Effects of Winding Attachment Positions on Output Characteristics of Flux‐Modulating Synchronous Machines

The flux‐modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d‐‐q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air‐gap side of the stator teeth and that the reduction leads to an increase in output power.     

Isolation of antimicrobial agent from the marine algae Cystoseira hakodatensis

Cystoseira hakodatensis is an unutilised brown algae belonging to family Sargassaceae. A crude methanol extract from the algae showed inhibitory effects on the growths of Bacillus cereus and Bacillus licheniformis. To isolate the major antimicrobial agent, a sequential active‐guided isolation procedure was applied: liquid–liquid extraction, column chromatography and bio‐autography. A marked antimicrobial agent (active α) was isolated in hydrophobic fraction and was determined to phenolics without carbohydrates and proteins by phytochemical test. Regarding the antimicrobial potential, the isolated active α showed better inhibitory effects against B. cereus and B. licheniformis at 2 and 4 times of lower concentrations (62.5 and 31.3 μg mL^?1) in comparison with epigallocatechin gallate. These results showed that C. hakodatensis is a potential source of antimicrobial agent capable of preventing the growth of the two bacteria.     

10 Gbit/s optical soliton transmission over 7200 km by using amonolithically integrated MQW-DFB-LD/MQW-EA modulator light source

The authors demonstrate 10 Gbit/s optical soliton transmission in a recirculating loop through the use of a monolithically integrated MQW-DFB-LD/MQW-EA modulator light source. The timing jitter due to the Gordon-Haus effect is successfully reduced by the optical bandpass filters conventionally used in the cascaded EDFAs to avoid the accumulation of amplified spontaneous emission. The transmission distance of 7200 km is achieved at a bit error rate of 10^-9     

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.     

Characterization and electrochemical properties of CF4 plasma-treated boron-doped diamond surfaces

The effect of CF₄ plasma etching on diamond surfaces, with respect to treatment time, was investigated using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. SEM observations and Raman spectra indicated an increase in surface roughening on a scale of 10–20 nm, and an increase in crystal defect density was apparent with treatment time in the range of 10 s to 30 min. In contrast, alteration of the diamond surface terminations from oxygen to fluorine was found to be rather rapid, with saturation of the F/C atomic ratio estimated from XPS analysis after treatment durations of 1 min and more. The redox kinetics of Fe(CN)₆^3−/4− was also found to be significantly modified after 10 s of CF₄ plasma treatment. This behavior shows that C–F terminations predominantly affect the redox kinetics compared to the effect on the surface roughness and crystal defects. The double-layer capacitance (C_dl) of the electrolyte/CF₄ plasma-treated boron-doped diamond interface was found to show a minimum value at 1 min of treatment. These results indicate that a short-duration CF₄ plasma treatment is effective for the fabrication of fluorine-terminated diamond surfaces without undesirable surface damage.     

Preparation of one-dimensional polymer films by modification of a hydroxymethylbenzene self-assembled monolayer on iron with alkyltriethoxysilanes for preventing iron corrosion

A self-assembled monolayer (SAM) of p-hydroxymethylbenzene HOCH₂C₆H₄ - (HOMB) moiety adsorbed on iron by the formation of a covalent bond between carbon and iron atoms was prepared by electrochemical derivatization of an iron electrode with p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH₂C₆H₄N₂BF₄. The electrode covered with the HOMB SAM was modified with alkyltriethoxysilanes C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18) to prepare a film of one-dimensional polymer. The protective ability of the polymer film was determined by polarization measurement of the covered electrode in an aerated 0.5 M NaCl solution. The ability was enhanced by modification of the HOMB SAM with C_nTES markedly. The iron surface coated with the one-dimensional polymer film of the HOMB SAM modified with C₈TES was characterized by contact angle measurement and FTIR reflection and X-ray photoelectron spectroscopies. The persistence in the protective ability of the polymer film against iron corrosion in 0.5 M NaCl may be associated with the strong adsorption via the covalent bond, revealed by electron-probe microanalysis.     

Direct digital design of computed torque controllers

Direct digital design of computed torque controllers for a robot manipulator is discussed in this article. A simple discrete-time model of the robot manipulator obtained by Euler's method is used for the design. Taking account of computation delay in the digital processor, we propose predictor-based designs of the PD and PID type controllers. The PID-type controller is designed based on a modified version of the discrete-time integral controller proposed by Mita. For both controllers, the feedback gains can be determined easily by using simple formulas. A simulation example is presented to illustrate the relevance of the proposed designs and the robustness of PID-type controller against physical parameter variations. © 1994 John Wiley & Sons, Inc.     

Electrophysiological studies of rat substantia nigra neurons in an in vitro slice preparation after middle cerebral artery occlusion

We studied sequential changes in electrophysiological profiles of the ipsilateral substantia nigra neurons in an in vitro slice preparation obtained from the middle cerebral artery-occluded rats. Histological examination revealed marked atrophy and neurodegeneration in the ipsilateral substantia nigra pars reticulata at 14 days after middle cerebral artery occlusion. Compared with the control group, there was no significant change in electrical membrane properties and synaptic responses of substantia nigra pars reticulata neurons examined at one to two weeks after middle cerebral artery occlusion. On the other hand, there was a significant increase in the input resistance and spontaneous firing rate of substantia nigra pars compacta neurons at 13-16 days after middle cerebral artery occlusion. Furthermore, inhibitory postsynaptic potentials evoked by stimulation of the subthalamus in substantia nigra pars compacta neurons was suppressed at five to eight days after middle cerebral artery occlusion. At the same time excitatory postsynaptic potentials evoked by the subthalamic stimulation was increased. Bath application of bicuculline methiodide (50 microM), a GABA(A) receptor antagonist, significantly increased the firing rate of substantia nigra pars compacta neurons from intact rats. These results strongly suggest that changes in electrophysiological responses observed in substantia nigra pars compacta neurons is caused by degeneration of GABAergic afferents from the substantia nigra pars reticulata following middle cerebral artery occlusion. While previous studies indirectly suggested that hyperexcitation due to deafferentation from the neostriatum may be a major underlying mechanism in delayed degeneration of substantia nigra pars reticulata neurons after middle cerebral artery occlusion, the present electrophysiological experiments provide evidence of hyperexcitation in substantia nigra pars compacta neurons but not in pars reticulata neurons at the chronic phase of striatal infarction.