• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.339-344
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• 2021

In order to improve the PEMFC (Proton Exchange Membrane Fuel Cell) durability, it is important to accurately evaluate the durability of the membrane in a short time. Recently, DOE (Department of Energy) reported a protocol that combines the chemical and mechanical durability of membranes to evaluate them effectively. This protocol applies chemical/mechanical deterioration to the membrane by repeating wet/dry while OCV (Open Circuit Voltage) holding. The problem of this protocol is that it is highly affected by electrode degradation due to change cycles in OCV and that the evaluation time is long. By using oxygen instead of air as the cathode gas while leaving the other conditions of the DOE protocol as it is, the durability evaluation time could be reduced from 408 hours to 144 hours. By reducing the number of voltage change cycles to 1/3, the electrode degradation due to the voltage change cycle was reduced to 1/12 when oxygen was used compared to air at the end, thereby enabling more accurate evaluation of polymer membrane durability.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.284-293
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• 2020

Rice consumption in Korea has been decreasing as the eating habits of the Korean people have diversified with rapid economic growth. Recently, floury endosperm rice cultivars were developed to boost rice consumption and replace wheat flour consumption with rice flour, which is vulnerable to viviparity under wet weather during the grain-filling stage because of its loosely packed starch granule structures. To overcome this limitation, it is necessary to find a suitable rice transplanting date to produce high-quality rice flour by altering the heading ecology type and changing the cultivation time by region. We examined four floury endosperm rice cultivars (FERC) in the Cheongju (central plain area) and Boeun (mid-mountainous area) regions of Korea from 2017 to 2019. Of the FERCs, the mid-late maturing types (MMT) Seolgaeng (SG), Hangaru (HGR), and Shingil (SGL) exhibited high yield and yield components after transplanting May 30 in both regions; the early maturing type (EMT) Garumi 2 (GRM2) also exhibited high yield after transplanting June 20 in Cheongju. In addition, MMTs showed the same tendency as the characteristics shown in Cheongju when grown in the Boeun region, and EMT displayed high yield and yield components after transplanting June 10. The FERCs could easily present pre-harvest sprouting in the rainy season during the grain-filling stage after 20 days post-heading because the mean temperature and frequency of more three-day rainfalls have increased over the last 5 years from the previous annual averages. Viviparity of HGR and GRM2 decreased as the transplanting date was delayed, with decreases of 2.3%-4.6% in HGR and 11.9%-23.1% in GRM2 according to the region. SGL was generally resistant to viviparity because of the Tongil type. To minimize pre-harvest sprouting and produce high yield of rice flour in the Chungbuk province, the most suitable transplanting time was the end of May in MMT and the middle and end of June in EMT.

• Journal of Chest Surgery
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• v.29 no.8
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• pp.816-821
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• 1996

Lung transplantation is the established treatment for the end stage lung disedse find preservation of the organ is a major obstacle In performing lung transplantation. For solving this problem, we evaluated the histopathologic changes for various preservation solutions. Male mongrel dogs of similar size and weight (15∼20 kg) were used. The dog lungs were flushed with 4fl normal saline(group 1 'n:5): Modified Euro-Collins solution(group 2 n:5) and University of Wisconsin solution (group 3 : n=6), 60m11kg through a catheter placed in the main pulmonary artery aft r flushing of PGE 1 (20ng1kg). The lungs were preserved for 60 hours and measured dry and wet weights. Histologic specimens were taken every 6 hours and %toed for light microscopic evaluation. The edema ratio of the lungs peaked in 12 hours although there was no difference between the groups. Histologically, alveolar septal changes developed in one case (20%) after 1 hour preservation with normal saline. In case of the University of Wisconsin solution, the alveolar septal distortions and swellings were seen in 1 cases (20%) after 6 hours preservation compared with 3 cases (60%) after 6 hours preservation with Modified Euro-Collins solution. Changes of the pneumocytes were observed after 24 hours preser- vation in group 1, after 48 hours preservation in group 2 and after 60 hours preservation in group 3. We conclude that University of Wisconsin solution might have a superior preservation effect compare to normal saline and Modified Euro-Collins solutions.

• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.185-194
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• 2012

A Macroscopic combination of two or more distinct materials is commonly referred to as a "Composite Material", having been designed mechanically and chemically superior in function and characteristic than its individual constituent materials. Composite materials are used not only for aerospace and military, but also heavily used in boat/ship building and general composite industries which we are seeing increasingly more. Regardless of the various applications for composite materials, the industry is still limited and requires better fabrication technology and methodology in order to expand and grow. An example of this is that the majority of fabrication facilities nearby still use an antiquated wet lay-up process where fabrication still requires manual hand labor in a 3D environment impeding productivity of composite product design advancement. As an expert in the advanced composites field, I have developed fabrication skills with the use of machinery based on my past composite experience. In autumn 2011, the Korea government confirmed to fund my project. It is the development of a composite sanding machine. I began development of this semi-robotic prototype beginning in 2009. It has possibilities of replacing or augmenting the exhaustive and difficult jobs performed by human hands, such as sanding, grinding, blasting, and polishing in most often, very awkward conditions, and is also will boost productivity, improve surface quality, cut abrasive costs, eliminate vibration injuries, and protect workers from exposure to dust and airborne contamination. Ease of control and operation of the equipment in or outside of the sanding room is a key benefit to end-users. It will prove to be much more economical than normal robotics and minimize errors that commonly occur in factories. The key components and their technologies are a 360 degree rotational shoulder and a wrist that is controlled under PLC controller and joystick manual mode. Development on both of the key modules is complete and are now operational. The Korean government fund boosted my development and I expect to complete full scale development no later than 3rd quarter 2012. Even with the advantages of composite materials, there is still the need to repair or to maintain composite products with a higher level of technology. I have learned many composite repair skills on composite airframe since many composite fabrication skills including repair, requires training for non aerospace applications. The wind energy market is now requiring much larger blades in order to generate more electrical energy for wind farms. One single blade is commonly 50 meters or longer now. When a wind blade becomes damaged from external forces, on-site repair is required on the columns even under strong wind and freezing temperature conditions. In order to correctly obtain polymerization, the repair must be performed on the damaged area within a very limited time. The use of pre-impregnated glass fabric and heating silicone pad and a hot bonder acting precise heating control are surely required.

• Korean Journal of Food Science and Technology
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• v.28 no.4
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• pp.609-615
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• 1996

To study the effects of the fructooligosaccharide (FOS) intake on the intestinal microflora, the FOS (8g) was served to each of 5 volunteers (adult men $23{\sim}28$ years old) after every lunch for 4 weeks. Changes in fecal microflora, fecal moisture, and fecal pH were observed during the FOS intake and after the FOS intake, respectively. The fecal moisture content of the control period (4 weeks before the intake of FOS) was $81.77{\pm}1.18%$. The moisture content of the feces increased significantly at the end of the 4th week of FOS intake, and these effects lasted for 3 weeks after stopping FOS intake. The fecal pH before FOS intake was $6.56{\pm}0.09%$, while it decreased significantly (p<0.01) during the period of FOS intake. The pH reduction lasted for 4 weeks after stopping the intake of FOS. The log fecal number of Bifidobacteria during the period was $7.88{\pm}1.43%$ (CFU/g of wet feces) and it increased significantly during the FOS intake. After stopping the intake of FOS, the number of Bifidobacteria returned to those of control period. The log fecal number of Lactobacilli before the intake was $6.76{\pm}1.34%$ and significantly increased in 3 weeks due to the FOS intake. After stopping the intake of FOS, however, the number of Lactobacilli returned to those of control period. No remarkable changes were observed in the number of coliforms throughout all durations.

• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.373-388
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• 2016

