Solution intercalation of polystyrene and the comparison with poly(ethyl methacrylate)

Polystyrene nanocomposites have been prepared via solution intercalation method. Combination of wide-angle X-ray diffraction and thermogravimetric analysis is used to study the effect of solvents on the morphology of the nanocomposites as a function of the amount of residual solvent. d-Spacing of the polystyrene nanocomposites has a minimum value when the residual solvent concentration is between 2 and 4 wt%. Different interaction level between the solvent molecules and polymer chains is considered to be the reason for this special d-spacing change behavior. By comparing the solution intercalation of polystyrene and poly(ethyl methacrylate) from different solvents, it is concluded that the interactions between polymer-surfactant, solvent-surfactant, and polymer-solvent play important role for the solution intercalation of polymers.     

Suppression control method for torque vibration of three-phase HB-type stepping motor utilizing feedforward control

This paper proposes a method to reduce the vibration of the three-phase HB-type stepping motor with cogging torque by the feedforward compensation control. The compensation signal to suppress the vibration of the motor frame is obtained by the repetitive controller installing an online Fourier transformer and utilizing an acceleration sensor attached to the motor frame or an acoustic sensor such as a microphone placed close to the frame. The sensor is used only for the acquisition of the feedforward compensation data. The feedforward compensation signal at an arbitrary operating point is derived from the amplitude and phase data of the frequency components and the operating point data. Compensation data obtained by the repetitive controller is applied to the operating point changed by reference frequency and load condition in steady state. The compensation signal for the new operating point will be generated from compensation data utilizing polynomial equation approximation and linear interpolation method. The effectiveness of this proposed method is confirmed by the experimental results.     

Digitally tunable optical filters using arrayed-waveguide grating(AWG) multiplexers and optical switches

Two novel configurations for digitally tunable optical filters based on arrayed-waveguide grating (AWG) multiplexers are described in detail with emphasis on the connection of the AWG multiplexer and optical switches. Performance comparisons show that conventional configurations are disadvantaged by the switch size required and loss imbalance among the optical frequency-division-multiplexed (FDM) channels; the proposed configurations require only O(√(N)) switch elements to select one of N FDM channels, and the loss imbalance is lower by up to 75% in decibel     

Continuous hydrolysis of olive oil by lipase in microporous hydrophobic membrane bioreactor

Continuous hydrolysis of olive oil byCandida cylindracea’s lipase was studied in a microporous hydrophobic membrane bioreactor. Olive oil and buffer solution, fed continuously through two compartments partitioned by membrane, caused reaction at the interface of lipase-adsorbed membrane and buffer solution. Fatty acid was obtained in a single phase without being mixed with components of other phases. At all mean residence times, countercurrent flow mode was superior to cocurrent one. The lipase was adsorbed onto the membrane, and its adsorption was suggested to be partially specific from the experiments with enzymes having various levels of purity. The percent hydrolysis depended hyperbolically on the interfacial enzyme concentration. The hydrolysis seemed to be limited by diffusion of fat or fatty acid through the micropores of the membrane at higher interfacial enzyme concentrations. The lipase was stabilized significantly by glycerol added to the buffer solution. Satisfactory performance of the membrane bioreactor was obtained in a longterm continuous operation which lasted for 24 days by feeding buffer-glycerol (18.0%) solution over the adsorbed lipase. The operational half-life of the adsorbed enzyme was 15 days at 40 C.     

Rutile-type TiO2 thin film for high-k gate insulator

We investigated rutile-type titanium dioxide (TiO₂) films for possible use as a high-k gate insulator. The TiO₂ thin films were directly deposited on Si substrates using a RF magnetron sputtering method with a sintered oxide target. A single phase of rutile-type TiO₂ whose dielectric constant of approximately 75 was obtained when the film was deposited in an inert gas atmosphere and annealed at 800 °C in an oxidizing gas atmosphere. The oxygen ions were deficient in the as-deposited film, and consequently, a sufficient oxygen supply was needed to crystallize the film to a single phase of rutile during the post-annealing. However, the interfacial SiO₂ layer between the TiO₂ and the Si substrate simultaneously grew thicker than 2 nm. As the interfacial SiO₂ grew, the leakage current was decreased and the equivalent oxide thickness was increased, in the Au/rutile-type TiO₂/Si capacitor. Therefore, we concluded that the growth of the interfacial SiO₂ layer thicker than 2 nm is inevitable to form the single phase of rutile-type TiO₂ and to decrease the leakage.     

Modified Imidazoles: Degradation Inhibitors and Adhesion Promoters for Polyimide Films on Copper Substrates

Polyimide films on copper substrates that are exposed to elevated temperatures and an oxidizing environment will be subject to degradation. In order to halt this degradation without changing the properties of the system, a polymeric agent could be placed between the polyimide and the copper. This paper will investigate three such materials that will not only slow down the degradation of the polyimide and the oxidation of the copper, but will also improve adhesion within the system. Fourier transform infrared reflection-absorption spectroscopy (FTIR-RAS) will be used to investigate the polyimide/polymeric agent/copper system.     

Infrared sensing properties of positive temperature coefficient thermistors with large temperature coefficients of resistivity

Infrared (IR) detecting elements were prepared using positive temperature coefficient (PTC) thermistors with large temperature coefficients of resistivity (α). Their compositions were denoted as Ba_1−x Sr _x Nb_0.003Ti_0.997O₃ + 1 mol % TiO₂ + 0.07 mol %MnO (x=0, 0.2), and their temperature coefficients of resistivity were 78 and 50% K⁻¹, respectively. Their IR sensing properties were measured under the self-regulating heating conditions, and were compared with those of a detector with small α (18 % K⁻¹). It was shown that large α was effective for controlling the element temperature by self-regulating heating and for improving sensitivity. The responsivity,R _v of the element withx=0.2 was 980 VW⁻¹, and was as large as those of pyroelectric detectors. Expressions which normalize the sensitivity and the thermal time constant were derived. From these expressions, criteria for improving some IR sensing properties were obtained.     

10 Gbit/s optical BPSK homodyne detection experiment with solitaryDFB laser diodes

Solitary DFB laser diodes with 174 kHz beat linewidth are applied to a 10 Gbit/s optical BPSK homodyne detection system for the first time: a sensitivity of -38.9 dBm was achieved. A three-electrode laser forms the local oscillator and is modulated with a partial push-pull scheme to improve its frequency response     

66/77-kV C-GIS using composite insulation in SF6 gas

A second-generation model of cubicletype gas-insulated switchgear (C-GIS) with composite insulation incorporating SF₆ gas has been developed. The design does not require a gas process in field assembly; it has high reliability and its installation is more rapid; and a further reduction in size is achieved. The design principles are described in detail.