• Applied Microscopy
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• 제6권1호
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• pp.1-7
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• 1976

To investigate the nature of typhoid cells, three cases of clinically, serologically and histopathologically proven typhoid lesions of the small intestine and regional lymph nodes were studied light and electron microscopically, Light microscopically, typhoid cells were swollen mononuclear cells characterized by abundant amount of eosinophilic cytoplasm and frequent phagocytoses of red blood cells, bacterial clumps and other tissue debris. These cells were pyronin negative, Electron microscopically, these cells showed marked and diffuse dilatation of RER cisternae and disappearance of ordinary cytoplasmic organelles, but frequent phagocytosed materials, The meaning and reason of RER cisternal dilatation and reduction of cytoplasmic organelles were discussed, and are regarded as degenerative process due to bacterial endotoxin. Although there was hot enough cytoplasmic organelles to pinpoint the origin of typhoid cells, active phagocytosis and evidences against being either plasmacytic or lymphocytic nature favored retuculoendothelial nature of the typhoid cells.

• 한국분말재료학회지
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• 제7권4호
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• pp.197-204
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• 2000

Gas atomization mechanical alloying and hot pressing have successfully made high temperature Al-9.45Fe-4.45Cr alloy. The microstructure and mechanical properties of this alloy has been studied by using optical microscope, scanning electron microscope, transmission electron microscope, X-ray diffractometer and compressive tester. It contains high concentration of transition elements of Fe and Cr, which form thermally stable dispersoids in the aluminum matrix. Proper oxidation of powders during ball milling strengthens the bulk extrudates by providing the obstacle particles. The oxide particles are very chemically and thermally stable and prevent the coarsening of the intermediate compounds.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.68-70
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• 2006

For the aluminum material of the thick-thickness more than 100mm Penetration depth Electron beam welding is effectively applicable with a characteristic of high energy intensity. But Al 6061 alloy has high crack sensitivity due to minor alloys, which are silicon, magnesium, copper etc. With a sample block of 135mm thickness EBW test was performed in vertical position. As tensile strength has $210{\sim}220N/mm^2$ with weld area broken. Bend test shows low ductility with fracture of partly specimens. Chemical contents of alloys show no difference between weld and base metal. Defect in middle weld area figures out typical hot crack due to low melting materials. Micro structure of weld area has some difference compare to HAZ and base metal. As a result of EBW test for Al 6061 alloy, it shows that weld defect could be occurred even though establishing of optimum weld parameter condition.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.168-170
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• 2005

Nickel base brazes containing boron and silicon as melting point depressants are used extensively in the joining and repair of hot-section components in next generation nuclear reactor and aero-engine. Therefore, the present study has investigated the preliminary applicability of nickel based alloying nano powders. Nano Ni-based alloying powders synthesized by Pulsed Wire Evaporation (PWE) method. It's powder morphology and phase transformation temperature were analyzed by scanning electron microscopy, transmission electron microscopy, and differential scanning calorimeter(DSC). The powder particle size was approximately 10${\sim}$100nm and exhibits a quite even equiaxed shape. The results of DSC measurement show that both the nano Inconel 625 nano powder and Inconel 718 nano powder presents similar liquidus temperatures approximately $1373^{\circ}C$ and $1380^{\circ}C$ respectively.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.369-369
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• 2011

In the current work, we demonstrate the gas phase plasma synthesis of ultrafine boron nanoparticles by decomposing boron trichloride (BCl3) gas in an argon-hydrogen thermal plasma and quenching the hot plasma by expansion through a ceramic nozzle, driving the homogeneous nucleation of nanoparticles. It is shown that ultrafine nanoparticles can be produced from the experiments. We also show the characterization results regarding the oxidation of boron nanoparticles at room temperature using X-ray Photoelectron Spectroscopy (XPS) and the combined Scanning Transmission Electron Microscope (STEM) and Electron Energy Loss Spectroscopy (EELS).

• International Journal of Korean Welding Society
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• 제3권2호
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• pp.29-39
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• 2003

The durability and reliability of thermal barrier coatings (TBCs) play an important role in the service reliability, availability and maintainability (RAM) of hot­section components in advanced turbine engines for aero and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary non­destructive evaluation (NDE) techniques for quality control and life­remain assessment of TBCs. This paper overviews the governing principles and applications of the luminescence and the impedance examined in the light of residual stress, phase constituents and resistance (or capacitance) in TBC constituents including the thermally grown oxide (TGO) scale. Results from NDE by PSLS and EIS are discussed and related to the microstructural development during high temperature thermal cycling, examined by using a variety of microscopic techniques including focused ion beam (FIB) in­situ lift­out (INLO), transmission and scanning transmission electron microscopy (TEM and STEM).

