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    Wyświetlanie 1-28 z 28
    Tytuł:
    Gauss sums for orthogonal groups over a finite field of characteristic two
    Autorzy:
    Kim, Dae
    Park, Young
    Powiązania:
    https://bibliotekanauki.pl/articles/1390833.pdf
    Data publikacji:
    1997
    Wydawca:
    Polska Akademia Nauk. Instytut Matematyczny PAN
    Tematy:
    Gauss sum
    multiplicative character
    additive character
    orthogonal group
    Kloosterman sum
    Bruhat decomposition
    maximal parabolic subgroup
    Clifford algebra
    Źródło:
    Acta Arithmetica; 1997, 82, 4; 331-357
    0065-1036
    Pojawia się w:
    Acta Arithmetica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Construction of the real dihedral number fields of degree 2p. Applications
    Autorzy:
    Louboutin, Stéphane
    Park, Young-Ho
    Lefeuvre, Yann
    Powiązania:
    https://bibliotekanauki.pl/articles/1390504.pdf
    Data publikacji:
    1999
    Wydawca:
    Polska Akademia Nauk. Instytut Matematyczny PAN
    Tematy:
    dihedral field
    dihedral group
    CM-field
    Źródło:
    Acta Arithmetica; 1999, 89, 3; 201-215
    0065-1036
    Pojawia się w:
    Acta Arithmetica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A comparison of the impact of extensive and intensive reading approaches on the reading attitudes of secondary EFL learners
    Autorzy:
    Park, A Young
    Powiązania:
    https://bibliotekanauki.pl/articles/780769.pdf
    Data publikacji:
    2020
    Wydawca:
    Uniwersytet im. Adama Mickiewicza w Poznaniu
    Tematy:
    extensive reading
    intensive reading
    reading attitudes
    EFL learners
    proficiency levels
    Opis:
    Extensive reading (ER) which encourages second or foreign (L2) learners to engage in a great deal of reading, has long been recognized as an efficient approach in L2 reading pedagogy. While many attempts have been made to understand the effect of ER on the cognitive domains of L2 learners, there has been insufficient investigation into how ER influences their affective domains. Particularly, reading attitudes, one of the key elements of affective factors involved in L2 reading, have received little attention. This classroom-based intervention study investigated the impact of ER on English as a foreign language (EFL) learners’ attitudes toward English reading compared to the influence of the traditional intensive reading (IR) approach. In addition, this study explored whether the impact of the ER approach on EFL learners’ reading attitudes is different depending on L2 proficiency. The study included two intact classes of EFL secondary learners (N = 72) who received either ER or IR instructional treatments for a 12-week period. For the results, ANCOVA showed that the ER approach fostered positive reading attitudes significantly more than the IR approach. In addition, the analysis indicated that the participants’ proficiency levels did not have a significant effect upon changes in their reading attitudes. That is, regardless of proficiency level, the ER approach demonstrated a significantly positive effect on participants’ reading attitudes in comparison with the IR approach.
    Źródło:
    Studies in Second Language Learning and Teaching; 2020, 10, 2; 337-358
    2083-5205
    2084-1965
    Pojawia się w:
    Studies in Second Language Learning and Teaching
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Knots in $S^2 x S^1$ derived from Sym(2, ℝ)
    Autorzy:
    Lee, Sang
    Lim, Yongdo
    Park, Chan-Young
    Powiązania:
    https://bibliotekanauki.pl/articles/1205027.pdf
    Data publikacji:
    2000
    Wydawca:
    Polska Akademia Nauk. Instytut Matematyczny PAN
    Tematy:
    geodesic
    symmetric matrix
    Shilov boundary
    2-periodic knot
    Opis:
    We realize closed geodesics on the real conformal compactification of the space V = Sym(2, ℝ) of all 2 × 2 real symmetric matrices as knots or 2-component links in $S^2 × S^1$ and show that these knots or links have certain types of symmetry of period 2.
