• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.1
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• pp.16-24
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• 2022

A computational study of combined thermal and solutal convection (double diffusive convection) in a sealed crystal growth reactor is presented, based on a two-dimensional numerical analysis of the nonlinear and strongly coupled partial differential equations and their associated boundary conditions. The average Nusselt numbers for the source regions are greater than those at the crystal regions for 9.73 × 10³ ≤ Gr_t ≤ 6.22 × 10⁵. The average Nusselt numbers for the source regions varies linearly and increases directly with the thermal Grashof number form 9.73 × 10³ ≤ Gr_t ≤ 6.22 × 10⁵ for aspect ratio, Ar (transport length-to-width) = 1 and 2. Additionally, the average Nusselt numbers for the crystal regions at Ar = 1 are much greater than those at Ar = 2. Also, the occurrence of one unicellular flow structure is caused by both the thermal and solutal convection, which is inherent during the physical vapor transport of Hg₂Br₂. When the aspect ratio of the enclosure increases, the fluid movement is hindered and results in the decrease of thermal buoyancy force.

• Korean Journal of Exercise Nutrition
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• v.23 no.1
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• pp.55-62
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• 2019

[Purpose] The effect of acute nitrate supplementation on muscle fatigue is largely unknown. This study aimed to evaluate the effect of acute nitrate supplementation on muscle fatigue. [Methods] Thirty-five recreationally active subjects consumed 140 ml of beetroot (BR) juice (nitrate: 8 mmol·d^-1) or placebo (PL) 12 and 2.5 hours before two exercise sessions. Peak torque was measured during 50 repetitions, at maximal effort, and during concentric knee extensions at 90°·s^-1. Blood pressure (BP) was recorded pre- and post-exercise. [Results] Peak torque, maximum work, rate of fatigue, and rate of work fatigue were similar between the BR and PL conditions. Post-exercise diastolic BP (BR: 67.2 ± 9.8 vs. PL: 64.5 ± 7.9 mmHg, p < 0.05) and mean arterial pressure (BR: 91.6 ± 9.3 vs. PL: 88.8 ± 8.2 mmHg, p < 0.05) were higher with BR supplementation. [Conclusion] These findings suggest that the acute intake of BR juice had no effect on knee extensor muscle strength or fatigue but increased BP in a healthy recreationally active population.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.3
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• pp.127-136
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• 2021

This paper is dedicated to numerical simulation for diffusion-advective convection in a square cavity during physical vapor transport of Hg₂Br₂. Flow characteristics of the temperature difference between the source and crystal regions, 50℃ (300℃ → 250℃), partial pressures of component argon of 20 Torr and 100 Torr are investigated and presented as velocity vectors and streamlines, isotherms and iso-mass concentrations contours. Moreover, alterations of average Nusselt and average Sherwood numbers with (a) the source and crystal regions, (b) the pressures of component argon of 20 Torr and 100 Torr are analyzed and addressed in details. Both average Nusselt and average Sherwood numbers are seen to decrease with the increasing values of the partial pressures of component argon. Also, it is found that for the two different partial pressures of component argon, average Nusselt numbers at the source region are greater than at the crystal region, and inversely, average Sherwood numbers at the crystal region are greater than the source region by a factor of 3.

• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.355-361
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• 1991

The separative preconcentration of trace mercury[Hg(II)] in a water sample was studied by a coprecipitation flotation technique. The trace Hg(II) was precipitated together with Ce(OH)$_3$ by adding 3.0 ml of 0.1M Ce$^{3+}$ solution to 1,000 ml of water sample and adjusting pH to 11.0 with 1.0M NaOH solution. The hydrophobic precipitate[Ce(OH)$_3$-Hg(OH)$_2$], which was formed by adding 2.0 ml of 0.1${\%}$ ethanolic sodium oleate solution, were floated on the surface with an aid of tiny nitrogen gas bubbles. The floated materials were quatitatively collected in a suction flask and dissolved with 5.0 ml of 2.0M HNO$_3$. The solution was marked to 25.00 ml with a deionized water. The content of Hg(II) was determined by cold vapor atomic absorption spectrophotometry. Any interferences of concomitants such as Ag$^+$, Br$^-$, I$^- $, etc. were not observed on the whole procedure. The analytical result showed that Hg(II) found in the wastewater of Seochang Campus, Korea University was 1.98 ng/ml with the relative standard deviation of 3.6${\%}$. And recoveries of Hg(II) in the wastewater into which 1.0 ng/ml and 2.0 ng/ml were added were 95${\%}$ and 91${\%}$, respectively. From such results, this procedure could be concluded to be tolerably accurate and reproducible for the determination of trace mercury in a water sample.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.176-176
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• 2007

Flat-panel direct conversion detectors used in compound substance of semiconductor are being studied for digital x-ray imaging. Recently, such detectors are deposited by physical vapor deposition(PVD) generally. But, most of materials (HgI2, PbI2, TlBr, PbO) deposited by PVD have shown difficult fabrication and instability for large area x-ray imaging. Consequently, in this paper, we propose applicable potentialities for screen printing method that is coated on a substrate easily. It is compared to electrical properties among semiconductors such as $HgI_2$, $PbI_2$, PbO, HgBrI, InI, and $TlPbI_3$ under investigation for direct conversion detectors. Each film detector consists of an ~25 to $35\;{\mu}m$ thick layer of semiconductor and was coated onto the substrate. Substrates of $2cm{\times}2cm$ have been used to evaluate performance of semiconductor radiation detectors. Dark current, sensitivity and physics properties were measured. Leakage current of $HgI_2$ as low as $9pA/mm^2$ at the operation bias voltage of ${\sim}1V/{\mu}m$ was observed. Such a value is not better than PVD process, but it is easy to be fabricated in high quality for large area x-ray Imaging. Our future efforts will concentrate on optimization of growth of film thickness that is coated onto a-Si TFT array.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3459-3464
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• 2014

