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    Wyświetlanie 1-13 z 13
    Tytuł:
    Analysis and Optimization of Micro Speaker-Box Using a Passive Radiator in Portable Device
    Autorzy:
    Jiang, Y.-W.
    Kwon, J.-H.
    Kim, H.-K.
    Hwang, S.-M.
    Powiązania:
    https://bibliotekanauki.pl/articles/176530.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    passive radiator
    speaker box
    SPL improvement
    Sound Pressure Level
    Opis:
    With the rapid development of multimedia devices such as smart phones and tablet PCs, microspeakers have been recently increasingly used for audio equipment. Improving the acoustic performance of a microspeaker is always a main concern, especially in the low frequency range. To avoid sound cancelation, a microspeaker unit is usually inserted into a speaker box. A passive radiator is also used in speaker boxes to improve the sound performance in the loudspeaker system. However, passive radiators have not been applied into microspeaker system. In this study, a speaker box with a passive radiator was analyzed and optimized to achieve a higher Sound Pressure Level (SPL) in a microspeaker system. The Finite Element Method (FEM), two-degree-of-freedom (DOF) vibration theory, and a plane circular piston sound source were used to study the electromagnetic, vibration, and acoustic characteristics, respectively. Optimization was conducted by changing the mass, stiffness, and size of the passive radiator. Based on the optimized parameters, a new sample was manufactured. The experiment results show that the SPL of the optimized speaker box with a passive radiator is improved by 5 dB at 200 Hz compared with the one without a radiator. The analysis results also matched the experiment results.
    Źródło:
    Archives of Acoustics; 2017, 42, 4; 753-760
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Atomistic Analysis Of Radiation-Induced Segregation In Ion-Irradiated Stainless Steel 316
    Analiza w skali atomowej indukowanej promieniowaniem segregacji w stali nierdzewnej 316
    Autorzy:
    Lee, G.-G.
    Jin, H.-H.
    Chang, K.
    Lee, B. H.
    Kwon, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/354713.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    atom probe tomography (APT)
    radiation-induced segregation (RIS)
    ion irradiation
    irradiation defects
    stainless steel
    APT
    RIS
    stal nierdzewna
    segregacja
    Opis:
    Stainless steel (SS) is a well-known material for the internal parts of nuclear power plants. It is known that these alloys exhibit radiation-induced segregation (RIS) at point defect sinks at moderate temperature, while in service. The RIS behavior of SS can be a potential problem by increasing the susceptibility to irradiation-assisted stress corrosion cracking. In this work, the RIS behavior of solute atoms at sinks in SS 316 irradiated with Fe4+ ions were characterized by atom probe tomography (APT). There were torus-shaped defects along with a depletion of Cr and enrichment of Ni and Si. These clusters are believed to be dislocation loops resulting from irradiation. The segregation of solutes was also observed for various defect shapes. These observations are consistent with other APT results from the literature. The composition of the clusters was analyzed quantitatively almost at the atomic scale. Despite the limitations of the experiments, the APT analysis was well suited for discovering the structure of irradiation defects and performing a quantitative analysis of RIS in irradiated specimens.
    Źródło:
    Archives of Metallurgy and Materials; 2015, 60, 2B; 1179-1184
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Factor Analysis of Safety for Visitors to a Mega-Event
    Autorzy:
    Kwon, Y. G.
    Park, H. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/90888.pdf
    Data publikacji:
    2002
    Wydawca:
    Centralny Instytut Ochrony Pracy
    Tematy:
    factor analysis
    safety
    mega-event
    event tourism
    czynniki bezpieczeństwa
    bezpieczeństwo uczestników imprez
    turystyka
    Opis:
    This paper investigated the safety factors considered by visitors to the Kwangju Biennale 2000 and analyzed the correlation between the safety factors and the demographic characteristics of the visitors. Global tourism increased throughout the 1990s, with the biggest surge occurring in the Asia-Pacific region. Long-distance travel is also increasing, and at a rate faster than the global average. The opportunities for event tourism appear to be strong almost everywhere, even though recessions may have an impact on these destinations. Along with this upward trend, competition for more desirable tourists is also surging (Getz, 1997). Therefore event tourism is appearing as a powerful method in the fierce competition around the tourism industry.
