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Abstract

Hydrogen titanate nanotubes were prepared by K2Ti2O5 with water vapour treatment. TG/DTG techniques were used to investigate their water content and dehydration kinetics. It was shown that chemical formula for hydrogen titanate nanotubes is TiO2·0.58H2O which is close to H2Ti2O5. The activation energy of dehydration from hydrogen titanate nanotubes is about 60 kJ/mol according the calculation of Friedman and Flynn–Wall–Ozawa methods. With multivariate non-linear regression calculation, it was found that dehydration of hydrogen titanate nanotubes is a two-step consecutive reaction. The first step is a reaction of nth order with autocatalysis. The second step is a reaction of nth order.

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Abstract

The combustion behaviors and kinetic parameters of three parent coals (A1, A2, and A3) and their blends (A1/A2 and A2/A3) have been evaluated under oxidizing atmosphere (O2 and N2 mixtures), using a non-isothermal thermo-gravimetric analyzer. The aim of this study is to investigate the interaction between the blended components during the process of co-combustion, and the effects of blending ratio and oxygen concentration (10, 15, and 21%) on combustion performance of blended coals. When high reactivity and low reactivity coals are co-combusted, double peaks are observed in the DTG curves, and significant interaction occurs in the temperature range between the two peaks (T p1 and T p2). The activation energies obtained by Coats–Redfern method indicate that the activation energies of blended coals are lower than that of parent coals. The combustibility index S is used to evaluate the combustion performance of blended coals, and the results show the non-additive effects of the combustion characteristics of blended coals. The increased oxygen concentration results in a significant improvement of combustion performance of blended coals. In addition, as the blending ratio of high reactivity coal is increased, the oxygen can greatly enhance the combustion stability of blended coals.

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Abstract  

Environmental samples of beach sand taken at northern Taiwan have been monitored using a coincident gamma-ray spectrometer. The concentration of134Cs, under intense interference from natural and other artificial radioactivity, is determined as low as 0.2 Bq/kg dry. The accumulation of trace levels of134Cs originates from the discharge of nuclear power plants nearby.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Fanxing Gao
,
Changshui Wang
,
Lisheng Liu
,
Jianhua Guo
,
Shangwen Chang
,
Li Chang
,
Ruixue Li
, and
Yinggen Ouyang

Abstract  

In the first part, LiCl-KCl-UCl3 and LiCl-KCl-UCl3-UCl4 molten salts were prepared, which were studied employing cyclic voltammetry and chronopotentiometry techniques, respectively. It was determined that the reduction of U(IV) to uranium metal takes two steps. Firstly, U(IV) is reduced to U(III). Then, the reduction of U(III) to uranium metal occurs in a step with a global exchange of three electrons. Cyclic voltammetry studies indicated that at low sweep rates, the reduction of U(III) to uranium is reversible. However, a mixed control of both diffusion and electrontransfer is observed as the sweep rate increases. The diffusion coefficient of U(III) and the formal potential of U(III)/U versus Ag/AgCl reference electrode in these two salt systems were calculated respectively. In second part, based on the data of the electrode processes of uranium ions, electrodeposition of uranium metal was carried out. Uranium deposits were prepared adopting a 304 stainless steel electrode in the molten LiCl-KCl-UCl3 and LiCl-KCl-UCl3-UCl4, respectively by employing suitable electrolytic techniques. The morphology of the deposits and the cross-section of the cathode were investigated by SEM. It was determined that at the beginning of the deposition process, uranium product alloys with stainless steel and forms a thin layer, and then uranium begins to grow adhering to the layer.

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Abstract  

Many concerns over unsafe or unknown properties of multi-walled carbon nanotubes (MWNTs) have been raised. The thermal characteristics regarding stability would represent potential hazards during the production or utilization stage and could be determined by calorimetric tests for various thermokinetic parameters. Differential scanning calorimetry (DSC) was employed to evaluate the thermokinetic parameters for MWNTs at various compositions. Thermoanalytical curves showed that the average heat of decomposition (ΔH d) of the MWNTs samples in a manufacturing process was about 31,723 J g−1, by identifying them as an inherently hazardous material. In this study, significant thermal analysis appeared in the presence of sulfuric acid (H2SO4). From the DSC experiments, the purification process of MWNTs could induce an unexpected reaction in the condition of batch addition with reactants of H2SO4. The results can be applied for designing emergency relief system and emergency rescue strategies during a perturbed situation or accident.

