• Journal of Information Processing Systems
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• v.18 no.5
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• pp.688-700
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• 2022

A composite bionic soft gripper integrated with electromagnets and magneto-active elastomers is designed by combining the structure of the human hand and the snake's behavior of enhancing friction by actively adjusting the scales. A silicon-based polymer containing magnetized hard magnetic particles is proposed as a soft finger, and it can be reversibly bent by adjusting the magnetic field. Experiments show that the length, width, and height of rectangular soft fingers and the volume ratio of neodymium-iron-boron have different effects on bending angle. The flexible fingers with 20 vol% are the most efficient, which can bend to 90° when the magnetic field is 22 mT. The flexible gripper with four fingers can pick up 10.51 g of objects at the magnetic field of 105 mT. In addition, this composite bionic soft gripper has excellent magnetron performance, and it can change surface like snakes and operate like human hands. This research may help develop soft devices for magnetic field control and try to provide new solutions for soft grasping.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.833-841
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• 2021

During the postulated severe accident of nuclear reactor, eutectic reaction leads to low-temperature melting of fuel cladding and early failure of core structure. In order to model eutectic melting with the moving particle semi-implicit (MPS) method, the eutectic reaction model is developed to simulate the eutectic reaction phenomenon. The coupling of mass diffusion and phase diagram is applied to calculate the eutectic reaction with the uniform temperature. A heat transfer formula is proposed based on the phase diagram to handle the heat release or absorption during the process of eutectic reaction, and it can combine with mass diffusion and phase diagram to describe the eutectic reaction with temperature variation. The heat transfer formula is verified by the one-dimensional melting simulations and the predicted interface position agrees well with the theoretical solution. In order to verify the eutectic reaction models, the eutectic reaction of uranium and iron in two semi-infinite domains is simulated, and the profile of solid thickness decrease over time follows the parabolic law. The modified MPS method is applied to calculate Transient Reactor Test Facility (TREAT) experiment, the penetration rate in the simulations are agreeable with the experiment results. In addition, a hypothetical case based on the TREAT experiment is also conducted to validate the eutectic reaction with temperature variation, the results present continuity with the simulations of TREAT experiment. Thus the improved method is proved to be capable of simulating the eutectic reaction in the severe accident.

• Korean Journal of Materials Research
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• v.33 no.4
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• pp.151-158
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• 2023

In this study, a new type of composite material combined with carbonyl iron, a relatively strong ferromagnetic material, was prepared to overcome the current application limitations of Prussian blue, which is effective in removing radioactive cesium. The surface of the prepared composite was analyzed using SEM and XRD, and it was confirmed that nano-sized Prussian Blue was synthesized on the particle surface. In order to evaluate the cesium removal ability, 0.2 g of the composite prepared for raw cesium aquatic solution at a concentration of 5 ㎍ was added and reacted, resulting in a cesium removal rate of 99.5 %. The complex follows Langmuir's adsorption model and has a maximum adsorption amount (q_e) of 79.3 mg/g. The Central Composite Design (CCD) of the Response Surface Method (RSM) was used to derive the optimal application conditions of the prepared composite. The optimal application conditions achieved using Response optimization appeared at a stirring speed of pH 7, 17.6 RPM. The composite manufactured through this research is a material that overcomes the Prussian Blue limit in powder form and is considered to be excellent economically and environmentally when applied to a cesium removal site.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.97-104
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• 2022

