• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.206-209
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• 2010

The visualization device for hybrid rocket is fabricated to investigate the combustion phenomena. Visualization device were composed with ignition system, oxidizer supply system, control system and data acquisition system, combustion visualization system. GOX as oxidizer and HDPE, Paraffin-LDPE Blending, Paraffin sd were used. As results, combustion phenomena and fuel droplet entrainment were observed.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1199-1202
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• 2002

본 논문은 모바일 환경의 특성을 고려한 사용자 맞춤형 원스탑 정보 서비스 시스템에 대하여 기술한다. 모바일 환경은 그 이름대로 휴대성을 가장 큰 장점으로 한다. 그러나 아직까지 정보 입력 및 표현의 한계성은 극복되지 못하고 있다. 따라서 복잡하고 방대한 인터넷 서비스를 모바일 환경상에 구현하기 위하여는 사용자에 최적화된 서비스만이 구성되어 제공되어야 한다. 본 논문은 이러한 문제점들을 극복하기 위해 "사용자 맞춤형 원스탑 정보 서비스(One-Stop Service: OSS) 시스템" 을 제시한다. OSS 시스템은 사용자 맞춤형 정보 제공을 위해 개인화 기술을 이용한다. 여기서 OSS 란 다양한 서비스들의 집합으로 사용자 취향에 적합하게 동적으로 생성된 서비스의 묶음을 말하는 것이다. 본 논문에서 제안하는 시스템은 향후 모바일 환경 어플리케이션이 나아가야 할 방향을 제시하고 있다는데 그 의미가 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.251-254
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• 2008

Ground firing test facility and test field for firing test of hybrid rocket engine were constructed. Ground firing test facility were composed of hybrid rocket engine, thrust stand, oxidizer storage/supply system, control system and data acquisition system. Firing tests of thrust 50 kgf class were conducted. Stable performance data was obtained and operational reliability of ground firing test facility were found.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.180-182
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• 2021

This paper proposes a method for estimating the location of a user using a beacon to provide a service in an indoor environment. To estimate the location using the beacon, a Gaussian filter was applied to the RSSI value of the beacon, and the distance conversion function was obtained through the filtered RSSI value to estimate the tag location by trilateration. Then, in the indoor space where the beacons are installed, the location estimation accuracy of 8 places where 3 beacons are at a certain distance was confirmed. As a result, it was possible to confirm the position estimation accuracy of ±0.097 standard deviation and 0.242 distance error.

• Korean Journal of Optics and Photonics
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• v.33 no.6
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• pp.260-266
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• 2022

A diffraction grating structure composed of two matching layers and two grating layers was formed, and a diffraction grating with high transmission diffraction efficiency in the -1st order was designed through an optimization technique. The designed diffraction grating had a transverse electric wave diffraction efficiency of 99.997% at the design center wavelength, and had a wavelength width of 80 nm and an incident angle width of 20.0° that maintained a diffraction efficiency of 95% or more. By performing the grating tolerance analysis, it was confirmed that the thickness tolerance for a diffraction efficiency of 95% or more was secured to at least 60 nm, and the diffraction efficiency could be maintained even in a trapezoidal shape with an internal angle of less than 10°.

• Korean Journal of Ecology and Environment
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• v.35 no.4 s.100
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• pp.295-305
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• 2002

Benthic macro- invertebrates were collected in a 200 m reach located in the $3^{rd}$ order Yangjae Stream, a tributary of the Han River, Seoul, from April 1996 to March 1998. Although species richness was relatively low due to organic pollution, community abundance patterns appeared to be different depending upon location of the sampling sites. At the sample sites in the straight zone with high water velocity and large substrates, species richness was high and species relatively less-tolerant to organic pollution was additionally present. At the sample sites in the pool zone with lower velocity and high sedimentation, species richness was low and a few tolerant species to organic pollution were abundantly collected. The principle component analysis indicated that some sample sites in the straight zone appeared to be related to water velocity and shear velocity, and associated with diverse taxa less tolerant to organic pollution. Additionally the sample site transplanted with large substrates was associated wit]h hydraulic characters such as substrate diversity and roughness, and was related to species indicating partial recovery of water. The sample sites located at the pool zone tended to be associated with organic matter that had sedimented on to the substrates and the taxa tolerant to organic pollution, including Oligochaeta and Chironomus.