    Źródło:
    Fundamenta Mathematicae; 2000, 164, 3; 241-252
    0016-2736
    Pojawia się w:
    Fundamenta Mathematicae
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparative Study on the Electrical and Mechanical Characteristics of Ni-30wt%Co and Cu-2wt%Be Alloy for Development of Semiconductor Test Probe Pin
    Autorzy:
    Park, Jin-Young
    Kim, Young-Choon
    Kim, Jae-Gyun
    Powiązania:
    https://bibliotekanauki.pl/articles/353264.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    probe pin
    Be-Cu Alloy
    Ni-Co Alloy
    test socket
    mechanical properties
    electrical properties
    Opis:
    Ultra-precision testing is a very important procedure to secure the reliability of the products as well as for the technology development in the areas of semiconductor and display. Accordingly, companies manufacturing equipment for testing of semiconductor and display have been continuously executing researches for the improvement of the performances of test sockets used in test equipment. Through this study, characteristics of the materials in accordance with the mechanical and electrical properties of Ni-30wt%Co alloy and newly developed Cu-2wt%Be alloy were analyzed in order to select the probe pin material of the socket, which is a key component used in the semiconductor testing equipment. In addition, finite element interpretation was executed by using Ansys Workbench 14.0 to comparatively analyze the finite element interpretation results and experimental results. Experiment was executed for the mechanical properties including tensile strength, elasticity modulus, specific heat, thermal expansion coefficient and Contact Force, for electrical properties, experiment on surface resistance, specific resistance and electrical conductivity was executed to measure the properties. It was confirmed that the results of finite element interpretation and experiment displayed similar trend and it is deemed that the Contact Force value was superior for Be-Co alloy. Through this study, it was confirmed that the newly developed Be-Co alloy is more appropriate as probe pin material used as the core component of test socket used in the semiconductor testing equipment than the existing Ni-Co alloy.
    Źródło:
    Archives of Metallurgy and Materials; 2019, 64, 3; 943-947
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Principal Instructional Leadership and Teaching for Learner Autonomy: A Multilevel Analysis of the Case of South Korea
    Autorzy:
    Ham, Seung-Hwan
    Ahn, Sung-Ho G.
    Cha, Yun-Kyung
    Ju, Mi-Kyung
    Kim, Sunah
    Ku, Hara
    Lee, Sun-Kyung
    Park, Young Serk
    Powiązania:
    https://bibliotekanauki.pl/articles/18104543.pdf
    Data publikacji:
    2013-09-30
    Wydawca:
    Wydawnictwo Adam Marszałek
    Opis:
    This study aims to explore how teachers’ use of instructional strategies to foster learner autonomy varies depending on principal instructional leadership. Based on a nationally representative sample of approximately 2,200 teachers in 131 middle schools in South Korea, a series of hierarchical generalized linear modeling analyses has been conducted. The main findings from this study lend credence to the idea that teachers whose school principals provide greater instructional leadership are significantly more likely to integrate instructional strategies to advance learner autonomy into their classroom teaching. This result appears very robust even after a range of variables pertaining to school and teacher characteristics is simultaneously taken into account.
    Źródło:
    The New Educational Review; 2013, 33; 247-260
    1732-6729
    Pojawia się w:
    The New Educational Review
    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:
    Improvement of Microwave Absorption Characteristics by Coating Layer in Substituted U-Type Ferrites
    Autorzy:
    Jeong, Kwang-Pil
    Kim, Jeong-Gon
    Yang, Su-Won
    Choi, Jin-Hyuk
    Park, Seung-Young
    Powiązania:
    https://bibliotekanauki.pl/articles/353196.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    hexagonal ferrite
    U-type ferrite
    silicon oxide layer
    microwave absorption
    Opis:
    The U-type ferrite is a kind of hexagonal ferrite, and it is known as a microwave absorber in the X-band. The magnetic and dielectric loss of the U-type ferrite change to the composition and coating layer, etc. In this study, the silicon oxide layer was coated on the substituted U-type ferrites to improve microwave absorption characteristics. The complex permittivity and complex permeability were measured using toroidal specimens that were press-molded and the measured frequency range was set from 2-18 GHz. The improvement of the microwave absorption rate was different according to the type of the substituted U-type ferrites. Only in the substituted U-type ferrites with nickel and zinc, an improvement in the microwave absorption rate due to enhancement of magnetic loss was confirmed. The highest microwave absorption was 99.9% at 9.6 GHz, which was S_Z0.5 U.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 4; 1287-1291
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Incidentally diagnosed epithelioid trophoblastic tumor immediately after delivery: a case report
    Przypadkowe rozpoznanie nowotworu nabłonkowatokomórkowego trofoblastu bezpośrednio po porodzie – opis przypadku
    Autorzy:
    Kwon, Hyun Young
    Park, Jung-Woo
    Powiązania:
    https://bibliotekanauki.pl/articles/1030115.pdf
    Data publikacji:
    2016
    Wydawca:
    Medical Communications
    Tematy:
    epithelioid trophoblastic tumor
    gestational trophoblastic disease
    rare tumor
    uterine neoplasm
    Opis:
    Epithelioid trophoblastic tumor is a rare malignant lesion of gestational trophoblastic disease, and constitutes an abnormal proliferation of placental trophoblasts. Patients with epithelioid trophoblastic tumor are usually of reproductive age, and have had previous gestations including full-term deliveries, molar pregnancies and abortions. The interval between antecedent gestational events and the diagnosis of epithelioid trophoblastic tumor usually ranges from 0 to 264 months (mean, 84 months). Herein, we report a 42-year-old Korean woman (gravida 2, para 2). At 38 weeks of gestation, she underwent a repeat cesarean section and then hysterectomy due to uterine atony. She was incidentally diagnosed with epithelioid trophoblastic tumor, and postoperatively no metastatic disease was observed. The patient presented no clinical evidence of tumor recurrence for 5 years after surgery. This case is remarkable because epithelioid trophoblastic tumor is a rare disease, and the diagnosis of epithelioid trophoblastic tumor followed immediately after delivery.
