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J^* INTEGRAL OF THE SPECIFIC DEVIATOR STRAIN ENERGY AND ITS APPLICATION
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作者 蒋玉川 王启智 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2004年第1期110-122,共13页
First the deviator strain energy is introduced, then the problem of plane-crack critical growth was discussed, a path independent line integral J* was defined, furthermore its conservation was proved strictly. As appl... First the deviator strain energy is introduced, then the problem of plane-crack critical growth was discussed, a path independent line integral J* was defined, furthermore its conservation was proved strictly. As application examples, Mode-I stress intensity factors of cracked beams were obtained with present approach. The results are shown to agree well with those available in the open literature. 展开更多
关键词 deviator strain energy CONSERVATION stress intensity factor
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纤维加筋膨胀土的蠕变规律及模型预测
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作者 郝建斌 孙小洁 +1 位作者 赵振洋 崔福庆 《西安科技大学学报》 CAS 北大核心 2024年第1期104-113,共10页
膨胀土是具有流变性质的灾害性土,其蠕变行为直接影响到工程结构的稳定性和安全性。为探究剑麻纤维加筋膨胀土的蠕变特性及应力-应变数学模型,采用室内固结排水三轴蠕变试验,分别进行了不同含水率、不同围压和不同偏应力条件下素膨胀土... 膨胀土是具有流变性质的灾害性土,其蠕变行为直接影响到工程结构的稳定性和安全性。为探究剑麻纤维加筋膨胀土的蠕变特性及应力-应变数学模型,采用室内固结排水三轴蠕变试验,分别进行了不同含水率、不同围压和不同偏应力条件下素膨胀土和剑麻纤维加筋膨胀土的蠕变特性研究,根据蠕变特征曲线提出了基于Mesri蠕变经验模型的剑麻纤维加筋膨胀土的修正蠕变模型。结果表明:相同条件下,剑麻纤维加筋土的蠕变变形量明显小于素土的蠕变变形量,说明掺入剑麻纤维可有效提高膨胀土的结构性能和抗变形能力;素土和剑麻纤维加筋土的蠕变变形量随含水率增大而增大,而随围压的增大呈减小趋势;素土和剑麻纤维加筋土在受到偏应力时均会产生瞬时应变量和蠕变变形量,其蠕变变形量随偏应力的增大而增大;素土和加筋土的蠕变曲线分4个阶段,分别为弹性变形阶段、稳态蠕变阶段、衰减蠕变阶段和加速蠕变阶段;高偏应力下,基于传统Mesri蠕变经验模型的剑麻纤维加筋土蠕变预测误差高达37.95%,对Mesri蠕变经验模型进行修正后预测误差降至1.5%内,说明修正模型能较好地描述剑麻纤维加筋土的蠕变特性。此研究结果可为膨胀土工程提供理论参考。 展开更多
关键词 膨胀土 纤维加筋土 蠕变试验 修正蠕变模型 偏应力
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中间主应力系数对页岩气渗流特性及气体滑脱效应的影响
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作者 范翔宇 张昕宇 +4 位作者 胡小媛 蒋长宝 张千贵 赵鹏斐 陈昱霏 《天然气勘探与开发》 2024年第2期97-103,共7页
页岩气的渗流特性极大地影响着采收率,但对页岩气渗流特性的研究大多是在不同围压条件下开展的,其结果尚不能揭示中间主应力对渗透率的影响。因此,选用涪陵页岩气区块志留系龙马溪组页岩露头立方体岩石试件,采用自主研发的“多功能真三... 页岩气的渗流特性极大地影响着采收率,但对页岩气渗流特性的研究大多是在不同围压条件下开展的,其结果尚不能揭示中间主应力对渗透率的影响。因此,选用涪陵页岩气区块志留系龙马溪组页岩露头立方体岩石试件,采用自主研发的“多功能真三轴流固耦合试验系统”开展了页岩真三轴流固耦合试验,利用Klinkenberg方程拟合试验数据分析不同中间主应力系数对页岩气渗流特性和气体滑脱效应的影响。试验结果表明:①当偏应力较小时,中间主应力对页岩渗透率演化的影响较小,而当偏应力增加时,其影响越大且越不可忽略;②滑脱系数—固有渗透率的关系式与试验数据的拟合结果显示二者具有良好的相关性,可用于对同区块页岩滑脱系数的预测;③当偏应力小于或等于35 MPa时,滑脱效应贡献率保持在65%以上,表明此时滑脱效应主导着页岩中气体的渗流。 展开更多
关键词 中间主应力系数 页岩气渗流特性 真三轴 滑脱效应贡献率 偏应力
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不同应力养护条件对水泥土力学性能影响试验研究
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作者 陈昌富 吕晨阳 +1 位作者 蔡焕 张根宝 《铁道科学与工程学报》 EI CAS CSCD 北大核心 2024年第2期637-647,共11页
为更好地了解水泥土在养护时期所受应力大小对其后期力学性能的影响,研发恒温等压或偏压条件下水泥土试样的养护装置和相应的试验方法。基于改制的恒温恒压水泥土试样养护装置,制作等压和偏压养护条件下不同龄期的水泥土试样。通过无侧... 为更好地了解水泥土在养护时期所受应力大小对其后期力学性能的影响,研发恒温等压或偏压条件下水泥土试样的养护装置和相应的试验方法。基于改制的恒温恒压水泥土试样养护装置,制作等压和偏压养护条件下不同龄期的水泥土试样。通过无侧限压缩试验(UCT),获得等压和偏压养护条件下水泥土试样的应力-应变曲线及其无侧限抗压强度(UCS)和变形模量E_(50)随龄期的演化规律。试验结果表明:等压养护时围压σ_(c)从0.1 MPa增加到0.3 MPa,水泥土试样在龄期为7 d和14 d时的无侧限抗压强度和变形模量E_(50)均随着围压的增加而增大,但28 d龄期水泥土样的UCS和E_(50)随围压σ_(c)的增长而减小,甚至0.3 MPa围压养护试样的UCS已低于无围压养护试样的UCS,水泥土存在“高围压养护长期强度降低效应”;不同轴压比λ下偏压养护的水泥土样,其60 d龄期的UCS在偏压较小(即λ<λ_(c),λ_(c)为临界轴压比)时逐渐增加,而在偏压较大(即λ>λ_(c))时逐渐下降,即水泥土又存在“小偏压养护强度增加,大偏压养护强度降低的效应”。通过对试验结果进行回归分析,分别建立等压养护下计入围压参数σ_(c)的水泥土UCS和E_(50)的演化方程、偏压养护下水泥土UCS和E_(50)与轴压比λ的经验关系式。研究成果对于深刻理解环境条件对水泥土力学性能的影响机制和指导工程实践,具有较好的理论和工程实际意义。 展开更多
关键词 水泥土 无侧限抗压强度 变形模量 等压养护 偏压养护
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Computing large deviation prefactors of stochastic dynamical systems based on machine learning
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作者 李扬 袁胜兰 +1 位作者 陆凌宏志 刘先斌 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第4期364-373,共10页
