• Journal of the Korean Magnetics Society
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• v.23 no.5
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• pp.149-153
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• 2013

The electronic structures of $TCr_2O_4$ (T = Fe, Co, Ni) spinel oxides have been investigated by employing synchrotron radiation-based soft X ray absorption spectroscopy (XAS). The measured 2p XAS spectra of transition-metal ions reveal that Cr ions are trivalent ($Cr^{3+}$), and all the T (T = Fe, Co, Ni) ions are divalent ($Fe^{2+}$, $Co^{2+}$, $Ni^{2+}$). It is also found that most of T (T = Fe, Co, Ni) ions occupy the A sites under the tetrahedral symmetry, while Cr ions occupy mainly the B sites under the octahedral symmetry. These findings show that the structures of $TCr_2O_4$ (T = Fe, Co, Ni) are very close to the normal spinel structures. Based on these findings, it is expected that Jahn-Teller (JT) effects are important in $FeCr_2O_4$ and $NiCr_2O_4$. In contrast, $CoCr_2O_4$ maintains the cubic structure without having the JT distortion since both $Cr^{3+}$ and $Co^{2+}$ ions are non-JT ions. This work suggests that the antiferromagnetic interaction between $Cr^{3+}$ and $T^{2+}$ ions plays an important role in determining the magnetic properties of $TCr_2O_4$ (T = Fe, Co, Ni).

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.289-299
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• 2005

The ball shear force was investigated in terms of test parameters, i.e. displacement rate and probe height, with an experimental and non-linear finite element analysis for evaluation of the solder joint integrity in area array packages. The increase in the displacement rate and the decrease in the probe height led to the increase in the shear force. Excessive probe height could cause some detrimental effects on the test results such as unexpected high standard deviation and probe sliding from the solder ball surface. The low shear height conditions were favorable for assessing the mechanical integrity of the solder joints. The mechanical and electrical properties of the Sn-37Pb/Cu and Sn-3.5Ag/Cu BGA solder joints were also investigated with the number of reflows. The total thickness of the intermetallic compound (IMC) layers, consisting of Cu6Sn5 and Cu3Sn, was increased as a function of cubic root of reflow time. The shear force was increased up to 3 or 4 reflows, and then was decreased with the number of reflows. The fracture occurred along the bulk solder, in irrespective of the number of reflows. The electrical resistivity was increased with increasing the number of reflows.

• Bulletin of the Korean Chemical Society
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• v.22 no.1
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• pp.30-36
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• 2001

The crystal structures of fully dehydrated $Pd^{2+}$ - and $TI^{+}$ -exchanged zeolite X, $Pd_{18}TI_{56}Si_{100}Al_{92}O_{384}(Pd_{18}TI_{50-}X$, a = $24.935(4)\AA$ and $Pd_{21}TI_{50}Si_{100}Al_{92}O_{384}(Pd_{21}TI_{50-}X$ a = $24.914(4)\AA)$, have been determined by single-crystal X-ray diffraction methods in the cubic space group Fd3 at $21(1)^{\circ}C.$ The crystals were prepared using an exchange solution that had a $Pd(NH_3)_4Cl_2\;:TINO_3$ mole ratio of 50 : 1 and 200 : 1, respectively, with a total concentration of 0.05M for 4 days. After dehydration at $360^{\circ}C$ and 2 ${\times}$$10^{-6}$ Torr in flowing oxygen for 2 days, the crystals were evacuated at $21(1)^{\circ}C$ for 2 hours. They were refined to the final error indices $R_1$ = 0.045 and $R_2$ = 0.038 with 344 reflections for $Pd_{18}Tl_{56-}X$, and $R_1$ = 0.043 and $R_2$ = 0.045 with 280 reflections for $Pd_{21}Tl_{50-}X$; I > $3\sigma(I).$ In the structure of dehydrated $Pd_{18}Tl_{56-}X$, eighteen $Pd^{2+}$ ions and fourteen $TI^{+}$ ions are located at site I'. About twenty-seven $TI^{+}$ ions occupy site II recessed $1.74\AA$ into a supercage from the plane of three oxygens. The remaining fifteen $TI^{+}$ ions are distributed over two non-equivalent III' sites, with occupancies of 11 and 4, respectively. In the structure of $Pd_{21}Tl_{50-}X$, twenty $Pd^{2+}$ and ten $TI^{+}$ ions occupy site I', and one $Pd^{2+}$ ion is at site I. About twenty-three $TI^{+}$ ions occupy site II, and the remaining seventeen $TI^{+}$ ions are distributed over two different III' sites. $Pd^{2+}$ ions show a limit of exchange (ca. 39% and 46%), though their concentration of exchange was much higher than that of $TI^{+}$ ions. $Pd^{2+}$ ions tend to occupy site I', where they fit the double six-ring plane as nearly ideal trigonal planar. $TI^{+}$ ions fill the remaining I' sites, then occupy site II and two different III' sites. The two crystal structures show that approximately two and one-half I' sites per sodalite cage may be occupied by $Pd^{2+}$ ions. The remaining I' sites are occupied by $TI^{+}$ ions with Tl-O bond distance that is shorter than the sum of their ionic radii. The electrostatic repulsion between two large $TI^{+}$ ions and between $TI^{+}$ and $Pd^{2+}$ ions in the same $\beta-cage$ pushes each other to the charged six-ring planes. It causes the Tl-O bond to have some covalent character. However, $TI^{+}$ ions at site II form ionic bonds with three oxygens because the super-cage has the available space to obtain the reliable ionic bonds.

