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[en] A highly sensitive spectrophotometric method with b-correction is developed for the determination of trace amount of cadmium using the reaction with o-chlorobenzenediazoaminobenzene-p-azobenzene (OCDA). The method makes it possible to exclude the effect of OCDA excess in colored solution of its cadmium chelate, determine the complex formation coefficient, real molar absorption, and the factor of chelate instability. The threshold of cadmium determination is 0.008 mg/liter and detection limit is 95±7.5 % in analysis of metals. Relative standard deviation of determination is no more than 4.1 % at n=6. 16 refs.; 6 figs.; 1 tab
[en] This paper reviews the safety and security of radioactive sources, summarizes the successful experiences and the existing problems of the radiation safety management during the period of Beijing 2008 Olympic games, and gives the suggestions for the better radiation safety management in the future. (author)
[en] Highlights: • SGO–ZnO–Ag composites were synthesized through a stepwise process. • Surface plasmon resonant. • Enhanced light absorption. • Reduced charge recombination rate. • Fast photodegradation and disinfection rate. -- Abstract: Synthesis of efficient visible-light-driven photocatalyst is urgent but challenging for environmental remediation. In this work, for the first time, the hierarchical plasmonic sulfonated graphene oxide–ZnO–Ag (SGO–ZnO–Ag) composites were prepared through nanocrystal-seed-directed hydrothermal method combining with polyol-reduction process. The results indicated that SGO–ZnO–Ag exhibited much faster rate in photodegradation of Rhodamine B (RhB) and disinfection of Escherichia coli (E. coli), than ZnO, SGO–ZnO and ZnO–Ag. SGO–ZnO–Ag totally degraded RhB dye and kill 99% of E. coli within 20 min under visible light irradiation. The outstanding performences of SGO–ZnO–Ag were attributed to the synergtic merits of SGO sheets, ZnO nanorod arrays and Ag nanoparticles. Firstly, the light absorption ability of SGO–ZnO–Ag composite in the visible region was enhanced due to the surface plasmon resonance of Ag. In addition, the hierarchical structure of SGO–ZnO–Ag composite improved the incident light scattering and reflection. Furthermore, SGO sheets faciliated charge transfer and reduce electron–hole recombination rate. Finally, the tentative mechanism was proposed and verified by the photoluminescence (PL) measurement as well as the theoretical finite-difference time-domain (FDTD) simulation. In view of above, this work paves the way for preparation of multi-component plasmonic composites and highlights the potential applications of SGO–ZnO–Ag in photocatalytic wastewater treatment field
[en] WO3–Cr2O3 semiconducting thin films were prepared by sol–gel method. Acetone gas sensing properties were investigated. Monoclinic phase was obtained as determined by X-ray diffraction after WO3–Cr2O3 films were sintered in oxygen atmosphere for 1 h at 500 °C (quenched after sintering). Porous structure was observed by using field emission scanning electron microscopy. Electrical properties were studied by conductivity measurement. The acetone vapor sensing properties of these thin films were found strongly influenced by the porous structure, the content of Cr2O3, the sintering temperature, and the cooling way. As-prepared WO3–Cr2O3 thin films exhibit excellent acetone vapor sensing properties with the maximum sensitivity ∼ 8.91 at 320 °C in air atmosphere with fast response and recovery time. - Highlights: ► Porous structure was prepared to improve the thin film's gas-sensing properties. ► Dissymmetrical monoclinic structure was obtained to improve selectivity to acetone. ► Quenching after sintering enables obtain dissymmetrical structure. ► Effects of the sintering temperature and the Cr2O3 content were discussed. ► As prepared sensors can diagnose diabetes based on human breath analysis.