We present a large deviation theory that characterizes the exponential estimate for rare events in stochastic dynamical systems in the limit of weak noise.We aim to consider a next-to-leading-order approximation for m... We present a large deviation theory that characterizes the exponential estimate for rare events in stochastic dynamical systems in the limit of weak noise.We aim to consider a next-to-leading-order approximation for more accurate calculation of the mean exit time by computing large deviation prefactors with the aid of machine learning.More specifically,we design a neural network framework to compute quasipotential,most probable paths and prefactors based on the orthogonal decomposition of a vector field.We corroborate the higher effectiveness and accuracy of our algorithm with two toy models.Numerical experiments demonstrate its powerful functionality in exploring the internal mechanism of rare events triggered by weak random fluctuations. 展开更多
关键词 machine learning large deviation prefactors stochastic dynamical systems rare events
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Path Planning and Tracking Control for Parking via Soft Actor-Critic Under Non-Ideal Scenarios
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作者 Xiaolin Tang Yuyou Yang +3 位作者 Teng Liu Xianke Lin Kai Yang Shen Li 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2024年第1期181-195,共15页
Parking in a small parking lot within limited space poses a difficult task. It often leads to deviations between the final parking posture and the target posture. These deviations can lead to partial occupancy of adja... Parking in a small parking lot within limited space poses a difficult task. It often leads to deviations between the final parking posture and the target posture. These deviations can lead to partial occupancy of adjacent parking lots, which poses a safety threat to vehicles parked in these parking lots. However, previous studies have not addressed this issue. In this paper, we aim to evaluate the impact of parking deviation of existing vehicles next to the target parking lot(PDEVNTPL) on the automatic ego vehicle(AEV) parking, in terms of safety, comfort, accuracy, and efficiency of parking. A segmented parking training framework(SPTF) based on soft actor-critic(SAC) is proposed to improve parking performance. In the proposed method, the SAC algorithm incorporates strategy entropy into the objective function, to enable the AEV to learn parking strategies based on a more comprehensive understanding of the environment. Additionally, the SPTF simplifies complex parking tasks to maintain the high performance of deep reinforcement learning(DRL). The experimental results reveal that the PDEVNTPL has a detrimental influence on the AEV parking in terms of safety, accuracy, and comfort, leading to reductions of more than 27%, 54%, and 26%respectively. However, the SAC-based SPTF effectively mitigates this impact, resulting in a considerable increase in the parking success rate from 71% to 93%. Furthermore, the heading angle deviation is significantly reduced from 2.25 degrees to 0.43degrees. 展开更多
关键词 Automatic parking control strategy parking deviation(APS) soft actor-critic(SAC)
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Spatiotemporal characteristics of cultivated land use eco-efficiency and its influencing factors in China from 2000 to 2020
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作者 LI Shaoting MU Na +1 位作者 REN Yanjun Thomas GLAUBEN 《Journal of Arid Land》 SCIE CSCD 2024年第3期396-414,共19页
