• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.73-87
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• 1996

The mechanical properties of 2D ceramic composites fabricated bythe newly developed powder infiltration and subsequent multiple impregnation process were characterised by both 3-point flexure and tensile tests. These tests were performed with strain gauge and acoustic emission instrument. The woven fabric composites used for the test have the basic combinations of $Al_{2}$$O_{3}$ fabric/$Al_{2}$$O_{3}$ and SiC fabric (Tyranno)/SiC. Uniaxially aligned SiC fibre(Textron SCS-6)/SiC composites were also tested for comparison, The ultimate flexural strength and first-matrix cracking stress of SiC fabric/SiC composite with 73% of theoretical density were about 300 MPa and 77 MPa respectively. However, the ultimate tensile strengths of composite were generally one third of flexural strengths, and first-matrix cracking stress in a tension test was also much lower than the value obtained from flexure test. The lower mechanical properties measured by tension test were analysed quantitatively bythe differences in stressed volume using Weibull statistics. This showed that the ultimate strength and the firs-tmatrix cracking stress of woven laminate composites were mainly determined bythe gauge length of fibres and the stressed volume of matrix respectively. Incorporation of SiC whiskers into the matrix increased first-matrix cracking stress by increasing the matrix failure strain of composites.

• Asian Journal of Turfgrass Science
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• v.15 no.4
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• pp.157-168
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• 2001

This study was carried out to investigate the offsets of pyroligneous acid on the growth of ‘Penncross’Creeping Bentgrass (Agrostis palustris Huds.) and to propose the practical use for ecologically responsive management in Korean golf courses. In the plots affected by 300, 500, and 800 times diluted pyroligneous acid, the turfgrass growth increment and the visual quality were measured at fixed periods. The data were subjected to paired samples T-test. The results summarized are as follows； 1) In leaf growth increment, density, and root spread depth, turfgrass affected by 500 and 800 times diluted pyroligneous acid were superior to the control continually. It was reliable in the statistics. Especially, 500 times diluted solutions was superior to the others. 2) In color, texture, uniformity, and recuperative strength, the visual quality of turfgrass affected by 500 and 800 times diluted pyroligneous acid were superior to the control continually. It was reliable in the statistics except the recuperative strength. Espe-cially, 500 times diluted solutions tended to be superior to the others. 3) There was no symptom of a disease in all plots. The existing management was thought to be suitable in this golf course. 500 and 800 times diluted pyroligneous acid were not thought to trigger or promote a disease, 4) After investigating the effect of pyroligneous acid on turfgrass growth, the soils of all plots were analyzed. In all plots, the chemical properties of the soils were not changed obviously. 5) Considering the results mentioned above, the practical use of 500 and 800 times diluted solutions might decrease the amount of nutrients and agricultural chemicals used in golf courses as well as promote turfgrass growth in golf courses.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.430-438
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• 2013

In this study, the seasonal field survey was conducted in Goseong Jaran Bay(22 stations), Geoje Hansan Bay(15 stations) and Jinhae Bay(18 stations). We analyzed the sediment environmental parameters(Chemical Oxygen Demand, Ignition Loss, Acid Volatile Sulfides, Total Organic Carbon) and biotic parameters of macrobenthic polychaetes(number of species, density, diversity, evenness). It had a good correlation between total organic carbon and polychaete diversity(R=0.61, P<0.01), and we made a decision them as representative environmental indices. As a result of that, regarding the criteria in the assessment of farm environment, we suggest concentrations of total organic carbon : Peak Point = 15 mg/g dry, Warning Point = 26 mg/g dry, Contaminated Point = 31 mg/g dry and polychaete diversity : ~2.6(Good), 2.6~2.1(Moderate), 2.1~1.2(Poor) and 1.2~(Bad). This could be a scientific basis to establish the environmental standards for fishery management.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.601-608
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• 2020

In this work, Ag₃PO₄/In₂S₃ nanocomposites with low loading of In₂S₃ (5-15 wt %) are fabricated by two step chemical precipitation approach. The microstructure, composition and improved photoelectrochemical properties of the as-prepared composites are studied by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photocurrent density, EIS and amperometric i-t curve analysis. It is found that most of In₂S₃ nanoparticles are deposited on the surfaces of Ag₃PO₄. The as-prepared Ag₃PO₄/In₂S₃ composite (10 wt%) is selected and investigated by SEM and TEM, which exhibits special morphology consisting of lager size substrate (Ag₃PO₄), particles and some nanosheets (In₂S₃). The introduction of In₂S₃ is effective at improving the charge separation and transfer efficiency of Ag₃PO₄/In₂S₃, resulting in an enhancement of photoelectric behavior. The origin of the enhanced photoelectrochemical activity of the In₂S₃-modified Ag₃PO₄ may be due to the improved charge separation, photocurrent stability and oriented electrons transport pathways in environment and energy applications.