To understand human activity in the past, the information about past environmental change including geomorphological and climatic conditions is essential and this can be traced by using age dating and geochemical analysis of sediments from the prehistoric sites. The sedimentary sequence of Seokgwan-dong Paleolithic Site located in Seoul was 5m long unconsolidated sediments and consists of lower part bedrock weathering sediments, slope deposits and upper-part fluvial deposits. In this study, upper part sediments were used to reconstruct past environmental change through age dating and various physical and chemical analyses including grain size, magnetic susceptibility and mineral and elements. The fluvial sediments can be divided into 4 units including three organic layers. Grain size analysis results showed that the sediments were very poorly sorted with fining upward features. Magnetic susceptibility was relatively high in the organic layers, indicating environmental changes causing mineral composition change at that times. The mineral and major element composition are similar to Jurassic biotite granite which mainly consists of quartz, K-feldspar, biotite and muscovite. The radiocarbon age of $14,240{\pm}80yr$ BP was obtained from the lower most organic layer of Unit III(O), suggesting that the fluvial sediments formed at least from the early stage of deglacial period after the end of Last Glacial Maximum. Subsequent wet and warm climates and resultant fluvial process including slope sedimentation during the Holocene may have been responsible for the sedimentary sequence in Seokgwan-dong paleolithic site and surrounding area. The observed organic layers suggests frequent wetland occurrence combined with natural levee changes in this area.

• Journal of Nutrition and Health
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• v.1 no.1
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• pp.9-18
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• 1968

Dividing into six(6) experimental groups; Stock Diet(SD) Group, Rice Diet(RD) Group, Rice Diet supplemented with Barley(RD-BD) Group, Barley Diet(BD) Group, Rice Diet supplemented with Millet(RD-MD) Group, and Millet Diet(MD) Group, biochemical and nutritional effects of rice, barley, and millet on rats are studied. The grains used in this experiment are polished ones and purchased from market. Six(6) weaning male albino rats are housed into the individual cages in each group and fed with each experimental diet and water ad libitum for 21 weeks. The composition of the experimental diets are shown in Table 1. At the end of experiment, the appearences of rats are observed and the bloods are sampled by heart puncture method following ether anesthesia for determinations of serum protein and serum cholesterol. And the livers are sampled immediately right after heart after heart puncture for determinations of liver weight, liver nitrogen, liver fat, and liver glycogen. And also liver tissues are observed histologically. The result of growth experiment is shown in Table 2 and Figure 7. The results of blood analysis are shown in Table 3 and the results of liver analysis are shown in Table 4. And the histological observations of liver tissue are shown in Figures 1, 2, 3, 4, 5, and 6. According to the above results, it could be summarized as follows; 1) The normal appearences are observed at SD Group and BD Group. Alopecia is observed at RD, RD-­BD, RD-MD, and MD groups and the wet appearences of hair are observed at RD-MD and MD groups. The color of hair is changed to yellowish white at RD, RD-MD groups. The maximum growth inhibition, is observed at MD group and the growths of RD, RD-BD, BD, and RD-MD groups are significantly lower than that of SD group. The growth of RD group is lower than those of RD-BD and BD groups, though this difference is not significant. 2) At the blood analysis, the highest serum protein content is shown at SD group and the lowest serum protein is observed at MD group. The serum cholesterol contents are not significantly different among the six(6) experimental groups. 3) The highest liver weight is observed at SD group and the lowest weight is shown at MD group. However, oppositely the highest liver weight per 100 grams of body weight at MD group and the lowest liver weight per 100 grams of body weight at SD group are observed as shown in Table 6. 4) The differences of liver nitrogen contents of RD, RB-BD, BD, RD-MD, and MD Groups are not significant except SD group showing the highest content. 5) The significant highest content of liver fat is observed at RD group and the lowest content of liver fat is shown at SD group. And no significant differences in contents of liver glycogen are observed among the six(6) experimental groups. 6) No significant abnormal histological changes of liver tissue are observed at SD, RD-BD, and BD groups. However, the fat metamorphosis at peripheral zone of liver tissue is observed at RD Group and the some histological abnormal changes are observed at RD-MD and MD groups. According to the above summaries, the followings might be estimated and recommended; 1) The BD group shows histological normality of liver tissue, improvement of liver fat and liver nitrogen, normality of appearence, and better growth compared with RD Group. This could be indicated that barley is nutritionally and biochemically better than rice as the feeding diet on rat. And it might be considered that there might be the species speciality for nutritionary evaluation of food. 2) Recently, Marshall indicated that the high consumption of carbohydrate causes fatty liver and Kondo reported that the higher consumption of rice causes the more heart disease and the shorter life span. Considering these reports, the higher consumption of rice as a main dish in our country should be considered as an important national nutritional problem. And this might be improved by supplementing with barley or other grains to rice.