With a small particle size, specific surface area and chemical nature, Pd/Cu-Fe nanocomposites can efficiently remove the organic compounds. In order to understand the applicability for in situ remediation of contaminated groundwater, the degradation of p-nitrophenol by Pd/Cu-Fe nanoparticles was investigated. The degradation results demonstrated that these nanoparticles could effectively degrade p-nitrophenol and near 90% of degradation efficiency was achieved by Pd/Cu-Fe nanocomposites for 120 min treatment. The efficiency of degradation increased significantly when the Pd content increased from 0.05 wt.% and 0.10 wt.% to 0.20 wt.%. Meanwhile, the removal percentage of p-nitrophenol increased from 75.4% and 81.7% to 89.2% within 120 min. Studies on the kinetics of p-nitrophenol that reacts with Pd/Cu-Fe nanocomposites implied that their behaviors followed the pseudo-first-order kinetics. Furthermore, the batch experiment data suggested that some factors, including Pd/Cu-Fe availability, temperature, pH, different ions (SO42-, PO43-, NO3-) and humic acid content in water, also have significant impacts on p-nitrophenol degradation efficiency. The recyclability of the material was evaluated. The results showed that the Pd/Cu-Fe nanoparticles have good recycle performance, and after three cycles, the removal rate of p-nitrophenol is still more than 83%.

• Archives of Metallurgy and Materials
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• v.64 no.2
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• pp.623-626
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• 2019

Rare earth Nd-Fe-B, a widely used magnet composition, was synthesized in a shape of powders using gas atomization, a rapid solidification based process. The microstructure and properties were investigated in accordance with solidification rate and densification. Detailed microstructural characterization was performed by using scanning electron microscope (SEM) and the structural properties were measured by using X-ray diffraction. Iron in the form of α-Fe phase was observed in powder of about 30 ㎛. It was expected that fraction of Nd₂Fe₁₄B phase increased rapidly with decrease in powder size, on the other hand that of α-Fe phase was decreased. Nd-rich phase diffused from grain boundary to particle boundary after hot deformation due to capillary action. The coercivity of the alloy decreased with increase in powder size. After hot deformation, Nd₂Fe₁₄B phase tend to align to c-axis.

• Composites Research
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• v.30 no.3
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• pp.181-187
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• 2017

The effect of nanoscopic and microscopic Fe, $Fe_3O_4$, and Ni particles and their shapes and substrate materials on the heating behavior of thermoplastic polyurethane (TPU) adhesive films was investigated via induction heating. The heat generation tendency of $Fe_3O_4$ particles was higher than that shown by Fe and Ni particles in the TPU adhesive films. When the Fe and Ni particle size was larger than the penetration skin depth, the initial heating rate and maximum temperature increased with an increase in the particle size. This is attributed to the eddy current heat loss. The heating behavior of the TPU films with Ni particles of different shapes was examined, and different hysteresis heat losses were observed depending on the particle shape. Consequently, the flake-shaped Ni particles showed the most favorable heat generation because of the largest hysteresis loss. The substrate materials also affected the heating behavior of the TPU adhesive films in an induction heating system, and the thermal conductivity of the substrate materials was determined to be the main factor affecting the heating behavior.

• Journal of the Korean Society of Radiology
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• v.9 no.5
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• pp.295-300
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• 2015

There are various type of particle accelerators such as Kyoungju 100-MeV proton beam accelerator in Korea. And Korea plans to build large particle accelerator such as heavy ion accelerator and 4th generation light source facility. The accelerated high energy particles of these facility produce 2nd neutron after nuclear reaction with target materials. And then these 2nd neutron activate structural materials and surrounding environment. Accordingly, it is important to consider the activation and shielding calculation on design of facility for safety operation. In this study, we tried to calculate and compare the neutron flux from the interaction $^{la}150$ beam with target material(Cu) according to thickness of iron and concrete shielding material by MCNPX 2.7 with nuclear library JENDL/HE 07and la150. To verify the properties of nuclear library, we compared computational results with experimental value. These results can be used for dose evaluation technology in planning of the shielding of large particle accelerator.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.3
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• pp.167-173
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• 2008