• Polymer(Korea)
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• v.33 no.6
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• pp.602-607
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• 2009

A polyurethane (PU) surface enabling in vivo endothelialization via endothelial progenitor cell (EPC) capture was prepared for cardiovascular applications. To introduce CD34 monoclonal antibody (mAb) inducing EPC adhesion onto a surface, poly (poly (ethylene glycol) acrylate-co-butyl methacrylate) and poly (PEGA-co-BMA) were synthesized and then coated on a surface of PU, followed by immobilizing CD34 mAb. $^1H$-NMR analysis demonstrated that poly(PEGA-co-BMA) copolymers with a desired composition were synthesized. Poly(PEGA-co-BMA)-coated PU was much more effective for the immobilization of CD34 mAb, comparing with PEG-grafted PU prepared in our previous study, as demonstrated by that surface density and activity of CD34 mAb increased over 32 times. Physico-chemical properties of modified PU surfaces were characterized by X-ray photoelectron spectroscopy (XPS), water contact angle, and atomic force microscopy (AFM). The results demonstrated that the poly(PEGA-co-BMA) coating was effective for CD34 mAb immobilization and feasible for applying to cardiovascular biomaterials.

• Journal of Korean Society of Forest Science
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• v.106 no.1
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• pp.10-18
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• 2017

This study was carried out to suitable plantation site from comparison and analysis of regional early growth characteristics of planted Larix kaempferi trees in harvested L. kaempferi plantations. Two-year-old bare-root seedlings of L. kaempferi were planted with the density of $3000\;seedlings\;ha^{-1}$ at four sites (Yeongju, Gimcheon, Chuncheon, and Inje). All sites were established with three plots ($400m^2$ per plot) in 2010. We analyzed soil physical and chemical properties in October 2010 and 2013. We measured root collar diameter (RCD) and height of trees in October from 2010 to 2014, and then calculated H/D ratio and stem volume. Soil pH was significantly increased and available P was significantly decreased 3 years after planting. Annual mean RCD, height, and stem volume of 5-to 7-year-old in the Chuncheon site were significantly higher than those in the other sites, however them in the Yeongju site were the lowest. It is related to the fact that total nitrogen, available phosphorus, and organic matter concentrations in the Yeongju site were relatively lower than those in the other sites. As a results of this study, we could confirm the correlation between soil properties of L. kaempferi plantations and growth of L. kaempferi trees. We could suggest values of soil properties for reforestation of L. kaempferi.

• Ecology and Resilient Infrastructure
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• v.2 no.3
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• pp.224-236
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• 2015

We conducted the algicidal activity screening tests using 10 L microcosm to investigate the possibility of the field application of naphthoquinone derivative Nq 4-6 compound as an algicide. We determined its application range to assess its algicidal effects on the phytoplankton and to evaluate the response of the planktonic community and the water environment to this chemical. From results of the microcosm experiments, Nq 4-6 compound showed high algicidal activity on the centric diatoms such as Stephanodiscus hantzschii and Cyclotella meneghiniana, but it had no effect on other phytoplankton. The abundance of S. hantzschii continuously increased in the control, but its cell density decreased 1 day after the Nq 4-6 treatment. In particular, Nq 4-6 showed algicidal activity of 94.4% against S. hantzschii 7 days after the treatment. The dominance index of phytoplankton community was lower in the treatment than in the control. The diversity index, richness index and evenness index of phytoplankton community was higher in the treatment. Environmental factors and biological factors did not show specific changes after the Nq 4-6 compound treatment. Therefore, the results of this study demonstrates that Nq 4-6 is an effective agent for the control of S. hantzschii blooms, and that the microcosm tests play a crucial role when assessing field application.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.1 no.1
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• pp.28-44
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• 1998

