at noon (54.24±11.35 µmol electrons m^-2 s^-1) and reached its lowest point at 16:00 (26.17±4.75 µmol electrons m^-2 s^-1). These findings suggest that the productivity of benthic microalgae varies significantly depending on the survey time and sediment depth. Therefore, to quantify the productivity of benthic microalgae using Diving-PAM, surveys should be conducted based on tidal conditions, and simultaneous pigment analysis of sediment layers should also be performed.

• Korean Journal of Ichthyology
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• v.36 no.3
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• pp.220-229
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• 2024

This study investigated the early life history of Rhinogobius giurinus in the Botongcheon stream and compared the differences with related species. The fertilized egg size (long×short) of the 3.46×1.17 mm (n=30) on average. The time required for hatching at the water temperature of 22.5±1℃ was 213 hours and 30 mins. Immediately after hatching, the egg yolk had an average total length of 2.34±0.05 mm (n=30), and the mouth and anus were not opened, and the number of myotomes was 23~25. 3 days after hatching (DAH), the preflexion larvae had an average total length of 2.70±0.09 mm (n=30), and live food intake began as the mouth and anus were opened. 22 DAH, the flexion larvae had an average total length of 5.26±0.16 mm (n=30), and the tip of the vertebrae began to bend upward. 48 DAH, the postflexion larvae had an average total length of 11.1±0.53 mm (n=30), and the tip of the vertebrae was completely bent 45° upward. 60 DAH the juveniles had an average total length of 14.9±0.69 mm (n=30) was reached to the integer with 6 first dorsal fins, 8~10 second dorsal fins, 9 anal fins, 15 caudal fins, and 5 ventral fins for each fin. As a result of the study, the melanophore differed from other postflexion larvae of the Gobiidae fishes in that it was deposited above the gill lid, on the back and body, and the xanthophore was deposited on the head and body.

• Journal of Korean Society of Forest Science
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• v.30 no.1
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• pp.19-29
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• 1976

The fiberboard and paper mills in this country are much affected by the price hikes and shortage of phenolic resins, since phenolic acid as a raw material depends on imported good. It is prerequisite to fiberboard industry to help replace with other sized and stabilize the prices and supply of them, improving the quality of boards. Thus, the present study was carried out to examine the effect of strength increasing sized such as urea formaldehyde resin (anion and cation type) and urea melamine copolymer resin, on the quality of the wet forming hardboard, and comparing them with two types of proprietary modified melamine resins, and ordinary size, phenol resin. The Asplund pulp was prepared from wood wastes mixed with 20 percent of lauan and 80 percent of pines as a fibrous material. After sizing agents were added at a pH of 4.5 for 10 minutes with alum in the beater, the stock was made in the form of wet sheet, prepared, and then performed by hot pressing cycle: $180^{\circ}C$, $50-6-5kg/cm^2$, 1-2-7 minutes. The properties of hardboard were examined after air conditioning. The results obtained are summarized as follows: 1. There is a significant difference in specific gravity among hardboards that were treated with strength increasing resins, but no difference is effected by the increase in the resin content. In the case of modified melamine resin, its specific gravity is highest. The middle group comprises cation type of urea resin, anion type of urea resin, and acid colloid of urea-melamine copolymer resin. The lowest is phenolic resin. 2. The difference of the moisture content of hardboard both by the resins and by the amount of each resin applied is significant. The moisture content of hardboard becomes lower along with the increase of each resin content, but there is no difference between 2 and 3 percent. 3. For water absorption, there is a significant difference both in the adhesives used and in the amount of paraffin wax emulsion. The water resistance becomes higher inn proportion to the content of the paraffin wax emulsion. To satisfy KS F standards of the water resistance, a proprietary modified melamine resin (p-6100) and modified cation type of urea resin (p-1500) do not require any paraffin wax emulsion, but in the case of anion type of urea resin, cation type of urea resin, and urea-melamine copolymer resin, 1 percent of paraffin wax emulsion is needed, and 2 percent of paraffin wax emulsion in the case of phenolic resin. 4. The difference of flexural strength of hardboard both by the resins and by the amount of each resin is significant. Modified melamine resin shows the highest degree of flexural strength. Among the middle group are urea-melamine copolymer resin, p-1500, anion type of urea resin, and cation type of urea resin. Phenolic resin is the lowest. The cause may be attributable to factors combined with the pressing temperature, sizing effect, and thermal efficiency of press platens heated electrically. 5. Considering the economic advantages and properties of hardboard, it is proposed that urea-melamine copolymer resin and cation type of urea resin be used for the development of the fiberboard industry. It is desirable to further develop the modified urea-melamine copolymer resin and cation type of urea resin through continuous study.

