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Wyświetlanie 1-15 z 29
Tytuł:
Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder
Autorzy:
Ali, B.
Choi, S. H.
Seo, S. J.
Maeng, D. Y.
Lee, C. G.
Kim, T. S.
Park, K. T.
Powiązania:
https://bibliotekanauki.pl/articles/352709.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
water atomization
Fe-based powder
oxide reduction
powder metallurgy
sinter-hardening alloys
Opis:
The water atomization of iron powder with a composition of Fe-3Cr-0.5Mo (wt.%) at 1600°C and 150 bar creates an oxide layer, which in this study was reduced using a mixture of methane (CH4) and argon (Ar) gas. The lowest oxygen content was achieved with a 100 cc/min flow rate of CH4, but this also resulted in a co-deposition of carbon due to the cracking of CH4. This carbon can be used directly to create high-quality, sinter hardenable steel, thereby eliminating the need for an additional mixing step prior to sintering. An exponential relationship was found to exist between the CH4 gas flow rate and carbon content of the powder, meaning that its composition can be easily controlled to suit a variety of different applications.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 2B; 1119-1124
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
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:
Preparation of Submicroscale Ag-Coated Cu Particles by Multi-Step Addition of Ag Plating Solution and Antioxidation Properties for Different Ag Shell Thicknesses
Autorzy:
Choi, E. B.
Lee, J.-H.
Powiązania:
https://bibliotekanauki.pl/articles/351202.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Ag-coated Cu particle
submicrometer
Glycol-based Ag plating solution
mult-step addition
antioxidation
Opis:
For application as a low-cost conductive filler material, submicroscale Cu@Ag particles were fabricated at room temperature without any reductants by a multi-step addition method using an ethylene glycol-based Ag plating solution. Scanning electron microscopy images of the Ag-coated Cu particles demonstrated the formation of discrete Ag particles less than 100 nm in size as well as a thin Ag coating on Cu particles, during the early addition steps. However, as the thickness of the Ag coating increased, the small Ag particles agglomerated into Ag coatings with an increase in the number of Ag plating steps. Owing to the absence of additives such as surfactants, a comparison between the microstructural images and calculations indicated increased agglomeration between fabricated Ag-coated Cu particles with an increase in the number of Ag plating steps. However, thermogravimetric-differential scanning calorimetry of the agglomerated Ag-coated Cu particles after the fifth addition of the Ag plating solution demonstrated their antioxidation behavior even after 70 min in air at 150°C.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 2B; 1137-1142
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Development of Carbon Nanotube Based Reflection Type X-ray Source
Autorzy:
Choi, H.
Kim, J.
Lee, C.
Powiązania:
https://bibliotekanauki.pl/articles/1807922.pdf
Data publikacji:
2009-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.47.Lx
75.47.Gk
73.50.Fq
Opis:
X-ray imaging technology is a useful and leading medical diagnostic tool for health care professionals to diagnose disease in human body. Carbon nanotube based X-ray source, which we have developed in this study, could be also useful and supply integrated diagnostic X-ray imaging tool in diagnosis. Conventionally, thermionic type of tungsten filament X-ray tube is widely employed in the field of biomedical and industrial application fields. However, intrinsic problems, such as poor emission efficiency, low imaging resolution, and high electrical energy consumption etc., may cause the limitation of using the X-ray tube. To fulfill the current market requirement, specifically for medical diagnostic field, we have developed rather a portable and compact carbon nanotube based X-ray device in which microfocus high imaging resolution can be feasible.
Źródło:
Acta Physica Polonica A; 2009, 115, 6; 1078-1080
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Flexible pavement analysis considering temperature profile and anisotropy behavior in hot mix asphalt layer
Autorzy:
Choi, J.
Seo, Y.
Kim, S. H.
Beadles, S.
Powiązania:
https://bibliotekanauki.pl/articles/230733.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
zachowanie anizotropowe
metoda elementów skończonych
kruszywo
nawierzchnia
HMA
anisotropic behavior
finite element method
aggregate base
pavement
Opis:
A three Dimensional finite element model (FEM) incorporating the anisotropic properties and temperature profile of hot mix asphalt (HMA) pavement was developed to predict the structural responses of HMA pavement subject to heavy loads typically encountered in the field. In this study, ABAQUS was adopted to model the stress and strain relationships within the pavement structure. The results of the model were verified using data collected from the Korean Highway Corporation Test Road (KHCTR). The results demonstrated that both the base course and surface course layers follow the anisotropic behavior and the incorporation of the temperature profile throughout the pavement has a substantial effect on the pavement response predictions that impact pavement design. The results also showed that the anisotropy level of HMA and base material can be reduced to as low as 80% and 15% as a result of repeated loading, respectively.
