• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.4
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• pp.365-372
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• 2024

The South Korean marine industry is emerging as a significant market, driven by the growing popularity of various water leisure activities, including sailing. This trend suggests a rising demand for sailing yachts. Consequently, since 2022, the design and development of a 28ft sailing yacht have been ongoing, supported by the government and the Ministry of Oceans and Fisheries, to promote yachting culture in South Korea. The Velocity Prediction Program (VPP) analysis was conducted using WinDesign during the preliminary design stage to evaluate performance and determine design parameters. The hydrodynamic model used for this vessel is based on regression methods developed from years of experience in naval architecture and yacht research at the Wolfson Unit, providing reliable estimates for most modern yachts. However, owing to the lack of specific hydrodynamic data from towing tank tests or CFD numerical analysis, verification of the hydrodynamic model has faced some challenges. Additionally, an incomplete weight estimate resulted in variable VCG values, potentially affecting stability and overall performance. The optimal boat speed for this vessel was determined at true wind speeds (TWS) of 4, 8, 12, 16, and 20 knots, using both the jib (up to 120° TWA) and the spinnaker (from 80° TWA). The optimized speed of the yacht was found to be comparable to that of international similar-class yachts.

• Korean Chemical Engineering Research
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• v.62 no.4
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• pp.335-343
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• 2024

This study was conducted to confirm the potential of adhesive resins formulated with rapeseed flour (RSF), which is a residue in the production of edible oil, for the manufacture of medium-density fiberboards (MDF). The RSF-based adhesive resins were formulated with the weight ratio of RSF hydrolyzates (80, 70, 60 wt%) to PF prepolymer(20, 30, 40 wt%), MDF was fabricated in accordance with its resin content and target density using the RSF-based adhesive resin, and then the physical properties(density, moisture content, bending strength, internal bonding strength and thickness swelling) and formaldehyde emission of the MDF were measured. The effect of the weight ratio of RSF hydrolyzate to PF prepolymer was the greatest, followed by that of target density and resin content. The values of MDF fabricated with RSF-based adhesive resins exceeded those with urea-formaldehyde resins, which is mostly used as a resin in the manufacture of MDF. Based on the results of MDF per experimental factors, the optimal conditions were determined to target density of 0.7 g/cm³, resin content of 5% and PF-prepolymer weight ratio of 40 wt% in RSF-based adhesive resin, and physical properties and formaldehyde emission of the MDF fabricated with the conditions satisfied the requirements for MDF and E₀ grade, which was designated by National Institute of Forest Science, except for thickness swelling. In conclusion, the potential of RSF-based adhesive for the production of MDF could identify on the basis of the results of this study. However, the stable securement of RSF through the development of bio-refinery process for rape plant is required to commercialize RSF-based adhesive resins for MDF production.

• Composites Research
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• v.37 no.4
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• pp.343-349
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• 2024

The use of composite materials for structural fasteners is increasingly common, making it crucial to assess the deformation of these fasteners under fatigue behavior. In this study, clamp-type fasteners were manufactured using carbon fiber reinforced composites, and their structural stability and sectional damage rates were evaluated using electrical resistance measurement during fatigue behavior. While clamp-type composite fasteners exhibited minimal deformation in flat sections, significant deformation occurred in the bent sections due to fatigue. It was observed that insufficient angular stability led to concentrated damage in the bent sections. The dynamic fatigue behavior showed that the length change rate of the composite fasteners was within 0.6%, but the angular change rate reached up to 6%, indicating that the bent sections are the most critical areas. By utilizing the self-sensing capability of the composite fasteners, sectional damage behavior was assessed through electrical resistance measurement. Significant damage was noted in the bent sections due to fatigue, and 3D-CT results revealed substantial deformation and interfacial damage when the initial bend angle of the fasteners was less than 90 degrees. These findings highlight the importance of reinforcing the stiffness of the bent sections and establishing systematic angular standards in the development of composite fasteners.

• Korean Journal of Environmental Agriculture
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• v.38 no.4
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• pp.225-236
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• 2019

