Microbial fuel cells (MFCs) represent a novel platform for treating wastewater and at the same time generating electricity. Using Pseudomonas putida (BCRC 1059), a wild-type bacterium, we demonstrated that the refinery wastewater could be treated and also generate electric current in an air-cathode chamber over four-batch cycles for 63 cumulative days. Our study indicated that the oil refinery wastewater containing 2213 mg/L (ppm) chemical oxygen demand (COD) could be used as a substrate for electricity generation in the reactor of the MFC. A maximum voltage of 355 mV was obtained with the highest power density of 0.005 mW/cm² in the third cycle with a maximum current density of 0.015 mA/cm² in regard to the external resistor of 1000 Ω. A maximum coulombic efficiency of 6 × 10⁻²% was obtained in the fourth cycle. The removal efficiency of the COD reached 30% as a function of time. Electron transfer mechanism was studied using cyclic voltammetry, which indicated the presence of a soluble electron shuttle in the reactor. Our study demonstrated that oil refinery wastewater could be used as a substrate for electricity generation.

Concrete is a composite material composed mainly of water, sand, aggregate, and cement. The characteristics of high attenuation of concrete for ultrasound degrade the performance of ultrasonic testing (UT), especially when the size of the target is much smaller than the aggregate. Thanks to recent improvements in electronic devices and computing technology, the total focusing method (TFM) and the phased array (PA) technique have been applied to facilitate UT for concrete. However, the question of which approach is better for the UT of concrete has not yet been addressed. Thus in this preliminary study, a synthetic PA image, which is similar to an image acquired by the PA system, and a synthetic TFM image, which is similar to an image acquired by the TFM system, were made for the UT of concrete. The qualities of these images were compared with those produced by the traditional B-scan and the synthetic aperture focusing technique (SAFT). Excluding the expense, difficulty, complexity, and efficiency of these techniques, the results of this study show modern (TFM and PA) techniques are always better than traditional (B-scan and SAFT) methods based on 100 kHz ultrasonic experiments with a low signal-to-noise ratio (SNR) condition. The SAFT method can only slightly improve the quality of the B-scan image. In addition, a moderate distance between the source and receiver is suggested for detecting shallow and small targets in concrete in order to avoid near-source backward scattering. However, the PA technique has superior performance in detecting a small target at a specific depth in concrete. On the other hand, while detecting a large target in concrete, the TFM shows better performance than the PA technique. Study results indicate both the PA and the TFM have their own merits and demerits. The PA shows good performance in the status of a low SNR environment, and the TFM works better in a high SNR situation. In conclusion, to detect a small target at a specific depth in concrete, the PA technique is recommended. Otherwise, to detect a large target in concrete, the TFM is a better choice.

Much of the earth's crust appears to have some degree of elastic anisotropy (Crampin, 1981; Crampin and Lovell, 1991; Helbig, 1993). The phenomena of elastic wave propagation in anisotropic media are more complex than those in isotropic media. Shear-wave propagation in an orthorhombic physical model is most complex when the direction of the wave is close to the neighborhood of the cusp on the group velocity surfaces (Brown et al., 1991). The first identification of singularities in wave propagation through sedimentary basins occurred in the examination of shear-wave splitting in multioffset vertical seismic profiles (VSPs) at a borehole site in the Paris Basin (Bush and Crampin, 1991), where large variations in shear-wave polarizations in propagation directions close to point singularities were observed. Computation of synthetic seismograms for layer sequences showed that the shear-wave polarizations and amplitudes were irregular near point singularities (Crampin, 1991).

Exploration Geophysics is published by CSIRO PUBLISHING on behalf of the Australian Society of Exploration Geophysicists. Papers published report the results of significant case histories and relevant original research in geophysics, with emphasis on the Australian and similar environments.

The synthetic aperture focusing technique (SAFT) can improve the image resolution of ultrasonic testing (UT) by applying a delay-and-sum (DAS) process to the received echoes. The drawback of using current SAFT to test a multi-layer medium is that the computation of delays is complicated and time-consuming. In this study, we propose a fast and simple method to calculate the approximated delays for using in SAFT to image flaws in multi-layer media without losing the resolution of the SAFT image. The approximated delays can be easily and quickly calculated by a hyperbolic time-distance relationship which is a function of the root-mean-square velocity (V _rms ) of layers under circumstances of short lateral distance and horizontal layers. The error of approximated delays is very small when incorporating the amplitudes radiated from the transducer into the processing of SAFT. Two extreme experiments of immersion testing were carried out to test and evaluate the proposed method. The experimental results show that the proposed method is feasible. Thus, the approximated delays calculated by the V _rms for using in SAFT to enhance the resolution of the scan image for testing the flaws in multi-layer medium are recommended.