• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.5
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• pp.47-56
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• 2004

This study was carried out to analyze forest vegetation of the Jangtaesan, Haetaesan, Ahnpyoungsan and Gubongsan in Daejeon. Employing the releve method of Braun-Blanquet, 76 plots were sampled. The communities were classified into Quercus mongolica community, Quercus variabilis community, and Pinus densiflora community. Average coverage rate was 85% in tree layer, 44% in subtree layer, 37% in shrub layer, 25% in herb layer, respectively. The importance values were 58.76 in Pinus densiftora, 44.86 in Quercus monegolica, 44.06 in Quercus variabilis, 33.00 in Quercus serrata, 18.73 in Rhus trichocarpa, 18.07 in Prunus sargentii. DBH range of most Pinus densiflora, Quercus mongolica and Quercus variabilis was between 5cm and 20cm. Therefore, Pinus densiflora, Quercus mongolica and Quercus variabilis will be dominant species in the study area for several more decades. Quercus mongolica community was distributed mainly on the north and east slope in a high-altitude and relative good nutrition condition. Querucus variabilis community was distributed mainly on the south slope in a middle-altitude and medium nutrition condition. Pinus densiflora community was distributed mainly in a low-altitude and poor nutrition condition.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.93-97
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• 1999

In order to lower the surface energy of unsaturated polyester(UPE) resin, small amount of siloxane-ester copolymers were incorporated. The copolymers were synthesized by a condensation polymerization using ethylene glycol and hydroxy termintated polydimethylsiloxane as diols and maleic anhydride and phthalic anhydride as dibasic acids. The modified UPE resin surface was characterized by dynamic contact angle (DCA), peel strength measurements of pressure sensitive adhesives and X-ray photoelectron spectroscopy(ESCA). As the copolymer content in the blend and PDMS content in the copolymer are increased, both advancing and receding contact angles against water are increased. The strength required to peel-off the pressure sensitive adhesive tape from the modified UPE resin decreased dramatically with the addition of the copolymer. ESCA results indicated that polydimethylsiloxane segments are predominated at the outer surface of the modified UPE resin.

• Korean Journal of Environment and Ecology
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• v.24 no.5
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• pp.582-590
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• 2010

Baekdudaegan field survey has been proposed and presented as a various plan such as field survey analysis, management and restoration plan, etc. Whereas, the concerns of the Jeongmaek has increased continuously, nevertheless there is no research of present condition for Jeongmaek. This paper is to contribute to suggest for management and restoration as a basic study of vegetation structure in Yongso valley. We set up 30 plots($100m^2$) to verify the vegetation structure. As a result of classification analysis used by DCA, the type of 5 communities i.e. Pinus densiflora community, Betula schmidtii community, Populus maximowiczii community, Quercus mongolica community, Q. variabilis community were the most representative of Yongso valley vegetation communities. P. densiflora community was mainly distributed in the ridge of mountain, ridge of steep slope and stony area. In that reason, they avoid to compete with B. schmidtii community and Q. spp. community. In addition, the appearance of Rhododendron micranthum was mainly characteristics in the P. densiflora community. Species diversity indices(H') of groups were ranged from 0.7914~0.9942, the tree ages were 30~115 years. According to these results, the forests of Yongso valley not only form muti-layer vegetation structures but also have a great ecological value for protection and preservation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9B
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• pp.1126-1142
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• 2011

This paper addresses the stereoscopic 3D broadcasting technology that delivers the 3DTV contents through the digital cable networks. In order to convey the 3D contents via DCA TV network, specifications of 3D video format, compression, multiplexing, signalling and transport are to be developed. Since 3D has some constraints unlike 2D, it is required to be well designed by considering the capacity of the additional view and the backward/forward compatibility. This paper goes with the latest trends of 3D standard, requirements and service scenarios and then covers the 3D format, compression, multiplexing and signaling, service information and transport/reception technologies.

