Influence of the position and depth of pre-cutting kerfs on the rock breaking by SBM cutter

The combination of water-jet and disc-cutter rock breaking is a key technology to improve the rock breaking efficiency of the full-face shaft boring machine and achieve the mechanized development of deep resources. It is a crux problem of selecting reasonable parameters for pre-cutting kerfs. In this paper, firstly, it examined the working characteristics of rock breaking with a disc-cutter driven by a conical cutter-head. Then, based on the cohesive element method, a discrete-continuous coupled numerical model for rock breaking with a disc-cutter under pre-cutting kerfs conditions was established. Comparing the intact rock mass, the influence of different pre-cut kerfs distances and depths on the stress and rock fragmentation characteristics of the rock breaking was analyzed. The three stage characteristics of dense core formation, blocky rock slag formation, and Hertz crack propagation during rock cutting with a disc-cutter were elaborated. The asymmetric fragmentation characteristics of the rock mass and the formation mechanism of rock slag in different regions were presented. Finally, a comprehensive analysis was conducted from four aspects: the force acting on the disc cutter, the rock breaking area, the specific energy consumption for rock breaking, and the degree of rock slag crushing, and the optimal range of distance and depth values for pre-cutting kerfs was determined. The research results indicate that the pre-cutting kerfs can significantly reduce the penetration force and lateral force during the rock breaking process of the SBM cutters. Compared with intact rock masses, the peak penetration force decreased by 44.0%−10.3%. The peak lateral force decreased by 35.2%−6.5%. When the spacing and depth of pre-cut kerfs are small, it will limit the range of rock breaking by the disc-cutter, and at the same time make the fragmentation of the rock mass smaller, resulting in an increase in specific energy consumption for rock breaking. As the pre-cut depth increases, the rock breaking volume first increases and then tends to be stabilized, while the specific energy consumption first decreases and then remains unchanged. Finally, it was determined that the cutting distance was 70−90 mm, and the best rock breaking effect was achieved when the cutting distance was 60−80 mm. The rock breaking volume was doubled compared to the case without cutting, and the specific energy consumption for rock breaking decreased by 69.2%. This provides a reference for the parameter design and determination of the cutter head

Experimental Investigation of the Matching Relationship between Asphalt Particle and Reservoir Pore in Profile Control Process

Modified sulfonated asphalt particles have a bright application prospect of the profile control of thick reservoirs due to the low cost, extensive sources, and good compatibility with reservoir. Nevertheless, the matching relationship between asphalt particles and reservoir pore has seldom been investigated till now. Oversized particles always block the near-wellbore area, which causes high injection pressures, while undersized particles cannot plug large pores. We designed a core for this experiment which has a high permeability zone in front of it and many pressure measuring points. We could quantitatively assess the matching relationship by measuring the on-way resistance coefficient, residual resistance factor, and relative change of permeability of man-made cores after injecting asphalt. Experimental results indicate that asphalt particles with sizes of 0.02 mm, 0.02–0.06 mm, and 0.08–0.1 mm match with reservoir permeability of 500 mD, 1000 mD, and 2000 mD, respectively. Undersized or oversized particles can reduce the conformance control effect, and the concentration of asphalt particles in the injectant can limit their migration ability. When the concentration of asphalt particles increases to 3000 mg/L, accumulations of asphalt particles can be caused in the formation, in which a scheme with asphalt particles alternative water injection is proposed to avoid the accumulation

Neural EGFL-Like 1 Is a Downstream Regulator of Runt-Related Transcription Factor 2 in Chondrogenic Differentiation and Maturation

Recent studies indicate that neural EGFL-like 1 (Nell-1), a secretive extracellular matrix molecule, is involved in chondrogenic differentiation. Herein, we demonstrated that Nell-1 serves as a key downstream target of runt-related transcription factor 2 (Runx2), a central regulator of chondrogenesis. Unlike in osteoblast lineage cells where Nell-1 and Runx2 demonstrate mutual regulation, further studies in chondrocytes revealed that Runx2 tightly regulates the expression of Nell-1; however, Nell-1 does not alter the expression of Runx2. More important, Nell-1 administration partially restored Runx2 deficiency–induced impairment of chondrocyte differentiation and maturation in vitro, ex vivo, and in vivo. Mechanistically, although the expression of Nell-1 is highly reliant on Runx2, the prochondrogenic function of Nell-1 persisted in Runx2−/− scenarios. The biopotency of Nell-1 is independent of the nuclear import and DNA binding functions of Runx2 during chondrogenesis. Nell-1 is a key functional mediator of chondrogenesis, thus opening up new possibilities for the application of Nell-1 in cartilage regeneration. © 2017 American Society for Investigative Patholog

Genome-wide variation study and inter-tissue communication analysis unveil regulatory mechanisms of egg-laying performance in chickens

