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Wyświetlanie 1-15 z 15
Tytuł:
Analysis and Verification of Physical Properties of an AISI 4140 Steel by Vickers Indentation Analysis According to the Presence of Residual Stresses
Autorzy:
Jung, Changho
Lee, Moon G.
Jeon, Yongho
Powiązania:
https://bibliotekanauki.pl/articles/354154.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Vickers indentation
residual stress
FEM analysis
material property
surface treatment
Opis:
Residual stress has a great influence on the metal, but it is difficult to measure at small area using a general method. Residual stress calculations using the Vickers indentation can solve this problem. In this paper, a numerical simulation has been made for the residual stress measurement method of metal material deformed by high-speed impact. Then, the stress-strain curve at the high-speed deformation was confirmed through actual experiments, and the residual stresses generated thereafter were calculated by the Vickers indenter method. A Vickers indentation analysis under the same conditions was performed at the position where a residual stress of about 169.39 MPa was generated. Experiments were carried out and high speed impact was applied to the specimen to generate residual stress. The obtained results indicate that it is possible to identify residual stresses in various metals with various shapes through Vickers indentation measurements, and to use them for process and quality control.
Źródło:
Archives of Metallurgy and Materials; 2019, 64, 3; 823-827
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Certain new M-matrices and their properties with applications
Autorzy:
Mohan, Ratnakaram
Kageyama, Sanpei
Lee, Moon
Yang, G.
Powiązania:
https://bibliotekanauki.pl/articles/729710.pdf
Data publikacji:
2008
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
M-matrices
non-orthogonality
orthogonal number
Hadamard matrix
partially balanced incomplete block (PBIB) design
regular graph
Opis:
The Mₙ-matrix was defined by Mohan [21] who has shown a method of constructing (1,-1)-matrices and studied some of their properties. The (1,-1)-matrices were constructed and studied by Cohn [6], Ehrlich [9], Ehrlich and Zeller [10], and Wang [34]. But in this paper, while giving some resemblances of this matrix with a Hadamard matrix, and by naming it as an M-matrix, we show how to construct partially balanced incomplete block designs and some regular graphs by it. Two types of these M-matrices have been considered. Also we will make a mention of certain applications of these M-matrices in signal and communication processing, and network systems and end with some open problems.
Źródło:
Discussiones Mathematicae Probability and Statistics; 2008, 28, 2; 183-207
1509-9423
Pojawia się w:
Discussiones Mathematicae Probability and Statistics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructural Analysis of Asymmetric Dilution by Rotating Direct Metal Deposition
Autorzy:
Choi, Byungjoo
Lee, Gwang-Jae
Yeom, Hyun-Ho
Lee, Moon-Gu
Jeon, Yongho
Powiązania:
https://bibliotekanauki.pl/articles/356931.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
rotating direct metal deposition
asymmetric dilution
cross-sectional analysis
microstructure
metallurgical composition
Opis:
In this study, cross-section analysis was performed on a novel rotating direct-metal deposition method capable of preliminary surface treatment and damage repair of cylindrical inner walls. The cross-sectional shape, microstructure, and metallurgical composition were analyzed to verify feasibility. No defects such as porosity or cracks were found in the cross section, but asymmetric dilution was observed because of the non-coaxial powder nozzle. Microstructural coarsening was confirmed over a higher dilution area by high-magnification optical microscope images. As the dilution ratio was increased, hard carbides in the dendrite were bulkdiffused into inter-dendrite spaces, and the toughness was lowered by Fe penetration into the deposit. Therefore, the increased laser heat input can be modulated to the typical dilution by decreasing the laser scanning velocity.
Źródło:
Archives of Metallurgy and Materials; 2019, 64, 2; 535-538
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:
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:
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:
High Temperature Oxidation Property of Ni Based Superalloy CM247LC Produced Via Selective Laser Melting Process
Autorzy:
Lee, Jung-Uk
Kim, Young-Kyun
Seo, Seong-Moon
Lee, Kee-Ahn
Powiązania:
https://bibliotekanauki.pl/articles/2203720.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Ni-based superalloy
selective laser melting
directional solidification
microstructure
high temperature oxidation property
Opis:
CM247LC alloy was manufactured by using selective laser melting (SLM) process, one of the laser powder bed fusion (L-PBF) methods. The hot isostatic pressing (HIP) process was additionally conducted on the SLM-built CM247LC to control its microstructures and defects. The high temperature oxidation property was investigated, and it was compared with conventional DS247LC sample (reference) prepared via the directional solidification process. The L-PBF HIP sample showed blocky-type MC carbides generated along the grain boundary with average size of about 200 nm. A semi-spherical primary γ' phase of size 0.4-1.0 μm was also observed inside the grains. Moreover, the DS247LC sample displayed a coarse eutectic γ' phase and many script-type MC carbides. Furthermore, cuboidal-type γ' with an average size of about 0.5 μm was detected. High-temperature oxidation tests were conducted at 1000°C and 1100°C for 24 hours. The results at 1100°C oxidation temperature showed that the measured oxidation weight gains for HIP and DS247LC were 1.96 mg/cm2 and 2.26 mg/cm2, respectively, indicating the superior high-temperature oxidation resistance of the L-PBF HIP sample. Based on the above results, a high-temperature oxidation mechanism of the CM247LC alloys manufactured by the SLM process and the directional solidification process has been proposed.
