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     

High sensitivity of VPE-grown InGaAs/InP-heterostructure APD with buffer layer and guard-ring structure

A planar-type InGaAs/InP-heterostructure APD with an InGaAsP buffer layer was made by using a VPE technique. To avoid the edge breakdown, a guard-ring structure was employed. The average received optical power for a 10?9 error rate at 280 Mbit/s was as low as ?43 dBm, which corresponded to 2 and 7 dB improvements over a Ge-APD at 1.52 and 1.59 ?m, respectively.     

A novel catalyst fabricated from Al–Cu–Fe quasicrystal for steam reforming of methanol

The optimum preparation condition of Al–Cu–Fe quasicrystalline (QC) catalyst with excellent catalytic performance for steam reforming of methanol (SRM) has been investigated. The QC alloy is superior to the other crystalline Al–Cu–(Fe) alloys (i.e., beta and theta phase) as a catalyst material because of the brittle nature of QC. The wet milling process (in ethanol) for the QC powders is much better than the dry milling process to obtain fine particles with high surface area. The QC powder prepared by the wet process followed by leaching in Na₂CO₃ aq. at 323 K exhibited the highest catalytic performance (activity and stability) in the present study. From these findings, it is clear that the QC catalyst with the excellent catalytic performance could be obtained by controlling the initial grain size of the QC powder and the leaching temperature.     

Hall effect of photocurrent in CVD diamond film

Transient Hall voltage of photocurrent excited by the modulated light with photon energies near bandgap is observed in undoped and B-doped CVD diamond films. It is seen that photo-carriers created in the films by the band-to-band excitation higher than 5.5 eV are almost holes and the contribution of electrons is about 7% in the undoped film and 0% in the B-doped film. Photo-carriers excited by the light with photon energies 4.7 to 5.5 eV, in which the step-like absorption band is observed, are holes, which agrees with the result of the temperature dependence of the photocurrent excited by the light with the photon energies.