• Bulletin of the Korean Chemical Society
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• v.16 no.10
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• pp.923-929
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• 1995

Four crystal structures of M3-A (M3Na9-xHx-A, M=Rb or K and x=1 or 0), Rb3Na8H-A(a=12.228(1) Å and R1=0.046), Rb3Na9-A (a=12.258(3) Å and R1=0.058), K3Na8H-A (a=12.257(3) Å and R1=0.048) and K3Na9-A (a=12.257(3) Å and R1=0.052), have been determined by single crystal x-ray diffraction technique in the cubic space group Pm3^m at 21 ℃. In all structures, each unit cell contained three M+ ions all located at one crystallographically distinct position on 8-rings. Rb+ ions are 3.12 and 3.21 Å away respectively from O(1) and O(2) oxygens, about 0.40 Å away from the centers of the 8-rings, and K+ ions are 2.87 and 2.81 Å apart from the corresponding oxygens. These distances are the shortest ones among those previously found for the corresoponding ones. Eight 6-rings per unit cell are occupied by eight Na+ ions, each with a distance of 2.31 Å to three O(3) oxygens. The twelfth cation per unit cell is found as Na+ opposite 4-ring in the large cavities of M3Na9-A and assumed to be H+ for M3Na8H-A. With these noble non-framework cationic arrangements, larger M+ ions preferably on all larger 8-rings and the compact Na+ ions on all 6-rings, the bond angles in the 8-rings of M3-A, 145.1 and 161.0 respectively for (Si,Al)-O(1)-(Si,Al) and (Si,Al)-O(2)-(Si,Al), turned out to be remarkably stable and smaller, by more than 12 to 17°, than the corresponding angles found in the crystal structures of zeolites A with high concentration of M+ ions. It is to achieve these remarkably relaxed 8-rings, the main windows for the passage of gas molecules, with simultaneously maximized cavity volumes that M3-A have been selected as one of the efficient zeolite A systems for gas encapsulation.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.228-228
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• 2015

Water reuse plays significant role in water saving and water environmental protection, and it helps alleviate the shortage of water resources. China's water reuse was put into practice since 1980s by means of pilot and promotion in National Fifth-year Plan and other strategies. The effects of water reuse is beneficial in both economic, social and environmental aspects. But some shortcomings still undermine future development of water reuse in China. To overcome and boost water reuse, Ministry of Water Resources conducted a successive survey across China. The aim of this study is to demonstrate the current condition of water reuse in China in construction, funds, legislation, planning, policy aspects, to summarize problems and its reasons underneath, to make suggestions for further development. Basically, in 2010, China's water reuse is 2.83 billion cubic meters and the utilization rate is 10.35%. Water reuse in China has four major characteristics: the first one is water reuse differences in amount occur national-widely and North of China has the main percentage as 47.3%; the second one is water reuse is mainly in environment maintenance (42.1%) and industry cooling (29.8%); the third one is funds for water reuse station and pipe construction is main in non-fiscal budget which take percentage as 56.8%; the fourth one is progresses of administrative system, political system, price management, standard system and technologies go rapidly recently. The problems of water reuse such as lack in water reuse station, delay in pipe constriction and limits on water reuse amount still exist due to some reasons. As a think tank of Ministry of Water Resources, we give some suggestions: firstly, water reuse needs to be integrated with traditional water resources allocation; secondly, public budgets need to be strengthened and income mechanism should also be constructed; thirdly, water resources integrated administrative of city and county should be boosted and roles as water reuse need to be clear and precise; fourthly, national, provincial and regional water reuse planning should be made in time; fifthly, regulations on water reuse should be programmed as soon as possible.

