• 한국통신학회논문지
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• 제17권6호
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• pp.629-639
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• 1992

본 논문에서 근거리 통신망에서의 정보보호 취약성, 요구 서비스, 정보보호 적용대안에 대하여 정리하고, 근거리 통신망에 적합한 새로운 키이 분배 방식을 제안하였다. 제안된 방식은 Time Quantum을 암호화 키이에 적용하여 암호화 키이 사용시간과 키이를 이용한 암호화 메시지 양을 제한하였다. 제안된 방식은 키이 concurrency와 상대방에 대한 인증을 더욱 확실하게 할 수 있으며, 프레임 단위 도청으로 인하여 암호화 키이 노출이 발생하더라도 전체 전송 메시지의 내용을 알 수 없으므로 정보보호 및 안정성을 더욱 강화하는 특징을 갖도록 하였다.

• 자원환경지질
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• 제30권3호
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• pp.263-275
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• 1997

Compound calcrete deposits are recognized from the Dadaepo Formation in Dusong peninsula, Pusan, and their textures, structures, morphology, and stratigraphic distribution are examined. The Dadaepo Formation in study area consists of fluvial plain deposits including floodplain-lake deposits, and the compound calcrete deposits occur above floodplain deposits and below lacustrine deposits. The compound calcrete deposits are composed of nodular to massive (micritic), laminar, nodular, nodular to massive (marly), and marly calcrete deposits. In these calcretes, circumgranular and curved cracks, alveolar structures, fitted peloids, tubular fenestrae with laminar micrite wall (rootlet casts), microstalactic calcite, and tepee structures are observed, which indicates that they are calcic paleosols. Considering their stratigraphic occurrences and pedogenic origin, compound calcrete deposits are interpreted to have formed on distal fluvial plain to palustrine environment by the repetetion of deposition and subsequent calcification due to alternation of lake expansion and contraction. The repetetion of calcrete formation suggests that arid climatic condition was alternated with humid condition in short-term period. Such alternated paleoclimatic condition is similar to those of the Sindong and Hayang groups, and indicates that short-term fluctuations from arid to humid climate were prevailing in overall Gyeongsang Basin. In stratigraphic sense, the compound calcrete deposits can be used as a marker deposit for the correlation of the Dadaepo Formation.

• 응용통계연구
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• 제11권2호
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• pp.335-350
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• 1998

X11ARIMA는 1965년 미국 센서스국에서 개발된 X11분석 방법에 기초한 시계열 분석방법으로 Dagum(1975)에 의해 개발되었다. 이 기법은 Dagum(1988)에 의하여 북미지역의 174개의 경제지수를 바탕으로 일부 기본모형이 수정·보완되어 오늘날에 이르고 있다. 최근에는 회귀 모형과 ARIMA모형을 동시에 고려하여 특이치와 추세 변환효과(outlier arid Trend-change effects), 계절변동(seasonal effect), 그리고 달력효과(calendal effect) 등을 추정한 William 등(1995)과 Chen과 Findley(1995)의 X12ARIMA분석 방법이 소개되었다. 그러나 위의 모든 기법들은 주로 북미지역의 경제지수를 기초로 하고 있다. 본 논문에서는 우리나라의 산업중분류에서 산출되는 102개(생산(27), 출하(27), 재고(27), 가동률(21))의 지수에 대한 우리나라의 표준 ARIMA모형을 제시하고, 우리나라에 적합한 이동평균항수를 제공하고자 한다. 그리고 우리나라의 설, 추석 등의 명절효과를 태양력으로 전환함과 동시에, 최근에 논의되고 있는 X12ARIMA에서 사용되는 회귀모형과 ARIMA모형을 동시에 고려하는 명절효과를 도출하고자 한다.