Źródło:
Archives of Civil Engineering; 2011, 57, 4; 347-356
1230-2945
Pojawia się w:
Archives of Civil Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Differences in gait pattern between the elderly and the young during level walking under low illumination
Autorzy:
Choi, J.-S.
Kang, D.-W.
Shin, Y.-H.
Tack, G.-R.
Powiązania:
https://bibliotekanauki.pl/articles/307026.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
gait
illumination
elderly
stance ratio
toe clearance
safety margin
chód
iluminacja
wiek
palec nogi
Opis:
The purpose of this study was to compare changes in the gait pattern between the elderly and young during level (i.e., even surface) walking under low illumination. Vision during walking plays a role in avoiding obstacles and uneven surfaces, as well as an important role in the proactive control of dynamic stability and route planning for level walking. Fourteen elderly and fourteen young male subjects walked on a 7 m walkway with two illumination conditions using self-selected walking speed: walking with normal (>300 lux) and low illumination (<10 lux). Walking speed, stance phase ratio, toe clearance on swing phase, and range of motion at the center of mass were used to compare the differences in gait pattern between two illumination conditions and ages. During walking with low illumination, walking speed and stance phase ratio of the young decreased, and toe clearance of the young increased. However, there was no difference in these variables due to low illumination in the elderly subjects. Despite level walking conditions, there were some differences in gait pattern between the young and the elderly due to illumination conditions. This implies that the young showed a more positive change of gait pattern, due to low illumination, than that of the elderly. In this respect, further study is necessary to identify differences between the young and the elderly, when they walk on an uneven or obstacle walkway with low illumination.
Źródło:
Acta of Bioengineering and Biomechanics; 2014, 16, 1; 3-9
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fabrication of a Spherical Titanium Powder by Combined Combustion Synthesis and DC Plasma Treatment
Autorzy:
Choi, S. H.
Ali, B.
Hyun, S. K.
Sim, J. J.
Choi, W. J.
Joo, W.
Lim, J. H.
Lee, Y. J.
Kim, T. S.
Park, K. T.
Powiązania:
https://bibliotekanauki.pl/articles/356067.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
combustion synthesis
DC plasma treatment
titanium powder
3D printing process
combustion parameters
Opis:
Combustion synthesis is capable of producing many types of refractory and ceramic materials, as well as metals, with a relatively lower cost and shorter time frame than other solid state synthetic techniques. TiO2 with Mg as reductant were dry mixed and hand compacted into a 60 mm diameter mold and then combusted under an Ar atmosphere. Depending on the reaction parameters (Mg concentration 2 ≤ α ≤ 4), the thermocouples registered temperatures between 1160°C and 1710°C . 3 mol of Mg gave the optimum results with combustion temperature (Tc) and combustion velocity (Uc) values of 1372°C and 0.26 cm/s respectively. Furthermore, this ratio also had the lowest oxygen concentration in this study (0.8 wt%). After combustion, DC plasma treatment was carried out to spheroidize the Ti powder for use in 3D printing. The characterization of the final product was performed using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and N/O analysis.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 2B; 1057-1062
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reaction Kinetics and Morphological Study of TiNb2O7 Synthesized by Solid-State Reaction
Autorzy:
Choi, S. H.
Ali, B.
Choi, K. S.
Hyun, S. K.
Sim, J. J.
Choi, W. J.
Joo, W.
Lim, J. H.
Lee, T. H.
Kim, T. S.
Park, K. T.
Powiązania:
https://bibliotekanauki.pl/articles/355326.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
solid state reaction
kinetic analysis
quantitative phase analysis
TiNb2O7 synthesis
Opis:
Although TiNb2O7 is regarded as a material with high application potential in lithium-ion batteries (LIBs) and solid-oxide fuel cells (SOFCs), it has been difficult to find suitable cost-effective conditions for synthesizing it on a commercial scale. In this study, TiNb2O7 compounds were synthesized by a solid state synthesis process. For stoichiometrically precise synthesis of the TiNb2O7 phase, the starting materials, TiO2 and Nb2O5 were taken in a 1:1 molar ratio. Activation energy and reaction kinetics of the system were investigated at various synthesis temperatures (800,1000,1200, and 1400°C) and for various holding durations (1,5,10, and 20 h). Furthermore, change in the product morphology and particle size distribution were also evaluated as a function of synthesis temperature and duration. Additionally, quantitative phase analysis was conducted using the Rietveld refinement method. It was found that increases in the synthesis temperature and holding time lead to increase in the mean particle size from 1 to 4.5 μm. The reaction rate constant for the synthesis reaction was also calculated.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 2B; 1051-1056
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Flexible Software Design for Korean WA-DGNSS Reference Station
Autorzy:
Choi, W.S.
