• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.7
• /
• pp.1539-1545
• /
• 2015

GPS (global positioning system) is a popular system that provides location information by measuring arrival time difference at the receiver between several GPS satellite signals. GPS is widely used in commercial area as well as military systems. Reliable GPS signal reception is more important in the military systems. However, since the carrier frequencies of the GPS signals are well known, the GPS receivers are vulnerable to intentional jamming attacks. To remove jammers but maintain GPS signals at the received signals, a popular technique is an adaptive beam steering method based on array antenna. Among adaptive beam steering techniques, this paper considers MVDR (minimum variance distortionless response) algorithm, and proposes a new adaptive technique that preserves the received signals at desired direction, but removes the jamming signals adaptively. The performance of the proposed method is verified through computer simulation.

• Journal of The Geomorphological Association of Korea
• /
• v.20 no.1
• /
• pp.75-83
• /
• 2013

Human-induced modifications in coastal area may cause strong geomorphic responses by disturbing sediment supply, transport and deposition regimes. Morever, engineering structure have been built to stabilize coastal change, these effort impact on other morphologic change. In case of coastal area, there are lack of sediment yield data. This study focus on the tendency of long-term shoreline change, estimate method od sediment discharge which is a major factor of coastal change and adduced to way for considering design load influenced to coastal road.

• The Korean Journal of Ecology
• /
• v.4 no.3_4
• /
• pp.80-92
• /
• 1981

The vegetation of Saeng-il Island was surveyed over four times from July, 1979 to May, 1981. The results obtained are summarized as follows: Plants of this island consisted of 3 foma, 28 varieties, 211 species, 203 genera, and 89 families. Evergreen broad-leaved trees consisted of 24 species, including Camellia japonica and Castanopsis cuspidata var. sieboldii. The vegetatiion of the southwest slope was more favorable than that of the northeast slope and the vegetation of other areas were negligible. Pueraria thunbergiana and Clerodendron trichotomum were predominant in the area between Yucheon-ri and Geummo-ri. Evergreen broad-leaved trees, such as Camellia Japonica, Neolitsea sencea, Castanopsis cuspidata var. sieboldii, etc. were predominated in the areas of Gulzeon-ri, Yongchul-ri and Geummo-ri. However, artificial succession to pinus thunbergii presently dominating the areas has taken place due to human interferences (for charcaol, building materials, grazing etc.). It seems to be worthy of conserving the community of Camellia japonica on the back slope of Geummo-ri and that of Castanopsis cuspidata var. sieboldii between Gulzeon-ri and Hangdo-dong. It is notceable, in particular, that Damnacanthus indicus distributed in Jeju and Dolsan islands was also discovered in this island.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.396-396
• /
• 2019

습지는 가장 생산적인 생태계 중 하나이며, 인류에게 수문학적, 경제적, 문화적 가치로도 매우 귀중한 역할을 하고 있다. 하지만 기후변화와 인간의 영향으로 수위저하와 건조, 수문체계에 변화를 주어 습지의 건조화 현상이 나타나고 이로 인해 생태계에도 영향을 미치고 있다. 특히 산지습지는 인위적 간섭에 매우 취약하고 환경변화에 민감하여 불규칙한 강수패턴 및 무분별한 개발은 습지수문환경에 영향을 미쳐 습지의 건조화를 심화시키는 원인이 되고 있다. 그 결과 자연적으로 습지의 면적이 감소하고 식생의 패턴 변화로 다양한 생물들과 보호가 필요한 종들이 사라질 것이므로 변화에 대응하기 위해서 건조화를 방지할 필요가 있다. 따라서 본 연구에서는 습지 내 지하수위 저하 또는 유입 유출량의 변화로 습지 토양의 수분이 감소하여 말라가는 현상을 습지 가뭄이라 정의하고 가뭄지수를 활용하여 이를 지수화 하였다. 현재 산지습지를 대상으로 가뭄을 지수화 시킨 선행연구가 거의 없기 때문에 향후 산지 습지의 가치를 보존하고 생태계 관리의 목적으로 후속 연구의 방향을 제시하는데 도움을 줄 것으로 예상된다.

