Masahiro Utiyama

Improvement in Propene Sensing Characteristics by the Use of Additives to In2O3 Sensing Electrode of Mixed-Potential-Type Zirconia Sensor

In an effort to improve propene (C 3 H 6 ) selectivity and long-term stability of the mixed-potential-type yttria-stabilized zirconia (YSZ)-based tubular sensor attached with In 2 O 3 sensing electrode (SE), each of the nanosized noble metals (Pt, Ru, Pd, Rh, or Ir) and YSZ powder was added to In 2 O 3 SE. It was found that the addition of nanosized Pt (0.3 wt %) gave considerable improvement in C 3 H 6 selectivity, and the addition of YSZ powder (10 wt %) exhibited great improvement in long-term stability of the sensor. Thus, the sensor attached with composite SE consisting of In 2 O 3 , 0.3 wt % Pt, and 10 wt % YSZ was fabricated and its sensing characteristics to C 3 H 6 were examined. As a result, the present sensor exhibited high selectivity and excellent long-term stability to C 3 H 6 at 450°C under the wet condition for the examined period of about 1 month. Based on the results obtained from the measurement of catalytic activity for CO oxidation to CO 2 , the observation of morphology, and the analysis of composition of SEs, it was speculated that the added Pt nanoparticles could promote the oxidation of CO and H 2 and then improve the C 3 H 6 selectivity, while the added YSZ powder could stabilize the morphology of the SE/YSZ interface and give better long-term stability.

YSZ-based Sensor Using NiO Sensing Electrode for Detection of Volatile Organic Compounds in ppb Level

A mixed-potential-type yttria-stabilized zirconia (YSZ)-based tubular sensor utilizing a NiO sensing-electrode (SE) was fabricated and examined, with aspirations of monitoring very low concentrations of volatile organic compounds (VOCs) at the ppb level. It was shown that the present sensor gave higher sensitivities towards each of the six different VOCs (toluene, m-xylene, benzene, ethylbenzene, styrene and formaldehyde) than other gases, such as C 3 H 6 , H 2 , CO and NO 2 . Responses to different concentrations of pseudo-total VOC (p-TVOC, composed of gas mixture of toluene, m-xylene and formaldehyde) for the present sensor were also measured. It was found that the present sensor could detect very low concentrations of p-TVOC, lower than the current Japanese guideline value of < 175 ppb. In addition, the present sensor exhibited good accuracy for the measurement of p-TVOC concentration, being comparable to that of a commercial hydrocarbon analyzer. The effect of NiO-SE thickness with respect to gas-sensing characteristics was also evaluated and it was found that a decrease in NiO-SE thickness enhanced the sensitivities to all the gases examined for the present sensor. The sensing mechanism for all VOCs tested was confirmed to be in good agreement with the mixed-potential sensing model.

Mixed-Potential-Type YSZ-Based Sensor Capable of Detecting Propene at Several Tens ppb Level

The mixed-potential-type yttria-stabilized zirconia (YSZ)-based sensors using each of several oxide sensing-electrodes (SEs) were fabricated and examined for detection of propene (C 3 H 6 ) at its very low concentration level. Among five oxide-SEs tested, the In 2 O 3 -SE was found to give the highest sensitivity to C 3 H 6 with an acceptable response rate even at 450°C. The A electromotive force value of the sensor varied logarithmically with the C 3 H 5 concentration in the examined range of 10-200 ppb. In addition, the sensor exhibited a relatively good selectivity to C 3 H 6 over the other gases, such as NO 2 , CO, H 2 , and CH 4 , in the respective environmentally existing level.

Some Measurement Results on Sulfate Aerosol Concentration in and above a Pine Canopy

Profile of sulfate aerosol (SO42−) concentration was measured for four days at six heights in and above a 15m-high canopy of pine plantation during 6th and 10th August. 1999. The concentration was the lowest (about 2 nmol/m3) on 6th, and gradually increased to 9th showing the maximum values of about 13 nmol/m3, and then decreased to 2 nmol/m3 on 10th. The vertical profiles of SO42− concentration showed mostly higher in the canopy than above the canopy. As for the vertical profiles above the canopy on 8th and 10th, the minimum was observed just above the canopy (16m), showing SO42− transport from the upper air layer to the canopy. While on 9th the profiles that are higher concentration just above the canopy and lower at the upper air layer were observed, suggesting SO42− emission from the canopy to the upper air layer.

Development of the floating structure for the Sailing-type Offshore Wind Farm

Feasibility studies for the sailing-type offshore wind farm have been carried out by National Institute for Environmental Studies. This system is composed of a very large floating offshore structure with sails and a lot of wind turbines on the structure. Conventional catenary mooring system is no longer practical for station-keeping a kilometer sized floating structures in over hundreds meters of water depth. This floating structure sails around EEZ of Japan seeking appropriate breezing and avoiding meeting heavy storm. This floating structure has self-mobile and station-keeping capability using the sail control system and semi-sub hull structure. This paper presents the development of this floating structure based on the hydro-elastic response analysis in waves and structural optimization.

Fine Particle Dry Deposition onto a Cropland — a Trial to Estimate Deposition Velocity

The dry deposition velocity of fine particles is usually on the order of several tenths of cm s−1, and accordingly, the concentration gradient of particles above the surface is very small. This makes the application of the gradient method to the determination of the particle deposition velocity very difficult. This study is a trial to find a way around this difficulty. The idea is to evaluate the thickness of the molecular diffusion layer, zb by simultaneously measuring the concentration gradient of gaseous species such as SO2 ; zb is obtained by combining the turbulent and molecular transport equations for the gas. Then the particle deposition velocity is estimated on the basis of zb and the Brownian diffusion coefficient with an assumption that zb is equal to the thickness of the Brownian diffusion layer. By applying this method to the data collected in a field observation, the velocity of deposition onto a cropland was estimated for submicron particles.

Rate of Sulfur Dioxide Removal Artificial Cloud Experiments Utilizing a Long Vertical Shaft

Removal of sulfur dioxide through the absorption into cloud droplets is the initial stage of acid rain formation. We studied this process by forming an artificial cloud with a spatial scale close to the real one. We used a vertical shaft of 430 m in length in an abandoned mine, and operating an electric fan placed at the top of the shaft, generated an updraft of about 1 m s−1 of the air humidified by underground water. This produced an artificial cloud rising about 400m above the cloud base observed at a height of about 35 m from the bottom. At the bottom of the shaft, we emitted SO2 gas into the air stream, and measured its concentration profile by an SO2-meter loaded on an elevator going up and down in the shaft. From the slope of the observed decay curve, we evaluated the rate constant for the absorption to be 0.010 s−1. This value was found to agree in order of magnitude with an estimate derived on the basis of the laminar film model for mass transfer.