• Journal of Environmental Science International
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• v.33 no.1
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• pp.87-95
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• 2024

The giant jellyfish, Nemopilema nomurai, is an endemic species found in Northeast Asian waters and their population structures, such as size and genetics, and their environmental characteristics were investigated. N. nomurai was obtained from the Yellow and Northern East China Seas during the summers of 2006, 2007, and 2009. In the northern Yellow Sea, small-sized jellyfish were found to be dominant and towards the southern seas, the size of the jellyfish increased. In the northern East China Sea, only one mode of jellyfish was found in May, and the number of modes increased up-to five in July. However, at the center of the Yellow Sea, one or two modes were found in July, 2007. Thus, different jellyfish populations were present in the northern East China Sea and the Yellow Sea. However, based on first appearance and a cohort analysis using the bell diameter, the jellyfish population in the northern Yellow Sea might be recognized as a distinct group that differed from those found in the northern East China Sea. Furthermore, mitochondrial DNA sequences (cytochrome c oxidase subunit I) of N. nomurai were, determined and compared with genetic structures obtained from jellyfish in the Yellow Sea. The genetic diversity of N. nomurai was highest in the regions around the northern East China Sea and at the center of the Yellow Sea and was the lowest around the northern Yellow Sea. Thus, N. nomurai populations in the Yellow Sea and northern East China Sea might be different concerning their seeding places.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.1-7
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• 2014

In this study, the effect of velocity ratio and particle size on the flow mixing characteristics in the secondary combustor was investigated. Both PIV(Particle Image Velocimetry) technique and LES(Large Eddy Simulation) were applied. Two sizes of Polystyrene PIV seeding particle of 5 and $50{\mu}m$, and three velocity ratios of 5, 3, and 1.5 were considered. Results showed that the mixing of two air streams created reattachment and recirculation regions. The size of the recirculation region was decreased as the velocity ratio increased. For the larger particle cases, due to the increased momentum by the larger particles, the size of the recirculating regions were larger than that of the smaller particle cases and the effect of the velocity ratio was not as significant as in the smaller particle case.

• Korean Journal of Plant Resources
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• v.23 no.4
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• pp.360-367
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• 2010

The genetic diversity and structure of P. tongkangensis in 5 populations from 3 regions was investigated using 56 markers derived from 6 ISSR primers. Genetic diversity at the species level (P=94.6, SI=0.377, h=0.240) was substantial considering the limited distribution and small size of populations. Genetic differentiation among regions (12%) and among populations (13%) in the region was not clearly evident, which suggested a moderate level of gene flow among adjacent populations. The Mantel test revealed a significant correlation between genetic differentiation (${\Phi}_{ST}$) and geographic distance among populations. This was supported by cluster analysis and principal coordinate analysis (PCoA). The significant difference in marker band frequency at many loci and their fixation in opposite directions in the smallest and most isolated population SC were considered due to genetic drift. Therefore, the genetic diversity of P. tongkangensis could be compromised if the distribution area or the size of the population was further reduced. In particular, small and isolated populations could be at great risk of extinction. Considering this, the unique habitats of P. tongkangensis should be protected and the reduction of population size should be closely monitored. Conservation efforts including the seeding and planting of seedlings should be done carefully based on their genetic and ecological traits. Our data support the argument that establishing an integrated management system for the efficient conservation of P. tongkangensis is critical.

• Journal of the Korean association of regional geographers
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• v.2 no.1
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• pp.51-67
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• 1996

There are three main rice-growing regions in the United States: the prairie region along the Mississippi River Valley in eastern Arkansas; the Gulf Coast prairie region in southwestern Louisiana and southeastern Texas; and the Central Valley of California. The Central Valley of California is producing about 23% of the US rice(Fig. 1). In California. most of the crop has been produced in the Colusa, Sutter, Butte, Glenn Counties of the Sacramento Valley since 1912, when rice was commercially grown for the first time in the state(Fig. 2). Roughly speaking, the average annual area sown to rice in California is about 300,000 acres to 400,000 acres during the last forty years(Fig. 3). California rice is grown under a Mediterranean climate characterized by warm, dry, clear days, and a long growing season favorable to high photosynthetic rates and high rice yields. The average rice yield per acre is probably higher in California than in any other rice-growing regions of the world(Fig. 4). A dependable supply of irrigation water must be available for a successful rice culture. Most of the irrigation water for California rice comes from the winter rain and snow-fed reservoir of the Sierra Nevada mountain ranges. Less than 10 percent of rice irrigation water is pumped from wells in areas where surface water is not sufficient. It is also essential to have good surface drainage if maximum yields are to be produced. Rice production in California is highly mechanized, requiring only about four hours of labor per acre. Mechanization of rice culture in California includes laser-leveler technology, large tractors, self-propelled combines for harvesting, and aircraft for seeding, pest control, and some fertilization. The principal varieties grown in California are medium-grain japonica types with origins from the cooler rice climates of the northern latitudes (Table 1). Long-grain varieties grown in the American South are not well adapted to California's cooler environment. Nearly all the rice grown recently in California are improved into semidwarf varieties. Choice of variety depends on environment, planting date, quality desired, marketing, and harvesting scheduling. The Rice Experiment Station at Biggs is owned, financed, and administered by the rice industry. The station was established in 1912, as a direct result of the foresight and effort of Charles Edward Chambliss of the United States Department of Agriculture. Now, The station's major effort is the development of improved rice varieties for California.

