Design optimization and application of bolt-shotcrete support for East Tianshan tunnel project in China

Bolt-shotcrete support is a form of support with low cost, convenient for construction, uniform structural stress, which is widely used in international tunnel engineering. In this paper, the 2# inclined shaft of East Tianshan tunnel in China is taken as the research object. The stress characteristics of composite lining support and bolt-shotcrete support are analyzed and compared by FLAC3D software, and the bolt-shotcrete support scheme suitable for this project is put forward. Based on the principle of orthogonal experiment, the most reasonable shotcrete material proportion is selected, and structural stress and displacement monitoring is carried out during the construction stage of typical sections. The results show that: (1) in FLAC3D simulation calculation, the interface element is applied between different layers, which can simulate the interaction between different layers of lining structure and reflect the mechanical characteristics and displacement characteristics of the interface between layers; (2) from the aspect of mechanical performance, single layer lining which can meet the requirements of tunnel support with thinner structural thickness and has higher economic efficiency, is better than composite lining; (3) the field monitoring results show that the deformation of bolt-shotcrete support structure is small, the structural stress meets the material performance requirements, and there is no structural damage during the construction of the test section; (4) during the implementation of bolt-shotcrete support, the cost of support per meter is reduced by 36.78%, and the average excavation efficiency is increased by 38.9%, which verifies the applicability and advantages of the optimization scheme. The research results in this paper can provide reference for the follow-up construction of tunnels and similar projects. Please click Additional Files below to see the full abstract

Preparation, characterization and application of functional surfaces based on porous polymethacrylates

Porous polymethacrylates have numerous important applications in different research and industrial fields. These materials have been used as stationary phases for separation and catalysis, as substrates for thin layer chromatography, as materials for solid-phase extraction or filtration, or for making valves in microfluidic devices. The main advantage of porous polymethacrylates is that their physical and chemical properties, such as porosity, pore and polymer globule size, stiffness, hydrophobicity or hydrophilicity, as well as surface functional groups can be conveniently controlled by adjusting the composition of the polymerization mixtures. Porous polymethacrylate can be also functionalized using available surface modification strategies. This unique ability to control properties of porous polymethacrylates makes them suitable for the design and synthesis of novel functional materials. Surprisingly, most of the applications of porous polymethacrylates have been limited to their use inside columns, capillaries or microfluidic channels and their applications as open surfaces remained to a great extent unexplored. The goals of my PhD thesis were to: (1) develop methods for the preparation of (bio)functional porous polymethacrylate surfaces with well-defined surface properties; (2) characterize produced surfaces; (3) explore their unique properties in different biological applications. Surfaces with gradient properties have been widely used in many cell-surface interaction studies because these gradient surfaces offer the possibility to avoid the difficulties associated with the one-sample-for-one-measurement approach as well as the problems with sample variations. However, up to now, there are only a few methods for the preparation of surfaces with gradient properties. Taking advantage of the tunable porous properties of polymethacrylates, porous poly(butyl methacrylate-co-ethylene dimethacrylate) (BMA-EDMA) surfaces with gradient surface morphologies were prepared using a PDMS microfluidic chip designed and produced for this study. The produced BMA-EDMA surface possessed a gradient polymer globule size ranging from ~ 0.1 µm to ~ 0.5 µm. The surface with the globule size gradient in this range is useful for cell studies such as investigation of the effect of surface morphology on cell behavior. Porous polymethacrylate surfaces with a gradient in density of functional groups were also prepared via photografting by gradually varying the UV dosage along one direction on the surface during surface modification. The formation of the gradient was confirmed with X-ray photoelectron spectroscopy and water contact angle measurements. To show the potential of using the surface with a gradient density of functional groups, the behavior of human fibrosarcoma HT-1080 cells was studied on the surface. Recently, bio-inspired slippery liquid infused porous surfaces have attracted much attention due to their unique liquid repellent and self-cleaning properties. In this thesis, stable slippery surfaces were prepared by infusing the porous BMA-EDMA surface with water immiscible hydrophobic poly(hexafluoropropylene oxide) or perfluorotripentylamine. The antibacterial and anti-marine fouling properties of the slippery BMA-EDMA surfaces were carefully investigated. Our results demonstrated that the slippery BMA-EDMA surfaces had good antibacterial and anti-marine fouling properties. However, the results also revealed that the antibacterial property of the slippery BMA-EDMA surface was bacterial strain dependent. In addition, Ulva sporelings (young plants) were able to firmly attach to the slippery surface although the surface is able to resist Ulva spore adhesion. The ability to transform a superhydrophobic surface to a superhydrophilic one is essential for many applications such as creating superhydrophobic-superhydrophilic micropatterns or microarrays. Most of the existing methods for this transformation are time consuming or require harsh conditions. In this thesis, a new facile method to transform the superhydrophobic BMA-EDMA surface to a superhydrophilic one was developed. This method is based on the physisorption of an amphiphilic phospholipid on the hydrophobic surface of porous BMA-EDMA through hydrophobic-hydrophobic interactions. Using this method, superhydrophobic-superhydrophilic micropatterns could be fabricated simply by printing the phospholipid “ink” on the superhydrophobic BMA-EDMA surface with a contact printer