Improving cultivated land use eco-efficiency(CLUE)can effectively promote agricultural sustainability,particularly in developing countries where CLUE is generally low.This study used provincial-level data from China t... Improving cultivated land use eco-efficiency(CLUE)can effectively promote agricultural sustainability,particularly in developing countries where CLUE is generally low.This study used provincial-level data from China to evaluate the spatiotemporal evolution of CLUE from 2000 to 2020 and identified the influencing factors of CLUE by using a panel Tobit model.In addition,given the undesirable outputs of agricultural production,we incorporated carbon emissions and nonpoint source pollution into the global benchmark-undesirable output-super efficiency-slacks-based measure(GB-US-SBM)model,which combines global benchmark technology,undesirable output,super efficiency,and slacks-based measure.The results indicated that there was an upward trend in CLUE in China from 2000 to 2020,with an increase rate of 2.62%.The temporal evolution of CLUE in China could be classified into three distinct stages:a period of fluctuating decrease(2000-2007),a phase of gradual increase(2008-2014),and a period of rapid growth(2015-2020).The major grain-producing areas(MPAs)had a lower CLUE than their counterparts,namely,non-major grain-production areas(non-MPAs).The spatial agglomeration effect followed a northeast-southwest strip distribution;and the movement path of barycentre revealed a"P"shape,with Luoyang City,Henan Province,as the centre.In terms of influencing factors of CLUE,investment in science and technology played the most vital role in improving CLUE,while irrigation index had the most negative effect.It should be noted that these two influencing factors had different impacts on MPAs and non-MPAs.Therefore,relevant departments should formulate policies to enhance the level of science and technology,improve irrigation condition,and promote sustainable utilization of cultivated land. 展开更多
关键词 cultivated land use eco-efficiency(CLUE) slacks-based measure(SBM)model barycentre model standard deviation ellipse(SDE) panel Tobit model carbon emissions nonpoint source pollution
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Further Analysis of Machine Tool Dimensional Accuracy and Thermal Stability under Varying Floor Temperature
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作者 Joel Arumun Shadrack Abiola 《World Journal of Engineering and Technology》 2024年第2期258-273,共16页
Machining is as old as humanity, and changes in temperature in both the machine’s internal and external environments can be of great concern as they affect the machine’s thermal stability and, thus, the machine’s d... Machining is as old as humanity, and changes in temperature in both the machine’s internal and external environments can be of great concern as they affect the machine’s thermal stability and, thus, the machine’s dimensional accuracy. This paper is a continuation of our earlier work, which aimed to analyze the effect of the internal temperature of a machine tool as the machine is put into operation and vary the external temperature, the machine floor temperature. Some experiments are carried out under controlled conditions to study how machine tool components get heated up and how this heating up affects the machine’s accuracy due to thermally induced deviations. Additionally, another angle is added by varying the machine floor temperature. The parameters mentioned above are explored in line with the overall thermal stability of the machine tool and its dimensional accuracy. A Robodrill CNC machine tool is used. The CNC was first soaked with thermal energy by gradually raising