• Journal of the Korean Magnetics Society
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• v.5 no.6
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• pp.921-927
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• 1995

The micro particle,s shapes of the magnetic films obtained by electrode position of Iron ions and Cobalt-Iron mixed ions in aluminum anodic oxidized films are dependent on the size of particle diameter. When the diameter of deposited particles is larger than $300\AA$, the film plane anisotropy caused by bottom extremity increases, and the crystalization orientation of FeC deposited unusually in the part of the bottom extremities affects on the coercive force Hc and the magnetic anisotropy energy Ku. It was confirmed that the shape anisotropy of particle affects on the both Hc and Ku because the FeC did not deposit in the Iron deposited samples entirely, but in the Cobalt-Iron alloy deposited samples, the effects by the very strong crystalization orientation of the FeC is larger than that of the shape anisotropy. From these results, the Cobalt-Iron alloyed films could switchover the film plane magnetic anisotropy to the perpendicular magnetic anisotropy energy by using the constrainting method of FeC deposition with Cu deposition instead of Cobalt-Iron alloy in the bottom extremities.

• Advances in nano research
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• v.10 no.5
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• pp.449-460
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• 2021

Flexoelectricity is an interesting materials' property that is more touchable in small scales. This property beside the sandwich structures placed in the center of scientists' attention due to their extraordinary effects on the mechanical properties. Furthermore, in the passage of decades, more elaborated sandwich structures took into consideration results from using honeycomb core. This kind of structure, inspiring from honeycomb core, provides more stiffness to weight ratio, which plays a crucial role in different industries. In this paper, based on the Love-Kirchhoff's hypothesis, Hamilton's principle, modified couple stress theory and Fourier series analytical method, equations of motion for a sandwich plate containing a honeycomb core integrated by two face-sheets have derived and solved analytically. The equations of both face sheets have derived by flexoelectricity consideration. Moreover, it should be noticed that the whole structure rests on the visco-Pasternak foundation. Conducting current research provided an acceptable and throughout study based on flexoelectricity to address the effect of materials' characteristics, length-scale parameter, aspect, and thickness ratios and boundary conditions on the natural frequency of honeycomb sandwich plates. Also, based on the presented figures and tables, there is a close agreement between previous studies and recent work. Due to the high ratio of strength to weight, current model analyzing is capable of taking into account for different vehicles' manufacturing in a high range of industries.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.27-37
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• 2021

The use of additive manufacturing processes for the repair and remanufacturing of mechanical parts has attracted considerable attention because of strict environmental regulations. Directed energy deposition (DED) is widely used to retrofit mechanical parts. In this study, finite element analyses (FEAs) were performed to investigate the influence of the substrate phase and inclination angle on the heat transfer characteristics in the vicinity of Hastelloy X regions deposited via DED. FE models that consider the bead size and hatch distance were designed. A volumetric heat source model with a Gaussian distribution in a plane was adopted as the heat flux model for DED. The substrate and the deposited powder were S45C structural steel and Hastelloy X, respectively. Temperature-dependent thermal properties were considered while performing the FEAs. The effects of the substrate phase and inclination angle on the temperature distributions and depth of the heat-affected zone (HAZ) in the vicinity of the deposited regions were examined. Furthermore, the influence of deposition paths on depths of the HAZ were investigated. The results of the analyses were used to determine the suitable phase and inclination angle of the substrate as well as the appropriate deposition path.

• Korean Journal of Environmental Agriculture
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• v.41 no.2
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• pp.115-124
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• 2022

BACKGROUND: Methane is a major greenhouse gas attributed to global warming partly contributed by agricultural activities from ruminant fermentation and rice paddy fields. Methanotrophs are microorganisms that utilize methane. Their unique metabolic lifestyle is enabled by enzymes known as methane monooxygenases (MMOs) catalyzing the oxidation of methane to methanol. Rice absorbs, transports, and releases methane directly from soil water to its stems and the micropores and stomata of the plant epidermis. Methylobacterium species associated with rice are dependent on their host for metabolic substrates including methane. METHODS AND RESULTS: Methylobacterium spp. isolated from rice were evaluated for methane oxidation activities and screened for the presence of sMMO mmoC genes. Qualitatively, the soluble methane monooxygenase (sMMO) activities of the selected strains of Methylobacterium spp. were confirmed by the naphthalene oxidation assay. Quantitatively, the sMMO activity ranged from 41.3 to 159.4 nmol min^-1 mg of protein^-1. PCR-based amplification and sequencing confirmed the presence and identity of 314 bp size fragment of the mmoC gene showing over 97% similarity to the CBMB27 mmoC gene indicating that Methylobacterium strains belong to a similar group. CONCLUSION(S): Selected Methylobacterium spp. contained the sMMO mmoC gene and possessed methane oxidation activity. As the putative methane oxidizing strains were isolated from rice and have PGP properties, they could be used to simultaneously reduce paddy field methane emission and promote rice growth.

