• Korean Journal of Plant Resources
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• v.23 no.4
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• pp.274-292
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• 2010

The flora of resource plants in Middle and Northern region of Yangsan-si were investigated for 7 times from March to Sept., 2009. The study indicated that, based on voucher specimens, the flora of this area consist of 427 taxa in total; 90 families, 256 genera, 376 species, 4 subspecies, 41 varieties and 6 forms. The resource plants in this area were categorized by their use into 9 groups inclusive of 1 unidentified group. Resources plants which were investigated in this area were 167 edible, 132 pasturing, 118 medicinal, 98 stainable, 52 ornamental, 15 timber, 6 fiber, 2 industrial taxa and 101 unknown resource plants, respectively. Also, there were remarkable plants such as 16 taxa of Korean endemic plants and 36 taxa of specific plants which were designated by the Ministry of Environment. Furthermore, 22 taxa of naturalized plants were observed in this investigated area where Urban Indexn UI) was 8.9%. Although the ecological status of investigated area was comparatively well conserved, the degree of (UI) was relatively high. Based on the results of this investigation, UI has been rapidly increased due to urbanization and construction of recreation objects in this area.

• Korean Journal of Plant Resources
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• v.23 no.4
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• pp.327-349
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• 2010

This study was carried out to investigate the distribution of vascular plants and their use from 2007 to 2009 in Mt. Unmum(Cheongdo-gun, Gyeongsangbuk-Do). The vascular plants were summarized as 605 taxa including 98 families, 304 genus, 514 species, 3 subspecies, 68 varieties, and 20 forma. Among the investigated 605 taxa, 21 rare and endangered plants, 29 Korean endemic plants were included. Based on the list of specially designated plants by Ministry of Environment, 70 taxa included Iris odaesanensis and Gastrodia elata were recorded in the investigated area. The naturalized plants were identified as 23 taxa and the percent of naturalized index(NI) was 3.8% of total 605 taxa vascular plants. Usage of 605 taxa were consists of 225 taxa(37.2%) of edible plants, 191 taxa(31.6%) of medicinal plants, 64 taxa(10.6%) of ornamental plants, 46 taxa(7.6%) of pasture plants, 18 taxa(3.0%) of timber plants, 14 taxa(2.3%) of fiber plants, and 3 taxa(0.5%) of industrial plants. To management of natural resource, we suppose that it is required to establish an ecological learning area to minimize human disturbance and an effective managemet strategy by continuous monitoring for ecosystem change.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2498-2508
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• 1993

$Al/SiC/Al_{2}O_{3}$ hybrid composites are fabricated by squeeze infiltration method. From the misconstructive of $Al/SiC/Al_{2}O_{3}$ hybrid composites fabricated by squeeze infiltration method, uniform distribution of reinforcements and good bondings are found. Hardness value of $Al/SiC/Al_{2}O_{3}$ hybrid composites increases linearly with the volume fraction of reinforcement because SiC whisker and $Al_{2}$O$_{3}$ fiber have an outstanding hardness. Optimal aging conditions are obtained by examining the hardness of $Al/SiC/Al_{2}O_{3}$ hybrid composites with different aging time. Tensile properties such as Young's modulus and ultimate tensile strength are improved up to 30% and 40% by the addition of reinforcements, respectively. Failure mode of $Al/SiC/Al_{2}O_{3}$ hybrid composites is ductile on microstructural level. Through the abrasive wear test and wear surface analysis, wear behaviour and mechanism of 6061 aluminum and $Al/SiC/Al_{2}O_{3}$ hybrid composites are characterized under various testing conditions. The addition of SiC whisker to $Al/SiC/Al_{2}O_{3}$ composites gives rise to improvement of the wear resistance. The wear resistance of $Al/SiC/Al_{2}O_{3}$ hybrid composites is superior to that of Al/SiC composites. The wear mechanism of aluminum alloy is mainly abrasive wear at low speed range and adhesive and melt wear at high speed range. In contrast, that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is abrasive wear at all speed range, but severe wear when counter material is stainless steel. As the testing temperature increases, wear loss of aluminum alloy decreases because the matrix is getting more ductile, but that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is hardly varied. Oil lubricant is more effective to reduce the wear loss of aluminum alloy and $Al/SiC/Al_{2}O_{3}$ hybrid composites at high speed range.

