Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station

According to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large-magnitude over-voltages were confirmed to occur under some special system conditions. Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier. The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition. Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.     

Application of microwaves and millimeter waves for thecharacterization of teeth for dental diagnosis and treatment

This paper presents applications of microwaves and millimeter waves for the characterization of teeth. This is done by measuring the complex permittivity over the frequency range from 0.04 to 40 GHz. These measurements have revealed that dental caries are significantly more lossy to microwaves and millimeter waves than the healthy tooth, and this difference can be used for dental diagnosis. The experimental results have been confirmed by using the finite-difference time-domain (FDTD) method. In addition, millimeter-wave heating of the lossy dental caries can be used as a sterilization treatment. It is concluded that millimeter waves can be used for dental medical diagnosis as well as dental medical treatment     

A Unified Approach to Submicron DC MOS Transistor Modeling for Low-Voltage ICs

A unified single-equation approach for the MOS transistordrain current modeling for energy-efficient submicron MOS circuitsis presented. Instead of three sets of separate equations forthe triode, saturation, and weak inversion regions, only a continuousexpression which is valid to describe the behavior of drain currentand the derivatives in all operation regions can be realizedby using a combination of hyperbola, sigmoid, and interpolationmethods. The model expression can predict accurate results forthe current, output conductance, and transconductance with continuousand smooth characteristics. The simulation results agree wellwith experimental data.     

Prognostic factors in radiation-treated esophageal carcinoma

Prognostic factors in esophageal carcinoma treated with irradiation were examined. The prognosis of 111 patients without metastasis who had received more than 60 Gy was analyzed. Significant associations were found between survival rates and tumor length, stage, radioresponse of the primary tumor and the s.c. X-P classification based on barium contrast radiography; superficial type (tumor limited to the surface of the esophageal wall), tumorous type (solid mass without ulceration), Ul-A type (tumor with shallow ulceration with regular margin), Ul-B type (tumor with deep ulceration or irregular ulcer margin), and funneled type (tumor invading the esophageal wall in a scirrhous pattern). In multiple regression analysis, the X-P classification had the strongest correlation with survival and the survival rates of patients with the superficial type, the tumorous type and the s.c. Ul-A type were significantly higher than those of patients with the other tumor types (p < 0.001).     

Changes in Aging Behavior and Defect Structure of Yttria-Fully-Stabilized ZrO2 with Sc2O3 Doping

Methods of suppressing decreased conductivity in 8 mol% Y₂O₃-stabilized–92 mol% ZrO₂ (8YSZ) with aging were investigated. Different amounts of Sc₂O₃ were doped into 8YSZ. The electrochemical properties of Sc₂O₃-doped 8YSZ were measured, and the microstructural and local structural changes were characterized. The present results indicate that an appropriate amount of Sc₂O₃ doping, 3 or 4 mol%, effectively suppresses decreased conductivity with aging in 8YSZ.     

A new method for power generation planning and problems of uncertainty

This paper presents a new method for power system planning which considers uncertainties of various system parameters as a part of the criterion function. The criterion function involves both the expected values of total system costs and the cost variances of different power plants. Previously, the authors proposed that these cost variances be evaluated from the existing power system plans in the form of the solutions to the inverse optimization problem, and then applied this procedure to the planning of power systems in Japan. However, because of the correlation between fuel and facility costs, the cost variances could not be determined as specific values. Here, to overcome this difficulty, the authors now introduce hydropower plants into the model as the so-called nonrisky elements and focus on the expenditure shares rather than the plant capacity shares. As a result, more reasonable results are obtained. This improved methodology is applied and the derived cost variances are shown. Further, using the resultant cost variances, the authors make Pareto-optimal power generation plans and demonstrate also the robustness of the method to price fluctuations.     