• Journal of the Korean Wood Science and Technology
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• v.2 no.2
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• pp.25-31
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• 1974

1. Various gluing qualities applying Resorcinol Plyophen #6000 were studied on aiming the strength relationships of laminated woods resulted by single species [poplar (Populus deltoides), larch(Larix leptolepis)], mixed species of (poplar and larch), preservatives, treated poplar the scarf joint with mixed species of poplar and larch and the scarf joint treated with preservatives. 1. 1 On the block shear and on the DVL tension test, the mean wood failure ratio showed an excellent value i.e., above 65% and the tangential strength for larch was higher than that of radial, but it was reversed for poplar as shown in Tables 1 and 2. 1. 2 The lamina treated with Na-PCP reduced slightly the strength but the limited strength allowed for manufacturing laminated wood was not influenced by treating Na-PCP as shown in Tables 3 and 4. 1. 3 The safe scarf ratio in the plane scarf joint was above 1/12 for larch and 1/6 for poplar regard less of the chemical treatment or untreatment as shown in Tables. 5, 6, 7 and 8. 2. In the normal and boiled state, the gluing quality of the laminated wood composed of single[poplar (Populus deltoides), larch (Larix leptolepis)] and double species (poplar and larch) glued with Resorcinol Plyophen #6000 were measured as follow, and also represented the delamination of the same laminated wood. 2.1 The normal block shear strength of the straight and curved laminated wood (in life size) were more than three times of the standards adhesion strength. And, the value of the boiled stock was decreased to one half of the standard shear adhesion strength, but it was more than twice the standard strength for the boiled stock. Thus, it was recognized that the water resistance of the Resorcinol Plyophen #6000 was very high as shown in Tables 9 and 10. 2. 2 The delamination ratio of the straight and curved laminated woods in respect of their composition were decraesed, in turn, in the following order i. e., larch, mixed stock (larch+poplar) and poplar. The maximum value represented by the larch was 3.5% but it was below the limited value as shown in Table 11. 3. The various strengthes i.e., compressive, bending and adhesion obtainted by the straight laminaced wood which were constructed by five plies of single and double species of lamina i. e., larch (Larix leptolepis) and poplar (Populus euramericana), glued with urea resin were shown as follows: 3. 1 If desired a higher strength of architectural laminated wood composed of poplar (P) and larch (L), the combination of the laminas should be arranged as follows, L+P+L+P+L as shown in Table 12. 3.2 The strength of laminated wood composed of laminas which included pith and knots was conside rably decreased than that of clear lamina as shown Table 13. 3.3 The shear strength of the FPL block of the straight laminated wood constructed by the same species which were glued with urea adhesives was more than twice the limited adhesion strength, thus it makes possible to use it for interior constructional stock.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.3
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• pp.318-332
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• 2015