    Nowotwór nabłonkowatokomórkowy trofoblastu (epithelioid trophoblastic tumor) to rzadka złośliwa postać ciążowej choroby trofoblastycznej. Charakteryzuje się nieprawidłowym rozrostem komórek trofoblastu. Zmiany tego typu rozpoznaje się u kobiet w wieku rozrodczym z ciążą w wywiadzie, zarówno donoszoną, jak i przedwcześnie zakończoną, również z zaśniadem groniastym. Czas między ciążą a rozpoznaniem nowotworu nabłonkowatokomórkowego trofoblastu wynosi od 0 do 264 miesięcy (średnio 84 miesiące). Przedstawiamy przypadek 42-letniej pacjentki z Korei (gravida 2, para 2), u której w 38. tygodniu ciąży wykonano cięcie cesarskie, a następnie histerektomię ze względu na atonię macicy. Przypadkowo rozpoznano nowotwór nabłonkowatokomórkowy trofoblastu, a po zabiegu nie zaobserwowano przerzutów. Pacjentka nie wykazywała cech nawrotu przez 5 lat po zabiegu. Prezentowany przypadek jest szczególny, ponieważ nowotwór nabłonkowatokomórkowy trofoblastu to rzadkość, a rozpoznano go bezpośrednio po porodzie.
    Źródło:
    Current Gynecologic Oncology; 2016, 14, 3; 174-177
    2451-0750
    Pojawia się w:
    Current Gynecologic Oncology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of Milling Duration on the Thermoelectric Properties of n-Type Bi2Te2.7Se0.3
    Autorzy:
    Park, Min-Soo
    Koo, Hye-Young
    Park, Yonh-Ho
    Ha, Gook-Hyun
    Powiązania:
    https://bibliotekanauki.pl/articles/354698.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    thermoelectric
    bismuth telluride
    powder
    milling
    Opis:
    In this study, an oxide reduction process and a reduction-sintering process were employed to synthesize a thermoelectric alloy from three thermoelectric composite oxide powders, and the thermoelectric properties were investigated as a function of the milling duration. Fine grain sizes were analyzed by via X-ray diffraction and scanning electron microscopy, to investigate the influence of the milling duration on the synthesized samples. It was found that microstructural changes, the Seebeck coefficient, and the electrical resistivity of the compounds were highly dependent on the sample milling duration. Additionally, the carrier concentration considerably increased in the samples milled for 6 h; this was attributed to the formation of antisite defects introduced by the accumulated thermal energy. Moreover, the highest value of ZT (=1.05) was achieved at 373K by the 6-h milled samples. The temperature at which the ZT value maximized varied according to the milling duration, which implies that the milling duration of the three thermoelectric composite oxide powders should be carefully optimized for their effective application.
    Źródło:
    Archives of Metallurgy and Materials; 2019, 64, 2; 591-595
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    In postmenopausal women, some uterine leiomyosarcomas mimic a cystic degeneration of uterine myoma: two case reports and a literature review
    U kobiet w okresie pomenopauzalnym mięsak gładkokomórkowy macicy może imitować zwyrodnienie torbielowate mięśniaka macicy – opis dwóch przypadków i przegląd literatury
    Autorzy:
    Young Kwon, Hyun
    Rha, Seo-Hee
    Park, Jung-Woo
    Powiązania:
    https://bibliotekanauki.pl/articles/1029733.pdf
    Data publikacji:
    2017
    Wydawca:
    Medical Communications
    Tematy:
    degenerating cystic uterine leiomyoma
    uterine leiomyosarcoma
    uterine malignancies
    Opis:
    Uterine leiomyosarcoma is an uncommon malignancy accounting for approximately 1% of gynecologic oncology cases. Most uterine leiomyosarcomas occur in menopausal women and they are notorious for their aggressive character, early dissemination, and poor prognosis. It is difficult to accurately differentiate uterine leiomyosarcoma from leiomyomas, especially when leiomyomas undergo degenerative changes. We treated two menopausal women with a uterine mass showing cystic change. Clinical work-up included needle aspiration, sonography, computed tomography, and serum tumor markers to differentiate uterine leiomyosarcoma from leiomyoma. All results were negative for malignancy, but uterine leiomyosarcoma was ultimately diagnosed by pathological examination. Until an accurate preoperative diagnostic method is available, menopausal women diagnosed with a degenerating cystic uterine fibroid should be considered to have a malignancy intraoperatively in order to prevent tumor cells from intraperitoneal spreading.