[en] Highlights: •Chemically ordered Pt3Co and PtCo catalysts with a unique structure of stable Pt shell covering an ordered core were generally synthesized. •These core shell structures ordered catalysts show superior catalytic activity and stability toward the oxygen reduction reaction when compared to commercial Pt/C catalyst. •The ordered structure of the Pt3Co/C-700 and PtCo/C-700 catalysts is maintained after stability test. -- Abstract: Surface microstructure plays a key role in tuning the catalytic performance of Pt base nanomaterials as the oxygen reduction reaction (ORR) catalysts in fuel cell. In this work, carbon supported chemically ordered Pt3Co and PtCo nanoparticles (NPs) with stable Pt shell were synthesized using a polyol reduction process and followed by annealing. The structural characterizations show that the as-synthesized Pt3Co/C-700 and PtCo/C-700 catalysts have small particle sizes (∼5 nm) and are composed of ordered core and Pt-rich shell. The electrochemical tests show that the ORR catalytic activities of Pt3Co/C-700 and PtCo/C-700 are 0.4978 A mg−1Pt and 0.4092 A mg−1Pt, which are higher than that (0.1646 A mg−1Pt) of the commercial Pt/C catalyst. The stability tests show that the Pt shell of the ordered catalysts was electrochemically stable and the chemically ordered structure was well remained after 5000 potential cycles. The mass activity decreases for the Pt3Co/C-700 (8.60%) and PtCo/C-700 (38.65%) catalysts are less than that (55.22%) of the commercial Pt/C catalyst, displaying superior catalytic stability. The improved catalytic performance of the ordered catalysts was attributed to the synergistic effect of compact arrangement of surface Pt atoms and ordered core. Here we propose a strategy for optimization design of Pt-base catalysts with both high catalytic activity and stability for the ORR.
[en] Highlights: •Unique grass-like CuO nanostructures prepared by simple hydrothermal reactions. •The influence of calcination in N_2 atmosphere on CuO nanostructures was discussed. •Study of processing-structure-property relationship of different CuO samples. •As-prepared sensors exhibited excellent electrochemical catalytic performance. •As-synthesized sensors show great application potential of detecting H_2O_2. -- Abstract: In this research, grass-like CuO nanostructure was synthesized via a simple hydrothermal reaction at 100 °C for 6 h without using any surfactant. The as-prepared sample was further calcined at 500 °C for 1 h in nitrogen atmosphere for comparison. The surface morphology, crystal structure and chemical composition of the products were investigated by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and room temperature photoluminescence spectroscopy (PL). The as-synthesized samples were also characterized systematically by electrochemical methods including cyclic voltammetry (CV), amperometric detection (i-t) and electrochemical impedance spectroscopy (EIS). It was found that the sample prepared after calcination in a nitrogen atmosphere exhibited better electrochemical catalytic performance for the determination of H_2O_2. In addition, high sensitivity (119.35 μA/mM) and fast amperometric response (< 3 s) were achieved; mainly due to the large specific surface area of the grass-like morphology, efficient electron charge transfer property resulting from the increased crystallinity after calcination, as well as more available and active absorption sites induced by surface defects and the CuO/Cu_2O heterostructure, thus making it one of the promising candidates for the efficient and sensitive non-enzymatic amperometric detection of H_2O_2
[en] The Kosterlitz Thouless transition in two-dimensional arrays of proximity-coupled superconducting weak links has been studied in this paper. The samples were prepared by application of the vacuum-evaporation/photoengraving/chemical-etching technique. The experimental results of measurements on some samples of array film showed the existence of the K-T transition in these samples and were consistent with the theory of Lobb, Abraham, and Tinkham
[en] The PI controller which is used widely in water level control of pressurizer in reactor control system usually leads dynamic overshoot and long setting time. The improvement project for intelligent fuzzy controller to take the place of PI controller is advanced. This paper researches the water level control of pressurizer in reactor control system of Daya Bay Phase I, and describes the method of intelligent fuzzy control in practice. Simulation indicates that the fuzzy control has advantages of small overshoot and short settling time. It can also improve control system's real time property and anti-interference ability. Especially for non-linear and time-varying complicated control systems, it can obtain good control results. (authors)
[en] This paper briefly introduces monitoring results of environmental and radioactive effluents for Beijing Tungsten-molybdenum Material Factory using standard methods recommended by the Technical Criteria for Radiation Environmental Monitoring (HJ/T 61-2001), monitoring items include: γ radiation air absorbed dose rate, total α and total β radioactivity in water, specific activities of radionuclides in soil and 232Th concentrations in aerosol. The results show that under normal operation conditions, no detectable influence to radioactive environment was found in surrounding of Beijing Tungsten-molybdenum Material Factory, except that traces of 232Th had been monitored at exhaust outlet of the intermingling workshop and sometimes total activity concentration of waste water in the precipitating pool was over the National Standard. (authors)
[en] II you 838 is a hybrid of mutant, Fu-Hui 838(male)x II-32A(female). Field-testing showed that II you 838 had a great tolerance to high temperature. Superoxide dismutase, catalase and peroxidase are major antioxidases and play an important role in the tolerance. The expression of SOD, CAT and POD in sword leaves of heat treating group and control group during the blossoming day and the next day were analyzed by using Realtime-PCR method. The result shows that the expression level of these three antioxidases genes in heat treating group were significantly higher than that in control group. (authors)