the machine floor temperature to a certain level before putting the machine in operation. The machine was monitored, and analytical methods were deplored to evaluate thermal stability. Secondly, the machine was run idle for some time under raised floor temperature before it was put into operation. Data was also collected and analyzed. It is observed that machine thermal stability can be achieved in several ways depending on how the above parameters are joggled. This paper, in conclusion, reinforces the idea of machine tool warm-up process in conjunction with a carefully analyzed and established machine floor temperature variation for the approximation of the machine tool’s thermally stability to map the long-time behavior of the machine tool. 展开更多
关键词 Dimensional Accuracy Machine Tool Machine Floor Thermal Stability TEMPERATURE Thermal Deviation
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Spatial Morphology Evolution Characteristics Analysis of the Resident Population Distribution in Henan, China
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作者 Kaiguang Zhang Hongling Meng +1 位作者 Mingting Ba Danhuan Wen 《Journal of Geoscience and Environment Protection》 2024年第3期163-180,共18页
The population spatial distribution pattern and its evolving pattern play an important role in regional allocation of social resources and production factors, formulation of regional development plans, construction of... The population spatial distribution pattern and its evolving pattern play an important role in regional allocation of social resources and production factors, formulation of regional development plans, construction of a better life society, and promotion of regional economic development. Based on the resident population statistics data of Henan province from 2006 to 2021, with county as the basic study unit, the paper studies the spatial morphology characteristics and its evolution patterns of resident population distribution, by using spatial analysis methods such as population distribution center, standard deviation ellipse, and spatial auto correlation analysis. The results show that: the resident population spatial distribution shows unbalanced state, the population agglomeration areas mainly distribute in the northeast part and north part, where the resident population growth rate is significantly higher than other regions, over time, this trend is gradually becoming significant. The resident population distribution has a trend of centripetal concentration, with the degree and trend of centripetal gradually strengthening. The resident population distribution has obvious directional characteristics, but the significance is not high, the weighted resident population average center is approximately located at (4.13740˚N, 113.8935˚E), and the azimuth of the distribution axis is approximately 11.19˚. The population distribution has obvious agglomeration characteristics, with the built-up areas of Zhengzhou and Luoyang as their centers, where have a significant siphon effect on the surrounding population. The southern and southwestern regions in the province form a relatively stable belt area of Low-Low agglomeration areas. 展开更多
关键词 Resident Population Spatial Distribution Spatial Morphology Temporal and Spatial Evolution Center Migration Standard Deviation Ellipse Spatial Autocorrelation
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2.5维有限元分析高铁荷载下弹塑性地基动偏应力与沉降
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作者 高广运 耿建龙 +2 位作者 毕俊伟 张继严 徐晨晓 《同济大学学报(自然科学版)》 EI CAS CSCD 北大核心 2023年第7期1054-1064,共11页