    Mięsak gładkokomórkowy macicy to rzadki nowotwór złośliwy odpowiadający za około 1% przypadków nowotworów narządów rodnych. Nowotwór ten występuje głównie u kobiet w okresie pomenopauzalnym i jest znany z agresywnego przebiegu, wczesnego rozsiewu oraz złego rokowania. Przeprowadzenie dokładnej diagnostyki różnicującej mięsaka gładkokomórkowego i mięśniaków jest trudne, zwłaszcza w przypadku zmian degeneracyjnych tych drugich. W pracy przedstawiono przypadki dwóch kobiet w okresie pomenopauzalnym, u których w macicy stwierdzono obecność masy wykazującej zmianę torbielowatą. W ramach diagnostyki klinicznej wykonano biopsję aspiracyjną, badanie ultrasonograficzne, tomografię komputerową oraz oznaczono stężenia markerów nowotworowych w surowicy krwi w celu zróżnicowania mięsaka gładkokomórkowego i mięśniaka. Chociaż wszystkie badania dały wynik ujemny dla nowotworu złośliwego, badanie histopatologiczne potwierdziło rozpoznanie mięsaka gładkokomórkowego macicy. Dopóki nie będzie dostępna dokładna metoda diagnozowania przedoperacyjnego, w przypadku kobiet w okresie pomenopauzalnym z rozpoznaniem zwyrodnienia torbielowatego mięśniaka macicy należy śródoperacyjne założyć obecność nowotworu złośliwego w celu uniknięcia dootrzewnowego rozsiewu komórek nowotworowych.
    Źródło:
    Current Gynecologic Oncology; 2017, 15, 2; 142-145
    2451-0750
    Pojawia się w:
    Current Gynecologic Oncology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Morphology Control of One-Dimensional Gallium Nitride Nanostructures by Modulating the Crystallinity of Sacrificial Gallium Oxide Templates
    Autorzy:
    Ko, Yun Taek
    Park, Mijeong
    Park, Jingyeong
    Moon, Jaeyun
    Choa, Yong-Ho
    Lee, Young-In
    Powiązania:
    https://bibliotekanauki.pl/articles/2049246.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    GaN
    nanofiber
    nanotube
    electrospinning
    chemical transformation
    Opis:
    In this study, we demonstrated a method of controllably synthesizing one-dimensional nanostructures having a dense or a hollow structure using fibrous sacrificial templates with tunable crystallinity. The fibrous Ga2O3 templates were prepared by calcining the polymer/gallium precursor nanofiber synthesized by an electrospinning process, and their crystallinity was varied by controlling the calcination temperature from 500°C to 900°C. GaN nanostructures were transformed by nitriding the Ga2O3 nanofibers using NH3 gas. All of the transformed GaN nanostructures maintained a one-dimensional structure well and exhibited a diameter of about 50 nm, but their morphology was clearly distinguished according to the crystallinity of the templates. When the templates having a relatively low crystallinity were used, the transformed GaN showed a hollow nanostructure, and as the crystallinity increased, GaN was converted into a denser nanostructure. This morphological difference can be explained as being caused by the difference in the diffusion rate of Ga depending on the crystallinity of Ga2O3 during the conversion from Ga2O3 to GaN. It is expected that this technique will make possible the tubular nanostructure synthesis of nitride functional nanomaterials.
    Źródło:
    Archives of Metallurgy and Materials; 2021, 66, 3; 709-712
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Economic Analysis of Charitable Donations
    Autorzy:
    Young Kang, Moon
    Park, Byungho
    Lee, Sanghak
    Kim, Jaehwan
    Allenby, Greg
    Powiązania:
    https://bibliotekanauki.pl/articles/540580.pdf
    Data publikacji:
    2016
    Wydawca:
    Uniwersytet Warszawski. Wydawnictwo Naukowe Wydziału Zarządzania
    Tematy:
    direct utility model
    hierarchical Bayes
    altruism
    non-profit marketing
    Opis:
    This paper examines the effect of message characteristics on donation behavior using an economic model of giving. The utility of giving can come from one’s own contribution and possibly from the combined contributions of others. Donors are assumed to be constrained utility maximizers, and the message attributes affect the degree to which they react altruistically or egoistically. The model is estimated with data from an incentive-aligned study of South Korean consumers, and implications for message optimization and donor targeting are explored.
