• Korean Journal of Crystallography
• /
• v.3 no.1
• /
• pp.9-22
• /
• 1992

Two crystal structures of bromine sorption complexes of vacuum dehydrated Cd(ll)-exchanged zeolite A have been determined by single-crystal xray diffraction techniques in the cubic space group Pm3m at 21(1) ℃. Both crystals were ion exchanged in flowing streams of exchange solution In which mole ratio of Cd(NO3)2 and Cd(OOCCH3)B was 1:1 with a total concentration of 0.05 M. First crystal was dehydrated at 450℃ and 2 ×10-6 Torr for two days. Second crystal was dehydrated at 650℃ and 2 ×10-6 Torr for two days. Both crystals were then treated with 160 Torr for two days. Second crystal was dehydrated at 650℃ and 2 × 10-6 Torr for two days. Both crystals were then treated with 160 Torr of zeolitically dried bromine vapor at 24℃. Full-matrix least-squares refinements of toe first crystal(a: 12.250(1) A )· and the second crystal(a: 12.204(2) A ) have contecoed to final error indices, Rl:0.075 and Ra:0.079 with 212 reflections, and Rl : 0.089 and Ra = 0.078 with 128 reflections, respectively, for which I >3σ(I). Crystallographic analyses of both crystals show that six Cd2+ ions are located on two different threefold axes of unit cell associated with 6-ring oxygens. Each 4.5 Cd2+ ion is recessed ca.0. 441 A Into the large cavity to complex either with Brsor with Br3from the (111) plane of 0(3), whereas each 1.5 Cd2+ ions recessed ca. 0.678 A into we sodalite unit. Approximately 1.5 Br5-and 1.5 Br3-ions are sorbed per unit cell. Each Brsion interacts and stabilized by complexing with two Cd2+ ions and framework oxide ions, while each Br3ion interacts with one Cd2+ ion and framework oxide ions. Because of residual water molecules the following reactions may be occurred inside of zeolite cavity:

• Clean Technology
• /
• v.17 no.1
• /
• pp.78-82
• /
• 2011

For effectively photochemical hydrogen production, P (negative semiconductor) and B (positive semiconductor) ions (0.1, 0.2, 0.5, and 1.0 mol%) incorporated $TiO_2$ (P- and B-$TiO_2$) nanometer sized particles were prepared using a solvothermal method as a photocatalyst. The characteristics of the synthesized P- and B-$TiO_2$ photocatalysts were analyzed by X-ray Diffraction (XRD), Transmission electron microscopy (TEM), W-visible spectroscopy (UV-Vis), and Photoluminescence spectra (PL). The evolution of $H_2$ from methanol/water (1:1) photo-splitting over B-$TiO_2$ photocatalysts was enhanced compared to those over pure $TiO_2$ and P-$TiO_2$ photocatalysts; 0.42 mL of $H_2$ gas was evolved after 10 h when 0.5 g of a 1.0 mol% B-$TiO_2$ catalyst was used.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.7
• /
• pp.1048-1052
• /
• 2006

Ab initio calculations of the structure, atomic charges and natural bond orbital (NBO) have been performed at HF/6-311G** and B3LYP/6-311G** levels for the title compound of dibenzothiazyl-disulfide. The calculated results show that the two nitrogen atoms have the biggest negative charges and they are the potential sites to react with the metallic ions, which make the title compound become a di-dentate ligand. Vibrational frequencies of the title compound have been obtained and compared with the experimental value and the comparison indicates that B3LYP/6-311G** level is better than HF/6-311G** level to predict the vibrational frequencies for the system studied here. For the title compound, electronic absorption spectra calculated by time?ependent density functional theory (TD-DFT) are more accurate than Hartree-Focksingle-excitation CI (CI-Singles) method. NBO analyses show that the electronic transitions are mainly derived from the contribution of bands $\pi\rightarrow\pi^{*}$. Thermodynamic calculated results show that the formation of the title compound from 2-mercaptobenzothiazole is a spontaneous process at room temperature with the change of free Gibbs being negative value.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.2 s.245
• /
• pp.186-192
• /
• 2006

We applied a new charging system using the condensation and evaporation method to charge the submicron particles with a uniform charging performance. The monodispersed NaCl submicron particles were condensed by n-butanol vapor and grew up to micron droplets with a same size, regardless of their initial size. Those condensed droplets were charged in an indirect corona charger. The indirect corona charger consisted of the ion generation zone and the particle charging zone. In the ion generation zone, Ions were generated by corona discharge and some of them moved into the particle charging zone by a carrier gas and mixed with the condensed droplet. And finally, the charged and condensed droplets dried through an evaporator to shrink to their original size. The average charge and penetration rate of the particles before and after evaporation were measured by CPC and aerosol electrometer and compared with those of a conventional corona charger. The results showed that the average charge was $5\~7$ charges and the penetration rate was over $90\%$, regardless of the initial particle size.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.518-521
• /
• 2004

