高地应力硬岩非爆式掘进失效是深部矿山开采掘进工程中的难题,研究硬岩诱导卸荷与多截齿协同破岩理论和实验的新方法,是深部矿山掘进亟须开展的基础性工作。本文采用数值模拟和试验分析相结合的方法,分析硬岩卸荷规律,确定最优钻孔参数,研究硬岩卸荷作用下截齿截割特性,确定截齿截割最优参数,建立钻孔与截割的混杂系统模型,阐明钻孔诱导卸荷与多截齿协同破岩规律,在高地应力硬岩掘进技术及岩爆灾害防治等方面具有重要理论意义和广阔的应用前景。采用ABAQUS有限元方法建立了钻孔岩石诱导卸荷数值模型,模拟研究了高地应力岩石在不同钻孔条件下的卸荷规律。结果表明:当深度相同时,切片深度由浅入深的同时应力集中的范围起初缩小后期增大,当深度不同时,应力集中区随钻孔深度加大呈现先增大后缩小趋势;当钻孔直径不变时,切片深度由浅入深的同时应力集中的范围起初缩小后期增大,当直径改变时,应力集中区随钻孔直径加大而增大;在不同地应力工况下,最优钻孔参数随地应力的变化而产生波动,最终处于稳定状态;当钻孔间距增大时,所有钻孔布置方式下卸荷后岩体的最大卸荷残余应力比例都先增大后缩小,且减小速率不及增大速率,其中钻孔间距为0.2m和0.25m时大致相同,因此,当钻孔间距超过一定值后,钻孔对岩体的卸荷能力降低。根据高地应力岩石在不同钻孔参数下的诱导卸荷规律,利用有限元分析方法对比研究了卸荷岩石的截齿截割特性。结果表明:30°角截割时,全过程处于高应力作用下,不适宜对含孔卸荷后花岗岩的掘进,截割角度为45°和60°时截割效果较优,当截割角度为60°时截齿受力最小,为含孔卸荷岩石的最佳截割角度;0.08m、0.085m的截齿间距下,截齿所受三向应力偏大,不宜选取,截齿间距为0.075m时,截割花岗岩的效果最好;多截齿同步截割时1号截齿和2号截齿所受的X向和Z向应力最大特征值小于异步截割的1号截齿和2号截齿,因此同步截割要优于异步截割。通过将卸荷场分解成初始应力、应变场和卸荷后的卸荷应力、应变场,建立了卸荷等效模型,分别分析了泊松比、弹性模量、内摩擦角与内聚力随卸荷量的变化规律,利用MATLAB拟合得到的函数值误差较小,可直接应用到工程计算中;利用ABAQUS有限元分析软件建立了冲击钻头与岩石的物理模型,通过数值模拟冲击钻头破岩情况,得到了单位深度破岩能耗值,为岩石冲击性能的评价模型研究提供了理论参考。在混杂系统理论基础上,对诱导卸荷与连续截割系统进行了结构分析、模型建、与求解。结果表明:钻孔截割协同破岩过程包含大量连续变量（位移、速度、压力等）和离散驱动事件（电机、阀门等状态）,具有明显的混杂特性,是典型的混杂系统,因此基于混杂Petri网建模方法建立了对应破岩过程的HPN模型;利用改进粒子群算法MPSO对上述混杂系统模型进行了非线性方程组求解,为现场测试分析提供了理论支撑。在工作面现场进行了掘进截割实验,测试了诱导卸荷与连续截割系统在不同地应力条件下的实际截割性能。结果表明:在40MPa、50MPa地应力条件下,当工作面采用钻孔卸荷方案时,掘进性能和效果得到了大幅度改善,截割电机的电流峰值相应降低,达到了节能降耗的目的。矩形卸荷方案为最佳方案,其对应的截割电机电流峰值最小,六边形卸荷方案卸荷效果略差于矩形卸荷方案,但是其卸荷效果优于三角形卸荷方案。该论文有图79幅,表40个,参考文献124篇。

