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    Wyświetlanie 1-8 z 8
    Tytuł:
    The multiplicity of solutions and geometry of a nonlinear elliptic equation
    Autorzy:
    Choi, Q-Heung
    Chun, Sungki
    Jung, Tacksun
    Powiązania:
    https://bibliotekanauki.pl/articles/1287320.pdf
    Data publikacji:
    1996
    Wydawca:
    Polska Akademia Nauk. Instytut Matematyczny PAN
    Opis:
    Let Ω be a bounded domain in $ℝ^n$ with smooth boundary ∂Ω and let L denote a second order linear elliptic differential operator and a mapping from $L^2(Ω)$ into itself with compact inverse, with eigenvalues $-λ_{i}$, each repeated according to its multiplicity, 0 < λ_{1} < λ_{2} < λ_{3} ≤ ... ≤ λ_{i} ≤ ... → ∞. We consider a semilinear elliptic Dirichlet problem $Lu+bu^+-au^-=f(x)$ in Ω, u=0 on ∂ Ω. We assume that $a < λ_{1}$, $λ_{2} < b < λ_{3}$ and f is generated by $ϕ_{1}$ and $ϕ_{2}$. We show a relation between the multiplicity of solutions and source terms in the equation.
    Źródło:
    Studia Mathematica; 1996, 120, 3; 259-270
    0039-3223
    Pojawia się w:
    Studia Mathematica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Defect Detection Using Deep Learning-Based YOLOv3 in Cross-Sectional Image of Additive Manufacturing
    Autorzy:
    Choi, Byungjoo
    Choi, Yongjun
    Lee, Moon-Gu
    Kim, Jung-Sub
    Lee, Sang-Won
    Jeon, Yongho
    Powiązania:
    https://bibliotekanauki.pl/articles/2048889.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    additive manufacturing
    deposition defect
    data augmentation
    YOLOv3
    object detection
    Opis:
    Deposition defects like porosity, crack and lack of fusion in additive manufacturing process is a major obstacle to commercialization of the process. Thus, metallurgical microscopy analysis has been mainly conducted to optimize process conditions by detecting and investigating the defects. However, these defect detection methods indicate a deviation from the operator’s experience. In this study, artificial intelligence based YOLOv3 of object detection algorithm was applied to avoid the human dependency. The algorithm aims to automatically find and label the defects. To enable the aim, 80 training images and 20 verification images were prepared, and they were amplified into 640 training images and 160 verification images using augmentation algorithm of rotation, movement and scale down, randomly. To evaluate the performance of the algorithm, total loss was derived as the sum of localization loss, confidence loss, and classification loss. In the training process, the total loss was 8.672 for the initial 100 sample images. However, the total loss was reduced to 5.841 after training with additional 800 images. For the verification of the proposed method, new defect images were input and then the mean Average Precision (mAP) in terms of precision and recall was 0.3795. Therefore, the detection performance with high accuracy can be applied to industry for avoiding human errors.
    Źródło:
    Archives of Metallurgy and Materials; 2021, 66, 4; 1037-1041
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structural, Electrical, and Optical Properties of ZnO Films Grown by Atomic Layer Deposition at Low Temperature
    Autorzy:
    Park, Ji-Young
    Weon, Ye Bin
    Jung, Myeong Jun
    Choi, Byung Joon
    Powiązania:
    https://bibliotekanauki.pl/articles/2174578.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    zinc oxide
    ZnO
    atomic layer deposition
    low temperature growth
    optoelectronic properties
    Opis:
    Zinc oxide (ZnO) is a prominent n-type semiconductor material used in optoelectronic devices owing to the wide bandgap and transparency. The low-temperature growth of ZnO thin films expands diverse applications, such as growth on glass and organic materials, and it is also cost effective. However, the optical and electrical properties of ZnO films grown at low temperatures may be inferior owing to their low crystallinity and impurities. In this study, ZnO thin films were prepared by atomic layer deposition on SiO2 and glass substrates in the temperature range of 46-141℃. All films had a hexagonal würtzite structure. The carrier concentration and electrical conductivity were also investigated. The low-temperature grown films showed similar carrier concentration (a few 1019 cm-3 at 141°C), but possessed lower electrical conductivity compared to high-temperature (>200°C) grown films. The optical transmittance of 20 nm thin ZnO film reached approximately 90% under visible light irradiation. Additionally, bandgap energies in the range of 3.23-3.28 eV were determined from the Tauc plot. Overall, the optical properties were comparable to those of ZnO films grown at high temperature.
    Źródło:
    Archives of Metallurgy and Materials; 2022, 67, 4; 1503--1506
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Friction and Wear Behavior of Direct Metal Deposition on SUH3
    Autorzy:
    Choi, Byungjoo
    Cho, In-Sik
    Jung, Do-Hyun
    Lee, Moon G.
    Jeon, Yongho
    Powiązania:
    https://bibliotekanauki.pl/articles/352111.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    direct metal deposition
    heat pretreatment
    friction test
    wear test
    micro-hardness
    Opis:
    Poppet valves made from high-frequency heat-treated SUH3 steel have insufficient durability, and scratches appear on the valve face in prolonged use. It is necessary to develop surface treatment technology with excellent durability to prevent the deterioration of engine performance. Therefore, a surface treatment technology with higher abrasion resistance than existing processes was developed by direct metal deposition to the face where the cylinder and valve are closed. In this study, heat pretreatment and deposition tests were performed on three materials to find suitable powders. In the performance evaluation, the hardness, friction coefficient, and wear rate were measured. Direct metal deposition using Inconel 738 and Stellite 6 powders without heat pretreatment were experimentally verified to have excellent durability.