BACKGROUND: Hydroponics is one of the methods for evaluating plant production using the inorganic nutrient solutions, which is applied under the artificial light conditions of plant factory system. However, the application of the conventional inorganic nutrients for hydroponics caused several environmental problems: waste from culture mediums and high nitrate concentration in plants. Organic nutrients are generally irrigated as a supplementary fertilizer for plant growth promotion under field or greenhouse conditions. Hydroponic culture using organic nutrients derived from the agricultural by-products such as dumped stems, leaves or immature fruits is rarely considered in plant factory system. Effect of organic or conventional inorganic nutrient solutions on the growth and nutrient absorption pattern of green and red leaf lettuces was investigated in this experiment under fluorescent lamps (FL) and mixture Light-Emitting Diodes (LEDs). METHODS AND RESULTS: Single solution of tomatoes (TJ) and kales (K) deriving from agricultural by-products including leaves or stems and its mixed solution (mixture ration 1:1) with conventional inorganic Yamazaki (Y) were supplied for hydroponics under the plant factory system. The Yamazaki solution was considered as a control. 'Jeockchima' and 'Cheongchima' lettuce seedlings (Lactuca sativa L.) were used as plant materials. The seedlings which developed 2~3 true leaves were grown under the light qualities of FL and mixed LED lights of blue plus red plus white of 1:2:1 mixture in energy ratio for 35 days. Light intensity of the light sources was controlled at 180 μmol/㎡/s on the culture bed. The single and mixture nutrient solutions of organic and/or inorganic components which controlled at 1.5 dS/m EC and 5.8 pH were regularly irrigated by the deep flow technique (DFT) system on the culture gutters. Number of unfolded leaves of the seedlings grown under the single or mixed nutrient solutions were significantly increased compared to the conventional Y treatment. Leaf extension of 'Jeockchima' under the mixture LED radiation condition was not affected by Y and YK or YTJ mixture treatments. SPAD value in 'Jeockchima' leaves exposed by FL under the YK mixture medium was approximately 45 % higher than under conventional Y treatment. Otherwise, the maximum SPAD value in the leaves of 'Cheongchima' seedlings was shown in YK treatment under the mixture LED lights. NO₃-N contents in Y treatment treated with inorganic nutrient at the end of the experiment were up to 75% declined rather than increased over 60 % in the K and TJ organic treatment. CONCLUSION: Growth of the seedlings was affected by the mixture treatments of the organic and inorganic solutions, although similar or lower dry weight was recorded than in the inorganic treatment Y under the plant factory system. Treatment Y containing the highest NO₃-N content among the considered nutrients influenced growth increment of the seedlings comparing to the other nutrients. However effect of the higher NO₃-N content in the seedling growth was different according to the light qualities considered in the experiment as shown in leaf expansion, pigmentation or dry weight promotion under the single or mixed nutrients.

• Journal of Korean Society of Forest Science
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• v.31 no.1
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• pp.1-7
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• 1976

When haploid plant would be appeared by the anther culture, the large quantity of young plant multiplied maternal inheritance and the same pure line rapidly in the short length of time, which will be effected to cut down much expences efforts and time for the production of seeds or seedlings. Therefore, the development of the technique for this would be much profited in the country industry. In the late of a few years studies were early attempted in this field, but up this time there were a few success of plants only and none of perennial plant. In this status of the country condition required earnestly for the development of the green industry, this researcher attempted to culture the anther of late uninucleate microspore or early binucleate microspore of the Prunus mume and other three psecies, economic trees estimated specially economic, on the place of Modified Murashige and Skoog's medium supliment with Kinetine, 2.4-D, and N.A.A for inducing haploid plants. The obtained results were as follows: 1. 2,000 anthers were cultured and there were shown that 2N callus in Prunus mume had 82 as 4.1%, 2N callus in Prunus tomentosa 15 as 0.8%, 2 N callus in Prunus salisina 75 as 4% 2. N callus had shown 40 as 2% from Prunus armeniaca var. ansu only, and the other trees showed all 2N callus. 3. Callus had appeared in every tree but 2N callus appeared was all filaments and there showed from only connective tissue N callus appeared was all from anther locule inside. 4. Then Prunus armeniaca var. ansu only was not callus of somatic anther tissue origin, but as there was callus origined from microspore which was changed in to swollen microspores or polynucleate microspores, it was certained to need haploid plant.

• Journal of The Korean Society of Grassland and Forage Science
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• v.5 no.2
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• pp.136-142
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• 1985

