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        검색결과 535

        261.
        2013.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        TiB2-reinforced iron matrix composite (Fe-TiB2) powder was in-situ fabricated from titanium hydride (TiH2) and iron boride (FeB) powders by the mechanical activation and a subsequent reaction. Phase formation of the composite powder was identified by X-ray diffraction (XRD). The morphology and phase composition were observed and measured by field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The results showed that TiB2 particles formed in nanoscale were uniformly distributed in Fe matrix. Fe2B phase existed due to an incomplete reaction of Ti and FeB. Effect of milling process and synthesis temperature on the formation of composite were discussed.
        4,000원
        262.
        2013.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The iron oxides nanoparticles and iron oxide with other compounds are of importance in fields including biomedicine, clinical and bio-sensing applications, corrosion resistance, and magnetic properties of materials, catalyst, and geochemical processes etc. In this work we describe the preparation and investigation of the properties of coated magnetic nanoparticles consisting of the iron oxide core and organic modification of the residue. These fine iron oxide nanoparticles were prepared in air environment by the co-precipitation method using of Fe2+ : Fe3+ where chemical pre- cipitation was achieved by adding ammonia aqueous solution with vigorous stirring. During the synthesis of nanoparti- cles with a narrow size distribution, the techniques of separation and powdering of nanoparticles into rather monodisperse fractions are observed. This is done using controlled precipitation of particles from surfactant stabilized solutions in the form organic components. It is desirable to maintain the particle size within pH range, temperature, solution ratio wherein the particle growth is held at a minimum. The iron oxide nanoparticles can be well dispersed in an aqueous solution were prepared by the mentioned co-precipitation method. Besides the iron oxide nanowires were prepared by using similar method. These iron oxide nanoparticles and nanowires have controlled average size and the obtained products were investigated by X-ray diffraction, FESEM and other methods.
        4,000원
        264.
        2013.04 구독 인증기관·개인회원 무료
        The developmental time of immature stages of Paromius exiguus (Distant) was studied at eight different constant temperatures (17.5, 20, 22.5, 25, 27.5, 30, 32.5 and 35°C) with a photoperiod of 14:10 (L:D) h on two host plants, Imperata cylinderica and Calamagrostis epigeios. On both host plants, the developmental time decreased with increasing temperatures. A significant difference in the developmental times was observed between two host plants for each nymphal stage and for the total nymphal stage as well. For completion of the total nymphal stage, the development time at 17.5 and 35°C were 69.6 and 16.6 days on I. cylinderica and 38.6 and 13.8 days on C. epigeios, respectively. The relationship between developmental rate and temperature was fitted to a linear regression model and the six nonlinear models (Lactin 1, Lactin 2, Briere 1, Briere 2, Logan 6 and Taylor). Except for the Taylor model, all of the five nonlinear models fitted the data for the total nymphal stage of the current study well, according to the high r2 value, on both host plants. The distribution of completion of each development stage was well described by the two-parameter Weibull function.
        266.
        2013.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Nanosphere lithography is an inexpensive, simple, high-throughput nanofabrication process. NSL can be done in different ways, such as drop coating, spin coating or by means of tilted evaporation. Nitride-based light-emitting diodes (LEDs) are applied in different places, such as liquid crystal displays and traffic signals. The characteristics of gallium nitride (GaN)-based LEDs can be enhanced by fabricating nanopatterns on the top surface of the LEDs. In this work, we created differently sized (420, 320 and 140 nm) nanopatterns on the upper surfaces of GaN-based LEDs using a modified nanosphere lithography technique. This technique is quite different from conventional NSL. The characterization of the patterned GaN-based LEDs revealed a dependence on the size of the holes in the pattern created on the LED surface. The depths of the patterns were 80 nm as confirmed by AFM. Both the photoluminescence and electroluminescence intensities of the patterned LEDs were found to increase with an increase in the size of holes in the pattern. The light output power of the 420-nm hole-patterned LED was 1.16 times higher than that of a conventional LED. Moreover, the current-voltage characteristics were improved with the fabrication of differently sized patterns over the LED surface using the proposed nanosphere lithography method.
