• Korean Journal of Environment and Ecology
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• v.6 no.2
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• pp.134-146
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• 1993

A survey of the Chundong valley forest in Mt. Sobaek was conducted using 20 sample plots of 500$m^2$ size. The classification by TWINSPAN and DCA, CCA ordination techniques were applied to the study area in order to classify them into several groups based on woody plants and environmental variables. By TWINSPAN techniques, the plant community were divided into four groups. The dividing groups are Pinus densiflora community, Qurcus variabilis -Q. mongolica -P. densiflora community, Fraxinus rhynchophylla community. The successional trends of tree species by DCA ordination techniques and DBH class distribution analysis seems to be from P. densiflora through Q. mongolica. Q. variabilis to F rhynchophylla. The correlation between the score of first two axes and soil pH, soil humus, soil calcium concentration, soil magnesium concentration was significantly positive in CCA ordination. The positive correlation between the score of first two axes of F. rhynchophylla community and soil humus, soil magnesium concentration and between ones of P. densiflora community and soil pH were calculated. But there is no correlation between species and environmental variables.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.157-166
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• 2008

To investigate the relationship between compressive strength ($q_u$) of Lightweight Air-mixed soil (LAS) and its physical deformation coefficient ($E_{50}$), a series of unconfined compressive tests have been performed on specimens of LAS according to various dredged soil types by percentage of sand, silt and clay. From the results it was found that the cement content ($C_i$) and unit weight (${\gamma}_m$) are most influence factors on strength, and percentage of sand, silt, clay by grain size analysis (KS F2302) have more effect on compressive strength than other physical properties of soil. It was also found that the rate of strength (a) increases with curing time, but it reduces with the increase of percentage of clay ($C_%$).

• Korean Journal of Microbiology
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• v.31 no.4
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• pp.261-266
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• 1993

A new methyltrophic bacterium which utilizes methanol as a sole source of carbon and energy was isolated from soil. It was Gram-negative, nonmotile, nonspore-forming rod, and strictly aerobic bacterium. Catalase and oxidase activities were present. Nitrate was reduced to nitrite. Vitamins and other growth factors were not required. Generation time was 1.6 hr under the optimal condition. The isolate assimilated methanol via the ribulose mono-phosphate pathway (Enter-Doudoroff varient) and did not have .alpha.-ketoglutarate dehydrogenase. It assimilated ammonia through glutamate dehydrogenase. The guanine plus cytosine content of the DNA was 61.0 mol%. The celular fatty acid composition was primarily straight-chain saturated $C^{16 : 0}$ acids (palmitic acids) and unsaturated $C_{16 :1}$ acid (palmitoleic acids), and the isolate also contained two unidentified $C_{17}$ branched fatty acids. The major ubiquinone was Q-8, and Q-6 and Q-7 were present as minor components. Phosphatidylethanolamine and phosphatidylglycerol were predominantly present, and diphosphatidyglycerol was also detected. Based on the physiological and biochemical properties, the isolate was assigned to a novel species of the genus Methylobacillus, Methylobacillus methanolovorus sp. nov.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.149-155
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• 2013

In this study, factors that affect the air entrainment within a closed conduit by air drawn in through an air vent are investigated using a hydraulic scale model, which represents a gated circular conduit system connected to the intake tower of an irrigation reservoir. In addition, using data obtained during the hydraulic experiments, experimental equations are developed to estimate the amount of air drawn in through the air vent. In case of pressurized flow conditions downstream of hydraulic jumps, the relationships between $\frac{Q_a}{Q_w}$ and $Fr_g-1$ of the data form a experimental equation, $\frac{Q_a}{Q_w}=0.0304(Fr_g-1)^{1.0622}$; in case of free surface flow conditions, $\frac{Q_a}{Q_w}=0.0271(Fr_g-1)^{1.8205}$. Comparing two data sets observed under the two flow regimes with the results of previous researchers, patterns of the data sets are similar to the results estimated using the equations presented previously, and this indicates that the quality of the data obtained during the hydraulic experiments is ensured. In addition, it is revealed that air entrainment phenomena in the regions close to air vents are affected by the characteristics of supercritical flows downstream of gates. Finally, it is concluded that the equation developed for pressurized flow conditions can be applied to design of air vents.

