• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.2
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• pp.57-65
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• 2008

Wastewater containing strong organic matter is very difficult to treat by utilizing general sewage treatment plant. but the wastewater is adequate to generate biomass energy (bio-gas; methane gas) by utilizing anaerobic digestion. EcoDays Plug Flow Reactor (E-PFR), which was already proved as an excellent aerobic wastewater treatment reactor, was adapted for anaerobic food wastewater digestion. This research was performed to improve the efficiency of bio-gas production and to optimize anaerobic wastewater treatment system. Food wastewater from N food waste treatment plant was applied for the pilot scale experiments. The results indicated that the efficiency of anaerobic wastewater treatment and the volume of bio-gas were increased by applying E-PFR to anaerobic digestion. The structural characteristics of E-PFR can cause the high efficiency of anaerobic treatment processes. The unique structure of E-PFR is a diaphragm dividing vertical hydraulic multi-stages and the inversely protruded fluid transfer tubes on each diaphragm. The unique structure of E-PFR can make gas hold-up space at the top part of each stage in the reactor. Also, E-PFR can contain relatively high MLSS concentration in lower stage by vertical up-flow of wastewater. This hydraulic flow can cause high buffering capacity against shock load from the wastewater in the reactor, resulting in stable pH (7.0~8.0), relatively higher wastewater treatment efficiency, and larger volume of bio-gas generation. In addition, relatively longer solid retention time (SRT) in the reactor can increase organic matter degradation and bio-gas production efficiency. These characteristics in the reactor can be regarded as "ideal" anaerobic wastewater treatment conditions. Anaerobic wastewater treatment plant design factor can be assessed for having 70 % of methane gas content, and better bio-gas yielding and stable treatment efficiency based on the results of this research. For example, inner circulation with generated bio-gas in the reactor and better mixing conditions by improving fluid transfer tube structure can be used for achieving better bio-gas yielding efficiency. This research results can be used for acquiring better improved regenerated energy system.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.2
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• pp.81-87
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• 1975

A pot experiment was conducted to study the effect of two methods of applying potassium fertilizer to rice. One basic application was compared with the split of same total quantity into four applications as follows: 15 days after transplanting (40%), Ear formation stage (30%), 13 days before heading (20%) and 7 days after heading (10%) Each of these two treatments was carried out on both untreated soil and soil to which wollastonite and lime material had been added. The number of ripened grains or the 1,000 grain weight was increased by application of potassium to untreated soil. However, on soil treated with lime and wollastonite only the number of total grains was increased by potassium application. In both cases, split application of the potassium was more affective than a single basic application. No significant increase in yield was obtained from a single basic application of potassium. However, split application of the same total quantity of potassium did give a significant increase in yield. A negative correlation was found between the content of $K_2O$ and that of other nutrients in the rice plant at two stages of growth. Significant negative correlation was obtained between the content of $K_2O$ and magnesium, phosphorus and nitrogen at ear formation stage, and between the content of $K_2O$ and calcium and silicate including magnesium, phosphorus and nitrogen at heading stage. This result also indicated that the depression of uptake of phosphorus and magnesium at ear formation stage and that of calcium and silicate at heading stage were decreased by potassium split application. However, the degression of uptake of nitrogen at ear formation stage and that of magnesium at heading stage were increased by potassium split application.

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.309-315
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• 2009

Maintenance of adequate soil water content during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil water movement for precision irrigation would allow efficient supply of water to crops, thereby resulting in minimization of water drainage and contamination of ground water. This research reports on the characterization of spatial and temporal variations in water contents through three different textured soils, such as loam, sandy loam, and loamy sand, when water is applied on the soil surface using an one-line drip irrigation system and the soils are dried after the irrigation stops, respectively. Water contents through each soil profile were continuously monitored using three Sentek probes, each consisting of three capacitance sensors at 10, 20, and 30cm depths. Spatial variability in water content for each soil type was strongly influenced by soil textural class. There were big differences in wetting pattern and the rate of downward movement between loam and sandy loam soils, showing that the loam soil had a wider wetting pattern and a slower rate of downward movement than did the sandy loam soil. The wetting pattern in loamy sand soil was not apparent due to a low variability in water content (< 10%) by a lower-water holding capacity as compared to those measured in the loam and sandy loam soils, implying that the rate of water drainage below a depth of 30cm was high. When soils were dried, there were highly exponential relationships between water content and time elapsed after irrigation stops ($r^2$${\geq}$0.98). It was estimated that equilibrium moisture contents for loam, sandy loam, and loamy sand soils would be 17.6%, 6.2%, and 4.2%, respectively.

