• Korean Journal of Environment and Ecology
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• v.20 no.4
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• pp.493-502
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• 2006

This study analyzed greenspace structure focused on greenspace areas and vegetation structure for Yanggu, investigated resident attitudes to the greenspace, and explored strategies to improve greenspace functions in a rural region. Woody plant cover was approximately 29% for parks and only 3% for commercial gardens. The amount of planting for Yanggu was poor, as compared with the results of similar studies for urban areas. Trees, of which dbh was below 20cm, accounted for 91% of all trees and the tree-age structure was largely characterized by a young, growing tree population. Based on the analysis of mean importance values (MIV) of woody plant species, only a few were different in dominant species from urban areas. Four species among 10 species with highest MIV in Yanggu were very common species also ranked among 10 in cities. The most dominant species planted in residential and commercial gardens were practical plants such as fruit or edibles. Greenspace covered about 69% of parks, 39% of residential gardens, 37% of institutional gardens, 24% of streets, and 15% of commercial gardens, respectively. Tree planting potential revealed that present woody plant cover can be increased additionally by 6 times in the streets and by 2 times in the residential and commercial gardens. Based on the results of greenspace structure, planting patterns, and questionary investigation, some strategies were suggested to enlarge greenspace including its environmental functions. They included identifying each street section through setting up themes and planting appropriate species, creating multilayered vegetation structures, and promoting planting in bare grounds of gardens and around a buildings for saving energy.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.7-12
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• 2024

The durability of the catalyst support has a significant effect on the durability of proton exchange membrane fuel cells (PEMFC). The accelerated durability evaluation of the catalyst support is performed at a high voltage (1.0 to 1.5 V), and the catalyst and ionomer binder in the catalyst layer are also deteriorated, hindering the evaluation of the durability of the support. The existing protocol (DOE protocol) was improved to find conditions in which the support, which is a durability evaluation target, deteriorates further. A protocol (MDOE) was developed in which the relative humidity was lowered by 35% and the number of voltage changes was reduced. After repeating the 1.0 ↔ 1.5 V voltage change cycle, the catalyst mass activitiy (MA), electrochemical active area (ECSA), electrical double layer capacity (DLC), Pt dissolution and particle growth were analyzed. Reaching 40% reduction in mass activity, the MDOE protocol took only 500 cycles, reducing the number of voltage changes compared to the DOE method and increasing the degradation of the carbon support by 50% compared to the DOE protocol.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.217-228
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• 2003

Co-ordinate growth of the brain and skull is achieved through a series of tissue interactions between the developing brain, the growing bones of the skull and the sutures that unite the bones. Craniosynostosis, the premature fusion of cranial sutures, presumably involves disturbance of these interactions. Bmp2, one of bone morphogenetic proteins (Bmps), is involved in the regulation of the shapes of individual bones and the relative proportions of the skeleton. Mutations in the homeobox gene Msx2, known as a downstream gene of Bmp, cause Boston-type human craniosynostosis. The phenotype of Dlx5 homozygote mutant mouse presents craniofacial abnormalities including a delayed ossification of calvarial bone. These facts suggest important roles of Bmp2, Msx2 and Dlx5 genes in the cranial bone growth and suture morphogenesis. To elucidate the function of these molecules in the early morphogenesis of mouse cranial sutures, we first analyzed by in situ hybridization the expression of Bmp2(E15-18), Msx2 and Dlx5 genes in the developing sagittal suture of calvaria during the embryonic stage. Bmp2 mRNA was intensely expressed in the osteogenic fronts and also at the low level in the periosteum of parietal bones during embryonic stage, Msx2 mRNA was intensely expressed in the sutural mesenchyme and mildly expressed in the dura mater during the embryonic stage. Dlx5 mRNA was intensely expressed osteogenic fronts and parietal bones. To further examine the role of Bmp signaling in cranial suture, we did in vitro experiments in E15.5 mouse calvarial explants. Interestingly, implantation of Bmp2-soaked beads onto the osteogenic fronts after 48 hours organ culture resulted in the increase of the tissue thickness and cell number around Bmp2 beads, compared to BSA control beads. In addition Bmp2 induced etopic expressions of Msx2 and Dlx5 genes. On the other hand, overexpression of FGF2 did not induce the expression of Msx2 and Dlx5. Taken together, these data indicate that Bmp2 signaling molecule has a important role in regulating the cranial bone growth and early morphogenesis of cranial suture. We also suggest that Bmp signaling is involved in all the stages of osteogenesis of cranial bones and the maintenance of cranial suture by regulating Msx2 and Dlx5 genes, and that Msx2 and Dlx5 genes are specific transcription factors of Bmp signaling pathway.

