Influence of canopy ratio of powered roof support on longwall working stability——A case study

The case study describes longwall coal seam A in a hard coal mine,where longwall coal face stability loss and periodic roof fall occurrences had been registered.The authors have attempted to explain the situation based on in-situ measurements and observations of the longwall working as well as numerical simulation.The calculations included several parameters,such as powered roof support geometry in the form of the canopy ratio,which is a factor that influences load distribution along the canopy.Numerical simulations were realized based on a rock mass model representing realistic mining and geological conditions at a depth of 600 m below surface for coal seam A.Numerical model assumptions are described,while the obtained results were compared with the in-situ measurements.The conclusions drawn from this work can complement engineering knowledge utilized at the stage of powered roof support construction and selection in order to improve both personnel safety and longwall working stability,and to achieve better extraction.

Thermal stability of cold worked microstructure of MP159 alloy

In order to know the longest permissible thermal exposure time during which the cold worked (CW) microstructure would remain unchanged, the effect of the thermal exposure at temperatures ranging from 910?℃ to 1?070?℃ on the microstructure was investigated for MP159 alloy by optical microscopy and transmission electron microscopy (TEM). Such a study can provide guidance for determining reasonable hot forging parameters of fasteners. The results indicate that the intersecting network of fine platelets in CW microstructure are thermal stable when thermal exposure temperature does not exceed 920?℃. When thermal exposure temperature exceed 920?℃, the intersecting network of fine platelets will dissolve, but the thermal exposure temperature has the longest permissible thermal exposure time during which the intersecting network of fine platelets will not dissolve.

Macroregulation in all-around recovery:Maintain stability and orient to long-term priorities

Since last October, loose monetary and credit policies and the stimulus package have produced desired results. The economy has entered into a "V-shaped" recovery in the second quarter of this year after hitting the bottom in the first quarter, with various economic indicators rising fast, rescue missions completed and short-term objectives basically met. In this context, the next step of macro-regulation should focus on long-term objectives, speed up institutional innovation and restructuring, control the intensity, pattern and pace of short-term policy loosening and prevent inflation and wild swings in the economy so as to achieve a new round of sustained and rapid economic growth.

LaB6 Work Function and Structural Stability under High Pressure

The work functions of the （110） and （10（3） surfaces of LaB6 are determined from ambient pressure to 39.1 GPa. The work function of the （110） surface slowly decreases but that of the （100） surface remains at a relatively constant value. To determine the reason for this difference, the electron density distribution （EDD） is determined from high-pressure single-crystal x-ray diffraction data by the maximum entropy method. The EDD results show that the chemical bond properties in LaB6 play a key role also investigated by single-crystal x-ray diffraction. In observed from ambient pressure to 39.1 GPa. The structural stability of LaB6 under high pressure is this study, no structural or electronic phase transition is

Multidimensional Governance Logic and Path to Maintain Social Stability

With China’s reform and development entering a critical period,the interweaving of various interest relations and the superimposing of the old and new contradictions have intensified social risks.Based on the concept of“pluralism,sharing,participation,cooperation and tolerance”,social stability can be maintained by the balanced protection of civil rights and the full realization of the development strategy.In addition,with the guidance of comprehensive legal thinking and core socialist values,the legal regulation of administrative behavior and rights-protection behavior is strengthened.In this way,the win-win of maintaining rights and stability can be realized in the positive-sum game that will help resolve social risks and achieve high-quality social stability.

Ground stability of new surface buildings erected on site above worked-out area

The subsided area caused by mining is expanding gradually in coal mining areas. In order to occupy less or no farmland, many mining areas are constructing or intend to erect new buildings (structures) on the ground sites above the worked-out areas. The long-term safety of the new buildings is of great importance. This matter should be, therefore, handled with great care. Following an analysis of the different conditions of the worked-out areas, and the characteristics of the failure of different types of worked-out areas and their overlying strata, the cause for the occurrence of residual deformation of the surface above the worked-out area was explained. The techniques for (evaluating) the stability of ground site for erecting new buildings above worked-out area, and the technical measures for protecting such buildings were proposed. The ground stability evaluation techniques were introduced by reference to specific cases.