    Źródło:
    Journal of Marketing and Consumer Behaviour in Emerging Markets; 2016, 2(4); 40-57
    2449-6634
    Pojawia się w:
    Journal of Marketing and Consumer Behaviour in Emerging Markets
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    FERMENTED ORIENTAL MEDICINAL INSECT EXTRACT HAS A SYNERGISTIC EFFECT ON INHIBITING TGF-ß1- OR H2O2-INDUCED HEPATIC FIBROGENESIS IN LX-2 AND HEPG2 CELLS
    Autorzy:
    Choo, Young-Moo
    Choi, Young-Ji
    Park, In-Sun
    Son, Yu-Kyog
    You, Kang-Yeol
    Kim, Jiyoung
    Powiązania:
    https://bibliotekanauki.pl/articles/895380.pdf
    Data publikacji:
    2019-06-28
    Wydawca:
    Polskie Towarzystwo Farmaceutyczne
    Źródło:
    Acta Poloniae Pharmaceutica - Drug Research; 2019, 76, 3; 599-603
    0001-6837
    2353-5288
    Pojawia się w:
    Acta Poloniae Pharmaceutica - Drug Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of Adding Niobium and Vanadium to Fe-Based Oxide Dispersion Strengthened Alloy
    Autorzy:
    Park, Chun Woong
    Choi, Won June
    Byun, Jong Min
    Kim, Young Do
    Powiązania:
    https://bibliotekanauki.pl/articles/353024.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Fe-based ODS
    vanadium
    niobium
    superalloy
    hardness
    Opis:
    In this study, the effects of adding niobium and vanadium to Fe-based oxide dispersion strengthened alloys are confirmed. The composition of alloys are Fe-20Cr-1Al-0.5Ti-0.5Y2 O3 and Fe-20Cr-1Al-0.5Ti-0.3V-0.2Nb-0.5Y2 O3. The alloy powders are manufactured by using a planetary mill, and these powders are molded by using a magnetic pulsed compaction. Thereafter, the powders are sintered in a tube furnace to obtain sintered specimens. The added elements exist in the form of a solid solution in the Fe matrix and suppress the grain growth. These results are confirmed via X-ray diffraction and scanning electron microscopy analyses of the phase and microstructure of alloys. In addition, it was confirmed that the addition of elements, improved the hardness property of Fe-based oxide dispersion strengthened alloys.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 4; 1265-1268
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Laser Cladding of WC/T-800 Cermet: Fabrication, Microstructure and Wear Properties
    Autorzy:
    Kim, Kyoung-Wook
    Kim, Young-Kyun
    Park, Sun-Hong
    Lee, Kee-Ahn
    Powiązania:
    https://bibliotekanauki.pl/articles/2049250.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    CoMoCr alloy
    WC
    cermet
    laser cladding
    microstructure
    wear properties
    Opis:
    This study fabricated a WC/T-800 cermet coating layer with Co-Mo-Cr (T-800) powder and WC powder using laser cladding, and analyzed its microstructure, hardness and wear properties. For comparison, casted bulk T-800 was used. Laser cladded WC/T-800 cermet coating layer showed circular WC phases in the Co matrix, and dendritic laves phases. The average laves phase size in the cermet coating layer and bulk T-800 measured as 7.9 µm and 60.6 µm, respectively, indicating that the cermet coating layer had a relatively finer laves phase. Upon conducting a wear test, the cermet coating layer added with WC showed better wear resistance. In the case of laser cladded WC/T-800 cermet coating layer, abrasion wear was observed; on the contrary, the bulk T-800 showed pulled out laves phases. Based on the above findings, the WC/T-800 cermet coating layer using laser cladding and the relationship between its microstructure and wear behavior were discussed.
    Źródło:
    Archives of Metallurgy and Materials; 2021, 66, 3; 713-717
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Microstructure and Mechanical Properties of Al 3003 Alloy Weld by Stationary Shoulder Friction Stir Welding Process
    Autorzy:
    Jung, Woo-Chul
    Park, Joo-Heon
    Yoon, Sang-Min
    Kim, Young Kyun
    Powiązania:
    https://bibliotekanauki.pl/articles/2203728.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    stationary shoulder friction stir welding
    aluminum 3003 alloy
    microstructure
    mechanical properties
    Opis:
    The lap joint welding of Al 3003 alloy by stationary shoulder friction stir welding (SSFSW) was performed under the conditions of tool rotation and welding speed, and it was confirmed that the welding was performed under all conditions. The tunnel defects and pores were formed in the weld zone at the lowest tool rotation and welding speed, and it is increased, the weld surface has been improved. At the same tool rotation speed at the welding speed is increased, the grain size was refined in the stir zone (SZ) and thus the hardness increased by about 14% compared to the base metal. The tensile shear strength is measured to be 10 kN or more under most conditions, and in the 4000 rpm with high heat input, the shear tensile strength was measured relatively lower than other conditions due to excessive heat input of the material.