为分析高铁荷载引起的弹塑性地基动偏应力分布规律并据此开展沉降计算,建立了高铁荷载下弹塑性地基2.5维有限元计算模型,将高铁荷载分别简化为准静态列车荷载和考虑随机激振力的修正列车荷载,对比了2种荷载下弹塑性地基中动偏应力的分... 为分析高铁荷载引起的弹塑性地基动偏应力分布规律并据此开展沉降计算,建立了高铁荷载下弹塑性地基2.5维有限元计算模型,将高铁荷载分别简化为准静态列车荷载和考虑随机激振力的修正列车荷载,对比了2种荷载下弹塑性地基中动偏应力的分布规律,并利用循环荷载下软黏土累积塑性应变模型计算了均质弹塑性地基沉降。研究表明,弹塑性地基中动偏应力呈马鞍形分布,最大值出现在道床边缘附近土体中;车速小于土体瑞利波速时沿地基表面和轨道中心沿深度方向土体动偏应力的衰减曲线光滑,车速接近或大于土体瑞利波速时,在马赫效应的影响下动偏应力呈波动衰减;修正列车荷载下弹塑性地基中动偏应力分布更符合实际情况;高铁运营初期地基沉降较快,随时间增加沉降速率逐渐趋于稳定;计算高铁运行产生的地面沉降时,需同时考虑列车运行速度和随机激振力的影响。 展开更多
关键词 高铁 2.5维有限元 弹塑性地基 动偏应力 沉降
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Assessment of cyclic deformation and critical stress amplitude of jointed rocks via cyclic triaxial testing
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作者 Waranga Habaraduwa Peellage Behzad Fatahi Haleh Rasekh 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第6期1370-1390,共21页
Jointed rock specimens with a natural replicated joint surface oriented at a mean dip angle of 60were prepared,and a series of cyclic triaxial tests was performed at different confining pressures and cyclic deviatoric... Jointed rock specimens with a natural replicated joint surface oriented at a mean dip angle of 60were prepared,and a series of cyclic triaxial tests was performed at different confining pressures and cyclic deviatoric stress amplitudes.The samples were subjected to 10,000 loading-unloading cycles with a frequency of 8 Hz.At each level of confining pressure,the applied cyclic deviatoric stress amplitude was increased incrementally until excessive deformation of the jointed rock specimen was observed.Analysis of the test results indicated that there existed a critical cyclic deviatoric stress amplitude(i.e.critical dynamic deviatoric stress)beyond which the jointed rock specimens yielded.The measured critical dynamic deviatoric stress was less than the corresponding static deviatoric stress.At cyclic deviatoric stress amplitudes less than the critical dynamic deviatoric stress,minor cumulative residual axial strains were observed,resulting in hysteretic damping.However,for cyclic deviatoric stresses beyond the critical dynamic deviatoric stress,the plastic strains increased promptly,and the resilient moduli degraded rapidly during the initial loading cycles.Cyclic triaxial test results showed that at higher confining pressures,the ultimate residual axial strain attained by the jointed rock specimen decreased,the steadystate dissipated energy density and steady-state damping ratio per load cycle decreased,while steadystate resilient moduli increased. 展开更多
关键词 Cyclic triaxial test Jointed rock Joint surface Confining pressure Cyclic deviatoric stress amplitude FAILURE Residual deformation Dissipated energy
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A new mixed-mode phase-field model for crack propagation of brittle rock
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作者 Qiuhua Rao Chenchen Zhao Wei Yi 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第5期1186-1199,共14页
Study on crack propagation process of brittle rock is of most significance for cracking-arrest design and cracking-network optimization in rock engineering.Phase-field model(PFM)has advantages of simplicity and high c... Study on crack propagation process of brittle rock is of most significance for cracking-arrest design and cracking-network optimization in rock engineering.Phase-field model(PFM)has advantages of simplicity and high convergence over the common numerical methods(e.g.finite element method,discrete element method,and particle manifold method)in dealing with three-dimensional and multicrack problems.However,current PFMs are mainly used to simulate mode-I(tensile)crack propagation but difficult to effectively simulate mode-II(shear)crack propagation.In this paper,a new mixed-mode PFM is established