Hirokazu Okawa

Underground Imaging Method Using Magnified Cross-Correlation Analysis

When underground piping for a water supply or gas supply is buried, some obstacles such as unknown pipes or stones can be encountered. To avoid such situations, an examination of the underground condition from the ground surface is needed. For such an examination, the ultrashallow reflection method is used. We use a giant-magnetostriction vibrator as a seismic source and a magnified cross-correlation analysis as an analysis method. This analysis is performed to obtain the arrival time of waves reflected from underground objects. In this study, an underground imaging method is proposed using the magnified cross-correlation analysis and a simulation is conducted. Then the experiment of detecting a buried concrete block is conducted. Finally, the imaging method is applied to the experimental result, and then the underground image is obtained. With this imaging method, the position of the buried concrete block can be estimated.

Detection of underground concrete block using giant-magnetostriction vibrator applying magnified cross-correlation analysis

When underground piping for a water supply or gas supply is buried, some obstacles such as unknown pipes or stones can be encountered. To avoid such situations, an examination of the underground condition from the ground surface is needed. For such an examination, the ultra-shallow reflection method is used. We use a giant-magnetostriction vibrator as the seismic source. In this study, first, the P-wave directivity of the giant-magnetostriction vibrator is clarified. Second, the experiment of detecting a buried concrete block is conducted. In this experiment, the cross-correlation analysis is applied. However, the arrival time of the wave reflected from the concrete block is not confirmed. On the basis of the P-wave directivity of the giant-magnetostriction vibrator, the causes are assumed. To obtain good results, the magnified cross-correlation analysis is proposed. By this analysis, the depth at which the concrete block is buried can be estimated with high accuracy.

Effects of Different Ultrasound Irradiation Frequencies and Water Temperatures on Extraction Rate of Bitumen from Oil Sand

Low (28 kHz) and high (200 kHz) frequency sonication combined with hot water treatments at 45 and 75 °C were investigated to assess the effects of different ultrasound frequencies and water temperatures on the extraction of bitumen from oil sand. A mechanical stirrer was also used to compare the efficiency of separation. Bitumen extraction tests were performed under argon, air, and nitrogen atmospheres. Sonication at 200 kHz was shown to extract bitumen effectively from oil sand at 75 °C. The bitumen extraction rate for sonication at 200 kHz was slightly higher than that at 28 kHz. For low temperature (45 °C) solutions, only sonication at 28 kHz could extract bitumen from oil sand, demonstrating that sonication at 28 kHz can effectively breakdown the oil sand aggregates into a suspension.

The Sterilization of Suspensions Contaminated with Microorganisms Using Ultrasound Irradiation

We investigated the influence of suspended particles on the sterilization efficiency of ultrasound wave applied to microbial suspensions. A microbial solution containing 2.0×102 cfu/ml of Bacillus bacteria but no suspended particles was sterilized more efficiently by 28 kHz irradiation inducing a strong impact-like physical action compared to 200 kHz irradiation inducing a strong chemical reaction through the generation of radicals and heat. This sterilization effect was enhanced by the suspension of silicon dioxide or green tuff when irradiated at 28 kHz. However, the irradiation of green tuff microbial suspension at 200 kHz resulted in a remarkable decrease in the sterilization efficiency. This reduction was caused by divalent iron in green tuff reacting with radicals generated by 200 kHz irradiation, thus reducing the amount of radicals used for sterilization. Our results suggest that 28 kHz ultrasound irradiation is optimal for the sterilization of microbial suspensions.

Ultrasound irradiation for desorption of carbon dioxide gas from aqueous solutions of monoethanolamine

In this study, we investigated the use of ultrasound irradiation to remove CO2 gas from aqueous solutions of monoethanolamine (MEA). The desorption rate of CO2 was measured while MEA solutions were exposed to 28 kHz ultrasound irradiation at 25 °C. The results showed that the rate of CO2 desorption from a low-concentration MEA (0.2 mol/l) solution is significantly increased by ultrasound irradiation as compared with that of desorption by stirring at a low temperature (25 °C). It was also found that decreasing the concentration of MEA solutions increased the rate of CO2 desorption. In addition, we considered the process of desorption of CO2 from MEA solutions according to experimental results.

