[en] Three chelating ion-exchange resins based on macroreticular polyacrylonitrile-divinylbenzene copolymers with thioglycollic acid and cysteine as functional groups have been tested for separation of molybdenum(VI) and tungsten(VI). On a short column of the thioglycollic acid resin, molybdenum(VI) and tungsten(VI) can be selectively sorbed from pH-4.3 acetate buffer and eluted with 2 M hydrochloric acid and a mixture of 0.1 M sodium hydroxide and 0.1 M sodium chloride, respectively, with quantitative recovery even at very low concentrations. Simulated sea-water samples have been analysed. (author)

[en] Controlling and measuring the concentration of para-D₂ is an essential step toward realizing solid deuterium as an intense ultra-cold neutron source. To this end, we implemented an experimental technique to convert para- to ortho-deuterium molecules by flowing D₂ gas through a cryogenic cell filled with paramagnetic hydrous ferric oxide granules. This process efficiently reduced the para-D₂ concentration from 33.3% to 1.5%. Rotational Raman spectroscopy was applied to measure the residual para-D₂ contamination to better than 2 parts in 10³, and the hydrogen contamination to 1 part in 10³. We also contrast our optical technique to conventional thermal conductivity measurements of the para-D₂ concentration, reporting some of the relevant strengths and weaknesses of our implementation of each technique

[en] Dihydroisoxazole derivatives are well known as important nitrogen-containing five-membered heterocyclic compounds with various bioactivity. 3,5-Diphenyl-4,5-dihydroisoxazole was synthesized by using CaO as solid basic catalyst. It was found that 72.1% yield of 3,5-diphenyl-4,5-dihydroisoxazole was obtained at ratio of hydroxylamine/chalcone of 1.2:1 after 3h under reaction temperature of 65 degree C. The reaction efficiency was greatly enhanced with the yield reaching to 88.2% when the CaO was modified by benzyl bromide in a simple way. The effects of modification and reaction conditions on yields as well as the mechanism were studied thoroughly. From the results of Fourier transform-infrared (FT-IR) and Thermogravity analysis (TG) characterization, the modifier was found to bond on CaO surface chemically and almost no Ca(OH)/sub 2/ formed during the modification process. (author)

[en] Addition of 2Ca-V and Bi-species into the yttrium-iron garnet (YIG) materials markedly lowers the sintering temperature necessary for densification of the materials. Sintering temperature (T_s) needed for achieving a density larger than 97% theoretical density (T.D.) decreases from 1425 deg. Cx6 h for pure YIG to 1280 deg. Cx6 h for 0.6 (2Ca-V)-doped YIG, (Ca_1.2Y_1.8)(V_0.6Fe_4.4)O₁₂, CVG. The sintering temperature needed is even lower 1100 deg. Cx6 h for Bi-doped CVG, (Bi_0.75Ca_1.2Y_1.05)(V_0.6Fe_4.4)O₁₂. The magnetic properties of these YIG-series materials vary with the sintering temperature pronouncedly, which is ascribed to the change in sintered density with sintering temperature. The addition of Bi-species does not degrade the magnetic and microwave properties of the materials. A low temperature co-firable ceramic material, possessing good microwave magnetic properties has thus been obtained

[en] Addition of 2Ca-V or Bi-species into the Yttrium Iron garnet (YIG) materials markedly lowers the sintering temperature necessary for densifying the materials. Sintering temperature (T_s) needed for achieving a density larger than 97% theoretical density decreases form 1450 deg. Cx6 h for pure YIG to 1250 deg. Cx6 h for 0.6 (2Ca-V)-doped YIG, (Y_1.8Ca_1.2)(Fe_4.4V_0.6)O₁₂ and to 1020 deg. Cx6 h for 1.0 Bi-doped YIG, (Y₂Bi)Fe₅O₁₂, the Bi species addition not only reduces more markedly the sintering temperature necessary for achieving high density YIG materials, but also degrades loss extensively the magnetic and microwave properties of the materials. As compared with the 2Ca-V incorporation, the magnetic properties of these YIG-series materials vary with the sintering condition pronouncedly even for the samples with the same high density, which is ascribed to the change in granular structure with sintering temperature. Moreover, the linewidth of magnetic resonance peak ΔH) is insignificantly degraded due to Bi- incorporation

