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  • Author or Editor: Dong Kim x
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Abstract  

We consider the asymptotic behavior of the distribution functions defined by FN(z)=1N{1≦ n ≦ N : f(n)≦ z (mod 1)} in the case when f is q-additive. We give necessary and sufficient conditions for a q-additive function to have a uniform distribution modulo 1 or to have a non-uniform distribution modulo 1.

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Abstract  

Separation of lithium isotope by NTOE compound was carried out with 0.01M HCl solution. The ion exchange capacity of NTOE was 0.8 meq/g. The separation factor, α=(7Li/6Li) solid (7Li/6Li) liquid was 1.0242 by the elution chromatography. The lighter isotope,6Li was concentrated in the liquid phase, while the heavior isotope,7Li was enriched in the solid phase.

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The past three decades have seen increasing progress in the integration and process diversification of microfluidic systems for use in chemistry, biochemistry, and analysis. Here we summarize recent achievements in microreaction modules and microseparation units. We look into recent developments of microreaction systems fabricated by various 3D printing techniques for chemical synthetic applications. Moreover, we take a look at the recent achievements of newly developed microseparation technologies with enhanced separation efficiency realized by adopting single or hybrid principles as well as novel device concepts. Emerging technologies of 3D printing have potential to realize a vertically stacking the microchannels and miniaturization of bulky microreaction accessories. When the advanced microreaction systems are integrated with newly developed microseparation technologies, automated synthesis of industrial compounds, such as pharmaceuticals which need multiple types of salification chemistry, will be almost completed. Many opportunities are open to developing innovative microreaction systems with these techniques that can also be highly durable under harsh conditions.

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Abstract  

The chromatographic separation of lithium isotopes was investigated by chemical exchange with the recently synthesized polymer-bound dibenzo pyridino diamide azacrown (DBPDA) and reduced dibenzo pyridino diamide azacrown (RDBPDA). Column chromatography was employed for the determination of the effect of solvents and ligand conformation on the separation coefficients. The maximum separation coefficients, , for the DBPDA and RDBPDA at 20.0±0.02°C with acetonitrile as eluent, were found to be 0.034±0.002 and 0.035±0.002, respectively. The isotope separation coefficient and adsorption capability of the lithium ion on the DBPDA and RDBPDA were only slightly dependent on ligand structure, but strongly dependent on the solvent. DBPDA and RDBPDA appeared to have almost the same value for the isotope separation coefficient of lithium.

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Plain and N-doped carbonaceous particles are synthesized from biomass resources such as glucose via continuous hydrothermal carbonization (HTC) process at 200 °C and 250 psi for the first time using a microfluidic system in a fast and continuous manner. The continuous HTC is controlled by reaction time (3.7–30 min) and concentration (0–10 wt.%) of ethylenediamine as a nitrogen additive to produce a series of the plain carbonaceous and N-doped carbonaceous particles with size range from 0.8 to 1.2 um. The as-synthesized and the pyrolyzed particles are characterized by various analytical instruments to understand their chemical structures with elemental compositions, morphology of particles, and thermal defunctionalization.

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Abstract  

The formation of precipitates by hydrazine was experimentally examined in the simulated high level liquid waste (HLLW), which was composed of 9 elements (Nd, Fe, Ni, Mo, Zr, Pd, Ru, Cs, Sr). Palladium was precipitated over 90% above 0.05M of hydrazine concentration and at 2M HNO3, while all of the other elements were hardly precipitated. The elements of Pd and Zr were precipitated 93% and 70% in the simulated solution in which the concentrations of Zr and Mo were decreased from 0.069M to 3.45·10–3M and 6.9·10–3M, respectively, and the acid concentration was decreased to about 0.5M after denitration. In a Pd solution of 0.5M and 2M HNO3, the precipitation yield of Pd increased with hydrazine concentration and reached over 98% at 0.1M. The precipitation yield of Pd at 0.5M HNO3 was higher than at 2M HNO3. The Pd precipitate, formed by adding hydrazine to an acidified solution, was an amorphous compound consisting of Pd, hydrazine, nitrate and hydrate.

