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Now showing items 1 - 16 of 39

  • Structural and magnetocaloric properties of novel gadolinium borohydrides

    Pascal Schouwink   Emilie Didelot   Young-Su Lee   Thomas Mazet   Radovan Černý  

    Abstract Novel Gd-based mixed-metal borohydrides A n Gd(BH 4 ) n+3 (A = K, Cs) are described in view of their magnetic cooling properties at cryogenic temperatures. The magnetic entropy changes correlate well with Gd 3+ isolation and structural dimensionality in the discovered perovskite-type and other compounds. Crystal structures are resolved from Synchrotron X-ray Powder Diffraction and refined with solid state calculations. The isolated Gd-centres in five-fold coordination in K 2 Gd(BH 4 ) 5 , the first representative of a new structure type, lead to exceptionally high mass magnetic entropy change of 54.6 J kg −1 K −1 at the maximum field change of 9 T. Graphical abstract Highlights • We investigate novel gadolinium borohydride salts in view of magnetic refrigeration. • DFT-optimized structural properties are correlated with magnetic entropy changes. • Two new 5-fold coordination polyhedra [Gd(BH 4 ) 5 ] 2− are discovered. • A large magnetocaloric effect is attained with the lightweight borohydride linker.
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  • Mechanism for Z-phase formation in 11CrMoVNbN martensitic heat-resistant steel

    Myung-Yeon Kim   Sung-Min Hong   Kyu-Ho Lee   Woo-Sang Jung   Young-Su Lee   Young-Kook Lee   Jae-Hyeok Shim  

    Abstract The mechanism for the formation of Z-phase was investigated for samples of an 11CrMoVNbN steel aged at 593 °C for up to 50,000 h. X-ray diffraction indicates that Z-phase appears after 5000 h of aging, and its amount gradually increases up to 50,000 h aging at the expense of mainly Cr 2 N. Transmission electron microscopy shows that Z-phase nucleates in the V-enriched rim region of Cr 2 N precipitates, which forms due to the diffusion of V into the precipitates from the matrix. Nucleated Z-phase tends to grow relatively rapidly compared with the preexisting precipitates such as Nb(C,N) and M 23 C 6 . Z-phase seems to consume Cr 2 N by the nucleation and growth mechanism rather than the transformation mechanism. The main difference in the aged samples is that the Nb content of Z-phase is lower and that Z-phase does not replace Cr 2 N completely, compared to the results of the crept samples. Graphical abstract Image 1 Highlights • Precipitation is studied for a martensitic steel aged at 593 °C for up to 50,000 h. • Z-phase nucleates in the V-enriched rim region of Cr 2 N precipitates after 5000 h. • Z-phase seems to consume Cr 2 N by the nucleation and growth mechanism.
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  • Boron–nitrogen based hydrides and reactive composites for hydrogen storage

    Lars H. Jepsen   Morten B. Ley   Young-Su Lee   Young Whan Cho   Martin Dornheim   Jens Oluf Jensen   Yaroslav Filinchuk   Jens Erik Jørgensen   Flemming Besenbacher   Torben R. Jensen  

    Hydrogen forms chemical compounds with most other elements and forms a variety of different chemical bonds. This fascinating chemistry of hydrogen has continuously provided new materials and composites with new prospects for rational design and the tailoring of properties. This review highlights a range of new boron and nitrogen based hydrides and illustrates how hydrogen release and uptake properties can be improved.
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  • Stability of quadratic functional equations in generalized functions

    Young-Su Lee  

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  • On the stability of a mixed type quadratic-additive functional equation

    Young-Su Lee   Junyeop Na   Heejong Woo  

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  • Image forming apparatus

    An image forming apparatus includes a main body; at least one developer including an image carrier unit having an image carrier and a charged body charging the image carrier, a developing unit installed to swing at a predetermined angle with respect to the image carrier unit and having a developing roller, and a pressing member pressing the developing unit so that the developing roller comes in contact with the image carrier, and separably installed in the main body; a nip separation unit installed in the main body on one side of the developer to swing the developing unit so that the developing unit is in a position that is separated from the image carrier; and a control unit controlling the developer and the nip separation unit according to a print command.
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  • Superstability of generalized cauchy functional equations

    Young-Su Lee   Soon-Yeong Chung  

    In this paper, we consider the stability of generalized Cauchy functional equations such as Especially interesting is that such equations have the Hyers-Ulam stability or superstability whether g is identically one or not. 2000 Mathematics Subject Classification: 39B52, 39B82.
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  • Stability of quadratic functional equations in tempered distributions

