Results 21 - 30 of 64
Results 21 - 30 of 64. Search took: 0.016 seconds
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[en] In this study, we examined the sorption and desorption behavior of U(VI) on/from a Chinese bentonite in the solid-liquid system using batch experiments, and the influence of pH, ionic strength and humic acid (HA) on the sorption-desorption hysteresis in the solid-liquid system were quantitatively calculated. It was revealed that the hysteresis was enhanced with increasing pH and increasing ionic strength. HA promoted the sorption, but lower the sorption-desorption hysteresis. Meanwhile, hysteresis in ternary bentonite-HA-U system was found to be higher than that in bentonite-U-HA system, indicating different sorption structures formed because of different addition sequence. (author)
[en] The sorption and desorption of uranium(VI) on GMZ bentonite was investigated as functions of contact time, pH, ionic strength, foreign ions, HSs and initial U(VI) using batch experiments. It is revealed that the sorption strongly depended on pH, cations (Li"+, Na"+ and K"+) and anions (CO_3"2"-, SO_4"2"- and PO_4"3"-). HA benefits the sorption at pH <7.0, while inhibited the sorption at higher pH. Moreover, the hysteresis occurred in the sorption-desorption process in the presence/absence of humic substances. The results could provide data base for the safety assessment of the deep geological disposal repository of high radioactive waste. (author)
[en] This paper is to study the rising of the explosion clouds in the uniform atmosphere, the numerical model is based on the assumption that effects the clouds are gravity and buoyancy. The model is testified by Rayleigh-Taylor unsteady problem. The evolution of the density and the velocity during the rising of the explosion clouds are provided, and the computational results are reasonable compared to the rising of the real nuclear explosion cloud. (authors)
[en] Selenium is both a nutrient and a toxin. Selenium—especially organic selenium—is a core component of human nutrition. Thus, it is very important to measure selenium in biological samples. The limited sensitivity of conventional XRF hampers its widespread use in biological samples. Here, we describe the use of high-energy (100 kV, 600 W) linearly polarized beam energy-dispersive X-Ray fluorescence spectroscopy (EDXRF) in tandem with a three-dimensional optics design to determine 0.1–5.1 μg g"−"1 levels of selenium in biological samples. The effects of various experimental parameters such as applied voltage, acquisition time, secondary target and various filters were thoroughly investigated. The detection limit of selenium in biological samples via high-energy (100 kV, 600 W) linearly polarized beam energy-dispersive X-ray fluorescence spectroscopy was decreased by one order of magnitude versus conventional XRF (Paltridge et al., 2012) and found to be 0.1 μg/g. To the best of our knowledge, this is the first report to describe EDXRF measurements of Se in biological samples with important implications for the nutrition and analytical chemistry communities. - Highlights: • The high-energy (100 kV, 600 W) linearly polarized beam energy-dispersive X-Ray fluorescence spectroscopy (EDXRF) was used to determine 0.1−5.1 μg g"−"1 levels of selenium in biological samples. • High-pressure pressed powder pellet technique (1500 kN) is used for sample preparation. • The detection limit of selenium in biological samples found to be 0.1 μg/g.
