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  • Author or Editor: D. Yang x
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Abstract  

With pulse decay discrimination function and using diisopropylnaphthalene based scintilation cocktail, liquid scintillation analysis (LSA) becomes a rapid and reliable method for monitoring emitting nuclides in environmental samples. Recent developments of instrumentation and cocktail of LSA are described. Procedures and results of monitoring gross activity in vegetable samples and plutonium in soil samples are given. The Minimum Detectable Activity was 4.5×10–2 Bq/Kg for vegetable samples and was 6.6×10–5 Bq/g for soil samples.

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Abstract  

Let G be a bounded locally compact Vilenkin group. We study the boundedness of potential operators and the maximal operators associated with them in the weighted Herz space, the weighted Hardy space and the weighted Herz-type Hardy space over G. We also discuss the boundedness of these operators on the weighted weak Lebesgue space and the weighted weak Herz space whose sharpness are also discussed.

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Abstract  

We completely classify Lorentzian surfaces with parallel mean curvature vector in
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{bbm} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\mathbb{E}_2^4$$ \end{document}
. The main result states that there exist 22 families of such surfaces.
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Abstract  

Simple, rapid and sensitive methods are very important for the bioassay of plutonium. In this work, modern liquid scintillation technique combined with selective extraction separation and / pulse decay discrimination were studied and evaluated for the bioassay of plutonium. After sample decomposition and partial evaporation, cyclohexanone and trialkylphosphine oxide (TRPO) were used for the separation of plutonium from matrix. Several different cocktails were tested for liquid scintillation analysis of urine samples. The minimum detectable activity (MDA) of this method was estimated to be 0.01 Bq/500ml urine with 100 minutes measuring time and 3 confident level.

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Abstract  

This work discusses thermal behavior of Ni/MH battery with experimental methods. The present work not only provides a new way to get more exactly parameters and thermal model, but also concentrates on thermal behavior in discharging period. With heat generation rate gained by experiments with microcalorimeter, heat transport equations are set up and solved. The solutions are compared with experiment results and used to understand the reactions inside the battery. Experiments with microcalorimeter provide more reliable data to create precise thermal model.

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Abstract  

Two series of antibacterial compounds were synthesized using montmorillonite and chlorhexidine acetate (CA) by ion-exchange reaction. The resulting samples were characterized by high-resolution thermogravimetric analysis (HRTG), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and their antibacterial activity was assayed by halo method. In this study, the loaded amounts of CA in the resultant compounds were evaluated by the HRTG curves. CA adopts a lateral monolayer arrangement in the resulting samples with low CA loading, while a special state with partial overlapping of organic molecules is supposed for the resulting samples prepared at 1.0–4.0 CEC. After the intercalation with CA, the hydrophilic surfaces of montmorillonite are changed to hydrophobic ones, reflected by the frequency shift of the symmetric ν1(O-H) stretching vibration from low to high. This study shows that the interlayer cations in raw montmorillonite have little influence on the structure of the resulting samples. Antibacterial activity test against E. coli demonstrates that the antibacterial activity of the resulting samples strongly depends on the content of the loaded CA and these resulting materials show a long-term antibacterial activity that can last for at least one year.

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Abstract  

Poly(AN—co—St) (PAS) and poly(AN—St—MMA)(PASM) were synthetized by emulsion polymerisation. The glass transition temperatures (T g) of the copolymers and the relationship between T g and the components of the copolymers were investigated by differential scanning calorimetry. The results show that T g for the AN—St bipolymers has apeak value in the range 115–118°C at a content of 50 mass% St. When methyl methacrylate was added, the T g of the terpolymer was decreased by about 2–6°C.The thermostability and the activation energy E of degradation were determined by thermogravimetric analysis.

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Abstract  

The combustion behavior of Shuangya Mountain (SYM) coal dust has been investigated by means of TG in this paper. The reaction fraction can be obtained from isothermal TG data. The regressions of g(), an integral function of vs. t for different reaction mechanisms were performed. The mechanism of nucleation and nuclei growth is determined as the controlling step of the coal dust combustion reaction by the correlation coefficient of the regression, and the kinetic equation of the SYM coal dust combustion reaction has been established.

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Thermal degradation of poly(vinyl butyral) (PVB) and its mixtures with alumina, mullite and silica was investigated by non-isothermal thermogravimetry in the temperature range of 323 to 1273 K. The analysis of the data was carried out using a three-dimensional diffusion model. Results showed that the kinetic parameters (activation energy and pre-exponential factor) of the PVB degradation are different for polymer alone, and ceramic/polymer composites. The overall weighted mean apparent activation energy showed an increasing reactivity in the order of PVB<alumina+PVB<mullite+PVB<silica+PVB. This shows that the acidic and basic surface characteristics of the ceramics promote the thermal degradation of PVB and, the more acidic silica affects the degradation more than mullite and alumina. The effect of pellet compression pressure in the range of 4000 to 8000 psig is also investigated.

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Abstract  

The extraction of Am(III) and Eu(III) using a γ-pre-irradiated N,N′-dimethyl-N,N′-dibutyltetradecyl malonamide (DMDBTDMA) modified with N,N′-dihexyloctanamide (DHOA) in n-dodecane (NDD) at 4.5M HNO3 has been studied as a function of the absorbed dose up to 2×106 Gray. The distribution ratios of Am(III) and Eu(III) were almost constant until a dose of 1×105 Gray and then they decreased gradually up to a dose of 2×106 Gray. The decrease of the distribution ratios of Am(III) and Eu(III) are due to the decreasing concentration of the DMDBTDMA by a γ-pre-irradiation and these results were supported by a determination of the DMDBTDMA concentration with a gas chromatography method. The distribution ratios of Am(III), Eu(III), Ce, Nd and Y with γ-pre-irradiated (DMDBTDMA-DHOA)/NDD have also been studied as a function of the nitric acid concentration and the extraction temperature.

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