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.113-130
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• 2002

In this paper, we developed DNL(Dynamic Network Loading) model based on Moving cell theory to analyze the dynamic characteristics of traffic flow in congested network. In this paper vehicles entered into link at same interval would construct one cell, and the cells moved according to Cell following rule. In the past researches relating to DNL model a continuous single link is separated into two sections such as running section and queuing section to describe physical queue so that various dynamic states generated in real link are only simplified by running and queuing state. However, the approach has some difficulties in simulating various dynamic flow characteristics. To overcome these problems, we present Moving cell theory which is developed by combining Car following theory and Lagrangian method mainly using for the analysis of air pollutants dispersion. In Moving cell theory platoons are represented by cells and each cell is processed by Cell following theory. This type of simulation model is firstly presented by Cremer et al(1999). However they did not develop merging and diverging model because their model was applied to basic freeway section. Moreover they set the number of vehicles which can be included in one cell in one interval so this formulation cant apply to signalized intersection in urban network. To solve these difficulties we develop new approach using Moving cell theory and simulate traffic flow dynamics continuously by movement and state transition of the cells. The developed model are played on simple network including merging and diverging section and it shows improved abilities to describe flow dynamics comparing past DNL models.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.64-73
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• 1998

In twin spool aero-engine, there may be a S shaped annular duct between high pressure and low pressure spools. The flow passing this S shaped duct experiences the flow acceleration and deceleration due to the convex and concave surface of the duct as well as the increase of blockage according to the boundary layer growth along the surfaces. So, the high pressure compressor which is located behind the S shaped duct is influenced by the non-uniform flow field generated by the geometry of inlet duct. To study the influence of the S shaped duct on the centrifugal stage, performance tests were implemented for the compressor with straight cylindrical inlet duct and with S shaped inlet duct, respectively. The test results showed that the performance, such as pressure ratio and efficiency, of the compressor with S shaped duct was worse than that of the compressor with cylindrical duct. And the compressor with S shaped duct had reduced maximum flow rate around design speed. To investigate the cause of performance degradation, flow anlaysis was performed for the impeller in front of which is located S shaped annular duct. The result of CFD showed the strong acceleration of the flow in the axial direction around the inducer tip region which caused the increase of relative mach number and the decrease of incidence angle of the flow.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.3
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• pp.170-179
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• 2020

Tidal asymmetry would occur owing to shallow water tides at the Western Coast of macro tidal area. Especially, as ebb dominance of Mokpo coastal zone is known as the most prominent in Korea, it had been studied by domestic researchers. The cause of ebb dominance in Mokpo area is considered due to extensive inter-tidal zone in Muan Bay, and this has been studied based on amplification ratio, relative phase and skewness of tide/tidal flow curves in order to analyze qualitative tidal asymmetry. Furthermore, it was possible to figure out tidal characteristics with the difference of tidal amplitude and phase with Mokpo Harbor by observing the tide for 15 days in Muan Bay, which showed 40 minutes shorter ebbing time than at Mokpo Harbor. In addition, tidal flow prediction data in Mokpo North Harbor and Mokpo-Gu were analyzed. Meanwhile, the basis regarding qualitative interpretation of bed sediment and suspended sediment was provided by examining the qualitative changes in tidal asymmetry for spring-neap tidal cycle through the PCA/SWA indices. In addition, by examining long-term changes of ebb dominance in Mokpo Port, tidal characteristics of the past, present and future in this area, which is related to tidal asymmetry, is also provided.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.613-621
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• 2011