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Abstract

This paper employs bibliometric methods to observe collaboration patterns of scientific publications in biotechnology, information and computer technology, future energy, and nanotechnology among different institutions in Taiwan. The results show primary domestic and international collaborative patterns, the effect of collaborative papers on the world-wide average, collaborative networks, and the distribution of institutions on global map. The findings suggest that domestic collaboration in each area is higher in proportion than international collaboration. Biotechnology leads in both domestic and international collaborative percentage. Among cooperative benchmarking countries, the US and China are the main partners. Collaboration among research institutes and universities is the most frequent collaborative pattern in each area except biotechnology, which tends to occur between hospitals and universities. On average, international collaborative papers tend to have greater effect, except in nanotechnology. Academia Sinica collaborated frequently with foreign institutes in each research field. A further analysis on how each collaborative group forms is recommended, especially collaboration among the Triple-Helix relationships.

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Abstract

The decomposition of organic peroxides by their relatively weak oxygen linkage and hydroperoxide radical in the presence of reaction solution is one of the thermal hazards for triggering a runaway reaction. Runaway incidents may occur in oxidation reactors, vacuum condensation reactors, tank lorries, or storage tanks. In NFPA 432 organic peroxides in NFPA 432 are classified as flammable. The exothermic behaviors of solid organic peroxides, dicumene peroxide, benzoyl peroxide, and lauroyl peroxide, were determined by differential scanning calorimetry (DSC), and vent sizing package 2 (VSP2). Relevant data detected by DSC provided thermal stability information, such as exothermic onset temperature (T 0), maximum heat-releasing peak (T max), and heat of decomposition (ΔH d). VSP2 was used to perform the bench scale situation for pushing the expected or unexpected reaction to undergo runaway reaction. Onset temperature, maximum pressure, self-heating rate ((dT dt −1)max), and pressure-release rate ((dP dt −1)max) were therefore obtained and explained. These results are essentially crucial in process design for an inherently safer approach.

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Abstract  

Activity concentrations using gamma-ray spectrometer and distributions of natural radionuclides in soil samples collected were investigated to assess the environmental radioactivity and characterization of radiological hazard. The average concentrations of 238U, 232Th series and 40K in the 5 cm depth soil were 22.53, 33.43 and 406.62 Bq kg−1, respectively, which was within world median ranges in the UNSCEAR 2000 report. The average absorbed dose rate estimated by soil activity and annual effective doses were 49.32 nGy h−1 and 60.48 μSv, respectively. Since the soil is an important building material, the mean radium equivalent activity (Ra eq), external (H ex) and internal (H in) hazard index using various models given in the literature for the study area were evaluated as 101.72 Bq kg−1, 0.27 and 0.34, respectively, which were below the recommended limits. The effects of pH value, conductivity, true density and textural properties of soil samples on the natural radionuclide levels were also studied. The application of cluster analysis (CA) and principal component analysis (PCA), coupled with Pearson correlation coefficient analysis, were utilized to analyze the data, identify and clarify the effects of physico-chemical properties on natural radioactivity levels. The CA and PCA results showed that the former method yielded three distinctive groups of the soil variables whereas the latter one yielded the number of variables into three factors with 87.5% variance explanation.

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The objective of this study was to establish and optimize high-performance thin-layer chromatography (HPTLC) analysis of gatifloxacin and related substances by the method of design of experiment (DOE). First, preliminary screening of 22 solvents was performed using uniform design (UD) to establish the developing solvent proposed to be optimized. The optimal proportions of components in the developing solvent were established by using central composite design (CCD) to establish and validate HPTLC analysis of gatifloxacin and related substances. Using DOE, it was found that the optimal proportions (by volume) of components in the developing solvent in the HPTLC analytical method were methanol-1,2-dichloroethane-concentrated ammonia solution-acetonitrile (2.8:7.2:0.5:0.5, v/v). Methodological validation showed that the established HPTLC method could separate gatifloxacin and 8 related substances with similar structures effectively. In particular, impurity pairs with the greatest separation difficulty (due to their similar polarities and dipole moments), e.g., impurity #3 (8-fluorogatifloxacin) and impurity #8 (gatifloxacin 2-methylpiperazine), impurity #3, and substance #9 (gatifloxacin), could also be separated effectively. The HPTLC method was simple, accurate, reliable, and suitable for rapid qualitative analysis of gatifloxacin and related substances in routine tests. Additionally, the analytical results presented here may provide useful supplemental information on the current reversed phase high-performance liquid chromatography (RP-HPLC) method, especially in terms of the mechanism of normal-phase separation.

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Abstract  

The i-butyldodecylsulfoxide (BDSO) was synthesized. The extraction of uranium(VI) has been carried out with BDSO in toluene from various HNO3 concentrations. It was found that the distribution ratio increases with increasing nitric acid concentration up to 3.0 mol/l and then decreases. The distribution ratios also increase with increasing extractant concentration. The extracted species appears to be UO2(NO3)2·2BDSO and the equilibrium constant value is 15.2. The influence of temperature, sodium nitrate and oxalate concentrations on the extraction was also investigated, and the thermodynamic functions of the extraction reaction were obtained.

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