• Journal of Dairy Science and Biotechnology
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• v.29 no.1
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• pp.23-31
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• 2011

Domestic dairy industry is now standing at the crossroad for planning next fifty years, mainly because economic and environmental situations surrounding Korean peninsula are fast changing. For the aspects of dairy consumption, fresh milk consumed less, while consumption of the other milk and dairy products is slightly increasing every year. In 2010, it is approximately estimated that 1,939,000 tons of raw milk was used and the supply would be short by about 35,000 tons, based on the amounts in the previous year. Currently, multilateral negotiations against US and EU are underway. When it will be in effect in the future, significant damage would be expected in the dairy and livestock sectors, leading to cut domestic milk supply. Quality of farm-gate milk is graded as 1A on average 90% or more, loaded with very low in microbial and somatic cell counts. Therefore, policy implications have to be placed toward switch currently the UHT processing method to Pasteurization or the LTLT technology, by which natural flavors and nutrients in milk mostly remain after heat treatment. Domestic cheese products comprise only 10% and the rest is occupied by the various kinds of imported natural products. The market size keeps increasing up to 65,423,000 tons last year. When it comes to vitalization of our natural cheese industry, cheese whey, which is a main by-product in cheese manufacture, is a critical issue to be solved and also "On-Farm Processing" would be combined with a growth of big dairy companies when few immediate issues among the relevant regulations will be eased and alleviated in the near future. Fermented milk market is recorded as a single area of gradual increase in the past 10 years, Korea. Fermented yogurts with health claims targeted stomach, liver, and intestine are popular and has grown fast in sales amounts. In this context, researches on beneficial probiotic lactic acid bacteria are one of the important projects for domestic milk and dairy industries. Labelling regulations on efficacy or health-promoting effects of functional dairy products, which is the most important issue facing domestic dairy processors, should be urgently examined toward commercial expression of the functionality by lawful means. Colostrum, a nutrition-rich yellowish fluid, is roaded with immune, growth and tissue repair factors. Bovine colostrum, a raw material for immune milk preparations and infant formula, can be used to treat or prevent infections of the gastrointestinal tract. Nanotechnology can be applied to develop new milk and dairy products such as micro-encapsulated lactase milk for consumers suffering lactose intolerance. Raw milk is suggested to be managed by its usage in the processing line because imbalance of supply and demand is structural problem in every country and thus the usage systems as in the advanced dairy countries is worth of bench-marking to stabilize milk supply and demand. Raw milk produced is desirable to divide into the three parts; domestic, import, and buffering purposes. It is strongly recommended that a domestic dairy control center as an institutional framework should be urgently established as is Dairy Board in New Zealand and Australia. Lastly, government policy should be directed to foster the highly-educated people who are majoring in Dairy Sciences or working in the dairy industry by means of financial support in studying and training abroad as well.