• The Korean Journal of Ecology
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• v.10 no.2
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• pp.63-80
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• 1987

Detrended correspondence analysis(DCA) and two way indicator species analysis(TWINSPAN) were applied to Pinus densiflora stands nearby Seoul area in order to classify them into several groups based on herbaceous species and environmental relationships. The eighteen Pinus densiflora stands were perferenially selected, In each stand, 30 to 60 quadrats, (20X20)cm, were randomly estabilished. In each quadrat, all stems for herbaceous plants were recorded by species and their covers were measured. In addition environmental factors such as soil depth, thickness of litter layer, soil compressibility, tree density, basal area, elevation, slope and exposure were detemined for each stand. Four to twelve soil cores were collected and physical and KDICical properties were determined. This survey was conducted form 15, July, 1985 to 22, September, 1985. Analysis of the vegetation and environmental data were performed with DECORANA and TWINSPAN. Stand ordination (DECORANA) and classification (TWINSPAN) based on herbaceous species suggest that the stands can be classified into five groups in terms of herbaceous species composition and environmental relationships. Type I, Type II, Type III, Type IV and Type V were classified to SUBMESIC-CLO-SED-CANOPY (Artemisia keiskeana, Carex nanella), MESIC-CLOSED CANOPY (Spodiopogon sibiricus, Miscanthus sinensis, Carex nanella, Pteridum aquilinum, Melampyrum rosium), SUBMESIC-OPEN CANOPY (Carex nanella, Spodiopogon sibiricus, Miscanthus sinensis), XERIC-CLOSED CANOPY (Carex nanella, Spodiopogon sibiricus, Carex nanella), and XERIC-OPEN CANOPY (Arundinella hirts, Spodiopogon sibiricus, Carex nanella), respectively. These results were consitent with environmental trends on stan ordination. Application of the ordination and classifiaction to Pinus densiflora stands were effective as a approach on obtaining perliminary ecological information.

• The Korean Journal of Ecology
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• v.24 no.2
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• pp.111-115
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• 2001

Vegetational changes along elevational and topographical gradients were studied in Mt. Jumbong which is located at the core area of the Mt. Sorak Biosphere Reserve in Kangwon-do Province in central Korea. Two 500 m north-south transects crossing two valleys and a small ridge were laid out, and fifty-one 10 m$\times$10 m permanent quadrats were systematically set up. All trees bigger than 2.5 cm DBH were marked with numbered aluminum tags, and their DBH measured and the species identified. Coverage of plant species in the herb layer were determined in two 2 m $\times$ 2 m subquadrats in each of the permanent quadrats. Thirty-two species of woody plants occurred in the tree layer in the permanent quadrats studied. Quercus mongolica was the dominant species across the study site, and Acer pseudosieboldianum and Carpinus cordata were also important. Quercus mongolica occurred on the ridges and south-facing slopes, and Acer pseudosieboldianum occurred extensively except for valleys. In contrast, Fraxinus mandshurica, Acer mono, Acer triflorum, and Ulmus laciniata were common in valleys. At the herbaceous layer, 112 species were identified. Dominant species were Ainsliaea acerifolia and Sasa borealis on the ridges, Meehania urticifolia on north-facing slopes, and Deutzia glabrata on valleys. Soil environmental factors were compared among the quadrats. pH was lower in the quadrats located on ridges and south-facing slopes, and organic matter was lowest on south-facing slopes. Quadrats located on valleys were generally higher in pH, organic matter, N, P, K, Ca and Mg. DCA ordinations for tree layer and herb layer were carried out in order to identify the dominant environmental factors affecting the distribution of plant species along the environmental gradients. Correlation analysis between ordination axis scores and environmental factors showed that axis one was negatively correlated with elevation and positively correlated with soil organic matter, pH, Ca, Mg, and P, but that axis two was positively correlated with elevation. These results indicate that vegetation responds very sensitively to elevational and topographical gradients although the study area is relatively small with about 100 m in elevational variation.