• Journal of The Korean Society of Grassland and Forage Science
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• v.34 no.1
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• pp.1-8
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• 2014

Field studies were conducted from the years 2009 to 2012 in order to determine the cultivation limit as well as to evaluate the characteristics and forage production of warm season grass in Korea. Two bermudagrass [Cynodon dactylon (L.) Pers.] cultivars, two bahiagrass (Paspalum notatum Flugge) cultivars and a Kleingrass [Panicum coloratum L.] cultivar were compared for forage production and quality in the mid-southern regions of Korea. The experimental design was a randomized block design (RBD) with three replications. The number of days to seedling emergence for bremudagrass and bahiagrass was observed as approximately 12 days and 28 days after seeding, respectively. In Kwangju, the heading dates of bahiagrass and kleingrass were 21 August and 10 July, respectively,. Warm season grass did not winter in the mid-regions (Kimjea, Cheonan) of Korea. All of the Bermudagrass cultivars had higher dry matter (DM) than bahiagrass at the first harvest. The dry matter yield of kleingrass was usually greater than the other entries at all study sites. Peak forage DM production of bermudagrass and bahiagrass cultivars occurred in June and July, respectively. The contents of crude protein (CP) and total digestibility nutrient (TDN) for bermudagrass cultivars were usually greater than the other entries at all study sites. Further, acid detergent fiber (ADF) and in vitro DM digestibility (IVDMD) were similar across all cultivars.

• Journal of Korean Society of Forest Science
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• v.90 no.1
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• pp.90-104
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• 2001

This study is aimed to analyze and to evaluate the revegetation and soil conservation technology in desertification-affected sandy land, resulting from the project of "Studies on the desertification combating and sand industry development". Main native plants for combating desertification : The general characteristics of vegetation distribution in desertified regions are partially concentrated vegetation distribution types including the a) desert plants in low zone of desert or sanddune of depressed basin, b) salt-resistant plants around saline lakes, c) grouped vegetation with Poplar and Chinese Tamarix of freshwater-lakes, saline-lakes and river-banks, d) gobi vegetation of gravel desert and e) grassland and oasis-woods around the alluvial fan of rivers, etc. Generally, Tamarix ehinensis Lour., Haloxylon ammodendron Bunge., Calligonum spp., Populus euphratica Oliver., Elaeagnus angustifolia L., Ulmus pumila L., Salix spp., Hedysarum spp., Caragana spp., Xanthoceras sorbifolia Bunge., Nitraria tangutorum Bobr., Lespedeza bicolor, Alhagi sparsifolia Shap., Capparis spinosa L., Artemisia arenaria DC., etc. are widely distributed in desertified regions. It is necessary for conducting research in the native plants in desertified regions. Analysis of intensive revegetation technology system for combating desertification : In the wind erosion region, the experimental research projects of rational farming systems (regional planning, shelterbelts system, protection system of oasis, establishment of irrigation-channel networks and management technology of enormous farmlands, etc.), rational utilization technology of plant resources (fuelwood, medicinal plants, grazing and grassland management, etc.), utilization technology of water resources (management and planning of watershed, construction of channel and technology of water saving and irrigation, etc.), establishment of sheltetbelts, control of population increase and increased production technology of agricultural forest, fuelwood and feed, etc. are preponderantly being promoted. And in water erosion region, the experimental research projects of development of rational utilization technology of land and vegetation, engineering technology and protection technology of crops, etc. are being promoted in priority. And also, the experimental researches on the methods of utilization of water (irrigation, drainage, washing and rice cultivation, etc.), agricultural methods (reclamation of land, agronomy, fertilization, seeding, crop rotation, mixed-cultivation and soil dressing works, etc.) and biological methods (cultivation of salt-resistant crops and green manure and tree plantation, etc.) for improvement of saline soil and alkaline soil in desertified-lands are actively being promoted. And the international cooperations on the revegetation technology development projects of desertified-lands are sincerely being required.