        4,000원
        267.
        2013.01 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Opal glass samples having different chemical compositions were synthesized and transparent glass was obtained after melting. The effects of TiO2, BaF2, and CeO2 content on the color of the opal glass were studied by observing images of the opal samples and analyzing the results via ultraviolet visible spectroscopy and color spectrometry. The aesthetic properties of the opal glass were determined by studying the transmittance of visible light in the 400 nm to 700 nm range. The basic chemical composition of opal glass was SiO2 52.9 wt%, Al2O3 12.35 wt%, Na2CO3 15.08 wt%, K2CO3 10.35 wt%, Ca3(PO)4 4.41 wt%, MgCO3 1.844 wt%, LiCO3 2.184 wt%, and TiO2 0.882 wt%. The glass samples were prepared by varying the weight percentage of TiO2, BaF2, and CeO2. The transmittance of visible light was decreased from 95 % to 75 % in the glass samples in which TiO2 content was increased from 0 to 3.882 wt%. In the blue spectrum region, as the content of TiO2 increased, the reflectance value was observed to become higher. This implies that TiO2 content induces more crystal formation and has an important effect on the optical properties of the glass. The opalescence of opal samples that contained CeO2 or BaF2 is stronger than that in the samples containing TiO2. Opal glass samples comprising TiO2 had tetragonal lattice structures; samples including CeO2 as an additive had cubic lattice structures (FCC, CeO2).
        4,000원
        268.
        2012.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        An Individual-Based Model (IBM) was developed by employing natural and toxic survival rates of individuals to elucidate the community responses of benthic macroinvertebrates to anthropogenic disturbance in the streams. Experimental models (doseresponse and relative sensitivity) and mathematical models (power law and negative exponential distribution) were applied to determinate the individual survival rates due to acute toxicity in stressful conditions. A power law was additionally used to present the natural survival rate. Life events, covering movement, exposure to contaminants, death and reproduction, were simulated in the IBM at the individual level in small (1 m) and short (1 week) scales to produce species abundance distributions (SADs) at the community level in large (5 km) and long (1~2 years) scales. Consequently, the SADs, such as geometric series, log-series, and log-normal distribution, were accordingly observed at severely (Biological Monitoring Working Party (BMWP⁄10), intermediately (BMWP⁄40) and weakly (BMWP›50) polluted sites. The results from a power law and negative exponential distribution were suitably fitted to the field data across the different levels of pollution, according to the Kolmogorov-Smirnov test. The IBMs incorporating natural and toxic survival rates in individuals were useful for presenting community responses to disturbances and could be utilized as an integrative tool to elucidate community establishment processes in benthic macroinvertebrates in the streams.
        6,100원
        269.
        2012.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        3,000원
        270.
        2012.10 구독 인증기관·개인회원 무료
        Paromius exiguus (Distant, 1883) is a serious insect pest in rice field adjacent to reclaimed land. They suck young ear of rice causing empty head of grain or pecky rice grain. During 2010 to 2012, we conducted to investigate the host-plant change of P. exiguus in Siwha reclaimed land, Hwaseong-si. In 2012, we also studied dispersal ability of P. exiguus from reclaimed land to adjacent rice fields. In early May, the adults aggregated on the grain parts of cogon grass (Imperata cylindrica) (Poales: Poaceae) after overwintering, and laid their eggs and nymphs developed into adults on the same host plants from middle May to late June. Second generation was observed at wood small-reed (Calamagrostis epigeios) (Poales: Poaceae) from late June to late July. At shooting stage of rice, adults moved to adjacent rice fields and third generation might be started. Although dispersal ability of adult of P. exiguus penetrated about 10 km into inland areas of Hwaseong-si, number of individuals of P. exiguus population was significantly declined with increasing distance from reclaimed land (Pearson’s correlation coefficient, r=-0.7357, p<0.0001). Unfortunately, further studies on population dynamics of P. exiguus in rice fields could not investigated, because pesticides were widely sprayed by aerial application in 14 August, 2012. Nevertheless, this results will be a useful information for management and control of P. exiguus in rice fields adjacent to reclaimed land.
