Localized water reverberation phases and its impact on back-projection images

Coherent radiators imaged by backprojections (BP) are commonly interpreted as part of the rupture process. Nevertheless, artifacts introduced by structure related phases are rarely discriminated from the rupture process. In this study, we use a calibration event to discriminate between rupture and structure effects. We reexamine the waveforms and BP images of the 2012 M_w 7.2 Indian Ocean earthquake and a calibration event (M_w 6.2). The P wave codas of both events present similar shape with characteristic period of approximately 10 s, which are backprojected as coherent radiators near the trench. S wave BP does not image energy radiation near the trench. We interpret those coda waves as localized water reverberation phases excited near the trench. We perform a 2-D waveform modeling using realistic bathymetry model and find that the steep near-trench bathymetry traps the acoustic water waves forming localized reverberation phases. These waves can be imaged as coherent near-trench radiators with similar features as that in the observations. We present a set of methodologies to discriminate between the rupture and propagation effects in BP images, which can serve as a criterion of subevent identification

Comparative Study on Dynamic Mechanical Properties and Energy Dissipation of Rocks under Impact Loads

Geological conditions are often complex during rock engineering construction (such as blasting and drilling) and usually involve rocks of several or multiple lithologies. However, comparative studies on the dynamic mechanical response of rocks of different lithologies are relatively few. To study differences in dynamic mechanical properties and energy dissipation of rocks of different lithologies, three kinds of rock that are common in rock engineering and have large differences in wave impedance were selected: red sandstone, gray sandstone, and granite. Samples of these three rocks were subjected to impact compression tests at different impact speeds, and the rock fragments after impact compression were screened to quantify the degree of fragmentation. The characteristics of stress wave propagation, dynamic stress-strain relationships, degree of fragmentation, and energy dissipation laws of the three rock types were compared and studied. The results show the following: (1) affected by the wave impedance matching relationship, the reflected waves, strain rates, and reflected energy of the three kinds of rock showed significant differences under the same incident stress wave. (2) The dynamic mechanical characteristics and energy dissipation laws of the rocks all had obvious strain rate effects, but the dynamic uniaxial compressive strength and energy dissipation density of the three rock types had different sensitivities to the strain rate. (3) The change trend of the energy utilization efficiency of the gray sandstone with incident energy was different from that of the red sandstone and granite; there was no obvious extreme point in the incident energy range. The three kinds of rock required different incident energies to reach maximum energy utilization efficiency. (4) The equivalent average fragment size of the three rock types decreased as a function of power with increasing impact velocity and energy dissipation density. (5) Under the same incident wave, although the reflection energy, transmission energy, and degree of fragmentation of the three kinds of rock showed significant differences, the differences in dissipation energy were small

Experiments and numerical simulations on dynamic crack behavior at the interface of layered brittle material

Crack behavior at the interface between two materials is the core problem of layered material fracturing. In this paper, first, experimental tests were conducted on layered material using a drop weight test system following the caustics method. The layered material was made of poly (methyl methacrylate) (PMMA) and epoxy resin bonded with Loctite-330 at two inclination angles (30 degrees and 60 degrees). A corresponding numerical simulation was carried out using continuum-discontinuum element methods. Crack propagation is found to mainly occur in mode I in the PMMA and epoxy resin but follows a mixed cracking mode at the interface. The fracture parameters of the crack tip in the layered materials changed substantially owing to the existence and change of the interface structure. After the crack enters the interface, the crack propagation speed increases significantly. Higher crack dip angles are associated with greater crack propagation speed increases after entering the interface. The simulation results indicate that the interface strength properties affect crack behavior at the interface. This effect also varies as a function of interface inclination and impact velocity

The mechanism of directional fracture controlled blasting and its application

Synthetically using methods including high speed laser tattoo shadow, super dynamic strain testing technology, digital laser dynamic caustics experimental system, this paper studies the cutting seam cartridge explosion wave propagation mechanism, multi-angle observation of the detonation wave propagation process, clearly observed explosion stress wave and explosive gas separating phenomenon.Air interval cutting seam cartridge blasting cement mortar model testing was carried out.The spatial distribution law of stress was summarized.The cutting seam cartridge decoupling blasting explosive raw crack dynamic fracture effect was analyzed.The different charge structures influence on critical raw crack extension was compared.The best decoupling coefficient is 1.67 with directional fracture controlled blasting effect was determined.It studied double hole grooving method, initiation at the same time, through the crack between the two hole and the hole of the lateral dynamic behavior of crack propagation.Finally the cutting seam cartridge directional fracture controlled blasting technology was applied in shaft and tunnel blasting construction.The directional fracture of cutting seam cartridge blasting effect was verified.This research will provide experimental basis and theoretical guidance for engineering practice

LncRNA ADAMTS9-AS1 knockdown restricts cell proliferation and EMT in non-small cell lung cancer