This study was conducted to suggest the ecological restoration strategies for the disturbed landscapes by theoretical study. Especially, it is aimed to suggest three objectives for restoration by using native plants ; (1) prevention or reduction of wind and water erosion, (2) provision of food and cover for variety of animal species, (3) improvement of the visual or aesthetic quality of disturbed sites. The main results were summarized as follows. 1. Cooperation between restoration ecologists and restoration practitioners is needed to delineate a scientific approach to restoration ; (1) Being aware of published literature that describes similar work and/or establish general principles. (2) Preparedness to carry out proper experiments to test ideas. (3) Preparedness to monitor fundamental parameters in a restoration scheme. (4) Providing information about the behavior of species. (5) Publish results. 2. There are three models of succession in theories of plant succession. The tolerance and facilitation models were recommended to ecological restoration. The inhibition model applies in most secondary succession, but the actual species which are introduced first may inhibit the germination and growth of slower-growing species, or they may prevent the growth of other species whose propagules arrive later. 3. The objectives of erosion control, wildlife habitat provision, and visual quality improvement are not mutually exclusive. However, many revegetation practices in the past have emphasized one of these aspects at the expense of the others. 4. A native plant community can be the model of ecological restoration. By stylization/abstraction of native plant community, trying to learn the most essential characteristics of community types - environmental factors ; dominant, prevalent, and "visual essence" species composition - in order to use such information in restoration. 5. After developing mass/spaces plan, match plant communities to the mass/space plan. In utilizing community grouping, there needs aesthetic ability to understand design elements. 6. Several hydrophytes such as Pennisetum saccharifluous, Themeda triandra, Cirsium pendulum show relatively good germination rates. In case of mesophytes and xerophytes, Arundinella hina, Artemisia princeps, Oenothera odorata and legumes seem to have quick-germinating abilities at barren sites. Pinus thunbergii, Rhus chinensis, Evodia daniellii, Alnus firma and Albizzia julibrissin can be considered as "late succession" woody plants because they show low germinating rates and slow growing habitat. 7. The seeds used for restoration should be collected within a certain radius of where it will be planted. Consideration in genetic issues in the collection and use of germplasm can increase the odds for successful restoration efforts. 8. The useful model in the "drift" pattern occurs so abundantly in naturally evolving landscapes. As one species diminishes in density, a second or third species are increased. Thus, dynamic interactions between species are created. Careful using of "drift phenomenon" in planting was recommended. 9. Virtually no stand of vegetation today is immune from the introduction and/or spreading of exotic species. Therefore, the perpetuation of a restored sites requires conscious monitoring and management. Thus, management would be the most important process in ecological restoration. 10. In order to keep the sites "natural", alternative management strategies would be applied in management ; Atenative management strategies are decelerating successional process, accelerating successional processes or modifying species composition. As management tools, mechanical, chemical, biological or environmental factor manipulation, e.g., fire could be used.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.2
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• pp.151-158
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• 2010

In order to measure the deposition velocity of $I_2$ vapor for radish plants and its translocation factor for their roots, radish plants were exposed to $I_2$ vapor for 80 min. at different growth stages between 29 and 53 d after sowing. The exposure was performed in a transparent chamber during the morning time. Deposition velocities ($ms^{-1}$) were on the whole in the range of $1.0{\times}10^{-4}{\sim}2.0{\times}10^{-4}$ showing an increasing tendency with an increase in the biomass density. The results showed some agreement with existing reports that a higher relative humidity would lead to a higher deposition velocity. The acquired deposition velocities were lower than by factors of several tens than some field measurements probably due to a very low wind speed (about $0.2\;ms^{-1}$) in the chamber. Translocation factors (ratio of the total iodine in the roots at harvest to the total plant deposition), estimated in a more or less conservative way, were $1.3{\times}10^{-3}$ for an exposure at 29 d after sowing and $5.0{\times}10^{-3}$ for an exposure at 53 d after sowing. In using the present experimental data, meteorological conditions and chemical and physical forms of iodine need to be carefully considered.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.21-30
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• 2008

The fuel cell generation convert fuel source, and gas directly to electricity in an electro-chemical process. Unlike traditional and conventional turbine engines, the process of fuel cell generation do not burn the fuel and run pistons or shafts, and it has not revolutionary machine, so have fewer efficiency losses, low emissions and no noisy moving parts. A high power density allows fuel cells to be relatively compact source of electric power, beneficial in application with space constraints. In this system, the fuel cell itself is nearly small-sized by other components of the system such as the fuel reformer and power inverter. So, the fuel cell energy's stationary fuel cells produce reliable electrical power for commercial and industrial companies as well as utilities. In this paper, a fuel cell system has been modeled using PSCAD/EMTDC to analyze its electric signals and characteristics. Also the power quality of the fuel cell system has been evaluated and the problems which can be occurred during its operation have been studied by modeling it more detailed. Particularly, we have placed great importance on its power quality and signal characteristics when it is connected with a power grid.