• Journal of Ecology and Environment
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• v.32 no.1
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• pp.55-60
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• 2009

We analyzed the factors driving succession and the structure, and dynamics of vegetation on sand and gravel bars in order to clarify the differences in vegetation succession in rivers with different river bed substrates. Woody plant communities (dominated by Salix), perennial herb communities (dominated by Miscanthus), and annual plant communities (dominated by Persicaria) appeared in that order from upstream to downstream on the sandbar. The results of DCA ordination based on vegetation data reflected a successional trend. This result suggests that sandbars grow in a downstream direction. Various vegetation types different in successional stage, such as grassland, young stands of Korean red pine (Pinus densiflora), two-layered stands of young and mature pines, and mature pine stands also occurred on gravel bars, but the vegetation in earlier successional stage was established upstream, which is the opposite to the direction found on sandbars. Those results demonstrate that the dynamics of the bed load itself could be a factor affecting vegetation succession in rivers. In fact, sands suspended by running water were transported downstream over the vegetated area of sand bar and thereby created new areas of sandbar on the downstream end of the sandbar. Meanwhile, gravel, which is heavy and thereby is shifted by strong water currents, accumulated on the upstream end of the vegetated area, and thus created new areas of gravel bar in that direction. These results showed that allogenic processes drive vegetation succession on sand and gravel bars in streams and rivers.

• The Journal of Advanced Prosthodontics
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• v.10 no.4
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• pp.308-314
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• 2018

PURPOSE. Plasma activation of hydrophobic zirconia surfaces might be suitable to improve the bond strength of luting materials. The aim of this study was to analyze the influence of nonthermal argon-plasma on the shear bond strength (SBS) between zirconia and different combinations of 10-MDP adhesive systems and luting composites after artificial aging. MATERIALS AND METHODS. Two hundred forty Y-TZP specimens were ground automatically with $165{\mu}m$ grit and water cooling. Half of the specimens received surface activation with nonthermal argon-plasma. The specimens were evenly distributed into three groups according to the adhesive systems ([Futurabond U, Futurabond M, Futurabond M + DCA], VOCO GmbH, Germany, Cuxhaven) and into further two subgroups according to the luting materials ([Bifix SE, Bifix QM], VOCO GmbH). Each specimen underwent artificial aging by thermocycling and water storage. SBS was measured in a universal testing machine. Statistical analysis was performed using ANOVA and $Scheff{\grave{e}}$ procedure with the level of significance set to 0.05. RESULTS. Surface activation with nonthermal plasma did not improve the bond strength between zirconia and the tested combinations of adhesive systems and luting materials. The plasma-activation trended to reveal higher bond strength if the self-etch luting material (Bifix SE) was used, irrespective of the adhesive system. CONCLUSION. Plasma-activation seems to be suitable to improve bond strength between zirconia and self-etch resin materials. However, further research is necessary to identify the influence of varying plasma-parameters.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.567-575
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• 2015

Species composition in the coastal waters off Ulleungdo of Korea were examined based on catches bimonthly collected by trammel net in 2013. A total of 711 individuals and 181.9 Kg were caught and catches were composed of 4 classes 15 orders 27 families 52 species including 44 Pisces, 4 Gastropoda, 3 Cephalopoda, and 1 Echinodermata. The dominant species in biomass were File fish (Thamnaconus modestus), Atka mackerel (Pleurogrammus azonus), and Greenling (Hexagrammos otakii). Data were summarized using hierarchical cluster analysis (HCA) and detrended correspondence analysis (DCA) to examine similarity in species composition for each month, and community structure in Ulleungdo was divided into two groups. Community structures in February, April and December with low temperature and well-mixed surface water were distinguished from those in June, August and October with high temperature and strong stratification, which could be attributed to temporal changes in dominant species. Atka mackerel and Spear squid mainly caught in February and April, disappearing in June, August and October, and File fish outburst was shown in October. Because the water off Ulleungdo has been under low human pressure, it could be a good case study to elucidate effects of climate change on community structure and ecosystem in the East sea. Continuous surveys and further studies are required to demonstrate migration route and distribution of dominant species and long-term changes in community structure in the water of Ulleungdo.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.37-43
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• 2009

This paper describes a monolithic Darlington-cascade amplifier (DCA) operating at X-band, realized with a 0.35-micron SiGe bipolar process, which provides 45 GHz $f_T$. A conventional cascade amplifier was also designed on the same process and tested to establish a reference. Compared to the reference cascade amplifier, the proposed monolithic amplifier circuit exhibits an improved gain of 2.5 dB and improved output power 1-dB compression point of 5.2 dB with 72% wider bandwidth. Measurement results show 19.5 dB gain, 11.2 dBm 1-dB compression power, and 3.1 GHz bandwidth. These results demonstrate that the Darlington-cascade cell is an advantageous substitute to the conventional cascade amplifier.