Forward prediction for tunnel geology and classification of surrounding rock based on seismic wave velocity layered tomography

Excavation under complex geological conditions requires effective and accurate geological forward-prospecting to detect the unfavorable geological structure and estimate the classification of surrounding rock in front of the tunnel face. In this work, a forward-prediction method for tunnel geology and classification of surrounding rock is developed based on seismic wave velocity layered tomography. In particular, for the problem of strong multi-solution of wave velocity inversion caused by few ray paths in the narrow space of the tunnel, a layered inversion based on regularization is proposed. By reducing the inversion area of each iteration step and applying straight-line interface assumption, the convergence and accuracy of wave velocity inversion are effectively improved. Furthermore, a surrounding rock classification network based on autoencoder is constructed. The mapping relationship between wave velocity and classification of surrounding rock is established with density, Poisson's ratio and elastic modulus as links. Two numerical examples with geological conditions similar to that in the field tunnel and a field case study in an urban subway tunnel verify the potential of the proposed method for practical application

Temperature segregation of warm mix asphalt pavement: Laboratory and field evaluations

© 2017 Elsevier Ltd Temperature segregation refers to as different mixture cooling areas during construction in asphalt pavements. The objective of this study is to evaluate the effect of temperature segregation on warm mix asphalt (WMA) with laboratory and field tests. The performance of WMA compacted at four various temperatures was evaluated in the laboratory. The temperatures were measured during construction in the field sections with infrared thermography and plug-in thermometers. The pavement quality indicator (PQI) was applied to measure the density and the air void content at 216 testing locations the day after construction. In addition, field cores were collected to verify some of the PQI results. The test results showed that temperature segregation of WMA had a remarkable effect on the aggregate structure, density, water stability, high temperature stability, low temperature cracking and tensile strength. The reason for temperature segregation and related preventive measures are recommended at the same time. Based on the study, the preliminary temperature segregation criteria are recommended with the consideration of the field measurement. In application, the temperature segregation of a typical gradation with a nominal maximum aggregate size of 19 mm, referred to as AC-20 WMA, was suggested to be divided into four levels in view of the air void content: no segregation, low-level segregation, medium-level segregation and high-level segregation. The corresponding temperature differences were \u3c 3 °C, 3–8 °C, 8–18 °C and \u3e 18 °C, respectively

Analysis of the Carreau Model Mixed Mechanism with a Stir Shaft in Color FDM Printing

Conventionally, fused deposition modeling (FDM) 3D printing allows for multiple color printing, but it is limited to only various monochromatic colors. Consequently, the effect of progressive color transition cannot be reflected. To produce the progressive 3-D color printing effect, the only solution is to implement stereolithography technology, which is particularly expensive. Therefore, the aim of this paper is to develop a color mixing mechanism to be incorporated into an FDM 3D printer, which is relatively inexpensive. The underlying idea is to pre-mix the color so that the FDM 3D printer can produce a progressive color printing effect. Three conceptual color mixing mechanisms are designed, i.e., a triangular stirring shaft, a rectangular spoiler stirring shaft, and a spiral blade stirring shaft. The mixing process is modeled based on the non-Newtonian fluid theory, in which the Carreau model is used to simulate the motion of pseudoplastic fluids in FDM 3D printing under forced mixing. The resulting mixing ratio produced by all the designs is computed, which inspires the integrated design of rectangular spoiler stirring shaft and the spiral blade string shaft. Subsequently, the axial velocity of the mixed-color fluid, which increases from inlet to outlet, is verified. The integrated design is then fabricated and incorporated into the FDM 3D printer, and the progressive color printing effect is practically demonstrated

Isolation and Identification of Volatile Substances with Attractive Effects on <i>Wohlfahrtia magnifica</i> from Vagina of Bactrian Camel

Vaginal myiasis is one of the most serious parasitic diseases in Bactrian camels. At present, there are no reports on biological control measures of the disease. In this paper, the metabolomic analysis of vaginal secretions from susceptible and non-susceptible camels was performed by ACQUITY UPLC H-Class Ultra Performance Liquid Chromatograph. The results matched in 140 vaginal compounds. Methylheptenone, 1-octen-3-ol, and propyl butyrate and their mixtures were selected for gas chromatography-electroantennography (GC-EAD), electroantennography (EAG), behavioral experiments and trapping experiments of Wohlfahrtia magnifica (W. magnifica). Results showed that the W. magnifica had EAG responses to the three compounds, respectively. The EAG responses of female flies to different concentrations of methylheptenone were significantly different, but to the others had no significant difference, and there was no significant difference in the same compounds between the different sexes. Behavioral and trapping experiments showed that methylheptenone and 1-octen-3-ol have significant attraction to W. magnifica, but there was no significant difference to propyl butyrate. When methylheptenone and 1-octen-3-ol were mixed in different proportions, it was found that a mixture at the ratio of 1:1 and 0.5:1 had extremely significant and significant attraction, respectively, to both male and female W. magnifica. The study showed that, except for propyl butyrate, the higher the concentrations of the other two compounds, the stronger the attractivity to the W. magnifica, and a mixture at the ratio of 1:1 could enhance the attractivity to the W. magnifica