我国是世界上煤炭储量和生产大国,煤炭行业是国家经济体系的重要组成部分。煤炭行业的发展水平将直接影响我国经济水平的发展。煤炭作为重要战略资源,在热、电等基础行业起到关键性的作用。目前,我国煤炭开采量逐年降低,并逐步向薄煤层、坚硬煤层等难采煤层方向发展,针对坚硬煤层开采,目前滚筒式采煤机为主的机械化开采备受煤炭生产商们的青睐。但是,煤层硬度的提高,会导致采煤机在截割煤层时,截割效率降低,能耗大,机身振动增大,滚筒、螺旋叶片、截齿的磨损也会加剧,更会导致由于机械故障、频繁更换截齿、滚筒引起的设备停机维护。同时,煤层硬度的提高也会导致矿井下粉尘浓度升高,若采煤机运行参数不匹配,还会降低割落煤块的块煤率,大大增加了原煤的浪费,减小了煤炭生产企业的利润空间,不利于我国煤炭行业向绿色高效方向发展。因此,本文针对井下硬质煤层开采难度大的问题,从改变煤层内部应力分布角度出发,综合目前现有方法,选用高压水注入方法,对煤层进行预裂卸荷,联合截齿对煤层进行截割。煤层内部裂隙发育、截割过程是一个复杂的力学过程,从理论角度出发,研究了煤壁弹塑脆性模型的应变曲线及破坏准则。结合能量耗散理论,分析了煤壁水压致裂的起裂机理,给出了起裂临界水压的数学模型。裂隙的扩展是从翼裂隙扩展开始,在裂隙发育模型中,建立了翼裂隙长度发育模型,给出了理论计算公式。最后分析了截齿截割力学模型,分析了镐形截齿瞬时截割阻力理论计算模型。通过对采煤机结构和水预裂工艺进行分析,根据相似理论,得到高压水预裂辅助截割实验台相似模型的相似比,研制了高压水预裂辅助破煤岩实验系统,包括截割平台、注水预裂系统、数据采集系统。数据采集系统包括转矩采集系统和声发射信号采集与分析系统。实验室浇筑3种不同煤-水泥配比的模拟煤壁试件,对试件进行了测试标定,确定了f3-f5硬度煤岩试件的骨料配比方案。建立了煤岩劣化强度随预裂水压和注水时间的变化关系,为后续实验和分析提供试件和性能参数。为研究不同水压、不同注水时间对预裂裂隙时空分布情况及裂隙发育效果影响,采用声发射传感器,通过时差定位算法,对定位误差进行了分析,并得到了3MPa-10MPa注水压力下的裂隙空间分布情况。当注水压力靠近并大于临界起裂水压值时,煤壁内部裂隙的空间分布更好,随着注水压力的增大,裂隙的发育时间加快,煤壁表面出现水渍,但煤壁内部裂隙发育范围较小。通过对5MPa预裂水压的煤壁进行声发射定位点进行时域分析,得到了60min内不同时段的声发射统计值和空间分布情况,空间随时间分布结果与声发射事件数统计结果基本相同。为研究不同截割参数、煤岩参数下的截割比能耗和块煤率,对预裂和未预裂煤壁进行截割实验。实验结果显示,相较于未预裂煤壁,预裂后煤壁的截割转矩均值下降了约27.36%,截割转矩峰值下降了约26.24%,转矩波动下降了约43.75%。对比截割比能耗和成块率可得,截割比能耗下降约41.20%,成块率提高约14.43%。结果验证了预裂方法的有效性。研究了截割转速、牵引速度对截割比能耗、块煤率的影响规律,随着截割转速的增加,截割比能耗和块煤率随之增加;随着牵引速度的增加,截割比能耗随之降低,块煤率先升高后降低。综合分析不同硬度煤岩下,截割转速和牵引速度对二者的影响,得到不同硬度煤岩下,截割比能耗最低时截割参数为截割转速40r/min,牵引速度3m/min;块煤率最高时截割参数略有不同,其中在硬度为f3煤壁时,最大块煤率截割参数为80r/min,2m/min;在硬度为f4煤壁时,最大块煤率截割参数为60r/min,3m/min;在硬度为f5煤壁时,最大块煤率截割参数为60r/min,2m/min。为建立预裂参数、截割参数与煤岩参数的最佳匹配模型,设计了基于深度强化学习与Pareto算法结合的多目标优化算法,建立了最小比能耗和最大块煤率的目标函数,以煤岩硬度、截割转速、行走速度、注水压力、注水时间为决策变量,引入经济效益和成本评价指标作为回报值,对算法全局更新原则进行局部优化,挖掘了目标期望中决策参数的相互关系,建立了基于GD、DM、HV、IGD等6个评价指标的算法性能评价体系,证明了本文提出的算法在收敛性、多样性、广泛性的优势,得到了任意煤岩硬度下高压水预裂和截齿截割参数的最佳匹配关系,针对不同的工程需求提供经济高效的优化方案。该论文有图70幅,表32个,参考文献174篇。