Pearlescent pigments have been widely used in cosmetic applications. Up to date; the most widely used pearl effect pigment is the mica-based pigment, which uses natural mica as the substrate that is in turn coated with metal of oxide interference layer. However, when natural mica is employed as a base material the final product often has a yellowish color, mainly due to the fact that natural mica contains low levels of iron as an impurity[1,2]. This study was focused on developing a pearl pigment which might have a similar sparkling effect as snow. This effect was found to be due to its structure and purity, and this concept was also applied to development of our pearl pigments. More specifically, this invented pearl effect pigments are the mixture of glass-flake and glass-flake coated metal oxides and present the optical properties of snow matrix such as refractive index and particle size, unlike only the glass-flake or glass-flake coated metal oxides to be applied in. Using base material having similar physical properties (refractive index and particle size) as snow matrix as platelet for pearl effect pigments, these invented pigments present a three-dimensional glittering effect of the snow matrix. With this invented figments an applied; we achieved the beauty of snow crystal from makeup products containing these pigments.

• Safety and Health at Work
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• v.10 no.2
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• pp.229-236
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• 2019

Background: Emerging reports suggest the potential for adverse health effects from exposure to emissions from some additive manufacturing (AM) processes. There is a paucity of real-world data on emissions from AM machines in industrial workplaces and personal exposures among AM operators. Methods: Airborne particle and organic chemical emissions and personal exposures were characterized using real-time and time-integrated sampling techniques in four manufacturing facilities using industrial-scale material extrusion and material jetting AM processes. Results: Using a condensation nuclei counter, number-based particle emission rates (ERs) (number/min) from material extrusion AM machines ranged from $4.1{\times}10^{10}$ (Ultem filament) to $2.2{\times}10^{11}$ [acrylonitrile butadiene styrene and polycarbonate filaments). For these same machines, total volatile organic compound ERs (${\mu}g/min$) ranged from $1.9{\times}10^4$ (acrylonitrile butadiene styrene and polycarbonate) to $9.4{\times}10^4$ (Ultem). For the material jetting machines, the number-based particle ER was higher when the lid was open ($2.3{\times}10^{10}number/min$) than when the lid was closed ($1.5-5.5{\times}10^9number/min$); total volatile organic compound ERs were similar regardless of the lid position. Low levels of acetone, benzene, toluene, and m,p-xylene were common to both AM processes. Carbonyl compounds were detected; however, none were specifically attributed to the AM processes. Personal exposures to metals (aluminum and iron) and eight volatile organic compounds were all below National Institute for Occupational Safety and Health (NIOSH)-recommended exposure levels. Conclusion: Industrial-scale AM machines using thermoplastics and resins released particles and organic vapors into workplace air. More research is needed to understand factors influencing real-world industrial-scale AM process emissions and exposures.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.680-687
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• 1999

To understand the role of shelf sediment in phosphorus biogeochemical cycle, we carried out sequential sediment extraction (SEDEX) of P and porewater analysis on 14 core samples collected in the South Sea of Korea, SEDEX classified P-pools into 5 phases and results are grouped into two categories: reactive P (loosely sorbed-P and Fe bound-P) and refractory P (detrital inorganic-p, authigenic mineral-P and organic-P). Total P concentrations are decreased with sediment depth in all samples as a result of dissolution to porewater. Reactive P comprises about $20\~50\%$ of total P, and iron bound-P is the major form consisting $70\~80\%$ of reactive P-pool. Iron bound-P decreases sharply with depth. Depth profiles of dissolved P concentration in porewater show mirror image of iron bound-P, revealing the role of FeOOH as a regulator of reactive P supply to overlying water column. Authigenic mineral-P consists less than $5\%$ of total P, thus removal of reactive P by converting into refractory P seems inefficient in shelf sediment. This implies that continental shelf sediment sequesters P temporarily rather than permanently. Results show local variation. Nakdong estuary receiving large amount of terrigenous input shows the highest concentration of total P and reactive P. Here iron oxyhydroxides at the surface sediment control the water column flux of P from sediment. Although total P content at the surface is comparable (500$\~$600 ${\mu}g{\cdot}g^{-1}$) between the South Sea and East China Sea, the former contains more iron bound-P and less derital inorganic-P than the latter. Reasons for the difference seem due in part to particle texture, and to biological productivity which depends roughly on the distance from land.