    Źródło:
    Archives of Metallurgy and Materials; 2019, 64, 3; 841-844
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new marine ciliate, Metaurostylopsis antarctica nov. spec. (Ciliophora, Urostylida) from the Antarctic Ocean
    Autorzy:
    JUNG, Jae-Ho
    Baek, Ye-Seul
    Kim, Sanghee
    Choi, Han-Gu
    Min, Gi-Sik
    Powiązania:
    https://bibliotekanauki.pl/articles/763640.pdf
    Data publikacji:
    2011
    Wydawca:
    Uniwersytet Jagielloński. Wydawnictwo Uniwersytetu Jagiellońskiego
    Tematy:
    Antarctic Ocean, marine ciliate, Metaurostylopsis antarctica, infraciliature, morphogenesis, SSU rRNA
    Opis:
    In this study, a new marine urostylid ciliate, Metaurostylopsis antarctica nov. spec. collected from the Antarctic Ocean was investigated using morphological, morphometrical, and molecular methods. Metaurostylopsis antarctica nov. spec. is characterized as follows: slender to ellipsoid form in body shape; two types of cortical granules, ellipsoid large one (type I, yellow-green, 1.5 × 1 μm) in rows along dorsal kineties and cirri, circular small one (type II, colourless, 0.3 μm in diameter) scattered throughout whole body; 19–24 adoral membranelles, 4 frontal cirri, 2–5 frontoterminal cirri, 1 buccal and 2 transverse cirri; 3–5 midventral pairs, 10–15 cirri of midventral row; 1 right and 2 left marginal rows; 3 dorsal kineties; about 43 macronuclear nodules. This new species mainly differs from the congeners by the number of marginal rows (1 vs. 3 or more on right side; 2 vs. 3 or more on left side). In addition, proter’s oral primordium  developed on the right side of the oral cavity (vs. in center of oral cavity), and the rightmost anlage splits into two parts, nam ely, the frontoterminal cirri and a transverse cirrus (vs. only frontoterminal cirri). Inter-specific dissimilarities of the SSU rRNA gene between the congeners range from 3.3 to 4.4%.
    Źródło:
    Acta Protozoologica; 2011, 50, 4
    1689-0027
    Pojawia się w:
    Acta Protozoologica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Corrosion Behavior of Hastelloy® C-2000® Ni-Cr-Mo-Fe Alloys in the Entrained-Flow Coal Gasification Syngas Plants
    Autorzy:
    Lee, Sungkyu
    Kim, Min-Jung
    Choi, Nuri
    Hwang, Sang Yeon
    Chung, Seok-Woo
    Lee, Seung-Kong
    Yun, Yongseung
    Powiązania:
    https://bibliotekanauki.pl/articles/352403.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    mixed oxidant corrosion
    Hastelloy® C-2000® Ni-Cr-Mo-Fe alloy
    coal gasification
    high temperature halogencorrosion
    hydrated chlorides
    Opis:
    A mechanistic exposure experiment was performed on the commercially available and welded Ni-Cr-Mo-Fe alloy samples used in the piping materials of the coal gasification pilot plant. Thermodynamic Ellingham-Pourbaix stability diagrams were constructed to provide insight into the mechanism of the observed corrosion behavior. The thermodynamic inference on the corrosion mechanism was supplemented with the morphological, compositional and microstructural analyses of the exposed samples using scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy analyses. X-ray diffraction result revealed stable corrosion products of NiO, MoNi4 and Cr4.6 MoNi2.1 after accumulated total exposure duration of 139 h to the corrosive atmosphere. Scanning electron microscopy and energy-dispersive X-ray spectroscopy positively identified formation of rather continuous and adherent pre-oxidation corrosion products although extensively peeled-off oxides were finally observed as corrosion scales on the post-exposure alloy samples, which were attributed to the chlorination/oxidation into thin (spalled) oxides.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 2; 869-878
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Design and performance of dual-band MWIR/LWIR focal plane arrays based on a type-II superlattice nBn structure
    Autorzy:
    Lee, Hyun-Jin
    Eom, Jun Ho
    Jung, Hyun Chul
    Kang, Ko-Ku
    Ryu, Seong Min
    Jang, Ahreum
    Kim, Jong Gi
    Kim, Young Ho
    Jung, Han
    Kim, Sun Ho
    Choi, Jong Hwa
    Powiązania:
    https://bibliotekanauki.pl/articles/2204217.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    InAs/GaSb type-II superlattice
    dualband detector
    dark current
    spectral quantum efficiency
    noise equivalent temperature difference
    Opis:
    Dual-band infrared detector, which acquires more image information than single-band detectors, has excellent detection, recognition, and identification capabilities. The dual-band detector can have two bumps to connect with each absorber layer, but it is difficult to implement small pitch focal plane arrays and its fabrication process is complicated. Therefore, the most effective way for a dual-band detector is to acquire each band by biasselectable with one bump. To aim this, a dual-band MWIR/LWIR detector based on an InAs/GaSb type-II superlattice nBn structure was designed and its performance was evaluated in this work. Since two absorber layers were separated by the barrier layer, each band can be detected by bias-selectable with one bump. The fabricated dual-band device exhibited the dark current and spectral response characteristics of MWIR and LWIR bands under negative and positive bias, respectively. Spectral crosstalk that is a major issue in dualband detectors was also improved. Finally, a 20 µm pitch 640 x 512 dual-band detector was fabricated, and both MWIR and LWIR images exhibited an average noise equivalent temperature difference of 30 mK or less at 80 K.
    Źródło:
    Opto-Electronics Review; 2023, 31, Special Issue; art. no. e144560
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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