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- Author or Editor: P. Wang x
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Abstract
The calorimetric data of binders containing pure Portland cement, 20% fly ash, 20% slag and 10% silica fume respectively are determined at different initial casting temperatures using an adiabatic calorimeter to measure the adiabatic temperature rising of concrete. The calorimetric data of binders with different dosages of fly ash at two water binder ratios (w/b) are determined, too. Elevation of initial casting temperature decreases the heat evolution of binder, enhances the heat evolution rate of binder and increases the heat evolution rate of binder at early age. The dosage of fly ash in concrete has different effects on the heat evolution of binder with different w/b. At high w/b ratio the heat evolution of binder decreases when dosage of fly ash increases. At low w/b ratio the heat evolution of binders increases when dosage of fly ash increases from 0 to 40% of total binder quantity. The heat evolution of binder decreases after the dosage of fly ash over 40%. An appropriate dosage of fly ash in binder benefits the performance of concrete at low w/b ratio.
Abstract
The thermal decomposition kinetics of irradiated and unirradiated ammonium perchlorate and ammonium perchlorate powder-aluminum particle mixtures has been studied by determining decomposition gas pressurevs. heating time with samples at a controlled temperature Qualitatively the radiation induced changes are similar to those obtained in previous studies on ‘pure’ ammonium perchlorate. The induction period is shortened and the acceleratory and decay period rate constants are increased. The data have been analyzed using Avrami-Erofeev kinetics. The results for pure unirradiated material are in accord with published results. The activation energies for the induction, acceleratory and decay periods for pure pellets were found to be 133.5±6.7, 131.8±6.7 and 127.2±6.7 kJ·mol, respectively. Samples were exposed to either a single gamma-ray irradiation, fission neutron irradiation followed by a gamma-ray irradiation, or to a proton irradiation. When compared on an equal energy deposited basis, the fast neutron induced changes are appreciably larger than the gamma-ray changes. However, the proton induced changes are comparable or slightly more than the gamma-ray effects. Some, or all, of the fast neutron effects can be attributable to the concentrated radiation damage ‘spikes’ along the path of lattice atom recoils. It is likely that these become thermal decomposition sites when the crystals are heated. Protons create fewer spikes than fast neutrons. Overall, the results indicate that any ammonium perchlorate-aluminum propellant mixtures that may be exposed to radiation environments, such as used in this study, should be subjected to a thorough radiation effects analysis if reliable performance is required.
Abstract
Advantages of X-ray fluorescence with the use of Synchrotron Radiation are emphasized (intensity, polarization, tunability of energy). The experimental set-up and the fast computer system for the data reduction without standards are presented. The results are in good agreement with standard references. Examples of applications are presented: old coins and potteries were studied in archaeological domain; metal alloys were analyzed; element composition of bulk samples of volcanic rocks, sublimates and aerosols were determined.
Abstract
Improvements in the detection limits of thorium and uranium in acrylics by neutron activation analysis are described. The average of results from 10 g samples was found to be higher than the results from 450 g samples taken from the same acrylic sheet. Using eighteen large (450 g) samples from a single sheet of acrylic gave an average value of 3.2±0.3 pg/g thorium and 1.1±0.7 pg/g uranium. Interpretation of the results is discussed. Epithermal neutron activation with Cd shielded irradiations did not improve the detection sensitivity for thorium.
Abstract
A new method of thermal desorption chromatography, in which hydrogen is used as carrier instead of helium, and a water bath instead of an air bath, is presented for determining the specific surface area of uranium compounds. The method proposed has a higher accuracy and a better applicability.
Triclocarban (TCC) and triclosan (TCS) are used in a wide range of household and personal care products and have been the most frequently detected organic pollutants in both wastewater and surface water. This paper presented a rapid analytical method for simultaneous determination of TCC and TCS in wastewater. The method involves the extraction and cleanup of the target compounds by using silicon dioxide/polystyrene composite microspheres solid-phase extraction and detection with ultra-high-pressure liquid chromatography. Under the optimized conditions, the limits of detection were 0.028 μg/L and 0.040 μg/L for TCC and TCS, respectively. Under the concentrations of the spiking level ranging from 0.100 μg/L to 2.000 μg/L, the spiked recoveries of TCC and TCS in wastewater samples achieved in the range of 89.5–102.8% with RSD below 6.3% for TCC and 95.5–103.6% with RSD below 6.9% for TCS. This method was successfully used in monitoring the water samples from three traditional wastewater treatment plants.
Summary
A new method using ultra-performance liquid chromatography (UPLC) in combination with tandem mass spectrometry and a multiple reaction monitoring mode (UPLC-MS/MS-MRM) was developed for simultaneous quantitative determination of anthraquinone derivatives in Radix et Rhizoma Rhei-based medicines. A multi-mode electrospray/chemical ionization (ESCI) and negative ion mode with [M-H]− and its fragments under collision-activated conditions were employed in MS/MS-MRM. The quantitative method was validated and applied to simultaneous determination of anthraquinone derivatives in 21 Radix et Rhizoma Rhei-based medicines. The limits of quantification were in the range of 3.90–9.09 ng mL−1. Average recoveries were between 95.5% and 99.8% with relative standard deviations from 1.8% to 5.3%.
Abstract
The free-radical bulk polymerization of 2,2-dinitro-1-butyl-acrylate (DNBA) in the presence of 2,2′-azobisisobutyronitrile (AIBN) as the initiator was investigated by DSC in the non-isothermal mode. Kissinger and Ozawa methods were applied to determine the activation energy (E a) and the reaction order of free-radical polymerization. The results showed that the temperature of exothermic polymerization peaks increased with increasing the heating rate. The reaction order of non-isothermal polymerization of DNBA in the presence of AIBN is approximately 1. The average activation energy (92.91±1.88 kJ mol −1) obtained was smaller slightly than the value of E a=96.82 kJ mol−1 found with the Barrett method.
Abstract
It has been generally accepted when estimating sedimentation rates using the 137Cs dating method that the position of the 137Cs maximum in a sediment profile represents the year 1963. In this paper we validated this approach by developing a model in which the annual 137Cs global fallout flux for the Yangtze River estuary was established on the basis of the Tokyo flux corrected for precipitation rates observed in Shanghai. As the 137Cs maxima in the sediment deposition profiles depend on the sedimentation rates, the sub-sampling intervals were calculated accordingly. Higher measured than the calculated values were found in some cores, what may be due to fluctuating sedimentation rates and an additional deposition of 137Cs from land-based sources. The study provides useful information on the reliability of the measured 137Cs maxima in sediment profiles frequently used for dating of sediments in marine (coastal regions, open seas) as well as in terrestrial (lakes) environments.
Abstract
A manganese dioxide coprecipitation procedure is utilized to replace a time-consuming evaporation step for the extraction of thorium, uranium and cerium from freshwater samples. The average recovery for 20-liter samples is greater than 95% for234Th and144Ce. The data indicate that the manganese dioxide coprecipitation process does not affect the recovery of thorium and uranium during our routine analytical procedure.