The degradation characteristics of MgO protective layer and phosphors have been investigated in terms of the ion-induced secondary electron emission coefficient ${\gamma}$ and static margin of discharge voltages, respectively, in this experiment. The ion-induced secondary electron emission coefficients ${\gamma}$ for the degraded MgO protective layer and phosphors have been studied by ${\gamma}$ -focused ion beam system. The energy of Ne+ ions used is from 80 eV to 200 eV in this experiment. The degraded MgO and phosphor layers are found to have higher ${\gamma}$ than that of normal ones without degradations or aged one. Also, the static margin of discharge voltages for test panels with degraded MgO protective layer and phosphors been found to be seriously decreased in comparison with those of normal ones without degradations.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.5 no.3
• /
• pp.233-239
• /
• 1995

$La_{1/3}NbO_3$ and $La_{1/3}TaO_3$ large single crystal was prepared by the infrared floating zone method and their crystal structure and dielectric properties were investigated from the viewpoint of A - site vacancy. In $La_{1/3}TaO_3$ crystal, the crystal symmetry and approximate lattice constants was tetragonal and a $\approx$ 0.397, b $\approx$ 0.397 and c $\approx$ 0.775 from the nonextinction and the reciprocal lattice point length seen on Weissenberg and Precession photographs. The jump of some $2/3La^{3+}$ ions leads to increase the moving paths due to the generation of new vacancies at middle empty sites and thus this result is confirmed to provoke the dielectric anomaly.

• Microbiology and Biotechnology Letters
• /
• v.20 no.1
• /
• pp.40-45
• /
• 1992

Acidic nucleotidase from Asfiergilius nlger has been partially purified by Sepharose CL-6B gel filtration and DEAE-Sephacel ion exchange chromatography. The optimum pH and temperature for the enzyme reaction with 5'-AMP or 3'-AMP as a substrate were 4.5 and 55%, respectively. However, the optimum temperature became 70% when p-nitrophenyl phosphate was used as a substrate. The enzyme was stable at acidic pH. The enzyme activity was not affected by addition of various nucleotides, nucleosides and inorganic phosphates. Ferric, aluminium, vanadate and molybdate ions inhibited the enzyme activity dramatically. In kinetic studies, $K_m$), values for 3'-AMP, 5'-AMP and p-nitrophenyl phosphate were 1.39 mM, 1.5 mM and 5.77 mM, respectively. The substrate efficiency ($V_{max}/K_m$) shows 3'-AMP is the prefered substrate for the enzyme among tested substrates.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.7 no.2
• /
• pp.244-252
• /
• 1997

The pseudo-spinel type solid solution, $LiAl_{2.5}/Fe_{2.5}O_8$ was prepared by reaction of $LiCO_3, Al_2O_3, Fe_2O_3$ mixture at 1620K, which can be used for cathode material in lithium batteries. Its structure was investigated by Rietveld profile-analysis of XRD in detail. The space group of solid solution is $P4_3$32(a=8.1293$\AA$) and the final residual index of structure refinement was about 5%. Cations $Al^{3+}, Fe^{3+}$ are located at both tetra- and octahedral-coordination and $Li^+$ ions are occupied in the octahedral 4b-, 12d-site of the inverse spinel.

• Journal of Plant Biotechnology
• /
• v.7 no.1
• /
• pp.1-15
• /
• 2005

Salinity is one of the major limiting factors for agricultural productivity. In plants, accumulation of osmolytes plays a pivotal role in abiotic stress tolerance. Likewise, exclusion or compartmentation of $Na^+$ ions into vacuoles provides an efficient mechanism to avert deleterious effects of $Na^+$ in the cytosol. Both vacuolar and plasma membrane sodium transporters and $H^+-ATPases$ can provide the necessary ion homeostasis. A variety of crop plants were engineered with respect to the synthesis of osmoprotectants and ion-compartmentation, but there are other cellular pathways involved in the salinity responses that are still not completely explored. Genomics approaches are increasingly used to identify genes and pathway changes involved in salt-tolerance. The new knowledge may be used via guided genetic engineering of multiple genes to create crop plants with significantly increased productivity in saline soils. This review surveys how plants deal with high salt conditions and how salt tolerance can be improved by transgenic approaches.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.5
• /
• pp.407-412
• /
• 2014

A new apparatus for seawater desalination, based on the principle of gas hydrates, is suggested. The equipment continuously produces and pelletizes gas hydrates by a squeezing operation in a dual cylinder unit, which is able to extract pure hydrate pellets from the seawater-containing reactor. Desalination efficiency for each dissolved ion from seawater samples was tested by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ion chromatography (IC) analysis. This study demonstrates that the suggested method and the stated apparatus may solve the difficulty of separating hydrate crystals from concentrated brine solutions, and therefore may be applied to improve the efficiency of existing desalination processes.