深埋大断面开切眼大厚度泥岩顶板冒顶机理及其梯次支护技术研究

针对深埋大断面开切眼大厚度泥岩顶板易发生冒顶的问题,以张家洼煤矿9 m宽的大断面开切眼为研究对象,采用室内试验、现场实测、理论分析及数值模拟等研究了该类巷道的围岩变形破坏特征与应力场分布特征,揭示了冒顶机理,并提出了锚网梁+长短锚索的梯次主动支护与单体柱+木垛的联合被动支护相组合的协同控制技术。结果表明:发生冒顶的内在原因是直接顶的大厚度泥岩强度低,外在原因是水对泥岩的崩解破坏、单体柱反复加卸载的疲劳损伤以及深部高应力,主要原因是支护参数不合理。通过梯次支护中9.3 m的短锚索与锚网梁将顶板中下部的软岩有效组合在一起,形成一个具有承载作用的锚固体,且受力均匀;通过梯次支护中12.3 m的长锚索将该锚固体悬吊于深部稳定岩层。再配合该联合被动支护的有效支撑与信号作用,协同实现该条件下巷道围岩的有效控制。采用梯次支护技术后,1305开切眼围岩稳定性显著提高。     

Role of exchange coupling between the hard and soft magnetic phases on the absorption of microwaves by SrFe10Al2O19/Co0.6Zn0.4Fe2O4 nanocomposite

(1-x)SrFe₁₀Al₂O₁₉/(x)Co_0.6Zn_0.4Fe₂O₄-(SFAO/CZFO) hard/soft nanocomposite ferrite materials were synthesized by ‘one-pot’ self-propagating combustion route. The co-existence of the two magnetic phases were confirmed by XRD, FESEM, EDS and VSM. The prepared nanocomposite samples were also characterized by TGA/DSC, Raman spectroscopy and VNA. Exchange coupling between the hard and the soft magnetic grains was observed by determining the switching field distribution (SFD) curve. As a result of the competing effects of exchange interaction and dipolar interaction, magnetic parameters were observed to be sensitive to the incorporation of soft magnetic phase into the nanocomposite. Results showed that with the inclusion of soft magnetic phase, exchange coupling behaviour between the hard and the soft ferrite phases had significant influence on the microwave absorption capacity of the samples. Related electromagnetic parameters and impedance matching ratio of the nanocomposite system were discussed. A minimum reflection loss of ?42.9 dB with an absorber thickness of 2.5 mm was attained by the nanocomposite (90 wt%)SrFe₁₀Al₂O₁₉/(10 wt %)Co_0.6Zn_0.4Fe₂O₄ at a matching frequency of 11.45 GHz. This assured the candidacy of SrFe₁₀Al₂O₁₉/Co_0.6Zn_0.4Fe₂O₄ nanocomposite as a promising microwave absorption material in the X-band (8–12 GHz).     

Biomimetic Lamellar Chitosan Scaffold for Soft Gingival Tissue Regeneration

Mucogingival surgery has become a common procedure for soft gingival tissue reparation in dental clinical practice, which mainly relies on autograft or commercial collagen membranes (CM). However, the autograft faces grand challenges in source availability and long-term post-surgery pain management, and the CM is restricted by its poor mechanical properties in an aqueous environment. Here, it is reported that a bio-inspired lamellar chitosan scaffold (LCS) with long range ordered porous structure, manufactured through a bidirectional freezing method, can serve as a promising gingival tissue engineering material. The LCS not only exhibits excellent mechanical properties in the hydrated state but also accelerates vessel formation and soft tissue regeneration in vivo. Most interestingly, the LCS is found to be capable of inducing macrophage differentiation to M2 macrophages, which is thought to play an important role in tissue regeneration. These advantages combined with its easy and low-cost preparation process make the LCS a promising candidate for dental clinical applications.     

软土地区双侧基坑施工对邻近地铁隧道的影响分析

以上海某邻近地铁区间隧道的双侧基坑工程为背景,分析基于隧道变形控制的基坑设计要点,即严控双侧基坑施工工序与工况,采用大刚度的支护结构、可靠的止水体系、突出地铁保护的支撑布置,并加强对施工组织的要求.结合监测数据,进一步分析了基坑支护结构、区间隧道的变形特征与变化规律.监测数据表明设计方案对基坑变形与地铁影响的控制效果较...     

CFG桩网复合地基加固物流地坪深厚软土地基的三维数值模拟分析

结合湖州某物流园采用CFG桩网复合地基处理大面积深厚软土的工程实例,运用Midas GTS有限元软件建立桩网人工复合地基三维固结模型,计算模拟不同垫层厚度、土工格栅层数、桩长等设计参数对沉降变形的影响以及土工格栅在桩网固结模型中的受力特征.计算结果表明:地基整体沉降变形随填土垫层厚度的增加而增大,随土工格栅层数的增加而...     

古书院矿软煤易泥化围岩超高巷道支护技术研究

为确保15#煤西三盘区水仓超高巷道围岩控制效果,针对软弱易泥化围岩控制过程中存在的问题,提出采用高强锚杆+锚索+底板注浆+表层喷浆方式对围岩进行控制.支护方案现场应用后,超高巷道顶板、两帮、底鼓量最大分别为15 mm、30 mm、21 mm,有效解决了易泥化围岩超高巷道围岩控制难题,取得显著应用成果.     

软岩孤岛工作面顺槽失稳机理分析及支护实践

根据软岩顺槽围岩的基本特性和软岩孤岛工作面顺槽失稳的机理,提出了“中空注浆锚索+锚网梁”联合支护方式,1307工作面顺槽收敛和顶板离层得到了有效控制,达到了预期目的,支护效果较好.     

变频移相混合式控制CLL谐振变换器

为适应宽范围输入电压场合,该文结合变频控制(variable frequency control,VFC)和移相控制(phase shift control,PSC)这2种控制方式的特点,提出在输入高压时变换器进行移相控制,输入低压时进行变频控制的混合式控制方法.详细分析了在2种不同模式控制下全桥CLL谐振变换器的原理...     

Bioinspired Triboelectric Soft Robot Driven by Mechanical Energy

A sustainable power source is a key technical challenge for practical applications of electrically responsive soft robots, especially the required voltage is over several thousand volts. Here, a practicable new technology, triboelectric soft robot (TESR) system with the primary characteristics of power source from mechanical energy, is developed. At its heart is TESR with bioinspired architectures made of soft-deformable body and two triboelectric adhesion feet, which is driven and accurately controlled through triboelectric effect, while reaching maximum crawling speeds of 14.9 mm s⁻¹ on the acrylic surface. The characteristics of the TESR, including displacement and force, are tested and simulated under the power of a rotary freestanding triboelectric nanogenerator (RF-TENG). Crawling of TESR is successfully realized on different materials surfaces and different angle slopes under the driven of RF-TENG. Furthermore, a real-time visual monitoring platform, in which TESR carries a micro camera to transmit images in a long narrow tunnel, is also achieved successfully, indicating that it can be used for fast diagnosis in an area inaccessible to human beings in the future. This study offers a new insight into the sustainable power source technologies suitable for electrically responsive soft robots and contributes to expanding the applicability of TENGs.     

AC/DC开关电源建模与仿真研究

文章对全桥型开关电源结构进行分析,对关键元器件的作用、参数计算方法进行阐述.在Multisim仿真软件中搭建整体电路模型,研究改变电路参数对于电路性能的影响,验证开关电源仿真的可行性.针对硬开关产生的开关损耗问题,建立ZVS-移相全桥变换器的简化模型,仿真研究开关管的软开关过程.