Power variation control of a wind generator by using feed forward control

The pitch control of wind generators is usually made by a feed back control concept. However, under the conditions where a wind speed changes very frequently due to geographic reasons of the site and the target system has large rotor inertia, the feed back signal which is applied to the control system to compensate disturbance such as wind speed variations is delayed, and consequently the control strategy to keep the generated power at a constant value does not work well. If the wind speed shows too much variation, this will cause a violent variation of power and result in step out operation of the generator from the power system due to magnetic saturation. This paper proposes a control strategy to reduce the power variations by introducing feed forward control combining with the conventional feed back control.     

Characteristics of N2/SF6 mixture gas in creeping discharge developing in narrow gap with backside electrode

The flashover voltage with a backside electrode was found to be lower than that without the backside electrode. Under microsecond pulse voltage application, we describe the characteristics of a creeping discharge developed in the narrow gap with the backside electrode. Using a CCD camera and ultrahigh‐speed camera, we observed the corona extension processes. The lowest flashover voltage was found to be obtained at positive polarity with a SF₆ content D = 3%. In the corona extension obtained using an ultrahigh‐speed camera, peculiar differences were observed in the corona extension process. The corona extension increased, and rapid flashover was observed at D = 3%. Using a CCD camera, small coronas were detected from the backside electrode. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 31–38, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20431     

Low-loss polymeric optical waveguides fabricated with deuteratedpolyfluoromethacrylate

Deuterated polyfluoromethacrylate which has high transparency, low birefringence and good processability was newly synthesized for use as optical waveguide materials, and both single-mode and multimode optical waveguides were fabricated using the polymer. The propagation loss and waveguide birefringence of the single-mode waveguides were as low as 0.10 dB/cm and -5.5×10^-6 at 1.31 μm, respectively. The propagation losses of the multimode waveguides were less than 0.02 dB/cm at both 0.68 and 0.83 μm, and 0.07 dB/cm at 1.31 μm     

Gas phase oxidation of benzene to phenol using Pd-Cu composite catalysts. Effect of temperature,feeding gas and catalyst composition

Catalytic oxidation of benzene in the gas phase has been studied as a function of the catalyst composition, reaction temperature and the feed conditions of reactant gases, hydrogen, oxygen, benzene as well as diluting inert gas. The catalyst tested is composed of Pd and Cu(I) ions, both of which are supported on silica gel. If one of the two metal species is lacked from the catalyst, no catalytic activity appears. The product is almost exclusively phenol and some accompanying benzoquinone, in particular at lower temperatures, as minor byproduct.On leave from Hua-Dong Institute of Technology, Nanjing, People's Republic of China.     

Performance of ternary PtRuRh/C electrocatalyst with varying Pt:Ru:Rh ratio for methanol electro-oxidation

Highly dispersed ternary PtRuRh/C anode catalysts for direct methanol fuel cells were prepared with various contents and their electro-catalytic activities towards methanol oxidation at 25 °C and 60 °C were examined to investigate the influence of the catalyst composition. Electrocatalysts were prepared by a co-impregnation method using ethanolic solutions of metal precursors and carbon black followed by pyrolysis under reducing conditions. X-ray diffraction analysis revealed that the fcc peaks shifted to higher diffraction angles with increasing Rh content, indicating the alloying of Rh into the fcc structure. In terms of the mass specific current density, the activity towards methanol oxidation differed significantly depending on the catalysts composition and cell temperature. The catalyst prepared at a ratio of Pt:Ru:Rh = 1:1:2 exhibited the highest activity at 60 °C of 155 A (g-Pt)⁻¹ at 0.5 V vs. RHE.     

A molecular orbital study on the chemical interaction across the indomethacin/silica interparticle boundary due to mechanical stressing

A discrete variational-Xα (DV-Xα) method was applied to elucidate the formation of C-O-Si bridging bonds, produced when a silanol group of SiO₂ comes close enough to react with a carboxyl group of indomethacin (IM). A decrease in the coordination number (CN) of oxygen atoms per silicon atom at the SiO₂ surface increased the net charge (NC) of the silanolic hydrogen atom and decreased the bond overlap population (BOP) between the silanolic oxygen and hydrogen atoms. These changes favored the formation and stabilization of C-O-Si bridging bonds with simultaneous dehydration. The computational results agreed well with our previous experimental study of a ground indomethacin-SiO₂ mixture to obtain a better solid dispersion of the drug.     

Photo-rechargeability of film electrodes prepared by pulsed laser deposition

The film electrodes of TiO₂, which have two functions of opto-electric conversion and storage of electrochemical energy, were prepared by pulsed laser deposition. To investigate the relationship between the photo-rechargeability and the surface structure, the TiO₂ film electrodes with different surface morphology were prepared by changing the inert gas pressure during the deposition. The photo-charged quantity was found to be proportional to the third power of the rms of surface roughness. The results suggest that not only the surface but also the interstices between crystal grains near the surface contribute to the photo-charging with low photo-emf.     

Photosensitized hydrogen evolution from water using a single-walled carbon nanotube/fullerodendron/SiO2 coaxial nanohybrid

A coaxial nanohybrid consisting of a single-walled carbon nanotube (SWCNT), fullerodendron, and SiO(2) shows high-efficiency light-driven hydrogen evolution from water. Upon visible light irradiation, SWCNT/fullerodendron/SiO(2) coaxial nanohybrid shows hydrogen evolution activity in the presence of methyl viologen (MV(2+)), benzyldihydronicotinamide (BNAH), and a colloidal polyvinyl alcohol(PVA)-Pt.