• Archives of Metallurgy and Materials
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• 제64권2호
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• pp.539-542
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• 2019

Pre-alloyed Astaloy CrL^TM (Fe-1.5 wt% Cr-0.2 wt% Mo), a commercial Fe-based alloy powder for high strength powder metallurgy products, was sintered and hot forged with additions of 0.5 wt% C and 0~2 wt% Cu. To investigate the influence of various Cu contents, the microstructural evolution was characterized using density measurements, scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). Transverse rupture strength (TRS) was measured for each composition and processing stage. The correlation between Cu additions and properties of sinter-forged Fe-Cr-Mo-C alloy was discussed in detail.

• 천문학회보
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• 제37권1호
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• pp.93.1-93.1
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• 2012

In this study, we investigated the generation of consecutive electrostatic solitary waves (ESWs) using by one-dimensional electrostatic particle-in-cell (PIC) simulation. For a given Gaussian perturbation, it is found that electron two-stream instability occurs in local grids region. Thus because of this instability, the electrostatic potential grows rapidly so as to be separated into electron and ion in perturbation region, and then electrons are trapped with heating during growing instability. It is found that these heated and trapped electrons are caused the generation of ESW, and ions are reflected backward and forward at the boundary of the initial perturbation, then form cold ion beam whereas electrons are confined to inside of the potential. Furthermore backward reflected ion beam forms ion holes by ion two-stream instability. On the other hand, as the confined electrons are released, and then released electrons also form hot electron beam, which play an important role in the generation of consecutive ESWs such as broadband electrostatic noise (BEN) observed frequently in space environment. Therefore the reason of the generation of consecutive ESWs is the existence of heated electrons which can sufficiently support energy to produce ESWs.

• 대한의생명과학회지
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• 제15권4호
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• pp.335-342
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• 2009

This study was investigated to evaluate the contents of polyphenols and flavonoids, and physiological activities of various extracts from Calystegia japonica roots for making good use of their functional materials. The roots of C. japonica were extracted with water (WE), ethanol (EE) and hot water (HWE) by different methods. Among these extracts, the highest extracting yield was 30.30% of HWE, while the highest contents of total polyphenols and flavonoids were 40.85% and 6.40% of WE, respectively. The nitrite scavenging abilities were ranged from 31.31% (HWE) to 37.46% (EE) at pH 1.2 and 1.0 mg/ml concentration. In the measurements of electron donating abilities, EE showed the highest effect as 91.83% at 0.3 mg/ml assay concentration, and the electron donating ability was decreased as the extract concentration was increased. In the results of superoxide dismutase (SOD)-like activity, HWE showed the highest effect as 7.15% at 1.0 mg/ml. The tyrosinase inhibition activities of WE and EE were 15.28% and 14.97%, respectively. The xanthine oxidase inhibitory effects were ranged from 97.50 to 99.28% at 1.0 mg/ml. These results indicate that C. japonica extract has a good antioxidant effects and could be useful for developing functional products.

• 대한전자공학회논문지
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• 제27권4호
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• pp.534-540
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• 1990

In this paper the characteristics of submicron gate GaAs MESFET's have been studied using a particle model which takes into account the hot-electron transport phenomena, i.e., the velocity overshoot. \ulcornervalley(<000> direction), L valley (<111>direction), X valley (<100>direction) as the GaAs conduction energy band and optical phonon, acoustic phonon, equivalent intervalley, nonequivalent intervalley scattering as the scattering models, have been considered in this simulation. And the GaAs material and the device simulation have been done by determination of the free flight time, scattering mechanism and scattering angle according to Monte-Carlo algorithm which makes use of a particle model. As a result of the particle simulation, firstly the electron distribution, the potential energy distribution and the situation of electron displacement in 0.6 \ulcorner gate length device have been obtained. Secondly, the cutoff frequency, obtained by this method, is k47GHz which is in good agreement with the calculated result of theory. And the current-voltage characteristics curve which takes account of the buffer layer effect has been obtained. Lastly it has been verified that parasitic current at the buffer layer can be analyzed using channel depth modulation.