    Źródło:
    International Journal of Occupational Safety and Ergonomics; 2002, 8, 3; 365-375
    1080-3548
    Pojawia się w:
    International Journal of Occupational Safety and Ergonomics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Implementation of a Novel Audio Network Protocol
    Autorzy:
    Lee, J.
    Jeon, H.
    Choi, P.
    Kwon, S.
    Lee, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/178062.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    audio mixer
    AoIP
    audio over internet protocol
    DANTE
    SR System
    Opis:
    Recently, the rapid advancement of the IT industry has resulted in significant changes in audio-system configurations; particularly, the audio over internet protocol (AoIP) network-based audio-transmission technology has received favourable evaluations in this field. Applying the AoIP in a certain section of the multiple-cable zone is advantageous because the installation cost is lower than that for the existing systems, and the original sound is transmitted without any distortion. The existing AoIP-based technology, however, cannot control the audio-signal characteristics of every device and can only transmit multiple audio signals through a network. In this paper, the proposed Audio Network & Control Hierarchy Over peer-to-peer (Anchor) system enables all audio equipment to send and receive signals via a data network, and the receiving device can mix the signals of different IPs. Accordingly, it was possible to improve the system-application flexibility by simplifying the audio-system configuration. The research results confirmed that the received audio signals from different IPs were received, mixed, and output without errors. It is expected that Anchor will become a standard for audio-network protocols.
    Źródło:
    Archives of Acoustics; 2018, 43, 4; 637-645
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of patterns on image-based modelling of texture-less objects
    Autorzy:
    Hafeez, J.
    Jeon, H.-J.
    Hamacher, A.
    Kwon, S.-C.
    Lee, S.-H.
    Powiązania:
    https://bibliotekanauki.pl/articles/221814.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    structure-from-motion
    feature detection
    patterns analysis
    3D reconstruction
    surface comparison
    Opis:
    The task of generating fast and accurate three-dimensional (3D) models of objects or scenes through a sequence of non-calibrated images is an active field of research. The recent development in algorithm optimization has resulted in many automatic solutions that can provide an accurate 3D model from texture-full objects. Structure-from-motion (SfM) is an image-based method that uses discriminative point-based feature identifier, such as SIFT, to locate feature points in the images. This method faces difficulties when presented with the objects made of homogenous or texture-less surfaces. To reconstruct such surfaces a well-known technique is to apply an artificial variety by covering the surface with a random texture pattern prior to the image capturing process. In this work, we designed three series of image patterns which are tested based on the contrast and density ratio which increases from the first to the last pattern within the same series. The performance of the patterns is evaluated by reconstructing the surface of a texture-less object and comparing it with the true data. Using the best-found patterns from the experiments, a 3D model of a Moai statue is reconstructed. The experimental results demonstrate that the density and structure of a pattern highly affects the quality of the reconstruction.
    Źródło:
    Metrology and Measurement Systems; 2018, 25, 4; 755-767
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An analysis on the thermal characteristics according to the viscosity of bearing lubricant and the cooling condition for the high speed motor spindle
    Autorzy:
    Choi, D. B.
    Lee, J. J.
    Kim, S. T.
    Kwon, H. D.
    Kim, C. Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/1429194.pdf
    Data publikacji:
    2008
    Wydawca:
    Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
    Tematy:
    high speed motor spindle
    thermal displacement cooling condition
    lubricant viscosity
    Opis:
    Thermal displacement of the high speed machine tools has a large influence on machining accuracy. The high speed motor spindle with many heat sources is widely used for the high speed machine tools recently. The important problem in this spindle is to reduce and minimize the thermal effects by motor and bearings. This paper presents the analysis on thermal characteristics for high speed motor spindle system with oil-air lubricated angular contact ceramic ball bearings and built-in motor. An analysis on the thermal characteristics of spindle is performed according to the cooling conditions and the viscosity of bearing lubricants by using finite element method. This results can be applied to the design and manufacturing for the high speed motor spindle.
