검색결과

검색조건
좁혀보기
검색필터
결과 내 재검색

간행물

    분야

      발행연도

      -

        검색결과 343

        83.
        2009.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The tropopause fold event that took place on January 1, 1997 over mid-region on the Korean Peninsula is examined by means of a numerical simulation based on a Mesoscale Model (MM5). The purpose of this paper is to investigate the effects of moisture in reinforcing a tropopause fold linked to an explosive cyclone. Two types of simulations were carried out; 1) simulations for moist conditions in which full physical and dynamic processes are considered and 2) simulations for dry conditions in which cumulus parameterization and cloud microphysics process are excluded. The results of the moist condition simulations demonstrate that the intensity of the central pressure of the cyclone was overestimated compared with the observed values and that the location of the center and the pressure deepening rates (-17 hPa/12 hr) complied with the observed values. The potential vorticity (PV) anomaly on the isentropic surface at 305 K continued to move in a southeast direction on January 1, 1997 and thus created a single tube of tropopause fold covering the northern and the middle area of the Korean Peninsula and reaching the ground surface at 0300 UTC and 0600 UTC. The results of the dry condition simulations show that the tropopause descended to 500 and 670 hPa in 0300 and 0600 UTC, respectively at the same location for the moist condition simulation; however, there was no deep tropopause fold observed. A comparison of the simulated data between the moist and the dry conditions suggests that a deep tropopause fold should happen when there is sufficient moist in the atmosphere and significantly large PV in the lower atmosphere pulls down the upper atmosphere rather than when the tropopause descends itself due to dynamic causes. Thus, it is estimated that moisture in the atmosphere should have played a crucial role in a deep tropopause fold process.
        4,900원
        84.
        2009.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Using the spectroscopic data secured with the Hamilton Echelle Spectrograph at Lick Observatory, we found the physical condition of the planetary Nebula NGC 6210. The spectral line profiles of the permitted and forbidden lines have been analyzed using IRAF and StarLink/Dipso. The hydrogen number densities (NH) are 2,000-20,000 cm-3, and the electron temperatures are 8,100-10,300 K based on the forbidden lines. The expansion velocities, derived from the Full Width at Half Maximum (FWHM) and the double peak of the line profiles, are in the range of 10 to 45 kms-1. The expansion velocities imply a shell structure with an accelerated nebular gas. We also derived abundances from the permitted lines of CII, CIII, NII, NIII, OII, and OIII, which may have been formed through the fluorescence mechanism. NGC 6210 is likely to be evolved from a progenitor of more than 3M⊙, which had been born near the Galactic plane.
        4,200원
        85.
        2009.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study intended to the optimal conservation method and to make an application scheme for the fossil locality of the Quaternary Hamori Formation at the northeastern coast of Mt. Songak. Many kinds of innumerable fossils are found from the Hamori Formation in the study area: Footprints of hominid, trace fossils of invertebrates, bird, artiodactyla, proboscidea, carnivores, unclassified footprints, and body fossils (arthropoda, gastropoda, mollusca, and plants). The formation has been outcropped and eroded out with innumerous fossils by the strong wave action of storm and typhoon. Korean government recognized the dangerous situation of the important fossils and decided to conserve the formation for the national heritage. Method D1 (conservation hall or museum on the fossil locality) may be the best way to protect the fossil locality from all the natural activities and to do the research, exhibition, education, and sightseeing together. The application of the geologic materials from the fossil locality should preferentially focus on the collection and research which should be accompanied by exhibition, education, and sightseeing. The application scheme may be stepped into three stages during 10 years: (1) systematic conservation and publicity during 2005-2007, (2) establishment of wellorganized museum during 2008-2010, and (3) international museum with the optimized roles 2011-2014.
        4,000원
        86.
        2009.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The Yongdong basin developed during Early Cretaceous in the central part of the Korean Peninsula and bounded on the northwest and southeast by northeast trending mega-scale strike-slip Yongdong Fault. An 8 km thick succession of exclusively terrigeneous sediments can be grouped into two mega-sequences. In concert with the migration of depocenter, the upper sequence overlaps the lower and occupies northern part of the basin during basin evolution. Alluvial and lacustrine environments were predominantly formed from early to late stage of the basin formation. Several lines of evidence support that the basin was formed within intra-arc tectonic environments and destroyed by polyphase tectonic force. Schematic evolutionary diagram of the basin is proposed.