Some experimental findings in compression-after-impact (CAI) tests of CF/PEEK (APC-2) and conventional CF/epoxy flat plates

Compression-after-impact (CAI) tests have been conducted for quasi-isotropic thick plates with 48 plies by using the NASA method and on plates with 32 plies by using the SACMA method. Specimens are made of CF/PEEK (APC-2) and conventional CF/epoxy for the NASA plates and CF/epoxy for the SACMA plates. In the NASA CAI tests, the sequence of delamination buckling and its propagation is clearly revealed through various experimental techniques. One major technique is moiré topography, and the other is thermo-mechanical stress analysis with a high-accuracy infrared sensor. The arrest of delamination propagation just before catastrophic failure due to high fracture toughness is clearly captured by the moiré camera. This behavior provides good CAI values of CF/PEEK. The initial buckling properties of the delaminated region by the impact are then extensively discussed. Numerical predictions of initial buckling stress have been obtained by modelled geometry of the delaminated region simplified from its precise structure clarified by ultrasonic C-scanning. They agree fairly well with the experimental results. The in-plane stress distribution in the delaminated region before initial buckling is measured by an infrared stress graphic system. This compared favorably with finite element predictions. Two types of symmetric buckling modes with respect to the central plate surface, twin and single peak ones, are experimentally captured.     

A shell for signal interpretation expert systems

System monitoring and diagnosis through signal interpretation are important tasks in many engineering fields. Although monitoring or diagnosis expert systems help human experts a lot, it is not so easy to build a signal interpretation expert system. We have developed two expert systems for speech signal processing. The close analysis of the two systems revealed common functions and modules applicable to wide range of signal interpretation problems. On the basis of the experience, we have developed a shell for signal interpretation expert systems named SSI. In order to evaluate SSI, we also developed two expert systems by using it and obtained satisfactory results. This paper describes the design philosophy and architecture of SSI together with some examples.     

Decolorization of reactive brilliant red X-3B by heterogeneous photo-Fenton reaction using an Fe–Ce bimetal catalyst

Decolorization of reactive brilliant red X-3B was studied by using an Fe–Ce oxide hydrate as the heterogeneous catalyst in the presence of H₂O₂ and UV. The decolorization rate was in the order of UV–Fe–Ce–H₂O₂ > UV–Fe³⁺–H₂O₂ > UV–H₂O₂ > UV–Fe–Ce ≥ Fe–Ce–H₂O₂ > Fe–Ce. Under the conditions of 34 mg l⁻¹ H₂O₂, 0.500 g l⁻¹ Fe–Ce, 36 W UV and pH 3.0, 100 mg l⁻¹ X-3B could be decolorized at efficiency of more than 99% within 30 min. The maximum dissolved Fe during the reaction was 1 mg l⁻¹. From the fact that the decolorization rate of the UV–Fe–Ce–H₂O₂ system was significantly higher than that of the UV–Fe³⁺–H₂O₂ system at Fe³⁺ = 1 mg l⁻¹, it is clear that the Fe–Ce functioned mainly as an efficient heterogeneous catalyst. UV–vis, its second derivative spectra, and ion chromatography (IC) were employed to investigate the degradation pathway. Fast degradation after adsorption of X-3B is the dominant mechanism in the heterogeneous catalytic oxidation system. The first degradation step is the breaking down of azo and CN bonds, resulting in the formation of the aniline- and phenol-like compounds. Then, the breaking down of the triazine structure occurred together with the transformation of naphthalene rings to multi-substituted benzene, and the cutting off of sulphonic groups from the naphthalene rings. The last step includes further decomposition of the aniline structure and partial mineralization of X-3B.     

Network formation and swelling behavior of photosensitive poly(vinyl alcohol) gels prepared by photogenerated crosslinking

Poly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is insolubilized by photoirradiation. An association takes place in SbQ groups. The association of polymer chains becomes marked with increasing the number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermolecular crosslinks are obtained. The proportion of the free water to the bound water in PVA-SbQ gels was 3.3?2.9 despite of the large change in conversion of photodimerization of SbQ groups, x=0.27?0.58. The water uptake after swelling of the gels in water increased 6–27 times compared to the original weight at pH=7. The higher the degree of photocrosslinking, the lower was the degree of swelling. The water diffusion coefficients, D, were (2.2?5.8) × 10^?5 cm² S^?1 for a 88% saponified PVA with 1 . 3 mol% SbQ groups. The volume of the gel increased discontinuously about 10-fold for the 99% saponified PVA with 0 . 096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transition decreased with increasing the degree of saponification of the PVA.