Stability for the Manifold of Equilibrium State of the Autonomous Birkhoff System

Studies the stability for them manifold of equilibrium state of the autonomous Birkhoffsystem. Uses the Liapunov's direct method and the first approximation method to obtain thestability criterion for the manifold of equilibrium state of the system. Gives an example toillustrate the application of the result.

Instability characteristics of the cracked roof rock beam under shallow mining conditions

To establish the movement relationship for the roof breaking under shallow mining conditions, the mechanical model of the roof rock beam was built, then the structure instability process of the roof rock beam was analyzed. The changing criterion of the vertical displacement was established and the relationship between the deflection and the rotary motion of roof block was determined. Regarding a mining face in Shangwan Mine, the responsing laws of the deflection and horizontal thrust of the roof rock beam were obtained through FLAC3D numerical analysis. The results show that the structure instability of the cracked roof rock beam depends on the interaction between the vertical load and the horizontal thrust.For the roof rock beam, when the vertical load keeps constant, the horizontal thrust fluctuating rises with increasing deflection. The horizontal thrust increases constantly with the deeper buried depth and the smaller span.

Analysis and control of hydraulic support stability in fully-mechanized longwall face to the dip with great mining height

The working condition of the hydraulic support in working face can be divided into three kinds of situations in the following： roof fall and col,lapse with cavity, advancing support and supporting. Took single support with four-pole in Iongwall face to the dip as research object, control method was studied to avoid support instability in three situations mentioned above. Based on these researches, the major factors of influencing on support stability and its controlling measures were put forward. According to specific conditions of working face 1215（3）, which is fully-mechanized and Iongwall face to the dip with great mining height in Zhangji Coal Mine, Huainan Mining Group, the effective measures was taken to control supports stability..

Evaluation Method for Tunneling Stability of TBM Cutterhead

In the process of tunneling of tunnel boring machine (TBM), different geological conditions often correspond to different working conditions, and the randomness of geological conditions also causes the order of occurrence of each working condition to be different. Under the conversion of different working conditions, this makes the vibration of different types of cutterheads different. How to choose the appropriate type of cutterhead according to different geological conditions is very important for saving engineering cost and increasing cutterhead life. In view of the above situation, this paper proposes a stability evaluation method during the TBM tunneling process to select the appropriate cutterhead type. Firstly, the corresponding relationship between geology and working conditions is established according to different geological conditions, and the input loads corresponding to geological conditions are obtained. Then, it is substituted into the dynamic model of the cutterhead system, the vibration response boundaries of each degree of freedom are obtained by solving. And the average value of the maximum boundary amplitude of each degree of freedom is taken to represent the extreme vibration of the cutterhead under the corresponding working conditions. Finally, by comparing the fluctuation of the ultimate vibration amplitude of each type of cutterhead in the process of working condition conversion, the results are as follows: when the transition between homogeneous strata and composite strata is normal and there is no large turning and deviation correction, the vibration response of the two-part cutterhead is the smallest, and the two-part cutterhead is the best choice. Otherwise, the five-part cutterhead is the best choice, while the stability of the integrated cutterhead is the worst.

The Central Economic Work Conference Sets the Tone for Annual Economic Work

The annual Central Economic Work Conference,which analyzes China’s economic situation and prepares plans for the development of the national economy in the coming year,is also the top-level economic conference each year.This year’s conference conveyed a lot of information,from which we have selected several sets of key phrases.Key phrases 1:pursue progress while ensuring stability,consolidate stability through progress,and establish the new before abolishing the old The Central Economic Work Conference pointed out that,generally speaking,favorable conditions outweigh unfavorable factors in China’s development,the fundamental trend towards economic recovery and a long-term positive outlook has not changed,and it is important to increase confidence.The conference stressed that it is important to stick to high-quality development.Regarding work in the coming year,the conference called for efforts to pursue progress while ensuring stability,to consolidate stability through progress,and to establish the new before abolishing the old.