• Journal of Korean Society of Forest Science
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• v.78 no.2
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• pp.151-159
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• 1989

The present study has been designed to define the effects of photosynthetically active radiation, leaf temperature, and water stress on photosynthesis and respiration of leaves of four oak species (Quercus mongolica, Quercus aliens, Quercus variabilis, and Quercus serrate). The results obtained are as follows : 1. The estimated light compensation points at which Pn approached zero were 38, 24, 20, and $18{\mu}Em^{-2}s^{-1}$ for Q. aliens, Q. variabilis, Q, mongolica, and Q. serrate, respectively. The light saturation points occurred at $500{\mu}Em^{-2}s^{-1}$ in three oak species except Q, aliens. 2. The maximum rates of Pn were 19.7, 15.2, 11.2, and 11.0 mg $CO_2$ $dm^{-2}h^{-1}$ for Q. variabilis, Q. serrate, Q. monglica, and Q. aliens leaves, respectively. 3. The transpiration rates of Q. variabilis and Q. serrate leaves were slightly higher than those of Q. mongolica and Q. aliens leaves at various photosynthetically active radiations(PAR), but cuticular transpiration rates at dark were similar in four oak species. 4. The optimum photosynthesis occurred at $25^{\circ}C$ in Q. aliens, Q. variabilis, and Q. serrate leaves, but $20^{\circ}C$ in Q. mongolica leaves. In four oak species, the net photosynthesis approached zero at about $40^{\circ}C$. 5. The dark respiration rates of leaves exhibited the following ranking of species : Q, variabilis > Q. mongolica > Q. aliens > Q. serrate. 6. The maximum productive efficiency (Pg/Rd) of leaves occurred highest in Q, serrate at $20^{\circ}C$, then in Q. mongolica at $20^{\circ}C$, then in Q, aliens at $25^{\circ}C$, and finally in Q. variabilis at $15^{\circ}C$. 7. The decrease of net photosynthesis in Q. serrate began at about -1.2 MPa, and then approached zero at -2.9 MPa of leaf water potential. The decrease of net photosynthesis began at 3% of water loss, and then approached zero at 17.5% of water loss. 8. As indicated by tissue-water relations parameters, it may be suggested that Q. aliens and Q. variabilis are more tolerant and favored on xeric forest soils than Q. mongolica and Q. serrate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.198-208
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• 2011

When a structure which has relatively low load constructs on soft clay, the bearing capacity of the ground will be improved by sand overlying clay. In this condition, verifying the bearing capacity is difficult from the P.B.T etcetera in the in-situ. So, it is needed to estimate precise bearing capacity in the design process. In this study, 2-dimensional chamber tests and FEM analyses are conducted to evaluate behavior of bearing capacity for shallow foundations on a sand overlying clay. Because depth ratio H/B and bearing capacity ratio $q_c/q_s$ are selected as main factors, height of a sand, undrained shear strength of a clay and width of a loading are designated as variables. Results from chamber tests are very similar with those of FEM analyses. And it shows that punching shear mechanism is more suitable than the equation of Okamura et al.(1998). To make continual application of load spread mechanism, the equivalent load spread angle is proposed for H/B and $q_c/q_s$. Also, the linear regression equation of critical depth ratio Hf is suggested for $q_c/q_s$.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.299-308
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• 2006