• Journal of Korean Society of Forest Science
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• v.74 no.1
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• pp.37-46
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• 1986

To study the changes of soil and vegetational composition of Pinus densiflora community by campsite impact of its users, located in Kumo Mountain Provincial Park, the South part of Korea, three sites were selected according to the density of users. The heavy-use sites in this study has changed in the following ways. (1) The concentration of total nitrogen, available phosphate and Ca ion have decreased greatly. (2) From 68 to 73 percent of the undergrowth vegetation has been removed from the $2.000m^2$ camp area, leaving a sparse vegetation cover quite dissimilar in composition to nonuse campsite. (3) The soil hardness was $38.9kg/cm^2$ in heavyuse site and $1.76kg/cm^2$ in nonuse site. (4) The tolerant trees to campsite impact is Acer palmatum, Stephanandra incisa, Rhus trichocarpa, Rubus crataegifolitus and Parthenocissus tricuspidata. (5) Species diversity decreased to a degree at the heavy-use site. Similarity index was 25.38% between the heavy-use and nonuse site.

• Korean Journal of Environment and Ecology
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• v.16 no.1
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• pp.22-33
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• 2002

This study was conducted to investigate the effects of fragmentation on the bird community in Seongduck-ri and Hanggum-ri agricultural landscapes of Kangha-myon, Yangpyong-gun, Kyonggido. We analyzed the composition of tree species, forest environmental structures, structures of agricultural landscapes, avifaunas and guild structures. Number and density of tree species ranging from 6 to 10cm in D.B.H. were high in Seongduck-ri, but basal area was high in Hanggum-ri. Coverages of foliage layers under two meters and over 12 meters were high in Hanggum-ri. Meanwhile, Seongduck-ri agricultural landscapes consisted of twelve patches, dominated by Larix leptolepsis and Robinia pseudoacacia Hanggum-ri landscapes was composed of eleven patches, and dominated by Pinus rigida, Castanea crenate, Larix leptolepsis and paddy field. Dominant bird species showed the same order in two study areas, thirty-six species of birds were observed in Hanggum-ri landscapes, but twenty species were in Seongduck-ri landscapes. Number of species and density belonging to hole-, bush-, ground-nesting and water-, bush-, ground-foraging guild were high in Hanggum-ri landscapes. Number of species and density belonging to hole-nesting guild showed the high value in Hanggum-ri landscapes that was not fragmented. It could be attributed to the low human disturbance and relative high density of medium and large trees in D.B.H. Also, number of species and density belonging to bush-, ground- and water- foraging guild showed the high value in Hanggum-ri landscapes that had the high foliage amounts in the foliage layer under two meters. It will be related with the paddy field, dry field and brook, which patches covered the 28.4% of Hanggum-ri landscapes. Therefore, road not only dominate the heterogeneous patch in agricultural landscapes, but also easily cause the human disturbance. Thus, road construction would decrease the natural patch diversity and edge effects that are important for sustaining the diverse avifauna in agricultural landscapes.

• Journal of Korean Society of Forest Science
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• v.79 no.1
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• pp.21-25
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• 1990

To investigate and analyze the change of the vegetation community structure between the severely damaged time (in 1980) and the restored time (in 1987) by the pine gall midge. Thecodoplosis japonensis, four plots with five subplots were sampled at Gwangju-gun of Kyongki-do. The total number of woody species per $500m^2$ changed 39 in 1980 to 41 in 1987. According to the damage restoring, the importance value of the genus Quercus as substituting in the severely damaged forest showed a slight decrease but the importance value of Carpinus laxiflora, Sorbus alnifolia and Styrax obassia increased. As to changes of the vegetation community structure for seven years, the diversity of vegetation structure has increased. The similarity indices between 1980 and 1987 were 52.9% and 51.9% in the understory and shrub stratum, respectively.

• Journal of the Korean Institute of Landscape Architecture
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• v.36 no.2
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• pp.42-52
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• 2008

This paper categorized the functions of and investigated the characteristics of planting in Pyeonghwa Park near the Seoul World Cup Stadium as a preliminary study for improving tree planting in the park. The functions of planting were deduced based on related theoretical studies and an analysis of the intention of design and environmental factors. The characteristics of planting were analyzed after drawing the distribution and stratification of dominant planting species and setting samples by function. The functions of planting were classified into natural landscape planting, buffer planting, and shade planting. For dominant planting species, pine trees and elm-like trees have been widely observed while various species in addition to pine trees in natural landscape planting areas have been introduced in terms of the function of planting. These trees that were randomly planted before the park was developed have been obstacles in the formation of natural landscapes. For buffer planting and topographical correction, tall trees were planted. However, it seems that comprehensive complementary measures should be taken on the under-story planting.