Synthesis,Crystal Structural and Electrical Conductivity Properties of Fe-Doped Zinc Oxide Powders at High Temperatures

The synthesis,crystal structure and electrical conductivity properties of Fe-doped ZnO powders(in the range of 0.25-15 mol%) were reported in this paper.I-phase samples,which were indexed as single phase with a hexagonal(wurtzite) structure in the Fe-doped ZnO binary system,were determined by X-ray diffraction(XRD).The solubility limit of Fe in the ZnO lattice is 3 mol% at 950℃.The above mixed phase was observed.And the impurity phase was determined as the cubic-ZnFe 2 O 4 phase when compared with standard XRD data using the PDF program.This study focused on single I-phase ZnO samples which were synthesized at 950℃ because the limit of the solubility range is the widest at this temperature.The lattice parameters a and c of the I-phase decreased with Fe-doping concentration.The morphology of the I-phase samples was analyzed with a scanning electron microscope.The grain size of the I-phase samples increased with heat treatment and doping concentration.The electrical conductivity of the pure ZnO and single I-phase samples was investigated using the four-probe dc method at 100-950℃ in air atmosphere.The electrical conductivity values of pure ZnO,0.25 and 3 mol% Fe-doped ZnO samples at 100℃ were 2×10-6,1.7×10-3 and 6.3×10-4 S.cm-1,and at 950℃ they were 3.4,8.5 and 4 S.cm-1,respectively.     

Comparison of photophysicochemical properties of hexaphenoxycyclotriphosphazenyl-substituted metal-free,mono- and bis-lutetium phthalocyanines

The aim of this study is to compare the photophysicochemical properties of hexaphenoxycyclotriphosphazenyl-substituted metal-free (1), mono-(phthalocyaninato) lutetium(III) (2) [Lu^III(AcO)(Pc)] (Pc = phthalocyaninato, AcO = acetate) and bis-(phthalocyaninato) lutetium(III) (3) [Lu^IIIPc₂]. The synthesis and characterization (using the elemental analysis, mass spectrometry, IR, ¹H, and ³¹P NMR and UV–vis spectroscopy) of new compounds (2, 3) are described in this study. The electronic absorption and fluorescence spectral properties of compounds 1–3 are investigated. Photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen and photodegradation quantum yields) measurements are also studied on hexaphenoxycyclotriphosphazenyl-appended metal-free, mono- and bis-lutetium phthalocyanines in dimethylsulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanines are very useful for photodynamic therapy (PDT) applications. Singlet oxygen quantum yields (Φ_Δ) give an indication of the potential of the complexes as photosensitizers in PDT applications. Hexaphenoxycyclotriphosphazenyl-substituted mono-(phthalocyaninato) lutetium(III) complex (2) gave good singlet oxygen quantum yield (0.66) in DMSO. Thus, this complex shows potential as Type II photosensitizer for PDT of cancer.     

The use of novel photobleachable phthalocyanines to image DNA

The interaction of cationic photobleachable cobalt 1 and palladium 2 phthalocyanines (pcs) with calf thymus (CT) DNA was investigated by UV/vis spectrophotometric methods and gel electrophoresis. With the addition of pcs, the change in the thermal denaturation profile of DNA was observed. The results indicated that these molecules exhibit efficient DNA binding activity. The new cationic cobalt derivative 1 was characterized by elemental analysis, UV, IR and mass spectrophotometry.     

New polyurethanes with conjugated triple bonds

Summary Urethane polymers possessing two conjugated -C≡C- triple bonds per repeating unit are synthesized. Polyurethanes are characterized by their infrared absorption spectra, UV abrsorption spectra and elementel analysis. Their molecular weights and limit intrinsic viscosities are determined. Solutions of these polymers in various solvents do not show any reactivity when exposed to light or heat. However the solid polyurethanes and solvent cast polyurethane films obtained from trimethyl hexamethylene diisocyanate, and isophoron diisocyanate quite rapidly develop red-brown colour on annealing at elevated temperatures, below their melting point. During this process the polymers themselves and solvent cast polymer films become insoluble in any of the solvents. Their IR and UV absorption spectra before and after annealing are examined and the band gaps are calculated from the spectral data.     

Improving biped walk stability with complementary corrective demonstration

We contribute a method for improving the skill execution performance of a robot by complementing an existing algorithmic solution with corrective human demonstration. We apply the proposed method to the biped walking problem, which is a good example of a complex low level skill due to the complicated dynamics of the walk process in a high dimensional state and action space. We introduce an incremental learning approach to improve the Nao humanoid robot’s stability during walking. First, we identify, extract, and record a complete walk cycle from the motion of the robot as it executes a given walk algorithm as a black box. Second, we apply offline advice operators for improving the stability of the learned open-loop walk cycle. Finally, we present an algorithm to directly modify the recorded walk cycle using real time corrective human demonstration. The demonstrator delivers the corrective feedback using a commercially available wireless game controller without touching the robot. Through the proposed algorithm, the robot learns a closed-loop correction policy for the open-loop walk by mapping the corrective demonstrations to the sensory readings received while walking. Experiment results demonstrate a significant improvement in the walk stability.     

The influence of zinc ions discharged in a non-aqueous cell on a copper catalyst on the rate of cyclohexanol dehydrogenation reaction

Results of studies on the influence of a copper catalyst modification with zinc ions on the activity in the reaction of cyclohexanol dehydrogenation are presented. The modification has been performed by electrochemical discharging-insertion of zinc ions on a copper electrode in a non-aqueous cell. It has been demonstrated that the catalyst activity depends on the amount of discharged zinc ions as well as on the nature and concentration of the electrolyte. In the case of zinc ions discharged from a solution of ZnCl₂ in propylene carbonate, the yield of cyclohexanone increased up to five times and using Zn(BF₄)₂ in dimethylformamide almost twenty times. The activity of the system in the competing reaction of dehydration was low, hence the selectivity in the dehydrogenation reaction was high.     

Effect of intermittent polishing on low-cycle fatigue of pure aluminium

Low-cycle fatigue tests of aluminium were interrupted in order to remove surface roughening and superficial cracks produced by prior loading. Depending on the frequency of intermittent polishing and the strain level considerable increases in endurance life were observed.Nomenclature _t total strain range - _p plastic strain range - _e elastic strain range - N _p the number of cycles at which the intermittent polishing is carried out (single-step tests) - N _mp the number of cycles at which the last intermittent polishing action is performed in addition to preceding ones in every 50 cycles (multi-step tests) - N _pf the endurance life in the case of intermittent polishing (single- or multi-step tests) - N _f the endurance life without intermittent polishing