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The Mirpur earthquake of Mw 5.8 on 24 September 2019 severely damaged villages in the epicentral area. The earthquake-triggered ground dynamics produced widespread liquefaction features on the surface (e.g., fractured road structure and sand boils) and in the shallow subsurface (e.g., elevated groundwater table, fractures, and sand dikes). Due to complexity of liquefaction-induced deformation and timing of field surveys, the structural and hydrogeologic features that develop in the near surface during seismic events are often poorly resolved on ground-penetrating-radar (GPR) profiles. To track and delineate the internal architecture and coseismic changes in groundwater levels and/or pressures due to liquefaction, a GPR survey was carried out soon after the Mirpur earthquake. The sudden pore water pressure changes in the shallow aquifer system caused a rise in the water table via upward groundwater movement and fracturing followed by rapid infiltration. This cascade phenomenon has adverse effects on soil, water resources, civil infrastructure, and public health and safety. To better understand induced changes in the physical properties of road infrastructure and the shallow subsurface, we performed synthetic modeling of electromagnetic wave propagation by employing the finite-difference time-domain method. Based on the available information at multiple scales (borehole and geophysical), subsurface physical models representing the most common and important coseismic features were considered for synthetic modeling. Likewise, synthetic tests of paved road were conducted to simulate the radar response of structural discontinuities (fractures) developed at different angles. To validate synthetic results by identifying a similar dynamic response of the induced hydrogeologic changes in the form of coseismic liquefaction features, a field GPR survey was conducted. Our results clearly demonstrate that the GPR technique is a potential candidate for hydrogeophysical detection and characterization of features of interest in the case of paved roads as well as agricultural and residential areas. Additionally, the successful application of GPR proves it to be a cost-effective, high-resolution, and speedy tool for better assessment of hydrogeologic hazard, socioeconomic consequences, and mitigation in the Mirpur area. The proposed approach may find applications in other seismically active regions around the world.

SUMMARY Full waveform inversion (FWI) is a highly non-linear optimization problem that aims to reconstruct high-resolution subsurface structures. The success of FWI in reflection seismology relies on appropriate updates of low-wavenumber background velocity structures, which are generally driven by the diving waves in conventional FWI. On the other hand, the reflected waves mainly contribute to updating high-wavenumber components rather than low-wavenumber components. To extract low-wavenumber information from the reflected waves in addition to the diving waves, we propose a two-step FWI strategy that separates a given model into the reflectivity and background velocity models and then alternately update them using the scale-separation technique based on diffraction-angle filtering (DAF; which was proposed to effectively control wavenumber components of the FWI gradient). Our strategy first inverts the high-wavenumber reflectivity model by suppressing energy at large diffraction angles, which are necessary to compute the reflection wave paths (i.e. the rabbit-ears-shaped kernels) for low-wavenumber updates in the subsequent stage. Then, we extract low-wavenumber components due to the diving (banana-shaped kernels) and reflected waves (rabbit-ears-shaped kernels) from the gradient by suppressing energy at small diffraction angles. Our strategy is similar to reflection waveform inversion (RWI) in that it separates a given model into high- and low-wavenumber components and uses the rabbit-ears-shaped kernels for low-wavenumber updates. The main difference between our strategy and RWI is that our strategy adopts the DAF-based scale-separation technique in the space domain, which makes our algorithm of using both the banana-shaped and rabbit-ears-shaped kernels computationally attractive. By applying our two-step inversion strategy to the synthetic data for the Marmousi-II model and the real ocean-bottom cable data from the North sea, we demonstrate that our method properly reconstructs low-wavenumber structures even if initial models deviate from the true models.

In the early stage of acoustic full-waveform inversion (AFWI), it is important to exploit the long-wavelength features of the gradient and suppress its short-wavelength features to update the backg...

Full-waveform inversion (FWI), which is among the most powerful seismic data processing techniques for imaging subsurface geological structures, has a huge computational cost in proportion to the n...