Bog bean (Menyanthes trifoliata L.) is an endangered species in Korea, inhabiting in montane wetlands. Its' habitats are decreasing due to artificial disturbances and climate change in Korea. Interspecies competitions determine the distribution of a species and it is important to examine the effects of companion species on the growth of a species. To reveal the effects of habitat substrate and companion species on the growth of bog bean, we compared the growth parameters of bog bean at three substrate conditions where plant communities were formed: water column, Sphagnum mat, and paddy soil. Bog bean had the highest relative coverage at Sphagnum mat condition and there are few species whose height were higher than it. In contrast, there were many species larger than bog bean at paddy soil condition. The maximum coverage of bog bean was the largest at water column condition, and the lowest at paddy soil condition. Our results indicate that the growth of bog bean was more restricted by interspecific competition at paddy soil condition than at Sphagnum mat condition. Those results suggest that bog bean avoid competitions by expansion of rhizome rather than elongation of its height. For conservation or creation of bog bean habitats, it is necessary to offer the environment where other species cannot survive well.

• Elastomers and Composites
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• v.46 no.4
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• pp.335-342
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• 2011

The virgin and recycled polyethylene composites with various ratio of fly ash were manufactured by using a fully intermeshing co-rotating twin screw extruder for the reuse of fly ash from power plant and post-consumed polyethylene. Fly ash were blended with virgin HDPE and recycled polyethylene at the weight fraction of 0 to 40 wt.%. Mechanical properties such as yield strength, abrasion resistance, and slow crack resistance were measured with ISO and ASTM standards. The experimental results for the various composites showed that the elongation at break and the yield stress of the composites decreased with increasing fly ash contents. Generally, the abrasion resistance of PEs decreased with increasing sandpaper grits but the abrasion resistance of the composites increased with fly ash content at finer abrasive surface. The slow crack growth resistance of virgin HDPE, recycled JRPE and the JRPE composite showed higher slow crack growth resistance up to 50% of load at notch depth of 20% and 30%, but KRPE and the KRPE composite showed much lower resistance than virgin HDPE, JRPE and the JRPE composite. Time to break, measured with NCLS test method, of all PEs and the composites satisfies the regulation of Korean Industrial Specification for sewer pipe and support application.

• Journal of Korea Port Economic Association
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• v.25 no.3
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• pp.183-206
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• 2009

The purpose of this study is to suggest the new strategies for strengthening the competi tiveness of Incheon port. To measure the calling factors and satisfaction of ports, this study developed a list of 24 items using a seven-point Likert scale through the previous literature reviews, pilot test and emerging factors. Factor analysis, regression analysis, one sample T-test, IPA and SPSS were conducted to verify the determinants choosing ports and customer satisfaction. The result of an empirical study revealed that the cargo volume and information system, etc. in Incheon port was evaluated as satisfied factors and berth availability and port charge, etc. as dissatisfied factors. Based on the outcomes of this study, to strengthen the competitiveness of Incheon port, several strategies were advised such as the inducement of North American and European cargo, port infrastructure, dedicated terminal and GTO inducement, hinterland construction, logistics companies inducement and cooperation with neighboring ports.

• Korea Trade Review
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• v.48 no.1
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• pp.215-241
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• 2023

As competition between ports intensifies, port efficiency has always been a hot topic in the port and shipping economy. Boosting regional and national economies by improving port efficiency and promoting sustainable development of ports is also a concern for port operators and local and national governments. In this situation, this study has the following objectives. First, using panel data from 2010 to 2017, the efficiency of 14 major inland ports along the Yangtze River was analyzed, and changes in port efficiency over time were examined. Second, 14 inland ports are divided into the middle, upper, and lower Yangtze River port groups to compare and review differences in efficiency levels of ports by basin. For the study, we applied a three-step DEA analysis method, which evaluated the pure relative efficiency of the port itself by removing the effects of environmental factors and statistical noise that could affect the efficiency evaluation and presented the results. As a result, it was confirmed that there was a clear difference in the efficiency value of the port between the first-stage and the third-stage efficiency evaluation result. In addition, the downstream ports showed relatively high efficiency compared to the middle and upstream ports.