[en] It presents the experimental research and numerical modeling on the movement of explosion clouds. The experiment was performed under two kinds of recorder, one is high speed CCD recorder which was mainly used to record the process of the fireball when the TNT was detonated, and the other is SONY vidicon that was mainly used to record the movement of the clouds. Based on the assumption that the effects on the clouds were gravity and buoyancy, the numerical model on the thermal was established. The initial condition of the thermal that was to say the initial cloud dimension was gained through the results of the recording of the highly CCD recorder. Followed this, the results of the numerical simulation were presented. And the computational results of the rising cloud are reasonable compared to that of the experiment. Thus, it can be seen that the numerical modeling and experimental research methods presented in this paper are reasonable and it can be serve as a reference to related person. Finally, the problems about the experiment and the model are pointed to establish a more accurate model. (authors)
[en] We introduce a new kind of random stationary, scalar beam named Laguerre-cosine-Gaussian correlated Schell-model (LcGCSM) beam whose spectral degree of coherence (SDOC) is a Gaussian function modulated by both non-conventional Laguerre- and cosine-type factors. The analytical expressions for the cross-spectral density of a LcGCSM beam propagating through a paraxial ABCD optical system are derived. The intensity distributions of such beams focused through a thin lens are illustrated numerically. It is found that a LcGCSM beam exhibits self-splitting and self-shaping properties during propagation, evolving into multiple optical cages near the focal region. By directly modulating the spatial structure of the SDOC in the source plane, the characteristics of the optical cages derived from the proposed LcGCSM beams can be adjusted flexibly. Moreover, we demonstrate that these nontrivial focusing properties of a LcGCSM beam can be well elucidated with the combination effect of individual merits associated with each non-conventional SDOC component of the entire SDOC. Therefore, our results provide a new route for generating and controlling multiple optical cages, and will be useful for trapping multiple particles, guiding multiple atoms and optical communications. (paper)
[en] The distribution of thorium on the lunar surface provides the important evidence for lunar evolution history. It is difficult to obtain the distribution of thorium on the lunar surface from CE2-GRS because of noise in the spectrum. The method for smoothing the spectrum is proposed which is based on cluster NASVD. The counting rate map of thorium on the lunar surface is achieved from CE2-GRS. Counting rate map of thorium gamma-rays shows a surface thorium distribution that is in general agreement with other measurement from LP-GRS and SLENE GRS which have better accuracy. It is more effectively to reduce the noise and get the weak information of characteristic peak used the method of cluster NASVD than other traditional methods for smoothing gamma-ray spectrum. (authors)
[en] A 1064 nm pulsed Nd:YAG laser is used for the ablation of an iron bar sample in air at atmospheric pressure and the laser-induced plasma characteristics are examined. The electron number density of 8.7×10"1"7 cm"-"3 in the iron plasma is inferred from the Stark broadened profile of Fe I 376.553 nm averaged with 10 single spectra. In order to minimize relative errors in calculation of the electron temperature, an improved iterative Boltzmann plot method is used. Experimental results show that the electron temperature is 8058 K with a regression coefficient of 0.981 38. Based on the experimental results, the plasma is verified to be in local thermodynamic equilibrium (LTE) and free from self-absorption. Considering the laser photon frequency (2.82×10"1"4 Hz) is larger than the plasma frequency (8.3×10"1"2 Hz), the loss of energy due to reflection of the laser beam from the plasma can be assumed to be insignificant. Experiments also demonstrate that the inverse Bremsstrahlung (IB) absorption is the dominant photon absorption process during the laser-plasma interaction, and the corresponding IB absorption coefficient is 0.14 cm"-"1. (authors)
[en] This paper is intends to analysis several experimental research and also the numerical modeling on the movement of explosion clouds. Following this, the paper gives some development of the numerical modeling and also its restriction during its application to the gas in Nuclear Explosion Clouds. Finally, the model applied to different stage are pointed out. (authors)
[en] Co/ZnO films were deposited on glass substrates by magnetron sputtering at room temperature. The structure of the as-deposited films is studied by means of x-ray diffraction, x-ray photoelectron spectroscopy, and the zero-field-cooled and field-cooled magnetization curves. It is shown that the as-deposited samples consist of a mixture of regions of metallic Co and semiconducting ZnO. Large negative magnetoresistance of 26% and 11.9% are observed in the as-deposited Co/ZnO film with Co concentration of 50.7 at. % at 10 K and room temperature, respectively. Structural analysis, the temperature dependence of the conductivity and magnetoresistance reveal that the magnetoresistance is induced by spin-dependent tunneling between regions of conducting magnetic Co through the ZnO semiconducting barriers. The enhanced magnetoresistance in the low temperature regime may be related to the existence of higher-order tunneling processes between large Co regions mediated by small Co particles.