For better grassland development in the forest, this field experiment was carried out to investigate the effect of thirteen different fertilizer levels of nitrogen(N), phosphorus ($P_2O_5$) and potassium ($K_2O$) on the botanical composition, growth and dry matter yield of grass-clover mixtures grown under trees with 40-50% of shading level. This experiment was arranged as a randomized block design with replications, and performed on the experimental field in the suburban forest of Suweon in 1984. The results obtained are summarized as follows: 1. Plant height and cover degree of grasses found to be high with 28 and 42kg N fertilizer per 10a, while those were the lowest with zero and N-zero fertilizer levels. The degree of bare land after the fourth cut was also high in the low N level. 2. A significant higher degree of leaf green and chlorophyll content of leaf blade was observed in the plot of 28 and 42 kg N per 10a when compared with low N fertilizer plot. However, leaf decay and plant type of grasses tended to be a little poor as the high N was applied. 3. the regrowth plant length and dry weight of grasses after the first cut increased significantly with 28 and 42 kg N fertilizer. However, those showed slightly increased regrowth in the plot of zero and N-zero fertilizer levels. 4. The dry matter yield of grasses was higher with 28 and 42 kg N than that of low N fertilizer level. Higher yields were obtained in the plot of standard ($N-P_2O_5-K_2O$=28-20-24 kg/10a), 50% increase of $N,P_2O_5K_2O$ and N-50% increase, although there were no significant differences among three fertilizer levels. 5. Growth, botanical composition, regrowth and yield of grasses grown under pine trees were significantly influenced by N fertilizer level, regardless of $P_2O_5\;and\;K_2O$. The fertilizer level of $N-P_2O_5-K_2O$ was 28-20-24 kg per 10a for more forage production in the forest. Considering economic yield in this study, however, the optimum fertilizer level of N, $P_2O_5\;and\;K_2O$ was suppose to be 21-28, 10-15, and 12-18kg per 10a, respectively.

• Korean journal of applied entomology
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• v.50 no.2
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• pp.157-165
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• 2011

Enterobacteria were isolated in the gut of the predacious multicolored Asian ladybird beetle, Harmonia axyridis, and their effects to the development of H. axyridis were examined. Populations of H. axyridis in this experiment were collected from Kimjae at Cheonbuk province (JK population), Geumsan at Chungnam province (CK population) and laboratory population at Laboratory of Insect Physiology in Chungnam National University, Daejeon. Thirty-four enterobacteria isolates were purified and isolated from the digestive tract of H. axyridis, and a total of 4 strains were classified into group by analysis of 16S rRNA gene sequences. About 70% of total isolates were phylogenetic groups of Bacillus genus and Staphylococcus genus, and they were commonly separated from the digestive tract of H. axyridis. After investigating their susceptibility against antibiotics with 18 representative enterobacteria isolates, ofloxacin and penicillin were selected for examination in this study of their ability to inhibit the growth of all of isolates. In order to remove the enterobacteria from the aphids, ofloxacin and penicillin were given to the green peach aphid, Myzus persicae, and the turnip aphid, Lipaphis erysimi. These aphids were provided to H. axyridis as prey. The weight of pupa, developmental periods of each larval instar, the number of eggs and their hatching ratio of H. axyridis with treatment aphids were lower compared with non-treatment aphids. Staphylococcus saprophyticus is a representative enterobacteria and commonly isolated from the digestive tract of H. axyridis. In the absence of S. saprophyticus, the developmental periods of each larval instar increased; however, the weights of pupa, the number of eggs, and their hatching ratio decreased.

• Korean Journal of Poultry Science
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• v.31 no.4
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• pp.265-271
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• 2004

A feeding trial was conducted to investigate the influence of feeding Lactobacillus reuteri culture (LR) on productive performance, intestinal microflora and availability in laying hens. Four hundred and eighty, Isa-Brown layers, 49 weeks of age, were fed diets supplemented with LR at the level of 0 (control), 0.1, 0.2, and $0.4\%$ of the diets for eight weeks. Egg production and egg weight were measured daily. Feed intake was weighed every two weeks. Egg quality was measured three times at the start, mid-term, and end of the experiment. Intestinal microflora were examined for Lactobacillus spp., E. coli and Salmonella at the end of the experiment. Overall egg production was the highest in $0.2\%$ LR (P<0.05), but that of $0.1\%$ or $0.4\%$ LR treatments did not significantly differ from that of control. Egg weight was significantly higher in LR feeding group than the control (P<0.05). Daily egg mass was significantly higher in $0.2\%$ and $0.4\%$ LR treatments compared to the control and $0.1\%$ LR (P<0.05). The number of jumbo and extra large eggs were increased in LR supplemented groups, especially in $0.1\%$ LR. Feed intake of layers fed LR supplemented diets tended to be lower than the control. However, feed conversion ratio significantly improved in LR supplemented groups (P<0.05). Availability of dry matter and crude protein improved significantly in $0.4\%$ LR treatment (P<0.05). But, those of ether extract and crude ash were not significantly different among treatments. Eggshell breaking strength and eggshell thickness were not significantly influenced by LR supplementation, and Haugh unit and yolk index were also similar to the control. Total number of Lactobacillus spp. in ileum and cecum fed LR supplemented diets were significantly higher than those of the control (P<0.05). There were no significant differences in intestinal E. coli and Salmonella in all treatments. Therefore, it is concluded that dietary supplementation of Lactobacillus reuteri culture can improve the laying performance, feed efficiency and intestinal Lactobacillus.