        4,900원
        87.
        2009.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In 2007, just after the recession of the Changma, anomalously long rainy period (from July 30 to August 15) occurred in Korea. To identify the cause of the sustained rainy period, we performed synoptic analysis and the associated air motions. The behavior of each air parcel trajectory associated with atmospheric motion was then investigated. As a result, three particular phenomena occurring at latitudes lower than 40˚N were discovered. First, a mass of relatively cold air, referred to as E, made a deep intrusion from 20˚N to 60˚N. Second, this intrusion was accompanied by another mass of air called dE. It was colder and drier than E and originated from the mid-troposphere over the tropical ocean. Third, dE and E rotated clockwise three times over a period of 17 days over the Northwestern Pacific and blocked the westerly waves imbedded in the zonal flow from propagating. Two additional phenomena were observed at latitudes higher than 40˚N. First, the cold core system, while approaching from the west with low geopotential values at its center, was stagnated over Shanxi China. It enhanced the northward intrusion of dE and E, and then diminished. The subsequent low system showed similar evolution as the first one. Second, a warm core anticyclone was formed over Lake Baikal, blocking the westerlies for 13 days and contributed to the persistent northward incursion of warm moist air. Moreover, a horizontally extended intrusion of upper level clouds from the tropics to 50˚N, which may be interpreted as a tropical plume, was found around the end of the period (from August 12 to 15, 2007) with successive tropical nights over Korea.
        5,700원
        88.
        2009.07 구독 인증기관 무료, 개인회원 유료
        This study focuses itself on designing a guide for workplace self-directed lifelong learning and assessment in distance learning. The areas the guide is designed on are: ①diagnosing learners’ needs, ②formulating self-learning goals, ③identifying human and material resources, ④selecting and implementing appropriate SDL strategies and ⑤evaluating own performance. The five instruments comprise a comprehensive qualification framework where each of the five is placed under the circular relationship nexus so that upward and downward interplay among each element works functionally. Task of designing a guide for workplace self-directed lifelong learning and assessment in distance learning is suggested to be a 21c challenge each nation faces in knowledge-based digital and globalization era.
        6,100원
        89.
        2009.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was carried out to evaluate the nuclear, cytoplasmic maturation and developmental potential of bovine oocytes selected by brilliant cresyl blue (BCB) as indirect measurement of oocytes growth phase. Cumulus-oocyte complexes (COCs) were collected from 2 to 8 mm follicles from slaughterhouse Hanwoo ovaries. The COCs were divided into stained cytoplasm to blue (BCB+) and unstained (BCB-) according to their ooplasm BCB coloration stained by of BCB after 90 min. Selected COCs were cultured in a TCM 199 for 18 to 26 h. Nuclear maturation and total cell number was evaluated after in vitro maturation (IVM) or in vitro culture (IVC) using Hoechst 33342, and cytoplasmic maturation was evaluated by intracellular glutathione (GSH) assay before (0 h) and after (24 h) IVM. The oocyte diameters were not differed significantly between BCB+ () and BCB+ () groups (p>0.05). However, the proportion of metaphase II oocytes in BCB+ group was significantly higher than BCB- group after IVM (p<0.05). GSH content of BCB+ group oocytes was significantly higher than that of BCB- group just after collection ( vs. , p<0.05), but not varied after IVM( and for BCB+ and BCB- respectively; p>0.05). The proportion of blastocyst formation and total cell number in BCB+ group (23.5% and ) was significantly higher than that in BCB- (9.8% and ; p<0.05). The results indicate that BCB+ group oocytes may provide a cellular and functional basis for the greater developmental competence in Korean Native Cow (KNC) oocytes.
        4,000원
        90.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The Galactic planetary nebulae emit many strong recombination and forbidden lines. By analyzing such lines, the physical condition of the planetary nebulae has been inferred using the strategically important diagnostic line ratios. In order to fully understand the physical condition of a planetary nebula and to derive its chemical abundances, the photoionization model codes, e.g., CLOUDY and NEBULA, were employed for an analysis of gaseous nebular spectra. For the well-studied, relatively simple planetary nebula NGC 7026, theoretical investigation was done with about the same input parameters in models. The predictions made by both codes seem to be in good accord. However, the predicted physical conditions, such as electron temperature and density, are slightly different. Especially, the electron temperatures are predicted to be higher in CLOUDY, which may cause a problem in chemical abundance determination. Our analysis shows that the main discordance may occur due to the diffuse radiation.