This study was conducted to investigate differences in energy content of Quercus mongolica stands in the Republic of Korea with respect to latitude and altitude. Study sites were located in Mt. Joongwang, Pyeongchang-gun, Gangwon-do (altitude 1,300 m, 1,000 m, 800 m), Mt. Taehwa, Gwangju-gun, Gyeonggi-do (altitude 350 m), Mt. Wolak, Jecheon-si, Chungcheongbuk-do (altitude 300 m), Mt. Baekwoon, Gwangyang-gun, Jeollanam-do (altitude 800 m), and Mt. Halla, Jeju-do (altitude 1,000 m) by northern and southern aspect. Total energy content and annual energy fixation of Q. mongolica stands were 2,916-6,550 GJ/ha and 250-440 GJ/ha, respectively during the study period, Lower latitude (NE) stands of Q. mongolica showed more energy contents and annual energy fixation than higher latitude stands. Energy content and annual energy fixation of Q. mongolica stands were increased in low altitude. Energy content of Q. mongolica stands were higher in northern aspect than southern aspect. However, there were no significant differences in annual energy fixation between the aspects. Annual energy fixation of Q. mongolica stands was highly correlated with warm index and followed by descending orders: altitude, stand age, aspect, annual solar radiation and latitude.

• Journal of the Korean Vacuum Society
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• v.14 no.3
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• pp.126-131
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• 2005

Small-angle neutron scattering (SANS) is a very powerful techniques for nanostructure characterization. In this paper, we report the conceptual design and technical description of the 40 in small angle neutron scattering (SANS) insoument which is being developed by KAIST and KAERI for installation at 30 MW HANARO research reactor. For the optimal design of 40 m SANS, a series of computer simulation were pe.to.mod. The Q-.ange of the 40m SANS inst.ument is $0.0005\;\AA^{-1}-1.0\AA^{-1}$ which is a world top-class SANS Q-range. When the cold neutron spectrum used in the simulation is realized, the neutron flux at sample position is expected to be comparable to the current state-of-art SANS instrument in the world.

• Korean Journal of Environment and Ecology
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• v.25 no.3
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• pp.378-388
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• 2011

This study was done to classify the vegetation structure and ecological characteristics in Nakdong-jeongmaek. Therefore, we set up 34 plots($100m^2$) in 9km range. As a result of vegetation analysis, the vegetation of Seongsi valley was classified into the type of 6 communities i.e. Pinus densiflora community, Quercus variabilis community, Q. mongolica community, Q. serrata community, Betula schmidtii community, Larix leptolepis community. The average number of species and individuals were ranged from 8.5~10.5 and 27.5~75.6 respectively. Species diversity index(H') of groups were ranged from 0.6061~0.8736 per units, and it was highest and lowest in B. schmidtii and P. densiflora communities respectively. Similarity index of groups were slightly low. It was low in P. densiflora community, Q. mongolica community and L. leptolepis community, and lowest in Q. variabilis-Q. mongolica community.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.449-455
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• 2018

This study was conducted to analyze the correlation between changes in white matter and homocysteine concentration through brain computed tomography of healthy 50-75 year old subjects without stroke or dementia history. We studied 722 out of 900 patients who underwent health screening at one hospital from 2016 to 2017. Based on the medical records, retrospective studies were conducted and analyzed using SPSS. A chi-square test, T-test and univariate logistic regression analysis were used for analysis. After the subjects were divided into the group with and without white matter changes, the population characteristics were analyzed. The mean age, homocysteine concentration and prevalence of hypertension and diabetes were higher and the duration of education was shorter in the group with white matter changes. In the group with white matter changes, the population increased as homocysteine concentration increased. When the odds ratio was compared based on the lowest group (Q1), age [p<0.001], hypertension [p<0.001] and hyperhomocysteinemia [p=0.021] were risk factors for white matter changes. We also identified modifiable risk factors such as hypertension and hyperhomocysteinemia to prevent complications of white matter changes. However, there has been no report of risk for the each causes of hyperhomocysteinemia and relationship between white matter changes and homocysteine concentration in Koreans. Therefore, large scale prospective studies are needed to better understand this topic.