Microscopic observation of voids and transverse crack initiation in CFRP laminates

In situ three-point bending tests under observation using scanning electron microscopy were performed for specimens including voids to investigate the effect of voids on transverse crack initiation in carbon fiber-reinforced plastic (CFRP) laminates. First, initial failure load (i.e. applied load at the first transverse crack initiation) was investigated. Microscopic strain distributions were then measured by digital image correlation analysis using SEM pictures taken before and during loading in the in situ tests. In addition, specimens including voids and transverse cracks after the in situ tests were observed using X-ray computed tomography to clarify transverse crack onset locations with respect to void shapes and distributions. These experiment results suggested that voids actually caused strain concentration and corresponding local plastic deformation, and finally resulted in reduction of macroscopic initial failure strains in CFRP laminates.     

One-day- through seven-day-ahead electrical load forecasting in consideration of uncertainties of weather information

This paper proposes an approach to one-day-through seven-day-ahead electrical load forecasting based on a realistic problem formulation which should contribute to more reliable and economic weekly power stations operation. Generally, the load forecasting has the following problems:

• 1 (1) although the load is affected by various factors, such as temperatures, in the load forecasting, it is impossible to consider all of them;
• 2 (2) the relationships between the load and some factors are not clear, and often vary with time; and
• 3 (3) uncertainties in forecasts of the temperatures sometimes make the results of load forecasting worse.

They are very influential in the power station operation. While a number of methods have been proposed to solve the problems (1) and (2), there have been few attempts to solve the problem (3). The following approach is proposed in this paper, taking these problems into consideration. First, concerning the problem (1), the focus is on such factors that have major influence on the load and whose values are obtainable on a weekly basis. The other factors are all regarded as stochastic and are not included in the forecasting model. Second, regarding the problem (2), a self-organizing approach is used where the algorithm itself finds the optimal model structure or the optimal set of factors to be included in the model day by day. Finally, addressing the problem (3), a new performance index of model structures is proposed which can measure the balance between: i) improvement of the load-forecasting accuracy due to inclusion of a factor in the model; and ii) degradation caused by uncertainty or error in the factor included. Using this index, a model is constructed which does not yield a large error in spite of errors in the temperature forecasts. Examples show that this approach improves the forecasted results when erroneous temperature forecasts are fed into the model, and verifies its effectiveness.     

Multifunctional High‐Power Sources for Smart Contact Lenses

Powering an electrical contact lens is a significant challenge for wearable applications such as augmented reality displays and iontophoretic drug delivery to the eye. Here a hybrid power generation device is developed comprising a wireless power transfer system and a bioabsorbable metal–air primary battery, which provides a multifunctional direct current (DC) and/or alternating current (AC) output. The DC power is generated by Zn loop anode and a bilirubin oxidase (BOD) biocathode in an artificial tear. The Zn‐based loop anode is also used as the antenna of a wireless power transfer system that results in high power transfer efficiency of 17.6% at 13.56 MHz. The wireless‐powered AC voltage is boosted from 1.5 to 1.5 V + 0.5 V_pp by a DC offset, enabling red light‐emitting diode (LED) emission. Furthermore, the hybrid AC and DC offset voltages are boosted to 2.3 V + 0.5 V_pp by a capacitive booster circuit that provides blue LED emission. No hydrogen evolution or pH change is observed in the tear electrolyte. The present hybrid power source can potentially power wearable electronics in body fluids.     

Simple Method to Obtain Large‐Size Single‐Crystalline Oxide Sheets

Synthetic techniques to prepare large‐size, flexible, and high‐quality single‐crystalline sheets of transition metal oxides are crucial to developing low‐energy consumption devices. One promising way is a lift‐off and transfer technique using a heterostructure of polymer supporting oxide and Sr₃Al₂O₆ (SAO) layers grown on a single‐crystalline substrate. By removing the water‐soluble SAO and the supporting layers, the oxide sheet is obtained. Although some ferroelectric flexible sheets are prepared by this method, a simpler method for obtaining large‐size sheets is required. Herein, a lift‐off and transfer method is proposed without a supporting layer. With this simple method, single‐crystalline SrRuO₃ and BaTiO₃ flexible sheets with a lateral size of a few millimeters are successfully prepared. The SrRuO₃ sheet exhibits high crystallinity and conductivity. Meanwhile, the ferroelectricity of the BaTiO₃ sheet is successfully observed via polarization hysteresis loop measurements. In addition to the simplicity, this method has low costs and the substrate is reusable. Accordingly, the proposed method could enhance the development of various kinds of large‐size functional oxide sheets.     

