• 소성∙가공
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• 제30권1호
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• pp.35-42
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• 2021

Magnesium alloys are used in electronic devices such as laptops due to their lightweight features as well as vibration absorption and electromagnetic shielding properties. However, the precision of electronics is limited by the large number of small and precise ribs, the cost-effective manufacture of which requires appropriate technology. Plate forging is an efficient manufacturing process that can address these challenges. In this study, plate forging of magnesium alloys was investigated specifically for the fabrication of laptop cover. The plate forging process with back-pressure was used for near-net shape formation. Finite element analysis was used to select appropriate variables for back-pressure formation to generate ribs of various sizes and shapes without defects. The reliability of the analysis was verified to manufacture the prototype. The effect of back-pressure can be verified via fabrication of prototypes as well as structure and forming analysis based on finite element method. The process design factor of back-pressure increases formability without defects of under-filling and flow-through. Moreover, the tensile strength was maintained even after high temperature plate forging at 370 ℃, and the elongation was improved.

• 방사성폐기물학회지
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• 제21권2호
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• pp.255-269
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• 2023

Compared to operational wastes, nuclear power plant (NPP) decommissioning wastes are generated in larger quantities within a short time and include diverse types with a wider range of radiation characteristics. Currently used 200 L drums and IP-2 type transport containers are inefficient and restrictive in packaging and transporting decommissioning wastes. Therefore, new packaging and transport containers with greater size, loading weight, and shielding performance have been developed. When transporting radioactive materials, radiological safety should be assessed by reflecting parameters such as the type and quantity of the package, transport route, and transport environment. Thus far, safety evaluations of radioactive waste transport have mainly targeted operational wastes, that have less radioactivity and a smaller amount per transport than decommissioning wastes. Therefore, in this study, the possible radiation effects during the transport from NPP to disposal facilities were evaluated to reflect the characteristics of the newly developed containers and decommissioning wastes. According to the evaluation results, the exposure dose to transport workers, handling workers, and the public was lower than the domestic regulatory limit. In addition, all exposure dose results were confirmed, through sensitivity analysis, to satisfy the evaluation criteria even under circumstances when radioactive materials were released 100% from the container.

• 열처리공학회지
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• 제35권2호
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• pp.88-95
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• 2022

Titanium alloy for bio-medical applications have been developed to reduce the toxicity of alloying elements and avoid the stress-shielding effect which is caused by relatively high elastic modulus compared to bone. Ti-39Nb-6Zr (TNZ40) alloy of elastic modulus exhibits around 40 GPa in the case of beta single phase. However, the strength of this alloy is lower than the other types of titanium alloys. Many research found that adding oxygen to beta-titanium alloys is beneficial for improving the strength through solid solution strengthening. In this study, TNZ40 ingots with addition of O were prepared by an arc remelting process (Ti-39Nb-6Zr-0.16O (wt.%), Ti-39Nb-6Zr-0.26O (wt.%)). Thermo-mechanical processing (i.e., heat treatment, cold swaging and aging heat treatment) has been performed under various conditions. Therefore, the aim of this study is to investigate the effect of oxygen content and ω phase formation on microstructure and mechanical properties.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1009-1014
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• 2023

Muon tomography is a useful method for monitoring special nuclear materials (SNMs) such as spent nuclear fuel inside dry cask storage. Multiple Coulomb scattering of muons can be used to provide information about the 3-dimensional structure and atomic number(Z) of the inner materials. Tomography using muons is less affected by the shielding material and less harmful to health than other measurement methods. We developed a muon detector for muon tomography, which consists of a plastic scintillator, 64 long wavelength-shifting (WLS) fibers attached to the top of the plastic scintillator, and silicon photomultipliers (SiPMs) connected to both ends of each WLS fiber. The muon detector can acquire X and Y positions simultaneously using a position determination algorithm. The design parameters of the muon detector were optimized using DETECT2000 and Geant4 simulations, and a muon detector prototype was built based on the results. Spatial resolution measurement was performed using simulations and experiments to evaluate the feasibility of the muon detector. The experimental results were in good agreement with the simulation results. The muon detector has been confirmed for use in a muon tomography system.