• Journal of the Korean Society of Floral Art and Design
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• no.41
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• pp.45-59
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• 2019

The characters that could be connected to diverse cultural contents have formed diverse platforms with the development of digital technology, and the size of the relevant industry and market is rapidly growing. Recently, the utilization of character emoticons for smartphone messenger has been rapidly increased, so that the characters are settled down as a tool for non-verbal communication, on top of drawing attention as an independent area. With the expansion of character market, the importance of design that could give interest and familiarity to consumers is more emphasized. The body proportion of characters includes the implicative and symbolic meanings that could express diverse personalities. Thus, this study examined the body proportion of the characters with the high consumers' preference, and then analyzed the characteristics of formative elements of character design in accordance with the body proportion. In the results of the analysis, the exaggerated form of SD characters in two or three-head figure, and the realistic Real characters in seven or eight-head figure were preferred. For the SD characters, the colors with a high chroma showing the cute and cheerful image were used. For the Real characters, the cubic effect was expressed through the colors with active images and the light and shade of color. Even though the SD characters have limited motions due to the omitted body parts, the facial movements of animation characters are exaggerated while the Real characters describe the realistic and dynamic motions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.575-589
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• 2008

In the present work, we investigate the hydrodynamic behavior of a turbulent bore, such as tsunami bore and tidal bore, generated by the removal of a gate with water impounded on one side. The bore generation system is similar to that used in a general dam-break problem. In order to the numerical simulation of the formation and propagation of a bore, we consider the incompressible flows of two immiscible fluids, liquid and gas, governed by the Navier-Stokes equations. The interface tracking between two fluids is achieved by the volume-of-fluid (VOF) technique and the M-type cubic interpolated propagation (MCIP) scheme is used to solve the Navier-Stokes equations. The MCIP method is a low diffusive and stable scheme and is generally extended the original one-dimensional CIP to higher dimensions, using a fractional step technique. Further, large eddy simulation (LES) closure scheme, a cost-effective approach to turbulence simulation, is used to predict the evolution of quantities associated with turbulence. In order to verify the applicability of the developed numerical model to the bore simulation, laboratory experiments are performed in a wave tank. Comparisons are made between the numerical results by the present model and the experimental data and good agreement is achieved.

• Korean Journal of Agricultural Science
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• v.9 no.1
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• pp.357-370
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• 1982

Recent concern regarding price and availability of fossil fuels has spurred the interest in alternative sources for farm crop drying. Among the available options such as biomass energy, wind power, nuclear energy and solar energy etc., the increasing attention is being directed to the utilization of heat from solar energy especially for farm crop drying. Even though solar energy is dispersed over a large land area and only a relatively small amount of energy can be simply collected, the advantages of solar energy is that the energy is free, non-polluting. The study reported here was designed to help supply the informations for the development of simple and relatively inexpensive solar warehouse for farm crop drying and storage. Specifically, the objectives of this study were to determine the performance of the solar collector fabricated, to compare solar supplemented heat drying with natural air drying and to develop a simulation model of temperature in stored grain, which can be used to study the effects due to changes in ambient air temperature. For those above objectives, solar collector was fabricated from available materials. Corrugated steel galvanized sheet, painted flat black, was used as absorbers and clear 0.2mm polyethylene sheet was the cover material. The warehouse for rough rice drying and storage was constructed with concrete block, and the solar collector was used as the roof of warehouse instead of original roofing system of it. The results obtained in this study were as follows: 1. The thermal efficiency of the solar collector was average 26 percent and the overall heat transfer coefficient of the collector was approximately $25kJ/hr.m^2\;^{\circ}K$. 2. Solar heated air was sufficient to dry one cubic meter of rough rice from 23.5 to 15.0 percent in 7 days and natural air was able to dry the same amount of rough rice from 20.0 to 5 percent in l2 days. 3. Drying with solar heat reduced the required drying time to dry the same amount of rough rice into a half compared to natural air drying, but overdrying problems of the bottom layer were so severe that these problems should be thoroughly analyzed. 4. Simulation model of temperature in stored grain was developed and the results of predicted temperature agreed well with test results. 5. Based on those simulated temperature, changes in the grain-temperature were a large at the points of the wallside and the damage of the grain would be severe at the contact area of wall.