Źródło:
Archives of Metallurgy and Materials; 2023, 68, 1; 107--112
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Direct Energy Deposition of Mo Powder Prepared by Electrode Induction Melting Gas Atomization
Autorzy:
Roh, Goo-Won
Park, Eun-Soo
Moon, Jaeyun
Lee, Hojun
Byun, Jongmin
Powiązania:
https://bibliotekanauki.pl/articles/2049331.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
molybdenum powder
electrode induction melting gas atomization
direct energy deposition
porosity
hardness
Opis:
Molybdenum (Mo) is used to form a barrier layer for metal wiring in displays or semiconductor devices. Recently, researches have been continuously attempted to fabricate Mo sputtering targets through additive manufacturing. In this study, spherical Mo powders with an average particle size of about 37 um were manufactured by electrode induction melting gas atomization. Subsequently, Mo layer with a thickness of 0.25 mm was formed by direct energy deposition in which the scan speed was set as a variable. According to the change of the scan speed, pores or cracks were found in the Mo deposition layer. Mo layer deposited with scan speed of 600 mm/min has the hardness value of 324 Hv with a porosity of approximately 2%. We demonstrated that Mo layers with higher relative density and hardness can be formed with less effort through direct energy deposition compared to the conventional powder metallurgy.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 3; 795-798
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
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:
The Effect of Lumbar Erector Spinae Muscle Endurance Exercise on Perceived Low-back Pain in Older Adults
Autorzy:
Tufail, Muhammad
Lee, Haebin
Moon, YangGyu
Kim, Hwang
Kim, KwanMyung
Powiązania:
https://bibliotekanauki.pl/articles/1933088.pdf
Data publikacji:
2021-09-22
Wydawca:
PPHU Projack Jacek Wąsik
Tematy:
trunk muscle endurance
perceived low-back pain
perceived exercise fatigue
Opis:
This study investigates changes in lumbar erector spinae (LES) muscle endurance, perceived low-back pain (LBP), and perceived exercise fatigue in older adults, and analyzes the trends of these changes during a 5-week lumbar exercise. Sixteen older adults with LBP were equally and randomly divided into two groups: the experimental group with incline-standing and the control group with the levelstanding positions. They were separately treated with lumbar exercise tasks and 10 seconds of muscle endurance tests using surface electromyography (sEMG). There was a trend of changes in both groups. The exercise tasks led to increase LES muscle endurance in the experimental group (53.7%) and the control group (45.4%) and decrease perceived LBP score significantly with the incline-standing position. There was no significant difference between the two groups in perceived exercise fatigue (p>0.05). Trunk flexion and extension with an incline-standing position can be an effective method to increase LES muscle endurance and reduce LBP in older adults.