• Weed & Turfgrass Science
• /
• v.3 no.1
• /
• pp.50-55
• /
• 2014

This study is aimed at classifying the syntaxa of Ceratopteris thalictroides dominant community on the Nakdong River, and to collect basic data for research of habitat. The communities were carried out by using the Z.-M. School's method and numerical classification technique. The result of syntaxa was classified three communities such as Persicaria japonica-Ceratopteris thalictroides community, Lindernia procumbens-Ceratropteris thalictroides community, and Limnophila indica-Ceratopteris thalictroides community. The ordination analysis displayed the vegetation types with respect to complex environmental gradients. After ordination and clustering analysis, the effective humidity, soil stability, trampling effects, anthropogenic effects and flooding frequency were identified as the important factors deciding the vegetation pattern. It was pointed out to establish a long-term ecological site for protecting such vulnerable vegetation against overexploitation and global climate change.

• Journal of Biomedical Engineering Research
• /
• v.16 no.2
• /
• pp.231-238
• /
• 1995

Tc-99m-MIBI (Sestamibi) myocardial SPECT along with TI-201 tomographic Imaging has demonstrated wide application and high image quality sufficient for the diagnosis of myocardial perfusion defect, which consequently reflects regional myocardial blood flow. The qualitative values of myocardial SPECT with Tc-99m-MIBI as well ds the quantitative cases depend in some degree on the reconstruction techniques of multiple projections. Filtered backprojection (FBP) Is the common standard method for reconstruction rather than the complicated and time-consuming arithmetic methods. In FBP it is known that the distribution of radioactivity in reconstructed transverse slices varies with the selected litter parameters such as cutoff frequencies and order (Butterworth case) The cutoff frequencies used in clinicAl practice partially remove and decrease the true radioactive distribution and alter the pixel counts, which lead to underestimation of true counts in specific myocardial regions. In this study, we have investigated the effect of cutoff frequencies of reconstruction filter on the artifactually induced perfusion defects, which are often demonstrated near inferior and/or inferoseptal cardiac walls due to the intense hepatic uptake of Tc-99m-MIBI. A computerized method for Identifying the relative degree of artifactual perfusion defect and for comparing those degrees along with the relative amount of hepatic uptake to myocardium was developed and patient images were studied to observe the quantitative degree of underestimation of myocardial perfusion, and to propose some reasonable threshold of cutoff frequency in the diagnosis of perfusion defect quantitatively. We concluded that from the quantitative viewpoint cutoff frequencies may be used as high as possible with the sacrifice of homogeneity of image quality, and those frequencies lower than the common 0.3 Wyquist frequency would reveal severe degradation of radioactive distribution near inferior and/or inferoseptal myocardium when applying Butterworth or low pass filter.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.41 no.4
• /
• pp.40-48
• /
• 2023