The maize production in South-eastern Asian countries showed a continuous increase with increasing poultry-livestock from the beginning of the 1990s to early 2010. Also the need for a new variety development of each contries was increased rapidly in the same period. Single-Cross hybrid varieties have been developed and supplied from 2001 instead of multi-cross maize varieties since 1992 in Indonesia. In Cambodia, CP group is mainly manufacturing feeds with most of the forage maize from farmers who are growing its seeds from the company. Cambodian main cultivars are varieties of multinational corporations such as DK8868 from Monsanto, NK6326, NK7328 from Syngenta and CP333 from CP group including local business company. Vietnam is the main maze importing country in South-Eastern Asia which had imported 13 times scale of amount compared to exports in average from 1990 to 2011. Vietnamese government has developed a range of varieties for improving their efficiency in production, such as the LVN-10 with political investments. Their production has been reached to 80% of the total. According to the 2012 MIFAFF (Ministry for Food, Agriculture, Forestry and Fisheries) data in Korea, domestic edible maize cultivation area was approximately 15,000ha. It showed 74,399 tons of production, 3.8% of food self-sufficiency in maize and around 0.9% of grain self-sufficiency rate. The consumption of grain is mostly rely on imports in Korea. To overcome the limit of the domestic seed market and increase maize self-sufficiency, the need to develop maze varieties for world-class is increasing at present through analyzing the market trend and prospect of the seed industry in South-eastern Asia.

• Korean Journal of Soil Science and Fertilizer
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• v.11 no.1
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• pp.43-50
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• 1978

In order to compare the effectiveness of different phosphorus forms (pulverized as regranulized) and formulars (compound fertilizers) of fused phosphate and to compare the effectiveness of boron from different forms (straight borax, granulized with fused phosphate and included in compound fertilizer), a field experiment was conducted on a relatively fertile upland soil using soybean as a test crop. Results are summarized as following. 1. Yield of soybean was significantly higher in the plots fertilized with P when compared to check plot (no p). However, no significant differences were observed among the different forms or formulars of fused phosphate, indicating that the regranulization or formulation of compound fertilizer did not influence the effectiveness of phosphorus. 2. The application of boron, regardless of its formular, brought about higher B content in plant tissue and higher grain yield. There was a tendency that boron contained in ragranulized fused phosphate was more effective than straight borax. The results also indicated that when boron is to be included in NPK compound fertilizer, its content should be at the least 1.5% as $B_2O_3$. 3. The effectiveness of boron appeared as increased number of pod, higher B, and Ca contents in plant and the amounts of uptake of these elements by soybean. 4. The analysis of soil after the experiment indicated that different forms or formulars of fused phosphate were similarly effective in increasing the available P, Ca, and Mg contents in the soil. 5. Slight increase in available B contents in the experimental plot soils applied with boron fertilizer was observed after the trial.

• Journal of Korean Society of Forest Science
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• v.24 no.1
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• pp.45-52
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• 1974

This study was carried out to examine the subsitution possibility into water soluble amino resins instead of phenolic resin as a sizing material for the strength increase on the wet forming hardboard. The properties of hardboard, manufactured with amino-resins based urea, melamine, formaline, and methanol which were low priced domestic products, were examined in comparison with those of hardboard treated with phenolic resin. In this study by the results and discussions, it may be summarized as follows: 1. Amino-resins are able to be substituted for the phenolic resin as a good sizing material for strength increase in the manufacture of wet forming hardboard. Under the considerations of economic advantages and properties of hardboard, modified urea-melamine resin was given a best results. 2. The specific gravities of hardboard that were treated with phenolic resin was equal to that treated with modified amino type resin, and in case of urea-melamine resin, the specific gravity value were lowest among them. 3. The results of moisture contents were satisfied the standard which calls for 13 percent or below. There were no differences in moisture contents between hardboards, treated with melamine resin and modified urea-melamine resin but phenolic resin. The moisture contents of hardboard treated with phenolic resin was shown the lowest. 4. The water absorption of hardboard treated with phenolic resin was greater than those treated with amino resins, and to satisfy the standard of water resistance, the treatment of 2 percent paraffin wax emulsion was needed in this case. There were no differences in water absorptions between hardboards, treated with melamine resin and modified urea-melamine resin. To satisfy the standard of water resistance in this case the treatment of 1 percent paraffin wax emulsion was shown good results. 5. The differences among the flexural strength in using tested three adhesives were significant. The flexural strength were shown the signification by order of melamine resin, modified urea-melamine resin, and phenolic resin. In all cases to satisfy the standard of flexural strength, the treatment of 3 percent sizing materials for strength increase was needed.