• Korean Journal of Plant Resources
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• v.28 no.5
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• pp.616-634
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• 2015

This study was carried out to elucidate the distribution of vascular plants and their usefulness of Mt. Cheongnyangsan (870 m) in Gyeongsangbuk-do. The vascular plants that were collected 16 times 2006 and 2014 consisted a total of 614 taxa; 97 families, 330 genera, 541 species, 3 subspecies, 61 varieties and 9 forms. For the Korean endemic plants, 21 taxa were recorded and 8 taxa of Vulnerable Species (VU) and 5 taxa of Least Concerned species (LC) categorized by the Korean Forest Service as rare plants were investigated in this region. Furthermore, Ⅴ, Ⅳ, Ⅲ degrees of floristic regional indicator plants designated by the Korean Ministry of Environment included 2 taxa, 10 taxa and 18 taxa, respectively. Moreover, four species of distributional interesting plants, Aconitum austro-koreense Koidz., Allium spirale Willd., Dipsacus japonicus Miq. and Pinellia tripartita (Blume) Schott, in Mt. Cheongnyangsan were discovered by this study. Among them, edible, pasturing, medicinal, ornamental, timber, dye, fiber and unknown usefulness plants included 234 taxa, 213 taxa, 174 taxa, 62 taxa, 16 taxa, 12 taxa, 11 taxa and 167 taxa, respectively. In addition, 32 taxa of naturalized plants were observed.

• Environmental Analysis Health and Toxicology
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• v.21 no.1 s.52
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• pp.45-56
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• 2006

This study was conducted to investigate seasonal distributions of fine particles ($PM_{2.5}$) and associated polycyclic aromatic hydrocarbons (PAHs) at three cities. $PM_{2.5}$ samples were collected on glass fiber filters at urban (Chuncheon), metropolitan (Seoul), and industrial complex sites (Ulsan) from September, 2002 to February, 2004 using the Andersen FH 95 Particulate Sampler. About five 24-hour samples were collected from each site per season. The filters were analyzed for mass and six selected PAHs concentrations. $PM_{2.5}$ concentrations were the highest either in winter or spring, which could be attributed to the increase of fossil fuel combustion in winter or the transport of yellow sand to the Korean peninsula from China in spring, respectively. Regional $PM_{2.5}$ concentrations were higher in the order of Seoul>Chuncheon>Ulsan without statistical difference among cities. The filters were extracted using dichloromethane in an ultrasonicator and analyzed for six PAHs (anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, and benzo[a]pyrene) with HPLC. Total PAHs concentrations were statistically different among seasons in each site, and the highest concentrations were observed in winter at each sampling site. For total samples collected, the median total PAHs concentrations in Chuncheon ($4.6ng/m^3$) and Seoul ($4.4ng/m^3$) were approximately two times higher than that in Ulsan ($2.1ng/m^3$). Chrysene was a component found in the highest proportion among total PAHs at each site. Carcinogenic risks calculated based on the BaP toxic equivalency factors (TEFs) over the whole sampling period were higher in the order of Chuncheon>Seoul>Ulsan. This study suggests that the atmosphere of Chuncheon is contaminated with particulate matter and PAHs at the levels equivalent to those of Seoul and that an appropriate measure needs to be taken to mitigate human health risks from inhalation exposure to airborne fine particles.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.317-327
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• 2012

The average specific cake resistance, the most important indicator for cake filtration and solid-liquid separation, is measured by filtration experiment. But the exact value is difficult to measure because of the other influences such as sedimentation during filtration. This study, a little more stable method named filtration-permeation is proposed for measuring average specific cake resistance. The filtration-permeation is composed of permeation of particle eliminated water through pre-formed cake by filtration. Using 1 wt% calcium carbonate suspension, the filtration-permeation experiments were performed for 8 kinds of filter media at the conditions of 0.5 atm and 0.2 atm, 1 and 3 sheets of filter media. At each specific condition, three to five times filtration-permeation were accomplished. As a result, stable permeation speed is measured. According to this experimental result, the characteristics of permeation and the effect of sedimentation are analyzed with Ruth's equation. The one way analysis of variance (one way ANOVA) is applied to the average specific cake resistances of filtration and permeation obtained with the selected three kinds of filter media. The average specific cake resistances between 0.5 atm and 0.2 atm by filtration do not distinguished, but those by permeation is perfectly distinguished. The experimental results during permeation have a very narrow distribution than that measured during filtration. The analysis of filtration experiments, it was verified that the resistance of filter medium by traditional method is of no significance. Finally, the migration of small particles through the medium composed of fiber glass at low pressure was studied.