• Journal of The Korean Society of Grassland and Forage Science
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• v.30 no.4
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• pp.317-324
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• 2010

Recently, fallow paddy land located in the mid-mountain area (FPL) due to a decrease in rice consumption has increased in some regions of our country. So, grasses and forage crops available for years in once sowing should be introduced in FPL. This study was conducted to develop the technique for cultivation of grasses and forage crops using animal manure in FPL The field experiments were carried out from 2007 to 2009 on FPL at Kumsan, Chungbuk province in Korea. Cattle feedlot manure (CFM) was prepared by mixing feces and urine of cattle with rice straw in cattle feedlot for 6 months. The experimental plots were consisted of four treatments; tall fescue-based mixed pasture applied with chemical fertilizer (Control), mono-tall fescue pasture (MTFP), tall fescue-based mixed pasture (TFBMP), mono-Perennial ryegrass (MPR-FCM), mono-Italian ryegrass (MIR-FCM), mono-Red clover (MRC-FCM) and mono-Reed canarygrass (MRCG-FCM) applied with FCM. The field of tall fescue-based pasture had been sown with a grasses mixture containing 'Fawn' tall fescue, 'potomac' orchardgrass, 'Reveille' Perennial ryegrass, and 'kenblue' Kentuky bluegrass, 'Kenland' Red clover. Seeding rates were 16, 6, 4, 2 and $2\;ha^{-1}$, respectively. DM yields of forages and rates of grass coverage was higher in MTFP, TFBMP and MRCG-FCM as compated with control treatment. This result means that FPL has contained with favorable conditions for growing grass, because forage productivity is more than 15 tons per ha per year in fallow paddy land. In addition, the farmer can save the trouble of repeated plowing and sowing every year, due to the introduction of perennial grasses. The farmer must conduct the re-seeding and induce the improvement of management methods for the elevation of the persistence of red clover and perennial ryegrass, because both red clover and perennial ryegrass having high nutritive value and palatability was less persistent. Therefore, we suggest that FPL may be the good land for forage production utilizing FCM and FCM can be applied on FPL without any negative effects on DM production and the property of soil. FPL of Korea can be better utilized by applying FCM to the mono and/or mixed swards.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.71-79
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• 2015

This paper describes vegetation based soil-media hydroseeding measures that have been previously applied as slope revegetation methods show problems such as insufficient binding force, drying, and insufficient organic matter. In particular, in the case of slope faces in regions where scattering is severe, a vicious circle exists in which remarkably low vegetation cover rates and increases in withering rates over time lead to further decreases in vegetation cover rates, which lead to further increases in erosion and scattering. Therefore, in the present study, environment friendly soil stabilizers were applied for resistance against erosion or scattering and engineering evaluations such as long-term immersion tests and flow resistance tests were conducted to determine appropriate mixing ratios. According to the results of long-term immersion tests utilizing environment friendly soil stabilizers and existing greening soil based materials, 100% collapse occurred at 30 hours and 40 days in the case of soil stabilizer mixing ratios of 0% and 2%, respectively. While the original form of the samples remained intact until the experiment was completed in the case of mixing ratios exceeding 4% indicating that 2% or higher soil stabilizer mixing ratios could affect the maintenance of forms even under extreme conditions. In addition, artificial rainfall tests were conducted on 40, 45, and 55 degree slope faces to evaluate the structural stability of vegetation based materials. Flow resistance tests were conducted on soil stabilizer mixing ratios of 0, 4, 8% to evaluate erosion resistance capability. Based on the results of the tests, environment friendly soil stabilizers applied for prevention of scattering or resistance against erosion by rainwater are considered to provide large effects to reduce losses and loss rates showed a tendency of decreasing rapidly when soil stabilizers were mixed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.6
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• pp.413-417
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• 2002

This study was conducted to determine $\beta$-amylase gene expression and degradation of starch granules in the endosperm near scutellar epithelium of rice cultivars under the submerged soil at hypoxia 18$^{\circ}C$, which is practically important condition for farmers in temperate regions. In case of cv. Janghyangdo, accumulation of $\beta$-amylase mRNA was detected in the aleurone layer on the ninth day after seeding. However that of cv. Suwon 287 and Norm 6 were not detected in the aleurone layer in submerged soil(hypoxia) at 18$^{\circ}C$. $\beta$-amylase of cv. Janghyangdo was synthesized de novo in aleurone cells not in the scutellar epithelium. Degradation of starch granules in the endosperm near scutellar epithelium of c.v. Janghyangdo and Ginbozu, which have a strong $\beta$-amylase activity, was greater than that of cv. Suwon 287 and Norm 6 with no $\beta$-amylase activity in submerged soil(hypoxia) at 18$^{\circ}C$. This result may indicate that $\beta$-amylase gene expression and degradation of starch granules of germinating rice seed are related to the emergence of rice under the submerged soil condition at low temperature.

• Journal of The Korean Society of Grassland and Forage Science
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• v.39 no.4
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• pp.195-206
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• 2019

This experiment was carried out to study the effects of different environmental conditions and cultivation techniques on productivity of forage corn in central and southern area of Korea on 2017 and 2018. Average dry matter yield of forage corn at 34 cultivation regions was 13,510kg/ha. Forage productivity of forage corn cultivated at actual production sites have positive correlation with cultivation techniques(p<0.01) but not correlated with cultivation environments. Forage productivity of forage corn have positive correlation with seeding techniques(p<0.01) but not correlated with fertilization techniques. These results suggest that practices of cultivation techniques are more important than cultivation environments for increasing the forage productivity of forage corn. Therefore, yield prediction techniques of forage corn in Korea have to be considered the practices of cultivation techniques along with soil and climate conditions.