    Young-Su Lee  

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  • Developing unit and image forming apparatus employing the same

    A developing unit includes a toner storage portion containing toner and including a toner supply member, a development portion disposed above the toner storage portion and containing the toner supplied from the toner storage portion by the toner supply member, and including a developing roller and a supply roller to supply the toner to the developing roller, and a partition wall to divide the toner storage portion and the development portion, and including an opening portion disposed under the lowest portion of the supply roller and forming a path of the toner supplied from the toner storage portion to the development portion.
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  • Mooring system for a vessel

    A mooring system for a vessel includes an attachment unit configured to be detachably attached to a hull of the vessel; a robot arm including a plurality of arms, the arms being coupled to each other to turn in a vertical direction, the robot, arm extending by an arm actuator provided thereto to transfer the attachment unit to an attachment position of the hull; a rotation unit connected to the robot arm and allowing the robot arm to turn in a horizontal direction; and a mooring winch for winding a mooring cable to draw the attachment unit. A floating body or a quay wall may include the mooring system.
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  • Wiping assembly and image forming apparatus having the same

    An inkjet image forming apparatus includes a main body frame, a medium supplying unit which is coupled to the main body frame and supplying a print medium, an image forming cartridge which is coupled to the main body frame, forms an image on the supplied print medium, and including a nozzle to eject ink, and a wiping assembly which wipes the nozzle. The wiping assembly includes a wiping sheet storage unit in which the wiping sheet is stored as being wound, a transfer shuttle which moves along arrangement of the nozzle by a driving force of a driving source, a pressing member which is provided in the transfer shuttle and presses a region of the wiping sheet against the nozzle to perform wiping using the wiping sheet, and a wiping sheet support unit which is provided in the transfer shuttle and restricts move of the wiping sheet while the nozzle is wiped.
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  • On the stability of a mixed type functional equation in generalized functions

    Young-Su Lee  

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  • OFDM receivers using oversampling with rational sampling ratios

    Young-Su Lee   Bo-Seok Seo  

    In this paper, we propose orthogonal frequency division multiplexing (OFDM) receivers using oversampling, where the oversampling ratio is extended from integers to rational numbers. We propose several receiver structures, which reveal the same performance, with the same oversampling ratio. Since the low-pass filters in general OFDM receivers are not ideal, additional noise is introduced into the side bands of the demodulated signal. If we increase the sampling frequency above the symbol rate, subcarriers with higher frequencies than we want are obtained and composed of noise only. Removing the unwanted higher frequency components we can reduce the noise and obtain signal-to-noise power ratio gain compared to the conventional symbol rate receivers. Through computer simulations, we verify the proposed method.
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  • Ink supply unit, print head assembly and image forming apparatus

    A printhead assembly, an image forming apparatus and an ink supply unit supply color inks to a plurality of printheads which are arranged in a direction transverse to an advancing direction of a printing medium. The ink supply unit may include a first channel member to receive different color inks, a second channel member engaged with the first channel member to divide each of the supplied color inks to a plurality of sets of first unit channels corresponding in number to the plurality of printheads, and a third channel member engaged with the second channel member. A plurality of second unit channels of the third channel member may supply each of the color inks being supplied from the first unit channels to each of the printheads. A support plate may be used to support the first, second, and third channel members in a stack structure.
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  • Array printhead and inkjet image forming apparatus having the same

    An array printhead and an image forming apparatus having the same. The array printhead includes a first member, a second member, and a third member. The first, second, and third members sequentially overlap and couple to each other. The first member supplies ink of different colors to the second member and the second member separately receives the ink of different colors supplied from the first member and allows the ink to flow to the third member. The third member includes a plurality of head chips. A plurality of supply grooves are formed in a side of the third member on which the plurality of head chips are mounted. The plurality of supply grooves includes a plurality of supply holes that provide the ink of different colors supplied from the second member to the plurality of head chips. The plurality of supply holes are located on an axis different from axes of other adjacent supply holes with respect to a direction perpendicular to a width direction of a print medium.
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  • Array type printhead and inkjet image forming apparatus having the same

    An array printhead and an inkjet image forming apparatus having the same are include a first member, a second member, a third member, and a support member. The first through third members and the support member sequentially overlap and couple to each other. The first member supplies ink of different colors into the second member and the second member separately receives the ink of different colors supplied from the first member. The third member includes a plurality of head chips that eject ink supplied from the second member thereon and the support member fixes the first member, the second member, and the third member using a plurality of coupling elements.
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