    Źródło:
    Journal of Machine Engineering; 2008, 8, 4; 88-98
    1895-7595
    2391-8071
    Pojawia się w:
    Journal of Machine Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect Of The Desorption-Recombination Temperature On The Microstructure And Magnetic Properties Of HDDR Processed Nd-Fe-B Powders
    Wpływ temperatury desorpcji-rekombinacji na mikrostrukturę i właściwości magnetyczne proszków Nd-Fe-B przetwarzanych metodą HDDR
    Autorzy:
    Lee, J.-G.
    Cha, H.-R.
    Liu, S.
    Yu, J.-H.
    Baek, Y.-K.
    Kwon, H.-W.
    Powiązania:
    https://bibliotekanauki.pl/articles/353723.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Nd-Fe-B
    HDDR
    permanent magnet
    grain boundary
    metoda HDDR
    magnes trwały
    granica ziarna
    Opis:
    The effect of the desorption-recombination temperature on the microstructure and magnetic properties of hydrogenation-disproportionation-desorption-recombination (HDDR) processed Nd-Fe-B powders was studied. The NdxB6.4Ga0.3Nb20.2Febal (x=12.5-13.5, at.%) casting alloys were pulverized after homogenizing annealing, and then subjected to HDDR treatment. During the HDDR process, desorption-recombination (DR) reaction was induced at two different temperature, 810°C and 820°C. The higher Nd content resulted in enhanced coercivity of the HDDR powder, and which was attributed to the thicker and more uniform Nd-rich phase along grain boundaries. But this uniform Nd-rich phase induced faster grain growth. The remanence of the powder DR-treated at 820°C is higher than that DR-treated at 810°C. In addition, it was also confirmed that higher DR temperature is much more effective to improve squareness.
    Źródło:
    Archives of Metallurgy and Materials; 2015, 60, 2B; 1499-1501
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Intrastratal flow in the Cretaceous Gyeokpori Formation (SW South Korea)
    Autorzy:
    Byun, Uk Hwan
    Van Loon, A.J. (Tom)
    Kwon, Yi Kyun
    Ko, Kyoungtae
    Powiązania:
    https://bibliotekanauki.pl/articles/2060260.pdf
    Data publikacji:
    2020
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    intrastratal flow
    Gyeokpori Formation
    soft-sediment deformation structures
    lacustrine environment
    Cretaceous
    Opis:
    Intrastratal flow is a process that is still poorly understood, rarely described and difficult to interpret in ancient rocks. Sediments in the Cretaceous lacustrine Gyeokpori Formation of southwestern South Korea contain some chaotically deformed sandstone layers with deformed mudstone clasts that are ascribed to this process. The interpretation is based on the fact that these layers cannot be explained as a result of subaqueous debris flows or mass transport, whereas the sedimentary context, including the presence of other soft-sediment deformation structures, indicates that intrastratal flow must have been physically possible. The sedimentary setting was a lake in which mainly siliciclastic rocks were deposited, with some interbedded volcaniclastics. The nearby volcanic activity caused seismic shocks that affected the unstable lake margins resulting in the dominance of gravity-flow deposits, but also in a high sedimentation rate that facilitated soft-sediment deformation partly caused by intrastratal flow. This must have happened fairly frequently during a probably limited time-span, as several layers showing traces of intrastratal flow are present within a succession of only <1 m thick. The combined data on the geological setting and our findings regarding the origin of the various soft-sediment deformation structures may help to recognize the traces left by intrastratal flow elsewhere in the geological record.