• International Journal of High-Rise Buildings
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• v.12 no.1
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• pp.93-105
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• 2023

Seismic isolation and vibration control techniques have been developed and put into practical use by challenging researchers and engineers worldwide since the latter half of the 20th century, and after more than 40 years, they are now used in thousands of buildings, private residences, highways in many seismic areas in the world. Seismic isolation and vibration control structures can keep the structures undamaged even in a major earthquake and realize continuous occupancy. This performance has come to be recognized not only by engineers but also by ordinary people, becoming indispensable for the formation of a resilient society. However, the dynamic characteristics of seismically isolated bearings, the key elements, are highly dependent on the size effect and rate-of-loading, especially under extreme loading conditions. Therefore, confirming the actual properties and performance of these bearings with full-scale specimens under prescribed dynamic loading protocols is essential. The number of testing facilities with such capacity is still limited and even though the existing labs in the US, China, Taiwan, Italy, etc. are conducting these tests, their dynamic loading test setups are subjected to friction generated by the large vertical loads and inertial force of the heavy table which affect the accuracy of measured forces. To solve this problem, the authors have proposed a direct reaction force measuring system that can eliminate the effects of friction and inertia forces, and a seismic isolation testing facility with the proposed system (E-isolation) will be completed on March 2023 in Japan. This test facility is designed to conduct not only dynamic loading tests of seismic isolation bearings and dampers but also to perform hybrid simulations of seismically isolated structures. In this paper, design details and the realization of this system into an actual dynamic testing facility are presented and the outcomes are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.17-17
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• 1998

Synchrotron radiation is produced when charged particles moving with relativistic velocities a are accelerated - for example, deflected by the bending magnets which guide the electron or p positrons in circular accelerators or storage rings. By using special focusing magnetic lattices i in the particle accelerators it is possible to make the dimensions of the particle beam very small with a hi맹 charge density which results in a light source with high b디lIiance. Synchrotron light h has important properties which make it ideal for a wide range of investigations in surface s science. The fact that the spectrum of electromagnetic radiation emitted in a bending magnet e extends in a continuum from the 얹r infra red region to hard x-rays means that it is id않I for a v variety of spectroscopic studies. Since there are no convenient lasers, or other really bright l light sources, in the vacuum ultraviolet and soft x-ray re.밍ons the development of synchrotron r radiation has enabled enormous advances to be made in this di펌C비t spectr따 re밍on. P Polarization-dependent measurements, for ex없nple ellipsometry or circular dichroism studies a are possible because the radiation has a well-defined polarization - linear in the plane of orbit w with additional right-circular, or left-circular, components for emission an생es above, or below, t the horizontal, respectively. Since the synchrotron light is emitted from a bunch of charge c circulating in a ring the light is emitted with a well-defined time structure with a short flash of l light every time a bunch passes an exit port. The time structure depends on the size of the ring a and the number and sequence of filling of the bunches. A pulsed light source enables time¬r resolved studies to be performed which provide direct information on the lifetimes and decay m modes of excited states and in addition opens up the possibility of using time of flight t techniques for spectroscopic studies. The fact that synchrotron radiation is produced in a clean u ultrahi야 vacuum environment is of gr않t importance for surce science studies. The current t비rd generation synchrotron light sources provide exceptionally high baliance and stability a and open up possibilities for experiments which would have been inconceivable only a short time ago.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.171-176
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• 1997

UO$_2$-Gd$_2$O$_3$fuel has been sintered to study the effect of powder property and sintering atmospheres on densification and microstructure. Three types of powders have been used; AUC-UO$_2$ powder and ADU-UO$_2$ powder were mixed with Gd$_2$O$_3$ Powder, and co-milled AUC-UO$_2$ and Gd$_2$O$_3$ powder. UO$_2$-(2, 5, 10)wt% Gd$_2$O$_3$pellets have been sintered at 168$0^{\circ}C$ for 4 hours in the mixture of H$_2$ and $CO_2$ gases, of which oxygen potential has been controlled by the ratio of $CO_2$ to H$_2$ gas. Densities of UO$_2$-Gd$_2$O$_3$ fuel pellets are quite dependent on powder types, and UO$_2$-Gd$_2$O$_3$ fuel using co-milled UO$_2$ powder yields the highest density. A long range homogeneity of Gd is determined by powder mixing. As the oxygen potential of sintered atmosphere increases, the sintered densities of UO$_2$-Gd$_2$O$_3$ pellets decrease but grain size increases. In addition, (U, Gd)O$_2$ solid solution becomes more homogeneous. The UO$_2$-Gd$_2$O$_3$fuel having adequate density and homogeneous microstructure can be fabricated by co-milling powder and by high oxygen potential.

