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[en] Highlights: • Measured solubility data of CO2 in 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate and 3-methoxybutyl acetate. • Calculated Henry’s constant and thermodynamic properties of selected systems. • Concluded that selected absorbents have potential research value for CO2 capture. - Abstract: The solubilities of CO2 in 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, and 3-methoxybutyl acetate were measured by isothermal synthesis method under pressures up to 1.2 MPa and at temperatures ranging from (293.15 to 333.15) K. Henry’s constant was calculated based on experimental data regression. The solubilities of CO2 were found to increase with decreased temperature and increased the methyl group to the molecular structure of the absorbent. Henry’s constant and volumetric solubility of selected absorbents at T = 298.15 K were compared with those of commercial absorbents and common solvents. 3-Methoxybutyl acetate showed the best performance by mole fraction, and 2-methoxyethyl acetate behaved the best by volumetric fraction. Based on Henry’s constant, thermodynamic properties such as Gibbs free energy of solution, enthalpy of solution, and absorption entropy of solution were determined. These properties are very essential for designing an absorption process
[en] We studied the blue luminescence at about 2.9 eV in unintentional doped GaN films, which were grown on (0 0 0 1) oriented sapphire substrates by MOCVD. The intensity ratio of the blue luminescence to the band-edge emission is large in high compensation ratio's GaN films, and it decreases with the decrease of the compensation ratio. The FWHM of double-crystal X-ray diffraction obviously increases with the increase of the intensity ratio of the blue luminescence to the band-edge emission. Our results indicate that blue luminescence is the transition from the free electron to acceptor levels that are due to some intrinsic defects. We also observed that the peak position of the blue luminescence shifted to higher energy with decreasing excitation density in a high background electron carrier concentration GaN sample. We consider that this phenomenon is due to the screening effects of the free carriers
[en] Ag/Au bimetallic nanoparticles possess the combinatory advantages of Au and Ag nanoparticles and can also be utilized to tune the properties of localized surface plasmon resonance. Ag/Au bilayer nanorods were prepared by electron beam lithography, and their spectral properties were investigated. Compared with Ag monolayer nanorods, Ag/Au bilayer nanorods show broader localized surface plasmon resonance bands, and the longitudinal mode and transverse mode localized surface plasmon bands show blueshift and redshift, respectively. The maximum near-field intensity of the longitudinal mode of the Ag/Au nanorod is less than half that of the Ag/Au nanorod without gold layer. Shape-induced modification of Ag/Au bilayer nanorods on their spectral properties was also discussed.
[en] Objective: To investigate the method of establishing the percutaneous renal channel under the guidance of color Doppler ultrasonography, to evaluate the success rate and safety of this technique, and to discuss its clinical application in percutaneous nephrolithotomy. Methods: Under the guidance of color Doppler ultrasonography, percutaneous renal channel was successfully established in 209 patients with renal and upper ureteral calculi. The clinical data were retrospectively analyzed. The whole course of the removal of stones was monitored. The initial experience and the technical points were summarized. Results: Under the guidance of color Doppler ultrasonography, an effective and safe percutaneous renal access was successfully established in all patients. The success rate of puncturing was 99% (207/209). The success rate by single puncturing was 94.7% (198/209). In 9 patients successful puncturing was accomplished with twice procedures. In two fat patients, successful puncturing was achieved with the help of C-arm radiography. No serious complications occurred during and after the treatment. Conclusion: The operation of establishing a percutaneous renal access under the guidance of color Doppler ultrasonography is technically simple, clinically safe and reliable, with high success rate. Therefore, it should be regarded as the imaging-guided localizing method of first choice. (authors)
[en] Space object orbital covariance data is required for collision risk assessments, but publicly accessible two line element (TLE) data does not provide orbital error information. This paper compared historical TLE data and GPS precision ephemerides of CHAMP to assess TLE orbit accuracy from 2002 to 2008, inclusive. TLE error spatial variations with longitude and latitude were calculated to analyze error characteristics and distribution. The results indicate that TLE orbit data are systematically biased from the limited SGP4 model. The biases can reach the level of kilometers, and the sign and magnitude are correlate significantly with longitude.
[en] A series of Bi/Eu single-doped and co-doped BaScTaO phosphors was prepared by traditional high-temperature solid state reaction method. Their structure and photoluminescence properties of the samples were systematically studied by X-ray diffraction (XRD) analysis, scanning electron microscopy, excitation and emission spectra, and decay curves. The observation of XRD patterns shows that all samples are pure phases. Under the UV excitation, the emission color of BaScTaO:Bi, Eu can be tuned by Bi/Eu ratio change from amaranth to orange–red, which is realized by Bi–Eu energy transfer. In addition, the energy transfer mechanism, luminescence decay curves and chromaticity coordinates are discussed in detail. The results show that BaScTaO:Bi, Eu is a promising red phosphor for white light-emitting diodes.
[en] A method is developed to calculate probability of collision. Based on geometric features of space objects during the encounter, it is reasonable to separate the radial orbital motions from those in the cross section for most encounter events that occur in a near-circular orbit. Therefore, the probability of collision caused by differences in both altitude of the orbit in the radial direction and the probability of collision caused by differences in arrival time in the cross section are calculated. The net probability of collision is expressed as an explicit expression by multiplying the above two components. Numerical cases are applied to test this method by comparing the results with the general method. The results indicate that this method is valid for most encounter events that occur in near-circular orbits
[en] A series of orange–red light-emitting Sm activated BaScNbO (x = 0.03, 0.05, 0.08, 0.10, 0.12, 0.14, and 0.16) phosphors were prepared through a traditional high temperature solid-state method. The properties of the samples were characterized by X-ray diffraction and scanning electron microscope. The emission and excitation spectrum, concentration quenching mechanism, and fluorescence attenuation of the phosphors were also investigated in detail. Upon excitation with near-Ultraviolent (407 nm), the emission spectra are composed of 564 nm, 598 nm and 645 nm emission peaks, corresponding to the different transitions of Sm ions G → H (J = 5/2, 7/2, and 9/2), respectively. The strongest emission at 598 nm comes from the G → H transition of Sm, which produces bright orange–red emission. The optimum doping concentration of Sm ion in BaScNbO is 8 mol% and the critical transfer distance (R) of Sm was calculated to be 20.97Å. The thermal stability of BaScNbO:Sm phosphor was tested by temperature-dependent emission spectroscopy. In addition, the Commission International deL’Eclairage the chromaticity coordinate of BaScNbO:0.08Sm phosphor is (0.5435, 0.4514), which located in the orange reddish region. All the results show that the BaScNbO:xSm phosphors can be used as orange–red light-emitting material for white light-emitting diodes.
[en] In this work, porous Cu-doped VO·nHO thin film electrodes have been directly synthesized via low-temperature annealing and simple drop-casting method from VO/HO sol with various concentration copper ion (Cu). It is interesting to find that the mass fraction of Cu has effects on the morphologies, valence state of vanadium, and electrochemical performance of Cu-doped VO·nHO thin film. When the mass fraction of Cu is 1 wt.%, the obtained Cu-doped VO·nHO thin film electrode shows network porous nanostructure. Moreover, it still shows high discharge specific capacity of 344 mAh g at a current density of 250 mA g. Excellent cycling stability with only 0.14% per cycle degradation during 104 cycles can be obtained even at a high current density of 550 mA g. Improvement of electrochemical performance is attributed to unique network porous nanostructure, accelerating the lithium-ion transfer rate in the de-intercalation or intercalation process.