        4,000원
        91.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, solar eclipse records were investigated during the Three Kingdoms era of ancient Korea using astronomical calculations and numerical simulations. Under the condition that the solar eclipses were actually observed at the well known capitals of the Three Kingdoms, I investigated the probabilities that the optimal observation areas of the Early Silla, Goguryeo, and Baekje records would appear around Chinese continent. I found higher probabilities than those suggested by Park and La (1994), although the numerical values are still low, especially in the case of the Early Silla records. On the other hand, the probability that the optimal observation area of the Later Silla records will be present around South Korea is only 13.6%, although the area shows a good match with the known capital. I also analyzed the number distribution of the eclipse records for the Three Kingdoms (except for the latter Silla's) according to the observers' locations: at the optimal observation areas and at the known capitals. And then I compared with the number distribution of all eclipses observable from those locations. From the χ2-test, I found that the Goguryeo and Baekje records had better representation of their population distributions at the latter regions (χ2=27.93 and 205.5) than at the former ones (χ2=34.19 and 211.5). Therefore, it is difficult to conclude that the observers' locations during the Three Kingdoms period were either near China, as suggested by Park and La, or in the Korean peninsula, solely based on these results. It is thus recommended that more studies are required to confirm the real observers' locations during the Three Kingdoms era.
        4,200원
        92.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Hydrogeologic properties of a well field around middle mountainous areas in Pyosun, Jeju volcanic island were examined based on water level monitoring, geologic logging and pumping test data. Due to the alternating basaltic layers with varying permeability in the subsurface, it is difficult to analyze the hydraulic responses to artificial pumping and/or natural precipitation. The least permeable layer, detrital materials with clay, is found at a depth of 200 m below surface, but it is not an upper confining bed for lower main aquifer. Nevertheless, this layer may serve as a natural barrier to vertical percolation and to contaminant migration. Water levels of the production wells are dominantly affected by pumping frequently, while those of the remote observation wells are controlled by ambient precipitation. Results of pumping tests revealed a possible existence of horizontal anisotropy of transmissivity. However, some results of this study include inherent limitations enforced by field conditions such as the consistent of groundwater production and the set of time periods for the cessation of the pumping prior to pumping tests.
        4,300원
        93.
        2008.09 구독 인증기관 무료, 개인회원 유료
        Real-time hybrid testing technique (RT-HYTT) is a structural dynamic testing method that the numerical calculation of the equations of motion of a structure and the experimental measurement of the reaction forces resulting from the application of this motion to the numerical structure are simultaneously implemented in real time. In this paper, structural control performance of the magneto-rheological (MR) damper installed in a real-scaled 5 story building is experimentally evaluated through real-time hybrid test method. In this method, a numerical substructure is based on a structural model identified from the forced vibration testing results of a real-story building, and an MR damper that is used as an experimental substructure is physically tested with a universal testing machine (UTM). In the test, load cell on the UTM measure the force necessary to attain the required story displacement and these structural reaction forces are returned to the computer for use in next time step calculation of a numerical structural model. Test results show that the higher level of control force generated by the Mr damper causes the lower level of controlled response of a structure.
        4,000원
        94.
        2008.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In the present study, effects of concentration of cryoprotectant solutions on the nuclear maturation of vitrified-thawed porcine oocytes were examined. Also, the developmental capacity of vitrified-thawed immature porcine oocytes following ICSI was investigated. Oocytes were cultured in NCSU-23 medium supplemented with 5% FBS at in 5% and air. The in vitro maturation rate of vitrified-thawed oocytes () was lower than that of the control (, p<0.05). The in vitro maturation rate of vitrified-thawed oocytes treated with CB + NCSU- 23 medium were , , , , respectively. The in vitro maturation rate () of the vitrified-thawed oocytes treated with CB for 30 min was the highest of all vitrification groups. When the in vitro developmental rates of the vitrified-thawed (with EDS and EDT) oocytes following ICSI were , , respectively. This results were lower than the control group ().
