• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3026-3034
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• 2021

Multi-target X-ray tube is a new type X-ray source, and can be applied in many fields such as sensitive X-ray fluorescence analysis and medical imaging. In this work, we report an electric field modulation multi-target X-ray tube, which contains four targets (Cr, Ni, Au, Mo) coated on a Beryllium (Be) window. A four-valve electric field deflector was developed to deflect the electron beam to bombard the corresponding targets. Particle dynamics analysis software was employed to simulate the particle tracking of electron beam. The results show that the 30 keV electron beam could get a 6.7 mm displacement on the target plane by 10⁵ V/m electric field. The focus areas are about 2 mm × 5 mm and 4 mm × 2.5 mm after deflection in two directions. Thermal behavior calculated by ANSYS shows that the designed target assembly could withstand a 10 W continuous power. The optimum target thicknesses and emission spectra were obtained by Geant4 when the thickness of Be window was 300 mm and the electron beam incident angle was 0.141 rad. The results indicate that this multi-target X-ray tube could provide different X-ray sources effectively.

• Journal of the Korean Physical Society
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• v.73 no.10
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• pp.1495-1501
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• 2018

We have developed an extended three-dimensional free-electron laser (3D FEL) code with source-dependent expansion to calculate the intensity of the radiation field and the spot size in a free-electron laser oscillator. The effect of the wiggler field errors was evaluated for the case of a planar wiggler generated by a magnet stack with parabolic shaped pole faces by using the extended three-dimensional equations in a free-electron laser oscillator based on the proposed FEL facility which is to be operated in the far-infrared and the infrared regions. The radiation spot size due to the wiggler field errors also have been analyzed for wiggler errors of ${\Delta}B/B=0.0$, 0.03, 0.06 and 0.09% at z = 1 m and z = 2 m. The effect of the diffraction of radiation field due to the wiggler field errors of ${\Delta}B/B=0.0$ and ${\Delta}B/B=0.09%$ at 200 passes was evaluated by using the extended 3D code that we developed. The variation of the curvature of the phase front and the effect of the radiation field intensity due to the wiggler field errors were also evaluated for B = 0.5 T and B = 0.7 T with the wiggler error of ${\Delta}B/B=0.09%$ at 200 passes and the results were compared to those of without errors. The intensity of the radiation, behavior of the radiation spot size and the variation of the curvature of the phase were highly sensitive to the wiggler error of ${\Delta}B/B$ > 0.09%, but were less sensitive to the wiggler errors for ${\Delta}B/B$ < 0.09% in a free-electron laser (FEL) oscillator based on the proposed FEL facility.

• The Journal of Korean Academy of Prosthodontics
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• v.22 no.1
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• pp.95-108
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• 1984

Even though the tarnishing and corrosion problems characteristic with dental silver-palladium alloy are not yet fully solved, it is recently widely used because of its low cost. However the effects of major alloying elements on the various properties of this system are not fully understood. The object of this research is to clarify the effects of In and Zn additives on the corrosion and tarnishing resistances and precipitation hardening behavior of this sytem, using electrodynamic polarization, immersion, and Vicker's microhardness test and X-ray diffraction and electron probe micro analysis methods. The obtained results were as follows: I. As indium content is increased, both the corrosion resistance in Cl-solution and microhardness are also increased while the tarnishing resistance is decreased. 2. As Zinc content is increased, the corrosion resistance is decreased, but tarnishing resistance is increased 3. At 70Ag-25Pd-2.5Zn-2.5In composition, the precipitation harding behavior was mot significant. The optimum aging temperature was $450^{\circ}C$ and the time was 2 hrs. The resulting specimen of this work carried 180VHN. 4. Under the heat treatment, the changes in the mechanical property are due to the changes in the shape and composition of dendrite matrix, namely, it is because of the precipitation hardening behavior which has been proved by electron probe micro analysis and optical microscopic finding.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.429-436
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• 2013

This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.

• Korean Journal of Materials Research
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• v.23 no.11
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• pp.649-654
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• 2013

The effect of interstitial elements on the ductile-brittle transition behavior of austenitic Fe-18Cr-10Mn-2Ni alloys with different nitrogen and carbon contents was investigated in this study. All the alloys exhibited ductile-brittle transition behavior because of unusual low-temperature brittle fracture, even though they have a faced-centered cubic structure. With the same interstitial content, the combined addition of nitrogen and carbon, compared to the sole addition of nitrogen, improved the low-temperature toughness and thus decreased the ductile-brittle transition temperature (DBTT) because this combined addition effectively enhances the metallic component of the interatomic bonds and is accompanied by good plasticity and toughness due to the increased free electron concentration. The increase in carbon content or of the carbon-to-nitrogen ratio, however, could increase the DBTT since either of these causes the occurrence of intergranular fracture that lead to the deterioration of the toughness at low temperatures. The secondary ion mass spectroscopy analysis results for the observation of carbon and nitrogen distributions confirms that the carbon and nitrogen atoms were significantly segregated to the austenite grain boundaries and then caused grain boundary embrittlement. In order to successfully develop austenitic Fe-Cr-Mn alloys for low-temperature application, therefore, more systematic study is required to determine the optimum content and ratio of carbon and nitrogen in terms of free electron concentration and grain boundary embrittlement.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.60-65
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• 2014