In this study, molecular dynamics simulation was employed to analyze the temperature changes in pure iron models using the same cutting process. Thus, the effects of a micro-grain boundary on the cutting temperature change of the cutting teeth were investigated. The cutting teeth are key parts of a heading machine and wear-out failure is a significant factor influencing the extent of their lifetime. In this study, nanoscopic cutting models for both single-crystal and polycrystalline iron were developed. The results showed that the thermal conductivity of the polycrystalline iron model was much lower than that of the single-crystal iron model, and the entanglement and accumulation of grain boundary dislocations enhanced its ability to resist plastic deformation. The strength of polycrystalline iron was improved, and more cutting heat was generated, resulting in a higher cutting temperature in the polycrystalline iron model. The developed approach is of practical significance in research on the wear-out failure of cutting teeth. © 2022 by Begell House, Inc.

The chain link corrosion model was constructed by the finite element analysis software ABAQUS to evaluate the plain link chain impact under the changing behavior of different corrosion states. The link chain simulation study at different corrosion states was conducted (corrosion depth, area, and density), the curve of stress and energy variation with time was plotted. The stress distribution and related energy variations remained approximately the same at heavy loads. The steady stress of the corrosion chain link, friction dissipation energy, plastic dissipation energy, as well as steady internal energy, and corrosion depth, area, and density are fitted by third-degree polynomial relations. The maximum steady stress occurred at corrosion state III, which already exceeded the yield strength of the link chain below 20°C so that it made easy for the corrosion fracture to occur. This method provided important grounds for the design optimization and lifetime prediction of plain link chains. © 2021, Springer Science+Business Media, LLC, part of Springer Nature.

This paper proposes a multi-frequency vibration picking power supply device for scraper conveyor tension detection, in view of the difficulty that scraper conveyor tension detection sensors cannot be wired for power supply. The experimental analysis of the spatial type multi-frequency picking energy characteristics at different vibration frequencies of 5 Hz, 10 Hz, 15 Hz, 20 Hz, 25 Hz and 30 Hz. The results show that: The maximum power production is achieved in the vibration frequency range of 15-20 Hz, achieving a resonance with the external environmental frequency of the scraper, and the sustainable and stable power supply of the scraper conveyor tension detection sensor is verified through experimentation. © 2021, Politechnica University of Bucharest. All rights reserved.

针对粒子群算法性能很大程度上取决于惯性权重的选择,提出细粒度指数惯性权重自适应策略的粒子群算法。选用10个经典函数进行仿真实验测试新算法的性能,使用SPSS软件对最优值、平均值和均方差进行Wilcoxon符号秩检验和Friedman检验,分析和检验结果与惯性权重高斯递减粒子群算法、双指数递减粒子群算法进行比较。将其应用于蒸汽动力系统调度问题。仿真实验和工程实例研究结果表明,新的策略对粒子的觅食行为有着显著作用,改善了粒子群算法摆脱局部极值点的能力,具有收敛速度快等优点,能较好地处理蒸汽动力系统优化调度问题。