• 한국지형학회지
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• 제26권3호
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• pp.69-85
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• 2019

Humans have been important driver to reconfigure the terrestrial surface of the Earth by altering its morphology and processes. The effect of human activities on the physical landscape, however, shows substantially uneven geographical patterns. Most of anthrogemorphoogical studies regarding human-induced denudation have focused on areas with a long history of human modifications such as humid landscapes, so the hypothesis is naturally a great human impact on landscapes. The effect of human activities on dryland Earth surfaces are far less commonly studied, although erosion is one of major concerns in arid and semi-arid region regarding land and water quality degradation. The urban metropolis of Phoenix, Arizona, USA provides an opportunity to explore the impact of the Anthropocene. The Phoenix metropolitan area rests on classic desert landforms, such as extensive pediments, alluvial fans and sand sheets. Human activities including cattle crazing, wildfire resulting from introduced grass species by human, and recent urbanization processes have impacted these classic desert landforms and altered geomorphic processes. The purpose of this paper, therefore, rests in examining Anthropocene in the geomorphology of the north-central Sonoran Desert. The objectives of this paper are: i) to understand the impact of the Anthropocene on the geomorphological processes and forms through field observations; ii) to quantify the magnitude of human impacts on landscape using a published two-decade long record of erosion dataset and natural background erosion dataset in submitted manuscript at the sprawling edge of the Phoenix metropolitan region; iii) to examine how geomorphic outcome can affect the sustainability of cities through the estimation of sediment yield under the condition of urban sprawl.

• Journal of Forest and Environmental Science
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• 제40권2호
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• pp.73-81
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• 2024

As a phreatophyte, pistachio (Pistacia vera L.) is widely grown in water-limited conditions and recognized as an economically valuable crop in semi-arid regions. In Tajikistan, pistachio grows naturally and artificially in 79,000 ha, but the nut yield is very low due to less-developed plantation technologies. In this study, differences in pistachio plantation technologies of the major pistachio-producing countries and Tajikistan were analyzed to suggest ways to improve plantation technologies in Tajikistan. In the major pistachio-producing countries such as Iran, the United States and Turkey, seedlings of high nut-yielding varieties are grafted before planting. As a result, annually 349-4,479 kg ha^-1 of nuts are harvested in those countries. On the other hand, Tajikistan annually produces only 0.6-3.7 kg ha^-1. While seven suitable high nut-yielding varieties (Albina, Dangarinka, Saboh, Green girl, Mountain pearl, October, and Orzu) have been identified as suitable for Tajikistan's environment, the plantation area with grafted individuals using these varieties is limited to only 1.5 ha, necessitating widespread adoption. The low utilization of the high nut-yielding varieties is attributed to the lack of grafting specialists and skills, which have hindered increasing pistachio nut production in Tajikistan. Therefore, improving the basic capability of pistachio grafting should be prioritized to expand the economic profits from the pistachio forests in Tajikistan.

• Asian-Australasian Journal of Animal Sciences
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• 제26권3호
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• pp.366-377
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• 2013

We examined the nutritive value of common grass species in the semi-arid rangelands of Borana in southern Ethiopia using local experience based herbage preference (LEBHP) perception and laboratory techniques. Local pastoralists in the study area were asked to identify common grass species and rank them according to the species' preferences and palatability to cattle. The pastoralists listed a total of 15 common grass species which were then sampled during the main rain and cold dry seasons and analyzed for crude protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF) and ash content to verify pastoralists' claim regarding the quality of individual species. The relative feed value (RFV) and dry matter digestibility (DMD) were also calculated using NDF and ADF contents. Spearman's rank correlation was used to examine possible relationships between laboratory results and pastoralists' experience on grass quality. Cenchrus ciliaris, Chrysopogon aucheri, Digitaria milanjiana, Eragrostis papposa and Panicum maximum were the top five species based on LEBHP perception. There were indications of inconsistency in terms of LEBHP perception among the different pastoral communities. The chemical composition of all grass species showed significant (p<0.05) variation between sites, seasons and species. The results showed that the CP values for the Borana rangelands were in the range of 8.7% in the main rain season to 5.1% for the cold dry season. The fiber constituents were relatively low in the main rain season compared to the cold dry season. Overall, Digitaria milanjiana had the highest CP (16.5%) content, while the least was recorded with Heteropogon contortus (10.8) and Aristida adoensis (9.8%) during the main rain season. It seems that the spatial variability of landscapes within the wider geographical regions, soil properties and texture, and land-use patterns probably contributed to site differences in species quality. Generally, the RFV of individual grass species was significantly (p<0.05) varied between and within sites. The ranking of species by pastoralists according to their preferences by cattle was highly correlated with the chemical composition of laboratory results of individual grass species with 'r' values for CP (0.94), ash (0.95), NDF (-0.98), ADF (-0.93) and ADL (-0.93). We suggest the complimentary use of LEBHP and laboratory techniques in evaluating the nutritive quality of rangeland forage species for sustainable animal production.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.426-429
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• 2007