Tailoring the Spectra of White Organic Light-Emitting Devices by Trap Effect of a Concentration-Insensitive Dopant

Highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by using a novel iridium complex, bis[2-(3′,5′-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,C2′]iridium(III) (acetylacetonate) [(tbpbt)2Ir(acac)], as the emitter. With a wide doping ratio ranging from 15 wt% to 25 wt%, the PhOLEDs maintained a comparable high performance, indicating concentration-insensitive property of the (tbpbt)2Ir(acac). On the basis of the unique characteristic of concentration insensitivity, the application of this phosphor was explored by fabricating white organic light-emitting devices (WOLEDs) with altered doping ratio, indicating that trap effect of (tbpbt)2Ir(acac) could effectively tailor WOLEDs spectra. Typically, a high-power efficiency, current efficiency, and external quantum efficiency of 30.0 lm/W, 38.8 cd/A, 18.1%, were achieved by 20 wt% doped WOLEDs

Comparison of Concentration Transport Approach and MP-PIC Method for Simulating Proppant Transport Process

In this work, proppant transport process is studied based on two popular numerical methods: multiphase particle-in-cell method (MP-PIC) and concentration transport method. Derivations of governing equations in these two frameworks are reviewed, and then similarities and differences between these two methods are fully discussed. Several cases are designed to study the particle settling and conveying processes at different fluid Reynolds number. Simulation results indicate that two physical mechanisms become significant in the high Reynolds number cases, which leads to big differences between the simulation results of the two methods. One is the gravity convection effect in the early stage and the other is the particle packing, which determines the shape of sandbank. Above all, the MP-PIC method performs better than the concentration transport approach because more physical mechanisms are considered in the former framework. Besides, assumptions of ignoring unsteady terms and transient terms for the fluid governing equations in the concentration transport approach are only reasonable when Reynolds number is smaller than 100

Learning a More Continuous Zero Level Set in Unsigned Distance Fields through Level Set Projection

Latest methods represent shapes with open surfaces using unsigned distance functions (UDFs). They train neural networks to learn UDFs and reconstruct surfaces with the gradients around the zero level set of the UDF. However, the differential networks struggle from learning the zero level set where the UDF is not differentiable, which leads to large errors on unsigned distances and gradients around the zero level set, resulting in highly fragmented and discontinuous surfaces. To resolve this problem, we propose to learn a more continuous zero level set in UDFs with level set projections. Our insight is to guide the learning of zero level set using the rest non-zero level sets via a projection procedure. Our idea is inspired from the observations that the non-zero level sets are much smoother and more continuous than the zero level set. We pull the non-zero level sets onto the zero level set with gradient constraints which align gradients over different level sets and correct unsigned distance errors on the zero level set, leading to a smoother and more continuous unsigned distance field. We conduct comprehensive experiments in surface reconstruction for point clouds, real scans or depth maps, and further explore the performance in unsupervised point cloud upsampling and unsupervised point normal estimation with the learned UDF, which demonstrate our non-trivial improvements over the state-of-the-art methods. Code is available at https://github.com/junshengzhou/LevelSetUDF .Comment: To appear at ICCV2023. Code is available at https://github.com/junshengzhou/LevelSetUD

Solitude profiles and psychological adjustment in Chinese late adolescence: a person-centered research

Objectives: From the perspective of person-centered research, the present study aimed to identify the potential profiles of solitude among late adolescents based on their solitary behavior, motivation, attitude, and time alone. In addition, to echo the paradox of solitude, we further explored the links between solitude profiles and adjustment outcomes.Methods: The participants of the study were 355 late adolescents (56.34% female, M age = 19.71 years old) at three universities in Shanghai, China. Measures of solitary behavior, autonomous motivation for solitude, attitude toward being alone, and time spent alone were collected using adolescents' self-report assessments. The UCLA Loneliness Scale, the Beck Depression Inventory, and the Basic Psychological Needs Scales were measured as indices of adjustment.Results: Latent profile analysis revealed four distinct groups: absence of the aloneness group (21.13%), the positive motivational solitude group (29.01%), the negative motivational solitude group (38.03%), and the activity-oriented solitude group (11.83%). Differences emerged among these four groups in terms of loneliness, depressive symptoms, and basic needs satisfaction, with adolescents in the negative motivational solitude group facing the most risk of psychological maladjustment.Conclusion: Findings revealed the possible heterogeneous nature of solitude among Chinese late adolescents and provided a theoretical basis for further understanding of adolescents' solitary state