矢车菊-3-葡萄糖苷提取纯化、生物活性及稳态化技术的研究进展

矢车菊-3-葡萄糖苷(Cyanidin-3-glucoside,C3G)是自然界中分布最为广泛的一种花青素,富含于水果、蔬菜和谷物中,具有抗氧化、抗癌、抗炎以及维持视觉健康等生理功能,在食品、医药等行业备受关注。提取纯化是利用C3G的重要步骤,但C3G在储存、加工过程中易受外界环境的影响而失去原有的颜色和生理价值。为促进C3G在食品领域的应用,该文汇总了C3G在不同食物中的含量及常见的提取纯化方法,概述了C3G抗氧化、抗癌、抗炎以及维持视觉健康等生物活性,并从生物大分子复合和分子修饰两个方面介绍了C3G的稳态化方法,为未来研究和综合开发利用C3G提供理论依据。

大豆调质塔下料器的效率及平稳性数值仿真研究

为了提高大豆调质塔下料器的工作效率和下料平稳性,结合离散元方法模拟大豆在下料器内的运动过程,分析转子叶片数量、淌料板角度、进出料口夹角对下料器工作效率和下料平稳性的影响。结果表明:当下料器转速为12 r/min时,转子叶片数量对下料器的工作效率和下料平稳性呈显著的负相关关系。淌料板角度对下料器的工作效率及平稳性影响不明显,但会导致物料在进料口处残留。进出料口夹角值越大,下料器的工作效率越低,但下料平稳性越好。研究表明,当转子叶片数量为6个,淌料板角度为40°,进-出料口夹角为180°时,下料器的工作效率及平稳性综合达到最优。

“反向闹大”式集体行动何以成功——兼论“维稳”意涵的拓展与进阶

进入新时代,随着国家治理体系与治理能力现代化建设水平的不断提高,特别是“人民至上”执政理念的深入践行,国家与社会在“维稳”场域内的互动逻辑发生转变。典型案例研究表明,传统“大闹→闹大”式抗争逻辑的效用呈衰变态势,而“不闹→闹大”的“反向闹大”式集体行动逻辑形成,并取得成功。根本原因在于,新时代国家“维稳”意涵的丰富化,具体表现为:从“机制”到“价值”的进阶、从“秩序”到“人本”的深化、从“事件”到“问题”的拓展。民众从“大闹”到“不闹”的行为选择,触发了国家“维稳”意涵层级的转换,进而引发了政府应对策略的转变与升级。“反向闹大”式集体行动逻辑的提出,丰富了“闹大”议题既有的研究谱系,拓展了研究视野,同时为社会抗争的有效治理提供了新思路。

苏州出口贸易保稳提质策略研究——基于深圳和上海出口贸易的经验

出口作为拉动经济增长的三驾马车之一,对属于典型外向型经济的苏州来讲更是如此。然而,作为贸易强市的苏州面临制造业新的竞争优势还未形成、外资企业对出口的贡献不断下降、对主要目标市场的出口不增反降、贸易数字化发展水平较低等出口困境,2023年以来出口贸易额出现了明显下滑。在此情况下,文章研究了深圳和上海出口贸易持续高质量发展的经验,认为苏州应该从强化贸易产业链视角出台组合政策,形成贸易促进合力;大力推动数智技术赋能出口贸易,增强制造业和贸易数字化对出口贸易的支撑力度;加大对民营企业的支持力度,不断提高出口贸易发展韧性;坚持市场多元化策略,降低出口贸易过度依赖少数市场带来的风险。