• Korean Journal of Environment and Ecology
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• v.31 no.1
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• pp.1-23
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• 2017

Gwangchiryeong, located adjacent to the Korean DMZ, is a mountain pass connecting Yang-Gu, Gangwon-do with In-je. It reaches a height of 800m (2,624ft) and stands on the flank of Mt. Daeam-san, which has an elevation of 1,304m (4,278ft). It is important to survey the flora of Gwangchiryeong in that not only the area encompassing the waterfall and the valley along with dense old-growth forest has various plant species but also it is a way to make out what kind of plant species exist in the DMZ due to the geographical characteristics of Gwangchiryeong adjacent to the Korean DMZ. Therefore, this study was conducted to elucidate the distribution of vascular plants and their value in Gwangchiryeong. The vascular plants that were collected 9 times from April 2014 to September 2015, and consisted of a total of 513 taxa: 88 families, 297 genera, 441 species, 4 subspecies, 62 varieties and 6 forms. Among those observed species, the rare plant species designated by Korea Forest Service were 22 taxa including Hanabusaya asiatica, Paeonia japonica, Saxifraga octopetala, etc. Endemic species were 22 taxa containing Cirsium setidens, Heloniopsis koreana, Salvia chanryoenica, etc. 18 taxa were recorded as naturalized plants and their naturalized rate and urban index were noted as 3.5% and 5.6%. Among the surveyed 513 taxa, edible, medicinal, pasturing, ornamental, timber, dye, fiber and industrial plants were 197 taxa, 154 taxa, 180 taxa, 49 taxa, 24 taxa, 8 taxa, 4 taxa and 3 taxa, respectively.

• Elastomers and Composites
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• v.47 no.4
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• pp.297-309
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• 2012

Different amounts of foaming agents were employed in natural rubber(NR)/butadiene rubber(BR) blends to understand the foaming behavior in presence of nano-reinforcing agent, zinc methacrylate (ZMA). The ZMA greatly improved most of the mechanical properties of the rubber foams, however it did not show considerable effect on the cell morphology, such as cell size, density and porosity. It was also observed that the foaming agent concentration affected all the mechanical parameters. When the content of foaming agent was increased, the number of foams was increased leading to a decrease in density of the compounds. But the size and distribution of foams remained unchanged with increased foaming agent. The effect of high styrene-butadiene rubber (HSBR) was also studied. The size of cells became smaller and the cell uniformity was improved with increasing HSBR. The foam rubber compounds showed much efficient energy absorbing capability at higher strains.

• Journal of Navigation and Port Research
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• v.40 no.3
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• pp.159-164
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• 2016

The goal of this study is to implement a communication system that can monitor the status of the nacelle using the power cable itself, without the dedicated communication lines such as an UTP cable and optical fiber for the offshore wind turbine. An inductive coupling powerline communication system for a MW class offshore wind turbine was proposed and its communication performance was demonstrated. The inductive couplers was designed for operation at up to 500 A using a ferrite composite materials. Field test was carried out on the wind farms of Jeju island. Using the iperf communication test program, we have obtained more than 15 Mbps data transmission rate through the 100 m power cable that was installed between the nacelle and the bottom of the power converter. In the data transmission stability test for a week, there was no failure ever. The minimum transmission rate was 15 Mbps and the average data rate was about 20 Mbps. Next, we have installed an infrared camera inside the nacelle in order to measure the temperature distribution and variation of the nacelle. The real-time thermal image taken by the camera was successfully sent to the monitoring system without error.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.79-86
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• 2009

With the substantial increase of the size of structure, the management of excavation becomes more difficult. Therefore, massive collapses which are related to retaining wall recently increase. However, since the study on measuring and monitoring the pre-stressing force of anchor is insufficient, behavior of anchor may not be predicted and monitored appropriately by the existing strain gauge and load cell type monitoring system. FBG Sensor, which is smaller than strain gauge and has better durability and does not have a noise from electromagnetic waves, is adapted to measure the strain and pre-stressing force of 7-wire strand, so called smart tendon. A series of pullout tests were performed to verify the feasibility of smart tendon and find out the load transfer mechanism around the steel wire tendon fixed to rock with grout. Distribution of measured strains and estimated shear stresses are compared with those predicted by theoretical solutions. It was found that developed smart tendon can be used effectively for measuring strain of 7-wire strand anchor and theoretical solutions underestimate the magnitude of shear stress and load transfer depth.