    Źródło:
    Archives of Metallurgy and Materials; 2023, 68, 1; 113--118
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fabrication of Molybdenum Alloy with Distributed High-Entropy Alloy Via Pressureless Sintering
    Autorzy:
    Choi, Won June
    Park, Cheon Woong
    Byun, Jong Min
    Kim, Young Do
    Powiązania:
    https://bibliotekanauki.pl/articles/353990.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    molybdenum alloy
    high-entropy alloys
    core-shell powder
    Opis:
    In this study, a molybdenum alloy with dispersed high-entropy particles was fabricated using the powder metallurgy method. The high-entropy powder, composed of Nb, Ta, V, W, and Zr elements with a same atomic fraction, was prepared via high-energy ball milling. Using this powder, an ideal core-shell powder, composed of high-entropy powder as core and Mo powder as shell, was synthesized via the milling and reduction processes. These processes enabled the realization of an ideal microstructure with the high-entropy phase uniformly dispersed in the Mo matrix. The sintered body was successfully fabricated via uniaxial compaction followed by pressureless sintering. The sintered body was analyzed by X-ray diffraction and scanning electron microscope, and the high-entropy phase is uniformly dispersed in the Mo matrix.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 4; 1269-1272
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Towards ensuring software interoperability between deep learning frameworks
    Autorzy:
    Lee, Youn Kyu
    Park, Seong Hee
    Lim, Min Young
    Lee, Soo-Hyun
    Jeong, Jongwook
    Powiązania:
    https://bibliotekanauki.pl/articles/23944833.pdf
    Data publikacji:
    2023
    Wydawca:
    Społeczna Akademia Nauk w Łodzi. Polskie Towarzystwo Sieci Neuronowych
    Tematy:
    deep learning
    interoperability
    validation
    verification
    deep learning framework
    model conversion
    Opis:
    With the widespread of systems incorporating multiple deep learning models, ensuring interoperability between target models has become essential. However, due to the unreliable performance of existing model conversion solutions, it is still challenging to ensure interoperability between the models developed on different deep learning frameworks. In this paper, we propose a systematic method for verifying interoperability between pre- and post-conversion deep learning models based on the validation and verification approach. Our proposed method ensures interoperability by conducting a series of systematic verifications from multiple perspectives. The case study confirmed that our method successfully discovered the interoperability issues that have been reported in deep learning model conversions.
    Źródło:
    Journal of Artificial Intelligence and Soft Computing Research; 2023, 13, 4; 215--228
    2083-2567
    2449-6499
    Pojawia się w:
    Journal of Artificial Intelligence and Soft Computing Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Characteristics of a new respiratory syndrome associated with the use of a humidifier disinfectant: humidifier disinfectant-related respiratory syndrome (HDRS)
    Autorzy:
    Leem, Jong Han
    Joh, Joon-Sung
    Hong, Young-Seoub
    Kim, Jungwon
    Park, Soyoung
    Lim, Soyeoun
    Kim, Yangho
    Powiązania:
    https://bibliotekanauki.pl/articles/2116504.pdf
    Data publikacji:
    2020-10-20
    Wydawca:
    Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
    Tematy:
    pneumonitis
    respiratory
    lung
    disinfection
    injuries
    humidifier
    Opis:
    ObjectivesThe purpose of this study was to characterize a new respiratory syndrome associated with exposure to a humidifier disinfectant (HD) in South Korea that is distinct from the well-known HD-related lung injury (HDLI). The authors identified this condition in 24 study subjects who were family members of patients with definite or probable HDLI (referred to as index cases), and were exposed to HD in the same room as the index cases.Material and MethodsThe authors reviewed medical records of 236 family members in 110 families who were exposed to HD in the same rooms and residences as the index cases.ResultsThey identified 24 family members who were exposed to HD in the same rooms and residences as the index cases, and who developed respiratory disorders that were distinct from HDLI. The clinical signs and symptoms of these individuals were in the upper respiratory tract, such as allergic rhinitis and croup, or in the lower respiratory tract, such as bronchitis and pneumonia. The diffusing capacity of the lung fordetermicarbon monoxide was reduced in 9 of 12 children (data not available for 1 child), and in 4 of 5 adults (data not available for 6 adults). The percent forced vital capacity and forced expiratory volume in one second/forced vital capacity ratios were within the normal ranges in most patients. The computed tomography findings, which mostly indicated non-specific inflammation, were inconsistent with the radiological diagnostic criteria for HDLI, but were abnormal in 8 of 11 adults, and in 2 of 13 children.ConclusionsThe authors propose a new condition, i.e., HD-related respiratory syndrome (HDRS), which is characterized by mild to moderate or atypical respiratory symptoms and signs, and is related to HD exposure, but is distinct from HDLI. The recognition of HDRS may provide a basis for understanding the natural history of HD-related respiratory problems, and for capturing the whole spectrum of HD-related clinical manifestations in the respiratory tract.