Molybdenum disulfide (MoS2) is considered a promising material in energy storage systems, and is thus drawing considerable attention. However, the relatively low conductivity of bulk MoS2 has been a threat for practical applications. This study developed a simple and scalable fabrication method of few-layer MoS2 sheets embedded in a nanoporous graphene film (NGF) as a high capacitance active material. Transfer of MoS2/NGF onto a flexible substrate followed by plotter cutting produced a highly efficient micro-supercapacitor with superior flexibility, mechanical stability, and great potential for applications in wearable electronics. Notably, MoS2/NGF-based mSC revealed a high volumetric capacitance of 55 F cm−3 and 82.2% of capacitance retention after 20 000 cycles, which are superior to the reported data for solid-state micro-supercapacitors. With these performances, the flexible MoS2/NGF mSC exhibited an ultrahigh energy density of 7.64 mW h cm−3 and power density of 9.96 W cm−3 in a H3PO4 gel polymer electrolyte. The high volumetric capacitance and energy/power densities of MoS2/NGF as micro-supercapacitor electrodes are due to direct growth of ultra-thin MoS2 onto the interconnected 3D nanoporous graphene film with extended active sites and good conductivity. The MoS2/NGF mSC integrated on the skin efficiently powered a light emitting diode and strain sensors. This work suggests a meaningful way to realize film type MoS2 active materials in flexible micro-supercapacitors for wearable applications.

To compare gasless laparoscopy with conventional laparoscopy for the surgical management of postmenopausal patients.The medical records of 80 postmenopausal patients who underwent laparoscopic surgeries between February 2016 and February 2020 were reviewed. Forty patients underwent gasless laparoscopy and 40 patients underwent conventional single-port access (SPA) laparoscopy. The two groups were compared in terms of surgical outcomes.: Of 80 patients, 42 underwent adnexal surgeries and 38 underwent uterine surgeries such as total hysterectomy or myomectomy. Between the gasless SPA and conventional SPA laparoscopic groups, no significant differences were observed in terms of age, body mass index, parity or history of previous abdominal surgery. The mean retraction setup time from skin incision was 6.8 ± 1.2 min with gasless laparoscopic surgery. There was no significant difference in mean total operation times for the gasless (71.3 ± 31.4 min) and conventional (82.5 ± 36.4 min) groups. There was also no significant difference between the groups in terms of operation type, laparotomy conversion rate or duration of hospitalisation. There were no major complications in either group.Gasless laparoscopy is a safe and feasible alternative to conventional laparoscopy for postmenopausal women.

To improve the computational efficiency of reverse-time migration (RTM) for vertically transverse isotropic (VTI) media, various acoustic approximations of the elastic wave equations have been pres...

Reduced graphene oxide (rGO) composites for energy-related applications have attracted increasing attention. However, previous studies on rGOs still showed limitations because of unresolved several...

Wearable electronics is a growing field that has important applications in advanced human-integrated systems with high performance and mechanical deformability, especially foldable characteristics. Although foldable electronics such as rollable TVs (LG signature OLED R) or foldable smartphones (Samsung Galaxy Z fold/flip series) have been successfully established in the market, these devices are still powered by rigid and stiff batteries. Therefore, to realize fully wearable devices, it is necessary to develop state-of-the-art foldable batteries with high performance and safety in dynamic deformation states. In this review, we cover the recent progress in developing materials and system designs for foldable batteries. The Materials section is divided into three sections aimed at helping researchers choose suitable materials for their systems. Several foldable battery systems are discussed and the combination of innovative materials and system design that yields successful devices is considered. Furthermore, the basic analysis process of electrochemical and mechanical properties is provided as a guide for researchers interested in the evaluation of foldable battery systems. The current challenges facing the practical application of foldable batteries are briefly discussed. This review will help researchers to understand various aspects (from material preparation to battery configuration) of foldable batteries and provide a brief guideline for evaluating the performance of these batteries.