Frequency Domain Full Waveform Inversion Method of Acquiring Rock Wave Velocity in Front of Tunnels

Ahead geological prospecting, which can estimate adverse geology ahead of the tunnel face, is necessary in the process of tunnel construction. Due to its long detection range and good recognition effect on the interface, the seismic method is widely used in tunnel ahead prospecting. However, the observation space in tunnels is quite narrow compared to ground seismic prospecting, which leads to some problems in the acquisition of wave velocity, including: the velocity of the direct wave is used to replace the wave velocity of the forward rock approximately; the arrival time information of seismic waves is the main factor in time-travel inversion or the tomography method, which is sufficient to provide a simple model rather than deal with complex geological conditions. In view of the above problems, the frequency domain full waveform inversion method in ground prospecting is introduced to tunnel seismic prospecting. In addition, the optimized difference format is given according to the particularity of the tunnel environment. In this method, the kinematics and dynamics of the seismic wavefield are fully used to obtain more accurate wave velocity results. Simultaneously, forward modeling and inversion simulations on tunnel samples with typical adverse geological bodies are given here, which verified the validity and reliability of the proposed method

Effects of the Surface Charge of Graphene Oxide Derivatives on Ocular Compatibility

The incorporation of functional groups endows graphene oxide (GO) with different surface charges, which plays important roles in biological interactions with cells. However, the effect of surface charge of GO derivatives on ocular biocompatibility has not been fully elucidated. Previously, we found that positively, negatively and neutrally charged PEGylated GO (PEG-GO) nanosheets exerted similar effect on the viability of ocular cells. In this work, we performed in vitro and in vivo studies to comprehensively study the effect of surface charge of PEG-GO on ocular compatibility. The in vitro results showed that the cellular uptake efficacy of negatively charged PEG-GO nanosheets was significantly decreased compared with positively charged and neutrally charged analogs. However, three kinds of PEG-GO nanosheets produced similar amounts of intracellular reactive oxygen species and showed similar influence on mitochondrial membrane potential. By analysis of global gene expression profiles, we found that the correlation coefficients between three kinds of PEG-GO-treated cells were more than 0.98. Furthermore, in vivo results showed that all these PEG-GO nanosheets had no significant toxicity to ocular structure and function. Taken together, our work suggested that surface charge of PEG-GO exerted negligible effect on its ocular compatibility, except for the cellular uptake. Our work is conducive to understanding the relationship between surface charge and biocompatibility of GO derivatives

Core-shell Au@PtIr nanowires with dendritic alloy shells as efficient bifunctional catalysts toward methanol oxidation and hydrogen evolution reactions

Nanocatalysts with combination of unique morphologies and synergistic interactions have a potential to enhance electrocatalytic ability related to the reactions in fuel cells. Here, we show a wet-chemistry-based synthesis of dendritic Au@PtIr nanowires (NWs) with core-shell constructions regarding Te NWs as sacrificial templates for methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER). Regarding the synthesis of Au@PtIr NWs, Au NWs are firstly obtained through galvanic replacement with Te templates, followed by growth of alloy PtIr shells in subsequent seed-mediated growth. The as synthesized core-shell Au@PtIr nanowires combine the advantage of one-dimensional (1D) dendritic feature that facilitate fast electron transport and provide more interfaces and interstices between catalytic active sites and electrolyte, with the synergistic interactions in alloy shells. Consequently, the as-prepared Au@PtIr NWs show good catalytic properties in MOR and HER in terms of higher activity, larger electrochemically active surface areas (ECSAs) and better anti-toxicity than commercial Pt/C. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Precise Gene Modification Mediated by TALEN and Single-Stranded Oligodeoxynucleotides in Human Cells

<div><p>The development of human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) facilitates <i>in vitro</i> studies of human disease mechanisms, speeds up the process of drug screening, and raises the feasibility of using cell replacement therapy in clinics. However, the study of genotype-phenotype relationships in ESCs or iPSCs is hampered by the low efficiency of site-specific gene editing. Transcription activator-like effector nucleases (TALENs) spurred interest due to the ease of assembly, high efficiency and faithful gene targeting. In this study, we optimized the TALEN design to maximize its genomic cutting efficiency. We showed that using optimized TALENs in conjunction with single-strand oligodeoxynucleotide (ssODN) allowed efficient gene editing in human cells. Gene mutations and gene deletions for up to 7.8 kb can be accomplished at high efficiencies. We established human tumor cell lines and H9 ESC lines with homozygous deletion of the microRNA-21 (miR-21) gene and miR-9-2 gene. These cell lines provide a robust platform to dissect the roles these genes play during cell differentiation and tumorigenesis. We also observed that the endogenous homologous chromosome can serve as a donor template for gene editing. Overall, our studies demonstrate the versatility of using ssODN and TALEN to establish genetically modified cells for research and therapeutic application.</p></div