• 한국방사선학회논문지
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• 제2권3호
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• pp.33-35
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• 2008

In the neutron capture experiment and calculation, the neutron absorption and scattering are very important. Especially these effects are conspicuous in the resonance energy region and below the thermal energy region. In the present study, we obtained energy dependent neutron absorption ratios of natural rhodium in energy region from 0.003 to 100 eV by MCNP-4B Code. The coefficients for neutron absorption was calculated for several types of thickness. In the lower energy region, neutron absorption is larger than higher region, because of large capture cross section (1/v). Furthermore it seems very different neutron absorption in the large resonance energy region. These results are very useful to decide the thickness of sample and shielding materials.

• 한국방사선학회논문지
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• 제3권3호
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• pp.23-25
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• 2009

Gd-157 material has very large neutron capture cross section in the thermal region. So it is very useful to shield material for thermal neutrons. Futhermore, in the neutron capture experiment and calculation, the neutron absorption and scattering are very important. Especially these effects are conspicuous in the resonance energy region and below the thermal energy region. In the case of very narrow resonance, the effect of scattering is to be more considerable factor. In the present study, we obtained energy dependent neutron absorption ratios of natural indium in energy region from 0.003 to 100 keV by MCNP-4B Code. The coefficients for neutron absorption was calculated for circular type and 1 mm thickness. In the lower energy region, neutron absorption is larger than higher region, because of large capture cross section (1/v). Furthermore it seems very different neutron absorption in the large resonance energy region. These results are very useful to decide the thickness of sample and shielding materials.

• 한국정밀공학회지
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• 제27권1호
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• pp.99-104
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• 2010

Magnesium and magnesium alloys, the lightest structural materials, have been received plenty of global attention recently. These alloys could be applied in various fields, especially the electronics industry, because of their excellent electromagnetic interference shielding. However, the welding technique of magnesium alloys has not been established. This study is related to the welding of AZ31B magnesium alloy by a short-pulsed a Nd:YAG laser. Two types of pulse waves, square pulse and variable pulse, were used to control weld defects. Results show that the crack and porosity, generated in the weld, had not been controlled by general square pulse. But through the application of variable pulse, the defects could be prevented and the good weld zone was obtained.

• 한국응용과학기술학회지
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• 제8권1호
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• pp.45-49
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• 1991

The synthesis of urocanic acid which was started D-fructose, and its alkyl esters, urocanic ethyl ester and urocanic isobutyl ester, were prepared by esterificated. Urocanic ethyl ester and urocanic isobutyl ester were insoluble in water and soluble most organic solvents (ethanol, benzene, toluene, pyridine, THF, DMF) which adds to their practical applicability, and absorb ultraviolet light of greater wavelength than the free acid and there by are more effective for shielding sensitive materials, including the humanbody, from the chemically most effective portion of the solar ultraviolet spectrum.

• 전기학회논문지
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• 제56권6호
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• pp.1130-1132
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• 2007

In this research, 3D position exploring system was developed to detect direction and position of radiation source by using two general CCD camera. This system consists of a radiation detection device, a controlling device, and a monitoring device. A radiation detection device is composed of a collimator, a scintillator, CCD sensor, and radiation shielding part. Incident radiation is firstly collimated with direction and converted into visual lights in a scintillator. The CCD sensor detect the converted visual light and send a signal as an image. This can explore a radiation source with direction and distance from geometrical structure of two sensors. From these information, the developed 3D position exploring system can provide 3D radiation source information. This research will be useful for managing and processing radioactive materials in remote.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2006년도 High Temperature Superconductivity Vol.XVI
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• pp.50-50
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• 2006