An efficient reduction method to obtain high-quality graphene sheets from mass-producible graphene oxide is highly desirable for practical applications. Here, we report an in situ deoxidation and graphitization mechanism for graphene oxide that allows for high-quality reduced graphene oxide sheets under the low temperature condition (

Reflection traveltime tomography has been used to describe subsurface velocity structures which, in practice, can be used as a background or initial model for pre‐stack depth migration or full waveform inversion. Conventional reflection traveltime tomography is performed by solving an optimization problem based on a ray‐tracing method. As a result, reflection traveltime tomography requires heavy computational efforts to carry out ray tracing and solve a large matrix equation. In addition, like most data‐domain tomography methods, reflection traveltime tomography depends on initial guesses and suffers from non‐uniqueness and uncertainty of solutions. In this research, we propose a deterministic ray‐based reflection traveltime tomography method by applying seismic interferometry. This method does not suffer from the non‐uniqueness problem and does not require a priori information on subsurface media. By adding a virtual layer (whose properties are known) on top of the real surface and applying convolution‐type interferometry, we approximately determine the stationary points (i.e., incident raypaths in the virtual layer). Then, we generate reflection points for a range of assumed velocities and estimate the velocity by considering the number of reflection points and the traveltime difference between the observed and calculated data. The reflection surface can then be recovered by using the estimated velocity. Once the first target layer is resolved, we can recover the whole media by recursively applying the same method to the lower layers. Numerical examples using surface seismic profile data for homogeneous‐layer (with a low‐velocity layer) and inhomogeneous‐layer models and real field data experiments on the Congo data set demonstrate that our method can successfully recover the velocities and depths of subsurface media without initial guesses. However, our method has some limitations for multi‐layer models because the method does not have sufficient reflection points for the deeper layers.

Ground penetrating radar (GPR) is one of the most widely used geophysical survey methods to locate cavities under roads due to its speedy exploration and high-resolution imaging. To locate underground cavities using GPR, we need to distinguish between cavity-induced reflections and other reflections, which can be achieved by examining the polarity change in reflections compared to the polarity of the transmitted signal. The polarity change can be measured from the phase shift between the target and first reflections. To estimate the phase shift in reflections, the method of computing the power spectrum difference between the original trace and background signal was proposed, but the method has a limitation for shallow reflectors. As an alternative method to avoid this limitation, we propose using only one component of the power spectrum difference, the cross-correlation between the target reflection and background signal. The cross-correlation has its maximum peak at a time lag between the target and first reflection (from the air-ground interface). Additionally, the phase at that time lag represents a phase shift between the two reflections. We compare our cross-correlation-based method with the conventional method of computing the whole power spectrum difference and investigate the feasibility of our method for distinguishing cavity-induced reflections using a 2D field data set acquired in a testbed in Sudeoksa, Korea.

Utilizing the broad-band solar spectrum for sea water desalination is a promising method that can provide fresh water without sophisticated infrastructures. However, the solar-to-vapour efficiency has been limited due to the lack of a proper design for the evaporator to deal with either a large amount of heat loss or salt accumulation. Here, these issues are addressed via two cost-effective approaches: I) a rational design of a concave shaped supporter by 3D-printing that can promote the light harvesting capacity via multiple reflections on the surface; II) the use of a double layered photoabsorber composed of a hydrophilic bottom layer of a polydopamine (PDA) coated glass fiber (GF/C) and a hydrophobic upper layer of a carbonized poly(vinyl alcohol)/polyvinylpyrrolidone (PVA/PVP) hydrogel on the supporter, which provides competitive benefit for preventing deposition of salt while quickly pumping the water. The 3D-printed solar evaporator can efficiently utilize solar energy (99%) with an evaporation rate of 1.60 kg m-2 h-1 and efficiency of 89% under 1 sun irradiation. The underlying reason for the high efficiency obtained is supported by the heat transfer mechanism. The 3D-printed solar evaporator could provide cheap drinking water in remote areas, while maintaining stable performance for a long term.

To reconstruct long-wavelength structures in full waveform inversion (FWI), the wavefield-damping and weighting techniques have been used to synthesize and emphasize low-frequency data components in frequency-domain FWI. However, these methods have some weak points. The application of wavefield-damping method on filtered data fails to synthesize reliable low-frequency data; the optimization formula obtained introducing the weighting technique is not theoretically complete, because it is not directly derived from the objective function. In this study, we address these weak points and present how to overcome them. We demonstrate that the source estimation in FWI using damped wavefields fails when the data used in the FWI process does not satisfy the causality condition. This phenomenon occurs when a non-causal filter is applied to data. We overcome this limitation by designing a causal filter. Also we modify the conventional weighting technique so that its optimization formula is directly derived from the objective function, retaining its original characteristic of emphasizing the low-frequency data components. Numerical results show that the newly designed causal filter enables to recover long-wavelength structures using low-frequency data components synthesized by damping wavefields in frequency-domain FWI, and the proposed weighting technique enhances the inversion results.

