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  • Author or Editor: Lin Li x
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Abstract  

A number of generalized metric spaces have been defined or characterized in terms of g-functions. Symmetric g-functions are discussed by C. Good, D. Jennings and A. M. Mohamad. In this paper, some questions about symmetric g-functions are answered, particularly it is shown that every sym-wg-space is expandable.

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It is shown that every separable k'-space with a point-countable k-system has a countable k-system, which gives an affirmative answer to Y. Tanaka's Question posed in 1982.

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Abstract  

In this paper the relations among k-covers, cs *-covers and k-systems are discussed. The following question is partially answered: Does every separable k'-space with a point-countable k-system have a countable k-system?

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To order to examine experimentally the modified monostandard method implemented in the program MULTINAA, the FRM reactor in Garching (Germany) was calibrated and an INAA of a standard reference material NIST/SRMI1633b Coal Fly Ash was performed. The relative, thek 0-and the modified monostandard standardizations are applied. This work shows that for all of the examined 1/-nuclides the modified monostandard method provides identical analytical results to those determined by thek 0-method. For the non-1/ nuclides177Lu and152Eu the monostandard results are correct. Compared with the certified values of the analysed SRM1633b sample and also with the results of the relative method, it can be concluded that the modified monostandard method performed at our experimental conditions gives analytical results with accuracy better than 5%.

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The problem when a paratopolgical group (or semitopological group) is a topological group is interesting and important. In this paper, we continue to study this problem. It mainly shows that: (1) Let G be a paratopological group and put τ = ω H s(G); then G is a topological group if G is a P τ-space; (2) every co-locally countably compact paratopological group G with ω H s(G) ≦ ω is a topological group; (3) every co-locally compact paratopological group is a topological group; (4) each 2-pseudocompact paratopological group G with ω H s(G) ≦ ω is a topological group. These results improve some results in [11, 13].

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In this paper, we characterize k-semi-stratifiable spaces by semi-continuous functions and give some applications. Also we give the similar characterizations of MCM spaces and K-MCM spaces.

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Abstract

The thermal decomposition of copper(II) acetate monohydrate (CuAc2·H2O) under 500 °C in air was studied by TG/DTG, DTA, in situ FTIR and XRD experiments. The experimental results showed that the thermal decomposition of CuAc2·H2O under 500 °C in air included three main steps. CuAc2·H2O was dehydrated under 168 °C; CuAc2 decomposed to initial solid products and volatile products at 168–302 °C; the initial solid products Cu and Cu2O were oxidized to CuO in air at 302–500 °C. The copper acetate peroxides were found to form between 100 and 150 °C, and the dehydration of these peroxides resulted in the presence of CuAc2·H2O above 168 °C. The initial solid products were found to be the admixture of Cu, Cu2O, and CuO, not simply the single Cu2O as reported before. Detailed reactions involved in these three steps were proposed to describe the complete mechanism and course of the thermal decomposition of CuAc2·H2O in air.

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Abstract  

A compute program MULTINAA was developed to facilitate the evaluation of NAA data. It is written for the VAX/VMS syste and opeates in the Canberra/ND Genie spectroscopy software environment. MULTIINAA can be appliede to relative,k 0-, monostandard (modified) and absolute methods, including the fast neutron threshold reaction. For each calculation, the available standardizations can be used individually or mixed. In all the standardization modes MULTINAA fetches the data directly from the -ray spectra and libraries, thus reducing the manual work to a minimum. MULTINAA is flexibkle to meet various situations in NAA practical work. The required neutron flux parameters all the non-relative methods are supplied by an accompanying program MULTIFLUX.

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Abstract

Four series of nano-sized HZSM-5 zeolite catalysts were prepared with different steaming and HNO3 leaching processes. These samples were studied by XRD, NH3-TPD, FT-IR, n-hexane and cyclohexane adsorption, and fixed-bed aromatization of C4 liquefied petroleum gas (C4 LPG). Results show that, with the steaming temperature increasing, the acidity of catalyst decreased gradually, which was attributed to the removal of Al species from the framework of the zeolite. When steaming is combined with acid leaching, we found that acid leaching-steam catalysts exhibit stronger acidity than steam-acid leaching catalysts. Besides, acid leaching also played an important role in enhancing the diffusibility of catalysts. Catalysts which underwent acid leaching twice exhibit the best microporous diffusibility. Through correlating the acidity and diffusibility of the catalysts with their aromatization performance, it is found that the product distribution of aromatization is mainly determined by catalyst acidity rather than diffusibility. On the other hand, the average coking speed of the catalysts is not only influenced by the acidity of the catalyst, but also by its microporous diffusibility. The improvement of microporous diffusibility remarkably favors suppressing the coking deactivation of nano-sized ZSM-5 zeolite in C4 LPG aromatization.

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Abstract  

In the present study, the characteric-structure relationship of epoxidized soybean oils (ESO) with various degrees of epoxidation has been investigated. FTIR analysis was used to identify the relative extent of epoxidation of the samples during the epoxidation reaction. The viscosities of ESO were much higher than that of the raw oil, viscosity increased with degree of epoxidation. The viscous-flow activation energy of ESO was determined to be higher than that of the raw oil (20.72 to 77.93% higher). Thermogravimetry analysis (TG) of ESO was used to investigate the thermodynamic behavior of the samples. With increasing degree of epoxidation, the thermal stability of the samples initially decreased, then increased at the final reacting stage. Differential scanning calorimeter (DSC) indicated that the melting point of ESO was higher than that of soybean oil. Gel permeation chromatography (GPC) indicated the molecular mass of the samples increased initially, then decreased, with an increase in the extent of epoxidation.

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