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        검색결과 9,514

        6685.
        2003.03 구독 인증기관 무료, 개인회원 유료
        During the expedition of Mt. Chanbai-shan, China in 1999 to 2002, a total of 67 species belonging to 47 genera, 7 subfamilies are recognized. Of these, 11 species, Eudonia hiranoi Inoue, Scoparia yamanakai Inoue, Crambus argyrophorus Butler, Goniorhynchus exemplaris Hampson, Herpetogramma moderatalis (Christoph), Herpetogramma pseudomagna Yamanaka, Opsibotys perfuscalis Munroe et Mutuura, Pleuroptya harutai (Inoue), Pyrausta rubiginalis (Hubner), Hypsopygia regina Butler, and Orthopygia nannodes (Butler) are reported for the first time from China. The synonymies, distributional ranges, and photographs of newly reported species are provided.
        4,200원
        6686.
        2003.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We introduce and describe performance of the 6-meter telescope of Seoul Radio Astronomy Observatory (SRAO). All the softwares and instruments except the antenna structure and its driving system are developed for ourselves. The SIS mixer type receiver resulted in the receiver noise temperature less than 50 K (DSB) over the whole 3-mm radio window. An autocorrelation spectrometer, developed first in Korea, provides maximum 50 MHz band width over 1024 channels. Antenna surface is measured and adjusted using template method and radio holography which resulted in a superb surface accuracy bet-ter than 30μm. Accordingly, the aperture and beam efficiences amount to 70% and 75%, respectively, largely independent of frequency in the 85 - 115 GHz range. It is also found that telescope pointing errors are less than 10" in both azimuth and elevation and that antenna gain is almost constant against elevation greater than 20°, without adjusting sub-reflector position. The SRAO 6-meter telescope is now fully operational and all these characteristics verify that observations are carried out with high precision and fidelity.
        4,000원
        6687.
        2003.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        ASTRO-F /FIS will carry out all sky survey in the wavelength from 50 to 200 μm. At far infrared, stars and galaxies may not be good calibration sources because the IR fluxes could be sensitive to the dust shell of stars and star formation activities of galaxies. On the other hand, asteroids could be good calibration sources at far infrared because of rather simple spectral energy distribution. Recent progresses in thermal models for asteroids enable us to calculate the far infrared flux fairly accurately. We have derived the Bond albedos and diameters for 559 asteroids based on the IRAS and ground based optical data. Using these thermal parameters and standard thermal model, we have calculated the spectral energy distributions of asteroids from 10 to 200 μm. We have found that more than 70% of our sample asteroids have flux errors less than 10% within the context of the best fitting thermal models. In order to assess flux uncertainties due to model parameters, we have computed SEDs by varing external parameters such as emissivity, beaming parameter and phase integral. We have found that about 100 asteroids can be modeled to be better than 5.8% of flux uncertainties. The systematic effects due to uncertainties in phase integral are not so important.
        4,200원
        6688.
        2003.03 구독 인증기관 무료, 개인회원 유료
        인체 트롬보포이에틴(hTPO)은 megakaryopoiesis 과정에 주요한 역할을 하는 사이토카인이다. 따라서 이러한 트롬보포이에틴을 유선조직에서 직접적으로 발현시키기 위하여 소 베타 카제인 프로모터, 인체 트롬보포이에틴 cDNA 및 네오유전자로 구성된 발현벡터를 구축하였다. 소 귀조직 세포로부터 유도된 섬유아세포에 lipoffctamine을 이용하여 발현벡터(pBT-L n대)의 삽입을 유도하였다. G4l8 저항성을 지닌 세포의 콜로니 형성을 유도하기 위하여 2주 이상 배양을 실시하였다. 형질전환 콜로니는 PCR에 의해 동정하였으며, 이들 콜로니를 핵치환 전까지 계속적으로 증식을 유도하였다. 형질전환 세포에 의해 재구성된 난자는 전기적인 융합과 calcium ionophore와 6-DMAP를 이용한 활성화를 실시하였으며, 체외에서 7일간 배양을 실시하였다. 총 35개의 콜로니를 PCR에 의해 분석한 결과, 이 중 29(82.9%)개가 형질전환된 콜로니였다. 형질전환된 세포로 재구성된 난자의 난할율 및 배반포로의 발달율은 65.1%와 23.8%로 나타났다. 형질전환된 세포로 재구성된 난자로부터 발달한 29개의 배반포 중 27개가 형질전환으로 확인되었다. 따라서 이러한 결과들은 형질전환 소 수정란을 형질전환된 세포를 이용한 체세포 복제 기법을 통해 효과적으로 생산할 수 있다는 것을 제시하고있다.
        4,000원
        6689.
