• Steel and Composite Structures
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• v.34 no.1
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• pp.91-105
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• 2020

Steel-concrete composite beam with profiled steel sheet has gained its popularity in the last two decades. Due to the ageing of these structures, retrofitting in terms of flexural strength is necessary to ensure that the aged structures can carry the increased traffic load throughout their design life. The steel ribs, which presented in the profiled steel deck, limit the use of shear connectors. This leads to a poor degree of composite action between the concrete slab and steel beam compared to the solid slab situation. As a result, the shear connectors that connects the slab and beam will be subjected to higher shear stress which may also require strengthening to increase the load carrying capacity of an existing composite structure. While most of the available studies focus on the strengthening of longitudinal shear and flexural strength separately, the present work investigates the effect of both flexural and longitudinal shear strengthening of steel-concrete composite beam with composite slab in terms of failure modes, ultimate load carrying capacity, ductility, end-slip, strain profile and interface differential strain. The flexural strengthening was conducted using carbon fibre reinforced polymer (CFRP) or steel plate on the soffit of the steel I-beam, while longitudinal shear capacity was enhanced using post-installed high strength bolts. Moreover, a combination of both the longitudinal shear and flexural strengthening techniques was also implemented (hybrid strengthening). It is concluded that hybrid strengthening improved the ultimate load carrying capacity and reduce slip and interface differential strain that lead to improved composite action. However, hybrid strengthening resulted in brittle failure mode that decreased ductility of the beam.

• The Korean Journal of Mycology
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• v.37 no.2
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• pp.161-166
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• 2009

The purpose of the present study is to develop a simple, fast and sensitive LC/MS method for simultaneous separation and the determination of an active component in the oriental medicinal mushroom Cordyceps militaris. Based on this work, the contents of cordycepin in Cordyceps militaris fruiting cultivated on various media were determined and compared. And also, the nutritional components such as minerals and vitamins were determined in order to provide useful information to consumer as a food material. The analysis methods of nutritional components were chosen on the basis of AOAC. The optimum separation for cordycepin was achieved using a solvent gradient consisting of the mixture of 0.1% formic acid in methanol (solvent B) in a background of 0.1% formic acid in water (solvent A) as a mobile phase and a 3.0${\times}$150 Waters XTera column. Selective ion monitoring (SIR) mode ([M+H]+ at m/z 252) was used for quantitative analysis of cordycepin. The cultivated Cordyceps militaris on various media contained 1~14 /g of cordycepin, 0.65~1.08% of thiamine, 0.86~7.17% of riboflavin, and 3.01~5.26% of niacin. The content of mineral components varied on categories, especially contained 500~3500% of potassium as a major mineral. Cordycepin, niacin and potassium were found much higher in the fruiting cultivated with soy power media (gold 10) than other media.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.2
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• pp.102-107
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• 2003

This study puts focus on the optimization of growth temperature of CIGS absorber layer which affects severely the performance of solar cells. The CIGS absorber layers were prepared by three-stage co-evaporation of metal elements in the order of In-Ga-Se. The effect of the growth temperature of 1st stage was found not to be so important, and 350$^{\circ}C$ to be the lowest optimum temperature. In the case of growth temperature at 2nd/3rd stage, the optimum temperature was revealed to be 550$^{\circ}C$. The XRD results of CIGS films showed a strong (112) preferred orientation and the Raman spectra of CIGS films showed only the Al mode peak at 173cm$\^$-1/. Scanning electron microscopy results revealed very small grains at 2nd/3rd stage growth temperature of 480$^{\circ}C$. At higher temperatures, the grain size increased together with a reduction in the number of the voids. The optimization of experimental parameters above mentioned, through the repeated fabrication and characterization of unit layers and devices, led to the highest conversion efficiency of 15.4% from CIGS-based thin film solar cell with a structure of Al/ZnO/CdS/CIGS/Mo/glass.

• Applied Biological Chemistry
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• v.28 no.3
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• pp.124-130
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• 1985

Adsorption experiments of N-methylcarbamate insecticides on soils were carried out as a function of soil pH ana soil organic matter content with wet-and dry-land soils that were either oxidized or non-oxidized. The results obtained may be summarized as follows: The adsorption of N-methylcarbamate insecticides on soils was nearly leached to equilibrium after shaking for 12 hours. The adsorption of N-methylcarbamate insecticides was higher on sandy clay than sandy loam. The presence of organic matter in soil increased the adsorption of N-methrlcarbamate insecticides on soils. The mode of isothermal adsorption of N-methylcarbamate insecticides on soils was coincident with the Freundlich equation. Little effect of soil pH on the adsorption might be interpreted as that the adsorption was due to physical adsorption between N-methylcarbamate molecules and soil surface.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1852-1865
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• 2017

The vibration of the structures with restrained motion has long been observed in various engineering fields. When the motion of vibrating structure is restrained due to the adjacent objects, the frequencies and the mode shapes of the structure change and its vibration characteristics becomes unpredictable, in general. Although the importance of the study on this type of vibration model increases in many engineering areas, most studies conducted so far are limited to the theoretical study on dynamic responses of the structure with stops, including some experimental works. Specially, the study on the nonlinear phenomena due to the impact between the structure and the stops have been mainly performed theoretically. In the paper, both numerical analyses and experiments are conducted to study the chaotic vibration characteristics of the nonlinear motion and the dynamic response of a cantilevered beam which has restrained motion at the free end by the stops. Results are presented for various magnetic forces and gaps between the beam and stops. The conclusions are as follows : Firstly, Numerical simulation results have a good agreement with experimental ones. Secondly, the effect of higher modes of beams are increased with increasing magnitude of exciting force, and displacement and velocity curves become more complicated shapes. Thirdly, nonlinear characteristics tend to appear greatly with increasing magnitude of exciting force, and fractal dimension is increased.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.73-83
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• 1998