• Korean Journal of Agricultural Science
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• v.5 no.2
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• pp.127-135
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• 1978

For improvement and new design of tillage equipments, indoor test is very useful and more desirable than outdoor because the experiment of outdoor is very difficult and its cost is expensive. This study was carried out to determine the physical properties of artificial soil suitable for the indoor test with the soil bin manufactured at the workshop of the Dept. of Agricultural Machinery Engineering. The artificial soil being studied was made with very similarity to the natural soil of the experimental plots of Chungnam National University, and it consist of 39.35 percent, by weight of bentonite and 48.10 percent of sand with 12.55 percent of SAE 10W oil. The results are summarized as follows: 1. Bulk density increased with increasing number of rolling, and its relationship could be expressed. $y=1.073200+0.070780x-0.002263x^2$ where, y=bulk density ($g/cm^3$), x=number of rolling. These results could be explained that the effect of rolling velocity on the bulk density was not singnificant in the range of 4.5~10.4 em/sec. 2. The absolute soil hardness depended directly upon number of rolling, and their relationship could be expressed by the equation. $y=37.74(0.64 +0.17x-0.0054x^2)/(3.36-0.17x-0.0054x^2)^3$. where, y=absolute soil hardness($kg/cm^3$), x=number of rolling. 3. Relationship between the bulk density and absolute soil hardness could be expressed by the equation; $y=37.74(2.46x-2.02)/(6.02-2.46x)^3$. where, y=absolute soil hardness, x=bulk density. 4. The cohesion and the angle of internal friction of artificial soil were increased with increasing its bulk density. According to the cohesion and angle of internal friction, at the range of 1.60~1.75 ($g/cm^3$) of bulk density, this artificial soil was similar with sandy loam of 29.5% moisture content of natural soil. 5. Sliding-fricfion coefficient of steel plate on the artificial soil was 0.3~0.4 and rubber plate on it is 0.64~0.72. Those values were very similar with those of natural soil being studies by many others.

• Journal of dental hygiene science
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• v.14 no.4
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• pp.468-476
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• 2014

The aim of this study was to examine whether there is an association between vitamin intakes and established periodontitis in Korean adult population. The 6,245 subjects aged over 19 years old, who participated in health survey, oral examination and nutrition survey were selected for this study from the database of the Fourth Korean National Health and Nutrition Examination Survey. Established periodontitis was defined as ${\geq}$ code 3 in community periodontal index. Vitamin intake was assessed with the food-frequency questionnaire. In analysis, participants were classified by quintile of vitamin intakes. We also considered covariates as socio-demographic characteristics, health-related behaviors including physical activities, systemic diseases and oral health-related behaviors. Multiple logistic regression was performed to assess the crude and adjusted associations. All analyses considered a complex sampling design using SAS 9.2. In crude analysis, less intake of vitamin A, retinol and vitamin B2 significantly increased the risk of periodontitis (vitamin A, odds ratio [OR] Q1=1.00, Q2=0.73, Q3=0.80, Q4=0.77, Q5=0.78; retinol, OR: Q1=1.00, Q2=0.86, Q3=0.73, Q4=0.62, Q5=0.55; vitamin B2, OR: Q1=1.00, Q2=0.70, Q3=0.63, Q4=0.67, Q5=0.68). However, after adjusting for socio-demographics, general and oral health status and behaviors, only vitamin B2 was significantly associated with established periodontitis (OR: Q1=1.00, Q2=0.72, Q3=0.73, Q4=0.76, Q5=0.84). An adequate vitamin B2 intake was significantly associated with a decreased risk of periodontitis. This finding shows that nutrient intake is slightly correlated with periodontitis in Korean adult population. Further studies are needed to understand this association between nutrients intake and periodontitis in more details.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.3
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• pp.206-214
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• 2014

This study is to evaluate how different bearing surface angles of abutment screw affect the mechanical stability of the joint in the conical seal design implant system. Materials and Methods: Internal connection type regular implants, two-piece cemented type abutments and tungsten carbide/carbon-coated titanium alloy abutment screws were selected. Titanium alloy screws with conical ($45^{\circ}$) and flat ($90^{\circ}$) head designs which fit on to abutment were fabricated. The abutments were tightened to implants with 30 Ncm by digital torque gauge. The loading was applied once to the central axis of abutment. The mean axial displacement was measured using micrometer before and after the tightening and loading (n = 5). The abutment was tightened to implants with 30 Ncm and T-shape stainless steel crown was cemented. Then the change in the amount of reverse-torque was measured after the repeated loading to the central axis, and the place 5 mm away from the central axis. Compressive bending and fatigue strength were measured at the place 5 mm away from the central axis (n = 5). Results: Both groups showed the largest axial displacement when abutment screw tightening and total displacement was greater in the flat head group compared to conical head group (P < 0.05). However, there were no significant differences in reverse torque value, compressive bending and fatigue strength (P > 0.05). Conclusion: Within the limitations of this study, the abutment screw head design had no effect on two groups regarding the joint stability, however the conical head design affected the settlement of abutment resulting in the reduced total displacement.