to simulate both mode-I and mode-II crack propagation of brittle rock by distinguishing the volumetric elastic strain energy and deviatoric elastic strain energy in the total elastic strain energy and considering the effect of compressive stress on mode-II crack propagation.Numerical solution method of the new mixed-mode PFM is proposed based on the staggered solution method with self-programmed subroutines UMAT and HETVAL of ABAQUS software.Three examples calculated using different PFMs as well as test results are presented for comparison.The results show that compared with the conventional PFM(which only simulates the tensile wing crack but not mode-II crack propagation)and the modified mixed-mode PFM(which has difficulty in simulating the shear anti-wing crack),the new mixed-mode PFM can successfully simulate the whole trajectories of mixed-mode crack propagation(including the tensile wing crack,shear secondary crack,and shear anti-wing crack)and mode-II crack propagation,which are close to the test results.It can be further extended to simulate multicrack propagation of anisotropic rock under multi-field coupling loads. 展开更多
关键词 New mixed-mode phase-field model(PFM) Mode-I and mode-II crack propagation Volumetric strain energy deviatoric elastic strain energy Compressive stress Brittle rock
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含砂量对砂-粉土混合物强度特性的影响试验研究 被引量:1
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作者 常留成 王红雨 +1 位作者 曹静 王亚 《长江科学院院报》 CSCD 北大核心 2023年第10期96-102,共7页
为研究砂粒对砂-粉土混合物强度特性的影响规律及作用机制,对不同含砂量的砂-粉土混合物进行三轴固结排水剪切试验和压汞试验。研究结果表明:随含砂量的增加,砂-粉土混合物的内摩擦角和峰值偏应力增大,黏聚力降低,含砂量≤30%时变化幅... 为研究砂粒对砂-粉土混合物强度特性的影响规律及作用机制,对不同含砂量的砂-粉土混合物进行三轴固结排水剪切试验和压汞试验。研究结果表明:随含砂量的增加,砂-粉土混合物的内摩擦角和峰值偏应力增大,黏聚力降低,含砂量≤30%时变化幅度最明显,其后较弱并趋于稳定;同时,峰值偏应力增幅随着围压的增加而增大。含砂量<15%时,砂-粉土混合物的强度由黏聚强度控制,随着含砂量增大,摩擦强度逐步超过黏聚强度对强度起主要作用。砂-粉土混合物的体积收缩致使土体更加密实,从而导致砂-粉土混合物内摩擦角和峰值偏应力的增加。 展开更多
关键词 砂-粉土混合物 含砂量 峰值偏应力 压汞试验 微观机制 强度特性
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临近断层构造带不规则工作面开采诱冲机制研究 被引量:1
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作者 李士栋 杨增强 +4 位作者 周涛 孔震 袁腾飞 周广飞 蔡武 《煤炭工程》 北大核心 2023年第11期83-88,共6页
针对临近断层构造带不规则工作面开采期间容易诱发严重冲击地压显现难题,通过现场调研、理论分析、数值模拟和矿压观测相结合的方法,对7447不规则工作面回采期间覆岩破断特征及其诱冲机制进行了研究。结果表明:在静载作用下宽工作面段... 针对临近断层构造带不规则工作面开采期间容易诱发严重冲击地压显现难题,通过现场调研、理论分析、数值模拟和矿压观测相结合的方法,对7447不规则工作面回采期间覆岩破断特征及其诱冲机制进行了研究。结果表明:在静载作用下宽工作面段较窄工作面段的巷道更容易发生破坏,且临近断层构造带侧的运输平巷相较于轨道平巷更容易发生变形破坏;宽工作面段较窄工作面段更易在采空区上方形成破坏高度更大的梯形体结构,此时覆岩中厚硬关键层发生破断而形成剧烈动载扰动。现场支架工作阻力随工作面回采推进距离变化规律进一步揭示了不规则工作面开采诱冲机制,为具有类似工程背景的冲击地压研究奠定了基础。 展开更多
关键词 冲击地压 不规则工作面 数值模拟 偏应力 工作阻力
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考虑工作面出煤柱尺度效应的下位回采巷道布置优化 被引量:1
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作者 吕凯 何富连 +3 位作者 许旭辉 王福忠 秦宾宾 李亮 《煤炭科学技术》 CAS CSCD 北大核心 2023年第3期52-60,共9页
针对遗留煤柱对下位巷道及采场产生的不利影响,以近距离煤层下行开采为背景,采用理论解析及现场实测等方法,对煤柱下底板偏应力不变量的区域特征、工作面出煤柱压架灾害的发生机理及其尺度效应展开研究。结果表明:①当上煤层相邻工作面... 针对遗留煤柱对下位巷道及采场产生的不利影响,以近距离煤层下行开采为背景,采用理论解析及现场实测等方法,对煤柱下底板偏应力不变量的区域特征、工作面出煤柱压架灾害的发生机理及其尺度效应展开研究。结果表明:①当上煤层相邻工作面开切眼位置不平齐时,下位巷道通过采取平错式布置,在保障巷道自身稳定的前提下,成功将工作面全长出一侧采空煤柱转化为2次小范围的出煤柱过程,实现对采场压架灾害的提前防治。②采用偏应力第二不变量(J_(2))、偏应力第三不变量(J_(3))和偏应力第二不变量(J_(2))水平变化率解析煤柱下方底板岩层的应力状态,并对底板进行分区,确定下位巷道平错距离的下限值为24 m。③工作面出煤柱期间,初次来压或周期来压与顶板-煤柱系统突变失稳产生的动载矿压耦合叠加形成冲击是压架灾害发生的根本原因,计算出煤柱尺度效应,得到平错距离上限值为36 m。燕子山煤矿工业性实践验证了下位巷道采取平错式布置且平错距离为30 m的可行性与合理性。 展开更多
关键词 近距离煤层 巷道布置 遗留煤柱 平错式布置 出煤柱 顶板-煤柱系统
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窄高水材料巷旁充填沿空留巷围岩偏应力演化及控制 被引量:3
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作者 鄢德恒 《煤炭工程》 北大核心 2023年第2期45-51,共7页
