Experimental and theoretical investigation on mechanisms performance of the rock-coal-bolt(RCB)composite system

For coal mines,rock,coal,and rock bolt are the critical constituent materials for surrounding rock in the underground engineering.The stability of the“rock-coal-bolt”(RCB)composite system is affected by the structure and fracture of the coal-rock mass.More rock bolts installed on the rock,more complex condition of the engineering stress environment will be(tensile-shear composite stress is principal).In this paper,experimental analysis and theoretical verification were performed on the RCB composite system with different angles.The results revealed that the failure of the rock-coal(RC)composite specimen was caused by tensile and shear cracks.After anchoring,the reinforcement body formed inside the composite system limits the area where the crack could occur in the specimen.Specifically,shearing damage occurred only around the bolt,and the stress-strain curve presented a better post-peak mechanical property.The mechanical mechanism of the bolt under the combined action of tension and shear stress was analyzed.Additionally,a rock-coal-bolt tensile-shear mechanical(RCBTSM)model was established.The relationship(similar to the exponential function)between the bolt tensile-shear stress and the angle was obtained.Moreover,the influences of the dilatancy angle and bolt diameter of the RCB composite system were also considered and analyzed.Most of the bolts are subjected to the tensile-shearing action in the post-peak stage.The implications of these results for engineering practice indicated that the bolts of the RCB composite system should be prevented from entering the limit shearing state early.

Field investigations of high stress soft surrounding rocks and deformation control

Field investigations of high stress soft rock deformations show that the high stress soft rock roadway can slide with large deformation. Severe extrusion and floor heave can also be subsequently observed. The supported roadway can be locally damaged or completely fail, where the floor has a large deformation and/or is seriously damaged. The factors inducing large deformation of surrounding rocks in deep roadway are rock strengths, structure face cutting types, stress states, stress release, support patterns, and construction methods. Based on the deformation characteristics of high stress soft rock roadway, a comprehensive support scheme is proposed. The overall support technology of＂step-by-step and joint, hierarchical reinforcement＂for roadway is presented, and the anchor cable and bolt parameters to check the design methods are also given. Finally, the proposed comprehensive support method＂bolt t metal mesh t U-steel arch t shortcrete t grouting and cable＂ is used in the extension section of east main haulage roadway at ？850 m level of Qujiang coal mine. The 173-day monitoring results show that the average convergence of sidewalls reaches 208 mm, and the average relative convergence of roof and floor reaches 448 mm, suggesting that this kind of support technology for controlling large deformation of high stress soft surrounding rock roadway is effective.

混合体系:一种改善水系钾离子全电池能量密度和稳定性的有效方式

水系钾基电池(APBs)因具有高安全性和环境友好的性质而被广泛研究.然而,由于电极材料和工作机制的限制,APBs在倍率性能和能量密度方面需要进一步提高,以满足发展需求.针对上述问题,我们首次成功设计并组装了以Z n金属作为阳极,K1.9 2C u0.6 2M n0.3 8-[Fe(CN)6]0.968·□0.0 3 2·H_(2)O0.35作为阴极,2 mol L-1Zn(SO_(3)CF3)2+12 mol L-1KSO_(3)CF3作为电解液的水系钾基电池.这种混合离子体系的设计优点是:(i)选择金属锌作为阳极,提高了APBs的工作电位;(ii)双阳离子储存机制缩短了离子传输路径;(ⅲ)来自双阳离子电解质的K+通过静电屏蔽作用抑制了锌枝晶的生长.因此,组装后的全电池具有1.75 V的高工作电位,并具有优异的倍率性能(在10,000 mA g-1的电流密度下,保持原有容量的83.3%).此外,通过理论相场模拟和综合表征充分揭示了原位静电屏蔽效应,显著抑制了锌阳极的枝晶生长,提高了全电池稳定性.混合离子电池的结构设计为高性能APBs的发展提供了思路.

Micro-nanofiber composite biomimetic conduits promote long-gap peripheral nerve regeneration in canine models

Peripheral nerve injuries may result in severe long-gap interruptions that are challenging to repair.Autografting is the gold standard surgical approach for repairing long-gap nerve injuries but can result in prominent donor-site complications.Instead,imitating the native neural microarchitecture using synthetic conduits is expected to offer an alternative strategy for improving nerve regeneration.Here,we designed nerve conduits composed of high-resolution anisotropic microfiber grid-cordes with randomly organized nanofiber sheaths to interrogate the positive effects of these biomimetic structures on peripheral nerve regeneration.Anisotropic microfiber-grids demonstrated the capacity to directionally guide Schwann cells and neurites.Nanofiber sheaths conveyed adequate elasticity and permeability,whilst exhibiting a barrier function against the infiltration of fibroblasts.We then used the composite nerve conduits bridge 30-mm long sciatic nerve defects in canine models.At 12 months post-implant,the morphometric and histological recovery,gait recovery,electrophysiological function,and degree of muscle atrophy were assessed.The newly regenerated nerve tissue that formed within the composite nerve conduits showed restored neurological functions that were superior compared to sheaths-only scaffolds and Neurolac nerve conduit controls.Our findings demonstrate the feasibility of using synthetic biophysical cues to effectively bridge long-gap peripheral nerve injuries and indicates the promising clinical application prospects of biomimetic composite nerve conduits.

A batch microfabrication of a self-cleaning,ultradurable electrochemical sensor employing a BDD film for the online monitoring of free chlorine in tap water

Free chlorine is one of the key water quality parameters in tap water.However,a free chlorine sensor with the characteristics of batch processing,durability,antibiofouling/antiorganic passivation and in situ monitoring of free chlorine in tap water continues to be a challenging issue.In this paper,a novel silicon-based electrochemical sensor for free chlorine that can self-clean and be mass produced via microfabrication technique/MEMS(Micro-Electro-Mechanical System)is proposed.A liquid-conjugated Ag/AgCI reference electrode is fabricated,and electrochemically stable BDD/Pt is employed as the working/counter electrode to verify the effectiveness of the as-fabricated sensor for free chlorine detection.The sensor demonstrates an acceptable limit of detection(0.056 mg/L)and desirable linearity(R^(2)=0.998).Particularly,at a potential of+2.5 V,hydroxyl radicals are generated on the BBD electrode by electrolyzing water,which then remove the organic matter attached to the surface of the sensor though an electrochemical digestion process.The performance of the fouled sensor recovers from 50.2 to 94.1%compared with the initial state after self-cleaning for 30 min.In addition,by employing the MEMS technique,favorable response consistency and high reproducibility(RSD<4.05%)are observed,offering the opportunity to mass produce the proposed sensor in the future.A desirable linear dependency between the pH,temperature,and flow rate and the detection of free chlorine is observed,ensuring the accuracy of the sensor with any hydrologic parameter.The interesting sensing and selfcleaning behavior of the as-proposed sensor indicate that this study of the mass production of free chlorine sensors by MEMS is successful in developing a competitive device for the online monitoring of free chlorine in tap water.