Compositional analysis of deasphalted oil before and after hydrocracking over zeolite catalyst by Fourier transform ion cyclotron resonance mass spectrometry

Elemental compositions of components in feed and catalytically processed deasphalted oils were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The processed oils which were hydrocracked over a zeolite catalyst at three different reaction temperatures (370, 380, and 390 °C) were analyzed. Species of the deasphalted oils were ionized either by electrospray ionization (ESI) or by in-beam electron ionization (EI). The ESI mass spectra were obtained from every feed and processed deasphalted oil. Over 550 chemically different compounds were observed in the feed oil mass spectra. Molecular formulas for the detected peaks were calculated by using accurate mass. The compounds with one N atom as well as one N and S atoms were detected as major and minor component, respectively, in every mass spectrum. The number of the detected species in processed deasphalted oil decreases as the reaction temperature increases. However, the carbon distribution of NS-containing species shifts to high number as the reaction temperature increases. Molecular formulas distribution against Z-value (Z-value is defined as C_nH_2n + ZN_mS_sO_o) and C-number were investigated for the ESI mass spectra. Z-value distribution of the peaks assigned to N-compounds was convergent in its compounds with Z = − 25 as increasing the reaction temperature. Detailed mass spectrum analysis reveals that compounds which were not detected in the feed oil were observed in the mass spectra of processed oils; N, S, and O-containing compounds. For the in-beam EI only the processed oil at 390 °C yields approximately 700 resolved peaks at adopted probe temperature (300 °C) of EI. Molecular formula analysis for the observed peaks was conducted as well as ESI. It reveals that the molecular formulas having Z-value (− 30 < Z < 2) and carbon number ranged from 8 to 31 except for (− 18 < Z < − 12, 15 < C-number < 22) were contained in the processed deasphalted oil. Using complementary ionization techniques to characterize the feed and catalytic reacted deasphalted oils provide better understanding of fuel processing conditions.     

Mechanism of decomposition of aromatics over charcoal and necessary condition for maintaining its activity

Decomposition of mono- to tetra-aromatics over charcoal was investigated under conditions such as temperature; 700–900 °C, inlet concentrations of aromatics, steam and H₂; 7.5–15 g/Nm³, 0–15.5 vol% and 0–15.5 vol%, respectively, gas residence time within charcoal bed; 0.2 s, particle size of charcoal; 1.3–2.4 mm. The charcoal, with an initial surface area of 740 m²/g, was active enough to decompose naphthalene completely even at 750 °C. Aromatics with more rings per molecule were decomposed more rapidly. The aromatics were decomposed over the charcoal by coking rather than direct steam reforming irrespective of temperature and steam/H₂ concentrations. The coking, i.e., carbon deposition from the aromatics, caused loss of micropores and thereby activity of the charcoal, while steam gasification of the charcoal/coke formed or regenerated micropores. Relationship between the overall rate of carbon deposition by the coking and gas formation by the gasification within the charcoal bed showed that progress of the gasification at a rate equivalent with or greater than that of the carbon deposition was necessary for maintaining the activity of the charcoal.     

Stability condition of a class of nonlinear feedback systems:reduction to a convex problem

This paper gives a new criterion for input-output stability of a class of nonlinear feedback systems, roughly speaking, it is most useful in such a practical situation where the nonlinearity in the system is “almost time-invariant and memoryless” but with “slight time-variations and dynamics”. It involves two free parameters and contains the circle criterion and the Popov criterion as special cases. In fact, it extends these two famous criteria in such a way that the conservatism of the circle criterion can be reduced when the time-variations and dynamics of the nonlinearity are “relatively small”. It is also shown that the existence of the free parameters that fulfil the stability condition can be checked exactly by reducing it to a convex problem in the frequency domain     

Measurements of Vapor Pressures of Sc,La, and Ce by Multi-Knudsen Cell Mass Spectrometry

The vapor pressures of Sc, La, and Ce were determined by multi-Knudsen cell mass spectrometry with ionized cross sections as described in the literature. The vapor pressure of Sc at temperatures from 1373 K to 1573 K was measured using Cu as a reference material, and those of La and Ce from 1473 K to 1573 K were measured using Y as a reference material. From the measured vapor pressures, the Gibbs energy of formation of each gaseous element was derived.     

Low threshold 650 nm band real refractive index-guided AlGaInPlaser diodes with strain-compensated MQW active layer

650 nm band real refractive index-guided AlGaInP laser diodes with a strain-compensated MQW active layer have been successfully fabricated. A threshold current of 9 mA, which is the lowest ever reported was achieved and 5 mW operation was obtained up to 120°C. These lasers have been operated for >3000 h under 5 mW at 90°C     

Re‐ignition surge and high‐frequency arc extinction phenomena at 550‐kV shunt reactor current interruption

At substations connected with transmission lines and cables, shunt reactors are sometimes installed to compensate the capacitive current of these lines and cables. It is known that re‐ignitions occur and high‐frequency currents flow during interruption of the shunt reactor currents by switches. When the high‐frequency currents are interrupted immediately after the re‐ignitions (which is called high‐frequency arc extinction), the result is often repetitive re‐ignitions or voltage escalations that produce dangerous overvoltages. The authors investigated the occurrence of high‐frequency arc extinctions in a 550‐kV one‐break SF₆ gas circuit breaker during interruption of a 550‐kV shunt reactor current. Computations for a real 550‐kV substation gave a minimum frequency of 290 kHz for the high‐frequency current. However, 550‐kV reactor current interruption tests showed that high‐frequency arc extinctions did not occur even when this frequency was lowered to 26 kHz. Since high‐frequency arc extinction is generally likely to occur at lower frequencies, it was concluded that high‐frequency arc extinction will not occur in a 550‐kV one‐break SF₆ gas circuit breaker during interruption of shunt reactor current in real substations. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 18–25, 2001