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        검색결과 417

        243.
        2006.09 구독 인증기관·개인회원 무료
        The paper investigates the possibility to avoid extrinsic embrittlement of , also increasing the high temperature strength, by alloying with both Fe - of a high strengthening effect and Cr - able to remove a part of diffused oxygen along the grain boundaries. As Cr homogenization in is difficult because of its low diffusion coefficient, for its improving a mechanical alloying (MA) step before the compound synthesis by Self-propagating High-temperature Synthesis (SHS) was adopted. The obtained better homogenization resulted in higher mechanical resistance and deformability than of the unalloyed alloys of the same composition obtained without MA step.
        244.
        2006.09 구독 인증기관·개인회원 무료
        Considering the idea that some properties, especially the mechanical properties of at ambient temperature can be improved by adding of some substitutional/interstitial elements, our goal was to obtain these materials starting from mechano-composites powders. In this aim, using mechanical alloying techniques three type of mechano-composite powders starting from elemental powders were obtained. Then, by reactive sintering in argon atmosphere at temperature over , alloyed materials were realized. This paper presents our research results regarding the microstructural aspects and phase formation in obtained materials.
        247.
        2006.04 구독 인증기관·개인회원 무료
        Behavior of stoichiometric and near-stoichiometric NiAl at plasma spray deposition, without and with a bond coat, for coating layers realization on a low alloyed steel substrate, has been investigated. In all variants, NiAl particle melting and subsequent welding at the impact with substrate were observed, forming a relatively compact and adherent coating layer with the NiAl stability maintaining - all assuring the coating layer oxidation and corrosion resistance. Good results from these points of view, also validated through corrosion tests, were obtained for 45:55 Ni:Al composition without a bond coat but adopting an Ar protective surrounding of plasma jet.
        248.
        2006.04 구독 인증기관·개인회원 무료
        The present paper investigates the possibilities of niobium using for the mechanical properties of the common low alloyed Cu-Ni-Mo-C sintered structural steels enhancing. On both thermodynamic and experimental bases there were demonstrated the Nb nitrides/carbides/carbonitrides preferential formation in these steels during sintering in dissociated ammonia at both common and elevated temperatures. The obtained results for fine Nb powder and 0.3% graphite additions to Distaloy AB iron base powder cold compacted and sintered in dissociated ammonia proved the expected strengthening effect, leading to higher mechanical properties of the processed steels than of the common Cu-Ni-Mo-C ones.
        249.
        2006.04 구독 인증기관·개인회원 무료
        The process of coprecipitation of biocomposite hydroxyapatite/chitosan from aqueous solution at low temperature in alkali environnement was examined. We have shown that initially we have the formation of amorphous octocalcium phosphates and the transferring from OCP to amorphous calcium phosphate , and then from TCP to calcium-deficient hydroxyapatite and hydroxyapatite . The transformation of ACP to HAP was inhibited in the presence of chitosan. The result suggests that there is an affinity binding between ACP and chitosan and subsequently blocking the active growth site of ACP.
        250.
        2006.04 구독 인증기관·개인회원 무료
        The paper presents some results regarding the obtaining of some copper heat pipes with a porous copper internal layer for electronic components cooling. The heat pipes were realized by sintering of spherical copper powders of size directly on the internal side of a copper pipe of 18 mm in diameter. The obtained pipes were then brazed in order to obtain a heat pipe of 0.5 m in length. After that, the heat pipe was sealed and filled with a small quantity of distilled water as working fluid. To establish the total heat transport coefficient and the thermal flow transferred at the evaporator, some external devices were realized to allow the heating of the evaporator and the cooling of the condenser. Water heat pipes are explored in the intermediate temperature range of 303 up to 500 K. Test data are reported for copper water heat pipe, which was tested under different orientations. The obtained results show that the water heat pipe has a good thermal transfer performance in the temperatures range between 345 and 463 K.
        251.
        2006.04 구독 인증기관·개인회원 무료
        In the present research work was searched the influence of severe plastic deformation (SPD) realized by ECAP (equalchannel angular pressing) on structural, mechanical and plastic properties of IF (interstitial free) steel. For physical simulation ECAP process with right angle channels was used. The ECAP process was numerical simulated (namely its course of temperature, strain and stress fields and deformation forces) by FormFEM software, too.
        252.