• Journal of Aquaculture
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• v.10 no.4
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• pp.449-456
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• 1997

This study was concuted to determine the optimal conditions for raising the freshwater rotifer, Brachinus calyciflorus. The authors presented some biological informatin obtained from incubation experiment under the various controlled temperatures. Lorica size of the rotifer was divided into two groups : the length and the width for the S-type was $141.0\pm16.7\mu m$($110.1-182.5\;\mu m, n=44$)and $107.0\pm20.3\mu m\;(75.3-152.3\mu m, n=44)$, and those for the L-type was $262.8\pm15.2\mu m\;(234.4-288.6\mu m,\;n=20)\;and\;182.6\pm13.4\mu m (159.8-207.0\mu m,\;n=20$), respectively. The number of eggs being attached on the female varied from 1 to 11 at various culture conditions. Egg type was divided into two groups, large and small. Large and small egg was measured in its major axis as 85a.7-107.8$\mu$m and 55.1-65.2$\mu$m for S-type, and 104.9-121.8 $\mu$m and 62.8-89.1$\mu$m for L-type respectively. The maximum density was reached at 4th day after incubation. The density was 583.9 rotifers/$m\ell$ for $25^{\circ}C$-experimental. group and 421.3 rotifers/$m\ell$ for $22^{\circ}C$-experimental. group respectively. In the case of $28^{\circ}C$-experimental. group, it suddenly decreased into 4.7 rotifers/$m\ell$ at 1st day after incubations and did not recover to its initial density. The maximum rate of increase of populatin per day was reached 0.802 for $22^{\circ}C$-experimental. group at day 2 and fluctuated thereafter. For $25^{\circ}C$-experimental. group it increased to 0.964 at day 3 of incubation and then declined. And the egg ratio of female was reached the maximum of 0.614 for 22$^{\circ}C$- at 3rd day and 0.772 for $25^{\circ}C$-experimental. group at 4th day of incubation.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.2
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• pp.61-70
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• 2000

Soil erosion in the hilly and mountainous uplands in the Daekwanryong area, Kangwon-Do, were investigated through a field plot experiment. The plot size was 15m long and 2.5m wide with the average slope of 12.5 percents. Soil erodibility factor (K), surface coverage (SC), soil aggregate percentage and wind erodibility (I) were evaluated in the mountainous soils under different management practices for corn and potato cultivations. Soil erodibility factor (K) was greater in upper part than in lower part of the plots. Surface coverage (SC) values ranged from 0.01 to 0.84 depending on the amounts of crop residues. Soils having a greater crop residue in surface were less subjected to soil erosion. SC values after corn harvest were 0.4 to 0.8, while those after potato harvest were 0.4 to 0.5, indicating potato might be better than corn for erosion control. Soil aggregate percentages of the experimental plots ranged from 49.7 to 79.8%. Those were higher in potato-cultivated plots with higher surface coverage, organic fertilizer treatment and contour tillage. Soil aggregate percentage of potato-cultivated plots was significantly correlated to crop residue coverage after harvest. The dried soil aggregate percentage, showing the ranges of 26.4 to 56.4%, were higher in the plots with the increased crop residue incorporation. Wind erodibility (I) of the soil was decreased with increasing surface coverage. When soil had 26.4% of the dried aggregate percentage, wind erodibility was estimated to be $183Mgha^{-1}$ which was equivalent to soil loss of $0.5Mg\ha^{-1}day^{-1}$.