Taking ARTS-GROWL, for instance, experimental results indicate that artificial sparsity improved the signal-to-noise ratio and normalized root-mean-square error of non-Cartesian PPI. Magn Reson Med 78:271-279, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

A continuous water injection test was conducted to halt the reduction in steam production in the Okuaizu Geothermal Field, Japan. Understanding the factors triggering microseismicity associated with water injection is essential to ensuring effective steam production. We identified possible triggering processes by applying methods based on microseismic monitoring, including a new method to determine the presence of water in local fractures using scattered P-waves. We found that the evolving microseismicity near the injection point could be explained by a diffusion process and/or water migration. We also found that local microseismicity on a remote fault was likely activated by stress fluctuations resulting from changes in the injection rate. A mediator of this fluctuation might be water remaining in the fracture zone. After the injection was terminated, microseismicity possibly associated with the phase transition of the liquid was found. We conclude that a variety of triggering processes associated with water injection may exist.

A new iterative reconstruction technique for electrical capacitance tomography (ECT) is presented. This method applies iterative soft thresholding to penalize the total variation of the ECT image. This method is shown to allow for sharp changes between different regions of simulated ECT images, unlike conventional iterative reconstruction techniques such as ART, SIRT and the Landweber iteration. The technique is demonstrated on experimental results for a phantom with distinct regions of gas and solid. The technique is therefore appropriate for the imaging of multiphase systems.

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In this paper, we focus on the detection of the interlayer debonding of the asphalt airport pavement by the Groundpenetrating Radar (GPR) system. Since the interlayer debonding usually occurs in the shallow region of the asphalt airport pavement (several centimeters), it is difficult to interpret the anomalies or the defects from the GPR signals composed of many waves under the boundary conditions. Moreover, the wavelength of the ordinary GPR system is over several centimeters. Therefore, the spatial resolution of the system is not accurate enough to consider the millimeter thickness of the debonding layer. To overcome these problems, we propose a new method based on evaluating the lateral wave behavior of common midpoint (CMP) gathers collected by a multiple static GPR system. The multi-static GPR system is a stepped frequency continuous wave (SFCW) radar system, which consists of 8 transmitting and 8 receiving bowtie antennas. The system operates in the frequency range from 50 MHz to 1.5 GHz. After the validation of the simulation, the results of the interlayer debonding detection were evaluated by a field experiment obtained at Tokyo International Airport. The proposed method can detect the debonding layers which are less than 1mm. Also, it is shown that our proposed method has a high consistency with the conventional acoustic finding method in the field measurement. It provides an innovative and effective method for the interlayer debonding detection of a partially damaged airport asphalt pavement, which is difficult to be observed by the ordinary GPR signals.

We developed a silicon (Si) dielectric diplexer module for 600-GHz-band frequency-division multiplexing wireless communication. This diplexer was developed based on Si dielectric waveguide technology, which provides low-loss transmission characteristics compared with the conventional metallic terahertztransmission platform, such as metallic hollow waveguides. It includes straight waveguides based on an effective medium composed of Si and air, and a coupler comprising of two adjacent unclad Si waveguides. Furthermore, for the communication system integration, we developed a practical and low-insertion loss module with WR1.5 metallic hollow waveguide input-output interfaces and modularized the diplexer. We performed transmission measurement experiments with the fabricated diplexer module and achieved 3-dB bandwidths of 101 and 37 GHz, and crosstalk of −34 dB at 680 GHz and −41 dB at 618 GHz in the cross and bar directions, respectively. Finally, we performed a two-channel wireless communication experiment using the developed diplexer module in the 600-GHz band. We achieved error-free communication at 10 and 6 Gbit/s on the cross and bar channels, respectively. In addition, we achieved a data rate of up to 12.5 Gbit/s at the forward error correction limits for both channels.

Abstract The injection of water into geothermal systems is an important procedure required to recover subsurface water resources and enhance permeability for increasing the reservoir volume. The injected water often leads to microseismic events during migration, which can be used to directly track the location of the injected water. However, in rare cases, unexpectedly large induced seismicity occurs after the injection termination. For risk control, understanding the differences between cases that cause post-termination seismicity and those that do not is necessary. For this purpose, we used microseismic monitoring to examine the behavior of water during two injection tests, including their post-termination periods, in Okuaizu geothermal field, Japan. In this field, a new remote microseismic cluster, apart from the injection well, was created in the post-termination period of the first injection test. However, this cluster was not well activated in the second injection test. As a result, we revealed that this microseismic cluster was created on a structure that was different from the target fracture of the injection, possibly owing to pore-pressure migration in the post-termination period of the first injection. Its inactivation in the second post-termination period may be attributable to the lower magnitude of pore-pressure migration derived from the smaller amount of injected volume compared with that of the first injection test. The lower pore-pressure migration was insufficient to reactivate the seismicity. We concluded that the occurrence of seismicity after injection termination may depend on the magnitude of pressure in the injection well at the shut-in time. The Kaiser effect (i.e., a fault is not reactivated by stress that is less than the maximum stress loaded previously) could explain the observed phenomena.

Plasmonic nanoslits have great potential for single molecule applications. We report a wafer scale process for these structures using process steps compatible with a standard CMOS fab environment. This process allows a large scale fabrication of designed nanoslits with extremely small gap sizes and lengths tuned to exhibit optical resonances. Moreover, adjacent grating nano-antennas were successfully implemented, generating strong and localized electric fields in the nanoslit. These slits have practical applications in surface enhanced Raman spectroscopy-based molecular sensing and plasmonic tweezers.