Wyniki wyszukiwania - BazTech

1

Microstructure and Corrosion Behaviors of Biodegradable Mg-1Zn-1Zr-xSn Alloys Prepared by Powder-In-Tube Rolling

Zakiyuddin A., Lee K.

Archives of Metallurgy and Materials

|

2018

|

Vol. 63, iss. 3

1467--1471

EN

The objective of the present study was to investigate the effects of Sn addition on the mechanical and corrosion properties of Mg-1Zn-1Zr-xSn (x = 1, 2, 3, 4, 5 wt.%) alloys prepared by powder-in-tube rolling (PTR) method. The PTR-treated Mg alloys reached 98.3% of theoretical density. The hardness of the alloy increased with Sn addition. Two main intermetallic phases, Mg2Sn and Zn2Zr3, were formed in the alloys. The Mg2Sn intermetallic particles were observed along the grain boundaries, while the Zn2Zr3 particles were distributed in the Mg matrix. The addition of 1 wt. % Sn caused the corrosion potential to shift toward a more positive value, and the resulting alloy exhibited low corrosion current density.

2

Influence of the Calcination Temperature on the Optical and Mechanical Properties of Y2O3-MgO Nanocomposite

Yong S.-M., Choi D. H., Lee K., Ko S.-Y., Cheong D.-I.

Archives of Metallurgy and Materials

|

2018

|

Vol. 63, iss. 3

1481--1484

EN

Y2O3-MgO nanocomposites are one of the most promising materials for hypersonic infrared windows and domes due to their excellent optical transmittance and mechanical properties. In this study, influence of the calcination temperature of Y2O3-MgO nanopowders on the microstructure, IR transmittance, and hardness of Y2O3-MgO nanocomposites was investigated. It was found that the calcination temperature is related to the presence of residual intergranular pores and grain size after spark plasma sintering. The nanopowders calcined at 1000°C exhibits the highest infrared transmittance (82.3% at 5.3 μm) and hardness (9.99 GPa). These findings indicated that initial particle size and distribution of the nanopowders are important factors determining the optical and mechanical performances of Y2O3-MgO nanocomposites.

3

Enhanced Microwave Absorption of CNT Composites Mixing with Fe3O4 and Carbonyl Iron

Park J. H., Choi J., Lee K., Park J., Song J. K., Jeon E.

Archives of Metallurgy and Materials

|

2018

|

Vol. 63, iss. 3

1513--1516

EN

We fabricated two different kinds of composite materials for absorbing microwave in a frequency range of 2 to 18 GHz using coaxial airline and thru-reflect-line (TRL) method. The composite materials having carbon nanotube (CNT) with carbonyl iron (CI) or iron oxide (Fe3 O4 ) were fabricated by mixing each components. Magnetic properties were measured by SQUID equipment. Complex permittivity and complex permeability were also obtained by measuring S-parameters of the toroidal specimen dispersing CI/CNT and Fe3 O4 /CNT into the 50 weight percent (wt%) epoxy resin. The real permittivity was improved by mixing the CNT however, the real permeability was same as pure magnetic powders. The CI/CNT had a maximum value of real permittivity and real permeability, 11 and 1.4 at 10 GHz, respectively. The CNT composites can be adapted to the radar absorbing materials, band width 8-12 GHz.

4

Development of a service robot for indoor operation using distributed computing

Mazumdar A., Lee K., Evran E., Algorri M.-E.

Zeszyty Naukowe Instytutu Pojazdów / Politechnika Warszawska

|

2017

|

z. 3/112

31--40

EN

Service robots already take over some chores of our daily life, for example as autonomous vacuum cleaners or lawn mowing machines. In the near future it is expected that service robots can fully undertake many domestic tasks and assist in different operating places like restaurants, hospitals or industries. We have developed a cost effective prototype of a mobile service robot that can operate in indoor environments. The robot works under ROS and has a kinect sensor for vision and tracking. The robot maps the environment using SLAM and can navigate between locations avoiding permanent and temporary obstacles. Our objective is to deploy image processing algorithms and advanced decision making abilities using low computing power on the Robot. Using distributed ROS nodes the robot sends the image stream from its sensors to a server to be processed using deep learning algorithms. The results of the processing are sent back to the robot to guide its navigation and operations.