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Abstract  

The removal of Cs and Re (as a surrogate for Tc) by selective precipitation from the simulated fission products which were co-dissolved with uranium during the oxidative dissolution of spent fuel in a Na2CO3–H2O2 solution was investigated in this study. The precipitations of Cs and Re were examined by introducing sodium tetraphenylborate (NaTPB) and tetraphenylohosponium chloride (TPPCl), respectively. The precipitation of Cs by NaTPB and that of Re by TPPCl each took place within 5 min, and an increase in temperature up to 50 °C and a stirring speed up to 1000 rpm hardly affected their precipitation rates. The most important factor in the precipitation with NaTPB and TPPCl was found to be a pH of the solution after precipitation. Since Mo tends to co-precipitate with Cs or Re at a lower pH, an effective precipitation with NaTPB and TPPCl was done at pH of above 9 without the co-precipitation of Mo. More than 99% of Cs and Re were precipitated when the initial concentration ratio of NaTPB to Cs was above 1 and when that of TPPCl to Re was above 1. The precipitation of Cs and Re was never affected by the concentration of Na2CO3 and H2O2, even though they were raised up to 1.5 and 1.0 M, respectively. Precipitation yields of Cs and Re in a Na2CO3–H2O2 solution were found to be dependent on the concentration ratios of [NaTBP]/[Cs] and [TPPCl]/[Re].

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Abstract  

Sediment core samples taken from the Jinheung catchment located in the middle of the Korean Peninsula were used to know environmental radionuclide distribution. The grain sizes of the sediment cores were found at depth of about 17 cm suggesting that it might have occurred during a dry period of 1969. The radionuclides, 137Cs, 237Np, 239Pu, 240Pu, 234U, 238U, 228Th, 230Th, 232Th, were analyzed by sector type ICP-MS and gamma-spectrometry. The Cs and Pu distribution changed with the depth, in which the maximum ranged from 14 to 22 cm. This was due to the high activity of the results of nuclear bomb tests in the air from 1960s and showed different distribution pattern on the soil surface. The average activity ratio of 240Pu/239Pu and 237Np/239Pu was 0.173 and 0.45, respectively. These values were similar to the north hemisphere global fallout ratio of 240Pu/239Pu (0.18) and 237Np/239Pu (0.45). The 237Np/239Pu ratio showed a higher value than the global fallout ratio above 14 cm depth. The U, Th and their daughter radionuclides kept secular equilibrium in the sediment core because the average activity ratios were nearly 1.

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Abstract  

Uranium dendrites which were deposited at a solid cathode of an electrorefiner contained a certain amount of salts. These salts should be removed for the recovery of pure metal using a cathode processor. In the uranium deposits from the electrorefining process, there are actinide chlorides and rare earth chlorides in addition to uranium chloride in the LiCl–KCl eutectic salt. The evaporation behaviors of the actinides and rare earth chlorides in the salts should be investigated for the removal of salts in the deposits. Experiments on the salt evaporation of rare earth chlorides in a LiCl–KCl eutectic salt were carried out. Though the vapor pressures of the rare earth chlorides were lower than those of the LiCl and KCl, the rare earth chlorides were co-evaporized with the LiCl–KCl eutectic salt. The Hertz–Langmuir relation was applied for this evaporation, and also the evaporation rates of the salt were obtained. The co-evaporation of the rare earth chlorides and LiCl–KCl eutectic were also discussed.

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Abstract  

Complexes of UO2 2+, Ce3+ and Nd3+ (M) with acetohydroxamic acid (AHA or L) in an aqueous solution have been investigated by the pH-spectral titration method at 25 °C in an aqueous medium of 1.0 M NaClO4 ionic strength. Cerium(III) and neodymium(III) form [ML]2+, [ML2]+, [ML3] complexes with acetohydroxamic acid, while in case of UO2 2+ form [UO2L]+, [UO2L2] complexes with acetohydroxamic acid. Data processing with SQUAD program calculates the best values for the stability constants from pH-spectrophotometric titration data. The protonation constant obtained was pK1 = 9.15 ± 0.04 at 25 °C. The stability constants for acetohydroxamic acid with UO2 2+, Ce3+ and Nd3+ were β1 = 7.22 ± 0.011, β2 = 14.89 ± 0.018 for UO2 2+ and β1 = 5.05 ± 0.062, β2 = 10.60 ± 0.076, β3 = 16.23 ± 0.088 for Ce3+ and β1 = 5.90 ± 0.028, β2 = 12.22 ± 0.038, β3 = 18.58 ± 0.042 for Nd3+, respectively.

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