Fe-based amorphous coatings were fabricated on a soda-lime glass substrate by the vacuum kinetic spray method. The effect of the gas flow rate, which determines particle velocity, on the deposition behavior of the particle and microstructure of the resultant films was investigated. The as-fabricated microstructure of the film was studied by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Although the activation energy for transformation from the amorphous phase to crystalline phase was lowered by severe plastic deformation and particle fracturing under a high strain rate, the crystalline phases could not be found in the coating layer. Incompletely fractured and small fragments 100~300 nm in size, which are smaller than initial feedstock material, were found on the coating surface and inside of the coating. Also, some pores and voids occurred between particle-particle interfaces. In the case of brittle Fe-based amorphous alloy, particles fail in fragmentation fracture mode through initiation and propagation of the numerous small cracks rather than shear fracture mode under compressive stress. It could be deduced that amorphous alloy underwent particle fracturing in a vacuum kinetic spray process. Also, it is considered that surface energy caused by the formation of new surfaces and friction energy contributed to the bonding of fragments.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3717-3723
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• 2022

For the first time, two-dimensional temporal behavior of the edge localized mode (ELM) filament is measured in the edge tokamak plasma with a multi-channel electrical probe array (MCEP). MCEP, which has 16 floating probes (4 × 4), is mounted at the far scrape-off layer (SOL) region in the KSTAR. An electron temperature and an ion flux are measured by sideband method (SBM), which can achieve two-dimensional measurements with high time resolution. Furthermore, temporal evolutions of the electron temperature and the ion flux are obtained during the ELM occurrence. In the H-mode period, short spikes from ELM bursts are observed in measured plasma parameters, and the trend is similar to that of typical Hα signal. Interestingly, when blob-like ELM filaments crash the probe, the heat flux is significantly higher in a local region of the probe array. The results show that our probe array using the SBM can measure the ELM behavior and the plasma parameters without the effect of the stray current caused by the huge device. This study can provide valuable data needed to understand the interaction between the SOL plasma and the plasma facing components (PFCs).

• ETRI Journal
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• v.34 no.6
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• pp.950-953
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• 2012

Schottky barrier single electron transistors (SB-SETs) and Schottky barrier single hole transistors (SB-SHTs) are fabricated on a 20-nm thin silicon-on-insulator substrate incorporating e-beam lithography and a conventional CMOS process technique. Erbium- and platinum-silicide are used as the source and drain material for the SB-SET and SB-SHT, respectively. The manufactured SB-SET and SB-SHT show typical transistor behavior at room temperature with a high drive current of $550{\mu}A/{\mu}m$ and $-376{\mu}A/{\mu}m$, respectively. At 7 K, these devices show SET and SHT characteristics. For the SB-SHT case, the oscillation period is 0.22 V, and the estimated quantum dot size is 16.8 nm. The transconductance is $0.05{\mu}S$ and $1.2{\mu}S$ for the SB-SET and SB-SHT, respectively. In the SB-SET and SB-SHT, a high transconductance can be easily achieved as the silicided electrode eliminates a parasitic resistance. Moreover, the SB-SET and SB-SHT can be operated as a conventional field-effect transistor (FET) and SET/SHT depending on the bias conditions, which is very promising for SET/FET hybrid applications. This work is the first report on the successful operations of SET/SHT in Schottky barrier devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.100-104
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• 2000

Diamond film was deposited on Si substrate by using microwave plasma-enhanced chemical vapor deposition (MPECVD) system. After thinning the cross section between diamond film and Si substrate by ion milling method, we investigated its interface via transmission electron microscopy We could observe that the diamond film was grown either directly on Si substrate or via the interlayer between diamond film and Si substrate. Thickness of the interlayer was varied along the cross section. The interlayer might mainly composed of Sic andlor amorphous carbon. We could observe the well-developed electron diffraction pattern of both Si and diamond around the interface. Based on this result, we can conjecture the initial growth behavior of diamond film on Si substrate.

• Composites Research
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• v.15 no.2
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• pp.40-47
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• 2002

The di-functional epoxy resins, i.e., diglycidylether of bisphenol A(DGEBA) and diglycidylethere of bisphenol F(DGEBF) were initiated by cationic catalyst, i.e., benzylquinoxalinium hexafluoroantimonate(BQH) using electron-beam(EB) technique. And the effect of structure of DGEBA and DGEBF on thermal stabilities and cure behaviors was investigated. According to the experimental results, the decomposed activation energy based on Horowitz-Metzger method was higher in the case of DGEBA, but intergral procedural decomposition temperature(IPDT) of DGEBA was lower than DGEBF. This could be interpreted in terms of high crosslink density resulted from hydroxyl bond of DGEBF backbone. It was confirmed in increasing the hydroxyl band at $7000\;cm^{-1}$ and $5235\;cm^{-1}$ using near-infrared spectroscopy(NIRS).