Mechanism of capacitance aging under DC-bias field in X7R-MLCCs

Capacitance aging under DC electric fields has been studied on multilayer ceramic capacitors (MLCCs) with the X7R characteristics. The capacitance change with time was divided into two stages, the first- and the second-stage. The first-stage was due to the nonlinear permittivity of dielectrics and it should not be involved in the aging phenomenon. The second-stage depended on the MnO content, grain size and firing condition of dielectrics. From the behavior of the second-stage, it was concluded that the capacitance aging was caused by the 90-degree domain switching in BaTiO₃ in the core. The first-stage was due to the nonlinear permittivity but the domain switching was also included in the first-stage if the domain walls moved by the first application of DC field. The change in the aging behavior with the intensity of DC field could be explained by separating capacitance change into the nonlinear permittivity and the domain switching according to the mechanism proposed in this study.     

Effective cell separation utilizing poly(N-isopropylacrylamide)-grafted polypropylene membrane containing adsorbed antibody

We previously developed a cell separation method using a poly(N-isopropylacrylamide)-grafted polypropylene (PNIPAAm-g-PP) membrane containing an adsorbed monoclonal antibody (mAb). The purpose of this study is to elucidate the cell separation mechanism in detail and to design an optimal method. As the grafting yield of PNIPAAm increased, the level of the adsorption of IgG(1) and cell adhesion to the membrane decreased. After BSA was adsorbed to a PNIPAAm-g-PP membrane at 6 degrees C, where PNIPAAm was hydrophilic, a small amount of IgG(1) was adsorbed to the membrane at 37 degrees C, where PNIPAAm was hydrophobic. The desorption of the adsorbed IgG(1) was not enhanced even though temperature was reduced to 10 degrees C, where PNIPAAm was hydrophilic. These results indicate that the antibody adsorbed to the intact PP surface of the membrane predominantly contributes to the capture of target cells through the antigen-antibody reaction and that a thermoresponsive transition of PNIPAAm contributes to the detachment of the captured cells. The total number of cells recovered from a PNIPAAm-g-PP membrane containing the adsorbed mAb decreased as the grafting yield increased. A PNIPAAm-g-PP membrane with a 1.7% grafting yield containing adsorbed anti-human CD34 mAb enriched CD34-positive KG-1a cells to 85% from a 1:1 cell suspension of KG-1a cells and CD34-negative Jurkat cells.     

Electron scattering by Friedel oscillations in carbon nanotubes

Multi-walled carbon nanotube networks were confirmed to exhibit a linear decrease in resistivity with increasing temperature from 100 to above 400 K.The linearity was explained using a defect scattering model that involved Friedel oscillations(that is,electron-electron interactions).The applicability of this model,which was originally proposed for graphene,to carbon nanotubes was assessed based on a comparison of various experimental data.Increases in the slopes of the resistivity-temperature plots following the introduction of defects,as well as an effect of charge concentration on the slope were key predictions of this model.The results obtained from few-walled carbon nanotube networks are also shown.In the literature,linear resistivity-temperature plots were obtained from other graphene derivatives,indicating that the linearity originates from the hexagonal symmetry of these materials.The present work also indicated a relationship between the appearance of linearity and negative magnetoresistance above 100 K.Based on a mechanism incorporating scattering in association with Friedel oscillations and conventional electron conduction models,the universality of resistivity-temperature plots obtained from carbon nanotube networks is introduced.     

Using Decision Trees to Construct a Practical Parser

This paper describes a novel and practical Japanese parser that uses decision trees. First, we construct a single decision tree to estimate modification probabilities; how one phrase tends to modify another. Next, we introduce a boosting algorithm in which several decision trees are constructed and then combined for probability estimation. The constructed parsers are evaluated using the EDR Japanese annotated corpus. The single-tree method significantly outperforms the conventional Japanese stochastic methods. Moreover, the boosted version of the parser is shown to have great advantages; (1) a better parsing accuracy than its single-tree counterpart for any amount of training data and (2) no over-fitting to data for various iterations. The presented parser, the first non-English stochastic parser with practical performance, should tighten the coupling between natural language processing and machine learning.     