        271.
        2012.10 구독 인증기관 무료, 개인회원 유료
        A field experiment was conducted to study the effect of selenium priming on growth and productivity of maize at Agronomy Research Area, University of Agriculture, Faisalabad. Maize seeds were primed with different concentrations of selenium (0, 5, 25, 50 and 100 JlM) while untreated seeds were taken as control. Results showed that seed priming with all levels of selenium improved the germination parameters, growth and yield of maize. Seed priming with 50 JlM of selenium recorded maximum grain yield (2.35 t ha- 1) while minimum (1.66 t ha-1) grain yield was observed in case of untreated seeds (control). Further research should be carried out to find out mechanisms of growth and yield improvement of maize as a result of seed priming with selenium.
        3,000원
        272.
        2012.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The production of functional activated carbon materials starting from inexpensive natural precursors using environmentally friendly and economically effective processes has attracted much attention in the areas of material science and technology. In particular, the use of plant biomass to produce functional carbonaceous materials has attracted a great deal of attention in various aspects. In this study the preparation of activated carbon has been attempted from rice husks via a chemical activation-assisted microwave system. The rice husks were milled via attrition milling with aluminum balls, and then carbonized under purified N2. The operational parameters including the activation agents, chemical impregnation weight ratio of the calcined rice husk to KOH (1:1, 1:2 and 1:4), microwave power heating within irradiation time (3-5 min), and the second activation process on the adsorption capability were investigated. Experimental results were investigated using XRD, FT-IR, and SEM. It was found that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area. The activated carbons prepared by microwave heating with an activation process have higher surface area and larger average pore size than those prepared by activation without microwave heating when the ratio with KOH solution was the same. The activation time using microwave heating and the chemical impregnation ratio with KOH solution were varied to determine the optimal method for obtaining high surface area activated carbon (1505 m2/g).
        4,000원
        273.
        2012.06 구독 인증기관 무료, 개인회원 유료
        ADB는 경제를 활성화하고 빈곤을 감소시키기 위해 3개의 전략을 시행하였다.3개의 전 략은 포괄적인 경제성장 환경적으로 지속 가능한 성장, 지역적 통합이라 채택되었다. ADB 는 교육은 성장이라는 큰 그림에서 제외 될 수 없는 중요한 요인이라는 점을 강조하였다. 또한 ADB는 교육 이외에 (1) 사회기반시설, (2) 환경, (3) 지역적 협력과 통합 (4) 재정적 측면의 핵심영역을 가지고 있다. ADB는 교육이란 지속 가능한 개발과 지역적 통합을 지원하기 위한 의식을 고조 시키고 능력을 개발하는 점에서 매우 중요하며. 각기 다른 분야에서의 협력이 필요하다고 주장한 다. 그리고 협력은 아시아의 급속한 성장에 기인하여 연구 기업을 더 넓은 지역으로 확대 함으로써 국경을 넘어 선 협력과 지역적 통합을 이룰 수 있을 것이라 예측한다. 그리고 ADB는 지역적 통합 수립을 위하여 GMS. C돼EC. SASEC 와 같은 프로그램을 시행하고 있다.
        4,000원
        276.
        2012.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The present paper gives an overview about the Atom Probe Tomography technique and its application to powder materials. The preparation of needle-shaped Atom Probe specimens from a single powder particle using focused-ion-beam milling is described. Selected experimental data on mechanically alloyed (and sintered) powder materials are presented, giving insight into the atomic-scale elemental redistribution occurring under powder metallurgical processing.
        4,000원
        277.