DE

Serviceroboter übernehmen schon heute einige Aufgaben des täglichen Lebens, zum Beispiel als autonome Staubsauger oder Rasenmäher. In naher Zukunft, so wird erwartet, werden Serviceroboter eine Vielzahl von Hausarbeiten erledigen und in verschieden Bereichen wie Restaurants, Krankenhäusern oder der Industrie eingesetzt werden. Wir haben einen kostengünstigen mobilen Prototypen eines Serviceroboters für den Innenbereich entwickelt. Der Roboter läuft unter ROS und verfügt über einen Kinekt-Sensor für maschinelles Sehen und Tracking. Der Roboter kartografiert die Umgebung mittels SLAM und navigiert zwischen Positionen und weicht dabei permanenten und temporären Hindernissen aus. Unser Ziel ist es Bildverarbeitungsalgorithmen und komplexe Entscheidungsprozesse für geringe Computerleistung im Roboter einzusetzen. Über verteilte ROS-Knoten sendet der Roboter den Videostream vom Sensor zum Server, wo er mit Deep Learning Algorithmen verarbeitet wird. Die Verarbeitungsergebnisse werden zum Roboter zurückgesendet um seine Navigation und Funktionen zu steuern.

5

Effect of Alloying Elements on Plastic Workability and Corrosion Behavior of Ti-X (X = 6 Co, 8 Cr, 4 Fe, 6 Mn, 10 Mo, and 36 Nb) Binary Alloys

Zhao Z., Lee K.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2B

1185--1190

EN

The purpose of this study was to investigate the effect of the alloying elements on the plastic workability and corrosion behavior of Ti-X (wt.%) (X = 6 Co, 8 Cr, 4 Fe, 6 Mn, 10 Mo, and 36 Nb) binary alloys. The alloys with a molybdenum equivalence of 10 wt.% were fabricated by a vacuum arc re-melting process and were then homogenized at a temperature 20°C greater than the beta transus temperature for 14.4 ks. The plastic workability was investigated under uniaxial cold rolling, while the corrosion behavior was examined in Ringer’s solution at 37°C. Among the Ti-X alloys, the Ti-8 wt.% Cr and Ti-6 wt.% Mn alloys showed an outstanding plastic workability and corrosion resistance, respectively.

6

Compressive Deformation Behavior of Thick Micro-Alloyed HSLA Steel Plates at Elevated Temperatures

Lee J.-H., Kim D.-O., Lee K.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2B

1191--1196

EN

The hot deformation behavior of a heavy micro-alloyed high-strength low-alloy (HSLA) steel plate was studied by performing compression tests at elevated temperatures. The hot compression tests were carried out at temperatures from 923 K to 1,223 K with strain rates of 0.002 s-1 and 1.0 s-1. A long plateau region appeared for the 0.002 s-1 strain rate, and this was found to be an effect of the balancing between softening and hardening during deformation. For the 1.0 s-1 strain rate, the flow stress gradually increased after the yield point. The temperature and the strain rate-dependent parameters, such as the strain hardening coefficient (n), strength constant (K), and activation energy (Q), obtained from the flow stress curves were applied to the power law of plastic deformation. The constitutive model for flow stress can be expressed as σ = (39.8 ln (Z) – 716.6) · ε(−0.00955ln(Z) + 0.4930) for the 1.0 s-1 strain rate and σ = (19.9ln (Z) – 592.3) · ε(−0.00212ln(Z) + 0.1540) for the 0.002 s-1 strain rate.

