• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.555-559
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• 2008

Junction temperature of quantum dot laser diodes is investigated by utilizing forward voltage-temperature method. In the case of ridge type laser diodes with deep mesa the increasing rate of junction temperature to current is about 0.05 K/mA, while in the case of shallow mesa the increasing rate is about 0.07 K/mA. It is explained that the relatively low increasing rate in the deep mesa results from the heat expansion to the lateral direction of mesa.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.51.1-51.1
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• 2020

The Rosette Nebula is the most actively star-forming region in the Monoceros OB2 association. This region hosts more than three stellar groups, including the most populous group NGC 2244 at the center of the region and the smaller stellar groups around the border of the H II bubble. To trace their formation process, we investigate the kinematic properties of these groups using the Gaia astrometric data and high-resolution spectra taken from observation with Hectochelle on MMT. The proper motions of stars in NGC 2244 show a pattern of radial expansion. The signature of cluster rotation is also detected from their radial velocities. On the other hand, the small groups appear to be physically associated with some clouds at the ridge of the H II region. Among them, the group near the eastern pillar-like gas structure shows the signature of feedback-driven star formation. In this presentation, we will further discuss the formation process and dynamical evolution of the stellar groups in the Rosette Nebula, based on the observation and results of N-body simulations.

• Korean Journal of Organic Agriculture
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• v.20 no.4
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• pp.503-518
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• 2012

Korean type of no-tillage cultivation method which was applied on this study used the ridge and the furrow and constantly recycling them as it was suitable for Korea's weather and farming conditions. This no-tillage cultivation was reported to have little negative impact such as reduction of production (Kwon et al., 1997). In addition, it was found to have a lot of benefits as it requires less agro-materials and energy costs as well as shortened working hours because tillage operation is not needed. (Yang et al., 2012). According to an analysis, no-tillage cultivation can reduce greenhouse gas emissions by $344.7kgCO^2$ (58%) in every 10a ($1,000m^2$) compared to ordinary pepper farming technique (Korea averages). Direct-indirect reduction effects from using fertilizer and using less amount of energy were 92% and 44% respectively both of which can be considered very high. Besides the direct effects of no-tillage cultivation, soil management using no-tillage technique raises carbon sequestration effect on soil as time goes on (West & Marland, 2002), that is why the technique is expected to have constant carbon emission reduction effect. For theses reasons, distribution and expansion of Korean type no-tillage cultivation are expected to play a role as major agro-green technologies for achieving our goal of reducing greenhouse gas emissions in agricultural sector.

• Journal of Periodontal and Implant Science
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• v.31 no.4
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• pp.669-687
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• 2001

On the basis of the evidence that electrical stimulation could promote healing and regeneration of bone, this study was performed to investigate the effects of electrical stimulation on rat extraction socket, and to evaluate the potential of clinical application of electrical stimulation. Forty rats were used and divided into control groups(l0)and the experimental groups(30) in this study. The maxillary 1st molar were extracted in both groups. In experimental group, electrical stimulation was given at the current intensity of lmA(Test-1), l0mA(Test-2), 25mA(Test-3) each day. At 1,3,5,7 days after the tooth extraction, rats in both groups were serially sacrificed. And the specimens were prepared with Hematoxylin-Eosin stain for the light microscopic evaluation. The results of this study were as follows; 1. At 1 day after the extraction, the periodontal ligament was found in the extraction socket wall. The formation of blood clot with dense infiltration of inflammatory cells in control group and there were less inflammatory cells in test group. 2. At 3 day after the extraction, the cells and collagen of the periodontal ligament were so actively proliferated and synthesized that invaded into the connective tissue of the extraction sockets in the control group. There were the formation of new bone in the basal & lateral portion of socket wall in test -2 and -3. 3. At 5 days after the extraction, there were no formation of new bone in control group. But the more electrical stimulation was applied, the more formation of new bone in test group. 4. At 7 days after the extraction, the extraction sockets were almost filled with trabecular bone in each group. Bone maturarity was remarkable in test-3. 5. The electrical stimulation at l0mA and 25mA was more effective in the bone formation at 5 and 7 days after the extraction. From the above results, electrical stimulation could promote the extraction socket wound healing, and be utilized in the clinical application of the residual ridge expansion.

• Korean Journal of Environment and Ecology
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• v.35 no.4
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• pp.347-376
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• 2021

Investigating and evaluating regionally distributed plant resources provide fundamental information (inventory) to conserve plant diversity in target areas. Nevertheless, the examination of inventory to collect information in areas with little interest has been insufficient. In this study, the vicinity of Mt. Baegamsan(1,004m) was investigated for plant resources in the central and southern part of the Korean peninsula, which has received low interest. Nine surveys identified a total of 638 taxa consisting of 108 families, 339 genera, 572 species, 12 subspecies, 49 varieties, and 5 forms. One taxon was designated to be the endangered wild plant by the Ministry of Environment, and a total of 29 taxa were designated to be endemic species in Korea. Floristic target species identified by the surveys included 1 taxon for grade V, 13 taxa for grade IV, 36 taxa for grade III, 29s taxa for grade II, and 34 taxa for grade I. A total of 38 taxa were identified to be naturalized plants, and 3 of them were designated as invasive alien plants by the Ministry of Environment. There was a difference in plant distribution between western and eastern areas of Mt. Baegamsan. The endangered and valuable plants for conservation were mainly identified from Mt. Baegamsan peak area, the ridge, and the western area. Considering the plant distribution, the Mt. Baegamsan region, located on Nakdong-jungmaek, was estimated to be dispersal routes for plant expansion and retreat.