In this paper, a modified variational method is developed to study the free and forced vibration of coupled straight–curved beam systems with an arbitrary number of eccentric discontinuities (EDs). Based on the generalized shell theory, the kinetic and potential functional of the curved beam with arbitrary subtended angles is formulated. Since the shear and inertial (or radial–tangential–rotational coupling) effects are included for the curved beam, the longitudinal vibration is also introduced to the energy functional for a straight Timoshenko beam. Using corresponding coordinate transformations, the Lagrange multiplier method and least-square weighted residual method are employed to impose the continuity constraints on the internal interfaces and boundaries among the straight and curved beams. The proposed method allows a flexible choice of the admissible functions and can be used for various combinations of the straight and curved beams to model corresponding engineering structures. Concentrated forces, uniformly distributed loads and space-dependent loads are considered to demonstrate great efficiency and accuracy of the present approach for the forced as well as the free vibration of the coupled system. Most of the present results are compared with those from finite element program ANSYS, and good agreement is observed. Influences of the EDs on the dynamic responses of the coupled system are also examined.
© 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

In this paper, a modified variational method is developed to study the free and forced vibration of coupled straight–curved beam systems with an arbitrary number of eccentric discontinuities (EDs). Based on the generalized shell theory, the kinetic and potential functional of the curved beam with arbitrary subtended angles is formulated. Since the shear and inertial (or radial–tangential–rotational coupling) effects are included for the curved beam, the longitudinal vibration is also introduced to the energy functional for a straight Timoshenko beam. Using corresponding coordinate transformations, the Lagrange multiplier method and least-square weighted residual method are employed to impose the continuity constraints on the internal interfaces and boundaries among the straight and curved beams. The proposed method allows a flexible choice of the admissible functions and can be used for various combinations of the straight and curved beams to model corresponding engineering structures. Concentrated forces, uniformly distributed loads and space-dependent loads are considered to demonstrate great efficiency and accuracy of the present approach for the forced as well as the free vibration of the coupled system. Most of the present results are compared with those from finite element program ANSYS, and good agreement is observed. Influences of the EDs on the dynamic responses of the coupled system are also examined. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

为实现采煤机截割过程中截齿磨损状态的智能化监测,采用声发射信号采集装置对截割4种不同比例煤岩试件的信号进行采集,应用3层小波包分解及重构技术对信号进行处理,并提取特征值作为样本空间,利用D-S证据理论方法对截齿磨损程度进行智能识别。结果表明:12.5～25.0 kHz频段和37.5～50.0 kHz频段内能量集中,且能量随截齿磨损程度的增加而减小,因此选取上述2个频段能量占总能量的比值作为特征值,在4种工况的证据体联合作用下,截齿磨损状态智能识别精度达到约90%。此方法可为准确掌握截齿磨损状态,确定截齿更换周期,提高采煤机的截割效率,实现井下智能化开采提供基础。

Cu2BaSn(S1-xSex)(4) has shown great prospects in the photoelectric field due to Earth-abundance, low toxicity, cost efficiency, direct bandgap, high absorption coefficient (> 104 cm(-1)) and reduced anti-site disorder relative to Cu2ZnSn(S1-xSex)(4). A fully-tunable ratio of S/Se is the key to broaden the bandgap of Cu2BaSn(S1-xSex)(4). Here, we introduce a thionothiolic acid metathesis process to readily tune the stoichiometry of Cu2BaSn(S1-xSex)(4) films for the first time. Different stoichiometric Se/(S.+.Se) of Cu2BaSn(S1-xSex)(4) from zero to one can vary the bandgap range from 2 to 1.68 eV. The grain size of Cu2BaSn(S1-xSex)(4) films can be grown more than 10 mu m. The optimized bandgap and high-quality growth of Cu2BaSn(S1-xSex)(4) films ensure the best power conversion efficiency of 2.01% for solution-processed Cu2BaSn(S1-xSex)(4) solar cells. This method provides an alternative solution-processed way for the synthesis of fully stoichiometric Cu2BaSn(S1-xSex)(4).