• Advances in nano research
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• v.10 no.2
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• pp.115-128
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• 2021

In this article, free vibration behavior of electro-magneto-thermo sandwich Timoshenko beam made of porous core and Graphene Platelet Reinforced Composite (GPLRC) in a thermal environment is investigated. The governing equations of motion are derived by using the modified strain gradient theory for micro structures and Hamilton's principle. The magneto electro are under linear function along the thickness that contains magnetic and electric constant potentials and a cosine function. The effects of material length scale parameters, temperature change, various distributions of porous, different distributions of graphene platelets and thickness ratio on the natural frequency of Timoshenko beam are analyzed. The results show that an increase in aspect ratio, the temperature change, and the thickness of GPL leads to reduce the natural frequency; while vice versa for porous coefficient, volume fractions and length of GPL. Moreover, the effect of different size-dependent theories such as CT, MCST and MSGT on the natural frequency is investigated. It reveals that MSGT and CT have most and lowest values of natural frequency, respectively, because MSGT leads to increase the stiffness of micro Timoshenko sandwich beam by considering three material length scale parameters. It is seen that by increasing porosity coefficient, the natural frequency increases because both stiffness and mass matrices decreases, but the effect of reduction of mass matrix is more than stiffness matrix. Considering the piezo magneto-electric layers lead to enhance the stiffness of a micro beam, thus the natural frequency increases. It can be seen that with increasing of the value of WGPL, the stiffness of microbeam increases. As a result, the value of natural frequency enhances. It is shown that in hc/h = 0.7, the natural frequency for WGPL = 0.05 is 8% and 14% less than its for WGPL = 0.06 and WGPL = 0.07, respectively. The results show that with an increment in the length and width of GPLs, the natural frequency increases because the stiffness of micro structures enhances and vice versa for thickness of GPLs. It can be seen that the natural frequency for aGPL = 25 ㎛ and hc/h = 0.6 is 0.3% and 1% more than the one for aGPL = 5 ㎛ and aGPL = 1 ㎛, respectively.

• Journal of Bio-Environment Control
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• v.15 no.3
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• pp.231-238
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• 2006

The physical properties of seven perlites different in particle size distribution were investigated to develop perlite bag culture in Korea. Particle sizes of 1.0-2.8mm and larger than 2.8 mm were rather evenly distributed in S-1 (1.2-5 mm), S-2 (0.15-5 mm) and S-5 (parat No.1). Larger particles were less in S-3 (1-3 mm), S-4 (Parat No.2), S-6 (OTAVI) and S-7 (Agroperl B-3). S-4, S-6 and S-7 contained lots of particles less than 1 mm in size. Total porosity was similar among substrates with the value of $59{\sim}62%$. Container capacity was between 35-40% regardless of substrates except in S-2 with 27.7%. Water content, which was about 60% at 0 kPa, was decreased sharply at 4.90 kPa regardless of substrates, which meant the easily available water was plenty in any kind of perlite tested. Substrates, S-1, S-2 and S-3 with different particle size distribution, were investigated to evaluate for perlite bag culture. Six tomatoes (Licopersicon esculentum Mill. cv. Rokkusanmaru) were planted in a perlite bag of 40 liters with the dimension of 120cm in length and 34cm in width. The amount of nutrient solution supplied and its drainage dependent on daily integrated radiation didn't show any regular trend during the growth. Roots in the bag were distributed evenly in S-1 and S-2 than in S-3. Plant grown in S-1 showed the highest total and marketable yield of 8,628 and 7,759 kg/10a, respectively. The number of small size fruits and malformed fruits were more in S-3. Consequently, S-1 with the particle size distribution of 1.2-5 mm is suggested as desirable substrate for perlite bag culture.

• Journal of the Korean Chemical Society
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• v.44 no.4
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• pp.350-355
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• 2000

The compounds, CaAl$_2$(BO$_3$)$_2$O, SrAl$_2$(BO$_3$)$_2$O and BaAl$_2$(BO$_3$)$_2$O, are good host lattices for highly efficient $Eu^{2+}$ luminescence. The europium emission peaks at 450 nm in $Eu^{2+}$:CaAl$_2$(B0$_3$)$_2$O, 411 nm in $Eu^{2+}$: SrAl$_2$(BO$_3$)$_2$O and 375 nm in $Eu^{2+}$: BaAl$_2$(BO$_3$)$_2$O. The $Eu^{2+}$: CaAl$_2$(BO$_3$)$_2$O Phosphor shows a high output and should be a good maintenance in VUV Xe lamps. It is ideally suited for use in PDP phosphors. The $Eu^{2+}$ ion is interesting because the Stokes shift emission is a strong host dependent. The difference in the Stokes shift is oneimportant factor leadingto a difference in wavelength. If the 5d level of $Eu^{2+}$ ion is lower in energy,according to a decrease in the doping lattice size, then the emission wavelength will be longer and the Stokes shift will be smaller. Therefore, a knowledge of the relationship between the crystal lattice size and the Stokes shift. (orthe energy of the 5d level),is essential for beingable to predict $Eu^{2+}$ emission properties.