Chhattan, S.S.
Kye, J.E.
Han, W.Y.
Yun, H.
Kee, C.
Powiązania:
https://bibliotekanauki.pl/articles/116770.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
Global Navigation Satellite System (GNSS)
Flexible Software Design
Wide area Reference Station (WRS)
Opis:
In this paper, we describe the software design results of WA‐DGNSS reference station that will be constructed in Korea in the near future. Software design of the WRS (Wide area Reference Station) is carried out by applying object oriented software methodology in order to provide flexibilities: easy of model change (namely ionospheric delay model etc) and system addition (Galileo, GLONASS in addition to GPS etc). Software design results include the use case diagrams for the functions to be executed, the architecture diagram showing components and their relationships, the activity diagrams of behaviors and models among them, and class diagrams describing the attribute and operation.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2013, 7, 1; 75-78
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Recovery of Pig Iron from Copper Smelting Slag by Reduction Smelting
Autorzy:
Erdenebold, U.
Choi, M.-H.
Wang, J.-P.
Powiązania:
https://bibliotekanauki.pl/articles/355067.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
copper slag
reduction
pig iron
fayalite
recovery
Opis:
Copper slag is a by-product obtained during smelting and refining of copper. Copper smelting slag typically contains about 1 wt.% copper and 40 wt.% iron depending upon the initial ore quality and the furnace type. Main components of copper slag are iron oxide and silica. These exist in copper slag mainly in the form of fayalite (2FeO ·SiO2 ). This study was intended to recover pig iron from the copper smelting slag by reduction smelting method. At the reaction temperature of below 1400°С the whole copper smelting slag was not smelted, and some agglomerated, showing a mass in a sponge form. The recovery behavior of pig iron from copper smelting slag increases with increasing smelting temperature and duration. The recovery rate of pig iron varied greatly depending on the reaction temperature.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 4; 1793-1798
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Iterative methods for efficient sampling-based optimal motion planning of nonlinear systems
Autorzy:
Ha, J. S.
Choi, H. L.
Jeon, J. H.
Powiązania:
https://bibliotekanauki.pl/articles/330028.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
optimal motion planning
sampling based algorithm
nonlinear dynamics
planowanie ruchu
algorytm próbkowania
dynamika nieliniowa
Opis:
This paper extends the RRT* algorithm, a recently developed but widely used sampling based optimal motion planner, in order to effectively handle nonlinear kinodynamic constraints. Nonlinearity in kinodynamic differential constraints often leads to difficulties in choosing an appropriate distance metric and in computing optimized trajectory segments in tree construction. To tackle these two difficulties, this work adopts the affine quadratic regulator-based pseudo-metric as the distance measure and utilizes iterative two-point boundary value problem solvers to compute the optimized segments. The proposed extension then preserves the inherent asymptotic optimality of the RRT* framework, while efficiently handling a variety of kinodynamic constraints. Three numerical case studies validate the applicability of the proposed method.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2018, 28, 1; 155-168
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oxide Formation In Metal Injection Molding Of 316L Stainless Steel
Tworzenie tlenków podczas wtryskiwania proszku stali nierdzewnej 316L
Autorzy:
Jang, J. M.
Lee, W.
Ko, S.-H.
Han, C.
Choi, H.
Powiązania:
https://bibliotekanauki.pl/articles/351352.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
powder injection molding
sintering
316L stainless steel
sintering atmosphere
micro parts
wtryskiwanie proszku
spiekanie
stal nierdzewna 316L
mikro-część
Opis:
The effects of sintering condition and powder size on the microstructure of MIMed parts were investigated using water-atomized 316L stainless steel powder. The 316L stainless steel feedstock was injected into micro mold with micro features of various shapes and dimensions. The green parts were debound and pre-sintered at 800°C in hydrogen atmosphere and then sintered at 1300°C and 1350°C in argon atmosphere of 5torr and 760torr, respectively. The oxide particles were formed and distributed homogeneously inside the sample except for the outermost region regardless of sintering condition and powder size. The width of layer without oxide particles are increased with decrease of sintering atmosphere pressure and powder size. The fine oxides act as the obstacle on grain growth and the high sintering temperature causes severe grain growth in micro features due to larger amount of heat gain than that in macro ones.