A Method for Estimating the Location of the Drill-Bit During Horizontal Directional Drilling Using a Giant-Magnetostrictive Vibrator

Horizontal directional drilling (HDD) is a commonly used method for laying pipelines that avoids the need to make an open cut. However, the location of the drill-bit underground must be known at all times when using this method. As conventional electromagnetic wave-based methods are known to have several problems, for example buildings in the line of construction, the moisture content of the ground and the presence of steel towers near the construction site. Herein we suggest a new method based on the propagation of elastic waves in the ground. Thus, measurement of the elastic waves generated by a giant-magnetostrictive vibrator by sensors set on the ground allows us to obtain the differences in arrival time of this wave at each sensor by applying a cross-correlation analysis to the waveforms detected. Finally, an approximate three-dimensional (3D) location method based on these differences was designed.

Synthesis of large scorodite particles using short period time sonication to enhance agglomeration of precursor

The effect of various sonication frequencies (28 kHz, 200 kHz, and 1.7 MHz) on the size of synthesized scorodite particles was investigated. First, the growth of the precursor with oxidation was observed in a synthesis process using stirring. The precursor size changed with the elapsed time and was 3 µm at 20 min. The scorodite particles were then synthesized following different procedures such that a different size of the precursor was irradiated by each ultrasound frequency for 10 min during the oxidation process with stirring for a total duration of 180 min. For each frequency, the size of the synthesized particles varied depending on the size of the precursor. Large scorodite particles can be synthesized (70 °C) by irradiating for only 30 min at various frequencies after the size of the precursor particles reaches the optimal range.

Size and morphology of scorodite particles synthesized using ultrasound irradiation

The synthesis of large scorodite particles (>10 µm) at low temperature (50–70 °C) with a short reaction time (3 h) using 200 kHz ultrasound irradiation was investigated. Large scorodite particles (>10 µm) were obtained using ultrasound irradiation at 70 °C. The growth of scorodite particles was confirmed by scanning electron microscopy (SEM). The precursor agglomerated at the early stage of the synthesis using ultrasound irradiation. Ultrasound irradiation was applied to agglomerate the precursor. Large scorodite particles were synthesized without fine particles using ultrasound irradiation for a short time at the early stage of the synthesis followed by oxidation using stirring and oxygen flow without ultrasound irradiation.

Ultrasound-assisted oxidative desulfurization of bitumen

Bitumen contains a high percentage of sulfur (about 4.6 wt %). A hydrodesulfurization method is used to remove sulfur from bitumen. The drawback of this method is the requirement for a high temperature of >300 °C. Most of the sulfur in bitumen exists as thiophene. Oxidative desulfurization (ODS), involving oxidizing sulfur using H2O2, then removing it using NaOH, allows the removal of sulfur in thiophene at low temperatures. We removed sulfur from bitumen using ODS treatment under ultrasound irradiation, and 52% of sulfur was successfully removed. Additionally, the physical action of ultrasound assisted the desulfurization of bitumen, even at low H2O2 concentrations.

Improved battery performance using Pd nanoparticles synthesized on the surface of LiFePO4/C by ultrasound irradiation

LiFePO4 has been attracting interest as a cathode material for Li-ion batteries due to its high energy density, low cost, and eco-friendliness. The electrochemical performance of LiFePO4 is limited because it exhibits low Li-ion diffusivity and low electronic conductivity. Numerous solutions have been considered, such as carbon coating, which is widely known to improve the electronic conductivity of LiFePO4. The deposition of metal nanoparticles (NPs) on the surface of carbon-coated LiFePO4 further enhances the electronic conductivity. In this study, we deposited Pd NPs onto the surface of LiFePO4/C and investigated the resulting electrochemical performance. Sonochemical synthesis was used to prepare the metal NPs; the procedure did not require any surfactants and the reaction was rapid.