Egg-laying performance is of great economic importance in poultry, but the underlying genetic mechanisms are still elusive. In this work, we conduct a multi-omics and multi-tissue integrative study in hens with distinct egg production, to detect the hub candidate genes and construct hub molecular networks contributing to egg-laying phenotypic differences. We identifiy three hub candidate genes as egg-laying facilitators: TFPI2, which promotes the GnRH secretion in hypothalamic neuron cells; CAMK2D, which promotes the FSHβ and LHβ secretion in pituitary cells; and OSTN, which promotes granulosa cell proliferation and the synthesis of sex steroid hormones. We reveal key endocrine factors involving egg production by inter-tissue crosstalk analysis, and demonstrate that both a hepatokine, APOA4, and an adipokine, ANGPTL2, could increase egg production by inter-tissue communication with hypothalamic-pituitary-ovarian axis. Together, These results reveal the molecular mechanisms of multi-tissue coordinative regulation of chicken egg-laying performance and provide key insights to avian reproductive regulation.</p

Design of dual-material lattice structures with compression-torsion bistability

Lattice structures with bistability can maintain additional equilibrium states after external loads are removed. While conventional bistable structures typically realize compression and torsional bistabilities under compression and twisting loads, this paper introduces a new design of bistable structures that exhibit torsional bistability under uniaxial compression. The proposed structure is composed of two co-axis polygonal prisms connected by struts. Torsional bistability is achieved by opposite rotations of two co-axial polygonal prisms under compression, which result in snap-through instabilities in the connecting struts. An analytical model and numerical simulations demonstrate that dual-material design for the inclined and connecting struts is required to induce bistability. A parameter study is conducted to illustrate the effect of the volume fractions of soft material in struts and the modulus ratios between two materials on bistability characteristics. One such design is practically fabricated by multi-material 3D printing, and experiments are conducted to demonstrate the existence of the second equilibrium state. Furthermore, a lattice structure is designed by periodically arraying the unit structures, which exhibit multiple stable states due to existence a sequence of bistable states arising in a layer-by-layer manner. This compression-torsion bistability breaks the restriction on the direction of the bistable deformation and the applied load, and provides inspiration for novel functional designs in the areas of logic gates and deformation control

Unequal error protection based on objective video evaluation model

ABSTRACT Usually unequal error protection schemes mostly focus on protecting video data parameters with unequal rates or levels depending on their sensitivities to errors. This paper first proposes a novel effective and reliable objective video evaluation model based on fuzzy synthetic judgment. This model highlights a comprehensive evaluation by taking account of multiple properties of the compressed video which affect the whole video sequence, such as quality, fluency and motion information. Secondly, a novel unequal protection scheme is proposed. The protection levels are calculated according to the output of the fuzzy evaluation results. The whole coded video can be transmitted efficiently since the protection is based on the video quality evaluation. Simulation results demonstrate the advantages of the fuzzy objective video quality evaluation model, especially in comprehensive judgment of the whole video, and show the subjective quality improvement obtained by applying the proposed unequal protection approach

The Effect of Microwave Pretreatment on the Impregnation of Poplar Wood

Microwave pretreatment can increase the transverse permeability of wood. The effects of impregnation on microwave-pretreated wood with low-molecular weight phenol formaldehyde resin was investigated. The results showed that the improved transverse permeability of poplar wood that had received microwave pretreatment resulted in a positive influence on the effect of the impregnation. The maximum impregnation weight gain rate was 51.08%, with the average being approximately 40%. The average density of the specimens impregnated for 1.50 h at 0.8 MPa was 584.8 kg•m-3. During the course of the study, the resin present in the wood became distributed evenly in the vessel elements, wood fiber lumens, and intercellular spaces. Finally, the chromogenic reaction area accounted for 78.11% of the total area in the fluorescent staining diagram of the cross section

Design of hierarchical microstructures with isotropic elastic stiffness

Elastic stiffness is one of the most fundamental properties of materials. Design of the microstructures with isotropic stiffness has been an attractive area in the field of metamaterials for over three decades. Despite many classes of isotropic microstructures, exploring novel isotropic microstructures based on innovative mechanics principles has attracted great and continuing interests. This paper presents a novel family of isotropic hierarchical microstructures (Iso-HMs). These hierarchical microstructures are modeled by replacing the solid parts of prescribed single-level microstructures with arrayed microstructures in the second level, where the key task is to identify the correct geometries of the second-level microstructures by conducting parameter space exploring. These Iso-HMs realize isotropic stiffness based on synergistic deformations of the members in the two levels, which is essentially different from existing isotropic microstructures replying on deformations of the members in a single level. Two categories of Iso-HMs with rectangular holes and Vidergauze-type struts are designed. Considering the large size difference in the designed Iso-HMs, additive manufacturing becomes a unique technique for manufacturing the designed Iso-HMs, where the size ratio between the 3D-printed specimens and the minimal features reaches 400:1. Both numerical and experimental results validate the isotropic stiffness of the designed Iso-HMs. Furthermore, the results of a microstructural instability analysis show that the designed Iso-HMs can gain improved buckling strength up to a hundred times higher than their single-level counterparts. The hierarchical design provides a new way to identify novel functional microstructures for applications, and the hierarchical configurations expand the space of the already-known families of isotropic microstructures