        2003.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, densified 4D carbon/carbon composites were made from carbon fiber and coal tar pitch through the process of pressure impregnation and carbonization and then followed by carbonization and graphitization. To improve the oxidative resistance of the prepared carbon/carbon composites, the surface of carbon/carbon composites was coated on SiC by the pack cementation method. The SiC coated layer was created by depending on the constitution of pack powder, and reaction time of pack-cementation. The morpology of crystalline and texture of these SiC coated carbon/carbon composites were investigated by XRD, SEM/EDS observation. So the coating mechanism of pack-cementation process was proposed. The oxidative res istance were observed through the air oxidation test, and then the optimal condition of pack cementation was found by them. Besides, the oxidative mechanism of SiC formed was proposed through the observation of SiC coated surface, which was undergone by oxidation test.
        4,000원
        6690.
        2003.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Recently, the control of pore-characteristics of nano-porous materials has been studied extensively because of their unique applications, which includes size-selective separation, gas adsorption/storage, heterogeneous catalysis, etc. The most widely adopted techniques for controlling pore characteristics include the utilization of pillar effect by metal oxide and of templates such as zeolites. More recently, coordination polymers constructed by transition metal ions and bridging organic ligands have afforded new types of nano-porous materials, porous metal-organic framework(porous MOF), with high degree and uniformity of porosity. The pore characteristics of these porous MOFs can be designed by controlling the coordination number and geometry of selected metal, e.g transition metal and rare-earth metal, and the size, rigidity, and coordination site of ligand. The synthesis of porous MOF by the assembly of metal ions with di-, tri-, and poly-topic N-bound organic linkers such as 4,4'-bipyridine(BPY) or multidentate linkers such as carboxylates, which allow for the formation of more rigid frameworks due to their ability to aggregate metal ions into M-O-C cluster, have been reported. Other porous MOF from co-ligand system or the ligand with both C-O and C-N type linkage can afford to control the shape and size of pores. Furthermore, for the rigidity and thermal stability of porous MOF, ring-type ligand such as porphyrin derivatives and ligands with ability of secondary bonding such as hydrogen and ionic bonding have been studied.
        4,000원
        6691.
        2003.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The Iowa Chautauqua Program has provided effective staff development for over 2,700 K-12 science teachers during the past two decades. This is a review of the features of the program, its instructional staff, and a description of the outcomes as disclosed from evaluative studies conducted by staff, teacher participants, doctoral students, and outside evaluators. Examples of outcomes are included as revealed from the qualitative studies reported in newsletters, published papers, dissertations, annual staff reports, and evidences of success reported to accrediting groups. The Chautauqua stresses student-centeredness, constructivist learning, and the visions of reform featured in the National Science Education Standards.
        4,000원
        6692.
        2003.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This is a descriptive study to identify patterns of teacher questioning discourse. Transcripts from Korean secondary science classrooms were examined while extensive review of literature on classroom discourse was carried out. When it is assumed that teacher questioning discourse can be categorized into different patterns by considering together the apparent exchange structures and pedagogical functions, various patterns of teacher questioning discourse were revealed. Although most patterns found illustrate the centrality of the teacher, a few of them are considered alternatives to the typical IRE discourse. A framework for classifying teacher questioning discourse is suggested and its implications for science teacher education and future research discussed.
        4,500원
        6693.
        2003.02 구독 인증기관 무료, 개인회원 유료
        Frequency shift, due to quartz crystal resonator aging, has been identified as one of the most important quality control problems of quartz crystal products. The problem becomes more significant due to the device miniaturization and high precision standards for telecommunication applications. Since aging induced frequency shift occurs during a long time frame, it is necessary to predict the long-term behavior of the devices based on the short-term data obtained under an accelerated environment. One the other hand, frequency shift is associated with quite large random variation, and thus, a proper probabilistic theory should be used for analyzing test data and for developing a reliable prediction model. Accelerated testing was performed for various types of crystal resonators under elevated temperatures. The frequency shifts of the devices were measured at different testing periods. Markov chain model was used to characterize the frequency shift of the devices. The obtained short-term test results were used for calibrating the probabilistic transition matrix of Markov chain model. The model can then be used for predicting the long-term frequency shift. The time-temperature superposition principle in viscoelasticity was adopted to address the shift in time under different temperatures.
        4,000원
        6694.
        2002.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        5,800원
        6695.
        2002.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Cassegrain interface module (CIM) of the fiber-fed high resolution echelle spectrograph has been designed and manufactured for the 1.8 m reflector at the Bohynsan Optical Astronomy Observatory. We also constructed a long slit spectrograph attached to this CIM, which would replace the earlier rather inefficient medium dispersion spectrometer. We present detailed description for design and manufacturing concepts of the CIM which consists of a slit assembly, slit monitoring system, calibration lamp system and a long slit spectrograph, in order to provide how the overall system and each part. are constructed. The preliminary performance test carried out so far seems to indicate a successful result.
        4,000원
        6696.
        2002.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        4,800원
        6697.
        2002.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PM (Particulate Matter) samples contained fungal spores were collected in the ambient air of Seosan, west Korea, in springtime of 2000 and 2001. PM concentrations were 199.8μg m-3 in the 1st Asian Dust Storm period (March, 23 ~ 24) and 249.4μ
        4,000원