为了解决高水材料窄巷旁充填沿空留巷围岩破坏严重及难以控制的问题,以登茂通公司2202综采工作面1.4m窄高水材料巷旁充填沿空留巷为工程背景,基于实验室实验测试了水灰比为1.6∶1高水材料的强度特征,通过数值模拟及现场工程试验研究了... 为了解决高水材料窄巷旁充填沿空留巷围岩破坏严重及难以控制的问题,以登茂通公司2202综采工作面1.4m窄高水材料巷旁充填沿空留巷为工程背景,基于实验室实验测试了水灰比为1.6∶1高水材料的强度特征,通过数值模拟及现场工程试验研究了高水材料窄巷旁充填沿空留巷围岩偏应力分布规律及其失稳破坏机制。结果表明:①随着超前工作面距离的不断增加,偏应力峰值带位置逐渐发生偏转,偏应力峰值大小逐渐减小,越靠近工作面采动影响越剧烈;②超前工作面40m范围内的巷道围岩偏应力峰值带主要集中在巷道右上肩角与左下肩角,超前工作面距离大于50m时的围岩偏应力峰值带主要集中在巷道顶底板围岩深部处,且近似呈对称状分布;③工作面回采且留巷完成后,留巷围岩偏应力峰值主要集中于实体煤帮与实体煤侧顶板处,支护时需保证锚索杆体穿过实体煤帮及顶板围岩偏应力峰值带位置。基于此提出高水材料窄巷旁充填沿空留巷围岩采用“顶板全锚索支护+巷内三排单体支柱+实体煤侧补强锚索加固+巷旁高水材料充填墙”对拉预紧锚杆并辅以单体柱护墙+采空区侧单体柱撑顶并辅以锚杆加固顶板的分区域非对称综合控制技术,通过现场工程实践证明了留巷围岩控制技术的合理性,保障了高水材料窄巷旁充填沿空留巷的稳定性。 展开更多
关键词 沿空留巷 高水材料 巷旁充填 偏应力 围岩控制
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Analysis and Simulations of Open-Source Intelligence Process System Dynamics from User’s Perspective 被引量:1
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作者 Huan Liu Zhenyu Tang +1 位作者 Ning Zhao Wei Qian 《Computer Modeling in Engineering & Sciences》 SCIE EI 2023年第1期541-558,共18页
In today’s society with advanced Internet,the amount of information increases dramatically with each passing day,which leads to increasingly complex processes of open-source intelligence.Therefore,it is more importan... In today’s society with advanced Internet,the amount of information increases dramatically with each passing day,which leads to increasingly complex processes of open-source intelligence.Therefore,it is more important to rationalize the operation mode and improve the operation efficiency of open-source intelligence under the premise of satisfying users’needs.This paper focuses on the simulation study of the process system of opensource intelligence from the user’s perspective.First,the basic concept and development status of open-source intelligence are introduced in details.Second,six existing intelligence operation process models are summarized and their advantages and disadvantages are compared in focus.Based on users’preference,the open-source intelligence system simulation theory model is constructed from four aspects:intelligence collection,intelligence processing,intelligence analysis,and intelligence delivery.Meanwhile,the dynamics model of the open-source intelligence process system is constructed based on the open-source intelligence system simulation theoretical model,which specifically includes five parts:determination of system boundary,construction of causal loop diagram,construction of stock flow diagram,writing ofmathematical equations,and system sensitivity test.Finally,the system simulation results were analyzed.It was found that improving the system of intelligence agencies,opening up government affairs,improving the professional level of intelligence personnel,strengthening the communication and cooperation among personnel of various intelligence departments,and expressing intelligence products through diverse forms can effectively improve the operational efficiency of the open-source intelligence process system. 展开更多
关键词 Open-source intelligence system dynamics FEEDBACK user demand deviation
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深部连续开采充填工作面沿空掘巷围岩偏应力演化与控制 被引量:1
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作者 汪隆靖 邢世坤 +1 位作者 易恩兵 焦小建 《矿业安全与环保》 CAS 北大核心 2023年第3期81-88,共8页
为解决深部连续充填工作面沿空掘巷围岩控制问题,以邢东矿1128运输巷为工程背景,借助FLAC3D数值模拟软件,探究1126工作面采空区在不同充填率条件下沿空掘巷围岩偏应力分布规律,模拟分析充填开采工作面超前段受开采影响的围岩偏应力演化... 为解决深部连续充填工作面沿空掘巷围岩控制问题,以邢东矿1128运输巷为工程背景,借助FLAC3D数值模拟软件,探究1126工作面采空区在不同充填率条件下沿空掘巷围岩偏应力分布规律,模拟分析充填开采工作面超前段受开采影响的围岩偏应力演化特征。研究发现:巷道浅部围岩形成环全断面低偏应力区,顶板低值区深度明显小于两帮与底板,低值区外的巷道四边均有一个偏应力高值区;围岩最大偏应力区位于巷道右上部,峰值大于20 MPa,当充填率大于90%时,巷道围岩四周偏应力值逐渐减小且沿巷道两帮呈对称分布;充填开采对超前段巷道围岩形成的高集中应力主要分布在工作面前方0~15 m,巷道顶、底板两尖角处围岩受巷道围岩偏应力影响形成4个“突出变形区”。结合模拟分析结果、锚杆索预应力承载结构及采空区高水材料充填性能,提出巷道围岩“超强锚杆+大直径高延伸率锚索”联合支护技术,并应用于现场工程实践,结果表明该技术可实现对深部连续开采充填工作面沿空掘巷围岩的有效控制。 展开更多
关键词 深井 充填开采 沿空掘巷 偏应力 围岩控制