Źródło:
Archives of Metallurgy and Materials; 2015, 60, 2B; 1281-1285
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect Of Grain Size On The Mechanical Properties Of Aluminum
Wpływ wielkości ziarna na właściwości mechaniczne aluminium
Autorzy:
Jeong, G.
Park, J.
Nam, S.
Shin, S.-E.
Shin, J.
Bae, D.
Choi, H.
Powiązania:
https://bibliotekanauki.pl/articles/351200.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nanocrystalline aluminum
grain size
microstructure
mechanical properties
tensile behavior
aluminium
wielkość ziarna
mikrostruktura
rozciąganie
właściwości mechaniczne
Opis:
Although many studies have focused on the unique plastic deformation behavior of nanocrystalline aluminum (e.g., the positive deviation from Hall-Petch relation, the unusual yield-drop phenomenon in tensile mode, etc.), the data reported by different research groups are inconsistent with each other, possibly because of different fabrication processes. In this study, aluminum samples with a wide grain-size spectrum – from a few micrometers down to 100 nanometers – are manufactured by powder metallurgy. The grain size was measured by X-ray diffraction analysis and transmission electron microscope observation. Furthermore, the tensile behavior, which varied according to a grain size, is discussed with a comparison of the theoretical models.
Źródło:
Archives of Metallurgy and Materials; 2015, 60, 2B; 1287-1291
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Properties of Multi-Stacked InAs Quantum Dots Embedded in GaAs/InGaAs Strained Layer and its Annealing Behaviors
Autorzy:
Kim, D.
Kim, G.
Jeon, S.
Cho, M.
Choi, H.
Kim, M.
Lee, D.
Kim, J.
Eom, G.
Leem, J.
Powiązania:
https://bibliotekanauki.pl/articles/1537752.pdf
Data publikacji:
2010-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
78.55.Cr
81.05.Ea
Opis:
Multi-stacked InAs QDs embedded in ten periods of GaAs/$In_{0.1}Ga_{0.9}As$ strained layers were grown by MBE and their optical properties were investigated by using PL spectroscopy. For the QDs embedded in ten periods of GaAs/$In_{0.1}Ga_{0.9}As$ strained layers, the PL intensity is enhanced about 4.7 times and a narrower FWHM of 26 meV is observed compared to those of the conventional multi-stacked QDs. The PL spectra of the InAs QDs show blue-shifts of about 50 meV with increasing annealing temperature up to 850°C. At annealing temperature of 600°C, the FWHM of the PL peak is reduced to 16 meV and PL intensity is enhanced compared to those of the as-grown sample, which indicates improvement of size uniformity and crystal quality of the QDs.
Źródło:
Acta Physica Polonica A; 2010, 117, 6; 941-944
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Effect on the Growth Rate and Physical Characteristics of SnO2 Thin Films Grown by Atomic Layer Deposition
Autorzy:
Kim, D.
Kim, D. H.
Riu, D.-H.
Choi, B. J.
Powiązania:
https://bibliotekanauki.pl/articles/353808.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
atomic layer deposition
tin oxide
growth rate
film density
optical band gap
Opis:
Among the various thin film coating techniques, atomic layer deposition (ALD) has features of good controllability of the thickness, excellent step-coverage in 3-dimensional object even in the sub-nm thickness range at the relatively low deposition temperature. In this study, SnO2 thin films were grown by ALD in the variation of substrate temperatures from 150 to 250°C. Even such a low temperature may influence on the growth kinetics of the ALD reaction and thus the physical characteristics of thin films, such as crystallinity, film density and optical band gap, etc. We observed the decrease of the growth rate with increasing substrate temperature, at the same time, the density of the film was decreased with increasing temperature. Steric hindrance effect of the precursor molecule was attributed to the inverse relationship of the growth temperature and growth rate as well as the film density. Optical indirect band gap energy (~3.6 eV) of the ALD-grown amorphous SnO2 films grown at 150°C was similar with that of the literature value, while slightly lower band gap energy (~3.4 eV) was acquired at the films grown at higher temperature.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 2; 1061-1064
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 29

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