    Źródło:
    International Journal of Occupational Medicine and Environmental Health; 2020, 33, 6; 829-839
    1232-1087
    1896-494X
    Pojawia się w:
    International Journal of Occupational Medicine and Environmental Health
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mismatch in working hours and workaholism in permanent waged workers
    Autorzy:
    Park, Shin-Goo
    Kim, Hyung-Doo
    Min, Jin-Young
    Min, Kyoug-Bok
    Hwang, Sang-Hee
    Jang, Eun-Chul
    Powiązania:
    https://bibliotekanauki.pl/articles/2116653.pdf
    Data publikacji:
    2020-03-13
    Wydawca:
    Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
    Tematy:
    workaholism
    working hours mismatch
    waged worker
    workaholic
    mismatched
    weekly working hours
    Opis:
    ObjectivesA cross-sectional study was conducted to investigate whether working hours mismatch is associated with workaholism.Material and MethodsThis study used the data from the 17th wave (2014) of the nationwide Korean Labor and Income Panel Study. Workaholism was evaluated using the Workaholism Analysis Questionnaire. The final study involved 3157 subjects who answered questions regarding both workaholism and working hours mismatch. To identify the association between working hours mismatch and workaholism according to weekly working hours, a stratification analysis was conducted by dividing the number of working hours/week into 3 groups (≤40 h, 41–59 h, and ≥60 h). The odds ratios were calculated using a multiple logistic regression model, which was adjusted for potential confounders.ResultsThe workers working more hours than desired showed the greatest frequency of workaholism. As regards workaholism, in all weekly working hours groups, the odds ratios of the group working more hours than desired were 4.28, 95% CI: 2.29–7.99 (≥40 h), 2.14, 95% CI: 1.34–3.43 (41–59 h), 3.40, 95% CI: 1.60–7.21 (≤60 h), which were statistically significant compared to the reference (matched) group. There was no statistically significant relationship between working hours and workaholism when stratified according to the mismatch in working hours.ConclusionsThe workers’ working hours mismatch can be significantly related to workaholism.
    Źródło:
    International Journal of Occupational Medicine and Environmental Health; 2020, 33, 2; 187-194
    1232-1087
    1896-494X
    Pojawia się w:
    International Journal of Occupational Medicine and Environmental Health
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simple synthesis of Black TiO2 Nanofibers Via Calcination in Inert Atmosphere
    Autorzy:
    Ji, Myeongjun
    Kim, Eung Ryong
    Park, Mi-Jeong
    Jeon, Hee Yeon
    Moon, Jaeyun
    Byun, Jongmin
    Lee, Young-In
    Powiązania:
    https://bibliotekanauki.pl/articles/2174573.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    black TiO2
    nanofibers
    electrospinning
    calcination
    atmosphere
    Opis:
    Black TiO2 nanofibers have recently emerged as a promising material that has both advantages of black metal oxide and one-dimensional nanostructure. However, current reduction-based synthesis approaches are not compatible with practical applications because these processes require high process costs, complicated processes, and sophisticated control. Therefore, it is still necessary to develop a simple and facile method that can easily introduce atomic defects during the synthesis process. This work suggests an electrospinning process with an antioxidant and subsequent calcination process for the facile synthesis of black TiO2 nanofibers. The synthesized black TiO2 nanofiber has an average diameter of 50.3 nm and a rutile structure. Moreover, this nanofiber represented a noticeable black color and a bandgap of 2.67 eV, clearly demonstrating the bandgap narrowing by the introduced atomic defects.
    Źródło:
    Archives of Metallurgy and Materials; 2022, 67, 4; 1481--1486
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Post-Heat Treatment on the Impact Toughness and Crack Propagation Mechanism of AISI D2 Tool Steel Manufactured by Direct Energy Deposition
    Autorzy:
    Park, Jun-Hyung
    Kim, Kyu-Sik
    Koo, Yong-Mo
    Kim, Jin-Young
    Kim, Min-Chul
    Lee, Kee-Ahn
    Powiązania:
    https://bibliotekanauki.pl/articles/2203722.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    AISI D2 tool steel
    direct energy deposition
    post-heat treatment
    impact toughness
    fractography
    Opis:
    This study investigated the effect of heat treatment on the microstructure and impact toughness property of AISI D2 manufactured with direct energy deposition (DED) and compared the results with conventional wrought material. The fracture crack propagation behavior was examined in connection with microstructures through fracture surface analysis. AISI D2 manufactured with DED had a eutectic structure that turned into a net-type carbide after heat treatment, and Cr-rich needle-type secondary carbide was observed. Impact toughness of DED AISI D2 measured 2.0 J/cm2 in the as-built sample and 1.1 J/cm2 in the heat-treated sample. Compared to a wrought heat-treated AISI D2, DED AISI D2 had relatively low impact toughness. DED AISI D2 and wrought material had different crack propagation mechanisms. In DED AISI D2, the eutectic structure and net-type carbide boundary were identified as the major microstructural factor decreasing impact toughness.