This study is part of a foundational research effort aimed at developing a suitability index for breeding grounds related to avian activities along the domestic South and West coasts, including islands. Focus Group Interviews (FGI) and Analytic Hierarchy Process (AHP) analyses were conducted. The results are as follows. First, as a result of determining the value of the suitability of coastal bird breeding sites, the 'Natural Value(0.763)' was higher than the 'Artificial Value(0.237)'. Other artificial values were identified as sub-ranked except for 'Protected Areas' to ensure continuous integrity of breeding spaces. Second, as a result of re-establishing the 25 evaluation items classified in the two-time FGI as higher concepts, nine natural values and five artificial values were finally selected as a total of 14. Third, the results of the mid-classification evaluation of the importance of the suitability of coastal bird breeding sites were identified in the order of 'Ecological Value(0.392)', 'Topographic Value(0.251)', 'Passive Interference(0.124)', 'Geological Value(0.120)', and 'Active Interference(0.113)'. Fourth, the results of the priority of evaluation items of coastal bird breeding sites were in the order of 'Vegetation Distribution (0.187)', 'Area of Mudflats(0.118)', 'Presence or Absence of Mudflats(0.092)', 'Appearance of Natural Enemies(0.087)', 'Protected Areas(0.08)', 'Island Area (0.069)', 'Over-Breeding devastation(0.064)', 'Soil Composition Ratio(0.056)', 'Distance from Land(0.054)', 'Ocean farm area (0.045)', 'Cultivated land area(0.041)', 'Cultivation behavior(0.038)', 'Angle of the Surface(0.036)', and 'Land Use(0.033)'. It is judged that the weighting result value of the evaluation items derived in this study can be used for priority evaluation focusing on the coastal bird breeding area space. However, it seems that the correlation with the unique habitat suitability of bird individuals needs to be supplemented, and spatial analysis research incorporating species-specific characteristics will be left as a future task.

• Korean Journal of Environment and Ecology
• /
• v.28 no.6
• /
• pp.725-740
• /
• 2014

To figure out the vegetation situation in the ridge of the Naknam-Jeongmaek, six intensive survey sites were selected considering environmental factors and human interferences, 132 quadrats (area $100m^2$) were installed to survey appearing species of trees and major environmental factors, and the characteristics of vegetation structures were analyzed. The surveyed plots were divided into six groups according to the analysis of classification by TWINSPAN; Quercus mongolica-Q. variabilis community, Pinus densiflora-Q. dentata community, Chamaecyparis obtusa community, Q. mongolica-P. densiflora community, P. densiflora-P. thunbergii community, P. koraiensis community, Rhododendron spp.-Lespedeza cyrtobotrya community. P. densiflora-Q. dentata community, Q. mongolica-P. densiflora community, and P. densiflora-P. thunbergii community are expected to be succeeded by deciduous oaks because the power of deciduous oaks is strong in their lower layer. C. obtusa community, P. densiflora community, and Rhododendron spp.-L.cyrtobotrya community are artificial forests that were artificially formed and are expected to be maintained in the current state for some time because the dominance value of planted species of trees is high. Most vegetations in Naknam-Jeongmaek were secondary forests or artificial forests formed for forest tree production and forestation for erosion control. In particular the top regions and hilly sections of the mountain were mostly dominated by deciduous oaks such as Q. mongolica, Q. variabilis showed some P. densiflora community competing with deciduous oaks. On the other hand, low sections and regions adjacent to the city showed severe artificial interference since exotic species such as P. thunbergiil, C. obtusa, P. koraiensis, and Rhododendron spp. were planted.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.2
• /
• pp.1-8
• /
• 2013

This study presents relations between the time lag and interaction index of the impinging-jet injectors using the time lag model in a model chamber. The response of the flame is analyzed to artificial perturbation with 5% amplitude of oxidizer speed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. In this method, time lag or delay is calculated by the characteristic length and the average velocity obtained from numerical results. The tendency that the time delay decreases with axial jet velocity has been observed.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.3
• /
• pp.491-498
• /
• 2017

GPS (global positioning system) is a popular system that provides location information by measuring arrival time difference at the receiver between several GPS satellite signals. GPS is widely used in commercial area as well as military systems. Reliable GPS signal reception is more important in the military applications such as guided missiles. However, since the carrier frequencies of the GPS signals are well known and the received power is extremely low, the GPS systems are vulnerable to intentional jamming attacks. To remove jammers while maintaining GPS signals at the received signals, a popular technique is an adaptive beam steering method based on array antenna. Among adaptive beam steering techniques, this paper considers MVDR (minimum variance distortionless response) algorithm, and proposes a new adaptive technique that preserves the received signals at desired directions, but removes the unknown jamming signals adaptively. The performance of the proposed method is verified through computer simulation.