Źródło:
Physical Activity Review; 2021, 2, 9; 82-92
2300-5076
Pojawia się w:
Physical Activity Review
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 Composition on Strain-Induced Martensite Transformation of FeMnNiC Alloys Fabricated by Powder Metallurgy
Autorzy:
Choi, Seunggyu
Jeon, Junhyub
Seo, Namhyuk
Moon, Young Hoon
Shon, In-Jin
Lee, Seok-Jae
Powiązania:
https://bibliotekanauki.pl/articles/356419.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
FeMnNiC alloy
spark plasma sintering
strain induced martensite
austenite stability
hardness
Opis:
We investigated the austenite stability and mechanical properties in FeMnNiC alloy fabricated by spark plasma sintering. The addition of Mn, Ni, and C, which are known austenite stabilizing elements, increases its stability to a stable phase existing above 910°C in pure iron; as a result, austenitic microstructure can be observed at room temperature, depending on the amounts of Mn, Ni, and C added. Depending on austenite stability and the volume fraction of austenite at a given temperature, strain-induced martensite transformation during plastic deformation may occur. Both stability and the volume fraction of austenite can be controlled by several factors, including chemical composition, grain size, dislocation density, and so on. The present study investigated the effect of carbon addition on austenite stability in FeMnNi alloys containing different Mn and Ni contents. Microstructural features and mechanical properties were analyzed with regard to austenite stability.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 3; 1001-1004
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructural and Mechanical Characteristics of Non-Equiatomic High Entropy Alloy FeMnCoCr Prepared by Spark Plasma Sintering
Autorzy:
Seo, Namhyuk
Jeon, Junhyub
Choi, Seunggyu
Moon, Young Hoon
Shon, In-Jin
Lee, Seok-Jae
Powiązania:
https://bibliotekanauki.pl/articles/354220.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
non-equiatomic high entropy alloys
phase stability
heat treatment
microstructural characteristics
Opis:
In this study, a non-equiatomic high entropy alloy was fabricated using the spark plasma sintering method, and its microstructural features and mechanical properties were investigated. The chemical composition of FeMnCoCr was determined by using the entropy calculation related to the design of high entropy alloys. A bulk sample with the same composition was also prepared using the conventional metallurgical processes of casting and hot rolling. The microstructures of the samples fabricated by these different processes were compared by microscope observation, and a quantitative phase analysis was carried out using FE-SEM. Hardness measurement was used to evaluate mechanical properties. Particular attention was paid to microstructural changes due to heat treatment, which was analyzed by considering how austenite stability is affected by grain refinement.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 3; 1005-1009
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of TiC Addition on Strain-Induced Martensite Transformation and Mechanical Properties of Nanocrystalline Fe-Mn Alloy Fabricated by Spark Plasma Sintering
Autorzy:
Jeon, Junhyub
Choi, Seunggyu
Seo, Namhyuk
Moon, Young Hoon
Shon, In-Jin
Lee, Seok-Jae
Powiązania:
https://bibliotekanauki.pl/articles/354736.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Fe-Mn alloy
ceramic reinforcement
austenite stability
mechanical properties
spark plasma sintering
Opis:
The effect of TiC content on the microstructure and mechanical properties of a nanocrystalline Fe-Mn alloy was investigated by XRD analysis, TEM observation, and mechanical tests. A sintered Fe-Mn alloy sample with nano-sized crystallites was obtained using spark plasma sintering. Crystallite size, which is used as a hardening mechanism, was measured by X-ray diffraction peak analysis. It was observed that the addition of TiC influenced the average size of crystallites, resulting in a change in austenite stability. Thus, the volume fraction of austenite at room temperature afterthe sintering process was also modified by the TiC addition. The martensite transformation during cooling was suppressed by adding TiC, which lowered the martensite start temperature. The plastic behavior and the strain-induced martensite kinetics formed during plastic deformation are discussed with compressive stress-strain curves and numerical analysis for the transformation kinetics.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 4; 1249-1254
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on Recovery of Valuable Metals in Spent Lithium-Ion Batteries by Al2O3-SiO2-CaO-Fe2O3 Slag System
Autorzy:
Moon, Tae Boong
Han, Chulwoong
Hyun, Soong-Keun
Park, Sung Cheol
Son, Seong Ho
Lee, Man Seung
Kim, Yong Hwan
Powiązania:
https://bibliotekanauki.pl/articles/2049176.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
spent lithium-ion battery
smelting
Al2O3-SiO2-CaO-Fe2O3
recovery
slag
Opis:
This study investigated the recovery behavior of valuable metals (Co, Ni, Cu and Mn) in spent lithium ion-batteries based on Al2O3-SiO2-CaO-Fe2O3 slag system via DC submerged arc smelting process. The valuable metals were recovered by 93.9% at the 1250°C for 30 min on the 20 Al2O3-40SiO2-20Cao-20Fe2O3 (mass%) slag system. From the analysis of the slag by Fourier-transform infrared spectroscopy, it was considered that Fe2O2 and Al2O3 acted as basic oxides to depolymerize SiO4 and AlO4 under the addition of critical 20 mass% Fe2O3 in 20 Al2O3-40SiO2-Cao-Fe2O3 (Cao + Fe2O3 = 40 mass%). in addition, it was observed that the addition of Fe2O3 ranging between 20 and 30 mass% lowers the melting point of the slag system.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 4; 983-986
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-15 z 15

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