• Development and Reproduction
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• v.14 no.4
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• pp.269-279
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• 2010

Some characteristics of germ cell differntiations and the function of accessory cells during spermatogenesis, and mature sperm ultrastructure in male Protothaca (N.) jedoensis were investigated by transmission electron microscope observations. The morphology of the spermatozoa of this species has a primitive type and is similar to those of other species in the subclass Heterodonta. Accessory cells, which are connected to adjacent germ cells, are involved in the supplying of the nutrients for germ cell development. The morphologies of the sperm nucleus and the acrosome of this species are the cylindrical type and cap shape, respectively. Spermatozoa are approximately $46{\sim}50{\mu}m$ in length including a long sperm nucleus (about $2.44{\mu}m$ in length), an acrosome (about $0.45{\mu}m$ in length), and tail flagellum (about $42{\sim}46{\mu}m$). The axoneme of the sperm tail shows a 9+2 structure. As some characteristics of the acrosomal vesicle structures, the basal and lateral parts of basal rings show electron opaque part (region), while the anterior apex part of the acrosomal vesicle shows electron lucent part (region). These characteristics of the acrosomal vesicle were found in the family Veneridae and other several families in the subclass Heterodonta. These common characteristics of the acrosomal vesicle in the subclass Heterodonta can be used for phylogenetic and systematic analysis as a taxonomic key or a significant tool. The number of mitochondria in the midpiece of the sperm of this species are four, as one of common characteristics appear in most species in the family Veneridae and other families in the subclass Heterodonta. However, exceptionally, only three species in Veneridae of the subclass Heterodonta contain 5 mitochondria. The number of mitochondria in the sperm midpiece can be used for the taxonomic analysis of the family or superfamily levels as a systematic key or an important tool.

• Journal of agricultural medicine and community health
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• v.21 no.2
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• pp.173-193
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• 1996

This study was carried out to elucidate the causes of farmer's disease and greenhouse disease in the rural area of Kyungnam province during 1996. 2,171 (69.1%) of the 3,140 adults above 20 years old who had lived in the selected 20 villages in Uiryong County of Kyungnam Province were selected in order to over both residents who live in the green house distracts and conventional rural area. The results were as follows: 1. Among the subjects, the male was 42.2% and female was 57.6%. The average age for the male was 52.3, 55.6 for the female. 2. The proportion of the farmers in the subjects was 81.5%. Among these 78.0% were engaged in the greenhouse farming. 3. Among the eight symptoms of Nofusho(japanese farmer's comples), lumbago was the most frequently complained and followed by shoulder stiffness and parenthesis of hand or foot. 4. The total score of farmer's disease was evidently higher in the female and the older the score was clearly bigger. 5. The prevalence of Nofusho(Japanese farmer's comples)was 26.8% and 43.15% was for the suspected Nofusho. In the male, the prevalence of Nofusho was 13.6% and 40.9% for the suspected Nofusho and in the female 36.5% and 44.7% were shown, comparatively. 6. According to the multiple classification analysis, sex, age, and occupation were selected as significant variables to explain the total score of Nofusho. 7. The correlations between the total score of Nofusho and the number of sick day, working years, and age were significant, comparatively. 8. According to the multiple classification analysis corolling interaction between independent variables, age was the only variable which was significant in the male and age, pesticide work in the female. 9. The score of greenhouse disease was highest in the group who engaged in greenhouse farming and conventional farming(2.76 for male, 3.77 for female) followed by the group who engaged only in greening house farming(2.66 for male, 3.49 for female) and by the group who engaged only in conventional farming(2.27 for male, 3.05 for female) 10. According to the multiple classification analysis with the total score of greenhouse disease as dependent variable, corolling interaction between independent variables, age and pesticide work were revealed as significant variables in the male, while, pesticide work and farming type were significant in the female. According to the above results, the following could be suggested. Because lumbago, shoulder stiffness, paresthesia of hand and foot were the most frequently complained symptoms in the respondent, the development of farming tool to reduce the body burden and periodical physical exercise and rest is highly recommended. It is revealed that both in the farmer' disease and greenhouse disease the score was higher in the female than in the male. So the reasonables measures is recommended to reduce the working hours of the female. Pesticide work was revealed as the significant variable in the female in farmer's disease and both in the male and the female in greenhouse disease. So the development of the safe method of pesticide spraying including safety education should be introduced. Particularly the female should be excluded in pesticide spraying.