We report a three-dimensional graphene network decorated with nickel nanoparticles as a current collector to achieve outstanding performance in Ni(OH)2-based supercapacitors with excellent energy density. A cost-efficient and single-step fabrication method creates nickel-particle decorated three-dimensional graphene networks (Ni–GNs) with an excellent electrical conductivity of 107 S m−1 and a surface area of 16.4 m2 g−1 that are superior to those of carbon alternatives and commercial 3D-Ni foam, respectively. The supercapacitor in which Ni(OH)2 active materials are deposited on Ni–GNs exhibited an outstanding capacitance value of 3179 F g−1 at 10 A g−1 in a three-electrode system and 90% of capacitance retention after 10 000 cycles. Furthermore, it showed an outstanding energy density of 197.5 W h kg−1 at a power density of 815.5 W kg−1 when tested in a two-electrode system. To the best of our knowledge, our device realized the world record value of energy density with a high rate capability and good cycle stability among Ni(OH)2-based supercapacitors. The excellent electrical properties of easily synthesized Ni–GNs as the ideal current collector clearly suggest a straightforward way to achieve great performance supercapacitors with both high energy density and power density.

We have discovered a carbonized polymer film to be a reliable and durable carbon-based substrate for carbon enhanced Raman scattering (CERS). Commercially available SU8 was spin coated and carbonized (c-SU8) to yield a film optimized to have a favorable Fermi level position for efficient charge transfer, which results in a significant Raman scattering enhancement under mild measurement conditions. A highly sensitive CERS (detection limit of 10–8 M) that was uniform over a large area was achieved on a patterned c-SU8 film and the Raman signal intensity has remained constant for 2 years. This approach works not only for the CMOS-compatible c-SU8 film but for any carbonized film with the correct composition and Fermi level, as demonstrated with carbonized-PVA (poly(vinyl alcohol)) and carbonized-PVP (polyvinylpyrollidone) films. Our study certainly expands the rather narrow range of Raman-active material platforms to include robust carbon-based films readily obtained from polymer precursors. As it uses broad...

A rapid, facile, and eco-friendly electron beam (EB)-based method for the reduction of graphene oxide (GO) is demonstrated in this research. GO prepared by the well-known modified Hummer׳s method was dispersed in an ethanol/water solution, and then reduced by EB irradiation. The analytical results revealed that reduced GO (RGO) was successfully prepared by the EB irradiation of GO suspensions, and the chemical structure, thermal stability, and dispersibility of the resulting RGO depended on the absorbed dose. Noticeably, the prepared RGO exhibited an electrical conductivity of 1.50×10 −2 S/cm even at 50 kGy (5 min), which further increased up to 4.50 S/cm with an increase in the absorbed dose to 200 kGy (20 min). These results indicate that this fast and eco-friendly EB irradiation-induced reduction method can strongly support the mass production of RGO for practical applications.

We investigated that high-energy electron beam irradiation (HEEBI) performed in air at room temperature affected remarkably the properties of Al-doped ZnO (AZO) films grown on SiO 2 substrates by radio frequency magnetron sputtering techniques. Hall and photoluminescence measurements revealed that the n -type conductivity was preserved in HEEBI treated films with low dose up to 10 15 electrons/cm 2 and converted to p -type conductivity with further increase in the amount of dose. X-ray photoelectron spectroscopy confirmed the conversion of conductivity by showing that in-diffusion of O 2 from the ambient as well as out-diffusion of Zn from the films took place as a result of HEEBI treatment at high dose of 10 16 electrons/cm 2 . X-ray diffraction analysis indicated that all as-grown films were found to have compressive stress, which was enhanced by HEEBI treatment with the increase of doses. It was also found that worse crystallinity with a smaller grain size was observed in HEEBI treated films with a higher dose, which was correlated with rougher surface morphologies of films observed by an atomic force microscope.