    Źródło:
    Geological Quarterly; 2020, 64, 3; 611--625
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new type of slumping-induced soft-sediment deformation structure: the envelope structure
    Autorzy:
    Byun, Uk Hwan
    van Loon, A. J. (Tom)
    Kwon, Yi Kyun
    Ko, Kyoungtae
    Powiązania:
    https://bibliotekanauki.pl/articles/950457.pdf
    Data publikacji:
    2019
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    Gyeokpori Formation
    Cretaceous
    lacustrine environment
    slumping
    conglomerate
    kreda
    środowisko jeziorne
    opadanie
    konglomerat
    Opis:
    The sediments of the Cretaceous Gyeokpori Formation in south-western South Korea accumulated in a lake in which mainly siliciclastic rocks were deposited, with some interbedded volcaniclastics. The nearby volcanic activity resulted in unstable lake margins inducing a dominance of gravity-flow deposits. The high sedimentation rate facilitated soft-sediment deformation on the sloping margin. The deposition of numerous gravity-flow deposits resulted in a vertically heterolithic stratification. The slumps are composed of different lithologies, which is expressed in different types of deformation due to the difference in cohesion between sandy and mussy layers within the slumps. Coarser-grained (cohesionless) slumps tend to show more chaotic deformation of their lamination or layering. The difference in slumping behaviour of the cohesive and non-cohesive examples is explained and modelled. A unique soft-sediment deformation structure is recognized. This structure has not been described before, and we call it ‘envelope structure’. It consists of a conglomerate mass that has become entirely embedded in fine-grained sediment because slope failure took place and the fine-grained material slumped down with the conglomerate ‘at its back’. The cohesive laminated mudstone formed locally slump folds that embedded the non-cohesive overlying conglomerate unit, possibly partly due to the bulldozing effect of the latter. This structure presumably can develop when the density contrast with the underlying and overlying deposits is exceptionally high. The envelope structure should be regarded as a special – and rare – type of a slumping-induced deformation structure.
    Źródło:
    Geologos; 2019, 25, 2; 111-124
    1426-8981
    2080-6574
    Pojawia się w:
    Geologos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of InAs Coverage on Transition of Size Distribution and Optical Properties of InAs Quantum Dots
    Autorzy:
    Kim, G.
    Jeon, S.
    Cho, M.
    Choi, H.
    Kim, D.
    Kim, M.
    Kwon, Y.
    Choe, J.
    Kim, J.
    Leem, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535820.pdf
    Data publikacji:
    2010-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.15.Hi
    68.37.Ps
    78.55.Cr
    78.67.Hc
    Opis:
    The influence of InAs coverage on the formation of self-assembled quantum dots grown by molecular-beam epitaxy was investigated by atomic force microscopy and photoluminescence measurements. As the InAs coverage increased from 2.0 to 3.0 monolayers, the quantum dot density decreased from 1.1 × $10^{11}$ to 1.36 × $10^{10} cm^{-2}$. This result could be attributed to the coalescence of neighboring small InAs quantum dots resulting in the formation of much larger InAs quantum dots with lower quantum dot density. Atomic force microscopy results revealed that as the InAs quantum dot coverage increased, the transition of size distribution of InAs quantum dots from single-modal to multimodal occurred. The temperature-dependent photoluminescence spectra showed that the photoluminescence spectra red shifted and the photoluminescence peak intensity decreased as the InAs coverage increased. The thermal activation energy was strongly dependent on the InAs coverage, and for InAs quantum dots with 3.0 ML thick InAs coverage, this energy was estimated to be 147 meV.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 4; 673-676
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Morphology Change Of Si Deposit In Molten Salt Electrorefining
    Zmiana morfologii osadu Si podczas elektrorafinacji w stopionych solach
    Autorzy:
    Ryu, H. Y.
    Kwon, S. C.
    Han, M. H.
    An, Y. S.
    Lee, J. S.
    Lee, J. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/354346.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    molten salt
    silicon
    morphology
    electrorefining
    current density
    sól stopiona
    krzem
    morfologia
    elektrorafinacja
    gęstość prądu
    Opis:
    The effects of processing parameters on the morphology change in a Si deposit recovered by means of molten salt electrorefining are evaluated using electrochemical techniques such as cyclic voltammetry and chronopotentiometry at 800°C. It was found that concentration of K2SiF6 and current density were important parameters in determining deposit size. Higher concentrations of K2SiF6 were effective in coarsening the silicon deposit and decreasing the cell potential. Silicon nanofiber was recovered at 5 wt% of K2SiF6 whereas dense particles were prepared at 30 and 50 wt% of K2SiF6. The morphology of the Si deposit was determined by the concentration of Si in the electrolyte which is related to the formation of crystal and growth of Si. The formation mechanism of the Si deposit was interpreted by using high resolution TEM as well as electrochemical properties.