7

RF Magnetron Sputtering Coating Of Hydroxyapatite On Alkali Solution Treated Titanate Nanorods

Lee K., Shin G.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 2B

1319--1322

EN

Hydroxyapatite (HA) is a material with outstanding biocompatibility. It is chemically similar to natural bone tissue, and has therefore been favored for use as a coating material for dental and orthopedic implants. In this study, RF magnetron sputtering was applied for HA coating. And Alkali treatment was performed in a 5 M NaOH solution at 60°C. The coated HA thin film was heat-treated at a range of temperatures from 300 to 600°C. The morphological characterization and crystal structures of the coated specimens were then obtained via FE-SEM, XRD, and FT-IR. The amorphous thin film obtained on hydrothermally treated nanorods transformed into a crystalline thin film after the heat treatment. The change in the phase transformation, with an enhanced crystallinity, showed a reduced wettability. The hydrothermally treated nanorods with an amorphous thin film, on the other hand, showed an outstanding wettability. The HA thin film perpendicularly coated the nanorods in the upper and inner parts via RF magnetron sputtering, and the FT-IR results confirmed that the molecular bonding of the coated film had an HA structure.

8

Large-Area Sodium Titanate Nanorods Formed On Titanium Surface Via NaOH Alkali Treatment

Lee K., Yoo D.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 2B

1371--1374

EN

Ti surfaces covered with large sodium titanate nanorods act as efficient electrodes for energy conversion and environmental applications. In this study, sodium titanate nanorod films were prepared on a Ti substrate in a 5M NaOH aqueous solution followed by heat treatment. The morphological characterization and the crystal structures of the sodium titanate nanorods were investigated via scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Thin amorphous sodium titanate layers formed during the alkali-treatment, and sodium titanate nanorods were obtained after heat treatment at a temperature of 700°C. The sodium titanate nanorods obtained at this temperature had a thickness of about 80 nm and a length of 1 μm. The crystal structure of the sodium titanate was identified with the use of Na2Ti5O11. The nanorods were agglomerated at a temperature above 900°C, and large-scale nanorods formed on the Ti surface, which may be used for electrodes for energy conversion applications.

9

Ellipse Invariant Algorithm for Texture Classification

Yao C. C., Lee K.

Fundamenta Informaticae

|

2012

|

Vol. 114, nr 2

203-220

EN

The classification of texture images, especially those with spatial rotation and region shift, is a challenge and important problem in image analysis and classification. This paper proposes a novel algorithm design, an ellipse invariant algorithm, to improve the capability of texture classification for spatial rotation and region shift. The principle of an ellipse invariant algorithm is to use a minimum ellipse to enclose specific representative pixels extracted by the subtracting clustering method. After translating the coordinates, the ellipse in the rotated texture would be formulated as the ellipse in original texture. Also in this paper a hybrid texture filter is proposed. In the hybrid texture filter the scheme of texture feature extraction include Gabor wavelet, neighboring grey level dependence matrix and the ellipse invariant algorithm. Support vector machines (SVMs) are introduced as the classifier. The proposed hybrid texture filter can classify both the stochastic textures and structural textures. Experimental results reveal that this proposed algorithm outperforms existing design algorithms.

10

Development of a large beam facility

Oh B., In S., Lee K., Jeong S., Seo C., Chang D.

Nukleonika

|

2006

|

Vol. 51, nr 1

37-42

EN

A large beam facility for the application of high power ion beams has been developed at the Korea Atomic Energy Research Institute (KAERI). The primary usage of this facility is to develop an 8 MW neutral beam heating system for a tokamak, but other applications using a large beam would also be possible in the near future. The facility is composed of a bucket ion source (120 kV, 65 A), related beam line components including a large vacuum chamber (3 m x 4 m x 5 m), power supplies for the ion source, control and DAS (Data Acquisition System), beam diagnostics system, and a water circulation system (2 MW) for cooling of the beam line components. The maximum beam parameters at present are a beam energy of 87 kV and a beam current of 17.5 A with a beam size of 13 x 45 cm2. A maximum pulse length of 10 s could be achieved with a 1 MW beam power. The beam power with a hydrogen ion will be increased up to 7.5 MW during 5 s.