A recent bioinformatics analysis identified long non‐coding RNA antisense 1 ADAMTS9-AS1 as an independent prognostic marker in several tumors, including prostate cancer and bladder cancer. Nevertheless, the prognostic value and functional role of ADAMTS9-AS1 in non-small cell lung cancer (NSCLC) remain elusive. Here, we first found that the expression of ADAMTS9-AS1 was significantly upregulated in NSCLC tissues compared with adjacent normal tissues using quantitative real time PCR analysis. Clinically, we observed that ADAMTS9-AS1 expression was associated with TNM stage, lymph node metastasis and poor prognosis in NSCLC patients. By performing lossof-function assay in A549 and 95D cells, our in vitro experiments further showed that knockdown of ADAMTS9-AS1 remarkedly suppressed cell proliferation, caused cell cycle G0/G1 arrest and apoptosis, and inhibited cell migration and invasion in NSCLC cells using CCK-8, colony formation, flow cytometry and transwell assays. Moreover, we found that ADAMTS9-AS1 knockdown downregulated the expression of CDK4, N-cadherin, Vimentin, but upregulated the expression of Bad and E-cadherin. In summary, our results revealed that ADAMTS9-AS1 may serve as a potential therapeutic target for the treatment of patients with NSCL

Value-Consistent Representation Learning for Data-Efficient Reinforcement Learning

Deep reinforcement learning (RL) algorithms suffer severe performance degradation when the interaction data is scarce, which limits their real-world application. Recently, visual representation learning has been shown to be effective and promising for boosting sample efficiency in RL. These methods usually rely on contrastive learning and data augmentation to train a transition model, which is different from how the model is used in RL---performing value-based planning. Accordingly, the learned representation by these visual methods may be good for recognition but not optimal for estimating state value and solving the decision problem. To address this issue, we propose a novel method, called value-consistent representation learning (VCR), to learn representations that are directly related to decision-making. More specifically, VCR trains a model to predict the future state (also referred to as the "imagined state'') based on the current one and a sequence of actions. Instead of aligning this imagined state with a real state returned by the environment, VCR applies a Q value head on both of the states and obtains two distributions of action values. Then a distance is computed and minimized to force the imagined state to produce a similar action value prediction as that by the real state. We develop two implementations of the above idea for the discrete and continuous action spaces respectively. We conduct experiments on Atari 100k and DeepMind Control Suite benchmarks to validate their effectiveness for improving sample efficiency. It has been demonstrated that our methods achieve new state-of-the-art performance for search-free RL algorithms

Coupling of material point and continuum discontinuum element methods for simulating blast-induced fractures in rock

A rock blasting simulation method is proposed that couples the material point method (MPM) and continuum discontinuum element method (CDEM). Blast-induced rock fractures are captured by the CDEM using normal and shear springs, and the explosive detonation is simulated by the MPM with a Jones-Wilkins-Lee equation of state. A particle-surface/edge contact method is introduced into the MPM-CDEM to calculate the interaction between the detonation products and rock medium. Three numerical examples are presented to verify the effectiveness of the proposed method. The fracture degree is represented as the ratio of the number of fractured springs to the total number of springs, and is used to analyze the evolution of shear and tension cracks under blasting. The simulation results show that the proposed numerical method well simulates blast-induced rock fractures and considers both progressive rock fracturing and the real explosive detonation. In particular, the expansion of the detonation gas, crushed zone around the blasthole, radial cracks, and effects of pre-existing stress on the blast-induced fractures are all successfully simulated

Numerical investigation of the effect of holes on dynamic fracturing in multi-flawed granite

A numerical study is conducted using the improved continuum-based discrete element method (CDEM) to investigate the effect of holes on the dynamic fracturing of multi-flawed rocks. The specimen geometries contain a perpendicular crack-like flaw, a hole-like flaw, and an inclined crack-like flaw. A fracture model is implemented into the improved CDEM that combines the nonlinear pressure-dependent shear strength and tensile strength of rocks. The digital image correlation method combined with ultra-high-speed photography is applied in a split Hopkinson pressure bar system to verify the accuracy of the proposed model. The experimental results show that the improved CDEM accurately reproduces dynamic crack behavior in rocks. The simulation results show that hole-like flaws significantly affect crack behavior compared with the two investigated crack-like flaws. However, this effect gradually weakens with increasing loading stresses. This study provides important insight into the dynamic fracturing of multi-flawed rocks

Mapping Aquaculture Areas with Multi-Source Spectral and Texture Features: A Case Study in the Pearl River Basin (Guangdong), China

Aquaculture has grown rapidly in the field of food industry in recent years; however, it brought many environmental problems, such as water pollution and reclamations of lakes and coastal wetland areas. Thus, the evaluation and management of aquaculture industry are needed, in which accurate aquaculture mapping is an essential prerequisite. Due to the difference between inland and marine aquaculture areas and the difficulty in processing large amounts of remote sensing images, the accurate mapping of different aquaculture types is still challenging. In this study, a novel approach based on multi-source spectral and texture features was proposed to map simultaneously inland and marine aquaculture areas. Time series optical Sentinel-2 images were first employed to derive spectral indices for obtaining texture features. The backscattering and texture features derived from the synthetic aperture radar (SAR) images of Sentinel-1A were then used to distinguish aquaculture areas from other geographical entities. Finally, a supervised Random Forest classifier was applied for large scale aquaculture area mapping. To address the low efficiency in processing large amounts of remote sensing images, the proposed approach was implemented on the Google Earth Engine (GEE) platform. A case study in the Pearl River Basin (Guangdong Province) of China showed that the proposed approach obtained aquaculture map with an overall accuracy of 89.5%, and the implementation of proposed approach on GEE platform greatly improved the efficiency for large scale aquaculture area mapping. The derived aquaculture map may support decision-making services for the sustainable development of aquaculture areas and ecological protection in the study area, and the proposed approach holds great potential for mapping aquacultures on both national and global scales