“稳中求进”工作总基调的历史演进及新时代内涵

“稳中求进”的工作总基调及重要原则,经历了从思想萌芽到逐渐成熟、不断丰富内涵的历史演进,包括计划经济体制下稳定与增长的理论争论,伴随改革开放的理论提出与实践试错。这一理论是习近平治国理政思想的重要组成部分,蕴含着马克思主义辩证法及生产力与生产关系矛盾的运动规律。它包含着以增强风险意识和底线思维为核心,确保经济在合理区间内平稳运行以及社会发展平稳有序的“稳”的主基调,又包含着以供给侧结构性改革为主线,构建新发展格局、加快促进经济增长方式质的转变以及经济社会全面发展的“进”的目标。这一工作总基调和原则,是我国面对未来发展“危”与“机”的应对之策,以全面落实“稳”和“进”之间的融合发展,助力实现中国式现代化。

冷阴极触发管工作稳定性研究

随着直列式爆炸箔起爆/点火技术的发展,对其安全性和可靠性提出更高要求,高压开关是该技术中的关键元器件,使用环境也十分苛刻,要求高压开关的电阻和电感小、导通能力高、寿命长、稳定可靠。现普遍使用的一种高压开关—冷阴极触发管自击穿电压和延迟时间的稳定性直接影响了直列式点火技术使用的安全性和可靠性,通过分析放电机理、改善电极表面状态、优化老炼方案并通过试验对比分析,对其工作稳定性进行研究,得出结论:采用电化学抛光提高电极表面状态,小电流和大电流老炼方案稳定放电特性的措施提高了冷阴极触发管自击穿电压和延迟时间的稳定性,提高了冷阴极触发管在直列式爆炸箔起爆/点火技术使用的安全性和可靠性。

Effect of hot working on microstructure and mechanical properties of TC11/Ti_2AlNb dual-alloy joint welded by electron beam welding process

The influence of hot working on the microstructures of TC11/Ti2 Al Nb dual-alloy joints welded by electron beam welding(EBW) process was investigated. The tensile tests were performed at room temperature for specimens before and after thermal exposure. The results show that the fusion zone of TC11/Ti2 Al Nb dual-alloy joint welded by EBW is mainly composed of β phase. After deformation and heat treatment, the grain boundaries of the as-cast alloy are broken and the fusion zone mainly consists of β, α2and α phases. The fusion zone performs poor property in the tensile test. Specimens before and after thermal exposure all fail in this area under different deformation conditions. The ultimate tensile strength of specimens after heat treatment is up to 1190 MPa at room temperature. The joints by water quenching after deformation have better plasticity with an elongation up to 4.4%. After thermal exposure at 500 °C for 100 h, the tensile strength of the specimen slightly rises while the ductility changes a little. SEM observation shows that the fracture mechanism is predominantly transgranular under different deformation conditions.

电化学储能参与电网暂态功角稳定控制研究

针对电网传统紧急控制资源的日益匮乏,利用电化学储能功率控制的快速性与双向控制能力,研究将其应用于电网暂态功角稳定控制。首先推导了计及电化学储能的双机等值模型,基于扩展等面积定则分析了储能改善电网暂态稳定裕度的原理。其次,提出了一种考虑设备保护与系统保护动作时序差异的储能电站有效工作时长计算方法,改善了紧急控制储能的工作效率。提出了计及储能的基于性能代价比多类措施协调控制策略制定方法,兼顾紧急控制的安全性与经济性,为电网暂态紧急控制提供在线辅助决策支撑。进一步提出了储能电站全景监控系统架构,为实现储能电站与电网紧急控制系统的交互提供了技术实践思路。最后西北电网实际算例验证了所提方法的有效性与合理性。研究结论可为规模化储能与高比例新能源电网第二道防线的扩展与建设提供理论参考。

轻骨料混凝土泵送稳定性测试与评价方法研究

文中针对当前用于泵送压力作用下轻骨料混凝土工作性能稳定性的测试与评价方法存在的局限,提出了一种操作简便、可量化表征的轻骨料混凝土泵送稳定性测试与评价方法,通过大量轻骨料混凝土生产数据的采集、跟踪与分析,验证了所提出方法的准确性与可靠性。结果表明,该方法可用于轻骨料混凝土泵送施工性能的表征。