        2005.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present mm observations with the IRAM 30m radiotelescope of the HCN (J=1-0) and HCO+ (J=1-0) emission lines from Giant Moleculat Clouds (GMC) in the disk of the Andromeda Galaxy, The selected GMC targets have various morphology and environments, including locations within spiral arms or in interarm regions and with galactocentric radii ranging from 2.4 to 15.5 kpc over the disk. The radial distributions of the ratios HCN/CO and HCO+ /CO are discussed and their values are compared to other galaxies.
        3,000원
        253.
        2005.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present the high-resolution (2"-4") images of the molecular envelopes surrounding the evolved stars, V Hya, VY CMa, and π1 Gru observed with the Submillimeter Array. The CO J=2-1 and 3-2 images of the carbon star V Hya show that the circumstellar structure of this star consists of three kinematic components; there is a flattened disk-like envelope that is expanding with a velocity of ~16 km s-1, the second component is the medium-velocity wind having a deprojected velocity of 40-120 km s-l moving along the disk plane, and the third one is the bipolar molecular jet having an extreme velocity of 70-185 km s-l. The axis of this high velocity jet is perpendicular to the plane of the disk-like envelope. We found that the circumstellar structure of the S-star π1 Gru traced by the CO J =2-1 resembles that of V Hya quite closely; the star is surrounded by the expanding disk-like envelope and is driving the medium-velocity wind along the disk plane. We also obtained the excellent images of VY CMa with the CO and 13CO J=2-1 and SO 65-54 lines. The maps of three molecular lines show that the envelope has a significant velocity gradient in the east-west direction, suggesting that the envelope surrounding VY CMa is also flattened and expanding along its radial direction. The high-resolution images obtained with the SMA show that some AGB stars are associated with the asymmetric mass loss including the equatorial wind and bipolar jet.
        3,000원
        256.
        2004.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present an update on our proposal that during the 'quasar era' (1.5 ≲ z ≲ 3), powerful radio galaxies could have played a major role in the enhanced global star-formation, and in the widespread magnetization and metal pollution of the universe. A key ingredient of this proposal is our estimate that the true cosmological evolution of the radio galaxy population is likely to be even steeper than what has been inferred from flux-limited samples of radio sources with redshift data, when an allowance is made for the inverse Compton losses on the cosmic microwave background which were much greater at higher redshifts. We thus estimate that a large fraction of the clumps of proto-galactic material within the cosmic web of filaments was probably impacted by the expanding lobes of radio galaxies during the quasar era. Some recently published observational evidence and simulations which provide support for this picture are pointed out. We also show that the inverse Compton x-ray emission from the population of radio galaxies during the quasar era, which we inferred to be largely missing from the derived radio luminosity function, is still only a small fraction of the observed soft x-ray background (XRB) and hence the limit imposed on this scenario by the XRB is not violated.
        4,000원
        258.
        2002.10 구독 인증기관 무료, 개인회원 유료
        At present, most of web-based applications are on the basis of HTML-based form documents. These HTML-based form documents only play a role as user interfaces, but they don"t involve the procedures or rules of processing business works that aim to documents. However, form documents imply methods for treating documents, and these procedural knowledge embedded can utilize to actively perform business work processes. Procedural knowledge is defined in ERML(Executable Rule Markup Language), which is a XML-based rule markup language that has a format of Prolog rules. The ERML is not only executable in an inference engine, but also can be geared with WfMS (Workflow Management System) and can be used in a heterogeneous rule-based application. Thus, this paper proposes a ERML-based scheme for processing active documents as device for automating a workflow that involve a process of treating documents. Our active documents themselves involve declarative knowledge to support the process and control of business rules embedded in documents and the automation of processing documents. Also, we propose a framework for processing the defined active documents. In order to demonstrate the usefulness of the proposed framework, a prototype called ActiveWebForm is designed and implemented for a case of processing a request for requisition of IP(Internet Procurement) system. As a result, our approach is expected to contribute to intelligence and automation of Internet applications as processing documents by embedding declarative knowledge.
        4,000원
        259.
        2001.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Modified inert gas condensation method was used to produce the nanocluster composites of . High-resolution TEM, SEM and catalytic measurements have been used to characterize the samples and study the synergistic effect between the CuO phase and (ceria) support. By varying the He pressure, the heating temperature and configuration of the heating boats inside the modified gas condensation chamber, nanoclusters of varying sizes, shapes and composition can be produced. The composition and nanostructured morphology were shown to influence the catalytic properties of the system. A copper content around 10 at% with a morphology that favors high-energy surfaces of ceria is shown to be beneficial for a high catalytic activity.
        3,000원