One of the widely used applications of remote sensing studies is environmental change detection and biodiversity conservation. The study area Hustai Mountain is situated in the transition zone between the Siberian taiga forest and Central Mongolian arid steppe. Hustai National Park carries out one of several reintroduction programs of takhi (wild horse or Equus ferus przewalskii) from various zoos in the world and it represents one of a few textbook examples of successful reintroduction of an animal extinct in the wild. In this paper we describe the results of an analysis on the change of remaining forest area over the 7-year period since Hustai Mountain was designated as a protected area for reintroduction to wild horses. Today the forested area covers approximately 5% of the Hustai National Park, mostly the north-facing slopes above 1400 m altitude. Birch (Betula platyphylla) and aspen (Populus tremula) trees are predominant in the forest. We used Landsat ETM+ images from two different years and multi temporal MODIS NDVI data. Land types were determined by supervised classification methods (Maximum Likelihood algorithm) verified with ground-truthing data and the Land Change Modeler (LCM) which was developed by Clark Labs. Forested area was classified into three different land types, namely the forest land, mountain meadow and mountain steppe. The study results illustrate that the remaining birch forest has rapidly changed to fragmented forest land and to open areas. Underlying causes for such a rapid change during the 15-year period may be manifold. However, the responsible factors appear to be the drying off and outbreak of forest pest species (such as gypsy moth or Lymantria dispar) in the area.

• 한국지구과학회지
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• 제37권5호
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• pp.295-308
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• 2016

Nine species of fossil plants were described based on the new material collected from the Hasandong Formation. They are as follows: Thallites yabei, Onychiopsis elongata, Cladophlebis denticulata, C. shinshuensis, C. (Eboracia ?) lobifolia, C. (Klukia ?) koraiensis, Brachyphyllum japonicum, Elatocladus tennerima, and Taeniopteris ? sp. cf. T. auriculata. The floristic composition of the Hasandong flora is very similar to that of the Nakdong flora. This means that both floras might have flourished under subtropical warm arid climate. This flora contains both the Tetori-type and Ryoseki-type floras. It is considered that the Hasandong flora is a member of the Mixed-type floras that existed in eastern Eurasia during the Late Jurassic to Early Cretaceous time.

• 한국전산유체공학회지
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• 제10권1호
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• pp.31-38
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• 2005

Three-dimensional flow over the sand dunes have been studied numerically by using Large-Eddy Simulation (LES) method. In the direction of initial flow and span direction cyclic boundary conditions are imposed for velocity and pressure. The movement of the sand dune which is formed by converging wind direction has been investigated. The numerical method employed in this study can be divided into three parts: (i) calculation of the air flow over the sand dune using standard MAC method with a generalized coordinate system; (ii) estimation of the sand transfer caused by the flow through the friction; (iii) determination of the shape of the sand surface. Since the computational area has been changed due to step (iii), (i)-(iii) are repeated. The simulated dune, which has initially elliptic cross section, extends at the converging direction, which is known as linear dunes.

• 한국지구과학회지
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• 제22권2호
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• pp.105-111
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• 2001

충남 보령시 명암 지역에 분포하는 트라이아스기 후기의 아미산층으로부터 7개의 빗방울자국 표본이 발견되었다. 빗방울자국은 습윤한 아열대의 호성환경하에서 일시적 또는 계절적으로 건조한 기후에 수면의 저하시기에 형성된것으로 해석된다. 이들 빗방울자국은 하부 중생대 남포층군에서는 처음으로 발견된 것이다.