    Źródło:
    Archives of Metallurgy and Materials; 2015, 60, 2B; 1491-1497
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Study On The Metal Carbide Composite Diffusion Bonding For Mechanical Seal
    Badanie łączenia dyfuzyjnego kompozytu metal węglik na mechaniczne uszczelnienie
    Autorzy:
    Kim, D.-K.
    Shon, I.-J.
    Song, J.
    Ryu, W.-J.
    Shin, H.-Ch.
    Kwon, E.-Y.
    Shin, H.
    Kang, S.-J.
    Powiązania:
    https://bibliotekanauki.pl/articles/356399.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    diffusion bonding
    nanostructures
    mechanical seal
    hard metal
    mechanical properties
    łączenie
    nanostruktura
    uszczelnienie mechaniczne
    twardy metal
    właściwości mechaniczne
    Opis:
    Mechanical Seal use highly efficient alternative water having a great quantity of an aqueous solution and has an advantage no corrosion brine. Metal Carbide composites have been investigated as potential materials for high temperature structural applications and for application in the processing industry. The existing Mechanical seal material is a highly expensive carbide alloy, and it is difficult to take a price advantage. Therefore the study of replacing body area with inexpensive steel material excluding O-ring and contact area which demands high characteristics is needed. The development of WC-Ni base carbide alloy optimal bonding composition technique was accomplished in this study. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. The bonding statuses of this test specimen were excellent. The hardness of specimen and bonding rate were measured using ultrasound equipment. In this work, Powder of WC (involved VC, Cr), Co and Mo2C mixed by attrition milling for 24hours. Nanostructured WC-27.6wt.%Ni-1.5wt.%Si-0.11wt.%VC-1.1wt.%B4C composite were fabricated at 1190°C by high temperature vacuum furnace. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. Its relative density was about 99.7%. The mechanical properties (hardness and fracture toughness) were 87.2 HRA and 4.2 M·Pam1/2, respectively. The bonding status of this test specimen was excellent and the thickness of bonding layer was 20 ~30§ at 1050 and 1060°C bonding temperature.
    Źródło:
    Archives of Metallurgy and Materials; 2015, 60, 2B; 1479-1483
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect Of Ti Powder Addition On The Fabrication Of TiO2 Nanopowders
    Wpływ dodatku nanoproszku Ti na zagęszczanie i spiekanie nanoproszków TiO2
    Autorzy:
    Raihanuzzaman, R. M.
    Park, H. Y.
    Ghomashchi, R.
    Kwon, T. H.
    Son, H.-T.
    Hong, S.-J.
    Powiązania:
    https://bibliotekanauki.pl/articles/353186.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    TiO2 nanopowder
    magnetic pulsed compaction
    densification
    sintering
    nanoproszek Ti
    magnetyczne zagęszczanie impulsowe
    zagęszczanie
    spiekanie
    Opis:
    Sintered samples of Ti added TiO2 nanopowders were fabricated by combined application of magnetic pulsed compaction (MPC) and sintering. The effect of Ti nano powder on density, shrinkage and hardness of the samples were investigated as part of the study. The optimum processing conditions were found to be around 0.5 GPa MPC pressure and 1450°C sintering temperature, illustrating maximum density, hardness and minimum shrinkage. High pressure compaction using MPC was found to enhance density with increasing MPC pressure up to 0.9 GPa, and significantly reduce the total shrinkage (about 16% in this case) in the sintered bulks compared to other general processes (about 18%). While sintered samples blended with micro Ti showed presence of microstructural cracks, the samples with 1-2% nano Ti had less or no cracks on them. Overall, the inclusion of nano Ti indicated improvement in mechanical properties of TiO2 nanopowders sintered preforms as opposed to micro Ti-added TiO2.
    Źródło:
    Archives of Metallurgy and Materials; 2015, 60, 2B; 1473-1477
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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