[en] Self-folding, whereby a 2D net autonomously folds into a pre-ordained 3D shape when exposed to a stimulus, shows potential, in a manner similar to 3D printing, as a means of easily customisable digital manufacture. It also presents some inherent advantages over conventional additive manufacturing techniques, such as the low cost associated with mass-production of polymer sheets and coatings, the compatibility with most planar manufacturing techniques, and the ease of storage and transportation. A self-folding mechanism was developed by inkjet printing silver nanoparticle suspensions onto polyethylene terephthalate (PET) sheets. By providing sufficient electrical power to the printed tracks, resistive heating causes folding to occur along the printed silver lines. A bilayer strip model was adapted to analyse the steady-state fold angle of the PET substrate, which shows good qualitative agreement, and reasonable quantitative agreement, with the experimental data. Furthermore, inkjet-printed silver tracks are known for a significant reduction in resistivity as the sintering temperature increases. Therefore, a power control system that utilises a real-time resistance sensor was developed to enable power reference tracking. The developed mechanism was able to achieve folds up to 90° and a fast actuation time of 35 s when 2.25 W was provided to a 3 mm by 40 mm silver track. (paper)

[en] GaAs/AlGaAs quantum dots (QDs) are fabricated by low-energy ion beam sputtering and molecular beam epitaxy (MBE) re-growth. Temperature (6.5-78 K) and excitation power density (0.49-3.06 W cm^-2) dependent photoluminescence (PL) are presented and discussed in detail. The low-temperature PL emission at 720 nm is attributed to GaAs QDs with height of ∼6.1 nm and base width of ∼23 nm, calculated based on the quantum box model with infinite potential barrier. The calculated QD dimensions are in good agreement with those obtained from atomic force microscopy (AFM) analysis. Nonradiative recombination and Auger-assisted recombination are found to be the main PL quenching mechanisms at high temperature

[en] Conductive Ti-oxide thin films are produced using a reactive sputtering and post-annealing process. The lowest resistivity of Ti-oxide thin films (2.30 x 10^-2Ω-cm) can be achieved after annealing for 1 h at 400 deg. C in ambient O₂. Additionally, the Hall measurement results indicate that the carrier concentration increases during the initial 1-h annealing process before decreasing during subsequent annealing. By curve fitting the O_ls core-level peaks in the x ray photoelectron spectroscopy (XPS) spectrum of the annealed Ti-oxide thin films, we found that the oxygen (O) vacancy concentration monotonically increases with annealing time, which differs from the behavior of the carrier concentration regarding annealing time. This means that the O-vacancy mechanism alone cannot explain the formation of carriers in Ti-oxide thin films. By curve-fitting core-level Ti peaks in the XPS spectrum of annealed Ti-oxide thin films, a Ti³⁺-to-Ti⁴⁺ substitution reaction in the TiO₂ phase of the Ti-oxide thin film after annealing plays the dominant role in the formation of conduction carriers. Instead of the O-vacancy mechanism, the Ti³⁺-to-Ti⁴⁺ substitution mechanism can explain the concentration of carriers in Ti-oxide thin films following annealing.

[en] To enhance the stability of beam orbit, a Fast Orbit Feedback System (FOFB) eliminating undesired disturbances was installed and tested in the 3^rd generation synchrotron light source of Taiwan Photon Source (TPS) of National Synchrotron Radiation Research Center (NSRRC). The effectiveness of the FOFB greatly depends on the output performance of Fast Corrector Power Supply (FCPS); therefore, the design and implementation of an accurate FCPS is essential. A rigorous mathematical modelling is very useful to shorten design time and improve design performance of a FCPS. A rigorous mathematical modelling derived by the state-space averaging method for a FCPS in the FOFB of TPS composed of a full-bridge topology is therefore proposed in this paper. The MATLAB/SIMULINK software is used to construct the proposed mathematical modelling and to conduct the simulations of the FCPS. Simulations for the effects of the different resolutions of ADC on the output accuracy of the FCPS are investigated. A FCPS prototype is realized to demonstrate the effectiveness of the proposed rigorous mathematical modelling for the FCPS. Simulation and experimental results show that the proposed mathematical modelling is helpful for selecting the appropriate components to meet the accuracy requirements of a FCPS.

[en] True spontaneous emission (TSE) measurements on InAs/InGaAs/GaAs quantum dot (QD) lasers have been performed as a function of injection current and cavity length. For each laser, TSE from both the ground state (GS) transition and the excited state (ES) transition has been analyzed. It is found that Auger processes are the major nonradiative recombination (NR) processes for both the GS and ES transitions. In particular, for the first time, the existence of Auger like NR features in ES transitions has been experimentally demonstrated. In addition, obvious competition for carriers between the ES transition and the GS transition has been observed in TSE analysis. Furthermore, the QD laser's cavity length has a strong effect on the NR process in GS transitions, due to GS gain saturation. Therefore, when analyzing the NR processes in operating QD lasers, gain saturation due to cavity length limits should be properly considered.