Considering dynamic behaviors according to initial tension forces, geometric nonlinearity and the effect of higher eigen modes to participate in dynamic behaviors increase as initial tension forces decrease, and from phase portrait we can realize that period attractors are produced in many area with complexity. If initial tension forxes increase, difference between linear and nonlinear solutions will decrease and the first eigen mode dominate the dynamic behaviors and observing phase portrait, period attractors appear in certain area regularly. These results may offer meaningful informations to nonlinear dynamic analysis using modal reduction methods such as Lanczos modal analysis. And actually nonlinear dynamic analysis needs very large computational efforts. So, if we determine the number of eigen modes to take part in modal analysis corresponding to initial tension forces we will get more accurate data close to exact nonlinear dynamic solutions.

• Journal of the Korean Wood Science and Technology
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• v.43 no.2
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• pp.168-176
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• 2015

This study was performed to investigate the effects of heat treatment the on mechanical properties of two species of wood under different heating conditions including at $180^{\circ}C$ for 12 h and 24 h, and at $210^{\circ}C$ for 3 h and 6 h. Two species of wood, Pinus densiflora and Larix kaempferi, were exposed to different heat treatments to assess the effects on the volume change, bending properties in static and dynamic mode and compressive strength. The results showed heat treatment caused significant changes in mechanical properties such as the static and dynamic moduli of elasticity ($MOE_d$ and $MOE_s$), and the modulus of rupture (MOR). The volume of the wood after heat treatment decreased as the heating temperature and time were increased. The bending strength performance of the wood after heat treatment decreased as the heating temperature and time were increased. The effect of heat treatment at a high temperature on the bending MOR was greater in both species than that for a long time. However, the compressive strengths of all the heat-treated samples were higher than the control sample. Furthermore, highly significant correlations between $MOE_d$ and MOR, and $MOE_s$ and MOR were found for all heating conditions.

• Journal of the Korean Wood Science and Technology
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• v.48 no.5
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• pp.710-721
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• 2020

This study used a building model made up of cement, brick, and wood to measure temperature and relative humidity for 3 days in a closed environment with a diameter of 900 mm, and performed a comparative analysis of the effect of types of building materials on the indoor temperature environment and heat transfer characteristics. The water installed inside the building model represented the person in the room and was used to assess how the environment effects the person. Wooden building model showed the lowest heat loss due to the higher thermal insulation properties than cement and brick buildings. The thermal comfort of each building model was calculated using temperature and relative humidity, and the wooden building model created a more pleasant environment than the cement and brick building models.

• ALGAE
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• v.28 no.2
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• pp.193-202
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• 2013

Nitrogen availability and cell density each affects growth and cellular astaxanthin content of Haematococcus pluvialis, but possible combined effects of these two factors on the content and productivity of astaxanthin, especially under outdoor culture conditions, is less understood. In this study, the effects of the initial biomass densities IBDs of 0.1, 0.5, 0.8, 1.5, 2.7, 3.5, and 5.0 g $L^{-1}$ DW and initial nitrogen concentrations of 0, 4.4, 8.8, and 17.6 mM nitrate on growth and cellular astaxanthin content of H. pluvialis Flotow K-0084 were investigated in outdoor glass column photobioreactors in a batch culture mode. A low IBD of 0.1 g $L^{-1}$ DW led to photo-bleaching of the culture within 1-2 days. When the IBD was 0.5 g $L^{-1}$ and above, the rate at which the increase in biomass density and the astaxanthin content on a per cell basis was higher at lower IBD. When the IBD was optimal (i.e., 0.8 g $L^{-1}$), the maximum astaxanthin content of 3.8% of DW was obtained in the absence of nitrogen, whereas the maximum astaxanthin productivity of 16.0 mg $L^{-1}\;d^{-1}$ was obtained in the same IBD culture containing 4.4 mM nitrogen. The strategies for achieving maximum Haematococcus biomass productivity and for maximum cellular astaxanthin content are discussed.

• Food Science and Biotechnology
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• v.17 no.6
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• pp.1391-1395
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• 2008

Leuconostoc citreum HJ-P4 is a strain isolated for kimchi fermentation with its low temperature-adapted growth feature and its high dextransucrase activity. The detailed characteristics of cell growth and dextran sucrase activities were investigated at various environmental conditions such as temperatures, pHs, salts, and raw ingredients. This strain showed almost 2-fold higher maximal cell concentration ($X_{max}$) than that of the type culture Leuconostoc mesenteroides B-512F at $10^{\circ}C$. The $X_{max}$ of the strain was maximum at pH 7 and the cell growth was inhibited by salts in a dose-dependent mode up to 7%. Addition of pepper (<6%), garlic (<10%), and ginger (<2%) in kimchi gave no inhibition effect on the growth of HJ-P4. Dextransucrase synthesized by this strain retained over 80% of its maximum activity at $10^{\circ}C$ showing a comparable cold-adapted feature to its host microbe. This culture can be used as a starter culture in the industrial kimchi production giving desirable functions and predominance at low temperature.