        2011.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was focused on improvement of milk production in Mongolian dairy industry by artificial insemination (AI) technology, supported by ODA of KOICA in Republic of Korea. This program was started in January 2009 and it is in years. This manuscript summarized the data especially on estrus synchronization and pregnancy establishment in dairy cows (Holstein) this year. A total of 81 dairy cows from 4 private farms (38 from Undarmal milk and that of 30, 8 and 5 dairy cows from Onjin (Enkhbayer), Jargalant, and BRM School farms respectively) were synchronized with 5 ml Lutalyse (i.m.) in the dump of dairy cows and then estrus was detected 2 to 3 days after injection. The synchronized dairy cows were inseminated with 0.5 ml dairy frozen semen by conventional artificial insemination (AI) techniques. Pregnancy was diagnosed about 60 days after AI by palpation method. About 96.3% (78/81) of synchronized cows were responded to single injection. Total 75 over 78 dairy cows (90.1%) inseminated were diagnosed as pregnant. The estrus induction and pregnancy rates were very effective using Lutalyse injection and conventional AI techniques in Mongolian dairy cow. The present results indicated that AI after estrus induction in Mongolian dairy cows could be applied to dairy breeding technology for improving breeding efficiency and milk production of the country.
        4,000원
        278.
        2011.11 구독 인증기관 무료, 개인회원 유료
        Mongolia is aiming at connect and expand global trade to third countries using Russia, China and East Asian ports. Also, trying to evolve infrastructure and super-frastructure in international maritime transportation. This paper presents maritime development trends in Mongolia and focuses on discussing the current situation of international maritime plan and points out some issues currently facing by the policy to develop promotion. Finally, this paper presents some future directions for developing the maritime transportation in Mongolia.
        3,000원
        279.
        2011.10 구독 인증기관·개인회원 무료
        This study was focused on improvement of milk production in Mongolia dairy industry by artificial insemination (AI) technology, of which was supported from ODA project of KOICA in Republic of Korea. The study was started from January 2009 to present and 3rd years in this year. So, all data, especially synchronization and pregnancy of dairy cows (Holstein) will be summarized in final result in this year. For synchronization, total 81 dairy cows selected from 4 private farms that were 38, 30, 8 and 5 in Undarmal milk, Onjin (Enkhbayer), Jargalant, and BRM School, respectively. All the dairy cows were injected intramuscular (IM) of 5 ml PGF2α in the vulva and detected estrus 2 to 3 days after PGF2α injection. Total 78 out of 81 dairy cows (96.3%) were detected estrus by only 1 time injection of PGF2α. The dairy cows that were induced estrus, inseminated with 0.5 ml dairy frozen semen by conventional AI techniques. The pregnancy diagnosis of the AI dairy cows was detected by uterus palpation after 60 days of insemination. Total 75 from 78 inseminated dairy cows (90.1%) were diagnosis pregnant. The estrus induction and pregnant rate were very effective using PGF2α injection and conventional AI techniques in Mongolia dairy cow. The results indicated that AI after estrus induction in Mongolia dairy cows could be applied to dairy breeding technology to improve the breeding efficiency and milk production.
        280.
        2011.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In vitro maturation and activation of oocytes are primary steps towards biotechnological manipulation in embryology. The objectives of the present study were to determine the oocyte recovery rate per ovary, in vitro maturation rates of oocytes and rates of parthenogenetically activation of matured oocytes in Black Bengal goats. All visible follicles were aspirated to recover follicular fluid from individual ovaries (number of ovaries = 456). The immature cumulus oocyte complexes (COCs; n = 1289) were cultured in tissue culture medium (TCM)-199 supplemented with 10% (v/v) fetal bovine serum (FBS) for 27 hours at with 5% in humidified air. The matured oocytes (n = 248) were activated with 5 ionomycin for 5 minutes followed by treatment with 2 mM 6-dimethylaminopurine (6-DMAP) for 4 hours. After activation, oocytes were cultured for another 14 hours in TCM-199 supplemented with bovine serum albumin (BSA) at with 5% in humidified air. The pronucleus formation in activated oocytes was determined by staining with 1% orcein (whole mount technique). Matured oocytes (n = 176) without activation stimuli were used as control. The mean number of oocytes recovered per ovary was . The proportion of oocytes matured in vitro, confirmed by the presence of first polar body, was . Parthenogenetic activation, evidenced by formation of pronucleus, occurred in of matured oocytes. No pronucleus formation was observed in control oocytes. In conclusion, a combination of ionomycin and 6-DMAP induces activation in one third of Black Bengal goats' oocytes.
        4,000원