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鲁西黄泛区淤积粉土动力特性研究
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作者 韩超 崔学仕 +2 位作者 王旭锋 谭浩 张永飞 《山西建筑》 2023年第5期67-70,共4页
鲁西黄泛区淤积粉土与其他地区粉土有较大差异,其在偏压影响下的抗液化特性尚不明确。开展了不同围压、偏压和幅值工况的动三轴试验,重点分析了围压及偏压对动强度、动剪切模量和阻尼比的影响规律。试验结果表明:围压与偏压对鲁西黄泛... 鲁西黄泛区淤积粉土与其他地区粉土有较大差异,其在偏压影响下的抗液化特性尚不明确。开展了不同围压、偏压和幅值工况的动三轴试验,重点分析了围压及偏压对动强度、动剪切模量和阻尼比的影响规律。试验结果表明:围压与偏压对鲁西黄泛区淤积粉土动强度的影响较大且规律性明显,动强度曲线随围压和偏压的增加逐渐升高;相同动剪应变下,动剪切模量比随着围压及偏压的增大而增大;阻尼比随着偏压的增大而逐渐降低。 展开更多
关键词 黄泛区 粉土 动三轴 偏压
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A promising resilience parameter for breeding:the use of weight and feed trajectories in growing pigs
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作者 Wim Gorssen Carmen Winters +7 位作者 Roel Meyermans Lea Chapard Katrijn Hooyberghs Steven Janssens Abe Huisman Katrijn Peeters Han Mulder Nadine Buys 《Journal of Animal Science and Biotechnology》 SCIE CAS CSCD 2023年第6期2363-2382,共20页
Background Increasing resilience is a priority in modern pig breeding.Recent research shows that general resilience can be quantified via variability in longitudinal data.The collection of such longitudinal data on we... Background Increasing resilience is a priority in modern pig breeding.Recent research shows that general resilience can be quantified via variability in longitudinal data.The collection of such longitudinal data on weight,feed intake and feeding behaviour in pigs has been facilitated by the development of technologies such as automated feeding stations.The goal of this study was to investigate resilience traits,which were estimated as deviations from longitudinal weight,feed intake and feeding behaviour data during the finishing phase.A dataset with 324,207 records between the age of 95 and 155 days on 5,939 Pietrain pigs with known pedigree and genomic information was used.We provided guidelines for a rigid quality control of longitudinal body weight data,as we found that outliers can significantly affect results.Gompertz growth curve analysis,linear modelling and trajectory analyses were used for quantifying resilience traits.Results To our knowledge,this is the first study comparing resilience traits from longitudinal body weight,feed intake and feeding behaviour data in pigs.We demonstrated that the resilience traits are lowly to moderately heritable for deviations in body weight(h2=2.9%–20.2%),in feed intake(9.4%–23.3%)and in feeding behaviour(16.2%–28.3%).Additionally,these traits have good predictive abilities in cross-validation analyses.Deviations in individual body weight and feed intake trajectories are highly correlated(rg=0.78)with low to moderate favourable genetic correlations with feed conversion ratio(rg=0.39–0.49).Lastly,we showed that some resilience traits,such as the natural logarithm of variances of observed versus predicted body weights(lnvarweight),are more robust to lower observation frequencies and are repeatable over three different time periods of the finishing phase.Conclusions Our results will help future studies investigating resilience traits and resilience-related traits.Moreover,our study provides first results on standardization of quality control and efficient data sampling from automated feeding station data.Our findings will be valuable for breeding organizations as they offer evidence that pigs’general resilience can be selected on with good accuracy.Moreover,this methodology might be extended to other species to quantify resilience based on longitudinal data. 展开更多
关键词 DEVIATIONS GENETICS Gompertz growth curves HERITABILITY PIGS Predictive ability RESILIENCE Trajectory analysis
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