• Journal of Korean Society of Archives and Records Management
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• v.1 no.1
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• pp.37-52
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• 2001

1. establishment and development of China archives science: With the centuries-old history of archives and archives management, early China archives science came into being in 1930s, and the research pushed forward by archives enterprise has made great achievements since then. 1.1 Expanding research fields: Foundation

• Journal of Korean Society of Forest Science
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• v.87 no.3
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• pp.493-500
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• 1998

To investigate the effects of light intensity on the growth, and the critical minimum light intensity for growing of Cornus controversa seedlings at the stage of cotyledon, hypocotyl elongation, cotyledon expansion, the times of leaves appearance, dry weights of each organ, and specific leaf area(SLA) were measured on a growth chamber with several light intensity gradients(385, 32, 17, 8, and $5{\mu}mol\;m^{-2}s^{-1}$). There was a positive correlationship between the size of cotyledon and the biomass of cotyledon and total seedling. Hypocotyl was more elongated under relatively low light intensities, such as 32, 17, 8, and $5{\mu}mol\;m^{-2}s^{-1}$ than under $385{\mu}mol\;m^{-2}s^{-1}$ light intensity, however, dry weight of the hypocotyl was adverse. As the light intensities decreased, the leaf appearance was delayed and the number of leaves decresed. In addition, leaves did not appear under $8{\mu}mol\;m^{-2}s^{-1}$ and $5{\mu}mol\;m^{-2}s^{-1}$ light intensity. Although cotyledons were more fully expanded under 32 and $17{\mu}mol\;m^{-2}s^{-1}$ light intensities than $385{\mu}mol\;m^{-2}s^{-1}$ light intensity, the dry weights of cotyledons were greater under the high light intensity. The dry weight of cotyledon, hypocotyl, root and leaves showed a decreased pattern with decreasing light intensities, but root to shoot(hypocotyl+leaves) ratio rapidly increased. Roots did not develop below $8{\mu}mol\;m^{-2}s^{-1}$ light intensity. In conclusion, the results showed that the critical minimum light intensity for growing of Cornus controversa seedlings was above $17{\mu}mol\;m^{-2}s^{-1}$ light intensity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.4
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• pp.464-473
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• 1996

Two-month feeding experiment was conducted to investigate the optimum dietary protein level and energy to protein ratio in fat cod (Hexagrammos otakii Jordan et STARKS). The fish averaging 29 g were fed with one of the isocaloric diets containing 30, 40, 50 or $60\%$ of protein, or with one of the isoproteic diets containing 9, 10, 11 or 12 of available energy/protein (E/P) ratio. Weight gain and feed efficiency increased significantly with dietary protein level up to $50\%$, then decreased with $60\%$ protein diet (P<0.05). Daily protein intake increased significantly with dietary protein level, whereas protein efficiency ratio decreased with dietary protein level (P<0.05). Second order polynomial regression analyses of percent weight gain and daily protein intake may indicate that the adequate dietary protein level is $45\%$ and daily protein requirement per 100g fish is 1.5g for maximal growth. Weight gain, feed efficiency and protein efficiency from fish led the diet containing 12 of E/P ratio were significantly higher than those from fish fed the other diets (P<0.05). Daily feed or protein intake from fish fed the diet containing 12 of E/P ratio was significantly lower than those from fish fed the other diets (P<0.05). Daily lipid intake increased significantly with dietary E/P ratio (P<0.05).