Efficient heat utilization of a space cooling system over a range of atmospheric temperatures and solar radiation

Behavior of a space cooling system using the diurnal range of atmospheric temperatures in the summer is examined by numerical simulation. The system consists of radiators, a thermal energy storage tank, fan‐coil coolers, and an electric cooler. Conditions for the calculation were obtained from actual weather records and characteristics of appliances. Total consumption of electric power was used for evaluating the system performance. The larger the volume of the storage tank becomes, the smaller the consumption. The consumption is smaller when the radiator is operated for a period of some limited hours than when operating through the night. To decrease the consumption, there are optimum values of the flow rate of the pumps and in the on–off temperature of the fan‐coil cooler. Stratified tanks could reduce the consumption compared with mixed ones. This system has the possibility of reducing demand for electricity or of shifting the demand to off‐peak hours. © 2001 Scripta Technica, Heat Trans Asian Res, 30(2): 126–138, 2001     

Preparation of Hydroperoxides by N‐Hydroxyphthalimide‐Catalyzed Aerobic Oxidation of Alkylbenzenes and Hydroaromatic Compounds and Its Application

An efficient approach to phenols and aldehydes through the formation of hydroperoxides from alkylbenzenes was successfully achieved by aerobic oxidation using N‐hydroxyphthalimide (NHPI) as a catalyst. The oxidation of various alkylbenzenes with dioxygen by NHPI followed by treatment with a Lewis acid or triphenylphosphine led to phenols or aldehydes, respectively, in good yields. For example, the aerobic oxidation of cumene in the presence of a catalytic amount of NHPI at 75 °C and subsequent treatment with H₂SO₄ gave phenol in 77% yield. 1,4‐Dihydroxybenzene (61%) and 4‐isopropylphenol (33%) were obtained from 1,4‐diisopropylbenzene. On the other hand, dibenzyl ether was converted into phenol or benzaldehyde upon treatment of the resulting hydroperoxide with InCl₃ or PPh₃, respectively.     

Creating the hydrogen absorption capability of CeNi5 through the addition of Al

The hydrogenation capacities of CeNi_5?xAl_x (x = 0, 0.75, 1.0, 1.25, 1.5 and 1.75) alloys were assessed. In contrast to LaNi₅-based alloys, the addition of Al to CeNi₅ enables hydrogen absorption by creating larger interstitial sites as the result of an expanded lattice. Structure analyses indicate that each of these alloys maintained a CeNi₅ (CaCu₅-type) structure in which Al atoms exclusively occupied Ni 3g sites. Among these specimens, CeNi₄Al absorbed the greatest proportion of hydrogen atoms, decreasing its c/a ratio from 0.826 to 0.802 upon the formation of CeNi₄AlH_4.3. This drastic decrease in the c/a ratio is attributed to an anisotropic lattice expansion along the a-axis, as verified by in situ X-ray diffraction under H₂. The enhanced hydrogen absorption of these alloys is thought to be associated with the preferential situation of hydrogen atoms at interstitial sites located at the centers of octagons as well as a charge transition of Ce ions upon hydrogenation. It is verified that CeNi₄Al after hydrogenation shows high catalytic activity toward propyne hydrogenation: 100% conversion of propyne even at room temperature.     

Hydrogen sensing ability of Cu particles coated with ferromagnetic Pd–Co layer

A new hydrogen sensor utilizing a ferromagnetic hydrogen absorbing alloy was developed. An optimum sensing element, Cu particles coated with Pd–Co hydrogen absorbing alloy was prepared by the barrel sputtering technique. The surface of prepared Cu particle was covered uniformly by Pd–Co thin layer constituted of aggregated nanoparticles. The sensitivity of the sensing element to H₂ concentrations under flowing dry N₂ and dry air gases was examined. The element has a reasonable sensitivity to the H₂ concentration of the range from 3.8% to 0.2%, and the lower limit of detectable H₂ concentration was estimated to be less than 0.1%. In dry air, the water formation on the Pd–Co surface affected its sensing ability, because the temperature of the sensing element increased by the exothermic reaction. The effect of moisture on the H₂ sensing ability was also investigated. The moisture slightly degraded the output signal under flowing air. It could be ascribed to an additional consumption of hydrogen atoms by water molecules and oxygen atoms on the Pd–Co surface. This sensor takes advantage of magnetic susceptibility measurement, which requires no electrical wire between the sensing element and an electric circuit, leading to a safe evaluation system of H₂ concentration in air.     

A TEA‐CO2 laser oscillation by an inductive energy storage pulsed‐power generator using a wire‐fuse opening switch

We have carried out experiments on TEA‐CO₂ laser oscillation using the inductive energy storage pulsed‐power generator, which has a copper wire fuse as an opening switch. Maximum laser output energy of about 1 J/pulse was obtained in the case of a fuse length of 5 cm and energy storage inductance of 8 μH. The laser output energy depends on the energy storage inductance and the parameters of the fuse. In this paper, the dependencies of laser output energy on inductance and fuse length, and a comparison between the inductive and capacitive system were described. Furthermore the laser efficiency was discussed by calculating the electron energy distribution of laser main discharge region. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 15–21, 2000