        3,000원
        96.
        2008.05 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        This paper presents results and observations obtained from a study of the optical and thermal properties of alkali tellurite depending on the composition. Fourier transform infrared (FT-IR) spectra showed evidence of chemical modification from TeO4 trigonal bipyramids (tbp) to TeO3 trigonal pyramids (tp) in tellurite glasses. The optical band gaps of the different glass samples calculated using Tauc's method were found to range from 3.5-3.8 eV. The glass transition temperature (Tg) and glass stability (δT) of alkali tellurite glasses were investigated, as M2O [M: Li, Na, K] amounted to 25 mol%, through the use of differential thermal analysis (DTA). The coefficient of thermal expansion (CTE) was measured in a thermo mechanical analysis (TMA) with a slow heating rate after the glass samples were annealed. The results confirm that the optical band gap of alkali tellurite glasses depends on the Te-O-Te structural relaxation related to the ratio of bridging/non bridging oxygen (BO/NBO). In contrast, the thermal properties are related to the ionic field strength of the Te-O-M and M-O-M bonds, and the Te-O-Te breakage depends on the ratio of BO/NBO.
        4,000원
        97.
        2008.05 구독 인증기관·개인회원 무료
        The multicolored Asian ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is common to a wide range of natural and agricultural habitats. Applications of gamma irradiation minimized the losses of stored food and the death or failure of emergence in larval and pupal stages. On the other hand, degrade toxin waste as one of alternative to chemical pesticide for both quarantine and sprout control purposes of storage crop pest. So, we have investigated whether gamma irradiation exposed to eggs, lava, pupa and adults of H. axyridis. It may be affected the emergence, fertility, fecundity, development period and sex ratio of H. axyridis. Some changes of physiological characteristics may be applied to more efficient agents as biological control of several aphids. Insects were exposed to gamma irradiation from 0 to 500 Gy of 60Co depended on their developmental stages. The results showed that the first instar, eggs, third instar, pupae, and adults were more sensitive in order of irradiation dose. And fecundity and fertility of female adults were significantly decreased with increasing gamma irradiation dose at all tested individuals.
        98.
        2008.05 구독 인증기관·개인회원 무료
        The multicolored Asian ladybird beetle, Harmonia axyridis, which demonstrates typical genetic polymorphism in its elytra color patterns. Early studies have color polymorphism in terms of geographical clines while a few investigated temporal populations in Coccinellidae. Nevertheless, note that geographical and temporal morph variation does not always correspond to what is expected from thermal and industrial adaption theories. A recent study of transformation and RNAi of the ladybird beetle, however, there is yet no evidence to indicate the variation is genetic or environmental factors. Here we describe a relatively new molecular fingerprinting technique, amplified fragment length polymorphism (AFLP). Because we think that color polymorphism in Coccinellidae is affected by genetic polymorphism. In total 38 markers were scored from which some markers were polymorphic. Supsequent UPGMA cluster analysis revealed 3 major group of Harmonia axyridis populations. But for strains that are more genetically similar, different primer combinations may be need to generate enough polymorphic marker.
        99.
        2008.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 철근콘크리트 특수모멘트골조(SMF)내 보-기둥 접합부의 비탄성 회전능력에 대한 연구결과를 조사한 것이다. 모든 실험체들은 ACI 318-02에 정의된 설계 및 세부지침에 따라 특수모멘트골조로 분류되었다. AISC(2002)기준에서 모멘트골조의 접합부에 대한 내진성능의 만족 기준을 이용하여 보-기둥 접합부를 평가하였다. 총 39개의 실험체들에 대해 자세하게 조사되었다. 특수모멘트골조에 대한 내진설계기준을 만족하는 대부분의 접합부들은 3%의 소성회전까지 휨강도의 심각한 감소 없이 연성이 유지되었다. 이는 특수모멘트골조 접합부들에 대한 엄격한 콘크리트 내진설계 규정에 따른 것으로 조사되었다. 접합부내의 횡방향 보의 존재는 보-기둥 접합부의 구속력과 전단에 대한 저항성을 증가시킨 것으로 조사되었다 접합부 전단응력에 대한 ACI 328-02 제한조건을 만족하는 모든 특수모멘트골조의 접합부들은 요구되는 내진성능을 만족하는 것으로 나타났다.
        4,000원
        100.
        2008.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        A 532 nm Nd-YAG laser was applied to crystallize amorphous Si thin films in order to evaluate the applicability of a Nd-YAG laser to low-temperature polycrystalline Si technology. The irradiation of a green laser was controlled during the crystallization of amorphous Si thin films deposited onto glass substrates in a sophisticated process. Raman spectroscopy and UV-Visible spectrophotometry were employed to quantify the degree of crystallization in the Si thin films in terms of its optical transmission and vibrational characteristics. The effectiveness of the Nd-YAG laser is suggested as a feasible alternative that is capable of crystallizing the amorphous Si thin films.
        3,000원
        1 2 3 4 5