• Korean Journal of Heritage: History & Science
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• v.42 no.3
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• pp.26-47
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• 2009

This study examined dwelling site from among the sites of the Neolithic age found in the Asan Bay(牙山灣) area, and the temporal-spatial location and meaning of the dwelling site (settlement). The majority of the settlements in the area are of a square style but some coexist with rectangular-style settlements, which is noteworthy. The dwelling sites of the Neolithic age found in Asan Bay area are mostly located in a ridge of hilly areas, divided into gentle, low areas (20~50 meters above sea level) and relatively high areas (50~80 meters above the sea level). Although location strongly corresponded to the residents' subsistence and the technical levels within the culture, it likely was greatly affected by natural environment where they lived, as well. In examining radiocarbon dating results and the excavated artifacts, the settlements found in Asan Bay were determined to belong to the period II(3,500~3,000 B.C.) stated in the Relative Chronological table of Dwelling sites in the Neolithic age, written by the author. Said Dwelling sites are proven to have a close relationship with those found on the coast of Gyeonggi Province(京畿道) and in the Geum River(錦江) valley. This is deemed to be the result of expansion and interchange between Gyeonggi Province(京畿道) group and Geum River(錦江) valley group, who constituted the large settlements. Additionally, the Daecheon-ri type dwelling sites in the Geum River valley were verified to be the result of exchange, and spread to the Asan Bay area in the same era. Two forms of Dwelling sites coexisted dynamically in the Asan Bay area around 3,500 B.C. Such a phenomenon resulted primarily from the expansion of the dwelling site due to the introduction of primitive agriculture, as well as environmental (temperature), biological and social changes at those times.

• Korean Journal of Environment and Ecology
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• v.30 no.6
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• pp.939-961
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• 2016

For effective conservation of endangered wild plants, it is necessary to understand their interactions with environmental factors in each habitat together with life traits of target species. First, the characteristics of their distribution were investigated followed by their monitoring for 4 years focusing on the habitats in the lagoon. Also, their life traits were compared including production of hibernacles, fruits, and seeds by the soil fertilization and light intensities. Next, the information on the species was secured by germination experiment using the generated seeds from the cultivation experiment. The habitat of Glaux maritima var. obtusifolia Fernald in Korea was located in the rear edge of the worldwide distribution and its four habitats were isolated and distributed far away each other. Two of them were located in small salt-marsh and fine sand estuaries formed in the rocky area of the seashore, and the other two were inhabited with the sandy soil in the lagoon which was connected by river-mouth to the sea. Glaux maritima var. obtusifolia Fernald tends to be distributed in the sites where the establishment and growth of the competitor were inhibited by salinity, periodic flooding, and lower layer of the soil to extend a roots. It maintained its population by recruitments of hibernacles and seedling. The production of hibernacle was assumed to be affected by the particle consist of the sand together with organic matters in the soil. Seedling recruitment was observed only in the salt-marsh area located in the rear sites of sand ridge where was the shore of the lagoon. Glaux maritima var. obtusifolia Fernald was observed to have different threatening factors by each population. Its population in Pohang seemed the sedimentation of fine sand which affected the recruitment of hibernacles had been eroded due to the construction of the coastal road. The population in Ulsan appeared rapid expansion of competitor and reduction of its distribution area due to the interruption of eluted water supplied to the habitat. On the other hand, the habitat in the lagoon maintained the population relatively stable. Especially, the population in Songji-ho was determined to be the most stable one. To sustain the population of Glaux maritima var. obtusifolia Fernald distributed in the lagoon, it is suggested that the wide ranged scale of conservational activities is necessary to maintain the mechanisms including the entrance of seawater which belongs to the lagoon, and periodic flooding.

• Korean Journal of Environment and Ecology
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• v.27 no.1
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• pp.99-112
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• 2013

This study aims to show the changes of characteristics of vegetation structure for 20 years(1991~2010) in Naejangsan National Park. As a result of analysis of actual vegetation, the mixed community of Quercus variabilis and Quercus serrata was distributed with 56.1%, and Q. variabilis community showed in southern steep slope with 17.6%. Pinus densiflora community(5.8%) was observed on the ridge and Carpinu tschonoskii community distributed in the slope of the valley with 6.6%. Zelkova serrata and Prunus sargentii community were distributed in valley. The classification by TWINSPAN, ordination by DCA considering importance percentage and property of vegetation class were divided into 4 communities, which are community I(P. densiflora-Q. variabilis community), community II(Q. variabilis community), community III(C. tschonoskii community) and community IV(Mixed deciduous broad-leaved trees community). The age of Pinus densiflora was 32years old and Q. serrata was 36 years old in the community I, that of Q. variabilis was 64 years old in the community II, Q. serrata was 46 years old and C. tschonoskii was 45 years old in the community III, and Acer palmatum was 54 years old and Cornus controversa was 47 years old in the community IV. As the result of Shannon's index of species diversity, the community Iwas ranged from 0.9751 to 1.4199, community II was ranged from 1.0765 to 1.3278, community III was ranged from 1.0353 to 1.2881, and community IV was ranged from 1.1412 to 1.3807. The change of vegetation structure analyzed through the comparison with results of studies carried out 20 years ago were natural selection of P. densiflora, expansion of Quercus spp. and increase of C. tschonoskii. Especially, A. palmatum is dominated by Q. variabilis in canopy layer like the result of study 20 years ago. A. palmatum was analysed by 14.6% in the canopy layer of only mixed deciduous broad-leaved trees community. As a result of analysis of habitat property of Q. variabilis and A. palmatum, Q. variabilis was distributed in dry area with the low value of pH, O.M., exchangeable cations and Avail. P, and A. palmatum was located in the wet valley with huge value of nourishment. The tendency of reduction of bio-diversity by Sasa borealis is same as previous study but, the distributed areas were reduced in Naejangsan area.