Synthesis and structural characterization of mercury(II) halides and perchlorate complexes (1-4) of bis-$OS_2$-macrocycle (L) are reported. L reacts with mercury(II) chloride and bromide to yield an isostructural 2D coordination polymers with type $[Hg(L)X_2]_n$ (1: X = Cl and 2: X = Br). In 1, each Hg atom which lies outside the cavity is six-coordinate with a distorted octahedral geometry, being bound to four adjacent ligands via monodentate Hg-S bonds and two remaining sites are occupied by two terminal chlorido ligands to form a fishnet-like 2D structure. When reacting with mercury(II) iodide, L afforded a 1D coordination polymer $\{[Hg_2(L)I_4]{\cdot}CHCl_3\}_n$ (3) in which each exocyclic Hg atom is four-coordinate, being bound to two sulfur donors from different ligands doubly bridging the ligand molecules in a head-to-tail mode. The coordination sphere in 3 is completed by two iodo terminal ligands, adopting a distorted tetrahedral geometry. On reacting with mercury(II) perchlorate, L forms solvent-coordinated 1D coordination polymer $\{[Hg_2(L)(DMF)_6](ClO_4)_4{\cdot}2DMF\}_n$ (4) instead of the anion-coordination. In 4, the Hg atom is five-coordinate, being bound to two sulfur donors from two different ligands doubly bridging the ligand molecules in a side-by-side mode to form a ribbon-like 1D structure. The three remaining coordination sites in 4 are completed by three DMF molecules in a monodentate manner. Consequently, the different structures and connectivity patterns for the observed exocyclic coordination polymers depending on the anions used are influenced not only by the coordination ability of the anions but also by anion sizes.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.145-152
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• 2023

The average Nusselt numbers in the source and crystal region for the variation of thermal Grashof number (Gr_t) in the range of 2.31 × 10⁴ ≤ Gr_t ≤ 4.68 × 10⁴ are obtained through numerical simulations. It is shown the average Nusselt number in the crystal region is more than twice as large as the average Nusselt number in the source region. The average Nusselt number in the source region shows an increasing tendency with increasing the thermal Grashof number, Gr_t, while the average Nusselt number in the crystal region shows a decreasing tendency with increasing thermal Grashof number, Gr_t. For the variation of the solutal Grashof number (Gr_s) in the ran ge of 3.28 × 10⁵ ≤ Gr_s ≤ 4.43 × 10⁵, the average Sherwood number in the source region and crystal region tends to decrease as the solutal Grashof number, Gr_s increases. The average Sherwood number in the crystal region is about four times greater than the average Sherwood number in the source region.

• Journal of Environmental Science International
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• v.2 no.1
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• pp.61-72
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• 1993

Result of this study indicate that two criteria must be met in order to have effective macrocycle-mediated transport in these emulsionsystem. First, one must effective extraction of the post transition metals, $Cd^{2+}$. $Pb^{2+}$ and $Hg^{2+}$ , into toluene membrane. The effectiveness of this extraction is greatest if log K values for the metal-macrocycle interaction is large. Second, the ratio of the log K values for the metal ion-receiving phase to the metal ion-macrocycle interaction must be large enough to ensure quantitative stripping of the metal ion at the toluene phase interface. Control of the first step can be obtained by appropriate selection of macrocycle donor atom, substituents, and cavity radius. The second step can be controlled by selecting the proper complexing agent for inclusion in the receiving phase. The order of the transport, when using the several $A^-$ species such as $SCN^-$, $1^-$, $Br^-$ and $Cl^-$ is the order of the changing degree of solvation for $A^-$ and the transport of the metals is also affected by the control of concentration for receiving species because of solubility-differences. In this study, we can seperate each single metal ion from the mixture of $Cd^{2+}$, $Pb^{2+}$, and $Hg^{2+}$ ions by using the toluene membranes controlled by optimized conditions. Transport of the single metal is also very good, and alkaline and alkaline earth metals as interferences ions did not affect the seperation of the metals in this macrocycle-liquid membrances but transition metal ions were partially affected as interferences for the post transition metal ions.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.75-80
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• 2014

The convective flow structures in the vapor phase on earth are shown to be single unicellular, indicating the solutally dominant convection is important. These findings reflect that the total molar fluxes show asymmetrical patterns in a viewpoint of interfacial distributions. With decreasing the gravitational level form $1g_0$ down to $1.0{\times}10^{-4}g_0$, the total molar fluxes decay first order exponentially. It is also found that the total molar fluxes decay first order exponentially with increasing the partial pressure of component B, PB (Torr) form 5 Torr up to 400 Torr. Under microgravity environments less than $1g_0$, a diffusive-convection mode is dominant and, results in much uniformity in front of the crystal regions in comparisons with a normal gravity acceleration of $1g_0$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.392-395
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• 2003

For the purpose of digital x-ray imaging, many materials such as $PbI_2$, $HgI_2$, TlBr, CdTe and CdZnTe have been under development for servaral years as direct converter layer. $Hgl_2$ film detector have recently been shown as one of the most promising semiconductor materials to be used as direct converters in x-ray digital radiography. This paper, the $HgI_2$ films are deposited on conductive-coated glass by screen printing, in which $HgI_2$ powder is embedded in a binder and solvent, and the slurry is used to coat the conductive-coated glass. We investigated electrical characteristic of the fabricated $HgI_2$ films. The x-ray response to radiological x-ray generator of 70Kvp using the current integration mode will be reported for screen printing films. These results indicate that $HgI_2$ detectors have high potential as new digital x-ray imaging devices for radiography.