    Źródło:
    Archives of Metallurgy and Materials; 2023, 68, 1; 119--122
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Phase Evolution During Extraction and Recovery of Pure Nd from Magnet
    Autorzy:
    Rasheed, Mohammad Zarar
    Nam, Sun-Woo
    Lee, Sang-Hoon
    Park, Sang-Min
    Cho, Ju-Young
    Kim, Taek-Soo
    Powiązania:
    https://bibliotekanauki.pl/articles/2048880.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Liquid Metal Extraction
    rare earth recycling
    vacuum distillation
    phase transformation
    Opis:
    Liquid Metal Extraction process using molten Mg was carried out to obtain Nd-Mg alloys from Nd based permanent magnets at 900°C for 24 h. with a magnet to magnesium mass ratio of 1:10. Nd was successfully extracted from magnet into Mg resulting in ~4 wt.% Nd-Mg alloy. Nd was recovered from the obtained Nd-Mg alloys based on the difference in their vapor pressures using vacuum distillation. Vacuum distillation experiments were carried out at 800°C under vacuum of 2.67 Pa at various times for the recovery of high purity Nd. Nd having a purity of more than 99% was recovered at distillation time of 120 min and above. The phase transformations of the Nd-Mg alloy during the process, from Mg12Nd to α-Nd, were confirmed as per the phase diagram at different distillation times. Pure Nd was recovered as a result of two step recycling process; Liquid Metal Extraction followed by Vacuum Distillation.
    Źródło:
    Archives of Metallurgy and Materials; 2021, 66, 4; 1001-1005
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Mg Ratio on the Extraction of Dy from (Nd,Dy)-Fe-B Permanent Magnet Using Liquid Mg
    Autorzy:
    Park, Sang-Min
    Nam, Sun-Woo
    Cho, Ju-Young
    Lee, Sang-Hoon
    Hyun, Seung-Keun
    Kim, Taek-Soo
    Powiązania:
    https://bibliotekanauki.pl/articles/353657.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    dysprosium
    liquid metal extraction
    (Nd,Dy)-Fe-B magnet
    extraction behavior
    diffusion
    Opis:
    Recently, since the demand of rare earth permanent magnet for high temperature applications such as an electric motor has increased, dysprosium (Dy), a heavy rare earth element, is becoming important due to severe bias in its production. To fulfillthe increasing need of Dy, recycling offers as a promising alternative. In recycling of rare earths, Hydro-metallurgical extraction method is mainly used however it has adverse environmental effects. Liquid metal extraction on the other hand, is an eco-friendly and simple method as far as the reduction of rare earth metal oxide is concerned. Therefore, liquid metal extraction was studied in this research as an alternative to the hydro-metallurgical recycling method. Magnesium (Mg) is selected as solvent metal because it doesn’t form intermetallic compounds with Fe, B and has a low melting and low boiling point. Extraction behavior of Dy in (Nd,Dy)-Fe-B magnet is observed and effect of Mg ratio on extraction of Dy is confirmed.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 4; 1281-1285
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Process Variables on Friction Stirred Microstructure and Surface Hardness of AZ31 Magnesium Alloy
    Autorzy:
    Kim, Jae-Yeon
    Hwang, Jung-Woo
    Lee, Seung-Mi
    Hyun, Chang-Young
    Park, Ik-Keun
    Byeon, Jai-Won
    Powiązania:
    https://bibliotekanauki.pl/articles/355106.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    friction stir process
    AZ31 alloy
    diamond particle
    process variable
    grain size
    Opis:
    Effects of various friction stir processing (FSP) variables on the microstructural evolution and microhardness of the AZ31 magnesium alloy were investigated. The processing variables include rotational and travelling speed of the tool, kind of secondphase (i.e., diamond, Al2 O3 , and ZrO2 ) and groove depth (i.e., volume fraction of second phase). Grain size, distribution of second phase particle, grain texture, and microhardness were analyzed as a function of the FSP process variables. The FSPed AZ31 com-posites fabricated with a high heat input condition showed the better dispersion of particle without macro defect. For all composite specimens, the grain size decreased and the microhardness increased regardless of the grooved depth compared with that of the FSPed AZ31 without strengthening particle, respectively. For the AZ31/diamond composite having a grain size of about 1 μm, microhardness (i.e., about 108 Hv) was about two times higher than that of the matrix alloy (i.e., about 52 Hv). The effect of second phase particle on retardation of grain growth and resulting hardness increase was discussed.
    Źródło:
    Archives of Metallurgy and Materials; 2019, 64, 3; 907-911
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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